Passive Wireless Detection Method and System for Battery Stress and Strain Based on SAW Resonator

Abstract

The present invention discloses a passive wireless detection method and system for battery stress and strain based on a SAW resonator. The method includes preparing a piezoelectric thin film on the metal shell of the battery; preparing a SAW resonator on the piezoelectric thin film; detecting the resonance frequency of the SAW resonator and characterizing the resonance frequency as battery stress and strain information; connecting the electrical lead-out of the SAW resonator to an antenna and transmitting a radio frequency signal containing the battery stress and strain information to a terminal device through the antenna, so that the terminal device can determine whether the battery is bulging according to the battery stress and strain information. The present invention can use a passive wireless SAW resonator to in-situ monitor the stress and strain generated by battery bulging, overcoming the defects of traditional battery bulging monitoring schemes that cannot provide quantitative stress and strain data, cannot perform real-time in-situ monitoring, and cannot prepare sensors in-situ, and meeting the requirement of passive wireless in-situ real-time monitoring of the stress and strain generated by battery bulging.

Description

Technical Field

[0001] The present invention relates to the technical field of battery detection, and particularly to a passive wireless detection method and system for battery stress and strain based on a SAW resonator. Background Art

[0002] As a common type of battery, lithium-ion batteries may experience bulging during use. Battery bulging may be caused by internal gas generation, pressure increase, or structural failure, etc., resulting in a decline in battery performance and even safety problems such as leakage and rupture. Therefore, it is of great significance to monitor the stress and strain parameters of the battery during cyclic charge and discharge in real time and evaluate the bulging state.

[0003] At present, the means for monitoring battery bulging mainly include the following: First, visual inspection, which judges whether bulging occurs by observing the shape change of the battery shell with the naked eye. This is a simple and intuitive method, limited to checking obvious bulging conditions and unable to provide quantitative data. Second, physical measurement, which uses tools such as a micrometer and a vernier caliper to measure the size change of the battery shell. This method can provide quantitative data, but each measurement requires disassembling the battery and manually performing contact measurement on the battery, and it is impossible to monitor the bulging phenomenon in real time in-situ. Third, with the help of externally installed sensors, sensors for monitoring strain are installed on the battery shell, and the bulging situation is judged by measuring the strain on the shell. Commonly used strain sensors include resistive, capacitive, and inductive strain sensors. These sensors can perform real-time bulging monitoring, but these sensors are generally active and wired, that is, these sensors need to be externally powered and require signal lines to transmit the strain information from the sensors to electronic devices. Moreover, installing these strain sensors on the battery shell usually involves operations such as drilling, which cannot achieve the purpose of in-situ sensor preparation. Therefore, there is an urgent need for a battery bulging monitoring method that can meet the requirements of passive wireless in-situ real-time monitoring. Summary of the Invention

[0004] The object of the present invention is to meet the requirement of passive wireless in-situ real-time monitoring of the stress and strain generated by battery bulging. To achieve the above object, the present invention provides a passive wireless detection method and system for battery stress and strain based on a SAW resonator.

[0005] In a first aspect, an embodiment of the present invention provides a passive wireless detection method for battery stress and strain based on a SAW resonator, including:

[0006] Preparing a piezoelectric thin film on the metal shell of the battery;

[0007] Preparing a SAW resonator on the piezoelectric thin film;

[0008] Detect the resonant frequency of the SAW resonator and characterize the resonant frequency as battery stress and strain information;

[0009] Connect the electrical lead-out of the SAW resonator to the antenna, and transmit the radio frequency signal containing the battery stress and strain information to the terminal device through the antenna, so that the terminal device determines whether the battery is bulged according to the battery stress and strain information.

[0010] Preferably, preparing a piezoelectric thin film on the metal casing of the battery includes:

[0011] Prepare a piezoelectric thin film on the metal casing of the battery by spin coating, and the piezoelectric thin film at least includes PVDF, PVDF-TrFE, ZnO and AlN.

[0012] Preferably, preparing the SAW resonator on the piezoelectric thin film includes:

[0013] Prepare the SAW resonator on the piezoelectric thin film by photolithography process.

