Cylindrical battery center tube and method of making same

Abstract

The present application relates to the technical field of cylindrical battery, and particularly relates to a cylindrical battery center tube, comprising: a support base layer for providing radial support; a liquid storage function layer arranged on the surface and / or aperture of the support base layer for absorbing and storing electrolyte; and a preparation method of the cylindrical battery center tube, comprising loading acrylic ester block copolymer on the support base layer by spraying or dipping coating. The cylindrical battery center tube of the present application provides anti-collapse physical support while realizing intelligent electrolyte supply for the central liquid deficiency area, and inhibiting the lithium precipitation problem caused by electrolyte drying in the later life. The liquid storage material is arranged in the central area which needs electrolyte supply most, thereby realizing the effect of fixed-point liquid supplement, and the material utilization rate is high, and the effect is more accurate compared with the full-pole dispersed addition mode.

Description

Technical Field

[0001] This invention relates to the field of cylindrical battery technology, and in particular to a cylindrical battery center tube and its preparation method. Background Technology

[0002] Large cylindrical batteries (cylindrical batteries with a diameter ≥ 32cm) face two major technical challenges during charge-discharge cycles: First, the collapse of the central hole. As the number of cycles increases, the internal stress generated by the volume expansion of the electrode material continuously accumulates towards the center of the core, causing plastic deformation or even collapse of the central hole. This leads to internal structural disorder within the core, making it prone to large-scale lithium plating, accelerating battery failure, and causing a sharp drop in cycle capacity. Second, uneven electrolyte distribution and lithium plating. The winding structure results in a large inner curvature and tighter pressure on the electrodes, causing the electrolyte to be gradually squeezed out of the central region during cycling, resulting in electrolyte deficiency in the inner region and subsequently triggering localized lithium plating. Research indicates that electrolyte scarcity in the central region is one of the key factors contributing to the degradation of cycle life in large cylindrical batteries.

[0003] Chinese patent CN 222483434 U discloses a woven mesh tubular liner structure that can effectively suppress the collapse of the central hole. However, this solution only provides physical support and does not involve electrolyte management functions. Chinese patent CN 222562715 U discloses a battery central tube and battery. The aerogel structure effectively improves the wettability of the electrolyte in the battery and promotes the wetting rate of the electrolyte during periodic extrusion and wetting processes, ensuring the battery's electrical performance. However, the aerogel has poor mechanical properties and is difficult to effectively provide support to prevent the collapse of the central hole. Currently, common liquid-retaining additives on the market improve the liquid-retaining capacity of the electrode by adding highly swollen polymers to the negative electrode slurry. However, these additives are dispersed throughout the entire negative electrode coating, requiring a large amount of material and failing to provide targeted replenishment to the most liquid-deficient central area.

[0004] Therefore, there is an urgent need for an integrated central tube that combines structural support and intelligent electrolyte replenishment, so that the electrolyte-retaining material is concentrated in the central area where electrolyte replenishment is most needed, to achieve "fixed-point replenishment and on-demand release". Summary of the Invention

[0005] To address the aforementioned problems, in a first aspect, the present invention provides a cylindrical battery center tube, comprising: a supporting substrate layer for providing radial support; and a liquid-retaining functional layer disposed on the surface and / or in the pores of the supporting substrate layer for absorbing and storing electrolyte.

[0006] In the cylindrical battery central tube of the present invention, the function of the supporting substrate layer is to provide stable radial mechanical support, resist the internal stress generated by the volume expansion of the electrode material, avoid plastic deformation or collapse of the central hole of the cylindrical battery during cycling, and maintain the stability of the internal structure of the core; at the same time, its porous or mesh structure also provides space for electrolyte retention and flow, which facilitates the timely release and replenishment of electrolyte stored in the liquid-retaining functional layer when the central area is short of liquid.

