Particle morphology-dynamics characterization method based on in-situ ct and single particle electrochemistry

Abstract

The application discloses a particle morphology-dynamics characterization method based on in-situ CT and single-particle electrochemistry, relates to the field of electrochemical testing, and comprises the following steps: encapsulating a single-particle microelectrode, a counter electrode and a reference electrode into a micro three-electrode electrochemical cell to seal a test cell; testing the test cell, collecting impedance spectrum data and projection data sequences of target active particles in electrochemical cycles; performing equivalent circuit fitting on the impedance spectrum data to obtain a charge transfer resistance, and calculating an exchange current density of the target active particles; performing linear fitting on a low-frequency diffusion part of the impedance spectrum data to obtain a Warburg coefficient, and calculating a lithium ion diffusion coefficient in the target active particles; performing three-dimensional reconstruction on the projection data sequences to obtain a three-dimensional volume data model and extract three-dimensional morphology parameters of the target active particles; and evaluating material intrinsic dynamics characteristics which are not disturbed by geometric shape changes based on the exchange current density, the diffusion coefficient and the three-dimensional morphology parameters.

Description

Technical Field

[0001] This application relates to the field of electrochemical testing, and in particular to a particle morphology-kinetic characterization method based on in-situ CT and single-particle electrochemistry. Background Technology

[0002] Achieving in-situ, dynamic, and quantitative correlation between electrochemical performance and three-dimensional microstructural evolution at the single-particle scale remains a major technical challenge. Existing mainstream characterization techniques, such as scanning electron microscopy (SEM), while offering high resolution, typically only provide surface, static, and two-dimensional information. Furthermore, the high-vacuum environment and sample preparation process can disrupt the true electrochemical state, making continuous in-situ observation of the same particle impossible. Although some in-situ devices based on microscopy exist, most struggle to simultaneously acquire complete information on the changes in the three-dimensional structure within the particle, let alone accurately correlate real-time measured macroscopic electrochemical curves with the microscopic structural parameters within the particle. In particular, during charge and discharge, particle expansion and fracture significantly alter the effective contact area with the electrolyte, and this dynamic change in geometry is strongly coupled with intrinsic material ion diffusion capabilities, electrochemical reactivity, and other kinetic parameters.

[0003] Current technologies lack effective means to decouple the changes in apparent performance caused by particle morphology and structural evolution from the intrinsic kinetic parameters of the material. This makes it difficult to quantitatively distinguish whether the root cause of battery performance degradation stems from the material's own activity decay or merely from physical contact problems caused by particle breakage. Therefore, developing a technique capable of simultaneous, in-situ, three-dimensional structural imaging and electrochemical measurement of individual active particles under real-world operating conditions, and establishing a quantitative analytical model between structural and kinetic parameters, has become a critical technological bottleneck that urgently needs to be overcome in this field. Summary of the Invention

[0004] The purpose of this application is to provide a particle morphology-kinetic characterization method based on in-situ CT and single-particle electrochemistry, which can effectively solve the problems of existing technologies in achieving in-situ, dynamic, and quantitative correlation between electrochemical performance and three-dimensional microstructure evolution at the single-particle scale, as well as the difficulty in decoupling the apparent performance changes caused by particle morphology and structure evolution from the intrinsic kinetic parameters of the material.

