KR20180035602A - Electrode assembly for all-solid battery comprising porous current collector - Google Patents

Abstract

The present invention relates to an electrode assembly for an all-solid battery having a porous current collector. More specifically, the present invention a high loading electrode assembly having an electrode composite material supported in a porous current collector. According to the present invention, an electron transfer path can be secured in an electrode by using an electrode assembly to which the porous current collect is applied, thereby reducing an electrode resistance, and smoothly transferring an electron inside the electrode even if the electrode is produced through high loading. In addition, since the current collector substitutes for a conductor, the conductive material content in a slurry composition can be reduced or removed, thereby reducing a distribution issue of a conductive material generating in slurry production, and making a more uniform electrode structure.

Description

TECHNICAL FIELD [0001] The present invention relates to an electrode assembly for a full-solid battery including a porous collector,

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an electrode composite for a full-solid battery including a porous current collector, and more particularly to a high-loading electrode composite in which an electrode composite material is supported on a porous current collector.

BACKGROUND ART [0002] In recent years, demand for secondary batteries has increased in various applications such as power sources for PCs, video cameras, cellular phones, and the like, or power sources for electric vehicles and power storage media. Among secondary batteries, particularly, lithium secondary batteries have higher capacity density than other secondary batteries and can operate at a higher voltage. Therefore, they are used for information-related devices and communication devices as secondary batteries for miniaturization and weight reduction. Recently, A lithium secondary battery having a high output and a high capacity is being developed.

A typical lithium secondary battery is composed of an electrolyte containing a positive electrode (positive electrode, cathode), a negative electrode (negative electrode, anode) and a lithium salt interposed therebetween, and a nonaqueous liquid electrolyte or a solid electrolyte is used as such electrolyte. When a non-aqueous liquid electrolyte is used for the electrolyte, since the electrolyte penetrates into the inside of the anode, the interface between the cathode active material constituting the anode and the electrolyte tends to be formed, so that the electrical performance is high.

However, since the lithium-based secondary battery uses a combustible organic solvent for the liquid electrolyte, it is necessary to install a safety device in order to prevent ignition or rupture that may be caused by overcurrent due to short-circuit I will. Further, in order to prevent such a phenomenon, there are cases where the selection of the battery material or the design of the battery structure is restricted.

Therefore, the development of all solid-state cells using solid electrolytes instead of liquid electrolytes has been underway. Since all solid batteries do not contain a flammable organic solvent, they are advantageous in that a safety device can be simplified, and thus it is recognized that the battery is excellent in manufacturing cost and productivity. Further, since it is easy to laminate the junction structures including the pair of electrode layers including the positive electrode and the negative electrode and the solid electrolyte layer interposed between the electrode layers in series, it is possible to manufacture a battery having a high capacity and a high output, Is expected as a technology.

On the other hand, it is known that the contact resistance between the particles of the active material particles responsible for the battery reaction or between the active material particles and the solid electrolyte particles greatly affects the internal resistance of the battery in all solid state batteries. Particularly, with the repetition of charging and discharging, a change in the volume of the active material occurs, so that the contact with the active material and the solid electrolyte, the conductive material and the like is lowered, and the internal resistance tends to increase and the capacity tends to decrease . Accordingly, various techniques have been proposed to improve the contact properties between the particles of the active material and the solid electrolyte, and to suppress the increase of the internal resistance and the like.

For example, there is an attempt to improve the performance of the all-solid battery by paying attention to the interface between the positive electrode active material and the solid electrolyte material. For example, in a paper called "LiNbO ₃ -coated LiCoO ₂ as cathode material for all solid-state lithium secondary batteries" by Narumi Ohta, Electrochemistry Communications 9 (2007), 1486-1490, the surface of LiCoO ₂ (cathode active material) LiNbO ₃ (lithium niobate) is described as a coating material. This technique is to obtain a high power battery in such a manner as to reduce the interface resistance between the surface of LiCoO ₂ is coated with LiNbO _3, LiCoO ₂ as solid by suppressing the reaction between the electrolyte material, the solid electrolyte material and LiCoO _2.

