高电压尖晶石镍锰酸锂材料表面及其电池界面的优化

High-voltage spinel LiNi0.5Mn1.5O4 material with the operation voltage of 4.7 V, fast three-dimensional Li+ diffusion pathway, and good electrical conductivity, can effectively improve the energy density and power density of battery. However, due to its high working voltage and the strong oxidation on the surface, the electrochemical stability of LiNi0.5Mn1.5O4 in high voltage LIBs is limited by not only its own surface chemical property but also the significant interface challenges when using the commercial available components in LIBs, such as liquid organic electrolytes, polymer separators, conductive additives, binders, and current collector. Aim to improve the performance of LiNi0.5Mn1.5O4 battery, a hierarchical "gradient doping and surface atomic layer deposition" approach is proposed to prepare the LiNi0.5Mn1.5O4 material with controllable surface chemical property. Combined with the design of high-voltage electrolyte applied in LiNi0.5Mn1.5O4 battery, the electrode/electrolyte interface is optimized. The high-voltage stability of the polymer separators and non-active materials is verified, and the corresponding modification or screening methods are proposed, based on its impact mechanism. Improve the characteristics of anode interfacial film, and combine the optimized components to explore the interaction mechanism between battery interfaces. This program will provide theoretical basis and technical support for material selection and battery design of LiNi0.5Mn1.5O4 battery.

高电压镍锰酸锂材料具有4.7V的电压平台，三维的快速Li+扩散通道以及良好的电子电导率，兼具高的能量密度以及功率密度。但是由于镍锰酸锂材料高工作电压以及具有强氧化性表面的特点，镍锰酸锂材料的表面特性及其电池内各组件（电解液、隔膜以及非活性物质）的耐高压稳定性及相关界面问题成为镍锰酸锂电池性能快速衰减的主要原因。为了改善镍锰酸锂电池的性能，本项目基于“梯度掺杂+表面原子层沉积”多级结构的设计思想，制备具有可控表面化学状态的镍锰酸锂材料；结合可应用于镍锰酸锂电池的高压电解液设计，优化镍锰酸锂/电解液界面；验证隔膜及非活性物质材料的高压稳定性，并基于其作用机理进行改性或筛选。通过改善负极界面膜特性，并结合优化的各组件探求电池关联界面之间的相互作用机制，为镍锰酸锂电池的材料选型及电池设计提供理论依据和技术支撑。

本项目针对高电压镍锰酸锂材料表面特性及其电池内各组件（电解液、隔膜以及非活性物质）的耐高压稳定性及相关界面问题展开研究。以降低材料表面氧化性和抑制金属离子溶解为目的，从阴阳离子掺杂、结构/形貌调控以及表面涂层修饰等多个方面，开展多类型的镍锰酸锂材料设计，实现具有可控表面化学状态的镍锰酸锂材料制备，研制的高电压镍锰酸锂全电池在0.5C下常温循环性能大于600次。进一步的，从耐高压电解液、隔膜、粘结剂等方面优化了电池关联界面的性能。耐高压电解液的氧化电位提高到5V以上。同时评价了多种隔膜、粘结剂在高电压下的稳定性，并优化了适用于镍锰酸锂材料的多种辅助材料。最后，分别设计了以石墨或钛酸锂为负极的镍锰酸锂全电池，揭示了负极类型对全电池影响的作用机制。项目研究成果为镍锰酸锂电池的材料选型及电池设计提供理论依据和技术支撑。