The electrochemical properties of V-doped Li2Ti6O13 and Na2Ti6O13 anode materials

Abstract

Li2Ti6−xVxO13 and Na2Ti6−xVxO13 (where x = 0, 0.025, 0.05, 0.1) are prepared by conventional ion exchange method and solid-state reaction technique, respectively. According to XRD analysis, increasing V contents in the structures cause the formation of LiVO3 and LiV3O8 phases for x ≥ 0.025 substitutions for Li2Ti6O13 and Na4V2O7 in structure for Na2Ti6O13 x ≥ 0.025. It was observed two redox peaks for both undoped compositions which are related to insertion and deinsertion of Li/Na ions in the structure. The battery performances were investigated for Li2Ti6−xVxO13 and Na2Ti6−xVxO13 systems and it is found that pure Li2Ti6O13 sample has showed the capacity of 36 mAh g−1 and 27 mAh g−1 for 1 and 1000 cycle respectively which show better capacity fade when compared with the other anode materials. The battery performance of undoped Na2Ti6O13 sample has 40 mAh g−1 and 34 mAh g−1 for 1 and 1000 cycle respectively. In addition to this, the x = 0.05 V-substitution has showed 66 mAh g−1 for the first cycle which is higher than that of the undoped sample. It was investigated the structural deformation of the cells by in situ XRD during to CV process and ex situ XRD and Raman techniques after cycling of the cells. It is predicted that the changes of the reflection planes of the crystallites/grains during to cycling of the cells may be the main reason of the decrease of the battery performance which is related to insertion and de-insertion energy of the Li-ions.