In-situ testing device and method based on cryo-transmission X-ray

Abstract

An in-situ testing device and method based on cryo-transmission X-rays belongs to the field of battery characterization technology. The device includes a battery mold, a metal shell, a freezing unit, an insulation unit and a support; the battery mold is detachably mounted and fixed on the back of the cover plate of the metal shell, the inner walls around the metal shell are provided with a double-layer insulation layer, and the double-layer insulation layer around the inner wall of the metal shell is provided with grooves, the insulation unit is filled into the groove, the liquid nitrogen guide tube of the freezing unit is connected to the bottom of the metal shell, the center of the metal shell is provided with a ray passing hole one, the center of the battery mold is provided with a ray passing hole two, and the temperature sensor of the freezing unit is installed in the inner cavity of the metal shell; the upper end of the support is detachably fixedly connected to the bottom of the metal shell. Before testing, the assembled in-situ test battery containing the ray passing hole three is installed on the battery mold, and the center lines of the three ray passing holes are overlapped for transmitting X-rays. The present invention is used for electrochemical analysis of button-type solid-state batteries.

Description

Technical Field

[0001] The present invention relates to a battery testing device and method, and in particular to an in-situ testing device and method based on cryo-transmission X-rays, belonging to the technical field of battery characterization. Background Art

[0002] Since the advent of lithium-ion batteries, they have been widely used in transportation, special operations and other fields due to their advantages such as high specific energy, high voltage and high power. Among them, solid-state batteries are favored due to their high safety, but the existence of interface problems leads to poor fast charging performance. Therefore, improving the charging speed of solid-state lithium-ion batteries can reduce downtime and further improve operating efficiency.

[0003] At present, the research on fast charging of batteries mainly focuses on the modification of active materials, the development of new electrolytes, and the design of battery structures. Although the fast charging performance of batteries can be improved to a certain extent, there is little research on the fast charging mechanism of solid-state batteries, and the internal reaction path is not clear. It is urgent to develop new characterization devices and methods for the internal reaction mechanism of batteries.

[0004] Most existing technologies are non-in-situ and take a long time to measure, which inevitably leads to the neglect of the rapid evolution process inside the battery particles during the measurement, resulting in delayed test results, and ultimately leading to a deviation in the understanding of the reaction mechanism. The X-ray characterization technology based on synchrotron radiation has high penetration and is an important method for analyzing the internal reaction mechanism of battery particles. However, there are problems such as sample damage and difficulty in capturing transient information. Therefore, the present invention designs a new imaging method that uses freezing technology to protect samples from damage under a synchrotron radiation light source, and can capture the rapid reaction signals inside electrode particles in situ, which is used to analyze the internal reaction mechanism of solid-state batteries. Summary of the invention

[0005] The purpose of the present invention is to address the problems existing in the background technology and to provide an in-situ testing device and method based on cryo-transmission X-rays, which is used to analyze new reaction mechanisms that are difficult to capture by conventional methods during the charging and discharging process of solid-state batteries.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] An in-situ testing device based on cryo-transmission X-rays, the device comprising a battery mold, a shell, a freezing unit, an insulation unit and a support; the battery mold is detachably mounted and fixed on the back of a cover plate of the shell, a double-layer insulation layer is provided on the inner wall around the shell, grooves are provided in the double-layer insulation layer around the inner wall of the shell, the insulation unit is filled into the grooves, a liquid nitrogen guide pipe of the freezing unit is connected to the bottom of the shell, a ray passing hole 1 penetrating from front to back is provided at the center of the shell, a ray passing hole 2 coinciding with the center line of the ray passing hole 1 is provided at the center of the battery mold for transmitting X-rays; a temperature sensor of the freezing unit is installed in the inner cavity of the shell; the upper end of the support is detachably fixedly connected to the bottom of the shell.

[0008] Furthermore, the thermal insulation unit includes a thermal insulation medium, a phase change material and a nano-aerogel coating; the thermal insulation medium and the phase change material are filled into the groove and sealed with a sealing insulating glue, and the groove and the shell surface are coated with a nano-aerogel coating.

[0009] Furthermore, the shell includes a cover plate and a base; the back of the cover plate and the surface of the assembled battery mold are covered with insulating tape, the cover plate and the base port are detachably fixedly connected, two openings are provided at the base port, the cover plate and the base bottom are both provided with the ray passing hole 1 with the center line coinciding, and the inner wall around the base is provided with the double-layer insulation layer.

