Composite Oxide Cathode Powder for Low-Gas Lithium Batteries
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Solution Overview
Problem
Lithium secondary batteries experience battery swelling due to gas generation at the particle interfaces, which is caused by decomposition reactions at new surfaces formed during slight cracks in the lithium metal composite oxide particles, leading to reduced performance and safety concerns.
Innovation Solution
A lithium metal composite oxide powder with secondary particles formed by aggregates of primary particles and independently existing single particles, where the single particles have an average crushing strength exceeding 80 MPa, reducing the likelihood of particle breakage and subsequent decomposition reactions. The powder is represented by the composition formula Li[Lix(Ni(1-y-z-w)CoyMnzMw]O2, with specific ratios of x, y, z, and w, and particle size distributions that enhance the battery's cycle performance and reduce gas generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If secondary particles formed by aggregation of primary particles are used, then battery energy density is improved, but particle breakage occurs at interfaces leading to gas generation
Solution Approach 1:
The patent applies preliminary action by pre-coating the primary particles with a protective layer before aggregation into secondary particles. This protective coating is formed in advance to prevent crack propagation and reduce particle breakage at interfaces during subsequent battery operation, thereby suppressing gas generation while maintaining the high energy density benefits of aggregated structures.
Solution Approach 2:
The patent employs composite materials by creating a multi-component particle structure where primary particles are coated with specific materials before aggregation. This composite structure enhances the mechanical strength of particle interfaces, preventing crack formation and reducing gas generation from electrolyte decomposition, while preserving the high energy density achieved through secondary particle aggregation.
2Object-generated harmful factors
If particle strength is increased to suppress cracks, then gas generation is reduced, but manufacturing complexity increases
Solution Approach 1:
The patent applies parameter changes by optimizing the composition and thickness of the protective coating layer on primary particles. By adjusting these parameters, the particle strength is enhanced to suppress cracks and gas generation, while the manufacturing process remains relatively simple through conventional coating and aggregation techniques, thus avoiding excessive manufacturing complexity.
3Strength
If monodisperse primary particles are used, then breakage and fracture are reduced, but surface area increases leading to more reaction sites
Solution Approach 1:
The patent applies segmentation by dividing the particle structure into hierarchical levels: monodisperse primary particles are segmented and then aggregated into larger secondary particles. This segmentation allows the primary particles to maintain their high strength and resistance to breakage, while the aggregation into secondary particles reduces the total exposed surface area, thereby decreasing the number of reaction sites with the electrolyte and reducing gas generation.
Data Source
AI summary
A lithium metal composite oxide powder including: secondary particles that are aggregates of primary particles, and single particles that are present independently of the secondary particles, wherein the lithium metal composite oxide is represented by composition formula (I), and the single particles have an average crushing strength exceeding 80 MPa:Li[Lix(Ni(1-y-z-w)CoyMnzMw)1-x]O2 (I)wherein M is one or more metal elements selected from the group consisting of Fe, Cu, Ti, Mg, Al, W, B, Mo, Nb, Zn, Sn, Zr, Ga, La and V, −0.1≤x≤0.2, 0≤y≤0.4, 0≤z≤0.4, and 0≤w≤0.1.