Battery Separator Coating for Particle Retention and Thermal Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Secondary batteries face safety issues due to internal short circuits and thermal instability, particularly at high temperatures, which can lead to explosions, and existing separators fail to effectively hold inorganic particles and prevent excessive binder dissolution in electrolyte solutions.
Innovation Solution
A separator for secondary batteries comprising a porous substrate with a coating layer made of polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP) and inorganic particles, using a polar organic solvent with a boiling point of at least 120°C to maintain appropriate lamellar thickness and prevent binder swelling, thereby enhancing mechanical durability and thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional coating layer is used to prevent internal short circuits, then thermal stability is improved, but inorganic particles are not effectively held and binder dissolves excessively in electrolyte solution
Solution Approach 1:
The patent uses a composite coating layer comprising PVDF-HFP binder and inorganic particles (such as Al2O3, SiO2, or TiO2). This composite structure allows the binder to provide thermal stability while the inorganic particles are effectively retained through the binder matrix, preventing both particle loss and excessive binder dissolution in the electrolyte solution.
Solution Approach 2:
The patent optimizes the lamellar thickness of PVDF-HFP to a specific range (2.5-3.2 nm) and controls the content of HFP monomers (8-15 wt%). These parameter changes ensure that the coating layer maintains appropriate solubility in the electrolyte solution, preventing excessive binder dissolution while retaining inorganic particles effectively.
2Reliability
If excessive coating is applied to prevent separator shrinkage and ignition, then safety is improved, but cell capacity is reduced and cell resistance increases
Solution Approach 1:
The patent applies a thin, uniform coating layer with optimized PVDF-HFP lamellar thickness (2.5-3.2 nm) only where needed on the porous substrate surface. This localized quality approach provides sufficient safety protection against separator shrinkage and ignition while minimizing the coating thickness to avoid excessive cell resistance and capacity loss.
Solution Approach 2:
By controlling the PVDF-HFP lamellar thickness within a specific range (2.5-3.2 nm) and optimizing the HFP monomer content (8-15 wt%), the patent achieves the minimum effective coating thickness that provides safety protection without causing excessive cell resistance or capacity reduction.
3Strength
If binder solubility in electrolyte solution is increased to prevent binder delamination, then mechanical durability is improved, but inorganic particles are not retained effectively
Solution Approach 1:
The patent creates a composite coating layer where PVDF-HFP binder and inorganic particles work synergistically. The binder provides mechanical durability through controlled solubility, while the inorganic particles are retained through the binder matrix. The specific lamellar thickness (2.5-3.2 nm) ensures optimal balance between binder solubility for mechanical strength and particle retention.
Solution Approach 2:
The patent optimizes the PVDF-HFP lamellar thickness (2.5-3.2 nm) and HFP monomer content (8-15 wt%) to achieve appropriate binder solubility in the electrolyte solution. This parameter optimization ensures that the binder has sufficient solubility to provide mechanical durability through controlled dissolution, while simultaneously maintaining enough structural integrity to retain inorganic particles effectively.
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 effectively prevents binder delamination and maintains inorganic particle retention, improving mechanical durability, heat resistance, and overall stability of the secondary battery.
Implementation Method 1
swelling caused by the binder absorbing the electrolyte solution
Implementation Method 2
effectively holding inorganic particles even at high temperatures after injection of electrolyte solution
Data Source
AI summary
Disclosed is a separator for a secondary battery that improves the stability of the secondary battery. In one embodiment of the present disclosure, the separator includes: a porous substrate; and a coating layer disposed on at least one surface of the porous substrate. The coating layer includes polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP) and inorganic particles. In the coating layer, the PVDF-HFP has a lamellar thickness of 2.5 to 3.2 nm.