阅读说明：本技术 一种标记荧光量子点散斑的电极应变场原位监测装置及方法 (Electrode strain field in-situ monitoring device and method for marking fluorescent quantum dot speckles ) 是由 栾伟玲 姚逸鸣 吴森明 陈莹 王畅 陈浩峰 于 2021-07-15 设计创作，主要内容包括：本发明涉及一种标记荧光量子点散斑的电极应变场原位监测装置及方法,所述装置的不锈钢壳体正下方开孔,石英玻璃视窗覆盖开孔处作为实验观察窗口。以内腔底部开孔处为中心叠放非观测电极、隔膜以及观测电极,实现对观测电极的光学观察；再通过聚四氟乙烯套环、氟橡胶密封圈、螺纹紧固件、弹簧等对实现装置的导电通路和内部密封；本发明基于设计的可长时循环的原位观测装置,利用荧光量子点作为标记散斑,通过记录标记散斑的位移情况,对位移情况图片进行数字图像相关处理分析,可以得到电极材料表面的应变场演化情况。(The invention relates to an electrode strain field in-situ monitoring device and method for marking fluorescent quantum dot speckles. Stacking a non-observation electrode, a diaphragm and an observation electrode by taking an opening at the bottom of the inner cavity as a center to realize optical observation of the observation electrode; then, a conductive path and the interior of the device are sealed through a polytetrafluoroethylene lantern ring, a fluororubber sealing ring, a threaded fastener, a spring and the like; the invention is based on the designed in-situ observation device capable of long-term circulation, utilizes fluorescent quantum dots as marked speckles, and carries out digital image correlation processing analysis on displacement condition pictures by recording displacement conditions of the marked speckles, so as to obtain the strain field evolution condition of the surface of the electrode material.)

1. An electrode strain field in-situ monitoring device for marking fluorescent quantum dot speckles, the device comprising: a hole is formed in the center of the position right below the stainless steel shell (1), and the quartz glass window (2) covers the hole; a polytetrafluoroethylene insulating sleeve ring (3) is placed in an inner cavity of the stainless steel shell (1), and a non-observation electrode (4), a diaphragm (5) and an observation electrode (6) are sequentially stacked by taking an opening at the bottom of the inner cavity as a center; a stainless steel pressing block (7) is placed above the observation electrode (6), a groove is formed in the ring side of the stainless steel pressing block (7), and a first fluororubber sealing ring (8) is sleeved in the groove; a spring (9) is placed above the stainless steel pressing block (7), a threaded fastening part is used for sealing the inner cavity and pressing the spring (9), the threaded fastening part is composed of a stainless steel locking block (10), a PTFE threaded sleeve ring (11) and a stainless steel upper cover (12), and the threaded fastening part and the stainless steel shell (1) are sealed through a second fluorine rubber sealing ring (13); and a non-observation electrode conductive column (14) and an observation electrode conductive column (15) which are connected with the circulating charge and discharge equipment are respectively arranged at the stainless steel shell (1) and the stainless steel upper cover (12).

2. The device as claimed in claim 1, wherein the diameter of the opening at the center right below the stainless steel shell (1) is 2mm-5mm, the diameter of the quartz window glass (2) is larger than the diameter of the opening and the thickness is 0.1mm-0.2mm, and neutral silicone weather-resistant glue is used for bonding and sealing between the quartz window glass (2) and the stainless steel shell (1).

3. The device according to claim 1, characterized in that the non-viewing electrode (4) and the diaphragm (5) are centrally perforated with a diameter of 2mm to 5mm by means of laser cutting.

4. The device according to claim 1, characterized in that the outer diameter of the fluorine rubber sealing ring (8) embedded in the ring side of the stainless steel pressing block (7) is in interference fit with the inner diameter of the PTFE insulating sleeve ring (3), and the PTFE insulating sleeve ring (3) is in interference fit with the inner cavity of the stainless steel shell (1).

