Countering Voltage Decay and Capacity Fading of Lithium-Rich Cathode Material at 60 °C by Hybrid Surface Protection Layers

摘要

Li-rich layered metal oxides have attracted much attention for their high energy density but still endure severe capacity fading and voltage decay during cycling, especially at elevated temperature. Here, facile surface treatment of Li1.17Ni0.17Co0.17Mn0.5O2 (0.4Li2MnO3·0.6LiNi1/3Co1/3Mn1/3O2) spherical cathode material is designed to address these drawbacks by hybrid surface protection layers composed of Mg2+ pillar and Li-Mg-PO4 layer. As a result, the surface coated Li-rich cathode material exhibits much enhanced cycling stability at 60 °C, maintaining 72.6% capacity retention (180 mAh g−1) between 3.0 and 4.7 V after 250 cycles. More importantly, 88.7% average discharge voltage retention can be obtained after the rigorous cycle test. The strategy developed here with novel hydrid surface protection effect can provide a vital approach to inhibit the undesired side reactions and structural deterioration of Li-rich cathode materials and may also be useful for other layered oxides to increase their cycling stability at elevated temperature.