KR20020007618A - Lithium ion secondary battery - Google Patents

Abstract

PURPOSE: A lithium ion secondary cell is provided which has a high energy density, excellent durability and high assembly productivity and can prevent an electrolyte from leaking. CONSTITUTION: The cell includes (i) a laminated body consisting of a plurality of anode plates, each of which has coating layers of lithium metal composite oxide as an anode active material at both sides and a first free-pattern protrusion; a plurality of cathode plates, each of which has coating layers of carboneous cathode active material capable of absorbing and releasing lithium at both sides and a second free-pattern protrusion; and a plurality of separators(302), each of which encloses each of the anode plates so as to separate from the cathode plates in the manner that the first free pattern protrusions are exposed, and contains an electrolytic solvent of a non-aqueous organic solvent and a lithium salt, (ii) a first and a second connector for connecting the first free-pattern protrusions with each other and the second free-pattern protrusions with each other, respectively, (iii) a metallic can(700) for receiving the laminated body having an anode terminal(730) insulated itself, (iv) a cap disposed at the top of the metallic can for sealing the metallic can, and (v) an anode tab for electrically connecting the first connectors with the anode terminal and a cathode tab for electrically connecting the second connectors with the metallic can.

Description

Lithium ion secondary battery

The present invention relates to a lithium ion secondary battery, and more particularly, to a lithium ion secondary battery having a high energy density capable of preventing leakage of electrolyte as well as high assembly productivity.

As the market for portable electronic devices such as mobile phones, camcorders, and notebook computers expands and diversifies, demand for rechargeable rechargeable batteries is increasing. Miniaturization, weight reduction, high performance, and multifunctionality of portable electronic devices require continuous improvement of energy storage density of secondary batteries used as power sources. Accordingly, as a result of many years of research to satisfy this problem, a lithium ion secondary battery employing a carbon cathode capable of reversible insertion and release of lithium and a cathode material capable of reversible insertion and release of lithium has emerged. This lithium-ion secondary battery is rapidly becoming a new energy source of portable electronic devices in recent years because of its relatively high energy density and charge / discharge life per unit weight when compared with conventional aqueous secondary batteries such as nickel-cadmium and nickel-hydrogen. It replaces existing battery. However, with the rapid development and diversification of portable electronic devices, the demand for higher energy density and battery selection of various standards has rapidly increased, and thus, lithium ion secondary batteries do not satisfy such demands at present. In particular, the rapid thinning and miniaturization of electronic devices are rapidly expanding the demand for thinner, thinner lithium ion secondary batteries. However, when the structure of the existing lithium ion secondary batteries is applied as it is, the decrease in energy density per volume due to the thinning is achieved. This is too big. Therefore, when a thin battery of 5 mm or less is employed in high-performance portable electronic devices such as mobile phones, camcorders, and notebook computers, it is difficult to obtain sufficient driving time. Therefore, development of a thin lithium ion secondary battery having a high energy density per volume is considered essential for achieving miniaturization, weight reduction, and thickness reduction of various portable electronic devices.

Accordingly, the present inventors have revealed problems of the conventional lithium ion secondary battery and a method of manufacturing the same, and in order to improve the problem, a lithium ion secondary battery having a high energy density and durability and a method of manufacturing the same have been developed by Korean Patent Application No. 2000-21513. It was initiated through a call. According to the technology disclosed in Korean Patent Application No. 2000-21513, the internal short circuit and corner mismatch of two electrodes are improved because the material and structure of the exterior material, the stacking alignment structure of the laminate including the positive electrode plate, the negative electrode plate, and the separator inserted into the exterior material are improved. In addition to eliminating the problem, it is possible to provide a lithium ion secondary battery having improved productivity and battery stability and a method of manufacturing the same. However, in the assembly process of the lithium ion secondary battery, there is some inconvenience in terms of productivity because the alignment rod is used to stack and align a plurality of positive electrode plates, negative electrode plates, separators.

Therefore, the present inventors have developed a technology that improves it and disclosed it through Korean Patent Application No. 2000-25609. In Korean Patent Application No. 2000-25609, the uncoated parts of the positive electrode plates and the uncoated parts of the negative electrode plates are welded to each other, and the positive electrode plate is electrically connected to the metal cap and the metal can by the positive electrode tab and the negative electrode tab by the negative electrode tab, respectively. Disclosed is a structure of a lithium ion secondary battery in which a metal cap is connected as a positive terminal and a metal can functions as a negative terminal.

