中国科学院大学刘向峰团队报道了通过自旋态调制减少Co/O带重叠，实现LiCoO2 的4.6V高稳定容量。相关研究成果发表在2023年4月25日出版的《美国化学会杂志》。

高压LiCoO₂（LCO）由于其高比容量而引起人们的极大兴趣，但它存在氧释放、结构退化和容量快速下降的问题。这些令人生畏的问题源于高电压下触发的氧阴离子氧化还原（OAR）的较差热力学和动力学。

该文中，通过原子工程高自旋LCO证明了几乎只有Co氧化还原的调谐氧化还原机制。高自旋Co网络减少了Co/O带的重叠，消除了O₃→ H_1–3的不利相变，延迟了O_2p带超过费米能级，并导致过量的 高电压下O→Co的共电荷转移。该功能本质上促进Co氧化还原并抑制O氧化还原，从根本上解决了O₂释放和耦合有害Co还原的问题。此外，由于慢OAR的抑制和快Co氧化还原的激发，Co/O氧化还原中心的不同动力学引起的化学机械异质性和慢O氧化还原动力学限制的较差速率性能同时得到改善。调制LCO可获得216 mAh g^–1（1C）和195 mAh g^-1（5C）的超高速率容量，以及90.4%（100次循环时）和86.9%（500次循环）的高容量保持率。

该项工作为广泛的O氧化还原阴极的设计提供了新的线索。

附：英文原文

Title: Reducing Co/O Band Overlap through Spin State Modulation for Stabilized High Capability of 4.6 V LiCoO2

Author: Jicheng Zhang, Deniz Wong, Qinghua Zhang, Nian Zhang, Christian Schulz, Maciej Bartkowiak, Ke An, Lin Gu, Zhongbo Hu, Xiangfeng Liu

Issue&Volume: April 25, 2023

Abstract: High-voltage LiCoO2 (LCO) attracts great interest because of its large specific capacity, but it suffers from oxygen release, structural degradation, and quick capacity drop. These daunting issues root from the inferior thermodynamics and kinetics of the triggered oxygen anion redox (OAR) at high voltages. Herein, a tuned redox mechanism with almost only Co redox is demonstrated by atomically engineered high-spin LCO. The high-spin Co network reduces the Co/O band overlap, eliminates the adverse phase transition of O3 → H1–3, delays the exceeding of the O 2p band over the Fermi level, and results in excessive O → Co charge transfer at high voltages. This function intrinsically promotes Co redox and restrains O redox, fundamentally addressing the issues of O2 release and coupled detrimental Co reduction. Moreover, the chemomechanical heterogeneity caused by different kinetics of Co/O redox centers and the inferior rate performance limited by slow O redox kinetics is simultaneously improved owing to the suppression of slow OAR and the excitation of fast Co redox. The modulated LCO delivers ultrahigh rate capacities of 216 mAh g–1 (1C) and 195 mAh g–1(5C), as well as high capacity retentions of 90.4% (@100 cycles) and 86.9% (@500 cycles). This work sheds new light on the design for a wide range of O redox cathodes.

DOI: 10.1021/jacs.3c01128

Source: https://pubs.acs.org/doi/10.1021/jacs.3c01128