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

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 similar to 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%.