TEM sample preparation method of liquid battery

Abstract

The invention relates to the technical field of TEM sample preparation, and particularly discloses a liquid battery TEM sample preparation method, which comprises: S1, sample freezing; s2, carrying out Cryo-FIB / SEM sample preparation; s3, carrying out Cryo-TEM (Transmission Electron Microscope) characterization; by adopting the low-temperature inert transfer cabin and / or the full-vacuum interconnection system, it is ensured that a sample is in a low-temperature inert or vacuum environment in the whole process from disassembling, freezing, FIB sample preparation to TEM observation, air exposure is completely eradicated, and phase change, oxidation, decomposition, cracking and ice crystal damage caused by contact with air or temperature fluctuation of the sample are fundamentally avoided.

Description

Technical Field

[0001] This invention relates to the field of TEM sample preparation technology, specifically to a method for preparing TEM samples of liquid batteries. Background Technology

[0002] Liquid batteries are commonly used devices in the energy storage field. However, the instability of the electrode-electrolyte interface severely limits their capacity, lifespan, and other performance characteristics. Therefore, using transmission electron microscopy (TEM) to analyze the crystal structure of the electrode-electrolyte interface is crucial for improving the performance of liquid batteries. However, electrolytes typically possess a certain degree of chemical reactivity. In traditional TEM sample preparation processes, whether through conventional mechanical grinding, ion thinning, or focused ion beam (FIB) processing, samples are inevitably exposed to air or subjected to significant temperature fluctuations. This leads to changes in the composition at the interface, resulting in the formation of lithium-rich phases or the precipitation of non-stoichiometric decomposition products, the generation of gaseous products such as CO2, and the formation of bubbles and voids. Therefore, when using ion beams / electron beams to process and characterize liquid batteries, problems such as decomposition and irradiation damage occur at the interface, making it impossible to obtain the true interface structure.

[0003] Currently, a glove box filled with inert gas (99.999% high-purity argon, H2O / O2 < 0.1ppm) is used as a protective device to directly place the liquid sample into pre-cooled liquid ethane to obtain a sample containing liquid electrolyte. The cooled sample is then transferred through air into a cryo-focused ion beam microscope for cryo-sample preparation. The prepared sample is then briefly exposed to air before being transferred into a cryo-transmission electron microscope for high-resolution imaging (HRTEM), scanning transmission imaging (STEM), electron energy loss spectroscopy (EELS), and energy dispersive spectroscopy (EDS) characterization.

[0004] However, conventional TEM sample preparation techniques established for solid or stable materials cannot be directly applied to liquid batteries. The fundamental reason is the inability to maintain the original liquid interface state of the sample and isolate it from environmental interference throughout the preparation process. Samples prepared in a glove box are exposed to air during transfer to Cryo-FIB / SEM and Cryo-TEM, leading to problems such as phase transitions, gas generation, cracking, and pulverization. Furthermore, liquid ethane may react with the liquid electrolyte, generating interfering phases, ultimately preventing the acquisition of interface information for the liquid battery. Therefore, we propose a TEM sample preparation method for liquid batteries. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing TEM samples of liquid batteries, so as to solve the problem of obtaining the true interface structure of TEM samples of liquid batteries mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing TEM samples of liquid batteries, comprising the following steps: S1. Sample freezing: Under inert gas protection, the liquid battery is disassembled to obtain the electrode containing the electrolyte. The electrode is fixed and subjected to low-temperature freezing treatment to obtain a frozen sample. S2. Cryo-FIB / SEM Sample Preparation: Using a low-temperature transfer device, the frozen sample is transferred to the Cryo-FIB / SEM sample chamber. Then, at -170℃ to -195℃, the frozen sample is sequentially subjected to low-temperature deposition of a protective layer, coarse cutting, U-cutting, and thinning using Cryo-FIB / SEM to obtain sample slices. S3, Cryo-TEM characterization: The sample sheet is transferred to the Cryo-TEM sample holder using the same low-temperature transfer device (same as S2). The Cryo-TEM is then used to characterize the sample sheet at low temperature to examine the interior of the liquid battery electrode and the electrode-electrolyte interface.

[0007] Preferably, in step S1, the inert gas is argon; The cryogenic freezing process involves immersing the sample stage with the electrode fixed on it in liquid nitrogen for freezing.

