KR20100094898A - Lithium battery and its assembly method - Google Patents

Abstract

PURPOSE: A lithium battery is provided to prevent contamination of the inner part of an electrode without using an adhesive, to have a simple electrode assembly process, to secure electrochemical stability, and to maintain properties of electrode materials. CONSTITUTION: A method for manufacturing a lithium battery comprises the following steps: manufacturing an electrode assembly comprising a microporous polymer separator(72), an anode(73), and a cathode(71) using an ultraviolet welding device; and manufacturing a laminate by laminating the anode and the cathode by turns and covering an outermost cathode with the microporous polymer separator. The cathode is lithium metal oxide, lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, or their mixture.

Description

Lithium battery and its manufacturing method {Lithium Battery and its assembly method}

The present invention discloses a method of manufacturing an electrode body for a lithium battery and a lithium battery using the same. Here, the lithium battery includes a lithium primary battery that is used and discarded once, and a lithium ion secondary battery that can be used continuously after being charged.

The present invention relates to a method of manufacturing a lithium battery, in particular, in order to maximize the use of the internal space of the battery using the electrode punched in a predetermined shape to facilitate the battery assembly to increase the energy density of the battery and simplify the assembly of the battery assembly processability Can improve.

1. Battery Market Status

The battery is playing a decisive role in the opening of the information age. As the demand for portable electronic devices, toys, and electronic products soars, the demand for various batteries used as power sources is also increasing. Batteries are divided into primary batteries that are used and discarded only once, and rechargeable batteries that can be recharged. Lithium batteries are widely used because of their relatively high energy density and high driving voltage. As of 2007, lithium secondary batteries have a market size of about $ 6.1 billion. The domestic market is expected to be about 250 million units in quantity and about 1 billion to 2 billion dollars in amount [battery overview and lithium ion battery, electronic parts research institute, technology policy office, July 2008].

2. Lithium Battery Structure

The lithium secondary battery is composed of a positive electrode, a negative electrode, a separator, and an electrolyte. The anode is mainly composed of a lithium metal oxide, and a layered oxide such as LiCoO2 or LiNiO2 and a spinel structure oxide such as LiMn2O4 are mainly used.

Others use LiFePO4, which offers excellent safety and low cost.

Although artificial graphite and natural graphite are frequently used as a cathode, studies using silicon-based compounds such as Si-O and Si-C, which have high energy density, are being actively conducted.

Polyolefin-based microporous polymer membranes are mainly used as separators, and composite membranes, celluloses, and inorganic membranes, which have enhanced safety, may be used.

As the electrolyte, a non-aqueous organic solvent and a lithium salt may be used as an additive having enhanced safety or enhanced at high temperature durability.

3. Problems in the existing assembly method

In Republic of Korea Patent Publication 10-1999-0059180

An adhesive was applied to both sides of the separator to bond the electrodes, thereby adhering the punched electrode plate to a constant size and cutting the electrode body to a constant size. In this method, the assembly process becomes complicated due to the handling of the adhesive, the application of the separator, the lamination, the cutting, and the like, and the possibility of shrinkage of the separator due to the heating of the electrode front part exists. This may pose a big issue for safety in using batteries.

In Republic of Korea Patent Publication 10-2001-0005861

The basic laminate is formed by using the positive electrode, the separator, and the negative electrode in sequence, and by stacking a plurality of layers, the lamination is carried out as many as necessary according to the capacity of the battery. Here, a third component is used to make the unit stack as in Korean Patent Laid-Open Publication No. 10-1999-0059180. This is a structure in which the adhesive is applied to a porous separator or a polymer electrolyte polymer film used to prevent a short circuit between the anode electrode and the cathode electrode, and then fixed to each electrode on both sides, followed by thermal fusion. This may additionally include a process of applying the separator with an adhesive and a process of heat fusion after lamination may result in poor workability. There is also a possibility of damaging the membrane by heat during the heat welding operation.

In Republic of Korea Patent Publication 10-2000-0056104

Using the third component of the adhesive is the same, but the adhesive method of the separator and the separator is applied, not directly bonded to the electrode and the separator.

