Excitation current generation circuit, measurement device and method

Abstract

The present disclosure provides an excitation current generation circuit, an electrochemical impedance spectroscopy measurement device and a method for multi-bit electrochemical impedance spectroscopy measurement. The excitation current generation circuit comprises: a simple harmonic signal generator generating a simple harmonic signal with a specified frequency; an N-bit quantizer quantizing the simple harmonic signal into a binary digital code, where N≥2; and N controlled resistance branches, each controlled resistance branch being connected in series with a weighted resistance and a switch, and each controlled resistance branch being connected in parallel between the positive and negative electrodes of a battery cell. The on-off states of the switches are controlled based on the binary digital code to generate an excitation current with a waveform similar to the simple harmonic signal on the battery cell. The measurement device further comprises an analog front-end circuit, an analog-to-digital converter and a discrete Fourier transform module.

Description

Technical Field

[0001] This disclosure belongs to the field of battery monitoring technology, and particularly relates to an excitation current generation circuit, an electrochemical impedance spectroscopy measuring device, an excitation current generation method, and an electrochemical impedance spectroscopy measurement method for multi-bit electrochemical impedance spectroscopy measurement. Background Technology

[0002] With the rapid development of new energy vehicles, energy storage systems, and various electronic devices, the safety and reliability of battery systems are receiving increasing attention. In a Battery Management System (BMS), real-time and accurate monitoring of cell status has become a crucial means of ensuring battery safety, extending lifespan, and optimizing energy management.

[0003] Existing BMS (Battery Management System) monitors battery status primarily by monitoring physical parameters such as battery voltage, temperature, and current, and then calculates status parameters such as State of Charge (SOC), State of Health (SOH), or Direct Current Resistance (DCR) based on these parameters.

[0004] Electrochemical impedance spectroscopy (EIS) is a frequency domain response of an electrochemical system to external stimuli. It can be used to analyze the ohmic internal resistance, double-layer capacitance, and Faraday impedance of a battery. The impedance spectra exhibited by a battery under different state parameters such as state of charge (SOC), state of equilibrium (SOH), and current-temperature response (DCR) are not consistent. Therefore, EIS detection can enable more sensitive and proactive battery state assessment, allowing for the early identification of potential anomalies before significant changes in voltage and temperature.

[0005] However, existing EIS testing solutions for batteries typically suffer from high costs, large size, and complex procedures. They often rely on external DC-DC converters or high-precision, high-speed digital-to-analog converters (DACs) to inject different frequencies of excitation into the battery cells. Currently, they are mainly used in laboratories for battery research and analysis, and cannot achieve online status detection during battery use, nor can they be widely adopted in BMS systems.

[0006] While injecting excitation into the battery using a single-bit (e.g., pulse / square wave) switching resistor method is simple and low-cost, the excitation waveform has high harmonics and limited effective sinusoidal fundamental components, which reduces impedance extraction accuracy and increases the burden on subsequent filtering and spectrum analysis. How to generate a multi-level excitation current that more closely approximates a sinusoidal waveform and closely coordinate it with on-chip analog-to-digital conversion and frequency domain calculations has become a pressing technical problem to be solved.

[0007] Furthermore, during online battery use, there are often background frequency components on the load side that may overlap with the EIS test frequency. If the excitation frequency coincides with this background component, it will reduce measurement accuracy.

[0008] Therefore, how to design an excitation current generation scheme for multi-bit electrochemical impedance spectroscopy that can generate an excitation current with an approximate harmonic signal waveform at a low hardware cost, facilitate integration with battery monitoring chips, and support complete electrochemical impedance spectroscopy measurements has become a technical problem that needs to be solved in this field. Summary of the Invention

[0009] This disclosure provides an excitation current generation circuit, an electrochemical impedance spectroscopy measurement device, an excitation current generation method, and an electrochemical impedance spectroscopy measurement method for multi-bit electrochemical impedance spectroscopy measurement.

[0010] According to one aspect of this disclosure, an excitation current generation circuit for multi-bit electrochemical impedance spectroscopy measurement is provided for providing an excitation current signal to a battery cell to measure the electrochemical impedance spectrum of the battery cell. The excitation current generation circuit includes: a simple harmonic signal generator for generating a simple harmonic signal of a specified frequency; an N-bit quantizer for receiving the simple harmonic signal and quantizing the simple harmonic signal into a binary digital code, where N≥2; and N controlled resistor branches, each controlled resistor branch consisting of a weighted resistor and a switch connected in series. The weighted resistors in each controlled resistor branch have different resistance weights and are connected in parallel between the positive and negative terminals of the battery cell. Based on the binary digital code, the switching of the N controlled resistor branches is controlled to generate an excitation current with an approximate simple harmonic signal waveform on the battery cell.

[0011] According to this technical solution, by generating a simple harmonic signal in the digital domain and performing multi-bit quantization, the controlled resistor branch connected in parallel across the two ends of the battery cell is directly controlled by binary digital code, forming a multi-level, approximately sinusoidal excitation current on the battery cell. Compared with solutions that rely on external high-precision high-speed DACs or independent DC-DC excitation sources, this solution has a simple hardware structure, is easy to integrate with the digital domain of battery monitoring chips, and can improve the sinusoidal approximation of the excitation waveform relative to single-bit solutions while controlling costs. This solves the technical problem that existing EIS excitation methods struggle to balance low cost and waveform quality, and are not conducive to online BMS applications.

[0012] According to at least one embodiment of this disclosure, the resistance values ​​of the weighted resistors in the N controlled resistor branches are set according to binary weights, such that the resistance value of the weighted resistor in the i-th controlled resistor branch is... , where i=1,2,…,N, and R is the reference resistance value.

[0013] By configuring the resistors of each branch according to binary weights, multiple levels of current amplitude with equal or approximately equal intervals can be generated by combining N switches, realizing multi-bit current-type digital-to-analog conversion function. The control logic of the excitation current is simple, which is conducive to achieving the desired current resolution with fewer components.

[0014] According to at least one embodiment of this disclosure, different on / off combinations of the N controlled resistor branches generate on the battery cell. The excitation current has different amplitude levels, and the binary digital code varies with the amplitude of the simple harmonic signal. The excitation current has a stepped waveform that approximates the simple harmonic signal.

