Low-melting-point tab glue

Abstract

A low-melting-point tab adhesive is characterized in that a tab is composed of a metal belt for leading out current and a tab adhesive body used for being sealed with a lithium battery flexible package film in a heat sealing mode, the tab adhesive body and the lithium battery flexible package film have high bonding strength and have the characteristic of resisting the high temperature of 130 DEG C or above, and the tab adhesive body and the metal belt have the characteristic that before the internal temperature of a lithium battery rises to 100 DEG C to 130 DEG C, the tab adhesive body is not prone to falling off. Opening pressure relief is performed between the tab glue and the metal belt, so that internal short-circuit fire combustion is avoided; the tab glue is of a film structure with an inner layer, a middle layer and an outer layer, and the melting point of the outer film is 130-150 DEG C; the melting point of the inner film is 90-130 DEG C; and a middle film. And before the internal temperature of the lithium battery rises to 100-130 DEG C, the pressure is released from the packaging opening at the tab, so that internal short-circuit fire and combustion are avoided. The production process of the lithium battery is not changed at all, top sealing and heat sealing process parameters do not need to be changed, use of a user is greatly facilitated, and a new thought for solving the packaging safety problem of the lithium battery is developed.

Description

Technical Field

[0001] The invention relates to the technical field of lithium battery soft packaging, in particular to a low melting point ear glue. Background Art

[0002] At present, the inner film of the aluminum-plastic composite packaging film for soft-package lithium batteries is made of polypropylene materials that can be self-heat-melted and sealed, and its melting point is higher than 130°C. Due to the high safety risks and high technical difficulty of aluminum-plastic packaging films for lithium batteries, the localization rate of aluminum-plastic packaging films required for mid-to-high-end demands is low, and domestic products are only suitable for low-end products. However, the demand for domestic mid-to-high-end products is getting higher and higher, and the domestically produced lithium battery soft packaging films cannot meet the requirements of high-end lithium batteries. Summary of the invention

[0003] The technical problem to be solved by the present invention is to address the deficiencies in the prior art and propose a low-melting-point ear glue that can solve the problem of short circuit and fire inside lithium battery packaging and reduce safety risks.

[0004] The technical problem to be solved by the present invention is achieved through the following technical scheme: a low melting point ear glue, which is characterized in that: the ear is composed of a metal belt for drawing out current and an ear glue for heat-sealing with a lithium battery soft packaging film, the ear glue and the lithium battery soft packaging film have strong bonding strength and high temperature resistance above 130°C, and there is an opening between the ear glue and the metal belt to release pressure before the internal temperature of the lithium battery rises to 100-130°C, thereby avoiding internal short circuit and fire; The ear glue is a three-layer film structure of inner, middle and outer layers. The outer film is a polypropylene material for hot-melt sealing of lithium battery soft packaging film, with a tensile strength of ≥195±5 kg / cm², a shear strength of ≥32 Mpa, and a melting point between 130 and 150°C. The inner film is made of maleic anhydride modified polyethylene material, which has good hot melt bonding strength with the metal belt, and its melting point is between 90~130℃ The middle film is a co-extruded film made by mixing 30-70% maleic anhydride modified polypropylene pellets and 70-30% maleic anhydride modified polyethylene pellets, and its melting point is between 90-170°C.

[0005] The technical problem to be solved by the present invention can be further achieved by the following technical solution: the inner, middle and outer layers of the ear glue are processed into a co-extruded cast film structure by a three-layer co-extrusion casting device.

[0006] The technical problem to be solved by the present invention can also be further achieved by the following technical solution: the mass ratio of the maleic anhydride modified polypropylene particles and the maleic anhydride modified polyethylene particles in the middle film is 50-70%: 50-30%.

[0007] Compared with the existing technology, the present invention solves the safety problem of short circuit and fire inside the lithium battery packaging by changing the structure of the pole ear. The pole ear is an important component of the soft-package lithium battery. Before the internal temperature of the lithium battery rises to 100-130°C, the packaging opening at the pole ear is depressurized to avoid internal short circuit and fire. The production process of the lithium battery is not changed at all, and there is no need to change the top sealing and heat sealing process parameters, which greatly facilitates the use of users and opens up a new idea for solving the safety problem of lithium battery packaging. DETAILED DESCRIPTION

[0008] The specific technical solutions of the present invention are further described below. To make the purpose, technical solutions and advantages of the embodiments of the present invention clearer and to facilitate those skilled in the art to further understand the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of them, and do not constitute a limitation on the rights thereof. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present invention.