[0008] Preferably, in step S2, the low-temperature deposited protective layer is a Pt protective layer deposited using ion beam assisted deposition; Preferably, in step S2, the coarse cutting, U-cutting, and thinning are carried out at -170℃ to -195℃, and the final sample sheet thickness is 80~100nm.

[0009] Preferably, in step S3, the sample sheet is transferred from the cryogenic inert transfer chamber to the Cryo-TEM sample rod using cryogenic tweezers; The Cryo-TEM characterization includes at least one of HRTEM, STEM, 4D-STEM, EELS, and EDS.

[0010] Preferably, in steps S2 and S3, the sample sheet transfer is achieved through a full-vacuum interconnection system; The all-vacuum interconnected system includes a glove box, a cryogenic transfer module, a Cryo-FIB / SEM, and a Cryo-TEM. The glove box, cryogenic transfer module, Cryo-FIB / SEM, and Cryo-TEM are connected in sequence via an ultra-high vacuum pipeline. The sample sheet was transported in a fully vacuum interconnected system without any atmospheric exposure.

[0011] Preferably, the cryogenic transfer module is a multi-port vacuum interconnected cavity with a built-in valve control system.

[0012] Preferably, in step S1, the liquid battery is a lithium-ion battery or a sodium-ion battery.

[0013] This invention has at least the following beneficial effects: 1. This invention provides a method for transferring liquid battery samples in a low-temperature inert environment throughout the entire process. By using a low-temperature inert transfer chamber and / or a full vacuum interconnection system, it ensures that the sample is in a low-temperature inert or vacuum environment throughout the entire process from disassembly, freezing, FIB sample preparation to TEM observation, completely eliminating air exposure and fundamentally avoiding phase transition, oxidation, decomposition, cracking and ice crystal damage caused by contact with air or temperature fluctuations.

[0014] 2. Under the protection of low temperature throughout the process, combined with the low temperature FIB precision shearing process, this invention can prepare electronically transparent thin films with a thickness of 80-100 nm, which preserves the bulk structure of the electrode material and the original interface state between the electrode and the liquid electrolyte to the greatest extent, providing the possibility for studying the real solid-liquid interface chemistry and morphology.

[0015] 3. The inert environment throughout the process of this invention not only protects the sample, but also greatly reduces the risk of combustion or explosion of the highly active material - sodium metal anode - during operation, making it safe to be applied to the research of a wider range of liquid battery systems such as sodium-ion batteries.

[0016] 4. The low-temperature inert transfer concept upon which this invention is based can be further expanded into a fully vacuum interconnected automated system integrating a glove box, Cryo-FIB / SEM, and Cryo-TEM. This system can achieve automatic transfer of samples with zero exposure, improving preparation efficiency and consistency while providing a reliable common technology platform for the research of cutting-edge battery materials that are extremely sensitive to air and moisture. Attached Figure Description

[0017] Figure 1 This is a flowchart of the low-temperature inert transfer process of the present invention; Figure 2 To prepare non-destructive samples of liquid batteries for the present invention using Cryo-FIB / TEM; Figure 3 The preparation of liquid battery interface phases using Cryo-FIB / SEM for this invention; Figure 4 Porous samples of liquid batteries were prepared using Cryo-FIB / SEM for this invention; Figure 5 Electron-transparent liquid battery samples were prepared using Cryo-FIB / SEM for this invention; Figure 6This invention relates to the deposition of a protective layer on the surface of a liquid battery using Cryo-FIB / SEM. Figure 7 This is a schematic diagram of the cryogenic inert transfer chamber of the present invention; Figure 8 To prepare coarse-cut samples of liquid sodium-ion batteries for this invention using Cryo-FIB / SEM; Figure 9 Thin-cut samples of liquid sodium-ion batteries were prepared using Cryo-FIB / SEM for this invention. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Example 1

