Tuning anion chemistry enables high-voltage and stable potassium-based tellurium-graphite batteries

Potassium-based dual-ion batteries (KDIBs) are promising large-scale energy-storage devices due to cost benefits, high output voltage, and abundant K resources, but their advancements are restricted by alternative anodes, low-capacity graphite cathode, and electrolyte decomposition. Herein, high-voltage and stable KDIBs composed of tellurium-decorated porous carbon nanosheets (TeCNs) anode and graphite cathode are constructed by regulating salt types and electrolyte concentrations. Compared with potassium hexafluorophosphate/carbonate electrolytes, high-concentrated potassium bis(fluorosulfonyl)imide (KFSI)-based electrolytes enable high capacity and cyclability of graphite cathode. The weak anion-solvent interaction avoids solvent co-intercalation, whereas the strong coordination of K+-FSI--carbonate complexes facilitates antioxidation and interphase stability. By inheriting the excellent K+-ion storage of TeCNs and electrochemical compatibility with the 4.0 m electrolyte, Te-graphite KDIBs deliver a high discharge voltage plateau of 4.37 V, the capacity of 130.8 mAh g(-1) after 500 cycles, and high-power densities. This work discloses the important roles of ion-solvent pairs, and provides clear guidelines for electrolyte design in DIBs.

Automated summary

The study constructs high-voltage and stable potassium-based dual-ion batteries (KDIBs) with tellurium-decorated carbon nanosheets as the anode and graphite as the cathode, enabled by high-concentration KFSI electrolytes. The use of KFSI electrolyte enhances the capacity and cyclability of the graphite cathode, while avoiding solvent co-intercalation and improving antioxidation and interphase stability. The Te-graphite KDIBs show a high discharge voltage plateau, high capacity after cycles, and high-power densities, providing important insights for electrolyte design in DIBs.