High energy density potassium-based dual graphite battery with high concentration carbonate electrolyte

Dual ion batteries (DIBs) differ from traditional lithium-ion and sodium-ion batteries in that the electrolyte acts as a significant source of active materials in DIBs, directly influencing the specific capacity, charge-discharge efficiency, and cycle life. Traditional potassium (K)-based dual ion batteries use electrolytes with concentrations below 1 m (mol kg−1), which exhibit a comparatively low oxidation potential of ∼4.4 V versus K/K+. This limits the operational longevity and energy density of the batteries. To enhance the electrochemical stability of the electrolyte and improve the capacity and reversibility of anions/cations intercalating into graphite electrodes, this study introduces a 10.0 m potassium bis(fluorosulfonyl)imide (KFSI) in carbonate ester electrolytes. The results show that increasing the electrolyte concentration effectively raises the oxidation potential to 6.1 V vs. K/K+. A K-dual graphite dual ion battery (K-DGDIB) is assembled using 10.0 m KFSI/ethylene carbonate (EC):dimethyl carbonate (DMC) electrolyte and incorporates both a graphite cathode and a graphite anode. This battery provides a discharge capacity of 94.2 mAh g−1 at 100 mA g−1, a discharge medium voltage of ∼4.24 V, and an energy density of ∼5.8 Wh kg−1 considering the total mass of all added electrolyte and the total mass of the active materials. •The high-concentration strategy expands the electrolyte's voltage window to 6.1 V.•Enhances the intercalation/deintercalation of K+ and FSI− within the graphite layers.•Promotes the main salt decomposition while inhibiting solvent decomposition.