Lithium cobalt oxide is widely employed in different consumer electronic products due to its high energy density, rate performance, and thermal stability. With the advancement of artificial intelligence and 5G communication technology. A higher energy density of LiCoO₂ (LCO) batteries is required. In this study, lithium cobalt oxide was coated with B₂O₃ using the simple solid-state approach. The resistance of B₂O₃ modified LiCoO₂ (BLCO) was much lower than the pristine LiCoO₂ (LCO). The discharge capacity of BLCO at 3-4.55 V and room temperature reach 201.2 mAh/g, which was greater than 192.64 mAh/g of the pure LCO. The capacity retention of BLCO after 500 cycles was 194.8 mAh/g, which was higher than 184.37 mAh/g of the pristine LCO. This enhancement can be attributed to the higher electronic conductivity and smaller interface impedance of BLCO. Our research provides a method to enhance the capacity of lithium cobalt oxide. The failure mechanism of lithium cobalt oxide material cycled at high voltage was also investigated, which will be helpful for the design of high voltage lithium cobalt oxide in the future.

As one of the four basic components of lithium-ion batteries (LIBs), cathode material determines the electrochemical performance of LIBs. Nickel-rich cathode LiNi _x Co _y Mn_1-x-y O₂ (NCM, x≥0.6) has attracted extensive attention and is considered as one of the most potentially available cathode materials owing to its high specific capacity and excellent rate performance. However, this cathode material type suffers from poor cyclic stability, poor thermal stability, and safety issues, which hinder its extensive practical large-scale application in electric and hybrid electric vehicles. Therefore, research on nickel-rich ternary cathode material NCM is very important for improving the current LIB system. Following the development in fabrication methods, the electrochemical properties of Ni-rich ternary cathode materials have significantly improved. In this study, the recent research progress of Ni-rich ternary cathode materials is reviewed. This work introduces the crystal structure and deterioration mechanisms of NCM cathode materials, such as cation mixing, poor cyclic stability, and residual alkali and by-products on the material surface. This work also summarizes the improvement in NCM cathode materials using element doping, surface coating, integration of doping and coating, construction of single-crystalline materials, and construction of core-shell and gradient structures. Finally, a brief outlook for future research direction and development of nickel-rich ternary layered oxide for LIBs is presented.

The effect of lithium acrylate content on the electrochemical performance of natural graphite was systematically analyzed using lithium acrylic, an organic small molecule salt containing carbon-carbon double bonds, to form an elastic solid electrolyte interphase (SEI) layer on the graphite surface through self-polymerization. The results reveal that at 5% lithium acrylic content, the overall electrochemical performance of lithium-ion batteries, including the first Coulomb efficiency, multiplicity performance, and high current long cycle performance, is significantly improved, thereby effectively suppressing side reactions on the graphite surface and inhibiting the rise of electrode impedance during the electrochemical cycle.

Soft carbon is one of the candidate materials for the fast-charging lithium-ion battery anode. Creating soft carbon with high power density is currently a research focus. Soft carbon's electrochemical properties are primarily determined by its microstructure, which is heavily influenced by the carbonization temperature of the precursor. The structural evolution of soft carbon derived from needle coke at a carbonization temperature of 900—1700 ℃ was traced in this paper by varied characterizations of SEM, XPS, XRD, Raman, and N₂ isothermal adsorption. Electrochemical characterizations of CV, GCPL, and EIS were also used to investigate the relationship between microstructure and lithium-storage kinetics. The results show that the carbonization temperature of soft carbon can be divided into three dominant steps based on the change of microstructures (amorphous, turbostratic and graphitic), which has a significant impact on the electrochemical properties of soft carbon. The soft carbon has abundant pores in the region dominated by amorphous structure, and the lithium-storage kinetics is fast, but the specific capacity (195 mAh/g) and the Coulomb efficiency (< 60%) were low; The Coulombic efficiency is highest (80%) in the region dominated by graphitic structure, but the lithium-storage kinetics are significantly reduced; In the region dominated by turbostratic structure, the optimum microstructure can be obtained, which achieves a good balance between reversible capacity, coulomb efficiency and rate performance. This paper offers suggestions for the rational design of soft carbon for fast-charging lithium-ion batteries.

