KR20090061269A - Thin film battery having enhanced surface area of electrode and enhanced contact area between electrode and electrolyte and method for producing the same - Google Patents

Abstract

A method for producing a thin film battery is provided to increase amount of an electrode and contact area between the electrode and electrolyte and to uniformly form thin film which successively are laminated on the etched face. A thin film battery comprises a substrate(10); a first collector(20) formed on the substrate; a cathode(30) formed on the first collector; an electrolyte layer(40) formed on the cathode; an anode(50) formed on the electrolyte layer; and a second collector contacted with the anode. Many grooves with hemi-circular section or semi-spherical grooves are formed on the surface of the substrate or the first collector. The other elements are deposited on the upper side of the substrate or the first collector through physical gas deposition.

Description

Thin film type battery having increased surface area of electrode and contact area between electrode and electrolyte, and method of manufacturing the same

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film type battery and a manufacturing method thereof, and more particularly, to a thin film type battery in which the amount of an electrode and the contact area between an electrode and an electrolyte are increased.

Thin-film batteries are known to be very safe due to the use of solid electrolytes, which have little self-discharge during non-use and there is no risk of leakage or explosion. However, in order to solve the low capacity, which is a disadvantage in the thin film battery, the thickness of the anode thin film should be increased, but there is a limit in increasing the thickness due to the PVD method such as sputtering in the manufacturing process of the thin film battery.

Particularly, lithium transition metal compounds commonly known as LiCoO ₂ , LiMn ₂ O ₄ , LiNiO ₂ , etc., must be present in the crystal phase to efficiently perform intercalation of lithium, but can exhibit performance as a battery. However, sputtering and electron beam If a method such as deposition, vacuum thermal deposition, or laser thin film deposition is used, a lithium transition metal compound is present in an amorphous state during initial thin film deposition, and a separate heat treatment process is required to crystallize.

However, as the thickness of the thin film increases, a process such as cracking during the heat treatment process is difficult due to an increase in the stress in the thin film, and when the battery is actually formed using such a thin film, it results in poor yield and reliability. In addition, when the thickness of the anode increases, the conductivity in the anode decreases, which causes a disadvantage in that output characteristics such as high rate discharge are degraded.

Therefore, a method for solving the above disadvantages is to increase the surface area of the substrate which is the starting material of the thin film battery and increase the amount of the anode thin film to be deposited thereon, thereby simultaneously increasing battery capacity and improving output characteristics.

As a method for increasing the surface area of the substrate, there is a method of increasing the surface area by three-dimensionally etching the surface of the substrate. The etching method is a wet method consisting of an isotropic etching using a liquid solution, anisotropic such as reactive ion etching, sputter etching, vapor phase etching, etc. There is a dry method of etching. These etching methods also differ in their use according to their characteristics.

Dry etching has an advantage in that it has an excellent aspect ratio and can control an elaborate shape of several micrometers or less, but it has the disadvantage of using expensive dry etching equipment.

In particular, when manufacturing a thin-film battery, an anisotropic etching surface, in particular, the collector, the cathode, the solid electrolyte, and the anode must be uniformly deposited on the side of the etching surface to form a good battery without a short circuit. Existing sputtering, electron beam deposition, vacuum deposition According to the physical vapor deposition (Physical Vapor Deposition) and the like there is a problem that can not deposit a uniform thin film on the anisotropic etching surface by dry etching. Therefore, in this case, uniform thin film formation is possible only by chemical vapor deposition using a precursor gas. However, thin film battery manufacturing by chemical vapor deposition (CVD) requires a separate device for reprocessing the exhaust gas after the process is completed because the process is complicated and the gases used are mostly toxic.

Prior arts in this field suggest methods to increase the surface area of substrates to solve the low capacity of thin-film batteries, but use anisotropic etching by dry method with excellent aspect ratio for surface area expansion or planarity of substrates. Since it follows the method of forming irregularities, holes, etc. having a plane perpendicular to the surface, when forming other components on the substrate having an enlarged surface area, the chemical vapor deposition method is inevitably employed. Has For example, US Pat. No. 6,197,450 also attempts to widen the surface area of a substrate by using a silicon wafer perforated with holes having a large aspect ratio as a substrate, but the deposition of the thin film is based on chemical vapor deposition (CVD).

