Secondary battery and battery pack

Abstract

Embodiments of the present application disclose a secondary battery and a battery pack, wherein the secondary battery comprises: a shell comprising: a side wall, a bottom wall and a first connecting portion, the side wall extends along a first direction, the bottom wall is arranged on one side of the side wall in the first direction, and the side wall and the bottom wall cooperate to enclose a containing cavity; two ends of the first connecting portion are connected with the side wall and the bottom wall respectively; an electrode assembly arranged in the containing cavity; and a first insulating coating arranged on an outer wall surface of the first connecting portion; wherein the thickness of the first insulating coating is H1 mm, and the following formula is satisfied: H1 = 0.09175 + 0.00294X + 0.06165X 2 - 0.03236X 3 , X = R x sin(alpha / 2) x sin(180°-beta). According to the present application, the risk of insulation breakdown of the shell is reduced, the safety performance of the shell is improved, and the safety performance of the secondary battery is improved.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to a secondary battery and battery pack. Background Technology

[0002] With the rapid development of mobile phones, laptops, electric vehicles, power tools, and other electronic devices, batteries with high capacity, long cycle life, and high safety performance have been widely used and developed. Simultaneously, the demand for batteries with even greater capacity, greater durability, and enhanced safety is extremely urgent. Safety performance is a core performance characteristic of batteries, and the safety performance of the battery casing is closely related to the overall safety performance of the secondary battery. Therefore, how to improve the safety performance of the casing, thereby improving the safety performance of the secondary battery, has become a pressing issue that needs to be addressed. Summary of the Invention

[0003] Embodiments of this application provide a secondary battery and battery pack to improve the safety performance of the casing, thereby improving the safety performance of the secondary battery.

[0004] To address the aforementioned technical problems, embodiments of this application disclose the following technical solutions:

[0005] On one hand, a secondary battery is provided, having a first orientation, comprising:

[0006] A housing, comprising: a sidewall, a bottom wall, and a first connecting portion; the sidewall extends along a first direction; the bottom wall is disposed on one side of the sidewall in the first direction; the sidewall and the bottom wall cooperate to form an accommodating cavity; the two ends of the first connecting portion are respectively connected to the sidewall and the bottom wall; the outer wall surface of the first connecting portion away from the accommodating cavity is an arc surface; the outer wall surface has a first outer edge contour line near the sidewall and a second outer edge contour line near the bottom wall; the first connecting portion also has a reference line, the reference line connecting the first outer edge contour line and the second outer edge contour line, and the reference line is the shortest connecting line between the first outer edge contour line and the second outer edge contour line;

[0007] Electrode assembly, disposed within the accommodating cavity; and

[0008] A first insulating coating is disposed on the outer wall surface of the first connecting portion;

[0009] The thickness of the first insulating coating is H1 mm, satisfying: H1 = 0.09175 + 0.00294X + 0.06165X 2 -0.03236X 3 , X=R×sin(α / 2)×sin(180°-β), 60°≤α≤90°, 140°≤β≤170°;

[0010] R mm is the radius of the outer wall surface, α is the maximum central angle corresponding to the outer wall surface, and β is the angle between the reference line and the bottom wall.

[0011] In some embodiments, the thickness H1 mm of the first insulating coating also satisfies: 0.092 mm ≤ H1 ≤ 0.128 mm.

[0012] In some embodiments, the radius R mm of the outer wall surface also satisfies: 1 mm ≤ R ≤ 3 mm.

[0013] In some embodiments, the secondary battery further has a second direction and a third direction that intersect the first direction in pairs;

[0014] The sidewall includes: a first sub-sidewall opposite to each other in the first direction, and a second sub-sidewall opposite to each other in the second direction, wherein the first sub-sidewall and the second sub-sidewall are connected by the first connecting portion.

[0015] In some embodiments, the housing further includes a second connecting portion, which is connected to the first sub-sidewall, the second sub-sidewall, and the bottom wall, respectively;

[0016] The secondary battery further includes: a second insulating coating disposed on the outer surface of the second connection portion;

[0017] The thickness of the second insulating coating is H2 mm, satisfying: H2=1.5k×H1;

[0018] Where k is a variable coefficient, and 0.7≤k≤0.9.

[0019] In some embodiments, the thickness H2 mm of the second insulating coating also satisfies: 0.097 mm ≤ H2 ≤ 0.173 mm.

[0020] In some embodiments, the second insulating coating includes a first sub-coating and a second sub-coating, wherein the first sub-coating is disposed near the second connection portion relative to the second sub-coating;

[0021] The thickness of the first sub-coating is H3 mm, and the thickness of the second sub-coating is H4 mm, satisfying: H2 = H3 + H4.

[0022] In some embodiments, the thickness H3 mm of the first sub-coating also satisfies: 0.092 mm ≤ H3 ≤ 0.128 mm.

[0023] In some embodiments, a third insulating coating is also included, disposed on the outer surfaces of the sidewalls and the bottom wall;

[0024] The thickness of the third insulating coating is H5 mm, satisfying: 0.8≤H1 / H5≤2.

[0025] In some embodiments, the thickness H5 mm of the third insulating coating also satisfies: 0.046 mm ≤ H5 ≤ 0.16 mm.

[0026] On the other hand, a battery pack is further disclosed, in some embodiments of which the battery pack includes a housing; and a secondary battery as described in any of the preceding claims, the secondary battery being housed within the housing.

[0027] One of the above technical solutions has the following advantages or beneficial effects: In this application, the thickness H1 mm of the first insulating coating is limited to satisfy: H1 = 91.75 + 2.94X + 61.65X 2 -32.36X 3 X = R × sin(α / 2) × sin(180° - β). By limiting the maximum central angle α corresponding to the outer wall surface 1131 to the range of 60° to 90°, and limiting the included angle β between the reference line 1134 and the bottom wall 112 to the range of 140° to 170°, the thickness of the first insulating coating 130 is reasonably designed according to the structural dimensions at the first connecting part 113. This reasonable design of the thickness of the first insulating coating 130 ensures the uniformity of the thickness of the first insulating coating, reduces the risk of insulation breakdown of the shell, improves the safety performance of the shell, and thus improves the safety performance of the secondary battery. At the same time, it improves the first pass rate of the first insulating coating spraying, thereby improving the processing efficiency of the shell and ultimately improving the production efficiency of the secondary battery. Attached Figure Description

[0028] The technical solution and other beneficial effects of this application will become apparent from the following detailed description of specific embodiments in conjunction with the accompanying drawings.

