KR101115382B1 - High Power Secondary Battery of Series Connection Structure - Google Patents

Abstract

The present invention is a secondary battery that is heat-sealed and sealed by sealing the outer peripheral surface of the case in a state in which two or more unit cells are mounted in the case accommodating unit, wherein the unit cells have their positive electrode tabs and negative electrode tabs formed at opposite positions, respectively; The electrolytes of the unit cells are physically separated by the diaphragm, and one electrode tab ('outer electrode tab') of the outermost unit cells protrudes out of the case and an opposite electrode tab ('inner electrode tab') It is connected to the inner unit cell in a series connection method, the internal electrode tab provides a secondary battery, characterized in that the heat sealing is made of a structure together with the case sealing portion in the state where the diaphragm is interposed.

Therefore, since the secondary battery according to the present invention includes a plurality of unit cells connected in series, the secondary battery can exhibit high voltage and high output, and has a compact structure, thereby improving battery capacity and lifespan, and configuring the battery pack. In this case, the number of cells to be managed in a battery management system (BMS) is reduced, so that management is easy. In addition, it is possible to manufacture by a simple assembly process, it is possible to reduce the part price has a low production cost has the advantage of high production efficiency.

Description

High Power Secondary Battery of Series Connection Structure

The present invention relates to a high output secondary battery having a series connection structure, and more particularly, to a secondary battery sealed by heat-sealing the outer peripheral surface sealing portion of a case in a state in which two or more unit cells are mounted in a case accommodation unit. The positive electrode tab and the negative electrode tab are formed at opposite positions, the electrolytes of the unit cells are physically separated by the diaphragm, and the one electrode tab ('external electrode tab') of the outermost unit cells is moved out of the case. The protruding side and the opposite electrode tab ('inner electrode tab') are connected in series with the inner unit cell, and the inner electrode tab has a structure in which the inner electrode tab is heat-sealed together with the case sealing part in a state where the diaphragm is interposed therebetween. It provides a secondary battery characterized by.

BACKGROUND ART [0002] In recent years, rechargeable secondary batteries have been widely used as energy sources for wireless mobile devices. In addition, the rechargeable battery is also attracting attention as a power source for electric vehicles (EVs) and hybrid electric vehicles (HEVs), which are proposed as a way to solve air pollution of conventional gasoline and diesel vehicles that use fossil fuels. I am getting it.

In a small mobile device, one or two or more battery cells are used per device, while a middle- or large-sized battery module such as an automobile is used as a middle- or large-sized battery module in which a plurality of battery cells are electrically connected due to the necessity of a large-

Since the medium-large battery module is preferably manufactured in a small size and weight, the rectangular battery, the pouch-type battery, etc., which can be charged with high integration and have a small weight to capacity, are mainly used as battery cells of the medium-large battery module. In particular, a pouch-type battery using an aluminum laminate sheet or the like as an exterior member has attracted much attention in recent years due to the advantages of low weight and low manufacturing cost.

1 is a perspective view schematically showing a typical representative pouch-type battery. The pouch-type battery of FIG. 1 has a structure in which two electrode leads 11 and 12 protrude from each other to protrude from an upper end and a lower end of the battery main body 13, respectively. The exterior member 14 is composed of two upper and lower units, and both side surfaces 14b and upper and lower ends 14a, which are mutually contacting portions, with electrode assemblies (not shown) mounted on an accommodating portion formed on an inner surface thereof. The battery 10 is made by attaching 14c). The exterior member 14 has a laminate structure of a resin layer / metal foil layer / resin layer, and can be attached by mutually fusion bonding the resin layer by applying heat and pressure to both side surfaces 14b and the upper and lower ends 14a and 14c which are in contact with each other. In some cases, the adhesive may be attached using an adhesive. Since both side surfaces 14b are in direct contact with the same resin layer of the upper and lower exterior members 14, uniform sealing is possible by melting. On the other hand, since the electrode leads 11 and 12 protrude from the upper end 14a and the lower end 14c, the sealing properties are improved in consideration of the thickness of the electrode leads 11 and 12 and the heterogeneity with the material of the exterior member 14. Heat-sealing is carried out in the state which interposed the film-like sealing member 16 between the electrode leads 11 and 12 so that it may be made.

