KR20160048324A - Secondary battery and manufacturing method thereof - Google Patents

Abstract

Provided is a secondary battery capable of preventing durability degradation caused by electrolyte depletion by processing a charging/discharging cycle and neglecting for a long period of time. According to the present invention, the secondary battery comprises: an electrode assembly including a positive electrode, a negative electrode, and a separator, and having an electrolyte immersed therein; a case for receiving the electrode assembly; and an electrolyte storage member received in the case, and supplying the electrolyte to the electrode assembly.

Description

TECHNICAL FIELD [0001] The present invention relates to a secondary battery and a method of manufacturing the same,

The present invention relates to a secondary battery and a method of manufacturing the same. More particularly, the present invention relates to a secondary battery including an electrolyte solution supply member, which can improve an endurance life and charge / discharge efficiency of a secondary battery by utilizing an inactive space formed in the secondary battery case, and a method of manufacturing the same.

Recently, rechargeable secondary batteries have attracted attention as energy sources for electric vehicles and hybrid electric vehicles, which are proposed as solutions for air pollution such as wireless mobile devices, existing gasoline vehicles using diesel fuel, and diesel vehicles. . Therefore, the application of the secondary battery is diversified due to the advantages of the secondary battery, and it is expected that the secondary battery will be applied to many fields and products in the future.

Such a lithium secondary battery uses a lithium-based oxide as a cathode active material and a carbonaceous material as an anode active material. Generally, a battery using a liquid electrolyte is referred to as a lithium ion battery, and a battery using a polymer electrolyte is referred to as a lithium polymer battery, which is classified as a liquid electrolyte cell and a polymer electrolyte cell, depending on the type of the electrolyte. In addition, the lithium ion secondary battery is manufactured in various shapes. Typical shapes include a cylindrical shape, a square shape, and a pouch shape.

On the other hand, in manufacturing a secondary battery, accumulating a lot of electricity in a battery having a small volume and weight is the most important target, and increasing the power amount per unit time, that is, power is also an important problem depending on the field of use of the battery. In order to expand electric power, it is necessary to increase the area of the electrode active material contacting the electrolyte. Normally, the active material is coated broadly on the electrode plate in order to increase the surface area of the active material and to increase the ratio of the active material contributing to the amount of electric power.

FIG. 1 illustrates a structure of a conventional secondary battery, and FIG. 3 illustrates a cross-sectional view of the secondary battery. 1 and 3, a conventional secondary battery 100 includes an electrode assembly 20 including an anode 10, a cathode 12, and a separator 14 and impregnated with an electrolyte solution. An internal space (62) in which the electrode assembly (20) is received; And a sealing region (C) formed on an outer circumferential surface of the inner space (62).

The positive electrode 10 and the negative electrode 12 coated with the active material can be wound in a roll form to form the secondary battery into a small volume. As shown in FIG. 1, a plurality of electrodes are alternately stacked in accordance with the polarity, and the laminated state is referred to as " jelly roll ", and electrode plates of the same polarity are electrically connected together. An electrode may be formed. At this time, the separator 14 is interposed between the electrodes of different polarity and the electrodes to prevent the internal short circuit. A sealing member 22 (see FIG. 1) for holding the jelly roll shape is formed on the outer peripheral surface of the electrode assembly 20 Is attached. For example, it may be a fixed tape.

The positive electrode lead portion 40a and the negative electrode lead portion 40b are bonded to the positive electrode tab 44a and the negative electrode tab 44b and to the positive electrode tab 44a and the negative electrode tab 44b, Wherein the positive electrode lead 44a and the negative electrode tab 44b are connected to the positive electrode lead 48a and the negative electrode lead 48b which are connected to the positive electrode lead 48a and the negative electrode lead 48b, (46a) and a second joint (46b). An insulating tape made of polyimide or the like is usually attached to the first and second joints 46a and 46b for the purpose of preventing a short circuit.

At this time, the inner space 62 of the case 60 includes an active area A where the electrode assembly 20 is located; And the inactive region B including the positive electrode lead portion 40a and the negative electrode lead portion 40b protruding from the positive electrode 10 and negative electrode 12 of the electrode assembly 20 and extending outside the case 60 The inactive region (B) is an inactive space that can not contribute to the capacity of the battery, but must be secured inevitably.

As the secondary battery continues to charge / discharge, the electrolyte is consumed and the available secondary battery is insufficiently charged. As a result, the life of the secondary battery is shortened and the charging / discharging efficiency of the secondary battery is lowered .

Korean Utility Model Publication No. 20-1998-0021641

SUMMARY OF THE INVENTION It is an object of the present invention to provide a secondary battery capable of improving durability degradation due to electrolyte depletion due to the progress of charge / discharge cycles and long-term storage.

Another object of the present invention is to provide a secondary battery which is excellent in economical efficiency and can secure structural stability while preventing short-circuiting of electrode materials.

