Nitrile-based solid polymer electrolytes for novel energy storage systems: A perspective from ion transport mechanism to applications in solid-state batteries

Considering several challenges for traditional liquid batteries and liquid electrolytes, solid-state batteries (SSBs) and solid-state electrolytes (SSEs) offer a means to significantly improve the safety and energy density of energy storage devices. The utilization of SSEs in lithium metal batteries (LMBs) is widely recognized as a crucial step in designing next-generation high-performance energy storage devices. Nitrile-based solid polymer electrolytes (SPEs), exemplified by polyacrylonitrile (PAN), have gained prominence due to their exceptional mechanical strength, effective lithium salt dissociation capabilities and excellent interfacial contact. Exploration and modification of intrinsic active functional groups of polymers are emerging as pivotal strategies for advanced SSBs, simultaneously providing foundational framework for analyzing the intricate relationship between microscopic mechanisms and macroscopic performance. This review initially focuses on the dissociation-coupling of ion behavior, kinetics, and various types of nitrile-based polymers. Specifically, focusing on the advantages of nitrile-containing functional groups, the key limiting factors and empirical formula ions transport in SSEs and are summarized. In addition, a brief introduction of numerous achievements related to the diverse applications of nitrile-based organic compounds in SSEs and electrolyte additives with a detailed exposition of current mainstream modification strategies are highlighted, designed to provide direction for optimization and development of nitrile-based SPEs.