KR101687808B1 - A Lithium Ion Conductive Materials - Google Patents

Abstract

The present invention relates to a lithium ion conductor having a structure represented by the following formula (1).
[Chemical Formula 1]
Li _x BaZr _{1 - x} M _x O ₃
(Wherein x = 0.1 to 0.5 and M is Ga, Al or In).

Description

[0002] Lithium Ion Conductive Materials [0003]

The present invention relates to a lithium ion conductor, and more particularly to a lithium ion conductor doped with aluminum, gallium or indium.

Solid-state electrolyte Li-ion battery is a next-generation secondary battery under active research. This is a lithium secondary battery made by replacing a conventional liquid electrolyte composed of a solvent such as EC, DMC, EMC or the like with a solid material having a high diffusion coefficient of Li ion as shown in Fig. 1 (a) No separation membrane is required, and the electrode and the electrolyte are all solid materials, so the stability is high.

This solid electrolyte lithium ion battery has a Li transference number of about 1.0, which is the ion conductivity due to pure cations. Therefore, even if the conductivity of the Li ion is lower than that of the conventional liquid electrolyte (0.3-0.5) It has the advantage of showing performance.

LLTO (Li _{3 x} La _{(2/3) -x? (1/3) -2x} TiO ₃ ) is the candidate material that can be used as such a solid electrolyte. Li- It has a disadvantage in that it can not use Li-metal electrode due to its reactivity with metal, and the weight becomes heavy when the density becomes large. Next, there is thio-LISICON (Li ₁₀ GeP ₂ S ₁₂ ), which is excellent in Li ion conductivity at room temperature, but it has a disadvantage that it is difficult to synthesize and is very vulnerable to moisture, and releases poisonous gas upon reacting with moisture. In addition, there is a hydrate system (LiBH _4, etc.), which is easy to synthesize, has a large bandgap, can be used at high voltage, has a low density and is light and has a strong reducing property, There is a disadvantage that the structural stability is low.

Accordingly, there is a need to develop a solid electrolyte lithium ion battery that is an insulator, has a fast diffusion rate of Li ions, and can operate at a temperature higher than room temperature, without the above problems.

Japanese Patent Application Laid-Open No. 2006-286599 A

In order to solve the above problems of the prior art,

An object of the present invention is to provide a lithium ion conductor which can be used as a solid electrolyte for a lithium ion battery which is an insulator and has a high diffusion rate of Li ions and can operate at a temperature higher than room temperature.

In order to achieve the above object,

The present invention provides a lithium ion conductor having a structure represented by the following formula (1).

[Chemical Formula 1]

Li _x BaZr _{1 - x} M _x O ₃

(Wherein x = 0.1 to 0.5 and M is Ga, Al or In).

The present invention also provides a solid electrolyte for a lithium secondary battery comprising the lithium ion conductor.

The present invention also provides a lithium secondary battery comprising the solid electrolyte.

The lithium ion conductor of the present invention is not only an insulator but also has a high diffusion rate of Li ions, a very high melting point, a low chemical resistance and corrosion resistance so that it can operate at a temperature higher than room temperature and has excellent thermal stability. And the coefficient of thermal expansion is very small.

In addition, since the lithium ion conductor of the present invention has an insulator having a relatively wide band gap, there is no interfacial reaction or decomposition with electrodes when operated under a high voltage, and when the electrode is made of a single crystal, its visible light transmittance is excellent and a transparent electrolyte can be realized .

In addition, the lithium ion conductor of the present invention has an advantage that it is stable to moisture in the air as compared with a sulfide, and can be operated in a general drainer environment.

Therefore, the lithium ion conductor of the present invention can be used as a solid electrolyte for a lithium ion battery due to the above advantages.

1 is a view showing a lithium secondary battery using a lithium secondary battery and a solid electrolyte using a liquid electrolyte.
FIG. 2 is a graph showing the activation energy when a proton is moved to an interstitial site between Ba and O. FIG.
3 is a schematic diagram showing Schottky defects of trivalent cations and Li-interstitials using the lattice structure in BaZrO ₃ of the perovskite structure.
4 is a graph showing distances of Ba-O in a lattice according to lithium ion conductors of Examples and Comparative Examples.
5 is a graph showing the magnitudes of activation energies required when Li ⁺ ions of the lithium ion conductors of Examples and Comparative Examples migrate to the interstitial sites of adjacent lattices.
FIG. 6 is a graph showing band gaps of lithium ion conductors of Examples and Comparative Examples measured using a GGA exchange-correlation function. FIG.

Hereinafter, the lithium ion conductor of the present invention will be described in detail.

The lithium ion conductor of the present invention is characterized by having a structure represented by the following general formula (1).