Lithium (Li) metal is regarded as an ideal anode material for realizing next-generation high-energy-density batteries due to its high theoretical capacity and low electrochemical potential. However, numerous difficulties, such as large volume growth and uneven Li deposition, severely limit its practical implementation. The introduction of a three-dimensional composite Li anode is an essential approach for modulating Li plating/stripping. Furthermore, a high-energy-density Li metal pouch battery should rely on practical conditions, such as ultrathin Li metal anode (<50 μm), low negative/positive electrode areal capacity ratio (<3.0), and lean electrolyte (<3.0 g/Ah). This study outlines the behavior of Li plating/stripping under actual situations and concludes that the use of composite Li anodes is an effective solution to overcome the aforementioned difficulties. Furthermore, the research development of composite Li anode based on the material structure under realistic conditions is discussed. Currently, the prepared composite Li anode has also been gradually assessed under practical conditions, and has been used in pouch cells and achieved good performance. Host materials will invariably introduce new interfaces, and ion transport regulation at these interfaces should be explored. Li plating/stripping behaviors within the host should be regulated to limit the formation of Li dendrites in the internal space. The intrinsic property of lithiophilicity should be explored further.Furthermore, the effect of single host characteristics on plating/stripping behaviors should be studied using a deciphering approach to achieve logical host material design. Finally, the challenges and future research directions of composite Li anode are discussed to promote the development of high-energy-density Li metal batteries.

Based on gas-solid phase regulation, this work has achieved mass production of high-performance silicon oxide carbon (SiO _x @C) anode materials for lithium-ion batteries using fluidized bed chemical vapor deposition (FB-CVD) technology. Ordinarily, for micron-sized silicon oxide carbon powder, significant interparticle van der Waals forces impede fluidization through severe agglomeration and island-like deposition on the surface. This behavior adversely affects the resulting electrochemical performance. To address this, first, particle phase pressure was introduced to construct the particle-like van der Waals state equation. Next, based on stability analysis, the gas-solid phase regulation diagram was used to guide secondary particle design. This allowed attainment of full fluidization in the FB for CVD carbon coating. Agglomeration was suppressed by virtue of stable fluidization. Additionally, high-efficiency mass- and heat-transfer ensured a change from island growth to near-layer growth for carbon deposition onto the surfaces of silicon oxide particles. As a result, uniform deposition of carbon onto silicon oxide was successfully accomplished. Through various electrochemical tests, characterization, and analyses, the as-prepared SiO _x @C anode material revealed outstanding cyclability and rate performance. This technology has achieved pilot production volumes at present, and it is expected to gain industrial scale-up to 100 tons in the near future.

Owing to its high energy density, moderate charging and discharging platform, and abundant reserves, silicon-based material has emerged as one of the most promising anode materials for lithium-ion batteries. However, its low cyclic stability limits its usefulness. To date, previous studies have mainly concentrated on electrochemically driven interfacial reactions during cycling and have neglected the intrinsic chemical reactivity between the anode and the electrolyte. This paper reviews previous research on the intrinsic reaction between silicon and electrolyte and strategies for suppressing the side reaction. Other factors affecting the interface stability of silicon base anode were discovered on the basis of the reaction kinetics of silicon base material and electrolyte, and effective strategies for inhibiting side reactions were proposed. To suppress the side reaction effectively, a protective layer should be designed on the surface of silicon, which could suppress the penetration of fluorine to protect the silicon. Furthermore, the protective layer should have the ability to allow the lithium ion and electron to pass through. An appealing perspective was proposed to improve the performance of silicon anodes and effectively guide their development.

Popularizing innovative energy vehicles is a strategic decision for promoting green growth and ensuring energy security. It is a significant step in reducing carbon emissions in the automobile industry, particularly toward achieving carbon neutrality and carbon peaking in China. As the core power source for innovative energy vehicles, the green recycling and effective use of spent lithium-ion batteries are directly related to the realization of green and sustainable development in the electric vehicle industry. Graphite is currently the state-of-the-art anode material for commercial lithium-ion batteries owing to its high reversible capacity and good cycling stability. Therefore, the recovery and recycling of used graphite anode materials should be actively investigated. This study discusses recent technology for recovering and treating anode graphite from spent lithium-ion batteries. Several recovery and treatment approaches, such as deep purification, selective lithium extraction, and residual electrolyte removal, and their limits are described. The diversified resource recycling paths of recycled graphite and its products are summarized on the basis of different graphite structural characteristics, including its role as anode material or raw material for catalysts, graphene, and composite films. Furthermore, the life cycle evaluation of graphite recycling is outlined, and the environmental effect advantages and disadvantages of various graphite recycling treatment systems are explored. Finally, the technological problems and future developments of graphite recovery and resource recycling for lithium-ion battery anodes are explored. In addition, we recommend that future research should concentrate on the following four-in-one development: elucidating the battery failure mechanism, realizing the efficient recovery of all components, adhering to the new idea of green chemistry, and widening the market of high-value applications.

