An explosion-proof valve plate, a preparation method of the explosion-proof valve plate and a lithium ion battery

Abstract

In order to overcome the problem that the battery micro-short circuit corrosion explosion-proof valve in the prior art causes electrolyte to leak at the notch of the explosion-proof valve, an explosion-proof valve sheet, a preparation method of the explosion-proof valve sheet and a lithium ion battery are provided; the explosion-proof valve sheet comprises a first surface with a notch and a second surface arranged opposite to the first surface in the thickness direction of the explosion-proof valve sheet; the explosion-proof valve sheet is provided with an anodic oxidation film layer on the first surface and the second surface, or the explosion-proof valve sheet is provided with an anodic oxidation film layer on the second surface; the projection area of the anodic oxidation film layer on the explosion-proof valve sheet is greater than the projection area of the notch on the explosion-proof valve sheet. The explosion-proof valve sheet provided by the application covers the second surface of the explosion-proof valve sheet with the anodic oxidation film layer, forms a protective layer on the surface of the valve sheet, improves the corrosion resistance of the explosion-proof valve sheet, covers the notch area with the anodic oxidation film layer, ensures that the notch area is also protected by the anodic oxidation film layer, and further improves or avoids the problem that the notch of the explosion-proof valve sheet is corroded and penetrated when the battery appears micro-short circuit.

Description

Technical Field

[0001] This invention belongs to the field of battery manufacturing technology, specifically relating to an explosion-proof valve plate, a method for preparing the explosion-proof valve plate, and a lithium-ion battery. Background Technology

[0002] Lithium batteries are subject to the risk of internal gas expansion and increased pressure due to thermal runaway during use. To address this, an explosion-proof valve is installed, which can rupture to release gas and pressure when the pressure reaches a certain level, thus ensuring battery safety.

[0003] In lithium batteries, the explosion-proof valve is connected to the aluminum casing of the battery cell. The aluminum casing often experiences a micro-short circuit with the negative electrode of the cell. When the negative electrode tabs are scattered, have burrs, contain metallic foreign matter, or the plastic insulating film encasing the current collector is damaged, micro-contact channels can form between the negative electrode and the casing, leading to a micro-short circuit. Once a micro-short circuit occurs, lithium ions in the electrolyte migrate towards the aluminum casing and form lithium-aluminum compounds, causing corrosion of the aluminum casing. When this corrosion occurs at the explosion-proof valve, it can easily cause the scored areas of the valve to be corroded through, leading to valve failure and electrolyte leakage. Summary of the Invention

[0004] To address the problem in existing technologies where micro-short circuits corrode the explosion-proof valve, leading to electrolyte leakage at the grooves on the explosion-proof valve, this paper provides an explosion-proof valve plate, a method for preparing the explosion-proof valve plate, and a lithium-ion battery.

[0005] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows:

[0006] On one hand, the present invention provides an explosion-proof valve plate, including a first surface having grooves and a second surface disposed opposite to the first surface in the thickness direction of the explosion-proof valve plate;

[0007] The explosion-proof valve plate has an anodic oxide film layer on both the first surface and the second surface.

[0008] Alternatively, the explosion-proof valve plate has an anodized film layer on the second surface;

[0009] The projected area of ​​the anodic oxide film on the explosion-proof valve plate is greater than the projected area of ​​the etched marks on the explosion-proof valve plate.

[0010] Optionally, the outline of the anodic oxide film is the same as the outline of the groove.

[0011] Optionally, the width of the anodic oxide film is a, the width of the groove is b, and the width of the anodic oxide film satisfies ab≥0.2mm.

[0012] Optionally, the outline of the anodic oxide film is the same as the outline of the explosion-proof valve plate.

[0013] Optionally, the projected area of ​​the anodic oxide film layer on the explosion-proof valve plate is smaller than the cross-sectional area of ​​the explosion-proof valve plate in its thickness direction;

[0014] The distance c between the edge of the anodic oxide film and the edge of the explosion-proof valve plate is ≥ 0.5 mm;

[0015] The distance d between the edge of the anodic oxide film and the projection of the indentation onto the first and / or second surfaces of the explosion-proof valve plate is ≥0.1 mm.

[0016] Optionally, the thickness H1 of the anodic oxide film layer on the first or second surface of the explosion-proof valve plate is 1μm-20μm.

[0017] Optionally, the thickness H1 of the anodic oxide film is 1 μm-12 μm.

[0018] Optionally, the projected area of ​​the anodic oxide film layer on the explosion-proof valve plate is the area of ​​the second surface.

[0019] Optionally, when the explosion-proof valve plate is provided with the anodic oxide film layer on both the first surface and the second surface, the thickness of the anodic oxide film layer on the first surface and / or the second surface is the same, and the thickness H5 of the anodic oxide film layer is 1μm-10μm;

[0020] When the explosion-proof valve plate is provided with an anodic oxide film layer on the second surface, the thickness H2 of the anodic oxide film layer is 1μm-20μm.

[0021] Optionally, the anodic oxide film layer forms a non-welded area and a welded area surrounding the non-welded area on the explosion-proof valve plate. The projected area of ​​the non-welded area on the second surface is larger than the projected area of ​​the groove on the second surface. The thickness of the anodic oxide film layer on the welded area is different from the thickness on the non-welded area.

[0022] Optionally, the welding area is arranged around the outside of the non-welding area, and the edge of the welding area is a distance e from the projection of the groove on the second surface, wherein the distance e is ≥ 0.1 mm.

[0023] Optionally, the thickness H3 of the welding area of ​​the anodic oxide film is 1μm-12μm;

[0024] The thickness H4 of the non-welding area of ​​the anodic oxide film is 1μm-20μm.

[0025] On the other hand, the present invention provides a method for preparing the explosion-proof valve plate, comprising the following operations:

[0026] Pretreatment of valve plates;

[0027] Anodizing treatment of valve plates: Take the valve plates that have completed the pretreatment and place them in anodizing solution to perform anodizing, forming an anodized film layer on the valve plates.

[0028] Optionally, it may also include at least one of the following technical features:

[0029] a. The anodizing time is 2.5 min - 60 min;

[0030] b. The voltage for anodizing is 20V-30V;

[0031] c. The current density for anodizing is 0.1 A / m 2 -10 A / m 2 .

[0032] On the other hand, the present invention also provides a lithium-ion battery, including a cover plate, a cell, a housing, and the aforementioned explosion-proof valve plate, or an explosion-proof valve plate prepared by the aforementioned explosion-proof valve plate preparation method; the explosion-proof valve plate is disposed on the cover plate, and the cell is placed inside the housing.

