Lithium Plating Detection in Electrified Vehicle Batteries
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Solution Overview
Problem
Lithium-ion batteries in electrified vehicles are susceptible to lithium plating, which degrades battery capacity and can lead to internal short circuits, particularly under low operating temperatures and high charging currents, and existing detection methods are not robust enough to accurately detect plating under varying conditions.
Innovation Solution
A controller is programmed to detect lithium plating by analyzing the ratio of differential cell voltage to cell charging rate over time, using existing vehicle and battery sensors, and adjust the charging rate or apply heating to mitigate plating, without requiring additional hardware.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high charging current is applied to the battery, then charging speed and productivity are improved, but lithium plating occurs which degrades battery capacity and reliability
Solution Approach 1:
The control system continuously monitors the ratio of differential voltage to cell charging rate and compares it against threshold values. When the ratio exceeds the threshold indicating lithium plating, the system provides feedback to reduce the charging current, thereby preventing capacity degradation while enabling high-speed charging when conditions are favorable
Solution Approach 2:
The charging current is dynamically adjusted based on real-time battery conditions. The system transitions between different charging rates (high, medium, low) according to the calculated plating risk ratio, allowing maximum charging speed when safe and reducing current when plating is detected, optimizing both productivity and reliability
2Device complexity
If lithium plating detection is implemented using existing sensors, then device complexity is reduced, but measurement precision may be insufficient to accurately detect plating under varying conditions
Solution Approach 1:
Instead of relying on a single measurement parameter, the system calculates the ratio of two parameters (differential voltage and cell charging rate) to detect lithium plating. This ratio-based approach compensates for variations in battery conditions and provides accurate detection using only existing voltage and current sensors, maintaining low device complexity while achieving high measurement precision
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 enables online, non-destructive detection and control of lithium plating, extending battery life and capacity by reducing irreversible damage and providing accurate detection across varying operating conditions.
Implementation Method 1
metallic lithium may be deposited on the negative electrodes of battery cells under some operating conditions, which may degrade battery capacity and charge availability and can lead to internal short circuits
Implementation Method 2
cycle the battery to generate heat using cell internal resistance
Data Source
AI summary
A vehicle having a traction battery with at least one cell includes a controller coupled to the traction battery and programmed to control charging and discharging of the traction battery in response to detecting lithium plating in the at least one cell indicated by a ratio of differential voltage of the at least one cell as a function of time to cell charging rate of the at least one cell. In various embodiments, the ratio is compared to a threshold associated with current battery state of charge to indicate lithium plating when the ratio is below the threshold. Lithium plating can also be detected based on a measured cell open circuit voltage (OCV) relative to a previously stored OCV value. In various embodiments, the measured OCV value is calculated based on a measured cell voltage and current, and a previously stored cell internal resistance.