Preparation method of high-compaction NFPP positive pole piece

Abstract

The invention discloses a preparation method of a high-compaction NFPP positive pole piece, and relates to the technical field of sodium ion batteries, the preparation method of the positive pole piece comprises the following steps: S1, homogenizing: mixing and dispersing a positive active material NFPP, a conductive agent, a binder and a dispersant in a solvent to obtain positive pole slurry; s2, coating: uniformly coating a current collector with the positive electrode slurry obtained in S1; and S3, rolling: rolling the positive pole piece obtained in the S2 in a hot pressing manner to obtain the high-compaction NFPP positive pole piece. According to the prepared positive pole piece, the NFPP pole piece is obtained by means of adjusting the slurry mixing proportion, the coating surface density, the hot pressing parameters and the like, the NFPP pole piece has relatively high compaction density and relatively low battery internal resistance, the energy density of the battery is improved, and the cycle life of the battery is prolonged.

Description

Technical Field

[0001] This invention relates to the field of sodium-ion batteries, and specifically to a method for preparing a high-pressure compacted NFPP positive electrode sheet. Background Technology

[0002] With the widespread application of batteries in new energy vehicles, 3C electronic products, energy storage systems, and other fields, improving battery energy density has become a core requirement of the industry, and therefore, battery energy density has always attracted attention from all sectors. As a decisive component of battery capacity, the compaction density of cathode materials directly affects their energy density to a certain extent.

[0003] Sodium iron pyrophosphate (Na4Fe3(PO4)2P2O7) has a theoretical specific capacity of up to 129 mAh / g, which can meet the high energy density requirements of sodium-ion batteries. Its operating voltage is close to 3.1V, and this high voltage platform helps to improve the energy output of sodium-ion batteries. Its stable crystal structure can maintain good integrity during the insertion and extraction of sodium ions, reducing the structural degradation and capacity decay of the material. It has extremely excellent cycle stability and is a very promising cathode material for sodium-ion batteries.

[0004] NFPP has stable three-dimensional Na + Transmission channel, N It has high diffusion efficiency in materials, but its crystal structure contains large polyanionic groups (such as PO4). 3- and P2O7 4- This obstruction of electron transport paths limits the compaction density of NFPP powder, thus limiting its electrochemical performance. To improve its electrochemical performance, carbon coating is typically applied during processing, further reducing the material's compaction density. Therefore, the compaction density of commercially available NFPP cathode powders is generally between 1.8 and 2.1 g / cm³. 3 Between (5.0T pressure). After NFPP cathode powder is homogenized into electrode sheets, there are a large number of gaps between the spheres of equal size, which means that the theoretical limit of compaction density of the electrode sheet will not exceed 2.1 g / cm³. 3 Lower compaction density not only increases battery cost, but also leads to higher Na content during charge and discharge. +Migration in the electrolyte and deintercalation on the surface of the negative electrode are hindered, which is detrimental to the battery capacity. CN202311275260.5 discloses a method for preparing a positive electrode sheet of a layered oxide sodium-ion battery with improved compaction density. The invention points out that adding a small amount of NFPP positive electrode powder in the homogenization process can improve the compaction density of the layered oxide positive electrode sheet without affecting the battery capacity and cycle life. The principle is that small-diameter NFPP particles (D50=1-5um) and large single-crystal layered oxide particles (D50=4-12um) fill each other, reducing the interparticle gaps inside the electrode sheet. However, in actual experiments, the instability of layered oxides easily leads to gelation of the mixture, increasing the difficulty of the process. In addition, the voltage window of layered oxides is 2.0-4.2V, while that of NFPP is 1.5-3.6V. During long cycles, NFPP and layered oxide particles undergo complex and irreversible phase transitions and severe interfacial changes under high voltage, resulting in the formation of sodium dendrites that pierce the diaphragm, posing a serious safety hazard. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing a high-pressure compacted NFPP positive electrode sheet, so as to solve the following technical problems: How to improve the compaction density of NFPP electrodes and reduce the surface resistance of electrodes without changing the original voltage window, thereby improving the mass energy density of the battery.

