Effect of microstructure and Sn/C ratio in SnO2–graphene nanocomposites for lithium-ion battery performance

Abstract

Sn based nanocomposite anodes with a pristine graphene matrix were synthesized in order to investigate the performance improvements that are related to the microstructure variation. Four nanocomposites with varying SnO₂ contents (25, 43, 60, and 82 wt%) were prepared with a controlled hydrothermal synthesis route. TEM measurements indicated that the 25/75 wt% SnO₂–graphene nanocomposite had the highest dispersivity with a 2–3 nm particle size and ∼2 nm inter-particle spacing. Increasing SnO₂ content led to increasing particle size and decreasing inter-particle spacing. For the anode with more dispersed and smaller nanoparticles, the capacity retention and rate capability were noticeably improved compared with anodes that have clusters of SnO₂ nanoparticles. The 25/75 wt% SnO₂–graphene nanocomposite exhibited enhanced specific capacity of 662 mA h g⁻¹ after 150 cycles when discharged–charged at 50 mA g⁻¹. It also demonstrated an outstanding rate capability of 525, 445 and 230 mA h g⁻¹ at higher current densities of 300, 500 and 1000 mA g⁻¹, respectively. TEM and EIS studies revealed that after 100 electrochemical cycles, the nanoparticles retained the original size of 2–3 nm and cell's charge transfer resistance decreased by 52%.