KR100779001B1 - Lithium rechargeable battery - Google Patents

Abstract

The present invention relates to a lithium secondary battery, and more particularly, to a lithium secondary battery having an upper insulating plate having a plurality of holes, and a lower insulating plate having grooves for increasing mobility of the electrolyte, thereby improving the impregnation of the electrolyte. .

Lithium Secondary Battery, Insulation Plate, Impregnation

Description

Lithium rechargeable battery

1 is a perspective view of a cylindrical lithium secondary battery according to an embodiment of the present invention

2 is a cross-sectional view taken along the line A-A of FIG.

3A is a plan view of a phase insulating plate according to an embodiment of the present invention.

FIG. 3B is a cross-sectional view taken along the line B-B in FIG. 3A

Figure 4a is a plan view of a lower insulating plate according to an embodiment of the present invention

4B is a cross-sectional view taken along the line C-C in FIG. 4A

<Description of Symbols for Main Parts of Drawings>

100-cylindrical lithium secondary battery 200-electrode assembly

210-Positive Plate 215-Positive Tab

220-Negative Plate 225-Negative Tab

230-Separator 241-Phase Insulation Plate

242-Hole 243-Hole for Positive Tab

244, 248-Hollow 245-Lower insulation plates

246-Home 300-Can

310-side plate 320-bottom plate

400-cap assembly

The present invention relates to a lithium secondary battery, and more particularly, to a lithium secondary battery having an upper insulating plate having a plurality of holes, and a lower insulating plate having grooves for increasing mobility of the electrolyte, thereby improving the impregnation of the electrolyte. .

Recently, compact and lightweight electric / electronic devices such as mobile phones, notebook computers, and camcorders have been actively developed and produced. These portable electric / electronic devices have a battery pack that can be operated in a place where no separate power source is provided. The built-in battery pack includes at least one battery therein for outputting a predetermined level of voltage for driving the portable electric / electronic device for a period of time.

In view of economical aspects, the battery pack employs a secondary battery capable of charging and discharging. Representative secondary batteries include lithium secondary batteries such as nickel-cadmium batteries, nickel-hydrogen batteries, lithium batteries and lithium ion batteries.

In particular, the lithium secondary battery has an operating voltage of 3.6 V, which is three times higher than that of a nickel-cadmium battery or a nickel-hydrogen battery, which is widely used as a power source for portable electronic equipment, and is rapidly expanding in terms of high energy density per unit weight. It is a trend.

Such lithium secondary batteries mainly use lithium-based oxides as positive electrode active materials and carbon materials as negative electrode active materials. In general, the battery is classified into a liquid electrolyte battery and a polymer electrolyte battery according to the type of electrolyte. A battery using a liquid electrolyte is called a lithium ion battery, and a battery using a polymer electrolyte is called a lithium polymer battery. In addition, the lithium secondary battery is manufactured in various shapes, and typical shapes include cylindrical, square, and pouch types.

Typically, the cylindrical lithium secondary battery is positioned between a positive electrode plate coated with a positive electrode active material, a negative electrode plate coated with a negative electrode active material, and between the positive electrode plate and the negative electrode plate to prevent a short and allow only movement of lithium ions. An electrode assembly in which the separator is wound in a substantially cylindrical shape, a cylindrical case accommodating the electrode assembly, and an electrolyte solution injected into the cylindrical case to allow lithium ions to move.

This cylindrical lithium secondary battery is manufactured as follows.

First, a cathode electrode plate coated with the cathode active material and a cathode electrode plate connected with a cathode active material, an anode electrode plate coated with a cathode active material, an anode tab connected with a separator, and a separator are stacked, and then wound in a substantially cylindrical shape to prepare an electrode assembly. Thereafter, the electrode assembly is accommodated in the cylindrical case to prevent the electrode assembly from being separated, the electrolyte is injected into the cylindrical case, and then sealed to complete the cylindrical lithium secondary battery.

Meanwhile, before inserting the electrode assembly into the cylindrical case, a lower insulating plate is inserted to insulate the electrode assembly from the cylindrical case. In addition, after the electrode assembly is inserted, a phase insulating plate is inserted to insulate the electrode assembly from the cap assembly before sealing.

In addition, in the case of the rectangular lithium secondary battery, an insulating case for supporting the cap assembly and insulating between the terminal plate and the electrode assembly and a lower insulating plate for insulating between the rectangular case and the electrode assembly are inserted.

