三明治结构石墨烯纳米片@LiNi0.5Mn1.5O4@石墨烯纳米片复合材料的原位/可控制备及相关机理

Based on the unique merits(excellent electrical conductivity, large specific surface area, soutstanding flexibility, fast lithium ion transportations,etc) of graphene nanosheets(GNRs) and the characteristic(short transport distance for both electron and lithium ion) of nano-LiNi0.5Mn1.5O4 (n-LNMO), a sandwich-structured composite of GNRs@n-LNMO@GNRs is designed to overcome the shortcomings(poor cycling stability and rate capability) of LNMO, which is thought as a promising cathode material for lithium ion batteries. In the sandwich-structured composite of GNRs@n-LNMO@GNRs, GNRs are grown in-situ on the surface of n-LNMO particles with 100-200 nm in diameter by means of in situ graphitizing organic compounds. Benefiting from the improved electrical conductivity, facile lithium ion transportations, and good surface stability of LNMO under high voltage, the sandwich-structured composite of GNRs@n-LNMO@GNRs is expected to be obtained as a high voltage cathode material for lithium ion batteris with high discharge capacity and coulombic efficiency, good cycling stability and superior rate capability.The controllable synthesis and formation mechanism of GNRs@n-LNMO@GNRs, the structure-activity relationship of sandwich-structure to electrochemical performance of GNRs@n-LNMO@GNRs composite,the improvment mechanisms of electron/lithium ion conductivity and the protection mechanism of GNRs to the surface of n-LNMO electrode will be studied in detail. The research results will provide theory references and experimental evidences for the design and application of cathode material for lithium ion batteries with high performances.It is also beneficial to the clean and efficient utilization of manganese resources in Xiangxi and even in China.

针对高电压正极材料LiNi0.5Mn1.5O4(LNMO)循环稳定性和倍率性能不理想的缺点，利用石墨烯纳米片(GNRs)导电性能优良、比表面积巨大、机械弹性好和锂离子扩散性能优良，以及纳米LNMO(n-LNMO)锂离子和电子传输路径短等特点，采用原位石墨化有机物法，在n-LNMO颗粒表面生成GNRs，形成三明治结构GNRs@n-LNMO@GNRs，提高LNMO的电子导电性、锂离子扩散性和高电压下LNMO的表面稳定性，获得放电容量和库仑效率高、循环性能稳定、倍率性能优异的高电压复合正极材料。研究GNRs@n-LNMO@GNRs复合材料的可控合成与形成机制、阐明三明治结构与复合材料电化学性能之间的构效关系、探讨复合材料电子/锂离子导电性的改善机理和GNRs对n-LNMO电极的保护机理，为高性能锂离子电池正极材料的设计与应用提供理论借鉴和实验依据，为湘西乃至我国锰资源的高效清洁利用提供新思路。

针对高电压正极材料LiNi0.5Mn1.5O4(LNMO)循环稳定性和倍率性能不理想的缺点，利用石墨烯纳米片(GNRs)导电性能优良、比表面积巨大、机械弹性好和锂离子扩散性能优良，以及纳米LNMO(n-LNMO)锂离子和电子传输路径短等特点，制备出复合材料GNRs@n-LNMO@GNRs，通过研究制备材料的温度、pH、处理方式、碳含量等因素时制备出复合材料的结构相貌和电化学性能，进而得出对复合材料形成机理、三明治结构与复合材料电化学性能之间的构效关系、复合材料电子/锂离子导电性的改善机理和GNRs对n-LNMO电极的保护机理。在研究周期内，课题组先后在《Ionics》、《Vacuum》、《Microchimica Acta》、《J.Mater.Chem.A》、《Solid State Ionics》、《International Journal of Electrochemical Science》、《Journal of Electroanalytical Chemistry》、《Frontiers in Chemistry》、《Journal of Alloys and Compounds》、《中国有色金属学报》等期刊上发表标注的研究论文28篇，其中：学术论文28篇；被SCI收录16篇、EI收录17篇；参加国际国内学术会议11次，提交会议论文6篇。申请国家发明专利1项。培养毕业和正在培养硕士研究生共8名，课题组成员1人晋升副教授职称。