The anode catalysts used in proton exchange membrane (PEM) water electrolysis must be resistant to the harsh oxidation environment that occurs during the oxygen evolution reaction (OER). The investigation and application of in-situ/operando characterization techniques are critical for developing acidic OER catalysts with high stability and activity. Herein, several in-situ/operando characterization techniques for acidic OER research are introduced, including in-situ/operando X-ray photoelectron spectroscopy, in-situ/operando X-ray absorption spectroscopy, in-situ/operando X-ray diffraction/scattering, in-situ/operando electrochemical infrared spectroscopy, in-situ/operando electrochemical Raman spectroscopy, in-situ/operando inductively coupled plasma mass spectrometry, differential electrochemical mass spectrometry/on-line electrochemical mass spectrometry, in-situ/operando electro-chemical infrared spectroscopy, in-situ/operando electrochemical Raman spectroscopy, in-situ/operando inductively coupled plasma mass spectrometry, differential electrochemical mass spectrometry/on-line electrochemical mass spectrometry, electrochemical quartz crystal microbalance. Special attention is paid to the device structure and application value of these in-situ/operando characterization techniques for OER in acidic media. Finally, the characteristics of these techniques are summarized, and the challenges for the development of in-situ characterization techniques, such as the development of new techniques and the combination of in-situ techniques, the improvement of in-situ devices, and space-time resolution, are highlighted.

Clean energy technologies such as fuel cells, water electrolysis, and metal-air batteries have improved energy efficiency and could become new energy consumption methods in the future to peak carbon dioxide emissions and achieve carbon neutrality. The sluggish kinetics of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) hinder the development of these clean energy technologies. Although noble metal catalysts are considered superior, they have apparent disadvantages, such as poor durability, low selectivity, and high cost. The determination of noble metal-free catalysts has become a trend in related researches. As an emerging class of polymer materials linked by special covalent bonds, covalent organic frameworks (COFs) demonstrate advantages of tunable structure, low density, high stability, and large specific surface area. COFs are widely considered as promising electrocatalysts that can be gradually applied utilizing reasonable design strategies. Herein, this review aims to research 2D COFs suitable for ORR, OER, and bifunctional electrocatalysis in recent years and primarily introduces the strategies of pristine COF as an electrocatalyst, composite structure formation, and pyrolysis. The key factors for forming electrocatalytic active centers or improving electrocatalytic activity have been summarized from the molecular design and electronic tuning aspects, which are expected to serve as a reference in future works.

Oxygen evolution reaction (OER) is a limiting process in energy conversion and storage due to its sluggish kinetics, especially in water electrolysis. The critical challenge in this area is to explore alternative precious-metal-free catalysts to promote the OER process. Transition metal-based compounds have attracted much attention in electrochemical water splitting because of their unique chemical and physical properties, as well as low cost. In this review, we summarize the recent research status and progress of spinel, perovskite and layered double hydroxides as electrocatalysts for OER, which have been extensively studied in recent years. The researcher strategies developed to promote electrocatalytic activities and stability are described, along with the electrochemical properties of theses developed catalysts. Based on related references, we observed that there are generally two strategies to improve OER catalyst activities: (1) introduce more active sites and expose them to the catalyst surface and (2) optimize the conductivity of OER catalysts. These requirements can be met to some extent by the controlling size, morphology, intrinsic and lattice defects, oxygen vacancies, phase and composition of OER catalysts, and by the incorporation of conducting materials in composites. Finally, the future development of OER electrocatalysts is briefly discussed.

Oxygen reduction reaction (ORR) is a key process in fuel cell and metal-air cells, and whose sluggish reaction kinetics is the bottleneck restricting its development. MXene-based materials (including MXenes composite materials) as a new type of two-dimensional (2D) layered structural materials have unique structural features such as rich composition, high specific surface area and high chemical stability, tunable electronic state, a large number of exposed active sites and so on, and they are considered to be the most promising ORR electrocatalysts or electrocatalyst supports. Therefore, the development of high-performance MXene-based ORR catalysts provides a new way to accelerate the sluggish ORR of fuel cells and/ or metal-air battery cathodes. Herein, we classify and summarize the development of recent related literatures, reviewing of the design principles of MXene-based ORR catalysts, focusing on the latest research progress of MXenes and MXenes composite materials in terms of synthesis strategy, structure-activity relationship between components, morphology, structure and its electrocatalytic performance, as well as the electrocatalytic reaction mechanism of materials. Comprehensive analysis shows that MXenes composite materials, such as MXene/ transition metal oxides, MXene/ transition metal choridides, MXene/ transition metal nitrides, MXene/ carbon-based materials and MXene/ metal, are expected to achieve high performance and high stability of MXene-based ORR catalysts. Finally, some challenges in the current application of MXene-based nanomaterials are presented, and the future prospects of the MXene-based ORR electrocatalysts are proposed.

As an attractive energy conversion system, solid oxide fuel cell (SOFC) has a broad development prospect due to its high energy conversion efficiency, environmental friendliness, and wide fuel selectivity. To date, Ni-based anode is the most commonly used anode material for SOFCs from the view of low cost, good stability, and high catalytic activation. However, the carbon deposition is demonstrated to be a main issue when using hydrocarbon as the fuel, leading to the reduction of the output performance and operational stability of SOFCs. Therefore, it is of important scientific significance that the carbon deposition mechanism and promotion strategy of SOFCs are studied. We review recent advances in the carbon deposition mechanism and improvement strategy of Ni-based anode SOFCs. The latest research progress and future development direction of several anode materials are also summarized and analyzed. This work provides a valuable reference for the further development of high-performance SOFC anode materials.

As the third generation fuel cell, solid oxide fuel cell (SOFC) has attracted much attention due to its high energy conversion efficiency, a wide range of fuel applications, environmental friendliness, all-solid-state, and many other advantages. As an essential component of a solid oxide fuel cell, the bipolar plate (also known as a connector) serves as a series-parallel single cell, isolating fuel gas and air in the SOFC stack, and has a significant impact on cell performance and commercial cost. Different bipolar plate materials have different performance issues, with the main focus being on electrical conductivity, oxidation resistance, chemical stability, and thermal expansion coefficient matching. In this paper, the development history and current research progress of traditional ceramic materials, alloy materials, new ceramic materials, and composite bipolar plates are reviewed by reading recent relevant literature, and component optimization design and surface modification (coating active oxide coating, composite bipolar plates) are primarily introduced. Rare earth perovskite coating and spinel coating can improve the ability to inhibit the outward diffusion of cadmium, oxidation resistance, and conductivity of the alloy. The comprehensive analysis demonstrates that high-performance and low-cost bipolar plate materials can be obtained through component optimization design and surface modification to compensate for the performance defects of alloy as bipolar plate materials and that new ceramic materials or composites can be prepared to realize the large-scale commercial application of SOFC.

Three-dimensional (3D) printing, also known as additive manufacturing technology, is a method of producing three-dimensional objects using a layer-by-layer printing method that involves machinery, computers, numerical control, materials, and other technologies. It has been widely used in the areas of aerospace, biomedical, electronic, energy, and chemical industries. This paper primarily introduces several common 3D printing technologies, with a focus on the 3D printing of cathodes, anodes, electrolytes, and cell stacks for solid oxide fuel cells (SOFCs). It is thought to improve a SOFC's electrochemical performance by tailoring its microstructure, specific surface area, or composition distribution. The structural design of monolithic stack support is expected to improve the internal transport behavior of cell stacks. Using a 3D printing method, the SOFC stack preparation process can be simplified and optimized, or even integrated into one step, avoiding material mismatch caused by a large number of joints and assemblies and improving the stability and service life of the cell stack. 3D printing also provides distinct advantages in the design and preparation of SOFC stack auxiliary systems, as well as significant potential in the integrated preparation of stack components and stacks. Furthermore, the technical challenges of 3D printing technologies in the SOFC field are highlighted. In addition, some solutions to the problems and deficiencies of SOFCs prepared using the 3D printing method are proposed. The research and development of high-resolution ceramic 3D printing technologies, the innovations and developments of fuel cell slurry, and the manufacturing of hybrid and multi-material 3D printers could all become important directions for resolving existing problems.

