Bilateral Helmholtz Plane Tailoring in Low-Concentration Electrolytes for Practical Zinc–Vanadium Batteries

Vanadium-based zinc-ion batteries (ZIBs) fail due to electrolyte concentration-dependent bilateral instabilities at the inner Helmholtz plane (IHP). This work demonstrates bilateral IHP tailoring that unlocks stable battery operation in low-concentration electrolytes. Cathodically, a compact AN-derived adlayer suppresses V–OH deprotonation and induces charge reversal, while electrostatic and spatial effects inhibit proton-triggered vanadium dissolution/shuttling. Anodically, acetonitrile (AN) facilitates Zn²⁺-OTf^–contact ion pair formation, inducing in situ generation of a hydrophobic/zincophilic solid electrolyte interphase. Coupled with its selective adsorption on Zn metal and suppression of water activity, this system blocks interfacial H⁺/H₂O accumulation, enabling instantaneous Zn nucleation and dendrite-free (002)-oriented deposition. Consequently, the Zn//NVO coin cells exhibit 10000 cycle longevity with 82% capacity retention over the initial 3000 cycles. Practical Zn//VO₂pouch cells sustain 1200 cycles with high cumulative capacity exceeding 550 Ah, surpassing prior benchmarks. This work establishes a universal bilateral IHP tailoring framework toward cost-effective, durable ZIBs.