Battery Separator Coating with 3D and Wire Particles for Thin Cells
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Solution Overview
Problem
Current rechargeable lithium batteries face challenges in achieving high capacity and safe operation due to limitations in separator thickness, adhesion to electrodes, and heat resistance, which can lead to issues like electrode detachment and reduced cycle life.
Innovation Solution
A separator for rechargeable lithium batteries is designed with a substrate coated sequentially with a heat-resistant layer containing three-dimensional structured particles and wire-type particles, and an adhesive layer, optimizing particle size and ratio to enhance packing density, heat resistance, and adhesive strength, even at thin thicknesses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the thickness of the separator is reduced to increase battery capacity, then the battery capacity is improved, but the adhesion to electrode and heat resistance deteriorate
Solution Approach 1:
The separator is constructed as a composite material system consisting of a base separator layer and a coating layer. The coating layer contains three-dimensional structured particles (providing heat resistance through thermal expansion and structural stability) and wire-type particles (providing adhesion through interlocking and bridging effects). This composite structure enables the thin separator to maintain both mechanical adhesion and thermal resistance properties despite reduced thickness.
Solution Approach 2:
The coating layer is applied selectively on one or both surfaces of the separator, concentrating the functional properties (adhesion and heat resistance) at the critical interfaces where the separator contacts the electrodes. This local enhancement allows the bulk separator to remain thin while the surface regions provide the necessary performance characteristics for reliable operation.
2Use of energy by moving object
If the separator thickness is reduced to enhance battery performance, then the energy density is improved, but the heat resistance deteriorates
Solution Approach 1:
The coating layer combines three-dimensional structured particles with high heat resistance (such as alumina, silica, or boehmite) and wire-type particles. The three-dimensional structured particles form a thermally stable network that maintains structural integrity at elevated temperatures, preventing separator collapse and maintaining safety even when the overall separator thickness is reduced to improve energy density.
Solution Approach 2:
The invention changes the physical and chemical parameters of the separator surface by applying a coating layer with specific particle size distributions, particle shape ratios, and material compositions. These parameter modifications enhance the thermal properties of the thin separator, enabling it to resist heat-induced degradation while maintaining the reduced thickness necessary for high energy density.
3Quantity of substance
If the separator thickness is reduced to increase battery capacity, then the capacity is improved, but the adhesion to electrode deteriorates
Solution Approach 1:
The coating layer incorporates wire-type particles (such as nanofibers or whiskers) that provide exceptional adhesion strength through their high aspect ratio and ability to form mechanical interlocks with both the separator and electrode surfaces. The three-dimensional structured particles complement this by creating a rough, interlocking surface topology. This composite particle system ensures strong adhesion even when the separator thickness is minimized to maximize battery capacity.
Solution Approach 2:
The three-dimensional structured particles provide surface curvature and irregularity that enhance mechanical interlocking with the electrode. The varied shapes and sizes of these particles create a rough surface topology that increases the contact area and mechanical bonding strength between the separator and electrode, compensating for the reduced separator thickness.
Data Source
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AI summary
Disclosed is a separator for a rechargeable lithium battery comprising a substrate, a heat resistance layer and an adhesive layer sequentially on one surface of the substrate. The heat resistant layer includes three-dimensional structured particles and wire-type particles. An average particle diameter (D50) of the three-dimensional structured particles is 100 nm to 1,000 nm measured by laser diffraction. An average length of the wire-type particles is 100 nm to 3 µm and an average diameter of the wire-type particles is 1 nm to 100 nm, wherein the average length and the average diameter of the wire-type particles are each independently, the average length and the average diameter measured by scanning electronic microscope (SEM) analysis. The average length of the wire-type particles is at least 5 times as large as its average diameter, and a ratio of the average length of the wire-type particles and the average diameter of the three-dimensional structured particles is 30:1 to 1:10. The adhesive layer includes an adhesive binder.