Entropy-Repaired Solvation Structure Strategy for High-Efficiency Phosphate-Based Localized High-Concentration...

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Potassium-ion batteries (PIBs) are promising for energy storage, but their safety and stability depend heavily on the electrolyte.
• Weak Lewis acidity of potassium ions leads to excessive weak solvation in localized high-concentration electrolytes, hindering performance.
• Existing electrolytes face challenges in achieving stable cycling and high efficiency in PIBs.

Purpose of the Study:

• To develop an entropy repair strategy to optimize the solvation structure of potassium ions in electrolytes.
• To design and investigate a novel, moderately weakly solvated, high-entropy localized high-concentration electrolyte for PIBs.
• To evaluate the electrochemical performance and stability of the designed electrolyte in potassium symmetric batteries and potassium metal pouch cells.

Main Methods:

• Systematic design of a high-entropy localized high-concentration electrolyte incorporating an entropy repair strategy.
• Electrochemical testing of potassium symmetric batteries to assess Coulombic efficiency and cycling stability.
• Performance evaluation of potassium metal pouch cells with different cathode materials (K1.92Fe[Fe(CN)6]0.94·0.5H2O and perylene-3,4,9,10-tetracarboxylic dianhydride) under various conditions.

Main Results:

• The repaired electrolyte achieved an average stable Coulombic efficiency of 99.4% on the Cu collector.
• Potassium symmetric batteries demonstrated stable cycling for over 10,000 hours at 0.5 mA cm⁻² and 1 mAh cm⁻² deposition capacity.
• Potassium metal pouch cells showed 87.5% capacity retention after 2000 cycles (0.5 A g⁻¹) and stable operation at -20°C (94.0 mAh g⁻¹) and -40°C (77.3 mAh g⁻¹).

Conclusions:

• The entropy repair strategy effectively mitigates weak solvation issues in potassium-ion battery electrolytes.
• The designed high-entropy electrolyte significantly enhances the safety and cycling stability of PIBs.
• This approach offers a viable pathway for developing high-performance, low-temperature potassium-ion batteries.