Energy Storage Science and Technology ›› 2020, Vol. 9 ›› Issue (2): 617-625.doi: 10.19799/j.cnki.2095-4239.2019.0237

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Recent progresses in non-aqueous redox flow batteries

XING Xueqi, LIU Qinghua(), LEMMON John   

  1. National Institute of Clean-and-Low-Carbon Energy, Beijing 102211, China
  • Received:2019-10-22 Revised:2019-11-13 Online:2020-03-05 Published:2020-03-15
  • Contact: Qinghua LIU E-mail:qinghua.liu.n@chnenergy.com.cn

Abstract:

Redox flow batteries (RFBs) are promising large-scale energy storage devices with high safety, long cycling life, decoupled power and energy, and high efficiency. RFBs are applied to the reduction of renewable curtailment, auxiliary service, transmission and distribution, distributed energy sources, and user side. Most traditional RFBs that are based on water have optimum safety; however, their energy density is lower than 50 W·h/L because of the narrow electrochemical window of water, which limits the application of RFBs. Non-aqueous RFBs enable higher cell voltage and higher concentration of active species, and it has become a hot topic in the flow battery research area. In this study, the progress of non-aqueous RFBs in recent years is briefly reviewed. On the basis of the active materials used, the non-aqueous flow batteries are divided into non-aqueous metal complex RFBs, organic RFBs, polymer RFBs, and lithium/organic hybrid RFBs. The advantages and challenges of each type of non-aqueous system are briefly described. Recently, some non-aqueous RFBs have exhibited an open circuit voltage of 3 V and the theoretical energy density over 200 W·h/L. These results show the advantage of high energy density, which allows RFBs to be applied as power batteries in electric vehicles (EVs). Here RFBs may provide a dual advantage: the flow battery application scenarios can be considerably changed and technical routes for EV can be considerably enriched.

Key words: redox flow battery, metal complex active material, organic active material, energy density

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