Polyacrylonitrile coated Li2MnO3 cathode material for lithium ion batteries





Recent 20 years, there was a number of investigations to improve energy density of Lithium ion battery (LIB), increase safety and lifetime. Various novel cathode materials are under development including Li-rich intercalation materials. One of the attractive cathode material is Li2MnO3 due to its high theoretical capacity. However, this Li- rich cathode material suffers from rapid capacity fading due to dissolution of intermediate products into liquid electrolyte [1]. Severalmethodssuchasmetaliondoping and surface modification were used to stabilize the structure and overcome the above drawbacks. For example, Kim at al. sucsessfully developed stable TiO2 coated Li2MnO3 material to improve the cyclability of the electrode material [2]. However, the thickness of such insulating coating should be in nanometers range in order to provide electron conductivity. In this project we will develop electron conductive polyacrylonitrile (PAN) coating on Li2MnO3 tostabilizeit.PANisthepromisingmaterialas coating due to simplicity of preparation, low cost and chemical stability [3]. The aim of this project is a fabrication of a stable and protective coating at Li2MnO3 by conductive polymer such as polyacrylonitrile. Moreover, optimal conditions of coatingsfabricationwillbedeterminedbyvariationof parameters such as heat treatment temperature, duration, polymer concentration etc. Mn -basedmaterial suffers from dissolution of Mn+2. The coating should be permeable for Li ions but simultaneously prevents a dissolutionofMnO2.Thereisaco-calledHunterreaction,literallythereactionMn+3->Mn+4 + Mn+2 [1]. The resulting Mn+2 dissolves into electrolyte(LiPF6)whichdecreasestheamountofactive material. The mechanism is related to the reaction with HF.Anelectrolyteconsistsatleast1%ofH20.It is react and HF will be synthesized. After that HF dissolves all Mn ions. PAN coated Li2MnO3prevent this dissolution. In order to achieve this goal, the following objectives will be considered. Objective 1. Synthesis of Li2MnO3 Objective 2. Fabrication of PAN coating and optimizations of its parameters. Objective 3. Physical-chemical characterization of obtained coated Li2MnO3. Objective 4. Investigation electrochemical performanceofbatterieswithcoatedLi2MnO31.Naturematerials,2013,12,827-835.2. Journal of Power Sources, 2016, 304, 119–127. 3. J. Mater. Chem., 2011, 21, 6807-6810