KR20080010166A - Electrode havig improved interfacial adhesion with separator and electrochemical device comprising the same - Google Patents

Abstract

An electrode, a method for preparing the electrode, and an electrochemical device containing the electrode are provided to improve the high temperature stability of a battery by increasing the interference adhesive strength between an inorganic/inorganic composite porous film and an electrode. An electrode comprises an electrode active material layer comprising electrically connected electrode active materials on one or both sides of a current collector, wherein an organic/inorganic porous film is formed on the one or both surface of an electrode. The organic/inorganic porous film comprises an integrated porous polymer support adhered to the surface of an electrode active material layer; and a composite coating layer comprising an inorganic particle and a binder polymer formed on at least one region selected from the surface of the polymer support and the some pore part of the supporter. The organic/inorganic porous film can act as a separator.

Description

ELECTRODE HAVIG IMPROVED INTERFACIAL ADHESION WITH SEPARATOR AND ELECTROCHEMICAL DEVICE COMPRISING THE SAME}

1 is a structural diagram showing an electrode in which an organic / inorganic composite porous film is directly introduced on an electrode surface according to the present invention.

FIG. 2 is a scanning electron microscope (SEM) photograph of the electrode of Example 1, in which an organic / inorganic composite porous film is introduced on an electrode surface.

3 is a discharge capacity curve of a battery manufactured by stacking a bicell using an electrode prepared in Example 1. FIG.

The present invention provides an electrode capable of achieving excellent thermal safety and an increase in manufacturing process rate of an electrochemical device, specifically, an electrode in which an organic / inorganic composite porous film that can replace a separator is directly introduced onto an electrode surface, and a method of manufacturing the same; And an electrochemical device comprising the electrode.

Currently, polyolefin-based separators are used as separators to prevent a short circuit between the anode and the cathode in an electrochemical device. However, due to the membrane material and processing characteristics, that is, the polyolefin series has a physical property that is usually melted below 200 ℃, when the stretching process to control the pore size and porosity, the original size at a high temperature It has the weakness of heat shrinking. As a result, when the battery rises to a high temperature due to an internal / external stimulus, there is a high possibility that the positive electrode and the negative electrode are shorted to each other due to shrinkage or melting of the separator. Will be shown. Therefore, it is essential to develop an electrolyte that does not undergo heat shrinkage at such a high temperature.

In order to improve the problems of the polyolefin-based separators as described above, many attempts have been made to develop electrolytes to which inorganic substances can be substituted for the conventional separators, which can be broadly classified into two types. First, a solid composite electrolyte is prepared by mixing inorganic particles having no lithium ion transfer capability with a polymer having lithium ion transfer capability. However, such a composite electrolyte is intended to replace a conventional separator and a liquid electrolyte, but has a lower ion conductivity than a liquid electrolyte, and when the inorganic material and the polymer are mixed, the interface resistance between the inorganic material and the polymer becomes very large, and an excessive amount of inorganic material is added. It is known that there is no further progress in the research due to the difficulty of handling due to the tendency of the electrolyte to be brittle, and the difficulty of assembling the battery using the same (Japanese Patent Laid-Open No. 2003-022707, "Solid State Ionics"). vol. 158, n.3, p. 275, (2003), "Journal of Power Sources"-vol. 112, n.1, p. 209, (2002), "Electrochimica Acta"-vol. 48, n .14, p.2003, (2003), etc.).

Secondly, the inorganic particles are mixed with a gel polymer electrolyte composed of a polymer and a liquid electrolyte to prepare an electrolyte (US Pat. No. 6,544,689, Japanese Patent Laid-Open No. 2002-008724, Japanese Patent Laid-Open No. 1995-19). 314995, International Patent Application Publication No. 02/092638, International Patent Application Publication No. 00/038263, "Journal of Electrochemical Society"-v.147, p.1251, (2000) and the like). However, the polymers used in the above attempts were inferior in binding capacity and could not use a large amount of inorganic materials. Therefore, the inorganic material added in a small amount compared to the polymer and the liquid electrolyte has only an auxiliary function of assisting lithium ion transfer by the liquid electrolyte, and the gel-type polymer electrolyte has lower ion conductivity than the liquid electrolyte, thereby degrading battery performance. There is.

In particular, most of the studies conducted to date have attempted to develop all composite electrolytes containing inorganic materials in the form of free standing films, but in this case, it is difficult to apply a battery due to poor mechanical properties such as brittleness. . Even when the mechanical properties are improved by reducing the diarrhea and inorganic content, if the battery is assembled after mixing with the liquid electrolyte in advance, the mechanical properties are greatly reduced by the liquid electrolyte, and the battery assembly becomes impossible. In the case of pouring the liquid electrolyte, since the polymer content is high in the organic / inorganic composite membrane, it takes a very long time to disperse the electrolyte in the battery, and the actual electrolyte wettability is also poor.

In addition, US Pat. No. 6,432,586 describes a composite membrane in which a polyolefin-based separator is coated with silica as a method for improving mechanical properties such as breakage of an organic / inorganic composite membrane. However, this uses a polyolefin-based separator has a disadvantage that does not show a great effect on the safety enhancement, including the prevention of high temperature heat shrinkage. In addition, an organic / inorganic composite separator in which silica (SiO ₂ ) or alumina (Al ₂ O ₃ ) was applied to a nonwoven polyester support was developed by Creavis of Germany, but high mechanical properties are expected due to the characteristics of the nonwoven fabric. Not only is this difficult, but the chemical structure of the polyester has the disadvantage of being susceptible to electrochemical reactions, so it is expected that there will be many problems in practical cell application ["Desalination"-vol. 146, p. 23 (2002)].

