Waterborne Polyurethane Binder for Lithium Battery Electrodes
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Solution Overview
Problem
Conventional lithium battery electrodes face limitations in miniaturization and manufacturing complexity due to the use of polyvinylidene fluoride (PVDF) binders, which have low elongation and require organic solvents, while styrene-butadiene rubber (SBR) binders offer weak binding forces leading to reduced battery capacity and lifetime.
Innovation Solution
A waterborne polyurethane binder with double bonds is developed, allowing dispersion in water without organic solvents and providing excellent elastic and recovery properties through crosslinking with a crosslinking agent or water-soluble initiator, enhancing the binding force and charge/discharge properties of lithium battery electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If PVDF based polymer is used as binder, then binding force is strong, but elongation is very small (about 10%) and large amount is required limiting miniaturization
Solution Approach 1:
The invention changes the chemical composition parameters of the binder from PVDF-based polymer to waterborne polyurethane polymer with specific molecular weight range (1,000-10,000) and functional group content (2-10 mmol/g). This parameter change enables the binder to achieve both strong adhesion and high elongation (50-200%), eliminating the need to use large amounts of binder while maintaining strong binding force.
2Strength
If PVDF based polymer is used as binder, then binding force is strong, but organic solvent is required complicating manufacturing process
Solution Approach 1:
The invention changes the solvent system parameter from organic solvent (N-methyl-2-pyrrolidone) to water-based system. The waterborne polyurethane polymer is dispersed in water to form a slurry that can be directly applied to electrodes, eliminating the need for organic solvent removal steps and simplifying the manufacturing process while maintaining strong binding force.
Solution Approach 2:
The invention converts the typically harmful organic solvent requirement into a beneficial water-based system. Water, which is environmentally friendly and easy to handle, replaces the toxic organic solvent, turning a manufacturing disadvantage into an advantage by simplifying the process and improving environmental compatibility.
3Stability of the object's composition
If SBR is used as binder, then elastic capacity is excellent, but binding force is very weak reducing battery capacity and lifetime
Solution Approach 1:
The invention creates a composite binder system by combining waterborne polyurethane polymer (providing elastic capacity) with conductive carbon materials (providing binding force and electrical conductivity). This composite approach allows the binder to simultaneously exhibit excellent elastic properties (50-200% elongation) and strong binding force, overcoming the limitations of SBR which has weak binding force despite good elasticity.
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 waterborne polyurethane binder enables improved charge/discharge performance and extended battery life by maintaining electrode volume and binding force during cycling, with a more environmentally friendly and cost-effective manufacturing process.
Implementation Method 1
A waterborne polyurethane binder according to an embodiment of the present invention can be dispersed in water because it includes dispersants chemically bonded to itself
Implementation Method 2
The polyurethane binder crosslinked by the crosslinking agent or the water-soluble initiator provides a excellent elastic forces and recovery properties with a high crosslinkage density
Data Source
AI summary
A polyurethane binder prepared by a polyurethane compound having double bonds and by crosslinking the polyurethane compounds. The polyurethane binder having double bonds can be dispersed in water with the dispersant including a reactive group such as a carboxyl group, and thus an organic solvent is not required to produce an electrode. The crosslinked polyurethane binder with a high crosslinking density provides an excellent elastic force and binding force, and thus the electrode and the lithium battery employing the polyurethane binder have improved recovery properties and charge/discharge properties.