Stabilizing SEI by cyclic ethers toward enhanced K+ storage in graphite

The poor cycling stability of graphite in traditional ester electrolyte limits its applications as anodes for potassium ion batteries (KIBs). Herein, we demonstrate that the introduction of cyclic ether co-solvents into ester electrolytes can remarkably enhance the cycling stability of graphite anodes. The graphite anode in ester electrolyte with cyclic ether could achieve a reversible capacity of 196.1 mAh g−1 after 100 cycles at 0.3 C (1 C = 280 mA g−1), about three times higher than those in ester electrolytes with or without linear ether. Compared with the SEI formed in ester electrolytes, the addition of tetrahydrofuran promotes the generation of K2CO3 and ethylene oxide oligomers (PEO), of which the K2CO3 is expected to be more conductive and PEO is mechanically robust. The more uniform, conductive and stable solid electrolyte interphases (SEIs) on graphite in electrolytes with cyclic ethers contribute to the enhancement of the electrochemical performances of graphite. This work provides a novel design of commercialized electrolytes to achieve high-performance anodes for KIBs, which potentially accelerates the development of KIBs.