KR101772800B1 - Secondary battery - Google Patents

Abstract

In the present invention, the pouch type battery case, the electrode assembly mounted inside the pouch type battery case, the positive electrode lead and the negative electrode lead having one end connected to the electrode assembly and the other end protruding to the outside of the battery case, The electrode assembly fixing part including a photo-curing binder in an inner space between the battery case and the electrode assembly, the battery assembly comprising: The movement of the electrode assembly is prevented from being applied to the secondary battery when the impact from the secondary battery is applied to the secondary battery, so that safety can be remarkably improved without fear of occurrence of an internal short circuit.

Description

Secondary Battery {SECONDARY BATTERY}

The present invention relates to a secondary battery which suppresses the internal flow of the electrode assembly in the battery case to prevent internal shorting and as a result, has significantly improved safety against external impact and pressure.

As technology development and demand for mobile devices are increasing, the demand for batteries as energy sources is rapidly increasing, and accordingly, a lot of researches on batteries that can meet various demands have been made. Typically, there is a high demand for a pouch-type secondary battery that can be applied to products such as mobile phones with a thin thickness in terms of the shape of the battery. In terms of materials, lithium ion batteries having high energy density, discharge voltage and output stability, lithium- There is a high demand for lithium secondary batteries such as lithium secondary batteries.

FIG. 1 schematically shows a general structure of a typical conventional pouch-type secondary battery as an exploded perspective view.

1, the pouch type secondary battery 10 includes an electrode assembly 30 and electrode tabs extending from the electrode assembly 30, that is, a positive electrode tab 31 and a negative electrode tab 32, The positive electrode lead 41 and the negative electrode lead 42 and the battery case 20 accommodating the electrode assembly 30, which are welded to the electrode assemblies 31 and 32, respectively.

The electrode assembly 30 is a power generation element in which an anode and a cathode are sequentially stacked in a state where a separation membrane is interposed therebetween, and has a stacked or stacked / folded structure. The electrode tabs 31 and 32 extend from each pole plate of the electrode assembly 30 and the cathode lead 41 and the cathode lead 42 are welded to a plurality of electrode tabs 31 and 32 extending from each pole plate And is partially exposed to the outside of the battery case 20. The battery case 20 is a battery case. An insulating film 45 is attached to part of the upper and lower surfaces of the cathode lead 41 and the cathode lead 42 in order to increase the degree of sealing with the battery case 20 and ensure an electrically insulated state, And includes anode and cathode V-forming portions 43 and 44 at a welded portion of the cathode lead 410 and the cathode lead 420. [ The battery case 20 is made of an aluminum laminate sheet and provides a space for accommodating the electrode assembly 30, and has a pouch shape as a whole.

The secondary battery has a structure in which the electrode assembly 30 is embedded in the housing portion of the battery case 20 and an electrolyte (not shown) is injected. Then, the outer periphery of the battery case 20 contacting the lower laminate Fusing process.

1, a plurality of positive electrode tabs 31 and a plurality of negative electrode tabs 32 may be joined together to the positive electrode lead 41 and the negative electrode lead 42. In the stacked electrode assembly 30, (20) are spaced apart from the electrode assembly (30) by a predetermined distance.

FIG. 2 is a partially enlarged view of an upper part of a battery case in which positive electrode tabs are connected in a dense form in the secondary battery of FIG. 1 and connected to the positive electrode lead.

2, a plurality of positive electrode tabs 31 protruding from the positive electrode collector 33 of the electrode assembly 30 are bonded to the bonded portion 46 integrally joined by welding, for example, And is connected to the positive electrode lead 41 in the form of a wire. The positive electrode lead 41 is sealed by the battery case 20 in a state in which the opposite end portion 47 to which the positive electrode tab weld portion is connected is exposed.

The inner upper end of the battery case 20 is spaced apart from the upper end surface of the electrode assembly 30 by a certain distance and the positive electrode tabs 31 of the welded portion are connected to each other, (The connection portion between the electrode tabs and the positive electrode lead or the negative electrode lead is also referred to as a V-forming portion).

