Method for preparing section sample of new energy automobile battery powder material

Abstract

The invention discloses a method for preparing a section sample of a new energy automobile battery powder material, and relates to the technical field of battery material analysis, and the method comprises the following steps: uniformly mixing a battery powder material with a liquid conductive adhesive solution; pouring the mixture into a mold for curing, and demolding to obtain a conductive sample block with a regular shape; directly loading the conductive sample block in an ion beam cutting system for ion cutting to obtain a flat sample section; and surface metal spraying treatment is not needed, and electron microscope observation and analysis are directly carried out. According to the preparation method, the conductive adhesive solution is adopted for inlaying and is combined with mold forming, so that time-consuming mechanical grinding and polishing procedures in a traditional method are omitted, and the preparation period is greatly shortened; and meanwhile, an in-situ conductive network formed after the glue solution is cured is utilized to effectively inhibit the charge effect, so that direct observation without metal spraying is realized, sample preparation damage and plating interference are avoided, and the authenticity and accuracy of an analysis result are ensured. The method is simple and convenient to operate and good in repeatability.

Description

Technical Field

[0001] This application relates to the field of battery material analysis technology, and in particular to a method for preparing cross-sectional samples of powder materials for new energy vehicle batteries. Background Technology

[0002] In the research and quality control of new energy vehicle battery materials, especially ternary cathodes, lithium-rich manganese-based cathodes, or silicon-carbon anodes, accurate characterization of their internal microstructure, interface state, elemental distribution, and defects is crucial. Scanning electron microscopy (SEM) combined with energy dispersive spectroscopy (EDS) is a key technology for achieving this characterization. Obtaining a high-quality, non-destructive, and flat cross-section that truly reflects the intrinsic information of the material is a prerequisite for effective analysis.

[0003] Currently, the conventional technical approach used in the industry for preparing cross-sectional samples of this type of powder material is as follows: First, the powder is mixed with insulating polymer embedding materials such as epoxy resin, and then cured to form a hard block sample. Subsequently, the sample block undergoes multiple passes of mechanical grinding and polishing, using sandpaper and polishing paste of varying coarseness to gradually remove the surface resin, thereby exposing the cross-section of the powder particles. To obtain a higher quality cross-section, the mechanically polished sample must be placed in an ion beam cutting system (such as an argon ion cross-section polisher) for final fine finishing.

[0004] However, the aforementioned conventional technical solutions have inherent drawbacks in practical applications. First, from the perspective of sample preparation efficiency, the machining process, which involves multiple grinding and polishing passes, is extremely time-consuming. Furthermore, the sample needs to be cleaned between each step, making the entire process cumbersome and complex, thus prolonging the preparation cycle from raw powder to a final analyzable sample. Second, this method is highly dependent on the operator's experience and skill. The polishing force, time, and technique all affect the flatness and quality of the final cross-section, leading to poor consistency between samples prepared by different batches or by different operators, thus impacting the reproducibility of experimental data.

[0005] More importantly, this traditional method is prone to compromising the accuracy of the analytical results. On the one hand, the stress applied during mechanical grinding can easily cause hard battery particles to detach from the softer resin matrix, or create a smearing effect at the particle-resin interface. These are structural artifacts introduced during sample preparation that are not inherent to the material itself. On the other hand, because epoxy resin is an excellent insulator, the prepared sample is generally non-conductive, resulting in a severe charging effect when observed under an electron microscope. A conductive metal film (such as gold or carbon) must be sprayed onto the sample surface for proper imaging. This additional gold spraying step not only obscures the nanoscale fine structure of the material surface, but the introduced foreign elements also interfere with the quantitative analysis of the composition by energy dispersive spectroscopy (EDS), ultimately affecting the accuracy and reliability of the analytical data. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing cross-sectional samples of powder materials for new energy vehicle batteries, which at least solves one of the technical problems in the prior art, namely, the complexity and time-consuming process caused by the use of insulating resin embedding and mechanical polishing, the easy introduction of mechanical damage artifacts, and the serious sample charge effect that affects the final analysis efficiency and accuracy.

[0007] This invention provides the following solution:

[0008] A method for preparing cross-sectional samples of powder materials for new energy vehicle batteries includes the following steps:

[0009] S1. Embedded Mixing: The battery powder material to be analyzed is mixed with the liquid conductive adhesive at a preset volume ratio to obtain a viscous mixture;

[0010] S2, Pouring and Curing: The viscous mixture is poured into the groove of the mold and cured under a preset environment. After demolding, a conductive sample block with a regular shape is obtained.

[0011] S3. Sample loading: The conductive sample block is attached to the sample stage of the ion beam cutting system, and the sample position is adjusted so that it partially exposes the baffle.

[0012] S4. Ion cutting: In a vacuum environment, the exposed part of the conductive sample block is cut by ion beam bombardment using an ion beam cutting system to obtain a flat sample cross section.

[0013] S5. Observation and analysis: Place the cut sample under an electron microscope for microscopic morphology or energy dispersive spectroscopy analysis.