5. The device as claimed in claim 1, wherein the threaded fastening part is characterized in that a square boss of the stainless steel upper cover (12) is matched with a central square hole of the PTFE threaded collar (11) to realize common rotation; the stainless steel locking block (10) is screwed into the square boss thread groove of the stainless steel upper cover (12) to realize the fixation of the parts; the upper section of the stainless steel shell is screwed with the PTFE threaded lantern ring of the component.

6. An in-situ electrode strain field monitoring method based on marked fluorescent quantum dot speckle by using the device of claim 1, wherein the method comprises the following steps:

1) preparing a quantum dot-toluene-acetone mixed solution;

2) coating quantum dots on the observation electrode (6);

3) assembling an in-situ observation device and building an in-situ observation platform;

4) the in-situ observation device carries out cyclic charge and discharge experiments and continuously shoots the surface pictures of the observation electrode;

5) digital image correlation processing software analyzes and observes the change of the electrode strain field.

7. The method for in-situ monitoring of the electrode strain field based on the marked fluorescent quantum dot speckle as claimed in claim 6, wherein the preparation method of the quantum dot-toluene-acetone mixed solution in step 1) is to weigh the quantum dots and dissolve the quantum dots in toluene, perform ultrasonic treatment to dissolve the quantum dots uniformly to obtain a quantum dot toluene solution with a concentration of not less than 1mg/mL, and mix the obtained quantum dot toluene solution with acetone according to the ratio of the quantum dot toluene solution: and mixing acetone (2:1) - (1:1) in a volume ratio, and uniformly mixing by using ultrasonic waves to obtain the quantum dot-toluene-acetone solution.

8. The quantum dot in step 1) of claims 6 and 7 is one selected from the group consisting of CdSe, CdS, CdTe, CdSe/ZnS, CdS/ZnS, CdTe/CdS.

9. The in-situ monitoring method according to claim 6, wherein the step 2) of coating the quantum dots on the observation electrode (6) comprises immersing the sample in the quantum dot-toluene-acetone mixed solution, dropping the quantum dot-toluene-acetone mixed solution, or brushing the quantum dot-toluene-acetone mixed solution with a brush.

10. The in-situ monitoring method according to claim 6, wherein the in-situ observation platform of step 3) comprises a fluorescence confocal microscope, a computer, a battery cycle charging and discharging device and an in-situ observation device which are connected with each other.

11. The in-situ monitoring method of claim 6, wherein the step 5) is to introduce the picture of the quantum dot marking speckle on the surface of the electrode in the cyclic charge and discharge process of the in-situ observation device into Vic-2D software, process the introduced picture by using a digital image correlation method, and analyze the change of the strain field on the surface of the electrode.

Technical Field

The invention relates to an in-situ optical monitoring device and method for an electrode material strain field, which are used for analyzing the strain distribution condition and the evolution rule of an electrode pole piece in charge-discharge circulation of a lithium ion battery. The method can mark the fluorescent quantum dot speckles and record the displacement condition of the speckles in the cyclic charge and discharge process of the electrode material, so as to obtain the strain fields of the electrode material at different times, and belongs to the field of in-situ characterization and mechanical measurement of the electrode material of the lithium battery.

Background

Since the 21 st century, fossil energy crisis and global warming issues have attracted attention all over the world. The domestic and foreign centralize the strength to explore green sustainable energy and develop clean electric energy. With the rapid development of new energy automobiles, mobile electronic equipment, aerospace equipment and the like, higher requirements are put forward on the performance of the battery. Among them, compared with other conventional batteries, lithium ion batteries have become an important development direction due to a series of advantages of small volume, large theoretical capacity, high conversion efficiency, no environmental pollution, low self-discharge rate, and the like.