[0015] N-bit binary code corresponds to Types of open and closed combinations and With each current level, as the binary digital code updates and changes sinusoidally over time, the cell current tracks the sinusoidal envelope in a stepwise manner. This method approximates continuous sinusoidal excitation with discrete levels without introducing a high-precision simulated sinusoidal current source, facilitating the subsequent extraction of fundamental impedance information through discrete Fourier transform.

[0016] According to at least one embodiment of this disclosure, the excitation current is equal to the sum of the currents in each of the conducting controlled resistor branches, and the current in each conducting controlled resistor branch is the ratio of the voltage of the battery cell to the resistance of the weighted resistor in that controlled resistor branch.

[0017] The current in each conducting branch is determined by the cell voltage and the weighted resistance of that branch, and the total excitation current is the sum of the currents in each branch. This relationship clarifies the composition of the excitation current, allowing the current amplitude to be uniquely determined by the resistor network and binary digital code, which facilitates subsequent calibration and impedance normalization calculations.

[0018] According to at least one embodiment of this disclosure, the simple harmonic signal generator and the N-bit quantizer are integrated in the digital domain of the battery monitoring chip, the N controlled resistor branches are disposed outside the battery monitoring chip, and the binary digital code output by the N-bit quantizer is used to control the switching of the N controlled resistor branches.

[0019] By placing sine wave generation and quantization processing in the digital domain within the chip and placing the resistor network outside the chip, the chip's digital resources can be fully utilized while the resistors can be flexibly selected. Control codes can be output through the chip pins to drive external switches, balancing integration and engineering feasibility.

[0020] According to at least one embodiment of the present disclosure, the N-bit quantizer employs at least one of the following structures: Flash type, successive approximation type, pipelined type, Sigma-Delta type, pipelined successive approximation type, or noise-shaping successive approximation type.

[0021] The quantizer can be implemented using a variety of mature digital / mixed-signal structures, and can be flexibly selected according to frequency range, power consumption, area and quantization noise requirements, without changing the overall architecture of the multi-bit code driving weighted resistor network.

[0022] According to at least one embodiment of this disclosure, the switch is a MOS switch, and the excitation current is a pull-down current flowing from the positive terminal of the battery cell to the negative terminal through a controlled resistor branch.

[0023] According to at least one embodiment of this disclosure, N=4, and the resistance values ​​of the weighted resistors in the four controlled resistor branches are R, R / 2, R / 4 and R / 8, respectively.

[0024] According to at least one embodiment of this disclosure, a shunt is further included, the shunt being used to provide a voltage signal reflecting the battery load signal when the excitation current is not applied, the voltage signal being capable of analyzing the background frequency components of the battery load signal, the harmonic signal generator being configured to: determine whether frequency hopping is required based on the background frequency components; if the battery load signal contains frequency components that coincide with or fall within a predetermined neighborhood of the test frequency point of the electrochemical impedance spectroscopy to be measured, then change the specified frequency to avoid the frequency components.

[0025] According to another aspect of this disclosure, an electrochemical impedance spectroscopy (EIS) measuring device is provided, comprising: an excitation current generation circuit as described in any of the preceding claims, for applying an excitation current of an approximate harmonic signal waveform to a battery cell; an analog front-end circuit for acquiring a response voltage signal generated by the battery cell under the action of the excitation current, and filtering and amplifying the response voltage signal; an analog-to-digital converter for converting the filtered and amplified response voltage signal into a digital signal; and a discrete Fourier transform module for performing a discrete Fourier transform on the digital signal and the harmonic signal, and calculating the electrochemical impedance of the battery cell at a specified frequency based on the transform result.

[0026] Based on the use of a multi-bit resistor network to generate an approximate sinusoidal current on the excitation side, the measurement device is further configured with an analog front-end, analog-to-digital conversion and discrete Fourier transform (DFT) calculation, so that excitation, sampling and frequency domain impedance extraction form a closed loop, which can directly obtain electrochemical impedance at a specified frequency and meet the requirements of EIS online measurement.

[0027] According to at least one embodiment of this disclosure, the analog front-end circuit includes an anti-aliasing filter and an amplifier, and the response voltage signal is sequentially filtered by the anti-aliasing filter and amplified by the amplifier before being input to the analog-to-digital converter.

[0028] Anti-aliasing filtering can suppress high-frequency interference and harmonic aliasing before sampling, while the amplifier matches the response voltage to the input range of the analog-to-digital converter and improves the signal-to-noise ratio, thereby ensuring the quality of the digital response signal and improving the accuracy of impedance calculation.

[0029] According to at least one embodiment of this disclosure, the discrete Fourier transform module obtains the frequency domain components of the excitation current and the frequency domain components of the response voltage signal, respectively. Obtaining electrochemical impedance ,in The frequency domain component of the response voltage signal is... Let be the frequency domain component of the excitation current.

[0030] According to at least one embodiment of this disclosure, the simple harmonic signal generator is configured to sequentially generate a plurality of simple harmonic signals of different specified frequencies, and the discrete Fourier transform module calculates the electrochemical impedance at each specified frequency to form the electrochemical impedance spectrum of the battery cell.

[0031] By changing the specified frequency and repeating the excitation and calculation, impedance data at multiple frequency points can be obtained, thus forming a complete electrochemical impedance spectrum.

[0032] According to at least one embodiment of this disclosure, the harmonic signal generator, the N-bit quantizer, the analog front-end circuit, the analog-to-digital converter, the discrete Fourier transform module, and the oscillator are integrated in a battery monitoring chip. The N controlled resistor branches are located outside the battery monitoring chip and are controlled to be connected through the pins of the battery monitoring chip. The oscillator is used to provide a clock for the harmonic signal generator and the analog-to-digital converter.

[0033] According to another aspect of this disclosure, a method for generating excitation current for multi-bit electrochemical impedance spectroscopy is provided for providing an excitation current signal to a battery cell to measure the electrochemical impedance spectrum of the battery cell. The method includes: generating a simple harmonic signal of a specified frequency using a simple harmonic signal generator; quantizing the simple harmonic signal into binary digital code using an N-bit quantizer, where N≥2; and controlling the switching of N controlled resistor branches based on the binary digital code. Each controlled resistor branch is composed of a weighted resistor and a switch connected in series. The weighted resistors in each controlled resistor branch have different resistance weights and are connected in parallel between the positive and negative terminals of the battery cell, thereby generating an excitation current with an approximate simple harmonic signal waveform on the battery cell.

