Fabrication of β-CoV3O8 nanorods embedded in graphene sheets and their application for electrochemical charge storage electrode

Abstract

Fabrication of β-CoV3O8 nanorods embedded in graphene sheets and its application as electrochemical charge storage electrodes is reported. From surfactant treatment of raw graphite, graphene was directly prepared and its nanocomposite with β-CoV3O8 nanorods distributed between graphene layers (β-CoV3O8-G) was synthesized by hydrothermal method. When applied as anode in lithium-ion batteries, the β-CoV3O8-G anode exhibits greatly improved charge and discharge capacities of 790 and 627 mAhbold dotg-1, respectively, with unexpectedly high initial efficiency of 82%. The observed discharge capacity reflected that at least 3.7 mol of Li+ is selectively accumulated within the β-CoV3O8 phase (LixCoV3O8, x > 3.7), indicative of significantly improved Li+ uptake when compared with aggregated β-CoV3O8 nanorods. Moreover, very distinct peak plateaus and greatly advanced cycling performance are observed, showing more improved Li+ storage within the β-CoV3O8 phase. As a supercapacitor electrode, moreover, our composite electrode exhibits very high peak pseudocapacitances of 2.71 Fbold dotcm−2 and 433.65 Fbold dotg−1 in β-CoV3O8 phase with extremely stable cycling performance. These remarkably enhanced performances in the individual electrochemical charge storage electrodes are attributed to the novel phase formation of β-CoV3O8 and its optimized nanocomposite structure with graphene, which yield fast electrical conduction through graphene, easy accessibility of ions through the open multilayer nanosheet-structure, and a relaxation space between the β-CoV3O8-G.