KR20180036858A - Electrode Assembly and Secondary Battery Using the Same, and Method for Manufacturing the Electrode - Google Patents

Abstract

The present relates to an electrode assembly, and a method for manufacturing a secondary battery and an electrode which can prevent a disconnection between an anode and a cathode by a disconnection prevention layer even if a battery is overheated by forming the disconnection prevention layer composed of a porous polymer web of a heat-resistant polymer fiber on the surface of an electrode with high coherence. The electrode assembly comprises: the anode having an anode active material layer formed in an anode current collector through pressurization; the cathode having a cathode active material layer formed in a cathode current collector through pressurization; a separator inserted between the anode and the cathode to separate the anode and the cathode; and the disconnection prevention layer for surrounding at least any one of the anode active material layer and the cathode active material layer, wherein the disconnection prevention layer is composed of a porous polymer fiber web having a plurality of pores by accumulating super fine fibers of a heat-resistant polymer material.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode assembly and a method for manufacturing the same,

The present invention relates to an electrode assembly capable of preventing a short circuit between a positive electrode and a negative electrode even if a short-circuiting layer made of a porous polymer web of heat-resistant polymer fibers is formed on the surface of the electrode with high bonding force, And a method of manufacturing a battery and an electrode.

The lithium secondary battery generates electric energy by oxidation and reduction reactions when lithium ions are intercalated / deintercalated at the positive electrode and the negative electrode. The lithium secondary battery is manufactured by using a material capable of reversibly intercalating / deintercalating lithium ions as an active material for the positive electrode and the negative electrode, and filling an organic electrolytic solution or a polymer electrolyte between the positive electrode and the negative electrode.

The basic function of the separator of the lithium secondary battery is to prevent short circuit by separating the positive electrode and the negative electrode, and further, it is important to maintain high ionic conductivity by sucking the electrolyte necessary for the battery reaction.

A secondary battery including a lithium ion secondary battery and a lithium ion polymer battery having a high energy density and a large capacity must have a relatively high operating temperature range and the temperature is raised when the battery is continuously used in a high rate charge / discharge state, The separator is required to have higher heat resistance and thermal stability than those required for ordinary separators.

As the material for the separator, a polyolefin-based microporous polymer membrane such as polypropylene or polyethylene or a multi-layer thereof is usually used. Conventional separators have the drawback that the porous separator also shrinks due to pores of the porous membrane due to internal short-circuiting or heat generation due to overcharging, because the porous membrane layer is in the form of sheet or film. Therefore, when the sheet-like separator shrinks due to internal heat generation of the battery and shrinks, the separator shrinks and the missing portion directly contacts the anode and cathode, resulting in ignition, rupture and explosion.

In addition, the film-like separator causes an excessive space between the cathode and the film at the time of overcharging, and lithium ions that can not enter the cathode accumulate on the surface of the cathode, that is, the excited space between the cathode and the film, A dendrite is formed. Lithium dendrites have a problem that a positive electrode and a negative electrode are in contact with each other through a film-like separator, and at the same time side reactions occur between the lithium metal and the electrolyte, and the battery is ignited and exploded by heat generation and gas generation.

On the other hand, Korean Patent Laid-Open Publication No. 10-2008-13208 (Patent Document 1) discloses a heat-resistant polymer resin made of electrospinning and having a melting point of 180 or higher and having no melting point, A heat-resistant ultrafine fibrous separator made of ultrafine fibrous polymer resin capable of swelling in an electrolytic solution together with ultrafine fibers, a method for producing the same, and a secondary battery using the same.

Conventionally, a polyolefin film type separator or a film type separator made of a nanofiber web as disclosed in Patent Document 1 has been manufactured in a state of being separated from an electrode and then inserted between an anode and a cathode, .

That is, a high degree of alignment accuracy is required during assembly by inserting the film type separator between the anode and the cathode, and the manufacturing process is troublesome, and when the impact is applied, the electrode is pushed to cause a short circuit.

Particularly, in order to construct a large-capacity battery for an electric vehicle, when stacking a plurality of unit cells in a stacked manner, a bicell or a full cell is stacked using a continuous separation film of a long length, Type structure, the assembly process is complicated and the wettability of the electrolyte solution is low.

