Pulse charging method and device for integrated electrochemical impedance spectroscopy measurement and storage medium

Abstract

The invention relates to a pulse charging method and device for integrated electrochemical impedance spectroscopy measurement and a storage medium. The method comprises the following steps: acquiring an excitation waveform; wherein the excitation waveform is composed of pulse signals; performing signal amplification on the excitation waveform based on a converter to obtain pulse current; charging a lithium battery according to the pulse current; in the charging process of the lithium battery, collecting a voltage signal and a current signal of the lithium battery; and measuring an electrochemical impedance spectrum of the lithium battery based on the voltage signal and the current signal, so as to adjust the frequency and amplitude of the excitation waveform according to the electrochemical impedance spectrum. According to the method, the excitation waveform composed of the pulse signals can be subjected to signal amplification based on the converter to obtain the pulse current, and the voltage signal and the current signal of the lithium battery are collected in the lithium battery charging process according to the pulse current, so that impedance spectroscopy measurement is carried out while charging is carried out, and simplicity and convenience of impedance spectroscopy measurement and cost reduction are taken into account.

Description

Technical Field

[0001] The present application relates to the field of lithium battery technology, and in particular to a pulse charging method, device and storage medium integrated with electrochemical impedance spectroscopy measurement. Background Art

[0002] Lithium-ion batteries have the advantages of light weight, small size, and high specific energy, and are widely used in electric vehicles. During the use of lithium batteries, the state of lithium batteries can be detected by electrochemical impedance spectroscopy (EIS) measurement, thereby evaluating the system safety of lithium batteries. However, most of the current impedance measurements require disconnecting the battery from the system and using commercial instruments such as electrochemical workstations for measurement. Such offline measurement equipment is usually expensive and has high requirements for experimental conditions and equipment maintenance. A small number of online measurements require the injection of disturbance signals or the setting of special working modes, which will affect the normal operation of the on-board converter. Therefore, how to achieve low-cost and simple electrochemical impedance spectroscopy measurement of lithium batteries has become an urgent problem to be solved. Summary of the invention

[0003] The present application provides a pulse charging method, device and storage medium integrated with electrochemical impedance spectroscopy measurement to solve the technical problem of how to realize electrochemical impedance spectroscopy measurement of lithium batteries in a low-cost and simple manner.

[0004] In a first aspect, the present application provides a pulse charging method with integrated electrochemical impedance spectroscopy measurement, the method comprising:

[0005] Acquire an excitation waveform; wherein the excitation waveform is composed of a pulse signal;

[0006] Amplifying the excitation waveform based on a current transformer to obtain a pulse current;

[0007] Charging the lithium battery according to the pulse current;

[0008] During the charging process of the lithium battery, collecting the voltage signal and the current signal of the lithium battery;

[0009] The electrochemical impedance spectrum of the lithium battery is measured based on the voltage signal and the current signal, so as to adjust the frequency and amplitude of the excitation waveform according to the electrochemical impedance spectrum.

[0010] Optionally, amplifying the excitation waveform based on a current transformer to obtain a pulse current includes:

[0011] Obtaining an expected charging current value of the lithium battery;

[0012] The converter amplifies the excitation waveform according to the expected charging current value to obtain the pulse current.

[0013] Optionally, adjusting the frequency and amplitude of the excitation waveform according to the electrochemical impedance spectrum includes:

[0014] Acquire a pre-stored first mapping relationship; wherein the first mapping relationship is a functional relationship between impedance, temperature and battery health status;

[0015] Determining a current temperature and a current battery health state of the lithium battery according to the electrochemical impedance spectrum and the first mapping relationship;

[0016] The frequency and amplitude of the excitation waveform are adjusted according to the current temperature and the current battery health state.

[0017] Optionally, adjusting the frequency and amplitude of the excitation waveform according to the current temperature and the current battery health state includes:

[0018] Obtaining a pre-stored aging index and temperature rise index; wherein the aging index is a mapping relationship between the battery health state and the frequency and amplitude of the charging sequence, which is used to characterize the aging rate of the lithium battery; the temperature rise index is a mapping relationship between the lithium battery temperature and the frequency and amplitude of the charging sequence, which is used to characterize the temperature rise rate of the lithium battery;

[0019] Determine a first frequency and a first amplitude according to the current temperature of the lithium battery and the temperature rise index;

[0020] Determine a second frequency and a second amplitude according to the current battery health state and the aging index of the lithium battery;

[0021] adjusting the frequency of the excitation waveform according to the first frequency and the second frequency;

[0022] The amplitude of the excitation waveform is adjusted according to the first amplitude and the second amplitude.

[0023] Optionally, obtaining an excitation waveform includes:

[0024] A series of sampling frequencies are calculated according to the set minimum pulse interval; wherein any sampling frequency in the series of sampling frequencies does not exceed the Nyquist limit frequency;

[0025] Initializing a multi-sine signal, by cyclically summing the series of sampling frequencies according to different frequencies to obtain an initialization sequence;

[0026] Iteratively optimizing the initialization sequence to obtain an optimized discrete interval binary sequence; wherein the iterative optimization is used to adjust the frequency spectrum of the initialization sequence;

[0027] Resampling the optimized discrete-interval binary sequence according to a preset format to obtain a discrete-interval binary sequence signal; wherein the preset format meets the format requirements of the converter;

[0028] The discrete interval binary sequence signal is used as the excitation waveform.

[0029] Optionally, iteratively optimizing the initialization sequence to obtain an optimized discrete interval binary sequence includes:

[0030] Calculating an objective function; wherein the objective function is used to characterize the difference between the current signal and the expected signal;

[0031] If the objective function is greater than or equal to a convergence tolerance, adjusting at least one of a phase angle and an initialization sequence, and recalculating the objective function;

[0032] If the objective function is smaller than the convergence tolerance, the iterative optimization is completed and the optimized discrete interval binary sequence is obtained.