Further, when the negative electrode active material reacts with the solid electrolyte material, a high resistance portion is generally formed on the surface of the negative electrode active material, so that the interface resistance between the negative electrode active material and the solid electrolyte material is increased. In order to solve such a problem, Japanese Laid-Open Patent Publication No. 2004-206942 discloses a method for producing a solid electrolyte membrane, which is chemically unreactive with a first solid electrolyte and has a lower ion conductivity than a first solid electrolyte layer (a sulfide-based solid electrolyte material) Discloses a pre-solid battery formed between the first solid electrolyte layer and a cathode made of metal lithium. This is to suppress the reaction between the first solid electrolyte layer and the metal lithium through formation of the second solid electrolyte layer having low ion conductivity.

However, attempts to improve the performance of such all-solid-state cells have failed to sufficiently lower the interfacial resistance between the anode and the anode active material and the solid electrolyte material, making them unsuitable for manufacturing a high-output, high-capacity battery.

Japanese Laid-Open Patent Publication No. 2004-206942

Electrochemistry Communications 9 (2007), 1486-1490

In order to solve the above-described problems, the inventors of the present invention have confirmed that it is possible to realize a high capacity battery by suppressing an increase in resistance at the interface by changing the electrode structure of the entire solid electrolyte.

Accordingly, it is an object of the present invention to provide an electrode composite for an all solid battery and a pre-solid battery using the same.

To achieve the above object, the present invention provides a porous collector, And an electrode active material supported on the porous collector electrode and a solid electrolyte.

The present invention also provides a pre-solid battery comprising the electrode composite.

The use of the electrode composite with the porous current collector according to the present invention can secure an electron transfer path inside the electrode, reduce the electrode resistance, and secure the electron transfer path through the current collector, It is possible to smoothly transfer electrons into the inside of the electrode. In addition, since the collector serves as a conductor, it is possible to reduce or eliminate the conductive material content in the slurry composition, thereby reducing the dispersion problem of the conductive material generated in the slurry production and making a more uniform electrode structure.

1 is a schematic view of a conventional electrode composite for a full solid battery.
2 is a schematic diagram of an electrode composite for a full-solid battery according to the present invention.

Hereinafter, the present invention will be described in detail in order to facilitate understanding of the present invention.

The present invention relates to a porous collector; And an electrode active material supported on the porous collector electrode and a solid electrolyte.

When charge and discharge occur, lithium ions and electrons move simultaneously in the same material to maintain the electrical neutrality of the material. At this time, lithium ions and electrons must escape from the same position as much as possible, so that the time required for ions or electrons to move within the material, that is, the resistance, can be reduced. In the case of an existing battery using a liquid electrolyte, the liquid electrolyte is impregnated inside the electrode, and the electrode active material and the conductor can form a liquid-solid-solid three-phase interface at the same time and the resistance is relatively small. This is because when the liquid seeps into the solid-solid interface, it is possible to make contact, through which ions and electron transfer paths can be connected in a line-contact manner.

However, since only the solid-solid-solid-solid contact exists in the anode electrode of the all-solid-state cell using the solid electrolyte, the ion and the electron transfer path are connected only in point contact. In this case, there are many points where ion and electron transfer are interrupted within the electrode, and the total resistance of the electrode is large.

According to the present invention, since the electrode active material is impregnated into the voids of the current collector when the charge and discharge are repeated in the case of the porous current collector, the electrode active material is prevented from being separated from the current collector, , Since the porous structure itself can contain the electrode active material, the conductive material can be omitted in the production of the active material slurry. That is, in the case of the porous current collector, the current collecting role and the role of the conductive material can be performed simultaneously.

