Battery Separator Edge Coating to Prevent Shrinkage Short Circuits
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Solution Overview
Problem
Batteries face a high risk of short circuits between positive and negative electrode plates due to mechanical or heat abuse, leading to thermal runaway, as the separator can shrink and lose adhesion, especially with thinner separators that are more prone to deformation.
Innovation Solution
The implementation of a separator coating layer with adhesive properties, applied to the edges of the base separators, enhances adhesion and prevents shrinkage, reducing the likelihood of short circuits by ensuring tighter bonding between the separator and electrode plates, and improving the overall hot pressing uniformity and cycle performance of the battery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the separator is made thinner to reduce battery size, then the volume and weight of the battery are reduced, but the separator becomes more prone to shrinkage and deformation under mechanical or heat abuse, increasing the risk of short circuits
Solution Approach 1:
The patent applies composite materials by combining a base separator with a separator coating layer. The base separator provides the fundamental separation function, while the coating layer (comprising materials such as polyvinylidene fluoride, polyhexafluoropropylene, or their copolymers) enhances mechanical strength, thermal stability, and adhesion to electrode plates. This composite structure allows the separator to maintain thin dimensions for compact battery design while the coating layer prevents shrinkage and deformation under heat or mechanical abuse, thereby resolving the contradiction between reduced volume and maintained reliability.
2Quantity of substance
If the separator is made thinner to improve energy density, then the battery capacity per volume increases, but the adhesion between separator and electrode plates deteriorates, leading to lithium ion precipitation and short circuit risks
Solution Approach 1:
The separator coating layer acts as an adhesive interface between the base separator and electrode plates. The coating layer materials (polyvinylidene fluoride, polyhexafluoropropylene, or their copolymers) provide strong adhesion to both the separator and electrode surfaces, preventing delamination even when the separator is thin. This ensures maintainable adhesion strength for high energy density designs.
Solution Approach 2:
The patent modifies the physical and chemical parameters of the separator by adding a coating layer with specific properties: thickness of 1-10 micrometers, controlled porosity (30-70%), and specific material composition. These parameter changes enhance adhesion strength without significantly increasing overall separator thickness, allowing thin separators to maintain strong bonding to electrode plates and prevent lithium ion precipitation, thus resolving the contradiction between energy density and adhesion strength.
3Length of moving object
If the separator is made thinner to reduce cell size, then the battery dimensions are reduced, but the hot pressing uniformity deteriorates, causing poor cycle performance
Solution Approach 1:
The separator coating layer serves as a buffer and stress-distributing layer during the hot pressing process. The coating layer's intermediate mechanical properties (between the rigid base separator and the electrode plates) help distribute pressing forces more uniformly across the electrode-separator interface. This prevents localized deformation and ensures consistent contact, improving hot pressing uniformity even when the overall separator thickness is reduced for compact battery dimensions, thereby resolving the contradiction between size reduction and manufacturing precision.
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
This solution effectively reduces the risk of short circuits and thermal runaway by maintaining separator integrity under stress conditions, enhancing the battery's safety and performance through improved adhesion and uniformity.
Implementation Method 1
a separator coating layer with adhesive properties, applied to the edges of the base separators, enhances adhesion and prevents shrinkage
Data Source
AI summary
A battery includes a first base separator and a second base separator that are located on two sides of an electrode plate and that are adjacent to each other, and a first-type separator coating layer that is adhered to an edge region of the first base separator and an edge region of the second base separator. Another battery includes a second-type separator coating layer adhered to a middle region of a base separator, and a third-type separator coating layer adhered to an edge region of a first base separator, where the second-type separator coating layer includes an adhesive polymer with a first mass content, the third-type separator coating layer includes an adhesive polymer with a second mass content, and the second mass content is greater than the first mass content.