[0006] The objective of this invention can be achieved through the following technical solutions: In a first aspect, the present invention discloses a method for preparing a high-pressure NFPP positive electrode sheet, comprising the following steps: S1. Homogenization: The positive electrode active material NFPP, conductive agent, binder and dispersant are mixed and dispersed in a solvent to obtain the positive electrode slurry; S2, Coating: The positive electrode slurry obtained in S1 is uniformly coated onto the current collector; S3, Rolling: The positive electrode sheet obtained in S3 is rolled using a hot pressing method to obtain a high-pressure compacted NFPP positive electrode sheet.

[0007] Preferably, the conductive agent in S1 includes a first conductive agent and a second conductive agent; the first conductive agent is carbon nanotubes (CNTs); the second conductive agent is conductive carbon black (SP); the binder in S1 is polyvinylidene fluoride (PVDF); the dispersant in S1 is hydrogenated nitrile butadiene rubber (HNBR); and the solvent in S1 is NMP.

[0008] Preferably, the mass ratio of each component of the slurry in S1 is NFPP:CNT:PVDF:SP:dispersant = 94-95:1.0:2.5-2.8:1.3-1.8:0.2.

[0009] Preferably, the mass ratio of each component of the slurry in S1 is NFPP:CNT:PVDF:SP:dispersant 94.2:1.0:2.8:1.8:0.2.

[0010] Preferably, the CNT solids content of the slurry in S1 is 6%, and the dispersant solids content is 7.9%.

[0011] Preferably, the specific steps in S1 are as follows: weigh PVDF and NMP, dissolve them completely, add CNT, disperse for 30 min, add SP and NMP, disperse for 30 min, add NFPP and NMP, stir for 15 min, add dispersant, disperse at high speed at 4200 rpm for 120 min, add water to disperse and reduce the viscosity to 3000 mPa·s, and finally obtain a uniform NFPP positive electrode slurry.

[0012] Preferably, the current collector in S2 is aluminum foil.

[0013] Preferably, the areal density of the double-sided coating in S2 is 290-310 g / cm³. 2 The preferred value is 310g / cm³. 2 .

[0014] Preferably, the roller pressing in S3 is performed by hot pressing, with a temperature of 75°C and a pressure of 9-10 mPa.

[0015] Preferably, the electrode sheet after rolling in step S3 can be repeatedly folded five times without breaking or separating after being sampled by the sampler.

[0016] Secondly, the present invention also discloses a high-pressure NFPP positive electrode sheet, which is obtained by the above-described preparation method.

[0017] The beneficial effects of this invention are: This invention uses NFPP as the positive electrode material and produces an NFPP positive electrode sheet by hot pressing. By adjusting the slurry ratio, coating density, and hot pressing parameters, the adhesion between the NFPP positive electrode material and the conductive agent is enhanced, so that the produced NFPP positive electrode sheet maintains a high compaction density, a low battery internal resistance, improves the battery's mass energy density, extends battery cycle life, and improves battery utilization. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the first 0.1C charge-discharge cycle in Embodiment 1 of the present invention; Figure 2 This is a schematic diagram of the charge-discharge specific capacity and efficiency of a half-cell in Embodiment 1 of the present invention after 39 cycles at 0.1C. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0020] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Unless otherwise specified, the materials and reagents used in the following examples are all commercially available. The NFPP, CNT, SP, PVDF, dispersant, aluminum foil, and other related materials used above were all purchased commercially. Specifically, the NFPP is a product sold by Zhenjiang Yingna New Energy Materials Co., Ltd., model YN-NFPP-3; the CNT is a product sold by Xiamen Kaina Graphene Technology Co., Ltd., model KNG-C0429; the SP is a product sold by Tianjin Xinglongtai Chemical Products Technology Co., Ltd., model HCD-6; the PVDF is a product sold by Hunan Huiju New Energy Co., Ltd., model HJ-S130; the dispersant is a product sold by Shenzhen Haofei New Materials Co., Ltd., model HFF-2968; and the aluminum foil is a product sold by Hangzhou Wuxing Aluminum Co., Ltd., model TC-12280.

