A fiber microstructure for detecting lithium battery electrolyte based on SERS and a design method and application thereof

Abstract

The present application belongs to the technical field of lithium battery detection, and particularly relates to a fiber microstructure for detecting lithium battery electrolyte based on SERS, a design method and application, wherein the fiber microstructure comprises an excitation end fiber, a receiving end fiber, a Raman spectrometer and a filter added at the end of the receiving end fiber; the excitation end fiber, the receiving end fiber and the Raman spectrometer are connected; the optical structure of the excitation end fiber is a tapered structure, and the optical structure of the receiving end fiber is a convex lens structure. The fiber microstructure has the advantages of small volume, flexible use, strong corrosion resistance, light weight and the like; the fiber microstructure can effectively detect the Raman signal of the electrolyte, and can detect the Raman signal of the electrode material at about 3000 cm ‑1 The present application can directly evaluate the dynamic change of the electrolyte and the abnormal situation that may occur in the battery during the cycle charging and discharging process of the lithium battery.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lithium battery detection, and particularly relates to a fiber microstructure for detecting lithium battery electrolyte based on SERS and a design method and application thereof. BACKGROUND

[0002] New energy lithium batteries are a kind of high-performance and high-energy-density battery technology, which are widely used in electric vehicles, energy storage systems and portable electronic devices. They have the advantages of high efficiency, environmental protection, long life, etc., and play an important role in promoting the development of renewable energy and reducing carbon emissions. New energy lithium batteries may face some problems during use, such as capacity attenuation, safety and life challenges. Therefore, it is very important to effectively detect and evaluate new energy lithium batteries to ensure their performance and safety. New energy lithium batteries are usually evaluated according to the following situations. Capacity and health state detection: the capacity and health of the battery are analyzed by measuring and analyzing the charge and discharge behavior of the battery; safety evaluation: the safety of new energy lithium batteries is a key issue, and modern battery management systems (BMS) are equipped with various safety detection technologies to ensure the safety of the battery; cycle life evaluation: cycle life is an indicator of durability, and is usually studied by experimental and simulation methods to study the life degradation mechanism of the battery during charging and discharging cycles. There is room for improvement and improvement.

[0003] As a non-destructive and non-contact detection technology, fiber Raman technology has attracted widespread attention in the field of new energy lithium batteries. Fiber Raman technology can be applied to the capacity, health state detection, safety evaluation and cycle life evaluation of new energy lithium batteries, and has good prediction results, but it also has the problems of high skill and equipment requirements, possible external interference, high equipment cost, limited test precision, etc.

[0004] Raman detection technology is widely used in the quality control and research of lithium batteries, especially for the application effect of electrolyte in thin lithium ion batteries. Raman technology can provide very useful information. However, when using Raman technology to detect soft-pack lithium batteries during charging and discharging, there are some defects in the instrument device. One common problem is the poor contact between the redox electrode in the electrolyte container and the fiber immersed in the electrolyte, and between the fiber and the current collector, which may cause distortion of the detection signal and unreliability of the test. Another problem is that during the charging and discharging test, the electrolyte inside the battery may change due to evaporation and consumption of the electrolyte, which will cause changes in the properties of the battery, ultimately affecting the accuracy and repeatability of the test results. SUMMARY

[0005] The application aims to overcome the defects in the prior art and provide a fiber microstructure for detecting lithium battery electrolyte based on SERS, a design method and application.

[0006] To achieve the above object, one of the technical solutions of the application is a fiber microstructure for detecting lithium battery electrolyte based on SERS, comprising an excitation end fiber, a receiving end fiber, a Raman spectrometer and a filter attached to the end of the receiving end fiber; the excitation end fiber and the receiving end fiber are connected to the Raman spectrometer through an interface; the optical structure of the excitation end fiber is a taper structure, and the optical structure of the receiving end fiber is a convex lens structure; the taper structure and the convex lens structure are taper type, not a fusion structure.

[0007] In a preferred embodiment of the application, the excitation end fiber and the receiving end fiber are both micron-level fibers, which help to increase the reception of Raman signals.

[0008] In a preferred embodiment of the application, the excitation end fiber and the receiving end fiber are fixed side by side, and the cross sections of the two are in the same horizontal plane.

[0009] In a preferred embodiment of the application, the excitation end fiber and the receiving end fiber are multimode fibers with a diameter greater than or equal to 105 μm, and the wavelength of the filter is 500-650 nm.

