An in-situ observation device for observing the interface evolution of alkali metal solid-state batteries

Abstract

This invention relates to an in-situ observation device for the evolution of the interface of an alkali metal solid-state battery. The device includes a sample clamp for holding the alkali metal solid-state battery and conducting tests under different temperatures and charge / discharge conditions. The cross-section of the interface between the positive and negative electrodes and the solid electrolyte is 0.1 mm–1 mm higher than the top surface of the current collector. A scanning electron microscope (SEM) system characterizes the morphology and composition of the interface cross-section, with the interface cross-section parallel to and perpendicular to the incident electron beam direction of the SEM. A synchrotron radiation diffraction (SDR) system characterizes the structural evolution of the interface. The interface is perpendicular to the incident direction of the synchrotron radiation beam. This invention allows for free switching between SEM and SDR characterization under air-isolated conditions, enabling in-situ observation of the interface morphology, composition, and structural evolution information. This overcomes the limitations of traditional in-situ methods and significantly saves synchrotron radiation time.

Description

Technical Field

[0001] This utility model relates to new energy batteries, and more specifically to an in-situ observation device for observing the interface evolution of alkali metal solid-state batteries. Background Technology

[0002] Alkali metal solid-state batteries have long been considered key to solving the problem of green renewable energy storage, especially lithium metal solid-state batteries, which have attracted attention for their excellent electrochemical and safety performance. However, due to the highly reactive nature of alkali metal anodes, they are not only very sensitive to air, readily reacting with water and oxygen, but also prone to generating numerous dendrites at the electrode-solid electrolyte interface during charge-discharge cycles, piercing the solid electrolyte and causing short circuits or explosions. To better study the internal electrochemical reaction processes of alkali metal solid-state batteries, especially lithium metal solid-state batteries, and to explore failure mechanisms, batteries at different cycle stages are often disassembled, and the electrode reaction interfaces are then characterized. This non-in-situ characterization method not only fails to observe the evolution of electrode reaction interface failure in real time, but also damages the internal structure of the battery and may even expose the alkali metal anode to air and cause contamination.

[0003] Existing in-situ observation methods are mostly single-method approaches, often with insurmountable limitations: for example, while optical microscopy offers a large field of view, its magnification is limited and resolution is low, making it difficult to identify the causes of failure and degradation in alkali metal solid-state batteries at the nanoscale; while transmission electron microscopy (TEM) achieves sub-nanometer resolution, its field of view is limited to the micrometer scale, making it difficult to capture the electrochemical reaction processes at the battery interface and requiring highly precise sample preparation; and while scanning electron microscopy (SEM) combines the testing field of view (millimeter-scale observation range) of optical microscopy with the resolution (nanometer-scale observation resolution) of TEM, it can only observe the electrode surface morphology and composition, and cannot penetrate the electrode-electrolyte interface. While synchrotron radiation diffraction (SDR) in situ observation can penetrate the battery and provide precise quantitative and qualitative analysis of its internal structure, the inhomogeneous local reactions at the battery interface often necessitate two-dimensional synchrotron radiation diffraction (2D) to pinpoint the locations of these inhomogeneous local reactions. Obtaining a sufficient range of 2D synchrotron radiation diffraction patterns requires scanning point by point. For example, at the Shanghai Synchrotron Radiation Facility (SSRF) BL14B1 diffraction line, the maximum spot size is only 200µm high and 300µm wide. To obtain sufficiently high flux and clear synchrotron radiation diffraction data, the scanning time is typically 30s per point. For a typical coin cell, with a diameter of approximately 1-2cm, scanning a 1×1cm... 2To obtain diffraction information with higher spatial resolution, a smaller spot size and a longer scanning time are required. Furthermore, since the battery reaction occurs internally, it is often difficult to accurately determine the reaction time points at the microscopic interface based solely on the fluctuations in the macroscopic electrochemical charge-discharge curve. This means that a significant amount of valuable synchrotron radiation time must be spent continuously scanning two-dimensional diffraction patterns over a large area in order to potentially capture useful information about the local reactions at the battery interface.

[0004] In summary, combining different in-situ techniques for comprehensive in-situ observation of alkali metal batteries is essential. Scanning electron microscopy (SEM) and synchrotron radiation diffraction (SDR) are particularly suitable for observing sample areas of similar size (both on the millimeter scale). SEM can rapidly observe morphological changes in the micro-regions of the battery interface within seconds, with spatial resolution accurate to the nanometer scale. Simultaneously, combining SEM with energy dispersive spectroscopy (EDS) can quickly obtain the compositional distribution of the micro-regions of the battery interface within minutes. This allows for in-situ characterization of the morphological and compositional changes at the interface of alkali metal solid-state batteries, accurate identification of key nodes of microscopic reactions at the battery interface, and rapid location of regions experiencing localized interface reactions. This, in turn, helps determine the in-situ observation nodes and diffraction test locations for synchrotron radiation diffraction, guiding the characterization of the battery interface structure evolution and saving significant time. These two methods are highly suitable for combining for in-situ observation of alkali metal batteries. However, scanning electron microscopes (SEMs) operate in high-vacuum chambers, while synchrotron radiation diffraction (SRD) stations are open, non-vacuum environments at ambient pressure. Furthermore, alkali metal solid-state batteries are highly susceptible to air contamination, and unlike conventional liquid batteries with surface-contact electrode-electrolyte interfaces, the electrode-electrolyte interface in alkali metal SEMs is primarily point-contact, making it extremely fragile and prone to misalignment and damage during disassembly and relocation. This makes it very difficult to directly and repeatedly load, unload, and transfer alkali metal SEM samples under completely air-isolated conditions in either of these devices without damaging the electrode-electrolyte interface. In addition, SEM uses a reflective optical path, while synchrotron radiation diffraction uses a transmission optical path, making them inherently difficult to combine. Information obtained from the reflective optical path of SEM is needed to guide the transmission optical path of synchrotron radiation diffraction at key time points and local reaction locations to detect the same region of the same sample. This further complicates the integration of these two techniques for observing the in-situ electrochemical reaction interface evolution of the same alkali metal SEM sample in the same reaction region. Utility Model Content

[0005] To address the problem of relying on a single in-situ observation method in the existing technology, this invention provides an in-situ observation device that combines different in-situ technologies to observe the interface evolution of alkali metal solid-state batteries.

