Lithium strip splicing method and lithium strip

Abstract

The invention discloses a lithium strip splicing method and a lithium strip, and belongs to the technical field of lithium battery materials. The lithium strip splicing method comprises the following steps that to-be-spliced ends of two to-be-spliced basic lithium strips are in lap joint, and the lap joint is welded in an ultrasonic welding mode; wherein the welding process is carried out under the conditions that the environment dew point is less than or equal to-40 DEG C and the room temperature; the resonant frequency for welding is 15KHz-60KHz, and the amplitude is greater than or equal to 6 microns and less than or equal to 10% of the thickness of the lithium strip; the welding pressure ranges from 0.01 MPa to 1 MPa, and the welding time is smaller than or equal to 9.99 s. The method is simple, easy to operate, efficient, energy-saving, high in safety and capable of obtaining stable welding quality. According to the method, the spliced lithium strip with good splicing strength and uniform thickness can be obtained, the spliced lithium strip can be further used for preparing a lithium battery, the production cost of the lithium battery can be reduced, and the economic benefit is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium battery materials, and in particular to a lithium ribbon splicing method and a lithium ribbon. Background Art

[0002] With the continuous development of new energy technologies, people's demand for high-energy-density lithium-ion batteries is becoming more and more urgent. The academic and business communities continue to invest resources to try to develop batteries with higher energy density. Solid-state batteries, lithium-sulfur batteries, and lithium-air batteries are considered to be the development direction of the next generation of high-energy-density batteries. The lithium metal used in the negative electrode of these batteries plays a key role. However, due to the special properties of lithium metal, the processing cost and processing efficiency of metal lithium strips are still one of the factors limiting the application of lithium metal negative electrodes.

[0003] At present, the mechanical extrusion-calendering method is commonly used to produce metal lithium ribbons. Lithium metal itself is relatively soft in texture. During the processing, it is often affected by internal or external factors. Lithium ribbons are often prone to defects or even broken. On the other hand, in downstream applications, battery manufacturing customers often have requirements for the continuity of lithium ribbons due to quality and efficiency requirements, such as requiring 1,000 meters or 1,500 meters of continuous rolls. In the production process of lithium ribbons, if the entire roll of lithium ribbon is discarded due to local defects or broken ribbons, it will seriously affect production efficiency and production costs.

[0004] In view of this, the present invention is proposed. Summary of the invention

[0005] The object of the present invention is to provide a lithium ribbon splicing method and a lithium ribbon to solve or improve the above technical problems.

[0006] The present invention can be implemented like this:

[0007] In a first aspect, the present invention provides a lithium ribbon splicing method, which comprises the following steps: overlapping the ends of two basic lithium ribbons to be spliced, and welding the overlapped portions by ultrasonic welding;

[0008] The welding process is carried out under the condition of ambient dew point ≤-40℃ and room temperature;

[0009] The resonant frequency used for welding is 15KHz~60KHz, the welding amplitude is ≥6μm and when the thickness of the basic lithium strip is ≥60μm, the welding amplitude is ≤10% of the thickness of the basic lithium strip; the welding pressure is 0.01MPa~1MPa, and the welding time is ≤9.99s.

[0010] In an alternative embodiment, the thickness of the lithium ribbon is 20 μm to 3 mm.

[0011] In an optional embodiment, the resonant frequency used for welding is 20KHz to 40KHz;

[0012] and / or, the welding pressure is 0.05 MPa to 0.5 MPa;

[0013] And / or, the welding time is 0.01s to 1s.

[0014] In an optional embodiment, the welding input energy is ≤2500J, preferably ≤1200J.

[0015] In an optional embodiment, the material of the ultrasonic mold includes aluminum alloy, titanium alloy, hard alloy steel or polymer resin.

[0016] In an optional embodiment, the polymer resin includes at least one of epoxy resin, TPU resin and phenolic resin.

[0017] In an optional embodiment, an isolation film is firstly provided on each contact surface between the base lithium strip and the ultrasonic mold, and then ultrasonic welding is performed.

[0018] In an optional embodiment, the material of the isolation film includes at least one of PET, PI, BOPP, PP and PE;

[0019] In an optional embodiment, the thickness of the isolation film is 25 μm to 150 μm, preferably 50 μm to 100 μm.

[0020] In an optional embodiment, anti-sticking oil is firstly coated on each contact surface between the base lithium strip and the ultrasonic mold, and then ultrasonic welding is performed.

[0021] In an alternative embodiment, the anti-sticking oil includes at least one of silicone oils, lipids, palm oil and white oil.

[0022] In an optional embodiment, the silicone oil includes at least one of dimethyl silicone oil, diethyl silicone oil, diphenyl silicone oil, cyclopentasiloxane and cyclohexasiloxane; the lipid includes at least one of dimethyl carbonate and diethyl carbonate.

[0023] In an optional embodiment, before welding, the ends of the basic lithium strips to be spliced ​​are first thinned and rolled.

[0024] In an optional embodiment, after welding, the welded spliced ​​lithium strip is subjected to thinning rolling.

[0025] In an optional embodiment, the material of the base lithium strip is metallic lithium or lithium alloy.