[0010] The structure of the existing Raman probe mainly includes the focusing effect of the objective lens and the different layouts of the excitation end and the receiving end, so as to collect more Raman signals. For the fiber, the excitation end fiber and the receiving end fiber belong to different fibers, the excitation end has a taper as the basic optical structure, which can focus the laser and accurately hit the sample to be measured, thereby reducing the loss of light; the receiving end has a lens model as the basic optical structure, which can collect more Raman signals in a limited volume end face. The excitation end fiber and the receiving end fiber are connected to the Raman spectrometer to form a new Raman detection system. When detecting the Raman signals of the lithium battery electrolyte, the excitation end fiber and the receiving end fiber are fixed side by side and close to each other to avoid misalignment between the two; then the arranged fiber is inserted into the lithium battery (one side of the positive electrode or the negative electrode) and the electrolyte is injected; finally, the filter is attached to the end of the receiving end fiber, the fiber is connected to the spectrometer through the SMA905 interface, and a simple and portable fiber Raman spectrometer is designed.

[0011] In order to achieve the above object, the second technical scheme of the present application is: application of a fiber microstructure based on SERS detection of lithium battery electrolyte in multi-scene real-time working condition detection of electrochemical energy systems.

[0012] In order to achieve the above object, the third technical scheme of the present application is: a design method of a fiber microstructure based on SERS detection of lithium battery electrolyte, including unique design of fiber structure and building of fiber optical path, and the specific steps are as follows:

[0013] S1: remove the coating layer of the excitation end fiber and the receiving end fiber, and reserve the cladding layer and the core design optical microstructure; the laser can penetrate the remaining cladding layer to excite the Raman signal;

[0014] S2: add a filter at the end of the receiving end fiber to obtain a Raman spectrum with little interference to the characteristic peak;

[0015] S3: fix the excitation end fiber and the receiving end fiber side by side together so that their cross sections are at the same horizontal plane, the laser passes through the excitation end fiber to produce Raman scattered light on the surface of the sample molecules, and the receiving end fiber collects the Raman signal.

[0016] In a preferred embodiment of the present application, the collection time of the Raman signal in step S3 is 10-30s, and the power is 15-25mw.

[0017] In a preferred embodiment of the present application, the receiving end fiber which is in a horizontal position or slightly lower than the excitation end fiber in step S3 can collect the Raman signal.

[0018] The receiving end receives not only Raman scattered light of a specific wavelength, but also some other stray light, and it is necessary to eliminate the useless stray light before the optical signal enters the spectrometer. For conventional Raman, the signal intensity is inherently weak, and a little interference will affect the identification of the characteristic peak. Therefore, a filter is added at the end of the receiving end fiber to obtain a "clean" Raman spectrum with little interference to the characteristic peak.

[0019] In order to achieve the above object, the fourth technical scheme of the present application is: a method for detecting electrolyte in a lithium battery based on the above fiber microstructure, comprising the following steps:

[0020] S1: insert the fiber into the soft pack lithium battery, and package in an oxygen-free environment to avoid oxygen entering the battery and causing errors in the test results;

[0021] S2: charge the packaged soft pack lithium battery;

[0022] S3: The soft package lithium battery is clamped by the clamp, the clamp can make the gap between the electrode materials smaller, and the contact is more sufficient; the rated charge and discharge current is 0.02-0.06A, the charge and discharge voltage is 0-3.65V, and the charge and discharge is cycled between 0-3.65V;

[0023] S4: The static open-circuit electrolyte Raman signal is measured by using a Raman spectrum detector, and the Raman signal in the soft package lithium battery during normal charge and discharge is detected.

[0024] In a preferred embodiment of the application, the charging in step S2 is performed by a charging workbench, and the charging time of the soft package lithium battery is 2-4h.

[0025] In a preferred embodiment of the application, the detection frequency of the Raman signal of the soft package lithium battery during normal charge and discharge in step S4 is once every 5min, and the change of the electrolyte state of the soft package lithium battery in ten charge and discharge cycles is detected.

[0026] In a preferred embodiment of the application, the Raman spectrum detector in step S4 is one of a portable Raman spectrometer, a confocal Raman spectrometer and a handheld Raman spectrometer, and the laser excitation wavelength of the Raman spectrum detector is 532nm.

