Observation method and observation device for in-situ observation of alkali metal solid-state battery interface evolution

Abstract

The invention relates to an observation method and device for in-situ observation of alkali metal solid-state battery interface evolution, and the method comprises the steps: obtaining the section morphology and component evolution of an alkali metal solid-state battery interface through a scanning electron microscope and an energy spectrum thereof, and determining a key reaction node and a local reaction generation region; under a key reaction node, isolating air, transferring to an open environment of a synchrotron radiation diffraction line station, simulating a synchrotron radiation light spot position through laser, and positioning to a reaction generation area determined by an electron microscope through rapid two-dimensional diffraction scanning; carrying out fine single-point / point-by-point two-dimensional diffraction on the region to characterize interface structure evolution; under the condition of air isolation, free switching between an electron microscope and synchrotron radiation diffraction is realized, and comprehensive in-situ observation is carried out on the morphology, component and structure evolution process of the alkali metal solid-state battery interface. According to the method, the scanning electron microscope is combined with synchrotron radiation diffraction for in-situ observation of the alkali metal solid-state battery, the defect that a traditional in-situ method is single is overcome, and synchrotron radiation machine time is greatly saved.

Description

Technical Field

[0001] The present invention relates to new energy batteries, and more particularly to an observation method and an observation device for in-situ observation of interface evolution of alkali metal solid-state batteries. Background Art

[0002] Alkali metal solid-state batteries have always been considered the key to solving the problem of green renewable energy storage, especially lithium metal solid-state batteries, which have attracted attention for their excellent electrochemical performance and safety performance. However, due to the very active nature of the alkali metal negative electrode, it is not only very sensitive to air and easily reacts with water and oxygen in the air, but also easily generates a large number of dendrites at the interface between the electrode and the solid electrolyte during the charge and discharge cycle, piercing the solid electrolyte, causing the battery to short circuit or explode. In order to better study the electrochemical reaction process inside alkali metal solid-state batteries, especially lithium metal solid-state batteries, and explore the failure mechanism, batteries of different cycle processes are often disassembled, and then the electrode reaction interface of the battery is characterized. This non-in situ characterization method not only cannot observe the evolution process of electrode reaction interface failure in real time, but also destroys the internal structure of the battery and even causes the alkali metal negative electrode to be exposed to the air and contaminated.

[0003] Most of the existing in-situ observation methods are single methods, which often have limitations that are difficult to overcome: for example, although the in-situ observation field of an optical microscope is large, the magnification is limited and the resolution is low, making it difficult to discover the causes of failure and attenuation of alkali metal solid-state batteries at the nanoscale; in-situ observation using a transmission electron microscope, although the resolution reaches the sub-nanometer level, the field of view is limited to the micron level, which not only makes it difficult to capture the uneven electrochemical reaction process at the battery interface, but also places high demands on the preparation of in-situ samples; in-situ observation using a scanning electron microscope, although it has both the test field of view of an optical microscope (millimeter-scale observation range) and the resolution of a transmission electron microscope (nanometer-scale observation resolution), can only observe the surface morphology and composition of the battery electrode, and it is difficult to penetrate the battery electrode and electrolyte interface. The surface can be observed and the internal structural evolution of the battery can be characterized. Although the synchrotron radiation diffraction in situ observation technology can penetrate the battery and perform accurate quantitative and qualitative analysis on the internal structural evolution of the battery, because the reaction at the battery interface is an uneven local reaction, it is often necessary to perform synchrotron radiation two-dimensional scanning diffraction spectrum to determine the location of the uneven local reaction. In order to obtain a two-dimensional synchrotron radiation diffraction spectrum within a certain range, it is necessary to scan point by point. Taking the BL14B1 diffraction line station of the Shanghai Light Source as an example, its maximum spot size is only 200µm high and 300µm wide. In order to obtain a high enough flux to make the synchrotron radiation diffraction data clear enough, the scanning time is generally 30s / point. Taking a conventional button battery as an example, the diameter of the battery is mostly about 1-2cm, so scanning 1×1cm 2To obtain diffraction information with higher spatial resolution, a smaller spot size and longer scanning time are required. Furthermore, since battery reactions occur internally, it is often difficult to accurately determine the timing of microscopic interface reactions based solely on fluctuations in the electrochemical charge and discharge curves. This means that a significant amount of valuable synchrotron radiation time must be spent continuously scanning large areas of two-dimensional diffraction patterns to capture useful information about local reactions at the battery interface.

[0004] In summary, it is extremely necessary to combine different in situ techniques to conduct comprehensive in situ observations of alkali metal batteries. The area sizes of the samples observed by scanning electron microscopy and synchrotron diffraction are matched (both are on the millimeter scale), and the scanning electron microscope can quickly observe the morphological changes in the microregion of the battery interface in just a few seconds, with spatial resolution accurate to the nanometer level. At the same time, combined with the scanning electron microscope energy spectrum, the composition distribution of the battery interface microregion can be quickly obtained in a maximum of a few minutes. This not only allows for in situ characterization of the morphology and composition changes of alkali metal solid-state battery interface reactions, but also accurately determines the key nodes where microscopic reactions occur at the battery interface and quickly locates the areas where localized interface reactions occur, thereby determining the in situ observation nodes and diffraction test positions for synchrotron diffraction, and then guiding synchrotron diffraction in characterizing the battery interface structure evolution, saving a large amount of valuable synchrotron radiation machine time. These two methods are very suitable for combining together for in situ observations of alkali metal batteries. However, the scanning electron microscope cavity is a high-vacuum cavity, while the synchrotron radiation diffraction station is an open, atmospheric-pressure, non-vacuum environment without a cavity. Furthermore, alkali metal solid-state batteries are sensitive to air contamination. Unlike conventional liquid batteries, which have surface-contact electrodes and electrolytes, the contact interfaces between the electrodes and the solid electrolyte in alkali metal solid-state batteries are mostly point contacts, which are very fragile and easily dislocated and damaged during disassembly and movement. This makes it very difficult to directly and repeatedly load, unload, and transfer alkali metal solid-state battery samples between these two devices under fully airtight conditions without damaging the electrode-solid electrolyte contact interface. In addition, the scanning electron microscope uses a reflected light path, while the synchrotron radiation diffraction uses a transmitted light path. The two are already very difficult to combine, and the information obtained from the scanning electron microscope's reflected light path is needed to guide the synchrotron radiation diffraction's transmitted light path to detect the same area of ​​the same sample at key time nodes and local reaction locations. This further makes it difficult to combine these two techniques to observe the in situ electrochemical reaction interface evolution process in the same interface reaction area of ​​the same alkali metal solid-state battery sample. Summary of the Invention

[0005] In order to solve the problem of the single in-situ observation method in the above-mentioned prior art, the present invention provides an observation method and an observation device for in-situ observation of the interface evolution of alkali metal solid-state batteries by combining different in-situ technologies.

[0006] According to the present invention, the observation method for in-situ observation of the interface evolution of alkali metal solid-state batteries includes the following steps: S1, in-situ observation of the surface morphology and composition changes of the cross-section of the interface between the positive and negative electrodes and the solid electrolyte of the alkali metal solid-state battery during the charge and discharge process at different voltages and currents under different temperature conditions through a scanning electron microscope and its energy spectrum, accurately determining the key reaction time node of the alkali metal solid-state battery interface reaction, and obtaining the position of the uneven local reaction area where the morphology and composition change; S2, pausing the charge and discharge process of the alkali metal solid-state battery at the key reaction node, transferring the paused alkali metal solid-state battery to an open environment of a synchrotron radiation diffraction line station under air-isolated conditions, simulating the synchrotron radiation spot position by laser, and marking the top surface of the current collector with a clamp. The object is used as a reference, and the position of the uneven local reaction occurrence area observed by the scanning electron microscope and its energy spectrum is quickly located by synchrotron radiation fast two-dimensional point-by-point diffraction scanning; S3, under the same temperature and charge-discharge conditions as the scanning electron microscope, the located reaction occurrence area at the key reaction time node is subjected to fine single-point diffraction and / or fine point-by-point two-dimensional diffraction scanning by synchrotron radiation diffraction to in situ characterize the structural evolution of the interface reaction zone of the alkali metal solid-state battery; S4, according to the need for in situ observation of the interface reaction process of the alkali metal solid-state battery, S1-S3 are cyclically performed to achieve unlimited switching between the scanning electron microscope and synchrotron radiation diffraction at any time under air-isolated conditions, and to perform in situ observation of the interface reaction process of the alkali metal solid-state battery under the same temperature and the same charge-discharge conditions.