[0029] Figure 1 This is a three-dimensional structural view of a secondary battery provided according to an embodiment of this application;

[0030] Figure 2 This is an exploded structural view of a secondary battery according to an embodiment of this application;

[0031] Figure 3 This is a three-dimensional structural view of the housing provided according to an embodiment of this application;

[0032] Figure 4 This is a three-dimensional structural view of the housing from another perspective according to an embodiment of this application;

[0033] Figure 5 This is a cross-sectional view of the housing along the AA direction provided according to an embodiment of this application;

[0034] Figure 6 yes Figure 5 A magnified view of a section at point C;

[0035] Figure 7 This is a cross-sectional view of the housing along the BB direction according to an embodiment of this application;

[0036] Figure 8 yes Figure 7 A magnified view of a section at point D.

[0037] Explanation of reference numerals in the attached figures:

[0038] 100. Secondary batteries;

[0039] 110. Shell; 111. Sidewall; 1111. First sub-sidewall; 1112. Second sub-sidewall; 112. Bottom wall; 113. First connecting part; 1131. Outer wall surface; 1132. First outer edge contour line; 1133. Second outer edge contour line; 1134. Reference line; 114. Second connecting part; 115. Receiving cavity;

[0040] 120. Electrode assembly;

[0041] 130. First insulating coating;

[0042] 140. Second insulating coating; 141. First sub-coating; 142. Second sub-coating;

[0043] 150. Third insulating coating;

[0044] 160. End cap. Detailed Implementation

[0045] To make the objectives, technical solutions, and beneficial effects of this application clearer, the following detailed description, in conjunction with the accompanying drawings and specific embodiments, further illustrates this application. It should be understood that the specific embodiments described in this specification are merely for explaining this application and are not intended to limit it.

[0046] In the description of this application, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing this application 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, and therefore should not be construed as a limitation of this application. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of the stated features. In the description of this application, "a plurality of" means two or more, unless otherwise explicitly specified.

[0047] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, a direct connection, or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0048] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0049] With the continuous development of secondary battery surface treatment technology, the existing method of applying PET film (such as blue film) to the battery surface can no longer meet the high shear strength and insulation withstand voltage requirements of the latest battery packs. Although the surface of existing secondary batteries can be treated with spray coating technology, uneven coating thickness distribution may occur at irregular edges and corners of the secondary battery surface, resulting in weak points in the coating at these corners. This can easily lead to insulation withstand voltage test breakdown, affecting the safety performance of the casing and consequently the safety performance of the secondary battery. At the same time, it also affects the pass rate of the surface coating production, leading to increased production costs and reduced production efficiency for secondary batteries.

[0050] To address the aforementioned problems, this application provides a secondary battery 100 in its embodiments. The secondary battery 100 has a first direction Z, a second direction X, and a third direction Y that intersect each other. For example, the secondary battery 100 also has a first direction Z, a second direction X, and a third direction Y that are perpendicular to each other. Here, "perpendicular" refers to a state where the angle formed by two lines, a line and a surface, or a surface is 89° to 91°.

[0051] The secondary battery 100 refers to a battery that can be recharged after discharge to activate the active materials and continue to be used. For example, the secondary battery 100 can be a lithium-ion battery, sodium-ion battery, sodium-lithium-ion battery, lithium metal battery, sodium metal battery, lithium-sulfur battery, magnesium-ion battery, nickel-metal hydride battery, or nickel-cadmium battery, but is not limited to these.

[0052] The secondary battery 100 can also be cylindrical, flat, rectangular or other shapes.

[0053] Specifically, the secondary battery 100 includes: a housing 110, an electrode assembly 120, a first insulating coating 130, and an end cap 160.

[0054] Specifically, the housing 110 includes: a side wall 111, a bottom wall 112, and a first connecting portion 113. The side wall 111 extends along the first direction Z, and the bottom wall 112 is disposed on one side of the side wall 111 in the first direction Z. The side wall 111 and the bottom wall 112 cooperate to form an accommodating cavity 115. The two ends of the first connecting portion 113 are respectively connected to the side wall 111 and the bottom wall 112.

[0055] The outer wall surface 1131 of the first connecting portion 113 facing away from the receiving cavity 115 is an arc surface; the outer wall surface 1131 has a first outer edge contour line 1132 near the side wall 111 and a second outer edge contour line 1133 near the bottom wall 112; the first connecting portion 113 also has a reference line 1134, which connects the first outer edge contour line 1132 and the second outer edge contour line 1133, and the reference line 1134 is the shortest connecting line between the first outer edge contour line 1132 and the second outer edge contour line 1133. For example, in this application, the reference line 1134 may be perpendicular to the first outer edge contour line 1132 and the second outer edge contour line 1133, so that the reference line 1134 is the shortest connecting line.

[0056] Electrode assembly 120 is disposed in accommodating cavity 115; first insulating coating 130 is disposed on outer wall surface 1131 of first connecting part 113; end cap 160 is disposed at one end of housing 110 in the first direction Z.

[0057] The housing 110 described above may be made of a strong material such as metal, but is not limited to this. For example, the housing 110 described above is made of aluminum profile, but is not limited to this.

[0058] The end cap 160 is fixedly connected to the housing 110, for example, by welding or other processes. This application does not impose specific limitations and can be configured according to actual circumstances. For example, in this application, the end cap 160 and the housing 110 are separate components, and the end cap 160 and the housing 110 are fixed together by welding.

