Improved performance as a lithium-ion battery anode material through carbon layer coating and Li-modification of silicon nanoskeleton structure

초록

As the global electric vehicle (EV) market expands, increasing the driving range of EVs is a critical challenge. High-capacity silicon-based anodes are being actively researched to enhance the energy density of lithium-ion batteries. However, silicon anodes experience structural instability due to significant volume expansion during the alloying reaction with lithium ions while charging. This leads to irreversible capacity loss from repeated damage to the solid electrolyte interface (SEI) layer. Although nano-sized silicon anodes have been explored to address these issues, the high cost of nanoparticle production and increased side reactions due to a larger electrolyte interface render these solutions suboptimal. This study introduces a novel, cost-effective approach by wet-etching aluminum-silicon alloy particles to obtain a silicon nanoskeleton. This nanoskeleton was coated with a polymer layer using resorcinol as a carbon source, which was then converted into a protective carbon layer through carbonization. This carbon layer prevents direct contact between the silicon and the electrolyte, minimizing volume expansion. Furthermore, the carbon-coated silicon anodes underwent a post-treatment immersion in a lithium-ion solution to enhance capacity and initial coulombic efficiency. This improvement is likely due to the formation of a compact pre-SEI layer on the carbon layer's outer shell, facilitated by the lithium ions in the post-treatment solution. These innovations demonstrate a significant improvement in the initial coulombic efficiency and capacity of silicon anodes through a simplified process. Ongoing research is necessary to elucidate the underlying mechanisms and optimize the post-treatment process in various solutions.