However, since the mechanical rigidity of the exterior member 14 itself is not excellent, in order to manufacture a battery module having a stable structure, battery cells are manufactured by mounting battery cells (unit cells) in a pack case such as a cartridge. However, since a mounting space is generally limited to a device or a vehicle on which a medium / large battery module is mounted, when the size of the battery module is increased due to the use of a pack case such as a cartridge, there is a problem of low space utilization. In addition, the low mechanical stiffness of the battery cell results in repeated expansion and contraction of the battery cell during charging and discharging, thereby causing a case where the heat fusion sites are separated.

In addition, since a battery module is a structure in which a plurality of battery cells are combined, when some battery cells are overvoltage, overcurrent, and overheating, safety and operation efficiency of the battery module are greatly detrimental, and thus a means for detecting them is necessary. Therefore, safety systems such as fuses, bimetals, and battery management systems (BMS) are provided to check and control the operation state in real time or at regular intervals. This safety system is difficult to manage the larger the number of cells, the mounting or connection of such detection means makes the assembly process of the battery module very complicated and there is a risk of short circuit due to a number of wiring for this.

Apart from this, when constructing a medium-large battery module using a plurality of battery cells or a medium-large battery module using a plurality of unit modules consisting of a predetermined unit of battery cells, for the mechanical fastening and electrical connection of the Since many members are needed, the process of assembling these members is very complicated. Moreover, space is required for joining, welding, soldering, etc. a plurality of members for mechanical fastening and electrical connection, thereby increasing the size of the entire system. This increase in size is not desirable in view of the above-described, high voltage and high output characteristics, can be easily and easily manufactured and managed, there is a high need for a secondary battery having a compact and excellent structural stability.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-described problems of the prior art and the technical problems required from the past.

An object of the present invention is to provide a secondary battery having a structure comprising two or more unit cells, and connected in series with each other so as to exhibit high voltage and high output characteristics.

Still another object of the present invention is to provide a method for manufacturing a secondary battery including two or more unit cells connected in series in a simple and easy manner.

The secondary battery according to the present invention for achieving the above object is a secondary battery that is sealed by heat-sealing the outer peripheral surface sealing portion of the upper case and the lower case in a state in which two or more unit cells are mounted in the case accommodating part. The positive electrode tab and the negative electrode tab are formed at opposite positions, the electrolytes of the unit cells are physically separated by the diaphragm, and the one electrode tab ('external electrode tab') of the outermost unit cells is moved out of the case. The protruding side and the opposite electrode tab ('inner electrode tab') are connected in series with the inner unit cell, and the inner electrode tab has a structure in which the inner electrode tab is heat-sealed together with the case sealing part in a state where the diaphragm is interposed. .

Therefore, since the secondary battery according to the present invention includes a plurality of unit cells connected in series, the secondary battery can exhibit high voltage and high output, and can be manufactured as a battery having high efficiency compared to volume by having a compact structure. For example, when one unit cell is applied to a lithium secondary battery generating an electromotive force of about 3.6 V, an electromotive force of about 7.2 V is generated, and thus, when the unit cell is applied to HEV or EV, which requires a high operating voltage, excellent performance is obtained. Can be exercised.

In addition, when a plurality of secondary batteries according to the present invention is connected to constitute a battery module, the number of cells to be managed in a battery management system (BMS) is reduced compared to the same standard, thereby enabling efficient management. In addition, the number of cells required to be installed or connected to the detection means, etc. is reduced, which simplifies the assembly process of the battery module, reduces the risk of short circuit due to a large number of wirings, and reduces the cost of parts. There is this.

In the present invention, the outer electrode tabs on one side of the outermost unit cells protrude out of the case, and the opposite inner electrode tabs are connected in series to the inner unit cells. That is, only internal electrode tabs exist in the unit cells existing inside the unit cells except the outermost unit cells. For example, the external electrode tab may be coupled to an electrode lead and connected to an external input / output terminal.

In order to serially connect the unit cells, internal electrode tabs having opposite polarities must be electrically connected to each other. In this case, in one preferred example for facilitating the connection of the inner electrode tabs, the outer electrode tabs of adjacent unit cells may have opposite polarities. Therefore, the internal electrode tabs of adjacent unit cells are connected to each other, and the external electrode tabs may be connected to an external input / output terminal to form a series connection structure.

