KR100946750B1 - Li-B-W-O BASED SOLID ELECTROLYTE THIN FILM FOR SECONDARY BATTERIES USING THERMAL EVAPORATION AND FABRICATION THEREOF - Google Patents

Abstract

The present invention relates to a Li-BWO-based solid electrolyte thin film for a secondary battery using a thermal evaporation method and a method of manufacturing the same, more specifically, the general formula Li _x -B _y -W _z -O _δ (where 0.5≤x≤1.2; The present invention relates to a solid electrolyte thin film for a secondary battery having excellent mass production efficiency, having a composition of 0.5 ≦ y ≦ 1.1; 0.6 ≦ z ≦ 1.5; and 0.5 ≦ δ ≦ 1.5).

Description

Li-B-W-O-BASED SOLID ELECTROLYTE THIN FILM FOR SECONDARY BATTERIES USING THERMAL EVAPORATION AND FABRICATION THEREOF}

The present invention relates to a Li-B-W-O-based solid electrolyte thin film for a secondary battery using a thermal evaporation method and a method of manufacturing the same.

Batteries that convert chemical energy into electrical energy have been widely used due to their high energy conversion efficiency and simple structure. Among them, lithium batteries have high potentials and high energy density, which is one of the most active researches in the field of batteries today. A lithium battery basically consists of a negative electrode (eg, lithium metal, a lithium alloy and graphite capable of removing and inserting lithium), a positive electrode (eg, LiCoO ₂ , Li ₂ MnO ₄ and V ₂ O ₅ ), and an electrolyte. One of the most closely related to the performance of the battery today is the electrolyte that provides the passage of lithium ions. Examples of electrolytes for lithium batteries include liquid electrolytes and solid electrolytes.

The liquid electrolyte is an electrolyte widely used in a conventional lithium battery and has an advantage of exhibiting high ionic conductivity. However, this is basically an acid solution, which is environmentally undesirable and poses a problem of leakage. In order to solve this problem, a solid electrolyte is proposed, which can be roughly classified into a solid polymer electrolyte and a solid thin film electrolyte.

Solid polymer electrolytes are currently based on the discovery that a polymer matrix composed of polyethylene oxide (PEO) is conductive to lithium ions, and is currently a polymer electrolyte of various compositions such as polyacrylonitrile (PAN), polyvinyl chloride (PVC), etc. This is under development. However, such a solid polymer electrolyte is basically assumed to be used in a bulk battery, and its use is limited to an electrolyte for a thin film battery having a total size of only a few μm.

Solid oxide electrolytes are emerging as electrolytes for thin-film batteries, and basically include network modifiers that form the backbone of the network and network modifiers that modify the backbone of the network. May include a network dopant to enhance.

Representative examples of such solid thin film electrolytes include U.S. Patent No. 5,338,625, which includes Li-P-O-N as a component, and U.S. Patent No. 5,455,126, which is a divided application thereof. These solid-state thin film electrolytes of the U.S. patent have a network forming agent that forms a skeleton of the network, and a network modifier that forms a net structure by modifying the skeleton of the network by cutting, condensation polymerization, branching, etc. of the network skeleton. has N as its (network modifier).

In addition, it is a lithium-containing solid electrolyte thin film of deposited using one of the sputtering (sputtering) method of the conventional physical vapor deposition (physical vapor deposition) Document _{1 [Li 2 .9 PO 3 .3} N 0 .46; J. Vac. Sci. & Technol. A 14 (1), Jan 1996, p34, deposition rate: 0.8 nm / min. ~ 2.2 nm / min] and Li 2 electrolytes (Li-Si-O system, Li-PO system, Li-Si-PO system; Solid state ionics 5-56 (1992), p655-661; deposition rate: 0.5 to 1 nm / min] These documents report that a thin film electrolyte having a Li ion conductivity level in the range of 10 ⁻⁶ S / cm is formed by a sputtering method.

However, according to the results of the inventors' prior studies, when the secondary battery electrolyte material is manufactured by the sputtering method under conditions similar to those of the previously reported secondary battery electrolyte material, the manufacturing process time of the product is about 10 to 14 hours long. It has been found that there is a problem that the possibility of use in the mass production process is very small. This problem is due to the limitation that the electrolyte thin film process should be a room temperature process, and in order to obtain a meaningful thickness to solve the short-circuit problem between the positive electrode and the negative electrode, it is practically impossible to commercialize. Nevertheless, sputtering is preferred because it is easy to obtain a relatively dense thin film.

