Gel electrolyte featuring parasitic salt-phobic network enables anode-free lithium batteries with long cycle life and enhanced thermal stability

Gel polymer electrolytes are promising for lithium batteries due to their high ionic conductivity, excellent thermal stability, unique rigid-flexible frameworks, and favorable chemical compatibility with lithium metal. Despite these advances, the fundamental relationship between polymer backbone chemistry and lithium-ion solvation and transport remains poorly understood, and the intrinsic role of the polymer framework in regulating Li⁺ solvation structure has often been overlooked. In this work, we design an in situ fluoroacrylate-based gel polymer electrolyte featuring a parasitic salt-phobic network that successfully promotes an anion-rich solvation structure, enabling both extended cycling life and enhanced thermal stability in an anode-free lithium battery. The secondary salt-phobic networks within the polymer matrix act as nanoscale domain walls that attract solvents but repel lithium salts, thereby inducing chemical inhomogeneity in the electrolyte and promoting anion-rich solvation of Li⁺ ions due to the reduced availability of nearby solvent molecules. Importantly, the anion-rich solvation structure is confirmed by Raman spectroscopy, nuclear magnetic resonance, and molecular dynamics simulations. Moreover, such a tailored solvation environment promotes an anion-derived solid electrolyte interphase that effectively stabilizes lithium plating/stripping and mitigates interfacial parasitic reactions. The parasitic salt-phobic network design not only deepens the mechanistic understanding of solvation chemistry for polymer electrolytes in anode-free systems but also provides a practical pathway toward next-generation safe and durable energy storage systems. • A parasitic salt-phobic network is constructed in the gel polymer electrolyte • Such a network attracts solvents but repels salts, enabling anion-rich solvation • Anode-free pouch cell shows excellent cycling life and enhanced thermal stability A parasitic salt-phobic network is constructed in the gel polymer electrolyte Such a network attracts solvents but repels salts, enabling anion-rich solvation Anode-free pouch cell shows excellent cycling life and enhanced thermal stability Anode-free lithium metal batteries offer high energy density but suffer from poor cycle life and thermal instability due to unstable anode morphology and parasitic interfacial reactions. We address these challenges by developing a gel polymer electrolyte featuring a parasitic salt-phobic network. Copolymerization of a branched acrylate and a fluoroacrylate forms the primary gel matrix, while fluoroacrylate-driven interchain interactions induce a secondary network that attracts solvents but excludes salts, creating nanoscale compositional inhomogeneity and promoting anion-rich solvation. This regulated microstructure enhances Li deposition/stripping reversibility, cycling life, and thermal stability. In 4.8 mAh/cm² Cu/NCA pouch cells, 80.3% of the initial 192.2 mAh/g is retained after 100 cycles, while 240 mAh anode-free cells maintain 81.2% after 70 cycles with 2.8 g/Ah electrolyte at 3.0–4.3 V and exhibit no thermal runaway in drilling tests. This work highlights polymer backbone chemistry as a powerful handle for tuning solvation and enabling safe, high-energy anode-free batteries.