In-situ electrochemical transmission kikuchi diffraction testing device and method for positive electrode material

Abstract

The present application relates to the field of transmission Kikuchi diffraction test and battery technology, and particularly relates to a kind of in-situ electrochemical transmission Kikuchi diffraction test device and method of positive electrode material.The test device is composed of battery positive electrode slice to be measured, FIB half carrier network for carrying and fixing battery positive electrode slice to be measured, carrier network frame for fixing FIB half carrier network, nanomanipulator for forming electrochemical loop, electrochemical workstation, the test method comprises: preparing battery positive electrode slice to be measured;Preparation of negative electrode, negative electrode current collector and solid electrolyte;The installation of battery positive electrode slice to be measured and test device;Transmission Kikuchi diffraction test under in-situ electrochemical condition.The present application can be used in various models of scanning electron microscope, in the state of loading in-situ electrochemistry, transmission Kikuchi diffraction characterization is carried out to positive electrode particles, and the orientation, shape and size information of crystal grain under different potential states are obtained, which provides support for the development of positive electrode material.

Description

Technical Field

[0001] This invention relates to the fields of transmission Kikuchi diffraction testing and battery technology, specifically to an in-situ electrochemical transmission Kikuchi diffraction testing device and method for cathode materials. Background Technology

[0002] Lithium-ion battery cathode materials, such as lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, lithium nickel cobalt manganese oxide, or lithium nickel cobalt aluminum oxide, are all crystalline cathode materials. Except for lithium iron phosphate, which shows almost no significant crystal structure change during charge and discharge, other high-capacity mono- or multi-component lithium oxides exhibit electrochemical performance degradation due to crystal structure deterioration during charge and discharge. Phase transitions and microcracks generated during cycling are the main factors leading to the decline in the cycle performance of cathode materials. The former is closely related to its lattice evolution, while the latter is mainly affected by primary particles. Therefore, it is necessary to analyze the crystal shape, orientation, and size of primary particles, as well as the phase transitions and stress states during charge and discharge.

[0003] Electron backscatter diffraction (EBSD) is a technique based on scanning electron microscopy that uses Kikuchi patterns generated by backscattered electron diffraction to analyze the crystal structure and orientation information of a sample. Transmission Kikuchi diffraction (TKD) is a special form of EBSD that collects Kikuchi patterns generated by transmission electron diffraction for analysis. Because the interaction area between transmitted electrons and the sample is smaller, TKD technology improves the spatial resolution from the sub-micron level of ordinary EBSD to the nanometer level, enabling the analysis of cathode materials with particle sizes ranging from tens to hundreds of nanometers. However, it cannot achieve real-time observation and in-situ tracking under electrochemical conditions.

[0004] The main problem with in-situ electrochemical transmission Kikuchi diffraction (TKD) testing is that traditional methods involve charging and discharging the battery to a certain voltage, disassembling the battery, removing the electrodes, and preparing a TKD sample using focused ion beam (FIB, also known as dual-beam electron microscopy) for testing. To obtain TKD results under different charge-discharge states, a series of batteries must be prepared and disassembled for testing under different charge-discharge states. It is not possible to observe the changes at a specific location on the same sample during the charge-discharge process. Summary of the Invention

[0005] To address the aforementioned shortcomings in the existing technology, the present invention aims to provide an in-situ electrochemical transmission Kikuchi diffraction testing device and method for cathode materials. This device and method can perform transmission Kikuchi diffraction characterization on cathode materials with primary particles of tens to hundreds of nanometers in size during the charging and discharging process.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] An in-situ electrochemical transmission Kikuchi diffraction testing device for cathode materials comprises a cathode sheet to be tested, a FIB half-segmentation grid for supporting and fixing the cathode sheet, a grid frame for fixing the FIB half-segmentation grid, a nano-manipulator for forming an electrochemical circuit, and an electrochemical workstation. The specific structure is as follows:

[0008] The positive electrode sheet of the battery under test has a protective layer, a positive electrode material, a thin region, and a positive electrode current collector. The protective layer is located on top of the positive electrode material, and the positive electrode current collector is located on the left and right sides of the positive electrode material and the protective layer. The height of the positive electrode current collector is the same as the height of the positive electrode material with the protective layer, and the positive electrode current collector is integrated with the positive electrode material. The upper half of the positive electrode material is a thin region, which is integrated with the protective layer.

[0009] Copper pillars are evenly distributed on the FIB semi-distribution grid. Each copper pillar has a copper pillar pit. SiO2 insulating layers are deposited on both sides of the copper pillar pit. The SiO2 insulating layers on both sides of the copper pillar pit are symmetrical and their upper surfaces are on the same horizontal plane. The positive electrode sheet of the battery under test is vertically straddled on the top of the copper pillar near the vertical side of the two SiO2 insulating layers. The positive electrode sheet of the battery under test is fixedly connected to the SiO2 insulating layers by SiO2 welding agent.

[0010] The carrier frame consists of a carrier frame body, bolts, carrier frame pressure plate, and carrier frame recess. Carrier frame recesses for assembly and positioning are opened on both sides of the lower part of the carrier frame body. The FIB half carrier is installed at one end of the carrier frame pressure plate, and the carrier frame pressure plate is fixed to the middle of the carrier frame body by bolts.