[0005] To achieve the above objectives, this application provides the following solution: Firstly, this application provides a particle morphology-kinetic characterization method based on in-situ CT and single-particle electrochemistry, including: The tip of a tungsten needle coated with insulating resin is welded to a target active particle to obtain a single-particle microelectrode; the target active particle is selected from the electrode material. The single-particle microelectrode, counter electrode, and reference electrode are encapsulated together in a micro three-electrode electrochemical cell, injected with electrolyte, and sealed to form an in-situ electrochemical testing cell. An in-situ electrochemical test cell was placed in a micron-CT device to perform an electrochemical test procedure, and electrochemical impedance spectroscopy data and CT projection data sequences of the target active particles were collected during the electrochemical cycle. The electrochemical impedance spectroscopy data are fitted with an equivalent circuit to obtain the charge transfer resistance, and the exchange current density of the target active particle is calculated according to the first calculation formula. Linear fitting is performed on the low-frequency diffusion portion of the electrochemical impedance spectroscopy data to obtain the Warburg coefficient, and the diffusion coefficient of lithium ions inside the target active particles is calculated according to the second calculation formula. The CT projection data sequence is reconstructed in three dimensions to obtain a three-dimensional volume data model of the target active particle, and the three-dimensional morphology parameters of the target active particle are extracted from the three-dimensional volume data model. Based on exchange current density, diffusion coefficient, and three-dimensional morphology parameters, the intrinsic dynamic properties of materials unaffected by geometric changes are evaluated through an analytical model.

[0006] Optionally, the single-particle microelectrode, counter electrode, and reference electrode are encapsulated together in a micro three-electrode electrochemical cell, injected with electrolyte, and sealed to form an in-situ electrochemical testing cell, specifically including: The micro three-electrode electrochemical cell uses a polyimide tube as the cell body. A top cover with the single-particle microelectrode is inserted into one end of the polyimide tube. After injecting electrolyte, a top cover with a counter electrode and a reference electrode is inserted into the other end of the polyimide tube. All interfaces and gaps are sealed and cured with epoxy resin to form an in-situ electrochemical test cell. The counter electrode and the reference electrode are tungsten needles with lithium metal sheets fixed at their tips. The micro three-electrode electrochemical cell is a micro three-electrode electrochemical cell with an X-ray transmission window.

[0007] Optionally, the formula expression for the first calculation formula is: ; in, j 0 For current density, j For exchange current density, α For the transmission coefficient, F It is Faraday's constant. R The gas constant is T For temperature, η This is an overpotential.

[0008] Optionally, the formula expression for the second calculation formula is: ; in, R The gas constant is T For temperature, σ The effective area of ​​the electrode. F It is Faraday's constant. is the diffusion coefficient.

[0009] Optionally, the CT projection data sequence is reconstructed in three dimensions to obtain a three-dimensional volumetric data model of the target active particle, specifically including: The target active particles were three-dimensionally imaged using a submicron CT system. The acquired CT projection sequences were then imported into Avizo software for filtering, alignment, and three-dimensional reconstruction to obtain three-dimensional volumetric data models of the target active particles at different times.

[0010] Optionally, the tip of a tungsten needle coated with insulating resin is welded to the target active particle to obtain a single-particle microelectrode, specifically including: A target active particle is selected in a dual-beam scanning electron microscope, and the tip of a tungsten needle coated with insulating resin is welded to the target active particle to form a single-particle microelectrode with the tungsten needle as the current collector.

[0011] According to the specific embodiments provided in this application, the following technical effects are disclosed: This application provides a particle morphology-kinetic characterization method based on in-situ CT and single-particle electrochemistry. By combining in-situ micron-level CT with single particles, simultaneous, in-situ, three-dimensional structural imaging and electrochemical measurements of individual active particles can be performed under real-world working conditions. In the characterization method, the acquired electrochemical impedance spectroscopy data and CT projection data sequences are processed and analyzed to calculate key parameters such as exchange current density and diffusion coefficient. The three-dimensional morphology parameters of the target active particle are extracted, and the intrinsic kinetic properties of the material, unaffected by geometric shape changes, are evaluated using an analytical model. This achieves an in-situ, dynamic, and quantitative correlation between electrochemical performance and the evolution of the three-dimensional microstructure. Attached Figure Description

