Core-Shell Cathode Active Material for Stronger Li-Ion Particles
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Solution Overview
Problem
Existing lithium-metal composite oxides used in lithium ion secondary batteries face issues with reduced particle strength and durability due to high porosity or complex structures like hollow, porous, or multilayer structures, which affect battery characteristics.
Innovation Solution
A coated lithium-metal composite oxide is developed with a core-shell structure, where the core has a porous structure and the shell is solid, and a coating compound containing lithium and/or tungsten is applied to the surface of primary and secondary particles, enhancing particle strength and lithium ion conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a lithium-metal composite oxide with high porosity or complex structure (hollow, porous, multilayer) is used to improve battery characteristics, then battery capacity and output characteristics are improved, but particle strength and durability are reduced
Solution Approach 1:
The particle is divided into multiple functional regions: a core region with high porosity (20-60%) for lithium ion storage and transport, and a shell section with solid structure (porosity ≤5%) for mechanical strength. This segmentation allows each region to perform its specialized function, resolving the contradiction between capacity and strength.
Solution Approach 2:
The invention uses a composite structure combining porous material (for high capacity) with solid material (for strength), creating a core-shell composite particle. The porous core provides high lithium ion conductivity and capacity, while the solid shell maintains particle integrity and durability, simultaneously achieving both improved battery performance and particle strength.
2Ease of operation
If a porous structure is adopted to increase specific surface area and improve electrolyte flow, then lithium ion movement resistance is reduced, but particle strength is compromised
Solution Approach 1:
Different regions of the particle are assigned different structural qualities: the core has high porosity (20-60%) to facilitate lithium ion movement and electrolyte penetration, while the shell has solid structure (porosity ≤5%) to provide mechanical strength. This local differentiation allows the particle to simultaneously achieve low lithium ion resistance and high strength.
Data Source
Figure 1A~1B
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AI summary
Provided is a positive electrode active material for a lithium ion secondary battery excellent in particle strength while maintaining favorable battery characteristics. The positive electrode active material for a lithium ion secondary battery includes a coated lithium-metal composite oxide that is composed of a lithium-metal composite oxide including secondary particles formed by aggregation of primary particles or both the primary particles and the secondary particles and a coating compound on surfaces of the primary particles and the secondary particles of the lithium-metal composite oxide. The coated lithium-metal composite oxide contains lithium, nickel, manganese, and cobalt. The coating compound contains lithium and/or tungsten. The coated lithium-metal composite oxide has a particle strength of 10 to 50 MPa. The secondary particles each include a core occupying an inside of the particle and a shell section surrounding the core and covering its outside. When the cross section of the secondary particle is observed by imaging, the secondary particle has the conditions of: (a) the core having the porous structure with a porosity of 20 to 60%; (b) the shell section having the solid structure with a porosity of 5% or less; and (c) an overall porosity of the secondary particle of 10 to 50%.