A separator composed of a porous ceramic layer in which particles of a ceramic filler are combined with a heat-resistant binder has been proposed in the past in order to stably prevent an internal short-circuit between electrodes at a high temperature. The ceramic layer has high safety against internal short circuit and is coated and adhered on the electrode plate, so there is no problem of shrinking or melting at the time of internal short circuit.

However, when a ceramic slurry is cast into an active material of a negative electrode or a positive electrode to form a thin film, a lithium secondary battery having a porous ceramic layer (i.e., ceramic separator) is formed uniformly in a uniform thickness over a whole area without desorbing the ceramic material A very high process precision is required and a crack occurs when the battery is assembled by laminating the cathode and the anode, and when the coated ceramic is desorbed, there is a problem that the ceramic particles cause the performance deterioration.

The use of the above ceramic separator affects the movement of lithium ions during charging and discharging, and in particular, in the case of a high output battery, it may act as a cause of deterioration of battery performance

Korean Patent Laid-Open Publication No. 10-2016-006766 (Patent Document 2) discloses a method of forming a ceramic coating layer by coating a ceramic slurry made of a ceramic material and a binder on one surface or both surfaces of a polyolefin-based film type separator so as to improve heat- Heat-resistant membranes having reduced heat shrinkage have been proposed. However, there is a problem that a manufacturing process of forming a ceramic material with a uniform thickness uniformly over the entire area without requiring desorption requires a very high process precision. Furthermore, Patent Document 2 has become a factor of cost increase by using a ceramic material of high purity.

Furthermore, Korean Patent Laid-Open Publication No. 10-2008-13208 (Patent Document 3) discloses a porous polymer web layer made of a mixture of a heat-resistant polymer or a heat resistant polymer, a swelling polymer, and inorganic particles on an inorganic polymer film layer, There has been proposed an electrode assembly in which the laminated separator is formed on one or both surfaces of a cathode or anode, or an inorganic polymer film layer made of a polymer capable of swelling electrolyte and capable of conducting electrolytic ions covers the cathode.

In the electrode assembly of Patent Document 3, since the inorganic co-polymer film layer formed on the surface of the electrode affects the movement of lithium ions, it may act as a cause of battery performance deterioration particularly in the case of a high output cell.

: Korean Patent Publication No. 10-2008-13208 : Korean Patent Publication No. 10-2016-006766 : Korean Patent Publication No. 10-2008-13208

The present inventors have found that when a porous film made of a heat-resistant polymer fiber is formed on the surface of a negative electrode or a positive electrode, shorting between the positive electrode and the negative electrode can be prevented from occurring even if the temperature inside the battery rises and shrinkage of the separation membrane occurs, It has been found that the migration of lithium ions is not disturbed by the high porosity and the uniform pore distribution, so that deterioration of the cell performance does not occur.

When the heat-resistant polymer coating layer is formed on the surface of the electrode, the electrode active material cast on the electrode current collector of the negative electrode or the positive electrode is pressed to form the heat-resistant polymer coating layer on the electrode surface, Point.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a short-circuiting layer made of a porous polymer web of heat-resistant polymer fibers with a high bonding force on the surface of an electrode, And to provide a secondary battery and a method of manufacturing an electrode using the electrode assembly, which can prevent a short circuit between the anode and the cathode to improve the stability.

Another object of the present invention is to provide an electrode assembly and a secondary battery using the electrode assembly, which can prevent a short circuit due to separation of a microactive material by integrally forming a short-circuiting prevention layer on an electrode surface.

Another object of the present invention is to provide a secondary battery which has a small heat shrinkage, a high heat resistance, an excellent ionic conductivity and adhesion to an electrode, excellent cycle characteristics in a battery configuration, and high capacity and high output.

It is a further object of the present invention to provide a separator which is manufactured in a state in which a separator is separated from an electrode and then inserted between an anode and a cathode to assure high alignment accuracy when assembled, And to provide a secondary battery using the electrode assembly.