[0012] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0013] Figure 1 A schematic flowchart of a particle morphology-kinetic characterization method based on in-situ CT and single-particle electrochemistry provided in an embodiment of this application; Figure 2A diagram of a micron-CT device provided in an embodiment of this application; Figure 3 Micrometer CT Cell Design Provided in an Embodiment of this Application Figure 1 ; Figure 4 Micrometer CT Cell Design Provided in an Embodiment of this Application Figure 2 ; Figure 5 An EIS diagram of a single-particle lithium intercalation process provided in an embodiment of this application; Figure 6 This is a single-particle lithium intercalation exchange current density diagram provided in an embodiment of this application; Figure 7 The graph shows the change in single-particle volume and surface area as a function of lithium intercalation, according to an embodiment of this application. Detailed Implementation

[0014] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0015] With the rapid development of electric vehicles, large-scale energy storage, and other fields, higher requirements are being placed on the energy density and cycle life of energy storage devices such as lithium-ion batteries. The overall performance of a battery fundamentally depends on the microscopic behavior of its internal active particles during charging and discharging. Therefore, directly observing and understanding the dynamic evolution of active particles under operating conditions at the microscopic scale, such as the volume expansion caused by lithium-ion insertion and extraction, and the generation and propagation of cracks, is of vital importance for revealing battery failure mechanisms and guiding the design of high-performance electrode materials.

[0016] The purpose of this application is to provide a particle morphology-kinetic characterization method based on in-situ CT and single-particle electrochemistry, which can effectively solve the problems of existing technologies in achieving in-situ, dynamic, and quantitative correlation between electrochemical performance and three-dimensional microstructure evolution at the single-particle scale, as well as the difficulty in decoupling the apparent performance changes caused by particle morphology and structure evolution from the intrinsic kinetic parameters of the material.

[0017] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0018] Example 1 like Figure 1 As shown, this embodiment provides a particle morphology-kinetic characterization method based on in-situ CT and single-particle electrochemistry, including: Step 1: Weld the tip of a tungsten needle coated with insulating resin to the target active particle to obtain a single-particle microelectrode; the target active particle is selected from the electrode material. Step 2: The single-particle microelectrode, counter electrode, and reference electrode are encapsulated together in a micro three-electrode electrochemical cell, electrolyte is injected, and the cell is sealed to form an in-situ electrochemical testing cell. Step 3: Place the in-situ electrochemical test cell in the micron-CT device to perform the electrochemical test program, and collect the electrochemical impedance spectroscopy data and CT projection data sequence of the target active particles during the electrochemical cycle; Step 4: Perform equivalent circuit fitting on the electrochemical impedance spectroscopy data to obtain the charge transfer resistance, and calculate the exchange current density of the target active particle according to the first calculation formula; Step 5: Perform linear fitting on the low-frequency diffusion portion of the electrochemical impedance spectroscopy data to obtain the Warburg coefficient, and calculate the diffusion coefficient of lithium ions inside the target active particles according to the second calculation formula; Step 6: Perform three-dimensional reconstruction on the CT projection data sequence to obtain a three-dimensional volume data model of the target active particle, and extract the three-dimensional morphology parameters of the target active particle from the three-dimensional volume data model; Step 7: Based on the exchange current density, diffusion coefficient, and three-dimensional morphology parameters, evaluate the intrinsic dynamic properties of the material that are not affected by changes in geometry by using an analysis model.

[0019] In some embodiments, when performing steps 1-7, the specific steps may be as follows: In a dual-beam scanning electron microscope, a target active particle is precisely located and selected from the electrode material; then, a robotic arm is used to weld the tip of a tungsten needle coated with insulating resin to the target active particle, thereby preparing an independent single-particle microelectrode that can be used for electrochemical testing. Inside an inert atmosphere glove box, a single-particle microelectrode, serving as the working electrode, is packaged together with a prepared lithium metal counter electrode and a reference electrode in a specially designed micro three-electrode electrochemical cell with a high X-ray transmission window (such as a polyimide tube). A measured amount of electrolyte is then injected into the cell. Epoxy resin and other sealing materials are used to rigorously seal the electrode leads and cell joints, ensuring that the electrolyte does not leak and that the cell maintains stable performance during CT rotational scanning and long-term testing.

