Dry-method electrode preparation system

Abstract

The utility model relates to the technical field of batteries, in particular to a preparation system of a dry-method electrode, which comprises an on-line detection device of a dry-method electrode material, the on-line detection device comprises an optical fiber probe, a spectrograph and a computer, the optical fiber probe is sequentially connected with the spectrograph and the computer, and the optical fiber probe is used for enabling light waves to enter the dry-method electrode material. According to the preparation system, the mixing uniformity of the dry-method electrode material can be accurately monitored in real time, the mixing time of the electrode material can be rapidly adjusted in real time or defective dry-method electrode films or dry-method electrodes can be screened out on the basis of the monitoring result, and high-quality dry-method electrodes can be efficiently and continuously produced on a large scale.

Description

Technical Field

[0001] The utility model relates to the technical field of batteries, and specifically provides a dry electrode preparation system. Background Art

[0002] As the name suggests, dry-process electrodes do not use any liquid solvents during the electrode forming process. The corresponding electrode film is produced only through mixing, calendering, and compounding of materials. Compared with traditional wet coating processes, dry-process electrode processes do not require the use of organic solvents during processing. There is no drying step for the electrode sheets, which can significantly reduce the costs of equipment and space, energy consumption, and toxic solvent recovery and disposal. It also avoids the impact of residual and volatilized organic solvents on electrode performance, facilitating large-scale, low-cost, and environmentally friendly manufacturing of electrodes.

[0003] However, dry-process electrodes face certain processing challenges in manufacturing. For example, the wet-process electrodes that compete directly with them can directly use the existing slurry viscosity, fineness, solid content, etc. to evaluate the fluidity and manufacturability of the slurry during manufacturing, and then prepare electrodes that meet the requirements. However, due to the limitations of processing characteristics, dry-process electrodes require the active materials and auxiliary materials to be dry-mixed according to a certain mixing process during mixing. It is impossible to directly refer to the methods used in the wet-process electrode production process to characterize the manufacturability of the slurry to characterize the mixing and dispersion uniformity of the dry electrode materials. The dispersion uniformity between the active materials and auxiliary materials directly affects the performance of the dry electrode and the performance of the final battery cell.

[0004] There are also few directly applicable solutions in the traditional field of particle mixing and polymer processing. In the field of powder mixing, the particle size distribution of the mixed powder is often tested to characterize the mixing uniformity of the dry-blended material. However, since this type of method requires offline sampling at regular intervals, it is not feasible in actual continuous large-scale production. In the rubber calendering molding process, which is similar to the dry electrode processing process, offline characterization methods such as Mooney viscosity are mainly used to confirm the processability of the rubber. However, this method is only applicable to products with a certain molecular weight and is obviously not suitable for direct reference in dry electrodes.

[0005] Therefore, how to establish an online characterization method for the mixing uniformity of dry electrode materials to guide the production of high-quality dry electrodes is particularly important for large-scale promotion of dry electrode manufacturing technology and reducing battery cell production costs. Utility Model Content

[0006] The present invention aims to address the problem in existing dry-process manufacturing processes that the lack of an effective method for evaluating the mixing uniformity of electrode materials results in difficulty in ensuring the quality of dry-process electrodes or low production efficiency of high-quality dry-process electrodes. The invention provides a dry-process electrode preparation system that can accurately monitor the mixing uniformity of dry-process electrode materials in real time and, based on the monitoring results, rapidly adjust the mixing time of the electrode materials or screen out defective dry-process electrode films or dry-process electrodes in real time, facilitating the efficient, continuous, and large-scale production of high-quality dry-process electrodes.

[0007] The present invention provides a dry electrode preparation system, including an online detection device for dry electrode materials. The device comprises a fiber optic probe, a spectrometer, and a computer. The fiber optic probe is sequentially connected to the spectrometer and the computer and is used to inject light waves into the dry electrode materials. This preparation system can monitor the mixing uniformity of dry electrode materials in real time. Compared to offline spectral detection using sampling, this system can adjust production and optimize production efficiency in real time, facilitating continuous large-scale production. Furthermore, spectral detection has a high degree of accuracy.

[0008] In a specific embodiment of the above-mentioned preparation system, the optical fiber probe is used to transmit the light waves emitted by the spectrometer to the dry electrode material and receive the light signal scattered by the dry electrode material when excited, and the computer is used to perform data acquisition and analysis on the light signal to obtain the mixing uniformity of the dry electrode material.

[0009] In a specific embodiment of the above preparation system, the spectrometer is an infrared spectrometer or a Raman spectrometer, and the type of spectrometer can be selected according to different substances to be detected.

[0010] In a specific embodiment of the above preparation system, the spectrometer is a portable spectrometer.

[0011] In a specific embodiment of the above-mentioned preparation system, the dry electrode material is a dry electrode powder or a dry electrode membrane.

