Bimodal Cathode Powder Mix for High-Density Calendaring Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current lithium-ion battery positive electrode materials, such as LiCoO2, face challenges in achieving high energy density and cycle stability due to brittleness and particle breaking during calendaring, leading to increased surface area and side reactions, while materials like NMC struggle with high Ni content causing brittleness and electrode biting issues.
Innovation Solution
A bimodal lithium transition metal oxide powder mixture with a narrow particle size distribution and a combination of large spherical polycrystalline and small monolithic particles, optimized for high pressed density and reduced surface area, is used to enhance energy density and prevent particle breaking and electrode biting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high Ni content NMC material is used to increase capacity and gravimetric energy density, then the theoretical capacity increases, but the material becomes more brittle and prone to particle breaking during calendaring
Solution Approach 1:
The patent divides the positive electrode material into two distinct particle size ranges: small particles (D10-D50: 3-15 μm) and large particles (D50-D90: 15-30 μm). This segmentation allows the small particles to provide high capacity while the large particles provide structural stability and reduce brittleness during calendaring, resolving the contradiction between high capacity and mechanical strength.
2Volume of stationary object
If high pressed density is achieved by increasing calendaring pressure, then electrode density increases, but particle breaking and electrode biting occur more frequently
Solution Approach 1:
The patent changes the particle size distribution parameters by introducing a bimodal distribution with specific D10, D50, and D90 values. This parameter change allows the material to achieve high pressed density (≥3.6 g/cm³) at lower calendaring pressures, reducing particle breaking and electrode biting while maintaining high electrode density.
3Speed
If particle size is reduced to increase surface area for reaction, then reaction kinetics improve, but total surface area increases leading to more side reactions with electrolyte
Solution Approach 1:
The patent segments the particle size distribution into two ranges, with the small particles (D10-D50: 3-15 μm) providing sufficient surface area for good reaction kinetics, while the large particles (D50-D90: 15-30 μm) limit the total surface area to reduce side reactions. This segmentation optimizes the balance between reaction kinetics and side reaction suppression.
4Ease of manufacture
If uniform particle size distribution is used for simplicity, then manufacturing is easier, but pressed density and energy density are reduced
Solution Approach 1:
The patent creates a composite particle size distribution combining two distinct size ranges (small particles D10-D50: 3-15 μm and large particles D50-D90: 15-30 μm). This composite approach achieves high pressed density (≥3.6 g/cm³) and high energy density while remaining manufacturable through conventional processes, overcoming the limitation of uniform particle size distributions.
Data Source
AI summary
A bimodal lithium transition metal oxide based powder mixture comprises a first and a second lithium transition metal oxide based powder. The first powder comprises particles of a material A comprising the elements Li, a transition metal based composition M and oxygen. The first powder has a particle size distribution characterized by a (D90−D10)/D50<1.0. The second powder comprises a material B having single crystal particles, said particles having a general formula Li+bN′−bO2, wherein −0.03≤b≤0.10, and N′=NixM″yCozEd, wherein 0.30≤x≤0.92, 0.05≤y≤0.40, 0.05≤z≤0.40 and 0≤d≤0.10, wherein M″ is one or both of Mn or Al, and E is a dopant different from M″. The first powder has an average particle size D50 between 10 and 40 μm. The second powder has a D50 between 2 and 4 μm. The weight ratio of the second powder in the mixture is between 15 and 60 wt %.