WO2024114474A1 - Composite cover plate structure of steel shell button cell and button cell - Google Patents

Abstract

A composite cover plate structure of a steel shell button cell and a button cell. The composite cover plate structure comprises: a pole (1), a first welding layer (2), a modified layer (3), a second welding layer (4), and a cover plate body (5). The pole (1) is provided with a connecting column (11), and the connecting column (11) is provided on the bottom of the pole (1); the first welding layer (2), the modified layer (3), and the second welding layer (4) are sequentially stacked and sleeved on the connecting column (11); the cover plate body (5) is mounted below the second welding layer (4) and is sleeved on the connecting column (11), the outer peripheral edge of the cover plate body (5) is of a rounded structure, and a soldering portion is provided at the top of the cover plate body (5); and when the internal temperature of the cell reaches a preset temperature, the first welding layer (2) and the second welding layer (4) are softened, and the pole (11) is opened, so as to relieve the pressure of the cell. By optimizing the composite cover plate structure, gas in the cell can be discharged, and the risk of combustion explosion caused by overlarge internal pressure of the cell is prevented.

Description

Composite cover plate structure of steel shell button battery and button battery Technical Field

The present invention belongs to the technical field of battery production and manufacturing, and specifically relates to a composite cover plate structure of a steel shell button battery and a button battery.

Background technique

With the development of portable electronic products, smart wearable products, medical instruments, etc., batteries are becoming more miniaturized, so a battery with small size, high specific energy, good sealing, low self-discharge and high reliability has been developed. Because of its button-like shape, it is called button battery or button battery. There are many types of button batteries, among which lithium-ion button batteries have the highest energy density and the highest operating voltage. Solving its industrial manufacturing difficulties can enable a wider range of applications.

Steel shell button battery consists of three parts: cover plate, battery cell and shell. Among them, the cover plate is divided into welded composite cover plate and riveted cover plate. The battery cell is divided into stacked type and winding type. The shell is made of stainless steel and has the following defects: 1. The welded composite cover plate needs to be surface treated before welding. During the treatment process, the metal parts are stacked, resulting in incomplete treatment of the welded surface. The metal components with incomplete surface treatment are made into composite cover plates by welding, which leads to large internal resistance of the battery in high temperature and high humidity storage, and the composite channel forms a channel to cause leakage; 2. The composite cover plate and the shell are combined and laser welded into a sealed cavity. An explosion-proof valve is required. The existing explosion-proof valve is realized by laser scoring, which is high in cost and precision. The scoring depth cannot be fully inspected, and the scoring opening pressure is too large; 3. The composite cover plate and the shell cover are completed by gap matching. At present, most of them use flat cover plates. Due to tolerance matching, the outer edge of the cover plate is stuck to the edge of the shell when closing the cover, and the closing yield is low, resulting in poor welding when the top cover is sealed.

Summary of the invention

One of the purposes of the present invention is to address the deficiencies of the prior art and provide a composite cover plate structure for a steel shell button battery. By optimizing the composite cover plate structure, the gas inside the battery can be discharged to prevent the risk of combustion and explosion caused by excessive internal pressure in the battery.

In order to achieve the above object, the present invention adopts the following technical solution:

A composite cover plate structure for a steel shell button cell, comprising: a pole having a connecting column, the connecting column being arranged at the bottom of the pole; a first welding layer, a modified layer and a second welding layer, which are stacked in sequence and sleeved on the connecting column; a cover plate body, which is installed below the second welding layer and sleeved on the connecting column, the outer peripheral edge of the cover plate body being a chamfered structure; when the internal temperature of the battery reaches a preset temperature, the first welding layer and the second welding layer soften, and the pole opens to relieve the pressure of the battery.

Preferably, the thickness T of the cover plate body and the radius R of the rounded corner satisfy the relationship: T<R≤3T.

Preferably, the first welding layer, the modified layer, the second welding layer and the cover plate body are all provided with through holes matching the connecting pillars.

