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

Lithium-rich layered oxides, xLi(2)MnO(3)center dot(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 0.5Li(2)MnO(3)center dot 0.5LiNi(0.5)Co(0.2)Mn(0.3)O(2) 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 0.5Li(2)MnO(3)center dot 0.5LiNi(0.5)Co(0.2)Mn(0.3)O(2) 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 100th cycle.