However, despite these US patents and the literature reported so far, the development of solid thin film electrolytes is still in its infancy, and it is possible to produce electrolyte thin films in a short time and provide various types of cells that can provide better cell performance. There is still a need for the development of a solid oxide electrolyte.

Accordingly, an object of the present invention is to provide a process gain by shortening the manufacturing time when manufacturing a solid oxide electrolyte of a secondary battery, and at the same time, has excellent electrical properties such as adhesion characteristics and ion conductivity, and has high mass production efficiency. The present invention provides a BWO-based solid electrolyte thin film and a method of manufacturing the same.

In order to achieve the above object, the present invention has a composition of the general formula Li _x -B _y -W _z -O _δ (hereinafter, LBWO), wherein 0.5≤x≤1.2; 0.5 ≦ y ≦ 1.1; 0.6 ≦ z ≦ 1.5; And 0.5 ≦ δ ≦ 1.5, which provides a solid electrolyte thin film for secondary batteries.

In addition, the present invention locates source powders of Li, B, W and O on a boat in a vacuum chamber; Heat is applied to the powder to evaporate or sublime the powder to form a general formula Li _x -B _y -W _z -O _δ (where 0.5≤x≤1.2; 0.5≤y≤1.1; 0.6≤z≤1.5; and It provides a method for producing a solid electrolyte thin film for a secondary battery, comprising forming a solid electrolyte having a composition of 0.5≤δ≤1.5) in a thin film form.

According to the present invention, a thin film type solid electrolyte can be produced economically and efficiently by a very simple process by thermal evaporation method, and the process gain can be obtained by shortening the production time, and the mass production efficiency of the secondary battery can be increased. The thin-film solid electrolyte is excellent in electrical properties such as adhesion characteristics and ion conductivity, and can be stabilized and improved in efficiency, and thus can be easily applied or utilized for mass production of next-generation secondary batteries including lithium secondary batteries.

The solid electrolyte for secondary batteries of the present invention is a quaternary thin film electrolyte containing four atoms of Li, B, W, and O, specifically, the following general formula (1):

Li _x -B _y -W _z -O _δ (1)

(In the above formula, 0.5≤x≤1.2; 0.5≤y≤1.1; 0.6≤z≤1.5; and 0.5≤δ≤1.5).

The materials forming the network of the solid electrolyte thin film are Li, B, W and O, but these are mixed powders thereof (hereinafter referred to as LBWO powders) or oxides such as LiO, B ₂ O ₃ , WO ₂ , WO _3, and the like. The powder can be supplied as a starting material. At this time, Li may be contained in the mixed powder in an amount exceeding 40% or less than the stoichiometric ratio, the glass phase easily appears in this region to produce a single-phase thermal evaporation pellets for simple thermal evaporation This makes it possible to produce an electrolyte thin film.

Such LBWO mixed powder may be used as a starting material of the deposition material according to the thermal evaporation method to prepare the solid electrolyte thin film of the present invention, which specifically locates the LBWO powder on a boat in a vacuum chamber; The heat is applied to the LBWO powder to evaporate or sublime the LBWO powder to form a general formula Li _x -B _y -W _z -O _δ (where 0.5 ≦ x ≦ 1.2; 0.5 ≦ _y ≦ 1.1; 0.6 ≦ _z ≦ 1.5; And forming a solid electrolyte having a composition of 0.5 ≦ δ ≦ 1.5) in the form of a thin film. Electrical properties such as impedance and ion conductivity may be excellently expressed in the composition range.

Here, the thermal evaporation apparatus for manufacturing the solid electrolyte thin film of the present invention, as illustrated in FIG. 1, includes a vacuum chamber, a substrate and a metal mask provided on the upper portion of the vacuum chamber. And a boat (eg, tungsten boat) which is installed in a grounded state directly below the metal mask and is provided with a cooling means (not shown), and a LBWO mixed powder which is installed on both sides of the boat and placed in the boat. And a hot electron emission source (eg, a copper block) for emitting hot electrons for heating, and a hot electron acceleration electrode (not shown) for accelerating hot electrons emitted from the hot electron emission source.

