PVDF Separator Adhesive Layer for Battery Cycle Life
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Solution Overview
Problem
Conventional separators with a polyvinylidene fluoride-based resin for non-aqueous secondary batteries face challenges in achieving strong and consistent adhesion between the electrode and separator across a wide temperature range, leading to reduced cycle life and handling issues due to electrostatic charging.
Innovation Solution
A separator with an adhesive porous layer containing a polyvinylidene fluoride-based resin, where the β-phase-crystal-derived peak area intensity ratio is controlled between 10% to 100% using x-ray diffraction, and optionally including a layered clay mineral, to enhance adhesion and reduce electrostatic charging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a porous layer containing a polyvinylidene fluoride-based resin is formed on a polyolefin microporous film to improve adhesion between electrode and separator, then the cycle life is improved, but the separator is liable to electrostatically adsorb foreign substances such as dust, resulting in inferior handling property
Solution Approach 1:
The patent changes the physical and chemical parameters of the polyvinylidene fluoride-based resin by controlling the β-phase crystal content to be 30% or more, and by controlling the melting temperature to be 160°C or higher. These parameter changes reduce electrostatic charging while maintaining adhesion properties, thus improving handling property without sacrificing cycle life.
Solution Approach 2:
The patent creates a composite adhesive porous layer by combining polyvinylidene fluoride-based resin with specific crystal structure (β-phase) and controlled melting temperature characteristics. This composite material approach allows simultaneous achievement of good adhesion, reduced electrostatic charging, and improved handling property.
2Strength
If the temperature range of heat-pressing is expanded to realize sufficient adhesiveness between electrode and separator, then the adhesion is improved, but the manufacturing process complexity increases
Solution Approach 1:
The patent changes the melting temperature parameter of the adhesive porous layer to be 160°C or higher, which expands the temperature range for effective heat-pressing. This allows sufficient adhesion to be achieved at higher temperatures, providing more flexibility in the heat-pressing process and reducing process complexity.
Solution Approach 2:
The patent introduces dynamics by making the adhesive properties temperature-dependent through the controlled melting temperature of 160°C or higher. The adhesive porous layer transitions from a less adhesive state at lower temperatures to a highly adhesive state at elevated temperatures, enabling effective bonding across a wider temperature range and simplifying process control.
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 a wide temperature range for adequate adhesion, improved oxidation resistance, and reduced electrostatic charging, leading to enhanced battery performance and stability in soft pack batteries.
Implementation Method 1
When superimposed on an electrode and heat-pressed, the separator is favorably bound to the electrode with the porous layer interposed therebetween
Implementation Method 2
the adhesive porous layer would exhibit a ratio of an area intensity of a β-phase-crystal-derived peak of the polyvinylidene fluoride-based resin to a SUM of an area intensity of an α-phase-crystal-derived peak of the polyvinylidene fluoride-based resin and the area intensity of the β-phase-crystal-derived peak of the polyvinylidene fluoride-based resin of from 10% to 100% when an x-ray diffraction spectrum is obtained
Data Source
AI summary
A separator for a non-aqueous secondary battery, the separator including: a porous substrate; and an adhesive porous layer provided on one or both sides of the porous substrate and including a polyvinylidene fluoride-based resin, the adhesive porous layer would exhibit a ratio of an area intensity of a β-phase-crystal-derived peak of the polyvinylidene fluoride-based resin to a sum of an area intensity of an α-phase-crystal-derived peak of the polyvinylidene fluoride-based resin and the area intensity of the β-phase-crystal-derived peak of the polyvinylidene fluoride-based resin of from 10% to 100% when an x-ray diffraction spectrum is obtained by performing measurement by an x-ray diffraction method.