Bipolar Electrode Cathode Particle Structure for Lower Resistance
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Solution Overview
Problem
Bipolar electrodes experience increased resistance and durability issues due to insufficient contact between cathode active materials and conductive materials, leading to complex current paths and reduced performance.
Innovation Solution
A bipolar electrode design incorporating a first cathode active material with a larger particle size and a second cathode active material with a smaller particle size, where the particle size ratio and distribution are optimized to enhance conductive paths and reduce resistance, while maintaining thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If bipolar electrode structure is used to improve energy density, then energy density is improved, but contact among cathode active materials is insufficient leading to increased resistance
Solution Approach 1:
The patent applies particle size distribution control as a parameter change to resolve the contradiction. By optimizing the particle size distribution of cathode active materials to satisfy specific mathematical relations (D150/D250 ratio and span value constraints), the invention ensures sufficient contact between particles while maintaining the bipolar electrode structure's energy density advantages. This parameter optimization creates effective conductive paths without increasing resistance.
Solution Approach 2:
The patent uses composite cathode active materials with controlled particle size distributions. By combining particles with different size characteristics that satisfy the specified mathematical relationships, the invention creates a composite structure where smaller particles fill gaps between larger particles, ensuring continuous conductive paths and sufficient contact while maintaining high energy density.
2Ease of manufacture
If cathode and anode are pressed simultaneously in bipolar electrode, then manufacturing is simplified, but cathode is not sufficiently pressed reducing contact
Solution Approach 1:
The patent compensates for insufficient pressing by optimizing particle size distribution parameters. The controlled D150/D250 ratio and span value constraints ensure that even with simultaneous pressing of cathode and anode, the cathode active materials achieve sufficient contact through their optimized size relationships, where smaller particles naturally fill gaps and create conductive paths.
3Reliability
If particle size is reduced to improve contact, then contact is improved, but thermal stability deteriorates
Solution Approach 1:
The patent applies controlled parameter changes in particle size distribution to balance contact quality and thermal stability. By constraining the D150/D250 ratio and span value, the invention ensures sufficient contact through optimized particle size relationships while preventing excessive fine particle content that would compromise thermal stability. The mathematical constraints create an optimal balance point.
Solution Approach 2:
The patent applies local quality optimization by controlling the distribution of different particle sizes in specific proportions. The smaller particles (with D250 satisfying the mathematical relation) are concentrated in regions where they can effectively fill gaps and create conductive paths, while the overall distribution maintains thermal stability by limiting fine particle content through the span value constraint.
Data Source
AI summary
In the bipolar electrode, a cathode active material layer, an electrode current collector, and an anode active material layer are provided in this order, the cathode active material layer includes a first cathode active material and a second cathode active material having a layered crystal structure, the first cathode active material has a number-based first particle size distribution, the second cathode active material has a number-based second particle size distribution, and the first cathode active material and the second cathode active material satisfy the following relationship (1): 1.5<(D150/D250)≤15 (1). In Expression (1), D150 indicates a particle size having an integrated value of 50% in the first particle size distribution, and D150 has a unit of μm, and in Expression (1), D250 indicates a particle size having an integrated value of 50% in the second particle size distribution, and D250 has a unit of μm.