Preparation, Characterization and Electrochemical Performance of LiNi_xCo_yCu_zMn_(2-x-y-z)O_4 as Positive Electrodes in Lithium Rechargeable Batteries

摘要

A series of spinel compounds including LiCu_(0.25)Co_(0.25)Ni_(0.25)Mn(1.25)O_4 and LiMn_2O_4 were prepared by the sol–gel method using glycine, ethanol, and ammonia solutions. The structural and magnetic properties were examined by X-ray diffraction, Scanning Electron Microscopy, and electron spin resonance. The prepared powders have spinet phase cubic structure with space group Fd3m. It is found that the Curie constant "C_p" and the effective magnetic moment "μ_(eff)" values decrease with the more metal doping. The electrochemical properties were characterized and found to be superior for the LiCu_(0.25)Co_(0.25)Ni_(0.25)Mn_(1.25)O_4. It was observed that the Warburg impedance coefficient (σ_w) was 122 Ω.s~(-0.5) for LiCu_(0.25)Co(0.25)Ni_(0.25)Mn_(1.25)O_4 (sample B), which was lower than the value for LiMn_2O_4 (sample A), 819 Ω.s~(-0.5) Also, the diffusion coefficient (D) values of the lithium ions diffusing into the bulk electrode materials were calculated. Sample B had a higher "D" value than sample A. The prepared multi-doped lithium manganate spinet material delivered a higher specific discharge capacity of ～150 mAhg~(-1) compared to 115 mAhg~(-1) for LiMn_2O_4 after 150 cycles.