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

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||LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811) solid-state full cells. This work provides a new strategy for regulating Li⁺/anion coordination in advanced SPEs toward durable SSLMBs.