[0033] The beneficial effects of the present invention are as follows: The explosion-proof valve plate provided by the present invention includes a first surface with grooves and a second surface disposed opposite to the first surface in the thickness direction of the explosion-proof valve plate. An anodic oxide film layer is disposed on both the first and second surfaces, or only on the second surface. The anodic oxide film layer covers the second surface of the explosion-proof valve plate and forms a dense oxide protective layer on the surface of the valve plate, thereby improving the corrosion resistance of the explosion-proof valve plate. At the same time, the projected area of ​​the anodic oxide film layer on the explosion-proof valve plate is larger than the projected area of ​​the grooves on the explosion-proof valve plate, indicating that the anodic oxide film layer can completely cover the grooved area, ensuring that the grooved area can also be protected by the anodic oxide film layer, thereby improving or avoiding the problem of corrosion penetration of the grooves of the explosion-proof valve plate when a micro-short circuit occurs in the battery. Attached Figure Description

[0034] Figure 1 This is a three-dimensional structural diagram of the explosion-proof valve plate provided in the first embodiment of the present invention;

[0035] Figure 2 This is a top view of the explosion-proof valve plate provided in the first embodiment of the present invention;

[0036] Figure 3 This is a bottom view of the explosion-proof valve plate provided in the first embodiment of the present invention;

[0037] Figure 4yes Figure 2 Sectional view at point AA;

[0038] Figure 5 yes Figure 4 A magnified view of a section at point A1;

[0039] Figure 6 This is a top view of the explosion-proof valve plate provided in the second embodiment of the present invention;

[0040] Figure 7 This is a bottom view of the explosion-proof valve plate provided in the second embodiment of the present invention;

[0041] Figure 8 yes Figure 6 Sectional view at point BB;

[0042] Figure 9 yes Figure 8 A magnified view of a section at point B1;

[0043] Figure 10 This is a top view of the explosion-proof valve plate provided in the third embodiment of the present invention;

[0044] Figure 11 This is a bottom view of the explosion-proof valve plate provided in the third embodiment of the present invention;

[0045] Figure 12 yes Figure 10 Sectional view at CC;

[0046] Figure 13 yes Figure 12 A magnified view of a section at point C1;

[0047] Figure 14 This is a bottom view of the explosion-proof valve plate provided in the fourth embodiment of the present invention;

[0048] Figure 15 yes Figure 14 Sectional view at point DD;

[0049] Figure 16 yes Figure 15 A magnified view of a section at point D1;

[0050] Figure 17 This is a bottom view of the explosion-proof valve plate provided in the fifth embodiment of the present invention;

[0051] Figure 18 yes Figure 17 Sectional view at EE;

[0052] Figure 19 yes Figure 18 A magnified view of a section at point E1;

[0053] Figure 20This is a top view of the explosion-proof valve plate provided in the sixth embodiment of the present invention;

[0054] Figure 21 yes Figure 20 Sectional view at FF;

[0055] Figure 22 yes Figure 21 A magnified view of the area at F1 in the middle;

[0056] Figure 23 This is a surface appearance diagram of the explosion-proof valve plate provided in the eighth embodiment of the present invention after undergoing corrosion resistance testing;

[0057] Figure 24 This is a surface appearance diagram of the explosion-proof valve plate provided in the first comparative example of the present invention after corrosion resistance performance testing.

[0058] The reference numerals in the accompanying drawings are as follows:

[0059] 101. First surface; 102. Second surface; 1021. Welding zone; 1022. Non-welding zone;

[0060] 10. Scratches; 20, 201, 202 anodic oxide film layers. Detailed Implementation

[0061] To make the technical problems solved, the technical solutions, and the beneficial effects 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 of the invention and are not intended to limit the invention.

[0062] In the description of this invention, it should be understood that the terms "longitudinal," "radial," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the 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, and therefore should not be construed as a limitation of the invention. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0063] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" 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 or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0064] Reference Figure 1-22 This invention provides an explosion-proof valve plate, including a first surface 101 with grooves 10 and a second surface 102 disposed opposite to the first surface 101 in the thickness direction of the explosion-proof valve plate. The first surface 101, due to the grooves 10, has different thicknesses in the thickness direction of the explosion-proof valve plate. In the thickness direction of the explosion-proof valve plate, all surfaces opposite to the second surface 102 are collectively referred to as the first surface 101. In this invention, Figures 1-20 The shape of the notch 10 shown is for illustrative purposes only. The present invention does not limit the shape and arrangement of the notch 10 provided on the first surface 101.

[0065] like Figures 1-22 As shown, the present invention provides an explosion-proof valve plate having an anodic oxide film layer 20 on both the first surface 101 and the second surface 102, or having the anodic oxide film layer 20 on the second surface 102. By providing the anodic oxide film layer 20 on the explosion-proof valve plate, a dense oxide protective layer is formed on the surface of the explosion-proof valve plate, thereby improving the corrosion resistance of the explosion-proof valve plate.

[0066] Furthermore, the projected area of ​​the anodic oxide film layer 20 on the explosion-proof valve plate provided by the present invention is larger than the projected area of ​​the groove 10 on the explosion-proof valve plate. Thus, the anodic oxide film layer 20 completely covers the projected area of ​​the groove 10 on the second surface 102 of the explosion-proof valve plate, so that the weakest groove 10 area of ​​the explosion-proof valve plate can be protected by the anodic oxide film layer 20, thereby improving or avoiding the problem of the groove 10 of the explosion-proof valve plate being corroded and penetrated when a micro short circuit occurs in the battery.

[0067] To avoid adverse effects on the explosion-proof valve plate during subsequent welding processes and to meet the detonation pressure requirements in the application of the explosion-proof valve plate, it is also necessary to control the thickness of the anodic oxide film 20 set on the explosion-proof valve plate body.

[0068] The anodic oxide film layer 20 in the explosion-proof valve plate provided by this invention is formed by reacting with aluminum during the anodizing process to create an aluminum anodic oxide film. The main component of this aluminum anodic oxide film is Al2O3. This process consumes the thickness of the explosion-proof valve plate substrate itself. Furthermore, the explosion-proof valve plate uses high-elongation aluminum, which differs significantly from the hard and brittle aluminum oxide film. Therefore, to ensure the plasticity and detonation pressure requirements of the explosion-proof valve plate, the thickness of the anodic oxide film layer 20 also needs to be controlled. Therefore, the thickness H1 of the anodic oxide film layer 20 on the first surface 101 or the second surface 102 in the explosion-proof valve plate provided by this invention is 1 μm-20 μm. That is, the thickness H1 of the anodic oxide film layer 20 on the first surface 101 or the second surface 102 of the explosion-proof valve plate can be 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 16μm, 16μm, 17μm, 18μm, 19μm, 20μm, or any value between any two of the above ranges. When the thickness of the anodic oxide film is set in the range of 1μm-20μm, it can enhance the corrosion resistance of the explosion-proof valve plate without affecting the welding of the explosion-proof valve plate, and at the same time meet the detonation pressure requirements in the application of the explosion-proof valve plate.