[0033] Optionally, obtaining an excitation waveform includes:

[0034] Configure the minimum frequency, maximum frequency, minimum time interval and frequency sweep time of the signal; wherein the frequency sweep time is determined based on the minimum frequency and the minimum time interval;

[0035] Generate a linear frequency modulation pulse sequence according to the minimum frequency, the maximum frequency, the minimum time interval and the frequency sweep time;

[0036] Extracting a time domain diagram of a preset time period from the linear frequency modulation pulse sequence as an original reference signal;

[0037] Performing a fast Fourier transform on the original reference signal to obtain spectrum information of the preset time period;

[0038] Performing homogenization processing on the frequency spectrum information of the preset time period to obtain a signal time domain spectrum diagram;

[0039] Resampling the signal time domain spectrum graph by a first preset number of data points to obtain a sampled spectrum graph;

[0040] The sampling spectrum diagram is binarized according to a preset threshold value to obtain the excitation waveform.

[0041] Optionally, obtaining an excitation waveform includes:

[0042] Configure signal constraint parameters; wherein the constraint parameters include minimum frequency, maximum frequency and signal duration;

[0043] Determine the order of the maximum length sequence signal according to the desired frequency resolution;

[0044] Generate a maximum length sequence original signal under the constraint parameters according to the maximum length sequence generation function and the order;

[0045] Normalizing the original signal of the maximum length sequence to obtain a normalized signal;

[0046] Calibrate the effective value of the normalized signal, and perform fast Fourier transform processing on the effective value to obtain spectrum information;

[0047] Resampling the spectrum information by a second preset number of data points to obtain sampled data;

[0048] The sampled data is output according to a preset format to obtain the excitation waveform; wherein the preset format meets the format requirements of the converter.

[0049] In a second aspect, the present application provides a pulse charging device integrated with electrochemical impedance spectroscopy measurement, the device comprising:

[0050] An acquisition module, used for acquiring an excitation waveform; wherein the excitation waveform is composed of a pulse signal;

[0051] A signal amplification module, used for amplifying the excitation waveform based on a current transformer to obtain a pulse current;

[0052] A charging module, used for charging the lithium battery according to the pulse current;

[0053] A collection module, used for collecting the voltage signal and current signal of the lithium battery during the charging process of the lithium battery;

[0054] The impedance spectrum measurement module is used to measure the electrochemical impedance spectrum of the lithium battery based on the voltage signal and the current signal, so as to adjust the frequency and amplitude of the excitation waveform according to the electrochemical impedance spectrum.

[0055] In a third aspect, the present application provides an electronic device, including a processor, a communication interface, a memory, and a communication bus, wherein the processor, the communication interface, and the memory communicate with each other via the communication bus;

[0056] Memory, used to store computer programs;

[0057] The processor is used to implement the pulse charging method for integrated electrochemical impedance spectroscopy measurement described in any embodiment of the first aspect when executing the program stored in the memory.

[0058] In a fourth aspect, the present application provides a computer-readable storage medium having a computer program stored thereon, wherein when the computer program is executed by a processor, the pulse charging method for integrated electrochemical impedance spectroscopy measurement as described in any embodiment of the first aspect is implemented.

[0059] The above technical solution provided by the embodiment of the present application has the following advantages over the prior art: the method provided by the embodiment of the present application obtains an excitation waveform; wherein the excitation waveform is composed of a pulse signal; the excitation waveform is amplified based on a current transformer to obtain a pulse current; the lithium battery is charged according to the pulse current; during the charging process of the lithium battery, the voltage signal and current signal of the lithium battery are collected; the electrochemical impedance spectrum of the lithium battery is measured based on the voltage signal and the current signal, so as to adjust the frequency and amplitude of the excitation waveform according to the electrochemical impedance spectrum. The method can obtain a pulse current by amplifying the excitation waveform composed of a unit pulse signal based on a current transformer, and collect the voltage signal and current signal of the lithium battery during the charging process of the lithium battery according to the pulse current, so as to realize the impedance spectrum measurement while pulse charging, taking into account the simplification of impedance spectrum measurement and the reduction of cost, and the excitation waveform for pulse charging can be adjusted according to the measured electrochemical impedance spectrum, thereby improving the service life of the lithium battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0061] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0062] One or more embodiments are exemplarily described by pictures in the corresponding drawings, and these exemplified descriptions do not constitute limitations on the embodiments. Elements with the same reference numerals in the drawings represent similar elements, and unless otherwise stated, the figures in the drawings do not constitute proportional limitations.

[0063] Figure 1 A system architecture diagram of a pulse charging method with integrated electrochemical impedance spectroscopy measurement provided in one embodiment of the present application;

[0064] Figure 2 A schematic flow chart of a pulse charging method with integrated electrochemical impedance spectroscopy measurement provided in one embodiment of the present application;

[0065] Figure 3A schematic diagram of a multi-sinusoidal signal provided for one embodiment of the present application;

[0066] Figure 4 A schematic diagram of an optimized discrete interval binary sequence provided for one embodiment of the present application;

[0067] Figure 5 A schematic diagram of a discrete interval binary sequence signal provided for one embodiment of the present application;

[0068] Figure 6 A schematic diagram of an impedance spectrum obtained by measurement provided by an embodiment of the present application;

[0069] Figure 7 A schematic diagram of spectrum information provided for an embodiment of the present application;

[0070] Figure 8 A signal time domain spectrum diagram provided for one embodiment of the present application;

[0071] Fig. 9 A sampling spectrum diagram after binarization provided by an embodiment of the present application;

[0072] Fig.10 A schematic diagram of an impedance spectrum provided for one embodiment of the present application;

[0073] Fig.11 A schematic diagram of an original signal of a maximum length sequence provided by an embodiment of the present application;