[0011] The first nanomanipulator contacts the current collector of the positive electrode of the battery under test, and the second nanomanipulator contacts the bottom of the thin sheet of the positive electrode of the battery under test, forming a complete electrochemical circuit. The electron beam generated by the dual-beam electron microscope interacts with the thin area of ​​the thin sheet of the positive electrode of the battery under test, and the resulting diffraction signal is received by the EBSD probe. The electrochemical workstation is connected to the first nanomanipulator and the second nanomanipulator respectively, and the battery under test is charged and discharged and the open circuit voltage is measured through the electrochemical workstation.

[0012] The in-situ electrochemical transmission Kikuchi diffraction testing device for the cathode material further includes a sample stage, which has a sample stage groove and spring positioning beads. A mesh frame is inserted into the sample stage groove, and the mesh frame recess corresponds to the spring positioning beads on both sides of the sample stage groove at one end of the sample stage. The mesh frame recess and the spring positioning beads engage to fix the mesh frame in the sample stage groove, and the sample stage is mounted on the scanning electron microscope sample stage base.

[0013] The in-situ electrochemical transmission Kikuchi diffraction test device for the cathode material has a grid frame with an angle of 20 degrees to the horizontal plane, that is, the direction of movement of the grid frame when it is inserted into the groove of the sample stage has an angle of 20 degrees to the horizontal plane.

[0014] The in-situ electrochemical transmission Kikuchi diffraction testing device for the cathode material is used to form the first and second nanomanipulators of the electrochemical pathway. The first and second nanomanipulators use metals Pt, Au, or W as probes with a tip diameter not exceeding 5 μm. The first and second nanomanipulators are mounted on the sample stage base of the scanning electron microscope.

[0015] The in-situ electrochemical transmission Kikuchi diffraction testing device for the cathode material has a protective layer made of materials including but not limited to Pt, Au, or W, and the protective layer is one or two layers with a thickness of 2~3μm; the cathode current collector is a metal column, and the cathode current collector is made of materials including but not limited to Pt, Au, or W.

[0016] An in-situ electrochemical transmission Kikuchi diffraction method for positive electrode materials includes the following steps:

[0017] Step 1, Prepare the positive electrode sheet of the battery to be tested:

[0018] 1-1. Take positive electrode particles and add them to anhydrous ethanol. After ultrasonic dispersion, a dispersion is obtained. Use a dropper to draw the dispersion and drop it onto a clean silicon wafer substrate. Place it in a vacuum oven to dry thoroughly.

[0019] 1-2, The dried positive electrode particles and silicon wafer substrate are transferred to a dual-beam electron microscope, and a protective layer and a positive electrode current collector are deposited on the outside of the positive electrode particles;

[0020] 1-3, the protective layer is located on top of the positive electrode particle, the positive electrode current collector is located on the left and right sides of the positive electrode particle and the protective layer, the height of the positive electrode current collector is the same as the height of the positive electrode particle with the protective layer, and the positive electrode current collector and the positive electrode particle are connected as one.

[0021] 1-4. A copper pillar recess is dug on the top of the copper pillar of the FIB semi-distributed grid using a focused ion beam, and SiO2 insulating layers are deposited on both sides of the copper pillar recess. The SiO2 insulating layers on both sides of the copper pillar recess are symmetrical and their upper surfaces are on the same horizontal plane.

[0022] 1-5. Using a focused ion beam, the portion of the positive electrode particle not covered by the protective layer is cut off from the top to form a thin positive electrode sheet of the battery under test, which is separated from the silicon wafer substrate and lifted out by a robotic arm. The robotic arm is then manipulated to place the thin positive electrode sheet of the battery under test vertically on the upper end of the SiO2 insulating layer on the side of the top of the arc-shaped copper pillar. SiO2 is deposited as a welding agent at the contact position between the two to fix the thin positive electrode sheet of the battery under test to the SiO2 insulating layer on the copper pillar.

[0023] 1-6. After reducing the thickness of the positive electrode sheet of the battery under test to 400~600nm using a focused ion beam, a portion of the positive electrode material at the bottom of the positive electrode sheet of the battery under test is removed to obtain a flat bottom edge for contact with the second nanomanipulator.

[0024] 1-7. The upper half of the positive electrode sheet of the battery under test is further thinned to below 200 nm using a focused ion beam to obtain a thin region for transmission Kikuchi diffraction testing. The positive electrode material in the positive electrode sheet of the battery under test is the positive electrode of the battery under test.

[0025] Step 2: Preparation of the negative electrode, negative electrode current collector, and solid electrolyte:

[0026] 2-1, The lithium sheet is transferred to the focused ion beam through a vacuum chamber;

[0027] 2-2, The probe tip of the second nanomanipulator is placed near the surface of the lithium sheet. A region on the lithium sheet close to the probe of the second nanomanipulator is selected. The lithium sheet is cut away from the probe using a focused ion beam. The cut lithium is redeposited on the probe of the second nanomanipulator to form metallic lithium. The probe serves as the current collector of the negative electrode of the battery under test, and the metallic lithium serves as the negative electrode of the battery under test.

[0028] 2-3. Open the focused ion beam chamber door and place the tip of the second nanomanipulator probe with lithium metal deposition in the air to oxidize the lithium metal surface into lithium oxide, which serves as the solid electrolyte of the battery under test.

[0029] Step 3, Installation of the positive electrode sheet of the battery under test and the testing device:

[0030] 3-1. Fix the FIB half-segment carrier mesh containing the positive electrode sheet of the battery to be tested onto the carrier mesh frame using bolts and carrier mesh clamping plates;

[0031] 3-2. Insert the mesh carrier into the groove of the sample stage until the spring positioning beads on both sides of the groove of the sample stage engage with the recesses of the mesh carrier on both sides of the mesh carrier.