During the charging and discharging process of the battery, the gradient distribution of the lithium concentration can cause the stress mismatch between the material components, thereby causing different deformations between the material components. When the degree of deformation or stress of the material exceeds a certain value, cracks occur in the particles, and thus the strains between the active particles cannot be matched with each other, so that contact between the active particles or between the particles and the conductive agent and the binder is lost. Strain mismatch between the electrode material and the current collector can also cause active species to be shed. The mechanical attenuation can be divided into the following parts according to scale: cracking inside the electrode particles, separation of the electrode particles from the conductive carbon and the binder, separation of the active material from the current collector, and electrode delamination. A testing method capable of monitoring the strain change of the electrode material on line for a long time is developed, and the testing method has important significance for the mechanism of the performance decline of the lithium ion battery electrode.

The digital image correlation method is a feasible way for realizing in-situ measurement of the stress strain of the electrode material. The method needs to form high-quality speckles on the surface of an electrode material, the electrode material is assembled into a complex visual simulation battery device to carry out cyclic charge and discharge tests, and the displacement field and the strain field of the electrode material are obtained by observing and analyzing the change of the positions of the speckles. The speckle preparation and the high-performance visual simulation battery device are important links for realizing the stress-strain in-situ measurement of the electrode material.

Related studies have been conducted by scholars for strain field monitoring of battery electrodes.The team performs an in-situ strain field monitoring experiment on the LMO positive electrode, and researches the relation between capacity reduction caused by cycle number and strain field change through marking natural spots of electrode materials (Rajput S,White S,et al.Strain evolution in lithium manganese oxide electrodes[J]Experimental Mechanics,2018,58(4): 561-. However, this study has two problems: firstly, the shape of the material can change along with the charging and discharging process so that the position change of natural spots of the material cannot be identified; secondly, the cycle performance of the in-situ observation device cannot be matched with a button cell or a soft package battery, so that the change of a strain field in the long-term cycle process of the electrode material cannot be researched.

Disclosure of Invention

The invention provides an electrode strain field in-situ monitoring device and method for marking fluorescent quantum dot speckles, aiming at the problems in the background art. The device can realize the in-situ observation of long-term charge-discharge circulation, and monitor the evolution condition of the electrode strain field by using the mark of the fluorescent quantum dot speckles.

The invention is realized by the following technical scheme:

an electrode strain field in-situ monitoring device for marking fluorescent quantum dot speckles, the device comprising: a hole is formed in the center of the position right below the stainless steel shell 1, and the quartz glass window 2 covers the hole; placing a Polytetrafluoroethylene (PTFE) insulating lantern ring 3 into an inner cavity of a stainless steel shell 1, and stacking a non-observation electrode 4, a diaphragm 5 and an observation electrode 6 in sequence by taking an opening at the bottom of the inner cavity as a center; a stainless steel pressing block 7 is placed above the observation electrode 6, a groove is formed in the ring side of the stainless steel pressing block 7, and a first fluororubber sealing ring 8 is sleeved in the groove; a spring 9 is arranged above the stainless steel pressing block 7, a threaded fastening part is used for sealing the inner cavity and pressing the spring 9, the threaded fastening part is composed of a stainless steel locking block 10, a PTFE threaded lantern ring 11 and a stainless steel upper cover 12, and the threaded fastening part and the stainless steel shell 1 are sealed through a second fluorine rubber sealing ring 13; an observation electrode conductive column 15 and a non-observation electrode conductive column 14 which are connected with the circulating charge and discharge equipment are respectively arranged on the side surface of the stainless steel shell 1 and the stainless steel upper cover 12.

The diameter of an opening at the center right below the stainless steel shell 1 is 2-5 mm, so that an enough observation area is provided, and the contact between an electrode current collector and the inner cavity of the shell is not influenced; the diameter of the quartz window glass 2 is larger than the diameter of the opening and the thickness of the quartz window glass is 0.1mm-0.2mm, so that the observation objective lens can be close to the observation electrode as much as possible, and neutral silicone weather-resistant glue is used for bonding and sealing between the quartz window glass 2 and the stainless steel shell 1.