The electrolyte is an important part of the lithium ion battery, which plays a role in ion transmission between the cathode and anode. When the traditional organic electrolyte system is facing the heat of the battery, it is difficult to block it in time. The development of smart materials provides ideas for solving the problem. This article reviews the smart electrolyte materials of lithium ion batteries in recent years. When facing different abuse conditions, the intelligent response processes and application instances of the electrolytes have been introduced. For example, the thermal response polymer electrolytes can timely block the abnormal heating process through the change between different structures, the phase transformation of the shear thickened electrolyte can effectively respond to the mechanical impact and the addition of REDOX shuttle agent can reduce the risk of thermorunaway in the case of overcharge. Finally, this article also briefly summarizes the intelligence of the remaining components of the lithium ion battery. The study has a certain reference value for improving the safety of lithium ion batteries and the development of intelligent response materials.

Currently, the critical challenges of lithium-ion batteries are how to improve their energy density and safety. With the help of nonflammable solid electrolytes and improved compatibility with Li-metal-based anode, solid state lithium batteries can effectively alleviate these two issues. Solid polymer electrolyte (SPE) is one of the most promising solid-state-electrolytes because of its high flexibility, ease of processing, and good interfacial contact. The ionic conductivity, electrochemical window, and electrode stability all play important roles in the overall performance of solid lithium metal batteries. According to the different electrochemical stability windows, this study reviews the typical SPE systems classified by low-and high-voltage stable SPEs. The strategies of chemical modification, electrode/electrolyte interface engineering, and multilayer structure design are discussed, aiming to improve the ionic conductivity and broaden the electrochemical window of SPEs. This review summarizes the different electrochemical stability windows: ① Low-voltage-stable SPEs with good lithium metal compatibility and Li⁺ conductivity that can be improved by crosslinking, blending, copolymerization, and being composites with inorganic fillers; ② High-voltage-stable SPEs with lower highest occupied molecular orbital (HOMO) energy and match high voltage cathode for improving the energy density of lithium metal batteries; and ③ Multilayer SPE systems that can withstand the simultaneous reduction of lithium metal anode and oxidation of high voltage cathode, providing a new strategy for the development of high energy density batteries. These SPE systems summarize the research focus of low-voltage-stable SPE to improve ionic conductivity and mechanical properties. The key to high-voltage-stable SPE is to reduce the HOMO energy and/or establish a stable CEI layer with a cathode. The research focus of multilayer SPE is the appropriate design of battery and electrode structure. The construction of highly Li-conducting polymer structures, which can stabilize or form an interface passivating layer with both cathode and anode simultaneously, is a future research focus.

To investigate the cycle safety performance of batteries under low-pressure conditions, such as those found on the space station, aircrafts were used. The pouch batteries Li(NiCoMn)O₂ were cycled at 0.5 ℃ at a pressure of 0 kPa in a low-pressure cabin. After the experiment, the cycle characteristics changed greatly compared with the standard pressure environment. With the increase in cycles, severe large-scale areas of unrecoverable deformation occurred on the batteries, and the thickness increased. Furthermore, the capacity decreased rapidly, and it was >80% after 10 cycles. However, when the pressure is increased from 0 kPa to 95 kPa, a small portion of the cycle capacity is recovered. Under vacuum pressure, the processes of expansion and contraction within the battery during charging and discharging are accelerated. It hastens capacity attenuation and causes false loss of some capacity due to massive internal and external pressures. Besides, the battery periodic heating and cooling accelerates, and the temperature inhomogeneity deteriorates within the cycle. Therefore, the maximum temperature difference between the charge and the discharge is 12.9 ℃. Obviously, the battery's thermal stability and safety deteriorate, whereas the potential thermal hazard during charging and discharging increases under low-pressure conditions. Capacity differential analysis demonstrates that the loss of active lithium and the destruction of the electrode material structure are essential factors that decrease the cyclic charging and discharging performance of the battery in a low-pressure vacuum environment.

