Sample table for in-situ electrochemical-mechanical test of frozen FIB-SEM solid-state battery

Abstract

The invention discloses a frozen FIB-SEM solid-state battery in-situ electrochemical-mechanical test sample table which comprises a sample table bottom support, an insulating seat and a pressure applying module, the insulating seat and the pressure applying module are fixedly mounted on the sample table bottom support, and the pressure applying module comprises an upper pressing plate, a lower base and a plurality of fastening insulating screws. The lower base is fixedly mounted on the insulating seat and is made of a conductive material, a battery sample is clamped between the upper pressing plate and the lower base, and the fastening insulating screw is used for penetrating through the upper pressing plate and being screwed into the lower base; an electrical connection port is formed in the lower base, an FIB compatible groove is formed in one side of the lower base, a special FIB carrying net support is contained and fixed in the FIB compatible groove, a plurality of FIB carrying nets can be placed in the special FIB carrying net support at the same time, and batch sample preparation is achieved. The problems of mechanical environment simulation, air sensitive material protection and the like in solid-state battery in-situ research are solved.

Description

Technical Field

[0001] This invention relates to the fields of energy materials science and electrochemical detection technology, specifically to a sample stage for in-situ electrochemical-mechanical testing of frozen FIB-SEM solid-state batteries. Background Technology

[0002] Solid-state battery technology replaces traditional organic electrolytes with solid-state electrolytes, fundamentally solving the safety issues of battery systems and enabling the achievement of higher energy and power densities. However, the application of solid-state battery technology still faces a series of challenges, including the interfacial stability between the solid-state electrolyte and electrode materials, lithium dendrite growth, and the mechanical properties of the materials. Research shows that external pressure and the physical / electrochemical properties of the solid-state electrolyte together constitute key factors affecting solid-solid interface contact and dendrite behavior. Therefore, it is crucial to elucidate the pressure-regulated interfacial deposition and delamination behavior and to gain a deeper understanding of battery failure mechanisms.

[0003] Scanning electron microscopy (SEM) and its coupled focused ion beam (FIB) system are powerful tools for studying the microstructure of materials. In the field of energy materials, especially in the study of air-sensitive alkali metal solid-state batteries (such as lithium metal and sodium metal solid-state batteries), researchers urgently need to directly observe the evolution of their key interfaces. However, for novel battery technologies like alkali metal solid-state lithium batteries, achieving in-situ observation under SEM faces three major technical bottlenecks: First, the lack of mechanical environment simulation: The electrochemical performance (such as interfacial impedance) of most solid electrolytes strongly depends on the contact pressure between them and the electrodes. During battery operation, a constant and controllable mechanical pressure must be maintained to ensure effective lithium-ion transport and interfacial stability. Existing SEM sample stages are usually simple stages that lack the ability to apply and maintain controllable pressure on the sample within a vacuum chamber. Furthermore, it is difficult to ensure stable current introduction and extraction while applying pressure, especially for battery samples requiring contact on both sides. This results in the inability to simulate the actual working state of solid-state batteries, leading to distorted observation results or even making observation impossible. II. Discontinuity in Subsequent Sample Preparation: After identifying a specific region of research value (such as lithium dendrites) under SEM, researchers often wish to use focused ion beam (FIB) to finely cut this region and prepare transmission electron microscopy (TEM) samples for higher-resolution crystal structure or chemical composition analysis. However, the traditional procedure requires removing the sample from the SEM stage and transferring it to the FIB-SEM dual-beam system. This process can damage the original state of the sample, especially for materials sensitive to air and moisture (such as metallic lithium), which can rapidly oxidize and deteriorate during transfer, leading to the loss of original information about the region of interest. Moreover, FIB processing of active materials such as lithium metal usually requires low temperatures to prevent flow, oxidation, or crystal structure damage. Ordinary metal sample stages conduct heat too quickly, which is not conducive to maintaining the low temperature of the sample. III. Transfer Issues of Air-Sensitive Materials: Samples such as metallic lithium are extremely sensitive to air and moisture. During the transfer of samples from the glove box to the SEM chamber, without reliable protective measures, the samples will rapidly oxidize and deteriorate, leading to distorted observation results. Although there are inert atmosphere protected transfer devices on the market (such as Thermo Fisher Scientific's argon protected transfer module), traditional functional sample stages are often incompatible due to their special structure or excessive size.

