Battery Cell Formation Using Impedance Feedback for SEI Control
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Solution Overview
Problem
Existing battery cell formation processes are inefficient and inconsistent due to reliance on empirical current and voltage profiles, leading to variations in the quality of the solid electrolyte interphase (SEI) formation, and are time- and energy-intensive without complete quality control.
Innovation Solution
The method involves using complex-valued internal cell resistance measurements, particularly through electrochemical impedance spectroscopy, to control and regulate the formation process by adjusting current and voltage based on the measured resistance, optimizing the formation for each individual cell.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If empirical current and voltage profiles are used for formation, then the process is simple to implement, but the quality of SEI formation varies and the process is time- and energy-intensive
Solution Approach 1:
The patent implements feedback control by continuously measuring the complex-valued internal cell resistance during formation and using this measurement to adjust the current and voltage in real-time. This closed-loop approach replaces empirical open-loop profiles with adaptive control that responds to actual cell state, thereby improving SEI formation quality consistency while maintaining ease of implementation through automated control
Solution Approach 2:
The patent changes the control parameter from simple current/voltage profiles to complex-valued internal cell resistance as the feedback variable. By measuring both magnitude and phase of the internal resistance, the system gains deeper insight into SEI formation progress and uses this information to dynamically adjust formation parameters, achieving better quality control
2Ease of manufacture
If standard formation processes are used, then the process is straightforward, but reject rates are higher and productivity is lower due to lack of cell-specific control
Solution Approach 1:
The patent applies local quality by tailoring the formation process to each individual cell's characteristics. By measuring the complex-valued internal cell resistance specific to each cell and adjusting the formation current and voltage accordingly, the system provides cell-specific control rather than applying a uniform process to all cells, thereby reducing reject rates and improving productivity
Solution Approach 2:
The patent introduces dynamics into the formation process by making the current and voltage adaptive rather than static. The formation parameters dynamically adjust based on real-time measurements of internal cell resistance, allowing the process to respond to each cell's unique formation trajectory and optimize formation time and quality
3Manufacturing precision
If complex-valued internal cell resistance measurement is implemented, then SEI formation can be precisely controlled, but the device complexity increases
Solution Approach 1:
The patent replaces mechanical/procedural complexity with electrical measurement sophistication. Instead of using complex mechanical control systems or multiple sensors, the invention uses electrochemical impedance spectroscopy to measure complex-valued internal resistance, substituting a sophisticated electrical measurement approach for what would otherwise require complex control machinery
Solution Approach 2:
The patent uses complex-valued internal cell resistance as an intermediary variable that mediates between the formation current/voltage and the SEI formation quality. This single complex measurement (containing both magnitude and phase information) serves as a comprehensive indicator of SEI formation progress, simplifying the control task compared to monitoring multiple separate parameters
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 tailored, efficient formation processes that reduce reject rates and save time and energy by ensuring optimal SEI formation, with cell-specific control and monitoring.
Implementation Method 1
The method involves using complex-valued internal cell resistance measurements, particularly through electrochemical impedance spectroscopy, to control and regulate the formation process
Implementation Method 2
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 between the electrode and electrolyte additives within specific voltage and, if necessary, temperature ranges
Implementation Method 3
Cell internal resistance is fundamentally complex-valued, meaning it has a real part and an imaginary part, or equivalently, a magnitude and a phase. Cell internal resistance is generally frequency-dependent
Data Source
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AI summary
A method for forming a battery cell, in particular for forming a solid-electrolyte interface (SEI), is proposed, in which a time-dependent current (1', 2', 3') and/or voltage is used for the formation of the battery cell. The method is characterized in that a complex-valued internal cell resistance (1, 2, 3) of the battery cell is repeatedly detected during the formation process, and the current (1', 2', 3') and/or voltage are controlled as a function of the detected internal cell resistance (1, 2, 3). The invention further relates to a device for controlling the formation of a battery cell.