With the coming era of large-scale energy storage, development of next-generation non-Li-based rechargeable battery technologies is imperative. Owing to the abundance, economy, and high energy density, K-ion batteries (KIBs) have attracted much attention. However, the overlarge K-ion can greatly destroy the electrode materials during potassiation-depotassiation process, resulting in a sharp decrease of the cycle life, which will enormously restrict the applications of KIBs. Currently, one of the effective strategies is adopting potassium bis(fluorosulfonyl)imide (KFSI) to replace conventional KPF 6 as solute in electrolytes. Such KFSI-containing electrolyte can induce forming stable solid-electrolyte interphase (SEI) layer, which is in favor of the stability of electrode material after cycles. In this review, we summarize all current materials cooperated with KFSI-containing electrolytes for KIBs and attempt to provide a better understanding of the improving mechanism for K-ion storage and the effect of the unique SEI layer. In addition, some critical issues and perspectives of KFSI-containing electrolytes for K-ion storage are also discussed, which will provide a developmental direction of KIBs. (C) 2019 The Authors. Published by Elsevier Ltd.