Accordingly, the electrode can be formed by directly or indirectly supporting the electrode active material on the electrode layer, or by adding only a small amount of the conductive material to the electrode layer. At this time, the current collector functions not only to collect the electrons generated by the electrochemical reaction of the electrode active material, to supply the electrons necessary for the electrochemical reaction, but also to provide the electrode active material with the 3D And to provide a network structure.

The porous current collector according to the present invention includes a conductive skeleton and voids, and the skeleton may have a three-dimensional structure. The diameter or the thickness of the skeleton may vary depending on the loading amount of the electrode active material and the solid electrolyte, and therefore is not particularly limited in the present application.

The porous collector is preferably a web having a three-dimensional network structure. For example, a carbon paper, a conductive carbon foam, or an aluminum foam may be used as the porous collector. This shape can easily fill the electrode active material and the solid electrolyte in the pores and thus minimize the use of additional binders for their bonding, so that the electrode active material content in the electrode composite can be increased, and the amount of the conductive material used Can be reduced. Further, since the separation of the electrode active material is prevented, the utilization ratio of the electrode and the cycle life are increased.

The porous current collector is not particularly limited as long as it is porous without causing any chemical change to the entire solid electrolyte and has conductivity. Metals such as aluminum, nickel, copper, iron, nickel, cobalt, chromium, molybdenum and tungsten; Carbon such as natural graphite, artificial graphite, expanded graphite, carbon fiber, hard graphitizable carbon, carbon black, carbon nanotube, fullerene and activated carbon; And a combination thereof.

The pore size of the porous current collector is preferably 1 to 10 mm, and the porosity may be 10 to 90%, preferably 20 to 80%, more preferably 30 to 80%. If the pore size is less than 1 占 퐉 or the porosity is less than 10%, there is no impregnation effect of the active material. If the pore size exceeds 10 mm or the porosity exceeds 90%, the active material is impregnated with remaining voids, It can act as a resistor and can not perform the role of current collecting because it does not make contact with the active material.

For example, when the pre-solid battery according to the present invention is a pre-solid lithium secondary battery, the electrode active material occludes or releases lithium ions. In addition, the electrode active material used in the present invention can react with the above-described solid electrolyte material so that a high-resistance portion is generated at the interface between the electrode active material and the solid electrolyte material during the charge and discharge operations of the battery.

The porous current collector supporting the electrodes serves as a bridge between the materials and thus can reduce the interfacial resistance against the movement of electrons across the interface between the electrode active material and the solid electrolyte material, Can be suppressed.

The electrode active material and the solid electrolyte carried on the porous current collector may be located inside the porous structure and may be located at least a part of the external surface. If the electrode active material and the solid electrolyte are located on the entire outer surface of the porous structure, the electron transporting role of the porous current collector can be reduced. When the electrode active material and the solid electrolyte are located on a part of the outer surface of the porous structure or only inside the porous structure, the conductive metal or carbon exposed on the surface can perform an electron transferring role, It is preferable to increase the area.

The electrode active material carried on the porous collector may be a cathode active material when the electrode is a positive electrode or a negative active material when it is a negative electrode. At this time, each of the electrode active materials may be any active material applied to the conventional electrode, and may be determined according to the type of the conductive ion of the intended pre-solid battery, and is not particularly limited in the present invention.

