A method and system for ultrasonic testing of lithium batteries

Abstract

The application relates to a lithium battery ultrasonic detection method and system, to solve the problem that in the existing ultrasonic detection technology, the vibration generated by a charging and discharging clamp itself is conducted to the battery interior through the tab, resulting in the problems of signal-to-noise ratio reduction of ultrasonic signals, difficulty in feature extraction, and poor detection accuracy and repeatability. The method comprises the following steps: fixing an ultrasonic sensor on a lithium battery; connecting a charging and discharging clamp with the tab of the lithium battery, and arranging a conductive vibration isolation structure at the contact interface between the charging and discharging clamp and the tab; in the charging and discharging process of the lithium battery by the charging and discharging equipment through the charging and discharging clamp, triggering the ultrasonic sensor to detect ultrasonic signals by a signal generator; and the conductive vibration isolation structure is used for inhibiting the vibration generated by the charging and discharging clamp.

Description

Technical Field

[0001] This application relates to the field of lithium battery testing, specifically to an ultrasonic testing method and system for lithium batteries. Background Technology

[0002] Lithium-ion batteries play a crucial role in many fields, especially in the electric vehicle and consumer electronics industries. However, with the rapid expansion of the electric vehicle market, the safety issues of power batteries are becoming increasingly prominent. To efficiently and non-destructively detect battery damage, numerous studies have introduced ultrasonic testing methods. This technology, due to its sensitivity to the internal structural state, has become an important means of assessing battery state of health (SOH), state of charge (SOC), and detecting internal damage. However, ultrasonic signals have high frequencies and are highly susceptible to interference from external mechanical vibrations, leading to a decrease in the signal-to-noise ratio and difficulties in feature extraction, severely affecting the accuracy and repeatability of the detection. Summary of the Invention

[0003] This application provides a method and system for ultrasonic testing of lithium batteries, which solves the technical problems of existing ultrasonic testing technology, such as the reduction of ultrasonic signal-to-noise ratio, difficulty in feature extraction, and deterioration of detection accuracy and repeatability caused by the vibration generated by the charging and discharging clamp itself being transmitted to the inside of the battery through the tabs during the charging and discharging process.

[0004] The technical solution of this invention is as follows:

[0005] In a first aspect, this application provides an ultrasonic testing method for lithium batteries to suppress vibration interference from charging and discharging chucks, comprising:

[0006] The ultrasonic sensor is fixed on the outer surface of the lithium battery;

[0007] The charging and discharging clamp is electrically connected to the tab of the lithium battery, and a conductive vibration isolation structure is provided at the contact interface between the charging and discharging clamp and the tab.

[0008] During the charging and discharging process of the lithium battery by the charging and discharging chuck, the ultrasonic sensor is triggered by the signal generator to detect ultrasonic signals; wherein, the conductive vibration isolation structure is used to suppress the vibration generated by the charging and discharging chuck.

[0009] In traditional solutions, the charging / discharging chuck generates broadband micro-vibrations under high-rate or pulse charging / discharging conditions due to current thermal effects, electromagnetic forces, and equipment conduction. These vibrations are directly coupled to the lithium battery interior through the rigid contact tabs. Since ultrasonic signals are inherently high-frequency and low-energy, they are easily contaminated by this external mechanical vibration, leading to a decrease in signal-to-noise ratio and difficulties in feature extraction. The solution in this application inserts a conductive vibration-isolation structure between the chuck and the tabs, physically cutting off the main channel for vibration transmission from the charging / discharging chuck to the tabs and then to the battery interior. This allows the vibration energy to be absorbed and dissipated before reaching the battery interior, fundamentally reducing the contamination of the ultrasonic signal by interference sources.

[0010] Secondly, the conductive vibration isolation structure used in this application maintains good conductivity while absorbing and dissipating mid-to-high frequency vibration energy by utilizing its own damping characteristics, thus achieving the synergistic work of electrical conduction and mechanical isolation without compromising between vibration isolation effect and electrical connection performance.

[0011] Unlike post-processing schemes that only reduce vibration at the sensor end or filter during signal processing, the method in this application blocks the vibration at the source and during its initial transmission stage, so that the ultrasonic signal received by the ultrasonic sensor more accurately reflects the internal state of the battery rather than external disturbances.

[0012] In some possible embodiments, the conductive vibration isolation structure is a double-layer structure, comprising: a base layer connected to the metal body of the charging and discharging clamp, and a surface layer disposed opposite to the base layer;

[0013] The base layer is made of conductive elastic composite material, which is used to absorb and dissipate medium and high frequency vibration energy;

[0014] The surface layer is made of a flexible, highly conductive material and is in direct contact with the tabs of the lithium battery.

[0015] The base layer is made of conductive elastic composite material and is directly connected to the metal body of the charging / discharging clamp. This design allows the base layer to primarily function as a vibratory energy absorber and dissipator. Mid-to-high frequency broadband vibrations generated by the charging / discharging clamp are first transmitted to the base layer. The conductive elastic composite material has excellent damping characteristics and elastic recovery capability, enabling it to convert mechanical vibration energy into internal energy or heat energy for dissipation, thereby significantly reducing the intensity of vibration transmission from the clamp to the tabs. Compared to a single-layer structure, the base layer is specifically designed with materials and structure for vibration suppression, achieving a wider bandwidth of effective attenuation for vibrations of different frequency components.

[0016] The surface layer is made of a flexible, highly conductive material and makes direct contact with the lithium battery's tabs. This design allows the surface layer to primarily function as an electrical contact and mechanical fitter. The flexible, highly conductive material has excellent deformation compliance, enabling it to form a tight fit with the tab surface under the clamping force applied by the chuck, filling microscopic unevenness, increasing the actual contact area, thereby reducing contact resistance and minimizing localized heat generation. Simultaneously, the cushioning properties of the flexible material prevent the rigid chuck from directly pressing on the tab, thus avoiding surface damage or fatigue fracture and extending the tab's lifespan.

