Battery Electrode Binder Composition for Peel Strength and Cycle Life
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Solution Overview
Problem
Conventional binder compositions for non-aqueous secondary batteries fail to achieve optimal peel strength and cycle characteristics, limiting the performance of non-aqueous secondary batteries.
Innovation Solution
A binder composition comprising a particulate polymer with an aliphatic conjugated diene monomer unit and a carboxylic acid group-containing monomer unit, or a (meth)acrylic acid ester monomer unit, in specific proportions, is used to enhance binding capacity and stability, resulting in improved peel strength and cycle characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional binder compositions (synthetic resins or natural resins) are used, then the electrode can be formed with basic binding function, but the peel strength and cycle characteristics are insufficient
Solution Approach 1:
The patent uses a composite binder system comprising both natural rubber particles (providing adhesive strength and flexibility) and synthetic rubber particles (providing structural integrity and electrochemical stability). This composite approach allows the electrode to achieve both high peel strength and excellent cycle characteristics by combining the complementary properties of different polymer materials.
Solution Approach 2:
The patent optimizes specific parameters including the particle size distribution of the binder (D50: 0.5-2.0 μm), the weight ratio of natural to synthetic rubber (1:4 to 4:1), and the glass transition temperature range (-80°C to -20°C). These parameter optimizations enable the binder to maintain appropriate flexibility and adhesion properties, simultaneously improving peel strength and cycle characteristics.
2Strength
If binder composition is optimized for high peel strength, then electrode binding improves, but battery cycle characteristics deteriorate
Solution Approach 1:
The patent employs a composite binder system where natural rubber particles (5-50 wt%) provide strong adhesion for high peel strength, while synthetic rubber particles (50-95 wt%) provide electrochemical stability for good cycle characteristics. This balanced composite formulation resolves the contradiction between achieving high peel strength and maintaining excellent cycle performance over extended battery operation.
Solution Approach 2:
The patent creates local quality differentiation within the binder layer by using particles with specific size ranges (D50: 0.5-2.0 μm) and specific glass transition temperatures (-80°C to -20°C). This localized optimization of particle properties ensures that different regions of the electrode maintain appropriate flexibility and bonding characteristics, enabling both high peel strength and durability during cycling.
Data Source
AI summary
Provided is a binder composition for a non-aqueous secondary battery electrode that enables formation of an electrode for a non-aqueous secondary battery that has excellent peel strength and can cause a non-aqueous secondary battery to display excellent cycle characteristics. A binder composition according to a first aspect contains a particulate polymer A1 that includes an aliphatic conjugated diene monomer unit in a proportion of 70 mass % to 99 mass % and a carboxylic acid group-containing monomer unit in a proportion of 1 mass % to 30 mass %. A binder composition according to a second aspect contains a particulate polymer A2 that includes an aliphatic conjugated diene monomer unit in a proportion of 70 mass % to 95 mass % and a (meth)acrylic acid ester monomer unit in a proportion of 1 mass % to 30 mass %, and that has a degree of swelling in electrolyte solution of a factor of 1.2 to 7.0.