Electrical connection between the internal electrode tabs may be achieved by a separate connection member or may be directly coupled. In consideration of the ease and economical efficiency of the manufacturing process, it is preferable to form the same direction and position in which the inner electrode tabs protrude from adjacent unit cells in the same manner, so as to be directly coupled by welding or the like without a separate connecting member.

The external electrode tab protrudes out of the case from the outermost unit cell and is connected to an external input / output terminal. When all of the external input / output terminals are located on the top surface of the battery case, the external electrode tabs may preferably have a structure protruding to the top of the case. At this time, since the negative electrode tab and the positive electrode tab should not be in contact with each other, in order to minimize the possibility of such contact, it is preferable to be formed at positions spaced from each other, for example, it may be formed on the left and right of the upper case, for example.

Therefore, in one preferred example for minimizing the contact between the inner electrode tab and the outer electrode tab and the possibility that the tabs of opposite polarities are in contact with each other, the inner electrode tabs are all formed at the center of the top or bottom of the unit cells, The external electrode tabs may be formed at the upper left and right sides of the case, respectively.

On the other hand, the internal electrode tabs, for example, by connecting to each other by welding or soldering can be connected in a series connection method. The welding method may be carried out by a known method and is not particularly limited, and examples thereof include resistance welding, spot welding, ultrasonic welding, laser welding, electron beam welding, arc welding, and the like. In one preferred embodiment, the coupling portion of the inner electrode tab may be located between the end of the septum and the end of the outer peripheral surface of the case. That is, the coupling portion has a length shorter than the end of the outer peripheral surface of the case and does not protrude to the outside of the case. Internal electrode tabs may be interconnected at locations between the ends. As a result, the length of the inner electrode tab may be configured such that the inner electrode tabs overlap each other at the length between the end of the diaphragm and the outer peripheral surface end.

The number of unit cells included in the secondary battery in the present invention is not particularly limited, and may be variously configured according to the thickness of the unit cell, the size of the battery case, the desired battery capacity or voltage. For example, in the case of a pouch type case of laminate sheets, the laminate sheets are very thin in structure and generally do not easily form an accommodating portion having a depth of 15 mm or more. Therefore, when the upper case and the lower case each formed with the receiving portion, the thickness of the battery case is up to about 30 mm. Thus, for example, if the thickness of the electrode assembly (power generation element) is about 15 mm, two unit cells may be mounted, and if it is about 10 mm, three unit cells may be mounted.

In one preferred example, the secondary battery may have a structure composed of two unit cells of a first unit cell and a second unit cell. Such a structure can provide a high output secondary battery because it has twice the voltage as compared with the case of including one unit cell. In this structure, the outer electrode tab of the first unit cell and the outer electrode tab of the second unit cell have opposite polarities, and the inner electrode tab of the first unit cell and the inner electrode tab of the second unit cell have opposite polarities. It can be connected in series by being configured to have.

In a specific example, the outer electrode tab and the inner electrode tab of the first unit cell and the second unit cell protrude from the upper and lower ends of the unit cell, respectively, in the first unit cell, the outer electrode tab is a cathode, and the inner electrode tab is The cathode may be an anode, and the outer electrode tab may be an anode in the second unit cell, and the inner electrode tab may be a cathode. Accordingly, by connecting the positive electrode tab of the first unit cell and the negative electrode tab of the second unit cell to each other, and connecting the other negative electrode tab and the positive electrode tab, which is the outer electrode tab of the first unit cell and the second unit cell to the external input and output terminals, Two battery cells are connected in series. In the present invention, the diaphragm which serves to physically separate the unit cells and the electrolyte from each other may be formed by, for example, inserting a separate member between the unit cells. The material of such a diaphragm is not particularly limited, and is not particularly limited as long as it has electrolyte resistance and can prevent the movement of lithium ions. Examples of such diaphragms include polyethylene (PE), polypropylene (PP), polystyrene (PS), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyethylene-terephthalate (PET), polymethyacrylate (PMMA), and polyacrylonitrile (PAN). It is made of one or two or more materials selected from the group consisting of, preferably a polyolefin-based polymer sheet such as PE, PP.

