The CaCO₃/CaO thermochemical energy storage system is promising in the field of clean energy power generation because it helps to peak carbon dioxide emissions and achieve carbon neutrality as soon as possible. In this study, CaCO₃/CaO composite heat storage materials doped with TiO₂ were prepared by employing the physical mixing method. The effects of TiO₂ doping on the cyclic stability and the reaction performance in the exothermic and endothermic processes were then systematically investigated. The composite exhibited the best cyclic stability at a molar doping ratio of 100∶2.5 (Ca∶Ti). Its conversion rate was 1.65 times that of the control group after 15 cycles. Characterization showed that the CaCO₃-TiO₂ composite heat storage material with the best doping ratio had a smaller particle size and more developed pores, leading to a better anti-sintering ability in the cycle process. In the exothermic process of carbonation, CaCO₃-TiO₂-2.5 illustrated higher reaction conversion rate and thermal release/storage enthalpy ratio at a high temperature range (i.e., 750 ℃. and 800 ℃). However, its enthalpies in the exothermic and endothermic processes decreased due to the low CaCO₃ content in the composite material. During the isothermal decarbonation process, the TiO₂ doping increases the reaction rate and reduces the reaction time in the N₂ atmosphere, and decreases the initial decarbonation temperature and promotes earlier reaction in the CO₂ atmosphere. In contrast, during the non-isothermal decarbonation process (10 ℃/min), the TiO₂ doping reduces the initial decarbonation temperature of the pure CaCO₃ from 897.16 ℃ to 870.92 ℃ in the CO₂ atmosphere. The TiO₂ modification is generally of far-reaching significance for the practical application of the CaCO₃/CaO thermal storage technology.

The compatibility of alloy material and container shell is one of the critical factors affecting the service life of the heat transfer and storage system. This paper modifies a previously developed Sn-Bi-Zn heat transfer and storage alloy by adding In element to study the corrosion effect of liquid alloy on 20 carbon steel, 304 stainless steel, and 316 stainless steel at 700 ℃. The experiment adopts the constant temperature full immersion corrosion method. It analyzes the micromorphology and element distribution of alloy matrix and container material before and after corrosion by scanning electron microscope and energy dispersive spectrometer. Differential scanning calorimetry and flash thermal conductivity were used to study the thermal properties of the samples before and after corrosion. The corrosion kinetics shows that the experimental results conform to the parabolic law, and the diffusion coefficient is in the order of D(20C)>D(304)>D(316). The thermal conductivity of the alloy matrix increases slightly during the corrosion process due to the elements' dissolution in the steel sheet and the diffusion and consumption of the matrix alloy elements. Mechanism analysis shows that the Gibbs free energy of the oxidation reaction of In element is smaller than that of the container material. Therefore, an oxide layer can be formed at the corrosion interface to prevent dissolution and oxidation corrosion of the container material.

In this study, high-thermal conductivity expanded graphite (EG) is added to prepare a composite phase-change material (PCM) to improve the poor thermal conductivity and the insufficient heating capacity of paraffin. The influence of the EG addition on the composite PCM is then investigated. The results of the thermal performance test show that when the mass fraction of EG increases from 0 to 12%, the thermal conductivity of the composite PCM increases by 12 times that of pure paraffin. Moreover, the latent heat decreases from 190.8 J/g of pure paraffin to 152.1 J/g, and the phase transition temperature is approximately 62 ℃?, showing a fluctuation of approximately 0.43 ℃?. Comprehensively considering the thermal conductivity and the thermal storage density, 8% (mass fraction) composite PCM with 3.059 W/(m·K) thermal conductivity and 159.8 J/g latent heat is selected as the thermal storage material. The novel idea of a prefabricated wall block is applied to design the modular units for the heating system construction. The structure of and the installation method for the modular prefabricated thermal storage wall blocks are also introduced. The experimental study on the charging and discharging performances of different PCMs in the thermal storage unit illustrates that compared with pure paraffin, the 8% (mass fraction) EG/paraffin composite PCM improves the charging efficiency from 93% of pure paraffin to 97%. In addition, the effective discharging efficiency increases from 67.92% of pure paraffin to 84.65%. Accordingly, an economic analysis of the application of the modular prefabricated thermal storage wall blocks in a Nanjing office building with 1500 m² of heating area is performed. Under the current peak and off-peak electricity prices in Jiangsu Province, the net present value of the wall blocks within a 20-year operation period is approximately 139?100 yuan, and the payback period is approximately 14 years. In summary, the application of the prefabricated wall blocks is feasible, but has a long payback period and a low annual income.

Magnesium nitrate hexahydrate-lithium nitrate eutectic phase change materials were successfully prepared by melting blending method with different mass percentage of lithium nitrate. The eutectic point of magnesium nitrate hexahydrate-lithium nitrate eutectic salt is around 85∶15 mass ratio. The phase transition temperature and latent heat of eutectic phase change materials were 72.46 ℃ and 193.7 kJ/kg by differential scanning calorimeter. The exothermic platform of eutectic salt was obvious and the supercooling degree was less than 1.5 ℃ by step cooling curve. X-ray diffraction test showed that there was no chemical reaction between magnesium nitrate hexahydrate and lithium nitrate in eutectic salt. After several cold and hot cycles, the eutectic salt has good stability with little change of phase transition temperature and no phase separation phenomenon. In order to improve the photothermal properties of eutectic phase change materials, expanded graphite was added to improve the photothermal properties of the materials due to their weak light absorption. The phase change materials obtained in this work have suitable phase change temperature, high latent heat value, it solves the problem that the phase change temperature of magnesium nitrate hexahydrate mismatches the heating end temperature area and has good light absorption capacity, which can be used as candidate materials in the field of solar clean heating system with the radiator at the end of building heating.

