Battery-type electrode materials store charge through chemical reactions, leading to low power densities and rendering it difficult to reach the performance levels associated with capacitors. This study introduces a coordination polymer electrode material for hybrid supercapacitors, specifically, poly[tri-μ-ethanolato-di-μ3-sulfido-hexakis (μ4-2-sulfidobenzoato) dinickel (II) tetranickel (III) dipotassium (I) [potassium (I) /sodium (I) (0. 60/0. 40) ] quaterhydrate], NiIII4NiII2K2. 60Na0. 40 (C2H5O) 3 (C7H4O2S) 6S2·0. 25H2On or Ni-mba-K (Na), where H2mba is 2-mercaptobenzoic acid, (1). As a hybrid capacitor electrode material, Ni-mba-K (Na) exhibits the characteristics of battery-type electrode materials but demonstrates a capacitor-level power density and cycling stability. The microstructure, element composition, phase structure and thermodynamic stability of Ni-mba-K (Na) are characterized through techniques such as crystal structure determination and X-ray photoelectron spectroscopy. Single-crystal X-ray diffraction shows that compound (1) consists of a hexanuclear nickel cluster, two mononuclear K nodes and a mononuclear K0. 60/Na0. 40 shared node, resulting in the formation of a complex covalent three-dimensional network. Due to this novel structure, Ni-mba-K (Na) exhibits supercapacitor performance that combines high energy density and high power density.
Wu et al. (Wed,) studied this question.