A sample preparation method for anode-free all-solid-state battery current collector / solid electrolyte interface characterization

Abstract

The application discloses a sample preparation method for characterizing a current collector / solid electrolyte interface of a full-solid-state battery without a negative electrode, which comprises the following steps: a composite sample comprises a current collector and a solid electrolyte layer in contact with the surface of the current collector; a notch is made on the surface of the solid electrolyte layer away from the current collector; a rigid constraint layer is arranged on the surface of the current collector away from the solid electrolyte layer; the composite sample is placed in a flexible packaging bag, then placed in a metal box with an exhaust structure, and then placed in a cryogenic container containing a cryogenic medium for cryogenic treatment; after being taken out, a transient mechanical impact is applied to the surface of the rigid constraint layer of the composite sample, so that the sample is subjected to low-temperature impact fracture along the notch, and the interface between the current collector and the solid electrolyte layer is exposed. The method can well solve the technical problems of a small interface exposure area, easy deformation of the current collector, fragmentation of the solid electrolyte layer and interface pollution in the prior art.

Description

Technical Field

[0001] This invention relates to the fields of solid-state battery interface characterization, low-temperature fracture sample preparation, and in-situ experimental sample preparation. Specifically, it relates to a low-temperature protected impact fracture sample preparation method for exposing the initial interface between the metal current collector and the solid electrolyte in a negative electrode-free solid-state battery. This initial interface can be used for in-situ observation of the morphology of the deposited metal layer during subsequent electrochemical deposition / stripping processes. This method is also applicable to the interface exposure and morphology observation of other metal / ceramic solid electrolyte composite samples. Background Technology

[0002] Electrodeless solid-state batteries are a novel battery system that does not pre-deposit a metal anode, but instead electrochemically deposits metallic lithium (or sodium, etc.) directly onto the surface of the solid electrolyte as the anode during the first charge. Compared with traditional solid-state batteries containing an excess of metal anode, the electrodeless structure can significantly improve the energy density of the battery, simplify the manufacturing process, and reduce material costs, and has become a research hotspot in the field of solid-state batteries.

[0003] In electrodeless solid-state batteries, the initial interfacial contact state (including porosity distribution, bonding tightness, and flatness) between the metal current collector (such as copper foil) and the solid electrolyte directly affects the uniformity of lithium morphology and dendrite growth behavior during subsequent electrochemical deposition / stripping. Specifically, a flat, clean, and uncontaminated initial interface can reduce local current density, promote uniform lithium deposition, and inhibit dendrite growth, thereby improving the battery's coulombic efficiency and cycle life. Conversely, interfacial defects (such as voids, contaminant layers, and high roughness) can lead to uneven deposition and accelerate battery failure. Therefore, obtaining an initial current collector / solid electrolyte interface with sufficient observation range, a flat and clean morphology, and a tight, void-free bond between the current collector and electrolyte, and conducting in-situ observation experiments on deposition / stripping based on this interface, is crucial for elucidating the failure mechanism of electrodeless batteries and optimizing interface engineering.

[0004] However, existing current collector / solid electrolyte interface sample preparation methods cannot simultaneously meet the above requirements. They are mainly divided into the following categories: (1) Conventional mechanical sample preparation methods (including mechanical cutting, sandpaper polishing and room temperature fracture): The cross section is obtained by cutting with a blade, polishing with sandpaper or breaking directly. These methods will cause plastic deformation (curling, stretching, dragging) of the current collector. The crack path of the solid electrolyte layer is uncontrollable. The exposed interface is uneven and the area is small. In severe cases, the current collector will cover or tear the interface, which cannot reflect the true interface morphology. (2) Focused ion beam (FIB) local cutting: Although it can achieve precise positioning of micro areas, the processing area is usually only tens of micrometers, which makes it difficult to obtain a large area of ​​continuous interface. The equipment is expensive and time-consuming. Long-term ion beam bombardment may also introduce surface redeposition and thermal effects. (3) Conventional liquid nitrogen brittle fracture method: This method has been used in the fields of non-metallic inclusion detection in steel (CN119334989A), microporous lithium battery separator cross-section sample preparation (CN111089872A, brittle fracture assisted by pressurized liquid filling), and positive electrode cross-section observation (CN116111043A, used to test the surface coverage of active particles). However, these applications are all for single metal matrix, polymer separator or positive electrode composite material, and do not involve the heterogeneous inorganic interface between metal current collector and ceramic solid electrolyte.