[0069] In addition, when the thickness H1 of the anodic oxide film layer 20 is in the range of 1μm-20μm, it can provide good corrosion protection for the explosion-proof valve plate. The anodic oxide film layer 20 can effectively isolate the contact between air, moisture and other corrosive media and the valve plate substrate, prevent the explosion-proof valve plate from being corroded, and thus extend the service life of the explosion-proof valve plate. If the anodic oxide film layer 20 is too thick, it will reduce the flexibility of the explosion-proof valve plate and make it prone to brittle fracture when subjected to pressure.

[0070] Preferably, while taking into account the welding requirements and detonation pressure of the explosion-proof valve plate, it can also have a good anti-corrosion protection effect. The thickness H1 of the anodic oxide film layer 20 in the explosion-proof valve plate provided by the present invention is 1μm-12μm. That is, the thickness H1 of the anodic oxide film layer 20 on the first surface 101 or the second surface 102 of the explosion-proof valve plate can be 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm or any value between any two of the above ranges.

[0071] First embodiment:

[0072] Reference Figure 1-5 This is a three-dimensional structural diagram and related schematic diagram of the explosion-proof valve plate provided in the first embodiment of the present invention. In this embodiment, as shown... Figure 1As shown, the outline of the anodic oxide film 20 is the same as that of the notch 10. Specifically, the identical outline of the anodic oxide film 20 and the notch 10 facilitates precise coverage of the notch 10. Since the notch 10 is a critical part of the explosion-proof valve plate under pressure, the identical outline of the anodic oxide film 20 provides all-around protection, preventing external factors from interfering with the structural integrity of the notch 10 and ensuring that the notch 10 ruptures as expected under pressure, thus improving the reliability of the explosion-proof valve plate. Because the two have the same outline, when pressure is applied to the explosion-proof valve plate, the notch 10 and the surrounding area protected by the anodic oxide film 20 are subjected to force more evenly, resulting in smoother and more symmetrical pressure transmission. This helps the explosion-proof valve plate to open more precisely and quickly when the detonation pressure is reached, achieving timely pressure release and improving the sensitivity and accuracy of the explosion-proof valve plate's pressure response.

[0073] Meanwhile, since the anodic oxide film 20 is located at the notch 10, when the explosion-proof valve plate is installed on the battery casing and a micro-short circuit occurs between the casing and the negative electrode, the anodic oxide film 20 can effectively protect the notch 10 of the explosion-proof valve plate, blocking the micro-corrosion in the notch 10 area of ​​the explosion-proof valve plate. This can effectively improve and avoid the problem of the battery electrolyte causing micro-corrosion in the notch 10 area of ​​the explosion-proof valve plate and eroding the explosion-proof valve plate.

[0074] Reference Figures 2-4 As shown, in this embodiment, the explosion-proof valve plate has an anodic oxide film layer 20 on both the first surface 101 and the second surface 102. Figure 1 and Figure 2 As shown, the first surface 101 of the explosion-proof valve plate has grooves 10, and an anodized film layer 20 is covered on the grooves 10. Figure 3 As shown, an anodized film layer 20 is provided on the second surface 102 of the explosion-proof valve plate, and the shape of the anodized film layer 20 is the same as the shape of the groove 10 located on the first surface 101. Figure 4 As shown in the cross-sectional view of the explosion-proof valve plate, an anodic oxide film layer 20 is provided on both the upper and lower sides along the thickness direction of the explosion-proof valve plate. That is, an anodic oxide film layer 20 is provided on both the front and back sides of the explosion-proof valve plate in the thickness direction, and the anodic oxide film layer 20 is distributed on the upper and lower sides of the groove 10 area of ​​the explosion-proof valve plate, thereby providing targeted protection for the groove 10 area of ​​the explosion-proof valve plate.

[0075] Reference Figure 2The width of the anodic oxide film 20 is 'a', and the width of the notch 10 is 'b'. The width of the anodic oxide film 20 satisfies ab ≥ 0.2 mm. The notch 10 is a key component of the explosion-proof valve plate for detonation under pressure, and its surrounding area is also susceptible to external environmental factors (such as corrosion and wear). When the width of the anodic oxide film 20 satisfies ab ≥ 0.2 mm, it ensures that the anodic oxide film 20 is at least 0.1 mm away from the edge of the notch 10 on one side, ensuring that the anodic oxide film 20 completely covers the area where the notch 10 is located. This provides a reliable protective boundary around the notch 10. A wider anodic oxide film 20 can better isolate the area around the notch 10 from external factors, effectively preventing the notch 10 from prematurely failing due to surrounding damage or abnormally rupturing under pressure when a micro-short circuit occurs in the battery. This improves the reliability and stability of the explosion-proof valve plate under various environmental conditions. Furthermore, when the width of the anodic oxide film layer 20 satisfies ab≥0.2mm, the projected area of ​​the anodic oxide film layer 20 on the explosion-proof valve plate is greater than the projected area of ​​the notch 10 on the explosion-proof valve plate, so as to ensure that the anodic oxide film layer 20 can effectively protect the notch 10 area on the explosion-proof valve plate.

[0076] Reference Figure 4-5 In this embodiment, the anodic oxide film layer 20 is shown in the cross-sectional view and partial enlarged view at the notch 10. The surface of the explosion-proof valve plate with the notch 10 along its thickness direction is the first surface 101. Because of the notch 10, three surfaces with different heights along the thickness direction are formed, all of which are the first surfaces 101 of the explosion-proof valve plate. The anodic oxide film layer 20 on the first surface 101 is also located on the first surface 101 at different heights. All anodic oxide film layers 20 on the first surface 101 have the same thickness. Meanwhile, the surface without the notch 10 along the thickness direction of the explosion-proof valve plate is the second surface 102. The second surface 102 is a plane, and the anodic oxide film layer 20 on the second surface 102 has the same thickness. The thickness of the anodic oxide film layer 20 on the first surface 101 can be the same as or different from the thickness of the anodic oxide film layer 20 on the second surface 102. In this embodiment, the thickness H1 of the anodic oxide film layer 20 on the first surface 101 is the same as the thickness H1 of the anodic oxide film layer 20 on the second surface 102, which is 7 μm.

[0077] Second embodiment:

[0078] Reference Figure 6-9 This is a top view and related schematic diagram of the explosion-proof valve plate provided in the second embodiment of the present invention. In this embodiment, as... Figure 6As shown, the first surface 101 of the explosion-proof valve plate has grooves 10, but no anodic oxide film layer 20 is provided on the first surface 101 of the explosion-proof valve plate. Figure 7 As shown, an anodized film layer 20 is provided on the second surface 102 of the explosion-proof valve plate, and the outline of the anodized film layer 20 is the same as the outline of the groove 10 of the explosion-proof valve plate.