The electrochemical synthesis of H₂O₂ via oxygen reduction reaction (ORR) is a low-cost, environment-friendly, and green synthesis method. However, the kinetics of ORR is very slow, and is also accompanied by the competitive reaction of 4 electron (4e^-) ORR to generate H₂O. The catalysts are therefore required. In recent years, carbon-based materials with low prices, abundant resources, competitive activity, and easy adjustability, have received extensive attention in this field. Herein, this review first briefly introduces the mechanism of ORR to the synthesis of H₂O₂, and the key factors of the catalytic performance of electrochemical synthesis of H₂O₂. Further, the strategy to improve the ORR activity and selectivity of carbon-based catalysts is reviewed, in which the doping of non-metallic atoms and the construction of transition metal single atoms on carbon-based materials are emphasized. Finally, the existing problems, challenges, and perspectives of carbon-based catalysts toward the electrosynthesis of H₂O₂ were described.

Direct carbon solid oxide fuel cells (DC-SOFCs) are new-type energy conversion devices that directly convert the chemical energy of solid carbon into electricity. They have many advantages like high theoretical efficiency, wide range of fuel sources, low cost, and pollution. As per the working principle of DC-SOFCs, the cell operation is controlled by kinetics process. The effective coupling between the electrochemical oxidation reaction of CO in the anode and the reverse Boudouard reaction in carbon fuel ensures the efficient and stable operation of DC-SOFCs. The relatively slow reverse Boudouard reaction is the determining factor for the electrochemical performance of DC-SOFCs. Therefore, it is an effective way to promote the industrialization process of DC-SOFCs by improving the reverse Boudouard reaction. Much effort has been taken to achieve this goal. Among these, the simplest and effective means are to directly use a high-activity catalyst or the biochar due to their naturally existing catalyst and porous structure. Based on the frontier research in recent years, we review recent advances in the reverse Boudouard reaction catalysts and carbon fuels of DC-SOFCs in this paper. Moreover, the present status, challenges facing, and future directions of DC-SOFCs are also systematically summarized, in order to provide a more valuable reference for the development of high-performance and long-life DC-SOFCs.

Due to the accelerating global trend of low-carbon energy transformation and China's strategy of facilitating "carbon peaking and carbon neutralization," China's local governments have been intensively issuing fuel cell vehicle policies in recent years to seize the opportunity of hydrogen energy development and create new momentum for the local economy and society. This study evaluates the local policy status of fuel cell vehicles based on the overall situation of fuel cell vehicles and their relative national policies in China. Twenty representative cities covering all the seven regions in China are selected to research policy readiness for fuel cell vehicles since cities are the key target for industry development and policy implementation. Taking "fuel cell vehicle" as the key theme while giving due consideration to "hydrogen energy" and "fuel cell," 197 local policy texts of fuel cell vehicles issued from 2018 to the first half of 2021 are statistically explored. This study constructs an evaluation index system and model for city policy readiness using the analytic hierarchy process (AHP), Delphi, and content-analysis methods. The index system is composed of four dimensions, namely planning goals, fiscal and tax policies, non-fiscal and tax policies, as well as cooperation mechanisms. Furthermore, there are 13 corresponding secondary indicators for the four dimensions, such as vehicle promotion goals, and 39 tertiary indicators, such as application fields, determined with their respective weights and included in the index system. The policy readiness of fuel cell vehicles for 20 representative cities is measured and ranked by deploying the evaluation model. The results show that the overall readiness level of fuel cell vehicle policies in these Chinese cities is not high. In contrast, a local policy system guided by planning goals, supported by non-fiscal tax policies, and cross-regional cooperation and coordination has been preliminarily formed. This study summarizes regional policy imbalance and points out city policy highlights and weaknesses by analyzing differences of specific policy dimensions and indicators among cities. Finally, suggestions to optimize the local policies of fuel cell vehicles have been put forward, such as adjusting measures to local conditions, strengthening city demonstration goal guidance, short-term supply-oriented policies, long-term environmental support policy tools, and focusing more on sustainable development policies for the after-demonstration stage.

Ammonia is an ideal energy storage material and hydrogen energy carrier. Its utilization and synthesis in proton-conducting solid oxide electrochemical devices can realize efficient and clean power generation and energy storage. In this paper, we review the advances in experimental and theoretical studies on the utilization and synthesis of ammonia in proton-conducting solid oxide electrochemical devices. In the aspect of experimental study, the development of electrolytes and ammonia electrode materials are comprehensively analyzed. While in the aspect of theoretical study, the research progress of thermodynamic-electrochemical models and density functional theory (DFT) are discussed emphatically. Since the proton conductivity of electrolyte materials and the catalytic activity of ammonia electrodes are the critical factors affecting the performance of electrochemical devices, the development of electrolyte materials with high proton conductivity and ammonia electrodes with high catalytic activity are still the main research topics. Thermodynamic-electrochemical models and DFT-based theoretical researches can provide guidance and ideas for the structural design of electrochemical device/optimization of operating conditions and development of ammonia electrode materials, respectively. However, theoretical studies of higher-level (three-dimensional) thermal-electrochemical models and the electrochemical activation mechanism of nitrogen on ammonia electrode materials still deserve further study. Finally, the future research directions of ammonia utilization and synthesis in electrochemical devices are also summarized.

Electrocatalytic hydrogen evolution reaction (HER) is a promising hydrogen energy conversion method. To develop high-performance and low-cost hydrogen evolution electrocatalysts, single- and double-atom catalysts (SACs, DACs) with transition metals (e.g., Fe, Ni, and Co) as the active center and nitrogen-doped graphene (N-graphene) as the substrate are selected for HER utilizing density functional theory calculations. The selected catalytic materials exhibit exceptional stability against sintering. We then chose H adsorption energy as the descriptor for analyzing the HER activity, and the results demonstrate that the CoN₄ site exhibits excellent HER activity over other candidates. In contrast, NiN₄ and Ni₂N₆ sites display inferior HER activity. In addition, the electronic structures of the catalysts are systematically discussed to uncover the origin of catalytic activity. This work reveals that DACs have poor HER activity compared to SACs and DACs, while the SACs (e.g., CoN₄, FeN₃, and FeN₄) show low overpotential in HER. Therefore, the SACs can substitute commercial precious metals catalysts (Pt/C) for HER catalysts.

The Pt/C catalyst was modified by premodification and postmodification methods using tin-silicon binary oxide to prepare two composite catalysts. Furthermore, two composite catalysts were used on the anode to prepare a membrane electrode assembly (MEA). First, the influence of modification methods on the performance of MEA was investigated. The cell performance test of two MEAs demonstrated that the Pt/SnO₂-SiO₂/C composite catalyst prepared by the premodification method had better cell performance: the current density at 0.6 V is as high as 1100 mA/cm² under complete humidification at 50 ℃. At the same time, the MEA also exhibited excellent self-humidification performance and stability: the current density at 0.6 V is 930 mA/cm² at a 50 ℃ cell temperature and with no humidification (dry gas); after the 10 h stability test, the performance only decreased by 13%, while the performance of blank MEAs decreases by 63% within 2 h. Further comparisons of the MEA performance under different relative humidity conditions shows that the MEA exhibits excellent self-humidification performance under low relative humidity conditions. According to the experimental data, the self-humidification mechanism of a Pt/SnO₂-SiO₂/C composite catalyst is preliminarily speculated.