[0006] The in-situ observation device for observing the interface evolution of alkali metal solid-state batteries according to this invention includes a sample clamp comprising a current collector and a heating element. The alkali metal solid-state battery is assembled in a first air-isolation device providing an inert atmosphere and then clamped between two current collectors. The top surface of the current collectors is marked. The current collectors maintain 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-1 mm higher than the top surface of the current collectors to facilitate uninterrupted diffraction characterization of the synchrotron radiation beamline through the interface between the positive and negative electrodes and the solid electrolyte. The heating element is installed inside the current collectors to control the temperature of the alkali metal solid-state battery. A scanning electron microscope system is included, which has a vacuum chamber. A second air-isolation device is detachably installed in the vacuum chamber. The contact interface between the positive and negative electrodes and the solid electrolyte of the metal solid-state battery is parallel to the incident direction of the electron beam. The cross-section of the contact interface between the positive and negative electrodes and the solid electrolyte of the alkali metal solid-state battery is perpendicular to the incident electron beam of the scanning electron microscope. The scanning electron microscope and the energy dispersive spectroscopy (EDS) spectrometer work together to observe the morphology and compositional changes of the cross-section of the alkali metal solid-state battery interface in the vacuum chamber of the scanning electron microscope. The synchrotron radiation diffraction system has an open, cavity-free, movable sample stage. A third air isolation device is detachably installed on the sample stage. The contact interface between the positive and negative electrodes and the solid electrolyte of the alkali metal solid-state battery is perpendicular to the incident direction of the synchrotron radiation beam. The synchrotron radiation beam irradiates the interface of the alkali metal solid-state battery at a position higher than the current collector to characterize the structural evolution of the interface of the alkali metal solid-state battery.

[0007] In a preferred embodiment, the observation device further includes an electrochemical workstation and a temperature controller. The electrochemical workstation and temperature controller are connected to the sample holder via wires through the scanning electron microscope cavity flange and then through the adapter of the second air-isolation device. Alternatively, the electrochemical workstation and temperature controller are connected to the sample holder via wires through the adapter of the third air-isolation device 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.

[0008] In a preferred embodiment, the top surface of the current collector has markers for marking the reaction zone, the markers being screws, grooves, and marked edges on the surface of the current collector.

[0009] In a preferred embodiment, the observation device further includes a laser for simulating synchrotron radiation spots in a synchrotron radiation diffraction system, using the marker position as a reference, to quickly locate the local reaction region determined by the aforementioned scanning electron microscope and its energy spectrum through rapid point-by-point two-dimensional diffraction scanning of synchrotron radiation.

[0010] In a preferred embodiment, the top of the third air-isolated device is provided with an observation window, through which 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.

[0011] In a preferred embodiment, instead of directly loading, unloading, and moving the sample holder containing the alkali metal solid-state battery, the alkali metal solid-state battery sample is repeatedly transferred indefinitely into the second and third air-isolated devices via a combination of scanning electron microscopy and synchrotron radiation diffraction to observe the interfacial reaction process of the alkali metal solid-state battery, rather than a specific reaction state. It should be understood that the first, second, and third air-isolated devices, along with the scanning electron microscope vacuum chamber, form an air-isolated pathway.

[0012] In a preferred embodiment, the second air-isolation 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-isolation device via a wire, or the mechanical transmission device is connected to an electric controller outside the vacuum chamber of the scanning electron microscope via a wire through the cavity flange of the scanning electron microscope, so as to drive the mechanical transmission device to close and open.

[0013] In a preferred embodiment, the cross-section of the alkali metal solid-state battery interface is higher than the opening of the box, and the lid can be moved up and down by means of a stepped height difference.

[0014] In a preferred embodiment, the first air-isolation device is a glove box, the second air-isolation device is a vacuum transfer box, and the third air-isolation device is a synchrotron radiation vacuum transfer hood.

[0015] In a preferred embodiment, the second air-isolation device is a non-magnetic titanium alloy housing with good corrosion resistance and thermal stability.

[0016] In a preferred embodiment, the third air-isolation device comprises a load-bearing steel frame sealed by a Cape Town membrane.

[0017] The in-situ observation device for observing the interface evolution of alkali metal solid-state batteries according to this invention combines scanning electron microscopy (SEM) with synchrotron radiation diffraction (SDR). This overcomes the difficulties of different optical path directions between SEM and SDR, large differences between high vacuum and ambient pressure in the testing environment, and the difficulty of directly and repeatedly disassembling and moving sensitive and fragile test samples. It enables the use of information obtained from the reflected optical path of the SEM to guide the transmitted optical path of the SDR to detect the same area of ​​the same sample at key time points and local reaction locations. This saves a lot of valuable time in synchrotron radiation testing. Furthermore, it achieves the goal of comprehensive, rapid, and accurate real-time characterization and analysis of the morphology, composition, and structure of the contact interface between the air-sensitive alkali metal solid-state battery electrode and the solid electrolyte under different operating currents, voltages, and temperatures. Attached Figure Description

[0018] Figure 1The present invention illustrates an in-situ observation using a scanning electron microscope to observe the interface evolution of alkali metal solid-state batteries according to a preferred embodiment of the present invention.

[0019] Figure 1a Show Figure 1 The lid is driven by a stepped height difference.