[0032] 3-3. Fix the sample stage containing the battery to be tested onto the scanning electron microscope sample stage base;

[0033] 3-4. Secure the first and second nano-manipulators to the base using the matching bolts and nuts.

[0034] 3-5. Secure the installed nanomanipulator and base to the scanning electron microscope sample stage base using the matching bolts and nuts;

[0035] 3-6. Fix the vacuum electrode to the side wall of the scanning electron microscope sample chamber using the matching bolts and nuts;

[0036] 3-7, connect the power supply to the controller, the controller to the vacuum electrode, and the vacuum electrode to the nanomanipulator in sequence;

[0037] Step 4, in-situ electrochemical transmission Kikuchi diffraction test:

[0038] 4-1. Adjust the working distance of the scanning electron microscope sample stage to 6~10mm;

[0039] 4-2, Electron beam accelerating voltage 15~30kV, beam current 3.2~13nA, find the region of interest, insert the electron backscatter diffraction probe, and perform transmission Kikuchi diffraction characterization on the uncharged sample;

[0040] 4-3, temporarily retract the electron backscatter diffraction probe, the first nanomanipulator and the second nanomanipulator approach the positive electrode sheet of the battery under test and stop at a distance of 4~6μm, and insert the electron backscatter diffraction probe;

[0041] 4-4, the first nanomanipulator contacts the current collector of the positive electrode of the battery under test, and the second nanomanipulator contacts the bottom of the thin sheet of the positive electrode of the battery under test, forming a complete electrochemical circuit;

[0042] 4-5. Connect the electrochemical workstation and the nanorobot to measure the open-circuit voltage to confirm whether the battery under test is normal.

[0043] 4-6. After confirming that everything is normal, charge the battery and perform a transmission Kikuchi diffraction test after charging is complete.

[0044] 4-7. After the experiment, the experimental results were analyzed.

[0045] In the in-situ electrochemical transmission Kikuchi diffraction test method for the cathode material, in steps 1-3, the width of the protective layer is 2 μm, the length of the protective layer is increased by 2 μm on both sides of the diameter of the cathode particle, and it is uniformly coated on the surface of the cathode particle.

[0046] In the in-situ electrochemical transmission Kikuchi diffraction test method for the cathode material, in steps 1-4, the top of the copper pillar is arc-shaped or V-shaped, and the cross-section of the copper pillar pit at the top of the copper pillar is rectangular with a width of 9~11μm.

[0047] In the in-situ electrochemical transmission Kikuchi diffraction test method for the cathode material, in step 3-1, the carrier frame used to fix the FIB half-sub-carrier is long and narrow. The carrier frame has recesses on both sides of the lower part of the carrier frame body. The recesses correspond to the spring positioning beads on both sides of the sample stage groove at one end of the sample stage, which are used to fix the FIB half-sub-carrier in conjunction with the spring positioning beads. The FIB half-sub-carrier is installed on one end of the carrier plate, and the carrier plate is fixed to the carrier frame body by bolts.

[0048] In the in-situ electrochemical transmission Kikuchi diffraction test method for the cathode material, in steps 4-2 and 4-6, transmission Kikuchi diffraction characterization is performed using an electron beam emitted by a dual-beam electron microscope. The electron beam excites the backscattered electron signal in the cathode sheet of the battery under test, and some of the backscattered electron signal diffracts to form Kikuchi lines. The electron backscatter diffraction probe identifies crystal information by receiving the Kikuchi lines.

[0049] The design concept of this invention is as follows:

[0050] To achieve crystallographic analysis of cathode materials during charge-discharge processes, this invention designs an in-situ electrochemical transmission Kikuchi diffraction (TKD) testing device and method for cathode materials. The primary particle size in cathode materials ranges from tens to hundreds of nanometers, and traditional EBSD characterization cannot cover all size requirements. Therefore, this invention chooses TKD for characterization, which achieves nanometer-level spatial resolution, meeting the requirements. To realize charge-discharge testing in a scanning electron microscope (SEM), this invention selects FIB (fiber-embedded binarization) to prepare a test battery suitable for in-situ charge-discharge. A nanomanipulator is used as a lead wire, contacting the positive and negative electrodes of the test battery to form an electrochemical pathway, enabling in-situ charge-discharge in the SEM. Combined with the aforementioned transmission Kikuchi diffraction characterization method, TKD testing is performed at a specific voltage during in-situ charge-discharge to obtain the changes in crystallographic information of the primary particles during the in-situ charge-discharge process.

[0051] The advantages and beneficial effects of this invention are as follows:

[0052] 1. This invention uses transmission Kikuchi diffraction for characterization, which has excellent spatial resolution and can effectively characterize cathode materials with primary particle sizes ranging from tens to hundreds of nanometers.

[0053] 2. The method for preparing the battery to be tested proposed in this invention not only successfully constructs an in-situ battery and observes the changes in particle morphology during charging and discharging, but also performs transmission Kikuchi diffraction characterization.

[0054] 3. The apparatus and testing method proposed in this invention can be widely applied to crystallographic analysis of positive electrode materials with crystal structures during in-situ charge and discharge processes. Attached Figure Description

[0055] Figure 1 This is a schematic diagram showing the relative positions of the positive electrode sheet of the battery under test and the FIB semi-distribution network.

[0056] Figure 2 This is a top view of Pt metal deposited on the outside of polycrystalline cathode particles.

