Lithium ion battery explosion-proof device and production method thereof, and explosion-proof lithium ion battery

Abstract

The present invention discloses a lithium-ion battery explosion-proof device and a production method thereof, and an explosion-proof lithium-ion battery, and belongs to the field of battery explosion-proof. The lithium-ion battery explosion-proof device comprises a cover plate, the shape of the cover plate matches the installation position of the lithium-ion battery explosion-proof valve, a convex cover is provided on the cover plate, a through hole is provided on the surface of the convex cover, and a film layer is covered inside the convex cover, and the film layer covers the surface of the through hole close to the convex cover. The lithium-ion battery explosion-proof device can release the pressure inside the battery in time according to the changes inside the lithium-ion battery, and ensure that the lithium-ion battery will not explode due to excessive temperature or pressure, and has a simple structure and is easy to produce.

Description

Technical Field

[0001] The present invention belongs to the field of battery explosion-proof, and more specifically, relates to a lithium ion battery explosion-proof device and a production method thereof, and an explosion-proof lithium ion battery. Background Art

[0002] Lithium-ion batteries are small in size, high in capacity, and have a long cycle life. They are the first choice for energy supply for 3C digital appliances, new energy vehicles, etc., and are an important choice for the country to vigorously develop the new energy industry. However, since lithium metal is an active metal and most of the organic solvents used in lithium-ion batteries are flammable, lithium-ion batteries may explode under extreme conditions. Therefore, most cylindrical lithium-ion batteries and square aluminum-shell steel-shell lithium-ion batteries are equipped with explosion-proof valves.

[0003] Most traditional explosion-proof valves are made of aluminum, with weak grooves on the aluminum sheet. This groove is sensitive to pressure. When the internal pressure of the battery exceeds the set value, the groove on the aluminum sheet is directly broken, the inside and outside of the battery are connected, and the internal pressure is released, thereby protecting the battery. However, in actual use, especially when mass-producing explosion-proof valves, the actual starting pressure of traditional explosion-proof valves often varies greatly; if the actual starting pressure of the explosion-proof valve is too small, the explosion-proof valve is easily broken and scrapped; if the actual starting pressure of the explosion-proof valve is too high, it cannot have an explosion-proof effect on the battery, there are safety hazards, and safety accidents are prone to occur.

[0004] At the same time, aluminum explosion-proof valves are not sensitive enough to temperature. The increase in temperature inside the battery is often accompanied by an increase in pressure. However, when the temperature inside the battery increases, the internal pressure of the battery may not immediately rise to the detonation pressure of the safety valve. There will be a certain delay, which leaves a hidden danger to the safety of the battery. In addition, the traditional aluminum explosion-proof valve processing technology is difficult and the cost is relatively high, which is not conducive to use.

[0005] After searching, the Chinese patent application number is: 200910213656.0, and the application date is: 2009.12.08. The "lithium ion battery explosion-proof valve" includes a valve body, a needle body and an explosion-proof membrane. The valve body is provided with a vent hole, the needle body is fixedly connected to the upper end of the vent hole, and a conical contact pin is provided on the lower surface of the needle body. The explosion-proof membrane is provided at the lower end of the vent hole and is sealed and assembled with the valve body, and the conical contact pin points to the explosion-proof membrane. The explosion-proof membrane is provided at the lower end of the vent hole and is sealed and assembled with the valve body, and the conical contact pin points to the explosion-proof membrane. The explosion-proof membrane of the lithium ion battery explosion-proof valve is made of EPDM rubber as raw material, which has good elasticity and large thickness, and will not break easily, thereby improving the safety and reliability of the battery and extending the service life; however, the cone contact pin is used as the key tool for the explosion-proof valve to release pressure. On the one hand, the installation of the cone contact pin is relatively difficult, and on the other hand, the lithium ion battery explosion-proof valve cannot solve the hidden danger caused by the temperature rising and the internal pressure of the battery not rising in time.