[0074] Fig.12 A schematic diagram of spectrum information provided for an embodiment of the present application;

[0075] Fig.13 A schematic diagram of sampled data after resampling provided by an embodiment of the present application;

[0076] Fig.14 A schematic diagram of an impedance spectrum provided for one embodiment of the present application;

[0077] Fig.15 A pulse charging sequence adjustment schematic diagram provided for one embodiment of the present application;

[0078] Fig.16 A pulse charging impedance spectrum measurement block diagram provided for one embodiment of the present application;

[0079] Fig.17 A schematic diagram of the structure of a pulse charging device with integrated electrochemical impedance spectroscopy measurement provided in one embodiment of the present application;

[0080] Fig.18 A schematic diagram of the structure of an electronic device provided in accordance with an embodiment of the present application. DETAILED DESCRIPTION

[0081] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0082] The disclosure below provides many different embodiments or examples to realize the different structures of the present application. In order to simplify the disclosure of the present application, the parts and settings of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the present application. In addition, the present application can repeat reference numbers and / or letters in different examples. This repetition is for the purpose of simplification and clarity, and does not itself indicate the relationship between the various embodiments and / or settings discussed.

[0083] Some traditional methods for impedance spectroscopy measurement include frequency scanning method, electrochemical workstation method and pseudo-random binary sequence (PRBS) method, etc. Next, we will first introduce the principles, advantages and disadvantages of traditional methods.

[0084] Frequency sweep method:

[0085] Principle: By applying sinusoidal wave excitation signals of different frequencies in a wide frequency range, measuring the voltage and current response of the battery, and then calculating the impedance values ​​at different frequencies, the impedance spectrum is finally obtained.

[0086] Advantages: It can obtain more accurate and detailed impedance spectrum information, covering a wider frequency range, which is very useful for studying various electrochemical processes and mechanisms inside the battery.

[0087] Disadvantages: The measurement time is long, especially in the low frequency band, it takes a lot of time to obtain a stable response; it has high requirements on equipment and requires precise signal generators and measuring instruments.

[0088] Electrochemical workstation method:

[0089] Principle: An electrochemical workstation is an instrument specifically used for electrochemical research. It can accurately control the potential or current applied to the battery and measure the corresponding response. By setting different measurement modes and parameters, the impedance spectrum of lithium batteries can be measured.

[0090] Advantages: It has high precision and high stability, can provide rich measurement functions and data analysis tools, and can conduct in-depth research on the electrochemical performance of batteries.

[0091] Disadvantages: The equipment is expensive, the operation is relatively complicated, and requires professional operators and certain experimental skills.

[0092] Pseudo-random binary sequence (PRBS) method:

[0093] Principle: PRBS is a binary sequence with pseudo-random characteristics. By applying it to the battery as an excitation signal, the voltage response of the battery is measured, and then the impedance spectrum of the battery is calculated using a related algorithm.

[0094] Advantages: The impedance information of the battery can be obtained quickly, and the measurement time is short; the equipment requirements are relatively low and easy to implement.

[0095] Disadvantages: Due to the characteristics of binary signals, the spectrum energy distribution is uneven, which may affect the accuracy of the measurement results; the measurement effect in the low frequency band may not be good.

[0096] In addition, there are methods such as DC superimposed small pulse current to measure impedance spectrum. The DC superimposed small pulse current method is to superimpose a small pulse current (AC component) on the working current (DC) of the battery. DC current is used to maintain the normal charge and discharge state of the battery, so that it is in a specific state of charge (SOC). The pulse current is used to stimulate the battery to produce a corresponding voltage response. By analyzing the relationship between the voltage response and the pulse current, the impedance information of the battery can be obtained. Compared with the previous impedance spectrum measurement methods, this method of measuring the battery impedance spectrum can measure in real time during the battery charging and discharging process, obtain the impedance spectrum under different SOCs, and help study the performance changes of the battery during the entire use process. However, the presence of DC current may mask some weak AC signal characteristics, especially when measuring low-impedance batteries or measuring in low frequency bands. DC bias will cause the operating point of the measurement system to shift, so that the measurement range of the AC signal is limited, thereby affecting the accurate measurement of the battery impedance. At the same time, the method of measuring impedance spectrum with DC superimposed small pulse current requires a power supply that can accurately provide stable DC current and small pulse current, as well as a voltage measuring instrument with high resolution and high precision. These devices are usually expensive and have high requirements for experimental conditions and equipment maintenance.

[0097] In terms of lithium battery charging technology, the traditional high-power constant current-constant voltage (CC-CV) charging method is widely used in lithium-ion battery charging. Its charging process is mainly divided into two stages: constant current charging stage and constant voltage charging stage. In the constant current charging stage, the charger charges the battery with a constant current. In this stage, the battery voltage will gradually increase until it reaches the set voltage threshold. The advantage of this stage is that it can charge the battery at a relatively high speed, especially when the battery power is low, it can quickly increase the battery power level. For example, in the early stage of charging of some electronic products, we can observe that the charging speed is fast, which is mainly due to the constant current CC stage. When the battery voltage reaches the set threshold, the charging enters the constant voltage charging stage. In this stage, the charger will keep the output voltage constant, while the charging current gradually decreases. As the current decreases, the battery power gradually saturates. The purpose of the constant voltage charging stage is to ensure that the battery is fully charged while avoiding damage to the battery due to overcharging.

