Design method of electrochemical in-situ charging and discharging device based on synchrotron radiation USAXS characterization

Abstract

The invention discloses a design method of an electrochemical in-situ charging and discharging device based on synchrotron radiation USAXS characterization, and belongs to the field of in-situ real-time measurement equipment for microstructure changes of battery materials during charging and discharging. The technical scheme is used for solving the problems that the existing electrochemical test method cannot accurately and timely reflect the internal structure change of the battery, and the existing detection method cannot observe the large-size cluster (gt; by means of the testing method, in-situ and real-time observation of microscopic changes of the electrode material and the electrolyte during charging and discharging can be achieved.

Description

Technical Field

[0001] This patent relates to the field of in-situ real-time measurement equipment for microstructural changes in battery materials. Background Art

[0002] In order to reveal the failure mechanism of electrochemical materials (such as electrode materials, electrolytes and catalysts) during the charge and discharge process, such as short circuit, battery capacity attenuation, etc. Small angle X-ray scattering (SAXS) can detect nanoscale structural information, which is crucial for the microstructural characterization of electrochemical materials. Information such as particle size distribution, morphology, internal pore structure and surface characteristics of the material can be obtained through SAXS. CN116930014A provides a method for detecting the size of nanophase particles based on SAXS technology, which can perform statistical analysis on nanophase particles. CN117832480A provides a method for regulating the degree of graphitization according to the SAXS curve, so that the graphite material has better cycle performance.

[0003] In-situ characterization technology can obtain real-time information on the structure, morphology and chemical state of materials under actual working conditions. This is of great significance for understanding the mechanism of electrochemical reactions, optimizing material design and improving performance. The in-situ electrochemical device is a platform that can characterize the dynamic changes of the internal microstructure of battery materials in situ, and has become a hot topic of research. In-situ characterization requires the design of a suitable electrochemical in-situ device. Applying SAXS to an electrochemical in-situ device can monitor the changes in materials and interfaces in real time during the electrochemical reaction, which is very effective for studying fast charging and discharging battery materials, transient electrochemical phenomena and short-lived intermediates. CN202221708999.1 discloses an in-situ monitoring device for electrochemical reactions, which can monitor electrochemical reaction intermediates, reactants and products, thereby realizing in-situ characterization of electrochemical reactions.

[0004] However, SAXS can only characterize materials with a scale of 1-100nm. There is still a lack of effective in-situ characterization methods for structures larger than 100nm (such as the pore size of the diaphragm, the particle size of the electrode nanoparticle catalyst, etc.). Ultrasmall angle X-ray scattering (USAXS) can characterize nanostructured materials with a scale of 100nm-1500nm (0.002-0.05°), which can meet the needs of structural characterization of battery materials on a large length scale. The present invention is based on the design of an electrochemical in-situ charge and discharge device characterized by synchrotron radiation USAXS, which can observe in-situ the in-situ dynamic changes of electrochemical materials in the range of 100-1500nm. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide an electrochemical in-situ charge and discharge test method based on synchrotron radiation USAXS technology to measure the in-situ changes of electrocatalysts and diaphragm pore size during the charge and discharge process. X-rays can pass through the in-situ cell. Combined with the battery testing system, the in-situ change patterns of the diaphragm pore size and the electrode catalyst particle size in the range of 100-1500nm can be observed in situ.

[0006] An electrochemical in-situ charge-discharge test method based on synchrotron radiation USAXS technology includes synchrotron radiation X-rays, an electrochemical in-situ cell, and a battery test system. The synchrotron radiation USAXS technology refers to a beam of X-rays passing through a sample, and the X-ray signal scattered by the sample is received by a detector at a certain distance.

[0007] The electrochemical in-situ cell can be disassembled into two parts, an upper part and an lower part, between which a rubber gasket is arranged, and the two parts are connected by bolts. The electrode material, the electrolyte and the diaphragm are placed in the electrochemical in-situ cell.

[0008] The electrochemical in-situ cell is composed of a positive electrode shell, a negative electrode shell, a fluorine gasket, a metal boss, a positive electrode material, a negative electrode material and an electrolyte.

[0009] The electrochemical in-situ cell can be disassembled into two parts, an upper part and an lower part, between which there is a rubber gasket, which is connected by bolts. Electrode materials, diaphragms and electrolytes are placed in the electrochemical in-situ cell.

[0010] The positive electrode shell of the electrochemical in-situ cell has a circular X-ray incident window, and the negative electrode shell has an X-ray exit window at the same position. The window material is made of high-light-transmittance material. The X-ray incident window is coaxial with the X-ray exit window, and X-rays can pass through the electrochemical in-situ cell.

