Preparation And Electrochemical Performance Of Chromium Oxide Composites As Lithium Ion Battery Anodes

With the advantages of high energy density, long lifespan and environmental benignity, lithium ion battery (LIBs) has been widely used in mobile phones, notebook computer, camera and video camera. The graphite, as traditional anode material for lithium ion batteries, cannot meet the new requirememt of high-performance lithium ion batteries because of its limited theoretical capacity of 372 mAh g-1. In recent years, transitionmetal oxides (such as NiO, CuO, Fe2O3, Fe3O4, MnCh, CO3O4, etc.), have become potential anode materials of the lithium ion battery and caused wide spread concern, due to their high theoretical specific capacity and better safety performance.Among the transitionmetal oxides, chromium (Ⅲ) oxide (Cr2O3) has also been reported as anode materials for LIBs with a theoretical capacity of 1058 mAh g-1. Such a high specific capacity has important significance to the improvement on the energy density of lithium ion battery. However, Cr2O3 has large volume change during charge/discharge process, which even causes rapid anode pulverisation and rapid capacity fading during cycling. Therefore, improving the cycling stability is the focus for the modification of this kind material.This work is aiming at improving the cycling performance by synthesizing composite anodes. The main research contents and results are as follows:(1) Cr2O3-C were fabricated by combining a sol-gel approach with an efficient carbonization process and investigated in the application of anode materials for lithium-ion batteries. The results gained by SEM and TEM show that Cr2O3 nanoparticles are embedded into carbon sheets and the Cr2O3 nanoparticles have a size distribution ranging from 20 to 40 nm. The TG result shows that carbon accounts for 14.2% of the total weight in the formed Cr2O3-C. The electrochemical performance was tested by charge/discharge progress, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). It was found that the sample of Cr2O3-C achieves a reversible capacity of 465.5 mAh g-1 after 150 cycles at a current density of 100 mA g-1. Compared with pure Cr2O3, the as-prepared nanocomposites obtain better cycling and rate performances.(2) With TiO2 microspheres as precursors, using a infusion method and a calcining process followed by a carbonization process, we obtained TiO2-Cr2O3@C composite microspheres. The results gained by SEM show that the diameter of the TiO2-Cr2O3@C composite microspheres is about 600 nm. Cyclic voltammetry (CV), galvanostatically cycling and rate cycling were used to determine the electrochemical performance. It is indicated that after 50 cycles at a current density of 100 mA g-1, the sample of TiO2-Cr2O3@C composite microspheres remain stable capacity of about 280 mAh g-1, which was much better than that of pure TiO2。...