Preparation Method and Preparation Device for Lithium-Ion Battery Electrodes

Abstract

A method for preparing a lithium-ion battery electrode includes the following steps: preparing a carbon nanotube raw material; providing a lithium-ion battery electrode active material and a solvent; mixing the carbon nanotube raw material and the electrode active material with the solvent and ultrasonically dispersing for a period of time to make the carbon nanotube raw material and the electrode active material mix with each other to form an electrode mixture; spraying the electrode mixture on a substrate to form an electrode layer, and removing the substrate after drying the electrode layer to form a lithium-ion battery electrode. The present invention further relates to a device for preparing a lithium-ion battery electrode.

Description

Technical Field

[0001] The present invention relates to a preparation method and a preparation device for an electrode of a lithium-ion battery. Background Art

[0002] Energy storage of lithium-ion batteries is widely used in fields such as mobile electronics, electric transportation, and power energy storage. With the increasing application demands of high-endurance electric vehicles, large-scale industrial energy storage, smart grids, and other high-energy storage devices, the energy density of lithium-ion batteries urgently needs to be improved. Taking current commercial lithium-ion batteries as an example, active materials, conductive agents, binders, and current collectors together form positive and negative electrode sheets. However, it should be noted that all the conductive agents, binders, and current collectors in the positive and negative electrode sheets are inactive substances and cannot provide capacity. Therefore, reducing the content of inactive substances as much as possible can effectively improve the energy density of lithium-ion batteries. For example, preparing electrodes with a high active material areal loading to reduce the mass ratio of the current collector, etc.

[0003] Active materials can be evenly distributed in electrode sheets with a low areal loading. However, when the areal loading of active materials in the electrode is increased, the conductive agent and the binder need to be improved simultaneously, otherwise the active materials cannot be evenly distributed in the electrode sheet. After the areal loading is increased, microcracks appear on the surface of the electrode sheet. This is due to the fact that as the thickness of the electrode increases, the non-uniformity of the electrode intensifies, resulting in uneven local bonding effect and uneven surface tension distribution. The existence of these microcracks will lead to increased electrolyte consumption and a decrease in structural stability. Summary of the Invention

[0004] Therefore, it is indeed necessary to provide a preparation method and a preparation device for an electrode of a lithium-ion battery, in which the active materials in the prepared electrode of the lithium-ion battery are evenly distributed.

[0005] A preparation method for an electrode of a lithium-ion battery includes the following steps: preparing a carbon nanotube raw material; providing an active material for the electrode of the lithium-ion battery and a solvent; mixing the carbon nanotube raw material and the electrode active material with the solvent and ultrasonically dispersing for a period of time to make the carbon nanotube raw material and the electrode active material mix with each other to form an electrode mixture; spraying the electrode mixture on a substrate to form an electrode layer, and removing the substrate after drying the electrode layer to form an electrode of the lithium-ion battery.

[0006] A preparation device for an electrode of a lithium-ion battery includes a rotating device, a recovery device, a substrate, and a spray gun. When the rotating device works, it rotates around its rotation axis. The recovery device is fixed on the rotating device. The substrate is fixed inside the recovery device. The spray gun is arranged above the substrate for spraying the electrode mixture onto the substrate.

[0007] Compared with the prior art, the method for preparing a lithium-ion battery electrode provided by the present invention has the following beneficial effects: Spraying the electrode mixture directly on the substrate with a spray gun can ensure the uniformity of the electrode mixture, enabling the electrode active material and the carbon nanotubes to have the same sedimentation rate to form a uniform lithium-ion battery electrode, and effectively avoiding the generation of electrode microcracks at the same high loading; The spraying process using a spray gun greatly reduces the loss of the electrode active material, which is beneficial to improving the cycling performance of the lithium-ion battery. The device for preparing the lithium-ion battery electrode has the following advantages: Preparing the lithium-ion battery electrode by spraying the electrode mixture with a spray gun can ensure the uniformity of the electrode mixture and form a lithium-ion battery electrode with a uniform distribution of active substances; At the same time, the device for preparing the lithium-ion battery electrode realizes the recycling of the electrode mixture, can save electrode materials, and improve the efficiency of manufacturing lithium-ion battery electrodes. Description of the Drawings

[0008] Figure 1 It is a schematic structural diagram of the device for preparing the lithium-ion battery electrode provided by the present invention.