[0057] Figure 3 This is a schematic diagram of the structure of the thin positive electrode sheet of the battery under test.

[0058] Figure 4This is a schematic diagram showing the relative positions of the FIB semi-substructure and the carrier frame, as well as the structure of the carrier frame.

[0059] Figure 5(a) is a cross-sectional view of the sample stage slot; Figure 5(b) is the AA cross-sectional view in Figure 5(a).

[0060] Figure 6 This is a schematic diagram showing the relative positions of the sample stage and the carrier frame, as well as the normal operation of the in-situ device.

[0061] Figure 7 This is a schematic diagram showing the relative positions of the nanomanipulator, the electron beam, and the thin film of the positive electrode of the battery under test during normal operation.

[0062] Figure 8 For LiNi 0.86 Co 0.08 Mn 0.06 TKD surface distribution diagrams before and after O2 charging. Among them, (a) and (b) are before charging, (c) and (d) are after charging, (a) and (c) are phase distribution diagrams, and (b) and (d) are orientation distribution diagrams.

[0063] In the figure: 1. Positive electrode sheet of the battery under test; 1-1. Protective layer (also serving as part of the positive electrode current collector); 1-2. Polycrystalline positive electrode material; 1-3. Thin area (dashed area); 1-4. Positive electrode current collector; 2. FIB semi-substructured grid (copper grid); 2-1. Copper pillar; 2-2. Copper pillar recess (dashed area); 2-3. SiO2 insulating layer; 3. Grid frame; 3-1. Grid frame body; 3-2. Bolt; 3-3. Grid pressing sheet; 3-4. Grid frame recess; 4. First nanomanipulator; 5. Electron beam; 6. Second nanomanipulator; 7. Sample stage; 7-1. Sample stage groove; 7-2. Spring positioning bead. Detailed Implementation

[0064] like Figures 1-7 As shown, this invention proposes an in-situ electrochemical transmission Kikuchi diffraction testing device for cathode materials, comprising a cathode sheet 1 to be tested, a FIB half-segmentation grid 2 for supporting and fixing the cathode sheet 1, a grid frame 3 for fixing the FIB half-segmentation grid 2, nanorobotic arms (first nanorobotic arm 4 and second nanorobotic arm 6) for forming an electrochemical circuit, a sample stage 7, and an electrochemical workstation, the specific structure of which is as follows:

[0065] like Figure 3As shown, the positive electrode sheet 1 of the battery under test has a protective layer 1-1, a polycrystalline positive electrode material 1-2, a thin region 1-3, and a positive electrode current collector 1-4. The protective layer 1-1 is located on top of the polycrystalline positive electrode material 1-2, and the positive electrode current collector 1-4 is located on the left and right sides of the polycrystalline positive electrode material 1-2 and the protective layer 1-1. The height of the positive electrode current collector 1-4 is the same as the height of the polycrystalline positive electrode material 1-2 with the protective layer 1-1, and the positive electrode current collector 1-4 is integrated with the polycrystalline positive electrode material 1-2. The upper half of the polycrystalline positive electrode material 1-2 is the thin region 1-3 used for testing, and it is integrated with the protective layer 1-1.

[0066] like Figure 1 As shown, a copper pillar 2-1 has a copper pillar recess 2-2. SiO2 insulating layers 2-3 are deposited on both sides of the copper pillar recess 2-2. The SiO2 insulating layers 2-3 on both sides of the copper pillar recess 2-2 are symmetrical and their upper surfaces are on the same horizontal plane. The positive electrode sheet 1 of the battery under test is vertically straddling the two SiO2 insulating layers 2-3 on the top side of the copper pillar 2-1 near the vertical side. The positive electrode sheet 1 of the battery under test is fixedly connected to the SiO2 insulating layers 2-3 by SiO2 welding agent.

[0067] like Figure 4 As shown, the carrier frame 3 is provided with a carrier frame body 3-1, bolts 3-2, carrier frame pressure plate 3-3, and carrier frame recess 3-4. Carrier frame recess 3-4 are provided on the lower part of both sides of the carrier frame body 3-1. The FIB half-split carrier frame 2 is installed on one end of the carrier frame pressure plate 3-3. The carrier frame pressure plate 3-3 is fixed to the middle of the carrier frame body 3-1 by bolts 3-2. Copper pillars 2-1 are evenly distributed on the FIB half-split carrier frame 2.

[0068] Figure 5- Figure 7 As shown, the sample stage 7 has a sample stage groove 7-1 and spring positioning beads 7-2. The mesh frame 3 is inserted into the sample stage groove 7-1. The mesh frame recess 3-4 corresponds to the spring positioning beads 7-2 on both sides of the sample stage groove 7-1 at one end of the sample stage 7. The mesh frame recess 3-4 and the spring positioning beads 7-2 cooperate to fix the mesh frame 3 in the sample stage groove 7-1. The first nanomanipulator 4, the second nanomanipulator 6, and the sample stage 7 are mounted on the scanning electron microscope sample stage base. The first nanomanipulator 4 is in contact with the current collector 1-4 of the positive electrode of the battery under test, and the second nanomanipulator 6 is in contact with the bottom of the thin sheet 1 of the positive electrode of the battery under test, forming a complete electrochemical circuit. The electron beam 5 generated by the dual-beam electron microscope corresponds to the thin region 1-3 of the thin sheet 1 of the positive electrode of the battery under test. The electrochemical workstation is connected to the first nanomanipulator 4 and the second nanomanipulator 6 respectively, and the open circuit voltage is measured through the electrochemical workstation.

