Electrochemical Lithiation Mechanism of Nickel Silicide Electrode

Yasuhiro DOMI; Hiroyuki USUI; Takumi ANDO; Ryuto TANAKA; Kazuma GOTOH; Takeo HOSHI; Kei NISHIKAWA; Hiroki SAKAGUCHI

Article Electrochemical Lithiation Mechanism of Nickel Silicide Electrode

Yasuhiro DOMI ; Hiroyuki USUI ; Takumi ANDO ; Ryuto TANAKA ; Kazuma GOTOH ; Takeo HOSHI ; Kei NISHIKAWA ; Hiroki SAKAGUCHI

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Yasuhiro DOMI, Hiroyuki USUI, Takumi ANDO, Ryuto TANAKA, Kazuma GOTOH, Takeo HOSHI, Kei NISHIKAWA, Hiroki SAKAGUCHI. Electrochemical Lithiation Mechanism of Nickel Silicide Electrode. Electrochemistry. 2025, 93 (3), 25-00015.

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Pure silicide electrodes have attracted attention as a promising anode material in lithium-ion batteries using certain ionic liquid electrolytes. However, the reaction mechanisms of the silicide electrodes, in particular the lithiation sites in the crystal lattice and the reaction parts (bulk or surface), are still unclear. Here, we investigated the electrochemical lithiation mechanism of an NiSi2 electrode. It is revealed that no phase separation of NiSi2 occurred and no lithiation of Si generated from NiSi2 arose by X-ray diffraction, transmission electron microscopy and so on. In contrast, 7Li magic angle spinning nuclear magnetic resonance demonstrated that stable deposition-dissolution of Li metal did not occur on the NiSi2 electrode and the electrochemical lithiation of NiSi2 itself proceeded. Additionally, we investigated the lithiation sites based on the computational chemistry. The peak positions that appeared in the NMR spectra were different from those predicted by the calculated valence electron numbers. This is due to the increase in conduction electrons near the Fermi energy associated with the amount of Li stored in the NiSi2 crystal lattice and the followed by Knight shift.

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