The centers of the non-observation electrode 4 and the diaphragm 5 are provided with holes so as to carry out optical observation on the observation electrode, the diameter of the holes is 2mm-5mm, and the laser cutting method is adopted in the hole opening mode to ensure that the diaphragm and the electrode are not damaged in the hole opening process.

The outer diameter of a fluororubber sealing ring 8 embedded in the ring side of the stainless steel pressing block 7 is in interference fit with the inner diameter of a PTFE insulating sleeve ring 3, the PTFE insulating sleeve ring 3 is in interference fit with the inner cavity of the stainless steel shell 1, and therefore the sealing performance is enhanced and the electrolyte is guaranteed not to leak in the inner space.

The square boss of the stainless steel upper cover 12 in the threaded fastening part is matched with the central square hole of the PTFE threaded sleeve ring 11 to realize common rotation; the stainless steel locking block 10 is screwed into the square boss thread groove of the stainless steel upper cover 12 to realize the fixation of the components; the upper section of the stainless steel shell is screwed with the PTFE threaded lantern ring to realize threaded fastening, so that the sealing performance of the whole device and the normal conduction of a circuit are ensured.

An in-situ electrode strain field monitoring method based on marked fluorescent quantum dot speckle by using the device of claim 1, wherein the method comprises the following steps:

1) preparing a quantum dot-toluene-acetone mixed solution;

2) coating quantum dots on the observation electrode 6;

3) assembling an in-situ observation device and building an in-situ observation platform;

4) the in-situ observation device carries out cyclic charge and discharge experiments and continuously shoots the surface pictures of the observation electrode;

5) digital image correlation processing software analyzes and observes the change of the electrode strain field.

The preparation method of the quantum dot-toluene-acetone mixed solution in the step 1) comprises the steps of weighing quantum dots, dissolving the quantum dots in toluene, carrying out ultrasonic treatment to enable the quantum dots to be uniformly dissolved to obtain a quantum dot toluene solution with the preparation concentration of not less than 1mg/mL, and mixing the obtained quantum dot toluene solution with acetone according to the ratio of the quantum dot toluene solution: and mixing acetone (2:1) - (1:1) in a volume ratio, and uniformly mixing by using ultrasonic waves to obtain the quantum dot-toluene-acetone solution.

The quantum dots in the step 1) can be one of CdSe, CdS, CdTe, CdSe/ZnS, CdS/ZnS, CdTe/ZnS and CdTe/CdS.

The method for coating the quantum dots on the observation electrode 6 in the step 2) comprises the steps of immersing the sample in the quantum dot-toluene-acetone mixed solution, and carrying out drop coating by using the quantum dot-toluene-acetone mixed solution or brush coating by dipping the quantum dot-toluene-acetone mixed solution with a brush.

The in-situ observation platform in the step 3) comprises a fluorescence confocal microscope, a computer, a battery circulating charge-discharge device and an in-situ observation device.

And 5) importing the picture of the electrode surface quantum dot marked speckles into V digital image related processing software in the cyclic charge and discharge process of the in-situ observation device, processing the imported picture by using a digital image related method, and analyzing the change of the electrode surface strain field.

Advantageous effects

The invention provides an electrode strain field in-situ monitoring device and method for marking fluorescent quantum dot speckles. The charge-discharge performance of the in-situ observation device is close to that of a button cell, so that long-time charge-discharge circulation can be realized, and the electrode material in the charge-discharge circulation process under different working conditions can be optically observed.

By coating quantum dots on the surface of the electrode material as a fluorescent marker, the displacement condition of the marked speckles can be recorded while the electrode material is observed in situ, and the strain field evolution condition is analyzed by using a digital image correlation method.

The method is suitable for the strain field research of different lithium ion battery electrodes.

