Cathode Current Collector Geometry for Nail Penetration Safety
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Solution Overview
Problem
Existing electrochemical cells face safety issues such as overcharge and internal short-circuiting, particularly with needle penetration, which current safety methods like protective circuits and heat blocking mechanisms are inadequate in preventing explosions and combustion.
Innovation Solution
The cell design features a cathode current collector with cathode active material coated on one side, covering both outer surfaces, and having a thickness of 70 to 150% of the coated layer, preventing direct contact with a needle-shaped conductor and reducing resistance during penetration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If protective circuits and heat blocking mechanisms are used to improve cell safety, then cell safety is improved, but device complexity increases and cost increases
Solution Approach 1:
The invention extracts the safety function from external protective circuits and heat blocking mechanisms, and integrates it directly into the electrode structure itself. The current collector is designed with specific geometric features (protrusions and recesses) that inherently prevent nail penetration and internal short-circuiting, eliminating the need for separate safety devices.
Solution Approach 2:
The electrode structure serves its own safety function through its own geometric design. The current collector's protrusions and recesses create a mechanical barrier that automatically prevents penetration without requiring external monitoring or intervention systems.
2Reliability
If separator heat blocking is used to prevent internal short-circuiting, then cell safety is improved, but it is ineffective when heat generation occurs abruptly
Solution Approach 1:
The safety barrier is prepared in advance through the predetermined geometric structure of the current collector. The protrusions and recesses are built into the electrode design before assembly, creating a pre-positioned mechanical barrier that immediately prevents penetration without requiring thermal response time.
3Reliability
If organic electrolyte additives are used to prevent overcharge, then cell safety is improved, but cell performance deteriorates
Solution Approach 1:
The invention replaces chemical safety mechanisms (electrolyte additives that react chemically to prevent overcharge) with a mechanical safety mechanism (geometric structure of current collector that physically prevents penetration). This mechanical approach does not interfere with electrochemical performance.
4Quantity of substance
If cathode active material is coated on both sides of current collector to maximize capacity, then capacity density is improved, but safety against needle penetration deteriorates
Solution Approach 1:
The current collector is designed with non-uniform geometry featuring protrusions and recesses. The protrusion portions extend toward the separator to create a mechanical barrier, while recess portions provide space for active material coating. This local variation in geometry optimizes both safety (through protrusions) and capacity (through recesses).
Solution Approach 2:
The current collector breaks symmetry by having different heights at different locations (protrusions versus recesses). This asymmetric structure creates a directional barrier against penetration while maintaining adequate active material coating areas, resolving the conflict between safety and capacity.
Data Source
AI summary
Provided is a cell wherein out of electrodes constituting the cell, the outermost two electrodes are both cathodes, cathode current collectors of the cathodes are single-side coated with cathode active materials on the first surfaces thereof, other sides of cathode current collectors non-coated with cathode active materials are disposed toward the outside of a cell assembly and the thickness of cathode current collectors is 70 to 150% of that of the cathode active material coated layer. The cell in accordance with the present invention exhibits excellent safety in a nail penetration test.