The present invention is a method of increasing the surface area by etching the surface of the substrate and the like, while increasing the amount of the electrode and the contact area between the electrode and the electrolyte (Electrolyte), using the physical vapor deposition method as it is uniformly stacked on the etch surface by using the physical vapor deposition method It is an object of the present invention to provide a thin film battery and a method for manufacturing the same, which can be formed to be easily formed.

The present invention provides a substrate, a first collector formed on the substrate, a cathode formed on the first collector, an electrolyte layer formed on the cathode, an anode formed on the electrolyte layer, and a second contacting the anode. In the thin-film battery comprising a collector,

A plurality of grooves or hemispherical grooves having a semicircular cross section are formed on the surface of the substrate or the first collector by wet etching, and other components are formed by physical vapor deposition on the substrate or the first collector. Provided is a thin film battery characterized by being deposited.

In addition, the present invention

Forming a first collector on the substrate;

Forming a cathode on the first collector;

Forming an electrolyte layer on the cathode,

Forming an anode on the electrolyte layer, and

In the manufacturing method of a thin film battery comprising the step of forming a second collector in contact with the anode,

Wet etching the surface of the substrate or first collector to form a plurality of grooves or a plurality of hemispherical grooves that are semicircular in cross section, and other components formed on top of the substrate or first collector. It provides a method of manufacturing a thin film battery, characterized in that formed by physical vapor deposition.

According to the present invention, while increasing the surface area by etching the surface of the substrate or the first collector, while increasing the amount of the electrode and the contact area between the electrode and the electrolyte (Electrolyte), using the physical vapor deposition method as it is sequentially on the etching surface Since it is possible to uniformly form the thin films to be stacked, it is possible to improve the capacity and output density of the thin film battery very economically.

The present invention provides a substrate, a first collector formed on the substrate, a cathode formed on the first collector, an electrolyte layer formed on the cathode, an anode formed on the electrolyte layer, and a second contacting the anode. In the thin-film battery comprising a collector,

A plurality of grooves or hemispherical grooves having a semicircular cross section are formed on the surface of the substrate or the first collector by wet etching, and other components are formed by physical vapor deposition on the substrate or the first collector. It relates to a thin film battery characterized by being deposited.

The thin film battery of the present invention forms a plurality of grooves or a plurality of hemispherical grooves having a semicircular cross section in a substrate or a first collector, and when formed in the first collector, an increase in the amount of electrodes and a contact area between the electrodes and the electrolyte. There is an advantage that it can be formed more widely, but it should be taken into consideration that it is not easy to implement unless the thickness of the first collector film is more than several tens of microns.

In the present invention, the semicircular cross-section of a plurality of grooves having a semicircular cross section means a cross-sectional shape that is typically produced when a photoresist pattern is formed to form grooves and etching isotropically by a wet method. In the present invention, the size, number, arrangement, etc. of the grooves except for the cross-sectional shape may be any shape and are not particularly limited. For example, a stripe type, a check type, etc. are mentioned.

In addition, the hemispherical shape of a plurality of hemispherical grooves means a shape of a groove that is typically generated when a photoresist pattern is formed to form the grooves and etching isotropically by a wet method. In the present invention, the size, number, arrangement, etc. of the grooves may be in any form and are not particularly limited. For example, hemispherical grooves are formed only in the grids adjacent to each other in the diagonal direction among the square grids.

In particular, in the present invention, the formation of a plurality of hemispherical grooves on the surface of the substrate or the first collector is advantageous in terms of surface area increase rather than the formation of a plurality of grooves having a semicircular cross section. For example, based on a square substrate having a width of 10 cm and a height of 10 cm, the surface area is 100 cm ² , and in the case of 50 hemispherical grooves (check pattern), the surface area is 139.23 cm ² , and the cross-section is If semicircular grooves are formed (5 pieces), the surface area is 128.5 cm ² .

In the thin film battery of the present invention, the surface area of the electrode and the contact area between the electrode and the electrolyte are formed by subjecting the substrate or the first collector to isotropic etching by a wet method to form a plurality of grooves or a plurality of hemispherical grooves having a semicircular cross section. And, consequently, increase the capacity and output of the thin film battery. In addition, as a result of the isotropic etching by the wet method as described above, even if a substrate having a plurality of grooves or a plurality of hemispherical grooves or other films formed on the first collector are formed by physical vapor deposition, a uniform film may be formed. It is possible.