In recent years, lithium ion capacitors (LICs) attract much attention due to their high power density and relatively high energy density with rapid development of electric vehicles and energy storage. Niobium pentoxide (Nb₂O₅) is one of the most important anode materials owning to its high capacity and superior rate capability. However, complicated fabrication process or special treatments are required in the synthesis of Nb₂O₅ based anode material. Herein, a fast synthesis of multilayer Nb₂O₅ nanosheets by oxidizing the multilayer Nb₂C MXene material is developed. The multilayer Nb₂O₅ nanosheets are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), specific surface area analysis, X-ray photoelectron spectroscopy (XPS) and electrochemical analysis. Initially, the precursor transform into orthorhombic Nb₂O₅ (T-Nb₂O₅) which inherit the multilayer nanosheet microstructure. With prolonged sintering time, the orthorhombic phase turns into pseudohexagonal Nb₂O₅ (TT-Nb₂O₅) nanoparticles. Compared with TT-Nb₂O₅ nanoparticles, multilayer T-Nb₂O₅ nanosheet electrode shows higher specific capacity and better rate capability. The T-Nb₂O₅ electrode also shows excellent cycle performances both in half-cells and LICs. The excellent lithium storage performances of the multilayer T-Nb₂O₅ material may be due to the synergistic effect of its multi-layer microstructure, inherent quasi-2D Li-ion channel and rapid pseudocapacitive response.

Spent lithium iron phosphate (SLFP) batteries recycling is increasingly being researched. In this study, an electrochemical recycling method for SLFP is proposed based on solid-phase electrolysis; in reference to that, the technology exhibits complex procedures, extra secondary wastes, and high cost, resulting in reduced risk of secondary pollution and improved yield, and lower price. Phosphoric acid electrolysis system and stepwise precipitation method were adopted to prepare FePO₄·2H₂O and Li₃PO₄. The study covers parameter optimization in the electrolysis process and factor analysis for the precipitation separation. It analyzes the effect of parameters such as cell voltage, H₃PO₄ electrolyte concentration, and soaking time before electrolysis on Fe and Li leaching rates. After 60 min of soaking, with 30 min electrolysis in 0.6 mol/L H₃PO₄ electrolyte at 2.5 V, the Fe and Li leaching rates were 91.3% and 95.6%, respectively. The solution pH was controlled by stepwise addition of ammonia water to precipitate FePO₄·2H₂O and Li₃PO₄, of which a corresponding 98.8% and 99.4% recovery rates were achieved. respectively.

The in-situ optical microscopy equipment is increasingly used to observe the micro-behavior of the lithium ion batteries (LIBs). Herein, an in-situ optical microscopy system was used to observe the change of thicknesses and morphologies of the anodes during charging and discharging process for the pouch LIBs. The voltage-current curve, the thickness change of electrode and the morphological change of anodes were recorded simultaneously. The electrochemical and physical behavior of SiO/graphite composite anode with different ratio of SiO/graphite was studied. The thickness of fully charged anode increased as the content of SiO raised. When the percentage of SiO was raised to 12%, the anode material peeled off from the current collector,and it had a strong correlation with cycle performance of the cell. The lithium dendrite morphology at different charging and discharging rates was studied. When the charging current was small (0.05 C, 0.2 mA/cm²), whisker-like lithium dendrites were observed on the lithium metal electrode; the thicker branch-like lithium dendrites were observed when the charging current increased (0.25 C, 1.0 mA/cm²). The in-situ observation of macro-and micro-change of electrode morphology make the observation of the internal electrochemical process of batteries readily available, which will help people in the study of battery mechanism, failure analysis and battery modification.

The research progress of chromatography-mass Spectrometry technology in the field of lithium-ion batteries is reviewed. Lithium-ion batteries have been widely used in electric vehicles, energy storage, mobile phones, etc. based on their green, excellent performance and other advantages. As one of the core components of electric vehicles, the performance of lithium batteries largely determines the technical level of electric vehicles. The electrical performance, safety performance, and stability of lithium-ion batteries directly affect the operating state of electric vehicles. In order to further improve the performance of lithium-ion batteries, product generation analysis and mechanism analysis will be of a great importance during charging and discharging. And accurate product detection is one of the key factors to ensure the accuracy of the analysis results. In this article, the progress of lithium metal anode passivation technology was introduced from the following three aspects, including: ① the solid electrolyte mesophase (ie SEI membrane) composition and electrolyte degradation analysis using TOF-SIMS and LC-IT-TOF-MS; ② the SEI membrane composition and morphology of different forms of graphite using TOF-SIMS and other combined technology; ③ the gas production under the conditions of abuse of lithium batteries and gas evolution behaviors for several cathode materials in lithium-ion batteries using GC-MS technology.

Lignin is an aromatic polymer with abundant reserves on Earth. It is rich in hydroxyl, carboxyl, ether, and other functional groups. The presence of these functional groups allows the selective modification of this complex compound. Lignin is a by-product of the pulp and paper industry, which is inexpensive and has a wide range of sources. The porous lignin-based carbon prepared by a simple and mild chemical activation has become a research hotspot in the fields of environmental purification, electrocatalysis, and energy storage, especially as an anode material for lithium-ion batteries. This review briefly introduces the energy storage mechanism and the characteristics of lithium-ion batteries and summarizes the mechanism, preparation methods, and research status of lignin in the anode materials of lithium-ion batteries. The anode materials are divided into lignin-based layered porous carbon, carbon microsphere, carbon fiber, carbon nanotube, and other composites. The application of lignin to a lithium-sulfur battery is also investigated. Finally, the existing problems faced by lignin used as the electrode materials for lithium-ion batteries are put forward, and future work is prospected.

Zinc-iron flow batteries are one of the most promising electrochemical energy storage technologies because of their safety, stability, and low cost. This review discusses the current situations and problems of zinc-iron flow batteries. These batteries can work in a wide range of pH by adopting different varieties of iron couples. An alkaline zinc-iron flow battery usually has a high open-circuit voltage and a long life cycle performance using porous electrode and membrane. In an acidic zinc-iron flow battery, the iron ions in the positive side have good solubility and reversible chemical stability, while zinc in the negative side is greatly affected by the pH. The neutral zinc-iron flow battery has attracted more attention due to its mild condition and low cost using a porous membrane. However, all kinds of zinc-iron flow battery suffer from zinc dendrite and low areal capacity, which hinders its commercial development. Some prospects for developing new electrolyte, electrode, membrane, and battery structures combining experiment and accurate physical models are finally proposed.

