Oh Juhyun, Lee Seung-Yong, Kim Hwangsun, Ryu Jinseok, Gil Byeongjun, Lee Jongki, Kim Miyoung
Department of Materials Science and Engineering and Research Institute of Advanced Materials, Seoul National University, Seoul, 08826, Republic of Korea.
Division of Materials Science and Engineering, Hanyang University, Seoul, 04763, Republic of Korea.
Adv Sci (Weinh). 2022 Nov;9(32):e2203639. doi: 10.1002/advs.202203639. Epub 2022 Sep 11.
Overcharging is expected to be one of the solutions to overcome the current energy density limitation of lithium-ion battery cathodes, which will support the rapid growth of the battery market. However, high-voltage charging often poses a major safety threat including fatal incendiary incidents, limiting further application. Numerous researches are dedicated to the disadvantages of the overcharging process; nonetheless, the urgent demand for addressing failure mechanisms is still unfulfilled. Herein, it is revealed that overcharging induces phase heterogeneity into layered and cobalt oxide phases, and consequent "twin-like deformation" in lithium cobalt oxide. The interplay between the uncommon cobalt(III) oxide and the deformation is investigated by revealing the atomistic formation mechanism. Most importantly, abnormal cracking is discovered in the vicinity of the cobalt oxide where structural instability induces substantial contraction. In addition, surface degradation is widely observed in the crack boundary inside the particle. As unintentional overcharging can occur due to local imbalance in state-of-charge in severe operating conditions such as fast charging, the issues on overcharging should be emphasized to large extent and this study provides fundamental knowledge of overcharge by elucidating the crack development mechanism of layered cathodes, which is expected to broaden the horizon into high voltage operation.
过充电有望成为克服当前锂离子电池阴极能量密度限制的解决方案之一，这将推动电池市场的快速增长。然而，高压充电常常带来重大安全威胁，包括致命的燃烧事故，从而限制了其进一步应用。众多研究致力于探讨过充电过程的弊端；尽管如此，解决失效机制的迫切需求仍未得到满足。在此，研究发现过充电会在层状和钴氧化物相中引发相不均匀性，并进而在锂钴氧化物中导致“孪晶状变形”。通过揭示原子形成机制，研究了罕见的三氧化二钴与变形之间的相互作用。最重要的是，在钴氧化物附近发现了异常开裂，此处的结构不稳定性导致了大量收缩。此外，在颗粒内部的裂纹边界处广泛观察到表面降解。由于在诸如快速充电等严苛工作条件下，由于局部充电状态不平衡可能会发生意外过充电，因此过充电问题应在很大程度上得到重视，并且本研究通过阐明层状阴极的裂纹发展机制，提供了过充电的基础知识，有望拓宽高压操作的视野。