Ionizing radiation is a type of high-energy radiation with a maximum energy of MeV. This high energy can ionize or excite initially stable molecules or atoms, generating ions, free electrons, free radicals, and other active intermediates to initiate copolymerization, grafting, and chemical reactions such as cross-linking. In this study, a liquid lithium battery was irradiated and solidified into a gel state lithium battery in situ using a strong penetrating and extremely high energy γ-ray. The effects of the same irradiation dose of γ-ray on the curing degree, ionic conductivity, and electrochemical window of precursor solutions with various components were discussed. A nonwoven membrane containing ammonium polyphosphate flame retardant was prepared using electrospinning, and the flame retardant porous film was used as the matrix of the irradiated precursor solution, providing additional assurance for the battery's safety. The results show that the successfully cured gel electrolyte has an ionic conductivity of 2.5×10^-4 S/cm. The in-situ solidified gel electrolyte has a certain inhibitory effect on the growth of lithium dendrites, according to scanning electron microscope images of the disassembled lithium anode. The assembled lithium iron phosphate half-battery was activated at 0.05 ℃ at room temperature and cycled for 100 cycles at 0.5 ℃, and the discharge specific capacity remains at 144.8 mAh/g, with a capacity retention rate of 97.5%. The solidified lithium-ion battery is cross-linked by high-energy γ-ray in-situ irradiation and has no leakage, high ionic conductivity, flame retardancy, and lithium dendrites inhibition. This study will aid in the advancement of industrial applications and the development of high-capacity lithium-ion batteries.

Lithium-ion battery (LIB) is one of the most promising electrochemical devices for energy storage. The safety of batteries is under threat. It is critical to conduct research on battery intelligent fire protection systems to improve the safety of energy storage systems. Here, we summarize the current research on the safety management of LIBs. Currently, battery safety research is primarily focused on intrinsic safety, detection safety, and fire safety, which can essentially cover the upstream and downstream LIB safety issues. However, due to the delayed start of such research in this field, numerous issues still exist. The enhancement in intrinsic safety should also consider the users' demand for battery energy density, the advancement of detection safety should eliminate the shackles of traditional fire prevention ideology, and fire protection safety requires finding effective fire extinguishing agents that can cope with the complicated conditions of LIB combustion. Based on the progress of LIB safety research, we demonstrate the thermal runaway process and fire characteristics of LIBs, highlight the challenges in current battery fire protection techniques, and propose the basic framework of intelligent fire protection systems and research methods. By examining the actual and experimental conditions, the experimental hardware and test indices are discussed. We concentrate on the research platform's carrier design, thermal runaway mode, and fire extinguishing system design. By summarizing the relevant equipment, a reference test specification can be provided for future research. Simultaneously, the limitations of the existing fire detection system in the field of LIBs are proposed. The important warning prediction of intelligent fire protection for LIBs based on temperature, voltage, and early gas generation and analysis methods in the research are presented in detail, which will assist researchers in better designing their experiments and providing more effective data for intelligent fire protection for LIBs. We combined the existing LIBs safety-related research devices, methods, and detection standards by summarizing them with the intelligent fire protection analysis of LIBs, which has some reference value for future research in this field.

Electrochemical energy storage is a key technology to achieve low-carbon electricity system. With the rapid growth of energy storage station construction, safety issues also became prominent gradually. In the past decade, several fire and explosion accidents occurred in energy storage stations around the world, illustrating the urgent requirement of safer, more efficient and stable operation. Lithium-ion energy storage system with high safety and reliability is an inevitable choice for the development of the power industry. Present monitoring technology based on module level has met its limitation on efficient early warning, requiring the development of new intelligent sensing techniques. Integrated sensing techniques at the cell level is an effective way to enhance the safety and stability of energy storage lithium-ion batteries. Integrated sensing techniques based on cell level can obtain internal information of battery, including temperature, strain, pressure, and gas, which would be useful for early warning, early isolation, and early handling. This review systematically introduced the difficulties, challenges, and latest progress of this advanced technology, from the following three aspects. To achieve accurate measurement, sensors need to solve the contradiction between long lifetime and electrochemical corrosion inside battery. To meet successful implantation, the contradiction between need for integrated sensors and stable working battery during its lifetime needs to be solved. To realize signal transmission, sensing signals need to solve the contradiction between effective transmission and electromagnetic shielding of battery case. The applications of integrated sensing technology in early warning of thermal runaway and electrochemical characteristics with all lifetime have further prospected.

With the rapid development and popularization of electric vehicles (EVs), accurate evaluation of the state of health (SOH) of vehicle power batteries has become a pressing issue. To address the problem, this study adopts a machine learning approach based on the Light Gradient Boosting Machine (LightGBM) framework. This approach involves collecting data, processing characteristics, carrying out training, and finally constructing a data-driven battery SOH analytic system. As a first step, six characteristics are extracted from the original data: the time of minimum discharge voltage; the 75th percentile of load voltage; the average discharge voltage; the 25th percentile of discharge load voltage; the 25th percentile of discharge voltage; and the standard deviation of discharge voltage. Secondly, the data are further processed to reduce memory consumption and computing cost. This processing utilizes LightGBM's key algorithms: histogram-based decision tree learning, Gradient-Based One-Side Sampling, and Exclusive Feature Bundling. Finally, system function is verified and compared with similar work, using data from the NASA Ames Prognostics Center of Excellence. Results demonstrate that the SOH platform can deliver high predictive accuracy (a root-mean-square error of 0.0103). The system represents significant progress in vehicle battery SOH prediction methodology and has high potential for practical application.