According to an aspect of the present invention, there is provided an electrode assembly for a secondary battery, comprising: a positive electrode having a positive electrode active material layer formed by compression on a positive electrode collector; A negative electrode on which a negative electrode active material layer is formed by squeezing; A separator interposed between the anode and the cathode to separate the anode and the cathode; And a short-circuiting layer surrounding at least one of the positive electrode active material layer and the negative electrode active material layer, wherein the short-circuit prevention layer is made of a porous polymeric fiber web having accumulated therein microfine fibers of a heat- do.

The cathode active material layer or the anode active material layer and the porous polymeric fibrous web may be simultaneously thermocompression bonded.

The heat-resistant polymer material may have a melting point of 180 ° C or higher.

The fibers may range in diameter from 100 nm to 1.5 [mu] m. The porous polymer web may have a thickness of 3 to 4 탆 and a porosity of 40 to 80%.

The separation membrane may be a porous nonwoven fabric serving as a support and having micropores; And a porous fibrous web layered on at least one side of the porous nonwoven fabric and serving as an ion-impregnated layer.

The secondary battery according to the present invention includes the electrode assembly described above; And an electrolyte or an electrolyte.

According to another aspect of the present invention, there is provided a method of manufacturing an electrode, comprising: preparing a slurry including an electrode active material; Casting a prepared slurry on at least one surface of an electrode current collector to form an electrode active material layer; Dissolving the heat resistant polymer material in a solvent to prepare a spinning solution; Forming a porous polymer fiber web on which the heat-resistant polymer fibers are accumulated by electrospinning the spinning solution on the cast electrode active material layer; And forming a short-circuiting layer surrounding the surface of the electrode by thermocompression bonding the electrode active material layer cast on the electrode current collector and the porous polymeric fiber web at the same time.

The thermocompression bonding may be a roll pressing method.

The method of manufacturing an electrode assembly according to the present invention may further include a drying step for adjusting the solvent and moisture remaining on the surface of the porous polymeric fiber web to control the strength and porosity of the web before the thermocompression .

In addition, the short-circuit prevention layer may be a porous polymeric fiber web having a plurality of pores as the heat-resistant polymer fibers are filled in the irregularities and gaps on the surface of the electrode active material layer. As a result, a concave-convex structure corresponding to the concavity and convexity of the surface of the electrode active material layer is formed between the short-circuit prevention layer and the electrode active material layer, so that a strong coupling is achieved.

As described above, in the present invention, an electrode active material is cast on a current collector of a negative electrode or a positive electrode, and then a short-circuiting layer made of a porous polymer web of heat-resistant polymer fibers is formed by using an electrospinning method The short-circuiting layer prevents short-circuit between the positive electrode and the negative electrode so that the stability can be improved even if the battery is overheated while satisfactorily bonding between the electrode and the short-circuit prevention layer is performed.

In addition, in the present invention, by forming the short-circuiting prevention layer integrally on the electrode surface, it is possible to prevent micro-short circuit due to desorption of the fine active material.

Further, in the present invention, Has a small heat shrinkage, has heat resistance, is excellent in ionic conductivity and adhesion to electrodes, has excellent cycle characteristics in battery construction, and is capable of high capacity and high output.

According to the present invention, when the separator is manufactured in a state in which it is separated from the electrode and then inserted between the anode and the cathode to assemble, high alignment accuracy is not required, and even if the electrode is pushed after impact after the assembly, short- .

In the present invention, since the short-circuiting layer is made of the porous polymer web having a high porosity and a uniform pore distribution as compared with the prior art in which ceramic is coated on the electrode surface, performance deterioration can be prevented even at a high output.

In addition, compared with the conventional ceramic coating technology using a high-purity ceramic, the short-circuiting layer using the heat-resistant polymer material is excellent in cost-competitiveness.

1 is a schematic cross-sectional view showing an electrode assembly according to the present invention.
2 is a cross-sectional view showing an electrode according to the present invention formed in a bi-cell structure.
3 and 4 are cross-sectional views illustrating a separator usable in a secondary battery according to the present invention.
5 is an enlarged sectional view showing a state of engagement between the electrode and the short-circuit prevention layer according to the present invention.
6 is a manufacturing process diagram showing a manufacturing process of an electrode according to the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The sizes and shapes of the components shown in the drawings may be exaggerated for clarity and convenience.

