Lithium ion batteries (LIB) are widely used for mobile energy storage due to their high energy density and long cycle life. However, the limited resources of lithium severely limit its application in large-scale energy storage. In recent years, sodium ion batteries (SIB) have become a promising alternative to LIB due to their low cost and high safety. Hard carbon, with its low redox potential, stable structure, large layer spacing and relatively low cost, is widely used as an anode material for SIB. However, the poor multiplicative performance and low initial Coulomb efficiency of hard carbon anode limit the performance of SIB. This paper reviews the research progress of hard carbon anode for sodium ion batteries, including the mechanism of sodium storage in hard carbon, selection of precursors and the effect of preparation process on the performance of hard carbon.

Lithium ion batteries are widely used in energy storage systems with high energy density, high power density and long service life. The accurate estimation of the usable capacity in the long-term operation state is the key for the energy storage system to participate in power regulation. In order to solve this problem, this paper proposes a method for estimating the usable capacity loss of lithium ion batteries based on Singular Value Decomposition-Double Adaptive Unscented Kalman Filter (SVD-DAUKF) algorithm, which firstly constructs the expression of battery usable capacity considering aging, and then uses the SVD-DAUKF algorithm combined with the equivalent circuit model to identify the model parameters and estimate the state of charge. Finally, combined with the parameter identification results and the definition of usable capacity, the estimation results of usable capacity loss are verified at 1 C, and the estimation error of usable capacity loss is less than 4%.

In order to solve the problem of appearance deformation in the production process of the pouch cell, the possible deformation mechanism in the whole process of the cell production was analyzed, and then a series of solutions were put forward, such as reducing the capacitance current, pressurizing the capacitance and full electrochemical formation. The experimental results show that the heating and pressurization can effectively optimize the bad appearance, reduce the stack thickness of the cell, and improve the interface to enhance the cycle performance of the cell. However, the aging stage after full electrochemical process will consume active substances, resulting in a decrease in cell capacity. Therefore, the loss of cell capacity can be reduced by further adjusting and reducing the charge state of the cell after the cell is fully electrolyzed to improve its appearance, so as to achieve the best improvement effect.

In recent years, with the rapid development of the new energy industry, the high-nickel ternary cathode materials (NCM/NCA) have become widely used in the lithium battery industry due to their high specific capacity and energy density. Increasing nickel content can enhance the reversible capacity and energy density, but introduce some challenges, such as cation mixing (Li⁺ and Ni²⁺), lattice oxygen release, electrolyte decomposition, and decreased thermal stability. These factors contribute to the performance degradation and safety risks. In order to address these issues, recent research has focused on the surface coating, micro/nanostructure design, and element doping to improve the battery performance and safety by protecting particle surfaces or optimizing crystal structures and particle morphology. These improvement strategies for high nickel cathode materials were summarized and compared.

Silicon-based anode materials have problems of volume expansion, surface instability or low electron conductivity. In this paper, porous silicon-carbon composites are obtained by Si morphology control, conductive net-work design, porous structure construction and carbon coating. Si nanosheets can be obtained via balling based on different cleavage energies in different facets of Si. Spray drying of the well-distributed slurry containing silicon nanosheets, carbon nanotubes, and graphite yields porous structures. Liquid state carbon coating of the porous structures leads to the entire carbon coating on both the surfaces of the silicon nanosheets and the whole composites. Coin test shows the composite deliver a specific capacity of 1 000.8 mAh/g and a high initial coulombic efficiency of 93.9%. Full cell tests display high rate property at 1 C and good cycling behavior. These good performances are derived from the conductive net-work structure, the porous structure construction, and the dual-carbon coating of the composite.

Lithium ion batteries are prone to capacity degradation during long-term operation, with varying degrees of degradation and different underlying mechanisms under different operating conditions. Through the study of cycle failure of lithium ion batteries under different conditions, the mechanisms are investigated in order to provide insights for optimizing battery design to enhance the safety and durability of lithium ion battery use. This article summarizes the situation of cycle capacity degradation and failure mechanisms under different temperatures, pressures, charge-discharge rates, overcharging and overdischarging, as well as State of Charge (SOC) cycling ranges. Relevant strategies are proposed to improve the performance of lithium ion batteries and ensure their safe and stable operation.

