Battery Separator Adhesive Layer Porosity Control
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Solution Overview
Problem
Conventional non-aqueous secondary battery separators face challenges in achieving both excellent adhesion to electrodes and ion permeability, particularly when subjected to severe heat pressing conditions, which can damage the porous structure of the adhesive porous layer, leading to insufficient battery characteristics.
Innovation Solution
A separator with a porous substrate and an adhesive porous layer composed of a combination of polyvinylidene fluoride resins A and B, where resin A has a low hexafluoropropylene content and resin B has a higher content, providing a porosity of 30-60% and average pore size of 20-100 nm, ensuring robust adhesion and ion permeability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a polyvinylidene fluoride resin layer is used as an adhesive porous layer to join electrodes and separator, then adhesion between electrode and separator is improved, but ion permeability deteriorates when subjected to severe heat pressing conditions
Solution Approach 1:
The patent applies parameter changes by precisely controlling the porosity (30-60%) and average pore size (20-100 nm) of the adhesive porous layer, and by controlling the hexafluoropropylene content (1.5-15 mol%) in the polyvinylidene fluoride copolymer. These parameter optimizations enable the adhesive layer to maintain both strong adhesion and sufficient ion permeability even after severe heat pressing conditions.
Solution Approach 2:
The patent uses composite materials by combining polyvinylidene fluoride copolymer with specific hexafluoropropylene content with other components to create an adhesive porous layer that balances adhesion and ion permeability. The specific composition and structure of this composite material allow it to withstand heat pressing while maintaining functional performance.
2Weight of moving object
If the outer casing is made of aluminum laminate for soft pack battery, then weight and size are reduced, but uniform retention of adhesive property deteriorates due to space formation between electrode and separator
Solution Approach 1:
The patent applies preliminary action by forming an adhesive porous layer on the separator before battery assembly. This pre-formed adhesive layer ensures uniform adhesion between the electrode and separator, preventing space formation during charging and discharging cycles that would otherwise occur in soft pack batteries with aluminum laminate casings.
Solution Approach 2:
The patent applies local quality by creating a specific adhesive porous layer with controlled porosity (30-60%) and pore size (20-100 nm) at the interface between electrode and separator. This localized structural modification ensures uniform adhesive property retention in the critical bonding region without affecting the overall lightweight aluminum laminate casing structure.
3Strength
If hexafluoropropylene content in polyvinylidene fluoride copolymer is increased to enhance adhesion, then adhesive property is improved, but ion permeability deteriorates
Solution Approach 1:
The patent applies parameter changes by optimizing the hexafluoropropylene content within the specific range of 1.5-15 mol%. This controlled parameter adjustment ensures that the adhesive porous layer achieves sufficient adhesion strength while maintaining adequate ion permeability, resolving the trade-off between these two critical properties.
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 proposed separator exhibits enhanced adhesion to electrodes and ion permeability, even under severe conditions, resulting in improved cycle life and energy density for non-aqueous secondary batteries with aluminum laminate pack outer casings.
Implementation Method 1
a porous substrate, and an adhesive porous layer that is formed at one side or both sides of the porous substrate
Implementation Method 2
The adhesive porous layer functions as an adhesive that favorably joins the electrode and the separator together
Data Source
AI summary
The present invention provides a separator for a non-aqueous secondary battery including a porous substrate, and an adhesive porous layer that is formed at one or both sides of the porous substrate, that contains polyvinylidene fluoride resin A and polyvinylidene fluoride resin B, and that has a porosity of from 30% to 60% and an average pore size of from 20 nm to 100 nm.