[0020] The sealed in-situ electrochemical cell is placed in the micro / nano CT sample stage and connected to the electrochemical workstation. During the operation of the set electrochemical program, the micro / nano CT device is simultaneously activated to perform intermittent or continuous X-ray scanning on the target particles, realizing the time-series synchronous acquisition of electrochemical signals and three-dimensional structural images.

[0021] Equivalent circuit fitting was performed on the synchronously acquired electrochemical impedance spectroscopy to obtain the charge transfer resistance of the single particle under a specific charging state.

[0022] Through the first calculation formula Calculate its exchange current density; in, j 0 Current density (A / m) 2 ), j Exchange current density (A / m) 2 ), α For the transmission coefficient, F It is the Faraday constant (96485 C / mol). R It is the gas constant (8.314 J / (mol·K)). T Temperature (K) η This is an overpotential (V).

[0023] Analysis of the low-frequency diffusion region of the impedance spectrum revealed a linear relationship between the imaginary part (-Z'') and the real part (Z'), which is the Warburg impedance region. The slope of this linear relationship is related to the chemical diffusion coefficient (D) of lithium ions in the electrode active material.

[0024] Through the second calculation formula Calculate the diffusion coefficient of lithium ions within the particles.

[0025] in, σ Effective electrode area (cm²) 2 σ is obtained by linearly fitting EIS low-frequency data. The diffusion coefficient is given. The EIS results for the single-particle lithium intercalation process are as follows: Figure 5 As shown.

[0026] The synchronously acquired CT projection data sequence was reconstructed in three dimensions using Avizo software to obtain a high-precision three-dimensional volumetric data model of the target active particle at different times. From this model, the evolution sequence of key morphological parameters over time, such as the volume, surface area, contact area with electrolyte, and volume and surface area of ​​internal cracks of the target active particle, was quantitatively extracted.

[0027] The intrinsic kinetic parameters (exchange current density and diffusion coefficient) at the same time point are correlated with three-dimensional morphology parameters. By establishing an analytical model, the effects of geometric factors such as the increase in effective reaction area due to particle expansion and the exposure of new active surfaces due to crack formation on the measured apparent exchange current density and diffusion coefficient are distinguished and quantified, thereby approximating and evaluating the intrinsic kinetic properties of the material that are not affected by changes in geometry.

[0028] In one specific embodiment, the particle morphology-kinetic characterization method based on in-situ CT and single-particle electrochemistry can be as follows: Obtain the exchange current density of SiOC particles (e.g.) Figure 6 (As shown).

[0029] Specifically, the SiOC to be studied is dispersed on a conductive substrate and placed in the sample stage of a dual-beam scanning electron microscope (DEM). In SEM mode, individual active particles with the size and morphology matching the research target are identified. Switching to FIB mode, a layer of platinum or carbon is deposited near the target particle using a gas injection system as a welding medium. A tungsten probe with its tip pre-coated with insulating resin is manipulated to bring its tip into contact with the platinum layer deposited on the particle. A small current or mechanical pressure is applied using the ion beam of the FIB or a nanomanipulator on the probe stage to achieve a firm weld between the tungsten needle tip and the particle. Thus, a "single-particle microelectrode" using a tungsten needle as the current collector and a single active particle as the working medium is completed. The insulating resin layer is used to prevent side reactions between the tungsten needle shaft and the electrolyte during operation.

