Method for efficiently assembling lithium ion button cell and lithium ion cell

Abstract

The invention belongs to the technical field of battery manufacturing, and particularly relates to a method for efficiently assembling a lithium ion button battery and the lithium ion battery. The invention provides a method for efficiently assembling a lithium ion button cell, which comprises the following steps: (1) mixing a positive active material, a conductive agent, a binder and a solvent, and homogenizing to obtain positive slurry with the solid content of 35-60%; the homogenization is performed once, and the revolving speed of the revolution is 2000 to 3000r / min; the rotating speed of the autorotation is 2560 to 4260 r / min; the homogenizing time is 3 to 6 minutes; the homogenizing process also comprises a step of vacuumizing; the vacuumizing time is 30 to 60 seconds, and the vacuum degree is 80 to 95 mPa; (2) preparing a positive pole piece; and (3) preparing the lithium ion button cell. The button cell preparation method is short in button cell preparation time and high in efficiency, and button cells prepared in the same batch are high in consistency.

Description

Technical Field

[0001] The invention belongs to the technical field of battery manufacturing, and in particular relates to a method for efficiently assembling lithium ion button cells and a lithium ion battery. Background Art

[0002] Lithium-ion batteries are favored by scholars because of their advantages such as high safety, low cost and environmental friendliness. Button batteries are widely used in the field of lithium-ion batteries because of their small size, portability and suitability for application in various fields. They also have high energy density, long service life and excellent discharge performance.

[0003] In the prior art, when preparing button batteries, the positive electrode slurry is often divided into low speed, high speed, and medium speed for segmented homogenization, and the homogenization times are many and the homogenization time is long, which greatly reduces the work efficiency; when assembling button batteries, the positive electrode shell, positive electrode sheet, electrolyte, diaphragm, negative electrode lithium sheet, and negative electrode shell are assembled in the order of assembly, which has low assembly efficiency and is prone to offset after adding electrolyte, resulting in problems such as decreased button battery performance, short circuit, and difficulty in subsequent battery assembly. Therefore, it is necessary to provide a method for efficiently assembling lithium ion button batteries that can prepare positive electrode slurry simply and quickly assemble button batteries. Summary of the invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the defects of the prior art such as complicated and time-consuming steps for preparing positive electrode slurry, low efficiency and poor performance in assembling button batteries, so as to provide a method for efficiently assembling lithium-ion button batteries and a lithium-ion battery.

[0005] To this end, the present invention provides the following technical solutions.

[0006] The present invention provides a method for efficiently assembling lithium ion button batteries, comprising the following steps:

[0007] (1) mixing a positive electrode active material, a conductive agent, a binder and a solvent and homogenizing the mixture to obtain a positive electrode slurry, wherein the solid content of the positive electrode slurry is 35-60%;

[0008] The homogenization is performed once, and the homogenization satisfies the following AC items:

[0009] A. The revolution speed and the rotation speed during the homogenization process satisfy the relationship 1;

[0010] Rotation speed = revolution speed × (1 + a%) Relationship 1

[0011] The a% is the ratio of rotation to revolution, and a is 28-42;

[0012] The revolution speed is 2000-3000r / min; the rotation speed is 2560-4260r / min;

[0013] B. The homogenization time is 3-6 min;

[0014] Preferably, the homogenization time is ≤4 min,

[0015] As an example, the homogenization time is 3 min, 3.5 min, 4 min, 4.5 min, 5 min, 5.5 min or a range consisting of any two values;

[0016] C. The homogenization process also includes a vacuuming step; the vacuuming time is 30-60s, and the vacuum degree is 80-95mPa;

[0017] The vacuuming is performed 1-3 minutes after the homogenization is started;

[0018] (2) preparing a positive electrode sheet;

[0019] (3) Prepare a lithium-ion button battery according to the following steps: lay the negative electrode shell flat, place the lithium sheet, inject the electrolyte first, place the separator, inject the electrolyte second, place the positive electrode sheet, place the gasket, place the spring, cover the positive electrode shell, and seal;

[0020] The diameter of the diaphragm is larger than the diameter of the lithium sheet, and the diameter of the lithium sheet is larger than the diameter of the positive electrode sheet.

[0021] There is no requirement for the specific injection amount of the first injected electrolyte and the second injected electrolyte; the conventional injection amount in the art can be used;

[0022] In an optional embodiment, the spring piece is bell-mouth shaped.

