Polymer Layer Anode Separator Nail Penetration Safety
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Solution Overview
Problem
Lithium-ion batteries face safety issues due to external force punctures, leading to potential explosions, as the existing safety technology is not mature enough to prevent short circuits during nail penetration, which can cause significant heat generation and anode active material failure.
Innovation Solution
An electrochemical device with a polymer layer between the anode active material layer and the separator, comprising spherical polymer particles with specific sphericity, melting temperature, and porosity, which increases the electric resistance and binding force, preventing direct contact between the cathode current collector and the anode active material layer during nail penetration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a polymer layer is added between the anode active material layer and the separator to prevent short circuits during nail penetration, then safety performance is improved, but device complexity increases
Solution Approach 1:
A polymer layer is introduced as an intermediary component between the anode active material layer and the separator. This polymer layer acts as a mediator that prevents direct contact between the cathode current collector and anode active material during nail penetration, thereby eliminating short circuits without fundamentally changing the battery's core structure.
Solution Approach 2:
The polymer layer is implemented as a thin film structure with specific thickness (0.5-5 μm) that provides protective functionality. This thin film approach allows the safety mechanism to be integrated with minimal additional volume and structural complexity while maintaining effectiveness in preventing nail penetration short circuits.
2Reliability
If the polymer layer thickness is increased to improve nail penetration resistance, then safety performance is improved, but kinetic performance deteriorates
Solution Approach 1:
The polymer layer parameters are precisely optimized within specific ranges: thickness of 0.5-5 μm, porosity of 20-80%, and particle diameter of 0.2-2 μm. These parameter changes create an optimal balance where the layer is thick enough to provide nail penetration resistance but thin and porous enough to allow sufficient lithium ion transport for maintaining kinetic performance.
Solution Approach 2:
The polymer layer is designed with controlled porosity (20-80%) which allows lithium ions to pass through during normal charging and discharging operations. This porous structure ensures that while the layer provides mechanical protection against nail penetration, it does not significantly hinder ion transport, thus maintaining kinetic performance.
3Reliability
If polymer particles with high sphericity are used to improve binding force and prevent short circuits, then safety performance is improved, but manufacturing precision requirements increase
Solution Approach 1:
The polymer particles are specified with a sphericity range of 0.70-1.0 rather than requiring perfect spheres. This parameter specification balances the need for high binding force (achieved with higher sphericity particles) against the practical constraints of manufacturing precision, allowing for a realistic production tolerance while maintaining effective safety 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
The polymer layer enhances the mechanical safety performance by preventing internal short circuits and reducing the likelihood of thermal runaway during nail penetration, improving the nail penetration pass rate and maintaining kinetic performance.
Implementation Method 1
increases the electric resistance and binding force, preventing direct contact between the cathode current collector and the anode active material layer during nail penetration
Implementation Method 2
the polymer particles have a melting temperature of about 80°C to about 500°C
Data Source
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AI summary
This application relates to an electrochemical device having safety performance. Specifically, this application provides an electrochemical device, including: an anode, the anode comprising an anode active material layer; a separator; and a polymer layer, wherein the polymer layer is disposed between the anode active material layer and the separator. The polymer layer comprises polymer particles, and the polymer particles according to some embodiments of this application have a sphericity of about 0.70 to about 1.0. This application effectively protects the anode by providing a non-conductive or poorly conductive inactive substance (for example, non-conductive polymer particles) between the anode active material layer and the separator, so as to ensure that the electrochemical device does not generate an internal short circuit when being impacted, penetrated or squeezed by an external force, which causes a failure of the electrochemical device.