Method for preparing positive electrode slurry suitable for battery cell of electronic cigarette, positive electrode sheet for electronic cigarette, battery cell, and lithium-ion battery

Abstract

The present application provides a method for preparing a positive electrode slurry suitable for a battery cell of an electronic cigarette, a positive electrode sheet for an electronic cigarette, a battery cell, and a lithium-ion battery. The method for preparing a positive electrode slurry comprises the following steps: S1, stirring a binder and a first solvent at the speeds of W1 and V1 for t1 min to obtain a glue solution; S2, stirring the glue solution and a first conductive agent at the speeds of W2 and V2 for t2 min to obtain a first conductive slurry; S3, stirring the first conductive slurry and a second conductive agent at the speeds of W3 and V3 for t3 min to obtain a second conductive slurry; S4, stirring the second conductive slurry and a positive electrode active material at the speeds of W4 and V4 for t4 min to obtain a mixture; and S5, stirring the mixture and a second solvent at the speeds of W5 and V5 for t5 min to prepare a positive electrode slurry.

Description

Preparation method of positive electrode slurry suitable for positive electrode of battery for electronic cigarette, positive electrode plate for electronic cigarette, battery and lithium ion battery

[0001] The present application claims priority to the Chinese patent application No. 202410994543.3, filed on July 23, 2024, and entitled "Preparation method of positive electrode slurry suitable for positive electrode of battery for electronic cigarette, positive electrode plate for electronic cigarette, battery and lithium ion battery", the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0002] The present application relates to the technical field of battery, in particular to a preparation method of positive electrode slurry suitable for positive electrode of battery for electronic cigarette, positive electrode plate for electronic cigarette, battery and lithium ion battery. BACKGROUND

[0003] Electronic cigarette, as a substitute or complementary product of burning tobacco, has developed rapidly because it can keep pace with the times. With the rise and popularity of electronic cigarettes, users have increasingly high requirements for the service life of electronic cigarettes. Most electronic cigarettes on the market currently use lithium ion batteries, and the cycle life of lithium ion batteries is related to the service life of electronic cigarettes.

[0004] Unlike the use scene of conventional lithium ion batteries, the battery for electronic cigarette needs to be discharged at a large current to power the heating module to quickly heat it up when smoking, and needs to be discharged at a small current to keep the heating module at a certain temperature when stopping smoking, forming an alternating pulse discharge phenomenon between large and small currents. The existing lithium ion battery for electronic cigarette on the market has a stepwise capacity decline under the condition of large and small current pulse discharge cycles (1.3C charge / 5C discharge for 10 seconds, 0.5C discharge for 270 seconds, 1 minute rest, alternating discharge to 3V), and its cycle life is less than 500 cycles, and only 300 cycles at high temperature. SUMMARY

[0005] The short cycle life of the existing electronic cigarette cannot meet the increasingly high use requirements of users.

[0006] In order to solve the problem that the battery for electronic cigarette and the lithium ion battery have a short cycle life due to the rapid capacity decline under large and small current pulse discharge, and cannot meet the use requirements of users, and to improve the cycle performance and cycle life of the battery for electronic cigarette and the lithium ion battery, the present application provides a preparation method of positive electrode slurry suitable for positive electrode of battery for electronic cigarette, positive electrode plate for electronic cigarette, battery and lithium ion battery.

[0007] According to a first aspect of the present application, a preparation method of positive electrode slurry suitable for positive electrode of battery for electronic cigarette is provided, comprising the following steps:

[0008] S1. After pre-mixing the binder with the first solvent, stirring and dispersing at a revolution speed 、 a rotation speed for 30 minutes, to obtain a glue solution;

[0009] S2. After pre-mixing the glue solution with the first conductive agent, stirring and dispersing at a revolution speed 、 a rotation speed for 30 minutes, to obtain a first conductive slurry;

[0010] S3. After pre-mixing the first conductive slurry with the second conductive agent, stirring and dispersing at a revolution speed 、 a rotation speed for 30 minutes, to obtain a second conductive slurry;

[0011] S4. After pre-mixing the second conductive slurry with the positive active material, stirring and dispersing at a revolution speed 、 a rotation speed for 30 minutes, to obtain a mixture;

[0012] S5. After stirring and dispersing the mixture with the second solvent at a revolution speed 、 a rotation speed for 30 minutes, to obtain the positive electrode slurry;

[0013]

[0014] According to a second aspect of the present application, a positive electrode sheet for an electronic cigarette is provided, which comprises a positive electrode current collector and a positive electrode active coating layer, the positive electrode active coating layer being prepared from a positive electrode slurry, the positive electrode slurry being prepared by the above-mentioned method for preparing a positive electrode slurry for an electric core of an electronic cigarette.

[0015] According to a third aspect of the present application, an electric core for an electronic cigarette is provided, which comprises the above-mentioned positive electrode sheet for an electronic cigarette.

[0016] According to a fourth aspect of the present application, a lithium ion battery for an electronic cigarette is provided, which comprises the above-mentioned electric core for an electronic cigarette.

[0017] Advantages:

[0018] ​​​​​The positive electrode slurry prepared by the preparation method of the positive electrode slurry provided in the application is applied to the preparation of the positive electrode sheet, the battery cell and the lithium ion battery for electronic cigarettes, so that the surface resistance of the positive electrode sheet, the alternating current internal resistance of the battery cell and the voltage difference between large and small currents are reduced, and the cycle performance of the battery cell for electronic cigarettes under large and small pulse discharges is improved, thereby prolonging the cycle life of the lithium ion battery for electronic cigarettes. Embodiments of the application

[0019] The existing lithium ion battery cell for electronic cigarettes on the market at present presents a stepwise decrease in capacity under large and small current pulse discharge cycle conditions (1.3C charging / 5C discharging for 10 seconds, 0.5C discharging for 270 seconds, standing for 1 minute, and alternating discharge to 3V), and rapidly decays, with a cycle life of less than 500 weeks, and only 300 weeks at high temperature. The short cycle life of the existing electronic cigarette cannot meet the increasingly high use requirements of users.

