Non-contact inspection of battery or battery component, system and method of forming the same

Abstract

Various embodiments may relate to a system for non-contact inspection of a battery or a battery component. The system may include a pulsed laser source configured to generate a pulsed laser beam. The system may also include an optical system configured to generate one or more laser array pattern geometries on the battery or the battery component based on the pulsed laser beam using non-polarization optics, thereby generating narrowband ultrasonic waves in a desired wave propagation direction. The system may additionally include a probe device configured to measure or sense harmonic frequency components resulting from self-interaction of a narrowband ultrasonic wave in the presence of a defect of the battery or the battery component and / or combined harmonic frequency components resulting from mutual interaction of two narrowband ultrasonic waves in the presence of the defect of the battery or the battery component.

Description

NON-CONTACT INSPECTION OF BATTERY OR BATTERY COMPONENT, SYSTEM AND METHOD OF FORMING THE SAME CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of priority of Singapore application No.10202500434S filed February 18, 2025, the contents of it being hereby incorporated by reference in its entirety for all purposes.TECHNICAL FIELD

[0002] Various embodiments of this disclosure may relate to a system for non-contact inspection of a battery or a battery component Various embodiments of this disclosure may relate to a method of forming a system for non-contact inspection of a battery or a battery component. Various embodiments of this disclosure may relate to a method of non-contact inspection of a battery or a battery component.BACKGROUND

[0003] Lithium-ion batteries have become increasingly important in various aspects of human life such as electric vehicles, medical devices, and energy storage systems. Despite significant advancements in energy capacity, density, and life cycle, safety remains a primary challenge due to the potential risk of fires caused by battery failures. Reported incidents, such as the grounding of the Boeing 787 aircrafts and battery fires in electric vehicles, have been attributed to manufacturing defects (e.g., welding issues on the electrode surface) or external factors such as fast charging and overheating, which trigger thermal runaway. Therefore, nextgeneration batteries would need to incorporate enhanced safety protocols. FIG. 1A shows a general illustration of the characteristics that next-generation batteries may be required topossess. During production and operation, issues such as wrinkling, poor infiltration, weld defect, and delamination may arise, adversely affecting battery efficiency and performance. For instance, uneven coating of the inner core or diaphragm wrinkling can lead to non-uniform internal resistance distribution, impacting cycle performance. Furthermore, in various stages of battery life, over-charging or over-discharging may generate gases such as hydrogen and carbon dioxide, which, if accumulated, can compromise battery performance and safety. Studies indicate that during thermal runaway, gas generation occurs early, accompanied by crack formation in components like the current collector, making early detection and inspection crucial for preventing thermal runaway events.

[0004] Defects are more likely to occur during the complex production process of batteries (pouch and cylindrical) The most common manufacturing defects include delamination, voids / porosity, poor welds, critical structural changes, cycling induced particle cracking, and aging mechanisms (mechanical deformation). These defects can have a significant impact on battery performance, leading to reduced capacity, and can pose serious safety concerns. Accordingly, a battery management system (BMS) should be employed to monitor the battery states (e g., State-of-Charge (SOC) and State-of-Health (SOFT)) and internal physical properties (e.g., electrode thickness, temperature, gas accumulation, and porosity), in order to reduce the risk of thermal runaway in real-time The battery industry faces the common problem of not having a quick technique to assess the overall health of batteries throughout the different stages of their life cycle. This includes testing, production, bench assembly, post fabrication and sealing.

[0005] FIG. IB shows a schematic illustrating the various stages of the lifecycle of a battery. Failures can occur at any stage of production, assembly or operation, and may result in catastrophic events. Currently, about 85% of power device failures may be attributed to batteryfailures. However, industries typically inspect only about 1 - 2.5% of batteries, meaning 10 -25 out of 1,000 batteries.

[0006] Conventional inspection methods such as voltage tests, visual inspections, and destructive testing do not provide a comprehensive understanding of the underlying reasons for battery defects and degradation. The X-ray technique can provide a detailed image of manufacturing defects, but is not suitable for online inspections due to its slow inspection speed, risks of radiation exposure, and high costs. In the vision inspection technique, a charge-coupled device camera is used to segment defects in the battery at the pixel level after supervised learning on defect and intact images. However, this technique is only applicable to visible defects and not invisible defects. The current techniques used to diagnose the physical condition of a battery, particularly when performed on a large scale, are known to be destructive, contact, offline and not suitable for battery diagnostics while the battery is being used. It is widely acknowledged that there is a demand for non-destructive evaluation (NDE) techniques that can be scaled up and do not cause damage to monitor and evaluate the internal state of a battery. These techniques can provide valuable information for further analysis of the battery's physical condition, such as determining the SOC, SOH, defects, and other physical properties of the battery. Recently, NDE techniques have been used for testing batteries, such as electrochemical impedance spectroscopy (EIS), eddy current, fiber optic sensors (FOS) and contact-based ultrasonic transducers. The EIS method involves measuring the response of battery impedance to a sinusoidal excitation signal. However, gathering data on the impedance spectrum requires measurements across a broad frequency range, which adds complexity to the computations. EIS measurements demand a longer testing duration and stable testing environment, rendering them inconvenient for online applications The eddy current technique, which measures the magnetic field variation induced by defects, is utilized to inspect the weld seam at the battery stack. However, this technique requires a contact-type probe. Additionally, factors such as changes inthe medium thickness, lift-off distance between the probe and target surface, and defects can affect the eddy current signal. FOS, resistant to electromagnetic interference, have been embedded within pouch cells to monitor both internal strain and temperature. However, the major drawback of FOS is its reliance on contact SOC measurement and susceptibility to environmental factors such as temperature and humidity, which can affect accuracy.SUMMARY

[0007] Various embodiments may relate to a system for non-contact inspection of a battery or a battery component. The system may include a pulsed laser source configured to generate a pulsed laser beam. The system may also include an optical system configured to generate one or more laser array pattern geometries on the battery or the battery component based on the pulsed laser beam using non-polarization optics, thereby generating narrowband ultrasonic waves in a desired wave propagation direction. The system may additionally include a probe device configured to measure or sense harmonic frequency components resulting from selfinteraction of a narrowband ultrasonic wave in the presence of a defect of the battery or the battery component and / or combined harmonic frequency components resulting from mutual interaction of two narrowband ultrasonic waves in the presence of the defect of the battery or the battery component.