The crystal structure and electrochemical performance of Sr deficient Sr_2-xFe_1.5Mo_0.5O_6-δ perovskite oxides were systematically investigated. XRD result indicates that the introduce of Sr deficiency increases the unit volume of Sr₂Fe_1.5Mo_0.5O_6-δ oxide and decreases the initial temperature of oxygen desorption, improving the lattice oxygen activity in Sr₂Fe_1.5Mo_0.5O_6-δ. Among Sr_2-xFe_1.5Mo_0.5O_6-δ oxides, Sr_1.95Fe_1.5Mo_0.5O_6-δ exhibits the highest conductivity with a maximum value of 38.4 S/cm¹. At 800 ℃, the values of polarization resistance (R_p) of Sr₂Fe_1.5Mo_0.5O_6-δ, Sr_1.95Fe_1.5Mo_0.5O_{6-δand Sr1.9Fe1.5Mo0.5O6-δ are 0.102, 0.070 and 0.096 Ω·cm², respectively, suggesting that Sr1.95Fe1.5Mo0.5O6-δ has the best oxygen reduction reaction activity. At fuel cell mode, NiO-YSZ(SL)/NiO-YSZ(FL)/YSZ/SDC/Sr1.95Fe1.5Mo0.5O6-δ delivers a maximum power density of 1459、953, 682 and 420 mW·cm^-2, respectively at 850, 800, 750 and 700 ℃, while a current density of -1300 mA·cm^-2 was observed at electrolysis cell mode when 20%H2O-H2 was used fuel and static air as oxidant. Finally, the single cell exhibits excellent stability (～100 h) under 800 ℃ and -500 mA·cm^-2.}

Noble metal nanoclusters have received widespread attention due to their special structure and distinct chemical composition. Bimetallic metal nanoclusters with precise particle size and structure were used in this study to investigate the effect of electronic and geometric structure on the catalytic reaction. The electron coupling between heteroatom and the host atom could regulate the catalytic performance. To create the well-dispersed electrochemical catalysts, carbon nanosheets supported Au₄Pd₂ nanoclusters (NCs) with a high surface area. The X-ray photoelectron spectroscopy (XPS) test revealed that the synergistic effect of AuPd and the support could promote ORR and HER stability. The ORR performance of Au₄Pd₂-CNs-2 with the initial potential of 0.95 V and the half-wave potential of 0.81 V was better than those of commercial Pd/C in the 0.1 mol/L KOH. The catalyst also demonstrated excellent catalytic activity towards HER with the overpotential of 129 mV at 10 mA/cm² in 0.5 mol/L H₂SO₄. The structure and morphology of catalysts are determined using X-ray diffraction (XRD) and transmission electron microscopy (TEM), and electrochemical measurements are used to test the electrocatalytic performances. Ultra-small single-cluster catalysts could improve the utilization and electrocatalytic activity of atoms, and the synergy effects between Au and Pd also enhance the catalytic activity of catalysts. By optimizing the doping ratio of Au₄Pd₂ NC_s, bifunctional catalysts with excellent oxygen reduction and hydrogen evolution performance were obtained, providing a new direction for developing non-platinum-based catalysts with high efficiency and stability.

Integrated gasification solid oxide fuel cell (IG-SOFC) power generation system, which uses feed gas obtained from coal gasification (syngas) to achieve near-zero emissions, is a promising clean-coal power generation technology, especially given China's coal-based resource temperament. The paper firstly proposes a test design scheme of the IG-SOFC grid-connected power generation system. Then a SOFC grid-connected power generation test platform is built, which could be applied to the operation mode of both "grid-connected test mode" and "grid-connected power generation mode." The feasibility of the design plan is then validated using the experimental results of a self-developed 5 kW SOFC tower module with syngas as the feed gas. The results show that when the SOFC tower module's generation power reaches 4.5 kW, the grid-connected generation power is 4.25 kW, the power generation efficiency of the stack module is 55.1%, the power generation efficiency of the system is 52.0%, and the inversion efficiency is approximately 94.5%. Finally, the long-period performance stability of the system is verified by the 168 h long-cycle test under "grid-connected test mode."

The bidirectional interleaved parallel DC-DC (BDC) converter is an important device for hydrogen fuel cell vehicle power supply reliability and energy recovery. The BDC converter experiences slow response speed, low stability, and output current ripple when using traditional control methods. Aiming at the above problems, a constrained model predictive current control is proposed. First, mathematical models for the various working modes of the BDC converter are established, and an improved current prediction model for the various working modes of the BDC converter based on the vector working principle is constructed. The cost function is then optimized to solve the problem of frequent switch jitter in the model predictive control process, and the control variable increment is added to the constraint condition; to solve the output current ripple problem, the model predictive control strategy is improved by calculating the switch duty cycle online. Finally, calculate the vector action time and create the cost function to achieve the control objective. The traditional current control method's response time and current ripples are 0.1 s and 5 A, respectively. In contrast, the improved MPC model predictive control response time and current ripples are 0.02 s and 1.5 A. The experimental and simulation comparison results show that Model predictive current control with constraints has a better dynamic response and stable performance, which verifies the algorithm's effectiveness.

The temperature distribution on the surface of the membrane electrode assembly of the proton exchange membrane fuel cell will affect the performance, life and reliability of proton exchange membrane fuel cell. In order to investigate the heat transfer of proton exchange membrane fuel cell, a prediction model of the temperature distribution of the membrane electrode assembly based on neural network is proposed. This study selected the radial basis function (RBF) neural network and generalized regression neural network (GRNN), two kinds of neural network, with the location of the current density and temperature point as network input, the different position as network output, the temperature of the parallel port of proton exchange membrane fuel cell, serpentine flow proton exchange membrane fuel cell neural network prediction model is established, respectively. The results showcase the average root mean square error of RBF neural network prediction is 0.464, the average absolute percentage error is 1.179%, the average root mean square error of GRNN neural network prediction is 0.7155, the average absolute percentage error is 2.27%. Compared with GRNN neural network, RBF neural network has higher accuracy. The relative error between the predicted value and the experimental value of 96% for the temperature distribution prediction model based on RBF neural network is within 5%. The relative error between the predicted value and the 95% experimental value of the temperature distribution prediction model based on RBF neural network for the membrane electrode assembly of PEMFC is less than 5%.

Carbon materials with adjustable pore structure and surface chemical properties were prepared at different carbonization temperatures using freeze-dried agaric as a precursor. The measured results show that carbon materials prepared at carbonization temperatures ranging from 450—650 ?℃ have oxygen-containing functional groups without pore structure. While carbon materials prepared at 800—900 ?℃ contain the amount of microporous and mesoporous (795 m²/g) without surface groups. Carbon materials were used as sulfur hosts to prepare carbon-sulfur composite materials to analyze the relationship between the structural properties of the carbon materials and the electrochemical properties of the C/S composites. It was found that LD900 material with plenty of microporous and mesoporous shows three discharge platforms due to the limitation of microporous structure towards sulfur-containing species. However, the micropores and small mesopores are easily blocked during the cycle process, resulting in LD900-S's poor cycle stability. While the LD450 has plenty of polar oxygen-containing functional groups, it has plenty of chemisorption towards sulfur-containing species. In addition, the prepared LD450-S cathode exhibits improved cycle stability and rate performance. After 100 cycles at 0.1 C, the specific discharge capacity is 577 mA·h/g, and at 1 C, the specific discharge capacity is still 650 mA·h/g.

Single-ion polymer electrolytes were recently developed and used in solid-state batteries. In single-ion polymer electrolytes, anions are attached to the main chain of polymers, and only lithium ions are allowed to pass through into the electrolyte. As a result, the single-ion polymer electrolytes had a high lithium-ion migration number, which will be beneficial in reducing the concentration polarization of lithium batteries. However, the low ion conductivity of single-ion polymer electrolytes limits their application in lithium batteries. In the present work, chlorosulfonic acid, polyvinylidene fluoride (PVDF), and lithium hydroxide were used to prepare sulfonated polyvinylidene fluoride (SPVDF) and polyvinylidene fluoride sulfonate lithium (SPVDFLi). The chemical structures of PVDF and SPVDF were confirmed by the 1H nuclear magnetic resonance spectra. A series of single-ion polymer electrolytes (SIPEx) were prepared by a solvent casting method from PVDF and SPVDFLi mixture solution. To improve the electrolyte's ion conductivity, PVDF/SPVDFLi/LiTFSI composite electrolytes (SPVDFLi/LiTFSI-y) were created by varying the amount of LiTFSI in the SIPE. The ion conductivity of SIPEs increased by increasing the content of SPVDFLi. The ion conductivity of PVDF/SPVDFLi/LiTFSI composite electrolytes further increased by increasing the content of LiTFSI, SPVDFLi/LiTFSI-40 showed the conductivity of 1.41×10^-4 S/cm at 25 ℃, the steady voltage of up to 4.84 V, and the capacity retention rate of is 99.1% after 50 cycles at 0.2 C, because of its high conductivity, high lithium-ion migration number, and high efficiency in inhibiting the growth of lithium dendrites SPVDFLi, the excellent lithium-ion battery assembled with SPVDFLi/LiTFSI-40. These findings suggest that the PVDF/SPVDFLi/LiTFSI composite electrolytes will be used to create high-performance solid-state lithium-ion batteries.

