An in-situ detection device for lithium dendrite growth based on light scattering and its detection method

Abstract

The present invention discloses an in-situ detection device and a detection method for lithium dendrite growth based on light scattering. The in-situ detection device for lithium dendrite growth includes a data acquisition terminal, an alarm, and a light scattering detection unit. The light scattering detection unit includes a detection light source, a beam splitter, a reflector, an incident lens, a converging lens, a diaphragm, and a photodetector. The light scattering detection unit is encapsulated in a corrosion-resistant encapsulation box with an optical window and is embedded in the inner surface of the battery electrode in an array form. The present invention can be used for online detection of the growth of lithium dendrites inside various lithium-ion batteries. Compared with the prior art, the present invention has the characteristics of high measurement accuracy, direct in-situ measurement, high timeliness, etc., and can accurately detect lithium dendrites on the electrode surface without damaging the lithium-ion battery, thereby avoiding battery short-circuit safety accidents caused by lithium dendrites.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion batteries, and particularly relates to an in-situ detection device for lithium dendrite growth based on light scattering and a detection method thereof. Background Art

[0002] The electrochemical energy storage system is a key direction for China to achieve the transformation of new energy storage. With the development of lithium-ion battery technology, the lithium energy storage system has the potential to support the grid-connected operation of a high proportion of renewable energy. However, due to internal short circuits caused by mechanical abuse, electrical abuse, and thermal abuse of lithium-ion batteries, thermal runaway disasters are extremely likely to occur, thereby threatening the safety of personnel and property. Among them, due to over-discharge and over-charge of the battery, lithium dendrites are easily formed. When the lithium dendrites grow to a certain extent and pierce the separator, it is extremely easy to cause an internal short circuit in the lithium battery and trigger thermal runaway. Therefore, how to prevent and detect the growth of lithium dendrites in lithium-ion batteries is an important research direction for breaking through the whole-process safety technology, and it provides guarantee for improving the overall safety design of energy storage power stations and supporting the safe operation of large-scale energy storage power stations.

[0003] Existing lithium dendrite detection methods each have certain drawbacks. The patent with the authorization announcement number CN 213749640 U discloses a lithium dendrite detection device for a lithium-ion battery. The cavity design optimizes the process of cutting and encapsulating the battery electrode sheet before optical microscopy detection, but does not involve the optimization of lithium dendrite detection technology. The patent with the authorization announcement number CN 109387564 A discloses a method and device for detecting the formation of lithium dendrites based on the characteristic ultrasonic waveform image of a lithium-ion battery. This solution requires pre-acquiring the original state of the lithium-ion battery to be measured and the ultrasonic waveform information after lithium dendrites are generated inside. There are many prior conditions, and the judgment of waveform differences has a certain degree of subjectivity. The patent with the authorization announcement number CN 112730548 A discloses a method and system for on-line monitoring of lithium precipitation and lithium dendrite generation in a lithium-ion battery. This method establishes a connection between the terminal voltage of the battery and the lithium precipitation capacity. However, the indirect measurement principle is difficult to meet the measurement accuracy and response speed in the actual complex growth scenario of lithium dendrites. The patent with the authorization announcement number CN 114325509 A discloses an intelligent separator and detection method for detecting the growth of lithium dendrites. The separator at the location where lithium dendrites are generated will be magnetic. This method of detecting lithium dendrites through magnetic detection has good timeliness, but the impact of separator implantation on battery performance and the disturbance of environmental magnetism need to be further verified. The patent with the authorization announcement number CN 213455925 U discloses a lithium dendrite in-situ detection system based on an optical fiber sensor. By measuring the change in the surface stress of the electrode to infer the growth of lithium dendrites, this method still belongs to the form of indirect measurement, and in addition to the optical fiber system, a set of electrochemical test systems also need to be coupled, and the system complexity is relatively high. Currently, there are no reports on the research and technology of light scattering measurement technology in the monitoring of lithium dendrite generation inside lithium-ion batteries, but the micro light scattering measurement system has been preliminarily applied in some foreign fields such as the internal control of robotic arms. Summary of the Invention

[0004] In view of the above problems, the present invention proposes an in-situ detection device and detection method for lithium dendrite growth based on light scattering. By using the change in the scattered light signal at the measurement point to judge the growth of lithium dendrites, it has the characteristics of non-contact, on-line, high reliability, etc.