[0020] Figure 2 This invention illustrates a synchrotron radiation diffraction in-situ observation device for observing the interface evolution of alkali metal solid-state batteries according to a preferred embodiment of the present invention. Detailed Implementation

[0021] The preferred embodiments of this utility model are given below with reference to the accompanying drawings and described in detail.

[0022] In this document, unless otherwise specified, the terms “installation,” “fixing,” and “placement” are interpreted broadly, such as mechanical installation, fixing, and placement; direct installation, fixing, and placement; or indirect installation, fixing, and placement with intermediate components as connections. Those skilled in the art who read this utility model can understand the meaning of the above terms in this utility model according to the specific circumstances.

[0023] Considering the matching size of the observation sample area for scanning electron microscopy (SEM) and synchrotron radiation diffraction (taking the Zeiss Gemini 300 field emission SEM and the Shanghai Synchrotron Radiation Facility BL14B1 diffraction line station as examples, the observation area can be measured in millimeters), and that SEM can be combined with SEM energy dispersive spectroscopy to quickly capture the morphological changes and compositional segregation of the micro-regions at the battery interface to accurately determine the key time points of the reaction at the interface of alkali metal solid-state batteries and quickly locate the local reaction areas of interface inhomogeneity, thereby determining the time points for in-situ observation and the location of in-situ diffraction detection for synchrotron radiation diffraction, so as to guide the structural evolution characterization of the reaction process at the interface of alkali metal solid-state batteries by synchrotron radiation diffraction, saving a lot of valuable synchrotron radiation time, this utility model combines SEM and synchrotron radiation diffraction to conduct comprehensive in-situ observation of the interface evolution process of alkali metal solid-state batteries. In particular, the cavity of a scanning electron microscope (SEM) is a high-vacuum cavity, while synchrotron radiation diffraction (SDR) is an open environment without a cavity at atmospheric pressure. Furthermore, the optical path of an SEM is perpendicular to the sample surface, while the beamlines of a synchrotron radiation diffraction (SDR) penetrate the sample parallel to it. The optical paths are completely different, making them very difficult to combine. In addition, alkali metal solid-state batteries are sensitive to air contamination. Compared with traditional liquid batteries, the contact interface between their electrodes and solid electrolytes is mostly point contact, which is very fragile and easily misaligned and damaged during disassembly and movement. This makes it very difficult to repeatedly load, unload, and transfer alkali metal solid-state batteries under completely air-isolated conditions in these two types of equipment and combine them to observe the evolution of the in-situ electrochemical reaction interface.

[0024] This invention can comprehensively characterize the morphology, composition, and structural evolution of the in-situ reaction process at the electrode and solid electrolyte interface of alkali metal solid-state batteries. Simultaneously, scanning electron microscopy (SEM) allows for precise control of key time points in the battery interface reaction and rapid localization of non-uniform reaction sites, providing guidance and basis for synchrotron radiation diffraction experiments and saving significant time. Furthermore, by changing the temperature and externally applied current and voltage during cyclic charging and discharging, the effects of different test conditions on the electrochemical reaction process of alkali metal solid-state batteries can be studied, further investigating the failure mechanism of alkali metal solid-state batteries.

[0025] The use of the observation device of this utility model first includes step S1, which involves observing the surface morphology and compositional changes of the interface between the positive and negative electrodes and the solid electrolyte of the alkali metal solid battery under different temperature conditions, voltages and currents during charging and discharging using a scanning electron microscope and its energy dispersive spectroscopy (EDS). This allows for the precise determination of the key reaction time points of the alkali metal solid battery interface reaction and the rapid acquisition of the location of the non-uniform local reaction zone where morphology and composition change (i.e., the location of the non-uniform local interface reaction).

[0026] Step S1 includes sub-step S11, in which the cross-sections of each component of the alkali metal solid-state battery (i.e., the positive electrode, solid electrolyte, and negative electrode) are first flattened in the first air-isolated device, then the components are assembled to form the alkali metal solid-state battery 5, and then the assembled alkali metal solid-state battery 5 is vertically mounted on the fixture with the flattened interface facing upwards. See [link to relevant documentation]. Figure 1 .

[0027] In a preferred embodiment, the first air-isolation device is a glove box providing inert atmosphere protection. Under the inert atmosphere protection of the glove box, the positive electrode, solid electrolyte, and negative electrode, after being flattened at the interface cross-section, are assembled sequentially 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 the positive electrode being a lithium iron phosphate electrode sheet and the negative electrode being a lithium sheet. In a preferred embodiment, the solid electrolyte can also be a semi-solid electrolyte formed by impregnating a membrane (e.g., a polyolefin film) with an ionic liquid. In a preferred embodiment, the positive electrode, semi-solid electrolyte, and polymer electrolyte are cut with scissors or a scalpel to form a flat cross-section; the solid ceramic electrolyte is polished with sandpaper to flatten its cross-section; and the negative electrode is cut with a scalpel to make its cross-section flat to meet the requirements of scanning electron microscopy. In the embodiment of the solid electrolyte, the solid electrolyte size is larger than the positive and negative electrode sizes, and the solid electrolyte is clamped between the positive and negative electrodes and pressed tightly to ensure good contact.

[0028] 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 battery 5 is assembled in the order of positive electrode, solid electrolyte and negative electrode. The assembled alkali metal solid battery 5 is placed vertically into the fixture and clamped by the two current collectors 8 of the fixture. It is ensured that the top surface of the alkali metal solid battery 5 (i.e. the cross-section of the alkali metal solid battery interface) is 0.1mm-1mm higher than the top surface of the current collector 8, so as to ensure good contact with the current collector 8 (i.e. tight contact, such as electrical contact or thermal contact). At the same time, the synchrotron radiation beam spot is not disturbed by the fixture and passes through the interface between the positive and negative electrodes and the solid electrolyte for diffraction characterization. It is ensured that the cross-section of the 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 in synchrotron radiation diffraction.