[0020] According to a first aspect of the application, a preparation method of a positive electrode slurry suitable for a battery cell for electronic cigarettes is provided, comprising the following steps:

[0021] S1. After the binder is pre-mixed with the first solvent, stirring and dispersing are performed at a revolution speed , a rotation speed for 30-60 minutes to obtain a glue solution;

[0022] S2. After the glue solution is pre-mixed with the first conductive agent, stirring and dispersing are performed at a revolution speed , a rotation speed for 30-60 minutes to obtain a first conductive slurry;

[0023] S3. After the first conductive slurry is pre-mixed with the second conductive agent, stirring and dispersing are performed at a revolution speed , a rotation speed for 30-60 minutes to obtain a second conductive slurry;

[0024] S4. After the second conductive slurry is pre-mixed with the positive electrode active material, stirring and dispersing are performed at a revolution speed , a rotation speed for 30-60 minutes to obtain a mixture;

[0025] S5. The mixture is stirred and dispersed with the second solvent at a revolution speed , a rotation speed for 30-60 minutes to obtain the positive electrode slurry;

[0026] ​​​​​

[0027] The performance of lithium-ion batteries is closely related to the slurry mixing process. The stirring and dispersing speed and time during the slurry mixing process affect the slurry mixing effect, which in turn directly affects the performance of the positive electrode, the cell, and the battery.

[0028] The inventors discovered that the capacity of lithium-ion cells used in e-cigarettes decays rapidly under large and small current pulse discharge cycle conditions. This is mainly because the conventional positive electrode has limited ion conduction capacity under large and small current pulse discharge conditions. When the current jumps from large to small, the voltage difference is large, and polarization accumulates continuously, leading to the rapid capacity decay of existing lithium-ion cells used in e-cigarettes. This, in turn, affects the cycle performance and cycle life of lithium-ion cells used in e-cigarettes.

[0029] This application controls the order of adding materials in the preparation steps of the positive electrode slurry and maintains the rotation speed of each material during mixing and dispersion between 5 and 50 rpm. This ensures that the rotation speed is consistent in each step, guaranteeing that each material has appropriate shear force during mixing, resulting in better mixing and a more uniform and stable final positive electrode slurry. Furthermore, maintaining consistent rotation speeds in steps S3, S4, and S5 facilitates the formation of conductive networks between different conductive agents and improves the homogenization effect between the conductive agents and the positive electrode active material. Simultaneously, it controls the rotation speed... Controlling the speed and time within a specific range can improve the homogenization effect and stability of the positive electrode slurry, resulting in better dispersion uniformity of various materials in the positive electrode slurry, reducing the risk of agglomeration of conductive agents, and facilitating the formation of an excellent conductive network by the conductive agents. When the positive electrode slurry prepared using the method provided in this application is applied to the preparation of positive electrode sheets and cells for electronic cigarettes and lithium-ion batteries, it can reduce the surface resistance of the positive electrode sheet, the AC internal resistance of the cell, and the voltage difference between large and small currents, thereby improving the cycle performance of the electronic cigarette cell under large and small pulse discharges, and ultimately extending the cycle life of the lithium-ion battery for electronic cigarettes.

[0030] If the stirring and dispersion speed is too fast or the time is too long during the preparation of the positive electrode slurry, it will easily lead to low viscosity and poor stability of the positive electrode slurry, and the material in the slurry will settle too quickly. At the same time, the conductive agent will be sheared and broken into short chain structures, making it difficult to form an excellent conductive network. This will lead to an increase in the sheet resistance of the positive electrode and a decrease in the cycle performance of the battery cell. If the stirring and dispersion speed is too slow or the time is too short during the preparation of the positive electrode slurry, it will be difficult to stir the positive electrode slurry evenly. The conductive agent will easily agglomerate, which will lead to a significant increase in the sheet resistance of the positive electrode and a significant decrease in the cycle performance of the battery cell.

[0031] Preferably, the mass ratio of binder: first conductive agent: second conductive agent: positive electrode active material is 0.2~2: 0.2~2: 0.12~1.2: 94.8~99.48.

[0032] Preferably, in S2, the first conductive agent is conductive carbon black (SP).

[0033] Preferably, in S3, the second conductive agent is a mixture of multi-walled carbon nanotubes (MWCNTs) and single-walled carbon nanotubes (SWCNTs) in a mass ratio of 0.1~1:0.02~0.2.

[0034] Compared to positive electrode slurries that use one or two of SP, MWCNT, and SWCNT as conductive agents, this scheme uses a combination of SP+MWCNT+SWCNT as conductive agents and adds them stepwise while stirring and dispersing. This helps to reduce the film resistance of the obtained positive electrode sheet, resulting in smaller internal resistance and voltage difference between large and small currents in the final battery cell, and improves the cycle performance of the battery cell.

[0035] Preferably, in S1, the first solvent comprises N-methylpyrrolidone (NMP).

[0036] Preferably, in S1, the binder comprises polyvinylidene fluoride (PVDF).

[0037] Preferably, in S5, the second solvent comprises N-methylpyrrolidone (NMP).

[0038] Preferably, in S1, the solid content of the adhesive solution is 1-10%, and the viscosity is 1000-10000 mPa·s. Preferably, in S5, the solid content of the positive electrode slurry is 60-80%, and the viscosity is 2000-6000 mPa·s.