[0007] In a preferred embodiment, step S1 includes the following sub-steps: S11, first flattening the cross-sections of the components of the alkali metal solid-state battery in the first air-isolating device, then assembling the components to form an alkali metal solid-state battery, and then vertically mounting the flattened interface cross-section of the assembled alkali metal solid-state battery on a fixture with the cross-section facing upward; S12, mounting the fixture with the alkali metal solid-state battery mounted in the first air-isolating device in a second air-isolating device; S13, removing the second air-isolating device from the first air-isolating device and mounting it in the vacuum chamber of a scanning electron microscope, closing the vacuum chamber of the scanning electron microscope and evacuating the chamber; S14, when the vacuum degree reaches 10 -4 When the mba is above, the second air-isolating device is opened to carry out an in-situ electrochemical reaction with controllable temperature, and the cross-sectional morphology and composition changes of the interface between the positive and negative electrodes and the solid electrolyte of the alkali metal solid-state battery during the charge and discharge process at different voltages and currents under different temperature conditions are observed in situ by scanning electron microscopy and its energy spectrum.

[0008] In a preferred embodiment, in step S14, the key time node of the interfacial reaction is accurately determined through the morphology and composition change information, and the marker on the top surface of the current collector is used as a reference to calibrate the reaction area where the morphology and composition changes occur, so as to facilitate subsequent rapid positioning.

[0009] In a preferred embodiment, after determining the reaction area, the magnification is reduced in sequence so that the reaction area and the marker on the top surface of the current collector appear on the observation screen at the same time. By taking photos, the relative position of the marker on the top surface of the current collector and the reaction area is measured.

[0010] In a preferred embodiment, step S2 includes the following sub-steps: S21, taking out the second air-isolating device from the vacuum chamber of the scanning electron microscope, and transferring the fixture in the second air-isolating device to the third air-isolating device in the first air-isolating device; S22, after taking the third air-isolating device out of the first air-isolating device, installing it on the open cavity-free sample stage of the synchrotron radiation diffraction line station, using a laser beam to simulate the synchrotron radiation spot position, by moving the position of the synchrotron radiation diffraction line station sample stage loaded with the third air-isolating device, and observing through the top observation window of the third air-isolating device, the laser spot is irradiated near the reaction area according to the position of the collector marker and its relative position to the reaction area; S23, turning off the laser, opening the synchrotron radiation beam line shutter, performing a two-dimensional point-by-point rapid scan of the synchrotron radiation diffraction, and quickly locating the reaction area by referring to the position of the collector marker and comparing the position of the weak change in the two-dimensional rapid scanning diffraction signal with the position of the reaction area determined by the scanning electron microscope and its energy spectrum.

[0011] In a preferred embodiment, in step S23, the scanning time of the synchrotron radiation diffraction two-dimensional rapid point-by-point scanning of the diffraction signal is 1-5 s / point.

[0012] In a preferred embodiment, in step S3, the scanning time of the synchrotron radiation diffraction fine single-point diffraction and / or the two-dimensional fine point-by-point diffraction scanning is 20-60 s / point.

[0013] In a preferred embodiment, step S4 includes the following sub-steps: S41, removing the third air-isolated device from the sample stage of the synchrotron diffraction station, and transferring the fixture in the third air-isolated device to the second air-isolated device in the first air-isolated device; S42, after taking the second air-isolated device out of the first air-isolated device, installing it on the sample stage in the scanning electron microscope cavity, opening the second air-isolated device, and using a scanning electron microscope and its energy spectrum to perform in situ observation of the morphology and composition evolution of the cross-sectional area of ​​the contact interface between the positive and negative electrodes and the solid electrolyte of the alkali metal solid-state battery under the same temperature and charge and discharge conditions as the synchrotron diffraction in-situ test; S43, under the guidance of the scanning electron microscope and its energy spectrum test results, using synchrotron diffraction to characterize the in-situ structural evolution of the contact interface between the positive and negative electrodes and the solid electrolyte of the alkali metal solid-state battery under the same temperature and the same charge and discharge conditions as the scanning electron microscope; S44, S41-43 are cycled multiple times at different key reaction time nodes.

[0014] According to the observation device for in-situ observation of the interface evolution of alkali metal solid-state batteries of the present invention, it includes a sample clamp, which includes a current collector and a heating element. The alkali metal solid-state battery is assembled in a first air-isolating device providing an inert atmosphere and then clamped by two current collectors. The top surface of the current collector has a marker. The current collector maintains close contact with the positive and negative electrodes of the alkali metal solid-state battery. The cross-section of the interface of the alkali metal solid-state battery is 0.1mm-1mm higher than the top surface of the current collector, so that the synchrotron radiation beam line spot can pass through the positive and negative electrodes and the solid electrolyte interface without interference for diffraction characterization. The heating element is installed inside the current collector to control the temperature of the alkali metal solid-state battery; the scanning electron microscope system has a vacuum chamber, and the second air-isolating device is detachably installed in the vacuum chamber. The alkali metal The contact interface between the positive and negative electrodes of the solid-state battery and the solid electrolyte is parallel to the incident direction of the electron beam, and the cross-section of the contact interface between the positive and negative electrodes of the alkali metal solid-state battery and the solid electrolyte is perpendicular to the incident electron beam of the scanning electron microscope. The scanning electron microscope and the scanning electron microscope energy spectrometer cooperate to observe the cross-sectional morphology and composition changes of the interface of the alkali metal solid-state battery in the vacuum chamber of the scanning electron microscope; the synchrotron radiation diffraction system has an open, cavity-free movable sample stage, and the third air-isolating device is detachably mounted on the sample stage. The contact interface between the positive and negative electrodes of the alkali metal solid-state battery and the solid electrolyte is perpendicular to the incident direction of the synchrotron radiation beam line. The synchrotron radiation beam line is irradiated on the interface of the alkali metal solid-state battery above the current collector to characterize the structural evolution of the interface of the alkali metal solid-state battery.

[0015] In a preferred embodiment, the observation device also includes an electrochemical workstation and a temperature controller, which are connected to the sample holder through a wire through the scanning electron microscope cavity flange and then through the adapter of the second air-isolating device, or the electrochemical workstation and the temperature controller are connected to the sample holder through a wire through the adapter of the third air-isolating device to control the charging and discharging process and temperature of the alkali metal solid-state battery, and the temperature range is room temperature-200°C.

[0016] In a preferred embodiment, the top surface of the current collector has markers for marking the reaction zone, and the markers are screws, grooves, and marked edges on the surface of the current collector.

[0017] In a preferred embodiment, the observation device also includes a laser for simulating a synchrotron radiation spot in a synchrotron radiation diffraction system, and uses the marker position as a reference to quickly locate the local reaction area determined by the aforementioned scanning electron microscope and its energy spectrum by combining synchrotron radiation rapid point-by-point two-dimensional diffraction scanning.

