Regulated surface hydroxyl groups improve the cycling performance of micrometer-sized silicon anodes

Compared to nano‑silicon, micron-sized silicon offers broader raw material availability, can be derived from industrial-grade silicon powder, features simplified fabrication processes, lower costs and avoids the agglomeration issues associated with nanoparticles, demonstrating greater potential for large-scale applications. However, its severe volume expansion during cycling triggers structural instability and cycling performance degradation, severely hindering commercialization. Therefore, this study utilizes the Si-OH groups on the surface of micron-sized silicon to form hydrogen bonds and covalent bonds with polyacrylic acid binders to improve cycling performance. Vacuum high-temperature treatment is employed to promote the formation of Si–O–C(O)– covalent bonds between the Si-OH on the silicon surface and polyacrylic acid. The influence of surface Si-OH density on cycling performance was investigated, as this density needs to balance the long-cycle stability of micron-sized silicon with the parasitic side reactions caused by Si-OH groups. The appropriate quantity of Si-OH will enhance the structural stability of the electrode, promote the formation of more Li 2 CO 3 /LiF, and mitigate the electrical contact and capacity loss caused by the volume expansion of micron-sized silicon. Si-OH-10-180 electrode prepared under vacuum high temperature exhibits a high reversible capacity of 1264 mAh g −1 at 0.5 A g −1 after 200 cycles. Compared to the Si-105 electrode, which has a capacity of 63 mAh g −1 after 45 cycles at 2 A g −1 , the Si-OH-10-180 electrode maintains a reversible capacity of 453 mAh g −1 after 300 cycles. This work provides a direct approach to enhance the cycling performance of high-capacity micrometer-sized silicon-based anodes.