PPy@NiCo2S4 nanosheets anchored on graphite foam with bicontinuous conductive network for high-areal capacitance and high-rate electrodes

Abstract

A three-dimensional (3D) free-standing polypyrrole@NiCo2S4/GF electrode with internal/external bicontinuous conductive network has been prepared via a two-step hydrothermal process coupled with subsequent in situ polymerization method. The NiCo2S4 nanosheets coated with highly conductive polypyrrole (PPy) shell were uniformly grown on 3D interconnected conductive graphite foam (GF) network. The ultrathin NiCo2S4 nanosheets with 2D layered structure can offer sufficient electrolyte/active materials interface and high capacitance; while GF substrate coupled with PPy conductive shell can serve as an internal/external bicontinuous conductive network, which can greatly enhance the electron transfer rate. The PPy@NiCo2S4/GF-2 electrode could deliver a high areal specific capacitance of 8.5 F/cm2 at 1 mA/cm2, and a high rate performance of 53% retention can be achieved even under 50 mA/cm2. This bicontinuous conductive network fabrication strategy may be applied to high performance energy storage electrodes with industrial-scale.