Impedance on-line measuring device of high-power electrochemical module

Abstract

The invention discloses an impedance online measuring device of a high-power electrochemical module, and belongs to the technical field of energy. The impedance measuring device comprises a power supply module, an electronic load, a load module, a loop current measuring module and a response voltage measuring module. The anode output end of the power module is connected with the anode input end of the electronic load, the cathode output end of the electronic load is connected with the anode input end of the load module, the cathode output end of the load module is connected with the anode input end of the loop current measuring module, and the cathode output end of the loop current measuring module is connected with the cathode input end of the power module. The response voltage measurement module is connected with the power supply module or the load module. According to the invention, the energy consumption type electronic load is connected in series with the power loop, so that the disturbance current can be ensured to be completely loaded to the tested electrochemical module, the current shunting effect caused by insufficient bandwidth of the power supply module or the load module is avoided, and the high-precision measurement of the impedance of the electrochemical module is further realized.

Description

Technical Field

[0001] This invention belongs to the field of energy technology, specifically relating to an online impedance measurement device suitable for various high-power electrochemical modules. Background Technology

[0002] Electrochemical modules, as a core method for achieving efficient conversion between electrical and chemical energy, have broad application prospects in energy and transportation fields. These modules achieve bidirectional or unidirectional conversion between electrical and chemical energy through electrode reactions, forming a crucial support for the current clean energy system. Currently, mainstream electrochemical modules fall into three categories: ① lithium batteries and flow batteries capable of bidirectional charging and discharging; ② fuel cells capable of unidirectional discharging; and ③ electrolyzers capable of unidirectional charging (electrolysis reaction). As the power levels and size of electrochemical modules in industrial applications continue to increase, reliability, durability, and safety have become bottlenecks restricting their large-scale commercial application. In industrial applications, electrochemical modules typically have a large number of stacked sections and a large reaction area, and their operating performance and lifespan are influenced by both the module's internal design and external operating conditions. To achieve high reliability, high safety, long durability, and low energy consumption operation of electrochemical modules, a deep understanding of their internal polarization processes is crucial for revealing the mechanisms underlying performance and lifespan changes. However, the electrochemical module involves multi-field, multi-scale coupled processes such as mass transport, charge transfer, and ion transport. These complex mechanisms are difficult to fully observe and resolve using traditional methods. Therefore, the key challenge is to explore the operating state of the electrochemical module and optimize its internal design and external operating conditions using some kind of technical means.

[0003] Electrochemical impedance spectroscopy (EIS) is an indirect, non-invasive sensing method that can study the impedance characteristics of electrochemical modules at different frequencies, thereby revealing key information such as polarization processes, electrochemical reaction kinetics, and internal operating states. EIS can be used to analyze the mechanisms and evolution of the effects of external operating conditions and internal flow channel design on electrochemical modules. Existing impedance measurement methods are mainly geared towards small-area, low-power modules in the laboratory research and development stage. This traditional measurement method typically relies on direct measurement using an electrochemical workstation. An electrochemical workstation includes core modules such as a frequency response analyzer, potentiostat, and galvanostat, which can apply excitation current or voltage to the electrochemical module and analyze the response signal to calculate the impedance. With the energy industry's trend towards large-scale development, the demand for industrial-grade high-power electrochemical modules is increasing, with reaction areas reaching the square meter level and power reaching the megawatt level. Faced with such large-area, high-power electrochemical modules, the power output capability of traditional electrochemical workstations, even with externally connected power amplifiers, is far from meeting the actual measurement needs of industrial-grade electrochemical modules. Nevertheless, electrochemical impedance spectroscopy (EIS) is a highly efficient diagnostic tool with significant value in the research, development, production, operational optimization, and health assessment of high-power electrochemical modules. Therefore, developing online impedance measurement technologies suitable for high-power electrochemical modules is crucial for promoting their large-scale application. However, in practical industrial applications, online impedance measurement methods for high-power electrochemical modules are still lacking. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention proposes an online impedance measurement device for high-power electrochemical modules. This invention applies an AC current disturbance to the power stage by connecting an energy-consuming electronic load in series to the power circuit. Then, it combines this with an instrument capable of frequency response signal analysis to measure the excitation current and response voltage of the signal stage, thereby calculating the electrochemical impedance spectrum. This method overcomes the limitations of the power output capability of traditional electrochemical workstations, enabling online measurement of the impedance of high-power electrochemical modules. It is characterized by low cost and ease of implementation.

