Self-charging aqueous hydrogen gas batteries

Self-charging aqueous metal-based batteries are attracting extensive attention for use in energy conversion and storage technologies. However, they are constrained to the chemically self-charging mode by oxygen gas (O₂) reactants and suffer from serious battery failure after cycling due to the accumulation of solid byproducts on the electrodes. Herein, we report a universal approach to develop self-charging aqueous hydrogen gas (H₂) batteries (SCAHGBs) with three different working modes, i.e., chemically self-charging, short-circuit induced self-charging, and low-energy-input triggered quasi-self-charging. The SCAHGBs can be self-recharged by the spontaneous chemical reaction between the discharged cathode and O₂ reactants or the electrochemical reaction between the discharged cathode and electrocatalytic O₂ electrode. Notably, the SCAHGBs after self-charge/discharge cycles only involve the generation of clean water by the combination of OH⁻ and H⁺ ions, which can completely avoid the generation of solid byproducts thus guaranteeing excellent cycling stability with high-capacity retention of 90-100%. Interestingly, the self-charging capacity of the short-circuit induced self-charging battery can reach the practical capacity of 76% in only 15 min, and the low-energy-input triggered quasi-self-charging battery can achieve a high output voltage of 1.69 V. This work provides promising strategies for designing advanced self-charging battery systems.