Unlocking Polyanion-Type Materials through High-Entropy Effect for Aqueous Potassium-Ion Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Aqueous battery research often mimics organic electrolyte systems, facing limitations with V-based polyanion materials.
• V-based polyanions show promise in organic electrolytes but struggle with limited cation activity and dissolution in aqueous potassium-ion batteries.

Purpose of the Study:

• To develop stable and reversible aqueous potassium-ion storage using V-based polyanion materials.
• To investigate the charge storage mechanism in entropy-tuned polyanionic electrodes for aqueous potassium-ion batteries.

Main Methods:

• Employed a high-entropy strategy to modify V-based polyanion materials.
• Utilized in situ spectroscopic characterizations to analyze the charge storage mechanism.
• Applied time-of-flight secondary ion mass spectrometry and density functional theory simulations to assess ion migration and solubility.

Main Results:

• Achieved reversible and stable aqueous potassium-ion storage via a solid-solution process, unlike traditional phase-transition mechanisms.
• Demonstrated suppressed ion migration barriers and reduced material solubility in entropy-tuned cathodes.
• Obtained ultrahigh initial Coulombic efficiency (98.7%), excellent rate capability (36C), and long-term cycling stability (3500 cycles).

Conclusions:

• The high-entropy strategy effectively activates V-based polyanion cathodes for aqueous potassium-ion batteries, even in dilute electrolytes.
• This research bridges the understanding of charge storage differences between organic and aqueous electrolyte systems.
• Provides a new pathway for utilizing other electrode materials in aqueous battery environments.