[0014] Preferably, making the terminal device determine whether the battery is bulged according to the battery stress and strain information includes:

[0015] Judge whether the resonant frequency changes. If it changes, it is determined that the battery bulges.

[0016] Preferably, making the terminal device determine whether the battery is bulged according to the battery stress and strain information further includes:

[0017] Calculate the change amount of the resonant frequency;

[0018] Judge the bulging degree of the battery according to the change amount.

[0019] Preferably, judging the bulging degree of the battery according to the change amount includes:

[0020] If the change amount is higher than the preset threshold, it is determined that the bulging degree of the battery is serious, otherwise it is determined that the bulging degree of the battery is slight.

[0021] Preferably, judging the bulging degree of the battery according to the change amount further includes:

[0022] If the bulging degree is serious, replace the battery;

[0023] If the bulging degree is slight, change the charging strategy of the battery.

[0024] In a second aspect, an embodiment of the present invention further provides a passive wireless detection system for battery stress and strain based on a SAW resonator, including:

[0025] A piezoelectric thin film preparation module for preparing a layer of piezoelectric thin film on the metal shell of the battery;

[0026] A resonator preparation module for preparing a SAW resonator on the piezoelectric thin film;

[0027] A resonance frequency detection module for detecting the resonance frequency of the SAW resonator and characterizing the resonance frequency as battery stress and strain information;

[0028] A bulge detection module for connecting the electrical lead-out of the SAW resonator to the antenna and transmitting a radio frequency signal containing the battery stress and strain information to the terminal device through the antenna, so that the terminal device determines whether the battery bulges according to the battery stress and strain information.

[0029] Preferably, it further includes:

[0030] A bulge processing module for replacing the battery if the bulge degree is severe and replacing the charging strategy of the battery if the bulge degree is slight when the battery bulges.

[0031] Compared with the prior art, the battery stress and strain passive wireless detection method and system based on a SAW resonator in an embodiment of the present invention have the beneficial effects that: the stress and strain generated by the battery bulge can be in-situ monitored by using the passive wireless SAW resonator, overcoming the defects of the traditional battery bulge monitoring scheme that cannot provide quantitative stress and strain data, cannot perform real-time in-situ monitoring, and cannot prepare sensors in-situ, and meeting the requirement of passive wireless in-situ real-time monitoring of the stress and strain generated by the battery bulge. Description of the Drawings

[0032] Figure 1 is a schematic flow chart of a battery stress and strain passive wireless detection method based on a SAW resonator in an embodiment of the present invention;

[0033] Figure 2 is a schematic process flow chart of preparing a PVDF-TrFE thin film on the metal shell of the battery in an embodiment of the present invention;

[0034] Figure 3 is a schematic process flow chart of preparing a SAW resonator in an embodiment of the present invention;

[0035] Figure 4 is a schematic structural diagram of a SAW resonator in an embodiment of the present invention;

[0036] Figure 5 is a schematic diagram of S parameter definition in an embodiment of the present invention;

[0037] Figure 6It is a schematic structural diagram of a passive wireless detection system for battery stress and strain based on a SAW resonator according to an embodiment of the present invention. Detailed implementation manners

[0038] The following combines the accompanying drawings and embodiments to further describe in detail the specific implementation manners of the present invention. The following embodiments are used to illustrate the present invention, but are not used to limit the scope of the present invention.

[0039] In the description of the present invention, it should be understood that the term "SAW" is adopted in the present invention. The surface acoustic wave (SAW) is an elastic wave propagating along the surface of an object.

[0040] As Figure 1 shown, an embodiment of the present invention provides a passive wireless detection method for battery stress and strain based on a SAW resonator, including the steps of:

[0041] S1. Prepare a piezoelectric thin film on the metal shell of the battery;

[0042] Specifically, a piezoelectric thin film is prepared on the metal shell of the battery by spin coating. The piezoelectric thin film at least includes PVDF, PVDF-TrFE, ZnO, and AlN. In this embodiment, taking the organic piezoelectric thin film as an example, the process flow of preparing a PVDF-TrFE thin film on the metal shell of the battery by spin coating is as Figure 2 shown. Specifically: Add N,N-dimethylformamide (DMF) and acetone to a certain amount of PVDF-TrFE powder, heat and stir magnetically for a period of time to prepare a transparent and uniform PVDF-TrFE precursor solution. After spin coating the PVDF-TrFE precursor solution on the metal shell of the battery, it is dried at low temperature and annealed at high temperature to obtain a PVDF-TrFE thin film. The piezoelectric thin film has the characteristics of flexibility and is convenient to be prepared on the metal shell of any-shaped battery, which is beneficial to overcoming the defect that the traditional battery bulging monitoring scheme cannot be prepared in situ and monitored in situ.

