An ultrasonic monitoring device for lithium-ion batteries

Abstract

The application discloses a lithium ion battery ultrasonic monitoring device, which comprises a fixed shell symmetrically arranged on the bottom surface of a lithium ion battery, wedge blocks respectively arranged in the fixed shell, ultrasonic transmitting crystals and ultrasonic receiving crystals respectively arranged on the inclined surfaces of the wedge blocks, the ultrasonic transmitting crystals are used for transmitting ultrasonic pulses, the ultrasonic pulses are incident on the bottom surface of the lithium ion battery at a certain angle, and are received by the ultrasonic receiving crystals after multiple reflections in the lithium ion battery, and a signal transceiving processing module is electrically connected with the ultrasonic receiving crystals, is used for carrying out empirical mode decomposition on the ultrasonic pulses received by the ultrasonic receiving crystals, and calculating a battery health state value. The application has the advantages of non-invasiveness, strong real-time performance, high accuracy, low cost and the like, and can effectively evaluate and warn the health state of the lithium ion battery.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, and specifically relates to an ultrasonic monitoring device for lithium-ion batteries. Background Technology

[0002] In electrochemical energy storage technology, lithium-ion batteries, as a core technology, possess advantages such as high energy density, long cycle life, and no memory effect, and are currently widely used in grid energy storage, new energy vehicles, and electronic devices. However, due to factors such as insufficient battery consistency and environmental abuse, batteries undergo continuous aging and degradation during service. If not detected and addressed in time, this can easily lead to thermal runaway accidents. Currently, traditional analytical methods based on battery parameters such as voltage, current, internal resistance, and temperature to predict battery aging and failure often cannot effectively assess the actual state of the battery and cannot effectively prevent thermal runaway accidents. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide an ultrasonic monitoring device for lithium-ion batteries to accurately assess the health status of lithium-ion batteries and improve the real-time early warning capability of lithium-ion batteries.

[0004] To solve the above-mentioned technical problems, the present invention provides an ultrasonic monitoring device for lithium-ion batteries, comprising:

[0005] A fixed outer casing symmetrically arranged on the bottom surface of the lithium-ion battery;

[0006] Wedges respectively installed inside the fixed housing;

[0007] An ultrasonic transmitting chip and an ultrasonic receiving chip are respectively installed on the inclined surface of the wedge; the ultrasonic transmitting chip is used to emit ultrasonic pulses, which are incident from the bottom surface of the lithium-ion battery at a certain angle, and are received by the ultrasonic receiving chip after multiple reflections inside the lithium-ion battery.

[0008] The signal transceiver processing module is electrically connected to the ultrasonic receiving chip and is used to perform empirical mode decomposition on the ultrasonic pulses received by the ultrasonic receiving chip to calculate the battery health status value.

[0009] Furthermore, the signal transceiver processing module is specifically used for:

[0010] Empirical mode decomposition is performed on the ultrasonic pulses received by the ultrasonic receiving chip to obtain the intrinsic mode functions (IMFs).

[0011] The energy of the ultrasonic pulse at the center frequency of the ultrasonic cell is calculated based on the intrinsic mode function (IMF).

[0012] The battery health factor is calculated based on the energy of the ultrasonic pulse and the probe spacing between the ultrasonic transmitting crystal and the ultrasonic receiving crystal.

[0013] The battery health status value is calculated based on the battery health factor and the initial battery health factor.

[0014] Furthermore, when the battery health status value is less than or equal to the first threshold, the lithium-ion battery is in an unhealthy state; when the battery health status value is greater than the first threshold and less than or equal to the second threshold, the lithium-ion battery is in a healthy state.

[0015] Furthermore, the battery health factor is calculated by dividing the energy of the ultrasonic pulse corresponding to the center frequency of the ultrasonic chip by the probe spacing between the ultrasonic transmitting chip and the ultrasonic receiving chip.

[0016] Furthermore, the battery health status value is calculated by dividing the battery health factor by the initial battery health factor.

[0017] Furthermore, the ultrasonic emitting crystal has an oblique incident probe, the angle between which is 15° to 45° with the bottom surface of the lithium-ion battery.

[0018] Furthermore, the probe spacing between the ultrasonic transmitting chip and the ultrasonic receiving chip satisfies the following relationship:

[0019]

[0020] Where L is the probe distance between the ultrasonic transmitting crystal and the ultrasonic receiving crystal, n is a positive integer, f is the frequency of the emitted ultrasonic pulse, θ is the incident angle, and v is the speed of sound.

[0021] Furthermore, when the battery health status value is less than or equal to the first threshold, n takes the value of 1 or 2; when the battery health status value is greater than the first threshold and less than or equal to the second threshold, n takes the value of a positive integer greater than or equal to 3.

[0022] Furthermore, the center frequencies of the ultrasonic transmitting chip and the ultrasonic receiving chip are between 50 kHz and 300 kHz.

[0023] Furthermore, the wedge is made of one or more of polystyrene, polycarbonate, nylon 1010, and polysulfone.