[0010] Furthermore, the battery mold includes a battery clamp made of polytetrafluoroethylene material and metal pole ears installed on both sides of the battery clamp, the metal pole ears are fixedly connected to one end of the wire, the other end of the wire is connected to an external charge and discharge tester, and the battery clamp is provided with the radiation passing hole 2 in the center; before the test, the assembled in-situ test battery including the radiation passing hole 3 is installed on the battery clamp, and the radiation passing hole 3 is made to coincide with the center lines of the radiation passing hole 2 and the radiation passing hole 1.

[0011] Furthermore, the battery mold is detachably mounted and fixed to the back of the cover plate of the shell by four copper bolts.

[0012] Furthermore, the freezing unit includes a liquid nitrogen flow guide tube, a cold medium and a temperature sensor; one end of the liquid nitrogen flow guide tube is connected to the bottom of the shell, and the cold medium is introduced into the inner cavity of the shell through the liquid nitrogen flow guide tube, and is discharged through one of the openings after gasification; the temperature sensor is installed in the inner cavity of the base, and the temperature sensor is connected to the external computer signal.

[0013] Furthermore, the support includes a threaded cylinder and a circular base, the upper end of the threaded cylinder is threadedly fastened to the threaded hole provided at the lower end of the shell, the lower end of the threaded cylinder is detachably fixed to the circular base, and the bottom of the circular base is provided with multiple magnetic suction grooves for magnetic adsorption and fixation to the transmission X-ray microscope operating table.

[0014] An in-situ testing method based on cryo-transmission X-rays, the method comprising the following steps:

[0015] Step 1: In-situ testing of battery assembly;

[0016] Step 2: Assemble and test the in-situ test battery with the in-situ test device; the specific steps are as follows:

[0017] Step 21: Install the assembled in-situ test battery on the battery fixture, and then fix the battery fixture to the back of the cover plate with copper bolts, ensuring that the center lines of the ray passing through hole 1 of the shell, the through hole 3 of the in-situ test battery, and the ray passing through hole 2 of the battery fixture coincide with each other;

[0018] Step 22: Install and fix the assembled cover plate at the base port, and insulate and seal it with the copolymer through an insulating tape;

[0019] Step 23: Fix the in-situ test device on the transmission X-ray microscope operating table, turn on the X-ray source, use X-rays to find the positive electrode active particles, and adjust the X, Y, and Z rotation axis positions to ensure that the particles are in the center of the field of view;

[0020] Step 24: Turn off the X-ray source, connect the battery mold to an external charge and discharge tester, perform a charge and discharge test on the in-situ test battery, and after reaching the target voltage / current, open the liquid nitrogen guide tube and inject liquid nitrogen;

[0021] Step 25: The temperature sensor is connected to the external computer signal, the temperature sensor is turned on, and the internal temperature of the shell detected by the temperature sensor is displayed by the external computer. When the temperature reaches the stable temperature of the internal phase change material, the X-ray source is turned on, and the energy range, scanning speed and exposure time of each segment are adjusted to perform in-situ cryo-transmission X-ray microscopy testing;

[0022] Step 26: Repeat steps 24 and 25 until all in-situ tests are completed, adjust the position of the transmission X-ray microscope operating table, move the field of view to a particle-free area, keep the energy range, scanning speed and exposure time of each segment unchanged to image the background and remove background noise during the test.

[0023] Furthermore, in step 1, the specific steps of in-situ testing battery assembly are as follows:

[0024] Step 11: weighing a positive electrode active material, a conductive agent, a solid electrolyte and a binder in a dehydrated and deoxygenated atmosphere, and mixing them in a weight ratio of 59:5:34:2, and then adding an excess organic solvent of 300% by weight as a diluent to dilute the slurry;

[0025] Step 1 and 2: The slurry is evenly coated on the carbon-coated aluminum foil with a thickness of 50 microns, and transferred to a heating table, and dried at 60-80°C for 1-3 hours to form a positive electrode sheet;

[0026] Step 13: Under a dehydrated and deoxygenated atmosphere, weigh the solid electrolyte and the binder, and mix them in a ratio of 9:1 by mass. Then, add an organic solvent in a mass ratio of 1:1 to dilute, and transfer the slurry to a mortar and mix evenly.

[0027] Step 14: Take the dried positive electrode sheet, apply the solid electrolyte slurry prepared in step 13 on the positive electrode sheet with a thickness of 200 microns, then transfer it to a heating table and dry it at 60-80°C for 1-3 hours;

[0028] Step 15: prepare a negative electrode sheet in a dehydrated and deoxygenated atmosphere according to an NP ratio of 1.1-1.5, wherein the negative electrode slurry includes a negative electrode active material, a solid electrolyte, a conductive agent, and a binder, and is mixed in a mass ratio of 50:46:1:3, and then coated on a carbon-coated aluminum foil with a thickness of 100 microns, and dried at 60-80°C for 1-3h to prepare a negative electrode sheet; finally, the slurry mixed in step 13 is also coated on the negative electrode sheet with a thickness of 200 microns, and dried at 60-80°C for 1-3h;

[0029] Step 16: Cut the positive and negative electrodes according to the selected battery shell size and assemble them, and drill through holes 3 at the center of the positive and negative electrodes, battery shell and internal metal components to ensure X-ray penetration.

