Solid-State Battery Binder Composition for Brittle Sheet Moldability
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Solution Overview
Problem
All-solid-state secondary batteries face issues with moldability and processability due to the brittleness of pressure-molded bodies containing solid electrolytes and active materials, leading to powder fall-off and cracking during production, which affects yield and performance.
Innovation Solution
A binder for all-solid-state secondary batteries comprising a conjugated diene-based copolymer with specific elastic modulus and loss tangent values, along with a liquid medium, enhances adhesiveness and flexibility, improving moldability and cycle life characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a pressure-molded body of a mixture containing solid electrolyte and active material is prepared to increase contact area, then energy density is improved, but moldability deteriorates due to brittleness
Solution Approach 1:
A binder component formed of a polymer compound is introduced as an intermediary substance between the solid electrolyte and active material particles. This binder acts as a mediating material that binds the brittle particles together, enabling the pressure-molded body to maintain structural integrity during handling and processing while preserving the close contact necessary for high energy density.
Solution Approach 2:
The pressure-molded body is formulated as a composite material system consisting of solid electrolyte particles, active material particles, and a polymer binder. This composite structure combines the high-density packing of the inorganic particles with the flexibility and adhesiveness of the organic binder, resolving the contradiction between contact area and moldability.
2Ease of manufacture
If binder component is added to improve moldability, then ease of manufacture is improved, but flexibility deteriorates
Solution Approach 1:
The polymer binder is specifically selected and formulated with controlled molecular weight, glass transition temperature, and composition parameters to achieve optimal balance between moldability and flexibility. By adjusting these physical and chemical parameters of the binder, the pressure-molded body attains sufficient softness for easy molding while maintaining adequate flexibility to prevent cracking during 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 improves adhesiveness and flexibility, resulting in enhanced moldability, lithium ion conductivity, and a satisfactory cycle life characteristic, enabling high yield and performance of all-solid-state secondary batteries.
Implementation Method 1
a solid electrolyte sheet for an all-solid-state secondary battery formed by applying the slurry onto a substrate and drying the slurry
Data Source
AI summary
Provided are a binder for an all-solid-state secondary battery, which is excellent in adhesiveness and flexibility, has a satisfactory cycle life characteristic, and can achieve a high yield, and a binder composition for an all-solid-state secondary battery containing the binder. The binder for an all-solid-state secondary battery according to the present invention includes a conjugated diene-based copolymer (A) that: has an aromatic vinyl unit based on an aromatic vinyl compound and a conjugated diene unit based on a conjugated diene compound; and has a storage elastic modulus (G') of 4.0×104 Pa or more and 2.0×105 Pa or less and a loss tangent (tan6) of 0.10 or more and 0.80 or less, which are measured using a dynamic viscoelasticity-measuring apparatus under conditions of a measurement temperature of 25°C, a frequency of 0.1 Hz, and a strain amount of 1%.