Layered K_0.28MnO₂·0.15H₂O as a Cathode Material for Potassium-Ion Intercalation

Area of Science:

• Materials Science
• Electrochemistry
• Inorganic Chemistry

Background:

• Potassium-ion batteries (KIBs) are promising for large-scale energy storage.
• Developing stable and high-performance cathode materials is crucial for KIB advancement.
• Layered transition metal oxides offer potential but often suffer from structural degradation during cycling.

Purpose of the Study:

• To investigate K_0.28MnO₂·0.15H₂O as a two-dimensional intercalation host for potassium ions.
• To elucidate the role of interlayer water molecules in stabilizing the cathode structure.
• To evaluate the electrochemical performance of K_0.28MnO₂·0.15H₂O in KIBs.

Main Methods:

• Synthesis of K_0.28MnO₂·0.15H₂O with a layered structure.
• Operando X-ray diffraction to study structural evolution during cycling.
• Electrochemical testing of K_0.28MnO₂·0.15H₂O as a cathode in K-cells.

Main Results:

• K_0.28MnO₂·0.15H₂O exhibits a layered structure with a large basal spacing (∼7.3 Å), facilitating K+ ion mobility.
• Interlayer water molecules act as structural pillars, maintaining framework integrity during de/potassiation.
• The material delivered a high reversible capacity of 150 mA h g^-1 over 100 cycles at 0.1 C and showed acceptable power capability up to 5 C.

Conclusions:

• K_0.28MnO₂·0.15H₂O is a viable cathode material for KIBs due to its open framework and structural stability.
• The presence of interlayer water is critical for achieving long cycle life and good electrochemical performance.
• This material demonstrates potential for efficient potassium storage applications.