Polycrystalline X-ray diffraction is an important tool to study the crystal structure of the material. Through analysis of the diffraction data, the structural parameters, e.g. lattice parameters, atomic site, grain size, grain orientation and stress distribution, can be retrieved, providing crucial information for studying relationship between structure and performance. This review briefly introduces the fundamental principles and experimental measurement methods and the commonly used Rietveld refinement method of polycrystalline X-ray diffraction. The applications of polycrystalline X-ray diffraction on study of lithium batteries are also discussed.

Lithium-ion batteries have gained rapid development in the feld of frequency regulation of energy storage power stations. In order to meet the voltage and power requirements of the frequency modulation power station, a large number of battery cells need to be connected in series, then battery cells imbalance problem may occur. Moreover, the high rate and frequent switching of the charge and discharge state of battery packs in the frequency modulation process increase the degree of inconsistency, which seriously affects the cycle life and safety performance of the battery packs. In view of the problems mentioned above, this paper summarizes the causes of the inconsistency problem of series-connected lithium-ion battery packs, and evaluates the strategies which are used to improve the consistency of the battery packs. Among them, the balancing topologies are sorted according to the energy flow, while the balancing strategies are based on the different objectives. On this basis, the development trend of equalization technology for lithium-ion frequency modulation battery packs is prospected.

As direct contact thermal energy storage technology has intensifed the heat transfer effect in the heat accumulator, improved the heat storage and release rate by using the characteristic that heat transfer working medium contacts with heat storage material to form convective heat transfer, it has attracted extensive attention at home and abroad. This paper has summarized the development and current research situation of direct contact thermal energy storage technology from three aspects of heat storage materials, heat accumulators and application cases. In this paper, common materials of direct contact thermal energy storage technology are categorized into organic materials and inorganic materials. Then, this paper has compared thermophysical parameters and properties of the materials, discussed the key indicators influencing material properties such as undercooling, phase separation, low heat conductivity coefficient and thermostability. In terms of heat accumulator, this paper has summarized the melting and flow rules of materials in direct contact heat accumulator, summarized the heat transfer and optimization methods of direct contact heat accumulator, analyzed the current solutions to material deposition problem in direct contact heat accumulator, and proposed suggestions and measures. In the end, this paper has reviewed the application of direct contact thermal energy storage technology combined with demonstration projects or business cases, aimed at summarizing application experience, providing basis and support for further promotion of the technology.

The application of metallic sulfide in sodium-ion battery is reviewed. Sodium and lithium are of the same group, and sodium ion battery is expected to be a promising energy storage device like lithium-ion battery. Therefore, its electrode materials is the current research hotspot. The current problems of these materials are introduced. The large radius of sodium ions leads to difficult intercalation/deintercalation of Na⁺ for in the electrode materials, and volume expansion etc. In view of good sodium-intercalation platforms of layered metal sulfides, they have attracted extensive attention from researchers. Summarized the electrochemical properties of the molybdenum disulfide, tungsten disulfide, tin disulfide,vanadium disulfide, titanium disulfide several layered transition metal disulfide and nickel sulfide, zinc sulfide, copper sulfide, several kinds of non-disulfide anode materials in sodium-ion batteries, including the capacity and cycle performance etc, Volume expansion、slow diffusion of Na⁺、low efficiency of charge and discharge、polysulfide dissolving-shuttling of the main problems faced by these materials at present are analyzed. It is pointed out that the methods to alleviate the volume expansion of sulfides are carbon composite, nano-materials, morphology control etc. For layered transition metal disulfides. the electrochemical performance can be improved by enlarging the interlayer spacing and adjusting the cut-off voltage. Finally, the research prospect of transition metal sulfide anode materials is viewed.

With the vigorous development of the electrochemical energy storage market, the safety of electrochemical energy storage batteries has attracted more and more attention. How to minimize the fre risk of energy storage batteries is an urgent problem in large-scale application of electrochemical energy storage. This paper reviews the existing research results on thermal runaway of lithium ion batteries at home and abroad, including combustion characteristics, fire hazard grades of lithium iron phosphate batteries and thermal runaway and thermal diffusion parameters of lithium ion batteries used in early warning systems of energy storage power plants; combing the fre extinguishing efficiency of different extinguishers for battery fires; and summarizing the selection of fre extinguishing systems of electrochemical energy storage power plants for power grid storage. It can provide reference for engineering application and effectively support large-scale engineering requirements of lithium ion energy storage battery.