In such a pouch-type secondary battery, the electrode assembly is easily moved along the interface with the battery case due to the vacancy of the V-forming portion when the battery is vibrated or dropped. Particularly, the lithium salt-containing electrolyte injected into the battery case acts as a kind of lubricant at the interface between the electrode assembly and the battery case, thereby further promoting the movement of the electrode assembly. Such movement of the electrode assembly causes internal short-circuiting due to contact of different electrodes at the V-forming region and ultimately degrades the safety of the battery. Therefore, a method for securing safety in the pouch-shaped battery is required .

Particularly, when the battery vibration test is performed to check the safety of the battery, the safety of the pouch type battery can be ensured because the lead is folded or torn due to vibration and the electrode is more likely to be displaced Is more urgently required.

Korean Patent No. 0863730 (Oct. Korean Patent No. 0905390 (June 24, 2009) Japanese Unexamined Patent Publication No. 2003-257387 (September 12, 2003)

SUMMARY OF THE INVENTION A first object of the present invention is to provide a secondary battery which suppresses internal flow of an electrode assembly in a battery case to prevent an internal short circuit and as a result has a significantly improved safety against external impact and pressure .

A second technical problem to be solved by the present invention is to provide a battery module and a battery pack including the secondary battery.

However, the technical problem to be solved by the present invention is not limited to the above-mentioned problems, and other matters not mentioned can be clearly understood by those skilled in the art from the following description.

In order to solve the above problems, according to one embodiment of the present invention,

A pouch type battery case;

An electrode assembly mounted inside the battery case;

A positive electrode lead and a negative electrode lead each having one end connected to the electrode assembly and the other end protruding outside the battery case; And

And a sealing portion that bonds an upper sheet and a lower sheet of the battery case,

And an electrode assembly fixing part formed in an inner space between the battery case and the electrode assembly,

And the electrode assembly fixing part includes a photocurable binder.

Furthermore, the present invention provides a battery module and a battery pack including the secondary battery.

Other details of the embodiments of the present invention are included in the following detailed description.

The secondary battery according to the present invention prevents internal movement of the electrode assembly in the battery case, so that there is no fear of occurrence of an internal short circuit, and the battery can exhibit significantly improved safety against impacts and pressures from external shocks and external impacts.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate exemplary embodiments of the invention and, together with the description of the invention, It should not be construed as limited.
1 is an exploded perspective view of a conventional structure of a conventional pouch type secondary battery.
FIG. 2 is a partial cross-sectional view of an upper part of a battery case in which positive electrode tabs are connected in a densely packed manner to the positive electrode lead in the secondary battery of FIG. 1;
3 is an exploded perspective view illustrating a structure of a secondary battery according to an embodiment of the present invention.
4 is a plan view of the secondary battery of FIG.
5 is a plan view showing the structure of a secondary battery according to another embodiment of the present invention.
6 is a conceptual view showing various embodiments of a possible electrode assembly fixing unit in a secondary battery according to another embodiment of the present invention.

Hereinafter, the configuration and operation according to the present invention will be described in detail with reference to the accompanying drawings. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the following description with reference to the accompanying drawings, the same reference numerals denote the same elements regardless of the reference numerals, and redundant description thereof will be omitted. The terms first, second, etc. may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another.

FIG. 3 is an exploded perspective view showing the structure of a secondary battery according to an embodiment of the present invention, and FIG. 4 is a sectional view thereof.

3 and 4, a secondary battery 100 according to an embodiment of the present invention includes a pouch-shaped battery case 200, an electrode assembly 300 mounted inside the battery case, The positive electrode lead 410 and the negative electrode lead 420 having ends (for example, one end) connected to the electrode assembly and the other end (for example, the other end) protruding outside the battery case 200, And a sealing part 210 which bonds the upper sheet and the lower sheet of the case to each other and a photocurable binder is provided in the spacing space formed between the battery case 200 and the electrode assembly 300, And an electrode assembly fixing part including the electrode assembly fixing part.

In the case of the conventional pouch type secondary battery, as shown in FIG. 1, the space between the electrode assembly 30 and the battery case 20 is left as an empty space. Accordingly, the electrode assembly is easily moved by an external force such as an impact, which may cause an internal short circuit.

3 and 4, the electrode assembly fixing part 220 is formed in the inner space X formed by the electrode assembly 300 and the battery case 200, The battery can be made more stable by removing the space in advance.

