Degradation analysis during fast lifetime cycling of sulfide-based all-solid-state Li-metal batteries using in situ electrochemical impedance spectroscopy

Abstract

All-solid-state Li-metal batteries (ASSLMBs) can achieve high specific energy density and excellent safety; however, their maturation and commercialization have experienced significant delay owing to the high reducibility and complex interfacial features of Li metal. In this study, we fabricated sulfide-based ASSLMBs and examined their degradation behavior during the lifetime cycle based on their electrochemical performance and internal resistance analyses. The fabricated ASSLMB (initial discharge capacity = 159.28 mAh g-1 at 0.5C) exhibited four degradation regimes over 1000 cycles, namely, cathodic defect formation (CDF), anodic interface deterioration (AID), electrode defect growth (EDG), and cell failure. In the CDF regime (0-100 cycles), defects are primarily initiated over the cathode layer. In the subsequent AID regime (100-700 cycles), cracks and voids are rapidly formed in the interfacial layer adjacent to the Li-metal anode, which quadruple the internal resistance value and reduce the discharge capacity (approximately 78.15 mAh g-1 at 700 cycles). The EDG regime (700-900 cycles) is characterized by rapid defect growth in the entire electrode. In the final regime, the cell resistance increases by approximately a factor of 11 compared with the initial value, leading to cell failure. The findings of this study will lead to a comprehensive understanding of degradation behavior during the lifetime cycle of ASSLMBs, thereby providing new insights and strategies for achieving next-generation ASSLMBs.