[0098] The pulse charging (PC) method does not continuously deliver current to the battery like traditional constant current charging or constant voltage charging, but charges the battery with a pulse current of a certain frequency. The pulse charging method can effectively extend the life of lithium batteries by allowing the battery to have an interval time to balance the internal chemical reaction during the charging process, reducing the heat generation inside the battery and the irreversible damage of the electrode material. For example, at the battery level, the impact of pulse charging is affected by the frequency of the current pulse. As the current pulse frequency increases, for example, from 100 Hz to 2000 Hz, the cycle stability of the battery is significantly improved. At the electrode level, PC charging effectively reduces the structural changes of graphite and NMC532 electrodes and the impedance of the electrode-electrolyte interface, where "NMC" stands for Nickel-Manganese-Cobalt ternary material, and "532" means that the molar ratio of the three metal elements of nickel, manganese and cobalt is 5:3:2, especially the solid electrolyte interface film (Solid-Electrolyte Interphase, SEI film) on the graphite anode. At the material level, the effects of PC charging on NMC532 / graphite electrode materials and electrolytes include: During the lithium-ion intercalation process of the pulsed current that allows structural relaxation, the intercalated lithium ions are more evenly distributed in the graphite, alleviating the mechanical strain, thereby inhibiting the fracture / crushing and volume expansion of the graphite particles. Due to the primary reduction of the carbonate-based electrolyte, the SEI layer on the graphite anode appears thinner and has a relatively higher proportion of organic compounds.

[0099] In order to solve the technical problem of how to realize the electrochemical impedance spectroscopy measurement of lithium batteries in a low-cost and simple manner in the prior art, the present application provides a pulse charging method, device and storage medium with integrated electrochemical impedance spectroscopy measurement, which can realize impedance spectrum measurement while charging the lithium battery, taking into account the simplification of impedance spectrum measurement and cost reduction.

[0100] The first embodiment of the present application provides a pulse charging method with integrated electrochemical impedance spectroscopy measurement, which can be applied to Figure 1 The system architecture shown includes at least a pulse charging and impedance spectrum measurement module 101 and a lithium battery 102. The pulse charging and impedance spectrum measurement module 101 can measure the electrochemical impedance spectrum (hereinafter also referred to as impedance spectrum or EIS) of the lithium battery 102 while pulse charging the lithium battery 102.

[0101] This method can be applied to the pulse charging and impedance spectrum measurement module 101 in the system architecture. Next, the pulse charging method for integrated electrochemical impedance spectroscopy measurement is described in detail based on the system architecture. Figure 2 , the pulse charging method for integrated electrochemical impedance spectroscopy measurement includes:

[0102] Step 201, obtaining an excitation waveform; wherein the excitation waveform is composed of a pulse signal.

[0103] The excitation waveform can be a sequence signal obtained in a variety of different ways, such as a discrete interval binary sequence (DIBS) signal, a linear frequency modulation pulse sequence (LSC) signal, a maximum length sequence (MLS) signal, etc. Different excitation waveforms are described in detail in the following embodiments.

[0104] Step 202: Amplify the excitation waveform based on the current transformer to obtain a pulse current.

[0105] In one embodiment, the excitation waveform is amplified based on the converter to obtain the pulse current, including: obtaining the expected charging current value of the lithium battery; and the excitation waveform is amplified based on the converter according to the expected charging current value to obtain the pulse current.

[0106] In this embodiment, the unit pulse signal in the excitation waveform can be used as a current reference, and the unit pulse signal can be amplified by a current transformer to the expected charging current value of the lithium battery, so that the impedance spectrum can be measured while charging while retaining the waveform of the pulse signal.

[0107] Step 203, charging the lithium battery according to the pulse current.

[0108] Step 204 , collecting the voltage signal and current signal of the lithium battery during the charging process of the lithium battery.

[0109] During the charging process of lithium batteries, since they are charged by pulse current, the charging pulse current can be used as the disturbance signal of the lithium battery, and the voltage signal and current signal during the charging process of the lithium battery can be collected, thereby providing a data basis for impedance spectrum measurement.

[0110] Step 205 , measuring the electrochemical impedance spectrum of the lithium battery based on the voltage signal and the current signal, so as to adjust the frequency and amplitude of the excitation waveform according to the electrochemical impedance spectrum.

[0111] The method can obtain a pulse current by amplifying an excitation waveform composed of a pulse signal based on a current transformer, and collect a voltage signal and a current signal of a lithium battery during charging of the lithium battery according to the pulse current, thereby realizing impedance spectrum measurement while pulse charging, taking into account the simplification of impedance spectrum measurement and the reduction of costs, and the excitation waveform for pulse charging can be adjusted according to the measured electrochemical impedance spectrum, thereby increasing the service life of the lithium battery.

[0112] In one embodiment, the excitation waveform is a discrete interval binary sequence (DIBS) signal. The specific design process of the signal can first generate a multi-sine signal by MATLAB code, and generate an optimized DIBS signal by an iterative optimization method. In addition, various analyses and processing are performed on the generated optimized DIBS signal, including drawing the signal waveform, calculating the spectrum, scaling the signal, calculating the root mean square value, resampling and converting to binary, and outputting the binary resampled DIBS signal data in a specific format.

[0113] Specifically, obtaining an excitation waveform includes: calculating a series of sampling frequencies according to a set minimum pulse interval; wherein any sampling frequency in the series of sampling frequencies does not exceed the Nyquist limit frequency; initializing a multi-sine signal, and summing a series of sampling frequencies according to different frequencies by cyclically performing sinusoidal wave summing to obtain an initialization sequence; iteratively optimizing the initialization sequence to obtain an optimized discrete interval binary sequence; wherein the iterative optimization is used to adjust the spectrum of the initialization sequence; resampling the optimized discrete interval binary sequence according to a preset format to obtain a discrete interval binary sequence signal; wherein the preset format meets the format requirements of the converter; and using the discrete interval binary sequence signal as an excitation waveform.