With the popularity of lithium-ion batteries in life and work, the safety accidents of lithium-ion batteries have increased year by year, and the safety research of lithium-ion batteries has gradually attracted the attention of the academic community. Studying the thermal safety of lithium-ion batteries can effectively analyze the internal causes of ignition and explosion of lithium-ion batteries and guide the research on the safety of lithium-ion batteries. This paper describes the sources and influencing factors of heat production during the operation of lithium-ion batteries, as well as the internal reaction and temperature corresponding to the thermal runaway of lithium-ion batteries, and summarizes the thermal characteristics of the battery when it is out of control.

The current situation of electric energy storage in the global energy storage field in recent years and the application scale of electric energy storage in the existing energy storage system are introduced. According to the analysis of the mature electrochemical energy storage battery at present, the characteristics of zinc-nickel batteries are emphatically analyzed. Firstly, the low-temperature discharge performance, life and high current charge-discharge performance of zinc-nickel batteries are described. The results of charge-discharge experiments of simulated energy storage system show that zinc-nickel batteries have the characteristics of long cycle life and high charge-discharge efficiency. Secondly, the working principle of single-fluid zinc-nickel batteries is introduced. The current pilot-scale products of single-fluid zinc-nickel batteries and 50 kW·h energy storage system are summarized and discussed. The analysis shows that as a new type of battery, zinc-nickel batteries have long cycle life, good safety performance, low manufacturing and maintenance costs. With the development of new materials in recent years, manganese cathode successful experiments on zinc-based batteries have promoted the research and development of zinc-based batteries such as zinc-air batteries and zinc-iron batteries. In the future, zinc-nickel batteries will be brilliant in the energy storage market.

The energy storage system can effectively solve problem of intermittence, volatility and source-load misalignment of distributed renewable energy,especially wind-solar generation in the micro-grid system. Different energy storage forms have their own characteristics in terms of response time, power and energy capacity, technological maturity and cost, etc. The hybridization of two or more types of energy storage technology will be a good solution to meet the technical and economic requirements of energy utilization system. In this paper, a hybrid energy storage system consisting of compressed air energy storage, lithium battery and supercapacitor is proposed, and mathematical modellings of three energy storage systems are established. For different characteristics, a power allocation method based on secondary moving average filtering and a capacity optimal allocation method based on continuous operation are proposed. Based on a practical customer load requirement, the power and capacity confguration results of the hybrid energy storage system are obtained, and the operational characteristics are analyzed. The research indicates that in the system of distributed renewable energy micro-grid, the coupling of multiple energy storage technologies can not only fully utilize the advantages of each type of energy storage, but also compensate for their respective disadvantages through mutual cooperation. That has an important role and significance of fully utilize renewable energy and satisfy demand of electric load, and has a good engineering application prospect in the feld of distributed energy utilization.

Despite the high theoretical energy density and specifc capacity, the practical application of Li-S battery is still impeded because of the low electrical conductivity of sulfur and the dissolution of lithium polysulfides in electrolyte. Edge sites of 2D layered transition metal dichalcogenides have been show advantages than in-plane sites on preventing the shuttling effects of polysulfdes. While the synthesis of 3D hierarchical MoS₂ structures with abundant active edge sites is still a challenge. Herein, vertically aligned MoS₂ nanosheets with richly exposed (002) plane edges on the carbon cloth were fabricated via hydrothermal process and served as the host of sulfur to improve its electrochemical performance. Besides the carbon cloth as ideal supporting material to facilitate electron/ion transport, edge-rich layered MoS₂ nanosheets with abundant dangling Mo-S bonds can localized the size of sulfur particles to 5~10 nm, which results a high utilization of active substances (~1174 mA·h·g^-1 at 0.1 C) and improve the reversibility and polysulfde redox kinetics. Furthermore, the edge sites have strong rules to absorb and catalyze the conversion of polysulfdes. Therefore, the self-supporting cathode can deliver a specifc discharge capacity (based on sulfur) of 857 mA·h·g^-1 at 1 C after 400 cycles and 579 mA·h·g^-1 at 2 C after 800 cycles.