Therefore, there is a need in the art for the development of a technology for an electrolyte that can serve as a separator or a separator capable of improving the performance and safety of an electrochemical device.

Meanwhile, the inventors of the present invention have a fine defect or crack in the coating process when forming an organic / inorganic composite porous coating layer that can replace a conventional separator by coating a mixture of inorganic particles and a polymer that can be impregnated into an electrolyte on an electrode surface. In addition to the internal short circuit of the positive electrode through the micro-defects, it was found that the decrease in the manufacturing process rate of the battery due to the reduction in the mechanical properties of the organic / inorganic composite porous coating layer. In addition, it has been found that the safety and performance effects of the battery appear to conflict with each other due to the heterogeneous morphology of the formed organic / inorganic composite porous coating layer.

Accordingly, the present inventors can continuously maintain the morphology of the coating layer and introduce a porous polymer support on the electrode as a backbone to prevent desorption with the electrode when assembling the battery. The present invention has been completed by contemplating that the above-described problems can be solved when integrated through direct attachment on the electrode surface.

SUMMARY OF THE INVENTION An object of the present invention is to provide an electrode capable of improving the interfacial adhesion with the electrode and a uniform morphology of the coating layer, a method of manufacturing the same, and an electrochemical device including the same.

The present invention provides an electrode including an electrode active material layer in which electrode active material particles are electrically connected on one or both surfaces of a current collector, comprising: (a) a porous polymer support attached to the surface of an electrode active material layer and integrated; And (b) an inorganic / inorganic composite porous film including an inorganic particle and a binder polymer-containing composite coating layer formed on at least one region selected from the group consisting of a surface of the polymer support and a portion of pores in the support, on one or both surfaces of the electrode surface. The present invention provides an electrode, a method of manufacturing the same, an electrochemical device including the electrode, and preferably a lithium secondary battery.

In addition, the present invention is a polymer film in which a plurality of nanofibers are added to or coated on one or more regions of the electrode active material particles and the interior of the pores of the electrode while the electrode active material particles maintain the pore structure, thereby forming a porous web. It provides an electrode comprising a layer.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

In the present invention, the organic / inorganic composite porous coating layer that can replace the role of the conventional separator through excellent thermal safety and electrolyte transfer ability, but instead of coating directly on the electrode substrate, the coating layer on the electrode surface As a support for firmly bonding and maintaining their compositional morphology uniformly, a porous polymer support that is directly attached on the electrode surface and integrated is used.

1) The electrode having an organic / inorganic composite porous coating layer composed of a mixture of inorganic particles and a binder polymer on the surface of a conventional electrode was able to achieve excellent thermal safety compared to a conventional polyolefin-based separator, whereas the size and shape of electrode particles And / or the affinity with the coating liquid is different according to the surface properties thereof, so that the composition morphology of the coating layer is not maintained uniformly, there was a problem that the battery assembly characteristics and the safety effect of the battery appear to conflict with each other.

That is, even if coated with the same composition, when the composition of the inorganic particles and the binder polymer in the formed coating layer is different, for example, in the coating portion having a high polymer content, the resistance to peeling and scratching is increased and battery assembly characteristics are improved. As a result, the content of inorganic particles becomes relatively small, which leads to a decrease in the movement of lithium ions due to low porosity and a decrease in performance of the battery. In addition, a decrease in physical properties due to external stress causes a safety of the internal short circuit of the battery. The problem is caused to be significantly reduced. On the other hand, when the content of the inorganic particles is large, the performance and safety of the battery is improved, but the resistance to peeling and scratech, etc. is reduced, the battery assembly characteristics are significantly reduced.

On the contrary, in the present invention, by using the porous polymer support directly attached on the electrode substrate, the structure and composition morphology of the organic / inorganic composite porous coating layer described above can be continuously maintained, and thus the electrode is used. The resulting effects can be elevated to each other.

2) Also, like the conventional organic / inorganic composite porous coating layer formed on the electrode, the organic / inorganic composite porous film of the present invention also serves as a spacer for passing ions while preventing electronic contact between the anode and the cathode. It acts as a separator. When an incomplete coating layer or crack occurs due to internal or external factors when the coating layer is formed, the electrode into which the organic / inorganic composite porous coating layer is introduced causes contact between both electrodes through the incomplete coating layer or cracks, and thus causes an internal short circuit of the battery. Thereby, the assembly process rate of a battery will fall remarkably. In addition, even if there are no micro-defects such as cracks in the coating layer, mechanical properties such as brittleness of the organic / inorganic composite porous coating layer may be deteriorated, resulting in a problem that the coating layer is detached from the electrode during the winding assembly process.

In contrast, in the present invention, the organic / inorganic composite porous coating layer is introduced on the porous support attached directly on the electrode and excellent in interfacial adhesion with the electrode, thereby improving battery assembly characteristics regardless of the type of battery assembly method. . Even if cracks or the like exist in the coating layer, the contact between the positive electrodes is blocked by the polymer support attached to the electrodes, thereby greatly improving the defect rate generated in the battery assembly process.

The support directly attached on the electrode surface according to the present invention is a polymer that is easy to coat and bond on the electrode substrate, and has no special limitation as long as it has a porous structure to allow the transfer of lithium ions between both electrodes. .

The porous polymer support may be in the form of a nonwoven fabric in which a porous web is formed by crossing nanofibers, or in the form of a porous membrane including a plurality of pores. For example, it may be in the form of a spunbond or melt blown composed of long fibers. Particularly, a nonwoven fabric having a large number of large pore structures therein to improve the electrolyte impregnation rate is preferable.

