Splicing and forming lithium ribbon and forming method thereof

Abstract

The application provides a spliced formed lithium strip with better thickness consistency and stable connection between base lithium strips and a forming method thereof, and relates to the technical field of energy storage devices. The forming method of the spliced formed lithium strip comprises the following steps: providing at least two base lithium strips; laying the base lithium strips on the upper surface of a horizontally arranged bearing layer in turn and side by side, so that the base lithium strips are attached together with the upper surface of the bearing layer, and a spacing is arranged between adjacent base lithium strips to form a welding area filled with welding material; filling molten lithium liquid in the welding area to weld the base lithium strips into a whole, so as to form the spliced formed lithium strip, wherein, a protective gas is arranged during the filling of the molten lithium liquid to protect the molten lithium liquid and cool and solidify the molten lithium liquid.

Description

Technical Field

[0001] This invention relates to the field of energy storage device technology, specifically to a spliced ​​lithium strip and its forming method. Background Technology

[0002] In recent years, with the increasing market penetration of new energy vehicles, traditional fuel vehicles have also been continuously reducing costs to consolidate their market share. To fully promote vehicle electrification, the energy density of lithium-ion batteries must achieve breakthroughs to meet people's demands for longer driving ranges in new energy vehicles. With the technological iterations of various battery manufacturers, the next generation of high-energy-density lithium-ion batteries has gradually entered the market. Among them, silicon-containing pre-lithiation anodes and lithium metal anodes are considered the most likely to achieve large-scale commercialization in the short term. However, the high cost of lithium metal strips makes pre-lithiation or direct use of lithium metal anodes significantly more expensive than traditional lithium-ion batteries, thus restricting the development of high-energy-density lithium-ion batteries to some extent. Due to the special properties of lithium metal, the processing cost of lithium metal strips currently accounts for more than 40% of the total cost. Therefore, improving the production efficiency or utilization efficiency of lithium strips has a direct effect on cost reduction. The width of the lithium strip is a major factor restricting utilization efficiency. Because the width of lithium metal strips produced by mechanical extrusion is limited by the inner diameter of the extrusion barrel, ultra-wide lithium metal strips cannot be obtained. Currently, the width of mass-produced anode sheets can reach more than one meter, far exceeding the width of existing lithium strips. To address this, Chinese patent CN210467983U and published invention patent CN112310412A mention using two or more basic lithium strips, each less than 170mm thick and more than 0.2mm thick, spliced ​​together to form an ultra-wide spliced ​​lithium strip. The increase in thickness at the splicing point of the spliced ​​lithium strip does not exceed 6% of the thickness of the basic lithium strip. However, this splicing method has an overlap area of ​​1-3mm, making it difficult to reduce the thickness of the overlap area through longitudinal rolling without affecting the morphology of the lithium strip in the non-spliced ​​area, and the connection stability between the basic lithium strips is poor. Chinese patent CN113967699A proposes a splicing method and equipment for ultra-thin lithium foil or lithium strip, which involves laying at least two basic lithium strips with a support film, less than 100μm thick, flat on a supporting layer, and then using a rolling mill to adhere the basic lithium strips to the supporting layer to achieve splicing. This method also has difficulty in ensuring the connection stability between the basic lithium strips. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a splicing and forming method for lithium strips that facilitates thickness consistency control and provides more stable connections between basic lithium strips.

[0004] The technical solution adopted by this invention to solve its technical problem is: a method for forming spliced ​​lithium strips, comprising the following steps: Provide at least two basic lithium strips; The basic lithium strips are laid side by side on the upper surface of the horizontally set support layer, so that the basic lithium strips are attached to the upper surface of the support layer, and there is a gap between adjacent basic lithium strips to form a welding area filled with welding material. Molten lithium is filled into the welding zone to weld the base lithium strip into a whole, thereby forming the spliced ​​lithium strip. During the filling of molten lithium, a protective gas is provided to protect the molten lithium and cool and solidify it.

[0005] Furthermore, the protective gas is argon, helium, or neon.

[0006] Furthermore, the supporting layer is polyamide-imide, polyimide, polyetheretherketone, polytetrafluoroethylene, polyphenylene, polyetherimide, polyphthalamide, polyethylene terephthalate, steel strip, copper strip, or aluminum strip.

[0007] Furthermore, the thickness of the base lithium strip is 0.02–3 mm, preferably 0.5–2 mm.

[0008] Furthermore, the width of the basic lithium strip is 40–200 mm, preferably 90–160 mm.

[0009] Furthermore, the temperature of the molten lithium liquid is 200-300℃.

[0010] Furthermore, the cooling rate of the molten lithium liquid is 10℃ / s to 30℃ / s.

[0011] Furthermore, the molten lithium liquid, after solidification, has a high... Satisfaction, when When ≤0.1 mm, ≤5μm, when At 0.1 mm, %,in, This refers to the thickness of the base lithium strip.

[0012] Furthermore, the width of the welding area is 5–15 mm.

