Lithium Cathode Recycling via Redox Mediator and Soxhlet Extraction

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Solution Overview

Problem

Current methods for recycling lithium-ion battery cathode materials are energy and cost intensive, and existing processes fail to efficiently recover lithium and other valuable elements due to the decomposition of polymer binders like PVDF, which leads to toxic byproducts and structural changes in the cathode material, making it difficult to achieve high-throughput room-temperature recycling.

Innovation Solution

The use of redox mediators, such as 3,5-di-tert-butyl-o-benzoquinone (DTBQ), to facilitate room-temperature relithiation of end-of-life cathode materials by shuttling lithium ions and electrons, along with the employment of a Soxhlet extractor for PVDF binder removal, enabling efficient recycling without the need for high temperatures and minimizing waste generation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of substance

If high temperature processing is used for cathode recycling, then the polymer binder PVDF decomposes and releases toxic gases, but the cathode material loses its physical properties and structure

Engineering Contradiction:

ImprovePVDF binder removalVSAvoidtoxic gas emission

Core Design Contradiction:

Loss of substanceVSObject-affected harmful factors

Solution Approach 1:

The invention changes the temperature parameter from high temperature (which causes PVDF decomposition and toxic gas release) to low temperature processing. This parameter change allows for effective binder removal or transformation without triggering the harmful decomposition reactions that occur at elevated temperatures, thus resolving the contradiction between binder removal and toxic gas emission.

Inventive Principle:

Principle #35Parameter changes

2Loss of substance

If traditional acid bath method is used to extract cobalt, then cobalt recovery is achieved, but the process is very cost and energy intensive

Engineering Contradiction:

Improvecobalt recoveryVSAvoidprocess energy consumption

Core Design Contradiction:

Loss of substanceVSUse of energy by moving object

Solution Approach 1:

The invention replaces the traditional mechanical/chemical acid bath extraction process with an electrochemical approach. By applying electrical potential, lithium ions are selectively extracted from the cathode material through electrochemical reactions, substituting the energy-intensive acid dissolution process with an electro-driven ion transport mechanism that is more energy-efficient and environmentally friendly.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The invention changes the extraction mechanism from chemical dissolution (acid bath) to electrochemical ion transport. This parameter change in the extraction method allows for selective lithium recovery with reduced energy consumption and without the need for large amounts of chemical reagents, thus resolving the contradiction between effective metal recovery and high energy consumption.

Inventive Principle:

Principle #35Parameter changes

3Loss of substance

If PVDF binder is removed at elevated temperature, then binder removal is achieved, but Li inventories of cathode material are reduced and structural changes occur

Engineering Contradiction:

ImprovePVDF binder removalVSAvoidcathode material integrity

Core Design Contradiction:

Loss of substanceVSReliability

Solution Approach 1:

The invention changes the processing temperature parameter from elevated temperature to low temperature. At this reduced temperature, the PVDF binder can be removed or transformed without causing lithium inventory loss or inducing structural changes in the cathode material, thus maintaining cathode integrity while achieving binder removal.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention introduces an intermediary approach where the PVDF binder is not directly thermally decomposed but rather removed through a mediated process at low temperature. This intermediary method prevents direct thermal damage to the cathode structure and lithium inventory, allowing binder removal while preserving cathode material integrity.

Inventive Principle:

Principle #24Intermediary (Mediator)

4Use of energy by moving object

If room temperature process is used for cathode recycling, then energy consumption is reduced, but high throughput capability is not achieved

Engineering Contradiction:

Improveenergy consumptionVSAvoidrecycling throughput

Core Design Contradiction:

Use of energy by moving objectVSProductivity

Solution Approach 1:

The invention introduces dynamic control of electrochemical parameters (voltage, current density, electrolyte composition) to optimize the recycling process. By dynamically adjusting these parameters, the system achieves effective lithium extraction at room temperature while maintaining high throughput capability, resolving the contradiction between low energy consumption and high productivity.

Inventive Principle:

Principle #15Dynamics

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 allows for scalable, cost-effective, and energy-efficient recycling of lithium cathode materials, preserving the structural integrity of the cathode and reducing environmental impact by minimizing toxic byproduct formation, with the potential to lower recycling costs and increase the recyclability of cathode materials.

Implementation Method 1

The use of redox mediators, such as 3,5-di-tert-butyl-o-benzoquinone (DTBQ), to facilitate room-temperature relithiation of end-of-life cathode materials by shuttling lithium ions and electrons

Methodology Applied

Scientific EffectRedox reactions: Redox Reactions