Cylindrical Battery Heat-Resistant Electrode Tape
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Solution Overview
Problem
Cylindrical secondary batteries with jelly-roll type electrode assemblies face issues with heat resistance, leading to extreme thermal shrinkage of separators, which can cause detachment of cathode edge tapes and increase the risk of short circuits and fires due to uncoated electrode portions coming into contact.
Innovation Solution
A cylindrical secondary battery design featuring a jelly-roll type electrode assembly with a polymeric resin film tape having a melting point of at least 130 °C attached to the uncoated portions of the electrodes, along with a center pin and a cap assembly including a PTC thermistor and safety vent, to prevent thermal shrinkage and potential fires.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a porous polyolefin separator is used in a jelly-roll type electrode assembly, then the battery structure is simple and easy to manufacture, but the separator undergoes extreme thermal shrinkage at temperatures of 100°C or higher causing detachment of cathode edge tapes and increasing fire risk
Solution Approach 1:
The patent uses a composite structure consisting of a porous polyolefin separator combined with a heat-resistant tape made of polyimide or aramid material. This composite structure allows the separator to maintain its porosity and ion conductivity while the heat-resistant tape prevents thermal shrinkage and maintains structural integrity at high temperatures, thus resolving the contradiction between ease of manufacture and heat resistance.
Solution Approach 2:
The heat-resistant tape is wrapped around and contains the porous polyolefin separator, forming a nested structure. The inner separator provides the necessary porosity for ion transport, while the outer heat-resistant tape provides thermal stability. This nested configuration allows both materials to function together, maintaining manufacturing simplicity while improving heat resistance.
2Ease of manufacture
If the separator is elongated during production, then the manufacturing process is simplified, but the separator experiences extreme thermal shrinkage at high temperatures leading to core deformation and electrode contact
Solution Approach 1:
The patent combines an elongated porous polyolefin separator with a heat-resistant tape that has been pre-treated to minimize thermal shrinkage. The composite structure allows the separator to benefit from elongation during manufacturing while the heat-resistant tape compensates for thermal shrinkage, maintaining dimensional stability at high temperatures.
Solution Approach 2:
The heat-resistant tape is applied to the separator before final assembly, creating a preliminary constraint that counteracts the thermal shrinkage forces. This preliminary anti-action prevents the separator from deforming during subsequent thermal exposure, maintaining dimensional stability while preserving the benefits of elongation during manufacturing.
3Device complexity
If a conventional electrode assembly without additional protective structures is used, then the device complexity is low, but the uncoated portions of electrodes can come into contact during thermal shrinkage increasing fire risk
Solution Approach 1:
The patent creates a composite protective structure by combining the conventional electrode assembly with a heat-resistant tape layer. This additional layer adds minimal complexity to the overall device while providing a physical barrier that prevents contact between uncoated electrode portions during thermal shrinkage, thereby reducing fire risk.
Solution Approach 2:
The heat-resistant tape acts as an intermediary protective layer between the electrodes and the thermal environment. It mediates the interaction between thermal shrinkage forces and electrode structures, preventing direct contact between uncoated portions while adding minimal complexity to the device design.
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 solution effectively prevents direct contact between uncoated electrode portions during thermal shrinkage, reducing the risk of short circuits and fires, thereby enhancing the heat resistance and safety of the battery.
Implementation Method 1
a first electrode tape including a polymeric resin film having a melting point of at least 130 °C is attached to a first surface of an uncoated portion of the first electrode
Implementation Method 2
a cap assembly including a PTC thermistor and safety vent
Data Source
Figure 1~2
Figure 3~4b
Figure 5~6
AI summary
A cylindrical secondary battery is disclosed. The cylindrical secondary battery includes a jelly-roll type electrode assembly, a center pin inserted to penetrate the central portion of the jelly-roll type electrode assembly, a can accommodating the electrode assembly and the center pin, a cap assembly coupled to an upper opening of the can to seal the can, and a gasket interposed between the can and the cap assembly. In the jelly-roll type electrode assembly, a first electrode, a second electrode and a separator interposed between the two electrodes are wound together. An electrode tape is attached to at least one surface of an uncoated portion of the first electrode at a core of the jelly-roll type electrode assembly. The electrode tape includes a polymeric resin film having a melting point of at least 130 °C.