[0026] In an alternative embodiment, the lithium alloy includes at least one of a lithium aluminum alloy, a lithium magnesium alloy, a lithium zinc alloy, a lithium indium alloy, a lithium boron alloy, and a lithium tin alloy.

[0027] In a second aspect, the present invention provides a lithium ribbon, which is obtained by splicing at least two basic lithium ribbons using the lithium ribbon splicing method of any one of the aforementioned embodiments.

[0028] The beneficial effects of the present invention include:

[0029] This method welds two basic lithium ribbons by ultrasonic welding. The ultrasonic welding head transmits high-frequency vibration waves to the surfaces of the two basic lithium ribbons to be welded. At the joint of the basic lithium ribbons, the vibration energy is converted into heat energy by friction, so that the welding area is heated and melted to achieve atomic-level fusion. The method is simple, easy to operate, efficient, energy-saving, and safe, and can obtain stable welding quality. Through this method, a spliced ​​lithium ribbon with good splicing strength and uniform thickness can be obtained. The spliced ​​lithium ribbon can be further used to prepare lithium batteries, which can reduce the production cost of lithium batteries and improve economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0031] Figure 1 A schematic diagram of the spliced ​​portion of a spliced ​​lithium ribbon obtained by the lithium ribbon splicing method provided in Example 1;

[0032] Figure 2 A schematic diagram of the spliced ​​portion of a spliced ​​lithium ribbon obtained by the lithium ribbon splicing method provided in Example 2;

[0033] Figure 3 Schematic diagram of the spliced ​​portion of the spliced ​​lithium ribbon obtained by the lithium ribbon splicing method provided in Example 3. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0035] The lithium ribbon splicing method and the lithium ribbon provided by the present invention are specifically described below.

[0036] The inventor proposed: Lithium metal is an active metal. Even if it is placed in dry air, its surface will gradually react with trace amounts of water and nitrogen in the air to form a very thin oxide layer or nitride layer, collectively referred to as an impurity layer. Due to the existence of the impurity layer, it is difficult to achieve a dense and stable connection between two metal lithium ribbons only by conventional simple pressing methods. If there is a virtual connection area, in the subsequent application of the negative electrode of the battery, serious problems such as electrode detachment and local lithium precipitation may occur. Therefore, if the splicing of lithium ribbons is performed by simple calendering, it is difficult to ensure a dense and stable splicing between the lithium ribbons. In addition, if the splicing type lithium ribbon is prepared by filling the welding area with molten lithium liquid, it will be difficult to accurately control the amount of molten lithium liquid added, and it involves high-temperature processing, making the operation difficult.

[0037] In view of this, the present invention proposes a lithium strip splicing method, which comprises the following steps: overlapping the ends of two basic lithium strips to be spliced, and welding the overlapping parts by ultrasonic welding.

[0038] This method transmits high-frequency vibration waves to the surfaces of two basic lithium ribbons to be welded through the welding head of an ultrasonic welder. At the joint of the basic lithium ribbons, the vibration energy is converted into heat energy through friction, so that the welding area is heated and melted, achieving atomic-level fusion, thereby providing a low-cost lithium ribbon splicing method with good splicing quality, simplicity, efficiency and safety.

[0039] In some optional embodiments, the material of the basic lithium strip may be metallic lithium or a lithium alloy. That is, a basic lithium strip made of metallic lithium may be spliced ​​with a basic lithium strip made of metallic lithium, a basic lithium strip made of metallic lithium may be spliced ​​with a basic lithium strip made of a lithium alloy, or a basic lithium strip made of a lithium alloy may be spliced ​​with a basic lithium strip made of a lithium alloy.

[0040] The lithium alloy may include at least one of a lithium aluminum alloy, a lithium magnesium alloy, a lithium zinc alloy, a lithium indium alloy, a lithium boron alloy and a lithium tin alloy.

[0041] In some optional embodiments, the thickness of the basic lithium belt can be 20μm to 3mm, such as 20μm, 50μm, 100μm, 500μm, 1mm, 1.5mm, 2mm, 2.5mm or 3mm, etc., or other values ​​within the range of 20μm to 3mm. In addition, it is not excluded that the basic lithium belt can be other thicknesses outside the range of 20μm to 3mm. In actual operation, basic lithium belts of the same thickness can be used, and basic lithium belts of different thicknesses can be used for splicing, preferably with basic lithium belts of the same thickness. In addition, the widths of the basic lithium belts to be spliced ​​can be the same or different.

[0042] In some optional embodiments, the two basic lithium strips can be aligned in the length direction to ensure that the overlap is in the same straight line. For example, a clamp or positioning device can be used to ensure the accuracy of the lithium strip docking, improve production efficiency and welding quality.

[0043] In some optional embodiments, the splicing method can be splicing in the length direction or splicing in the width direction. Preferably, the splicing is used in the length direction.

[0044] The splicing method can be direct overlap, that is, the two basic lithium belts are overlapped in a certain area and welded in the overlapping area; in addition, the method of thinning and then overlapping can also be adopted. The thinning method can be that the areas of the two basic lithium belts that need to be welded are each thinned to a certain extent by a roller machine, and then the thinned areas are overlapped and welded. This method can further reduce the thickness fluctuation of the welding area and improve the welding quality.

