LFP Battery Recycling via Selective Leaching and Deep Purification
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Solution Overview
Problem
Existing methods for recycling lithium iron phosphate batteries struggle with high-impurity materials, leading to complex processes, low economic benefit, and environmental issues due to ineffective impurity removal and phase transition during leaching, especially in industrial-scale recycling.
Innovation Solution
A method involving selective leaching of lithium and impurities, followed by deep purification using dilute strong acid and alkaline solutions to prevent phase transition, resulting in high-purity iron phosphate-graphite slag for battery-grade synthesis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional acid dissolution methods are used on iron phosphate slag, then lithium recovery is achieved, but iron phosphate leaching becomes difficult and impurities fail to dissolve
Solution Approach 1:
The patent changes the pH parameter during leaching by adding alkaline solution to maintain pH between 1.5-3.0, preventing iron phosphate phase transition and keeping it in a leachable state while allowing impurity dissolution
Solution Approach 2:
The patent performs preliminary impurity removal by dissolving impurities in the iron phosphate slag before main leaching, using controlled acidification followed by alkaline treatment to remove aluminum and copper impurities while preserving iron phosphate structure
2Manufacturing precision
If metal complexing agents or precipitants are added to remove impurities, then impurity removal is achieved, but organic matter and metal impurities are introduced affecting subsequent synthesis
Solution Approach 1:
The patent uses simple, inexpensive reagents (sulfuric acid, sodium hydroxide, ammonium hydroxide) for impurity removal instead of expensive complexing agents, achieving effective purification without introducing harmful organic substances
Solution Approach 2:
The patent uses pH parameter control to selectively dissolve impurities at specific pH ranges, then precipitates them by adjusting pH, achieving separation without complexing agents that would contaminate the product
3Productivity
If high-impurity battery black mass is processed, then industrial-scale recycling is achieved, but the process becomes complex with excessive waste residue
Solution Approach 1:
The patent combines multiple operations into integrated steps: impurity removal and iron phosphate purification are combined in the same leaching system, and lithium recovery is integrated with the impurity removal process, reducing overall process complexity
Solution Approach 2:
The patent converts the high-impurity content from a problem into an advantage by using the impurities as indicators for pH control and utilizing the slag structure itself as the purification medium, eliminating the need for separate complex purification steps
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 achieves high impurity removal efficiency, short process flow, and economic benefit by controlling leaching conditions to maintain the heterosite structure, allowing for efficient recovery of high-purity iron phosphate.
Implementation Method 1
selective leaching: a spent lithium iron phosphate battery material is selectively leached at 20-65°C using a leaching agent to obtain a leachate and an iron phosphate-graphite slag
Implementation Method 2
at 30-65°C, the iron phosphate-graphite slag obtained in step (1) is subjected to a first reaction in a dilute strong acid solution
Implementation Method 3
an alkaline solution is added dropwise to a product of the first reaction for a second reaction, to obtain a deeply purified iron phosphate-graphite slag and an impurity-containing filtrate
Implementation Method 4
the leaching conditions are optimized to prevent crystal phase transformation of iron phosphate
Data Source
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AI summary
Provided is a method for recycling spent lithium iron phosphate batteries. The method comprises selective leaching, deep purification, and battery-grade iron phosphate preparation. In the present application, lithium and iron phosphate materials are separated in one step via selective leaching, and the leaching conditions are optimized to prevent crystal phase transformation of iron phosphate, thereby avoiding difficulties in iron-phosphorus leaching and failure of impurities to undergo dissolution; the obtained iron phosphate-graphite slag is used as a raw material for synthesizing iron phosphate and further purified by dilute strong acid and alkaline solution (deep purification), thereby reducing complicated subsequent processes such as liquid-phase impurity removal of phosphorus-iron solution. Finally, the purified iron phosphate-graphite slag is subjected to acid leaching to obtain a high-purity filtrate containing phosphorus and iron, which can be directly used for the synthesis of battery-grade iron phosphate. The entire process features low acid consumption, capability to handle high-impurity battery materials, high impurity element removal efficiency, short process flow, and high economic benefit.