Revisiting potassium intercalation in graphite: an operando characterisation and computational approach

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Potassium-ion batteries (KIBs) are a promising alternative to lithium-ion systems due to potassium's abundance and similar intercalation chemistry.
• Understanding potassium intercalation into graphite, especially early stages and K+ ordering, is crucial but not fully elucidated.

Purpose of the Study:

• To elucidate the correlation between electrochemical potassiation and structural evolution in graphite anodes for KIBs.
• To unravel the specific mechanisms of potassium-ion storage in graphite.

Main Methods:

• Utilized a multi-modal operando characterization approach.
• Employed operando electrochemical dilatometry, synchrotron X-ray diffraction (XRD), Raman spectroscopy, density-functional theory (DFT), optical microscopy, and UV-vis spectroscopy.

Main Results:

• Precisely quantified macroscopic volume expansion during potassiation.
• Recorded ordered phase transitions and formation of distinct graphite intercalation compound (GIC) phases during early intercalation.
• Revealed in-plane ordering of K+ and stacking modes, linked optical properties to GICs and electronic structure.

Conclusions:

• Provided fundamental mechanistic insights into K-ion storage in graphite.
• The findings pave the way for the rational design of high-performance KIB anodes.