[0030] Then, the in-situ CT electrochemical cell (i.e., the in-situ electrochemical test cell) is assembled and sealed, such as... Figure 4 As shown, the details are as follows: Prepare a polyimide tube with an inner diameter of 4mm and a fixed length of 30mm as the cell body. This material has extremely low X-ray absorption. Fabricate two polyetheretherketone (PEEK) top caps with precision through-holes for electrode fixation and sealing. Prepare the counter and reference electrodes: Securely wrap a small piece of lithium metal around the tips of two tungsten needles using tweezers. Carefully hold a tungsten needle with a pre-welded single particle (the particle-free end) using ceramic tweezers and insert it through the through-hole in the center of the top cap. Initially fix and seal it using the sealing rubber ring inside the top cap and the external fastening bolts. Adjust the position of the tungsten needle so that its tip (the particle-containing end) extends into the center of the predetermined cell space, approximately 1-2mm from the inner wall of the top cap. Holding the top cap with the working electrode installed, slowly slide one end of the polyimide tube onto the raised sealing ring of the top cap. Using a disposable syringe, draw an appropriate amount of lithium-ion battery electrolyte and slowly inject it along the inner wall of the polyimide tube until the liquid level reaches approximately 2 / 3 of the tube's length. This operation avoids the formation of air bubbles. Holding the working electrode cap, tilt the entire device at approximately 60° to prevent electrolyte overflow from the other end. Carefully insert the other cap, already fitted with the counter and reference electrodes, into the polyimide tube from the other end and push it into a sealed position. Ensure the lithium plates of the two electrodes are close but not in contact with the working electrode particles. Remove the preheated two-component epoxy resin to a fluid state from the glove box oven. Using a fine needle or toothpick, apply the epoxy resin in small amounts multiple times to the connections between the two caps and the polyimide tube, as well as the gaps between the tungsten needles of the three electrodes and the through-holes in the caps. The resin will seep into the gaps due to capillary action, achieving an absolute seal after curing. Let the assembled in-situ CT cell stand in the glove box for at least 12 hours to ensure the epoxy resin is completely cured and the cell reaches a mechanically and electrochemically stable state.

[0031] The in-situ electrochemical test cell was placed in such a position as Figure 2 The micron-scale CT device shown is used to perform an electrochemical testing procedure to acquire electrochemical impedance spectroscopy data and CT projection data sequences of the target active particles during the electrochemical cycle, as detailed below: The in-situ CT pool after settling (e.g.) Figure 4 (As shown) Remove the sample from the glove box and install it on the sample rotation stage of the micro / nano CT. Connect the ends of the three electrodes to the working, counter, and reference electrode interfaces of the electrochemical workstation, respectively. Place the electrochemical cell system in a grounded electromagnetic shielding box to eliminate the influence of external electromagnetic interference on the weak single-particle current signal. The entire shielding box is placed on an air-bearing vibration-isolated optical platform to isolate ground vibration and ensure the stability of high-resolution CT imaging. Set the test program of the electrochemical workstation, and after standing at the open circuit potential for 1 hour, perform constant current charge-discharge cycles. After standing for 30 minutes, perform electrochemical impedance spectroscopy tests under different charge states. Perform micron-level CT scans at specific time points during the electrochemical program's execution. Finally, a three-dimensional morphology and correlation analysis is performed, which can be done as follows: To quantitatively characterize the three-dimensional morphology evolution of SiO@C single particles during lithium intercalation, voxel-level spatial registration was performed on the three-dimensional reconstructed data under multiple potential states using Avizo software. Since tungsten needles are chemically inert and exhibit excellent mechanical stability, their morphology does not change significantly during charge and discharge; therefore, they were used as spatial reference points. A rigid registration algorithm (ICP iterative closest point) was used to align the particle volume data of different lithium intercalation states to the same coordinate system. The particle surface / volume information was extracted using a grayscale threshold segmentation algorithm in Avizo software, and the calculated surface area was 376 μm². 2 The volume is 282μm 3 This is consistent with the theoretical value of an ideal sphere (a diameter of 8 μm corresponds to a surface area of ​​201 μm). 2 Volume 268μm 3 The deviation stems from the actual particle surface roughness and non-strict spherical geometric characteristics, meeting the quantitative analysis requirements of submicron-level in-situ imaging.