However, according to the techniques disclosed in Korean Patent Application Nos. 2000-21513 and 2000-25609, since the wide perimeter of the battery has a structure sealed by a can, a cap, and a gasket, the battery As the width of the wire becomes wider and the capacity increases, there is a fear that leakage of the electrolyte may occur when there are defects in components and assembly.

Therefore, the technical problem to be achieved by the present invention is to use the stacking alignment structure disclosed in the Korean Patent Application Nos. 2000-21513 and 2000-25609, while significantly improving the assembly performance of the battery while electrically integrating the can and the cap It is to provide a lithium ion secondary battery.

Another technical problem of the present invention is to provide a lithium ion secondary battery which can increase the sealing property between the can and the cap and can prevent leakage of the electrolyte solution.

Another technical problem of the present invention is to provide a lithium ion secondary battery having a structure in which a separate electrode terminal is provided according to the electrical integration between the can and the cap, and the insulation is maintained well.

1A and 1B are plan views illustrating pole plate materials for making a positive electrode plate and a negative electrode plate used in a lithium ion secondary battery according to an embodiment of the present invention;

2 is a view showing a layout of punching shapes for a positive electrode plate and a negative electrode plate used in a lithium ion secondary battery according to an embodiment of the present invention;

3A and 3B are views for explaining a process of making the punched negative electrode plate integral with the separator;

4 is a view illustrating a lamination order of a laminate used in a lithium ion secondary battery according to an embodiment of the present invention and a lamination frame for forming a laminate;

5 is a plan view of only a part of the laminate used in the lithium ion secondary battery according to the embodiment of the present invention;

6a and 6b are views showing an electrical connection between a plurality of positive plates and a plurality of negative plates; And

7A to 7C are views illustrating metal can accommodation states of a laminate used in a lithium ion secondary battery according to an embodiment of the present invention;

8 is a view for explaining a laser welding method of the sealing method of the packaging material for housing the laminate of the lithium ion secondary battery of the present invention;

9 is a view for explaining a crimping method of the sealing method of the packaging material for housing the laminate of the lithium ion secondary battery of the present invention; And

10 is a view for explaining the electric welding method of the sealing method of the packaging material for housing the laminate of the lithium ion secondary battery of the present invention.

The lithium ion secondary battery of the present invention for achieving the above technical problem: a plurality of positive electrode plates of the same shape each having a coating layer of the lithium metal composite oxide as the positive electrode active material and the first plain protrusions, and occludes and discharges the lithium A plurality of negative electrode plates having the same shape each having a carbonaceous negative electrode active material coating layer and a second plain protrusion, and each of the positive electrode plates are pocketed to expose only the first plain protrusion and separated from the negative electrode plates. A laminate comprising a plurality of separators containing an electrolyte consisting of a non-aqueous organic solvent and a lithium salt are aligned stacked; The first plain protrusions and the second plain protrusions are aligned at a position spaced apart from each other, the first plain protrusions are electrically connected to the first plain protrusions, and the second plain protrusions are electrically connected to each other. One first and second connections; A metal can inserting the stack therein and including an anode terminal insulated therein; A cap positioned at an upper end of the metal can and forming a sealed metal container together with the metal can; And a cathode tab electrically connecting the first connector and the cathode terminal, and a cathode tab electrically connecting the second connector and the metal can.

At this time, the laminate inserted into the metal can is: a single-side coating anode plate, a double-coated positive electrode plate pocketed on the separator membrane, a double-sided coating negative electrode plate, a separator, a single-side coated positive electrode plate laminated in the order, the double-coated positive electrode plate and pocketed on the separator It is preferable that the double-coated negative electrode plate is repeatedly laminated at least once.

On the other hand, the metal can and the cap is preferably welded and sealed by at least one method of laser welding, mechanical crimping by crimping, electrical welding by resistance.

The anode terminal may be formed on any portion of the metal can, but preferably may be formed on the sidewall of the metal can.

In this case, electrical insulation between the anode terminal and the metal can may be achieved by a gasket.

In addition, it is preferable that the positive electrode tab is prevented from contacting all the conductors connected to the negative electrode plate by an insulating tape adhered to the inner surface of the metal can.

On the other hand, it is preferable that the positive electrode tab and the negative electrode tab extend in the protruding direction, respectively, to the first and second plain protrusions.

Hereinafter, with reference to the accompanying drawings will be described a preferred embodiment of the present invention.