Preferably, the forward projection area of the through hole of the cover body is S1, and the forward projection overlapping area of the pole and the cover body is S2, wherein S1 and S2 satisfy the relationship: S1/S2=m%, m=8-20; more preferably, m=12-15.

Preferably, the pole and the cover plate body are fixedly connected by heating and pressurizing.

Preferably, the contact surface of the second welding layer and the cover plate body is nickel-plated.

Preferably, it further comprises insulating tape, wherein the insulating tape is pasted on a side of the cover body facing the battery.

Preferably, the pole, the first welding layer, the modified layer, the second welding layer and the cover plate body are composited into an integrated structure by heating and pressurizing.

Preferably, the first welding layer, the modified layer and the second welding layer are all made of PP glue.

Preferably, the radius R of the rounded corner is greater than 0.1 mm.

Preferably, the pole is a T-shaped structure, and the cross-section of the cover plate body is a U-shaped structure.

A second object of the present invention is to provide a button battery, comprising a shell and a composite cover plate structure of the steel shell button battery as described above, wherein the cover plate body is embedded in the shell, and a welding portion is provided on the top of the cover plate body.

Preferably, the groove depth H of the cover plate body and the radius R of the chamfer satisfy the relationship: 0.2H<R≤0.6H; and the height A of the welding portion satisfies the relationship: A=H–R.

Preferably, the height A' of the molten portion of the weld at the weld portion satisfies the relationship: A'≤A.

The beneficial effect of the present invention is that the present invention forms a composite cover plate structure by bonding the pole, the first welding layer, the modified layer, the second welding layer and the cover plate body by heating and pressurizing. The pole is designed as a T-shaped structure, and the cross section of the cover plate body is designed as a U-shaped structure, which plays a role in preventing material stacking during surface treatment and improving the effect of surface treatment. In the case of battery overcharge, high temperature, and short circuit, if the internal heat of the battery is greater than 120°C (for example, at 130°C), the first welding layer and the second welding layer begin to soften, and the attached pole automatically opens under the internal pressure of the battery, which plays a role in pressure relief, so that the gas inside the battery is discharged, and the risk of combustion and explosion caused by excessive internal pressure of the battery is prevented, which helps to improve the safety of the battery. At the same time, the shell positioning and welding structure of the U-shaped structure can be located above the shell, without occupying the radial space of the battery core; the relationship between the welding area and the cover plate area is limited to ensure the composite sealing and composite strength of the composite cover plate structure and the ability to play a safe explosion-proof role under a suitable pressure value; the relationship between the welding part is limited to ensure the welding sealing and welding structure stability between the composite cover plate structure and the shell.

BRIEF DESCRIPTION OF THE DRAWINGS

The features, advantages and technical effects of the exemplary embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG1 is a schematic structural diagram of the present invention.

FIG. 2 is a front view of the structure of the cover plate body of the present invention.

FIG. 3 is a front view schematic diagram of the cover plate body after welding of the present invention.

FIG. 4 is a schematic diagram of the classification of the present invention.

FIG. 5 is an exploded schematic diagram of a button battery of the present invention.

The reference numerals are described as follows:

1-pole; 11-connecting column;

2-first welding layer;

3- modified layer;

4-second welding layer;

5-cover body;

6-Insulation tape;

7- housing;

8-Through hole;

H-groove depth of cover plate body;

T-the thickness of the cover body;

R-the radius of the rounded corners of the cover body;

A-the height of the welding part of the cover body;

A'-the height of the molten part of the welding part of the cover body;

S1-the forward projection area of the through hole of the cover body;

S2- The overlapping area of the forward projection of the pole and the cover body.

Detailed ways

For example, certain words are used in the specification and claims to refer to specific components. Those skilled in the art should understand that hardware manufacturers may use different terms to refer to the same component. This specification and claims do not use differences in names as a way to distinguish components, but use differences in the functions of components as the criteria for distinction. For example, "including" mentioned throughout the specification and claims is an open term, so it should be interpreted as "including but not limited to". "Approximately" means that within an acceptable error range, those skilled in the art can solve technical problems within a certain error range and basically achieve technical effects.