[0114] In this embodiment, the sampling frequency fs is first calculated according to the given minimum pulse interval to generate a series of frequencies frequencies (a series of frequencies here refers to a pulse signal that can generate frequencies between the minimum and maximum of the Nyquist limit). Next, the multi-sine signal multisine_signal is initialized, and the sine waves of different frequencies are summed up by looping to obtain an initialization sequence. For example, the formula for generating a multi-sine signal by looping to superimpose sine waves of different frequencies can be multisine_signal=multisine_signal+sin(2*pi*f*t), where f refers to the sampling frequency corresponding to the superimposed sine wave signal, and t is time. Figure 3 It is a schematic diagram of a multi-sine signal, where the horizontal axis is time and the vertical axis is amplitude. After obtaining the initialization sequence, it is possible to check whether the maximum frequency fmax exceeds the Nyquist limit. Exceeding the limit will affect the charging, and will produce aliasing, signal distortion and other effects. Therefore, a warning is required if it exceeds the limit. Initialize the sequence d(n)(b_hat) and the corresponding Fourier coefficients (such as the current Fourier coefficient Cbk_desired, the expected Fourier coefficient Cdk_desired and the phase angle phi_k). The initialization sequence is iteratively optimized. After the iteration is completed, the final optimized discrete interval binary sequence is obtained. The iterative optimization is used to adjust the spectrum of the initialization sequence. Figure 4 This is a schematic diagram of an optimized discrete interval binary sequence, where the horizontal axis is time and the vertical axis is the binary value. The optimized discrete interval binary sequence is resampled according to the preset format to obtain a discrete interval binary sequence signal. Figure 5 The figure is a schematic diagram of a discrete interval binary sequence signal, wherein the horizontal axis is time and the vertical axis is binary value. The preset format meets the format requirements of the converter; the discrete interval binary sequence signal is used as the excitation waveform.

[0115] Specifically, various analyses and processing can be performed on the DIBS signal, for example, including drawing the waveform of the original multi-sine signal, the intermediate iteration result, and the final DIBS signal, calculating and drawing the amplitude spectrum and energy spectrum, scaling the signal, calculating the root mean square value, calculating the Fourier spectrum of the scaled signal, resampling the signal and converting it to binary, and finally outputting the binary resampled DIBS signal data in a specific preset format. By drawing the original multi-sine signal, the initial signal shape can be intuitively seen, including its amplitude, frequency components and other characteristics. It provides a basis for subsequent comparison with the discrete interval binary sequence (DIBS) signal after iterative optimization. The final DIBS waveform can provide a reference for subsequent signal processing steps. Resampling is to reduce the amount of data and increase the operation speed.

[0116] In one embodiment, the initialization sequence is iteratively optimized to obtain an optimized discrete interval binary sequence, including: calculating an objective function; wherein the objective function is used to characterize the difference between the current signal and the expected signal; if the objective function is greater than or equal to the convergence tolerance, adjusting at least one of the phase angle and the initialization sequence, and recalculating the objective function; if the objective function is less than the convergence tolerance, the iterative optimization is completed to obtain the optimized discrete interval binary sequence.

[0117] In this embodiment, during the iterative optimization process, the actual Fourier coefficient (Cbk_current) of the signal is made as close as possible to the desired Fourier coefficient (Cdk_desired) by continuously adjusting the binary sequence, and the current Fourier coefficient Cbk_current is calculated, and then the objective function J is calculated. If the change of J is less than the convergence tolerance tol, the iteration stops; otherwise, the iterative optimization is performed again after the phase angle phi_k, the current Fourier coefficient Cdk_current and the sequence b_hat are updated.

[0118] After resampling according to the preset format to obtain a discrete interval binary sequence signal, the converter can be used to boost and amplify the unit DIBS pulse signal as a reference through the current loop PI control, and the amplitude of the generated binary unit pulse can be amplified and input into the lithium battery as a pulse current as the charging current. At the same time, the voltage and current signals of the lithium battery are measured, so as to calculate the impedance spectrum information based on the voltage and current information. Figure 6 Schematic diagram of the impedance spectrum obtained by charging and measuring based on the DIBS signal at 25 degrees Celsius.

[0119] In one embodiment, an example is given in which the excitation waveform is a linear frequency modulation pulse sequence (LSC) signal.

[0120] Acquiring an excitation waveform includes: configuring a minimum frequency, a maximum frequency, a minimum time interval and a frequency sweep time of a signal; generating a linear frequency modulation pulse sequence according to the minimum frequency, the maximum frequency, the minimum time interval and the frequency sweep time; intercepting a time domain diagram of a preset time period from the linear frequency modulation pulse sequence as an original reference signal; performing a fast Fourier transform on the original reference signal to obtain frequency spectrum information of the preset time period; performing a homogenization process on the frequency spectrum information of the preset time period to obtain a signal time domain spectrum diagram; resampling the signal time domain spectrum diagram for a first preset number of data points to obtain a sampled spectrum diagram; performing a binarization process on the sampled spectrum diagram according to a preset threshold value to obtain an excitation waveform.

[0121] In this embodiment, the key parameters of the signal can be defined in Matlab, such as the minimum frequency fmin is 1Hz, fmax is 500Hz, and the minimum time interval delta_t is 0.001 seconds (i.e. 1ms). Calculate a reasonable sweep time T_sweep. The sweep time is determined based on the minimum frequency and the minimum time interval. For example, the sweep time can be selected as the maximum value of 1 / fmin and delta_t*100 to achieve reasonable coverage from the lowest frequency to the highest frequency. According to the given frequency modulation formula phase=2*pi*(fmin*t+(fmax-fmin)*t^2 / (2*T_sweep)), a linear frequency modulation pulse sequence under ideal conditions is generated. Then, the time domain diagram of 0-0.4s is intercepted as the original reference signal, and a fast Fourier transform (fft) is performed to obtain the spectrum information. The specific spectrum information schematic diagram is shown as follows. Figure 7 The intercepted 0-0.4s data is homogenized and the amplitude is adjusted to 0-1. Then the effective value of the signal is calculated. The time domain spectrum of the processed signal is shown in Figure 8 As shown. The data is resampled and the original data is resampled into 200 data points using the new time vector t_resampled. Then the threshold is set to 0.5 to perform binarization on the signal. The sampling spectrum after binarization is shown in Fig. 9 The processing result is a linear frequency modulation pulse sequence signal. Pulse charging and impedance spectrum measurement are performed according to the linear frequency modulation pulse sequence signal, and the impedance spectrum measured at 25 degrees Celsius is obtained as shown in FIG. Fig.10 shown.