Using the above thermal evaporation apparatus, the LBWO powder is first placed on a boat, and then the pressure inside the chamber for stably performing thermal evaporation is for example in the range of 1 × 10 ^-3 to 10 ^-10 Torr. Maintain in vacuum. At the same time, the source of hot electrons is heated to raise the temperature of the boat in the range of 300 ° C. to 1,200 ° C., wherein the means for heating the LBWO mixed powder or the release of hot electrons is for example an electron beam, an electric filament or an arc. Or the like, but is not limited thereto. This temperature can be controlled by monitoring the thickness of the solid electrolyte thin film, wherein the solid electrolyte is preferably in the form of a thin film and the film thickness can be controlled appropriately, but considering both the electrical characteristics and the short circuit, the final thickness is about 1 It is preferable that it is to 1.5 micrometers. This solid electrolyte thin film can be adjusted to the final thickness by maintaining a deposition rate of more than 0 to 1 nm / second, preferably 0.5 to 1 nm / second at a pressure of 1 × 10 ^-3 to 10 ^-10 Torr. .

However, a weak adhesion characteristic between electrodes or thin films that are commonly shown in the thermal evaporation method may be a problem, which is solved by adjusting the power (W) applied in the vacuum chamber and the distance between the substrate and the boat (eg tungsten boat). This can be easily determined as needed by those skilled in the art. Preferably, suitable power in the present invention, and the distance between the substrate and the boat are 100 to 300 W, and 5 to 10 cm, respectively, but are not limited thereto.

After the evaporation deposition is completed, the present invention is completed by lowering the temperature in the chamber and collecting the resulting solid electrolyte thin film. As described above, it takes about 20 to 30 minutes to produce the solid electrolyte thin film of the present invention.

The electrolyte according to the present invention maintains its amorphous form by a thermal evaporation process, which results in high charge carrier concentrations, high vacancy or interstitial site concentrations, and low ion transfer activation energy. Thereby forming an amorphous thin film of electrolyte having high ion conductivity, and the obtained solid electrolyte thin film has an ion conductivity in the range of about 1.5 × 10 ⁻⁶ to 3 × 10 ⁻⁶ S / cm, which is required for sputter deposition. Accordingly compared to the values reported in Documents 1 and 2.

Note that during the fabrication of the solid electrolyte thin film, thermal evaporation may cause a short circuit between the positive electrode and the negative electrode when the density of the thin film to be formed is less than or equal to 1 μm, which is the same thickness as sputtering. Increasing the ionic conductivity may lower the ion conductivity can not be used as an electrolyte, in the composition section as shown in the general formula (1) of the present invention easily appears in the glass phase is relatively high density at room temperature synthesis, Accordingly, the electrolyte thin film in which short circuit is suppressed can be synthesized. That is, since the pellet for thermal evaporation deposition of a single phase can be manufactured in the area | region comprised as Formula (1) of this invention, preparation of the electrolyte thin film by simple thermal evaporation is attained.

The produced solid electrolyte of the present invention is an all-solid-state battery, and can be typically used in an all-solid-state thin film lithium secondary battery, and the configuration of the battery is typically a substrate, a first current collector, a first electrode, a solid electrolyte, and a second. The electrode and the second current collector is sequentially stacked, wherein the first electrode and the second electrode may be an anode or a cathode differently from each other, and when the substrate and the electrodes to be laminated are conductive The whole and the second collector are not necessary. It is also possible to stack several such solid-state batteries.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the following examples are only for illustrating the present invention, and the scope of the present invention is not limited or limited only to the following examples.

Example  1: Preparation of solid electrolyte thin film

a) Pellet  making

The content of Li in the mixed composition of LiO powder (Aldrich, purity: 99.5% or more), B ₂ O ₃ powder (Aldrich, purity: 99.5% or more) and WO ₂ powder (Aldrich, purity: 99.5% or more) is 40 atomic% The mixture was mixed in excess of and the mixed powder was heated up to 750 ° C. at a temperature increase rate of 4 ° C./min, followed by preheating for 6 hours. Then, it was pulverized again in the mortar and produced in the form of 2 inch pellets. The compressed pellet was heated to 750 ° C. at a temperature increase rate of 4 ° C./min, and then heat-treated at this temperature for 4 hours to prepare LBWO pellets.

