Enhanced cycling performance of surface-doped LiMn2O4 modified by a Li2CuO2-Li2NiO2 solid solution for rechargeable lithium-ion batteries

Abstract

A series of surface-doped LiMn2O4 samples modified by a Li2CuO2-Li2NiO2 solid solution were synthesized using a simple and facile sol-gel method to achieve the enhanced cycling performance, especially at elevated temperatures. The corresponding phase structure and morphology were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The modified layer on the surface of LiMn2O4 particles, featuring a LiNiδMn2–δO4-like phase, together with a Li2CuO2-Li2NiO2 solid solution, as confirmed by XRD and transmission electron microscopy (TEM), plays a key role in alleviating the dissolution of manganese, thus enhancing the cycling performance and rate capability relative to bare LiMn2O4. The 0.5wt.%-modified LiMn2O4 sample delivers a discharge capacity of 113mAhg−1 and a capacity retention of 93.2% following 300 cycles at 1C and 25°C, which is higher than the values of 96mAhg−1 and 81.2% for bare LiMn2O4. In addition, at 55°C, a capacity retention of 81.2% at 1C is obtained for the 0.5wt.%-modified LiMn2O4 sample after 200 cycles, compared to 70.0% for bare LiMn2O4. Modifying the surface of the latter by a LiNiδMn2–δO4-like phase mixed with a Li2CuO2-Li2NiO2 solid solution, is an effective strategy for improving electrochemical properties.