A lithium ion battery thick electrode plate, a spraying device and a construction method thereof

Abstract

The application discloses a kind of lithium ion battery thick pole piece, including current collector and the conductive agent layer and active material layer coated on current collector, conductive agent layer includes conductive carbon black layer and conductive carbon tube layer, active material layer includes far from current collector large particle active coating and close to current collector small particle active coating, in addition, preparation of lithium ion battery thick pole piece is disclosed spraying device, including slurry storage tank, pressure gauge, slurry pipe and spray nozzle, slurry pipe has flowmeter, it further includes the thickness gauge, speed detector and on-line area density instrument for detecting the thickness, width and speed of spraying slurry.The spraying device of the application not only simply and conveniently controls micron level coating thickness and width, on-line real-time calculation coating area density, but also makes slurry free from environmental dust pollution, water absorption and other problems, the lithium ion battery thick pole piece prepared increases the absorption of electrolyte, and the internal resistance of lithium ion battery is reduced, energy density is promoted, and cycle life is prolonged.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical technology, specifically relating to a thick electrode sheet for lithium-ion batteries, its coating device, and its construction method. Background Technology

[0002] Lithium-ion batteries are among the most widely used energy storage devices. With the rapid development of electric vehicles, mobile electronic devices, and industrial energy storage, increasingly higher demands are being placed on the energy density and lifespan of lithium-ion batteries. How to further improve energy density and lifespan based on existing technologies is a key issue facing lithium-ion battery technology. Battery material systems and battery configuration design are two crucial aspects affecting performance. Currently, lithium-ion batteries use thick electrode configurations to improve energy density. Thick electrodes can reduce the amount of current collector and separator used, increase the proportion of active materials, and thus improve the battery's specific energy. However, increasing electrode thickness not only lengthens the transport path of lithium ions and electrons, increasing impedance, but also causes lithium ions to react only in the shallow electrode layer. As the cycle life increases, the shallow and deep electrodes gradually separate, affecting battery life.

[0003] Therefore, precise design of the thick electrode structure is essential, but this precise design relies heavily on advanced coating equipment. Currently available coating equipment lacks the capability for precise design of thick electrodes. To address these issues, a device and method for constructing thick electrodes for lithium-ion batteries is urgently needed. Summary of the Invention

[0004] The technical problem to be solved by this invention is to address the shortcomings of the prior art by providing a thick electrode sheet for lithium-ion batteries. This thick electrode sheet consists of a current collector and a conductive agent layer and an active material layer coated on the current collector. The current collector serves as the external circuit of the battery, transporting electrons. By coating the current collector with conductive agent layers (i.e., conductive carbon black and conductive carbon nanotube layers), the electrode accelerates the conduction of electrons and ions, increasing the absorption of electrolyte. By coating the current collector with active material layers (i.e., large-particle and small-particle active coatings), the electrode's conductivity and electrolyte absorption capacity are increased, thereby reducing battery internal resistance, extending battery life, and improving energy density.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a thick electrode sheet for lithium-ion batteries, characterized in that the thick electrode sheet for lithium-ion batteries includes a current collector and a conductive agent layer and an active material layer coated on the current collector, wherein the conductive agent layer includes a conductive carbon black layer and a conductive carbon nanotube layer, and the active material layer includes a large-particle active coating layer far away from the current collector and a small-particle active coating layer close to the current collector. In this invention, the current collector is the external circuit of the battery, serving to transport electrons. By coating the current collector with a conductive agent layer, namely a conductive carbon black layer and a conductive carbon nanotube layer, the conduction of electrons and ions is accelerated, increasing the absorption of electrolyte by the electrode. By coating the current collector with an active material layer, namely a large-particle active coating and a small-particle active coating, the conductivity and electrolyte absorption capacity of the electrode are increased, thereby reducing the battery's internal resistance, extending its lifespan, and improving its energy density. In this invention, the large-particle active coating is far from the current collector, while the small-particle active coating is close to the current collector because the large-particle active coating has a larger porosity, which promotes electrolyte penetration to the bottom of the electrode, thereby increasing the electrode's conductivity and electrolyte absorption capacity, thus reducing the battery's internal resistance, extending its lifespan, and improving its energy density. In this invention, the conductive carbon black layer is close to the current collector because electrons are transported towards the current collector, while the conductive carbon nanotube layer is relatively far away because lithium ions are transported towards the separator.

