With the rapid development of the new energy industry, lithium-ion batteries are extensively used in the energy storage field. To better prevent and control fire and explosion accidents in energy storage stations, the thermal runaway characteristic of lithium iron phosphate batteries for energy storage requires to be examined more thoroughly. In this study, under adiabatic conditions 280 Ah lithium iron phosphate battery thermal runaway experiment was performed, and the self-generated thermal temperature T₁ was 70.26 ℃, the thermal runaway trigger temperature T₂ was 200.65 ℃, and the maximum thermal runaway temperature was 340.72 ℃. Two temperature rise rate peaks of 3.59 ℃/s and 1.28 ℃/s occurred during the thermal runaway process. Meanwhile, the kinetic parameters of the battery were also quantified in the self-generated thermal phase, and the total heat released during the thermal runaway of the battery was 1511 kJ. Finally, the study analyzed the causes of battery rupture and damage in the adiabatic environment that was due to the high internal pressure and violent reaction. The research content of this study compensated the gap in the study of thermal runaway characteristics of 280 Ah large lithium iron phosphate battery under adiabatic conditions and has theoretical guidance importance for fire and explosion accidents in energy storage stations.

With the widespread use of electrochemical energy storage, safety accidents in energy storage systems occur frequently. In the energy storage system, once the thermal runaway of lithium-ion batteries occurs, the combustible fumes are very simple to ignite, leading to fire and explosion mishaps. In large energy storage systems, the gas flow from thermal runaway and thermal runaway propagation of batteries is exceedingly harmful and expensive to test. Therefore, it is necessary to examine the behavior of thermal runaway gas flow in an energy storage cabin based on the model. In this study, a test of thermal runaway venting gas production was conducted for a lithium-ion battery with a LiFePO₄ cathode, and the battery venting gas production rate and gas composition were obtained as model inputs. A megawatt-hour level energy storage cabin was modeled using Flacs, and the gas flow behavior in the cabin under different thermal runaway conditions was examined. Based on the simulation findings, it was discovered that the volume of gas inside the energy storage cabin after the battery's thermal runaway was influenced by the battery location and the number of thermal runaway batteries. When the number of thermal runaway batteries is <3, the higher the module position, the larger the area of combustible gas diffusion. When the number of thermal runaway batteries is >3, the number of batteries increases, and the lower the module position where thermal runaway occurs, the larger the area of combustible gas diffusion. For the same height of the module, the volume of combustible gas formed at various locations was the same, and the combustible gas in the battery room will spread to the control room. Additionally, adding pressure relief plates on both sides of the energy storage cabin can efficiently release gas from the cabin, but the impact of pressure relief is affected by the pressure relief plates' location and area.

This study explores the ability of cold plates to inhibit the thermal runaway propagation of lithium-ion battery packs using a numerical method. Topology optimization was conducted to decrease the fluid temperature and power consumption of traditional cold plates with straight channels. The thermal runaway propagation model of a prismatic lithium-nickel-cobalt-manganese oxide battery pack was built using the Arrhenius formula. To confirm the proposed model's high accuracy, its results were compared with those of existing models. A follow-up study was conducted based on this model, and a cold plate was placed between the batteries. To ensure the cold plate reliability in a high-temperature environment, the fluid temperature within the plate was first analyzed. The results showed that the maximum fluid temperature with straight channels exceeded the boiling point when the flow rates were 0.01 m/s and 0.05 m/s during the thermal runaway, inducing the danger of local high pressure. When the flow rate was 0.1 m/s, the maximum fluid temperature with straight channels was lower than the boiling point, and the cold plate inhibited the thermal runaway propagation of the battery pack. A variable density method was used to optimize the cold plate topology, aiming to improve the excessive fluid temperature of the cold plate with straight channels. The performance of the optimized cold plate was analyzed and compared with that of the straight channel plate. The results showed that the inhibition effect of the optimized cold plate was better. The fluid temperature and power consumption were lower than those of the traditional cold plate with straight channels; when the flow rates were 0.05 and 0.1 m/s, the maximum fluid temperatures were 33 ℃ and 28 ℃ lower than those of the cold plate with straight channels, and the power consumptions were 17% and 26% lower, respectively.

