Secondary Battery Separator With Adhesive Layer For High-Temperature Stability
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Solution Overview
Problem
Lithium ion secondary battery separators with polyolefin microporous membranes and adhesive porous layers face issues with insufficient adhesion to electrode active materials, leading to mechanical strength loss during winding, risk of short circuits, and poor anti-blocking properties, especially when exposed to high temperatures.
Innovation Solution
A secondary battery separator is developed with a heat-durable layer and an adhesive layer, using specific polymers to enhance adhesion and durability, comprising a microporous membrane with non-conductive particles and a binder, and a particulate polymer with a glass transition temperature for improved adhesion and ion conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a polyolefin microporous membrane with an adhesive porous layer is used as a separator, then ion permeability and electrolyte solution preservability are improved, but adhesion to electrode active materials is insufficient, leading to mechanical strength loss during winding
Solution Approach 1:
The patent applies composite materials by combining a polyolefin microporous membrane (providing ion permeability and electrolyte preservability) with a heat-durable porous layer containing inorganic particles and binder, and an adhesive layer with specific polymer components. This multi-layer composite structure resolves the contradiction by assigning different functions to different layers: the base membrane handles ion transport while the adhesive layer provides mechanical strength and electrode adhesion.
Solution Approach 2:
The patent implements local quality by creating distinct layers with specialized properties: the heat-durable porous layer provides thermal stability and structural support where needed, while the adhesive layer with specific polymers (acrylic acid ester, vinylidene fluoride, carboxylic acid-containing monomers) provides localized adhesion enhancement at the electrode interface. Each layer is optimized for its specific function rather than attempting to make the entire separator uniformly possess all properties.
2Reliability
If the separator is exposed to high temperatures, then the polyolefin microporous membrane maintains shutdown function, but the adhesive porous layer shrinks, causing positive and negative electrodes to contact and enlarge short-circuited area
Solution Approach 1:
The patent applies parameter changes by carefully selecting materials with appropriate glass transition temperatures and thermal properties. The adhesive layer uses polymers with Tg values that maintain flexibility at operating temperatures while the heat-durable porous layer uses inorganic particles and high-temperature stable binders that prevent shrinkage above 150°C. This parameter optimization allows the separator to maintain both shutdown function and dimensional stability across the temperature range.
Solution Approach 2:
The heat-durable porous layer acts as a thermal stabilizer in the composite structure, using inorganic particles (alumina, silica, titania) and heat-resistant binders to counteract the shrinkage tendency of the polyolefin membrane at high temperatures. This composite approach allows the separator to maintain dimensional stability while preserving the shutdown function of the polyolefin base layer.
3Strength
If heat pressing is performed to improve adhesion between the separator and electrode active materials, then mechanical strength is enhanced, but non-conductive particles in the porous layer may be removed
Solution Approach 1:
The patent applies local quality by concentrating the adhesion function in a dedicated adhesive layer containing specific polymer components (acrylic acid ester polymers, vinylidene fluoride polymers, carboxylic acid-containing monomers) that are applied only at the electrode interface. The heat-durable porous layer with inorganic particles is positioned between the polyolefin membrane and the adhesive layer, protecting the particles from direct heat pressing contact while still allowing the adhesive layer to provide strong bonding to the electrode active 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 solution provides excellent heat durability, adhesion properties, and anti-blocking performance, enhancing the high-temperature cycle and rate properties of lithium ion secondary batteries, particularly suitable for cylinder-type batteries.
Implementation Method 1
a particulate polymer having a glass transition temperature (Tg) of 10 to 100°C
Implementation Method 2
excellent adhesion property with an electrode active material layer formed on a current collector
Implementation Method 3
a microporous membrane formed of a polyolefin resin
Implementation Method 4
The porous membrane contains non-conductive particles and a polymer binder
Implementation Method 5
the heat-durable porous layer preserves the polyolefin microporous membrane even at a temperature that is equal to or higher than the shutdown temperature
Implementation Method 6
excellent heat durability
Implementation Method 7
a polymer binder for effecting binding of the non-conductive particles to each other, and binding of the non-conductive particles with the organic separator
Implementation Method 8
binding of the non-conductive particles to each other
Implementation Method 9
When inner-battery temperature rises to around 130°C, the organic separator melts and occludes the micropores. The organic separator thus has a shut-down function that inhibits migration of lithium ions and cuts off the electric current
Data Source
AI summary
Provided are a secondary battery separator having good heat durability, high adhesion property with the electrode active material layer formed on the current collector, and good anti-blocking property, and a secondary battery having such a secondary battery separator. The secondary battery separator of the present invention includes an organic separator layer, a heat-durable layer formed adjacent to at least one surface of the organic separator layer, and an adhesive layer formed on the heat-durable layer, wherein the heat-durable layer contains non-conductive particles and a binder, and the adhesive layer contains a particulate polymer having a glass transition temperature (Tg) of 10 to 100°C.