Graphene film current collector welded battery cell, lithium battery and preparation method

Abstract

The application discloses a graphene film current collector welded battery cell, a lithium battery and a preparation method. The preparation method comprises the following steps: performing punching treatment on tab regions of a graphene film current collector laminated battery cell to form a plurality of through holes; each layer of the through holes of the tab regions of the graphene film current collector laminated battery cell after the punching treatment corresponds to each other, metal solder is inserted between through hole regions of two adjacent layers of the graphene film current collector laminated battery cell, the metal solder covers the through hole regions, and a graphene film current collector laminated battery cell with inserted metal solder is obtained; the tab regions of the graphene film current collector laminated battery cell with inserted metal solder are aligned with metal tabs, welding is performed by using a high-frequency resistance welding mode, and cooling is performed to room temperature, so that a graphene film current collector welded battery cell is obtained; and the application is compatible with existing lithium battery production equipment, and provides technical support for industrialized mass production of high-performance graphene film current collector lithium batteries.

Description

Technical Field

[0001] This invention relates to the field of lithium battery manufacturing and welding technology, and in particular to graphene film current collector welding cells, lithium batteries and their preparation methods. Background Technology

[0002] Traditional lithium-ion batteries typically use copper foil (negative electrode) and aluminum foil (positive electrode) as current collectors. However, these metal current collectors suffer from drawbacks such as high density, limited thermal conductivity, and insufficient chemical stability, making it difficult to meet the demands of high-performance lithium-ion batteries for lightweight design and high safety. Graphene film, as a novel non-metallic current collector, possesses excellent properties such as lightweight, high thermal conductivity, high electrical conductivity, and high chemical stability. Its application in lithium-ion batteries can significantly reduce battery weight, increase energy density, and enhance thermal management and cycle stability, demonstrating broad application prospects.

[0003] However, graphene films, being carbon materials, lack metallic active sites on their surface, resulting in poor compatibility with metal tabs and making reliable connection impossible using the ultrasonic welding methods commonly employed with traditional metal current collectors. This welding technology bottleneck hinders the efficient and stable connection of graphene film current collectors with metal tabs, significantly impeding their large-scale application and mass production in lithium-ion batteries. Currently, research on welding methods for graphene film current collectors and metal tabs is limited, and a mature industrial solution has not yet been developed. Therefore, developing a reliable, efficient welding method compatible with existing production equipment is crucial for promoting the application of graphene film current collectors in the lithium-ion battery field. Summary of the Invention

[0004] The purpose of this invention is to provide a graphene film current collector welded battery cell, a lithium battery, and a preparation method thereof, overcoming the welding difficulties between the graphene film current collector and the metal tab in the prior art. By rationally designing the through-hole structure, selecting suitable metal solder, and optimizing the welding parameters, a firm connection between the graphene film current collector and the metal tab is achieved, ensuring good conductivity and stability at the battery tab welding point, which helps to improve the overall performance and production efficiency of graphene film current collector lithium batteries.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for preparing a graphene film current collector welded battery cell, comprising the following steps: The tab area of ​​the graphene film current collector stacked battery cell is perforated to form several through holes; the number of positive electrode layers in the graphene film current collector stacked battery cell is 1-60, and the number of negative electrode layers is one more than the number of positive electrode layers. After the perforation process, each layer of the tab area of ​​the graphene film current collector stacked battery cell has a corresponding through hole. Metal solder is inserted between the through hole areas of two adjacent layers of the graphene film current collector stacked battery cell. The metal solder covers the through hole area and forms a riveting structure with the tab of the graphene film current collector stacked battery cell to obtain a graphene film current collector stacked battery cell with inserted metal solder. Align the tab area of ​​the graphene film current collector stacked cell with the metal tab inserted with the metal tab, weld it using high-frequency resistance welding, and cool it to room temperature to obtain a graphene film current collector welded cell. The diameter of the through hole is 0.1-10 mm, and the through hole penetrates the upper and lower surfaces of the tab of the graphene film current collector stack.

[0006] In some possible implementations, the metal solder needs to be polished and cleaned before insertion to remove the oxide layer; the drilling process includes mechanical drilling.

