Optical probe of closed space lithium battery thermal runaway gas real-time spectrum monitoring system

Abstract

The invention discloses an optical probe of a closed space lithium battery thermal runaway gas real-time spectrum monitoring system, and the optical probe comprises a laser, Raman scattering light emitted by the laser is emitted in parallel through a collimating mirror, enters a narrow band filter, is reflected by a plane mirror, enters a dichroscope for refraction, and is reflected by a light source. The target detection objective lens gathers on a detected target; raman scattering light returned by the detected target passes through an objective lens target detector and a dichroscope, is modulated by a long-wave-pass optical filter, and is converged into an optical fiber receiving end through a Raman scattering light collecting mirror to enter a spectrograph system. The Raman spectrum technology is applied to monitoring gas component changes in the electrochemical reaction process when the lithium battery is charged and discharged in the closed space, and the lithium battery thermal runaway real-time monitoring based on the Raman spectrum technology can provide a guarantee for the thermal runaway risk in the transportation and storage process of the lithium battery.

Description

Technical Field

[0001] The invention relates to a confined space lithium battery thermal runaway monitoring system, and in particular to an optical probe of a confined space lithium battery thermal runaway gas real-time spectrum monitoring system. Background Art

[0002] At present, as the technology of lithium batteries becomes more and more mature, due to its advantages such as long cycle life, high output voltage, high energy density, no pollution, and fast charging speed, it has quickly occupied a leading position in the field of energy storage and is regarded as the main important technology for converting electrical energy into chemical energy. In the field of transportation, including airplanes, cars, trains and ships, lithium batteries are successfully used in electric vehicles, especially because of their high energy density and power density. From 2020 to 2025, the global lithium battery market is expected to increase from US$44 billion to US$94 billion. In addition, as the government turns to the use of renewable energy, there is a higher demand for energy storage. Lithium batteries can also be used for the storage of other energy sources, such as solar and wind energy.

[0003] At present, the safety issues of lithium batteries are mainly concentrated on thermal runaway, which is generally caused by internal short circuit of lithium batteries under abuse conditions. Abuse mainly includes thermal abuse, mechanical abuse and electrical abuse, which may cause internal short circuit of the battery, causing the battery temperature to rise sharply. As the temperature further increases, the solid electrolyte interface (SEI) layer breaks down at 130°C, followed by a series of self-heating reactions. Finally, a large amount of heat and gas accumulate inside the battery, causing the battery to swell. When the internal pressure reaches the threshold, the safety valve opens, and the gas inside the battery spurts out, causing fire or even explosion. The heat generated by the faulty battery will continue to transfer everywhere, causing a domino effect with catastrophic consequences. As of 2019, the U.S. Consumer Product Safety Commission has recorded more than 25,000 overheating or fire incidents in 5 years, involving more than 400 overheated lithium battery-powered consumer products.

[0004] Many researchers have focused on finding safer lithium battery materials or adopting safer structural designs. Similarly, it is also necessary to provide theoretical support for improving the safety level of lithium batteries from the perspective of thermal runaway principles. Therefore, it is crucial to adopt effective monitoring methods, detect thermal runaway in a timely manner, take emergency measures, and thus avoid the spread of thermal runaway.

[0005] When laser light interacts with matter, incident photons can be absorbed and scattered. If the energy of the incident photon matches the energy difference between the ground state and the excited state of the molecule, the photon is likely to be absorbed and the molecule is raised to the excited state. When the excited molecule subsequently relaxes to the ground state by emission, fluorescence occurs. On the other hand, scattering occurs because the incident photon distorts the electron cloud. There are two typical scatterings in the visible and near-infrared spectral range: Rayleigh scattering and Raman scattering. In comparison, Rayleigh scattering, which occurs when only the electron cloud is distorted, there is no energy exchange and is an elastic process. If the vibrational state of the molecule changes, energy transfer occurs, which is an inelastic process, Raman scattering. In general, Raman scattering is a weak process, with approximately only one in every 106-108 scattered photons.