[0012] Optionally, the dry electrode material includes at least polytetrafluoroethylene (PTFE) and one or more binders selected from polyvinylidene fluoride (PVDF), polyacrylic acid (PAA), polyethylene oxide (PEO) and polyethylene (PE).

[0013] In a specific embodiment of the above-mentioned preparation system, the preparation system also includes a mixing device for mixing dry electrode powder. The mixing device has a window through which the optical fiber probe transmits light waves into the mixed dry electrode powder. This solution can optimize the mixing time of the dry electrode powder in real time to improve production efficiency. For example, increasing the mixing time can avoid poor dry electrode film quality caused by uneven powder mixing, or avoid energy waste caused by continued mixing after the powders are evenly mixed.

[0014] Preferably, the window is a transparent window that does not affect the light release and absorption of the optical fiber spectroscopy probe.

[0015] Optionally, the mixing device is selected from one of a high-speed stirrer, a ball mill, a grinder, a kneader, a jet mill, an internal mixer, an open mixer, a single-screw extruder, a twin-screw extruder and a stirrer.

[0016] In a specific embodiment of the above-mentioned preparation system, the preparation system further includes: a mixing device for mixing dry-process electrode powder; and a film-forming device for rolling the mixed dry-process electrode powder into a film. The film-forming device includes multiple rolling rollers, at least one of which is provided with a bracket above which the optical fiber probe is mounted for incident light waves on the surface of the dry-process electrode film. This solution can be used to screen out defective dry-process electrode films during the film-forming process in real time, thereby improving the yield rate of the dry-process electrode films. Defective dry-process electrode films can also be recycled and reused by being re-crushed and rolled into films, reducing raw material waste.

[0017] In a specific embodiment of the above-mentioned preparation system, the film-forming device includes a first calendering roller, a second calendering roller, a third calendering roller, a fourth calendering roller, a fifth calendering roller, a sixth calendering roller, and a seventh calendering roller. The bracket is positioned above the seventh calendering roller, and the optical fiber probe is mounted on the bracket to project light waves onto the surface of the dry electrode film. The use of seven calendering rollers in the film-forming device allows for better control of the surface density of the dry electrode film.

[0018] Optionally, the bracket is a reciprocating bracket, which can drive the optical fiber probe installed on the bracket to perform a "Z"-shaped path scan on the electrode diaphragm to obtain the dispersion uniformity information of the dry electrode diaphragm in the MD (Machine Direction) and TD (Transverse Direction) directions; it can also drive the optical fiber probe installed on the bracket to move to a certain position and then remain stationary to perform continuous fixed-point scanning on the dry electrode diaphragm to obtain the dispersion uniformity information of the diaphragm.

[0019] Optionally, the bracket is a fixed bracket, and the optical fiber probe installed on the bracket can be kept in a stationary state to perform continuous fixed-point scanning on the electrode membrane to obtain dispersion uniformity information of the membrane. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a structural schematic diagram of the dry electrode preparation system provided in Example 1 of the present utility model.

[0021] Figure 2 This is a graph showing the change in relative concentration of the binder PTFE over time during the mixing process, which is detected online using the dry electrode preparation system provided in Example 1 of the present invention.

[0022] Figure 3 This is a structural schematic diagram of the dry electrode preparation system provided in Example 2 of the present utility model.

[0023] Figure 4 This is a graph showing the change in relative concentration of -CF2- groups in a dry electrode membrane over time, detected online using the dry electrode preparation system provided in Example 2 of the present invention.

[0024] 1. Online detection device; 11. Fiber optic probe; 12. Spectrometer; 13. Computer; 2. Mixing device; 21. Window; 3. Unloading device; 4. Film forming device; 41. First calendering roller; 42. Second calendering roller; 43. Third calendering roller; 44. Fourth calendering roller; 45. Fifth calendering roller; 46. Sixth calendering roller; 47. Seventh calendering roller; 48. Bracket; 5. Pole piece. DETAILED DESCRIPTION

[0025] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0026] It should be noted that, in the description of this utility model, terms such as "upper" and "lower" indicating directions or positional relationships are based on the directions or positional relationships shown in the accompanying drawings. This is for ease of description only and does not indicate or imply that the device or component described must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, it should not be understood as limiting the utility model. In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance.

[0027] In this utility model, unless otherwise specified or limited, terms such as "installation" and "connection" should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integration; mechanical connection, electrical connection; direct connection, or indirect connection through an intermediate medium; internal communication between two components, or interaction between two components, unless otherwise specified. Those skilled in the art will understand the specific meanings of the above terms in this utility model based on specific circumstances.

[0028] Example 1

[0029] like Figure 1 As shown, this embodiment discloses a dry electrode preparation system, which includes an online detection device 1 and a mixing device 2 for dry electrode materials.