The spawn bond method is a single continuous process, receives heat and melts to form long fibers, and is stretched by hot air to form a web. The melt blown process is a process of spinning a polymer capable of forming a fiber through a spinneret formed of hundreds of small orifices. It is a three-dimensional fiber with a spider-web structure.

The porous polymer support is directly attached to the electrode to have a structure integrated with the electrode, in which the method of attaching the polymer support on the electrode is not particularly limited. For example, a polymer solution in which a polymer is dissolved in a solvent is discharged and coated on a surface of an electrode manufactured by a high voltage applied spinning nozzle in an electrospinning apparatus, or includes a plurality of pores on the surface of the electrode. The porous membrane may be bonded by heat fusion.

The electrode integrated with the porous polymer support by the direct attachment may have a shape in which a plurality of nanofibers are coated to a predetermined thickness or more by inserting a plurality of nanofibers into the pore portion of the electrode or the electrode where the electrode active material particles maintain the pore structure. Or may be in the form of bonding with the porous membrane. Therefore, unlike a battery structure in which a conventional electrode and a separator are simply laminated (lamination, stack), the interfacial adhesion may be significantly improved.

The porous polymer support is not particularly limited as long as it can be attached to the electrode through spinning, coating, fusion, or the like. Non-limiting examples of these include high density polyethylene, low density polyethylene, linear low density polyethylene, ultra high molecular weight polyethylene, polypropylene terephthalate, polyethylene terephthalate, polybutylene terephthalate, polyester, Polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone, polyethersulfone, polyphenyleneoxide, polyphenylene Sulfidero (polyphenylenesulfidro), polyethylenenaphthalene (polyethylenenaphthalene) or a mixture thereof. In particular, in order to raise the thermal safety effect, it is preferable to use a heat resistant polymer or other engineering plastics with a melting temperature of 200 ° C. or higher.

The thickness of the porous polymer support is not particularly limited, but is preferably in the range of 1 to 100 μm, more preferably in the range of 5 to 50 μm. If it is less than 1 μm, it is difficult to achieve a desired effect, and if it is more than 100 μm, it may act as a resistive layer. In addition, pore size and porosity is also not particularly limited, pore size is in the range of 0.01 to 50㎛, porosity is preferably in the range of 5 to 95%.

One of the constituents of the organic / inorganic composite porous coating layer formed on the surface of the porous polymer support and / or a part of the pores of the support according to the present invention is an inorganic particle commonly used in the art.

The inorganic particles serve as a main component for preparing the final organic / inorganic porous coating layer, and form micro pores by enabling an interstitial volume between the inorganic particles. It also serves as a kind of spacer to maintain physical shape. In addition, since the inorganic particles generally have a property that mechanical properties do not change even at a high temperature of 200 ° C. or higher, the formed organic / inorganic porous coating layer has excellent heat resistance.

The inorganic particles are not particularly limited as long as they are electrochemically stable. That is, the inorganic particles that can be used in the present invention are not particularly limited as long as the oxidation and / or reduction reactions do not occur in the operating voltage range of the battery to be applied (for example, 0 to 5 V on the basis of Li / Li ⁺ ). In particular, in the case of using the inorganic particles having the ion transfer ability, since the ion conductivity in the electrochemical device can be improved to improve the performance, it is preferable that the ion conductivity is as high as possible. In addition, when the inorganic particles have a high density, it is not only difficult to disperse during coating, but also has a problem of weight increase during battery manufacturing, and therefore, the smallest density is desirable. In addition, in the case of the inorganic material having a high dielectric constant, it is possible to improve the dissociation degree of the electrolyte salt, such as lithium salt, in the liquid electrolyte, thereby improving the ionic conductivity of the electrolyte solution.

For the foregoing reasons, the inorganic particles are preferably high dielectric constant inorganic particles having a dielectric constant of 5 or more, preferably 10 or more, inorganic particles having a lithium ion transfer ability, or a mixture thereof.

Non-limiting examples of inorganic particles having a dielectric constant of 5 or more include BaTiO ₃ , Pb (Zr, Ti) O ₃ (PZT), Pb _1-x La _x Zr _1-y Ti _y O ₃ (PLZT), PB (Mg ₃ Nb _2/3 ) O ₃ -PbTiO ₃ (PMN-PT), hafnia (HfO ₂ ), SrTiO ₃ , SnO ₂ , CeO ₂ , MgO, NiO, CaO, ZnO, ZrO ₂ , Y ₂ O ₃ , Al ₂ O ₃ , TiO _2, SiC Or mixtures thereof.

An inorganic particle having a lithium ion transfer capacity is referred to in the present invention an inorganic particle having a function of transporting lithium ions without containing lithium, but containing lithium element, the inorganic particle having a lithium ion transfer capacity is inside the particle structure. Since lithium ions can be transferred and transported due to a kind of defect present, lithium ion conductivity in the battery is improved, thereby improving battery performance. Non-limiting examples of the inorganic particles having a lithium ion transfer capacity include lithium phosphate (Li ₃ PO ₄ ), lithium titanium phosphate (Li _x Ti _y (PO ₄ ) ₃ , 0 <x <2, 0 <y <3) , Lithium aluminum titanium phosphate (Li _x Al _y Ti _z (PO ₄ ) ₃ , 0 <x <2, 0 <y <1, 0 <z <3), 14Li ₂ O-9Al ₂ O ₃ -38TiO ₂ -39P (LiAlTiP) _x O _y series glass such as ₂ O ₅ (0 <x <4, 0 <y <13), lithium lanthanum titanate (Li _x La _y TiO ₃ , 0 <x <2, 0 <y <3 ), Li germanium thiophosphate such as Li _3.25 Ge _0.25 P _0.75 S ₄ (Li _x Ge _y P _z S _w , 0 <x <4, 0 <y <1, 0 <z <1, 0 <w < 5), lithium nitrides such as Li ₃ N (Li _x N _y , 0 <x <4, 0 <y <2), SiS ₂ series glass such as Li ₃ PO ₄ -Li ₂ S-SiS ₂ (Li _x P ₂ S ₅ series glass (Li _x P _y S _z , 0 <, such as Si _y S _z , 0 <x <3, 0 <y <2, 0 <z <4), LiI-Li ₂ SP ₂ S _5, etc. x <3, 0 <y <3, 0 <z <7) or mixtures thereof.

