Composite lithium ribbon, lithium metal battery and preparation method

Abstract

The application discloses a composite lithium strip, a lithium metal battery and a preparation method, and a preparation method of the composite lithium strip, which comprises the following steps: rolling a separator on a lithium strip in a dry environment, wherein the separator comprises a first separator and a second separator, and the first separator and the second separator are respectively rolled on the upper surface and the lower surface of the lithium strip; coating an adhesive on the edges of the inner surfaces of the first separator and the second separator, so that the first separator and the second separator are bonded to completely wrap the lithium strip, thereby obtaining a composite lithium strip; and winding the composite lithium strip. Through the method, the super-thin lithium strip with poor toughness and soft texture is wrapped with the separators on both sides, the strength of the metal lithium strip is enhanced, the prepared composite lithium strip can match the existing battery manufacturing equipment and be wound, and the lithium strip will not be broken or stick to the roller under the wrapping of the separators with high toughness.

Description

Technical Field

[0001] This invention relates to the field of lithium batteries, specifically to a composite lithium strip, a lithium metal battery, and a preparation method thereof. Background Technology

[0002] To improve the power density of batteries, ultra-thin positive electrodes capable of high-rate discharge and ultra-thin negative electrodes with matching capacity are required. In systems that match current lithium-containing positive electrode materials, lithium negative electrodes are inevitably in large excess. Therefore, it is necessary to reduce the amount of lithium negative electrodes and decrease their ineffective mass to further improve the mass energy density of lithium metal batteries. The ultra-thinning of lithium strips (less than 100 μm) is an inevitable trend.

[0003] Lithium metal is soft, highly ductile, and has low specific strength. The thinner the lithium strip, the lower its processability and strength, and the more prone it is to breakage, deformation, and sticking to rollers. Lithium is also chemically reactive, readily reacting with moisture in the air, leading to a decline in its performance. Therefore, the manufacturing of lithium metal batteries cannot be integrated with existing battery manufacturing equipment and cannot be carried out continuously in air-exposed conditions, hindering the commercial development of lithium metal batteries.

[0004] Existing technologies extend the lifespan of lithium batteries by processing coatings onto lithium strips. However, artificially manufactured structures similar to SEI films do not alter the flexibility of lithium strips and cannot be used in ordinary environments with high water content. Summary of the Invention

[0005] The purpose of this invention is to provide a method for manufacturing composite lithium strips that is compatible with existing winding equipment, and to further process the composite lithium strips into lithium batteries in an indoor atmospheric environment.

[0006] To achieve the above objectives, the present invention provides a method for preparing a composite lithium strip, comprising:

[0007] In a dry environment, a diaphragm is rolled onto a lithium strip, the diaphragm comprising a first diaphragm and a second diaphragm, which are respectively rolled onto the upper and lower surfaces of the lithium strip;

[0008] An adhesive is applied to the edges of the inner surfaces of the first diaphragm and the second diaphragm, so that the first diaphragm and the second diaphragm are bonded together and completely cover the lithium strip, thus obtaining a composite lithium strip;

[0009] The composite lithium strip is wound up.

[0010] Optionally, the outer surface of the diaphragm is subjected to hydrophobic treatment, including: immersing the diaphragm in a hydrophobic agent, or spraying a hydrophobic agent onto the outer surface of the diaphragm, and finally drying the diaphragm.

[0011] Optionally, the hydrophobic agent is a silane coupling agent.

[0012] Optionally, ceramic powder, cellulose, or a solid electrolyte may be coated on the inner surface of the diaphragm.

[0013] Optionally, the tabs are machined onto the diaphragm or the lithium strip before rolling.

[0014] Optionally, the first diaphragm and the second diaphragm are bonded together using a micro-pressure device.

[0015] Optionally, the width of the diaphragm is greater than that of the lithium strip.

[0016] The present invention also provides a composite lithium strip, prepared by the above method, comprising a lithium strip and a separator, wherein the separator comprises a first separator covering the upper surface of the lithium strip and a second separator covering the lower surface of the lithium strip, and the composite lithium strip is capable of being wound up.

