锂离子电池高压电解液研究进展

To satisfy the increasing discharge capacity demand of next generation electric devices, various high working voltage cathodes have been explored. However, traditional carbonate solvents, such as ethylene carbonate and ethyl methyl carbonate-based electrolytes are prone to oxidative decomposition at high voltage (>4.3 V, vs. Li/Li ⁺ ), which results in the increase of irreversible capacity and the inferior cycling performance of lithium ion batteries. To solve the problem, it is necessary to design high-voltage tolerant electrolyte based on theories and experiments. Specifically, new high-voltage solvents such as sulfone and ionic liquid are determining factors to improve the stability of electrolyte as they could improve the interfacial stability between the high voltage cathode and the electrolyte intrinsically. Another method to solve the problem is the addition of high-voltage additives because a small amount of additives could form an effective solid electrolyte interface layer and decrease the interfacial reaction dynamically. Moreover, additives can solve the problem economically and effectively. In addition, optimizing the physical and chemical properties of conventional electrolyte is a new strategy to exhibit new properties. For example, a novel formula such as superconcentrated electrolyte has wide electrochemical window and superior cycling performance. However, it is well known that high voltage solvents are often characterized by high viscosity, low reductive stability and reductive decomposition products cannot form an effective interfacial layer on the anodes. The addition of additives may have negative impact on other properties of lithium ion batteries such as the initial coulombic efficiency. And the superconcentrated electrolyte is very expensive and high viscosity. Although they have some defects, it is also very significant to study them because they can give a guide to investigate electrolyte with superior performance. Thus, this review summarized the advances and perspectives on the development of high-voltage solvents, additives and superconcentrated electrolyte of lithium ion batteries. Key learning points: (1) High voltage solvents can stabilize the electrode/electrolyte interface intrinsically. (2) A small amount of high voltage additives can improve the battery performance economically. (3) Superconcentrated electrolyte is characterized by superb properties like high oxidative and reductive stability, Al-anti corrosion and high rate performance.