A BMS protection board for power lithium batteries

Abstract

This invention relates to the field of battery management technology and discloses a BMS protection board for a power lithium battery. The protection board includes a main control unit, an electrochemical measurement unit, a piezoelectric transducer array, and a synchronous demodulation module. The system controls the piezoelectric transducer array to generate a focused acoustic field at a predetermined location on the battery to modulate local electrochemical characteristics, while simultaneously applying a global AC excitation. The synchronous demodulation module demodulates the signal marked by the acoustic field from the global voltage response and calculates the local electrochemical impedance at that location. A local electrochemical impedance distribution information map can be generated by scanning. This map can be compared with an initial reference baseline to diagnose local aging. Furthermore, the piezoelectric array can passively monitor acoustic emission and, after locating the damage source, perform focused impedance measurements to assess sudden damage. This invention achieves high-resolution imaging of the battery's internal state, accurately identifies early failures, and improves safety.

Description

Technical Field

[0001] This invention relates to the field of battery management technology, specifically to a BMS protection board for a power lithium battery. Background Technology

[0002] Lithium-ion batteries are core components of electric vehicles and large-scale energy storage systems, and their performance and safety are of paramount importance. Battery Management Systems (BMS), as a key technology for ensuring battery safety and extending lifespan, are responsible for real-time monitoring and management of the battery's state. Existing BMS technologies primarily estimate the state of charge (SOC) and state of health (SOH) by measuring macroscopic parameters such as the terminal voltage, charge / discharge current, and surface temperature of the battery pack and individual cells. Some advanced BMS systems integrate online electrochemical impedance spectroscopy (EIS) measurement capabilities, analyzing the battery's impedance response at different frequencies to obtain information about electrode / electrolyte interface processes and ion transport characteristics.

[0003] However, existing BMS diagnostic methods have inherent technical limitations. Whether based on conventional voltage and current monitoring or electrochemical impedance spectroscopy analysis, they all obtain global, averaged parameters for the entire battery. These methods treat the large and complex internal structure of the battery as a single, lumped circuit element, and therefore cannot provide spatial distribution information about the internal state of the battery. The aging and failure evolution processes inside the battery are often spatially non-uniform, such as uneven thickening of the solid electrolyte interphase (SEI) film on the electrode surface, localized pulverization or peeling of active material from the current collector, and dangerous early lithium dendrite precipitation. These localized, early degradations, because they represent a very small proportion of the entire battery, have their impact on the overall battery terminal voltage or total impedance masked by the response of the vast healthy area, making it impossible for existing BMS systems to effectively identify them in the initial stages of degradation.

[0004] This technological limitation leads to diagnostic lag. BMS systems only issue alerts when significant degradation occurs in macroscopic performance parameters of the battery, such as total capacity or total internal resistance. By this time, localized damage has already progressed to a relatively severe level, missing the optimal window for prevention and intervention. Furthermore, diagnostic methods relying solely on electrochemical parameters are prone to misdiagnosis when faced with complex failure modes. This is because different internal failure modes can trigger similar global electrochemical responses; for example, a simple increase in impedance is difficult to distinguish between general aging and a localized anomaly caused by a micro-short circuit. Existing technologies lack a collaborative verification mechanism involving multiple physical information sources, reducing the reliability and comprehensiveness of diagnostic results and failing to meet the increasingly sophisticated safety management needs of power lithium batteries. Summary of the Invention

[0005] Current battery management systems (BMS) for power lithium batteries primarily assess the battery's state of health (SOH) and predict its remaining life (SUL) by measuring macroscopic average parameters such as overall battery voltage, current, and temperature. This method cannot detect or quantify the spatial inhomogeneity of the battery's internal electrochemical state. However, battery aging processes, such as uneven thickening of the solid electrolyte interphase (SEI) film, degradation of active materials in localized areas, and early localized lithium deposition (a serious safety hazard), all occur at a microscopic and localized scale. Due to the lack of technical means to acquire localized state information, existing BMS systems cannot perform early and accurate diagnosis of these localized, progressive degradations, resulting in limited accuracy in SOH estimation and insufficient early warning capabilities for safety risks such as thermal runaway caused by localized anomalies.

[0006] Therefore, there is an urgent need in this field to provide a technical solution that can penetrate the limitations of macroscopic average parameters of batteries and achieve spatially resolved measurement of key electrochemical states inside batteries.

[0007] The present invention provides a BMS protection board for a power lithium battery, comprising: a main control unit; an electrochemical measurement unit; a piezoelectric transducer array; and a physical field excitation and electrochemical response synchronous demodulation module.

[0008] The electrochemical measurement unit is connected to the main control unit and is used to apply an electrochemical excitation signal to the power lithium battery and measure the electrochemical response of the power lithium battery.

[0009] The piezoelectric transducer array is connected to the main control unit and is arranged on the surface of the power lithium battery to generate an acoustic wave field according to the instructions of the main control unit.

[0010] The physical field excitation and electrochemical response synchronous demodulation module is connected to the main control unit, the piezoelectric transducer array, and the electrochemical measurement unit.

[0011] In one core technical solution of the present invention, the physical field excitation and electrochemical response synchronous demodulation module performs the following operations:

[0012] First, under the control of the main control unit, the piezoelectric transducer array is controlled to generate an acoustic wave field with a specific frequency at a predetermined location on the power lithium battery. This acoustic wave field induces localized, periodic pressure changes at the electrode-electrolyte interface at the predetermined location.

[0013] Simultaneously, the physical field excitation and electrochemical response synchronous demodulation module controls the electrochemical measurement unit to apply an AC excitation signal of a preset frequency to the entire power lithium battery, and the electrochemical measurement unit acquires the global AC voltage response of the entire battery at this moment. The AC excitation signal can be expressed as:

[0014] ,in, The current amplitude, The electrochemical excitation angular frequency, For time The changing instantaneous alternating current excitation current.