In other words, the polymer film containing the adhesive component is punched into an adhesive shape, and then an electrode is placed inside the film, and then the membrane is covered and thermally fused. This has the advantage of facilitating the assembly of the unit stack, while generating a large loss of adhesive polymer film. Like the above patent, there is a possibility that damage to the separator may be caused by supplying heat necessary for fusion between the adhesive and the separator over the entire surface of the separator.

In Republic of Korea Patent Publication 10-2003-0049852

After applying a blade prepared in the electrode shape was heated to higher than the melting temperature of the battery separator, and after applying heat to the separator for a certain time, it was bonded. This method minimizes the possibility of contamination inside the cell by using no adhesive material, but increases the possibility of membrane damage by using a heat source heated to a high temperature. In addition, since the adhesive surface is cut after the separator is heated to a high temperature, there is a high possibility of cutting residues. In this method, since the adhesive shape of the separator is a line rather than a face, it may cause difficulty in aligning electrodes unless a separate electrode fixing method is applied.

4. Combination between anode electrode and cathode electrode

While lithium ion batteries have a very high energy density, cautions for use due to safety issues of the batteries are important. The use at high temperatures and the risk of overcharging are well known. At a high temperature of 135 degrees or higher, there is a risk of explosion accompanied by thermal runaway due to short circuit caused by direct contact between the positive electrode and the negative electrode due to shrinkage of the polyolefin separator. In case of excessive charging of 4.5V or more, thermal runaway occurs due to the continuous reaction leading to precipitation of lithium ions at the cathode electrode, thermal decomposition of the electrolyte, and decomposition of the anode electrode. In particular, lithium ion precipitation increases the possibility of a direct internal short between the positive electrode and the negative electrode. Accordingly, in the case of the negative electrode, it is common to design the amount of the active material in excess of the positive electrode. This surplus design is usually reflected as an extension of the electrode area, which results in a decrease in the energy density of the battery if the cathode area is excessively large compared to the anode area. Typically, the design proceeds by distributing the active material amount and the electrode area in the range of about 105 to 130%.

Assembly of the electrode body must proceed to follow this design. Assembly of the electrode body should proceed so that the anode area can be placed unbiased on one side of the cathode. Therefore, an auxiliary means for correctly positioning the anode electrode and the cathode electrode is required, and for this purpose, an adhesive is sprayed at an appropriate position of the separator to bond the electrode and the separator (Korea Patent Publication 10-1999-0059180), An adhesive guide may be provided on the outer surface (Korean Patent Publication No. 10-2000-0056104), or a method of attaching an anode electrode and a cathode electrode by coating an adhesive on a separator (Korean Patent Application Publication No. 10-2001-0005861). In addition, as a method of not applying an auxiliary means such as an adhesive, there is a method of bonding a separator using a blade heated to a high temperature (Korea Patent Publication No. 10-2003-0049852), but this method has a residual bonding due to the bonding at a high temperature. There is a disadvantage that water is generated and workability is poor. In addition, since the adhesion of the separator is a line, the electrodes may be aligned to one side when the space inside the junction is larger than the electrode size. This may cause lithium precipitation and dendrites, etc. during use of the battery, which may result in a structure that is vulnerable to battery stability.

5. Ultrasonic Welding Technology

Ultrasonic welding refers to a method in which ultrasonic waves are used for welding plastic thermoplastics, welding films and films, and synthetic fibers, and quickly and cleanly and efficiently.

Ultrasonic welding does not require a third component or an adhesive for adhesion between films, and has good airtightness with strong adhesion. In general, it can be bonded within 10 seconds, mass production is good, and power consumption is low.

Ultrasonic welding converts electric energy into oscillator through the oscillator and converts it into mechanical vibration energy and generates instantaneous strong frictional heat on the welded joint through the horn. Molecular bonds are a phenomenon.

When ultrasonic vibration is applied for the first time, the fine surface relief of the weld surface is generated very quickly. The protruding portion of the surface relief is concentrated more stress than other places, and consumes most of the large strain and vibration energy, so that the protruding portion of the welded portion melts and flows to the other portion. At this moment, a thin layer of molten layer is formed on the entire welding surface, and a short time diffusion is achieved by continuous vibration of ultrasonic waves, and the remaining atoms are bonded to the other atoms to form a primary molecular bond with the other atoms. An important factor of the welding condition is the pressing force (P), welding time (T), amplitude (A) and the like affect the welding strength.

