LFP Battery Abnormality Detection via Mixed Oxide Voltage
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Solution Overview
Problem
Lithium iron phosphate batteries exhibit a small voltage change during charging and discharging, making it difficult to estimate the state of the battery based on voltage changes, which complicates abnormality detection in assembled batteries.
Innovation Solution
An abnormality detection method that uses a mixture of lithium iron phosphate and lithium transition metal oxide as positive active materials, allowing for lithium ion insertion and extraction reactions in a higher potential range, enabling accurate state estimation and abnormality detection by measuring voltage near the charge end point during charge-discharge cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If lithium iron phosphate is used as the positive active material, then the battery is inexpensive and has good safety, but the voltage change during charging and discharging is small making state estimation difficult
Solution Approach 1:
The patent changes the measurement parameter from standard operating voltage to open circuit voltage measured after a predetermined time period following current interruption. This parameter change allows accurate state estimation despite the inherently small voltage changes in LFP batteries during normal operation.
Solution Approach 2:
The patent performs preliminary action by interrupting the current and allowing a predetermined time period to elapse before measuring the open circuit voltage. This preliminary waiting period ensures the voltage stabilizes to its true open circuit value, enabling accurate state estimation that can be used for abnormality detection.
2Ease of operation
If voltage measurement is used for state estimation in LFP batteries, then the measurement method is simple, but the estimation accuracy is insufficient due to small voltage changes
Solution Approach 1:
The patent changes when the voltage measurement is taken - specifically measuring open circuit voltage after current interruption rather than measuring during active charging/discharging. This temporal parameter change captures larger, more detectable voltage signals while maintaining measurement simplicity through automated timing control.
Solution Approach 2:
The patent implements feedback by using the measured open circuit voltage to determine the state of charge, then using this state information to detect abnormalities in individual battery cells within the assembled battery. The system continuously monitors and compares voltage measurements to identify deviations indicating internal short circuits or other faults.
3Reliability
If the charge-discharge range is limited to the lithium iron phosphate potential range, then the battery operates safely, but abnormality detection capability is reduced
Solution Approach 1:
The patent performs preliminary charging to a voltage higher than the typical LFP charge end point voltage, then interrupts current and measures open circuit voltage after a predetermined time. This preliminary over-charge followed by stabilization allows detection of voltage deviations that indicate abnormalities, while the actual operating range remains within safe limits.
Solution Approach 2:
The patent applies partial excessive action by temporarily charging to a voltage slightly higher than the normal operating range to enable better state estimation, then immediately interrupting and measuring. The excessive voltage application is brief and controlled, maintaining overall safety while improving detection capability during the measurement phase.
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 allows for effective detection of internal short-circuits, capacity deterioration, and state of charge deviations among energy storage devices, improving the reliability of abnormality detection in assembled batteries.
Implementation Method 1
Each of the energy storage devices contains, as a positive active material, lithium iron phosphate and lithium transition metal oxide that allows insertion and extraction reaction of a lithium ion in a potential range higher than that of the lithium iron phosphate
Data Source
AI summary
An abnormality detection method detects abnormality of an assembled battery including energy storage devices by an abnormality detection device. Each energy storage device contains, as a positive active material, lithium iron phosphate and lithium transition metal oxide that allows insertion and extraction reaction of a lithium ion in a potential range higher than that of the lithium iron phosphate. A ratio of an amount of charge based on a total amount of the lithium transition metal oxide to an amount of charge based on a total amount of the positive active material in a charge-discharge range, in which the energy storage device is used, is 5% or more. The abnormality detection device acquires voltage of each of the energy storage devices near a charge end point in the charge-discharge range where the energy storage device is used and detects abnormality in the assembled battery using the acquired voltage of the energy storage devices.