Improved electrochemical performance of SnO2–mesoporous carbon hybrid as a negative electrode for lithium ion battery applications

Abstract

To utilize the high specific capacity of SnO₂ as an anode material in lithium-ion batteries, one has to overcome its poor cycling performance and rate capability, which result from large volume expansion (∼300%) of SnO₂ during charging–discharging cycles. Hence, to accommodate the volume change during cycling, SnO₂ nanoparticles of 6 nm diameter were synthesized specifically only on the outer surface of the mesopores, present within mesoporous carbon (CMK-5) particles, resulting in an effective buffering layer. To that end, the synthesis process first involves the formation of 3.5 nm SnO₂ nanoparticles inside the mesopores of mesoporous silica (SBA-15), the latter being used as a template subsequently to obtain SnO₂–CMK-5 hybrid particles. SnO₂–CMK-5 exhibits superior rate capabilities, e.g. after 30 cycles, a specific discharge capacity of 598 mA h g⁻¹, at a current density of 178 mA g⁻¹. Electrochemical impedance spectroscopy reveals that the SnO₂–CMK-5 electrode undergoes a significant reduction in solid–electrolyte interfacial and charge transfer resistances, with a simultaneous increase in the diffusion coefficient of lithium ions, all these in comparison to an electrode made of only SnO₂ nanoparticles. This enhances the potential of using the SnO₂–CMK-5 hybrid as a negative electrode, in terms of improved discharge capacity and cycling stability, compared to other electrodes, such as only SnO₂ or only CMK-5.