[0023] In an optional embodiment, zirconium beads are added to the mixture;

[0024] Preferably, the mass ratio of the zirconium beads to the positive electrode slurry is 1:(1.4-2.9);

[0025] Preferably, the diameter of the zirconium beads is 6-10 mm.

[0026] In an optional embodiment, the mass ratio of the positive electrode active material, the conductive agent and the binder is (8-9.8):(0.1-0.5):(0.1-0.5);

[0027] Preferably, the binder comprises polyvinylidene fluoride;

[0028] Preferably, the conductive agent comprises at least one of acetylene black, carbon nanotubes, superconducting carbon and conductive carbon black;

[0029] Preferably, the binder is added in the form of glue.

[0030] The adhesive solution of the present invention can be prepared according to conventional methods in the art. As an example, the preparation steps of the polyvinylidene fluoride solution include: dissolving 6g of polyvinylidene fluoride powder in 94g of solvent and mixing at a rotation speed of 300r / min.

[0031] In an alternative embodiment, the solvent comprises N-methylpyrrolidone.

[0032] In an optional embodiment, the step of preparing the positive electrode sheet specifically includes: uniformly coating the positive electrode slurry on the positive electrode current collector, and first drying to obtain the positive electrode sheet.

[0033] The purpose of the first drying is to dry the solvent so that the positive electrode active material and the current collector are closely combined;

[0034] In an optional embodiment, the positive electrode current collector comprises aluminum foil;

[0035] In an optional embodiment, the temperature of the first drying is 85-110°C;

[0036] In an optional embodiment, the first drying time is 45-60 minutes.

[0037] In an optional embodiment, the aluminum foil is a single-sided smooth aluminum foil.

[0038] In an optional embodiment, the step (2) further comprises: rolling the positive electrode sheet to a compaction density of 2.5-3.2 g / cm 3 ; Cut into discs with a diameter of 12-14 mm, and dry for the second time;

[0039] In an optional embodiment, the step (3), the specific steps of sealing include: first increasing the pressure to 70-85 MPa, then reducing the pressure to 0 MPa, and taking out the button battery;

[0040] In an optional embodiment, in the step (3), the electrolyte is injected through a pipette.

[0041] In an optional embodiment, the temperature of the second drying is 100-140°C;

[0042] In an optional embodiment, the second drying time is 3-12 hours.

[0043] The present invention also provides a lithium ion button battery assembled by the above method.

[0044] The technical solution of the present invention has the following advantages:

[0045] 1. The method for efficiently assembling lithium-ion button batteries provided by the present invention comprises the following steps: (1) mixing a positive electrode active material, a conductive agent, a binder and a solvent and homogenizing the mixture to obtain a positive electrode slurry, wherein the solid content of the positive electrode slurry is 35-60%; the homogenization is performed once, and the homogenization satisfies the following AC items: A. During the homogenization process, the revolution speed and the rotation speed satisfy the relationship 1: rotation speed = revolution speed × (1 + a%); a% is the ratio of rotation to revolution, and a is 28-42; the revolution speed is 2000-3000 r / min; the rotation speed is 2 560-4260r / min; B. The homogenization time is 3-6min; C. The homogenization process also includes a vacuum step; the vacuum time is 30-60s, and the vacuum degree is 80-95mPa; (2) preparing positive electrode plates; (3) preparing lithium-ion button batteries according to the following steps: laying the negative electrode shell flat, placing lithium plates, first injecting electrolyte, placing diaphragm, second injecting electrolyte, placing the positive electrode plates, placing gaskets, placing springs, covering the positive electrode shell, and sealing; the diameter of the diaphragm is larger than the diameter of the lithium plates, and the diameter of the lithium plates is larger than the diameter of the positive electrode plates. The button-type batteries prepared by the present invention are short in time and high in efficiency, and the button-type batteries prepared in the same batch have high consistency. Specifically, the positive electrode slurry prepared by the present invention only needs to be mixed once, and the preparation can be completed within 6 minutes. The positive electrode active material, the conductive agent and the binder are added at one time, and the positive electrode slurry is prepared by mixing and homogenizing once, which greatly shortens the mixing time and improves the efficiency of preparing the positive electrode slurry. The homogenization of the present invention is carried out at a ratio of rotation to revolution of 28-42%; the revolution speed is 2000-3000r / min; the rotation speed is 2560-4260r / min; the bubbles in the slurry can be effectively removed, and the uniformity of the slurry can be improved; the homogenization process also includes vacuuming for 30-60s, and the vacuum degree is 80-95mPa; not only can the bubbles in the slurry be further removed, but also the slurry can be prevented from generating heat and reacting with moisture in the air during the high-speed rotation of the homogenization, thereby reducing the performance of the positive electrode slurry.

