Copolymer Electrode Binder to Prevent Slurry Agglomeration Cracks
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Solution Overview
Problem
Lithium-sulfur secondary batteries face issues such as high solubility of lithium polysulfide, low life and output characteristics, low electrical conductivity of sulfur, and low stability due to the use of lithium metal, which affect the adhesive force and flexibility of the electrode, leading to degradation of charging/discharging performance.
Innovation Solution
A random copolymer binder composed of polyacrylic acid (PAA) and polyethylene oxide (PEO) is used, allowing lithium ions to move through the first block and providing flexibility through the second block, preventing phase separation and improving the adhesive force of the electrode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If polyacrylic acid (PAA) and polyethylene oxide (PEO) are used as binders, then adhesive force is improved, but phase separation occurs and processability deteriorates
Solution Approach 1:
The patent combines PAA and PEO into a single copolymer binder rather than using them as separate components. This merging approach prevents phase separation while maintaining the adhesive benefits of both polymers, as they are chemically bonded at the molecular level within the copolymer structure.
Solution Approach 2:
The invention creates a composite polymer material by synthesizing a copolymer that integrates the functional groups of PAA (for adhesion) and PEO (for flexibility and processability) into a unified material system, eliminating the phase separation issues inherent in physical mixtures.
2Strength
If PAA is used as binder, then adhesive force is improved, but electrode flexibility deteriorates due to rigid tendency
Solution Approach 1:
The copolymer structure distributes PAA segments and PEO segments throughout the polymer chain, creating local regions with different properties. The PAA segments provide adhesive force at the electrode substrate interface, while the PEO segments provide flexibility within the binder matrix, achieving both requirements simultaneously.
Solution Approach 2:
By creating a copolymer composite material, the invention integrates the rigid, adhesive PAA segments with the flexible PEO segments at the molecular level, producing a unified binder that exhibits both strong adhesion and electrode flexibility without the drawbacks of separate polymer layers.
3Strength
If strong hydrogen bonding occurs between acrylic acids in PAA, then adhesive force is improved, but electrode flexibility deteriorates due to very low flexibility
Solution Approach 1:
The copolymer structure segments the hydrogen-bonding PAA units and separates them with flexible PEO units along the polymer chain. This segmentation prevents the formation of extensive hydrogen-bonding networks that would cause rigidity, while maintaining localized adhesive interactions where PAA segments contact the substrate.
Solution Approach 2:
The invention creates local adhesive zones where PAA segments provide hydrogen bonding to the substrate, while the bulk of the binder matrix contains PEO segments that provide flexibility. This spatial separation of functions resolves the contradiction between strong adhesion and electrode flexibility.
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 random copolymer binder enhances the charging/discharging characteristics and life characteristics of lithium-sulfur batteries by ensuring even dispersion of active materials and conductive materials in the slurry, reducing surface roughness and cracks, and improving the adhesive force of the electrode.
Implementation Method 1
A random copolymer binder is developed, combining PAA and PEO
Implementation Method 2
PAA containing functional groups substitutable with lithium ions
Data Source
AI summary
A binder, an electrode and a lithium secondary battery comprising the same are described, wherein the binder includes a first block including a polymer containing functional groups substitutable with lithium ions and a second block. The second block may include a polymer containing oxygen atoms in the main chain. With such a binder, it is possible to prevent the agglomeration of the slurry for preparing the electrode, thereby preventing the occurrence of cracks on the surface of the electrode and improving the life characteristics of the lithium secondary battery.