Bimodal Cathode Powder Composition for Dense Li-Ion Electrodes
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Solution Overview
Problem
Existing positive electrode materials for lithium-ion batteries face challenges such as high cobalt costs, limited resource availability, brittleness leading to particle breaking, and electrode biting during manufacturing, which affect energy density and cycle stability.
Innovation Solution
A bimodal lithium transition metal oxide powder mixture is developed, comprising a large spherical polycrystalline lithium transition metal oxide and a small monolithic lithium transition metal oxide, with a specific particle size distribution and weight ratio to enhance energy density and reduce particle breaking and electrode biting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high Ni content (≥60 mol %) is used in NMC to increase capacity and gravimetric energy density, then the capacity and gravimetric energy density are improved, but the material becomes more brittle leading to particle breaking during manufacturing
Solution Approach 1:
The patent divides the positive electrode material into two distinct particle size fractions: a first fraction with D50 between 8-20 μm and a second fraction with D50 between 3-6 μm. This segmentation allows the larger particles to provide structural integrity and reduce brittleness, while the smaller particles fill voids to increase density without significantly increasing overall brittleness of the electrode material
Solution Approach 2:
The patent applies the nesting principle by having the smaller second fraction particles occupy the void spaces between the larger first fraction particles. This nested arrangement maximizes the volumetric energy density of the electrode while the larger outer particles provide a protective framework that reduces particle breaking during manufacturing processes
2Volume of stationary object
If high pressed density is achieved to increase volumetric energy density, then the volumetric energy density is improved, but particle breaking and electrode biting occur during the pressing process
Solution Approach 1:
The patent segments the particle size distribution into two fractions with specific D50 ranges. The larger first fraction particles provide structural framework that resists breaking during pressing, while the smaller second fraction particles fill interstitial voids to achieve high pressed density without requiring excessive pressing force that would cause particle breaking
Solution Approach 2:
The patent changes the particle size distribution parameters by defining specific D50 ranges for two fractions and controlling their weight ratios (first fraction: 40-80 wt%, second fraction: 20-60 wt%). This parameter optimization allows achieving high pressed density while maintaining particle integrity during the pressing process
3Volume of stationary object
If LCO is used as positive electrode material to achieve high electrode density and low bulging, then the electrode density and cycle life are improved, but the cobalt cost becomes significant for large batteries
Solution Approach 1:
The patent uses NMC (Lithium Nickel Manganese Cobalt Oxide) as a composite material that combines multiple transition metals. This composite approach reduces cobalt content compared to pure LCO while maintaining good electrochemical performance and electrode density characteristics, thereby reducing material cost for large-scale battery applications
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≤1.5. 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 4.5 μm. The weight ratio of the second powder in the mixture is between 15 and 60 wt %.