Locally Fluorinated Electrolyte Medium Layer for High-Performance Anode-Free Li-Metal Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Anode-free lithium-metal batteries (AFLBs) face challenges with low cycling Coulombic efficiency (CE) and uncontrolled lithium dendrite growth.
• Uniform lithium deposition and suppression of interfacial side reactions are critical for developing stable AFLBs.

Purpose of the Study:

• To develop a functional electrolyte strategy for enhancing the performance of AFLBs.
• To inhibit immoderate lithium dendrite growth and suppress interfacial reactions in AFLBs.

Main Methods:

• A locally fluorinated electrolyte (LFE) medium layer was designed and applied to Cu foils.
• The LFE comprised highly concentrated LiTFSI in a fluoroethylene carbonate and/or succinonitrile plastic mixture.
• Density functional theory (DFT) calculations were used to investigate the LiF/Li interface properties.

Main Results:

• The CE of Cu||LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811) AFLB increased to 99%.
• Significant improvements in cycling stability were observed.
• A uniform, dense, and LiF-rich solid-electrolyte interphase (SEI) was formed, promoting uniform lithium deposition.

Conclusions:

• The LFE effectively tailors SEI composition, inhibiting dendrite growth and interfacial reactions.
• The LiF-rich SEI contributes to uniform lithium deposition due to high interfacial energy.
• This approach offers a simple and effective method for enhancing high-energy-density AFLBs.