Engineering Electrode/Electrolyte Interphase Chemistry toward High-Rate and Long-Life Potassium Ion Full-Cell

Controlling the interfacial chemistries of the cathode and anode in potassium ion full-cells is critically important for better K+ storage; however, the correlation between cathode electrolyte interphase (CEI) and solid electrolyte interphase (SEI) and its effect on electrochemical performance is poorly understood, not mention their rational matchup. In this study, an electrochemical modification strategy has been employed for the tailored design of both the CEI on a K2Fe[Fe(CN)6] (KFeHCF) surface and the SEI on a graphite (Gr) surface. The optimized matchup between CEI and SEI realized a good rate and cycling performance in KFeHCF/Gr full-cells, which is attributed to the presence of a robust, homogeneous, and conductive SEI that contains chemically stable PEO (−(CH2CH2O)n−) and K2CO3. Our results not only promoted fundamental understanding of interfacial chemistry on K+ storage, but also provided rational design strategy to realize enhanced efficiency and durability of potassium ion full-cells, which can also be extended to other energy storage systems.