Overcoming Jahn-Teller distortion for spinel Mn phase스피넬 망간상에서 Jahn-Teller distortion 해결

Abstract

LixMn2O4 (x=1) has a cubic spinel structure with space group symmetry Fd3m. For 1≤x≤2, the lithium insertion into LiMn2O4 results in the transition of the structure from cubic into tetragonal Li2Mn2O4, which is accompanied by the Jahn-Teller distortion. Here we report the synthesis and electrochemical performance of a new sulfur-doped spinel material, LiAl0.24Mn1.76O3.96S0.4, which overcomes the Jahn-Teller distortion. LiAl0.24Mn1.76O3.98S0.02 powders were prepared by a sol-gel method using glycolic acid as a chelating agent according. Transmission electron microscope (TEM) and selected area electron diffraction pattern (SADP) of the individual oxide particles in the powders and cycled electrodes were used to investigate the structural integrity of the oxysulfide spinel host. Our synthesized material overcomes the Jahn-Teller distortion in all the operating voltage regions. The material shows the capacities of 103, 128, and 230 mAh/g in the 4 V, 3 V, and both the 3 and 4 V regions, respectively, with excellent cyclability. The selected area electron diffraction pattern (SADP) of the lattice image also exhibits unequivocal evidence of the cubic spinel phase. Further TEM investigations showed the same patterns in the as-prepared powders and electrodes cycled in the 3 V and 4 V region.