Cationic polymer-in-salt electrolytes for fast metal ion conduction and solid-state battery applications

Area of Science:

• Materials Science
• Electrochemistry
• Polymer Chemistry

Background:

• Solid-state batteries offer enhanced safety and energy density compared to conventional batteries.
• Developing polymer electrolytes with high ionic conductivity and transference numbers for alkali metals (Na, K, Mg) is crucial but challenging.

Purpose of the Study:

• To demonstrate the efficacy of polymeric ionic liquids (PolyILs) as polymer solvents for sodium (Na) and potassium (K) solid-state electrolytes.
• To elucidate the ion transport mechanisms in PolyIL-based electrolytes using molecular simulations.
• To experimentally validate the performance of these novel electrolytes for battery applications.

Main Methods:

• Molecular simulations were employed to predict and understand ion transport mechanisms in PolyILs.
• Polymeric ionic liquid-based electrolytes were synthesized and characterized.
• Electrochemical performance was evaluated using ionic conductivity measurements, transference number determination, and symmetric cell cycling tests.

Main Results:

• Molecular simulations revealed fast alkali metal ion transport via a structural diffusion mechanism in a polymer-in-salt environment within PolyILs.
• Experimental results showed ionic conductivities up to 1.0 × 10⁻³ S cm⁻¹ at 80°C for Na and K electrolytes.
• A Na⁺ transference number of approximately 0.57 was achieved, alongside stable Na plating/stripping for over 100 hours in a symmetric cell.

Conclusions:

• Polymeric ionic liquids are versatile solvents for designing high-performance solid-state electrolytes for Na and K batteries.
• The polymer-in-salt strategy using PolyILs facilitates high ionic conductivity and transference numbers, addressing key challenges in solid-state battery development.
• This approach offers a promising alternative for next-generation sustainable battery chemistries.