[0027] Compared with the prior art, the application has the following beneficial effects:

[0028] 1. The optical fiber microstructure has the advantages of small volume, flexible use, strong corrosion resistance, light weight and the like;

[0029] 2. The optical fiber microstructure can effectively detect the Raman signal of the electrolyte, and can detect the Raman signal of the electrode material around 3000cm -1 Wave number, which can directly evaluate the dynamic change of the electrolyte and the abnormal situation of the battery during the cycle charge and discharge process;

[0030] 3. The optical fiber microstructure can complete the detection in 10-30s, and has the advantages of short time, high accuracy and convenient operation, and can be fully applied to the detection of the health state of the modern new energy automobile battery. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 The application is an optical fiber microstructure based on conventional Raman detection of lithium battery electrolyte,

[0032] In the figure: 1-excitation end optical fiber, 2-receiving end optical fiber, 3-optical filter, 4-SMA905 interface, 5-soft package lithium battery, 6-LiPF6 electrolyte, 7-VC additive, 8-aluminum tape, 9-laser, 10-Raman spectrometer, 11-upper computer.

[0033] Figure 2 A fiber excitation end drawing of a fiber microstructure design based on conventional Raman detection of lithium battery electrolyte according to the present application;

[0034] Figure 3 A fiber receiving end drawing of a fiber microstructure design based on conventional Raman detection of lithium battery electrolyte according to the present application;

[0035] Figure 4 A fiber excitation end and receiving end position schematic drawing of a fiber microstructure design based on conventional Raman detection of lithium battery electrolyte according to the present application;

[0036] Figure 5 A lithium battery packaging drawing of a fiber microstructure design based on conventional Raman detection of lithium battery electrolyte according to the present application;

[0037] Figure 6 A charge curve drawing of a fiber microstructure design based on conventional Raman detection of lithium battery electrolyte according to the present application;

[0038] Figure 7 A discharge curve drawing of a fiber microstructure design based on conventional Raman detection of lithium battery electrolyte according to the present application;

[0039] Figure 8 A Raman spectrum drawing of a fiber microstructure design based on conventional Raman detection of lithium battery electrolyte according to the present application;

[0040] Figure 9 An electrolyte open circuit spectrum drawing based on fiber Raman testing according to the present application. DETAILED DESCRIPTION

[0041] In order to make the objects, technical solutions and advantages of the present application clearer, the present application will be described in more detail below with reference to the drawings and specific embodiments. However, the protection scope of the present application is not limited to these embodiments. The same reference signs in the text always represent the same elements, and similar reference signs represent similar elements.

[0042] In the description of the present application, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "horizontal", "vertical", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship shown in the perspective view of the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0043] A kind of optical fiber microstructure based on SERS detection lithium battery electrolyte, including excitation end optical fiber, receiving end optical fiber, Raman spectrometer and filter added in the end of receiving end optical fiber;The excitation end optical fiber and receiving end optical fiber are connected with Raman spectrometer by interface;The optical structure of the excitation end optical fiber is tapered structure, and the optical structure of receiving end optical fiber is convex lens structure, and the tapered structure and convex lens structure are pull-tapered.

[0044] The excitation end optical fiber and receiving end optical fiber are both micron-level optical fibers, which help to increase the reception of Raman signals.

[0045] The excitation end optical fiber and receiving end optical fiber are fixed side by side together, and the cross sections of the two are in the same horizontal plane.

[0046] The excitation end optical fiber and receiving end optical fiber are multimode optical fibers with a diameter greater than or equal to 105 μm, and the filter has a wavelength of 500-650 nm.

[0047] The application of a kind of optical fiber microstructure based on SERS detection lithium battery electrolyte in real-time working condition detection of multiple scenarios of electrochemical energy system.

[0048] A design method of an optical fiber microstructure based on SERS detection of lithium battery electrolyte, the specific steps are as follows:

[0049] S1: remove the coating layer of the excitation end optical fiber and the receiving end optical fiber, and retain the cladding and core design optical microstructure;

[0050] S2: add a filter at the end of the receiving end optical fiber;

[0051] S3: fix the excitation end optical fiber and the receiving end optical fiber side by side together, so that the cross sections of the two are in the same horizontal plane, and the laser generates Raman scattered light on the surface of the sample molecules through the excitation end optical fiber, and the receiving end optical fiber collects the Raman signal.

[0052] The collection time of the Raman signal in step S3 is 10-30 s, and the power is 15-25 mw.

[0053] In step S3, the receiving end optical fiber, which is in a horizontal position or slightly lower than the excitation end optical fiber, can collect the Raman signal.

