In the low cost tin-graphite dual ion battery, expanded graphite is used as anode, and potassium hexafluorophosphate as electrolyte. The potassium ions in the electrolyte move to the surface tin foil cathode to form a potassium-tin alloy, and the hexafluorophosphate is intercalated into the graphite at the anode. When K+ is discharged, the hexafluorophosphate anion is desorbed back into the electrolyte. The new type of potassium-based dual-ion battery achieves 50mA g-1 constant current charge and an energy density of 155Wh/kg, equivalent to a traditional lithium-ion battery. After 300 cycles, it maintained 93% capacity.

CAS news release, April 10, 2017