Gel polymer electrolyte based on polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP) is regarded as a promising solid electrolyte for addressing the problem of lithium power safety. However, because they contain a lot of flammable substances, gel solid polymer electrolytes are still not guaranteed at the moment. Therefore, a new type of gel polymer electrolyte based on PVDF-HFP was synthesized. Using succinonitrile (SN) as a plasticizer and lithium bis(trifluoromethanesulphonyl)imide (LiTFSI) as the lithium salt, a new gel solid polymer electrolyte (GSPE) with high thermal stability was prepared in situ by the thermal cross-linking method. At 25 ℃, the optimized gel polymer electrolyte's ionic conductivity can reach 3.7×10^-3 S/cm, and the electrochemical window can reach 4.5 V. In addition, the gel polymer electrolyte has good electrode interface compatibility. The assembled lithium iron phosphate battery is circulated 80 times at 1 C, with an 89% capacity retention rate. This study shows that high-performance gel polymer electrolytes have great potential applications in improving the cycle stability and safety of lithium-ion batteries.

Nanocarbon particles (CRN) were prepared from red willow, which mostly exists planted in the northwest of China, processed by the mechanical crushing method after drying, pyrolysis, and pickling treatment processing. The electrochemical properties of a lithium-ion anode based primarily on CRN were investigated. X-ray diffractometry (XRD), Raman, and scanning electron microscopy (SEM) were used to examine the phase structure, degree of graphitization, and surface topography, respectively. Constant current charge and discharge were used to test the anode's specific capacity, magnification, and cycle stability. An electrochemical work-station was used to analyze the anode's electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) (CHI660E). The results show that the CRN prepared at 600 ℃ in the pyrolyzed temperature (500 ℃, 600 ℃, 700 ℃, and 800 ℃) has better cycle stability, higher specific capacity, and the best magnification. This study shows that the CRN prepared from red willow can be used properly as the anode of lithium-ion batteries.

Zinc-air batteries have gained popularity due to their high capacity, low cost, and low self-discharge performance. Zinc-air button batteries are the preferred power source for hearing aids, particularly in the medical field. German company Varta, American company Rayovac, and Chinese company ZeniPower are the main manufacturers of zinc-air hearing-aid button cells. The commercial air electrodes of zinc-air batteries are frequently manufactured using a wet process that involves preparing catalyst powders, which is time-consuming and energy-intensive. This study introduced a novel method using a 3000 rpm high-speed cutting machine without adding any solvent for the granulating process. Then after being treated by 12 mesh sieve, highly free-flowing dry catalyst powders were obtained for further treatment. Scanning electron microscope shows that the polytetrafluoroethylene (PTFE) binders in the catalyst powders are widely and completely fibrillated, which is beneficial to binding the catalyst powders together tightly even in the long term of storage. The above catalyst powders were then pressed into a roll-to-roll catalyst layer by self-made rollers and relevant machines. The current collector, waterproof and air permeable films, and the catalyst layer were pressed together to obtain the solvent-free fabrication of commercial zinc-air electrodes. A traditional commercial wet process was utilized to prepare the catalyst powders and air electrodes to make a comparison. It demonstrates that the discharge capacity of zinc-air batteries using solvent-free electrodes is 5% higher than the wet method, which could be attributed to the solvent-free fabrication process's widespread and complete formation of strong fibrillated PTFE fibers. Different electrode densities and thicknesses, as well as different waterproof and air permeable films, were also investigated. It shows that electrodes with a low density of 1.15 g·cm^-3 have better capacity performance after storage, possibly because there is higher bonding strength between the catalyst layer and PTFE film in the air electrode. Electrodes with larger thicknesses as 0.52 mm contribute to higher power density resulting from more three-phase active sites in the catalyst layer. Because of the high strength of carbon-fluorine bonds, pure PTFE film functioned as waterproof and air permeable films with better anti-leakage performance. To summarize, this solvent-free process is simple, energy-efficient, and appropriate for commercializing metal-air batteries. More applications in various types of metal-air batteries, such as large-size, solid-state, flexible, and secondary batteries, could benefit from this commercialized technology in the future.

The low electrochemical activity of the polyacrylonitrile graphite felt electrode limits the development of all vanadium redox flow battery (VRFB). Nitrogen and sulfur co-doped carboxylic multi-walled carbon nanotubes (MWCNTs-COOH-NS) were prepared as a VRFB catalyst using thiourea as a doping source to improve the performance of positive electrodes in VRFB. Composite electrodes were manufactured by attaching MWCNTs-COOH-NS to polyacrylonitrile graphite felt. Scanning electron microscopy (SEM), specific surface area (BET), X-ray photoelectron spectroscopy (XPS), conductivity measurement, cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and charge-discharge tests were used to investigate the surface morphology and electrochemical properties of the composite electrode. According to the results, the composite electrode had a larger surface area and a lower internal resistance. When the current density is 80 mA/cm², the battery's energy efficiency is 81.70%, and the discharge capacity is 782.60 mA·h. Under the condition of 160 mA/cm², the battery's energy efficiency can still reach 72.73%. On the positive side, MWCNTs-COOH-NS modified graphite felt electrode exhibits good catalytic activity and electrochemical reversibility for the redox reaction of vanadium ions. In the charge-discharge test, the cell shows good cycle stability. This study is helpful to promote the development of VRFB electrode catalysts.

Activated carbon cathode and graphite anode were prepared using dry and wet processes, respectively. The 066090-type flexible packing lithium-ion capacitor (LIC) monomer was made, which the anode was pre-lithiation by charging and discharging at constant current with a theoretical lithiation depth of 85%. Scanning electron microscopy, peeling strength, and electrical performance tests were used to investigate the effects of the dry and wet coating processes on the electrode structure and morphology, bonding performance, and electrical performances. The effects of electrode structure on flexible packing LIC capacity, internal resistance, endurance, cycling, and low-temperature performance were described. The results reveal that sufficient fibrous structures of the binder are observed in the dry electrode, and the carbon particles have close contact. The bulk density of the dry electrode increase by more than 8% compared with that of the wet coating electrode, and its peel strength is more than 50% higher than that of the wet coating electrode. When the areal density ratio of activated carbon cathode to graphite anode is 1, the initial capacity and internal resistance of the flexible packing LIC are 645 F and 25.5 mΩ at the potential range 2.2—3.8 V, respectively, both of which are higher than those of the wet coating electrode. The capacity of the flexible packing LIC assembled with dry electrode maintains above 97% after 1000 h endurance test, maintaining 88% after 100,000 cycles, and maintaining 76% at -30 ℃, which are superior to those of the products assembled with wet coating electrode. This research will help promote the use of dry electrodes in LIC products and serve as an experimental foundation for the research and development of high-performance LICs.

The positive electrode was a lithium titanate@activated carbon composite material, and the negative electrode was commercial hard carbon. A series of steps were taken to prepare a lithium-ion capacitor (LIC) with pre-inserted lithium hard carbon/lithium titanate@ activated carbon. Pre-intercalating hard carbon with various lithium contents resulted in a variety of pre-inserted lithium hard carbon pole pieces in this thesis. The LIC assembled with the prepared pre-inserted lithium hard carbon pole pieces was then electroporated in a series of steps. The chemical performance test investigated the effect of lithium insertion into the hard carbon pole piece on the specific energy and specific power of LIC. The results showed that doping lithium powder in hard carbon can significantly increase the specific energy of LIC while decreasing its specific power. The assembled LIC when the mass ratio of hard carbon to lithium powder was 3∶1 was one of them. After 2000 cycles of charge and discharge at a current density of 2 A/g, the energy density can reach 29.69 W·h/kg, the power density can reach 7.57 kW/kg, and the capacity retention rate can reach 83.11%.