[0014] By adopting the above technical solution, and by using liquid conductive adhesive as the embedding medium in conjunction with mold forming and ion beam cutting technology, this invention achieves a dual improvement in sample preparation efficiency and observation quality through the following physical mechanism:

[0015] First, the construction mechanism of the in-situ conductive network: Utilizing the fluidity and curing properties of liquid conductive adhesives (such as silver paste or carbon paste), during the mixing stage, conductive particles (silver powder or carbon powder) in the conductive adhesive fully wet and encapsulate the battery powder particles under test at the microscale. During the curing stage, as the solvent evaporates, the conductive particles come into contact with each other to form a continuous three-dimensional conductive percolation network. This network macroscopically constitutes a low-impedance electron transport channel from the battery powder particles to the sample stage base. When the high-energy electron beam of an electron microscope bombards the cross-section of the insulating or semiconductor battery powder, the accumulated charge generated can be rapidly dissipated to ground through this in-situ conductive network, thereby eliminating surface charge accumulation at the physical level. This eliminates the need for traditional metal sputtering treatment to suppress the charging effect and preserves the true elemental distribution information of the material.

[0016] Second, near-net-shape forming and interface stress relief mechanism: A mold is used to form the viscous mixture into a near-net-shape, and the cured sample block directly possesses the geometry and sharp edges suitable for the ion beam cutting system. This process completely replaces the mechanical cutting, grinding, and polishing processes required for traditional epoxy resin inlay, avoiding powder particle breakage and detachment caused by shear stress during machining, as well as the step effect at the soft-hard composite interface. The mold forming surface serves as the initial reference surface for ion cutting; its flatness and edge sharpness directly meet the grazing conditions of the ion beam, significantly shortening the time required for ion beam trimming of the cross-section.

[0017] Third, the non-destructive ion polishing mechanism: Combining the aforementioned conductive substrate and regular surface, the ion beam can bombard the sample with a stable beam current density. Since the thermal conductivity of the conductive substrate is better than that of traditional epoxy resin, it can more effectively dissipate the heat generated by ion bombardment and reduce the thermal damage layer; at the same time, the uniform difference in substrate etching rate (relative to the huge difference between resin and powder) helps to reduce the curtain effect, thereby obtaining a high-quality flat cross-section.

[0018] Preferably, in step S1, the liquid conductive adhesive is a high-purity conductive silver paste or a high-purity conductive carbon paste; the preset volume ratio of the battery powder material to the liquid conductive adhesive is 1:3-1:5.

[0019] By adopting the above technical solution, the volume ratio of powder to adhesive is controlled between 1:3 and 1:5. Through the regulation of rheological properties, this ensures that the mixture has sufficient fluidity to fill the mold microstructure, while also ensuring the mechanical support strength of the conductive matrix for the powder particles after curing. If the proportion of adhesive is too low, a continuous conductive film cannot be formed and the particles are prone to detachment; if the proportion of adhesive is too high, it increases the workload of ion cutting and reduces the number of effective particles per unit field of view.

[0020] Preferably, in step S2, the mold is a silicone mold or a polyurethane mold with a square groove, the groove having a depth of 0.5mm-1.5mm, a length of 5mm-15mm, and a width of 3mm-8mm.

[0021] By adopting the above technical solution, the mold size design directly matches the sample loading area size of the ion beam cutting system (such as an argon ion cross-section polisher). The thickness range of 0.5mm-1.5mm ensures that the sample can stand stably upright on the side of the sample stage, and will not cause the baffle to fail due to excessive thickness or insufficient mechanical strength due to excessive thinness.

[0022] Preferably, in step S2, the preset environment and curing method include any one of the following:

[0023] Room temperature curing: Allow to stand at room temperature for at least 2 hours.

[0024] Accelerate curing: Place in an oven at 50℃-60℃ for at least 1 hour.

[0025] By adopting the above technical solutions, a flexible curing process window is provided. Room temperature curing is suitable for heat-sensitive materials and avoids thermal stress; heating curing utilizes heat convection to accelerate the evaporation rate of organic solvents, shortens the sample preparation cycle, and moderate heating helps to improve the crosslinking density and conductivity of the conductive adhesive layer.

[0026] Preferably, in step S3, adjusting the sample position specifically involves adjusting the distance and height between the sample stage and the baffle, so that the upper end of the conductive sample block protrudes from the edge of the baffle in a range of 30μm-50μm.

[0027] By employing the above technical solution, precisely controlling the exposure height is key to balancing cutting efficiency and cross-sectional quality. A height setting of 30μm-50μm ensures that the ion beam completely covers the area to be observed, while avoiding problems such as ion beam energy dispersion, exponentially increasing cutting time, and intensified thermal effects caused by excessive exposure.

[0028] Preferably, in step S4, the vacuum level of the vacuum environment is ≤1×10⁻⁶. −5 mbar.

[0029] By adopting the above technical solutions, the high vacuum environment ensures the mean free path of the ion beam, reduces energy loss and beam divergence caused by gas molecule scattering, and ensures that the ion beam bombards the sample surface with high directionality.

[0030] Preferably, the ion cutting in step S4 adopts a step-by-step cutting method, including a first cutting and a second cutting; the first cutting is used for rough cutting, and its process parameters are controlled as follows: voltage 6kV-8kV, current 2.2mA-3.0mA, and cutting time 3.0h-4.0h.

[0031] By adopting the above technical solution, the first cutting is performed using a high-energy, high-current ion beam, which can quickly remove the blocky material exposed by the baffle and expose the internal structure of the particles in a short time, mainly playing the role of material removal.

[0032] Preferably, the second cut is used for fine grinding, and its process parameters are controlled as follows: voltage 4kV-5kV, current 1.5mA-2.0mA, and cutting time 1h-1.2h.

[0033] By employing the above technical solution, a second cutting is performed using a low-energy, low-current ion beam, primarily for surface modification. The low-energy ion beam can effectively remove the amorphous damage layer and microscopic striations left over from the high-energy cutting stage, reducing cross-sectional roughness and thus obtaining an observation plane with atomically flatness.