[0015] Finally, the physical field excitation and electrochemical response synchronous demodulation module processes the acquired global AC voltage response. Due to the perturbation of the local interface electrochemical environment by the acoustic wave field, the local electrochemical impedance at the predetermined location is modulated by the frequency of the acoustic wave field. This modulation effect is reflected in the global AC voltage response. Based on the known characteristics of the global AC voltage response and the acoustic wave field, the module demodulates and calculates the local electrochemical impedance at the predetermined location, thereby obtaining the electrochemical state information of the power lithium battery at a specific location, which is used to generate the local electrochemical impedance distribution information of the power lithium battery.

[0016] Preferably, the physical field excitation and electrochemical response synchronous demodulation module is also used to control the acoustic wave field to scan the surface of the power lithium battery along a preset path, and synchronously and sequentially calculate the local electrochemical impedance at multiple predetermined positions along the scanning path, and finally combine the local electrochemical impedance values ​​at all positions to generate a complete two-dimensional local electrochemical impedance distribution information map.

[0017] In one specific embodiment, the acoustic wavefield is a focused sound beam. Using a focused sound beam can concentrate acoustic energy into a smaller region, thereby improving spatial resolution.

[0018] In one specific embodiment, the physical field excitation and electrochemical response synchronous demodulation module performs demodulation calculations using a lock-in amplification algorithm. Specifically, the acquired global AC voltage response signal is multiplied by a reference signal and low-pass filtered. The frequency of the reference signal is related to the frequency of the acoustic wave field. This algorithm enables the accurate extraction of the weak signal amplitude modulated by the acoustic wave field from the noisy global response. This amplitude is proportional to the local electrochemical impedance at the predetermined location, thereby achieving the calculation of the local electrochemical impedance.

[0019] Preferably, the main control unit is further configured to perform the aforementioned local electrochemical impedance measurement process once in the initial or healthy state of the power lithium battery, and store the generated local electrochemical impedance distribution information as a reference baseline in the memory.

[0020] Furthermore, the main control unit is also used to periodically generate new local electrochemical impedance distribution information during the subsequent use of the battery, and compare the new information with the stored reference baseline point by point or regionally. By analyzing the magnitude and spatial distribution of impedance changes, it is used to identify abnormal states such as local aging, activity degradation or lithium plating of the power lithium battery.

[0021] Preferably, the BMS protection board provided by the present invention further includes a MEMS flexible stress sensor array. The MEMS flexible stress sensor array is arranged on the surface of the power lithium battery and is used to monitor the surface stress distribution of the power lithium battery in real time due to charging and discharging or abnormal gas generation.

[0022] In one specific embodiment, the main control unit is further configured to fuse the local electrochemical impedance distribution information generated by the method of the present invention with the surface stress distribution monitored by the MEMS flexible stress sensor array to comprehensively diagnose the health status of the power lithium battery. For example, when a local impedance abnormal increase and stress abnormal concentration occur simultaneously at a certain location, it can be determined that the risk level of local lithium plating or severe structural degradation at that location is higher.

[0023] Preferably, the main control unit is also used to control the piezoelectric transducer array to operate in a passive monitoring mode. In this mode, the piezoelectric transducer array does not actively emit acoustic wave fields, but acts as a highly sensitive acoustic sensor to continuously monitor acoustic emission signals generated inside the power lithium battery due to events such as microscopic material fractures or dendrite growth, in order to diagnose sudden internal physical damage.

[0024] In one specific embodiment, the main control unit is further configured to, after detecting an acoustic emission signal in the passive monitoring mode, first locate the source position of the acoustic emission signal by analyzing the time difference of the signal reaching different piezoelectric transducers; then, immediately control the physical field excitation and electrochemical response synchronous demodulation module to precisely guide the acoustic wave field (e.g., a focused sound beam) to the located source position and perform a focused local electrochemical impedance measurement. This collaborative working method enables rapid confirmation and characterization of sudden safety risk events.

[0025] This invention provides a BMS protection board for power lithium batteries. It has the following advantages:

[0026] 1. This invention provides a method for obtaining spatial distribution information of electrochemical impedance inside a power lithium battery. By using a physical field excitation and electrochemical response synchronous demodulation module to coordinate the control of the local acoustic wave field generated by the piezoelectric transducer array and the global AC excitation applied by the electrochemical measurement unit, this invention can demodulate and calculate the local electrochemical impedance at a predetermined location in the battery, overcoming the technical limitation of traditional electrochemical impedance spectroscopy methods that can only obtain the overall average impedance value of the battery.

[0027] 2. This invention enhances the early diagnostic capability for localized battery aging. By generating localized electrochemical impedance distribution information through the main control unit and comparing it with a stored reference baseline, it can accurately identify and quantify impedance changes in localized areas caused by factors such as uneven thickening of the solid electrolyte interphase (SEI) film, deactivation of active materials, or early lithium deposition. This allows for early warning of localized degradation problems before significant degradation of the battery's macroscopic performance parameters occurs.

[0028] 3. This invention constructs a multi-physical-dimensional collaborative diagnostic mechanism, improving the reliability of diagnostic results. The main control unit can integrate the local electrochemical impedance distribution information obtained by the method of this invention with the surface stress distribution information monitored by the MEMS flexible stress sensor array for comprehensive analysis, or perform targeted local impedance measurement at the signal source location after detecting internal acoustic emission signals. Through cross-validation of multi-dimensional information, the misjudgment that may be caused by a single information source is effectively reduced, making the assessment of battery health status more comprehensive. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the system architecture of the present invention;

[0030] Figure 2 This is a flowchart illustrating a method for establishing a reference baseline according to an embodiment of the present invention;

[0031] Figure 3 This is a schematic flowchart of a method for generating impedance distribution information maps according to an embodiment of the present invention;

[0032] Figure 4 This is a flowchart illustrating a method for diagnosing localized aging of a battery according to an embodiment of the present invention.

