Ultrafast Hopping Transfer Enables High-Anion Conduction

Based on anion intercalation chemistry, dual-ion batteries (DIBs) show advantages including high operating voltages (>5.0 V), intrinsic safety of oxygen-free graphite cathode, metal-free environmental friendliness, and competitive cost. In stark contrast to the well-established diffusion mechanisms for small cations (e.g., Li⁺, Na⁺) in conventional "rocking-chair" batteries, the transport behavior of anions, which act as the pivotal capacity-determining charge carriers in DIBs, remains largely unexplored, particularly regarding how their large ionic radii and distinct solvation dynamics dictate diffusion kinetics. Herein, an ultrafast anion-hopping mechanism is identified, which is intrinsically governed by large ionic radius and high charge delocalization that engender weaker Coulombic interactions with solvent molecules and a consequently loose solvation microenvironment. To thermodynamically favor this low-barrier transport while suppressing parasitic solvent cointercalation, the anion-solvent affinity is further attenuated by engineering an oxidation-resistant localized high-concentration electrolyte (LHCE) paired with a wettable cellulose separator. Through this synergistic strategy, an inorganic-rich cathode-electrolyte interphase (CEI) is constructed to effectively inhibit detrimental solvent cointercalation while facilitating rapid anion desolvation to fully realize the intrinsic high-rate kinetics. As a result, the DIBs based on anion intercalation chemistry retain a reversible capacity of 69.10 mAh g^-1 at an ultrahigh rate of 200C with a long lifespan over 50,000 cycles. The understanding of anion transport behavior and solvation microenvironment offers insights for designing electrolytes toward the development of high-voltage DIBs with fast reaction kinetics and other high-energy batteries.