[0017] The present invention also provides a method for preparing a lithium metal battery, comprising: preparing a composite lithium strip by the above method, compounding a positive electrode material under indoor conditions, winding, cutting and packaging the composite lithium strip to obtain a lithium metal battery.

[0018] The present invention also provides a lithium metal battery prepared by the above method.

[0019] The beneficial effects of this invention are as follows:

[0020] (1) By using the method provided by the present invention, a separator is wrapped on both sides of an ultra-thin lithium strip with poor toughness and soft texture, which can enhance the strength of the metal lithium strip. The resulting composite lithium strip can be matched with existing battery manufacturing equipment and wound. The lithium strip will not break or stick to the roller when wrapped with a tough separator.

[0021] (2) The diaphragm is hydrophobically treated so that the lithium strip under the protection of the diaphragm can be protected from the interference of moisture in the air. The rewound composite lithium strip can be processed in the air without having to keep the processing environment dry at all times.

[0022] (3) The method for preparing composite lithium strip provided by the present invention is compatible with existing lithium battery manufacturing equipment, is simple to operate, saves costs, and facilitates subsequent work such as winding and packaging, thereby realizing continuous production of lithium metal batteries. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the composite lithium strip preparation process of the present invention.

[0024] In the figure, 1-outer surface of the diaphragm, 2-inner surface of the diaphragm, 3-coating roller, 4-lithium belt, 5-roll press, 6-micro pressure device, 7-automatic winding equipment, 8-tab. Detailed Implementation

[0025] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. 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.

[0026] In the description of this invention, it should be noted that the terms "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0027] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0028] In existing technologies, thick lithium blocks are pressed into thin lithium strips using a roller press in a dry environment. The lithium strips are then cut and assembled layer by layer with positive electrode sheets and separators to form lithium metal batteries. Because the lithium strips need to be processed in a dry environment with a dew point above -30°C, and the equipment for processing lithium batteries is very large, the energy consumption in low-water environments is enormous.

[0029] This invention provides a method for preparing composite lithium strips. This method is compatible with existing lithium battery processing equipment, and the resulting composite lithium strips can be directly further processed into lithium metal batteries under normal conditions. Figure 1 As shown, the method for preparing the composite lithium strip provided by the present invention includes:

[0030] Step 1: In a dry environment, roll the diaphragm 2 onto the lithium belt 4.

[0031] The diaphragm includes a first diaphragm and a second diaphragm, with the first diaphragm roller pressed against the upper surface of the lithium strip and the second diaphragm roller pressed against the lower surface of the lithium strip.

[0032] The width of the separator is greater than that of the lithium strip. In some embodiments, the width of the lithium strip is 55 mm, and the width of the separator is 61 mm to 65 mm. The thickness of the lithium strip is 50 μm to 150 μm, and the thickness of the separator is 25 μm.

[0033] The lithium strip can be a pure metallic lithium strip, an alloy lithium strip, or a lithium strip coated on a metal foil. For sodium batteries, it can also be a sodium strip or its extension strip.

[0034] In some embodiments, the first diaphragm and the second diaphragm are respectively rolled onto the upper and lower surfaces of the lithium strip 4 by a roller press 5, and the spacing of the roller press 5 is the sum of the thicknesses of the lithium strip and the diaphragm.

[0035] The tab 8 can be attached to one side of the separator with polymer adhesive before rolling or pre-pressed onto the fixed position of the lithium strip. The tab 8 can be nickel, nickel mesh, nickel-plated copper, carbon cloth, carbon mesh, or a full tab of metal sheet. For high-power electrodes, a full tab of thin metal sheet is preferred.

[0036] Step 2: Apply adhesive to the edge of the inner surface 2 of the diaphragm.

[0037] An adhesive is applied to the edges of the inner surfaces of the first and second diaphragms, bonding them together to completely cover the lithium strip, thus obtaining a composite lithium strip. The adhesive application step can also be performed before the diaphragms are rolled onto the lithium strip.

[0038] In some embodiments, the edges of the upper and lower diaphragms are bonded together using a micro-pressure device 6. By adjusting the pressure of the micro-pressure device 6, the distance between the micro-pressure devices 6 can be adjusted so that the distance between the micro-pressure devices 6 is equal to the sum of the thicknesses of the first and second diaphragms, thus sealing the edges and ensuring that the first and second diaphragms are connected by a polymer adhesive to isolate moisture from the air.

