KR101002509B1 - Lithium secondary battery - Google Patents

Abstract

The present invention relates to a lithium secondary battery, comprising a first electrode and a second electrode, a separator interposed therebetween, and an electrode including a first electrode tab and a second electrode tab respectively connected to the first electrode and the second electrode. Assembly; And an insulating case disposed on the electrode assembly and having a stepped portion to secure a space in which the bent electrode tab can be accommodated.

Lithium secondary battery, insulation case, step part, short circuit

Description

Lithium secondary battery

1 is a partial cross-sectional view showing a conventional lithium secondary battery.

Figure 2a is a perspective view of an insulating case of a lithium secondary battery according to an embodiment of the present invention.

FIG. 2B is a plan view of the insulating case shown in FIG. 2A. FIG.

Figure 3 is a partial cross-sectional view showing a lithium secondary battery according to an embodiment of the present invention.

<Description of the symbols for the main parts of the drawings>

70.Insulation case 71.Main body of insulation case

72.Step

73, 74.Short-side support of insulated case

75, 76 ... long side support of insulated case

77.Electrode tap outlet of insulated case

78.Electrode tab lead-out groove in insulated case

79.Electrolyte inlet in insulated case

10 ... can 12 ... electrode assembly

13 ... First electrode 14 ... Separator

15 ... Second electrode 16 ... First electrode tab                 

17.2nd electrode tab 20 ... cap assembly

30 ... electrode terminal 40 ... cap plate

41.Terminal injection 42.Electrolytic injection hole

43 ... plug 44 ... safety vent

46.Gasket 50.Insulation plate

60 ... terminal plate

The present invention relates to a lithium secondary battery, and more particularly, to a lithium secondary battery capable of preventing a short circuit of an electrode tab by securing a space in which a bent electrode tab can be accommodated.

As miniaturization and light weight of portable electronic devices have recently advanced, the necessity for miniaturization and high capacity of batteries used as driving power sources thereof is increasing. In particular, the lithium secondary battery has an operating voltage of 3.6 V or more, 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 devices, and is rapidly expanded in terms of high energy density per unit weight. There is a trend.

Lithium secondary batteries generate electrical energy by oxidation and reduction reactions when lithium ions are intercalated / deintercalated at the positive and negative electrodes. A lithium secondary battery is prepared by using a reversible insertion / desorption material of lithium ions as an active material of a positive electrode and a negative electrode, and by filling an organic electrolyte or a polymer electrolyte between the positive electrode and the negative electrode.

Lithium-containing metal oxides such as lithium cobalt oxide (LiCoO ₂ ), lithium nickel oxide (LiNiO ₂ ), and lithium manganese oxide (LiMnO ₂ ) are used as a cathode active material of a lithium secondary battery. Lithium metal or lithium alloy is used, but when lithium metal is used, there is a risk of explosion due to battery short circuit due to the formation of dendrite, and it is being replaced by carbon-based materials such as amorphous carbon or crystalline carbon instead of lithium metal. Lithium secondary batteries are produced in various shapes, and typical shapes include cylindrical, square, and pouch types.

1 is a partial cross-sectional view showing a conventional lithium secondary battery.

Referring to FIG. 1, in a lithium secondary battery, an electrode assembly 12 including a first electrode 13, a second electrode 15, and a separator 14 is accommodated in a can 10 together with an electrolyte solution. It is formed by sealing the upper end of the (10) with the cap assembly (20). The cap assembly 20 includes a cap plate 40, an insulating plate 50, a terminal plate 60, and an electrode terminal 30. The cap assembly 20 is insulated from the electrode assembly 12 by a separate insulating case 70 to be coupled to the upper opening of the can 10 to seal the can 10.