Referring to FIG. 1, an electrode assembly will be described when a secondary cell of the present invention forms a full cell.

The electrode assembly 100 for a secondary battery according to an embodiment of the present invention is encapsulated in a can or a pouch together with an electrolyte to constitute a secondary battery. The electrode assembly 100 includes an anode 110, a cathode 120, and a separator 130 .

The positive electrode 110 includes a positive electrode collector 111 and a positive electrode active material layer 112. The negative electrode 120 includes a negative electrode collector 121 and a negative electrode active material layer 122, The anode collector 111 and the anode collector 121 may be realized in the form of a sheet having a predetermined area.

That is, the positive electrode 110 and the negative electrode 120 can be formed by pressing the positive and negative active materials on one surface of the current collectors 111 and 121, respectively, and then pressing them to form the positive and negative active material layers 112 and 122. At this time, the active material layers 112 and 122 may be provided for the entire area of the current collectors 111 and 121, or may be partially provided for some areas.

The anode 110 and the cathode 120 may include a pair of electrode active material layers on both sides of the electrode collector to form a bicell. FIG. 2 shows a cathode having a bi-cell structure.

The anode current collector 121 and the anode current collector 111 may be made of a thin metal foil or mesh and may be formed of a metal such as copper, aluminum, stainless steel, nickel, titanium, chromium, manganese, iron, cobalt, zinc, molybdenum, Tungsten, silver, gold, and alloys thereof.

The positive electrode collector 111 and the negative electrode collector 121 may have a positive electrode terminal and a negative electrode terminal protruding from the respective bodies for electrical connection with an external device.

The positive electrode active material layer 112 includes a positive electrode active material capable of reversibly intercalating and deintercalating lithium ions. Typical examples of the positive electrode active material include LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , LiMn _{2 O 4, LiNiCoO 2, LiNi 1} -x- y Co x M y O 2 (0≤x≤1, 0≤y≤1, 0≤x + y≤1, M is such as Al, Sr, Mg, La lithium, such as a metal) - transition metal oxide, NCM (lithium Nickel Cobalt Manganese) based active material, LiFeO lithium, such as _{2, V 2 O 5, V} 6 O 13, TiS, MoS, or the organic disulfide compound and the organic polysulfide compound Absorbing and releasing substances can be used, and a mixture of at least one of them can be used.

The negative electrode active material layer 122 may include a negative electrode active material capable of reversibly intercalating and deintercalating lithium ions. Examples of the negative electrode active material include crystalline or amorphous carbon, carbon fiber, or carbon composite material. A carbon-based negative electrode active material, a tin oxide, a lithium-based material, lithium, a lithium alloy, and a mixture of at least one of these materials. Here, the carbon may be at least one selected from the group consisting of carbon nanotubes, carbon nanowires, carbon nanofibers, graphite, activated carbon, graphene and graphite.

However, the positive electrode active material and the negative electrode active material used in the present invention are not limited thereto, and any of the commonly used positive electrode active material and negative electrode active material may be used.

The separator 130 is disposed between the anode 110 and the cathode 120. The separator 130 may be a single layer or a multi-layered polyolefin-based porous separator having a shutdown function.

The separation membrane 130 may be formed by coating a ceramic slurry of a ceramic material and a binder on one side or both sides of a polyolefin porous separator to improve the heat resistance, thereby forming a ceramic coating layer, thereby using a high- It is possible.

3, the separation membrane used in the present invention is a porous polymer fiber web layer (hereinafter referred to as " porous polymer fiber web layer ") composed of a mixture of a heat-resistant polymer or a heat resistant polymer and a swellable polymer, It is also possible to use a separation membrane 130a in which an inorganic polymeric film layer 132 serving as an adhesive layer is laminated on a substrate 131 (see FIG.