[0034] According to at least one embodiment of this disclosure, the resistance values ​​of the weighted resistors in the N controlled resistor branches are set according to binary weights, and different on / off combinations of the switch generate 2^N excitation currents with different amplitude levels on the battery cell. The binary digital code changes with the amplitude of the simple harmonic signal, so that the excitation current presents a stepped waveform approximating the simple harmonic signal.

[0035] According to at least one embodiment of this disclosure, the generation of the simple harmonic signal and the quantization are performed in the digital domain of the battery monitoring chip, the N controlled resistor branches are located outside the battery monitoring chip, and the binary digital code obtained by quantization is used to drive the switching of the N controlled resistor branches.

[0036] According to at least one embodiment of this disclosure, before generating a simple harmonic signal of a specified frequency by a simple harmonic signal generator, the method further includes: obtaining a voltage signal reflecting a battery load signal when the excitation current is not applied; the simple harmonic signal generator determining whether frequency hopping is required based on the background frequency components; if the battery load signal contains frequency components that coincide with or fall within a predetermined neighborhood of the test frequency point of the electrochemical impedance spectroscopy to be measured, then changing the specified frequency to avoid the frequency components.

[0037] According to another aspect of this disclosure, an electrochemical impedance spectroscopy measurement method is provided, comprising: applying an excitation current of an approximate harmonic signal waveform to a battery cell using the excitation current generation method as described in any of the preceding claims; acquiring a response voltage signal generated by the battery cell under the action of the excitation current, and filtering and amplifying the response voltage signal; converting the filtered and amplified response voltage signal into a digital signal via analog-to-digital conversion; performing a discrete Fourier transform on the digital signal and the harmonic signal, and calculating the electrochemical impedance of the battery cell at a specified frequency based on the transform result.

[0038] According to at least one embodiment of this disclosure, calculating the electrochemical impedance of the battery cell at the specified frequency includes: obtaining the frequency domain component of the excitation current and the frequency domain component of the response voltage signal, respectively; through Obtaining electrochemical impedance ,in The frequency domain component of the response voltage signal is... Let be the frequency domain component of the excitation current.

[0039] According to at least one embodiment of this disclosure, it further includes: changing a specified frequency of the simple harmonic signal and repeatedly performing the excitation, acquisition and calculation steps to obtain electrochemical impedance at multiple frequencies and form the electrochemical impedance spectrum of the battery cell.

[0040] Additional aspects and advantages of this disclosure will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this disclosure. Attached Figure Description

[0041] The accompanying drawings illustrate exemplary embodiments of the present disclosure and, together with the description thereof, serve to explain the principles of the present disclosure. These drawings are included to provide a further understanding of the present disclosure and are incorporated in and constitute a part of this specification.

[0042] Figure 1 A schematic block diagram of an electrochemical impedance spectroscopy measuring apparatus according to one embodiment of the present disclosure is shown.

[0043] Figure 2 A schematic circuit diagram of a controlled resistor branch network in an excitation current generation circuit according to one embodiment of the present disclosure is shown.

[0044] Figure 3 A schematic diagram of the excitation current path in an electrochemical impedance spectroscopy measuring apparatus according to one embodiment of the present disclosure is shown.

[0045] Figure 4 A schematic circuit diagram of a shunt configuration for detecting background frequency components of a battery load signal according to one embodiment of the present disclosure is shown.

[0046] Figure 5 A flowchart of an excitation current generation method according to one embodiment of the present disclosure is shown.

[0047] Figure 6 A flowchart of an excitation current generation method according to one embodiment of the present disclosure is shown.

[0048] Figure 7 A flowchart of an electrochemical impedance spectroscopy measurement method according to one embodiment of the present disclosure is shown. Detailed Implementation

[0049] The present disclosure will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the disclosure. Furthermore, it should be noted that, for ease of description, only the parts relevant to the present disclosure are shown in the accompanying drawings.

[0050] It should be noted that, where there is no conflict, the embodiments and features described in this disclosure can be combined with each other. The technical solutions of this disclosure will now be described in detail with reference to the accompanying drawings and embodiments.

[0051] Unless otherwise stated, the exemplary implementations / embodiments shown are to be understood as providing exemplary features of various details that provide ways in which the technical concepts of this disclosure can be implemented in practice. Therefore, unless otherwise stated, the features of various implementations / embodiments may be additionally combined, separated, interchanged and / or rearranged without departing from the technical concepts of this disclosure.

[0052] Before describing the technical solutions of this disclosure in detail, some terms will be explained first in order to better understand the technical content of this disclosure.

[0053] Electrochemical impedance spectroscopy (EIS) typically involves applying a perturbation signal to an electrochemical system, monitoring the system's response, and analyzing the system's electrochemical properties using the response signal. Unlike DC excitation, EIS applies a frequency-controlled, low-amplitude AC excitation. The measured values ​​are usually the ratio of AC voltage to AC current (i.e., impedance) as a function of frequency, or the impedance phase angle as a function of frequency. By equating the electrochemical system to a series-parallel network of basic components such as resistors, capacitors, and inductors, EIS can determine the equivalent circuit structure and component parameters, thereby analyzing the battery's ohmic internal resistance, double-layer capacitance, charge transfer resistance, and Warburg impedance.

[0054] The battery cell in this embodiment can be a lithium-ion battery, lithium metal battery, lead-acid battery, nickel-cadmium battery, nickel-metal hydride battery, lithium-sulfur battery, lithium-air battery, or sodium-ion battery, etc., and is not limited thereto. In terms of scale, a battery cell can refer to a single battery cell, or it can refer to a module, battery pack, or battery assembly including multiple battery cells, and is not limited thereto. In terms of application scenarios, the battery cell can be used in power devices such as automobiles, ships, and electric bicycles, and can also be used in electronic devices such as mobile phones.

[0055] Existing EIS technologies either rely on external high-precision excitation sources, making them difficult to apply online in battery management systems; or they employ simple single-bit switched resistor excitation, resulting in large harmonic distortion and limited effective fundamental components. This disclosure provides an excitation current generation circuit, measurement device, and method for multi-bit electrochemical impedance spectroscopy (EIS) measurement. It generates and quantizes a simple harmonic signal in the digital domain, uses multi-bit codes to control an off-chip (external to the chip) weighted resistor network, and generates a stepped, approximately sinusoidal excitation current on the battery cell. The response voltage is then acquired via an analog front-end, and the impedance is calculated using DFT. This improves the excitation waveform quality and integration convenience while controlling hardware costs. In this disclosure, the simple harmonic signal can be a sine wave or a cosine wave, etc.