The electrode assembly fixing part 220 may be formed in a spaced space formed between the battery case 200 and the electrode assembly 300, Or may be formed in at least one region of the inner space.

5 is a plan view showing the structure of a secondary battery according to another embodiment of the present invention in which the electrode assembly fixing unit 220 is formed in at least one region of the internal space as described above.

5, the electrode assembly fixing unit 220 may be disposed between the end a of the electrode assembly 300 on which the positive electrode lead 410 and the negative electrode lead 420 are formed and the battery case 200, A space region 220a; The positive electrode lead 410 and the negative electrode lead 420 may be formed in the space region 220b between the end portion b of the electrode assembly 300 and the battery case 200 on which the negative electrode lead 420 is not formed.

In the space region 220a between the end portion (a) on the electrode assembly 300 side where the positive electrode lead 410 and the negative electrode lead 420 are formed and the battery case 200, the electrode assembly fixing portion 220 may be formed in the space region captured by the positive electrode lead 410 and the negative electrode lead 420 and the electrode assembly 300 and the battery case 200, Or may be partially formed in a part of the space area or in an area adjacent to the space area within the range. The electrode assembly fixing unit 220 may be formed below the cathode lead 410 and the cathode lead 420 together with the space region. Here, the lower portion means a space portion on the lower sheet side of the battery case.

Specifically, the electrode assembly fixing unit 220 includes a space region between the positive electrode lead 410 and the negative electrode lead 420; The positive electrode lead 410 and the negative electrode lead 420 may be formed in a space region between the electrode assembly 300 and the sealing portion protruding from the positive electrode lead 410 and the negative electrode lead 420.

The electrode assembly fixing unit 220 includes a space region between the cathode lead 410 and the cathode lead 420; A space region between the electrode assembly 300 and the sealing portion protruding from the positive electrode lead 410 and the negative electrode lead 420 is formed in a region including the lower portion of the positive electrode lead 410 and the negative electrode lead 420, .

The electrode assembly fixing unit 220 includes a space region between the cathode lead 410 and the cathode lead 420; The positive electrode lead 410 and the negative electrode lead 420 may be formed in a region adjacent to a space region between the electrode assembly 300 and the sealing portion protruding from the positive electrode lead 410 and the negative electrode lead 420.

In addition, the secondary battery includes electrode tabs extending from the respective electrode plates of the positive electrode and the negative electrode, that is, the positive electrode tab 310 and the negative electrode tab 320, and the electrode tabs and the electrode leads, Forming portions 411 and 421 of a positive electrode and a negative electrode to which the negative electrode lead 420 and the negative electrode lead 420 are welded.

In this case, in the space region 220a between the end a of the electrode assembly 300 on which the positive electrode lead 410 and the negative electrode lead 420 are formed and the battery case 200, the electrode assembly fixing portion 220 may be provided on each of the positive and negative V-forming portions 411, 421, the electrode assembly 300, and the space trapped by the sealing portion 210, Or may be partially formed only in a part of the spatial area or in an area adjacent to the spatial area.

Of course, the structure of the electrode assembly fixing unit 220 is the same as the structure of the electrode assembly 300 and the sealing unit 210, which are captured by the V-forming units 411 and 421 of the positive and negative electrodes inside the electrode assembly, It can be formed in a structure that is variously deformed in addition to a space-like structure.

Referring to FIG. 6, there is shown a schematic plan view showing a modified embodiment of the electrode assembly fixing unit 220 described above.

The structure shown in FIG. 6A has a structure in which the electrode assembly 300 is fixed to the space where the positive and negative V-forming portions 411 and 421, the electrode assembly 300, and the sealing portion 210 are captured, (B) illustrates a structure in which the electrode assembly fixing section is extended to the lower portions of the cathode lead 410 and the cathode lead 420, and FIG. (c) is a structure ('bc' region) in which an electrode assembly fixing portion is formed in an area other than the above-described space, and the structure shown in (d) 'ad' region). It is needless to say that the present invention is not limited thereto and it is possible to prevent the electrode assembly 300 from flowing by adding the electrode assembly fixing portion to any part of the space formed in the inner space of the electrode assembly 300 and the battery case 200 It is possible.

