Method for in-situ observation of alkali metal solid-state battery

Abstract

The invention relates to a method for in-situ observation of an alkali metal solid-state battery. The method comprises the following steps: S1, observing morphology and component changes of interface cross sections of a positive electrode, a negative electrode and an electrolyte of the alkali metal solid-state battery through a scanning electron microscope; and S2, carrying out structure evolution characterization on an interface of the positive electrode, the negative electrode and the electrolyte of the alkali metal solid-state battery through synchrotron radiation X-ray diffraction. According to the method for in-situ observation of the alkali metal solid-state battery, the scanning electron microscope is combined with the synchrotron radiation X-ray diffraction, so that the defect that a traditional in-situ characterization method is single is overcome, and morphology, morphology and morphology of an air-sensitive alkali metal solid-state battery electrode and an electrolyte contact interface under the conditions of different working currents, voltages and temperatures are realized. And comprehensive and accurate real-time characterization and analysis of components and structures are realized.

Description

Technical Field

[0001] The present invention relates to new energy batteries, and more specifically to a method for in-situ observation 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 in the air and easy to react with water and oxygen in the air, but also very easy to generate a large number of dendrites at the electrode interface, 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 with 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 using an optical microscope has a large observation field, the magnification is limited and the resolution is low, which makes it difficult to discover the causes of failure and attenuation of alkali metal solid-state batteries from a nanoscale perspective. Although the resolution of in-situ observation using a transmission electron microscope has reached the angstrom level, the field of view is limited to the range of hundreds of microns, which not only makes it difficult to capture the uneven electrochemical reaction process at the battery interface, but also requires high requirements for the preparation of in-situ samples. Although the in-situ observation using a scanning electron microscope has both the test field of view of an optical microscope (millimeter observation range) and the resolution of a transmission electron microscope (nanometer observation resolution), it can only observe the surface morphology and composition of the sample, and it is difficult to characterize the structural evolution of the sample. Although the in-situ observation using synchrotron radiation X-ray diffraction has stronger penetration than conventional X-ray diffraction (XRD, X-Ray Diffraction), it can penetrate solid-state batteries and perform accurate quantitative and qualitative analysis of the internal structural evolution of the battery, but it has limitations in detecting uneven nanoscale micro-interface reactions. Summary of the invention

[0004] In order to solve the limitation problem of the single in-situ observation method in the above-mentioned prior art, the present invention provides a method for in-situ observation of alkali metal solid-state batteries.

[0005] According to the method of alkali metal solid-state battery of the present invention, it comprises the following steps: S1, observing the morphology and composition changes of the cross-section of the interface between the positive and negative electrodes and the electrolyte of the alkali metal solid-state battery by scanning electron microscopy; and S2, characterizing the structural evolution of the interface between the positive and negative electrodes and the electrolyte of the alkali metal solid-state battery by synchrotron radiation X-ray diffraction.

[0006] In a preferred embodiment, step S1 includes the following sub-steps: S11, assembling an alkali metal solid-state battery in an air-isolating device and installing it on a fixture, S12, installing the fixture with the alkali metal solid-state battery installed in a vacuum transfer box in the air-isolating device, S13, moving the closed vacuum transfer box out of the air-isolating device and installing it in the cavity of a scanning electron microscope, closing the cavity of the scanning electron microscope and then evacuating it, and S14, opening the vacuum transfer box to perform an in-situ electrochemical reaction with controllable temperature, and observing the morphology and composition changes of the interface cross-section of the positive and negative electrodes and the electrolyte of the alkali metal solid-state battery through a scanning electron microscope.

[0007] In a preferred embodiment, the sub-step S11 includes: cutting out the cross-sectional area of ​​the interface between the positive and negative electrodes and the electrolyte, placing the alkali metal solid-state battery vertically into a fixture so that it is clamped by two current collectors of the fixture, ensuring that the positive and negative electrodes are 0.1 mm-1 mm higher than the current collectors so that the synchrotron radiation diffraction spot can pass through the positive and negative electrodes without interference for characterization.

[0008] In a preferred embodiment, the vacuum transfer box is made of non-magnetic titanium alloy, and a mechanical transmission device is mounted on the vacuum transfer box to close and open the vacuum transfer box by controlling the movement of the lid.