[0006] The aforementioned thick electrode sheet for a lithium-ion battery is characterized in that the current collector is coated with a small-particle active material layer consisting of a conductive carbon black layer, a conductive carbon nanotube layer, and a small-particle active coating layer sequentially coated; the small-particle active material layer is coated with a large-particle active material layer consisting of a conductive carbon black layer, a conductive carbon nanotube layer, and a large-particle active coating layer sequentially coated; the number of both the small-particle and large-particle active material layers is not less than three; and the large-particle active material layer is further coated with a conductive carbon black layer and a conductive carbon nanotube layer sequentially coated. This invention increases the overall conductivity and electrolyte absorption capacity of the thick electrode sheet for lithium-ion batteries by controlling the specific structures of the small-particle and large-particle active material layers, thereby reducing battery internal resistance, extending lifespan, and increasing energy density. Furthermore, the specific number of small-particle and large-particle active material layers can be controlled according to actual needs to achieve applications under different requirements.

[0007] The aforementioned thick electrode sheet for a lithium-ion battery is characterized in that the conductive carbon nanotube layer is made of single-walled carbon nanotubes, and the large-particle active material in the large-particle active coating is D... 50 It is lithium iron phosphate with a particle size of 6μm to 10μm, and the small particulate active material in the small particulate active coating is D. 50 It is lithium iron phosphate with a thickness of 1.5μm to 5μm, and the areal density of the thick electrode sheet of the lithium-ion battery on one side is not less than 200g / cm³. 2 This invention achieves the fabrication of thick electrodes by controlling the areal density of one side of the thick electrode sheet in lithium-ion batteries.

[0008] In addition, the present invention also provides a spraying device for preparing thick electrode sheets for lithium-ion batteries, characterized in that the spraying device includes a slurry storage tank, a pressure reducing gauge is installed on the slurry storage tank, the pressure reducing gauge is connected to a spray nozzle through a slurry delivery pipe, a flow meter is installed on the slurry delivery pipe, and the spraying device also includes a thickness gauge, a speed measuring instrument, and an online surface density meter for detecting the thickness, width, and speed of the sprayed slurry.

[0009] The above-mentioned device is characterized in that the slurry storage tank has a built-in plastic tube, the bottom of which is connected to a stirring paddle, and the top of the slurry storage tank is equipped with a vacuum valve and a pressure valve.

[0010] The aforementioned device is characterized in that the pressure reducing gauge is equipped with a low-pressure gauge, a high-pressure gauge, and a safety valve; the low-pressure gauge has a range of 0–4 MPa; the high-pressure gauge has a range of 0–25 MPa; and the flow meter is a high-viscosity, high-pressure mass flow meter with a viscosity range of 0–10000 Pa·s.

[0011] The device described above is characterized in that the spray nozzle has a built-in 200-500 mesh screen.

[0012] In addition, the present invention also provides a method for constructing a thick electrode sheet for a lithium-ion battery, characterized in that the method includes the following steps:

[0013] Step 1: Dissolve active material A, conductive carbon black, conductive carbon nanotubes and binder in solvent to obtain slurry A; dissolve active material B, conductive carbon black, conductive carbon nanotubes and binder in solvent to obtain slurry B; dissolve conductive carbon black in solvent to obtain slurry C; dissolve conductive carbon nanotubes in solvent to obtain slurry D.