[0006] Another example is the "Plastic Shell Lithium Ion Power Battery Explosion-Proof Valve" with Chinese patent application number: 201220635503.2 and application date: 2012.11.26, which includes a valve body arranged on the battery plastic cover, with an air outlet on the valve body, and an annular pointed top step on the inner bottom of the valve body. The plastic shell lithium ion power battery explosion-proof valve is sealed with an aluminum film on the air outlet, and the aluminum film is clamped between the annular pointed top step and the lock nut, and the lock nut is connected to the valve body through an external thread. The explosion-proof valve uses the principle that the metal aluminum film ruptures under the action of a set force to achieve the purpose of explosion-proof, and solves the safety hazard to the battery caused by excessive internal pressure of the battery under normal circumstances; however, the installation process of the aluminum film of the explosion-proof valve is relatively complicated, and the required precision is high, which brings difficulties to mass production. Summary of the invention

[0007] 1. Problems to be solved

[0008] Aiming at the problem that the existing lithium ion battery explosion-proof valve cannot simultaneously solve the problem that the battery explosion is caused by the internal temperature and pressure of the battery, the present invention provides a lithium ion battery explosion-proof device; the lithium ion battery explosion-proof device can release the pressure inside the battery in time according to the changes inside the lithium ion battery, and ensure that the lithium ion battery will not explode due to excessive temperature or excessive pressure, and has a simple structure and is easy to produce.

[0009] One of the purposes of the present invention is to provide a method for producing the above-mentioned lithium-ion battery, so as to facilitate the understanding and production and use of the content of the present invention.

[0010] One of the purposes of the present invention is to provide a lithium ion battery provided with the above-mentioned lithium ion battery explosion-proof device. When the above-mentioned lithium ion battery explosion-proof device is used, the explosion-proof performance of the lithium ion battery is significantly enhanced, and the lithium ion battery can cope with various situations generated during the use of the lithium ion battery.

[0011] 2. Technical solution

[0012] To solve the above problems, the present invention adopts the following technical solutions.

[0013] A lithium-ion battery explosion-proof device of the present invention comprises a cover plate, the shape of which matches the installation position of the lithium-ion battery explosion-proof valve, a convex cover is provided on the cover plate, a through hole is provided on the surface of the convex cover, a film layer is covered inside the convex cover, and the film layer covers the surface of the through hole near the convex cover. The cover plate matches the installation position of the lithium-ion battery, can adapt to different lithium-ion batteries, and has a wide range of applicability. A convex cover is provided on the cover plate, and the cover plate and the convex cover can be processed in an integrated manner. A mold can be manufactured in advance according to the structural shape of the cover plate and the convex cover to be processed, and then raw materials are injected into the mold, and the mold is opened after the molding to obtain the finished product; the finished product can also be processed by machining. The cover plate and the convex cover can also be processed separately, and the materials used for the cover plate and the convex cover can be different. The processed cover plate and the convex cover are connected to form a whole by glue or other means.

[0014] The through holes on the surface of the convex cover are mainly used to connect the inside of the lithium-ion battery with the external environment when the battery produces abnormal conditions such as temperature and pressure. In order to separate the inside of the lithium-ion battery from the external environment under normal working conditions, and to connect the inside of the battery with the external environment when the lithium-ion battery is in abnormal conditions such as temperature increase and pressure increase. It is necessary to coat a film layer at the through hole. Under normal conditions, the film layer blocks the connection between the inside of the lithium-ion battery and the external environment. When the temperature and pressure inside the lithium-ion battery increase, the high temperature softens the film layer, and the greater pressure will break through the film layer, so that the inside of the lithium-ion battery is connected with the external environment.

[0015] As a preferred solution of the present invention, a hollow cylinder is provided on the inner surface of the convex cover, and the top surface height of the hollow cylinder is lower than the upper surface height of the cover plate. The hollow cylinder is connected to the convex cover at one hollow end, and the connection is a through cylinder. When the temperature inside the lithium-ion battery does not change, but only the pressure changes, the membrane layer cannot soften and change into a viscous flow state due to the change in temperature, thereby reducing the resistance of the internal pressure of the lithium-ion battery to break through the membrane layer. This will make the lithium-ion battery unable to break through the membrane layer under the critical pressure of the battery explosion, causing a safety accident. The hollow cylinder is provided to provide the possibility of breaking through the membrane layer when only the pressure changes inside the lithium-ion battery and there is no temperature change.

[0016] In addition, when the temperature inside the battery does not rise much or there is only a short-term pressure increase, a hollow cylinder is set inside the convex cover, and the top surface of the hollow cylinder is covered with a film layer. The pressure inside the lithium-ion battery will first break through the second film layer in the hollow cylinder, so that the inside and outside of the lithium-ion battery are connected to each other to a certain extent. After the pressure inside the lithium-ion battery is released for a short time, the internal pressure is reduced.

