Conductive 2D metal-organic framework for high-performance cathodes in aqueous rechargeable zinc batteries
In this investigation, we have introduced utilizing a conductive 2D metal-organic framework with large one-dimensional channels, as a zinc battery cathode, which relies upon intercalation pseudocapacitance mechanism or realizing the high rate capability.
Although Li-ion batteries are widely used in devices such as laptops and mobile phones, their application to larger systems such as electric vehicles is inhibited by high production costs and concerns in relation to safety. This investigation focuses on the development of an alternate type of energy storage device for use in large-scale applications, based on rechargeable aqueous ZBs. These batteries provide a comparatively large capacity, low cost, and increased safety.
We present a Cu3(HHTP)2, a two-dimensional (2D) conductive metal-organic framework (MOF) with large one-dimensional channels, as a zinc battery cathode (Fig. 1). 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.
Fig. 1 | Zn-Cu3(HHTP)2 chemistry. a, Schematic illustration of the rechargeable Zn-2D MOF cell. b, Structure of Cu3(HHTP)2 viewed down the c axis, which exhibits slipped-parallel stacking of 2D sheets with a honeycomb lattice. The cyan, red, and grey spheres represent Cu, O, and C atoms, respectively. The H atoms are omitted for the sake of clarity.
The Cu3(HHTP)2 electrode exhibited (Fig. 2a) capacities of 191.4, 189.2, 152.4, and 124.5 mAh g−1 when the current density was increased, respectively, by 2, 4, 10, and 80 times (100, 200, 500, and 4000 mA g−1) from 50 mA g−1. These results correspond to capacity retentions of 89.0, 88.0, 70.9, and 57.9%, respectively, with respect to the initial capacity of 215.0 mAh g−1. Furthermore, at an extremely high current density of 4000 mA g−1 (~18C), 75.0% of the initial capacity (124.4 mAh g−1) was maintained (Fig. 2b) after 500 cycles. This cyclability reflects the structural stability of Cu3(HHTP)2 during repeated (de)intercalation of the Zn2+ ions.
Fig. 2 | Electrochemical performance of Cu3(HHTP)2. a, Discharge–charge voltage profiles of Cu3(HHTP)2 at various current densities. b, Cycling performance of Cu3(HHTP)2 at a current density of 4000 mA g−1.
We believe that this work indicates clearly the potential of this Cu3(HHTP)2 2D conductive MOF for use in large-scale energy storage systems. This investigation paves the way for further exploration of 2D conductive MOFs that may be used with other transition metals in order to increase the efficiency of large-scale batteries.
For more details, please check out our paper “Conductive 2D metal-organic framework for high-performance cathodes in aqueous rechargeable zinc batteries” in Nature Communications: https://doi.org/10.1038/s41467-019-12857-4