Nano hollow carbon sphere buffering design to address volume expansion in micro-silicon anodes of lithium-ion batteries

Abstract

Silicon-based materials are known as promising anodes for new-generation lithium-ion batteries due to their high theoretical capacity and various properties, but the huge volume expansion of silicon-based electrodes greatly limits their development. Herein, this study designs an integrated co-carbonized layer (CCL) silicon-based anode with nano hollow carbon sphere (HCS) buffer materials (HCSs/Si/G-CCL) to regulate the volume expansion of electrodes and effectively increase the content of active materials. As a result, the HCSs/Si/G-CCL electrode with buffer materials offered a good buffer effect, and the electrode expansion degree was only 4.0% after cycling, which was far lower than that of commercial anodes (174.3%), effectively mitigating the severe volume expansion of silicon during lithiation. The HCSs/Si/G-CCL exhibited a reversible capacity of 702 mAh g⁻¹ after 100 cycles at 1.0 A g⁻¹, with the capacity retained around 75%. The full cell also manifested excellent cycle stability, exhibiting commercial-level areal capacities of 1.9 mAh cm⁻² after 100 cycles. This work presents a general electrode design approach that mitigates the volume expansion of silicon-based anodes, enabling their practical large-scale application in lithium-ion batteries.