[0009] 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 and the 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 and the electrolyte is perpendicular to the incident electron beam.

[0010] In a preferred embodiment, the sub-step S14 includes: placing the fixture fixed in the vacuum transfer box under the lens barrel of a scanning electron microscope, performing a charge and discharge cycle test on the alkali metal solid-state battery, and adjusting the operating temperature between room temperature and 200°C, and observing the cross-sectional portion of the contact interface between the positive and negative electrodes and the electrolyte.

[0011] In a preferred embodiment, the sub-step S14 further includes combining a scanning electron microscope (EDS, Energy Dispersive Spectrometer) so as to analyze the type, content and distribution of elements while the scanning electron microscope provides surface morphology information.

[0012] In a preferred embodiment, step S2 includes the following sub-steps: S21, taking out the vacuum transfer box from the cavity of the scanning electron microscope, and transferring the fixture in the vacuum transfer box to the synchrotron radiation vacuum transfer cover in the air-isolating device, and S22, after taking out the synchrotron radiation vacuum transfer cover from the air-isolating device, installing it on the sample stage of the synchrotron radiation X-ray diffraction station, and characterizing the structural evolution of the interface between the positive and negative electrodes and the electrolyte of the alkali metal solid-state battery at the key cycle node by synchrotron radiation X-ray diffraction.

[0013] In a preferred embodiment, the air-isolating device is a glove box providing inert atmosphere protection.

[0014] In a preferred embodiment, the synchrotron radiation vacuum transfer enclosure is sealed with a load-bearing steel frame and a Cape Town membrane that is transparent to X-rays.

[0015] According to the method for in-situ observation of alkali metal solid-state batteries of the present invention, a scanning electron microscope is combined with synchrotron radiation X-ray diffraction, which has the advantages of light weight of the device, convenient loading and unloading and transportation, air isolation during the entire transportation and testing process, and flexible switching between vacuum and normal pressure environments. Compared with the traditional single scanning electron microscope or synchrotron radiation diffraction and spectroscopy combined in-situ electrochemical method, 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 X-ray beam of the synchrotron radiation diffraction is horizontal), the large difference between the high vacuum and normal pressure of the test environment (the scanning electron microscope is a high vacuum environment, and the synchrotron radiation diffraction is a normal pressure environment), and the difficulties that the test sample is sensitive, fragile, and easily damaged and difficult to directly disassemble and move (the alkali metal solid-state battery is air-sensitive, and its interface is easily dislocated and damaged during the disassembly and movement process), so as to make up for the single deficiency of the traditional in-situ characterization method, the present invention overcomes the difficulties of the different optical path directions of the scanning electron microscope and the synchrotron radiation diffraction (the electron beam optical path of the scanning electron microscope is vertical, and the X-ray beam of the synchrotron radiation diffraction is horizontal), the high vacuum and normal pressure of the test environment (the scanning electron microscope is a high vacuum environment, and the synchrotron radiation diffraction is a normal pressure environment), and the sensitive, fragile, and easily damaged test sample is difficult to directly disassemble and move (the alkali metal solid-state battery is air-sensitive, and its interface is easily dislocated and damaged during the disassembly and movement process), and achieves the purpose of comprehensive and accurate real-time characterization and analysis of the morphology, composition and structure of the air-sensitive alkali metal solid-state battery electrode and electrolyte contact interface under different working currents, voltages and temperatures. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The in-situ testing steps of a scanning electron microscope according to the method for in-situ observation of an alkali metal solid-state battery of the present invention are shown.

[0017] Figure 2 The synchrotron radiation X-ray diffraction in-situ testing steps of the method for in-situ observation of alkali metal solid-state batteries according to the present invention are shown. DETAILED DESCRIPTION

[0018] The specific embodiments of the present invention will be further described in detail below in conjunction with the drawings and implementation cases of the present invention. The implementation cases described are to facilitate understanding by those of ordinary skill in the art and to facilitate acquisition without inventiveness, and cannot be used as limitations on the scope of the present invention. Improvements and / or modifications made by those of ordinary skill in the art based on the principles of the present invention should also be regarded as the scope of rights of the present invention.

