Effective utilization of energy requires the storage and conversion device with high ability. For well-developed lithium ion batteries (LIBs) and highly developing sodium ion batteries (SIBs), this ability especially deno. ••The structures of iron sulfides are systematically. With the rapid development of society, nonrenewable natural resources are becoming scarcer and scarcer, such as coal, petroleum and natural gas. It is urgent to explore green. 2.1. FeSTo date, there are totally eight polymorphs of FeS discovered as listed in Table 1. FeS can crystallize in the cubic, monoclinic, orthorhombic, tet. As mentioned above, the binary iron sulfides are usually obtained from their respective minerals via mining and separation. On the other hand, they also can be produced. 4.1. FeSIron sulfides as promising electrode materials for energy storage applications result from their abundant and inexpensive components in n.