Separator Heat Resistance Layer Composition Gradient
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Solution Overview
Problem
In non-aqueous electrolyte secondary batteries, the adhesion between the heat resistance layer and the electrode or base material layer is compromised during high-load charging and discharging, leading to reduced performance and potential separation of the heat resistance layer from the base material layer, especially under high temperatures, which affects the battery's ability to suppress heat shrinkage and maintain uniform electrode reactions.
Innovation Solution
A non-aqueous electrolyte secondary battery design featuring a separator with a heat resistance layer containing inorganic particles and a resin binder, where the composition ratio of the resin binder varies across different portions to enhance adhesion and ion permeability, with higher ratios near interfaces and lower ratios in the central portion, using different types of binders and thicknesses to prevent compatibility and segregation, ensuring robust adhesion and ion permeability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the composition ratio of resin binder in the heat resistance layer is increased to improve adhesion between the heat resistance layer and the electrode, then adhesion is improved, but ion permeability deteriorates
Solution Approach 1:
The heat resistance layer is designed with spatially varying composition ratios of resin binder. The first end portion (near electrode interface) has a resin binder composition ratio of 8-30 mass%, while the central portion has 2-7 mass%. This local quality variation ensures high adhesion at the electrode interface where it is most needed, while maintaining adequate ion permeability in the central region where resin binder content is lower.
2Ease of manufacture
If the heat resistance layer is made with uniform composition to simplify manufacturing, then manufacturing complexity is reduced, but adhesion and ion permeability cannot be simultaneously optimized
Solution Approach 1:
The heat resistance layer employs a gradient composition structure where the resin binder content varies through the thickness direction. The first end portion has 8-30 mass% resin binder for electrode adhesion, the central portion has 2-7 mass% for ion permeability, and the second end portion has 8-30 mass% for base material layer adhesion. This localized composition optimization allows each region to perform its specific function effectively.
3Power
If the electrode is designed with high capacity for high load applications, then power output is improved, but electrode expansion and contraction increase, reducing adhesion to the heat resistance layer
Solution Approach 1:
The first end portion of the heat resistance layer, which directly interfaces with the electrode, is designed with a resin binder composition ratio of 8-30 mass%. This higher resin binder content in the region subject to electrode expansion and contraction provides enhanced adhesion strength, allowing the heat resistance layer to maintain intimate contact with high-capacity electrodes even under mechanical stress from charging and discharging cycles.
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 battery achieves improved adhesion between the heat resistance layer and electrodes, and between the heat resistance layer and the base material layer, maintaining performance under high load and preventing separation during temperature increases, thus enhancing resistance to heat shrinkage and ion permeability.
Implementation Method 1
adhesion between the heat resistance layer and the electrode and between the heat resistance layer and the base material layer is improved
Implementation Method 2
ion permeability is enhanced
Data Source
AI summary
A separator includes a base material layer and a heat resistance layer. The heat resistance layer includes, in a direction of thickness of the heat resistance layer, a central portion and a first end portion and a second end portion between which the central portion lies. The first end portion includes an interface with an electrode. The second end portion includes an interface with the base material layer. A composition ratio of a resin binder to a total mass of inorganic particles and the resin binder in the first end portion and the second end portion is not lower than 8 mass % and not higher than 30 mass %. A composition ratio of the resin binder to a total mass of the inorganic particles and the resin binder in the central portion is not lower than 2 mass % and not higher than 7 mass %.