[0019] Unless otherwise clearly specified and explained, the terms "installation", "fixation" and "placement" are interpreted in a broad sense, such as mechanical installation, fixing and placement, direct installation, fixing and placement, or indirect installation, fixing and placement with intermediate components as connections. For ordinary technicians who read this patent, they can understand the meaning of the above terms in the present invention according to specific circumstances.

[0020] The inventors noticed that the area sizes of the observation samples of the scanning electron microscope and the synchrotron radiation X-ray diffraction match (taking the Zeiss Gemini300 field emission scanning electron microscope and the Shanghai synchrotron radiation light source BL14B1 diffraction line station as examples, the observation area range can be achieved in the micrometer to centimeter 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-area to determine the key nodes where the battery interface reacts, thereby determining the synchrotron radiation X-ray diffraction in-situ observation nodes to guide the synchrotron radiation X-ray diffraction to characterize the battery interface structure evolution. Therefore, the present invention combines the scanning electron microscope and the synchrotron radiation X-ray diffraction to perform comprehensive in-situ observation of the alkali metal solid-state battery interface. In particular, the cavity of the scanning electron microscope is a high-vacuum cavity, while the synchrotron radiation X-ray diffraction is a normal-pressure non-vacuum cavity. In addition, the optical path of the scanning electron microscope is vertically irradiated on the sample surface, while the X-ray beam of the synchrotron radiation diffraction penetrates the sample in parallel. The optical paths are completely different and very difficult to combine. In addition, alkali metal solid-state batteries are sensitive to air contamination, and their electrode and electrolyte contact interface is very fragile and can be easily damaged during disassembly and movement. This makes it very difficult to load and unload and transfer alkali metal solid-state batteries between these two devices and combine them for in-situ experimental testing.

[0021] The method for in-situ observation of an alkali metal solid-state battery according to the present invention first comprises assembling an alkali metal solid-state battery 5 in an air-isolated device and installing it on a fixture, see Figure 1 .

[0022] In a preferred embodiment, the air-isolating device is a glove box that provides inert atmosphere protection. Under the inert atmosphere protection of the glove box, the alkali metal solid-state battery 5 is assembled from the positive electrode, the negative electrode and the electrolyte. In a preferred embodiment, the alkali metal solid-state battery 5 is a lithium metal solid-state battery, the positive electrode uses a lithium iron phosphate electrode sheet, and the negative electrode uses a lithium sheet. In a preferred embodiment, the electrolyte is a semi-solid electrolyte formed by a solid electrolyte or a diaphragm (such as a polyolefin film) infiltrating an ionic liquid. In a preferred embodiment, the cross-sectional area of ​​the interface between the positive and negative electrodes and the electrolyte is cut out, and the alkali metal solid-state battery 5 is vertically placed in a fixture so that it is clamped by two current collectors 8 of the fixture, ensuring that the positive and negative electrodes are 0.1mm-1mm higher than the current collectors so that the synchrotron radiation diffraction spot passes through the positive and negative electrodes without interference for characterization, ensuring that the electrode and electrolyte contact interface can be vertically irradiated in a scanning electron microscope and horizontally penetrated in synchrotron radiation X-ray diffraction. In a preferred embodiment, the positive electrode, semi-solid electrolyte and polymer electrolyte are cut by scissors and scalpels to form a flat cross section, the ceramic electrolyte is polished by sandpaper to make the cross section flat, and the negative electrode is cut by a scalpel to make its cross section flat for easy observation. In the embodiment of the semi-solid electrolyte, the size of the diaphragm is larger than the size of the positive and negative electrodes. The diaphragm is clamped with the positive and negative electrodes and then pressed to ensure good contact, and then cut flat with scissors. 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 that contact 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 positive and negative electrodes are 0.2 mm higher than the current collector 8. In a preferred embodiment, the alkali metal solid-state battery 5 is placed vertically in the clamp, so that the positive and negative electrodes, the electrolyte and the current collector 8 are parallel, and 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 breaking due to poor contact.

[0023] The method for in-situ observation of alkali metal solid-state batteries according to the present invention then includes installing the fixture with the alkali metal solid-state battery 5 installed in the vacuum transfer box 3 in an air-isolated device, see Figure 1 .

[0024] 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 in the vacuum transfer box 3. After the wire of the fixture is connected to the connector of the vacuum transfer box 3, it is led out of the vacuum transfer box 3, and the bottom of the fixture is fixed to the bottom of the vacuum transfer box 3 with four fastening screws. The lid 4 is driven by the motor and the mechanical transmission device to close the opening above the vacuum transfer box 3, and the vacuum transfer box 3 is sealed by the O-ring 6, so as to form air-proof protection for the alkali metal solid-state battery 5 in the vacuum transfer box 3. In a preferred embodiment, the vacuum transfer box 3 is made of a lightweight non-magnetic titanium alloy and is equipped with a mechanical transmission device, which is connected to the external electric controller of the scanning electron microscope through a wire, and the lid 4 can be manually controlled to open and close in the high vacuum environment of the scanning electron microscope.

[0025] The method for in-situ observation of alkali metal solid-state batteries according to the present invention then includes removing the sealed vacuum transfer box 3 from the air-isolating device and installing it in the cavity of the scanning electron microscope, closing the cavity of the scanning electron microscope and then evacuating the cavity, see Figure 1 .

[0026] 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 device of the electron microscope through the interface of the vacuum transfer box 3 and the flange on the cavity of the scanning electron microscope, and the door is closed to evacuate the vacuum. In this way, the vacuum transfer box 3 cooperates with the fixture to realize 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 the air, so as to avoid the contamination of the alkali metal solid-state battery 5 by water and oxygen in the air. 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 electrolyte is parallel to the incident direction F of the electron beam, and the cross section M of the interface between the positive and negative electrodes of the alkali metal solid-state battery 5 and the electrolyte is perpendicular to the incident electron beam, so as to facilitate the scanning electron microscope observation.

[0027] The method for in-situ observation of alkali metal solid-state batteries according to the present invention then includes opening the vacuum transfer box 3 to perform an in-situ electrochemical reaction with a controllable temperature, and observing the morphology and composition changes of the interface cross section of the positive and negative electrodes and the electrolyte of the alkali metal solid-state battery 5 by scanning electron microscopy combined with scanning electron microscope energy spectrum, see Figure 1 .

[0028] In a preferred embodiment, after the scanning electron microscope is evacuated, the lid 4 is driven by the external circuit control motor and the mechanical transmission device to open the vacuum transfer box 3, revealing the fixture and the alkali metal solid-state battery 5 in the vacuum transfer box 3, and the alkali metal solid-state battery 5 is placed under the lens barrel 1 of the scanning electron microscope, and 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, and after selecting a suitable observation area and range, the alkali metal solid-state battery 5 is subjected to a charge and discharge cycle test, and the working temperature is adjusted between room temperature and 200°C, and the cross-sectional part of the positive and negative electrodes and the electrolyte contact interface is observed. In a preferred embodiment, the scanning electron microscope 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 provides surface morphology information, the energy spectrometer can analyze the element type, content and distribution. In a preferred embodiment, the current collector 8 is connected to the electrochemical workstation outside the scanning electron microscope through the wire drawn from the inside of the fixture through the vacuum transfer box interface and the flange of the scanning electron microscope cavity, and the alkali metal solid-state battery 5 is subjected to precise electrochemical charge and discharge test. In a preferred embodiment, a ceramic heating rod 7 is installed inside the current collector 8. The ceramic heating rod 7 is connected to the temperature controller outside the scanning electron microscope through a wire led out from the inside of the fixture via the vacuum transfer box interface and the flange of the scanning electron microscope cavity, so as to accurately control the temperature of the alkali metal solid-state battery 5 and realize the functions of heating and powering on at the same time.

[0029] The method for in-situ observation of alkali metal solid-state batteries according to the present invention then comprises 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 to the synchrotron radiation vacuum transfer cover 9 in an air-isolated device, see Figure 2 .

[0030] In a preferred embodiment, the scanning electron microscope observation controls the motor and the mechanical transmission device by manipulating the external circuit to drive the lid 4 to close the vacuum transfer box 3, takes out the vacuum transfer box 3 from the cavity of the scanning electron microscope, puts it into the glove box, and under the protection of the inert gas in the glove box, opens the vacuum transfer box 3, takes out the fixture, and places it 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 with fastening screws to the cover door 14 and sealed with a sealing O-ring to ensure airtightness, and then taken out of the glove box, thereby avoiding the transfer process from damaging the reaction interface of the alkali metal solid-state battery 5 by loading and unloading and moving the fixture instead of directly loading and unloading and moving the alkali metal solid-state battery 5, thereby ensuring that the fragile and vulnerable electrode and electrolyte contact interface is suitable for the scanning electron microscope and synchrotron radiation X-ray 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 X-rays.