[0033] Figure 5 This is a flowchart illustrating a multiphysics information fusion diagnostic method according to an embodiment of the present invention;

[0034] Figure 6 This is a flowchart illustrating a collaborative diagnostic method for sudden security risks according to an embodiment of the present invention.

[0035] Among them, 10 is the main control unit; 20 is the electrochemical measurement unit; 30 is the piezoelectric transducer array; 40 is the physical field excitation and electrochemical response synchronous demodulation module; and 50 is the MEMS flexible stress sensor array. Detailed Implementation

[0036] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] See attached document Figure 1 The BMS protection board for a power lithium battery provided by the present invention may include: a main control unit 10, an electrochemical measurement unit 20, a piezoelectric transducer array 30, and a physical field excitation and electrochemical response synchronous demodulation module 40. In one embodiment, the BMS protection board may further include a MEMS flexible stress sensor array 50.

[0038] The main control unit 10 is connected to the electrochemical measurement unit 20, the piezoelectric transducer array 30, the physical field excitation and electrochemical response synchronous demodulation module 40, and the MEMS flexible stress sensor array 50 via an internal bus or dedicated control line. The physical field excitation and electrochemical response synchronous demodulation module 40 is also connected to the electrochemical measurement unit 20 and the piezoelectric transducer array 30 to perform coordinated control.

[0039] The main control unit 10 (e.g., a microcontroller (MCU) or digital signal processor (DSP)) is the control core of the BMS protection board. The main control unit 10 is used to execute preset control logic and algorithms, process data collected by other modules, generate control commands based on the processing results, and is responsible for data storage and external communication.

[0040] The electrochemical measurement unit 20 is electrically connected to the positive and negative electrodes of the power lithium battery. The electrochemical measurement unit 20 performs two types of functions:

[0041] First, perform routine DC parameter measurements, including battery terminal voltage and charging / discharging current;

[0042] Secondly, according to the instructions of the physical field excitation and electrochemical response synchronous demodulation module 40, a preset AC excitation signal is applied to the power lithium battery, and the global AC voltage response of the power lithium battery at this moment is simultaneously acquired. The AC excitation signal can be expressed as: ,in, The current amplitude, The electrochemical excitation angular frequency, For time The changing instantaneous alternating current excitation current.

[0043] The piezoelectric transducer array 30 consists of multiple piezoelectric transducer units arranged in a two-dimensional array on the surface of the power lithium battery casing. Under the control of the main control unit 10, the piezoelectric transducer array 30 has two switchable operating modes:

[0044] One is the active excitation mode, which is used to generate an acoustic wave field of a specific shape at a predetermined position on the surface of the power lithium battery in coordination with the driving signal generated by the physical field excitation and electrochemical response synchronous demodulation module 40.

[0045] The second is the passive monitoring mode, in which each piezoelectric transducer unit is used as an acoustic sensor to monitor the acoustic emission signals generated inside the power lithium battery.

[0046] In one specific implementation, the diagnosis of sudden internal physical damage combines the passive listening mode and active excitation mode of the piezoelectric transducer array 30. This diagnostic process is executed by the main control unit 10.

[0047] When the piezoelectric transducer array 30 operates in passive monitoring mode, each piezoelectric transducer unit continuously monitors the acoustic signal. If the energy or amplitude of the detected acoustic emission signal exceeds a preset event threshold, the main control unit 10 initiates a process to locate the source of the acoustic emission signal.

[0048] The source localization process is calculated based on the Time Difference of Arrival (TDOA) of the acoustic emission signals received by each piezoelectric transducer unit. This calculation is performed for any two piezoelectric transducer units in the piezoelectric transducer array 30. and The difference in geometric distance from the acoustic emission source to the two cells is equal to the product of the time difference in sound wave arrival at the two cells and the speed of sound wave propagation in the battery medium. This relationship forms a hyperbolic equation.

[0049] Therefore, for a given acoustic emission source coordinate... That is, the subsequent predetermined position, which satisfies the following system of equations:

[0050] ,in, and The first The and the first The known planar coordinates of a piezoelectric transducer unit; and The acoustic emission signal reaches the first The and the first The moment of each piezoelectric transducer unit; The average propagation speed of sound waves in the internal materials of a power lithium battery is a pre-calibrated system parameter.

[0051] By selecting at least three different piezoelectric transducer units, a system of equations containing at least two independent hyperbolic equations is established. The main control unit 10 is able to solve this system of equations, thereby determining the unique coordinates of the acoustic emission source. This refers to the subsequent reserved location.

[0052] After determining the coordinates of the acoustic emission source, the main control unit 10 uses these coordinates as the target predetermined position and immediately controls the physical field excitation and electrochemical response synchronous demodulation module 40 to perform the aforementioned key measurement of local electrochemical impedance at the source position.

[0053] The measurement results can be used to assess in real time changes in local electrochemical properties caused by sudden internal physical damage, such as cracking of electrode material or peeling from the current collector.

[0054] The physical field excitation and electrochemical response synchronous demodulation module 40 is a dedicated hardware circuit module. The physical field excitation and electrochemical response synchronous demodulation module 40 is used to implement the core measurement function of this invention, and its specific functions include:

[0055] Receive measurement task instructions issued by the main control unit 10, which include the target location information to be measured;

[0056] The wave field excitation signal for driving the piezoelectric transducer array 30 is generated according to the instructions;

[0057] The electrochemical measurement unit 20 is controlled to apply an AC excitation signal and acquire the global AC voltage response in synchronization with a high-precision clock.