[0122] In one embodiment, an example is given in which the excitation waveform is a maximum length sequence (MLS) signal.

[0123] Acquiring an excitation waveform includes: configuring constraint parameters of a signal; wherein the constraint parameters include a minimum frequency, a maximum frequency, and a signal duration; determining the order of a maximum length sequence signal according to a desired frequency resolution; generating a maximum length sequence original signal under the constraint parameters according to a maximum length sequence generation function and the order; normalizing the maximum length sequence original signal to obtain a normalized signal; calibrating an effective value of the normalized signal, and performing a fast Fourier transform on the effective value to obtain spectrum information; resampling the spectrum information by a second preset number of data points to obtain sampling data; outputting the sampling data in a preset format to obtain an excitation waveform; wherein the preset format meets the format requirements of the converter.

[0124] In this embodiment, the three input parameters of the minimum frequency fmin, the maximum frequency fmax, and the signal duration can be defined as the constraint parameters of the signal, and the sampling frequency fs can be determined to be 10 times the maximum frequency to ensure the smooth progress of subsequent sampling. The order (number of registers) n of the MLS signal is determined according to the desired frequency resolution desired_resolution (which can be set to 1Hz), and the mls(n) function is used to generate the MLS signal. The mls(n) function is a function used in MATLAB to generate a maximum length sequence. The schematic diagram of the original signal of the maximum length sequence is shown in Fig.11 As shown, the horizontal axis is time and the vertical axis is amplitude.

[0125] Normalize the original signal, adjust the amplitude between 0 and 1, calibrate the effective value of the adjusted signal, and perform FFT analysis to obtain the spectrum information. The specific analysis result is the spectrum information as follows Fig.12 As shown. Generate a new time vector t_resampled, and use linspace(t(1), t(end), 200) to make it have 200 points, ranging from the starting point to the end point of the original time vector t. Resample the original data into 200 data points. The schematic diagram of the resampled sampling data is as follows Fig.13 As shown, the horizontal axis is time and the vertical axis is binary amplitude. The sampled data is formatted and output as the reference value of the converter, and the pulse current is obtained after signal amplification. The voltage signal and current signal of the lithium battery are collected during the process of charging the lithium battery according to the pulse current. The impedance spectrum measured at 25 degrees Celsius is as follows Fig.14 shown.

[0126] In the above embodiments of the present application, a lithium battery charging method for simultaneous pulse charging and impedance spectrum measurement is proposed, and a corresponding pulse charging generation program and measurement process are proposed, which is different from the traditional pulse charging and impedance spectrum measurement method in that charging and impedance spectrum measurement are performed simultaneously. The generation methods of the three excitation current sequences DIBS, LSC, and MLS proposed in the above specific embodiments cover more frequency information than the existing excitation sequences, and the generation of the sequence has lower hardware requirements, which is conducive to cost control.

[0127] In one embodiment, the frequency and amplitude of the excitation waveform are adjusted according to the electrochemical impedance spectrum, including: obtaining a pre-stored first mapping relationship; wherein the first mapping relationship is a functional relationship between impedance, temperature, and battery health status; determining the current temperature and current battery health status of the lithium battery according to the electrochemical impedance spectrum and the first mapping relationship; and adjusting the frequency and amplitude of the excitation waveform according to the current temperature and the current battery health status.

[0128] In this embodiment, the first mapping relationship may be a functional relationship between impedance, temperature and battery health status obtained in advance through multiple offline measurements, such as a functional relationship of Z=F(T, SOH), where Z represents impedance, T represents temperature, and SOH represents battery health status. Based on the electrochemical impedance spectrum of the lithium battery measured online combined with the first mapping relationship, the current temperature and current battery health status of the lithium battery under the current impedance can be determined, so that the frequency and amplitude of the excitation waveform can be adjusted according to the current temperature and current battery health status, so that the pulse signal of the excitation waveform better matches the current state of the lithium battery.

[0129] In one embodiment, adjusting the frequency and amplitude of the excitation waveform according to the current temperature and the current battery health state includes:

[0130] Obtaining pre-stored aging index and temperature rise index; wherein the aging index is a mapping relationship between the battery health state and the frequency and amplitude of the charging sequence, which is used to characterize the aging rate of the lithium battery; the temperature rise index is a mapping relationship between the lithium battery temperature and the frequency and amplitude of the charging sequence, which is used to characterize the temperature rise rate of the lithium battery;

[0131] Determine a first frequency and a first amplitude according to a current temperature and a temperature rise index of the lithium battery;

[0132] Determining a second frequency and a second amplitude according to a current battery health state and an aging index of the lithium battery;

[0133] adjusting the frequency of the excitation waveform according to the first frequency and the second frequency;

[0134] The amplitude of the excitation waveform is adjusted according to the first amplitude and the second amplitude.