Drawings

FIG. 1 is a schematic structural diagram of an electrode strain field in-situ monitoring device for marking fluorescent quantum dot speckles according to the invention;

wherein, 1: steel casing, 2: quartz glass window, 3: polytetrafluoroethylene insulating collar, 4: non-observation electrode, 5: a separator, 6: observation electrode, 7: stainless steel briquetting, 8: first fluororubber gasket, 9: spring, 10: stainless steel locking block, 11: PTFE threaded collar, 12: stainless steel upper cover, 13: second fluorine rubber seal ring, 14: non-observation electrode conductive column, 15: the observation electrode conducts the columns.

FIG. 2 is a graph of the decay in capacity of the in situ observation device of the present invention with cycle number;

FIG. 3 is a fluorescent confocal microscope dark field diagram of the electrode material for marking fluorescent quantum dots according to the present invention;

FIG. 4 is a graph of a change in a strain field cloud of the electrode material of the present invention;

FIG. 5 is a graph showing the change in strain number of the electrode material according to the present invention.

Detailed Description

The invention is further illustrated by the following description and examples in connection with the accompanying drawings, without limiting the scope of the invention.

The structural schematic diagram of the electrode strain field in-situ monitoring device for marking the fluorescent quantum dot speckles is shown in figure 1. The center under the stainless steel shell 1 is provided with a hole, the diameter is 2mm-5mm, an enough observation area is provided, the contact between an electrode current collector and the inner cavity of the shell is not affected, quartz window glass 2 covers the hole and serves as an experiment observation window, the diameter is larger than the diameter of the hole, the thickness is 0.1mm-0.2mm, an observation objective lens can be close to an observation electrode as far as possible, and neutral silicone weather-resistant glue is used between the quartz window glass 2 and the stainless steel shell 1 for bonding and sealing. The neutral silicone weather-resistant adhesive has good sealing property and corrosion resistance. The non-observation electrode 4, the diaphragm 5 and the observation electrode 6 are stacked by taking the opening at the bottom of the inner cavity as the center, the centers of the non-observation electrode 4 and the diaphragm 5 are opened to carry out optical observation on the observation electrode, the diameter of the opening is 2mm-5mm, and the diaphragm is folded by finding out that the hole with smaller diameter on the diaphragm is not suitable for being opened by a punching mode through actual operation, so that the diaphragm and the electrode are not damaged by the opening process by adopting a laser cutting method. Put into Polytetrafluoroethylene (PTFE) insulating lantern ring 3 in 1 inner chamber of stainless steel casing, PTFE insulating lantern ring 3 and 1 inner chamber interference fit of stainless steel casing to this strengthens the leakproofness and guarantees that electrolyte does not reveal in this inner space, and this insulating lantern ring can use the cleaner lubrication and strike when dismantling and take out. A stainless steel pressing block 7 is placed above the observation electrode 6, a groove is formed in the annular side of the stainless steel pressing block 7, a fluororubber sealing ring 8 is sleeved in the groove, and the outer diameter of the fluororubber sealing ring 8 embedded in the annular side of the stainless steel pressing block 7 is in interference fit with the inner diameter of the PTFE insulating sleeve ring 3, so that the sealing property of an inner cavity can be enhanced, and the electrolyte can be prevented from leaking; a spring 9 is arranged above the stainless steel pressing block 7, a thread fastening part is used for sealing the inner cavity and pressing the spring 9, the thread fastening part is composed of a stainless steel locking block 10, a PTFE thread sleeve ring 11 and a stainless steel upper cover 12, and a square boss of the stainless steel upper cover 12 in the thread fastening part is matched with a central square hole of the PTFE thread sleeve ring 11 to realize common rotation; the stainless steel locking block 10 is screwed into the square boss thread groove of the stainless steel upper cover 12 to realize the fixation of the components; the upper section of the stainless steel shell is screwed with the PTFE threaded lantern ring to realize threaded fastening, so that the sealing performance of the whole device and the normal conduction of a circuit are ensured. The fastening part and the stainless steel shell 1 are sealed by a fluorine rubber sealing ring 13; and a non-observation electrode conductive column 14 and an observation electrode conductive column 15 are respectively connected to the stainless steel shell 1 and the stainless steel upper cover 12 to connect with the circulating charge and discharge equipment, and the connection mode can be selected from threaded connection or welding.

