Graphene/Ta2o5 Co-Coating to Improve the Electrochemical Performance of Cathode Material Lini0.5co0.2mn0.3o2 for Lithium-Ion Batteries

Abstract

LiNi0.5Co0.2Mn0.3O2 (NCM523) has been explored as the cathode materials of lithium-ion batteries for its advantages of high energy density, low self-discharge and good thermal stability. However, its practical application is limited by severe capacity decay and unsatisfactory rate performance due to the both insufficient structural stability and intrinsic electron/ion conductivities. In this paper, a graphene/Ta2O5 co-coating layer is successfully fabricated on the surface of NCM523 to form a cathode material of GTa-NCM523 to enhance both the electron and lithium-ion transport during cathode operation. The GTa-NCM523 cathode material achieves a discharge specific capacity of 147.4 mAh g−1 after 600 cycles at a voltage of 3.0-4.5 V and a rate of 1 C (180 mA g−1) with a capacity retention rate of 81.4 %. In contrast, the uncoated NCM523 only retains 63.2 % of its capability at the same conditions. At an elevated rate of 10 C (1800 mA g−1), the GTa-NCM523 can achieve a discharge-specific capacity of up to 113.5 mAh g−1, which is 43.7 % higher than the uncoated NCM523. The co-coating layer can separate the electrode from the electrolyte, prevent HF erosion and accelerate the movement of lithium-ions and electrons, which account for the superior electrochemical characteristics of the co-coating layer comprised of graphene and Ta2O5.

Keywords: LiNi0.5Co0.2Mn0.3O2, Co-coating layer, Surface modification, Cathode material, Lithium-ion battery