[0034] Preferably, the battery powder material is selected from one of ternary materials, lithium-rich manganese-based materials, or silicon-carbon materials.

[0035] By adopting the above technical solution, this method is widely applicable to various mainstream lithium-ion battery positive and negative electrode powder materials. Whether it is layered oxide or composite negative electrode material, high-quality cross-section preparation can be achieved through this method.

[0036] Preferably, in step S5, the observation and analysis are performed directly without metal sputtering the sample cross-section.

[0037] By adopting the above technical solution, the obscuring of microscopic details on the sample surface by exogenous metal coatings (such as gold and platinum) is avoided, the interference of gold-sprayed particles on nanopores or grain boundary structures at high magnification (such as >50000×) is eliminated, and the signal overlap of coating elements on light element analysis by energy dispersive spectroscopy (EDS) is avoided, thus realizing the true restoration of the intrinsic information of the material.

[0038] The above solution achieves the following beneficial technical effects:

[0039] This application replaces the mechanical grinding and polishing processes required after traditional epoxy resin embedding by directly casting liquid conductive adhesive into a mold. This process simplification eliminates time-consuming and cumbersome mechanical processing steps, significantly reducing the total time from powder mixing to obtaining a regular sample block suitable for ion cutting, thereby improving overall sample preparation efficiency.

[0040] This application utilizes an in-situ three-dimensional conductive network formed after the conductive adhesive has cured, effectively absorbing the accumulated charge generated when the electron beam bombards the sample, thereby suppressing the charging effect without surface metal sputtering. This not only avoids the obscuring of the true morphology of the sample by the metal coating and the interference of the signal in energy dispersive spectroscopy (EDS) analysis, but also eliminates sample preparation artifacts such as particle breakage, detachment, and interface coating caused by grinding stress by eliminating mechanical grinding, ensuring that the observation results can truly reflect the intrinsic microstructure of the material.

[0041] The effectiveness of traditional mechanical polishing largely depends on the operator's experience and technique, resulting in poor consistency. This application employs mold shaping, standardizing the operation process, making it easy to master, and enabling the acquisition of highly reproducible sample morphologies. This method does not rely on complex manual polishing techniques, lowering the operational threshold and ensuring greater consistency in samples prepared by different operators, which is beneficial for cross-sectional comparison of experimental data. Attached Figure Description

[0042] Figure 1 This is a flowchart of a method for preparing cross-sectional samples of new energy vehicle battery powder materials according to one or more embodiments of the present invention.

[0043] Figure 2 This is a schematic diagram of a preparation mold for a method of preparing cross-sectional samples of new energy vehicle battery powder materials provided in one or more embodiments of the present invention. Detailed Implementation

[0044] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. 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.

[0045] Reference Figure 1 , Figure 1 This is a flowchart illustrating a method for preparing cross-sectional samples of new energy vehicle battery powder materials according to one or more embodiments of the present invention;

[0046] Reference Figure 2 , Figure 2 This is a schematic diagram of a preparation mold for a method of preparing cross-sectional samples of new energy vehicle battery powder materials provided in one or more embodiments of the present invention.

[0047] Examples 1-4:

[0048] Example 1:

[0049] This embodiment provides a method for preparing cross-sectional samples by embedding conductive silver paste with ternary cathode material powder and using an ion beam cutting system. The method is characterized by the use of room temperature curing and relatively fine ion cutting parameters, and includes the following steps:

[0050] Embedding and mixing: Take a small amount of positive electrode ternary material powder sample and high-purity conductive silver paste, and mix them thoroughly at a volume ratio of 1:3 to ensure that the powder particles are uniformly coated with silver paste to form a viscous mixture.

[0051] Mold pouring and curing: Slowly pour the mixture into a clean silicone mold. The sample groove in the mold should be 0.5 mm deep, 10 mm long, and 5 mm wide. Place the mold at room temperature for 2 hours to allow it to air dry and cure naturally.

[0052] Demolding: After the sample has completely solidified, demolding is performed to obtain a sample block with a regular shape.

[0053] Loading the ion cutting system: Use carbon conductive tape to attach the demolded sample block to the sample preparation stage of the three-ion beam cutting system, ensuring the flat surface closest to the mold is against the sample stage. Adjust the distance and height between the sample stage and the baffle so that the upper part of the sample protrudes 50 μm above the baffle.

[0054] Vacuuming: Start the equipment to evacuate the system until the vacuum level reaches 1×10⁻⁶. −5 mbar.

[0055] First ion cutting: The cutting voltage was set to 6kV, the current to 2.2mA, and the cutting time to 3h.

[0056] Second ion cutting: The cutting voltage was set to 4kV, the current to 1.5mA, and the cutting time to 1h.

[0057] Sample Removal and Analysis: After cutting, release the vacuum and remove the sample. Use conductive tape to attach the ion-cut cross-section of the sample to the scanning electron microscope (SEM) stage, with the observation surface facing upwards. No gold sputtering is required; the ternary material cross-section can be directly analyzed using a scanning electron microscope in conjunction with an energy dispersive X-ray spectroscopy (EDS) system.

[0058] Example 2:

[0059] This embodiment provides a method for preparing cross-sectional samples by embedding conductive silver paste with negative electrode silicon-carbon material powder and using an ion beam cutting system. The method is characterized by using an oven to accelerate curing and relatively coarse ion beam cutting parameters, and includes the following steps:

[0060] Embedding and mixing: Take a small amount of negative electrode silicon carbon material powder sample and high-purity conductive silver paste, and mix them thoroughly at a volume ratio of 1:5 to ensure that the powder particles are uniformly coated by the silver paste to form a viscous mixture.