[0056] Figure 1 A schematic block diagram of an electrochemical impedance spectroscopy measuring device 100 according to one embodiment of the present disclosure is shown.

[0057] like Figure 1 As shown, the electrochemical impedance spectroscopy measurement device 100 may include an excitation current generation circuit 110, an analog front-end circuit 120, an analog-to-digital converter (ADC) 130, a discrete Fourier transform (DFT) module 140, and an oscillator. The excitation current generation circuit 110 is used to apply an excitation current with an approximately harmonic signal waveform to the cell 200. The analog front-end circuit 120 is used to acquire the response voltage signal generated by the battery cell 200 under the action of excitation current. The system filters and amplifies the response voltage signal. The analog-to-digital converter 130 converts the filtered and amplified response voltage signal into a digital signal. The discrete Fourier transform module 140 performs discrete Fourier transforms on the digital signal and the harmonic signal, and calculates the electrochemical impedance of the cell 200 at a specified frequency based on the transform results. The oscillator is used to provide a clock signal reference for the harmonic signal generator 111 and the analog-to-digital converter 130 to ensure that the excitation generation and response sampling are synchronized in time, which helps to improve the accuracy of impedance phase calculation.

[0058] In one embodiment, the harmonic signal generator 111 and the N-bit quantizer 112 in the excitation current generation circuit 110 can be integrated with the analog front-end circuit 120, the analog-to-digital converter 130, the discrete Fourier transform module 140, and the oscillator in the battery monitoring chip 10; N controlled resistor branches 113 are disposed outside the battery monitoring chip 10 and are controlled to be connected through the pins of the battery monitoring chip 10, wherein the weighted resistors of each controlled resistor branch 113 have different resistance values. Figure 1 As shown, the oscillator's clock output can be connected to the harmonic signal generator 111 and the analog-to-digital converter 130, respectively. The battery monitoring chip 10, also known as a battery monitoring chip, cell monitoring chip, or voltage acquisition chip, is typically used to collect parameters such as the actual voltage of the battery cell during use for use by the battery management system (BMS). By reusing or expanding the pins of the battery monitoring chip, the EIS function can be integrated into the existing monitoring architecture.

[0059] It should be noted that, although Figure 1 The Discrete Fourier Transform module 140 is shown within the chip, but without departing from the concept of this disclosure, some or all frequency domain calculations can also be performed by the BMS main control processor (microprocessor). As long as the excitation side adopts the multi-bit quantization and controlled resistor branch structure of this disclosure, and cooperates with response sampling and impedance calculation, it falls within the protection scope of this disclosure.

[0060] The excitation current generation circuit 110 is used to provide an excitation current signal to the cell 200 for measuring the electrochemical impedance spectroscopy of the cell 200. For example... Figure 1As shown (dotted line box), the excitation current generation circuit 110 includes a simple harmonic signal generator 111, an N-bit quantizer 112, and N controlled resistor branches 113.

[0061] The simple harmonic signal generator 111 is used to generate a simple harmonic signal of a specified frequency. For example... Figure 1 As shown, the harmonic signal generator 111 can receive a clock signal provided by an oscillator and generate a digital domain harmonic signal sequence based on that clock signal reference. This harmonic signal can be a discrete-time sequence in the digital domain, and its frequency can be configured according to EIS measurement requirements. As an example, the specified frequency can be in the range of approximately 100 MHz to approximately 5 kHz, and can be extended or narrowed according to cell characteristics and algorithm requirements. The harmonic signal generator 111 can sequentially output multiple different specified frequencies to support frequency sweep measurements. The harmonic signal generator 111 can employ circuits from the prior art, etc., and this disclosure does not limit it.

[0062] The N-bit quantizer 112 receives a simple harmonic signal and quantizes the simple harmonic signal generated by the simple harmonic signal generator 111 into a binary digital code, where N ≥ 2. The quantized result is an N-bit binary digital code, with each bit corresponding to the control state of a controlled resistor branch switch. For example, when N = 4, the binary digital code can take values ​​between 0000 and 1111, corresponding to 16 quantization levels. It should be noted that the quantization here includes both amplitude quantization of the continuous amplitude sinusoidal signal and the processing of mapping the high-bit-width sinusoidal signal into an N-bit control code in the digital domain, essentially to obtain a multi-bit digital code for driving the switching network.

[0063] The N-bit quantizer 112 can be implemented using at least one of the following circuit structures: Flash type, successive approximation (SAR) type, pipeline type, Sigma-Delta type, pipelined successive approximation type, or noise-shaping successive approximation (SAR) type. For a purely digital implementation, equivalent quantization can also be achieved using amplitude comparison and bit mapping logic. The specific structure can be selected based on the target frequency, power consumption, chip area, and requirements for quantization noise / harmonics. The quantizer 112 can adopt circuit structures from existing technologies, etc., and is not limited thereto in this disclosure.

[0064] Figure 2 A schematic circuit diagram of a controlled resistor branch network is shown. Each controlled resistor branch consists of a weighted resistor 114 and a switch 115 connected in series. N controlled resistor branches are connected in parallel between the positive (+) and negative (-) terminals of the battery cell 200. Based on the binary digital code output by the N-bit quantizer 112, the on / off state of the switches of the N controlled resistor branches is controlled, thereby generating an excitation current with an approximately harmonic signal waveform on the battery cell 200. Each bit (control bit) of the binary digital code is either 0 or 1. Figure 1 and Figure 2 As shown, the quantizer 112 outputs N bits of binary digital code, S1, S2, S3, ..., SN, which are used to control the on / off state of the switch 115 in the corresponding controlled resistor branch.

[0065] In a preferred embodiment, the resistance values ​​of the weighted resistors in the N controlled resistor branches are set according to binary weights, such that the resistance value of the weighted resistor in the i-th controlled resistor branch is... Where i = 1, 2, ..., N, and R is the reference resistance value. For example, when N = 4, the weighted resistance values ​​of the four controlled resistor branches can be R, R / 2, R / 4, and R / 8, respectively. Different on / off combinations of the switch can produce on the battery cell... The excitation currents of different amplitude levels, with binary digital codes varying with the amplitude of the simple harmonic signal, cause the excitation currents to exhibit a stepped waveform that approximates the simple harmonic signal waveform.