[0005] Even in the field of lithium batteries, the liquid nitrogen brittle fracture of separators and positive electrodes cannot be directly transferred to a cathode-less solid-state battery system. The main reasons are as follows: ① The samples in the aforementioned patents do not contain current collectors, so there is no need to address the issue of metal plastic deformation; however, the metal current collectors (such as copper) in this invention still have plasticity at low temperatures, and direct brittle fracture will cause curling and tearing, so a metal protective layer must be introduced for constraint. ② The separator or positive electrode adhesive layer in the aforementioned patents is flexible and does not have the problem of thermal stress cracking; however, the ceramic solid electrolyte in this invention has low thermal conductivity and high brittleness, and direct immersion in liquid nitrogen will cause random microcracks due to thermal stress, so a covered, slotted aluminum box must be used for slow cooling to avoid rapid cooling. ③ The aforementioned patents do not require inert protection of the cross-section, and exposure of the cross-section to air does not affect its observation purpose; however, this invention requires exposure to fresh interfaces that are extremely sensitive to air (such as the lithium deposition interface), so it must be transferred in an inert atmosphere. To address the aforementioned deficiencies, this invention utilizes the synergistic effects of pretreatment with scoring to guide crack formation, a metal protective layer to suppress curling, flexible packaging bag for positioning, a covered aluminum box with slits for slow cooling and embrittlement, and inert atmosphere transfer to obtain a large-area, flat, and clean initial current collector / solid electrolyte interface, thus meeting the needs of subsequent in-situ deposition / stripping observation.

[0006] An ideal initial current collector / solid electrolyte interface should have the characteristics of large area, flatness, and cleanness. This facilitates clear observation under a high-resolution electron microscope and allows for direct in-situ deposition / exfoliation experiments in an inert atmosphere, avoiding the influence of interface contamination or morphological distortion on the analysis results.

[0007] In summary, existing sample preparation methods cannot obtain a large-area, flat, and clean initial current collector / solid electrolyte interface without damaging the current collector and solid electrolyte layer. Therefore, there is an urgent need to develop a low-temperature protected impact fracture sample preparation method specifically for electrodeless solid-state batteries to solve the above-mentioned technical challenges and provide reliable samples for subsequent in-situ observation of deposition / stripping. Summary of the Invention

[0008] The purpose of this invention is to provide a sample preparation method for characterizing the current collector / solid electrolyte interface in a negative electrode-free all-solid-state battery, so as to solve the technical problems of small interface exposure area, easy deformation of the current collector, fragmentation of the solid electrolyte layer and interface contamination in the prior art.

[0009] To achieve the above objectives, the present invention provides the following technical solution: A sample preparation method for characterizing the current collector / solid electrolyte interface in a negative electrode-free all-solid-state battery includes the following steps: Step 1: Provide a composite sample, the composite sample including a current collector and a solid electrolyte layer in contact with the surface of the current collector; make indentations on the surface of the solid electrolyte layer away from the current collector, the depth of the indentations being less than the thickness of the solid electrolyte layer, and provide a rigid constraint layer on the surface of the current collector away from the solid electrolyte layer; Step 2: Place the composite sample from Step 1 in a flexible packaging bag, then place it together in a metal box with a venting structure, and place the metal box in a cryogenic container filled with liquid nitrogen for cryogenic treatment. This causes the solid electrolyte layer to become brittle at low temperature, while the cooling rate is slowed down by the buffering effect of the metal box, thus preventing microcracks from forming in the ceramic layer due to thermal stress. Step 3: After the processing in Step 2 is completed, remove the metal box and then remove the flexible packaging bag containing the composite sample. Immediately apply a momentary mechanical impact to the surface of the rigid constraint layer of the composite sample, causing the sample to fracture at low temperature along the grooves and the pre-treatment grooves on one side of the solid electrolyte layer. At this time, the current collector remains flat under the constraint of the rigid constraint layer, without curling, warping, or tearing, and the fracture edge of the current collector is neat. The solid electrolyte layer fractures neatly along the direction of the pre-treatment grooves, with no random microcracks on the fracture surface. Thus, the initial interface between the current collector and the solid electrolyte layer is exposed in a large area, flat, and clean state, with no metal dragging or ceramic debris contamination at the interface. Step 4: Transfer the sample processed in Step 3, along with the flexible packaging bag, to a glove box filled with an inert atmosphere under air-isolated conditions. Remove the flexible packaging bag containing the sample to obtain the interface characterization sample.