[0008] Various embodiments may relate to a method of forming a system for non-contact inspection of a battery or a battery component. The method may include providing a pulsed laser source configured to generate a pulsed laser beam. The method may also include arranging an optical system configured to generate one or more laser array pattern geometries on the battery or the battery component based on the pulsed laser beam using non-polarization optics, thereby generating narrowband ultrasonic waves in a desired wave propagation direction. The method may additionally include providing a probe device configured to measure or senseharmonic frequency components resulting from self-interaction of a narrowband ultrasonic wave in the presence of a defect of the battery or the battery component and / or combined harmonic frequency components resulting from mutual interaction of two narrowband ultrasonic waves in the presence of the defect of the battery or the battery component.

[0009] Various embodiments may relate to a method of non-contact inspection of a battery or a battery component. The method may include generating a pulsed laser beam using a pulsed laser source such that one or more laser array pattern geometries are generated on the battery or the battery component based on the pulsed laser beam using non-polarization optics, thereby generating narrowband ultrasonic waves in a desired wave propagation direction. The method may also include measuring or sensing harmonic frequency components resulting from selfinteraction of a narrowband ultrasonic wave in the presence of a defect of the battery or the battery component and / or combined harmonic frequency components resulting from mutual interaction of two narrowband ultrasonic waves in the presence of the defect of the battery or the battery component using a probe device.BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In the drawings, like reference characters generally refer to the same parts throughout the different views. The drawings are not necessarily drawn to scale, emphasis instead generally being placed upon illustrating the principles of various embodiments. In the following description, various embodiments of the invention are described with reference to the following drawings.FIG. 1 A shows a general illustration of the characteristics that next-generation batteries may be required to possess.FIG. IB shows a schematic illustrating the various stages of the lifecycle of a battery.FTG. 2 shows a general illustration of a system for non-contact inspection of a battery or a battery component according to various embodiments.FIG. 3 shows a general illustration of a method of forming a system for non-contact inspection of a battery or a battery component according to various embodimentsFIG. 4 shows a general illustration of a method of non-contact inspection of a battery or a battery component according to various embodiments.FIG. 5A shows a schematic of a system for non-contact inspection of a battery or a battery component according to various embodiments.FIG. 5B shows (a) nonlinear wave mixing by the optical system according to various embodiments, and (b) nonlinear harmonic generation by one arm of the optical system according to various embodimentsFIG. 5C shows some possible laser array pattern geometries according to various embodiments. FIG. 6A illustrates nonlinear laser ultrasonics with narrowband frequencies on a defective cell according to various embodiments.FIG. 6B illustrates the principles used by the non-contact inspection system according to various embodiments.FIG. 7 shows a schematic illustrating a linear laser array pattern and the spatial bandwidth of the linear laser array pattern according to various embodiments.FIG. 8 shows illustrations of various ultrasonic measurement strategies (a) pitch-catch, (b) pulse-echo and (c) through-transmission according to various embodiments.FIG. 9A shows a plot of amplitude (in arbitrary units or a.u.) as a function of frequency (in kilohertz or kHz) illustrating the first cycle when the pouch cell is charged at 100% State-of-Charge (SOC) according to various embodiments.FIG. 9B shows a plot of acoustic nonlinearity parameter as a function of the State-of-Charge (SOC) (in percent or %) of the pouch cell according to various embodiments.FTG. 10A provides a summary of the shortcomings of conventional battery inspection methods. FIG. 10B shows a table comparing the non-contact inspection system according to various embodiments and various conventional battery inspection methodsDESCRIPTION

[0011] The following detailed description refers to the accompanying drawings that show, by way of illustration, specific details and embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. Other embodiments may be utilized and structural, logical, and electrical changes may be made without departing from the scope of the invention. The various embodiments are not necessarily mutually exclusive, as some embodiments can be combined with one or more other embodiments to form new embodiments.

[0012] Features that are described in the context of an embodiment may correspondingly be applicable to the same or similar features in the other embodiments. Features that are described in the context of an embodiment may correspondingly be applicable to the other embodiments, even if not explicitly described in these other embodiments. Furthermore, additions and / or combinations and / or alternatives as described for a feature in the context of an embodiment may correspondingly be applicable to the same or similar feature in the other embodiments.

[0013] In the context of various embodiments, the articles “a”, “an” and “the” as used with regard to a feature or element include a reference to one or more of the features or elements.

[0014] Tn the context of various embodiments, the term “about” or “approximately” as applied to a numeric value encompasses the exact value and a reasonable variance, e g. within 10% of the specified value.

[0015] As used herein, the term “and / or” includes any and all combinations of one or more of the associated listed items. In other words, “A and / or B” may include or refer to A, B, or both A and B

[0016] By “comprising” it is meant including, but not limited to, whatever follows the word “comprising”. Thus, use of the term “comprising” indicates that the listed elements are required or mandatory, but that other elements are optional and may or may not be present.

[0017] By “consisting of’ is meant including, and limited to, whatever follows the phrase “consisting of’. Thus, the phrase “consisting of’ indicates that the listed elements are required or mandatory, and that no other elements may be present.

[0018] Embodiments described in the context of one of the systems are analogously valid for the other systems, embodiments described in the context of a method are analogously valid for a system, and vice versa.

[0019] The current NDE techniques have limitations. These include: (i) no nonlinear and non-contact laser ultrasonic method for battery defect detection and health evaluation; and (ii) the relationship between the battery's internal health and thermal runaway is not fully understood. Additionally, these NDE techniques are generally slow in inspection speed, making it difficult to inspect each battery thoroughly without slowing down the production line in a high-volume manufacturing environment. As a result, traditional methods often sacrifice thorough inspection for production speed. This trade-off may result in only a sample of the production being inspected, potentially allowing defective products to be overlooked.

[0020] Various embodiments may seek to address one or more shortcomings faced by conventional inspection techniques.