In particular, the aforementioned Pb (Zr, Ti) O ₃ (PZT), Pb _1-x La _x Zr _1-y Ti _y O ₃ (PLZT), PB (Mg ₃ Nb _2/3 ) O ₃ -PbTiO ₃ (PMN -PT) and hafnia (HfO ₂ ) not only exhibit high dielectric constants with dielectric constants of more than 100, but also have piezoelectricity in which electric charges are generated when a tension or tension is applied under a constant pressure, thereby causing a potential difference between both sides. It is possible to fundamentally improve the safety of the battery by preventing the occurrence of internal short circuit of the positive electrode due to external impact. In addition, synergistic effects of the high dielectric constant inorganic particles and the inorganic particles having lithium ion transfer ability may be doubled.

In the present invention, by adjusting the size of the inorganic particles, the content of the inorganic particles and the composition of the inorganic particles and the polymer constituting the organic / inorganic composite porous coating layer, pores included in the electrode, pores included in the porous polymer support attached to the electrode and In addition, it is possible to form and control the pore structure of the organic / inorganic composite porous coating layer. The pore structure is then filled with the liquid electrolyte to be injected, resulting in a significant reduction in the interfacial resistance generated between the inorganic particles or between the inorganic particles and the binder polymer.

The size of the inorganic particles is not limited, but is preferably in the range of 0.001 to 10 ㎛ as much as possible in order to form a coating layer of uniform thickness and appropriate porosity. If it is less than 0.001㎛ dispersibility is difficult to control the physical properties of the organic / inorganic porous coating layer, if it exceeds 10㎛, the thickness of the organic / inorganic porous coating layer made of the same solid content is increased, mechanical properties are lowered, In addition, an excessively large pore size may increase the probability of internal short circuits during battery charging and discharging.

According to the present invention, one of the components of the organic / inorganic composite porous coating layer formed on the surface of the porous polymer support directly attached to the electrode and / or a part of the pores of the support may connect and fix the inorganic particle (s). Binder polymers conventional in the art can be used.

In particular, it is possible to use a glass transition temperature (Tg) as low as possible, preferably in the range of -200 to 200 ℃. This is because the mechanical properties such as flexibility and elasticity of the final film can be improved. The polymer faithfully plays a role of a binder for stably connecting and stabilizing inorganic particles and particles, thereby contributing to the prevention of mechanical property deterioration of the organic / inorganic composite coating layer to be finally manufactured.

In addition, the binder polymer does not necessarily have an ion conducting ability, but when the polymer having an ion conducting ability is used, the performance of the electrochemical device may be further improved. Therefore, the binder polymer is preferably as high as possible dielectric constant. In fact, since the dissociation degree of the salt in the electrolyte depends on the dielectric constant of the electrolyte solvent, the higher the dielectric constant of the polymer, the higher the salt dissociation in the electrolyte of the present invention. The dielectric constant of the polymer may be in the range of 1.0 to 100 (measurement frequency = 1 kHz), particularly preferably 10 or more.

In addition to the functions described above, the binder polymer of the present invention may have a feature that can exhibit a high degree of swelling of the electrolyte by gelling when the liquid electrolyte is impregnated. Accordingly, polymers having a solubility index of 15 to 45 MPa ^1/2 are preferred, more preferably in the range of 15 to 25 MPa ^1/2 and 30 to 45 MPa ^1/2 . Therefore, hydrophilic polymers having more polar groups than hydrophobic polymers such as polyolefins are preferable. This is because when the solubility index is less than 15 MPa ^{1/2 and more} than 45 MPa ^1/2 , it is difficult to be swelled by a conventional battery liquid electrolyte.

Non-limiting examples of binder polymers that can be used include polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichloroethylene, Polymethylmethacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, ethylene vinyl acetate copolymer, polyethylene oxide ( polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, cyanoethylpolyvinylalcohol Cyanoethylcellulose (cyanoeth ylcellulose, cyanoethylsucrose, pullulan, carboxyl methyl cellulose, acrylonitrile-styrene-butadiene copolymer, polyimide or these And mixtures thereof. In addition, any material can be used singly or in combination as long as it contains the above-described properties.

The composition ratio of the inorganic particles and the binder polymer as the coating layer component is not particularly limited, but may be controlled within a range of 5:95 to 99: 1 wt%, particularly preferably in a range of 50:50 to 99: 1 wt%. If the ratio is less than 5: 95% by weight, the polymer content becomes excessively large, resulting in a decrease in pore size and porosity due to a decrease in the void space formed between the inorganic particles, resulting in deterioration of final cell performance. When exceeding, the polymer content is too small, which may lower the mechanical properties of the final organic / inorganic composite porous coating layer due to the weakening of the adhesion between the inorganic materials.

The thickness of the coating layer formed by coating the mixture of the inorganic particles and the binder polymer is not particularly limited, but may be adjusted in consideration of battery performance, and may be independently adjusted on the positive electrode and the negative electrode. In the present invention, in order to reduce the internal resistance of the battery, it is preferable to adjust the thickness of the coating layer within a range of 1 to 100 μm, more preferably 1 to 30 μm.

