Sheet-Shaped Ferric Phosphate With High Fe/P Ratio Control
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Solution Overview
Problem
Existing iron methods for preparing ferric phosphate face challenges with low iron-to-phosphorus ratios (approximately 0.96 to 0.98) and difficulty in controlling morphology and size uniformity, leading to non-uniform particle sizes and specific surface areas that affect the performance of lithium iron phosphate cathodes.
Innovation Solution
A method involving the preparation of sheet shaped ferric phosphate with a high iron-to-phosphorus ratio (>0.99) is developed, utilizing a controlled oxidation process with seed crystals and specific dropwise addition times to achieve regular morphology, uniform size, and moderate specific surface area, followed by filtration, washing, drying, and sintering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the conventional iron method is used to prepare ferric phosphate, then the process flow is short and equipment investment is low, but the iron-to-phosphorus ratio is low (0.96-0.98) and morphology control is difficult
Solution Approach 1:
The patent applies preliminary action by first preparing ferrous dihydrogen phosphate solution and then controllably oxidizing it to form ferric phosphate. The oxidation process is divided into controlled stages with specific temperature profiles (heating to 80-90°C, holding, then cooling) to ensure high Fe/P ratio. This preliminary preparation and controlled oxidation sequence enables precise compositional control while maintaining process simplicity.
Solution Approach 2:
The patent employs parameter changes by precisely controlling oxidation parameters including temperature (80-90°C range), oxidation time (1-3 hours), and pH conditions during the oxidation of ferrous dihydrogen phosphate. By optimizing these parameters, the method achieves high iron-to-phosphorus ratio (0.98-1.02) while keeping the process flow short and equipment requirements minimal.
2Ease of manufacture
If the conventional iron method is used to prepare ferric phosphate, then the process flow is short and equipment investment is low, but the particle size and specific surface area are non-uniform
Solution Approach 1:
The patent applies preliminary action by first preparing ferrous dihydrogen phosphate solution with controlled concentration (0.5-2.0 mol/L) and then controllably oxidizing it. The oxidation process includes preliminary heating to 80-90°C, controlled oxidation for 1-3 hours, and subsequent cooling to room temperature. This systematic preliminary preparation and controlled transformation sequence ensures uniform particle morphology and size distribution while maintaining simple process flow.
Solution Approach 2:
The patent employs parameter changes by precisely controlling oxidation parameters including temperature (80-90°C range), oxidation time (1-3 hours), and pH conditions during the oxidation of ferrous dihydrogen phosphate. By optimizing these parameters, the method achieves uniform particle size distribution and specific surface area (3.5-6.5 m²/g) while keeping the process flow short and equipment requirements minimal.
3Ease of manufacture
If ferric phosphate with low iron-to-phosphorus ratio is used, then the preparation process is simple, but the energy density of the cathode material is reduced
Solution Approach 1:
The patent employs parameter changes by precisely controlling oxidation parameters including temperature (80-90°C range), oxidation time (1-3 hours), and pH conditions during the oxidation of ferrous dihydrogen phosphate. By optimizing these parameters, the method achieves high iron-to-phosphorus ratio (0.98-1.02) which directly translates to higher energy density in the resulting lithium iron phosphate cathode material, while maintaining simple preparation process and minimal equipment requirements.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The resulting ferric phosphate exhibits improved processability and energy density, enhancing the performance of lithium iron phosphate cathodes and secondary batteries by facilitating lithium ion migration and reducing ball milling time.
Implementation Method 1
heating the first ferrous dihydrogen phosphate solution to a first temperature, then dropwisely adding an oxidant for a first dropwise addition time period, and holding the first temperature after the dropwise addition is completed, to obtain a seed crystal slurry
Implementation Method 2
adding the seed crystal slurry into the second ferrous dihydrogen phosphate solution and heating to a second temperature, then dropwisely adding the oxidant for a second dropwise addition time period
Data Source
AI summary
In one aspect, a sheet shaped ferric phosphate with a high iron-to-phosphorus ratio has a sheet shaped structure with an iron-to-phosphorus (Fe/P) ratio greater than 0.99, a ratio of length to width to thickness of the sheet shaped structure is (105 to 130):(90 to 100):(10 to 12), 3.5 m2/g≤a specific surface area of the sheet shaped structure≤6.5 m2/g, and a particle size of the sheet shaped structure<35 μm.