Mitigating capacity fade by constructing highly ordered mesoporous Al2O3/polyacene double-shelled architecture in Li-rich cathode materials

Abstract

Lithium-rich layered oxides, xLi₂MnO₃·(1 − x)LiMO₂ (M = Ni, Mn, Co), have been considered as one of the most promising cathode active materials for rechargeable lithium-ion batteries due to their high capacity over 250 mA h g⁻¹ between 2.0 and 4.8 V. However, the commercialized application of these cathodes has so far been hindered by their severe capacity fading and transition metal dissolution during high voltage cycling (>4.5 V vs. Li/Li⁺). To overcome this barrier, a double-shelled architecture consisting of an inner conductive polyacene layer and an outer mesoporous Al₂O₃ layer is constructed. A polyacene layer with high electron conductivity is first coated on the surface of a 0.5Li₂MnO₃·0.5LiNi_0.5Co_0.2Mn_0.3O₂ cathode material, followed by a hydrothermal method combined with an in-sol treatment to produce a highly ordered mesoporous Al₂O₃ layer. Compared to previous studies, this double-shelled architecture has substantially improved the electrochemical performance of the 0.5Li₂MnO₃·0.5LiNi_0.5Co_0.2Mn_0.3O₂ cathode material. Two striking characteristics are obtained for this double-shelled lithium-rich layered oxide cathode material: (1) the electrochemical capacity is greatly improved, reaching 280 mA h g⁻¹ (2.0 V–4.8 V at 0.1 C) and (2) the transition from the layered phase to spinel is delayed, leading to a superior capacity retention of 98% after the 100^th cycle.