[0046] The present invention can quickly and efficiently complete the assembly of button cells through the assembly sequence of laying the negative electrode shell flat, placing the lithium sheet, first injecting electrolyte, placing the diaphragm, second injecting electrolyte, placing the positive electrode sheet, placing the gasket, placing the spring sheet, covering the positive electrode shell, and sealing, and in conjunction with a specific homogenization process, the positive electrode sheet is not easily offset; the diameter of the lithium sheet is larger than the diameter of the positive electrode sheet, and during the assembly process, the lithium sheet with a large diameter is placed first, and then the positive electrode sheet with a small diameter is placed, which is easier to position and assemble, and the diameter of the diaphragm is larger than the positive electrode sheet, and the lithium sheet and the positive electrode sheet can also be safely separated to avoid short circuits.

[0047] 2. The method for efficiently assembling lithium-ion button batteries provided by the present invention adds zirconium beads during mixing, which further shortens the homogenization time and improves the homogenization efficiency; the spring piece is trumpet-shaped and has greater elasticity, and the height can be actually adjusted according to the height of the internal auxiliary material, thereby ensuring that the button battery has good sealing and will not have problems such as leakage and short circuit that lead to a decrease in the performance of the button battery; at the same time, the spring piece cannot directly contact the positive electrode plate, and a gasket is added in the middle to isolate it; the present invention uses a pipette to inject electrolyte, which can accurately control the injection amount of the electrolyte, greatly improving the consistency of the button battery. DETAILED DESCRIPTION

[0048] The following examples are provided for a better understanding of the present invention, but are not intended to limit the best mode of implementation, nor to limit the content and protection scope of the present invention. Any product identical or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with other prior arts shall fall within the protection scope of the present invention.

[0049] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in the field can be used. If no manufacturer is specified for the reagents or instruments used, they are all conventional reagent products that can be obtained commercially.

[0050] Example 1

[0051] This embodiment provides a method for efficiently assembling lithium-ion button batteries, comprising the following steps:

[0052] (1) Preparation of polyvinylidene fluoride glue: Add 6 g of polyvinylidene fluoride into 94 g of N-methylpyrrolidone and stir at 300 r / min for 24 h.

[0053] The nickel cobalt lithium manganese oxide material, acetylene black and polyvinylidene fluoride are mixed in a mass ratio of 9:0.5:0.5, the concentration of the polyvinylidene fluoride glue is 6wt%, and then an appropriate amount of N-methylpyrrolidone is added, and 5 zirconium beads with a diameter of 6mm are added to the homogenizer. The rotation and revolution ratio a% is 35%, the revolution speed is 2500r / min, and the rotation speed is calculated according to the relationship 1 to be 3375r / min;

[0054] Rotation speed = revolution speed × (1 + a%) Relationship 1

[0055] Homogenize for 4.5 minutes, start vacuuming 2 minutes after homogenization, vacuuming time is 30 seconds, vacuum degree is 90mPa, and positive electrode slurry is obtained, the solid content of the positive electrode slurry is 44.83%; the mass ratio of zirconium beads to positive electrode slurry is 1:1.8; the fineness of the positive electrode slurry detected by a scraper fineness meter is 20μm;

[0056] (2) The positive electrode slurry is evenly coated on a piece of aluminum foil with a scraper, dried in an oven at 100°C for 60 minutes, and rolled to a target thickness of 48-50 μm and a compaction density of 2.8-3.1 g / cm 3 ; Cut into 6 discs with a diameter of 13 mm using a cutting machine, and dry in a vacuum drying oven at 120°C for 6 hours to obtain 6 positive electrode sheets;

[0057] (3) Move a positive electrode sheet, a diaphragm, a negative electrode shell and a positive electrode shell into a glove box, place the CR2032 negative electrode shell flat on the assembly table, place the lithium sheet in the center of the negative electrode shell with the smooth surface facing up; inject 40 μL of electrolyte with a pipette, hold the diaphragm with tweezers and align it with the edge of the negative electrode shell, evenly cover the lithium sheet with the diaphragm, and then inject 40 μL of electrolyte with a pipette, gently shake the electrolyte to fully soak the diaphragm; place the positive electrode sheet in the center on the diaphragm, then place the gasket and spring in the center, and cover the positive electrode shell; put the negative electrode shell into the sealing machine with the negative electrode shell facing up, lock the oil valve, and manually raise the pressure to 70 MPa, then wait until the pressure drops to 0 MPa, and use insulated tweezers to take out the button battery cell1. Repeat step (3) 5 times, assemble the remaining 5 positive electrode sheets separately to obtain 5 batteries, which are the first group of samples and are numbered cell2-6 respectively.

