High‐Rate Discharge Minimizes Volume Expansion of Lithium Metal Electrodes under Lean Electrolyte and High Areal Capacity Conditions

Abstract

AbstractThe demand for practical implementation of lithium metal batteries (LMBs) is increasing due to their superior energy density. However, poor cycle life and safety concerns regarding dendrite formation remain significant challenges. Recent studies have shown empirical improvements in cycle life through the use of high‐rate discharge protocols, but the precise mechanism behind this enhancement is still unclear due to difficulties in analyzing the lithium electrode, especially in LMB cells with high energy density designs. In this study, X‐ray computed tomography (XCT) analysis, a non‐destructive technique, was employed to investigate the lithium metal electrode in pouch‐type cells with a cell‐level energy density exceeding 350 Wh kg−1. XCT analysis revealed significant volume expansion of the lithium electrode during charge/discharge cycles, particularly under high‐rate charging conditions, which promoted dendritic growth due to inhomogeneous current distribution. However, such undesired volume expansion was largely suppressed during high‐rate discharge, leading to improved cycle life. This study underscores the importance of non‐destructive techniques in comprehending the degradation mechanisms of high‐energy‐density LMBs.