[0010] Furthermore, the current collector is selected from copper, aluminum, or stainless steel; the solid electrolyte layer is selected from LLZTO, LATP, LAGP, or other oxide solid electrolytes.

[0011] Furthermore, the current collector is Cu, the solid electrolyte layer is LLZTO, the thickness of the current collector is 5–30 μm, and the thickness of the solid electrolyte layer is 400–1000 μm.

[0012] Furthermore, the solid electrolyte layer is disposed below the current collector, and a scoring guide groove is formed in the middle of the bottom surface of the solid electrolyte layer, extending along the length of the solid electrolyte layer. The purpose of pre-treating the surface of the solid electrolyte layer to form the scoring guide groove is to allow the composite sample to fracture along the scoring guide groove and guide the crack to propagate along a predetermined path when a momentary mechanical impact is subsequently applied to the composite sample.

[0013] Furthermore, the length of the grooved guide is the same as the length of the solid electrolyte layer.

[0014] Furthermore, the rigid constraint layer is a metal sheet that covers the outside of the current collector. The metal sheet is made of copper, aluminum, stainless steel, nickel, or molybdenum, or other metal materials that maintain rigidity and provide support at cryogenic temperatures.

[0015] Furthermore, the thickness of the rigid constraint layer is 5-50 micrometers, preferably 10-20 micrometers. The rigid constraint layer is used to provide planar constraint for the current collector during cryogenic treatment and impact fracture processes, preventing it from plastically curling, warping, or tearing.

[0016] Furthermore, the flexible packaging bag is a low-temperature resistant flexible packaging bag. The purpose of using a flexible packaging bag is to prevent fragments from scattering when the sample breaks.

[0017] Furthermore, the metal box is immersed in liquid nitrogen in a cryogenic container, with the liquid nitrogen level below the venting structure of the metal box, and the cryogenic treatment in step 2 is held for 5 to 15 minutes.

[0018] Furthermore, the metal box with the exhaust structure is a covered aluminum box, and a gap is left between the cover and the box body to balance the internal and external air pressure, so that the covered aluminum box is in a non-completely sealed state.

[0019] Furthermore, in step 3, an instantaneous mechanical impact is applied using an impact hammer to cause the solid electrolyte layer to undergo low-temperature impact fracture along the pre-treatment groove, and to reduce the plastic drag of the current collector during the fracture process.

[0020] Further, in step 4, the sample processed in step 3, along with its flexible packaging bag, is placed into the transition chamber of the glove box. After vacuuming and inert gas replacement, it is transferred to the working chamber of the glove box. After removing the flexible packaging bag containing the sample, the interface characterization sample is obtained. The transition chamber of the glove box is used to vacuum and replace the atmosphere of the sample after low-temperature impact fracture, ensuring that the fresh exposed interface of the interface characterization sample does not come into direct contact with air before entering the inert atmosphere glove box, thereby reducing the risk of oxidation, moisture absorption, or air contamination.

[0021] Compared with the prior art, the present invention has at least the following beneficial effects: First, the present invention sets pre-treatment grooves on one side of the solid electrolyte layer, and combines liquid nitrogen cryogenic treatment and instantaneous mechanical impact to cause the solid electrolyte layer to fracture preferentially along the pre-treatment grooves in a low-temperature embrittlement state; at the same time, the current collector is protected and confined by a metal protective layer, a flexible packaging bag and a lidded aluminum box, reducing the curling, stretching, tearing and plastic dragging of the current collector during the impact fracture process, thereby making the fracture process of the composite sample more controllable.

[0022] Secondly, under the synergistic effect of the above-mentioned scoring-guided cracking, low-temperature embrittlement and protective limiting, the present invention can obtain a smoother current collector fracture edge and a smoother solid electrolyte layer fracture surface, and reduce the risk of the interface area being dragged and covered by the current collector or contaminated by debris, thereby improving the exposure integrity and smoothness of the current collector / solid electrolyte layer interface.