[0039] The solid content and viscosity of the cathode slurry are affected by the content of the binder, the stirring and dispersion speed and time. Taking into account the above factors, controlling the solid content and viscosity of the final cathode slurry within the above range is beneficial to improving the coating performance of the cathode slurry and enabling the cathode slurry to better match the coating process.

[0040] If the solid content of the positive electrode slurry is too high, it will increase the viscosity of the positive electrode slurry, resulting in a decrease in the uniformity of the coating. If the solid content of the positive electrode slurry is too low, it will lead to difficulties in coating and baking the positive electrode slurry, easy cracking of the positive electrode active coating, and easy floating of the binder and conductive agent, ultimately resulting in poor uniformity of the positive electrode sheet and low peel force between the positive electrode active coating and the positive electrode current collector.

[0041] If the viscosity of the positive electrode slurry is too high, its leveling properties will be poor during the coating process, resulting in large fluctuations in the areal density of the positive electrode active coating obtained after coating, and poor uniformity of the resulting positive electrode sheet. If the viscosity of the positive electrode slurry is too low, severe tailing will occur during the coating process, which will reduce the performance of the positive electrode sheet, battery cell, and battery.

[0042] Preferably, in S4, the positive electrode active material is selected from at least one of lithium cobalt oxide material and ternary positive electrode material.

[0043] Preferably, the particle size D50 of the positive electrode active material is 5~10 μm, and the specific surface area is 0.1~0.5 m². 2 / g, tap density is 2~3g / cm³ 3 .

[0044] Preferably, in S1, S2, S3, and S4, the premixing operating conditions are as follows: revolution speed 5~50 rpm, rotation speed 50~500 rpm, and stirring and dispersion time 5~50 minutes.

[0045] Preferably, the premixing operation is carried out in a mixing tank, and after the premixing is completed, the material on the tank wall and the agitator is scraped into the mixing system.

[0046] Pre-stirring and scraping the tank during the preparation of the cathode slurry can prevent uneven stirring and dispersion in the area between the stirring slurry and the tank wall, which is beneficial to improving the particle size and fineness of the cathode slurry.

[0047] Preferably, during the stirring and dispersion operations of S1, S2, S3, S4, and S5, the reaction system is evacuated and the temperature of the reaction system is controlled at 15~45℃.

[0048] Preferably, during the stirring and dispersion operations of S1, S2, S3, S4, and S5, the temperature of the reaction system is controlled by circulating cooling water.

[0049] Vacuuming and cooling water operation are carried out during the preparation of positive electrode slurry. Vacuuming can eliminate air bubbles generated during the stirring and dispersion of positive electrode slurry, and improve the quality of the positive electrode active coating formed after coating. Cooling water operation can improve the stability of positive electrode slurry by ensuring that the stirring temperature is within the range of 15~45℃.

[0050] The stirring and dispersion process is a continuous heat-generating process. If the temperature during the stirring and dispersion of the positive electrode slurry is not controlled, the system temperature will increase as the stirring and dispersion process continues, and the viscosity of the positive electrode slurry will decrease. After the stirring and dispersion is stopped, the viscosity of the positive electrode slurry will rebound severely, affecting the coating quality of the positive electrode slurry. If the temperature during the stirring and dispersion of the positive electrode slurry is too low, the viscosity of the positive electrode slurry will be too high, and the shearing effect will be too strong, which will be more destructive to the conductive agents, especially MWCNT and SWCNT. This is not conducive to homogenization, and it also makes MWCNT and SWCNT easy to be sheared into short chain structures, affecting the formation of the conductive network, and thus degrading the performance of the positive electrode sheet and the battery cell.

[0051] According to a second aspect of this application, a positive electrode sheet for electronic cigarettes is provided, the positive electrode sheet comprising a positive current collector and a positive active coating, the positive active coating being prepared from a positive electrode slurry, the positive electrode slurry being prepared by the above-described method for preparing a positive electrode slurry suitable for electronic cigarette cells.

[0052] Preferably, the thickness of the positive electrode current collector is 8~16μm.

[0053] Preferably, the areal density of the positive electrode active coating is 100~350 g / m2.

[0054] Preferably, the thickness of the positive electrode sheet is 33~103μm.

[0055] According to a third aspect of this application, an electronic cigarette battery cell is provided, the battery cell including the aforementioned positive electrode for electronic cigarettes.

[0056] According to a fourth aspect of this application, a lithium-ion battery for electronic cigarettes is provided, the lithium-ion battery comprising the aforementioned electronic cigarette cell.

[0057] The technical features of the technical solution provided by the present invention will be further clearly and completely described below with reference to specific embodiments. 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0058] Examples 1-3

[0059] A lithium-ion battery for electronic cigarettes, the preparation method of which includes the following steps:

[0060] 1. Preparation of positive electrode sheet

[0061] S1. Add the binder polyvinylidene fluoride (PVDF) and the first solvent N-methylpyrrolidone (NMP) to the mixing tank. After premixing, open the mixing tank and scrape the binder from the tank wall and the agitator into the first solvent. Then, at the revolution speed... Rotation speed Disperse by stirring After minutes, a gel solution with a solid content of 1-10% and a viscosity of 1000-10000 mPa·s is obtained;

[0062] S2. Add the first conductive agent to the above adhesive solution. After premixing, open the stirring tank and scrape the SP from the tank wall and the stirring paddle into the adhesive solution. Then, at the revolution speed... Rotation speed Disperse by stirring Minutes later, the first conductive paste was obtained;

[0063] The first conductive agent is conductive carbon black (SP);

