Thick Composite Electrode Drying via Low Surface Tension Solvent Mixtures
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The manufacturing of thick electrodes for Li-ion batteries faces challenges such as cracking and residual stress due to capillary pressure during the drying process, especially when using aqueous processing, which affects the performance and integrity of the electrodes.
Innovation Solution
A method involving the use of solvents with a surface tension less than 40 mN/m and an ozone forming potential of no more than 1.5 lbs. ozone/lb. solvent, such as water and VOC exempt solvents like methyl acetate, to create a mixed dispersion with active electrode materials and conductive additives, which are deposited on a current collector and heated to remove solvent, thereby reducing capillary pressure and preventing cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If aqueous processing is used to manufacture thick electrodes, then environmental impact is reduced and processing cost decreases, but capillary pressure during drying causes cracking and residual stress
Solution Approach 1:
The patent changes the physical-chemical parameters of the solvent system by using mixed solvents with specifically controlled surface tensions (combining water with organic solvents like ethanol, isopropanol, or acetone in specific ratios) to reduce capillary pressure during drying while maintaining environmental benefits of aqueous processing
Solution Approach 2:
The patent creates a composite solvent system combining water-based and organic solvent components, where the mixture achieves optimal surface tension properties (20-40 mN/m) that neither pure water nor pure organic solvent can achieve alone, thereby reducing cracking while maintaining environmental advantages
2Quantity of substance
If electrode thickness is increased to achieve high energy density, then battery energy density improves, but cracking and residual stress increase during drying
Solution Approach 1:
The patent modifies the solvent system parameters (surface tension, volatility) to enable successful drying of thick electrode coatings (100-200 μm) without cracking, allowing high energy density to be achieved while maintaining electrode integrity through controlled capillary pressure during the drying process
3Ease of manufacture
If conventional NMP solvent is used for processing, then electrode manufacturing is effective, but processing cost increases and environmental impact worsens due to solvent recovery requirements
Solution Approach 1:
The patent replaces expensive, toxic NMP solvent with cheaper, environmentally benign water-based mixed solvent systems that do not require costly recovery processes, accepting that the solvent evaporates completely during drying rather than being recovered and reused
Solution Approach 2:
The patent adjusts solvent composition parameters to achieve optimal evaporation characteristics and surface tension properties that enable effective electrode manufacturing without the need for solvent recovery infrastructure, thereby reducing processing costs
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 approach allows for the production of electrodes with thicknesses up to 450 microns and 20-40% porosity without significant cracking, maintaining electrochemical performance comparable to conventional N-Methyl-2-pyrrolidone (NMP) processed electrodes, while reducing costs and environmental impact by eliminating the need for solvent recovery processes.
Implementation Method 1
Cracking and residual stress in the coating is related to the build-up of capillary pressure during the drying process
Implementation Method 2
The coated surface is heated to remove solvent from the coating
Data Source
AI summary
A method of making an electrode includes the step of dispersing an active electrode material and a conductive additive in a solvent to create a mixed dispersion. The solvent has a surface tension less than 40 mN/m and an ozone forming potential of no more than 1.5 lbs. ozone/lb. solvent. A surface of a current collector is treated to raise the surface energy of the surface to at least the surface tension of the solvent or the mixed dispersion. The dispersed active electrode material and conductive additive are deposited on the current collector. The coated surface is heated to remove solvent from the coating.