[0024] The present invention offers the following advantages: the ultrasonic monitoring device for lithium-ion batteries provided by this invention has the advantages of being non-invasive, highly real-time, accurate, and low-cost, and can effectively assess and provide early warnings of the health status of lithium-ion batteries. This device utilizes intrinsic mode functions to monitor and analyze ultrasonic waves of specific frequencies inside the battery, obtaining more detailed and accurate battery status information, avoiding errors and blind spots present in traditional parameter analysis methods, and effectively reducing the risk of battery thermal runaway. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram of the structure of an ultrasonic monitoring device for lithium-ion batteries according to an embodiment of the present invention. Detailed Implementation

[0027] The following description of the embodiments is taken with reference to the accompanying drawings, which illustrate specific embodiments in which the invention can be implemented.

[0028] During the charge and discharge cycle of a battery, its solid electrolyte interface film will continuously grow, and the electrolyte will gradually be lost. The interface acoustic impedance caused by the loss of the electrolyte interface film or electrolyte will change. The interface evolution of battery aging will cause the acoustic signal to be attenuated to varying degrees. Therefore, the internal aging state of the battery can be evaluated by acoustic characteristic values.

[0029] Therefore, please refer to Figure 1 As shown, an embodiment of the present invention provides an ultrasonic monitoring device for lithium-ion batteries, comprising:

[0030] A fixed outer casing 7 symmetrically arranged on the bottom surface of the lithium-ion battery;

[0031] Wedges 6 are respectively installed inside the fixed housing 7;

[0032] An ultrasonic emitting crystal 8 and an ultrasonic receiving crystal 9 are respectively installed on the inclined surface of the wedge block 6; the ultrasonic emitting crystal 8 is used to emit ultrasonic pulses, which are incident from the bottom surface of the lithium-ion battery at a certain angle, and are received by the ultrasonic receiving crystal 9 after multiple reflections inside the lithium-ion battery.

[0033] The signal transceiver processing module is electrically connected to the ultrasonic receiving chip 9 and is used to perform empirical mode decomposition on the ultrasonic pulses received by the ultrasonic receiving chip 9 to calculate the battery health status value.

[0034] Specifically, taking a hard-shell lithium-ion battery 3 as an example, it has a positive electrode tab 1 and a negative electrode tab 2. An ultrasonic emitting crystal 8 serves as an ultrasonic emitting transducer, and an ultrasonic receiving crystal 9 serves as an ultrasonic receiving transducer. The ultrasonic emitting transducer and the ultrasonic receiving transducer are located on the same side of the bottom surface of the lithium-ion battery. A damping block 4 is provided on the inclined surface of the ultrasonic emitting crystal 8 and the ultrasonic receiving crystal 9 away from the wedge block 6 to increase the vibration damping of the crystal and absorb the ultrasonic waves emitted from the back of the crystal.

[0035] Both the ultrasonic transmitting chip 8 and the ultrasonic receiving chip 9 are connected to the wedge block 6 and assembled via the fixed housing 7. After the ultrasonic transmitting chip 8 emits an ultrasonic pulse, it is incident at a certain angle from the bottom surface of the hard-shell battery 3. After multiple reflections inside the battery, it is received by the ultrasonic receiving chip 9 and then transmitted to the signal transceiver processing module via the cable 5. The signal transceiver processing module performs empirical mode decomposition on the received ultrasonic pulse to obtain the intrinsic mode functions (IMFs).

[0036]

[0037] The signal obtained through mode decomposition has intrinsic mode function components whose frequencies decrease sequentially from high to low, and the frequency components within each frequency band are different. The original signal is the sum of all intrinsic mode components and the remainder term, i.e., x(t) is:

[0038]

[0039] Where, r n () represents the residual amount after decomposition, c i () represents the i-th eigenmode function component, from which the energy E(i) of the ultrasonic pulse corresponding to the center frequency of the ultrasonic cell can be obtained:

[0040]

[0041] Where T is the total number of sampling points;

[0042] Solve for the energy E of the ultrasonic pulse corresponding to the center frequency of the ultrasonic chip (i.e., the energy of a function corresponding to a certain eigenmode), and record the battery health factor when the probe spacing between the ultrasonic transmitting chip 8 and the ultrasonic receiving chip 9 is L. The initial health factor of the battery is denoted as δ0. The battery health state value is then calculated. And based on the calculated battery health status value, it determines whether the lithium-ion battery is healthy. Specifically: when At that time, the battery is unhealthy. At that time, the battery is in a healthy state.

[0043] In this embodiment, the length of the hard-shell lithium-ion battery 3 is greater than 60 cm. The ultrasonic emitting chip 8 has an oblique incidence probe, the angle between which is 15° to 45° with the bottom surface of the hard-shell lithium-ion battery 3.

[0044] Furthermore, the incident ultrasonic wave frequency f, incident angle θ, sound velocity v, and probe spacing L satisfy the following relationship: Where n is a positive integer, it can achieve the best ultrasonic propagation effect. The incident angle θ and the probe spacing L are adjustable, thus allowing the acquisition of defect information in multiple directions inside the battery.

[0045] As the battery health status decreases, the probe spacing L also decreases accordingly. The probe spacing L is related to the battery health status value. Satisfy the following relationship: when When n takes the value 1 to 2; when When n≥3.