[0023] Third, the present invention uses a covered aluminum box with gaps for low-temperature treatment. The covered aluminum box can provide external mechanical protection and low-temperature conduction path for composite samples, and can also realize the exchange of low-temperature gas or liquid nitrogen vapor through the gap between the cover and the box body, avoiding the formation of a closed pressurized environment during the liquid nitrogen low-temperature treatment, and improving the safety and stability of the sample preparation process.

[0024] Fourth, compared with the method of local cutting to expose the interface by FIB, the present invention does not rely on point-by-point small-scale cutting by ion beam, and can quickly obtain a large area of ​​current collector / solid electrolyte layer interface exposure area, and reduce the local redeposition, thermal effect or surface morphology change that may be caused by long-term ion beam processing.

[0025] Fifth, the interface characterization sample obtained by this invention does not come into direct contact with air during sample preparation and transfer, resulting in a large, clean, and flat interface. Based on this high-quality initial interface, subsequent in-situ electrochemical deposition / exfoliation experiments can be performed directly in an inert atmosphere to observe the deposition and exfoliation morphology evolution of lithium at the current collector / solid electrolyte interface in real time (such as deposition uniformity, dendrite growth, exfoliation residue, etc.). The flat interface facilitates the acquisition of high-resolution electron microscopy images, while the clean interface avoids spurious morphology or side reaction interference caused by contaminants, thereby significantly improving the reliability and reproducibility of in-situ experimental data and facilitating subsequent SEM observation, FIB local refinement, energy dispersive spectroscopy analysis, in-situ electrochemical testing, or in-situ mechanical testing. Attached Figure Description

[0026] Figure 1 This is a SEM image of the interface characterization sample prepared by the low-temperature protected impact fracture sample preparation method in Example 1 of the present invention. Figure 2 SEM images of the interface characterization samples prepared by FIB local cutting in Comparative Example 1; Figure 3 The image shows the SEM image of the interface characterization sample prepared by direct mechanical cutting in Comparative Example 1. Figure 4 This is a SEM image of the interface characterization sample prepared by method three using room temperature mechanical fracture in Comparative Example 1. Figure 5 This is a SEM image of the in-situ deposition experiment at the Cu / LLZTO interface in Example 2 of this invention. Part a shows the initial Cu / LLZTO interface morphology exposed using the sample preparation method of this invention (another independent sample); Part b shows the deposition capacity at the interface shown in Part a reaching 2 mAh / cm³. 2 The first part is a view of the interface shape at that time; part c is a magnified view of part b.

[0027] Figure 6 This is a schematic diagram demonstrating the sample preparation method of the present invention; Figure 7 This is a SEM image of the Cu / LLZTO interface of the sample prepared in Comparative Example 2. Detailed Implementation

[0028] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that the following embodiments are only for illustrating the present invention and are not intended to limit the scope of protection of the present invention; without departing from the concept of the present invention, those skilled in the art can make equivalent substitutions for the order of steps, types of materials, processing time, packaging methods and impact methods.

[0029] Example 1: Cryogenic protected impact fracture preparation of Cu / LLZTO interface characterization samples This embodiment provides a method for preparing a low-temperature protected impact fracture sample for characterizing a Cu / LLZTO interface. The Cu / LLZTO composite sample includes a Cu layer (current collector) and an LLZTO layer (solid electrolyte layer) in contact with each other, wherein the Cu layer (current collector) is a thin metal layer, and the LLZTO layer (solid electrolyte layer) is a solid electrolyte layer. The sample preparation method includes the following steps (refer to...). Figure 6 ): S1, a Cu / LLZTO composite sample is provided, with a Cu layer (current collector) on top and an LLZTO layer (solid electrolyte layer) on the bottom. In this embodiment, the thickness of the Cu layer (current collector) is approximately 10 μm, and the thickness of the LLZTO layer (solid electrolyte layer) is approximately 600 μm.

[0030] S2, a groove is formed at the center of the bottom surface of the LLZTO layer. The groove extends along the length of the LLZTO layer and is the same length as the LLZTO layer. The groove guides the crack along a predetermined path during fracture, thereby reducing the risk of incomplete interface exposure or uneven fracture surface caused by random crack propagation.

