LFP Black Mass Recycling via Ion Exchange and Iron Phosphate Precipitation
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Solution Overview
Problem
Conventional recycling methods for lithium iron phosphate (LFP) batteries are inefficient in recovering valuable materials like iron and iron phosphate, and fail to properly handle impurities such as fluoride and aluminium, leading to significant material loss and equipment damage.
Innovation Solution
A method involving alkaline leaching, acid leaching, ion-exchange columns for fluoride and copper removal, and iron precipitation steps to isolate and recover lithium, iron, and other materials from LFP black mass, ensuring high purity and minimizing impurity effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If conventional recycling methods focus on recovering lithium through chemical processes, then lithium recovery efficiency is improved, but iron and iron phosphate are removed together with aluminium and copper impurities, resulting in loss of valuable materials
Solution Approach 1:
The recycling process is divided into distinct stages: alkaline leaching to remove aluminium, acid leaching to dissolve iron and copper, selective precipitation to separate iron from copper, and lithium recovery. This segmentation allows each impurity to be removed at the optimal stage with appropriate chemistry, preventing co-removal of valuable iron and iron phosphate with impurities.
Solution Approach 2:
The process utilizes parameter changes including pH adjustment (alkaline to acidic conditions), oxidation state changes (Fe2+ to Fe3+), and solubility product changes through selective precipitation. These parameter changes enable selective separation of different metals at different stages, achieving high purity recovery of iron, iron phosphate, and lithium without co-removal losses.
2Loss of substance
If conventional processes remove aluminium by changing pH levels, then aluminium removal is achieved, but iron is removed together with aluminium, causing material loss
Solution Approach 1:
Aluminium removal is segmented into a separate alkaline leaching stage performed before acid leaching. This timing separation allows aluminium to be selectively dissolved and removed when pH is high, while iron remains in the solid residue. Subsequent acid leaching then dissolves iron without re-dissolving the already-removed aluminium, preventing co-removal.
Solution Approach 2:
Aluminium is removed as a preliminary action before iron recovery. The alkaline leaching step pre-removes aluminium from the black mass, so that subsequent acid leaching and iron precipitation steps operate on material already depleted of aluminium, eliminating the risk of co-removal and simplifying downstream iron recovery.
3Loss of substance
If conventional processes remove copper by cementation or precipitation with sodium hydroxide, then copper removal is achieved, but iron phosphate is removed with copper, resulting in material loss
Solution Approach 1:
Copper removal utilizes parameter changes including oxidation (Fe2+ to Fe3+ using hydrogen peroxide), pH adjustment to precipitation range, and selective solubility exploitation. Iron phosphate precipitates at controlled pH and oxidation states, while copper remains in solution or is removed separately, preventing co-precipitation and preserving iron phosphate.
Solution Approach 2:
Copper is extracted from the leachate through selective precipitation or cementation after iron has been precipitated as iron phosphate. This sequential extraction ensures copper is removed from the solution phase without affecting the already-precipitated iron phosphate solid, preventing co-removal of valuable iron phosphate with copper impurities.
4Productivity
If manual dismantling is used to separate cathodes from spent batteries, then material separation is achieved, but the process becomes labour intensive and time consuming
Solution Approach 1:
The invention extracts and removes the need for manual dismantling by directly processing the entire spent battery or shredded black mass through chemical leaching. The chemical process selectively dissolves and separates materials based on their chemistry rather than physical separation, eliminating labour-intensive mechanical pre-processing steps while maintaining effective material recovery.
Solution Approach 2:
Manual mechanical dismantling is replaced with chemical leaching processes. Instead of using labour-intensive mechanical separation, the invention uses alkaline and acid leaching chemistry to selectively dissolve and separate aluminium, iron, copper, and lithium based on their different chemical properties, achieving separation without mechanical pre-processing.
5Reliability
If fluoride impurities are not removed from black mass, then processing simplicity is maintained, but fluorine compounds damage recycling equipment and affect purity of extracted elements
Solution Approach 1:
Fluoride removal is segmented into a specific stage within the overall process flow. The alkaline leaching step selectively dissolves aluminium fluoride compounds into the leachate, separating fluoride from the solid residue before acid leaching. Subsequent processing of the leachate removes fluoride through precipitation or ion exchange, protecting equipment downstream from fluoride damage while integrating removal into the existing process sequence.
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
This method effectively recovers valuable materials with high purity (>99.5% iron (III) phosphate) while minimizing the impact of impurities, reducing material loss and equipment damage, and improving the recyclability of LFP batteries.
Implementation Method 1
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
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 the first resin column
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
Implementation Method 5
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
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.