Furthermore, the terms “first”, “second”, etc. are used for descriptive purposes only and are not to be understood as indicating or implying relative importance.

In the invention, unless otherwise clearly specified and limited, the terms such as "install", "connect", "connect", "fix" and the like should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal connection of two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances.

The present invention will be further described in detail below with reference to FIGS. 1 to 5 , but the present invention is not limited thereto.

Implementation

The steel shell button cell comprises a battery cell, a shell 7 and a composite cover plate structure. The composite cover plate structure comprises: a pole 1 having a connecting column 11, which is arranged at the bottom of the pole 1; a first welding layer 2, a modified layer 3 and a second welding layer 4, which are stacked in sequence and sleeved on the connecting column 11; a cover plate body 5, which is installed below the second welding layer 4 and sleeved on the connecting column 11; when encapsulating, the cover plate body 5 is embedded in the shell 7 to form a cavity for accommodating the battery cell.

Among them, the pole 1 is a T-shaped structure, and the connecting column 11 faces the inside of the battery. The cover body 5 adopts a stainless steel cover plate and adopts a U-shaped design, that is, the outer edge of the cover body 5 is a rounded structure, and the rounded position faces the inside of the battery. The rounded structure can prevent the bottom edge of the cover body 5 from scratching the winding core and damaging the winding core. At the same time, it also prevents the outer edge of the cover body 5 from getting stuck on the edge of the shell when closing the cover, plays a role in positioning the shell, and greatly improves the closing yield and closing efficiency.

Since the first welding layer 2, modified layer 3 and second welding layer 4 in the composite cover plate are in contact with the electrolyte and air, they are prone to delamination failure, resulting in leakage of electrolyte. Therefore, the surface of the cover plate body 5 that contacts the second adhesive layer 4 needs to be nickel-plated to ensure the stability of the bonding force between the second welding layer 4 of PP material and the metal cover plate body 5. At the same time, the composite surface of the pole 1 and the cover plate body 5 needs to be cleaned and passivated to prevent easy bonding failure.

Since the existing explosion-proof valve is implemented by laser scoring, it is costly, accurate, and the depth of the scoring cannot be fully inspected. Therefore, the present invention bonds the pole 1, the first welding layer 2, the modified layer 3, the second welding layer 4, and the cover body 5 by heating and pressurizing to form a composite cover structure. The pole 1 is designed as a T-shaped structure, and the cross-section of the cover body 5 is designed as a U-shaped structure, which prevents the stacking of materials during surface treatment and improves the effect of surface treatment. In the case of battery overcharge, high temperature, and short circuit, if the internal heat of the battery is greater than 120°C (for example, at 130°C), the first welding layer 2 and the second welding layer 4 begin to soften, and the attached pole 1 automatically opens under the pressure inside the battery, which plays a role in pressure relief, allowing the gas inside the battery to be discharged, preventing the risk of combustion and explosion caused by excessive internal pressure of the battery, and helping to improve the safety of the battery.

In the composite cover plate structure of the steel shell button battery of the present invention, the first welding layer 2, the modified layer 3, the second welding layer 4 and the cover plate body 5 are all provided with through holes matching the connecting column 11. The connecting column 11 can pass through the first welding layer 2, the modified layer 3, the second welding layer 4 and the cover plate body 5, so that the connecting column 11 can be connected to the positive or negative electrode of the winding core.

The radius R of the rounded corners of this embodiment is greater than 0.1mm. When the cover is closed with the shell 7, the rounded corners play a guiding role to prevent the poor K value caused by the rounded corners being too small or the right angles and the internal resistance of the shell 7 being too large or the metal dust caused by the scratches falling into the battery, thereby avoiding problems such as the inability to embed the cover in place, deformation of the cover, poor welding or failure of the battery cell. In this embodiment, the thickness T of the cover body 5 and the radius R of the rounded corners satisfy the relationship: T<R≤3T. For example, when the thickness T of the cover body 5 is 0.1mm, the relationship between the radius R of the rounded corners of the cover body 5 and the thickness T is: 0.1mm<R≤0.3mm, for example, R can be 0.15mm, 0.2mm or 0.3mm. Under the limitation of this relationship, it can ensure that the cover body 5 and the shell 7 can be better adapted, and play a better limiting role, thereby improving the stability and reliability of the button battery shell structure.

