Polymer-derived bifunctional anchoring coatings for mechanically resilient Si-based nanocomposite anodes

Enhancing electrical conductivity and structural stability of Si-based anodes is crucial to attaining efficient and stable capacity output, promoting their practical applications. Here, we developed a polymer-derived bifunctional coating of nano-Si, which simultaneously provides conductive networks and elastic encapsulation to facilitate electron/ion transport and accommodate Si volume expansion during repeated lithiation/delithiation. A covalent bonding SiOC coating was firstly build onto nano-Si by ball-milling micro-Si with polyvinyl alcohol (PVA), then a cyclized-polyacrylonitrile (cPAN) coating was wrapped onto the above composite through low-temperature pyrolysis of PAN, forming polymer-derived anchoring coatings of nano-Si. The covalent SiOC anchoring layer serves as a bridge for fast electrical conduction and efficient stress buffer, and the cyclized-PAN conformal coating further improves electrical conductivity and mechanical resilience of the whole nanostructure. The as-prepared nanocomposite exhibits excellent electrical and mechanical properties, enabling outstanding electrochemical performance in Li-ion batteries. It exhibits a high initial capacity of 3477 mAh g^-1 and retains 1660 mAh g^-1 after 300 cycles at 1 A g^-1. The graphite-Si/SiOC@cPAN//NCM811 full-cell exhibited a high initial capacity of 180.6 mAh g^-1 and 89% capacity retention after 300 cycles at 1C. This work provides a facile and scalable way to fabricate high-performance Si-based anode materials for high-energy-density Li-ion batteries.