[0069] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0070] Example

[0071] In this embodiment, an in-situ electrochemical TKD testing device and method were used to study LiNi. 0.86 Co 0.08 Mn 0.06 The primary crystallographic changes of O2 (abbreviated as N86) cathode material during charge and discharge are performed as follows (the robotic arm mentioned in the steps refers to the robotic arm built into the focused ion beam equipment, which is different from the nanorobotic arm):

[0072] Step 1, as follows Figures 1-3 As shown, a thin film of the positive electrode of the battery to be tested (including the positive electrode and the positive electrode current collector) is prepared:

[0073] (1) Take 0.1g of polycrystalline positive electrode particles and add them to 5mL of anhydrous ethanol. After ultrasonic dispersion for 5min, a dispersion is obtained. Use a dropper to draw the dispersion and drop it onto a clean silicon wafer substrate. Place it in a vacuum oven to dry for 30min.

[0074] (2) The dried polycrystalline cathode particles and silicon wafer substrate were transferred to a dual-beam electron microscope (FIB-SEM). A layer of Pt metal with a length of 11 μm, a width of 2 μm, and a thickness of 3 μm was deposited on the outside of the polycrystalline cathode particles as a protective layer 1-1 and a cathode current collector 1-4. The cathode current collector 1-4 is a Pt metal pillar, see [link to relevant documentation]. Figure 2 ;

[0075] (3) The protective layer 1-1 is located on the top of the polycrystalline positive electrode particle, and the positive electrode current collector 1-4 is located on the left and right sides of the polycrystalline positive electrode particle and the protective layer 1-1. The height of the positive electrode current collector 1-4 is the same as the height of the polycrystalline positive electrode particle with the metal Pt protective layer 1-1, and the positive electrode current collector 1-4 is integrated with the polycrystalline positive electrode particle. The width of the protective layer 1-1 is 2μm, and the length of the protective layer 1-1 is 2μm longer than the diameter of the polycrystalline positive electrode particle on both sides. It should be uniformly coated on the surface of the polycrystalline positive electrode particle as much as possible.

[0076] (4) Using FIB, a copper pillar recess 2-2 is dug out on the top of the arc-shaped copper pillar 2-1 of the FIB half-load net 2. The cross-section of the copper pillar recess 2-2 is a rectangle with a length of 15μm and a width of 10μm. A layer of SiO2 with a length of 10μm and a width of 7μm is deposited on each side surface of the copper pillar recess 2-2 as an insulating layer. The SiO2 insulating layers 2-3 on both sides of the copper pillar recess 2-2 are symmetrical and their upper surfaces are on the same horizontal plane.

[0077] (5) The polycrystalline positive electrode particles in the area not covered by the protective layer are cut off from the top using a focused ion beam (FIB) to form the positive electrode sheet 1 of the battery under test and separate it from the silicon wafer substrate. The sheet is then lifted out by a robot arm. The robot arm is manipulated to place the lifted positive electrode sheet 1 of the battery under test vertically on the upper end of the SiO2 insulating layer 2-3 on the side of the top of the arc-shaped copper pillar 2-1 near the vertical side. SiO2 is deposited at the contact position between the two using a welding agent to fix the positive electrode sheet 1 of the battery under test and the SiO2 insulating layer 2-3 on the copper pillar 2-1 in a good manner.

[0078] (6) After reducing the thickness of the 8μm wide region of the positive electrode sheet 1 of the battery under test to 500nm using FIB, a portion of the polycrystalline positive electrode material at the bottom of the positive electrode sheet 1 of the battery under test is removed to obtain a flat bottom edge with a width of 8μm for contact with the second nanomanipulator 6.

[0079] (7) The upper half of the positive electrode sheet 1 of the battery under test is further thinned to 200 nm using FIB to obtain the thin region 1-3 for TKD testing. The polycrystalline positive electrode material 1-2 in the positive electrode sheet 1 of the battery under test is the positive electrode of the battery under test. When thinning the positive electrode sheet 1 of the battery under test, the bottom should not be thinned to ensure the overall strength of the battery under test and prevent the sheet from breaking when the second nanomanipulator 6 comes into contact with the positive electrode.

[0080] Step 2: Preparation of the negative electrode, negative electrode current collector, and solid electrolyte:

[0081] (1) Take a lithium sheet from the glove box and transfer it to the FIB through a vacuum container;

[0082] (2) The probe tip of the second nanomanipulator 6 is placed near the surface of the lithium sheet. A larger ion beam is used to cut the lithium sheet. An FIB with an accelerating voltage of 30kV and a beam current of 20nA is used. The area on the lithium sheet close to the probe of the second nanomanipulator 6 is selected and the lithium sheet is cut in a direction away from the probe. The cut lithium will be deposited on the probe of the second nanomanipulator 6 in a redeposition manner to form metallic lithium. The probe serves as the current collector of the negative electrode of the battery under test, and the metallic lithium serves as the negative electrode of the battery under test.

[0083] (3) Open the FIB door and briefly place the tip of the second nanomanipulator 6 probe with lithium metal deposition in the air to oxidize the lithium metal surface into lithium oxide, which serves as the solid electrolyte of the battery under test.