[0007] In some possible implementations, the positive and negative electrode sheets of the graphene film current collector stacked cell include a graphene film current collector and positive and negative electrode materials coated on the surface of the graphene film current collector. The graphene film current collector is prepared by forming a film from a benzene ring-containing aromatic organic precursor, followed by low-temperature carbonization and high-temperature graphitization, and finally roll pressing to obtain the final product. The low-temperature carbonization temperature is 600-2000 ℃, and the high-temperature graphitization temperature is 2000-3500 ℃. The benzene ring-containing aromatic organic precursor includes one or more combinations of polyimide, graphene oxide, aramid, or poly(p-phenylenebenzodioxazole).

[0008] In some possible implementations, the thickness of the graphene film current collector is 5-200 μm.

[0009] In some possible implementations, the number of through holes is 1-50, and the center-to-center distance between adjacent through holes is 1-50 mm; the shape of the through holes includes one or more combinations of circles, squares, rhombuses, ellipses or polygons.

[0010] In some possible implementations, the metal solder includes one or more of Sn, Cu, Zn, Al, Ag, Ti and Ni and their alloys; the metal solder is in the form of flakes, powder, wire or granules, and the flakes are 0.01-0.5 mm thick.

[0011] In some possible implementations, the high-frequency resistance welding method specifically includes: Set the welding voltage to 0.1-5 V, the current to 0.1-20 kA, the frequency to 2-50 kHz, the electrode pressure to 0.1-10 MPa, the time to 0.1-20 s, and the holding pressure to 1-10 s.

[0012] In some possible implementations, the metal tab is made of copper, aluminum, nickel or an alloy thereof, and has a thickness of 0.1-1.0 mm.

[0013] In a second aspect, the present invention provides a graphene film current collector welded battery cell, which is prepared based on the welding method of graphene film current collector stacked battery cell and metal tabs described in any one of the first aspects, and is applied in the field of graphene film current collector lithium battery.

[0014] Thirdly, the present invention also provides a graphene film current collector lithium battery, characterized in that it is prepared by the graphene film current collector welded cell described in the second aspect through subsequent packaging, liquid injection, formation, and secondary sealing.

[0015] Compared with the prior art, the present invention has the following beneficial effects: (1) Solving the welding dilemma: In the prior art, when graphene film is used as a current collector, the welding process is difficult to complete by conventional ultrasonic welding. This invention uses through holes, metal solder and high frequency resistance welding to achieve rapid melting of metal solder and rapid welding of multilayer current collectors; The existing technology CN 119650713 A uses a method of melting solder by filling through holes with low-melting-point metal and binder, followed by hot-press welding. This is equivalent to heating the solder for welding, which makes it difficult for the solder to melt and fill the through holes. It requires a long hot-pressing time, and the temperature is difficult to transfer after multiple layers, resulting in slow efficiency and poor welding effect. However, this invention uses a different method of melting solder - high-frequency resistance welding. That is, the instantaneous Joule heat generated by the current is used to melt the solder and form a connection with the metal tab. By drilling holes in the current collector tab part of the graphene film and filling them with metal solder, the defect of poor compatibility between graphene film as a carbon material and metal tab is overcome, and reliable welding of the two is achieved, breaking through the technical bottleneck that traditional ultrasonic welding cannot be applied.

[0016] Traditional pure ultrasonic welding can easily damage the hole edges of the current collector, reducing the overall strength after welding. The high-frequency resistance welding of this invention utilizes the high conductivity and thermal conductivity of the graphene film current collector. Resistance welding can quickly melt the solder for welding, which is a welding method for specific current collector batteries.

[0017] (2) Excellent welding performance: The metal solder penetrates into the through hole and the contact interface to form a strong metallurgical joint. The tensile breaking strength of the welded joint is ≥5 MPa and the volume resistivity is ≤2×10 -6 Ω·m, which can meet the long-term use requirements of lithium batteries.

[0018] (3) High flexibility: The number, shape, and diameter of the through holes, the type and form of the solder, and the welding parameters can all be adjusted according to the type of graphene film precursor, the number of current collector layers, and the material of the metal tabs, to meet the production needs of different specifications of lithium batteries. Attached Figure Description

[0019] Figure 1 A schematic diagram of the perforated tab structure of the graphene film current collector stacked battery cell provided by the present invention; Figure 2 A schematic diagram of the stacking of solder and the current collector of the graphene film after drilling, provided by the present invention, in the tab area of ​​the stacked battery cell. Figure 3 A schematic diagram of the welded joint cross-section after welding is completed, provided for the present invention.

