Superior Pseudocapacitive Storage of a Novel Ni₃Si₂/NiOOH/Graphene Nanostructure for an All-Solid-State...

Recent developments in the synthesis of graphene-based structures focus on continuous improvement of porous nanostructures, doping of thin films, and mechanisms for the construction of three-dimensional architectures. Herein, we synthesize creeper-like Ni₃Si₂/NiOOH/graphene nanostructures via low-pressure all-solid melting-reconstruction chemical vapor deposition. In a carbon-rich atmosphere, high-energy atoms bombard the Ni and Si surface, and reduce the free energy in the thermodynamic equilibrium of solid Ni-Si particles, considerably catalyzing the growth of Ni-Si nanocrystals. By controlling the carbon source content, a Ni₃Si₂ single crystal with high crystallinity and good homogeneity is stably synthesized. Electrochemical measurements indicate that the nanostructures exhibit an ultrahigh specific capacity of 835.3 C g^-1 (1193.28 F g^-1) at 1 A g^-1; when integrated as an all-solid-state supercapacitor, it provides a remarkable energy density as high as 25.9 Wh kg^-1 at 750 W kg^-1, which can be attributed to the free-standing Ni₃Si₂/graphene skeleton providing a large specific area and NiOOH inhibits insulation on the electrode surface in an alkaline solution, thereby accelerating the electron exchange rate. The growth of the high-performance composite nanostructure is simple and controllable, enabling the large-scale production and application of microenergy storage devices.