[0032] like Figure 7 As shown, a Princeton electrochemical workstation was used to perform constant current discharge (-1 nA) on a SiOx@C single-particle electrode to drive lithium ion insertion into the particle. Initially, the open-circuit voltage of the system was 1.65 V, representing the state of the unintercalated particles. Subsequently, in-situ imaging was performed in a submicron CT system (X-ray source voltage 80 kV, power 70 W): the geometric magnification (100 ×) was optimized by precisely adjusting the distance between the X-ray source and the sample (<1 mm) and the detector position, and manual calibration was performed to ensure that the sample tube was centered in the imaging field of view (0° and 90° viewing angle deviation <0.1°). The exposure time was dynamically adjusted according to the signal intensity at the center of the field of view (typical value 2 s / frame) to stabilize it >5000 counts. After selecting a suitable filter, scanning was performed, and finally, a full-angle scan from -180° to 180° was completed (a total of 401 projected frames), with an imaging resolution of 360 nm.

[0033] During the discharge process, the above CT scan procedure was repeated at cutoff potentials of 1.45V, 0.7V, and 0.005V to ensure that the imaging parameters (voltage / power / geometric configuration) were strictly consistent. Gray-scale thresholding and 3D reconstruction were performed on the data at different potentials using Avizo software. Quantitative analysis showed that as the lithium-ion embedding depth increased, the SiOx@C particle volume increased from the initial 282μm. 3 Expand to the lithium intercalation endpoint of 426 μm 3 (Expansion rate 51.1%), surface area increased from 376 μm 2 Increased to 481μm 2 (Increase of 28.0%), details are as follows Figure 7 As shown.

[0034] The three-dimensional morphological evolution shows that the particle surface gradually becomes smoother from an initial rough and porous structure, indicating that the lithiation process is accompanied by surface stress release and densification phenomena caused by volume expansion. By temporally coupling electrochemical excitation and submicron CT in-situ imaging, the synchronous dynamic analysis of the lithiation kinetics and micromorphological evolution of a single-particle electrode was achieved for the first time. This verifies the high spatiotemporal resolution advantage of the combined platform in the study of interface behavior of lithium-ion battery anode materials and provides a methodological basis for revealing multi-scale structural failure mechanisms.

[0035] The electrochemical impedance spectroscopy obtained from the experiment was fitted with an equivalent circuit using ZView. The equivalent circuit includes solution resistance, charge transfer resistance, double-layer capacitance, and a Warburg element reflecting diffusion. Exchange current density calculation: The charge transfer resistance was obtained from the fitting results. Combined with parameters such as the test temperature and the effective surface area of ​​the particle (calculated from the CT 3D model), these parameters were substituted into the relevant formulas of the Butler-Volmer equation to calculate the exchange current density of the particle in its current state. Figure 7 As shown. Diffusion coefficient estimation: A linear fit is performed on the linear portion (Warburg region) of the low-frequency region of the impedance spectrum to obtain the Warburg coefficient. Combined with geometric parameters such as particle radius, the diffusion coefficient of lithium ions in the particles can be calculated.

[0036] Example 2 This embodiment provides an in-situ electrochemical testing cell, comprising: a cell body, a first top cover, a second top cover, a working electrode, a counter electrode, a reference electrode, and a sealing component; the cell body is a tube made of X-ray transmission material; the working electrode is a single-particle microelectrode, which passes through the first top cover and extends into the cell body; the counter electrode and the reference electrode are tungsten needles with lithium metal sheets fixed at their tips, which pass through the second top cover and extend into the cell body; the first top cover, the second top cover, and the two ends of the cell body are sealed together by the sealing component; the working electrode, the counter electrode, and the reference electrode are fixed and connected to an external circuit through through holes and fastening bolts on the first and second top covers.

[0037] The pool body is a polyimide tube, the first and second top covers are made of polyetheretherketone, and the sealing components are epoxy resin or sealing rubber rings.