It is still another object of the present invention to provide a method for manufacturing the secondary battery.

One aspect of the present invention relates to a secondary battery. The secondary battery includes an electrode assembly including an anode, a cathode, and a separator, the electrolyte being impregnated with the electrolyte; A case for accommodating the electrode assembly; And an electrolyte storage member accommodated in the case and supplying an electrolyte solution to the electrode assembly.

In one embodiment, the secondary battery further includes a cathode lead portion and a cathode lead portion protruding from the anode and the cathode, respectively, and extending to the outside of the case.

In one embodiment, the positive electrode lead portion includes a positive electrode tab tangent to the positive electrode; And a positive electrode lead which is joined to the positive electrode tab and extends to the outside of the case, wherein the negative electrode lead portion includes a negative electrode tab which is in contact with the negative electrode; And a negative electrode lead joined to the negative electrode tab and extending to the outside of the case, wherein the positive electrode tab and the positive electrode lead are joined through a first joint, the negative electrode tab and the negative electrode lead are joined through a second joint, The electrolyte storage member is formed in contact with the first junction and the second junction, and the electrolyte storage member includes a porous polymer, and the electrolyte can be contained in the pores of the porous polymer.

In one embodiment, the porous polymer may have a melting point (Tm) of 150 ° C to 250 ° C.

In one embodiment, the porous polymer may comprise at least one of polymethyl methacrylate, polycarbonate, polyvinyl chloride, polyethylene and polypropylene.

In one embodiment, the porosity of the porous polymer may be 20% to 60% and the average pore size may be 50 to 800 μm.

In one embodiment, the weight ratio of the electrolytic solution impregnated in the electrode assembly to the electrolytic solution contained in the electrolyte storage member may be 1: 0.1-0.7.

Another aspect of the present invention relates to a method of manufacturing the secondary battery. The method for manufacturing a secondary battery includes the steps of: placing an electrolyte storage member in an internal space of a case accommodating an electrode assembly including an anode, a cathode, and a separator; Injecting an electrolyte into the space inside the case to impregnate the electrode assembly and the electrolyte storage member with the electrolyte solution; And sealing the case.

In one embodiment, the secondary battery further includes a cathode lead portion and a cathode lead portion protruding from the anode and the cathode, respectively, and extending to the outside of the case.

In one embodiment, the positive electrode lead portion includes a positive electrode tab tangent to the positive electrode; And a positive electrode lead which is joined to the positive electrode tab and extends to the outside of the case, wherein the negative electrode lead portion includes a negative electrode tab which is in contact with the negative electrode; And a negative electrode lead joined to the negative electrode tab and extending to the outside of the case, wherein the positive electrode tab and the positive electrode lead are joined through a first joint, the negative electrode tab and the negative electrode lead are joined through a second joint, The electrolyte storage member is formed in contact with the first junction and the second junction, and the electrolyte storage member includes a porous polymer, and the electrolyte can be contained in the pores of the porous polymer.

In one embodiment, the porous polymer may have a melting point (Tm) of 150 ° C to 250 ° C.

In one embodiment, the porous polymer may comprise at least one of polymethylmethacrylate, polyvinyl chloride, polycarbonate, polyethylene and polypropylene.

In one embodiment, the porous polymer The porosity may be from 20% to 60%, and the average pore size may be from 50 μm to 800 μm.

In one embodiment, the weight ratio of the electrolytic solution impregnated in the electrode assembly to the electrolytic solution contained in the electrolyte storage member may be 1: 0.1-0.7.

The secondary battery according to the present invention can further improve the service life deterioration due to the depletion of the electrolyte due to the progress of the charge / discharge cycle and the long-term storage of the secondary battery by further providing the electrolyte solution supply member therein without changing the outer dimensions of the secondary battery case , It is possible to secure the structural stability while being excellent in economy and preventing expansion of the secondary battery and short-circuiting of the electrode material.

1 shows a structure of a conventional secondary battery.
2 illustrates a structure of a secondary battery according to an embodiment of the present invention.
3 is a cross-sectional view of a conventional secondary battery.
4 is a cross-sectional view of a secondary battery according to an embodiment of the present invention.
5 is a graph comparing changes in capacity retention rate with increase in charge / discharge cycles of a secondary battery according to an embodiment of the present invention and a comparative example according to the present invention.

In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.

As used herein, the term " secondary battery " may include a " lithium secondary battery ", which is defined as including lithium ion, lithium polymer, and lithium ion polymer secondary battery as well as a secondary battery using lithium metal .

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

One aspect of the present invention relates to a secondary battery. FIG. 2 illustrates a structure of a secondary battery according to one embodiment of the present invention, and FIG. 4 illustrates a cross section of the secondary battery. Referring to FIGS. 2 and 4, the secondary battery 200 of the present invention includes an electrode assembly 20 including an anode 10, a cathode 12, and a separator 14 and impregnated with an electrolyte solution. A case 60 for accommodating the electrode assembly 20; And an electrolyte storage member (50) accommodated in the case (60) and supplying an electrolyte solution to the electrode assembly (20).

