KR100836256B1 - Lithium ion conducting solid oxide electrolyte composed of Li-B-W-O LBWO system - Google Patents

Abstract

The present invention has a high lithium ion conductivity in the amorphous phase, exhibits a low self-discharge rate, has the form of an amorphous thin film by vacuum deposition, and is within a range of 0.5 to 4.5 V (vs. Li / Li ⁺ ) of a typical lithium battery. It is relatively stable electrochemically in the section and provides an oxide electrolyte composed of Li-BWO 4-component oxide (LBWO) oxide, so that a thin film battery can be manufactured in combination with a positive electrode and a negative electrode thin film, and a stable interface with the positive electrode and the negative electrode can be obtained. In addition, simple sputtering or thermal evaporation can reduce the film formation time compared to the conventional solid electrolyte thin film.

Solid electrolyte, sputtering, thermal evaporation method, lithium battery, thermal evaporation method, LBWO

Description

Lithium ion conducting solid oxide electrolyte composed of Li-B-W-O (LBWO) system

FIG. 1A illustrates a current collector structure for fabricating an LBWO thin film, and FIG. 1B illustrates an embodiment of a structure of an LBWO-based oxide electrolyte thin film.

2 is a plan view illustrating an embodiment of an LBWO thin film formed on a substrate.

3 is a side view showing an embodiment of an LBWO thin film formed on a substrate.

4 and 5 are external photographs of LBWO pellets and sputtering targets prepared as vacuum deposition raw materials according to an embodiment of the present invention.

Figure 6 is a SEM photograph showing the cross-sectional structure of the LBWO thin film produced by vacuum deposition according to an embodiment of the present invention.

FIG. 7 is a graph illustrating a cyclic voltammetry (CV) curve at a blocking electrode having a Pt / LBWO / Li structure according to an embodiment of the present invention.

8 is a graph showing charge and discharge characteristics of a thin film battery composed of a V ₂ O ₅ anode, a Li cathode, and an LBWO-based oxide solid electrolyte according to an embodiment of the present invention.

9 is a chart showing the various possible composition ratios of the LBWO-based oxide solid electrolyte.

<Description of symbols on the main parts of the drawings>

100: current collector thin film pattern 101: electrode region

102: active area 103: connection area

110: lower current collector thin film 120: upper current collector thin film

200: LBWO-based oxide solid electrolyte thin film 300: substrate

The present invention relates to a solid electrolyte which is the most essential element in constructing an all-solid-state lithium battery. Despite the successful development of lithium batteries and many advantages, the efficiency, stability, and capacity reduction due to charge and discharge cycling still remain challenges. The solid inorganic electrolyte is expected to enable the design of the next-generation lithium battery because it has advantages in safety, operating temperature range and the like. In addition, the use of such a solid electrolyte can prevent short-circuit of the battery due to the dendrite, so that lithium metal can be used as a negative electrode to store higher energy, and can be used as a core technology for manufacturing a thin film battery having a micro unit thickness. Can be. Recently, many studies on solid electrolytes have been conducted worldwide and attempts have been made to apply them to lithium batteries. SUMMARY OF THE INVENTION An object of the present invention is to provide an inorganic solid electrolyte material having the above advantages and satisfying basic electrolyte requirements such as high ionic conductivity, low electrical conductivity, chemical stability with an electrode, electrochemical stability within a driving voltage law, and ease of fabrication of a thin film. It is to suggest composition and production method.

The present invention relates to the fabrication of a Li-BWO (LBWO) -based solid electrolyte thin film as an electrolyte thin film in the manufacture of a thin-film ultra-small battery having a very low self discharge rate. Thin-film ultra-small battery is a secondary battery in which components of the battery such as cathode, anode, and electrolyte are made of solid thin film. As electronic devices are recently miniaturized and lightened, and ultra-fine devices using micro technology are developed, It is attracting attention as a circle. LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ , V ₂ O _5, and Li (Co, Mn, Ni) O ₂ are used as the anode of the thin film battery, and the cathode has a high energy density. Nano-structured Si thin films are used for Li metal and very high capacity. Solid electrolytes applicable to thin film batteries can be classified into inorganic and polymer electrolytes. To be used as an electrolyte thin film, not only have high Li ⁺ ion conductivity, but also react with Li metal at 0 to 5 V operating range. It must have electrochemical stability that does not. Recently, a polymer electrolyte having a ionic conductivity similar to that of an organic solvent electrolyte has been developed as a solid electrolyte for a bulk type secondary battery, but its application to a thin film battery has been limited due to the reaction with Li metal. Therefore, the amorphous glass-based electrolyte, among the inorganic materials, has attracted attention as an electrolyte for thin film batteries, and research on this has been actively conducted.