[0019] Please see Figure 1 This invention provides a technical solution: a method for preparing TEM samples of liquid batteries, comprising the following steps: S1. Sample freezing: In a glove box filled with argon gas (purity not less than 99.999%, and the contents of H2O and O2 are both less than 0.1ppm), the liquid battery (lithium-ion battery or sodium-ion battery) is disassembled to obtain the electrode containing the electrolyte. The electrode is fixed and subjected to low-temperature freezing treatment to obtain a frozen sample. S2. Cryo-FIB / SEM Sample Preparation: Using a low-temperature transfer device, the frozen sample is transferred to the Cryo-FIB / SEM sample chamber. At -170℃ to -195℃, the frozen sample is sequentially subjected to low-temperature deposition of a protective layer, coarse cutting, U-cutting, and thinning using Cryo-FIB / SEM to obtain sample slices. The cryogenic transfer device is a combination of a cryogenic inert transfer chamber and a PFIB cryogenic inert transfer rod. In use, the cryogenic inert transfer chamber, filled with liquid nitrogen, is opened and placed into the FIB cryogenic sample inlet. The PFIB cryogenic inert transfer rod is used to transfer the sample stage into the Cryo-FIB / SEM instrument. The Cryo-FIB / SEM is cooled to -170℃ to -195℃ using liquid nitrogen. After cryogenic deposition of a protective layer, coarse cutting, U-cutting, and thinning (Xe ion beam, coarse cutting current parameters 1nA-60nA, U-cutting current parameters 0.1nA-1nA, thinning current parameters 30pA-0.1nA), the prepared sample sheet is transferred into the cryogenic inert transfer chamber using the cryogenic inert transfer rod. Cryogenic tweezers are used to transfer the liquid battery sample into the cryo-transmission electron microscope (CTEM) rod, which is then inserted into the CTEM.

[0020] The purpose of a cryogenic inert transfer chamber is twofold: firstly, it rapidly freezes electrodes containing electrolyte, preserving the intact electrolyte interface; secondly, it completely prevents contact with air during transfer to Cryo-FIB / SEM, ensuring the electrodes do not deteriorate. The purpose of the PFIB cryogenic inert transfer rod is to rapidly transfer the sample stage from the cryogenic inert transfer chamber to the Cryo-FIB / SEM instrument under an inert atmosphere, avoiding contact with air.

[0021] The Cryo-Focused Ion Beam Scanning Electron Microscopy (Cryo FIB-SEM) is an analytical instrument that integrates the precision machining capabilities of focused ion beam (FIB) with the high-resolution imaging functions of scanning electron microscopy (SEM). Its core functions include observation of material microstructures, three-dimensional characterization, transmission electron microscopy sample preparation, and nanoscale fabrication. It is widely used in semiconductor failure analysis, materials science, and nanotechnology. This equipment achieves precise etching and deposition using a Ga / Xe ion source, with a maximum resolution of 0.7 nm (electron beam) and 30 nm (ion beam).

[0022] Cryo-transmission electron microscopy (Cryo-TEM) preserves the sample morphology using liquid nitrogen freezing technology. It involves projecting an accelerated and focused electron beam onto a very thin sample. The electrons collide with atoms in the sample and change direction, thus producing solid angle scattering. The collected signals are then used to create an image.

[0023] S3. Cryo-TEM Characterization: The sample sheet was transferred to a Cryo-TEM sample holder using a cryogenic transfer device. Cryo-TEM was then used to characterize the liquid battery sample using HRTEM, STEM, 4D-STEM, EELS, and EDS to obtain information about the electrode interior and interface. HRTEM was used to obtain crystal structure information of the electrode interior and the electrode-electrolyte interface, clearly observing microstructures such as lattice fringes and grain boundaries. STEM was used to observe the elemental distribution and morphological characteristics of the sample, presenting the three-dimensional structural information of the sample through bright-field and dark-field imaging comparison. 4D-STEM technology was used to obtain dynamic information such as phase and strain of the sample through electron beam scanning and detection. Simultaneously, EELS was used to analyze the chemical state and elemental valence states of the sample, especially the elemental interactions at the electrode-electrolyte interface. EDS was used for qualitative and quantitative elemental analysis to determine the elemental composition and content distribution in the interface region. By combining multiple characterization techniques, comprehensive and accurate information on the structure, composition, and chemical state of the electrode interior and interface was obtained, providing data support for the optimization of liquid battery performance.

[0024] Among them, the solid electrolyte interphase (SEI) is a special thin film formed inside the battery, commonly found on the surface of the negative electrode of a lithium battery. This film is naturally formed during the first charge and discharge of the battery, and like skin, it wraps around the electrode material to prevent the electrolyte from continuously decomposing. Its presence directly affects the battery life and safety. A good interphase can make the battery last longer, while a bad one may cause a short circuit or even a fire. The positive electrolyte interphase (CEI) is a passivation layer formed on the surface of the positive electrode material during the first charge of a lithium-ion battery when the electrolyte undergoes an oxidation reaction at a high potential of the positive electrode (such as NCM, LFP, etc.). Its core function is to isolate the positive electrode from the electrolyte and inhibit the dissolution of transition metals and side reactions.