Lifespan and safety are the core challenges for the large-scale application of lithium-ion batteries, and lithium plating is an important cause of safety issues such as accelerated battery life decay and thermal runaway. Therefore, lithium plating detection has always been a research focus in the field of batteries. Electrochemical impedance spectroscopy(EIS) is a non-destructive in-situ electrochemical analysis method that can reveal the electrode kinetics of different time scales inside the battery, including charge transfer reactions, interface evolution, and mass transfer processes that are affected by lithium plating. Therefore, it can be used as a lithium plating detection method. The lithium plating detection methods were summarized based on EIS in recent years, including: static EIS method, dynamic EIS method, and current interruption method. The principles, advantages, and disadvantages of the three methods were reviewed, and the application prospects of the above methods were prospected.

LiFePO₄ batteries are widely used in new energy vehicles and new energy storage fields due to their high safety and low cost, but their applications are limited by the greatly reduced performance in cold winters, high altitude areas, aviation base stations, and other low-temperature environments. This review focused on the low-temperature performance degradation mechanism of LiFePO₄ batteries, and summarized the recent domestic and international research developments of LiFePO₄ batteries from three aspects: electrode materials modification, electrolyte optimization, and low-temperature heating technology. Finally, a new insight was put forward for improving the low-temperature performance of LiFePO₄ batteries and the future development direction was indicated.

Owning to the low cost and eco-friendliness, water-based processing for the preparation of electrode films is attractive in Li-ion battery industry. A composite binder suitable for water-based processing of Li-rich layered oxide cathodes(LLOs) was prepared by sodium alginate(SA) and polyacrylic acid(PAA). The result demonstrats that adjusting the mass ratio of SA and PAA can control the degree of cross-linking between the hydroxyl group of SA and the carboxyl group of PAA, thus regulating the electrode structure and improving the electrode kinetics. The LLOs electrode films prepared by the water-based processing has excellent electrochemical performance when the mass ratio of SA/PAA is 3∶1. The LLOs‖Li half-cells have a discharge specific capacity of 293.8 mAh/g(4.8 V), and 179.2 mAh/g at a high current density of 3 C. The study will help to design and optimize binders for 4.8 V high voltage LLOs.

This paper presents an original solution to the issue of the silicon-based negative electrode's high volume expansion and ease of detachment from the collector during battery cycling: a modified copper foil collector with graphene coating. The graphene coating makes the collector's surface rougher, which improves adhesion between the collector and the active material and prevents the phenomena of collector detachment from active material. The rate performance and cycle stability of batteries with modified collectors coated with graphene are significantly better than those with Cu foil collectors. At a high rate of 2 C, the silicon-based negative electrode with the improved collector covered with graphene had a discharge specific capacity of 467.2 mAh/g. After 80 cycles at 0.2 C, retention of capacity is still above 50%. In contrast, the one with normal copper foil collector only retained 18.2% of capacity.

During the cycle aging process of lithium-ion batteries, the side reactions occur, such as the structure collapse of the active material in cathode and anode and the decomposition and gas production of electrolyte, leading to the battery swelling and capacity degradation. Studying the evolution law of battery swelling force during its life cycle has great engineering significance for strengthening battery life management. However, there are few literature reports on this field of research. The evolution trend of swelling force and life of lithium-ion batteries during the aging process was explored. It’s found that after differentiating the charging peak value of the swelling force and capacity value during cycling, the absolute values of both show simultaneously the increase trend, indicating a strong correlation between battery swelling force and cycling life. Introducing the swelling force into the battery life prediction model can improve the accuracy of lithium-ion battery life warning model.

All-solid-state lithium batteries (ASSLBs) are considered to be the preferred choice for next-generation energy storage batteries due to their safety and potential high energy density. Solid-state electrolytes, a key component of ASSLBs, have received much attention in recent years due to their nonflammability and good adaptability to lithium metal anodes. Among the current solid electrolytes, garnet-type oxide composite electrolytes show great potential for application. Due to its combination of the advantages of single-phase inorganic oxide solid electrolytes and polymer solid electrolytes, it not only increases ionic conductivity but also effectively reduces interface resistance, which can effectively improve the safety and energy density of batteries. In this paper, the component composition, composite mode, structure, lithium ion transport mechanism of garnet-type oxide composite solid-state electrolyte and interfacial issues in composite electrolytes were elaborated, the existing problems in the composite solid-state electrolyte were pointed out, and their applications prospects were forecasted.

