Wang Yuxing, Liu Tongjie, Kumar Jitendra
University of Dayton Research Institute, 300 College Park, Dayton, Ohio 45469-7531, United States.
University of Dayton, 300 College Park, Dayton, Ohio 45469-7531, United States.
ACS Appl Mater Interfaces. 2020 Aug 5;12(31):34771-34776. doi: 10.1021/acsami.0c06201. Epub 2020 Jul 24.
Fundamental challenges for lithium metal anode cycling against solid electrolytes (SEs) at high current densities and high areal capacities include lithium dendrite penetration during Li deposition and void formation during Li stripping. These two dynamic processes have a distinct dependency on the external pressure. The majority of research to date on Li cycling behaviors adopt symmetric cell (Li/SE/Li) configurations, where the stack pressure and the failure associated with the deposition and the stripping processes cannot be delineated. In this work, we investigate the effect of external pressure on the deposition and the stripping of Li metal anodes separately against a sulfide-based SE by employing asymmetric cell configurations. We show that (1) for Li striping, the pressure required is positively correlated with stripping current densities; (2) for Li deposition, higher pressure leads to lower maximum allowed current densities, defined as the current densities beyond which dendrite penetration occurs. The apparent opposing requirement for external pressure of Li deposition and Li stripping elucidates why the methodology of Li metal cycling in symmetric cell configurations is fundamentally flawed and highlights the importance of refined pressure regulation in all-solid-state Li metal batteries.
锂金属负极在高电流密度和高面积容量下与固体电解质（SEs）进行循环时面临的基本挑战包括锂沉积过程中的锂枝晶穿透以及锂剥离过程中的空隙形成。这两个动态过程对外部压力有明显的依赖性。迄今为止，大多数关于锂循环行为的研究采用对称电池（Li/SE/Li）配置，其中堆叠压力以及与沉积和剥离过程相关的失效无法区分。在这项工作中，我们通过采用不对称电池配置，分别研究了外部压力对锂金属负极相对于硫化物基SE的沉积和剥离的影响。我们表明：（1）对于锂剥离，所需压力与剥离电流密度呈正相关；（2）对于锂沉积，更高的压力会导致更低的最大允许电流密度，最大允许电流密度定义为超过该值会发生枝晶穿透的电流密度。锂沉积和锂剥离对外部压力明显相反的要求阐明了为什么对称电池配置中锂金属循环的方法从根本上存在缺陷，并突出了在全固态锂金属电池中精细压力调节的重要性。