The present invention also provides

Forming a first collector on the substrate;

Forming a cathode on the first collector;

Forming an electrolyte layer on the cathode,

Forming an anode on the electrolyte layer, and

In the manufacturing method of a thin film battery comprising the step of forming a second collector in contact with the anode,

Wet etching the surface of the substrate or first collector to form a plurality of grooves or a plurality of hemispherical grooves that are semicircular in cross section, wherein other components formed on top of the substrate or first collector It relates to a method for manufacturing a thin film battery, characterized in that formed by physical vapor deposition.

The wet etching of the surface of the substrate or the first collector to form a plurality of grooves or a plurality of hemispherical grooves having a semicircular cross section may include, for example,

Applying and soft baking the photoresist on the substrate or the first collector;

Contacting, exposing and developing a photomask fabricated so as to form specific grooves or hemispherical grooves on the substrate or the first collector; And

And hard etching the formed photoresist pattern, followed by wet etching.

The photomask for forming specific grooves may be, for example, a stripe type, a check type, or the like.

As a photomask for forming particular hemispherical grooves, for example, a photomask manufactured to allow light to pass through only adjacent grids in a diagonal grid pattern.

Hereinafter, the present invention will be described in more detail with reference to the drawings.

As shown in FIG. 1, in the case of dry methods (FIG. 1, (a)) such as reactive ion etching, sputter etching, and vapor phase etching, the aspect ratio is excellent and a fine pattern within several μm is possible. However, in such anisotropic etching, it is impossible to sequentially deposit other components of the cell uniformly on the etching surface by methods such as sputtering and electron beam deposition in which atoms are moved in a straight line, and thus, such as chemical vapor deposition (CVD), etc. The same expensive process is essential. However, the wet method (Fig. 1, (b)) is not possible to etch the aspect ratio and precise patterns, but isotropic etching is possible, so even when the physical vapor deposition method (PVD) such as sputtering, electron beam deposition and vacuum deposition is used, It is possible to deposit other components of the substrate relatively uniformly. Thus, it provides the effect of increasing the surface area of the electrode relatively easily without expensive process conversion.

In the present invention, a photolithography process including the step of increasing the surface area of the substrate by isotropic etching using the wet method is performed as illustrated in FIG. 2.

In FIG. 2, (b) shows a process of applying the photoresist on the substrate (a). The photoresist is applied and typically subjected to soft bake. (c) shows a step of bringing the photomask into close contact with the photoresist layer and exposing it so that a desired pattern is formed in the photoresist. It develops after the said exposure and completes a photoresist pattern. (d) shows a step of hard baking the formed photoresist pattern. (e) shows an isotropic etching process by the wet method. (f) shows the substrate from which the photoresist was removed after etching was completed.

A method of constructing a thin film battery using the substrate having the enlarged surface area manufactured as described above is illustrated in FIG. 3.

First, in step (a), an isotropically etched substrate 10 is prepared by a wet method. The substrate can be used without particular limitation as long as it is used in this field, and examples thereof include silicon, titanium (Ti), nickel (Ni), stainless steel (SUS), and mica.

In the next step (b), the first collector 20 is formed on the substrate. The first collector-forming material can also be used without particular limitation as long as it is used in the art, and examples thereof include Pt or Au. The first collector 20 is deposited in a shape including a groove by physical vapor deposition. Here, an adhesive layer (not shown) may be further included to improve adhesion between the substrate 10 and the first collector 20. The adhesive layer may include any one metal of Al, Ti, Co, Cr, Nb, Ta, W, Fe, or may be formed of an indium tin oxide (ITO) layer.

Next, in step (c), the cathode 30 is formed on the first collector 20. The cathode forming material may also be used without particular limitation as long as it is used in this field. For example, a lithium transition metal such as LiCoO ₂ , LiMn ₂ O ₄ , LiNiO ₂ , or a metal such as V ₂ O ₅ , MoO ₃ , MnO _2, or the like. And oxides. The cathode 30 is deposited in a shape including a groove or a groove by physical vapor deposition.

Next, in step (d), the electrolyte layer 40 is formed on the cathode 30. The material for forming the electrolyte layer 40 may also be used without particular limitation as long as it is used in this field. For example, an inorganic solid electrolyte or a polymer electrolyte such as LiPON may be used. The electrolyte layer 40 is also deposited in a shape including grooves or grooves by physical vapor deposition.