[0020] Among them, 1-graphene film current collector stacked cell, 2-the tab area of ​​the graphene film current collector stacked cell after drilling, 3-metal solder, 4-metal tab, 5-the through hole area after welding (metal solder fills the through hole area after welding), 11-the tab area. Detailed Implementation

[0021] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application. Furthermore, in the description of the embodiments of this application, the terms "first," "second," etc., are only used for distinguishing descriptions and should not be construed as indicating or implying relative importance. Therefore, features defined with "first" or "second" may explicitly or implicitly include one or more features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0022] Example 1 This embodiment provides a graphene film current collector welding battery cell, the preparation method of which includes the following steps: Mechanical perforation is performed on the tab area of ​​the graphene film current collector stacked battery cell to form several through holes; the positive electrode layer of the graphene film current collector stacked battery cell has 5 layers, and the negative electrode layer has one more layer than the positive electrode layer. It should be noted that the graphene film current collector stacked cell is obtained by stacking layers of negative electrode sheet, separator sheet, positive electrode sheet, separator sheet, negative electrode sheet, and so on. The positive and negative electrode sheets include two regions: one is the coating area of ​​positive and negative electrode materials, and the other is the uncoated tab area.

[0023] The positive and negative electrode sheets of the graphene film current collector laminated battery cell include a graphene film current collector and positive and negative electrode materials coated on the graphene film current collector. The graphene film current collector is prepared by using polyimide as a precursor, followed by low-temperature carbonization and high-temperature graphitization treatments, and finally roll pressing to obtain the final product. The low-temperature carbonization temperature is 1000 ℃, the high-temperature graphitization temperature is 2900 ℃, and the thickness is 17 μm. The pore diameter is 3 mm, and the pores penetrate the upper and lower surfaces of the tab area of ​​the graphene film current collector laminated battery cell. There are 3 pores, which are circular in shape, and the center-to-center distance between adjacent pores is 5 mm. Figure 1 As shown.

[0024] After perforation, each layer of the graphene film current collector laminated battery cell has a corresponding through-hole in its tab region. Metal solder is inserted between the through-hole regions of two adjacent graphene film current collector laminated battery cells, covering the through-hole regions. The metal solder forms a riveting structure with the tabs of the graphene film current collector laminated battery cell, resulting in a graphene film current collector laminated battery cell with inserted metal solder. Figure 2 As shown; the metal solder is an Al sheet with a thickness of 13 μm, which needs to be polished and cleaned before insertion to remove the oxide layer.

[0025] The tab area of ​​the graphene film current collector stacked cell with inserted metal solder is aligned with the metal tab, and welding is performed using high-frequency resistance welding. The welding voltage is set to 2 V, the current to 0.1 kA, the frequency to 10 kHz, the electrode pressure to 1.2 MPa, the time to 0.1 s, the holding pressure to 3 s, and then cooled to room temperature to obtain the graphene film current collector welded cell. Figure 3 As shown. In this embodiment, the metal tab is made of aluminum and has a thickness of 0.1 mm.

[0026] Example 2 This embodiment provides a graphene film current collector welding battery cell, the preparation method of which includes the following steps: Mechanical perforation is performed on the tab area of ​​the graphene film current collector stacked battery cell to form several through holes; the positive electrode layer of the graphene film current collector stacked battery cell has 12 layers, and the negative electrode layer has one more layer than the positive electrode layer. The positive and negative electrode sheets of the graphene film current collector laminated battery cell include a graphene film current collector and positive and negative electrode materials coated on the graphene film current collector. The graphene film current collector is prepared by using graphene oxide as a precursor, followed by low-temperature carbonization and high-temperature graphitization treatments, and finally roll pressing to obtain the final product. The low-temperature carbonization temperature is 1300 ℃, the high-temperature graphitization temperature is 3000 ℃, and the thickness is 32 μm. The pore diameter is 2 mm, and the pores penetrate the upper and lower surfaces of the tab area of ​​the graphene film current collector laminated battery cell. There are 6 pores in total, with a square shape, and the center-to-center distance between adjacent pores is 4 mm. Figure 1 As shown.

[0027] After perforation, each layer of the graphene film current collector stacked cell has a corresponding through hole in the tab area. Metal solder is inserted between the through hole areas of two adjacent graphene film current collector stacked cells, covering the through hole areas. The metal solder and the tab of the graphene film current collector stacked cell form a riveting structure, resulting in a graphene film current collector stacked cell with inserted metal solder. The metal solder is Al foil with a thickness of 20 μm, which needs to be polished and cleaned before insertion to remove the oxide layer.