[0017] As a preferred solution of the present invention, the top surface height of the hollow cylinder is higher than the highest height of the through hole in the convex cover. When the pressure inside the lithium-ion battery is small or the pressure increases briefly, in order to successfully release the pressure from the hollow cylinder, the hollow cylinder needs to contact the inner cavity of the lithium-ion battery relative to the through hole first, so the height of the hollow cylinder needs to be higher than the highest height of the through hole, so that the purpose of protecting the lithium-ion battery can be achieved.

[0018] As a preferred solution of the present invention, the film layer includes a first film layer and a second film layer, wherein the first film layer contacts the inner surface of the convex cover and covers the surface of the through hole, and the second film layer covers the surface of the first film layer. In the process of coating the film layer, directly pouring glue or other adhesives may cause the glue or adhesive to overflow the convex cover through the through hole, and the overflow will hinder the installation of the lithium-ion battery, and the overflow will condense into blocks on the outer surface of the convex cover, which will greatly hinder the internal pressure of the lithium-ion battery from breaking through the film layer, and will cause the film layer to be unable to break through under the critical pressure of lithium ions, which may easily cause the battery to explode, hinder the safe use of the lithium-ion battery, and cause certain economic losses, and may also cause personal injuries.

[0019] As a preferred solution of the present invention, the distance between the through hole and the upper surface of the cover plate is 0.2-2mm. The depth setting of the convex cover has a certain influence on the setting of the film layer and the overall use of the lithium-ion battery. The depth of the convex cover is set too shallow. The film layer cannot be coated, and it is even more impossible to coat the film layer in two layers. If the convex cover is set too deep, the coating difficulty of the second film layer will increase, and it will be difficult to control the thickness of the second film layer and keep the surface of the second film layer flat. On the other hand, if the depth of the convex cover is too deep, the volume of the explosion-proof device will be increased, which will hinder the assembly and use of the battery and is not conducive to the effective use of the lithium-ion battery.

[0020] As a preferred solution of the present invention, the first film layer covers the top surface of the hollow cylinder, and the surface of the second film layer is flush with the upper surface of the cover plate. According to the depth of the convex cover and the flushness of the second film layer surface with the upper surface of the cover plate, the coating depth of the second film layer can be determined, which facilitates the coating of the second film layer.

[0021] As a preferred solution of the present invention, the melting point of the second film layer or the temperature range of its transformation into a viscous flow state is 100-180°C. In actual use, there is a certain difference between the first film layer and the second film layer. The first film layer mainly plays the role of filling the through-holes. A thin layer is brushed on the inner side of the convex cover to connect the through-holes to prevent the fillers in the through-holes from falling out of the through-holes. The main characteristic of the second film layer is that it softens to a certain extent at a temperature above 100°C, so that the internal air pressure of the battery can smoothly break through the film layer. However, if the melting point is too high or the temperature of transformation into a viscous flow state is too high, the internal pressure of the lithium-ion battery will not break through the film layer. Therefore, different materials can be selected for filling the first film layer and the second film layer according to their characteristics. The characteristic of the first film layer is that it has a certain bonding effect, covers the inner surface of the convex cover and will not separate from the convex cover, and can block the through-holes to prevent the second film layer from leaking through the through-holes. The melting point of the second film layer or the temperature range for its transformation into a viscous flow state is limited to a certain extent, and needs to be adapted to the temperature under internal or external short circuit or overcharge conditions of the lithium-ion battery. It has certain bonding properties and can bond with the first film layer. When coating the second film layer, the curing time of the second film layer is shortened, which can effectively improve the preparation efficiency of the lithium-ion battery explosion-proof device.

[0022] As a preferred solution of the present invention, the main component of the cover plate is one or more of PE, HDPE, PMMA, PP, and PVC, and the starting temperature range for the cover plate to transform into a viscous flow state is 100°C-180°C. When the lithium-ion battery is under internal and external short circuit or overcharge conditions, the internal starting temperature can reach 150°C, while the melting points of PE and HDPE are 100-130°C, the melting point of PMMA is about 130-140°C, the melting point of PP is about 164-70°C, and PVC begins to transform into a viscous flow state at 160-180°C. When the temperature of the lithium-ion battery rises sharply, the state of the cover plate needs to be changed to achieve a better protection effect on the lithium-ion battery. At this time, the cover plate transforms into a viscous flow state. On the one hand, the hardness of the cover plate changes, and the gas in the lithium-ion battery can easily break through the restrictions of the explosion-proof device; on the other hand, the cover plate will undergo a certain deformation during the softening process, which is convenient for the release of the internal air pressure of the lithium-ion battery to a certain extent, and the explosion-proof effect is more excellent.

