Bimodal Cathode Particle Composition for Higher Sodium-Ion Density
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Solution Overview
Problem
The compacted density of sodium iron phosphate pyrophosphate (Na4Fe3(PO4)2(P2O7) remains relatively low, limiting its potential as a positive electrode material for sodium-ion batteries.
Innovation Solution
A positive-electrode active material is composed of first and second active particles with specific size distributions and ratios, where the first particles are smaller than the second particles, allowing them to fill voids formed by the larger second particles, thereby increasing the compacted density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of stationary object
If a single particle size of sodium iron phosphate pyrophosphate is used, then the material structure is simple, but the compacted density remains relatively low
Solution Approach 1:
The patent segments the particle population into two distinct size groups: first active particles with smaller size (D50: 5-15 μm) and second active particles with larger size (D50: 20-40 μm). This segmentation allows small particles to fill voids between large particles, increasing compacted density from conventional levels to 2.1-2.3 g/cm³ while maintaining manageable structural complexity through controlled bimodal distribution
Solution Approach 2:
The patent implements a nested arrangement where smaller first active particles are positioned within the interstitial voids formed by larger second active particles. This nesting configuration maximizes space utilization and achieves high compacted density by ensuring that no significant void space remains unfilled, effectively creating a hierarchical particle packing structure
2Volume of stationary object
If smaller particles are used to increase compacted density, then the void filling capability improves, but the particle size distribution becomes more complex to control
Solution Approach 1:
The patent specifies precise parameter ranges for particle size distribution to optimize both void filling and manufacturability. First active particles have D50 of 5-15 μm with D90/D10 ratio of 1.2-1.8, while second active particles have D50 of 20-40 μm with D90/D10 ratio of 1.5-2.0. These controlled parameter variations ensure adequate void filling capability while maintaining manufacturing precision through defined size distributions
Solution Approach 2:
The patent creates a composite particle system combining two distinct particle populations with different size characteristics. The first active particles (smaller) and second active particles (larger) form a composite structure where each component contributes specific functions: small particles provide void filling while large particles provide structural framework, achieving high compacted density with controllable manufacturing parameters
Data Source
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AI summary
Provided are a positive-electrode active material, a preparing method thereof, and a battery. The positive-electrode active material of the present disclosure includes first active particles (100) and second active particles (200). An average particle size of the first active particles (100) is smaller than an average particle size of the second active particles (200); in a particle size distribution curve of the positive-electrode active material, the first active particles (100) have a first peak (10), the second active particles (200) have a second peak (20), and a ratio r1 of a value of a peak top of the first peak (10) to a value of a peak top of the second peak (20) satisfies: 0.3≤r1≤0.8.