[0014] Step 2: Using a spraying device, spray slurry C onto the current collector and dry it to obtain the positive electrode layer L1;

[0015] Step 3: Spray slurry D onto the positive electrode layer L1 obtained in step 2 and dry it to obtain the positive electrode layer L2;

[0016] Step 4: Spray slurry A onto the positive electrode layer L2 obtained in step 3 and dry it to obtain the positive electrode layer L3;

[0017] Step 5: Spray slurry C onto the positive electrode layer L3 obtained in step 4 and dry it to obtain the positive electrode layer L4;

[0018] Step 6: Spray slurry D onto the positive electrode layer L4 obtained in step 5 and dry it to obtain the positive electrode layer L5;

[0019] Step 7: Repeat steps 4, 5 and 6 multiple times to obtain the positive electrode layer L6;

[0020] Step 8: Spray slurry B onto the positive electrode layer L6 obtained in step 7 and dry it to obtain the positive electrode layer L7.

[0021] Step 9: Spray slurry C onto the positive electrode layer L7 obtained in step 8 and dry it to obtain the positive electrode layer L8;

[0022] Step 10: Spray slurry D onto the positive electrode layer L8 obtained in step 9 and dry it to obtain the positive electrode layer L9;

[0023] Step 11: Repeat steps 8, 9 and 10 multiple times to obtain the positive electrode layer L10;

[0024] Step 12: Spray slurry D onto the positive electrode layer L10 obtained in step 11 and dry it to obtain the positive electrode layer L11;

[0025] Step 13: The positive electrode layer L11 obtained in step 12 is baked, rolled and formed sequentially to obtain a thick electrode sheet for lithium-ion batteries.

[0026] The above method is characterized in that the active material A in step one is D. 50 It is lithium iron phosphate with a thickness of 1.5μm to 5μm, and the active material B is D. 50 The material is lithium iron phosphate with a thickness of 6μm to 10μm. The binder is polyvinylidene fluoride, and the solvent is N-methylpyrrolidone. The mass ratio of active material A, conductive carbon black, conductive carbon nanotubes, and binder is 92-97:1-2:1-2:1-4, and the mass ratio of active material B, conductive carbon black, conductive carbon nanotubes, and binder is also 92-97:1-2:1-2:1-4. The viscosity of both slurry A and slurry B is 1000 Pa·s. This invention ensures optimal performance of the thick electrode sheet for lithium-ion batteries by controlling the type and proportion of raw materials.

[0027] The above method is characterized in that the aluminum current collector in step two is an aluminum foil with a thickness of 15μm to 20μm, and the areal density of the slurry A layer obtained after spraying slurry A in step four is 31g / cm³. 2 ~35g / cm 2 The areal density of the slurry B layer obtained after spraying slurry B in step eight is 31 g / cm³. 2 ~35g / cm 2In step two, the thickness of the sprayed slurry C is 1 μm to 1.5 μm; in steps five and nine, the thickness of the sprayed slurry C is 0.5 μm to 1 μm; in step three, the thickness of the sprayed slurry D is 1 μm to 1.5 μm; and in steps six, ten, and twelve, the thickness of the sprayed slurry D is 0.5 μm to 1 μm. This invention controls the surface density of the single layer obtained after each spraying of slurry A and slurry B, and controls the number of spraying operations, ensuring that the surface density of the single-sided thick electrode sheet of the lithium-ion battery is not less than 200 g / cm³. 2 By controlling the thickness of spray slurry C and spray slurry D, the acceleration effect of ion conduction, electron conduction and electrolyte penetration into the deeper layers is ensured to be optimal. Furthermore, the thickness of slurry C and slurry D is highest in the uppermost and lowermost layers, which also ensures the stability of the overall structure.

[0028] Compared with the prior art, the present invention has the following advantages:

[0029] 1. In this invention, the thick electrode sheet of the lithium-ion battery is composed of a current collector and a conductive agent layer and an active material layer coated on the current collector. The current collector is the external circuit of the battery, which plays the role of transporting electrons. By coating the current collector with a conductive agent layer, namely a conductive carbon black layer and a conductive carbon nanotube layer, the conduction of electrons and ions is accelerated, increasing the absorption of electrolyte by the electrode sheet. By coating the current collector with an active material layer, namely a large particle active coating and a small particle active coating, the conductivity and electrolyte absorption capacity of the electrode sheet are increased, thereby reducing the internal resistance of the battery, extending its lifespan, and increasing its energy density.

