Electrode Interface Engineering in Lithium-Sulfur Batteries Enabled by a Trifluoroacetamide-Based Electrolyte

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Lithium-sulfur batteries (LSBs) suffer from cycle instability and capacity fading due to lithium sulfide (Li2S) passivation.
• This passivation layer hinders electrochemical reactions and limits the practical application of LSBs.

Purpose of the Study:

• To investigate trifluoroacetamide (TFA) as an electrolyte additive to mitigate Li2S passivation in LSBs.
• To enhance the solubility of Li2S and improve the overall cycle stability and performance of LSBs.

Main Methods:

• Employing trifluoroacetamide (TFA) as an electrolyte additive in lithium-sulfur battery configurations.
• Analyzing the solubilization effect of TFA on Li2S through intermolecular hydrogen and O-Li bonds.
• Investigating the deposition behavior of Li2S and the formation of a LiF-rich solid electrolyte interface (SEI) layer.

Main Results:

• TFA significantly increases Li2S solubility, promoting flower-like 3D deposition and alleviating electrode passivation.
• A LiF-rich SEI layer effectively protects the Li metal anode and suppresses dendrite growth.
• LSBs with TFA exhibit excellent capacity retention (681.2 mA h g⁻¹ after 400 cycles at 0.5 C) and high Coulombic efficiency (99%).
• The batteries demonstrate remarkable stability under harsh conditions, including high rates, high sulfur loadings, lean electrolytes, and elevated temperatures.

Conclusions:

• Trifluoroacetamide is a highly effective additive for enhancing the cycle stability of lithium-sulfur batteries.
• The improved performance is attributed to TFA's ability to increase Li2S solubility and promote favorable deposition and SEI formation.
• This study offers a promising strategy for overcoming practical challenges and advancing the development of high-performance LSBs.