[0058] It receives the global AC voltage response signal, executes demodulation algorithms such as lock-in amplification, calculates the local electrochemical impedance value at the target location, and finally reports the calculation results to the main control unit 10.

[0059] In one embodiment, the BMS protection board further includes a MEMS flexible stress sensor array 50. The MEMS flexible stress sensor array 50 is conformally attached to the surface of the power lithium battery and is used to monitor the surface stress distribution of the power lithium battery in real time due to electrode volume expansion or abnormal gas generation during charging and discharging. The MEMS flexible stress sensor array 50 sends the surface stress distribution data it monitors to the main control unit 10 for subsequent multi-physics information fusion diagnosis.

[0060] The core of this invention, local electrochemical impedance spectroscopy, involves using an acoustic wave field to controllably perturb the electrochemical characteristics of a local region within a power lithium battery, and then demodulating the position and state information carried by this perturbation through global electrochemical measurements. This process is based on the acoustic-electrochemical coupling physical effect.

[0061] The electrochemical impedance of power lithium batteries mainly originates from the electrochemical processes at the electrode-electrolyte interface, which occurs at a predetermined location. Local impedance density It is mainly composed of components such as double-layer capacitance, charge transfer resistance, and impedance related to ion diffusion. The magnitude of these components is directly related to factors such as the electrolyte ion concentration in the local area, the surface state of the electrode material, and the thickness and density of the solid electrolyte interphase (SEI) film.

[0062] In the implementation of this invention, the acoustic wave field generated by the piezoelectric transducer array 30, such as a focused sound beam, is precisely guided to a predetermined position on the surface of the power lithium battery. The acoustic wave field penetrates the battery casing, generating a local pressure field that varies periodically with time at the corresponding internal electrode-electrolyte interface. This periodic pressure change will cause corresponding changes in the electrochemical environmental parameters of the local area.

[0063] Specifically, local pressure field The effect of this will cause periodic fluctuations in one or more of the following physicochemical parameters:

[0064] First, the local concentration of active ions in the electrolyte. Pressure changes can cause slight compression or dilution of the electrolyte, leading to fluctuations in the concentration of active ions (such as lithium ions) near the electrode interface. According to the Nernst equation, changes in ion concentration will directly result in changes in the local equilibrium potential.

[0065] Second, the kinetics of charge transfer reactions. Pressure changes can alter the activation energy of the charge transfer process. According to the Butler-Folmer equation, this change in activation energy will affect the local charge transfer resistance. cyclical changes.

[0066] Third, the mass transport process. Acoustic pressure gradients can cause small local acoustic flow effects or change the diffusion path and rate of ions in porous electrodes and membranes, thereby affecting the diffusion-related impedance components.

[0067] Therefore, under the influence of the acoustic wave field, the predetermined position The local electrochemical impedance density is no longer a constant value. Instead, it is modulated by the acoustic wave field. If the angular frequency of the acoustic wave field is... Then the modulation process can be described as a quantity that varies with time. :

[0068] ;

[0069] in, It is the static local impedance density at that location when it is unaffected by the sound field; It is the amplitude of acoustic pressure; This is the acoustic-electrochemical coupling coefficient, the magnitude of which depends on the location. The physical and chemical state of the material, such as the characteristics of the SEI membrane and the health status of the active substances.

[0070] When the electrochemical measurement unit 20 applies a global AC excitation current to the entire battery At this time, the current flows across the entire electrode surface. The global AC voltage response across the battery terminals... It is the surface integral of all local voltage responses across the entire electrode surface. Under the action of an acoustic wave field... At point, The structure will include a special component contributed by this point, which is the local current density and the modulated local impedance density. The product of . This results in the global AC voltage response. In addition to including the electrochemical excitation frequency In addition to the relevant fundamental response, it also carries an additional frequency of The modulated sideband signal.

[0071] Frequency is The amplitude of the modulated sideband signal is proportional to the coupling coefficient. With static local impedance density The product of . Since the acoustic wave field exists only at the predetermined location. The modulation is applied at this location, thus the modulated sideband signal uniquely identifies the electrochemical information at this position. Through subsequent synchronous demodulation processing, this sideband signal can be accurately separated from the global AC voltage response, and the correlation with the predetermined position can be calculated. The associated local electrochemical impedance information enables spatial localization and quantification of the information.

[0072] In the physical principle of acoustic-electrochemical coupling, the core intrinsic physical quantity is the static local impedance density. The ultimate goal of the local electrochemical impedance holographic imaging performed in this invention is to obtain an image with static local impedance density through a series of executable engineering steps. A one-to-one, quantifiable measurement result. In this invention, this measurement result is defined as the local electrochemical impedance value. The final output value calculated by the physical field excitation and electrochemical response synchronous demodulation module 40 through the demodulation algorithm is the local electrochemical impedance value. The magnitude of this value corresponds to the static local impedance density at the corresponding location. Proportional. Therefore, by measuring a series of local electrochemical impedance values The generated distribution information map is a static local impedance density of the entire electrode surface. A direct, spatially resolved representation of the distribution.

[0073] See attached document Figure 2 To effectively track and evaluate the status of power lithium batteries throughout their entire lifecycle, the BMS protection board performs a system initialization and reference baseline establishment process at the initial stage of putting the power lithium battery into use. This process aims to acquire and store initial local electrochemical impedance value distribution information representing the health status of the power lithium battery.

[0074] In one specific embodiment, the process of establishing a reference baseline is triggered when the power lithium battery undergoes its first standardized full charge-discharge cycle. The main control unit 10 enters a preset reference baseline establishment mode.