[0007] Furthermore, the supporting matrix layer has a porous or mesh structure, and the material of the supporting matrix layer is selected from one or more combinations of polypropylene, polyethylene, and polyoxymethylene, or the material of the supporting matrix layer is a glass fiber reinforced modified material with a glass fiber content of 10~50wt%.

[0008] In the cylindrical battery central tube of the present invention, the function of the electrolyte retention layer is to absorb and store the excess electrolyte in the central region of the cylindrical battery. When the electrolyte in the central region is insufficient during cycling, the stored electrolyte can be released in time to achieve targeted replenishment of the central liquid-deficient area, avoid local lithium plating problems caused by the lack of electrolyte in the inner ring, delay battery capacity decay, and improve cycle life. At the same time, it is loaded on the surface and pores of the supporting substrate layer and does not occupy additional structural space of the central tube, so as to achieve the integration of the electrolyte retention function while ensuring the support effect.

[0009] Furthermore, the thickness of the electrolyte retention layer is 20~200μm, and the electrolyte retention layer contains an acrylate block copolymer, wherein the acrylate block copolymer is a polyacrylate-b-polystyrene block copolymer with a number average molecular weight of 50,000~200,000, the molar percentage of acrylate segments is 60%~80%, and the molar percentage of styrene segments is 20%~40%; the acrylate block copolymer can absorb 10~30 times its own weight of electrolyte, and has excellent electrolyte storage and release capabilities.

[0010] In a second aspect, the present invention provides a method for preparing the above-mentioned cylindrical battery center tube, comprising loading an acrylate block copolymer onto a support substrate layer by spraying or impregnation coating.

[0011] Specifically, the spraying method includes: diluting the acrylic block copolymer emulsion to a solid content of 5-15%; spraying it onto the surface of the supporting substrate layer; and drying and curing it at 60-100°C. The advantages of the spraying method are: simple process, low equipment requirements, easy control of the thickness of the liquid-retaining functional layer, suitability for large-scale mass production, and easy assurance of coating uniformity.

[0012] Specifically, the impregnation coating method includes: preparing an acrylic block copolymer emulsion with a solid content of 10-30% and a particle size of 200-1000 nm; immersing the supporting matrix layer in the emulsion for 1-10 minutes; drying and curing at 60-100°C; and optionally repeating the impregnation-drying step 1-3 times. The advantages of the impregnation coating method are: it allows the acrylic block copolymer to fully penetrate the internal pores of the supporting matrix layer, achieving uniform loading of the liquid-retaining functional layer inside and on the surface of the supporting matrix layer, improving the overall liquid-retaining capacity, and adapting to supporting matrix layers with different pore structures.

[0013] The cylindrical battery central tube of this invention achieves both mechanical support and fixed-point electrolyte replenishment through a composite design of a supporting substrate layer and a liquid-retaining functional layer. This solves the problem of central hole collapse during the cycling process of large cylindrical batteries and improves the problems of uneven electrolyte distribution and easy lithium precipitation in the central area. It can effectively improve the cycle life of large cylindrical batteries, and the manufacturing process is simple and suitable for industrial production applications.

[0014] This invention provides a cylindrical battery center tube that offers physical support against collapse while intelligently replenishing electrolyte in the central electrolyte-deficient area, suppressing lithium plating caused by electrolyte drying in the later stages of the battery's lifespan. The electrolyte-retaining material is concentrated in the central area most in need of replenishment, achieving targeted replenishment. Compared to the method of dispersing electrolyte across all electrodes, this method offers higher material utilization and more precise results. The naturally occurring electrode expansion force during cycling serves as a trigger signal, enabling "on-demand" electrolyte release without the need for additional control components. The liquid absorption and expansion properties of the electrolyte-retaining material enhance the mechanical properties of the support tube, improving its support capacity. By effectively preventing central hole collapse and utilizing the self-triggered electrolyte replenishment device, the invention effectively delays interface degradation and lithium plating caused by electrolyte deficiency, with an expected cycle life improvement of over 30%. Attached Figure Description

[0015] Figure 1 The images are CT images of the cylindrical battery center tubes of Examples 1-3 and Comparative Examples 1-2 when they are cycled to 80% capacity retention.

