Asymmetric K/Li-Ion Battery Based on Intercalation Selectivity

Using ab initio calculations combined with experimental confirmation, we design an asymmetric intercalation battery using K₂NiFe^II(CN)₆ as the cathode, commercial graphite as the anode, and an organic electrolyte containing mixed lithium and potassium salts. It works by reversible K-ion intercalation at the cathode side and reversible Li-ion intercalation at the anode side simultaneously. The π-electron coordination environment in K₂NiFe^II(CN)₆ ensures the preferred reversible intercalation of the K-ion, and the small ionic radius ensures the preferred reversible intercalation of the Li-ion in graphite. It also shows a high working voltage (∼3.6 V) and an ultralong cycling life with no capacity fading even after 5000 cycles.