Process for preparing a positive electrode slurry doped with lithium manganate

Abstract

The application provides a preparation process of a positive electrode slurry doped with lithium manganate, and comprises the following steps: mixing anhydrous ethanol and monocarboxylic acid to obtain a pH value regulator; adding the pH value regulator into a methylpyrrolidone solution for weak acid treatment, so that the methylpyrrolidone solution is weakly acidic; pretreating a mixture of a positive electrode active material, a conductive agent and polyvinylidene fluoride; stirring the pretreated mixture of the positive electrode active material, the conductive agent and the polyvinylidene fluoride to obtain a powder; wetting the powder to obtain a positive electrode slurry semi-product; pre-kneading the positive electrode slurry semi-product; kneading the pre-kneaded positive electrode slurry semi-product; and dispersing the kneaded positive electrode slurry semi-product to obtain a positive electrode slurry after dispersion treatment. The preparation process of the positive electrode slurry doped with lithium manganate ensures the cycle performance of the battery and reduces the toxicity of the battery.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of sodium ion batteries, in particular to a preparation process of a positive electrode slurry doped with lithium manganate. BACKGROUND

[0002] The positive electrode slurry comprises a positive electrode active material, and the alkaline substance in the positive electrode active material is more likely to attack the C-F bond on the polyvinylidene fluoride, so that the polyvinylidene fluoride generates a double bond by decomposing HF, the double bond is easy to react with oxygen in the air to generate a peroxide, the peroxide decomposes to generate oxygen free radicals, and then the oxygen free radicals couple to cause the polyvinylidene fluoride to crosslink, and further cause a gel phenomenon. When the pH of the positive electrode slurry is greater than 10, the gel reaction is easy to occur.

[0003] The traditional process uses oxalic acid to neutralize the positive electrode slurry, although the effect of reducing the gel is achieved, however, the oxalic acid can corrode the aluminum foil, and the oxalic acid reacts with the alkaline substance in the positive electrode active material to generate an oxalate, the thermal stability of the oxalate is poor, the thermal decomposition of the oxalate generates gas, which affects the cycle performance of the battery; in addition, the oxalic acid is toxic. SUMMARY

[0004] The application aims to overcome the defects in the prior art, and provide a preparation process of a positive electrode slurry doped with lithium manganate, which can ensure the cycle performance of the battery and reduce the toxicity of the battery.

[0005] The application is achieved by the following technical scheme: a preparation process of a positive electrode slurry doped with lithium manganate, comprising the following steps:

[0006] Mixing anhydrous ethanol and monocarboxylic acid to obtain a pH value adjusting agent;

[0007] Adding the pH value adjusting agent into a methylpyrrolidone solution for weak acid treatment, so that the methylpyrrolidone solution is weakly acidic;

[0008] Pretreating a mixture of a positive electrode active material, a conductive agent and polyvinylidene fluoride;

[0009] Stirring the pretreated mixture of the positive electrode active material, the conductive agent and the polyvinylidene fluoride to obtain a powder;

[0010] Wetting the powder to obtain a positive electrode slurry semi-product;

[0011] Pretorqueing the positive electrode slurry semi-product;

[0012] Torqueing the positive electrode slurry semi-product after pretorqueing;

[0013] The positive electrode slurry semi-product after the kneading treatment is subjected to a dispersion treatment, so as to obtain the positive electrode slurry after the dispersion treatment.

[0014] In one of the embodiments, the step of obtaining the positive electrode slurry by wetting the powder is specifically as follows: the methyl pyrrolidone solution after the weak acid treatment is added into the powder, and then the methyl pyrrolidone solution after the weak acid treatment and the powder are stirred.

[0015] In one of the embodiments, the mass ratio of the anhydrous ethanol to the monobasic carboxylic acid is 1:1.

[0016] In one of the embodiments, the mass ratio of the pH value regulator to the positive electrode active material is 0.002-0.003.

[0017] In one of the embodiments, the pH value regulator is added into the methyl pyrrolidone solution for the weak acid treatment under the condition that the methyl pyrrolidone solution is subjected to the ultrasonic vibration stirring operation, so as to make the methyl pyrrolidone solution weakly acidic.

[0018] In one of the embodiments, the ultrasonic frequency of the ultrasonic vibration stirring operation is 20 kHz-50 kHz, and the time of the ultrasonic vibration stirring operation is 5 min-10 min.

[0019] In one of the embodiments, the pH value regulator is added into the methyl pyrrolidone solution for the weak acid treatment under the condition that the methyl pyrrolidone solution is subjected to the nitrogen gas passing operation and the vacuumizing operation, so as to make the methyl pyrrolidone solution weakly acidic; wherein the temperature of the nitrogen gas is 40℃-50℃.

[0020] In one of the embodiments, the time of the nitrogen gas passing operation is 3 min-5 min.

[0021] In one of the embodiments, the time of the vacuumizing operation is 2 min.

[0022] In one of the embodiments, the positive electrode active material includes a sodium ion positive electrode active material and a lithium manganate positive electrode active material.

[0023] Compared with the prior art, the present application has at least the following advantages:

[0024] 1) The preparation process of the manganese-doped lithium manganate positive electrode slurry of the present application mixes anhydrous ethanol and monocarboxylic acid to obtain a pH value regulator, adds the pH value regulator to the methylpyrrolidone solution for weak acid treatment, so that the methylpyrrolidone solution is weakly acidic, that is, the monocarboxylic acid is added to the methylpyrrolidone solution to neutralize the free ammonia in the methylpyrrolidone solution, and the pH value regulator has high volatility to inhibit ammonia volatilization of methylpyrrolidone.

[0025] 2) The preparation process of the manganese-doped lithium manganate positive electrode slurry of the present application continues to add monocarboxylic acid to the methylpyrrolidone solution after neutralizing the free ammonia, until the methylpyrrolidone solution is weakly acidic, that is, there is monocarboxylic acid in the methylpyrrolidone solution after weak acid treatment, which is used to neutralize the alkaline substances in the positive electrode active material during subsequent wetting treatment, pre-kneading treatment, kneading treatment and dispersion treatment, so that the pH of the positive electrode slurry semi-finished product and the positive electrode slurry is always weakly alkaline or neutral, avoiding the problem of gelation of polyvinylidene fluoride in an alkaline environment with a pH greater than 10, thereby ensuring that polyvinylidene fluoride plays a role in bonding the positive electrode active material, thereby making the subsequent stirred positive electrode slurry more stable, reducing the problem of particle powder caused by uneven positive electrode slurry, thereby reducing the phenomenon of voltage drop caused by powder short circuit carbonization, thereby ensuring the stability of battery voltage, cycle performance and charge-discharge rate performance.

[0026] 3) The preparation process of the manganese-doped lithium manganate positive electrode slurry of the present application avoids the problem of corrosion of aluminum foil due to the weak acid nature of monocarboxylic acid and the small number of carboxyl groups in monocarboxylic acid, and the reaction of monocarboxylic acid with alkaline substances in the positive electrode active material to form monocarboxylic acid salt, which has good thermal stability, avoiding the problem of affecting the cycle performance of the battery due to thermal decomposition to produce gas, and the almost non-toxic nature of monocarboxylic acid, thereby reducing the toxicity of the battery. BRIEF DESCRIPTION OF DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be considered as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0028] Figure 1 The preparation process of the manganese-doped lithium manganate positive electrode slurry of the present application is shown in the schematic diagram of an embodiment of the present application.

[0029] Figure 2 The flow chart of the preparation process of the manganese-doped lithium manganate positive electrode slurry of another embodiment of the present application is shown in the flow chart of another embodiment of the present application. DETAILED DESCRIPTION

[0030] For the purposes of this disclosure, reference will be made to the accompanying drawings which form a part of the disclosure. The drawings are not necessarily to scale of the preferred embodiments of the application. It is to be understood that the variations in the drawings can serve to illustrate the principles of the application. Thus, the present application can be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and fully convey the scope of the application to those skilled in the art.

[0031] It is to be understood that where the terms such as "fixed", "connected" or "linked" are used herein, they are to be interpreted broadly to encompass a direct connection or linkage as well as an indirect connection or linkage, i.e., through one or more intermediate elements. As used herein, the terms "vertical", "horizontal", "left", "right" and similar terms are used for explanation only and are not to be construed as limiting.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. The term "and / or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items.

[0033] The preparation process of the manganese-doped lithium manganate positive electrode slurry of an embodiment includes some or all of the following steps:

[0034] S101, mixing anhydrous ethanol and monocarboxylic acid to obtain a pH value adjusting agent;

[0035] S103, adding the pH value adjusting agent to the methylpyrrolidone solution for weak acid treatment, so that the methylpyrrolidone solution is weakly acidic;

[0036] S105, pretreating the mixture of the positive electrode active material, the conductive agent and the polyvinylidene fluoride;

[0037] S107, stirring the pretreated mixture of the positive electrode active material, the conductive agent and the polyvinylidene fluoride to obtain a powder;

[0038] S109, wetting the powder to obtain a positive electrode slurry semi-product;

[0039] S111, pre-kneading the positive electrode slurry semi-product;

[0040] S113, kneading the pre-kneaded positive electrode slurry semi-product;

[0041] S115, performing dispersion treatment on the positive electrode slurry semi-finished product after the kneading treatment to obtain a positive electrode slurry after the dispersion treatment.