[0009] Figure 2 It is a flowchart of the method for preparing the lithium-ion battery electrode provided by the present invention.

[0010] Figure 3 It is a scanning electron microscope (SEM) photograph of the positive electrode of the lithium-ion battery in Example 1 provided by the present invention.

[0011] Figure 4 It is a scanning electron microscope (SEM) photograph of the positive electrode of the lithium-ion battery in Example 1 provided by the present invention.

[0012] Figure 5 It is a scanning electron microscope (SEM) photograph of the positive electrode of the lithium-ion battery in Comparative Example 1 provided by the present invention.

[0013] Figure 6 It is a thermogravimetric analysis (TGA) curve of the positive electrode of the lithium-ion battery in Example 1 provided by the present invention in an air atmosphere.

[0014] Figure 7 It is a performance comparison chart of the coin cells in Example 2 and Comparative Example 2 provided by the present invention at a 0.5C rate.

[0015] Figure 8 It is a performance comparison chart of the coin cells in Example 2 and Comparative Example 2 provided by the present invention at a 1C rate.

[0016] Figure 9 It is a comparison chart of the rate performance of the coin cells in Example 2 and Comparative Example 2.

[0017] Figure 10Capacity-voltage curve of the positive electrode of the lithium-ion battery in Example 1 at different rates.

[0018] Figure 11 Capacity-voltage curve of the positive electrode of the lithium-ion battery in Comparative Example 1 at different rates.

[0019] Figure 12 Electrochemical impedance (EIS) curve of the positive electrode of the lithium-ion battery in Example 1 before and after cycling.

[0020] Figure 13 EIS curve of the positive electrode of the lithium-ion battery in Comparative Example 1 before and after cycling.

[0021] Figure 14 Performance comparison chart of the coin cell in Example 3 and the coin cell in Comparative Example 3 at a rate of 0.5C.

[0022] Description of main component symbols

[0023] Preparation device 100 for the electrode of a lithium-ion battery

[0024] Spray gun 10

[0025] Substrate 12

[0026] Support 14

[0027] Recovery device 16

[0028] Rotating device 18

[0029] Electrode 20 of a lithium-ion battery

[0030] The following specific embodiments will further illustrate the present invention in conjunction with the above-mentioned drawings. Specific embodiments

[0031] The preparation device 100 for the electrode of a lithium-ion battery provided by the embodiments of the present invention will be further described in detail below in conjunction with the drawings and specific embodiments.

[0032] Please refer to Figure 1 , the present invention provides a preparation device 100 for the electrode of a lithium-ion battery. The preparation device 100 for the electrode of a lithium-ion battery includes a rotating device 18, a recovery device 16, a substrate 12, and a spray gun 10. When the rotating device 18 works, it rotates around its rotation axis. The recovery device 16 is fixed on the rotating device 18. The substrate 12 is fixed inside the recovery device 16. The spray gun 10 is arranged above the substrate 12 for spraying an electrode mixture onto the substrate 12.

[0033] The substrate 12 is used to carry the electrode mixture. The substrate 12 can be a solid planar structure, for example, polymers such as polytetrafluoroethylene and polyethylene, metals such as aluminum and copper, glass plates, etc. The substrate 12 can also be a grid structure, for example, stainless steel filter screens, molecular sieves, etc. In this embodiment, the substrate 12 is a stainless steel filter screen with a mesh count of 1000 meshes.

[0034] The substrate 12 is fixed inside the recovery device 16. Further, the substrate 12 can be fixed inside the recovery device 16 through a support 14. The support 14 is used to carry the substrate 12. The support 14 is arranged on the recovery device 16. Specifically, the support 14 includes a main body and at least three support columns. The main body of the support 14 is used to carry the substrate 12. Further, it can be understood that the main body of the support 14 can include a groove structure, and the substrate 12 is arranged in the groove. Additionally, the main body of the support 14 can be a hollow frame, and the substrate 12 is arranged on the hollow frame and is suspended inside the recovery device 16. The area of the substrate 12 is smaller than the cross-sectional area of the recovery device 16. The support columns of the support 14 are fixed on the recovery device 16. The support columns of the support 14 can be fixed on the outer surface of the recovery device 16 or can be fixed on the inner surface of the recovery device 16, as long as it is ensured that the substrate 12 is arranged inside the recovery device 16. The manner in which the support columns of the support 14 are fixed on the recovery device 16 is not limited. It can be fixed on the recovery device 16 by a snap-fastening method or can be fixed on the recovery device 16 by an adhesive. The substrate 12 includes a first surface (not labeled in the figure) and a second surface (not labeled in the figure) opposite to the first surface. The first surface is arranged on the support 14. Preferably, the height of the second surface of the substrate 12 is lower than the height of the recovery device 16 and the height of the first surface of the substrate 12 is higher than the height of the electrode mixture carried in the recovery device 16, so as to better recover the electrode mixture that is not sprayed on the substrate 12. In this embodiment, the support 14 includes a main body and three support columns. The support columns are fixed on the outer surface of the recovery device 16 by an adhesive. The main body is a hollow frame, and the filter screen is arranged on the hollow frame.