[0075] In the preset reference baseline establishment mode, the main control unit 10 first selects a measurement window where the electrochemical state is relatively stable, such as a specific state of charge (SOC) range in the constant current (CC) stage.

[0076] Subsequently, the main control unit 10 sends a command to the physical field excitation and electrochemical response synchronous demodulation module 40 to initiate a full-area scan measurement of the battery surface. The physical field excitation and electrochemical response synchronous demodulation module 40 performs the following operations according to the command:

[0077] First, the piezoelectric transducer array 30 is controlled to generate a focused sound beam, and the focal position is moved sequentially according to a preset two-dimensional scanning path, such as serpentine scanning or grating scanning, until the effective area defined by the entire battery surface is covered.

[0078] Second, the focal point of the sound beam is located at a predetermined position on each scanning path. Simultaneously, a local electrochemical impedance measurement and calculation is performed. This process includes applying acoustic and electrochemical excitation, acquiring the global AC voltage response, and demodulating using a lock-in amplification algorithm to ultimately obtain the predetermined position. Corresponding initial local electrochemical impedance value .

[0079] After completing measurements at all predetermined locations, the physical field excitation and electrochemical response synchronous demodulation module 40 combines all calculated initial local electrochemical impedance values. and its corresponding spatial coordinates, i.e., the predetermined position. The data are combined to generate a complete, initial local electrochemical impedance distribution map.

[0080] Finally, the main control unit 10 obtains the initial local electrochemical impedance distribution information map from the physical field excitation and electrochemical response synchronization demodulation module 40, and associates it with state parameters such as the current timestamp, cycle number, and battery temperature, storing it as a complete data packet in its internal non-volatile memory. This stored initial local electrochemical impedance distribution information map, representing the initial health state of the battery, constitutes the reference baseline used for subsequent state diagnosis and comparison in this invention.

[0081] At a specific predetermined location During local electrochemical impedance spectroscopy, the main control unit 10 sends the coordinates of the predetermined position to the physical field excitation and electrochemical response synchronous demodulation module 40. Upon receiving the instruction, the physical field excitation and electrochemical response synchronization demodulation module 40, based on its internal high-precision clock source, synchronously executes acoustic excitation and electrochemical excitation operations.

[0082] In the implementation of acoustic excitation, the physical field excitation and electrochemical response synchronous demodulation module 40 first determines the predetermined position coordinates contained in the instruction. The specific set of driving signals required to drive each piezoelectric transducer unit in the piezoelectric transducer array 30 is calculated. This is to drive the signal at a predetermined position on the surface inside the power lithium battery. A focused sound beam is formed at the point, and each signal in this driving signal group has a precisely calculated phase delay. Phase delay The calculation is based on sound waves from the first Each piezoelectric transducer unit propagates to the target focal point. Time required Acoustic excitation angular frequency :

[0083] ,in, For sound waves from the first Units to the focal point The distance of transmission Let be the average propagation speed of sound waves in the battery material. The physical field excitation and electrochemical response synchronous demodulation module 40 applies this driving signal group to the piezoelectric transducer array 30, causing the angular frequency emitted by each piezoelectric transducer unit to be . The acoustic waves propagate to the target point Constructive interference occurs, concentrating acoustic energy at this point and forming a localized, periodic pressure field. Acoustic excitation angular frequency The selection range is usually in MHz to Between MHz, to balance spatial resolution and the attenuation of sound waves propagating inside the battery.

[0084] During the implementation of electrochemical excitation, the physical field excitation and electrochemical response synchronous demodulation module 40 sends commands to the electrochemical measurement unit 20 in strict synchronization. Based on the commands, the electrochemical measurement unit 20 immediately begins applying a preset AC excitation signal to the entire power lithium battery (i.e., both the positive and negative electrodes). This AC excitation signal is a sinusoidal alternating current, and its mathematical expression is:

[0085] ,in, For time The changing instantaneous alternating current excitation current; The amplitude of the AC excitation current typically ranges from 10mA to the C / 20 current value of the battery's rated capacity. This refers to the angular frequency of the electrochemical excitation. The selection is based on the interface process to be detected, for example, selecting Hz to Used to characterize charge transfer processes, or selected Hz to Hz is used to characterize the lithium-ion diffusion process.

[0086] Acoustic excitation angular frequency With electrochemical excitation angular frequency They are set to different values, and there is no integer multiple relationship between them (i.e.) (Not an integer) to avoid signal spectrum overlap. The physical field excitation and electrochemical response synchronous demodulation module 40 ensures that the deviation between the application start time of the acoustic wave field and the application start time of the global AC excitation signal is less than 10 μs, and maintains both throughout the measurement. During this co-excitation, the electrochemical measurement unit 20 operates at a frequency not less than... The sampling rate is used to continuously acquire the global AC voltage response of the battery. The response signal is then transmitted in real time to the physical field excitation and electrochemical response synchronous demodulation module 40 for further processing.

[0087] The physical field excitation and electrochemical response synchronous demodulation module 40 receives the global AC voltage response transmitted in real time by the electrochemical measurement unit 20. It immediately executes a synchronous demodulation and computation process to extract data from a specific predetermined location. Relevant local electrochemical impedance information.

[0088] This process is based on the lock-in amplification algorithm. Its core is to analyze the global AC voltage response, which includes strong background signals and noise. In the middle, the acoustically excited part at the predetermined position is precisely separated. This generates a weak modulation sideband signal. As described above, this modulation sideband signal appears at the sum and difference frequencies of the electrochemical excitation angular frequency and the acoustic excitation angular frequency, i.e. .