With the rapid advancement of electrochemical energy storage technology, intrinsic safety concerns about energy storage systems have emerged. Nonetheless, the "short board effect" of the battery system caused by the mismatch of inherent differences in battery cells and the traditional fixed series parallel grouping method is the primary reason for the current electrochemical energy storage system's safety and economic problems. Recently, digital energy storage systems based on dynamically reconfigurable battery network (DRBN) have received extensive attention. By deeply coupling low-power semiconductor devices to the batteries, DRBN transforms the battery from an electrochemical reaction device to a new type of digital device and eliminates the thermal accumulation and thermal runaway problems caused by overcharge and overdischarge in principle by reconfiguring the topology of the physical connection of the battery in milliseconds, achieving intrinsic safety at the battery system level. Furthermore, DRBN can quickly diagnose and remove faulty batteries and keep the electrochemical energy storage system running, which greatly improves the availability and reliability of the system. This paper explains the intrinsic safety mechanism of digital energy storage systems in the online diagnosis of sudden faults and rapid automatic isolation of suspected faults using an actual engineering case study, paving a new path for the safety and economy of electrochemical energy storage systems.

The effectiveness of early warning from different detectors in an energy storage cabin is essential for the safe operation of an energy storage system. First, the thermal runaway process and gas production mechanism of lithium iron phosphate batteries are introduced. A typical energy storage cabin environment was constructed, taking 13 Ah and 50 Ah prismatic lithium iron phosphate batteries as research objects. A 1 C current was used to overcharge the battery cells to thermal runaway. At the same time, H₂, CO, volatile organic compounds (VOCs), combustible detectors, smoke, and temperature sensors were used to provide a safety early warning, and the effectiveness of different detectors for the early warning of battery thermal runaway was analyzed. The test results showed that when overcharging batteries with different capacities to thermal runaway, the alarms of all detectors were generally H₂, CO, VOCs, smoke detectors, and combustible gas detectors, but the temperature detectors did not provide an alarm. A higher battery capacity was associated with larger amounts of gas and white smoke produced after overcharging and an earlier alarm time from the characteristic gas detectors, such as H₂, CO, and VOCs, which is more conducive to the thermal runaway warning of large-capacity batteries. Among them, the H₂ detector had an early alarm time and obvious change characteristics, which is more suitable for early warning of battery thermal runaway. The alarm time of the smoke detector was too late, and it did not provide an effective warning. These results can provide effective experimental data to highlight the need for an early warning of thermal runaway in lithium iron phosphate energy storage cabins.

Various issues associated with the application of electrochemical energy storage include thermal runaway, fire, and explosion. Therefore, the safety application of electrochemical energy storage has attracted significant attention, and experimental studies on the thermal runaway of prefabricated cabin energy-storage cabinets are being conducted. This study analyzes the tendency of the voltage, temperature, oxygen concentration, carbon monoxide concentration, and other parameters for the electrochemical energy storage system under the heat abuse trigger, and some useful conclusions have been drawn. Further, the thermal runaway process and its early warning have been discussed systematically. The experimental results show that the cell temperature increases rapidly, reaching a maximum temperature up to 1000 ℃, and the change in voltage values and its early characteristics occur earlier than that of temperature under the heat abuse, indicating that the cell voltage is an obvious signal for the thermal runaway warning process. The temperature changes in the electric battery module show that the liquid cooling system's partition effectively delays the temperature change within the electric module box, ensuring the battery system's safety while thermal control occurs below the electric module box. Based on the analysis of the generating gas of the thermal runaway process, changes in CO concentration in the electric battery module and cabinet can provide basic data for the setting and application of a gas alarm detector. The anticipated peak value of the heat release rate based on oxygen concentration is high, while total heat is low, allowing for early detection and control of the energy storage system fire. Multi-information fusion detection and early warning technology should be developed for the complex characteristics of the electrochemical energy storage system thermal runaway process, which is meaningful and valuable.

The research object was a square aluminum shell lithium manganate cell and a lithium manganate battery pack to study the combustion and explosion characteristics of a lithium-ion battery pack. 2 C current constant flow charging and setting a high cut-off voltage was used to analyze its combustion and explosion characteristics. The experimental results revealed that the safety valve rupture, jet fire, and an explosion occurred instantly after the lithium-ion battery was overcharged for 774 s, with the maximum explosion pressure reaching 556 kPa at 45 cm from the explosion center. In the event of overcharging without a BMS, the battery pack, which was composed of 13 cells in series, experienced safety valve rupture, discharged fire, and local explosion. During the experiment, multiple pressure peaks are formed, and the maximum explosion pressure at 45 cm from the explosion center was 915 kPa. When lithium-ion battery packs were placed at a distance of 6.5 cm apart, overcharging one of the battery packs without a BMS can cause combustion of the other battery packs, resulting in a fire spread.

