JP2018154504A - Inorganic composition, glass electrolyte, and secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inorganic composition capable of forming a glass electrolyte excellent in lithium ion conductivity, which contains no GeOcomponent.SOLUTION: An inorganic composition is an LiO-NbO-PO-MoOsystem, where based on an oxide, a content Cof an LiO component, a content Cof an NbOcomponent, a content Cof a POcomponent, and a content Cof an MoOcomponent preferably satisfy the following relationships: 50 mol%≤C≤60 mol%; 5 mol%≤C≤30 mol%; 15 mol%≤C≤30 mol%; and 0 mol%<C≤30 mol%.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an inorganic composition capable of forming a glass electrolyte that can function as a solid electrolyte, a glass electrolyte composed of the inorganic composition, and a secondary battery including the glass electrolyte.

For example, Patent Document 1 contains a Li ₂ O component, a P ₂ O ₅ component, a GeO ₂ component, and an M ₂ O ₅ component (M is one or more selected from Ta, Nb, and V) on an oxide basis, glass electrolytes have been disclosed li ₂ O content component is 30 to 65 mol%.

Japanese Patent Laying-Open No. 2015-63447

The GeO ₂ component, which is an essential component in the invention described in Patent Document 1, is a component that facilitates vitrification, but by containing it, the melting temperature of the composition is increased, or lithium ion Decrease conductivity. Further, the GeO ₂ component is a relatively expensive material.

An object of the present invention is to provide an inorganic composition that can form a glass electrolyte excellent in lithium ion conductivity and does not contain a GeO ₂ component. The present invention also provides a glass electrolyte made of the above inorganic composition and a secondary battery including the glass electrolyte.

The present invention, which is provided to solve the above-mentioned problems, is an inorganic composition characterized by being Li ₂ O—Nb ