Ceramic-Coated Battery Separator for Heat-Stable Ion Transfer
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Solution Overview
Problem
Rechargeable lithium batteries face safety issues due to the mechanical shrinkage or damage of separators at high temperatures, leading to potential short circuits and explosions.
Innovation Solution
A separator for rechargeable lithium batteries is developed, comprising a porous substrate with a coating layer containing polyethylene particles and a first ceramic in a specific weight ratio, and an adhesive layer with a second ceramic and a binder, where the first and second ceramics have different average sizes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a separator is made from a porous material to transfer ions, then ion transfer capability is improved, but mechanical strength and thermal stability deteriorate at high temperatures
Solution Approach 1:
The separator is constructed as a composite material consisting of a polyolefin base layer combined with a ceramic coating layer containing alumina and boehmite particles. This composite structure combines the ion transfer capability of the porous polyolefin with the high temperature stability and mechanical strength of the ceramic coating, resolving the contradiction between ion permeability and thermal-mechanical stability.
Solution Approach 2:
The separator utilizes a porous polyolefin base layer that maintains excellent ion transfer capability through its controlled pore structure. The porosity is optimized to ensure adequate ion transport while the ceramic coating provides the necessary mechanical reinforcement at elevated temperatures.
2Productivity
If a separator is made thin to reduce battery size, then energy density is improved, but safety and mechanical integrity worsen
Solution Approach 1:
The thin separator maintains mechanical integrity through the ceramic coating layer applied on the polyolefin base. The coating layer provides reinforcement that compensates for the reduced thickness, allowing the separator to be made thinner for higher energy density while maintaining safety and mechanical strength.
Solution Approach 2:
The ceramic coating is applied locally on the surface of the polyolefin base layer, providing enhanced mechanical strength and thermal stability precisely where needed at the separator surfaces, while the bulk remains thin for high energy density.
3Device complexity
If a separator uses a single-layer coating to simplify structure, then manufacturing complexity is reduced, but adhesive force and cycle life deteriorate
Solution Approach 1:
The coating is segmented into two distinct functional layers: a first ceramic coating layer containing alumina and boehmite for thermal stability and mechanical strength, and a second ceramic coating layer for enhanced adhesion to electrodes. This segmentation provides superior performance in both adhesive force and cycle life compared to a single-layer coating.
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 separator exhibits excellent adhesive force to electrodes, improved cycle-life characteristics, and air permeability, effectively preventing short circuits and enhancing battery safety.
Implementation Method 1
a coating layer positioned on at least one surface of the porous substrate and including polyethylene particles and a first ceramic
Implementation Method 2
The separator may be a porous material that may transfer ions or electrolytes
Data Source
AI summary
Provided are a separator for a rechargeable lithium battery and a rechargeable lithium battery including same and the separator for a rechargeable lithium battery comprising: a porous substrate, a coating layer positioned on at least one surface of the porous substrate and comprising polyethylene particles and a first ceramic at a weight ratio of 6:4 to 8:2, and an adhesive layer positioned on one surface of the coating layer and comprising a second ceramic and a binder at a weight ratio of 7:3 to 5:5, wherein the binder comprises polyvinylidene fluoride and a polyvinylidene-hexapropylene copolymer at a weight ratio of 6:4 to 4:6, and the first ceramic and the second ceramic have different average sizes.