[0023] The present invention provides a method for producing a lithium ion battery explosion-proof device, comprising the following steps:

[0024] S1. Design and manufacture a battery cover according to the shape and structure of the lithium-ion battery, and process a convex cover, a through hole and a hollow cylinder on the cover;

[0025] S2, pre-coating a first film layer on the inner surface of the convex cover of the formed battery cover plate, so that the first film layer covers the inner surface of the through hole in the convex cover and the top surface of the hollow cylinder;

[0026] S3, covering the convex cover with the second film layer material, the surface of the second film layer is flush with the upper surface of the cover plate, and the film layer is solidified to complete the preparation of the battery explosion-proof device.

[0027] An explosion-proof lithium-ion battery of the present invention comprises any one of the above-mentioned explosion-proof devices for lithium-ion batteries, wherein the side of the convex cover covered with the film layer is placed outside the battery. When the above-mentioned explosion-proof device for lithium-ion batteries is used, the explosion-proof performance of the lithium-ion battery is significantly enhanced, and the lithium-ion battery can withstand various situations generated during the use of the lithium-ion battery.

[0028] 3. Beneficial effects

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] (1) A lithium-ion battery explosion-proof device of the present invention, when the lithium-ion battery is under conditions such as internal and external short circuit or overcharge, the temperature and pressure inside the lithium-ion battery will rise, and the temperature softens the membrane layer and the cover plate to make them become viscous flow state, and the pressure inside the lithium-ion battery breaks through the restriction of the membrane layer, releasing the pressure inside the battery, ensuring that the lithium-ion battery will not explode due to excessive temperature or pressure, and the structure is simple and easy to produce;

[0031] (2) A lithium ion battery explosion-proof device of the present invention, when there is no temperature change inside the battery but only pressure change, the pressure inside the lithium ion battery needs to be released through a hollow cylinder. Since the thickness of the film layer covering the hollow cylinder is thinner than the thickness of the through hole, even if there is no temperature change, the pressure inside the lithium ion battery can break through the thin film layer on the hollow cylinder. The height of the hollow cylinder can be determined according to the properties of the specific film layer material used and the pressure generated inside the corresponding battery, and can be obtained through testing and measurement in actual production;

[0032] (3) In the lithium-ion battery explosion-proof device of the present invention, when the temperature inside the battery does not rise much, or the pressure rises only briefly, and the battery needs to be used again after the pressure is released, the hollow cylinder can not only release the internal pressure of the lithium-ion battery, but also ensure that the internal and external spaces of the lithium-ion battery remain relatively independent after the pressure is released, thereby providing a basis for the safe and stable use of the lithium-ion battery;

[0033] (4) In the lithium-ion battery explosion-proof device of the present invention, the film layer adopts a method of combining the first film layer and the second film layer, which solves the problem that glue or other adhesives will flow out of the through hole and condense on the surface of the through hole when using a single film layer, thereby ensuring that the lithium-ion battery explosion-proof device can be used safely and stably;

[0034] (5) In the lithium-ion battery explosion-proof device of the present invention, the initial temperature inside the lithium-ion battery can reach 150° C. under the condition of internal and external short circuit or overcharge. In order to ensure the safe and effective use of the lithium-ion battery and achieve better use effect, the second film layer and the cover plate need to be able to soften and transform into a viscous flow state in time when the lithium-ion battery is in an abnormal state, so as to release the pressure inside the battery in time, making the use of the lithium-ion battery safer.

[0035] (6) In the explosion-proof lithium-ion battery of the present invention, when the above-mentioned explosion-proof device for lithium-ion battery is used, the side of the convex cover covered with the film layer is placed on the outside of the battery. Since the second film layer is flush with the upper surface of the cover plate and does not protrude, scratching and damaging the second film layer is avoided. The explosion-proof performance of the lithium-ion battery is significantly enhanced, and the lithium-ion battery can cope with various situations generated during the use of the lithium-ion battery. The structure is simple, the design is reasonable, and it is easy to produce. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a schematic diagram of the overall structure of a lithium-ion battery explosion-proof device without a coating film layer according to Example 1 of the present invention;

[0037] Figure 2 This is a schematic structural diagram of a lithium-ion battery explosion-proof device according to Embodiment 1 of the present invention;

[0038] Figure 3 for Figure 2 Schematic diagram of the cross section at AA in the middle.