[0030] 2. The spraying equipment used in this invention not only allows for simple and convenient control of coating thickness and width at the micron level and online real-time calculation of coating areal density, but also protects the slurry from environmental dust pollution and water absorption. Furthermore, compared with existing single-layer thick electrode coating technology, the thick electrode sheet precisely constructed using the spraying device not only increases the absorption of electrolyte by the electrode sheet, but also reduces the internal resistance of the lithium-ion battery, increases the energy density, and extends the cycle life.

[0031] 3. This invention not only solves the problems of low thickness accuracy, coating rate and complex operation of existing thick electrode coating equipment, but also solves the problems of high impedance, short life and low energy density of lithium-ion batteries in thick electrodes.

[0032] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the structure of the thick electrode sheet for the lithium-ion battery of the present invention.

[0034] Figure 2 This is a schematic diagram of the coating device for the thick electrode sheet of the lithium-ion battery of the present invention.

[0035] Figure 3 This is a schematic diagram showing how the thick lithium-ion battery electrode sheet prepared in Example 2 of the present invention and the lithium-ion battery electrode sheet prepared in Comparative Example 1 are stacked with the same negative electrode sheet to form a 2500mAh soft-pack battery cell, and then charged at 0.5C and discharged at 1C under room temperature conditions (1C = 2000mAh).

[0036] Figure 4 This is a schematic diagram comparing the lithium-ion battery thick electrode sheet prepared in Example 2 of the present invention and the lithium-ion battery electrode sheet prepared in Comparative Example 1 with the same negative electrode sheet to form a 2500mAh soft-pack battery cell, and then performing 1C charging and 1C discharging cycles at room temperature (1C = 2000mAh).

[0037] Explanation of reference numerals in the attached figures:

[0038] 1—Current collector; 2—Conductive carbon black layer; 3—Conductive carbon nanotube layer;

[0039] 4—Large particle active coating; 5—Small particle active coating; 6—Slurry storage tank;

[0040] 6-1—Pressure valve; 6-2—Plastic tubing; 6-3—Agitator;

[0041] 6-4—Vacuum valve; 7—Pressure reducer; 7-1—Low pressure gauge;

[0042] 7-2—High pressure gauge; 7-3—Safety valve; 8—Slurry delivery pipe;

[0043] 8-1—Flow meter; 9—Spray nozzle; 10—Thickness gauge;

[0044] 11—Velocity meter; 12—Online surface density meter. Detailed Implementation

[0045] Figure 1 This is a schematic diagram of the structure of the thick electrode sheet of the lithium-ion battery of the present invention. Figure 1 As can be seen from the figure, the current collector 1 of the thick electrode sheet of the lithium-ion battery of the present invention is coated with a multilayer small particle active material layer composed of a conductive carbon black layer 2, a conductive carbon nanotube layer 3 and a small particle active coating 5. The small particle active material layer is coated with a multilayer large particle active material layer composed of a conductive carbon black layer 2, a conductive carbon nanotube layer 3 and a large particle active coating 4. The large particle active material layer is also coated with a conductive carbon black layer 2 and a conductive carbon nanotube layer 3 in sequence. The arrows in the figure indicate the direction of lithium ion transfer when the thick electrode sheet of the lithium-ion battery is charged after being prepared into a battery.

[0046] The present invention provides a spraying apparatus for preparing thick electrode sheets for lithium-ion batteries, which is described in detail in Example 1.

[0047] Example 1

[0048] like Figure 2 As shown, the spraying device for constructing thick electrode sheets of lithium-ion batteries in this embodiment includes a slurry storage tank 6. The slurry storage tank 6 is equipped with a pressure valve 6-1 and a pressure reducing gauge 7 connected to each other. The pressure reducing gauge 7 is connected to a spray nozzle 9 through a slurry delivery pipe 8. A flow meter 8-1 is installed on the slurry delivery pipe 8. The spraying device also includes a thickness gauge 10, a speed measuring instrument 11, and an online surface density meter 12 for detecting the thickness, width, and speed of the sprayed slurry.

