Sodium alginate/chitosan double-network based high-performance free-standing silicon anodes

In traditional Si-based anodes, bio-based binders can partially address the inherent drawbacks of silicon anodes. However, plenty of inactive materials hinder the improvement of the electrochemical performance of traditional Si-based anodes. To settle the issues above, sodium alginate (SA)/chitosan (CS) double-network is constructed to design a free-standing Si anode. The two physically cross-linked networks, reinforced by carbon nanotubes (CNTs), form a 3D-structured electrode that firmly anchors Si nanoparticles via forming dynamic hydrogen bonds. Furthermore, the in-situ -reduced copper particles act as the point-like conductive agent, CNTs function as the connecting conductive networks, and SA/CS aerogel sheets serve as the conductive plane, synergistically forming a three-dimensional conductive network (points-lines-planes) around Si particles. This double-network structure effectively alleviates Si volume expansion and endows the free-standing electrode with a high capacity of 1194 mAh/g (based on the whole weight of the electrode) and an excellent capacity retention rate of 85.1% after 100 cycles at 0.5 A/g. This strategy is anticipated to produce high-performance free-standing silicon anodes, therefore supporting lightweight and high-capacity electronics.