electrochemical characterization of Ni-F co-doped Nano LiMn2O4 cathode materials

Abstract:

Ni-F co-doped Nano LiNi0.03Mn1.97O3.95F0.05 (LNMOF) cathode material was synthesized by a molten-salt combustion method. The results show that Ni-F co-doped markedly elevates the rate performance, cycling stability and specific capacity of the LNMOF. At 5, 10, 15, 20 C and 25 ℃, LNMOF exhibits the initial discharge capacity of 101.4, 92.5, 89.4 and 66.8 mAh?g-1 respectively. After 1000 cycles, the LNMOF deliver capacity retention rate of 77.9, 70.8, 70.9 and 72.9% respectively. Cyclic voltammetry and electrochemical impedance spectroscopy show that LNMOF cathode material exhibits lower apparent activation energy 24.72 KJ?mol-1 and greater diffusion coefficient of lithium ion 1.174×10-8 cm2?s-1, when compared to the LiMn2O4 sample. The electrode of before and after 1000 cycles were investigated via XRD, it was demonstrated that the crystal structure of the LNMOF sample has hardly changed. Moderate Ni-F co-doping effectively inhibits Jahn-Teller distortion, stabilizes crystal structure and improves the specific capacity and enhances the cycle performance of LiMn2O4 cathode materials at the same time.

Key words:Ni-F co-doping;spinel LiMn2O4; molten-salt combustion method; cathode material; Jahn-Teller distortion