Improving Electrochemical Performance of High-Voltage Spinel LiNi_0.5Mn_1.5O₄ Cathodes by Silicon Oxide Surface Modification

Spinel LiNi0.5Mn1.5O4(LNMO) is considered as a next generation lithium-ion battery (LIB) cathode material worth studying on account of its outstanding features. However, it is held back by poor cycling performance originated from the structure instability and side reactions. Here, spinel LNMO is decorated homogeneously via a facile hydrolysis and adsorption of γ-methyl-propylene trimethoxysilane (KH570), followed by thermal treatment at 750 °C, to bring a SiO2 modification shell at the surface of LNMO and realize the ion doping of Si. The sintering process also brings more Mn3+ in LNMO. However, only a moderate increase of Mn3+ in LNMO can enhance the conductivity of ions and electrons, benefiting the enhancement of rate performance. The 0.8%-SiO2@LNMO cathode exhibits a high reversible capacity of 129 mAh g–1, retaining a great capacity retention of 88% after 800 cycles at 1 C and 89.7% after 1000 cycles at 3 C. Meanwhile, a superior rate capability (90 mAh g–1 at 5 C) is achieved by applying the galvanostatic charge/discharge test.