Recent advancements in polymer matrices-based composite electrolytes for all-solid-state lithium metal batteries: Challenges, strategies, and future directions

Organic liquid electrolytes in lithium-ion batteries pose significant safety risks, including flammability, leakage, and thermal instability. As a safer alternative, solid-state polymer-based composite electrolytes (PCEs) provide enhanced thermal stability, reduced flammability, and improved overall safety. However, PCEs still face critical challenges, including low ionic conductivity (σ), narrow electrochemical stability windows, intrusion growth (i.e., dendrites), and inadequate interfacial, thermal runaway, and mechanical stability. This review examines recent advancements in PCEs, concentrating on strategies to overcome these limitations while analyzing key performance parameters and polymer matrices. It also explores the role of fillers, lithium salts, and residual solvents in enhancing the σ and electrochemical stability. Additionally, the review discusses interfacial stability between electrolytes and electrodes, progress in high-voltage cathode materials, and feasible pathways for the industrialization of all-solid-state lithium metal batteries (ASSLMBs). Emphasizing the importance of innovative material design and advanced processing techniques, this review provides insights into the latest developments in PCEs. Finally, it outlines future research directions to accelerate the commercialization of high-energy-density ASSLMBs, paving the way for next-generation energy storage technologies.