Jiao Zhang, Zhen Cao, Lin Zhou, Gang Liu, Geon-Tae Park, Luigi Cavallo, Limin Wang, Husam N. Alshareef, Yang-Kook Sun, Jun Ming
ACS Energy Letters, (2020)
Potassium ion batteries (KIBs) are attractive alternatives to lithium-ion batteries (LIBs) due to their lower cost and global potassium sustainability. However, designing compatible electrolytes with the graphite anode to store potassium ions (K+) remains challenging. This is because the electrolyte decomposition and/or graphite exfoliation (due to K+-solvent co-insertion) always exist, which is much harder to overcome compared to the case of LIBs due to the higher activities of K+. Herein, we report a general principle to design compatible electrolytes with graphite anode, where the K+ can be reversibly (de-)intercalated. We find that the electrolyte composition is critical to determining the graphite performance, which can be tuned by the kind of solvent, anion, additives, and concentration. We present a new interfacial model to understand the variation in performance (i.e., K+ (de-)intercalation, or K+-solvent co-insertion or decomposition) in different electrolytes. Our interfacial model is distinctly different from the solid electrolyte interphase (SEI) interpretation, which has been commonly invoked to explain graphite stability. This work offers new opportunities to design high-performance potassium-ion battery and potassium-ion sulfur batteries. Particularly, we present a new guideline to design electrolytes for KIBs and other advanced mobile (ion) batteries.