Battery Cell SEI Charge Estimation for Formation Process Control
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Solution Overview
Problem
Existing battery cell formation processes face challenges in achieving uniform and efficient formation of the solid-electrolyte interface (SEI) due to variations in current and voltage settings, leading to suboptimal performance and increased energy consumption.
Innovation Solution
A method to determine the charge quantity of the SEI by measuring the charge on the positive and negative electrodes and using a setpoint curve to control the formation process, ensuring consistent SEI formation across individual battery cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If empirical current and voltage profiles are used for formation process control, then the process can be implemented with simple measurements, but the manufacturing precision of SEI formation deteriorates due to variations in cell quality
Solution Approach 1:
The patent implements feedback control by continuously monitoring the differential capacitance during formation and adjusting the current profile accordingly. The system uses the measured differential capacitance value to determine whether to continue charging or switch to constant voltage mode, creating a closed-loop control system that adapts to individual cell characteristics and eliminates quality variations.
2Productivity
If the formation process is accelerated to improve productivity, then the process time is reduced, but the manufacturing precision of SEI formation deteriorates due to incorrect potential development
Solution Approach 1:
The patent employs dynamic current profiling where the charging current is continuously adjusted based on real-time differential capacitance measurements. The system transitions from constant current to constant voltage mode at precisely determined points, and can modulate current magnitude dynamically to optimize both formation speed and SEI quality for each individual cell.
3Manufacturing precision
If complex measurement and control methods are implemented to improve SEI formation precision, then the manufacturing precision improves, but the device complexity increases
Solution Approach 1:
The patent replaces complex mechanical or chemical measurement systems with electrical measurements of differential capacitance. By using electrochemical impedance spectroscopy or similar electrical techniques, the system achieves precise SEI formation monitoring and control through simple voltage and current measurements, avoiding the need for complex physical or chemical analysis equipment.
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 optimized SEI formation, reducing process time and energy consumption while maintaining consistent quality across battery cells.
Implementation Method 1
In lithium-ion cells and related technologies, the formation process aims to create a well-defined solid electrolyte interphase (SEI) on the surface of the anode. This interphase forms through reactions of the electrolyte with electrolyte additives within specific voltage and, if necessary, temperature ranges, which are traversed during the charging and discharging cycles of the formation process.
Implementation Method 2
For example, the cycle is performed until the measured differential capacitance falls below a certain threshold.
Implementation Method 3
Newer methods aim to measure the overvoltage during formation. This can be achieved using current pulses or impedance measurements.
Data Source
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AI summary
A method for determining the charge QSEI(t) of a solid-electrolyte interface (SEI) of a battery cell (1) is proposed, wherein the battery cell (1) has a positive and a negative electrode (11, 12), and a time-dependent voltage V(t) is applied to the battery cell (1). The method is characterized by at least the following steps: - Determining an open-circuit voltage V0(t) of the battery cell (1); - Determining a charge Q+(t) of the positive electrode (11); - Determining a charge Q_(t) of the negative electrode (12) using the determined charge Q+(t) of the positive electrode (11) and the determined open-circuit voltage V0(t); and - Determining the charge QSEI(t) of the solid-electrolyte interface (SEI) using the determined charge Q+(t) and Q-(t) of the electrodes (11, 12).Furthermore, the invention relates to a method for controlling a formation process of a battery cell (1), a manufacturing method of a battery cell (1) and a device for controlling a formation process of a battery cell (1).