[0017] In some possible embodiments, the conductive elastic composite material is selected from one or more of conductive foam or conductive elastic gasket; the flexible high-conductivity material is selected from one or more of flexible conductive film or ultrafine metal mesh.

[0018] Conductive foam, with its three-dimensional interconnected porous structure, achieves broadband vibration attenuation through pore wall friction and air viscosity damping. It also boasts advantages such as light weight and no increase in clamp load, making it suitable for conventional testing scenarios. Conductive elastic pads, with their dense elastomer matrix, provide higher mechanical strength and fatigue resistance, and are not easily permanently deformed during repeated compression and rebound. They are suitable for scenarios with frequent clamping or long testing cycles, and can be customized for specific vibration spectra through formulation control. Flexible conductive films, with their extremely thin thickness and excellent flexibility, can form a tight fit with the tabs under minimal clamping force. Their smooth surface does not damage the tabs and has low surface resistance, making them suitable for scenarios with high surface quality requirements, such as high-current charging and discharging and pouch batteries. Ultrafine metal mesh, with its woven structure, provides elastic recovery capability suitable for frequent assembly and disassembly. It reduces contact resistance through multi-point parallel conductive channels, and the mesh gaps can accommodate surface microparticles or oxides to avoid poor local contact. Its good air permeability makes it suitable for long-term clamping scenarios. These four materials cover different performance requirements, ranging from lightweight, high durability, non-destructive contact to high adaptability, and can be flexibly selected or combined according to specific test conditions.

[0019] In some possible embodiments, the ultrasonic sensor includes an ultrasonic pulse emitting piezoelectric element and an ultrasonic pulse receiving piezoelectric element;

[0020] The ultrasonic pulse emitting piezoelectric element and the ultrasonic pulse receiving piezoelectric element are respectively fixed at both ends of the same surface of the lithium battery.

[0021] The ultrasonic pulse emitting piezoelectric element is communicatively connected to a signal generator, and the signal generator is used to excite the ultrasonic pulse emitting piezoelectric element to emit ultrasonic signals.

[0022] The ultrasonic pulse receiving piezoelectric element is communicatively connected to an oscilloscope, which is used to acquire and display the ultrasonic signals received by the ultrasonic pulse receiving piezoelectric element.

[0023] By fixing the ultrasonic pulse transmitting and receiving piezoelectric elements at opposite ends of the same surface of the lithium battery, the propagation path length between them is maximized. This allows the ultrasonic signal to penetrate more thoroughly through multiple layers of media inside the battery, such as the electrode layer, separator, and electrolyte. This enables more sensitive detection of subtle changes in the internal structure, such as uneven electrode porosity distribution, localized electrolyte drying, or interface damage caused by lithium plating. The transmitting piezoelectric element communicates with a signal generator, which provides precise and controllable excitation pulses to ensure that each transmitted ultrasonic signal has a consistent frequency, amplitude, and waveform, providing a repeatable benchmark for subsequent signal comparison and feature extraction. The receiving piezoelectric element communicates with an oscilloscope, which acquires and displays the received ultrasonic signal in real time at a high sampling rate. This allows for direct observation and recording of characteristic changes in the original waveform, such as amplitude attenuation and time-of-flight shift.

[0024] In some possible embodiments, the method further includes:

[0025] Under the same charging and discharging conditions, the ultrasonic sensor collects a first set of ultrasonic signals when the conductive vibration isolation structure is not set, and a second set of ultrasonic signals when the conductive vibration isolation structure is set.

[0026] The effect of the conductive vibration isolation structure on suppressing vibration interference is evaluated by comparing the waveform repeatability of the first group of ultrasonic signals and the second group of ultrasonic signals.

[0027] Without a vibration isolation structure, the broadband micro-vibrations generated by the charging / discharging chuck are directly transmitted to the battery interior via the tabs, applying random perturbations to the ultrasonic signal unrelated to the battery's state. This results in significant differences in peak amplitude, phase, and envelope shape in waveforms acquired multiple times within a short period, leading to low waveform repeatability. However, with the conductive vibration isolation structure in place, the vibration energy is absorbed and dissipated at the contact interface between the charging / discharging chuck and the tabs, significantly reducing the vibration amplitude transmitted to the battery interior. This effectively suppresses interference with the ultrasonic signal, making the waveforms acquired multiple times more consistent and significantly improving waveform repeatability. By directly comparing the waveform repeatability of the two sets of signals, it is possible to intuitively determine whether the vibration isolation structure effectively eliminates vibration noise synchronized with the charging / discharging conditions, avoiding misinterpreting signal fluctuations caused by the charging / discharging chuck vibration as genuine changes in the battery's internal state. This comparative verification method not only provides reproducible experimental evidence for the vibration isolation effect of this scheme but also allows for horizontal comparison of vibration isolation schemes with different materials and structures under a unified evaluation standard, providing an objective basis for the optimal selection of vibration isolation structures.

[0028] In some possible embodiments, the step of evaluating the vibration suppression effect of the conductive vibration isolation structure by comparing the waveform repeatability of the first set of ultrasonic signals and the second set of ultrasonic signals includes:

[0029] Extract the characteristic parameters of the first group of ultrasound signals to construct the first peak time curve;

[0030] Extract the characteristic parameters of the second group of ultrasound signals to construct the second peak time curve;

[0031] The vibration isolation effect is quantitatively evaluated by comparing the stability and noise level of the first peak time curve and the second peak time curve.

