Potassium-based dual-carbon battery with pure ionic liquid electrolyte

Dual-carbon batteries (DCBs) have attracted considerable attention as they are environmentally friendly, economical, and exhibit a high cost-to-performance ratio. However, severe electrolyte decomposition and Al current collector corrosion lead to moderate reversible capacity and low average coulombic efficiency in DCBs, limiting their practical application. This paper reports a potassium-based DCB using a pure ionic liquid (IL) electrolyte with asymmetric FTA− anions (FTA = (fluorosulfonyl)(trifluoromethylsulfonyl)amide) and graphite electrodes, with a high charge–discharge capacity and long cycle-life. ILs are intrinsically highly concentrated electrolytes composed of cations and anions that enable the construction of high energy density DCBs. Here, symmetric dual-carbon full cells with the FTA-based IL electrolyte and graphite positive and negative electrodes delivered a high discharge capacity of 81 mAh g−1 with an average discharge voltage of ∼4.35 V up to 300 cycles. Further, ex-situ X-ray diffraction measurements conducted at 298 K indicated the formation of stage 1 FTA-graphite intercalation compounds at the full-charged state. This study facilitates the construction of cost-effective DCBs with a high operating voltage, fast charge–discharge, and long cycling, without the use of toxic metals.