[Chemical Formula 1]

Li _x BaZr _{1 - x} M _x O ₃

(Wherein x = 0.1 to 0.5 and M is Ga, Al or In).

The lithium ion conductor having the structure of the above formula (1) has BaZrO ₃ having a perovskite structure as a host, substituting a part of Zr with M, and inserting Li ions into an interstitial site .

The BaZrO ₃ has a perovskite structure. For example, Y-doped BaZrO ₃ has been widely applied as a proton (H ⁺ ) conductor. For example, " J. Phys. Chem. 2, Proton moves to an interstitial site between Ba-O, and Proton () is transferred to an interstitial site between Ba-O, It is disclosed that the activation energy is a usable level of proton conductor at 0.54 eV.

In order to form Li-interstitial in BaZrO ₃ having the perovskite structure as described above, the lithium ion conductor of the present invention is prepared by mixing Al, which is a trivalent cation in Zr ^{4 +} Ga or In. As a result, the substituted trivalent cations such as Al, Ga or In and the Li-interstitial are Schottky defects, which have the chemical formula Li _x BaZr _{1 - x} MxO ₃ . This would more Zr ^{4 +} ion size is less Al ^{3 +,} Ga ^{3 +} and 3 of cationic substitution for Zr ^{4 +} position, the distance between the Ba-O in the lattice of BaZrO ₃ in the perovskite structure becomes large relative to The Li ⁺ ions are easily inserted into the interstitial site as shown in FIG. 3 (b).

When the Li ⁺ ion is inserted into the interstitial site of the lithium ion conductor of the present invention, unlike the Y-doped BaZrO ₃ used as the proton conductor, the interstitial diffusion of the Li ⁺ It is advantageous to substitute Ga, Al, and In ions smaller than Zr to widen the distance between Ba and O. In this case, Ba atoms in the lattice of the lithium ion conductor having the formula Li _x BaZr _1-x MxO ₃ And the O atom may have a distance of 3.0 to 4.0 ANGSTROM, more preferably 3.23 to 3.30 ANGSTROM.

May be shown as Interstitial place the Li ⁺ ion is a 3 (b) inserted (interstitial site) of the lithium ion conductor of the present invention, A- interstitial lattice of the Li ⁺ ions are in the adjacent position B- The activation energy to be overcome when moving to the interstitial site is the lowest value for Li _0.125 BaZr _0.875 M _0.125 O ₃ (M = Ga, Al, In) in which Ga, Al, 0.5 to 0.8 eV, more preferably 0.7 to 0.79 eV. This shows an improved value compared to undoped BaZrO ₃ and Y, Gd-doped BaZrO ₃ .

In the lithium ion conductor of the present invention, Al ^3+, Ga ³⁺ is a trivalent cation, such as substituted for Zr ⁴⁺ place, Li ⁺ ions are inter-stitch the Li _{0.125 0.875} BaZr inserted into the differential position M _0.125 O ₃ (M In the case of GaAs, Al, and In, the band gap is 2.5 to 5.0 eV using the GGA exchange-correlation function as a result of calculation of partial density of states (PDOS) using VASP based on a density functional theory. And more preferably 2.5 to 3.0 eV, which indicates that the lithium ion conductor of the present invention is an insulator.

The present invention provides a solid electrolyte for a lithium secondary battery comprising the lithium ion conductor. The solid electrolyte for a lithium secondary battery is not particularly limited, but may be deposited on a substrate using a vacuum deposition method to form a thin film. The vacuum deposition method may be performed by a sputtering method, a pulse laser deposition method (PLD), a thermal evaporation method, an electron-beam evaporation method, a molecular beam epitaxy method, an activated reactive evaporation method (ARE), a laser ablation method, or an ion plating method.

The present invention provides a lithium secondary battery including the solid electrolyte. The lithium secondary battery includes a negative electrode; A solid electrolyte on the negative electrode; And a positive electrode on the solid electrolyte. In the lithium secondary battery of the present invention, the solid electrolyte may include a lithium ion conductor.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope and spirit of the invention as disclosed in the accompanying claims. Changes and modifications may fall within the scope of the appended claims.

Example

Manufacture of lithium ion conductor

[Example 1]

BaCO ₃ powder (1.0 mol), Ga ₂ O ₃ powder (0.0625 mol) and ZrO ₂ The powder (0.875 mol) was mixed, placed in a PE container with ethanol for 15 hours, and then mixed with a zirconia ball. After calcination at 1200 ° C for 10 hours, milling was performed for 4 hours using a planetary mill. After that, sintering was carried out with Li ₂ O (0.0625 mol) at a temperature of 1700 ° C to substitute Ga in the Zr ^{4 +} site of BaZrO ₃ having a perovskite structure, and Li ⁺ And the oxygen vacancy was removed while inserting it into the substituted interstitial site to prepare Li _0.125 BaZr _0.875 Ga _0.125 O ₃ .

