Cathode Tab Insulation Layer for Battery Safety
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Solution Overview
Problem
Secondary batteries face safety issues due to potential short circuits between the cathode and anode, particularly during high-temperature conditions, where the separator's heat resistance is insufficient, and misalignment or sharp edges can lead to microscopic internal shorts, compromising battery performance.
Innovation Solution
A cathode with a cathode tab protruding from the current collector, coated with an insulation layer made of insulating materials such as butyl acrylate, styrene, or styrene-butadiene rubber, which enhances insulation and reduces the likelihood of physical short circuits by increasing the insulation area and preventing exfoliation during bending.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a microporous membrane separator is used to maintain electrical insulation between cathode and anode, then electrical insulation is provided under normal conditions, but heat resistance properties are insufficient at high temperatures causing separator shrinkage and thermal runaway
Solution Approach 1:
The insulation function is divided into two segments: the microporous membrane separator handles electrical insulation under normal conditions, while the insulating coating layer on the cathode tab provides high-temperature insulation protection. This segmentation allows each component to specialize in its optimal temperature range.
Solution Approach 2:
An insulating coating layer is pre-applied to the cathode tab before battery assembly. This preliminary action ensures that when high-temperature conditions occur, the insulation protection is already in place, preventing thermal runaway before it can initiate.
2Reliability
If insulation tape is wrapped around the electrode tab to prevent short circuits, then short circuit prevention is improved, but the winding operation becomes highly complicated and the wrapped portion increases electrode assembly thickness
Solution Approach 1:
The mechanical winding process of insulation tape is replaced with a coating process. The insulating material is applied as a liquid or paste coating that cures to form a protective layer, eliminating the complex winding operation while providing equivalent or superior insulation protection.
Solution Approach 2:
The insulating material is changed from a solid tape form to a coating form (liquid or paste). This parameter change in physical state allows for simpler application methods and eliminates the complexity of winding operations while maintaining insulation effectiveness.
3Reliability
If insulation tape is wrapped extended length from upper end to bottom to ensure coverage, then insulation coverage is improved, but the wrapped portion causes increase in electrode assembly thickness and may be easily loosened during bending
Solution Approach 1:
The insulating coating layer is applied as a thin film on the cathode tab surface. This thin film provides adequate insulation coverage without significantly increasing the electrode assembly thickness, unlike extended insulation tape wrapping.
Solution Approach 2:
The insulating coating is merged with the cathode tab structure itself, forming an integrated component. This eliminates the need for separate insulation tape layers and reduces overall thickness while maintaining coverage.
4Productivity
If edges of cathode or anode coated with polymer electrolyte are stacked, then battery assembly is completed, but sharp parts with irregular surfaces cause microscopic internal short circuits due to uneven coating
Solution Approach 1:
An insulating coating layer is applied to the cathode tab edges before assembly. This beforehand cushioning protects against potential short circuits that could occur during stacking, compensating for the irregular surfaces and uneven polymer electrolyte coating at the edges.
Data Source
Figure 1~2A
Figure 2B~3B
Figure 4~5
AI summary
Provided is a cathode including a cathode current collector, a cathode tab protruding from the cathode current collector, and an insulation layer coated with an insulating material on the cathode tab, and a secondary battery including the cathode. Since the cathode of the present invention includes an insulation layer on a cathode tab, the present invention may prevent an internal short circuit which may occur due to cell deformation or sharp edges of electrodes, which are formed during cutting of the electrodes in a preparation process of the battery, when the electrodes are stacked, or may prevent a physical short circuit between the cathode and the anode due to shrinkage of a separator in a high-temperature atmosphere. In a case where the cathode is used in a lithium secondary battery, safety and reliability in battery performance may be significantly improved.