Date Published: April 23, 2018
Publisher: John Wiley and Sons Inc.
Author(s): Jingyi Ma, Xiaotian Guo, Yan Yan, Huaiguo Xue, Huan Pang.
Iron oxides (FeOx), such as Fe2O3 and Fe3O4 materials, have attracted much attention because of their rich abundance, low cost, and environmental friendliness. However, FeOx, which is similar to most transition metal oxides, possesses a poor rate capability and cycling life. Thus, FeOx‐based materials consisting of FeOx, carbon, and metal‐based materials have been widely explored. This article mainly discusses FeOx‐based materials (Fe2O3 and Fe3O4) for electrochemical energy storage applications, including supercapacitors and rechargeable batteries (e.g., lithium‐ion batteries and sodium‐ion batteries). Furthermore, future perspectives and challenges of FeOx‐based materials for electrochemical energy storage are briefly discussed.
Currently, with the rapid development of the economy, the overconsumption of fossil fuels has resulted in great demand for energy. As a consequence, a sustainable and low‐cost way to store energy more efficiently has been continuously explored in recent years, especially for studies on electrochemical energy storage. Green electrochemical energy storage devices mainly include supercapacitors (SCs)1, 2 and rechargeable batteries3 (lithium‐ion batteries (LIBs),4 sodium‐ion batteries (SIBs), lithium–sodium ion batteries (LSBs), and so on).5, 6
To explore better performances for the applications in electrochemical energy storage, the charge storage mechanism and the effect of crystal structures on the electrochemical performances should be studied.
In the modern society, Fe2O3 materials play an important role in electrochemical energy storage systems.21 Due to its abundance, environmental friendliness, good electrochemical activity, high stability under ambient conditions, and low cost, Fe2O3 has attracted much attention as a negative electrode material in electrochemical energy storage.
FeO is black power without magnetism which can be applied in electrochemical energy storage, including SCs226 and LIBs.227, 228, 229 A method which using oleic acid (OA) and oleylamine (OAm) to react with iron(III) acetylacetonate ([Fe(acac)3]) at high temperature to synthesize the FeO NPs was reported by Hou et al.230 In fact, pure FeO NPs are difficult to prepare because they were easy to be oxidized to Fe2O3 and Fe3O4 owing to the chemically unstable structure. Hydrothermal method was used for the synthesis of FeO/CVO with FeO nanospheres and CVO (cobalt vanadium oxide hydrate) in SCs by Centre et al.226 It was demonstrated that a specific capacitance of 968 mA h g−1 was achieved at 1 A g−1 and a capacitance retention of 95% was achieved after 5000 cycles.
Currently, FeOx have been paid more attention because of the good theoretical capacity, rich abundance, low cost, and environmental friendliness. Apart from the advantages, they also have the drawbacks of poor conductivity and unstable structures. To overcome the problems, considerable efforts have been done by the scientists for better electrochemical performances. This review provides an overview of FeOx (Fe2O3/Fe3O4)‐based materials for applications in energy storage devices, including SCs, LIBs, SIBs, and other batteries.231, 232 The synthetic methods, morphologies, and electrochemical performance are mainly introduced. The combination of different materials with Fe2O3/Fe3O4 achieved electrochemical properties of high capacity, good rate capability, and cycling life.
The authors declare no conflict of interest.