Bottom‐up Approach for Designing Cobalt Tungstate Nanospheres through Sulfur Amendment for High‐Performance Hybrid Supercapacitors

Nanofabrication of heteroatom‐doped metal oxides into a well‐defined architecture via a “bottom‐up” approach is crucial to overcome the boundaries of the metal oxides for energy storage systems. In the present work, this issue was addressed by developing sulfur‐doped bimetallic cobalt tungstate (CoWO4) porous nanospheres for efficient hybrid supercapacitors via a single‐step, ascendable bottom‐up approach. The combined experimental and kinetics studies revealed enhanced electrical conductivity, porosity, and openness for ion migration after amendments of the CoWO4 via sulfur doping. As a result, the sulfur‐doped CoWO4 nanospheres exhibited a specific capacity of 248.5 mA h g−1 with outstanding rate capability and cycling stability. The assembled hybrid supercapacitor cell with sulfur‐doped CoWO4 nanospheres and activated carbon electrodes could be driven reversibly in a voltage of 1.6 V and exhibited a specific capacitance of 177.25 F g−1 calculated at 1.33 A g−1 with a specific energy of 63.41 Wh kg−1 at 1000 W kg−1 specific power. In addition, the hybrid supercapacitor delivered 94.85 % initial capacitance over 10000 charge‐discharge cycles. The excellent supercapacitive performance of sulfur‐doped CoWO4 nanospheres may be credited to the sulfur doping and bottom‐up fabrication of the electrode materials. Sulfur‐modified CoWO4 nanospheres designed via a single‐step “bottom‐up” approach prove superior redox chemistry. The hybrid supercapacitor assembled with S−CoWO4 cathode demonstrates the high‐energy storing capacity with long‐term stability that might be useful in real energy storage applications.