SiC-Free Carbon-Silicon Alloys Prepared by Delithiation as Lithium-Ion Battery Negative Electrodes

Carbon-silicon alloys in different stoichiometric ratios are synthesized by delithiation of carbon-lithium-silicon ternary alloys with ethanol followed by washing with HCl and distilled water. The as-prepared carbon-silicon materials are air and water stable. In contrast to mechanically milled or sputtered C-Si alloys studied in the past, the method of synthesizing C-Si alloys introduced in this work avoids the formation of inactive SiC even after two hours high energy ball milling. This results in C-Si alloys with significantly greater volumetric and specific capacity. When cycled in Li half-cells, C-Si alloys exhibit good cycling performance and lower volume expansion compared to conventionally made Si alloys. This is attributed to the presence of void spaces in the structure which can accommodate some of the Si volume expansion.