The results reported so far indicate that LiPON electrolyte can be applied to actual thin film batteries. This material is available from Dr. Oak Ridge National Lab (ORNL). The patent is filed by J. Bates Group. For example, by sputtering a Li ₃ PO ₄ target by RF reactive sputtering in a nitrogen atmosphere Li _{2 .9} PO _{3 .3} N ₀ there is produced in the proportion of 3.3 × 10 ^-6 relatively high ion _.46 of the S / cm at room temperature It has been reported to have conductivity and a wide electrochemical stability range of 0 to 5 V, as well as to form a very stable mechanical and chemical interface with the cathode and anode. Nevertheless, there are no reports of successful commercialization of the complete thin film ultra-compact battery using LiPON. This is because, despite the various structural and electrochemical stability of LiPON as mentioned above, the process speed and its reproducibility have not yet reached the level of commercialization.

La _{2 / 3- x} Li _3x TiO ₃ (LLT) oxides reported by Inaguma, Ogumi and Kawai et al. Have an ionic conductivity of about 10-100 times higher than that of LiPON. Investigations into application of electrolytes have been reported focusing on bulk materials. However, in the case of LLT, the application may be limited due to the high ion conductivity and the instability of the interface generated by the contact with Li, and the recent report reports that the application to the thin film state is impossible. This is because if the LLT is in contact with the Ti in the LLT Li ^{3 +} ions are oxidized to Ti ^{4 +} ions. Higher electronic conductivity can be lowered by crystallization of LLT, but this process is not applicable because the elements that make up the thin-film microcell are chemically unstable (above 500 ^° C) at the temperatures required for crystallization. In addition, one of the problems of the crystalline thin film electrolyte is that the electrolyte does not correspond to the stress caused by the volume change of the electrode active material involved in charging and discharging the battery, and the electrolyte is destroyed to cause a short inside the battery.

Accordingly, an object of the present invention is to prepare a novel Li-B-W-O (LBWO) -based oxide electrolyte having both advantages and disadvantages of LLT and LiPON, that is, having high ionic conductivity in an amorphous phase. In addition, according to the present invention, LBWO has an ion conducting property in an amorphous state, and thus, it is advantageous to apply a room temperature synthesis process differently from LLT. In the case of using a simple argon (Ar) ion sputtering or vacuum thermal evaporation method has the advantage of shortening the manufacturing time can be utilized as an electrolyte suitable for thin film ultra-compact battery.

The present invention provides a Li-B-W-O (LBWO) -based oxide solid electrolyte having a high ionic conductivity in an amorphous phase, an LBWO thin film and an LBWO thin film manufacturing method using the same.

The present invention provides an LBWO-based oxide solid electrolyte in which a solid electrolyte used in an all-solid-state lithium battery is composed of an LBWO 4 component system of Li ₂ O—Li ₂ WO ₄ —B ₂ O ₃ .

Preferably, the composition ratio of the LBWO 4 component system may be arbitrarily selected.

Also preferably, the B (Boron) component, which is a glass former of the four-component system of LBWO, may be replaced with P (Phospher).

In addition, the LBWO-based oxide solid electrolyte is preferably formed by any one of physical vapor deposition and chemical vapor deposition.

The present invention also provides an LBWO thin film comprising a current collector thin film / LBWO-based oxide solid electrolyte / current collector thin film, wherein the LBWO-based oxide solid electrolyte is any one selected from the above-described LBWO-based oxide solid electrolyte. Preferably, each current collector thin film includes an active region that reacts with the LBWO-based oxide solid electrolyte, an electrode region that serves as a current collector, and a connection region that connects the active region and the electrode region. In addition, each current collector thin film is preferably formed such that the size of the active area is smaller than that of the LBWO-based oxide solid electrolyte. In addition, it is preferable that each current collector thin film is formed in an electrode area, which is a current collector, in a different direction and does not contact each other. Also preferably, the LBWO thin film is formed by any method selected from a dry thin film production method and a wet thin film production method. Also preferably, the LBWO thin film may be arbitrarily determined in size, shape and thickness. In addition, each current collector thin film is preferably formed of any one of platinum (Pt) and stainless iron (sus).

