Uniformly dispersed AgF inorganic additives in molecular level enables high-performance composite polymer...

Achieving high ionic transport and interfacial stability remains a critical challenge for polymer-based solid electrolytes. Herein, we report a solvation-assisted approach to uniformly disperse AgF additives at the molecular level within a PEO matrix reinforced by electrospun PAN fibers. The resulting composite electrolyte PPA-0.5 exhibits a highly homogeneous structure and strong Ag⁺-EO coordination, which reduces polymer crystallinity and forms continuous Li⁺ transport channels. Electrochemical analyses demonstrate that the optimized PPA-0.5-LiTFSI delivers a remarkable ionic conductivity of 6.75 × 10^-5 S cm^-1 at 30 °C and a low activation energy of 0.146 eV. The strong Lewis acidity of Ag⁺ promotes Li⁺/Na⁺ dissociation and suppresses TFSI^- aggregation, yielding elevated cation transference numbers (t_Li⁺ = 0.41, t_Na⁺ = 0.53). Moreover, the released F^- ions induce in-situ formation of a robust LiF/NaF-rich SEI, ensuring uniform alkali-metal deposition and superior cycling stability. Symmetric Li||Li and Na||Na cells exhibit ultra-long lifespans of >2000 h and > 1400 h at 0.1 mA cm^-2 with negligible polarization, confirming dendrite suppression and interfacial stability. In full cells, the LFP||Li battery maintains 73.9 % capacity retention after 1000 cycles at 1C and 60 °C, while the NVP||Na cell preserves 84.3 % after 710 cycles at 2C. The synergistic effects of Ag⁺-EO coordination and F^--driven SEI reconstruction endow the composite electrolyte with high ionic mobility, mechanical robustness, and interfacial compatibility, providing an effective strategy for constructing durable, high-performance solid-state alkali-metal batteries.