In the context of global carbon neutrality, the international energy pattern is changing from the absolute dominance of fossil energy to the integration of low-carbon and multi-energy. As a key technology for promoting the transformation of renewable energy from alternative energy to main energy, the energy storage technology has attracted increasing attention from the industry. This study analyzes the strategic layout, project deployment, and key demonstration projects of the electrochemical energy storage technology in the United States, the European Union, Japan, and other major countries as well as regions. China has committed to carbon peak by 2030 and carbon neutral by 2060. In relation to this, the Chinese government has paid increasing attention to the development of the electrochemical energy storage technology by issuing a series of supporting policies, launching major research and development projects to perform technical research, and deploying several demonstration projects for electrochemical energy storage. However, although China has made efforts to catch up with advanced-technology countries, such as Europe, the United States, Japan, and South Korea, in terms of the electrochemical energy storage manufacturing technology, a certain gap remains to exist between China and these developed countries when it comes to energy storage battery mechanism research, technological breakthrough, and key material manufacturing. The demonstration and application of various types of electrochemical energy storage technology in China have just started. Therefore, further measures must be taken from the aspects of top-level design, technology research and development, industrial layout, and infrastructure construction to accelerate the wide application of the new next-generation electrochemical energy storage technology, promote energy-efficient utilization, multi-energy integration, and complementarization, and build a "clean, low-carbon, safe, efficient, and modern" energy pattern.

Energy storage is a key supporting technology for solving the problem of large-scale grid connection of renewable energy generation, promoting the development of new energy vehicles, and achieving the medium-and long-term goals of carbon peak and carbon neutralization. The hybrid energy storage system composed of an energy-type energy storage device and a power-type energy storage device is an efficient system for energy and power management that gives full play to the durability of the energy-type energy storage and the rapidity of the power-type energy storage. It also greatly improves the comprehensive performance and economy of the energy storage system. This paper summarizes the energy and power electrochemical energy storage technologies, and characteristics and various battery-supercapacitor hybrid energy storage systems (BSHESS). The application of the hybrid energy storage system in the power grid energy storage, new energy vehicles, rail transit, and other fields is analyzed. The key technologies of the BSHESS, including their control and energy management, are analyzed in detail, and the control methods commonly used in the hybrid energy storage system are summarized. Moreover, an analysis of the parameter matching and technical economy of the BSHESS is performed. The topological structure classification of the BSHESS is summarized, and the advantages and disadvantages of each topological structure are discussed. In addition, a simulation comparison between the BSHESS and the single energy storage system is performed to verify the superiority of the former over the latter. Finally, development prospects are proposed.

Battery energy storage system has broad development prospects due to its advantages of convenient installation and transportation, short construction cycle, and strong environmental adaptability. However, battery safety accidents of energy storage systems characterized by thermal runaways occur frequently, which seriously threatens power consumption and life safeties of relevant personnel with the continuous improvement of overall energy density and the reduction of manufacturing costs. Therefore, the research on preventing thermal runaway of battery energy storage systems has recently become a hot spot in the field of the energy storage system. From the perspective of energy storage battery safety, the mechanism and research status of thermal runaway of container energy storage system are summarized; the cooling methods of the energy storage battery (air cooling, liquid cooling, phase change material cooling, and heat pipe cooling) and the suppression measures of thermal runaway are introduced, and the latest research results are reviewed. This paper expounds on the influence of temperature and humidity on batteries, comprehensively outlines the methods to improve the safety and reliability of container energy storage systems, and projects the development direction of thermal management technology. This paper aims to promote the development of safety management methods and strategies of the energy storage system and then improve the energy storage system's safety.

The material recycling of LiFePO₄ batteries has low value; hence, the only way to maximize their value is to reuse them. In this study, a three-stage simulation test is established with different loads to verify the reuse feasibility of LiFePO₄ batteries. The experiment results show that all samples can regularly attenuate before the capacity retention rate becomes higher than 50%. The individual samples suffer from sudden death when the capacity decays to less than 50%. Based on research on the battery decay law during the test, proposals are suggested for the application scenarios of LiFePO₄ batteries at different stages.

In this study, COMSOL Multiphysics software is used to establish a phase-change cooling-coupled air-cooled lithium battery pack heat dissipation model to explore the influence of single cell arrangement on the thermal management performance of lithium battery packs. The temperature field changes under different cell spacing and phase-change material (PCM) consumptions are simulated. When the single cells are evenly arranged, the maximum temperature difference first decreases and then increases with the spacing increase. The temperature uniformity is the best at 10 mm. Under the same amount of PCM, the cell spacing from the center to the outer edge of the battery pack is reduced in an orderly manner to optimize the battery layout. Compared to those under a uniform arrangement, the maximum temperature and the maximum temperature difference under a non-uniform arrangement increases and decreases, respectively. Consequently, the thermal management performance is improved. The larger the convective heat transfer coefficient of the external air cooling, the better the optimization effect. The amount of PCM is further optimized on the basis of an optimized arrangement. The performed simulation shows that the maximum temperature rise in the battery string is basically unchanged under the optimized arrangement when the amount of PCM is reduced by 12%. The maximum temperature difference is reduced by approximately 34%. These results indicate that the optimization of single battery spacing can improve the thermal management performance of the battery pack and reduce the amount of PCM. The optimized battery pack structure is an effective reference for the thermal management system under the phase-change cooling strategy.