[0030] Furthermore, the positive electrode active material and the negative electrode active material are both one of the nickel-cobalt-manganese series ternary materials, lithium cobalt oxide materials, lithium iron phosphate materials, and nickel-cobalt-aluminum series ternary materials, the conductive agent is one or more of conductive carbon black, conductive graphite, carbon nanotubes, graphene, and carbon fibers, the solid electrolyte is one of Li6PS5Cl, Li10GeP2S12, and Li3PS4, and the binder and the coordinated organic solvent are polyvinylidene fluoride-N-methylpyrrolidone or nitrile rubber-xylene.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] 1. The present invention proposes an in-situ testing device and method based on cryo-transmission X-rays, which can be applied to the 18B beam station and 16 beam station of Shanghai Light Source and the future Beijing Huairou Light Source, thereby improving the imaging quality.

[0033] 2. The present invention utilizes cold media to remove environmental energy, rapidly reduces the reaction rate inside the battery, and captures the rapidly evolving battery reaction mechanism in slow motion, which greatly expands the understanding of the battery evolution mechanism.

[0034] 3. The present invention uses highly penetrating X-rays generated by a synchrotron radiation source to characterize active battery particles, and combined with the freezing effect, achieves rapid electrochemical analysis on a single particle scale.

[0035] 4. The in-situ testing device based on cryo-transmission X-ray of the present invention is easy to operate and has a flexible scope of use. In addition to being applicable to the method described in the present invention, it can also be applied to a variety of cryo-imaging technologies.

[0036] 5. The method of the present invention solves the problem of instantaneous signal loss caused by the low resolution limit of traditional characterization methods. At the same time, its overall process is simple and easy to operate. It can be applied to the research of various battery systems (such as lithium-ion liquid batteries, lithium-ion solid-state batteries, lithium-sulfur batteries, etc.), providing a new analytical method for the development of next-generation batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a front view of an in-situ testing device based on cryo-transmission X-rays of the present invention, with the cover plate not shown;

[0038] Figure 2 It is a front view of an in-situ testing device based on cryo-transmission X-rays of the present invention;

[0039] Figure 3 It is the front view of the cover;

[0040] Figure 4 yes Figure 3 A cross-sectional view of section AA;

[0041] Figure 5 It is the main view of the base;

[0042] Figure 6 yes Figure 5 A cross-sectional view of the BB section;

[0043] Figure 7 yes Figure 5 A cross-sectional view of the CC section;

[0044] Figure 8 This is a physical picture of an invented in-situ testing device based on cryo-transmission X-rays;

[0045] Fig. 9 This is a scanning electron microscope image of a prepared single-layer active particle electrode; Fig. 9 (a) is a scanning electron microscope image of the prepared single-layer active particle electrode in backscattering mode; Fig. 9 (b) is a scanning electron microscope image of the prepared single-layer active particle electrode in secondary electron mode;

[0046] Fig.10 is a schematic diagram of an assembled in-situ button cell;

[0047] Fig.11 It is a schematic diagram of fixing an in-situ testing device based on cryo-transmission X-rays of the present invention on a transmission X-ray microscope sample stage for testing;

[0048] Fig.12 This is a comparison chart of the experimental results of cryo-transmission X-ray microscopy.

[0049] The names and reference numerals of the components involved in the above drawings are as follows:

[0050] Battery mold 1, radiation passing hole 2 101, battery clamp 102, metal pole ear 103, shell 2, cover plate 201, groove 202, radiation passing hole 1 203, base 204, opening 205, freezing unit 3, liquid nitrogen flow guide tube 301, temperature sensor 302, insulation unit 4, support 5, threaded cylinder 501, circular base 502. DETAILED DESCRIPTION

[0051] The technical solution of the present invention is further described below in conjunction with the accompanying drawings, but it is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention shall be included in the protection scope of the present invention. The reagents and instruments used in the following description are all conventional commercial reagents, so that professionals in the field can easily implement or use the present invention.

