Synthesis of spinel LiMn2O4 powders for lithium ion battery by mechanical alloying of Li2O2 and Mn2O3

Using the oxides of Li2O2 and Mn2O3 as starting materials, the spinel LiMn2O4 for lithium rechargeable batteries was directly synthesized by optimized mechanical alloying (MA). The prepared powders had low crystallinity, increased surface area and aggregates of particles smaller than 1 μm. To obtain well-crystallized pure spinel phase at lower temperature, the effects of subsequent firing temperature, times and the initial mixed molar ratio of Li/Mn on the synthesized phase were investigated and compared with the case of sample prepared by the conventional solid-state reaction. On firing at 700 deg. C for only 2 h of mechanically alloyed sample with a initial molar ratio of Li/Mn=0.55, a well-crystallized pure spinel phase was obtained, which exhibited the best electrochemical cycling performance. In contrast, the pure spinel without retained Mn2O3 could not be obtained by the solid-state reaction under the same firing conditions. The maximum discharge capacity of the sample by MA and firing at 700 deg. C was 125 mAh/g, and the capacity retention after 30 cycles was ∼95%