For fixed-type large-scale ground solar power projects, how to choose the installation tilted angle and spacing has a significant impact on the economics of the project. This article mainly introduces how to optimize the system's optimal tilted angle and pitch based on the conditions of a specific project. The conventional methods are analyzed and compared. In order to achieve the purpose of reducing the LCOE of the project, the optimization can be implemented according to the characteristics of the project during the execution of a project.

FeF₃-FeF₂ cathode material was prepared by solvothermal and high temperature calcination methods, and its physical and electrochemical properties were characterized. The test results show that the specific surface area of FeF₃-FeF₂ cathode materials is 11.8 m²/g, which is much larger than FeS₂ (0.5 m²/g). The initial thermal decomposition temperature of FeF₃-FeF₂ cathode materials is 850 ℃, which is about 300 ℃ higher than FeS₂ and about 200 ℃ higher than CoS₂. The no-load voltage of FeF₃-FeF₂ single cell battery is 3.22 V, which is much higher than the no-load voltage of FeS₂ (2.05 V). The initial discharge voltage of LiB/LiF-LiCl-Li₂SO₄/FeF₃-FeF₂ single cell battery is 2.65 V at the current density of 150 mA/cm². When the cut-off voltage is 1.5 V, it can discharge for 308 s. The specific discharge capacity of LiB/LiF-LiCl-Li₂SO₄/FeF₃-FeF₂ single cell battery reaches 160.4 mAh/g, which is 75.3% and 43.5% higher than the LiCl-KCl and LiF-LiCl-LiBr electrolyte systems, exhibiting a longer working time. Therefore, for the development of high voltage, high specific energy, and high specific power thermal batteries, FeF₃-FeF₂ is a promising cathode material for thermal batteries.

Capacity fading of LiFePO₄/graphite (LFP) cell was investigated at different temperatures and an optimal cycling temperature range was found for this type of battery. Also, by using dV/dQ-Q curve, it is found that when capacity loss is 20% of its initial value, the main factor is the loss of active lithium (LLI), which occupies more than 80% of the total loss. The loss of anode material is between 12% and 14% and the loss of cathode material was about 4%-6%. This result provides a theoretical basis for designing and improving of cycle performance of LFP battery. Further, the cycle life was fitted and could be predicted by using temperature acceleration model. And the prediction model is very accurate in the specific temperature range.

In recent years, lithium ion batteries(LIBs) are the state-of-the-art battery technology, which has been widely used in portable electronic devices, electric vehicles, energy storage systems. However, there are still some problems that result the decay of energy and power density of LIB under low-temperature condition, restricting its application in extreme working condition for the following reasons: the diffusion of Li⁺ in the electrode material, the charge transfer and desolvation process at the interface are relatively slow. The increase of the viscosity of the electrolyte results in the deterioration of the wettability of the active material and separator. In addition, charging under low-temperature may lead to the growth of lithium dendrites, which trigger internal short circuit and thermal runaway accidents in the worst case. Based on years of experience in the development of low-temperature LIB and related literature reports, the strategies were reviewed to improve low-temperature performance from the perspective of electrolyte, focusing on the effects of co-solvents with low viscosity and wide liquid range, new lithium salts with high conductivity and low desolvation energy, and additives to form thin and dense SEI, and their challenges on low-temperature performance. Moreover, the future development direction of low temperature LIB was prospected.

Anode-free lithium metal battery has become an academic hotspot due to its high theoretical capacity, energy density and low cost. However, due to the lithium-sparse property of copper foil and the high activity of lithium metal, the lithium deposition/stripping is not uniform, resulting in many problems such as lithium dendrites and excessive lithium consumption, which limits the practical application. In this paper, the advantages, challenges and solutions of anode-free lithium metal batteries were comprehensively reviewed. Four improvement strategies were discussed in detail, including modifying the current collector, constructing a stable solid electrolyte interface(SEI) film, introducing lithium supplementation technology and optimizing the electrolyte. The mechanism of the negative side affecting the deposition / stripping of lithium metal, the advantages of the positive side additional lithium source and the influence of the electrolyte on the reversibility of the anode-free lithium metal battery were discussed. The advantages and disadvantages of the four strategies and the future development direction were summarized.