The non-observation electrode conducting column 14, the stainless steel shell 1, the non-observation electrode 4, the diaphragm 5, the observation electrode 6, the stainless steel pressing block 7, the spring 9, the stainless steel locking block 10, the stainless steel upper cover 12 and the observation electrode conducting column 15 form a conducting path of the in-situ observation device. The quartz window glass 2 and the surrounding sealant, the PTFE insulating sleeve ring 3, the fluororubber sealing ring 8 and the fluororubber sealing ring 13 ensure the sealing performance of the in-situ observation device, avoid electrolyte leakage and ensure that the inside of the device does not enter air.

The invention relates to a strain field monitoring method of an electrode material for marking fluorescent quantum dot speckles, which comprises the following steps:

1) selecting green fluorescent CdSe/ZnS core-shell structure nanocrystals as fluorescent quantum dots, adding the CdSe/ZnS core-shell structure fluorescent quantum dots into toluene, placing the solution in ultrasonic equipment for ultrasonic oscillation to enable the solution to be dissolved uniformly, and performing ultrasonic oscillation to enable the solution to be dissolved uniformly to obtain a quantum dot toluene solution with the configuration concentration of not less than 1 mg/mL; mixing the obtained quantum dot toluene solution with acetone according to the ratio of the quantum dot toluene solution: mixing acetone (2:1) - (1:1) in a volume ratio, and performing ultrasonic treatment again to obtain a quantum dot-toluene-acetone solution which is uniformly dissolved, so that the condition that the speckle effect is poor due to quantum dot aggregation can not occur when the electrode material is coated;

2) the quantum dot-toluene-acetone solution is uniformly coated on the surface of the electrode material by adopting a method of soaking, wolf hair brush coating or dropper dropping coating. After coating, the electrode material is placed in a vacuum drying oven and dried for 12 hours at 60 ℃;

3) before assembling the in-situ device, cleaning the parts of the in-situ device by water and alcohol. After cleaning, the mixture is placed in a blast drying oven to be dried for 12 hours at the temperature of 60 ℃. After drying, the in situ device parts and the electrode material were removed and transferred to an argon filled glove box (water oxygen concentration below 0.1 mg/L). The required in-situ device parts, electrode material, diaphragm (laser drilled), electrolyte are placed in the operating area. The PTFE insulating lantern ring 3 is plugged into the stainless steel shell 1 and contacts with the bottom of the inner cavity of the shell. Placing the non-observation electrode 4 at the right center of the bottom of the inner cavity of the stainless steel shell 1, and dropwise adding electrolyte; and a diaphragm 5 is covered on the non-observation electrode 4, the center of the opening is aligned with the center of the non-observation electrode 4, the outer diameter can be subjected to laser cutting according to the inner diameter of the PTFE insulation sleeve ring 3 in order to ensure accurate alignment of the centers, and electrolyte is dripped. The membrane 5 is covered with an observation electrode 6. A stainless steel pressing block 7 embedded with a fluororubber seal ring 8 is placed on the observation electrode 6. The stainless steel pressing block 7 is sleeved with the pressing spring 9. And assembling a threaded fastening part, namely sleeving the PTFE threaded collar 11 into the stainless steel upper cover 12, screwing the stainless steel locking block 10 into the square boss of the stainless steel upper cover 12 and simultaneously pressing the PTFE threaded collar 11 to finish the threaded fastening part. And screwing the threaded fastening part into the stainless steel shell 1, and pressing the compression spring 9 and the fluororubber sealing ring 13 to complete the assembly of the in-situ observation device. After the assembly is completed, 705 silicon sealant can be coated between the threaded fastening part and the gap of the stainless steel shell 1, so that the sealing performance can be enhanced, and meanwhile, the sealant is easy to remove, and the repeated use of the in-situ observation device can be ensured. After the assembly is completed, the in-situ observation device is placed in the glove box for 12 h. After standing, taking out the in-situ device, connecting the in-situ device with a fluorescence confocal microscope, charging and discharging equipment, an in-situ observation device and a computer, and building an in-situ observation platform;

