Lithium Iron Phosphate Recycling With Oxidative Alkaline Leaching
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Solution Overview
Problem
Current methods for recycling lithium iron phosphate waste batteries, particularly hydrometallurgy processes, face inefficiencies in aluminum removal, leading to reduced purity of iron phosphate products and high energy consumption, with low reaction rates and incomplete metal recovery.
Innovation Solution
A method involving disassembly, crushing, and screening of lithium iron phosphate waste, followed by alkaline leaching in an oxidizing atmosphere to partially oxidize divalent iron, converting slag to a liquid phase, and using an ionic membrane liquid alkali to remove impurities, resulting in high-purity lithium phosphate and ferroferric oxide.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional hydrometallurgy recycling process is used to recover lithium and iron phosphate, then metal elements can be extracted, but aluminum impurities remain in the acid leaching solution which reduces the purity of the iron phosphate product
Solution Approach 1:
The patent applies preliminary action by performing alkaline leaching to remove aluminum impurities before the main acid leaching process. The lithium iron phosphate waste is first treated with alkaline solution (NaOH) to convert aluminum to soluble aluminate, which is then removed in the filtrate. This preliminary removal of aluminum prevents it from contaminating the subsequent iron phosphate product during acid leaching, thereby improving product purity while maintaining metal recovery.
2Ease of operation
If alkaline leaching is performed without heating and stirring to remove aluminum, then the process is simple, but the reaction rate and reaction degree are low resulting in average aluminum removal effect
Solution Approach 1:
The patent applies parameter changes by optimizing the alkaline leaching conditions: using a controlled temperature range (room temperature to 60°C) and specific pH range (11-13) to enhance aluminum removal efficiency. The patent also controls the alkaline solution concentration (3-6 mol/L NaOH) and contact time (1-6 hours) to achieve high aluminum removal rates while maintaining process simplicity and avoiding excessive energy consumption.
3Manufacturing precision
If high concentration NaOH solution is used for aluminum removal at elevated temperature for extended time, then aluminum removal effect improves, but energy consumption increases
Solution Approach 1:
The patent applies parameter changes by identifying optimal ranges for alkaline leaching conditions that balance aluminum removal efficiency with energy consumption. The patent specifies using 3-6 mol/L NaOH solution at pH 11-13, with temperature controlled at room temperature to 60°C and reaction time of 1-6 hours. These optimized parameters achieve high aluminum removal rates (above 90%) without requiring excessive heating or extended reaction times, thus reducing energy consumption while maintaining effective aluminum removal.
4Quantity of substance
If multiple calcination operations are performed to recover metal elements comprehensively, then resource recovery rate improves, but overall energy consumption increases significantly
Solution Approach 1:
The patent applies the extraction principle by selectively removing aluminum impurities through alkaline leaching before acid leaching, rather than using multiple calcination operations. The aluminum is extracted into the alkaline solution as aluminate, separated by filtration, and the purified solid residue proceeds to acid leaching for metal recovery. This approach achieves comprehensive metal element recovery while avoiding the high energy consumption associated with repeated calcination cycles.
Solution Approach 2:
The patent replaces the thermal-mechanical calcination process with a chemical leaching process. Instead of using high-temperature calcination to separate and recover metals, the patent employs sequential alkaline and acid leaching operations that dissolve and separate metal elements at lower temperatures. This substitution of chemical processes for thermal-mechanical processes significantly reduces energy consumption while maintaining comprehensive metal recovery.
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
Achieves an aluminum removal rate of over 70%, minimal iron loss, and lithium recovery rates above 95%, with significant economic benefits and improved product quality, while reducing energy consumption.
Implementation Method 1
adding the diluted ionic membrane liquid alkali to the lithium iron phosphate powder and stirring to perform a reaction
Implementation Method 2
alkaline leaching in an oxidizing atmosphere to partially oxidize divalent iron, converting slag to a liquid phase
Implementation Method 3
alkaline leaching in an oxidizing atmosphere to partially oxidize divalent iron
Implementation Method 4
filtering to obtain a leachate and a lithium phosphate slag
Implementation Method 5
evaporating the ammonia aqueous solution containing lithium phosphate to obtain lithium phosphate
Data Source
AI summary
The present disclosure discloses a method for recycling lithium iron phosphate waste and its application. The method comprises the following steps: disassembling, crushing, and sieving the lithium iron phosphate waste to obtain a lithium iron phosphate powder; Diluting a ionic membrane liquid alkali, adding the lithium iron phosphate powder to the alkali, stirring under an oxidizing atmosphere in water bath to perform a reaction; filtering a resulting product to obtain a leachate and a lithium phosphate slag; drying the lithium phosphate slag, adding an ammonia aqueous solution to the slag to perform a reaction, filtering to obtain an ammonia aqueous solution containing lithium phosphate and a filter residue; the ammonia aqueous solution containing lithium phosphate is evaporated to obtain lithium phosphate. By adopting the present method of removing aluminum by alkaline leaching under an oxidizing atmosphere, the aluminum content in the obtained lithium iron phosphate slag is 0.08%.