[0042] The preparation process of the above-mentioned positive electrode slurry doped with lithium manganate mixes anhydrous ethanol and monocarboxylic acid to obtain a pH adjuster, adds the pH adjuster into the methylpyrrolidone solution for weak acid treatment, so that the methylpyrrolidone solution is weakly acidic, that is, the monocarboxylic acid is added to the methylpyrrolidone solution to neutralize the free ammonia in the methylpyrrolidone solution, and the pH adjuster has high volatility to inhibit ammonia volatilization of methylpyrrolidone. In addition, after the free ammonia is neutralized by the monocarboxylic acid, the methylpyrrolidone solution continues to be added with the monocarboxylic acid dropwise until the methylpyrrolidone solution is weakly acidic, that is, the monocarboxylic acid exists in the methylpyrrolidone solution after the weak acid treatment, which is used to neutralize the alkaline substances in the positive electrode active material during the subsequent wetting treatment, pre-kneading treatment, kneading treatment and dispersion treatment, so that the pH of the positive electrode slurry semi-finished product and the positive electrode slurry is always weakly alkaline or neutral, avoiding the problem of gelation of polyvinylidene fluoride in an alkaline environment with a pH greater than 10, thereby ensuring the bonding effect of polyvinylidene fluoride on the positive electrode active material, thereby making the subsequent stirred uniform positive electrode slurry more stable, reducing the problem of particle powder caused by non-uniform positive electrode slurry, thereby reducing the phenomenon of voltage drop caused by powder short circuit carbonization, thereby ensuring the stability of battery voltage, cycle performance and charge-discharge rate performance. In addition, since the monocarboxylic acid is weak acid and has fewer carboxyl groups, the problem of corrosion of aluminum foil is avoided, and the monocarboxylic acid reacts with the alkaline substances in the positive electrode active material to form a monocarboxylic acid salt, which has good thermal stability, avoiding the problem of affecting the cycle performance of the battery due to thermal decomposition to generate gas, and the monocarboxylic acid is almost non-toxic, thereby reducing the toxicity of the battery.

[0043] Further, the weak acid refers to a pH greater than or equal to 4 and less than 7.

[0044] It should be noted that the A arrow indicates the flow direction of nitrogen, and the B arrow indicates the flow direction of the methylpyrrolidone solution after the weak acid treatment.

[0045] In one of the embodiments, the step of wetting the powder to obtain the positive electrode slurry is specifically: adding the weakly acidic treated methyl pyrrolidone solution into the powder, and then stirring the weakly acidic treated methyl pyrrolidone solution and the powder. It can be understood that the powder includes the positive electrode active material, the positive electrode active material has alkaline substances, the weakly acidic treated methyl pyrrolidone solution contains monobasic carboxylic acid, and the monobasic carboxylic acid is used for neutralizing the alkaline substances in the positive electrode active material during the wetting process, so that the pH of the positive electrode slurry semi-finished product is always weakly alkaline or neutral, the problem of gelation of polyvinylidene fluoride in an alkaline environment with a pH greater than 10 is avoided, the adhesion of polyvinylidene fluoride to the positive electrode active material is ensured, the subsequent uniform stirring of the positive electrode slurry is ensured, the problem of particle powder caused by non-uniform positive electrode slurry is reduced, the problem of short-circuit carbonization of the powder is avoided, the problem of voltage drop caused by short-circuit carbonization of the powder is reduced, and the stability, cycle performance, and charge-discharge rate performance of the battery are ensured.

[0046] In one of the embodiments, the mass ratio of the anhydrous ethanol to the monobasic carboxylic acid is 1:1. It can be understood that the monobasic carboxylic acid is added to the methyl pyrrolidone solution to neutralize the free ammonia in the methyl pyrrolidone solution, and the pH adjuster has high volatility to inhibit ammonia volatilization of the methyl pyrrolidone. The monobasic carboxylic acid is used for neutralizing the alkaline substances in the positive electrode active material during the wetting process, the pre-kneading process, the kneading process, and the dispersion process, so that the pH of the positive electrode slurry semi-finished product and the positive electrode slurry is always weakly alkaline or neutral, the problem of gelation of polyvinylidene fluoride in an alkaline environment with a pH greater than 10 is avoided, the adhesion of polyvinylidene fluoride to the positive electrode active material is ensured, the subsequent uniform stirring of the positive electrode slurry is ensured, the problem of particle powder caused by non-uniform positive electrode slurry is reduced, the problem of short-circuit carbonization of the powder is avoided, the problem of voltage drop caused by short-circuit carbonization of the powder is reduced, and the stability, cycle performance, and charge-discharge rate performance of the battery are ensured. The monobasic carboxylic acid is a weak acid, and the monobasic carboxylic acid has fewer carboxyl groups, so the problem of corrosion of the aluminum foil is avoided, the monobasic carboxylic acid reacts with the alkaline substances in the positive electrode active material to generate a monobasic carboxylic acid salt, the monobasic carboxylic acid salt has good thermal stability, the problem of influence on the cycle performance of the battery caused by thermal decomposition to generate gas is avoided, and the monobasic carboxylic acid is almost non-toxic, so the toxicity of the battery is reduced.

[0047] In one embodiment, the mass ratio of the pH regulator to the positive active material is 0.002-0.003. It can be understood that when the mass ratio of the pH regulator to the positive active material is 0.002-0.003, the pH of the positive slurry is more easily adjusted to neutral, avoiding the problem that the gel phenomenon of polyvinylidene fluoride occurs in an alkaline environment with a pH greater than 10, thereby ensuring the binding effect of polyvinylidene fluoride on the positive active material, thereby making the positive slurry stirred uniformly more stable, reducing the phenomenon that granular powder is generated due to uneven positive slurry, thereby leading to the carbonization of the powder short circuit, thereby reducing the voltage drop phenomenon caused by the carbonization of the powder short circuit, thereby ensuring the stability of the battery voltage, the cycle performance, and the charge-discharge rate performance.

[0048] In one embodiment, the pH regulator is added to the p-methyl pyrrolidone solution to perform weak acid treatment under the condition of ultrasonic vibration stirring operation of the p-methyl pyrrolidone solution, so that the p-methyl pyrrolidone solution is weakly acidic. It can be understood that ultrasonic vibration is a higher frequency vibration, and the shear force generated by the higher frequency vibration makes the p-methyl pyrrolidone solution oscillate at a higher frequency, thereby making the p-methyl pyrrolidone solution and the pH regulator mix uniformly, thereby ensuring the consistency of the weakly acidic treated p-methyl pyrrolidone solution added in the subsequent wetting treatment, pre-kneading treatment, kneading treatment, and dispersion treatment, that is, ensuring the consistency of the concentration of monocarboxylic acid in the added p-methyl pyrrolidone solution, that is, ensuring the uniformity of the weakly acidic treated p-methyl pyrrolidone solution added in the subsequent wetting treatment, pre-kneading treatment, kneading treatment, and dispersion treatment, thereby making the pH of the positive slurry semi-finished product in the subsequent wetting treatment, pre-kneading treatment, kneading treatment, and dispersion treatment more easily adjusted to weakly alkaline or neutral, avoiding the problem that the gel phenomenon of polyvinylidene fluoride occurs in an alkaline environment with a pH greater than 10, thereby ensuring the binding effect of polyvinylidene fluoride on the positive active material, thereby making the subsequent positive slurry stirred uniformly more stable, reducing the phenomenon that granular powder is generated due to uneven positive slurry, thereby leading to the problem of carbonization of the powder short circuit, thereby reducing the voltage drop phenomenon caused by the carbonization of the powder short circuit, thereby ensuring the stability of the battery voltage, the cycle performance, and the charge-discharge rate performance.

[0049] In one of the embodiments, the ultrasonic frequency of the ultrasonic vibration stirring operation is 20 kHz to 50 kHz, and the time of the ultrasonic vibration stirring operation is 5 min to 10 min. It can be understood that the ultrasonic frequency of 20 kHz to 50 kHz is a higher ultrasonic frequency. When the ultrasonic frequency of the ultrasonic vibration stirring operation is 20 kHz to 50 kHz, and the time of the ultrasonic vibration stirring operation is 5 min to 10 min, the ultrasonic vibration makes the methylpyrrolidone solution produce a higher frequency and longer time of oscillation, and then the methylpyrrolidone solution is fully mixed and uniform with the pH adjuster, and then the consistency of the weakly acidic treated methylpyrrolidone solution added in the subsequent wetting treatment, pre-kneading treatment, kneading treatment and dispersion treatment is ensured, that is, the consistency of the concentration of monocarboxylic acid in the added methylpyrrolidone solution is ensured, that is, the uniformity of the weakly acidic treated methylpyrrolidone solution added in the subsequent wetting treatment, pre-kneading treatment, kneading treatment and dispersion treatment is ensured, and then the pH of the positive electrode slurry semi-finished product in the subsequent wetting treatment, pre-kneading treatment, kneading treatment and dispersion treatment is more easily adjusted to weak alkaline or neutral, avoiding the problem that the gel phenomenon of polyvinylidene fluoride occurs in the alkaline environment with a pH greater than 10, and then ensuring the adhesion of polyvinylidene fluoride to the positive active material, and then the positive electrode slurry which is subsequently stirred uniformly is more stable, reducing the problem that the particle powder is generated due to the uneven positive electrode slurry, and then leading to the problem of powder short circuit carbonization, and then reducing the phenomenon of voltage drop caused by powder short circuit carbonization, and then ensuring the stability of the battery voltage, the cycle performance and the charge-discharge rate performance, and avoiding the problem of cost increase of higher frequency ultrasonic vibration.