[0005] The technical solution adopted in this invention is as follows:

[0006] An online impedance measurement device for a high-power electrochemical module includes a power supply module, an electronic load, a load module, a loop current measurement module, and a response voltage measurement module.

[0007] The positive output terminal of the power supply module is connected to the positive input terminal of the electronic load, the negative output terminal of the electronic load is connected to the positive input terminal of the load module, the negative output terminal of the load module is connected to the positive input terminal of the loop current measurement module, the negative output terminal of the loop current measurement module is connected to the negative input terminal of the power supply module, and the response voltage measurement module is connected to either the power supply module or the load module.

[0008] Furthermore, the electronic load is a high-bandwidth energy-consuming electronic load, and the loop current measurement module is a high-bandwidth current sensor. The bandwidth of the electronic load and the loop current measurement module is more than twice the highest frequency of the AC impedance being measured.

[0009] The present invention provides an online impedance measurement device for a high-power electrochemical module, which has the following two application conditions:

[0010] (1) Application Condition A: When the electrochemical module under test is a lithium battery, flow battery or electrolyzer in a charging state, the electrochemical module under test is the load module in the device circuit. The power supply module provides operating power to the load module under test, and the response voltage measurement module measures the voltage of the load module (i.e. the electrochemical module under test).

[0011] (2) Application Condition B: When the electrochemical module under test is a lithium battery, flow battery or fuel cell in a discharged state, the electrochemical module under test is the power module in the device circuit. The load module consumes the power of the power module under test, and the response voltage measurement module measures the voltage of the power module (i.e. the electrochemical module under test).

[0012] Furthermore, under application condition A, the maximum current and voltage output by the power supply module should not be less than the maximum current and voltage of the electrochemical module under test; the maximum voltage that the electronic load can withstand should not be less than the voltage of the power supply module; the power supply module operates in constant voltage mode, and the electronic load operates in constant current mode.

[0013] Furthermore, under application condition A, the impedance measurement process is as follows:

[0014] (1) Power supply to the loop current measurement module;

[0015] (2) Set the power supply module to constant voltage mode, set the voltage value to the maximum voltage that the electrochemical module under test can withstand, and set no limit on the current value;

[0016] (3) Set the energy-consuming electronic load to the constant current mode of external waveform control, and obtain the ratio between the external control voltage signal and the constant current by selecting the current range. The voltage value of the electronic load is not limited.

[0017] (4) The DC bias current set by the electronic load is used as the working current of the electrochemical module. After adjusting the working current to the target set value, the frequency change AC disturbance is superimposed on the working current by the electronic load to start the impedance measurement. Then, the current and voltage data of the electrochemical module are measured by the loop current measurement module and the response voltage measurement module, and the impedance spectrum under the working current is calculated.

[0018] (5) After the impedance spectrum measurement is completed, the DC bias current is gradually reduced to zero through an electronic load, and the measurement ends.

[0019] Furthermore, under application condition B, the maximum current and voltage that the load module can withstand should not be less than the maximum current and voltage of the electrochemical module under test, and the maximum voltage that the electronic load can withstand should not be less than the voltage of the electrochemical module under test. The load module operates in constant voltage mode, and the electronic load operates in constant current mode.

[0020] Furthermore, under operating condition B, the impedance measurement process is as follows:

[0021] (1) Power supply to the loop current measurement module;

[0022] (2) Set the load module to constant voltage mode, set the voltage value to the minimum voltage that the electrochemical module under test can withstand, and set no limit on the current value;

[0023] (3) Set the energy-consuming electronic load to the constant current mode of external waveform control, and obtain the ratio between the external control voltage signal and the constant current by selecting the current range. The voltage value of the electronic load is not limited.

[0024] (4) The DC bias current set by the electronic load is used as the working current of the electrochemical module. After adjusting the working current to the target set value, the frequency change AC disturbance is superimposed on the working current by the electronic load to start the impedance measurement. Then, the current and voltage data of the electrochemical module are measured by the loop current measurement module and the response voltage measurement module, and the impedance spectrum under the working current is calculated.