[0021] Example 1

[0022] The preparation method of the NFPP positive electrode sheet adopts the following steps: S1: Homogenization: The mass ratio of NFPP:CNT:PVDF:SP:dispersant is 94.2:1.0:2.8:1.8:0.2. Weigh 297.2g of PVDF and 3949.0g of NMP, dissolve them completely, add 1769.3g of CNT with a solid content of 6%, disperse for 30 min, then add 191.1g of conductive carbon black SP and 800.0g of NMP, disperse for 30 min, then add 10000.0g of NFPP and 2000.0g of NMP, stir for 15 min, then add 268.2g of dispersant with a solid content of 7.9%, disperse at 4200rpm for 120 min, then add water to disperse and reduce the viscosity to 3000mPa.s, finally obtaining a uniform NFPP positive electrode slurry; S2: Coating: The slurry from S1 is evenly coated onto both sides of the carbon-coated aluminum foil, with the surface density controlled at 310 g / cm³. 2 ; S3: Roll pressing: Hot pressing is used, with the temperature controlled at 75℃ and the pressure controlled at 10mPa. The rolled electrode sheet must be able to withstand being folded in half 5 times after being sampled by the sampler without breaking or separating. Example 2 S1: Homogenization: The mass ratio of NFPP:CNT:PVDF:SP:dispersant is 94.5:1.0:2.5:1.8:0.2. Weigh 264.6g of PVDF and 3514.7g of NMP, dissolve them completely, add 1763.7g of CNT with a solid content of 6%, disperse for 30 min, then add 190.5g of conductive carbon black SP and 800.0g of NMP, disperse for 30 min, then add 10000.0g of NFPP and 2000.0g of NMP, stir for 15 min, then add 267.4g of dispersant with a solid content of 7.9%, disperse at 4200rpm for 120 min, then add water to disperse and reduce the viscosity to 3000mPa.s, finally obtaining a uniform NFPP cathode slurry; S2: Coating: The slurry from S1 is evenly coated onto both sides of the carbon-coated aluminum foil, with the surface density controlled at 310 g / cm³. 2 ; S3: Roll pressing: Hot pressing is used, with the temperature controlled at 75℃ and the pressure controlled at 12mPa. The rolled electrode sheet must be able to withstand being folded in half 5 times after being sampled by the sampler without breaking or separating. Example 3 S1: Homogenization: The mass ratio of NFPP:CNT:PVDF:SP:dispersant is 94.5:1.0:2.8:1.5:0.2. Weigh 296.3 g of PVDF and 3936.5 g of NMP, dissolve them completely, add 1763.7 g of CNT with a solid content of 6%, disperse for 30 min, then add 158.7 g of conductive carbon black SP and 800.0 g of NMP, disperse for 30 min, then add 10000.0 g of NFPP and 2000.0 g of NMP, stir for 15 min, then add 267.4 g of dispersant with a solid content of 7.9%, disperse at 4200 rpm for 120 min, then add water to disperse and reduce the viscosity to 3000 mPa·s, finally obtaining a uniform NFPP positive electrode slurry; S2: Coating: The slurry from S1 is evenly coated onto both sides of the carbon-coated aluminum foil, with the surface density controlled at 310 g / cm³. 2 ; S3: Roll pressing: Hot pressing is used, with the temperature controlled at 75℃ and the pressure controlled at 12mPa. The rolled electrode sheet must be able to withstand being folded in half 5 times after being sampled by the sampler without breaking or separating. Example 4 S1: Homogenization: The mass ratio of NFPP:CNT:PVDF:SP:dispersant is 95.0:1.0:2.5:1.3:0.2. Weigh 263.2 g of PVDF and 3496.2 g of NMP, dissolve them completely, add 1754.4 g of CNT with a solid content of 6%, disperse for 30 min, then add 136.8 g of conductive carbon black SP and 800.0 g of NMP, disperse for 30 min, then add 10000.0 g of NFPP and 2000.0 g of NMP, stir for 15 min, then add 266.0 g of dispersant with a solid content of 7.9%, disperse at high speed at 4200 rpm for 120 min, then add water to disperse and reduce the viscosity to 3000 mPa·s, finally obtaining a uniform NFPP positive electrode slurry; S2: Coating: The slurry from S1 is evenly coated onto both sides of the carbon-coated aluminum foil, with the surface density controlled at 310 g / cm³. 2 ; S3: Roll pressing: Hot pressing is used, with the temperature controlled at 75℃ and the pressure controlled at 16mPa. The rolled electrode sheet must be able to withstand being folded in half 5 times after sampling by the sampler without breaking or separating.