[0064] S3. Add the second conductive agent to the first conductive slurry, and after premixing, proceed at the revolution speed. Rotation speed Disperse by stirring Minutes later, a second conductive paste was obtained;

[0065] The second conductive agent is composed of multi-walled carbon nanotubes (MWCNTs) and single-walled carbon nanotubes (SWCNTs) in a mass ratio of 0.1~1:0.02~0.2;

[0066] S4. Add the positive electrode active material to the second conductive paste mentioned above, and after premixing, then... (The sentence is incomplete and ends abruptly.) Rotation speed Disperse by stirring Minutes later, a mixture is obtained;

[0067] The positive electrode active material has a particle size D50 of 5~10μm and a specific surface area of ​​0.1~0.5 m². 2 / g, tap density is 2~3 g / cm³ 3 Lithium cobalt oxide;

[0068] S5. Add the second solvent NMP to the above mixture and rotate at the specified speed. Rotation speed Disperse by stirring Within minutes, a positive electrode slurry with a solid content of 60-80% and a viscosity of 2000-6000 mPa·s was obtained;

[0069] S6. The above positive electrode slurry is coated on both surfaces of the positive electrode current collector aluminum foil (10 μm thick) to form an areal density of 280 g / m². 2 The positive electrode active coating is cold-pressed and vacuum-dried to obtain a positive electrode sheet with a thickness of 80 μm.

[0070] In S1, S2, S3, and S4, the premixing conditions are as follows: revolution speed 5~50 rpm, rotation speed 50~500 rpm, and stirring and dispersion time 5~50 minutes;

[0071] Based on the mass ratio, the ratio of binder: first conductive agent: second conductive agent: positive electrode active material is 0.2~2: 0.2~2: 0.12~1.2: 94.8~99.48.

[0072] During the stirring and dispersion operations of S1, S2, S3, S4, and S5, the reaction system is evacuated and the cooling water circulation is turned on to control the temperature of the reaction system to 15~45℃.

[0073] In Example 1, the mass ratio of binder: first conductive agent: second conductive agent: positive electrode active material was calculated as 2:2:1.2:94.8; the temperature of the reaction system was controlled at 15°C.

[0074] In Example 2, the mass ratio of binder: first conductive agent: second conductive agent: positive electrode active material was calculated as 1:1:0.5:97.5; the temperature of the reaction system was controlled at 30°C.

[0075] In Example 3, the mass ratio of binder: first conductive agent: second conductive agent: positive electrode active material was calculated as 0.2:0.2:0.12:99.48; the temperature of the reaction system was controlled at 45°C.

[0076] Table 1 shows the stirring and dispersion speeds and times in the preparation methods of the positive electrode slurry in Examples 1-3.

[0077]

[0078]

[0079] 2. Preparation of negative electrode sheet

[0080] The negative electrode active material graphite, the binder sodium carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), and the conductive agent conductive carbon black (SP) were mixed in a mass ratio of 96:1.5:1.5:1 and then added to the solvent deionized water. After mixing evenly, a negative electrode slurry with a solid content of 48% and a viscosity of 2500 mPa·s was obtained. The negative electrode slurry was coated on both surfaces of the negative electrode current collector copper foil (with a thickness of 6 μm) to form a negative electrode active coating. After vacuum drying, the negative electrode sheet was obtained.

[0081] 3. Preparation of the diaphragm

[0082] A polyethylene membrane with a thickness of 8μm was selected as the diaphragm.

[0083] 4. Preparation of electrolyte

[0084] Ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) were mixed in a volume ratio of 1:1:1 to obtain an organic solvent. Then, fully dried lithium salt LiPF6 was dissolved in the organic solvent to prepare an electrolyte with a concentration of 1M.

[0085] 5. Assembly of lithium-ion batteries

[0086] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator acting as a separator between the positive and negative electrodes. The cells are then wound to obtain a battery cell. The battery cell is placed in an outer packaging shell, dried, and then injected with the electrolyte. After vacuum sealing, settling, formation, and shaping, a lithium-ion battery is obtained.

[0087] Example 4

[0088] This embodiment provides a lithium-ion battery for electronic cigarettes. Compared with Embodiment 1, the difference lies in the type of conductive agent used in step S3 of the positive electrode preparation. Specifically, the second conductive agent used in this embodiment is SP. Apart from the above differences, the materials, formulation ratios, and preparation operations used in this embodiment are strictly consistent with those in Embodiment 1.

[0089] Example 5

[0090] This embodiment provides a lithium-ion battery for electronic cigarettes. Compared with Embodiment 1, the difference lies in the type of conductive agent used in step S3 of the positive electrode preparation. Specifically, the second conductive agent used in this embodiment is MWCNT. Apart from the above differences, the materials, formulation ratios, and preparation operations used in this embodiment are strictly consistent with those in Embodiment 1.

[0091] Example 6

[0092] This embodiment provides a lithium-ion battery for electronic cigarettes. Compared with Embodiment 1, the difference lies in the type of conductive agent used in step S3 of the positive electrode preparation. Specifically, the second conductive agent used in this embodiment is SWCNT. Apart from the above differences, the materials, formulation ratios, and preparation operations used in this embodiment are strictly consistent with those in Embodiment 1.

[0093] Example 7

[0094] This embodiment provides a lithium-ion battery for electronic cigarettes. Compared with Embodiment 1, the difference lies in the type of conductive agent used in steps S2 and S3 of the positive electrode preparation. Specifically, the first conductive agent used in this embodiment is MWCNT, and the second conductive agent is SWCNT. Apart from the above differences, the materials, formulation ratios, and preparation operations used in this embodiment are strictly consistent with those in Embodiment 1.