[0045] In some optional embodiments, the welding process of the present invention is performed under the conditions of an ambient dew point ≤ -40°C and room temperature.

[0046] In some optional embodiments, the ambient dew point during welding may be -40°C, -45°C, -50°C, -55°C or -60°C, etc.

[0047] The above-mentioned "room temperature" means that no additional heating or cooling operation is performed, and the process can be performed directly under normal temperature conditions. Usually, room temperature can be understood as 10°C to 30°C, preferably around 25°C.

[0048] It should be noted that lithium metal is relatively active and tends to react in high temperature or humid environments. By controlling the welding environment within the above humidity and temperature range, it can ensure that the lithium ribbon is operated in a low humidity environment, avoiding the adverse effects of oxidation and moisture on the lithium ribbon, which is beneficial to improving the stability of the process.

[0049] In some embodiments, the resonant frequency used for welding can be 15KHz to 60KHz, such as 15KHz, 18KHz, 20KHz, 25KHz, 28KHz, 30KHz, 35KHz, 40KHz, 45KHz, 50KHz, 55KHz or 60KHz, etc., or other values ​​within the range of 15KHz to 60KHz. In some typical embodiments, the resonant frequency used for welding is 20KHz to 40KHz, such as 20KHz, 28KHz, 30KHz, 35KHz or 40KHz, etc.

[0050] The resonant frequency is determined by the natural frequency of the system, and the ultrasonic welder power is inversely related to the resonant frequency. Welding lithium metal strips requires precise control of energy input, and the welding power should not be too high or too low.

[0051] In some embodiments, the welding amplitude is ≥6 μm and when the thickness of the base lithium ribbon is ≥60 μm, the welding amplitude is ≤10% of the thickness of the base lithium ribbon.

[0052] Welding amplitude = transducer surface amplitude × modulator gain × welding head gain. The transducer surface amplitude is directly related to the resonant frequency and generally cannot be adjusted. The modulator (also called amplitude transformer) is used to adjust the amplitude. The gain ratio of the modulator can be, for example, 1:0.6, 1:1, 1:1.5 or 1:2.

[0053] In some embodiments, the welding pressure may be 0.01 MPa to 1 MPa, such as 0.01 MPa, 0.05 MPa, 0.1 MPa, 0.5 MPa, 1 MPa, 1.5 MPa, 2 MPa, 2.5 MPa or 3 MPa, or other values ​​within the range of 0.01 MPa to 1 MPa. In some typical embodiments, the welding pressure is 0.05 MPa to 0.5 MPa, such as 0.05 MPa, 0.1 MPa, 0.15 MPa, 0.2 MPa, 0.25 MPa, 0.3 MPa, 0.35 MPa, 0.4 MPa, 0.45 MPa or 0.5 MPa.

[0054] It should be noted that appropriate welding pressure can promote the fusion of the welding interface and ensure the welding quality. In addition, reducing the gap of the welding interface through appropriate welding pressure is conducive to the formation and diffusion of the molten pool and improves the welding strength. However, since lithium metal is relatively soft and has low mechanical strength, it is easy to deform under pressure. By controlling the pressure and amplitude of ultrasonic welding within the above range, excessive deformation or damage of the welding area under pressure can be avoided.

[0055] In some optional implementations, the welding time is ≤9.99s, such as 9.99s, 9s, 8.5s, 8s, 7.5s, 7s, 6.5s, 6s, 5.5s, 5s, 4.5s, 4s, 3.5s, 3s, 2.5s, 2s, 1.5s, 1s, 0.5s, 0.1s, 0.05s or 0.01s, etc., or other values ​​within the range of ≤9.99s. In some typical implementations, the welding time is 0.01s to 1s.

[0056] In some optional embodiments, the welding input energy is ≤2500 J, such as 2500 J, 2000 J, 1500 J, 1000 J, 500 J, 200 J or 100 J, etc., or other values ​​within the range of ≤2500 J. In some more typical embodiments, the welding input energy is ≤1200 J, such as 1200 J, 1000 J, 800 J, 600 J, 400 J, 200 J or 100 J, etc.

[0057] Lithium metal has a low melting point. By controlling the energy input of ultrasonic welding within the above range, overheating that causes excessive melting of the metal can be avoided.

[0058] It should be noted that the welding time is set differently according to the different working modes of the ultrasonic welder. There are two common modes for ultrasonic welders, namely time mode and energy mode. In time mode, the welder stops at the specified time according to the set amplitude / pressure. The welding time can be selected in the range of 0 to 9.99s, preferably 0.01S to 1s. In energy mode, the welder acts according to the set amplitude / pressure and automatically calculates the time it takes for the input energy to reach the set value. In energy mode, the input energy range can be selected from 0 to 2500J, preferably 0 to 1200J to obtain better welding results.

[0059] As mentioned above, there is a basic rule for ultrasonic welding: welding energy = power × time = pressure × frequency × amplitude × time, that is, the welding energy of ultrasonic welding is determined by welding pressure, resonant frequency, welding head amplitude and welding time. Lithium metal has a low melting point (about 180°C), and the energy input of ultrasonic welding needs to be precisely controlled to avoid overheating and excessive melting of lithium metal. At the same time, lithium metal is relatively soft, and the welding pressure and amplitude of ultrasonic welding need to be precisely controlled to avoid excessive deformation of the welding area due to pressure or excessive amplitude causing lithium belt breakdown.