In addition, the present invention provides a method for producing an LBWO thin film, the first step of manufacturing a current collector thin film in a specific pattern; Forming a LBWO-based oxide solid electrolyte on the current collector thin film formed by the first step; It provides a method for producing an LBWO thin film comprising a; a third step of manufacturing a current collector thin film of a specific pattern on the LBWO-based oxide solid electrolyte formed by the second step. Preferably, the LBWO-based oxide solid electrolyte of the second step is vacuum deposited from any one of the LBWO 4-component oxide pellets and the sputtering target. Also preferably, the LBWO-based oxide solid electrolyte of the second step is preferably vacuum deposited by argon ions.

Hereinafter, the present invention will be described in more detail based on a preferred embodiment of the present invention with reference to the drawings. However, the scope of the present invention is not limited by the following description, and the scope of the present invention will be limited only by the description of the following claims.

First, referring to an embodiment of FIG. 1A, the pattern 100 of the current collector thin film may include an active region 102 in contact with the LBWO-based oxide electrolyte thin film and an electrode region 101 in contact with the LBWO-based oxide electrolyte thin film, The connection region 103 connects the active region 102 and the electrode region 101. Referring to one embodiment of FIG. 1B, the LBWO-based oxide electrolyte thin film 200 should be sized to completely cover the active region 102 of the current collector thin film. 2 and 3, the LBWO-based oxide electrolyte thin film 200 is formed in a sandwich form between the current collector thin films 110 and 120. This is because when the LBWO-based oxide electrolyte thin film 200 is smaller than the size of the current collector thin films 110 and 120, the current collector thin films 110 and 120 are in electrical contact with each other and short.

4 and 5 illustrate LBWO-based oxide pellets for thermal deposition and sputtering targets for sputter deposition, respectively, in an embodiment for forming an LBWO-based oxide electrolyte thin film.

In particular, the following description was given an example of fabricating the LBWO-based oxide electrolyte thin film of the present invention using a physical vapor deposition method such as thermal deposition or sputter deposition in the vacuum deposition method. However, those skilled in the art can use a material having a composition similar to the four-component system of Li-B-W-O described above while embodying the spirit of the present invention.

The embodiments of the four different compositions of LBWO-based oxide solid electrolyte thin films were prepared by vacuum deposition and their electrochemical characteristics were analyzed.

1. Fabrication of upper and lower current collectors

In order to fabricate the current collector thin film, the electrode region 101, the active region 102, and the connection region 103 are formed by DC sputtering using Pt, sus, or V ₂ O ₅ , as in the embodiment of FIG. 1A. The lower current collector thin film 110 was deposited on the substrate 300 in a specific pattern 100. In this embodiment, the active region 102 of the lower current collector thin film 110 has a size of 1.0 cm × 1.0 cm, and the thickness of the lower current collector thin film 110 is about 300 nm. 2 and 3, after forming the LBWO-based oxide solid electrolyte thin film 200 on the current collector thin film 110 fabricated in a specific pattern, the same conditions as the fabrication of the lower current collector thin film 110 are performed. The upper current collector thin film 120 is formed using Pt or sus. At this time, instead of Pt or sus as the upper current collector thin film 120, the result of observing the reactivity between Li and LBWO by depositing Li is shown in FIGS. 7 and 8.

2. Fabrication of LBWO Electrolyte Thin Film

After fabrication of the lower current collector thin film 110, as shown in FIG. 1B, Li ₂ O, Li ₂ WO ₄ , and B ₂ O ₃ may be formed on the lower current collector film 110 by thermal evaporation with an area of 1.5 cm × 1.5 cm. The LBWO-based oxide solid electrolyte thin film 200 was deposited at an arbitrary composition ratio of 60:15:25, 65:10:25, 60:20:20, and 65:15:20. Examples of LBWO pellets and sputtering targets prepared for thermal evaporation are shown in FIGS. 4 and 5, respectively. At this time, the deposition pressure was 5 × 10 ^-5 torr and 5 × 10 ^-3 torr in the case of thermal vapor deposition and sputtering, respectively.

3. Characterization

The cross section of the fabricated sus-LBWO-based oxide solid electrolyte thin film structure was observed with a high resolution scanning electron microscope (SEM), and the photograph is shown in FIG. 6. Regardless of the composition, no chemical reaction or any diffusion phenomenon was observed between the lower current collector thin film and the LBWO-based oxide solid electrolyte thin film regardless of the composition, which plays a very important role in interfacial stability. .

