Engineering Anion-Diluent Matrix for Ion-Decoupled Localized High-Concentration Electrolytes toward Highly Stable...

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Aqueous zinc-ion batteries offer safety but face electrolyte degradation.
• Localized high-concentration electrolytes (LHCEs) improve stability but hinder ion transport.
• Excessive cation-anion interactions in LHCEs lead to sluggish kinetics.

Purpose of the Study:

• To design an ion-decoupled LHCE (ID-LHCE) to overcome limitations of conventional LHCEs.
• To improve interfacial stability and ionic conductivity in aqueous zinc-ion batteries.
• To enable dendrite-free zinc deposition and enhance battery cyclability.

Main Methods:

• Utilized amphiphilic 2,2,3,3-tetrafluoro-1-propanol (TFP) as an anion-affinity diluent.
• Formulated a TFP-mediated anion-diluent matrix (ADM) to decouple ions.
• Investigated the electrolyte's effect on solvation sheaths, ionic transport, and solid electrolyte interphase (SEI) formation.
• Tested full cells with NaV3O8·1.5H2O cathodes and high mass loading pouch cells.

Main Results:

• Achieved an elevated Zn2+ transference number of 0.72 by liberating anions from solvation sheaths.
• Established biphasic H2O-rich/poor nanodomains, reducing water activity and suppressing hydrogen evolution.
• Formed a gradient heterogeneous SEI with inner ZnF2-ZnS and outer oligomer layers.
• Demonstrated dendrite-free zinc deposition with 3,000 hours of cyclability at 1 mA cm-2 and 99.88% coulombic efficiency.
• Full cells retained 72.5% capacity after 2,000 cycles; demonstrated stable operation of 1.04 Ah pouch cells.

Conclusions:

• The ID-LHCE strategy effectively decouples ions, reduces transport barriers, and enhances stability.
• The developed electrolyte enables robust, dendrite-free zinc plating and long cycle life.
• This work presents a multiscale design paradigm for advanced electrolyte nanostructures in energy storage devices.