[0060] In some optional embodiments, the material of the ultrasonic mold (welding head) may include, for example, aluminum alloy, titanium alloy, cemented carbide steel or polymer resin.

[0061] The polymer resin may include at least one of epoxy resin, TPU resin and phenolic resin.

[0062] The ultrasonic mold can be a handheld portable welding head or a non-handheld fixed welding head.

[0063] The shape of the ultrasonic mold can be, for example but not limited to, circular, square, knife-shaped, or ring-shaped.

[0064] The ultrasonic mold (welding head) can be provided with patterns of various shapes, such as dots, stripes, crosses or teeth, etc., or it can be flat (without patterns).

[0065] In some optional embodiments, the welding method can be discontinuous welding (such as spot welding) or continuous welding (such as roller welding).

[0066] In some optional embodiments, an isolation film is provided on each contact surface between the basic lithium strip and the ultrasonic mold before ultrasonic welding is performed. For example, an isolation film can be added between the upper and lower sides of the two basic lithium strips and the upper and lower molds of the welder to prevent adhesion between the lithium strips and the welding head.

[0067] The material of the isolation film may include at least one of PET, PI, BOPP, PP and PE.

[0068] The thickness of the isolation film may be 25 μm to 150 μm, such as 25 μm, 36 μm, 50 μm, 75 μm, 100 μm, 125 μm or 150 μm, or other values ​​within the range of 25 μm to 150 μm. In some typical embodiments, the thickness of the isolation film is 50 μm to 100 μm.

[0069] In some optional embodiments, anti-sticking oil is applied to the contact surfaces of the basic lithium strip and the ultrasonic mold before ultrasonic welding. For example, anti-sticking oil can be applied to the upper and lower sides of the welding area of ​​the two basic lithium strips. The anti-sticking oil acts like a release agent to prevent the lithium strip from sticking to the upper and lower molds of the welder.

[0070] The anti-sticking oil may include at least one of silicone oils, lipids, palm oil and white oil.

[0071] Silicone oils may include at least one of dimethyl silicone oil, diethyl silicone oil, diphenyl silicone oil, cyclopentasiloxane and cyclohexasiloxane. Lipids may include at least one of dimethyl carbonate and diethyl carbonate.

[0072] It should be noted that lithium metal exhibits strong adhesion when in contact with other metals. In order to avoid affecting the life of the welding head and the welding effect, the present invention adopts suitable welding head materials and anti-sticking methods (setting an isolation film or coating anti-sticking oil) to avoid adhesion problems.

[0073] In some optional embodiments, after welding, the welded spliced ​​lithium strips are subjected to thinning rolling. That is, after the metal lithium strips are spliced, in order to ensure that the spliced ​​lithium strips have a stable connection and uniform thickness in the length direction or the width direction, thinning rolling can be performed. Lithium metal has good plastic processing properties and can be easily processed by plastic processing techniques such as rolling, thereby solving the problem of thick thickness at the splicing.

[0074] Specifically, a precision rolling mill is prepared, which can precisely control the roll gap, and the roll gap control accuracy should reach ±α, and ±α should be less than or equal to the acceptable fluctuation rate of the thickness of the lithium strip after finishing rolling. For example, the acceptable thickness of the lithium strip after finishing rolling is 100μm±5μm, and the control accuracy of the roll gap is ±α≤±5μm.

[0075] Rolling parameter setting:

[0076] Basic lithium strip thickness (d1 / d2): D≤d1+d2, where D is the thickness of the joint before rolling.

[0077] Reducing the thickness of the lithium strip after rolling (h): This is achieved by adjusting the width of the rolling mill roll gap (H), where h=H.

[0078] Roll gap width setting (H): To ensure the thickness consistency of the lithium strip after finish rolling, set the roll gap width H≤min(d1,d2).

[0079] Rolling process:

[0080] Threading preparation: thread the welded basic lithium strip on the rolling mill to ensure that the lithium strip is flat and correctly aligned;

[0081] Roll gap adjustment: According to the target thickness h, the roll gap width of the rolling mill is accurately adjusted to H±α;

[0082] Rolling speed setting: Set the appropriate rolling speed to ensure the stability and uniformity of the lithium strip when passing through the rolling mill;

[0083] Start the rolling mill: When the rolling mill is started, the lithium strip will undergo longitudinal plastic stretching and become thinner. As lithium metal has good plasticity, the thicker part of the joint will be stretched to a greater extent during the rolling process, and finally reach a uniform thickness.

[0084] Rolling effect:

[0085] Thickness consistency: After being processed by a precision rolling mill, the thickness of the spliced ​​lithium strip will be uniformly rolled to h±α to ensure thickness consistency;

[0086] Weld mark treatment: Due to the good plasticity of lithium metal, the weld marks that may exist at the joints will be reduced or eliminated during the thinning rolling process. The greater the degree of thinning rolling, the better the effect of eliminating weld marks. For areas with obvious weld marks, multiple rolling can be considered to further eliminate the weld marks.

