Department of Materials Science and Engineering, Research Institute of Advanced Materials (RIAM), Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul, 151-742, Republic of Korea.
LiB Materials Research Group, Research Institute of Industrial Science & Technology (RIST), 100 Songdogwahak-ro, Yeonsu-gu, Incheon, Republic of Korea.
Nat Commun. 2023 Jul 12;14(1):4149. doi: 10.1038/s41467-023-39838-y.
Lithium-rich layered oxides, despite their potential as high-energy-density cathode materials, are impeded by electrochemical performance deterioration upon anionic redox. Although this deterioration is believed to primarily result from structural disordering, our understanding of how it is triggered and/or occurs remains incomplete. Herein, we propose a theoretical picture that clarifies the irreversible transformation and redox asymmetry of lithium-rich layered oxides by introducing a series of global and local dynamic structural evolution processes involving slab gliding and transition-metal migration. We show that slab gliding plays a key role in trigger/initiating the structural disordering and consequent degradation of the anionic redox reaction. We further reveal that the 'concerted disordering mechanism' of slab gliding and transition-metal migration produces spontaneously irreversible/asymmetric lithiation and de-lithiation pathways, causing irreversible structural deterioration and the asymmetry of the anionic redox reaction. Our findings suggest slab gliding as a crucial, yet underexplored, method for achieving a reversible anionic redox reaction.
富锂层状氧化物尽管作为高能密度阴极材料具有潜力，但由于阴离子氧化还原反应会导致电化学性能恶化而受到阻碍。尽管这种恶化主要被认为是由于结构无序化引起的，但我们对其触发和/或发生的机制仍不完全了解。在此，我们提出了一个理论模型，通过引入一系列涉及片层滑动和过渡金属迁移的全局和局部动态结构演化过程，阐明了富锂层状氧化物的不可逆转变和氧化还原不对称性。我们表明，片层滑动在触发/引发结构无序化以及随后的阴离子氧化还原反应降解中起着关键作用。我们进一步揭示了片层滑动和过渡金属迁移的“协同无序化机制”自发产生不可逆/不对称的锂化和脱锂途径，导致不可逆的结构恶化和阴离子氧化还原反应的不对称性。我们的研究结果表明，片层滑动是实现可逆阴离子氧化还原反应的一个关键但尚未得到充分探索的方法。