The electrode terminal 30 is inserted into the terminal through-hole 41 formed in the center of the cap plate 40. When the electrode terminal 30 is inserted into the terminal through-hole 41, the tubular gasket 46 is coupled to the outer surface of the electrode terminal 30 and inserted together to insulate the electrode terminal 30 and the cap plate 40. . After the cap assembly 20 is assembled to the upper end of the can 10, the electrolyte is injected through the electrolyte injection hole 42, and the electrolyte injection hole 42 is closed by a stopper 43.

The electrode terminal 30 is one of the second electrode tab 17 of the second electrode 15 and the first electrode tab 16 of the first electrode 13, for example, the second electrode tab 17. ) Is electrically connected to and serves as a second electrode. The electrode tab, for example, the first electrode tab 16, which is not electrically connected to the electrode terminal 30, is connected to the lower surface of the cap plate 40 so that the can 10 serves as the first electrode.

The second electrode tab 17 or the first electrode tab 16 electrically connected to the electrode terminal 30 in the lithium secondary battery is welded to the terminal plate 60 and then bent at a predetermined position to form a can ( 10) is inserted. However, when the bent electrode tab electrically connected to the electrode terminal 30 is inserted into the can 10 and then contacts the inner surface of the can 10 or the cap assembly 20, a short circuit of the battery occurs. The temperature of the silver battery may rise abnormally, which may cause serious problems in the stability of the battery.

The present invention is to solve the above problems, an object of the present invention is provided with an insulating case having a stepped portion is formed to secure a space in which the bent electrode tab can be accommodated, the bent electrode tab is different It is to provide a lithium secondary battery that can prevent a short circuit by contacting the inside of the can having a polarity.

In order to achieve the above object, the lithium secondary battery of the present invention includes a first electrode and a second electrode, a separator interposed therebetween, and a first electrode tab and a second electrode connected to the first electrode and the second electrode, respectively. An electrode assembly comprising a tab; And an insulating case positioned on the electrode assembly and having a stepped portion formed to secure a space in which the bent electrode tab can be accommodated.

The step between the step portion and the periphery is preferably formed within 50% of the thickness of the insulating case.

In addition, the insulating case is preferably made of an insulating polymer resin.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the accompanying drawings.

2A is a perspective view of an insulating case of a rechargeable lithium battery according to one embodiment of the present invention. FIG. 2B is a plan view of the insulating case illustrated in FIG. 2A.

2A and 2B, an insulating case 70 of a lithium secondary battery according to an exemplary embodiment of the present invention may include a main body 71 having a stepped portion 72, and short side support portions 73 and 74. And long side supports 75 and 76.

The main body 71 is a flat plate having a shape and a size corresponding to the opening of the can of the lithium secondary battery, and electrically insulates the electrode assembly and the cap assembly. The outer surface of the main body portion 71 is preferably in contact with the inner wall of the can to be sealed.                     

The body portion 71 is formed with a stepped portion 72 for securing a space for accommodating the bent electrode tab. The step between the step portion 72 and the periphery is preferably formed within 50% of the thickness of the body portion 71 of the insulating case 70 in which the step portion is formed, and is formed within 25%. More preferred. As the step difference between the step portion 72 and the periphery increases, more space can be obtained for the electrode tabs to be bent. However, if the step level is excessively increased, the strength of the insulating case is lowered, causing the battery to fall. It is easy to deform when a physical shock such as a test is applied. Therefore, according to the material of the insulating case, it is preferable to select a suitable step within a range that minimizes the strength degradation of the insulating case.

The position and area where the step portion 72 is formed may be formed at a predetermined area at any position of the main body portion 71, and at least in an area capable of covering the electrode tab bent in the vicinity of the electrode tab. It is preferable to form over. When the formation area of the step portion 72 becomes too large, there is a fear that the strength of the insulating case is lowered.

Short side support portions 73 and 74 are formed on the short side surface portion of the main body portion 71. The short side support parts 73 and 74 protrude a predetermined height upward along the short side edge of the main body part 71. The short side support parts 73 and 74 support the main body part 71 more stably, and increase adhesion to the inner wall of the can when the insulating case 70 is accommodated in the can. The flow of can be suppressed.

