Composite Battery Separator with Dry-Mixed Ceramic Fillers
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Solution Overview
Problem
Existing lithium ion battery separators face challenges with mechanical stability, flexibility, and safety due to high filler content, which can lead to dendrite growth and electrical shorting, and require the use of plasticizer oil, solvent, or process oil, resulting in environmental concerns and increased production costs.
Innovation Solution
A dry mixing process using a twin-screw compounding method to incorporate surface-treated fillers uniformly into a polyolefin matrix, eliminating the need for plasticizer oil or solvent, and generating pores within the polymer matrix for a porous separator with improved mechanical and thermal properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a ceramic composite layer with high filler loading (90-95 wt. %) is applied to block dendrite growth and maintain dimensional stability, then thermal resistance and dimensional stability are improved, but ceramic particles fall off from the surface and production cost increases
Solution Approach 1:
The patent uses a composite material system consisting of polyolefin base resin and ceramic filler particles. The ceramic particles (Al2O3, SiO2, TiO2, or ZrO2) are uniformly dispersed within the polymer matrix to create a composite separator that combines the thermal stability of ceramics with the flexibility and adhesion of the polymer matrix, preventing particle fallout while maintaining thermal resistance.
Solution Approach 2:
The ceramic filler is distributed throughout the bulk of the separator rather than concentrated in a surface coating layer. This uniform distribution ensures that thermal resistance is provided throughout the separator structure while the polymer matrix continuously binds the ceramic particles, preventing surface particle fallout.
2Reliability
If a ceramic composite coating layer is added to prevent electronic shorting and block dendrite growth, then safety performance is improved, but total thickness of the separator increases
Solution Approach 1:
The patent merges the functions of the base separator and the ceramic reinforcement layer into a single integrated structure. The ceramic filler is incorporated throughout the polyolefin matrix, combining the mechanical properties, ionic conductivity, and thermal stability functions into one homogeneous separator rather than using separate layers.
Solution Approach 2:
By creating a composite polyolefin-ceramic separator where the ceramic particles are dispersed within the polymer matrix, the patent achieves both safety performance (dendrite blocking, thermal stability) and maintains reasonable thickness, as the ceramic particles provide functional benefits throughout the bulk material rather than requiring a thick surface coating.
3Ease of manufacture
If plasticizer oil or solvent is used to incorporate ceramic fillers for easier handling, then filler incorporation is improved, but environmental impact increases and production cost increases
Solution Approach 1:
The patent removes the harmful plasticizer oil or solvent from the manufacturing process entirely. Instead of using these additives to facilitate filler incorporation, the method relies on mechanical mixing and the natural compatibility between the polyolefin matrix and ceramic fillers, eliminating environmental contamination while maintaining ease of manufacture.
Solution Approach 2:
The polyolefin matrix inherently provides the necessary binding and dispersion properties for ceramic fillers without requiring external plasticizers or solvents. The polymer itself serves the function of facilitating filler incorporation through its viscosity and compatibility characteristics, making the process environmentally friendly while maintaining ease of manufacture.
4Temperature
If high content of thermal-resistant filler (30-80 wt. %) is used to achieve desired thermal resistance, then thermal resistance is improved, but the polyolefin loses flexibility and adhesion of filler with matrix is reduced
Solution Approach 1:
The patent optimizes the ceramic filler content within a controlled range (5-50 wt. %) rather than using very high concentrations. This parameter optimization ensures sufficient thermal resistance is achieved while maintaining adequate flexibility and adhesion. The specific filler types (Al2O3, SiO2, TiO2, ZrO2) are selected for their compatibility with polyolefin to maximize thermal performance at lower loadings.
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 method produces a monolayer separator with enhanced mechanical properties, thermal resistance, and safety performance, reducing the risk of dendrite growth and electrical shorting, while being environmentally friendly and cost-effective.
Implementation Method 1
a dry mixing process, preferably in a twin-screw extruder
Implementation Method 2
extruding the compounded mixture prepared in step 1) to obtain a cast film
Implementation Method 3
stretching the cast film prepared in step 2) to obtain the porous membrane
Implementation Method 4
the hydrophobic filler is substantially uniformly distributed in the polymer matrix... reducing the risk of dendrite growth and electrical shorting
Data Source
AI summary
A method for manufacturing a porous membrane suitable for use as a separator of a lithium ion battery, comprising the following steps: 1) compounding a polymer and hydrophobic filler by dry mixing; 2) extruding the compounded mixture to obtain a cast film and 3) stretching the cast film to obtain the porous membrane. A porous membrane suitable for use as a separator of a lithium ion battery, a separator for a lithium ion battery, a lithium ion battery, and a device are also provided.