Bimodal Cathode Particle Distribution for Li-Ion Power and Energy
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Solution Overview
Problem
Lithium ion batteries face challenges in achieving high power and energy density in compact sizes due to the trade-offs between large particle active materials, which provide high energy density but suffer from mass transport limitations, and small particle materials, which offer better power density but have lower packing density and cycle life.
Innovation Solution
Cathode formulations comprising lithium ion-based electroactive materials with particle sizes ranging from 1 µm to 6 µm and carbon black with BET surface areas between 130 to 700 m²/g, along with a bimodal particle size distribution, are developed to enhance both power and energy density by combining small and large active particles, thereby improving pulse power and energy density without sacrificing cycle life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If large particle active materials are used, then energy density is improved, but mass transport limitations worsen
Solution Approach 1:
The cathode formulation uses a bimodal particle size distribution with both large particles (5-15 μm) for energy density and small particles (1-5 μm) for mass transport. The small particles are segmented and distributed throughout the electrode to provide efficient lithium ion transport pathways while the large particles maintain high energy density.
Solution Approach 2:
The invention creates a composite cathode structure combining large and small active material particles in specific proportions (30-70 wt% large particles, 70-30 wt% small particles). This composite approach allows the system to simultaneously achieve the energy density benefits of large particles and the mass transport advantages of small particles.
2Power
If small particle active materials are used, then power density is improved, but packing density worsens
Solution Approach 1:
The cathode formulation uses a bimodal particle size distribution with both large particles (5-15 μm) for energy density and small particles (1-5 μm) for mass transport. The small particles are segmented and distributed throughout the electrode to provide efficient lithium ion transport pathways while the large particles maintain high energy density.
Solution Approach 2:
The invention creates a composite cathode structure combining large and small active material particles in specific proportions (30-70 wt% large particles, 70-30 wt% small particles). This composite approach allows the system to simultaneously achieve the energy density benefits of large particles and the mass transport advantages of small particles.
3Power
If small particle active materials are used, then power density is improved, but cycle life worsens
Solution Approach 1:
The invention creates a composite cathode structure combining large and small active material particles in specific proportions (30-70 wt% large particles, 70-30 wt% small particles). This composite approach allows the system to simultaneously achieve the energy density benefits of large particles and the mass transport advantages of small particles.
Solution Approach 2:
The cathode formulation applies different particle sizes in specific locations and proportions to optimize local performance. The bimodal distribution ensures that small particles are available where high power density is needed while large particles provide structural stability for long cycle life, creating local quality variations that resolve the contradiction.
4Power
If high surface area carbon black is used, then electrical conductivity is improved, but manufacturing efficiency worsens
Solution Approach 1:
The invention specifies carbon black with BET surface area in the range of 130-700 m²/g, optimizing the surface area parameter to achieve adequate electrical conductivity while maintaining manufacturability. This parameter optimization resolves the contradiction between conductivity and manufacturing efficiency by finding the optimal range rather than maximizing surface area.
Data Source
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AI summary
Disclosed herein are cathode formulations comprising a lithium ion-based electroactive material having a D50 ranging from 1 μm to 6 μm; and carbon black having BET surface area ranging from 130 to 700 m2/g and an OAN ranging from 150 mL/100 g to 300 mL/100 g. Also disclosed are cathode formulations comprising a first lithium ion-based electroactive material having a particle size distribution of 1 μm ≤ D50 < 5 μm, and a second lithium ion-based electroactive material having a particle size distribution of 5 μm < D50≤ 15 μm. Cathodes comprising these active materials can exhibit a maximum pulse power in W/kg and W/L of the mixture higher than maximum pulse power of the first or second electroactive material individually, or an energy density in Wh/kg and Wh/L of the mixture higher than energy density of the first or second electroactive material individually. The cathode formulations can further comprise carbon black having BET surface area ranging from 130 to 700 m2/g- Also disclosed are cathodes comprising the cathode formulations, electrochemical cells comprising the cathodes, and methods of making the cathode formulations and cathodes.