At the moment, there are numerous issues with single inorganic solid electrolytes and polymer solid electrolytes, such as low ionic conductivity, dendrite formation, unstable interfaces, and so on. In varying degrees, composite solid electrolytes formed by organic polymer electrolytes and inorganic electrolytes can improve conductivity, inhibit dendrite formation, improve mechanical strength, interface stability, and compatibility. This paper reviews the improvement direction and measures of composite solid-state electrolytes in improving lithium ion conductivity, inhibiting lithium dendrite, and improving electrochemical stability. In addition, the development direction of the composite solid-state battery is anticipated, which serves as a reference for the development and application of the composite solid-state battery.

Titanium niobium oxide (TNO) has become one of the preferred anode materials for high-power and long-life lithium-ion power batteries due to its high specific capacity, safe Li⁺-intercalation potential, fast Li⁺-intercalation path, and stable Li⁺-intercalation structure. The relatively low electronic conductivity of TNO anode materials, on the other hand, limits their high rate of performance. TNO's structural characteristics, preparation methods, and modification strategies are discussed in this paper. The crystal structures of several TNO materials with different Ti/Nb ratios are discussed, as well as the synergistic mechanism of both redox and intercalation pseudocapacitance, and the mechanism of rapid lithium conduction is elucidated. Furthermore, several methods and their advantages for TNO preparation are introduced, including solid-state reaction, sol-gel method, electrospinning method, template method, and solvothermal method. In addition, the effects of doping, defect, and composite on electron and charge conductivities, as well as the electrochemical performance of TNO, are emphatically analyzed. Finally, the research status, existing issues, and applications of TNO as anode material in two different energy storage systems of lithium-ion battery and hybrid lithium-ion capacitor are also discussed. Comprehensive analysis reveals that element doping and defect design can change the electronic structure of TNO, and conductive material composite can be used to construct a multi-dimensional electronic path. The combination of various modifications, in particular, can significantly improve the rate performance and cycle stability of TNO materials, which is expected to make it a good application in high-power energy storage devices.

Aqueous batteries have attracted interest due to their environmental friendliness, safety, and low cost. The charge carrier is an important component of rechargeable batteries, affecting the reaction mechanism and performance. Non-metallic cations such as NH₄⁺, H⁺, H₃O⁺ have received little attention in comparison to aqueous batteries that use metal-ion charge carriers. Compared with metal-ion charge carriers, non-metallic cations with smaller ionic radius and lower molar mass, showing higher ion diffusion rate, long cycling life, and low manufacturing costs. However, developing suitable cathode electrode materials for the insertion of non-metal charge carriers remains a challenge. In this section, we reviewed and investigated recent references in the field. First, we introduced and compared the differences between metal charge carriers and non-metal charge carriers; second, we summarized the most recent advances in the exploration and development of cathode materials for aqueous batteries with non-metallic charge carriers. The new proposed battery chemistry and reaction mechanism will be highlighted and introduced. To summarize, we proposed that optimizing the structure of electrolytes and expanding the voltage range of electrolytes could significantly improve the electrochemical performance of aqueous non-metallic batteries.

Si is regarded as one of the most promising anode materials for next-generation high-performance lithium-ion batteries due to its ultrahigh theoretical lithium storage capacity. However, due to the large volume change of Si during lithiation/de-lithiation, Si anodes suffer from particle pulverization, the formation of unstable solid-electrolyte interphase (SEI) layer, and the loss of electric contact, resulting in rapid decay in capacity. Two common strategies for improving the electrochemical performance of Si anodes are the development of novel binders and the fabrication of Si/C composites. Biopolymers are low-cost, environmentally friendly, and rich in polar groups, making them ideal materials for the development of silicon anode binders and the fabrication of Si/C composites. We summarize recent research development of biopolymer-based binders for Si anodes and Si/C composites with biopolymers as carbon precursors in this review. Sodium alginate (SA), chitosan (CS), and starch-based binders are discussed in detail. The most common biopolymer-based binder modification strategies are summarized. Biopolymers are typically modified by grafting special groups, mixing with other polymers, or crosslinking to improve adhesion, electron/ion conductivity, or the formation of 3D networks. The physical and chemical properties, as well as the microstructures, of Si/C composites containing cellulose, chitosan, starch, and lignin as carbon sources, as well as their influence on electrochemical properties, are specifically discussed. On this basis, the deficiencies and potential development directions of current biopolymer-based binders and Si/C composites containing biopolymers as carbon sources are identified.

A single energy storage technology cannot meet high-quality building energy supply-demand due to the diversity and uncertainty of user load demand. By combining various types of energy storage equipment, hybrid energy storage technology was created, which allows for the coordination and complementation of multiple energy sources. This paper first introduces the principle of hybrid energy storage technology in building energy application, then summarizes the research process of hybrid energy storage technology from the perspective of building energy demand, and finally identifies the main research direction of hybrid energy storage at this stage. Secondly, based on several common matching methods of hybrid energy storage, this paper summarizes the application status of hybrid energy storage technology of heat energy, gas chemical energy, and electric energy and introduces the system composition, operation strategy, and system characteristics of corresponding hybrid energy storage according to typical cases, and explains how to meet the multi-energy demand of building users. Finally, the performance and economy of the hybrid energy storage system are examined, and important indexes for evaluating the hybrid energy storage system's performance and the main factors influencing its economy are proposed.

Active distribution networks and isolated micro-grids are typically combined to supply the electricity in remote areas of China. However, it is difficult to eliminate the influence of renewable generation's randomness, volatility, and anti-peak shaving characteristics when using a small-scale battery. At the same time, a large-scale battery will have an impact on the economy. In addition, traditional distribution ring network cabinets are limited by problems such as five-proof interlock protection and sparse standby intervals, which could not provide rapid access to mobile energy storage. In recent years, new switchgear with branch line fast plug-in function has provided the physical basis for the utilization of mobile energy storage. As a result, based on the regional battery sharing mode, this paper proposes a coordinated economic dispatch strategy for active distribution networks and islanded microgrids. Firstly, the truck is proposed to transfer batteries to realize energy storage sharing. The new node cabinet's fast plug-in function establishes a time-shifting model with dynamic vehicle-storage correlation constraints. An active distribution network-microgrid collaborative optimal tidal model is built on this basis by extending the dispatching cycle to 48 h and assessing the uncertainty of renewable energy generation using the distribution robust optimization method. Finally, simulation results based on an IEEE 14-node distribution network and typical microgrids show that the proposed strategy could significantly reduce power grid operation costs while improving rates of renewable energy and energy storage system. As a result, this paper offers a fresh look at the economics of the distribution network and islanded microgrid.

Lithium-ion batteries have been widely used in manufacturing and daily life as common energy storage and power device. However, thermal runaway can occur under abusive conditions, so its safety must be investigated. The thermal runaway simulation has significant advantages over the experimental method and is an important tool for studying the thermal runaway of lithium-ion batteries. This paper analyzes the research status of thermal runaway simulation from three aspects, thermal runaway simulation, thermal propagation simulation, and the application of thermal runaway simulation. The heat generation mechanism and simulation method of thermal runaway caused by different inducements (thermal abuse, mechanical abuse, and electrical abuse), the research status of the simulation in heat spread in the battery pack and how to restrain the heat spread, and the research on thermal runaway prediction method are all introduced emphatically. The thermal runaway model is already accurate enough to simulate the main exothermic side reactions when the battery thermal runaway occurs. On the other hand, the battery is complex, with chemical reactions and physical changes, and the parameters are difficult to measure and calculate. As a result, further research into the thermal runaway simulation of lithium-ion batteries is required.

