Electrochemical property of NH_4V_3O_8·0.2)H_2O flakes prepared by surfactant assisted hydrothermal method

摘要

NH_4V_3O_8·O.2H_2O is synthesized by sodium dodecyl sulfonate (SDS) assisted hydrothermal method and its electrochemical performance is investigated. The as-prepared material is characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), infrared (IR) spectrum, differential scanning calorimetry and thermal gravimetry (DSC/TG), cyclic voltammetry (CV), and charge-discharge cycling test. The results show a pure NH_4V_3O_(8-0..2)H_2 phase with flake-like morphology is obtained and the average flake thickness is about 150 nm. The NH_4V_3O_(8-0..2)H_2O electrode has a good lithium ion insertion/extraction ability with the highest discharge capacity of 225.9mAh g~(-1) during 1.8-4.0V versus Li at the constant current density of 15 mA g~(-1). After 30 cycles, it still maintains a high discharge capacity of 209.4 mAh g~(-1), demonstrating good cyclic stability. Interestingly, at the discharge process a new (NH4)Li_Xv_3O_(8- 0.2)H_2O compound is formed due to the new lithium ion from lithium metal anode.