Single-Particle Cathode Morphology for Nickel-Rich Battery Stability
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Solution Overview
Problem
Conventional lithium metal oxides used in positive electrodes of lithium secondary batteries face issues such as particle breakage, poor lithium mobility, and deteriorated lifetime and output characteristics due to high nickel content, leading to increased gas generation and structural collapse.
Innovation Solution
A single particle-based positive electrode material is developed with controlled primary particle shape, characterized by specific ratios of convexity, aspect ratio, and surface roughness, using a lithium nickel-based oxide composition and optionally a coating layer, analyzed through an AI-driven image processing method.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium nickel cobalt manganese oxide with high nickel content is used to improve initial capacity characteristics, then capacity is improved, but structural collapse occurs during charging and discharging leading to increased degradation rate
Solution Approach 1:
The patent applies parameter changes by precisely controlling the nickel content within 80-95 mol% and adjusting the ratios of cobalt and manganese to achieve optimal balance between capacity and structural stability. The sintering temperature is also optimized at 900-950°C to form single particles with desired properties
Solution Approach 2:
The patent uses composite materials by creating lithium nickel cobalt manganese oxide with a specific composition formula Li[Ni0.85-Co0.05-Mn0.10]O2, combining multiple transition metals to achieve both high capacity from nickel and structural stability from cobalt and manganese
2Quantity of substance
If conventional secondary particles with many primary particles are used, then rolling density is improved, but particle breakage occurs during rolling process and cracks form during charge/discharge
Solution Approach 1:
The patent applies segmentation by dividing the particle structure into controlled aggregates of 2-5 primary particles forming single particles, rather than using conventional secondary particles with tens to hundreds of primary particles. This segmentation reduces internal stress and prevents crack formation
Solution Approach 2:
The patent changes the particle morphology parameter by controlling the sintering process to form single particles with specific size distribution (D50: 3-8 μm) and spherical shape, optimizing both rolling density and particle strength
3Reliability
If single particle-based material is used to reduce particle breakage, then lifetime characteristics are improved, but lithium mobility becomes poor and resistance increases
Solution Approach 1:
The patent optimizes particle size parameters by controlling D50 at 3-8 μm and adjusting the size distribution, which balances lithium diffusion distance with particle strength. The sintering temperature is optimized at 900-950°C to achieve desired density and conductivity
Solution Approach 2:
The patent uses composite materials with specific element ratios (Ni: 80-95 mol%, Co: 3-10 mol%, Mn: 1-20 mol%) to enhance electronic conductivity and lithium ion mobility while maintaining structural stability for long cycle life
Data Source
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AI summary
The present invention relates to a positive electrode material comprising a plurality of single-particle-based positive electrode active material particles. The single-particle-based positive electrode active material particles include 1 to 30 primary particles. The ratio of the arithmetic mean of the curvature of the primary particles to the average aspect ratio of the primary particles is at least 0.63 as measured from a segmentation image divided into units of primary particles and obtained by image-processing a scanning electron microscope (SEM) image of the positive electrode material. The curvature is defined by expression 1 below, and the single-particle-based positive electrode active material includes a lithium nickel-based oxide represented by chemical formula 1 below. [Expression 1]: Curvature = Pc/Pr In expression 1, Pr is the actual circumference of each primary particle measured in the segmentation image, and Pc is the circumference of a virtual figure obtained by connecting the outermost points of each of the primary particles measured in the segmentation image. [Chemical formula 1]: Lia[NixCoyM1zM21-x-y-z]O2 In chemical formula 1, M1 includes Mn, Al, or a combination thereof, M2 includes at least one selected from the group consisting of B, Ba, Ce, Cr, F, Mg, Al, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, P, and Sr, 1,0≤a≤1.3, 0.5≤x<1.0, 0<y<0.5, and 0<z<0.5.