Effect of Pressure on Lithium Metal Deposition and Stripping against Sulfide-Based Solid Electrolytes

Abstract

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.

Review on Interface and Interphase Issues in Sulfide Solid-State Electrolytes for All-Solid-State Li-Metal Batteries

“…Third, it was proposed that the relatively high stacking pressure in ASSBs accelerates Li penetration through the SSEs [91][92][93]. Although some degree of stack pressure is required to ensure contact between an SSE and Li-metal anode [94], too high of a stack pressure results in Li dendrite penetration through the SSE and thus a short circuit. Recently, Meng's group investigated the effect of stack pressure of ASSBs on the short-circuit behavior using the pressuremonitoring system shown in Figure 8f [91].…”

Electrochemical Compatibility of Solid‐State Electrolytes with Cathodes and Anodes for All‐Solid‐State Lithium Batteries: A Review

“…[126] Although applying pressure is practical in sulfide-based ASSLMBs as the electrolytes are deformable without cracking, as shown in Figure 9e, Li-In/In cells applied with external pressure could be steadily discharged at 2 mA cm À2 . [127] However, this method cannot suppress the decomposition of the electrolytes by lithium metal. There have been methods focusing on enhancing the electrochemical compatibility of the sulfide/Li interface thermodynamically.…”

“…(e) Reproduced with permission. [127] Copyright 2020, American Chemical Society. (f ) Reproduced with permission.…”

Solid electrolyte-electrode interface based on buffer therapy in solid-state lithium batteries

“…The yield strength of Li metal is creepdominated at room temperature and it needs to be correlated with the stack pressure applied on ASSBs during cycling to fully understand the mechanical behavior of the lithium metal anode [55]. Ying Shirley Meng and his co-workers used the Li 6 PS 5 Cl sulfide electrolyte to study the effect of stack pressure on the dendrite growth of lithium metal anode, they found that a low stack pressure of 5 MPa allows reliable plating and stripping in a lithium symmetric cell for more than 1000 h, and a Li|Li 6 PS 5 Cl|LiNi 0.80 Co 0.15 Al 0.05 O 2 full cell, plating more than 4 µm of lithium per charge, able to cycle over 200 cycles at room temperature [56]. Jitendra Kumar and colleagues have demonstrated that high external pressure is needed for stripping Li at high rates, whereas external pressure lower than 4.5 MPa allows depositing of Li at 0.6 mA/cm 2 for 3 mA•h•cm −2 [57].…”