[0021] FIG. 2 shows a general illustration of a system for non-contact inspection of a battery or a battery component (alternatively referred to as non-contact inspection system) according to various embodiments. The system may include a pulsed laser source 202 (e.g., a pulsed laser)configured to generate a pulsed laser beam. Tn various embodiments, the pulsed laser source 202 may be spaced apart from the battery or the battery component. The system may also include an optical system 204 configured to generate one or more laser array pattern geometries on the battery or the battery component based on the pulsed laser beam using non-polarization optics, thereby generating narrowband ultrasonic waves in a desired wave propagation direction Tn other words, the optical system 204 may include various optical components that do not polarize the pulsed laser beam. By using non-polarization optics, the energy of the pulsed laser beam may be fully utilized, thereby improving efficiency. The system may also include a probe device 206 configured to measure or sense harmonic frequency components resulting from self-interaction of a narrowband ultrasonic wave in the presence of a defect of the battery or the battery component and / or combined harmonic frequency components resulting from mutual interaction of two narrowband ultrasonic waves in the presence of the defect of the battery or the battery component. The presence of the defect in the battery or battery component may lead to non-linearities in the narrowband ultrasonic waves that have interacted with the defect, thereby resulting in the harmonic frequency components and / or the combined harmonic frequency components.

[0022] For avoidance of doubt, the “narrowband ultrasonic wave” involved in selfinteraction to generate the harmonic frequency components in the presence of the defect, and the “two narrowband ultrasonic waves” involved in mutual interaction to generate the combined harmonic frequency components in the presence of the defect may be part of the “narrowband ultrasonic waves” generated by the optical system 204.

[0023] In the current context, a “defect” may refer to a manufacturing flaw or issue within a battery or battery component that significantly impacts its performance, causing it to not function as intended, potentially leading to reduced capacity, premature failure, and / or even safety hazards like overheating or leaking. Defects may include, for instance, delamination,voids / porosity, poor welds, critical structural changes, cycling induced particle cracking, and / or aging mechanisms (mechanical deformation).

[0024] The term “narrowband ultrasonic wave” is a well known term in the field, may refer to an ultrasonic wave with a predefined upper frequency limit as well as a predefined lower frequency limit. In various examples, a significant portion, e.g., above 99% or above 95% of an energy of the ultrasonic wave may fall between the lower frequency limit and the upper frequency limit.

[0025] In various embodiments, the one or more laser array pattern geometries may be selected from a group consisting of linear array patterns, circular array patterns and arc array patterns. In various embodiments, the optical system 204 may be configured to control the wave propagation direction of the nonlinear narrowband ultrasonic waves by controlling an orientation of the one or more laser array pattern geometries. Various embodiments may enable the generation of various geometric configurations of laser array patterns, such as linear, circular, and arc arrays. These configurations may enhance the directivity of ultrasonic wave generation and may concentrate the energy of the generated waves at a focal point, thereby improving accuracy. Various embodiments may include a cylindrical convex lens to adjust the orientation of the laser array source, allowing precise targeting of narrowband ultrasonic wave propagation direction. This flexibility in orientation may be critical for applications requiring targeted wave propagation.

[0026] In various embodiments, the pulsed laser beam (generated by the pulsed laser source 202) may be a nanosecond pulsed laser beam or a picosecond pulsed laser beam

[0027] In various embodiments, the probe device 206 may be a continuous laser beam system. The continuous laser beam system may be configured to generate a probe laser beam to measure or sense the nonlinear narrowband ultrasonic waves. The continuous laser beamsystem may serve as a laser interference receiving unit, used for sensing the narrowband ultrasonic waves generated.

[0028] In various embodiments, the battery may be any suitable battery, e.g., a pouch battery cell, a prismatic battery cell or cylindrical battery cell. In various embodiments, the battery component may be any suitable battery component, e.g., a busbar or a cap.

[0029] In various embodiments, the system may further include a chamber for holding the battery or the battery component, the chamber having optical windows. In various embodiments, the pulsed laser source 202, the probe device 206 and the optical system 204 may be provided external to the chamber.

[0030] In various embodiments, the optical system 204 may be configured to form a first sub-beam and a second sub-beam based on the pulsed laser beam, the first sub-beam for generating a first laser array pattern of the one or more laser array pattern geometries, and the second sub-beam for generating a second laser array pattern of the one or more laser array pattern geometries. A first ultrasonic wave of the narrowband ultrasonic waves generated by the first laser array pattern may have first set of frequency components of the harmonic frequency components. A second ultrasonic wave of the narrowband ultrasonic waves generated by the second laser array pattern may have second set of frequency components of the hannonic frequency components. The first ultrasonic wave generated by the first laser array pattern and the second ultrasonic wave generated by the second laser array pattern may interact simultaneously to form the combined harmonic frequency components.

[0031] In various embodiments, the optical system 204 may be an interferometry -based optical path setup with a beam expander lens. In various embodiments, the optical system 204 may include a deflecting mirror configured to deflect the first sub-beam The optical system 204 may also include a first beam expander arranged such that the deflected first sub-beam passes through the first beam expander. The optical system 204 may additionally include a firstoptical subsystem configured to generate the first laser array pattern on the battery or the battery component based on the deflected and expanded first sub-beam. The first optical subsystem may include a first beam splitter configured to separate the deflected and expanded first subbeam into two daughter beams, a first cylindrical convex lens, and a first pair of mirrors configured to direct the two daughter beams to the first cylindrical convex lens such that the two daughter beams form the first laser array pattern via interference effects. The optical system 204 may additionally include an optical prism to modify a beam shape of the second sub-beam. The optical system 204 may further include a second beam expander arranged such that the modified second sub-beam passes through the second beam expander. The optical system 204 may also include a second optical subsystem configured to generate the second laser array pattern on the battery or the battery component based on the modified and expanded second sub-beam. The second optical subsystem may include a second beam splitter configured to separate the modified and expanded second sub-beam into two further daughter beams, a second cylindrical convex lens, and a second pair of mirrors configured to direct the two further daughter beams to the second cylindrical convex lens such that the two further daughter beams form the second laser array pattern via interference effects.

[0032] In various embodiments, both the harmonic frequency components and the combined frequency harmonic components may be measured or sensed. In various embodiments, the harmonic frequency components measured or sensed may be the first set of frequency components resulting from self-interaction of the first ultrasonic wave or the second set of frequency components resulting from self-interaction of the second ultrasonic wave.

[0033] In various embodiments, one sub-beam selected from a group consisting of the first sub-beam and the second sub-beam may be blocked such that a laser array pattern of the one or more laser array pattern geometries, the laser array pattern generated by a remaining unblocked sub-beam of the group consisting of the first sub-beam and the second sub-beam, on the batteryor the battery component is configured to generate the narrowband ultrasonic wave with the harmonic frequency components resulting from self-interaction of the narrowband ultrasonic wave.