[0066] The switch is preferably a MOS switch (e.g., an N-channel or P-channel power MOSFET, or an external MOS switch driven by chip pins). Figure 3 In the example shown, when the first and third controlled resistor branches are on (i.e., S1=1 and S3=1), and the remaining control bits are 0, the excitation current is a pull-down current flowing from the positive terminal of cell 200 through the on-state first and third controlled resistor branches to the negative terminal. This is achieved by combining the on / off states of the controllable discharge branches of the cell to form a multi-level excitation current. Those skilled in the art will understand that by changing the polarity of the branch connections or adding a symmetrical pull-up / bidirectional network, other directions or differential forms of excitation current can be constructed. As long as the multi-level approximately sinusoidal current is still generated by the weighted resistor branches controlled by multi-bit codes, it does not depart from the technical concept of this disclosure.

[0067] The excitation current is equal to the sum of the currents in each conducting branch of the controlled resistor, such as... Figure 3 In this configuration, the total excitation current equals the sum of the currents flowing through the first and third controlled resistor branches. Ideally, the current in each conducting controlled resistor branch is the ratio of the cell voltage to the resistance of the weighted resistor in that branch. Let the cell terminal voltage be V. BAT Each bit of the N-bit binary code is b. N , b N-1 b1 (with values ​​of 0 or 1, where 1 indicates the corresponding switch is on and 0 indicates the corresponding switch is off), then the excitation current at a certain moment can be expressed as: .

[0068] When the binary code updates over time according to a sinusoidal pattern... It tracks the sinusoidal change in a step-like manner, that is... The continuous sinusoidal envelope is quantized into several current steps, the number of steps increases with the increase of N, and the harmonic distortion tends to decrease.

[0069] In practical circuits, the on-resistance of switches, wiring resistance, and resistance tolerance can affect current accuracy. This can be mitigated by selecting switches with low on-resistance, calibrating and compensating for the switch's on-resistance, using high-precision resistors, or introducing a known scaling factor into impedance calculations. Furthermore, control strategies can avoid unnecessary large jumps between adjacent digital codes, or perform simple shaping of the digital codes to reduce glitches caused by step switching.

[0070] Compared to schemes that directly output analog sinusoidal excitation using high-precision, high-speed voltage / current-type DACs, this disclosure achieves multi-bit current excitation using a network of switches and weighted resistors. This significantly reduces reliance on an on-chip high-precision analog DAC, resulting in lower hardware cost and power consumption, making it more suitable for integration into the peripheral circuitry of a BMS battery monitoring chip. Compared to single-bit pulse excitation using only a single resistor and a single switch, multi-bit binary weighting provides… With different current levels, the excitation waveform is closer to a sine wave, and the fundamental component is more concentrated, which helps to improve the signal-to-noise ratio of EIS impedance extraction and reduce the pressure of subsequent filtering.

[0071] In one implementation, a harmonic signal generator 111 and an N-bit quantizer 112 are integrated into the digital domain of the battery monitoring chip 10 (the digital domain may also include a discrete Fourier transform module 140). N controlled resistor branches 113 are located externally to the battery monitoring chip 10. The binary digital code output by the N-bit quantizer 112 is output via chip pins to control the switching of the N controlled resistor branches. This approach allows for on-chip digital logic as the primary component, while externally configuring resistor power and accuracy flexibly, facilitating adjustments to the value of R based on different cell capacities and allowable excitation amplitudes. The selection of R should ensure that the maximum excitation current is within the cell's safe disturbance range (small-signal linear region), while simultaneously ensuring that the response voltage exceeds the effective resolution of the analog front-end and the ADC.

[0072] Cell 200 at excitation current The action generates a response voltage signal It should be noted that the response voltage can be the AC component of the cell's terminal voltage, or it can be the disturbance response obtained after AC coupling or baseline subtraction.

[0073] The analog front-end circuit 120 is used to acquire the response voltage signal and perform filtering and amplification. In one embodiment, the analog front-end circuit 120 may include an anti-aliasing filter and an amplifier, with the response voltage signal being filtered by the anti-aliasing filter and amplified by the amplifier before being input to the analog-to-digital converter 130. The anti-aliasing filter is used to attenuate noise and interference above the Nyquist frequency to prevent sampling aliasing. The amplifier is used to increase the signal amplitude, match the ADC input range, and improve the signal-to-noise ratio. The amplifier may be an instrumentation amplifier, a programmable gain amplifier, or other suitable amplification circuit. The analog front-end may also include AC coupling capacitors, bias circuits, differential input stages, etc., as needed, but this disclosure is not limited thereto.

[0074] An analog-to-digital converter (ADC) 130 converts the filtered and amplified response voltage signal into a digital signal. The ADC 130 can employ single-ended or differential input. Differential input is beneficial for suppressing common-mode interference. In one embodiment, the ADC 130 can reuse the ADC resources originally used in the battery monitoring chip for acquiring the cell's operating voltage, and switch between the operating voltage channel and the EIS response channel in a time-division multiplexing manner using a multiplexer; alternatively, a separate ADC can be configured for the EIS. This disclosure does not limit the specific values ​​of the ADC bit depth and sampling rate, as long as the sampling theorem and accuracy requirements at the target highest excitation frequency are met.

[0075] The Discrete Fourier Transform (DFT) module 140 performs DFT on the digital signal and the harmonic signal, and calculates the electrochemical impedance of the battery cell at a specified frequency based on the transform results. In one embodiment, the DFT module 140 obtains the frequency domain components of the excitation current. and frequency domain components of the response voltage signal and according to Obtaining electrochemical impedance ,in In response to the frequency domain components of the voltage signal, This represents the frequency domain component of the excitation current. It is generally a complex number, which can be represented as ,in This is the real part (resistive component). This is the imaginary part (reactive component).

[0076] Regarding the frequency domain components of the excitation current The information can be obtained in at least one of the following ways. The first way is to use the digital simple harmonic signal output by the simple harmonic signal generator as the phase and frequency reference, combined with binary digital code, resistor network parameters, and cell voltage V. BAT A defined current amplitude scale is constructed or converted to obtain The first method involves performing a discrete Fourier transform on the quantized multi-bit digital code. The second method involves reconstructing the quantized multi-bit digital code using a weighted resistance relationship. Then, a Discrete Fourier Transform is performed. The third method, when current sampling conditions are available, involves sampling the actual excitation current and then performing a Discrete Fourier Transform.

