Asymmetric Ion Transport in Tunnel‐Type Cobalt Vanadate for High‐Performance Mn ²⁺ /H ⁺ Hybrid Aqueous Batteries

Aqueous manganese batteries are attractive owing to the deeper Mn/Mn 2 ⁺ redox potential (–1.19 V vs SHE) compared with Zn, yet their development has been hindered by sluggish Mn 2 ⁺ diffusion and parasitic interfacial reactions. Here, the concept of asymmetric‐ion transport is introduced, where Mn 2 ⁺ and protons occupy distinct diffusion channels and act synergistically rather than competitively. Using Co(VO 3 ) 2 ·2H 2 O as a model host, direct structural evidence is provided from Fourier electron density maps and ICP‐OES that 0.50 mol of Mn 2 ⁺ is reversibly accommodated alongside 0.14 mol of H⁺. Migration‐barrier calculations further reveal orthogonal pathways with balanced activation energies (0.602 eV for Mn 2 ⁺, 0.334 eV for H⁺), rationalizing the coexistence of Mn‐dominant storage and proton‐assisted kinetics. This dual‐ion mechanism enables high reversibility, robust cycling stability, and quasi–zero‐strain behavior. When paired with a Mn metal anode, the full cell delivers 1.3 V, substantially 0.4 V higher than Zn analogues, while highlighting the necessity of Mn anode interface stabilization. Beyond a new cathode material, this study establishes asymmetric‐ion transport as a generalizable paradigm for reconciling multivalent‐ion storage with fast kinetics in high‐voltage aqueous batteries.