[0059] The aforementioned secondary battery 100 also includes an electrolyte, terminals, and other functional components. The electrolyte can be a conventional electrolyte or a special electrolyte with additives. The electrolyte is used to wet the electrode assembly 120. The electrode assembly 120 is the component in the secondary battery 100 where electrochemical reactions occur, and there can be one or more electrode assemblies. The electrode assembly 120 is mainly formed by stacking or winding a positive electrode, a separator, and a negative electrode. The active material portions of the positive and negative electrode form the main body of the electrode assembly 120, while the non-active material portions of the positive and negative electrode each form a tab. During the charging and discharging process of the secondary battery 100, the positive and negative active materials react with the electrolyte, and the tabs and terminals are electrically connected to form a current circuit, enabling the secondary battery 100 to function normally.

[0060] The first insulating coating 130 is made of polyurethane acrylate resin, epoxy acrylate resin, or ceramic material, but is not limited to these. The ceramic material may be made of one or more of the following: aluminum oxide, titanium dioxide, silicon dioxide, zirconium dioxide, tin dioxide, magnesium oxide, zinc oxide, boron nitride, aluminum nitride, and magnesium nitride, but is not limited to these. Furthermore, the raw materials of the first insulating coating 130 may also contain a photoinitiator (such as at least one of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide and 1-hydroxycyclohexylphenyl ketone) and a diluent (including at least one of benzyl acrylate, phenoxyethyl acrylate, and 1,6-hexanediol diacrylate). The mass percentage of the main material in the raw materials of the first insulating coating 130 is 10%-50%, the mass percentage of the photoinitiator is 2%-8%, and the mass percentage of the reactive diluent is 40%-80%.

[0061] Specifically, the thickness of the first insulating coating 130 is H1 mm, satisfying: H1 = 0.09175 + 0.00294X + 0.06165X 2 -0.03236X 3 , X=R×sin(α / 2)×sin(180°-β).

[0062] Where R mm is the radius of the outer wall 1131, α is the maximum central angle corresponding to the outer wall 1131, and β is the angle between the reference line 1134 and the bottom wall 112.

[0063] Specifically, the maximum central angle α corresponding to the outer wall surface 1131 also satisfies: 60°≤α≤90°. That is, the maximum central angle α corresponding to the outer wall surface 1131 can be controlled within the range of 60° to 90°. For example, the maximum central angle α corresponding to the outer wall surface 1131 can be one of 60°, 65°, 70°, 75°, 80°, 85°, or 90°, or any combination thereof. The specific values ​​of α mentioned above are only given as examples, and any value within the range of 60° to 90° is within the protection scope of this application. By controlling the maximum central angle α corresponding to the outer wall surface 1131 within the range of 60° to 90°, this application reasonably designs the size of the maximum central angle corresponding to the outer wall surface 1131, thereby reasonably designing the thickness of the first insulating coating 130, ensuring the uniformity of the thickness of the first insulating coating 130, reducing the risk of insulation withstand voltage breakdown of the shell 110, improving the safety performance of the shell 110, and thus improving the safety performance of the secondary battery 100.

[0064] Specifically, the included angle β between reference line 1134 and bottom wall 112 also satisfies: 140° ≤ β ≤ 170°. That is, the included angle β between reference line 1134 and bottom wall 112 can be controlled within the range of 130° to 170°. For example, the included angle β between reference line 1134 and bottom wall 112 can be one of 140°, 145°, 150°, 155°, 160°, 165°, or 170°, or any combination thereof. The specific values ​​of β mentioned above are merely illustrative, and any value within the range of 140° to 170° is within the protection scope of this application. This application controls the included angle β between the reference line 1134 and the bottom wall 112 within the range of 140° to 170°. By rationally designing the size of the included angle between the reference line 1134 and the bottom wall 112, the thickness of the first insulating coating 130 can be rationally designed, ensuring the uniformity of the thickness of the first insulating coating 130, reducing the risk of insulation breakdown of the housing 110, improving the safety performance of the housing 110, and thus improving the safety performance of the secondary battery 100.

[0065] The included angle β between the reference line 1134 and the bottom wall 112 can be either the angle between the reference line 1134 and the surface of the bottom wall 112 near the receiving cavity 115, or the angle between the reference line 1134 and the surface of the bottom wall 112 away from the receiving cavity 115, but is not limited thereto. No specific limitation is made in this application; the appropriate angle can be selected based on the actual situation.

[0066] The thickness H1 mm of the first insulating coating 130 can be obtained by disassembling the actual secondary battery 100, cutting the casing 110 using a cutting device to obtain a measurement sample at the first connecting part 113 of the casing 110, curing the measurement sample with A / B epoxy adhesive, polishing the sample, and then repeatedly observing and measuring the thickness of the first insulating coating 130 at different positions on the surface of the first connecting part 113 using a measuring tool and calculating the average value. The measuring tool can be any one of, but is not limited to, an X / β-ray micro-spot surface density meter, a laser thickness gauge, a CCD microscope, or other dimensional measuring instruments.

[0067] Among them, the radius R mm of the outer wall surface 1131, the maximum central angle α corresponding to the outer wall surface 1131, and the included angle β between the reference line 1134 and the bottom wall 112 can be used to disassemble the actual secondary battery 100 and cut the shell 110 along a section perpendicular to the second direction X using a cutting device to obtain a test sample. The test sample of the shell 110 is placed in the measurement space of a three-dimensional measuring instrument. The coordinate positions of the outer wall surface 1131 and the bottom wall 112 of the first connecting part 113 of the test sample of the shell 110 are obtained using the three-dimensional measuring instrument. Then, based on the spatial coordinate values ​​of multiple outer wall surfaces 1131 and bottom walls 112, the coordinate positions of the outer wall surface 1131 and the bottom wall 112 are obtained. The contour shape of the outer wall surface 1131 and the contour shape of the bottom wall 112 at the test sample section of the housing 110 are directly generated and displayed using a three-dimensional measuring instrument. At the same time, the three-dimensional measuring instrument is used to generate and display auxiliary lines such as the first outer edge contour line 1132, the second outer edge contour line 1133, and the reference line 1134. The radius R of the outer wall surface 1131 at the test sample section of the housing 110, the maximum central angle α corresponding to the outer wall surface 1131 at the test sample section of the housing 110, and the specific values ​​of the angle β between the reference line 1134 and the bottom wall 112 are directly calculated, but not limited to these.