[0077] Since the digital harmonic signal and the digital code used for excitation share the same origin, the excitation and response are well aligned in time in the digital domain, which is beneficial for improving the accuracy of impedance phase calculation. The Discrete Fourier Transform (DFT) can employ direct DFT, the Goertzel algorithm, the Fast Fourier Transform (FFT), or equivalent frequency domain extraction methods such as orthogonal correlation (phase-locked demodulation) for a single frequency point. The Discrete Fourier Transform module in this disclosure encompasses a digital processing unit capable of extracting the amplitude and phase (or real and imaginary parts) at a specified frequency.

[0078] After completing the impedance calculation at a specified frequency, the harmonic signal generator 111 can be configured to sequentially generate multiple harmonic signals at different specified frequencies. The discrete Fourier transform module 140 calculates the electrochemical impedance at each specified frequency, thereby forming the electrochemical impedance spectrum of the battery cell. The impedance at different frequencies can be plotted as a Nyquist plot or a Bode plot, which can then be used for subsequent SOC / SOH / DCR estimation, internal resistance analysis, thermal runaway early warning, etc. As an example, several frequency points within the range of 100 mHz to 5 kHz can be measured sequentially; alternatively, only a few key frequency points can be measured depending on the application.

[0079] Optionally, the measured electrochemical impedance spectroscopy can be compared or fitted with a reference spectrum or an equivalent circuit model of the battery to infer the cell's state parameters. State parameters may include at least one of SOC, SOH, and DCR, and may also include internal resistance, internal temperature-related characteristics, etc. This disclosure does not limit the specific algorithm for state estimation based on impedance spectroscopy.

[0080] In actual battery use, the battery cell is often not in a completely open circuit or static load state, and background signals may exist on the load side. These background signals may fall within the frequency range of the EIS measurement frequency or its adjacent frequency band. If a simple harmonic signal is applied directly to this frequency and the response is extracted, the background component will be superimposed on the excitation response, resulting in measurement deviation. Figure 4 A schematic circuit diagram of a shunt configuration for detecting background frequency components of a battery load signal, according to one embodiment of the present disclosure, is shown. Figure 4As shown, a shunt 300 (or a sampling resistor or current sensing resistor) is connected in series in the current loop of the battery cell 200. The shunt 300 is preferably a low-resistance precision resistor, one end of which can be connected to the negative terminal of the battery cell or system ground, and the other end connected to the analog front-end circuit 120 (an analog front-end channel such as a multiplexer (MUX)) so that the voltage signal across the shunt can be acquired by an analog-to-digital converter when needed. In the multi-bit EIS excitation scheme, the shunt 300 can be used in conjunction with the excitation current generation circuit 110, the analog front-end circuit 120, and the analog-to-digital converter 130. That is, when no EIS excitation current is applied, the switches of each controlled resistor branch are turned off or kept open, and the voltage on the shunt 300 is acquired; when EIS excitation is applied, the controlled resistor branches are controlled according to binary digital codes to generate an approximately harmonic excitation current.

[0081] Without applying EIS excitation current, the voltage signal on the shunt 300 is acquired by the analog front-end circuit 120 and converted into a digital signal by the analog-to-digital converter 130. The digital signal is then subjected to a Discrete Fourier Transform (DFT) by the Discrete Fourier Transform (DFT) module 140. The background frequency components of the battery load signal are obtained by analyzing the positions of spectral peaks whose amplitudes exceed a preset threshold. This threshold can be set according to actual conditions. When generating a harmonic signal as EIS excitation, the desired specified frequency is compared with the aforementioned background frequency components. If a test frequency coincides with a background frequency component or falls within a predetermined neighborhood centered on the background frequency component, a frequency conflict is identified, requiring frequency hopping. During frequency hopping, the harmonic signal generator actively adjusts the specified frequency to a new frequency that avoids the conflict, for example, shifting it to the nearest available frequency outside the neighborhood. If there is no conflict, the original test frequency is maintained. Therefore, whether or not frequency hopping occurs depends on the battery load frequency components actively monitored when no excitation is applied. When the load contains a certain EIS test frequency, the accuracy of the test results is ensured by actively changing the harmonic signal frequency to avoid that frequency.

[0082] After completing the frequency hopping decision, the excitation current is generated and applied according to the multi-bit quantization and controlled resistor branch method described above, the response voltage is collected, and the electrochemical impedance at the specified frequency is calculated.

[0083] It should be noted that, in addition to background frequency detection, the shunt 300 can also be used to sample the actual excitation current when conditions permit, in order to help obtain the frequency domain components of the excitation current.

[0084] Figure 5 A flowchart of an excitation current generation method according to one embodiment of the present disclosure is shown. The method is used to provide an excitation current signal to a battery cell to measure the electrochemical impedance spectroscopy of the cell, and includes steps S510 to S530.

[0085] In step S510, a simple harmonic signal of a specified frequency is generated by a simple harmonic signal generator.

[0086] In step S520, the simple harmonic signal is quantized into binary digital code by an N-bit quantizer, where N≥2.

[0087] In step S530, the switching of N controlled resistor branches is controlled based on binary digital code. Each controlled resistor branch is composed of a weighted resistor and a switch connected in series. Each controlled resistor branch is connected in parallel between the positive and negative terminals of the battery cell, thereby generating an excitation current with an approximate simple harmonic signal waveform on the battery cell.

[0088] In a further embodiment, the resistance values ​​of the weighted resistors in the N controlled resistor branches are set according to binary weights, and different on / off combinations of the switches generate on the battery cell. The excitation currents, each with different amplitude levels, are encoded using binary digital codes that vary with the amplitude of a simple harmonic signal, causing the excitation currents to exhibit a stepped waveform approximating the simple harmonic signal. The generation and quantization of the simple harmonic signal can be completed in the digital domain of the battery monitoring chip. N controlled resistor branches are located outside the battery monitoring chip, and the quantized binary digital codes are used to drive the switching of the N controlled resistor branches.

[0089] Figure 6 A flowchart of an excitation current generation method according to one embodiment of the present disclosure is shown. The method is used to provide an excitation current signal to a battery cell to measure the electrochemical impedance spectroscopy of the cell, and includes steps S610 to S660.