Since the commercial application of lithium-ion batteries (LIBs), the capacity decline of lithium-ion batteries working in low temperature has attracted much attention from scholars. This paper analyzed and discussed the influencing factors of poor performance of LIBs in low temperature, and summarized the methods to improve the dynamics of low-temperature batteries in recent years from four aspects: electrolyte design, cathode material modification, anode material modification and battery heating technology. Finally, the methods to improve the performance of low-temperature LIBs were summarized and new insights and schemes were put forward to promote the sustainable development of high-performance low-temperature LIBs.

Lithium ion battery dominates the market of portable electronic products and electric vehicles and energy storage. However, more and more attention has recently been paid to the cost and resource availability of lithium. Sodium ion batteries are considered to be the ideal choice for grid-level energy storage systems. There are still various challenges need to be overcome, however, before its commercial application. Among them, the low initial coulombic efficiency is a critical issue that seriously limits the improvement of practical energy density of the sodium ion full battery. This review analyzed the influence factors of low initial coulomb efficiency, such as the solid electrolyte interphase formed due to the decomposition of electrolyte during the first cycle, and the poor reversibility of sodium ion insertion/deintercalation process, as well as the defects and surface functional groups. Also, the paper summarized the emerging strategies to improve the initial coulomb efficiency of sodium ion batteries, such as electrolyte optimization, structure/morphology design, surface modification, and binder optimization, which is of great significance for promoting and realizing the practical application of high energy sodium ion batteries.

Using FePO₄ as the iron source,the LiFePO₄ was prepared by carbothermaI reduction. By changing the feed rate and crushing pressure,the final product LiFePO₄ has different particle size distributions. The current collector made up the cell,which contains the final product LiFePO₄ conductive agents and binders. The results show that the D_max of final product LiFePO₄ is whthin 20 μm and the granularity of mixed liquids is within 35 μm. The compacting density of the coating layer is greater than 2.44 g/m³ and the 0.1 C discharge specific capacity exceeds 159 mAh/g. The final product LiFePO₄ has good performance in practicability.

Despite their wide range of applications, lithium-ion batteries (LIBs) are severely degraded in terms of capacity, rate capability and lifetime at low temperatures, which greatly limits their applications in low-temperature fields. A number of factors cause poor low-temperature performance of LIBs. The microscale processes occurring near the electrode/electrolyte interface, particularly the increased energy barrier for lithium ion (Li⁺) desolvation at the solid electrolyte interphase (SEI) and the slow transport of Li⁺ through the SEI, play a crucial role in the low-temperature performances of LIBs. Therefore, the improvement and development of electrolytes is of significant importance for the further exploration of low-temperature LIBs. This review started by examining the factors that limit the low-temperature kinetics of LIBs, and analyzed the low-temperature rate-determining steps. It then further explored how solvents, salts, and additives improve the low-temperature performances in different battery systems. This Review is expected to provide the informative outlook for the design of the next-generation low-temperature LIBs.

At present, the statues of satellite electrical power supply system is to use Agilent 34980A ground power supply and ground power supply distributor for integration. This paper puts forward an intelligent electrical power supply and distribution test equipment design scheme for the integrated and intelligent test requirements for ground power supply test system. It is composed of channel relay module, command sending module, telemetry state acquisition module and staues display module. It has the characteristics of high reliability, strong versatility and good maintenance. It realizes the modularization and miniaturization of electrical power supply and distribution test equipment, as well as remote monitoring, intelligent monitoring and other functions. At present, it has been applied in the satellite platform test system which has played a strong role in supporting the satellite ground automatic test system.