[0095] Example 8

[0096] This embodiment provides a lithium-ion battery for electronic cigarettes. Compared with Embodiment 1, the difference lies in the type of conductive agent used in steps S2 and S3 of the positive electrode preparation. Specifically, the first conductive agent used in this embodiment is MWCNT+SWCNT, and the second conductive agent is SP. Apart from the above differences, the materials, formulation ratios, and preparation operations used in this embodiment are strictly consistent with those in Embodiment 1.

[0097] Example 9

[0098] This embodiment provides a lithium-ion battery for electronic cigarettes. Compared with Embodiment 1, the difference in structure is that the reaction system was not vacuumed during the preparation of the positive electrode slurry. Apart from the above differences, the materials, formulation ratios, and preparation operations used in this embodiment are strictly consistent with those in Embodiment 1.

[0099] Example 10

[0100] This embodiment provides a lithium-ion battery for electronic cigarettes. Compared with Embodiment 1, the difference in configuration is that the cooling water circulation was not turned on during the preparation of the positive electrode slurry, and the temperature of the reaction system exceeded 45°C during the stirring and dispersion process. Apart from the above differences, the materials, formulation ratios, and preparation operations used in this embodiment are strictly consistent with those in Embodiment 1.

[0101] Example 11

[0102] This embodiment provides a lithium-ion battery for electronic cigarettes. Compared with Embodiment 1, the difference in configuration is that the temperature of the reaction system is controlled below 15°C during the preparation of the positive electrode slurry. Apart from the above differences, the materials, formulation ratios, and preparation operations used in this embodiment are strictly consistent with those in Embodiment 1.

[0103] Comparative Example 1

[0104] This comparative example provides a lithium-ion battery for electronic cigarettes. Compared with Example 1, the difference in composition is that the preparation method of the positive electrode slurry is different in the preparation process of the positive electrode sheet.

[0105] The method for preparing the positive electrode used in this comparative example is as follows:

[0106] S1. Polyvinylidene fluoride is uniformly added to an N-methylpyrrolidone solution and stirred under vacuum to obtain a polyvinylidene fluoride adhesive solution, wherein the volume ratio of polyvinylidene fluoride to N-methylpyrrolidone solution is 1:14.

[0107] S2. Add the conductive agent to the above polyvinylidene fluoride adhesive solution and disperse it evenly to obtain a uniformly dispersed conductive adhesive solution. The conductive agent is composed of conductive carbon black and single-walled carbon nanotubes mixed in a mass ratio of 1:1.

[0108] S3. The positive electrode active material is added evenly to the conductive adhesive in portions, and a solvent is added during the process. The mixture is stirred and dispersed for 30 minutes at a revolution speed of 25 rpm and a rotation speed of 135 rpm to obtain a primary kneaded slurry with a solid content of 75%.

[0109] S4. Add solvent to the primary kneaded slurry and stir and disperse at a revolution speed of 25 rpm and a rotation speed of 160 rpm for 30 min to obtain a secondary kneaded slurry with a solid content of 73%.

[0110] S5. The secondary kneaded slurry was stirred and dispersed at a revolution speed of 35 rpm and a rotation speed of 3500 rpm to obtain a positive electrode slurry with a viscosity of 6500 mPa·s and a solid content of 67%.

[0111] S6. The above positive electrode slurry is coated on both surfaces of the positive electrode current collector aluminum foil (10 μm thick) to form an areal density of 280 g / m². 2 The positive electrode active coating is cold-pressed and vacuum-dried to obtain a positive electrode sheet with a thickness of 80 μm.

[0112] Apart from the differences mentioned above, the materials, formulation ratios, and preparation procedures used in this comparative example are strictly consistent with those in Example 1.

[0113] Comparative Example 2

[0114] This comparative example provides a lithium-ion battery for electronic cigarettes. Compared with Example 1, the difference in structure is that the premixing step is omitted in steps S1, S2, S3, and S4 of the positive electrode preparation. Apart from the above differences, the materials, formulation ratios, and preparation operations used in this comparative example are strictly consistent with those in Example 1.

[0115] Comparative Example 3

[0116] This comparative example provides a lithium-ion battery for electronic cigarettes. Compared with Example 1, the difference in composition is that the stirring and dispersion speed during the preparation of the positive electrode is different. Specifically, in this comparative example, = = = = =3rpm; = =80 rpm, = = =250 rpm. Except for the differences mentioned above, the materials, formulation ratios, and preparation procedures used in this comparative example are strictly consistent with those in Example 1.

[0117] Comparative Example 4

[0118] This comparative example provides a lithium-ion battery for electronic cigarettes. Compared with Example 1, the difference in composition is that the stirring and dispersion speed during the preparation of the positive electrode is different. Specifically, in this comparative example, = = = = =60 rpm; = =3100 rpm, = = =3100 rpm. Except for the differences mentioned above, the materials, formulation ratios, and preparation procedures used in this comparative example are strictly consistent with those in Example 1.

[0119] Comparative Example 5

[0120] This comparative example provides a lithium-ion battery for electronic cigarettes. Compared with Example 1, the difference in composition is that the stirring and dispersion time during the preparation of the positive electrode is different. Specifically, in this comparative example, = =40 min, = = =5min. Except for the differences mentioned above, the materials, formulation ratios, and preparation procedures used in this comparative example are strictly consistent with those in Example 1.

[0121] Comparative Example 6

[0122] This comparative example provides a lithium-ion battery for electronic cigarettes. Compared with Example 1, the difference in composition is that the stirring and dispersion time during the preparation of the positive electrode is different. Specifically, in this comparative example, = =510min, = = =110min. Except for the differences mentioned above, the materials, formulation ratios, and preparation procedures used in this comparative example are strictly consistent with those in Example 1.

