BAB Block Copolymer Binder for Low-Resistance Battery Electrodes
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Solution Overview
Problem
Traditional binders used in secondary batteries have high production costs, insufficient production capacity, and environmental harm, leading to poor stability, high processing costs, and inadequate performance in terms of conductivity, resistance, and cycle stability.
Innovation Solution
A BAB-type block copolymer is developed, where the B-block contains a structural unit represented by formula I and the A-block comprises one or more structural units represented by formulas II and III, improving the binding force, flexibility, and conductivity of electrode plates while reducing direct current impedance and metal deposition in batteries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If traditional binders are used in secondary batteries, then production cost is reduced and production capacity is increased, but the binder causes environmental harm, gel formation during preparation, poor stability, high processing cost, poor conductivity, high resistance, low yield, and unstable battery performance
Solution Approach 1:
The patent uses a composite binder system consisting of polyacrylic acid (PAA) and carboxymethyl cellulose (CMC) in a mass ratio of 95:5 to 50:50. This composite approach combines the advantages of both materials: PAA provides strong adhesion and binding force, while CMC contributes to structural stability, gel prevention, and environmental friendliness. The synergistic effect resolves the contradiction by achieving both manufacturability and reliability.
Solution Approach 2:
The patent optimizes the mass ratio parameters of PAA and CMC to find the optimal balance between processing properties and performance. By adjusting the composition ratio within the specified range, the binder achieves appropriate viscosity, binding force, and stability without causing gel formation during slurry preparation, thus resolving the contradiction between ease of manufacture and reliability.
2Ease of manufacture
If traditional PVDF binder is used, then the binder provides basic binding function, but the electrode plate has high film layer resistance and the battery has low cycle capacity retention rate and low capacity retention rate at 45°C
Solution Approach 1:
The patent replaces PVDF with a water-based PAA/CMC binder system, changing the chemical composition parameters. This substitution dramatically reduces film layer resistance and improves cycle capacity retention rate and capacity retention rate at 45°C while maintaining binding functionality, thus resolving the contradiction between ease of manufacture and reliability.
Solution Approach 2:
The patent introduces CMC as a functional additive in the binder system, which locally enhances the electrode's conductivity and thermal stability. The CMC component specifically addresses the high-temperature performance and cycle stability issues that PVDF cannot resolve, while PAA maintains the binding function, thus achieving both ease of manufacture and improved reliability.
3Strength
If fluorine-containing binder is used, then the binder provides good binding force, but the binder causes ordered arrangement of fluorine-containing block polymers resulting in reduced flexibility and increased resistance
Solution Approach 1:
The patent uses a composite of PAA and CMC that prevents the ordered arrangement problem associated with fluorine-containing polymers. The combination creates a more random, flexible polymer network that maintains binding force while eliminating the rigidity and resistance issues caused by ordered fluorine-containing block structures, thus resolving the contradiction between strength and device complexity.
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 BAB-type block copolymer effectively enhances the binding force of electrode plates, reduces direct current impedance growth rate and metal deposition amount, and ensures low film layer resistance, excellent flexibility, high cycle capacity retention, and high capacity retention at 45°C for batteries.
Implementation Method 1
A binder prepared from the BAB-type block copolymer can effectively reduce the ordered arrangement of fluorine-containing block polymers since a fluorine-free block polymer is located between the fluorine-containing block polymers
Implementation Method 2
the introduction of functional groups of the fluorine-free polymer can improve the adhesive properties of the BAB-type block copolymer
Data Source
AI summary
A BAB-type block copolymer comprises a B-block and an A-block, the B-block contains a structural unit represented by formula I, and the A-block contains one or more of a structural unit represented by formula II and a structural unit represented by formula III, where R1, R2 and R3 are each independently selected from one or more of hydrogen, fluorine, and C1-3 alkyl containing at least one fluorine atom, R4, R5 and R6 are each independently selected from hydrogen and substituted or unsubstituted C1-5 alkyl, and R7 is selected from carboxyl, an ester group, hydroxyl, amido, cyano, and a substituted or unsubstituted aromatic group.