[0061] Mold pouring and curing: Slowly pour the mixture into a clean silicone mold. The sample groove in the mold should be 1mm deep, 10mm long, and 5mm wide. Place the mold in an oven at 50℃ for 1 hour to accelerate drying and curing.

[0062] Demolding: After the sample has completely solidified, demolding is performed to obtain a sample block with a regular shape.

[0063] Loading the ion cutting system: Use carbon conductive tape to attach the demolded sample block to the sample preparation stage of the three-ion beam cutting system, ensuring the flat surface closest to the mold is against the sample stage. Adjust the distance and height between the sample stage and the baffle so that the upper end of the sample protrudes 30 μm above the baffle.

[0064] Vacuuming: Start the equipment to evacuate the system until the vacuum level reaches 1×10⁻⁶. −5 mbar.

[0065] First ion cutting: The cutting voltage was set to 8kV, the current to 3.0mA, and the cutting time to 3h.

[0066] Second ion cutting: The cutting voltage was set to 5kV, the current to 2.0mA, and the cutting time to 1h.

[0067] Sample Removal and Analysis: After cutting, release the vacuum and remove the sample. Use conductive tape to attach the ion-cut cross-section of the sample to the scanning electron microscope (SEM) stage, with the observation surface facing upwards. No gold sputtering is required; the cross-section of the silicon-carbon material can be directly analyzed using a scanning electron microscope in conjunction with energy dispersive X-ray spectroscopy (EDS).

[0068] Example 3:

[0069] This embodiment provides a method for preparing cross-sectional samples by embedding lithium-rich manganese-based material powder with conductive carbon paste and then using an ion beam cutting system. The method is characterized by the use of conductive carbon paste, room temperature curing, and relatively fine ion beam cutting parameters. It also demonstrates applications at different mold depths and includes the following steps:

[0070] Embedded mixing: Take a small amount of positive electrode lithium-rich manganese-based material powder sample and high-purity conductive carbon paste, and mix them thoroughly at a volume ratio of 1:3 to ensure that the powder particles are uniformly coated by the carbon paste to form a viscous mixture.

[0071] Mold pouring and curing: Slowly pour the mixture into a clean polyurethane mold. The sample groove in the mold should be 1.5 mm deep, 10 mm long, and 5 mm wide. Place the mold at room temperature for 2 hours to allow it to air dry and cure naturally.

[0072] Demolding: After the sample has completely solidified, demolding is performed to obtain a sample block with a regular shape.

[0073] Loading the ion cutting system: Use carbon conductive tape to attach the demolded sample block to the sample preparation stage of the three-ion beam cutting system, ensuring the flat surface closest to the mold is against the sample stage. Adjust the distance and height between the sample stage and the baffle so that the upper part of the sample protrudes 50 μm above the baffle.

[0074] Vacuuming: Start the equipment to evacuate the system until the vacuum level reaches 1×10⁻⁶. −5 mbar.

[0075] First ion cutting: The cutting voltage was set to 6kV, the current to 2.2mA, and the cutting time to 3h.

[0076] Second ion cutting: The cutting voltage was set to 4kV, the current to 1.5mA, and the cutting time to 1h.

[0077] Sample Removal and Analysis: After cutting, the vacuum is released, and the sample is removed. The ion-cut cross-section of the sample is attached to the scanning electron microscope (SEM) stage with the observation surface facing upwards using conductive tape. No gold sputtering is required; the cross-section of the lithium-rich manganese-based material is directly analyzed using a scanning electron microscope in conjunction with energy dispersive X-ray spectroscopy (EDS).

[0078] Example 4:

[0079] This embodiment provides a method for preparing cross-sectional samples by embedding conductive carbon paste with negative electrode silicon carbide material powder and using an ion beam cutting system. The method is characterized by the use of conductive carbon paste, accelerated curing in an oven, and relatively precise ion beam cutting parameters, and includes the following steps:

[0080] Embedding and mixing: Take a small amount of negative electrode silicon-carbon material powder sample and high-purity conductive carbon paste, and mix them thoroughly at a volume ratio of 1:4 to ensure that the powder particles are uniformly coated by the carbon paste to form a viscous mixture.

[0081] Mold pouring and curing: Slowly pour the mixture into a clean silicone mold. The sample groove of the mold should be 0.8 mm deep, 10 mm long, and 5 mm wide. Place the mold in an oven at 60°C for 1.5 hours to accelerate drying and curing.

[0082] Demolding: After the sample has completely solidified, demolding is performed to obtain a sample block with a regular shape.

[0083] Loading the ion cutting system: Use carbon conductive tape to attach the demolded sample block to the sample preparation stage of the three-ion beam cutting system, ensuring the flat surface closest to the mold is against the sample stage. Adjust the distance and height between the sample stage and the baffle so that the upper end of the sample protrudes 40 μm above the baffle.

[0084] Vacuuming: Start the equipment to evacuate the system until the vacuum level reaches 1×10⁻⁶. −5 mbar.

[0085] First ion cutting: The cutting voltage was set to 7kV, the current to 2.5mA, and the cutting time to 3.5h.

[0086] Second ion cutting: The cutting voltage was set to 4.5kV, the current to 1.8mA, and the cutting time to 1.2h.