1A and 1B are plan views illustrating pole plate materials for making a positive electrode plate and a negative electrode plate used in a lithium ion secondary battery according to an embodiment of the present invention.

Referring to FIG. 1A, the positive electrode active material 102 is coated in a stripe shape so as to coincide with both surfaces of the positive electrode plate material 100. The coating is performed through a conventional coater, and after coating, the coated positive plate material 100 is compressed using a conventional presser used in an existing cell manufacturing process. Referring to FIG. 1B, the negative electrode active material 112 is coated in a stripe shape on both sides of the negative electrode material 110 in the same manner as the positive electrode material. However, in order to stably occlude lithium ions emitted from the positive electrode, the coating area of the negative electrode plate material is made larger than the coating area of the positive electrode plate material. On the other hand, in the outermost position of the electrode plate to be stacked is used a single-side coated positive plate and a single-side coated negative plate. The reason for this is to prevent the outermost positive electrode or the negative electrode because it does not have the opposite electrode facing each other and is wasted without performing the performance of the battery.

2 is a view showing the layout of the punching shape for the positive electrode plate and the negative electrode plate used in the lithium ion secondary battery according to an embodiment of the present invention. Referring to FIG. 2, it can be seen that the positive electrode plate or the negative electrode plate is formed by punching the positive electrode plate material 100 coated with the positive electrode active material 102 or the negative electrode plate material 110 coated with the negative electrode active material 112 along a dotted line. The punched positive electrode plate or negative electrode plate includes a plain protrusion 104 that is not coated with the active material. In FIG. 2, the positive electrode plate and the negative electrode plate are shown in the same manner, and this is for explaining the punching process, and the width and length of the active material coating surface of the negative electrode plate are actually greater than the length and width of the active material coating surface of the positive plate. The punching shape should be determined so that the size of the anode plate is smaller than that of the cathode plate. This is essential to stably occlude lithium ions emitted from the anode.

3A and 3B are views for explaining a process of making the punched anode plate integral with the separator; Referring to Figure 3a showing the assembling process in cross-section, as shown in Figure 2, the edge of the separation membrane 302 is surrounded by the separation membrane 302 of the punched double-side coating 300 is surrounded by the separation membrane 302 It can be seen that it is fused by 304. 3A is a cross-sectional view of the positive electrode plate 301 in the shorter length direction thereof. Therefore, the first plain projections included in the positive plate do not appear.

FIG. 3B is a plan view of the process output described in FIG. 3A. For clarity, the positive electrode plate 301 in the separator 302 is shown through perspective. Referring to FIG. 3B, a positive electrode plate 301 having a double-sided coating layer 300 is surrounded by a separator 302. The four edge portions indicated by hatched lines are the fusion regions of the separator 302, and the fusion regions surround all of the fusion regions except for the portion where the first plain protrusion 104a for connecting to the electrode terminal is exposed to the outside. This type of assembly is called pocketing, which makes the membrane difficult to align and integrates with the positive electrode plate with a certain strength, thereby increasing the speed and yield of the electrode stacking process and increasing the negative electrode and positive electrode. Assembly method to rule out the possibility of corner mismatch between the active surfaces of the The positive electrode plate-membrane assembly formed by the pocketing is made equal to the size of the negative electrode plate. As such, the edges of the positive electrode plate-membrane assembly and the negative electrode plate coincide with each other to automatically satisfy the condition that all surfaces facing the positive electrode should be covered with the negative electrode. Equipment used for pocketing is a device operated on the same principle as a conventional vacuum packaging machine. The device places two separators 302 below and above the positive plate 301, and then applies the appropriate pressure and temperature to all the edges except for the first plain projection 104a to fuse the separators 302 together. At this time, the pressure used is usually any pressure of 0.5kg / cm ² or less can be used, the temperature is preferably adjusted within ± 20 ℃ based on the melting point of the separator 302. The adhesion time is usually a few seconds or so, preferably 0.1 to 3 seconds.

4 is a view showing a stacking sequence of the laminate used in the lithium ion secondary battery according to an embodiment of the present invention and a laminate for forming the laminate. Referring to FIG. 4, the single-side coated negative plate 403a is positioned at the bottom of the laminate, and the single-side coated positive plate 404a is positioned at the top of the laminate. In between, the positive electrode plate 400 and the double-coated negative electrode plate 403 pocketed by the separator are alternately stacked at least one or more times. On the other hand, only one sheet of separator 402 is placed directly below the top-side coated positive plate 404a at the top of the laminate to separate the single-side coated positive plate 404a and the double-coated negative plate 403. The stacks stacked in this order are aligned in a stacking frame 420 whose three sides have the same shape as the metal can that will ultimately house the stack. Three surfaces of the stacking frame 420 are blocked, and one surface of the electrode tab and the electrode where the electrode is to be described later is opened.

