Lithium Recycling via Nanofiltration for Sodium-Free Purification
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Solution Overview
Problem
Conventional lithium-ion battery recycling methods face challenges in separating pure lithium from sodium contaminants, leading to low recycling yields and high costs due to the difficulty in separating sodium ions from lithium ions.
Innovation Solution
The method involves leaching black mass from lithium-ion batteries using an aqueous solution of an oxidizing agent like ammonium persulfate, followed by nanofiltration and additional purification steps to produce highly purified lithium salts, avoiding the introduction of sodium ions and improving lithium recovery efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional sodium-based reagents are used during leaching steps, then the leaching process is simple and cost-effective, but sodium salts are difficult to separate from lithium salts resulting in low lithium purity and contamination
Solution Approach 1:
The patent extracts and removes sodium ions from the leach solution using ion exchange resins and nanofiltration membranes, separating them from lithium ions to achieve high purity lithium recovery without carrying forward the contamination problem
Solution Approach 2:
The patent introduces ammonium salts as an intermediary leaching reagent instead of sodium-based reagents. Ammonium salts enable effective lithium leaching while avoiding the introduction of sodium ions that are difficult to separate, thus resolving the contradiction between leaching effectiveness and product purity
2Ease of manufacture
If conventional leaching methods are used, then the process is straightforward, but the recycling yield of lithium is low due to difficulty in separating sodium ions from lithium ions
Solution Approach 1:
The patent segments the lithium recovery process into distinct stages: leaching with ammonium salts, filtration, ion exchange, and nanofiltration. This segmentation allows each stage to target specific impurities systematically, improving overall lithium recovery yield while maintaining process clarity
Solution Approach 2:
By using ammonium salts as an intermediary leaching agent, the patent enables straightforward leaching operations while the ammonium ions serve as a temporary carrier that can be easily removed in subsequent steps, thereby improving lithium recycling yield without complicating the overall process
3Manufacturing precision
If ammonium salt oxidizing agents are used for leaching, then sodium contamination is avoided and lithium purity is improved, but the process complexity increases due to additional purification steps
Solution Approach 1:
The patent employs a continuous sequence of purification operations (filtration, ion exchange, nanofiltration) that build upon each other, with each step removing specific impurities. This continuous approach achieves high lithium purity while managing process complexity through systematic rather than random processing steps
Solution Approach 2:
The patent utilizes ion exchange resins and nanofiltration membranes with specific pore structures and selectivities. These porous materials automatically perform selective separation based on ion size and charge, reducing the need for complex mechanical separation equipment and simplifying the overall purification process while maintaining high lithium purity
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 approach achieves a lithium recovery yield of 95% or higher with a purity of at least 99% lithium sulfate, effectively overcoming the sodium contamination issue and enhancing the efficiency of lithium recycling.
Implementation Method 1
leaching black mass from the recycling stream in an aqueous solution of an oxidizing agent
Implementation Method 2
subjecting the leach solution to nanofiltration (NF) to form a nanofiltration permeate and a nanofiltration concentrate
Implementation Method 3
The NF permeate can be further purified, such as with an ion exchange (IX) resin to yield a solution that is at least 99% lithium sulfate
Data Source
AI summary
A recycling method for generating purified lithium salts from a recycling stream of lithium-ion (Li-ion) batteries includes leaching black mass from the recycling stream in an aqueous solution of an oxidizing agent. Delithiated black mass is filtered from the aqueous solution to generate a Li-rich leach solution, which is subjected to nanofiltration to form a nanofiltration permeate from which the purified lithium salt is obtained.