PVDF-HFP Binder Layer Separator for Battery Integration
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Solution Overview
Problem
Lithium secondary batteries face safety issues due to weak integration of electrodes and separators, leading to resistance increases and potential fires or explosions during charging and discharging cycles, along with inadequate air permeability.
Innovation Solution
A separator with a porous coating layer comprising a mixture of inorganic particles and a binder, specifically a combination of polyvinylidene fluoride (PVDF) and polyvinylidene fluoride-co-hexafluoropropylene (HFP) compounds, where the HFP content difference is 3 wt% or higher, forming a binder layer with a fraction of HFP between 10% and 99%, enhancing adhesiveness and ionic conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a binder is used to increase binding force between electrodes and separator, then integration strength is improved, but air permeability may deteriorate
Solution Approach 1:
The binder layer is designed with a porous structure that allows air and electrolyte to pass through while maintaining binding functionality. The pores enable ion transport and air permeability while the binder material itself provides the necessary adhesion between electrode and separator, thus resolving the contradiction between strength and permeability.
Solution Approach 2:
The binder layer comprises a composite of multiple components including inorganic particles and organic binder materials. This composite structure provides both mechanical strength for integration and controlled porosity for air permeability, balancing the opposing requirements through material composition optimization.
2Strength
If a porous coating layer is formed to improve integration, then binding force is improved, but resistance may increase
Solution Approach 1:
The binder layer's composition parameters are optimized by controlling the fraction of compound (II) between 10-99%, with specific HFP content differences of 3 wt% or higher between compounds (I) and (II). These parameter changes enable the binder to provide strong adhesion while maintaining low resistance by facilitating ion transport through the coating layer.
3Strength
If a binder layer with high fraction of compound (II) is used to improve adhesiveness, then integration is improved, but manufacturing complexity increases
Solution Approach 1:
By defining specific parameter ranges for the binder composition (fraction of compound (II) between 10-99% and HFP content difference ≥3 wt%), the patent simplifies manufacturing by providing clear formulation guidelines. This parameter-based approach allows for systematic optimization of adhesiveness without requiring complex multi-step processes, as the performance can be achieved through compositional control alone.
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 strengthens the integration of electrodes and separators, inhibits resistance increases, and improves air permeability, thereby enhancing the safety and cycle characteristics of lithium secondary batteries.
Implementation Method 1
a binder layer comprising at least one compound of formula (I) and at least one compound of formula (II), wherein a fraction of the compound of formula (II) in both of the porous coating layer and the binder layer is greater than 10% and less than 99%
Implementation Method 2
a porous substrate having multiple pores
Implementation Method 3
inhibit a resistance increase in interfaces between the electrodes and the separator
Implementation Method 4
a porous coating layer formed on at least one surface of the porous substrate comprising a mixture of inorganic particles and a binder
Data Source
AI summary
The present disclosure provides a separator comprising a porous substrate, a porous coating layer and a binder layer, the binder comprising at least one homopolymer of polyvinylidene fluoride and at least one copolymer of polyvinylidene fluoride (PVDF)-co-hexafluoropropylene (HFP) so that a content difference of hexafluoropropylene (HFP) present in the two compounds is about 3 wt % or higher.