Electrochemical Cell Impedance Measurement With Coherent Sampling
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Solution Overview
Problem
Electrochemical Impedance Spectroscopy (EIS) measurements in electrochemical cells are prone to errors due to variations in cell chemistry over time, leading to distorted downstream signal processing.
Innovation Solution
Implementing coherent sampling techniques to stabilize impedance measurements by ensuring a specific ratio between the stimulation frequency and sampling frequency, using digital-to-analog and analog-to-digital converters clocked coherently, and applying Fourier transforms and band-pass filters to analyze the stability of impedance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If EIS is used to interrogate an electrochemical cell to obtain information about cell condition, then measurement information is improved, but measurement precision deteriorates due to chemistry variations over time
Solution Approach 1:
The patent applies periodic sinusoidal stimuli at multiple frequencies to the electrochemical cell during EIS interrogation. By using periodic actions at different frequencies and analyzing the periodic responses, the system can extract impedance information while accounting for time-varying chemistry conditions, thus maintaining measurement precision despite temporal variations
Solution Approach 2:
The patent implements feedback by measuring the actual response of the electrochemical cell to applied stimuli and using this information to adjust subsequent measurements. The system continuously monitors impedance changes and uses this feedback to compensate for chemistry variations, thereby maintaining accurate measurements over time
2Stability of the object's composition
If chemistry within the cell varies substantially over time, then cell condition information is obtained, but impedance measurement precision deteriorates
Solution Approach 1:
The patent transitions from assuming static cell chemistry to dynamically adapting to chemistry changes. By implementing time-varying measurement strategies and continuously updating impedance models based on observed chemistry variations, the system maintains measurement precision even as cell composition changes over time
Solution Approach 2:
The patent changes measurement parameters such as stimulus frequency, amplitude, and timing based on observed cell chemistry variations. By adapting these parameters in response to chemistry changes, the system maintains accurate impedance measurements across different cell states
3Adaptability or versatility
If impedance measurements are distorted due to chemistry variations, then cell characterization is achieved, but downstream signal processing reliability deteriorates
Solution Approach 1:
The patent performs preliminary characterization of the electrochemical cell by measuring impedance at multiple frequencies before conducting downstream signal processing. This preliminary action establishes baseline cell properties and expected response patterns, enabling more reliable downstream processing even when chemistry variations occur during operation
Data Source
AI summary
Circuitry for characterising an electrochemical cell comprising at least one first electrode and a second electrode, the circuitry comprising: drive circuitry configured to apply a stimulus to the at least one first electrode of electrochemical cell, the stimulus having a first stimulation frequency; and measurement circuitry configured to sample a response of the electrochemical cell to the stimulus at a sampling frequency to generate a digital output signal; and processing circuitry configured to determine an impedance of the cell at the first stimulation frequency based on the digital output signal, wherein a first ratio of the first stimulation frequency to the sampling frequency is substantially equal to a second ratio of a number of oscillations of the stimulus to a number of samples obtained by the measurement circuit over a given time period.