Composite Battery Separator for Impact-Resistant Short-Circuit Prevention
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Solution Overview
Problem
Lithium ion batteries face safety concerns due to the poor tensile strength and elongation at break of commercial separators, which can lead to short circuits under external forces, compromising their safety performance.
Innovation Solution
A separator design featuring a first porous substrate combined with a second porous substrate, where the second substrate has higher elongation at break and tensile strength, along with inorganic particles and a binder layer, to enhance mechanical and thermal properties, preventing short circuits and improving safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a commercial separator made of polyolefin materials is used, then the cost is low and mechanical properties are good, but the tensile strength and elongation at break are poor under high deformation external forces
Solution Approach 1:
The separator is constructed as a composite structure comprising a polyolefin base layer combined with a non-polyolefin porous coating layer. This composite approach allows the base layer to provide mechanical strength and thermal stability, while the coating layer enhances elongation at break and impact resistance. The synergistic combination of different materials resolves the contradiction between maintaining simple structure and improving tensile strength under external forces.
Solution Approach 2:
The separator design applies local quality by concentrating the high-elongation material (non-polyolefin porous coating) specifically on the surface layers where it is most needed for preventing short circuits under deformation, while the bulk polyolefin base layer maintains its excellent mechanical properties and thermal stability. This localized application optimizes performance without unnecessarily complicating the overall structure.
2Reliability
If the separator has high elongation at break to prevent short circuit, then the safety performance improves, but the heat resistance may be compromised
Solution Approach 1:
The composite structure combines polyolefin materials known for excellent heat resistance and melting point characteristics with non-polyolefin porous materials providing high elongation at break. The polyolefin base layer ensures the separator maintains dimensional stability and shutdown function at elevated temperatures, while the coating layer provides the necessary ductility to prevent short circuits under mechanical deformation, thus resolving the contradiction between safety performance and heat resistance.
3Stability of the object's composition
If a single-layer separator structure is used, then the manufacturing is simple, but the elongation at break is insufficient under impact forces
Solution Approach 1:
The non-polyolefin porous coating layer is pre-formed and then coated onto the polyolefin base layer during the separator manufacturing process. This preliminary preparation of the coating layer allows for optimized material selection and processing of the high-elongation component without significantly complicating the overall manufacturing流程, as the coating can be applied using standard coating techniques followed by lamination.
Solution Approach 2:
The two-layer composite structure is designed to be manufactured using conventional separator production techniques, with the non-polyolefin porous coating applied as a surface layer on the extruded or formed polyolefin base. This approach maintains manufacturing simplicity while achieving the desired elongation at break through the synergistic properties of the composite materials.
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 composite separator significantly increases the pass rate of impact and nail tests, improving the safety performance of lithium ion batteries by maintaining high tensile strength and elongation at break while maintaining lithium ion conductivity.
Implementation Method 1
the second porous substrate has a tensile strength of 150 kgf/cm2 or more in the machine and the transverse directions; the elongation at the break of the second porous substrate is greater than an elongation at a break of the first porous substrate
Implementation Method 2
the second porous substrate further includes an inorganic particle, and the inorganic particle is one or more selected from the group consisting of alumina, silica, magnesia, titania, hafnium dioxide, tin oxide, cerium oxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide or barium sulfate
Implementation Method 3
the binder layer includes a binder selected from one or more of polyvinylidene fluoride, polytetrafluoroethylene, polyacrylate, carboxymethyl cellulose sodium, styrene butadiene rubber, or polyurethane
Implementation Method 4
it mainly functions to isolate the positive and negative electrodes, prevents short circuit due to the direct contact between the positive and negative electrodes, and also functions to conduct lithium ions
Data Source
AI summary
A separator includes: a first porous substrate; and a second porous substrate arranged on at least one surface of the first porous substrate; wherein the elongation at break of the second porous substrate is greater than the elongation at break of the first porous substrate in at least one of the machine and transverse directions of the separator. The separator has a high tensile strength and an elongation at break and good heat resistance, and may improve the safety performance of the energy storage device when the separator is applied to the energy storage device.