The diaphragm may be combined by inserting a separate adhesive or the like by being inserted into the case sealing part, or may be combined by heat fusion with the sealing part. For example, a battery case made of a laminate sheet is bonded to each other by heat-sealing internal resin layers positioned inside the case. Therefore, in one preferred embodiment, it is preferable to use a material that is the same as or similar in physical properties to the material of the internal resin layer, and more preferably unstretched polypropylene (cPP) for excellent bonding between the diaphragm and the internal resin layer. It may be a polymer sheet of.

The area of the diaphragm may be larger than the cross-sectional area of the housing so that the area of the diaphragm may be located on the sealing portion formed on the outer circumferential surface of the housing. In addition, the upper case and the lower case may be of a size smaller than the cross-sectional area of the outer peripheral surface of the case in order to at least partially directly heat-sealed to exert high bonding force and minimize waste of unnecessary material.

If the thickness of the diaphragm is too thick, the thermal conductivity during thermal fusion is lowered, and the gap between the upper case and the lower case is widened, so that bonding by thermal fusion is not easy, and there is a problem of increasing the thickness of the battery. On the contrary, when too thin, it may be difficult to sufficiently achieve electrolyte sealing between unit cells due to deformation of the membrane itself during charge and discharge. In consideration of this point, the thickness of the diaphragm may be preferably 10 μm to 500 μm.

In the present invention, the battery case is composed of an upper case and a lower case, and includes at least one housing portion and an outer circumferential sealing portion, and the upper case and the lower case by performing a heat fusion process at a portion where the laminate sheets are in contact with each other along the outer circumferential surface sealing portion. Can be combined.

The battery case may be formed from, for example, a laminate sheet composed of an outer coating layer of a polymer film, a barrier layer of metal foil, and an inner sealant layer of a polyolefin series. Since the outer coating layer must have excellent resistance from the external environment, it is necessary to have a tensile strength and weather resistance of at least a predetermined level. In such aspect, a stretched nylon film or polyethylene terephthalate (PET) may be preferably used as the polymer resin of the outer resin layer. The barrier layer is preferably aluminum may be used to exhibit a function of improving the strength of the battery case in addition to the function of preventing the inflow or leakage of foreign substances such as gas, moisture. The inner sealant layer has a heat sealability (heat adhesiveness), low hygroscopicity to suppress the penetration of the electrolyte, polyolefin resin that is not expanded or eroded by the electrolyte may be preferably used, More preferably unstretched polypropylene (cPP) can be used.

On the other hand, since the external electrode tab is coupled to the electrode lead can be connected to the external input and output terminals, the sealing member in the form of a film between the electrode lead to increase the sealing property in consideration of the thickness of the electrode lead and heterogeneity with the case material It can heat bond in the state interposed.

The accommodating part may be formed in a size corresponding to the electrode assembly on one side of the battery case, or may be formed on both sides of the battery case. In addition, the upper case and the lower case of the battery case may be formed integrally by forming a unit of one unit ('integral battery case'), may be formed of a separate unit consisting of two units ('removable battery case' It may be ').

Preferably, the outer circumferential surface sealing portion may be formed on all four sides of the receiving portion so that the sealing portion of the battery case may be inserted into the inner electrode tab.

Although the widths of the sealing parts may all be the same, in one preferred embodiment for preventing the sealing force of the sealing part from being lowered due to the location of the inner electrode tabs, a surface into which the inner electrode tabs are inserted among the four surface sealing parts. The width of the sealing portion of may be greater than the width of the sealing portion of the remaining surface. In addition, in order to increase the bonding force of the sealing portion, an adhesive insulating tape may be further attached to the contact surface of the inner electrode tab with the sealing portion.

The unit cell is composed of an electrode assembly having a stack structure of an anode, a separator, and an anode, and the type of the electrode assembly is not particularly limited, and may be one selected from a stack type, a stack type, a folding type, or a folding type electrode assembly. have. In the case of using the folding electrode assembly, the cross-sectional shape may be substantially rectangular by pressing.

In particular, the secondary battery according to the present invention may be preferably applied to a pouch type secondary battery in which an electrode assembly is embedded in a laminate sheet including a metal layer and a resin layer, and in one specific example, an aluminum laminate sheet. In the present invention, the secondary battery is preferably a lithium secondary battery having a high energy density, a discharge voltage, and an output stability, and a lithium ion polymer secondary battery is more preferable. Since other components and a manufacturing method of the lithium secondary battery are well known in the art, detailed description thereof will be omitted herein.

