Safety is a major concern of the large-scale application of lithium-ion batteries. The safety performance of lithium-ion batteries not only depends on materials and cell design, but would also changes during aging process. The effects of aging on the battery safety performance require further investigation to ensure the full-life cycle safety of lithium-ion batteries. This paper has reviewed the recent progress on the evolution of battery safety performance under different aging conditions (including cycling and storage). The correlations between aging mechanisms and the changes of battery safety performance are further summarized. Lithium plating on anode surface is found to be the key factor of full-life cycle safety of lithium-ion batteries. Furthermore, the problems and future researches on the evolution of battery safety performance are discussed.

The increase in energy density of power batteries places higher demands on the test and evaluation methods of battery safety. This paper summarizes and analyzes the current test and evaluation methods for safety of power battery. Specifically, at the battery cell level, it includes the characterization method of intrinsic safety (i.e., thermal stability) and the status and trend of the test and evaluation standard system that triggers safety. At the system level, the standard system of battery system safety testing and the test method of thermal diffusion test are discussed in detail. It is expected that this work can provide reference for establishing more scientific quantitative testing and evaluation methods.

Compared with commercial organic based lithium (Li) ion batteries, aqueous lithium-ion batteries (ALIBs) present high safety, low cost and environment-friendly. However, due to the limitation of the electrochemical window of aqueous solution (1.23 V), it is excluded the most of electrochemical couples with the output voltage above 1.5 V. The invention of the Water-in-salt (WIS) electrolyte firstly expand stable electrochemical window of the aqueous electrolyte above 3.0 V which conceives of a series of high voltage ALIBs. The review mainly summarized research progress on Water-in-salt electrolyte and its relative following works, including the derivative electrolytes such as Water-in-bisalt electrolyte and its expanding applications on Li ion batteries, lithium-sulfur batteries and hybrid-ion batteries, and meanwhile introduces the fundamental investigation on the solid electrolyte interphase (SEI) formation mechanism and Li ion transport mechanism in WIS electrolytes.

The "mileage anxiety" has been plaguing the development of electric vehicle industry. Except loading batteries of high energy, consumers expect electric vehicles can be charged in 10 minutes, just as convenient and fast as fuel vehicles. Electric vehicles generally are charged between 0.5 and 2 hours as fast-charge, more than 2 hours as ordinary-slow-charging, and less than 10 minutes as called extreme-fast-charging (XFC). In this review, the science and engineering challenges in XFC, specifically for Li-ion batteries powered electric vehicles, are analyzed in terms of infrastructural equipment/facilities, battery pack/powertrain, battery thermal management, single cell design, battery chemistry and material and so on. This paper also analyzes the gap between technical status quo and XFC requirements, clarifies the technical difficulties that need to be solved in extremely fast charging. Although extremely fast charging has not yet been achieved, this paper proposes future R&D directions.

Lithium secondary batteries has a wide application prospect in portable consumer electronic products, electric vehicles and energy storage etc. owing to its advantages of high energy density, long cycle life, no memory effect and environmentally friend. At present, the energy density and safety of lithium secondary batteries are the hot spot in the world. However, for conventional lithium-ion batteries with liquid electrolytes, although various improvement measures have been taken from the aspects of materials, modules, power management, thermal management and system design, the safety issues in high-energy density cells are still prominent, and it is difficult to avoid the problem of thermal runaway completely. Therefore, in order to improve the safety of lithium ion battery, the development of non-flammable solid-state lithium battery is a necessary way to solve the safety problem of conventional lithium ion battery. This paper compares cell structures between the traditional liquid lithium ion battery and solid-state lithium battery, and their respective advantages and disadvantages are summarized. The fundamental causes of safety problems in traditional liquid lithium ion batteries are analyzed, and the approach of replacing the liquid electrolyte with solid-electrolyte is put forward as the best solution to solve the problem of safety issues in lithium ion batteries. Finally, the high safety characteristics of solid-state lithium-ion batteries are confirmed depending on the safety test results of some kind of solid-state lithium batteries which are developed independently.

