Asymmetric Ceramic Separator for Li-Ion Battery Safety
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Solution Overview
Problem
Ceramic separators for electric devices, such as lithium ion secondary batteries, face challenges in maintaining high cycle property and output performance due to the resolution of electrolysis solution components, particularly on the negative electrode side, leading to decreased durability and ion conductivity.
Innovation Solution
A separator design featuring a porous substrate layer with first and second ceramic layers, where the specific surface area of the first ceramic layer is smaller than the second, positioned on the negative electrode side to minimize contact with electrolysis solution components and enhance ion conductivity on the positive electrode side.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a ceramic layer is formed on the porous substrate to prevent foreign substances from entering, then safety is improved, but cycle property decreases due to resolution of electrolysis solution components
Solution Approach 1:
The patent applies different ceramic layer configurations to different regions of the separator. The first ceramic layer on the negative electrode side has different properties (thickness, porosity, ceramic particle composition) than the second ceramic layer on the positive electrode side. This local differentiation allows the negative electrode side to minimize electrolysis solution contact and prevent component resolution, while the positive electrode side maintains sufficient ion conductivity, thereby resolving the contradiction between safety and cycle property.
2Power
If a ceramic layer with high porosity is used to maintain ion conductivity, then output performance is improved, but foreign substances can enter through pores reducing safety
Solution Approach 1:
The patent employs composite ceramic layers combining different ceramic particles with varying pore structures. The first ceramic layer uses ceramic particles with smaller specific surface area and controlled pore size to block foreign substances while maintaining ion transport. The second ceramic layer uses ceramic particles with larger specific surface area to ensure high ion conductivity. This composite approach resolves the contradiction between safety and output performance by integrating materials with complementary properties.
3Reliability
If the specific surface area of ceramic particles is increased to improve foreign substance blocking, then safety is improved, but ion conductivity decreases reducing output performance
Solution Approach 1:
The patent strategically assigns ceramic particles with different specific surface areas to different locations. The first ceramic layer on the negative electrode side uses particles with smaller specific surface area (0.3-3.0 μm) optimized for blocking foreign substances. The second ceramic layer on the positive electrode side uses particles with larger specific surface area (3.0-10.0 μm) optimized for maintaining ion conductivity. This spatial differentiation resolves the contradiction between safety and output performance.
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 configuration ensures high cycle property and prevents a decrease in output performance by reducing the resolution of electrolysis solution components on the negative electrode side while maintaining sufficient ion conductivity, effectively addressing the limitations of existing ceramic separators.
Implementation Method 1
A ceramic separator has a constitution in which a ceramic layer containing ceramic particles and a binder is formed on a surface of a porous substrate. The ceramic separator provided with the ceramic layer thereon can prevent foreign substances from entering through pores of the porous substrate.
Implementation Method 2
the separators used in the lithium ion secondary battery generally include porous substrates for conducting ions therethrough. Namely, the porous substrates have a large number of pores due to the porous structure thereof so that the foreign substances easily enter through the pores.
Data Source
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AI summary
A separator for an electric device (1) includes: a porous substrate layer (3); and first and second ceramic layers (5a, 5b) formed on the respective surfaces of the porous substrate layer and each containing ceramic particles and a binder, wherein a specific surface area of the first ceramic layer (5a) is smaller than a specific surface area of the second ceramic layer (5b), and the first ceramic layer (5a) is located towards a negative electrode of an electric device.