Gao Haowen, Ai Xin, Wang Hongchun, Li Wangqin, Wei Ping, Cheng Yong, Gui Siwei, Yang Hui, Yang Yong, Wang Ming-Sheng
State Key Laboratory of Physical Chemistry of Solid Surfaces, College of Materials, Xiamen University, 361005, Xiamen, China.
State Key Laboratory of Material Processing and Die & Mould Technology, Department of Mechanics, School of Aerospace Engineering, Huazhong University of Science and Technology, Wuhan, 430074, Hubei, China.
Nat Commun. 2022 Aug 27;13(1):5050. doi: 10.1038/s41467-022-32732-z.
Solid electrolytes hold the promise for enabling high-performance lithium (Li) metal batteries, but suffer from Li-filament penetration issues. The mechanism of this rate-dependent failure, especially the impact of the electrochemo-mechanical attack from Li deposition, remains elusive. Herein, we reveal the Li deposition dynamics and associated failure mechanism of solid electrolyte by visualizing the Li|LiLaZrO (LLZO) interface evolution via in situ transmission electron microscopy (TEM). Under a strong mechanical constraint and low charging rate, the Li-deposition-induced stress enables the single-crystal Li to laterally expand on LLZO. However, upon Li "eruption", the rapidly built-up local stress, reaching at least GPa level, can even crack single-crystal LLZO particles without apparent defects. In comparison, Li vertical growth by weakening the mechanical constraint can boost the local current density up to A·cm level without damaging LLZO. Our results demonstrate that the crack initiation at the Li|LLZO interface depends strongly on not only the local current density but also the way and efficiency of mass/stress release. Finally, potential strategies enabling fast Li transport and stress relaxation at the interface are proposed for promoting the rate capability of solid electrolytes.
固态电解质有望实现高性能锂金属电池，但存在锂丝穿透问题。这种速率依赖性失效的机制，尤其是锂沉积引起的电化学机械攻击的影响，仍然难以捉摸。在此，我们通过原位透射电子显微镜（TEM）观察锂|锂镧锆氧化物（LLZO）界面的演变，揭示了固态电解质的锂沉积动力学及相关失效机制。在强机械约束和低充电速率下，锂沉积引起的应力使单晶锂在LLZO上横向扩展。然而，在锂“喷发”时，迅速积累的局部应力达到至少吉帕水平，甚至能使无明显缺陷的单晶LLZO颗粒开裂。相比之下，通过减弱机械约束实现的锂垂直生长可将局部电流密度提高到安培·平方厘米水平而不损坏LLZO。我们的结果表明，锂|LLZO界面处的裂纹萌生不仅强烈依赖于局部电流密度，还依赖于质量/应力释放的方式和效率。最后，提出了在界面实现快速锂传输和应力松弛的潜在策略，以提高固态电解质的倍率性能。