Next, in step (e), an anode 50 is formed on the electrolyte layer 40. The material for forming the anode 50 may also be used without particular limitation as long as it is used in this field, and examples thereof include Li, Sn, and Si-based alloys. The anode 50 is also deposited in a shape including grooves or grooves by physical vapor deposition.

After forming the anode 50, a second collector may be formed through a planarization process. In this case, the second collector may be formed immediately without the planarization process. The protective film process may be performed before forming the second collector. In this case, the anode 50 itself is used as the second collector, or a second collector is formed on the side of the battery to connect the anode 50 and the second collector.

FIG. 4 is a photomask manufactured by closely contacting a photomask manufactured to allow light to pass through only adjacent grids in a diagonal grid pattern to a photoresist layer, exposing and developing a photoresist pattern on a substrate, and isotropically etching by a wet method. It is a top view which showed the case anticipated.

Specifically, the method for forming a plurality of hemispherical grooves in the substrate or the first collector includes the following steps.

Applying and soft baking the photoresist on the substrate or the first collector;

Contacting, exposing and developing a photomask manufactured to allow light to pass through only adjacent grids in a diagonal direction among square grid patterns; And

Performing a hard bake on the formed photoresist pattern, followed by wet etching.

5 illustrates a substrate on which a plurality of hemispherical grooves formed by the above process are formed. (a) is the surface of the titanium substrate before etching, (b) is the state after etching, (c) is the SEM photograph after the deposition of LiCoO ₂ as the cathode active material, and (d) is the wall surface of the hole where LiCoO ₂ is deposited. SEM picture.

 FIG. 6 is a SEM photograph of a substrate manufactured by the photolithography process described in FIG. 5, showing that a hemispherical groove is uniformly formed in a checkered pattern, thereby increasing the surface area of the substrate compared to before etching.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the scope of the present invention is not limited by the following example.

Example  1: of substrate Surface area  Fabrication of Increased Substrates

After applying a photoresist on a Ti substrate having a diameter of 5 mm and soft baking it, a photomask on which a lattice pattern (a square having a size of 20 μm × 20 μm, FIG. 4) is drawn is brought into close contact with the photoresist layer. Ultraviolet rays were irradiated. After development, the remaining photoresist portion was hard baked and then isotropically etched using piranha or Ti etching solution as an etching solution. After the etching process was completed, the remaining photoresist layer was removed using a stripper. As a result, a substrate having an increased surface area having an etched surface formed in a semicircle having a diameter of about 40 μm and a depth of about 15 μm was manufactured.

Example  2: Fabrication of Thin Film Battery with Improved Discharge Capacity and Output Characteristics

A battery was prepared in a batch using the substrate prepared in Example 1 above. The thin film type battery is a positive electrode current collector on a metal substrate, and Pt is deposited to a thickness of 250 nm by DC sputtering, and a LiCoO ₂ cathode active material is deposited to a thickness of 3 μm by RF sputtering and rapidly heat-treated to form a hexagonal structure anode. Was prepared. At this time, Ti 20nm and Co 30nm were successively deposited to increase adhesion between the Pt current collector and the Ti metal substrate. The solid electrolyte was a 1.5 μm thick LiPON electrolyte in which oxygen in Li ₃ PO ₄ was replaced with some nitrogen atoms by reactive sputtering under a pure nitrogen atmosphere using a Li ₃ PO ₄ target, and the negative electrode was purified using vacuum thermal evaporation. Lithium thin film was used by evaporating to a thickness of 2㎛. At this time, the effective area of the negative electrode was 12.56 mm ² .

Comparative example  1: Fabrication of Thin Film Battery Using Flat Substrate

A thin film type battery was manufactured in the same manner and in the same manner as in Example 2, except that a flat substrate without etching was used.

Test Example  1: Evaluation of discharge characteristics of thin film battery

The discharge test was performed by applying a constant current of 20 mA to each cell using a thin film battery manufactured using a wet etched substrate and a non-etched flat substrate prepared in Example 2 and Comparative Example 1, respectively. As a result, the thin film type battery using the wet etched substrate exhibited a typical LiCoO ₂ discharge curve without short-circuit of the battery compared to the unetched flat substrate, and exhibited a capacity increase of about 25% (see FIG. 7).

