Abstract: Spinel LiMn₂O_4-xY_x(Y=F, Cl, Br) compounds were prepared by solid-state reaction and the electrochemically galvanostatic charge-discharge cycles were performed using as-prepared compounds as cathode material. The influence of halogens on their lattice constants and the relation of electrochemical properties and their lattice constants were investigated. It is concluded that when the lattice constants are smaller than that of LiMn₂O₄, the reversible capacity fade is suppressed and the initial capacity sacrifice is observed. When the content of fluorine is 0.05, the lattice constant of LiMn₂O_3.95F_0.05 is larger than that of LiMn₂O₄, the initial capacity is improved. An efficient method was found to control the lattice constants of LiMn₂O₄ through the addition of halogen, and to improve the electrochemical performance of LiMn₂O₄. The LiMn₂O_3.95F_0.05 shows excellent electrochemical charge-discharge performance, with high initial capacity of 143mAh/g and nearly no capacity loss after 116 cycles.

Key words:  spinel LiMn₂O_4-xY_x; lattice constant; cathode materials; lithium-ion rechargeable battery; halogen