Intermolecular Interaction-Driven Contact Ion Pair-Dominated Solvation Structure Enabling Stable...

Area of Science:

• Materials Science
• Electrochemistry
• Polymer Chemistry

Background:

• Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) polymer electrolytes offer high ionic conductivity for quasi-solid-state lithium metal batteries (QSSLMBs).
• Nonuniform solvation structures in PVDF-HFP electrolytes lead to poor interfacial stability and sluggish ion transport, hindering battery performance.
• Existing electrolytes face challenges with electrochemical instability at the electrode-electrolyte interface, especially in high-voltage applications.

Purpose of the Study:

• To precisely modulate the solvation structure within PVDF-HFP electrolytes.
• To enhance ionic transport kinetics and stabilize electrode-electrolyte interfaces in QSSLMBs.
• To develop high-voltage (4.5 V) QSSLMBs with improved cycling stability.

Main Methods:

• Utilizing ZIF-67 filler to interact with DMF solvent in PVDF-HFP electrolytes.
• Engineering a uniform contact ion pair (CIP)-dominated solvation structure via specific adsorption of DMF's C═O group by ZIF-67's Co-N site.
• Testing Li//Li symmetric cells and Li//NCM811 full cells to evaluate cycling stability and performance.

Main Results:

• Achieved a uniform CIP-dominated solvation structure through ZIF-67 and DMF interaction.
• Enhanced ionic transport kinetics and stabilized electrode-electrolyte interfaces.
• Demonstrated ultralong cycling stability (>5600 h) in Li//Li symmetric cells and excellent cycling (>1600 cycles at 4.3 V, 200 cycles at 4.5 V) in Li//NCM811 full cells.

Conclusions:

• Precise modulation of solvation structure via ZIF-67 is a viable strategy for high-performance QSSLMBs.
• The developed electrolyte significantly improves ionic conductivity and interfacial stability.
• This interfacial modulation paradigm offers fundamental guidance for advancing high-voltage QSSLMB technology.