[Example 2]

Li _0.125 BaZr _0.875 Al _0.125 O ₃ was prepared in the same manner as in Example 1, except that Al ₂ O ₃ was used instead of Ga ₂ O ₃ .

[Example 3]

Li _0.125 BaZr _0.875 In _0.125 O ₃ was prepared in the same manner as in Example 1, except that In ₂ O ₃ was used instead of Ga ₂ O ₃ .

[Comparative Example 1]

BaZrO ₃ with a perovskite structure was used.

[Comparative Example 2]

Li _0.125 BaZr _0.875 Y _0.125 O ₃ was prepared in the same manner as in Example 1, except that Y ₂ O ₃ was used instead of Ga ₂ O ₃ .

[Comparative Example 3]

Li _0.125 BaZr _0.875 Gd _0.125 O ₃ was prepared in the same manner as in Example 1, except that Gd ₂ O ₃ was used instead of Ga ₂ O ₃ .

Experimental Example

The lithium ion conductors prepared in the above Examples and Comparative Examples were analyzed as follows.

1) the lattice volume of the lithium ion conductor and the lattice volume within the lattice Ba -O distance measurement

The lattice volume of each of the lithium ion conductors prepared in Example 1 (Ga doping), Example 2 (Al doping), Example 3 (In doping), Comparative Example 2 (Y doping) and Comparative Example 3 (Gd doping) And the distance of Ba-O in the lattice are measured using VASP, a density functional theory-based code, and are shown in Fig.

As shown in Figure 4, if the ion size is less Al ^{3 +,} Ga ^{3 +} ion than Zr ^{4 +} is substituted for Zr ^{4 +} place, it was found that the distance between the Ba-O is relatively large, if such a Li ⁺ Ion is likely to be inserted into the interstitial site.

2) activation energy of lithium ion conductor ( activation energy )

(Ga doping), Example 2 (Al doping), Example 3 (In doping), Comparative Example 1 (No doping), Comparative Example 2 (Y doping), and Comparative Example 3 (Gd doping) The activation energy required when the Li ⁺ ions of each lithium ion conductor migrate to the interstitial site of the adjacent lattice is measured using VASP, a density functional theory-based code, Respectively.

As shown in FIG. 5, the activation energy of the lithium ion conductors of Examples 1 to 3 in which Ga, Al, and In were substituted was lower than that of Comparative Examples 1 to 3.

3) Activation energy of lithium ion conductor ( activation energy )

VASP, a density functional theory based code, was used for each of the lithium ion conductors prepared in Example 1 (Ga doping), Example 2 (Al doping) and Example 3 (In doping) (partial density of states), and then the bandgap is measured using the GGA exchange-correlation function, and is shown in FIG.

As shown in Figs. 6 (a) to 6 (c), the band gap was about 2.5 eV, and the actual band gap could be expected to be larger than 3.0 eV.

Claims (10)

A lithium ion conductor having a structure represented by the following formula (1).
[Chemical Formula 1]
Li _x BaZr _{1 - x} M _x O ₃
(Wherein x = 0.1 to 0.5 and M is Ga, Al or In). The method according to claim 1,
The lithium ion conductor is a lithium-
A lithium ion conductor characterized in that BaZrO ₃ having a Perovskite structure is used as a matrix and a part of Zr is substituted with M and Li ions are inserted into an interstitial site. The method of claim 2,
Wherein a distance between Ba atoms and O atoms of the lithium ion conductor is 3.0 to 4.0 ANGSTROM. The method of claim 2,
Wherein a distance between Ba atoms and O atoms of the lithium ion conductor is 3.23 to 3.30 ANGSTROM. The method of claim 2,
Wherein the activation energy required when the Li ion of the lithium ion conductor moves to the interstitial site of the adjacent lattice has a value of 0.5 to 0.8 eV. The method of claim 2,
Wherein the activation energy required when the Li ion of the lithium ion conductor moves to the interstitial site of the adjacent lattice has a value of 0.7 to 0.79 eV. The method of claim 2,
And the band gap of the partial density of states (PDOS) value of the lithium ion conductor is 2.5 to 5.0 eV. The method of claim 2,
Wherein a band gap of a partial density of states (PDOS) value of the lithium ion conductor is 2.5 to 3.0 eV. A solid electrolyte for a lithium secondary battery comprising the lithium ion conductor according to claim 1. A lithium secondary battery comprising the solid electrolyte of claim 9.

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