[0050] In one of the embodiments, the pH value regulator is added to the methylpyrrolidone solution for weak acid treatment under the condition that nitrogen is passed into the methylpyrrolidone solution and then the methylpyrrolidone solution is vacuumized to make the methylpyrrolidone solution weakly acidic; wherein the temperature of the nitrogen is 40-50℃. It can be understood that the nitrogen is passed into the methylpyrrolidone solution, and the temperature of the nitrogen is 40-50℃. The nitrogen with the temperature of 40-50℃ can replace the moisture in the methylpyrrolidone solution to remove the moisture in the methylpyrrolidone solution. Then the methylpyrrolidone solution is vacuumized to remove the moisture. The subsequent anode slurry semi-finished product in the wetting treatment, pre-kneading treatment, kneading treatment and dispersion treatment is in a water-free environment, which avoids the problem of agglomeration of the subsequent anode slurry semi-finished product with moisture, and avoids the problem of non-solvent induced phase separation caused by the extraction of polyvinylidene fluoride by moisture during the subsequent wetting treatment, pre-kneading treatment, kneading treatment and dispersion treatment, thereby making the anode slurry more uniform, thereby ensuring the cycle performance of the battery, and also avoiding the problem of poor adhesion effect caused by the absorption of polyvinylidene fluoride by water after the subsequent mixing of the methylpyrrolidone solution and the powder, thereby avoiding the problem of powder falling during the charging process caused by poor adhesion effect, thereby affecting the voltage drop, thereby ensuring the stability of the battery voltage, the cycle performance and the charge-discharge rate performance, and also avoiding the direct impact of moisture on the cycle performance of the battery, i.e. further ensuring the cycle performance of the battery.

[0051] Further, the temperature of the nitrogen is 40-50℃, which avoids the problem of changing the properties of the methylpyrrolidone solution or causing the methylpyrrolidone solution to react, thereby further ensuring the cycle performance of the battery.

[0052] In one of the embodiments, the time for the N-methylpyrrolidone solution to be subjected to the nitrogen gas is 3-5 minutes. It can be understood that when the time for the N-methylpyrrolidone solution to be subjected to the nitrogen gas is 3-5 minutes, the nitrogen gas can displace the water from the N-methylpyrrolidone solution to remove the water in the N-methylpyrrolidone solution, and then the N-methylpyrrolidone solution is subjected to the vacuumizing operation to remove the water, which, in combination with the subsequent obtained water-free powder, enables the positive electrode slurry semi-finished product in the subsequent wetting treatment, pre-kneading treatment, kneading treatment and dispersion treatment to be in a water-free environment, avoids the problem of the subsequent positive electrode slurry semi-finished product to be agglomerated with the water, and avoids the problem of the water to extract the polyvinylidene fluoride to cause the non-solvent induced phase separation in the subsequent wetting treatment, pre-kneading treatment, kneading treatment and dispersion treatment, which further enables the positive electrode slurry to be relatively uniform, which further ensures the cycle performance of the battery, and also avoids the problem of the water absorption of the polyvinylidene fluoride to affect the bonding effect after the subsequent N-methylpyrrolidone solution is mixed with the powder, which further avoids the problem of the poor bonding effect to cause the powder to drop in the charging process and thus to affect the voltage drop, which further ensures the stability of the battery voltage, cycle performance and charge-discharge rate performance, and also avoids the direct influence of the water on the cycle performance of the battery, i.e., further ensures the cycle performance of the battery.

[0053] In one of the embodiments, the time for the vacuumizing operation is 2 minutes. It can be understood that when the time for the vacuumizing operation is 2 minutes, the vacuumizing operation can remove the water by the nitrogen gas, which, in combination with the subsequent obtained water-free powder, enables the positive electrode slurry semi-finished product in the subsequent wetting treatment, pre-kneading treatment, kneading treatment and dispersion treatment to be in a water-free environment, avoids the problem of the subsequent positive electrode slurry semi-finished product to be agglomerated with the water, and avoids the problem of the water to extract the polyvinylidene fluoride to cause the non-solvent induced phase separation in the subsequent wetting treatment, pre-kneading treatment, kneading treatment and dispersion treatment, which further enables the positive electrode slurry to be relatively uniform, which further ensures the cycle performance of the battery, and also avoids the problem of the water absorption of the polyvinylidene fluoride to affect the bonding effect after the subsequent N-methylpyrrolidone solution is mixed with the powder, which further avoids the problem of the poor bonding effect to cause the powder to drop in the charging process and thus to affect the voltage drop, which further ensures the stability of the battery voltage, cycle performance and charge-discharge rate performance, and also avoids the direct influence of the water on the cycle performance of the battery, i.e., further ensures the cycle performance of the battery.

[0054] In one of the embodiments, the positive electrode active material includes a sodium ion positive electrode active material and a lithium manganate positive electrode active material. It can be understood that the positive electrode active material obtained by doping the lithium manganate positive electrode active material into the sodium ion positive electrode active material has a relatively high crystal structure stability, i.e., the positive electrode material structure has a relatively high stability, which improves the cycle performance of the battery.

[0055] In one embodiment, the pH adjusting agent is added to the methylpyrrolidone solution by the ultrasonic stirring device 100 to perform weak acid treatment, so that the methylpyrrolidone solution is weakly acidic. It can be understood that the ultrasonic stirring device is used to provide ultrasonic vibration to the methylpyrrolidone solution, and the ultrasonic vibration is a high-frequency vibration. The shear force generated by the high-frequency vibration causes the methylpyrrolidone solution to vibrate at a high frequency, thereby causing the methylpyrrolidone solution to mix uniformly with the pH adjusting agent, thereby ensuring the consistency of the methylpyrrolidone solution treated by weak acid after being added in subsequent wetting treatment, pre-kneading treatment, kneading treatment and dispersion treatment, i.e. ensuring the consistency of the concentration of monocarboxylic acid in the methylpyrrolidone solution added, i.e. ensuring the uniformity of the methylpyrrolidone solution treated by weak acid after being added in subsequent wetting treatment, pre-kneading treatment, kneading treatment and dispersion treatment, thereby making it easier to adjust the pH of the positive electrode slurry semi-finished product to weak alkaline or neutral during subsequent wetting treatment, pre-kneading treatment, kneading treatment and dispersion treatment, thereby avoiding the problem of gelation of polyvinylidene fluoride in an alkaline environment with a pH greater than 10, thereby ensuring the binding effect of polyvinylidene fluoride on the positive electrode active material, thereby making the subsequently stirred positive electrode slurry more stable, reducing the generation of granular powder due to uneven positive electrode slurry, thereby reducing the problem of carbonization caused by powder short circuit, thereby reducing the voltage drop phenomenon caused by powder short circuit, and thereby ensuring the stability of the battery voltage, the cycle performance and the charge-discharge rate performance.

[0056] In one embodiment, the mixture of positive electrode active material, conductive agent and polyvinylidene fluoride is pretreated by the double planetary stirring cylinder device 200; and the pretreated mixture of positive electrode active material, conductive agent and polyvinylidene fluoride is stirred to obtain a powder. It can be understood that the pH adjusting agent is added to the methylpyrrolidone solution by the ultrasonic stirring device 100 to perform weak acid treatment, so that the methylpyrrolidone solution is weakly acidic. The ultrasonic stirring device and the double planetary stirring cylinder device are two independent devices, i.e. the steps of treating the methylpyrrolidone solution and obtaining the powder are performed separately, so that the methylpyrrolidone solution added in the powder is weakly acidic, mixed uniformly and has removed moisture.

[0057] It can be understood that the methylpyrrolidone solution treated by weak acid is neutralized with an alkaline substance, so that the pH of the positive electrode slurry semi-finished product and the positive electrode slurry is always weakly alkaline or neutral, thereby avoiding the problem of gelation of polyvinylidene fluoride in an alkaline environment with a pH greater than 10, thereby ensuring the binding effect of polyvinylidene fluoride on the positive electrode active material, thereby making the subsequently stirred positive electrode slurry more stable, reducing the generation of granular powder due to uneven positive electrode slurry, thereby reducing the problem of carbonization caused by powder short circuit, thereby reducing the voltage drop phenomenon caused by powder short circuit, and thereby ensuring the stability of the battery voltage, the cycle performance and the charge-discharge rate performance.

[0058] It can be understood that the methylpyrrolidone solution is mixed more uniformly, ensuring the consistency of the weakly acidic treated methylpyrrolidone solution added in the subsequent wetting treatment, pre-kneading treatment, kneading treatment and dispersion treatment, i.e. ensuring the consistency of the concentration of monocarboxylic acid in the methylpyrrolidone solution added, i.e. ensuring the uniformity of the weakly acidic treated methylpyrrolidone solution added in the subsequent wetting treatment, pre-kneading treatment, kneading treatment and dispersion treatment, and then the pH of the positive electrode slurry semi-finished product in the subsequent wetting treatment, pre-kneading treatment, kneading treatment and dispersion treatment is more easily adjusted to weak alkaline or neutral, avoiding the problem that the gel phenomenon of polyvinylidene fluoride occurs in an alkaline environment with a pH greater than 10, and then ensuring the bonding effect of polyvinylidene fluoride on the positive electrode active material, and then the positive electrode slurry which is stirred uniformly is more stable, reducing the problem that the particle powder is generated due to the uneven positive electrode slurry, and then the voltage drop phenomenon caused by the powder short circuit carbonization is reduced, and then the stability of the battery voltage, the cycle performance and the charge-discharge rate performance are ensured.