To investigate the diffusion process of injected gas after the thermal runaway of the lithium-ion battery for vehicles, the CONVERGE CFD model was selected to simulate the gas injection of the thermal runaway cell of the square ternary lithium-ion battery under the 100% SOC state. The diffusion law of thermal runaway gas inside the battery pack, the accumulation situation, and the gas mass flow characteristics at the battery pack exhaust port under the four schemes were analyzed using the tracer particle labeling method. The research results show that the thermal runaway gas diffuses to the top of the box when it is sprayed for 4.3 s. The gas gradually spread to the surroundings after accumulating at the top of the box. The gas can diffuse to the upper half of the entire box at the fastest 22.3 s. The position of the upper exhaust port affects the diffusion and accumulation of gas within the battery pack. A comparison of the four schemes reveals that setting the exhaust port on the upper part of the box and increasing the number of exhaust ports will aid in the discharge of gas from the battery pack, reducing the accumulation of internal gas; solely relying on the exhaust port will not deplete all the thermal runaway gas in the box, and obvious gas accumulation can be observed in the battery pack's inner corner.

The prefabricated cabin energy storage with a double-layer structure can effectively minimize floor space, and is suitable for applications in areas with limited land resources. However, this form of energy storage doubles the battery capacity per unit area, and its safety under extreme conditions such as thermal runaway is severely tested. In this study, a numerical simulation method of a gas explosion is used to investigate the consequences of thermal runaway gas explosion in a double-layer prefabricated cabin lithium iron phosphate energy storage power station. First, the double-layer structure prefabricated cabin energy storage is introduced; then, a simplified model of the double-layer prefabricated cabin energy-storage power station is established using the explosion simulation software FLACS; finally, the vaporized electrolyte caused by the lithium-ion battery′s thermal runaway is used as the fuel, and the thermal runaway combustion and explosion characteristics of the double-layer prefabricated energy storage tank were simulated and studied. The study shows that the shock wave generated by the gas explosion in the double-layer energy storage cabin spreads to the surroundings when the pressure relief hole is opened, and impacts the adjacent energy storage cabins, which may result in several explosions. Compared with the lower energy storage cabin's explosion, that of the upper storage energy storage is low. Space is open after the cabin pressure relief hole is opened, the pressure relief cooling effect is more significant, and the high temperature and overpressure shock effect caused by the explosion is low. The results of this study can provide theoretical and data support for the safety and fire protection design of a prefabricated cabin energy-storage power station with a double-layer structure.

In the context of carbon peak and carbon neutralization, renewable energy sources, such as wind and light, are gradually becoming the dominant energy sources. Energy storage facilities, primarily lithium iron phosphate batteries in prefabricated energy storage cabins, are required. However, lithium iron phosphate batteries with a high risk of thermal runaway are likely to cause great fire hazards. Although perfluoro-2-methyl-3-pentanone is an excellent substitute for halons and HFCs fire extinguishing agents, its suitability for extinguishing energy storage lithium battery fires and suppressing thermal runaway is debatable. A perfluoro-2-methyl-3-pentanone fire extinguishing method combining "local application" and "total submersion" is proposed based on some experimental results of perfluoro-2-methyl-3-pentanone applied to lithium iron phosphate battery fires. The fire-extinguishing mechanism is verified by model tests, and the relevant design parameters are obtained. An engineering case is used to discuss the application scheme of a perfluoro-2-methyl-3-pentanone fire-extinguishing system in a prefabricated energy storage cabin.

With the continuous application of lithium-ion batteries in EMU, subway, tram, and other rail vehicles, the safety and safety performance evaluation of lithium-ion batteries in use has always been a major concern, and major standardization organizations and application enterprises at home and abroad have developed the corresponding safety evaluation standards. This study briefly introduces the current guidance and normative standards in the field of rail transit at home and abroad, including TJ/JW 126—2020, Q/CRRC J39—2019, TJ/JW 127—2020, Q/CRRC J37.1—2019 and IEC 62928:2017, IEC 62619:2017. This section focuses on the battery monomer, module, and pack, compares and analyzes the battery safety performance evaluation methods of IEC and domestic standards, and presents the differences in the application scope, test objects, test methods, and test requirements at home and abroad. A comprehensive analysis of the three aspects of machinery, environment, and electrical safety requirements reveals that domestic standards for power lithium-ion battery setting test projects are relatively comprehensive and higher than the requirements of foreign standards, but the foreign standard test focus more on the electrical safety requirements. Finally, based on the differences in service and working conditions between the locomotive and electric vehicles, suggestions for further improvement in lithium-ion battery safety standards for rail transit are proposed to evaluate the rail transit battery system more scientifically and targeted and provide a crucial basis for the application and development of new energy storage systems in rail transit.