4) and (3) carrying out charge-discharge cycle test on the in-situ observation device: connecting the in-situ observation device with charge and discharge test equipment, performing set charge and discharge multiplying power charge and discharge cycle tests such as (0.1C, 0.5C and 1C … …) under a constant potential voltage window corresponding to the electrode material, and setting cycle times such as 1, 10 or 100 times of different batteries to obtain a decay curve of the battery capacity along with the cycle times. Fluorescence confocal microscope in-situ observation experiment: in the charging and discharging process of the in-situ device, a fluorescence confocal microscope is used for carrying out optical observation on the electrode material through a quartz glass window, and computer software is used for recording the change of the surface speckle position of the fluorescence-labeled electrode material in a view field;

5) and (3) importing the picture of the electrode surface quantum dot marked speckles into Vic-2D software in the cyclic charge and discharge process of the in-situ observation device, and processing the imported picture by using a digital image correlation method. The method comprises the steps of selecting an electrode surface fluorescence speckle picture when the electrode material is not charged and discharged as a reference picture, selecting a square area in the reference picture as a digital image correlation method analysis area, and analyzing the change of a strain field on the electrode surface in the area to obtain the change of a strain field cloud picture and the change of strain number values of different position points in the charging and discharging process of the electrode material.

Example (b): in-situ monitoring of the change condition of the strain field of the NCM523 positive electrode material in the cyclic charge-discharge process comprises the following specific contents:

the positive electrode material, 9600g, 1200g and 1200g of SuperP and PVDF are weighed in sequence by an analytical balance, the weighed positive electrode material and conductive carbon black are added into a mortar, and the mixture is dry-ground in the mortar until the mixture is uniformly mixed. Adding 1200g of PVDF into 20ml of NMP solution, stirring the NMP-PVDF suspension in a magnetic stirrer until the suspension is clear, adding the mixture of the positive electrode material and the conductive carbon black powder, and stirring for 12 hours by using the magnetic stirrer to prepare positive electrode slurry. The slurry is uniformly coated on the surface of the aluminum foil by an automatic coating machine, the aluminum foil coated with the slurry is placed in a vacuum drying oven at 105 ℃ for drying for 3h, and finally, a punching machine is used for punching into a circular pole piece with the diameter of 12 mm. And coating the prepared CdSe/ZnS core-shell structure quantum dot-toluene-acetone solution on an electrode plate.

And the negative electrode material is a lithium sheet, and the lithium sheet is punched in the glove box by using a designed hole-opening die. And assembling the NCM523, the diaphragm and the lithium sheet into an in-situ observation device, and dripping electrolyte during assembly. Standing for 12h after the assembly is completed, and building an in-situ observation platform.

As the electrode materials are NCM523 and the lithium sheet, the in-situ observation device selects to carry out charge-discharge cycle test with the charge-discharge multiplying power of 1C (the charge current is 0.6mA) under the constant potential voltage window of 2.8-4.3V, and the obtained attenuation curve of the capacity of the in-situ observation device along with the cycle times is shown in figure 2, which indicates that the in-situ observation device can realize long-term cycle.

An image of the electrode material under a fluorescence confocal microscope is shown in fig. 3, which illustrates that the fluorescent quantum dots can form high-quality uniformly-distributed marked speckles on the surface of the electrode material. Recording the marked speckle change pattern of the electrode material in the cyclic charge-discharge process, and importing the pattern into digital image correlation processing software. An electrode material strain cloud graph (figure 4) and a change graph (figure 5) of a strain numerical value of a certain point of the electrode material can be obtained through analysis by a digital image correlation method, and the method can be used for monitoring the strain field of the electrode material in situ.