[0035] The recovery device 16 is fixed on the rotating device 18 for carrying the electrode mixture. The recovery device 16 is supported by the rotating device 18 and rotates with the rotation of the rotating device 18. The recovery device 16 has a groove 162. The substrate 12 and at least a part of the support 14 are arranged in the groove 162. The groove 162 is used for carrying the electrode mixture. The material of the recovery device 16 is not limited as long as it can carry the electrode mixture. The size and shape of the recovery device 16 can be selected according to actual needs. In this embodiment, the material of the recovery device 16 is glass, and the recovery device 16 is a cylindrical structure.

[0036] The rotating device 18 is used for carrying and fixing the recovery device 16, so that the recovery device 16 rotates with the rotation of the rotating device 18, and further drives the substrate 12 to rotate together. When the rotating device 18 rotates, the position of the spray gun 10 remains unchanged. The shape and material of the rotating device 18 are not limited as long as it can drive the recovery device 16 to rotate. In this embodiment, the rotating device 18 is a turntable.

[0037] The spray gun 10 is used for spraying the electrode mixture onto the substrate 12. The spray gun 10 includes an air inlet 102 and a liquid inlet 104. The liquid inlet 104 is connected to a liquid inlet pipe 106, and the end of the liquid inlet pipe 106 is arranged in the groove 162 to contact the electrode mixture, for providing the electrode mixture to the spray gun 10 so that the electrode mixture can be recycled. The air inlet 102 is connected to an air inlet pipe 108 for providing air to the spray gun 10.

[0038] The preparation device 100 for the lithium-ion battery electrode provided by the present invention has the following advantages: Preparing the lithium-ion battery electrode by spraying the electrode mixture with a spray gun can ensure the uniformity of the electrode mixture and form a lithium-ion battery electrode with uniformly distributed active substances. At the same time, the preparation device 100 for the lithium-ion battery electrode realizes the recycling of the electrode mixture, can save electrode materials, and improve the efficiency of manufacturing the lithium-ion battery electrode.

[0039] Please refer to Figure 2 , the present invention provides a method for preparing a lithium-ion battery electrode, which includes the following steps:

[0040] Step S1, preparing a carbon nanotube raw material;

[0041] Step S2, providing a lithium-ion battery electrode active material and a solvent;

[0042] Step S3, mixing the carbon nanotube raw material and the electrode active material with the solvent, and ultrasonically dispersing for a period of time to make the carbon nanotube raw material and the electrode active material mix with each other to form an electrode mixture;

[0043] Step S4: Spray the electrode mixture on a substrate to form an electrode layer, and after drying the electrode layer, remove the substrate to form a lithium-ion battery electrode.

[0044] In step S1, the carbon nanotube raw material is composed of multiple carbon nanotubes. The carbon nanotubes include single-walled carbon nanotubes, double-walled carbon nanotubes, or multi-walled carbon nanotubes. The diameter of the carbon nanotubes is 1 nm to 200 nm. The length of the carbon nanotubes is greater than 100 μm, preferably greater than 300 μm. The lengths of the carbon nanotubes can be equal or unequal. Preferably, the lengths of the carbon nanotubes are equal. The carbon nanotubes are preferably carbon nanotubes with a pure surface and no impurities. The preparation method of the carbon nanotube raw material is as follows: Prepare a carbon nanotube array on a substrate; scrape the carbon nanotube array from the substrate to obtain the carbon nanotube raw material. When the carbon nanotube raw material is directly obtained from the carbon nanotube array, the lithium-ion battery electrode prepared using this carbon nanotube raw material has greater strength. Preferably, the carbon nanotube array is a super-aligned carbon nanotube array. The so-called super-aligned carbon nanotube array means that the carbon nanotubes in the carbon nanotube array have a longer length, generally greater than 300 μm, the surface of the carbon nanotubes is pure, and basically does not contain impurities such as amorphous carbon or residual catalyst metal particles, and the arrangement directions of the carbon nanotubes are basically the same. The preparation method of the carbon nanotube array is not limited and can be chemical vapor deposition method, arc discharge preparation method, aerosol preparation method, etc.

