Synthesis of Fe2O3 Nanorod as Anode Material for Lithium Ion Batteries
Abstract
During the lithiation process, extreme volumetric expansion of Fe2O3 nanoparticles occurs, causing a degradation of the material’s structural integrity and electrochemical performance. To address this issue, a synthesis procedure for Fe2O3 nanorods with a carbon shell composite has been developed using a unique polymer coating method. The added integrity of the carbon shell will allow for stable electrochemical performance and increased structural support during the lithiation volume expansion. Herein, a summary of the experimental procedures and characterizations of these novel materials will be presented.
Introduction
The fast growing demands of portable electronic devices and electric vehicles have spontaneously stimulated the rapid development of lithium-ion batteries (LIBs) with high energy and power densities. Currently, graphite is the most commonly used commercial anode in LIBs with a relatively low theoretical capacity (372 mAh g-1) which is a major barrier to its further application in high performance LIBs. Various species of iron oxides have received much attention for their application as anodic material in LIBs for their high theoretical capacities, low cost, ease of fabrication and environmental friendliness.
Iron (III) Oxide (Fe2O3) is a promising candidate for LIB anode material for its ability to store 6 electrons per formula unit (Fe2O3 + 6Li+ + 6e- ↔ 3Li2O + 2Fe) via reversible reactions, resulting in a high theoretical capacity (~1005mAh g-1). However, these species greatly suffer from poor conductivity, large volume expansion, and poor structural integrity during electrochemical cycling. One solution to these problems is to form composites with carbon species or conductive polymers with high conductivity and increased structural integrity.
In this work, we develop two synthesis procedures of Fe2O3@C nanorods for battery anodes.
Experimental Section (requested from Luo)
Characterization
The Structure and composition of the synthesized products was recorded by the Rigaku Miniflex II X-ray powder diffractometer (XRD) with Cu Kα radiation (λ=1.5418 Å). The morphology was determined the Hitachi H-7650 transmission electron microscope (TEM). Annealing temperatures and thermal behavior of composites were determined using PerkinElmer Pyris 1 thermogravimetric analysis (TGA) in the temperature range of 25-650oC.
Results and Discussion (Figures requested from Luo)
Before any characterization test could be completed, an annealing temperature was determined using TGA analysis. The morphology of the microstructures was determined using TEM. Figures show the typical microstructures of the as synthesized FeOOH nanorods and Fe2O3 nanorods after the annealing process under different conditions. The carbon shell will provide the structural integrity and conductivity that is required for stability during the charge-discharge process. In order to confirm the crystalline nature of our synthesized product, XRD tests were carried out. The typical XRD patterns confirm the conversion of FeOOH to Fe2O3 during the annealing process.