[0028] The tab area of ​​the graphene film current collector laminated cell with inserted metal solder is aligned with the metal tab, and welding is performed using high-frequency resistance welding. The welding voltage is set to 5 V, the current to 4 kA, the frequency to 20 kHz, the electrode pressure to 0.8 MPa, the time to 0.3 s, and the holding time to 4 s, resulting in a graphene film current collector welded cell. In this embodiment, the metal tab is made of aluminum with a thickness of 0.2 mm.

[0029] Example 3 This embodiment provides a graphene film current collector welding battery cell, the preparation method of which includes the following steps: Mechanical perforation is performed on the tab area of ​​the graphene film current collector stacked battery cell to form several through holes; the positive electrode layer of the graphene film current collector stacked battery cell has 20 layers, and the negative electrode layer has one more layer than the positive electrode layer. The positive and negative electrode sheets of the graphene film current collector laminated battery cell include a graphene film current collector and positive and negative electrode materials coated on the graphene film current collector. The graphene film current collector is prepared by using polyimide as a precursor, followed by low-temperature carbonization and high-temperature graphitization treatments, and finally roll pressing to obtain the final product. The low-temperature carbonization temperature is 1500 ℃, the high-temperature graphitization temperature is 3100 ℃, and the thickness is 25 μm. The pore diameter is 2 mm, and the pores penetrate the upper and lower surfaces of the tab area of ​​the graphene film current collector laminated battery cell. There are 10 pores in total, and they are circular in shape. The center-to-center distance between adjacent pores is 3 mm. Figure 1 As shown.

[0030] After perforation, each layer of the graphene film current collector stacked cell has a corresponding through hole in the tab area. Metal solder is inserted between the through hole areas of two adjacent graphene film current collector stacked cells, covering the through hole area. The metal solder and the tab of the graphene film current collector stacked cell form a riveting structure, resulting in a graphene film current collector stacked cell with inserted metal solder. The metal solder is a Sn-Ag-Cu alloy sheet with a thickness of 100 μm, which needs to be polished and cleaned before insertion to remove the oxide layer.

[0031] The tab area of ​​the graphene film current collector stacked cell with inserted metal solder is aligned with the metal tab, and welding is performed using high-frequency resistance welding. The welding voltage is set to 4 V, the current to 10 kA, the frequency to 25 kHz, the electrode pressure to 2.5 MPa, the time to 1 s, and the holding time to 5 s, resulting in a graphene film current collector welded cell. In this embodiment, the metal tab is made of nickel-plated copper with a thickness of 0.2 mm.

[0032] The following tests were performed on the welded joints of the graphene film current collector welding cells of Examples 1-3: Resistivity Testing: A four-wire method was used for micro-resistance testing. Two current probes of a constant DC power supply were connected to the free end of the electrode tab and a current collector 10-20 mm outside the welding area, respectively. Voltage measuring probes were connected to the two boundaries of the welding area along the current direction, ensuring the voltage sampling point was inside the current injection point. A constant DC current I was applied, and the voltage drop U between the voltage probes was measured. The distance d between the voltage measuring probes was recorded, and the resistivity at the weld joint was calculated using a formula. Five valid test data points were taken from each sample group, and the average value was calculated. Peel strength test: The peel strength of the electrode tab weld joint was tested using a universal testing machine with a 180° peel test method. Electrode and tab samples containing the weld area were cut, with a sample length ≥100 mm. The free end of the tab was bent 180° in the opposite direction and fixed with a clamp. The electrode portion was fixed to a rigid stainless steel plate with double-sided tape, and the clamp held the free end of the tab. The testing machine peeled at a constant speed of 50 mm / min, and the peel force curve was recorded in real time. The average force value of the relatively stable segment in the middle of the peel curve was taken. Peel strength = average peel force (N) / tab width (cm). Each group of samples was tested 5 times, and the average value was taken. Fracture strength test: The axial tensile test method was used. The electrode portion was fixed to the lower clamp of the universal testing machine, and the electrode lugs were extended vertically and clamped to the upper clamp. The initial clamp spacing was set to 50 mm. The testing machine applied a constant tensile force at a tensile speed of 1 mm / min, and the tensile force-displacement curve was recorded until the specimen fractured. The maximum force value and fracture location were recorded. Each group of samples was tested 5 times, and the average value was taken.

[0033] The graphene film current collector welded cells of Examples 1-3 were subsequently packaged, injected with electrolyte, formed, and sealed to obtain the graphene film current collector lithium batteries of Examples 1-3. The internal resistance of the graphene film current collector lithium batteries of Examples 1-3 was tested.