Transmitting large-scale wind power through a line-commutated converter-based high-voltage direct current (LCC-HVDC) system has become a common trend in China. Under this condition, the transient overvoltage in the sending end caused by HVDC blocking faults or commutation failures will cause a cascaded trip-off of doubly fed induction generators (DFIG), which seriously threatens the safety and stability of power systems. The internal mechanism of the process of the DFIG cascaded trip-off caused by the HVDC blocking faults is revealed by establishing the equivalent model of the wind power integrated sending end system and by analyzing the transient response of the DFIG under the transient overvoltage. A coordinated fault ride through scheme based on the rotor side superconducting magnetic energy storage system (SMES) and modified DFIG control strategies is proposed herein. While the DFIG generates demagnetizing and reactive currents, the SMES cooperates to quickly inject demagnetizing and reactive currents into the DFIG rotor side. Simulation and real-world cases conducted in MATLAB/Simulink verified that compared with demagnetization and traditional vector control, the proposed scheme can always limit the key parameters of the DFIG in a safe range and suppress the transient overvoltage, consequently reducing the risk of cascaded tripping.

Hybrid Energy Storage System (HESS), composed of all-vanadium flow batteries and supercapacitors, can effectively suppress wind power fluctuations. In order to improve the flexibility and safety of the energy storage system, a hybrid energy storage power distribution method based on parameter optimization Variational Mode Decomposition (VMD) is proposed. Firstly, the exponential smoothing method is used to filter the wind power according to the grid connection standard to obtain the required wind power grid flowing into grid, and the wind fluctuation power which needs to be smoothed by energy storage system is calculated. Then, the fitness function is constructed by three signal decomposition evaluation indexes,and a Sparrow Search Algorithm (SSA) is adopted to optimize the mode number K and the secondary penalty factor α for VMD algorithm. Based on the optimized values of K and α, VMD algorithm is used to decompose the fluctuating wind power and then distribute it reasonably between the batteries and the supercapacitors. Finally, a fuzzy controller is employed to optimize the state of charge (SOC) of storage device to realize the secondary distribution of HESS. Example results show that the proposed method can not only adaptively decompose the wind power fluctuation power signal, effectively suppress the wind power fluctuation, reduce modal mixing and complete the reasonable distribution of HESS power, but also optimize the charge and discharge range of energy storage equipment, avoid the occurrence of overcharge and excessive discharge of energy storage equipment, and ensure the charge state of energy storage equipment in a fixed range, which realizes the safe and stable operation of HESS.

An in-depth study is conducted on the grid-connected switch control problem suitable for the seamless switching control of a microgrid. Moreover, the influence of the zero-crossing turn-off characteristics of the silicon-controlled rectifier (SCR) switch on the local load is analyzed. The SCR forced shutdown control strategy is proposed to ensure the stability and reliability of the local load power supply. This study also investigates the factors affecting the turn-off time and obtains the transformation relationship between the local load voltage and the grid-connected current. Finally, an experimental platform is built, and related experiments are performed. The experimental results prove the rationality and the effectiveness of the theoretical analysis and the strategies proposed herein. In summary, the proposed strategy can ensure well the safety of the load's power consumption during the on-grid/off-grid switching process of the microgrid.

A decision-making method for energy storage planning considering double uncertainties is proposed herein to solve the influence of planning scenarios, decision maker preferences, and other uncertainties on energy storage planning and improve the application efficiency of the energy storage. First, the energy storage operation in the two scenarios of normal operation and extreme recovery is considered. Daily operation is optimized by minimizing the network loss, while extreme recovery is optimized by minimizing the power loss and mobile costs. Moreover, an index system is proposed to comprehensively evaluate the energy storage contribution to different application scenarios. Second, considering the uncertainties of both the planning scenario and the decision maker facing risk, this study introduces the prospect theory to deal with the index matrix, takes the comprehensive prospect value as the attribute value of each index, uses the gray target decision to determine the index matrix weight based on the prospect value, and finally determines the scheme through the optimal prospect value of the scheme. Finally, an example is given to verify the effectiveness and the feasibility of the proposed method.

In view of the problems of uneven power output and bus voltage drop in the traditional droop control method adopted in the DC microgrid in the energy storage control strategy, the microgrid is proposed to stabilize the DC bus and load constant power operation of the energy storage device in the island mode. The hierarchical control strategy divides the microgrid optimization control process into two layers: the energy storage under the primary control layer is used as the main energy distribution device of the microgrid, and a droop control strategy based on double closed loops is proposed to pass the energy storage battery converter P-f and Q-u carry out double-layer droop control to achieve constant power operation of the load; the energy storage under the secondary control layer is used as a device to stabilize the DC bus voltage and compensate for the primary energy storage. The Synchronous Reference Frame Control (SRFC) strategy is proposed, and add a Self Tuning Filter (STF) in the control to achieve the filtering of harmonics in the AC signal. Finally, Matlab/Simulink is used for simulation verification. The simulation results show that the hierarchical optimization strategy enables the load to run at constant power while stabilizing the DC bus voltage.

In order to investigate the diffusion behavior of the released gas in the module after the pressure relief valve is opened, 1∶1 geometric model is established based on the actual size of the 100% SOC LiFePO₄ battery module. Thermal runaway occurs in the battery inside the module, and the pressure relief valve opens to release gas. The diffusion of H₂, CO, CH₄ and CO₂ released from lithium-ion battery was analyzed by using Fire Dynamics Simulator software. The results show that after the pressure relief valve of the lithium-ion battery is opened, the gas will be filled to the upper side of the whole battery module in 8 s, and the internal temperature above the battery module box is maintained at 55 ℃. After 30 s, the gas spatial distribution in the module tends to be balanced and does not change with a lot time. CO₂ accounts for about 30% of the gases released, the largest of the four types of gas. The research results of this paper provide a reference for the design of lithium-ion battery module and the design of gas monitoring and monitoring system.

