Silicon is considered as one of the most favorable anode materials for next-generation lithium-ion batteries. Nanoporous silicon is synthesized via a green, facile, and controllable vacuum distillation method from the commercial MgSi alloy. Nanoporous silicon is formed by the evaporation of low boiling point Mg. In this method, the magnesium metal from the MgSi alloy can be recycled. The pore sizes of nanoporous silicon can be secured by adjusting the distillated temperature and time. The optimized nanoporous silicon (800 °C, 0.5 h) delivers a discharge capacity of 2034 mA h g at 200 mA g for 100 cycles, a cycling stability with more than 1180 mA h g even after 400 cycles at 1000 mA g, and a rate capability of 855 mA h g at 5000 mA g. The electrochemical properties might be ascribed to its porous structure, which may accommodate large volume change during the cycling process. These results suggest that the green, scalable, and controllable approach may offer a pathway for the commercialization of high-performance Si anodes. This method may also be extended to construct other nanoporous materials.

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Potassium-ion batteries are now regarded as powerful competitors to lithium-ion batteries due to their merits of low-cost and abundant resource contrasted with state-of-art lithium ion batteries. However, the extremely flammable electrolytes may cause severe safety issues. Herein, we report an intrinsic non-flammable trimethyl phosphate-based potassium ion battery electrolyte. The problem of its poor electrochemical compatibility with graphite electrode is successful settled by using concentrated salt electrolyte. Graphite anode with high concentrated potassium bis(fluorosulfonyl)imide (KFSI)/trimethyl phosphate (TMP) electrolyte demonstrates high Coulombic efficiency and stable cyclability after 80 cycles. The performance enhancement mechanism is further probed via X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Raman spectroscopy, and scanning electron microscopy (SEM). The flame-retarding character of the concentrated electrolyte with stable electrochemical performance paves the way toward low cost and highly safe potassium ion batteries.