[0058] Repeat steps (1)-(3) once to prepare six button cells as the second group of samples, numbered cell1-6 respectively.

[0059] The 12 button cells were charged once at 1.2C and discharged once at 0.25C in the voltage range of 2.75-4.3V to obtain the first cycle discharge specific capacity. There are 12 sets of data in total. The results are shown in Table 1.

[0060] The present invention takes 4.5 minutes to prepare the positive electrode slurry, which is shorter than the prior art and more efficient.

[0061] Example 2

[0062] This embodiment provides a method for efficiently assembling lithium-ion button batteries, comprising the following steps:

[0063] (1) Preparation of polyvinylidene fluoride glue: Add 6 g of polyvinylidene fluoride into 94 g of N-methylpyrrolidone and stir at 300 r / min for 24 h.

[0064] Lithium cobalt oxide material, acetylene black and polyvinylidene fluoride are mixed in a mass ratio of 9.5:0.25:0.25, the concentration of polyvinylidene fluoride glue is 6wt%, and then an appropriate amount of N-methylpyrrolidone is added, and 3 zirconium beads with a diameter of 6mm are added to the homogenizer, the rotation and revolution ratio is 42%, the revolution speed is 3000r / min, and the rotation speed is calculated according to the relationship 1 to be 4260r / min, and the homogenization is 3min. After the homogenization is turned on, vacuum is drawn for 30s 1min later, and the vacuum degree is 80mPa to obtain a positive electrode slurry, and the solid content of the positive electrode slurry is 56.2%; the mass ratio of the zirconium beads to the positive electrode slurry is 1:2.5; the fineness of the positive electrode slurry detected by a scraper fineness meter is 21μm;

[0065] (2) The positive electrode slurry was evenly coated on a piece of aluminum foil with a scraper, dried in an oven at 85°C for 45 minutes, and rolled to a target thickness of 47-49 μm and a compaction density of 2.5-2.7 g / cm 3 ; Cut into 6 discs with a diameter of 12 mm using a cutting machine, and dry in a vacuum drying oven at 140°C for 3 hours to obtain 6 positive electrode sheets;

[0066] (3) Move a positive electrode sheet, a separator, a negative electrode shell and a positive electrode shell into a glove box, place the CR2032 negative electrode shell flat on the assembly table, place the lithium sheet in the center of the negative electrode shell with the smooth surface facing up; inject 35 μL of electrolyte with a pipette, hold the separator with tweezers and align it with the edge of the negative electrode shell, evenly cover the lithium sheet with the separator, and then inject 35 μL of electrolyte with a pipette, gently shake the electrolyte to fully soak the separator; place the positive electrode sheet in the center on the separator, then place the gasket and spring in the center, and cover the positive electrode shell; put the negative electrode shell into the sealing machine with the negative electrode shell facing up, lock the oil valve, and manually raise the pressure to 85 MPa. After the pressure drops to 0 MPa, use insulated tweezers to take out the button battery cell1. Repeat step (3) 5 times, assemble the remaining 5 positive electrode sheets separately to obtain 5 batteries, which are the first group of samples and are numbered cell2-6 respectively.

[0067] Repeat steps (1)-(3) once to prepare six button cells as the second group of samples, numbered cell1-6 respectively.

[0068] The 12 button cells were charged once at 0.1C and discharged once at 0.1C in the voltage range of 3.0-4.4V to obtain the first cycle discharge specific capacity. There are 12 sets of data in total. The results are shown in Table 1.

[0069] The present invention takes 3 minutes to prepare the positive electrode slurry, which is shorter than the prior art and has higher efficiency.

[0070] Example 3

[0071] This embodiment provides a method for efficiently assembling lithium-ion button batteries, comprising the following steps:

[0072] (1) Preparation of polyvinylidene fluoride glue: Add 6 g of polyvinylidene fluoride into 94 g of N-methylpyrrolidone and stir at 300 r / min for 24 h.