In addition, at least one long side support part 75, 76 may be formed on the long side face of the main body part 71. The long side support parts 75 and 76 protrude a predetermined height upward from a predetermined position of the long side face of the main body part 71, and preferably have the same height as the short side support parts 73 and 74. The long side support portions 75 and 76 reinforce the strength of the long side surface portion, which is weaker than the short side surface portion of the main body portion 71, and deforms the main body portion 71 when a physical shock is applied to the battery. You can prevent it.

Preferably, the short side support parts 73 and 74 and the long side support parts 75 and 76 are integrally formed with the main body part 71.

The main body portion 71 is formed with an electrode tab outlet 77 through which the electrode tab can be drawn out on one side, and an electrolyte inlet 79 that provides a path for the electrolyte to flow into the electrode assembly on the other side. It is. The long side surface portion of the body portion 71 is formed with an electrode tab extracting groove 78 having a predetermined width through which other electrode tabs can be drawn out.

3 is a partial cross-sectional view of a rechargeable lithium battery according to one embodiment of the present invention.

Referring to FIG. 3, a lithium secondary battery includes a can 10, an electrode assembly 12 accommodated in the can 10, and a cap assembly 20 coupled to an upper portion of the can 10. Is formed.

The can 10 is formed of a substantially rectangular metal material having an open top, and is preferably formed of light and ductile aluminum or aluminum alloy, stainless steel, etc., but is not limited thereto. The can 10 may itself serve as a terminal.

The electrode assembly 12 includes a first electrode 13, a second electrode 15, and a separator 14. The first electrode 13 and the second electrode 15 may be stacked through a separator 14 and then wound in a jelly-roll form. The first electrode tab 16 is connected to the first electrode 13, and the second electrode tab 17 is electrically connected to the second electrode 15 by welding or conductive adhesive such as laser welding, ultrasonic welding, or resistance welding. They are attached so as to be possible, and are drawn out upwards, respectively.

The first electrode 13 and the second electrode 15 may be different in polarity from each other and may be used as an anode or a cathode. The first electrode 13 and the second electrode 15 include a current collector and an electrode active material applied to at least one surface of the current collector, that is, a positive electrode active material or a negative electrode active material.

When the first electrode 13 or the second electrode 15 is used as an anode, as the electrode current collector, carbon, nickel, titanium on the surface of stainless steel, nickel, aluminum, titanium or alloys thereof, aluminum or stainless steel The surface-treated with silver, etc. can be used, Among these, aluminum or an aluminum alloy is preferable. When the first electrode 13 or the second electrode 15 is used as a cathode, as the electrode current collector, carbon, nickel, titanium on the surface of stainless steel, nickel, copper, titanium or alloys thereof, copper or stainless steel The surface treated with silver, etc. can be used, Among these, copper or a copper alloy is preferable.

As the cathode active material, a lithium-containing transition metal oxide or a lithium chalcogenide compound may be used, and representative examples thereof may be LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , or LiNi _1-xy Co _x M Metal oxides such as _y O ₂ (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1, and M is a metal of Al, Sr, Mg, La, etc.) may be used. As the negative electrode active material, a carbon material such as crystalline carbon, amorphous carbon, carbon composite, carbon fiber, lithium metal, lithium alloy, or the like may be used.

The separator 14 prevents a short circuit between the first electrode 13 and the second electrode 15 and provides a migration path for lithium ions. The separator 14 may be a polyolefin polymer membrane such as polypropylene or polyethylene, or a multilayer thereof. Known ones such as microporous films, woven fabrics and nonwovens can be used.