[0013] The present invention also provides a spliced ​​lithium strip, which is obtained by the above-described spliced ​​lithium strip forming method.

[0014] The beneficial effects of the present invention are as follows: The splicing and forming lithium strip and its forming method of the present invention melt the edges of the basic lithium strips by filling the gaps (welding areas) between the basic lithium strips, and then welding the basic lithium strips together after the lithium liquid solidifies to form a splicing and forming lithium strip. This can make the connection between the basic lithium strips more stable, that is, a splicing and forming lithium strip with more stable shape can be obtained. By precisely controlling the filling amount of molten lithium liquid, a splicing and forming lithium strip with better thickness consistency can be obtained. Attached Figure Description

[0015] Figure 1 This is a flowchart of the splicing and forming lithium strip method of the present invention; Figure 2 This is a schematic diagram of the production process for splicing and forming lithium strips; Figure 3 This is a schematic diagram showing the arrangement of the basic lithium strip on the carrier layer; Figure 4 This is a cross-sectional view of the assembled lithium strip; The diagram shows: 1. Spliced ​​lithium strip; 2. Bearing layer; 3. Lithium liquid filling equipment; 4. Welding protection box; 5. Basic lithium strip roll; 6. Unwinding roller; 7. Rewinding roller; 8. Air pipe; 9. Dry air cooling zone; 11. Basic lithium strip; 12. Welding zone. Detailed Implementation

[0016] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0017] like Figure 1 , Figure 2 As shown, the forming method of the spliced ​​lithium strip 1 of the present invention includes the following steps: Step 1: Provide at least two basic lithium strips 11, which can be formed by unwinding the basic lithium strip roll 5 by the unwinding roller 6; Step 2: Lay the basic lithium strips 11 side by side on the upper surface of the horizontally set support layer 2, so that the basic lithium strips 11 are attached to the upper surface of the support layer 2, and there is a gap between adjacent basic lithium strips 11 to form a welding area 12 filled with welding material. The width of the support layer 2 is generally greater than the width of the spliced ​​lithium strips 1. Step 3: Fill the welding area 12 with molten lithium liquid and weld the base lithium strip 11 into a whole to form the spliced ​​lithium strip 1. During the filling of molten lithium liquid, a protective gas is provided to protect the molten lithium liquid from reacting with components in the air and to cool and solidify it.

[0018] The protective gas in this invention is a gas that does not react with lithium, including but not limited to argon, helium or neon.

[0019] The strength of lithium strips fluctuates due to production and preparation conditions. The greater the tensile strength of the lithium strip, the lower the thickness change under tension during the roll-to-roll process. Ideally, the tensile strength σ of the basic lithium strip 11 should be ≥1.2 MPa.

[0020] The spliced ​​lithium strip forming method of the present invention melts the edges of the basic lithium strips 11 by filling the gaps (welding areas 12) between the basic lithium strips 11 with molten lithium liquid. After the lithium liquid solidifies, the basic lithium strips 11 are welded together to form the spliced ​​lithium strip 1. This method can make the connection between the basic lithium strips more stable, that is, it can obtain a spliced ​​lithium strip with a more stable morphology. The fracture strength at the weld joint can reach 1.0 MPa through experiments. In addition, this method has virtually no impact on the morphology of the basic lithium strips 11, such as flatness and thickness. Under the premise that the thickness fluctuation of the basic lithium strips is the same, the spliced ​​lithium strip with better thickness consistency can be obtained by precisely controlling the filling amount of molten lithium liquid. This is beneficial to improving the unit area capacity consistency of the spliced ​​lithium strip and preventing local lithium excess leading to lithium dendrite growth.

[0021] Specifically, the filling of the welding area 12 with molten lithium liquid is carried out by lithium liquid filling equipment 3. The lithium liquid filling equipment 3 can be an existing extrusion coating equipment that can achieve precise flow control, or a slit extrusion coating or gravure coating device commonly used in the lithium battery industry can be equipped with a heating device.

[0022] Specifically, rolling, bonding or other methods can be used to bond the base lithium strip 11 to the upper surface of the carrier layer 2. Figure 2 In the middle, the unwound base lithium strip 11 is attached to the upper surface of the bearing layer 2 by roller pressing.

[0023] The carrier layer 2 primarily serves to support the base lithium strip 11 and the molten lithium liquid. It is understood that the carrier layer 2 needs to withstand high temperatures to avoid being affected by the molten lithium liquid, and there should be no relative movement between the carrier layer 2 and the base lithium strip 11 before the molten lithium liquid solidifies. To prevent relative movement between the carrier layer 2 and the base lithium strip 11, both can be either prohibited from being installed or moved synchronously via rollers. The carrier layer 2 can be made of polyamide-imide, polyimide, polyetheretherketone, polytetrafluoroethylene, polystyrene, polyetherimide, polyphthalamide, polyethylene terephthalate, steel strip, copper strip, or aluminum strip. After the spliced ​​lithium strip 1 is assembled, the carrier layer 2 can be removed from the spliced ​​lithium strip 1, or it can be wound up together with the spliced ​​lithium strip 1 via the winding roller 7.

