Multilayer SiOx derived from Si–Ca alloy via Fe2O3 oxidization for Li-ion batteries†

Abstract

SiO_x is deemed a promising candidate for lithium-ion batteries owing to its high specific capacity and relatively low volume expansion. However, its low rate performance is a bottleneck for its application. Two-dimensional SiO_x with short lithium-ion pathways and large layer intervals has been a hot research topic for improving the electrochemical performance of lithium-ion batteries. Herein, a solid exfoliation method was designed to synthesize a multilayer SiO_x using CaSi₂ and Fe₂O₃. This multilayer SiO_x exhibited large layer intervals after the by-products were removed by HCl. The void space provided extra space for volume expansion, which prevented pulverization, and the thin monolayer shortened the Li⁺ pathways. Therefore, ML-SiO_x–Fe₂O₃ exhibited an excellent reversible capacity of 697.8 mA h g⁻¹ after 200 cycles at 0.5 A g⁻¹ with a capacity retention of 94.2%. Meanwhile, ML-SiO_x–Fe₂O₃ anode delivered a rate performance of 432.7 mA h g⁻¹ at 3 A g⁻¹, and it could be recovered to 1157.1 mA h g⁻¹ when the current density was converted to 0.1 A g⁻¹. This work opens up a new method for synthesizing multilayer SiO_x using metal oxides to exfoliate CaSi₂.