[0059] Further, the methylpyrrolidone solution from which the water is removed is combined with the subsequent obtained anhydrous powder, so that the positive electrode slurry semi-finished product in the subsequent wetting treatment, pre-kneading treatment, kneading treatment and dispersion treatment is in an anhydrous environment, avoiding the problem that the subsequent positive electrode slurry semi-finished product agglomerates with water, and avoiding the problem that water extracts polyvinylidene fluoride to generate non-solvent induced phase separation in the subsequent wetting treatment, pre-kneading treatment, kneading treatment and dispersion treatment, and then the positive electrode slurry is more uniform, and then the cycle performance of the battery is ensured, and further avoiding the problem that the bonding effect of polyvinylidene fluoride is affected due to the water absorption after the subsequent methylpyrrolidone solution is mixed with the powder, and then the problem that the charging process is affected due to the powder falling caused by the poor bonding effect, and then the stability of the battery voltage, the cycle performance and the charge-discharge rate performance are ensured, and further avoiding the direct influence of water on the cycle performance of the battery, i.e. further ensuring the cycle performance of the battery.

[0060] In one embodiment, a sealing feeding pipeline 300 is arranged between the ultrasonic stirring device and the double-planetary stirring cylinder device, a first valve is arranged between the ultrasonic stirring device and the automatic feeding pipeline, and a second valve is arranged between the double-planetary stirring cylinder device and the automatic feeding pipeline. It can be understood that the first valve is arranged between the ultrasonic stirring device and the automatic feeding pipeline, and the second valve is arranged between the double-planetary stirring cylinder device and the automatic feeding pipeline, so that the step of processing the methylpyrrolidone solution and the step of obtaining the powder are performed separately, and the methylpyrrolidone solution added in the powder is weakly acidic, mixed more uniformly and has removed water.

[0061] Further, the weakly acidic treated methylpyrrolidone solution is neutralized with a basic substance, so that the pH of the positive electrode slurry semi-finished product and the positive electrode slurry is always weakly alkaline or neutral, avoiding the problem that the gel phenomenon of polyvinylidene fluoride occurs in an alkaline environment with a pH greater than 10, thereby ensuring the bonding effect of polyvinylidene fluoride on the positive electrode active material, thereby making the subsequent uniformly stirred positive electrode slurry more stable, reducing the problem that granular powder is generated due to uneven positive electrode slurry, thereby leading to the problem of powder short circuit carbonization, thereby reducing the phenomenon of voltage drop caused by powder short circuit carbonization, thereby ensuring the stability of the battery voltage, the cycle performance, and the charge-discharge rate performance.

[0062] It can be understood that the methylpyrrolidone solution is mixed more uniformly, ensuring the consistency of the weakly acidic treated methylpyrrolidone solution added during subsequent wetting treatment, pre-kneading treatment, kneading treatment, and dispersion treatment, i.e., ensuring the consistency of the concentration of monocarboxylic acid in the methylpyrrolidone solution added, i.e., ensuring the uniformity of the weakly acidic treated methylpyrrolidone solution added during subsequent wetting treatment, pre-kneading treatment, kneading treatment, and dispersion treatment, thereby making the pH of the positive electrode slurry semi-finished product during subsequent wetting treatment, pre-kneading treatment, kneading treatment, and dispersion treatment more easily adjusted to be weakly alkaline or neutral, avoiding the problem that the gel phenomenon of polyvinylidene fluoride occurs in an alkaline environment with a pH greater than 10, thereby ensuring the bonding effect of polyvinylidene fluoride on the positive electrode active material, thereby making the subsequent uniformly stirred positive electrode slurry more stable, reducing the problem that granular powder is generated due to uneven positive electrode slurry, thereby leading to the problem of powder short circuit carbonization, thereby reducing the phenomenon of voltage drop caused by powder short circuit carbonization, thereby ensuring the stability of the battery voltage, the cycle performance, and the charge-discharge rate performance. Further, the sealing feeding pipeline is arranged between the ultrasonic stirring device and the double-planetary stirring cylinder device, so that the ultrasonic stirring device, the double-planetary stirring cylinder device, and the sealing feeding pipeline jointly form a sealed environment, avoiding the problem that in the traditional process, the baked powder is added to the stirring cylinder and contacts the outside world, thereby bringing in trace amounts of water, so that the methylpyrrolidone solution from which water has been removed is added to the powder without contacting the outside environment, so that the methylpyrrolidone solution remains in a state of not containing water, and similarly, the powder remains in a state of not containing water, thereby making the positive electrode slurry semi-finished product obtained from the methylpyrrolidone solution and the powder not contain water, i.e., the positive electrode slurry semi-finished product during subsequent wetting treatment, pre-kneading treatment, kneading treatment, and dispersion treatment is in a water-free environment, avoiding the problem that the positive electrode slurry semi-finished product agglomerates with water, and avoiding the problem that water extracts polyvinylidene fluoride during subsequent wetting treatment, pre-kneading treatment, kneading treatment, and dispersion treatment, thereby making the stirred positive electrode slurry more uniform, thereby ensuring the cycle performance of the battery, and avoiding the direct impact of water on the cycle performance of the battery, i.e., further ensuring the cycle performance of the battery.

[0063] In one of the embodiments, the step of pre-treating the mixture of the positive active material, the conductive agent and the polyvinylidene fluoride is specifically: nitrogen gas with a temperature of 40-50°C is introduced into the mixture of the positive active material, the conductive agent and the polyvinylidene fluoride, and then the mixture of the positive active material, the conductive agent and the polyvinylidene fluoride is subjected to vacuumizing operation. It can be understood that the introduction of the nitrogen gas with a temperature of 40-50°C into the mixture of the positive active material, the conductive agent and the polyvinylidene fluoride makes the water molecules adsorbed by the positive active material separate from the surface of the positive active material, and then the mixture of the positive active material, the conductive agent and the polyvinylidene fluoride is subjected to vacuumizing operation to extract the water, which, in combination with the subsequent addition of the anhydrous methylpyrrolidone solution, makes the positive slurry semi-finished product in the subsequent wetting treatment, pre-kneading treatment, kneading treatment and dispersion treatment be in an anhydrous environment, avoids the agglomeration of the positive slurry semi-finished product with the water, and avoids the problem of non-solvent-induced phase separation caused by the extraction of the polyvinylidene fluoride by the water in the subsequent wetting treatment, pre-kneading treatment, kneading treatment and dispersion treatment, thereby making the stirred positive slurry more uniform, thereby ensuring the cycle performance of the battery, and avoiding the influence of the water on the cycle performance of the battery, i.e. further ensuring the cycle performance of the battery, and the nitrogen gas temperature of 40-50°C avoids the problem of changing the properties of the methylpyrrolidone solution or causing the reaction of the methylpyrrolidone solution, thereby further ensuring the cycle performance of the battery.

[0064] In one of the embodiments, the nitrogen gas with a temperature of 40-50°C is introduced into the mixture of the positive active material, the conductive agent and the polyvinylidene fluoride, and the nitrogen gas is introduced for 5 min. It can be understood that when the nitrogen gas is introduced for 5 min, the nitrogen gas with a temperature of 40-50°C can replace the water in the mixture of the positive active material, the conductive agent and the polyvinylidene fluoride, and then the mixture of the positive active material, the conductive agent and the polyvinylidene fluoride is subjected to vacuumizing operation to extract the water by the nitrogen gas with a temperature of 40-50°C, which, in combination with the subsequent addition of the anhydrous methylpyrrolidone solution, makes the positive slurry semi-finished product in the subsequent wetting treatment, pre-kneading treatment, kneading treatment and dispersion treatment be in an anhydrous environment, avoids the agglomeration of the positive slurry semi-finished product with the water, and avoids the problem of non-solvent-induced phase separation caused by the extraction of the polyvinylidene fluoride by the water in the subsequent wetting treatment, pre-kneading treatment, kneading treatment and dispersion treatment, thereby making the stirred positive slurry more uniform, thereby ensuring the cycle performance of the battery, and avoiding the influence of the water on the cycle performance of the battery, i.e. further ensuring the cycle performance of the battery, and the nitrogen gas temperature of 40-50°C avoids the problem of changing the properties of the methylpyrrolidone solution or causing the reaction of the methylpyrrolidone solution, thereby further ensuring the cycle performance of the battery.