Since these insulating plates are usually made of polyethylene (PE) or polypropylene (PP), they are not familiar with the electrolyte solution. Therefore, the electrolyte solution is an obstacle to sufficient impregnation of the electrode assembly. Conventional phase insulation plate has a hole formed around the hollow in which the center pin is inserted, but the electrolyte is not sufficient to flow down to the electrode assembly located under the phase insulation plate. Rather, an electrolyte is formed in the hole around the hollow to block the hole. In addition, the lower insulating plate is in close contact with the electrode assembly, and the electrolyte flowing into the lower part of the case impedes the electrode assembly.

In addition, as the capacity of the battery increases, the electrode assembly also increases in density, resulting in an increase in the outer diameter of the electrode assembly. When the outer diameter of the electrode assembly is increased, the space between the cylindrical case and the electrode assembly is reduced, which makes the structure more difficult to impregnate the electrolyte. Therefore, there is a need to form the structure of the upper insulating plate and the lower insulating plate to facilitate the impregnation of the electrolyte.

The present invention is to solve the problems of the conventional lithium secondary battery described above, by forming the upper insulating plate or insulating case and the lower insulating plate of the lithium secondary battery in a structure that is easy to impregnate the electrolyte, even in the case of a high-density electrode assembly An object of the present invention is to provide a lithium secondary battery having improved electrolyte impregnation.

According to an aspect of the present invention, there is provided a lithium secondary battery including an electrode assembly, a case accommodating the electrode assembly, a lower insulation plate positioned between a lower portion of the electrode assembly, and a cap assembly sealing the case. In a lithium secondary battery comprising, a checkerboard groove is formed on at least one side of the lower insulating plate. In this case, the material of the lower insulating plate may be polyethylene (PE) or polypropylene (PP). In this case, the lower insulating plate may be formed in the form of a compressed nonwoven fabric.

In addition, the lower insulating plate may be coated with polyvinyl difluoride (PVdF). The polyvinyl difluoride (PVdF) is preferably any one of PVdF 761, PVdF 2801, a mixture of PVdF 761 and PVdF 2801.

According to another aspect of the present invention, a lithium secondary battery includes an electrode assembly, a cylindrical case accommodating the electrode assembly, a lower insulating plate positioned between the electrode assembly and the cylindrical case, a cap assembly sealing the cylindrical case, the electrode assembly and In the cylindrical lithium secondary battery comprising an upper insulating plate positioned between the cap assembly, the upper insulating plate is formed with a plurality of holes, the at least one side of the lower insulating plate characterized in that the groove is formed of a checkerboard shape do. At this time, the hole of the phase insulating plate may be formed in a mesh (mesh) shape.

In addition, the material of the upper insulating plate and the lower insulating plate may be polyethylene (PE) or polypropylene (PP). In this case, the upper insulating plate and the lower insulating plate may be coated with polyvinyl difluoride (PVdF). At this time, the polyvinyl difluoride (PVdF) is preferably any one of the mixture of PVdF 761, PVdF 2801, PVdF 761 and PVdF 2801.

In addition, the upper insulating plate and the lower insulating plate may be formed in the form of a compressed nonwoven fabric.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a perspective view of a cylindrical lithium secondary battery according to an exemplary embodiment of the present invention, and FIG. 2 is a sectional view taken along the line A-A of FIG. However, here, the description has been developed as a cylindrical lithium secondary battery for convenience, but the present invention may be applied to the case of a rectangular lithium secondary battery.

1 and 2, the cylindrical lithium secondary battery 100 includes an electrode assembly 200, a cylindrical can 300 containing the electrode assembly 200 and an electrolyte, and an upper portion of the cylindrical can 300. It is formed to include a cap assembly 400 for sealing the cylindrical can 300 to flow the current generated in the electrode assembly 200 to an external device.

Referring to FIG. 2, the electrode assembly 200 includes a positive electrode plate 210 coated with a positive electrode active material layer on a surface of a positive electrode current collector, a negative electrode plate 220 coated with a negative electrode active material layer on a surface of a negative electrode current collector, and the positive electrode plate. A separator 230 positioned between the 210 and the negative electrode plate 220 to electrically insulate the positive electrode plate 210 and the negative electrode plate 220 is wound and formed in a jelly-roll shape.