[0039] Before applying the adhesive, the outer surface 1 of the separator is treated with a hydrophobic agent. This can be done by immersing the separator in the hydrophobic agent or by spraying the hydrophobic agent onto the outer surface 1 of the separator, followed by drying the separator. Because the outer surface 1 of the separator is hydrophobic, it can prevent moisture in the air from corroding the lithium strip. Preferably, the hydrophobic agent is a silane coupling agent.

[0040] In some embodiments, before applying the adhesive, the inner surface 2 of the separator is coated with ceramic powder, cellulose, or a solid electrolyte, especially a solid electrolyte such as a sulfide solid electrolyte, a polymer solid electrolyte, or an oxide solid electrolyte. These solid electrolytes can not only ensure good contact between the separator and the lithium band and accelerate lithium-ion transport, but also effectively reduce lithium dendrite formation and improve the safety of lithium metal batteries due to the rigidity of the solid electrolyte.

[0041] The adhesive can be applied to the edge of the inner surface 2 of the diaphragm using an application roller 3, with a coating width of 1mm-10mm, preferably 2-5mm.

[0042] In some embodiments, the adhesive is one or more of PVDF, PVDF-HFP, CMC, SBR, polyimide, or PTFE, preferably polyimide double-sided adhesive.

[0043] Step 3: Wind up the composite lithium strip.

[0044] The present invention also provides a method for preparing a lithium metal battery, comprising: taking the composite lithium strip obtained in step 3 out of the dry environment and carrying out automated manufacturing of the lithium metal battery under indoor conditions without special treatment; and performing processes such as winding, cutting, and packaging of cylindrical or square batteries according to the electrode positive electrode sheet compounding to obtain different lithium metal batteries.

[0045] Example 1

[0046] First, in the drying chamber, nickel tabs (20mm wide, 75mm long) are pre-pressed onto a 150µm thick lithium strip (55mm wide) according to capacity calculations. The lithium strip is then fixed to a lithium strip support. A 25µm thick separator (61mm wide, cellulose-coated inner surface, hydrophobic outer surface) is placed on a separator holder, with the inner surfaces of the two separator rolls facing the lithium strip, positioning the lithium strip in the center. A 2mm wide polyimide adhesive is then applied to the separator edges. The distance between the rollers of the pressure roller press is adjusted to 200-210µm to ensure a tight fit between the separator and the lithium strip. A micro-pressure device (6) is used to further bond the edges of the two separator rolls. Finally, the separator is wound up. The wound composite lithium strip can be taken out of the drying chamber and used for automated manufacturing of lithium metal batteries under indoor conditions without special treatment. Depending on the electrode positive electrode, the process includes winding, cutting, and packaging of cylindrical or prismatic batteries to produce different models and types of lithium metal batteries.

[0047] Example 2

[0048] First, in the drying chamber, nickel tabs (20mm wide, 75mm long) are pre-pressed onto a 100µm thick lithium strip (55mm wide) according to capacity calculations. The lithium strip is then fixed to a lithium strip support. A separator (61mm wide, 25µm thick) with an inner cellulose coating and a hydrophobic outer layer is placed on a separator holder, ensuring the inner surfaces of the two separator rolls face the lithium strip, positioning the lithium strip in the center. A 2mm wide polyimide adhesive is then applied to the separator edges. The distance between the rollers of the pressure roller press is adjusted to 150-160µm to ensure a tight fit between the separator and the lithium strip. A micro-pressure device (6) is used to further bond the edges of the two separator rolls. Finally, the separator is wound up. The wound composite lithium strip can then be taken out of the drying chamber for automated lithium metal battery manufacturing under indoor conditions without special treatment. Depending on the electrode positive electrode, the process includes winding, cutting, and packaging of cylindrical or prismatic batteries to produce different models and types of lithium metal batteries.

