Fibrin biopolymer hydrogel-templated 3D interconnected Si@C framework for lithium ion battery anodes

Highlights: • Fibrin biopolymer hydrogel serves as a template for Si-based anodes in lithium-ion batteries. • Hydrogen bonding enables guided assembly of Si nanoparticles along fibrin fiber strands. • Pyrolysis creates 3D structures consisting of Si nanoparticles embedded in N-doped C network. • 3D Si@C electrodes demonstrate enhanced performances due to efficient charge transfer. Silicon is considered a promising candidate for lithium-ion battery anodes because of its exceptionally high capacity. However, employing Si in real applications remains a challenge, owing to dramatic reduction in the capacity after a few cycles. Redesigning the advanced electrode structure, including the available free volume and continuous conductive scaffold, may potentially circumvent this problem. Here, we demonstrate a new method of creating binder- and conductive additive-free three-dimensional (3D) porous network Si@C electrodes via fibrin hydrogel templating followed by pyrolysis. Hydrogen bonds between hydroxyl groups on Si and amides of fibrin enable the hierarchical 3D structures. These comprise well-distributed Si nanoparticles (SiNPs) in carbon frameworks, with each particle conformally encapsulated by the carbon layer. We confirm that carbon is doped with nitrogen and that pyridinic N and pyrrolic N are the predominant configurations. The 3D Si@C electrode exhibits a good rate performance (capacity of 730 mAh g⁻¹ at 1000 mA g⁻¹ (0.5C, Si + C basis)) and also a stable cycling property (54% capacity retention after 500 cycles at 500 mA g⁻¹). Compared to a conventional mixture (SiNPs/alginate/Super P), the 3D Si@C electrode exhibits significantly improved electrochemical properties.