Reviewing the current status and development of polymer electrolytes for solid-state lithium batteries

Commercial lithium-ion batteries still undergo safety concerns due to using perilous and flammable liquid electrolytes that are prone to fire and leakage issues. Meanwhile, the development of high energy density lithium-metal batteries with conventional liquid electrolytes has also encountered bottlenecks because of the growth of lithium-dendrites and parasitic reactions. Therefore, the use of flammable liquid electrolytes in lithium batteries is the main obstacle to be overcome, and at the same time, the contradiction between high energy density and high safety for practical applications needs to be addressed. Currently, solid polymer electrolyte has been considered as a promising solution, and hence solid polymer-based lithium batteries have attracted much attention due to their high safety compared to their counterparts. However, its low ionic conductivity, poor mechanical properties, and insufficient cycle life restrict their practical applications. At present, there are fewer comprehensive reviews available on lithium batteries based on polymer electrolyte systems, so it is substantial worthy of summarizing the existing literature and timely apprises of incessantly improving strategies of this field. This review summarizes the ion transfer mechanism and performance requirements of polymer electrolytes for lithium batteries, the classification and design of polymer electrolytes, and the essential principles and characterization for electrode/electrolyte interface construction and the research of composite electrolyte. Finally, the current status and development prospects of polymer electrolytes are briefly summarized and discussed, enabling a foundation for the wide application of solid polymer electrolyte-based batteries.