Synthesis and characterization of LiCo _xMn_2−xO₄ cathode materials

Abstract

LiCo _xMn_2−xO₄ cathode materials for lithium ion batteries were synthesized by mechanical activation-solid state reaction at 750°C for 24 h in air atmosphere, and their crystal structure, morphology, element composition and electrochemical performance were characterized with XRD, SEM, ICP-AES and charge-discharge test. The experimental results show that all samples have a single spinel structure, well formed crystal shape and uniformly particle size distribution. The lattice parameters of LiCo _xMn_2−xO₄ decrease and the average oxidation states of manganese ions increase with an increase in Co content. Compared with pure LiMn₂O₄, the LiCo _xMn_2−xO₄ (x=0.03–0.12) samples show a lower special capacity, but their cycling life are improved. The capacity loss of LiCo_0.09Mn_1.91O₄ and LiCo_0.12Mn_1.88O₄ is only 1.85% and 0.95%, respectively, after the 20th cycle. The improvement of the cycle performance is attributed to the substitution of Co at the Mn sites in the spinel structure, which suppresses the Jahn-Teller distortion and improves the structural stability.

Keywords

lithium ion batteries / cathode materials / spinel LiMn₂O₄ / mechanical activation-solid state method / Co-doping

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