[0005] An in-situ detection device for lithium dendrite growth based on light scattering proposed by the present invention includes a data acquisition terminal, an alarm, and a light scattering detection unit placed inside a housing; the light scattering detection unit is arranged in an array form on the electrode surface and includes a first mirror, a detection light source, a second mirror, a beam splitter, a converging lens, a photodetector, an incident lens, and a diaphragm; among them, the detection light generated by the detection light source is divided into two beams by the beam splitter, enters the incident lens for focusing after the optical path is adjusted by the first mirror, irradiates the target measurement point between the electrodes, and then the scattered light generated by the electrolyte or lithium dendrite at the measurement point returns to the incident lens, passes through the second mirror to adjust the optical path, passes through the converging lens and the diaphragm, and finally enters the photodetector, and the scattered light intensity is converted into a voltage signal for output; the data acquisition terminal receives the voltage signal emitted after the photoelectric conversion of the light scattering detection unit, and when the intensity of the corresponding voltage signal surges, it judges that a lithium dendrite structure appears at the measurement point and outputs an alarm signal; the alarm receives the alarm signal sent by the data acquisition terminal and triggers an alarm.

[0006] Further, the housing includes an optical window and a packaging box. The optical window is made of quartz material, and the packaging box is made of corrosion-resistant material.

[0007] Further, the detection light source should be a continuous monochromatic light source, and the wavelength of the light wave should be in the visible light band.

[0008] Further, the beam splitter should be a polarization-maintaining beam splitter, and the splitting ratio should be 50:50. The center of the beam splitter and the center position of the first mirror need to be set on the same straight line.

[0009] Further, the first mirror and the second mirror should be polarization-maintaining mirrors and match the wavelength of the light source.

[0010] Further, the incident lens should be a low spherical aberration lens, and the in-focus points within the split beam spacing should be consistent. The optical axis of the converging lens and the optical axis of the incident lens should satisfy the reflection condition based on the second mirror.

[0011] Further, the center of the incident lens and the center position of the second mirror need to be set on the same straight line.

[0012] Further, the center of the diaphragm, the focus of the converging lens, and the measurement area should coincide.

[0013] Further, the photodetector and the data acquisition terminal should meet the wireless transmission protocol, including but not limited to LoRa, NB-IOT, ZigBee, WiFi, Bluetooth, etc.

[0014] Further, in the above in-situ detection device for lithium dendrite growth based on light scattering, when there are no lithium dendrites in the measurement area, the monitored voltage value of the data acquisition terminal is at a relatively low normal level. When lithium dendrites appear in the measurement area, since the reflectivity of lithium dendrites is much higher than that of the electrolyte, the number of photons on the surface of the photodetector surges, resulting in a significant increase in the voltage signal. Taking a 5-fold signal enhancement as the judgment basis, when the monitored voltage value at the terminal is higher than the alarm threshold, the alarm system will be triggered.

[0015] The present invention also proposes an in-situ detection method for lithium dendrite growth based on light scattering implemented by the above detection device, including the following steps: 1) Emission step, two detection lights from the detection light source in the light scattering detection unit converge and irradiate the target measurement point between the electrodes; 2) Reception step, the electrolyte or lithium dendrites at the measurement point generate scattered light, which is received by the photodetector and converted into a voltage signal; 3) Judgment step, the data acquisition terminal receives the voltage signal from the photodetector. When the signal intensity surges, it is judged that a lithium dendrite structure appears at the set measurement point, and the alarm is triggered to issue an alarm.

[0016] Further, the light beam emitted by the detection light source is divided into two detection lights by a beam splitter, and the two detection lights respectively form a measurement area by focusing through the incident lens. The light waves of the two detection lights irradiating the surface of the object to be measured can be described as:

[0017] E1(t) = E0 cos(ω1t + θ1)

[0018] E2(t) = E0 cos(ω2t + θ2)

[0019] In the formula, E is the amplitude intensity, ω is the frequency, and θ is the initial phase.

[0020] Further, the scattered light emitted by the electrolyte or lithium dendrites at the measurement point returns to the lens and then passes through the second mirror, and is collected by the converging lens and enters the photodetector. A diaphragm is set in front of the photodetector, and the diameter selection of the diaphragm follows the formula:

[0021]

[0022] In the formula, d p is the diameter of the aperture diaphragm, l1 is the distance between the diaphragm and the collecting lens, l2 is the distance between the measurement area and the collecting lens, and d c is the width of the measurement area facing the diaphragm.