The pole 1, the first welding layer 2, the modified layer 3, the second welding layer 4 and the cover body 5 of this embodiment are combined into an integrated structure by heating and pressurizing. The first welding layer 2, the modified layer 3 and the second welding layer 4 are all PP glue, and the PP sol amount is in the range of 30%-70%, so that the battery has good sealing and insulation. In this embodiment, the forward projection area of the through hole 8 of the cover body 5 is S1, and the forward projection overlap area of the pole 1 and the cover body 5 is S2, and S1 and S2 satisfy the relationship: S1/S2=m%, m=8-20; more preferably, m=12-15, for example, S1/S2 can be 0.08, 0.1, 0.12, 0.15 or 0.2. When S1 and S2 meet the above relationship, when the composite distance between the pole 1 and the cover body 5 is greater than 1.2mm, the strength of the cover body 5 reaches 180N, and it can reach 72h without a through channel under the 85℃ high temperature electrolyte environment test, which can ensure the composite sealing and composite strength of the composite cover structure, and can also ensure that the composite cover plays a safe and explosion-proof role under the appropriate pressure value. The appropriate pressure value refers to the pressure value inside the battery when the battery is in thermal runaway, which is about 0.6-1.4Mpa. Different designs such as battery materials or sizes will cause the internal pressure value of the button battery to fluctuate in the range of 0.6-1.4Mpa in the case of thermal runaway, generally about 1Mpa.

A welding portion is provided at the top of the cover body 5. It should be noted that: during the manufacturing process of the battery, the cover body 5 forms a chamfered structure at the peripheral edge, and the cross section is U-shaped. The cover body 5 is embedded in the shell 7, and the two are conveniently positioned during the closing process. Moreover, the welding surface of the cover body 5 and the shell 7 is top welding, which not only shortens the welding time and reduces the heat conduction, but also has a simple mechanical design and low cost. It improves the welding efficiency and yield rate without affecting the welding quality, and does not occupy the radial space of the battery cell. In addition, the cover body 5 and the shell 7 are matched without steps, and the edge of the cover body 5 is matched with the inner wall of the shell 7 through the chamfered guide. Under the action of gravity, the cover body 5 is embedded in the shell 7, and the upper end surface of the shell 7 plays a limiting role to prevent the cover body 5 from being embedded too deeply due to overpressure. The shell 7 is preferably a steel shell.

In this embodiment, the groove depth H and the radius R of the rounded corner of the cover body 5 satisfy the relationship: 0.2H<R≤0.6H; the height A of the welding part satisfies the relationship: A=H–R. For example, when the groove depth H of the cover body 5 is 0.5mm, the relationship between the radius R of the rounded corner of the cover body 5 and the groove depth H is: 0.1mm<R≤0.3mm, and the relationship between the height A of the welding part of the cover body 5 and the groove depth H and the radius R of the rounded corner of the cover body 5 is: 0.2mm<A≤0.4mm. In this embodiment, the height A' of the welded molten part of the welding part satisfies the relationship: A'≤A. The relationship between the height of the welding part, the groove depth and the rounded corner radius of the cover body 5, and the height of the welded molten part of the welding part meets the above-mentioned restrictions, which can ensure the welding seal between the composite cover structure and the shell and the stability of the welding structure. If the height A'>A of the welded molten part of the welding part, the risk of welding debris falling into the battery will increase, which may cause the battery to be contaminated.

The composite cover structure of the steel shell button battery of the present invention also includes insulating tape 6, which is pasted on the side of the cover body 5 facing the battery to prevent the positive electrode adapter from contacting the negative electrode and causing a short circuit, thereby helping to improve the safety of the battery.

