NCM Cathode Precursor Particle Structure for Low-Gas Li-Ion Cells
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Solution Overview
Problem
Existing positive electrode materials for lithium secondary batteries face issues with reduced lifespan, increased resistance, and gas generation due to large specific surface area and weak particle strength, which affect electrochemical performance and thermal safety.
Innovation Solution
A positive electrode active material precursor with a specific surface area of 25 m²/g and average particle diameter of 2 to 6 µm, composed of nickel, cobalt, and manganese, is used to manufacture a metal oxide with a packing density of 3.1 g/cc, resulting in a medium-particle diameter single-particle structure that improves electrochemical characteristics and reduces gas generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of stationary object
If large-particle positive electrode material is used to increase pole plate density, then packing density is improved, but specific surface area increases causing large contact area with electrolyte and excessive gas generation
Solution Approach 1:
The positive electrode active material is divided into two distinct particle size ranges: small particles (D10-D30) with diameter 3-8 μm and large particles (D70-D90) with diameter 10-20 μm. Each size range serves specific functions - small particles provide high packing density while large particles reduce specific surface area. This segmentation resolves the contradiction by distributing the functions of density and gas control across different particle sizes rather than relying on a single particle size.
Solution Approach 2:
The invention optimizes specific particle size parameters (D10-D30 range of 3-8 μm, D70-D90 range of 10-20 μm) and their distribution to achieve the desired balance. By precisely controlling the particle size parameters and their distribution in the bimodal mixture, the patent achieves high packing density while maintaining low specific surface area, thereby reducing gas generation.
2Volume of stationary object
If small-particle positive electrode material is used to increase pole plate density, then packing density is improved, but particle strength decreases causing particle breakage and reduced battery life
Solution Approach 1:
The patent segments the particle population into small particles (3-8 μm) and large particles (10-20 μm) with distinct functional roles. The large particles provide mechanical strength and structural integrity, preventing the particle breakage that would occur with small particles alone, while the small particles contribute to high packing density. This segmentation allows the system to achieve high density without sacrificing reliability.
Solution Approach 2:
The positive electrode active material functions as a composite system combining two different particle size ranges in specific proportions (small particles: 20-40 wt%, large particles: 60-80 wt%). This composite approach allows the system to exhibit properties of both components - the high density contribution from small particles and the high strength contribution from large particles - thereby resolving the contradiction between density and reliability.
3Quantity of substance
If high Ni content NCM material is used to increase capacity, then energy density is improved, but electrochemical performance deterioration occurs across lifespan, resistance increase rate, and thermal safety
Solution Approach 1:
The patent optimizes the particle size parameters (D10-D30: 3-8 μm, D70-D90: 10-20 μm) and their distribution in the bimodal structure to resolve the contradiction associated with high Ni content. The controlled particle size distribution mitigates the negative electrochemical effects of high Ni content by reducing specific surface area and improving structural stability, thereby maintaining reliability while achieving high capacity.
Data Source
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AI summary
A positive electrode active material precursor for a lithium secondary battery according to an embodiment of the present disclosure includes metal hydroxide. The positive electrode active material precursor has a specific surface area of 25 m2/g or more.