[0052] The main principle of the present invention is to remove environmental energy through cold medium according to the Arrhenius formula, significantly increasing the influence of the temperature exponential term on the intrinsic diffusion coefficient. The ion vibration frequency is reduced without changing the diffusion path, thereby greatly slowing down the ion diffusion rate. This method can fragment the traditional TXM (transmission X-ray microscope) equalization results without affecting the duration of a single test or the quality of imaging data, thereby achieving effective tracking of lithium ion diffusion behavior and paths, further clarifying the reaction mechanism that is not easily observed inside the battery, and helping the development of the next generation of batteries.

[0053] Specific implementation method 1: Figure 1-Figure 8As shown, this embodiment records an in-situ testing device based on cryo-transmission X-rays, the device comprising a battery mold 1, a shell 2, a freezing unit 3, an insulation unit 4 and a support 5; the battery mold 1 is detachably mounted and fixed on the back of the cover plate 201 of the shell 2, the inner walls of the shell 2 are provided with a double-layer insulation layer, and the double-layer insulation layer located around the inner wall of the shell 2 is provided with a groove 202, the insulation unit 4 is filled into the groove 202, the liquid nitrogen guide tube 301 of the freezing unit 3 is connected to the bottom of the shell 2, the center of the shell 2 is provided with a ray passing hole 1 203 running through the front and back, and the center of the battery mold 1 is provided with a ray passing hole 2 101 (the shapes of the ray passing hole 1 203 and the ray passing hole 2 101 are both circular, and the diameters are both 5-7mm) for transmitting X-rays; the temperature sensor 302 of the freezing unit 3 is installed in the inner cavity of the shell 2; the upper end of the support 5 is detachably fixedly connected to the bottom of the shell 2.

[0054] Furthermore, the insulation unit 4 includes an insulation medium (insulation cotton material), a phase change material (ethyl acetate or methyl propionate) and a nano aerogel coating; the insulation medium and the phase change material are filled into the groove 202 and sealed with a sealing insulating glue, and the groove 202 and the surface of the shell 2 are coated with a nano aerogel coating.

[0055] Furthermore, the shell 2 (made of aluminum alloy) includes a cover plate 201 (a single-layer metal plate) and a base 204; the back of the cover plate 201 and the surface of the assembled battery mold 1 are covered with insulating tape, the cover plate 201 is detachably fixedly connected to the port of the base 204 (the four corners of the cover plate 201 are detachably fixedly connected to the port of the base 204 by four bolts), and two openings 205 are provided at the port of the base 204 (respectively used for wire lead-out and air pressure balance. Both openings 205 are arc-shaped), the center of the bottom of the cover plate 201 and the base 204 are provided with the ray passing hole 203 with the center lines coinciding, and the inner wall around the base 204 is provided with the double-layer insulation layer.

[0056] Furthermore, the battery mold 1 includes a battery clamp 102 made of polytetrafluoroethylene material and metal pole ears 103 installed on both sides of the battery clamp 102, the metal pole ears 103 are fixedly connected to one end of the wire (by welding), and the other end of the wire is connected to an external charge and discharge tester, and the battery clamp 102 is provided with the radiation passing hole 2 101 in the center; before the test, the assembled in-situ test battery including the radiation passing hole 3 is installed on the battery clamp 102, and the radiation passing hole 3 is made to coincide with the center lines of the radiation passing hole 2 101 and the radiation passing hole 1 203.

[0057] Furthermore, the battery mold 1 is detachably fixed to the back of the cover plate 201 of the shell 2 by four copper bolts (the four pure copper bolts are in contact with the cold medium of the freezing unit 3, and the copper cold conduction is used to enhance the freezing effect).

[0058] Furthermore, the freezing unit 3 includes a liquid nitrogen flow tube 301 (made of metal copper with high thermal conductivity), a cold medium (ultra-low temperature liquid nitrogen with a temperature of -80°C to -196°C) and a temperature sensor 302 (a temperature sensor 302 based on a thermistor); one end of the liquid nitrogen flow tube 301 is connected to the bottom of the shell 2, and the cold medium is introduced into the inner cavity of the shell 2 through the liquid nitrogen flow tube 301, and is discharged through one of the openings 205 after gasification; the temperature sensor 302 is installed in the inner cavity of the base 204 (for detecting the freezing effect), and the temperature sensor 302 is connected to an external computer signal (a hole is provided at the front end of the side wall of the shell 2, and the temperature sensor 302 is connected to an external computer signal through a signal line passing through the hole, and the computer is used to display the internal temperature of the shell).

[0059] Furthermore, the support 5 includes a threaded cylinder 501 and a circular base 502, the upper end of the threaded cylinder 501 is threadedly fastened to the threaded hole provided at the lower end of the shell 2, and the lower end of the threaded cylinder 501 is detachably fixedly connected to the circular base 502 (for example, the two can be connected by threaded fastening; or a platform can be set at the bottom of the threaded cylinder 501, and the platform is fixedly connected to the upper end surface of the circular base 502 by multiple bolts), and the bottom of the circular base 502 is provided with multiple magnetic suction grooves for magnetic adsorption and fixation to the transmission X-ray microscope operating table (for example, three magnetic suction grooves can be evenly distributed).

