宽温域锂电池电解液研究进展

Lithium-ion batteries have gained great success in energy storage market due to their high energy density and long cycling life. However, it is necessary to further increase energy density, prolong life-span and enhance rate performance. Moreover, exploring more application scenarios is another important development direction for lithium batteries. Application scenarios of polar exploration, space exploration require lithium batteries to meet the demand on working at low temperature, whereas application scenarios of oil industry, robot extreme detection need lithium batteries to operate at high temperature. Unfortunately, traditional lithium batteries can only operate well in the temperature range of 15–35°C. Therefore, to develop lithium battery with wide temperature range is urgent. Too low or high temperature has negative influences on lithium batteries. In general, too low operating temperature can cause the stronger interaction between Li⁺ and solvent molecules, increase viscosity and decrease salt solubility, leading to sluggish kinetic process of electrochemical reaction. As a result, internal resistance increases and reversible capacity decreases for lithium batteries. In addition, too low operating temperature may change the electrochemical reaction path. For example, at low temperature, Li⁺, which should be embedded into graphite anode in an electric field, may be reduced on the surface of graphite anode, forming dendrites and endangering the safety of the battery. It will cause safety risk for lithium-ion batteries. At high temperature, the solubility of lithium salt will increase, reducing the stability of electrode/electrolyte interphase. The side reactions, including electrolyte decomposition, transition metal ions dissolution, cathode crystal structure damage, are more possible to react. As a result, the cycling stability of lithium batteries decreases at high temperature. The key to solve the above problems is to develop a wide-temperature range electrolytes for lithium batteries. In recent years, some research advances have been achieved in this field. For low temperature electrolyte, using solvents with low freezing point, low viscosity is indispensable, to ensure the enough kinetics rate of electrochemical reaction. To weaken the too strong interaction between Li⁺ and solvent molecules caused by low temperature, using ether-based or fluoro-carbonate solvent are effective. Besides, to build electrode/electrolyte interphase with high Li⁺ diffusion rate can also increase the electrochemical performance of low-temperature lithium batteries. For high-temperature electrolyte, using solvents with high boiling point, high flash point is necessary. To build highly stable electrode/electrolyte interphase is helpful to suppress electrolyte decomposition and improve electrode structure stability. Eliminating impurities is also important for high temperature electrolyte. To summarize those research advances is necessary and urgent. In this review, the research and development progress of lithium battery electrolytes with wide temperature range are discussed. The contents include the choices of solvent and lithium salt, the influence on electrode/electrolyte interphase at extreme temperatures, high-temperature and low-temperature electrolytes. In addition, some outlook also be provided at last, from new characterization techniques, novel lithium battery systems, and the opportunity brought from extreme temperatures. While impressive research work continues to be reported, manufacturing and application of lithium batteries with a wide temperature range remain challenging. It is expected that this review can help the development of lithium battery electrolytes with wide temperature range.