Electrolyte is a key component of the lithium-ion battery. The basic function of electrolytes is to serve as the medium for the transport of lithium ions between the electrodes. The chemical composition of electrolytes has a direct influence on the characteristics of LIBs, such as energy density, cycleability, rate capability, storage performance and safety. After more than ten years of rapid development, China’s electrolyte industry has obtained the ability to compete in the global market. In this review, the development of the electrolyte industry, as well as the domestic market status are briefly summarized. Taking the patent ownership of commonly used electrolyte additives as an example, the differences in the patent applications of between domestic and foreign major enterprises are analysed. The characteristics of four types of electrolyte products, which are used for 3C batteries, xEV batteries, energy storage batteries and functional batteries respectively, are introduced. The design ideas of the former two types of products are emphasized. China’s industry standards of LIB-used electrolytes are also mentioned. The technical trend and industry prospect of commercial electrolytes are discussed.

Because of its good electrochemical performance and high operating voltage around 4.7 V, LiNi_0.5Mn_1.5O₄ spinel has become one of the most promising high voltage cathode materials for lithium ion batteries with high energy density. In this paper, we prepared LiNi_0.5Mn_1.5O₄ cathode materials through spray drying assisted annealing process with different heat treating conditions, the effect of heat treatment conditions on the structure and electrochemical performances was investigated. The crystal structures of the prepared LiNi_0.5Mn_1.5O₄ materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transformed infrared spectroscopy (FT-IR). The in situ synchrotron X-ray diffraction technique was carried out to study the online phase transition of LiNi_0.5Mn_1.5O₄ spinel during cycling. It has been found that the prepared LiNi_0.5Mn_1.5O₄ powders show phase-pure cubic spinel of Fd-3m structure. Its electrochemical performances were tested at different charge/discharge rates between the potential limit of 3.5~5.0 V, and the initial discharge capacity of the LiNi_0.5Mn_1.5O₄ spinel attained at 132.0 mA·h·g^-1, and the columbic efficiency at first cycle is 93.48%, and the electrochemical performances of the prepared materials are excellent.From the in situ XRD patterns and charge-discharge profile, it can be found that four phase transitions existed for LiNi_0.5Mn_1.5O₄ spinel during charge process, the phase transition from tetrahedral to cubic is reversible in the lithium insertion and extraction process.

This bimonthly review paper highlights 100 recent published papers on lithium batteries. We searched the Web of Science and found 2318 papers online from Oct.1, 2015 to Nov.30, 2015. 100 of them were selected to be highlighted. Layered oxide and high voltage spinel cathode materials are still under extensive investigations for influences of doping, coating and interface modifications on their cycling performances. Large efforts were devoted to Si and Sn based composite anode materials for analyzing the SEI and making nano structures. There are a few papers related to electrolyte additives, solid state electrolyte, Li/S and Li-air batteries, and more papers for state estimation and analyzing the fading and thermal safety mechanism of Li-ion batteries.

With the development of new energy technology, lithium ion batteries (LIBs) are required to have higher energy density. Iron fluorides (FeF₃ and FeF₂), with small molecular weight, multi-electron conversion reaction and high voltage, are good candidates for high energy density cathode materials of LIBs. However, their practical applications are hindered by the intrinsic poor electron conductivity and large over potential needed in the conversion reaction. The paper firstly introduces the basic properties and lithium storage mechanism of FeF₃ and FeF₂, and then describes specifically the approaches for improving the electrochemical performance, mainly including structural expansion and element substitution leading to several kinds of new phases (Fe_xF_y·mH₂O and FeOF), designing porous nanostructures and constructing composite with nanocarbon. The further research in the future is also prospected.

A new portable energy storage device based on sodium-ion battery (SIB) has been designed and assembled. Layered oxide NaNi_1/3Fe_1/3Mn_1/3O₂ was used as cathode and hard carbon was used as anode. The structure and thermal stability of the prepared material were measured by using XRD and DSC techniques. Soft pack battery with 1 A·h capacity has been designed and the electrochemistry and safety performance were tested. SIB packs of 0.1 kW·h were fabricated for the new portable energy storage device. This sodium ion energy storage device has a promising perspective on household electrical energy storage, military power supply, smart grid, low-speed electric vehicle, etc.