Currently, studies on the thermal runaway propagation characteristics of lithium-ion batteries mainly focus on the battery shape and trigger mode. This study uses a self-developed lithium-ion battery array cascade thermal-runaway experimental platform to investigate the thermal runaway propagation characteristics of lithium-ion batteries using different states of charge (SOC) and arrangement intervals. The results show that the rate of thermal runaway propagation decreases with a decrease in SOC. The total duration of thermal runaway propagation in a 70%SOC battery pack is 70 seconds longer than that in a 100%SOC battery pack. The maximum thermal runaway propagation temperature in a 100%SOC battery pack can reach 621.81 ℃, and no thermal runaway propagation occurs in a 50%SOC battery pack. For batteries with 100%SOC, the larger the transverse spacing between batteries, the more difficult it is for a thermal runaway to spread between battery packs. Thermal runaway will not spread in battery packs when the transverse spacing between batteries is 3 mm. The thermal runaway between batteries mainly propagates in a layer-by-layer approach. The research has a high application value for optimizing battery layout and preventing and controlling battery thermal runaway propagation.

The thermal management system is a key technology for maintaining the performance and service life of battery energy storage devices. It is difficult to perform a comprehensive numerical analysis of the entire thermal management system due to the numerous battery cells and the complex internal structures of large-capacity battery energy storage devices. This study proposes a porous medium modeling method for battery modules, and a conjugate heat transfer numerical analysis for the air-cooled thermal management system of MW-scale containerized battery energy storage is performed. The research shows that the method can simulate the flow and heat transfer in the battery energy storage cabin and the battery module simultaneously, resulting in more detailed and accurate flow and heat transfer characteristics. The temperature distribution difference between the battery modules and the cells in modules is caused by two main factors. The first is the uneven distribution of airflow in battery modules, while the second is the flow and heat transfer characteristics formed by the airflow and heat accumulation in the battery energy storage cabin. This study's proposed analysis method could provide technical support for the design and optimization of thermal management systems in large-capacity centralized battery energy storage.

The positive and negative electrodes of a lithium battery are crucial parts of the battery. The electrode coating quality is significantly related to the battery's performance and service life, and a defective electrode is often the cause of the battery's potential safety hazard. This study presents a set of algorithms based on a whale optimization algorithm-back propagation neural network (WOA-BPNN) to further improve the automation level of defect detection and recognition for lithium-battery electrode plate coating. First, image preprocessing is performed on the collected lithium-battery electrode plate coating image. Then, the shape, gray, and texture features of the defect target area are extracted after being segmented from the image. Next, the BPNN is built, and the fused feature vector after serial fusion is used as the network's input. Finally, the WOA is used to assist in parameter adjustment while training the neural network classification model to further improve the model's recognition accuracy. This algorithm can accurately detect and recognize eight types of common lithium-battery electrode plate coating defects, including scratch, metal exposure, hole, crack, abnormal pollution, and carbon spalling. The experimental results show that when the width of the lithium-battery electrode plate is 200 mm, the detection accuracy is 0.05 mm and the detection speed is 60 m/min, and the average missed detection rate of this algorithm is 1.68%, the average false detection rate is 0%, and the average classification and recognition accuracy is 97.08%. This algorithm can be used to effectively detect defects in lithium-battery electrode plate coating at high speeds and with high precision, and it has practical applications in the field of lithium battery intelligent manufacturing.

