Advanced gel polymer electrolytes for safe and durable lithium metal batteries: Challenges, strategies, and perspectives

Lithium metal batteries (LMBs) are attracting increasing interest owing to their high energy density and ultralow redox potential. However, the safety concerns in liquid electrolytes and performance degradation originating from dendrite growth and cathode electrochemistry have severely hindered the practical use of LMBs. Gel polymer electrolytes (GPEs), being considered as the most promising electrolyte replacing currently used liquid electrolytes, have advantages in safety and adaptability to current battery technologies. Hence fruitful work has reported the design and fabrication of functional GPEs that enable them to develop safe and durable LMBs. This review summarizes the recent progress on GPEs with specific functionalities, which are categorized with respect of the strategies for protecting Li metal anodes, controlling thermal runaway, and protecting cathodes. Finally, the future directions and remaining challenges of advanced GPEs for their commercially large-scale production and application in new energy storage systems are summarized to provide guidelines for the future development.