Improved Thermal and Structural Stability of LiNi0.8Co0.1Mn0.1O2 cathode materials by Surface Modification

Abstract

The Ni-based cathode materials have attracted a lot of attentions for the higher practical capacity than other cathode materials, but suffer from several inherent problems such as thermal instabilities and severe capacity fading. In order to overcome those problems, a lot of attempts such as surface coating or doping, were tried. However the intrinsic problems of Ni-based cathode materials are still not perfectly solved. Herein, to overcome the structural instability problem of the LiNi0.8Co0.1Mn0.1O2, we suggest a surface modification method that could reduce and delay the heat generation and also improve the electrochemical performances at 60℃. The magnesium phosphate, Mg3(PO4)2, was coated on the surface of the LiNi0.8Co0.1Mn0.1O2 in purpose to enhance the structural stability at high temperatures. This method could remove the surface lithium residues by forming olivine LixMgPO4 using the residual lithium ions with a nanoscale range. Since the olivine structure shows remarkable thermal stability due to the strong bonding of the phosphorous and oxygen atoms, thermal degradation of the material could be delayed. After the surface treatment, cyclability at high temperature (at 60℃) was improved up to 20% and the thermal stability is secured at the same time.