Internal short circuit (ISC) is one of the most common causes of thermal runaway accidents in lithium-ion batteries, as a potential safety threat. It is also a common link between mechanical abuse, electrical abuse and thermal abuse. In this review, the research progress of ISC mechanism is summarized including the substitute triggering approaches and the ISC evolution process. It is proposed that the ISC detection needs to be achieved in the early and middle stages. Furthermore, a variety of ISC detection methods are summarized. Finally, the perspective of ISC is discussed.

Energy density and safety of lithium ion batteries (LIBs) are the main obstacles that hinder the large-scale applications of LIBs in electric vehicles. With continuous improvement of LIBs in energy density, solving safety issue effectively is becoming increasingly urgent. These safety issues are intrinsically related to the present utilization of highly volatile and flammable organic solvents. Herein, the research status on safety of electrolyte in LIBs is summarized in this review, including the application of flame retardant, non-flammable fluorinated organic solvent, high concentration electrolyte and hybrid electrolyte from the point of combustibility of electrolyte. The paper analyzes mechanisms of enhancing safety for LIBs and provides an outlook of electrolyte in application development.

The latest research progress in mechanism, modeling and inhibition technology of thermal runaway propagation of lithium-ion power batteries in electric vehicles are reviewed. To meet the high energy requirements of automobiles, power batteries are required to be connected in series and in parallel to provide power. The safety of battery packs has become an important technical issue for large-scale applications of electric vehicles. When a battery cell in the battery pack is in thermal runaway, a large amount of heat is generated, causing the surrounding battery cells to be thermally out of control. Therefore, an important concern of the battery pack safety problem is the problem of thermal runaway propagation in the battery pack. In this paper, the research progress of thermal runaway propagation of lithium-ion batteries at home and abroad is reviewed, and the main factors affecting the thermal runaway propagation characteristics of different types of lithium-ion power batteries are analyzed. The thermal runaway modeling method in the literature is summarized, and the shortcomings of the existing methods are pointed out. From the point of view of thermal safety management of battery system, the research achievements and research directions of thermal runaway propagation inhibition technology are expounded and analyzed. Finally, the future research on thermal runaway propagation has been prospected.

Commercial lithium-ion batteries (LIBs) are easy to catch fire and even explode under abuse conditions such as mechanical shock, thermal shock, overcharge, and short circuit, et al. To resolve this safety concern, it is necessary to develop high safety flame retardant electrolytes replacing the highly flammable conventional carbonate-based electrolytes. This review presents the research progress of high safety flame retardant electrolytes for LIBs. Firstly, the mechanisms of combustion and flame retardant, together with the methods of flame retardant evaluation are introduced. Then, the LIBs demands on properties of flame retardant electrolytes are described, and flame retardant electrolytes are discussed by classifications:flame retardant additives; flame retardant solvents/cosolvents; highly concentrated electrolytes; ionic liquids; and flame retardant gel polymer electrolyte. The formulations, flame retardant effects, and applicable battery systems of these high safety flame retardant electrolytes are mainly focused. Finally, future research directions of high safety flame retardant electrolytes are prospected.

The long lifespan and high safety of lithium-ion battery (LIBs) greatly promote its applicability. Among various next generation energy storage devices, lithium-sulfur (Li-S) batteries have attracted much attention due to their high theoretical energy density, high natural abundance and environment friendly nature of sulfur. However, due to the flammability of organic solvents in liquid electrolytes, the continuous formation of lithium dendrites and the low ignition temperature of carbon-sulfur mixtures, safety of Li-S batteries has become a critical issue for their practical application. In recent years, some strategies have been put forward to improve the safety of Li-S batteries. In this paper, we firstly introduced the evaluation methods of high-safety batteries. Then two kinds of sulfur composite cathodes for Li-S batteries and their suitable safe electrolytes are summarized. The safety of lithium-sulfur batteries for common sulfur-carbon composites are mainly improved by non-flashing hydrofluoroether solvents. While for sulfurized polyacrylonitrile (S@pPAN) composite, safety is mainly enhanced by phosphorus-based flame retardant additives in the standard electrolytes. Finally, the future development direction for safe Li-S batteries is prospected.

