Electrolyte for lithium secondary batteries containing triallyl borate and lithium secondary batteries comprising the same

High-Nickel Batteries with TAB Additives Combining Borate CEI and Fluorine Scavenging

This technology introduces triallyl borate (TAB) as an electrolyte additive to form a borate-based Cathode-Electrolyte Interphase (CEI) layer on the cathode surface via electrochemical oxidation. Simultaneously, it chemically removes fluorine (F-) species from the electrolyte, enhancing the thermal and chemical stability of the cathode.

Nickel-rich layered oxide (LiNi0.83Co0.07Mn0.10O2) cathodes are highly reactive, leading to accelerated electrolyte decomposition during high-temperature cycling. This, combined with irreversible transition metal dissolution and surface side reactions, has historically limited cell lifespan.

This technology incorporates 0.1–2.0 wt% of TAB into the electrolyte to form a stable CEI layer on the cathode. The allyl functional groups of TAB undergo electrochemical decomposition to form the CEI, while the borate groups scavenge fluorine ions to suppress interfacial side reactions, improving high-temperature cycle performance. Suitable for EV/HEV cells using graphite anodes and NCM83 cathodes, as well as outdoor ESS exposed to summer heat, this single additive simplifies formulation by simultaneously enabling film formation and HF removal.

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Key Features:

• Electrolyte layer placed between the cathode and anode, containing 0.75 wt% triallyl borate (TAB), solvent, and lithium salt
• Cathode containing LiNi0.83Co0.07Mn0.10O2 and anode containing carbon materials such as natural graphite
• CEI layer formed on the cathode surface via electrochemical decomposition of triallyl borate to suppress electrolyte decomposition
• Electrolyte solvent containing ethylene carbonate and ethyl methyl carbonate in a 1:2 ratio with a lithium salt concentration of 0.01 to 2M

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