[0004] Currently, although some studies have attempted to design in-situ electrochemical sample stages for SEM, their functions are limited. They either focus only on electrochemical connectivity while neglecting the mechanical environment, or they cannot be seamlessly integrated with subsequent FIB sample preparation processes. Therefore, there is an urgent need for a novel sample stage that can achieve a fully integrated process from inert environment sample preparation and in-situ pressure-electrochemical testing to subsequent FIB low-temperature sample preparation. Summary of the Invention

[0005] To address the aforementioned technical problems in existing technologies, the present invention aims to provide a sample stage for in-situ electrochemical-mechanical testing of frozen FIB-SEM solid-state batteries. This sample stage can provide a controllable mechanical environment, a complete electrochemical testing circuit, interference-free FIB processing capability under large-angle tilting, and efficient low-temperature thermal management for the research of materials such as solid-state batteries. It is also compatible with commercial inert atmosphere transport systems, realizing a "one-stop" research from in-situ observation to fine analysis.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A sample stage for in-situ electrochemical-mechanical testing of frozen FIB-SEM solid-state batteries includes: The sample stage base is used to fix the sample holder of the scanning electron microscope; in this invention, the sample stage base is a nail-shaped leg (Φ3mm) of the sample stage interface, used to fix it on the frozen sample stage of the SEM. An insulating base is fixedly installed on the sample stage base; the insulating base is made of aluminum nitride to prevent short circuits in the electrical test circuit; and it is more suitable for low-temperature conduction, which helps to maintain the low temperature of the sample. The pressure application module includes an upper pressure plate, a lower base, and multiple fastening insulating screws. The lower base is fixedly installed on an insulating seat and is made of conductive material. The upper pressure plate and the lower base are used to clamp a battery sample. The fastening insulating screws are used to pass through the upper pressure plate and screw into the lower base. Controllable static pressure is applied to the battery sample by tightening the fastening insulating screws. An electrical connection module includes a conductive lower base and an electrical connection port connected to the lower base, the lower base being made of a conductive material to serve as an electrode in a battery circuit; The FIB-compatible module includes an FIB-compatible groove on one side of the base under the sample stage. The FIB-compatible groove accommodates and fixes a dedicated FIB mesh holder. Multiple FIB meshes can be placed in the dedicated FIB mesh holder at the same time to achieve batch sample preparation.

[0007] Furthermore, the upper pressure plate has a thickness of 2±0.5mm, with an observation window in its center to allow unobstructed irradiation of the battery sample by the electron and ion beams. The lower base has a main body thickness of 6.5±mm. The fastening insulating screws are made of PEEK high-performance engineering plastic, and there are at least four of them, evenly distributed around the upper pressure plate. The upper pressure plate has screw through holes, and the lower base has corresponding threaded holes. The fastening insulating screws pass through the screw through holes on the upper pressure plate and are screwed into the threaded holes on the lower base, pressing and fixing the two together. By precisely tightening the fastening insulating screws, the upper pressure plate is subjected to downward load, thereby applying uniform and controllable static pressure to the battery sample clamped in the middle. The applied pressure value can be quantitatively controlled by a pre-calibrated "screw torque-pressure" relationship curve or the screw insertion depth.

[0008] Furthermore, the lower base adopts a low-profile, angled semi-trapezoidal structure design. The upper surface of the lower base is a horizontal plane and one side has an inclined surface connected to the horizontal plane. The upper pressure plate is a corresponding curved plate structure, which ensures that when the sample stage can be tilted at a large angle during operation, there is a sufficient safety gap between the carrier and the sample and the electron gun pole piece of the SEM, thereby avoiding collision.

