Lithium-Ion Cathode Relithiation Using Reusable Ionic Liquids
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Solution Overview
Problem
Current recycling methods for lithium-based battery cathodes are often destructive, require harsh conditions, and are not environmentally friendly, making them inefficient and costly for relithiating spent cathode materials like NCM (LiNixCoyMnzO2) which suffer from irreversible structural changes due to lithium loss.
Innovation Solution
A method involving mixing delithiated cathode material with a lithium salt and an ionic liquid, heating the mixture to 100° C to 300° C for relithiation, and separating the ionic liquid, which can be reused, allowing for a mild, scalable, and cost-effective recycling process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional relithiation processes are used to restore cathode structure, then the pristine structure and stoichiometry can be achieved, but harsh conditions (high temperature and/or high pressure) are required
Solution Approach 1:
The patent changes the chemical environment parameters by introducing ionic liquids and lithium salts, which enable relithiation to proceed at lower temperatures (100-300°C) compared to conventional high-temperature processes. The ionic liquid acts as a medium that facilitates lithium ion transport and cathode material reconstruction under milder conditions.
Solution Approach 2:
The patent uses ionic liquids as an intermediary substance that mediates the relithiation process. The ionic liquid dissolves lithium salts and facilitates their transfer to the delithiated cathode material, enabling structure restoration without requiring extreme temperatures or pressures that would be needed in direct conventional processes.
2Quantity of substance
If pyrometallurgy or hydrometallurgy is used to recycle cathode materials, then valuable metals can be recovered, but the cathode particle structure is completely destroyed
Solution Approach 1:
The patent applies a selective recovering approach where only lithium is removed and then restored through relithiation, while the cathode particle structure and other valuable metals (Co, Ni, Mn) are preserved. This contrasts with pyrometallurgy and hydrometallurgy that completely decompose and discard the original structure, requiring energy-intensive reconstruction.
Solution Approach 2:
The patent segments the recycling process into distinct steps: (1) delithiation to remove lithium, (2) structure stabilization, and (3) selective relithiation to restore lithium content. This segmented approach allows recovery of lithium while preserving the cathode structure, unlike conventional methods that treat the entire cathode material as a single decomposable unit.
3Object-affected harmful factors
If ionic liquid is used as solvent for relithiation, then the process becomes environmentally friendly with low toxicity, but the ionic liquid must be separated and reused which adds process steps
Solution Approach 1:
The patent implements recovery and reuse of the ionic liquid after the relithiation process. The ionic liquid is separated from the relithiated cathode material (via filtration or decantation) and then reused in subsequent relithiation cycles. This recovering approach reduces the need for continuous ionic liquid production and minimizes waste, offsetting the added separation step complexity with environmental and economic benefits.
Solution Approach 2:
The ionic liquid serves multiple functions: (1) as a solvent to dissolve lithium salts, (2) as a medium to facilitate lithium ion transport to the cathode, and (3) as a recyclable green chemistry reagent. Its ability to perform multiple functions justifies the additional separation step, as the same ionic liquid can be reused across multiple batches, reducing overall process complexity over time.
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 restores the pristine structure and stoichiometry of the cathode material, achieving electrochemical performance comparable to new materials, with the added benefit of low toxicity and recyclability of the ionic liquid, thus addressing environmental concerns and cost-effectiveness.
Implementation Method 1
mixing delithiated cathode material and a lithium salt with an ionic liquid in which the lithium salt is at least partially soluble
Implementation Method 2
heating the initial mixture to a temperature of 100° C. to 300° C. to result in relithiation of the delithiated cathode material
Implementation Method 3
The ionic liquid may be separated from the relithiated cathode material in step (iii) by any suitable means, such as filtering or centrifugation
Data Source
AI summary
A method for relithiating cathode material from spent lithium-based batteries, the method comprising: (i) mixing delithiated cathode material and a lithium salt with an ionic liquid in which the lithium salt is at least partially soluble to form an initial mixture; (ii) heating the initial mixture to a temperature of 100° C. to 300° C. to result in relithiation of the delithiated cathode material; and (iii) separating the ionic liquid from the relithiated cathode material; wherein, in embodiments, the cathode material is a lithium metal oxide, wherein the metal is selected from the group consisting of Ni, Co, Fe, Mn, Al, Zr, Ti, Nb, and combinations thereof, or wherein the cathode material has the formula LiNixMnyCozO2, wherein x>0, y>0, z>0, and x+y+z=1; wherein, in some embodiments, the ionic liquid has a nitrogen-containing cationic portion, such as an imidazolium ionic liquid.