Aqueous Binder for Li-Ion Electrodes
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Solution Overview
Problem
Existing lithium ion battery electrodes face challenges with binders, such as environmental concerns with NMP solvents and low stability and adhesion issues with SBR binders, particularly when bent, leading to cracking and powder dropping on aluminum substrates, which affect electrochemical performance.
Innovation Solution
An aqueous composition comprising latex particles, polyvinyl alcohols, and water-soluble cellulose derivatives is used to create a slurry for forming electrodes, ensuring good adhesion, resistance to cracking, and maintaining electrochemical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If SBR binder is used in aqueous composition, then environmental friendliness is improved (replacing NMP), but adhesion to aluminum substrate deteriorates and stability in high voltage environments worsens
Solution Approach 1:
The patent uses a composite binder system combining SBR latex particles (providing adhesion and flexibility) with CMC (providing stability and structural integrity). This composite approach allows the binder to simultaneously achieve environmental friendliness by using water as solvent while maintaining both adhesion to aluminum substrate and stability in high voltage environments through the synergistic effects of the two materials.
Solution Approach 2:
The patent optimizes specific parameters of the binder composition including the molecular weight of SBR (100,000-500,000), the degree of substitution of CMC (0.6-0.9), and the ratio of SBR to CMC (90:10 to 50:50 by weight). By adjusting these parameters, the binder achieves both good adhesion to aluminum substrate and sufficient stability in high voltage environments while remaining environmentally friendly.
2Shape
If electrode is bent after applying SBR binder, then flexibility is improved, but adhesion loss, cracking, and powder dropping occur
Solution Approach 1:
The composite binder system of SBR and CMC provides both flexibility and strength. SBR latex particles contribute elasticity and flexibility allowing the electrode to bend, while CMC provides structural rigidity and adhesion strength. This composite structure prevents cracking and powder dropping during bending while maintaining the required flexibility for electrode formation.
Solution Approach 2:
The patent uses latex particles with specific size ranges (0.01-1.0 μm diameter) that can deform elastically during bending. The spherical shape and size distribution of these particles allow them to accommodate curvature changes without causing cracking, while the CMC matrix maintains overall structural integrity and adhesion during the bending process.
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 solution provides electrodes with improved adhesion to aluminum substrates, resistance to cracking, and maintains acceptable electrochemical performance, including cycling stability and capacity retention.
Implementation Method 1
good adhesion to the aluminum
Implementation Method 2
When a layer of the liquid was applied to a substrate and the liquid removed by evaporation
Data Source
AI summary
An aqueous composition for making lithium ion battery electrodes comprising (a) one or more polymers, (b) one or more polyvinyl alcohols, and (c) one or more water-soluble cellulose derivatives. Also, a method of making an electrode comprising (i) providing an aqueous slurry comprising (a) one or more polymers, (b) one or more polyvinyl alcohols, (c) one or more water-soluble cellulose derivatives, and (d) one or more conductive material; (ii) forming a layer of said slurry on a metal substrate; and (iii) drying said layer of said slurry. Also, an electrode comprising ingredients (a) through (d).