Insight into anion storage batteries: Materials, properties and challenges

In recent years, anion storage technology has been regarded as promising alternative for the typical metal ion batteries due to its high energy density in theory, including halogen anions (F−, Cl−, Br−, I−) and complex anions (PF6−, BF4−, FSI−, FTFSI−, TFSI−, FSA−, BETI−, HSO4−, ClO4−, AlCl4−, NO3−, [ZnCl4]2−). Research on the storage of anions can not only develop anion batteries, but also extend it to more novel battery concepts such as desalination batteries and dual-ion batteries (DIBs). However, the difference of theoretical and practical performance is a crucial problem for the development of anion storage. Thus, understanding the working mechanism of various batteries and the methods of performance improvement are necessary for the future development of anion battery systems. For this reason, this article reviews the research progress and challenges in electrode materials and electrolytes of various anion storage technologies in detail. Finally, possible development directions in this research area are also proposed.