[0034] In various embodiments, the system may also include a scanning stage to move the pulsed laser source, the probe device, or the battery or the battery component.

[0035] Various embodiments may possess the capability to gather information on various aspects including electrode thickness, porosity, temperature, defects, etc. Various embodiments may also measure the state of charge (SOC) and the state of health (SOH) of the battery or the battery component.

[0036] Various embodiments may employ a non-contact optical laser approach for ultrasonic wave generation, which may be more suitable for detecting manufacturing defects in batteries or battery components during production line operations as compared to contact-based approaches. Various embodiments may have less constraints on spatial resolution compared to use of contact transducers. Various embodiments may be less affected by environmental factors like temperature and humidity as compared to fiber optic sensors (FOS). Various embodiments may not require prior knowledge of the resonance modes of the battery or battery component to generate narrowband ultrasonic waves. Various embodiments may provide frequency control in narrowband ultrasound generation to obtain nonlinear ultrasound parameters for battery or battery component inspection.

[0037] FIG. 3 shows a general illustration of a method of forming a system for non-contact inspection of a battery or a battery component according to various embodiments The method may include, in 302, providing a pulsed laser source configured to generate a pulsed laser beam. The method may also include, in 304, arranging or forming an optical system configured to generate one or more laser array pattern geometries on the battery or the battery component based on the pulsed laser beam using non-polarization optics, thereby generating narrowbandultrasonic waves in a desired wave propagation direction The method may further include, in 306, providing or forming a probe device configured to measure or sense harmonic frequency components resulting from self-interaction of a narrowband ultrasonic wave in the presence of a defect of the battery or the battery component and / or combined harmonic frequency components resulting from mutual interaction of two narrowband ultrasonic waves in the presence of the defect of the battery or the battery component.

[0038] In other words, various embodiments may relate to a method of forming a system for non-contact inspection of a battery or a battery component (alternatively referred to as noncontact inspection system). The method may include providing a pulsed laser source, providing or forming an optical system configured to generate one or more laser array pattern geometries on the battery or the battery component based on the pulsed laser beam emitted by the pulse laser source, thereby producing narrowband ultrasonic waves, and providing or forming a probe device configured to sense / measure harmonic frequency components and / or combined harmonic components. The harmonic frequency components may be generated from self interaction of a narrowband ultrasonic wave (of the narrowband ultrasonic waves generated by the one or more laser array pattern geometries) in the presence of a defect present in the battery or the battery component. The combined harmonic components may be generated from mutual interaction of two narrowband ultrasonic waves (of the narrowband ultrasonic waves generated by the one or more laser array pattern geometries) in the presence of the defect present in the battery or the battery component.

[0039] For avoidance of doubt, FIG. 3 is intended to illustrate various steps of a method of forming a system according to various embodiments, and is not intended to limit the sequence of the various steps. For instance, step 302 may occur before, after or at the same time as step 304.

[0040] Tn various embodiments, the method may further include providing a chamber for holding the battery or the battery component, the chamber having optical windows. The pulsed laser source, the probe device and the optical system may be provided external to the chamber.

[0041] FIG. 4 shows a general illustration of a method of non-contact inspection of a battery or a battery component according to various embodiments. The method may include, in 402, generating a pulsed laser beam using a pulsed laser source such that one or more laser array pattern geometries are generated on the battery or the battery component based on the pulsed laser beam using non-pol arization optics, thereby generating narrowband ultrasonic waves in a desired wave propagation direction. The method may also include, in 404, measuring or sensing harmonic frequency components resulting from self-interaction of a narrowband ultrasonic wave in the presence of a defect of the battery or the battery component and / or combined harmonic frequency components resulting from mutual interaction of two narrowband ultrasonic waves in the presence of the defect of the battery or the battery component using a probe device.

[0042] In other words, various embodiments may relate to a method of non-contact inspection of a battery or a battery component, i.e., operating the non-contact inspection system as described herein for non-contact inspection of a battery or a battery component.

[0043] In various embodiments, both the harmonic frequency components and the combined harmonic frequency components may be measured or sensed.

[0044] In various embodiments, the method may further include determining thermal runaway of the battery or the battery component or a defect of the battery or the battery component based on the harmonic frequency components and the combined harmonic frequency components.

[0045] In various embodiments, the probe device may be a continuous laser beam system. In various embodiments, the harmonic frequency components or the combined harmonicfrequency components may be measured or sensed via a probe laser beam generated by the continuous laser beam system. The probe laser beam may be provided or projected onto the surface of the battery or the battery component to measure or sense the harmonic frequency components or the combined harmonic frequency components. The probe laser beam may be irradiated onto a circular spot on the surface of the battery or the battery component.

[0046] In various embodiments, the probe laser beam may be irradiated onto a circular spot of the battery or the battery component.

[0047] In various embodiments, the one or more laser array pattern geometries may be selected from a group consisting of linear array patterns, circular array patterns and arc array patterns.

[0048] In various embodiments, the nonlinear narrowband ultrasonic waves may be measured via pulse-echo, pitch-catch or through-transmission methods. The harmonic frequency components and / or the combined harmonic frequency components may be measured via the pulse-echo, pitch-catch or through-transmission methods.

[0049] In various embodiments, the pulsed laser beam, the probe device or the battery or the battery component may be moved along any one of three axes to perform scanning of the battery or the battery component.

[0050] In various embodiments, the scanning of the battery or the battery component may be performed using a C -scanning mode or a B-scanning mode.

[0051] In various embodiments, the method may further include providing data related to the nonlinear narrowband ultrasonic waves into a pre-trained machine learning model to output linear ultrasonic features and nonlinear ultrasonic features for evaluating or estimating degradation or failure of the battery or the battery component.

[0052] Various embodiments may relate to a non-contact, in-situ and in-line non-destructive evaluation (NDE) solution for inspection of batteries or battery components using nonlinearlaser ultrasonics. Various embodiments may relate to a non-contact inspection system, which may help to ensure the safety, reliability, and lifetime of batteries in industrial environments. The proposed NDE system may also offer significant advantages with its ability to both produce and detect narrowband nonlinear ultrasonic waves. Tunable narrowband ultrasonic waves with different frequencies may provide deep penetration, enabling thorough inspection of multiple layers such as electrodes, anodes, and separators to identify interfacial defects effectively. By covering a wide range of frequencies, the NDE system may allow comprehensive defect detection to address various defect types and sizes. Narrowband waves may focus on specific layers for detailed analysis. Narrowband frequency may further enhance the resolution, which may be particularly important for detecting small critical defects.

