Li₂ZrF₆-based electrolytes for durable lithium metal batteries

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Lithium metal batteries (LMBs) offer high energy density but suffer from lithium dendrite formation and capacity decay.
• A stable solid-electrolyte interphase (SEI) is crucial for high-rate, long-life LMBs, yet remains a significant challenge.
• Current non-aqueous electrolytes react with highly active lithium, compromising battery safety and performance.

Purpose of the Study:

• To develop a novel electrolyte additive for enhancing the stability and performance of lithium metal batteries.
• To investigate the in situ formation of a stable solid-electrolyte interphase using lithium hexafluorozirconate nanoparticles.
• To demonstrate improved Li-ion conductivity and dendrite suppression in LMBs.

Main Methods:

• Addition of excess monoclinic lithium hexafluorozirconate (m-Li2ZrF6) nanoparticles to a commercial LiPF6-based carbonate electrolyte.
• Electrochemical studies under applied voltage to induce ZrF6(2-) ion release and SEI formation.
• Computational modeling and cryogenic transmission electron microscopy (cryo-TEM) to analyze SEI structure and Li-ion transfer.
• Battery cycling tests with LiFePO4 cathodes and 3D Li-carbon anodes.

Main Results:

• In situ formation of a stable trigonal lithium hexafluorozirconate (t-Li2ZrF6)-rich SEI layer with high Li-ion conductivity.
• Marked enhancement of Li-ion transfer and significant suppression of lithium dendrite growth, confirmed by computational and cryo-TEM studies.
• LMBs demonstrated excellent cycling stability, retaining over 80.0% capacity after 3,000 cycles at 1C/2C rates.

Conclusions:

• The developed Li2ZrF6-based electrolyte effectively creates a robust SEI, addressing key challenges in LMB technology.
• This approach offers a reliable solution for durable, high-rate lithium metal batteries.
• The findings represent a significant advancement in materials for next-generation energy storage.