Photo-Initiated in situ synthesis of polypyrrole Fe-Coated porous silicon microspheres for High-performance Lithium-ion battery anodes

A simple and environmentally friendly photoinitiated fabrication approach based on the photoelectric effect of semiconductor silicon is designed to synthesize yolk-shell like polypyrrole-iron coated porous silicon microspheres (PSi@PPy-Fe) as anode materials for LIBs. The polymerization of pyrrole monomers only occurs on the interface of silicon matrix where the vacancies are available, which effectively avoids the production of free PPyFe particles. XPS and first-principles calculations reveal that both the hydrogen-bond interaction and the covalent linkage are formed between Si and PPy-Fe layer, which is of great significance for maintaining good contact and strengthening the structure stability. It is demonstrated that the PPy-Fe coating may accelerate charge transfer and ion diffusion as well as prevent the Si-based materials peeling off from Cu collector. More importantly, the PPy-Fe coating could alleviate the violent structural expansion of Si anode, thus ameliorating the mechanical strength of the electrode. Consequently, the as-prepared yolk-shell like polypyrrole-iron coated porous silicon microspheres present outstanding cycling ability (1853.7 mAh/g after 200 cycles at 1 A/g) and superior rate capability (1558.4 mAh/g at 4 A/g). This work indicates that the photochemical modification strategy for Si may have a bright prospect in a wide range of fields.