In addition, the pore size and porosity of the organic / inorganic composite porous coating layer is mainly dependent on the size of the inorganic particles, such a pore structure is to be filled with the electrolyte to be injected later, the electrolyte thus filled to act as an ion transfer do. Therefore, the pore size and porosity are important influence factors for controlling the ionic conductivity of the coating layer. Pore size and porosity (porosity) of the organic / inorganic composite porous coating layer of the present invention is preferably in the range of 0.01 to 10㎛, 5 to 95%, but is not limited thereto.

The organic / inorganic composite porous coating layer according to the present invention may further include other additives conventionally known in the art, in addition to the above-described inorganic particles and polymers.

The thickness of the organic / inorganic composite porous film of the present invention composed of the above-described porous polymer support and the organic / inorganic composite porous coating layer formed on the polymer support is not particularly limited and may be adjusted in consideration of battery performance. It is preferably in the range from 1 to 100 μm, more preferably in the range from 2 to 30 μm. By adjusting the thickness range, battery performance can be improved.

In addition, the pore size of the organic / inorganic composite porous film is preferably in the range of 0.01 to 50㎛ and porosity 5 to 95% range, but is not limited thereto.

Electrodes having an organic / inorganic composite porous film directly introduced on the electrode surface according to the present invention may be prepared according to conventional methods known in the art.

Hereinafter, for one preferred embodiment thereof, (a) attaching a porous polymer support on the surface of the electrode prepared; (b) dissolving the binder polymer in a solvent to prepare a polymer solution, and then adding and mixing the inorganic particles to the polymer solution; And (c) coating and drying one or more regions consisting of a surface of the porous polymer support and a portion of the pores of the support with the mixture of step (b).

First, 1) the porous polymer support is directly attached onto the prepared electrode surface.

The method of attaching the porous polymer support on the electrode surface is not particularly limited, and conventional methods known in the art may be used, such as coating, spinning, fusion, and the like.

As an example of electrospinning, the electrospinning method directly applies a positive (+) or a negative (-) voltage to the spinning nozzle part to charge the solution, and then discharges the charged solution through the spinning nozzle part to the air layer. And then through the stretching of the charged filaments in the air layer and through another filament branching to produce microfibers. The discharge filament in which the positive charge is charged through the application of the positive (+) voltage or the discharge filament in which the negative charge is charged through the application of the negative voltage is included in the electric field formed between the spinning nozzle unit and the collector. The microfibers undergo extreme fluctuations due to electrical effects such as mutual repulsion between adjacent filaments. The micro filaments formed as described above are nanofibers whose diameters correspond to nanoscale fibers, and are manufactured in the form of a web by being integrated on a grounded integrated portion or an integrated portion charged opposite to the polarity of the charged filament.

In the above-described electrospinning method, a polymer solution constituting a porous polymer support is injected into a barrel of an electrospinning apparatus, and then discharged through a spinning nozzle to which a high voltage is applied to coat a surface of a prepared electrode. And dry. At this time, the high voltage range, the discharge amount, the concentration of the polymer solution and the like is not particularly limited.

In addition, it is also possible to attach by a mechanical method, for example, a porous membrane (membrane) comprising a plurality of pores on the surface of the electrode can be bonded through thermal fusion. At this time, the pressure may be applied together with the heat, and the range of heat and pressure is not particularly limited.

The electrode may be prepared by a conventional method known in the art, for example, applying and drying an electrode slurry including an electrode active material, optionally a binder and / or a conductive agent on a current collector. After drying, pressing may be carried out through a pressing process.

2) A binder solution is dissolved in a suitable organic solvent to prepare a polymer solution.

As the solvent, the solubility index is similar to that of the polymer to be used, and a boiling point is preferably low. This is because the mixing can be made uniform, after which the solvent can be easily removed. Non-limiting examples of the solvent include acetone, tetrahydrofuran, methylene chloride, chloroform, dimethylformamide, N-methyl-2-pyrrolidone (N -methyl-2-pyrrolidone (NMP), cyclohexane, water or a mixture thereof.

3) A mixture of inorganic particles and a polymer is prepared by adding and dispersing inorganic particles to the prepared polymer solution.

The inorganic particles are preferably added to the binder polymer solution and then crushed. In this case, the crushing time is suitably 1 to 20 hours, and the particle size of the crushed inorganic particles is preferably 0.01 to 10 μm as mentioned above. As the shredding method, a conventional method can be used, and a ball mill method is particularly preferable.

The composition of the mixture consisting of inorganic particles and polymers is not particularly limited, and thus the thickness, pore size and porosity of the organic / inorganic composite porous coating layer of the present invention can be adjusted.

4) The mixture of the prepared inorganic particles and the polymer is coated on a porous polymer support attached on the electrode, and then dried to obtain an electrode on which an organic / inorganic composite porous film is formed.

At this time, the coating method of the mixture of the inorganic particles and the binder polymer on the porous polymer support may be used a conventional method known in the art, for example, dip (Dip) coating, die coating, roll ( Various methods may be used, such as roll coating, comma coating, or a mixture thereof.

The electrode of the present invention prepared as described above not only forms a rigid structure in which the electrode active material layer, the porous polymer support, and the organic / inorganic composite porous coating layer are organically bonded to each other, but also each layer, that is, (a) the electrode active material on the current collector. An electrode in which particles are formed while forming a pore structure; (b) a porous polymer support attached to the electrode surface; (c) an inorganic particle and a binder mixed coating layer formed on the surface of the porous polymer support and at least one region consisting of a part of pores of the porous polymer support, wherein the inorganic particles are connected and fixed by the binder polymer, and an empty space between the inorganic particles Due to the interstitial volume, a unique pore structure is present and maintained in both the organic / inorganic composite porous coating layer in which the pore structure is formed. Therefore, the lithium ion can be easily transferred through the plurality of pore structures present in each of the layers, and thus it can be predicted that the degradation of the battery due to the introduction of the coating layer can be minimized (see FIG. 1).