[0089] In one specific embodiment, the physical field excitation and electrochemical response synchronization demodulation module 40 performs the following steps:

[0090] The first step is to generate a reference signal. Based on its internal clock, synchronized with both the acoustic and electrochemical excitation sources, the module generates two signals with frequencies equal to a certain modulation sideband angular frequency (e.g., the difference frequency). And the two reference signals are orthogonal in phase. These two reference signals can be represented as:

[0091] ;

[0092] ;

[0093] in, For in-phase reference signal, This is an orthogonal reference signal;

[0094] The second step is to perform phase-sensitive detection. The module will receive the input global AC voltage response. The two intermediate signals are obtained by multiplying them with the two reference signals mentioned above. and :

[0095] ;

[0096] ;

[0097] in, This is the intermediate signal obtained by multiplying the global voltage response by the in-phase reference signal. This is the intermediate signal obtained by multiplying the global voltage response by the orthogonal reference signal;

[0098] The third step is to perform low-pass filtering. The module will filter the two intermediate signals. and Each through an extremely low cutoff frequency The low-pass filter. Cutoff frequency. The selection must meet the following requirements. This process filters out all high-frequency components, retaining only the DC component. The two stable DC voltage values ​​obtained after filtering are defined as the in-phase components. and orthogonal components .

[0099] The fourth step is to calculate the local electrochemical impedance value. (In-phase component) and orthogonal components The amplitude is proportional to the predetermined position. The real part of the local electrochemical impedance With the imaginary part The module calculates the local electrochemical impedance value at that location using the following formula. :

[0100] ,in, The imaginary unit; This is a calibration coefficient, the value of which is determined by the system's fixed parameters (including the amplitude of the AC excitation current). Acoustic pressure amplitude The coefficient is determined by factors such as the system gain, and is calibrated and stored before the system leaves the factory. intermediate signal The DC in-phase component obtained after low-pass filtering; intermediate signal The DC quadrature component is obtained after low-pass filtering. Ultimately, it represents the predetermined position. The amplitude of the local electrochemical impedance value and phase angle It was calculated and used as the result of this measurement.

[0101] See attached document Figure 3 The main control unit 10 performs measurements and calculations on all positions along a predetermined scanning path to generate a complete local electrochemical impedance spectroscopy (TIS) map. This generation process is controlled and executed by the main control unit 10. Following a preset two-dimensional scanning path, such as a grating scanning path, the main control unit 10 sequentially selects each predetermined position (x, y) as the current measurement point.

[0102] For each selected predetermined location Each time, the main control unit 10 executes the aforementioned complete process of coordinated excitation, synchronous demodulation, and calculation. After the process is completed, the physical field excitation and electrochemical response synchronous demodulation module 40 calculates the value representing the predetermined position. Local electrochemical impedance value Return to main control unit 10.

[0103] The main control unit 10 maintains a two-dimensional data matrix in its internal memory. The row and column indices of this data matrix correspond to the x and y coordinates of predetermined locations, respectively. Whenever a new local electrochemical impedance value is received... At that time, the main control unit 10 stores the value in the data matrix at the predetermined position. Within the corresponding elements. The spatial resolution of the final generated local electrochemical impedance distribution map is determined by two factors: first, the focal size of the acoustically focused beam, which is mainly affected by the acoustic excitation angular frequency. The limitations are: firstly, the aperture of the piezoelectric transducer array 30; and secondly, adjacent predetermined positions on the two-dimensional scanning path. The step distance between the two points. By adjusting the scanning step distance, you can achieve fine scanning of a specific area or a quick overview of the entire surface.

[0104] The main control unit 10 repeats this process until all predetermined positions on the scan path are covered. When all measurements and data filling at all positions are completed, the two-dimensional data matrix in the memory constitutes a complete local electrochemical impedance distribution information map containing complex information.

[0105] This infographic is a foundational data product. The main control unit 10 can use this infographic to further generate scalar distribution plots for specific analyses. These scalar distribution plots include:

[0106] Impedance amplitude diagram: The value at each coordinate point in this diagram is the amplitude of the local electrochemical impedance. ;

[0107] Impedance phase angle diagram: The value at each coordinate point in this diagram is the phase angle of the local electrochemical impedance value. ;

[0108] Resistance distribution diagram: The value at each coordinate point in this diagram is the real part of the local electrochemical impedance value. ;

[0109] Reactance distribution diagram: The value at each coordinate point in this diagram is the imaginary part of the local electrochemical impedance value. .

[0110] These generated distribution information maps are stored in the non-volatile memory of the main control unit 10 and associated with current timestamps, cycle counts, and other status information for subsequent battery health status diagnosis and evaluation.

[0111] See attached document Figure 4 The technical solution provided by this invention enables continuous, high-resolution monitoring of the internal health status of a power lithium battery throughout its entire service life. This embodiment details how to use the method of this invention to diagnose localized aging phenomena that occur in power lithium batteries after long-term cyclic use.

[0112] The BMS protection board continuously records the cumulative cycle count of the power lithium battery in the background. In one specific embodiment, the main control unit 10 is preset to automatically trigger a diagnostic process for local aging after the power lithium battery completes 50 standard charge-discharge cycles.

[0113] Once the diagnostic process is initiated, the main control unit 10 first waits and confirms that the power lithium battery has entered an electrochemical state window consistent with the one established at the reference baseline, for example, during the constant current charging phase when the state of charge (SOC) reaches 50%. This is intended to eliminate impedance differences caused by different SOC states and ensure the accuracy of subsequent comparisons.

