Lithium-Ion Battery Thermal Abuse Testing via Impedance-Matched Internal Short Circuit
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Solution Overview
Problem
Current methods for testing the thermal characteristics of lithium-ion batteries are inadequate in simulating realistic failure conditions, particularly in preventing propagation of cell failures, as they often involve unrealistic heating rates, physical damage, and fail to account for variations in cell designs and chemistries, leading to inaccurate safety evaluations.
Innovation Solution
A novel thermal abuse testing method that couples the physical characteristics of a lithium-ion cell with a heating element, using a power supply that matches the cell's impedance and energy profile to simulate internal short circuits and assess propagation risks, ensuring a more realistic and accurate representation of failure scenarios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional thermal abuse testing methods are used with external heating devices, then heating rate control is simplified, but the testing fails to simulate realistic internal short circuit conditions and produces inaccurate safety evaluations
Solution Approach 1:
The battery cell under test serves its own testing function by using its stored chemical energy to heat itself through controlled internal short circuits. The cell acts as both the test subject and the heating source, eliminating the need for external heating devices and accurately simulating realistic failure conditions where cells thermally run away due to internal defects.
Solution Approach 2:
The invention changes the fundamental parameter of heat source location from external to internal. By initiating short circuits within the cell rather than applying external heat, the testing methodology transforms from unrealistic thermal abuse to realistic failure simulation, thereby improving measurement precision of safety evaluations.
2Productivity
If unrealistic heating rates are applied in conventional testing, then thermal runaway can be triggered more quickly, but the testing does not represent real-world failure conditions
Solution Approach 1:
The cell's own chemical energy serves as the heat source, allowing thermal runaway to develop at naturally occurring rates rather than externally imposed rates. This self-heating mechanism ensures that the timing and progression of thermal events reflect real-world conditions while maintaining testing efficiency.
Solution Approach 2:
The heating rate parameter transitions from being externally controlled and unrealistic to being internally generated and realistic. By allowing the cell to heat itself through controlled short circuits, the testing achieves both speed and representativeness of actual failure conditions.
3Reliability
If physical damage methods like nail penetration are used to create internal short circuits, then cell failure can be reliably triggered, but the cell structure is damaged and gas buildup and venting behaviors become inaccurate
Solution Approach 1:
The cell initiates its own failure through internally generated short circuits rather than suffering external physical trauma. This self-failure mechanism triggers thermal runaway through electrochemical processes that naturally occur in defective cells, preserving the integrity of gas buildup and venting behaviors for accurate measurement.
Solution Approach 2:
The mechanical nail penetration method is replaced with an electrochemical short circuit initiation method. Instead of physically puncturing the cell structure, the invention uses electrical discharge to create controlled internal short circuits, thereby maintaining cell structural integrity while reliably triggering failure conditions.
4Productivity
If uniform heating is applied to all cells in a pack, then thermal runaway can be triggered consistently, but variations in cell designs and chemistries are not accounted for
Solution Approach 1:
Instead of applying uniform heating to all cells, the invention allows each cell to generate its own localized heat through internal short circuits. This localized heating approach accounts for individual cell characteristics, designs, and chemistries, as each cell's internal resistance and electrochemical properties determine its specific thermal response and failure behavior.
Solution Approach 2:
The heating approach changes from uniform external application to localized internal generation. This parameter change enables the testing to naturally adapt to variations in cell designs and chemistries, as each cell's internal properties dictate its thermal runaway characteristics without requiring standardized external heating protocols.
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
This approach enhances the fidelity of battery safety testing, allowing for more accurate evaluations of lithium-ion battery systems by simulating real-world failure conditions, reducing the risk of propagation, and improving the design of advanced battery systems.
Implementation Method 1
delivering current to the heating element. The delivery of the current includes using a power supply. The heating of the heating element, which results from the delivery of the current, causes a failure of the test cell
Data Source
AI summary
According to an exemplary embodiment of the inventive test method, heat is externally applied to an electrochemical “trigger” test cell via a heating element that receives electrical current from a power supply that is characterized by approximately the same impedance as the trigger test cell. For instance, the power supply and the trigger cell can be same or similar cells. The trigger test cell is proximate “propagation-vulnerable” test cells in a cell pack. Because of the impedance-matching between the power supply and the trigger test cell, the ensuing propagative behavior is at least substantially attributable to the short-circuit current failure of the trigger cell as brought about by the externally applied heat. The energy and/or power characterizing the power supply's current at least approximately equates to the energy and/or power characterizing the trigger test cell's short circuit current. Exemplary inventive testing is propitiously representative of real-world propagative failure events.