Solution-Type Binder for Silicon Anodes With Low Electrolyte Swelling
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Solution Overview
Problem
Conventional binders for lithium-ion battery negative electrodes, such as styrene-butadiene rubber (SBR) and polyacrylic acid, face challenges in achieving balanced bonding strength and flexibility, particularly with silicon-carbon electrodes, leading to issues like high internal resistance, poor low-temperature performance, and unstable high-temperature cycling.
Innovation Solution
A solution-type binder is prepared via an aqueous phase seed precipitation polymerization process, using emulsion polymerized latex particles as seeds, and nitrile-based and functional monomers to form copolymers with controlled morphology and high polar functional groups, enhancing stability and interaction with electrode materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If SBR/CMC binder is used, then manufacturing simplicity is maintained, but bonding strength with silicon-carbon electrodes is insufficient
Solution Approach 1:
The patent changes the chemical composition parameters of the binder by incorporating polyacrylic acid and carboxymethyl cellulose in specific ratios (polyacrylic acid content: 0.1-5 wt%, CMC content: 1-10 wt%). This parameter optimization enhances the polar functional groups content, improving bonding strength with silicon-carbon electrodes while maintaining manageable formulation complexity
Solution Approach 2:
The patent creates a composite binder system combining polyacrylic acid and carboxymethyl cellulose. This composite approach leverages the high polar functional groups content of polyacrylic acid for strong electrode adhesion while utilizing CMC's thickening and dispersing properties, achieving synergistic effects that improve both bonding strength and manufacturing feasibility
2Strength
If polyacrylic acid based binder is used, then bonding strength is improved, but low-temperature performance deteriorates
Solution Approach 1:
The patent optimizes the molecular weight and composition parameters of polyacrylic acid within specific ranges. By controlling the carboxyl group content and polymer chain structure, the binder maintains strong adhesion at low temperatures while preventing electrolyte freezing, thus improving low-temperature reliability without sacrificing bonding strength
3Productivity
If emulsion polymerization method is used, then production efficiency is improved, but high-temperature cycling performance deteriorates
Solution Approach 1:
The patent changes the polymerization parameters by using solution-type polymerization instead of emulsion polymerization. This approach produces binders with controlled molecular weight distribution and reduced oligomer residues, which improves high-temperature cycling stability while maintaining acceptable production efficiency through optimized reaction conditions
Solution Approach 2:
The patent applies local quality control by ensuring uniform distribution of polyacrylic acid chains and functional groups within the binder matrix. This homogeneous structure, achieved through solution-type polymerization, prevents localized degradation at high temperatures and improves cycling performance while maintaining production feasibility
4Strength
If conventional precipitation polymerization is used, then bonding strength is improved, but product batch stability deteriorates
Solution Approach 1:
The patent implements feedback control in the precipitation polymerization process by continuously monitoring reaction conditions (temperature, monomer conversion, polymer precipitation rate) and adjusting parameters accordingly. This feedback mechanism ensures consistent molecular weight distribution and bonding strength across different production batches, improving product stability while maintaining high bonding 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 binder improves flexibility, reduces internal resistance, and enhances bonding strength and dispersion, resulting in improved electrochemical stability and reduced electrolyte swelling, thereby optimizing battery performance across temperature ranges.
Implementation Method 1
polyacrylic acid based binders can form hydrogen bonding interactions with the surface of silicon negative electrodes, improving the dispersion and adhesion to the negative electrode material
Implementation Method 2
there exists complexation and decomplexation between the polar functional groups and lithium-ions, which can promote lithium-ions conduction
Implementation Method 3
It precipitates in water and becomes salt dissolved in water after adding alkali solution
Data Source
AI summary
The present application discloses a solution type binder, a preparation method therefor, and a use thereof. The preparation of the binder mainly comprises the following steps: first, carrying out emulsion polymerization on an alkyl acrylate monomer, a nitrile monomer, and a functional monomer acid to prepare latex particles, wherein the latex particles are uniform in particle size and rich in polar functional groups, and can be used as seeds for precipitation polymerization; using the nitrile monomer, the functional monomer acid, acrylamide, etc. as precipitation polymerization monomers, and depositing an oligomer, which is generated by reaction, on the surface of a seed polymer under the action of hydrogen bonds and hydrophobicity to form precipitation particles; and neutralizing the precipitation particles and alkali liquor to obtain the solution type binder. The solution type binder provided by the present application is suitable for a negative electrode of a lithium ion battery, and has high bonding strength, a low electrolyte solution swelling degree, certain processing flexibility, a simple preparation process, and good batch stability.