[0049] It should be noted that a slurry storage tank 6 is used to store the slurry, a pressure valve 6-1 controls the opening and closing of the slurry storage tank 6, a pressure reducing gauge 7 controls the output quality of the slurry and the thickness of the coating, and a slurry delivery pipe 8 and a spray nozzle 9 are used to uniformly spray the slurry onto the current collector 1, protecting the slurry from environmental dust pollution and water absorption. A flow meter 8-1 is installed on the slurry delivery pipe 8 to determine the output quality, and a thickness gauge 10, a speed meter 11, and an online areal density meter 12 are used to detect the thickness and speed of the sprayed slurry. This allows for simple and convenient control of the coating thickness and width at the micron level, and online real-time calculation of the coating areal density, enabling the precise construction of thick lithium-ion battery electrodes. This not only increases the absorption of electrolyte by the thick lithium-ion battery electrodes, but also reduces the internal resistance, increases the energy density, and extends the cycle life of the lithium-ion battery composed of thick lithium-ion battery electrodes.

[0050] It should be noted that the thickness gauge 10 and the velocity meter 11 are integrated into one unit. The online surface density meter 12 is connected to the flow meter 8-1 and the velocity meter 11 at the same time. The flow meter 8-1, the velocity meter 11, the thickness gauge 10 and the online surface density meter 12 need to be turned on simultaneously.

[0051] like Figure 2 As shown, in this embodiment, the slurry storage tank 6 has a built-in plastic pipe 6-2 for conveying slurry from the bottom of the slurry storage tank 6. A stirring paddle 6-3 is installed at the bottom of the plastic pipe 6-2, and a vacuum valve 6-4 is installed at the top of the slurry storage tank 6. The vacuum valve 6-4 is connected to a vacuum assembly. By using the plastic pipe 6-2, the slurry from the bottom of the slurry storage tank 6 is output for spraying. The stirring paddle 6-3 agitates the slurry, ensuring its uniformity and thus guaranteeing the spraying effect. The vacuum valve 6-4, connected to a vacuum assembly (a vacuum pump), evacuates the slurry storage tank 6, ensuring smooth slurry output.

[0052] like Figure 2As shown, in this embodiment, the pressure reducing gauge 7 is equipped with a low-pressure gauge 7-1, a high-pressure gauge 7-2, and a safety valve 7-3. The range of the low-pressure gauge 7-1 is 0–4 MPa, and the range of the high-pressure gauge 7-2 is 0–25 MPa. The flow meter 8-1 is a high-viscosity, high-pressure mass flow meter 8-1, with a viscosity range of 0–10000 Pa·s. The low-pressure gauge 7-1 is designed for coatings with low slurry viscosity and low coating speed, while the high-pressure gauge 7-2 is suitable for coatings with high slurry viscosity and high coating speed.

[0053] In this embodiment, the spray nozzle 9 has a built-in 200-500 mesh screen. This invention improves the spraying quality by filtering the slurry through the built-in screen in the spray nozzle 9.

[0054] The method for preparing thick electrode sheets for lithium-ion batteries according to the present invention is described in detail through Examples 2 to 4.

[0055] Example 2

[0056] This embodiment includes the following steps:

[0057] Step 1: Mix D in a mass ratio of 95:1:1:3 50 Lithium iron phosphate (1.5 μm), conductive carbon black, conductive carbon nanotubes, and polyvinylidene fluoride (PVDF) are dissolved in N-methylpyrrolidone to obtain slurry A with a viscosity of 1000 Pa·s. Then, D is added in a mass ratio of 95:1:1:3. 50 Lithium iron phosphate (6μm), conductive carbon black, conductive carbon nanotubes, and polyvinylidene fluoride are dissolved in N-methylpyrrolidone to obtain slurry B with a viscosity of 1000 Pa·s. Conductive carbon black is dissolved in N-methylpyrrolidone to obtain slurry C, and conductive carbon nanotubes are dissolved in N-methylpyrrolidone to obtain slurry D.

[0058] Step 2: Using a spraying device, slurry C is sprayed onto an aluminum foil with a thickness of 15μm and dried to obtain the positive electrode layer L1.