[0123] Test case

[0124] 1. Participants

[0125] This test example uses the positive electrode sheets, cells, and batteries prepared in Examples 1-11 and Comparative Examples 1-6 as test objects to conduct relevant performance tests.

[0126] 2. Test Content

[0127] (1) Surface resistivity of the positive electrode

[0128] At a temperature of 25±2℃, the sheet resistance of the positive electrode sheet was tested after the coating active coating was dried and before cold pressing using an electrode sheet resistance testing system with a pressure of 20MPa and a holding time of 20s. The sheet resistivity of the positive electrode sheet was then calculated.

[0129] (2) Internal resistance of the battery cell

[0130] At a temperature of 25±2℃, the lithium-ion battery was charged at a constant current rate of 0.5C to a state of charge (SOC) of 50%, and the internal resistance of the cell was measured using a voltage resistance meter.

[0131] (3) Current and voltage difference

[0132] At a temperature of 25±2℃, the lithium-ion battery was charged to full capacity at a constant current and constant voltage rate of 1.3C (cutoff current 0.05C), rested for 5 minutes, discharged at a constant current rate of 5C for 10 seconds, then discharged at a constant current rate of 0.5C for 270 seconds, rested for 1 minute, discharged at a constant current rate of 5C for 10 seconds, discharged at a constant current rate of 0.5C for 270 seconds, rested for 1 minute, and the discharge was repeated until 3V. The voltage at the 10th second of the 5C discharge and the voltage at the start of the 0.5C discharge were recorded. The difference between the two was taken as the voltage difference of the battery under the large (5C) and small (0.5C) current.

[0133] (4) 5C / 10C rate discharge capacity retention

[0134] At a temperature of 25±2℃, the lithium-ion battery was charged to full capacity at a constant current and constant voltage rate of 0.5C (cutoff current 0.05C), and then left to rest for 5 minutes. The battery was then discharged to 3V at currents of 1C / 5C / 10C respectively. The discharge capacity at 1C / 5C / 10C was recorded. The ratio of the 5C / 10C discharge capacity to the 1C discharge capacity was used as the 5C / 10C rate discharge capacity retention rate.

[0135] (5) Capacity retention rate during large and small current pulse discharge cycles at different temperatures

[0136] The batteries prepared in Examples 1-11 and Comparative Examples 1-6 were subjected to constant current and constant voltage charging at a rate of 1.3C to full charge (cutoff current 0.05C) at different temperatures (25°C, 45°C, 50°C, 55°C), respectively. After resting for 5 minutes, the lithium-ion batteries were subjected to constant current discharge at a rate of 5C for 10 seconds, and then to constant current discharge at a rate of 0.5C for 270 seconds. After resting for 1 minute, the lithium-ion batteries were subjected to constant current discharge at a rate of 5C for 10 seconds. The lithium-ion battery was subjected to constant current discharge at a rate of 0.5C for 270 seconds, rested for 1 minute, and then discharged again to 3V. This constituted one charge-discharge cycle. The discharge capacity of the lithium-ion battery before and after 800 charge-discharge cycles was tested. The capacity retention rate of the lithium-ion battery after 800 charge-discharge cycles was calculated according to the following formula: 800-cycle capacity retention rate = (discharge capacity of the 800th cycle / initial discharge capacity) × 100%; or the number of cycles when the capacity retention rate of the lithium-ion battery was less than 80%.

[0137] In the capacity retention test results of lithium-ion batteries, the capacity retention rate is correlated with the number of cycles. The specific method of expressing the test results is as follows: for example, if the capacity retention rate is 87.8% after 800 cycles at 25℃, it is recorded as 87.8%@800 cycles; if the capacity retention rate is 80% after 700 cycles at 55℃, it is recorded as 80%@700 cycles.

[0138] 3. Experimental Results

[0139] Table 1. Surface resistivity test results of the positive electrode before cold pressing.

[0140]

[0141] Table 2. Performance test results of battery cells and batteries

[0142]

[0143] The surface resistivity test results of the positive electrode sheets prepared in Examples 1-11 and Comparative Examples 1-6 before cold pressing are shown in Table 1. The relevant performance test results of the cells and batteries prepared in Examples 1-11 and Comparative Examples 1-6 are shown in Table 2.

[0144] Compared to Comparative Examples 1-6, the positive electrode sheets prepared in Examples 1-11 have lower surface resistivity, cell internal resistance, and voltage difference between large and small currents of the lithium-ion battery before cold pressing. Furthermore, the lithium-ion batteries prepared in Examples 1-11 have higher discharge capacity retention rates at 5C and 10C rates, as well as higher cycle capacity retention rates during pulse discharge at 25-55°C. The main reason for the above phenomenon is that the positive electrode slurry used in the preparation process of the positive electrode sheet of the lithium-ion battery provided in Examples 1 to 11 is prepared by first premixing the binder and the first solvent and then stirring and dispersing them to obtain a gel solution, then premixing the gel solution and the first conductive agent and then stirring and dispersing them to obtain a first conductive slurry, then premixing the first conductive slurry and the second conductive agent and then stirring and dispersing them to obtain a second conductive slurry, then premixing the second conductive slurry and the positive electrode active material and then stirring and dispersing them to obtain a mixture, and finally mixing the mixture with the second solvent and stirring and dispersing it evenly. This process involves controlling the order of adding each material in the preparation steps of the positive electrode slurry and controlling the stirring and dispersing of each material. The revolution speed is controlled between 5 and 50 rpm, and the rotation speed and time are controlled within a specific range, which can improve the homogenization effect and stability of the positive electrode slurry, make the dispersion uniformity of each material in the positive electrode slurry better, reduce the risk of agglomeration of conductive agent, and facilitate the formation of excellent conductive network by conductive agent. The positive electrode slurry prepared by the preparation method of the positive electrode slurry provided in this application can be applied to the preparation of positive electrode sheets and cells for electronic cigarettes and lithium-ion batteries. It can reduce the surface resistance of the positive electrode sheet, the AC internal resistance of the cell and the voltage difference between large and small currents, thereby improving the cycle performance of the cell for electronic cigarettes under large and small pulse discharge, and ultimately extending the cycle life of lithium-ion batteries for electronic cigarettes.

