Cylindrical lithium-ion battery with high impact resistance

Abstract

The application relates to the technical field of lithium ion batteries, and discloses a cylindrical lithium ion battery with high impact resistance, which comprises a positive electrode sheet, a diaphragm sheet and a negative electrode sheet, the diaphragm sheet is arranged between the positive electrode sheet and the negative electrode sheet to insulate the positive electrode sheet from the negative electrode sheet; the diaphragm sheet comprises a polyethylene film, the thickness of the diaphragm sheet ranges from 9 microns to 18 microns, the puncture strength of the diaphragm sheet is greater than or equal to 800 gf, the longitudinal tensile strength of the diaphragm sheet is greater than or equal to 200 MPa, and the transverse tensile strength of the diaphragm sheet is greater than or equal to 200 MPa; in this way, under the impact of a heavy object, the diaphragm sheet can remain intact, so that short circuit between the positive electrode sheet and the negative electrode sheet caused by puncture or tearing of the diaphragm sheet is avoided, the risk of thermal runaway is reduced, and the impact resistance of the cylindrical lithium ion battery is improved.

Description

Technical Field

[0001] This invention relates to the technical field of lithium-ion batteries, and more specifically, to cylindrical lithium-ion batteries with high impact resistance. Background Technology

[0002] As the energy density of cylindrical lithium-ion batteries continues to increase, their safety performance also faces more severe challenges. According to the national standard GB31241-2022, the heavy object impact test is one of the key items to measure whether lithium-ion batteries will catch fire or explode when subjected to mechanical impact.

[0003] For cylindrical lithium-ion batteries, due to their special winding structure, the separator is easily punctured or torn under the impact of heavy objects, causing the positive and negative electrodes to come into direct contact and short circuit, leading to thermal runaway. This is especially true for high-energy-density cells, where the risk of thermal runaway is higher and the severity is greater.

[0004] To address this challenge, existing technologies, for example, use high-elongation copper foil as the negative electrode current collector, hoping that the copper foil can maintain the integrity of the electrode structure when an impact occurs, reducing the risk of the separator being punctured. However, this places stringent requirements on the purity of raw materials, grain structure, and manufacturing process parameters, leading to an increase in material costs.

[0005] Therefore, there is an urgent need for a cylindrical lithium-ion battery that is highly resistant to impacts without significantly increasing raw material costs and manufacturing difficulty. Summary of the Invention

[0006] The purpose of this invention is to provide a cylindrical lithium-ion battery with high impact resistance, thereby solving the problem of insufficient impact resistance of cylindrical lithium-ion batteries in the prior art.

[0007] This invention is achieved as follows: a cylindrical lithium-ion battery with high impact resistance includes a positive electrode, a separator, and a negative electrode. The separator is located between the positive and negative electrodes to ensure insulation between them. The separator comprises a polyethylene film with a thickness ranging from 9 μm to 18 μm. The separator has a puncture strength ≥ 800 gf, a longitudinal tensile strength ≥ 200 MPa, and a transverse tensile strength ≥ 200 MPa.

[0008] Furthermore, the longitudinal elongation of the diaphragm is ≥100%, and the lateral elongation of the diaphragm is ≥100%.

[0009] Furthermore, the polyethylene film is coated with a ceramic layer, which is made of ceramic material.

[0010] Furthermore, the ceramic material is alumina, boehmite, magnesium hydroxide, or magnesium oxide.

[0011] Furthermore, the positive electrode sheet contains a positive electrode active material, which includes LiNi. x Co y M (1-x-y) O2, M is manganese (Mn) and / or aluminum (Al), 0.8≤x≤0.99, 0.01≤y≤0.10.

[0012] Furthermore, the negative electrode sheet contains a negative electrode active material, which includes one or more of the following: artificial graphite, natural graphite, mesophase carbon microspheres, hard carbon, soft carbon, silicon, and silicon-carbon.

[0013] Furthermore, the ceramic layers are coated on both sides of the polyethylene film, and the positive electrode and negative electrode are respectively covered on the ceramic layers on both sides of the polyethylene film.

[0014] Furthermore, the surface of the ceramic layer is raised to form a grid-like micro-protrusion structure, and the positive electrode and the negative electrode are respectively covered on the grid micro-protrusion structure.

[0015] Compared with the prior art, the cylindrical lithium-ion battery with high impact resistance provided by the present invention has a separator with a thickness ranging from 9μm to 18μm and a puncture strength of ≥800gf, making it difficult to be punctured by sharp objects such as lithium dendrites or foreign objects; and with a longitudinal tensile strength of ≥200MPa and a transverse tensile strength of ≥200MPa, the separator is difficult to tear when subjected to tensile stress.