[0009] A low melting point tab glue, the tab is composed of a metal strip for drawing out current and a tab glue for heat-sealing with a lithium battery soft packaging film, the outer surface of the tab glue and the lithium battery soft packaging film have strong bonding strength and high temperature resistance above 130°C, and the inner surface of the tab glue and the metal strip have an opening between the tab glue and the metal strip to release pressure before the internal temperature of the lithium battery rises to 100-130°C, thereby avoiding internal short circuit and fire; The ear glue is a three-layer film structure of inner, middle and outer layers. The outer film is a polypropylene material for hot-melt sealing of lithium battery soft packaging film, with a tensile strength of ≥195±5 kg / cm², a shear strength of ≥32 Mpa, and a melting point between 130 and 150°C. The inner film is made of maleic anhydride modified polyethylene material, which has good hot melt bonding strength with the metal belt, and its melting point is between 90~130℃ The middle film is a co-extruded film made by mixing 30-70% maleic anhydride modified polypropylene pellets and 70-30% maleic anhydride modified polyethylene pellets, and its melting point is between 90-170°C.

[0010] The inner, middle and outer layers of the ear glue can be processed into a co-extruded cast film structure by a three-layer co-extrusion cast equipment.

[0011] The mass ratio of the maleic anhydride modified polypropylene particles and the maleic anhydride modified polyethylene particles in the middle film is 50-70%:50-30%.

[0012] The present invention solves the safety problem of short circuit and fire inside the lithium battery packaging by changing the structure of the pole ear. The pole ear is an important component of the soft-package lithium battery. Before the internal temperature of the lithium battery rises to 100-130°C, the packaging opening at the pole ear is depressurized to avoid internal short circuit and fire. The production process of the lithium battery is not changed at all, and there is no need to change the top sealing and heat sealing process parameters, which greatly facilitates the use of users and opens up a new idea for solving the safety problem of lithium battery packaging.

[0013] In the present invention, the inner layer material of the ear glue has good hot melt bonding strength with the metal belt, and the outer layer material has good hot melt sealing strength with the lithium battery soft packaging film, but the two are difficult to composite with each other and are easily delaminated, and the strength requirements of the composite film layer cannot be met.

[0014] The present invention creatively adopts an intermediate transition film layer structure, and the middle film adopts an extruded film structure of maleic anhydride modified polypropylene particles and maleic anhydride modified polyethylene particles. In this way, the inner layer and the middle layer, the outer layer and the middle layer have good bonding strength, which can meet the sealing requirements of the tab sealant for lithium batteries.

[0015] The inner layer with the lowest melting point is bonded to the metal strip. Once the lithium battery gets hot inside, the metal strip of the tab is directly connected to the current collector inside the battery, so the temperature of the metal strip of the tab rises the fastest. Once it approaches or reaches the melting point of the inner layer, the adhesion between the inner layer and the metal strip of the tab will drop rapidly. Under high pressure inside the battery, the internal gas will break the adhesion between the inner layer and the metal strip and quickly release the internal pressure of the lithium battery, thereby effectively avoiding the huge risk of short circuit and fire caused by excessive temperature and internal pressure inside the lithium battery, resulting in shrinkage of the battery diaphragm and deformation of the current collector inside the battery.

Claims

1. A low melting point ear glue, characterized in that: The tabs are composed of a metal strip for drawing out current and a tab glue for heat-sealing with the lithium battery soft packaging film. The tab glue and the lithium battery soft packaging film have strong bonding strength and high temperature resistance above 130°C. When the internal temperature of the lithium battery rises to 100-130°C, the tab glue and the metal strip are opened to release pressure to avoid internal short circuit and fire. The ear glue is a three-layer film structure of inner, middle and outer layers. The outer film is a polypropylene material for hot-melt sealing of lithium battery soft packaging film, with a tensile strength of ≥195±5 kg / cm², a shear strength of ≥32 Mpa, and a melting point between 130 and 150°C. The inner film is made of maleic anhydride modified polyethylene material, which has good hot melt bonding strength with the metal belt, and its melting point is between 90 and 130°C; The middle film is a co-extruded film made by mixing 30-70% maleic anhydride modified polypropylene pellets and 70-30% maleic anhydride modified polyethylene pellets, and its melting point is between 90-170°C.

2. The low melting point ear glue according to claim 1, characterized in that: The inner, middle and outer layers of the ear glue are processed into a co-extruded cast film structure through a three-layer co-extrusion cast equipment.

3. The low melting point ear glue according to claim 1, characterized in that: The mass ratio of the maleic anhydride modified polypropylene particles and the maleic anhydride modified polyethylene particles in the middle film is 50-70%:50-30%.