The ultrasonic output W is expressed as ultrasonic output W = amplitude A * pressing force P * welding time T and each factor can be described as follows. The pressing force affects the initial temperature rise and the flow of the molten polymer to double the flow of the melt and accelerate the mixing of the chain. Therefore, the welding strength is increased by bringing the molten weld surface into close contact with each other through pressure.

  When the molten layer is formed on the weld surface, the welding strength is improved, so sufficient welding time is required. However, if the pressing force or the welding time is too excessive, the flow of the molten layer becomes too excessive and the arrangement of polymer chains to be perpendicular to the welding surface is generated in parallel with the welding surface, thereby lowering the welding strength. In general, the higher the amplitude, the higher the concentration of stress on the surface relief, which leads to faster initial temperature rise and melting. In addition, since the loss rate of ultrasonic vibration varies depending on the resin, it is necessary to select an appropriate amplitude according to the material.

In manufacturing a lithium battery through the present invention, it is intended to enable the assembly of the electrode body that can effectively utilize the internal space of the battery. This can maximize the battery energy density.

In order to assemble the electrode body, the spatial design of the efficient anode, cathode, and separator is essential. The shape of the electrode body is similar to that of the battery, and the shape of the electrode is similar to that of the battery. The circular battery has a circular electrode shape, and the triangular battery shape requires a triangular electrode shape.

At this time, in order to design the electrode body having the maximum energy density, a structure different from the traditional wound type (Wound Type) is required. The most effective way to solve this problem is to alternately accumulate the anode, separator and cathode after punching the electrode. In making the electrode body, it is important to protect the electrode with a separator so as to prevent the internal short circuit of the positive electrode and the negative electrode, and arrange the anode electrode shape to be located inside the cathode shape. For this purpose, an envelope-like structure capable of properly aligning the anode electrodes and covering the front surface is very advantageous.

On the other hand, the separator also needs to be punched into the same shape as the electrode and a design structure capable of efficiently bonding the separator. In addition, the method of simplifying the process and ensuring the reliability of the battery by using a separate adhesive in the bonding of the separator is very advantageous.

After the electrode body is placed in the battery case, a process of injecting electrolyte is followed. In this case, in order for the electrolyte to easily penetrate into the electrode body, it is advantageous to expose as much of the electrode body as possible. However, a large exposure to the outside increases the risk of internal short circuit between the positive electrode and the negative electrode and short circuit between the electrode and the battery case. Therefore, it is important to properly maintain the structure of the electrode body, to eliminate the risk of internal short circuit and to secure the electrolyte penetration space. In addition, a design structure in which the gas generated in the chemical conversion or the formation process easily escapes from the electrode body is also important in maintaining battery performance.

 By applying the present invention, it is possible to efficiently align the positive electrode, the negative electrode and the separator, and to bond the separator without using a third component such as an adhesive. In addition, by applying a method such as ultrasonic welding to prevent overheating that may occur when the membrane is bonded. This enables an effective electrode assembly to be as high as possible the energy density of the battery. In addition, it is possible to ensure the safety and reliability of the battery. In addition, it is possible to partially bond the separator and leave the rest unbonded, thereby facilitating the penetration of the electrolyte and allowing the gas generated during the activation process to be easily released.

To solve the problems mentioned above

Punching the positive electrode and the negative electrode according to the shape of the battery, that is, to maximize the space inside the battery,

Ultrasonic welding method enables the microporous polymer membrane of the battery to be bonded similarly to the shape of the electrode, and increases the reliability of the battery by not using an adhesive, and prevents damage to the membrane because heat is not transferred except at the adhesive part. Was applied to microporous polymer membrane adhesion.

By utilizing this, the electrode body can be manufactured in a form that can maximize the space inside the battery. By stacking the positive electrode body and the negative electrode body alternately, the electrode laminated body can be easily assembled. In addition, by minimizing the adhesive portion of the microporous polymer membrane, it is possible to minimize the impregnation time of the electrolyte, and to easily release the gas generated during the battery activation process.