This study combines the results of domestic and foreign research on the recycling of used lithium iron phosphate power batteries recently. Furthermore, it provides a detailed review of the latest technology for recycling used lithium iron phosphate power batteries, including pretreatment processes, positive and negative electrode materials, and electrolyte recycling methods. This study also focuses on the recovery process of positive electrode material, including the acid leaching process and bioleaching technology in pyrometallurgy and hydrometallurgy, and direct regeneration technology. It introduces the recycling technology of negative electrodes and the supercritical CO₂ recovery process of electrolytes. The recent progress in the recovery and utilization of waste lithium iron phosphate power batteries is systematically summarized, and the existing problems in the recovery and utilization of waste lithium iron phosphate power batteries are analyzed. In the future, we will conduct in-depth research on the recycling process and its principle, develop a clean, environmental-friendly and simple recycling process, and adopt different recycling methods for different types of recycled materials. Thus, the high efficiency and high-quality recovery of all waste lithium iron phosphate power battery components can be realized.

The only way to address the emerging "space anxiety" in rapidly developing energy storage devices is through "compact energy storage," or storing as much energy as possible in the smallest possible space. Carbon materials assembled from graphene basic units can be used as key components in electrodes to promote electrochemical reactions and play an important role in optimizing electrode and battery volumetric performance. This review summarizes the significance of compact energy storage in rechargeable batteries as well as the major challenges. We propose a compact energy storage methodology based on the dense self-assembly process of graphenes, as well as its application in high-volumetric-capacitor electrodes, and then extend it to build compact high-energy rechargeable batteries, particularly lithium-ion batteries. To achieve compact energy storage from materials to electrodes and devices, the strategy of densifying the electrodes using customized carbon structures is highlighted. For future development, special concerns about cycling stability, fast charging, and thermal safety under practical working conditions in compact batteries are discussed.

The O3-type NaNi_1/3Fe_1/3Mn_1/3O₂ materials have been considered as the most promising cathode materials for high-energy density layered sodium-ion batteries owing to their high capacity and structural stability. However, its poor cycling stability and rate performance as a layered oxide material limit its practical application. In this study, NaNi_1/3Fe_1/3Mn_1/3-x Sn _x O₂ cathode materials with different Sn-doping ratios were synthesized using a simple solid-phase method to improve the electrochemical performance. The analysis results revealed that optimized Sn doping retained the O3 layered structure with R3m space group. In addition, the NaNi_1/3Fe_1/3Mn_1/3-0.02Sn_0.02O₂ material exhibited the best comprehensive electrochemical performance. Mn, which was partially substituted by Sn, could increase the interlayer spacing, enhance the Na⁺ diffusion ability, and reduce lattice-structure damage caused by the Na⁺ insertion/extraction process. Moreover, Sn doping could shrink the length of the TM—O bond, thus enhancing the structural stability of the transition-metal layer. The transmission electron microscopy images showed that Sn-doped cathodes possess more perfectly layered lattice structure, which inhibited lattice distortion. Sn-replaced Mn could improve the redox reversibility of the cathode materials and possibly reduce the loss of favorable phase transition P phase. The NaNi_1/3Fe_1/3Mn_1/3-0.02Sn_0.02O₂ material exhibited the best comprehensive electrochemical performance in which 139.1 mAh/g of initial specific discharge capacity at 0.2 C was achieved. Excellent rate performance was also achieved, as evidenced by the 110.5 mAh/g of specific discharge capacity at 8 C rate and 80.1% capacity retention after 200 cycles in the voltage range of 2-4 V. This work demonstrated the Sn mechanism, which is very important in designing cathode materials with higher rate performance and cyclability.