Electrode assembly

2 and 4, the electrode assembly 20 includes an anode 10, a cathode 12, and a separator 14, and an electrolyte is impregnated.

In an embodiment of the present invention, the anode 10 comprises a positive electrode collector; And a cathode active material. In another embodiment, the anode 10 comprises a positive electrode collector; Polarity transfer; And a positive electrode binder and a positive electrode active material.

The positive electrode current collector may be formed by treating carbon, nickel, or titanium on the surface of copper or stainless steel in addition to stainless steel, aluminum, nickel, iron, copper, titanium, Mesh or the like can be used.

The cathode active material may be any conventional one. For example, LiCoO ₂ , LiNi _(1-x) M _x O ₂ (x is 0.95 to 1, M is Al, Co, Ni, Mn or Fe), or LiMn ₂ O ₄ .

The positive electrode electric conductor may be a carbon-based material such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black or carbon fiber; Metal powder or metal fibers such as copper, nickel, aluminum and silver; Polyphenylene derivatives, and the like can be used. One of them may be used alone or a mixture of two or more of them may be used.

The positive electrode binder may be selected from the group consisting of vinylidene fluoride / hexafluoropropylene copolymer (VDF / HFP), polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polymethylmethacrylate (PMMA) Ethylene (PTFE) or the like can be used. These may be used alone or in combination of two or more. As the solvent used for the positive electrode binder, water and an organic solvent may be used, but the present invention is not limited thereto. Examples of the organic solvent include, but are not limited to, NMP (N-methylpyrrolidone), DMF (dimethylformamide), acetone, and dimethylacetamide.

In the embodiment of the present invention, the cathode 12 may include a negative electrode collector and a negative electrode active material. In another embodiment, the cathode 12 may include a negative electrode collector, a negative electrode collector, a negative electrode active material, and a negative electrode binder.

Examples of the negative electrode conductive material include acetylene black, carbon black, and graphite.

As the negative electrode active material, various types of carbon-based or silicon-based materials including artificial graphite, natural graphite, and hard carbon capable of lithium insertion and desorption can be used.

The negative electrode binder may be selected from the group consisting of vinylidene fluoride / hexafluoropropylene copolymer (VDF / HFP), polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polymethylmethacrylate (PMMA) Ethylene (PTFE) or the like can be used. These may be used alone or in combination of two or more. Examples of the solvent used in the negative electrode binder include, but are not limited to, water and an organic solvent. Examples of the organic solvent include, but are not limited to, NMP (N-methylpyrrolidone), DMF (dimethylformamide), acetone, and dimethylacetamide.

The separator 14 may be any conventional one. For example, olefin-based polymers such as polypropylene having chemical resistance and hydrophobic properties; Sheet or nonwoven fabric made of glass fiber or polyethylene can be used.

As the electrolyte solution in the present invention, a conventional one can be used. For example, A ⁺ B ^- A salt of the structure such as the A ⁺ is Li ^+, the B, and including an alkali metal cation or an ion composed of a combination thereof, such as Na ⁺ and K ^{+ -} is PF ₆ ^{- _{, BF 4 -, Cl -,}} Br -, I -, ClO 4 -, AsF 6 -, CH 3 CO 2 -, CF 3 SO 3 -, N (CF 3 SO 2) 2- and C (CF ₂ SO ₂ ) ^3-, and an ion including an ion such as anion such as propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate carbonate, DMC), dipropyl carbonate (DPC), dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran, N-methyl-2-pyrrolidone (NMP), ethyl methyl carbonate (NMP) EMC), gamma-butyrolactone, or a mixture thereof, and dissolving and dissociating it in an organic solvent may be used.

In the present invention, the electrode assembly 14 may be in the form of a jelly roll, a stack, or a stack / folding configuration. For example, as a jelly roll structure.

The electrode assembly 20 can be manufactured by winding the separator 14 between the anode 10 and the cathode 12 and the separator 14 between the anode 10 and the cathode 12 . The separator 14 may be provided not only between the positive electrode 10 and the negative electrode 12 but also between the positive electrode 10 and the negative electrode 12 in a state where the positive electrode 10 and the negative electrode 12 are not wound, Can be intervened. When the positive electrode 10 and the negative electrode 12 are wound together with the separator 14 as described above, the negative electrode 12 or the positive electrode 10 and the negative electrode 12, It is possible to prevent contact. Referring to FIG. 2, a sealing member 22 for holding a jelly roll shape may be attached to an outer circumferential surface (outermost portion) of the electrode assembly 20 in the form of a jelly roll. In a specific example, the sealing member 22 may use a polymer insulating tape in the form of a mesh for impregnating the electrolyte easily.

