Combustion synthesis and electrochemical properties of LiNi_1/3Co_l/3Mn_l/3Br_xO_2-x and LiNi_1/3Co_l/3Mn_l/3Br_xO_2-x/graphene cathode material for Li-ion batteries

School of Materials Science and Engineering, Hefei University of Technology, Hefei, Anhui 230009, P R China

^* Corresponding author: Ji-ping ZHU; Tel:18919665197; E-mail: jpzh@ustc.edu.cn

Abstract

The layered LiNi_1/3Co_1/3Mn_1/3Br_xO_2-x (0≤x≤0.09) cathode materials were prepared by a combustion method. The XRD results indicate that the Br-doped LiNi_1/3Mn_1/3Co_1/3O₂ has the same layered structure as the pristine LiNi_1/3Mn_1/3Co_1/3O₂. FE-SEM results indicate that the particle size distribution of samples is uniform. Electrochemical tests reveal that Br-doped samples exhibit higher discharge capacity and rate capability compared with the pristine, especially the LiNi_1/3Co_1/3Mn_1/3Br_0.05O_1.95 sample shows initial discharge capacity, which can reach to 175.4 and 166.4mAh/g at 0.5 and 1.0C, respectively. Finally, an electronically conducting 2D network of graphene was introduced into LiNi_1/3Co_1/3Mn_1/3Br_0.05O_1.95 cathode material. The electrochemical properties of the materials were investigated by charge-discharge tests and electrochemical impedance spectroscopy. The charge-discharge tests demonstrate that this sample has better cycle stability than LiNi_1/3Co_1/3Mn_1/3Br_0.05O_1.95 which can be attributed to the excellent electronic conductivity and stable chemical properties of graphene. The EIS results reveal that the graphene coated greatly decreases the resistance of lithium batteries, especially the charge transfer resistance which can be attributed to the significantly improved electronic conductivity.