Li-Ion Cell Calibration for Fast Charging Without Lithium Plating
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Solution Overview
Problem
Lithium-ion batteries experience performance degradation due to metallic lithium deposition on the anode, leading to irreversible capacity loss and reduced lifespan, despite existing methods not fully addressing this issue.
Innovation Solution
A calibration method involving multiple charging and discharging cycles with different regimes, measuring anode potential, and calculating a limit value to interrupt or reduce charging when the anode potential becomes negative, coupled with a mathematical model linking the limit value to charging regime, initial surface capacity, and health state to extend battery lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If fast charging is performed, then charging speed is improved, but metallic lithium deposition occurs on the anode
Solution Approach 1:
The patent applies preliminary action by performing calibration cycles before actual charging to determine safe operating limits. The method pre-establishes the relationship between anode potential, state of charge, and charging rate through calibration, so that during subsequent charging operations, the predetermined characteristic quantity can be calculated and compared against stored limit values to prevent lithium deposition before it occurs.
Solution Approach 2:
The patent implements feedback by continuously calculating the predetermined characteristic quantity during charging based on measured anode potential and comparing it against stored limit values. The charging rate is dynamically adjusted based on this feedback - when the calculated quantity approaches the limit, the charging rate is reduced or interrupted, creating a closed-loop control system that prevents lithium deposition while maximizing charging speed.
2Productivity
If charging continues without interruption, then charging completeness is improved, but battery lifespan is reduced due to lithium deposition
Solution Approach 1:
The patent applies partial action by intentionally not charging the battery to 100% state of charge when it would exceed the predetermined limit. Instead, charging is interrupted or the rate is reduced when the calculated predetermined characteristic quantity approaches the stored limit value. This partial charging approach prevents lithium deposition and extends battery lifespan, accepting that some charging capacity remains unused to protect the battery's long-term health.
Solution Approach 2:
The patent implements dynamics by making the charging process adaptive rather than static. The charging rate is dynamically adjusted based on real-time calculation of the predetermined characteristic quantity and comparison with stored limit values. The method transitions between different charging rates (fast charging when safe, reduced charging when approaching limits) to balance charging completeness with battery lifespan extension.
3Adaptability or versatility
If calibration data is stored for multiple charging regimes, then adaptability is improved, but memory requirements and data complexity increase
Solution Approach 1:
The patent applies universality by creating a family of limit values that can be used across multiple charging regimes. Instead of storing completely separate calibration data for each charging rate, the method establishes limit values during calibration that are valid for different charging conditions. The same stored limit values can be applied universally across various charging regimes by adjusting the predetermined characteristic quantity calculation, reducing data storage requirements while maintaining adaptability.
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 method effectively determines the limit value for interrupting charging to prevent metallic lithium deposition, thereby extending the lifespan of lithium-ion batteries by accounting for their health state and performance degradation over time.
Implementation Method 1
measuring an electrical potential of an anode of the battery element provided
Implementation Method 2
when a Li-ion battery is charged, lithium ions Li+
Implementation Method 3
the formation of a deposit of metallic lithium on the surface of the graphite particles of the anode. Such a phenomenon generally occurs during battery charging, and is commonly referred to by the English expression 'lithium plating'
Implementation Method 4
When such a deposit comes into contact with the electrolyte, the lithium generally oxidizes to form lithium carbonate compounds (ROCO2 Li) or inorganic compounds (Li2CO3, LiF)
Data Source
Figure 1~3
Figure 4
Figure 5~6
AI summary
The invention relates to a calibration method for a family of Li-ion battery cells, comprising the steps of: - supplying a battery cell from the family, the battery cell (2) having a given initial surface capacitance; - evaluating a current state of health of the supplied battery cell (2); - for the supplied battery cell, carrying out a plurality of successive cycles each comprising a charging phase and a discharging phase, at least two charging phases being carried out at different charging rates; - for each charging phase: • measuring the anode potential of the battery cell; • calculating the value of a predetermined characteristic quantity of the battery cell; • determining a limit value of the predetermined characteristic quantity for which the anode potential becomes less than or equal to a predetermined threshold; • recording the limit value.