Thermoplastic Current Interrupt for Battery Short Circuit Protection
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Solution Overview
Problem
Direct shorting of primary electrochemical batteries leads to increased internal cell temperatures, causing electrolyte expansion and potential sudden disassembly due to hydraulic pressurization, necessitating a solution to mitigate temperature increases during short-circuit scenarios.
Innovation Solution
Incorporating a current interrupt assembly within the anode conducting assembly, featuring a thermoplastic component with a conductive plating, which deforms and reduces electrical conductivity when the temperature reaches its glass transition point, thereby limiting current flow and preventing further temperature increases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a conventional anode conducting assembly is used, then electrical conductivity is maintained, but temperature increases uncontrollably during short-circuit scenarios
Solution Approach 1:
The patent applies parameter changes by utilizing the glass transition temperature parameter of thermoplastic materials. The thermoplastic component is selected to undergo structural changes at a specific temperature range, transforming from a rigid state to a softened state, which automatically reduces electrical conductivity and interrupts current flow when overheating occurs during short-circuit conditions.
Solution Approach 2:
The thermoplastic component serves as an intermediary element between the anode current collector and the negative cover. This intermediary material provides the electrical conductive path under normal conditions but automatically deforms and increases resistance when temperature rises, thereby mediating the protection against thermal runaway without requiring external control systems.
2Reliability
If the thermoplastic glass transition temperature is set low, then current flow is interrupted earlier for safety, but normal operational current capacity is reduced
Solution Approach 1:
The patent applies local quality by designing the thermoplastic component with specific localized properties - selecting materials with glass transition temperatures in the range of 80°C to 150°C. This creates a localized thermal response zone that triggers current interruption only when temperature exceeds safe operating limits, while maintaining full current capacity during normal operational temperature ranges.
Solution Approach 2:
The thermoplastic component provides dynamic response to temperature changes. Under normal operating conditions, the material maintains its rigid structure and full electrical conductivity. When temperature approaches the glass transition range during abnormal conditions, the material dynamically softens and deforms, automatically reducing current flow capacity to protect the battery system.
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 decreases the risk of battery disassembly by throttling current output and reducing internal temperature increases during short-circuit conditions, ensuring safer battery operation.
Implementation Method 1
the thermoplastic of the current interrupt assembly has a glass transition temperature well-below the temperature at which the battery is at risk of sudden disassembly. Thus, when the temperature of the current interrupt assembly reaches the glass transition temperature of the thermoplastic material, the thermoplastic material deforms
Implementation Method 2
when the temperature of the current interrupt assembly reaches the glass transition temperature of the thermoplastic material (e.g., as a result of resistive heating)
Data Source
AI summary
To counteract the potentially destructive effects of temperature increases in primary batteries during short circuit conditions, a current interrupt may be positioned within an anode conductive path. The current interrupt may comprise a thermoplastic substrate having a low glass transition temperature, and having a conductive coating thereon to form a portion of the anode conductive path. During a short circuit, the temperature within the battery increases above the glass transition temperature of the thermoplastic substrate, thereby causing the current interrupt to deform, thereby degrading the portion of the anode conductive path defined by the current interrupt, decreasing the amount of current flowing through the anode conductive path, and effectively limiting the temperature increase within the battery interior.