[0011] The positive electrode shell and the negative electrode shell both have a socket, which is connected to the battery testing system through a wire. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 Detailed structural diagram of the electrochemical in-situ cell

[0014] Figure 2 Schematic diagram of electrochemical in-situ cell testing method

[0015] Figure 3 Schematic diagram of the left side of the electrochemical in-situ cell

[0016] Figure 4 Schematic diagram of the right side of the electrochemical in-situ cell

[0017] Figure 5 Cross-section diagram of the electrochemical in-situ cell

[0018] Figure 6One-dimensional USAXS curve of PVDF-HFP solid electrolyte changing with time during charge and discharge DETAILED DESCRIPTION

[0020] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention clearer and more understandable, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0021] Embodiment 1:

[0022] Step (1): Accurately weigh 4.3 g of lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) and 2.5 g of poly(vinylidene fluoride-hexafluoropropylene) copolymer (PVDF-HFP), place them in a blue-mouth bottle and stir them at 65°C for 12 h at room temperature on a magnetic stirrer to form a light yellow transparent viscous solution. The solution is coated on a PTFE dish using a 300 μm scraper and dried in an oven at 65°C for 12 h to obtain a PVDF-HFP solid electrolyte. The thickness of the PVDF-HFP solid electrolyte is about 150 μm.

[0023] Step (2): Assemble the battery in a glove box using the PVDF-HFP solid electrolyte in step (1) using an electrochemical in-situ cell, using a lithium iron phosphate positive electrode and a lithium sheet negative electrode. In order to ensure good contact between the PVDF-HFP solid electrolyte and the electrode interface, place the assembled in-situ cell in an oven and heat it at 60°C for 6 hours.

[0024] Step (3): Place the electrochemical in-situ cell on the BL10U1 time-resolved ultra-small angle scattering experimental station of the Shanghai Synchrotron Radiation Source, and adjust the position of the electrochemical in-situ cell so that X-Ray can pass through the window of the electrochemical in-situ cell.

[0025] Step (4): Connect the electrochemical in-situ cell to the blue battery test system through a wire, edit the charge and discharge program in the blue battery test system, and set the charge and discharge rate to 1C. Then start the test, and synchronously collect the two-dimensional scattering image while starting the charge and discharge.

[0026] Results Analysis

[0027] The Blue Power Battery Test System records the voltage changes during a charge and discharge cycle. Figure 5 Two-dimensional USAXS images during charge and discharge Figure 6 The corresponding one-dimensional USAXS. Figure 5 and Figure 6 Obvious changes in the electrochemical in situ cell during charge and discharge are demonstrated. Figure 5The two-dimensional image weakens with time, and the corresponding one-dimensional curve gradually weakens in low-q region. However, the slope of the one-dimensional curve increases, reflecting the increase in the average size of the battery system.

[0028] The above is only a preferred embodiment of the present invention, and does not limit the present invention in other forms. Any technician familiar with the profession may use the above disclosed technical content to change or modify it into an equivalent embodiment with equivalent changes. However, any simple modification, equivalent change and improvement made to the above embodiment according to the technical essence of the present invention without departing from the technical solution of the present invention still belongs to the protection scope of the technical solution of the present invention.

Claims

1. The design method of electrochemical in-situ charge-discharge device based on synchrotron radiation USAXS characterization, which includes synchrotron radiation X-ray, electrochemical in-situ cell, and battery testing system.

2. According to claim 1, the synchrotron radiation X-rays irradiate the electrode material and the electrolyte through the X-ray incident window, and the scattered signals are transmitted through the X-ray exit window.

3. The electrochemical in-situ cell according to claim 1 can be disassembled into a positive electrode shell and a negative electrode shell. Both the positive electrode shell and the negative electrode shell are provided with grooves. The electrode material and the electrolyte are placed in the electrochemical in-situ cell and connected by bolts.

4. The electrochemical in-situ cell according to claim 1 has circular X-ray incident windows and X-ray exit windows at the front and rear, the window material is made of high light transmittance material, and the X-ray incident window is coaxial with the X-ray exit window; the positive electrode shell of the electrochemical in-situ cell has an incident window that allows X-rays to pass through, and the negative electrode shell opposite to the positive electrode shell also has an exit window, the incident window and the exit window are coaxial, and X-rays can pass through the electrochemical in-situ cell.

5. According to claim 1, the window material of the positive electrode shell and the negative electrode shell is polyimide or beryllium window, and the scattered signal passing through the window is collected by the detector.

6. According to claim 1, a circular fluorine gasket is further arranged between the positive electrode shell and the negative electrode shell.

7. The positive electrode shell and the negative electrode shell according to claim 1 have openings at the tops, which can be connected with wires and connected to a battery testing system.

8. The battery testing system according to claim 1 can control the charge and discharge of the electrochemical in-situ cell; at the same time, the charge and discharge program can also be written according to demand.

9. The electrochemical in-situ charge-discharge device based on synchrotron radiation USAXS characterization according to claim 1, characterized in that: The device can collect in situ scattering information of changes in large-scale clusters (100nm-1500nm) inside the battery within high time resolution (2ms).

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