Covalently bonded Si-SiOC-C heterostructural nanocomposites as durable anode materials for high-energy lithium-ion batteries

Enhancing electrical conductivities and structural stabilities of Si-based anodes is critical to achieve efficient and stable capacity output, promoting their practical applications. Here, we design a covalently bonded heterostructural Si-SiOC-C nanocomposite to improve the above properties. Covalently bonded Si-polyvinyl alcohol (Si-PVA) nanocomposites are first fabricated via high-energy ball-milling of a mixture of micron-sized Si and PVA, and then dual-layered SiOC-C wrappers are in situ formed on the Si surface by low-temperature annealing. The obtained composite is thus a Si-SiOC-C heterostructure with good mechanical resiliency to accommodate Si volumetric expansion and also good mixed conductivity. Such a composite anode design enables excellent electrochemical performance, including high specific capacity and good cycle stability (2130 mA h g⁻¹ after 100 cycles at 0.2 A g⁻¹, and 1068 mA h g⁻¹ after 300 cycles at 1.0 A g⁻¹). Notably, the Si-SiOC-C anode demonstrates great potential for Li-ion batteries, where the Si-SiOC-C-graphite//NCM811 full-cell exhibits efficient and stable capacity output (initial capacity of 195 mA h g⁻¹ and a cycling capacity of 160 mA h g⁻¹ after 300 cycles at 1.0C). The simple and scalable manufacturing makes the Si-SiOC-C anode material potentially viable for commercialization.