The limited lithium reserves and the increasing cost of lithium sources have hampered extensive applications of lithium-ion batteries to large-scale electric energy storage. It is significantly urgent to develop alternative low-cost electric energy storage devices, during which rechargeable sodium-ion batteries (SIBs) have attracted extensive attention due to abundant sodium resources and similar electrochemical properties to lithium-ion batteries. Na₃V₂(PO₄)₂F₃ (NVPF) is considered as one of the most promising candidates, owing to the merits of super high ionic conductivity, high theoretical specific capacity, good thermal stability and small volume effect. In this work, through hydrothermal process and post calcination, nitrogen-doped carbon-coated NVPF (NVPF@C-N) composites were obtained by adding urea and citric acid during the hydrothermal process. Particularly, nitrogen doping could substantially enhance the pore structure and electrical conductivity of the carbon layer. When used as the SIB cathode, NVPF@C-N exhibited high reversible capacity and excellent rate capability. Under 1 C and 10 C rates, the NVPF@C-N cathode delivered initial discharge capacity of 121 mAh/g and 110 mAh/g, respectively. Even at the rate of 90 C, 66 mAh/g can be obtained. For the cycling stability of NVPF@C-N, the voltage plateau still could be well maintained even after 200 cycles at the rate of 1 C, and the electrode still retained a capacity of 111 mAh/g. Particularly, a retention of 87% was obtained after 1000 cycles at the rate of 10 C, and a retention of 54% was still maintained even after 6000 cycles.

Energy-storage technology is a critical technology for the construction of energy Internet, which is important for ensuring stable operation of power grids, optimizing energy transmission, absorbing clean energy, and improving power quality. Electrochemical energy-storage technology, which enjoys the advantages of small geographic-location restrictions and short construction period, is one of the mainstream energy-storage technologies. Currently, the most mature electrochemical energy-storage technology is lithium-ion battery. However, the shortage in lithium resources can alone limit the popularization of electric vehicles and large-scale energy-storage applications. Sodium-ion batteries have become the current research focus in energy-storage technology owing to rich sodium resources, low cost, high-energy conversion efficiency, long cycle life, low maintenance costs, and other advantages. This study analyzes the technical feasibility and technical economy of Na-ion battery energy-storage technology and compares it with the current mainstream energy-storage technologies. The advantages of Na-ion battery in the field of large-scale energy storage are analyzed in terms of the cost per kiloWatt-hour. A demonstration of a 1 MW·h Na-ion battery energy-storage system is also briefly introduced. Meanwhile, some views and suggestions on the application of Na-ion battery in energy-storage power stations are provided.

Using solid-state electrolytes (SSEs) to replace liquid electrolytes (LEs) can guarantee a high energy density and safety for developing solid-state batteries. Sulfide-based SSEs have received much attention because of their significant advantages, like high ionic conductivity. However, they face several challenges: poor electrode/electrolyte contact, interface side reaction with an electrode, and poor air stability. As a common solution, it frequently requires collaboration with some organics, such as organic solvents or polymers, to improve battery performance. This paper reviews the synergistic effects of different organics on sulfide-based SSEs. First, the development status of quasi solid-state batteries (QSSBs) based on sulfide-based SSEs is reviewed. From the perspective of adding LEs or solution at the cathode, electrolyte, anode, and mutual interfaces, the enhancement of adding organics to QSSBs, such as interface infiltration and constructing a protective layer, are described. Second, the wet-and dry-preparation of polymer/sulfide composite SSEs are introduced. The differences in the preparation processes between polar and non-polar polymer binders are compared, and the influence of organics on the ionic conductivity of composite electrolytes is emphatically analyzed. The process of improving the internal interface of the composite cathode using the solution method is described. Moreover, the preparation technology and the development prospect of the sheet-type electrode are introduced. Finally, the difficulties faced using organics in cooperating with sulfide-based SSEs are summarized. Future research work's development directions are proposed, providing ideas for assembling high-performance sulfide-based solid-state batteries.

Lithium sulfur (Li-S) battery is considered one of the most promising secondary batteries because of its ultra-high theoretical energy density and abundant sulfur resources. The sulfur cathode in a typical liquid Li-S battery undergoes a "solid-liquid-solid" conversion reaction, which produces soluble polysulfides throughout the charging and discharging process, causing the shuttle effect and resulting in active material loss and inadequate cycle life. The "solid-solid" conversion reaction of the sulfur cathode has been suggested and investigated to avoid the production of soluble long-chain polysulfides and essentially solve the shuttle problem. Various methodologies and research advances toward establishing a "solid-solid" conversion process in the sulfur cathode are discussed in this study. The sulfur limitation mechanisms in microporous structures, covalent sulfur fixing in organic polymers, inorganic heteroatom doping, and organic polymer skeleton/inorganic hybrid synergy are reviewed. Meanwhile, their optimization and enhancement techniques and future challenges are summarized. Furthermore, the solid-state electrolyte paired with the sulfur-positive electrode of the solid-solid conversion process is discussed, followed by a brief introduction to the common techniques of "quasi-solid" phase conversion. Finally, we propose the development of a high-energy density Li-S battery.