[0087] Sample Removal and Analysis: After cutting, release the vacuum and remove the sample. Use conductive tape to attach the ion-cut cross-section of the sample to the scanning electron microscope (SEM) stage, with the observation surface facing upwards. No gold sputtering is required; the cross-section of the silicon-carbon material can be directly analyzed using a scanning electron microscope in conjunction with energy dispersive X-ray spectroscopy (EDS).

[0088] Comparative Examples 1-3:

[0089] Comparative Example 1:

[0090] Compared to Example 1, the difference lies in the use of epoxy resin (comparative mounting material D) for mounting instead of conductive silver paste. Specifically, the ternary cathode material powder is mixed with epoxy resin and cured to form a sample block. The sample block is then mechanically polished to initially expose the cross-section, and then placed in an ion beam cutting system for fine cutting. Before scanning electron microscopy (SEM) observation, the sample cross-section is sputtered with gold (comparative conductive material E). The remaining steps and ion cutting parameters are the same as in Example 1.

[0091] Comparative Example 2:

[0092] Compared to Example 1, the difference lies in the use of epoxy resin (comparative mounting material D) for mounting, and the initial cross-section obtained by mechanical polishing, followed by fine polishing by ion cutting. The key difference is that this comparative example does not undergo any gold sputtering treatment before scanning electron microscopy (SEM) observation; the remaining steps and ion cutting parameters are the same as in Example 1.

[0093] Comparative Example 3:

[0094] Compared to Example 1, the difference lies in that although conductive silver paste (conductive adhesive 1) was used for embedding, a mechanical polishing step was added after the conductive silver paste cured to initially expose the cross-section, followed by ion cutting for fine polishing. The remaining steps and ion cutting parameters are the same as in Example 1.

[0095] Test Examples 1-5:

[0096] Test Example 1: Sample Formability and Demolding Performance Test

[0097] Experimental description:

[0098] This test aims to evaluate the physical molding effect and demolding convenience of samples prepared using different conductive adhesives (conductive silver paste, conductive carbon paste), different powder-to-adhesive volume ratios, and different curing conditions.

[0099] Experimental steps:

[0100] The samples were cured under the curing conditions (room temperature or oven heating) described in Examples 1-4.

[0101] After the curing time is over, demold the mold (silicone or polyurethane).

[0102] During the demolding process, the ease of separation between the sample block and the inner wall of the mold groove is qualitatively assessed, and any adhesion, tearing, or sample block damage is recorded.

[0103] After removing the sample block, visually inspect the geometric integrity of the sample block to determine whether its edges are clear and whether it completely replicates the (10mm×5mm) dimensions of the mold groove.

[0104] Assess the flatness of the bottom of the sample (the surface in contact with the bottom of the mold groove) and the top of the sample (the free surface), and record whether there is obvious warping, collapse or shrinkage.

[0105] Test results:

[0106] Table 1. Evaluation of the moldability and release properties of conductive adhesive embedded samples

[0107] Test object Adhesive type Volume ratio (powder: glue) Curing conditions Demolding status Shape integrity Bottom flatness Top flatness Example 1 Conductive silver paste 1:3 Room temperature 2h Easy to separate, no damage Sharp edges good good Example 2 Conductive silver paste 1:5 50℃1h Easy to separate, no damage Sharp edges good Slight unevenness Example 3 Conductive carbon paste 1:3 Room temperature 2h Slight adhesion, no damage Sharp edges good good Example 4 Conductive carbon paste 1:4 60℃1.5h Easy to separate, no damage Sharp edges good good

[0108] Results analysis:

[0109] Test results show that the liquid conductive adhesive (conductive silver paste or conductive carbon paste) has suitable rheological and curing properties. As shown in Table 1, within a volume ratio range of 1:3 to 1:5, the conductive adhesive can serve as a matrix material, effectively encapsulating and fixing battery powder particles, and can cure at room temperature or under heating (50℃−60℃) conditions to form samples with well-defined geometry (clear edges) and sufficient mechanical strength.

[0110] Meanwhile, the inlay composition exhibits low interfacial adhesion to silicone or polyurethane mold materials, demonstrating excellent demolding performance (primarily characterized by easy separation without damage), ensuring good flatness of the sample bottom (i.e., the surface subsequently bonded to the ion cutting sample stage). This result confirms the technical feasibility of using conductive adhesive instead of traditional epoxy resin for powder inlay to prepare regular samples suitable for subsequent ion cutting.

[0111] Test Example 2: Feasibility Test of Direct SEM Observation (Conductivity Verification)

[0112] Experimental description:

[0113] This test aims to verify whether cross-sectional samples prepared by conductive adhesive mounting, without surface gold sputtering, possess sufficient conductivity to dissipate the accumulated charge generated by electron beam bombardment, thereby meeting the high-quality imaging requirements of scanning electron microscopy (SEM). Example 1 (conductive silver paste mounting, without gold sputtering) and Comparative Example 2 (epoxy resin mounting, without gold sputtering) were selected as comparison objects.

[0114] Experimental steps:

[0115] The cross-sectional samples prepared in Example 1 and Comparative Example 2 were fixed on the SEM sample stage, ensuring good contact between the conductive tape at the bottom of the sample and the metal surface of the sample stage.

[0116] The sample is placed into the SEM sample chamber, and the vacuum level is evacuated to the operating vacuum level specified by the equipment (usually <5×10⁻⁶). −4 Pa).

[0117] Turn on the electron gun and adjust the acceleration voltage to three levels: 5kV, 10kV, and 20kV.

[0118] Focus the sample cross-sectional area at different magnifications (500× to 10000×).

[0119] Observe and record the image quality, focusing on monitoring for typical charging effect phenomena such as image drift, abnormally bright spots, scan line distortion, or discharge stripes.