[0038] When assembling the in-situ electrochemical test cell, carefully pick up the non-particle end of the single-particle microelectrode with tweezers and insert it into the top cover from the protrusion, so that the distance between the single-particle end and the top cover is only 1-2mm. Hold the top cover with one hand and a pre-cut polyimide tube (4mm in diameter) of a fixed length (30mm, not exceeding 30mm) with the other hand. Insert the top cover with the welded tungsten needle into the polyimide tube. Prepare two additional tungsten needles for the electrode. Cut a small piece of lithium sheet and fix it to the tip of the tungsten needle with tweezers (ensure it is secure and prevents it from falling off). Insert the reference + counter electrode into the top cover, with the needle length 35mm and 15mm exposed, so that the lithium sheet is close to the particle. Use a disposable syringe or a pointed tip to pull it thinner. Carefully inject lithium-ion battery electrolyte into the polyimide tube along the tube wall using a dropper. The electrolyte volume should be 2 / 3 of the tube. Install the top cap with the reference + counter electrode and the other end of the polyimide tube: Hold the top cap at a 60° angle upwards with the working electrode end to prevent electrolyte overflow. Carefully insert the top cap with the reference + counter electrode into the polyimide tube. Add epoxy resin taken from the oven in small amounts to the connection between the tube and the top cap, as well as the connection between the working / reference / counter electrode and the top cap, to seal the cell and fix the electrode. All the above installation procedures are carried out in a glove box. Do not shake the installed single-particle CT cell. Let it stand in the glove box for ≥12 hours before conducting in-situ single-particle electrochemical CT experiments.

[0039] Example 3 This embodiment provides an electrochemical kinetic characterization system based on in-situ micron-CT combined with single-particle imaging, including: an in-situ electrochemical test cell, a micron-CT device, an electrochemical workstation, an electromagnetic shielding box, and a vibration isolation test platform; the in-situ electrochemical test cell is installed on the sample stage of the micron-CT device; the electrodes of the in-situ electrochemical test cell are connected to the electrochemical workstation; the entire test system is placed inside the electromagnetic shielding box, and the electromagnetic shielding box is placed on the vibration isolation test platform.

[0040] Among them, such as Figure 3 As shown, the micron-CT device is a high-resolution micro / nano-CT system with sub-micron resolution, used to perform time-series CT scans on single particles within the in-situ electrochemical test cell.

[0041] In summary, this application has the following technical effects: 1) This application presents a single-particle charge-discharge in-situ characterization method based on micro-nano CT, which realizes true single-particle, in-situ, three-dimensional dynamic characterization: by combining micro-nano electrode fabrication technology with in-situ CT electrochemical cell technology, it is the first time that electrochemical cycling and synchronous three-dimensional non-destructive observation of the same active particle are realized in an electrolyte environment, and the data have unique correspondence.

[0042] 2) This application presents a single-particle charge-discharge in-situ characterization method based on micro / nano CT, providing a quantitative analytical dimension. It not only observes particle breakage but also accurately measures the volume and surface area increments of the cracks; it not only measures the degradation of electrochemical performance but also decomposes the degradation into geometric and intrinsic contributions. This represents a leap from qualitative to quantitative understanding of "how particles fail."

[0043] 3) This application presents a single-particle charge-discharge in-situ characterization method based on micro / nano-CT, decoupling structural evolution from kinetic processes: The core contribution of this application lies in establishing a quantitative bridge between structural and performance parameters through spatiotemporally synchronized data correlation, solving the long-standing problem of being unable to distinguish the root causes of performance changes. This provides direct decision support value for guiding material modification, such as optimizing particle size and morphology to suppress cracking. The system boasts high integration and strong practicality: the designed in-situ cell is reliably sealed, highly compatible, and the method flow is clear and reproducible, providing a powerful and universal standardized research tool for fundamental research on battery materials.

