LFP Battery Black Mass Recycling via Selective Leaching and Ion Exchange
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Solution Overview
Problem
Conventional recycling methods for lithium iron phosphate (LFP) batteries are inefficient in separating and recovering valuable materials like iron and iron phosphate, fail to adequately remove impurities such as aluminium and copper, and do not address the corrosive effects of fluorine compounds, leading to significant waste and decreased battery performance.
Innovation Solution
A multi-step process involving alkaline leaching, acid leaching, ion-exchange columns, and iron precipitation to separate and recover valuable materials, including the use of ion-exchange resins to remove fluoride and copper, and controlled pH adjustments to isolate iron phosphate, ensuring high purity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional crushing or shredding methods are used to process spent LFP batteries, then the batteries can be broken down into black mass, but the separation of valuable materials like iron and iron phosphate is inefficient and labour intensive
Solution Approach 1:
The patent segments the recycling process into distinct chemical leaching stages (alkaline leaching followed by acid leaching) that selectively target different materials. This segmentation allows iron phosphate to be separated and recovered in a dedicated precipitation step, avoiding the need for complex mechanical pre-processing and manual separation operations.
Solution Approach 2:
The patent replaces complex mechanical separation systems with a chemical processing system. Instead of using sophisticated shredding and sorting equipment to separate iron phosphate from other black mass components, the invention uses selective chemical leaching and precipitation to achieve automatic separation based on chemical properties.
2Reliability
If conventional pH adjustment methods are used to remove aluminium and copper impurities, then these impurities can be removed, but iron phosphate is also removed together with them, reducing recovery yield
Solution Approach 1:
The patent performs preliminary alkaline leaching before acid leaching to selectively dissolve aluminium and other impurities. This preliminary action removes interfering substances that would otherwise co-precipitate with iron phosphate during subsequent purification steps, enabling selective recovery of iron phosphate without loss.
Solution Approach 2:
The patent uses controlled pH adjustments at different stages with specific pH ranges (alkaline pH for initial leaching, then acidification to pH 1-2 for iron phosphate precipitation). These precise parameter changes enable selective dissolution and precipitation of different materials based on their solubility characteristics at different pH levels, separating iron phosphate from aluminium and copper impurities.
3Quantity of substance
If conventional recycling processes focus solely on lithium recovery, then lithium can be recovered as lithium carbonate, but other valuable materials like iron and iron phosphate are discarded as waste
Solution Approach 1:
The patent creates a multi-functional recycling process that simultaneously recovers multiple valuable materials from black mass. The chemical leaching and precipitation sequence is designed to recover lithium, iron, and iron phosphate in separate streams, transforming a single-purpose lithium recovery process into a comprehensive resource recovery system that captures multiple valuable components.
Solution Approach 2:
The patent systematically recovers materials that would otherwise be discarded. Instead of discarding iron and iron phosphate as waste after lithium extraction, the invention incorporates dedicated recovery steps that precipitate and collect these materials in high purity forms, converting waste streams into valuable products.
4Manufacturing precision
If black mass undergoes chemical separation to remove impurities like fluoride, aluminium and copper, then the purity of recovered materials improves, but the process complexity and number of processing steps increases
Solution Approach 1:
The patent employs a continuous sequence of chemical operations where each step prepares the material for the next. The alkaline leaching, acid leaching, and precipitation steps are arranged in a continuous flow that maintains material in process without intermediate storage or handling, reducing equipment complexity while achieving high purity through cumulative separation effects.
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 process achieves high purity recovery of iron phosphate (>99.5%) and effective removal of impurities, reducing waste and maintaining the quality of recovered materials for reuse.
Implementation Method 1
an alkaline leaching step, comprising adding an alkaline solution with a pH of 13-14 to the black mass to obtain a first leachate and a first solid residue
Implementation Method 2
an acid leaching step, comprising adding a 4M-6M acid solution to the first solid residue for a first duration to obtain a second leachate
Implementation Method 3
passing the second leachate through a first ion-exchange column wherein fluoride ions from the second leachate are retained in a first resin column to obtain a first eluate
Implementation Method 4
passing the first eluate through a second ion-exchange column wherein copper ions from the first eluate are retained in the second resin column to obtain a second eluate
Implementation Method 5
an iron precipitation step, comprising raising the pH of the second eluate to 2.5-5 and adding a quantity of phosphoric acid to the second eluate, to obtain a first solution and an iron (III) phosphate precipitate
Data Source
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AI summary
The invention relates to a method of recycling lithium iron phosphate batteries with the aim of enabling the isolated recovery of elements from black mass. Black mass comprising at least cathodic and anodic components is immersed in a pH 13-14 solution to obtain a first leachate and first solid residue. The first leachate is immersed in a 4-6M acid solution to obtain a second leachate. The second leachate is passed through a first ion-exchange column where fluoride ions are retained and a second ion-exchange column where copper ions are to obtain a second eluate. The pH of the second eluate is adjusted to about 2.5-5 and a quantity of phosphoric acid that is sufficient to achieve an equivalent stoichiometric ratio of ferric iron and phosphate anions is added to obtain a first solution and an iron (III) phosphate precipitate. The first solution is combined with the first leachate to obtain a second solution. The pH of the second solution is adjusted to about 6.5 to a residual precipitate and a lithium solution.