Lithium Metal Batteries Enabled by Interfacial‐Adhesive Amphoteric Polymer Nanosheets on Separator

ABSTRACT Functional modification of separators represents an effective strategy for enhancing the performance of lithium metal batteries, wherein robust interfacial adhesion between the coating and the separator substrate serves as a critical prerequisite for long‐term protection. Here, a functional separator coating based on amphoteric polymer nanosheets was developed. By compositing poly(p‐aminodiphenylamine) sulfonate nanosheets (p‐SPA NS) with a polyurethane (PU) binder and coating them onto an amine‐functionalized separator, good adhesion strength was achieved through strong interfacial interactions, thereby establishing a foundation for long‐term coating stability. The amphoteric structure of p‐SPA facilitated anion anchoring via its –NH + groups while synergistically promoting lithium salt dissociation and low‐energy‐barrier Li + transport through its sulfonate groups, significantly enhancing ion transport kinetics. Furthermore, the conjugated structure within the coating induced the formation of an inorganic‐rich SEI layer, which further improved deposition uniformity. Benefiting from this synergistic mechanism, the Li||LiFePO 4 battery equipped with the p‐SPA NS@PU separator demonstrated stable cycling for over 400 cycles under a high mass loading of 11.24 mg cm − 2 at 3C, with a capacity retention of 91.4%.