The production of button batteries includes:

1. Positive electrode column: The aluminum plate is made into two cylinders of different sizes by stamping. The cylinder at the bottom is the connecting column 11, and the cross section is T-shaped;

2. Stainless steel cover: The stainless steel plate is made into a U-shaped ring by stamping, and the center of the ring is penetrated for the T-shaped pole 1 to pass through, and the cross section is U-shaped;

3. First welding layer 2, modified layer 3, second welding layer 4: Cut the three layers of PP material into a circular ring-shaped material through a die cutter, and the T-shaped pole 1 passes through the central aperture;

4. Place the positive electrode column and stainless steel cover into the cleaning and passivation equipment, and then go through the processes of rinsing, pickling, passivation, etc.;

5. Put the stainless steel cover plate, PP glue and positive electrode into the composite fixture in sequence, and combine them together by heating and pressurizing to make a composite cover plate;

6. Stainless steel housing: The stainless steel plate is made into a barrel-shaped housing 7 by stamping, and the housing 7 is degreased and deburred by a cleaning device;

7. Winding core: The positive and negative electrode sheets after slitting are led out to the positive and negative electrode ears through sheet making, and then wound into a cylindrical winding core. The positive and negative electrode ears are led out from the two end faces of the winding core, and the positive and negative electrode lead-out angles are 90°±15°;

8. Assembly: The negative pole ear led out of the winding core is welded to the bottom of the shell 7 by laser. After welding, the battery cell is placed inside the shell 7. Then the positive pole ear led out of the winding core is welded to the pole 1 of the composite cover plate by laser. The insulating tape 6 is arranged between the cover plate body 5 and the winding core.

9. The welded battery is transferred to the baking-liquid injection process. During liquid injection, the cover plate is opened. After liquid injection, the cover plate and the opening of the shell 7 are closed, and then laser welding is performed to seal.

10. After sealing, clean the battery and let it stand, then perform chemical composition and activate and charge the battery.

In order to verify that S1/S2 can effectively meet the pressure opening requirements during battery thermal runaway and maintain the sealing and mechanical properties of the battery during normal use, a battery failure opening pressure test was carried out. Ten samples were grouped together. The test data are shown in Table 1 below.

Table 1

When S1/S2 is 0.04 and the test temperature is 130°C, the battery failure opening pressure (unit: MPa)	When S1/S2 is 0.05 and the test temperature is 130°C, the battery failure opening pressure (unit: MPa)	When S1/S2 is 0.08 and the test temperature is 130°C, the battery failure opening pressure (unit: MPa)	When S1/S2 is 0.12 and the test temperature is 130°C, the battery failure opening pressure (unit: MPa)	When S1/S2 is 0.15 and the test temperature is 130°C, the battery failure opening pressure (unit: MPa)	When S1/S2 is 0.2 and the test temperature is 130°C, the battery failure opening pressure (unit: MPa)
1.851	1.508	1.383	1.184	0.900	0.656
1.880	1.661	1.375	1.152	0.929	0.628
1.875	1.640	1.354	1.163	0.928	0.621
1.850	1.671	1.361	1.160	0.914	0.682
1.836	1.612	1.386	1.163	0.935	0.607
1.876	1.540	1.392	1.166	0.915	0.658
1.879	1.646	1.394	1.154	0.935	0.603
1.837	1.671	1.373	1.195	0.929	0.635
1.886	1.568	1.388	1.178	0.924	0.602
1.896	1.582	1.390	1.147	0.929	0.666

From the test data in Table 1 above, it can be seen that when the test temperature is 130℃, the forward projection area of the through hole of the cover body 5 is S1mm², and the forward projection overlap area of the pole 1 and the cover body 5 is S2mm², the ratio of S1 to S2 in the range of 8% to 20% can effectively meet the pressure opening requirements (0.6-1.4Mpa) when the battery fails, and can also maintain the sealing performance and mechanical properties of the battery during normal use. When the ratio of S1 to S2 is in the range of 12% to 15%, the opening pressure value is closer to 1Mpa.

