Cobalt carbonate hydroxides as advanced battery-type materials for supercapatteries: Influence of morphology on performance

Layered materials provide good electrochemical performance, but insufficient rate capability, which is the main issue in energy storage. Herein, we propose a facile synthesis of Co₂(CO₃)(OH)₂ nanoflakes and polyhedron flowers supported on Ni foam, a novel binder-free electrode. Power law revealed that Co₂(CO₃)(OH)₂ stores charge by a battery-type mechanism at the peak potential. The nanoflakes store more internal surface charge than the polyhedron-flower, which was confirmed via Trasatti plot. Benefiting from amorphous nanostructure, unique morphology and high surface area, the nanoflakes shows good performance. The areal capacitance (2111 mF cm⁻²), rate capability (80%), and energy density (0.152 mWh cm⁻²) are comparable to recent reports. The results suggest that the amorphous Co₂(CO₃)(OH)₂ nanoflakes are a suitable cathode candidate for the supercapattery. The assembled supercapattery (ASC) provides high specific capacitance (91 F g⁻¹), high energy density (26.22 Wh kg⁻¹ at power density 828 W kg⁻¹), and long cycle life (specific capacitance retention of 85% over 4000 cycles). The ASC device shows good potential in the field of energy storage devices.