[0023] Further, after the photodetector receives photons, a photocurrent is generated and converted into a voltage signal for output. The magnitude of the current is related to the light intensity amplitude:

[0024] I = [E1(t) + E2(t)] 2 .

[0025] Furthermore, the signal of the photodetector is remotely transmitted to the data acquisition terminal for monitoring and analysis. When there are no lithium dendrites at the measurement point, the scattered signal generated by the electrolyte is weak, and the signal intensity remains at a low level. The generation of lithium dendrites is accompanied by a sharp increase in the scattered signal. When an abnormal high-intensity signal is detected, the data acquisition terminal issues an alarm, achieving precise early warning of the generation of lithium dendrites before the battery electrodes are short-circuited.

[0026] Beneficial effects

[0027] In the present invention, the growth of lithium dendrites in a lithium-ion battery is directly measured based on the principle of light scattering. A non-contact optical path arrangement is adopted. The appearance of lithium dendrites at the measurement point replaces the electrolyte, which will cause a sharp increase in the reflectivity, thereby causing a rapid increase in the intensity of the scattered light. When the voltage signal output by the photodetector breaks through the monitoring threshold, an alarm is triggered. The monitoring process takes the appearance of lithium dendrites as the direct input, without introducing indirect variables, and the spatial position information of the growth of lithium dendrites can be obtained online, making this measurement method have great advantages over the above-mentioned other solutions in terms of timeliness, accuracy and reliability. Description of the drawings

[0028] Figure 1 It is a schematic structural diagram of an in-situ detection device for the growth of lithium dendrites based on light scattering in the embodiment of the present invention;

[0029] Figure 2 It is a schematic diagram of the internal optical path of the light scattering detection unit;

[0030] Figure 3 It is a schematic diagram of the housing of the light scattering detection unit.

[0031] Explanation of the marks in the figure: A is the positive electrode material; B is the lithium dendrite; C is the negative electrode material; 1 is the data acquisition terminal; 2 is the alarm; 3 is the light scattering detection unit; 3-1 is the first mirror; 3-2 is the detection light source; 3-3 is the second mirror; 3-4 is the beam splitter; 3-5 is the converging lens; 3-6 is the photodetector; 3-7 is the incident lens; 3-8 is the aperture; 3-9 is the optical window; 3-10 is the packaging box Specific embodiments

[0032] The present invention will be described in more detail below with reference to the drawings and in conjunction with the embodiments. It should be noted that, without conflict, the embodiments and features in the embodiments of the present invention can be combined with each other. It should be understood that the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative work shall fall within the protection scope of the present invention.

[0033] The specific examples are described as follows:

[0034] As Figure 1As shown in the figure, an in-situ detection device for lithium dendrite growth based on light scattering, the lithium dendrite detection device includes: a data acquisition terminal 1, an alarm 2, and a light scattering detection unit 3 (in the figure, A is the positive electrode material; B is the lithium dendrite; C is the negative electrode material). As Figure 2 shown, the light scattering detection unit 3 includes: a first mirror 3-1, a detection light source 3-2, a second mirror 3-3, a beam splitter 3-4, a converging lens 3-5, a photodetector 3-6, an incident lens 3-7, and a diaphragm 3-8. As Figure 3 shown, the light scattering detection unit 3 is placed in a housing, and the housing includes: an optical window 3-9 and a packaging box 3-10. Generally, quartz material is selected for the optical window, and the packaging box needs to be made of corrosion-resistant material.