LiFePO₄ batteries are widely used in the field of energy storage because of their safety. The test object was a soft-pack LiFePO₄ LFP battery with a rated capacity of 21 Ah that was float-charged at high voltages of 4.05 V, 4.25 V, 4.50 V, and 5.0 V for 24 h at 25 ℃. The high-temperature thermal runaway and battery material thermal stability were investigated. The results show that bulging occurs at voltages of 4.25 V, 4.50 V, and 5.0 V, and the bulging increases as the voltage increases. At the 5.0 V battery rupture, the anode active material was dissolved, the copper current collector was exposed, and a substantial amount of lithium was deposited simultaneously. In the high-temperature thermal runaway test after float charging at 4.05 V, 4.25 V, and 4.50 V, the battery's rupture temperature decreased as the voltage increased. The thermal runaway-triggering temperature increased from 249.86 ℃ to 278.65 ℃, and the early rupture-released energy raised the thermal runaway trigger temperature; however, the system was unsafe. The maximum temperature of the thermal runaway increased from 484.67 ℃ to 516.08 ℃, the maximum temperature rise rate also increased significantly, and the time of thermal runaway to the maximum temperature decreased. The battery's thermal stability deteriorated after high-voltage float-charging, and the thermal runaway became more severe. The separator begins to undergo a phase transition at 120.63 ℃ and begins to decompose at 367.06 ℃. However, the positive and negative electrodes did not decompose and had good thermal stability. Therefore, the float voltage must be precisely controlled to make the battery safe and stable to use.

Prismatic lithium iron phosphate (LiFePO₄) Li-ion cells at the end of life (EOL) were selected as the research subject. A testing metal plate was used to simulate the cell with a binding force in a battery system. The effects of the binding force on the over-discharge, overcharge, external short circuit, heating, and nail penetration performance were investigated systematically. The binding force strongly affected cell safety and could reduce the safety risks and improve safety performance. A binding force about 3 kN could lead to the following: less swelling, avoiding rupture and electrolyte leakage during over-discharge; lower probability of explosion during overcharge; retarded growth of internal resistance and swelling; reduced electrolyte leakage and internal short circuit occurrence in an external short circuit; reduced thermal runaway temperature in heating; improved the nail penetration safety, avoiding fire, flame, and thick smoke release. This research improves the understanding of the safety of LiFePO₄ power batteries and can provide useful data to assist in battery system design and safety standard formulation.

Lithium plating is induced in lithium-ion batteries during fast charging, resulting in severe capacity fading and possible safety issues. Therefore, the accurate detection of lithium plating is vital for the safe operation of lithium-ion batteries. This study explored the application of titration gas chromatography (TGC) quantitatively detect lithium plating in lithium-ion batteries. The TGC can accurately detect the amount of plated lithium on the graphite anode, with a detection limit of 2.4 μmol Li. First, the relationship between H₂ concentration and H₂ signal area detected using TGC was calibrated using a standard gas of known concentration. The feasibility of the experimental device was further analyzed through tests on samples containing different lithium metal contents, which demonstrated that the developed detection system could quantitatively detect lithium plating, and the relationship between the amount of metallic lithium and the H₂ concentration detected using TGC was determined. Moreover, the amount of plated lithium on the anode detected using the TGC method was consistent with the results measured by nuclear magnetic resonance, demonstrating the TGC method's high accuracy. Finally, the TGC method was used to detect the amount of plated lithium within two 1 Ah lithium-ion batteries after low-temperature charging. The results were consistent with the amount of plated lithium estimated from battery capacity loss, with errors less than 7%. This study demonstrates that the TGC method can be used to quantitatively detect lithium plating in lithium-ion batteries and that it has the advantages of low cost, feasibility, and scalability.

This study introduces a risk assessment method for the safe operation of batteries based on a combination of weighting and technique for order preference by similarity to ideal solution (TOPSIS) to prevent and improve the current situation of frequent fire and explosion accidents caused by poor battery operation in energy storage power stations. First, the causes of accidents are identified by consulting literature, standard specifications, and accident investigation reports, and the safe condition that the battery should have during operation is described based on current standards. The risk assessment system is established from six aspects: the battery's basic situation, the battery's service condition, external stimulation, the operating environment, the safety monitoring and protection system, and human factors. Second, the subjective and objective weights of indicators in the risk evaluation system are determined using the analytic hierarchy process and entropy weight method, and the two weights are combined. Finally, the TOPSIS method is compared with the standard value to comprehensively evaluate the battery's safe operating risk. This method is applied to the battery operation risk assessment of four energy storage power stations. The evaluation results show that three of them have some issues with battery operation, but the overall safety situation is relatively good, while one has more serious problems in the operation risk index management and urgently requires improvement. The results are consistent with the actual situation of battery operation risk at each site, demonstrating that the method is reasonable and feasible.

