A manufacturing method of a soft-pack lithium battery using a coated separator

Abstract

The present invention relates to a method for manufacturing a soft-pack lithium battery using a coated separator. A method for manufacturing a soft-pack lithium battery using a coated separator includes the steps of: S1, manufacturing electrode plates and a separator; S2, assembling the battery cells; S3, injecting electrolyte and performing a first high-temperature aging; S4, forming; S5, performing a second high-temperature aging and a second sealing. Compared with the prior art, the method for manufacturing a soft-pack lithium battery using a coated separator provided by the present invention first injects electrolyte during the production process, and then, after the first / second high-temperature aging and the second sealing operations, the battery is formed through shaping. This not only ensures a good bonding effect between the positive and negative electrode plates and the coated separator, but also enables the positive and negative electrode plates and the separator inside the battery cells to be fully infiltrated and activated.

Description

Technical Field

[0001] The present invention relates to the field of battery manufacturing, and particularly to a method for manufacturing a soft-pack lithium battery using a coated separator. Background Art

[0002] Soft-pack lithium-ion batteries have been widely used in fields such as 3C digital, new energy transportation, energy storage, military, and aerospace due to their advantages of flexible size change, high energy ratio, and light weight.

[0003] Due to their poor mechanical strength, especially the low hardness of large-size high-energy-density soft-pack lithium-ion batteries, they are prone to deformation under external forces during processing and use, which in turn affects their safety and service life. The patent with the application number CN201610943353 provides a method for manufacturing a soft-pack lithium-ion battery using a composite gel separator. It uses a polypropylene film coated with a copolymer of PVDF (Poly vinyli dene fluoride) and HFP (hexafluoropropylene) as the separator, and creatively performs hot pressing fusion on the battery core, so that the PVDF coated on the separator can be integrated with the electrode sheet, thus avoiding adverse phenomena such as electrode sheet displacement during the operation of the battery core. At the same time, other process steps and process parameters are optimized, making the finally manufactured battery have higher hardness and energy density, and the cycle performance and safety performance are also improved.

[0004] However, this additional hot and cold pressing process causes the electrode sheet and the coated separator to be bonded too tightly before liquid injection, which easily leads to poor wetting effects of the positive and negative electrode sheets and the coated separator, and has a certain impact on the cycle performance and safety of the battery.

[0005] Therefore, there are deficiencies in this field, and it is urgent for inventors to conduct research and innovation on this problem. There is a need to invent a technical solution that can not only ensure good bonding effects between the positive and negative electrode sheets and the coated separator, but also enable the positive and negative electrode sheets and the separator inside the battery core to be fully wetted and activated, so as to further improve the cycle performance and safety performance of the finally manufactured battery. Summary of the Invention

[0006] In view of the above deficiencies of the prior art, the purpose of the present invention is to provide a method for manufacturing a soft-pack lithium battery using a coated separator, which can not only ensure good bonding effects between the positive and negative electrode sheets and the coated separator, but also enable the positive and negative electrode sheets and the separator inside the battery core to be fully wetted and activated, so as to further improve the cycle performance and safety performance of the finally manufactured battery.

[0007] To achieve the above purpose, the present invention adopts the following technical solutions:

[0008] A manufacturing method of a soft-pack lithium battery using a coated separator, comprising the steps:

[0009] S1. Manufacturing the electrode sheets and the separator: Manufacturing the positive electrode sheet and the negative electrode sheet, selecting a polyethylene (PE) ceramic separator with a surface coated with a copolymer of PVDF and HFP, placing it in a vacuum oven at a temperature of 70 - 90 °C and a vacuum degree less than or equal to 100 Pa, baking for 2.5 - 3.5 h, and then taking out the separator after the temperature drops to room temperature;

[0010] S2. Cell assembly: Making a stacked core by Z-shaped laminating the positive electrode sheet, the separator, and the negative electrode sheet, and then obtaining a semi-finished cell through tab welding and primary sealing; placing the semi-finished cell in a vacuum oven at a temperature of 80 - 100 °C and a vacuum degree of 80 - 100 Pa, baking for 24 - 30 h, and taking out the cell after the temperature drops to room temperature;

[0011] S3. Injecting electrolyte and first high-temperature aging: Injecting electrolyte into the cell under the condition of humidity RH ≤ 10% to form a battery, and placing the battery in an aging chamber for high-temperature aging at a temperature of 40 - 50 °C for 24 - 30 h;

[0012] S4. Formation: Placing the battery after the first aging into a fixture formation cabinet and performing staged formation operations;

[0013] S5. Second high-temperature aging and second sealing: Placing the battery after formation into an aging chamber, performing second high-temperature aging at a temperature of 40 - 50 °C for 24 - 30 h, and then performing second sealing and shaping to make a soft-pack lithium-ion battery product.

