Accelerated Defluorination Kinetics for an Ultrathin Solid-Electrolyte Interphase in Durable Lithium Metal Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Battery Technology

Background:

• Lithium metal batteries suffer from short cycle life due to thick solid-electrolyte interphase (SEI) formation, which consumes electrolyte and lithium.
• Developing strategies for controlled SEI formation is crucial for enhancing battery durability.

Purpose of the Study:

• To propose and demonstrate an *in situ* method for generating an ultrathin SEI by accelerating electrolyte defluorination kinetics.
• To reduce electrolyte and lithium inventory consumption during SEI formation for more durable batteries.

Main Methods:

• Utilized a dimethoxy(dimethyl)silane (DMDMS)-based electrolyte, characterized by high Li salt solubility and weak solvating power.
• Investigated the formation of joint aggregates in the DMDMS electrolyte and their effect on defluorination rates.
• Analyzed the nucleation and growth of the SEI on the lithium metal surface.

Main Results:

• The DMDMS electrolyte facilitated the formation of joint aggregates, leading to fast defluorination and uniform nucleation sites.
• This resulted in the rapid passivation of the lithium anode and the formation of a compact, ultrathin SEI.
• The prototype pouch cell demonstrated 190 cycles with high energy retention (66% at -30 °C) and high initial energy density (≥500 Wh kg⁻¹).

Conclusions:

• The study reveals the SEI formation mechanism driven by electrolyte properties and aggregate formation.
• Meticulous SEI engineering through controlled electrolyte design is a promising strategy for developing durable lithium metal batteries.
• The proposed method offers a pathway to enhance the performance and longevity of next-generation energy storage systems.