High-nickel ternary lithium batteries for electric vehicles are being rapidly developed. However, under abuse conditions (e.g., heating, overcharging, and squeezing), they are more prone to serious fire and explosion accidents compared to other existing batteries because of their high energy density. Their promotion and application require more stringent safety tests. This study conducted a thermal runaway experiment to observe the fire process of an NCM811 battery at 0%, 50%, and 90% state of charge (SOC) and designed a lithium battery thermal runaway gas collection device to analyze the gas properties. The explosion properties of gas were also tested. The results show that the fire and explosion hazards of the NCM811 battery increase with the SOC increase. Accordingly, 90% of the SOC gas production reaches 124.21 mol; the flame temperature reaches 650 ℃; the overpressure in a 1 L container reaches 512 kPa; and the explosion limit is between 7% and 38%. The relevant safety measures that can prevent the thermal runaway of the surrounding batteries are recommended.

Lithium-ion batteries have been widely used in energy storage and electric vehicles, but there are risks of fire and explosion due to their flammability. This paper studied the thermal runaway characteristics of 40 A·h ternary lithium and 72 A·h LiFePO₄ batteries by external overheating at different positions. The experimental results showed that the LiFePO₄ battery does not ignite under the external overheating condition, but the ternary lithium battery ignited and sprayed spontaneously. The side heating can enter the thermal runaway faster than the bottom heating. From the heat transfer analysis, the heat conduction per unit heating area required for 40 A·h ternary lithium battery thermal runaway is 1650—3788.76 kJ/m². The heat conduction per unit heating area of 72 A·h LiFePO₄ battery is 3264.84—7856.67 kJ/m². In addition, the combustion spread characteristics of the battery pack were studied, taking a 720 A·h LiFePO₄ battery pack as the research object. The experimental results showed that if the heat source is in place till, after the external ignition, it spreads to the nearby battery and continues to spray. The heat transfer value of 39.7—43 kJ between the adjacent batteries is obtained from the heat transfer analysis. The results of this study can provide theoretical guidance for fire risk assessment of energy storage power stations and lithium battery fire protection.

In order to further reduce the temperature rise, maximum temperature difference and axial temperature difference of cylindrical lithium batteries under high thermal load, a honeycomb-like battery thermal management system combined paraffin/expanded graphite (EG) phase change material (PCM) with water-cooling was proposed. Through numerical simulation, the effects of the coolant flow rate, the number of micro-channels, the thickness of CPCM (composite phase change material) and the mass fraction of EG on the heat dissipation performance of the system was investigated at the ambient temperature of 40 ℃. The results show that when the liquid rate exceeds 0.05 m/s, the continued increase in flow rate does not significantly improve the heat dissipation performance of the system. Compared with pure PCM, the CPCM mixed EG can significantly improve the heat dissipation performance of the system. When the EG mass fraction is 12%, and at different liquid flow rates, the maximum temperature difference of the battery can be met, and the maximum temperature of the battery and the liquid phase ratio of CPCM can be ensured to be the lowest, namely, the system has the best heat dissipation effect; comprehensively considering the uniformity of battery temperature distribution, space utilization and the additional energy consumption of the system, the optimal thickness of CPCM is determined to be 2 mm. When the number of micro-channels is 6, maximum temperature difference and axial temperature difference of battery is the smallest at different liquid flow rates; Especially at a 4 C discharge rate, when the flow rate is 0.01 m/s, the maximum temperature, maximum temperature difference and axial temperature difference of the battery are 45.8 ℃, 1.7 ℃, and 0.04 ℃ respectively, which can ensure that the lithium battery works within the optimal temperature range.

The number of retired energy storage batteries is gradually increasing with the rapid development of the new energy electric vehicle industry. To evaluate, maintain, and utilize retired lithium batteries, this study proposes a quantitative analysis method for the key battery performance parameters of an aging lithium battery module that adopts the “zero time cost” rapid detection method without disassembly. The key battery parameters (kbps), including the internal resistance, relative charging time difference, and charging cut-off voltage, can be characterized at the single-cell level by only one charging datum. The abnormal cells can then be detected by a box diagram of these kbps. The rechargeable capacity of each monomer and the continuous discharge capacity at the discharge cut-off time are estimated and compared with the abnormal monomer based on the capacity increment curve. Accordingly, specific maintenance suggestions are put forward, including equalization or replacement, and the expected effect is given, that is, the effectiveness of maintenance measures can be evaluated before maintenance to avoid an invalid maintenance. Three experiments were performed herein, and the kbps at the cell level were quantitatively analyzed. In Experiment 1, only a replacement maintenance can be conducted because an abnormal kbp exists in the same cell. A capacity calculation estimated that the discharge capacity of the battery pack can be increased by 12.57% after maintenance. In Experiment 2, a balanced maintenance can be performed because an abnormal kbp exists in different cells. The capacity calculation also estimated that the discharge capacity of the whole module can be increased by 35.9% after maintenance. Lastly, in Experiment 3, no abnormal value was found in some kbps due to the small difference among the monomers; hence, no maintenance measures were needed.

This study proposes a lithium-ion battery model based on the sliding window and long short-term memory (LSTM) neural network to improve the model accuracy under complex working conditions. First, a lithium-ion battery model based on the LSTM neural network is established. Next, the basic structure of the neural network is determined. The time series feature extraction, feature fusion, and regression prediction are realized by combining the LSTM, vector splicer, and full connection layers. A sliding window input vector processing method is then proposed. The sliding window is advanced one time point at a time, and the data volume is limited by restricting the maximum number of letter elements within the time window. A computational margin is reserved for the parallel computation of the multiple LSTM layers and the deep hidden layers of the splicing and fully connected layers. Subsequently, the optimal selection of the depth of the recurrent network layer in the model is achieved. A training method using offline data set pre-training and online data parameter modification is proposed to solve the generalization problem under various complex working conditions. The model learns the common parts of the battery through the repetitive training of a large number of offline data sets. The network parameters are adjusted and used in the prediction by using a part of the online data. Finally, the datasets of the constant current/constant voltage, random current pulse, high-power pulse, and other working condition test profiles are applied for validation. The results show that the proposed modeling method can accurately predict the battery's output voltage and state of charge.

