Preparation and electrochemical properties of Li-Ni co-doping spinel LiMn₂O₄ single crystal polyhedron material

Spinel Li_1.02Ni_0.05Mn_1.93O₄ cathode material was synthesized via a flameless combustion method at 500℃ for 3 h followed by calcination at 600、650、700 and 750℃ for 6 h, respectively. The results show that Li-Ni co-doping material at different calcination temperatures does not change the cubic spinel structure of LiMn₂O₄. With the increase of calcination temperature, the particle size increases and the crystallinity is enhanced. At the secondary calcination temperature of 700℃, the cathode material of Li_1.02Ni_0.05Mn_1.93O₄ single crystal polyhedron possess 111, 110 and 100 surfaces. It exhibits an excellent electrochemical performance. The Li_1.02Ni_0.05Mn_1.93O₄ cathode material shows the first-discharge specific capacity of 108.2 mA·h·g⁻¹ and maintains the capacity retention of 76.8% after 500 cycles at 1 C. Moreover, it displays an initial discharge capacity of 99.0 and 71.3 mA·h·g⁻¹, while provides a capacity retention rate of 72.1 and 86.4% after 1000 cycles at 5 C and 500 cycles at 10 C, respectively. The optimized electrode has a large Li⁺ diffusion coefficient and low apparent activation energy. The Li-Ni co-doping material of LiMn₂O₄ single crystal polyhedron can inhibit the Jahn-Teller effect effectively and alleviate Mn dissolution as well as increase Li⁺ ions expressing channels. Hence, the crystal structure of material is stabilized, the rate and cycle performance are enhanced.