[0025] Please see Figure 2-4 The samples prepared by Cryo-FIB / SEM did not show any cracking under the entire low-temperature inert environment. Figure 2 The thinned sample clearly preserved the interfacial phase between the electrode and the electrolyte. Figure 3 ) and the porous structure of the electrode material itself ( Figure 4 Cryo-TEM can observe the interfacial phase between the liquid electrolyte and the electrode, and can obtain the true interfacial structure. The liquid battery sample is kept in an inert / vacuum environment below -170°C throughout the process, eliminating the problem of sample cracking due to temperature rise during sample transfer and eliminating the problem of ice crystal formation due to contact with air during transfer.

[0026] Devitrification refers to the process by which molecules in glassy ice, if the temperature rises (even if still well below 0°C), gain enough energy to rearrange themselves and transform from a non-static state to a crystalline state. This process of transitioning from glassy ice to crystalline ice is called "devitrification." Ice crystal damage refers to the process by which water molecules arrange themselves into ice crystals when a liquid is slowly frozen. Ice crystals have sharp edges and a well-defined lattice structure. In frozen samples, the growth of these ice crystals can compress, pierce, and tear the interfaces of frozen, fragile biological structures or battery materials, causing irreversible physical damage.

[0027] Please see Figure 5 After being thinned by focused ion beam at -170℃, electron-transparent samples with a thickness of 80~100nm can be obtained. This thickness can meet the requirements of TEM characterization for electron penetration, while preserving the internal microstructure of the electrodes in the liquid battery to the maximum extent, such as grain size, pore distribution, and the original interface state between the electrodes and the liquid electrolyte. This provides high-quality sample support for studying the real mechanism of solid-liquid interface.

[0028] Please see Figure 6 Direct deposition of the Pt protective layer at low temperatures avoids damage to the surface of the liquid battery sample by Xe ions, and protects the surface from damage during sample preparation. Figure 6 ).

[0029] Please see Figure 7 This method achieves low-temperature inert transfer of liquid batteries throughout the entire process, preventing side reactions such as frost formation, cracking, and decomposition on the sample surface, thus ensuring the true morphology and structure of the sample surface. Especially for liquid batteries containing metallic sodium anodes, such as sodium-ion batteries, this transfer method effectively isolates sodium from air, avoiding the risk of sodium combustion or even explosion due to oxidation. Figure 7 This greatly improves the safety of experimental operations.

[0030] Please see Figure 8-9 , Figure 8 Preparation of coarse-cut samples of liquid sodium-ion batteries for Cryo-FIB / SEM. Figure 9 Thin-film samples of liquid sodium-ion batteries were prepared for Cryo-FIB / SEM, enabling the preparation of TEM samples of electrodes in sodium-ion pouch batteries. The electrolyte and interface on the electrode surface, as well as the pore structure and composition inside the particles, were completely preserved, providing high-quality sample support for in-depth research on the failure mechanism of sodium-ion batteries. Example 2

[0031] The difference between this embodiment and Embodiment 1 is that a full vacuum interconnection system is used for sample preparation and transport, and a system is constructed that connects the glove box, cryogenic transport module, FIB-SEM dual-beam electron microscope, and TEM through an ultra-high vacuum pipeline.

[0032] The entire sample preparation process mentioned in Example 1 first requires disassembly in a glove box, then the FIB sample stage with the electrode attached is transferred into an inert transfer chamber, then transferred to the FIB cryogenic injection tank, and then transferred to the FIB machine via the FIB sample rod for coarse cutting and thinning. After thinning, the thin slice is transferred to the TEM electron microscope for observation via the sample box and liquid nitrogen tank.

[0033] However, in Example 2, the manual transfer operation will be eliminated. The glove box, inert transfer chamber, FIB injection tank, and TEM injection tank will all be connected through inert pipes and automated. The staff only needs to control the different devices on the computer to carry out automatic operation, so as to realize the preparation and transfer of the original liquid battery sample.