[0059] Step 3: Spray a 1μm thick slurry D onto the positive electrode layer L1 obtained in step 2 and dry it to obtain the positive electrode layer L2.

[0060] Step 4: Spray a surface density of 33 g / cm³ onto the positive electrode layer L2 obtained in Step 3. 2 The slurry A is dried to obtain the positive electrode layer L3;

[0061] Step 5: Spray a slurry C with a thickness of 0.5 μm onto the positive electrode layer L3 obtained in step 4 and dry it to obtain the positive electrode layer L4;

[0062] Step 6: Spray a slurry D with a thickness of 0.5 μm onto the positive electrode layer L4 obtained in step 5 and dry it to obtain the positive electrode layer L5;

[0063] Step 7: Repeat steps 4, 5 and 6 three times in sequence to obtain the positive electrode layer L6;

[0064] Step 8: Spray a surface density of 33 g / cm³ onto the positive electrode layer L6 obtained in step 7. 2 The slurry B is dried to obtain the positive electrode layer L7;

[0065] Step 9: Spray a slurry C with a thickness of 0.5 μm onto the positive electrode layer L7 obtained in step 8 and dry it to obtain the positive electrode layer L8;

[0066] Step 10: Spray a slurry D with a thickness of 0.5 μm onto the positive electrode layer L8 obtained in step 9 and dry it to obtain the positive electrode layer L9;

[0067] Step 11: Repeat steps 8, 9 and 10 three times in sequence to obtain the positive electrode layer L10;

[0068] Step 12: Spray a slurry D with a thickness of 0.5 μm onto the positive electrode layer L10 obtained in step 11 and dry it to obtain the positive electrode layer L11;

[0069] Step 13: The positive electrode layer L11 obtained in step 12 is baked, rolled and formed sequentially to obtain a thick electrode sheet for lithium-ion batteries.

[0070] Testing revealed that the areal density of the thick lithium-ion battery electrode sheet prepared in this embodiment is 200 g / cm³. 2 .

[0071] Comparative Example 1

[0072] This comparative example includes the following steps:

[0073] Step 1: Mix D in a mass ratio of 95:1:1:3 50 Lithium iron phosphate with a thickness of 1.5 μm, conductive carbon black, conductive carbon nanotubes, and polyvinylidene fluoride are dissolved in N-methylpyrrolidone to obtain slurry A with a viscosity of 1000 Pa·s;

[0074] Step 2: Using a spraying device, spray a coating with an area density of 200 g / cm³ onto an aluminum foil with a thickness of 15 μm. 2 The slurry A is dried to obtain the positive electrode layer L1;

[0075] Step 3: The positive electrode layer L1 obtained in Step 2 is baked, rolled and formed sequentially to obtain the lithium-ion battery electrode.

[0076] Testing revealed that the single-sided areal density of the lithium-ion battery electrode prepared in this comparative example was 200 g / cm³. 2 .

[0077] The lithium-ion battery thick electrode sheet prepared in Example 2 and the lithium-ion battery electrode sheet prepared in Comparative Example 1 were stacked with the same negative electrode sheet to form a 2500mAh soft-pack battery cell, and the results are shown in Table 1. The negative electrode sheet was prepared by dissolving graphite, conductive carbon black, sodium carboxymethyl cellulose and styrene-butadiene rubber in N-methylpyrrolidone in a mass ratio of 94:2:2:2 to obtain slurry A1. Slurry A1 was then coated on a copper foil with a thickness of 8μm, and then baked, rolled and formed into a sheet.

[0078] Table 1

[0079]

[0080] As can be seen from Table 1, the battery made from the lithium-ion battery thick electrode sheet prepared in Example 2 has lower internal resistance, greater liquid absorption, and higher mass energy density compared to the battery made from the lithium-ion battery electrode sheet prepared in Comparative Example 1.