[0009] Furthermore, the contact surfaces of the upper pressure plate and the lower base with the battery sample are both mirror-polished to ensure good electrical contact and pressure uniformity with the battery sample surface. That is, the surfaces of the upper pressure plate and the base that contact the sample are polished to ensure good electrical contact and pressure uniformity with the battery sample surface.

[0010] In this invention, the electrical connection module includes a conductive path disposed within the lower base. The lower base is made of conductive material and serves as an electrode path for the battery sample. An electrical connection port (conductive screw) is provided on its side for connection to an external electrochemical workstation via a conductive probe. This allows the lower electrode of the battery sample to be connected to an external circuit via the conductive lower base, while the upper electrode directly contacts the sample via the probe, ultimately forming a complete charge-discharge circuit.

[0011] Furthermore, the FIB-compatible module includes an upward-facing FIB-compatible groove on the upper left side of the lower base. A set screw threaded hole is provided on the left side of the lower base, which communicates with the FIB-compatible groove. A dedicated FIB carrier support is placed in the FIB-compatible groove. A fine-adjustment set screw is threaded through the set screw threaded hole and enters the FIB-compatible groove to tighten and fix the dedicated FIB carrier support.

[0012] The pressure application module has an application pressure range of 1MPa to 10MPa, which is quantitatively controlled by the relationship curve between screw torque and pressure.

[0013] The electrical connection module has at least two electrode ports, and each electrode port is connected to an external electrochemical workstation via a conductive probe.

[0014] The ceramic material is aluminum nitride. These materials ensure both low thermal conductivity for low-temperature experiments and sufficient mechanical strength and high vacuum compatibility.

[0015] Compared with the prior art, the present invention has the following advantages: This invention is the first to integrate controlled pressure application, in-situ electrochemical testing, and FIB compatibility onto a standard SEM sample stage, enabling full-process in-situ analysis of solid-state batteries, from mechanical loading and electrochemical cycling to microstructure observation and cross-scale sample preparation and transport. This design allows for multi-scale observation of the same region, enabling a more comprehensive analysis of the sample's microstructure and performance.

[0016] The insulating screws are screwed through the screw holes on the upper pressure plate into the threaded holes on the lower base. The pressure between the upper pressure plate and the lower base is calibrated by the amount of thread pressing. This method is simple and reliable, and can provide stable and uniform static pressure for solid-state batteries in the SEM vacuum chamber, simulating their real working state and greatly improving the reliability of the observation data.

[0017] The lower base of the multifunctional sample stage adopts a unique low-profile inclined structure design, and the upper pressure plate is a corresponding curved plate structure. This perfectly solves the interference problem with the pole shoes when tilting at large angles on such a multifunctional sample stage. This allows for immediate FIB section cutting or sample extraction after observing the region of interest, and direct transfer to the adjacent carrier grid. The process is seamless and highly efficient.

[0018] The aluminum nitride ceramic insulating base effectively reduces heat conduction, making it easier to maintain the low temperature of the sample during frozen FIB processing and preventing flow, oxidation or lattice damage to sensitive materials such as lithium metal caused by ion beam irradiation or environmental thermal disturbance.

