Silyl phosphate-based electrolyte additive and lithium secondary battery containing the same

Electrolyte additive using TMSPO, a dual-functional silyl phosphate, to protect high-Ni cathode interfaces

This technology utilizes TMSPO, which contains both phosphate and silyl functional groups, as an electrolyte additive. It enhances interface stability by forming a protective CEI layer on the high-Ni NCM cathode surface and removing fluorine-based substances that trigger transition metal dissolution.

High-Ni NCM cathode materials have historically suffered from interface instability during high-temperature charging and discharging, leading to continuous electrolyte side reactions. This results in transition metal dissolution and a significant decline in cycle life.

This technology involves adding 2 wt% of TMSPO to the electrolyte and performing an initial formation process at 25°C to create a dense, uniform CEI layer on the cathode surface. Applicable to NCM811-based long-range EV cells and power tool batteries prone to high-temperature operation, it provides the basis for electrolyte design in high-nickel cells that retain 82% capacity after 50 cycles at 60°C.

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Key Features:

• Cathode active material composed of a high-nickel ternary layered oxide, represented by the chemical formula LiNi0.8Co0.1Mn0.1O2
• Electrolyte containing 2 wt% of tris(trimethylsilyl) phosphate (TMSPO) relative to the total weight, with initial formation occurring at room temperature
• Phosphate functional group of TMSPO that forms a CEI layer on the high-nickel cathode surface during initial formation to suppress electrolyte side reactions
• Silyl functional group of TMSPO that removes fluorine-based substances that accelerate the dissolution of transition metals in high-nickel cathodes

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