As shown in FIG. 4, the separator used in the present invention may be laminated on one side or both sides of porous nonwoven fabric 133 having fine pores as a support. When the porous nonwoven fabric 133 is adhered to the opposing electrode, It is also possible to use a separation membrane 130b including a pair of porous polymeric fiber webs 131a and 131b serving as a humid layer.

For example, the porous nonwoven fabric 133 may be a nonwoven fabric made of PP / PE fibers having a double structure in which PE is coated on the outer periphery of a PP fiber as a core, a PET nonwoven fabric made of polyethylene terephthalate (PET) Can be used.

The inorganic polymeric film layer 132 is formed by dissolving a polymer capable of conducting electrolytic solution and capable of conducting electrolytic ions in a solvent to form a spinning solution and then electrospun spinning liquid to form a porous polymer fiber web And the porous polymeric fibrous web is calendered or heat-treated at a temperature lower than the melting point of the polymer (for example, PVDF) to obtain an inorganic porous polymer film layer.

The porous polymeric fiber web layer 131 is formed by dissolving a mixture of a heat-resistant polymer or a mixture of a heat-resistant polymer, a swellable polymer, and inorganic particles in a solvent to form a spinning solution, and then discharging the spinning solution onto the inorganic polymer film layer. Forming a porous polymer web made of fibrous material, and calendering the obtained porous polymer web at a temperature lower than the melting point of the polymer.

The inorganic particles are _{Al 2 O 3, TiO 2,} BaTiO 3, Li 2 O, LiF, LiOH, Li 3 N, BaO, Na 2 O, Li 2 CO 3, CaCO 3, LiAlO 2, SiO 2, SiO, SnO , SnO ₂ , PbO ₂ , ZnO, P ₂ O ₅ , CuO, MoO, V ₂ O ₅ , B ₂ O ₃ , Si ₃ N ₄ , CeO ₂ , Mn ₃ O ₄ , Sn ₂ P ₂ O ₇ , Sn ₂ B ₂ O ₅ , Sn ₂ BPO ₆ And at least one selected from mixtures of these may be used.

When the mixture is composed of a heat-resistant polymer or a heat-resistant polymer, a swellable polymer and inorganic particles, the content of the inorganic particles is preferably in the range of 10 to 25% by weight based on the total mixture when the size of the inorganic particles is between 10 and 100 nm . More preferably, the inorganic particles are contained in the range of 10 to 20 wt%, and the size is in the range of 15 to 25 nm.

When the mixture is composed of a heat-resistant polymer, a swellable polymer and an inorganic particle, the heat-resistant polymer and the swellable polymer are preferably mixed in a weight ratio ranging from 5: 5 to 7: 3, more preferably 6: 4. In this case, the swelling polymer is added as a binder to facilitate bonding between the fibers.

If the mixing ratio of the heat-resistant polymer and the swelling polymer is less than 5: 5 by weight, the heat resistance is lowered and the high temperature property is not obtained. If the mixing ratio is more than 7: 3 by weight, the strength is lowered and radiation trouble occurs.

The heat-resistant polymer resin usable in the present invention is a resin which can be dissolved in an organic solvent for electrospinning and has a melting point of 180 or more, for example, polyacrylonitrile (PAN), polyamide, polyimide, polyamideimide, poly (Metha-phenylene isophthalamide), polysulfone, polyether ketone, polyethylene terephthalate, polytrimethylene terephthalate, aromatic polyesters including polyethylene naphthalate, polytetrafluoroethylene, polydiphenoxipospazene , Polyphosphazenes including polybis [2- (2-methoxyethoxy) phosphazene], polyurethane copolymers including polyurethane and polyether urethane, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate (PES), and polyether imide (PEI). One or a mixture thereof.

The swellable polymer resin usable in the present invention is a resin which swells in an electrolytic solution and can be formed by ultrafine fibers by an electrospinning method. Examples of the swellable polymer resin include polyvinylidene fluoride (PVDF), polyvinylidene fluoride-co- Polypropylene), perfluoropolymers, polyvinyl chloride or polyvinylidene chloride, and copolymers thereof, and polyethylene glycol derivatives including polyethylene glycol dialkyl ethers and polyethylene glycol dialkyl esters, poly (oxymethylene-oligo- Polyvinyl acetate, poly (vinylpyrrolidone-vinyl acetate), polystyrene and polystyrene acrylonitrile copolymers, polyacrylonitrile methyl methacrylate copolymers, polyacrylonitrile methyl methacrylate copolymers, ≪ / RTI > Casting reel can be given to the copolymer, polymethyl methacrylate, polymethyl methacrylate copolymers and mixtures thereof.