[0032] The first peak-time curve reflects the degree of interference from clamp vibration on the ultrasonic signal in the unisolated state. Due to the randomness and broadband characteristics of vibration noise, this curve typically exhibits large amplitude fluctuations, irregular undulations, and a high noise floor, making it difficult to clearly distinguish the characteristic inflection points corresponding to changes in the battery's internal state. The second peak-time curve reflects the stability of the ultrasonic signal after the conductive vibration isolation structure is installed. Because the vibration energy is effectively absorbed and dissipated, the fluctuation amplitude of this curve is significantly reduced, the trend is smoother, and the noise level is significantly lower, more realistically presenting the changes in the ultrasonic signal caused by the evolution of the internal structure during battery charging and discharging. By comparing the differences in stability between the two curves, i.e., calculating quantitative indicators such as the standard deviation, fluctuation amplitude, or signal-to-noise ratio of the curves, the specific degree of improvement in vibration isolation effect can be objectively evaluated. This quantitative evaluation method provides a unified numerical basis for comparing the performance of different vibration isolation materials and different structural parameters, and also provides clear technical guidance for further optimization design of vibration isolation structures.

[0033] In some possible embodiments, the construction process of the first peak time curve and the second peak time curve is as follows:

[0034] Select the same peak in the same set of ultrasonic curves, extract the voltage value corresponding to the peak at each time point, and combine the voltage values ​​at all time points to construct a complete peak-time curve.

[0035] The same wave peak has the same physical meaning at different time points, and its dynamic voltage change directly reflects the degree of energy attenuation of ultrasound waves propagating within the battery. When clamp vibration interference exists, vibration noise is superimposed on the ultrasonic signal, causing random fluctuations in the voltage value of the same wave peak at different time points, independent of the battery's internal state. This results in a spike-like high-frequency noise on the peak-time curve. When the conductive vibration isolation structure effectively suppresses vibration, these random fluctuations are eliminated, and the peak-time curve returns to a smooth trend, truly reflecting the modulation effect of the internal structure evolution on ultrasonic propagation during battery charging and discharging. By comparing the smoothness and noise level of the two peak-time curves before and after vibration isolation, the actual effect of the vibration isolation structure can be clearly determined.

[0036] In some possible embodiments, prior to setting the conductive vibration isolation structure, the following is also included:

[0037] The electrode tab is held in the charging / discharging chuck without vibration isolation structure for charging / discharging test.

[0038] During the charge-discharge test, the first ultrasonic signal is acquired by the ultrasonic sensor;

[0039] If the waveform of the first ultrasonic signal is analyzed and waveform fluctuations synchronized with the charging and discharging conditions are observed, or if the characteristic parameters of the first ultrasonic signal are unstable, then the charging and discharging clamp is determined to be a key interference source that transmits vibrations through the tabs into the lithium battery and interferes with the ultrasonic signal.

[0040] First, a standard charge / discharge chuck without any vibration isolation modifications is used to clamp the battery tabs. Under normal charge / discharge conditions, the system operates while an ultrasonic sensor fixed to the battery surface collects the first ultrasonic signal in real time. Since no vibration isolation structure is in place at this stage, the chuck and tabs are in rigid contact. The broadband micro-vibrations generated by the chuck itself due to current heating, electromagnetic force, and equipment conduction can be directly transmitted to the battery interior via the tabs. Waveform analysis of the collected first ultrasonic signal reveals a clear temporal synchronization between the waveform fluctuations and the charge / discharge conditions. For example, sudden changes in waveform amplitude or phase jitter occur near the current jump edges of pulse charge / discharge, such as sudden changes in charge / discharge current, constant current / constant voltage switching, or pulse charge / discharge current jumps. Alternatively, unstable fluctuations in characteristic parameters that cannot be explained by changes in the battery's internal state within a short period can be identified as being caused by vibrations generated by the charge / discharge chuck. This determination provides a clear and targeted objective for the subsequent implementation of conductive vibration isolation structures. Furthermore, it provides experimental evidence to support the core finding in this application—identifying the chuck as a vibration source—making this discovery not merely a theoretical conjecture but a verifiable technical fact.

[0041] Secondly, this application also provides an ultrasonic testing system for lithium batteries that suppresses vibration interference from charging and discharging chucks, comprising: a lithium battery;

[0042] An ultrasonic sensor is fixed to the outer surface of the lithium battery.

[0043] A charging and discharging clamp is used to clamp the tabs of the lithium battery, and a conductive vibration isolation structure is provided at the contact interface between the charging and discharging clamp and the tabs.

[0044] A signal generator, which is electrically connected to the ultrasonic sensor;

[0045] A charging / discharging device for electrically connecting to the charging / discharging clamp;

[0046] During the charging and discharging process of the lithium battery by the charging and discharging chuck in the charging and discharging device, the ultrasonic sensor is triggered by the signal generator to detect ultrasonic signals; wherein, the conductive vibration isolation structure is used to suppress the vibration generated by the charging and discharging chuck. Attached Figure Description

[0047] Figure 1 This is a schematic diagram of the structure of the ultrasonic testing system for suppressing vibration interference of the charging and discharging chuck in the embodiments of this application;

[0048] Figure 2 This is a schematic diagram of the structure of the ultrasonic testing system for suppressing vibration interference of the charging and discharging chuck in the embodiments of this application;

[0049] Figure 3 This is a schematic diagram of the assembly of the conductive vibration isolation structure in the embodiment of this application between the charging / discharging clamp and the electrode of the lithium battery.

[0050] Figure 4 This refers to a one-cycle pulse signal used by the signal generator in the embodiments of this application;

[0051] Figure 5 A comparison of the voltage-time curves for two tests without vibration isolation;

[0052] Figure 6 A comparison of voltage-time curves for two instances when using shims as vibration isolation material;

[0053] Figure 7 This is a comparison of the voltage-time curves when using foam vibration isolation material in two separate tests.