5 is a plan view of only a part of the laminate used in the lithium ion secondary battery according to the embodiment of the present invention. Shown in FIG. 5 are a positive electrode plate 301 pocketed by a separator 302 and a negative electrode plate coated on both sides. The negative electrode plate is covered by the positive electrode plate 301 pocketed by the separator 302 so that only the second plain protrusion 104b is shown. Since the first plain protrusion 104a and the second plain protrusion 104b are spaced apart from each other when stacked, the protrusions 104a and 104b are spaced apart from each other even when a plurality of separator-anode plate assemblies and a plurality of negative electrode plates are stacked. Will be sorted on.

6A and 6B are diagrams illustrating an electrical connection method between a plurality of positive electrode plates and a plurality of negative electrode plates. FIG. 6A illustrates the electrical connection between the positive plates plated by the separator and the negative plates in FIG. 6B. For the sake of clarity, FIG. 6A omits the presence of the negative electrode plate in the laminate structure. The first plain protrusions 104a of all the anode plates pocketed by the separator 302 are laser welding, spot welding, and ultra-sonic, which are conventional welding methods. by means of laser thermal electrical resistance heat or ultrasonic wave, and interfacial structure disturbance is performed. The first flat projections 104a thus welded are electrically joined to the positive electrode tab 304a placed on the top by welding or riveting. This positive electrode tab is welded to a positive electrode terminal electrically separated with an insulating material to be described later.

For the sake of clarity, only the negative electrode plates are shown in FIG. 6B without the separator and the positive electrode plate. The second plain protrusions 104b of the stacked negative plates 403 are also welded as described in FIG. 6A and then electrically connected again to the negative electrode tab 304b placed at the bottom thereof.

7A to 7C are views illustrating metal can storage states of a laminate used in a lithium ion secondary battery according to an exemplary embodiment of the present invention. FIG. 7A is a plan view, and FIG. 7B is a sectional view taken along line AA ′ of FIG. 7A. 7C is a cross-sectional view taken along line BB ′ of FIG. 7A. Referring to FIG. 7A, a stacked and integrated stack is inserted into the metal can 700. At this time, the positive electrode plate-membrane assemblies, i.e., the positive electrode plates pocketed by the separator, and the negative electrode plates are aligned in such a manner that their three sides are completely in contact with and inserted into the inner wall of the can. The single-coated bipolar plate 404a is exposed because it is on the top layer of the stack, and the first plain protrusions 104a and the second plain protrusions 104b are aligned at different positions. The positive electrode tab 304a is positioned at the top of the first non-coated protrusions 104a electrically connected to each other, and the negative electrode tab 304b is positioned at the lowermost part of the second non-coated protrusions 104b electrically connected to each other.

Referring to FIG. 7B, the negative electrode tab 304a connected to the second plain protrusions 104b electrically connected to each other is welded to the bottom surface of the metal can 700. Meanwhile, referring to FIG. 7C, the positive electrode tab 304a welded to the electrically connected first plain protrusions 104a prevents contact with all the conductors connected to the negative electrode plate by the insulating tape 710 and at the same time the metal can. It is connected to the anode terminal 730 provided on the side wall of 700. The anode terminal 730 is electrically isolated from the metal can 700 by the gasket 720.

When the negative electrode tab and the positive electrode tab are connected in the same manner as described above and the metal can and the metal cap are sealed by the sealing method to be described later, the entire metal container serves as a negative electrode terminal.

8 is a view for explaining a laser welding method of the sealing method of the packaging material for housing the laminate of the lithium ion secondary battery of the present invention, Figure 8 (a) is a metal cap (750a), Figure 8 (b Each denotes a metal can 700a. Referring to FIG. 8B, a positive electrode terminal 730 is formed on the sidewall of the metal can 700a, and a gasket 720 is positioned around the metal can, and then the entire metal functions as a negative electrode terminal after sealing. It is electrically isolated between the container and the positive terminal. FIG. 8C is a perspective view showing a state in which the metal cap 750a and the metal can 700a are laser welded, and FIG. 8D is a front view of FIG. 8C.