b) Fabrication of solid electrolyte thin film

Using the thermal evaporation apparatus shown schematically in FIG. 1, the LBWO pellets were placed on a tungsten boat whose distance from the substrate was adjusted to 6 cm, and then the exhaust valve was used to maintain the pressure of the chamber below 10 ^-5 Torr. The heat deposition power was set to 200 W, and at the same time, a current was flowed through the electric filament to raise the temperature to 320 ° C. The LBWO pellet slowly evaporated due to heat, causing the vapors to diffuse into the upper chamber and the diffused vapor to be deposited at a rate of 0.1 nm / second onto the rotating substrate. Forming a _{Li 0 .5 -B 0.5 -W 0 .6} -O electrolyte thin film of _{1 .5} composition having a final thickness of 1.52 ㎚ by repeating 15 times throughout this process and adjust the film thickness to a thickness monitoring unit in 25 minutes It was. The scanning electron microscope measurement result of the obtained electrolyte thin film is shown to FIG. 2A. It can be seen from FIG. 2A that the surface of the solid electrolyte thin film is formed relatively evenly.

Example  2: Preparation of Laboratory Cells Containing Solid Electrolyte Thin Films

An experimental cell was prepared comprising the solid electrolyte thin film obtained in Example 1 as a solid electrolyte layer. Figure 2b is the result of measuring the cross-sectional view of the experimental cell produced in the present embodiment with a scanning electron microscope. As shown in FIG. 2B, the experimental cell was composed of a silicon substrate, a lower electrode (anode) layer, an electrolyte layer, and an upper electrode (cathode) layer.

First, a metal mask having a 10 mm × 10 mm window is placed on a predetermined position of a surface-treated silicon substrate having a surface roughness of 30 nm or less, and the appropriate temperature is maintained under the same conditions as in Example 1 while the substrate is rotated. Thermal deposition was performed on lithium manganate (LiMn ₂ O ₄ ) powder by adjusting to 1350 ° C. to form an anode layer having a final thickness of 300 nm. _{Then, Li 0 .5 -B 0.5 -W 0} .6 as in the above obtained positive electrode layer, in Example 1 to form an electrolyte layer of the composition O _1.5. Then, on the obtained electrolyte layer, under the same conditions as in Example 1, but by adjusting the appropriate temperature to 3730 ℃ heat deposition on the graphite was carried out to form a negative electrode layer having a final thickness of 1.50 nm.

<Evaluation>

a) process gain over manufacturing time

The biggest difference between the thermal evaporation method and the sputtering evaporation method is the deposition rate of the electrolyte material for the secondary battery considering the mass production process. In general, the thickness of the solid electrolyte material for a secondary battery is very important. If the thickness of the electrolyte material does not satisfy the appropriate thickness, as described above, about 1 to 1.5 [mu] m, there is a possibility that a short circuit may occur in the evaluation of the electrical properties.

As reported in the prior art documents 1 and 2, which are incorporated herein by reference, the preparation of the electrolyte material for the secondary battery by the sputtering deposition method requires about 10 to 14 hours of deposition time, whereas in the present invention When the thermal deposition method such as takes about 20 to 30 minutes deposition time, it has the advantage of reducing the deposition time of more than 95% compared to the sputter deposition.

As such, considering the manufacturing process of the material during mass production, if the material is manufactured by the thermal evaporation method proposed in this application compared to the material produced by the conventional sputtering, it may have a gain of more than 95% of the material process manufacturing time, and manufactured by such a thermal evaporation method The electrical properties of a material will also be discussed below, but shows excellent results compared to the properties produced by sputtering. Therefore, this thermal evaporation method is considered to be a method that can satisfy both the demands of economic and technical aspects for the use of the material of the present invention.

b) adhesion characteristics of the electrolyte membrane

In the case of using the thermal evaporation method, the adhesion characteristics which are conventionally exhibited can also be solved through the control of the applied power and the distance between the substrate and the tungsten boat, and suitably the power is 100 to 300 W, 200 W in Examples 1 and 2; The distance was adjusted to 1-10 cm, preferably 5-7 cm and 6 cm in Examples 1 and 2.