[0114] Once the measurement conditions are met, the main control unit 10 initiates a full-area scan measurement of the battery surface. Specifically, the main control unit 10 performs a full-area scan measurement on each predetermined position along the preset scan path. The system controls a complete local electrochemical impedance spectroscopy measurement, which includes implementing coordinated acoustic and electrochemical excitation and simultaneously demodulating and calculating the acquired global voltage response. This is achieved by measuring all predetermined locations... Through point-by-point measurements, the main control unit 10 ultimately generates a local electrochemical impedance distribution map that reflects the current state of the battery. We denote the local electrochemical impedance value corresponding to the predetermined position (x, y) in this map as... , here This refers to the local electrochemical impedance value obtained through the aforementioned calculation method. A specific example in the current diagnostic process.

[0115] Next, the main control unit 10 retrieves the reference baseline established at the initial stage of the battery life cycle, i.e., the initial local electrochemical impedance distribution information map, from its internal non-volatile memory. The impedance value at the corresponding location is... .

[0116] Subsequently, the main control unit 10 executes the core diagnostic comparison algorithm. This algorithm compares the two information maps point by point to quantify each predetermined position. The degree of aging. Specifically, the main control unit 10 will calculate a local impedance change rate distribution map. The value of each point Calculate using the following formula:

[0117] ,in, and In the current and initial states, at the same predetermined position The amplitude of the measured local electrochemical impedance. The value intuitively reflects the percentage increase in impedance at that location due to long-term use (such as thickening of the SEI film, loss of active materials, etc.).

[0118] Finally, the main control unit 10 plots the rate of change distribution graph. With a preset aging threshold (For example, =20%) for comparison. If there are one or more regions in the graph, its The value remains higher than The main control unit 10 then determines that the area is a localized aging hotspot. The BMS protection board will record the coordinates and aging severity (i.e., The battery can generate and store a detailed battery health status diagnostic report; issue a maintenance warning to the vehicle's central control unit or user terminal via a communication interface; or adjust the battery's thermal management and energy management strategies, such as more strictly controlling the temperature near the aging area, or appropriately reducing the load on that area during charging and discharging to slow down its aging process.

[0119] See attached document Figure 5 This embodiment aims to illustrate how to combine the local electrochemical impedance information obtained by the present invention with another key physical field information (such as temperature field) to achieve a more comprehensive and accurate integrated diagnosis of the health status of power lithium batteries, especially in identifying extreme failure modes such as potential thermal runaway risks.

[0120] In this embodiment, in addition to integrating a local electrochemical impedance holographic imaging system, the BMS protection board also integrates a surface temperature sensor array. This temperature sensor array is capable of measuring and generating a surface temperature distribution map aligned with the local electrochemical impedance distribution information map on spatial coordinates.

[0121] This comprehensive diagnostic process can also be triggered by the main control unit 10 based on preset conditions (e.g., fixed cycle intervals or specific diagnostic commands for the vehicle).

[0122] After the process is started, the main control unit 10 first waits for the power lithium battery to enter the preset measurement state window to ensure the consistency of measurement conditions.

[0123] Subsequently, the main control unit 10 simultaneously initiated two measurement tasks:

[0124] First, perform a complete local electrochemical impedance spectroscopy scan to generate a map of the current local electrochemical impedance distribution, corresponding to a predetermined location. The value is .

[0125] Second, the surface temperature sensor array is controlled to simultaneously acquire surface temperature data of the battery during the same time period of impedance scanning, generating a current surface temperature distribution map corresponding to a predetermined location. The value is .

[0126] After the measurement is completed, the main control unit 10 retrieves the initial local electrochemical impedance distribution information map from its internal non-volatile memory. ), and also retrieved the initial surface temperature distribution map stored synchronously at the beginning of the battery's life cycle ( ).

[0127] Next, the main control unit 10 executes a diagnostic decision-making algorithm based on multi-physics information fusion. This algorithm not only calculates the local impedance change rate distribution map... It also calculates a local temperature rise distribution map. The value of each point Calculate using the following formula:

[0128] ,in, and In the current and initial states, at the same predetermined position The measured surface temperature value.

[0129] Finally, the main control unit 10 performs diagnostics on each predetermined position according to a preset two-dimensional diagnostic matrix rule. The state is comprehensively evaluated. This rule considers the rate of change of local impedance. With local temperature rise Perform association analysis, for example:

[0130] Rule 1 (High-Risk Aging): If Above the aging threshold and Above the temperature rise threshold (For example If the impedance of this region increases significantly, then the region is identified as a high-risk aging area. This indicates that the region not only exhibits a significant increase in impedance but also displays abnormal heat generation characteristics under normal operating load.

[0131] Rule 2 (Potential Thermal Runaway): If Not significantly higher than the aging threshold ,but Abnormally higher than the temperature rise threshold If this condition is detected, the location is determined to be a potential internal micro-short circuit region. This situation may indicate a dangerous early thermal runaway risk, characterized by significant heat generation that has not yet manifested in the global impedance.

[0132] Rule 3 (General Aging): If Above the aging threshold but If it is still within the normal range, it is judged as a general aging area.

[0133] Based on different evaluation results, the BMS protection board can implement more targeted management strategies. For example, for high-risk aging areas, it can implement proactive power limiting; while for potential internal micro-short circuit areas, it may immediately trigger the highest level of safety alarm and implement emergency safety measures, including cutting off the main circuit and initiating forced cooling, thereby transforming traditional post-event response into precise, pre-event warning based on physical information fusion.

[0134] See attached document Figure 6 This embodiment illustrates how the present invention can perform rapid internal damage assessment and collaborative diagnosis in sudden scenarios caused by external events (such as mechanical abuse), thereby providing a basis for decision-making for immediate safety response.

[0135] This diagnostic process is not triggered by a fixed time or cycle, but rather by an external event signal. In a typical application scenario, the main control unit 10 is connected to the vehicle's safety systems, such as collision sensors or high-precision accelerometers. When these sensors detect a physical impact event that exceeds a preset safety threshold, they immediately send a high-priority diagnostic trigger signal to the main control unit 10.