Applying the present invention

In a lithium battery or a lithium secondary battery, an electrode body can be assembled without using a component such as an adhesive, and the assembly equipment configuration can be simplified. In addition, since there is no process such as direct heating of the separator, there is no physical property deformation of the battery material, thereby increasing reliability in battery use.

By maintaining the non-line side of the separator, it is possible to keep the electrode at a constant distance from the outermost side of the separator, thereby enabling a stable electrochemical combination of the positive electrode and the negative electrode. This ensures electrochemical stability.

In addition, it minimizes the adhesion on the side of the laminate to reduce the electrolyte impregnation time, and the large amount of gas generated during the battery activation process can easily escape from the laminate.

(1) microporous polymer membrane

Raw materials applied to the present invention are as follows. Polymer microporous membranes are mainly polyethylene (PE, Polyethylene), polypropylene (PP, Polypropylene), polyethylene / polypropylene (manufactured in the form of PP / PE / PP, PE / PP / PE as a composite of PE and PP) Shall be prepared. The prepared membranes generally have a thickness in the range of 5 to 30 μm, porosity in the range of 30 to 60%, pore diameter of 0.005 to 1 μm, tensile strength of 50 MPa or more, preferably 100 MPa or more. In addition, a polyolefin microporous membrane thickness is 0.1-50 micrometers, Preferably it is about 5-30 micrometers. If the thickness is less than 5 μm, it is difficult to be usefully used due to the lack of mechanical strength of the film. If the thickness is more than 50 μm, the effective resistance becomes large, which is not preferable.

If the porosity is too large (more than 60%), film production is difficult, and if it is less than 30%, the effective resistance becomes large. If the pore diameter is less than 0.005um, it is difficult to pass ions, and if the effective resistance is increased, if there is more than 1um, there is a risk of internal short circuit.

 The polymer microporous membrane to be applied to the present invention is based on an unprocessed thermoplastic resin. However, the polymer microporous membrane partially or wholly crosslinked by chemical polymerization may be used.

(2) lithium battery electrode

A battery consists of a positive electrode, a negative electrode, a separator, and an electrolyte.

In the case of lithium primary batteries, metal oxides are mainly used for the positive electrode, and pure lithium is used for the negative electrode. As the electrolyte, organic compounds such as carbonates that can withstand high voltage are mainly used.

In the case of a lithium secondary battery, that is, a lithium ion battery or a lithium ion polymer battery or a lithium polymer battery, all electrodes use a coating or coating of an electrode active material on a current collector. In general, the positive electrode active material is mainly composed of lithium metal oxide, and aluminum is used a lot as the current collector. The negative electrode active material is composed mainly of lithium adsorption materials such as lithium metal or carbon, and copper is mainly used as a current collector.

(3) Implementation method

Figure 1 shows a method for bonding the microporous polymer membrane by applying ultrasonic welding. The microporous polymer membrane is fixed between the upper tool horn 10 and the lower anvil 11. At this time, the welding condition is input at the operation part of the ultrasonic welding machine. When the operation switch is operated, the tool horn 10 is lowered by the air pressure and presses the object through the anvil 11. FIG. 1 (a) shows welding each side or one point to the shape 15 of the electrode when the size of the electrode is larger than the tool horn. Only the microporous polymer membrane is located between the tool horn 10 and the anvil 11. Figure 1 (b) shows the ultrasonic welding method when the electrode size is small enough to be located between the tool horn 16 and the anvil 17. The welding shape 21 of the tool horn 16 is very similar to the electrode shape, and is welded and bonded to the outer surface of the electrode. When the electrode is round in shape, the joining cross section 21 of the tool horn 16 is similar to the electrode. The shape of the round strip is pressurized using the air pressure to the lower anvil 17, and then ultrasonic welding proceeds.

