WO2008141474A1

WO2008141474A1 - Method for packaging lithium cell by injecting plastic

Info

Publication number: WO2008141474A1
Application number: PCT/CN2007/001617
Authority: WO
Inventors: Xusong Ruan; Jianyun Zeng
Original assignee: Huizhou Desay Battery Co., Ltd
Priority date: 2007-05-17
Filing date: 2007-05-17
Publication date: 2008-11-27
Also published as: CN101366131A; CN101366131B

Abstract

A method for packaging lithium cell by injecting plastic. A face cover of a electric core assembly can be formed by this method. The electric core assembly may be a lithium ion electric core assembly or a polymer electric core assembly, wherein the polymer electric core assembly was packaged by a metal flake in advance. The method for packaging a lithium cell includes: providing the electric core assembly with a output terminal into a cavity of a mould and locating therein with a location pin; melting thermoplastic polyamide resin desired to be inject at 170 to 230 degrees Centigrade, to make the viscosity of the thermoplastic polyamide resin in the range of 340OmPa •s to 10,000 mPa •s; injecting the said molten thermoplastic polyamide resin into the cavity of the metal mould at the pressure of the injecting plastic in the range of 1 MPa to 10MPa, so as to inject the said thermoplastic polyamide resin into the cavity of the metal mould and coat onto the front face of the electric core assembly to form a plastic face cover.

Description

Method for injection molding lithium battery

The invention relates to the technical field of an injection molding method, and in particular to a method for packaging and packaging a battery core assembly.

Background technique

With the increasing awareness of environmental protection, the use of toxic metals such as lead and cadmium is limited. Research and development of lithium-ion batteries is the trend of the times. Lithium-ion batteries are a new generation of chemical power sources that emerged in the 1990s. Due to their excellent electrochemical performance and non-polluting properties, lithium-ion batteries are an ideal power source for a variety of advanced portable electronic products.

Lithium-ion batteries are divided into two types: polymer lithium-ion batteries and liquid lithium-ion batteries. The biggest difference between a polymer lithium ion battery and a liquid lithium ion battery is that the electrolyte used in the two is different. The liquid lithium ion battery uses an electrolyte, and the battery core needs to be placed in a steel metal shell or an aluminum metal shell. The electrolyte used in the polymer lithium ion battery is a colloidal polymer, and the battery core does not need to be placed in the metal casing like the liquid lithium ion battery, but the polymer battery core is soft, and the battery core needs to be passed through the hard casing. Package. Because the lithium battery is usually installed through a battery case or the like, and is positioned and electrically connected by a pressing mechanism such as a spring, the battery needs to have a high rigidity.

At present, the lithium battery package form of the soft battery core is mostly made of a plastic case, and is integrally molded by injection molding the battery core. Usually, plastic materials for injection molding, such as polystyrene, are heated to a molten state during injection molding, and are injected into a cavity of a metal mold under a very high pressure (about lx 10 ⁸ Pa) to form an injection molded casing. In this injection-molded plastic case battery, the thickness of the battery is increased, and the injection molding is liable to form burrs, and at the same time, when the molten resin material is in contact with the battery in the metal mold during injection, the battery in the case is damaged. For the injection molding method of the packaged lithium battery, there is also a lower pressure injection molding of about 0. 3-0. 6MPa, although the low pressure injection molding can avoid damage and reduce the burrs generated by the injection molding, but the order of magnitude of the low pressure injection molding, the precision of the injection molding equipment and The process requirements are very high, and the general equipment is difficult to meet the requirements. Summary of the invention

The technical problem to be solved by the present invention is to provide an injection molding method in which the injection pressure is relatively high without damaging the lithium battery to be injection molded, and the general injection molding equipment and process can be realized, and the requirements for the injection molding equipment are reduced. .

The invention is achieved by the following technical solutions:

The method of injection molding a lithium battery of the present invention is achieved by using a metal mold having a cavity, and the specific steps are as follows:

The cell assembly having the output terminal is placed in the cavity of the mold and positioned by the positioning pin in the cavity of the mold; the molten thermoplastic resin having a melt viscosity in the range of 3400 mPa.s to 10000 mpa.s is at IMPa to The molten thermoplastic resin is injected into the cavity of the metal mold under the injection pressure in the range of 10 MPa, so that the plastic resin is filled into the cavity of the metal mold and applied to the front end surface of the battery assembly to form a plastic face cover.