[0135] In this embodiment, a pulse charging sequence adjustment schematic diagram is shown as follows: Fig.15The pulse charging sequence can be any excitation waveform, such as any one of DIBS, LSC, MLS, or other pulse charging sequences. In the process of pulse charging the lithium battery according to the pulse charging sequence, the voltage signal and current signal of the lithium battery are collected, and then the electrochemical impedance spectrum of the lithium battery is measured online based on the voltage signal and the current signal. The impedance spectrum can characterize the relationship with the temperature and SOH of the lithium battery, and the function relationship Z=F(T, SOH) obtained offline is obtained. According to the electrochemical impedance spectrum of the lithium battery measured online and combined with the function relationship, the current temperature and current battery health status of the lithium battery under the current impedance can be determined, and then the pre-stored aging index Drise and temperature rise index Trise can be obtained. Among them, Drise=F(f, A), Trise=F(f, A), the f in the brackets represents the frequency, A represents the amplitude, and the F outside the brackets represents the functional relationship. The first frequency and the first amplitude can be determined according to the current temperature and Trise, and the second frequency and the second amplitude can be determined according to the current SOH and Drise, so that the frequency of the excitation waveform (pulse charging sequence) can be adjusted according to the first frequency and the second frequency, and the amplitude of the excitation waveform can be adjusted according to the first amplitude and the second amplitude. For example, the frequency of the excitation waveform can be adjusted according to the average value of the first frequency and the second frequency, or a weight coefficient can be preset to adjust the frequency of the excitation waveform according to the weighted average value of the first frequency and the second frequency. There is no limitation. The amplitude is adjusted in the same way as the frequency, which will not be repeated.

[0136] This embodiment realizes impedance spectrum measurement during pulse charging, taking into account the simplification of impedance spectrum measurement and the reduction of cost. In addition, the excitation waveform for pulse charging can be adjusted according to the measured electrochemical impedance spectrum, thereby increasing the service life of the lithium battery.

[0137] In a specific embodiment, the pulse charging impedance spectrum measurement block diagram is as follows: Fig.16 As shown, the DIBS signal generation generates a DIBS signal composed of a pulse signal, which is amplified by the converter to obtain a pulse current. The pulse current charges the battery module (lithium battery). During the charging process, voltage and current signals are collected, and EIS is generated based on the voltage and current signals. At the same time, the DIBS signal is corrected based on the generated EIS, which can effectively protect the lithium battery.

[0138] Based on the same technical concept, the second embodiment of the present application provides a pulse charging device integrated with electrochemical impedance spectroscopy measurement, such as Fig.17 , the device comprises:

[0139] The acquisition module 1701 is used to acquire an excitation waveform; wherein the excitation waveform is composed of a unit pulse signal;

[0140] A signal amplification module 1702, configured to amplify the excitation waveform based on a current transformer to obtain a pulse current;

[0141] A charging module 1703, used to charge the lithium battery according to the pulse current;

[0142] The acquisition module 1704 is used to acquire the voltage signal and the current signal of the lithium battery during the charging process of the lithium battery;

[0143] The impedance spectrum measurement module 1705 is used to measure the electrochemical impedance spectrum of the lithium battery based on the voltage signal and the current signal, so as to adjust the excitation waveform according to the electrochemical impedance spectrum.

[0144] The device can obtain a pulse current by amplifying the excitation waveform composed of a unit pulse signal based on a current transformer, and collect the voltage signal and current signal of the lithium battery during the charging process of the lithium battery according to the pulse current, so as to realize impedance spectrum measurement while charging, taking into account the simplification of impedance spectrum measurement and the reduction of cost, and can adjust the excitation waveform for charging according to the measured electrochemical impedance spectrum, thereby increasing the service life of the lithium battery.

[0145] like Fig.18 As shown, an embodiment of the present application provides an electronic device, including a processor 111, a communication interface 112, a memory 113 and a communication bus 114, wherein the processor 111, the communication interface 112, and the memory 113 communicate with each other through the communication bus 114.

[0146] Memory 113, used for storing computer programs;

[0147] In one embodiment of the present application, the processor 111 is used to implement the pulse charging method for integrated electrochemical impedance spectroscopy measurement provided by any one of the aforementioned method embodiments when executing the program stored in the memory 113 .

[0148] The communication bus mentioned in the above terminal can be a Peripheral Component Interconnect (PCI) bus or an Extended Industry Standard Architecture (EISA) bus, etc. The communication bus can be divided into an address bus, a data bus, a control bus, etc. For ease of representation, only one thick line is used in the figure, but it does not mean that there is only one bus or one type of bus.

[0149] The communication interface is used for communication between the above terminal and other devices.

[0150] The memory may include a random access memory (RAM) or a non-volatile memory, such as at least one disk memory. Optionally, the memory may also be at least one storage device located away from the aforementioned processor.

[0151] The above-mentioned processor can be a general-purpose processor, including a central processing unit (CPU), a network processor (NP), etc.; it can also be a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components.

[0152] An embodiment of the present application also provides a computer-readable storage medium having a computer program stored thereon. When the computer program is executed by a processor, the pulse charging method for integrated electrochemical impedance spectroscopy measurement provided by any of the aforementioned method embodiments is implemented.

[0153] The device embodiments described above are merely illustrative, wherein the units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0154] Through the description of the above implementation methods, those skilled in the art can clearly understand that each implementation method can be implemented by means of software plus a general hardware platform, and of course, by hardware. Based on this understanding, the above technical solution is essentially or the part that contributes to the relevant technology can be embodied in the form of a software product, and the computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, a disk, an optical disk, etc., including a number of instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each embodiment or some parts of the embodiments.

[0155] It should be understood that the terms used herein are only for the purpose of describing specific example embodiments and are not intended to be limiting. Unless the context clearly indicates otherwise, the singular forms "one", "an" and "said" as used herein may also be meant to include plural forms. The terms "include", "comprise", "contain", and "have" are inclusive, and therefore specify the existence of stated features, steps, operations, elements and / or parts, but do not exclude the existence or addition of one or more other features, steps, operations, elements, parts, and / or combinations thereof. The method steps, processes, and operations described herein are not interpreted as necessarily requiring them to be performed in the specific order described or illustrated, unless the execution order is clearly indicated. It should also be understood that additional or alternative steps may be used.