[0045] In step S2, the lithium-ion battery electrode active material can be a lithium-ion battery positive electrode active material or a lithium-ion battery negative electrode active material. Specifically, when preparing a lithium-ion battery positive electrode, a lithium-ion battery positive electrode active material is used; when preparing a lithium-ion battery negative electrode, a lithium-ion battery negative electrode active material is used.

[0046] The positive electrode active material may include lithium iron phosphate (LiFePO 4 ), lithium nickel cobalt (LiNi 0.8 Co 0.2 O 2 ), lithium cobalt oxide (LiCoO 2 ), lithium nickel oxide (LiNiO 2 ), lithium cobalt phosphate (LiCoPO4), lithium manganese oxide (LiMn 2 O 4 ), LiNi0.8Co0.15Al0.05O2 (NCA), and lithium nickel cobalt manganese (LiNi x Co y Mn z O 2)(Among them, the ratio of x:y:z can be one or more of 1:1:1, 5:3:2, 8:1:1, or 9:0.5:0.5).

[0047] The negative electrode active material includes one or more of graphite, lithium titanate, silicon monoxide, silicon dioxide, silicon, and nanoalloy.

[0048] The solvent includes one or more of ethanol, ethylene glycol, propanol, isopropanol, acetone, and water. Preferably, the solvent is a volatile and non-toxic solvent. In this embodiment, ethanol is used as the organic solvent. When the solvent is a volatile and non-toxic solvent, the solvent can be directly evaporated without additional treatment processes, and the preparation method is simple.

[0049] In step S3, the order of mixing the carbon nanotube raw material and the electrode active material with the solvent is not limited. In this embodiment, after adding the carbon nanotube raw material and the electrode active material into the container, an appropriate amount of ethanol is added.

[0050] The ratio of the mass of the carbon nanotube raw material to the total mass of the carbon nanotubes and the electrode active material is greater than or equal to 0.1 wt% and less than or equal to 20 wt%, preferably 1% to 10%, and can be 3%, 5%, or 10%.

[0051] The power of the ultrasonic wave is 400 watts to 1500 watts, preferably 800 watts to 1000 watts. The time of ultrasonic oscillation is 2 minutes to 30 minutes, preferably 5 minutes to 10 minutes. After ultrasonic oscillation, the carbon nanotube raw material and the electrode active material are uniformly mixed to form an electrode mixture.

[0052] In step S4, the electrode mixture is sprayed on the substrate 12 by the spray gun 10 and dried to form the lithium-ion battery electrode 20. Please refer to again Figure 1 , in this step, the lithium-ion battery electrode preparation device 100 is used to prepare the lithium-ion battery electrode 20.

[0053] The method of using the lithium-ion battery electrode preparation device 100 to prepare the lithium-ion battery electrode 20 includes:

[0054] S41, placing the electrode mixture in the recovery device 16;

[0055] S42, placing the liquid inlet pipe 106 in the recovery device 16 and fixing the position of the spray gun;

[0056] S43, starting the rotating device 18 to drive the substrate 12 to rotate, and using the spray gun 10 to spray the electrode mixture on the surface of the substrate 12 to form the electrode layer;

[0057] S44. After drying the electrode layer, remove the substrate 12 to obtain a lithium-ion battery electrode.

[0058] In step S41, place the electrode mixture obtained in step S3 in the groove 162 of the recovery device 16.

[0059] In step S42, place the liquid inlet pipe 106 in the electrode mixture in the groove 162 to supply the electrode mixture to the spray gun 10. Fix the spray gun 10 so that the nozzle is perpendicular to the substrate 12, and control the gun distance to be 5 cm - 30 cm. In this embodiment, the gun distance is 20 cm.