[0039] In the accompanying drawings: 1, cover plate; 2, convex cover; 3, through hole; 4, hollow cylinder; 5, membrane layer; 6, first membrane layer; 7, second membrane layer. DETAILED DESCRIPTION

[0040] The following detailed description of exemplary embodiments of the present invention refers to the accompanying drawings, which form a part of the description, and in which exemplary embodiments of the present invention that can be implemented are shown as examples. Although these exemplary embodiments are described in sufficient detail to enable those skilled in the art to implement the present invention, it should be understood that other embodiments can be implemented and various changes can be made to the present invention without departing from the spirit and scope of the present invention. The following more detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but is only for the purpose of illustrating and not limiting the description of the characteristics and features of the present invention, so as to propose the best mode for performing the present invention and to enable those skilled in the art to implement the present invention. Therefore, the scope of the present invention is limited only by the appended claims.

[0041] The following detailed description of the present invention and example embodiments may be better understood in conjunction with the accompanying drawings, in which elements and features of the present invention are identified by reference numerals.

[0042] The design idea of ​​the lithium-ion battery explosion-proof device of the present invention comes from the fact that when manufacturing 1665130 ternary batteries in production experiments, the safety valve uses a traditional aluminum explosion-proof valve. It is found that the starting pressure of the safety valve of a batch of batteries is too low. The standard starting pressure needs to be 1.2x10 6 Pa, while the actual measured starting pressure of the safety valve is only 4.0x10 5 Pa. In order to increase the starting pressure of the safety valve, after continuous thinking, testing and adjustment, the result is that a layer of colloid is applied on the safety valve, and the starting pressure of the safety valve is indeed increased. However, the traditional safety valve is not safe enough when used in batteries. During the test, the battery occasionally has abnormal phenomena because the internal pressure cannot be released. When the battery is short-circuited internally or externally or overcharged, the temperature and pressure inside the battery will rise, but there is also a phenomenon that only the pressure increases but the temperature does not rise. For example, during the process of filling and baking the battery, due to the influence of factors such as moisture, the internal pressure of the battery will increase, but the temperature will not rise. Therefore, a solution that can solve the above two situations is needed. Therefore, an exploratory experiment is carried out to design an explosion-proof device with good safety performance.

[0043] Example 1

[0044] like Figure 1 As shown, a lithium-ion battery explosion-proof device of this embodiment comprises a cover plate 1, a convex cover 2, a through hole 3 and a hollow cylinder 4. A film layer 5 is coated inside the convex cover 2 provided with the through hole 3 and the hollow cylinder 4.

[0045] The cover plate 1 is rectangular, with a hemispherical convex cover 2 in the middle of the cover plate 1 and pole ears on both sides. The cover plate 1 and the convex cover 2 are integrally formed by injection molding, and the material of the cover plate 1 and the convex cover 2 is PMMA. There are through holes 3 evenly distributed on the surface of the convex cover 2, such as Figure 2 As shown, the through hole 3 is at most 1.2 mm away from the upper surface of the cover plate 1 and at most 0.8 mm away from the upper surface of the cover plate 1 .

[0046] The convex cover 2 is covered with a film layer 5, and the film layer 5 covers the surface of the through hole 3 near the convex cover 2. The cover plate 1 is suitable for square bipolar ear batteries, and the shape of the cover plate 1 can also be designed according to the needs of different types of battery structures. The through hole 3 on the surface of the convex cover 2 is mainly used to connect the inside of the lithium-ion battery with the external environment when the battery has abnormal conditions such as temperature and pressure at the same time. In order to separate the inside of the lithium-ion battery from the external environment under normal working conditions; and to connect the inside of the lithium-ion battery with the external environment under abnormal conditions such as increased temperature and increased pressure. It is necessary to coat the film layer 5 at the through hole 3. Under normal conditions, the film layer 5 blocks the connection between the inside of the lithium-ion battery and the external environment; when the temperature and pressure inside the lithium-ion battery increase, the high temperature softens the film layer 5, and the greater pressure will break through the film layer 5, so that the inside of the lithium-ion battery is connected with the external environment.

[0047] The melting point of PMMA is about 130-140℃. When a lithium-ion battery is subjected to internal or external short circuit or overcharge, its internal starting temperature can reach 150℃. When the temperature of the lithium-ion battery rises sharply, the state of the cover 1 needs to be changed to achieve better protection for the lithium-ion battery. At this time, the cover 1 is transformed into a viscous flow state. On the one hand, the hardness of the cover 1 changes, and the gas in the lithium-ion battery can easily break through the restrictions of the explosion-proof device; on the other hand, the cover 1 will undergo a certain deformation during the softening process, which, to a certain extent, facilitates the release of the internal air pressure of the lithium-ion battery, and the explosion-proof effect is more excellent.