[0054] A method for detecting electrolyte in a lithium battery based on the above optical fiber microstructure, comprising the following steps:

[0055] S1: insert the optical fiber into the soft pack lithium battery, and package in an oxygen-free environment;

[0056] S2: charge the packaged soft pack lithium battery;

[0057] S3: clamp the soft package lithium battery with the clamp; set the rated charge and discharge current to 0.02-0.06A, the charge and discharge voltage to 0-3.65V, and the charge and discharge cycle between 0-3.65V;

[0058] S4: use a Raman spectrometer to measure the static open-circuit electrolyte Raman signal, and then detect the Raman signal during the charge and discharge cycle of the soft package lithium battery.

[0059] The charging in step S2 is performed by a charging workbench, and the charging time of the soft package lithium battery is 2-4h.

[0060] The detection frequency of the Raman signal of the soft package lithium battery during normal charge and discharge in step S4 is once every 5min, and the electrolyte state change of the soft package lithium battery in ten charge and discharge cycles is detected.

[0061] The Raman spectrometer in step S4 is one of a portable Raman spectrometer, a confocal Raman spectrometer, and a handheld Raman spectrometer, and the laser excitation wavelength of the Raman spectrometer is 532nm.

[0062] Example 1

[0063] A fiber microstructure based on conventional Raman detection of lithium battery electrolyte, as shown in Figure 1 The fiber microstructure based on SERS detection of lithium battery electrolyte includes an excitation end fiber, a receiving end fiber, a Raman spectrometer, and a filter added at the end of the receiving end fiber; the excitation end fiber, the receiving end fiber, and the Raman spectrometer are connected through an SMA905 interface; the optical structure of the excitation end fiber is a tapered structure, and the optical structure of the receiving end fiber is a convex lens structure, both of which are taper type. The excitation end fiber and the receiving end fiber are both multimode optical fibers with a diameter of 105μm, and the two fibers are fixed side by side so that their cross sections are in the same horizontal plane. The wavelength of the filter is 500-650nm.

[0064] Application of a fiber microstructure based on SERS detection of lithium battery electrolyte in real-time working condition detection of multiple scenes of electrochemical energy systems.

[0065] First, the fiber with microstructure excites the Raman signal and collects it, and transmits it to the spectrometer for spectral processing. The SMA905 interface is specially used to connect the fiber and the spectrometer to ensure that the Raman signal is processed by the spectrometer. However, the Raman spectrum needs to be filtered by the filter before entering the spectrometer to eliminate stray light of redundant wavelengths. The CHI charging parameters are adjusted by the upper computer to charge, and then the Raman signal is collected for data acquisition.

[0066] A fiber microstructure based on SERS detection of lithium battery electrolyte is obtained by the following design method, comprising the following steps:

[0067] S1: Remove the coating of the multimode optical fiber with a diameter of 105 μm, leaving the cladding and core for designing the optical microstructure;

[0068] S2: Add a filter with a wavelength of 532 nm at the end of the receiving optical fiber;

[0069] S3: Fix the excitation optical fiber and the receiving optical fiber side by side together, with their cross sections at the same level; the laser passes through the excitation optical fiber to produce Raman scattered light on the surface of the sample molecules, and the receiving optical fiber collects the Raman signal, with a collection time of 20 s and a power of 25 mw. The receiving optical fiber and the excitation optical fiber are in a horizontal position.

[0070] A method for detecting electrolyte in a lithium battery based on the above optical fiber microstructure, comprising the following steps:

[0071] S1: Insert the optical fiber into the soft pack lithium battery, and package in an oxygen-free environment;

[0072] S2: Charge the packaged soft pack lithium battery through the Chenhua CHI charging workbench, with a charging time of 3 h;

[0073] S3: Clamping the above soft pack lithium battery with a clamp; set the rated charge and discharge current to 0.042 A, the charge and discharge voltage to 0-3.65 V, and the charge and discharge to cycle between 0-3.65 V;

[0074] S4: Measure the static open-circuit electrolyte Raman signal (tested twice, the results are shown in Figure 9 ) using a portable Raman spectrum detector; the Raman spectrum detector has a laser excitation wavelength of 532 nm; then detect the Raman signal of the soft pack lithium battery in a charge and discharge cycle every 5 min; detect the electrolyte state change in ten charge and discharge cycles of the soft pack battery.

