Cathode active material for lithium secondary batteries comprising a lithium tetramethylsilyl borate coating layer and manufacturing method thereof

High-Nickel Cathode with SN2 Reaction-Based Fluorine-Scavenging LTB Nano-Coating

This technology forms an artificial cathode-electrolyte interphase (CEI) layer by coating the surface of Ni-rich NCM cathode active materials with lithium tetramethylsilyl borate (LTB). This layer captures F- ions, which are impurities in the electrolyte, and enhances interfacial stability.

Ni-rich NCM cathodes have historically faced issues with electrolyte decomposition caused by Ni4+ species in high-voltage and high-temperature environments. This leads to transition metal dissolution, which significantly limits cycle life.

This technology involves adding LTB, synthesized by reacting tris(trimethylsilyl) borate with lithium trimethylsiloxide, to the cathode slurry to form a 1–20nm thick artificial CEI layer during electrode manufacturing. LTB undergoes an SN2 reaction with F- ions to produce fluorotrimethylsilane, preventing fluorine-related side reactions and increases in surface resistance. Suitable for high-voltage cells in EVs and power tools that operate frequently at high temperatures, it allows for improved 55℃ cycle performance without additional coating equipment by reducing the binder content proportionally to the additive amount.

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Key Features:

• A core comprising a lithium composite transition metal oxide represented by LiNiaCobMncO2 (0.6≤a≤0.9, a+b+c=1)
• A 1–20nm thick lithium tetramethylsilyl borate coating layer formed on the surface of the core with F- scavenging capability
• A step of preparing lithium tetramethylsilyl borate by mixing and reacting tris(trimethylsilyl) borate and lithium trimethylsiloxide
• A step of mixing lithium tetramethylsilyl borate into a cathode slurry containing a cathode active material, conductive agent, binder, and solvent

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