2 and 4, in the embodiment of the present invention, the secondary battery 200 includes a positive electrode lead portion protruding from the positive electrode 10 and a negative electrode 12 and extending to the outside of the case 60 40a and a negative electrode lead portion 40b.

4, the positive electrode lead portion 40a includes a positive electrode tab 44a contacting the positive electrode 10 and a positive electrode lead 46a joined to the positive electrode tab 44a and extending to the outside of the case 60 The negative electrode lead portion 40b includes a negative electrode tab 44b contacting the negative electrode 12; And a negative electrode lead 46b which is joined to the negative electrode tab 44b and extends to the outside of the case 60. [

case

2 and 4, the case 60 includes an internal space 62 in which the electrode assembly 20 is received. The electrode assembly 20 and the electrolyte storage member 50 are placed in the inner space 62 of the case 60 and the upper and lower surfaces of the case are covered with the outer peripheral surface of the inner space 62, To form a sealing region (C).

2 and 4, the range of the case 60 of the present invention includes the internal space 62 and the sealing region C formed on the outer peripheral surface of the internal space 62, and the internal space 62 ) Includes an active region (A) where the electrode assembly (20) is located; And an inactive region (B) including a positive electrode lead portion (40a) and a negative electrode lead portion (40b) protruding from the positive electrode (10) and the negative electrode (12) of the electrode assembly (20) and extending outside the case (60); . ≪ / RTI >

4, in one embodiment, in order to increase the degree of sealing with the case 60 and to secure an electrically insulated state, a portion of the upper and lower surfaces of the positive electrode lead 48a and the negative electrode lead 48b, The first insulating film 42a and the second insulating film 42b may be attached.

In the embodiment, the first insulating film 42a and the second insulating film 42b may be made of polypropylene (PP), polyethylene terephthalate (PET), or polyimide (PI).

In the present invention, the case 60 may be made of a common material. For example, an outer resin layer; An adhesive layer; And an inner metal layer formed on the inner surface of the laminate sheet. A polyethylene terephthalate outer resin layer in the embodiment; An unoriented polypropylene adhesive layer; And an aluminum inner metal layer may be used as the case of the aluminum laminate sheet.

In the present invention, the case 60 may be a conventional one. For example, it can be a cylindrical shape using a can, a square shape, a pouch shape, a coin shape, or the like. In embodiments, a pouch type may be used.

The electrolyte storage member

The electrolytic solution is stored in the electrolyte storage member 50, and the electrolytic solution is supplied to the electrode assembly to secure the insulation of the life electrode of the secondary battery, the deterioration of the service life due to the depletion of the electrolyte due to the progress of the charge / The structural stability of the secondary battery can be secured. Here, the " accommodation " may mean that the electrolyte is " housed " in the inner space of the electrolyte storage member or " impregnated " into the electrolyte storage member.

2 and 4, the electrolyte storage member 50 is located in the inactive region B, and can supply the electrolyte solution to the electrode assembly.

When the electrolyte storage member 50 is provided in the inactive region B as described above, it is possible to utilize a space inevitably secured inside the secondary battery without enlarging the outer dimensions of the secondary battery case 60, And thus the secondary battery is prevented from short-circuiting and the structural stability is secured.

In one embodiment, the electrolyte storage member 50 has a hollow shape to form an inner space, and the inner space may be filled with an electrolyte.

In another embodiment, the electrolyte storage member 50 has a porous form, a space is formed by the pores, and the space formed by the pores may be filled with the electrolyte.

In an embodiment, the electrolyte storage member 50 may be made of a porous polymer material. In this case, the electrolyte is contained in the pores formed in the porous polymer, and the electrolyte solution contained in the pores can be supplied to the electrode assembly. When the electrolyte storage member is used, the electrolyte solution stored in the pores can be easily moved to the electrode assembly, and the storage efficiency and storage stability of the secondary battery, the cathode lead portions 40a and 40b located in the inactive region B, The short circuit preventing effect of the negative electrode lead portion 40b can be excellent at the same time.

The porosity of the porous polymer may be 20% to 60%, and the average pore size may be 50 μm to 800 μm. In the above-described porosity and pore size, the storage efficiency of the electrolyte and the structural stability of the secondary battery are excellent at the same time. When the secondary battery is overcharged due to abnormal behavior such as gasification of the electrolyte or electrode active material, , The battery can be easily discharged to the outside through the electrolyte storage member 50 by using the elevated pressure inside the secondary battery. For example, the porosity of the porous polymer may be 35% to 50% and the average pore size may be 400 [mu] m to 700 [mu] m.

In embodiments, the electrolyte storage member 50 may be polyhedral or cylindrical. For example, it may be a rectangular parallelepiped shape as shown in Fig.

In an embodiment, the electrolyte storage member 50 may use a polymer having a melting point (Tm) of 150 ° C to 250 ° C. The storage efficiency of the electrolyte and the structural stability of the secondary battery can be excellent at the melting point.