[0060] Specific implementation method 2: Figure 1-Figure 8 As shown, this embodiment discloses an in-situ testing method based on cryo-transmission X-rays, the method is implemented based on the device described in any one of the specific embodiments of the third to seventh specific embodiments, and the method includes the following steps:

[0061] Step 1: In-situ test battery (through-hole solid-state battery with a single layer of active material, in-situ button cell) assembly;

[0062] Step 2: Assemble and test the in-situ test battery with the in-situ test device; the specific steps are as follows:

[0063] Step 21: Install the assembled in-situ test battery on the battery fixture 102, and then fix the battery fixture 102 to the back of the cover plate 201 through copper bolts, ensuring that the center lines of the ray passing through hole 1 203 of the shell 2, the through hole 3 of the in-situ test battery, and the ray passing through hole 2 101 of the battery fixture 102 coincide with each other (no dislocation problem);

[0064] Step 22: Install and fix the assembled cover plate 201 at the end of the base 204, and insulate and seal it with an insulating tape and a copolymer (such as a heat-insulating material such as aerogel);

[0065] Step 2 and 3: Fix the in-situ test device (through a magnetic suction slot) on the operating table of the transmission X-ray microscope, turn on the X-ray source, use X-rays to find the positive electrode active particles, and adjust the X, Y, and Z rotation axis positions to ensure that the particles are in the center of the field of view;

[0066] Step 24: turn off the X-ray source, connect the battery mold 1 to an external charge and discharge tester, perform a charge and discharge test on the in-situ test battery, and after reaching the target voltage / current, open the liquid nitrogen guide tube 301 and inject liquid nitrogen;

[0067] Step 25: The temperature sensor 302 is connected to the external computer signal, the temperature sensor 302 is turned on, and the internal temperature of the housing 2 detected by the temperature sensor 302 is displayed by the external computer. When the temperature reaches the stable temperature of the internal phase change material, the X-ray source is turned on, and the energy range, scanning speed and exposure time of each segment are adjusted to perform in-situ cryo-transmission X-ray microscopy testing;

[0068] Step 26: Repeat steps 24 and 25 until all in-situ tests are completed, adjust the position of the transmission X-ray microscope operating table, move the field of view to a particle-free area, keep the energy range, scanning speed and exposure time of each segment unchanged to image the background and remove background noise during the test.

[0069] Furthermore, in step 1, the specific steps of in-situ testing battery assembly are as follows:

[0070] Step 11: weighing a positive electrode active material, a conductive agent, a solid electrolyte and a binder in a dehydrated and deoxygenated atmosphere, and mixing them in a weight ratio of 59:5:34:2, and then adding an excess organic solvent of 300% by weight as a diluent to dilute the slurry;

[0071] Step 1 and 2: The slurry is evenly coated on the carbon-coated aluminum foil with a thickness of 50 microns, and transferred to a heating table, and dried at 60-80°C for 1-3 hours to form a positive electrode sheet;

[0072] Step 13: Under a dehydrated and deoxygenated atmosphere, weigh the solid electrolyte and the binder, and mix them in a ratio of 9:1 by mass. Then, add an organic solvent in a mass ratio of 1:1 to dilute, and transfer the slurry to a mortar and mix evenly.

[0073] Step 14: Take the dried positive electrode sheet, apply the solid electrolyte slurry prepared in step 13 on the positive electrode sheet with a thickness of 200 microns, then transfer it to a heating table and dry it at 60-80°C for 1-3 hours;

[0074] Step 15: prepare a negative electrode sheet in a dehydrated and deoxygenated atmosphere according to an NP ratio of 1.1-1.5, wherein the negative electrode slurry includes a negative electrode active material, a solid electrolyte, a conductive agent, and a binder, and is mixed in a mass ratio of 50:46:1:3, and then coated on a carbon-coated aluminum foil with a thickness of 100 microns, and dried at 60-80°C for 1-3h to prepare a negative electrode sheet; finally, the slurry mixed in step 13 is also coated on the negative electrode sheet with a thickness of 200 microns, and dried at 60-80°C for 1-3h;

[0075] Step 16: Cut the positive and negative electrodes according to the selected battery shell size and assemble them, and drill ray-through hole three (ray-through hole three is a circular hole with a diameter of 3-5mm) at the center of the positive and negative electrodes, battery shell and internal metal components to ensure X-ray penetration.