[0079] The difference between this embodiment and the first embodiment is that, Figure 8 As shown, the explosion-proof valve plate does not have an anodized film layer 20 on its first surface 101; the anodized film layer 20 is only provided on its second surface 102. Figure 9 As shown, in this embodiment, the anodic oxide film layer 20 is disposed on the second surface 102 and can completely cover the thinnest area of ​​the scribe line 10, thus providing protection for the scribe line 10. In this embodiment, the thickness of the anodic oxide film layer 20 is 11 μm.

[0080] Third embodiment:

[0081] Reference Figure 10-13 This is a top view and related schematic diagram of the explosion-proof valve plate provided in the third embodiment of the present invention. In this embodiment, as... Figure 10 As shown, the first surface 101 of the explosion-proof valve plate is provided with grooves 10 and an anodized film layer 20, and the outline of the anodized film layer 20 provided on the first surface 101 is consistent with the outline of the explosion-proof valve plate. Figure 11 As shown, an anodized film layer 20 is provided on the second surface 102 of the explosion-proof valve plate, and the outline of the anodized film layer 20 provided on the second surface 102 is consistent with the outline of the explosion-proof valve plate.

[0082] The difference between this embodiment and the first embodiment is that, Figure 11 As shown, the outline of the anodic oxide film layer 20 of the explosion-proof valve plate is the same as the outline of the explosion-proof valve plate. Specifically, when the outline of the anodic oxide film layer 20 is consistent with the outline of the explosion-proof valve plate, it means that the entire surface of the explosion-proof valve plate with the notch 10 can be uniformly covered by the anodic oxide film layer 20. Therefore, whether it is corrosion from the electrolyte inside the battery or external contact with humid air and corrosive substances, the anodic oxide film layer 20 can play a good protective role, ensuring that the explosion-proof valve plate maintains good performance in complex working conditions.

[0083] like Figure 10 and Figure 11 As shown, the projected area of ​​the anodic oxide film 20 on the explosion-proof valve plate is smaller than the cross-sectional area of ​​the explosion-proof valve plate in its thickness direction, meaning that the anodic oxide film 20 does not completely cover the entire surface of the explosion-proof valve plate. Furthermore, as... Figure 10 As shown, the distance c between the edge of the anodic oxide film layer 20 and the edge of the explosion-proof valve plate is ≥ 0.5 mm; that is, a gap of ≥ 0.5 mm is reserved between the edge of the anodic oxide film layer 20 and the edge of the explosion-proof valve plate to facilitate the welding operation between the explosion-proof valve plate and the battery casing. Maintaining a distance of ≥ 0.5 mm between the edge of the anodic oxide film layer 20 and the edge of the explosion-proof valve plate can avoid affecting the structural integrity of the valve plate edge due to the presence of the anodic oxide film layer 20 at the edge. A distance of ≥ 0.5 mm allows the edge of the explosion-proof valve plate to maintain good mechanical properties, improves the resistance of the explosion-proof valve plate to external mechanical stress, and also facilitates the welding operation between the explosion-proof valve plate and the battery.

[0084] Regarding the setting that the projected area of ​​the anodic oxide film layer 20 on the explosion-proof valve plate is smaller than the cross-sectional area of ​​the explosion-proof valve plate in its thickness direction, if the projected area of ​​the anodic oxide film layer 20 is too large, close to or equal to the cross-sectional area of ​​the explosion-proof valve plate in the thickness direction, it may change the overall stress distribution characteristics of the valve plate. When the explosion-proof valve plate is subjected to pressure, the large area of ​​the anodic oxide film layer 20 may cause stress concentration at the edges and other locations, causing the explosion-proof valve plate to rupture prematurely before reaching the predetermined detonation pressure. Making the projected area of ​​the anodic oxide film layer 20 smaller than its cross-sectional area helps maintain a more uniform stress distribution on the explosion-proof valve plate, ensuring that the explosion-proof valve plate can open accurately under the preset pressure and improving the reliability of the explosion-proof valve plate. If the anodic oxide film layer 20 extends too close to the edge of the explosion-proof valve plate and maintains a consistent thickness on one side of the explosion-proof valve plate, cracks may first appear at the junction of the anodic oxide film layer 20 and the edge of the explosion-proof valve plate when subjected to external impact, and then extend to the entire explosion-proof valve plate, reducing the reliability of the explosion-proof valve plate.

[0085] like Figure 10 As shown, the distance d between the edge of the anodic oxide film layer 20 and the projection of the notch 10 onto the first surface 101 and / or the second surface 102 of the explosion-proof valve plate is ≥ 0.1 mm. The single-sided distance between the edge of the anodic oxide film layer 20 and the edge of the notch 10 is at least 0.1 mm, ensuring that the anodic oxide film layer 20 completely covers the area of ​​the notch 10. This achieves the goal that the projected area of ​​the anodic oxide film layer 20 on the explosion-proof valve plate is larger than the projected area of ​​the notch 10. Maintaining a distance of 0.1 mm or more between the edge of the anodic oxide film layer 20 and the projection of the notch 10 avoids interference from the anodic oxide film layer 20 on the stress surrounding the notch 10.

[0086] like Figure 12 As shown, in this embodiment, an anodized film layer 20 is provided on both the first surface 101 and the second surface 102 of the explosion-proof valve plate, and as... Figure 13As shown, the thickness of the anodic oxide film 20 on the first surface 101 is h, and the thickness of the anodic oxide film 20 on the second surface 102 is H, wherein the thickness H of the anodic oxide film 20 on the second surface 102 is greater than the thickness h of the anodic oxide film 20 on the first surface 101. In this embodiment, the thickness h of the anodic oxide film 20 on the first surface 101 is 4 μm, and the thickness H of the anodic oxide film 20 on the second surface 102 is 8 μm.

[0087] Fourth embodiment:

[0088] Reference Figure 14-16 This is a bottom view and related schematic diagram of the explosion-proof valve plate provided in the fourth embodiment of the present invention. In this embodiment, as... Figure 14 and Figure 15 As shown, the first surface 101 of the explosion-proof valve plate has grooves 10, but no anodic oxide film layer 20 is provided on the first surface 101 of the explosion-proof valve plate. The second surface 102 of the explosion-proof valve plate has an anodic oxide film layer 20, and the outline of the anodic oxide film layer 20 is consistent with the outline of the explosion-proof valve plate.

[0089] The difference between this embodiment and the first embodiment is that, Figure 14 As shown, the anodic oxide film layer 20 of the explosion-proof valve plate is only disposed on the second surface 102 and is consistent with the outline of the explosion-proof valve plate. Furthermore, the cross-sectional area of ​​the anodic oxide film layer 20 on the explosion-proof valve plate is smaller than the cross-sectional area of ​​the explosion-proof valve plate in its thickness direction, that is, the edge of the anodic oxide film layer 20 is a certain distance away from the edge of the explosion-proof valve plate.

