Super SEI-Forming Anion for Enhanced Interfacial Stability in Solid-State Lithium Metal Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Lithium metal (Li°) electrodes exhibit high reactivity and volume changes, leading to interfacial degradation and poor cycling performance in rechargeable lithium metal batteries (LMBs).
• Current organic electrolytes struggle to maintain stable interfaces, hindering the practical application of LMBs.

Purpose of the Study:

• To introduce a novel super SEI-forming anion (SSA) designed to create stable interphases on Li° electrodes.
• To investigate the anion chemistry of SSA and its impact on interfacial properties and battery performance.

Main Methods:

• Synthesis and characterization of the super SEI-forming anion (SSA).
• Electrochemical testing of Li° electrodes and Li°||LiFePO₄ cells incorporating SSA in organic electrolytes.
• Analysis of interfacial properties and degradation mechanisms.

Main Results:

• The SSA, with its sulfonate and polyfluoroalkyl functionalities, promotes uniform distribution and conformal coating of interfacial species on Li° electrodes.
• Incorporation of SSA significantly improves Li° electrode cyclability, achieving over 575 mAh cm⁻² before failure.
• Rechargeable Li°||LiFePO₄ cells using SSA demonstrate a five-fold increase in lifespan compared to those with bis(fluorosulfonyl)imide (FSI).

Conclusions:

• The proposed super SEI-forming anion (SSA) offers a new strategy to overcome interfacial instability in lithium metal batteries.
• This anion chemistry approach provides a paradigm shift for enhancing the practical development of rechargeable LMBs and other metal batteries.