[0016] In this way, the separator can remain intact under the impact of heavy objects, so as to avoid short circuits between the positive and negative electrodes due to puncture or tearing of the separator, thereby reducing the risk of thermal runaway and improving the impact resistance of cylindrical lithium-ion batteries. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the internal structure of the cylindrical lithium-ion battery with high impact resistance provided by the present invention. Figure 2 This is a cross-sectional schematic diagram of the ceramic diaphragm provided by the present invention; In the figure: cylindrical lithium-ion battery 100, positive electrode 101, negative electrode 102, separator 103, ceramic layer 104, and mesh micro-convex structure 105. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0019] The implementation of the present invention will be described in detail below with reference to specific embodiments.

[0020] In the accompanying drawings of this embodiment, the same or similar reference numerals correspond to the same or similar components. In the description of this invention, it should be understood that if terms such as "upper," "lower," "left," and "right" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting this invention. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0021] Reference Figures 1-2 The image shows a preferred embodiment of the present invention.

[0022] A cylindrical lithium-ion battery with high impact resistance includes a positive electrode 101, a separator 103, and a negative electrode 102. The separator 103 is located between the positive electrode 101 and the negative electrode 102 to ensure an insulating arrangement between them. The separator 103 includes a polyethylene-based film with a thickness ranging from 9 μm to 18 μm. The separator 103 has a puncture strength ≥ 800 gf, a longitudinal tensile strength ≥ 200 MPa, and a transverse tensile strength ≥ 200 MPa.

[0023] The cylindrical lithium-ion battery with high impact resistance provided above has a separator 103 with a thickness ranging from 9μm to 18μm and a puncture strength of ≥800gf, making it difficult to be punctured by sharp objects such as lithium dendrites or foreign objects; and with a longitudinal tensile strength of ≥200MPa and a transverse tensile strength of ≥200MPa, the separator 103 is difficult to tear when subjected to tensile stress.

[0024] In this way, the separator 103 can remain intact under the impact of heavy objects, so as to avoid short circuit between the positive electrode 101 and the negative electrode 102 due to the separator 103 being punctured or torn, thereby reducing the risk of thermal runaway and improving the impact resistance of the cylindrical lithium-ion battery 100.

[0025] In this embodiment, the polyethylene base film is flexible, and when the separator 103 is subjected to impact, it can remain intact as the battery deforms, thus providing a flexible base film for the separator 103; in addition, the separator 103 maintains a relatively thin thickness to reduce the conduction path of lithium ions in the separator 103, thereby reducing the internal resistance of the battery.

[0026] Therefore, while maintaining a relatively thin profile, the separator 103 possesses high puncture strength and tensile strength, balancing the thinness of the separator 103 with its impact resistance, preventing short circuits between the positive electrode 101 and the negative electrode 102, and improving the impact resistance of the cylindrical lithium-ion battery 100.

[0027] As an extended embodiment, the longitudinal elongation of the diaphragm 103 is ≥100%, and the transverse elongation of the diaphragm 103 is ≥100%. In this way, the diaphragm 103 can generate a large deformation when stretched and is difficult to break. The diaphragm 103 can extend with the deformation of the battery and absorb impact energy.

[0028] When the cylindrical lithium-ion battery 100 is subjected to a heavy impact, the separator 103 is difficult to tear, thus maintaining the integrity of the separator 103 and preventing a short circuit between the positive electrode 101 and the negative electrode 102, thereby improving the impact resistance of the cylindrical lithium-ion battery 100.

[0029] As an extended embodiment, a ceramic layer 104 is coated on the polyethylene film. The ceramic layer 104 is made of ceramic material. Since ceramic material has high hardness and good high temperature resistance, after being coated on the polyethylene film, it can improve the puncture strength and tensile strength of the diaphragm 103, making it difficult for the diaphragm 103 to be punctured or torn when it is pierced or stretched by a sharp object.

[0030] Meanwhile, the ceramic layer 104 can maintain structural stability at high temperatures, preventing the separator 103 from shrinking under the high temperature caused by thermal runaway, which would lead to a short circuit between the positive electrode 101 and the negative electrode 102, thereby improving the impact resistance and safety performance of the cylindrical lithium-ion battery 100.

[0031] As an extended embodiment, the ceramic material is alumina, boehmite, magnesium hydroxide, or magnesium oxide. The ceramic material has high hardness and good high temperature resistance. After being coated on the polyethylene film to form a ceramic layer 104, it can improve the puncture strength and tensile strength of the diaphragm 103, making the diaphragm 103 difficult to be punctured or torn when subjected to impact. Meanwhile, these ceramic materials can maintain structural stability at high temperatures, preventing the separator 103 from shrinking under the high temperature caused by thermal runaway, which would lead to a short circuit between the positive electrode 101 and the negative electrode 102, thereby improving the impact resistance and safety performance of the cylindrical lithium-ion battery 100.

[0032] As an extended embodiment, the positive electrode 101 has a positive electrode active material, which includes LiNi. x Co y M (1-x-y)O2, M is manganese (Mn) and / or aluminum (Al), 0.8≤x≤0.99, 0.01≤y≤0.10.