[0090] In step S610, without applying EIS excitation current, the voltage signal across the shunt connected in series in the cell current loop is acquired. At this time, the switches of the controlled resistor branch are all turned off to avoid interference from the excitation network to the background monitoring.

[0091] In step S620, the voltage signal of the shunt is subjected to Discrete Fourier Transform (DFT) to analyze the background frequency components of the battery load signal.

[0092] In step S630, the specified frequency is compared with the background frequency components to determine whether there is a frequency conflict (overlap or falling into a predetermined neighborhood). If it is determined that frequency hopping is required, then proceed to step S640: change the specified frequency of the simple harmonic signal to generate a new specified frequency, avoiding the frequency points that conflict with the background frequency components; if it is determined that frequency hopping is not required, then keep the original EIS test frequency as the specified frequency.

[0093] In step S650, a simple harmonic signal is generated at a specified frequency after frequency hopping processing. In step S660, the simple harmonic signal is quantized into binary digital code using an N-bit quantizer. In step S670, after N-bit quantization, the controlled resistor branch is controlled to apply an excitation current with an approximate simple harmonic signal waveform to the battery cell. Steps S650 to S670 are related to... Figure 5 Steps S510 to S530.

[0094] pass Figure 6 The method shown can further suppress the impact of load background interference on EIS results and improve the accuracy of online measurement under a multi-bit low-cost excitation architecture.

[0095] Figure 7 A flowchart of an electrochemical impedance spectroscopy measurement method according to one embodiment of the present disclosure is shown. The method includes steps S710 to S740.

[0096] In step S710, an excitation current with an approximate simple harmonic signal waveform is applied to the battery cell using the above-described excitation current generation method.

[0097] In step S720, the response voltage signal generated by the battery cell under the action of excitation current is acquired, and the response voltage signal is filtered and amplified.

[0098] In step S730, the filtered and amplified response voltage signal is converted into a digital signal via analog-to-digital conversion.

[0099] In step S740, a discrete Fourier transform is performed on the digital signal and the harmonic signal, and the electrochemical impedance of the battery cell at a specified frequency is calculated based on the transform result.

[0100] In one embodiment, calculating the electrochemical impedance includes: obtaining the frequency domain components of the excitation current and the response voltage signal, respectively; through... Obtaining electrochemical impedance ,in The frequency domain component of the response voltage signal is... Let be the frequency domain component of the excitation current.

[0101] In a further embodiment, the method further includes: changing a specified frequency of the simple harmonic signal and repeatedly performing the excitation, acquisition and calculation steps to obtain electrochemical impedance at multiple frequencies and form the electrochemical impedance spectrum of the battery cell.

[0102] The following is a specific example with N=4 to provide a clearer understanding of this disclosure. This example does not constitute a limitation on the scope of this disclosure.

[0103] Example: Assume a reference resistance R = 1kΩ and a cell voltage V. BAT≈3.7 V, ignoring switch on-resistance. The four weighted resistors are 1 kΩ, 500Ω, 250Ω, and 125Ω respectively. When the binary code is 0000, all switches are off. ≈0; when the digital code is 0001, only the branch with the smallest resistance is conducting. ≈3.7 / 125 A≈29.6 mA; When the digital code is 1111, all four channels are on, and the equivalent conductance is the sum of the conductances of each branch. This achieves the maximum value (approximately 55.5 mA) for this configuration. In actual EIS measurements, a larger reference resistor can be selected or the control code amplitude can be scaled to keep the excitation current within a small signal disturbance range of several milliamps to tens of milliamps.

[0104] It should be noted that the above current values ​​are only used to illustrate the order of magnitude; in actual products, the excitation current amplitude is usually much smaller than the battery rated current and must meet the small signal conditions and safety specifications. The value of R, whether to insert a current limiting element, and whether to scale the control code can all be adjusted by those skilled in the art according to the cell specifications.

[0105] To reduce harmonic distortion of the stepped current, at least one of the following measures can be adopted: increasing the quantization bit depth N; increasing the codeword update rate; oversampling the digital sine wave before quantization; adding appropriate filter inductors / capacitors to the excitation circuit (without affecting the target frequency band); extracting only the fundamental component and suppressing harmonic frequencies in the DFT; averaging multiple measurement results. These measures can be used individually or in combination.

[0106] In the method and technical solution disclosed herein, the specific details of circuit structure, parameter selection, signal processing, etc., can be referred to in the previous description of the device and circuit. For the sake of brevity, they will not be repeated here.

[0107] In the description of this specification, the references to terms such as "one embodiment / mode," "some embodiments / modes," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment / mode or example is included in at least one embodiment / mode or example of this disclosure. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment / mode or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments / modes or examples. Furthermore, without contradiction, those skilled in the art can combine and integrate the different embodiments / modes or examples described in this specification, as well as the features of different embodiments / modes or examples.

[0108] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this disclosure, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0109] Those skilled in the art should understand that the above embodiments are merely for illustrating the present disclosure and are not intended to limit the scope of the disclosure. Those skilled in the art can make other changes or modifications based on the above disclosure, and these changes or modifications still fall within the scope of the present disclosure.

Claims

1. An excitation current generation circuit for multi-bit electrochemical impedance spectroscopy measurement, used to provide an excitation current signal to a battery cell to measure the electrochemical impedance spectrum of the battery cell, the excitation current generation circuit comprising: A simple harmonic signal generator, wherein the simple harmonic signal generator is used to generate a simple harmonic signal of a specified frequency; An N-bit quantizer receives the simple harmonic signal and quantizes the simple harmonic signal into binary digital code, where N≥2; as well as There are N controlled resistor branches, each consisting of a weighted resistor and a switch connected in series. The weighted resistors in each controlled resistor branch have different resistance values ​​and are connected in parallel between the positive and negative terminals of the battery cell. Based on the binary digital code, the on / off state of the switches of the N controlled resistor branches is controlled, thereby generating an excitation current with an approximate simple harmonic signal waveform on the battery cell.

2. The excitation current generating circuit as described in claim 1, characterized in that, The resistance values ​​of the weighted resistors in the N controlled resistor branches are set according to binary weights, such that the resistance value of the weighted resistor in the i-th controlled resistor branch is... , where i=1,2,…,N, and R is the reference resistance value.