[0053] FIG. 5A shows a schematic of a system for non-contact inspection of a battery or a battery component 508 according to various embodiments. The system may include a pulsed laser source 502 and a probe device 506, which may be a continuous laser beam system or source. The system may also include a designed optical system 504. The system may also include a chamber 510, which may be an explosive proof chamber. While FIG. 5A shows the pulsed laser source 502 and the probe device 506 are outside of the chamber 510 while the optical system 504 is within the chamber 510, in various embodiments, the pulsed laser source 502, the probe device 506 and the optical system 504 may be provided external to the chamber 510. The battery or a battery component 508 may be arranged within the chamber 510. The optical system 504 may be placed outside of the chamber 510 with the pulsed laser source 502 and the probe device 506 to protect them from thermal runways (e g., explosions). The system may also include a digital oscilloscope 512. The digital oscilloscope 512 may be connected to the pulsed laser source 502 and the probe device 506 (i.e., the continuous laser beam system or source). In various embodiments, the pulsed laser source 510 may generate a pulsed laser beam (e.g., of a wavelength of about 1064 nm), while the continuous laser beam system or source506 may generate a probe laser beam 518 (e g., of a wavelength of about 532 nm). A line-of-sight may need to be secured so that the laser beams can always access the target spots. The chamber 510 may include optical window 512a to allow laser beam(s) from the pulsed laser source 502 or the optical system 504 to pass through. The optical system 504 may generate one or more laser array pattern geometries 514 on the battery or the battery component 508. The one or more laser array pattern geometries 514 may be generated using non-polarization optics of the optical system 504, and may in turn generate harmonic components and combined harmonic components 516. The optical system 504 may form various laser array pattern geometries 514, e.g., linear array patterns, circular array patterns and arc array patterns, and may generate narrowband ultrasonic waves in a desired wave propagation direction by controlling the orientation of the laser array pattern geometries 514. The narrowband ultrasonic waves may be excited by the thermoelastic effect and may propagate through the battery or the battery component 508, before being measured, sensed or collected by the probe laser beam 518 generated by the continuous laser beam system or source 506. The chamber 510 may also include optical window 512b to allow the probe laser beam 518 from the continuous laser beam system or source 506 to pass through. Using the probe laser beam 518, ultrasonic signals (i.e., harmonic components and combined harmonic components 516) may be converted from mechanical vibrations to electrical signals, which may be detected or stored using the digital oscilloscope 512. The non-contact inspection system may be synchronized with the software during the battery operation to collect data in real-time. The non-contact inspection system may also utilize narrowband frequency ultrasonic waves to detect defects such as porosity, gas formation, etc., in battery components by analyzing the nonlinear ultrasonic frequencies. Furthermore, experiments on batteries under various operating conditions (e g., fast charging) can be conducted.

[0054] The non-contact inspection system may be capable of performing both nonlinear wave mixing and second harmonic generation as illustrated in FIG. 5B. FIG. 5B shows (a) nonlinear wave mixing by the optical system 504 according to various embodiments, and (b) nonlinear harmonic generation by one arm of the optical system 504 according to various embodiments. In (a), the laser beam 520 (from the pulsed laser source 502) and having a suitable wavelength, e g., 1064 nm, may pass through a beam splitter 522 to split into two sub-beams, i.e., a first sub-beam 524a and a second sub-beam 524b. The first sub-beam 524a and the second sub-beam 524b may have equal energy. The first sub-beam 524a may be deflected by a deflecting mirror 526. An optical prism 528 may be used to alter the beam shape (e.g., from circular to square) of the incident laser beam, i.e., the second sub-beam 524b. Utilizing the designed optical system 504, the circular first sub-beam 524a may produce narrowband ultrasonic frequency at fi, whereas the square second sub-beam 524b may produce narrowband ultrasonic frequency at £2. The first sub-beam 524a may pass through a first beam expander 530a, while the second sub-beam 524b may pass through a second beam expander 530b. The first sub-beam 524a may be separated or divided by a first beam splitter 532a into two daughter beams 534a, 534b The first daughter beam 534a may be guided toward the surface of the battery or a battery component 508 by mirror 536a. Meanwhile, the second daughter beam 534b may be reflected off the adjustable mirror 536b, which may allow for precise tilting, to converge with the first daughter beam 534a on the surface of the battery or a battery component 508. After passing through the first cylindrical convex lens 538a, two identical daughter beams 534a, 534b may interfere with each other to produce a first laser array pattern (e g., circular array pattern) on the surface of the battery or a battery component 508. This laser array pattern with an ultrasonic frequency of fi may be formed using various optical elements 536a, 536b, 538a. The designed optical system 504 may enable the formation of laser array patterns on the surface of the battery or a battery component 508, which may be oriented substantiallyperpendicular to the plane of propagation of the beams. Similarly, the second sub-beam 524b traveling through second beam expander 530b may pass through the second beam splitter 530b to split into two identical daughter beams 534c, 534d. The daughter beams 534c, 534d may be directed respectively by mirrors 536c, 536d to the second cylindrical convex lens 538b, such that the daughter beams 534c, 534d may interfere with each other to produce a second laser array pattern (e g., linear array pattern) on the surface of the battery or a battery component 508. This laser array pattern with an ultrasonic frequency of fz may be formed using various optical elements 536c, 536d, 538b. By using appropriate optical lenses such as concave or convex lenses, a laser beam may be focused in a way that produces arc-shaped array patterns.

[0055] In (b), the laser beam / light is blocked from one arm of the optical system 504. The laser beam 524c may pass through the beam expander 530b. The expanded laser beam 524c may then be divided into daughter beams 534e, 534f by beam splitter 532b. The daughter beams 534e, 534f may be directed respectively by mirrors 536c, 536d to the second cylindrical convex lens 538b, such that the daughter beams 534e, 534f may interfere with each other to produce a laser array pattern (e g., linear array pattern) on the surface of the battery or a battery component 508

[0056] FIG. 5C shows some possible laser array pattern geometries according to various embodiments. The laser array pattern geometries may be linear array patterns, circular array patterns or arc array patterns.