9 is a view for explaining the crimping method of the sealing method of the packaging material for housing the laminate of the lithium ion secondary battery of the present invention, Figure 9 (a) is a metal cap (750b), Figure 9 (b Each denotes a metal can 700b. Fig. 9C is a front view of the packaging material after crimping sealing. 9 (a) to 9 (c), it can be seen that the vertices of each of the metal cap 750b and the metal can 700b are curved to facilitate the crimping process.

10 is a view for explaining the electric welding method of the sealing method of the packaging material for housing the laminate of the lithium ion secondary battery of the present invention, Figure 10 (a) is a metal cap (750c), Figure 10 (b Each denotes a metal can 700c. 10C is a front view of the packaging material after electrowelding sealing. Referring to FIGS. 10A to 10C, unlike the case of the crimping process, the metal cap 750b and the metal can 700b may have a rectangular shape.

As a material of the metal cans of FIGS. 8 to 10, steel or stainless steel, which are generally used in the prior art, may be used. As the material of the metal cap, aluminum or an alloy thereof, or stainless steel having excellent corrosion resistance may be used. The can used in the lithium ion secondary battery of the present invention has a merit that the manufacturing process is easy and the manufacturing cost is lower than that of the conventional square battery having a high height, because the can has a low height unlike the prior art can. . In the present invention, the can height is usually 1 to 7 mm, preferably 1 to 5 mm, and more preferably about 1.5 to 4 mm. Thus, such cans are simple in their manufacture and can be made thinner than in the prior art, where the thickness of the cans is usually from 0.1 to 0.3 mm, preferably from 0.1 to 0.2 mm, more preferably. 0.15 to 0.2 mm is good. After the laminate is inserted into the metal can as described above, the battery is completed by covering the metal cap and sealing by laser welding, crimping, or electric welding.

As a result of investigating the performance of the curvature-shaped lithium ion secondary battery as follows.

[Example 1]

In the case of a battery produced in a square having a thickness of 3.2 mm, a short diameter of 54 mm and a long diameter of 85 mm, the reversible capacity was 1650 mAh. This translates to 411 Wh / liter in terms of energy density per volume.

[Second example]

In the case of a battery produced in a square having a thickness of 2.0 mm, a short diameter of 80 mm, and a long diameter of 120 mm, the reversible capacity was 2250 mAh. This corresponds to 420 Wh / liter in terms of energy density per volume.

According to the present invention as described above, it is possible to create a lithium-ion secondary battery with a new energy structure, excellent low-temperature and high-temperature performance, and improved stability than the conventional battery through a new internal structure, exterior material, laminated method and electrode connection method.

The present invention is not limited to the above embodiments, and it is apparent that many modifications are possible by those skilled in the art within the technical spirit of the present invention.

Claims (4)

A plurality of positive plates having the same shape each having a coating layer of the lithium metal composite oxide as the positive electrode active material and the first plain protrusion; A plurality of negative electrode plates having the same shape, each having a carbonaceous negative electrode active material coating layer capable of occluding and releasing lithium, and a second plain protrusion; A plurality of separators each of which is separated from the anode plates by pocketing each of the cathode plates to expose only the first plain protrusions, wherein the plurality of separators including an electrolyte comprising a nonaqueous organic solvent and a lithium salt are stacked and stacked; The first plain protrusions and the second plain protrusions are aligned at a position spaced apart from each other, the first plain protrusions are electrically connected to the first plain protrusions, and the second plain protrusions are electrically connected to each other. One first and second connections; A metal can inserting the stack therein and including an anode terminal insulated therein; A cap positioned at an upper end of the metal can and forming a sealed metal container together with the metal can; And a cathode tab electrically connecting the first connector and the cathode terminal, and a cathode tab electrically connecting the second connector and the metal can. The laminate of claim 1 wherein the laminate is inserted into the metal can: It is laminated in the order of single-side coated negative plate, double-coated positive plate plated on the separator, double-sided coated negative plate, separator, single-side coated positive plate, the double-coated positive plate and double-coated negative plate plated on the separator is repeatedly stacked at least once. Lithium ion secondary battery characterized by. The lithium ion secondary battery of claim 2, wherein the metal can and the cap are welded and sealed by at least one of laser welding, mechanical crimping by crimping, and electric welding by resistance. The lithium ion secondary battery of claim 2, wherein the positive electrode terminal is formed on a sidewall of the metal can, and the positive electrode terminal is electrically insulated from the metal can by a gasket.