Competitive coordination effect induced solvent-separated ion pairs enable fast Li⁺ ion transport and stable solid...

Area of Science:

• Materials Science
• Electrochemistry
• Polymer Chemistry

Background:

• Solvent coordination structures (CIPs, AGGs, SSIPs) in solid polymer electrolytes (SPEs) critically influence ionic conductivity and solid electrolyte interphase (SEI) formation.
• The specific impact of solvent-separated ion pairs (SSIPs) on SEI stability and ionic transport has been underexplored, despite their known collaborative effects.

Purpose of the Study:

• To investigate the unique role of SSIPs in SPEs by precisely controlling their concentration.
• To understand how SSIPs affect Li+ ion transport and SEI formation independently.

Main Methods:

• Synthesizing SPEs with varying SSIP concentrations (0-2.8%) by incorporating vinylene carbonate (VC).
• Conducting experimental analyses and theoretical calculations to evaluate ionic conductivity and SEI characteristics.
• Performing electrochemical testing on Li||Li symmetric cells and Li||LFP cells to assess cycling stability and performance.

Main Results:

• SSIPs, induced by competitive coordination, promote rapid Li+ ion transport.
• An organic/inorganic composite SEI is facilitated, leading to a stable electrochemical interface with uniformly distributed lithium fluoride (LiF).
• Li||Li symmetric cells achieved 1200 hours of stable cycling at 0.1 mA cm⁻², and Li||LFP cells demonstrated 550 cycles with >99.9% coulombic efficiency and 96.5% capacity retention.

Conclusions:

• Independently studying SSIPs in SPEs provides crucial insights into their role in battery performance.
• Tailoring SSIP concentration is a viable strategy for developing advanced lithium metal batteries with enhanced stability and conductivity.
• The findings offer a new avenue for optimizing SPEs for high-performance energy storage applications.