功能电解液添加剂与5V锂离子电池LiNi0.5Mn1.5O4正极的相容性及界面作用机理

There is a broad application prospect based on 5 volt high voltage material of LiNi0.5Mn1.5O4 in the field of lithium ion power battery. However, the self-discharge phenomenon of the battery based on LiNi0.5Mn1.5O4 as the cathode is serious, resulting in the poor comprehensive electrochemical performance of the material. Thus, from the point view of the compatibility between functional electrolyte additives and the electrode of LiNi0.5Mn1.5O4, thiophene derivative and organic fluorinated carbonate are calculated and selected by density functional theory (DFT) in this project. The conductive polymer films formed on the cathode due to decomposition of thiophene derivative, the excellent electrochemical stability of fluorinated carbonate and the good thermal stability of Mg(TFSI)2 and lts stable solid electrolyte interface film formed on the cathode due to its decomposition can reduce the reactivity, increase the compatibility between electrodes and electrolyte and improve the comprehensive electrochemical performances of the battery. This project is aimed to study the physical characteristics, electrochemical stability and the composition of interfacial film by modern analytical measurements and techniques, and reveal the compatibility between single additive and cathode electrode and interface mechanism, and then show the compatibility between composite additives and electrodes and their synergy mechanisms. The accomplishment of the project will be of great importance for the fundamental research and application of lithium ion power battery.

5V高电压正极材料LiNi0.5Mn1.5O4在锂离子动力电池领域具有广阔的应用前景。然而，以LiNi0.5Mn1.5O4为正极的电池自放电现象严重，导致材料综合电化学性能极差。本项目从功能电解液添加剂与LiNi0.5Mn1.5O4电极相容性的角度出发，基于密度泛函理论计算并筛选噻吩衍生物及氟代碳酸酯，创新性地利用噻吩衍生物在正极上生成聚合物导电膜的特性、氟代碳酸酯优异的电化学稳定性、Mg(TFSI)2良好的热稳定性及在正极上形成稳定的固体电解质相界面膜(SEI)的特征，降低电极与电解液的反应活性，提高彼此之间的相容性，改善电池的综合电化学性能。本项目旨在通过现代分析检测技术与手段系统研究电解液的理化性质及界面膜组分，揭示单一添加剂与正极的相容性及界面作用机理，明晰复合添加剂与电极的相容性及协同作用机制，为锂离子动力电池的基础研究和应用提供新思路。

5V高电压正极材料LiNi0.5Mn1.5O4在锂离子动力电池领域具有广阔的应用前景。然而，以LiNi0.5Mn1.5O4为正极的电池自放电现象严重，导致材料综合电化学性能极差。本项目采用喷雾干燥法和静电纺丝法制备了LiNi0.5Mn1.5O4，研究了材料的最佳制备和煅烧工艺，探究了电极过程动力学，合成出了一种性能相对较理想的高电压正极材料LiNi0.5Mn1.5O4。申请人通过量子化学计算筛选出了2-噻吩甲腈，考察了不同浓度的2-噻吩甲腈与LiNi0.5Mn1.5O4的相容性及电化学性能改善作用机理。同时，申请人研究发现了一种结构类似于Mg(TFSI)2的电解质添加剂三氟甲基磺酸镁Mg(MFS)2，明晰了Mg(MFS)2改善LiNi0.5Mn1.5O4电化学性能的机理，通过在负极形成锂镁合金抑制锂枝晶的形成和正极镍、锰的溶解。同时，申请人不仅向电解液中加入氟代碳酸酯，还尝试了一种新型的含氟添加剂六氟磷酸四丁胺(TH)，探究了其与LiNi0.5Mn1.5O4电极的相容性，TH也一定程度上改善了LiNi0.5Mn1.5O4的常温循环稳定性。申请人还制备了不同结构的锌负极，采用水热法制备了铝掺杂δ-MnO2材料。采用溶胶-凝胶法结合冷冻干燥技术合成了含钠锰基复合材料Na0.44MnO2/Mn2O3和Na2/3Fe1/2Mn1/2O2。采用静电纺丝法及溶胶凝胶法制备出MnO复合物，研究了储能机理及锰溶解、枝晶抑制机制。为高电压正极材料LiNi0.5Mn1.5O4性能的改善及镍、锰的溶解及其电解液的分解、锂枝晶的抑制提供了新思路。项目实施过程中，项目组先后发表基金标注的研究论文27篇，其中，被SCI或EI收录的论文累计24篇；项目在执行过程中，申请人获湖南省科技厅“湖湘青年英才”支持计划项目1项，获得湘西州重点研发计划2项，课题名称为“电解液添加剂在高电压锰基锂离子全电池中的应用与产业化研究”（2021年，No.7，20万，子课题(5万)/在研）、“湘西地区锰锌资源的材料化冶金及其在绿色储能中的应用”（2018年，No.2018GX2001，25万，主持/结题）；申请国家发明专利10件，授权5件；出版专著3部；参加国际国内学术会议17次，承办会议1次，协办会议3次；培养硕士研究生14名，本科生30余名。课题组成员2人晋升教授职称，4人晋升副教授职称。