[0084] Step 3, Installation of the positive electrode sheet of the battery under test and the testing device:

[0085] (1) such as Figure 4As shown, the carrier frame 3 used to fix the FIB half-cell carrier 2 is long and narrow. The lower part of the carrier frame body 3-1 of the carrier frame 3 has carrier frame recesses 3-4 on both sides. The carrier frame recesses 3-4 correspond to the spring positioning beads 7-2 on both sides of the sample stage groove 7-1 at one end of the sample stage 7, and are used to fix the FIB half-cell carrier 2 in place. The FIB half-cell carrier 2 is installed on one end of the carrier plate 3-3, and the carrier plate 3-3 is fixed to the carrier frame body 3-1 by bolts 3-2. The FIB half-cell carrier 2, where the positive electrode sheet 1 of the battery to be tested is located, is fixed to the carrier frame 3 by bolts 3-2 and the carrier plate 3-3, ensuring that the vertical side of the FIB half-cell carrier 2 faces downwards.

[0086] (2) Insert the carrier frame 3 into the sample stage groove 7-1 until the spring positioning beads 7-2 on both sides of the sample stage groove 7-1 engage with the carrier frame recesses 3-4 on both sides of the carrier frame 3. At this time, the carrier frame 3 has an angle of 20 degrees with the horizontal plane, that is, the movement direction of the carrier frame 3 when it is inserted into the sample stage groove 7-1 has an angle of 20 degrees with the horizontal plane.

[0087] (3) Fix the sample stage 7 with the battery to be tested on the scanning electron microscope sample stage base;

[0088] (4) The nanomanipulator (first nanomanipulator 4 and second nanomanipulator 6) is fixed on the base by matching bolts and nuts. The nanomanipulator used to form the electrochemical pathway uses metal W as a probe with a tip diameter of no more than 5 μm. The oxide layer on the surface of metal W has been removed by FIB to prevent insulation caused by the oxide layer.

[0089] (5) Fix the assembled nanomanipulator and base onto the scanning electron microscope sample stage base using the matching bolts and nuts;

[0090] (6) Fix the vacuum electrode to the side wall of the scanning electron microscope sample chamber using matching bolts and nuts;

[0091] (7) Connect the power supply to the controller, the controller to the vacuum electrode, and the vacuum electrode to the nanomanipulator in sequence.

[0092] Step 4, in-situ electrochemical transmission Kikuchi diffraction test:

[0093] (1) Adjust the working distance of the scanning electron microscope sample stage to 7 mm;

[0094] (2) Set the electron beam accelerating voltage to 30kV and the beam current to 13nA, find the region of interest (ROI), and insert the EBSD probe;

[0095] (3) Transmission Kikuchi diffraction characterization was performed on the uncharged sample. The EBSD camera mode was selected as Speed ​​2 mode (in this embodiment, the EBSD model is Symmetry from Oxford, UK, which has a faster testing speed in this mode). The testing area was 7.5μm×7μm, the step size was 15nm, and the layered phase (red) was used as the index to obtain the following results: Figure 8 The results are shown in (a) and (b);

[0096] (4) After the test is completed, temporarily retract the EBSD probe, manipulate the two nanorobotic arms to approach the positive electrode sheet 1 of the battery under test, and stop at a distance of about 5 μm, and insert the EBSD probe;

[0097] (5) As shown in Figure 5- Figure 7 As shown, two nanorobotic arms (first nanorobotic arm 4 and second nanorobotic arm 6) are controlled to contact the positive electrode sheet 1 of the battery under test in fine-tuning mode. Coarse-tuning mode should be avoided when controlling the nanorobotic arms just before contacting the sample. Specifically, the first nanorobotic arm 4 contacts the current collector 1-4 of the positive electrode of the battery under test, and the second nanorobotic arm 6 contacts the bottom of the positive electrode sheet 1 of the battery under test, forming a complete electrochemical circuit. Transmission Kikuchi diffraction is performed using the electron beam 5 generated by a dual-beam electron microscope. The electron beam is used to excite the backscattered electron signal in the positive electrode sheet 1 of the battery under test. The Kikuchi lines formed after the diffraction of some of the backscattered electron signals are received by the EBSD probe to identify crystal information.

[0098] (6) Connect the electrochemical workstation and the nanorobot, and measure the open circuit voltage to confirm whether the battery under test is normal;

[0099] (7) After confirming normal operation, charge the battery, maintain a constant voltage at the required TKD test potential for 10 minutes, then disconnect it to perform the TKD test. Select the EBSD camera mode as speed 2 mode, the test area as 7.5μm×7μm, the step size as 15nm, and use layered phase (red), spinel phase (blue), and rock salt phase (green) as indices to obtain... Figure 8 The results shown in (c) and (d) are as follows.

[0100] (8) After the experiment, the experimental results were analyzed.

[0101] from Figure 8 It can be seen that the crystal structure of the cathode material is well characterized. From Figure 8 (a) and (b) show that the unrecycled N86 cathode is a layered phase (red), with relatively large grain size, averaging around 500 nm. The grain shape is mostly equiaxed crystal, with random orientation. Figure 8As can be seen from (c) and (d), after charging, most of the crystals changed from the layered phase (red) to the rock salt phase (green), and the change was uneven. Most of the phase transformation occurred throughout the entire grain, while a small portion occurred within the grain. Many grain edges were no longer identifiable, indicating that a severe phase transformation had occurred on the grain surface, making them difficult to identify.

[0102] The results show that this invention can be used in various types of dual-beam electron microscopes (if the various parts of the battery to be tested are prepared in a dual-beam electron microscope, TKD characterization can also be performed in a scanning electron microscope). Under the condition of loading in-situ electrochemistry, the cathode particles are characterized by transmission Kikuchi diffraction to obtain information such as the orientation, shape and size of the grains under different potential states, which provides support for the development of cathode materials.

