Multi-faceted design of a silicon anode for high performance lithium ion batteries using silicon nanoparticles encapsulated by a multiple graphene aerogel electrode material and a tryptophan-functionalized graphene quantum dot–sodium alginate binder

Abstract

Silicon has great potential to revolutionize the energy storage capacities of lithium ion batteries (LIBs) to meet the ever increasing power demands of next generation technologies. The study reports a multi-faceted design of a silicon anode for high performance LIBs. First, silicon nanoparticles (Si) were encapsulated in three-dimensional interconnected networks of multiple graphene aerogel (MGA-n, inner shell). The inner shell offers a much higher mechanical strength and electronic conductivity compared to common graphene aerogel. Then, MGA-n/Si was embedded in the binder layer (outside shell) composed of tryptophan-functionalized graphene quantum dots (Trp-GQD) and sodium alginate. The introduction of Trp-GQD greatly improves the mechanical strength, elasticity and electronic conductivity of the outside shell. The integration of the inner shell with the outside shell achieves simultaneously good structural integrity, SEI stability at the silicon–electrolyte interface and high ionic/electronic conductivity of the silicon anode. As a result, the Trp-GQD@MGA-n/Si electrode exhibits excellent electrochemical performance for LIBs. The specific capacity is 1427 mA h g⁻¹ at 100 mA g⁻¹, 1115 mA h g⁻¹ at 1000 mA g⁻¹ and 637 mA h g⁻¹ at 4200 mA g⁻¹. The capacity retention is more than 93.3% after 100 cycles at 100 mA g⁻¹ with a high columbic efficiency of about 99.8%. Such a multi-faceted design can also be used for the fabrication of other large-volume-change electrodes for LIBs.