4V and 5V-based Cathode Materials for Li-Ion Batteries

Abstract

With the great surge of interest in energy issues, the application fields of lithium ion batteries (LIB) have been broaden not only portable devices but also hybrid-electric vehicle (HEV), electric vehicle (EV) and energy storage system (ESS). High power density, high energy density and high safety of LIBs are necessary to be applied in HEV and EV systems. One of methods to improve energy density is increasing charge voltage over 4.3V by using more lithium inside of structures. These conditions are one of demands for industries. But charge and discharge over 4.3V leads to degradation of structural stability hence it makes cycle and thermal stability worse. Therefore various modifications of cathode materials are essential to meet these conditions. The following components are the way to solve these problems. Firstly, various nano-sized cathode materials have been studied by synthesizing 0D, 1D, 2D, and 3D materials through various methods. These nano-sized particles can effectively reduce the diffusion length of lithium ions and increase the active site between electrolyte and cathode materials, which can improve the rate capability at the high current density. Secondly, there is heteroatom doping methods. This method can realize the synergistic effect between advantages of pristine transition metals and doping atoms by complementing drawback of the transition metals. More specifically, the doping method can enhance the cyclability and thermal stability by modifying surface structures. Further, it can increase the operation potentials according to the charge/discharge characteristic of doping atoms. Also, we can expect an economic effect by using inexpensive doping materials. Herein, I investigated the nano-size effect of LiCoO2 materials and the electrochemical performance of the nickel-doped 5V spinel with the morphology of the nanorod-nanoparticle cluster where the energy density was compared with the control materials fabricated by the sol-gel method. Finally, the novel cathode material that is newly optimized LiNi1-x-yCoxAlyO2 composition was evaluated the possibility to apply the HEV or EV system.