[0019] The overall dimensions of the multifunctional sample stage conform to the standards of commercial SEM sample stages, and it can be perfectly adapted to commercially available inert atmosphere protection transport systems, fundamentally solving the problem of isolation and protection of air-sensitive samples throughout the entire process from preparation to observation. Attached Figure Description

[0020] Figure 1 This is an exploded view of the multifunctional sample stage of the present invention; Figure 2 This is a side cross-sectional view of the multifunctional sample stage of the present invention; Figure 3 This is a schematic diagram showing the relative positions of the sample, the FIB carrier, and the electron gun pole piece when the sample stage is tilted 52° relative to the horizontal plane. Figure 4 This is a diagram showing the deposition of lithium metal at the interface between the copper current collector and the LLZTO solid electrolyte, as observed in Example 1. Figure 5 Example 1: Electrochemical curves corresponding to lithium deposition, i.e., voltage-time curves; Figure 6 This is a morphological image of lithium peeling at the interface between Cu and the electrolyte LLZTO observed under a scanning electron microscope in Example 1. Explanation of reference numerals in the attached figures: 1. Sample stage base; 2. Insulating seat; 3. Upper pressure plate; 4. Lower base; 5. Fastening insulating screws; 6. Battery sample; 7. Electrical connection port; 8. FIB compatible groove; 9. FIB dedicated carrier support; 10. Fine adjustment set screw; 11. Electron gun pole piece; 12. Ion gun. Detailed Implementation

[0021] 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. To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0022] Comparison Figure 1-3 A sample stage for in-situ electrochemical-mechanical testing of frozen FIB-SEM solid-state batteries, comprising: Sample stage base 1, used for fixed connection with the sample holder of the scanning electron microscope; Insulating base 2 is fixedly installed on the sample stage base 1; The pressure application module includes an upper pressure plate 3, a lower base 4, and multiple fastening insulating screws 5. The lower base is fixedly installed on an insulating seat and is made of conductive material. The upper pressure plate and the lower base are used to clamp the battery sample 6. The fastening insulating screws 5 are used to pass through the upper pressure plate 3 and screw into the lower base 4. Controllable static pressure is applied to the battery sample 6 by tightening the fastening insulating screws 5. An electrical connection module includes a conductive lower base 4 and an electrical connection port 7 connected to the lower base 4. The lower base is made of a conductive material to serve as an electrode in a battery circuit. The FIB-compatible module includes an FIB-compatible groove 8 located on one side of the base under the sample stage. The FIB-compatible groove 8 accommodates and fixes a dedicated FIB mesh holder 9. Multiple FIB meshes can be placed in the dedicated FIB mesh holder 9 at the same time to achieve batch sample preparation.

[0023] The lower base 4 adopts a low profile, semi-trapezoidal structure design with an inclination angle. The upper surface of the lower base is a horizontal plane and one side has an inclined surface connected to the horizontal plane. The upper pressure plate is a corresponding curved plate structure to ensure that when the sample stage can be tilted at a large angle during operation, there is a sufficient safety gap between the carrier and the sample and the electron gun pole piece of the SEM.

[0024] An observation window is provided in the middle of the upper pressure plate 3, which is used to allow the electron beam and ion beam to irradiate the battery sample 6 without obstruction.

[0025] The number of fastening insulating screws 5 is at least four, and they are evenly distributed around the upper pressure plate 3. The upper pressure plate 3 is provided with screw through holes, and the lower base 4 is provided with corresponding threaded holes. The fastening insulating screws pass through the screw through holes on the upper pressure plate 3 and are screwed into the threaded holes on the lower base 4 to press and fix the two together. The fastening insulating screws 5 are made of PEEK high-performance engineering plastic.

[0026] The FIB-compatible module includes an upward-facing FIB-compatible groove 8 on the upper left side of the lower base. A set screw threaded hole is provided on the left side of the lower base, which communicates with the FIB-compatible groove 8. A FIB-specific net carrier bracket 9 is placed in the FIB-compatible groove 8. A fine-adjustment set screw 10 is threaded through the set screw threaded hole, and the fine-adjustment set screw 10 enters the FIB-compatible groove 8 to tighten and fix the FIB-specific net carrier bracket 9.

