High-Capacitance Pseudocapacitors from Li⁺ Ion Intercalation in Nonporous, Electrically Conductive 2D Coordination Polymers

Electrochemical capacitors (ECs) have emerged as reliable and fast-charging electrochemical energy storage devices that offer high power densities. Their use is still limited, nevertheless, by their relatively low density. Because specific surface area electrical conductivity are widely seen key metrics for improving the density overall performance of ECs, materials excellent conductivities but otherwise nonporous, such coordination polymers (CPs), often overlooked. Here, we report a new nonporous CP, Ni3(benzenehexathiolate) (Ni3BHT), which exhibits over 500 S/m. When used an electrode, Ni3BHT delivers capacitances 245 F/g 426 F/cm3 in nonaqueous electrolytes. Structural studies relate favorable to pseudocapacitive intercalation Li+ ions between 2D layers Ni3BHT, charge-storage mechanism has thus far been documented only inorganic TiO2, Nb2O5, MXenes. This first demonstration ion CPs, class comprising thousands members with distinct structures compositions, provides important motivation exploring this vast family nontraditional, high-energy pseudocapacitors.