[0025] (5) After the impedance spectrum measurement is completed, the DC bias current is gradually reduced to zero through an electronic load, and the measurement ends.

[0026] This invention provides an online impedance measurement device for a high-power electrochemical module. Impedance measurement is achieved by applying an AC disturbance through an electronic load, the amplitude of which is typically 5-10% of the steady-state operating current. Specifically, by applying the AC disturbance through the electronic load, the amplitude ratio and phase difference of the AC current and the corresponding frequency in the response voltage of the electrochemical module are calculated to realize impedance measurement.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] 1. The present invention provides an online impedance measurement device for a high-power electrochemical module. By connecting an energy-consuming electronic load in series to the power circuit, it can ensure that the disturbance current is fully loaded onto the electrochemical module under test, avoiding the current shunting effect caused by insufficient bandwidth of the power supply module or load module, thereby realizing high-precision measurement of the impedance of the electrochemical module.

[0029] 2. The present invention provides an online impedance measurement device for a high-power electrochemical module, which integrates an energy-consuming electronic load into the existing application system configuration without changing the design of the original control system. It is easy to implement and maintain and has the advantage of low cost. Attached Figure Description

[0030] Figure 1 A schematic diagram of the structure of an online impedance measurement device for a high-power electrochemical module provided by the present invention;

[0031] Figure 2 This is a schematic diagram of the online impedance measurement device in the embodiment;

[0032] Figure 3 This is an example of an online impedance measurement device using an electrolytic cell as the electrochemical module under test;

[0033] Figure 4 The following are the impedance online measurement results using an electrolytic cell as the electrochemical module under test in the example; where (a) and (b) are impedance spectra at different current densities, (c) are impedance spectra at different operating temperatures, and (d) are impedance spectra at different deionized water flow rates.

[0034] Figure 5 This is a Kramers-Kronig relationship analysis diagram of the online impedance measurement results using an electrolytic cell as the electrochemical module under test in an example; where (a), (b), (c), and (d) respectively correspond to Figure 4 A diagram showing the relationship between (a), (b), (c), and (d). Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in conjunction with the following specific embodiments and with reference to the accompanying drawings.

[0036] The following non-limiting embodiments are intended to enable those skilled in the art to more fully understand the present invention, but do not limit the invention in any way.

[0037] Example

[0038] This embodiment uses a proton exchange membrane electrolyzer as the test object to describe the technical solution of the present invention in detail.

[0039] An online impedance measurement device for a high-power electrochemical module, such as Figure 2 As shown, it includes a power supply module 1, an electronic load 2, a load module 3, a loop current measurement module 4, and a response voltage measurement module 5;

[0040] The positive output terminal of the power supply module is connected to the positive input terminal of the electronic load, the negative output terminal of the electronic load is connected to the positive input terminal of the load module, the negative output terminal of the load module is connected to the positive input terminal of the loop current measurement module, and the negative output terminal of the loop current measurement module is connected to the negative input terminal of the power supply module, thus forming a complete power loop; the response voltage measurement module is connected to both ends of the load module (i.e., the electrolytic cell).

[0041] In the embodiment, an example block diagram of the measuring device using a proton exchange membrane electrolyzer as the object of measurement is shown below. Figure 3 As shown, the electrochemical module under test is an electrolytic cell, model QL-138D; the power supply module is FTP9050-80-170 from Fax Corporation; the electronic load is 63205A-150-500 from Chroma Electronics; the loop current measurement module is CT200 from Yokogawa Corporation; and the response voltage measurement module and impedance calculation module are PGSTAT204 and matching accessories from Metrohm, Switzerland.

[0042] In the impedance online measurement device of this embodiment, the electronic load is a high-bandwidth energy-consuming electronic load with a bandwidth of approximately 50 kHz; the loop current measurement module is a high-bandwidth current sensor with a bandwidth of approximately 500 kHz. The frequency range of the AC impedance being measured is from 0.1 Hz to 15 kHz, and the bandwidth of the electronic load and the loop current measurement module is more than twice that of the highest frequency of the AC impedance being measured.

