Two-Layer Battery Separator for Silicon Anode Detachment Prevention
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Solution Overview
Problem
Silicon-based negative electrodes in non-aqueous electrolyte batteries experience significant expansion and contraction during charging and discharging, leading to potential detachment of the separator, which can cause internal short circuits.
Innovation Solution
A two-layer separator is used, with a first layer having a low elastic modulus to accommodate the expansion and contraction of the silicon-based negative electrode, and a second layer with a higher elastic modulus to provide strength, preventing detachment while maintaining the separator's integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a separator with low elastic modulus is used to follow the expansion and contraction of silicon-based negative electrode, then detachment prevention is improved, but separator strength deteriorates
Solution Approach 1:
The separator is constructed as a composite structure with a first layer (low elastic modulus material such as polypropylene or polyamide) in contact with the silicon-based negative electrode to prevent detachment, and a second layer (high elastic modulus material such as polyethylene terephthalate or polystyrene) to provide mechanical strength. This composite approach allows each layer to fulfill its specific function, resolving the contradiction between flexibility for detachment prevention and rigidity for strength.
2Strength
If a coating such as aluminum oxide is applied to ensure separator strength, then separator strength is improved, but electric resistance increases adversely affecting battery characteristics
Solution Approach 1:
Instead of applying a high-resistance coating like aluminum oxide, the invention uses a second layer made of high elastic modulus polymer material (such as polyethylene terephthalate or polystyrene) that provides both mechanical strength and acceptable electrical properties. This layered composite structure achieves strength enhancement without the harmful increase in electric resistance that would result from inorganic coating 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 two-layer separator effectively prevents detachment from the silicon-based negative electrode, ensuring the strength and integrity of the battery without increasing the separator's thickness, thereby enhancing the battery's capacity and energy density.
Implementation Method 1
The first layer has a relatively low elastic modulus. Here, the low clastic modulus may be rephrased to mean that the Young's modulus of the material constituting the first layer is low. The first layer is relatively soft. Even when the silicon-based negative electrode significantly expands and contracts with charging and discharging of the non-aqueous electrolyte battery, the first layer can follow the expansion and contraction of the silicon-based negative electrode.
Implementation Method 2
The second layer has a relatively high clastic modulus. The high elastic modulus may be rephrased to mean that the Young's modulus of the material constituting the second layer is high. The second layer has a relatively high rigidity and more easily ensures strength than the first layer.
Data Source
AI summary
For preventing detachment of a separator of a non-aqueous electrolyte battery from a silicon-based negative electrode of the battery, the separator includes a first layer that is in contact with the silicon-based negative electrode, and a second layer that is in contact with the first layer and is interposed between the silicon-based negative electrode and a positive electrode. The second layer has a higher elastic modulus than the first layer.