[0057] Various embodiments may produce narrowband ultrasonic waves with a signal-to-noise ratio (SNR) higher than that achieved by existing methods such as slit masks. The designed optical system 504 may include beam expanders 530a, 503b to generate narrowband ultrasonic waves on the surface of the battery or a battery component 508. Here, beam expanders 530a, 530b may be used to adjust the size of the laser array patterns. Consequently, the optical system 504 may enable users to adjust the input frequency for ultrasonic waves,reaching mega-Hertz (MHz) frequencies and creating micrometers (pm)-scale wavelengths. To enhance the defect detection capabilities, various array patterns such as line array, arc array, and circular array may be generated by the designed optical system 504.

[0058] The laser-induced ultrasonic waves may be generated as a result of the thermal elastic effects of laser heat application and propagated through the battery or battery component 508, where the signal may be finally collected by a continuous laser beam emitted by a probe. The ultrasonic waves may cause surface displacements as they pass, and the phase of the reflected continuous laser beam may be changed by these surface displacements, and the change in the phase of the reflected continuous laser beam may be measured by the detector in the probe. Accordingly, ultrasonic signals may be converted from mechanical vibrations to electrical signals, which may be stored using a digital oscilloscope 512. A scanning stage was introduced in the system to reconstruct ultrasonic wave propagation images by scanning with either an excitation laser or a sensing laser. A computer was used to control the movement of the displacement stage and capture signals from the digital oscilloscope 512 with automatic scanning software. Various embodiments may employ a nanosecond / picosecond pulse laser to generate ultrasonic waves with a frequency of up to MHz. To accelerate the inspection speed, the critical measurement points and areas in the battery or battery component 508 may be identified by developing numerical simulation models.

[0059] Throughout the charge and discharge cycles of the cell, the mechanical properties such as modulus, Poisson’s ratio and density may undergo changes due to the lithiation and de-lithiation processes. Tn ultrasonic testing, the stress wave generated by ultrasonic transducer propagates through the cell thickness, carrying information about the material properties and internal structural changes Correlations can be established between the State-of-Charge (SOC) or State-of-Health (SOH) and linear ultrasonic features such as amplitude, wave attenuation and time of flight (TOF). These features are often combined in practice to improve the accuracyof SOC or SOH estimation. However, for effective cell state estimation, it may be crucial to have linear ultrasonic features that exhibit a linear relationship with the SOC or SOH. Studies have shown that the TOF and signal amplitude do not exhibit a perfect linear relationship with cell state, particularly below 20% SOC, and hysteresis behavior is observed during charge and discharge processes. This behavior may indicate that the same SOC can result in significantly different linear ultrasonic feature values during battery charging and discharging, leading to a notable margin of error in the SOC or SOH estimation. In contrast, nonlinear ultrasonic methods may assume a nonlinear relationship, generating higher harmonics and other nonlinear effects due to the interaction between ultrasonic waves and the material. Nonlinear ultrasonic methods may offer improved sensitivity to microstructural changes and defects, making them a popular choice for microstructural characterization and damage assessment. A battery or cell is a complex system characterized by high acoustic nonlinearity and significant microstructural changes during operation. This may necessitate the use of nonlinear ultrasonic features such as second and third harmonic frequencies to effectively detect the changes occurring within the cell as it charges and discharges and defects accurately. Unlike linear ultrasonics, battery defects may cause changes in both the amplitude and frequency of the output ultrasonic signal, leading to deviations from the input ultrasonic signal. However, the current linear and nonlinear ultrasonic methods rely on contact piezoelectric probes. These methods typically require a solid connection between the probes and the battery being tested, as well as the use of a liquid coupling agent for the detection process. In addition, these approaches are limited in terms of accessibility and spatial resolution for the inspection of battery safety.

[0060] FIG. 6A illustrates nonlinear laser ultrasonics with narrowband frequencies on a defective cell according to various embodiments. The top portion of FIG. 6A shows two laser array patterns focused onto a cell 616 to respectively generate narrowband ultrasonic frequencies fi and _ / j, as well as the corresponding plot of amplitude as a function of frequency.1The ideal results of the cell 616 may only include the responses at input frequencies fi and f2. During the battery charging or discharging processes (nonlinear), or when there are structural changes such as defects, nonlinear components such as combined harmonic frequency components with frequencies / .j and / ; 12 may be produced. On the other hand, as shown in the bottom portion of FIG. 6 A, a laser array pattern focused onto the cell 616 may generate harmonic frequency components 2 / and 3 / of the input frequency /

[0061] FIG. 6B illustrates the principles used by the non-contact inspection system according to various embodiments. Various embodiments may utilize non-contact narrowband wave generation. Various embodiments may detect narrowband ultrasonic waves excited for non-contact inspection. Fixed frequencies may target specific layers for detection of defects, while variable frequencies may scan multiple layers for detection of a wide range of defects. Various embodiments may utilize combined harmonic frequency components (i.e., mixed components) and harmonic frequency components (i.e., nonlinear harmonic components) for improving accuracy of battery inspection. Various embodiments may be used for both in-situ and in-line inspections.

[0062] FIG. 7 shows a schematic illustrating a linear laser array pattern and the spatial bandwidth of the linear laser array pattern according to various embodiments. The spatial bandwidth of the laser array pattern may be the narrowband ultrasonic frequency. As shown in FIG. 7, the laser array pattern may include 7 elements with a defined pitch between neighboring elements. The laser array pattern may result in the generation of a narrowband ultrasonic wave signal having a specific wavenumber and having a wavelength that matches the pitch. The width of the spatial spectrum and the peak position in the frequency can be adjusted by increasing the number of array elements and altering the pitch distance. Based on the interference principle, the intensity distribution of the laser array pattern may often be considered to be a cos2pattern. Thus, the spatial intensity distribution (In(x)) of the laser line array source can be written as<where Iois the maximum intensity of the laser beam, and D is the pitch distance, respectively. G and u are the standard deviation and mean, respectively. The pitch distance is calculated as follows:>where iaserand 9 are the wavelength of the laser beam and mirror angle, respectively. The acoustic nonlinearity parameters of the nonlinear components may be defined aswhere J41±2is the amplitude of the combined harmonic components at mixing frequencies fa ± fa. A±and A2are the amplitudes of the input waves fa and fa, respectively, ft* and ft denote the relative acoustic nonlinearity parameters of the combined harmonic and second harmonic components, respectively. J42and A? are the second harmonic and fundamental amplitudes of the received ultrasonic signals, respectively, y is the relative acoustic nonlinearity parameter of the third harmonic component.