[0029] In a preferred embodiment, the clamp can be a lightweight, high-temperature resistant, and insulating plastic clamp, such as polypropylene (PP) or polyethylene (PE). In a preferred embodiment, a highly conductive current collector 8, such as a copper current collector, is installed at both ends of the clamp that contact the alkali metal solid-state battery 5. 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 ensure close contact between the two current collectors 8 and the positive and negative electrodes, preventing failure and open circuit due to poor contact.

[0030] Step S1 includes sub-step S12, in which the fixture containing the alkali metal solid-state battery 5 is installed in the second air-isolated device (i.e., vacuum transfer box 3) within the first air-isolated device. It should be understood that, to avoid collisions between the vacuum transfer box 3 and the scanning electron microscope barrel and energy dispersive spectroscopy probe due to excessively close vertical distance, the cross-section of the interface of the alkali metal solid-state battery 5 should be higher than the box opening. Specifically, to prevent collisions between the box cover 4 and the sample 5 protruding above the box opening, the horizontal sliding track in the mechanical transmission device is designed as a horizontal stepped sliding track. The left and right movement of the box cover is achieved through horizontal sliding, and the up and down movement of the box cover 4 is achieved through the step height difference d. Figure 1a As shown. It should be understood that, Figure 1a This is merely a structural diagram; any other structure capable of achieving similar functionality may be used in this invention.

[0031] In a preferred embodiment, under the inert atmosphere of the glove box, the fixture with the alkali metal solid-state battery 5 installed is placed into the vacuum transfer box 3. The clamp's wires are connected to the connector of the vacuum transfer box 3 and then led out from the vacuum transfer box 3. Four fastening screws secure the bottom of the clamp to the bottom of the vacuum transfer box 3. A mechanical transmission device drives the cover 4 to close the opening at the top of the vacuum transfer box 3. An O-ring 6 installed at the opening seals the vacuum transfer box 3, thus providing air-isolated protection for the alkali metal solid-state battery 5 inside the vacuum transfer box 3. In a preferred embodiment, the vacuum transfer box 3 is made of high-strength non-magnetic titanium alloy, which has 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 cover 4. The mechanical transmission device is directly connected to an external electric controller via wires, allowing the opening and closing of the cover 4 to be controlled manually by the external controller in the inert gas protected environment of the glove box. The mechanical transmission device is connected to the vacuum chamber flange of the scanning electron microscope via a wire, and then connected to an external electric controller via the flange, allowing the opening and closing of the cover 4 to be controlled manually by the external controller in the high vacuum environment of the scanning electron microscope.

[0032] Step S1 includes sub-step S13, which involves removing the second air-isolating device from the first air-isolating device and installing it into the cavity of the scanning electron microscope. After closing the cavity of the scanning electron microscope, a vacuum is drawn. Figure 1 As shown.

[0033] In a preferred embodiment, after the vacuum transfer box 3 is removed from the glove box, it is installed on the sample stage inside the scanning electron microscope (SEM) cavity. The wires leading from the clamps inside the vacuum transfer box 3 are connected to the wire interface of the external controller via the interface of the vacuum transfer box 3 and the flange on the SEM cavity. After closing the chamber door, a vacuum is drawn. Thus, the vacuum transfer box 3, in conjunction with the clamps, allows the alkali metal solid-state battery 5 to be transferred into the vacuum cavity of the SEM under completely air-isolated conditions, avoiding contamination of the alkali metal solid-state battery 5 by water and oxygen in the air, and also avoiding damage to the battery's fragile interface caused by direct transfer, installation, and removal of the alkali metal solid-state battery 5. In a preferred embodiment, inside the SEM cavity, the interface between the positive and negative electrodes and the solid electrolyte of the alkali metal solid-state battery 5 is parallel to the electron beam incident direction, and the cross-section of the interface between the positive and negative electrodes and the solid electrolyte of the alkali metal solid-state battery 5 is perpendicular to the incident electron beam, facilitating SEM observation.

[0034] Step S1 includes sub-step S14, when the vacuum degree reaches 10... -4 When the temperature exceeds MBA, the second air-isolation device is activated to conduct an in-situ electrochemical reaction at a controlled temperature. The morphology and compositional changes of the interface between the positive and negative electrodes and the solid electrolyte of the alkali metal solid-state battery 5 are observed in situ using scanning electron microscopy and energy dispersive spectroscopy under different temperature conditions, voltages, and currents during charging and discharging. (See [reference needed]). Figure 1 .

[0035] In a preferred embodiment, after the scanning electron microscope is evacuated, for example when the vacuum level reaches 10... -4 At MBA level or above, the mechanical transmission device is controlled by the electric controller outside the scanning electron microscope (SEM) to drive the cover 4 to open the vacuum transfer box 3, exposing the clamps and alkali metal solid-state battery 5 inside the vacuum transfer box 3. After the alkali metal solid-state battery 5 is placed under the SEM tube 1, the sample stage with the vacuum transfer box 3 is moved and its position is adjusted by the sample stage positioning motor inside the SEM cavity. After selecting a suitable observation area and range, charge-discharge cycle tests of the alkali metal solid-state battery 5 are performed at different temperatures and with different voltages and currents. The operating temperature is adjusted between room temperature and 200°C, and the reaction process of the cross-section of the interface between the positive and negative electrodes and the solid electrolyte is observed in situ. In a preferred embodiment, the energy dispersive spectrometer (EDS) 2 is placed next to the tube 1. The SEM and EDS are combined so that while the SEM obtains information on the surface morphology evolution, the EDS 2 can analyze changes in element types, contents, and distribution. By observing the changes in morphology and composition, key cycle nodes can be accurately determined, and the reaction occurrence zone can be quickly identified.