The joint operation of wind power and energy storage can effectively deal with the uncertainty of wind power output and improve the competitiveness of wind power. However, optimizing and dispatching the joint operation of energy storage and wind power is a major difficulty. A day-ahead optimal scheduling method of the wind storage joint system based on improved K-means and multi-agent deep deterministic strategy gradient (MADDPG) algorithm is proposed to maximize the benefits of a wind-storage joint operation by ensuring the adjustable capacity of energy storage. First, the improved K-Means clustering algorithm optimized by the firefly algorithm is used to achieve energy storage grouping; then, the wind power and the grouped energy storage equipment are modeled as different agents to form a multi-agent system. The MADDPG algorithm is used to solve the problem, and the MADDPG algorithm's state space, action space, and reward function are designed. Finally, a simulation example is used to validate the algorithm. The results show that, when compared to conventional deep reinforcement learning, the proposed scheduling strategy can better coordinate the operation of wind power and energy storage, effectively smooth the fluctuation of wind power output, and improve the operating income of the wind storage combined system.

The real-time balance of reactive power based on reactive power compensation is critical to power systems' safe and stable operation. The energy storage converter has a four-quadrant operation function that allows it to output or absorbs reactive and active power simultaneously. It has the function of frequency and voltage regulation. Reactive power compensation technology based on energy storage has the advantages of fast response speed, continuously adjustable, and scale controllable, etc., and is suitable for new power systems with a high proportion of new energy and high electronization. Based on the principle of reactive power compensation for energy storage, this paper introduces reactive power control strategy, serie-parallel modular amplification, and medium, and high voltage cascade technology of energy storage converters of various topology structures. According to the types of energy storage and application scenarios, energy storage reactive power compensation technology and energy storage hybrid reactive power compensation technology is reviewed, and its development process and trend of the research status are mentioned. The early storage reactive compensation mainly adopts short-time scale energy storage technology, such as superconducting energy storage, super-capacitor energy storage, and flywheel energy storage. The advancement of battery energy storage technology can have a positive impact on power grid voltage regulation, black start, and other reactive power compensation fields. Energy storage, static synchronous compensator, and new energy units collaborate based on economic considerations to realize combined voltage regulation of active and reactive power to ensure system voltage level and improve power quality. The new power system based on new energy gives the reactive power compensation technology of energy storage a more crucial role. Transient steady-state cooperative control of energy storage, new energy units, and reactive power compensation devices is the main form of reactive power compensation of new energy stations in the future. The research focuses on energy storage reactive power compensation technology will be the coordinated control strategy between energy storage and other reactive power sources and the solution and optimization of joint programming problems.

Electric vehicles have become an important way to transform transportation in order to meet the "dual carbon" goal. However, because charging speed has an impact on the user experience of electric vehicles, it limits the promotion and application of electric vehicles to some extent. As a result, the development of high-power charging is a critical technical step toward increasing the penetration rate of electric vehicles. However, the accelerated aging of the power battery caused by high-power charging, as well as the inconsistency of the temperature distribution of the power battery pack caused by rapid heat generation, have introduced new challenges to the formulation of the rapid charging strategy of electric vehicles and the design of the thermal management system. The current research status of management technology for the high-power charging process of electric vehicles is summarized in this paper, based on the optimization of an electric vehicle's high-power charging strategy and the design of a battery thermal management system. The advantages and disadvantages of various charging strategies and thermal management system designs are evaluated with a focus on the impact of high-power charging methods on the performance of power batteries. On this basis, the difficulties in developing a high-power charging strategy and thermal management technology for electric vehicles are thoroughly analyzed.

The random problem of distributed power and load demand in the micro-grid system makes the selection of micro-grid energy storage capacity an important research topic. This paper proposes an energy storage capacity optimization method for micro-grid systems based on the randomness of source-load and the uncertainty of predicted output deviation over multiple time scales. his method is used to establish the system energy balance relationship and the robust economic coordination index, as well as to depict the quantitative relationship between the energy storage system capacity optimization method and the micro-grid stochastic factor Furthermore, the goal of the micro-grid operation economy is considered. In this paper, a two-layer optimization model of the energy storage capacity of the micro-grid with distributed power sources is established and solved using the multi-objective particle swarm optimization (MOPSO) algorithm. The simulation results demonstrate that the proposed method not only ensures the optimal configuration of the energy storage system capacity but also achieves good economic efficiency.

Large-scale photovoltaic (PV) stations will adversely affect the stability of the power system, while energy storage is considered to be one of the effective means to eliminate these effects. In this paper, the influence of PV plants on the power system and the function of the energy storage system (ESS) are analyzed from the perspective of power flow. First, the probability distribution model of power system components, storage model, Latin hypercube sampling (LHS) method, and Gram-Schmidt orthogonal sequence method are introduced in this paper. Second, this paper establishes the multiple objective optimization models that consider the energy storage system costs, the probability of a branch remaining active beyond the limit, and network loss. The genetic algorithm is used to find the best solution to the objective function (GA). Finally, the simulation is run on the IEEE 24 bus test system, including the effects of different PV capacities and access positions, as well as the effect of ESS. In this simulation, the optimal energy storage configuration for various PV capacities is obtained.

The thermal management of automotive lithium batteries during high-rate discharge is being investigated. Based on the thermal management concept of matching the heat generation and heat dissipation of the battery, the critical heat transfer coefficient h_cr is innovatively proposed to ensure the battery's safe operation, and a set of numerical solution methods for determining h_cr is developed. For numerical calculation, a thermoelectric coupling model of a single cell is established. The findings indicate that the critical heat transfer coefficient of a given lithium battery is related to the discharge rate and the temperature of the heat exchange environment, and is less affected by the battery's initial temperature. The critical heat transfer coefficient increases sharply once the ambient temperature exceeds 293.15 K. A thermal management operation strategy based on the intervention time τ_intv is proposed for the working condition of h<h_cr to further improve the battery's thermal safety operation capability. Furthermore, the numerical determination method, influencing factors, and intervention effect of intervention time are thoroughly examined. The results show that the intervention time of the lithium battery for a given h is greatly affected by the discharge rate, and the reduced rate operation of the lithium battery during the intervention time can effectively control the battery temperature within a safe range This work has important theoretical implications for the design and operation management of the vehicle lithium battery thermal management system.

The actual charging and discharging current of the battery in the cascaded H-bridge energy storage system and MMC energy storage system is the superposition of sinusoidal alternating current (AC) and constant direct current (DC), forming a sinusoidal pulsating current. The fluctuation of battery charging and discharging current has a great influence on the thermal characteristics of the battery, which determines the thermal management measures and battery service life. Based on this condition, the thermal characteristics of a LiFePO₄ battery under sinusoidal pulsating charge and discharge current were investigated in this study using a one-dimensional electrochemical model and compared to those under constant DC. The results show that the transient thermal power and internal resistance of the battery fluctuate periodically with the current; When the fluctuation amplitude of the sinusoidal AC component is 25% that of the DC component, the discharge and charge processes cause only 5% and 2.8% extra heating, respectively, when compared to the pure DC charge and discharge. However, as the fluctuation amplitude of the sinusoidal AC component increases further, the battery heating increases sharply; from the middle to both ends of SOC, the phase difference between voltage drop and current increases, indicating an increase in the capacitive effect; as the frequency of current pulsation increases, the heating of the battery decreases.

As the electric vehicle (EV) becomes more popular, the lithium-ion (Li-ion) power cell has become the primary power source for EVs, but thermal safety issues are becoming more prevalent. Based on this, battery cooling methods such as air cooling, liquid cooling, and phase change material cooling are introduced to address the severe thermal problems such as poor safety, unreliable operation, and short cycle life of Li-ion power batteries for EVs under service conditions, particularly at high temperatures. Furthermore, a thermal management system coupled with multi-cooling methods to improve heat dissipation efficiency than a single heat dissipation method is illustrated, which can improve the heat dissipation efficiency and improve the temperature uniformity of the battery. Furthermore, the optimization of air cooling channels, design of liquid cooling structure and analysis of cooling medium, application characteristics of phase change materials, cooling characteristics, and thermal characteristics of heat pipes are summarized in detail in conjunction with the research progress and key technologies of the aforementioned heat dissipation methods. Finally, to address the issues that exist in the current heat dissipation methods of power batteries, the battery thermal management system (BTMS) is proposed by combining it with the car occupant heat comfort, motor cabin heat management, and vehicle thermal environment to form a vehicle heat management system that will serve as a reference for future research on the design and development of BTMS.