[0060] In step S43, start the rotating device 18 to rotate the rotating device 18 and drive the substrate 12 to rotate. Pass air into the spray gun 10 through the air inlet pipe 108 and start the spray gun 10 to spray the electrode mixture onto the surface of the substrate 12. When the rotating device 18 rotates, the position of the spray gun 10 remains unchanged. The rotation speed of the rotating device 18 is 10 r / min - 200 r / min. In this embodiment, the rotating device 18 is a turntable, and the rotation speed of the turntable is 50 r / min. The air consumption of the spray gun 10 is 50 L / min - 250 L / min. In this embodiment, the air consumption of the spray gun 10 is 225 L / min. The air pressure of the spray gun 10 is 0.2 MPa - 0.5 MPa. In this embodiment, the air pressure of the spray gun 10 is 0.25 MPa. The ejection amount of the electrode mixture is 85 mL / min - 210 mL / min. In this embodiment, the ejection amount of the electrode mixture is 170 mL / min. The spray width of the spray gun 10 is 100 mm - 200 mm. In this embodiment, the spray width of the spray gun 10 is preferably 175 mm.

[0061] In step S44, stop spraying after the electrode mixture in the recovery device 16 becomes clear. Dry and evaporate the solvent in the electrode layer. After complete drying, peel the electrode off the substrate 12 to obtain a lithium-ion battery electrode. The thickness of the lithium-ion electrode can be prepared according to actual needs. In this embodiment, the electrode thickness is 100 microns. Further, it may include a cutting step to cut the lithium-ion battery electrode into the size required for lithium-ion battery assembly. For example, the lithium-ion battery electrode can be cut into a circular or square electrode plate required for battery assembly by using a core cutter or a blade.

[0062] The preparation method of the lithium-ion battery electrode provided by the present invention has the following beneficial effects: Spraying the electrode mixture directly on the substrate with a spray gun can ensure the uniformity of the electrode mixture, making the sedimentation rates of the electrode active material and the carbon nanotubes the same to form a uniform lithium-ion battery electrode, and effectively avoiding the generation of electrode microcracks at the same high loading; The spraying process using a spray gun greatly reduces the loss of the electrode active material, which is beneficial to improving the cycle performance of the lithium-ion battery; The preparation method of the lithium-ion battery electrode provided by the present invention does not require the addition of a binder. Therefore, the prepared lithium-ion battery electrode is composed of the lithium-ion battery electrode active material and carbon nanotubes, and the proportion of the lithium-ion battery electrode active material is relatively high; Since there is no barrier of insulating substances between the lithium-ion battery electrode active materials, the overall conductivity of the lithium-ion battery electrode will be correspondingly improved; Moreover, the preparation method of the lithium-ion battery electrode provided by the present invention is simple to operate and has a low cost.

[0063] Example 1

[0064] 0.2 g of super-aligned carbon nanotubes and 1 g of lithium iron phosphate (LFP) powder were ultrasonically dispersed in 600 mL of ethanol for 30 minutes to obtain an electrode mixture. The obtained electrode mixture was sprayed onto a 1000-mesh filter screen with a spray gun, and after drying, the self-supporting lithium-ion battery positive electrode was peeled off from the filter screen.

[0065] Comparative Example 1

[0066] The active material lithium iron phosphate, the conductive agent super-p (conductive carbon black), and the binder (PVDF) were mixed in a mass ratio of 8:1:1 and dispersed in NMP solvent to obtain a slurry. The slurry was coated on a metal current collector (Al or Cu) and dried to obtain the lithium-ion battery positive electrode.

[0067] Figure 3 and Figure 4 is the SEM photograph of the lithium-ion battery positive electrode of Example 1. Figure 5 is the SEM photograph of the lithium-ion battery positive electrode in Comparative Example 1. In Figures 3 to 5 , the lithium iron phosphate in the lithium-ion battery positive electrode of Example 1 and the lithium iron phosphate in the lithium-ion battery positive electrode of Comparative Example 1 have the same high areal loading. Specifically, the areal loading is 10 mg / cm 2 . From Figure 3 it can be seen that the lithium iron phosphate on the surface of the lithium-ion battery positive electrode of Example 1 is evenly distributed without microcracks. At the same time, as Figure 4 shows, from the SEM photographs of the front and back sides of the lithium-ion battery positive electrode of Example 1, it can be seen that the lithium-ion battery positive electrode of Example 1 has excellent uniformity. Refer to Figure 5, the surface of the positive electrode of the lithium-ion battery in Comparative Example 1 has microcracks and the lithium iron phosphate is unevenly distributed. Compared with the positive electrode of the lithium-ion battery in Comparative Example 1, at the same high loading, the positive electrode of the lithium-ion battery in Example 1 benefits from the excellent network structure of the carbon nanotube film and can effectively avoid the generation of microcracks. At the same time, the spraying method can ensure the uniformity of the electrode mixture, and thus can ensure the uniformity of the distribution of lithium iron phosphate in the positive electrode of the lithium-ion battery.