Some problems in the high nickel/silicon-carbon system of pouch batteries such as gas production at high temperatures and repeated rupture-growth of the solid-electrolyte interphase (SEI), which leads to poor cell cycling and storage performance. In this study, a graphite-based anode blended with 20% silicon-carbon and a ternary NCM811 cathode were employed to investigate the film-forming effect and mechanism of TVSi (Tetravinylsilane), an electrolyte additive, on the surfaces of both the anode and cathode. Experimental results demonstrate that TVSi can preferentially form a dense and stable interfacial film on the surfaces of both electrodes, which significantly enhances the battery's cycle and storage performance. Compared with the general electrolyte, the cell containing TVSi exhibits an increased cycle life by 112 times at 25 ℃, 407 times at 45 ℃, and an improved capacity recovery rate by 3% after 30 days of storage at 60 ℃. SEM and ICP were utilized to characterize the mechanism of TVSi action on the surfaces of both electrodes. The utilization of TVSi additives can address the current calendar life issues in high-nickel silicon-carbon battery systems, accelerating the industrialization of high-energy-density battery products.

In order to achieve the specific energy increase of lithium ion batteries, the use of silicon-based materials to increase the capacity of the negative electrode is a common method for high specific energy lithium ion batteries. SiO_x has been used in power batteries because of its excellent cycling performance. However, in the process of charging and discharging, the volume expansion and contraction rate of the SiO_x particle is large, which often affects the cycle life of the battery. It is helpful to improve the cycle life of silicon-containing high specific energy system to investigate the relationship between particle pulverization and the transition growth of SEI film and the preloading force during the process of expansion and contraction of SiO_x particles. In this paper, the failure mechanism of SiO_x particles was analyzed by analyzing the failure state of silicon anode particles after high specific energy lithium ion battery cycling under different stress conditions.

Thermal runaway of lithium ion batteries is one of major problems hindering the development of higher energy density batteries and their large-scale application. The thermal safety of lithium ion batteries not only depends on the electrode material and battery design, but also varies by their aging modes and degrees. The degradation of electrochemical performance and thermal runaway behavior of aged lithium ion batteries during cyclic aging at high temperature were investigated in this work. The NCM lithium ion batteries were cyclic aged at 72 ℃ and 25 ℃ under 1 C current at CC-CV mode. The electrochemical performances of fresh and aged batteries were first compared, then ARC was used to perform thermal runaway test on fresh and aged batteries to explore the thermal safety variations of batteries after cyclic aging at high temperature, finally, the post analysis of aged batteries was carried out to investigate their aging mechanism. Related results have shown that the electrochemical performance of batteries deteriorated seriously due to the loss of large amounts of active materials in both positive and negative electrodes. During the ARC tests, both fresh and aged batteries occurred thermal runaway. However, the dynamic process of thermal runaway was slowed down due to the consumption of large amounts of electrolyte in aged batteries, thus the overall harm of thermal runaway by high-temperature aged batteries was alleviated.

This work conducts the charge/discharge cycling tests of graphite||LiFePO₄ pouch batteries at temperatures of 25, 45, 60, 70, and 80 °C to calculate the battery cycling capacity degradation rate. Arrhenius formula is used to calculate the activation energy of LiFePO₄ batteries at different temperatures. Differential capacity vs. voltage (dQ/dV) curves is used for capacity loss analysis. Combined with characterization data such as SEM, ICP, XRD, etc., the results show that when the temperature exceeds 60 °C for cycling test, the growth of the SEI layer at graphite electrode interface accelerates, the microstructure of positive and negative electrode active materials ruptures, and the dissolution/precipitation of transition metal ions aggravates, leading to deterioration of battery performance and accelerated capacity degradation.

The process of the event that one of two circular solar arrays fails to deploy after Cygnus-18 cargo spacecraft of Northrop Grumman Company launched in orbit was sorted out. Combined with the total scheme of Cygnus-18 cargo spacecraft and the evolution of the solar array design scheme for power system, the design scheme of the spacecraft UltraFlex solar array was analyzed. Combined with the technology detail of the UltraFlex solar arrays for Orion spacecraft and the deploy failure of circular solar arrays for LUCY asteroid probe, the failure reason was analyzed and studied. Some suggestions for the development of circular flexible solar array for spacecraft in China were put forward. The progress of the event will be continually tracked, and the further in-depth research will be carried out.