[0065] In one of the embodiments, the mixture of the positive electrode active material, the conductive agent and the polyvinylidene fluoride is subjected to the vacuumizing operation, and the time of the vacuumizing operation is 2 min. It can be understood that when the time of the vacuumizing operation is 2 min, the vacuumizing operation can take away the moisture by nitrogen, and cooperate with the subsequent addition of the anhydrous methylpyrrolidone solution, so that the positive electrode slurry semi-finished product in the subsequent wetting treatment, pre-kneading treatment, kneading treatment and dispersion treatment is in anhydrous environment, thereby avoiding the problem of agglomeration of the positive electrode slurry semi-finished product with moisture, and avoiding the problem of non-solvent phase separation caused by the extraction of polyvinylidene fluoride by moisture in the subsequent wetting treatment, pre-kneading treatment, kneading treatment and dispersion treatment, thereby making the positive electrode slurry more uniform, thereby ensuring the cycle performance of the battery, and avoiding the influence of moisture on the cycle performance of the battery, i.e. further ensuring the cycle performance of the battery, and the temperature of the nitrogen is 40℃-50℃, thereby avoiding the problem of changing the properties of the methylpyrrolidone solution or causing the methylpyrrolidone solution to react, and further ensuring the cycle performance of the battery.

[0066] In one of the embodiments, the mixture of the pretreated positive electrode active material, the conductive agent and the polyvinylidene fluoride is subjected to the mixing and stirring operation by using the stirring assembly 400. In the embodiment, the linear speed of the stirring assembly is 10 m / min-12 m / min, and the revolving speed of the stirring assembly is 20 r / min-50 r / min. It can be understood that when the linear speed of the stirring assembly is 10 m / min-12 m / min, and the revolving speed of the stirring assembly is 20 r / min-50 r / min, the mixture of the positive electrode active material, the conductive agent and the polyvinylidene fluoride is more uniform, thereby ensuring the mixture of the positive electrode slurry to be more uniform, and thereby ensuring the cycle performance of the battery. In the embodiment, the stirring assembly can be a stirring shaft, a stirring knife or a stirring paddle.

[0067] In one of the embodiments, the time of the stirring operation on the mixture of the positive electrode active material, the conductive agent and the polyvinylidene fluoride is 30 min-60 min. It can be understood that when the time of the stirring operation on the mixture of the positive electrode active material, the conductive agent and the polyvinylidene fluoride is 30 min-60 min, the stirring time is longer, so that the mixture of the positive electrode active material, the conductive agent and the polyvinylidene fluoride is more uniform, thereby ensuring the mixture of the positive electrode slurry to be more uniform, and thereby ensuring the cycle performance of the battery.

[0068] In one of the embodiments, the mass ratio of the sodium ion positive electrode active material and the lithium manganate positive electrode active material is 1.5-4. It can be understood that when the mass ratio of the sodium ion positive electrode active material and the lithium manganate positive electrode active material is 1.5-4, the positive electrode active material obtained by doping the lithium manganate positive electrode active material into the sodium ion positive electrode active material has higher crystal structure stability, i.e. the positive electrode material structure has higher stability, thereby improving the cycle performance of the battery.

[0069] In one embodiment, the mass ratio of polyvinylidene fluoride to positive active material is 1:100. It can be understood that when the mass ratio of polyvinylidene fluoride to positive active material is 1:100, the adhesion effect of polyvinylidene fluoride on the positive active material is better, thereby making the stirred uniform positive slurry more stable, thereby ensuring the cycle performance of the battery.

[0070] In one embodiment, the step of wet-treating the powder to obtain the positive slurry semi-product is specifically: adding the weakly acidic treated methyl pyrrolidone solution to the powder to obtain the positive slurry semi-product, and then stirring the positive slurry semi-product. It can be understood that the powder includes the positive active material, and the positive active material has alkaline substances. The weakly acidic treated methyl pyrrolidone solution neutralizes the alkaline substances, so that the pH of the positive slurry semi-product is always weakly alkaline or neutral, avoiding the problem of gelation of polyvinylidene fluoride in an alkaline environment with a pH greater than 10, thereby ensuring the adhesion effect of polyvinylidene fluoride on the positive active material, thereby making the stirred uniform positive slurry more stable, thereby ensuring the cycle performance of the battery.

[0071] In one embodiment, the step of adding the weakly acidic treated methyl pyrrolidone solution to the powder is specifically: first calculating the addition speed s1 of the weakly acidic treated methyl pyrrolidone solution according to the formula s1 = w x a / t1, and then adding the weakly acidic treated methyl pyrrolidone solution to the powder at the addition speed s1 to obtain the positive slurry semi-product; wherein w is the mass of the positive active material, and t1 is the time for adding the weakly acidic treated methyl pyrrolidone solution to the powder. Further, a is 5% to 10%, and t1 is 5 minutes to 10 minutes. It can be understood that the more appropriate addition speed and addition amount of the methyl pyrrolidone solution are calculated according to the function formula, so that the positive slurry semi-product is dispersed more uniformly, thereby making the positive slurry more uniformly dispersed, reducing the phenomenon of particle powder due to non-uniform positive slurry, thereby leading to short-circuit carbonization of the powder, thereby reducing the phenomenon of voltage drop caused by short-circuit carbonization of the powder, thereby ensuring the stability, cycle performance and charge-discharge rate performance of the battery voltage.

[0072] In one of the embodiments, the stirring assembly is used to stir the positive electrode slurry semi-product. In this embodiment, the dispersion linear velocity of the stirring assembly is 3-5 min, and the revolution velocity of the stirring assembly is 10-12 r / min. It can be understood that when the dispersion linear velocity of the stirring assembly is 3-5 min and the revolution velocity of the stirring assembly is 10-12 r / min, the positive electrode slurry semi-product is stirred more uniformly, the positive electrode slurry semi-product is dispersed more uniformly, and the positive electrode slurry is dispersed more uniformly, thereby reducing the phenomenon of particle powder caused by the non-uniformity of the positive electrode slurry, and further reducing the phenomenon of powder short-circuit carbonization, thereby reducing the voltage drop caused by the powder short-circuit carbonization, and further ensuring the stability of the battery voltage, the cycle performance, and the charge-discharge rate performance.

[0073] In one of the embodiments, the weakly acidic treated methylpyrrolidone solution and the powder are subjected to nitrogen gas at 40-50°C, the adding speed s1 of the weakly acidic treated methylpyrrolidone solution is calculated according to the formula s1 = w x a / t1 first, and then the weakly acidic treated methylpyrrolidone solution is added to the powder at the adding speed s1 to obtain the positive electrode slurry semi-product; wherein w is the mass of the positive electrode active material, and t1 is the time for adding the weakly acidic treated methylpyrrolidone solution to the powder. In this embodiment, the nitrogen gas is subjected for 5-10 min. It can be understood that when the nitrogen gas is subjected for 5-10 min, the contact time of the nitrogen gas with the positive electrode active material and the water molecules adsorbed by the positive electrode active material is relatively long, the water molecules adsorbed by the positive electrode active material are separated from the surface of the positive electrode active material, so that the subsequent vacuum operation of the positive electrode slurry semi-product is performed to remove the water, and the subsequent addition of the anhydrous methylpyrrolidone solution is performed to make the positive electrode slurry semi-product in an anhydrous environment during the subsequent wetting treatment, the subsequent pre-kneading treatment, the subsequent kneading treatment, and the subsequent dispersion treatment, thereby avoiding the agglomeration of the subsequent positive electrode slurry semi-product with the water, and avoiding the problem of non-solvent induced phase separation caused by the extraction of the polyvinylidene fluoride during the wetting treatment, the pre-kneading treatment, the kneading treatment, and the dispersion treatment, thereby making the positive electrode slurry more uniform, and further ensuring the cycle performance of the battery. In addition, the problem of poor adhesion caused by the water absorption of the polyvinylidene fluoride after the mixing of the subsequent methylpyrrolidone solution and the powder is avoided, thereby avoiding the problem of powder falling during the charging process caused by the poor adhesion, and further ensuring the stability of the battery voltage, the cycle performance, and the charge-discharge rate performance. In addition, the direct influence of the water on the cycle performance of the battery is avoided, i.e., the cycle performance of the battery is further ensured.

[0074] In one of the embodiments, the step of pre-kneading the positive electrode slurry semi-product is specifically as follows: firstly, the adding speed s2 of the weakly acidic treated methyl pyrrolidone solution is calculated according to the formula s2 = w x b / t2, and secondly, the weakly acidic treated methyl pyrrolidone solution is added into the positive electrode slurry semi-product according to the adding speed s2; wherein w is the mass of the positive electrode active material, and t2 is the time of adding the weakly acidic treated methyl pyrrolidone solution into the powder. Further, b is 15% to 20%, and t2 is 10 min to 20 min. It can be understood that the more appropriate adding speed and adding amount of the methyl pyrrolidone solution calculated according to the function formula makes the positive electrode slurry semi-product more uniformly dispersed, and further makes the positive electrode slurry more uniformly dispersed, which reduces the phenomenon of particle powder caused by the non-uniform positive electrode slurry, and further reduces the phenomenon of voltage drop caused by the particle powder short circuit carbonization, and further ensures the stability of the battery voltage, the cycle performance and the charge-discharge rate performance.

[0075] In one of the embodiments, the positive electrode slurry semi-product is mixed and stirred by using the stirring assembly. In the embodiment, the dispersion linear speed of the stirring assembly is 6 m / min to 8 m / min, and the revolution speed of the stirring assembly is 12 rpm to 14 rpm. It can be understood that when the dispersion linear speed of the stirring assembly is 6 m / min to 8 m / min, and the revolution speed of the stirring assembly is 12 rpm to 14 rpm, the positive electrode slurry semi-product is more uniformly stirred, and further makes the positive electrode slurry more uniformly dispersed, which reduces the phenomenon of particle powder caused by the non-uniform positive electrode slurry, and further reduces the phenomenon of voltage drop caused by the particle powder short circuit carbonization, and further ensures the stability of the battery voltage, the cycle performance and the charge-discharge rate performance.