[0036] In step S14, the key time points of the interface reaction are accurately determined by the morphological and compositional change information. Simultaneously, the reaction zone exhibiting morphological and compositional changes is rapidly calibrated to facilitate subsequent rapid localization. Specifically, after determining the reaction zone, the magnification is sequentially reduced so that the reaction zone and the markers on the top surface of the current collector 8 appear simultaneously in the observation frame. By taking photographs, the relative positions of the markers on the top surface of the current collector (such as screws, grooves, or the edges of current collector markers on the current collector 8) and the reaction zone are measured, providing guidance for subsequent rapid localization of the reaction zone using synchrotron radiation diffraction.

[0037] In a preferred embodiment, the current collector 8 is connected to an electrochemical workstation outside the scanning electron microscope (SEM) via a wire extending from inside the fixture, through a vacuum transfer box interface, and a flange of the SEM cavity, to perform electrochemical charge-discharge tests on the alkali metal solid-state battery 5 at different voltages and currents. In another preferred embodiment, the current collector 8 contains a ceramic heating rod 7, which is connected to a temperature controller outside the SEM via a wire extending from inside the fixture, through a vacuum transfer box interface, and a flange of the SEM cavity, to control the temperature of the alkali metal solid-state battery 5 within a range from room temperature to 200°C, simultaneously providing heating and power-on functions.

[0038] The use of the observation device of this invention includes step S2, which involves pausing the charging and discharging process of the alkali metal solid-state battery at a critical reaction node, transferring the paused alkali metal solid-state battery to the open environment of a synchrotron radiation diffraction station under air-isolated conditions, simulating the position of the synchrotron radiation spot with a laser, using the marker on the top surface of the clamp current collector as a reference, and rapidly locating the non-uniform local reaction region observed by the scanning electron microscope and its energy spectrum through rapid two-dimensional point-by-point diffraction scanning of synchrotron radiation.

[0039] Step S2 includes sub-step S21, which involves removing the vacuum transfer box 3 from the cavity of the scanning electron microscope and transferring the clamp in the vacuum transfer box 3 from the first air-isolated device to the third air-isolated device (i.e., the synchrotron radiation vacuum transfer hood 9). See [link to relevant documentation]. Figure 2 It should be understood that the first, second, and third air-isolation devices can form a completely air-isolated 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 transfer between different devices and during in-situ testing in the open atmospheric environment of the synchrotron radiation diffraction station, thus avoiding contamination. This allows for continuous in-situ observation of the morphology, composition, and structure of the alkali metal solid-state battery interface under different test temperatures during charge-discharge cycles at different voltages and currents, through unlimited repeated switching between the scanning electron microscope and synchrotron radiation diffraction equipment.

[0040] In a preferred embodiment, after accurately determining the key reaction time points and rapidly locating the local reaction area, the scanning electron microscope (SEM) controls the mechanical transmission device via an external electric controller to drive the cover 4 to close the vacuum transfer box 3. Then, the vacuum transfer box 3 is removed from the SEM cavity and placed in a glove box. Under the protection of the inert gas in the glove box, the vacuum transfer box 3 is opened, the clamp is removed, and placed in the synchrotron radiation vacuum transfer hood 9. The clamp's wires are connected to the interface of the synchrotron radiation vacuum transfer hood 9 and led out from the synchrotron radiation vacuum transfer hood 9. The bottom of the clamp is fixed to the bottom of the synchrotron radiation vacuum transfer hood 9 with four fastening screws. The synchrotron radiation vacuum transfer hood 9 is then fixed to the door 14 with fastening screws and sealed with O-rings to ensure airtightness. It is then removed from the glove box. This method of loading, unloading, and moving the clamp, rather than directly loading, unloading, and moving the alkali metal solid-state battery 5, avoids damage to the fragile reaction interface of the alkali metal solid-state battery 5 during repeated installation, disassembly, and transfer. This ensures that the fragile and easily damaged electrode and solid electrolyte contact interface is suitable for the combined characterization of the SEM and synchrotron radiation diffraction methods of this invention. In a preferred embodiment, the synchrotron radiation vacuum transfer hood 9 is sealed with a load-bearing steel frame and a Cape Town membrane (polyethylene terephthalate, PET) that can penetrate synchrotron radiation beamlines.

[0041] Step S2 includes sub-step S22, in which the synchrotron radiation vacuum transfer hood 9 is removed from the first air isolation device and installed on the open, cavity-free sample stage of the synchrotron radiation diffraction station. The position of the synchrotron radiation beam line is simulated by using a laser beam. The position of the synchrotron radiation diffraction station sample stage, which is equipped with the third air isolation device, is moved and observed through the observation window on the top of the third air isolation device. The position of the current collector marker is used as a reference, and the laser spot is irradiated near the non-uniform local reaction area based on the position of the current collector marker and the relative position of the reaction area.

[0042] In a preferred embodiment, a window 15 is provided at the top of the synchrotron radiation vacuum transfer hood 9. A high-definition camera mounted above the synchrotron radiation diffraction station can observe the cross-section of the interface between the laser simulating the synchrotron radiation spot, the top surface marker of the current collector inside the synchrotron radiation vacuum transfer hood 9, and the interface of the alkali metal solid-state battery 5 through the window 15, thereby determining the observation position of the synchrotron radiation beamline spot. Specifically, by means 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 hood 9 and irradiate the interface of the alkali metal solid-state battery 5 at a position higher than the current collector 8. The left and right positions of the sample stage are adjusted, and with reference to the position of the top surface marker of the current collector, the laser beam is irradiated near the local reaction area previously located in the scanning electron microscope.