[0068] In this application, the thickness H1 mm of the first insulating coating 130 is defined to satisfy: H1 = 91.75 + 2.94X + 61.65X 2 -32.36X 3 X = R × sin(α / 2) × sin(180° - β). By limiting the maximum central angle α corresponding to the outer wall surface 1131 to the range of 60° to 90°, and limiting the included angle β between the reference line 1134 and the bottom wall 112 to the range of 140° to 170°, the thickness of the first insulating coating 130 is reasonably designed according to the structural dimensions at the first connecting part 113. This ensures the uniformity of the thickness of the first insulating coating 130, reduces the risk of insulation breakdown of the housing 110, improves the safety performance of the housing 110, and thus improves the safety performance of the secondary battery 100. At the same time, it improves the first-pass yield of the first insulating coating 130, thereby improving the processing efficiency of the housing 110 and ultimately improving the production efficiency of the secondary battery 100.

[0069] In one embodiment, the thickness H1 mm of the first insulating coating 130 further satisfies: 0.092 mm ≤ H1 ≤ 0.128 mm. That is, the thickness H1 mm of the first insulating coating 130 can be controlled within the range of 0.092 mm to 0.128 mm. For example, the thickness H1 mm of the first insulating coating 130 can be one of 0.092 mm, 0.975 mm, 0.1 mm, 0.1025 mm, 0.105 mm, 0.1075 mm, 0.11 mm, 0.1125 mm, 0.115 mm, 0.1175 mm, 0.12 mm, 0.1225 mm, 0.125 mm, or 0.128 mm, or any combination thereof. The specific values ​​of H1 mm mentioned above are merely illustrative examples, and any value within the range of 0.092 mm to 0.128 mm is within the protection scope of this application.

[0070] This application controls the thickness H1 mm of the first insulating coating 130 within the range of 0.092 mm to 0.128 mm to further optimize the design of the thickness of the first insulating coating 130, ensure the uniformity of the thickness of the first insulating coating 130, reduce the risk of insulation breakdown of the housing 110, improve the safety performance of the housing 110, and thus improve the safety performance of the secondary battery 100.

[0071] In one embodiment, the radius R mm of the outer wall surface 1131 also satisfies: 1 mm ≤ R ≤ 3 mm. That is, the radius R mm of the outer wall surface 1131 can be controlled within the range of 1 mm to 3 mm. For example, the radius R mm of the outer wall surface 1131 can be one of 1 mm, 1.4 mm, 1.8 mm, 2 mm, 2.2 mm, 2.6 mm, or 3 mm, or any combination thereof. The specific values ​​of R mm mentioned above are merely illustrative, and any value within the range of 1 mm to 3 mm is within the protection scope of this application.

[0072] This application controls the radius R mm of the outer wall surface 1131 within the range of 1 mm to 3 mm. By rationally designing the radius of the outer wall surface 1131, the thickness of the first insulating coating 130 can be rationally designed, further ensuring the uniformity of the thickness of the first insulating coating 130, reducing the risk of insulation breakdown of the housing 110, improving the safety performance of the housing 110, and thus improving the safety performance of the secondary battery 100.

[0073] In one embodiment, the sidewall 111 includes: a first sub-sidewall 1111 opposite to each other in a first direction X, and a second sub-sidewall 1112 opposite to each other in a second direction Y. The first sub-sidewall 1111 and the second sub-sidewall 1112 are connected by a first connecting portion 113, that is, the first sub-sidewall 1111, the second sub-sidewall 1112 and the first connecting portion 113 form an integral structure.

[0074] The first sub-sidewall 1111, the second sub-sidewall 1112, and the first connecting portion 113 can be integrally formed, meaning they form a single, integrated structure. Each pair of the first sub-sidewall 1111, the second sub-sidewall 1112, and the first connecting portion 113 is fixedly connected, for example, through welding or other processes. This application does not impose specific limitations and can be tailored to the specific circumstances. For instance, in this application, the first sub-sidewall 1111, the second sub-sidewall 1112, and the first connecting portion 113 are integrally formed.

[0075] The housing 110 also includes a second connecting part 114, which is connected to the first sub-side wall 1111, the second sub-side wall 1112 and the bottom wall 112 respectively.

[0076] The second connecting part 114 can be an arc-shaped structure, but is not limited to this.

[0077] The secondary battery 100 also includes a second insulating coating 140, which is disposed on the outer surface of the second connecting portion 114.

[0078] The second insulating coating 140 can be made of polyurethane acrylic resin, epoxy acrylate resin, or ceramic materials, but is not limited to these. The ceramic material can be made of one or more of the following: aluminum oxide, titanium dioxide, silicon dioxide, zirconium dioxide, tin dioxide, magnesium oxide, zinc oxide, boron nitride, aluminum nitride, and magnesium nitride, but is not limited to these. Furthermore, the raw materials of the second insulating coating 140 may also contain a photoinitiator (such as at least one of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide and 1-hydroxycyclohexylphenyl ketone) and a diluent (including at least one of benzyl acrylate, phenoxyethyl acrylate, and 1,6-hexanediol diacrylate). The mass percentage of the main material in the raw materials of the second insulating coating 140 is 10%-50%, the mass percentage of the photoinitiator is 2%-8%, and the mass percentage of the reactive diluent is 40%-80%.

[0079] Specifically, the thickness of the second insulating coating 140 is H2 mm, satisfying: H2=1.5k×H1; where k is a variable coefficient, designed to be different for different secondary batteries 100.

[0080] The method for measuring the thickness H2 mm of the second insulating coating 140 is the same as the method for measuring the thickness H1 mm of the first insulating coating 130, and will not be elaborated here. Please refer to the description above.