The essence of the safety problem of lithium-ion battery is the internal thermal runway. Inside the battery, the heat is continuously accumulated, causing the sustaining rise of temperature. Its external performances are combustion and explosion. Therefore, the safety of lithium-ion battery has certain contradictions with specific energy, operating temperature and rate performance. Higher energy density, higher rate performance and harsher operating environment are usually the causes to a more violent energy release, leading to the greater impact on the battery system and more serious safety problems. In general, the electrolyte of lithium-ion battery consists of carbonates with low flash point, lithium salt LiPF₆ with high sensitivity to H₂O and temperature, and other additives at present. Besides, the destruction of the interface film between the electrolyte and the electrode is considered to be the starting point of the battery thermal runway. Thus, electrolyte modification is a significant method to promote battery safety. In this paper, the enhancing effects of modified solvents such as ionic liquid and fluorinated solvent on the safety of electrolyte were analyzed. The positive impacts of various lithium salts on the safety of electrolyte were compared. The safety improvements by the electrolyte additives such as flame retardant, overcharge protector, lithium dendrite inhibitor and solid-electrolyte interface stabilizer were introduced. At last, from the perspective of the overall application performance of the battery, the further research and development directions of high-safety lithium-ion battery electrolyte were discussed.

Lithium-sulfur battery (Li-S) has been regarded as one of the most promising energy storage system due to its high energy density, environmental friendly, low cost and abundant resources of sulfur. Recently, the technology development of Li-S battery has been largely improved with the progress of sulfur trapping chemistry and sulfur cathode design. However, the commercialization of Li-S battery is still encountering a series of challenges, such as design of high loading sulfur cathode, activation of sulfur in lean electrolyte or solid electrolyte, stable electrode/electrolyte interface, and safety concerns. In which, the safety issue of Li-S battery is one of the key factors, which impede the commercialization process. In recent years, some strategies have been proposed to address the safety concerns of Li-S battery, including protection of Li metal anode, flame retardant electrolyte, modification of separator, solid electrolyte and accommodation of volume change during discharge and charge. In this review contribution, we summarize the research progress on the safety issue of Li-S battery, and discuss the future development of commercially available high-performance Li-S batteries featuring high energy density, stable cycle and high safety.

Based on the application of new energy vehicles in China and the actual development of policy, technology, industry and market, this study focuses on safety issues and countermeasures of key links in the secondary utilization of retired lithium-ion batteries (LIBs). It introduces secondary utilization modes of retired power battery, summarizes status and trend of scrapping and secondary utilization of power batteries in different cathode materials, points out the challenges and opportunities, analyzes the hidden dangers of power lithium ion batteries in production and vehicle-usage as well as the safety requirements and risks of the secondary utilization of the retired-power batteries in four different application scenarios. A safety strategy to optimize secondary utilization matching with different safety foundation of different type of power battery and vehicle application is proposed. Meanwhile, it is suggested to innovate power battery development and design mode, to develop key technologies for secondary utilization, to accelerate business model innovation and to foster a bigger and more successful industry as a comprehensive strategy to improve the safety of battery secondary utilization.

To study the suppression effectiveness of different fire extinguishing agent on large-capacity power lithium-ion battery fires, an extinguishing test platform was built. This platform was suitable for various fire-extinguishing agent. During the test, a 300W external electric heater was used to trigger the thermal runaway. The extinguishing behavior and efficiency were studied by changing the species of the extinguishing agent. The results showed that, for the fire of single cell with capacity of 38Ah, the ABC powder, HFC, water, C₆F₁₂O and CO₂ agent could suppress the open flame quickly, but the battery suppressed by CO₂ agent reburned after a while. During the suppression process, different fire extinguishing agents showed significant difference in inhibiting temperature rise. The water agent showed the best cooling efficiency among all the agents, followed by C₆F₁₂O, HFC, ABC powder and CO₂. The results of this study can provide experimental support for engineering applications and regulations formulation.

