PVDF Resin Separator for Battery Adhesion and Ion Permeability
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Solution Overview
Problem
Conventional separators for nonaqueous secondary batteries face challenges in achieving both strong adhesion to electrodes and sufficient ion permeability, particularly when using polyvinylidene-fluoride-based resins, which are compromised by severe heat pressing conditions that destroy the porous structure, and styrene-butadiene rubber electrodes that struggle with adhesion with conventional adhesive porous layers.
Innovation Solution
A separator with a polyvinylidene-fluoride-based resin having a weight average molecular weight of 600,000 to 3,000,000, applied as an adhesive porous layer on a porous substrate, ensuring high adhesion and ion permeability by maintaining the porous structure even under heat pressing, and suitable for both polyolefin microporous membranes and aluminum laminate pack outer casings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If severe heat pressing conditions are applied to improve adhesion, then adhesion strength is improved, but the porous structure is destroyed and ion permeability deteriorates
Solution Approach 1:
The patent changes the molecular weight parameter of the polyvinylidene-fluoride-based resin to a specific range (600,000 to 3,000,000) to achieve optimal balance between adhesion and ion permeability. This parameter change allows the adhesive porous layer to maintain sufficient adhesion strength while preserving the porous structure for ion transport
Solution Approach 2:
The patent uses a composite structure consisting of a porous substrate and an adhesive porous layer made of polyvinylidene-fluoride-based resin. This composite material design enables the separator to simultaneously achieve strong adhesion to electrodes and maintain ion permeability through the porous structure
2Strength
If binder resin content is increased to improve adhesion, then adhesion is improved, but energy density decreases
Solution Approach 1:
The patent introduces an adhesive porous layer as an intermediary between the separator and the electrode. This intermediate layer provides the necessary adhesion function without requiring increased binder resin content in the electrode, thereby preserving energy density while achieving sufficient adhesion
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 provides improved adhesion to electrodes and sustained ion permeability, enabling the production of high-energy-density, high-performance nonaqueous secondary batteries with enhanced cycle life and safety, suitable for both metal can and soft pack battery configurations.
Implementation Method 1
the adhesive porous layer with an electrolyte contained therein is stacked on an electrode and heat-pressed, the electrode and the separator can be well joined together, allowing the adhesive porous layer to function as an adhesive
Implementation Method 2
a porous substrate and an adhesive porous layer that is formed on at least one side of the porous substrate
Data Source
AI summary
An object of the invention is to provide a separator for a nonaqueous secondary battery, which has good adhesion to electrodes and is also capable of ensuring sufficient ion permeability even after attachment to an electrode. The separator for a nonaqueous secondary battery of the invention includes a porous substrate and an adhesive porous layer formed on at least one side of the porous substrate and containing a polyvinylidene-fluoride-based resin. The separator for a nonaqueous secondary battery is characterized in that the polyvinylidene-fluoride-based resin has a weight average molecular weight of 600,000 to 3,000,000.