[0063] FIG. 8 shows illustrations of various ultrasonic measurement strategies (a) pitchcatch, (b) pulse-echo and (c) through-transmission according to various embodiments. Various embodiments may employ or include various measurement methods such as pitch-catch, pulseecho and through-transmission as shown in FIG. 8. The laser excitation component 804 (i.e., component which generates the laser array pattern geometries for producing the narrowband ultrasonic waves in the battery or battery component 808) and the probe device 806 (i.e., a continuous laser beam system) may be used in these measurement methods. Nonlinear features (e.g., harmonics) may be extracted from ultrasonic data to evaluate the degradation and defectof the battery or battery component 808. Tn pulse-echo mode, laser excitation and laser detection may detect ultrasonic signal reflected from inside the battery or battery component 808. In the through-transmission mode, the laser excitation and laser detection may detect ultrasonic signal transmitted through the interior of the battery or battery component 808 as the laser excitation component 804 and the probe device 806 are positioned on opposite sides of the battery or battery component 808. Tn pitch-catch, the laser excitation component 804 and the probe device 806 may be positioned to detect ultrasonic signal throughout the battery or battery component 808 at some propagation distance. Different measurement methods may enhance defect detection by targeting specific layers (pulse-echo), enabling online monitoring (pitch-catch), or identifying large defects with significant attenuation (through-transmission). The effectiveness of the nonlinear features in terms of the accuracy of the cell defect measurement and the probability of early failure detection was investigated. Internal states such as SOC were estimated from the linear and nonlinear ultrasonic responses. Similar approaches can be used for the estimation of dimensions such as electrode thickness, temperature and porosity. The key battery properties and dimensions may be monitored for the cell states. Various embodiments may estimate various internal battery states, such as the SOC, SOH, dendrite growth, gas accumulation, temperature, electrode thickness, and electrode stiffness. For instance, ultrasonic wave speed in a battery may be directly related to the SOC and temperature. In addition, by utilizing either pulse-echo or through-transmission, it may be possible to estimate the changes in electrode thickness due to aging by measuring the reflection time of waves from the bottom of the cell.

[0064] A surface of a battery (pouch cell) may be excited using the laser excitation component and nonlinear ultrasonic signals may be collected using the probe device during charging and discharging of the pouch cell. FIG. 9 A shows a plot of amplitude (in arbitrary units or a.u.) as a function of frequency (in kilo-hertz or kHz) illustrating the first cycle whenthe pouch cell is charged at 100% State-of-Charge (SOC) according to various embodiments. The changes in the amplitude of the second harmonic component around 0.6 MHz allow the evaluation of battery degradation. FIG 9B shows a plot of acoustic nonlinearity parameter as a function of the State-of-Charge (SOC) (in percent or %) of the pouch cell according to various embodiments. The acoustic nonlinearity parameter may exhibit a linear correlation with the SOC of the pouch cell. The relationship between SOC and acoustic nonlinearity may reveal important insights into internal material changes in the pouch cell. The dynamic expansion and contraction of the electrodes during the lithium-ion insertion and extraction processes may impose considerable stress and strain on the materials used in the pouch cell, leading to nonlinear effects. In addition, the behavior of ultrasonic waves can be altered by interactions between the electrodes and the electrolyte. As the battery is charged, the evolving chemical and mechanical interactions between these components can give rise to notable nonlinear acoustic effects. In essence, the variations in the acoustic nonlinearity parameters observed during the charging and discharging cycles of the battery may arise from intricate physical and chemical transformations within the battery materials. The nonlinear parameter may provide a distinct measurement that signifies these shifts in the acoustic nonlinearity parameter throughout the charge and discharge cycles. Accordingly, manufacturing defects or material degradation may be detected by monitoring acoustic nonlinearity. The interplay between mechanical strain and chemical alteration may underscore the complexity inherent in the performance of batteries, offering valuable insights into the behavior and stability of battery materials as they undergo continuous use. Various embodiments may ensure battery safety and reliability by preventing conditions like manufacturing defects that could lead to catastrophic failure.

[0065] FIG. 10A provides a summary of the shortcomings of conventional battery inspection methods. The conventional battery inspection methods include electrochemical impedance spectroscopy (EIS) method, X-ray method, open circuit method and contact ultrasonic methods.There is demand for the noncontact and online inspection system FIG. 10B shows a table comparing the non-contact inspection system according to various embodiments and various conventional battery inspection methods.

[0066] Various embodiments may be used for non-contact measurement. Various embodiments may be used for fast inspection, e g., in seconds per battery. Various embodiments may be sensitive to microstructural changes of batteries1

Claims

Claims1. A system for non-contact inspection of a battery or a battery component, the system comprising:a pulsed laser source configured to generate a pulsed laser beam;an optical system configured to generate one or more laser array pattern geometries on the battery or the battery component based on the pulsed laser beam using non-polarization optics, thereby generating narrowband ultrasonic waves in a desired wave propagation direction; anda probe device configured to measure or sense harmonic frequency components resulting from self-interaction of a narrowband ultrasonic wave in the presence of a defect of the battery or the battery component and / or combined harmonic frequency components resulting from mutual interaction of two narrowband ultrasonic waves in the presence of the defect of the battery or the battery component.

2. The system according to claim 1,wherein the one or more laser array pattern geometries are selected from a group consisting of linear array patterns, circular array patterns and arc array patterns.

3. The system according to claim 1 or claim 2,wherein the optical system is configured to control the wave propagation direction of the nonlinear narrowband ultrasonic waves by controlling an orientation of the one or more laser array pattern geometries.

4. The system according to any one of claims 1 to 3,wherein the pulsed laser source is a pulsed laser.

5. The system according to any one of claims 1 to 4,wherein the pulsed laser beam is a nanosecond pulsed laser beam or a picosecond pulsed laser beam.

6. The system according to any one of claims 1 to 5,wherein the probe device is a continuous laser beam system.

7. The system according to claim 6,wherein the continuous laser beam system is configured to generate a probe laser beam to measure or sense the nonlinear narrowband ultrasonic waves.