[0087] In some specific implementation methods that can be referenced, the following steps can be referred to:

[0088] S1. Material preparation and docking:

[0089] Prepare two basic lithium ribbons in a drying room (the ambient dew point is below -40°C, the room temperature is around 25°C, and the entire process is in the drying room). Align the two lithium ribbons in the length direction and overlap them along the end direction.

[0090] S2. Ultrasonic welding:

[0091] S21: Adjust the parameters of the ultrasonic welder, adjust the overlap of the lithium ribbon to the working position of the ultrasonic welder, start the ultrasonic welder, and partially melt the overlap of the lithium ribbon through high-frequency vibration to achieve solid-state welding.

[0092] S22: Move the position of the lithium belt or the position of the ultrasonic welding machine welding head, and repeat the operation of S21 until the welding is completed.

[0093] S3, Thinning and Fine Rolling:

[0094] The welded lithium ribbon is rolled through a precision rolling mill to finally obtain a spliced ​​lithium ribbon with stable connection and uniform thickness.

[0095] In line with the above, the lithium ribbon splicing method provided by the present invention has at least the following advantages:

[0096] ①. High welding efficiency and energy saving:

[0097] High efficiency: Ultrasonic welding can complete the welding process in a short time, significantly improving production efficiency; Energy saving: Since ultrasonic welding mainly relies on mechanical vibration to generate heat, the energy utilization efficiency is high, reducing dependence on external heat sources.

[0098] ② No external filling material required:

[0099] Purity: Ultrasonic welding does not require external filler materials, which means that no impurities are introduced during the welding process, ensuring the purity of the welding area. For active lithium metal, reducing the introduction of external materials helps avoid unnecessary chemical reactions and maintain the chemical stability of the material.

[0100] ③. Good welding quality and strength:

[0101] High fusion strength: Ultrasonic welding can achieve fusion at the atomic level, ensuring high strength and reliability of the welding area; No defects: Since no pores or impurities are generated during the welding process, the quality of the welding area is high, which is suitable for the high requirements for splicing lithium strips.

[0102] ④. Process safety and cold processing:

[0103] No sparks: No sparks are generated during ultrasonic welding, which is very important for handling flammable and explosive lithium metal; Small thermal impact: Ultrasonic welding is close to cold processing, which reduces the thermal impact on metal materials and avoids deformation or reaction caused by overheating of lithium metal.

[0104] ⑤. Suitable for thin material welding:

[0105] Adaptability to thin materials: Ultrasonic welding is particularly suitable for the welding of thin materials, and metal lithium strips are usually thin, which makes ultrasonic welding very suitable for the splicing of metal lithium strips; Uniform thickness: Through the finishing process, the thickness uniformity of the spliced ​​lithium strips can be further ensured.

[0106] Through the above method provided by the present invention, the defective parts can be removed and the non-defective parts can be effectively spliced ​​(with high splicing strength and consistent thickness), so that the waste lithium raw materials can be effectively recycled, the production cost can be reduced, and the production efficiency of lithium belt processing can be improved.

[0107] Correspondingly, the present invention also provides a lithium ribbon, which is obtained by splicing at least two basic lithium ribbons using the lithium ribbon splicing method of any one of the aforementioned embodiments.

[0108] The lithium ribbon has good splicing strength and uniform thickness, and can be further used to prepare lithium batteries, thereby reducing the production cost of lithium batteries and improving economic benefits.

[0109] The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

[0110] Example 1

[0111] This embodiment provides a lithium ribbon splicing method, comprising the following steps:

[0112] S1: Prepare two basic lithium ribbons with a width of 150 mm, a thickness of 250 μm and neat edges. Overlap the two basic lithium ribbons along the end direction to ensure that the length directions of the two lithium ribbons are in the same straight line, and the overlap range (overlap width) is similar to the size of the welding head, which is about 10 mm.

[0113] The material of the two basic lithium belts mentioned above is pure metallic lithium.

[0114] S21: Adjust the overlapping area of ​​the two lithium belts to the working position of the ultrasonic welding machine, start the ultrasonic welding machine, and use ultrasonic waves to transmit energy to the contact interface of the two basic lithium belts. Under pressure, the high-frequency vibration kinetic energy is converted into friction work, deformation energy and limited temperature rise between the interfaces. Local melting occurs at the overlapping part of the lithium belts to achieve solid-state welding, thereby obtaining the first weld point.

[0115] Among them, the ultrasonic welding machine (resonance frequency is 35KHz), the welding head is square, the welding head material is titanium alloy, and the welding head size is 10mm×10mm. The welding time is set to 0.1s, the welding pressure is 0.1MPa, the curing (welding) time is 0.3s, and the amplitude is adjusted to 20μm. Accordingly, the welding process is carried out under the condition of ambient dew point of -40℃ and room temperature.

[0116] S22: Move the lithium belt or the ultrasonic welding machine head, repeat the welding operation of S21, and leave a certain gap between each welding point to obtain a non-continuous weld (such as Figure 1 shown).

[0117] Example 2

[0118] This embodiment provides a lithium ribbon splicing method, comprising the following steps:

[0119] S1: Same as Example 1.

[0120] S21: Same as Example 1.

[0121] S22: Move the lithium belt or the ultrasonic welding machine head, repeat the welding operation of S21, and place the next welding point next to the previous welding point, so as to obtain a continuous weld (such as Figure 2 shown).