[0030] The online detection device 1 is used to detect the mixing uniformity of dry electrode powder in real time, and includes a fiber optic probe 11, a spectrometer 12, and a computer 13. The fiber optic probe 11 is sequentially connected to the spectrometer 12 and the computer 13. The spectrometer is a portable Raman spectrometer or a portable infrared spectrometer.

[0031] Mixing device 2 is used to mix dry-process electrode powder. It has a transparent window 21. The transparent window is made of a transparent material, which does not affect the transmission of light waves into the dry-process electrode powder and feeds scattered light signals back to the fiber optic probe. Mixing device 2 is selected from the group consisting of a high-speed blender, a ball mill, a grinder, a kneader, a jet mill, an internal mixer, an open mixer, a single-screw extruder, a twin-screw extruder, and a stirrer.

[0032] The optical fiber probe 11 is used to transmit the light waves emitted by the spectrometer 12 to the mixed dry electrode powder through the transparent window on the mixing device and receive the light signal scattered by the excited electrode powder. The computer 13 is used to collect data and analyze the light signal to obtain the mixing uniformity of the mixed dry electrode powder.

[0033] Dry electrode powder is a known material for preparing dry electrodes, including active materials, conductive agents and binders. Active materials include but are not limited to lithium nickel cobalt manganese oxide (such as 5 series, 6 series, 7 series, 8 series, 9 series), lithium iron phosphate, and lithium nickel cobalt aluminum oxide. Binders include but are not limited to polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), PAA (polyacrylic acid), PEO (polyethylene oxide), and PE (polyethylene). Conductive agents include but are not limited to carbon black, carbon nanotubes, and carbon fibers. It is known that dry electrode powder has infrared and Raman spectral activity. The peak intensity of the characteristic functional groups with infrared and Raman spectral activity detected in real time by the online detection device of this embodiment can be used to obtain the dispersion uniformity of the dry electrode powder. When the characteristic peak intensity with spectral activity no longer changes with time, it is determined that the dry electrode powder is uniformly dispersed. The real-time concentration of the corresponding component can also be converted by the peak intensity of the characteristic functional groups with spectral activity. When the real-time concentration of the component no longer changes with time, it is determined that the dry electrode powder is uniformly dispersed.

[0034] For example, the dry electrode powder in this embodiment includes 96 wt% of active material NCM811, 1.4 wt% of conductive agent carbon black and 2.6 wt% of binder PTFE, and the electrode powder is mixed in a high-speed stirrer. Figure 2 As shown, in the early stage of mixing, through the online detection device provided in this embodiment, it can be clearly detected that the relative concentration of PTFE shows a violent oscillation trend. As the mixing time becomes longer, the degree of change in the detected relative concentration of PTFE decreases and gradually stabilizes. After 30 minutes of mixing, it can be basically considered that the internal materials have been mixed evenly. At this time, the evenly mixed dry electrode powder can be transported to the film forming device for rolling film formation. This can not only avoid the poor quality of the final dry electrode film due to uneven powder mixing, but also avoid energy waste caused by continued mixing of powder, thereby improving production efficiency. Although in this embodiment, the real-time relative concentration of PTFE is obtained by converting the peak intensity of the functional group detected online of the binder PTFE to judge the uniformity of the dispersion of the electrode powder, the uniformity of the dispersion of the electrode powder can also be judged by the peak intensity of the functional group detected online of other components such as the active material NCM811 or the real-time relative concentration of NCM811 obtained thereby.

[0035] Regarding the mixing device, it should be noted that although the mixing device in this embodiment is a high-speed stirrer, this is not a limitation of the present invention. Without departing from the principles of the present invention, a ball mill, a grinder, a kneader, a jet mill, a single-screw extruder or a twin-screw extruder can also be used as the mixing device.

[0036] Example 2

[0037] like Figure 3As shown, this embodiment discloses a dry electrode preparation system, which includes an online detection device 1 for dry electrode materials, a feeding device 3 and a film forming device 4.

[0038] The online detection device 1 is used to detect the mixing uniformity of the surface of the dry electrode membrane in real time. It also includes a fiber optic probe 11, a spectrometer 12, and a computer 13. The fiber optic probe 11 is connected to the spectrometer 12 and the computer 13 in sequence. The spectrometer is a portable infrared spectrometer, and the fiber optic probe is an infrared detection probe.

