Dry Electrode Fabrication Without Solvent Drying for Li-Ion Batteries
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Solution Overview
Problem
The existing slurry coating process for lithium ion battery electrodes is environmentally detrimental due to the use of harmful solvents like N-methyl-pyrrolidone (NMP), and it is energy and cost intensive, limiting its efficiency and scalability.
Innovation Solution
A solventless electrode fabrication process that involves mixing electrode active materials and conductive carbon additives with a polymer binder system at temperatures above the binder's melting or softening point, forming a dough that is then rolled into a thin layer and affixed to a metal current collector.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a slurry coating process with solvent is used to fabricate lithium ion battery electrodes, then the electrode materials can be effectively mixed and coated, but harmful solvents like NMP are released into the environment and require additional recycling facilities
Solution Approach 1:
The invention extracts and eliminates the harmful solvent component from the electrode fabrication process. By using a solventless slurry composition where binder polymers directly bind electrode particles without requiring NMP or other harmful solvents, the process removes the source of environmental contamination while maintaining effective particle binding and coating capabilities
Solution Approach 2:
The invention changes the physical and chemical parameters of the binding mechanism by transitioning from solvent-mediated binding to direct polymer-particle binding. The binder polymers are designed with specific functional groups that directly interact with electrode particles through adsorption and chemical bonding, eliminating the need for solvent as a mediator and thereby preventing environmental harm
2Manufacturing precision
If a slurry coating process with drying step is used to remove solvent, then a continuous layer of dry electrode film is formed, but energy intensive drying equipment is required which occupies large footprint and increases cost
Solution Approach 1:
The invention extracts and eliminates the drying step from the fabrication process by removing the solvent component entirely. The solventless slurry composition allows the electrode slurry to be applied and then directly sintered or cured, forming a continuous dry electrode film without requiring energy-intensive drying equipment or occupying large facility footprint
Solution Approach 2:
The invention performs preliminary action by pre-formulating the binder polymers with high binding strength and appropriate melting/curing characteristics. This allows the electrode particles to be effectively bound during the sintering or curing step itself, eliminating the need for a separate drying step to remove solvent before final formation
3Object-affected harmful factors
If solvent recycling facilities are added to prevent NMP release, then environmental compliance is achieved, but additional costs and process complexity are incurred
Solution Approach 1:
The invention extracts and eliminates the need for solvent recycling facilities by removing the harmful solvent NMP from the process entirely. The solventless slurry composition achieves environmental compliance at the source by preventing solvent release, thereby eliminating the need for additional recycling equipment and reducing overall process complexity
Solution Approach 2:
The invention converts the harmful aspect of solvent use into a benefit by designing a system where the binder polymers perform both the binding function and the solvent-free carrier function. This eliminates the need for separate solvent management systems while maintaining effective slurry formulation and application capabilities
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
This process achieves high energy density and efficient electrode fabrication with improved rate capability and cycle life, while being environmentally friendly and reducing the need for energy-intensive drying steps.
Implementation Method 1
a polymer binder system from 1-15% that binds the electrode active material particles and conductive carbon additives together
Implementation Method 2
The dough is formed into an electrode material sheet. At least a portion of the electrode material sheet is affixed to a metal current collector to form an electrode
Data Source
AI summary
A solventless method of making a dry electrode for an electrochemical cell is provided. A solventless electrode material mixture includes 85-99% electrode active material and from 0-10% conductive carbon additive. A polymer binder system is present from 1-15%. The polymer binder system includes one or more polymer binders. The electrode material mixture is mixed at a temperature greater than a softening point or a melting point of at least one polymer binder of the polymer binder system. The electrode material mixture is kneaded into an electrode material dough. The electrode material dough is formed into an electrode material sheet. At least a portion of the electrode material sheet is affixed to a metal current collector to form an electrode.