Transmission electron microscopy of presodiation in copper sulfide anode and its full cell application

Abstract

As industrialization progresses, the demand for rechargeable batteries used in portable electronic devices and electric vehicles is also rapidly increasing. Currently, many lithium-based batteries have been commercialized, but due to a surge in demand and its instability in raw material prices, it is essential to develop an another secondary battery to replace lithium-ion batteries. Studies on sodium-ion batteries have been actively conducted as an alternative to lithium-ion batteries. Copper sulfide has a high capacity (560 mA h g$^{-1}$) and high electrical conductivity (10^3 S/cm), and its research has been conducted for use as an anode material for sodium ion batteries. However, there are several disadvantages to be overcome for commercialization as a full cell battery, such as, low initial capacity, low initial coulombic efficiency and long recovering time to its maximum capacity. In this thesis, an optimized presodation of the copper sulfide anode is suggested to overcome its shortcomings. The initial performance and stability were improved, and the cause and mechanism were crystallographically analyzed with transmission electron microscope, and various electrochemical analysis techniques are conducted.