[0014] Preferably, in the manufacturing method of the soft-pack lithium battery using a coated separator, the primary sealing is the top sealing and side sealing of the aluminum-plastic film.

[0015] Preferably, in the manufacturing method of the soft-pack lithium battery using a coated separator, the second sealing is the edge cutting and encapsulation molding of the aluminum-plastic film.

[0016] Preferably, in the manufacturing method of the soft-pack lithium battery using a coated separator, the formation time is 1 - 3 h.

[0017] Preferably, in the manufacturing method of the soft-pack lithium battery using a coated separator, the staged formation includes primary formation and secondary formation;

[0018] The formation conditions of the primary formation include:

[0019] Temperature is 70 - 90 °C, pressure is 0.8 - 2.0 MPa, and time is 10 - 30 min;

[0020] The formation conditions of the secondary formation include:

[0021] The temperature is 50 - 70 °C, the pressure is 0.8 - 2.0 MPa, and the time is the remaining formation time.

[0022] Preferably, in the method for manufacturing a soft-pack lithium battery using a coated separator, in step S5, the conditions for shaping are: temperature 80 - 100 °C, pressure 1.2 - 2.0 MPa, and time 30 - 60 s.

[0023] Preferably, in the method for manufacturing a soft-pack lithium battery using a coated separator, step S1 includes:

[0024] Manufacturing a positive electrode sheet: Mixing a positive electrode active material, a positive electrode binder, a positive electrode conductive agent, and a positive electrode solvent in a first predetermined ratio to form a positive electrode slurry, and then through coating, drying, rolling, and die-cutting, a positive electrode sheet is obtained.

[0025] Preferably, in the method for manufacturing a soft-pack lithium battery using a coated separator, the positive electrode binder is PVDF.

[0026] Preferably, in the method for manufacturing a soft-pack lithium battery using a coated separator, step S1 includes:

[0027] Manufacturing a negative electrode sheet: Mixing a negative electrode active material, a negative electrode binder, a negative electrode conductive agent, and a negative electrode solvent in a second predetermined ratio to form a negative electrode slurry, and then through coating, drying, rolling, and die-cutting, a negative electrode sheet is obtained.

[0028] Preferably, in the method for manufacturing a soft-pack lithium battery using a coated separator, the negative electrode binder is styrene-butadiene rubber.

[0029] Compared with the prior art, in the method for manufacturing a soft-pack lithium battery using a coated separator provided by the present invention, during the production process, liquid injection is first carried out, and then after one-time / two-time high-temperature aging and a second sealing operation, the battery is shaped and manufactured. This not only ensures a good bonding effect between the positive and negative electrode sheets and the coated separator, but also enables the positive and negative electrode sheets and the separator inside the battery core to be fully infiltrated and activated. Description of the Drawings

[0030] Figure 1 is a flowchart of the method for manufacturing a soft-pack lithium battery using a coated separator provided by the present invention.

[0031] PE (polyethylene, polyethylene)

[0032] PVDF (Poly vinyli dene fluoride, polyvinylidene fluoride) Detailed Embodiments

[0033] In order to make the purpose, technical solution and effect of the present invention clearer and more specific, the present invention is further described in detail with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0034] Example 1

[0035] See also Figure 1 The present invention provides a method for making a soft-pack lithium battery using a glue-coated diaphragm, comprising the steps of:

[0036] S1. Making electrodes and diaphragms: Making positive and negative electrodes, using polyethylene PE ceramic diaphragms coated with PVDF and HFP copolymers, placing them in a vacuum oven at a temperature of 70-90°C and a vacuum degree of less than or equal to 100Pa, baking for 2.5-3.5h, and taking out the diaphragms after the temperature drops to room temperature; the room temperature is 20-30°C, and generally preferably 25°C;