[0031] S3, an aluminum foil protective layer is covered on the upper surface of the Cu layer, the thickness of which is approximately 10 μm. The aluminum foil protective layer is used to provide planar support and restraint for the Cu layer during low-temperature treatment and impact fracture, reducing warping, curling, stretching, tearing, or plastic dragging of the Cu layer.

[0032] S4, the Cu / LLZTO composite sample covered with the aluminum foil protective layer is placed into a flexible packaging bag for containment. The flexible packaging bag is made of aluminum-plastic film. The flexible packaging bag is used to flexibly constrain the Cu / LLZTO composite sample, so that the composite sample maintains a relatively stable position during subsequent low-temperature treatment and impact fracture, while preventing fragments from scattering when the sample breaks, and reducing secondary damage to the exposed interface caused by rigid clamping.

[0033] S5, the flexible packaging bag containing the Cu / LLZTO composite sample is placed into a lidded aluminum box. The lidded aluminum box includes a box body and a lid, with a gap between the lid and the box body, so that the lidded aluminum box is not completely sealed. The gap is used to allow for the exchange of cryogenic gas or liquid nitrogen vapor and to release pressure, avoiding the formation of a closed pressurized environment during liquid nitrogen cryogenic treatment; the lidded aluminum box also serves to provide external mechanical protection and a cryogenic conduction path for the composite sample.

[0034] S6, the covered aluminum box is placed in a liquid nitrogen insulated container filled with liquid nitrogen for cryogenic treatment. The box body is immersed in liquid nitrogen, and the liquid nitrogen level is lower than the gap between the lid and the box body. The liquid nitrogen insulated container provides a low-temperature environment, causing the LLZTO layer to rapidly become brittle at low temperatures, thereby reducing the plastic drag of the Cu layer during subsequent impact fracture. The restraining effect of the aluminum foil protective layer, flexible packaging bag, and covered aluminum box helps to obtain a smoother Cu foil fracture edge and a smoother LLZTO fracture surface. The cryogenic treatment time is 10 minutes, and the cryogenic treatment temperature is approximately -196℃.

[0035] S7. After the cryogenic treatment, the covered aluminum box is removed from the liquid nitrogen insulated container, and then the flexible packaging bag containing the composite sample is removed from the covered aluminum box. While still at low temperature, an instantaneous mechanical impact is immediately applied to the surface of the aluminum foil protective layer of the Cu / LLZTO composite sample, which is confined by the flexible packaging bag. This instantaneous mechanical impact causes the LLZTO layer to undergo cryogenic brittle fracture along the grooved guide. Under the confining effect of the aluminum foil protective layer and the flexible packaging bag, the curling, stretching, and plastic dragging of the Cu layer during the fracture process are reduced, exposing the interface between the Cu layer and the LLZTO layer in a relatively flat state. In this embodiment, an instantaneous mechanical impact is applied to the sample surface using an impact hammer.

[0036] In step S8, the sample, after being fractured by low-temperature impact in step S7, along with its flexible packaging bag, is transferred to the transition chamber of the glove box. After vacuuming and purging with argon atmosphere, it enters the argon-filled working chamber of the glove box. The flexible packaging bag is then removed, yielding the Cu / LLZTO interface characterization sample. During sample preparation and transfer, the Cu / LLZTO interface characterization sample does not come into direct contact with air, thus reducing the risk of oxidation, moisture absorption, or air contamination of the freshly exposed interface. The Cu / LLZTO interface characterization sample has a large and relatively flat Cu / LLZTO exposed interface, which can be used for SEM observation, FIB local refinement, energy dispersive spectroscopy analysis, and subsequent in-situ electrochemical or in-situ mechanical experiments.

[0037] The SEM image of the Cu / LLZTO interface prepared by the low-temperature protected impact fracture sample preparation method in Example 1 of this invention is shown below. Figure 1 .like Figure 1 As shown, the Cu / LLZTO interface has a large exposed area and is relatively clean and flat, which facilitates subsequent SEM observation, FIB local refinement and in-situ experiments.

[0038] Comparative Example 1: Cu / LLZTO interface samples prepared using other sample preparation methods Three additional Cu / LLZTO composite samples were prepared using the following sample preparation methods to create Cu / LLZTO interface samples: Method 1: Using FIB local cutting. The specific operation is as follows: the Cu / LLZTO composite sample is placed directly into the FIB and local cutting is performed using an ion beam. There is no need to cover it with an aluminum foil protective layer, score it, perform low-temperature treatment, or use a series of steps such as limiting it in a flexible packaging bag.