The electrode assembly fixing unit 220 may include a photocurable binder.

The photocurable binder has a low viscosity, allowing easy penetration of complex shapes and fine spaces. Accordingly, since it can be fixed including the overhang portion in the separation membrane, the stability can be improved. In the case of a thermosetting resin, there is a problem that the separator shrinks during the usual heating test. However, in the case of the photo-curing resin, since the resin is hardened and fixed between the separators, There is no concern. In addition, since the use of a curing agent is unnecessary, there is no fear of deterioration of battery characteristics due to the use of a curing agent, and there is no fear of thermal deformation or heat stress to the inner space because a heat treatment step is unnecessary.

The photocurable binder is a polymer, an oligomer, or a monomer that can be cured by light irradiation, specifically, ultraviolet (UV) irradiation at a wavelength of 200 to 500 nm, and can be used without particular limitation as long as it has dissolution resistance to an electrolyte solution.

Specifically, when the photocurable binder is a polymer, it may be a polycarbonate (PC) or a polyalkyl (meth) acrylate (for example, poly methyl methacrylate (PMM) Or a mixture of two or more of them may be used. The photocurable binder may be a cured product obtained by curing a prepolymer or a monomer component with a photopolymerization initiator such as benzophenone or benzoin ether. The prepolymer may be specifically a polyurethane, a polyester acrylate, a polyurethane acrylate, an epoxy acrylate, a polyether acrylate, and the like, alone or in a mixture of two or more. The above-mentioned monomer is specifically exemplified by dicyclopentanyl diacrylate, ethylene oxide (EO) modified bisphenol A acrylate, trimethylpropane triacrylate, EO-modified trimethylolpropane triacrylate, dipentaerythritol hexaacrylate And either one of them alone or a mixture of two or more thereof may be used.

The electrode assembly fixing unit 220 may further include a thermosetting binder including one or more selected from the group consisting of a thermosetting resin and a glue together with a photocurable binder.

When the thermosetting binder is used in combination, bonding is caused by the thermosetting binder, so that the adhesive force between the electrode assembly 30 and the battery case 20 can be further improved. As a result, It is possible to prevent micro-shrinkage and consequent deterioration of the fixing effect.

As the thermosetting binder, the thermosetting resin is not particularly limited as long as it is a polymer or oligomer that can be cured by heat, specifically at a temperature of 50 to 200 占 폚. Specifically, the thermosetting binder may be an epoxy resin, a phenol resin, a novolak epoxy resin, a polyethylene glycol resin, or a polypropylene glycol resin. Any one or two or more of them may be used in combination.

The glue is an adhesive mainly composed of collagen obtained by hot water extraction from leather, tendon, bone and the like.

The thermosetting binder may be used in an amount of 5 to 25 parts by weight based on 100 parts by weight of the photocurable binder. When the content of the thermosetting binder or glue is within the above range, a more excellent effect can be obtained.

The electrode assembly fixing unit 220 may further include one or both of an impact modifier and a flame retardant together with the photocurable binder.

The impact modifier may specifically be an acrylic impact modifier. More specifically, it may be an acrylic rubber or an acrylic-silicone rubber. The acrylic rubber may be an alkyl acrylate rubber having an alkyl structure having 1 to 6 carbon atoms, and more specifically may be a butyl acrylate rubber. The acrylic-silicone rubber may specifically be a silicone-butyl acrylate polymer rubber, or may be a composite rubber in which an acrylic rubber and a silicone rubber form a core-shell structure.

The impact modifier acts to improve weatherability and impact resistance of the fixing agent, and may be included in an amount of 5 to 25 parts by weight based on 100 parts by weight of the photocurable binder. When the content of the impact modifier is less than 5 parts by weight, the effect of improving impact resistance is insignificant. When the content of the impact modifier exceeds 25 parts by weight, the strength may be lowered.