[0049] Example 3

[0050] First, in the drying chamber, nickel tabs (20mm wide, 75mm long) are pre-pressed onto a 50µm thick lithium strip (55mm wide), based on capacity calculations. The lithium strip is then fixed to a lithium strip support. A 65mm wide, 25µm thick separator, coated with sulfide solid electrolyte powder on the inner surface and hydrophobic on the outer surface, is placed on a separator holder, with the inner surfaces of the two separator rolls facing the lithium strip, positioning the lithium strip in the center. A 3mm wide polyimide adhesive is then applied to the edges of the separator. The distance between the rollers of the pressure roller press is adjusted to 100-110µm to ensure a tight fit between the separator and the lithium strip. A micro-pressure device (6) is used to further bond the edges of the two separator rolls, and finally, the strip is wound up. The wound composite lithium strip can then be taken out of the drying chamber for automated lithium metal battery manufacturing under indoor conditions without special treatment. Depending on the electrode positive electrode, the process includes winding, cutting, and packaging of cylindrical or prismatic batteries to produce different models and types of lithium metal batteries.

[0051] A 100µm lithium strip without diaphragm coating was used as a comparative example, and compared with the lithium strips in Examples 1-3, which were taken out of the drying room. The specific results are shown in the table below:

[0052]

[0053] By comparison, the composite lithium strip sealed with a diaphragm can effectively isolate the internal metallic lithium from the corrosion of the metal by moisture in the air. Compared with the metallic lithium strip without a diaphragm seal, it can be taken out of the drying room, is compatible with the existing environment of current lithium-ion battery manufacturing equipment, can be carried out continuously, and can save the energy that needs to be prepared in the drying room in all steps, thus achieving the goal of energy conservation and emission reduction for enterprises.

[0054] In summary, the method provided by this invention can enhance the strength of a thin lithium strip with poor toughness and soft texture by wrapping a separator on both sides. The resulting composite lithium strip can be matched with existing battery manufacturing equipment and wound. Under the wrapping of the tough separator, the lithium strip will not break or stick to the roller.

[0055] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A method for preparing a composite lithium strip, characterized in that, include: The outer surface of the diaphragm is treated with a hydrophobic coating; In a dry environment, a diaphragm is rolled onto a lithium strip. The diaphragm includes a first diaphragm and a second diaphragm, which are rolled onto the upper and lower surfaces of the lithium strip, respectively. The width of the diaphragm is greater than the width of the lithium strip. An adhesive is applied to the edges of the inner surfaces of the first diaphragm and the second diaphragm, so that the first diaphragm and the second diaphragm are bonded together and completely cover the lithium strip, thus obtaining a composite lithium strip; The composite lithium strip is wound up.

2. The method for preparing the composite lithium strip as described in claim 1, characterized in that, The outer surface of the diaphragm is subjected to hydrophobic treatment, which includes: immersing the diaphragm in a hydrophobic agent, or spraying a hydrophobic agent onto the outer surface of the diaphragm, and finally drying the diaphragm.

3. The method for preparing the composite lithium strip as described in claim 2, characterized in that, The hydrophobic agent is a silane coupling agent.

4. The method for preparing the composite lithium strip as described in claim 1, characterized in that, The inner surface of the diaphragm is coated with ceramic powder, cellulose, or a solid electrolyte.

5. The method for preparing the composite lithium strip as described in claim 1, characterized in that, Before rolling, the tabs are processed onto the diaphragm or the lithium strip.

6. The method for preparing the composite lithium strip as described in claim 1, characterized in that, The first diaphragm and the second diaphragm are bonded together using a micro-pressure device.

7. A composite lithium strip, characterized in that, Prepared by the method according to any one of claims 1-6, comprising a lithium strip and a separator, the separator comprising a first separator covering the upper surface of the lithium strip and a second separator covering the lower surface of the lithium strip, the composite lithium strip being capable of being wound up.

8. A method for preparing a lithium metal battery, characterized in that, include: After preparing the composite lithium strip by the method described in any one of claims 1-6, the positive electrode material is compounded, and the composite lithium strip is wound, cut, and packaged under indoor conditions to obtain a lithium metal battery.

9. A lithium metal battery, characterized in that, Prepared by the method as described in claim 8.

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