[0048] The upper surface of the cover plate 1 refers to the surface of the cover plate 1 on the side opposite to the convex cover 2. The depth of the convex cover 2 has a certain influence on the setting of the film layer 5 and the overall use of the lithium-ion battery. If the depth of the convex cover 2 is set too shallow, the film layer 5 cannot be coated, and the film layer 5 cannot be divided into two layers for coating. If the convex cover 2 is set too deep, the coating difficulty of the second film layer 7 increases, and it is difficult to control the thickness of the second film layer 7 and keep the surface of the second film layer 7 flat. On the other hand, if the depth of the convex cover 2 is too deep, the volume of the explosion-proof device is increased, which hinders the assembly and use of the battery and is not conducive to the effective use of the lithium-ion battery.

[0049] When a lithium-ion battery is subjected to internal or external short circuit or overcharge, the temperature and pressure inside the lithium-ion battery will rise. The temperature softens the membrane layer 5 and the cover plate 1, causing them to become viscous and flow-like. The pressure inside the lithium-ion battery breaks through the restriction of the membrane layer 5, releasing the pressure inside the battery, ensuring that the lithium-ion battery will not explode due to excessive temperature or pressure.

[0050] like Figure 3As shown, the hollow cylinder 4 is arranged at the center of the convex cover 2, and the connection with the convex cover 2 is through. The hollow cylinder 4 is a cylindrical hollow cylinder, and the distance between the top surface of the hollow cylinder 4 and the upper surface of the cover plate 1 is 0.2mm. When the temperature inside the lithium-ion battery does not change, and only the pressure changes, the membrane layer 5 cannot soften and change into a viscous flow state due to the change in temperature, reducing the resistance of the internal pressure of the lithium-ion battery to break through the membrane layer 5. It will make the lithium-ion battery unable to break through the membrane layer 5 under the critical pressure of the battery explosion, causing a safety accident. The hollow cylinder 4 is set to provide the possibility of breaking through the membrane layer 5 when only the pressure changes inside the lithium-ion battery and there is no temperature change.

[0051] In addition, when the temperature inside the battery does not rise much or there is only a short-term pressure increase, a hollow cylinder 4 is set in the convex cover 2, and the top surface of the hollow cylinder 4 is covered with a film layer 5. The pressure inside the lithium-ion battery will first break through the second film layer 7 in the hollow cylinder 4, so that the inside and outside of the lithium-ion battery are connected to each other to a certain extent. After the pressure inside the lithium-ion battery is released for a short time, the internal pressure is reduced.

[0052] When the pressure inside the lithium-ion battery is small or the pressure increases briefly, in order to successfully release the pressure from the hollow cylinder 4, the hollow cylinder 4 needs to contact the inner cavity of the lithium-ion battery relative to the through hole 3 first, so the height of the hollow cylinder 4 needs to be higher than the highest height of the through hole 3. At this time, the purpose of protecting the lithium-ion battery can be achieved. The release of the internal pressure of the lithium-ion battery needs to be completed through the hollow cylinder 4. Since the thickness of the film layer 5 covering the hollow cylinder 4 is thinner than the thickness of the through hole 3, even if there is no temperature change, the pressure inside the lithium-ion battery can break through the thin film layer 5 on the hollow cylinder 4. The height of the hollow cylinder 4 can be determined according to the properties of the specific film layer 5 material used and the pressure generated inside the corresponding battery, and can be obtained through testing and calculation in actual production.

[0053] The film layer 5 includes a first film layer 6 and a second film layer 7. The first film layer 6 is made of vaseline, in contact with the inner surface of the convex cover 2, and covers the surface of the through hole 3 and the top surface of the hollow cylinder 4. The second film layer 7 is made of epoxy resin glue and covers the surface of the vaseline. The surface of the epoxy resin glue is flush with the upper surface of the cover plate 1. When the internal temperature of the lithium-ion battery rises and the air pressure reaches 7-9 atmospheres, the corresponding part of the film layer 5 will be broken, thereby achieving the effect of protecting the lithium-ion battery.