[0046] Preferably, the center frequencies of the ultrasonic transmitting chip 8 and the ultrasonic receiving chip 9 are between 50 kHz and 300 kHz.

[0047] The material of wedge 6 is one or more of polystyrene, polycarbonate, nylon 1010, and polysulfone, which can be well matched with the acoustic impedance of the battery.

[0048] The invention is described in detail below using a rectangular hard-shell lithium iron phosphate battery from the same batch as an example. The battery's length, width, and thickness are 80 cm, 15 cm, and 3 cm, respectively. A type 1-3 composite ceramic sheet is used as the crystal material for the ultrasonic transducer, and the wedge 6 is made of polystyrene. The probe is placed on the bottom surface of the battery, with the angle between the incident sound wave and the bottom surface of the battery being 30°. The average sound velocity inside the battery is 1500 m / s, and the center frequency of the ultrasonic transducer is 100 kHz. Calculations show that the wavelength of the sound wave inside the battery is 15 mm.

[0049] When the sound path is an integer multiple of the wavelength, better sound signal reception can be achieved. This is based on the relationship between sound path and wavelength: The minimum probe spacing was calculated to be 12.99 mm. Ultrasonic signals were measured under different conditions, processed, and analyzed. The results are shown in the table below:

[0050]

[0051] As can be seen from the table above, the battery health status prediction results obtained by using the present invention are quite close to the actual battery health status, indicating that the present invention has high accuracy.

[0052] As can be seen from the above description, compared with the prior art, the beneficial effects of the present invention are as follows: The lithium-ion battery ultrasonic monitoring device provided by the present invention has the advantages of being non-invasive, highly real-time, highly accurate, and low-cost, and can effectively assess and warn of the health status of lithium-ion batteries. This device utilizes intrinsic mode functions to monitor and analyze ultrasonic waves of specific frequencies inside the battery, which can obtain more detailed and accurate battery status information, avoiding the errors and blind spots present in traditional parameter analysis methods, and effectively reducing the risk of battery thermal runaway.

[0053] The above description is merely a preferred embodiment of the present invention and should not be construed as limiting the scope of the invention. Therefore, any equivalent variations made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. A lithium-ion battery ultrasonic monitoring device, characterized in that, include: A fixed outer casing symmetrically arranged on the bottom surface of the lithium-ion battery; Wedges respectively installed inside the fixed housing; An ultrasonic transmitting chip and an ultrasonic receiving chip are respectively mounted on the inclined surface of the wedge. The ultrasonic transmitting chip emits ultrasonic pulses, which are incident from the bottom surface of the lithium-ion battery at a certain angle, and are received by the ultrasonic receiving chip after multiple reflections inside the lithium-ion battery. The ultrasonic transmitting chip has an oblique incident probe, the angle between which is within the range of the bottom surface of the lithium-ion battery. The center frequencies of the ultrasonic transmitting and receiving crystals are between 50kHz and 300kHz. The signal transceiver processing module is electrically connected to the ultrasonic receiving chip and is used to perform empirical mode decomposition on the ultrasonic pulses received by the ultrasonic receiving chip to obtain the intrinsic mode function (IMF); calculate the energy of the ultrasonic pulse at the center frequency of the ultrasonic chip based on the IMF; and calculate the battery health factor based on the energy of the ultrasonic pulse and the probe spacing between the ultrasonic transmitting chip and the ultrasonic receiving chip. The battery health status value is calculated based on the battery health factor and the initial battery health factor. The battery health factor is calculated by dividing the energy of the ultrasonic pulse corresponding to the center frequency of the ultrasonic chip by the probe spacing between the ultrasonic transmitting chip and the ultrasonic receiving chip.

2. The ultrasonic monitoring device for lithium-ion batteries according to claim 1, characterized in that, When the battery health status value is less than or equal to the first threshold, the lithium-ion battery is in an unhealthy state; when the battery health status value is greater than the first threshold and less than or equal to the second threshold, the lithium-ion battery is in a healthy state.

3. The ultrasonic monitoring device for lithium-ion batteries according to claim 1, characterized in that, The battery health status value is calculated by dividing the battery health factor by the battery initial health factor.

4. The ultrasonic monitoring device for lithium-ion batteries according to claim 1, characterized in that, The probe spacing between the ultrasonic transmitting chip and the ultrasonic receiving chip satisfies the following relationship: in, L The distance between the probes of the ultrasonic transmitting chip and the ultrasonic receiving chip is denoted as . It is a positive integer. For the frequency of the emitted ultrasonic pulse, For the angle of incidence, The speed of sound.

5. The ultrasonic monitoring device for lithium-ion batteries according to claim 4, characterized in that, When the battery health status value is less than or equal to the first threshold The value is 1 or 2; when the battery health status value is greater than the first threshold and less than or equal to the second threshold, Take a positive integer greater than or equal to 3.

6. The ultrasonic monitoring device for lithium-ion batteries according to claim 1, characterized in that, The wedge is made of one or more of polystyrene, polycarbonate, nylon 1010, and polysulfone.

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