[0156] It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application. In the description, the suffixes such as "module", "component" or "unit" used to represent the elements are only used to facilitate the description of the present application and have no specific meaning in themselves. Therefore, "module", "component" or "unit" can be used in a mixed manner.

[0157] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features applied for herein.

Claims

1. A pulse charging method with integrated electrochemical impedance spectroscopy measurement, characterized in that: The method comprises: Acquire an excitation waveform; wherein the excitation waveform is composed of a pulse signal; Amplifying the excitation waveform based on a current transformer to obtain a pulse current; Charging the lithium battery according to the pulse current; During the charging process of the lithium battery, collecting the voltage signal and the current signal of the lithium battery; The electrochemical impedance spectrum of the lithium battery is measured based on the voltage signal and the current signal, so as to adjust the frequency and amplitude of the excitation waveform according to the electrochemical impedance spectrum.

2. The method according to claim 1, characterized in that The excitation waveform is amplified based on a current transformer to obtain a pulse current, including: Obtaining an expected charging current value of the lithium battery; The converter amplifies the excitation waveform according to the expected charging current value to obtain the pulse current.

3. The method according to claim 1, characterized in that Adjusting the frequency and amplitude of the excitation waveform according to the electrochemical impedance spectrum includes: Acquire a pre-stored first mapping relationship; wherein the first mapping relationship is a functional relationship between impedance, temperature and battery health status; Determining a current temperature and a current battery health state of the lithium battery according to the electrochemical impedance spectrum and the first mapping relationship; The frequency and amplitude of the excitation waveform are adjusted according to the current temperature and the current battery health state.

4. The method according to claim 3, characterized in that Adjusting the frequency and amplitude of the excitation waveform according to the current temperature and the current battery health state includes: Obtaining a pre-stored aging index and temperature rise index; wherein the aging index is a mapping relationship between the battery health state and the frequency and amplitude of the charging sequence, which is used to characterize the aging rate of the lithium battery; the temperature rise index is a mapping relationship between the lithium battery temperature and the frequency and amplitude of the charging sequence, which is used to characterize the temperature rise rate of the lithium battery; Determine a first frequency and a first amplitude according to the current temperature of the lithium battery and the temperature rise index; Determine a second frequency and a second amplitude according to the current battery health state and the aging index of the lithium battery; adjusting the frequency of the excitation waveform according to the first frequency and the second frequency; The amplitude of the excitation waveform is adjusted according to the first amplitude and the second amplitude.

5. The method according to claim 1, characterized in that Get stimulus waveforms, including: A series of sampling frequencies are calculated according to the set minimum pulse interval; wherein any sampling frequency in the series of sampling frequencies does not exceed the Nyquist limit frequency; Initializing a multi-sine signal, by cyclically summing the series of sampling frequencies according to different frequencies to obtain an initialization sequence; Iteratively optimizing the initialization sequence to obtain an optimized discrete interval binary sequence; wherein the iterative optimization is used to adjust the frequency spectrum of the initialization sequence; Resampling the optimized discrete-interval binary sequence according to a preset format to obtain a discrete-interval binary sequence signal; wherein the preset format meets the format requirements of the converter; The discrete interval binary sequence signal is used as the excitation waveform.

6. The method according to claim 5, characterized in that The initialization sequence is iteratively optimized to obtain an optimized discrete interval binary sequence, including: Calculating an objective function; wherein the objective function is used to characterize the difference between the current signal and the expected signal; If the objective function is greater than or equal to a convergence tolerance, adjusting at least one of a phase angle and an initialization sequence, and recalculating the objective function; If the objective function is smaller than the convergence tolerance, the iterative optimization is completed and the optimized discrete interval binary sequence is obtained.

7. The method according to claim 1, characterized in that Get stimulus waveforms, including: Configure the minimum frequency, maximum frequency, minimum time interval and frequency sweep time of the signal; wherein the frequency sweep time is determined based on the minimum frequency and the minimum time interval; Generate a linear frequency modulation pulse sequence according to the minimum frequency, the maximum frequency, the minimum time interval and the frequency sweep time; Extracting a time domain diagram of a preset time period from the linear frequency modulation pulse sequence as an original reference signal; Performing a fast Fourier transform on the original reference signal to obtain spectrum information of the preset time period; Performing homogenization processing on the frequency spectrum information of the preset time period to obtain a signal time domain spectrum diagram; Resampling the signal time domain spectrum graph by a first preset number of data points to obtain a sampled spectrum graph; The sampling spectrum diagram is binarized according to a preset threshold value to obtain the excitation waveform.

8. The method according to claim 1, characterized in that Get stimulus waveforms, including: Configure signal constraint parameters; wherein the constraint parameters include minimum frequency, maximum frequency and signal duration; Determine the order of the maximum length sequence signal according to the desired frequency resolution; Generate a maximum length sequence original signal under the constraint parameters according to the maximum length sequence generation function and the order; Normalizing the original signal of the maximum length sequence to obtain a normalized signal; Calibrate the effective value of the normalized signal, and perform fast Fourier transform processing on the effective value to obtain spectrum information; Resampling the spectrum information by a second preset number of data points to obtain sampled data; The sampled data is output according to a preset format to obtain the excitation waveform; wherein the preset format meets the format requirements of the converter.

9. An electronic device, characterized in that: It includes a processor, a communication interface, a memory and a communication bus, wherein the processor, the communication interface and the memory communicate with each other through the communication bus; Memory, used to store computer programs; The processor is used to implement the pulse charging method for integrated electrochemical impedance spectroscopy measurement as described in any one of claims 1 to 8 when executing the program stored in the memory.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the pulse charging method for integrated electrochemical impedance spectroscopy measurement as claimed in any one of claims 1 to 8 is implemented.

Images