[0081] Understandably, in this application, the thickness H2 mm of the second insulating coating 140 is limited to satisfy: H2 = 1.5k × H1, so that the thickness of the second insulating coating 140 is reasonably designed according to the thickness of the first insulating coating 130, ensuring the uniformity of the thickness of the second insulating coating 140, reducing the risk of insulation breakdown at the second connection 114 of the housing 110, further improving the safety performance of the housing 110, and further improving the safety performance of the secondary battery 100; at the same time, it improves the first-pass yield of the second insulating coating 140, further improves the processing efficiency of the housing 110, and ultimately improves the production efficiency of the secondary battery 100.

[0082] In one embodiment, the thickness H2 mm of the second insulating coating 140 further satisfies: 0.097 mm ≤ H2 ≤ 0.173 mm. That is, the thickness H2 mm of the second insulating coating 140 can be controlled within the range of 0.097 mm to 0.173 mm. For example, the thickness H2 mm of the second insulating coating 140 can be one or a combination of any two of the following: 0.097 mm, 0.098 mm, 0.099 mm, 0.1 mm, 0.11 mm, 0.12 mm, 0.13 mm, 0.14 mm, 0.15 mm, 0.16 mm, 0.17 mm, or 0.173 mm. The specific values ​​of H2 mm given above are merely illustrative, and any value within the range of 0.097 mm to 0.173 mm is within the protection scope of this application.

[0083] This application limits the thickness H2 mm of the second insulating coating 140 to within the range of 0.097 mm to 0.173 mm, thereby further optimizing the design of the thickness of the second insulating coating 140, further reducing the risk of insulation breakdown at the second connection 114 of the housing 110, further improving the safety performance of the housing 110, and further improving the safety performance of the secondary battery 100.

[0084] The coefficient k satisfies: 0.7 ≤ k ≤ 0.9. That is, the coefficient k can be controlled within the range of 0.7 to 0.9. For example, the coefficient k can be one of 0.7, 0.72, 0.74, 0.78, 0.8, 0.82, 0.84, 0.88, or 0.9, or any combination of two of these values. The specific values ​​of the coefficient k given above are merely illustrative examples; any value within the range of 0.7 to 0.9 is within the scope of protection of this application.

[0085] This application controls the coefficient k within the range of 0.7 to 0.9, so that different coefficient k can be selected according to different secondary batteries 100 to reasonably design the thickness of the second insulating coating 140, further ensuring the uniformity of the thickness of the second insulating coating 140, further reducing the risk of insulation breakdown at the second connection 114 of the housing 110, further improving the safety performance of the housing 110, and further improving the safety performance of the secondary battery 100.

[0086] In one embodiment, the second insulating coating 140 includes a first sub-coating 141 and a second sub-coating 142. The first sub-coating 141 is disposed near the second connecting portion 114 relative to the second sub-coating 142, that is, the first sub-coating 141 is coated on the outer surface of the second connecting portion 114, and the second sub-coating 142 is coated on the outer surface of the first sub-coating 141.

[0087] The materials of the first sub-coating 141 and the second sub-coating 142 can be the same or different. This application does not make specific limitations and can be set according to the actual situation.

[0088] The first sub-coating 141 and the second sub-coating 142 can be made of polyurethane acrylate resin, epoxy acrylate resin, or ceramic materials, but are not limited to these. The ceramic material can be made of one or more of the following, but are not limited to: aluminum oxide, titanium dioxide, silicon dioxide, zirconium dioxide, tin dioxide, magnesium oxide, zinc oxide, boron nitride, aluminum nitride, magnesium nitride, etc.

[0089] Specifically, the thickness of the first sub-coating 141 is H3 mm, and the thickness of the second sub-coating 142 is H4 mm, satisfying: H2=H3+H4, that is, the sum of the thickness of the first sub-coating 141 (H3 mm) and the thickness of the second sub-coating 142 (H4 mm) is the thickness of the second insulating coating 140 (H2 mm).

[0090] The methods for measuring the thickness H3 mm of the first sub-coating 141 and the thickness H4 mm of the second sub-coating 142 are the same as those for measuring the thickness H1 mm of the first insulating coating 130, and will not be elaborated further here. Please refer to the description above.

[0091] In one embodiment, the thickness H3 mm of the first sub-coating 141 further satisfies: 0.092 mm ≤ H3 ≤ 0.128 mm. That is, the thickness H3 mm of the first sub-coating 141 can be controlled within the range of 0.092 mm to 0.128 mm. For example, the thickness H3 mm of the first sub-coating 141 can be one of 0.092 mm, 0.095 mm, 0.10 mm, 0.105 mm, 0.11 mm, 0.115 mm, 0.12 mm, 0.125 mm, or 0.128 mm, or any combination thereof. The specific values ​​of H3 mm mentioned above are merely illustrative examples, and any value within the range of 0.092 mm to 0.128 mm is within the protection scope of this application.

[0092] This application limits the thickness H3 mm of the first sub-coating 141 to within the range of 0.092 mm to 0.128 mm to achieve a reasonable design of the thickness of the first sub-coating 141, and consequently, a reasonable design of the thickness of the second insulating coating 140. This further reduces the risk of insulation breakdown at the second connection portion 114 of the housing 110, further improves the safety performance of the housing 110, and further improves the safety performance of the secondary battery 100.

[0093] In one embodiment, the secondary battery 100 further includes a third insulating coating 150, which is disposed on the outer surfaces of the sidewall 111 and the bottom wall 112 to provide insulation protection for the sidewall 111 and the bottom wall 112, thereby providing insulation protection for the entire housing 110.

[0094] The third insulating coating 150 can be made from polyurethane acrylate resin, epoxy acrylate resin, or ceramic materials, but is not limited to these. For example, the ceramic material can be made from one or more of aluminum oxide, titanium dioxide, silicon dioxide, zirconium dioxide, tin dioxide, magnesium oxide, zinc oxide, boron nitride, aluminum nitride, and magnesium nitride, but is not limited to these. Furthermore, the raw materials of the third insulating coating 150 may also contain a photoinitiator (such as at least one of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide and 1-hydroxycyclohexylphenyl ketone) and a diluent (including at least one of benzyl acrylate, phenoxyethyl acrylate, and 1,6-hexanediol diacrylate). The mass percentage of the main material in the raw materials of the third insulating coating 150 is 10%-50%, the mass percentage of the photoinitiator is 2%-8%, and the mass percentage of the reactive diluent is 40%-80%.