[0034] The results of all the above tests are shown in Table 1. The fracture location is on the graphene film current collector, indicating that the strength of the welded joint is higher than that of the current collector itself. The test results show that this method has a good welding effect on the multilayer graphene film current collector stacked battery cell. A reliable connection is formed between the graphene film current collector stacked battery cell and the metal tab, which has good electrical conductivity and a stable mechanical structure.

[0035] Table 1. Resistivity, peel strength, fracture strength, and internal resistance of graphene film current collector stacked cells after welding. Obviously, those skilled in the art can make various modifications and variations to the embodiments of the present invention without departing from the spirit and scope of the invention. Therefore, if these modifications and variations fall within the scope of the claims of the present invention and their equivalents, the present invention also intends to include these modifications and variations.

Claims

1. A method for preparing a graphene film current collector welded battery cell, characterized in that, Includes the following steps: The tab area of ​​the graphene film current collector stacked battery cell is perforated to form several through holes; the number of positive electrode layers in the graphene film current collector stacked battery cell is 1-60, and the number of negative electrode layers is one more than the number of positive electrode layers. After the perforation process, each layer of the tab region of the graphene film current collector stacked battery cell has a corresponding through hole. Metal solder is inserted between the through hole regions of two adjacent layers of the graphene film current collector stacked battery cell. The metal solder covers the through hole region and forms a riveting structure with the graphene film current collector stacked battery cell to obtain a graphene film current collector stacked battery cell with inserted metal solder. Align the tab area of ​​the graphene film current collector stacked cell with the metal tab inserted with the metal tab, weld it using high-frequency resistance welding, and cool it to room temperature to obtain a graphene film current collector welded cell. The diameter of the through hole is 0.1-10 mm, and the through hole penetrates the upper and lower surfaces of the tab of the graphene film current collector stack.

2. The method for preparing a graphene film current collector welding battery cell according to claim 1, characterized in that, The metal solder needs to be polished and cleaned before insertion to remove the oxide layer; the drilling process includes mechanical drilling.

3. The method for preparing a graphene film current collector welding battery cell according to claim 1, characterized in that, The positive and negative electrode sheets of the graphene film current collector stacked battery cell include a graphene film current collector and positive and negative electrode materials coated on the surface of the graphene film current collector. The graphene film current collector is prepared by forming a film from a benzene ring-containing aromatic organic precursor, followed by low-temperature carbonization and high-temperature graphitization, and finally roll pressing to obtain the final product. The low-temperature carbonization temperature is 600-2000 ℃, and the high-temperature graphitization temperature is 2000-3500 ℃. The benzene ring-containing aromatic organic precursor includes one or more combinations of polyimide, graphene oxide, aramid, or poly(p-phenylenebenzodioxazole).

4. The method for preparing a graphene film current collector welding battery cell according to claim 3, characterized in that, The thickness of the graphene film current collector is 5-200 μm.

5. The method for preparing a graphene film current collector welding battery cell according to claim 1, characterized in that, The number of through holes is 1-50, and the center-to-center distance between adjacent through holes is 1-50 mm; the shape of the through holes includes one or more combinations of circles, squares, rhombuses, ellipses or polygons.

6. The method for preparing a graphene film current collector welding battery cell according to claim 1, characterized in that, The metal solder includes one or more of Sn, Cu, Zn, Al, Ag, Ti and Ni and their alloys; the metal solder is in the form of flakes, powder, wire or granules, and the flakes are 0.01-0.5 mm thick.

7. The method for preparing a graphene film current collector welding battery cell according to claim 1, characterized in that, The high-frequency resistance welding method specifically includes: Set the welding voltage to 0.1-5 V, the current to 0.1-20 kA, the frequency to 2-50 kHz, the electrode pressure to 0.1-10 MPa, the time to 0.1-20 s, and the holding pressure to 1-10 s.

8. The method for preparing a graphene film current collector welding battery cell according to claim 1, characterized in that, The metal tabs are made of copper, aluminum, nickel or their alloys, and have a thickness of 0.1-1.0 mm.

9. A graphene film current collector welded battery cell, prepared based on the welding method of graphene film current collector laminated battery cell and metal tabs according to any one of claims 1-8, characterized in that, It is applied in the field of graphene film current collector lithium batteries.

10. A graphene film current collector lithium battery, characterized in that, The graphene film current collector welding cell described in claim 9 is prepared by subsequent encapsulation, liquid injection, formation, and secondary sealing.

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