[0122] S3: Same as Example 1.

[0123] Example 3

[0124] This embodiment provides a lithium ribbon splicing method, comprising the following steps:

[0125] S1: Prepare two basic lithium ribbons with a width of 150 mm, a thickness of 250 μm and neat edges. Overlap the two basic lithium ribbons along the end direction to ensure that the length directions of the two lithium ribbons are in the same straight line, and the overlap range (overlap width) is similar to the size of the welding head, which is about 7 mm.

[0126] The material of the two basic lithium belts mentioned above is pure metallic lithium.

[0127] S21: Adjust the overlapping area of ​​the two lithium strips to the working position of the ultrasonic welding machine so that the tangent direction of the disc welding head is aligned with the weld to be welded. Start the ultrasonic welding machine, wherein the ultrasonic welding machine (resonance frequency is 35KHz), the welding head is a disc roller welding head, the welding head material is titanium alloy, and the welding head width is 7mm (roller gap width). The welding head rotation speed is 10m / min, the welding pressure is about 0.5MPa, the welding time is 0.3s, the amplitude is 20μm, and the welding process is carried out under the condition of ambient dew point of -40℃ and room temperature.

[0128] S22: The lithium belt moves with the rotation of the disc welding head, and finally a continuous weld will be formed in the welding area (such as Figure 3 shown).

[0129] Example 4

[0130] This embodiment provides a lithium ribbon splicing method, comprising the following steps:

[0131] S1: Prepare two basic lithium strips with a width of 150 mm, a thickness of 250 μm, and neat edges. Place the two basic lithium strips side by side with an overlap area of ​​about 7 mm, which is the location to be welded. The materials of the two basic lithium strips are the same as those in Example 3.

[0132] S21: Same as Example 3.

[0133] S22: Same as Example 3.

[0134] Example 5

[0135] This embodiment provides a lithium ribbon splicing method, comprising the following steps:

[0136] S1: Prepare two basic lithium ribbons with a width of 150 mm, a thickness of 50 μm and neat edges. Overlap the two basic lithium ribbons along the end direction to ensure that the length directions of the two lithium ribbons are in the same straight line, and the overlap range (overlap width) is similar to the size of the welding head, which is about 10 mm.

[0137] The materials of the above two basic lithium belts are both lithium-aluminum alloy.

[0138] S21: Adjust the overlapping area of ​​the two lithium belts to the working position of the ultrasonic welding machine, start the ultrasonic welding machine, and use ultrasonic waves to transmit energy to the contact interface of the two basic lithium belts. Under pressure, the high-frequency vibration kinetic energy is converted into friction work, deformation energy and limited temperature rise between the interfaces. Local melting occurs at the overlapping part of the lithium belts to achieve solid-state welding, thereby obtaining the first weld point.

[0139] Among them, the ultrasonic welding machine (resonance frequency is 40KHz), the welding head is annular, the welding head material is aluminum alloy, and the welding head size is 10mm×10mm. The welding time is set to 0.01s, the welding pressure is 0.05MPa, the curing time is 0.3s, and the amplitude is adjusted to 10μm. The welding process is carried out under the condition of ambient dew point of -40℃ and room temperature.

[0140] S22: Move the lithium belt or the ultrasonic welding machine head, repeat the welding operation of S21, and leave a certain gap between each welding point, so as to obtain a non-continuous weld.

[0141] Example 6

[0142] This embodiment provides a lithium ribbon splicing method, comprising the following steps:

[0143] S1: Prepare two basic lithium strips with a width of 150 mm, a thickness of 3 mm, and neat edges. Overlap the two basic lithium strips along the end direction to ensure that the length directions of the two lithium strips are in the same straight line, and the overlap range (overlap width) is similar to the size of the welding head, which is about 10 mm.

[0144] The materials of the two basic lithium belts mentioned above are both lithium-magnesium alloy.

[0145] S21: Adjust the overlapping area of ​​the two lithium belts to the working position of the ultrasonic welding machine, start the ultrasonic welding machine, and use ultrasonic waves to transmit energy to the contact interface of the two basic lithium belts. Under pressure, the high-frequency vibration kinetic energy is converted into friction work, deformation energy and limited temperature rise between the interfaces. Local melting occurs at the overlapping part of the lithium belts to achieve solid-state welding, thereby obtaining the first weld point.

[0146] Among them, the ultrasonic welding machine (resonance frequency is 20KHz), the welding head is square, the welding head material is titanium alloy, and the welding head size is 10mm×10mm. The welding time is set to 1s, the welding pressure is 1MPa, the curing time is 0.3s, and the amplitude is adjusted to 0.3mm. The welding process is carried out under the condition of ambient dew point of -40℃ and room temperature.

[0147] S22: Move the lithium belt or the ultrasonic welding machine head, repeat the welding operation of S21, and leave a certain gap between each welding point, so as to obtain a non-continuous weld.

[0148] Example 7

[0149] This embodiment provides a lithium ribbon splicing method, comprising the following steps:

[0150] S1: Prepare two basic lithium ribbons with a width of 150 mm, a thickness of 250 μm and neat edges. Overlap the two basic lithium ribbons along the end direction to ensure that the length directions of the two lithium ribbons are in the same straight line, and the overlap range (overlap width) is similar to the size of the welding head, which is about 10 mm.

