Solvent-Enriched Separator-Electrolyte Interface Stabilizes 4.7 V Ni-Rich Layered Cathodes.

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• High charging cutoff voltages are crucial for lithium metal batteries (LMBs).
• Parasitic solvent reactions at the electrode/electrolyte interface hinder performance and stability.
• Existing interface engineering methods struggle to prevent solvent decomposition near cathodic sites.

Purpose of the Study:

• To develop a novel strategy to suppress solvent decomposition in LMBs operating at high voltages.
• To enhance the stability of the cathode interface by controlling solvent behavior.
• To enable the practical application of ultrahigh-voltage LMBs.

Main Methods:

• Proposed a separator-adsorbed solvent strategy using a polytetrafluoroethylene (PTFE) separator.
• Investigated interactions between PTFE separator and carbonate solvents (C-H···F bonds, n→π* interactions).
• Fabricated gel polymer electrolyte with PTFE separator (GPE-PTFE) for Li||LiNi0.8Co0.1Mn0.1O2 cells.

Main Results:

• PTFE separator created adsorption sites, effectively competing with the cathode for solvent molecules.
• Suppressed solvent decomposition and stabilized the cathode interface.
• GPE-PTFE cells achieved 80% capacity retention over 671 cycles at 4.4 V, nearly doubling performance with PE separators.
• Achieved 90% capacity retention after 100 cycles at an ultrahigh 4.7 V cutoff.

Conclusions:

• The separator-adsorbed solvent strategy is effective in suppressing solvent decomposition and stabilizing the cathode interface in LMBs.
• PTFE separators show significant potential for enabling ultrahigh-voltage operation in lithium metal batteries.
• This work presents a new paradigm for designing advanced separators for high-performance energy storage devices.