Taking 280 Ah lithium iron phosphate(LFP) battery as the research object, the discharge curve of the battery under the current rate of 0.5 C was measured in the standard environment. First, the battery was discharged at 0.5 C to the state of charge(SOC) of 30% and rested for 3 h to record the stable open circuit voltage(OCV). Then the battery was discharged from 30%SOC to 10%SOC at 0.5 C, meanwhile the test was interrupted after every single step of 2%SOC and rested for 3 h to record the corresponding stable OCV. Finally the SOC-OCV curve was obtained. The result shows that the SOC-OCV curve of the battery between 30%-10% is nonlinear, especially in the range of SOC at 24%-26% with a significant slope change. Therefore, polynomial fitting of SOC to OCV between 30%-10% theoretical SOC is performed, and the adjusted R-square of polynomial fitting is 0.996 5. Meanwhile the linear fitting of SOC to OCV between 26%-32% SOC is performed, and the adjusted R-square of linear fitting is 0.999 49. Both fitting equations are of desirable goodness-of-fit. The battery is charged to 100%SOC and then discharged to nearly 30%SOC in order to ensure the performance and the outgoing state of charge. The OCV of battery during standby period, the discharge capacity from 100% SOC to nearly 30% SOC and the total discharge capacity are recorded as OCV, C_y and C, respectively. On the basis of the relation between SOC, C_y, C and OCV, this study proposes two capacity prediction models based on the above mentioned fitting equations, then OCV and C_y are brought into the capacity prediction model to obtain the prediction capacity. The following conclusions are drawn from this study: the capacity prediction errors under the stable OCV after rest for 12 h were within ±1.5%; in the case of a short standby time, a correction factor of predicted capacity should be introduced to ensure the same level of prediction error; the prediction methods are feasible, and the prediction errors under two models are basically the same in the range of SOC selected.

Using high nickel ternary cathode material and silicon carbon anode material, 3.6Ah 18650 lithium ion battery was successfully prepared through the selection of anode material and optimization of electrode surface density parameters. The 18650 battery has a volumetric energy density of 751 Wh/L, can be discharged at 3 C multiplication rate, and has an operating temperature range of –40~60 ℃. The battery has good multiplicity performance, cycling performance, low temperature discharge performance and high temperature discharge performance, with good overall performance, which can meet the requirements of wide temperature range and long cycle use.

In photovoltaic power generation systems, the output power of photovoltaic cells is susceptible to environmental factors such as light intensity and temperature, and has typical nonlinear characteristics. Therefore, in order to improve the efficiency of photovoltaic cells, the photovoltaic cells required a real-time tracking so as to ensure the maximum power output. This paper summarized the current research status of MPPT algorithms for photovoltaic arrays at home and abroad, introduced the algorithms for tracking maximum power points of photovoltaic arrays under uniform lighting and local shading conditions, analyzed the principles and compared their advantages and disadvantages, refined the existing problems, and sorted out the next research ideas. Finally, the current research direction of MPPT was discussed, and its future development trends were pointed out for readers' reference.

Building user-configured energy storage for the distributed PV can promote the consumption of the distributed PV. In the presence of the unaffordable high configuration cost of energy storage system for a single user, an optimal capacity model of user side shared energy storage power station was proposed. Based on time-of-use electricity price in the user side, the capacity optimization model of the shared energy storage was constructed with minimizing the daily operating cost of the user group with the configuration of the shared energy storage as the objective, including the investment and operation and maintenance cost of energy storage, the electricity cost of the user side, and the service cost of the shared energy storage. The tackling method of the nonlinear terms in the optimized model was provided. The extensive case studies were conducted based on the four typical daily scenarios of sunny, cloudy, rain and snow, verifying the economy of the proposed shared energy storage allocation considering multiple typical daily scenarios compared with the independent energy storage allocation, as well as the reliability of the proposed shared energy storage allocation compared with the allocation considering only a single special weather scenario.