[0090] like Figure 16 As shown, the anodic oxide film layer 20 is only disposed on the second surface 102, and the thickness H2 of the anodic oxide film layer 20 is 1μm-20μm. That is, the thickness H2 of the anodic oxide film layer 20 on the second surface 102 of the explosion-proof valve plate can be 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 19μm, 20μm, or any value between any two of the above ranges. In this embodiment, the thickness H2 of the anodic oxide film layer 20 is 9μm.

[0091] Fifth embodiment:

[0092] Reference Figure 17-19 This is a bottom view and related schematic diagram of the explosion-proof valve plate provided in the fifth embodiment of the present invention. In this embodiment, as... Figure 17 and 18As shown, the first surface 101 of the explosion-proof valve plate has grooves 10, but no anodic oxide film layer 20 is provided on the first surface 101. An anodic oxide film layer 20 is provided on the second surface 102 of the explosion-proof valve plate, and the outline of the anodic oxide film layer 20 is consistent with the outline of the explosion-proof valve plate. Furthermore, in this embodiment, the projected area of ​​the anodic oxide film layer 20 on the explosion-proof valve plate is the area of ​​the second surface 102. That is, the anodic oxide film layer 20 covers the entire second surface 102 of the explosion-proof valve plate, meaning that the second surface 102 is protected by the anodic oxide film layer 20.

[0093] like Figure 17 As shown, the anodic oxide film layer 20 forms a non-welded area 1022 and a welded area 1021 surrounding the non-welded area 1022 on the explosion-proof valve plate. The edge of the welded area 1021 is projected at a distance e from the notch 10 on the second surface 102, and this distance e ≥ 0.1 mm. Specifically, the projection distance between the edge of the welded area 1021 and the notch 10 on the second surface 102 is ≥ 0.1 mm. This provides sufficient buffer space for the heat generated during welding to dissipate before it is transferred to the notch 10 area, ensuring that the notch 10 can rupture as designed under pressure, maintaining the accurate pressure release function of the explosion-proof valve plate. Figure 17 In this embodiment, only the second surface 102 is shown. On the first surface 101 of the explosion-proof valve plate, the non-welded area 1022 and the welded area 1021 are also provided in the same way as the second surface 102. On the first surface 101, the non-welded area is used to provide grooves 10, and the welded area on the first surface 101 is used for fixed connection with the battery. In this embodiment, as... Figure 17 As shown, the projected area of ​​the non-welded area 1022 in the explosion-proof valve plate on the second surface 102 is greater than the projected area of ​​the notch 10 on the second surface 102.

[0094] like Figure 18-19As shown, the anodic oxide film layer 201 is on the welding area 1021, and the anodic oxide film layer 202 is on the non-welding area 1022. The thickness H3 of the anodic oxide film layer 201 on the welding area 1021 is different from the thickness H4 of the anodic oxide film layer 202 on the non-welding area 1022. The thickness of the anodic oxide film layer 20 differs between the welding area 1021 and the non-welding area 1022. In the welding area 1021, appropriately adjusting the thickness of the anodic oxide film layer 20 can improve welding performance. An excessively thick anodic oxide film layer 20 may affect the welding quality, resulting in a weak weld. An anodic oxide film layer 20 of appropriate thickness can ensure heat transfer and metal fusion during welding, improve the strength and reliability of the weld, and ensure a stable connection between the explosion-proof valve plate and other components. When setting the thickness of the anodic oxide film layer 20 in the non-welding area 1022 of the explosion-proof valve plate, it is necessary to meet the preset detonation pressure requirements of the explosion-proof valve plate in application, so that the notch 10 can accurately guide the valve plate to break, achieving safe pressure relief.

[0095] like Figure 19 As shown, the thickness H3 of the anodic oxide film 201 on the welding area 1021 is 1μm-12μm. Good conductivity is required during welding to ensure smooth current flow and effective melting and bonding of the metal. An anodic oxide film 20 with a thickness of 1μm-12μm maintains relatively suitable conductivity within this range. If the film is too thick, the resistance increases, leading to localized overheating or insufficient welding. The thickness H4 of the anodic oxide film 202 on the non-welding area 1022 is 1μm-20μm. The non-welding area 1022 serves to protect the explosion-proof valve plate from external environmental corrosion; a relatively thicker film (1μm-20μm) provides more effective isolation. By setting anodic oxide film 20 with different thickness ranges for the welding area 1021 and the non-welding area 1022, it is beneficial to ensure a balance between the welding performance, protective performance, and mechanical properties of the explosion-proof valve plate. In this embodiment, the thickness H3 of the anodic oxide film layer 201 on the welding area 1021 is 5 μm; the thickness H4 of the anodic oxide film layer 202 on the non-welding area 1022 is 10 μm.

[0096] Sixth embodiment:

[0097] Reference Figure 20-23 This is a top view and related schematic diagram of the explosion-proof valve plate provided in the sixth embodiment of the present invention. In this embodiment, a groove 10 is provided on the first surface 101 of the explosion-proof valve plate, and an anodized film layer 20 is provided on both the first surface 101 and the second surface 102 of the explosion-proof valve plate. It is noted that the outline of the anodized film layer 20 provided on the first surface 101 and the second surface 102 of the explosion-proof valve plate is the same as the outline of the explosion-proof valve plate.

[0098] The difference between this embodiment and the first embodiment is that, in this embodiment, the outline of the anodic oxide film layer 20 is consistent with the outline of the explosion-proof valve plate, and the projected area of ​​the anodic oxide film layer 20 on the explosion-proof valve plate is the area of ​​the second surface 102 of the explosion-proof valve plate. That is, the anodic oxide film layer 20 located on the first surface 101 completely covers the first surface 101 of the explosion-proof valve plate, and the anodic oxide film layer 20 located on the second surface 102 completely covers the second surface 102 of the explosion-proof valve plate.

[0099] like Figure 21 and Figure 22 As shown, an anodic oxide film layer 20 is provided on both the first surface 101 and the second surface 102 of the explosion-proof valve plate. The thickness of the anodic oxide film layer 20 on the first surface 101 and the thickness on the second surface 102 are the same, and the thickness H5 of the anodic oxide film layer 20 is 1μm-10μm. In this embodiment, the thickness H5 of the anodic oxide film layer 20 is 3μm.