[0035] The packaging box containing the light scattering detection unit 3 is embedded in the inner surface of the lithium-ion battery electrode in an array form, in direct contact with the electrolyte between the electrodes, and the optical measurement points cover more than 50% of the cross-sectional area between the two electrodes. The detection light source 3-2 generates a continuous laser beam with a wavelength of 532 nm. It is divided into two mutually perpendicular detection beams by a polarization-maintaining beam splitter 3-4 with a splitting ratio of 50:50. One of the beams passes through a polarization-maintaining mirror 3-1 with the same reflection wavelength of 532 nm and enters the incident lens 3-7 in parallel with the other beam. The incident lens uses a low-spherical aberration lens, which can ensure that the foci of the split beams with different spacings are consistent. The outgoing light is focused at the focal point of the incident lens as the lithium dendrite monitoring point. The objects at the measurement point include the electrolyte and the lithium dendrite. According to the different reflectivities, they will generate scattered light with different intensities. The reflectivity of the lithium dendrite is much higher than that of the electrolyte, and the intensity of the generated scattered light is also higher. After the scattered light at the measurement point returns along the optical path to the incident lens 3-7, it is reflected by the polarization-maintaining mirror 3-3, passes through the converging lens 3-5 and the diaphragm 3-8 and enters the photodetector 3-6. When arranging the entire optical path, it should be noted that: the center of the beam splitter 3-4 and the center position of the first mirror 3-1, the center of the incident lens and the center position of the second mirror 3-3 need to be set on the same straight line; the optical axis of the converging lens and the optical axis of the incident lens should meet the reflection condition based on the second mirror; the center of the diaphragm, the focal point of the converging lens, and the measurement area should coincide. The photodetector converts the light signals with different intensities into voltage signals in proportion and transmits them remotely to the data acquisition terminal. When there is no lithium dendrite in the measurement area, the monitoring voltage value of the data acquisition terminal is at a relatively low normal level. When a lithium dendrite appears in the measurement area, due to the much higher reflectivity of the lithium dendrite than that of the electrolyte, the number of photons on the surface of the photodetector surges, resulting in a significant increase in the voltage signal. Taking a 5-fold signal enhancement as the judgment basis, when the monitoring voltage value of the terminal is higher than the alarm threshold, the alarm system will be triggered. Finally, the real-time online monitoring of lithium dendrites between the electrodes of lithium-ion batteries is realized, and the lithium dendrites in the initial growth stage are accurately monitored and warned before the battery electrodes are short-circuited.

[0036] An in-situ detection method for lithium dendrite growth based on light scattering implemented by the above detection device proposed by the present invention includes the following steps: 1) Emission step, two detection lights from the detection light source 3-2 in the light scattering detection unit 3 converge and irradiate to the target measurement point between the electrodes; 2) Reception step, the electrolyte or lithium dendrite at the measurement point generates scattered light, which is received by the photodetector 3-6 and converted into a voltage signal; 3) Judgment step, the data acquisition terminal 1 receives the voltage signal of the photodetector 3-6. When the signal intensity surges, it is judged that a lithium dendrite structure appears at the set measurement point, and the alarm 2 is triggered to issue an alarm.

[0037] Among them, the light beam emitted by the detection light source is divided into two detection lights by the beam splitter 3-4, and are respectively focused by the incident lens 3-7 to form a measurement area. The light waves of the two detection lights irradiating the surface of the object to be measured can be described as:

[0038] E1(t) = E0 cos(ω1t + θ1)

[0039] E2(t) = E0 cos(ω2t + θ2)

[0040] In the formula, E is the amplitude intensity, ω is the frequency, and θ is the initial phase.

[0041] Among them, the scattered light emitted by the electrolyte or lithium dendrite at the measurement point returns to the lens and then passes through the second mirror 3-3, and is collected by the converging lens 3-5 and enters the photodetector 3-6. A diaphragm 3-8 is set in front of the photodetector. The selection of the diameter of the diaphragm follows the formula:

[0042]

[0043] In the formula, d p is the diameter of the aperture diaphragm, l1 is the distance between the diaphragm and the collecting lens, l2 is the distance between the measurement area and the collecting lens, and d c is the width of the measurement area facing the diaphragm.

[0044] Among them, the photodetector 3-6 generates a photocurrent after receiving photons and converts it into a voltage signal for output. The magnitude of the current is related to the light intensity amplitude:

[0045] I = [E1(t) + E2(t)] 2 .

[0046] Among them, the signal of the photodetector is remotely transmitted to the data acquisition terminal 1 for monitoring and analysis; when there is no lithium dendrite at the measurement point, the scattered signal generated by the electrolyte is weak and the signal intensity remains at a low level; the generation of lithium dendrites is accompanied by a surge in the scattered signal. When an abnormal high-intensity signal is detected, the data acquisition terminal 1 issues an alarm to achieve precise early warning of the generation of lithium dendrites before the battery electrode is short-circuited.