[0043] S2. Prepare a SAW resonator on the piezoelectric thin film;

[0044] Specifically, a SAW resonator is prepared on the piezoelectric thin film by photolithography. The process flow of preparing a SAW resonator on the PVDF-TrFE thin film by photolithography in this embodiment is as Figure 3As shown, the specific process is as follows: Magnetron sputter metal aluminum on the PVDF-TrFE film, spin-coat photoresist on the aluminum film, expose the photoresist using ultraviolet light, and develop the photoresist using a developer to form a photoresist pattern. Etch the aluminum film not protected by the photoresist to form a metal pattern. After removing the photoresist, a SAW resonator composed of a PVDF-TrFE film, interdigital transducers, a reflection grating, and electrical leads is obtained. After completing the device preparation, since the PVDF-TrFE film has almost no piezoelectricity, it needs to be corona polarized to make it have strong piezoelectricity. The SAW resonator prepared based on the PVDF-TrFE film is as Figure 4 shown.

[0045] S3. Detect the resonance frequency of the SAW resonator and characterize the resonance frequency as battery stress-strain information;

[0046] Specifically, the sensing principle of the SAW resonator is as follows: This device has two sets of interdigital transducers, one for signal input and the other for signal output. The input signal is converted into SAW through the inverse piezoelectric effect and transmitted to the other set of interdigital transducers through the piezoelectric film, and then converted into an electrical signal output through the direct piezoelectric effect. By calculating the ratio of the signals, the reflection coefficient S 11 and the transmission coefficient S 21 can be obtained. These coefficients are called S-parameters and are specifically expressed as follows:

[0047]

[0048]

[0049] where a1 represents the incident voltage wave at the input end, b1 represents the voltage wave reflected by the reflection grating at the input end, a2 represents the voltage wave reflected by the reflection grating at the output end, b2 represents the outgoing voltage wave at the output end, and the definition of the S-parameter can be found in Figure 5 .

[0050] Furthermore, when the frequency is taken as the abscissa and the loss defined by the reflection coefficient S 11 and the transmission coefficient S 21 is taken as the ordinate, the abscissa corresponding to the lowest loss is the resonance frequency f of the SAW resonator, which is specifically expressed as follows:

[0051]

[0052] where v represents the sound velocity of the SAW resonator and λ represents the wavelength of the SAW resonator. To facilitate the quantitative representation of battery stress-strain information, the resonance frequency is characterized as battery stress-strain information.

[0053] S4. Connect the electrical leads of the SAW resonator to the antenna, and transmit the radio frequency signal containing the battery stress and strain information to the terminal device through the antenna, so that the terminal device can determine whether the battery is bulging according to the battery stress and strain information.

[0054] Connect the electrical leads of the SAW resonator with the antenna, and transmit the radio frequency signal containing the battery stress and strain information to the terminal device through the antenna, so that the terminal device can determine whether the resonance frequency has changed. If it has changed, it is determined that the battery is bulging. Further, calculate the change amount of the resonance frequency, and judge the degree of battery bulging according to the change amount: if the change amount is higher than the preset threshold, it is determined that the degree of battery bulging is serious, otherwise it is determined that the degree of battery bulging is slight; if the degree of bulging is serious, replace the battery, if the degree of bulging is slight, replace the charging strategy of the battery. The SAW resonator can transmit the radio frequency signal containing the stress and strain information through the antenna, and has the characteristic of not requiring an external power supply. In this embodiment, the terminal device can be a mobile phone, a computer, or a smart watch. The terminal device of this solution needs to have a signal receiving function and be able to perform information interaction. Therefore, the terminal device is not limited to the above several types, as long as the terminal device that meets the above functions can be used.