As a kind of new solid electrolyte materials, ionic plastic crystals have received much attention in recent years. In this paper, a novel ionic plastic crystal N, N-dimethylpyrrolidinium bis (fluorosulfonyl)imide (P₁₁FSI) was firstly synthesized, and blended with pyrrolidinium-based polymeric ionic liquid (PILFSI) and lithium salt (LiFSI) to obtain a series of new solid electrolytes.The thermal and electrochemical properties of as-prepared solid electrolytes are investigated by differential scanning calorimeter, thermogravimetric analysis, impedance spectroscopy measurements, linear sweep voltammetry and symmetrical lithium cell test. The as-prepared solid electrolytes exhibit good flexibility and thermal stability, high ionic conductivity and electrochemical stability, as well as good compatibility with the lithium metal. Particularly, Li/LiFePO₄ cells assembled with as-obtained solid electrolytes present high discharge capacity (151.1 mA·h·g^-1), good cycle life and rate performance. This finding indicates that the solid electrolyte system obtained in our work has great potential for use in all-solid-state lithium ion batteries.

With the development of lithium-ion batteries, the demand for safety is critical, and temperature has an important influence on the life and safety. LiCoO₂/C is taken as the object, and the heat generation and thermal runaway behavior at different cycle are studied under different current by using accelerating rate calorimeter. Comparing the heat generation of the batteries at different cycle, it is found that there is a strong correlation between the rate of capacity decay, DC resistance and the heat generation rate. According to the thermal runaway behavior, the self-heating temperature of the fresh battery is 105.4℃, followed by continuous self-heating. Until the temperature reaches 149.7℃, the battery is out of control, and an internal short circuit occurs, which finally leads to the battery thermal runaway. The initial temperature of self-heating and thermal runaway changes slightly, but the time of thermal runaway progress is shortened greatly.

The mechanisms of safety testing and evaluation methods (mechanical abuse, thermal abuse and electrical abuse testing) for lithium-ion batteries were analyzed. Test methods of GB/T 31467.3/31485 and SAE J2464/UN 38.3, the representative safety test standards for lithium-ion batteries, were compared. X-ray 3D CT (Computed Tomography) technology was used to analyze the internal structure of lithium-ion battery before and after safety test. The prospect of X-ray 3D CT for safety test of lithium-ion battery was prospected. The direction of the safety failure mode for lithium-ion batteries analysis was indicated.

Lithium-ion battery overcharging is a major safty issue in using, if it is not protected as overcharge occurs, there will be a safety accident such as fire and explosion. A single cell has simple structure and the heat dissipation is good, it can be easily protected by its internal structure design and battery material formulation adjustment. The battery pack has the battery management system (BMS) and high voltage control device, and it is easy to be protected from overcharge.The battery module is in the middle level between the battery pack and the cell, and its safety is the last powerful barrier to ensure the safety of the battery pack. However, the module structure is relatively complicated, the heat dissipation is relatively poor compared to the cell, and its overcharge protection is more difficult than the cell. By analyzing the influencing factors and differences of cell and module overcharge protection, carrying out test verification, analyzing the voltage, current, temperature and other of the overcharge process, the key factors affecting the overcharge protection of the module was found and formulate corresponding improvement measures and solutions was proposed to realize the overcharge safety protection of the module.

In order to optimize the thermal stability of the ceramic coated separators and improve the safety and electrochemical performance of lithium ion batteries, polyimide (PI) with good thermal stability and poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) with excellent electrochemical stability are used as binder to coat the aluminum oxide (Al₂O₃) particles onto both sides of commercial PE separator in this work. According to the test results of ceramic coated separators prepared by different binder components, the PI binder can obviously improve the thermal stability of the ceramic coated separator, however the cell performance is not satisfying. In addition, the poor electrochemical properties of the PI binder can reduce the electrochemical stability and compatibilities with electrodes. PVDF-HFP has been widely used in lithium-ion batteries because of its excellent electrochemical properties. PVDF-HFP can swell in the electrolyte, the swollen PVDF-HFP can adhere electrode so that lithium ions can pass across the separator. Adding an appropriate amount of PVDF-HFP in the binder can improve the ionic conductivity, electrochemical stability, lithium metal-electrode compatibility and other properties of the ceramic coated separator while maintaining its good thermal stability because of the presence of PI binder. Therefore, the using of appropriate components of PI and PVDF-HFP binders can synergistically improve the performance of the using of ceramic coated separator. Finally, the cell performances of the Li|LiCoO₂ cells with the optimized inorganic composite separator are enhanced obviously. The capacity and the capacity retention of the cell using the optimized ceramic coated separator at 8 C is 109.3 mA·h·g^-1 and 66.1%, which are much better than those (88.7 mA·h·g^-1 and 54.7%) of the cell using the PE separator.

