Metal-free heteroatom integrated defect engineering of flexible carbon networks on tin oxide nanoparticles to enhance lithium-ion battery performance

We propose an innovative and straightforward approach to mitigate the mechanical strain of tin oxide nanoparticles via coating them with a heteroatom-integrated honeycomb-like carbon layer. This design improves the stability of the electrode–electrolyte interface. Tin oxide nanoparticles were coated with a carbon layer integrated with sulfur and nitrogen using phenolic resin and 2,5-mercapto-1,3,4-thiadiazole, followed by reduction and carbonization, resulting in the SnO₂@S,N–C nanocomposite. The heteroatom doping disrupts the carbon lattice, creating vacancies, defects, and functional groups that serve as active sites for lithium-ion adsorption and enhance ion diffusion. The porous carbon layer enables efficient electrolyte penetration and accommodates volume changes during cycling. The engineered SnO₂@S,N–C and SnO₂@C anode materials exhibited impressive lithium-ion storage capacities of 840 mAh g⁻¹ and 640 mAh g⁻¹ at 0.1 A g⁻¹, respectively, with a coulombic efficiency of over 99% sustained for up to 750 cycles. Additionally, SnO₂@S,N–C retained specific capacities of 505.79 and 387.99 mAh g⁻¹ at current densities of 0.6 A g⁻¹ and 1.0 A g⁻¹, respectively, maintaining a ≥ 99% coulombic efficiency for up to 100 cycles. Density functional theory (DFT) calculations confirmed a strong binding affinity for lithium ions on SnO₂@S,N–C. This method demonstrates a promising strategy for optimizing anode materials in high-performance lithium-ion batteries.