Claims

1. An in-situ electrochemical transmission Kikuchi diffraction testing device for cathode materials, characterized in that, It consists of a thin positive electrode sheet of the battery under test, a FIB semi-substructure grid for supporting and fixing the thin positive electrode sheet, a grid frame for fixing the FIB semi-substructure grid, a nano-manipulator for forming an electrochemical circuit, and an electrochemical workstation. The specific structure is as follows: The positive electrode sheet of the battery under test has a protective layer, a positive electrode material, a thin region, and a positive electrode current collector. The protective layer is located on top of the positive electrode material, and the positive electrode current collector is located on the left and right sides of the positive electrode material and the protective layer. The height of the positive electrode current collector is the same as the height of the positive electrode material with the protective layer, and the positive electrode current collector is integrated with the positive electrode material. The upper half of the positive electrode material is a thin region, which is integrated with the protective layer. Copper pillars are evenly distributed on the FIB semi-distribution grid. Each copper pillar has a copper pillar pit. SiO2 insulating layers are deposited on both sides of the copper pillar pit. The SiO2 insulating layers on both sides of the copper pillar pit are symmetrical and their upper surfaces are on the same horizontal plane. The positive electrode sheet of the battery under test is vertically straddled on the top of the copper pillar near the vertical side of the two SiO2 insulating layers. The positive electrode sheet of the battery under test is fixedly connected to the SiO2 insulating layers by SiO2 welding agent. The carrier frame consists of a carrier frame body, bolts, carrier frame pressure plate, and carrier frame recess. Carrier frame recesses for assembly and positioning are opened on both sides of the lower part of the carrier frame body. The FIB half carrier is installed at one end of the carrier frame pressure plate, and the carrier frame pressure plate is fixed to the middle of the carrier frame body by bolts. The nanorobotics used to form the electrochemical circuit are a first nanorobotic and a second nanorobotic. The first nanorobotic is in contact with the current collector of the positive electrode of the battery under test, and the second nanorobotic is in contact with the bottom of the thin sheet of the positive electrode of the battery under test, forming a complete electrochemical circuit. The electron beam generated by the dual-beam electron microscope interacts with the thin area of ​​the thin sheet of the positive electrode of the battery under test, and the resulting diffraction signal is received by the EBSD probe. The electrochemical workstation is connected to the first nanorobotic and the second nanorobotic, respectively, and the battery under test is charged and discharged and the open circuit voltage is measured through the electrochemical workstation.

2. The in-situ electrochemical transmission Kikuchi diffraction testing apparatus for cathode materials according to claim 1, characterized in that, It also includes a sample stage, which has a sample stage groove and spring positioning beads. The mesh frame is inserted into the sample stage groove. The mesh frame recess corresponds to the spring positioning beads on both sides of the sample stage groove at one end of the sample stage. The mesh frame recess and the spring positioning beads engage to fix the mesh frame in the sample stage groove. The sample stage is installed on the scanning electron microscope sample stage base.

3. The in-situ electrochemical transmission Kikuchi diffraction testing apparatus for cathode materials according to claim 2, characterized in that, The angle between the carrier frame and the horizontal plane is 20 degrees, that is, the angle between the direction of movement of the carrier frame when it is inserted into the groove of the sample stage and the horizontal plane is 20 degrees.

4. The in-situ electrochemical transmission Kikuchi diffraction testing apparatus for cathode materials according to claim 1, characterized in that, The first and second nanomanipulators used to form the electrochemical pathway use metals Pt, Au, or W as probes with a tip diameter not exceeding 5 μm. The first and second nanomanipulators are mounted on the sample stage base of a scanning electron microscope.

5. The in-situ electrochemical transmission Kikuchi diffraction testing apparatus for cathode materials according to claim 1, characterized in that, The protective layer is made of Pt, Au, or W, and consists of one or two layers with a thickness of 2-3 μm. The positive electrode current collector is a metal column, and its material includes Pt, Au, or W.