[0043] Step S2 includes sub-step S23: turning off the laser, opening the synchrotron radiation beamline shutter, and performing a large-scale two-dimensional point-by-point rapid scan of the synchrotron radiation diffraction spot. The scanning time for the two-dimensional rapid point-by-point scan of the synchrotron radiation diffraction signal is 1-5 s / point. By referring to the position of the current collector marker and comparing the location of the weak change in the two-dimensional rapid scan diffraction signal with the location of the local reaction region determined by the scanning electron microscope and its energy spectrum, the reaction region can be quickly located. It should be understood that although two-dimensional rapid scanning will severely lead to insufficient flux and signal attenuation, resulting in a weak difference in diffraction signals between the reaction region and the non-reaction region, since the aforementioned scanning electron microscope has confirmed that an inhomogeneous interface reaction has indeed occurred in this region, and the relative position of this inhomogeneous local reaction location with the marker has been determined, the aforementioned weak difference can be largely ruled out as being caused by error, thus allowing for rapid location of the local reaction region.

[0044] The use of the observation device of this invention includes step S3, which involves performing fine single-point diffraction and / or fine point-by-point two-dimensional diffraction scanning on the located reaction occurrence region at key reaction time points using synchrotron radiation diffraction to characterize the structural evolution of the reaction region at the interface of the alkali metal solid battery in situ under the same temperature and charge / discharge conditions as the scanning electron microscope.

[0045] In a preferred embodiment, the sample stage is moved so that the synchrotron radiation beam spot is moved to the pre-positioned local reaction region for narrowed-range fine single-point diffraction and / or two-dimensional diffraction scanning. The scanning time for fine single-point diffraction and / or two-dimensional point-by-point diffraction is 20-60 s / point, for example, 30 s / point. This saves a significant amount of synchrotron radiation diffraction time to obtain characterization information on the interface structure evolution of the alkali metal solid-state battery. The inlet 12 of the synchrotron radiation vacuum transfer hood 9 is connected to a nitrogen cylinder, and the outlet 13 is connected to a vacuum pump assembly to ensure that the alkali metal battery 5 is isolated from air. The wires led out from the fixture are connected to the circuitry of the electrochemical workstation and temperature controller outside the transfer hood via the interface of the synchrotron radiation vacuum transfer hood 9, providing the same charging, discharging, and temperature conditions as the aforementioned in-situ scanning electron microscope experiments. In a preferred embodiment, diffraction is performed using a synchrotron radiation beam of appropriate energy, 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 membranes is eliminated. It should be understood that a change in the diffraction pattern can indicate a structural change. However, this change is a change in the entire sample, not necessarily a change in a single component. Therefore, it is difficult to determine whether the interface structure has changed. Scanning electron microscopy and energy dispersive spectroscopy are needed to first observe changes in the cross-sectional morphology of the interface before performing diffraction. This helps to better avoid interference and errors and accurately obtain information on structural evolution. In a preferred embodiment, if the experiment time is short (e.g., no more than 24 hours), the synchrotron radiation vacuum transfer hood 9 does not need to be connected to an external vacuum pump and inert gas because the vacuum hood is airtight. If the time is long (e.g., more than 24 hours), the synchrotron radiation vacuum transfer hood 9 needs to be connected to an external vacuum pump and purged with inert gas simultaneously. Thus, the synchrotron radiation vacuum transfer hood 9, with its adapter fixture, achieves complete air isolation in a cavity-free, open environment for synchrotron radiation diffraction by connecting a vacuum pump to the synchrotron radiation vacuum transfer hood 9 for real-time vacuuming and the introduction of inert gas. Furthermore, the synchrotron radiation vacuum transfer hood 9 can be connected to the fixture via wires to an external electrochemical workstation and temperature controller. This allows for synchrotron radiation diffraction analysis in an air-isolated environment, under the same temperature and electrochemical charge-discharge conditions as in-situ scanning electron microscopy (SEM) testing. Guided by the rapid detection results from the SEM and its energy spectrum, the interface structure evolution process of the alkali metal solid-state battery 5 can be analyzed at the same interface reaction region at different key reaction time points.

[0046] The use of the observation device of this utility model includes step S4, which involves repeating steps S1-S3 in cyclically according to the in-situ observation requirements of the interface reaction process of alkali metal solid batteries. This allows for unlimited switching between scanning electron microscope and synchrotron radiation diffraction under air-isolated conditions, enabling in-situ observation of the interface reaction process of alkali metal solid batteries under the same temperature and charge / discharge conditions.

[0047] Step S4 includes the following sub-steps: S41, removing the third air isolation device from the sample stage of the synchrotron radiation diffraction station, and transferring the clamp in the third air isolation device to the second air isolation device within the first air isolation device; S42, after removing the second air isolation device from the first air isolation device, installing it on the sample stage inside the scanning electron microscope cavity, closing the cavity and evacuating it until the cavity vacuum reaches 10... -4 When the mba is above, the second air isolation device is turned on, and under the same temperature and charge / discharge conditions as the in-situ test of synchrotron radiation diffraction, the morphology and composition evolution of the cross-sectional region of the contact interface between the positive and negative electrodes and the solid electrolyte of the alkali metal solid battery 5 are observed in situ using a scanning electron microscope and its energy dispersive spectroscopy, which are the same reaction occurrence regions as previously located; S43, under the guidance of the test results of the scanning electron microscope and its energy dispersive spectroscopy, the in-situ structural evolution of the contact interface between the positive and negative electrodes and the solid electrolyte of the alkali metal solid battery 5 is characterized by synchrotron radiation diffraction under the same temperature and charge / discharge conditions as the scanning electron microscope; S44, S41-43 are repeated infinitely at different key reaction time points.

[0048] In a preferred embodiment, repeated cycles are permitted as needed, including but not limited to the following situations: if the interface structure of the alkali metal solid-state battery 5 changes and is difficult to interpret after in-situ synchrotron radiation diffraction experiments, the local reaction region can be observed again using scanning electron microscopy and energy dispersive spectroscopy for morphological and compositional analysis. After observing the local reaction region again using scanning electron microscopy and energy dispersive spectroscopy to obtain morphological and compositional analysis, the evolution of the interface structure of the alkali metal solid-state battery can be observed again using synchrotron radiation diffraction, and so on, until the alkali metal solid-state battery 5 completes the entire electrochemical charge-discharge cycle.