The electrode directly introduced with the organic / inorganic composite porous film of the present invention prepared as described above may be used as an electrode and separator of an electrochemical device, preferably a lithium secondary battery. In particular, when a gelable polymer is used as the coating layer component when the liquid electrolyte is impregnated, after the battery is assembled using the separator, the electrolyte and the polymer may react by injecting the electrolyte to form a gel-type organic / inorganic composite electrolyte.

The gel organic / inorganic composite electrolyte of the present invention is easier to manufacture than the gel polymer electrolyte of the prior art, and due to the pore structure, there are a large number of spaces filled with the liquid electrolyte to be injected, thereby exhibiting high ion conductivity and electrolyte impregnation rate. Battery performance can be improved.

The present invention provides an electrochemical device comprising an anode, a cathode, and an electrolyte, wherein the anode, the cathode, or the positive electrode is an electrode to which the aforementioned organic / inorganic composite porous film is introduced. .

The electrochemical device includes all devices that undergo an electrochemical reaction, and specific examples thereof include all kinds of primary, secondary cells, fuel cells, solar cells, or capacitors.

For example, a method of manufacturing an electrochemical device using the electrode manufactured as described above, without using a conventional polyolefin-based microporous separator, winding or stacking using only the electrode manufactured as described above. It may be manufactured by injecting an electrolyte after assembling through a process such as stacking.

The organic / inorganic composite porous film according to the present invention is not particularly limited, and the electrode active material may be prepared in a form bound to the electrode current collector according to conventional methods known in the art.

Non-limiting examples of the positive electrode active material of the electrode active material may be a conventional positive electrode active material that can be used for the positive electrode of the conventional electrochemical device, in particular lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide, lithium iron oxide or Lithium intercalation materials such as composite oxides formed by combination are preferred.

Non-limiting examples of the negative electrode active material may be a conventional negative electrode active material that can be used in the negative electrode of the conventional electrochemical device, in particular lithium metal or lithium alloy, carbon, petroleum coke, activated carbon, Lithium adsorbents such as graphite or other carbons are preferred. Non-limiting examples of the positive electrode current collector is a foil made by aluminum, nickel or a combination thereof, and non-limiting examples of the negative electrode current collector by copper, gold, nickel or copper alloy or a combination thereof Foils produced.

Electrolyte that may be used in the present invention is A ⁺ B ^- A salt of the structure, such as, A ⁺ is Li ^+, Na ^+, K ⁺ comprises an alkaline metal cation or an ion composed of a combination thereof, such as, and B ^- 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 -, C (CF 2 SO ₂ ) Salts containing ions consisting of anions such as ₃ ^- or combinations thereof include propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC) , Dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran, N-methyl-2-pyrrolidone (NMP), ethyl methyl carbonate (EMC), gamma butyrolactone (γ-butyrolactone Or dissolved in an organic solvent consisting of a mixture thereof, but is not limited thereto.

In the present invention, the electrolyte injection may be performed at an appropriate step in the manufacturing process of the electrochemical device, depending on the manufacturing process and the required physical properties of the final product. That is, it may be applied before the assembly of the electrochemical device or at the final stage of assembly of the electrochemical device.

In addition, since the electrode according to the present invention is integral with the separator and the electrode, the separator used in the related art is not necessarily required, but the electrode having the coating layer of the present invention may be formed of a polyolefin-based microporous separator according to the use and characteristics of the final electrochemical device. It can also be assembled together.

As a process of applying the electrode directly introduced into the organic / inorganic composite porous film of the present invention to a battery, a lamination and folding process of the electrode is possible in addition to the general winding process.

The electrochemical device manufactured by the above method is preferably a lithium secondary battery, and specific examples of the lithium secondary battery include a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery. .

In addition, the present invention is a polymer film in which a plurality of nanofibers are added or coated to one or more regions composed of the surface of an electrode and the inside of the pore of the electrode while the electrode active material particles maintain the pore structure, thereby forming a porous web. Provided is an electrode comprising a layer. In this case, the polymer film layer serves as a separator.

Hereinafter, preferred examples are provided to help understanding of the present invention, but the following examples are merely to illustrate the present invention, and the scope of the present invention is not limited to the following examples.

Example  One

(Anode manufacturing)

A positive electrode mixture slurry was prepared by adding 94 wt% of LiCoO ₂ as a cathode active material, 3 wt% of carbon black as a conductive agent, and 3 wt% of PVdF as a binder to N-methyl-2 pyrrolidone (NMP) as a solvent. . The positive electrode mixture slurry was applied to a thin film of aluminum (Al), which is a positive electrode current collector having a thickness of about 20 m, and dried to prepare a positive electrode.

(Cathode production)

A negative electrode mixture slurry was prepared by adding carbon powder as a negative electrode active material, PVdF as a binder, and carbon black as a conductive agent at 96 wt%, 3 wt%, and 1 wt%, respectively, to NMP as a solvent. The negative electrode mixture slurry was applied to a thin film of copper (Cu), which is a negative electrode current collector having a thickness of 10 m, and dried, thereby preparing a negative electrode.

