Effective anode materials for in situ Sn@C nano-lamellar assembly with doped nanotubes in lithium-ion batteries

Abstract

Lower lithium-ion diffusion rates and significant volumetric expansion present serious challenges for using SnO₂/SnO composites as promising anode materials in advanced lithium-ion batteries. To address this issue, we synthesized a novel Sn@C/CNT composite from a Sn-based organometallic complex with 2-methylimidazole and oxidized multi-wall carbon nanotubes. Structural analysis has confirmed that the tin-based composites consist of nano-lamellar assemblies modified by oxidized carbon nanotubes. In these composites, the tin active particles have an average size ranging from 2 to 3 nm, while the layered nano-lamellar structure has an average thickness of 6 nm. The resulting Sn@C/CNT anode material demonstrated a stable specific capacity of up to 688 mA h g⁻¹ even after 500 cycles at a higher charging–discharging current density of 1 A g⁻¹. The significant diffusion-controlled lithium ion diffusion coefficient of approximately 10⁻¹² cm² s⁻¹ indicates vigorous dynamic activity from reversible Sn–Li alloy electrochemical reactions. Additionally, the substantial capacity-controlled lithium ion diffusion coefficient, which drops to 10⁻¹⁶ cm² s⁻¹, illustrates the predominance of the pseudo-capacitance arising from interface reaction. By coupling electrochemical impedance spectroscopy, galvanostatic intermittent titration technique, and linear sweep voltammetry, the mixed lithium-ion diffusion effect was proposed to explain the remarkable adaptability of these Sn-based anode materials for cycling performance across a wide range of specific currents. This work provides a new intention for resolving the drastic volumetric expansion and unsatisfactory dynamic activity of Sn-based anode materials.