Synthesis And Electrochemical Characterization Of Vanadium Trioxide/carbon Composite Membrane As Anode For Lithium-ion Capacitors

Among various electrochemical energy devices,lithium ion capacitor(LIC)gains wide attention from science researchers on account of its high energy density(ED),high power density(PD)and long lifespan.At present,the research of LIC mainly focuses on anode materials and the effective match between anode materials and cathode materials.Metallic oxide vanadium trioxide(V2O3),whose tunnel structure is in advantageous for the deintercalation/intercalation of lithium ion(Li+),has a high theoretical capacity.Once it is used as anode material of LIC,it is difficult to satisfy the demand of the LIC with high ED,PD and long lifespan for the volume expansion and electrochemical instability during charge/discharge process.In this paper,the vanadium oxide hydrate(V3O7·H2O)nanowires synthesized by hydrothermal method were used as the precursor of V2O3.Basing on electrospinning technique and polydopamine-derived carbon coating technique,various V2O3/C composite anode materials of special construction were designed and prepared via different carbonization processes.The specific capacity and rate performance of V2O3-based composite anodes were effectively improved.The button type LICs were composed of the activated carbon(AC)cathodes and the two kinds of V2O3/C composite anodes.The effects of the compositions and structures of the V2O3/C composite anodes on the energy storage performances of the anodes and LIC devices were investigated.(1)The V2O3@C nanorods composite was prepared by poly dopamine-derived carbon coating technique combined with carbonization method.The effect of carbonization temperature on the morphology structure and electrochemical performance of the material was studied in detail.The V2O3@C-4h-700 anode with ultra-fine V2O3 nanoparticles obtained under carbonization temperature of 700? showed the highest reversible capacity and the best cycling performance.A novel LIC composed of the optimal V2O3@C-4h-700 anode and the AC cathode(AC//V2O3@C-4h-700)displayed an ED of 130.7 Wh kg-1,a PD of 17.8 kW kg-1(achieved at 34.6 Wh kg-1),and a capacitance retention of 70.0%after 3000 cycles at 1.0 A g-1.(1)Carbon nanofibers encapsulating V2O3 nanoparticles(V2O3@CNFs)were prepared as a self-supported anode through electrospinning technique combined with carbonization method.The influence of V2O3 nanoparticles content on the morphology structure and electrochemical performance of composite anodes was preliminarily investigated.A novel LIC composed of the optimal V2O3@CNFs-2 anode and the AC cathode(AC//V2O3@CNFs-2)displayed an ED of 97.6 Wh kg-1,a PD of 12.0 kW kg-1(achieved at 20.2 Wh kg-1),and a capacitance retention of 73.0%after 5000 cycles at 1.0 A g-1.