State of Health (SOH) is an important index for evaluating the aging degree and remaining service life of lithium-ion batteries. However, SOH cannot be obtained by direct measurement. This study proposes a method to extract indirect health feature parameters based on time warp profile (TWP) and estimate the SOH using a vector machine regression (SVR) model. First, TWP converts the different cycle charge-discharge voltage curves of a lithium-ion battery into a phase difference curve. Then, four indirect health features are extracted from the phase difference curve. Further, SOH is estimated using the SVR model of the linear kernel function. Finally, it is verified by measured data of energy storage power station and the open-source data sets of NASA, Underwriters Laboratories Inc.-Purdue University (UL-PUR). The experimental results of energy storage power station data show that the sample standard deviation (SSD) of the root mean square error and mean absolute error of the TWP-SVR model is less than 0.0015, and the interquartile range (IQR) is less than 0.0022; the SSD and IQR of mean absolute percentage error are 0.0152 and 0.0220, respectively, indicating that the proposed TWP-SVR method maintains high accuracy and good stability.

Lithium deposition on the negative electrode of lithium-ion batteries may induce thermal runaway that can lead to safety accidents. The occurrence of lithium precipitation side reactions can be reduced effectively by optimizing the battery design parameters. Therefore, this study proposes a parameter design optimization method for lithium-ion batteries based on a three-dimensional electrochemical, thermal coupled lithium precipitation model. First, the model parameters were classified, and the corresponding parameters were obtained using experiments, exact measurements, literature searches, and parameter identification, respectively. The reversible lithium re-embedding mechanism and heat production model were added to establish a three-dimensional electrochemical, thermal coupling lithium precipitation model. After constructing the model, the accuracy of the model was verified. The verification results showed that the model could simulate the changes in the terminal voltage of the battery at room temperature and low temperature and could quantitatively describe the nonhomogeneous phenomena, such as the degree of lithium precipitation and temperature distribution inside the battery during low temperature large rate charging. Finally, the effects of the battery design parameters on nonhomogeneous lithium precipitation were investigated by analyzing the electrode size and lug position. The simulation results showed that increasing the electrode length would increase the temperature difference in the electrode area and the inconsistency of the current density. The combined effect would advance the lithium precipitation time of the battery slightly, but the effect on the overall degree of lithium precipitation of the battery was relatively small. When the position of the battery tab was on the opposite side of the axis in the longitudinal direction, it could effectively alleviate lithium deposition on the negative electrode, and the relative lithium precipitation degree was reduced by 16.7%.

Lithium-ion batteries have become the main energy storage unit of electric vehicles due to their advantages of high specific energy density, high discharge power, and mature production technology. However, the lithium-ion battery generates much heat during the charging and discharging process, which seriously affects its operation safety and service life. Therefore, adding a thermal management system during the lithium-ion battery operation plays a vital role in improving the safety and service life of the lithium-ion battery module. In this paper, the 21700-capacity NCM811 lithium-ion power battery module is the research object. The experimental method is used to study the performance of an insulating oil immersion cooling system under the static cooling condition when the charge and discharge rates are 1 C, 1.25 C, and 1.5 C, respectively. Under insulating oil static cooling conditions, there were different oil immersion amounts (V_R = 0.2, 0.5, and 1) and ambient temperatures (15 ℃, 20 ℃, 25 ℃, and 30 ℃). Furthermore, under insulating oil dynamic cooling conditions, there were various oil immersion amounts (V_R = 0.2, 0.5, and 1), flow rates (3 mL/s, 6 mL/s, 9 mL/s, and 12 mL/s), and the position of the insulating oil inlet and outlet for the battery module's temperature rise characteristics. The results demonstrate that the application of an insulating oil immersion cooling system has a noticeable effect on reducing the maximum temperature and improving the temperature uniformity of the module. The thermal management effect is significantly improved with the increase in oil immersion and is very sensitive to ambient temperature changes under static cooling. Moreover, the thermal management effect of the battery module is considerably enhanced under dynamic cooling of the insulating oil with the increase in volume and flow rate, as well as the optimization of the import and export process.

