Sulfide Solid Electrolyte Binder Composition for Stable Battery Slurries
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Solution Overview
Problem
Conventional binder compositions for all-solid-state secondary batteries using sulfide inorganic solid electrolytes lack sufficient dispersibility, preservation stability, and ion conductivity in the solid electrolyte-containing layer.
Innovation Solution
A binder composition for all-solid-state secondary batteries containing a polymer with specific (meth)acrylic acid alkyl ester monomer units and an acetic acid ester solvent, with a defined mass ratio and optionally including vinyl cyanide and aromatic monomer units, to enhance dispersibility and preservation stability, and form a solid electrolyte-containing layer with improved ion conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If conventional binder compositions are used for sulfide inorganic solid electrolytes, then the basic structure of solid electrolyte-containing layers can be formed, but dispersibility and preservation stability of slurry composition are insufficient
Solution Approach 1:
The patent changes the chemical parameters of the binder composition by specifying a polymer containing particular (meth)acrylic acid alkyl ester monomer units with defined molecular weight ranges (weight-average molecular weight of 800,000 to 1,500,000) and specific compositional ratios (first monomer unit 40-70 mass%, second monomer unit 30-60 mass%). These parameter changes optimize both dispersibility and preservation stability of the slurry composition containing sulfide inorganic solid electrolyte.
Solution Approach 2:
The patent creates a composite binder system combining a polymer with specific (meth)acrylic acid alkyl ester monomer units and an acetic acid ester solvent. This composite material approach allows the polymer to provide structural integrity while the specific monomer composition and solvent interaction enhance both dispersibility of solid electrolyte particles and preservation stability of the slurry over time.
2Reliability
If conventional binder compositions are used, then solid electrolyte-containing layers can be formed, but ion conductivity of the layers is insufficient
Solution Approach 1:
The patent optimizes the molecular weight parameters of the polymer (weight-average molecular weight specifically in the range of 800,000 to 1,500,000) and the compositional parameters (mass ratios of different monomer units) to achieve optimal ion conductivity. These precise parameter changes allow lithium ions to pass through the binder matrix more efficiently while maintaining ease of manufacture through well-defined formulation specifications.
3Ease of manufacture
If the polymer structure is simplified for ease of manufacture, then production becomes easier, but dispersibility and ion conductivity deteriorate
Solution Approach 1:
The patent specifies precise parameter ranges for the polymer including weight-average molecular weight (800,000 to 1,500,000), compositional ratios (first monomer unit 40-70 mass%, second monomer unit 30-60 mass%), and excludes certain monomer units (no more than 10 mass% of third (meth)acrylic acid alkyl ester monomer units with carbon number 9 or more). These well-defined parameters balance ease of manufacture with optimal ion conductivity and dispersibility performance.
Data Source
AI summary
Provided is a binder composition for an all-solid-state secondary battery that can impart excellent dispersibility and preservation stability to a slurry composition for an all-solid-state secondary battery in which a sulfide inorganic solid electrolyte is used as a solid electrolyte and that can also cause a solid electrolyte-containing layer formed using the slurry composition for an all-solid-state secondary battery to display excellent ion conductivity. The binder composition for an all-solid-state secondary battery in which a sulfide inorganic solid electrolyte is used contains a polymer including a (meth)acrylic acid alkyl ester monomer unit and an acetic acid ester solvent in which a hydrocarbon group having a carbon number of 6 to 9 is bonded to a non-carbonyl oxygen atom. The (meth)acrylic acid alkyl ester monomer unit includes a first (meth)acrylic acid alkyl ester monomer unit in which an alkyl group having a carbon number of 3 to 8 is bonded to a non-carbonyl oxygen atom and a second (meth)acrylic acid alkyl ester monomer unit in which an alkyl group having a carbon number of 1 to 2 is bonded to a non-carbonyl oxygen atom. A mass ratio of the first (meth)acrylic acid alkyl ester monomer unit relative to the second (meth)acrylic acid alkyl ester monomer unit is 2.1 to 2.5.