Negative Electrode Binder Optimization for Gas Suppression
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Solution Overview
Problem
Non-aqueous electrolyte secondary batteries using aqueous binders face issues with gas generation and moisture retention, leading to decreased battery capacity and lifespan due to uneven reactions and electrolysis of the thickening agent's hydroxyl group.
Innovation Solution
The battery incorporates a negative electrode active material layer with an aqueous binder and a thickening agent containing hydroxyl and ester groups, with specific mass content ratios and a heating treatment to optimize moisture removal, reducing gas generation and maintaining binding strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If an aqueous binder is used in the negative electrode active material layer, then the binding effect is improved and active material ratio is increased, but gas generation increases during initial charge
Solution Approach 1:
The patent changes the chemical composition parameters of the thickening agent, specifying it must contain both hydroxyl groups and ester groups in particular ratios. This compositional parameter change allows the thickening agent to serve dual functions: maintaining binding effectiveness while reducing gas generation through its unique molecular structure that facilitates moisture removal.
Solution Approach 2:
The patent creates a composite system by combining the aqueous binder with a specifically designed thickening agent that contains both hydroxyl and ester groups. This composite material approach allows the thickening agent to provide both binding support and moisture removal functionality, resolving the contradiction between binding strength and gas generation.
2Loss of substance
If a thickening agent with hydroxyl group is used to remove moisture, then moisture removal is improved, but electrolysis of hydroxyl group occurs leading to gas generation
Solution Approach 1:
The patent designs a thickening agent that is a composite molecular structure containing both hydroxyl groups (for moisture removal) and ester groups (which prevent electrolysis). The ester groups act as protective functional groups that suppress the electrolysis reaction while allowing the hydroxyl groups to perform moisture removal, thus resolving the contradiction between moisture removal and gas generation from electrolysis.
Solution Approach 2:
The patent converts the potential harmful effect of hydroxyl group electrolysis into a beneficial outcome by introducing ester groups that prevent the electrolysis reaction. The ester groups act as protective moieties that redirect or suppress the electrolysis pathway, transforming what would be a harmful reaction into a safe moisture removal process.
3Power
If heating treatment is applied to remove moisture and excessive binder, then high load discharge property is improved, but binding strength may be reduced due to thermal decomposition
Solution Approach 1:
The patent optimizes the heating treatment parameters (temperature, time, atmosphere) to achieve sufficient moisture removal while preventing excessive thermal decomposition of the binder. The specific parameter range for heating treatment is determined to balance moisture removal efficiency with binder integrity preservation.
Solution Approach 2:
The patent uses controlled thermal treatment to convert the presence of excessive moisture and binder (which cause gas generation) into a benefit. By applying optimized heating, the excessive moisture and binder are selectively removed through evaporation and decomposition, transforming harmful residual substances into useful outcomes (improved discharge performance) while the thickening agent's unique composition protects the binder from excessive decomposition.
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 effectively suppresses gas generation and maintains battery capacity over long periods by controlling the ratio of carbonyl to hydroxyl peak intensities in the infrared spectrum and optimizing the heating treatment, ensuring stable binding and reduced electrolysis.
Implementation Method 1
By the heating treatment after the coating, thermal decompositions of the thickening agent and the aqueous binder are progressed, and excessive thickening agent and aqueous binder are removed
Implementation Method 2
drying the slurry
Implementation Method 3
electrolysis of the thickening agent's hydroxyl group
Data Source
Figure 1
Figure 2(a)~2(b)
Figure 3(a)~3(b)
AI summary
[Problems] Provided is a means capable of suppressing a reduction in the binding strength of a negative electrode active material layer by optimizing conditions for the suppression of gas generation and moisture removal when an aqueous binder and a thickening agent are used in the negative electrode active material layer in a non-aqueous electrolyte secondary battery or its negative electrode. [Solving Means] Disclosed is a negative electrode for a non-aqueous electrolyte secondary battery including a current collector, and a negative electrode active material layer containing a negative electrode active material, an aqueous binder and a thickening agent having a hydroxyl group and an ester group, in which the content of the aqueous binder in the negative electrode active material layer is 1 to 3% by mass relative to the total amount of the negative electrode active material layer, the content of the thickening agent in the negative electrode active material layer is 0.5 to 1.5% by mass relative to the total amount of the negative electrode active material layer, and the negative electrode active material layer satisfies Formula (1) : 0.10 ≤ X ≤ 1.00 (in the formula, X is a ratio of a peak intensity of an infrared absorption spectrum derived from a hydroxyl group of the negative electrode active material layer to a peak intensity of an infrared absorption spectrum derived from a carbonyl group of ester of the negative electrode active material layer (C=O peak intensity/-OH peak intensity).).