[0076] Furthermore, the positive electrode active material and the negative electrode active material are both one of the nickel-cobalt-manganese series ternary materials, lithium cobalt oxide materials, lithium iron phosphate materials, and nickel-cobalt-aluminum series ternary materials, the conductive agent is one or more of conductive carbon black, conductive graphite, carbon nanotubes, graphene, and carbon fibers, the solid electrolyte is one of Li6PS5Cl, Li10GeP2S12, and Li3PS4, and the binder and the coordinated organic solvent are polyvinylidene fluoride-N-methylpyrrolidone or nitrile rubber-xylene.

[0077] Embodiment 1:

[0078] This embodiment records an in-situ testing method based on cryo-transmission X-rays, which is implemented using an in-situ testing device based on cryo-transmission X-rays. First, a solid-state battery (button-type solid-state battery) with a through hole (the ray passes through hole three) having a single layer of active material is prepared. The button-type battery with a through hole is placed on a battery mold 1 (charging and discharging mold) and fixed to the back of the cover plate 201 of the shell 2, and placed in the shell 1. The center of the device is pierced by a circular hole with a radius of 3 mm to ensure the accurate passage of X-rays. The shell 2 has a double-layer insulation layer, and liquid nitrogen enters from the bottom and flows out from the top. A 1 mm circular hole is provided on the side of the shell 2 to ensure the air pressure balance in the shell cavity. Insulation cotton and phase change material are added to the groove 202 of the double-layer insulation layer to minimize heat transfer, and the metal is insulated and sealed by insulating tape and copolymers. By adjusting the X-ray energy range and the X, Y, and Z axis positions, the battery is charged and discharged in situ, and the environment is rapidly cooled by liquid nitrogen. After the temperature stabilizes, the exposure time is set to collect data on the rapid reaction mechanism of the battery that is not easy to capture. The device and method are simple to operate, have good effects, and are conducive to the development of the next generation of new battery systems.

[0079] Embodiment 2:

[0080] This embodiment describes an in-situ testing method based on cryo-transmission X-rays. The method is implemented using an in-situ testing device based on cryo-transmission X-rays (the method can achieve rapid electrochemical reaction capture). The specific implementation steps of the method are as follows:

[0081] (1) Assembly of an in-situ test device based on cryo-transmission X-ray: The in-situ test device is designed as follows: Figure 1-Figure 8 As shown, the whole is made of aluminum alloy, and the cover plate is provided with 8×M3 threaded holes for device closure and battery clamp fixation. The fixing bolts are made of pure copper and have good thermal conductivity. The thickness of the cover plate is controlled at 2mm, and a circular through hole of φ4 is provided at the center of the cover plate (i.e., the ray passes through hole 1). The wall thickness of the substrate is controlled at 14mm, and the side walls around the substrate are provided with a double-layer insulation layer. Six grooves are distributed around the double-layer insulation layer for adding insulation materials. A circular through hole of φ4 is also provided in the center of the substrate to ensure that the X-rays accurately pass through the test sample. In this embodiment, an insulation combination of insulation cotton and ethyl acetate is used, and the insulation cotton soaked with ethyl acetate is filled in the groove, and sealed with sealing glue. The battery clamp is made of polytetrafluoroethylene, and a circular through hole of φ5 is provided at the center. It is fixed to the back of the cover plate 201 by bolts. Finally, the two parts are combined and insulated and sealed by insulating tape and copolymer. Nano aerogel is coated on the surface of the shell 2 to further isolate heat.

[0082] (2) Preparation of single-layer active material electrode for solid-state battery: Weigh 20 mg of nitrile rubber and add it to 100 ml of xylene. Stir evenly and transfer 10 ml to a mortar. Weigh 59 mg of LiNi0.8Co0.1Mn0.1O2, 34 mg of Li6PS5Cl, and 5 mg of VGCF respectively. Mix and grind in a mortar for 15-20 min. Coat the mixed slurry on a carbon-coated aluminum foil with a thickness of 50 μm, transfer to a heating table and dry at 60°C to obtain a positive electrode sheet for use. The scanning electron microscopy results of the obtained positive electrode sheet are as follows: Fig. 9 As shown, it can be clearly seen that the particles are distributed in a single layer, which is helpful for subsequent imaging characterization. Weigh 500 mg Li6PS5Cl and add it to 40 ml of the above-configured nitrile rubber-xylene mixed solution. After the slurry is evenly mixed, it is coated on the pre-prepared positive electrode sheet with a thickness of 100 microns. The negative electrode sheet is mixed in a ratio of 50 mg graphite, 46 mg Li6PS5Cl, 1 mg VGCF, and 3 mg nitrile rubber, and coated on a carbon-coated aluminum foil with a thickness of 50 microns. Similar to the positive electrode sheet, a 100-micron thick electrolyte mixed slurry is also coated to obtain an electrode sheet with a positive and negative composite electrolyte.