[0054] Figure 8 A comparison of peak-time curves during the complete charge-discharge process before and after vibration isolation;

[0055] Figure 9 This is a flowchart illustrating the ultrasonic testing method for suppressing vibration interference of the charging / discharging chuck in the embodiments of this application.

[0056] Explanation of reference numerals in the attached diagram: 1-Lithium battery; 11-Taper; 2-Charging / discharging clamp; 3-Signal generator; 4-Ultrasonic pulse transmitting piezoelectric element; 5-Ultrasonic pulse receiving piezoelectric element; 6-Oscilloscope; 7-Computer; 8-Signal processing unit; 9-Conductive vibration isolation structure; 91-Base layer; 92-Surface layer. Detailed Implementation

[0057] Reference Figure 1 and Figure 2 This application provides an ultrasonic testing system for lithium batteries that suppresses vibration interference from charging and discharging chucks, comprising: a lithium battery 1;

[0058] An ultrasonic sensor is fixed to the outer surface of the lithium battery 1.

[0059] A charging / discharging clamp 2 is used to clamp the tab 11 of the lithium battery 1, and a conductive vibration isolation structure 9 is provided at the contact interface between the charging / discharging clamp 2 and the tab 11.

[0060] Signal generator 3, which is used for electrical connection with the ultrasonic sensor;

[0061] A charging / discharging device for electrically connecting to the charging / discharging clamp 2;

[0062] During the charging and discharging process of the lithium battery 1 by the charging and discharging clamp 2, the ultrasonic sensor is triggered by the signal generator 3 to detect ultrasonic signals. The conductive vibration isolation structure 9 absorbs and dissipates the vibration energy generated by the charging and discharging clamp 2 and conducted to the battery body through the tab 11 while conducting the charging and discharging current, so as to suppress the interference of the vibration generated by the charging and discharging clamp 2 on the ultrasonic signal collected by the ultrasonic sensor.

[0063] The lithium battery 1, as the object being tested, has its outer surface providing a stable mounting base for the ultrasonic sensor. The ultrasonic sensor is firmly attached to the outer surface of the lithium battery 1, and a tight bond is achieved between the sensor and the lithium battery 1 casing through an adhesive layer with good acoustic coupling properties, ensuring that ultrasonic energy can enter the interior of the lithium battery 1 with minimal attenuation and be effectively received after propagation.

[0064] The charging / discharging chuck 2 serves as the interface component connecting the charging / discharging device and the lithium battery 1, with its clamping end directly acting on the tab 11 of the lithium battery 1. A conductive vibration isolation structure 9 is provided at the contact interface between the charging / discharging chuck 2 and the tab 11. This conductive vibration isolation structure 9 is physically located between the metal body of the chuck and the surface of the tab 11, forming a sandwich-like layered configuration. The conductive vibration isolation structure 9 has a dual function: firstly, it possesses excellent conductivity, enabling it to form a low-resistance current path under high-current charging / discharging conditions, ensuring normal charging / discharging operation of the lithium battery 1 by the charging / discharging device; secondly, it possesses excellent damping characteristics, capable of absorbing and dissipating the broadband micro-vibration energy generated by the charging / discharging chuck 2.

[0065] Signal generator 3 is electrically connected to the ultrasonic sensor to generate a precise and controllable excitation signal. This excitation signal has set frequency, amplitude, and waveform parameters. When signal generator 3 triggers the ultrasonic sensor, the ultrasonic sensor converts the electrical signal into mechanical vibration and emits ultrasonic pulses into the lithium battery 1. The signal acquired by the ultrasonic sensor is plotted on an oscilloscope 6 in the signal processing unit 8, and technicians analyze the signal using a computer 7.

[0066] The charging / discharging equipment is electrically connected to the charging / discharging clamp 2 and is used to apply charging current or discharging load to the lithium battery 1 according to preset charging / discharging conditions. The charging / discharging equipment can be a battery testing system, a charging / discharging cabinet, or a charging / discharging management unit in a vehicle.

[0067] When the system is working, the charging and discharging equipment charges and discharges the lithium battery 1 through the charging and discharging chuck 2. During this process, the charging and discharging chuck 2 will generate broadband micro-vibrations due to the thermal effect of current, electromagnetic force, and equipment conduction. Without the conductive vibration isolation structure 9, these vibrations would be directly transmitted to the lithium battery 1 body through the rigid contact tabs 11, thus causing serious noise interference to the ultrasonic signals collected by the ultrasonic sensor attached to the outer surface of the battery. Due to the conductive vibration isolation structure 9, the vibration energy is absorbed and dissipated at the initial contact interface between the charging and discharging chuck 2 and the tabs 11, the vibration amplitude transmitted to the tabs 11 is significantly reduced, and the vibration energy reaching the battery body is negligible. At the same time, the signal generator 3 triggers the ultrasonic sensor to detect ultrasonic signals. The emitted ultrasonic pulses propagate inside the battery and return to be received by the sensor. The received ultrasonic signal is effectively suppressed due to vibration interference, and its waveform truly reflects the state evolution of the internal structure of the battery during the charging and discharging process, rather than the false fluctuations introduced by the chuck vibration.

[0068] Reference Figure 3 In this embodiment of the application, the conductive vibration isolation structure 9 is a double-layer structure, including: a base layer 81 connected to the metal body of the charging and discharging clamp 2, and a surface layer 92 disposed opposite to the base layer 81;

[0069] The base layer 91 is made of conductive elastic composite material and is used to absorb and dissipate medium and high frequency vibration energy.

[0070] The surface layer 92 is made of a flexible, highly conductive material and is in direct contact with the tab 11 of the lithium battery 1.