The present invention also provides a high-power large-capacity battery module using such a secondary battery as a unit.

The medium-large battery module according to the present invention can be assembled by treating two or more unit cells as a single battery cell, and since their coupling structure is dense, the overall assembly process of the battery module can be simplified and more compact. Can be prepared. In addition, there is an advantage that the risk of occurrence of a short circuit due to complicated wiring or the like can be reduced by easy BMS management.

The present invention also provides a method of manufacturing the secondary battery comprising the following steps (i) to (iv).

(i) mounting two or more unit cells so that the inner electrode tabs face each other in the case body in which one or two accommodating parts are continuously formed in the vertical direction;

(ii) inserting a diaphragm between unit cells mounted in step (i);

(iii) combining the diaphragm with the sealing portion of the case body into which the diaphragm is inserted in step (ii);

(iv) injecting the electrolyte solution and heat-sealing the outer peripheral surface sealing portion of the case.

The manufacturing method according to the present invention can be prepared according to a known secondary battery manufacturing method without having to go through a separate complicated process, and can be manufactured by a continuous process, so the process efficiency is very excellent.

In the step (i) of mounting the unit cell in the battery case receiving unit, in the case of the battery case is formed in each of the upper case and the lower case, the unit cells can be divided into each mounting, the housing is formed only in the lower case In the case of the battery case, a plurality of unit cells can be mounted together.

The step (ii) is a step of inserting the diaphragm, by mounting a diaphragm having a size that can completely seal the receiving portion between the unit cells, a portion of the diaphragm can be located on the outer peripheral surface sealing portion. Then, in the step (iii), the diaphragm and the outer circumferential sealing portion are joined, and the diaphragm and the sealing portion can be joined by a method such as heat fusion or an adhesive as described above.

In the step (iv), the injection of the electrolyte, for example, only the first three surfaces of the sealing portion may be injected first, and then the electrolyte may be injected, and in the final step, the remaining one surface may be manufactured to manufacture a battery.

In one preferred embodiment, at any point before or after the steps (i) to (iv), the step of welding the internal electrode tab of the unit cell by bonding. That is, the coupling of the inner electrode tab is not particularly limited as long as it is a time point before the upper case and the lower case are heat-sealed, and more preferably, may be performed before or after the step (i). For example, when manufacturing a secondary battery by mounting two unit cells in a battery case in which an accommodating part is formed in each of an upper case and a lower case, two unit cells in which internal electrode tabs are coupled to each other are respectively provided in the accommodating part. The internal electrode tabs may be connected to the unit cells after the unit cells are mounted in the storage units.

In the following, secondary batteries according to an embodiment of the present invention will be described with reference to the drawings, but this is for easier understanding of the present invention, and the scope of the present invention is not limited thereto.

2 schematically illustrates unit cells inserted into a secondary battery according to an exemplary embodiment of the present invention.

2, external electrode tabs 310 and 320 and internal electrode tabs 410 and 420 are formed in the unit cells 210 and 220, respectively. The inner electrode tabs 410 and 420 are positioned at the lower center of the unit cell, and the outer electrode tab 310 of the first unit cell 210 is formed at the upper left side of the unit cell, and the second unit cell 220 The external electrode tab 320 is formed at the upper right side of the unit cell. Insulating tapes 311 and 321 are attached to the external electrode tabs 310 and 320, respectively.

3 illustrates an exploded perspective view of a secondary battery including two unit cells according to FIG. 2 and manufactured as an integrated case according to a first embodiment of the present invention, and FIG. 4 illustrates a second embodiment of the present invention. An exploded perspective view of a rechargeable battery manufactured as a detachable case according to an embodiment is schematically illustrated. In addition, Figure 5 schematically shows a method of manufacturing a secondary battery manufactured by an integrated case according to another embodiment of the present invention. In FIGS. 3 to 5, all other components except for the shape of the case are the same, and for convenience of description, the same reference numerals are omitted for the same components as those in FIG. 4 and FIG. 5.

Referring to these drawings, the battery case of FIG. 3 is a lower case 610 in which the accommodating part 611 and the outer circumferential sealing part 630 are formed, and a bent upper case 620 which is continuously formed in one surface. consist of. The secondary battery may first be equipped with the first unit cell 210 in the accommodating part 611, insert the diaphragm 500, insert the second unit cell 220, and bend the upper case 620. Covering the lead portion 611, and heat-sealing the remaining three surfaces other than the top surface and then injecting the electrolyte through the top surface, respectively, and may be manufactured by heat-sealing the top surface.