[0049] In a preferred embodiment, in-situ observations using scanning electron microscopy (SEM) and synchrotron radiation diffraction (SDR) can be performed alternately an unlimited number of times under the same temperature and charge-discharge cycle conditions. This allows for the acquisition of comprehensive evolutionary information on the interfacial reaction process of the alkali metal solid-state battery, rather than a single reaction state. Because the morphology, composition, and structure of the alkali metal solid-state battery continuously change during the interfacial reaction, repeated observations using SEM and SDR can yield comprehensive information on the interfacial evolution process.

[0050] Example 1

[0051] The interface between the negative electrode and the solid electrolyte of a lithium metal solid-state battery was characterized. The lithium metal solid-state battery used lithium iron phosphate (LiFePO4) as the positive electrode and lithium metal as the negative electrode. The solid electrolyte was a PEO-based (polyethylene oxide) polymer solid electrolyte. The cross-sections of the interfaces of each component of the solid-state battery were first cut flat, and then assembled under pressure using a mold and placed in a fixture. Scanning electron microscopy combined with synchrotron radiation diffraction was performed at room temperature to obtain the cross-sectional morphology, composition, and structural information of the local reaction process at the interface between the negative electrode and the solid electrolyte. By using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) to capture the morphology and compositional evolution of the inhomogeneous interface reaction, key reaction time points such as the initiation point, intermediate point, and transition point of the interface reaction are precisely determined. Simultaneously, the size and location of the inhomogeneous reaction micro-regions are determined and calibrated using low-magnification SEM images. Rapid localization is achieved by measuring the relative position of the micro-region to the screw at the top surface of the current collector. The location is then quickly determined at a synchrotron radiation diffraction station. Under the same charge-discharge cycles and room temperature conditions, the structural evolution of the located region is observed in situ. Unexplained diffraction variations are again observed in situ under the same temperature and charge-discharge cycle conditions using SEM and EDS. This process is repeated until the entire electrochemical reaction cycle is completed.

[0052] Example 2

[0053] The interface between the negative electrode and the solid electrolyte of a lithium metal solid-state battery was characterized. The lithium metal solid-state battery used lithium iron phosphate as the positive electrode and lithium metal as the negative electrode. The solid electrolyte was an LLZO garnet-type inorganic solid electrolyte. Ionic liquid was added to wet the solid electrolyte. After cutting, grinding and polishing, the cross-section of the interface of each component of the solid battery was flattened. Then, it was assembled under pressure in a mold and placed in a fixture. Scanning electron microscopy combined with synchrotron radiation diffraction was performed at 80°C to obtain the cross-sectional morphology, composition and structural information of the interface between the negative electrode and the solid electrolyte. The morphology and compositional evolution were captured using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS), identifying key cyclic nodes such as the initiation point, intermediate point, and transition point of the interfacial reaction. Simultaneously, low-magnification SEM images were used to determine the size and location of inhomogeneous reaction micro-regions, such as marking their relative distance to the edge of the top surface marked with conductive adhesive on the current collector for rapid localization. Then, at different critical reaction time points, in-situ diffraction at the marked locations was performed at a synchrotron radiation diffraction station under the same current, voltage, and 80°C temperature conditions to characterize the structural evolution of the located reaction regions. Unexplained diffraction variations were again observed in-situ using SEM and EDS under the same temperature and charge-discharge cycle conditions. This process was repeated until the entire electrochemical reaction cycle was completed.

[0054] Example 3

[0055] 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 cathode and metallic sodium as the anode. The solid electrolyte was a PEO-based (polyethylene oxide) polymer solid electrolyte. The interfaces of the various components of the solid-state battery were first cut flat, then assembled under pressure using a mold and placed in a fixture. Scanning electron microscopy (SEM) combined with synchrotron radiation diffraction (SDR) was performed at room temperature to obtain the cross-sectional morphology, composition, and structural information of the interface between the anode and the solid electrolyte. The morphology and compositional evolution of the inhomogeneous interface reaction were captured using SEM and energy dispersive spectroscopy (EDS), and key cyclic nodes such as the reaction initiation point, reaction midpoint, and reaction transition point were determined. Simultaneously, the size and location of the inhomogeneous reaction micro-regions were calibrated using low-magnification SEM images, such as marking their relative distance to the conductive adhesive markers on the top surface of the current collector for rapid localization. Then, at different critical reaction time points, in-situ diffraction tests were performed at a synchrotron radiation diffraction station under the same current, voltage, and room temperature conditions at the marked locations. The structural evolution of the located reaction region was further observed in situ using synchrotron radiation diffraction. For any unexplained changes in diffraction information, in-situ observations of the morphology and composition of the diffraction patterns were performed again under the same temperature and charge-discharge cycle conditions using scanning electron microscopy and energy dispersive spectroscopy. This process was repeated until the entire electrochemical reaction cycle was completed.

[0056] The in-situ observation device for observing the interface evolution of alkali metal solid-state batteries according to this invention combines scanning electron microscopy (SEM) with synchrotron radiation diffraction (SDR). It features lightweight equipment, convenient loading, unloading, and transport; complete air isolation during transport and testing; and the ability to flexibly switch between high-vacuum chambers and open environments at ambient pressure for rapid and accurate detection. It can precisely determine key time points of local interface reactions in alkali metal solid-state batteries and quickly locate the local reaction sites, significantly saving valuable time in synchrotron radiation experiments. Compared to traditional in-situ characterization methods that combine SEM or SDR with spectroscopy, this invention overcomes the limitations of traditional methods by addressing the differences in optical path directions between SEM and SDR (the electron beam of an SEM is vertical, while the beam of a SDR is horizontal), and the limitations of testing... The significant difference between high vacuum and ambient pressure environments (scanning electron microscopy is a high vacuum chamber environment, while synchrotron radiation diffraction is an open ambient pressure environment), the difficulty of observing the internal structural evolution of the reaction interface with scanning electron microscopy, and the difficulty of accurately determining the key reaction time nodes and rapidly locating the local reaction area with synchrotron radiation diffraction, which requires a lot of valuable machine time for continuous testing, as well as the difficulty of changing the detection method by directly and repeatedly disassembling and moving the test sample due to its sensitivity and fragility (alkali metal solid-state batteries are air-sensitive, and their interfaces are mostly point contact interfaces, which are easily misaligned and damaged during repeated disassembly and movement), have enabled the comprehensive, rapid, and accurate real-time characterization and analysis of the morphology, composition, and structure of the electrode and solid electrolyte contact interface of air-sensitive alkali metal solid-state batteries under different operating currents, voltages, and temperatures.

