Designed hybrid nanostructure with catalytic effect: beyond the theoretical capacity of SnO(2) anode material for lithium ion batteries

Transition metal cobalt (Co) nanoparticle was designed as catalyst to promote the conversion reaction of Sn to SnO(2) during the delithiation process which is deemed as an irreversible reaction. The designed nanocomposite, named as SnO(2)/Co(3)O(4)/reduced-graphene-oxide (rGO), was synthesized by a simple two-step method composed of hydrothermal (1(st) step) and solvothermal (2(nd) step) synthesis processes. Compared to the pristine SnO(2)/rGO and SnO(2)/Co(3)O(4) electrodes, SnO(2)/Co(3)O(4)/rGO nanocomposites exhibit significantly enhanced electrochemical performance as the anode material of lithium-ion batteries (LIBs). The SnO(2)/Co(3)O(4)/rGO nanocomposites can deliver high specific capacities of 1038 and 712 mAh g(−1) at the current densities of 100 and 1000 mA g(−1), respectively. In addition, the SnO(2)/Co(3)O(4)/rGO nanocomposites also exhibit 641 mAh g(−1) at a high current density of 1000 mA g(−1) after 900 cycles, indicating an ultra-long cycling stability under high current density. Through ex-situ TEM analysis, the excellent electrochemical performance was attributed to the catalytic effect of Co nanoparticles to promote the conversion of Sn to SnO(2) and the decomposition of Li(2)O during the delithiation process. Based on the results, herein we propose a new method in employing the catalyst to increase the capacity of alloying-dealloying type anode material to beyond its theoretical value and enhance the electrochemical performance.