[0018] In a preferred embodiment, an observation window is provided at the top of the third air-isolating device, and a high-definition camera installed above the synchrotron radiation diffraction station observes the cross-section of the interface between the laser, the sample fixture, the top surface marker of the fixture current collector, and the alkali metal solid-state battery through the window.

[0019] In a preferred embodiment, by loading and unloading and moving the sample holder containing the alkali metal solid-state battery, rather than directly loading and unloading and moving the sample, the alkali metal solid-state battery sample is repeatedly transferred from the first air-isolated device to the second and third air-isolated devices in an infinite number of cycles, thereby achieving in situ observation of the alkali metal solid-state battery interfacial reaction process, rather than a specific reaction state, by combining scanning electron microscopy and synchrotron radiation diffraction. It should be understood that the first air-isolated device, the second air-isolated device, the third air-isolated device, and the vacuum chamber of the scanning electron microscope form an air-isolated passage.

[0020] In a preferred embodiment, the second air-isolating device has a cover, which is driven by a mechanical transmission device to close and open. The mechanical transmission device is connected to an electric controller inside the first air-isolating device through a wire, or the mechanical transmission device is connected to an electric controller outside the vacuum chamber of the scanning electron microscope after passing through a wire through the scanning electron microscope chamber flange to drive the mechanical transmission device to close and open.

[0021] In a preferred embodiment, the cross-section of the interface of the alkali metal solid-state battery is higher than the box opening, and the up and down movement of the lid is achieved by the step height difference.

[0022] In a preferred embodiment, the first air-isolating device is a glove box, the second air-isolating device is a vacuum transfer box, and the third air-isolating device is a synchrotron radiation vacuum transfer hood.

[0023] In a preferred embodiment, the second air-isolating device is a non-magnetic titanium alloy box body with good corrosion resistance and thermal stability.

[0024] In a preferred embodiment, the third air-isolating means comprises a load-bearing steel skeleton sealed by a Cape Town membrane.

[0025] According to the in-situ observation method and observation device for observing the interface evolution of alkali metal solid-state batteries of the present invention, a scanning electron microscope is combined with synchrotron radiation diffraction to overcome the difficulties of different optical path directions of the scanning electron microscope and synchrotron radiation diffraction, large difference between high vacuum and normal pressure in the test environment, and sensitive, fragile and easily damaged test samples that are difficult to directly disassemble and move repeatedly. The information obtained from the scanning electron microscope reflection light path is used to guide the synchrotron radiation diffraction transmission light path to detect the same area of ​​the same sample at key time nodes and local reaction positions, saving a large amount of precious machine time for synchrotron radiation testing, and achieving the purpose of comprehensive, rapid and accurate real-time characterization and analysis of the morphology, composition and structure of the contact interface of air-sensitive alkali metal solid-state battery electrodes and solid electrolytes under different working currents, voltages and temperatures. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 FIG. 1 shows in-situ observation using a scanning electron microscope (SEM) for in-situ observation of the interface evolution of alkali metal solid-state batteries according to a preferred embodiment of the present invention.

[0027] Figure 1a Show Figure 1 The box cover is driven by the step height difference.

[0028] Figure 2 The diagram shows the in-situ observation of synchrotron radiation diffraction using an observation device for in-situ observation of the interface evolution of alkali metal solid-state batteries according to a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0029] The preferred embodiments of the present invention are given below in conjunction with the accompanying drawings and described in detail.

[0030] In this document, unless otherwise specified and explained, the terms "installation", "fixation" and "placement" are interpreted in a broad sense, such as mechanical installation, fixation and placement, direct installation, fixation and placement, or indirect installation, fixation and placement with an intermediate component as a connection. For ordinary technicians reading this invention, they can understand the meaning of the above terms in the present invention according to specific circumstances.

[0031] Taking into account the matching area sizes of the observation samples of scanning electron microscopy and synchrotron diffraction (taking the Zeiss Gemini300 field emission scanning electron microscope and the BL14B1 diffraction line station of the Shanghai Synchrotron Radiation Light Source as examples, the observation area range can be achieved at the millimeter level), and the scanning electron microscope can be combined with the scanning electron microscope energy spectrum technology to quickly capture the morphological changes and composition segregation of the battery interface micro-region to accurately determine the key time nodes of the alkali metal solid-state battery interface reaction and quickly locate the local reaction area with uneven interface, thereby determining the in-situ observation time nodes of synchrotron diffraction and the position of the in-situ diffraction detection, so as to guide the synchrotron diffraction to characterize the structural evolution of the alkali metal solid-state battery interface reaction process, saving a lot of precious synchrotron radiation machine hours, the present invention combines scanning electron microscopy and synchrotron diffraction to perform comprehensive in-situ observation of the interface evolution process of alkali metal solid-state batteries. In particular, the cavity of the scanning electron microscope is a high vacuum cavity, while the synchrotron radiation diffraction is an open environment without a cavity at normal pressure. In addition, the optical path of the scanning electron microscope is vertically irradiated on the sample surface, while the beam line of the synchrotron radiation diffraction is parallel to the sample. The optical paths are completely different and very difficult to combine. In addition, the alkali metal solid-state battery is sensitive to air pollution. Compared with traditional liquid batteries, the contact interface between its electrodes and solid electrolytes is mostly point contact, which is very fragile and can easily be dislocated and damaged during disassembly and movement. This makes it very difficult to directly and repeatedly load, unload and transfer the alkali metal solid-state battery between the two devices under fully air-isolated conditions and combine it with the in-situ observation of the electrochemical reaction interface evolution process.

[0032] The present invention can comprehensively characterize the morphology, composition, and structural evolution of the in-situ reaction process at the interface between the electrode and solid electrolyte of an alkali metal solid-state battery. Furthermore, through scanning electron microscopy, the critical time nodes of the battery interface reaction can be precisely determined and the uneven local location of the reaction can be quickly located. This provides guidance and basis for synchrotron radiation diffraction experiments, saving a large amount of valuable synchrotron radiation diffraction experimental time. Furthermore, by varying the temperature and externally applied current and voltage during cyclic charge and discharge, the effects of different test conditions on the electrochemical reaction process of the alkali metal solid-state battery can be studied, further investigating the failure mechanism of the alkali metal solid-state battery.

[0033] The present invention first includes step S1, in which the surface morphology and composition changes of the cross section of the interface between the positive and negative electrodes and the solid electrolyte of the alkali metal solid-state battery are observed in situ by a scanning electron microscope and its energy dispersive spectrometer (EDS) during the charge and discharge process at different temperature conditions and different voltages and currents, so as to accurately determine the key reaction time node of the alkali metal solid-state battery interfacial reaction and quickly obtain the location of the uneven local reaction area where the morphology and composition change (i.e., the uneven local interface reaction location).

[0034] Said step S1 includes a sub-step S11, firstly flattening the cross-sections of the components of the alkali metal solid-state battery (i.e., the positive electrode, the solid electrolyte, and the negative electrode) in the first air-isolating device, then assembling the components to form the alkali metal solid-state battery 5, and then vertically mounting the assembled alkali metal solid-state battery 5 on a fixture with the flattened cross-section of the interface facing upward, see Figure 1 .

[0035] In a preferred embodiment, the first air-isolating device is a glove box that provides an inert atmosphere. Within the inert atmosphere of the glove box, the positive electrode, solid electrolyte, and negative electrode, after smoothing the interface cross-section, are assembled in sequence to form an alkali metal solid-state battery 5. In a preferred embodiment, the alkali metal solid-state battery 5 is a lithium metal solid-state battery, with a lithium iron phosphate electrode sheet being used for the positive electrode and a lithium sheet being used for the negative electrode. In a preferred embodiment, the solid electrolyte can also be a semi-solid electrolyte formed by impregnating an ionic liquid with a separator (e.g., a polyolefin film). In a preferred embodiment, the positive electrode, semi-solid electrolyte, and polymer electrolyte are cut with scissors or a scalpel to form a smooth cross-section. The solid ceramic electrolyte is polished with sandpaper to smooth its cross-section. The negative electrode is cut with a scalpel to smooth its cross-section to facilitate scanning electron microscopy observation. In the embodiment of the solid electrolyte, the solid electrolyte is larger than the positive and negative electrodes. The positive and negative electrodes are clamped around the solid electrolyte and then pressed tightly to ensure good contact.