Figure 2 schematically shows a case of bonding the microporous polymer membrane by applying ultrasonic welding. Figure 2 (a) shows the arrangement of the microporous polymer membrane and electrode before welding. The microporous polymer separator 31 is placed on the electrode 32, and the microporous polymer separator 33 is also placed on the bottom thereof. At this time, the electrode 32 inside the microporous polymer membrane may be both an anode or a cathode. Figure 2 (b) shows a cross section of the microporous polymer membrane after welding. The welding surface is formed by the movement and bonding of the polymer molecules through the ultrasonic energy, thereby forming a strong cutting surface. The electrode 35 is positioned inside the microporous polymer membrane envelope 34 to form an electrode body.

Figure 3 shows the type of microporous polymer membrane bonding applied ultrasonic welding. FIG. 3 (a) shows a case where the electrode outer surface is completely bonded when the electrode shape is circular. It is possible to fix the electrode by joining the outer surface 41 of the electrode 42. FIG. 3 (b) partially proceeds the junction along the electrode outer surface when the same circular electrode as in FIG. 3 (a) is used. In general, the more the junction part of the separator, the longer the impregnation time is because the electrolyte is difficult to penetrate into the electrode. Therefore, it is advantageous to reduce the adhesion area on the outer surface of the separator to shorten the time of the impregnation of the electrolyte solution to shorten the production process time of the lithium battery. In addition, during the activation process of the battery it is necessary to create a path that the gas generated in the electrode can easily escape from the electrode body. If the gas remains in the electrode body, it is a potential poor performance. Accordingly, avoiding sealing of the separator prevents battery performance instability due to gas generation. A band-shaped welding surface 43 is formed on the outer portion of the electrode 44. After battery assembly, the electrolyte solution is impregnated through the exposed portion 45, which is mainly not bonded. In addition, the gas generated in the electrode can be easily discharged through the exposed surface (45).

Fig. 3 (c) shows the junction cross section when the electrode shape is triangular. Only the minimum fixed portion of the electrode 47 is joined (46) to form an electrode body. 4 (d) shows a case where the rectangular electrode is bonded to the microporous polymer membrane. The edge part which can fix the electrode 49 is set to the welding surface 48, and is joined.

A battery is an energy source used in portable devices, and its power density as well as its energy density is one of the important factors. It is preferable to use an active material or an additive capable of increasing the conductivity of the electrode itself. Especially in devices requiring high current, increasing the electrode area can increase energy efficiency. For this reason, it is common to manufacture a battery with a structure that maximizes the area facing the positive electrode and the negative electrode. This made the electrode body in the form of a jelly roll or a laminated body. The tab Tab of the electrode is used as a means for connecting a plurality of electrodes to each other.

Figure 4 (e) is a case where the microporous polymer membrane is bonded on the assumption that there is a tab on the electrode. The tab 50, which is an electrical movement path, is attached to the electrode 51 to form a microporous polymer separation membrane in the form of an electrode, without interfering with the tab 50. In FIG. 4 (f), the electrode 53 and the electrode tab 54 having the same shape as those of FIG. 4 (f) are used, but in order to facilitate the impregnation of the electrolyte and the gas discharge inside the electrode, the microporous polymer membrane It shows that the area of the junction 55 is reduced. 3 (g) illustrates a case in which the junction 58 is assuming that the tab 56 is located at the corner in the case of the triangular electrode 57. 3 (h) illustrates a case where the junction 62 is assuming that the tab 60 is located at a portion other than a corner portion in the case of a rectangular electrode 61.

The method of easily impregnating electrolyte in a lithium primary battery or a lithium secondary battery is very important. To this end, by creating a pressurized or reduced pressure environment, the gas inside the laminate is removed and the electrolyte can be easily impregnated. It is also important to minimize the adhesion at the side of the laminate to favor electrolyte impregnation.

After the electrolyte is injected, the battery activation process and evaluation process are performed. In this process, a large amount of gas is discharged from the electrode or the electrolyte, it is important to optimize the process conditions or proceed with the cell design so that the generated gas can easily escape from the laminate. Similar to the electrolyte impregnation process, it is necessary to minimize the adhesive portion of the microporous polymer membrane so that the gas inside can be easily released.