A coordinated control strategy based on a multi-branch power conversion system (PCS) topology was designed to address the problem of simultaneous decommissioning among different battery modules in an energy storage system (ESS) using second-life electric vehicle (EV) batteries. Considering the power demand in different periods and the imbalance degree of battery state of health (SOH) in ESS, the priority output mode to utilize batteries with better health status or common output mode of the entire battery group was selected. Based on the distribution of battery state of charge (SOC), a control strategy employing real-time variable current as a positive feedback regulation value was used to achieve coordinated control and output balancing within the ESS's battery cluster. After multiple charges and discharges, the SOH of each battery module in one cluster tends to be asymptotically consistent, thus achieving the goal of decommissioning different batteries simultaneously. Finally, the simulation analysis confirmed that the strategy could simultaneously decommission each retired power battery pack in the energy storage system.

With the extensive production of various large electrochemical energy storage projects, the method to ensure the intrinsic safety of high-capacity energy storage batteries has emerged as the most pressing issue in the industry. This paper reviews the evolution of the concept of intrinsic safety and introduces the concept's connotation. To summarize, this study uses the design rules of intrinsically safe batteries in the coal industry as a guideline and proposes a grading scheme for intrinsic safety battery energy storage, which categorizes the safety level of energy storage batteries into three categories: intrinsic safety, extrinsic safety, and unsafe. Given the current state of energy storage batteries in the form of modules and containers, this study divides the intrinsic safety of energy storage batteries into three distinct aspects based on their composition, namely: battery cell, module, and container system, and discusses the intrinsic safety of the three composition forms separately. In addition, the technical route of different directions is introduced in light of the intrinsic safety of the battery core, based on the three technology routes of aqueous battery, solid-state battery, and safener injection, and the study and application progress related to them are discussed and ordered, and the intrinsic safety challenges faced by different routes, as well as the future application prospects of the high-capacity energy storage battery, are put forward.

In order to study the effects of fin number, inclination angle and phase change material on the heat transfer performance of power radiator with longitudinal fins, five different structure radiators with and without phase change material were experimentally studied under the condition of constant heat load of 16 W. The experiment is carried out through the experimental system composed of experimental section, DC power supply and data acquisition equipment. The specific effects of the number of fins (1～5), the inclination angle of the radiator (0°～90°) and the phase change material (n-eicosane) on the heat transfer performance of the radiator are analyzed experimentally. The thermal performance of the radiator is evaluated by the temperature rise characteristics and phase change heat transfer characteristics of the radiator containing phase change materials. The results show that the tilt angle and the number of fins play a key role in the formation, heat transfer and operation time of liquid phase change material convection unit. For the radiator with phase change material with an inclination of 0°, compared with one fin, the time required for five fins to reach the maximum allowable temperature increases by 80%, while when the inclination increases to 90°, the increase of the number of fins has no significant effect on the time. For all tilt angles, the PCM temperature at each measuring point decreases with the increase of the number of fins. When the dip angle increases, the phase transition region becomes larger due to the enhancement of buoyancy induced flow; Under the condition of single fin, the working time at 60° inclination angle is 78.6% longer than that at 0° inclination angle.

Accurate estimation of lithium-ion (Li-ion) batteries' state of charge (SOC) is significant for battery safety detection and energy-efficient utilization. A new verification model is proposed. Firstly, the battery partnership for a new generation of vehicles (PNGV) model is improved. Considering the difference between battery charging and discharging, the parallel network of diode resistors is adopted to replace the internal resistance of the traditional PNGV model. On this basis, a resistor-capacitor (RC) parallel network is employed to characterize the dynamic and static characteristics of the battery. Using a ternary Li-ion battery as the research object, online parameter identification of the improved model is performed using the forgetting factor recursive least square method. The main charging and discharging experiments were proposed to simulate and analyze the working characteristics of lithium batteries. The FFRLS-EKF algorithm is used to estimate the SOC under the custom DST condition. The experimental results show that the improved 2RC-PNGV model can reflect the operating characteristics of the Li-ion battery well. The average voltage error of the HPPC experiment is 0.17%, the model has higher accuracy. The average error of SOC estimation in the main charging process is 0.957%, and the maximum estimation error is 5.03%. In the main discharge process, the average error of SOC estimation is 0.807%, with a maximum estimation error of 3.38%. It is demonstrated that both the improved 2RC-PNGV model and the joint estimation algorithm can estimate SOC.

To accurately estimate the state-of-charge of high power lithium-ion battery in real-time, the ternary lithium-ion battery is used as the research object and a novel multiple weighted-adaptive extended Kalman filtering method is proposed. The estimation value is corrected multiple times using the residual and Kalman gain, and different weights are configured for each residual based on the amount of information contained. The current estimated value is adjusted and corrected ad-hoc based on the real-time update of system noise covariance and error covariance. To test the algorithm's logic, the second-order RC equivalent circuit model is used to characterize the dynamic characteristics of the battery, and experimental verification is performed under various working conditions. The experimental results show that the estimation root-mean-square-error under HPPC, DST, and BBDST working conditions is 1.31% and 1.23%, respectively, demonstrating the proposed algorithm's good accuracy and convergence. The novel multiple weighted-adaptive extended Kalman filtering method lays the theoretical groundwork for accurate state estimation and widespread application of lithium-ion batteries.

Lithium-ion batteries' state of health (SOH) is the central concern of a battery management system. An accurate evaluation of SOH can ensure that batteries operate safely and reliably. However, in practice, it is difficult to measure capacity, which makes SOH estimation difficult directly. To obtain accurate SOH, this paper proposes an attentional improved bidirectional gated recurrent unit (BiGRU)-based SOH estimation method for lithium-ion batteries. Firstly, parameters such as voltage, current, and impedance are extracted from the charge-discharge curve of the battery, and the auto encoder reduces the dimensions to extract the features and reduce the redundancy between the data. Secondly, an attention mechanism is introduced to assign weight to input variables and highlight the characteristic quantities that play a key role in SOH estimation. Finally, the BiGRU is used to learn the mapping relationship between input variables and capacity and capture long-term dependence under capacity decay. The results of the University of Maryland battery datasets with different charging rates show that the proposed method can estimate SOH with high precision for different types of batteries, with a root mean square error of less than 1.1%.

Accurate estimation of the state of charge (SOC) of Li-ion batteries is essential for the battery management system. Model parameter identification is the premise of SOC estimation and the key factor affecting its estimation accuracy. Bias compensation recursive least squares (BCRLS) is used for online parameter identification to effectively avoid noise's influence on parameter identification. The adaptive cubature Kalman filter (ACKF) algorithm is used to estimate the battery SOC on this basis, and the system noise is updated in real-time to improve estimation accuracy. In addition, for the problem that the square root cannot be decomposed due to the loss of positive definiteness of the covariance matrix in the calculation process, the singular value decomposition method is used instead of Cholesky decomposition to improve the stability of numerical calculation. Finally, BCRLS and ACKF are combined to realize joint estimation of model parameters and SOC, and the algorithm is validated under various working conditions and with incorrect initial values. The results show that the algorithm proposed in this paper has high accuracy, and the average absolute error is within 2%.