[0036] In sub-step S11, the cross-sectional area of ​​the interface between the positive and negative electrodes and the solid electrolyte is cut out and flattened to meet the requirements of scanning electron microscopy imaging. Then, the alkali metal solid-state battery 5 is assembled in the order of the positive electrode, the solid electrolyte and the negative electrode. The assembled alkali metal solid-state battery 5 is placed vertically in a fixture so that it is clamped by the two current collectors 8 of the fixture. It is ensured that the top surface of the alkali metal solid-state battery 5 (i.e., the cross-section of the alkali metal solid-state battery interface) is 0.1 mm to 1 mm higher than the top surface of the current collector 8, so as to facilitate good contact with the current collector 8 (i.e., close contact, such as electrical contact or thermal contact). At the same time, the synchrotron radiation beam line spot is not interfered by the fixture and passes through the interface between the positive and negative electrodes and the solid electrolyte for diffraction characterization, ensuring that the cross-section of the contact interface between the positive and negative electrodes and the solid electrolyte can be vertically irradiated by the electron beam in the scanning electron microscope and horizontally penetrated by the synchrotron radiation beam line in synchrotron radiation diffraction.

[0037] In a preferred embodiment, the clamp can be a lightweight, high-temperature resistant and insulating plastic clamp, such as polypropylene PP, polyethylene PE, etc. In a preferred embodiment, the two ends of the clamp in contact with the alkali metal solid-state battery 5 are installed with a current collector 8 with good conductivity, such as a copper current collector. A heating ceramic rod 7 is installed inside the current collector 8 to control the temperature of the in-situ test. In a preferred embodiment, the cross-section of the alkali metal solid-state battery interface is 0.2 mm higher than the top surface of the current collector 8. In a preferred embodiment, the fastening screws are tightened to make the two current collectors 8 in close contact with the positive and negative electrodes to prevent failure and circuit breaker due to poor contact.

[0038] The step S1 includes a sub-step S12, in which the fixture with the alkali metal solid-state battery 5 installed in the first air-isolating device is installed in the second air-isolating device (i.e., the vacuum transfer box 3). It should be understood that in order to avoid the vacuum transfer box 3 from colliding with the scanning electron microscope barrel and the energy spectrum probe due to being too close vertically, the cross-section of the interface of the alkali metal solid-state battery 5 should be higher than the box opening. In particular, in order to avoid the box cover 4 from colliding with the sample 5 that is higher than the box opening, the horizontal sliding track is designed as a horizontal step sliding track in the mechanical transmission device, and the left and right movement of the box cover is achieved by horizontal sliding, and the up and down movement of the box cover 4 is achieved by the step height difference d, as shown in FIG. Figure 1a As shown. It should be understood that Figure 1a It is only a schematic structural diagram, and any other structure capable of achieving similar functions can be used in the present invention.

[0039] In a preferred embodiment, under the inert atmosphere of a glove box, a fixture with the alkali metal solid-state battery 5 installed is placed in a vacuum transfer box 3. The fixture's wires are connected to the connectors of the vacuum transfer box 3 and then led out of the vacuum transfer box 3. The bottom of the fixture is fixed to the bottom of the vacuum transfer box 3 with four fastening screws. A mechanical transmission device drives the lid 4 to close the upper opening of the vacuum transfer box 3. The vacuum transfer box 3 is sealed by an O-ring 6 installed at the box opening, thereby isolating the alkali metal solid-state battery 5 in the vacuum transfer box 3 from the air. In a preferred embodiment, the vacuum transfer box 3 is made of a high-strength, non-magnetic titanium alloy with the advantages of high thermal stability and corrosion resistance. In a preferred embodiment, the vacuum transfer box 3 is equipped with a mechanical transmission device to control the opening and closing of the lid 4. The mechanical transmission device is directly connected to an external electric controller via wires, allowing the opening and closing of the lid 4 to be controlled by manual operation of the external controller in the inert gas protection environment of the glove box. The mechanical transmission device is connected to the flange of the scanning electron microscope vacuum chamber through a wire, and then connected to the electric controller outside the scanning electron microscope through the flange, allowing the opening and closing of the cover 4 to be controlled by manually operating the external controller in the high vacuum environment of the scanning electron microscope.

[0040] The step S1 includes a sub-step S13, wherein the second air-isolating device is removed from the first air-isolating device and installed in the cavity of the scanning electron microscope, and the cavity of the scanning electron microscope is closed and then vacuumed. Figure 1 shown.

[0041] In a preferred embodiment, the vacuum transfer box 3 is removed from the glove box and installed on the sample stage in the cavity of the scanning electron microscope. The wires led out of the fixture in the vacuum transfer box 3 are connected to the wire interface of the external controller through the vacuum transfer box 3 interface and the flange on the scanning electron microscope cavity. The door is closed and the vacuum is evacuated. In this way, the vacuum transfer box 3 cooperates with the fixture to achieve the transfer of the alkali metal solid-state battery 5 into the vacuum cavity of the scanning electron microscope under the condition of complete isolation from air, avoiding the contamination of the alkali metal solid-state battery 5 by water and oxygen in the air, and also avoiding the damage to the fragile interface of the battery by direct transfer, installation and removal of the alkali metal solid-state battery 5. In a preferred embodiment, in the cavity of the scanning electron microscope, the interface between the positive and negative electrodes of the alkali metal solid-state battery 5 and the solid electrolyte is parallel to the incident direction of the electron beam, and the cross section of the interface between the positive and negative electrodes of the alkali metal solid-state battery 5 and the solid electrolyte is perpendicular to the incident electron beam, so as to facilitate scanning electron microscope observation.

[0042] The step S1 includes a sub-step S14, when the vacuum degree reaches 10 -4 When the mba is above, the second air-isolating device is opened to conduct an in-situ electrochemical reaction with controllable temperature. The cross-sectional morphology and composition changes of the interface between the positive and negative electrodes and the solid electrolyte of the alkali metal solid-state battery 5 during the charge and discharge process at different voltages and currents under different temperature conditions are observed in situ by scanning electron microscopy and energy spectrum. Figure 1 .

[0043] In a preferred embodiment, after the scanning electron microscope is evacuated, for example, when the vacuum degree reaches 10 -4 When the mba is above, the mechanical transmission device is driven by the electric controller outside the scanning electron microscope to drive the lid 4 to open the vacuum transfer box 3, revealing the fixture and alkali metal solid-state battery 5 in the vacuum transfer box 3. After the alkali metal solid-state battery 5 is placed under the lens barrel 1 of the scanning electron microscope, the sample stage positioning motor in the cavity of the scanning electron microscope moves the sample stage with the vacuum transfer box 3 installed to adjust the position. After selecting a suitable observation area and range, the alkali metal solid-state battery 5 is subjected to different voltage and current charge and discharge cycle tests at different temperatures, and the operating temperature is adjusted between room temperature and 200 ° C. The reaction process of the cross section of the contact interface between the positive and negative electrodes and the solid electrolyte is observed in situ. In a preferred embodiment, the energy spectrometer 2 is arranged next to the lens barrel 1, and the scanning electron microscope energy spectrum is combined with the scanning electron microscope so that while the scanning electron microscope obtains surface morphology evolution information, the energy spectrometer 2 can analyze the changes in element type, content and distribution. The key cycle nodes are accurately determined by the changes in the above-mentioned morphology and composition, and the reaction occurrence area is quickly determined.