[0095] Specifically, the thickness of the third insulating coating 150 is H5 mm, satisfying: 0.8 ≤ H1 / H5 ≤ 2. That is, the ratio H1 / H5 of the thickness H1 mm of the first insulating coating 130 and the thickness H5 mm of the third insulating coating 150 can be controlled within the range of 0.8 to 2. For example, H1 / H5 can be one of 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, or 2, or any combination thereof. The specific values ​​of H1 / H5 given above are merely illustrative examples, and any value within the range of 0.8 to 2 is within the protection scope of this application.

[0096] The method for measuring the thickness H5 mm of the third insulating coating 150 is the same as the method for measuring the thickness H1 mm of the first insulating coating 130, and will not be elaborated here. Please refer to the description above.

[0097] This application controls the ratio H1 / H5 of the thickness H1 mm of the first insulating coating 130 and the thickness H5 mm of the third insulating coating 150 within the range of 0.8 to 2, so as to reasonably design the parameter relationship between the thickness H1 mm of the first insulating coating 130 and the thickness H5 mm of the third insulating coating 150, avoid the housing 110 from being broken down by the insulation withstand voltage of the first insulating coating 130 and the third insulating coating 150, reduce the risk of insulation withstand voltage breakdown of the housing 110, further improve the safety performance of the housing 110, and further improve the safety performance of the secondary battery 100.

[0098] In one embodiment, the thickness H5 mm of the third insulating coating 150 further satisfies: 0.046 mm ≤ H5 ≤ 0.16 mm. That is, the thickness H5 mm of the third insulating coating 150 can be controlled within the range of 0.046 mm to 0.16 mm. For example, the thickness H5 mm of the third insulating coating 150 can be one or a combination of any two of the following: 0.046 mm, 0.05 mm, 0.06 mm, 0.07 mm, 0.08 mm, 0.090 mm, 0.1 mm, 0.11 mm, 0.12 mm, 0.13 mm, 0.14 mm, 0.15 mm, or 0.16 mm. The specific values ​​of H5 mm given above are merely illustrative; any value within the range of 0.046 mm to 0.16 mm is within the scope of protection of this application.

[0099] This application controls the thickness H5 mm of the third insulating coating 150 within the range of 0.046 mm to 0.16 mm. By reasonably designing the thickness H5 mm of the third insulating coating 150, this application avoids the housing 110 being broken down by the insulation withstand voltage at the third insulating coating 150, reduces the risk of insulation withstand voltage breakdown of the housing 110, further improves the safety performance of the housing 110, and further improves the safety performance of the secondary battery 100.

[0100] In one embodiment, this application also provides a method for manufacturing a housing 110. Exemplarily, the method includes: die-casting aluminum material using a die-casting mold to obtain a preliminary model of the housing; cleaning the preliminary model of the housing using laser or plasma; after cleaning, uniformly spraying insulating material onto the outer surface of the preliminary model of the housing using UV spraying equipment; and after spraying, applying an energy density of 1–10 J / cm². 2 The insulating coating of the shell is cured by ultraviolet light, and the shell 110 in this application is finally obtained.

[0101] In one embodiment, the coating hardness of the first insulating coating 130, the second insulating coating 140, and the third insulating coating 150 is not less than HB. That is, only a pencil with a hardness of not less than HB can leave scratches on the first insulating coating 130, the second insulating coating 140, and the third insulating coating 150, so as to ensure that the first insulating coating 130, the second insulating coating 140, and the third insulating coating 150 have a certain hardness and avoid the first insulating coating 130, the second insulating coating 140, and the third insulating coating 150 being easily damaged.

[0102] The test method for the hardness of the first insulating coating 130, the second insulating coating 140, and the third insulating coating 150 is as follows: At 25°C, a pencil of a certain hardness is inserted into the testing instrument and fixed with a clamp to keep the instrument horizontal. The pencil tip is placed on the surface of the first insulating coating 130, the second insulating coating 140, or the third insulating coating 150. After the pencil tip contacts the insulating coating, the pencil is pushed at a speed of 0.5 mm / s to 1 mm / s to move at least 7 mm. Observe whether a scratch of at least 3 mm appears on the surface of the insulating coating. If no scratch appears, the test is repeated with a pencil of higher hardness. See GB / T6739-2006 for details.

[0103] On the other hand, in the embodiments of this application, this application also provides a battery pack, including: a housing; and a secondary battery 100 as described in any of the above embodiments, the secondary battery 100 being housed in the housing.

[0104] The aforementioned battery pack can be a three-tiered battery pack consisting of a secondary battery, a battery module, and a battery pack, or a module-less battery pack consisting of a secondary battery and a battery pack.

[0105] On the other hand, in embodiments of this application, an electrical device is also provided, including a battery pack as described above, which serves as the power supply for the electrical device. The electrical device may be, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0106] To better understand the technical solution of this application, specific embodiments are provided below for further explanation.

[0107] This embodiment provides a method for preparing the casing 110 of a secondary battery 100, the specific process of which is as follows:

[0108] 1. Preparation of the shell

[0109] A preliminary shell model is obtained by die-casting aluminum material using a die-casting mold. This preliminary shell model is then cleaned using laser or plasma. After cleaning, insulating material is evenly sprayed onto the outer surface of the preliminary shell model using UV spraying equipment. After spraying, an energy density of 1–10 J / cm³ is applied. 2 Ultraviolet light is used to cure the insulating coating of the shell to obtain the final shell. The insulating coatings are made of the following materials as examples.

[0110] The first insulating coating 130 is made of polyurethane acrylate resin as the main material, and is prepared according to the following mass percentages: polyurethane acrylate resin, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, and benzyl acrylate, which are 20%, 5%, and 75%, respectively.