The flame retardant is not particularly limited as long as it is used for improving the flame retardancy of the resin composition. Specifically, the flame retardant may be a phosphorus flame retardant, and more specifically, trimethyl phosphate, triethyl phosphate, triphenyl phosphate (TPP), tricresyl phosphate (TCP) , Trixylenyl phosphate (TXP), Resorcinol bis (diphenyl phosphate), RDP, Phenyl diresorcinol phosphate, Bisphenol diphenyl phosphate Bisphenol diphenyl phosphate (BDP), cresyl diphenyl phosphate, xylenyl diphenyl phosphate, phenyl di (isopropylphenyl) phosphate, triisophenyl Triisophenyl phosphate, Diphenyl Phosphate, Resorcinol di Phosphate, Orientate Aromatic Polyphosphate (APP), guanidine phosphate, ammonium phosphate, melamine phosphate or ammonium polyphosphate, and one or more of these may be used. More specifically, the flame retardant may be an aromatic polyphosphate (APP).

The flame retardant may be included in an amount of 5 to 10 parts by weight based on 100 parts by weight of the photocurable binder. If the content of the flame retardant is less than 5 parts by weight, the effect of improving the flame retardancy is insignificant, and if it exceeds 10 parts by weight, the strength may be lowered.

The electrode assembly fixing unit 220 may further include conventional additives such as a lubricant, an antioxidant, a UV stabilizer, a hydrolysis stabilizer, an antistatic agent, a pigment or an inorganic filler.

In addition, the electrode assembly fixing unit 220 includes the above-described photo-curable binder; And optionally at least one of a thermosetting resin, a glue, an impact modifier, a flame retardant, and other additives, is filled in a position where the electrode assembly fixing portion is formed, and then irradiated with ultraviolet light Lt; / RTI >

At this time, the ultraviolet ray irradiation may be performed according to a conventional method using an ultraviolet lamp or the like.

When the electrode assembly fixing unit 220 further includes a thermosetting resin, the thermocompression bonding process is performed at a temperature of 120 ° C. to 250 ° C. under the condition of 0.1 MPa to 10 MPa using the electric heat and the press after the light irradiation .

The thermocompression bonding process may be performed after the light irradiation or the thermocompression bonding process is performed even when the sealing portion 210 is formed. In this case, the thermocompression bonding process for thermosetting resin in the electrode assembly fixing portion may be simultaneously performed have.

Meanwhile, in the secondary battery, the pouch-shaped battery case 200 is composed of an upper laminate sheet and a lower laminate sheet, and the upper laminate sheet and the lower laminate sheet are thermally fused together along the outer circumferential surface of the battery case A sealing part 210 may be provided.

The upper and lower laminate sheets constituting the battery case 200 may be a laminate sheet including a metal layer and a resin layer covering the metal layer. More specifically, a polyolefin-based resin layer (polyolefin layer) having thermo-compression properties and serving as a sealing material, a metal foil layer (for example, a metal foil layer having a mechanical strength and serving as a barrier layer of moisture and oxygen And the like), and an outer layer (for example, a nylon layer or the like) serving as a protective layer are sequentially laminated. Commonly used as a polyolefin-based resin layer is CPP (Casted Polypropylene).

The sealing portion 210 is formed by thermally compressing the resin layer by applying heat and pressure to the outer circumferential surface portion where the upper laminate sheet and the lower laminate sheet of the battery case 200 are in contact with each other. At this time, since the upper and lower laminate sheets are the same resin layer, the outer periphery portion where the cathode lead 410 and the cathode lead 420 are not placed can be uniformly sealed by direct melting. Specifically, the thermocompression bonding process may be performed at 120 to 250 ° C under 0.1 MPa to 10 MPa using electric heat and press.

On the other hand, since the positive electrode lead 410 and the negative electrode lead 420 protrude from the outer peripheral surface of the upper end of the battery case 200 on which the positive electrode lead 410 and the negative electrode lead 420 are placed, The insulating film 430 is interposed between the cathode lead 410 and the anode lead 420 in order to enhance the sealing property in consideration of the thickness of the anode lead 420 and the heterogeneity with the battery case material But is not necessarily limited thereto.

In addition, in the secondary battery according to an embodiment of the present invention, the electrode assembly 300 is not particularly limited as long as it has a structure in which a plurality of electrode tabs 310 and 320 are connected to form an anode and a cathode.

Specifically, the electrode assembly may include a positive electrode including a positive electrode active material coating portion on at least one surface of a positive electrode collector, and a negative electrode including a negative electrode active material coating portion on at least one surface of the negative electrode collector, have.

