Selective Center Charge Density Enables Conductive 2D Metal−Organic Frameworks with Exceptionally High Pseudocapacitance and Energy Density for Energy Storage Devices
Situo Cheng, Wenzheng Gao, Zhen Cao, Yifan Yang, Erqing Xie, Jiecai Fu
Abstract
Abstract Conductive 2D conjugated metal−organic frameworks (c‐MOFs) are attractive electrode materials due to their high intrinsic electrical conductivities, large specific surface area, and abundant unsaturated bonds/functional groups. However, the 2D c‐MOFs reported so far have limited charge storage capacity during electrochemical charging and discharging, and the energy density is still unsatisfactory. In this work, a strategy of selective center charge density to expand the traditional electrode materials to the electrode−electrolyte coupled system with the prototypical of 2D Co‐catecholate (Co‐CAT) is proposed. Electrochemical mechanism studies and density functional theory calculations reveal that dual redox sites are achieved with the quinone groups (CAT) and metal‐ion linkages (Co−O) serving as the active sites of pseudocapacitive cation (Na + ) and redox electrolyte species (SO 3 2− ). The resultant electrode delivers an exceptionally high capacity of 1160 F g −1 at 1 A g −1 and a special self‐discharge rate (86.8% after 48 h). Moreover, the packaged asymmetric device exhibits a state‐of‐the‐art energy density of 158 W h kg −1 at the power density of 2000 W kg −1 and an excellent self‐discharge rate of 80.6% after 48 h. This success will provide a new perspective for the performance enhancement for the 2D‐MOF‐based energy storage devices.