3D Binder Composition for Silicon Anodes With Expansion Control
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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 due to active material desorption during charging and discharging.
Innovation Solution
A binder composition comprising a copolymer with specific repeating units and a polymer-type additive containing nitrogen bonded to two or three carbons, forming a three-dimensional structure that enhances mechanical properties and adhesion, thereby 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 polyethyleneimine, which together form a three-dimensional network structure through ionic crosslinking. This composite approach combines the volume suppression capability of polyacrylic acid with the adhesion enhancement of polyethyleneimine, resolving the contradiction between volume stability and adhesion strength.
Solution Approach 2:
The binder composition creates different functional zones: polyacrylic acid provides local volume control through its carboxyl groups, while polyethyleneimine provides local adhesion enhancement through its amine groups. The ionic crosslinking creates a heterogeneous network with regions optimized for different functions, allowing simultaneous achievement of volume stability and strong adhesion.
2Ease of manufacture
If conventional binders are used, then manufacturing is simple, but charge/discharge cycle characteristics deteriorate due to active material desorption
Solution Approach 1:
The invention changes the chemical parameters of the binder system by using ionic crosslinking between polyacrylic acid and polyethyleneimine instead of conventional physical mixing. This parameter change creates a more reliable three-dimensional network structure that maintains adhesion during cycling, while the solution-based application process maintains manufacturing simplicity.
Solution Approach 2:
The ionic crosslinking interaction between polyacrylic acid and polyethyleneimine acts as an intermediary mechanism that creates strong binding without requiring complex manufacturing processes. This intermediary chemical interaction provides the reliability needed for good cycle characteristics while keeping the manufacturing process simple and solution-based.
3Quantity of substance
If silicon-based active material is used to increase charge/discharge capacity, then capacity is significantly increased, but volume expansion reaches up to 300% affecting battery stability
Solution Approach 1:
The three-dimensional crosslinked network formed by polyacrylic acid and polyethyleneimine acts as a flexible binder matrix that can accommodate the large volume changes of silicon-based active material during lithiation and delithiation. This flexible network structure provides mechanical support while allowing the necessary volume expansion, maintaining electrode integrity and battery stability despite the 300% volume change.
Solution Approach 2:
The strong adhesion provided by the polyethyleneimine component prepares the binder system in advance to withstand the extreme volume expansion forces. The ionic crosslinking creates a pre-stabilized network that cushions against the 300% volume change, preventing particle detachment and maintaining electrode structure throughout the charge/discharge cycles.
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 composition effectively suppresses negative electrode expansion and improves charge/discharge cycle characteristics and battery performance by maintaining strong adhesion and stability, even with silicon-based active materials.
Implementation Method 1
the binder composition includes: a copolymer and a polymer-type additive comprising nitrogen (N) bonded to two or three carbons (C) in the repeating unit, wherein the copolymer repeating unit (a) of the following Chemical Formula 1, a repeating unit (b) of the following Chemical Formula 2, a repeating unit (c) of the following Chemical Formula 3, and a repeating unit (d) of the following Chemical Formula 4
Data Source
AI summary
Provided are a binder composition for a secondary battery, a negative electrode including the same, and a secondary battery including the same. More particularly, the binder composition for a secondary battery having a three-dimensional structure, which is prepared by mixing a copolymer having specific repeating units and a polymer-type additive containing nitrogen (N) bonded to two or three carbons (C) in the repeating unit, has excellent mechanical properties and may effectively improve a binding force. The negative electrode and the secondary battery including the binder composition 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.