：With having many advantages, Li-ion battery has become the key research topics for large capacity storage. Lithium ion battery management system must be designed to maintain the battery safety operation and prolong its cycle life. This paper proposes a new hierarchical management strategy for Li-ion battery, which may monitor and manage the cells, battery packs and the energy storage subsystem. At the same time, it discusses the structure and function of each layer and introduces the main function of the Li-ion battery management system, especially the cell data acquisition part, state-of-charge estimation and the balancing part. They are verified by the experiments. The experimental results show that the system can meet the need of the energy storage system, realized the high precision of state-of-charge estimation and the balancing management function of Li-ion battery. It provides a technical solution for managing large capacity lithium ion battery energy storage system and a good application prospect.

This article reviews recent worldwide developments in the storage of renewable electricity using fuel chemicals synthesized from captured carbon dioxide. The energy costs and exergy flows are briefly analyzed by mass and energy balance calculations and simulation methods to assess energy efficiency of methanol as an electricity storage vector in comparison with methane and hydrogen. Hydrogen energy storage has the shortest process with the highest efficiency, however, with no contribution to carbon sequestration. In term of carbon sequestration, electricity storage using methanol has a better atom-efficiency than methane which has higher calorific value and chemical reaction heat. The loss of energy efficiency is mainly caused by hydrogen electrolysis.

Aluminum plastic composite foil is the common sealing material for Li-ion battery, and its heat-sealing strength can influence the safety performance of batteries directly. In this article, the heat-sealing strength of aluminum plastic foil with different heat-sealing conditions (heat-sealing temperature and heat-sealing time) is studied, and uniaxial tensile tests are done to obtain the highest tensile strength and apparent elastic modulus to study the influences of heat-sealing temperature and heat-sealing time on the heat-sealing strength. It has been found that the heat-sealing strength of the specimens enhances firstly, and then becomes stable to a value with the temperature increasing. However, heat-sealing time has slight influence on the heat-sealing strength at a relative low temperature, while at the relative high temperatures, heat-sealing strength of the specimens enhances with the time extending until it becomes stable to a value. Meanwhile, there is similar influence of heat-sealing temperature and heat-sealing time on the apparent elastic modulus of specimens. It has also been found in the experiments that the tensile failure modes of specimens include interface failure, cohesive failure, peeling failure and root damage, and cohesive failure occurs most in these modes, and root damage occurs more when the heat-sealing time is increasing.

Since safety certification only applies for lithium-ion battery system up to 48V in Chinese Coal Mine Industry for underground application, standard battery energy storage system (BESS) cannot be directly used to provide emergency power for critical motor load such as fan / pump etc, which are normally rated at a few hundreds volts. This paper develops a modular design defined as Battery Electronic Building Block (BEBB) that integrates 48V battery-inverter pack as one “plug & play” module based on load requirement. It provides a novel integrated battery & power electronics control architecture that does not need a dedicated Battery Management System (BMS) to realize a more robust and reliable battery energy storage system. Based on this concept, a novel de-centralized energy system architecture defined as energy computer is further introduced based on an analogy with personal computer system.

A heat storage water tank containing phase change materials (PCMs) for an air source heat pump system is studied with an aim to optimize the heating system for non-continuous sources of energy, such as solar heat, and air and geothermal heat etc. The water tank has a volume of 6 m³, containing 686 kg of paraffin with a phase change temperature of 46.78℃, encapsulated within 304 stainless steel tubes. A real scale model was established and investigated numerically using a Fluent software package. The effective enthalpy method was used to deal with the phase change process. It was found that the storage system can store 102.4 kW·h of heat within 9.2 h and continuously heat a low energy building for 11.1 h, meeting the heat demand of the building at night. This illustrated that an air source heat pump, coupled with the heat storage tank containing the PCM could achieve a large span of intermittent heating.