Low-Metal Lignin Carbon for Stable Battery Anodes
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Solution Overview
Problem
Existing methods for producing carbon from lignin are inefficient in removing metals, particularly transition metals like iron and manganese, which affect the electrochemical properties and long-term stability of energy storage devices, and are not cost-effective for large-scale manufacturing.
Innovation Solution
A method involving the use of an acidic aqueous solution at 40-100°C to immerse lignin for at least 15 minutes, followed by separation and optional washing, to achieve a metal content below 200 ppm, combined with heat treatment at 300-1500°C to convert lignin to carbon, ensuring low metal content in the final product.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If lignin is precipitated from black liquor through the kraft process, then lignin can be obtained as a cost-efficient renewable resource, but the lignin will contain high metal content that interferes with energy storage applications
Solution Approach 1:
The patent extracts harmful metal impurities from lignin through sequential washing processes. First, lignin is washed with water to remove soluble metals, then treated with acidic solution to remove basic metal oxides and hydroxides, and finally washed with organic solvent to remove remaining impurities. This multi-stage extraction process reduces metal content from hundreds of ppm to below 10 ppm while preserving lignin structure.
Solution Approach 2:
The patent introduces acidic solution (e.g., HCl, H2SO4, or organic acids) as an intermediary washing medium to selectively remove metal impurities from lignin. The acid reacts with basic metal compounds forming soluble salts that can be washed away, while the lignin remains intact due to its aromatic structure resistance to acid degradation under controlled conditions.
2Object-affected harmful factors
If traditional washing methods are used to remove metals from lignin, then some metal removal is achieved, but transition metals like iron and manganese remain that catalyze electrolyte decomposition
Solution Approach 1:
The patent changes the chemical parameters of the washing process by using acidic solutions with controlled pH (typically pH 2-4) and specific acid types (mineral acids or organic acids). This parameter change enables selective removal of transition metals through acid-base reactions and complexation, achieving metal content below 10 ppm which is sufficient to prevent catalytic decomposition of electrolyte in energy storage devices.
Solution Approach 2:
The patent performs preliminary acid washing of lignin before carbonization or other processing steps. By removing metal impurities in advance, the lignin is prepared in a state suitable for energy storage applications, preventing subsequent catalytic degradation that would occur if metals remained in the material.
3Object-affected harmful factors
If multiple additional processing steps are added to remove metals from lignin, then metal content decreases, but process complexity and manufacturing cost increase
Solution Approach 1:
The patent combines multiple washing operations into a single integrated process flow. The sequential washing steps (water wash, acid wash, organic solvent wash) are merged into one continuous process where lignin passes through different washing stages without intermediate drying or handling. This integration reduces equipment requirements and operational complexity while achieving thorough metal removal.
Solution Approach 2:
The patent uses parameter changes in the washing process (pH adjustment, temperature control, solvent selection) to achieve efficient metal removal in fewer steps. By optimizing acid concentration and contact time, the process achieves below 10 ppm metal content without requiring excessive washing stages, thus balancing effectiveness with process simplicity.
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 effectively reduces metal content in lignin to suitable levels for energy storage applications, enhancing electrochemical properties and long-term cycling performance while being compatible with large-scale manufacturing.
Implementation Method 1
immersing the lignin in the acidic aqueous solution for at least 15 minutes, wherein the temperature of the acidic aqueous solution during the immersion is in the range of from 40° C. to 100° C., to remove metals from lignin to the acidic aqueous solution
Implementation Method 2
subjecting the lignin to heat treatment at one or more temperatures in the range of from 300° C. and 1500° C., wherein the heat treatment is carried out for a total time of from 30 minutes to 10 hours, to obtain carbon
Data Source
AI summary
The present invention relates to a method for producing carbon comprising the steps of: providing lignin having a total metal content of less than 200 ppm to heat treatment at one or more temperatures in the range of from 300° C. and 1500° C. to obtain carbon. The present invention also relates to carbon having a total metal content below 800 ppm; a negative electrode for a secondary battery comprising said carbon as active material; and use of said carbon as active material in a negative electrode of a secondary battery.