Negative Electrode Binder Composition for Swelling Suppression
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Solution Overview
Problem
Conventional binder compositions for non-aqueous secondary battery negative electrodes fail to effectively suppress the swelling of the electrode materials during repeated charging and discharging, leading to deterioration in electrical characteristics such as cycle characteristics.
Innovation Solution
A binder composition comprising a particulate polymer that is hydrogenated and densely cross-linked, formed from specific monomer units like ethylenically unsaturated carboxylic acid, aromatic vinyl, and alkylene structural units, which provides a synergistic effect in tracking the expansion and contraction of the negative electrode active material, thereby suppressing swelling and enhancing cycle characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional binder compositions are used, then the negative electrode can be formed, but the electrode swells during repeated charging and discharging leading to deterioration of cycle characteristics
Solution Approach 1:
The invention changes the physical and chemical parameters of the binder by specifying a glass transition temperature range of -50°C to 0°C and controlling the molecular weight (average molecular weight between crosslinks) to 100-10000. These parameter changes enable the binder to maintain appropriate flexibility and binding strength across different temperatures, preventing electrode swelling while maintaining good cycle characteristics.
Solution Approach 2:
The invention uses a composite binder system comprising specific polymers (polyacrylic acid, polyacrylamide, carboxymethyl cellulose, or starch) with controlled molecular weights and crosslinking densities. This composite approach combines the advantages of different polymer materials to achieve both flexibility for tracking electrode expansion and strength for maintaining structural integrity, thereby resolving the contradiction between reliability and compositional stability.
2Stability of the object's composition
If the binder composition does not track expansion and contraction effectively, then manufacturing is simpler, but the negative electrode swells and sheds active material
Solution Approach 1:
By precisely controlling the glass transition temperature (-50°C to 0°C) and molecular weight parameters of the binder, the invention enables the material to naturally track the expansion and contraction of the active material during charging and discharging. This parameter-based approach achieves effective swelling suppression without requiring complex multi-component systems or sophisticated structural designs.
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 proposed binder composition significantly reduces the maximum displacement of the binder film under compression, effectively preventing shedding of the active material and improving the cycle characteristics of the secondary battery by maintaining the structural integrity of the negative electrode.
Implementation Method 1
a binder composition comprising a particulate polymer that is hydrogenated and is also densely cross-linked... which provides a synergistic effect of the cross-linking and the hydrogenation in tracking expansion and contraction of a negative electrode active material
Implementation Method 2
the particulate polymer is formed of a polymer including an ethylenically unsaturated carboxylic acid monomer unit, an aromatic vinyl monomer unit, and an alkylene structural unit
Data Source
AI summary
A binder composition for a non-aqueous secondary battery negative electrode contains a particulate polymer and water. The particulate polymer is formed of a polymer including an ethylenically unsaturated carboxylic acid monomer unit, an aromatic vinyl monomer unit, and an alkylene structural unit. A binder film formed using the binder composition for a non-aqueous secondary battery negative electrode displays a maximum displacement of 30 μm or less when the binder film compressed to a maximum load of 20 mN at a loading rate of 0.2975 mN/s using a micro compression tester.