(Manufacture of electrodes into which nonwoven fabric and organic / inorganic composite porous coating layer applied directly on electrode are introduced)

The PP film of low melting point was heated to melt above the melting point, and then coated to have a thickness of about 10 μm on the surface of the electrode through a spinning process. Subsequently, BaTiO ₃ powder was added to the polyvinylidene fluoride-hexafluoropropylene copolymer (PVdF-HFP) polymer solution at a concentration of 37% by weight of the total solids and dispersed, and the mixed solution (BaTiO 3 / PVdF-HFP = 90/10 (weight) % Ratio)). The mixed solution thus prepared was coated on the PP layer attached on the electrode by using a dip coating method, wherein the thickness of the organic / inorganic composite porous coating layer was about 20 μm. Its structural diagram is shown in FIG.

(Battery manufacturing)

The positive and negative electrodes into which the organic / inorganic composite porous film was introduced were assembled by stacking, and 1M lithium hexafluorophosphate (LiPF ₆ ) was dissolved in the assembled battery. An ethyl carbonate (EC / PC / DEC = 30: 20: 50 wt%) based electrolyte was injected to prepare a lithium secondary battery.

[Comparative Examples 1 to 3]

Comparative example  One

A lithium secondary battery was manufactured in the same manner as in Example 1, except that the battery was assembled using the positive electrode, the polyolefin separator, and the negative electrode instead of the electrode to which the organic / inorganic composite porous film was directly introduced.

Comparative example  2

A lithium secondary battery was manufactured in the same manner as in Example 1, except that only the organic / inorganic composite porous coating layer was formed on the electrode surface without directly applying a PP layer on the electrode.

Comparative example  3

A lithium secondary battery was manufactured in the same manner as in Example 1, except that the electrode in which the PP layer was directly applied through the spinning process without forming an organic / inorganic composite coating layer was used. In this case, charging and discharging were impossible due to an internal short circuit of the battery.

Experimental Example  1. Surface Analysis of Electrodes

In order to analyze the surface of the electrode directly formed organic / inorganic composite porous film on the electrode according to the present invention, the following experiment was performed.

In Example 1, an electrode in which an organic / inorganic composite porous film (PP / PVdF-HFP / BaTiO ₃ ) was formed was used.

As a result of checking the surface by Scanning Electron Microscope (SEM), the electrode of the present invention has an organic / inorganic composite porous coating layer composed of inorganic particles and a binder polymer on the pores of the porous support and / or the surface of the support. Rather, it could be seen that a uniform pore structure was formed by the inorganic particles (see FIG. 2).

Experimental Example  2. Performance Evaluation of Lithium Secondary Battery

In order to evaluate the performance of a lithium secondary battery having an electrode in which an organic / inorganic composite porous film was directly formed on an electrode according to the present invention, it was performed as follows.

1-1. Defect rate improvement experiment

The lithium secondary battery of Example 1 having an organic / inorganic composite porous film directly formed on a surface thereof, a battery of Comparative Example 1 prepared according to a conventional method, and an electrode having an organic / inorganic composite porous coating layer formed without a porous support The defective rate in the manufacturing process of a lithium secondary battery was evaluated using the battery of the comparative example 2 provided.

As a result, the defect rate of the battery of Comparative Example 1 and the battery of Example 1 using the commercially available PP separator was almost zero, while in Comparative Example 2, the probability of internal short circuit was 20% or more. 1).

That is, the organic / inorganic nanocomposite porous film (or coating layer) formed on the electrode surfaces of Example 1 and Comparative Example 2 all play the same role as the conventional polyolefin-based separator. As in Comparative Example 2, when a mixture composed of inorganic particles and a binder polymer is directly coated on the electrode surface to have a fine incomplete coating layer, the internal short circuit of the battery is directly induced, while the polymer support is applied on the electrode in advance. When the inorganic composite porous coating layer was formed, it was confirmed that the defect rate due to internal short circuit of the battery could be greatly improved by keeping the morphology of the coating layer constant.

Condition Example 1 Comparative Example 1 Comparative Example 2 Defective rate 0.2% 0.2% 20%

1-2. Battery performance experiment

Each battery having a battery capacity of 30mAh was cycled at a discharge rate of 0.5C, 1C, and 2C, and their discharge capacities are shown in Table 2 by plotting the C-rate characteristics.

As a result, the batteries of Example 1 and Comparative Example 2, in which the organic / inorganic composite porous coating layer was formed instead of the separator, showed high-rate discharge (C-rate) characteristics comparable to those of Comparative Example 1 having a conventional polyolefin-based separator ( See Table 2).

Discharge rate Example 1 (mAh) Comparative Example 1 (mAh) Comparative Example 2 (mAh) 0.5C 31.77 31.62 31.55 1C 30.79 31.35 30.02 2C 23.54 20.95 23.23

As described above, the electrode in which the organic / inorganic composite porous film is directly formed on the electrode according to the present invention not only improves the weak high temperature safety of the conventional polyolefin-based separator, but also significantly reduces the battery failure rate in the manufacturing process. Can be.

Claims (22)