[0120] In energy dispersive spectroscopy (EDS) analysis mode, a cross-sectional micro-region was selected for point scanning to observe the image stability during fixed-point electron beam irradiation.

[0121] Test results:

[0122] Table 2. SEM Imaging Stability and Charge Effect Evaluation Records

[0123] Test object Accelerating voltage (kV) Magnification Image stability description Observation of charging phenomena Image quality assessment Example 1 5 1000× Image stable, no drift No obvious abnormalities excellent Example 1 10 5000× Image stabilization A faint bright edge may occasionally be seen, but it does not affect the observation. good Example 1 20 10000× Image stable, sharp focus No discharge phenomenon excellent Comparative Example 2 5 500× Slight shaking Abnormally high brightness in localized areas Difference Comparative Example 2 10 2000× Severe drift, difficult to focus Large areas of bright spots appeared, and the scan lines were distorted. Unobservable Comparative Example 2 15 1000× The image is jumping violently Continuous discharge occurs, field of view becomes completely white. fail

[0124] Results analysis:

[0125] Test data show that Example 1, which uses conductive adhesive (such as conductive silver paste) as the mounting substrate, exhibits excellent imaging stability under different accelerating voltages and magnifications.

[0126] The mechanism lies in the fact that a continuous electron transport network is constructed inside the matrix formed after the conductive adhesive has cured. This network encapsulates the battery powder particles and is directly connected to the conductive tape and sample stage at the bottom. When a high-energy electron beam bombards the cross-section of the low-conductivity battery powder (such as the cathode material), the accumulated charge generated can be rapidly conducted to the ground through this conductive matrix network, thereby effectively suppressing the accumulation of surface charge.

[0127] In contrast, Comparative Example 2 uses insulating epoxy resin as the matrix, which cuts off the electron exit path, causing a large accumulation of charge generated by electron beam bombardment on the sample surface, resulting in severe charging effects (manifested as image drift and high-brightness discharge), making normal observation impossible without gold plating.

[0128] In summary, the conductive adhesive embedding scheme proposed in this invention can meet the conductivity requirements of SEM for cross-sectional morphology and energy dispersive spectroscopy analysis of battery powder without additional surface metal sputtering treatment, simplifying the sample preparation process and preserving the original surface state of the sample.

[0129] Test Example 3: Comparison Test of Total Sample Preparation Time (Efficiency Comparison)

[0130] Experimental description:

[0131] This test aims to quantify and compare the time cost of the method of this invention (Example 1) with the conventional epoxy resin mounting method (Comparative Example 1) in the sample preparation stage. The test range is defined as from the moment the powder and matrix material begin to mix until the sample completes all pretreatment steps and is successfully loaded onto the ion beam cutting system sample stage. This period covers processes such as mixing, curing, machining (if any), and sample loading, but does not include the operation time of the ion beam cutting itself.

[0132] Experimental steps:

[0133] Example 1 (conductive silver paste inlay, no polishing required) and Comparative Example 1 (epoxy resin inlay, mechanical polishing) were selected as test objects. Three parallel samples were set up in each group and labeled as E1-1, E1-2, E1-3 and C1-1, C1-2, C1-3, respectively.

[0134] Start the timer and record the start time. ).

[0135] Mixing and curing stage: The example group was mixed with silver paste and air-dried at room temperature; the comparative group was mixed with epoxy resin under vacuum degassing and heat-cured (to ensure the rigor of the comparison, the comparative group used a 60℃ accelerated curing process to shorten the curing time difference). The time points of completion of curing and demolding were recorded.

[0136] Machining stage:

[0137] Example group: No machining is performed, and the process proceeds directly to the next step.

[0138] Comparative group: The insert was mechanically polished using a metallographic polishing machine (using 400#, 800#, and 2000# sandpaper in sequence) until a flat cross-section suitable for ion cutting was exposed. The time points for completion of polishing and cleaning were recorded.

[0139] Sample loading stage: Attach the sample to the ion cutting sample stage and adjust it to the specified height.

[0140] Record the final completion time ( ), calculate the total processing time for each sample. .

[0141] Experimental results:

[0142] Table 3. Comparison of time consumption for each step in the sample preparation stage

[0143] Sample number Group Mixing and curing time (min) Mechanical grinding and cleaning time (min) Time taken for ion cutting sample loading (min) Total preparation time (min) E1-1 Example 1 128 0 8 136 E1-2 Example 1 135 0 12 147 E1-3 Example 1 122 0 9 131 C1-1 Comparative Example 1 165 55 14 234 C1-2 Comparative Example 1 158 72 11 241 C1-3 Comparative Example 1 170 63 15 248

[0144] Results analysis:

[0145] Comparative test data shows that the total preparation time of the sample in Example 1 is shorter than that of Comparative Example 1. As shown in Table 3, the average preparation time of the Example group is about 138 minutes, while the average preparation time of the Comparative Example group is still 241 minutes even with the use of heating to accelerate curing. The method of the present invention shortens the preparation time by about 42%.

[0146] The efficiency improvement mechanism lies in the structural optimization of the sample preparation process by the technical solution of this invention. Traditional methods (Comparative Example 1) are limited by the insulating and embedding properties of epoxy resin, requiring a time-consuming mechanical grinding process to remove surface resin and expose the powder cross-section. Furthermore, the grinding process necessitates frequent cleaning and inspection to prevent human-induced damage. In contrast, this invention utilizes the volume shrinkage and mold-forming characteristics of the liquid conductive adhesive, combined with the deep processing capabilities of ion beam cutting, completely eliminating the mechanical grinding process. The sample block formed after the conductive adhesive cures is of uniform size and can be directly loaded to meet the sample introduction requirements of ion beam cutting, thereby achieving a significant improvement in sample preparation efficiency while ensuring sample quality.

