Abstract
Iron oxides (FeO (x) ), such as Fe(2)O(3) and Fe(3)O(4) materials, have attracted much attention because of their rich abundance, low cost, and environmental friendliness. However, FeO (x) , which is similar to most transition metal oxides, possesses a poor rate capability and cycling life. Thus, FeO (x) -based materials consisting of FeO (x) , carbon, and metal-based materials have been widely explored. This article mainly discusses FeO (x) -based materials (Fe(2)O(3) and Fe(3)O(4)) 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 FeO (x) -based materials for electrochemical energy storage are briefly discussed.