Crosslinked Silicon Anode Binder for Expansion and Adhesion
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Solution Overview
Problem
Existing binders for silicon-based negative electrode active materials in secondary batteries fail to adequately suppress volume expansion and adhesion, leading to reduced battery stability and performance.
Innovation Solution
A binder comprising a copolymer crosslinked by an aldehyde-group crosslinking agent, with specific repeating units, enhances mechanical properties and adhesion, effectively preventing exfoliation and desorption of the negative electrode active material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a binder such as carboxymethyl cellulose (CMC) and styrene butadiene rubber (SBR) is used to suppress volume expansion, then volume change is partially suppressed, but adhesion is insufficient causing active material desorption
Solution Approach 1:
The invention uses a composite binder system comprising polyacrylic acid and carboxymethyl cellulose (CMC) in a specific weight ratio range (95:5 to 50:50). This composite approach combines the volume suppression capability of CMC with the adhesion properties of polyacrylic acid, resolving the contradiction between volume stability and adhesion strength. The synergistic effect of the composite materials allows simultaneous achievement of both binding functions.
Solution Approach 2:
The invention optimizes the weight ratio parameters of the binder components to achieve the desired balance. By adjusting the proportion of polyacrylic acid and CMC within the specified range, the binder's dual functionality is optimized - sufficient adhesion strength is maintained while volume expansion suppression is enhanced. This parameter optimization resolves the trade-off between the two opposing requirements.
2Quantity of substance
If silicon-based active material is used to increase charge and discharge capacity, then capacity is significantly increased, but volume expansion reaches up to 300% affecting battery stability
Solution Approach 1:
The invention applies beforehand cushioning by using the binder system to pre-compress and constrain the silicon-based active material particles before volume expansion occurs during charging. The binder forms a protective matrix that cushions the material against the 300% volume expansion, maintaining structural integrity and preventing electrode disintegration while allowing the high-capacity silicon material to function.
Solution Approach 2:
The binder creates a flexible binding matrix that can accommodate the large volume changes of silicon-based materials. This flexible shell-like structure maintains adhesion to the active material particles throughout the expansion and contraction cycles, preventing desorption and maintaining electrode stability despite the extreme volume fluctuations associated with high-capacity silicon anodes.
3Duration of action of stationary object
If conventional binders are used to maintain electrode structure, then basic binding is provided, but adhesion strength is insufficient leading to active material desorption during charge and discharge
Solution Approach 1:
The composite binder system combines polyacrylic acid with excellent adhesion properties and CMC with good structural stability. This composite formulation achieves superior adhesion strength that prevents active material desorption during charge-discharge cycles, thereby extending battery life. The synergistic interaction between the two materials provides both strong binding and long-term durability.
Solution Approach 2:
By optimizing the weight ratio parameters of the binder components and controlling the saponification degree of polyacrylic acid (60-100%), the invention achieves optimal adhesion strength that maintains electrode integrity throughout the battery's operational life. This parameter optimization ensures sufficient binding force to prevent desorption while maintaining flexibility for volume changes.
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 binder improves charge/discharge cycle characteristics and battery performance by suppressing negative electrode expansion and active material desorption, even with silicon-based materials, resulting in enhanced stability and capacity retention.
Implementation Method 1
a copolymer which is crosslinked by a crosslinking agent including an aldehyde group
Data Source
AI summary
Provided are a binder for a secondary battery, a negative electrode including the same, and a secondary battery including the same. More particularly, the binder for a secondary battery prepared by reacting a copolymer including specific repeating units and a crosslinking agent including two or more aldehyde groups has excellent mechanical properties and effectively improves a binding force. The negative electrode and the secondary battery including the binder for a secondary battery effectively suppress expansion of a negative electrode to manufacture a secondary battery having excellent charge/discharge cycle characteristics and battery performance.