Hydrogen-Bond-Stabilized Organic Potassium-Ion Full Cell Operating at -40°C

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Low-temperature operation of energy storage systems is limited by slow ion kinetics and electrolyte freezing.
• Potassium-ion batteries (PIBs) are promising for cost-effective energy storage but require stable cathode materials for sub-zero temperatures.
• Existing cathode materials often lack the necessary stability and performance at ultra-low temperatures.

Purpose of the Study:

• To design and synthesize a novel organic small molecule cathode material for high-performance low-temperature PIBs.
• To investigate the structure-property relationships governing the electrochemical performance of organic cathodes.
• To demonstrate the potential of organic materials in overcoming the challenges of low-temperature energy storage.

Main Methods:

• Synthesis and characterization of the organic small molecule 1,4-dihydrobenzo[g]quinoxaline-2,3,5,10-tetraone (BQXTO).
• Electrochemical evaluation of BQXTO as a cathode material in potassium-ion cells at low temperatures.
• Analysis of intermolecular hydrogen bonds and π─π interactions influencing charge transfer and stability.

Main Results:

• The BQXTO cathode exhibits enhanced charge transfer and insolubility due to synergistic hydrogen bonding and π─π interactions.
• The assembled BQXTO||HC potassium-ion full cell achieved a high energy density of 188 Wh kg⁻¹ at -40 °C.
• Exceptional cycling stability was observed, with 88.2% capacity retention over 2000 cycles at low temperatures.

Conclusions:

• Organic small molecules, like BQXTO, can serve as effective cathode materials for advanced low-temperature potassium-ion batteries.
• Strategic molecular design, incorporating hydrogen bonds and π─π interactions, is crucial for enhancing electrochemical performance and stability.
• This work provides a new avenue for developing robust and efficient organic electrode materials for extreme-condition energy storage.