When using neural network methods to estimate the state of charge of lithium batteries, the traditional state of charge fitness evaluation function has the disadvantage of only considering the network weight parameters such as the mean square error and ignoring the influence of topology parameters on the model. Therefore, this paper proposes to consider the weighted influence of model topology parameters and network weight parameters, such as input/output timing correlation, and the number of hidden layer neurons, in the design of the fitness evaluation function and introduce it into a nonlinear autoregressive neural network with external input. Based on the improved longhorn whisker search algorithm, the estimation of the state of charge of the lithium battery in the modeling method involves the collaborative identification and optimization of the above-mentioned model topology parameters and network weight parameters. The simulation results show that the method proposed in this paper can improve the accuracy of estimating the state of charge of a lithium battery under a variety of complex working conditions. The root mean square error of the lithium battery state of charge under DST standard working condition and WLTC standard working condition is 3.38×10^-3 and 8.75×10^-4, respectively, which improves the estimation accuracy of the root mean square error by 42.4% and 20.5% when compared to the BAS-NARX neural network.

The state of charge (SOC) of lithium-ion batteries is studied, and a parallel Kalman filter-based SOC estimation algorithm is proposed, with the goal of solving the problem of power display and life prediction in new energy electric vehicles. The Thevenin battery's first-order RC equivalent circuit model is defined. Data processing of open circuit experiments results in the static OCV-SOC relationship expression. The least-square method with a dynamic forgetting factor is used to identify the model's parameters. The maximum likelihood estimation criterion is used to make the model noise covariance self-learning, using the Ampere-hour integral method as the state transfer equation and the extended Kalman filter as the state transfer equation. Given that the model parameters change as the battery life declines, a parallel structure filter is designed to estimate the battery state and modify the parameters accordingly, ensuring the purity and independence of the data transmission and allowing SOC estimation throughout the life. The simulation results show that the algorithm has fast convergence and real-time performance, and the estimation accuracy is less than 2%.

As an electrochemical energy storage technology, the all-vanadium redox flow battery (VRB) is the most promising large-scale energy storage technology with long life and low cost due to its high safety and flexible layout. This article summarizes the simulation model of all-VRB energy storage in two types of models, namely, circuit and electrochemical. Circuit models mainly comprise fixed circuit elements that simulate battery loops in series and parallel, while electrochemical mathematical models describe the internal battery parameters. At the same time, this article summarizes commonly used state of charge (SOC) monitoring methods for all-vanadium redox flow batteries, including the basic principles and usage methods of the open-circuit voltage method, current integration method, and Kalman filter algorithm. The SOC monitoring method supplements simulation models to build a complete all-VRB energy storage system.

The prediction of the Remaining Useful Life (RUL) of lithium-ion battery has significant value for the study of the usage and maintenance of batteries. A method for RUL prediction of lithium-ion batteries based on differential voltage and Elman neural network is proposed. Firstly, based on the National Aeronautics and Space Administration' (NASA) lithium-ion battery data set, the differential voltage curve and charge-discharge curve of the battery are analyzed, and the characteristic quantity of battery capacity degradation is extracted. Secondly, the correlation between characteristic parameters is studied by Pearson method. The inflexion point of charging differential voltage curve, peak value of discharging differential voltage curve, as well as the discharging time and resting time are determined as indirect health factors of battery RUL prediction. Finally, an Elman neural network employed the inputs of above indirect health factors and the output of battery capacity is established to predict RUL of lithium-ion batteries. The comparative experiments of four kinds of battery capacity prediction based on different indirect health factors and different neural networks show that the prediction accuracy of battery life can be improved by adding the initial inflection point of charging differential voltage curve and the peak value of discharge differential voltage curve into the indirect health factors, and the Elman neural network can accurately predict the battery capacity. The mean root mean square error (RMSE) of the prediction of battery RUL based on different cycle times is 1.55%.

To determine the techno-economic of seasonal cold storage technology applied to protected agriculture, a group of solar greenhouses in Jinan was selected as the research object. To achieve year-round cold and heat management of the group of solar greenhouses, a seasonal cold storage system based on an ice source heat pump was used. The cold storage loss model and the energy savings, economic, and environmental benefit evaluation models were developed. The system's cold storage capacity, primary energy ratio (PER), annual cost, dynamic investment payback period, and pollutant emission reduction were then analyzed and compared to other heat pump and boiler systems. The results showed that: The annual cold capacity loss of the seasonal cold storage tank was less than 5%, the maximum cold storage capacity was 170409.07 GJ, 14509.47 GJ was remaining at the end of the year, and the group solar greenhouses' annual cooling and heating demand was met. The PER of seasonal cold storage system for cooling was 6.27 and the annual PER was 1.71, which meant that the application of seasonal cold storage technology greatly improves the energy efficiency and the energy-saving effect of the system. The system's operating costs were extremely low, the annual costs were low, and the dynamic investment payback period was 3.9～6.9 years, indicating that this system had good economic feasibility. When compared to an air source heat pump, this system could reduce 13897.90 tons t of CO₂, 3.61 tons of SO₂, 7.16 tons of NO_x, and 1.41 tons of smoke and dust per year with an emission reduction rate of 77.3%, indicating that the use of seasonal cold storage technology significantly reduced greenhouse gas and pollutant emissions and has significant environmental benefits.

Constructing a new power system with new energy as the main body means that wind power and photovoltaic will become the main body of the future power system. Peak shaving problems will become more prominent due to the inherent randomness, intermittentness, and volatility of new energy power generation. The gas power station and electrochemical energy storage are expected to become an important peak shaving resource in the future due to their large adjustable range and fast response speed. First, the relevant policies and market rules of natural gas power generation peak shaving and energy storage peak shaving in various provinces were sorted out, and a comparative analysis was conducted in terms of entry barriers, participation methods, and declared prices. Second, a detailed analysis of the cost composition of energy storage power stations, including initial investment, operation and maintenance, and charging costs, is performed using the concept of levelized cost of electricity (LCOE). Finally, using a province as an example, compare the economics of gas-fired power generation peak shaving versus energy storage peak shaving, including a quantitative analysis of the initial investment, utilization hours, fuel/charge cost, and other factors influencing electricity costs. In comparison, as the cost of energy storage continues to fall, short-term peak shaving will become more competitive in the future than gas-fired power peak shaving.

The integrated energy system is studied with the park as the backdrop, based on the two modes of "ordering power by heat" and "ordering heat by power." This paper develops eight schemes to compare changes in output power of each subsystem and total cost when the system is configured with and without liquid-air energy storage using two typical summer and winter days as examples. When operating in the "ordering power by heat" mode, the results show that when liquid-air energy storage is configured in the park, the economic benefit is the greatest and the smallest energy loss. On Great Heat Day, the total cost is 6.1% less than the system without liquid-air energy storage. On a Great Cold Day, the total cost is 4.5% less than the system without liquid-air energy storage. Furthermore, the system's total cost operating in "ordering power by heat" is lower than that in the mode of "ordering heat by power" when the system is equipped with liquid-air energy storage. On Great Heat Day, the total cost is reduced by 9.5%, and on Great Cold Day, the total cost is reduced by 4.5%.

This bimonthly review paper highlights 100 recent published papers on lithium batteries. We searched the Web of Science and found 4209 papers online from Aug. 1, 2021 to Sep. 30, 2021. 100 of them were selected to be highlighted. High-nickel ternary layered, high-voltage LCO layered and Li-rich Mn-rich layered cathode materials are still under extensive investigations of the influences of doping and interface modifications on their electrochemical performances and surface and bulk evolution of structures under prolong cycling. The researches of lithium metal anode mainly focus on the surface modification and alternation of direction of lithium deposition. Large efforts have been devoted to solid state electrolytes including sulfide and oxide solid electrolyte, polymer solid electrolyte and composite solid-state electrolytes. The research works on liquid electrolytes involves mainly matching various electrolytes and solvents with battery materials, and searching for new additives. For solid-state batteries, the studies mainly focus on interface and for lithium-sulfur batteries, the works are mainly on improving the activity of sulfur and mitigating the shuttling effect. The focuses of characterization techniques are on bulk structure of materials and electrode-electrolyte interface and the hot topics are characterization interfaces of solid-state batteries. Furthermore, there are theoretical works for the surface oxygen activity of materials, interface structures, lithium transportation mechanisms, with interface structures concerning SEI formation. There are also some papers on modification of current collectors and pre-lithiation of electrodes.