锂离子电池正极界面修饰用电解液添加剂

Electrolyte Additives for Interfacial Modification of Cathodes in LithiumIon Battery

提高电压是提高锂离子电池比能量的重要途径之一。例如,Li Ni0.5Mn1. 5O4(4.7V)、Li Ni PO4(5.1V)和富锂锰基等电极材料在较高的充电截止电压下表现出较高的能量密度和较低的成本,具有很好的应用前景。另外,提高Li CoO2和三元电池体系的充电截止电压是提升电池能量密度的简单有效措施。但是,当电池充电截止电压提高时,不仅会造成电解液在正极/电解液界面的氧化分解,还会加速正极中金属阳离子在电解液中的溶解,造成电池循环性能和安全性下降。采用不同的正极界面修饰用电解液添加剂,既可以有效钝化正极/电解液界面,抑制电解液的分解,还可以有效抑制正极结构的破坏。本文从添加剂的分子结构出发,介绍了磺酸酯、硼酸酯、磷酸酯、氟代碳酸酯、腈类、酸酐和锂盐等添加剂在正极界面的相关研究成果,并对不同添加剂的作用机理进行了详细的解释和归纳;另外,介绍了添加剂的联用技术在不同电池体系中的最新研究成果;最后,对新型正极界面修饰用电解液添加剂的开发进行了展望。

Increasing the voltage is one of the important ways to improve the energy density of lithium ion batteries. For example, LiNi0. 5Mn1. 5O4(4. 7 V), LiNiPO4(5. 1 V) and lithium-rich manganese-based materials exhibit high energy density and low cost at high charge cut-off voltage, showing good application prospects. In addition, increasing the charge cut-off voltage of LiCoO2 and NMC battery systems is a simple and effective approach to increase the energy density. However, when the charge cut-off voltage is increased, not only the electrolyte will be oxidatively decomposed at the cathode/electrolyte interface, but also the dissolution of the metal cation from the cathode materials will be accelerated. These are the main causes for the decreased cycle stability and safety. The electrolyte additives can be used for modifying positive electrode interfaces, thus passivating the cathode/electrolyte interface and inhibiting the decomposition of the electrolyte. Moreover, the modified electrolyte can effectively suppress the destruction of the cathode structure. Based on the molecular structure of the additives, the related research results of additives such as sulfonate ester, boric acid ester, phosphate ester, fluorocarbonate, nitrile, anhydride and lithium salt at the positive electrode interface are introduced in this paper. The action mechanisms of different additives are explained and generalized. Furthermore, the combination technology of additives for different batteries are introduced. At last, the development of new electrolyte additives for cathode/electrolyte interface modification are discussed.