Nanostructured silicon as an anode material for Li-ion batteries is produced for the first time by inductively coupled plasma–plasma etching of Si wafers in the black silicon regime. The microscopic structure strongly resembles other types of nanostructured silicon, with a well-arranged nanostructure possessing a sufficient porosity for accommodating large volume expansion. Despite these features, however, a high first-cycle irreversible capacity loss and a poor cycle life are observed. The main reason for these poor features is the formation of a thick solid-electrolyte interphase (SEI) layer related to the surface condition of the pristine nanostructured black silicon (b-Si) electrode. Therefore, the cycle life of the b-Si electrode is heavily influenced by the constant reformation of the SEI layer depending upon the surface composition in spite of the presence of nanostructured Si. In the fast lithiation experiments, the nanostructure region of the b-Si electrode is detached from the Si substrate owing to the kinetics difference between the lithium ion diffusion and the electron injection and phase transformation in the nanostructured Si region. This means that more Si substrate is involved in lithiation at high current rates. It is therefore important to maintain balance in the chemical kinetics during the lithiation of nanostructured Si electrodes with a Si substrate.
Electrochemical characteristics of plasma-etched black silicon as anodes for Li-ion batteries
Gibaek Lee, Stefan L. Schweizer, Ralf B. Wehrspohn; Electrochemical characteristics of plasma-etched black silicon as anodes for Li-ion batteries. J. Vac. Sci. Technol. A 1 November 2014; 32 (6): 061202. https://doi.org/10.1116/1.4897609
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