Selectively fluorinated aromatic lithium salts regulate the solvation structure and interfacial chemistry for...

Area of Science:

• Materials Science
• Electrochemistry
• Polymer Chemistry

Background:

• Solid polymer electrolytes (SPEs) face challenges with polymer-dominated Li+ solvation, leading to unstable interfaces and poor battery performance.
• Developing stable electrolyte/electrode interphases is crucial for advancing all-solid-state lithium metal batteries (ASLMBs).

Purpose of the Study:

• To design novel selectively fluorinated aromatic lithium salts (SFALS) as single conducting lithium salts.
• To regulate Li+ solvation structure and interfacial chemistry in ASLMBs.
• To enhance the performance and stability of ASLMBs.

Main Methods:

• Synthesized and characterized a class of SFALS with tunable anionic structures.
• Investigated the Li+ solvation structure and ion transport mechanisms using spectroscopic and electrochemical methods.
• Fabricated and tested ASLMBs utilizing SFALS-based SPEs.

Main Results:

• SFALS weakened Li+-polyether coupling and enhanced Li+-anion coordination.
• Hydrogen bonding induced a "triad"-type solvation structure, improving electrolyte homogeneity and mechanical strength.
• Formation of an ultrathin, robust Li2O-rich solid electrolyte interphase (SEI) was promoted.
• Achieved stable cycling of over 1650 cycles (99.8% CE) in LiFePO4/Li half cells and 580 cycles (97.4% retention) in full cells.

Conclusions:

• Molecular engineering of SFALS offers a viable strategy to overcome limitations in SPEs.
• The developed SFALS significantly enhance interfacial stability and electrochemical performance in ASLMBs.
• This approach paves the way for practical applications of high-performance ASLMBs.