[0006] Raman spectroscopy is a non-destructive and non-contact spectral analysis method. Due to its non-contact, fast and non-destructive characteristics, it has shown great potential in the detection of solids and liquids. However, its application in gas detection is relatively small. This technology uses a single-frequency laser to achieve non-contact and non-destructive spectral information acquisition of multiple mixed gases.

[0007] Technical solution of prior art 1:

[0008] Many research teams have conducted research on the components of thermal runaway gases in lithium batteries. DPArbrahama et al. measured the gas by accelerated rate calorimetry (ARC) and then used gas chromatography-mass spectrometry (GC-MS) for sampling and analysis, explaining the source and possible mechanism of thermal runaway gas generation in high-power lithium-ion batteries. Fredrik Larsson et al. externally heated commercial lithium batteries of different aging degrees, studied the thermal runaway and gas explosion process, and used Fourier transform infrared absorption spectroscopy (FTIR) to detect and analyze the released gas. Y. Fernandes et al. studied the gas production process of lithium batteries under overcharge by real-time collection and analysis of the gas generated during thermal runaway, and matched the analysis results of GC-MS and FTIR with time.

[0009] The gases detected in the above experiments are mostly organic solvents of the electrolyte, various alkanes, fluorides, etc., reflecting the dangerous nature of the waste gas.

[0010] Disadvantages of prior art 1:

[0011] Existing technologies mainly focus on GC-MS and FTIR to analyze the gases collected from various lithium batteries after thermal runaway. However, there is little research on the gas dynamics of lithium batteries from normal to thermal runaway, and it is urgent to develop in-situ and online gas analysis technology. As a new gas analysis technology, Raman spectroscopy is still in its infancy in the field of thermal runaway of lithium-ion batteries. Therefore, how to develop new and efficient key technologies and equipment for real-time assessment of the risk of thermal runaway gas explosion of lithium batteries based on Raman spectroscopy has become a frontier and difficult problem in the field of thermal runaway of lithium batteries, and has important application prospects.

[0012] In view of this, the present invention is proposed. Summary of the invention

[0013] The purpose of the present invention is to provide an optical probe for a real-time spectral monitoring system of thermal runaway gases of a lithium battery in a confined space, so as to solve the above-mentioned technical problems existing in the prior art.

[0014] The objective of the present invention is achieved through the following technical solutions:

[0015] The optical probe of the real-time spectral monitoring system for thermal runaway gas of a lithium battery in a closed space of the present invention, the spectral monitoring system comprises a pyrolysis reactor, the gas pipeline of the gas outlet of the pyrolysis reactor enters the Raman optical testing system through a gas filtration system and an electronic pressure control valve, the outlet of the Raman optical testing system is connected to the gas return port of the pyrolysis reactor through a gas limiting valve, and an air pump is provided in the pyrolysis reactor or on the gas pipeline;

[0016] The Raman optical test system includes an optical probe, which includes a laser O1. Raman scattered light emitted by the laser O1 is emitted in parallel through a collimator L1, enters a narrow-band filter F1, is reflected by a plane reflector M1, is refracted by a dichroic mirror M2, and is converged onto a target by a target detection objective lens L2.

[0017] The Raman scattered light returned by the measured target passes through the objective lens target detection L2 and the dichroic mirror M2, is modulated by the long-wave pass filter F2, and is converged into the optical fiber receiving end O2 through the Raman scattered light collecting mirror L3 and enters the spectrometer system.

[0018] Compared with the prior art, the optical probe of the real-time spectral monitoring system for thermal runaway gas of lithium batteries in a confined space provided by the present invention applies Raman spectroscopy technology to monitor the changes in gas composition during the electrochemical reaction process of charging and discharging of lithium batteries in a confined space, and proposes a real-time monitoring device for thermal runaway of lithium batteries based on Raman spectroscopy technology, which can provide a guarantee for the risk of thermal runaway during the transportation and storage of lithium batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1This is a schematic diagram of a real-time spectral monitoring system for thermal runaway gases of a lithium battery in a confined space according to an embodiment of the present invention;

[0020] Figure 2 A schematic diagram of the principle of establishing a standard gas library for a Raman optical monitoring system according to an embodiment of the present invention;

