Olivine Phosphate Cathode Particle Size Control
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Solution Overview
Problem
Current methods to reduce fine powder and oversized single-crystal particles in olivine phosphate-based positive electrode active materials are inadequate, leading to rapid cycle life degradation and poor cycling performance in secondary batteries.
Innovation Solution
A positive electrode plate with a phosphate-based active material having controlled primary particle size distribution, where primary particles between 80 nm and 180 nm account for less than 10%, and oversized particles are minimized, along with a carbon coating layer, to enhance mechanical and chemical stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional production processes are used to manufacture olivine phosphate-based positive electrode active materials, then production efficiency is maintained, but fine powder particles are generated leading to rapid cycle life degradation
Solution Approach 1:
The patent changes the sintering parameters (temperature, time, atmosphere) to control particle growth and minimize fine powder generation. By optimizing these parameters, the process maintains high production efficiency while producing particles with reduced fine powder content, thereby improving cycle life without sacrificing productivity
Solution Approach 2:
The patent creates composite particle structures where primary particles are aggregated into secondary particles with controlled morphology. This composite structure reduces fine powder generation during processing and improves mechanical integrity, leading to better cycling performance while maintaining efficient production
2Reliability
If cyclone separation devices are used to remove fine powder particles, then fine powder content is reduced to some extent, but separation yield is low and oversized single-crystal particles remain
Solution Approach 1:
The patent extracts and removes fine powder particles through a multi-step process involving classification and separation techniques. By systematically removing fine particles while preserving larger particles, the method achieves effective fine powder reduction with high separation yield, avoiding the limitations of cyclone separation devices
Solution Approach 2:
The patent segments the particle size distribution into different ranges and applies specific treatment to each segment. Fine particles are separated and removed, while oversized single-crystal particles are retained and processed separately, achieving comprehensive particle uniformity improvement without compromising overall separation efficiency
3Device complexity
If oversized single-crystal particles are present in positive electrode active materials, then material structure is simplified, but mechanical integrity deteriorates and cycling performance decreases
Solution Approach 1:
The patent segments oversized single-crystal particles into smaller primary particles that aggregate into secondary particles with controlled size and morphology. This segmentation improves mechanical integrity by reducing internal stresses and preventing particle fracture during cycling, while maintaining structural simplicity through controlled aggregation
Solution Approach 2:
The patent applies different structural characteristics to different size ranges of particles. Primary particles have specific crystallographic orientations and sizes optimized for electrochemical performance, while their aggregation into secondary particles provides mechanical strength. This local quality differentiation achieves both structural simplicity and enhanced mechanical integrity
Data Source
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AI summary
A positive electrode plate, a preparation method thereof, a secondary battery, and an electric apparatus are provided. The positive electrode plate includes a current collector and a positive electrode film layer disposed on at least one side of the current collector, where the positive electrode film layer includes a positive electrode active material, and the positive electrode active material includes a substrate and a carbon coating layer disposed on a surface of the substrate. The substrate has a general formula LizFexMn(1-x-y)MyPO4, where 1≤z≤1.1; 0.5≤x≤1; 0≤y≤0.1; and M is at least one selected from Ti, V, and Mg. At least a portion of the positive electrode active material includes primary particles, and a particle size distribution of primary particles having a primary particle size greater than 80 nm and less than or equal to 180 nm in the positive electrode active material is less than or equal to 10%; and there are no more than 15 primary particles having a primary particle size greater than 1500 nm in a region of (250±5) µm2 in a cross section obtained by cutting an electrode plate prepared from the positive electrode active material. The primary particle size distribution concentration of the positive electrode active material in the positive electrode plate provided by this application is significantly improved, improving the cycling performance of batteries.