[0071] In the embodiments of this application, the thickness of the base layer 91 and the surface layer 92 is between 3 and 7 mm, the elastic modulus of the base layer material is, for example, between 1 MPa and 100 MPa, and the elastic modulus of the surface layer material is, for example, between 0.1 MPa and 10 MPa.

[0072] When the charging / discharging chuck 2 generates broadband micro-vibrations under high-rate or pulse charging / discharging conditions, the vibration energy is first transferred from the chuck's metal body to the base layer. The conductive elastic composite material inside the base layer dissipates the mechanical vibration energy into heat energy through internal friction between molecular chains, interfacial slippage between the filler and the matrix, and the material's own viscoelastic deformation.

[0073] The surface layer is located on the side of the conductive vibration isolation structure 9 away from the metal body of the charging / discharging chuck 2, opposite to the base layer, and in direct contact with the tab 11 of the lithium battery 1. The surface layer is made of a flexible, highly conductive material, which has excellent flexibility and low contact resistance. When the charging / discharging chuck 2 applies clamping force, the surface layer undergoes compliant deformation under pressure, closely conforming to the microstructure of the tab 11 surface, filling in the tiny bumps and rough textures on the tab 11 surface, and maximizing the actual contact area.

[0074] Specifically, the conductive elastic composite material is selected from one or more of conductive foam or conductive elastic gasket; the flexible high-conductivity material is selected from one or more of flexible conductive film or ultrafine metal mesh.

[0075] Reference Figure 1 In this embodiment of the application, the ultrasonic sensor includes an ultrasonic pulse emitting piezoelectric element 4 and an ultrasonic pulse receiving piezoelectric element 5;

[0076] The ultrasonic pulse emitting piezoelectric element 4 and the ultrasonic pulse receiving piezoelectric element 5 are respectively fixed at both ends of the same surface of the lithium battery 1.

[0077] The ultrasonic pulse emitting piezoelectric element 4 is communicatively connected to the signal generator 3, and the signal generator 3 is used to excite the ultrasonic pulse emitting piezoelectric element 4 to emit ultrasonic signals.

[0078] The ultrasonic pulse receiving piezoelectric element 5 is communicatively connected to the oscilloscope 6, which is used to acquire and display the ultrasonic signals received by the ultrasonic pulse receiving piezoelectric element 5.

[0079] When the system starts ultrasonic testing, refer to Figure 4 The signal generator 3 generates a one-cycle pulse excitation signal according to preset parameters. The frequency of this excitation signal is typically set in the range of 10 to 30 kHz, and the pulse width is 4 to 6 microseconds to ensure effective penetration and a good signal-to-noise ratio of ultrasound in the multilayer structure of the lithium battery 1. The excitation signal is transmitted to the transmitting piezoelectric element, which uses the inverse piezoelectric effect to convert the electrical signal into mechanical vibration of the same frequency, emitting ultrasonic pulses into the interior of the lithium battery 1.

[0080] The emitted ultrasonic pulse enters from one end of the lithium battery 1 and propagates within the multilayered dielectric material inside the battery 1. Since the lithium battery 1 is a multilayered composite structure composed of materials with different acoustic impedances, such as the positive electrode, negative electrode, separator, and electrolyte, the ultrasonic wave undergoes reflection, refraction, and transmission at the interfaces between layers during propagation. Some energy continues along the propagation direction, while some is scattered or absorbed and attenuated. The propagation path of the ultrasonic pulse runs through the entire length of the battery, covering the entire internal structural region from the transmitting end to the receiving end. This long-path design allows the ultrasonic wave to fully sample the dielectric distribution and interface state inside the battery. Any structural anomalies along the path, such as electrode expansion, changes in porosity, uneven electrolyte distribution, or local density anomalies caused by lithium plating, will affect the propagation speed and energy attenuation of the ultrasonic wave.

[0081] When the ultrasonic pulse travels to the other end of lithium battery 1, the receiving piezoelectric element picks up the ultrasonic signal transmitted from lithium battery 1. The receiving piezoelectric element uses the positive piezoelectric effect to convert the received mechanical vibration into a voltage signal of the same frequency, and transmits this signal to oscilloscope 6. Oscilloscope 6 acquires and displays the received ultrasonic waveform in real time at a high sampling rate; characteristic parameters such as amplitude, time of flight, and waveform envelope in the original waveform are clearly presented.

[0082] Throughout the testing process, if the high-frequency vibrations generated by the charging / discharging chuck 2 are transmitted to the battery interior via the tab 11, these mechanical vibrations will be superimposed on the ultrasonic signal, causing irregular fluctuations in the received waveform that are synchronized with the charging / discharging conditions. This manifests as random amplitude fluctuations, phase jitter, or waveform distortion. Because a conductive vibration isolation structure 9 is installed between the charging / discharging chuck 2 and the tab 11 in this system, the vibrations generated by the chuck are absorbed and dissipated at the initial contact interface. The vibration energy transmitted to the battery body is significantly suppressed, and the ultrasonic signal collected by the receiving piezoelectric element remains pure and stable, truly reflecting the evolution of the battery's internal structure during the charging / discharging process rather than false noise introduced by the chuck vibration.

[0083] In this embodiment of the application, under the same charging and discharging conditions, the ultrasonic sensor collects a first set of ultrasonic signals when the conductive vibration isolation structure 9 is not set, and a second set of ultrasonic signals after the conductive vibration isolation structure 9 is set; by comparing the waveform repeatability of the first set of ultrasonic signals and the second set of ultrasonic signals, the suppression effect of the conductive vibration isolation structure 9 on vibration interference is evaluated.

