Resin-Sandwiched Battery Current Collector for Over-Discharge Safety
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Solution Overview
Problem
Secondary batteries face safety risks during over-discharge due to short-circuiting between the negative and positive electrodes, which can lead to heat generation and ignition, especially when multiple cells are connected in series.
Innovation Solution
The secondary battery design includes a negative electrode with a thin conductive layer sandwiched between resin layers, which suppresses short-circuit formation by allowing the entire conductive layer to be deposited on the positive electrode during over-discharge, and incorporates a metal sheet for enhanced bonding and thermal conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional current collector with metal foil is used, then electrical conductivity is maintained, but safety risk increases due to short-circuiting during over-discharge
Solution Approach 1:
The patent converts the harmful effect of metal deposition during over-discharge into a beneficial safety mechanism. By using a conductive polymer layer instead of metal foil, the deposited material remains electrically insulating when thickened, transforming the potential short-circuit hazard into a protective barrier that prevents electrode contact.
Solution Approach 2:
The patent changes the material parameter from metallic to conductive polymer, fundamentally altering the electrical properties. The conductive polymer layer has sufficient conductivity for normal operation but becomes insulating when deposited in thick layers during over-discharge, providing intrinsic safety without additional components.
2Reliability
If the conductive layer thickness is increased to prevent short-circuiting, then safety improves, but energy density decreases
Solution Approach 1:
The patent optimizes the conductive layer thickness to a specific range (0.3-1.9 μm) that balances conductivity and safety. This parameter optimization allows the layer to provide adequate electrical conductivity for normal operation while being thin enough to maintain high energy density, resolving the contradiction between safety and energy density.
3Quantity of substance
If a thin conductive layer is used to maintain energy density, then manufacturing efficiency improves, but short-circuit protection is insufficient
Solution Approach 1:
The patent designs the system so that the harmful effect of excessive metal deposition during over-discharge automatically creates a thick insulating layer that protects against short-circuiting. The safety mechanism is self-activating and requires no additional components, maintaining energy density while providing robust protection.
4Power
If multiple cells are connected in series to increase voltage, then power output improves, but safety risk increases due to cumulative short-circuit hazards
Solution Approach 1:
The patent applies the conductive polymer current collector to each cell in the series connection, creating independent safety barriers in each cell. This prevents short-circuiting and heat generation at the cell level, eliminating the cumulative safety risks associated with series connections while maintaining the desired voltage output.
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 prevents short-circuiting, reduces the risk of heat generation and ignition, and enhances energy density, manufacturing efficiency, and safety of the battery.
Implementation Method 1
allowing the entire conductive layer to be deposited on the positive electrode during over-discharge
Data Source
AI summary
In one exemplary embodiment, a secondary battery is provided. The secondary battery includes a positive electrode, a first separator disposed on a side of one surface of the positive electrode, and a first negative electrode disposed to be spaced apart from the positive electrode in a lamination direction with the first separator interposed therebetween, where the first negative electrode includes a first current collector, the first current collector is configured with a first resin layer sandwiched between a pair of first conductive layers, and the pair of first conductive layers each have a thickness of 0.3 μm or more and less than 1.9 μm.