[0044] In step S14, the key time nodes of the interfacial reaction are accurately determined based on the morphology and composition change information, and the reaction area where the morphology and composition changes occur is quickly calibrated to facilitate subsequent rapid positioning. Specifically, after determining the reaction area, the magnification is reduced in sequence so that the reaction area and the marker on the top surface of the current collector 8 appear simultaneously on the observation screen. By taking photos, the relative position of the marker on the top surface of the current collector (such as screws, grooves, etc. on the current collector 8 or the edge of the current collector marker) and the reaction area is measured, providing guidance for the subsequent rapid positioning of the reaction area by synchrotron diffraction.

[0045] In a preferred embodiment, the current collector 8 is connected to an electrochemical workstation outside the scanning electron microscope via a wire extending from the interior of the fixture through a vacuum transfer box interface and a flange of the scanning electron microscope cavity, thereby performing electrochemical charge and discharge tests at different voltages and currents on the alkali metal solid-state battery 5. In a preferred embodiment, a ceramic heating rod 7 is installed inside the current collector 8. The ceramic heating rod 7 is connected to a temperature controller outside the scanning electron microscope via a wire extending from the interior of the fixture through a vacuum transfer box interface and a flange of the scanning electron microscope cavity, thereby controlling the temperature of the alkali metal solid-state battery 5 from room temperature to 200°C, thereby simultaneously achieving heating and powering functions.

[0046] The present invention then includes step S2, which pauses the charge and discharge process of the alkali metal solid-state battery at a key reaction node, transfers the paused alkali metal solid-state battery to an open environment of a synchrotron radiation diffraction station under air-isolated conditions, simulates the synchrotron radiation spot position by laser, uses the marker on the top surface of the fixture current collector as a reference, and uses synchrotron radiation fast two-dimensional point-by-point diffraction scanning to quickly locate the position of the uneven local reaction occurrence area observed by the scanning electron microscope and its energy spectrum.

[0047] The step S2 includes a sub-step S21, taking out the vacuum transfer box 3 from the cavity of the scanning electron microscope, and transferring the fixture in the vacuum transfer box 3 in the first air-isolating device to the third air-isolating device (i.e., the synchrotron radiation vacuum transfer cover 9), see Figure 2 It should be understood that the first, second and third air-isolating devices can form a fully air-isolating protective path with the high-vacuum chamber of the scanning electron microscope, protecting the alkali metal solid-state battery 5 from contact with air during the mutual transfer process between different devices and the in-situ testing process in the open atmospheric environment of the synchrotron radiation diffraction station, thereby avoiding contamination, thereby realizing the in-situ observation of the continuous changes in the morphology, composition and structure of the alkali metal solid-state battery interface at different test temperatures during the charge-discharge cycle process with different voltages and currents by switching the scanning electron microscope and the synchrotron radiation diffraction equipment repeatedly at any time.

[0048] In a preferred embodiment, after accurately determining the key reaction time node and quickly locating the local reaction area, the scanning electron microscope controls the mechanical transmission device by manipulating the electric controller outside the scanning electron microscope to drive the lid 4 to close the vacuum transfer box 3, and then takes out the vacuum transfer box 3 from the cavity of the scanning electron microscope and puts it into the glove box. Under the protection of the inert gas in the glove box, the vacuum transfer box 3 is opened, the fixture is taken out, and placed in the synchrotron radiation vacuum transfer cover 9. After the wires of the fixture are connected to the interface of the synchrotron radiation vacuum transfer cover 9, they are led out from the synchrotron radiation vacuum transfer cover 9, and the bottom of the fixture is fixed to the bottom of the synchrotron radiation vacuum transfer cover 9 with four fastening screws. The synchrotron radiation vacuum transfer cover 9 is fixed to the cover door 14 with fastening screws and sealed with a sealing O-ring to ensure airtightness, and then taken out of the glove box. In this way, by loading and unloading and moving the fixture instead of directly loading and unloading and moving the alkali metal solid-state battery 5, the fragile reaction interface of the alkali metal solid-state battery 5 is avoided from being damaged during repeated installation, disassembly and transfer, ensuring that the fragile and vulnerable electrode and solid electrolyte contact interface is suitable for the joint characterization of the scanning electron microscope and synchrotron radiation diffraction of the present invention. In a preferred embodiment, the synchrotron radiation vacuum transfer cover 9 is sealed with a load-bearing steel frame and a Cape Town film (polyethylene terephthalate, PET) that can penetrate the synchrotron radiation beam line.

[0049] The step S2 includes a sub-step S22, in which the synchrotron radiation vacuum transfer cover 9 is taken out from the first air-isolating device and installed on an open, cavity-free sample stage of a synchrotron radiation diffraction line station, and the position of the synchrotron radiation beam line is simulated by using a laser beam. The position of the sample stage of the synchrotron radiation diffraction line station loaded with the third air-isolating device is moved, and observed through the observation window on the top of the third air-isolating device, with the position of the collector marker as a reference, and based on the relative position of the collector marker position and the reaction area, the laser spot is irradiated near the uneven local reaction area.

[0050] In a preferred embodiment, a window 15 is provided at the top of the synchrotron radiation vacuum transfer cover 9. A high-definition camera mounted above the synchrotron radiation diffraction line station can observe through the window 15 the cross-section of the laser simulating the synchrotron radiation spot, the marker on the top surface of the fixture current collector inside the synchrotron radiation vacuum transfer cover 9, and the interface of the alkali metal solid-state battery 5, thereby determining the observation position of the synchrotron radiation beamline spot. Specifically, with the aid of the camera observing through the window 15, the height of the sample stage is adjusted so that the laser beam can penetrate the window 10 of the vacuum transfer cover 9 and illuminate the interface of the alkali metal solid-state battery 5 above the current collector 8. The left and right positions of the sample stage are adjusted, with reference to the position of the marker on the top surface of the current collector, so that the laser beam illuminates the vicinity of the local reaction region previously located in the scanning electron microscope.

[0051] The step S2 includes a sub-step S23, which turns off the laser, opens the synchrotron radiation beamline shutter, and performs a large-scale two-dimensional point-by-point rapid scan of the synchrotron radiation diffraction spot. The scanning time of the synchrotron radiation diffraction two-dimensional rapid point-by-point scanning diffraction signal is 1-5s / point. By referring to the position of the current collector marker and comparing the position where the two-dimensional rapid scanning diffraction signal changes slightly with the position of the local reaction occurrence area determined by the scanning electron microscope and its energy spectrum, the reaction occurrence area is quickly located. It should be understood that although the two-dimensional rapid scanning will seriously lead to insufficient flux and signal weakening, thereby resulting in a weak difference in the diffraction signal between the reaction occurrence area and the reaction non-occurrence area, because the aforementioned scanning electron microscope has been used to determine that an uneven interface reaction has indeed occurred in the area, and the relative position of the uneven local reaction position and the marker has been determined, the above-mentioned weak difference can be basically ruled out as caused by error, so that the local reaction occurrence area can be quickly located.

[0052] The present invention then includes step S3, which is to perform fine single-point diffraction and / or fine point-by-point two-dimensional diffraction scanning on the located reaction area at the key reaction time node by synchrotron radiation diffraction under the same temperature and charge and discharge conditions as the scanning electron microscope to in situ characterize the structural evolution of the interface reaction zone of the alkali metal solid-state battery.

