Electrode Binder Composition for Low-Resistance High-Temperature Cycling
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Solution Overview
Problem
Existing binder materials for electrical storage devices, such as those used in electric cars, lack sufficient repeated charge-discharge characteristics and durability under high temperature conditions, necessitating an improvement in adhesiveness and internal resistance reduction.
Innovation Solution
A binder composition comprising a polymer with specific repeating units derived from conjugated diene compounds, unsaturated carboxylic acids, and aromatic vinyl compounds, formulated to have dynamic viscoelastic properties with peak tan δ values at different temperature ranges, enhancing adhesiveness and electrolyte swelling ratios, and used in a slurry with an active material like silicon for improved electrode performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional binder materials are used, then manufacturing simplicity is maintained, but repeated charge-discharge characteristic and high temperature durability are insufficient
Solution Approach 1:
The invention uses a composite polymer binder consisting of multiple components: a first polymer component (acrylic or methacrylic polymer with specific Tg range), a second polymer component (polymer with carboxyl groups), and optionally a third polymer component (polymer with hydroxyl groups). This composite structure combines the advantages of each component to achieve both excellent repeated charge-discharge characteristics and high temperature durability, resolving the contradiction between reliability and complexity.
Solution Approach 2:
The invention precisely controls the glass transition temperature (Tg) of the first polymer component within -50°C to 0°C and the carboxyl group content of the second polymer component within 0.1-10 mmol/g. By optimizing these parameters, the binder achieves optimal balance between flexibility, adhesion, and stability, thereby improving reliability without excessive complexity.
2Reliability
If binder materials with higher adhesiveness are used, then charge-discharge durability under high temperature is improved, but internal resistance increases
Solution Approach 1:
The invention optimizes the glass transition temperature of the first polymer component to be within -50°C to 0°C, which provides sufficient flexibility at operating temperatures to maintain low internal resistance while ensuring strong adhesion for charge-discharge durability. The controlled carboxyl group content (0.1-10 mmol/g) in the second polymer component further fine-tunes the balance between adhesion and electrical properties.
Solution Approach 2:
The binder composition creates different functional zones: the first polymer component provides flexibility and conductivity throughout the binder matrix, while the second polymer component with carboxyl groups provides localized strong adhesion at the electrode-binder interface. This spatial differentiation of functions resolves the contradiction between adhesion and resistance.
3Productivity
If polymer with higher electrolyte swelling ratio is used, then charge-discharge characteristic is improved, but adhesiveness decreases
Solution Approach 1:
The composite binder system balances swelling and adhesion through component synergy: the first polymer component (acrylic/methacrylic) provides electrolyte swelling capability and charge-discharge performance, while the second polymer component with carboxyl groups provides strong interfacial adhesion. The optional third component with hydroxyl groups further enhances both swelling and adhesion, resolving the contradiction between productivity and strength.
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 significantly reduces internal resistance and enhances charge-discharge durability and adhesiveness, particularly when used with materials like graphite or silicon, leading to improved battery performance and longevity under high temperature conditions.
Implementation Method 1
polymer (A), and a liquid medium (B) wherein, with respect to 100 mass % in total of repeating units contained in the polymer (A)
Implementation Method 2
tan δ (loss elastic modulus/storage elastic modulus) in dynamic viscoelasticity of the polymer (A) has one peak top in a range of from −50° C. or more to less than 15° C. (tan δ1), one peak top in a range of from 15° C. or more to less than 85° C. (tan δ2), and one peak top in a range of from 85° C. or more to 150° C. or less (tan δ3)
Data Source
AI summary
Provided is a binder composition for an electrical storage device, which enables the production of an electrical storage device electrode excellent in repeated charge-discharge characteristic through a reduction in internal resistance and also excellent in charge-discharge durability characteristic under high temperature through an improvement in adhesiveness. The binder composition for an electrical storage device according to the present disclosure includes: a polymer (A); and a liquid medium (B), wherein, with respect to 100 mass % in total of repeating units contained in the polymer (A), the polymer (A) contains: 15 mass % to 60 mass % of a repeating unit (a1) derived from a conjugated diene compound; and 1 mass % to 30 mass % of a repeating unit (a2) derived from an unsaturated carboxylic acid, and wherein tan δ (loss elastic modulus/storage elastic modulus) in dynamic viscoelasticity of the polymer (A) has one peak top in a range of from −50° C. or more to less than 15° C. (tan δ1), one peak top in a range of from 15° C. or more to less than 85° C. (tan δ2), and one peak top in a range of from 85° C. or more to 150° C. or less (tan δ3).