To improve the prediction accuracy and stability of the lithium-ion battery state of health (SOH), a battery SOH prediction method combining one-dimensional convolution (1DCNN) and long and short-term memory network (LSTM) is proposed herein to solve the problems of the complex selection of conventional features and the inability to effectively use them. First, multichannel series voltage, current, and temperature are used to construct multi-dimensional features. Second, 1DCNN is used to extract advanced data features from the sample data and input them into the LSTM to effectively utilize historical information. Finally, the SOH prediction results of the battery are output through a full connection layer. The combined algorithm is verified by the capacity attenuation data of the NASA lithium battery. The results show that compared with other prediction algorithms, the algorithm based on the 1DCNN-LSTM has a more accurate prediction result of the SOH with a mean absolute error of 0.01 and a failure point error of less than two cycles.

The convective heat transfer coefficient (CHTC) is an important parameter in the process of the lithium-ion battery (LIB) thermodynamic simulation and is usually set to a fixed value during this process. Although satisfactory simulation results can be obtained, the simulation process cannot be consistent with the actual situation, and the temperature rise characteristics during the battery discharge cannot be accurately predicted. The variable CHTC (VCHTC) can change with the battery discharge and improve the simulation process accuracy. This study investigates the temperature rise characteristics of a single LIB (SLIB) under variable ambient temperatures and discharge rates. The battery heat generation optimization model is established using the VCHTC. The comparison results between the simulations and the experiments on the SLIB under normal working conditions show that the simulated process temperature of the VCHTC and the constant CHTC has mean absolute percentage errors of 1.1% and 6.9%, respectively, at various operating conditions.

A data-driven method based on Gaussian process regression (GPR) machine learning is adopted herein to improve the estimation accuracy of the state of charge (SOC) of lithium-ion batteries. The current and the voltage measured by the battery are taken as the input vectors of the model, while the SOC is taken as the output vector of the model for model training. The GPR model is improved to improve the model accuracy. The SOC-estimated values are then added to the moving window and used as the input vectors together with the current and the voltage. A high-precision SOC estimation model is trained by updating the training set with the window size. Compared with the GPR, least square support vector machine, support vector machine, and neural network, the root mean square error of the SOC estimated by the proposed model is controlled within 1.5%, verifying the effectiveness of the proposed method.

Accurate estimation of battery state of charge (SOC) is an important guarantee for the safe operation of energy storage devices. This work proposes a joint algorithm based on an improved grasshopper optimization algorithm and a backpropagation neural network (UGOA-BP). The algorithm introduces a uniform distribution function based on the standard grasshopper optimization algorithm, updates the control parameters, and builds a new system of random adjustment. The location update increases the population diversity and makes up for the limitations of the weak global search capability of the locust optimization algorithm. Historical data of energy storage equipment from a new energy company was used. The complete and partial discharge process data set of battery SOC from 100% to 0% and 52% to 49%, respectively, were selected. The proposed model, the grasshopper optimization algorithm BP neural network (GOA-BP), and the traditional BP neural network model were compared, tested, and analyzed from two dimensions. The simulation results show that the absolute errors of the UGOA-BP predicted values are all in the range of [-0.050, 0.050], with -0.046 maximum absolute error and 0.001 average mean square error. The average mean square errors of the GOA-BP model and the BP neural network are 0.009 and 0.067, respectively. Thus, the model prediction accuracy is better than other methods, with reasonable accuracy and engineering application value.

The electric vehicle industry is rapidly developing, and the performance of lithium-ion batteries is very important to the growing range of electric vehicles. A magnetic field is generated by the change of the moving charge or the electric field. When an external magnetic field is applied to a substance, the inside of that substance is magnetized, and many tiny magnetic dipoles appear. In this study, an experimental method is proposed to test the performance of lithium-ion batteries under the effect of a magnetic field and deeply analyze the influence of this magnetic field on the battery performance. The experiment platform included lithium-ion batteries, a battery charge and discharge test system, and a magnetic field generating system. Comparative experiments were performed on Panasonic 18650 lithium-ion batteries to study their charge and discharge performances and internal resistance. The experimental results show that lithium-ion batteries have good environmental adaptability and charge-discharge performance under the magnetic field effect. When different magnetic field effects were loaded, the charge and discharge capacities of the lithium-ion batteries changed and increased with the enhancement of the magnetic induction intensity. In the discharge process, the greater the magnetic induction intensity, the smaller the batteries' ohmic internal resistance and polarization internal resistance. The results prove that the problem of the short range of the current lithium-ion batteries can effectively be solved.

In view of the uncertainty of the load caused by the charging demand and the possibility that it may result in the overload of the charging station transformer during the peak period if not controlled, this study proposes a photovoltaic and energy storage configuration to improve the effective charging power or service capacity of the charging station, achieving the effect of load tracking by control algorithm optimization. This method takes the daily photovoltaic power generation, user load power, and daily time-of-use electricity price as the input. The profits brought by the cooperative control of the photovoltaic and the energy storage can be quantificationally computed by comparing three application scenarios. This study puts forward and compares two different algorithms, namely the particle swarm optimization (PSO) and the mixed integer linear programming algorithm, to effectively solve the model. The two algorithms can be applied to determine the energy storage control strategy and optimize the output of the optical energy storage system; however, both algorithms have advantages and shortcomings. The calculation results indicate that the simple charging and discharging modes of low-cost charging and high-cost discharging cannot quickly respond to the changing load power. The energy storage control strategy based on PSO can solve problems, such as load tracking, and obtain a local optimal solution, but cannot reach the maximum utilization rate of the energy storage. On the contrary, an algorithm based on mixed integer linear programming can achieve the overall optimal solution and reach nearly 100% energy storage utilization rate while reducing the users' daily operating costs. Moreover, by dynamically adjusting the charging and discharging power of the energy storage, the load power can be tracked; the peak load can be reduced to avoid transformer overload; and the purpose of dynamic changing scenarios can be achieved. This shows a flexible response to the complex and changeable power demand and supply sides.

