Study on Dynamic Activity and Excellent Cycling Performance of a 3d Reticulated Sn@C/Cnt Anode in Lithium Battery

Abstract

Lower lithium-ion diffusion rates and significant volumetric expansion present serious challenges for using Sn-based composites as promising anode materials in advanced lithium-ion batteries. To address this issue, we synthesized novel Sn@C/CNT composites with unique three-dimensional reticulated structures from Sn-based organometallic complex with 2-methylimidazole and oxidized multi-wall carbon nanotubes. Structural analysis confirmed that Sn active particles, with an average size of 2 to 3 nm, were evenly trapped and dispersed within a graphite-like layered micro-lamellar carbon matrix that has an average thickness of 6 nm. The resulting Sn@C/CNT anode materials demonstrated a stable specific capacity of up to 688 mAh/g even after 500 cycles at a higher charging-recharging current density of 1 A/g. The significant diffusion-controlled lithium ion diffusion coefficient of approximately 10−12 cm2/s indicates vigorous dynamic activity from reversible Sn-Li alloy electrochemical reactions. Additionally, the substantial capacity-controlled lithium ion diffusion coefficient, which drops to 10−6 cm2/s, illustrates the predominance of the pseudo-capacitance arising from interface reaction. Based on analyses using Nyquist plots and Randles-Sevcik plots, synergistic lithium ion diffusion mechanisms were proposed to explain the excellent electrochemical performance of these Sn-based anode materials. This work provides a new intention in resolving the drastic volumetric expansion and unsatisfied dynamic activity of Sn-based anode materials.

Keywords: dynamic activity, long-term cycling performance, nano Sn@C/CNT, 3D carbon matrix, diffusion coefficient