[0111] The second insulating coating 140 is made of polyurethane acrylic resin as the main material, and is prepared according to the following mass percentages: polyurethane acrylic resin, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, and benzyl acrylate, which are 25%, 5%, and 70%, respectively.

[0112] The third insulating coating 150 is made of polyurethane acrylate resin as the main material, and is prepared according to the following mass percentages: polyurethane acrylate resin, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, and benzyl acrylate, which are 30%, 5%, and 65%, respectively.

[0113] Among them, the housings of each embodiment and comparative example are all prepared according to the above preparation method. For the structural dimensions and performance test data of each embodiment and comparative example, refer to Table 1, Table 2 and Table 3.

[0114] Among them, in Examples 1 to 16 and Comparative Examples 1 to 4 in Table 1, the housings are prepared according to the above method. Compared with Example 1, in Examples 2 to 16 and Comparative Examples 1 to 4, the differences are: the changes in the values of R, α, β and H1.

[0115] In Examples 17 to 36 in Table 2, the housings are prepared according to the method of Example 1. Compared with Example 1, in Examples 17 to 36, the differences are: the changes in the values of H1, k, H3, H4 and H2.

[0116] In Examples 37 to 47 in Table 3, the housings are prepared according to the above method. Compared with Examples 37 to 47, the differences are: the changes in the values of H1, H5 and H1 / H5.

[0117] Perform performance tests on the housings 110 obtained from the above examples and comparative examples. The methods for specific test items are as follows:

[0118] 1. Test method for insulation breakdown of the housing of a secondary battery

[0119] At 25°C, place the housing in an insulation withstand voltage test device (set the upper limit of the current to 15 μA), control the insulation withstand voltage test device to apply a DC voltage of 3150 V to the housing for 30 s to obtain the leakage current of the housing and observe whether the housing shows a breakdown phenomenon. When the leakage current of the housing is not greater than 15 μA and the housing does not show a breakdown phenomenon, it means that the insulation performance of the housing is qualified.

[0120] 2. Test method for insulation resistance of the housing of a secondary battery

[0121] At 25°C, place the housing in an insulation withstand voltage test device (resistance upper limit 11 GΩ), control the insulation withstand voltage test device to apply a DC voltage of 1000 V to the housing to obtain the corresponding current value, and calculate the insulation resistance of the housing. Among them, when the insulation resistance is greater than 11 GΩ, it means that the insulation performance of the housing is qualified.

[0122] Record the relevant parameters and test results in the above examples and comparative examples in Table 1, Table 2 and Table 3 respectively.

[0123] Table 1 shows the influence of the parameter relationship between the radius R mm of the outer wall surface 1131 of the housing 110, the maximum central angle α corresponding to the outer wall surface 1131, the included angle β between the reference line 1134 and the bottom wall 112, and the thickness H1 mm of the first insulation coating 130 on the housing.

[0124] Table 1. Parameters and test results of Examples 1-16 and Comparative Examples 1-4

[0125]

[0126]

[0127] As shown in Table 1, in Comparative Examples 1, 3, and 4, the specific parameters of the housing 110 exceeded the range specified in this application, and the thickness of the first insulating coating 130 was relatively small, leading to breakdown of the housing 110. The housing 110 did not exhibit the corresponding insulation and withstand voltage performance. In Comparative Example 2, the specific parameters of the housing 110 exceeded the range specified in this application, and the thickness of the first insulating coating 130 was relatively thick, resulting in incomplete curing of the first insulating coating 130 during UV curing, leading to breakdown of the housing 110. The housing 110 did not exhibit the corresponding insulation and withstand voltage performance. However, in Examples 1 to 16, because the thickness H1 mm of the first insulating coating 130 was controlled within the range of 0.092 mm to 0.128 mm, it exhibited superior insulation, withstand voltage, and safety performance compared to Comparative Examples 1 to 4.

[0128] Therefore, this application limits the thickness H1 mm of the first insulating coating 130 to within the range of 0.092 mm to 0.128 mm, the radius R mm of the outer wall surface 1131 to within the range of 1 mm to 3 mm, the maximum central angle α corresponding to the outer wall surface 1131 to within the range of 60° to 90°, and the included angle β between the reference line 1134 and the bottom wall 112 to within the range of 130° to 170°. This allows for a reasonable design of the thickness of the first insulating coating 130 based on the structural dimensions at the first connecting part 113, ensuring the uniformity of the thickness of the first insulating coating 130, reducing the risk of insulation breakdown of the housing 110, improving the safety performance of the housing 110, and thus improving the safety performance of the secondary battery 100. At the same time, it increases the first-pass yield of the first insulating coating 130, thereby improving the processing efficiency of the housing 110 and ultimately improving the production efficiency of the secondary battery 100. Table 2 shows the influence of the parameter relationships between the thickness H1 mm of the first insulating coating 130, coefficient k, the thickness H3 mm of the first sub-coating 141, the thickness H4 mm of the second sub-coating 142, and the thickness H2 mm of the second insulating coating 140 on the housing 110.

[0129] Table 2. Parameters and test results of Examples 1 and 17-36

[0130]

[0131]

[0132] As shown in Table 2, in Examples 33 and 35, the specific parameters of the housing 110 exceeded the parameter range specified in this application, and the thickness of the second insulating coating 140 was relatively small, leading to breakdown of the housing 110. The housing 110 did not exhibit the corresponding insulation and withstand voltage performance. In Examples 34 and 36, the specific parameters of the housing 110 exceeded the parameter range specified in this application, and the thickness of the second insulating coating 140 was relatively large, resulting in incomplete curing of the second insulating coating 140 during ultraviolet light curing, leading to breakdown of the housing 110. The housing 110 did not exhibit the corresponding insulation and withstand voltage performance. However, the insulation and withstand voltage performance of the housings in Examples 1 and 17-32 showed a certain degree of improvement compared to Examples 33-36.