[0053] In a preferred embodiment, the sample stage is moved so that the synchrotron radiation beam line spot moves to the local reaction region located above, and a narrowed range of synchrotron radiation fine single point diffraction and / or two-dimensional diffraction scanning is performed. The scanning time of the synchrotron radiation fine single point diffraction and / or two-dimensional point-by-point diffraction scanning is 20-60s / point, for example, 30s / point. This can save a lot of synchrotron radiation diffraction machine time to obtain characterization information on the interface structure evolution of alkali metal solid-state batteries. The air inlet 12 of the synchrotron radiation vacuum transfer cover 9 is connected to the nitrogen bottle, and the air outlet 13 is connected to the vacuum pump group to ensure that the alkali metal battery 5 is isolated from the air. The wires drawn out of the fixture are connected to the circuit of the electrochemical workstation and temperature controller equipment outside the transfer cover through the synchrotron radiation vacuum transfer cover 9 interface, providing the same charge, discharge and temperature conditions as the aforementioned scanning electron microscope in situ experiment. In a preferred embodiment, a synchrotron radiation beam line of appropriate energy is used for diffraction, and the synchrotron radiation diffraction results are recorded. By comparing the changes in different diffraction results, the changes in the sample structure are determined. The influence of existing electrodes and diaphragms is eliminated. It should be understood that as long as the diffraction pattern changes, it can be judged that the structure has changed. However, this change is an overall change of the sample, not necessarily a change of a single component of the sample. Therefore, it is difficult to determine whether the interface structure has changed. A scanning electron microscope and its energy spectrum are needed to first observe the changes in the cross-sectional morphology of the interface. Only then can diffraction be performed to better avoid the introduction of interference and errors to accurately obtain structural evolution information. In a preferred embodiment, if the experimental time is short (for example, no more than 24 hours), the synchrotron radiation vacuum transfer cover 9 does not need to be connected to an external vacuum pump group and an inert gas because the vacuum cover is airtight. If the time is long (for example, more than 24 hours), the synchrotron radiation vacuum transfer cover 9 needs to be connected to an external vacuum pump group and an inert gas is introduced at the same time. In this way, the synchrotron radiation vacuum transfer cover 9 is adapted to the fixture, and the vacuum pump is connected to the synchrotron radiation vacuum transfer cover 9 to perform real-time vacuuming and introduction of inert gas to achieve full air isolation in the open environment of synchrotron radiation diffraction without a cavity, and the synchrotron radiation vacuum transfer cover 9 can be connected to the fixture with an external electrochemical workstation and a temperature controller through a wire, so that the air-isolated synchrotron radiation diffraction analysis can be performed under the same temperature and electrochemical charge and discharge conditions as the scanning electron microscope in-situ test in an air-isolated environment, and the interface structure evolution process of the alkali metal solid-state battery 5 can be analyzed at the same interface reaction area at different key reaction time nodes under the guidance of the rapid detection results of the scanning electron microscope and its energy spectrum.

[0054] The present invention then includes step S4, which loops through S1-S3 according to the need for in-situ observation of the interfacial reaction process of the alkali metal solid-state battery, thereby enabling unlimited switching between the scanning electron microscope and synchrotron radiation diffraction at any time under air-isolated conditions, and performing in-situ observation of the interfacial reaction process of the alkali metal solid-state battery under the same temperature and the same charge and discharge conditions.

[0055] The step S4 includes the following sub-steps: S41, taking the third air-isolating device from the sample stage of the synchrotron radiation diffraction station, and transferring the fixture in the third air-isolating device to the second air-isolating device in the first air-isolating device; S42, after taking the second air-isolating device out of the first air-isolating device, installing it on the sample stage in the scanning electron microscope chamber, closing the chamber and evacuating the chamber, and when the vacuum degree of the chamber reaches 10 -4 When the mba is above, open the second air-isolating device, and under the same temperature and charge-discharge conditions as the synchrotron radiation diffraction in-situ test, use a scanning electron microscope and its energy spectrum to perform in-situ observations on the morphology and composition evolution of the cross-sectional area of ​​the contact interface between the positive and negative electrodes and the solid electrolyte of the alkali metal solid-state battery 5 in the same reaction occurrence area as before; S43, under the guidance of the scanning electron microscope and its energy spectrum test results, use synchrotron radiation diffraction to characterize the in-situ structural evolution of the contact interface between the positive and negative electrodes and the solid electrolyte of the alkali metal solid-state battery 5 at the same temperature and the same charge-discharge conditions as the scanning electron microscope; S44, repeat S41-43 indefinitely at different key reaction time nodes.

[0056] In a preferred embodiment, the required repetitive cycles include, but are not limited to, the following situations: if, during in-situ synchrotron radiation diffraction testing, the interface structure of the alkali metal solid-state battery 5 undergoes certain changes that are difficult to explain, a scanning electron microscope and its energy spectrum can be used to observe the local reaction area in situ for morphological and compositional analysis. After the local reaction area is again observed in situ using a scanning electron microscope and its energy spectrum to obtain morphological and compositional analysis, the synchrotron radiation diffraction can be used to observe the evolution of the interface structure of the alkali metal solid-state battery in situ, and so on, until the alkali metal solid-state battery 5 completes the entire electrochemical charge and discharge cycle.

[0057] In a preferred embodiment, in-situ SEM and synchrotron diffraction observations can be performed alternately and indefinitely under the same temperature and charge-discharge cycle conditions. This allows for comprehensive information on the evolution of the interfacial reaction process in the alkali metal solid-state battery 5, rather than just a single reaction state. Because the morphology, composition, and structure of the interfacial reaction in alkali metal solid-state batteries continuously change during the reaction, repeated SEM and synchrotron diffraction observations can provide comprehensive information on the interfacial evolution process.

[0058] Example 1

[0059] The interface between the negative electrode and solid electrolyte of the lithium metal solid-state battery was characterized. The lithium metal solid-state battery uses lithium iron phosphate (LiFePO4) as the positive electrode and metallic lithium as the negative electrode. The solid electrolyte adopts PEO-based (polyethylene oxide) polymer solid electrolyte. The cross-section of the interface of each component of the solid-state battery is first cut flat, and then assembled under pressure with a mold and placed in a fixture. Scanning electron microscopy combined with synchrotron radiation diffraction tests are performed at room temperature to obtain the cross-sectional morphology and composition of the interface between the negative electrode and the solid electrolyte and the structural information of the local reaction process of the interface. By capturing the morphology and compositional evolution of the heterogeneous interfacial reaction using scanning electron microscopy and energy spectrum, the team accurately determined key reaction time points, such as the starting point, intermediate point, and transition point of the interfacial reaction. Low-magnification images taken with the scanning electron microscope were used to calibrate the size and position of the heterogeneous reaction microregion. The microregion was quickly located by measuring its relative position to the screw in the middle of the current collector's top surface. The team then used a synchrotron diffraction station to quickly locate the reaction site. The structural evolution of the located region was then observed in situ under the same charge-discharge cycle and room temperature conditions. Any changes in diffraction information that were difficult to explain were further observed in situ using scanning electron microscopy and energy spectrum under the same temperature and charge-discharge cycle conditions. This cycle was repeated until the entire electrochemical reaction cycle was complete.

