Hu Chunjing, Lou Xiaobing, Wu Xiang, Li Jingxin, Su Zhenhuang, Zhang Nian, Li Jiong, Hu Bingwen, Li Chao
Shanghai Key Laboratory of Magnetic Resonance, School of Physics and Electronic Science, East China Normal University, Shanghai 200241, China.
Anhui Key Laboratory of Condensed Matter Physics at Extreme Conditions, High Magnetic Field Laboratory, Chinese Academy of Science, Hefei 230021, China.
ACS Nano. 2024 May 21;18(20):13397-13405. doi: 10.1021/acsnano.4c03643. Epub 2024 May 10.
Integrating anion-redox capacity with orthodox cation-redox capacity is deemed as a promising solution for high-energy-density battery cathodes surmounting the present technical bottlenecks. However, the evolution of oxidized oxygen species during the electrochemical or chemical process easily jeopardizes the reversibility of oxygen redox and remains poorly understood. Herein, we showcase the gradual conversion of the π-interacting oxygen (localized hole states on O) to the σ-interacting oxygen upon resting at a high voltage for P3-type NaLiMnO with nominally stable ribbon-like superstructure, accompanied by the O-O dimerization and the local structural reorganization. We further pinpoint an abnormal Li migration process from the alkali-metal layer to the transition-metal layer for desodiated P3-NaLiMnO, thereby leading to a partial reconstruction of the ribbon superstructure. The high-voltage plateau of oxygen-redox cathodes is concluded to be exclusively controlled by the oxygen stabilization mechanism rather than the superstructure ordering. In addition, there exists a kinetic competition between π and σ interaction during the uninterrupted electrochemical process.
将阴离子氧化还原能力与传统的阳离子氧化还原能力相结合，被认为是克服当前技术瓶颈的高能量密度电池阴极的一种有前景的解决方案。然而，在电化学或化学过程中氧化氧物种的演变很容易危及氧氧化还原的可逆性，并且仍然知之甚少。在此，我们展示了对于具有名义上稳定的带状超结构的P3型NaLiMnO，在高电压下静置时，π相互作用氧（O上的局域空穴态）逐渐转变为σ相互作用氧，同时伴随着O-O二聚化和局部结构重组。我们进一步指出，对于脱钠的P3-NaLiMnO，存在从碱金属层到过渡金属层的异常Li迁移过程，从而导致带状超结构的部分重构。得出氧氧化还原阴极的高电压平台完全由氧稳定机制而非超结构有序性控制的结论。此外，在不间断的电化学过程中，π和σ相互作用之间存在动力学竞争。
