Electrolyte additive for secondary batteries, electrolyte for secondary batteries containing the same, and secondary battery

Electrolyte using triphenyl borate as an additive to remove residual lithium and form a CEI

This technology utilizes triphenyl borate as an electrolyte additive. Through a Lewis acid-base reaction, it removes residual lithium (LiOH, Li2CO3) from the surface of nickel-rich cathodes and forms a stable Cathode-Electrolyte Interphase (CEI) protective layer via electrochemical oxidation.

Lithium byproducts such as LiOH and Li2CO3 remaining on nickel-rich cathode surfaces decompose during charge and discharge cycles, generating gas that causes cell swelling. In high-voltage environments, these byproducts accelerate electrolyte decomposition, leading to nickel leaching, structural instability, and reduced cycle life.

This technology involves adding borate-based compounds, such as triphenyl borate, to the electrolyte at a concentration of 1–3% (optimally 2%) to chemically bind and remove residual lithium while forming a protective layer on the cathode surface. This inhibits further electrolyte decomposition and transition metal leaching, preventing internal cell pressure buildup and improving cycle life. Applicable to nickel-rich lithium-ion batteries used in communication devices, transportation, and energy storage systems, it effectively reduces the burden of cathode washing processes and minimizes swelling defects through simple electrolyte additive integration.

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Key Features:

• An electrolyte containing an electrolyte additive for secondary batteries composed of substituted or unsubstituted borate-based compounds such as triphenyl borate
• Nickel-rich cathode materials such as lithium nickel cobalt manganese oxide or lithium nickel cobalt oxide containing 50 to 70 wt% nickel
• A cathode-electrolyte interphase protective layer formed on the surface of the cathode material after charge-discharge cycles by the electrolyte additive
• An electrolyte containing a solvent with EC and EMC mixed in a 1:1 to 1:3 volume ratio and a LiPF6 electrolyte salt

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