[0060] Example 2

[0061] The interface between the negative electrode and solid electrolyte of the lithium metal solid-state battery was characterized. The lithium metal solid-state battery uses lithium iron phosphate as the positive electrode and metallic lithium as the negative electrode. The solid electrolyte adopts LLZO garnet-type inorganic solid electrolyte. Ionic liquid is added to wet the solid electrolyte. The cross-section of the interface of each component of the solid-state battery is flattened through cutting and grinding and polishing. Then, it is assembled under pressure with a mold and placed in a fixture. Scanning electron microscopy combined with synchrotron radiation diffraction test is carried out at 80°C to obtain the cross-sectional morphology and composition of the interface between the negative electrode and the solid electrolyte and the structural information of the interface. The morphology and composition evolution process is captured using a scanning electron microscope and its energy spectrum. Key cycle nodes such as the interface reaction starting point, reaction intermediate point, and reaction transition point are identified. Low-magnification images taken by the scanning electron microscope are also used to determine the size and position of the inhomogeneous reaction microregions. For example, the relative distance from one edge of the top surface of the current collector, marked with conductive adhesive, is marked for rapid location. Then, at different critical reaction time points, in situ diffraction measurements are taken at a synchrotron diffraction station at the marked position under the same current and voltage conditions and 80°C temperature to characterize the structural evolution of the located reaction region. Any changes in diffraction information that are difficult to explain are further observed in situ using scanning electron microscopy and its energy spectrum under the same temperature and charge-discharge cycling conditions. This cycle is repeated until the entire electrochemical reaction cycle is complete.

[0062] Example 3

[0063] The interface between the anode and solid electrolyte of a sodium metal solid-state battery was characterized. The battery used sodium vanadium phosphate as the positive electrode, sodium metal as the negative electrode, and a PEO-based (polyethylene oxide) polymer solid electrolyte. The cross-sections of the interfaces of the various components of the solid-state battery were flattened, assembled using a mold, and then placed in a fixture. Scanning electron microscopy combined with synchrotron diffraction measurements were performed at room temperature to obtain the cross-sectional morphology, composition, and structural information of the interface between the anode and solid electrolyte. The morphology and compositional evolution of the heterogeneous interfacial reaction were captured using scanning electron microscopy and energy spectrum analysis, and key cycle nodes such as the interface reaction starting point, reaction intermediate point, and reaction transition point were identified. Low-magnification images taken by the scanning electron microscope were used to calibrate the size and position of the heterogeneous reaction microregions, such as by marking their relative distance from a conductive adhesive marker on the center axis of the current collector top surface for rapid location. In situ diffraction measurements were then performed at the synchrotron diffraction station at different critical reaction time points under the same current and voltage conditions at room temperature. Synchrotron radiation diffraction was then used to in situ observe the structural evolution of the identified reaction region. Any changes in diffraction information that were difficult to explain were then further observed in situ using scanning electron microscopy and energy spectrum morphology and composition under the same temperature and charge-discharge cycling conditions. This cycle was repeated until the entire electrochemical reaction cycle was complete.

[0064] According to the in-situ observation method and observation device for observing the interface evolution of alkali metal solid-state batteries of the present invention, a scanning electron microscope is combined with synchrotron radiation diffraction, which has the advantages of light weight, convenient loading and unloading and transportation, air isolation during the entire transportation and testing process, unlimited flexible switching and fast and accurate detection between a high vacuum cavity and an open environment at normal pressure, and can accurately determine the key time nodes of the local interface reaction of the alkali metal solid-state battery and quickly locate the position of the local reaction area, significantly saving a large amount of precious machine time of synchrotron radiation experiments. Compared with the traditional in-situ characterization method using a single scanning electron microscope or synchrotron radiation diffraction combined with spectroscopy, the present invention overcomes the different optical path directions of the scanning electron microscope and synchrotron radiation diffraction (the electron beam optical path of the scanning electron microscope is vertical, and the synchrotron radiation diffraction beam is horizontal) in order to make up for the deficiency of the single traditional in-situ characterization method. The test environment is very different between high vacuum and normal pressure (scanning electron microscopy is a high vacuum cavity environment, and synchrotron radiation diffraction is an open normal pressure environment), and it is difficult for scanning electron microscopy to observe the internal structural evolution information of the reaction interface, and it is difficult for synchrotron radiation diffraction to accurately determine the key nodes of the reaction time and quickly locate the position of the local reaction area, which requires a lot of precious machine time to be wasted for continuous testing. In addition, the test samples are sensitive, fragile and easily damaged, and it is difficult to change the detection method by directly disassembling and moving the samples repeatedly (alkali metal solid-state batteries are air-sensitive, and their interfaces are mostly point contact interfaces that are easily dislocated and damaged during repeated disassembly and movement). This has achieved the purpose of comprehensive, rapid and accurate real-time characterization and analysis of the morphology, composition and structure of the air-sensitive alkali metal solid-state battery electrode and solid electrolyte contact interface under different working currents, voltages and temperatures.

[0065] In summary, compared with the traditional in-situ characterization method of a single scanning electron microscope or synchrotron radiation diffraction combined with spectroscopy, the combination of the two characterization methods of the present invention overcomes the shortcomings of the traditional single in-situ characterization method and achieves the purpose of comprehensive, rapid and accurate real-time characterization and analysis of the morphology, composition and structure of the contact interface of air-sensitive alkali metal solid-state battery electrodes and solid electrolytes under different operating current, voltage and temperature conditions.

[0066] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the present invention. Various modifications are possible. In other words, any simple, equivalent changes and modifications made in accordance with the claims and the description of the present invention fall within the scope of protection of the present invention. Anything not fully described in this invention constitutes conventional technology.

Claims

1. A method for in-situ observation of interface evolution in alkali metal solid-state batteries, characterized in that: The observation method includes the following steps: S1, using scanning electron microscopy and energy spectrum to in situ observe the surface morphology and composition changes of the cross-section of the interface between the positive and negative electrodes and the solid electrolyte of the alkali metal solid-state battery during the charge and discharge process at different temperature conditions and different voltages and currents, accurately determine the key reaction time nodes of the alkali metal solid-state battery interface reaction, and obtain the location of the uneven local reaction area where the morphology and composition changes; S2, pausing the charge and discharge process of the alkali metal solid-state battery at the key reaction node, and transferring the paused alkali metal solid-state battery to the open environment of the synchrotron radiation diffraction station under air-tight conditions. Using laser to simulate the position of the synchrotron radiation spot, with the marker on the top surface of the fixture current collector as a reference, and using synchrotron radiation fast two-dimensional point-by-point diffraction scanning to quickly locate the position of the uneven local reaction area observed by the scanning electron microscope and its energy spectrum; S3, under the same temperature and charge-discharge conditions as the scanning electron microscope, the structural evolution of the interface reaction zone of the alkali metal solid-state battery is characterized in situ by performing fine single-point diffraction and / or fine point-by-point two-dimensional diffraction scanning on the located reaction area at the key reaction time node by synchrotron radiation diffraction; S4, according to the need for in-situ observation of the interface reaction process of alkali metal solid-state batteries, S1-S3 are repeated to achieve unlimited switching between scanning electron microscopy and synchrotron radiation diffraction at any time under air-isolated conditions, and to conduct in-situ observation of the interface reaction process of alkali metal solid-state batteries under the same temperature and the same charge and discharge conditions.

2. The observation method according to claim 1, characterized in that The step S1 includes the following sub-steps: S11, first flattening the cross-sections of the components of the alkali metal solid-state battery in the first air-isolating device, then assembling the components to form an alkali metal solid-state battery, and then vertically mounting the assembled alkali metal solid-state battery on a fixture with the flattened cross-section of the interface facing upward; S12, installing the fixture having the alkali metal solid-state battery installed in the first air-isolated device into the second air-isolated device; S13, moving the second air-isolating device out of the first air-isolating device and installing it in the vacuum chamber of the scanning electron microscope, closing the vacuum chamber of the scanning electron microscope and then evacuating the chamber; S14, when the vacuum degree reaches 10 -4 When the mba is above, the second air-isolating device is opened to carry out an in-situ electrochemical reaction with controllable temperature, and the cross-sectional morphology and composition changes of the interface between the positive and negative electrodes and the solid electrolyte of the alkali metal solid-state battery during the charge and discharge process at different voltages and currents under different temperature conditions are observed in situ by scanning electron microscopy and its energy spectrum.