Specifically, scanning electron micrographs of the solid electrolyte thin films prepared according to Examples 1 and 2 were observed to determine the adhesion characteristics thereof. The results are shown in FIG. 2, and FIG. 2A shows the surface of the LBWO solid electrolyte material deposited using thermal evaporation, and FIG. 2B shows a cross section of the LBWO solid electrolyte material deposited using thermal evaporation. As a result of the observation, the adhesion property of the electrolyte material deposited between the upper and lower electrodes was analyzed to be very good, which is similar to the result of the sputtering deposition method.

c) electrical properties of the electrolyte membrane

In order to determine the electrical properties of the solid electrolyte thin film prepared according to Example 1, the impedance and ion conductivity of the solid electrolyte thin film were measured using the experimental cell obtained in Example 2. The instrument for measuring impedance and ionic conductivity was IM7e manufactured by Zahner, Germany. The frequency range was applied from 1 MHz to 100 mHz, and 10 mV of AC perturbation was applied. Impedance measurements were made in a glove box filled with argon (Ar). Impedance measurement results are shown graphically in Figure 3, and the resulting ion conductivity was measured, which are summarized in Table 1 below compared with the conventional electrolyte thin film.

From the results shown in FIG. 3 and Table 1, the solid electrolyte thin film of the present invention compared with the conventional solid electrolyte material has a low impedance and a ionic conductivity of 2.00 × 10 ⁻⁷ S / cm, which is about 10% increased. As such, it is expected that the ionic conductivity of the solid electrolyte thin film of the present invention can be increased by at least 10 times larger than the ionic conductivity of LLT or LLTON by selecting a Li-BWO-containing composition, and from this, the solid electrolyte thin film of the present invention Secondary batteries are expected to be able to deliver more power and energy.

1 is a schematic diagram of an LBWO solid electrolyte manufacturing apparatus for a secondary battery by thermal evaporation according to an embodiment of the present invention;

Figure 2a is a scanning electron micrograph of the surface of the LBWO solid electrolyte thin film deposited using a thermal vapor deposition method according to an embodiment of the present invention, Figure 2b is prepared by using the LBWO solid electrolyte thin film according to an embodiment of the present invention A scanning electron micrograph of a cross section of the cell;

3 is a graph illustrating impedance measurement results of cells fabricated using an LBWO solid electrolyte thin film according to an embodiment of the present invention.

Claims (9)

Represented by the general formula Li _x -B _y -W _z -O _δ , wherein 0.5 ≦ _x ≦ 1.2; 0.5 ≦ y ≦ 1.1; 0.6 ≦ z ≦ 1.5; And a solid electrolyte thin film for a secondary battery having a composition of 0.5 ≦ δ ≦ 1.5. The method of claim 1, A solid electrolyte thin film for secondary batteries, having an ion conductivity in the range of 1.5 × 10 ⁻⁶ to 3 × 10 ⁻⁶ S / cm. Source powders of Li, B, W and O are placed on the boat in the vacuum chamber; Heat is applied to the powder to evaporate or sublimate the powder to form a general formula Li _x -B _y -W _z -O _δ (where 0.5 ≦ _x ≦ 1.2; 0.5 ≦ _y ≦ 1.1; 0.6 ≦ _z ≦ 1.5; and To form a solid electrolyte having a composition represented by 0.5 ≦ δ ≦ 1.5) A method for producing a solid electrolyte thin film for a secondary battery, comprising the. delete The method of claim 3, wherein The heating is performed using an electron beam, an electric filament or an arc (Arc), a method for producing a solid electrolyte thin film for a secondary battery. The method of claim 3, wherein The pressure in the vacuum chamber is 1 × 10 ^-3 to 10 ^-10 Torr, the temperature is controlled in the range of 300 ℃ to 1,200 ℃, a method for producing a solid electrolyte thin film for a secondary battery. The method according to claim 3 or 6, wherein And evaporating the source powder at a deposition rate of 0.1 nm / sec at a pressure of 1 × 10 ⁻³ to 10 ⁻¹⁰ Torr to form a solid electrolyte having a final thickness of 1 to 1.5 μm. The method of claim 3, wherein The obtained solid electrolyte has the ion conductivity of the range of 1.5x10 <^-6> -3x10 <^-6> S / cm, The manufacturing method of the solid electrolyte thin film for secondary batteries. A secondary battery comprising the solid electrolyte thin film according to claim 1.

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