[0151] The materials of the two basic lithium belts mentioned above are lithium-zinc alloy and pure lithium belt respectively.

[0152] A layer of PET isolation film is added between the upper and lower sides of the two basic lithium strips and the upper and lower molds of the welder, and the thickness of the isolation film is 50 μm.

[0153] S21: Adjust the overlapping area of ​​the two lithium belts to the working position of the ultrasonic welding machine, start the ultrasonic welding machine, and use ultrasonic waves to transmit energy to the contact interface of the two basic lithium belts. Under pressure, the high-frequency vibration kinetic energy is converted into friction work, deformation energy and limited temperature rise between the interfaces. Local melting occurs at the overlapping part of the lithium belts to achieve solid-state welding, thereby obtaining the first weld point.

[0154] Among them, the ultrasonic welding machine (resonance frequency is 15KHz), the welding head is knife-shaped, the welding head material is hard alloy steel, and the welding head size is 10mm×10mm. The welding time is set to 1s, the welding pressure is 0.5MPa, the curing time is 0.3s, and the amplitude is adjusted to 25μm. The welding process is carried out under the condition of ambient dew point of -40℃ and room temperature.

[0155] S22: Move the lithium belt or the ultrasonic welding machine head, repeat the welding operation of S21, and leave a certain gap between each welding point, so as to obtain a non-continuous weld.

[0156] Example 8

[0157] This embodiment provides a lithium ribbon splicing method, comprising the following steps:

[0158] S1: Prepare two basic lithium ribbons with a width of 150 mm, a thickness of 20 μm and neat edges. Overlap the two basic lithium ribbons along the end direction to ensure that the length directions of the two lithium ribbons are in the same straight line, and the overlap range (overlap width) is similar to the size of the welding head, which is about 10 mm.

[0159] The material of the two basic lithium belts mentioned above is lithium-indium alloy.

[0160] A layer of anti-sticking oil is applied between the upper and lower sides of the two basic lithium strips and the upper and lower molds of the welder.

[0161] S21: Adjust the overlapping area of ​​the two lithium belts to the working position of the ultrasonic welding machine, start the ultrasonic welding machine, and use ultrasonic waves to transmit energy to the contact interface of the two basic lithium belts. Under pressure, the high-frequency vibration kinetic energy is converted into friction work, deformation energy and limited temperature rise between the interfaces. Local melting occurs at the overlapping part of the lithium belts to achieve solid-state welding, thereby obtaining the first weld point.

[0162] Among them, the ultrasonic welding machine (resonance frequency is 60KHz), the welding head is square, the welding head material is epoxy resin, and the welding head size is 10mm×10mm. The welding time is set to 0.1s, the welding pressure is 0.01MPa, the curing time is 0.3s, and the amplitude is adjusted to 6μm. The welding process is carried out under the condition of ambient dew point of -40℃ and room temperature.

[0163] S22: Move the lithium belt or the ultrasonic welding machine head, repeat the welding operation of S21, and leave a certain gap between each welding point, so as to obtain a non-continuous weld.

[0164] Example 9

[0165] This embodiment provides a lithium strip splicing method, which differs from Embodiment 2 in that: before welding, the ends of the basic lithium strips to be spliced ​​are first thinned and rolled; and the ultrasonic mold is provided with a dot pattern.

[0166] Example 10

[0167] This embodiment provides a lithium strip splicing method, which further performs a thinning and fine rolling step S3 on the basis of Embodiment 2.

[0168] Specifically, the spliced ​​lithium belt (20 m, with the splicing position located in the middle) obtained in Example 2 was operated as follows:

[0169] The first step is to test the thickness of the spliced ​​lithium belt (the length of the lithium belt is about 20 meters, and the splicing position is in the middle) and the thickness of three random positions in the non-spliced ​​position.

[0170] The second step is to pass the lithium strip through the finishing mill and complete the reel assembly. After setting the roller gap and rolling speed of the finishing mill, start the mill.

[0171] The third step is to test the thickness of the spliced ​​parts of the finely rolled lithium strip and randomly select three locations without splicing parts to test the thickness.

[0172] The results are shown in Table 1.

[0173] Table 1 Test results

[0174]

[0175]

[0176] It can be seen from Table 1 that the thickness of the spliced ​​portion of the lithium strip can be made substantially consistent with the thickness of the non-spliced ​​portion through rolling.

[0177] Comparative Example 1

[0178] This comparative example provides a lithium belt splicing method, comprising the following steps:

[0179] S1: Prepare two basic lithium ribbons with a width of 150 mm, a thickness of 250 μm and neat edges. Overlap the two basic lithium ribbons along the end direction to ensure that the length directions of the two lithium ribbons are in the same straight line.

[0180] S21: Prepare an electric roller machine (sheeting width greater than 150 mm) and adjust the roller gap to 250 μm.

[0181] S22: Start the roller machine, first feed a lithium belt into the roller machine, the lithium belt will move forward with the rotation of the roller machine, and when the lithium belt moves to only 10mm and is about to pass through the roller machine completely, stop the roller machine immediately. Feed the second lithium belt into the roller machine, ensure that it overlaps with the first lithium belt by about 10mm, and start the roller machine until the second lithium belt passes through the roller machine completely. The overlapping area is spliced ​​together due to the pressure of the roller machine.