Although not shown in detail in the drawing, the positive electrode plate 210 includes a positive electrode current collector made of a thin metal plate having excellent conductivity, for example, aluminum (Al) foil, and a positive electrode active material layer coated on both surfaces thereof. have. Both ends of the positive electrode plate 210 are provided with a positive electrode current collector region, that is, a positive electrode non-coating portion, in which a positive electrode active material layer is not formed. One end of the positive electrode non-coating portion is generally formed of aluminum (Al), and the positive electrode tab 215 protruding a predetermined length to the upper portion of the electrode assembly 200 is bonded.

In addition, the negative electrode plate 220 includes a negative electrode current collector made of a conductive metal thin plate, for example, copper (Cu) or nickel (Ni) foil, and a negative electrode active material layer coated on both surfaces thereof. Both ends of the negative electrode plate 220 are provided with a negative electrode current collector region, that is, a negative electrode non-coating portion, in which a negative electrode active material layer is not formed. One end of the negative electrode non-coating portion is generally formed of nickel (Ni), and the negative electrode tab 225 protruding a predetermined length to the lower portion of the electrode assembly 200 is bonded. In addition, the upper and lower portions of the electrode assembly 200 may further include insulating plates 241 and 245 for preventing contact with the cap assembly 400 or the cylindrical can 300, respectively.

3A is a plan view of an upper insulating plate having a plurality of mesh-shaped holes formed therein, and FIG. 3B is a cross-sectional view taken along line B-B of FIG. 3A.

2 and 3A, an upper insulation plate 241 is positioned between the cap assembly 400, in particular the safety vent 410 and the top of the electrode assembly 200. The phase insulation plate 241 prevents a short circuit that may occur between the electrode assembly 200 and the cap assembly 400 including the safety tab 410 electrically connected to the electrode tab, for example, the positive electrode tab 215. do. Referring to FIG. 3A, the phase insulating plate 241 includes a hole for electrolyte solution 242 serving as a passage through which the injected electrolyte is settled and an electrode tab, for example, a cathode tab serving as a passage through which the positive electrode tab 215 exits. A hole 243 and a hollow 244 in contact with one end of the center pin are formed.

The electrolyte hole 242 is formed in a mesh form. Accordingly, the phase insulating plate 241 has a myriad of electrolyte holes 242 formed therein, and when the electrolyte is injected, the electrolyte is precipitated into the battery through the electrolyte hole 242. The size of each electrolyte hole 242 is not limited as long as it can prevent a short circuit between the upper portion of the electrode assembly 200 and the safety vent 410. In addition, the number of the electrolyte holes 242 is inversely related to the size of each electrolyte hole 242. That is, as the size of each electrolyte hole 242 increases, the number of electrolyte holes 242 decreases.

As the material of the upper insulating plate 241, both a conventional hard solvent material and a hydrophilic material may be used. The poorly soluble materials include polyolefin resins such as polyethylene (PE), polypropylene (PP) and polyimide (PI).

Polyethylene has a low density, stretches well due to insufficient molecular arrangement, and has a small tensile strength but high impact resistance. Therefore, there is an advantage that the processing is easy. In addition, since it is composed of only CH2, it is excellent in electrical insulation, and as shown in the structural formula, it is also excellent as a high frequency insulating material because of its symmetry around the chain of carbon (C).

Polypropylene has an isotactic structure, and the methyl groups are arranged in the same direction as the structural formula. The crystallinity before molding is large, but decreases after molding. The electrical properties of polypropylene and polyimide are similar to polyethylene.

These polyethylenes and the like are poorly soluble solvents having poor affinity with the electrolyte solution because the surface energy difference with the non-aqueous electrolyte solution is large and bonding with the electrolyte molecules is not easy.

The lipophilic material includes a polymer material such as polyvinyl difluoride (hereinafter referred to as PVdF), or a polymer compound containing a functional atomic group such as an ester group or a carboxy group. These lipophilic materials have good wettability and spreadability to the electrolyte, and have excellent affinity with the electrolyte. Therefore, when polyethylene or polypropylene is used as the material of the phase insulating plate 241, the surface of the phase insulating plate 241 may be coated with PVdF or the like to further improve the impregnation of the electrolyte. As a result of the impregnation of the electrolyte solution, PVdF 761 and PVdF 2801 were found to have good spreadability and wettability among the non-aqueous electrolyte solution. Therefore, as the coating material of the insulating plate, it is preferable to use any one of the above-mentioned PVdF 761, the PVdF 2801, the mixture of the PVdF 761 and the PVdF 2801. Such a coating for surface modification exhibits a sufficient effect even at a thickness within 1 μm, and a sufficient effect can be obtained with almost a monolayer.

