Natural biochar based on protein in broken egg whites for Si@SnO2@C high-efficiency lithium-ion battery

Abstract

Biochar has been eagerly awaited as a sustainable carbon source. However, its use as a solid biomass in lithium-ion battery materials is subject to several restrictions. About 2–12% of eggs experience shell cracking yearly during production and transport. These broken eggs cannot be adequately consumed by humans and also cause significant economic losses and wastage. This biomass waste has never been focused on lithium-ion battery energy storage materials. This study utilised egg white gel as a carbon source to enhance the performance of Si and SnO2, which possess significant individual capacity. Hydrothermally, ingenious SnO2 layers were deposited in the vicinity of Si NPs. Then, Si@SnO2 was uniformly dispersed in a solution of egg whites; the resulting mixture was freeze-dried and annealed to form Si@SnO2@Biochar ternary composites. Si offers an exceptionally high specific capacity. The electrode structure is influenced by the outer biomass carbon's electrical conductivity enhancements. It, in conjunction with the SnO2 layer, limits the bulk effect of the electrode, a critical factor in improving conductivity and overall performance. The material composed of Si@SnO2@Biochar exhibits remarkable electrochemical stability across a range of current densities. Following 1000 cycles at 1 A g−1 and 100 cycles at 0.1 A g−1, the Si@SnO2@Egg white carbon capacities are 874.3 mAh g−1 and 888.7 mAh g−1, respectively. A critical step towards commercialising silicon anode materials, this work presents a novel, environmentally friendly method for energy storage.