6. An in-situ electrochemical transmission Kikuchi diffraction test method for the cathode material using the device described in any one of claims 1 to 5, characterized in that, Includes the following steps: Step 1, Prepare the positive electrode sheet of the battery to be tested: 1-1. Take positive electrode particles and add them to anhydrous ethanol. After ultrasonic dispersion, a dispersion is obtained. Use a dropper to draw the dispersion and drop it onto a clean silicon wafer substrate. Place it in a vacuum oven to dry thoroughly. 1-2, The dried positive electrode particles and silicon wafer substrate are transferred to a dual-beam electron microscope, and a protective layer and a positive electrode current collector are deposited on the outside of the positive electrode particles; 1-3, the protective layer is located on top of the positive electrode particle, the positive electrode current collector is located on the left and right sides of the positive electrode particle and the protective layer, the height of the positive electrode current collector is the same as the height of the positive electrode particle with the protective layer, and the positive electrode current collector and the positive electrode particle are connected as one. 1-4. A copper pillar recess is dug on the top of the copper pillar of the FIB semi-distributed grid using a focused ion beam, and SiO2 insulating layers are deposited on both sides of the copper pillar recess. The SiO2 insulating layers on both sides of the copper pillar recess are symmetrical and their upper surfaces are on the same horizontal plane. 1-5. Using a focused ion beam, the portion of the positive electrode particle not covered by the protective layer is cut off from the top to form a thin positive electrode sheet of the battery under test, which is separated from the silicon wafer substrate and lifted out by the robotic arm of the focused ion beam equipment. The robotic arm of the focused ion beam equipment is then manipulated to vertically place the thin positive electrode sheet of the battery under test on the upper end of the SiO2 insulating layer on the side of the top of the arc-shaped copper pillar. SiO2 is deposited as a welding agent at the contact position between the two to fix the thin positive electrode sheet of the battery under test to the SiO2 insulating layer on the copper pillar. 1-6. After reducing the thickness of the positive electrode sheet of the battery under test to 400~600nm using a focused ion beam, a portion of the positive electrode material at the bottom of the positive electrode sheet of the battery under test is removed to obtain a flat bottom edge for contact with the second nanomanipulator. 1-7. The upper half of the positive electrode sheet of the battery under test is further thinned to below 200 nm using a focused ion beam to obtain a thin region for transmission Kikuchi diffraction testing. The positive electrode material in the positive electrode sheet of the battery under test is the positive electrode of the battery under test. Step 2: Preparation of the negative electrode, negative electrode current collector, and solid electrolyte: 2-1, The lithium sheet is transferred to the focused ion beam through a vacuum chamber; 2-2, The probe tip of the second nanomanipulator is placed near the surface of the lithium sheet. A region on the lithium sheet close to the probe of the second nanomanipulator is selected. The lithium sheet is cut away from the probe using a focused ion beam. The cut lithium is redeposited on the probe of the second nanomanipulator to form metallic lithium. The probe serves as the current collector of the negative electrode of the battery under test, and the metallic lithium serves as the negative electrode of the battery under test. 2-3. Open the focused ion beam chamber door and place the tip of the second nanomanipulator probe with lithium metal deposition in the air to oxidize the lithium metal surface into lithium oxide, which serves as the solid electrolyte of the battery under test. Step 3, Installation of the positive electrode sheet of the battery under test and the testing device: 3-1. Fix the FIB half-segment carrier mesh containing the positive electrode sheet of the battery to be tested onto the carrier mesh frame using bolts and carrier mesh clamping plates; 3-2. Insert the mesh carrier into the groove of the sample stage until the spring positioning beads on both sides of the groove of the sample stage engage with the recesses of the mesh carrier on both sides of the mesh carrier. 3-3. Fix the sample stage containing the battery to be tested onto the scanning electron microscope sample stage base; 3-4. Secure the first and second nano-manipulators to the base using the matching bolts and nuts. 3-5. Secure the first nanomanipulator, the second nanomanipulator, and the base to the scanning electron microscope sample stage base using the matching bolts and nuts. 3-6. Fix the vacuum electrode to the side wall of the scanning electron microscope sample chamber using the matching bolts and nuts; 3-7, connect the power supply to the controller, the controller to the vacuum electrode, and the vacuum electrode to the nanomanipulator in sequence; Step 4, in-situ electrochemical transmission Kikuchi diffraction test: 4-1. Adjust the working distance of the scanning electron microscope sample stage to 6~10mm; 4-2, Electron beam accelerating voltage 15~30kV, beam current 3.2~13nA, find the region of interest, insert the EBSD probe, and perform transmission Kikuchi diffraction characterization on the uncharged sample; 4-3, temporarily retract the EBSD probe, the first nanomanipulator and the second nanomanipulator approach the positive electrode sheet of the battery under test and stop at a distance of 4~6μm, and insert the EBSD probe; 4-4, the first nanomanipulator contacts the current collector of the positive electrode of the battery under test, and the second nanomanipulator contacts the bottom of the thin sheet of the positive electrode of the battery under test, forming a complete electrochemical circuit; 4-5. Connect the electrochemical workstation and the nanorobot to measure the open-circuit voltage to confirm whether the battery under test is normal. 4-6. After confirming that everything is normal, charge the battery and perform a transmission Kikuchi diffraction test after charging is complete. 4-7. After the experiment, the experimental results were analyzed.

7. The in-situ electrochemical transmission Kikuchi diffraction test method for cathode materials according to claim 6, characterized in that, In steps 1-3, the width of the protective layer is 2μm, and the length of the protective layer is 2μm longer than the diameter of the positive electrode particle on both sides, and it is uniformly coated on the surface of the positive electrode particle.

8. The in-situ electrochemical transmission Kikuchi diffraction test method for cathode materials according to claim 6, characterized in that, In steps 1-4, the top of the copper pillar is arc-shaped or V-shaped, and the cross-section of the copper pillar recess at the top of the copper pillar is rectangular with a width of 9~11μm.

9. The in-situ electrochemical transmission Kikuchi diffraction test method for the cathode material according to claim 6, characterized in that, In step 3-1, the carrier frame used to fix the FIB half-split carrier is long and narrow. The carrier frame has recesses on both sides of the lower part of the carrier frame body. The recesses correspond to the spring positioning beads on both sides of the sample stage groove at one end of the sample stage. The recesses are used to fix the FIB half-split carrier in conjunction with the spring positioning beads. The FIB half-split carrier is installed on one end of the carrier plate. The carrier plate is fixed to the carrier frame body by bolts.

10. The in-situ electrochemical transmission Kikuchi diffraction test method for the cathode material according to claim 6, characterized in that, In steps 4-2 and 4-6, transmission Kikuchi diffraction characterization is performed using an electron beam emitted by a dual-beam electron microscope. The electron beam excites the backscattered electron signal in the positive electrode thin film of the battery under test, and some of the backscattered electron signal diffracts to form Kikuchi lines. The EBSD probe identifies crystal information by receiving these Kikuchi lines.

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