Composite Battery Current Collector for Heat Shutdown and Adhesion
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Solution Overview
Problem
Secondary batteries face issues with abnormal heating due to internal short-circuits, leading to potential fires and reduced cycle characteristics due to the peeling off of mixture layers from metallic foils during expansion and contraction.
Innovation Solution
Incorporating a current collector with a resin layer and roughened metallic foils, where the resin layer melts at a lower temperature than the metallic foils, causing the foils to break and interrupt the current, thereby preventing overheating and maintaining the integrity of the mixture layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the metallic foil is made thinner to increase battery capacity, then the energy density is improved, but the strength of the metallic foil decreases causing the mixture layer to peel off
Solution Approach 1:
The current collector is constructed as a composite material consisting of a resin layer and metallic foils. The resin layer has a melting point lower than the metallic foil, creating a temperature-dependent safety mechanism. This composite structure allows the metallic foil to be thin for high capacity while the resin provides structural support and emergency protection against thermal runaway.
2Reliability
If a thick metallic foil is used to prevent peeling of the mixture layer, then the cycle characteristics are improved, but the battery capacity decreases
Solution Approach 1:
The current collector uses a composite structure with resin layer and metallic foils. The resin layer serves as a support structure that prevents mixture layer peeling during cycling, allowing the metallic foil to be made thinner to increase capacity without compromising cycle characteristics.
3Object-affected harmful factors
If the resin layer melts during abnormal heating, then the current is interrupted preventing fire, but the metallic foil breaks
Solution Approach 1:
The resin layer is designed to melt during abnormal heating, converting the harmful thermal energy into a beneficial protective action. The melting resin expands and applies pressure to the metallic foil, causing it to break and interrupt the internal short circuit current, thereby preventing fire. The metallic foil breaking is an acceptable outcome as it achieves the primary safety goal.
4Reliability
If the metallic foil surface is roughened to improve mixture layer adhesion, then the cycle characteristics are improved, but the manufacturing precision becomes more difficult
Solution Approach 1:
The metallic foil surface is roughened locally at specific locations rather than uniformly across the entire surface. This localized roughening provides sufficient adhesion for the mixture layer while maintaining manufacturing feasibility and controlling the roughness parameters within acceptable ranges.
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 solution enhances safety by interrupting the current at lower temperatures during abnormal heating and improves cycle characteristics by preventing the peeling off of mixture layers from metallic foils.
Implementation Method 1
the resin layer melts at a lower temperature than the metallic foils, causing the foils to break
Implementation Method 2
A surface of the metallic foils on which the mixture layer is formed is roughened
Data Source
AI summary
A non-aqueous electrolyte secondary battery disclosed herein includes a positive electrode, a negative electrode, and a non-aqueous electrolyte. The positive and negative electrodes each include a current collector and a mixture layer formed on the surface of the current collector. The current collector includes a resin layer and metallic foils provided on both surfaces of the resin layer in at least one of the positive and negative electrodes. A surface of the metallic foils on which the mixture layer is formed is roughened. Furthermore, the average X (μm) of the thicknesses at the thinnest parts and the average Y (μm) of the thicknesses at the thickest parts of the metallic foil determined based on a plurality of obtained sectional SEM images in a stacked direction of the resin layer and the metallic foils satisfy the following relationship: 0.1 μm<X<4 μm, and 1.2≤Y/X.