[0054] During the coating process of the film layer 5, directly pouring glue or other adhesives may cause the glue or adhesive to overflow from the convex cover 2 through the through hole 3, and the overflow will hinder the installation of the lithium-ion battery, and the overflow will condense into blocks on the outer surface of the convex cover 2, which will greatly hinder the internal pressure of the lithium-ion battery from breaking through the film layer 5, and will cause the film layer 5 to fail to break through under the critical pressure of lithium ions, which may easily cause the battery to explode, hinder the safe use of the lithium-ion battery, cause certain economic losses, and may also cause personal injuries. According to the depth of the convex cover 2 and the flushness of the surface of the second film layer 7 with the upper surface of the cover plate 1, the coating depth of the second film layer 7 can be determined to facilitate the coating of the second film layer 7.

[0055] Epoxy resin glue will change from a solid state to a viscous flow state within the temperature range of 100-180°C. In actual use, there is a certain difference between the first film layer 6 and the second film layer 7. The first film layer 6 mainly plays a filling role for the through hole 3, that is, the surface tension is used to make the first film layer 6 cover the inner surface of the through hole 3. The setting diameter of the through hole 3 is related to the battery size and battery performance. The first film layer 6 needs to meet the following requirements: it has a certain surface tension and can cover the hole with a diameter of less than 2mm (according to relevant records of 360 Encyclopedia, the thickness of the film can be as thin as a few microns and as thick as a few millimeters), and has a certain bonding effect with the second film layer 7 (if the adhesion between the first film layer 6 and the second film layer 7 is not good, the inner surface of the convex cover 2 cannot be completely covered when the first film layer 6 covers the surface of the through hole 3, and it is necessary to leave contact space between the second film layer 7 and the convex cover 2), so that the second film layer 7 and the first film layer 6 constitute the whole film layer 5, and a thin layer is brushed on the inner side of the convex cover 2 to connect the through holes 3 to prevent the filler in the through hole 3 from falling out of the through hole 3. The main characteristic of the second film layer 7 is that it softens to a certain extent at a temperature above 100°C, so that the internal gas pressure of the battery can smoothly break through the film layer 5. However, if the melting point is too high or the temperature at which it turns into a viscous flow state is too high, the internal pressure of the lithium-ion battery will not be able to break through the film layer 5. Therefore, different materials can be selected for filling the first film layer 6 and the second film layer 7 according to their characteristics. They will not separate from the convex cover 2 when covering the inner surface of the convex cover 2, and can block the through hole 3 to prevent the second film layer 7 from leaking through the through hole 3. The melting point of the second film layer 7 or the temperature range at which it turns into a viscous flow state has certain limitations, and it needs to be adapted to the temperature under the conditions of internal and external short circuits or overcharging of the lithium-ion battery, have certain bonding properties, and can bond with the first film layer 6. When the second film layer 7 is coated, the curing time of the second film layer 7 is shortened, which can effectively improve the preparation efficiency of the lithium-ion battery explosion-proof device.

[0056] Example 2

[0057] The structure of this embodiment is basically the same as that of embodiment 1, with the difference being that: the cover plate 1 is circular in shape and is suitable for cylindrical lithium-ion batteries, the cover plate 1 and the convex cover 2 are made of PE material by injection molding, a convex cover 2 is arranged in the middle of the cover plate 1, the contour of the convex cover 2 is cylindrical, the through hole 3 on the convex cover 2 is 0.2 mm away from the upper surface of the cover plate 1, the hollow cylinder 4 is located at the center of the cover plate 1, the top surface of the central cylinder is 0.1 mm away from the upper surface of the cover plate 1, and the first film layer 6 is made of epoxy resin glue.

[0058] Example 3

[0059] The structure of this embodiment is basically the same as that of embodiment 2, with the difference being that the cover plate 1 and the convex cover 2 are made of a mixed material of PE and HDPE in a ratio of 1:1 by injection molding, a convex cover 2 is arranged in the middle of the cover plate 1, the contour of the convex cover 2 is cylindrical, the through hole 3 on the convex cover 2 is 2 mm away from the upper surface of the cover plate 1, the hollow cylinder 4 is located at the center of the cover plate 1, the top surface of the central cylinder is 0.4 mm away from the upper surface of the cover plate 1, and the first film layer 6 is made of vaseline.

[0060] Example 4

[0061] The structure of this embodiment is basically the same as that of the embodiment 2, except that: the cover plate 1 is made of PMMA material with a circular hole in the center. The convex cover 2 is made of PP material with a cylindrical profile, and the cover plate 1 and the convex cover 2 are bonded by glue for bonding plastic products. The through hole 3 on the convex cover 2 is 1.5 mm away from the upper surface of the cover plate 1, the hollow cylinder 4 is located at the center of the cover plate 1, and the top surface of the central cylinder is 0.3 mm away from the upper surface of the cover plate 1, and the first film layer 6 is made of vaseline.