Test Example  2: Evaluation of Output Characteristics of Thin Film Battery Cells

When a discharge was performed by applying the same current of 20 mA to each cell using a thin film battery manufactured using a wet etched substrate and a non-etched flat substrate, respectively prepared in Example 2 and Comparative Example 1. An initial capacity of 100 was applied to evaluate the output characteristics of the battery by applying a high current such as 200 mA and 400 mA. The test results are shown in FIG. 8 shows the capacity ratio and the discharge curve. In the thin film battery using the unetched flat substrate prepared in Comparative Example 1, the potential drop according to the internal resistance of the battery according to the increase in the discharge current, such as a-a'-a '', The capacity reduction rate was large, and it was confirmed that the internal resistance was about 1670 ohm. However, in the case of the thin film battery manufactured by performing wet etching (performed by wet etching), the potential drop according to the increase of the current was greatly reduced, as in b-b'-b ''. As a result of the internal resistance estimation, the resistance was also reduced by about 25% to about 1,253ohm.

1 shows a comparison of (a) anisotropic etching by the dry method and (b) isotropic etching by the wet method.

FIG. 2 illustrates a photolithography process that includes a step of increasing the surface area of a substrate by performing isotropic etching by a wet method.

3 illustrates a method of constructing a thin film battery using a substrate manufactured according to an embodiment of the present invention in order.

4 illustrates a process of forming a plurality of hemispherical grooves in one embodiment of the present invention.

5 is an embodiment of the present invention.

(a): SEM photograph of the surface of the titanium substrate before etching,

(b): SEM photograph (Example 1) after etching of the titanium substrate,

(c): SEM image (Example 2) after depositing LiCoO ₂ as a Pt current collector and a cathode active material on the substrate prepared in Example 1,

(d) is a wall SEM photograph of the hole on which LiCoO ₂ is deposited.

6 is a SEM image of the surface of a wet-etched titanium substrate prepared in one embodiment of the present invention.

7 is a graph showing the discharge capacity of the thin film battery prepared in Example 2 of the present invention and the thin film battery prepared in Comparative Example 1.

8 is a graph illustrating output characteristics of the thin film battery prepared in Example 2 of the present invention and the thin film battery prepared in Comparative Example 1.

* Description of Drawing Symbols *

10: substrate 20: first collector

30: cathode 40: electrolyte layer

50: anode

Claims (7)

A substrate, a first collector formed on the substrate, a cathode formed on the first collector, an electrolyte layer formed on the cathode, an anode formed on the electrolyte layer, and a second collector in contact with the anode In the thin film battery constituted by A plurality of grooves or hemispherical grooves having a semicircular cross section are formed on the surface of the substrate or the first collector by wet etching, and other components are formed by physical vapor deposition on the substrate or the first collector. A thin film battery characterized by being deposited. The thin film type as claimed in claim 1, wherein the plurality of hemispherical grooves are formed by forming a resist pattern on the substrate or the first collector by removing only the lattice neighboring in a diagonal direction among the square lattice patterns, and performing wet etching. battery. The thin film type battery of claim 1, wherein an adhesion increasing layer is formed between the substrate and the first collector. Forming a first collector on the substrate; Forming a cathode on the first collector; Forming an electrolyte layer on the cathode, Forming an anode on the electrolyte layer, and In the manufacturing method of a thin film battery comprising the step of forming a second collector in contact with the anode, Wet etching the surface of the substrate or first collector to form a plurality of grooves or a plurality of hemispherical grooves that are semicircular in cross section, and other components formed on top of the substrate or first collector. Method for manufacturing a thin film battery, characterized in that formed by physical vapor deposition. The method of claim 4, wherein the wet etching of the substrate or the first collector surface to form a plurality of grooves or a plurality of hemispherical grooves having a semicircular cross section, Applying and soft baking the photoresist on the substrate or the first collector; Contacting, exposing and developing a photomask fabricated so as to form specific grooves or hemispherical grooves on the substrate or the first collector; And After the hard bake the formed photoresist pattern, the method of manufacturing a thin-film battery, characterized in that it comprises a wet etching step. The method according to claim 5, wherein the photomask is a manufacturing method of a thin film battery, characterized in that only the lattice neighboring in the diagonal direction of the square lattice pattern is made to pass the light. The method of claim 4, wherein the forming of the first collector on the substrate comprises forming an adhesion increasing layer between the substrate and the first collector.

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