Electrolyte additive containing 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether and a lithium secondary battery comprising the same

Electrolyte for SiOx Anodes Implementing LiF-Rich SEI via Fluorinated Ether TFE

This technology enhances interfacial stability in lithium secondary batteries by adding 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TFE) to the electrolyte, which forms a LiF-rich artificial Solid Electrolyte Interphase (SEI) layer on the anode surface.

While SiOx anodes offer high theoretical specific capacity, they suffer from structural pulverization due to repeated volume expansion and contraction during charge/discharge cycles. This exposes fresh surfaces to the electrolyte, accelerating side reactions and degradation.

This technology utilizes a TFE additive at 5 wt% to less than 10 wt% of the total electrolyte weight, forming a robust LiF-based SEI layer on the SiOx anode surface through electrochemical reduction. Applicable to high-capacity mobile device cells using silicon oxide anodes or NCM811 cathode-based automotive batteries, it reduces electrolyte consumption by pulverized anode surfaces and improves long-term cycle capacity retention.

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Key Features:

• An electrolyte layer containing an electrolyte placed between the cathode and anode, comprising a solvent, a lithium salt, and an additive
• A TFE additive included in an amount of 5 wt% or more and less than 10 wt% based on 100 wt% of the electrolyte
• A solid electrolyte interphase (SEI) layer containing LiF, formed on the anode surface by TFE
• At least one lithium salt selected from the group consisting of LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiCF3SO3, and the like

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