Spinel LiMn2O4 Cathode Materials in Wide Voltage Window: Single-Crystalline versus Polycrystalline

Single-crystal (SC) layered oxides as cathodes for Li-ion batteries have demonstrated better cycle stability than their polycrystalline (PC) counterparts due to the restrained intergranular cracking formation. However, there are rare reports on comparisons between single-crystal LiMn2O4 (SC-LMO) and polycrystalline LiMn2O4 (PC-LMO) spinel cathodes for Li-ion storage. In this work, the Li-ion storage properties of spinel LiMn2O4 single-crystalline and polycrystalline with similar particle sizes were investigated in a wide voltage window of 2-4.8 V vs. Li/Li+. The SC-LMO cathode exhibited a specific discharge capacity of 178 mA center dot h center dot g(-1), which was a bit larger than that of the PC-LMO cathode. This is mainly because the SC-LMO cathode showed much higher specific capacity in the 3 V region (Li-ion storage at octahedral sites with cubic to tetragonal phase transition) than the PC-LMO cathode. However, unlike layered-oxide cathodes, the PC-LMO cathode displayed better cycle stability than the SC-LMO cathode. Our studies for the first time demonstrate that the phase transition-induced Mn(II) ion dissolution in the 3 V region rather than cracking formation is the limiting factor for the cycle performance of spinel LiMn2O4 in the wide voltage window.

Automated summary

Single-crystal layered oxides show better cycle stability compared to their polycrystalline counterparts in Li-ion batteries, mainly due to restrained intergranular cracking. In this study, the Li-ion storage properties of single-crystal and polycrystalline spinel LiMn2O4 cathodes with similar particle sizes were investigated in a wide voltage window. The single-crystal cathode exhibited higher specific capacity in the 3 V region, but the polycrystalline cathode displayed better cycle stability. This research reveals that the phase transition-induced Mn(II) ion dissolution rather than cracking formation is the limiting factor for the cycle performance of spinel LiMn2O4 in the wide voltage window.