Hydrogen energy, as a strategic emerging industry, is an essential part of the future national energy system and decarbonization energy carrier for end users. Hydrogen generation via water electrolysis benefits large-scale renewable energy consumption and the national energy structure transformation. To fulfill the need for large-scale, highly efficient, and long-life water electrolyzers, integrating interfacial engineering concepts and manufacturing methods to enhance nanotechnology industrialization is crucial. Based on interfacial engineering principles, this review summarizes recent progress on self-supported electrodes, with a focus on improving the stability of the electrode structure and electrocatalytic activity, and examines the influence of microstructure on catalytic performance, particularly at three key interfaces (catalytic sites/substrate interface, interface among catalysts, and electrode/electrolyte interface). Moreover, we discuss strategies for developing self-supported catalytic electrodes with high activity and stability.

Colloidal solution can be used to reduce Ru nanoparticles. The catalyst for electrochemical ammonia synthesis was Ru_c/CNT, which was created by supporting Ru nanoparticles on carbon nanotubes(CNT). By varying the volume of the Ru colloid solution, different Ru loadings of the Ru_c/CNT can be obtained. Catalyst were characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscope (TEM), contact angle meter, and electrochemical techniques. The results show that the Ru nanoparticles on Ru_c/CNT prepared by colloidal solution are smaller (1-5 nm) and disperse better than those on Ru/CNT. 0.025-Ru_c/CNT with a Ru load of 2.5% achieved the highest ammonia yield of 10.98 μg/(h·mg_cat.) and a Faraday efficiency of 2.18%. Nonetheless, Ru/CNT prepared by directly reducing Ru on carbon nanotubes had an ammonia yield of 5.19 μg/(h·mg_cat.) and a Faraday efficiency of 0.05%. Control experiments confirmed the source of the ammonia. The findings demonstrated that ammonia was produced by an electrochemical catalytic nitrogen reduction reaction. Ru nanoparticles are the catalyst's primary active sites. Reducing the size of Ru particles promotes charge transfer between the carrier and the Ru nanoparticles, weakens the high-energy N≡N triple bonds in the reaction process, and improves ammonia selectivity. CNT application provides sufficient loading sites for 0.025-Ru_c/CNT, and Ru nanoparticles with greater dispersion can expose more active sites. As a result, 0.025-Ru_c/CNT performs better for electrochemical ammonia synthesis.

Mixed alkane is a type of cryogenic phase change material (PCM) with superior performance, because of its adjustable phase change temperature and high phase change enthalpy. Currently, however, there are few studies on low-temperature mixed alkane systems. The thermodynamic properties of of C₈H₁₈, C₉H₂₀, C₁₀H₂₂ and C₁₁H₂₄ binary mixed alkanes systems are investigated. The solid-liquid phase diagram is drawn after studying the influence law of the phase transition temperature, phase transition enthalpy, and composition of the mixed alkane system. Different thermodynamic models predict the binary mixture's phase transition temperature and phase transition enthalpy, and the experimental results are mutually verified. The results show that C₉-C₁₀ and C₉-C₁₁ systems exhibit eutectic behavior, with the eutectic components being 88%C₉ (weight percentage)-12%C₁₀ and 90%C₉-10%C₁₁. The eutectic temperatures are 218.25 K and 215.15 K, respectively. Peritectic phenomena occur in the C₈-C₉ system, while isomorphous phenomena occur in the C₁₀-C₁₁ system. Their minimum melting points are 200.25 K and 234.35 K, respectively. Furthermore, the melting temperatures predicted by the UNIQUAC model are in better agreement with experimental data of C₈-C₉ and C₉-C₁₀ systems. The UNIFAC melting temperature model produces more accurate results for C₉-C₁₁ and C₁₀-C₁₁ systems. The Regular solution model can predict the melting enthalpy more accurately, and the average relative deviation is lower. As a result, the C₉-C₁₀ and C₉-C₁₁ eutectic systems are low-temperature phase change materials suitable for temperatures ranging from 210 K to 220 K, providing data for their use in low-temperature energy storage.

Phase-change emulsion is a type of latent functional thermal fluid with high energy-storage density, good fluidity, and excellent convective heat-transfer performance, which has been widely applied in the field of heat storage and thermal management. In this study, the types and preparation methods for phase-change emulsion are systematically introduced. The bottleneck problems of high undercooling and poor stability of phase-change emulsions and their solutions were analyzed, and the existing application research was summarized. Selection of special long-chain emulsifiers was pointed out to be the preferred method for reducing the supercooling degree of the emulsion. To improve emulsion stability, the mutual influence of various factors must be considered. In the practical application, the phase-change emulsion demonstrated a higher thermal-energy-storage capacity and better cooling performance than water. Subsequent development of functionalized new phase-change emulsions and expansion of new application areas are predicted to possibly become a future development trend.

