Shape Memory Current Interrupt for Battery Thermal Runaway
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Solution Overview
Problem
Current interrupt devices (CIDs) for electrochemical cells often fail to prevent catastrophic failure due to gas exposure and can lead to further damage, as they rely on internal pressure for current interruption, which is inefficient and unreliable.
Innovation Solution
A thermal trigger mechanism using shape memory and bi-metallic materials to open the electrical circuit before thermal runaway or short-circuit events, featuring a bus bar with an engineered fracture site that breaks at a predetermined temperature, disconnecting the current flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If internal pressure is used to interrupt current, then current interruption is achieved, but gas exposure occurs and catastrophic failure cannot be prevented
Solution Approach 1:
The patent replaces the mechanical pressure-based interruption system with a thermal-triggered shape memory alloy system. The shape memory alloy undergoes a phase transformation at a predetermined temperature to generate mechanical force that breaks the bus bar, eliminating the need for pressure accumulation and preventing gas exposure while achieving more reliable current interruption.
Solution Approach 2:
The patent changes the triggering parameter from pressure to temperature. By monitoring temperature through the shape memory alloy's phase transformation characteristics, the system can predict and respond to thermal runaway conditions before they lead to catastrophic failure, improving reliability without the harmful effects of pressure-based systems.
2Reliability
If thermal trigger mechanism is used, then current interruption occurs before thermal runaway, but component complexity increases
Solution Approach 1:
The shape memory alloy serves as both the temperature sensor and the actuator. It automatically detects the predetermined temperature through its phase transformation and generates the mechanical force needed to break the bus bar, eliminating the need for separate sensors, actuators, and control systems, thus reducing overall device complexity while maintaining high reliability.
Solution Approach 2:
The patent utilizes the phase transition properties of shape memory alloys to create a passive, automatic triggering mechanism. The phase transformation at a specific temperature naturally produces the mechanical action needed for current interruption, simplifying the device architecture by eliminating complex control systems while ensuring reliable catastrophic failure prevention.
3Measurement precision
If shape memory materials are used for current interruption, then current flow is precisely interrupted at predetermined temperature, but manufacturing precision requirements increase
Solution Approach 1:
The patent incorporates an engineered fracture site in the bus bar during manufacturing, pre-positioning the exact location where the bar will break. This preliminary action ensures that when the shape memory alloy activates, the fracture occurs at the precise intended location, maintaining measurement precision without requiring extremely tight manufacturing tolerances for the entire assembly.
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 thermal trigger mechanism effectively prevents catastrophic failure by precisely interrupting current flow at a predetermined temperature, reducing component complexity and cost while enhancing reliability and safety.
Implementation Method 1
the thermal trigger is dimensioned and configured to deform at a predetermined temperature to break the bus bar at the engineered fracture site
Implementation Method 2
use a thermal trigger (e.g., shape memory and/or bi-metallic materials) to open an electrical circuit
Data Source
AI summary
Embodiments described herein relate to current interrupt devices (CIDs) for electrochemical cells that use a thermal trigger (e.g., shape memory and/or bi-metallic materials) to open an electrical circuit just prior to a thermal runaway or during short-circuit event to prevent catastrophic failure of the electrochemical cell. Embodiments include CIDs comprising a housing, a bus bar coupled to the housing, and a thermal trigger operably coupled to the bus bar. In some embodiments, the bus bar can include an engineered fracture site. In some embodiments, the thermal trigger is dimensioned and configured to deform at a predetermined temperature to break the bus bar at the engineered fracture site. In some embodiments, a portion of the bus bar travels about a hinge, opening the electrical circuit and preventing overcharging, thermal runaway, and/or other catastrophic failure events.