The rational use of large-scale abandoned wind power in the northern region, especially for clean heating, has significant social benefits. This study investigates the matching relationship between abandoned wind power and heat storage capacity. To do this, the heat storage operation following the abandoned wind power of a provincial power grid for the past 5 years is evaluated. First, a configuration method for the heat storage capacity consuming the entire abandoned wind is proposed based on the annual abandoned wind power, maximum abandoned wind power, and maximum daily abandoned wind power. The allocation method for the heat storage capacity consuming the abandoned wind by a percentage based on the maximum abandoned wind power is also provided. Second, an evaluation model of the heat storage following the abandoned wind is built according to the operation characteristics of the distributed and centralized heat storages. Finally, the actual 5-year operation of a provincial grid is analyzed. The problems of consuming abandoned wind power in the whole heating season and the low load period of the heating season are investigated. Some conclusions are drawn from the results of the abandoned wind consumption and the heat storage configuration capacity. The results show that heat storage devices significantly affect the abandoned wind consumption of the power grid. Considering the increasing installed capacity of wind power, the heat storage configuration capacity should be raised to meet the demand for abandoned wind power. Furthermore, configuring the heat storage capacity without consuming the entire abandoned wind is more economical. The evaluation results of the heat storage following the abandoned wind power are presented herein. The heat storage capacity configuration based on the annual abandoned wind power is in accordance with the actual power grid operation. In conclusion, heat storage devices should operate following the law of abandoned wind to increase the abandoned wind consumption.

Anode carbon deposition in solid oxide fuel cells (SOFCs) is a bottleneck restricting efficiency and stabilization. This paper introduces the influence of anode carbon deposition on SOFC, reviews three specific research directions in this area, and exhibits their progress at home and abroad. Furthermore, a complete polarization numerical model of SOFC is established using a user-defined function (UDF) in the CFD software FLUENT. Numerical simulation and analysis of carbon deposition characteristics of a planar SOFC are carried out. First, the governing equations, polarization, and carbon deposition models of the numerical simulation are given. Then the boundary conditions and equation discretization method are introduced. The accuracy of the algorithm is verified by solving an IEA standard problem. Finally, the numerical results of the steady carbon deposition characteristics of planar SOFC demonstrate the following: the carbon deposition rate is relatively high at the fuel inlet of SOFC and rapidly reduces along the fuel flow direction; the generation of carbon deposition is greatly affected by CH₄, but less affected by temperature, and the concentration of H₂, H₂O, and CO gas. Our conclusion is helpful in exploring the mechanism of carbon deposition in SOFC and provides a means for the optimal control of SOFC operating parameters with natural gas as fuel.

This bimonthly review paper highlights 100 recent published papers on lithium batteries. We searched the Web of Science and found 3614 papers online from Oct. 1, 2021 to Nov. 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 prelithiation of electrodes.

Power battery is the core component of new energy vehicles, which plays a decisive role in the power, safety, driving range, and service life of new energy vehicles. Domestic and foreign standardization organizations have successfully formulated and issued power battery standards, including safety, electrical performance, and other aspects. However, the analysis found that the existing standards are still insufficient to cover the life of power batteries and actual complex application scenarios. In addition, advanced technologies represented by all-climate and solid/semi-solid state batteries have also put forward new requirements for power battery standardization. Therefore, this paper systematically summarizes the domestic and foreign power battery standardization organizations, such as UN/WP.29, ISO, IEC, and SAC/TC114/SC27 and the current state and main content of the published standards. Also, the paper analyzes the differences between domestic and foreign power battery standards in formulation ideas, technical requirements, test methods from standard classification, practical application scenarios, etc., providing a more comprehensive understanding of the various standards' specific contents. Furthermore, this paper focuses on examining the main missing items and new standardization requirements from the perspective of complete life cycle safety, service life, residual value, full climate all-around performance, environmental protection, compatibility, exchange, etc., by combining with the current state of domestic and foreign power battery standards and technology development trend. On this basis, some suggestions on the formulation, revision of specific standard items and standard systems are made, providing a reference for optimizing and improving the power battery standard system in China.

Energy storage technologies are crucial to build Global Energy Interconnection, where high-quality patents can characterize the core competitiveness of all parties, and it is necessary to analyze and grasp the international competition situation deeply. Given the deficiency of identifying high-quality patents using disruption index (D-index) and combining the technical features of energy storage technology, the improved disruption index model (I-D model) is designed to identify the high-quality patents in four key technospheres, i.e., physical, electrochemical, electromagnetic, and phase change energy storage technology. This study then analyzes the technical activity, technical impact, and market layout of energy storage technologies. The results show that the I-D model can scientifically and effectively identify high-quality patents. The overall international energy storage technology shows a steady upward trend, and each essential technosphere is at the development stage of the technology life cycle. Enterprises dominate high-level energy storage technologies in each country, and Chinese universities and research institutes show outstanding technical activity. Thus, the international knowledge flow of energy storage technology presents a diversified and balanced situation. China currently holds the largest number of high-quality patents and considerable local market dominance in the energy storage technosphere owing to its high-level technical activity but faces problems, such as low level of enterprise echelon construction, weak technological influence in most key technospheres, excessive dependence on knowledge elements of developed countries, and imbalance of international market layout. Based on these findings, this study suggests a high-quality development of energy storage technology in China, such as strengthening industry-university-research collaboration, striving for scientific and technological self-reliance, and cultivating international strategic thinking.

This study takes electrochemical energy storage systems (e.g., lithium-ion batteries, supercapacitors, lithium-sulfur batteries, lithium-air batteries, lithium-metal batteries, sodium-ion batteries, and lead carbon batteries) as the starting point to conduct a patent search on graphene applications and understand the current status of the patenting activity of graphene applications in the energy storage field. This paper also presents a detailed analysis of the global patent application trends, main source countries, applied patent distribution in various structural components, and important patent applicants. The results of this study are expected to provide a valuable reference for China's graphene energy storage technology innovation and industrial development planning.