In one embodiment, the porous polymer includes at least one of poly (methyl methacrylate), polycarbonate, polyvinyl chloride, polyethylene, and polypropylene. . When the porous polymer is used, the insulating property, the electrolyte storage efficiency, and the structural stability of the secondary battery can be excellent at the same time.

2 and 4, in the secondary battery 200 according to the embodiment of the present invention, the positive electrode tab 44a and the positive electrode lead 48a are bonded to each other through the first joint 46a, 44b and the negative electrode lead 48b may be joined through the second joint portion 46b.

In some embodiments, insulating tape (not shown) may be formed on the upper and lower surfaces of the first and second joints 46a and 46b. As the material of the insulating tape, a usual one can be used. In an embodiment, the insulating tape may be made of polypropylene (PP), polyethylene terephthalate (PET), or polyimide (PI).

Referring to FIG. 4, the electrolyte storage member 50 may be formed in contact with the first and second joint portions 46a and 46b.

In this specification, the " contact " is formed by inserting the first junction 46a and the second junction 46b into the electrolyte storage member 50 as shown in FIG. 4 or by inserting the first junction 46a and the second junction 46b on one surface of the electrolyte storage member 50 It may mean that the first joint portion 46a and the second joint portion 46b are formed in close contact with each other.

When the electrolyte storage member 50 is in contact with the first and second joint portions 46a and 46b as described above, it is possible to prevent a short circuit easily without attaching the insulating tape.

In a specific example, the weight ratio of the electrolytic solution impregnated in the electrode assembly 20 and the electrolytic solution stored in the electrolytic solution storage member 50 may be 1: 0.1-0.7. For example, it may be 1: 0.15 to 0.5. It is possible to efficiently use the inactive region (B) while preventing deterioration of the performance of the secondary battery in the weight ratio, and the storage efficiency of the electrolytic solution and the structural stability of the secondary battery can be excellent at the same time.

In one embodiment, the first junction 46a and the second junction 46b may be formed in a conventional manner. The first bonding portion 46a and the second bonding portion 46b can be formed by ultrasonically welding the positive electrode tab 44b and the negative electrode tab 44b and the positive electrode lead 48a and the negative electrode lead 48b.

Another aspect of the present invention relates to a method of manufacturing the secondary battery. The method for manufacturing the secondary battery includes the steps of: (a) positioning an electrode assembly and an electrolyte storage member; (b) an electrolyte injection step; And (c) a case sealing step. More particularly, the present invention relates to a method of manufacturing an electrode assembly, the method comprising: positioning an electrolyte storage member in an internal space of a case accommodating an electrode assembly including an anode, a cathode, and a separator; Injecting an electrolyte into the space inside the case to impregnate the electrode assembly and the electrolyte storage member with the electrolyte solution; And sealing the case.

Hereinafter, a method of manufacturing a secondary battery according to the present invention will be described in detail.

(a) Electrolyte storage member position step

This step is to place the electrolyte storage member 50 in the inner space 62 of the case 60 in which the electrode assembly 20 including the anode 10, the cathode 12 and the separator 14 is accommodated.

2 and 4, the inner space 62 of the case 60 in which the electrode assembly 20 is placed is divided into an active area A where the electrode assembly 20 is located and an electrode assembly 20 And an inactive region B including a positive electrode lead portion 40a and a negative electrode lead portion 40b which protrude from the positive electrode 10 and the negative electrode 12 of the case 60 and extend to the outside of the case 60, The storage member 50 is located in the inactive region B of the case interior space 62. [

In the present invention, the electrode assembly 20 can be manufactured by a conventional method. In one embodiment, the anode includes (10) a cathode slurry prepared by mixing the cathode active material, the anode conductive material, and the cathode binder with the solvent, and then applying the cathode slurry on at least one surface of the cathode current collector To form an active material coating layer.

In one embodiment, the negative electrode 12 is prepared by mixing the negative electrode active material and the negative electrode binder with a solvent to prepare a negative electrode slurry, coating the negative electrode slurry on at least one surface of the negative electrode collector, and drying the negative electrode active material coating layer Can be manufactured.

When the positive electrode 10, the negative electrode 12 and the separator 14 are provided as described above, the separator 14 is interposed between the positive electrode 10 and the negative electrode 12, A roll-shaped electrode assembly 20 can be manufactured. The positive electrode 10 and the negative electrode 12 may be interposed not only between the positive electrode 10 and the negative electrode 12 but also outside the positive electrode 10 and the negative electrode 12 in another embodiment. Therefore, when the positive electrode 10 and the negative electrode 12 are wound together with the separator 14, the positive electrode 10 or the negative electrode 12 or the positive electrode 10 and the negative electrode 12, It is possible to prevent contact. A sealing member 22 for holding a jelly roll shape may be attached to the outer circumferential surface (outermost portion) of the electrode assembly 20 in the form of a jelly roll.