When the mixed polymer is used, the porous polymer web layer 131 may be formed using a heat-resistant polymer such as PAN (polyacrylonitrile) or a swellable polymer such as PVDF.

The most important role of the separator in the secondary battery is to ensure safety by separating the anode 110 and the cathode 120 under any circumstances. Particularly, when the terminal body is operated for a long time, heat is generated in the secondary battery, shrinkage of the separator occurs due to internal heat generation of the battery, and when the battery is shrunk, the cathode and the anode may directly contact the missing part. In the case of a film-type separator, a lithium dendrite may be formed.

In order to solve the problems of the conventional secondary battery, the present invention is characterized in that, in addition to the separator 130 separating the anode 110 and the cathode 120, a short-circuiting layer (not shown) is formed on the surface of at least one of the anode 110 and the cathode 120 140 are integrally formed on the electrode surface.

In the present invention, for example, after a negative electrode active material layer 121 is formed by casting a negative electrode active material layer on a negative electrode current collector 121 of a negative electrode as shown in FIG. 5, A porous polymer web of a microfine fiber 10 made of a polymer is formed and subjected to thermocompression bonding to complete the short-circuit prevention layer 140.

Hereinafter, a manufacturing process of forming the short-circuit prevention layer 140 on the surface of the electrode will be described in detail with reference to FIG.

First, the anode 110 and the cathode 120 are mixed with an active material, a conductive agent, a binder, and an organic solvent in a predetermined ratio to prepare a slurry (S11). Then, the anode and anode current collectors 111, a foil or a mesh is cast on one or both sides (S12). In this case, the anode and anode current collectors 111 and 121 may use a strip-shaped electrode current collector so that a continuous subsequent process can be performed during mass production.

For example, the anode is formed by casting a slurry composed of LiCoO ₂ , Super-P carbon and PVdF as an active material, a conductive agent, and a binder in an aluminum foil, and the cathode is formed of MCMB (mesocarbon microbeads) , And PVdF can be cast on a copper (Cu) foil.

Next, a spinning solution is formed by dissolving, for example, PAN as a heat resistant polymer material in a solvent (S13), and spinning liquid is supplied to the positive and negative electrode active material layers 112 and 122 cast in the positive and negative electrode current collectors 111 and 121, To form a porous polymer fiber web in which the microfine fibers 10 radiated therefrom have been accumulated (S14). The porous polymeric fibrous web forms a short-circuiting layer 140. In this case, the fibers 10 of the heat-resistant polymer material to be electrospun is preferably formed to have a diameter in the range of 100 nm to 1.5 mu m.

5, after the slurry containing the negative electrode active material is cast on the negative electrode current collector 121 to form the negative electrode active material layer 122, the surface of the active material particles 30 is rough, And a gap.

When the spinning liquid is electrospinned on the surface of the anode active material layer 122, the ultrafine fibers 10 radiated from the spinning nozzle accumulate on the surface of the anode active material layer 122, and the porous polymer fibers having a large number of pores 20 It forms the web.

In this case, when the radiated ultrafine fibers 10 are accumulated on the surface of the anode active material layer 122, the irregularities and the gaps of the surface of the anode active material layer 122 are filled with a large area.

Next, a strip having a porous polymeric fiber web formed on the anode and anode active material layers 112 and 122 is dried to control the strength and porosity of the web by adjusting the solvent and moisture remaining on the surface of the porous polymeric fibrous web (S15).

Thereafter, the strip is subjected to roll pressing so that the anode and anode active material layers 112 and 122 cast on the anode and anode current collectors 111 and 121 and the porous polymer fiber web are simultaneously thermally compressed (S16).