Lithium-ion batteries are the mainstream power source of new energy vehicles. Their energy density directly determines the vehicle mileage and is related to the competitiveness and long-term development of the new energy vehicle industry. To investigate the global trend of technologies in this field, this study expounds the evolution of annual patent applications in the world and in China by comparing and analyzing the patent technology of major countries and applicants based on the search results of the Innojoy Patent Search Engine. Based on the IPC technology classification, this study analyzes the technical themes focused on and the efficacy achieved by major applicants. The results show that the number of patent applications for high-energy density Li-ion batteries for vehicles is growing steadily worldwide and in China. Although the applications from China account for the largest number in the world, they include a few basic and core patents, and their patent layout is mainly limited to the domestic scope. Compared to Japanese enterprises, Chinese enterprises still fall behind in the field of key technologies. Improving the main materials and the manufacturing process of the electric core and ameliorating the module-group technology of battery cells are the main technical paths for elevating the energy density. Technologies that consider both high energy density and high security are not only the weak area of the current research and development (R&D) but also the key position to seize the priority of R&D in the future. Based on a prior analysis, this study puts forward suggestions on the R&D and patent layout of high-energy density lithium-ion batteries for vehicles from the perspective of China.

Scientific and technological innovation accelerates the transformation of the global energy pattern toward green, low-carbon, clean, efficient, intelligent, and diversified directions. High-energy density energy storage devices are the key to realizing renewable energy consumption and promoting the electrification of terminal applications. As a next-generation high-energy density mainstream technology scheme in the industry, the all-solid-state lithium battery has attracted wide attention. This study reviews the research status of the solid electrolyte in all-solid-state lithium batteries, analyzes the main challenges faced by this kind of battery, and proposes the future development trends of this technology. Combined with literature and patent metrology, the innovation ability of an all-solid-state lithium battery is systematically analyzed herein. The results show that the R&D innovation ability of the all-solid-state lithium batteries in China is strong. In fact, more than 1000 related papers have been published, placing China on top of the rankings in this field. The Chinese Academy of Sciences topped the list with 241 papers. The statistical results of the patent results since 2015 indicate that the technology has shown a blowout development. The technical themes are mainly focused on the development and manufacturing of secondary batteries, electrode development, research and development of conductive materials, development and manufacturing of primary batteries, and research and development of special equipment for manufacturing conductive materials, among others. By far, Japan is leading in terms of the number of published patents in this field. As a suggestion, China should strengthen the protection of the intellectual property rights of this technology in the future, promote the market application of patents, and realize the commercial mass production of all solid-state lithium batteries as soon as possible to play a greater role in promoting its clean and efficient energy pattern and realizing the "double carbon" goal.

The rise and development of energy storage are inseparable from policy encouragement and mechanism support. The United Kingdom (UK) has a mature electricity market that provides the foundation and conditions for building an energy storage business model. In recent years, the UK also revised the policies and market rules that restrict the development of energy storage, gradually clearing away the obstacles to its large-scale application and participation in the power market. Obstacles are worth learning for China. This study first sorts out the status quo of energy storage in the UK and then analyzes this status quo from the aspects of market development focus, participant types, and project scale. The UK's energy storage is then analyzed in detail from the aspects of financial support and system reform, policy incentives, and rule revisions in terms of technological innovation, planning approval system, energy storage asset attribute definition, shared site rules, auxiliary service market, capacity market, and balance mechanism. Finally, based on the adjustment of policies and market rules, this study sorts out the sources of income and business models of UK energy storage projects and summarizes the enlightenment of British experience to our country.

At low temperature, lithium-ion batteries (LIBs) will show impedance increases, intercalated/deintercalated lithium imbalance, low cycle efficiency, capacity fading, and other phenomena, which would result in the charge becoming more difficult than the discharge. Consequently, this seriously affects the low-temperature performance of LIBs. The electrolyte has the greatest impact on the low-temperature performance of LIBs. The electrolyte viscosity increases at low temperature and at poor compatibility with the electrode materials and separators. This results in the decrease of the ionic conductivity and the increase of the charge transfer resistance, which will eventually lead to battery performance degradation. The present study analyzes the visualization map of the low-temperature electrolyte literature for LIBs based on the Web of Science Core Collection database. The CiteSpace analysis shows that research on low-temperature electrolytes can be divided into three stages: initial, stable, and rapid development stages. Research forces are mainly concentrated in China, the United States, Japan, and Germany, among other countries. Accordingly, China is gradually becoming the core force of scientific research. Moreover, countries and research institutions are closely cooperating with each other, and an increasing number of researchers are participating in studies. Two main routes are used to develop a new low-temperature electrolyte: ① a multi-component electrolyte with low viscosity and high ionic conductivity is designed and supplemented by functional additives to improve the low-temperature performance; and ② by studying the interface structure and properties of the SEI film, the electrode material with a high diffusion coefficient is designed to increase the Li⁺ mobility at low temperature and improve the low-temperature performance. In the future, the solid electrolyte breakthrough may completely solve the problem of the poor low-temperature performance of LIBs. At the same time, the combination of computational materials science can accelerate the research and development process and contribute to the deep integration of the industry, university, and research.

Low-cost energy storage is the pivot to future energy systems with a high variable renewable energy (VRE) penetration. Current economic studies on the energy storage measured by the levelized cost of storage (LCOS) are normally based on the technical specifications of storage products rather than on real-life operation conditions. The LCOS is highly influenced by the changing operation conditions when the VRE increases. This study focuses on the LCOS comparisons of various energy storage technologies based on provincial case studies in the western part of China, where the VRE has become the mainstream in the electric power supply. The key factors that are likely to influence the LCOS (e.g., power system regulation duration, regulation frequency, and VRE curtailment) are investigated individually herein.