In order to study the temperature characteristics of the power battery pack and maintain its working temperature within the optimal temperature range, a lithium-ion battery is taken as the research object, and a battery thermal management system for the hybrid vehicle is proposed. The air conditioning system and the engine exhaust system are used to regulate the temperature of battery pack. A three-dimensional transient heat generation numerical model of the lithium battery pack was established. The size of the battery pack and the inlet air flow rate were used as input parameters to reduce the maximum temperature rise of the battery pack and improve the temperature uniformity of the battery pack as output parameters, In order to reduce the maximum temperature rise of the battery pack and increase the temperature uniformity, the structure of the battery pack was designed and optimized by using FLUENT simulation software and DesignXplorer module. The optimized temperature rise of the battery pack was 5.39 K lower than that before optimization, and the temperature difference was reduced by 6.41 K. The effects of constant rate discharge and convective heat transfer coefficient on the temperature rise were analyzed. The research shows that the higher the discharge rate, the faster the temperature rise of the battery. The higher the temperature of the battery after the discharge is completed, the heat dissipation effect is obvious when the convective heat transfer coefficient is less than 30 W/(m²·K). By the simulation analysis of the heating or cooling of the battery pack under different conditions, the feasibility of the battery thermal management system was verified.

It is very important for the safe operation of the energy storage system to study the fire warning technology of Li-ion battery energy storage power station. The recognition of thermal runaway and thermal diffusion characteristics of lithium-ion batteries is discussed. The combustible gases will be generated slowly at the beginning the thermal runaway of lithium-ion batteries. if the gas of thermal runaway of batteries can be extracted and analyzed in the early state, the thermal runaway early warning system of the battery can be established on this basis. In this paper, heating and overcharging methods were used to trigger the battery thermal runaway and gas emission, and the gas composition is analyzed, it is confirmed that carbon monoxide can be detected to achieve early warning of Li-ion battery thermal runaway. It introduces the application status of fire warning system in energy storage power station and points out its shortcomings. The multilevel early warning and protect mechanism and security linkage strategy were studied. At last, the design framework of fire warning system for lithium ion battery energy storage power station is exported. The system is briefly explained from the aspects of system components, linkage communication and personnel safety. The system ensures fast and effective detection of the thermal runaway state of batteries while fast linkage of fire protection facilities, greatly improving the reliability of the energy storage system.

This bimonthly review paper highlights 100 recent published papers on lithium batteries. We searched the Web of Science and found 3283 papers online from Aug. 1, 2018 to Sep. 30, 2018. 100 of them were selected to be highlighted. This bimonthly review paper highlights 100 recent published papers on lithium batteries. We searched the Web of Science and found 3283 papers online from Aug. 1, 2018 to Sep. 30, 2018. 100 of them were selected to be highlighted. Layered oxide and high voltage spinel cathode materials are still under extensive investigations for the structure evolution and modifications. Large efforts were devoted to Si based anode material. The influence of the micro-structure of graphite on its performances are investigated. Number of papers related to metallic lithium and solid state batteries increasing very fast. There are a few papers related to solid state electrolyte, Li/S battery, Li-air battery, analyses methods, theoretical simulations, and modeling.

