Recent progress in ultra-thin solid polymeric electrolytes for next-generation lithium batteries

All-solid-state lithium batteries (ASSLBs) have become fantastic energy storage devices with intrinsic safety and high energy density. The solid electrolyte is located between the cathode and anode and is decisive for conducting lithium ion, which is crucial to the energy density, fast-charging performance and safety of ASSLBs. Based on the current cathode and anode material system, the ultra-thinning of solid polymeric electrolytes (< 20 μm) is the only way to realize energy-dense properties (>500 Wh kg−1) and high-rate performance (charge at 5 C). The advantages of ultra-thin solid polymeric electrolytes (SPEs) in processability, cost and large-scale manufacturing make it the most likely material for commercial applications. However, it is difficult to destroy the restrictions between ion transport behavior and stress properties during the thinning of the SPE. Therefore, it is necessary to design a reasonable structure, regulate the electrolyte components, to achieve high ionic conductivity and high mechanical properties of the ultra-thin SPE. In this review, the blending structure, layer structure and chemical construction of new structures are summarized and prospected in detail, providing a reference for designing the advanced ASSLBs with high safety, high energy density and fast-charging property.