The electrode assembly includes a positive electrode including a positive electrode active material coating portion on at least one surface of a positive electrode collector and a negative electrode including a negative electrode active material coating portion on at least one surface of the negative electrode collector, Assembly.

The electrode assembly includes a positive electrode including a positive electrode active material coating portion on at least one surface of a positive electrode collector and a negative electrode including a negative electrode active material coating portion on at least one surface of the negative electrode collector, And each of the overlapped portions is provided with a separation film, and the separation film may be a stack / folding type electrode assembly which surrounds each unit electrode assembly.

The stacked and jelly-roll type structures are well known in the art, and a description thereof will be omitted herein. Further, details of the electrode assembly of the stack / folding type structure are disclosed in Korean Patent Application Publication Nos. 2001-0082058, 2001-0082059 and 2001-0082060 of the present applicant, As a reference.

More specifically, in the secondary battery according to an embodiment of the present invention, the electrode assembly may be a stack-folding type electrode assembly, more specifically, exhibits a buffering effect on the volume expansion of the negative electrode active material due to charging / discharging A stack-folding type electrode assembly in which the negative electrode includes a cathode uncoated portion at both ends of the negative electrode active material coating portion to prevent cracks in the coated portion of the negative electrode active material and separation from the negative electrode current collector.

Meanwhile, in the electrode assembly, the negative electrode includes a negative electrode current collector, and a negative electrode active material coating portion coated on at least one surface, preferably both surfaces, of the negative electrode current collector.

In the negative electrode, the negative electrode current collector is not particularly limited as long as it has high conductivity without causing a chemical change in the battery. Examples of the negative electrode current collector include copper, stainless steel, aluminum, nickel, titanium, Surface of stainless steel surface treated with carbon, nickel, titanium or silver, aluminum-cadmium alloy, etc. may be used.

The anode current collector may have a thickness of 3 to 500 탆.

In addition, fine unevenness may be formed on the surface of the negative electrode collector to enhance the binding force of the negative electrode active material. For example, it can be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric.

The negative electrode active material coating portion includes a negative electrode active material, a binder, and a conductive material.

As the negative electrode active material, a compound capable of reversible intercalation and deintercalation of lithium may be used. Specific examples thereof include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber or amorphous carbon; Metal compounds capable of alloying with lithium such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys or Al alloys; Or composites comprising a metallic compound and a carbonaceous material; Or silicon-based compounds such as SiO _x (0 < x < 2), and one or a mixture of two or more of them may be used. Also, a metal lithium thin film may be used as the negative electrode active material.

The binder serves to improve the adhesion between the anode active material particles and the adhesion between the anode active material and the anode current collector. Specific examples include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, There may be mentioned polyethylene, polypropylene, ethylene-propylene-diene monomer (EPDM), sulfonated-EPDM, ethylene- (meth) acrylic acid copolymer, styrene-butadiene rubber, fluorine rubber or various copolymers thereof. One kind alone or a mixture of two or more kinds can be used. The binder may include 1 to 30% by weight based on the total weight of the negative electrode active material coating portion.

The conductive material is used for imparting conductivity to the electrode. The conductive material is not particularly limited as long as it has electron conductivity without causing chemical change. Specific examples thereof include graphite such as natural graphite and artificial graphite; Carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, summer black, or carbon fiber; Metal powder or metal fibers such as copper, nickel, aluminum and silver; Conductive whiskey such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; And polyphenylene derivatives. These may be used alone or in admixture of two or more. The conductive material may be included in an amount of 1 to 30% by weight based on the total weight of the negative electrode active material coating portion.

In addition, in the electrode assembly, the positive electrode includes a positive electrode collector, and a positive electrode active material coating portion coated with a positive electrode active material on at least one surface, preferably both surfaces, of the positive electrode collector.

In the above-described anode, the cathode current collector is not particularly limited as long as it has conductivity without causing chemical changes in the battery, and examples thereof include stainless steel, aluminum, nickel, titanium, sintered carbon or aluminum or stainless steel Such as carbon, nickel, titanium, or silver, may be used.

In addition, the cathode current collector may have a thickness of 3 to 500 탆, and fine unevenness may be formed on the surface of the cathode current collector to increase the adhesive force of the cathode active material. For example, it can be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric.

