Effect of the Electric Double Layer (EDL) in Multicomponent Electrolyte Reduction and Solid Electrolyte Interphase...

Area of Science:

• Electrochemistry
• Materials Science
• Battery Technology

Background:

• Stable solid electrolyte interphase (SEI) formation is critical for lithium-ion battery performance and longevity.
• The electric double layer (EDL) structure near electrodes significantly impacts SEI composition, yet remains poorly understood.
• Fluoroethylene carbonate (FEC) is a common additive used to create beneficial F-containing SEI components like LiF.

Purpose of the Study:

• To investigate the influence of the EDL on SEI formation in different electrolyte systems.
• To elucidate the differing roles of FEC in carbonate-based and ether-based electrolytes.
• To explain the observed temperature-dependent effects of FEC in ether-based electrolytes.

Main Methods:

• Utilized a newly developed computational model to simulate SEI formation.
• Analyzed SEI formation in two distinct electrolyte systems: carbonate-based and ether-based.
• Examined the behavior of FEC and anions within the EDL under varying conditions.

Main Results:

• FEC acts as the sole F-containing species reduced in carbonate-based electrolytes, with anions excluded from the EDL.
• In ether-based electrolytes, both FEC and anions (TFSI-) compete for reduction within the EDL.
• The competition within the EDL explains the enhanced effectiveness of FEC at low temperatures in ether-based electrolytes.

Conclusions:

• The EDL structure plays a pivotal role in dictating SEI formation mechanisms.
• Incorporating EDL effects into simulations and experiments is essential for predicting and controlling SEI properties.
• This understanding can guide the development of more stable and durable lithium-ion and lithium-metal batteries.