PTC Polymer Current Collector for Battery Short-Circuit Safety
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Solution Overview
Problem
Secondary batteries are prone to ignition or explosion due to short phenomena caused by direct contact between positive and negative electrodes, leading to increased heat generation and gas generation, which is exacerbated by overcharging, high temperatures, or external shocks.
Innovation Solution
A current collector with a polymer layer comprising a conductive copolymer that exhibits a positive temperature coefficient (PTC) effect, providing excellent adhesive force and controlling charge migration based on temperature, ensuring low resistance in normal states and increased resistance in abnormal states to prevent electrode assembly energization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a polymer layer is added to the current collector to improve safety, then the adhesive force and safety are improved, but the device complexity increases
Solution Approach 1:
The patent applies composite materials by combining a current collector body with a polymer layer containing conductive copolymer. This composite structure provides both the mechanical support of the current collector and the safety functions (adhesive force, PTC effect) of the polymer layer, resolving the contradiction between improved safety and increased device complexity through material-level integration rather than separate safety components
Solution Approach 2:
The polymer layer serves multiple functions simultaneously: it provides adhesive force to prevent electrode detachment, exhibits PTC effect for overcharge protection, and maintains electrical conductivity for normal operation. This multi-functionality eliminates the need for separate safety components, thereby improving safety without proportionally increasing device complexity
2Reliability
If the polymer layer uses conductive copolymer with PTC effect, then the safety in abnormal states is improved, but the manufacturing precision requirements increase
Solution Approach 1:
The patent utilizes parameter changes by selecting conductive copolymer with specific number average molecular weight (5,000-100,000 g/mol) to achieve the desired PTC effect characteristics. By optimizing the molecular weight parameter, the polymer layer exhibits appropriate resistance increase at elevated temperatures, providing safety in abnormal states while maintaining manufacturability within standard precision tolerances
3Reliability
If the adhesive force of the polymer layer is increased to 20 gf/20 mm or more, then the reliability is improved, but the manufacturing complexity increases
Solution Approach 1:
The patent achieves the required adhesive force (20 gf/20 mm or more) by optimizing polymer layer parameters including thickness (1-10 μm) and composition (conductive copolymer with specific molecular weight). These parameter optimizations enable sufficient adhesion through material properties rather than complex surface treatments or additional bonding processes, maintaining ease of manufacture
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 current collector maintains stable electrical performance in normal conditions while securing safety by blocking energization in abnormal conditions, preventing ignition or explosion.
Implementation Method 1
A current collector with a polymer layer comprising a conductive copolymer that exhibits a positive temperature coefficient (PTC) effect, providing excellent adhesive force and controlling charge migration based on temperature, ensuring low resistance in normal states and increased resistance in abnormal states to prevent electrode assembly energization
Data Source
AI summary
Disclosed is a current collector, and a method for using the current collector. The current collector is capable of forming an electrode, which does not affect performance and operation of a secondary battery by exhibiting, in a normal state, excellent electrical characteristics including low resistance, and can ensure stability by blocking, in an abnormal state, energization of an electrode assembly through resistance increase. The current collector is also capable of ensuring excellent adhesive force between layers forming the electrode.