[0100] In this embodiment, the explosion-proof valve plate is manufactured in one step using an anodizing process. The process is simple, easy to implement, has short processing time, low processing cost, and is suitable for large-scale mass production. Only one anodizing process is needed to complete the processing of the anodized film layer 20 on the entire explosion-proof valve plate. Furthermore, by controlling the anodizing time, voltage, and current during processing, the thickness of the anodized film layer 20 can be controlled, making its thickness between 1μm and 12μm. This protects the explosion-proof valve plate body while also meeting the welding requirements of the explosion-proof valve plate, avoiding the degradation of welding quality caused by the anodized film layer 20. At the same time, it also ensures that the grooves 10 set on the explosion-proof valve plate have the designed detonation pressure, ensuring the normal operation of the explosion-proof valve plate.

[0101] This invention also provides a method for preparing an explosion-proof valve plate, comprising the following operations:

[0102] S1: Pre-treatment of the valve plate. Step S1 includes the following steps:

[0103] S11: Pretreatment of valve plates: Degreasing, alkaline washing, and brightening are performed on the stamped valve plates to remove surface oil or impurities, ensuring good bonding between the subsequent anodized film layer 20 and the valve plate substrate. The anodizing process forms an oxide film layer 20 on the surface of the valve plate to effectively improve the corrosion resistance of the valve plate. The anodizing solution includes sulfuric acid or oxalic acid solution.

[0104] S12: Insulation treatment of valve plate: Apply or attach an insulating layer to the area of ​​valve plate where the Yangjiang oxide film layer 20 is not required, so that the area cannot achieve circuit conduction during the subsequent anodizing process, that is, cannot undergo electrochemical reaction.

[0105] S2: Anodizing of the valve plate: The pretreated valve plate is placed in an anodizing solution for anodizing, forming an anodized film layer 20 on the valve plate. Step S2 includes the following operations: the pretreated valve plate is placed in the anodizing solution, the valve plate is connected to the positive electrode, and the anodizing solution is connected to the negative electrode. Under voltage, an electrochemical reaction occurs between the valve plate and the anodizing solution, generating an anodizing current. By controlling the magnitude and duration of the current, the extent of the chemical reaction is controlled, thereby controlling the thickness of the anodized film.

[0106] The thickness of the anodic oxide film 20 on the explosion-proof valve plate can be controlled by adjusting the anodizing time, voltage, and current density in step S2: the anodizing treatment of the valve plate. In step S2, the anodizing time needs to be between 2.5 min and 60 min. This anodizing time needs to be matched with the voltage and current density during the anodizing process. Generally speaking, if the anodizing time is too short, less than 2.5 min, it cannot be guaranteed that an effective anodic oxide film layer can be formed on the surface of the valve plate in the thickness direction. If the anodizing time is too long, greater than 60 min, it may lead to an excessively thick anodic oxide film layer 20, affecting the detonation pressure of the explosion-proof valve plate, or even affecting the fixed connection between the explosion-proof valve plate and the battery.

[0107] Specifically, in step S2, the voltage for anodizing is 20V-30V. If the voltage exceeds 30V, the current during the anodizing process will be too high, resulting in an excessively fast formation speed of the anodized film 20. This can easily lead to poor uniformity and consistency in the formation of the anodized film 20. Furthermore, excessive voltage can easily cause defects in the anodized film 20, significantly reducing its corrosion resistance. If the voltage is less than 20V, the corresponding current is too low, which can easily lead to defects such as cracks or porosity in the anodized film 20, also affecting its film-forming performance.

[0108] Specifically, in step S2, the current density for anodic oxidation is 0.1 A / m. 2 -10 A / m 2 During the anodizing process, the current density is a key factor affecting the growth rate of the anolyte film 20. As the current density increases, the growth rate of the oxide film also accelerates. However, if the current density exceeds 10 A / m... 2If the oxide film formation speed is too fast, the uniformity and consistency of the anodic oxide film layer 20 thickness cannot be guaranteed. This can easily result in some areas having excessively thick films while others have not formed a film at all. Furthermore, due to the high current density, the voids in the oxide film layer are large, making the anodic oxide film layer 20 unable to effectively block external corrosion. Conversely, if the current density is too low, less than 0.1 A / m... 2 However, the film-forming time is too long. Although a relatively dense oxide film layer can be obtained, the production efficiency is low and the production speed is slow, which is not conducive to production and processing.

[0109] S3: Sealing treatment of valve plate film layer. After the anodizing operation, the obtained anodized film layer 20 is sealed.

[0110] Anodizing films are formed on metal surfaces using electrochemical methods. Based on their structure and performance characteristics, anodic oxide films are mainly classified into barrier oxide films and porous oxide films. Barrier oxide films are relatively dense oxide films formed directly on the metal surface during the anodizing process. Their thickness is limited by the maximum allowable oxidation voltage. In actual anodizing processes, when the applied oxidation voltage reaches a certain value, further increasing the voltage may cause the film layer to break down or trigger other adverse reactions. Therefore, the thickness of barrier oxide films generally does not exceed 1 μm, which may not fully meet the requirements for corrosion protection and other performance characteristics. Porous oxide films have a more complex structure, consisting of a barrier layer and a porous layer. The barrier layer has a similar structure and properties to the barrier film, adheres to the metal substrate surface, and possesses a certain degree of density and protective capability. The porous layer is located above the barrier layer and has multiple tiny pores.

[0111] Specifically, given the thickness limitations of barrier-type oxide films, this application requires oxide films to exhibit superior corrosion resistance. Therefore, this application selects a porous oxide film to prepare the anodic oxide film layer 20. Although the porous film already possesses a certain level of protection due to its barrier layer and porous structure, corrosive substances may still penetrate through the pores of the porous layer, affecting the overall corrosion resistance of the film. Therefore, a subsequent sealing process is required to control the porous layer. The sealing process typically employs chemical solutions or heat treatment methods to fill or seal the pores of the porous layer, thereby effectively preventing corrosive substances from penetrating into the metal substrate through the pores, ensuring the thickness of the total effective corrosion-resistant film layer, and improving the corrosion resistance of the anodic oxide film layer 20.

[0112] The present invention will be further illustrated by the following examples.

[0113] Seventh embodiment:

[0114] This embodiment illustrates the preparation method of the explosion-proof valve plate disclosed in this invention, including the following steps:

[0115] Preparation of explosion-proof valve plates:

[0116] The stamped valve plates undergo pretreatment processes including degreasing, alkaline washing, and brightening.

[0117] The pretreated valve plate was placed in the anodic oxidation solution, with the valve plate connected to the positive electrode and the anodic oxidation solution connected to the negative electrode. At 25 V, the valve plate and the anodic oxidation solution underwent an electrochemical reaction with an oxidation current density of 1 A / m. 2 Anodizing for 3 minutes, sealing the holes, anodizing the first and second surfaces of the explosion-proof valve plate, the outline of the anodized film layer is consistent with the outline of the explosion-proof valve plate, and the projected area of ​​the anodized film layer on the second surface is consistent with the cross-sectional area of ​​the second surface, that is, the first and second surfaces of the explosion-proof valve plate are completely covered by the anodized film layer, and the thickness of a single anodized film layer is 1μm.