Fires and explosive hazards of lithium-ion batteries resulted from thermal runaway (TRA) propagations presented threats on the public safety. In order to prevent large-scale hazard of battery systems, one effective method is TRA mitigation. In this work, epoxy resin board (ERB) was applied to mitigate the TRA propagation of prismatic battery modules. It was found that ERB can lower the highest temperature of the battery module, mitigate the TRA severity of the batteries, and avoid the generation of the jet flames. For the module with parallel electric connection, the average TRA propagation time was 198 s per battery number when 2 mm ERB was applied, which was 2.29 times compared to that without ERB. And it was extended to 5.57 times when 4 mm ERB was used. For the module with series electric connection, the average thermal runaway propagation time was extended to 2.09 times with 2 mm ERB applied. While TRA propagation was prevented when 4 mm ERB was used, which meant thermal runaway was more easily propagated in module with parallel connection than that with series connection, because of the additional joule heat caused by the formed electrical circuit.

Thermal storage technology can effectively solve the problems of clean energy, such as wind power, photovoltaic and nuclear power, become one of the research focuses of energy storage. We present a modeling and simulation method for a phase change material energy system using fluid-solid coupling. Numerical simulations were carried out by using the method. The modelling results were found to be consistent with the experimental data.

Numerical simulations were performed on forced convective heat transfer characteristics of molten salts in tubes. Correlations were proposed for the convective heat transfer coefficient. The numerical results were compared with experiments and a good agreement was obtained at a Reynold number between 10000 and 60000.

This paper proposes a method for economic evaluation of energy storage system capacity using an improved quantum genetic algorithm. First, a mathematical model was established for the peak-filling valley of the energy storage system with the capacity allocation of the energy storage system carried out under the constraints of charge and discharge, state of charge and power balance. On this basis, an internal point method was used to transform the constrained the problem into a solvable unconstrained one. Then the improved quantum genetic algorithm was used to optimize the energy storage system capacity configuration for shortening the calculation time, improving the algorithm calculation efficiency and global optimization ability, meeting the technical requirements and engineering indexes of the energy storage system, and minimizing the cost of the energy storage system. Finally, an example analysis was performed to validate that the proposed method, enabling the energy storage system to realize its optimal economic cost capacity configuration while satisfying the peak load and valley filling of the daily load.

Internal short circuit would be triggered when lithium ion batteries in nail penetration, it will generating massive heat and smokes and may cause thermal runaway damage. In this paper, the internal structure and thermogenesis mechanism of cylindrical LiFePO₄ battery after nail penetration are analyzed. An experimental platform for nail penetration test is established, Φ5 mm tungsten steel needle is used to penetrate the battery at initial ambient temperature 20℃. The battery thermal runaway process, battery voltage changes, battery surface temperature changes and so on are investigated. According to the experimental results, the following conclusions are obtained:(1) Intensity of thermal runaway about cylindrical LiFePO₄ batteries during nail penetration is random. (2) The battery voltage would drop to 0 V after battery penetrated, and will drop more rapidly if the battery sprays smoke and explodes. (3) The temperature of the battery will rise rapidly after nail penetration, and it will rise faster and higher as the battery belches smoke or explodes. The damage of nail penetration to the lithium iron battery is devastating and causes thermal runaway. Therefore, the battery structure should be designed to prevent nail penetration and provide extra protection.

This paper proposes a two-stage flywheel energy storage device based on the conventional one-stage flywheel configuration. It was found that, for a given energy storage capacity, the twostage device could have a lighter mass and a smaller volume. Based on the above, a 10th order modal analysis and an equivalent stress analysis were carried out on the flywheel rotor system in an Ansys software environment. The simulation results showed no resonance to the modified flywheel rotor system, meeting the strength requirements.

In view of the defect of BP (back propagation) neural network algorithm of clectric vehicle battery charge state SOC (state of charge) estimation. Taking lithium iron phosphate battery as the test object, the performance parameters of lithium battery were collected on the power battery test system of EVTS electric vehicle manufactured by ARBIN Company. Using terminal voltage and discharge current as input parameters and SOC as output parameters, fa-bp neural network model was established to estimate SOC in any state during charging and discharging of lithium ion batteries. The simulation results show that compared with the existing BP neural network estimation method, the method based on FA-BP neural network has high accuracy and good practicability.

