Iron Phosphate Preparation from Waste for Fine Battery-Grade Particles
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Solution Overview
Problem
Existing methods for producing iron phosphate for lithium iron phosphate batteries are costly due to the use of expensive oxidants like hydrogen peroxide and result in large particle sizes that are difficult to crush, affecting the performance of the batteries.
Innovation Solution
A method involving the calcination of iron phosphate waste, dissolution in acid, precipitation with alkali solutions, aging, and calcination to produce basic ammonium iron phosphate with controlled particle size and high tap density, using recyclable waste as a raw material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hydrogen peroxide is used as an oxidant to oxidize divalent iron to trivalent iron, then the oxidation reaction can be achieved, but the production cost increases due to the expensive oxidant
Solution Approach 1:
The patent changes the chemical parameters of the oxidation process by replacing hydrogen peroxide with air as the oxidant and using ferric nitrate as a catalyst. This parameter change maintains the oxidation effectiveness while dramatically reducing the production cost by eliminating the need for expensive chemical oxidants.
Solution Approach 2:
The patent uses air, which is freely available and costs nothing, as the oxidant instead of expensive hydrogen peroxide. The ferric nitrate catalyst is used in small amounts and can be regenerated, making the process economically viable. This replaces expensive consumable oxidants with cheap, readily available alternatives.
2Productivity
If basic ammonium iron phosphate is prepared using conventional methods, then the product can be obtained, but the particle size is large (D50 is large) making crushing difficult
Solution Approach 1:
The patent performs preliminary controlled crystallization during the aging process by adjusting temperature, pH, and aging time parameters. This preliminary action controls the nucleation and growth of crystals, producing fine particles with uniform size distribution before the final drying and calcination steps, thereby avoiding the need for subsequent crushing operations.
Solution Approach 2:
The patent changes multiple process parameters including aging temperature (80-100°C), pH value (1.5-4.5), and aging time (2-10 hours) to control the crystallization process. These parameter changes enable precise control over particle size and morphology, producing uniform fine particles suitable for battery applications without requiring post-processing crushing.
3Ease of manufacture
If divalent iron is present in the raw material, then the iron phosphate can be prepared, but a large amount of hydrogen peroxide is consumed to oxidize the divalent iron
Solution Approach 1:
The patent employs ferric nitrate as a catalyst that enables the oxidation of divalent iron by air. The catalyst facilitates the reaction without being consumed, allowing the system to use inexpensive air instead of expensive hydrogen peroxide. This self-sustaining oxidation process eliminates the need for large amounts of external oxidant addition.
Solution Approach 2:
The patent uses ferric nitrate as an oxidation catalyst that accelerates the oxidation of divalent iron to trivalent iron. This catalytic oxidation allows the process to use air (containing oxygen) as the oxidant instead of requiring strong chemical oxidants like hydrogen peroxide, thereby reducing substance consumption and cost.
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 method produces iron phosphate with small, uniform particle size, high tap density, and controlled morphology, suitable for high-performance lithium iron phosphate batteries, reducing production costs and environmental impact.
Implementation Method 1
subjecting iron phosphate waste to calcination to obtain calcinated waste
Implementation Method 2
dissolving the calcinated waste in an acid solution
Implementation Method 3
stirring a mixed solution of the solution A obtained in step (1) and a first alkali solution, adjusting pH of the mixed solution to acidity for reaction
Implementation Method 4
subjecting the yellow iron phosphate filter cake to aging, slurrying and heating, adding orthophosphoric acid and a second alkali solution thereto for reaction
Implementation Method 5
subjecting the basic ammonium iron phosphate crystal powder to calcination for dehydration
Data Source
AI summary
Disclosed are a preparation method and application of iron phosphate. The preparation method comprises: subjecting iron phosphate waste to calcination, dissolving it in an acid solution, and filtering to obtain filtrate, namely a solution A containing iron phosphorus; stirring a mixed solution of the solution A and a first alkali solution, adjusting pH of the mixed solution to acidity for reaction, and after washing and filtering to obtain second filter residue, namely an amorphous yellow iron phosphate filter cake; subjecting the yellow iron phosphate filter cake to aging and heating, adding phosphoric acid and a second alkali solution for reaction, followed by washing and filtering to obtain third filter residue, namely a basic ammonium iron phosphate filter cake, then drying to obtain basic ammonium iron phosphate crystal powder; and subjecting the basic ammonium iron phosphate crystal powder to calcination for dehydration and cooling to obtain iron phosphate.