Research of the transition from a aqueous zinc ion battery to an aqueous hydrogen proton battery triggered by the Cu@Cu₃₁S₁₆ cathode material development

The aqueous zinc ion battery (AZIB) has been widely studied due to its rapid kinetics and high specific capacity attributed to the chemical insertion of H⁺ protons. However, the current research landscape lacks comprehensive investigations into copper-based sulfide materials and the intricate co-embedding/extraction mechanism of H⁺/Zn²⁺. In this study, we employed an innovative in-situ etching method to synthesize a current collector-integrated Cu@Cu₃₁S₁₆ cathode material. Cu₃₁S₁₆ not only exhibits excellent stability and conductivity but also activates proton insertion chemistry. Consequently, we have demonstrated, for the first time, efficient and reversible co-embedding/extraction behavior of H⁺/Zn²⁺ in Zn-Cu₃₁S₁₆ batteries. Specifically, owing to the lower charging and discharging plateaus of zinc ions (0.65 V, 0.45 V) compared to H⁺ (0.97 V, 0.84 V) in Zn-Cu₃₁S₁₆ batteries, two distinct plateaus were observed. Moreover, we delved into the mechanism of ion co-embedding/extraction by exploring different ions (Zn²⁺, H⁺/Zn²⁺, H⁺) within varying voltage ranges. This exploration led to the development of three types of ion batteries, where Zn²⁺, H⁺/Zn²⁺, and H⁺ exhibit co-embedding/extraction within voltage ranges of 0.3-0.9 V, 0.3-1.05 V, and 0.5-1.05 V, respectively. These batteries have achieved impressive performance with specific capacities of 282.74 mAh g^-1, 587.4 mAh g^-1 and 687.3 mAh g^-1, respectively. Introducing the concept of "Voltage-Selective Ion Co-Embedding/Extraction", this study broadens the research scope of AZIBs. This research not only offers a feasible solution and theoretical guidance for future proton batteries but also underscores the tremendous potential of AHPB.