Lignin Negative Electrode Additive for Silicon Anode Swelling
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Solution Overview
Problem
The use of silicon-based active materials in negative electrodes of lithium ion secondary batteries leads to significant deterioration due to repeated charging and discharging, primarily due to volume expansion, resulting in decreased battery performance and capacity retention.
Innovation Solution
Incorporating a lignin component with specific ratios of extracted component to methoxy group, total decomposition product yield, and functional group content in the negative electrode additive, which includes lignin derivatives, to enhance the orientation and dispersibility of the additive, thereby stabilizing the electrode structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based active material is used to increase capacity, then battery capacity increases, but volume expansion causes structural deterioration and capacity retention decreases
Solution Approach 1:
Lignin component acts as an intermediary substance between silicon-based active material and electrolyte. It forms a protective interface layer that mediates the interaction, preventing direct contact between electrolyte and silicon, thereby suppressing volume expansion damage while maintaining lithium ion conductivity for high capacity
Solution Approach 2:
The invention changes the chemical composition parameters of the electrode by introducing lignin component with specific extracted component content (0.05 to 2.5 mass%) and methoxy group content (3 to 18 mass%). This parameter change modifies the electrode's physical and chemical properties, enabling it to accommodate silicon's volume expansion while maintaining structural integrity
2Stability of the object's composition
If high content of lignin and carboxymethyl cellulose is used in slurry, then electrode structure is stabilized, but battery performance becomes too low for actual use
Solution Approach 1:
The invention optimizes the chemical parameters of lignin by controlling extracted component content (0.05 to 2.5 mass%) and methoxy group content (3 to 18 mass%). This precise parameter control transforms lignin from a weak binder into a high-performance additive that provides both structural stability and excellent battery performance
Solution Approach 2:
The invention creates a composite electrode structure combining silicon-based active material with specifically modified lignin component and carboxymethyl cellulose. This composite approach synergistically combines the high capacity of silicon with the structural stability of lignin and CMC, achieving both electrode stability and high battery performance
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 lignin component effectively suppresses deterioration and enhances battery performance by maintaining capacity retention and improving the charge-discharge efficiency of silicon-based negative electrodes.
Implementation Method 1
when the silicon particles occlude lithium, the volume of the silicon particles swells to about three to four times, and therefore deterioration progresses due to repetition of charging and discharging
Implementation Method 2
when lithium is inserted into the active material containing silicon, fine cracks are generated in the electrode due to volume expansion
Implementation Method 3
the electrolytic solution enters the fine cracks, and a new coating (SEI layer) is formed
Data Source
AI summary
This negative electrode additive contains a lignin component containing at least a lignin derivative, in which a mass ratio of an extracted component amount to a methoxy group amount per solid content of the lignin component is 0.005 to 0.25, an extracted component amount per solid content of the lignin component is 0.05 to 2.5 mass%, and a methoxy group amount per solid content of the lignin component is 3 to 18 mass%.