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.