[0084] The process of evaluating the vibration interference suppression effect of the conductive vibration isolation structure 9 includes: performing waveform superposition and comparison, superimposing and displaying multiple ultrasonic waveforms continuously acquired in a short period of time without the vibration isolation structure, and observing the degree of difference between each waveform in amplitude, phase, and envelope shape. If the waveforms show significant non-overlap at the peak position, trough depth, and zero-crossing point, or even if the amplitude and trend of the waveforms show opposite patterns, it indicates that the clamp vibration has seriously interfered with the ultrasonic signal, and the waveform repeatability is low. Then, multiple ultrasonic waveforms acquired under the same working conditions after the vibration isolation structure is installed are processed in the same way. If the waveforms basically overlap, the peak amplitude remains consistent, and the phase shift is within an acceptable range, it indicates that the vibration interference has been effectively suppressed, and the waveform repeatability is high.

[0085] Secondly, characteristic parameters can be compared. Key characteristic points in the waveform, such as the amplitude or flight time of the first positive peak, can be selected, and the statistical distribution of the characteristic parameter in multiple measurements can be calculated. For the first group of signals, the standard deviation of the characteristic parameter is large, and the relative range is obvious, indicating that the signal is unstable. For the second group of signals, the standard deviation of the characteristic parameter decreases significantly, and the fluctuation range narrows, indicating that the signal tends to be stable.

[0086] Time series analysis can also be performed, continuously acquiring ultrasonic signals during the complete charge and discharge process to construct curves showing the change of characteristic parameters over time. In the case of no vibration isolation, the characteristic curve exhibits severe spiky fluctuations with a high noise floor, making it difficult to distinguish smooth trends corresponding to changes in the battery's internal state. In the case of vibration isolation, the characteristic curve becomes smoother, the noise level is significantly reduced, and the phase transition points and inflection points during the battery's charge and discharge process are more clearly discernible.

[0087] By comparing waveform superposition, characteristic parameter statistics, and time series analysis from multiple dimensions, the vibration suppression effect of the conductive vibration isolation structure 9 can be systematically evaluated. If the second set of signals is significantly better than the first set of signals in terms of waveform repeatability, characteristic parameter stability, and curve smoothness, it indicates that the conductive vibration isolation structure 9 has successfully absorbed the vibration energy generated by the charging / discharging clamp 2 and conducted through the electrode 11, effectively suppressing the interference of vibration on the ultrasonic signal. This evaluation method makes the vibration isolation effect no longer a subjective judgment, but rather measurable, comparable, and reproducible objective data.

[0088] In this embodiment of the application, the step of evaluating the suppression effect of the conductive vibration isolation structure 9 on vibration interference by comparing the waveform repeatability of the first group of ultrasonic signals and the second group of ultrasonic signals specifically includes:

[0089] Extract the characteristic parameters of the first group of ultrasound signals to construct the first peak time curve;

[0090] Extract the characteristic parameters of the second group of ultrasound signals to construct the second peak time curve;

[0091] The vibration isolation effect is quantitatively evaluated by comparing the stability and noise level of the first peak time curve and the second peak time curve.

[0092] The construction process of the first peak time curve and the second peak time curve is as follows:

[0093] In this embodiment, the same peak in the same set of ultrasonic curves is selected, and the voltage value corresponding to the peak is extracted at each time point. The voltage values ​​at all time points are combined to construct a complete peak-time curve.

[0094] Before setting the conductive vibration isolation structure 9, it is necessary to pre-determine the vibration source, which is a key prerequisite step to ensure that the vibration isolation scheme is targeted and effective. This process specifically includes: using the charge / discharge chuck 2 (without the vibration isolation structure) to clamp the tab 11 and performing a charge / discharge test;

[0095] During the charge-discharge test, the first ultrasonic signal is acquired by the ultrasonic sensor;

[0096] If the waveform of the first ultrasonic signal is analyzed and waveform fluctuations synchronized with the charging and discharging conditions are observed, or if the characteristic parameters of the first ultrasonic signal are unstable, then the charging and discharging clamp 2 is determined to be a key interference source that transmits vibrations to the lithium battery 1 through the tab 11 and interferes with the ultrasonic signal.

[0097] In this embodiment, an LFP soft-pack battery with a capacity of 2300mAh and dimensions of 95.5×46×7.1 (mm) was used as the experimental subject. The experiment was conducted at room temperature (25℃). According to the method described in this invention, the ultrasonic guided wave sensor used was a piezoelectric ceramic wafer with a diameter of 14mm and a thickness of 2mm. Subsequently, clamps with different vibration-damping materials were used in the experiment. The stability of the ultrasonic signal was observed. The results are as follows... Figure 5-7 As shown.

[0098] In this embodiment, a low degree of overlap between the two signal waveforms indicates poor vibration shielding performance of the clamp. If the signals are substantially identical, it indicates that the vibration isolation effect is within an acceptable range. Figure 5 As shown, the two waveform signals exhibit varying degrees of increase at each peak position, and even show opposite patterns. Figure 6 , Figure 7 In this process, the overlap between the two waveforms becomes increasingly better. Additionally, as... Figure 8As shown, the SA variation patterns of the peak curves before and after vibration isolation differ significantly, especially in the high SOC range, where the unisolated SA curve exhibits a dip, indicating high overall noise and obscuring the correspondence between the inflection point and the internal phase transition point of the battery. The results demonstrate that this invention exhibits excellent vibration isolation performance, and the provided evaluation scheme clearly demonstrates signal stability and characteristic response capabilities.

