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Highly pure silicon is an important component in photovoltaic applications and has potential in battery technology. In this study, the electrochemical behavior of Si (IV) was discussed in a NaF−LiF−Na2SiO3−SiO2 electrolyte at 750 °C, and lithium-ion battery performance with electrodeposited silicon powder as anode material were investigated. The cyclic voltammograms illustrated that the reduction of Si(IV) on an Ag electrode followed an irreversible two-step, two-electron process: Si(IV) → Si(II) and Si(II) → Si(0). Both reduction steps involved diffusion control, and the diffusion coefficients were 1.18 and 1.22 × 10−6 cm2 s−1, respectively. Nanoscale spherical silicon was deposited between potentials of −1.0 to −1.6 V (vs Pt) with support of X-ray diffraction patterns, Raman spectra, and scanning electron microscopy analysis. Combining the fabricated silicon with carbon, a Si@C composite anode material for lithium-ion batteries was prepared, and its specific capacity reached 1260 mA·h g−1. Notably, a capacity of 200 mA·h g−1 was maintained over 100 cycles.

Manganese dioxide (MnO2) has been extensively investigated as an electrode material for supercapacitors because of its high theoretical capacitance, great abundance, and low toxicity. To obtain satisfactory capacitance performance, in recent years, many efforts have been dedicated to the fabrication of MnO2 nanoparticles that offer a larger specific surface area and an escalated chemical activity. Beyond them, the ideal dispersibility of nanoparticles in a liquid medium is also of vital importance when processing those powdery materials into slurry ones for some particular uses, such as editable and ink‐printing supercapacitor devices. In this study, the as‐synthesized ultrafine MnO2 nanoparticles having excellent dispersibility in water can be prepared via a facile one‐step hydrothermal route, with a uniform size in diameter of 200 nm exhibiting a large specific surface area of ~389.7 m2 g−1, and a high specific capacitance of 135.7 F g−1 at 5 mV s−1.