[0027] Example 1: In-situ scanning electrochemical-mechanical study of a negative electrode-free lithium battery like Figure 1 and Figure 2As shown, the multifunctional sample stage provided by this invention has a sample stage base 1 with nail-shaped legs for mounting on a SEM base. The insulating base 2 is made of aluminum nitride and is used to insulate the frozen sample stage from the pressure and energized areas. The pressure application module consists of an upper pressure plate 3, a lower base 4, and four fastening insulating screws 5. The upper pressure plate is made of stainless steel, while the lower base 4 is entirely conductive. In a glove box, a Cu|electrolyte LLZTO|Li structure electrodeless battery 6 is assembled, and the battery sample 6 (lithium-coated side down, Cu side up) is placed between the upper pressure plate 3 and the lower base 4 in this orientation. By tightening the four fastening insulating screws 5 step by step using tools such as Allen wrenches, the upper pressure plate 3 moves downward. Using a pre-calibrated "screw torque-indentation-pressure" relationship curve, the pressure applied to the sample can be quantitatively controlled based on the number of turns or torque of the fastening insulating screws 5. This achieves a constant pressure of 1.5 MPa applied to the battery sample 6.

[0028] After sample fixation, the sample stage is placed in an inert atmosphere-protected transport device, transferred from the glove box to the FIB-SEM electron microscope's transport adapter, and finally transferred to the vacuum scanning chamber. By rotating the entire sample stage 52° relative to the horizontal plane, the electrode surface in the observation window of the upper pressure plate 3 is made perpendicular to the ion gun 12. An appropriate area is selected for ion beam cutting, with a cutting voltage and current of 30 kV and 9.3 nA. The cleaning voltage and current are 30 kV and 0.43 nA, obtaining the cross-sectional interface morphology of Cu and the electrolyte LLZTO. An electrical connection port 7 (screw) is located on the side of the lower base 4. By operating the robotic arm, a conductive probe is brought into contact with the electrical connection port 7, thereby connecting the circuit of the external electrochemical testing equipment to the positive electrode of the battery. The upper electrode of the battery can be connected to another electrical port through another conductive probe contacting the exposed electrode surface at the opening of the upper pressure plate 3, thus forming a charge-discharge circuit.

[0029] During the battery's cyclic charging and discharging process, such as Figure 4 Lithium deposition at the interface between Cu and the electrolyte LLZTO was observed using a focused ion beam scanning electron microscope. Figure 5 This is the electrochemical curve (voltage-time) corresponding to lithium deposition. Figure 6 Lithium stripping was observed at the interface between Cu and the electrolyte LLZTO under a scanning electron microscope. By varying the applied pressure (e.g., adjusting it within the range of 1 MPa to 10 MPa), the effects of pressure on lithium deposition morphology and dendrite growth inhibition can be systematically studied.

[0030] Example 2: In-situ low-temperature FIB sample preparation of sensitive electrode material like Figure 1 and Figure 3As shown, a FIB-compatible groove 8 is machined on the left side of the sample stage. The size of this FIB-compatible groove 8 is slightly larger than that of the standard FIB-specific grid holder 9. The FIB-specific grid holder 9 is fixed by tightening the side fine-adjustment screws 10. When a region of interest (such as lithium deposition) in the battery sample 6 is observed in situ in SEM, and it is necessary to use cryogenic FIB for cross-sectional cutting or extraction of that region, the insulating base 2 can be cooled by the cold stage. Due to the low thermal conductivity of the ceramic base, heat dissipation is slow, which can effectively maintain the battery sample 6 and the sample sheet to be extracted in the clamping area at a low temperature, protecting the original morphology of the sensitive sample.

[0031] The sample stage can be tilted 53° / 52° / 51° relative to the horizontal plane for cutting and extraction. For example... Figure 3 As shown, at this angle, the FIB-specific grid holder 9 placed in the FIB-compatible groove 8 and the highest point of the sample stage are both outside the safe range of the electron gun pole piece 11, effectively avoiding collision accidents. The sample is extracted to the FIB-specific grid holder 9 by a robotic arm. Since the height of the FIB-specific grid holder 9 is higher than the overall height of the sample stage, the feasible tilt angle can be expanded to 52°±4°, ensuring that the sample can undergo a complete thinning process. Throughout the process, the sample is always in a high vacuum, argon protection, and low temperature protection environment, effectively avoiding the oxidation and irradiation damage of lithium metal, and successfully preparing a high-quality TEM sample for subsequent atomic-scale structural analysis.