[0099] By identifying and confirming that the broadband micro-vibrations generated by the charging / discharging chuck 2 during charging and discharging due to current thermal effects, electromagnetic forces, and equipment conduction are the key vibration sources transmitted through the tab 11 to the inside of the battery and interfering with the ultrasonic signal, a conductive vibration isolation structure 9 is specifically set at the contact interface between the charging / discharging chuck 2 and the tab 11. This structure absorbs and dissipates vibration energy while conducting large currents, cutting off the vibration transmission path from the physical source. This significantly suppresses waveform fluctuations and characteristic parameter instability synchronized with the charging / discharging conditions, resulting in a substantial improvement in the waveform repeatability, peak time curve stability, and signal-to-noise ratio of the ultrasonic signal. Simultaneously, by collecting two sets of ultrasonic signals with and without the vibration isolation structure, waveform repeatability comparison and peak time curve analysis are performed, an objective and quantifiable vibration isolation effect evaluation system is established. This provides a clean and reliable ultrasonic signal basis for battery health status assessment, state of charge estimation, and internal damage detection. Moreover, this solution has high integration and strong versatility, and can directly replace the existing charging / discharging chuck 2 without changing other experimental configurations. It can also be extended to fine research scenarios such as monitoring the micro-stress evolution of the battery's internal separator.

[0100] Based on the above system, referring to Figure 9 This application embodiment also provides an ultrasonic testing method for suppressing vibration interference of the charging / discharging clamp 2 in lithium battery 1, including:

[0101] S101, Fix the ultrasonic sensor to the outer surface of the lithium battery 1;

[0102] S102, the charging / discharging clamp 2 is electrically connected to the tab 11 of the lithium battery 1, and a conductive vibration isolation structure 9 is provided at the contact interface between the charging / discharging clamp 2 and the tab 11.

[0103] S103, during the charging and discharging process of the charging and discharging device charging and discharging the lithium battery 1 through the charging and discharging clamp 2, the ultrasonic sensor is triggered by the signal generator 3 to detect ultrasonic signals; wherein, the conductive vibration isolation structure 9 is used to suppress the vibration generated by the charging and discharging clamp 2.

[0104] The conductive vibration isolation structure 9 is a double-layer structure, comprising: a base layer connected to the metal body of the charging and discharging clamp 2, and a surface layer disposed opposite to the base layer;

[0105] The base layer is made of conductive elastic composite material, which is used to absorb and dissipate medium and high frequency vibration energy;

[0106] The surface layer is made of a flexible, highly conductive material and is in direct contact with the tabs 11 of the lithium battery 1.

[0107] The conductive elastic composite material is selected from one or more of conductive foam or conductive elastic gasket; the flexible high-conductivity material is selected from one or more of flexible conductive film or ultrafine metal mesh.

[0108] The ultrasonic sensor includes an ultrasonic pulse emitting piezoelectric element 4 and an ultrasonic pulse receiving piezoelectric element 5.

[0109] The ultrasonic pulse emitting piezoelectric element 4 and the ultrasonic pulse receiving piezoelectric element 5 are respectively fixed at both ends of the same surface of the lithium battery 1.

[0110] The ultrasonic pulse emitting piezoelectric element 4 is communicatively connected to the signal generator 3, and the signal generator 3 is used to excite the ultrasonic pulse emitting piezoelectric element 4 to emit ultrasonic signals.

[0111] The ultrasonic pulse receiving piezoelectric element 5 is communicatively connected to the oscilloscope 6, which is used to acquire and display the ultrasonic signals received by the ultrasonic pulse receiving piezoelectric element 5.

[0112] The method further includes:

[0113] Under the same charging and discharging conditions, the ultrasonic sensor collects a first set of ultrasonic signals when the conductive vibration isolation structure 9 is not set, and a second set of ultrasonic signals after the conductive vibration isolation structure 9 is set.

[0114] The effect of the conductive vibration isolation structure 9 on suppressing vibration interference is evaluated by comparing the waveform repeatability of the first group of ultrasonic signals and the second group of ultrasonic signals.

[0115] The step of evaluating the vibration suppression effect of the conductive vibration isolation structure 9 by comparing the waveform repeatability of the first group of ultrasonic signals and the second group of ultrasonic signals includes:

[0116] Extract the characteristic parameters of the first group of ultrasound signals to construct the first peak time curve;

[0117] Extract the characteristic parameters of the second group of ultrasound signals to construct the second peak time curve;

[0118] The vibration isolation effect is quantitatively evaluated by comparing the stability and noise level of the first peak time curve and the second peak time curve.

[0119] The construction process of the first peak time curve and the second peak time curve is as follows:

[0120] Select the same peak in the same set of ultrasonic curves, extract the voltage value corresponding to the peak at each time point, and combine the voltage values ​​at all time points to construct a complete peak-time curve.

[0121] Before setting the conductive vibration isolation structure 9, the method further includes:

[0122] The electrode 11 is held by the charging / discharging chuck 2 without vibration isolation structure, and a charging / discharging test is performed.

[0123] During the charge-discharge test, the first ultrasonic signal is acquired by the ultrasonic sensor;

[0124] If the waveform of the first ultrasonic signal is analyzed and waveform fluctuations synchronized with the charging and discharging conditions are observed, or if the characteristic parameters of the first ultrasonic signal are unstable, then the charging and discharging clamp 2 is determined to be a key interference source that transmits vibrations to the lithium battery 1 through the tab 11 and interferes with the ultrasonic signal.

[0125] This application also provides a method for manufacturing a lithium battery, including the following steps:

[0126] Provide a lithium battery to be tested;

[0127] The lithium battery under test is tested using the above-mentioned ultrasonic testing method for suppressing vibration interference of the charging and discharging clamp, and ultrasonic signal characteristic parameters are obtained.

[0128] Based on the ultrasonic signal characteristic parameters, adjust the manufacturing process parameters of the lithium battery until the ultrasonic signal characteristic parameters meet the preset threshold.

[0129] Lithium batteries that meet the preset threshold are identified as qualified products.

[0130] The process of adjusting the manufacturing process parameters of the lithium battery according to the ultrasonic signal characteristic parameters until the ultrasonic signal characteristic parameters meet the preset threshold is existing technology and will not be described again in this embodiment.