[0068] Figure 6 Figure is the thermogravimetric analysis (TGA) curve of the positive electrode of the lithium-ion battery in Example 1 in an air atmosphere. By Figure 6 it is possible to determine the content of lithium iron phosphate in the positive electrode of the lithium-ion battery in Example 1. As Figure 6 shown, in an air atmosphere at 600 °C - 700 °C, the positive electrode of the lithium-ion battery has an obvious weight loss of 19.03%, which corresponds to the decomposition of carbon nanotubes in this temperature range. After 750 °C, the mass of the positive electrode of the lithium-ion battery tends to be stable. Therefore, the content of lithium iron phosphate can be determined to be 80.97%. The mass ratio for preparing the positive electrode of the lithium-ion battery in Example 1 is clearly recorded in the example, and the theoretical content of lithium iron phosphate in the positive electrode of the lithium-ion battery in Example 1 is 83.33%. By adopting the spraying process, it can be seen that the loss of the active substance lithium iron phosphate is greatly reduced.

[0069] Example 2

[0070] The positive electrode of the lithium-ion battery in Example 1 is used as the positive electrode, a polypropylene film is used as the separator, a lithium foil is used as the negative electrode, and a stainless steel gasket is used. They are successively stacked and assembled with a CR2016 battery case, and 1M LiPF6 in FEC:FEMC:HFE (mass percentage 2:6:2) is used as the electrolyte. The assembly process of the button battery is carried out in an argon glove box.

[0071] Comparative Example 2

[0072] The structure of the button battery in Comparative Example 2 is basically the same as that of the button battery in Example 1, the difference being that the positive electrode of the lithium-ion battery in Comparative Example 1 is used as the positive electrode.

[0073] Figure 7 Figure is the performance comparison chart of the button batteries in Example 2 and Comparative Example 2 at a 0.5C rate. By Figure 7It can be seen that the initial specific capacity of the button cell in Example 2 at 0.5C is 168.4 mAh / g, and it still remains 166.5 mAh / g after 150 cycles, corresponding to a capacity retention rate as high as 98.87% and an average Coulombic efficiency of 99.9924%. The initial specific capacity of the button cell in Comparative Example 2 at 0.5C is only 157.4 mAh / g, and it rapidly decays in the subsequent several cycles and can hardly release any capacity after 6 cycles. Thus, it can be seen that the performance of the button cell in Example 2 is significantly superior to that of the button cell in Comparative Example 2.

[0074] Figure 8 Figure for comparing the performance of the button cells of Example 2 and Comparative Example 2 at a current rate of 1C. As Figure 8 shown, the initial specific capacity of the button cell in Example 2 at 1C is 160.1 mAh / g, and it still remains 152.7 mAh / g after 300 cycles, corresponding to a capacity retention rate as high as 95.38% and an average Coulombic efficiency of 99.9842%. While the button cell in Comparative Example 2 has no cycling capacity at 1C.

[0075] Figure 9 Figure for comparing the rate performance of the button cells of Example 2 and Comparative Example 2. The two types of batteries are cycled at current rates of 0.2C, 0.5C, 1C, and 2C respectively, and then switched back to 0.2C and 0.5C to explore the reversibility of their electrodes. As Figure 9 shown, the cycling specific capacities of the button cell in Example 2 at 0.2C, 0.5C, 1C, and 2C are 170.9 mAh / g, 168.1 mAh / g, 163.3 mAh / g, and 155.2 mAh / g respectively. When the current density is switched to 0.2C and 0.5C, the cycling specific capacities are 170.9 mAh / g and 169.2 mAh / g respectively, which are almost the same as the cycling specific capacities at these two current rates before, demonstrating excellent electrode reversibility. While the button cell in Comparative Example 2 shows a specific capacity of 157.7 mAh / g at 0.2C. When the current increases to 0.5C, the initial capacity is 138.2 mAh / g and it rapidly decays. In the later stage of cycling at 0.5C, and at 1C and 2C current rates, there is no cycling specific capacity. When the current is increased to 0.2C again, the cycling specific capacity resumes to 158.5 mAh / g, but when it is increased to 0.5C again, there is still no cycling specific capacity. The above performance proves that the button cell in Comparative Example 2 can only work properly at extremely low current rates, meaning that the internal electron transfer and ion transport are extremely poor, while the button cell in Example 2 can significantly improve these problems.

