Dimethoxydimethylsilane-coated cathode active material for lithium-ion batteries and manufacturing method thereof

High-nickel cathode materials with silyl ether artificial CEI layers for scavenging fluoride ions

This technology forms an artificial cathode-electrolyte interface (CEI) layer containing silyl ether (Si-O) functional groups by coating Ni-rich NCM cathode active materials with dimethoxydimethylsilane (DODSi) and performing heat treatment. This suppresses side reactions with the electrolyte and enhances cathode stability.

Ni-rich NCM cathodes suffer from electrolyte decomposition at the surface due to chemically unstable Ni4+ in the charged state. The resulting nucleophilic fluoride (F-) ions cause transition metal dissolution and increased surface resistance, leading to a rapid decline in cycle life.

This technology involves coating the surface of NCM active materials with DODSi in an NMP solvent, followed by heat treatment at 400–800°C. The formed Si-O functional groups act as a protective layer to prevent electrolyte decomposition and selectively scavenge fluoride ions, inhibiting transition metal dissolution. Applicable to high-capacity cells for EVs and high-nickel cathode development, it helps improve cathode specifications requiring high-temperature cycle retention.

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Key Features:

• High-nickel cathode active material represented by the composition LiNiaCobMncO2 (a+b+c=1) with a nickel mole fraction between 0.6 and 0.9
• Dimethoxydimethylsilane coating layer on the surface in an amount of 1 wt% to 10 wt% relative to 100 wt% of the cathode active material
• Step of mixing dimethoxydimethylsilane and the cathode active material in an N-methyl-2-pyrrolidone solvent to coat the active material surface
• Step of heat-treating the dimethoxydimethylsilane-coated cathode active material at a temperature range of 400 to 800°C

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