[0016] Figure 2 The curves show the cycle capacity retention rates of the central tube of the cylindrical battery in Examples 1-3 and Comparative Examples 1-2.

[0017] Figure 3 The negative electrode sheet of the cylindrical battery prepared from the central tube of the cylindrical battery of Example 1 and Comparative Examples 1-2 after 750 cycles when fully charged. Detailed Implementation

[0018] The present invention will be described below with reference to examples. These examples are only used to explain the present invention and are not intended to limit the scope of the present invention.

[0019] Example 1 A cylindrical battery central tube includes a supporting substrate layer and a liquid-retaining functional layer. The supporting substrate layer is made of glass fiber reinforced PP material (glass fiber content 10wt%), and is prepared by injection molding into a mesh central tube with an outer diameter of 6mm, a wall thickness of 0.5mm, and a length of 120mm. The mesh pore size is 0.3mm. The liquid-retaining functional layer is attached to the supporting substrate layer and has a thickness of 80μm. It contains an acrylate block copolymer, which is a polyacrylate-b-polystyrene block copolymer with a number average molecular weight of 100,000. The acrylate segment molar percentage is 70%, and the styrene segment molar percentage is 30%. The acrylate block copolymer can absorb 30 times its own weight in electrolyte.

[0020] Example 1: The preparation method of the cylindrical battery center tube is as follows: The center tube is immersed in an acrylate block copolymer emulsion with a solid content of 20% and a particle size of 500nm for 5 minutes to ensure that the emulsion fully adheres to the inner and outer surfaces; after removal, it is dried in an oven at 80℃ for 2 hours to allow the emulsion particles to form a film; the immersion-drying step is repeated twice to obtain the final product.

[0021] Example 2 A cylindrical battery central tube includes a supporting substrate layer and a liquid-retaining functional layer. The supporting substrate layer is a polypropylene mesh structure tube, manufactured by injection molding, with an outer diameter of 6 mm, a wall thickness of 0.5 mm, a length of 120 mm, and a mesh pore size of 0.3 mm. The liquid-retaining functional layer is attached to the supporting substrate layer, has a thickness of 60 μm, and contains an acrylate block copolymer. The acrylate block copolymer is a polyacrylate-b-polystyrene block copolymer with a number average molecular weight of 200,000, a molar percentage of acrylate segments of 60%, and a molar percentage of styrene segments of 40%. The acrylate block copolymer can absorb 20 times its own weight in electrolyte.

[0022] Example 2: The preparation method of the cylindrical battery center tube is as follows: dilute the acrylate block copolymer emulsion to a solid content of 10%; spray it onto the surface of the support substrate layer; and dry and cure it at 80°C.

[0023] Example 3 A cylindrical battery central tube is disclosed, comprising a supporting substrate layer and a liquid-retaining functional layer. The supporting substrate layer is a polyoxymethylene mesh structure tube, manufactured by injection molding, with an outer diameter of 6 mm, a wall thickness of 0.5 mm, a length of 120 mm, and a mesh pore size of 0.3 mm. The liquid-retaining functional layer is attached to the supporting substrate layer, with a thickness of 70 μm, and contains an acrylate block copolymer. The acrylate block copolymer is a polyacrylate-b-polystyrene block copolymer with a number average molecular weight of 50,000, an acrylate segment molar percentage of 80%, and a styrene segment molar percentage of 20%. The acrylate block copolymer is capable of absorbing 10 times its own weight in electrolyte.

