Self-templating Scheme for the Synthesis of Nanostructured Transition-Metal Chalcogenide Electrodes for Capacitive Energy Storage

Because of their unique structural features including well-defined interior voids, low density, low coefficients of thermal expansion, large surface area and surface permeability, hollow micro-/nanostructured transition-metal sulfides with high conductivity have been investigated as a new class of electrode materials for pseudocapacitor applications. Herein, we report a novel self-templating strategy to fabricate well-defined single- and double-shell NiCo2S4 hollow spheres, as a promising electrode material for pseudocapacitors. The surfaces of the NiCo2S4 hollow spheres consist of self-assembled two-dimensional mesoporous nanosheets. This unique morphology results in a high specific capacitance (1263 F g(-1) at 2 A g(-1)), remarkable rate performance (75.3% retention of initial capacitance from 2 to 60 A g(-1)), and exceptional reversibility with a cycling efficiency of 93.8% and 87% after 10 000 and 20 000 cycles, respectively, at a high current density of 10 A g(-1). The cycling stability of our ternary chalcogenides is comparable to carbonaceous electrode materials, but with much higher specific capacitance (higher than any previously reported ternary chalcogenide), suggesting that these unique chalcogenide structures have potential application in next-generation commercial pseudocapacitors.