Control competing expansion and contraction of interplanar spacing in layer structured cathode for stable and...

Pre-intercalation has emerged as a highly effective strategy to enhance structural integrity and ion transport kinetics in cathodes for aqueous Zn-ion batteries. Here, we report a zinc-ion pre-intercalated hydrate vanadium oxide cathode, in which the initial insertion of Zn²⁺ induces a significant expansion of the interplanar spacing, followed by contraction at higher Zn²⁺ concentrations owing to strong electrostatic interactions with the VO framework. Such competing expansion and contraction of interplanar spacing enhances the overall electrochemical properties. In addition, the pre-intercalated Zn²⁺ facilitates the in situ formation of a Zn₃(OH)₂V₂O₇·2H₂O cathode-electrolyte interphase (CEI) layer, which not only suppresses vanadium dissolution but also regulates the desolvation of hydrated Zn²⁺, thus further enhancing the structural integrity and interfacial kinetics. Benefiting from these merits, the Zn²⁺ pre-intercalated hydrate vanadium pentoxide (denoted as 2Zn-VOH) cathode delivers a high capacity of 395 mA h g^-1 at 0.1 A g^-1, exhibits excellent cycling stability at both low and high current densities, and retains outstanding performance under low-temperature conditions (295 mAh g^-1 at 0.1 A g^-1 and - 10 °C, with 83.8 % capacity retention after 1000 cycles at 0.2 A g^-1).