Ceramic-Coated Battery Separator for Stable Bonding and Heat Resistance
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Solution Overview
Problem
Existing battery separators using PVDF as a bonding layer face issues with inconsistent agglomerate size and morphology, leading to unstable bonding, poor consistency, and reduced heat resistance, which affects the stability and safety of lithium-ion batteries.
Innovation Solution
A battery separator is developed using fluorine-free polymer resin particles and ceramic particles, with specific parameters to ensure a coating that balances bonding property, consistency, stability, and heat resistance, achieved through a controlled mixing and coating process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If PVDF is used as the bonding layer with spray coating, then bonding function is achieved, but bonding consistency and stability are poor due to uncontrollable agglomerate size and morphology
Solution Approach 1:
The patent changes the particle size parameter of PVDF from small molding particles to large particles with diameter of 10-50 μm. This parameter change enables the PVDF to form uniform agglomerates during coating, improving bonding consistency while maintaining bonding strength. The large particle size prevents excessive agglomeration and ensures uniform distribution on the separator surface.
Solution Approach 2:
The patent creates a composite coating structure by combining PVDF particles with ceramic particles (such as Al2O3, SiO2, or TiO2 with diameter of 1-10 μm). This composite material approach enhances both bonding strength and thermal stability, while the different particle sizes and properties work synergistically to improve coating uniformity and bonding consistency.
2Strength
If PVDF is used as the bonding layer, then bonding property is achieved, but heat resistance is reduced due to high melting point requiring high temperature and pressure
Solution Approach 1:
The patent combines PVDF with ceramic particles (Al2O3, SiO2, TiO2) to create a composite coating. The ceramic particles have high melting points and excellent thermal stability, which compensate for PVDF's high melting point (≥135°C). This composite structure maintains bonding property while significantly improving heat resistance and thermal stability of the separator.
Solution Approach 2:
The patent creates a multi-functional coating where different components serve different local functions: PVDF provides bonding property, ceramic particles provide heat resistance and thermal stability, and the porous structure provides electrolyte penetration. This local quality differentiation allows the coating to achieve multiple properties simultaneously without requiring extreme temperature and pressure conditions.
3Reliability
If coating surface density and ceramic particle size are adjusted, then bonding consistency is improved, but coating complexity increases
Solution Approach 1:
The patent establishes specific parameter ranges for coating surface density (0.5-2.0 mg/cm²) and ceramic particle size (1-10 μm) to achieve optimal bonding consistency. By defining these parameters within specific ranges rather than fixed values, the patent simplifies the coating process while ensuring consistent results. The sand mill technology automatically controls particle size distribution within these ranges.
Solution Approach 2:
The patent replaces complex multi-step coating processes with a simplified spray coating method using sand mill technology. The sand mill automatically disperses and sizes the particles during the coating process, eliminating the need for separate particle size classification and manual coating steps. This mechanical substitution reduces process complexity while maintaining high coating consistency.
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 separator with improved bonding strength, enhanced consistency, increased stability, and better heat resistance, enhancing battery performance and safety while maintaining energy density and cycle life.
Implementation Method 1
the fluorine-free polymer resin particles are in spherical form and dispersed within the ceramic particles
Implementation Method 2
after the finished slurry is coated onto surface(s) of the base film, drying with an oven to obtain a battery separator with coating
Data Source
Figure 1~2
AI summary
The present application provides a battery separator and a preparation method therefor, and a battery. The battery separator provided by the present application comprises a base film and a coating coated on one or both sides of the base film, wherein the coating comprises: fluorine-free polymer resin particles and ceramic particles; wherein the fluorine-free polymer resin particles have a primary particle morphology or a secondary agglomerate morphology, and the fluorine-free polymer resin particles in spherical form are dispersed within the ceramic particles, and a coating surface density ρ0, a coating thickness h0, an average radius r of fluorine-free polymer resin particles, a volume Vi occupied by fluorine-free polymer resin particles in the coating, a number N0 of fluorine-free polymer resin particles, a density ρ of fluorine-free polymer resin, and a coating density pi of pure ceramic coating satisfy the following relationship. The battery separator provided by the present application has a coating with good bonding property, high consistency, high stability, and good heat resistance.