[0047] The above are only the preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. An in-situ detection device for lithium dendrite growth based on light scattering, characterized in that, It includes a data acquisition terminal (1), an alarm (2), and a light scattering detection unit (3) placed inside a housing; The light scattering detection unit (3) is arranged in an array form on the electrode surface and includes a first mirror (3-1), a detection light source (3-2), a second mirror (3-3), a beam splitter (3-4), a converging lens (3-5), a photodetector (3-6), an incident lens (3-7), and a diaphragm (3-8); among them, the detection light generated by the detection light source (3-2) is divided into two beams by the beam splitter (3-4), enters the incident lens (3-7) for focusing after the optical path is adjusted by the first mirror (3-1), irradiates the target measurement point between the electrodes, and then the scattered light generated by the electrolyte or lithium dendrite at the measurement point returns to the incident lens, passes through the second mirror (3-3) to adjust the optical path, passes through the converging lens (3-5) and the diaphragm (3-8), and finally enters the photodetector (3-6), and the scattered light intensity is converted into a voltage signal for output; The data acquisition terminal (1) receives the voltage signal emitted after the photoelectric conversion of the light scattering detection unit (3), and when the intensity of the corresponding voltage signal surges, it judges that a lithium dendrite structure appears at the measurement point and outputs an alarm signal; The alarm (2) receives the alarm signal sent by the data acquisition terminal (1) and triggers an alarm; the center of the diaphragm (3-8) coincides with the focus of the converging lens (3-5) and the measurement area, and the diameter selection of the diaphragm follows the formula: Wherein, is the diameter of the aperture stop, is the distance between the stop and the collection lens, is the distance between the measurement area and the collection lens, is the width of the measurement area facing the stop.

2. The in-situ detection device for lithium dendrite growth based on light scattering according to claim 1, wherein, The housing includes an optical window (3-9) and a packaging box (3-10), the optical window (3-9) is made of quartz material, and the packaging box (3-10) is made of corrosion-resistant material.

3. The in-situ detection device for lithium dendrite growth based on light scattering according to claim 1, wherein The detection light source (3-2) is a continuous monochromatic light source, and the wavelength of the light wave is in the visible light band.

4. The in-situ detection device for lithium dendrite growth based on light scattering according to claim 1, characterized in that, The beam splitter (3-4) is a polarization-maintaining beam splitter, and the splitting ratio should be 50:50; the center of the beam splitter and the center position of the first mirror are set on the same straight line.

5. The in-situ detection device for lithium dendrite growth based on light scattering according to claim 1, wherein The first mirror (3-1) and the second mirror (3-3) are polarization-maintaining mirrors, which match the wavelength of the light source.

6. The in-situ detection device for lithium dendrite growth based on light scattering according to claim 1, characterized in that, The incident lens (3-7) is a low spherical aberration lens, and the inner focal points are consistent within the split beam spacing; the optical axis of the converging lens (3-5) and the optical axis of the incident lens (3-7) satisfy the reflection condition based on the second mirror (3-3), and the center of the incident lens (3-7) and the center position of the second mirror (3-3) are set on the same straight line.

7. The in-situ detection device for lithium dendrite growth based on light scattering according to claim 1, characterized in that, The photodetector (3-6) and the data acquisition terminal (1) satisfy a wireless transmission protocol, including LoRa, NB-IOT, ZigBee, WiFi, or Bluetooth.

8. A detection method implemented by an in-situ detection device for lithium dendrite growth based on light scattering according to any one of the above claims 1-7, characterized in that, It includes the following steps: Emission step, two beams of detection light from the detection light source (3-2) in the light scattering detection unit (3) converge and irradiate the target measurement point between the electrodes; Receiving step, the electrolyte or lithium dendrite at the measurement point generates scattered light, which is received by the photodetector (3-6) and converted into a voltage signal; Judgment step, the data acquisition terminal (1) receives the voltage signal of the photodetector. When the signal intensity surges, it judges that a lithium dendrite structure appears at the set measurement point and triggers the alarm (2) to issue an alarm.

9. The detection method according to claim 8, wherein The light beam emitted by the detection light source (3-2) is split into two detection lights by the beam splitter (3-4), and the two detection lights are respectively focused by the incident lens (3-7) to form a measurement area. The light waves irradiated on the surface of the object to be measured can be described as follows: wherein is the amplitude intensity, is the frequency, is the initial phase.

10. The detection method according to claim 8, characterized in that The scattered light emitted by the electrolyte or lithium dendrite at the measurement point returns to the incident lens (3-7), then passes through the second mirror (3-3), and is collected by the converging lens (3-5) and enters the photodetector (3-6). A diaphragm is arranged in front of the photodetector (3-6), and the diameter selection of the diaphragm follows the formula: Wherein, is the diameter of the aperture stop, is the distance between the stop and the collection lens, is the distance between the measurement area and the collection lens, is the width of the measurement area facing the stop.

11. The detection method according to claim 9, wherein After receiving photons, the photodetector (3-6) generates a photocurrent and converts it into a voltage signal for output. The magnitude of the current is related to the light intensity amplitude: 。

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