Effect of stack pressure on electrochemical performance and uniform Li plating feature of Li||NCM90 pouch cells

Abstract

Stack pressure significantly influences the performance of pouch type batteries, particularly those experiencing substantial volume changes, such as Li-metal batteries (LMBs). To gain a deeper understanding of the effects of pressure, it is important to examine how varying pressure conditions influence cell behavior and overall performance. In this study, Li||LiNi0.90Co0.05Mn0.05O2 (Li||NCM90) pouch cells is constrained by static or spring-based adjustable-tension compression jigs at initial pressures of 0.25, 0.78, and 1.4 MPa. A novel in situ cell-swelling measurement system is employed to capture real-time pressure distribution on the Li metal surface during cycling, providing unique insights into pressure-induced electrochemical “hotspots.” This approach leverages mechanical compression to achieve uniform pressure distributions and promote homogeneous electrochemical reactions across the electrode. Furthermore, COMSOL simulations are used to analyze the uniformity of pressure distribution and the deformation of the separator's pore structure at different pressure levels, offering a comprehensive understanding of the pressure-performance relationship. Overall, this study presents a novel perspective on the critical role of pressure in mitigating cell degradation and improving the performance of lithium metal batteries.