Delayed Phase Transition and Improved Cycling/Thermal Stability by Spinel LiNi<sub>0.5</sub>Mn<sub>1.5</sub>O<sub>4</sub> Modification for LiCoO<sub>2</sub> Cathode at High Voltages
Peipei Pang, Zheng Wang, Yaoming Deng, Junmin Nan, Zhenyu Xing, Hong Li
Abstract
Increasing the upper cutoff voltage is capable of achieving higher charge capacity, whereas this strategy always causes a dramatic degradation of cycling and thermal stability. In this study, we first report spinel LiNi0.5Mn1.5O4-modified LiCoO2 ([email protected]) as an outstanding cathode material. [email protected] retains capacity retention of 81.4% in a full cell between 4.45 and 3.00 V after 400 cycles at 0.5 C and is superior to 55.3% of pure LiCoO2. In situ X-ray diffraction at an upper cutoff voltage of 4.75 V in combination with differential capacity curve reveals that the promoted cycling performance is ascribed to a delay of O3 → H1–3 → O1 phase transitions and a suppression of cobalt dissolution-induced side reactions. Moreover, LiNi0.5Mn1.5O4 modification improves the thermal stability of LiCoO2 by depressing the release of oxygen and the formation of cobalt dendrites.