[0039] The film-forming device 4 is used to drop the mixed dry-process electrode powder through the feeding device 3 onto the calendering rollers, where it is gradually calendered into a film using a speed differential method. The device also includes a first calendering roller 41, a second calendering roller 42, a third calendering roller 43, a fourth calendering roller 44, a fifth calendering roller 45, a sixth calendering roller 46, and a seventh calendering roller 47. A reciprocating bracket 48 is located above the seventh calendering roller 47. A fiber optic probe 11 is mounted on bracket 48 and is used to direct infrared light waves emitted by the spectrometer 12 into the dry-process electrode membrane and receive light signals scattered by the excited electrode membrane. A computer 13 is used to collect and analyze data from this light signal to determine the dispersion uniformity of the dry-process electrode membrane. Among them, the optical fiber probe 11 is installed on a reciprocating bracket, and can move back and forth perpendicular to the running direction of the electrode membrane, and perform reciprocating measurements on the dry electrode membrane at a certain rhythm. At this time, a "Z"-shaped path scan relative to the electrode membrane is performed to obtain the dispersion uniformity information of the dry electrode membrane in the MD (Machine Direction) and TD (Transverse Direction) directions.

[0040] For example, the dry electrode powder in this embodiment includes 96% active material graphite, 1.4% conductive agent carbon black, 1.6wt% binder PTFE, and 1.0wt% binder PVDF. The optical fiber probe reciprocates with the bracket installed above the seventh calendering roller, with a scanning speed of 30s per round trip, to obtain the peak intensity information of the -CF2- functional group of the binder in the MD direction and TD direction of the dry electrode membrane, and average all the measured transverse data points (i.e., TD direction) and divide the electrode membrane into 4 regions according to the width of 500mm. Figure 4As shown, the peak intensity concentration of the -CF2- functional group of the electrode diaphragm at different measurement sites all showed a small fluctuation (i.e., MD direction), and the difference in the absolute value of the standard deviation was less than 0.1, indicating that the concentrations at the four test sites were not significantly different, indicating that the dispersion of PTFE and PVDF in the prepared electrode diaphragm was good. Although in this embodiment, the real-time relative concentration of PTFE in the diaphragm in the region was obtained by converting the infrared peak intensity of the functional group of the binder -CF2- detected online in the MD and TD directions of the dry electrode diaphragm to determine the uniformity of the dispersion of the electrode diaphragm, the real-time relative concentration of NCM811 in the diaphragm in the region obtained by converting the peak intensity of the functional group of the active substance NCM811 detected online in the MD and TD directions of the dry electrode diaphragm can also be used to determine the uniformity of the dispersion of the electrode diaphragm.

[0041] Regarding the online measurement of the mixing uniformity of the dry electrode in the composite stage (i.e., the composite of the current collector and the dry electrode film), on the basis of this embodiment, an optical fiber probe can be added between the two rollers before the final product dry electrode is rolled up, and the same method can be used to measure the mixing uniformity of the finished dry electrode.

[0042] Thus far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it is readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art may make equivalent changes or substitutions to the relevant technical features, and the technical solutions after such changes or substitutions will fall within the scope of protection of the present invention.

Claims

1. A dry electrode preparation system, characterized in that: include: An online detection device (1) for dry-process electrode materials comprises an optical fiber probe (11), a spectrometer (12), and a computer (13). The optical fiber probe (11) is sequentially connected to the spectrometer (12) and the computer (13). The optical fiber probe (11) is used to inject light waves into the dry-process electrode material.

2. The preparation system according to claim 1, characterized in that: The dry electrode material is dry electrode powder or dry electrode membrane.

3. The preparation system according to claim 1 or 2, characterized in that: The spectrometer (12) is an infrared spectrometer or a Raman spectrometer.

4. The preparation system according to claim 2, characterized in that: The preparation system further comprises a mixing device (2) for mixing the dry electrode powder. A window (21) is provided on the mixing device (2), and the optical fiber probe (11) injects light waves into the mixed dry electrode powder through the window (21).

5. The preparation system according to claim 4, characterized in that: The window (21) is a transparent window.

6. The preparation system according to claim 4, characterized in that: The mixing device (2) is selected from a high-speed stirrer, a ball mill, a grinder, a kneader, a jet mill, a banbury mixer, an open mixer, a single-screw extruder, a twin-screw extruder and a stirrer.

7. The preparation system according to claim 2, characterized in that: The preparation system also includes: A mixing device (2) for mixing the dry electrode powder; and A film-forming device (4) is used to roll the mixed dry electrode powder into a film, the film-forming device includes a plurality of rolling rollers, at least one of which is provided with a bracket (48) above, and the optical fiber probe (11) is mounted on the bracket (48) for incident light waves on the surface of the dry electrode membrane.

8. The preparation system according to claim 7, characterized in that: The bracket (48) is a reciprocating bracket.

9. The preparation system according to claim 7, characterized in that: The bracket (48) is a fixed bracket.

10. The preparation system according to claim 7, characterized in that: The film forming device includes a first calendering roller (41), a second calendering roller (42), a third calendering roller (43), a fourth calendering roller (44), a fifth calendering roller (45), a sixth calendering roller (46) and a seventh calendering roller (47), and the bracket (48) is arranged above the seventh calendering roller.

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