This study explores the structure of a novel type of liquid-cooled shell battery module using a numerical simulation method. Experiments were used to investigate the liquid-cooled shell structure's heat dissipation and spread suppression characteristics. The module comprised 4 × 5 cylindrical batteries, the liquid-cooled shell, and multiple flow channels inside the shell for the coolant flow. The equivalent circuit model (ECM) of the battery module was established to simulate the battery's heat generation while studying the influence of the internal flow channel arrangement on thermal performance. The maximum temperature, maximum temperature difference, and inlet and outlet pressure drop of the battery module were taken as the performance evaluation indexes, and the expectation function was introduced to obtain the shell's optimal flow channel arrangement. A liquid cooling shell with a single inlet and two outlets was prepared based on the optimized flow channel. A 18650 real battery module was assembled for the thermal performance experimental study. Notably, the thermal performance of the single-in-two-out structure outperformed that of the single-in-one-out structure. Compared with the baseline case, the maximum temperature of the optimized flow channel Case 1 (one in and two out on the short side) increased by 0.3%, but the temperature difference decreased by 8.87%, and the pressure difference decreased by 66.5% under a 3 C discharge and 1 m/s inlet flow rate. In the real battery module experiment, the higher the charge and discharge rates, the higher the battery temperature and the greater the influence of the joule effect of the bus discharge. A low-temperature coolant will lead to low discharge efficiency of the battery module. Finally, a high-power battery heat generation model was used to simulate the thermal runaway. The experimental results revealed that the temperature of adjacent batteries was 57.4 ℃ and that thermal runaway and thermal spread did not occur under 600 W of power. In other words, the new liquid-cooled shell had the functions of both heat dissipation and suppression of thermal propagation.

A lithium-ion capacitor (LIC) has the advantages of long cycle life, high power density, and high energy density. Comprehensive knowledge of LIC thermal characteristics is essential for its practical application. In this study, a temperature rise test of an LIC is performed under various charge and discharge rates, and its thermal model is established and studied based on MATLAB and COMSOL Multiphysics 5.4 software. The results demonstrate that the calorific value of LIC increases with the rise in charge and discharge rates. Based on the lumped parameter thermal model established in MATLAB, the mean absolute error in the temperature rise simulation can be limited to 0.2 ℃, and the temperature distribution variation increases with the rise in discharge rate. By installing the LIC lugs diagonally on the cell, the temperature difference is reduced, making the temperature more uniform, and the arrangement is advantageous in improving performance.

Water-based fire-extinguishing agents are used to extinguish lithium-battery fires with high specific-heat capacity and strong isolation. However, the water retention and adhesion capacity of traditional water extinguishing agents need to be improved. A hydrogel complex fire-extinguishing agent prepared by mixing Carboxymethyl Cellulose with AlCl₃ can solve this problem. Temperature-sensitivity studies show that the gel molecules exhibit strong water retention and adhesion, giving the agent good fluidity at low temperatures and enough viscosity at high temperatures. This phenomenon increases the overall cooling effect of lithium batteries. To explore the fire-extinguishing effect of hydrogel agents, we conducted a combustion experiment on lithium-ion battery (LIB) packs. In this study, the fire-extinguishing effect of the hydrogel agent was evaluated by analyzing the flame image, flame height, and battery temperature in cases where the hydrogel agent was used and when it was not used. The results show that the temperature of the battery packs reduced below 200 ℃ after spraying. The hydrogel agent has a certain restrictive effect on the jet flame and can hinder the heat transfer between multiple batteries; after the use of the hydrogel agent, the batteries did not reignite, indicating that the hydrogel has a good fire-extinguishing effect on LIB fire.

As a key component of new power systems, energy storage has achieved rapid growth in the market. Simultaneously, as the energy storage industry is developing, energy storage accidents are occurring regularly, the majority of which are lithium-ion battery energy storage accidents, raising public concerns about the safety of energy storage. The energy storage industry urgently needs to clarify the energy storage safety standards, improve the requirements for energy storage systems, and avoid vicious accidents.This study examines energy storage project accidents over the last two years, as well as the current state of energy storage accidents and the various types of energy storage technologies. This study focuses on sorting out the main IEC standards, American standards, existing domestic national and local standards, and briefly analyzing the requirements and characteristics of each standard for energy storage safety. Finally, from the perspective of the whole life cycle of the energy storage project, this study summarizes the issues to be further solved in the energy storage safety standards at various stages, such as design and construction, transportation, operation and maintenance, and emergency rescue and decommissioning, and provides relevant suggestions for the development of related work in the next step to promote the enhancement of relevant standards and lay a foundation for the safe and healthy development of the energy storage industry.