[0083] (3) In-situ button-type solid-state battery assembly: The positive electrode sheet and the negative electrode sheet were cut and weighed according to the ratio of NP=1.2, and 3 mm through holes were opened in the center of the button-type battery positive electrode shell, negative electrode shell, and gasket, respectively, so that the ray passed through hole three. The in-situ button-type battery was assembled in the order of negative electrode shell, negative electrode sheet, positive electrode sheet, double-layer gasket, spring sheet, and positive electrode shell. The assembled battery was pressed tightly at 7.5 MPa on a sealing machine to obtain an in-situ button-type battery such as Fig.10 shown.

[0084] (4) Rotation adjustment and single particle capture of the in-situ test device: The prepared in-situ button cell is mounted on the battery fixture and fixed inside the in-situ test device. The in-situ test device is placed on the transmission X-ray microscope sample stage and fixed by three magnetic grooves at the bottom. After the device is fixed, turn on the X-ray source, adjust the X-ray energy to 8.34-8.40Kev, adjust the X, Y, and Z axis distances, move the device's rays through the hole, the battery's rays through the hole center line and the X-ray to the same straight line, and fine-tune the distance until clear ternary electrode particles appear in the field of view.

[0085] (5) In-situ fast charging test: Turn off the X-ray source, connect the in-situ test device to the external charge and discharge tester via a wire, and fast charge the battery at a 2C rate, setting 4.3V as the test cutoff voltage.

[0086] (6) In-situ testing and background acquisition using a cryo-transmission X-ray microscope: When the battery reaches the above cut-off voltage, open the liquid nitrogen flow tube, inject liquid nitrogen into the device, turn on the thermistor temperature sensor, and start continuous data acquisition when the temperature stabilizes in the range of -90°C to -80°C. At the same time, observe the battery voltage changes through an external charge and discharge tester. When the voltage stabilizes, stop acquiring data. Move the sample (i.e., the in-situ test battery) until there is no material in the field of view, and acquire background data in the energy range of 8.34-8.40Kev to remove background noise. The scan rate is controlled at 1ev·s -1 -5ev·s -1 , the exposure time is controlled within 200ms-1000ms. The above in-situ test process is as follows Fig.11 shown.

[0087] (7) Data processing and test effect comparison: The data obtained by the method of the present invention is compared with the data obtained by traditional TXM. Fig.12 As shown, it can be found that the electrode particles obtained by the method of the present invention present a more obvious concentration gradient, which can better reflect the specific mechanism of lithium ion transmission inside the battery, indicating that the present invention plays an important role in revealing the internal reaction mechanism of the battery. At the same time, the present invention uses the Shanghai Synchrotron Radiation Light Source Test Center as the size standard, which has strong applicability.

