Understanding High-Rate K⁺-Solvent Co-Intercalation in Natural Graphite for Potassium-Ion Batteries

© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Graphite shows great potential as an anode material for rechargeable metal-ion batteries because of its high abundance and low cost. However, the electrochemical performance of graphite anode materials for rechargeable potassium-ion batteries needs to be further improved. Reported herein is a natural graphite with superior rate performance and cycling stability obtained through a unique K+-solvent co-intercalation mechanism in a 1 m KCF3SO3 diethylene glycol dimethyl ether electrolyte. The co-intercalation mechanism was demonstrated by ex situ Fourier transform infrared spectroscopy and in situ X-ray diffraction. Moreover, the structure of the [K-solvent]+ complexes intercalated with the graphite and the conditions for reversible K+-solvent co-intercalation into graphite are proposed based on the experimental results and first-principles calculations. This work provides important insights into the design of natural graphite for high-performance rechargeable potassium-ion batteries.