[0021] Figure 3 A schematic diagram of the structure principle of an optical probe provided by an embodiment of the present invention;

[0022] Figure 4 A point diagram of a Raman scattered light collection branch provided by an embodiment of the present invention;

[0023] In the figure:

[0024] O1 is the laser, L1 is the laser collimator, F1 is the narrowband filter, M1 is the plane reflector, L2 is the target detection objective lens, M2 is the dichroic mirror, F2 is the long-wave pass filter, L3 is the Raman scattered light collection mirror, and O2 is the optical fiber receiving end. DETAILED DESCRIPTION

[0025] The following is a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention; it is obvious that the described embodiments are only part of the embodiments of the present invention, not all of the embodiments, which does not constitute a limitation of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the protection scope of the present invention.

[0026] First, the terms that may be used in this article are explained as follows:

[0027] The term “and / or” means that either or both of them can be realized at the same time. For example, X and / or Y means both “X” or “Y” and “X and Y”.

[0028] The terms "include", "comprises", "contains", "has" or other descriptions with similar semantics should be interpreted as non-exclusive inclusion. For example, including certain technical feature elements (such as raw materials, components, ingredients, carriers, dosage forms, materials, dimensions, parts, components, mechanisms, devices, steps, procedures, methods, reaction conditions, processing conditions, parameters, algorithms, signals, data, products or products, etc.) should be interpreted as including not only certain technical feature elements explicitly listed, but also other technical feature elements known in the art that are not explicitly listed.

[0029] The term "consisting of..." means excluding any technical feature elements not explicitly listed. If this term is used in a claim, it will make the claim closed, so that it does not contain technical feature elements other than the technical feature elements explicitly listed, except for the conventional impurities related to them. If this term only appears in a clause of a claim, it only limits the elements explicitly listed in the clause, and the elements recorded in other clauses are not excluded from the overall claim.

[0030] Unless otherwise specified or limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example: it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this article can be understood according to specific circumstances.

[0031] The orientation or position relationship indicated by terms such as "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", etc. are based on the orientation or position relationship shown in the drawings and are only for the convenience and simplification of description, and do not explicitly or implicitly indicate that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation of this document.

[0032] The contents not described in detail in the examples of the present invention belong to the prior art known to professionals in the field. If no specific conditions are specified in the examples of the present invention, the conditions are carried out according to the conventional conditions in the field or the conditions recommended by the manufacturer. If the manufacturer is not specified in the reagents or instruments used in the examples of the present invention, they are all conventional products that can be purchased commercially.

[0033] The optical probe of the real-time spectral monitoring system for thermal runaway gas of a lithium battery in a closed space of the present invention, the spectral monitoring system comprises a pyrolysis reactor, the gas pipeline of the gas outlet of the pyrolysis reactor enters the Raman optical testing system through a gas filtration system and an electronic pressure control valve, the outlet of the Raman optical testing system is connected to the gas return port of the pyrolysis reactor through a gas limiting valve, and an air pump is provided in the pyrolysis reactor or on the gas pipeline;

[0034] The Raman optical test system includes an optical probe, which includes a laser O1. Raman scattered light emitted by the laser O1 is emitted in parallel through a collimator L1, enters a narrow-band filter F1, is reflected by a plane reflector M1, is refracted by a dichroic mirror M2, and is converged onto a target by a target detection objective lens L2.

[0035] The Raman scattered light returned by the measured target passes through the objective lens target detection L2 and the dichroic mirror M2, is modulated by the long-wave pass filter F2, and is converged into the optical fiber receiving end O2 through the Raman scattered light collecting mirror L3 and enters the spectrometer system.

[0036] A temperature and pressure sensor is installed in the pyrolysis reactor.

[0037] The wavelength of the incident laser is 532 nm, the radius of the optical fiber is 100 μm, the laser collimator L2 and the Raman scattered light collector L3 are matched with the connecting optical fiber, and the numerical aperture is 0.22.

[0038] The target detection objective lens L2 uses a set of double cemented lenses with a numerical aperture of 0.36.

[0039] The optical material is glass.