[0147] Test Example 4: Charge Effect Comparison Test (Conductivity Comparison)

[0148] Experimental description:

[0149] This test aims to quantify and compare the anti-charging ability of the method of this invention (Example 1, without gold sputtering) and the conventional method that fails due to insufficient conductivity (Comparative Example 2, epoxy resin mounting, without gold sputtering) during scanning electron microscopy (SEM) observation. The test evaluates the intensity of the charging effect caused by surface charge accumulation and the stable observation window by gradually increasing the operating parameters of the SEM (accelerating voltage and magnification).

[0150] Experimental steps:

[0151] Ion-cut cross-section samples from Example 1 (conductive silver paste inlay, no gold spraying) and Comparative Example 2 (epoxy resin inlay, no gold spraying) were selected.

[0152] Load the sample onto the SEM sample stage, ensuring reliable mechanical and electrical contact between the sample and the sample stage.

[0153] Set the initial parameters of the SEM: accelerating voltage 5kV, magnification 1000×.

[0154] While ensuring focus, the accelerating voltage was gradually increased to 20kV in steps of 1kV with each observation lasting 30s, and the amplification was increased to 10000× in steps of 1000×.

[0155] At each parameter point, record whether the image exhibits charging effects (such as image drift, abnormal brightness, or discharge flicker).

[0156] The critical stability parameter is defined as the SEM operating condition at which sustained image drift or obvious charge accumulation bright spots are first observed under this parameter.

[0157] Experimental results:

[0158] Table 4. Comparison of critical stability parameters for SEM imaging

[0159] serial number Inlay substrate Gold plating The highest voltage (kV) observed during stable operation Stable observation maximum magnification Critical charge effect description Example 1 Conductive silver paste none >20 >10000× No sustained charging phenomenon, image stable Comparative Example 2 Epoxy resin none 6 1500× At 7kV, obvious bright spots of charge accumulation began to appear. Example 1 Conductive silver paste none 15 7000× Slight intermittent edge drift at 16kV Comparative Example 2 Epoxy resin none 9 3000× At 10kV, the image drifts drastically and cannot be focused.

[0160] Results analysis:

[0161] Test results show that the cross-sectional sample prepared in Example 1 exhibits excellent anti-charge properties without gold sputtering, and its stable observed accelerating voltage and amplification are much higher than those of Comparative Example 2, which is inlaid with insulating epoxy resin.

[0162] The innovative mechanism of this invention lies in the use of a liquid conductive adhesive as the matrix material, within which metal or carbon particles construct a low-resistivity electron leakage channel. This channel directly connects the battery powder particles bombarded by the electron beam to the grounded sample stage of the SEM. When the incident electron beam causes localized charge accumulation in the powder material, this charge can be rapidly neutralized through the conductive matrix. This mechanism effectively suppresses the establishment of surface potential, thereby preventing the occurrence of charging effects.

[0163] In contrast, the epoxy resin used in Comparative Example 2 is essentially an electrically insulating material. Once the accelerating voltage or electron beam current density (corresponding to the magnification) increases, the accumulated charge cannot be effectively dissipated, leading to localized electrostatic discharge or surface potential distortion in the sample, directly compromising the imaging quality and data acquisition reliability of SEM. Therefore, this invention solves the charging problem of non-conductive or low-conductive powder materials during SEM observation by introducing a conductive adhesive in the mounting process, achieving efficient detection without gold sputtering.

[0164] Test Example 5: Comparison Test of Total Ion Cutting Time (Surface Smoothness Comparison)

[0165] Experimental description:

[0166] This test aims to investigate the influence of the initial surface smoothness and edge condition of the sample on the ion beam cutting efficiency. The test focuses on comparing the ion beam bombardment time required to obtain the same quality cross-section in Example 2 (conductive silver paste inlay, with the surface naturally shaped by a mold) and Comparative Example 3 (conductive silver paste inlay followed by a mechanical polishing step).

[0167] In theory, mechanical polishing can reduce surface roughness, but for composite systems of soft substrates (solvents) and hard particles (battery powder), mechanical polishing is prone to producing edge chamfers or step differences between materials of different hardness, which will conversely increase the workload of subsequent ion cutting to correct the flatness of the cross section.

[0168] Experimental steps:

[0169] Three cured samples prepared in Example 2 and Comparative Example 3 were selected and labeled as Group E2 and Group C3, respectively.

[0170] The sample was attached to the stage of the ion cutting system and positioned using an optical microscope.

[0171] Adjust the baffle position. For group E2, use the mold forming surface as the reference and make the sample protrude 30μm from the edge of the baffle; for group C3, use the polished surface as the reference and also make the sample protrude 30μm from the edge of the baffle.

[0172] Set ion beam cutting parameters:

[0173] Rough cutting stage: voltage 8kV, current 2.2mA. The goal is to remove the protruding material and eliminate the obvious curtain effect.

[0174] Finishing stage: Voltage 5kV, current 1.5mA. The goal is to remove the striations left by rough cutting and obtain a smooth cross-section.

[0175] The cutting process is initiated, and the cross-sectional state is observed through a real-time monitoring imaging system. The coarse cutting time required from the start of bombardment to the exposure of the complete, undeformed internal structure of the particles is recorded; subsequently, a fine cutting process is performed, and the fine cutting time required to obtain a high-quality, stripe-free cross-section is recorded.