[0037] S2, battery cell assembly: the positive electrode sheet, the separator and the negative electrode sheet are made into a stacked core through Z-shaped stacking, and then the tabs are welded and sealed to obtain a semi-finished battery cell; the semi-finished battery cell is placed in a vacuum oven at a temperature of 80-100°C and a vacuum degree of 80-100Pa, and baked for 24-30 hours, and the battery cell is taken out after the temperature drops to room temperature; the room temperature is 20-30°C, and generally preferably 25°C; the Z-shaped stacking is a unique patch method for soft-pack lithium-ion batteries, which can improve production efficiency, and make the single cell capacity of the battery cell larger, and can discharge with a larger current; the sealing, i.e., the one-time packaging, is an aluminum-plastic film top seal and side seal;

[0038] S3, liquid injection and primary high temperature aging: When the humidity RH is less than 10%, the battery cell is injected with liquid to form a battery, and the battery is placed in an aging room for high temperature aging at a temperature of 40-50℃ for 24-30h;

[0039] S4, formation: put the primary aged battery into the fixture formation cabinet and perform staged formation operation;

[0040] S5, secondary high temperature aging and secondary sealing: put the formed battery into the aging room, and perform secondary high temperature aging for 24-30 hours at a temperature of 40-50°C, and then perform secondary sealing and shaping to make soft-pack lithium-ion battery products. The secondary sealing is the aluminum-plastic film trimming and packaging molding; the shaping conditions are temperature 80-100°C, pressure 1.2-2.0MPa, and time 30-60S.

[0041] Specifically, the positive electrode sheet is prepared by mixing a positive electrode active material, a positive electrode binder, a positive electrode conductive agent, and a positive electrode solvent in a first predetermined ratio to form a positive electrode paste, which is then coated, dried, rolled, and die-cut to obtain the positive electrode sheet. Among them, the preferred solution is that the positive electrode active material is a ternary active material; the positive electrode binder is polyvinylidene fluoride; the positive electrode conductive agent includes carbon black and graphite; the positive electrode solvent is N-methylpyrrolidone. The positive electrode paste is evenly coated on both sides of the positive electrode conductive foil, dried in an oven, then rolled, and then slit, and finally cut into a positive electrode sheet of a set size through a knife die. The positive electrode conductive foil is preferably aluminum foil. The first predetermined ratio is a conventional ratio in the art and is not limited. The negative electrode sheet is prepared by mixing a negative electrode active material, a negative electrode binder, a negative electrode conductive agent, and a negative electrode solvent in a second predetermined ratio to form a negative electrode paste, which is then coated, dried, rolled, and die-cut to obtain the negative electrode sheet. The negative electrode active material is a graphite active material; the negative electrode binder is styrene-butadiene rubber; the negative electrode conductive agent is carbon black; the negative electrode solvent includes an aqueous solvent and sodium carboxymethylcellulose. The negative electrode paste is evenly coated on both sides of the negative electrode conductive foil, dried in an oven, then rolled, and then slit, and finally cut into a negative electrode sheet of a set size through a knife die. The negative electrode conductive foil is preferably copper foil. The second predetermined ratio is a conventional ratio in the art and is not limited.

[0042] Before the first high-temperature aging, the assembled battery cell is first filled with electrolyte according to the method provided by the present invention. After the first high-temperature aging, the formation result can maintain a good wetting effect of the battery cell. Then, after performing formation, the second high-temperature aging, the second sealing, and the shaping, the battery is manufactured, and the good wetting effect of the battery cell can still be maintained.

[0043] As a preferred solution, in this embodiment, in step S4, the formation time is 1-3h.

[0044] The staged formation includes primary formation and secondary formation.

[0045] The formation conditions for the primary formation include:

[0046] The temperature is 70-90°C, the pressure is 0.8-2.0 MPa, and the time is 10-30 min.

[0047] The formation conditions for the secondary formation include:

[0048] The temperature is 50-70°C, the pressure is 0.8-2.0 MPa, and the time is the remaining formation time.

[0049] Specifically, it is divided into temperature segments for formation. In the first segment, the temperature is relatively high, which can melt the PVDF and HFP copolymer in the separator, making the bonding between the electrode sheet and the separator better. In the second segment, the temperature is lowered. During formation, it is prevented that the molten colloid blocks the separator pores due to too long high-temperature time. Generally, the total formation time is 1-3 h, and the charging electric energy is 0.1-1 C.

