Modulating functional groups of GO to improve the electrochemical performance of Si/rGO anode

Silicon (Si)-based materials show attractive potentials as the anode for lithium-ion batteries (LIBs) due to their high theoretical specific capacity. For the conventional silicon/reduced graphene oxide (Si/rGO) composites, the electrical conductivity, C/O ratio, and defect structure of reduced graphene oxide (rGO) significantly impact their electrochemical properties. Herein, we use three methods to prepare graphite oxide (GO) to adjust the percentage of functional groups, which further enhance the physicochemical properties of rGO and thus improve the electrochemical properties of Si/rGO. The GOs were synthesized through Hummers method (labeled as GO-1), Hummers method with H2O modulation (labeled as GO-2), and Hummers method with H2O and H3BO3 modulation (labeled as GO-3). Due the H2O promotes the production of hydroxyl and epoxy groups, and H3BO3 forms complexes with hydroxyl groups,the ratio of hydroxyl and epoxy groups in GO-1 to GO-3 is increased. After reduction process, the reduced rGO-3 exhibits a high C/O ratio, large structural defects, and excellent electrical conductivity. Because of the excellent properties of rGO-3, as an electrode material, Si/rGO-3 exhibits excellent electrochemical performance, with the highest reversible capacity of about 780.8mAh/g after 150 cycles at 1A/g and a good rate performance of 657.0mAh/g at 5A/g. This work proves that modulation of rGO from the GO with different oxygen-containing functional groups lead to enhanced ionic conductivity, cyclic stability, and rate capability of the Si/rGO electrodes.