If the periphery of the microporous polymer membrane is less than 5% of the periphery of the electrode, it may be difficult to fix the electrode and the microporous polymer membrane may be unstable. In addition, in consideration of the area of the electrode tab and considering the impregnation of the electrolyte and the gas discharge, it is not preferable to make the adhesive portion larger than 95% of the periphery of the electrode.

Figure 4 shows the shape of the laminate in the case of making a laminate by ultrasonic welding the microporous polymer membrane. 4 (a) shows a laminate formed by joining both the positive electrode and the negative electrode with a microporous polymer membrane. The anode electrode and the cathode electrode are alternately stacked, and the number of stacked layers is determined by the design of the battery. The outermost electrode is the cathode 71, and is surrounded by the microporous polymer membrane 72, and the anode 73 is surrounded by the microporous polymer membrane 74. In this case, the microporous polymer separator 74 applied to the anode electrode 73 and the microporous polymer separator 72 applied to the cathode electrode 71 may not be the same material. In addition, the outermost electrode may use the anode electrode 73 instead of the cathode electrode 71. FIG. 4 (b) shows a case where only the anode electrode 76 is surrounded by the microporous polymer separator 77 and welded, and the cathode electrode 75 is laminated without using the separator. Similarly to the description of Fig. 4A, the outermost electrode may be the anode electrode 77. 4 (c) shows a case where only the cathode electrode 78 is weld-bonded with the microporous polymer separator 79 and the anode electrode 80 is laminated without using the separator. Also in this case, the anode electrode 80 may be applied to the outermost side.

Fig. 5 shows the electrode tab Tab for the arrangement when the ultrasonically welded electrode body is applied. In general, the shape or position of the electrode tab depends on the design structure of the battery. 5A illustrates a case where the cathode electrode tab 91 and the anode electrode tab 92 are placed in opposite directions. The anode electrode and the cathode electrode are alternately stacked as described with reference to FIG. 4, and are divided into microporous polymer separators 93 and bonded 94 by ultrasonic welding. Figure 5 (b) shows a case where the positive electrode tab 96 and the negative electrode tab 97 are placed in the same direction. As shown in FIG. 5A, the electrode 98 is separated by the microporous polymer separator 99, and the separator is bonded to the welding surface 100.

As described above, the circumference 101 of the bonding surface 100 of the microporous polymer membrane is greater than the minimum of 5% relative to the circumference of the electrode in consideration of the electrode fixing and the stability of the bonding, and the impregnation and gas release of the electrolyte are considered. Preferably less than 95%. The width 102 of the bonding surface 100 of the microporous polymer membrane is preferably at least 0.05 mm and at most 10 mm in consideration of the design between the anode electrode and the cathode electrode. As described above, if the negative electrode area considering the amount of the active material is smaller than the positive electrode area, it may cause deterioration of battery safety due to lithium deposition and dendrites, and if the negative electrode area is excessively larger than the positive electrode area, It causes a decrease in energy density of the battery.

2. Ultrasonic welding condition

The output energy of a general ultrasonic welding machine is less than 5kW. Considering the size of the equipment, it is desirable to apply equipment with an output in the range of 3 kW or less. The frequency range is 20 to 70 kHz, but 40 kHz or less is recommended. Weld time generally uses a range of less than 10 seconds, but considering the workability, it is recommended to proceed within 3 seconds. In order to allow welding of the welded object, externally applied energy presses the horn and anvil to efficiently supply the surface. At this time, it is common to apply air pressure or hydraulic pressure in the pressurization method, and the applied pressure is in the range of 1 ton or less. More preferably, it is recommended to proceed with the deformation of the object to a pressing force of less than 300kg.

Bonding of polymeric materials through ultrasonic welding obtains the energy required for bonding from the form of mechanical vibrations. The welding machine is paired with the welded object and moved in the vertical or horizontal direction. The welded object remains stationary. The welded objects are pressed together at the same time. The combination of static and dynamic forces combines parts without the use of auxiliary materials.

When joining thermoplastic polymer materials, the temperature rise at the joint is caused by the absorption of mechanical vibration, the reflection of the vibration at the joint, and the resistance at the surface of the part. The vibration is introduced vertically or horizontally. The welding quality is uniform in joining parts with similar melting points. This is because the energy transfer or the heat generation inside is constant because it is limited to the coupling part.