2 and 4, in the embodiment of the present invention, the secondary battery 200 includes a positive electrode lead portion 40a protruding from the positive electrode 10 and the negative electrode 12 and extending to the outside of the case 60, And a negative electrode lead portion 40b.

4, the positive electrode lead portion 40a includes a positive electrode tab 44a contacting the positive electrode 10 and a positive electrode lead 46a joined to the positive electrode tab 44a and extending to the outside of the case 60 The negative electrode lead portion 40b includes a negative electrode tab 44b contacting the negative electrode 12; And a negative electrode lead 46b which is joined to the negative electrode tab 44b and extends to the outside of the case 60. [

2 and 4, in the secondary battery 200 according to the embodiment of the present invention, the positive electrode tab 44a and the positive electrode lead 48a are bonded through the first joint 46a, The tab 44b and the negative electrode lead 48b may be joined through the second joint 46b.

In some embodiments, insulating tape (not shown) may be formed on the upper and lower surfaces of the first and second joints 46a and 46b. As the material of the insulating tape, a usual one can be used. In an embodiment, the insulating tape may be made of polypropylene (PP), polyethylene terephthalate (PET), or polyimide (PI).

Referring to FIG. 4, the electrolyte storage member 50 may be formed in contact with the first and second joint portions 46a and 46b. When the electrolyte storage member 50 is in contact with the first and second joint portions 46a and 46b as described above, it is possible to prevent a short circuit easily without attaching the insulating tape.

In one embodiment, the electrolyte storage member 50 has a hollow shape to form an inner space, and the inner space may be filled with an electrolyte.

In another embodiment, the electrolyte storage member 50 has a porous form, a space is formed by the pores, and the space formed by the pores may be filled with the electrolyte.

In an embodiment, the electrolyte storage member 50 may be made of a porous polymer material. In this case, the electrolyte is contained in the pores formed in the porous polymer, and the electrolyte solution contained in the pores can be supplied to the electrode assembly. When the electrolyte storage member is used, the electrolyte solution stored in the pores can be easily moved to the electrode assembly, and the storage efficiency and storage stability of the secondary battery, the cathode lead portions 40a and 40b located in the inactive region B, The short circuit preventing effect of the negative electrode lead portion 40b can be excellent at the same time.

The porosity of the porous polymer may be 20% to 60%, and the average pore size may be 50 μm to 800 μm. In the above-described porosity and pore size, the storage efficiency of the electrolyte and the structural stability of the secondary battery are excellent at the same time. When the secondary battery is overcharged due to abnormal behavior such as gasification of the electrolyte or electrode active material, , The battery can be easily discharged to the outside through the electrolyte storage member 50 by using the elevated pressure inside the secondary battery. For example, the porosity of the porous polymer may be 35% to 50% and the average pore size may be 400 [mu] m to 700 [mu] m.

In embodiments, the electrolyte storage member 50 may be polyhedral or cylindrical. For example, it may be a rectangular parallelepiped shape as shown in Fig.

In an embodiment, the electrolyte storage member 50 may use a polymer having a melting point (Tm) of 150 ° C to 250 ° C. The storage efficiency of the electrolyte and the structural stability of the secondary battery can be excellent at the melting point.

In one embodiment, the porous polymer may comprise at least one of polymethyl methacrylate, polycarbonate, polyvinyl chloride, polyethylene and polypropylene. When the porous polymer is used, the insulating property, the electrolyte storage efficiency, and the structural stability of the secondary battery can be excellent at the same time.

The porosity of the porous polymer may be 20% to 60%, and the average pore size may be 50 μm to 800 μm. In the above-described porosity and pore size, the storage efficiency of the electrolyte and the structural stability of the secondary battery are excellent at the same time. When the secondary battery is overcharged due to abnormal behavior such as gasification of the electrolyte or electrode active material, , The battery can be easily discharged to the outside through the electrolyte storage member 50 by using the elevated pressure inside the secondary battery. For example, the porosity of the porous polymer may be 35% to 50% and the average pore size may be 400 [mu] m to 700 [mu] m.

(b) Step of injecting electrolyte

In this step, the electrolytic solution is injected into the case internal space 62 to impregnate the electrode assembly 20 and the electrolyte storage member 50 with the electrolyte solution. In the specific example, ultrasonic vibration may be applied to the case 60 when the electrolyte is injected to improve electrolyte wettability.

In a specific example, the weight ratio of the electrolytic solution impregnated in the electrode assembly 20 and the electrolytic solution stored in the electrolytic solution storage member 50 may be 1: 0.1-0.7. For example, it may be 1: 0.15 to 0.5. It is possible to efficiently use the inactive region (B) while preventing deterioration of the performance of the secondary battery in the weight ratio, and the storage efficiency of the electrolytic solution and the structural stability of the secondary battery can be excellent at the same time.