[0081] Figure 3 This is a schematic diagram illustrating how the thick lithium-ion battery electrode sheet prepared in Example 2 of the present invention and the lithium-ion battery electrode sheet prepared in Comparative Example 1 are stacked with the same negative electrode sheet to form a 2500mAh soft-pack battery cell, and then subjected to 0.5C charging and 1C discharging at room temperature. Figure 1 C = 2000mAh Figure 4 This diagram illustrates the comparison of 2500mAh soft-pack battery cells fabricated by stacking the thick lithium-ion battery electrode sheet prepared in Example 1 of this invention and the lithium-ion battery electrode sheet prepared in Comparative Example 1 with the same negative electrode sheet, followed by 1C charging and 1C discharging cycles at room temperature. Figure 1 C = 2000 mAh, from Figure 3 and Figure 4 As can be seen from the above, the battery made from the lithium-ion battery thick electrode sheet prepared in Example 1 of the present invention has a slower cycle capacity decay and a longer cycle life compared to the battery made from the lithium-ion battery electrode sheet prepared in Comparative Example 1.

[0082] Example 3

[0083] This embodiment includes the following steps:

[0084] Step 1: Mix D in a mass ratio of 92:2:2:4 50 Lithium iron phosphate (3μm), conductive carbon black, conductive carbon nanotubes, and polyvinylidene fluoride (PVDF) are dissolved in N-methylpyrrolidone to obtain slurry A with a viscosity of 1000 Pa·s. Then, D is added in a mass ratio of 92:2:2:4. 50Lithium iron phosphate with a thickness of 8 μm, conductive carbon black, conductive carbon nanotubes, and polyvinylidene fluoride are dissolved in N-methylpyrrolidone to obtain slurry B with a viscosity of 1000 Pa·s. Conductive carbon black is dissolved in N-methylpyrrolidone to obtain slurry C, and conductive carbon nanotubes are dissolved in N-methylpyrrolidone to obtain slurry D.

[0085] Step 2: Using a spraying device, slurry C is sprayed onto an aluminum foil with a thickness of 18μm for 1.2μm and then dried to obtain the positive electrode layer L1;

[0086] Step 3: Spray a slurry D with a thickness of 1.2 μm onto the positive electrode layer L1 obtained in step 2 and dry it to obtain the positive electrode layer L2;

[0087] Step 4: Spray a surface density of 31 g / cm³ onto the positive electrode layer L2 obtained in Step 3. 2 The slurry A is dried to obtain the positive electrode layer L3;

[0088] Step 5: Spray a slurry C with a thickness of 0.8 μm onto the positive electrode layer L3 obtained in step 4 and dry it to obtain the positive electrode layer L4;

[0089] Step 6: Spray a slurry D with a thickness of 0.8 μm onto the positive electrode layer L4 obtained in step 5 and dry it to obtain the positive electrode layer L5;

[0090] Step 7: Repeat steps 4, 5 and 6 7 times in sequence to obtain the positive electrode layer L6;

[0091] Step 8: The surface density of the coating sprayed onto the positive electrode layer L6 obtained in step 7 is 31 g / cm³. 2 The slurry B is dried to obtain the positive electrode layer L7;

[0092] Step 9: Spray a slurry C with a thickness of 0.8 μm onto the positive electrode layer L7 obtained in step 8 and dry it to obtain the positive electrode layer L8;

[0093] Step 10: Spray a slurry D with a thickness of 0.8 μm onto the positive electrode layer L8 obtained in step 9 and dry it to obtain the positive electrode layer L9;

[0094] Step 11: Repeat steps 8, 9 and 10 seven times in sequence to obtain the positive electrode layer L10;

[0095] Step 12: Spray a slurry D with a thickness of 0.8 μm onto the positive electrode layer L10 obtained in step 11 and dry it to obtain the positive electrode layer L11;

[0096] Step 13: The positive electrode layer L11 obtained in step 12 is baked, rolled and formed sequentially to obtain a thick electrode sheet for lithium-ion batteries.

[0097] Testing revealed that the areal density of the thick lithium-ion battery electrode sheet prepared in this embodiment is 430 g / cm³. 2 .