[0076] Further, the stirring assembly is a stirring shaft, a stirring knife or a stirring paddle.

[0077] In one of the embodiments, the pre-kneading treatment is performed on the positive electrode slurry semi-product under the condition that the dehumidification operation is performed on the positive electrode slurry semi-product. In the embodiment, the dehumidification operation is repeated for 2-4 times. It can be understood that the dehumidification operation is repeated for 2-4 times to ensure that the moisture in the positive electrode slurry semi-product is removed, which avoids the problem that the subsequent positive electrode slurry semi-product is agglomerated with moisture, and avoids the problem that the moisture extracts the polyvinylidene fluoride to generate non-solvent induced phase separation during the pre-kneading treatment, the kneading treatment and the dispersion treatment, which further makes the positive electrode slurry more uniform, and further ensures the cycle performance of the battery, and also avoids the problem that the polyvinylidene fluoride absorbs water to affect the bonding effect after the subsequent methylpyrrolidone solution is mixed with the powder, which further avoids the problem that the poor bonding effect causes the powder to drop during the charging process to affect the voltage drop, which further ensures the stability of the battery voltage, the cycle performance and the charge-discharge rate performance, and also avoids the direct influence of the moisture on the cycle performance of the battery, i.e., further ensures the cycle performance of the battery.

[0078] In one of the embodiments, the step of performing the dehumidification operation on the positive electrode slurry semi-product specifically includes: introducing the nitrogen gas with a temperature of 40-50°C into the positive electrode slurry semi-product, and then performing the vacuumizing operation on the positive electrode slurry semi-product. In the embodiment, the time for introducing the nitrogen gas with a temperature of 40-50°C into the positive electrode slurry semi-product is 5-7 min. In the embodiment, the time for the vacuumizing operation is 3-5 min. It can be understood that when the time for introducing the nitrogen gas is 5-7 min, the contact time of the nitrogen gas with the positive electrode active material and the water molecules adsorbed by the positive electrode active material is relatively long, which makes the water molecules adsorbed by the positive electrode active material separate from the surface of the positive electrode active material, so as to perform the subsequent vacuumizing operation on the positive electrode slurry semi-product to remove the water, and cooperate with the subsequent addition of the anhydrous methylpyrrolidone solution, so that the positive electrode slurry semi-product during the subsequent wetting treatment, the pre-kneading treatment, the kneading treatment and the dispersion treatment is in an anhydrous environment, which avoids the problem that the subsequent positive electrode slurry semi-product is agglomerated with moisture, and avoids the problem that the moisture extracts the polyvinylidene fluoride to generate non-solvent induced phase separation during the pre-kneading treatment, the kneading treatment and the dispersion treatment, which further makes the positive electrode slurry more uniform, and further ensures the cycle performance of the battery, and also avoids the problem that the polyvinylidene fluoride absorbs water to affect the bonding effect after the subsequent methylpyrrolidone solution is mixed with the powder, which further avoids the problem that the poor bonding effect causes the powder to drop during the charging process to affect the voltage drop, which further ensures the stability of the battery voltage, the cycle performance and the charge-discharge rate performance, and also avoids the direct influence of the moisture on the cycle performance of the battery, i.e., further ensures the cycle performance of the battery.

[0079] In one of the embodiments, the step of kneading the pre-kneaded positive electrode slurry semi-product is specifically: firstly, the adding speed s3 of the weakly acidic treated methyl pyrrolidone solution is calculated according to the formula s3 = w x c / t3, and secondly, the weakly acidic treated methyl pyrrolidone solution is added to the pre-kneaded positive electrode slurry semi-product at the adding speed s3; wherein w is the mass of the positive electrode active material, and t3 is the time for adding the weakly acidic treated methyl pyrrolidone solution to the pre-kneaded positive electrode slurry semi-product. Further, c is 30% to 40%, and t3 is 20 min to 30 min. It can be understood that the more appropriate adding speed and adding amount of the methyl pyrrolidone solution calculated according to the function formula makes the positive electrode slurry semi-product more uniformly dispersed, and further makes the positive electrode slurry more uniformly dispersed, which reduces the phenomenon of particle powder caused by the non-uniform positive electrode slurry, and further reduces the phenomenon of voltage drop caused by the powder short circuit carbonization, and further ensures the stability of the battery voltage, the cycle performance and the charge-discharge rate performance.

[0080] In one embodiment, the pre-kneading processed positive electrode slurry semi-product is mixed and stirred by a stirring assembly. In this embodiment, the dispersion linear velocity of the stirring assembly is 10 m / min-12 m / min, and the revolution velocity of the stirring assembly is 15 r / min-16 r / min. It can be understood that when the dispersion linear velocity of the stirring assembly is 10 m / min-12 m / min and the revolution velocity of the stirring assembly is 15 r / min-16 r / min, the positive electrode slurry semi-product is stirred more uniformly, and thus the positive electrode slurry is dispersed more uniformly, which reduces the phenomenon of particle powder caused by the non-uniformity of the positive electrode slurry, and thus reduces the phenomenon of powder short-circuit carbonization, and thus reduces the voltage drop caused by the powder short-circuit carbonization, and thus ensures the stability of the battery voltage, the cycle performance, and the charge-discharge rate performance. In one embodiment, the pre-kneading processed positive electrode slurry semi-product is subjected to kneading treatment under the condition that the pre-kneading processed positive electrode slurry semi-product is subjected to water removal operation. In this embodiment, the water removal operation is repeated 3-5 times. It can be understood that because the time of the kneading treatment is longer than the time of the pre-kneading treatment, the water produced in the kneading treatment is more than the water produced in the pre-kneading treatment, and thus the number of times of repeating the water removal operation in the kneading treatment is more than the number of times of repeating the water removal operation in the pre-kneading treatment. The water removal operation in the kneading treatment is repeated 3-5 times, which ensures that the water in the positive electrode slurry semi-product is removed, avoids the problem of agglomeration of the subsequent positive electrode slurry semi-product and water, and avoids the problem of non-solvent-induced phase separation caused by the extraction of polyvinylidene fluoride in the kneading treatment and the dispersion treatment, and thus the positive electrode slurry is more uniform, and thus the cycle performance of the battery is ensured. It also avoids the problem that the water absorption of polyvinylidene fluoride affects the bonding effect after the subsequent methylpyrrolidone solution is mixed with the powder, and thus avoids the problem that the poor bonding effect causes powder dropping during the charging process, which affects the voltage drop, and thus ensures the stability of the battery voltage, the cycle performance, and the charge-discharge rate performance. It also avoids the direct influence of water on the cycle performance of the battery, i.e., further ensures the cycle performance of the battery.

[0081] In one of the embodiments, the step of performing the moisture removal operation on the pre-kneading processed positive electrode slurry semi-finished product is specifically: nitrogen gas is introduced into the pre-kneading processed positive electrode slurry semi-finished product, the temperature of the nitrogen gas is 40-50°C, and then the pre-kneading processed positive electrode slurry semi-finished product is subjected to a vacuum extraction operation. In this embodiment, the time for which the nitrogen gas is introduced into the pre-kneading processed positive electrode slurry semi-finished product is 5-7 minutes. In this embodiment, the time for the vacuum extraction operation is 3-5 minutes. It can be understood that when the time for which the nitrogen gas is introduced is 5-7 minutes, the contact time of the nitrogen gas with the positive electrode active material and the water molecules adsorbed by the positive electrode active material is relatively long, so that the water molecules adsorbed by the positive electrode active material are separated from the surface of the positive electrode active material, so as to facilitate the subsequent vacuum extraction operation on the positive electrode slurry semi-finished product to extract the water, cooperate with the subsequent addition of the anhydrous methylpyrrolidone solution, so that the positive electrode slurry semi-finished product in the kneading process and the dispersion process is in a water-free environment, thereby avoiding the problem of agglomeration of the subsequent positive electrode slurry semi-finished product with water, and avoiding the problem of non-solvent induced phase separation caused by the water extracting polyvinylidene fluoride during the kneading process and the dispersion process, thereby making the positive electrode slurry more uniform, thereby ensuring the cycle performance of the battery, and also avoiding the problem that the methylpyrrolidone solution and the powder are mixed, the water absorption of the polyvinylidene fluoride affects the bonding effect, thereby avoiding the problem that the poor bonding effect causes the powder to fall off during the charging process, thereby affecting the voltage drop, thereby ensuring the stability of the battery voltage, the cycle performance and the charge-discharge rate performance, and also avoiding the direct influence of water on the cycle performance of the battery, i.e. further ensuring the cycle performance of the battery.

