Controllable Preparation And Lithium-Storage Performance Of Fe₃O₄-based Nanocomposites As Anode Materials

In recent years, lithium ion batteries developed rapidly, and they were widely used in portable electronic products, electric tools, electric vehicles and large power storage equipment due to the advantages of high energy density, high power density, long cycle life and safety. To meet a better experience and respond more demanding environment, we hope to develop the electrode materials with higher power density, higher energy density and longer cycle life.Graphite is the traditional commercial anode material of the lithium-ion batteries which delivers a theoretical capacity about 372 mAh g^-1. However, with the development of high-capacity cathode materials, the graphite can not meet requirements now. Thus, to develop the anode materials with higher energy density is imminent. In various anode electrode materials, transition metal oxides has been widely concerned due to its high theoretical specific capacity, which is one popular negative electrode material in recent years. Fe-based oxides have become a promising candidate among them because of their earth abundance, low cost, nontoxic and so on. However, the low conductivity and the large volume expansion are the main problems of Fe-based oxides which seriously affect the rate and cycle performance. Therefore, how to improve the conductivity and reduce the volume expansion is the key to improve the performance of the Fe-based oxides. This paper focuses on how to improve the electrochemical properties of Fe₃O₄ and includes the following two aspects:1. G/Fe₃O₄ and MWCNTs/Fe₃O₄ nanocomposites were fabricated by adding graphene and multi-walled carbon nanotubes respectively in the process to synthesize Fe₃O₄. By comparison with pure Fe₃O₄, we discussed the effect of different carbon matrix on the Fe₃O₄, The results showed that both carbon matrixs have a significant improvement in its performance and graphene is better than the carbon nanotubes.2. There are a large number of active nanoparticles are still in the unprotected state in the most of common G/Fe₃O₄ composites, which will seriously impair the effects of the graphene additives. To solve this problem, a fully protected G/Fe₃O₄@C micro-/nanocomposite is rationally developed by carbon-boxing the common G/Fe₃O₄ microparticulates. We find that the fully protected G/Fe₃O₄@C exhibits the best lithium-storage properties compared to the common G/Fe₃O₄ composites and commercial Fe₃O₄ products when used as the anode for lithium-ion batteries.