[0118] Eighth embodiment:

[0119] This embodiment illustrates the preparation method of the explosion-proof valve plate disclosed in this invention, including most of the operation steps in the seventh embodiment, except that the thickness of the single-layer anodic oxide film is 2 μm.

[0120] like Figure 23 The image shown is a surface appearance diagram of the explosion-proof valve plate after corrosion resistance testing, as described in this embodiment. Figure 23 It can be clearly seen that in this embodiment, after the corrosion resistance test, no obvious corrosion marks appeared on the surface of the etched area of ​​the explosion-proof valve plate. Only two corrosion points appeared at the two anodic electrode clamping points on the edge of the explosion-proof valve plate. Because no anodic oxide film layer was formed at these corrosion points, corrosion occurred at these points after the corrosion resistance test.

[0121] Ninth embodiment:

[0122] This embodiment illustrates the preparation method of the explosion-proof valve plate disclosed in this invention, including most of the operation steps of the seventh embodiment, except that: an anodic oxide film layer is only provided on the second surface of the explosion-proof valve plate, and the thickness of the anodic oxide film layer is 6μm.

[0123] Tenth embodiment:

[0124] This embodiment illustrates the preparation method of the explosion-proof valve plate disclosed in this invention, including most of the operation steps in the seventh embodiment. The difference is that an anodic oxide film layer is only provided on the second surface of the explosion-proof valve plate, and the thickness of the anodic oxide film layer is 12 μm.

[0125] Eleventh Example:

[0126] This embodiment illustrates the preparation method of the explosion-proof valve plate disclosed in this invention, including most of the operation steps in the seventh embodiment, except that: an anodic oxide film layer is only provided on the second surface of the explosion-proof valve plate, and the thickness of the anodic oxide film layer is 15 μm.

[0127] Twelfth Example:

[0128] This embodiment illustrates the preparation method of the explosion-proof valve plate disclosed in this invention, including most of the operation steps in the seventh embodiment, except that: an anodic oxide film layer is only provided on the second surface of the explosion-proof valve plate, and the thickness of the anodic oxide film layer is 20 μm.

[0129] Comparative Example 1

[0130] This comparative example is used to illustrate the preparation method of the explosion-proof valve plate disclosed in this invention, including most of the operation steps in the seventh embodiment, the difference being that the explosion-proof valve plate undergoes natural oxidation and is not anodized. For example... Figure 24 The image shown is a surface appearance diagram of the explosion-proof valve plate in this embodiment after a corrosion resistance test. Figure 24 It is clear that after the explosion-proof valve plates underwent corrosion resistance testing, most of the explosion-proof valve plates that entered the electrolyte area showed obvious black corrosion marks.

[0131] Comparative Example 2

[0132] This comparative example is used to illustrate the preparation method of the explosion-proof valve plate disclosed in this invention, including most of the operation steps in the seventh embodiment. The difference is that, through anodizing, an anodized film layer is only formed on the first surface of the explosion-proof valve plate, and the thickness of the anodized film layer on the first surface is 20 μm. No anodized film layer is formed on the second surface.

[0133] Comparative Example 3

[0134] This embodiment illustrates the preparation method of the explosion-proof valve plate disclosed in this invention, including most of the operation steps in the seventh embodiment, except that the thickness of the single-layer anodic oxide film is 0.05 μm.

[0135] Comparative Example 4

[0136] This embodiment illustrates the preparation method of the explosion-proof valve plate disclosed in this invention, including most of the operation steps in the seventh embodiment, except that the thickness of the single-layer anodic oxide film is 25 μm.

[0137] Performance testing

[0138] The following performance tests were performed on Examples 1-12 and Comparative Examples 1-4 prepared above:

[0139] (1) Corrosion resistance test:

[0140] A dual-electrode system is used, with the working electrode connected to a valve plate and the counter electrode connected to a lithium plate. The electrodes are immersed in the electrolyte, and the two electrodes are short-circuited externally and their current is detected. After 24 hours, the appearance and current curve are observed to determine the corrosion resistance effect.

[0141] (2) Welding performance test:

[0142] The valve plate was pressed onto the cover plate using a tooling, and then welded using mass production laser welding parameters (power 400W, speed 50mm / S). After welding, a metallographic sample was made, and the internal porosity was observed under a metallographic microscope.

[0143] (3) Explosion pressure test: The valve plate is welded to the cover plate, which is placed in a special sealing fixture. One side of the cover plate is sealed and nitrogen gas at a certain pressure is introduced (simulating the cover plate forming the battery cell and the battery cell having internal pressure). The pressure is gradually increased by 0.01 MPa and maintained for 5 seconds. The minimum pressure at which the valve plate is opened is recorded. All helium tests are OK.

[0144] Fill in the above test results in Table 1.

[0145] Table 1

[0146]

[0147] As can be seen from the data in Table 1, in Examples 1-4, it is clearly visible to the naked eye that no corrosion was observed in the areas where the anodic oxide film was applied to the explosion-proof valve plate, while corrosion traces were visible in the areas where the anodic oxide film was not applied. Meanwhile, in Examples 5-12 and Comparative Example 4, the corrosion current of the explosion-proof valve plate was less than 0.005 mA, while the corrosion current of Comparative Example 1 (no anodizing), Comparative Example 2 (anodic oxide film applied only to the first surface, no anodic oxide film applied to the second surface), and Comparative Example 3 (anodic oxide film with a thickness of 0.1 μm applied to both the first and second surfaces) was approximately 5 mA. This clearly demonstrates that applying an anodic oxide film to the second surface of the explosion-proof valve plate can effectively improve its corrosion resistance and effectively prevent the electrolyte from corroding the valve plate.

[0148] In Examples 1-12 and Comparative Examples 1, 2, and 3, the weld porosity of the explosion-proof valve plates was ≤20%. Furthermore, as the thickness of the anodic oxide film in the welding area increased, the weld porosity increased, resulting in poorer weld quality; conversely, the lower the weld porosity, the better the weld quality. In Examples 1-10, it was clearly observed that when the total thickness of the anodic oxide film in the welding area was between 1μm and 12μm, the weld porosity was ≤10%, meeting international requirements for laser welding of aluminum. In Examples 11-12, the increased thickness of the anodic oxide film in the welding area (between 15μm and 20μm) affected heat transfer and metal fusion during welding, leading to a decrease in weld quality and the appearance of more pores, although it still barely met the basic requirements for welding the explosion-proof valve plate to the battery.