[0133] Therefore, this application limits the thickness H1 mm of the first insulating coating 130 to the range of 0.092 mm to 0.128 mm, the coefficient k to the range of 0.7 to 0.9, the thickness H3 mm of the first sub-coating 141 to the range of 0.092 mm to 0.128 mm, and the thickness H2 mm of the second insulating coating 140 to the range of 0.097 mm to 0.173 mm, so as to reasonably design the thickness of the second insulating coating 140 according to the various structural dimensions of the housing 110, ensure the uniformity of the thickness of the second insulating coating 140, reduce the risk of insulation withstand voltage breakdown of the housing 110, improve the safety performance of the housing 110, and thus improve the safety performance of the secondary battery 100.

[0134] Table 3 shows the effect of the parameter relationship between the thickness H1 mm of the first insulating coating 130 and the thickness H5 mm of the third insulating coating 150 on the housing.

[0135] Table 3. Parameters and test results of Examples 1 and 37-47

[0136]

[0137]

[0138] As shown in Table 3, in Example 46, the specific parameters of the housing 110 exceeded the parameter range in this application, and the thicknesses of the first insulating coating 130 and the third insulating coating 150 were both relatively small, resulting in a breakdown phenomenon in the housing 110. The housing 110 did not exhibit the corresponding insulation and withstand voltage performance. In Example 47, the specific parameters of the housing 110 exceeded the parameter range in this application, and the thicknesses of the first insulating coating 130 and the third insulating coating 150 were relatively large, resulting in incomplete curing of the first insulating coating 130 and the third insulating coating 150 during ultraviolet curing, leading to a breakdown phenomenon in the housing 110. The housing 110 did not exhibit the corresponding insulation and withstand voltage performance. However, the insulation and withstand voltage performance of the housings in Examples 1 and Examples 37-46 are improved to a certain extent compared to Examples 46-47.

[0139] Therefore, this application limits the thickness H1 mm of the first insulating coating 130 to the range of 0.092 mm to 0.128 mm, the thickness H5 mm of the third insulating coating 150 to the range of 0.046 mm to 0.16 mm, and the ratio H1 / H5 of the thickness H1 mm of the first insulating coating 130 and the thickness H5 mm of the third insulating coating 150 to the range of 0.8 to 2, so as to reasonably design the thickness of the first insulating coating 130 and the third insulating coating 150, avoid the casing 110 from being broken down by the first insulating coating 130 and the third insulating coating 150, reduce the risk of insulation breakdown of the casing 110, further improve the safety performance of the casing 110, and further improve the safety performance of the secondary battery 100.

[0140] The above steps are provided only to help understand the method, structure, and core ideas of this application. Those skilled in the art can make various improvements and modifications to this application without departing from its principles, and these improvements and modifications also fall within the scope of protection of the claims.

Claims

1. A secondary battery having a first orientation, characterized in that, include: A housing, comprising: a sidewall, a bottom wall, and a first connecting portion; the sidewall extends along a first direction; the bottom wall is disposed on one side of the sidewall in the first direction; the sidewall and the bottom wall cooperate to form an accommodating cavity; the two ends of the first connecting portion are respectively connected to the sidewall and the bottom wall; the outer wall surface of the first connecting portion away from the accommodating cavity is an arc surface; the outer wall surface has a first outer edge contour line near the sidewall and a second outer edge contour line near the bottom wall; the first connecting portion also has a reference line, the reference line connecting the first outer edge contour line and the second outer edge contour line, and the reference line is the shortest connecting line between the first outer edge contour line and the second outer edge contour line; Electrode assembly, disposed within the accommodating cavity; and A first insulating coating is disposed on the outer wall surface of the first connecting portion; The thickness of the first insulating coating is H1 mm, satisfying: H1 = 0.09175 + 0.00294X + 0.06165X 2 -0.03236X 3 , 0.092mm≤H1≤0.128mm; X=R×sin(α / 2)×sin(180°-β), 60°≤α≤90°, 140°≤β≤170°; R mm is the radius of the outer wall surface, satisfying: 1mm≤R≤3mm, α is the maximum central angle corresponding to the outer wall surface, and β is the angle between the reference line and the bottom wall.

2. The secondary battery as described in claim 1, characterized in that, The secondary battery also has a second direction and a third direction that intersect the first direction in pairs; The sidewall includes: a first sub-sidewall opposite to each other in the first direction, and a second sub-sidewall opposite to each other in the second direction, wherein the first sub-sidewall and the second sub-sidewall are connected by the first connecting portion.

3. The secondary battery as described in claim 2, characterized in that, The housing further includes: a second connecting portion, which is connected to the first sub-sidewall, the second sub-sidewall, and the bottom wall respectively; The secondary battery further includes: a second insulating coating disposed on the outer surface of the second connection portion; The thickness of the second insulating coating is H2mm, which satisfies: H2=1.5k×H1; Where k is a variable coefficient, and 0.7≤k≤0.

9.

4. The secondary battery as described in claim 3, characterized in that, The thickness H2mm of the second insulating coating also satisfies: 0.097mm≤H2≤0.173mm.

5. The secondary battery as described in claim 3, characterized in that, The second insulating coating includes: a first sub-coating and a second sub-coating, wherein the first sub-coating is disposed near the second connection portion relative to the second sub-coating; The thickness of the first sub-coating is H3mm, and the thickness of the second sub-coating is H4mm, satisfying: H2=H3+H4.

6. The secondary battery as described in claim 5, characterized in that, The thickness H3mm of the first sub-coating also satisfies: 0.092mm≤H3≤0.128mm.

7. The secondary battery as described in claim 1, characterized in that, It also includes: a third insulating coating, disposed on the outer surface of the sidewall and the bottom wall; The thickness of the third insulating coating is H5mm, which satisfies: 0.8≤H1 / H5≤2.

8. The secondary battery as described in claim 7, characterized in that, The thickness H5mm of the third insulating coating also satisfies: 0.046mm≤H5≤0.16mm.

9. A battery pack, characterized in that, include: Box; as well as The secondary battery as described in any one of claims 1 to 8, wherein the secondary battery is housed within the casing.

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