Graphite as a potassium ion battery anode in carbonate-based electrolyte and ether-based electrolyte

Abstract

The graphite as the potassium ion battery anode is studied in KPF6-EC/DMC and KPF6-DME electrolytes. It is found that the graphite demonstrates superior rate performance with a capacity of 87 mAh g−1 at a current rate of 10 C (corresponding to 2.8 A g−1) and excellent capacity retention ability of 84% after 3500 cycles in DME-based electrolyte. Moreover, its initial coulombic efficiency is 87.4%, higher than 69.6% in EC/DMC-based electrolyte. The K+ solvating with DME complexes co-intercalate into graphite leading a high operational voltage at ∼0.7 V vs. ∼0.2 V in carbonate-based electrolyte, a fast apparent K+ diffusion coefficient of 10−8 cm2 s−1, a negligible solid-electrolyte interface film, a small volume expansion (7.7% in (002) plane vs. 63% in EC/DMC electrolyte). This study addresses the importance of electrolyte in altering the potassium storage mechanisms to tune the energy density and power density in potassium ion batteries (KIBs).