[0023] Example 5

[0024] S1: Homogenization: The mass ratio of NFPP:CNT:PVDF:SP:dispersant is 94.2:1.0:2.8:1.8:0.2. Weigh 297.2g of PVDF and 3949.0g of NMP, dissolve them completely, add 1769.3g of CNT with a solid content of 6%, disperse for 30 min, then add 191.1g of conductive carbon black SP and 800.0g of NMP, disperse for 30 min, then add 10000.0g of NFPP and 2000.0g of NMP, stir for 15 min, then add 268.2g of dispersant with a solid content of 7.9%, disperse at 4200rpm for 120 min, then add water to disperse and reduce the viscosity to 3000mPa.s, finally obtaining a uniform NFPP positive electrode slurry; S2: Coating: The slurry in S1 is evenly coated onto both sides of the carbon-coated aluminum foil, with the surface density of both sides controlled at 290 g / cm³. 2 ; S3: Roll pressing: Hot pressing is used, with the temperature controlled at 75℃ and the pressure controlled at 9mPa. The rolled electrode sheet must be able to withstand being folded in half 5 times after sampling by the sampler without breaking or separating.

[0025] Comparative Example 1

[0026] S1: Homogenization: The mass ratio of NFPP:CNT:PVDF:SP:dispersant is 94.2:1.0:2.8:1.8:0.2. Weigh 297.2g of PVDF and 3949.0g of NMP, dissolve them completely, add 1769.3g of CNT with a solid content of 6%, disperse for 30 min, then add 191.1g of conductive carbon black SP and 800.0g of NMP, disperse for 30 min, then add 10000.0g of NFPP and 2000.0g of NMP, stir for 15 min, then add 268.2g of dispersant with a solid content of 7.9%, disperse at 4200rpm for 120 min, then add water to disperse and reduce the viscosity to 3000mPa.s, finally obtaining a uniform NFPP positive electrode slurry; S2: Coating: The slurry from S1 is evenly coated onto both sides of the carbon-coated aluminum foil, with the surface density controlled at 310 g / cm³. 2 ; S3: Roll pressing: Hot pressing is used, with the temperature controlled at 90℃ and the pressure controlled at 10mPa. The rolled electrode sheet must be able to withstand being folded in half 5 times after sampling by the sampler without breaking or separating.

[0027] The NFPP positive electrode sheets prepared in Examples 1-5 and Comparative Example 1 were subjected to performance tests, including sheet resistivity, electrode peel strength, and electrode compaction density tests. The test methods are as follows: I. Testing Surface Resistance Using the Two-Electrode Method Test instrument: Wuhan Chaodian Technology Co., Ltd., model SPC-TP-2000P.

[0028] The testing process is as follows:

[0029] 1. Prepare a two-electrode test setup, including a power supply, a voltmeter, an ammeter, and two electrodes.

[0030] 2. Fix the 10mm diameter electrode on the test fixture, ensuring that both ends of the electrode are in close contact with the two electrodes respectively.

[0031] 3. Connect the test circuit and ensure that the circuit connection is correct.

[0032] 4. Apply a voltage of 300V and record the readings of the ammeter and voltmeter at this time.

[0033] 5. Calculate the resistance value of the electrode based on Ohm's law, and then calculate the surface resistance by multiplying the electrode area by the resistance value.

[0034] II. Testing electrode peel strength

[0035] Test instrument: Guangdong Zhongye Precision Instrument Equipment Co., Ltd., model HTS-BLY2510.

[0036] Referring to the national standard GB / T 2790-1995 "Test Method for 180° Peel Strength of Adhesives", the test procedure is as follows:

[0037] 1. Cut an electrode sample with a blade, 20mm wide and 100-160mm long. Attach special double-sided tape to the steel plate, 20mm wide and 90-150mm long. Place the previously cut electrode sample on the double-sided tape, test side down, and then roll it three times in the same direction with a pressure roller.

