Synthesis, spectral character, electrochemical performance and in situ structure studies of Li1+xV3O8 cathode material prepared by tartaric acid assisted sol–gel process

Abstract

Lithium-ion battery cathode material Li1+xV3O8 was synthesized by a tartaric acid assisted sol–gel method and thermally treated at 350°C, 450°C and 550°C for 3h for the formation of Li1+xV3O8 phase. The synthesized samples were fully characterized by FTIR, TG/DTA, XRD and charge–discharge tests. Li1+xV3O8 material synthesized by tartaric acid assisted route, followed by heat treatment at 450°C for 3h shows best electro-chemical performance. It shows a high initial capacity of 249mAhg−1 and still reserves a discharge capacity of 260mAhg−1 after 50 cycles. Moreover, for all tartaric assisted products, no capacity decadence is observed in 50 cycles. The in situ X-ray measurements reveal a two-phase transition mechanism in the lithium intercalation/deintercalation process. During lithium extraction, the structure of the delithiated compound changes from Li4V3O8 (x>3.1) to the original LiV3O8 phase (x<1.4) via the coexistence state of these two phases (1.4<x<3.2). An obvious contraction, especially at Li(3)–Li(4) transition, along a axis and a slight expansion along b axis are also observed.