[0082] In one of the embodiments, the step of performing the dispersion process on the kneading processed positive electrode slurry semi-finished product to obtain the positive electrode slurry is specifically: first, the addition speed s4 of the weakly acidic treated methylpyrrolidone solution is calculated according to the formula s4 = w x d / t4, and then the weakly acidic treated methylpyrrolidone solution is added to the kneading processed positive electrode slurry semi-finished product at the addition speed s4; wherein w is the mass of the positive electrode active material, and t4 is the time for which the weakly acidic treated methylpyrrolidone solution is added to the kneading processed positive electrode slurry semi-finished product. Further, d is 50-60%, and t4 is 30-40 minutes. It can be understood that the relatively appropriate addition speed and addition amount of the methylpyrrolidone solution are calculated according to the function formula, so that the positive electrode slurry semi-finished product is dispersed more uniformly, thereby making the positive electrode slurry more uniformly dispersed, thereby reducing the phenomenon of particle powder caused by the non-uniformity of the positive electrode slurry, thereby reducing the phenomenon of voltage drop caused by the short circuit carbonization of the powder, thereby ensuring the stability of the battery voltage, the cycle performance and the charge-discharge rate performance.

[0083] In one of the embodiments, the kneading processed positive electrode slurry semi-product is subjected to a dispersion treatment under the condition that the dehumidification operation is performed on the kneading processed positive electrode slurry semi-product, and the positive electrode slurry semi-product is obtained. In this embodiment, the dehumidification operation is repeated 4-6 times. It can be understood that, since the time of the dispersion treatment is longer than that of the kneading treatment, the moisture generated in the dispersion treatment is more than that generated in the kneading treatment, and therefore the number of times of repeating the dehumidification operation in the dispersion treatment is more than that in the kneading treatment, and the dehumidification operation in the dispersion treatment is repeated 4-6 times, which ensures that the moisture in the positive electrode slurry semi-product is removed, avoids the problem of agglomeration of the subsequent positive electrode slurry semi-product with moisture, and avoids the problem of non-solvent induced phase separation caused by the extraction of polyvinylidene fluoride by moisture during the dispersion treatment, thereby making the positive electrode slurry more uniform, thereby ensuring the cycle performance of the battery, and also avoiding the problem of the influence of the water absorption of polyvinylidene fluoride on the bonding effect after the subsequent mixing of the methylpyrrolidone solution and the powder, thereby avoiding the problem of powder falling during the charging process caused by poor bonding effect, thereby affecting the voltage drop, and thereby ensuring the stability of the battery voltage, the cycle performance and the charge-discharge rate performance, and also avoiding the direct influence of moisture on the cycle performance of the battery, i.e. further ensuring the cycle performance of the battery.

[0084] In one of the embodiments, the step of performing the dehumidification operation on the kneading processed positive electrode slurry semi-product is specifically: nitrogen gas is introduced into the kneading processed positive electrode slurry semi-product, the temperature of the nitrogen gas is 40-50°C, and then the vacuum operation is performed on the kneading processed positive electrode slurry semi-product. In this embodiment, the time for introducing nitrogen gas into the pre-kneading processed positive electrode slurry semi-product is 5-7 min. In this embodiment, the time for the vacuum operation is 3-5 min. It can be understood that, when the time for introducing nitrogen gas is 5-7 min, the contact time of nitrogen gas with the positive electrode active material and the water molecules adsorbed by the positive electrode active material is relatively long, which makes the water molecules adsorbed by the positive electrode active material separate from the surface of the positive electrode active material, so as to facilitate the subsequent vacuum operation on the positive electrode slurry semi-product to remove the water, and cooperate with the subsequent addition of anhydrous methylpyrrolidone solution, so that the positive electrode slurry semi-product in the kneading treatment and the dispersion treatment is in a water-free environment, thereby avoiding the problem of agglomeration of the subsequent positive electrode slurry semi-product with moisture, and avoiding the problem of non-solvent induced phase separation caused by the extraction of polyvinylidene fluoride by moisture during the dispersion treatment, thereby making the positive electrode slurry more uniform, thereby ensuring the cycle performance of the battery, and also avoiding the problem of the influence of the water absorption of polyvinylidene fluoride on the bonding effect after the subsequent mixing of the methylpyrrolidone solution and the powder, thereby avoiding the problem of powder falling during the charging process caused by poor bonding effect, thereby affecting the voltage drop, and thereby ensuring the stability of the battery voltage, the cycle performance and the charge-discharge rate performance, and also avoiding the direct influence of moisture on the cycle performance of the battery, i.e. further ensuring the cycle performance of the battery.

[0085] In one of the embodiments, the proportion of the methylpyrrolidone solution in the positive electrode slurry is 30% to 40%. It can be understood that the proportion of the methylpyrrolidone solution in the positive electrode slurry is 30% to 40%, which makes the viscosity of the positive electrode slurry more appropriate, reduces the phenomenon that the positive electrode slurry is not uniformly dispersed due to the too high viscosity of the positive electrode slurry, and further reduces the phenomenon that the particle powder is generated due to the non-uniformity of the positive electrode slurry, which further leads to the phenomenon of powder short circuit carbonization, and further reduces the phenomenon of voltage drop caused by powder short circuit carbonization, thereby ensuring the stability of the battery voltage, the cycle performance and the charge-discharge rate performance. Moreover, the too high viscosity is not conducive to the leveling effect and the coating, and also reduces the problem of low drying efficiency of the coating caused by the too low viscosity of the positive electrode slurry, that is, improves the coating drying efficiency, and reduces the problems of coating cracking, slurry particle agglomeration and poor surface density consistency, that is, improves the uniformity of the coating.

[0086] In one of the embodiments, the proportion of the methylpyrrolidone solution in the positive electrode slurry is 35%. It can be understood that the proportion of the methylpyrrolidone solution in the positive electrode slurry is 35%, which makes the viscosity of the positive electrode slurry more appropriate, reduces the phenomenon that the positive electrode slurry is not uniformly dispersed due to the too high viscosity of the positive electrode slurry, and further reduces the phenomenon that the particle powder is generated due to the non-uniformity of the positive electrode slurry, which further leads to the phenomenon of powder short circuit carbonization, and further reduces the phenomenon of voltage drop caused by powder short circuit carbonization, thereby ensuring the stability of the battery voltage, the cycle performance and the charge-discharge rate performance. Moreover, the too high viscosity is not conducive to the leveling effect and the coating, and also reduces the problem of low drying efficiency of the coating caused by the too low viscosity of the positive electrode slurry, that is, improves the coating drying efficiency, and reduces the problems of coating cracking, slurry particle agglomeration and poor surface density consistency, that is, improves the uniformity of the coating.

[0087] The batteries of Examples 1 to 10 were subjected to performance tests as follows:

[0088] Table 1 is the viscosity of the positive electrode slurry of Examples 1 to 9 and Comparative Examples 1 to 3:

[0089] Number Upper layer viscosity of positive electrode slurry mPa.s Middle layer viscosity of positive electrode slurry mPa.s Lower layer viscosity of positive electrode slurry mPa.s Example 1 4720 4672 4760 Example 2 4630 4532 4612 Example 3 4686 4676 4710 Example 4 4733 4673 4801 Example 5 4692 4623 4725 Example 6 4752 4732 4805 Example 7 4632 4599 4612 Example 8 4612 4586 4710 Example 9 4566 4605 4636 Comparative Example 1 4571 4672 4872 Comparative Example 2 4525 4720 4910 Comparative Example 3 4628 4530 4880

[0090] As can be seen from Table 1, the ranges of the viscosity of the positive electrode slurries of Examples 1 to 9 are 99, 88, 34, 128, 102, 73, 33, 124 and 70 respectively, and the ranges of the viscosity of the positive electrode slurries of Comparative Examples 1 to 3 are 301, 385 and 350 respectively. Therefore,

[0091] The range of viscosity of the positive electrode slurry of the embodiments 1~9 is obviously smaller than the range of viscosity of the positive electrode slurry of the comparative examples 1~3, it can be seen that the mixing of the positive electrode slurry of the embodiments 1~9 is more uniform, it is indicated that the voltage drop phenomenon caused by the non-uniformity of the positive electrode slurry obtained by the preparation process of the lithium manganate doped positive electrode slurry of the application is lighter, therefore the battery obtained by the preparation process of the lithium manganate doped positive electrode slurry of the application has higher stability of voltage, at the same time has better cycle performance and better charge-discharge rate performance.

[0092] Table 2 is the voltage drop of the embodiments 1~10 and the comparative examples 1~10:

[0093] Comparison Voltage 1 (V) Voltage 2 (V) Standing time at room temperature h Voltage drop Mv / h Voltage drop average Mv / h Example 1 4.14258 4.13941 49.08 0.065 0.069 Example 2 4.14439 4.14105 48.44 0.069 Example 3 4.14516 4.14179 48.41 0.070 Example 4 4.14366 4.14029 49.17 0.069 Example 5 4.14364 4.14026 49.03 0.069 Example 6 4.14400 4.14060 48.49 0.070 Example 7 4.14499 4.14157 49.73 0.069 Example 8 4.14366 4.14017 49.36 0.071 Example 9 4.14404 4.14053 49.12 0.071 Example 10 4.14434 4.14082 50.29 0.070 Comparative Example 1 4.14398 4.13976 49.18 0.086 0.090 Comparative Example 2 4.14579 4.14153 49.44 0.086 Comparative Example 3 4.14306 4.13877 48.21 0.089 Comparative Example 4 4.14272 4.13836 48.37 0.090 Comparative Example 5 4.14355 4.13915 48.46 0.091 Comparative Example 6 4.14266 4.13824 49.49 0.089 Comparative Example 7 4.14292 4.13840 49.43 0.091 Comparative Example 8 4.14139 4.13683 50.45 0.090 Comparative Example 9 4.14167 4.13708 49.42 0.093 Comparative Example 10 4.14334 4.13875 49.49 0.093

[0094] The voltage drop of the embodiments 1~10 is 0.65 Mv / h~0.71 Mv / h, the voltage drop of the comparative examples 1~10 is 0.86 Mv / h~0.93 Mv / h, the voltage drop of the embodiments 1~10 is lower than the voltage drop of the comparative examples 1~10. Therefore, the voltage drop of the embodiments 1~10 is lower than the voltage drop of the comparative examples 1~10.