[0182] Comparative Example 2

[0183] The difference between this comparative example and Example 1 is that the resonance frequency used for welding is 10 KHz.

[0184] Comparative Example 3

[0185] The difference between this comparative example and Example 1 is that the resonance frequency used for welding is 65 KHz.

[0186] Comparative Example 4

[0187] The difference between this comparative example and Example 1 is that the welding amplitude is 30 μm.

[0188] Comparative Example 5

[0189] The difference between this comparative example and Example 1 is that the welding pressure is 1.5 MPa.

[0190] Comparative Example 6

[0191] The difference between this comparative example and Example 1 is that the welding time is 12 s.

[0192] Test example

[0193] The tensile strength of the spliced ​​lithium ribbons obtained in Examples 1 to 10 and Comparative Examples 1 to 6 was tested in accordance with GB / T1040.3-2006. The results are shown in Table 2.

[0194] Table 2 Test results

[0195]

[0196] It can be seen from Table 2 that the spliced ​​lithium belt obtained by the splicing method provided by the present invention has good tensile strength.

[0197] In summary, the present invention realizes melt splicing of two basic lithium belts through ultrasonic welding technology, and the lithium belt realizes atomic-level fusion at the welding point, and the lithium belt splicing obtained by the method has high splicing strength. In addition, the spliced ​​lithium belt obtained by the method has high strength (similar to the strength of the original lithium belt), and can be further thinned by the finishing process. Since the lithium belt at the splicing is thicker, the degree of longitudinal stretching will be higher when passing through the finishing mill. So that after the finishing process, the thickness of the lithium belt at the splicing is basically the same as that at the non-splicing point, and the thickness of the lithium belt is consistent. In addition, the method can be implemented at room temperature and in a drying room, and almost no new sources of danger (such as high heat, high pressure, etc.) are introduced. It is very friendly to materials with higher safety risks such as metal lithium, and has the advantages of fast, energy-saving, safe and easy operation. The method is used for lithium belt processing and production, which can greatly improve the utilization rate of raw materials and production efficiency, and help metal lithium belts to achieve industrial-level promotion in downstream applications, with significant economic and social benefits.

[0198] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A lithium ribbon splicing method, characterized in that: The following steps are involved: Overlap the ends of the two basic lithium strips to be spliced, and weld the overlapped parts by ultrasonic welding; The welding process is carried out under the condition of ambient dew point ≤-40℃ and room temperature; The resonant frequency used for welding is 15KHz-60KHz; the welding amplitude is ≥6μm and when the thickness of the basic lithium strip is ≥60μm, the welding amplitude is ≤10% of the thickness of the basic lithium strip; the welding pressure is 0.01MPa-1MPa, and the welding time is ≤9.99s.

2. The method according to claim 1, characterized in that The thickness of the lithium belt is 20 μm to 3 mm.

3. The method according to claim 1, characterized in that The resonant frequency used in welding is 20KHz~40KHz; and / or, the welding pressure is 0.05 MPa to 0.5 MPa; and / or, the welding time is 0.01s to 1s; Preferably, the welding input energy is ≤2500J, more preferably ≤1200J.

4. The method according to claim 1, characterized in that: The materials of ultrasonic molds used for welding include aluminum alloy, titanium alloy, hard alloy steel or polymer resin; Preferably, the polymer resin includes at least one of epoxy resin, TPU resin and phenolic resin.

5. The method according to claim 4, characterized in that Firstly, an isolation film is provided on each contact surface between the basic lithium strip and the ultrasonic mold, and then ultrasonic welding is performed; Preferably, the material of the isolation film includes at least one of PET, PI, BOPP, PP and PE; Preferably, the isolation film has a thickness of 25 μm to 150 μm, more preferably 50 μm to 100 μm.

6. The method according to claim 4, characterized in that First, anti-sticking oil is applied to each contact surface of the base lithium strip and the ultrasonic mold, and then ultrasonic welding is performed; Preferably, the anti-sticking oil comprises at least one of silicone oils, lipids, palm oil and white oil; Preferably, the silicone oil includes at least one of dimethyl silicone oil, diethyl silicone oil, diphenyl silicone oil, cyclopentasiloxane and cyclohexasiloxane; the lipid includes at least one of dimethyl carbonate and diethyl carbonate.

7. The lithium ribbon splicing method according to claim 1, characterized in that: Before welding, the ends of the basic lithium strips to be spliced ​​are firstly thinned and rolled.

8. The lithium ribbon splicing method according to claim 1, characterized in that: After welding, the welded spliced ​​lithium ribbon is thinned and rolled.

9. The lithium ribbon splicing method according to claim 1, characterized in that: The material of the basic lithium belt is metallic lithium or lithium alloy; Preferably, the lithium alloy includes at least one of a lithium aluminum alloy, a lithium magnesium alloy, a lithium zinc alloy, a lithium indium alloy, a lithium boron alloy and a lithium tin alloy.

10. A lithium belt, characterized in that: The lithium ribbon is obtained by splicing at least two basic lithium ribbons using the lithium ribbon splicing method described in any one of claims 1 to 9.

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