H2/VPO4F Gas Battery with a Semi‐Solid‐State Electrolyte

Abstract Hydrogen gas secondary batteries using an acidic electrolyte have garnered significant interest as a promising solution for emerging electrical energy storage due to their faster proton conductivity and lower overpotential for hydrogen evolution reaction (HER) compared to alkaline electrolytes. However, acidic electrolytes pose challenges such as equipment corrosion, side reactions, and material dissolution. Addressing these concerns, a semi‐solid‐state H 2 /VPO 4 F gas battery is proposed, comprising a VPO 4 F cathode, a Bentonite‐Phosphoric (BP) semi‐solid‐state electrolyte and a H 2 anode with the Pt catalyst. This battery operates via H + insertion/extraction in the VPO 4 F cathode and hydrogen evolution/oxidation in the anode. The results reveal that H₂ gas can be intercalated into the VPO₄F cathode once the H₂ pressure exceeds 2 MPa. As a result, both the discharge capacity and coulombic efficiency improve with increasing H₂ pressure, peaking at 2 MPa, and then decline when the pressure is further increased. Under the optimized H₂ pressure of 2 MPa, the battery exhibits a reversible capacity of 62.3 mAh g⁻¹ at 100 mA g⁻¹ and excellent cycling stability, retaining ≈80% of its capacity over 10,000 cycles at 2.5 A g⁻¹.