When S1/S2<8%, the battery failure opening pressure is too high, which will pose a safety hazard when the user uses it and easily cause safety risks; when S1/S2>20%, the sealing and mechanical properties of the battery will be greatly reduced, affecting the quality of the battery.

According to the disclosure and teaching of the above description, those skilled in the art to which the present invention belongs can also change and modify the above embodiment. Therefore, the present invention is not limited to the above specific embodiment, and any obvious improvement, replacement or modification made by those skilled in the art on the basis of the present invention belongs to the protection scope of the present invention. In addition, although some specific terms are used in this specification, these terms are only for the convenience of description and do not constitute any limitation to the present invention.

Claims (14)

1. A composite cover plate structure for a steel shell button cell, characterized by comprising:

   A pole (1) having a connecting pole (11), wherein the connecting pole (11) is arranged at the bottom of the pole (1);

   The first welding layer (2), the modified layer (3) and the second welding layer (4) are stacked in sequence and sleeved on the connecting column (11);

   A cover plate body (5) is installed below the second welding layer (4) and sleeved on the connecting column (11); the outer peripheral edge of the cover plate body (5) is a rounded structure;

   When the internal temperature of the battery reaches a preset temperature, the first welding layer (2) and the second welding layer (4) soften, and the pole (1) opens to relieve the pressure of the battery.
2. A composite cover plate structure for a steel shell button cell as claimed in claim 1, characterized in that: the thickness T of the cover plate body (5) and the radius R of the rounded corner satisfy the relationship: T<R≤3T.
3. A composite cover plate structure for a steel shell button cell according to claim 1, characterized in that: the first welding layer (2), the modified layer (3), the second welding layer (4) and the cover plate body (5) are all provided with a through hole (8) matching the connecting column (11).
4. A composite cover structure for a steel shell button cell as claimed in claim 3, characterized in that: the forward projection area of the through hole (8) of the cover body (5) is S1, and the forward projection overlapping area of the pole (1) and the cover body (5) is S2, wherein S1 and S2 satisfy the relationship: S1/S2=m%, m=8-20.
5. The composite cover plate structure of a steel shell button cell according to claim 1, characterized in that the pole (1) and the cover plate body (5) are fixedly connected by heating and pressurizing.
6. The composite cover plate structure of a steel shell button cell according to claim 1, characterized in that the contact surface between the second welding layer (4) and the cover plate body (5) is nickel-plated.
7. A composite cover plate structure for a steel shell button cell as claimed in claim 1, characterized in that it also includes insulating tape (6), wherein the insulating tape (6) is pasted on the side of the cover plate body (5) facing the battery.
8. A composite cover plate structure for a steel shell button cell according to claim 1, characterized in that the pole (1), the first welding layer (2), the modified layer (3), the second welding layer (4) and the cover plate body (5) are composited into an integrated structure.
9. The composite cover plate structure of a steel shell button battery according to claim 1, characterized in that: the first welding layer (2), the modified layer (3) and the second welding layer (4) are all PP glue.
10. The composite cover structure of a steel shell button battery as described in claim 1 is characterized in that the radius R of the chamfered corner is greater than 0.1 mm.
11. A composite cover plate structure for a steel shell button cell as claimed in claim 1, characterized in that: the pole (1) is a T-shaped structure, and the cross-section of the cover plate body (5) is a U-shaped structure.
12. A button battery, characterized in that it comprises a shell (7) and a composite cover plate structure of a steel shell button battery as described in any one of claims 1 to 11, wherein the cover plate body (5) is embedded in the shell (7); and a welding portion is provided on the top of the cover plate body (5).
13. A button battery as claimed in claim 12, characterized in that: the groove depth H of the cover body (5) and the radius R of the rounded corner satisfy the relationship: 0.2H<R≤0.6H; the height A of the welding portion satisfies the relationship: A=H–R.
14. A button battery as described in claim 13, characterized in that: the height A' of the molten portion of the welding portion satisfies the relationship: A'≤A.