When thermocompression by roll pressing is performed, the adhesion between the particles of the cast slurry and the metal foil is increased, and bonding between the spun ultra-fine fibers 10 forming the porous polymer fiber web is performed, The rigid coupling between the layers 112 and 122 and the porous polymer fiber web, that is, the short-circuit prevention layer 140, is achieved. That is, as the spun ultra-fine fibers 10 are filled in the irregularities and gaps in the surfaces of the active material layers 112 and 122, they are in contact with each other over a large area, so that they have a high bonding force between them. That is, between the short-circuit prevention layer 140 and the active material layers 112 and 122, concave-convex structure corresponding to the concavo-convex structure of the surface of the active material layer is formed.

In this case, the thermocompression bonding temperature is determined depending on the heat-resistant polymer to be used. For example, thermocompression is performed on the porous polymeric fibrous web at a high temperature of 170 to 210 ° C to form a web having a thickness of 3 to 4 μm Thin film, and the porosity is 40 to 80%.

The short-circuit prevention layer 140 made of the porous polymeric fiber web can not reliably ensure a short circuit between the anode 110 and the cathode 120 when the thickness is less than 3 占 퐉, and when the thickness exceeds 4 占 퐉, The performance of the battery is deteriorated.

In the case of constructing a high-capacity secondary battery, the active material layer is formed as a thick film. In the case of constructing a high-output secondary battery, the active material layer is formed as a thin film.

The short-circuit prevention layer 140 formed of the porous polymeric fiber web thermally pressed on the surfaces of the anode and anode active material layers 112 and 122 is formed of a heat resistant polymer material even if the separator 130 is shrunk or deformed or moved due to overheating of the battery. Since the short-circuit prevention layer 140 is formed integrally so as to cover at least any one surface of the anode 110 and the cathode 120 without causing shrinkage or deformation, the short-circuit prevention layer 140 formed between the anode 110 and the cathode 120 Thereby preventing a short circuit.

In addition, the short-circuit prevention layer 140 may be formed by bonding the positive and negative electrode active material layers 112 and 122 and the porous polymeric fiber web Prevention layer 140 is formed on the positive electrode 110 and the negative electrode 120 in the case where the separator 130 can not reliably separate the positive and negative electrodes 110 and 120 due to the occurrence of overheat of the battery due to the strong coupling between the positive and negative electrodes 120 and 120, 110 and the cathode 120 can be prevented, thereby improving the stability.

As a result, in the present invention, when the separator 130 is manufactured in a state in which it is separated from the electrodes, and then inserted between the anode 110 and the cathode 120 to assemble the separator 130, high alignment accuracy is not required, It is possible to prevent the occurrence of a short circuit even if the electrode is pushed.

In addition, in the present invention, by forming the short-circuit prevention layer 140 integrally on the electrode surface, it is possible to prevent micro-short circuit due to desorption of the micro active material.

In addition, since the short-circuit prevention layer 140 of the present invention has a porous web structure having a small heat shrinkage, heat resistance, and high porosity due to being made of a heat-resistant polymer, The short circuit is prevented and the ion conductivity is not affected.

In addition, the short-circuit prevention layer 140 of the present invention is integrally formed on the surface of the electrode to prevent the space between the cathode and the film-type separator from being formed, thereby preventing lithium ions from accumulating in the lithium metal. As a result, the formation of dendrite on the surface of the negative electrode can be suppressed, and the stability can be improved.

As described above, when the strip-shaped anode 110 and the cathode 120 are prepared, a unit anode cell and a unit cathode cell are formed while performing a process such as slitting, notching, 1, a separator 130 may be inserted between a unit positive electrode cell and a unit negative electrode cell to form one electrode assembly.

Further, a separator may be inserted between the strip-type anode 110 and the cathode 120, laminated, and then wound to form an electrode assembly.

After the electrode assembly is assembled, it is inserted into an aluminum or aluminum alloy can or similar container, the opening is closed with a cap assembly, and an electrolyte is injected to manufacture a lithium secondary battery.

In addition, when a large-capacity battery for an electric vehicle is constructed, a stack-folding structure having a structure in which a continuous separation film is used for the strip-type anode 110 and the cathode 120 can be easily realized.