The inner electrode tab 410 of the first unit cell 210 and the inner electrode tab 420 of the second unit cell 220 are positioned at a portion 650 in contact with the upper case 620, and the first unit cell. The external electrode tab 310 of the 210 and the external electrode tab 320 of the second unit cell 220 protrude outside the upper end of the case. At this time, the insulating tape attached to the external electrode tabs 310 and 320 is positioned on the outer circumferential surface sealing part 630 of the case.

Meanwhile, the battery case of FIG. 4 includes a lower case 610 'having an accommodating part 611' and an outer circumferential sealing part 630 ', and an accommodating part 621' and an outer circumferential sealing part 630 'substantially identical thereto. 3 is the same as the battery case of FIG. 3 except that the upper case 620 'is formed.

The internal electrode tab of the first unit cell 210 and the internal electrode tab of the second unit cell 220 are connected by a method such as welding to connect the first unit cell 210 and the second unit cell 220 in series. . The timing at which these internal electrode tabs are connected to each other is not particularly limited, and may be, for example, before heat fusion with the upper cases 620 and 620 'and the lower cases 610 and 610'. In addition, the diaphragm 500 may be inserted after the first unit cell 210 and the second unit cell 220 are mounted in the battery case while the internal electrode tabs are coupled to each other. This process can be confirmed in more detail in FIG.

Referring to FIG. 5, the battery case is integrated, and accommodating parts 621 ″ and 611 ″ are formed in both the upper case 620 ″ and the lower case 610 ″. The first unit cell 210 and the second unit cell 220 coupled to each of the battery case by welding are mounted, the diaphragm 500 is inserted, and the lower case ( 610 ") in the direction of the upper case 620", and heat-sealed the remaining three surfaces except for the upper surface that is opposite to the surface on which the bent portion 650 is formed, and then the respective receiving portions 621 ", 611 After the electrolyte is injected into the “), the secondary battery may be manufactured by heat sealing the upper end sealing part.

6 schematically illustrates a structure in which unit cells are connected in a secondary battery according to an embodiment of the present invention, and FIG. 7 schematically illustrates a front view of a secondary battery having a structure according to FIG. 6. 8A and 8B schematically show cross-sectional views of the straight line AA and the straight line BB in FIG. 7, respectively. For reference, the case is omitted in FIG.

First, referring to FIG. 6, the secondary battery 100 includes two unit cells 210 and 220. External electrode tabs 310 and 320 protruding from the upper end 201 are formed in the first unit cell 210 and the second unit cell 220, respectively, and internal electrode tabs 410 protruding from the lower end 202 are formed. 420 is formed. The inner electrode tabs 410 and 420 of the first unit cell 210 and the second unit cell 220 have opposite polarities, and the outer electrode tab 300 and the inner electrode tabs 410 and 420 in each unit cell. Have opposite polarities. Therefore, the two unit cells 210 and 220 are connected in series by interconnecting the internal electrode tabs 410 and 420. A diaphragm 500 is formed between the first unit cell 210 and the second unit cell 220 to physically separate the electrolytes of the unit cells 210 and 220 from each other.

In FIG. 7, the width of the sealing part 630 is sufficient to exert the coupling force between the upper case and the lower case, but the width L of the portion where the inner electrode tab is positioned to increase the coupling force is the width of the remaining sealing part. It may be desirable to be larger than (l). In addition, the area of the diaphragm 500 may be larger than the cross-sectional area of the accommodating part so as to seal the accommodating part, and smaller than the cross-sectional area of the whole case to ensure the bonding force in the sealing part 630. In this case, the outer periphery of the diaphragm 500 is located approximately in the middle of the sealing portion 630.

Referring to FIG. 8A, which is a side cross-sectional view of a straight line AA, and FIG. 8B, which is a side cross-sectional view of a straight line BB, the battery case includes an outer resin layer 601, a metal barrier layer 602, and an inner resin layer 603, the innermost layer. It consists of a laminate sheet having a laminated structure of. The diaphragm 500 is inserted in a part of the sealing part which is a contact surface of an upper case and a lower case, and the facing internal resin layer 603 is heat-sealed by heating / pressing. At this time, if the diaphragm 500 is made of a material having the same or similar physical properties as that of the internal resin layer 603, it may be easier to be thermally fused together. The inner electrode tabs 310 and 320 are separated from each other at the portion where the diaphragm 500 is inserted, but are coupled to each other at an end of the diaphragm 500.