[0050] Example 2, comparison of infiltration effects

[0051] Mix 97% by mass of the positive ternary active material, 1.5% of the binder polyvinylidene fluoride, 1.0% of the conductive carbon black, and 0.5% of the conductive graphite evenly to prepare the positive electrode slurry. After coating, drying, slitting, and die-cutting, the positive electrode sheet is obtained. Mix 95.5% by mass of the negative graphite active material, 2.0% of the binder styrene-butadiene rubber, 1.3% of the conductive carbon black, and 1.2% of sodium carboxymethyl cellulose evenly to prepare the negative electrode slurry. After coating, drying, slitting, and die-cutting, the negative electrode sheet is obtained. Select a coated ceramic separator, which is a polyethylene ceramic separator with a PVDF and HFP copolymer coated on the surface. Place the separator in a vacuum oven with a constant temperature of 80 °C, the vacuum degree ≤ 100 Pa, stop heating after baking for 3.0 h, and take out the separator after the temperature drops to room temperature. The specification of the separator is a 16-μm PE wet-process base film + 2-μm-thick ceramic coated on both sides + 1-μm-thick PVDF-HFP adhesive layer coated on both sides on this basis.

[0052] Preparation of the control group battery

[0053] Use the conventional method to prepare the battery with the above materials. The steps are as follows:

[0054] Manufacture the battery core: Overlap the positive electrode sheet, the separator, and the negative electrode sheet and wind them into a battery core;

[0055] Hot pressing and fusing: Place the battery core in a hot press for hot pressing and fusing;

[0056] Cooling and shaping: Place the battery core in a cold press for cold pressing and cooling to shape;

[0057] Manufacture the battery: Weld the tabs of the battery core and encapsulate it with an aluminum-plastic film to obtain the battery;

[0058] Battery baking: Place the battery in a vacuum oven, set the temperature to 90 °C, start baking after pumping the vacuum value to -0.10 MPa, stop heating after baking for 36 h, take out the battery core after the temperature drops below 35 °C, and inject electrolyte into the battery;

[0059] Aging: Place the battery after injecting electrolyte into an aging chamber and age it at a temperature of 50 °C for 36 h.

[0060] After stacking the positive electrode sheet, negative electrode sheet and separator into an electrode core, first perform cold and hot pressing, and then carry out aging after injecting electrolyte to manufacture a battery with a capacity of 18 Ah.

[0061] Preparation of experimental group batteries

[0062] Use the method provided by the present invention to prepare a battery with the same materials as the control group. The steps are as follows:

[0063] Stack the positive electrode sheet, the coated ceramic separator and the negative electrode sheet into a laminated core by "Z"-shaped lamination. After that, perform tab welding, top sealing and side sealing of the aluminum-plastic film to obtain a semi-finished electrode core.

[0064] Put the electrode core into a vacuum oven, set the temperature to 90 °C, the vacuum degree ≤ 100 Pa, stop heating after baking for 24 h, and take out the electrode core after the temperature drops to room temperature.

[0065] Inject electrolyte into the electrode core under the condition that the relative humidity RH ≤ 10%. Put the battery after injecting electrolyte into the aging room and age it for 24 h at 45 °C.

[0066] Place the aged electrode core in a fixture forming cabinet and perform staged formation charging.

[0067] Put the formed electrode core into the aging room and age it for 24 h at 45 °C.

[0068] Trim the aluminum-plastic film of the aged electrode core. After trimming and encapsulating the aluminum-plastic film, perform shaping at a temperature of 90 °C and a pressure of 2.0 MPa for 30 - 60 s, and then perform grading and sorting to obtain a soft-pack lithium-ion battery cell product.

[0069] After stacking the positive electrode sheet, separator and negative electrode sheet in a "Z" shape, through tab welding, top sealing and side sealing of the aluminum-plastic film, injecting electrolyte after baking, during the formation process, perform staged formation, as well as secondary high-temperature aging and second sealing to manufacture a battery with a capacity of 18 Ah.

