Cathode Tab Insulation Coating for Lithium Battery Short-Circuit Prevention
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Solution Overview
Problem
Current insulation methods for lithium secondary batteries, such as using microporous membranes and non-aqueous binders, are inadequate in preventing physical short circuits due to limitations in heat resistance, flexibility, and simultaneous coating processes, leading to safety concerns and performance issues.
Innovation Solution
A non-aqueous organic solvent-based insulation-layer forming composition using a conjugated diene copolymer with a specific Tg range, which allows for simultaneous cathode and insulating liquid coating, providing flexibility, insulating characteristics, and electrolyte resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a microporous membrane separator is used for insulation, then electrical insulation between cathode and anode is maintained, but heat resistance is insufficient leading to thermal runaway at temperatures above 120°C to 160°C
Solution Approach 1:
The patent combines the separator function with an insulating coating layer formed by a conjugated diene copolymer. The coating layer is applied on top of the microporous membrane separator, merging the electrical insulation function of the separator with the thermal stability function of the polymer coating, thereby achieving both electrical insulation and high-temperature resistance.
Solution Approach 2:
The patent uses a composite structure consisting of a microporous membrane separator and a conjugated diene copolymer coating layer. This composite material approach allows the system to benefit from the electrical insulation properties of the separator and the thermal stability of the copolymer, resolving the contradiction between electrical insulation and heat resistance.
2Reliability
If insulation tape is attached on the electrode tab to prevent short circuit, then physical short circuit prevention is improved, but the winding process becomes complicated and electrode assembly thickness increases
Solution Approach 1:
The patent merges the insulation function with the coating process by forming an insulating coating layer directly on the electrode tab during the slurry coating step. This eliminates the need for separate insulation tape attachment and winding operations, simplifying the manufacturing process while maintaining short circuit prevention.
Solution Approach 2:
The insulating coating layer is formed automatically during the normal slurry coating process without requiring additional insulation-specific operations. The coating process itself provides the insulation function, making the system self-sufficient and eliminating complex separate insulation steps.
3Strength
If non-aqueous binder (PVDF) is used for insulating layer, then adhesion is reduced, but if aqueous styrene-butadiene copolymer is used, then simultaneous coating with cathode slurry is impossible due to gelation
Solution Approach 1:
The patent changes the chemical composition parameters of the binder by using a conjugated diene copolymer with specific glass transition temperature characteristics. This parameter change allows the binder to maintain adhesion while remaining compatible with simultaneous coating processes, avoiding the gelation issue of aqueous styrene-butadiene copolymer and the poor adhesion of PVDF.
Solution Approach 2:
The patent applies the insulating coating layer with local insulating properties to the electrode tab region where it is needed. The conjugated diene copolymer provides localized insulation on the tab while allowing the rest of the electrode to maintain its normal structure and coating characteristics, enabling simultaneous coating.
4Reliability
If insulating layer is formed to prevent short circuit, then safety is improved, but manufacturing process complexity and cost increase
Solution Approach 1:
The patent combines the insulating layer formation with the existing slurry coating process. The insulating coating is applied in the same manufacturing step as the cathode slurry coating, merging two functions into one process step and avoiding additional manufacturing complexity.
Solution Approach 2:
The manufacturing process itself provides the insulation function through the conjugated diene copolymer coating formed during normal slurry application. No separate insulation manufacturing steps are needed, as the coating process serves both the electrode formation and insulation functions simultaneously.
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 physical short circuits and enhances the safety and performance of lithium secondary batteries by maintaining insulating properties and adhesion even in electrolyte environments, while simplifying the manufacturing process and reducing costs.
Implementation Method 1
the non-aqueous organic solvent-based insulation-layer forming composition using a conjugated diene copolymer with a specific Tg range, which allows for simultaneous cathode and insulating liquid coating, providing flexibility, insulating characteristics, and electrolyte resistance
Implementation Method 2
a non-aqueous organic solvent-based insulation-layer forming composition using a conjugated diene copolymer
Data Source
AI summary
An insulation-layer forming composition includes: a conjugated diene copolymer as a binder polymer; and a non-aqueous organic solvent as a dispersion solvent, the conjugate diene copolymer having a Tg of −10° C. to 40° C. According to one embodiment of the present disclosure, a physical short circuit between the cathode and the anode due to the defects, such as separator shrinkage and electrode folding in the lithium secondary battery, can be prevented. Moreover, cathode coating and insulating liquid coating can be simultaneously performed, by forming, on a tab portion of the cathode, an insulating layer satisfying all of flexibility, insulating characteristics, and electrolyte resistance characteristics. A cathode including the insulation-layer forming composition, a method of forming the cathode, and a lithium secondary battery including the cathode are also provided.