As a preferred method of the above method, the thermoplastic resin is a polyamide thermoplastic resin having a viscosity in the range of 3400 mPa· _s to 10,000 mPa.s, and the injection molding temperature is controlled in the range of 170 to 230 ° C.

The mold used in the above solution is composed of an upper mold and a lower mold, and the concave upper and lower molds are combined to form an injection cavity in which the battery core assembly can be placed, and a molding block is arranged in front of the cavity, and the molding block faces the cavity. A convex block is disposed on the side wall, and a positioning pin is disposed on the concave wall of the upper mold and the lower mold.

The lithium battery cell assembly packaged by the injection molding method of the present invention may be a liquid lithium ion battery cell assembly with a hard case or a soft polymer cell assembly. The liquid lithium ion battery core assembly comprises a liquid lithium ion battery core with a casing, a protective cover and a protection circuit substrate provided with an output terminal, and the protective cover is placed on the front end surface of the lithium ion battery core, in general, The shape of the protective cover will be larger than the cell in the thickness direction of the cell. A positioning angle is provided on the upper and lower walls of the protection circuit substrate. '

The soft polymer lithium ion battery cell of the soft polymer battery core assembly is packaged in a casing made of a metal sheet, and the casing surface of the casing close to the front end of the battery core is pre-molded on the metal casing. The plastic surface is provided with a protective circuit substrate with an output terminal, and the electrode on the front end surface of the battery core is connected to the output terminal on the protection circuit substrate through the plastic surface.

Compared with the prior art, the utility model has the following obvious effects:

1. The injection molding lithium battery of the invention adopts a glue injection pressure in the range of IMPa to lOMpa, and on the basis of ensuring that the packaged battery is not damaged, the injection molding process is simplified compared to the ultra-low pressure injection molding. Due to the use of less pressure for injection molding, the stability requirements of injection molding equipment are very high. When the product design such as the front end cover thickness of the battery core assembly is less than 0.50 mm, the defect rate will increase greatly. The invention has low requirements for the injection molding process and the injection molding equipment, and has good stability for the products with high molding technology requirements.

2. The injection mold of the present invention has a molding block corresponding to the shape of the injection molding cover, and the injection molding yield is high, and an effective insulating member can be added to the convex block on the molding block according to the needs of the injection molded battery assembly.

3. The battery core assembly of the injection molding package of the invention is connected with a plastic surface protection cover in front of the front end of the battery core having electrodes, which can be used as a positioning for connecting the nickel sheets, and more importantly, the explosion-proof opening of the front end surface of the battery core can be protected from the injection high pressure. Damage.

4. The soft polymer battery core assembly of the injection molding cover of the present invention, the soft battery core is protected by a metal sheet. The production of the soft polymer cell assembly with the metal sheet protective packaging is stable.

DRAWINGS

1 is a schematic view showing the appearance of a mold of an injection molded lithium battery of the present invention;

2 is a schematic structural view of an injection molded package cell assembly located in a cavity of the mold;

' Figure 3 is a partial enlarged view of the portion A of Figure 2;

4 is a schematic view of a battery core assembly of the injection molded package of the present invention;

Figure 5 is an exploded perspective view of the battery assembly of Figure 4 after injection molding the upper cover;

Figure 6 is a schematic view of the appearance of Figure 5;

Figure 7 is a schematic view of another battery core assembly in the present invention;

Figure 8 is an exploded perspective view of the battery pack of Figure 7 after injection molding the upper cover; Figure 9 is a schematic view of the appearance of Figure 8.

detailed description

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The method for injecting a packaged lithium battery of the present invention will be specifically described below by way of a specific embodiment. The cover of the packaged battery assembly can be formed by the method of the present invention, and the cover covers the electrode end of the battery core and the output terminal of the battery core. The mold used in the method of the present invention is as shown in Figures 1-3. The mold comprises an upper mold 11 and a lower mold 12. The upper mold and the lower mold respectively have inner concave portions, and the inner concave portions of the upper and lower molds are combined to form an injection molded hollow. The cavity, the packaged cell assembly 2 is placed in the cavity. A glue injection hole is arranged at the joint of the upper and lower molds, a thermoplastic resin is injected through the injection hole 10, and an injection molding surface cover is formed on the front end surface of the battery core assembly in the cavity, so that the injection molding of the lithium battery can be realized.