When welding the polymer material, high vibration energy is used to raise the temperature and make the material easier to process. Unlike other welding, it is not necessary to raise the temperature to the melting point of the welded object. The setting of welding conditions is determined by the thickness, surface structure and mechanical properties of the welded object.

Ultrasonic welding proceeds as follows.

  1) Mechanically vibrate one part against the counterpart while the welded object is pressurized by the welder.

  2) The film on both surface layers of the weld object is destroyed.

  3) Atoms in one part move to the other part.

  4) The actual bond is formed.

Sonot rods and anvils are used to roughen the surface or to grind the ribs or grooves. This is to strongly fix the welded object and to prevent slipping during welding.

 The following describes the present invention in detail with reference to practical examples, and the present invention is not limited to these practical examples.

 (1) Example 1

   The separator used for ultrasonic welding is a porous film manufactured by dry method using polyethylene as a raw material. The thickness is 20um, the porosity is 44%, and the Gurley transmittance is 250sec / 100ml. The breaking strength in the machine direction (MD) was about 2,000-2,200 kgf / cm2, the breaking strength in the vertical direction (TD) was 1,300-1,500 kgf / cm2, and the poking strength was 700-900 gf.

Ultrasonic welding machine used 40kHz / 800W output, and the welding method used the horizontal vibration (left and right) welding machine. The pressing force between Horn and Anvil used air injection, and a Nodal Support was used to maintain weld robustness. The welding area is determined by the area of the horn. In this experiment, a product of 10mm in width and 5mm in length was used.

  Weld strength measurement of the separator was carried out after fabricating the specimen in accordance with the KS test standard (KS M3006) at room temperature.

 The result of implementation at this time is as follows.

division Welding energy (J) Welding time (sec) Holding time (sec) Welding strength (gf / cm2) Experiment 1 13.4 0.1 0.5 Not welded Experiment 2 16.7 0.5 0.5 205 Experiment 3 23.2 1.0 0.5 215 Experiment 4 27.3 2.0 0.5 Ruptured

 (2) Example 2

   The separator used for ultrasonic welding was the same as in Example 1.

Ultrasonic welding machine used product with output of 20kHz / 3300W, and welding method used longitudinal vibration welding machine. Actuators that apply energy directly to the separator apply forced air-cooling to prevent overheating during the welding of the separator. The horn used in this experiment was a circular donut shaped product, which had an inner diameter of 8 mm and an outer diameter of 10 mm.

 The result of implementation at this time is as follows.

division Welding energy (J) Welding time (sec) Holding time (sec) Welding strength (gf / cm2) Experiment a 13.8 0.1 0.5 Not welded Experiment b 18.0 0.5 0.5 Not welded Experiment 22.1 1.0 0.5 184 Experiment d 27.3 2.0 0.5 196

 (3) Example 3

   The separator applied to ultrasonic welding is a microporous membrane (Korean patent application 10-2009-0000997) modified from a general polyolefin microporous polymer membrane. This product is a product that greatly improves heat resistance by crosslinking the general polyolefin separator used in lithium battery by irradiation with electron beam or gamma ray.

Ultrasonic welding machine used the product which has the output of lateral vibration system (Example 1, 40kHz / 800W) and longitudinal vibration system (Example 2, 20kHz / 3300W). In the case of applying the lateral vibration welding machine, the horn, anvil, and pressurizer used in Example 1 were used in the same manner. In the case of applying the longitudinal vibration welding machine, the actuator and horn used in Example 2 were used in the same manner.

 The result of implementation at this time is as follows.

division Welding energy
(J) Welding time
(sec) Retention time
(sec) Welding strength
(gf / cm2) vibration
system Experiment i 17.2 0.5 0.5 208 Lateral vibration Experiment ii 24.5 1.0 0.5 221 Lateral vibration Experiment iii 23.4 1.0 0.5 192 Longitudinal vibration Experiment iv 28.6 2.0 0.5 198 Longitudinal vibration

Figure 1 shows a method for bonding the microporous polymer membrane by applying ultrasonic welding.

Figure 2 schematically shows a case of bonding the microporous polymer membrane by applying ultrasonic welding.