8A and 8B, for the sake of explanation, a corresponding portion is expressed as a state before thermal fusion, but when the thermal fusion is actually performed, the inner resin layers 603 and the diaphragm 500 of the upper and lower cases are thermally fused to each other. No spaced parts will be lost.

9 illustrates a structure in which three unit cells are connected in a secondary battery according to still another embodiment of the present invention.

Referring to FIG. 9, the secondary battery 101 includes a first unit cell 211, a second unit cell 221, and a third unit cell 231, and each of the unit cells 211, 221, The diaphragm 501 is respectively inserted between 231. The external electrode tabs 311 and 331 protrude from the upper end of the first unit cell 211 positioned at the outermost side and the lower end of the third unit cell 231, respectively. The inner electrode tab 411 protruding to the lower end of the first unit cell 211 is connected to the inner electrode tab 421 adjacent to the second unit cell 221 and is formed in a position opposite to the second unit cell. The internal electrode tab 422 of 221 is connected to the internal electrode tab 431 of the third unit cell 231. Accordingly, the first unit cell 211, the second unit cell 221, and the third unit cell 231 are connected in series. Since the secondary battery can exert a voltage three times higher than that of a battery including one unit cell, the secondary battery can be preferably applied to a field in which high voltage and high power are emphasized.

Although described above with reference to the drawings according to an embodiment of the present invention, those of ordinary skill in the art will be able to perform various applications and modifications within the scope of the present invention based on the above contents.

As described above, in the secondary battery according to the present invention, since two or more unit cells physically separated by a diaphragm are connected in series, a secondary battery having high voltage and high output characteristics can be manufactured, and BMS management There is an effect that it is easy, and because it can be manufactured by a low cost and a simple assembly process has the advantage of high production efficiency.

1 is a perspective view of a typical representative pouch type battery;

2 is a schematic view of a unit cell inserted into a secondary battery according to one embodiment of the present invention;

3 and 4 are exploded perspective views of a secondary battery including two unit cells according to FIG. 2, FIG. 3 is a secondary battery manufactured with an integrated case according to a first embodiment of the present invention, and FIG. 4 is an embodiment of the present invention. It is a secondary battery made of a removable case according to a second embodiment of the;

5 is a schematic diagram of a manufacturing process of a secondary battery according to one embodiment of the present invention;

6 is a schematic diagram of a structure in which unit cells are connected in a secondary battery according to one embodiment of the present invention;

7 is a front view of a secondary battery having a structure according to FIG. 6;

8A and 8B are cross-sectional views of straight lines A-A and B-B in FIG. 7;

9 is a schematic diagram of a structure in which unit cells are connected in a secondary battery according to another embodiment of the present invention.

Claims (22)