Claims

1. A sample stage for in-situ electrochemical-mechanical testing of frozen FIB-SEM solid-state batteries, characterized in that, include: The sample stage base is used for fixed connection with the sample holder of the scanning electron microscope; An insulating base is fixedly installed on the sample stage base; The pressure application module includes an upper pressure plate, a lower base, and multiple fastening insulating screws. The lower base is fixedly installed on an insulating seat. The upper pressure plate and the lower base are used to clamp a battery sample. The fastening insulating screws are used to pass through the upper pressure plate and screw into the lower base. Controllable static pressure is applied to the battery sample by tightening the fastening insulating screws. An electrical connection module includes a conductive path disposed within the lower base and an electrical connection port connected to the conductive path within the lower base; The FIB-compatible module includes an FIB-compatible groove on one side of the base under the sample stage. The FIB-compatible groove accommodates and fixes a dedicated FIB mesh holder. Multiple FIB meshes can be placed in the dedicated FIB mesh holder at the same time to achieve batch sample preparation.

2. The sample stage according to claim 1, characterized in that, The lower base adopts a low-profile, angled semi-trapezoidal structure design. The upper surface of the lower base is a horizontal plane and one side has an inclined surface connected to the horizontal plane. The upper pressure plate is a corresponding curved plate structure, which ensures that when the sample stage can be tilted at a large angle during operation, there is a sufficient safety gap between the grid and the sample and the electron gun pole piece of the SEM.

3. The sample stage according to claim 1, characterized in that, The insulating base is made of aluminum nitride ceramic; the lower base is made of conductive material, and the lower base as a whole is conductive to form a conductive path to serve as an electrode of the battery circuit; the electrical connection port is connected to the side of the lower base.

4. The sample stage according to claim 1, characterized in that, An observation window is provided in the middle of the upper pressure plate, which is used to allow the electron beam and ion beam to irradiate the battery sample without obstruction.

5. The sample stage according to claim 1, characterized in that, The number of the fastening insulating screws is at least four, and they are evenly distributed around the upper pressure plate. The upper pressure plate is provided with screw through holes, and the lower base is provided with corresponding threaded holes. The fastening insulating screws pass through the screw through holes on the upper pressure plate and are screwed into the threaded holes on the lower base to press and fix the two together. The fastening insulating screws are made of PEEK high-performance engineering plastic.

6. The sample stage according to claim 1, characterized in that, The contact surfaces of the upper pressure plate and the lower base with the battery sample are both mirror-polished surfaces to ensure good electrical contact and pressure uniformity with the surface of the battery sample.

7. The sample stage according to claim 1, characterized in that, The FIB-compatible module includes an upward-facing FIB-compatible groove on the upper left side of the lower base. A set screw threaded hole is provided on the left side of the lower base, which communicates with the FIB-compatible groove. A dedicated FIB carrier support is placed in the FIB-compatible groove. A fine-adjustment set screw is threaded through the set screw threaded hole and enters the FIB-compatible groove to tighten and fix the dedicated FIB carrier support.

8. The sample stage according to claim 1, characterized in that, The pressure application module has an application pressure range of 1MPa to 10MPa, which is quantitatively controlled by the relationship curve between screw torque and pressure.

9. The sample stage according to claim 1, characterized in that, The electrical connection module has at least two electrode ports, and each electrode port is connected to an external electrochemical workstation via a conductive probe.

10. The sample stage according to claim 1, characterized in that, The thickness of the upper pressure plate is 2±0.5mm, and the thickness of the lower base body is 6.5±mm.

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