基于金属负极和锰酸锂正极的快充锂离子全电池的设计及性能研究

Metal Sn and Sb anodes have high specific capacities and suitable Li+ insertion potentials, which have great potential in practical application for Li-ion batteries. Unfortunately, during the battery charge/discharge process, their huge volume expansion and continual rupturing and reforming of SEI film result in the rapid decay of capacity. While for the low cost lithium manganese oxide cathodes (LiMnO2 and LiMn2O4), the low electronic conductivity, Mn2+ dissolution, and Jahn-Teller effect have hindered their practical applications. In this project we intense to directly grow 3D ordered high-capacity metal anodes (Sn and Sb) and Al2O3/MgO coated lithium manganese oxide cathodes (LiMnO2 and LiMn2O4) on conductive substrates, and further assemble them into 3D array structured full batteries with fast charging/discharging capability. The kinetics of Li4.4Sn/Li3Sb formation during lithiation and its size effect, as well as the dissolution mechanism of Mn2+ and the Jahn-Teller effect in Mn-based cathodes will also be studied. Based on these results, we will carry out the assembling and matching technologies of these 3D arrayed metal anodes and Mn-based cathodes, and fully study their electrochemical reaction mechanisms and performances.

金属锡、锑负极具有高锂离子储存容量和合适电化学反应平台，是一类具有实际应用前景的负极材料，但其电化学反应体积形变大及固态电解质界面膜不稳定造成了容量的急剧衰减，而锰酸锂（LiMnO2、LiMn2O4）正极的低电子导电率以及Mn2+溶解和Jahn-Teller畸变效应也严重限制了其实际应用。针对上述关键问题以及传统粉体电极材料的充电时间长、电极制备/加工过程繁琐等缺点，我们拟在导电集流体上可控生长三维有序的高容量金属Sn、Sb负极和Al2O3、MgO表面包覆的锰酸锂（LiMnO2、LiMn2O4）正极，构造快速充电自支撑结构锂离子全电池。我们将系统研究金属Sn、Sb循环过程中Li4.4Sn、Li3Sb合金形成的动力学特性及材料尺度效应对其影响规律，此外我们也将考察氧化物包覆的锰酸锂Mn2+溶解机理与规律，并在此基础上研究全电池的组装配对工艺，系统研究其电化学反应机制和性能。

本项目通过研究金属Sn、Sb、Bi等金属负极材料在水热反应体系下的结晶和生长规律，获得了具有结构可控的碳限域金属活性相，实现了稳定核壳结构的精细调控，在此基础之上研究金属负极脱嵌锂的尺寸效应规律并抑止其粗化现象。在项目执行期间，项目组成员以Sn、Sb、Bi等金属基材料为研究对象，通过碳材料的引入以及三维多孔结构的构建，有效提高了复合材料的比表面积和活性材料间的连通性，有效抑制了Sn、Sb、Bi等晶粒的粗化和体积膨胀。并以力学性能优异的碳布作为基底成功制备了具有自支撑特性的LixMn2O4正极材料，并对其全电池特性进行性了研究。同时以“金属锂负极”为研究对象，通过Co、Zn颗粒及N掺杂碳纳米片的协同作用有效抑制了锂枝晶的生成，并借助材料理论计算手段对探究了复合材料对锂枝晶的抑制作用的机理。