Anion Doping for Layered Oxides with a Solid-Solution Reaction for Potassium-Ion Battery Cathodes.

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Potassium-ion batteries (PIBs) face challenges with stable cathode materials due to the large K+ ion size.
• Reversible hosting of K+ ions often leads to structural degradation and capacity fading in PIBs.

Purpose of the Study:

• To investigate anionic doping as a strategy to enhance the stability and performance of layered oxide cathodes for PIBs.
• To explore the effect of fluorine (F-) doping on the structural and electrochemical properties of P2-type oxides.

Main Methods:

• Synthesis of fluorine-doped P2-type oxide cathode material (KMNTOF).
• Electrochemical characterization including galvanostatic cycling to assess capacity and stability.
• Structural analysis and theoretical calculations to understand the role of F- doping.

Main Results:

• Fluorine doping enlarged the interlayer distance of the P2-type oxide, facilitating K+ ion transport.
• Anionic doping increased the Mn redox activity and lowered the average Mn valence, enhancing reversible capacity.
• The KMNTOF cathode achieved a high reversible capacity of 132.5 mAh g-1 with 0.53 K+ intercalation.

Conclusions:

• Anionic doping is an effective strategy to overcome structural degradation and capacity fading in PIBs.
• Fluorine doping offers a promising route for developing stable and high-performance cathode materials for potassium-ion batteries.