[0031] The method for in-situ observation of alkali metal solid-state batteries according to the present invention then includes taking out the synchrotron radiation vacuum transfer cover 9 from the air-isolating device and installing it on the sample stage of the synchrotron radiation X-ray diffraction station, and characterizing the structural evolution of the interface between the positive and negative electrodes and the electrolyte of the alkali metal solid-state battery 5 at the key cycle node by synchrotron radiation X-ray diffraction, see Figure 2 .

[0032] In a preferred embodiment, the synchrotron radiation vacuum transfer cover 9 is transported to the synchrotron radiation diffraction line station and installed on the sample stage of the synchrotron radiation X-ray diffraction line station. By adjusting the height of the sample stage, the X-ray 11 can just penetrate the window 10 of the vacuum transfer cover 9 to the alkali metal solid-state battery 5 higher than the fixture. 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 is isolated from the air. The wires drawn out of the fixture are connected to the circuit of the transfer cover external device through the interface of the synchrotron radiation vacuum transfer cover 9, and the charge and discharge test and temperature control are carried out. In a preferred embodiment, X-rays of appropriate energy are used for diffraction, and the X-ray 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 excluded. It should be understood that as long as the diffraction pattern changes, it can be judged that the structure has changed, but this change is an overall change of the sample, not a change in a certain local area of ​​the sample. Therefore, it is difficult to determine whether the interface structure has changed. A scanning electron microscope is required to first observe the change in the cross-sectional morphology of the interface, and then perform diffraction detection of structural evolution. 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 a vacuum pump is connected to the synchrotron radiation vacuum transfer cover 9 to perform real-time vacuuming, and the synchrotron radiation vacuum transfer cover 9 can connect the fixture to an external electrochemical workstation and a temperature controller through a wire, so that the fixture can be transferred out of the high vacuum chamber of the scanning electron microscope in an air-tight environment, and synchrotron radiation diffraction analysis can be performed in an air-tight environment, and the interface structure evolution analysis of the alkali metal solid-state battery 5 can be performed under the same in-situ test conditions.

[0033] Example 1 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 electrolyte uses a PEO-based (polyethylene oxide) polymer solid electrolyte. After being assembled and pressed, it was placed in a fixture and tested by scanning electron microscopy combined with synchrotron radiation diffraction to obtain the morphology and composition of the interface between the negative electrode and the electrolyte and the structural information of the interface.

[0034] Example 2 The interface between the negative electrode and the solid electrolyte of the lithium metal solid-state battery was characterized. The lithium metal solid-state battery used lithium iron phosphate as the positive electrode and metallic lithium as the negative electrode. The electrolyte used was LLZO garnet-type inorganic solid electrolyte. After adding ionic liquid to wet the solid electrolyte, it was assembled and pressed and placed in a fixture. Scanning electron microscopy combined with synchrotron radiation diffraction tests were performed to obtain the morphology and composition of the interface between the negative electrode and the electrolyte and the structural information of the interface.

[0035] Example 3 The interface between the negative electrode and solid electrolyte of the sodium metal solid-state battery was characterized. The sodium metal solid-state battery used sodium vanadium phosphate as the positive electrode and metallic sodium as the negative electrode. The electrolyte used a PEO-based (polyethylene oxide) polymer solid electrolyte. After being assembled and pressed, they were placed in a fixture and tested by scanning electron microscopy combined with synchrotron radiation diffraction to obtain the morphology and composition of the interface between the negative electrode and the electrolyte and the structural information of the interface.

[0036] According to the method for in-situ observation of alkali metal solid-state batteries of the present invention, key information on the morphology, composition and structural evolution of the interface during the in-situ electrochemical reaction of the alkali metal solid-state battery 5 can be obtained by changing the voltage, current and operating temperature. The vacuum transfer box 3 and the synchrotron radiation vacuum transfer cover 9 can be respectively installed in the high vacuum cavity of the scanning electron microscope and the atmospheric environment of the synchrotron radiation diffraction station to test the interface reaction process of the alkali metal solid-state battery. The alkali metal solid-state battery 5 can be protected from contact with air during the mutual transfer between the scanning electron microscope and the synchrotron radiation diffraction and the in-situ testing process to avoid contamination. By changing the externally applied current, voltage, temperature and other cycle conditions, the influence of different test conditions on the electrochemical reaction process of the alkali metal solid-state battery 5 can be studied to further study the failure mechanism of the alkali metal solid-state battery 5.