In real-world vehicle operational scenarios, battery temperature distribution within a battery pack demonstrates non-uniform attributes. Particularly, under elevated operating temperatures, the pace of battery degradation escalates, potentially resulting in accelerated diminishment of both capacity and power. This study centers on lithium-ion batteries and employs extended cycles of 1 C charge-discharge to methodically characterize and assess battery pack attributes including temperature distribution, degradation behavior, and current dispersion. Furthermore, a comparison is drawn with individual baseline cells. Research findings unveil that all batteries within the battery pack encounter elevated temperature elevation and manifest a swifter degradation rate when contrasted with the baseline cell. In particular, following 1 815 cycles, the capacity of the central battery within the pack diminishes to 61.2% of its initial capacity, whereas the baseline cell sustains 86.5% of its capacity. Additionally, both resistance and current distribution within the battery pack manifest comparable patterns of alteration. Through experimental quantification of the influence of non-uniform temperature distribution on battery degradation, this study enhances the comprehension of the degradation tendencies of modular lithium-ion batteries subjected to temperature gradients. These insights bear substantial implications for the optimization of battery design, enhancement of battery performance, and extension of battery lifespan.

According to the temperature control requirements of battery pack for liquid cooling system under different discharge rates, a single input and double output parallel flow channel was designed, and a cooling scheme with four liquid cooling plates was proposed. The structure of the single input and double output parallel flow channel was optimized with the goal of the pressure drop and flow uniformity. The results show that the difference of the maximum temperature difference between the battery modules does not exceed 0.08 ℃ when cooling with the single input and double output parallel flow channel structure, the cooling effect is balanced, and the temperature consistency between the batteries is high. When the discharge rate is 2.5 C, compared with the cold plate placed on the side of the battery pack, the maximum temperature of the cold plate placed between the modules decreases by 1.27 ℃, and the maximum temperature difference decreases by 1.1 ℃. After the optimization of the flow channel structure, the maximum flow deviation of each flow channel decreases from 20% to 2.4%, and the pressure drop decreases by 30%. Compared with the serpentine flow channel, the maximum temperature and maximum temperature difference of the optimized flow channel reduce by 2.22 and 1.12 ℃

Commercial lithium iron phosphate/graphite cells for energy storage were selected as study objects for exploring their cycling performance evolution under different charging cut-off voltages (3.65, 4.20, 4.40, 4.60 and 4.80 V). The capacity loss model of lithium iron phosphate cells under different degrees of overcharge cycling was established for determining the cell capacity loss trend. Furthermore, with the help of non-destructive analysis of voltage differential curve (DV), combined with the microscopic topography characterization and elemental analysis of key electrode materials, the capacity attenuation mechanism of lithium iron phosphate cell under overcharge cycle condition was further studied. The results show that the higher the overcharge voltage, the faster the cell capacity decay. The average capacity decay rate reaches 0.232‰ per cycle under 4.60 V overcharge cycle, which is 3.1 times that of the normal cycle.

The efficient recycling and utilization of spent lithium-ion battery cathode materials aligns with China's new low-carbon development goals and promotes energy recycling. The capacity failure mechanism and pretreatment methods of spent lithium-ion batteries were introduced. The research status of traditional recycling methods such as pyrometallurgical recycling, hydrometallurgical recycling for the cathode materials obtained were analyzed. Direct recycling is the most ideal method for cathode materials of spent lithium-ion batteries. The characteristics of solid-phase regeneration, hydrothermal restoration, molten salts repairing, electrochemical regeneration methods were described, and the advantages and disadvantages of each method were summarized. Finally, the problems and challenges that recycling of spent lithium-ion batteries may face from multiple perspectives were discussed.

Excessive current density and high roughness of electrode surface during charging and discharging of lithium ion batteries will lead to uneven lithium deposition. The growth of lithium dendrites will puncture the SEI film ( Solid Electrolyte Interface film ) formed by the reaction of the anode material with the electrolyte. Lead to direct contact between lithium dendrites and electrolyte. Part of the dendritic fracture generates lithium metal particles. Part of the electrolyte and the continuous side reaction to produce lithium compounds, that is, dead lithium. It has a great influence on the safety and performance of lithium batteries. At present, the problems such as lithium dendrites and dead lithium in the SEI film are still not effectively solved. In this paper, the formation mechanism of SEI film, lithium dendrites and dead lithium in lithium batteries and some suppression methods proposed at this stage are reviewed. The key problems and future development directions are discussed. It provides a certain theoretical basis and practical guidance for the field of battery research.