Investigation of the lithium-ion depletion in the silicon-silicon carbide anode/electrolyte interface in lithium-ion battery via electrochemical impedance spectroscopy

Abstract

Silicon-based next generation Li-ion batteries play a pivotal role to address superior energy storage devices to fill out their customers need. Despite this, nano porous silicon, macro-honeycomb porous silicon, and silicon carbide nanocomposite as a professional anode have been synthesized by magnesiothermic and in situ carbothermic-magnesiothermic reduction at two oxygen-full and oxygen-free atmospheres. The FESEM and TEM results shows the porosity pattern depends on the reduction atmosphere. The first specific discharge capacity for Si-nano is delivered to 700 mAh g-1 with 40% irreversibility, 47.8% charge retention at 2nd after aging periods, and 98.5% columbic efficiency after 10 cycles, whilst, SiC is first discharged to 1125 mAh g-1, i.e. 78% of the theoretical capacity, with 85.7% charge retention at 2nd after the aging period, and 92.3% columbic efficiency after 10 cycles. The EIS analysis shows that the continuous mobility of electrons interior of SiC is too higher than the Li+ solvated sheath due to interstitial carbon atom in the silicon carbide composite, whilst, the formation of a thicken Li+ solvated sheath on the surface of macro pores causes an electrode blocking and eventually the finite length diffusion. The calculation of A×C indicates an irregularity in concentration of Li+ ions at different potentials to confirm the alloying mechanism for Li+ ion diffusivity at the active surface site in silicon at fresh electrolyte condition against depletion in the SEI layer as a second source of Lithium after 10 months aging.