Sodium (Potassium)-ion batteries are promising battery systems for large-scale energy storage applications owning to the low cost and resource abundance. However, the relatively larger radius of sodium (potassium) ions hinders the development of Na (K)-host materials. The organic electrode materials, especially carbonyl compounds, have been considered as one of the most promising electrode materials for SIBs and KIBs due to the structural diversity, high theoretical specific capacity and environmental friendliness. Moreover, the flexible frameworks demonstrate less restriction on the cation sizes. Therefore, constructing sodium (potassium) ion batteries based on organic carbonyl compounds are highly desirable for the next generation of "green batteries". This review offers an introduction on the classification, Na/K-storage performances and mechanisms of the organic carbonyl compounds, emphasizing on the existing problems and resolution strategies. Finally, the basic scientific problems, technical challenges and competitiveness of carbonyl compounds as electrode materials for Sodium (Potassium)-ion batteries are summarized, and the application of carbonyl-based organic electrode materials for large-scale energy storage applications are also forecasted.

Phosphorus, an emerging energy storage material, has various allotropes and topological structures. Among these allotropes, black phosphorus has aroused growing concern owing to its superior conductivity and excellent thermal stability. This paper has reviewed the applications of red phosphorus and black phosphorus in the lithium-ion batteries, sodium-ion batteries, lithium-sulfur batteries, magnesium-ion batteries, supercapacitors and solar cells. The characteristics and main problems of red and black phosphorus for rechargeable batteries are also analyzed in this paper. According to the different advantages and disadvantages between these two kinds of phosphorus, the specifical modifications of the two kinds of phosphorus electrodes were reviewed by the designs of the phosphorus-carbon binary topological structures. The applications and prospects of phosphorus-carbon composites based on different binary topological structures were analyzed.

Silicon based materials are the most ideal candidates for the next generation Li-ion battery with high specific energy density due to their excellent characteristics such as high theoretical specific capacity, safe lithium intercalation potential and low cost. Despite have been studied for a long time, silicon based anodes suffer from immense volume change and chronic capacity fading during cycling. The development of novel binders with high performance is an effective way to promote the commercial application of silicon-based anodes. The polymer binders with rigid and flexible properties at the same time can restrain pulverization of silicon based materials and maintain the integrity of electrode conductive network, thus improving the cycle performance of silicon based anodes effectively. In this paper, the characteristic requirement for binders in silicon-based anodes and the current research progress of some novel binders are reviewed. In addition, some potential research directions in this field have been presented, including the investigation of composite binders, the investigation of binders with special space structures, and the investigation of conductive binders; the investigation of self-supporting non-binder silicon based anode.

Sodium-ion batteries have attracted much attention as a type of promising energy storage system due to the abundant resources and low-cost of sodium. However, the larger radius of Na⁺ leads to a more difficult reversible intercalation/deintercalation of Na⁺ in electrode materials. Recently, metal compounds have been intensively investigated as anode materials for sodium-ion batteries with high theoretical capacities due to their conversion reaction mechanism of sodium storage. This paper summarizes the sodium-storage mechanism and research progress of metal compounds including oxides, sulfides and phosphides, investigates the sodium-storage performance, reveals the advantages of metal compounds as promising anode of sodium-ion batteries, and prospects the development of metal compound anodes for sodium storage.

The economic benefit of energy storage projects is one of the important factors restricted the application of energy storage systems. Its business model is closely related to the investment economic analysis. Given the structure and profitability of an energy storage project the relevant economic indicators such as internal rate of return and investment payback period are calculated and explained based on the analysis of the related policies and development status of domestic energy storage system. Further, since energy storage projects have commercial financing difficulties, this paper has introduced a direct financing lease model to evaluate the economics of projects under the low-cost procurement advantages of financial leasing companies.Through analysis, we can see that the introduction of the financial leasing model can ease the financial pressure of the company in previous years and improve the economic benefits of the project.

A porous carbon nanotube (CNT) network was deposited on the surface of carbon nanotube fibers (CNF) by low-potential electrophoretic deposition, and then a layer of polyaniline (PANI) was electrochemically deposited on the surface of the CNT-decorated carbon nanotube fiber to form a core-sheathed structure of three-dimensional porous CNF/CNT/PANI fiber electrode material. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy were used to characterize the morphology and microstructure of the electrode material surface. An electrochemical workstation was used to measure the electrochemical performances. The experiment results showed the porous CNTs framework provided more active sites for the redox reaction of PANI, while the PANI can immobilize the pre-deposited CNTs structure. The areal specific capacitance of the electrode modified with CNTs and PANI reached 77.28 mF·cm^-2 at the current density of 1 mA·cm^-2. Besides, a symmetrical all-solid-state flexible supercapacitor was prepared by using polydimethylsiloxane (PDMS) thin film as the substrate and PVA-H₃PO₄ as the electrolyte, and the areal specific capacitance achieved 61.25 mF·cm^-2 at the current density of 0.25 mA·cm^-2. After 4000 cycles of charge/discharge, the capacitance value remains 80%, and two capacitors in series can light up a 1.8 V LED bulb.