[0024] The protective gas is mainly provided through gas pipes 8, which can be one or more, guiding the protective gas to the welding area 12. To improve the utilization rate of the protective gas and better protect the molten lithium, the protective gas is introduced into the welding protection box 4 through the gas pipes 8. During welding, the base lithium strip 11 and the supporting layer 2 are introduced into the welding protection box 4 together, and then the welding area 12 is filled into the welding protection box 4 to protect the molten lithium from reacting with components in the air and to cool and solidify it. In this embodiment of the invention, the molten lithium is cooled to below 100°C by the protective gas. To facilitate the splicing and forming of lithium strips or to improve production efficiency, after the protective gas cooling, a dry air cooling zone 9 can be set up after the welding process to further cool the lithium in the welding area 12.

[0025] Preferably, the width of the base lithium strip 11 is 40–200 mm, and most preferably 90–160 mm; preferably, the thickness of the base lithium strip 11 is 0.02–3 mm, and most preferably 0.5–2 mm. When the thickness of the base lithium strip 11 is 0.5–2 mm, it is most advantageous to weld the base lithium strips 11 together using molten lithium.

[0026] The temperature of the molten lithium is generally 180-500℃, but other temperatures are also possible. In this invention, the optimal temperature of the molten lithium is 200-300℃. At this temperature, the edges of the base lithium strip 11 are melted, while the molten lithium is also cooled rapidly below its freezing point, minimizing its impact on the base lithium strip 11. In particular, when the thickness of the base lithium strip 11 is 0.1-2mm, a molten lithium temperature of 200-300℃ yields a more uniform thickness and better-shaped spliced ​​lithium strip 1.

[0027] To facilitate more uniform filling of the molten lithium liquid into the welding area 12 and to prevent deformation of the base lithium strip 11 due to excessive cooling of the molten lithium liquid, the cooling rate of the molten lithium liquid is preferably 10℃ / s to 30℃ / s.

[0028] The thickness of lithium strips used for pre-lithiation in lithium-ion batteries is generally controlled within 5μm, while the thickness of lithium strips used in lithium metal batteries is mostly controlled within 20μm. To meet the required thickness, spliced ​​lithium strips need to be further thinned. To ensure that the absolute thickness difference is sufficiently small when spliced ​​lithium strips are pressed to ultra-thin thickness, thus preventing the risk of lithium dendrite growth due to excessive lithium, optimally, such as... Figure 4 As shown, the molten lithium liquid, after solidification, has a high... Satisfaction, when When ≤0.1 mm, ≤5μm, when At 0.1 mm, %,in, The thickness of the base lithium strip 11.

[0029] The width of the welding area 12 can be any value greater than 0. To facilitate direct welding connection of the base lithium strip 11, the width of the welding area 12 is preferably 5 to 15 mm.

[0030] This invention also provides a spliced ​​lithium strip obtained using the above method. This spliced ​​lithium strip is welded and spliced ​​using the above method, resulting in a more stable connection between the base lithium strips. Furthermore, it facilitates obtaining spliced ​​lithium strips with better consistency in thickness.

[0031] Example:

Claims

1. A method for forming spliced ​​lithium strips, characterized in that, Includes the following steps: Provide at least two basic lithium strips (11), the thickness of which is 0.5 to 2 mm; The basic lithium strips (11) are laid side by side on the upper surface of the horizontally arranged support layer (2) so that the basic lithium strips (11) are attached to the upper surface of the support layer (2), and there is a gap between adjacent basic lithium strips (11) to form a welding area (12) filled with welding material; the width of the welding area (12) is 5 to 15 mm. Molten lithium is filled into the welding area (12) to weld the base lithium strip (11) into a whole, thereby forming the spliced ​​lithium strip (1). A protective gas is provided during the filling process to protect the molten lithium and cool and solidify it. The temperature of the molten lithium is 200-300℃. The cooling rate of the molten lithium is 10℃ / s to 30℃ / s. The height of the solidified molten lithium is... satisfy, %,in, The thickness of the base lithium strip (11).

2. The method for forming spliced ​​lithium strips as described in claim 1, characterized in that: The protective gas is argon, helium, or neon.

3. The method for forming spliced ​​lithium strips as described in claim 1, characterized in that: The supporting layer (2) is polyamide-imide, polyimide, polyether ether ketone, polytetrafluoroethylene, polyetherimide, polyphthalamide, polyethylene terephthalate, steel strip, copper strip or aluminum strip.

4. The method for forming spliced ​​lithium strips as described in claim 1, characterized in that, The width of the basic lithium strip (11) is 90-160 mm.

5. A spliced ​​lithium strip, characterized in that: Obtained by the forming method of splicing and forming lithium strip as described in any one of claims 1 to 4.

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