[0070] The results obtained are shown in the following table:

[0071] Liquid retention volume of a single finished battery cell Liquid retention coefficient of the battery cell Liquid retention volume of the separator of a single finished battery cell Liquid retention coefficient of the separator Control group 54.5g 3.03 g / Ah 7.58g <![CDATA[9.475g / m 2 > Experimental group 57.8g 3.21 g / Ah 8.84g <![CDATA[11.05g / m 2 >

[0072] The wetting effect of the positive / negative electrode sheets and the separator in the battery will directly affect the liquid retention amount of the electrode core and the separator in the battery, and further affect the electric energy storage capacity of the battery. As can be seen from the above table, the method for preparing a soft-pack lithium battery provided by the present invention can effectively improve the liquid retention amount of the electrode core and the separator in the battery significantly.

[0073] It can be understood that for those of ordinary skill in the art, equivalent substitutions or changes can be made according to the technical solution and inventive concept of the present invention, and all such changes or substitutions should fall within the protection scope of the appended claims of the present invention.

Claims

1. A method for making a soft-pack lithium battery using a glue-coated diaphragm, It is characterized in that Includes steps: S1. Making electrodes and diaphragms: Making positive and negative electrodes, using polyethylene PE ceramic diaphragms coated with PVDF and HFP copolymers, placing them in a vacuum oven at a temperature of 70-90°C and a vacuum degree of less than or equal to 100Pa, baking for 2.5-3.5h, and taking out the diaphragms after the temperature drops to room temperature; S2, battery cell assembly: the positive electrode sheet, the separator and the negative electrode sheet are made into a stacked core by Z-shaped stacking, and then the tabs are welded and sealed to obtain a semi-finished battery cell; the semi-finished battery cell is placed in a vacuum oven at a temperature of 80-100° C. and a vacuum degree of 80-100 Pa, and baked for 24-30 hours, and the battery cell is taken out after the temperature drops to room temperature; S3, liquid injection and primary high temperature aging: When the humidity is RH≤10%, the battery cell is injected with liquid to form a battery, and the battery is placed in an aging room for high temperature aging at a temperature of 40-50℃ for 24-30h; S4, formation: put the primary aged battery into the fixture formation cabinet and perform staged formation operation, the formation time is 1-3h; S5. Secondary high-temperature aging and secondary sealing: Place the formed battery in an aging room and perform secondary high-temperature aging for 24-30 hours at a temperature of 40-50°C, then perform secondary sealing and shaping to produce a soft-pack lithium-ion battery product; Wherein, the staged formation includes a primary formation and a secondary formation; The formation conditions of the primary formation include: The temperature is 70-90℃, the pressure is 0.8-2.0MPa, and the time is 10-30min; The formation conditions of the secondary formation include: The temperature is 50-70°C, the pressure is 0.8-2.0MPa, and the time is the remaining formation time; The shaping conditions are: temperature 80-100° C., pressure 1.2-2.0 MPa, and time 30-60 seconds.

2. The method for making a soft-pack lithium battery using a glue-coated diaphragm according to claim 1, It is characterized in that The seal is an aluminum-plastic film top seal and a side seal.

3. The method for making a soft-pack lithium battery using a glue-coated diaphragm according to claim 1, It is characterized in that The second sealing is aluminum-plastic film trimming and packaging molding.

4. The method for making a soft-pack lithium battery using a glue-coated diaphragm according to claim 1, It is characterized in that Step S1 includes: Making positive electrode sheets: mixing positive electrode active materials, positive electrode binders, positive electrode conductors, and positive electrode solvents in a first predetermined ratio to form positive electrode slurry, and then coating, drying, rolling, and die-cutting to make positive electrode sheets.

5. The method for making a soft-pack lithium battery using a glue-coated diaphragm according to claim 4, It is characterized in that The positive electrode binder is PVDF.

6. The method for making a soft-pack lithium battery using a glue-coated diaphragm according to claim 1, It is characterized in that Step S1 includes: Making negative electrode sheets: mixing negative electrode active materials, negative electrode binders, negative electrode conductive agents, and negative electrode solvents in a second predetermined ratio to form negative electrode slurry, and then coating, drying, rolling, and die-cutting to make negative electrode sheets.

7. The manufacturing method of a soft-pack lithium battery using a coated diaphragm according to claim 6, characterized in that, the negative electrode binder is styrene-butadiene rubber.

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