Carbon-Coated Single-Crystal Cathode Material for High-Nickel Stability
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Solution Overview
Problem
High nickel-based NCM positive electrode materials face issues with structural instability leading to microcracks, increased surface area reactions, gas generation, and cation mixing, which degrade their performance in lithium-ion batteries.
Innovation Solution
A positive electrode active material composed of single-crystalline particles with a carbon-containing amorphous coating layer is formed through a gas phase process, using carbon-containing gases during calcination to improve surface stability and reduce initial resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If single-crystalline particles are manufactured by calcination at higher temperature, then particle strength is improved and microcracks are reduced, but cation mixing increases leading to increased initial resistance
Solution Approach 1:
The patent changes the chemical composition parameter by introducing a carbon coating layer on the particle surface. This coating layer compensates for the increased initial resistance caused by cation mixing during high-temperature calcination, thereby resolving the contradiction between particle strength improvement and resistance increase.
Solution Approach 2:
The patent creates a composite structure consisting of the single-crystalline particle core and the carbon coating layer shell. This composite material approach allows the interior to benefit from high-temperature calcination (improved strength) while the exterior carbon layer mitigates the adverse effect (initial resistance from cation mixing).
2Quantity of substance
If nickel content is increased to achieve high capacity, then energy density is improved, but particle strength decreases leading to microcracks and increased surface area reactions
Solution Approach 1:
The patent changes the chemical composition by incorporating carbon in the coating layer, which fundamentally alters the surface properties of the high-nickel particles. This parameter change prevents the strength degradation and microcrack formation that would otherwise occur with high nickel content.
Solution Approach 2:
The carbon coating layer acts as an intermediary between the high-nickel particle and the external environment (electrolyte). This intermediary layer protects the particle from mechanical degradation and prevents direct harmful interactions, thereby maintaining particle integrity even with high nickel content.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The carbon-coated single-crystalline particles enhance high-rate output characteristics, maintain discharge capacity, and improve room-temperature and high-temperature life while increasing rolling density.
Implementation Method 1
subjecting the lithium metal oxide to a second calcination under conditions in which a carbon-containing gas is maintained to form a carbon-containing coating layer on a surface of the lithium metal oxide
Data Source
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AI summary
The present embodiments relate to a positive electrode active material, a method for manufacturing the same, and a lithium secondary battery including the same. A positive electrode active material for a lithium secondary battery according to an embodiment includes a metal oxide composed of single-crystalline particles; and a coating layer positioned on a surface of the metal oxide and containing carbon, wherein the coating layer includes an amorphous structure.