[0073] The lithium nickel manganese oxide material, acetylene black and polyvinylidene fluoride are mixed in a mass ratio of 8.0:0.1:0.1, and the concentration of the polyvinylidene fluoride glue is 6wt%. Then, an appropriate amount of N-methylpyrrolidone is added, and two zirconium beads with a diameter of 10mm are added to the homogenizer. The ratio of rotation to revolution is 28%, and the revolution speed is 2000r / min. According to the relationship 1, the rotation speed is 2560r / min, and the homogenization is 5.5min. After the homogenization is turned on, the vacuum is drawn for 50s for 3min, and the vacuum degree is 95mPa to obtain a positive electrode slurry. The solid content of the positive electrode slurry is 38.5%; the mass ratio of the zirconium beads to the positive electrode slurry is 1:1.5; the fineness of the positive electrode slurry is 20μm detected by a scraper fineness meter;

[0074] (2) The positive electrode slurry was evenly coated on a piece of aluminum foil with a scraper, dried in an oven at 110°C for 55 min, and rolled to a target thickness of 44-46 μm and a compaction density of 2.9-3.2 g / cm 3 ; Cut into 6 discs with a diameter of 14 mm respectively using a cutting machine, and dry in a vacuum drying oven at 100°C for 12 hours to obtain 6 positive electrode sheets;

[0075] (3) Move the positive electrode sheet, diaphragm, negative electrode shell and positive electrode shell into the glove box, place the CR2032 negative electrode shell flat on the assembly table, place the lithium sheet in the center of the negative electrode shell with the smooth surface facing up; inject 50μL of electrolyte with a pipette, hold the diaphragm with tweezers and align it with the edge of the negative electrode shell, evenly cover the lithium sheet with the diaphragm, and then inject 50μL of electrolyte with a pipette, gently shake the electrolyte to fully soak the diaphragm; place the positive electrode sheet in the center on the diaphragm, then place the gasket and spring in the center, and cover the positive electrode shell; put the negative electrode shell into the sealing machine with the negative electrode shell facing up, lock the oil valve, and manually raise the pressure to 80MPa. After the pressure drops to 0MPa, use insulated tweezers to take out the button battery cell1. Repeat step (3) 5 times, assemble the remaining 5 positive electrode sheets separately to obtain 5 batteries, which are the first group of samples and are numbered cell2-6 respectively.

[0076] Repeat steps (1)-(3) once to prepare six button cells as the second group of samples, numbered cell1-6 respectively.

[0077] The 12 button cells were charged once at 0.05C and discharged once at 0.05C in the voltage range of 2.5-4.3V to obtain the first cycle discharge specific capacity. There are 12 sets of data in total. The results are shown in Table 1.

[0078] The present invention takes 5.5 minutes to prepare the positive electrode slurry, which is shorter than the prior art and more efficient.

[0079] Comparative Example 1

[0080] This comparative example provides a method for assembling lithium ion button cells, which differs from Example 1 only in that in step (1), no vacuum is applied during the mixing process. The fineness of the positive electrode slurry is 24 μm as measured by a scraper fineness meter. A button cell 1 is obtained.

[0081] Repeat step (3) 5 times, and assemble the remaining 5 positive electrode sheets to obtain 5 batteries as samples, which are numbered as cell2-6 respectively.

[0082] The above 6 button batteries were charged once at 1.2C and discharged once at 0.25C in the voltage range of 2.75-4.3V to obtain the first-cycle discharge specific capacity. There are 6 sets of data in total. The results are shown in Table 1.

[0083] Comparative Example 2

[0084] This comparative example provides a method for assembling lithium ion button cells, which differs from Example 1 only in that the slurry is homogenized for 4.5 min at a rotation ratio of 21% and a rotation speed of 1500 r / min, and the fineness of the positive electrode slurry is 30 μm as measured by a scraper fineness meter. A button cell 1 is obtained.

[0085] Repeat step (3) 5 times, and assemble the remaining 5 positive electrode sheets to obtain 5 batteries as samples, which are numbered as cell2-6 respectively.

[0086] The above 6 button batteries were charged once at 1.2C and discharged once at 0.25C in the voltage range of 2.75-4.3V to obtain the first-cycle discharge specific capacity. There are 6 sets of data in total. The results are shown in Table 1.