[0024] Example 3: The preparation method of the cylindrical battery center tube is as follows: The center tube is immersed in an acrylate block copolymer emulsion with a solid content of 30% and a particle size of 200nm for 10 minutes to ensure that the emulsion fully adheres to the inner and outer surfaces; after removal, it is dried in an oven at 100℃ for 0.5 hours to allow the emulsion particles to form a film; the immersion-drying step is repeated 3 times to obtain the final product.

[0025] The cylindrical battery center tubes of Examples 1-3 were used in the assembly of 46120 large cylindrical batteries. Cells without center tubes were used as control group 1, and center tubes with only the supporting substrate and no impregnation coating were used as control group 2.

[0026] Figure 1 CT images of large cylindrical batteries prepared from the cylindrical battery center tubes of Examples 1-3 and Comparative Examples 1-2 at 80% capacity retention during cycling. It can be seen that Control Group 1, lacking a center tube, experienced severe internal collapse; Control Group 2, having a center tube, suffered reduced roundness of the center hole due to the lack of mechanical support; while the round holes of Examples 1-3 were relatively intact.

[0027] Figure 2 The figures show the cycle capacity retention curves of the cylindrical battery cells with the central tube in Examples 1-3 and Comparative Examples 1-2. It can be seen that the large cylindrical cells in Examples 1-3 still maintain 80% capacity retention after 1200 cycles, while the cycle performance of Control Group 1 is poor, with only 768 cycles at 80% capacity retention. Control Group 2, after adding the central tube, achieves 890 cycles at 80% capacity retention. Example 1 shows a 34.8% improvement in cycle life compared to Control Group 2.

[0028] Figure 3 The negative electrode sheets of the cylindrical batteries prepared from the center tubes of Examples 1 and 1-2 after 750 cycles are shown when fully charged. It can be seen that the negative electrode sheet near the inner side of the core in Example 1 still maintains good wettability, while the negative electrode sheets near the center hole in Control Groups 1 and 2 show more severe lithium plating, which corresponds to the battery capacity degradation.

[0029] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A cylindrical battery central tube, characterized in that, include: Supporting substrate layer, used to provide radial support; A liquid-retaining functional layer is disposed on the surface and / or in the pores of the supporting substrate layer for absorbing and storing electrolyte.

2. The cylindrical battery center tube according to claim 1, characterized in that, The supporting substrate layer has a porous structure or a mesh structure.

3. The cylindrical battery center tube according to claim 2, characterized in that, The material of the supporting substrate layer is selected from one or more combinations of polypropylene, polyethylene, and polyoxymethylene.

4. The cylindrical battery center tube according to claim 2, characterized in that, The material of the supporting matrix layer is a glass fiber reinforced modified material with a glass fiber content of 10~50wt%.

5. The cylindrical battery center tube according to claim 1, characterized in that, The thickness of the liquid-retaining functional layer is 20~200μm.

6. The cylindrical battery center tube according to claim 5, characterized in that, The electrolyte-retaining functional layer comprises an acrylate block copolymer, which is a polyacrylate-b-polystyrene block copolymer with a number average molecular weight of 50,000 to 200,000, an acrylate segment molar percentage of 60% to 80%, and a styrene segment molar percentage of 20% to 40%; the acrylate block copolymer can absorb 10 to 30 times its own weight in electrolyte.

7. A method for preparing the central tube of a cylindrical battery as described in any one of claims 1 to 6, characterized in that, This includes loading acrylate block copolymers onto a support matrix layer by spraying or dipping.

8. The method according to claim 7, characterized in that, The spraying method includes: diluting an acrylate block copolymer emulsion to a solid content of 5-15%; spraying it onto the surface of a supporting substrate layer; and drying and curing it at 60-100°C.

9. The method according to claim 7, characterized in that, The impregnation coating method includes: preparing an acrylate block copolymer emulsion with a solid content of 10-30% and a particle size of 200-1000 nm; immersing the support matrix layer in the emulsion for 1-10 minutes; drying and curing at 60-100°C; and repeating the impregnation-drying step 1-3 times.

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