[0136] Upon receiving the trigger signal, the main control unit 10 will immediately suspend all routine tasks and initiate an emergency full-domain scan. To obtain the macroscopic state of the battery's interior in the shortest possible time, this emergency scan can utilize a predetermined location that is sparser than that used in conventional aging monitoring. A grid, sacrificing some spatial resolution in exchange for extremely high scanning speed. This is achieved through these key pre-defined locations. Through rapid measurement, the main control unit 10 generates a map showing the current local electrochemical impedance distribution, with corresponding values... .

[0137] At the same time, the main control unit 10 retrieves the most recently stored local electrochemical impedance distribution information map of the healthy state from its internal non-volatile memory before the occurrence of this event, which we denote as... .

[0138] Next, the main control unit 10 executes a differential comparison algorithm designed to identify drastic changes. This algorithm calculates a local impedance anomaly distribution map. The anomaly evaluation value of each point Calculate using the following formula:

[0139] ,in, The symbol represents taking the modulus of the difference between two complex numbers. The value can sensitively reflect any significant impedance change caused by damage to the internal structure (such as electrode material peeling off from the current collector, diaphragm being punctured or wrinkled), regardless of whether the change is increasing or decreasing.

[0140] Finally, the main control unit 10 generates the anomaly distribution map. With a preset damage threshold Compare them.

[0141] If there are one or more regions in the graph, The value is significantly higher than And the real part of the impedance at that location Compared to If the real part of the signal drops sharply, the main control unit 10 determines that a high-risk internal short circuit has occurred in that area.

[0142] like The value is significantly higher than If the real or imaginary part of the impedance increases sharply, it is determined that structural damage caused by impact has occurred, such as pulverization of the electrode active material or poor interlayer contact.

[0143] Once any abnormality in internal electrochemical characteristics caused by physical damage is confirmed, the BMS protection board will immediately execute the highest level of safety response procedures. This includes, but is not limited to: immediately disconnecting the high-voltage main circuit contactor to isolate the battery pack, and broadcasting the precise coordinates of the damage location to the vehicle controller and cloud platform. The emergency alarm will be triggered, and if a fire suppression system is in place, it will be instructed to implement targeted, proactive containment measures on identified areas of internal damage.

Claims

1. A BMS protection board for a power lithium battery, characterized in that, include: One main control unit; An electrochemical measurement unit, connected to the main control unit, is used to apply an electrochemical excitation signal to the power lithium battery and measure the electrochemical response of the power lithium battery; A piezoelectric transducer array is connected to the main control unit. The piezoelectric transducer array is arranged on the surface of the power lithium battery to generate an acoustic wave field. And a physical field excitation and electrochemical response synchronous demodulation module, which is connected to the main control unit, the piezoelectric transducer array and the electrochemical measurement unit; The physical field excitation and electrochemical response synchronous demodulation module is used for: Under the control of the main control unit, the piezoelectric transducer array is controlled to generate an acoustic wave field at a predetermined position of the power lithium battery; Simultaneously, the electrochemical measurement unit is controlled to apply an AC excitation signal to the power lithium battery, and the global AC voltage response measured by the electrochemical measurement unit is obtained. Furthermore, based on the global AC voltage response and the acoustic wave field, the local electrochemical impedance at the predetermined location is demodulated and calculated to generate the local electrochemical impedance distribution information of the power lithium battery.

2. The BMS protection board for a power lithium battery according to claim 1, characterized in that, The physical field excitation and electrochemical response synchronous demodulation module is also used for: The acoustic wave field is controlled to scan the surface of the power lithium battery, and the local electrochemical impedance at multiple predetermined positions along the scanning path is calculated sequentially to generate the local electrochemical impedance distribution information of the power lithium battery.

3. The BMS protection board for a power lithium battery according to claim 1, characterized in that, The acoustic wave field is a focused sound beam.

4. The BMS protection board for a power lithium battery according to claim 1, characterized in that, The physical field excitation and electrochemical response synchronous demodulation module uses a lock-in amplification algorithm to demodulate the modulation signal related to the acoustic wave field from the global AC voltage response, which is then used to calculate the local electrochemical impedance.

5. The BMS protection board for a power lithium battery according to claim 1, characterized in that, The main control unit is also used for: In the initial state of the power lithium battery, the initial local electrochemical impedance distribution information of the power lithium battery is acquired and stored as a reference baseline.

6. The BMS protection board for a power lithium battery according to claim 5, characterized in that, The main control unit is also used for: The subsequently generated local electrochemical impedance distribution information is compared with the reference baseline to identify local aging or abnormal states of the power lithium battery.

7. The BMS protection board for a power lithium battery according to claim 1, characterized in that, Also includes: A MEMS flexible stress sensor array is arranged on the surface of the power lithium battery to monitor the surface stress distribution of the power lithium battery.

8. The BMS protection board for a power lithium battery according to claim 7, characterized in that, The main control unit is also used for: By integrating the local electrochemical impedance distribution information and the surface stress distribution, a comprehensive diagnosis of the health status of the power lithium battery is performed.

9. The BMS protection board for a power lithium battery according to claim 1, characterized in that, The main control unit is also used for: The piezoelectric transducer array is controlled to operate in passive listening mode to monitor the acoustic emission signal of the power lithium battery for the purpose of diagnosing sudden internal physical damage.

10. A BMS protection board for a power lithium battery according to claim 9, characterized in that, The main control unit is also used for: After detecting the acoustic emission signal, the source location of the acoustic emission signal is located, and the physical field excitation and electrochemical response synchronous demodulation module is controlled to perform local electrochemical impedance measurement at the source location.

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