In the above-described embodiment, the electrode assembly in which the secondary cell forms a full cell has been described. However, the present invention can be applied to an electrode assembly having a bicell structure.

In addition, although the lithium ion battery using the electrolytic solution has been described in the above embodiments, the present invention can also be applied to a polymer battery using a gel polymer electrolyte.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is clearly understood that the same is by way of illustration and example only and is not to be construed as limited to the embodiments set forth herein. Various changes and modifications may be made by those skilled in the art.

The present invention relates to an electrode assembly capable of preventing a short circuit between a positive electrode and a negative electrode even if a short-circuiting layer made of a porous polymer web of heat-resistant polymer fibers is formed on the surface of the electrode with high bonding force, Applicable to batteries.

10: fiber 20: porosity
30: active material particle 100: electrode assembly
110: anode 111: anode assembly
112: cathode active material 120: cathode
121: negative electrode collector 122: negative electrode active material
130-130b: separation membrane 131-131b: porous polymeric web
132; Inorganic hollow polymer film layer 133: Porous nonwoven fabric
140: short-

Claims (12)

A positive electrode on which a positive electrode active material layer is formed by pressing on a positive electrode current collector;
A negative electrode on which a negative electrode active material layer is formed by squeezing;
A separator interposed between the anode and the cathode to separate the anode and the cathode; And
And a short-circuiting layer surrounding at least one of the cathode active material layer and the anode active material layer,
Wherein the short-circuit prevention layer comprises a porous polymeric fibrous web having microporous fibers of a heat-resistant polymer material and having a plurality of pores. The method according to claim 1,
Wherein the positive electrode active material layer or the negative electrode active material layer and the porous polymeric fiber web are simultaneously thermally bonded to each other. The method according to claim 1,
Wherein the heat resistant polymer material has a melting point of 180 ° C or higher. The method of claim 3,
The heat resistant polymer material may be at least one selected from the group consisting of polyacrylonitrile (PAN), polyamide, polyimide, polyamideimide, poly (meta-phenylene isophthalamide), polysulfone, polyether ketone, polyethylene terephthalate, Polytetrafluoroethylene, polydiphenoxaphosphazenes, polyphosphazenes including polybis [2- (2-methoxyethoxy) phosphazene], polyesters such as poly (PEI), or a mixture thereof, selected from the group consisting of cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, polyester sulfone (PES), and polyether imide Electrode assemblies for secondary batteries. The method according to claim 1,
Wherein the fibers of the heat-resistant polymer material have a diameter ranging from 100 nm to 1.5 占 퐉. The method according to claim 1,
Wherein the thickness of the porous polymer web is 3 to 4 占 퐉 and the porosity is 40 to 80%. The method according to claim 1,
The separation membrane
A porous nonwoven fabric serving as a support and having micropores; And
And a porous fibrous web laminated on at least one side of the porous nonwoven fabric and serving as an ion-impregnated layer. An electrode assembly according to any one of claims 1 to 7; And
A secondary battery comprising an electrolyte or an electrolyte. Preparing a slurry comprising an electrode active material;
Casting a prepared slurry on at least one surface of an electrode current collector to form an electrode active material layer;
Dissolving the heat resistant polymer material in a solvent to prepare a spinning solution;
Forming a porous polymer fiber web on which the heat-resistant polymer fibers are accumulated by electrospinning the spinning solution on the cast electrode active material layer; And
And forming a short-circuiting layer surrounding the surface of the electrode by simultaneously thermally pressing the electrode active material layer cast on the electrode current collector and the porous polymeric fiber web. 10. The method of claim 9,
Wherein the thermocompression bonding is a roll pressing method. 10. The method of claim 9,
Further comprising a drying step for adjusting the solvent and moisture remaining on the surface of the porous polymeric fiber web to control the strength and porosity of the web before the thermocompression. 10. The method of claim 9,
Wherein the short-circuit prevention layer is a porous polymer fiber web having a plurality of pores while the heat-resistant polymer fibers are filled in the irregularities and gaps in the surface of the electrode active material layer.

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