Preparation of various Co/Cu and Co/Fe molar ratios and gel-modified nanomaterials as anodes for Li-ion batteries

Abstract

Co-based binary metal oxides with higher theoretical capacity have attracted increasing attention as anodes for lithium-ion batteries (LIBs). In this study, Co-based bimetallic oxides were prepared by optimizing different molar ratios of Cu/Co and Fe/Co using an electroconversion method. The purity and microstructure of the synthesized powders were investigated, and their lithium storage properties were studied by assembling half-cells. Cu/Co oxide exhibited three different microstructures, while Fe/Co oxide showed a nanoparticle morphology. The electrochemical performance results revealed that the optimal molar ratio of Co: Cu was 2:1, and the optimal molar ratio of Fe: Cu was 5:1. Particularly, Fe: Cu = 5:1 exhibited the best electrochemical stability and higher specific capacitance. Therefore, Fe3O4/Co3O4 (Fe: Cu = 5:1) was used as the raw material for modification, and a hydrogel method was employed with sodium alginate (SA) serving as the fixing agent and carbon source to prepare microspheres. Taking advantage of the natural freezing conditions in the winter of Northeast China, the dried microspheres were subjected to calcination to obtain Fe3O4/Co3O4/SA with enhanced conductivity. Even at a current density of 2 A/g, Fe3O4/Co3O4/SA still maintained a discharge capacity of around 280 mAh/g, demonstrating excellent cycling stability and rate capability.