[0040] A database was established with standard gases, and a quantitative analysis model was trained. N2 was used as the diluent gas to extract the Raman characteristic peaks of various mixed gases at different concentrations. The model includes:

[0041] The Raman optical testing system is connected to a mixed gas pool through an electronic control valve, and the mixed gas pool is connected to a target gas source and a dilution gas source.

[0042] In summary, it can be seen that the optical probe of the real-time spectral monitoring system for thermal runaway gas of a lithium battery in a confined space according to the embodiment of the present invention is applied to the real-time spectral monitoring system for thermal runaway gas of a lithium battery in a confined space. The device has optimized the design of the probe, with one end connected to the gas pool and the other end connected to the spectrometer, which greatly improves the sensitivity of the system. The device can be used for the detection of weak gas signals. The device is also suitable for civilian fields such as pharmaceuticals and rapid food testing.

[0043] In order to more clearly demonstrate the technical solution and technical effects provided by the present invention, the embodiments of the present invention are described in detail with specific embodiments below.

[0044] Example 1

[0045] Real-time spectral monitoring system for thermal runaway gases of lithium batteries in confined spaces, such as Figure 1 As shown:

[0046] The system installs temperature and pressure sensors in the pyrolysis reactor to record the changes in pressure and lithium battery temperature in real time. When the lithium battery has thermal runaway and produces gas, it first enters the filter valve through the outlet of the pyrolysis reactor to filter the gas to prevent particulate matter generated by the runaway lithium battery from entering the gas pipeline, causing pollution and interference to the Raman system. The gas then circulates clockwise through the vacuum pump, which is used to keep the gas in the gas path circulating continuously. The precision electronic pressure control valve regulates the air pressure. The function of the flow limiting valve is to control the pressure by controlling the gas flow out of the system.

[0047] The technical principle of the present invention is:

[0048] Using the Raman "fingerprint" spectral characteristics of gas, non-contact and non-destructive detection characteristics, it is necessary to establish a database with standard gases and train quantitative analysis models. Technical solutions such as Figure 2 As shown, N2 is used as the dilution gas to extract the Raman characteristic peaks of various mixed gases at different concentrations.

[0049] The technical principle of the optical probe designed by the present invention is as follows Figure 3 As shown:

[0050] For the incident laser wavelength of 532nm, the fiber radius is 100μm, and the object numerical aperture of the spectrometer is 0.22. The laser O1 is emitted in parallel through the collimator L1, enters the narrowband filter F1, is reflected by the M1 plane reflector, enters the dichroic mirror M2 for refraction, and is converged to the target by the target detection objective lens L2. The Raman scattered light then passes through the objective lens L2 and the dichroic mirror M2, is modulated by the long-wave filter F2, and converges into the spectrometer system through the Raman scattered light collecting mirror L3.

[0051] The image quality evaluation of the present invention is as follows Figure 4 The optical parameters of the system are shown in Table 1:

[0052] Table 1: Optical parameters of the embodiment of the present invention:

[0053]

[0054] All optical materials are made of domestic glass materials from Chengdu Guangming. The target detection objective lens L2 is shared by the laser emission optical path and the collection optical path. A set of double-cemented lenses is used to eliminate astigmatism. In order to better collect Raman scattered light, the numerical aperture is 0.36. The laser collimator and the Raman scattered light collector are connected to the optical fiber, which is a matching device with a numerical aperture of 0.22.

[0055] The design of the system meets the telecentric optical path conditions of the object and image sides, easily satisfies the pupil connection principle, and facilitates the matching of the lens groups.

[0056] Compared with the prior art solutions, the advantages of the present invention are:

[0057] (1) High resolution: Within the spectral range, the Raman peaks of different gases can be distinguished, and various gases in complex gas mixtures can be accurately distinguished.

[0058] (2) Non-destructive: No direct contact with gas is required, and the integrity of the system being measured can be well maintained. It is suitable for monitoring weak signal systems under high temperature and high pressure.

[0059] (3) Real-time: Raman spectroscopy detection is based on laser excitation, and the acquisition of spectral information is almost real-time, which can realize timely monitoring of gas changes and help to achieve timely response and management of the battery system.