In addition, when the material of the upper insulating plate is made of polyethylene, etc., it may be used by processing in the form of a compressed non-woven fabric to compensate for the poor affinity for the electrolyte. Nonwoven fabrics are made of felt in combination with fibers in a parallel or indefinite direction without a woven fabric process and combined with a synthetic resin adhesive, etc., and have a property of absorbing liquid well enough to be used in diapers, towels, and the like. By using a conventional non-woven fabric such as polyethylene (PE), polypropylene (PP) as it is processed by a compressed nonwoven fabric, the absorbing power to the electrolyte is increased to allow the electrolyte contained in the phase insulating plate to be impregnated into the electrode assembly.

FIG. 4A is a plan view of a lower insulating plate on which a checkerboard groove is formed, and FIG. 4B is a cross-sectional view taken along line C-C of FIG. 4A.

2 and 4A, the lower insulating plate 245 is positioned between the bottom plate 320 of the can and the lower portion of the electrode assembly 200. The lower insulating plate 245 prevents a short circuit that may occur between the electrode 300 and the can 300 including the lower plate 320 electrically connected to the electrode tab, for example, the negative electrode tab 225. . Referring to FIG. 4A, a hollow 248 is formed in the lower insulating plate 245 in contact with one end of the center pin.

The lower insulating plate 245 is formed with a checkerboard groove 246. The groove 246 may be formed only on a surface of the lower insulating plate 245 in contact with the lower side of the electrode assembly 200, or may be formed on both surfaces of the lower insulating plate 245 as shown in FIG. 4B. . The checkerboard-shaped grooves 246 communicate with each other so that portions of the checkerboard-shaped grooves 246 communicate with each other, so that the electrolyte may move to the entire grooves 246 formed in the lower insulation plate 245 even if only one of the grooves 246 flows. .

The lower insulating plate 245 is in close contact with the lower plate 320 of the electrode assembly 200 and the can. In addition, the material of the lower insulating plate 245 is typically polyethylene (PE) or polypropylene (PP), which is not familiar with the electrolyte. Therefore, when the surface of the lower insulating plate is flat, the electrolyte solution that has settled into the can hardly flows between the lower and lower insulating plates of the can and between the lower and lower insulating plates of the electrode assembly. As a result, the degree of impregnation of the electrolyte solution into the electrode assembly is reduced.

However, when the groove is formed on the surface of the lower insulating plate, the electrolyte flows into the groove, so that the electrolyte directly contacts the lower part of the electrode assembly, which is advantageous for impregnation of the electrolyte into the electrode assembly.

As in the case of the upper insulating plate 241 described above, in the case of the lower insulating plate 245, both a conventional hard solvent material and a solvent-soluble material can be used. At this time, in the case of using a poor solvent material such as polyethylene (PE), polypropylene (PP) as the material of the lower insulating plate 245, in order to further improve the impregnation of the electrolyte solution, the surface of the upper insulating plate 241 is It is preferable to coat with PVdF or the like. In this way, when the surface of the insulating plate is coated with a polymer material familiar with the electrolyte solution, the surface of the insulating plate is not exclusive to the electrolyte solution, so that the settling speed of the electrolyte solution and the impregnation rate of the electrolyte solution can be increased. Such a coating for surface modification exhibits a sufficient effect even at a thickness within 1 μm, and a sufficient effect can be obtained with almost a monolayer.

In addition, when the material of the lower insulating plate 245 is made of polyethylene or the like, in order to compensate for the fact that the affinity for the electrolyte is not good, as in the case of the upper insulating plate 241 described above, it may be used in the form of a compressed nonwoven fabric.