[0149] In Examples 1-12 and Comparative Examples 1, 2, and 3, the detonation pressure of the explosion-proof valve plates was all between 0.5 ± 0.1 MPa. The greater the thickness of the anodic oxide film at the notch, the lower the detonation pressure of the explosion-proof valve plate, causing it to deviate from the design value (0.5 ± 0.1 MPa). In Example 12, when the thickness of the anodic oxide film at the notch increased to 20 μm, the detonation pressure reached the design threshold of 0.4 MPa-0.44 MPa. Therefore, when the thickness of the anodic oxide film at the notch exceeds 20 μm, the explosion-proof valve plate cannot reach the designed detonation pressure, i.e., it cannot achieve the explosion-proof function.

[0150] Although the weld porosity of Comparative Example 1 was less than 2%, the corrosion current was approximately 5 mA due to the lack of anodizing, resulting in extremely poor corrosion resistance. Comparative Example 1 precisely addresses the problem of explosion-proof valve plates easily corroded by electrolytes in batteries, a problem that this invention urgently needs to solve.

[0151] In Comparative Example 2, an anodic oxide film is only formed on the first surface of the explosion-proof valve plate. Therefore, the 20μm thick anodic oxide film in the welding area results in a weld porosity of 15-20%, meaning this film will affect the welding performance between the explosion-proof valve plate and the battery. Simultaneously, because the second surface lacks an anodic oxide film, although the corrosion current is approximately 2.5mA, it cannot solve the problem of micro-corrosion between the second surface (the side closest to the inner side of the battery) and the electrolyte. In other words, Comparative Example 2 cannot effectively solve the problem of electrolyte corrosion of the explosion-proof valve plate when a micro-short circuit occurs in the battery.

[0152] In Comparative Example 3, although both the first and second surfaces of the explosion-proof valve plate are provided with anodized film layers, the thickness of the anodized film layer is extremely low. Therefore, the weld porosity is <2%, meaning that the anodized film layer does not affect the welding of the explosion-proof valve plate. Moreover, its corrosion current is about 5mA, which is also insufficient to achieve the effect of corrosion prevention. In other words, it cannot solve the problem of the explosion-proof valve plate being corroded by the electrolyte inside the battery when a micro-short circuit occurs in the battery in this application.

[0153] In Comparative Example 4, the total thickness of the anodic oxide film in the etched area is 25 μm, which allows the corrosion current to be less than 0.005 mA. This means that the explosion-proof valve plate has a good anti-corrosion effect and can prevent the etched area of ​​the explosion-proof valve plate from being corroded and penetrated by the electrolyte when the battery experiences a micro-short circuit. However, the total thickness of the anodic oxide film in the welded area is 25 μm, which results in a weld porosity greater than 20%. This causes the explosion-proof valve plate to fail to achieve effective fixation with the battery, significantly reduces the structural strength of the weld, makes the weld prone to brittle fracture, and causes leakage problems, thus failing to meet the sealing requirements.

[0154] In the comprehensive corrosion resistance and weldability tests, Examples 1-12 ensured good corrosion resistance while also meeting the weldability requirements, achieving a balance between the protective performance and weldability of the explosion-proof valve plate. That is, by rationally designing the anodic oxide film layer, the comprehensive performance of the explosion-proof valve plate can be effectively improved, avoiding electrolyte leakage while ensuring a stable connection between it and other components.

[0155] This invention also provides a lithium-ion battery, comprising a cover plate, a cell, a casing, and the aforementioned explosion-proof valve plate, or an explosion-proof valve plate prepared by the aforementioned method; the explosion-proof valve plate is disposed on the cover plate, and the cell is placed inside the casing. The lithium-ion battery provided by this invention utilizes the aforementioned explosion-proof valve plate, which gives the explosion-proof valve plate better and superior corrosion resistance, effectively solving the problem that the grooves on the explosion-proof valve plate are penetrated by corrosion when a micro-short circuit occurs in the battery, thereby improving the battery's safety performance and service life.

[0156] 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. An explosion-proof valve plate, characterized in that, It includes a first surface with grooves and a second surface disposed opposite to the first surface in the thickness direction of the explosion-proof valve plate; The explosion-proof valve plate has an anodic oxide film layer on both the first surface and the second surface. Alternatively, the explosion-proof valve plate has an anodized film layer on the second surface; The projected area of ​​the anodic oxide film on the explosion-proof valve plate is greater than the projected area of ​​the etched marks on the explosion-proof valve plate; The anodic oxide film completely covers the projection area of ​​the engraving on the second surface of the explosion-proof valve plate; The thickness of the anodic oxide film is 1μm-12μm; The anodic oxide film layer forms a non-welded area and a welded area surrounding the non-welded area on the explosion-proof valve plate. The projected area of ​​the non-welded area on the second surface is larger than the projected area of ​​the groove on the second surface. The thickness of the anodic oxide film layer on the welded area is different from the thickness on the non-welded area. The distance e between the edge of the welded area and the projected distance e of the groove on the second surface is ≥ 0.1 mm.

2. The explosion-proof valve plate according to claim 1, characterized in that, The width of the anodic oxide film is a, the width of the groove is b, and the width of the anodic oxide film satisfies ab≥0.2mm.

3. The explosion-proof valve plate according to claim 1, characterized in that, The outline of the anodic oxide film is the same as that of the explosion-proof valve plate.

4. The explosion-proof valve plate according to claim 3, characterized in that, The projected area of ​​the anodic oxide film on the explosion-proof valve plate is smaller than the cross-sectional area of ​​the explosion-proof valve plate in its thickness direction; The distance c between the edge of the anodic oxide film and the edge of the explosion-proof valve plate is ≥ 0.5 mm; The distance d between the edge of the anodic oxide film and the projection of the indentation onto the first and / or second surfaces of the explosion-proof valve plate is ≥0.1 mm.

5. The explosion-proof valve plate according to claim 3, characterized in that, The projected area of ​​the anodic oxide film on the explosion-proof valve plate is the area of ​​the second surface.

6. The method for preparing the explosion-proof valve plate according to any one of claims 1-5, characterized in that, Includes the following operations: Pretreatment of valve plates; Anodizing treatment of valve plates: Take the valve plates that have completed the pretreatment and place them in anodizing solution to perform anodizing, forming an anodized film layer on the valve plates.

7. The method for preparing the explosion-proof valve plate according to claim 6, characterized in that, It also includes at least one of the following technical features: a. The anodizing time is 2.5 min - 60 min; b. The voltage for anodizing is 20V-30V; c. The current density for anodizing is 0.1 A / dm³. 2 -10 A / dm 2 .

8. A lithium-ion battery, characterized in that, The device includes a cover plate, a battery cell, a housing, and an explosion-proof valve plate as described in any one of claims 1-5, or an explosion-proof valve plate prepared by the method described in any one of claims 6-7; the explosion-proof valve plate is disposed on the cover plate, and the battery cell is placed inside the housing.

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