[0043] In the impedance online measurement device of this embodiment, the maximum current of the electrolytic cell under test is 90A and the maximum voltage is 12V. The power supply module can output a maximum current of 170A and a maximum voltage of 80V, both exceeding the maximum current and voltage of the electrolytic cell under test. The electronic load can withstand a maximum voltage of 150V, exceeding the maximum voltage of 80V of the power supply module. The power supply module operates in constant voltage mode, and the electronic load operates in constant current mode.

[0044] The impedance online measurement device in this embodiment, taking the steady-state current operating point of the electrolytic cell at 40A as an example, performs the following impedance measurement process:

[0045] Step 1: Power on the circuit current measurement module (CT200).

[0046] Step 2: Set the power module FTP9050-80-170 to constant voltage mode, set the voltage value to the maximum voltage that the electrolytic cell can withstand, 12V, and do not set any current limit.

[0047] Step 3: Set the energy-consuming electronic load to constant current mode with external waveform control (external waveform voltage range 0-10V). By selecting the current range, set the current range to 0-250A, thereby preset the ratio between the load current and the external control voltage signal to 25A / V. The voltage value of the electronic load is not limited.

[0048] Step 4: Set the DC bias current to 40A as the operating current of the electrolyzer. Gradually adjust the operating current to the target set value of 40A. Then, initiate impedance measurement by superimposing a frequency-varying AC disturbance (disturbance amplitude 5%) onto this operating current. The disturbance frequency ranges from 0.1Hz to 15kHz. Based on the current and voltage data of the electrolyzer measured by the loop current measurement module and the response voltage measurement module, the impedance spectrum at the steady-state current operating point is calculated using a PGSTAT204 from Metrohm.

[0049] Step 5: After the impedance spectrum measurement is completed, gradually reduce the DC bias current of 40A to zero, and the measurement is finished.

[0050] The impedance information is measured by applying a current disturbance to an electronic load and calculating the amplitude ratio and phase difference of the corresponding frequencies in the AC disturbance and the electrolytic cell response voltage.

[0051] The embodiments tested the impedance spectrum of the electrolyzer under three operating conditions that significantly affect its performance: current density, operating temperature, and deionized water flow rate. The operating conditions of the electrolyzer on the test platform are shown in Table 1 below. The values ​​marked in bold are the baseline operating conditions. During sensitivity testing under a single condition, the other operating conditions remained at the baseline values.

[0052] Table 1. Operating conditions for electrolytic cell stack testing

[0053]

[0054] Electrochemical impedance spectroscopy (EIS) measurements were performed using a frequency sweep method, ranging from 0.1 Hz to 15 kHz, with 10 frequency points measured every tenth octave. A current perturbation was applied through an electronic load connected to the electrolytic cell, with the AC current amplitude selected as 10% of the steady-state operating current. Before EIS measurements, the electrolytic cell needed to be stabilized under appropriate conditions for 10 minutes until the voltage remained constant to ensure the accuracy of the experimental results. Furthermore, each experiment was repeated at least twice to ensure the reproducibility of the measurement results. The impedance spectra obtained under different operating conditions are shown in the attached figure. Figure 4 As shown.

[0055] To assess the reliability of measurement results, electrochemical device systems must meet the fundamental conditions of causality, linearity, stability, and finiteness. The Kramers-Kronig relation is an important tool for verifying whether impedance data meet these conditions. If the relative residual between the actual impedance value and the fitted value of the Kramers-Kronig relation does not exceed 1%, it indicates that the impedance data is of good quality and meets the requirements of the Kramers-Kronig relation. (The remaining text appears to be incomplete and requires further context.) Figure 4 The impedance spectrum shown was analyzed using Kramers-Kronig relationship, and the results are as follows: Figure 5 As shown. Under all test conditions, including different current densities (0.3-1.0 A·cm⁻¹), -2 Operating temperature (40-80℃) and deionized water flow rate (24.0-31.5 mL·min) -1 ·cm -2 The relative residuals between the measured impedance and the impedance fitted by the Kramers-Kronig relationship were mostly below 0.02%, which demonstrates the high quality of the electrochemical impedance spectroscopy data and the reliability of the online impedance measurement method.

