Coated Battery Separator Swelling Resistance
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Solution Overview
Problem
Vinylidene fluoride polymer-based battery separators swell in polar solvents, weakening their mechanical properties, and existing manufacturing processes are not cost-effective or environmentally friendly.
Innovation Solution
A battery separator is developed with a substrate layer partially coated using a composition of vinylidene fluoride copolymer particles with at least 10 wt % recurring units from hexafluoropropylene, combined with a mixture of primary particles of another vinylidene fluoride polymer, applied via an aqueous dispersion and dried at a low temperature, eliminating the need for solvents like N-methyl pyrrolidone and reducing energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If vinylidene fluoride polymer-based separators are used, then they provide good mechanical properties and chemical stability, but they swell in polar solvents which weakens their mechanical properties
Solution Approach 1:
The patent applies composite materials by combining vinylidene fluoride copolymer particles with at least 10 wt% hexafluoropropylene units with another vinylidene fluoride polymer. This composite structure reduces swelling in polar solvents while maintaining mechanical properties, as the specific copolymer composition provides resistance to solvent penetration while the combination maintains structural integrity.
2Manufacturing precision
If conventional solvent systems like N-methyl pyrrolidone are used for coating, then they enable good dispersion and adhesion, but they increase production cost and environmental impact
Solution Approach 1:
The patent replaces expensive and environmentally problematic solvents like N-methyl pyrrolidone with water as the dispersion medium. This substitution significantly reduces production costs and environmental impact while achieving adequate dispersion of polymer particles through aqueous processing methods.
Solution Approach 2:
The patent changes the dispersion medium from organic solvents to water, fundamentally altering the processing parameters. This parameter change enables the use of cheaper, environmentally friendly materials while maintaining the ability to achieve proper dispersion and adhesion through adjusted processing conditions.
3Reliability
If conventional drying temperatures are used, then they ensure complete solvent removal, but they increase energy consumption
Solution Approach 1:
The patent reduces the drying temperature from conventional high temperatures to below 50°C by changing the solvent system to water-based dispersions. This parameter change allows for lower energy consumption during drying while still achieving complete solvent removal, as water's lower boiling point enables efficient evaporation at reduced temperatures.
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 enhances adhesion and reduces swelling, providing a cost-effective and environmentally friendly method for producing battery separators with improved mechanical stability suitable for electrochemical devices.
Implementation Method 1
applying the coating composition (C) of step ii at least partially on at least one portion of the substrate layer (P)
Implementation Method 2
The coating composition (C) is applied at least partially onto a substrate layer (P)... enhances adhesion
Implementation Method 3
reduces swelling... because of affinity of separators based on vinylidene fluoride polymers with polar solvents in liquid organic electrolytes, the polymeric phase may undergo swelling, which weakens their mechanical properties
Implementation Method 4
drying the at least partially coated substrate layer (P) of step iii... dried at a low temperature
Data Source
AI summary
The present invention pertains to an at least partially coated separator for an electrochemical cell, to a method for its preparation and to an electrochemical cell comprising such separator.