Fibrous Adhesive Layer for Lithium Battery Separator Heat Shrinkage
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Solution Overview
Problem
Conventional lithium secondary batteries face safety issues due to extreme heat shrinkage of polyolefin-based porous substrates, leading to short circuits between electrodes, which compromises the battery's shape stability and output characteristics.
Innovation Solution
A fibrous adhesive layer is introduced on the separator or electrode, comprising ceramic particles and polymeric materials like PVDF, PVA, and PAA, with a thickness of 0.5 to 3 μm and fiber diameter of 100 to 900 nm, to enhance adhesion and prevent heat-induced shrinkage, thereby improving cell assembly and reducing cell resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a polyolefin-based porous substrate is used as a separator, then the separator can block physical contact between electrodes to prevent ignition and explosion, but the substrate exhibits extreme heat shrinkage at temperatures of 100°C or greater causing short circuits between electrodes
Solution Approach 1:
The patent applies composite materials by combining polyolefin-based porous substrate with heat-resistant inorganic particles (such as alumina, silica, or boehmite) to create a separator that maintains the original safety function while resisting heat-induced shrinkage. The inorganic particles are dispersed within the polyolefin matrix, forming a composite structure that prevents the separator from shrinking at temperatures of 100°C or greater, thereby eliminating short circuit risks while preserving the shutdown function.
2Shape
If the separator structure is modified to prevent heat shrinkage, then shape stability is improved, but the adhesion between separator and electrodes may be reduced
Solution Approach 1:
The patent applies local quality by creating regions with different functional properties within the separator structure. The bulk of the separator maintains the polyolefin-based porous structure for safety functions, while specific regions contain inorganic particles that provide heat resistance and dimensional stability. This localized modification ensures that heat-resistant properties are concentrated where needed to prevent shrinkage, while the overall separator structure retains its ability to adhere to electrodes through the polyolefin matrix.
3Strength
If a fibrous layer is introduced into the separator to improve adhesion, then the adhesion between electrodes and separator is enhanced, but the device complexity increases
Solution Approach 1:
The patent applies merging by integrating the heat-resistant inorganic particles directly into the polyolefin-based porous substrate during the manufacturing process, creating a unified composite separator structure. This approach combines the safety function of the polyolefin matrix with the heat resistance of inorganic particles in a single integrated component, eliminating the need for separate fibrous layers or additional adhesive coatings, thereby maintaining structural simplicity while achieving both adhesion and heat resistance.
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 fibrous adhesive layer improves the adhesion between electrodes and separators, ensuring shape stability and enhancing the battery's output characteristics by minimizing cell resistance and preventing short circuits, thus making the battery safer and more efficient.
Implementation Method 1
A fibrous adhesive layer is introduced on the separator or electrode
Implementation Method 2
The polyolefin-based porous substrate has an extreme heat shrinkage behavior at a temperature of 100° C. or greater due to material properties
Data Source
AI summary
Disclosed is lithium secondary battery that may include: a positive electrode; a negative electrode; an electrolyte; and a separator positioned between the positive electrode and the negative electrode. The separator may include: a separator substrate; and a fibrous adhesive layer formed on one or both surfaces of the separator substrate.