Referring to FIG. 2, the cylindrical can 300 may include a cylindrical side plate 310 having a predetermined diameter and a cylindrical side plate 310 to form a predetermined space in which the cylindrical electrode assembly 200 may be accommodated. When the lower surface plate 320 is formed to seal the lower portion, the upper portion of the cylindrical side plate 310 is opened to insert the electrode assembly 200. As the negative electrode tab 225 of the electrode assembly 200 is bonded to the center of the bottom plate 320 of the cylindrical can 300, the cylindrical can 300 itself serves as a negative electrode. In addition, the cylindrical can 300 is generally formed of aluminum (Al), iron (Fe) or an alloy thereof. In addition, the cylindrical can 300 is formed with a crimping portion 330 that is bent from the top to the top to press the upper portion of the cap assembly 400 coupled to the upper opening. In addition, the cylindrical can 300 is recessed inward to press the lower portion of the cap assembly 400 at a position spaced apart from the crimping portion 330 by a distance corresponding to the thickness of the cap assembly 400. Fine beading portion 340 is further formed.

2, the cap assembly 400 includes a safety vent 410, a current blocking means 420, a secondary protection element 480, and a cap up 490. The safety vent 410 has a plate-shaped protrusion projecting downward in the center thereof is located at the bottom of the cap assembly 400, the protrusion is deformed in the upper direction by the pressure generated inside the secondary battery. The positive electrode tab 215 drawn from the positive electrode plate 210 and the negative electrode plate 220 of the electrode assembly 200, for example, the positive electrode plate 210, is welded to a predetermined surface of the lower surface of the safety vent 410. The safety vent 410 and the positive electrode plate 210 of the electrode assembly 200 are electrically connected. Here, the other electrode plate, for example, the cathode, of the positive electrode plate 210 and the negative electrode plate 220 is electrically connected to the can 300 by a tab or direct contact method.

As described above, the present invention is not limited to the specific preferred embodiments described above, and any person having ordinary skill in the art to which the present invention pertains without departing from the gist of the present invention claimed in the claims. Various modifications are possible, of course, and such changes are within the scope of the claims.

According to the lithium secondary battery according to the present invention, the electrolytic solution inside the battery is formed by forming a structure capable of increasing the settling and impregnation rate of the electrolytic solution in the upper insulating plate and the lower insulating plate having a geometrical shape covering the entire upper and lower portions of the battery. Increased fluidity can improve the impregnation rate of the electrolyte solution with even impregnation, and as the impregnation of the electrolyte is improved, the impregnation process time, which takes up a large part of the overall process time, can be reduced, thereby improving productivity.

Claims (11)

A lithium secondary battery comprising an electrode assembly, a case accommodating the electrode assembly, a lower insulating plate positioned between the lower portion of the electrode assembly and the case, and a cap assembly sealing the case. At least one side of the lower insulating plate is a lithium secondary battery, characterized in that the groove of the checkerboard shape is formed. The method of claim 1, The material of the lower insulating plate is a lithium secondary battery, characterized in that polyethylene (PE) or polypropylene (PP). The method of claim 2, The lower insulating plate is a lithium secondary battery, characterized in that the compression nonwoven fabric. The method of claim 2, The lower insulating plate is a lithium secondary battery, characterized in that the surface is coated with polyvinyl difluoride (PVdF). The method of claim 4, wherein The polyvinyl difluoride (PVdF) is a lithium secondary battery, characterized in that any one of PVdF 761, PVdF 2801, a mixture of the PVdF 761 and PVdF 2801. An electrode assembly, a cylindrical case accommodating the electrode assembly, a lower insulating plate positioned between the electrode assembly and the cylindrical case, a cap assembly sealing the cylindrical case, and an upper insulating plate positioned between the electrode assembly and the cap assembly. In the cylindrical lithium secondary battery made of, A plurality of holes are formed in the upper insulating plate, and at least one side of the lower insulating plate is a cylindrical lithium secondary battery, characterized in that the groove is formed of a checkerboard shape. The method of claim 6, The hole of the phase insulating plate is a cylindrical lithium secondary battery, characterized in that formed in the form of a mesh (mesh). The method of claim 6, Cylindrical lithium secondary battery, characterized in that the material of the upper insulating plate and the lower insulating plate is polyethylene (PE) or polypropylene (PP). The method of claim 6, The upper insulating plate and the lower insulating plate is a cylindrical lithium secondary battery, characterized in that the surface is coated with polyvinyl difluoride (PVdF). The method of claim 9, The polyvinyl difluoride (PVdF) is a cylindrical lithium secondary battery, characterized in that any one of the mixture of PVdF 761, PVdF 2801, PVdF 761 and PVdF 2801. The method of claim 8, The upper insulating plate and the lower insulating plate is a cylindrical lithium secondary battery, characterized in that the compression nonwoven fabric.

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