[0033] By using a higher nickel content of 0.8 to 0.99, the positive electrode active material has a higher specific capacity, thereby improving the energy density of the cylindrical lithium-ion battery 100.

[0034] Furthermore, M, being manganese or aluminum, can stabilize the crystal structure of the positive electrode active material, thereby improving its thermal stability. Together with the high-impact-resistant separator 103, they enhance the safety performance of the cylindrical lithium-ion battery 100.

[0035] As an extended embodiment, the negative electrode 102 has a negative electrode active material, which includes one or more of artificial graphite, natural graphite, mesophase carbon microspheres, hard carbon, soft carbon, silicon, and silicon-carbon.

[0036] The negative electrode active material has a high specific capacity and good cycle stability, which enables the negative electrode 102 to be used in conjunction with the high-impact-resistant separator 103 to maintain the stability inside the battery. This can prevent short circuits between the positive electrode 101 and the negative electrode 102 when the cylindrical lithium-ion battery 100 is subjected to heavy impacts, thereby improving the impact resistance of the cylindrical lithium-ion battery 100.

[0037] As an extended embodiment, ceramic layers 104 are coated on both sides of the polyethylene film, and the positive electrode 101 and the negative electrode 102 are respectively covered on the ceramic layers 104 on both sides of the polyethylene film. In this way, both sides of the polyethylene film are supported by ceramic layers 104, which improves the overall puncture strength and tensile strength of the diaphragm 103. When the diaphragm 103 is subjected to impact, the ceramic layers 104 on both sides can resist the penetration and tensile tearing of sharp objects, making it difficult to be penetrated or torn.

[0038] Meanwhile, the positive electrode 101 and the negative electrode 102 are insulated and isolated by a polyethylene film and ceramic layers 104 on both sides, which avoids direct contact between the positive electrode 101 and the negative electrode 102 and short circuit, thereby improving the impact resistance and safety performance of the cylindrical lithium-ion battery 100.

[0039] As an extended embodiment, the surface of the ceramic layer 104 is raised to form a grid-like micro-protrusion structure 105, and the positive electrode 101 and the negative electrode 102 are respectively covered on the grid micro-protrusion structure 105.

[0040] When the cylindrical lithium-ion battery 100 is impacted, during the process of a sharp object piercing the separator 103, the mesh micro-convex structure 105 first contacts the sharp object, buffers the penetration of the sharp object, disperses the impact force, and prevents the separator 103 from being penetrated. This avoids a short circuit between the positive electrode 101 and the negative electrode 102 due to the separator 103 being penetrated, thus improving the impact resistance of the cylindrical lithium-ion battery 100.

[0041] 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, and improvements 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 lithium-ion battery with high impact resistance, characterized in that, The device includes a positive electrode, a separator, and a negative electrode. The separator is located between the positive and negative electrode to provide insulation between them. The separator comprises a polyethylene film with a thickness ranging from 9 μm to 18 μm. The separator has a puncture strength ≥ 800 gf, a longitudinal tensile strength ≥ 200 MPa, and a transverse tensile strength ≥ 200 MPa.

2. The cylindrical lithium-ion battery with high impact resistance as described in claim 1, characterized in that, The longitudinal elongation of the diaphragm is ≥100%, and the lateral elongation of the diaphragm is ≥100%.

3. The cylindrical lithium-ion battery with high impact resistance as described in claim 1 or 2, characterized in that, The polyethylene film is coated with a ceramic layer, which is made of ceramic material.

4. The cylindrical lithium-ion battery with high impact resistance as described in claim 3, characterized in that, The ceramic material is alumina, boehmite, magnesium hydroxide, or magnesium oxide.

5. The cylindrical lithium-ion battery with high impact resistance as described in claim 1 or 2, characterized in that, The positive electrode sheet contains a positive electrode active material, which includes LiNi. x Co y M (1-x-y) O2, M is manganese (Mn) and / or aluminum (Al), 0.8≤x≤0.99, 0.01≤y≤0.

10.

6. The cylindrical lithium-ion battery with high impact resistance as described in claim 1 or 2, characterized in that, The negative electrode sheet contains a negative electrode active material, which includes one or more of the following: artificial graphite, natural graphite, mesophase carbon microspheres, hard carbon, soft carbon, silicon, and silicon-carbon.

7. The cylindrical lithium-ion battery with high impact resistance as described in claim 3, characterized in that, The ceramic layers are coated on both sides of the polyethylene film, and the positive electrode and negative electrode are respectively covered on the ceramic layers on both sides of the polyethylene film.

8. The cylindrical lithium-ion battery with high impact resistance as described in claim 3, characterized in that, The surface of the ceramic layer is raised to form a grid-like micro-protrusion structure, and the positive electrode and the negative electrode are respectively covered on the grid micro-protrusion structure.

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