[0095] The average value of the voltage drop of the embodiments 1~10 is 0.069 Mv / h, the average value of the voltage drop of the comparative examples 1~10 is 0.090 Mv / h, the average value of the voltage drop of the embodiments 1~10 is lower than the average value of the voltage drop of the comparative examples 1~10. That is to say, the average value of the voltage drop of the embodiments 1~10 is lower than the average value of the voltage drop of the comparative examples 1~10.

[0096] It is reflected that the battery obtained by the preparation process of the lithium manganate doped positive electrode slurry of the application has higher voltage stability, better cycle performance and better charge-discharge rate performance.

[0097] Compared with the prior art, the application has at least the following advantages:

[0098] 1) The preparation process of the lithium manganate doped positive electrode slurry of the application mixes anhydrous ethanol and monobasic carboxylic acid to obtain a pH value adjusting agent, the pH value adjusting agent is added to the methylpyrrolidone solution for weak acid treatment, so that the methylpyrrolidone solution is weakly acidic, that is, the monobasic carboxylic acid is added to the methylpyrrolidone solution for neutralizing free ammonia in the methylpyrrolidone solution, and the pH value adjusting agent has high volatility for inhibiting ammonia volatilization of methylpyrrolidone.

[0099] 2) The preparation process of the manganese-doped lithium manganate positive electrode paste of the application, after neutralizing the free ammonia in the monocarboxylic acid, continue to add the monocarboxylic acid solution to the methyl pyrrolidone solution until the methyl pyrrolidone solution is weakly acidic, that is, the monocarboxylic acid exists in the methyl pyrrolidone solution after weakly acidic treatment, which is used for subsequent wet treatment, pre-kneading treatment, kneading treatment and dispersion treatment to neutralize the alkaline substances in the positive electrode active material, so that the pH of the positive electrode paste semi-finished product and the positive electrode paste is always weakly alkaline or neutral, avoiding the problem that the gel phenomenon of polyvinylidene fluoride occurs in an alkaline environment with a pH greater than 10, thereby ensuring that polyvinylidene fluoride plays a role in bonding the positive electrode active material, thereby making the subsequent stirring uniform positive electrode paste more stable, reducing the problem of particle powder caused by uneven positive electrode paste, thereby reducing the phenomenon of voltage drop caused by powder short circuit carbonization, thereby ensuring the stability of the battery voltage, cycle performance and charge-discharge rate performance.

[0100] 3) The preparation process of the manganese-doped lithium manganate positive electrode paste of the application, since the monocarboxylic acid is weakly acidic and has fewer carboxyl groups, the problem of corroding aluminum foil is avoided, and the monocarboxylic acid reacts with the alkaline substances in the positive electrode active material to form a monocarboxylic acid salt, which has good thermal stability, avoiding the problem of affecting the cycle performance of the battery due to thermal decomposition to produce gas, and the monocarboxylic acid is almost non-toxic, thereby reducing the toxicity of the battery.

[0101] The above-described embodiments only express several embodiments of the application, which are described in more detail and in detail, but should not be understood as limiting the scope of the patent. It should be noted that for ordinary skilled in the art, without departing from the concept of the application, a number of modifications and improvements can be made, which are within the scope of protection of the application. Therefore, the scope of protection of the patent of the application should be subject to the appended claims.

Claims

1. A process for the preparation of a cathode slurry doped with lithium manganate, characterized in that, The method comprises the following steps: mixing anhydrous ethanol and monobasic carboxylic acid to obtain a pH regulator; under the condition that nitrogen gas is introduced into the solution of methylpyrrolidone and then the solution of methylpyrrolidone is vacuumized, the pH regulator is added into the solution of methylpyrrolidone to perform weak acid treatment, so that the solution of methylpyrrolidone is weakly acidic, wherein the temperature of the nitrogen gas is 40-50°C, and the weak acid is pH≥4 and pH<7; pre-treating a mixture of the positive active material, the conductive agent and the polyvinylidene fluoride, specifically, introducing nitrogen gas with a temperature of 40-50°C into the mixture of the positive active material, the conductive agent and the polyvinylidene fluoride, and then vacuumizing the mixture of the positive active material, the conductive agent and the polyvinylidene fluoride; stirring the mixture of the pre-treated positive active material, the conductive agent and the polyvinylidene fluoride to obtain a powder; wetting the powder to obtain a positive electrode slurry semi-product, specifically, adding the weakly acidic methylpyrrolidone solution into the powder to obtain the positive electrode slurry semi-product, and then stirring the positive electrode slurry semi-product; adding the weakly acidic methylpyrrolidone solution into the powder, specifically, first calculating the adding speed s1 of the weakly acidic methylpyrrolidone solution according to the formula s1=w×a / t1, and then adding the weakly acidic methylpyrrolidone solution into the powder at the adding speed s1 to obtain the positive electrode slurry semi-product, wherein w is the mass of the positive active material, t1 is the time for adding the weakly acidic methylpyrrolidone solution into the powder, and a is 5%-10%, and t1 is 5-10 min; pre-kneading the positive electrode slurry semi-product, specifically, first calculating the adding speed s2 of the weakly acidic methylpyrrolidone solution according to the formula s2=w×b / t2, and then adding the weakly acidic methylpyrrolidone solution into the positive electrode slurry semi-product at the adding speed s2, wherein w is the mass of the positive active material, t2 is the time for adding the weakly acidic methylpyrrolidone solution into the positive electrode slurry semi-product, b is 15%-20%, and t2 is 10-20 min; removing water from the pre-kneaded positive electrode slurry semi-product, specifically, introducing nitrogen gas into the pre-kneaded positive electrode slurry semi-product, wherein the temperature of the nitrogen gas is 40-50°C, and then vacuumizing the pre-kneaded positive electrode slurry semi-product; The pre-kneading processed positive electrode slurry semi-product is subjected to kneading processing under the condition that the pre-kneading processed positive electrode slurry semi-product is subjected to moisture removal operation, specifically: firstly, the adding speed s3 of the weakly acidic processed methyl pyrrolidone solution is calculated according to the formula s3=w×c / t3, and secondly, the weakly acidic processed methyl pyrrolidone solution is added to the pre-kneading processed positive electrode slurry semi-product at the adding speed s3, wherein w is the mass of the positive electrode active material, t3 is the time for adding the weakly acidic processed methyl pyrrolidone solution to the pre-kneading processed positive electrode slurry semi-product, c is 30% to 40%, and t3 is 20 min to 30 min. The kneading processed positive electrode slurry semi-product is subjected to dispersion processing to obtain the dispersion processed positive electrode slurry, specifically: firstly, the adding speed s4 of the weakly acidic processed methyl pyrrolidone solution is calculated according to the formula s4=w×d / t4, and secondly, the weakly acidic processed methyl pyrrolidone solution is added to the kneading processed positive electrode slurry semi-product at the adding speed s4, wherein w is the mass of the positive electrode active material, t4 is the time for adding the weakly acidic processed methyl pyrrolidone solution to the kneading processed positive electrode slurry semi-product, d is 50% to 60%, and t4 is 30 min to 40 min.

2. The process for the preparation of a cathode slurry doped with lithium manganate according to claim 1, characterized in that, The mass ratio of the anhydrous ethanol to the monocarboxylic acid is 1:

1.

3. The process for the preparation of a cathode slurry doped with lithium manganate according to claim 1, characterized in that, The mass ratio of the pH value regulator to the positive electrode active material is 0.002 to 0.

003.

4. The process for the preparation of a doped lithium manganate positive electrode paste according to claim 1, characterized in that, The pH value regulator is added to the methyl pyrrolidone solution for weakly acidic processing under the condition that the methyl pyrrolidone solution is subjected to ultrasonic vibration stirring operation, so that the methyl pyrrolidone solution is weakly acidic.

5. The process for the preparation of a cathode slurry doped with lithium manganate according to claim 4, characterized in that, The ultrasonic vibration stirring operation has an ultrasonic frequency of 20 kHz to 50 kHz, and the ultrasonic vibration stirring operation has a time of 5 min to 10 min.

6. The process for the preparation of a doped lithium manganate-based cathode slurry as claimed in claim 1, wherein, The methyl pyrrolidone solution is subjected to nitrogen gas passing for a time of 3 min to 5 min.

7. The process for the preparation of a doped lithium manganate-based cathode slurry as claimed in claim 1, wherein, The methyl pyrrolidone solution is subjected to vacuum pumping operation for a time of 2 min.

8. The process for the preparation of a doped lithium manganate-based cathode slurry according to claim 1, characterized in that, The positive electrode active material includes a sodium ion positive electrode active material and a lithium manganate positive electrode active material.

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