[0038] 2. Insert a paper strip with a width equal to that of the electrode sample and a length of 250 mm into the current collector of the electrode and fix it with wrinkle glue.

[0039] 3. Turn on the power of the tensile testing machine (sensitivity 1N). The indicator light will illuminate. Adjust the limit block to the appropriate position and fix the end of the steel plate without the electrode sample using the lower clamp. Fold the paper tape upwards and fix it using the upper clamp. Use the "up" and "down" buttons on the manual controller provided with the tensile testing machine to adjust the position of the upper clamp, then perform the test and read the value. Divide the force when the electrode is in equilibrium by the width of the tape to obtain the peel strength per unit length of the electrode.

[0040] III. Testing the maximum compaction density of the electrode sheet

[0041] Operating steps

[0042] Cut the positive electrode sheet to 15mm. A 120mm test sample is prepared for use. The electrode is bent and folded in half and secured. A 2kg roller is used to press the sample once, checking for light transmission and metal leakage at the folded area. If no light transmission or metal leakage is observed, the electrode is folded back in half and secured again, and the same method is used to press it once more. The same method is repeated, checking for light transmission and metal leakage at the folded area. If no light transmission or metal leakage is observed after three repetitions, the electrode thickness is reduced, and the compaction density is increased. The test is repeated until light transmission and metal leakage occur after three repetitions of folding and pressing. The compaction density of the positive electrode that does not exhibit light transmission or metal leakage is taken as the maximum compaction density. The initial compaction density is the same for both the example and comparative examples. The compaction density increases by 0.01g / cm³ for each test. 3 .

[0043] Table 1. Preparation parameters of positive electrode sheet

[0044] Table 2 Test performance of positive electrode sheet

[0045] As shown in Table 2, considering the surface resistivity, peel strength, electrode compaction density, and thickness data, the positive electrode of Example 1 exhibits the best overall performance, with the highest compaction density of 2.15 g / cm³.3 .

[0046] As can be seen from the sheet resistance data in Table 2, comparing Example 1 and Example 2, it can be seen that changing the content of NFPP and PVDF only changed the sheet resistance value by 2%, indicating that the change in sheet resistance value is not significantly affected by NFPP and PVDF. Comparing Example 1 and Example 3, it can be seen that changing the SP content increased the sheet resistance from 0.48Ω to 0.74Ω, indicating that the sheet resistance is mainly determined by the conductive carbon black SP content.

[0047] As can be seen from the peel strength in Table 2, comparing Example 1 and Example 2, the peel strength decreased from 12.4 N / m to 7.6 N / m, indicating that the peel strength is greatly affected by NFPP and PVDF. Comparing Example 2 and Example 3, it can be seen that the peel strength is mainly determined by the PVDF content.

[0048] A comparison of Examples 1 and 2 shows that the electrode compaction density is 2.15 g / cm³. 3 Reduced to 1.91 g / cm³ 3 This indicates that the compaction density is significantly affected by NFPP and PVDF; comparing Example 2 and Example 3, the electrode compaction density increased from 1.91 g / cm³. 3 Increased to 2.02 g / cm³ 3 This indicates that the compaction density is significantly affected by PVDF and SP; a comparison between Example 1 and Example 4 shows that the electrode compaction density increased from 2.15 g / cm³. 3 Reduced to 1.93 g / cm³ 3 This indicates that the compaction density of the electrode is determined by NFPP, SP, and PVDF.

[0049] A comparison of Examples 1 and 5 shows that reducing the coating surface density reduces the sheet resistivity by 6.25%, peel strength by 0.81%, and electrode compaction density by 1.86%. A comparison of Examples 1 and 6 shows that increasing the temperature to 90℃ increases the sheet resistivity by 6.25%, reduces the peel strength by 0.81%, and decreases the electrode compaction density by 3.2%. This indicates that coating surface density and hot-pressing temperature have a significant impact on the performance of the NFPP positive electrode. Experiments show that when the mass ratio of NFPP:CNT:PVDF:SP:dispersant is 94.2:1.0:2.8:1.8:0.2, the coating surface density is 310 g / cm³. 2 When the hot-pressing temperature is 75℃, the particles of all sizes inside the NFPP positive electrode are tightly adsorbed, and the porosity reaches its minimum. The most obvious manifestation of this is its maximum compaction density.

