Multi-level carbon co-modified LiVPO4F cathode material for lithium batteries

Abstract

Cracking carbon, grapheme as well as carbon nanotube co-modified LiVPO4F material (LiVPO4F/C/G/CNT) and cracking carbon modified LiVPO4F material (LiVPO4F/C) were respectively prepared by a two-step process. Physicochemical properties, electrochemical datas and kinetic parameters of LiVPO4F/C/G/CNT and LiVPO4F/C materials were obtained by various detection means. X-ray diffraction analysis (XRD) demonstrates that co-modification of multi-level carbon cannot change fundamental crystallographic structure of LiVPO4F/C/G/CNT material. Scanning electron microscopy (SEM) and High resolution transmission electron microscopy (HRTEM) synergistically reveal that cross-linked network structures formed by cracking carbon, grapheme and carbon nanotube are evenly distributed among the LiVPO4F particles, helping for charge transfer throughout the inside and outside of cathode materials. Compared with LiVPO4F/C material, the LiVPO4F/C/G/CNT material possesses many advantages such as higher discharge specific capacity, higher charge-discharge rate performance, smaller charge transfer impedance (Rct), and higher Li+ diffusion coefficient (DLi+), indicating that the LiVPO4F/C/G/CNT cathode material prepared by a two-step process shows better potential application prospect for lithium batteries.