In the above-described positive electrode, the positive electrode active material coating portion may be coated on both surfaces of the positive electrode collector, or the active material may be coated on only one side of the positive electrode collector. However, considering the capacity of the secondary battery, It may be more preferable to be coated.

In addition, the positive electrode may include insulating tapes at both ends of the positive electrode active material coating portion, that is, at the start portion and the end portion of the positive electrode active material coating portion, in order to prevent a short circuit in the charging and discharging process. At this time, the insulating tape may be the same as that described above in the cathode.

Meanwhile, in the electrode assembly, the separator interposed between the positive electrode and the negative electrode may be an insulating thin film having high ion permeability and mechanical strength.

Specifically, the separation membrane may be a porous polymer film such as a porous polymer film made of a polyolefin-based polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer Or a laminated structure of two or more thereof. The separation membrane may be a nonwoven fabric made of a porous nonwoven fabric, for example, glass fiber of high melting point or polyethylene terephthalate fiber. In addition, the separation membrane may be a multi-layer structure having a ceramic layer formed on the porous polymer film.

In some cases, a gel polymer electrolyte may be coated on the separation membrane to improve the stability of the cell. Representative examples of such gel polymers include polyethylene oxide, polyvinylidene fluoride, polyacrylonitrile, and the like. When a solid electrolyte such as a polymer is used as an electrolyte, the solid electrolyte may also serve as a separation membrane.

The pores contained in the separation membrane may have a pore diameter of 0.01 to 10 m. The separation membrane may have a thickness of 5 탆 to 300 탆.

In addition, it is preferable that the separation membrane is extended longer than the end of the cathode plate so as to block the cathode electrode even if the separation membrane is contracted by heat. Specifically, the separation membrane may extend from the cathode end portion by 5 mm or more.

According to another embodiment of the present invention, there is provided a battery module including the lithium secondary battery as a unit cell and a battery pack including the same.

The battery module or the battery pack may include a power tool; An electric vehicle including an electric vehicle (EV), a hybrid electric vehicle (HEV), and a plug-in hybrid electric vehicle (PHEV); Or a power storage system, as shown in FIG.

Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily carry out the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

(Example 1)

An electrode assembly is housed in a receiving portion of a lower sheet of the battery case, and a plurality of taps protruding from the electrode assembly and the leads are welded to form a V-forming portion. A composition for forming an electrode assembly fixing portion was filled in upper and lower spaced spaces between the battery case and the electrode assembly, and ultraviolet rays (UV) were irradiated for 5 minutes using a UV lamp having a wavelength of? = 365 nm to remove the polycarbonate Thereby forming an electrode assembly fixing portion. The composition for forming the electrode assembly fixing portion includes 10 parts by weight of butyl acrylate rubber as an impact modifier, and 5 parts by weight of aromatic polyphosphate as a flame retardant, relative to 100 parts by weight of polycarbonate. Subsequently, an electrolyte is injected into the electrode assembly, and the outer circumferential surface of the upper case of the battery case contacting with the lower laminate is thermally fused at 150 DEG C and 1 MPa using an electric heat and a press to form a sealing portion in the battery case , A pouch-type secondary battery was fabricated.

(Example 2)

The same procedure as in Example 1 was carried out except that the entirety of the space between the battery case and the electrode assembly in Example 1 was filled with the composition for forming the electrode assembly fixing portion and cured to form the electrode assembly fixing portion To prepare a pouch-type secondary battery.

(Example 3)

Except that 20 parts by weight of glue, 10 parts by weight of butyl acrylate rubber as an impact modifier, and 5 parts by weight of aromatic polyphosphate as a flame retardant were added to 100 parts by weight of polycarbonate in place of the composition for forming the electrode assembly in Example 1 A pouch-type secondary battery was fabricated in the same manner as in Example 1, except that the composition for forming the electrode assembly was used.

(Comparative Example 1)

A pouch-type secondary battery was fabricated in the same manner as in Example 1, except that the electrode assembly fixing portion was not formed in Example 1.

(Experimental Example 1)

The drop test was performed on the batteries manufactured in Example 1 and Comparative Example 1, and the results are shown in Table 1 below.

