Waste glass microfiber filter-derived fabrication of fibrous yolk-shell structured silicon/carbon composite freestanding electrodes for lithium-ion battery anodes

Si is regarded as the most promising anode material for lithium-ion batteries owing to its high theoretical capacity and low working voltage. Waste glass microfiber filters (GFs) can be an optimal silica resource for nanostructured Si synthesis because they do not require crushing or acid leaching procedures, which are essential for other silica resources. In this study, benefiting from the original filter shape, fibrous yolk-shell structured Si/carbon composite freestanding electrodes are fabricated via magnesiothermic reduction (MgR) and carbon coating processes using GFs not only as the silica precursor for MgR but also as the hard template for carbon coating. The carbon shell acts as a conductive framework for the freestanding electrodes and encapsulates the Si nanoparticles (Si NPs) inside the shell with a void space. The freestanding electrodes exhibit good cycling performance and a high areal capacity of 2.2 mA h cm⁻² at the 150th cycle because of the yolk-shell structure, which accommodates the volume expansion of the Si NPs.