Polypyrrole as Dissociation Promoter and Interface Stabilizer of Solid Polymer Electrolytes for Solid-State Li Metal Batteries.

Abstract

Advanced solid polymer electrolytes (SPEs) are indispensable for enabling durable, safe, and high-energy-density solid-state lithium metal batteries (SSLMBs). However, the concurrent optimization of lithium-salt dissociation, Li+ transport, and lithium-metal interfacial chemistry remains a challenge over decades. In this study, a PPy-regulated solid polymer electrolyte (PPyPL) featuring chemically differentiated coordination sites is developed to reconstruct ion-solvation chemistry through site-selective Li+/anion coordination. The resulting coordination architecture affords differentiated molecular interactions in which pyrrolic nitrogen sites preferentially coordinate Li+, whereas hydrogen sites along the PPy backbone interact with bis(trifluoromethanesulfonyl)imide (TFSI-) anions, thereby simultaneously promoting lithium-salt dissociation, accelerating Li+ transport, and directing LiF/Li3N-rich interphase formation. Benefiting from the synergistic regulation of ion-solvation chemistry and interfacial evolution, PPyPL achieves an ionic conductivity of 0.76 mS cm-1 at room temperature (25°C), a Li+ transference number of 0.65, and ultralong Li plating/stripping stability over 8000 h. It further enables outstanding rate capability and durable cycling in both Li||LiFePO4 (LFP) and Li||LiNi0.8Co0.1Mn0.1O2 (NCM811) solid-state full cells. This work provides a new strategy for regulating Li+/anion coordination in advanced SPEs toward durable SSLMBs.