Micron-sized SiOx/N-doped carbon composite spheres fabricated with biomass chitosan for high-performance lithium-ion battery anodes

Abstract

To achieve superior lithium storage performance, SiO_x is usually designed into nanostructured SiO_x/C composites by complex or expensive methods. Here, micron-sized interconnected SiO_x/N-doped carbon (NC) microspheres composed of evenly dispersed SiO_x nano-domains and NC have been fabricated by a scalable microemulsion method and following pyrolysis, using vinyltriethoxysilane and chitosan as precursors. The unique structure of the micron-sized SiO_x/NC spheres leads to enhanced structural integrity and enables stable long-term cycling (800 cycles at 2 A g⁻¹). Benefiting from the enhanced electron/Li⁺ diffusion kinetics originated from the unique structure and N-doping, SiO_x/NC-2 presents considerable capacitive-controlled Li storage capacity, which leads to outstanding rate capability. Consequently, the assembled SiO_x/NC-2//LiFePO₄ full cell exhibits superior rate capability (106 mA h g⁻¹ at 4C) and stable long-term cycling at 2C (102 mA h g⁻¹ after 350 cycles). This work opens a new door for the application of chitosan in building micron-sized high-performance SiO_x/C anode materials, and to some extent facilitates the recycling of waste seafood shells.