[0044] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0045] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. Furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A particle morphology-kinetic characterization method based on in-situ CT and single-particle electrochemistry, characterized in that, include: The tip of a tungsten needle coated with insulating resin is welded to the target active particle to obtain a single-particle microelectrode. The target active particles are selected from the electrode material; The single-particle microelectrode, counter electrode, and reference electrode are encapsulated together in a micro three-electrode electrochemical cell, injected with electrolyte, and sealed to form an in-situ electrochemical testing cell. An in-situ electrochemical test cell was placed in a micron-CT device to perform an electrochemical test procedure, and electrochemical impedance spectroscopy data and CT projection data sequences of the target active particles were collected during the electrochemical cycle. The electrochemical impedance spectroscopy data are fitted with an equivalent circuit to obtain the charge transfer resistance, and the exchange current density of the target active particle is calculated according to the first calculation formula. Linear fitting is performed on the low-frequency diffusion portion of the electrochemical impedance spectroscopy data to obtain the Warburg coefficient, and the diffusion coefficient of lithium ions inside the target active particles is calculated according to the second calculation formula. The CT projection data sequence is reconstructed in three dimensions to obtain a three-dimensional volume data model of the target active particle, and the three-dimensional morphology parameters of the target active particle are extracted from the three-dimensional volume data model. Based on exchange current density, diffusion coefficient, and three-dimensional morphology parameters, the intrinsic dynamic properties of materials unaffected by geometric changes are evaluated through an analytical model.

2. The particle morphology-kinetic characterization method based on in-situ CT and single-particle electrochemistry according to claim 1, characterized in that, The single-particle microelectrode, counter electrode, and reference electrode are encapsulated together in a micro three-electrode electrochemical cell, injected with electrolyte, and sealed to form an in-situ electrochemical testing cell, specifically comprising: The micro three-electrode electrochemical cell uses a polyimide tube as the cell body. A top cover with the single-particle microelectrode is inserted into one end of the polyimide tube. After injecting electrolyte, a top cover with a counter electrode and a reference electrode is inserted into the other end of the polyimide tube. All interfaces and gaps are sealed and cured with epoxy resin to form an in-situ electrochemical test cell. The counter electrode and the reference electrode are tungsten needles with lithium metal sheets fixed at their tips. The micro three-electrode electrochemical cell is a micro three-electrode electrochemical cell with an X-ray transmission window.

3. The particle morphology-kinetic characterization method based on in-situ CT and single-particle electrochemistry according to claim 1, characterized in that, The formula expression for the first calculation formula is: ； in, j 0 For current density, j For exchange current density, α For the transmission coefficient, F It is Faraday's constant. R The gas constant is... T For temperature, η This is an overpotential.

4. The particle morphology-kinetic characterization method based on in-situ CT and single-particle electrochemistry according to claim 1, characterized in that, The formula expression for the second calculation formula is: ； in, R The gas constant is... T For temperature, σ The effective area of ​​the electrode. F It is Faraday's constant. is the diffusion coefficient.

5. The particle morphology-kinetic characterization method based on in-situ CT and single-particle electrochemistry according to claim 1, characterized in that, The CT projection data sequence is reconstructed in three dimensions to obtain a three-dimensional volumetric data model of the target active particles, specifically including: The target active particles were three-dimensionally imaged using a submicron CT system. The acquired CT projection sequences were then imported into Avizo software for filtering, alignment, and three-dimensional reconstruction to obtain three-dimensional volumetric data models of the target active particles at different times.

6. The particle morphology-kinetic characterization method based on in-situ CT and single-particle electrochemistry according to claim 1, characterized in that, The tip of a tungsten needle coated with insulating resin is welded to the target active particle to obtain a single-particle microelectrode, specifically including: A target active particle is selected in a dual-beam scanning electron microscope, and the tip of a tungsten needle coated with insulating resin is welded to the target active particle to form a single-particle microelectrode with the tungsten needle as the current collector.

Images