In the electrode comprising an electrode active material layer electrically connected to the electrode active material particles on one side or both sides of the current collector, (a) an integrated porous polymeric support adhered to the surface of the electrode active material layer; And (b) a composite coating layer containing an inorganic particle and a binder polymer formed on at least one region selected from the group consisting of a surface of the polymer support and a portion of pores in the support The electrode characterized in that the organic / inorganic composite porous film comprising a formed on one or both surfaces of the electrode surface. The electrode of claim 1, wherein the porous polymer support is in the form of a nonwoven fabric in which a porous web is formed by the intersection of nanofibers, or a porous membrane including a plurality of pores. The method of claim 2, wherein the porous polymer support (i) a polymer solution formed by discharging and coating a polymer solution dissolved in a solvent on a surface of an electrode prepared through a spinning nozzle to which high voltage is applied in an electrospinning apparatus; or (ii) an electrode which is attached by thermally fusion bonding a porous membrane including a plurality of pores on a surface of a prepared electrode. According to claim 1, The electrode is a plurality of nano-fiber is injected and coated on the surface of the electrode or the pores of the electrode electrode electrode material particles are bound while maintaining the pore structure; Or an electrode having improved interfacial adhesion by bonding to a porous membrane. The method of claim 1, wherein the components of the porous polymer support are high density polyethylene, low density polyethylene, linear low density polyethylene, ultra high molecular weight polyethylene, polypropylene terephthalate, polyethylene terephthalate, polybutylene terephthalate, polybutylene terephthalate, polyester (polyester), polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone, polyethersulfone, polyphenyleneoxide And at least one electrode selected from the group consisting of polyphenylenesulfidro and polyethylenenaphthalene. The electrode of claim 1, wherein the pore size of the porous polymer support is in the range of 0.01 to 50 μm, and the porosity is in the range of 5 to 95%. The composite coating layer of claim 1, wherein the inorganic particles and the binder polymer-containing composite coating layer are connected and fixed between the inorganic particles by a binder polymer, and a pore structure is formed due to an interstitial volume between the inorganic particles. Characteristic electrode. The electrode of claim 1, wherein the inorganic particles and the binder polymer-containing composite coating layer may serve as a separator. The electrode of claim 1, wherein the inorganic particles are composed of (a) inorganic particles having a dielectric constant of 5 or more, (b) inorganic particles having a lithium ion transfer ability, or a mixture thereof (a, b). The inorganic particle having a dielectric constant of 10 or more is BaTiO ₃ , Pb (Zr, Ti) O ₃ (PZT), Pb _1-x La _x Zr _1-y Ti _y O ₃ (PLZT), PB ( Mg ₃ Nb _2/3 ) O ₃ -PbTiO ₃ (PMN-PT), hafnia (HfO ₂ ), SrTiO ₃ , SnO ₂ , CeO ₂ , MgO, NiO, CaO, ZnO, ZrO ₂ , Y ₂ O ₃ , Al _At least one member selected from the group consisting of ₂ O _3, TiO ₂ and SiC; The inorganic particles having a lithium ion transfer capacity include lithium phosphate (Li ₃ PO ₄ ), lithium titanium phosphate (Li _x Ti _y (PO ₄ ) ₃ , 0 <x <2, 0 <y <3), and lithium aluminum titanium Spade (Li _x Al _y Ti _z (PO ₄ ) ₃ , 0 <x <2, 0 <y <1, 0 <z <3), (LiAlTiP) _x O _y series glass (0 <x <4, 0 <y <13), lithium lanthanum titanate (Li _x La _y TiO _3, 0 <x <2, 0 <y <3), lithium germanium thiophosphate (LixGeyPzSw, 0 <x <4, 0 <y < 1, 0 <z <1, 0 <w <5), Lithium Nitride (LixNy, 0 <x <4, 0 <y <2), SiS ₂ (LixSiySz, 0 <x <3, 0 <y <2 At least one electrode selected from the group consisting of 0 <z <4) series glass and P ₂ S ₅ (LixPySz, 0 <x <3, 0 <y <3, 0 <z <7) series glass. The electrode of claim 1, wherein the size of the inorganic particles ranges from 0.01 μm to 10 μm. The electrode of claim 1, wherein the content of the inorganic particles ranges from 5 to 99 wt% per 100 wt% of the mixture of the inorganic particles and the binder polymer. The electrode of claim 1, wherein the binder polymer has a solubility parameter ranging from 15 to 45 MPa ^1/2 . The method of claim 1, wherein the binder polymer is polyvinylidene fluoride-hexafluoropropylene (polyvinylidene fluoride-co-hexafluoropropylene), polyvinylidene fluoride-co-trichloroethylene (polyvinylidene fluoride-co-trichloroethylene), Polymethylmethacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, ethylene vinyl acetate copolymer, polyethylene oxide (polyethylene oxide), cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, cyanoethylpolyvinylalcohol ), Cyanoethylcellulose , Cyanoethylsucrose, pullulan, carboxyl methyl cellulose, acrylonitrile-styrene-butadiene copolymer and polyimide At least one electrode selected. The electrode of claim 1, wherein the pore size of the organic / inorganic composite porous film is in the range of 0.01 to 50 μm, and the porosity is in the range of 5 to 95%. The electrode of claim 1, wherein the organic / inorganic composite porous film has a thickness in a range of 1 to 100 μm. An electrochemical device comprising an anode, a cathode, and an electrolyte, wherein the anode, the cathode, or the positive electrode is an electrode according to any one of claims 1 to 16. 18. The electrochemical device of claim 17, wherein the electrochemical device further comprises a microporous separator. The electrochemical device of claim 17, wherein the electrochemical device is a lithium secondary battery. (a) attaching the porous polymeric support on the surface of the prepared electrode; (b) dissolving the binder polymer in a solvent to prepare a polymer solution, and then adding and mixing the inorganic particles to the polymer solution; And (c) coating and drying one or more regions consisting of a surface of the porous polymer support and a portion of the pores of the support with the mixture of step (b) The manufacturing method of the electrode in any one of Claims 1-16 containing a. The method of claim 20, wherein step (a) (i) injecting a polymer solution dissolved in a solvent into a barrel of an electrospinning apparatus, and then discharging it through a spinning nozzle to which a high voltage is applied to coat and dry the prepared electrode surface; or (ii) bonding a porous membrane including a plurality of pores on the surface of the prepared electrode through thermal fusion; Electrode comprising a polymer film layer in which a plurality of nanofibers are injected or coated on the surface of the electrode to which the electrode active material particles are bound while maintaining the pore structure, and at least one of the electrodes is formed or coated to form a porous web. .

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