8. The system according to any one of claims 1 to 7,wherein the battery is a pouch battery cell, a prismatic battery cell or cylindrical battery cell; andwherein the battery component is a busbar or a cap.

9. The system according to any one of claims 1 to 8, further comprising:a chamber for holding the battery or the battery component, the chamber having optical windows;wherein the pulsed laser source, the probe device and the optical system are provided external to the chamber.

10. The system according to any one of claims 1 to 9,wherein the optical system is configured to form a first sub-beam and a second sub-beam based on the pulsed laser beam, the first sub-beam for generating afirst laser array pattern of the one or more laser array pattern geometries, and the second sub-beam for generating a second laser array pattern of the one or more laser array pattern geometries;wherein a first ultrasonic wave of the narrowband ultrasonic waves generated by the first laser array pattern has first set of frequency components of the harmonic frequency components;wherein a second ultrasonic wave of the narrowband ultrasonic waves generated by the second laser array pattern has second set of frequency components of the harmonic frequency components; andwherein the first ultrasonic wave generated by the first laser array pattern and the second ultrasonic wave generated by the second laser array pattern interact simultaneously to form the combined harmonic frequency components.

11. The system according to claim 10,wherein the optical system comprises:a deflecting mirror configured to deflect the first sub-beam;a first beam expander arranged such that the deflected first sub-beam passes through the first beam expander; anda first optical subsystem configured to generate the first laser array pattern on the battery or the battery component based on the deflected and expanded first sub-beam, wherein the first optical subsystem includes:a first beam splitter configured to separate the deflected and expanded first sub-beam into two daughter beams;a first cylindrical convex lens; anda first pair of mirrors configured to direct the two daughter beams to the first cylindrical convex lens such that the two daughter beams form the first laser array pattern via interference effects; andwherein the optical system also comprises:an optical prism to modify a beam shape of the second sub-beam; a second beam expander arranged such that the modified second subbeam passes through the second beam expander; and a second optical subsystem configured to generate the second laser array pattern on the battery or the battery component based on the modified and expanded second sub-beam, wherein the second optical subsystem includes:a second beam splitter configured to separate the modified and expanded second sub-beam into two further daughter beams; a second cylindrical convex lens; anda second pair of mirrors configured to direct the two further daughter beams to the second cylindrical convex lens such that the two further daughter beams form the second laser array pattern via interference effects.

12. The system according to claim 10 or claim 11,wherein both the harmonic frequency components and the combined frequency harmonic components are measured or sensed; andwherein the harmonic frequency components measured or sensed are the first set of frequency components resulting from self-interaction of the first ultrasonicwave or the second set of frequency components resulting from self-interaction of the second ultrasonic w ave.

13. The system according to any one of claims 10 to 12,wherein one sub-beam selected from a group consisting of the first sub-beam and the second sub-beam is blocked such that a laser array pattern of the one or more laser array pattern geometries, the laser array pattern generated by a remaining unblocked sub-beam of the group consisting of the first sub-beam and the second sub-beam, on the battery or the battery component is configured to generate the narrowband ultrasonic wave with the harmonic frequency components resulting from self-interaction of the narrowband ultrasonic wave.

14. The system according to any one of claims 1 to 13, further comprising:a scanning stage to move the pulsed laser source, the probe device, or the battery or the battery component.

15. A method of forming a system for non-contact inspection of a battery or a battery component, the method comprising:providing a pulsed laser source configured to generate a pulsed laser beam; arranging an optical system configured to generate one or more laser array pattern geometries on the battery or the battery component based on the pulsed laser beam using non-pol arization optics, thereby generating narrowband ultrasonic waves in a desired wave propagation direction; andproviding a probe device configured to measure or sense harmonic frequency components resulting from self-interaction of a narrowband ultrasonic wave in the presence of a defect of the battery or the battery component and / or combinedharmonic frequency components resulting from mutual interaction of two narrowband ultrasonic waves in the presence of the defect of the battery or the battery component.

16. The method according to claim 15, further comprising:providing a chamber for holding the battery or the battery component, the chamber having optical windows;wherein the pulsed laser source, the probe device and the optical system are provided external to the chamber.

17. A method of non-contact inspection of a battery or a battery component, the method comprising:generating a pulsed laser beam using a pulsed laser source such that one or more laser array pattern geometries are generated on the battery or the battery component based on the pulsed laser beam using non-polarization optics, thereby generating narrowband ultrasonic waves in a desired wave propagation direction; andmeasuring or sensing harmonic frequency components resulting from selfinteraction of a narrowband ultrasonic wave in the presence of a defect of the battery or the battery component and / or combined harmonic frequency components resulting from mutual interaction of two narrowband ultrasonic waves in the presence of the defect of the battery or the battery component using a probe device.

18. The method according to claim 17,wherein both the harmonic frequency components and the combined harmonic frequency components are measured or sensed.

19. The method according to claim 18, further comprising:determining thermal runaway of the battery or the battery component or a defect of the battery or the battery component based on the harmonic frequency components and the combined harmonic frequency components.

20. The method according to any one of claims 17 to 19,wherein the probe device is a continuous laser beam system; and wherein the harmonic frequency components or the combined harmonic frequency components are measured or sensed via a probe laser beam generated by the continuous laser beam system.

21. The method according to claim 20,wherein the probe laser beam is irradiated onto a circular spot of the battery or the battery component.

22. The method according to any one of claims 17 to 21,wherein the one or more l ser array pattern geometries are selected from a group consisting of linear array patterns, circular array patterns and arc array patterns.

23. The method according to any one of claims 17 to 22,wherein the nonlinear narrowband ultrasonic waves are measured via pulseecho, pitch-catch or through-transmission methods.

24. The method according to any one of claims 17 to 23,wherein the pulsed laser beam, the probe device or the battery or the battery component is moved along any one of three axes to perform scanning of the battery or the battery component.

25. The method according to claim 24,wherein the scanning of the battery or the battery component is performed using a C-scanning mode or a B-scanning mode.

26. The method according to any one of claims 17 to 25, further comprising:providing data related to the nonlinear narrowband ultrasonic waves into a pretrained machine learning model to output linear ultrasonic features and nonlinear ultrasonic features for evaluating or estimating degradation or failure of the battery or the battery component.

Images