In the present invention, the cell assembly 2 placed in the cavity of the mold is illustrated by taking a liquid lithium ion battery assembly as an example. The battery assembly includes a liquid lithium ion battery core 27, and the front end of the battery core is protected. The cover 26, the protective cover is a pre-made plastic body, which is in the form of an open box, and the protective cover is placed at the explosion-proof opening at the front end of the battery core. A protective circuit substrate 23 is attached to the front of the explosion-proof port, and a battery output terminal is disposed thereon. The electrode at the front end of the battery core is connected to the output terminal through the positive nickel plate 25 and the negative nickel plate 24. A raised positioning angle 231 is provided on the upper and lower walls of the protection circuit substrate. A liquid lithium ion battery cell, a protective cover and a protection circuit substrate are arranged in a cavity of the mold. The cavity of the mold is in a "T" shape, and the end of the protection circuit substrate of the battery component is placed in the cavity. At the enlarged section, a wall of the cavity corresponding to the protection circuit substrate has a positioning pin 14 which cooperates with a positioning angle on the substrate of the protection circuit to function as a substrate for protecting the circuit. The protection circuit substrate of the embodiment of the present invention has a test terminal in addition to the output terminal, and in order to expose the output terminal and the test terminal when the package cover 22 is injection molded, a molding block 13 is provided in front of the mold cavity of the present invention. , that is, the forming block is located at the intersection of the upper and lower molds, and the convex block 131 having the same shape as that of the test terminal and the output terminal is respectively disposed on the side wall of the forming block facing the cavity, so as to ensure the test when the injection cover is pressed. No resin is attached to the terminals and the output terminals. The bumps that are mated to the test terminals as needed in the actual operation can be processed from an insulating material and have high operability.

The invention adopts the above-mentioned mold matched with the structure of the electric core component, and uses the specified resin material to enter Lithium battery injection molding. When the package is injection molded by the method of the present invention, the battery core assembly to be injection molded is first placed in the cavity of the mold, and the mold core is placed at a suitable position of the mold cavity by the positioning needle and the positioning angle; A thermoplastic resin for injection molding, such as a polyamide resin, is placed in a heater to be heated to melt. When the melt viscosity of the molten polyamide resin is

When the range is from 3400mPa.s to lOOOOmPa.s, the injection pressure is controlled within the range of l tPa to lOMPa for injection. The melting temperature of the injection molding is controlled at 170 ~ 230" C. Considering that the temperature of each point of the injection molding system changes greatly, the melting temperature referred to in the method of the present invention refers to the injection nozzle connected to the injection hole of the mold. temperature.

For the injection-molded thermoplastic resin, the melting temperature is not limited to the range of 170 ~ 23 (TC), and the normal temperature range selected by the present invention will achieve stable production, and the temperature will be too high, which will cause carbonization of the plastic. Accelerate, the viscosity of the injection molding resin becomes small, which causes unnecessary burrs in the injection molded product. In addition, due to the size of the usual battery, there is a change of about 0.10mm, and the injection temperature of 170 ~ 230 °C can be lowered. Requirements for mold and battery feed.

Finally, the molten resin is injected into the cavity of the mold through the mold injection hole within the specified pressure and temperature range, and the cover is injection molded at the front end of the core assembly of the mold cavity by the mold forming block. The pre-molded plastic bottom case of the cell assembly before the injection cap is bonded to the end of the cell assembly, and the finished product is obtained after the face is stamped and the trademark is obtained.

In the packaged battery core assembly used in the method, the protective cover is disposed on the front end explosion-proof port of the battery core, which can effectively improve the pressure resistance performance of the battery core, protect the weak portion of the battery core from the impact of the injection pressure, and protect the battery core. . At the same time, the requirements for injection molding equipment can be significantly reduced. Injection molding is performed using a relatively high injection pressure.