[0098] Example 4

[0099] This embodiment includes the following steps:

[0100] Step 1: Mix D in a mass ratio of 97:1:1:1 50 Lithium iron phosphate (5μm), conductive carbon black, conductive carbon nanotubes, and polyvinylidene fluoride (PVDF) are dissolved in N-methylpyrrolidone to obtain slurry A with a viscosity of 1000 Pa·s. Then, D is added in a mass ratio of 97:1:1:1. 50 Lithium iron phosphate (10 μm), conductive carbon black, conductive carbon nanotubes, and polyvinylidene fluoride are dissolved in N-methylpyrrolidone to obtain slurry B with a viscosity of 1000 Pa·s. Conductive carbon black is dissolved in N-methylpyrrolidone to obtain slurry C, and conductive carbon nanotubes are dissolved in N-methylpyrrolidone to obtain slurry D.

[0101] Step 2: Using a spraying device, slurry C is sprayed onto an aluminum foil with a thickness of 20μm by 1.5μm and then dried to obtain the positive electrode layer L1;

[0102] Step 3: Spray a slurry D with a thickness of 1.5 μm onto the positive electrode layer L1 obtained in step 2 and dry it to obtain the positive electrode layer L2;

[0103] Step 4: Spray a surface density of 35 g / cm³ onto the positive electrode layer L2 obtained in Step 3. 2 The slurry A is dried to obtain the positive electrode layer L3;

[0104] Step 5: Spray a 1μm thick slurry C onto the positive electrode layer L3 obtained in step 4 and dry it to obtain the positive electrode layer L4;

[0105] Step 6: Spray a 1μm thick slurry D onto the positive electrode layer L4 obtained in step 5 and dry it to obtain the positive electrode layer L5.

[0106] Step 7: Repeat steps 4, 5 and 6 5 times in sequence to obtain the positive electrode layer L6;

[0107] Step 8: Spray a surface density of 35 g / cm³ onto the positive electrode layer L6 obtained in step 7. 2 The slurry B is dried to obtain the positive electrode layer L7;

[0108] Step 9: Spray a 1μm thick slurry C onto the positive electrode layer L7 obtained in step 8 and dry it to obtain the positive electrode layer L8.

[0109] Step 10: Spray a slurry D with a thickness of 1 μm onto the positive electrode layer L8 obtained in step 9 and dry it to obtain the positive electrode layer L9.

[0110] Step 11: Repeat steps 8, 9 and 10 five times in sequence to obtain the positive electrode layer L10;

[0111] Step 12: Spray a 1μm thick slurry D onto the positive electrode layer L10 obtained in step 11 and dry it to obtain the positive electrode layer L11;

[0112] Step 13: The positive electrode layer L11 obtained in step 12 is baked, rolled and formed sequentially to obtain a thick electrode sheet for lithium-ion batteries.

[0113] Testing revealed that the areal density of the thick lithium-ion battery electrode sheet prepared in this embodiment is 310 g / cm³. 2 .

[0114] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Any simple modifications, alterations, and equivalent changes made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A thick electrode sheet for a lithium-ion battery, characterized in that, The thick electrode sheet of this lithium-ion battery includes a current collector and a layer of small-particle active material, a layer of large-particle active material, a layer of conductive carbon black, and a layer of conductive carbon nanotubes sequentially coated on the current collector. The small-particle active material layer comprises a layer of conductive carbon black, a layer of conductive carbon nanotubes, and a small-particle active coating, respectively. The large-particle active material layer comprises a layer of conductive carbon black, a layer of conductive carbon nanotubes, and a large-particle active coating, respectively. The large-particle active coating is located away from the current collector, while the small-particle active coating is located close to the current collector. Both the small-particle and large-particle active material layers have at least three layers. The large-particle active material in the large-particle active coating is D... 50 It is 6μm~10μm lithium iron phosphate, and the small particulate active material in the small particulate active coating is D. 50 It is lithium iron phosphate with a diameter of 1.5μm to 5μm.

2. The thick electrode sheet for a lithium-ion battery according to claim 1, characterized in that, The conductive carbon nanotube layer is made of single-walled carbon nanotubes, and the areal density of the thick electrode sheet of the lithium-ion battery is not less than 200 g / cm³. 2 .

Images