In this experiment, 20 batteries of Example 1 and Comparative Example 1 were repeatedly performed. In the forward drop test, the process of freely falling on the iron plate at a height of 180 cm so that the electrode terminal portion faces downward was repeated 100 times .

Number of batteries shorted when dropped () Example 1 0 Comparative Example 1 15

As a result of the test, the battery of Example 1 according to the present invention did not cause a short circuit in all 20 batteries in the drop test. On the other hand, the battery of Comparative Example 1 was short-circuited and ignited in 15 of 20 batteries, and in particular, it was short-circuited due to movement of the electrode assembly upon falling.

(Experimental Example 2)

Thermal characteristics were evaluated for the batteries prepared in Example 1 and Comparative Example 1, respectively. The results are shown in Table 2 below.

Specifically, ten batteries of each of the batteries manufactured in Example 1 and Comparative Example 1 were stored at 130 DEG C for 1 hour and evaluated for NS (no smoke), NF (No fire) and NE (No explosion).

Number of cells with NS, NF and NE characteristics () Example 1 7 Comparative Example 1 10

As a result of the test, the battery of Example 1 according to the present invention exhibited excellent thermal characteristics as compared with Comparative Example 1. [

10, 100: secondary battery
20, 200: Battery case
210: sealing part
220: electrode assembly fixing portion
30, 300: electrode assembly
31, 310: positive electrode tab
32, 320: negative electrode tab
33: anode current collector
41, 410: Positive electrode lead
42, 420: cathode lead
43, 44, 411, 421: V forming section
45, 430: Insulation film
46:
47: opposite end of the positive electrode lead
X: an inner space between the battery case and the electrode assembly

Claims (13)

A pouch type battery case;
An electrode assembly mounted inside the battery case;
A positive electrode lead and a negative electrode lead each having one end connected to the electrode assembly and the other end protruding outside the battery case; And
And a sealing portion that bonds an upper sheet and a lower sheet of the battery case,
And an electrode assembly fixing part formed in an inner space between the battery case and the electrode assembly,
Wherein the electrode assembly fixing part includes a photo-curable binder, a space area between the end of the electrode assembly side on which the positive electrode lead and the negative electrode lead are formed and the battery case; And the positive electrode lead and the negative electrode lead are not formed on an end portion of the electrode assembly side and the battery case.
delete delete The method according to claim 1,
Wherein the electrode assembly fixing portion includes: a space region between the positive electrode lead and the negative electrode lead; And the positive electrode lead and the negative electrode lead are formed in a space region between the electrode assembly and the sealing portion protruding from the positive electrode lead and the negative electrode lead.
The method according to claim 1,
Wherein the electrode assembly fixing portion includes: a space region between the positive electrode lead and the negative electrode lead; And a space region between the electrode assembly and the sealing portion where the positive electrode lead and the negative electrode lead protrude are formed in a region including the lower portion of the positive electrode lead and the negative electrode lead.
The method according to claim 1,
Wherein the electrode assembly fixing portion includes: a space region between the positive electrode lead and the negative electrode lead; And the positive electrode lead and the negative electrode lead are formed in a region adjacent to the space region between the electrode assembly and the sealing portion protruding from the positive electrode lead and the negative electrode lead.
The method according to claim 1,
Wherein the photocurable binder comprises any one selected from the group consisting of polycarbonate and polyalkyl (meth) acrylate, or a mixture thereof.
The method according to claim 1,
Wherein the electrode assembly fixing part further comprises 5 to 25 parts by weight of a thermosetting binder including 100 parts by weight of the photocurable binder, the thermosetting binder including any one selected from the group consisting of a thermosetting resin and a glue or a mixture thereof.
The method according to claim 1,
Wherein the electrode assembly fixing part further comprises any one selected from the group consisting of an impact modifier and a flame retardant or a mixture thereof.
A battery module comprising a secondary battery according to any one of claims 1 to 9 as a unit cell.
A battery pack comprising the battery module according to claim 10.
12. The method of claim 11,
A battery pack that is used as a power source for mid- to large-sized devices.
13. The method of claim 12,
Wherein the middle- or large-sized device is selected from the group consisting of an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle and a system for power storage.

Images