Effect of cationic and anionic substitutions on the electrochemical properties of LiNi_(0.5)Mn_(1.5)O_4 spinel cathode materials

摘要

Cationic and anionic doping in LiNi_(0.5)Mn_(1.5)O_4 has been prepared via a solid state method. The effect of substitution on the structure, morphology, and electrochemical properties were investigated. The XRD and Raman results indicate that all synthesized materials have a phase-pure spinel structure with a space group of Fd3 m and no obvious impurity phase peaks. Excellent cycle life is measured for these 5 V Cr and (or) F-doped electrodes. When the charge/discharge rate returns to 1 C after the test of rate capability (0.1-5 C), the capacity can be completely recovered and the capacity retention is about 98.6%, 98.8% and 96.2% after 100 cycles for LiNi_(0.45)Cr_(0.05)Mn_(1.5)O_4, LiNi_(0.45)Cr_(0.05)Mn_(1.5)O_(3.9)F_(0.1) and LiNi_(0.5)Mn_(1.5)O_(3.9)F_(0.1), respectively. Furthermore, rate capability is greatly influenced by the relative content of Mn~(3+). Cr and (or) F substitutions supply an efficient process to tune the Mn~(3+) concentration in the lattice.