Spin Polarization Promoted Hydronium Desolvation for Aqueous Proton Batteries

Among potential anodes for aqueous proton batteries (APBs), metal oxide offers high theoretical capacity but suffers from a sluggish desolvation process that limits cycling stability and capacity. Here we take MoO 3 as an example to develop a spin-engineering strategy for accelerating the desolvation by atomic doping of trace rhenium (Re-MoO 3, 1.8 at % Re per MoO 3 unit). The induced spin polarization, triggered by spin exchange interaction, reconstructs the electronic structure of the terminal O site, optimizing the charge transfer to significantly accelerate desolvation kinetics. Herein, Re-MoO 3 provides a high reversible capacity of 294 mAh g –1, which is 40% higher than that of MoO 3, outperforming the previously reported Mo-based electrode in an aqueous electrolyte, to the best of our knowledge. Moreover, benefiting from promptly removing the solvated H 2 O and the consequent alleviated Mo dissolution, Re-MoO 3 exhibits prominent cycling stability, retaining 98% capacity over 1000 cycles, ∼20 times higher than that of pure MoO 3 (5%). An exceptionally low average capacity fade of 0.0033% per cycle is observed over 10,000 cycles. The full cell provides a maximum energy density of 41.1 Wh kg –1 at room temperature, retaining negligible energy density loss (40.8 Wh kg –1 ) and a high-power output of 17.1 kW kg –1 at – 40 °C owing to the accelerated desolvation process.