Spherical NaFPP Positive Electrode Embedding for Higher Compacted Density
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Solution Overview
Problem
The compacted density of sodium iron phosphate pyrophosphate (Na4Fe3(PO4)2(P2O7) remains relatively low, which hinders its application in sodium-ion batteries, particularly affecting the use of sodium-ion batteries, the compacted density of sodium iron phosphate pyrophosphate Na4Fe3(PO4)2(P2O7) as a positive electrode material for large-scale sodium-ion batteries, particularly affecting the use of sodium iron phosphate pyrophosphate Na4Fe3(PO4)2(P2O7) as a positive electrode material for large-scale sodium-ion batteries, the compacted density of the existing Na4Fe3(PO4)2(P2O7) remains relatively low.
Innovation Solution
A positive electrode is designed with spheroidal or spherical sodium iron phosphate pyrophosphate particles embedded into a positive current collector, and a positive active layer, the positive active layer is made from sodium iron phosphate pyrophosphate, with a specific relationship between the depth of particle embedding, included angle, and distance to enhance compacted density and prevent cracking during the winding process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If sodium iron phosphate pyrophosphate is used as positive electrode material, then high voltage plateau and high capacity are achieved, but compacted density remains relatively low
Solution Approach 1:
The patent employs spheroidal or spherical positive electrode particles made from sodium iron phosphate pyrophosphate. The spherical morphology allows for better packing efficiency and higher compacted density compared to irregular shapes, while maintaining the material's inherent high voltage plateau and high capacity characteristics.
Solution Approach 2:
The patent embeds positive electrode particles partially into the positive current collector, creating a nested structure where particles are integrated within the collector matrix. This embedding approach increases the effective compacted density by utilizing the space within and around the current collector more efficiently.
2Strength
If particles are embedded into current collector to increase compacted density, then mechanical strength improves, but cracking may occur during winding process
Solution Approach 1:
The patent establishes a quantitative relationship b≤c·α/180° that defines the maximum embedding depth based on particle geometry parameters (c = distance from particle surface to current collector, α = included angle of tangents). By controlling the embedding depth within this mathematical boundary, the structure achieves optimal mechanical strength while preventing excessive stress concentration that would cause cracking during winding.
Solution Approach 2:
The patent proactively prevents cracking by pre-establishing the embedding depth constraint b≤c·α/180° during electrode fabrication. This preliminary control of particle embedding parameters prevents the formation of stress concentration points before the winding process occurs, thereby avoiding fractures that would otherwise happen during subsequent battery assembly.
Data Source
AI summary
A positive electrode includes a positive current collector and a positive active layer. The positive active layer is disposed on a preset surface of the positive current collector. The positive active layer includes positive electrode particles partially embedded into the positive current collector. The positive electrode particles are made from sodium iron phosphate pyrophosphate. The positive electrode particles are spheroidal or spherical. The positive electrode satisfies: b≤c·α/180°, where b denotes a depth to which the positive electrode particles are embedded into the positive current collector, α denotes an included angle between tangents at two points farthest away from each other on an intersection line of the preset surface and a surface of each of the positive electrode particles partially embedded, and c denotes a distance between an intersection of the tangents at two points farthest away from each other on the intersection line and the preset surface.