Strengthening reversibility at high rate of spinel LiMn2O4 by aluminum and copper Co-doping for lithium ion battery

Typical LiMn2O4 cathode materials for lithium ion batteries suffer from the Jahn-Teller distortion, unstable phase transformation and the Mn3+ disproportionation. In this work, the Cu and Al elements are designed to be respectively doped into Mn sites and Li sites to reinforce the structural stability and thereby improve cyclic capacity and stability under wide electrochemical window. A conventional sol-gel method is used to synthesis Cu and Al co-doped Li1-3xAlxMn1.75Cu0.25O4 (x = 0, 0.02, 0.08 and 0.14) of lithium manganese oxide (LMO) spinel. Benefitting from the enhanced structural stability, improved ionic/electronic conductivity and decreased JahnTeller effects, at a high current density of 5 C, the Li0.94Al0.02Mn1.75Cu0.25O4 provides an initial capacity of 106.3 mA h g � 1 within a wide potential window of 2 - 4.8 V and harvests a high reversible capacity of 90.2 mA h g � 1 after 300 cycles (84.9% capacity retention), which is much higher than LMO (77.3 mA h g � 1) and LMCO (69.0 mA h g � 1). The Cu doping can enhance the phase transformation reversibility between & lambda;-MnO2 and LiMn2O4, whereas the Al doping can strengthen the cubic-to-tetragonal reversibility. This work provides an effective strategy for engineering stable LiMn2O4 spinel cathodes under high current density and wide potential window for lithium ion battery.