材料科学
阴极
氧气
涂层
电介质
尖晶石
极化(电化学)
析氧
化学工程
电极
表面改性
纳米技术
电化学
光电子学
物理化学
冶金
化学
有机化学
工程类
作者
Wei Zhang,Yong‐Gang Sun,Hui Deng,Jianming Ma,Yi Zeng,Zhiqiang Zhu,Zhisheng Lv,Huarong Xia,Xiang Ge,Shengkai Cao,Yao Xiao,Shibo Xi,Yonghua Du,Cao A,Xiao Chen
标识
DOI:10.1002/adma.202000496
摘要
Abstract High‐energy Li‐rich layered cathode materials (≈900 Wh kg −1 ) suffer from severe capacity and voltage decay during cycling, which is associated with layered‐to‐spinel phase transition and oxygen redox reaction. Current efforts mainly focus on surface modification to suppress this unwanted structural transformation. However, the true challenge probably originates from the continuous oxygen release upon charging. Here, the usage of dielectric polarization in surface coating to suppress the oxygen evolution of Li‐rich material is reported, using Mg 2 TiO 4 as a proof‐of‐concept material. The creation of a reverse electric field in surface layers effectively restrains the outward migration of bulk oxygen anions. Meanwhile, high oxygen‐affinity elements of Mg and Ti well stabilize the surface oxygen of Li‐rich material via enhancing the energy barrier for oxygen release reaction, verified by density functional theory simulation. Benefited from these, the modified Li‐rich electrode exhibits an impressive cyclability with a high capacity retention of ≈81% even after 700 cycles at 2 C (≈0.5 A g −1 ), far superior to ≈44% of the unmodified counterpart. In addition, Mg 2 TiO 4 coating greatly mitigates the voltage decay of Li‐rich material with the degradation rate reduced by ≈65%. This work proposes new insights into manipulating surface chemistry of electrode materials to control oxygen activity for high‐energy‐density rechargeable batteries.
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