Synthesis and characterization of a new spinel, Li_1.02Al_0.25Mn_1.75O_3.97S_0.03, operating at potentials between 4.3 and 2.4 V

A new spinel material, oxysulfide Li_1.02Al_0.25Mn_1.75O_3.97S_0.03, has been synthesized using a sol-gel method. The cathode fabricated using the material shows the capacities of 89.5, 125, and 196 mAh/g in the 4 V (4.3 to 3.0 V), 3 V (2.4 to 3.5 V), and both the 3 and 4 V regions (4.3 to 2.4 V), respectively. This material exhibits no capacity loss after 30 cycles in both the 3 and 4 V regions during cycling. It was found that S doping was very effective in suppressing the formation of the tetragonal phase of LiMn₂O₄ in potential ranges of 2.4 to 4.3 V.