[0034] For example, in glove box 1, the intelligent device 1 attaches the disassembled battery to the PFIB sample stage. A robotic arm then guides the battery through an inert pipe from the left door of the inert transfer chamber into the chamber for freezing. After freezing, the right door of the inert transfer chamber automatically opens, and the battery is then transported through an automatic transport track in the inert pipe into the PFIB cryogenic injection tank in glove box 2. The robotic arm moves the PFIB cryogenic inert sample rod to transfer the sample stage from the PFIB cryogenic injection tank to the Cryo-FIB / SEM sample chamber and begin sample preparation. After sample preparation, the robotic arm again moves the PFIB cryogenic inert sample rod to remove the sample stage containing the sheet from the Cryo-FIB / SEM sample chamber and return it to the PFIB cryogenic injection tank in glove box 2. The sheet is then removed and transferred to the TEM cryogenic injection tank. After being transferred to the TEM cryogenic sample rod, the rod is removed from another interface in glove box 2 and inserted into the TEM for testing.

[0035] Throughout the entire preparation and transport process, the samples remained in an ultra-high vacuum or ultra-low temperature environment, completely eliminating any possibility of atmospheric exposure. From battery disassembly within the glove box to transport via the cryogenic transport module, and then to sample preparation for FIB-SEM and characterization for TEM, the samples never came into contact with impurities such as moisture, oxygen, or carbon dioxide in the air, achieving "zero contamination" and "zero deterioration" from sample preparation to final analysis. This characteristic is particularly important for ultra-highly reactive samples that are extremely sensitive to air and moisture (such as sodium anodes), because sodium readily reacts with oxygen at room temperature and pressure to form sodium oxide, and with moisture to form sodium hydroxide and release hydrogen gas, which can not only damage the sample structure but also pose a risk of combustion and explosion. In the all-vacuum interconnected system, the sodium anode is always in an oxygen-free and moisture-free environment, maintaining its chemical stability and effectively ensuring the integrity of the sample and the safety of the experiment.

[0036] This system employs a fully automated transmission mode, with a central control system centrally scheduling the operation of each device. Operators only need to input preset programs into the control system to achieve automatic sample disassembly, transfer, preparation, and characterization, eliminating tedious manual operation steps. This not only reduces human error, such as sample drops, contamination, and excessively long transfer times, but also significantly increases sample processing throughput. What previously required hours of manual transfer and preparation can now be shortened, greatly improving experimental efficiency. Simultaneously, automated transmission ensures experimental repeatability and consistency. Different batches of samples are processed under the same program control, avoiding fluctuations in experimental results caused by differences in human operation, and providing strong assurance for the reliability of research data. Example 3

[0037] The difference between this embodiment and Embodiment 1 lies in the upgrade of the transfer equipment. By optimizing the structure and improving the performance of key equipment during the sample transfer process, the protection effect of the sample is further enhanced, ensuring the structural integrity and chemical stability of the sample during the transfer process. Specifically, the upgrades include the following three aspects: 1. Upgraded Dedicated Cryogenic Transfer Sample Crate: A sample cassette with a more precise sealing design (such as a metal blade seal + Teflon gasket) replaces the simple bolt-fit sample cassette. The internal design features slots that precisely secure TEM samples, preventing shaking or collisions during transfer. This significantly improves sealing reliability, preventing liquid nitrogen ingress or vacuum leakage, and avoiding mechanical damage to the samples.

[0038] 2. Optimization of the transfer medium: A cryogenic transfer device is employed, using a dedicated "cryopreservative transfer Dewar" instead of a conventional liquid nitrogen container. This device contains a liquid ammonia storage layer, with the sample cartridge immersed in its gas phase, providing a more stable and uniform cryogenic environment below -190°C. This avoids frost formation on the sample surface due to a brief "warming" process when the sample cartridge is removed from the liquid ammonia. It eliminates temperature fluctuations during the transfer process and further prevents contamination from trace amounts of condensate (even trace amounts of moisture in the inert gas) on the sample surface.

[0039] 3. Integrated Miniature Cryostat in the Glove Box: A small liquid nitrogen cryostat is installed inside the glove box. After FIB sample preparation, all operations (such as cleaning and assembly) are performed directly on this cryostat inside the glove box, ensuring that the sample remains in a cryogenic state until it is placed into the sample box. This avoids the "warming up" of the sample in the glove box environment (although inert, the temperature is relatively high), protecting any potentially volatile electrolyte components. Example 4

[0040] The difference between this embodiment and Embodiment 1 lies in the overall operation process adjustment, including: 1. Integrated Cryo-Transfer Module: A multi-port, valved vacuum interconnected chamber is installed between the glove box and the FIB-SEM microscope. This module maintains a high vacuum or high-purity inert gas environment at all times.