[0060] (4) Multi-dimensional information acquisition: Information on multiple gases can be obtained simultaneously without the need for multiple sensors, which helps reduce system costs and simplifies the design of gas monitoring systems.

[0061] The position and intensity information of the Raman characteristic peaks can directly reveal the composition and concentration of the mixed gas discharged from the battery. The present invention uses laser Raman spectroscopy technology to achieve real-time detection of battery exhaust gas. The development of new lithium battery gas monitoring technology plays an important role in improving the safety of battery applications. The acquired Raman spectral data can accurately reflect the changes in gas information during thermal abuse of the battery. In the field of gas monitoring and analysis, Raman spectroscopy technology has broad application prospects.

[0062] Specific implementation alternatives include:

[0063] Adding optical lenses, changing the eccentricity or inclination angle of the optical surface, the distance between the surfaces, and the optical materials used, etc. These modifications and changes do not depart from the essential scope of the present invention.

[0064] The key technical points of the present invention are:

[0065] A Raman spectroscopy gas detection device with stray light suppression analysis is proposed, which is applied to the real-time spectral monitoring of thermal runaway gases in lithium batteries in confined spaces. The device can simultaneously obtain Raman spectral information of multiple gases, effectively simplifying the design of the gas monitoring system.

[0066] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with the technical field within the technical scope disclosed in the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims. The information disclosed in the background technology section of this article is only intended to deepen the understanding of the overall background technology of the present invention, and should not be regarded as an admission or in any form that the information constitutes prior art known to those skilled in the art.

Claims

1. An optical probe for a real-time spectral monitoring system of thermal runaway gases of a lithium battery in a confined space, characterized in that: The spectral monitoring system comprises a pyrolysis reactor, the gas pipeline of the gas outlet of the pyrolysis reactor enters the Raman optical testing system through a gas filtration system and an electronic pressure control valve, the outlet of the Raman optical testing system is connected to the gas return port of the pyrolysis reactor through a gas limiting valve, and a vacuum pump is provided in the pyrolysis reactor or on the gas pipeline; The Raman optical test system comprises an optical probe, which comprises a laser (O1). Raman scattered light emitted by the laser (O1) is emitted in parallel through a collimator (L1), enters a narrow-band filter (F1), is reflected by a plane reflector (M1), enters a dichroic mirror (M2), is refracted, and is converged onto a target by a target detection objective lens (L2); The Raman scattered light returned by the target is then passed through the objective lens target detection (L2) and the dichroic mirror (M2), modulated by the long-wave pass filter (F2), and converged into the optical fiber receiving end (O2) through the Raman scattered light collecting mirror (L3) and enters the spectrometer system.

2. The optical probe of the real-time spectral monitoring system for thermal runaway gas of a lithium battery in a confined space according to claim 1, characterized in that: A temperature and pressure sensor is installed in the pyrolysis reactor.

3. The optical probe of the real-time spectral monitoring system for thermal runaway gas of a lithium battery in a confined space according to claim 2, characterized in that: The incident laser wavelength is 532 nm, the fiber radius is 100 μm, the laser collimator (L2) and the Raman scattered light collector (L3) are matched with the connecting fiber, and the numerical aperture is 0.

22.

4. The optical probe of the real-time spectral monitoring system for thermal runaway gas of a lithium battery in a confined space according to claim 3, characterized in that: The target detection objective lens (L2) uses a set of double cemented lenses with a numerical aperture of 0.

36.

5. The optical probe of the real-time spectral monitoring system for thermal runaway gas of a lithium battery in a confined space according to claim 4, characterized in that: The optical material is glass.

6. The optical probe of the real-time spectral monitoring system for thermal runaway gas of a lithium battery in a confined space according to any one of claims 1 to 5, characterized in that: A database was established with standard gases, and a quantitative analysis model was trained. N2 was used as the diluent gas to extract the Raman characteristic peaks of various mixed gases at different concentrations. The model includes: The Raman optical testing system is connected to a mixed gas pool through an electronic control valve, and the mixed gas pool is connected to a target gas source and a dilution gas source.

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