Figure 3 shows the type of microporous polymer membrane bonding applied ultrasonic welding.

Figure 4 shows the shape of the laminate in the case of making a laminate by ultrasonic welding the microporous polymer membrane.

Fig. 5 shows the electrode tab Tab for the arrangement when the ultrasonically welded electrode body is applied.

Claims (9)

Microporous polymer membrane (72) After fixing the microporous separator between the tool horn 10 and the anvil 11 at the lower portion of the separator 72 formed in the shape of an electrode, the operation switch of the ultrasonic welding machine is operated. 10) is lowered to press the to-be-welded object 13 through the anvil (11) to adhere along the outer periphery of the electrode and At this time, the ultrasonic welding machine A press horn having a tool horn 10 and anvil 11 to join the separator 72 and a fixed device to which the separator 72 can be fixed, preferably hydraulic pressure, more preferably air pressure can be applied. And a vibrating device that can be vibrated in parallel with the to-be-welded object 13, The positive electrode 73 and the negative electrode 71 used in the lithium secondary battery In this case, the anode electrode (73) is lithium metal oxide, that is, lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide or a hybrid compound thereof, and the cathode electrode 71 is graphite, that is, using natural graphite and artificial graphite The separator 72, the cathode electrode 73 for a lithium secondary battery 73, and the cathode electrode 71 are made of an electrode body (FIG. 2B) by using an ultrasonic welding machine, and alternately stacked to form a laminate (FIG. 4A). ) The anode electrode and the cathode electrode are alternately stacked, and the outermost electrode is surrounded by the microporous polymer membrane 72 with the cathode 71, and the anode 73 electrode is surrounded by the microporous polymer membrane 74. In assembling lithium secondary battery Method of assembling using the above laminate The method of claim 1 Using the electrode used for electrode assembly (FIG. 2B) as the positive electrode 73 or applying both the positive electrode 73 and the negative electrode 71 The material of the separator used in claim 1 is polyethylene, polypropylene, polyurethane, polyimide, fluorocarbon, polyacryl-based film, acetal-based film, polycarbonate film, or the like, or a multilayer separator formed by a combination thereof. To apply. The electrode assembly (FIG. 2B) bonded to the separator 72 of claim 1 is formed at the same time as the ultrasonic welding, or after being punched in the shape of the electrode assembly (FIG. 2B) before the ultrasonic welding, or after the ultrasonic welding. do The word of claim 1, wherein The circumference 101 of the electrode body bonding surface 100 is bonded using a minimum of 5% to a maximum of 95% of the outer circumference (border) of the electrode 98, and the width 102 of the electrode body bonding surface is minimum. 0.05mm to the maximum 10mm. The method of claim 1 A press horn having a tool horn 10 and anvil 11 to join the separator 72 and a fixed device to which the separator 72 can be fixed, preferably hydraulic pressure, more preferably air pressure can be applied. Applying ultrasonic welding machines having vibrators capable of vibrating perpendicularly to the welded body, with attached devices The method according to any one of claims 1 to 5, The separator body 72 is used, and the anode electrode 73 is made of manganese oxide, sulfur, carbon fluoride, thionyl chloride, and the cathode electrode 71 is made of lithium metal. After manufacture, assembling a lithium primary battery using a laminated body (FIG. 4). The method of claim 1 Applying a separator in which the polyolefin microporous polymer separator is improved in heat resistance using an electron beam or gamma ray. The method of claim 1 The ultrasonic welding machine vibrates the tool horn 10 at an operating frequency of 20 to 200 kHz, preferably at an operating frequency of 20 to 70 kHz, more preferably at an operating frequency of 20 to 40 kHz, and causes the object 13 to be welded to the tool horn. Pressurized by (10) or anvil (11). At this time, the pressurization method applies air pressure or hydraulic pressure and the applied pressure is in the range of 1ton or less. More preferably applying a pressure of less than 300kg by applying air pressure. The welding power is applied to the ultrasonic welding machine of 5000W or less, preferably 3500W or less, and the welding time is applied within 10 seconds, preferably within 5 seconds, more preferably within 3 seconds.

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