[0145] Compared with Example 1, the positive electrode slurry used in the preparation process of the lithium-ion battery positive electrode sheet provided in Examples 4-8 uses different types of first and / or second conductive agents. The test results show that the surface resistivity, cell internal resistance and voltage difference of the lithium-ion battery before cold pressing of the positive electrode sheet prepared in Examples 4-8 are higher than those of Example 1. Moreover, the discharge capacity retention rate of the lithium-ion battery prepared in Examples 4-8 at 5C and 10C rates and the cycle capacity retention rate of large and small current pulse discharge at 25-55°C are lower than those of Example 1. The above results indicate that the type of the first and second conductive agent affects the performance of the positive electrode slurry, and thus the performance of the positive electrode sheet, battery cell, and lithium-ion battery. Compared with positive electrode slurries that use one or two of SP, MWCNT, and SWCNT as conductive agents, Example 1 uses SP as the first conductive agent and MWCNT and SWCNT as the second conductive agents, and adds them stepwise while stirring and dispersing. This helps to reduce the film resistance of the obtained positive electrode sheet, resulting in a smaller internal resistance and a smaller difference between the large and small currents and voltages in the final battery cell, and improves the cycle performance of the battery cell.

[0146] Compared with Example 1, Example 9 did not perform vacuum treatment on the system during the preparation of the positive electrode slurry; Example 10 did not turn on the cooling water circulation during the preparation of the positive electrode slurry, and the temperature of the reaction system exceeded 45°C during the stirring and dispersion of the slurry; Example 11 controlled the temperature of the reaction system below 15°C during the preparation of the positive electrode slurry. The test results showed that the surface resistivity, cell internal resistance, and voltage difference between large and small currents of the positive electrode sheets prepared in Examples 9-11 before cold pressing were all higher than those in Example 1. Furthermore, the capacity retention rate of the lithium-ion batteries prepared in Examples 9-11 at 5C and 10C rates, as well as the cycle capacity retention rate under pulse discharge at 25-55°C, were all lower than those in Example 1. The main reasons for the above results are as follows: Vacuuming and cooling water operation are performed during the preparation of the positive electrode slurry. Vacuuming eliminates air bubbles generated during the stirring and dispersion process, improving the quality of the positive electrode active coating formed after coating. Cooling water operation ensures the stirring temperature is within the range of 15~45℃, improving the stability of the positive electrode slurry. If the temperature during the stirring and dispersion process is not controlled, the system temperature will increase as the stirring and dispersion process continues, causing the viscosity of the positive electrode slurry to decrease. After stopping the stirring and dispersion, the viscosity of the positive electrode slurry rebounds severely, affecting the coating quality. If the temperature during the stirring and dispersion process is too low, the viscosity of the positive electrode slurry will be too high, resulting in excessive shearing and significant damage to the conductive agents, especially MWCNT and SWCNT. This is not conducive to homogenization and makes MWCNT and SWCNT easily sheared into short-chain structures, affecting the formation of the conductive network and thus degrading the performance of the positive electrode sheet and the battery cell.

[0147] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention, but such modifications or substitutions are all within the scope of protection of the present invention.

Claims

1. A method for preparing a positive electrode slurry for an electronic cigarette, comprising the following steps: S1, preparing a glue solution; S2, preparing a first conductive slurry; S3, preparing a second conductive slurry; S4, preparing a mixture; S5, preparing the positive electrode slurry; wherein the positive electrode slurry is prepared by mixing the glue solution, the first conductive slurry, the second conductive slurry and the mixture; and the mass ratio of the binder: the first conductive agent: the second conductive agent: the positive electrode active material is 0.2-2: 0.2-2: 0.12-1.2: 94.8-99.

48. S1. After the binder is premixed with the first solvent, the mixture is stirred at a revolution speed of 1000 rpm and a rotation speed of 100 rpm for 30 minutes. rotation speed under stirring In the S2, the first conductive agent is conductive carbon black, S2. After the solution of the glue is premixed with the first conductive agent, it is rotated at a revolution speed of 1000 rpm for 5 minutes. rotation speed under stirring and / or, S3. After the first conductive paste is premixed with the second conductive agent, the mixture is rotated at a revolution speed of 1000 rpm to 3000 rpm for 1 minute to 10 minutes. rotation speed under stirring In the S3, the second conductive agent is prepared by mixing multi-walled carbon nanotubes and single-walled carbon nanotubes in a mass ratio of 0.1-1: 0.02-0.

2. S4. After the second conductive paste is premixed with the positive active material, the mixture is rotated at a revolution speed of 1000 rpm for 10 minutes. rotation speed under stirring In the S1, the first solvent comprises N-methyl pyrrolidone, and the binder comprises polyvinylidene fluoride, S5. The mixture is mixed with a second solvent at a revolution speed of 2000 rpm for 5 minutes. rotation speed under stirring and / or, 2. The method for preparing the positive electrode slurry suitable for electronic cigarette cells as described in claim 1, wherein: In the S5, the second solvent comprises N-methyl pyrrolidone.