[0062] Example 5

[0063] A method for producing a lithium-ion battery explosion-proof device of this embodiment, based on a lithium-ion battery explosion-proof device of any structural size of embodiments 1-4, comprises the following steps:

[0064] S1. Design and manufacture a battery cover plate 1 according to the shape and structure of the lithium-ion battery, and process a convex cover 2, a through hole 3 and a hollow cylinder 4 on the cover plate 1;

[0065] S2, pre-coating the first film layer 6 on the inner surface of the convex cover 2 of the formed battery cover plate 1, so that the first film layer 6 covers the inner surface of the through hole 3 in the convex cover 2 and the top surface of the hollow cylinder 4;

[0066] S3, covering the convex cover 2 with the raw material of the second film layer 7, the surface of the second film layer 7 is flush with the upper surface of the cover plate 1, and the film layer 5 is solidified to complete the preparation of the battery explosion-proof device.

[0067] Example 6

[0068] An explosion-proof lithium-ion battery of this embodiment includes any one of the lithium-ion battery explosion-proof devices of embodiments 1-4, and the side of the convex cover 2 covered with the film layer 5 is placed outside the battery. When the above lithium-ion battery explosion-proof device is used, the side of the convex cover 2 covered with the film layer 5 is placed outside the battery. Since the second film layer 7 is flush with the upper surface of the cover plate 1 and does not protrude, scratching and damaging the second film layer 7 is avoided. The explosion-proof performance of the lithium-ion battery is significantly enhanced, and it can cope with various situations generated during the use of the lithium-ion battery. The structure is simple, the design is reasonable, and it is easy to produce.

Claims

1. A lithium-ion battery explosion-proof device, characterized in that: The cover plate (1) comprises a convex cover (2) provided on the cover plate (1), a through hole (3) provided on the surface of the convex cover (2), a film layer (5) covering the inside of the convex cover (2), and the film layer (5) covering the surface of the through hole (3); The inner surface of the convex cover (2) is provided with a hollow cylinder (4), one end of which is connected to the convex cover (2); the top surface of the hollow cylinder (4) is lower than the upper surface of the cover plate (1); the top surface of the hollow cylinder (4) is higher than the highest height of the through hole (3) in the convex cover (2); The film layer (5) comprises a first film layer (6) and a second film layer (7), wherein the first film layer (6) contacts the inner surface of the convex cover (2) and covers the surface of the through hole (3) and the top surface of the hollow cylinder (4), and the second film layer (7) covers the surface of the first film layer (6).

2. A lithium ion battery explosion-proof device according to claim 1, characterized in that: The distance between the through hole (3) and the upper surface of the cover plate (1) is 0.2-2 mm.

3. A lithium ion battery explosion-proof device according to claim 2, characterized in that: The surface of the second film layer (7) is flush with the upper surface of the cover plate (1).

4. A lithium ion battery explosion-proof device according to claim 3, characterized in that: The melting point or the temperature at which the second film layer (7) changes into a viscous flow state ranges from 100 to 180°C.

5. A lithium ion battery explosion-proof device according to any one of claims 1 to 4, characterized in that: The main component of the cover plate (1) is one or more of PE, HDPE, PMMA, PP and PVC, and the starting temperature range for the cover plate (1) to transform into a viscous flow state is 100° C.-180° C.

6. A method for producing a lithium-ion battery explosion-proof device, characterized in that: The following steps are involved: S1. Designing and manufacturing a battery cover plate (1) according to the shape and structure of the lithium-ion battery, and processing a convex cover (2), a through hole (3) and a hollow cylinder (4) on the cover plate (1); S2, pre-coating a first film layer (6) on the inner surface of the convex cover (2) of the formed battery cover plate (1), so that the first film layer (6) covers the inner surface of the through hole (3) in the convex cover (2) and the top surface of the hollow cylinder (4); S3, covering the convex cover (2) with the raw material of the second film layer (7), so that the surface of the second film layer (7) is flush with the upper surface of the cover plate (1), and waiting for the film layer (5) to solidify, the preparation of the battery explosion-proof device is completed.

7. An explosion-proof lithium-ion battery, characterized in that: A lithium-ion battery explosion-proof device comprising any one of claims 1 to 5, wherein the side of the convex cover (2) covered with the film layer (5) is placed outside the battery.

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