Nanofiber-Reinforced Composite Polymer Electrolyte Enables Continuous Lithium-Ion Transport and Anion-Rich Solvation Structure for 670 Wh kg–1 Lithium Batteries

Abstract Solid-state electrolytes are highly promising for high-energy lithium-metal batteries, yet their practical applications are severely restricted by insufficient oxidative stability, sluggish Li+ transport, and unstable electrode/electrolyte interphases under high-voltage operation. Herein, we report an in situ fabricated composite polymer electrolyte, denoted as LAFE, which integrates a designed main-chain fluorinated polyether matrix with an interconnected three-dimensional framework of Li- and F-codoped hydroxyapatite nanofibers (LANs). Distinct from conventional particle-filled composite electrolytes, the lithium-active LAN framework forms continuous Li+-conducting pathways while simultaneously providing abundant interfacial migration sites through strong Li+–LAN interactions, coupling bulk conduction with site-mediated Li+ hopping. The Li+-affinity contrast between LANs and the fluorinated polyether further induces heterogeneous Li-rich and Li-deficient domains, reconstructing the local solvation environment toward an anion-rich structure. This solvation regulation expands the electrochemical stability window to 3.0–5.7 V and promotes preferential anion-derived inorganic-rich LiF/Li3N/B–O-containing SEI and CEI layers, thereby suppressing Li dendrite growth, electrolyte oxidation, and high-voltage cathode degradation while strengthening abuse tolerance by immobilizing the electrolyte within a solidified framework. Consequently, LAFE enables Li||LiNi0.8Co0.1Mn0.1O2 cells to operate stably for 1000 cycles under 4.5–4.7 V and 5 C. At the pouch-cell level, 7 Ah Li||LiCoO2 and 10 Ah Li||Li-rich Mn-based oxide cells deliver energy densities of 677 Wh kg–1 and 632 Wh kg–1, respectively, while 5 Ah Li|| Ni0.8Co0.1Mn0.1O2 pouch cells pass nail penetration without leakage or combustion. This work establishes a lithium-active composite-electrolyte design principle for high-voltage, high-rate, and safe high-energy lithium-metal batteries.