3. The method of claim 2, wherein the positive electrode slurry for the battery cell for the electronic cigarette is prepared by the steps of: In the S1, the solid content of the glue solution is 1-10%, and the viscosity is 1000-10000 mPa·s, ​ and / or, In the S5, the solid content of the positive electrode slurry is 60-80%, and the viscosity is 2000-6000 mPa·s.

4. The method for preparing the positive electrode slurry suitable for electronic cigarette cells as described in claim 1, wherein: In the S4, the positive electrode active material is selected from at least one of lithium cobaltate material and ternary positive electrode material. In the S1, the S2, the S3 and the S4, the operating conditions of the pre-mixing are as follows: the revolution speed is 5-50 rpm, the rotation speed is 50-500 rpm, and the stirring and dispersing time is 5-50 minutes. In the operation process of the stirring and dispersing in the S1, the S2, the S3, the S4 and the S5, the reaction system is vacuumized, and the temperature of the reaction system is controlled to be 15-45℃.

5. The method of preparing the positive electrode slurry suitable for the battery cell for the electronic cigarette according to claim 1, wherein: 10.An electronic cigarette positive electrode sheet, comprising a positive electrode current collector and a positive electrode active coating layer, wherein the positive electrode active coating layer is prepared from a positive electrode slurry, and the method for preparing the positive electrode slurry comprises the following steps: S1, preparing a glue solution; S2, preparing a first conductive slurry; S3, preparing a second conductive slurry; S4, preparing a mixture; S5, preparing the positive electrode slurry; wherein the positive electrode slurry is prepared by mixing the glue solution, the first conductive slurry, the second conductive slurry and the mixture; and the mass ratio of the binder: the first conductive agent: the second conductive agent: the positive electrode active material is 0.2-2: 0.2-2: 0.12-1.2: 94.8-99.

48. In the S2, the first conductive agent is conductive carbon black, and / or, 6. The method of preparing a positive electrode slurry for an electric core for an electronic cigarette according to claim 1, wherein: In the S3, the second conductive agent is prepared by mixing multi-walled carbon nanotubes and single-walled carbon nanotubes in a mass ratio of 0.1-1: 0.02-0.

2.

7. The method of preparing the positive electrode slurry suitable for the battery cell for the electronic cigarette as claimed in claim 6, wherein: The particle size D50 of the positive electrode active material is 5 to 10 μm, the specific surface area is 0.1 to 0.5 m 2 / g, and the tap density is 2 to 3 g / cm 3 .

8. The method of claim 1, wherein the positive electrode slurry for the battery cell for the electronic cigarette is prepared by adding the binder to the mixture of the active material, the conductive material, and the thickener, and then stirring the mixture. 13.The electronic cigarette positive electrode sheet according to claim 10, wherein, 9. The method of preparing the positive electrode slurry suitable for the battery cell for the electronic cigarette as claimed in claim 8, wherein: In the S1, the first solvent comprises N-methyl pyrrolidone, and the binder comprises polyvinylidene fluoride, and / or, S1. After the binder is premixed with the first solvent, the mixture is stirred at a revolution speed of 1000 rpm and a rotation speed of 100 rpm for 30 minutes. rotation speed under stirring In the S5, the second solvent comprises N-methyl pyrrolidone. S2. After the solution of the glue is premixed with the first conductive agent, it is rotated at a revolution speed of 1000 rpm for 5 minutes. rotation speed under stirring 14.The electronic cigarette positive electrode sheet according to claim 10, wherein, S3. After the first conductive paste is premixed with the second conductive agent, the mixture is rotated at a revolution speed of 1000 rpm to 3000 rpm for 1 minute to 10 minutes. rotation speed under stirring In the S1, the solid content of the glue solution is 1-10%, and the viscosity is 1000-10000 mPa·s, S4. After the second conductive paste is premixed with the positive active material, the mixture is rotated at a revolution speed of 1000 rpm for 10 minutes. rotation speed under stirring and / or, S5. The mixture is mixed with a second solvent at a rotational speed of 1000 rpm for 5 minutes. rotation speed under stirring ​ 11. The positive electrode sheet for an electronic cigarette according to claim 10, wherein ​ 12. The positive electrode sheet for an electronic cigarette according to claim 10, wherein ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ In the S5, the solid content of the positive electrode slurry is 60-80%, and the viscosity is 2000-6000 mPa·s.

15. The positive electrode sheet for electronic cigarettes according to claim 10, wherein, In the S4, the positive electrode active material is selected from at least one of lithium cobaltate material and ternary positive electrode material.

16. The positive electrode sheet for electronic cigarettes according to claim 10, wherein, The particle size D50 of the positive electrode active material is 5 to 10 μm, the specific surface area is 0.1 to 0.5 m 2 / g, and the tap density is 2 to 3 g / cm 3 .

17. The positive electrode sheet for electronic cigarettes according to claim 10, wherein, In the S1, the S2, the S3, the S4, the operation conditions of the pre-mixing are as follows: the revolution speed is 5-50 rpm, the rotation speed is 50-500 rpm, and the stirring and dispersing time is 5-50 minutes.

18. The positive electrode sheet for electronic cigarettes according to claim 10, wherein, In the operation process of the stirring and dispersing in the S1, the S2, the S3, the S4, and the S5, the reaction system is vacuumized, and the temperature of the reaction system is controlled to be 15-45℃.

19. An electronic cigarette cell, comprising the positive electrode sheet for electronic cigarettes according to claim 10.

20. A lithium ion battery for electronic cigarettes, comprising the electronic cigarette cell according to claim 19.

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