Nitrogen‑sulfur doped graphene-loaded SiO2/Co9S8 composites as anode materials for improved lithium storage
Heteroatom-doped graphene lamellae can effectively modulate the physical and chemical surface activities of Co 9 S 8 materials. The addition of a second dopant atom, such as nitrogen (N) can further improve the composite properties. Herein, novel nitrogen‑sulfur double-doped graphene-loaded SiO 2 /Co 9 S 8 composites (SiO 2 /Co 9 S 8 @NSG) were prepared by a one-step solvothermal method using polyethylene glycol as the carbon source and cobalt chloride hexahydrate as the cobalt source to yield a Deep Eutectic Solvents (DESs) system. The precursor was then obtained by adding tetraethyl silicate as the silicon source, thiourea as the sulfur source, and urea as the nitrogen source. The uniform distribution of Co 9 S 8 in the N/S-doped graphene matrix formed graphene-coated SiO 2 particles SiO 2 /Co 9 S 8 @NSG with high specific surface area, superior ionic conductivity, and elevated theoretical specific capacity. The N/S co-doped graphene matrix not only improved the electrical conductivity and hindered the adhesion of the particles, but also buffered the volume of the Co 9 S 8 change and enhanced the electrochemical performance. The testing of SiO 2 /Co 9 S 8 @NSG composite as an anode for lithium-ion batteries (LIBs) revealed an impressive specific capacity with reversible capacity of 850 mA h/g after 900 cycles at a current density of 0.5 A/g and multiplicative capacity of 730 mA h/g at a current density of 0.1 A/g, confirming excellent cycling stability and a Coulombic efficiency close to 100 %. Overall, the proposed doping strategy looks promising for the development of high-performance LIBs.
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