3. The observation method according to claim 2, characterized in that: In step S14, the key time nodes of the interface reaction are accurately determined through the morphology and composition change information. At the same time, the markers on the top surface of the current collector are used as a reference to calibrate the reaction area where the morphology and composition changes occur, so as to facilitate subsequent rapid positioning.

4. The observation method according to claim 3, characterized in that: After determining the reaction area, reduce the magnification in sequence so that the reaction area and the marker on the top surface of the current collector appear on the observation screen at the same time. By taking photos, measure the relative position of the marker on the top surface of the current collector and the reaction area.

5. The observation method according to claim 4, characterized in that: The step S2 includes the following sub-steps: S21, taking out the second air-isolating device from the vacuum chamber of the scanning electron microscope, and transferring the fixture in the second air-isolating device to the third air-isolating device in the first air-isolating device; S22, after removing the third air-isolated device from the first air-isolated device, installing it on an open, cavity-free sample stage of a synchrotron radiation diffraction station, using a laser beam to simulate the position of the synchrotron radiation spot, by moving the position of the synchrotron radiation diffraction station sample stage on which the third air-isolated device is mounted and observing through an observation window on the top of the third air-isolated device, so that the laser spot is irradiated near the reaction area based on the position of the current collector marker and its relative position to the reaction area; S23, turn off the laser, open the synchrotron radiation beamline shutter, and perform a two-dimensional point-by-point rapid scan of the synchrotron radiation diffraction. By referring to the position of the collector marker and comparing the position where the weak change of the two-dimensional rapid scanning diffraction signal occurs with the position of the reaction area determined by the scanning electron microscope and its energy spectrum, the reaction area can be quickly located.

6. The observation method according to claim 5, characterized in that: In step S23, the synchrotron radiation diffraction two-dimensional fast point-by-point scanning of the diffraction signal has a scanning time of 1-5 s / point.

7. The observation method according to claim 1, characterized in that: In step S3, the scanning time of the synchrotron radiation diffraction fine single-point diffraction and / or the two-dimensional fine point-by-point diffraction scanning is 20-60 s / point.

8. The observation method according to claim 5, characterized in that: The step S4 includes the following sub-steps: S41, removing the third air-isolated device from the sample stage of the synchrotron radiation diffraction station, and transferring the fixture in the third air-isolated device to the second air-isolated device in the first air-isolated device; S42, after removing the second air-isolated device from the first air-isolated device, installing it on a sample stage in the scanning electron microscope chamber, opening the second air-isolated device, and performing in situ observation of the morphology and composition evolution of the cross-sectional area of ​​the contact interface between the positive and negative electrodes and the solid electrolyte of the alkali metal solid-state battery using a scanning electron microscope and its energy spectrum under the same temperature and charge-discharge conditions as the synchrotron diffraction in situ test; S43, guided by SEM and EDS test results, characterize the in situ structural evolution of the contact interface between the positive and negative electrodes and the solid electrolyte of alkali metal solid-state batteries by synchrotron diffraction under the same temperature and charge-discharge conditions as the SEM; S44, repeating S41-43 for multiple cycles at different critical reaction time nodes.

9. An observation device for in-situ observation of interface evolution of alkali metal solid-state batteries, characterized in that: The observation device includes: A sample fixture comprising a current collector and a heating element. The alkali metal solid-state battery is assembled in a first air-isolating device providing an inert atmosphere and then clamped by two current collectors. The top surface of the current collector has a marker. The current collector maintains close contact with the positive and negative electrodes of the alkali metal solid-state battery. The cross-section of the interface of the alkali metal solid-state battery is 0.1 mm to 1 mm higher than the top surface of the current collector to facilitate the synchrotron radiation beam line spot to pass through the interface between the positive and negative electrodes and the solid electrolyte without interference for diffraction characterization. The heating element is installed inside the current collector to control the temperature of the alkali metal solid-state battery. A scanning electron microscope system comprises a vacuum chamber, wherein a second air-isolating device is detachably mounted in the vacuum chamber, wherein the contact interface between the positive and negative electrodes of the alkali metal solid-state battery and the solid electrolyte is parallel to the incident direction of the electron beam, and a cross section of the contact interface between the positive and negative electrodes of the alkali metal solid-state battery and the solid electrolyte is perpendicular to the incident electron beam of the scanning electron microscope, and wherein the scanning electron microscope and a scanning electron microscope energy dispersive spectrometer cooperate to observe the morphology and composition changes of the cross section of the interface of the alkali metal solid-state battery in the vacuum chamber of the scanning electron microscope; A synchrotron radiation diffraction system has an open, cavity-free, movable sample stage, and a third air-isolating device is detachably mounted on the sample stage. The contact interface between the positive and negative electrodes of the alkali metal solid-state battery and the solid electrolyte is perpendicular to the incident direction of the synchrotron radiation beam. The synchrotron radiation beam is irradiated onto the interface of the alkali metal solid-state battery above the current collector to characterize the structural evolution of the interface of the alkali metal solid-state battery.

10. The observation device according to claim 9, characterized in that The observation device also includes an electrochemical workstation and a temperature controller, which are connected to the sample fixture through a connecting interface of a second air-isolating device after passing through a scanning electron microscope cavity flange via a wire, or the electrochemical workstation and the temperature controller are connected to the sample fixture through a connecting interface of a third air-isolating device via a wire to control the charging and discharging process and temperature of the alkali metal solid-state battery, with a temperature range of room temperature to 200°C.

11. The observation device according to claim 9, characterized in that The top surface of the current collector has markers for marking the reaction occurrence area, and the markers are screws, grooves and marked edges on the surface of the current collector.

12. The observation device according to claim 11, characterized in that The observation device also includes a laser for simulating a synchrotron radiation spot in a synchrotron radiation diffraction system. With the position of the marker as a reference, the local reaction area determined by the aforementioned scanning electron microscope and its energy spectrum is quickly located by combining synchrotron radiation rapid point-by-point two-dimensional diffraction scanning.

13. The observation device according to claim 12, characterized in that An observation window is provided at the top of the third air-isolating device, and a high-definition camera installed above the synchrotron radiation diffraction station observes the cross-section of the laser, the sample fixture, the marker on the top surface of the fixture current collector, and the interface of the alkali metal solid-state battery through the window.

14. The observation device according to claim 9, characterized in that By loading and unloading and moving the sample fixture installed with the alkali metal solid-state battery, rather than directly loading and unloading and moving the sample, the alkali metal solid-state battery sample can be repeatedly transferred in the first air-isolated device into the second air-isolated device and the third air-isolated device for an infinite number of times, thereby realizing the in-situ observation of the alkali metal solid-state battery interface reaction process, rather than a certain reaction state, by combining scanning electron microscopy and synchrotron radiation diffraction.

15. The observation device according to claim 9, characterized in that The second air-isolating device has a cover, which is driven by a mechanical transmission device to close and open. The mechanical transmission device is connected to the electric controller inside the first air-isolating device through a wire, or the mechanical transmission device is connected to the electric controller outside the vacuum chamber of the scanning electron microscope after passing through the scanning electron microscope chamber flange through a wire to drive the mechanical transmission device to close and open.

16. The observation device according to claim 15, characterized in that The cross-section of the interface of the alkali metal solid-state battery is higher than the box mouth, and the up and down movement of the lid is achieved through the step height difference.

17. The observation device according to claim 9, characterized in that The first air-isolating device is a glove box, the second air-isolating device is a vacuum transfer box, and the third air-isolating device is a synchrotron radiation vacuum transfer cover.

18. The observation device according to claim 9, characterized in that The second air-isolating device is a non-magnetic titanium alloy box body with good corrosion resistance and thermal stability.

19. The observation device according to claim 9, characterized in that The third air-isolating device comprises a load-bearing steel frame sealed by a Cape Town membrane.

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