(c) Case sealing step

This step is a step of sealing the case 60. The electrode assembly 20 and the electrolyte storage member 50 are placed in the inner space 62 of the case 60 and the upper and lower surfaces of the case are covered with the outer peripheral surface of the inner space 62, The sealing region C can be formed.

2 and 4, a portion of the upper and lower surfaces of the cathode lead 48a and the cathode lead 48b is partially covered with a first insulating film 42a to increase the degree of sealing with the case 60, And the second insulating film 42b may be attached.

In the embodiment, the first insulating film 42a and the second insulating film 42b may be made of polypropylene (PP), polyethylene terephthalate (PET), or polyimide (PI).

According to an embodiment of the present invention, after the case sealing step, pre-charging is performed on the electrode assembly 20, and the gas generated by the initial charging is discharged to the outside of the case 60 .

Hereinafter, the configuration and operation of the present invention will be described in more detail with reference to preferred embodiments of the present invention. However, the following examples are provided to aid understanding of the present invention, and the scope of the present invention is not limited to the following examples. The contents not described here are sufficiently technically inferior to those skilled in the art, and a description thereof will be omitted.

Examples and Comparative Examples

Example

A carbon fiber mesh sheet coated with copper on both sides was coated with a dispersion containing PVDF, NMP and acetylene black to prepare a positive electrode current collector. A positive electrode active material (carbon black) containing LiMn ₂ O ₄ (LMO) and LiNi _1/3 Co _1/3 Mn _1/3 O ₂ (NCM) in a weight ratio of 1: 1 on the positive electrode collector, A positive electrode slurry obtained by mixing a solvent (acetone) and a positive electrode binder (PVDF) was applied on both sides by a conventional method, followed by drying and rolling to form a positive electrode active material coating layer. In addition, an anode slurry prepared by mixing a carbonaceous anode active material, a cathode active material (carbon black), a solvent (acetone) and a cathode binder (PVDF) was prepared and then coated on the anode collector (copper foil) to form an electrode active material coating layer Thereby preparing a negative electrode.

The porous polyethylene separator 14 is interposed between the positive electrode 10 and the negative electrode 12 and the outside of the positive electrode 10 and the negative electrode 12 and wound by a winding machine to form a jelly roll Electrode assembly 20 was manufactured. After the jelly roll type electrode assembly 20 was dried, a sealing tape 22 in the form of a mesh was attached to maintain the jelly roll shape.

At this time, the positive electrode tab 44a and the negative electrode tab 44b formed at one end of the positive electrode 10 and the negative electrode 12 of the electrode assembly 20 are ultrasonically welded to the positive electrode lead 48a and the negative electrode lead 48b Thereby forming the first joint portion 46a and the second joint portion 46b, respectively.

Porous polymethyl methacrylate in the form of a rectangular parallelepiped having a melting point (Tm) of 150 DEG C, a porosity of 45% and an average pore size of 400 mu m as an electrolyte solution storage member as shown in Figs. 2 and 4 was prepared.

Next, as shown in FIGS. 2 and 4, a polyethylene terephthalate outer resin layer; An unoriented polypropylene adhesive layer; And a pouch case 60 made of an aluminum laminate sheet material including an aluminum inner metal layer and an electrode assembly 20 accommodated in an inner space 62 of the case to form an active area A where the electrode assembly is located, The inactive region B including the positive electrode lead portion 40a and the negative electrode lead portion 40b protruding from the positive electrode 10 and the negative electrode 12 of the electrode assembly 20 and extending to the outside of the case was formed. The electrolyte storage member 50 is placed in the inactive region B as shown in FIG. 4 so that the electrolyte storage member 50 is formed in contact with the first and second joint portions 46a and 46b.

An electrolyte containing LiPF ₆ dissolved in a concentration of 1 M in a mixed solution of ethyl carbonate (EC) / ethyl methyl carbonate (EMC) / diethyl carbonate (DEC) / propylene carbonate (PC) was prepared and injected into the case internal space 62 , The electrolytic solution was impregnated (received) into the electrode assembly 20 and the pores formed in the electrolyte storage member. At this time, the weight ratio of the electrolytic solution impregnated in the electrode assembly 20 and the electrolyte solution stored in the electrolytic solution storage member 50 was 1: 0.5.

Then, after covering the upper and lower surfaces of the case 60, the outer peripheral surface of the inner space 62 was sealed by heat fusion or the like to form a sealing region C. At this time, in order to increase the degree of sealing with the case 60 and to ensure an electrically insulated state, a first insulation film 42a of polyimide material and a second insulation film 42b of polyimide material are formed in portions of the upper and lower surfaces of the cathode lead 48a and the cathode lead 48b, A secondary battery having a capacity of 10 Ah was manufactured by attaching the film 42b to the electrode assembly 20. The electrode assembly 20 was then precharged and then the gas generated by the initial charging was discharged to the outside of the case 60 .