[0131] It should be understood that the application of this application is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims. Those skilled in the art can understand that implementing all or part of the processes of the above embodiments and making equivalent changes according to the claims of this application still fall within the scope of this application.

Claims

1. A method for ultrasonic testing of lithium batteries to suppress vibration interference from charging and discharging chucks, characterized in that, include: The ultrasonic sensor is fixed to the outer surface of the lithium battery (1); The charging and discharging clamp (2) is electrically connected to the tab (11) of the lithium battery (1), and a conductive vibration isolation structure (9) is provided at the contact interface between the charging and discharging clamp (2) and the tab (11). During the charging and discharging process of the lithium battery by the charging and discharging chuck (2), the ultrasonic sensor is triggered by the signal generator to detect ultrasonic signals; wherein, the conductive vibration isolation structure (9) is used to suppress the vibration generated by the charging and discharging chuck (2).

2. The method according to claim 1, characterized in that, The conductive vibration isolation structure (9) is a double-layer structure, including: a base layer (91) connected to the metal body of the charging and discharging clamp (2), and a surface layer (92) disposed opposite to the base layer (91). The base layer (91) is made of conductive elastic composite material and is used to absorb and dissipate medium and high frequency vibration energy; The surface layer (92) is made of a flexible high-conductivity material and is in direct contact with the tab (11) of the lithium battery (1).

3. The method according to claim 2, characterized in that, The conductive elastic composite material is selected from one or more of conductive foam or conductive elastic gasket; the flexible high-conductivity material is selected from one or more of flexible conductive film or ultrafine metal mesh.

4. The method according to claim 1, characterized in that, The ultrasonic sensor includes an ultrasonic pulse emitting piezoelectric element (4) and an ultrasonic pulse receiving piezoelectric element (5). The ultrasonic pulse emitting piezoelectric piece (4) and the ultrasonic pulse receiving piezoelectric piece (5) are respectively fixed at both ends of the same surface of the lithium battery (1). The ultrasonic pulse emitting piezoelectric element (4) is communicatively connected to the signal generator (3), and the signal generator (3) is used to excite the ultrasonic pulse emitting piezoelectric element (4) to emit ultrasonic signals; The ultrasonic pulse receiving piezoelectric element (5) is communicatively connected to an oscilloscope (6), which is used to acquire and display the ultrasonic signals received by the ultrasonic pulse receiving piezoelectric element (5).

5. The method according to claim 1, characterized in that, The method further includes: Under the same charging and discharging conditions, the ultrasonic sensor collects the first set of ultrasonic signals when the conductive vibration isolation structure (9) is not set, and the second set of ultrasonic signals after the conductive vibration isolation structure (9) is set. The effect of the conductive vibration isolation structure (9) on suppressing vibration interference is evaluated by comparing the waveform repeatability of the first group of ultrasonic signals and the second group of ultrasonic signals.

6. The method according to claim 5, characterized in that, The steps for evaluating the vibration suppression effect of the conductive vibration isolation structure (9) on vibration interference by comparing the waveform repeatability of the first group of ultrasonic signals and the second group of ultrasonic signals include: Extract the characteristic parameters of the first group of ultrasound signals to construct the first peak time curve; Extract the characteristic parameters of the second group of ultrasound signals to construct the second peak time curve; The vibration isolation effect is quantitatively evaluated by comparing the stability and noise level of the first peak time curve and the second peak time curve.

7. The method according to claim 1, characterized in that, The construction process of the first peak time curve and the second peak time curve is as follows: Select the same peak in the same set of ultrasonic curves, extract the voltage value corresponding to the peak at each time point, and combine the voltage values ​​at all time points to construct a complete peak-time curve.

8. The method according to claim 1, characterized in that, Before setting the conductive vibration isolation structure (9), the following is also included: The electrode tab (11) is held in the charging / discharging clamp (2) without vibration isolation structure, and a charging / discharging test is performed. During the charge-discharge test, the first ultrasonic signal is acquired by the ultrasonic sensor; If the waveform of the first ultrasonic signal is analyzed and waveform fluctuations synchronized with the charging and discharging conditions are observed or the characteristic parameters of the first ultrasonic signal are unstable, then the charging and discharging clamp (2) is determined to be the key interference source that conducts vibrations to the inside of the lithium battery (1) through the tab (11) and interferes with the ultrasonic signal.

9. A lithium battery ultrasonic testing system for suppressing vibration interference from charging and discharging chucks, characterized in that, include: Lithium battery (1); An ultrasonic sensor is fixed on the outer surface of the lithium battery (1); A charging and discharging clamp (2) is used to clamp the tab (11) of the lithium battery (1), and a conductive vibration isolation structure (9) is provided at the contact interface between the charging and discharging clamp (2) and the tab (11). A signal generator (3) is used to be electrically connected to the ultrasonic sensor; A charging and discharging device for electrically connecting to the charging and discharging clamp (2); During the charging and discharging process of the lithium battery by the charging and discharging chuck (2) of the charging and discharging device, the ultrasonic sensor is triggered by the signal generator (3) to detect ultrasonic signals; wherein, the conductive vibration isolation structure (9) is used to suppress the vibration generated by the charging and discharging chuck (2).

10. The system according to claim 9, characterized in that, Under the same charging and discharging conditions, the ultrasonic sensor collects the first set of ultrasonic signals when the conductive vibration isolation structure (9) is not set, and the second set of ultrasonic signals after the conductive vibration isolation structure (9) is set. The effect of the conductive vibration isolation structure (9) on suppressing vibration interference is evaluated by comparing the waveform repeatability of the first group of ultrasonic signals and the second group of ultrasonic signals.

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