[0076] Figure 10 Figure of the capacity-voltage curve of the positive electrode of the lithium-ion battery in Example 1 at different current rates. Figure 11Capacity-voltage curve of the positive electrode of the lithium-ion battery of Comparative Example 1 at different rates. The voltage-capacity curve can more intuitively show the charge and discharge conditions of the electrode at different rates, and can also explain why the positive electrode of the lithium-ion battery of Comparative Example 1 has no cycle capacity at high rates. As Figure 10 shown, for the positive electrode of the lithium-ion battery of Example 1, different rates have little effect on its charge and discharge plateau, and the polarization of the battery (the difference between the charge plateau potential and the discharge plateau potential) is also small. Therefore, the positive electrode of the lithium-ion battery of Example 1 still exhibits excellent cycle performance at high rates. However, the initial polarization of the positive electrode of the lithium-ion battery of Comparative Example 1 is large at 0.2C, and when the rate increases to 0.5C, the battery polarization further expands and approaches the cut-off voltage. Therefore, as the cycle progresses or the rate increases, the battery polarization will be further increased, resulting in no cycle capacity.

[0077] Figure 12 Electrochemical impedance (EIS) curve of the positive electrode of the lithium-ion battery of Example 1 before and after cycling. Figure 13 EIS curve of the positive electrode of the lithium-ion battery of Comparative Example 1 before and after cycling. The electrochemical impedance (EIS) test experiment can be used to further explain the principle of the improvement of the positive electrode of the lithium-ion battery of Example 1 on the battery performance. As Figure 12 shown, before cycling, the charge transfer impedance of the positive electrode of the lithium-ion battery of Example 1 is 39.6Ω, and it is only 34.2Ω after cycling. The magnitude of the charge transfer impedance represents the ease of charge transfer on the surface of the active material. The low charge transfer impedance of the positive electrode of the lithium-ion battery of Example 1 is due to the unique network structure of the carbon nanotubes. Contributed. Because the excellent conductivity of the carbon nanotube network provides a complete conductive network in all directions and at multiple sites for the active material particles loaded on it, and the porous structure in the carbon nanotube film can fully infiltrate the electrolyte, enabling lithium ions to be fully transported in the electrode. All of these enable the positive electrode of the lithium-ion battery of Example 1 to maintain excellent electron and ion transport capabilities even under high areal loading conditions. After cycling, the positive electrode of the lithium-ion battery of Example 1 still maintains a smaller charge transfer impedance, which shows that the positive electrode of the lithium-ion battery of Example 1 has excellent structural stability.

[0078] As Figure 13As shown, the charge transfer resistance of the positive electrode of the lithium-ion battery in Comparative Example 1 was as high as 247.9 Ω before cycling, and it even increased to 893.1 Ω after cycling. It can be seen that the transfer of electrons and ions inside the positive electrode of the lithium-ion battery in Comparative Example 1 under high areal loading conditions is extremely poor. This is because in the lithium-ion battery of Comparative Example 1, the positive active material particles only have point contact with a small amount of conductive agent. When the areal loading increases, the active material particles and the conductive agent particles will inevitably agglomerate respectively. And the generation of microcracks indicates that the bonding effect of the binder becomes poor, all of which lead to extremely poor electron and ion conduction in the positive electrode of the lithium-ion battery in Comparative Example 1 during the cycling process.

[0079] Example 3

[0080] 0.2 g of super-aligned carbon nanotubes and 1 g of NCA powder were ultrasonically dispersed in 600 mL of ethanol for 30 minutes to obtain an electrode mixture. The obtained electrode mixture was sprayed onto a 1000-mesh filter screen through a spray gun, and after drying, the self-supporting positive electrode of the lithium-ion battery was peeled off from the filter screen. Using the above positive electrode of the lithium-ion battery as the positive electrode, a polypropylene film as the separator, and a lithium foil as the negative electrode, and using a stainless steel gasket, they were successively stacked and assembled with a CR2016 battery case, and 1 M LiPF6 in FEC:FEMC:HFE (mass percentage 2:6:2) was used as the electrolyte. The assembly process of the button cell was carried out in an argon glove box.