The cap assembly 20 coupled to the upper portion of the can 10 includes a cap plate 40, an insulation plate 50, a terminal plate 60, and an electrode terminal 30. The cap plate 40 is formed of a metal plate having a size and shape corresponding to the top opening of the can 10. The terminal plate hole 41 of a predetermined size is formed in the center of the cap plate 40, the electrolyte injection hole 42 is formed on one side, the electrolyte is injected through the electrolyte injection hole 42 and then the electrolyte injection The ball 42 is combined with the stopper 43 to be sealed.

An electrode terminal 30 is inserted into the terminal through-hole 41, and a tube-shaped gasket 46 is installed on an outer surface of the electrode terminal 30 to electrically insulate the cap plate 40. An insulating plate 50 is provided on the lower surface of the cap plate 40, and a terminal plate 60 is disposed on the lower surface of the insulating plate 50. The bottom portion of the electrode terminal 30 is electrically connected to the terminal plate 60 in a state of interposing the insulating plate 50.

The first electrode tab 16 is welded to the bottom surface of the cap plate 40, and the second electrode tab 17 is welded to the terminal plate 60. The first electrode tab 16 and the second electrode tab 17 are made of nickel metal.

An upper portion of the electrode assembly 12 electrically insulates the electrode assembly 12 from the cap assembly 20, and the electrode assembly 12, the first electrode tab 16, and the second electrode tab 17. An insulating case 70 for fixing the position of the is provided. The insulating case 70 includes a stepped portion 72 formed around the second electrode tab 17 welded to the terminal plate 60 through the electrode tab outlet of the insulating case. The stepped portion 72 provides more space for accommodating the bent second electrode tab 17 so that the bent second electrode tab 17 has a different polarity. Can be prevented from contacting

The insulating case 70 is preferably made of an insulating polymer resin. As the insulating polymer resin, polypropylene (PP), polyphenylenesulfide (PPS), polyethersulfone (PES), modified polyphenylene oxide (PPO), or the like may be used. PPS is excellent in heat resistance, dimensional stability, chemical resistance, low absorption and flame retardancy, and has little change in electrical characteristics corresponding to temperature change. PES is a non-crystalline aromatic plastic resin and has a heat resistance of 200 ° C and is excellent in dimensional stability and water resistance. In addition, PES has good transparency, high glass transition temperature (T _g : 223 ° C.), low expansion (CTE: 2.3 × 10 ⁻⁵ / ° C.), and excellent mechanical strength. Modified PPO has excellent mechanical properties, heat resistance, small deterioration of physical properties even at low temperatures, small molding shrinkage, and flame retardant resin.

Although the present invention has been described with reference to the above embodiments, it is merely illustrative, and those skilled in the art will understand that various modifications and equivalent other embodiments are possible therefrom. . Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

As described above, a lithium secondary battery including an insulating case having a stepped portion for securing a space for accommodating a bent electrode tab according to the present invention may be formed in a can of which the bent electrode tab has a different polarity. It is possible to prevent the short circuit by contact.

Claims (9)

An electrode assembly including a first electrode and a second electrode, a separator interposed therebetween, and a first electrode tab and a second electrode tab connected to the first electrode and the second electrode, respectively; And And an insulating case disposed on the electrode assembly and having a stepped portion formed to secure a space in which the bent electrode tab can be accommodated. The lithium secondary battery according to claim 1, wherein the step between the stepped part and the periphery is formed within 50% of the thickness of the insulating case. The lithium secondary battery of claim 2, wherein the step between the stepped part and the periphery is formed within 25% of the thickness of the insulating case. The lithium secondary battery of claim 1, wherein the stepped portion is formed over an area capable of covering at least the bent electrode tab. The lithium secondary battery of claim 1, wherein the insulating case is made of an insulating polymer resin. The lithium secondary battery of claim 5, wherein the insulation case is polypropylene. The lithium secondary battery according to claim 5, wherein the insulating case is polyphenylene sulfide. The lithium secondary battery according to claim 5, wherein the insulating case is a polyether sulfone. The lithium secondary battery according to claim 5, wherein the insulating case is a modified polyphenylene oxide.

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