Spinel MgAl2O4 modification on LiCoO2 cathode materials with the combined advantages of MgO and Al2O3 modifications for high-voltage lithium-ion batteries

Abstract

In order to improve the electrochemical performance of LiCoO₂ cathode in a high-voltage range of 3.0–4.5 V, spinel MgAl₂O₄ has been modified on the surface of LiCoO₂ particle by a facile high-temperature solid state reaction. The structure and morphology of the MgAl₂O₄-modified LiCoO₂ are investigated in comparison with the pristine, Al₂O₃-modified and MgO-modified LiCoO₂. The MgAl₂O₄ modification is highly conformal and uniform just similar as the Al₂O₃ modification, while the MgO modification is not uniform. In terms of electrochemical performance as a high-voltage cathode material, the MgAl₂O₄-modified LiCoO₂ delivers an initial discharge capacity of 184 mA h g⁻¹ between 3.0 V and 4.5 V at 0.1C (1C-rate = 160 mA g⁻¹) and a capacity retention of 96.8% after 70 cycles at 1C rate. There is a significant improvement on high-voltage cycling stability for the MgAl₂O₄-modified LiCoO₂ since the capacity retention of the pristine LiCoO₂ is only 38.7% after 70 cycles. Moreover, the MgAl₂O₄-modified LiCoO₂ exhibits an enhanced rate capability. Compared with the Al₂O₃ modification and the MgO modification, spinel MgAl₂O₄ modification has the combined advantages of Al₂O₃ and MgO modifications on improving the electrochemical performance of the LiCoO₂ cathode for high-voltage applications. The modified spinel MgAl₂O₄ layer can effectively protect the charged Li_1−xCoO₂ cathode from structural collapse and impede the oxidation decomposition of the electrolyte for the high-voltage application of LiCoO₂.