[0056] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to the embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. An online impedance measurement device for a high-power electrochemical module, characterized in that, Includes a power supply module, electronic load, load module, loop current measurement module, and response voltage measurement module; The positive output terminal of the power supply module is connected to the positive input terminal of the electronic load, the negative output terminal of the electronic load is connected to the positive input terminal of the load module, the negative output terminal of the load module is connected to the positive input terminal of the loop current measurement module, the negative output terminal of the loop current measurement module is connected to the negative input terminal of the power supply module, and the response voltage measurement module is connected to either the power supply module or the load module.

2. The impedance online measurement device for a high-power electrochemical module according to claim 1, characterized in that, The electronic load is a high-bandwidth, energy-efficient electronic load, and the loop current measurement module is a high-bandwidth current sensor. The bandwidth of the electronic load and the loop current measurement module is more than twice the highest frequency of the AC impedance being measured.

3. The online impedance measurement device for a high-power electrochemical module according to claim 1, characterized in that, When the electrochemical module under test is an electrolyzer, a lithium battery in a charging state, or a flow battery in a charging state, the electrochemical module under test is the load module in the device, the power supply module provides operating power to the load module, and the response voltage measurement module measures the voltage of the load module. When the electrochemical module under test is a fuel cell, a lithium battery in a discharged state, or a flow battery in a discharged state, the electrochemical module under test is the power supply module in the device, the load module consumes the power of the electrochemical module under test, and the response voltage measurement module measures the voltage of the power supply module.

4. The online impedance measurement device for a high-power electrochemical module according to claim 3, characterized in that, When the electrochemical module under test is an electrolyzer, a lithium battery in a charging state, or a flow battery in a charging state, the maximum current and voltage output by the power supply module shall not be less than the maximum current and voltage of the electrochemical module under test; the maximum voltage that the electronic load can withstand shall not be less than the voltage of the power supply module; the power supply module shall operate in constant voltage mode, and the electronic load shall operate in constant current mode.

5. The online impedance measurement device for a high-power electrochemical module according to claim 3, characterized in that, When the electrochemical module under test is an electrolyzer, a lithium battery in a charging state, or a flow battery in a charging state, the impedance measurement process is as follows: (1) Power supply to the loop current measurement module; (2) Set the power supply module to constant voltage mode, and set the voltage value to the maximum voltage that the electrochemical module under test can withstand. (3) Set the energy-consuming electronic load to constant current mode controlled by external waveform; (4) The DC bias current set by the electronic load is used as the working current of the electrochemical module. After adjusting the working current to the target set value, the impedance measurement is started by applying the frequency change AC disturbance through the electronic load. Then, the current and voltage of the electrochemical module are measured by the loop current measurement module and the response voltage measurement module, and the impedance spectrum is calculated. (5) After the impedance spectrum measurement is completed, the DC bias current is gradually reduced to zero through an electronic load, and the measurement ends.

6. The online impedance measurement device for a high-power electrochemical module according to claim 3, characterized in that, When the electrochemical module under test is a fuel cell, a lithium battery in a discharged state, or a flow battery in a discharged state, the maximum current and voltage that the load module can withstand are not less than the maximum current and voltage of the electrochemical module under test, and the maximum voltage that the electronic load can withstand is not less than the voltage of the electrochemical module under test. The load module operates in constant voltage mode, and the electronic load operates in constant current mode.

7. The online impedance measurement device for a high-power electrochemical module according to claim 3, characterized in that, When the electrochemical module under test is a fuel cell, a lithium battery in a discharged state, or a flow battery in a discharged state, the impedance measurement process is as follows: (1) Power supply to the loop current measurement module; (2) Set the load module to constant voltage mode, and the voltage value is the minimum voltage that the electrochemical module under test can withstand; (3) Set the energy-consuming electronic load to constant current mode controlled by external waveform; (4) The DC bias current set by the electronic load is used as the working current of the electrochemical module. After adjusting the working current to the target set value, the impedance measurement is started by applying the frequency change AC disturbance through the electronic load. Then, the current and voltage of the electrochemical module are measured by the loop current measurement module and the response voltage measurement module, and the impedance spectrum is calculated. (5) After the impedance spectrum measurement is completed, the DC bias current is gradually reduced to zero through an electronic load, and the measurement ends.

8. The online impedance measurement device for a high-power electrochemical module according to claim 1, characterized in that, Impedance is measured by applying an AC disturbance to an electronic load, with the disturbance amplitude being 5 to 10% of the steady-state operating current.

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