High-rate proton storage in aqueous electrolyte based small organic molecules materials

Abstract

Aqueous proton battery (APB) is a promising energy storage system due to the smallest ion size and fastest kinetics of proton. However, its application development is still limited by unsatisfactory rate and cycling performance. Herein, two organic compounds, BPD and 2F-BPD, are demonstrated as anode for reversibly storage proton in an acid electrolyte, which exhibited high-rate capability. The full batteries were constructed by matching the two anodes with a high performance of CuHCF cathode. The BPD//CuHCF full battery achieved high capacities of 182 mAh g⁻¹ at 1 A g⁻¹ and 151 mAh g⁻¹ at 20 A g⁻¹ and an extremely long cycling stability over 10000 cycles with 79 % capacity retention at 10 A g⁻¹. Due to the hydrophobic effect of the F atom in 2F-BPD and extremely severe hydrogen evolution reaction (HER) in the 2F-BPD//CuHCF full battery, the capacity of the full battery based 2F-BPD anode is slightly lower and decays rapidly. The proton storage of BPD was further analyzed by ex-situ characterizations. During charging, the C=O and C=N bonds in the BPD anode combine with protons in the aqueous electrolyte. This work will inspire small organic molecules to achieve beneficial results in APBs and thus promote a breakthrough in the field of large-scale energy storage.