This paper investigates the heat transfer performance with air convection for different heat sink structures, in order to gain insight into the influence of microstructures on the heat transfer performance of heat sinks and to achieve efficient cooling under different operating conditions. By changing the simulation conditions, such as flow direction, flow velocity, and heat flux, the numerical simulation method of computational fluid dynamics is used to study the heat transfer efficiency and airflow of heat sinks with different microstructures. It has been discovered that heat sinks with hollow micro pin-fin arrays have a better cooling effect than heat sinks with micro plate-fin arrays or hybrid arrays. The benefit of hollow micro pin-fin arrays is that they promote local turbulence of air around them, which increases the average flow rate of cold air in the near-wall boundary layer. In the case of the vertical inflow, the design allows for the best use of air kinetic energy to flush the surface inside and outside the micro-pillar, improving convective heat transfer efficiency. According to the analysis, as the height of the microstructure increases, the percentage of heat transfer enhancement decreases. Meanwhile, as the microstructure density varies, there is a peak in the average heat transfer coefficient of the heat sink. This indicates the existence of an optimal value for the microstructure parameters when material utilization is taken into account. When compared to heat sinks with conventional micro plate-fin arrays, the newly optimized hollow micro pin-fin arrays at a height of 5 mm and pitch of 6 mm can reduce the average temperature of heat sink by 10%-15%, ensuring the efficient performance of microdevices in a variety of working conditions.

In order to study the performance of the column tube solid sodium chloride storage heat exchanger in a supercritical compressed air energy storage system, the whole storage heat exchanger is equated to all single heat exchanger tubes in parallel, the single heat exchanger tubes as well as the sodium chloride outside the tubes are divided into microelements, and the control equations are listed for each microelement, which are discretely solved according to the different input parameters of the storage, retention and release processes of the storage heat exchanger in actual operation, and finally the air temperature distribution, sodium chloride temperature distribution, outlet mass flow rate, heat dissipation, local heat transfer coefficient and local heat transfer at different moments of the storage, retention and release processes of the storage heat exchanger. The results show that the air outlet mass flow rate fluctuates, being smaller than the inlet flow rate during the storage and larger than the inlet flow rate during the release process; the heat transfer coefficient is greatest when the air temperature reaches the quasi-critical temperature during the cross-critical flow heat transfer in the tube, and the air temperature rise rate decreases and then increases due to the increase and then decrease of the specific heat of the air near the quasi-critical temperature; the difference in the initial temperature distribution of sodium chloride leads to the change of sodium chloride temperature at the end of the cooling process. The difference in the initial temperature distribution of sodium chloride leads to different changes in the temperature of sodium chloride at each location of the heat exchanger. This study reveals the flow heat transfer law of supercritical air in the column tube solid sodium chloride storage heat exchanger, which provides a theoretical basis for the application of indirect storage heat exchanger in supercritical air energy storage.

This paper proposes a novel liquefied-air energy-storage system that is coupled to liquefied natural gas (LNG) cold energy and organic rankine cycle (ORC) system. During off-peak period, the cold energy from LNG and liquid propane operate together to liquefy compressed air and store energy. During peak times, liquid air is released to generate electricity, and the cold energy of LNG is recovered by propane. The system combines the cold energy released by continuous gasification of LNG as auxiliary energy and the energy-storage system, which can flexibly release energy for power generation. In addition, the system employs cascade operation of the LNG cold energy (the cold energy is sequentially used for liquefied air, ORC, and data-center cooling), which improves the energy utilization rate and minimizes energy loss. By developing thermodynamic and economic-evaluation models of the coupled system, the proposed system was simulated using the Aspen HYSYS software, and the round-trip and exergy efficiency values are analyzed. By focusing on the regional power price of the Ningbo LNG receiving terminal in Zhejiang province, the net-present-value method was used to evaluate the economic feasibility of the system. The results demonstrated that the round-trip efficiency of the system was 110.20% higher than the recent related research results. The exergy efficiency was 59.71%, which was approximately 10% higher than that of conventional liquefied-air energy-storage system. The energy-storage project is economically feasible, and the peak-time electricity price exerts the largest effect on the economic benefits of the system. This research can provide important reference and basis for engineering application of LNG cold energy for energy storage and peak regulation in power plants.