作为下一代锂离子电池或固态电池的候选正极材料,镍锰酸锂LiNi0.5Mn1.5O4正在吸引研究者的兴趣。本工作介绍了LiNi0.5Mn1.5O4的晶体结构、合成方法、电化学反应机制、材料的电学属性以及材料的优势,同时介绍了目前阻碍其产业化应用所存在的技术障碍:高温循环差、过程库伦效率低、金属溶出及相变、高电压下电解液分解、全电池产气等。针对存在的主要技术问题,深入讨论分析其内在的原因,并总结了若干材料层面的解决思路:微观形貌调控、新黏结剂匀浆策略、掺杂、包覆、高电压电解液匹配、制备过程控制、全电池应用研究等,另外还推测了可能的应用场景。LiNi0.5Mn1.5O4材料的商业化应用还有赖于电池层面的精细结构设计。综述目的是希望研究者更加关注LiNi0.5Mn1.5O4材料的产业化应用研究。
As a candidate cathode material for next-generation Li-ion batteries or solid state batteries, the spinel LiNi0.5Mn1.5O4 is appealing researchers' interest. The 5 V spinel material of LiNi0.5Mn1.5O4 had ordered and disordered phases, and crystal structure, synthetic method and electrochemical reaction mechanism of which were discussed. Also, its electronic conductivity and lithium ion diffusion coefficient were highlighted compared with other cathode materials. The advantages of LiNi0.5Mn1.5O4, such as high discharge plateau, good rate performance, high thermal stability, abundant manganese resources and low cost, were introduced. Then technical obstacles hindering the industrialization of LiNi0.5Mn1.5O4 were discussed, including poor cycle performance at high temperature, low cycling coulombic efficiency, metal dissolution and phase transition, electrolyte decomposition at high voltages, gas generation in full cells. The main reason negatively affected the electrochemical performance of Li-ion batteries was electrochemical oxidation of carbonate esters at the LiNi0.5Mn1.5O4/electrolyte interface which resulted in Ni/Mn dissolution, crystal structural transformation and surface film formation, and eventually led to lower electronic conductivity and Li+ transport kinetics in Li-ion batteries. Some solution ideas were summarized at the material level, such as microscopic morphology control, new binder slurry strategy, doping, coating, high voltage matching electrolytes, synthetic control, and these material solution ideas should be coordinated with full cell design. In addition, this review speculated a few possible application scenarios on basis of its merits, for instance, start-and-stop power supply, low-temperature application, power tools and so on. Commercialization of LiNi0.5Mn1.5O4 relies on elaborate construction design at the battery level beside the materials design. More wide and thorough application research needs to be done to push the industrialization of LiNi0.5Mn1.5O4.