[0055] Specifically, the SAW resonator is fabricated on the metal shell of the battery. After manufacturing the battery with this shell, the stress and strain generated by the shell can be transmitted to the piezoelectric thin film. Due to the existence of stress and strain, on the one hand, the density and elastic constant of the piezoelectric thin film change, causing the sound velocity v of the SAW resonator to change, and on the other hand, the stress and strain cause the finger pitch of the interdigital transducer to change, that is, the wavelength λ of the SAW resonator to change. Therefore, the resonance frequency f of the SAW resonator also changes. The larger the change amount of f, the greater the stress and strain generated by the metal shell, and the greater the degree of battery bulging.

[0056] It can be understood that when no stress and strain are generated in the metal shell, f is a fixed value. In this embodiment, this value is set as x, with the unit of Hz. If the battery bulges, stress and strain are generated in the metal shell, resulting in f = x + Δx. Δx represents the change amount of f and has a linear relationship with stress and strain within a certain range. According to the size of Δx, the degree of battery bulging can be divided into two levels, namely slight and serious. When Δx > 40 kHz, it is determined that the degree of battery bulging is serious, otherwise it is determined that the degree of battery bulging is slight. When the degree of bulging is serious, take the measure of replacing the battery to prevent safety problems of the battery; when the degree of bulging is slight, take the measure of replacing the charging strategy to prevent the degree of battery bulging from becoming larger. In this embodiment, the preferably set preset threshold is 40 kHz, which can also be adaptively adjusted according to the monitoring requirements of battery bulging. If the monitoring requirements are higher, a smaller preset threshold can be set, and vice versa, the preset threshold can be adjusted accordingly.

[0057] An embodiment of the present invention provides a passive wireless detection method for battery stress and strain based on a SAW resonator. This method uses a passive wireless SAW resonator to in-situ monitor the stress and strain generated by battery swelling, overcoming the defects of traditional battery swelling monitoring schemes that cannot provide quantitative stress and strain data, cannot perform real-time in-situ monitoring, and cannot prepare sensors in-situ, meeting the requirement for passive wireless in-situ real-time monitoring of the stress and strain generated by battery swelling.

[0058] As Figure 6 shown, based on the above passive wireless detection method for battery stress and strain, an embodiment of the present invention also provides a passive wireless detection system for battery stress and strain based on a SAW resonator, including:

[0059] A piezoelectric film preparation module 1 for preparing a layer of piezoelectric film on the metal casing of the battery;

[0060] A resonator preparation module 2 for preparing a SAW resonator on the piezoelectric film;

[0061] A resonance frequency detection module 3 for detecting the resonance frequency of the SAW resonator and characterizing the resonance frequency as battery stress and strain information;

[0062] A swelling detection module 4 for connecting the electrical lead-out of the SAW resonator to the antenna and transmitting a radio frequency signal containing battery stress and strain information to a terminal device through the antenna, so that the terminal device can determine whether the battery is swollen according to the battery stress and strain information;

[0063] A swelling processing module 5 for, when the battery is swollen, replacing the battery if the swelling degree is severe, or replacing the charging strategy of the battery if the swelling degree is slight.

[0064] It should be noted that each module in the above passive wireless detection system for battery stress and strain based on a SAW resonator can be implemented in whole or in part by software, hardware, and their combination. The above modules can be embedded in or independent of a processor in a computer device in hardware form, or stored in a memory in a computer device in software form, so that the processor can call and execute the operations corresponding to each of the above modules. For the specific limitations of a passive wireless detection system for battery stress and strain based on a SAW resonator, refer to the limitations of a passive wireless detection method for battery stress and strain based on a SAW resonator in the above text. The two have the same functions and effects and will not be elaborated here.

[0065] In summary, the battery stress and strain passive wireless detection method and system according to an embodiment of the present invention can use a passive wireless SAW resonator to in-situ monitor the stress and strain generated by battery swelling, overcoming the defects of traditional battery swelling monitoring schemes that cannot provide quantitative stress and strain data, cannot perform real-time in-situ monitoring, and cannot prepare sensors in-situ, and meeting the requirement of passive wireless in-situ real-time monitoring of the stress and strain generated by battery swelling.

