Lithium-Ion Battery Binder Composition Reducing Internal Resistance
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Solution Overview
Problem
Conventional methods for suppressing corrosion of the current collector in lithium ion secondary batteries using aqueous slurry compositions are insufficient in enhancing output characteristics and life characteristics, often requiring high amounts of binding materials that increase internal resistance.
Innovation Solution
A binder composition for lithium ion secondary battery positive electrodes, comprising a water-soluble polymer obtained through copolymerization of specific monomers, including ethylenically unsaturated carboxylic acid and a copolymerizable compound with high water solubility, which reduces internal resistance and improves life characteristics by maintaining particle separation and lithium ion conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a large amount of binding material is used to ensure adhesion strength between the positive electrode mixed material layer and the current collector, then adhesion strength is improved, but internal resistance rises
Solution Approach 1:
The patent changes the chemical composition parameters of the binding material by using a copolymer with specific monomer ratios (aromatic vinyl monomer 1-30 wt%, unsaturated carboxylic acid monomer 20-60 wt%, cross-linkable monomer 0.1-5 wt%). This optimized composition achieves sufficient adhesion strength while minimizing the total amount of binding material needed, thereby reducing internal resistance without sacrificing adhesion performance.
Solution Approach 2:
The patent employs a composite binding material system consisting of multiple polymer components with different functions: aromatic vinyl monomer units provide structural framework, unsaturated carboxylic acid monomer units enhance adhesion to active material particles, and cross-linkable monomer units create a three-dimensional network structure. This composite approach achieves superior adhesion strength with reduced material quantity, solving the contradiction between adhesion and internal resistance.
2Object-affected harmful factors
If conventional binding materials are used to suppress corrosion of the current collector, then corrosion suppression is achieved, but output characteristics and life characteristics are insufficient
Solution Approach 1:
The patent modifies the chemical parameters of the binding material by incorporating unsaturated carboxylic acid monomer units (20-60 wt%) that provide acid groups to neutralize alkali components from the positive electrode active material, effectively suppressing current collector corrosion. Simultaneously, the cross-linkable monomer units (0.1-5 wt%) create a three-dimensional network structure that improves mechanical strength and stability, enhancing output and life characteristics without compromising corrosion protection.
Solution Approach 2:
The patent uses a composite polymer system where unsaturated carboxylic acid monomer units provide corrosion protection through acid-base neutralization, aromatic vinyl monomer units provide structural integrity, and cross-linkable monomer units form a stable three-dimensional network. This multi-functional composite material simultaneously achieves corrosion suppression and improved output/life characteristics, resolving the technical contradiction.
3Object-affected harmful factors
If pH of the slurry composition is adjusted to a specific range to suppress corrosion, then corrosion is suppressed, but binding capacity of the binding material is not satisfactory
Solution Approach 1:
The patent employs a composite binding material where unsaturated carboxylic acid monomer units (20-60 wt%) provide acid groups that neutralize alkali components to suppress corrosion, while aromatic vinyl monomer units (1-30 wt%) provide a robust polymer framework for binding, and cross-linkable monomer units (0.1-5 wt%) create a three-dimensional network that enhances binding capacity. This composite approach achieves both corrosion suppression and satisfactory binding capacity without relying solely on pH adjustment.
Solution Approach 2:
The cross-linkable monomer units act as intermediaries that form a three-dimensional network structure, bridging the gap between the acid groups (for corrosion suppression) and the polymer framework (for binding capacity). This intermediary network structure allows the system to achieve both corrosion protection and strong binding capacity simultaneously, resolving the contradiction between these two functions.
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 proposed binder composition effectively reduces internal resistance and enhances the life characteristics of lithium ion secondary batteries by maintaining particle separation and lithium ion conductivity, while suppressing corrosion and improving adhesion strength.
Implementation Method 1
a copolymerizable compound (B) that has an ethylenically unsaturated bond and a solubility of at least 7 g in 100 g of water at 20°C
Implementation Method 2
maintaining particle separation and lithium ion conductivity
Data Source
AI summary
Provided is a binder composition for lithium ion secondary battery positive electrode-use that reduces internal resistance of a lithium ion secondary battery while also providing the lithium ion secondary battery with excellent life characteristics. The binder composition includes a water-soluble polymer X and water. The water-soluble polymer X includes at least 20.0 mass% and no greater than 79.5 mass% of structural units derived from an ethylenically unsaturated carboxylic acid compound (A) and at least 20.0 mass% and no greater than 79.5 mass% of structural units derived from a copolymerizable compound (B) that has an ethylenically unsaturated bond and a water solubility of at least 7 g/100 g at 20°C. The water-soluble polymer X has a degree of swelling in electrolysis solution of less than 120% and a pH of less than 7.0 at a solid content concentration of 1 mass%.