Conductive copper ion-reinforced sodium alginate aerogel based free-standing Si anode for Li-ion storage

Abstract

Biomass materials with great advantages of wide accessibility, low cost and environmental benignity have favorable application prospects as Si anodes for lithium-ion batteries (LIBs). In order to alleviate the volume effect and improve the conductance of Si, we fabricated a conductive copper ion-reinforced sodium alginate (SA) aerogel based free-standing Si anode (Si@CNTs/Alg-Cu-II) containing silicon nanoparticles, sodium alginate aerogel, carbon nanotubes and Cu nanoparticles, via a simple, low-cost and sustainable process (under 1 × 10−1 Pa, 1 °C/min to 200 °C holding for 1 h). In the irregular lamellar porous aerogel, silicon particles with good dispersion are bound by macromolecular chains of SA via dynamic hydrogen bonds and subsequently restrained in the porous aerogel to release volume stress. The in situ generated Cu particles and well-dispersed carbon nanotubes (CNTs) construct the conductive network around Si particles to improve the electrical conductivity of the electrode. This unique structure delivers a capacity of 835.6 mAh/g after 100 cycles at 0.1 A/g based on the total mass of Si@CNTs/Alg-Cu-II composite (Si content of 25.62%). Moreover, it also shows outstanding stability under high current density (a capacity retention of 84.1% after 100 cycles at 0.5 A/g). The sustainable preparation method and excellent electrochemical performance of Si@CNTs/Alg-Cu-II provide a new strategy to develop high-performance free-standing Si-based anodes for LIBs.