In the above method of injection molding a lithium battery, the packaged battery core assembly is exemplified by a liquid lithium ion battery assembly. This method is also suitable for battery components composed of flexible polymer cells during actual injection molding. The soft polymer battery core assembly for injection molding the face cover of the present invention is pre-wrapped with a thin metal sheet, and the metal sheet encapsulating the packaged soft battery core is thinner than the injection molded package, thereby increasing the battery capacity.

Referring to Figures 6, 7 , the soft cell 36 of the flexible polymer cell assembly 3 is wrapped in a metal sheet. In the housing, and the electrode end face of the battery core is protected by a plastic surface, the plastic surface is similar to the protective cover in the liquid lithium ion battery assembly, and can protect the battery core when the electrode assembly is molded into the cover 32 The role. The housing made of the above metal sheet is composed of a box-shaped upper metal piece 37 and a lower metal piece 33. The front end surface of the upper metal piece is connected with a plastic surface 371 by injection molding, and the front end of the lower metal piece is open. The tail end is also connected to the tail plastic surface 34 by injection molding. When the upper and lower metal pieces are combined to form a casing, the plastic surface of the upper metal piece is aligned with the front end opening of the lower metal piece, and the electrode of the soft battery core can be extended at the matching gap so that the battery core electrode can be A protective plate 35 having an output terminal connected to the front of the housing is electrically coupled. Similarly, there are also positioning angles on the upper and lower walls for facilitating cooperation with the positioning pins of the mold cavity.

Preferably, the plastic surface of the metal sheet on the casing is a toothed surface, and when the soft polymer battery assembly is placed in the cavity of the mold to mold the surface of the package, the toothed plastic surface can be used for protecting the battery core, and the plastic injection molding is used for the injection molding. The strength of the cover, filling the gap between the protection plate and the battery core, can effectively protect the thermal shock and pressure shock of the polymer battery during the injection molding process.

Compared with lithium-ion batteries, the soft polymer batteries packaged with metal sheets have the appearance requirements. The surface of the metal sheets can be processed by laser or silk screen on the surface of the metal sheets. The effect of this, in order to increase the capacity of the battery.

Claims

Rights request

A method for injection molding a lithium battery, comprising: the steps of: placing a battery core assembly having an output terminal in a cavity of the mold and positioning by a positioning pin in the cavity of the mold;

The molten thermoplastic resin having a melt viscosity in the range of 3400 mPa·s to 10000 mpa.s is injected into the cavity of the metal mold under the injection pressure of IMPa to 10 MPa, so that the plastic resin is filled A plastic face cover is formed to the cavity of the metal mold and applied to the front end surface of the battery core assembly.

2. A method of injection molding a lithium battery according to claim 1, wherein the thermoplastic resin is a polyamide resin.

A method of injection molding a lithium battery according to claim 1, wherein said melting temperature is in the range of 170 to 230 °C.

4. The method of injection molding a lithium battery according to claim 3, wherein: the mold is composed of an upper mold (11) and a lower mold (12), and the upper and lower molds having the concave portion are formed to be placed An injection molding cavity of the cell assembly, a molding block (13) is disposed in front of the cavity, and a convex block (131) is disposed on the sidewall of the molding block facing the cavity, and the upper mold and the lower mold are recessed on the wall A positioning pin (14) is provided.

5. The method of injection molding a lithium battery according to claim 4, wherein: the battery core assembly comprises a liquid lithium ion battery core, a protective cover, and a protection circuit substrate provided with an output terminal, The protective cover is placed on the front end of the lithium ion battery.

The method of injection molding a lithium-ion battery according to claim 5, wherein the upper and lower walls of the protection circuit substrate are provided with a positioning angle (231).

7. The method of injection molding a lithium battery according to claim 4, wherein: said cell assembly comprises a flexible polymer cell, and the soft polymer cell is encapsulated in a case made of a metal sheet. In the body, the housing surface of the housing adjacent to the front end of the battery core is a plastic surface pre-molded on the metal housing, and a protective circuit substrate with an output terminal is disposed in front of the plastic body, and the front end surface of the battery core is The electrode is connected to the output terminal on the protection circuit substrate through the plastic surface.

8. The method of injection molding a lithium battery according to claim 7, wherein the plastic surface is a toothed surface.