A secondary battery in which two or more unit cells are mounted in a case accommodating part and heat-sealed and sealed at an outer circumferential surface sealing part of an upper case and a lower case, Each of the unit cells has a positive electrode tab and a negative electrode tab formed at opposite positions, the electrolytes of the unit cells are physically separated by a diaphragm, and one electrode tab ('external electrode tab') of the outermost unit cells The outer electrode tab ('inner electrode tab') protrudes out of the case and is connected to the inner unit cell in series, and the inner electrode tab has a case with a diaphragm having a thickness of 10 μm to 500 μm interposed therebetween. Secondary battery, characterized in that made of a heat-sealed structure together with the sealing portion. The secondary battery of claim 1, wherein internal electrode tabs of adjacent unit cells have opposite polarities. The secondary battery of claim 1, wherein each of the external electrode tabs is formed at an upper end of the case. The secondary battery of claim 1, wherein the inner electrode tabs protrude from adjacent unit cells in the same direction and position. The method of claim 1, wherein the inner electrode tabs are all formed at the center of the upper or lower end of the unit cell, the outer electrode tabs are formed on the upper end of the unit cell, the opposite electrode tabs of the upper left and right of the case Secondary batteries, characterized in that each is formed. The secondary battery of claim 1, wherein the inner electrode tab is positioned between an end portion of the diaphragm and an end portion of an outer circumferential surface thereof. The secondary battery of claim 1, wherein the secondary battery comprises two unit cells, a first unit cell and a second unit cell. The secondary battery of claim 1, wherein the diaphragm is formed by inserting a separate member. The secondary battery of claim 1, wherein the diaphragm is a polyolefin-based polymer sheet. The secondary battery of claim 9, wherein the diaphragm is an unstretched polypropylene (cPP) sheet. The secondary battery of claim 1, wherein the cross-sectional area of the diaphragm is larger than the cross-sectional area of the housing and smaller than the total cross-sectional area of the case. delete According to claim 1, wherein the case is formed on all four sides of the sealing portion, the inner electrode tab is inserted into any one of the four surface, the width of the sealing portion of the surface in which the inner electrode tab is inserted the sealing portion of the remaining surface Secondary battery, characterized in that larger than the width. The secondary battery of claim 1, wherein the internal electrode tabs are connected by series welding by soldering or soldering to each other. The secondary battery of claim 1, wherein the unit cell is selected from a group consisting of a stack type, a stack / fold type, and a folding type electrode assembly. The secondary battery of claim 1, wherein the case is made of an aluminum laminate sheet and is composed of one unit or two units. The secondary battery of claim 1, wherein the battery is a lithium secondary battery. A medium and large battery module having a high output capacity using the secondary battery according to claim 1 as a unit. A secondary battery in which two or more unit cells are mounted in a case accommodating part and heat-sealed and sealed at an outer circumferential surface sealing part of an upper case and a lower case, Each of the unit cells has a positive electrode tab and a negative electrode tab formed at opposite positions, the electrolytes of the unit cells are physically separated by a diaphragm, and one electrode tab ('external electrode tab') of the outermost unit cells It protrudes out of the case and the opposite electrode tab ('inner electrode tab') is connected in series with the inner unit cell, and the inner electrode tab is heat-sealed together with the case sealing part in the state where the diaphragm is interposed. As a manufacturing method of a secondary battery, characterized in that (i) mounting two or more unit cells so that the inner electrode tabs face each other in the case body in which one or two accommodating parts are continuously formed in the vertical direction; (ii) inserting a diaphragm between unit cells mounted in step (i); (iii) combining the diaphragm with the sealing portion of the case body into which the diaphragm is inserted in step (ii); (iv) injecting an electrolyte solution and heat-sealing the outer circumferential surface sealing portion of the case; Manufacturing method comprising a. The method of claim 19, further comprising: coupling the internal electrode tabs of the unit cells at an arbitrary time point before or after the steps (i) to (iv). A secondary battery in which two or more unit cells are mounted in a case accommodating part and heat-sealed and sealed at an outer circumferential surface sealing part of an upper case and a lower case, Each of the unit cells has a positive electrode tab and a negative electrode tab formed at opposite positions, the electrolytes of the unit cells are physically separated by a diaphragm, and one electrode tab ('external electrode tab') of the outermost unit cells It protrudes out of the case and the opposite electrode tab ('inner electrode tab') is connected in series with the inner unit cell, and the inner electrode tab is heat-sealed together with the case sealing part in the state where the diaphragm is interposed. It consists of, The inner electrode tabs are all formed at the center of the upper or lower end of the unit cell, the outer electrode tabs are formed at the upper end of the unit cell, and the opposite electrode tabs are formed at the upper left and right sides of the case, respectively. Secondary battery. A secondary battery in which two or more unit cells are mounted in a case accommodating part and heat-sealed and sealed at an outer circumferential surface sealing part of an upper case and a lower case, Each of the unit cells has a positive electrode tab and a negative electrode tab formed at opposite positions, the electrolytes of the unit cells are physically separated by a diaphragm, and one electrode tab ('external electrode tab') of the outermost unit cells It protrudes out of the case and the opposite electrode tab ('inner electrode tab') is connected in series with the inner unit cell, and the inner electrode tab is heat-sealed together with the case sealing part in the state where the diaphragm is interposed. It consists of, The case is formed on all four sides of the sealing portion, the inner electrode tab is inserted into any one of the four surface, the width of the sealing portion of the surface in which the inner electrode tab is inserted is larger than the width of the sealing portion of the other surface Secondary battery.

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