Core-Shell Cathode Precursor Balancing Porosity and Particle Strength
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Solution Overview
Problem
Existing lithium-metal composite oxides with high porosity or complex structures face issues with reduced particle strength and insufficient durability, leading to inadequate battery performance.
Innovation Solution
A precursor and intermediate for a positive electrode active material are developed, featuring secondary particles with a core-shell structure, where the core has a porous structure and the shell is solid, composed of metal composite hydroxides or oxides with specific compositions and properties, enhancing particle strength while maintaining favorable battery characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high porosity or complex particle structure is used to improve battery characteristics, then the specific surface area and electrolyte penetration are improved, but the particle strength and durability are reduced
Solution Approach 1:
The particle structure is segmented into distinct functional zones: a porous core region for electrolyte penetration and reaction, and a solid shell layer for mechanical strength. This segmentation allows each region to independently fulfill its specific function without compromising the other.
Solution Approach 2:
Different regions of the particle are assigned different structural qualities: the core has high porosity (0.3-0.6 ml/g) to facilitate electrolyte access, while the shell has low porosity (0.01-0.05 ml/g) to provide mechanical protection. This local differentiation resolves the contradiction between penetration and strength.
2Productivity
If the specific surface area is increased to improve reaction efficiency, then the battery output characteristics are improved, but the particle strength is reduced
Solution Approach 1:
The specific surface area is optimized in the core region (5-15 m²/g) to enhance reaction efficiency, while the shell region maintains sufficient thickness to preserve particle strength. This local optimization allows high productivity without sacrificing structural integrity.
Solution Approach 2:
The particle functions as a composite structure combining a porous core material for high surface area reactivity with a dense shell material for mechanical strength, achieving both high productivity and durability simultaneously.
3Ease of operation
If a porous structure is created to enhance electrolyte penetration, then the reaction resistance is reduced, but the particle durability is insufficient
Solution Approach 1:
The particle is segmented into a porous core for electrolyte penetration and a solid shell for durability protection, allowing each function to be optimized independently in its designated region.
Solution Approach 2:
The solid shell acts as a protective cushion that prevents particle degradation and maintains structural integrity during cycling, compensating for the potential weakness introduced by the porous core structure.
Data Source
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AI summary
Provided is a precursor and an intermediate for obtaining a positive electrode active material for a lithium ion secondary battery excellent in particle strength while maintaining favorable battery characteristics. The precursor of a positive electrode active material for a lithium ion secondary battery, the positive electrode active material including a lithium-metal composite oxide composed of secondary particles formed by aggregation of primary particles or both the primary particles and the secondary particles. The precursor is a metal composite hydroxide composed of the secondary particles formed by aggregation of the primary particles or both the primary particles and the secondary particles. The secondary particles each include a core occupying an inside of the secondary particle and a shell section surrounding the core and covering its outside. The core has the porous structure and the shell section has the solid structure. The metal composite hydroxide contains nickel, manganese, and cobalt, and has a pore volume of 0.2 to 0.5 ml/g and an average pore size of 11.5 to 15.0 nm.