As the cathode active material, materials known in the art can be used. For example, a lithium intercalation compound can be used, and specifically, a layered compound such as lithium cobalt oxide (LiCoO ₂ ), lithium nickel oxide (LiNiO ₂ ) Or compounds substituted with one or more transition metals; Lithium manganese oxides such as Li _{1 + x} Mn _{2 - x} O ₄ (where x = 0 to 0.33), LiMnO ₃ , LiMn ₂ O ₃ and LiMnO ₂ ; Lithium copper oxide (Li ₂ CuO ₂ ); Vanadium oxides such as LiV ₃ O ₈ , LiFe ₃ O ₄ , V ₂ O ₅ and Cu ₂ V ₂ O ₇ ; A Ni-site type lithium nickel oxide represented by the formula LiNi _{1 -x} M _x O ₂ (where M = Co, Mn, Al, Cu, Fe, Mg, B, or Ga and x = 0.01 to 0.3); Wherein M is at least _one element selected from the group consisting of LiMn _{2 - x} MxO ₂ where M = Co, Ni, Fe, Cr, Zn or Ta, x = 0.01 to 0.1, or Li ₂ Mn ₃ MO ₈ Or Zn); LiMn ₂ O _{4 in} which a part of Li in the formula is substituted with an alkaline earth metal ion; Disulfide compounds; Sulfide-based active materials; Sulfur; Titanium sulfide; Titanium disulfide; FeS; CuS; Sulfur carbon composite; And Fe ₂ (MoO ₄ ) ₃ , but are not limited thereto.

As the negative electrode active material, materials known in the art may be used. For example, carbon such as natural graphite, artificial graphite, expanded graphite, carbon fiber, hard graphitizable carbon, carbon black, carbon nanotube, fullerene, activated carbon, ; Metals such as Al, Si, Sn, Ag, Bi, Mg, Zn, In, Ge, Pb, Pd, Pt and Ti which can be alloyed with lithium; A compound including a metal such as Al, Si, Sn, Ag, Bi, Mg, Zn, In, Ge, Pb, Pd, P and Ti; Metals such as Al, Si, Sn, Ag, Bi, Mg, Zn, In, Ge, Pb, Pd, P and Ti; And lithium-containing nitride, but the present invention is not limited thereto.

The effect of the present invention can be enhanced when the particle size of the electrode active material according to the present invention is nano-sized. In the case of a nano-size material active material, the surface area of the active material per unit weight is large, and accordingly the amount of the conductive material and the binder increases, so that the amount of the electrode active material contained in the electrode is relatively small, And there is a possibility that the high rate charge / discharge characteristic is lowered. However, as in the present invention, when a porous current collector is used, an electrode can be manufactured using a small amount of a binder, electric conduction occurs three-dimensionally and a conductive material can be used less, The electrode capacity and the high rate charge / discharge characteristic can be improved.

In addition, the porous house a solid electrolyte that is full loaded on the polystyrene-molecular solid electrolyte, such as polyethylene oxide block _{copolymers, LLT (.. Li 0 35} La 0 55 TiO 3) crystal, such as solid electrolyte as an amorphous solid of the silica system A phosphate based solid electrolyte such as an electrolyte, LTP (2 [Li _{1 + x} Ti ₂ Si _x P _{3 - x} O ₁₂ ] - AlPO ₄ ), and LGP (Li _{1 + x} Al _x Ge _{2 - x} (PO ₄ ) ₃ ) , and sulfide-based solid electrolytes such as thio-LISICON. The solid electrolyte particles can be obtained by a commonly used solid-phase method or liquid-phase method.

The weight ratio of the electrode active material to the solid electrolyte is 1:99 to 99: 1, preferably 10:90 to 90:10, and 50:50 to 90:10. If the solid electrolyte is less than 1 weight, the ion transfer path is not properly formed in the electrode, and the output characteristics of the battery may be significantly deteriorated. When the weight of the solid electrolyte is 99 or more, the amount of the electrode active material is decreased, , There may be no significant advantage of the entire solid-state cell in terms of energy density per weight of the cell.

The electrode composite according to the present invention may further include a conductive material in the porous current collector, if necessary. The conductive material is not particularly limited as long as it has conductivity without causing chemical change in the battery, and includes, for example, graphite; Carbon black such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and summer black; Conductive fibers such as carbon fiber and metal fiber; Metal powders such as carbon fluoride, aluminum, and nickel powder; Conductive whiskey such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives and the like can be used. Concrete examples of commercially available conductive materials include acetylene black series such as Chevron Chemical Company, Denka Singapore Private Limited, Gulf Oil Company products, Ketjen Black, EC series Armak Company products, Vulcan XC-72 Cabot Company products and Super P (from Timcal) can be used.