[0057] In summary, the combination of the two characterization methods in this invention overcomes the shortcomings of traditional single in-situ characterization methods, compared with the single in-situ characterization method of scanning electron microscopy or synchrotron radiation diffraction and spectroscopy. It achieves the goal of comprehensive, rapid and accurate real-time characterization and analysis of the morphology, composition and structure of air-sensitive alkali metal solid battery electrodes and solid electrolyte contact interfaces under different operating currents, voltages and temperatures.

[0058] The above description is merely a preferred embodiment of this utility model and is not intended to limit the scope of this utility model. Various variations can be made to the above embodiments of this utility model. That is, all simple and equivalent changes and modifications made based on the claims and description of this utility model fall within the protection scope of the claims of this utility model. Any aspects not described in detail in this utility model are conventional technical content.

Claims

1. An in-situ observation device for observing the interface evolution of alkali metal solid-state batteries, characterized in that, The observation device includes: The sample holder includes a current collector and a heating element. The alkali metal solid-state battery is assembled in a first air-isolated device that provides an inert atmosphere and is then clamped by two current collectors. The top surface of the current collector is marked. 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 diffraction characterization of the synchrotron radiation beamline through the interface between the positive and negative electrodes and the solid electrolyte without interference. The heating element is installed inside the current collector to control the temperature of the alkali metal solid-state battery. The scanning electron microscope (SEM) system has a vacuum chamber, and a second air-isolation device is detachably installed in the vacuum chamber. The contact interface between the positive and negative electrodes and the solid electrolyte of the alkali metal solid battery is parallel to the incident direction of the electron beam. The cross section of the contact interface between the positive and negative electrodes and the solid electrolyte of the alkali metal solid battery is perpendicular to the incident electron beam of the SEM. The SEM and the SEM energy dispersive spectrometer work together to observe the morphology and compositional changes of the cross section of the alkali metal solid battery interface in the vacuum chamber of the SEM. The synchrotron radiation diffraction system has an open, cavity-free, movable sample stage. A third air isolation device is detachably mounted on the sample stage. The contact interface between the positive and negative electrodes and the solid electrolyte of the alkali metal solid battery is perpendicular to the incident direction of the synchrotron radiation beam. The synchrotron radiation beam irradiates the interface of the alkali metal solid battery at a position higher than the current collector to characterize the structural evolution of the interface of the alkali metal solid battery.

2. The viewing device of claim 1, wherein, The observation device also includes an electrochemical workstation and a temperature controller. The electrochemical workstation and temperature controller are connected to the sample holder via wires through the scanning electron microscope cavity flange and then through the adapter of the second air-isolation device. Alternatively, the electrochemical workstation and temperature controller are connected to the sample holder via wires through the adapter of the third air-isolation device to control the charging and discharging process and temperature of the alkali metal solid-state battery. The temperature range is room temperature to 200°C.

3. The observation device according to claim 1, characterized in that, The top surface of the current collector has markers for marking the reaction zone. The markers are screws, grooves, and marked edges on the surface of the current collector.

4. The viewing device of claim 3, wherein, The observation device also includes a laser for simulating synchrotron radiation spots in a synchrotron radiation diffraction system. Using the location of the marker as a reference, it rapidly locates the local reaction region determined by the aforementioned scanning electron microscope and its energy spectrum by combining rapid point-by-point two-dimensional diffraction scanning of synchrotron radiation.

5. The viewing device of claim 4, wherein, The top of the third air-isolated device has an observation window. A high-definition camera installed above the synchrotron radiation diffraction station observes the laser, sample clamp, the top surface marker of the clamp current collector, and the cross-section of the interface of the alkali metal solid-state battery through the window.

6. The viewing device of claim 1, wherein, Instead of directly loading, unloading, and moving the sample holder containing the alkali metal solid-state battery, the alkali metal solid-state battery sample is repeatedly transferred from the first air-isolated device to the second and third air-isolated devices indefinitely. This allows for in-situ observation of the interface reaction process of the alkali metal solid-state battery using a combination of scanning electron microscopy and synchrotron radiation diffraction, rather than observing a specific reaction state.

7. The viewing device of claim 1, wherein, The second air-isolation 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-isolation device via a wire, or the mechanical transmission device is connected to an electric controller outside the vacuum chamber of the scanning electron microscope via a wire through the cavity flange of the scanning electron microscope, so as to drive the mechanical transmission device to close and open.

8. The viewing device of claim 7, wherein, The cross-section of the interface of the alkali metal solid-state battery is higher than the opening of the box, and the lid can be moved up and down by means of a stepped height difference.

9. The viewing device of claim 1, wherein, The first air-isolation device is a glove box, the second air-isolation device is a vacuum transfer box, and the third air-isolation device is a synchrotron radiation vacuum transfer hood.

10. The viewing device of claim 1, wherein, The second air isolation device is a non-magnetic titanium alloy box with good corrosion resistance and thermal stability.

11. The viewing device of claim 1, wherein, The third air-isolation device consists of a load-bearing steel frame sealed with a Cape Town membrane.

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