Cathode active material for lithium secondary batteries containing fluorine and lithium secondary battery comprising the same

Long-life high-nickel cathode material with superlattice ordering induced by grain boundary fluorine coating

This technology controls the nickel oxidation state (Ni2+/Ni3+) by coating the grain boundaries of high-nickel cathode active materials with fluorine and applying heat treatment. It enhances structural stability by creating a long-range ordered superlattice structure through ion site swapping between the lithium and transition metal layers.

While high-nickel cathode active materials offer high capacity, they suffer from side reactions with the electrolyte during repeated charge-discharge cycles. Furthermore, they face limitations in lifespan due to structural collapse caused by H2-H3 phase transitions and microcracks within particles that obstruct lithium-ion pathways.

This technology forms a fluorine-containing coating layer on particle surfaces and grain boundaries using materials like ammonium fluoride, followed by heat treatment to adjust the Ni2+ ratio to 49–130%. This induces regular site swapping between lithium and nickel, creating an ordered structure with alternating mixed layers that prevents layered structure collapse during long-term cycling. Applicable to high-nickel cells for long-range EVs and high-power power tool batteries, it allows for higher nickel content while slowing capacity degradation caused by microcracks.

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Key Features:

• Layered cathode active material comprising a lithium layer consisting only of lithium and a transition metal layer consisting only of transition metals including nickel
• Transition metal layer where the nickel oxidation state is adjusted such that the Ni2+ to Ni3+ ratio increases as the fluorine content increases
• Grain coating layer comprising fluorine at the grain boundary of at least one primary particle in a secondary particle composed of multiple primary particles
• Superlattice formed by alternating layers of a first mixed layer with higher lithium content and a second mixed layer with higher transition metal content

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