[0050] Figure 1The diagram shows the first 0.1C charge-discharge cycle of Example 1, illustrating that the first discharge specific capacity of the NFPP electrode prepared in Example 1 is 112 mAh / g.

[0051] Figure 2 The diagram shows the charge-discharge specific capacity and efficiency of the half-cell in Example 1 after 39 cycles at 0.1C. It can be seen that the battery capacity of Example 1 decreases by less than 0.1% after 39 cycles, that is, the capacity retention rate of the half-cell in Example 1 is higher than 99.9%.

[0052] This invention improves the mass energy density of batteries assembled from NFPP positive electrode sheets by adjusting the proportions of NFPP, CNT, PVDF, SP, and dispersant, while also using appropriate coating density and hot-pressing parameters. Simultaneously, it significantly reduces the battery's internal resistance, improves its rate performance, and enhances its energy density and cycle life.

[0053] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0054] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a high-pressure NFPP positive electrode sheet, characterized in that, Includes the following steps: S1. Homogenization: The positive electrode active material NFPP, conductive agent, binder and dispersant are mixed and dispersed in a solvent to obtain the positive electrode slurry; S2, Coating: The positive electrode slurry obtained in S1 is uniformly coated onto the current collector; S3. Rolling: The positive electrode sheet obtained in S2 is rolled using a hot pressing method to obtain a high-pressure compacted NFPP positive electrode sheet.

2. The method for preparing the high-pressure NFPP positive electrode sheet according to claim 1, characterized in that, The conductive agent in S1 includes a first conductive agent and a second conductive agent; the first conductive agent is carbon nanotubes (CNTs); the second conductive agent is conductive carbon black (SP); the binder in S1 is polyvinylidene fluoride (PVDF); the dispersant in S1 is hydrogenated nitrile butadiene rubber (HNBR); and the solvent in S1 is NMP.

3. The method for preparing the high-pressure NFPP positive electrode sheet according to claim 1, characterized in that, The mass ratio of each component in the slurry described in S1 is NFPP:CNT:PVDF:SP:dispersant = 94-95:1.0:2.5-2.8:1.3-1.8:0.

2.

4. The method for preparing the high-pressure NFPP positive electrode sheet according to claim 3, characterized in that, The mass ratio of each component in the slurry described in S1 is NFPP:CNT:PVDF:SP:dispersant 94.2:1.0:2.8:1.8:0.

2.

5. The method for preparing the high-pressure NFPP positive electrode sheet according to claim 1, characterized in that, The slurry in S1 has a CNT solids content of 6% and a dispersant solids content of 7.9%.

6. The method for preparing the high-pressure NFPP positive electrode sheet according to claim 1, characterized in that, The specific steps described in S1 are as follows: Weigh PVDF and NMP, dissolve them completely, add CNT, disperse for 30 min, add SP and NMP, disperse for 30 min, add NFPP and NMP, stir for 15 min, add dispersant, disperse at high speed at 4200 rpm for 120 min, add water to disperse and reduce the viscosity to 3000 mPa·s, and finally obtain a uniform NFPP cathode slurry.

7. The method for preparing the high-pressure NFPP positive electrode sheet according to claim 1, characterized in that, The current collector mentioned in S2 is aluminum foil.

8. The method for preparing the high-pressure NFPP positive electrode sheet according to claim 1, characterized in that, The surface density of the double-sided coating described in S2 is 290-310 g / cm³. 2 .

9. The method for preparing the high-pressure NFPP positive electrode sheet according to claim 1, characterized in that, The roller pressing described in S3 is performed using a hot pressing method, with a temperature of 75℃ and a pressure of 9-10mPa.

10. A high-pressure NFPP positive electrode sheet, obtained by the preparation method according to any one of claims 1-9.

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