Battery Electrode Binder Composition for Expansion-Resistant Adhesion
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Solution Overview
Problem
Existing binders for non-aqueous secondary batteries fail to meet the demands for higher output, higher capacity, and longer service life, as they do not effectively maintain the binding properties between electrode active materials and current collectors during expansion and contraction, leading to decreased discharge capacity.
Innovation Solution
A binder composition for non-aqueous secondary batteries comprising a copolymer with specific structural units derived from monomers with ethylenically unsaturated bonds and carboxyl groups, combined with a tackifier such as hydrogen-added petroleum resin, enhances the binding properties between electrode active materials and current collectors, maintaining electrode integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional binders are used in non-aqueous secondary batteries, then the basic electrode assembly can be formed, but the cycle characteristics and electrode integrity deteriorate due to insufficient binding properties during expansion and contraction
Solution Approach 1:
The invention uses a composite binder system comprising both a polymer component (polyvinylidene fluoride or carboxymethyl cellulose) and a rubber component (polybutadiene or styrene-butadiene copolymer). This composite structure combines the electrochemical stability and adhesion of the polymer with the elasticity and binding strength of the rubber, resolving the contradiction between reliability and binding strength by leveraging the complementary properties of different materials.
Solution Approach 2:
The invention optimizes specific parameters including the glass transition temperature of the rubber component (−60°C to 0°C) and the weight ratio between polymer and rubber components (95:5 to 50:50). By controlling these parameters, the binder maintains appropriate flexibility and binding strength across temperature ranges and charge-discharge cycles, improving both cycle characteristics and electrode integrity simultaneously.
2Stability of the object's composition
If the binder composition is optimized for strong binding, then electrode integrity improves, but the discharge capacity and output may be compromised due to increased material complexity
Solution Approach 1:
The invention controls the glass transition temperature of the rubber component within a specific range (−60°C to 0°C) to ensure the binder remains flexible during battery operation. This parameter optimization allows the binder to maintain strong electrode integrity while not interfering with ion transport, thus preserving discharge capacity despite the enhanced binding functionality.
Solution Approach 2:
The binder composition is designed with differentiated local functions: the polymer component provides electrochemical stability and adhesion to the current collector, while the rubber component provides elasticity and binding strength between active material particles. This local quality differentiation allows each component to optimize its specific function without compromising overall electrode performance or discharge capacity.
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 improves the cycle characteristics of non-aqueous secondary batteries by maintaining electrode integrity, enhancing their performance and efficiency.
Implementation Method 1
a binder that fixes the electrode active material layer onto the current collector is contained
Data Source
Figure 1
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Figure 4
AI summary
This binder composition for a non-aqueous secondary battery contains a copolymer and a tackifier, the copolymer has a first structural unit derived from a monomer (a1) and a second structural unit derived from a monomer (a2), the monomer (a1) is a nonionic compound having only one ethylenically unsaturated bond, and the monomer (a2) is a compound having a carboxyl group and having only one ethylenically unsaturated bond.