In addition, the porous current collector acts as a bridge between the materials, and therefore, it is a moving path of electrons crossing the interface between the electrode active material and the solid electrolyte material, so that it is possible to reduce the amount of the conductive material used. Accordingly, the conductive material is added in consideration of conductivity within a range of 1 to 20 parts by weight based on 100 parts by weight of the total weight of the electrode active material and the solid electrolyte.

An electrode active material carried on the pores of the porous current collector, and a solid electrolyte, and may further include a binder as needed to bind and fix the conductive material. The binder is a component that assists in bonding between the electrode active material and the solid electrolyte or the like and bonding to the current collector, and is usually added in an amount of 1 to 50 wt% based on the total weight of the mixture containing the electrode active material. Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, poly Propylene, diene terpolymer (EPDM), sulfonated EPDM, styrene butylene rubber, fluorine rubber, various copolymers and the like.

The electrode composite for a full-solid-state cell according to the first embodiment of the present invention can be produced by a wet coating process for coating an electrode slurry containing an electrode active material and solid electrolyte particles on a porous current collector. A method of uniformly dispersing the electrode slurry on a porous current collector using a doctor blade or the like, a method of die casting, a comma coating, a screen printing, etc. . Thereafter, the substrate is formed on a separate substrate, and the electrode slurry is carried into the pores of the porous collector by pressing or lamination. At this time, the thickness of the coating to be finally coated can be controlled by adjusting the concentration of the slurry solution, the number of times of coating, and the like.

The electrode composite for a full-solid battery according to the second embodiment of the present invention is manufactured by a dry compression process in which the electrode active material and the solid electrolyte particles are powdered and then powdered and compressed into the pores of the porous current collector .

The electrode composite for a full solid battery according to the third embodiment of the present invention may be manufactured by melting the electrode active material using a low melting point and carrying it on the pores of the porous current collector together with the solid electrolyte particles.

The pre-solid battery according to the present invention can be manufactured by including at least one electrode composite. The production of the all solid battery having the above-mentioned constitution is not particularly limited in the present invention, and a known method can be used. For example, a solid electrolyte is disposed between an anode and a cathode (at least one of which is an electrode composite presented in the present invention), and then the cell is assembled by compression molding. The assembled cell is installed in the casing and then sealed by heat compression or the like. Laminate packs made of aluminum, stainless steel or the like, or cylindrical or square metal containers are suitable for the exterior material.

Claims (8)

Porous collector; And
And an electrode active material supported on the porous collector electrode and a solid electrolyte.
The method according to claim 1,
The porous collector may be made of a metal such as aluminum, nickel, copper, iron, nickel, cobalt, chromium, molybdenum or tungsten; Carbon-based materials such as natural graphite, artificial graphite, expanded graphite, carbon fiber, hard graphitizable carbon, carbon black, carbon nanotube, fullerene and activated carbon; And a combination thereof. The electrode composite for a full-solid battery according to claim 1,
The method according to claim 1,
Wherein the pore size of the porous current collector is 1 to 10 mm.
The method according to claim 1,
Wherein the porosity of the porous collector is 10 to 90%.
The method according to claim 1,
Wherein the weight ratio of the electrode active material to the solid electrolyte is from 1:99 to 99: 1.
The method according to claim 1,
Wherein the electrode composite further comprises a conductive material supported on the porous current collector gap.
The method according to claim 6,
Wherein the conductive material is contained in an amount of 1 to 20 parts by weight based on 100 parts by weight of the total weight of the electrode active material and the solid electrolyte.
A pre-solid battery comprising the electrode composite of any one of claims 1 to 7.

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