The active carbon/LiNi_0.5Co_0.2Mn_0.3O₂ (AC/NCM) composite cathode slices are successfully prepared via physical blending using (NMP+PVDF) organic system and subsequent ethanol extraction method, and the energy-power characteristics can be regulated by tuning the AC/NCM ratio. Here in this paper, the AC/NCM 1/3 weight ratio is emphatically employed as cathode and hard carbon (HC) as anode to fabricate the soft-package supercapacitor-type battery. Subsequent electrochemical tests demonstrate that the as-prepared devices perform nearly rectangular shape for CV curves and good linear correlation between voltage and time (V-t curves) in constant current charging-discharging processes. Moreover, the construction strategy of Three-dimensional Conductive Network (the weight ratio of SP/CNT/Graphene is 3/1/1) is introduced to effectively reduce the internal resistance of device. According to IEC 62660-1 standard, the highest measured energy density under 2.5~4.2 V window reaches 66.6 W·h/kg with 83.4 W·kg of power density, and the maximum power density is up to 6.5 kW·kg^-1 with 21.5 W·h·kg^-1 of energy density. The fully charged devices exhibit excellent high-temperature storage performance with 97.4% of energy retention in the case of no flatulence, and 27.5 mV·day^-1 of low average self-discharge rate after storing for 168 h at 65℃. The endurance evaluating at 14 C and 50 C show that the energy retention is up to 99.06% and 96.45%, respectively after 1000 cycles, revealing the long-life advantage of this kind of device. Furthermore, the pulse test even under the average discharge power density of 12 kW·kg^-1 indicates that the device displays excellent stability after undergoing 100 times of pulse discharge, which demonstrates potential applications in vehicle start-up, pulse devices and other fields.

Lithium-ion capacitor (LIC) is a new energy storage device that combines the advantages of lithium-ion battery and supercapacitor. Internal resistance under direct current (DC Resistance or DCR) is one of the most important electrochemical parameters for evaluating the performance of supercapacitors. However, there is no standard method for measuring and evaluating the internal resistance of LIC. This study tested and compared LIC devices using three different testing procedures and calculation methods for DCR. Comparison of internal resistance using initial voltage drop at 100ms to that of other methods indicates that this method provides consistent results and the value of resistance may be close to the true stead-state resistance.

Different proportions of granulated carbon black and activated carbon added in the negative paste of lead acid batteries. Partial state of charge state (PSoC) cycle times are tested respectively through constant-current charge-discharge. Carbon material and negative active materials (NAM) were characterized by SEM and XRD. The results show that both granulated carbon black and activated carbon can incorporate in lead to form the structure of lead carbon which may significantly improve the PSoC cycle performance.

Electrolyte is one of the key technologies of lithium-ion batteries. It plays a key role in conveying the lithium ions and current between cathode and anode, and affects the working voltage, energy density and safety performance of the battery. In recent years, with the development of cathode and cathode materials, the composition of electrolyte has changed a lot in order to match with the new materials. The existing standards and corresponding test methods of electrolytes need to be updated to realize the standardization of the product. This paper introduces the current situation and development trend of electrolyte, analyzes the current standards of electrolyte in China, and puts forward some suggestions for the new national standards of electrolyte.

The safety performance of lithium-ion batteries can be evaluated on the basis of calorimetric analysis on thermal runaway process. The heat release rate and accumulative heat release of the battery at different temperatures are the parameters to measure the thermal stability of the battery. Calorimetric analysis of large-format batteries is generally carried out by adiabatic rate calorimeter (ARC). This paper mainly introduces the testing principle and method of ARC, data analysis and safety evaluation.