NCM Cathode Particle Composition for Thermal Stability and Energy Density
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lithium-nickel-metal composite oxides exhibit low thermal stability due to the instability of their crystal structure during charging, leading to oxygen release and potential thermal degradation.
Innovation Solution
A nickel-cobalt-manganese-based positive electrode active material is formulated with a large particle group and a small particle group, where the large particles are polycrystal aggregate particles with specific crystallite sizes and peak intensity ratios, and the small particles are single or secondary particles with controlled aggregation, enhancing thermal stability and volumetric energy density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium-nickel-metal composite oxide is used as positive electrode active material, then high capacity is achieved, but thermal stability deteriorates due to crystal structure instability during charging
Solution Approach 1:
The positive electrode active material is divided into two distinct particle groups: a large particle group with average particle size of 6.0 μm or more and a small particle group with average particle size of less than 6.0 μm. This segmentation allows each particle group to contribute differently to overall performance, with the large particles providing structural stability and the small particles enhancing capacity.
Solution Approach 2:
Different regions of the positive electrode material have different properties: the large particle group provides thermal stability and structural integrity, while the small particle group contributes high capacity. This local differentiation of material properties resolves the contradiction between overall capacity and thermal stability.
2Volume of moving object
If small particle size is used to increase volumetric energy density, then packing efficiency improves, but surface area increases leading to higher reactivity and reduced stability
Solution Approach 1:
The material is segmented into two particle size groups, allowing the small particle group to improve packing efficiency and volumetric energy density, while the large particle group compensates for the reduced stability that would result from using only fine particles.
Solution Approach 2:
The positive electrode active material is a composite of two different particle size groups with complementary properties. The combination creates a material that achieves both high volumetric energy density through efficient packing and adequate stability through the presence of larger, more stable particles.
3Quantity of substance
If high nickel content is used to increase capacity, then energy density improves, but crystal structure instability increases leading to oxygen release
Solution Approach 1:
By dividing the high-nickel-content material into two particle groups, the patent localizes the high-capacity function in the small particles while the large particles provide a more stable structural framework that suppresses oxygen release, thus resolving the contradiction between energy density and harmful gas generation.
Data Source
AI summary
The present disclosure relates to a nickel-cobalt-manganese-based positive electrode active material comprising a large particle group and a small particle group. An average particle size D50 of the large particle group is greater than an average particle size D50 of the small particle group; the average particle size D50 of the large particle group is from 12 to 20 μm; the large particle group includes polycrystal aggregate particles; each polycrystal aggregate particle includes a secondary particle consisting of a plurality of primary particles aggregated together; each polycrystal aggregate particle has a primary particle size of 2.0 μm or less; a crystallite size of a (003) plane of each polycrystal aggregate particle is from 950 to 1210 Å; a crystallite size of a (104) plane of each polycrystal aggregate particle is from 500 to 750 Å; and a peak intensity ratio I(003)/I(104) of the polycrystal aggregate particles is 2.10 or less.