[0081] Comparative Example 3

[0082] The active material NCA, the conductive agent super-p (conductive carbon black), and the binder (PVDF) were mixed at a mass ratio of 8:1:1 and dispersed in NMP solvent to obtain a slurry. The slurry was coated on a metal current collector (Al or Cu) and dried to obtain the positive electrode of the lithium-ion battery. The structure of the button cell in Comparative Example 3 was basically the same as that of the button cell in Example 3, the difference being that the above positive electrode of the lithium-ion battery was used as the positive electrode.

[0083] Figure 14 It is a performance comparison chart of the button cell in Example 3 and the button cell in Comparative Example 3 at a 0.5C rate. As Figure 14 shown, the specific capacity of the button cell in Example 3 after 150 cycles at a 0.5C rate was 120.6 mAh / g. The specific capacity of the button cell in Comparative Example 3 after 150 cycles at a 0.5C rate was 45.3 mAh / g. Thus, it can be seen that when the active material is NCA, compared with the button cell in Comparative Example 3, the button cell in Example 3 still has good cycling performance.

[0084] It can be seen that the method for preparing the lithium-ion battery electrode in this case can spray different lithium-ion battery active materials by a spraying process to obtain a positive electrode or a negative electrode of the lithium-ion battery, and the formed lithium-ion battery electrode has good cycle performance.

[0085] In addition, those skilled in the art can also make other changes within the spirit of the present invention. Of course, these changes made according to the spirit of the present invention should all be included within the scope claimed by the present invention.

Claims

1. A preparation device for a lithium-ion battery electrode, comprising: a rotating device that rotates around its rotation axis during operation; a recovery device fixed to the rotating device, the recovery device having a groove for carrying an electrode mixture; a substrate fixed inside the recovery device; a spray gun disposed above the substrate for spraying the electrode mixture onto the substrate, the spray gun including an air inlet and a liquid inlet, the liquid inlet being connected to a liquid inlet pipe, the end of which is disposed in the groove in contact with the electrode mixture; The rotating device causes the recovery device to rotate with the rotation of the rotating device, further driving the substrate to rotate together.

2. The preparation device for a lithium-ion battery electrode according to claim 1, characterized in that the substrate is a filter screen with a mesh number of 1000 meshes.

3. A method for preparing a lithium-ion battery electrode using the preparation device for a lithium-ion battery electrode according to claim 1 or claim 2, comprising the following steps: S1, preparing a carbon nanotube raw material; S2, providing a lithium-ion battery electrode active material and a solvent; S3, mixing the carbon nanotube raw material and the electrode active material with the solvent and ultrasonically dispersing for a period of time to make the carbon nanotube raw material and the electrode active material mix with each other to form an electrode mixture; S4, spraying the electrode mixture onto a substrate to form an electrode layer, drying the electrode layer and then removing the substrate to form a lithium-ion battery electrode.

4. The preparation method for a lithium-ion battery electrode according to claim 3, characterized in that the preparation method of the carbon nanotube raw material is: providing a carbon nanotube array disposed on the surface of a substrate; scraping the carbon nanotube array from the substrate to obtain the carbon nanotube raw material.

5. The preparation method for a lithium-ion battery electrode according to claim 3, characterized in that the electrode active material is a positive electrode active material or a negative electrode active material.

6. The preparation method for a lithium-ion battery electrode according to claim 3, characterized in that the solvent includes one or more of ethanol, ethylene glycol, propanol, isopropanol, acetone and water.

7. The preparation method for a lithium-ion battery electrode according to claim 3, characterized in that the step of spraying the electrode mixture onto a substrate to form an electrode layer includes: starting a rotating device to drive the substrate to rotate, and using a spray gun to spray the electrode mixture onto the surface of the substrate.

8. The preparation method for a lithium-ion battery electrode according to claim 7, characterized in that the nozzle diameter of the spray gun is 0.8 mm - 1.8 mm, the spray pattern size of the spray gun is 100 mm - 200 mm, and the ejection amount of the electrode mixture is 85 mL / min - 210 mL / min.

9. The preparation method for a lithium-ion battery electrode according to claim 8, characterized in that the air usage amount of the spray gun is 50 L / min - 250 L / min, and the air pressure of the spray gun is 0.2 MPa - 0.5 MPa.

10. The method for preparing a lithium-ion battery electrode according to claim 8, characterized in that, the rotational speed of the rotating device is 10 r / min - 200 r / min.

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