[0176] Calculate the total ion cutting time for each sample.

[0177] Experimental results:

[0178] Table 5. Time Consumption Record of Ion Beam Cutting Process

[0179] Sample number Preprocessing methods Initial edge state Rough cutting time (min) Refinement time (min) Total ion cutting time (min) E2-1 Mold forming Sharp edges, vertical 175 58 233 E2-2 Mold forming Sharp edges, slightly constricted 182 60 242 E2-3 Mold forming Sharp edges, vertical 168 65 233 C3-1 Mechanical grinding The edges are rounded and have scratches. 245 62 307 C3-2 Mechanical grinding The edges are rounded and uneven. 268 75 343 C3-3 Mechanical grinding Localized detachment, step difference 230 60 290

[0180] Results analysis:

[0181] Test data revealed that despite the additional mechanical polishing treatment performed on Example 3, its total ion cutting time was significantly longer than that of Example 2, which was not polished.

[0182] The mechanism lies in the significant difference in hardness between the battery powder and the conductive adhesive. During mechanical polishing, the soft conductive adhesive matrix is ​​easily over-polished, leading to chamfering effects or matrix depressions at the sample edges, thus disrupting the ideal parallelism between the sample surface and the ion beam baffle. In the ion cutting stage, the high-energy ion beam not only needs to remove the target area but also requires considerable time to correct the edge rounding and deep damage layers caused by polishing before a smooth observation section can be exposed.

[0183] Conversely, Example 2 utilizes the natural leveling and curing shrinkage properties of the liquid conductive adhesive in the mold to directly form a sharp edge perpendicular to the sidewall after demolding. This edge adheres tightly to the ion beam baffle, allowing the ion beam to directly act on the effective cutting area and reducing ineffective bombardment time. Therefore, the mechanical grinding step is omitted in this invention, which not only simplifies the process but also improves the processing efficiency of ion beam cutting by maintaining the original sharpness of the sample edge.

[0184] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein; and these modifications or substitutions do not cause the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing cross-sectional samples of powder materials for new energy vehicle batteries, characterized in that, Includes the following steps: S1. Embedded Mixing: The battery powder material to be analyzed is mixed with the liquid conductive adhesive at a preset volume ratio to obtain a viscous mixture; S2, Pouring and Curing: The viscous mixture is poured into the groove of the mold and cured under a preset environment. After demolding, a conductive sample block with a regular shape is obtained. S3. Sample loading: The conductive sample block is attached to the sample stage of the ion beam cutting system, and the position of the conductive sample block is adjusted so that the conductive sample block protrudes from the baffle. S4. Ion cutting: In a vacuum environment, the exposed part of the conductive sample block is cut by ion beam bombardment using an ion beam cutting system to obtain a flat sample cross section. S5. Observation and analysis: Place the cut sample under an electron microscope for microscopic morphology or energy dispersive spectroscopy analysis.

2. The method for preparing cross-sectional samples of new energy vehicle battery powder materials according to claim 1, characterized in that, In step S1, the liquid conductive adhesive is a high-purity conductive silver paste or a high-purity conductive carbon paste; The preset volume ratio of the battery powder material to the liquid conductive adhesive is 1:3-1:

5.

3. The method for preparing a cross-sectional sample of a new energy vehicle battery powder material according to claim 1, characterized in that, In step S2, the mold is a silicone mold or a polyurethane mold with a square groove. The groove has a depth of 0.5mm-1.5mm, a length of 5mm-15mm, and a width of 3mm-8mm.

4. The method for preparing a cross-sectional sample of a new energy vehicle battery powder material according to claim 1, characterized in that, In step S2, the preset environment and curing method include any one of the following: Place at room temperature in a natural environment for at least 2 hours; Place in an oven at 50℃-60℃ for at least 1 hour.

5. The method for preparing a cross-sectional sample of a new energy vehicle battery powder material according to claim 1, characterized in that, In step S3, the specific location of the conductive sample block is as follows: Adjust the distance and height between the conductive sample block and the baffle so that the upper end of the conductive sample block protrudes from the edge of the baffle in the range of 30μm-50μm.

6. The method for preparing a cross-sectional sample of a new energy vehicle battery powder material according to claim 1, characterized in that, In step S4, the vacuum level of the vacuum environment is ≤1×10⁻⁶. −5 mbar.

7. The method for preparing a cross-sectional sample of a new energy vehicle battery powder material according to claim 1, characterized in that, In step S4, the ion cutting adopts a step-by-step cutting method, including a first cutting and a second cutting; The first cut is used for rough cutting, and the process parameters are controlled as follows: voltage 6kV-8kV, current 2.2mA-3.0mA, and cutting time 3.0h-4.0h.

8. The method for preparing a cross-sectional sample of a new energy vehicle battery powder material according to claim 7, characterized in that, The second cut is used for fine grinding, and the process parameters are controlled as follows: voltage 4kV-5kV, current 1.5mA-2.0mA, and cutting time 1h-1.2h.

9. The method for preparing a cross-sectional sample of a new energy vehicle battery powder material according to claim 1, characterized in that, The battery powder material is selected from one of the following: ternary materials, lithium-rich manganese-based materials, or silicon-carbon materials.

10. The method for preparing a cross-sectional sample of a new energy vehicle battery powder material according to claim 1, characterized in that, In step S5, the observation and analysis are performed directly without metal sputtering treatment on the sample cross-section.

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