Chemical prepotassiation design for long-cyclic graphite anode with inorganic-rich interphase

text Graphite is considered as a promising anode for potassium ion batteries due to low voltage plateau and reversible intercalation mechanism. However, it suffers from low initial Coulombic efficiency because of the undesired interfacial chemistry. Herein, an effective chemical prepotassiation strategy with K-4,4′-dimethylbiphenyl complex in the co-solvent of 1,2-diethoxyethane and cyclopentyl methyl ether is rationally designed. With a low redox potential of 0.18 V, this reagent enables effective prepotassiation for graphite anode via a certain soaking time. Moreover, benefitting from the dual weak solvation structure, it manifests exceptional weak solvation capability, which effectively protects the graphite structure after de-potassiation. Consequently, the prepotassiated graphite anode achieves a high ICE of 98.79 %. When paired with 3,4,9,10-perylenetetracarboxylic dianhydride cathode in a full cell, it delivers outstanding cycling stability exceeding 400 cycles at 500 mA g −1 with a capacity retention of 77.14 %. Characterization results of the interfacial formation pathway reveal that the pre-intercalation steps promote the preferential decomposition of anions in conventional carbonate electrolyte, leading to a thin and robust interface. Our work shows new perspectives in designing feasible prepotassiation system for high performance potassium ion batteries.