Cyclic voltammetry (CV) was performed at a scanning rate of 0.5 mV / sec from about 0.5 V to 4.5 V on a blocking electrode of Pt-LBWO-based oxide electrolyte thin film-Li structure fabricated for electrochemical characterization. , V ₂ O ₅ -LBWO-based oxide electrolyte thin film-lithium (Li) -based thin film battery was prepared and the charge and discharge characteristics were observed. All of these measurements were performed at room temperature, and the composition ratios of Li ₂ O, Li ₂ WO ₄ , and B ₂ O ₃ of the measured electrolyte were 60:20:20, and the results are shown in FIGS. 7 and 8, respectively. In the CV curve of FIG. 7, since there is no oxidation or reduction peak especially observed in the measurement potential section and almost no current flows, it can be seen that the oxide is stable in the use potential section of a general lithium battery. On the other hand, the charge and discharge curve of Figure 8 shows the characteristics of a typical V ₂ O ₅ anode, it can be seen that the reversible charging and discharging is possible when the all-solid-state thin film battery using the LBWO-based oxide electrolyte thin film. .

One of the important requirements of the lithium-based solid electrolyte is that it should not be reactive with lithium. When the lithium thin film is deposited with the LBWO thin film upper electrode to constitute the electrochemical cell as described above, the oxidation of lithium by the reaction between the lithium and the LBWO is Not observed. On the other hand, although the electrolyte LBWO thin film maintains the same deposition time for 10 minutes, the thickness of the thin film is 9,000, 7,100, 4,000, and 5,000Å according to its composition, and thus the deposition rate of the thin film varies depending on the composition. have. Ion conductivity was measured by measuring the ac impedance (Complex plane impedance spectra) by adjusting the deposition time to make the thickness of all thin films constant at 1.0 μm . The electrochemical impedance value was about 30 ~ 50Ω at the composition ratio of the four Li ₂ O, Li ₂ WO ₄ , B ₂ O ₃ , through which the ion conductivity value was calculated by the following equation.

σ = d / (R × A)

σ denotes an ion conductivity value (S / cm), d denotes an electrolyte thickness, R denotes each resistance value when measuring impedance of the LBWO thin film, and finally, A denotes an electrode area. The electrode area is 1.00 cm ² because it is the area of the active region 102 deposited through the 1.0 cm × 1.0 cm mask in the electrode pattern 100. The calculated value of ionic conductivity is on the order of 2 ~ 3 × 10 ^-6 S / cm, which is comparable to that of LiPON. As described above, the LBWO-based electrolyte thin film having both the advantages and disadvantages of the conventional LLT and LiPON thin films as an electrolyte for thin-film ultra-compact batteries is manufactured by argon (Ar) sputtering or thermal evaporation, which is a simpler process than reactive sputtering. This becomes possible.

9 shows various possible composition ratios of LBWO-based oxide solid electrolytes. _Four composition ratios are shown in which the composition ratios of Li ₂ O, Li ₂ WO ₄ , B ₂ O ₃ are 60:15:25, 65:10:25, 60:20:20, and 65:15:20, respectively. The composition ratio is a known part of several possible embodiments, it can be produced in other composition ratios.

As described above, the present invention is not limited to the above-described specific preferred embodiments, and various modifications can be made by those skilled in the art without departing from the gist of the present invention claimed in the claims. Of course, such changes are within the scope of the claims.

As described above, the LBWO thin film according to the present invention may be used as a solid electrolyte in a thin film battery, and may contribute to shortening the thin film deposition process time.

In addition, in the case of using lithium as a negative electrode when manufacturing a thin film battery, there is no interface reaction with lithium, there is an advantage that the interface with the positive electrode is also stable.

In addition, since the LBWO thin film has an amorphous structure, the LBWO thin film has an advantage of ensuring durability against a volume change of the electrode active material accompanying charging and discharging of a thin film battery.

Claims (4)

A solid electrolyte used in an all-solid-state lithium battery, the composition of which is composed of an LBWO 4-component system of Li ₂ O—Li ₂ WO ₄ —B ₂ O ₃ . The method of claim 1, Li ₂ O-Li ₂ WO ₄ -B ₂ O ₃ 3 forming a LBWO 4 component system The composition ratio of the components may be selected from 60:15:25, 65:10:25, 60:20:20, and 65:15:20, respectively. The method of claim 1, An LBWO-based oxide solid electrolyte, wherein a B (Boron) component, which is a glass former, is replaced by P (Phospher) among the four-component systems of LBWO. The method of claim 1, An LBWO-based oxide solid electrolyte is formed by any one of physical vapor deposition and chemical vapor deposition.

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