[0088] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other forms of assembly without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-restrictive, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations within the meaning and range of equivalents of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0089] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. An in-situ testing method based on cryo-transmission X-rays, characterized in that: The method is implemented by using an in-situ testing device based on cryo-transmission X-rays, the device comprising a battery mold (1), a shell (2), a freezing unit (3), a heat insulation unit (4) and a support (5); the battery mold (1) is detachably mounted and fixed on the back of a cover plate (201) of the shell (2); the inner walls of the shell (2) are provided with a double-layer heat-insulating layer, and the double-layer heat-insulating layer located around the inner wall of the shell (2) is provided with a groove (202); the heat insulation unit (4) is filled into the groove (202); the liquid nitrogen flow guide pipe (301) of the freezing unit (3) is connected to the bottom of the shell (2); the center of the shell (2) is provided with a ray passing hole (203) that passes through the front and back; the center of the battery mold (1) is provided with a ray passing hole (101) that coincides with the center line of the ray passing hole (203) for transmitting X-rays; the temperature sensor (302) of the freezing unit (3) is installed in the inner cavity of the shell (2); the upper end of the support (5) is detachably fixedly connected to the bottom of the shell (2); The heat insulation unit (4) comprises a heat insulation medium, a phase change material and a nano-aerogel coating; the heat insulation medium and the phase change material are filled into the groove (202) and sealed by a sealing insulating glue, and the groove (202) and the surface of the shell (2) are coated with the nano-aerogel coating; The shell (2) comprises a cover plate (201) and a base (204); the back of the cover plate (201) and the surface of the assembled battery mold (1) are covered by an insulating tape, the cover plate (201) and the base (204) ports are detachably fixedly connected, two openings (205) are provided at the base (204) ports, the cover plate (201) and the base (204) are both provided with the ray passing hole (203) whose center lines coincide, and the inner walls around the base (204) are provided with the double-layer thermal insulation layer; The method comprises the following steps: Step 1: In-situ testing of battery assembly; Step 2: Assemble and test the in-situ test battery with the in-situ test device; the specific steps are as follows: Step 21: Install the assembled in-situ test battery on the battery fixture (102), and then fix the battery fixture (102) to the back of the cover plate (201) by copper bolts, ensuring that the center lines of the ray passing through hole 1 (203) of the shell (2), the through hole 3 of the in-situ test battery, and the ray passing through hole 2 (101) of the battery fixture (102) coincide with each other; Step 22: Install and fix the assembled cover plate (201) at the end of the base (204), and insulate and seal it with the copolymer using an insulating tape; Step 23: Fix the in-situ test device on the transmission X-ray microscope operating table, turn on the X-ray source, use X-rays to find the positive electrode active particles, and adjust the X, Y, and Z rotation axis positions to ensure that the particles are in the center of the field of view; Step 24: turn off the X-ray source, connect the battery mold (1) to an external charge and discharge tester, perform a charge and discharge test on the in-situ test battery, and after reaching the target voltage / current, open the liquid nitrogen guide tube (301) and inject liquid nitrogen; Step 25: The temperature sensor (302) is connected to an external computer signal, the temperature sensor (302) is turned on, and the internal temperature of the shell (2) detected by the temperature sensor (302) is displayed on the external computer. When the temperature reaches the stable temperature of the internal phase change material, the X-ray source is turned on, and the energy range, scanning speed and exposure time of each segment are adjusted to perform in-situ cryo-transmission X-ray microscopy testing; Step 26: Repeat steps 24 and 25 until all in-situ tests are completed, adjust the position of the transmission X-ray microscope operating table, move the field of view to a particle-free area, keep the energy range, scanning speed and exposure time of each segment unchanged to image the background and remove background noise during the test.

2. The in-situ testing method based on cryo-transmission X-ray according to claim 1, characterized in that: In step 1, the specific steps of in-situ testing battery assembly are as follows: Step 11: weighing a positive electrode active material, a conductive agent, a solid electrolyte and a binder in a dehydrated and deoxygenated atmosphere, and mixing them in a weight ratio of 59:5:34:2, and then adding an excess organic solvent of 300% by weight as a diluent to dilute the slurry; Step 1 and 2: The slurry is evenly coated on the carbon-coated aluminum foil with a thickness of 50 microns, and transferred to a heating table, and dried at 60-80°C for 1-3 hours to form a positive electrode sheet; Step 13: Under a dehydrated and deoxygenated atmosphere, weigh the solid electrolyte and the binder, and mix them in a ratio of 9:1 by mass. Then, add an organic solvent in a mass ratio of 1:1 to dilute, and transfer the slurry to a mortar and mix evenly. Step 14: Take the dried positive electrode sheet, apply the solid electrolyte slurry prepared in step 13 on the positive electrode sheet with a thickness of 200 microns, then transfer it to a heating table and dry it at 60-80°C for 1-3 hours; Step 15: prepare a negative electrode sheet in a dehydrated and deoxygenated atmosphere according to an NP ratio of 1.1-1.5, wherein the negative electrode slurry includes a negative electrode active material, a solid electrolyte, a conductive agent, and a binder, and is mixed in a mass ratio of 50:46:1:3, and then coated on a carbon-coated aluminum foil with a thickness of 100 microns, and dried at 60-80°C for 1-3h to prepare a negative electrode sheet; finally, the slurry mixed in step 13 is also coated on the negative electrode sheet with a thickness of 200 microns, and dried at 60-80°C for 1-3h; Step 16: Assemble the positive and negative electrodes after cutting them according to the selected battery shell size, and drill through hole 3 at the center of the battery shell and internal metal components to ensure X-ray penetration.

3. The in-situ testing method based on cryo-transmission X-ray according to claim 2, characterized in that: The positive electrode active material and the negative electrode active material are one of the nickel-cobalt-manganese series ternary materials, lithium cobalt oxide materials, lithium iron phosphate materials, and nickel-cobalt-aluminum series ternary materials. The conductive agent is one or more of conductive carbon black, conductive graphite, carbon nanotubes, graphene, and carbon fiber. The solid electrolyte is Li6PS5Cl, Li 10 GeP2S 12 , Li3PS4, the binder and the formulated organic solvent are polyvinylidene fluoride-N-methylpyrrolidone or nitrile rubber-xylene.

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