[0087] Table 1 First cycle discharge specific capacity of each embodiment and comparative example

[0088]

[0089] As can be seen from Table 1, the button batteries prepared by the method for efficiently assembling lithium-ion button batteries provided by the present invention have good consistency, the difference in the first-cycle discharge specific capacity of the button batteries prepared in the same batch is within 0.8 mAh / g, and the error value of the batteries prepared after repeatedly preparing the slurry is also small.

[0090] By comparing Example 1 with Comparative Example 1, it can be seen that when the method provided by the present invention is not used to draw a vacuum during the mixing process, the difference in the first-cycle discharge specific capacity of the button battery obtained is up to 1.2 mAh / g, indicating that the button battery obtained by the method provided by the present invention has better consistency.

[0091] By comparing Example 1 with Comparative Example 2, it can be seen that if the rotation-revolution ratio and rotation speed of the present invention are not used for homogenization, the obtained positive electrode slurry has poor fineness and uniformity; the difference in the first-cycle discharge specific capacity of the obtained button battery is as high as 2.4 mAh / g, indicating that the battery consistency is better when the rotation-revolution ratio and rotation speed provided by the present invention are used for homogenization.

[0092] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from these are still within the scope of protection of the invention.

Claims

1. A method for efficiently assembling lithium-ion button batteries, characterized in that: The steps include: (1) mixing a positive electrode active material, a conductive agent, a binder and a solvent and homogenizing the mixture to obtain a positive electrode slurry, wherein the solid content of the positive electrode slurry is 35-60%; The homogenization is performed once, and the homogenization satisfies the following AC items: A. The revolution speed and the rotation speed during the homogenization process satisfy the relationship 1; Rotation speed = revolution speed × (1 + a%) Relationship 1 The a% is the ratio of rotation to revolution, and a is 28-42; The revolution speed is 2000-3000r / min; the rotation speed is 2560-4260r / min; B. The homogenization time is 3-6 min; C. The homogenization process also includes a vacuuming step; the vacuuming time is 30-60s, and the vacuum degree is 80-95mPa; (2) preparing a positive electrode sheet; (3) Prepare a lithium-ion button battery according to the following steps: lay the negative electrode shell flat, place the lithium sheet, inject the electrolyte first, place the separator, inject the electrolyte second, place the positive electrode sheet, place the gasket, place the spring, cover the positive electrode shell, and seal; The diameter of the diaphragm is larger than the diameter of the lithium sheet, and the diameter of the lithium sheet is larger than the diameter of the positive electrode sheet.

2. The method according to claim 1, characterized in that The spring piece is of a bell-mouth shape.

3. The method according to claim 1, characterized in that: The mixture is added with zirconium beads; Preferably, the mass ratio of the zirconium beads to the positive electrode slurry is 1:(1.4-2.9); Preferably, the diameter of the zirconium beads is 6-10 mm.

4. The method according to claim 1, characterized in that The mass ratio of the positive electrode active material, the conductive agent and the binder is (8-9.8):(0.1-0.5):(0.1-0.5); Preferably, the binder comprises polyvinylidene fluoride; Preferably, the conductive agent comprises at least one of acetylene black, carbon nanotubes, superconducting carbon and conductive carbon black; Preferably, the binder is added in the form of glue.

5. The method according to claim 4, characterized in that The solvent includes N-methylpyrrolidone.

6. The method according to claim 5, characterized in that The step of preparing the positive electrode sheet specifically includes: uniformly coating the positive electrode slurry on the positive electrode collector, and first drying to obtain the positive electrode sheet; Preferably, the positive electrode current collector comprises aluminum foil.

7. The method according to claim 6, characterized in that The temperature of the first drying is 85-110° C.; and / or, The first drying time is 45-60 minutes; and / or, The aluminum foil is a single-sided smooth aluminum foil.

8. The method according to claim 1, characterized in that: The step (2) further comprises: rolling the positive electrode sheet to a compaction density of 2.5-3.2 g / cm 3 ; Cut into discs with a diameter of 12-14 mm, and then dry for the second time; and / or, The specific steps of the step (3) of sealing include: first increasing the pressure to 70-85 MPa, then reducing the pressure to 0 MPa, and taking out the button battery; and / or, In the step (3), the electrolyte is injected through a pipette.

9. The method according to claim 8, characterized in that The temperature of the second drying is 100-140° C.; and / or, The second drying time is 3-12 hours.

10. A lithium ion button cell assembled by the method according to any one of claims 1 to 9.

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