LFP Black Mass Separation via pH-Controlled Leaching and Ion Exchange
Find Innovative SolutionsGenerate Solutions
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 waste and decreased battery performance.
Innovation Solution
A method involving alkaline leaching, acid leaching, ion-exchange columns for fluoride and copper removal, and iron precipitation to isolate and recover these materials, achieving high purity iron (III) phosphate and lithium solutions while 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 is achieved, but iron and iron phosphate are discarded as waste
Solution Approach 1:
The recycling process is divided into multiple sequential leaching stages: alkaline leaching to remove aluminium, acid leaching to dissolve iron and lithium, and selective precipitation to isolate iron phosphate. This segmentation allows each valuable material to be recovered in separate steps rather than being discarded together
Solution Approach 2:
The process utilizes controlled pH changes to selectively precipitate different materials. By adjusting pH to specific ranges (alkaline for aluminium removal, then controlled acidification for iron phosphate precipitation), the process selectively recovers iron and iron phosphate while maintaining lithium in solution for later recovery
2Object-affected harmful factors
If conventional processes remove aluminium by changing pH levels, then aluminium is removed, but iron is removed together with aluminium
Solution Approach 1:
Aluminium removal is separated from iron recovery into distinct sequential steps. The alkaline leaching step specifically targets aluminium removal at high pH, while subsequent controlled pH adjustment and iron phosphate precipitation recover iron separately, preventing co-removal
Solution Approach 2:
Different pH conditions are applied at different stages: highly alkaline conditions (pH 12-14) specifically for aluminium removal, then controlled moderate pH (2-4) for iron phosphate precipitation. This localized application of different pH qualities enables selective separation
3Object-affected harmful factors
If conventional processes remove copper by cementation or precipitation, then copper is removed, but iron phosphate is removed with copper
Solution Approach 1:
Copper removal is segmented into a dedicated step using ion-exchange columns after iron phosphate precipitation. This separates copper removal from the iron phosphate recovery process, allowing iron phosphate to be isolated first and copper to be removed subsequently without co-precipitation
Solution Approach 2:
Ion-exchange resin acts as an intermediary to selectively remove copper ions from the leachate after iron phosphate has been precipitated. The resin specifically binds copper while allowing other materials to pass through, enabling selective copper removal without affecting iron phosphate
4Manufacturing precision
If spent LFP batteries are dismantled to separate cathodes before crushing, then material separation is achieved, but the process is labour intensive and time consuming
Solution Approach 1:
The process merges cathode and anode materials into a single black mass feedstock that is processed together through sequential leaching steps. This eliminates the need for separate dismantling and processing of different battery components, significantly reducing time and labour while the chemical processes automatically separate materials based on their dissolution properties
5Loss of substance
If fluoride compounds are present in the recycling process, then lithium hexafluorophosphate is processed, but hydrogen fluoride is generated which is corrosive and damages equipment
Solution Approach 1:
The process converts the harmful fluoride compounds into useful calcium fluoride precipitate by adding calcium sources. The fluoride that would otherwise generate corrosive hydrogen fluoride is instead precipitated as stable, non-corrosive calcium fluoride, eliminating the harmful effect while managing the fluoride content
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, reducing waste and improving the efficiency of LFP battery recycling by isolating iron and lithium while managing impurities, thus enhancing the recycling process and battery performance.
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.