[0075] The structures of the excitation optical fiber and the receiving optical fiber are shown in Figure 2 and 3 ; the schematic diagram of the positions of the excitation optical fiber and the receiving optical fiber is shown in Figure 4 ; Figure 5 The packaging diagram of the soft pack lithium battery is shown in Figure 6 , the charge curve diagram is shown in Figure 7 , and the discharge curve diagram is shown in Figure 8 .

[0076] The soft package battery used in this embodiment is provided by Ningde Times, with a length of about 120 mm and a width of about 60 mm. The positive electrode material is LiFePO4, the negative electrode material is graphite, the electrolyte and the ratio of each component are as follows: 1M LiPF6 in EC:DMC:EMC = 1:1:1, the electrolyte additive is 5%wt vinyl carbonate (VC), and the configured electrolyte injection volume is 500 μL.

[0077] The above embodiments are only used to illustrate the technical solutions of the present application, but not to limit it; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that the technical solutions recorded in the foregoing embodiments can still be modified, or some or all of the technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A fiber-optic microstructure for SERS-based detection of lithium battery electrolytes, characterized in that, The application relates to a fiber microstructure for detecting a real-time working condition of an electrochemical energy source system in multiple scenes, which comprises an excitation-end optical fiber, a receiving-end optical fiber, a Raman spectrometer and a filter added at the end of the receiving-end optical fiber. The excitation-end optical fiber and the receiving-end optical fiber are connected with the Raman spectrometer through an interface; the optical structure of the excitation-end optical fiber is a taper structure, the optical structure of the receiving-end optical fiber is a convex lens structure, and the taper structure and the convex lens structure are pull-taper types; the excitation-end optical fiber and the receiving-end optical fiber are fixed together side by side, and the cross sections of the two are in the same horizontal plane.

2. The optical fiber microstructure of claim 1, wherein, The excitation-end optical fiber and the receiving-end optical fiber are multimode optical fibers with a diameter greater than or equal to 105 microns, and the wavelength of the filter is 500-650 nm.

3. Application of the optical fiber microstructure in claim 1 or 2 to detection of a real-time working condition of an electrochemical energy source system in multiple scenes.

4. A method of designing a microstructure of an optical fiber as claimed in claim 1 or 2, characterized in that, The application comprises the following steps: S1: removing the coating layer of the excitation-end optical fiber and the receiving-end optical fiber, and retaining the cladding layer and the optical microstructure of the core; S2: adding a filter at the end of the receiving-end optical fiber; S3: fixing the excitation-end optical fiber and the receiving-end optical fiber together side by side, so that the cross sections of the two are in the same horizontal plane; laser passes through the excitation-end optical fiber to generate Raman scattered light on the surface of sample molecules, and the receiving-end optical fiber collects the Raman signal.

5. The design method of claim 4, wherein, The collection time of the Raman signal in the step S3 is 10-30 seconds, and the power is 15-25 mw.

6. The design method of claim 4, wherein, The receiving-end optical fiber in the horizontal position with the excitation-end optical fiber collects the Raman signal in the step S3.

7. A method for detecting electrolyte in a lithium battery based on the optical fiber microstructure of claim 1 or 2, characterized by, The application comprises the following steps: S1: inserting the excitation-end optical fiber and the receiving-end optical fiber into a soft-pack lithium battery, and packaging in an oxygen-free environment; S2: charging the packaged soft-pack lithium battery; S3: clamping the soft-pack lithium battery by a clamp; setting the rated charge-discharge current as 0.02-0.06 A, the charge-discharge voltage as 0-3.65 V, and the charge-discharge cycle as 0-3.65 V; S4: measuring the static open-circuit electrolyte Raman signal by using a Raman spectrum detector, and detecting the Raman signal in the charge-discharge cycle of the soft-pack lithium battery during normal charge-discharge of the soft-pack lithium battery.

8. The method of detecting electrolyte in a lithium battery of claim 7, wherein, The charging in the step S2 is performed by a charging workbench, and the charging time of the soft-pack lithium battery is 2-4 hours.

9. The method of detecting electrolyte in a lithium battery of claim 7, wherein, The detection frequency of the Raman signal of the soft-pack lithium battery during normal charge-discharge in the step S4 is once every 5 minutes, and the electrolyte state change of the soft-pack lithium battery in ten charge-discharge cycles is detected; the Raman spectrum detector in the step S4 is one of a portable Raman spectrum detector, a confocal Raman spectrum detector and a handheld Raman spectrum detector, and the laser excitation wavelength of the Raman spectrum detector is 532 nm.

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