Comparative Example

A secondary battery was manufactured in the same manner as in Example except that the electrolyte storage member 50 was not included.

Test Example

The 10 Ah class lithium secondary batteries prepared in the above Examples and Comparative Examples were repeatedly subjected to charging and discharging to perform life test to evaluate the capacity retention according to an increase in charge-discharge cycle, and the results are shown in FIG. 5 .

As a result, as shown in FIG. 5, when the secondary battery of Comparative Example was charged and discharged for about 2,000 cycles, the capacity retention ratio with respect to the initial capacity dropped to less than 80%. However, in the case of the secondary battery including the electrolyte storage member of the present invention, The capacity retention rate was maintained at 80% even during charging / discharging. From this, it was found that when the electrolyte storage member of the present invention is included, the capacity reduction phenomenon due to an increase in the charge / discharge cycle of the secondary battery is remarkably improved.

10: anode 12: cathode
14: separator 20: electrode assembly
22: sealing member 40a: positive electrode lead portion
40b: cathode lead portion 42a: first insulating film
42b: first insulating film 44a: positive electrode tab
44b: negative electrode tab 46a: first joint
46b: second junction 48a: anode lead
48b: anode lead 50: electrolyte storage member
60: Case 62: Inner space
100, 200: secondary battery A: active area
B: inactive region C: sealing region

Claims (14)

An electrode assembly including an anode, a cathode, and a separator, the electrolyte assembly being impregnated with the electrolyte;
A case for accommodating the electrode assembly; And
And an electrolyte storage member accommodated in the case and supplying the electrolyte solution to the electrode assembly.
The secondary battery according to claim 1, wherein the secondary battery further comprises a cathode lead portion and a cathode lead portion protruding from the anode and the cathode to extend to the outside of the case.
The lithium ion secondary battery according to claim 2, wherein the positive electrode lead portion comprises: a positive electrode tab contacted with the positive electrode; And a positive electrode lead which is joined to the positive electrode tab and extends to the outside of the case,
The negative electrode lead portion includes a negative electrode tab that is in contact with the negative electrode; And a negative electrode lead which is joined to the negative electrode tab and extends to the outside of the case,
The positive electrode tab and the positive electrode lead are joined through the first joint,
The negative electrode tab and the negative electrode lead are joined through a second joint,
Wherein the electrolyte storage member is formed in contact with the first and second junctions,
Wherein the electrolyte storage member includes a porous polymer, and the electrolyte is contained in the pores of the porous polymer.
The secondary battery according to claim 3, wherein the porous polymer has a melting point (Tm) of 150 ° C to 250 ° C.
The secondary battery according to claim 3, wherein the porous polymer is at least one of polymethyl methacrylate, polycarbonate, polyvinyl chloride, polyethylene and polypropylene.
The method of claim 3, wherein the porous polymer Wherein the porosity is 20% to 60%, and the average pore size is 50 μm to 800 μm.
The secondary battery according to claim 1, wherein a weight ratio of the electrolyte impregnated in the electrode assembly to the electrolyte contained in the electrolyte storage member is 1: 0.1-0.7.
Placing an electrolyte storage member in an internal space of a case accommodating an electrode assembly including an anode, a cathode, and a separator;
Injecting an electrolyte into the space inside the case to supply the electrolyte solution to the electrode assembly and the electrolyte storage member; And
And sealing the case.
9. The method of claim 8, wherein the secondary battery further comprises a cathode lead portion and a cathode lead portion protruding from the anode and the cathode, respectively, and extending to the outside of the case.
10. The battery pack according to claim 9, wherein the positive electrode lead portion comprises: a positive electrode tab which is in contact with the positive electrode; And a positive electrode lead which is joined to the positive electrode tab and extends to the outside of the case,
The negative electrode lead portion includes a negative electrode tab that is in contact with the negative electrode; And a negative electrode lead which is joined to the negative electrode tab and extends to the outside of the case,
The positive electrode tab and the positive electrode lead are joined through the first joint,
The negative electrode tab and the negative electrode lead are joined through a second joint,
Wherein the electrolyte storage member is formed in contact with the first and second junctions,
Wherein the electrolyte storage member comprises a porous polymer, and the electrolyte solution stored in the pores of the porous polymer is supplied to the electrode assembly.
The method of claim 8, wherein the porous polymer has a melting point (Tm) of 150 ° C to 250 ° C.
9. The method of claim 8, wherein the porous polymer comprises at least one of polymethylmethacrylate, polycarbonate, polyvinyl chloride, polyethylene, and polypropylene.
The method of claim 8, wherein the porous polymer has a porosity of 20% to 60% and an average pore size of 50 to 800 μm.
The method of claim 8, wherein the weight ratio of the electrolyte impregnated in the electrode assembly to the electrolyte contained in the electrolyte storage member is 1: 0.1-0.7.

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