3. The excitation current generating circuit as described in claim 2, characterized in that, Optionally, different on / off combinations of the N controlled resistor branches are generated on the battery cell. The excitation current has several different amplitude levels, and the binary digital code varies with the amplitude of the simple harmonic signal. The excitation current exhibits a stepped waveform that approximates the simple harmonic signal. Optionally, the excitation current is equal to the sum of the currents in each of the conducting controlled resistor branches, and the current in each conducting controlled resistor branch is the ratio of the cell voltage to the resistance of the weighted resistor in that controlled resistor branch. Optionally, the simple harmonic signal generator and the N-bit quantizer are integrated in the digital domain of the battery monitoring chip, and the N controlled resistor branches are located outside the battery monitoring chip. The binary digital code output by the N-bit quantizer is used to control the switching of the N controlled resistor branches.

4. The excitation current generating circuit as described in any one of claims 1 to 3, characterized in that, Optionally, the N-bit quantizer adopts at least one of the following structures: Flash type, successive approximation type, pipelined type, Sigma-Delta type, pipelined successive approximation type, or noise-shaping successive approximation type. Optionally, the switch is a MOS switch, and the excitation current is a pull-down current flowing from the positive terminal of the battery cell through a controlled resistor branch to the negative terminal of the battery cell. Optionally, N=4, and the weighted resistors in the four controlled resistor branches have resistance values ​​of R, R / 2, R / 4, and R / 8, respectively. Optionally, it also includes a shunt for providing a voltage signal reflecting the battery load signal when the excitation current is not applied. The voltage signal can be analyzed to analyze the background frequency components of the battery load signal. The harmonic signal generator is configured to: determine whether frequency hopping is required based on the background frequency components; if the battery load signal contains frequency components that coincide with or fall within a predetermined neighborhood of the electrochemical impedance spectroscopy test frequency, then change the specified frequency to avoid the frequency components.

5. An electrochemical impedance spectroscopy measuring device, characterized in that, include: The excitation current generating circuit as described in any one of claims 1 to 4 is used to apply an excitation current with an approximate simple harmonic signal waveform to the battery cell; The analog front-end circuit is used to acquire the response voltage signal generated by the battery cell under the excitation current, and to filter and amplify the response voltage signal; An analog-to-digital converter is used to convert filtered and amplified response voltage signals into digital signals. as well as The Discrete Fourier Transform module is used to perform Discrete Fourier Transform on the digital signal and the harmonic signal, and calculate the electrochemical impedance of the battery cell at the specified frequency based on the transformation result.

6. The electrochemical impedance spectroscopy measuring device as described in claim 5, characterized in that, Optionally, the analog front-end circuit includes an anti-aliasing filter and an amplifier. The response voltage signal is filtered by the anti-aliasing filter and amplified by the amplifier before being input to the analog-to-digital converter. Optionally, the discrete Fourier transform module obtains the frequency domain components of the excitation current and the response voltage signal, respectively, according to... Obtaining electrochemical impedance ,in The frequency domain component of the response voltage signal is... Let be the frequency domain component of the excitation current. Optionally, the harmonic signal generator is configured to sequentially generate multiple harmonic signals of different specified frequencies, and the discrete Fourier transform module calculates the electrochemical impedance at each specified frequency to form the electrochemical impedance spectrum of the battery cell. Optionally, the harmonic signal generator, the N-bit quantizer, the analog front-end circuit, the analog-to-digital converter, and the discrete Fourier transform module are integrated in the battery monitoring chip, and the N controlled resistor branches are located outside the battery monitoring chip and connected to the pins of the battery monitoring chip.

7. A method for generating excitation current for multi-bit electrochemical impedance spectroscopy, used to provide an excitation current signal to a battery cell to measure the electrochemical impedance spectrum of the battery cell, characterized in that, The method includes: A simple harmonic signal of a specified frequency is generated using a simple harmonic signal generator; The simple harmonic signal is quantized into binary digital code using an N-bit quantizer, where N≥2; The binary digital code controls the switching of N controlled resistor branches. Each controlled resistor branch is composed of a weighted resistor and a switch connected in series. The weighted resistors in each controlled resistor branch have different resistance values ​​and are connected in parallel between the positive and negative terminals of the battery cell, thereby generating an excitation current with an approximate simple harmonic signal waveform on the battery cell.

8. The excitation current generation method as described in claim 7, characterized in that, Optionally, the resistance values ​​of the weighted resistors in the N controlled resistor branches are set according to binary weights, and different on / off combinations of the switch generate on the battery cell. The excitation current has different amplitude levels, and the binary digital code varies with the amplitude of the simple harmonic signal, causing the excitation current to exhibit a stepped waveform that approximates the simple harmonic signal. Optionally, the generation of the harmonic signal and the quantization are performed in the digital domain of the battery monitoring chip. The N controlled resistor branches are located outside the battery monitoring chip, and the binary digital code obtained by quantization is used to drive the switching of the N controlled resistor branches. Optionally, before generating a simple harmonic signal of a specified frequency using a simple harmonic signal generator, the method further includes: obtaining a voltage signal reflecting the battery load signal when the excitation current is not applied; the simple harmonic signal generator determining whether frequency hopping is required based on the background frequency components; if the battery load signal contains frequency components that coincide with or fall within a predetermined neighborhood of the electrochemical impedance spectroscopy test frequency, the specified frequency is changed to avoid the frequency components.

9. A method for measuring electrochemical impedance spectroscopy, characterized in that, include: An excitation current with an approximate simple harmonic signal waveform is applied to the battery cell using the excitation current generation method as described in claim 7 or 8. The response voltage signal generated by the battery cell under the excitation current is acquired, and the response voltage signal is filtered and amplified. The filtered and amplified response voltage signal is converted into a digital signal via analog-to-digital conversion. Perform Discrete Fourier Transform on the digital signal and the harmonic signal, and calculate the electrochemical impedance of the battery cell at the specified frequency based on the transform result.

10. The electrochemical impedance spectroscopy measurement method as described in claim 9, characterized in that, Optionally, calculating the electrochemical impedance of the battery cell at the specified frequency includes: obtaining the frequency domain components of the excitation current and the response voltage signal, respectively; through... Obtaining electrochemical impedance ,in The frequency domain component of the response voltage signal is... Let be the frequency domain component of the excitation current. Optionally, it further includes: changing a specified frequency of the simple harmonic signal and repeatedly performing the excitation, acquisition and calculation steps to obtain electrochemical impedance at multiple frequencies and form the electrochemical impedance spectrum of the battery cell.

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