Stabilization of Spinel-like Phase Transformation of o-LiMnO2 during 55 °C Cycling by Sol−Gel Coating of CoO

Low-temperature sol−gel coating of CoO on orthorhombic LiMnO 2 ( o -LiMnO 2 ) particles greatly stabilizes spinel-like phase transformation during electrochemical cycling at 55 °C. Enhanced structural stability of the coated o -LiMnO 2 is because discretely higher Co concentration at the surface than in the bulk improves the structural stability of cycling-induced LiMn 2 O 4 and Li 2 Mn 2 O 4 phases. The coated o -LiMnO 2 shows increased discharge capacity to 185 from 170 mAh/g at 0.2 C rate (=36 mA/g) cycled between 4.5 and 2 V. In addition, the coated o -LiMnO 2 exhibits smaller capacity fading than the bare one (35%), showing only 12% capacity loss of the discharge capacity after 50 cycles.