[0041] Operating procedure: Place the prepared sample into the module from the glove box, close the glove box valve, evacuate the module or fill it with inert gas, open the valve on the other side, and send the sample into the pre-evacuated FIB-SEM sample chamber.

[0042] Samples can be transferred without the need for manual transfer using sample boxes and liquid nitrogen tanks, achieving "exposure-free" transfer from the glove box to the FBB equipment, which is currently the standard solution for high-end laboratories.

[0043] 2. Fully Integrated Vacuum System: The glove box, cryogenic FIB-SEM, and cryogenic TEM are connected into a closed system through ultra-high vacuum pipelines.

[0044] Workflow: (1) The battery was disassembled and preliminarily processed in an inert gas glove box; (2) The sample is transferred to the frozen FIB-SEM through a vacuum channel for precise positioning and thin section preparation; (3) The prepared TEM sheet is directly grasped and transferred to the special TEM sample rod waiting inside the FIB-SEM through the vacuum channel again using the built-in nanomanipulator and locked.

[0045] (4) The TEM sample rod with the sample is directly transferred to the sample stage of the connected cryogenic TEM through the vacuum channel for observation.

[0046] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0047] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing TEM samples of a liquid battery, characterized in that, Includes the following steps: S1. Sample freezing: Under inert gas protection, the liquid battery is disassembled to obtain the electrode containing the electrolyte. The electrode is fixed and subjected to low-temperature freezing treatment to obtain a frozen sample. S2. Cryo-FIB / SEM Sample Preparation: Using a low-temperature transfer device, the frozen sample is transferred to the Cryo-FIB / SEM sample chamber. At -170℃ to -195℃, the frozen sample is sequentially subjected to low-temperature deposition of a protective layer, coarse cutting, U-cutting, and thinning using Cryo-FIB / SEM to obtain sample slices. S3. Cryo-TEM characterization: The sample sheet is transferred to the Cryo-TEM sample holder using the aforementioned low-temperature transfer device, and the sample sheet is used to characterize the interior of the liquid battery electrode and the electrode-electrolyte interface at low temperature using Cryo-TEM.

2. The method for preparing TEM samples of liquid batteries according to claim 1, characterized in that: In step S1, the inert gas is argon. The cryogenic freezing process involves immersing the sample stage with the electrode fixed on it in liquid nitrogen for freezing.

3. The method for preparing TEM samples of liquid batteries according to claim 2, characterized in that: In step S2, the low-temperature deposited protective layer is a Pt protective layer deposited using ion beam assisted deposition.

4. The method for preparing TEM samples of liquid batteries according to claim 1 or 3, characterized in that: In step S2, the coarse cutting, U-cutting, and thinning are performed at -170℃ to -195℃, and the final sample sheet thickness is 80~100nm.

5. The method for preparing TEM samples of liquid batteries according to claim 1, characterized in that: In step S3, the sample sheet is transferred from the cryogenic inert transfer chamber to the Cryo-TEM sample rod using cryogenic tweezers; The Cryo-TEM characterization includes at least one of HRTEM, STEM, 4D-STEM, EELS, and EDS.

6. The method for preparing TEM samples of liquid batteries according to claim 5, characterized in that: In steps S2 and S3, the sample sheet transfer is achieved through a full-vacuum interconnection system; The all-vacuum interconnected system includes a glove box, a cryogenic transfer module, a Cryo-FIB / SEM, and a Cryo-TEM. The glove box, cryogenic transfer module, Cryo-FIB / SEM, and Cryo-TEM are connected in sequence via an ultra-high vacuum pipeline. The sample sheet was transported in a fully vacuum interconnected system without any atmospheric exposure.

7. The method for preparing TEM samples of liquid batteries according to claim 6, characterized in that: The cryogenic transfer module is a multi-port vacuum interconnected cavity with a built-in valve control system.

8. The method for preparing TEM samples of liquid batteries according to claim 1, characterized in that: In step S1, the liquid battery is a lithium-ion battery or a sodium-ion battery.

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