A high-capacity cathode for rechargeable K-metal battery based on reversible superoxide-peroxide conversion

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Rechargeable potassium-ion batteries (KIBs) face limitations due to low cathode capacity.
• Anionic redox activity is a promising strategy for enhancing KIB capacity.
• Achieving anionic redox in sealed KIB systems remains a challenge.

Purpose of the Study:

• To develop a sealed potassium-ion battery system with enhanced capacity.
• To achieve reversible superoxide/peroxide interconversion in a sealed KIB.
• To improve the long-term cycling stability and energy efficiency of KIBs.

Main Methods:

• Utilized a potassium superoxide (KO2)-based cathode for reversible KO2/K2O2 conversion.
• Operated the battery in a sealed cell environment to prevent oxygen evolution and electrolyte decomposition.
• Employed electrolyte modification to enable coupling with a limited potassium metal anode.

Main Results:

• Successfully realized reversible superoxide/peroxide interconversion in a sealed KIB.
• Achieved a reversible charge capacity of 300 mAh/g with minimal cell degradation over 900 cycles.
• Developed a K-metal full-cell with high energy efficiency (~90%) and over 300 cycles stability.

Conclusions:

• The KO2-based cathode enables effective anionic redox in sealed KIBs.
• Controlled reversible KO2/K2O2 conversion significantly enhances KIB performance.
• This work paves the way for high-performance, low-cost potassium-ion energy storage.