Conductive 2D metal-organic framework for high-performance cathodes in aqueous rechargeable zinc batteries

Currently, there is considerable interest in developing advanced rechargeable batteries that boast efficient distribution of electricity and economic feasibility for use in large-scale energy storage systems. Rechargeable aqueous zinc batteries are promising alternatives to lithium-ion batteries in terms of rate performance, cost, and safety. In this investigation, we employ Cu₃(HHTP)₂, a two-dimensional (2D) conductive metal-organic framework (MOF) with large one-dimensional channels, as a zinc battery cathode. Owing to its unique structure, hydrated Zn²⁺ ions which are inserted directly into the host structure, Cu₃(HHTP)₂, allow high diffusion rate and low interfacial resistance which enable the Cu₃(HHTP)₂ cathode to follow the intercalation pseudocapacitance mechanism. Cu₃(HHTP)₂ exhibits a high reversible capacity of 228 mAh g⁻¹ at 50 mA g⁻¹. At a high current density of 4000 mA g⁻¹ (~18 C), 75.0% of the initial capacity is maintained after 500 cycles. These results provide key insights into high-performance, 2D conductive MOF designs for battery electrodes.