[0066] Each embodiment in this specification is described in a progressive manner. For parts that are the same or similar in each embodiment, reference can be made to each other. Each embodiment focuses on the differences from other embodiments. In particular, for the system embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and reference can be made to the partial description of the method embodiment for the relevant parts. It should be noted that the technical features of the above embodiments can be combined arbitrarily. For the sake of concise description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope recorded in this specification.

[0067] The above is only the preferred embodiment of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the technical principle of the present invention, several improvements and substitutions can be made, and these improvements and substitutions should also be regarded as the protection scope of the present invention.

Claims

1. A passive wireless detection method for battery stress and strain based on SAW resonators, characterized in that Including: Preparing a piezoelectric thin film on the metal shell of the battery; Preparing a SAW resonator on the piezoelectric thin film; Detecting the resonance frequency of the SAW resonator and characterizing the resonance frequency as battery stress and strain information; Connecting the electrical lead-out of the SAW resonator to the antenna and transmitting a radio frequency signal containing battery stress and strain information to the terminal device through the antenna, so that the terminal device determines whether the battery bulges according to the battery stress and strain information; The preparing a piezoelectric thin film on the metal shell of the battery includes: Preparing a piezoelectric thin film on the metal shell of the battery by spin coating, and the piezoelectric thin film at least includes PVDF, PVDF-TrFE, ZnO and AIN; The enabling the terminal device to determine whether the battery bulges according to the battery stress and strain information includes: Judging whether the resonance frequency changes. If it changes, it is determined that the battery bulges; The enabling the terminal device to determine whether the battery bulges according to the battery stress and strain information further includes: Calculating the change amount of the resonance frequency; Judging the bulging degree of the battery according to the change amount.

2. The battery stress and strain passive wireless detection method according to claim 1, characterized in that, The preparing a SAW resonator on the piezoelectric thin film includes: Preparing a SAW resonator on the piezoelectric thin film by photolithography process.

3. The battery stress and strain passive wireless detection method according to claim 1, wherein The judging the bulging degree of the battery according to the change amount includes: If the change amount is higher than a preset threshold, determining that the bulging degree of the battery is serious, otherwise determining that the bulging degree of the battery is slight.

4. The battery stress and strain passive wireless detection method according to claim 3, wherein The judging the bulging degree of the battery according to the change amount further includes: If the bulging degree is serious, replacing the battery; If the bulging degree is slight, replacing the charging strategy of the battery.

5. A passive wireless detection system for battery stress and strain based on SAW resonators, characterized in that, Including: A piezoelectric thin film preparation module for preparing a piezoelectric thin film on the metal shell of the battery; A resonator preparation module for preparing a SAW resonator on the piezoelectric thin film; A resonance frequency detection module for detecting the resonance frequency of the SAW resonator and characterizing the resonance frequency as battery stress and strain information; A bulging detection module for connecting the electrical lead-out of the SAW resonator to the antenna and transmitting a radio frequency signal containing battery stress and strain information to the terminal device through the antenna, so that the terminal device determines whether the battery bulges according to the battery stress and strain information; The preparing a piezoelectric thin film on the metal shell of the battery includes: Preparing a piezoelectric thin film on the metal shell of the battery by spin coating, and the piezoelectric thin film at least includes PVDF, PVDF-TrFE, ZnO and AIN; The enabling the terminal device to determine whether the battery bulges according to the battery stress and strain information includes: Judging whether the resonance frequency changes. If it changes, it is determined that the battery bulges; The enabling the terminal device to determine whether the battery bulges according to the battery stress and strain information further includes: Calculating the change amount of the resonance frequency; Judging the bulging degree of the battery according to the change amount.

6. The battery stress and strain passive wireless detection system according to claim 5, wherein, Further including: The bulging processing module is used to replace the battery when the battery bulges. If the degree of bulging is severe, the battery is replaced. If the degree of bulging is slight, the charging strategy of the battery is replaced.

Images