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 H 2 O modulation (labeled as GO-2), and Hummers method with H 2 O and H 3 BO 3 modulation (labeled as GO-3). Due the H 2 O promotes the production of hydroxyl and epoxy groups, and H 3 BO 3 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 780.8 mAh/g after 150 cycles at 1 A/g and a good rate performance of 657.0 mAh/g at 5 A/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. [Display omitted] • A series of silicon/reduced graphene oxide (Si/rGO) was fabricated with different graphene oxide (GO). • Larger defects, and better electrical conductivity of rGO-3 promote the electrochemical performance of Si/rGO-3. • Si/ rGO-3 achieves high initial coulombic efficiency and excellent cycling performance. [ABSTRACT FROM AUTHOR]