| Summary: | 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 LiMn<sub>2</sub>O<sub>4</sub> (SC-LMO) and polycrystalline LiMn<sub>2</sub>O<sub>4</sub> (PC-LMO) spinel cathodes for Li-ion storage. In this work, the Li-ion storage properties of spinel LiMn<sub>2</sub>O<sub>4</sub> single-crystalline and polycrystalline with similar particle sizes were investigated in a wide voltage window of 2–4.8 V vs. Li/Li<sup>+</sup>. The SC-LMO cathode exhibited a specific discharge capacity of 178 mA·h·g<sup>−1</sup>, 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 LiMn<sub>2</sub>O<sub>4</sub> in the wide voltage window.
|
|---|