The frequent occurrence of lithium-ion battery fire accidents in energy storage power stations has drawn attention to the thermal runaway characteristics of lithium-ion batteries, as well as their prevention and control technology. In this study, the thermal runaway evolution process of lithium-ion batteries in energy storage power stations under external abuse conditions is divided into three stages and six processes, which are the early stage of thermal runaway, the occurrence stage of thermal runaway, and the initial stage of fire, as well as three stages of heat release and gas production, pressurization, smoke, fire burning, and gas explosion. Each stage of the entire evolution process is not independent, and the chemical reactions overlap and intersect. Because the combustion characteristics of energy-storage power station fires and traditional fires are significantly dissimilar, targeted prevention and control measures must be developed based on the characteristics of the thermal runaway evolution process. This study reviewed the recent research progress on the thermal runaway characteristics of lithium-ion batteries, as well as their prevention and control technology. In addition, the evolution process of thermal runaway of lithium-ion batteries, monitoring and early warning technology, thermal runaway suppression, and fire extinguishing technology are summarized and prospected in this study.

Lithium-ion battery energy storage technology is developing rapidly. This development will adjust the Chinese energy consumption structure and increase their renewable energy. Energy storage fire-protection technology is the safety guarantee of electrochemical energy storage technology. To understand the research and development status of energy storage fire-protection technology, the patent data in the field of energy storage fire protection published by the China National Intellectual Property Administration was the object of analysis. This paper explores the domestic development of energy storage fire-protection technology using fire extinguishing agents (A62D), fire-protection devices for energy storage (A62C), and fire-protection strategy and logic method for energy storage (G06K) as the main content. It was analyzed from four aspects: patent year distribution, patent technology distribution, patent region analysis, and main applicants. The results show that the energy storage fire-protection technology and its application follow a rapid growth trend, in which the patent application of the fire-protection devices takes up a large proportion, the research and development of special fire extinguishing agents increases rapidly, and the design of fire-protection strategies and logic methods evolves.Universities and public institutions are the major applicants in northern China; whereas, commercial companies are the major applicants in southern China, which is related to the commercial application level of electrochemical energy storage. The fire-protection technology of energy storage systems still needs to be explored by major research and development units. It can be predicted that the number of fire-protection technology patents for energy storage systems will continue to evolve, and the combination of relevant policies and markets will stimulate the vitality of research and development of the technology.

Lithium-ion battery energy storage is an important aspect of power energy utilization, and safety is the premise that guarantees the application of energy storage technology. To understand the global development trend of technology in this field, this paper summarizes and analyzes the evolution trend of global and Chinese annual patent applications and compares and analyzes the main source countries of patent applicants, as well as the patent applications and patent value of the main applicants based on the search results of the IncoPat patent database. Based on the IPC technology classification, this paper summarizes the technical composition of the main applicant's research and development, the different branches of patented technology through the technical subject distribution, and the development trend of various technical subjects. According to the findings of the study, the number of applications for safety technology patents in the field of lithium-ion battery energy storage is consistent with the global development trend, which has been gradually increasing. Although the number of patents from Chinese applicants is the largest, the value of sharing is high; however, the proportion of patents is relatively small. The patent structure is primarily limited to the country, indicating that there is still a significant gap in key technology control between Chinese and Japanese and US companies. Current safety application technology branches in the field of lithium-ion battery energy storage primarily include battery material improvement, condition monitoring, diagnosis and early warning, thermal management, circuit balance management, and fire and explosion-proof fire-extinguishing technology.

Because of their high energy density and high energy conversion efficiency, lithium-ion batteries (LIBs) have become the most popular energy storage device. Among the embedded cathode materials, Mn-based Li-rich oxide xLi₂MnO₃·(1-x)LiMO₂ has the highest discharge specific capacity and high working voltage; however, its poor structural stability limits its application in the field of large-scale energy storage. Based on a review of recent relevant literature, the purpose of this paper is to summarize strategies for improving the structural stability and electrochemical properties of lithium-rich cathode materials, review the structural modification design of manganese-based lithium-rich oxide cathode materials by lattice doping and analyze the effects of different doping lattice sites: lithium (Li), transition metal (TM), and oxygen (O) on their structures and properties, including single-doping and double-doping. We compare the electrochemical properties of single doping at various positions and describe structural changes in doped materials as well as the mechanism of affecting properties. According to the comprehensive analysis, the lattice-doping strategy has a significant impact on the improvement of cycle performance, rate capability, first discharge capacity, first coulomb efficiency, and voltage attenuation mitigation. Double doping has greater structural stability and better electrochemical properties than single doping. It is hoped that it will serve as an experimental foundation for the widespread use of Li-rich cathode materials in the energy storage field of next-generation high energy density LIBs.