[0039] Method 2: Direct mechanical cutting is used. Specifically, the Cu / LLZTO composite sample is cut directly using a grinding and cutting machine. There is no need to cover it with an aluminum foil protective layer, score it, perform low-temperature treatment, or use a series of steps such as limiting it in a flexible packaging bag.

[0040] Method 3: Repeat the sample preparation method of Example 1, except that the low-temperature treatment process in step S6 is omitted. Instead, an instantaneous mechanical impact is applied directly to the surface of the aluminum foil protective layer of the Cu / LLZTO composite sample, which is constrained by a flexible packaging bag, at room temperature, while the other conditions remain unchanged.

[0041] SEM images of the Cu / LLZTO interface samples prepared by methods 1, 2, and 3 in Comparative Example 1 are shown below. Figure 2 , Figure 3 and Figure 4 As shown.

[0042] according to Figures 2-4 It can be seen that when using room-temperature mechanical fracture (i.e., Method 3) or mechanical cutting (i.e., Method 2), the Cu layer (current collector) is thin and ductile, making it prone to stretching, curling, or dragging, resulting in an uneven exposed interface or partial coverage of the interface area by the current collector. When using the FIB local cutting method (i.e., Method 1), it is necessary to simultaneously cut the Cu layer (current collector) and the LLZTO layer (solid electrolyte layer) in the target area to expose the Cu / LLZTO interface in a local cross-section. Although this method is suitable for micro-area localization analysis, it is usually difficult to quickly obtain a large area of ​​continuous interface due to limitations in ion beam processing window, sample geometry, clamping posture, and cutting efficiency.

[0043] like Figures 2-4 As shown, the surface smoothness and continuity of samples obtained using other sample preparation methods are lower than those obtained using the sample preparation method of Example 1 of this invention. Figures 2-4 compared to, Figure 1 The Cu / LLZTO interface characterization sample obtained by the low-temperature protected impact fracture sample preparation method described in this invention has a larger exposed area and better interface smoothness, which makes it easier for subsequent SEM observation, FIB local refinement and in-situ experiments.

[0044] Example 2: In-situ electrochemical deposition and morphological observation In this embodiment, the same sample preparation method as in Example 1 was used to prepare another Cu / LLZTO composite sample, resulting in an independent Cu / LLZTO interface characterization sample (initial interface exposed). First, the initial Cu / LLZTO interface morphology of the sample was observed, such as... Figure 5 As shown in part a, the initial Cu / LLZTO interface is flat, clean, and free from curling and debris contamination.

[0045] In an inert atmosphere glove box, using lithium metal as the counter electrode, the Cu / LLZTO interface sample was combined with the lithium metal counter electrode to form a Cu / LLZTO / Li battery. This battery was mounted on an in-situ electrochemical testing stage and then transferred to a focused ion beam / scanning electron microscope (FIB / SEM) system. Subsequently, in-situ electrochemical deposition was performed in constant current mode, and the deposition process of lithium metal on the Cu / LLZTO interface was observed in real time. When the deposition capacity reached 2 mAh / cm³, the deposition was successfully completed. 2 At that time, deposition was stopped and interface morphology images were acquired, such as... Figure 5 As shown in part b, lithium metal is uniformly deposited on the initial interface to form a dense lithium layer. Figure 5 part c is Figure 5 The magnified view of part b clearly shows the interfacial bonding state between the deposited lithium layer and the LLZTO electrolyte, with no obvious pores or dendrites.

[0046] In Example 2 of this invention, the same sample preparation method as in Example 1 was used, and in-situ deposition observation was carried out on this basis. Figure 5 Parts b and c are related to Figure 1 The comparison results confirm that, compared with Example 2, the initial interface obtained by Example 1 is flat and clean, which can achieve uniform and dense lithium deposition, proving the effectiveness of the sample preparation method.

[0047] This experiment demonstrates that the initial interface exposed using the method of this invention has sufficient flatness and cleanliness, and can be directly used for real-time observation of in-situ deposition behavior in electrodeless solid-state batteries.