In order to improve the carbonization yield and electrochemical properties of artificial graphite, the artificial graphite is coated with modified asphalt and carbonized after preoxidation treatment. The carbonized samples were characterized by laser particle size distributor, densitometer and specific surface and aperture tester, and the electrochemical performance was further studied. The results show that the preoxidation treatment in the carbonization process can effectively improve the agglomeration phenomenon and greatly improve the electrochemical properties of the cathode materials.

This bimonthly review paper highlights 100 recent published papers on lithium batteries. We searched the Web of Science and found 2208 papers on line from Feb. 1,2019 to Mar. 31,2019. 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 composite anode materials for analyzing the mechanism for Li storage and SEI formation. The cycling properties of metallic lithium electrode are improved by constructing 3D electrode, using different kinds of surface cover layer, substrate and electrolyte additives. The performances in Li-S and solid state battery are investigated. The studies of solid state electrolytes are focus on the method of preparation and the transport mechanism. Number of papers related to solid state batteries including electrode and battery design and manufacturing methods. There are a few papers related to Li/S battery, Li-air battery for improving their cycling performance. And more papers related to cell analyses, theoretical simulations, and modeling.

The rotor dynamics of a 250 kW/3 kW·h magnetic flywheel storage system was studied by using a combination of theoretical analysis, simulations and experimental testing. The Timoshenko beam theory was used first to obtain the motion equation of the rotor element. The ANSYS software was then used to calculate the critical speed and unbalanced response of the rotor. Finally, a radial magnetic bearing sensor was used to collect the displacement signal during speed increase for the determination of the vibration waveform and the validation of the accuracy of the dynamic parameters of the rotor and the simulation results. The spectrum waterfall diagram and the vibration displacement response curve of the rotor were compared with the Campbell diagram and the unbalanced response diagram of the simulation analysis. It was found that the experimental test results were consistent with the simulation results.

Lithium-ion battery is the most promising and effcient secondary battery, and is also the fastest development chemical energy storage power supply. It has become a hot competition in every country of world. Patent technology can reflect the current situation and process of the innovation and development of a technical field, which is an important information source for competitive intelligence. From the perspective of patent analysis of the lithium-ion battery energy storage system, to understand the development trend of lithium-ion storage system, it may provide references for the strategic decision of our government and enterprises.

Lithium-ion battery using liquidelectrolyte with flammable organic solvent have potential safety hazards. Solid electrolyte have obvious advantage in terms of safety and thermal stability. Therefore, the development of solid electrolyte is an effective way to improve the safety performance of power battery. New energy vehicle using lithium-ion power battery are currently developing strongly. As a leading company in the automotive field, Toyota has an important reference value for the development of lithium-ion solid battery for the automotive industry. This report mainly uses the search result in the CNABS patent database and the DWPI patent database as an analysis sample, and comprehensively counts Toyota's patent on lithium ion solid electrolyte from the perspective of patent literature. The results show that Toyota's patent application for lithium-ion solid battery are mainly distributed in Japan, the United States and China. The focus of research on solid electrolyte is sulfde solid electrolyte, and the focus is on improving lithium ion conductivity and reducing sulfde gas. Produce and reduce interface resistance.

With the development of energy internet, power energy storage technology is becoming more and more important. It is an important part of the whole process of power grid operation, such as "acquisition, transmission, distribution and storage". Especially, energy storage batteries, energy storage control, energy storage system integration, energy storage management and operation are the key technologies in the feld of energy storage, and technology competition is becoming increasingly fierce. Patent information is an important carrier of independent innovation achievements and an important information source for developing competitive intelligence. Based on the patent perspective and using the advanced semantic patent retrieval system, this paper analyses the number of patent applications, peer, PCT, region, applicant, applicant and international classification distribution in the feld of electric energy storage, reveals the situation of R&D and patent competition in the feld of electric energy storage, and provides decision-making and industrial layout for the government, enterprises and research Institutes in the field of electric energy storage. On the one hand, it puts forward three constructive development strategies:frst, patent strategy, development path, reasonable distribution of domestic and international markets according to energy storage market and its own strategy, focusing on their respective advantages to form technical barriers to competition, and grasping the right to speak.