[0037] The above is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. The above embodiment of the present invention can also be modified in various ways. That is, all simple, equivalent changes and modifications made according to the claims and the description of the present invention fall within the scope of protection of the claims of the present invention. The contents not described in detail in the present invention are all conventional technical contents.

Claims

1. A method for in-situ observation of alkali metal solid-state batteries, characterized in that: The method comprises the following steps: S1, observe the morphology and composition changes of the interface cross section of the positive and negative electrodes and electrolyte of the alkali metal solid-state battery by scanning electron microscopy; and S2, characterize the structural evolution of the interface between the positive and negative electrodes and the electrolyte of alkali metal solid-state batteries by synchrotron X-ray diffraction.

2. The method according to claim 1, characterized in that The step S1 includes the following sub-steps: S11, assembling an alkali metal solid-state battery in an air-tight device and installing it on a fixture, S12, installing the fixture having the alkali metal solid-state battery installed in a vacuum transfer box in the air-isolating device, S13, moving the sealed vacuum transfer box out of the air-isolating device and installing it in the cavity of the scanning electron microscope, closing the cavity of the scanning electron microscope and then evacuating the cavity, and S14, open the vacuum transfer box to carry out temperature-controlled in-situ electrochemical reaction, and observe the morphology and composition changes of the interface cross section between the positive and negative electrodes and the electrolyte of the alkali metal solid-state battery by scanning electron microscopy.

3. The method according to claim 2, characterized in that The sub-step S11 includes: cutting out the cross-sectional area of ​​the interface between the positive and negative electrodes and the electrolyte, placing the alkali metal solid-state battery vertically into a fixture so that it is clamped by two current collectors of the fixture, and ensuring that the positive and negative electrodes are 0.1mm-1mm higher than the current collectors so that the synchrotron radiation diffraction spot can pass through the positive and negative electrodes without interference for characterization.

4. The method according to claim 2, characterized in that: The vacuum transfer box is made of non-magnetic titanium alloy, and a mechanical transmission device is mounted on the vacuum transfer box to close and open the vacuum transfer box by controlling the movement of the cover.

5. The method according to claim 2, characterized in that: In the cavity of the scanning electron microscope, the interface between the positive and negative electrodes of the alkali metal solid-state battery and the 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 and the electrolyte is perpendicular to the incident electron beam.

6. The method according to claim 2, characterized in that The sub-step S14 includes: placing the fixture fixed in the vacuum transfer box under the lens barrel of the scanning electron microscope, performing a charge and discharge cycle test on the alkali metal solid-state battery, while adjusting the operating temperature between room temperature and 200° C., and observing the cross-sectional portion of the contact interface between the positive and negative electrodes and the electrolyte.

7. The method according to claim 2, characterized in that The sub-step S14 also includes combining a scanning electron microscope (SEM) with an energy dispersive spectrometer to analyze the type, content and distribution of elements while the SEM provides surface morphology information.

8. The method according to claim 2, characterized in that: The step S2 includes the following sub-steps: S21, taking out the vacuum transfer box from the chamber of the scanning electron microscope, and transferring the fixture in the vacuum transfer box to the synchrotron radiation vacuum transfer cover in an air-isolated device, and S22, after taking out the synchrotron radiation vacuum transfer cover from the air-isolating device, install it on the sample stage of the synchrotron radiation X-ray diffraction station, and use synchrotron radiation X-ray diffraction to characterize the structural evolution of the interface between the positive and negative electrodes and the electrolyte of the alkali metal solid-state battery at the key cycle node.

9. The method according to claim 8, characterized in that The air-isolating device is a glove box providing inert atmosphere protection.

10. The method according to claim 8, characterized in that The synchrotron radiation vacuum transfer enclosure is sealed with a load-bearing steel frame and a Cape Town membrane that can penetrate X-rays.

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