[0048] In other embodiments, the current collector can also be Al, stainless steel, or other current collectors, and the solid electrolyte layer can also be LATP, LAGP, or other solid electrolyte layers. As long as the composite sample has a current collector / solid electrolyte interface and requires a large exposed area and a relatively flat interface, the cryogenic protection impact fracture sample preparation method described in this invention can be used.

[0049] Comparative Example 2 and Comparative Example 2 are experimental methods that are repeated in Example 1, except that the processing step S3 is omitted, that is, the upper surface of the Cu layer is not covered with an aluminum foil protective layer, and the other conditions remain the same.

[0050] SEM images of the Cu / LLZTO interface of the sample prepared in Comparative Example 2 are shown below. Figure 7 .from Figure 7 It can be seen that without the aluminum foil protective layer, the fracture surface of the Comparative Example 2 sample is prone to plastic deformation of the copper foil and edge curling, and the interface flatness is significantly lower than that of the Example 1 sample with the protective layer.

[0051] The contents described in this specification are merely an enumeration of the implementation forms of the inventive concept, and the scope of protection of this invention should not be regarded as limited to the specific forms described in the embodiments.

Claims

1. A sample preparation method for characterizing the current collector / solid electrolyte interface in a negative electrode-free all-solid-state battery, characterized in that, Includes the following steps: Step 1: Provide a composite sample, the composite sample including a current collector and a solid electrolyte layer in contact with the surface of the current collector; make indentations on the surface of the solid electrolyte layer away from the current collector, the depth of the indentations being less than the thickness of the solid electrolyte layer, and provide a rigid constraint layer on the surface of the current collector away from the solid electrolyte layer; Step 2: Place the composite sample from Step 1 in a flexible packaging bag, then place it together in a metal box with a venting structure, and place the metal box in a cryogenic container filled with cryogenic medium for cryogenic treatment to make the solid electrolyte layer embrittled at low temperature. Step 3: After the processing in Step 2 is completed, remove the metal box and then remove the flexible packaging bag containing the composite sample. Immediately apply a momentary mechanical impact to the surface of the rigid constraint layer of the composite sample to cause the sample to fracture along the groove at low temperature, thereby exposing the interface between the current collector and the solid electrolyte layer. Step 4: Transfer the sample processed in Step 3, along with the flexible packaging bag, to a glove box filled with an inert atmosphere under air-isolated conditions. Remove the flexible packaging bag containing the sample to obtain the interface characterization sample.

2. The sample preparation method as described in claim 1, characterized in that, The current collector is selected from copper, aluminum, or stainless steel; the solid electrolyte layer is selected from LLZTO, LATP, or LAGP.

3. The sample preparation method as described in claim 2, characterized in that, The current collector is made of copper, the solid electrolyte layer is made of LLZTO, the thickness of the current collector is 5–30 μm, and the thickness of the solid electrolyte layer is 400–1000 μm.

4. The sample preparation method as described in claim 1, characterized in that, The solid electrolyte layer is disposed below the current collector, and a scoring guide groove is provided in the middle of the bottom surface of the solid electrolyte layer. The scoring guide groove extends along the length direction of the solid electrolyte layer and is used to guide the crack to expand along a preset path when fractured.

5. The sample preparation method as described in claim 1, characterized in that, The rigid constraint layer is a metal sheet that covers the outside of the current collector. The metal sheet is made of copper, aluminum, stainless steel, nickel, or molybdenum. The thickness of the rigid constraint layer is 5-50 micrometers.

6. The sample preparation method as described in claim 1, characterized in that, The cryogenic medium is liquid nitrogen. The metal box is immersed in liquid nitrogen in the cryogenic container. The liquid nitrogen level is lower than the venting structure of the metal box. The cryogenic treatment time in step 2 is 5 to 15 minutes.

7. The sample preparation method as described in claim 1, characterized in that, The metal box with the exhaust structure is a covered aluminum box, and a gap is left between the cover and the box body to balance the internal and external air pressure.

8. The sample preparation method as described in claim 1, characterized in that, In step 3, an instantaneous mechanical impact is applied using an impact hammer.

9. The sample preparation method as described in claim 1, characterized in that, In step 4, the sample processed in step 3, along with the flexible packaging bag, is placed into the transition chamber of the glove box. After vacuuming and inert gas replacement, it is transferred to the working chamber of the glove box. After removing the flexible packaging bag containing the sample, the interface characterization sample is obtained.

Images