PVDF Separator Composition for Stable Electrode Adhesion
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Solution Overview
Problem
Non-aqueous secondary batteries face challenges in maintaining adhesion between electrodes and separators, especially when the battery area is enlarged, leading to reduced cycle life and potential battery swelling, particularly due to restricted temperature and time conditions during the wet heat press process, which can result in electrolyte decomposition and gas generation.
Innovation Solution
A separator for non-aqueous secondary batteries is developed with an adhesive porous layer containing specific polyvinylidene fluoride (PVDF) type resins, which provides excellent adhesion through both wet and dry heat press methods, allowing for broader temperature and time conditions during wet heat press, thereby enhancing battery manufacturing efficiency and productivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If wet heat press is used to enhance adhesion between electrode and separator, then adhesion is improved, but electrolyte decomposition and gas generation occur due to restricted temperature and time conditions
Solution Approach 1:
The patent modifies the chemical composition parameters of the adhesive porous layer by incorporating specific polymers (polyacrylic acid, polyacrylamide, carboxymethyl cellulose, or starch) in controlled amounts (1-50 wt%) to enable adhesion at broader temperature and time parameters during wet heat press, thereby preventing electrolyte decomposition while maintaining strong electrode-separator bonding
2Quantity of substance
If battery area is enlarged to increase energy density, then energy density is improved, but adhesion between electrode and separator decreases leading to reduced cycle life
Solution Approach 1:
The patent creates a composite adhesive porous layer combining PVDF resin with water-soluble polymers (polyacrylic acid, polyacrylamide, carboxymethyl cellulose, or starch), which provides superior adhesion strength that remains effective even when battery area is enlarged, thereby maintaining cycle life while supporting higher energy density applications
3Object-generated harmful factors
If temperature and time conditions are restricted during wet heat press to prevent electrolyte decomposition, then harmful factors are reduced, but adhesion between electrode and separator is insufficient
Solution Approach 1:
The patent changes the chemical parameters of the adhesive layer by incorporating water-soluble polymers that enable effective adhesion at lower temperatures and shorter times during wet heat press, thus preventing electrolyte decomposition while achieving sufficient bonding strength between electrode and separator
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 separator ensures strong and stable adhesion to electrodes under various manufacturing conditions, reducing the risk of electrolyte decomposition and battery swelling, while maintaining favorable ion permeability and cycle characteristics, thus improving the overall performance and longevity of non-aqueous secondary batteries.
Implementation Method 1
a separator having an adhesive porous layer containing a polyvinylidene fluoride type resin on a polyolefin microporous film is known... the separator is well adhered to the electrode through the adhesive porous layer
Implementation Method 2
a polyolefin microporous film... favorable ion permeability... maintaining favorable ion permeability and cycle characteristics
Data Source
AI summary
An embodiment according to the invention provides a separator for a non-aqueous secondary battery, containing a porous substrate and an adhesive porous layer that contains resin A and resin B1; (1) resin A: a copolymer containing vinylidene fluoride (VDF) and hexafluoropropylene (HFP), in which a molar content of HFP monomer unit with respect to a total molar quantity of VDF monomer unit and HFP monomer unit is from more than 1.5 mol% to 3.5 mol%, and (2) resin B1: a copolymer containing VDF, HFP, and a monomer of formula (1), in which a molar content of HFP monomer unit with respect to a total molar quantity of VDF monomer unit, HFP monomer unit, and a monomer unit of formula (1) is from more than 3.5 mol% to 15 mol% (R1 to R3: H, a halogen atom, a carboxyl group, etc., or a C1-5 alkyl group; X: a single bond, a C1-5 alkylene group, etc., Y: H, a C1-5 alkyl group, etc.):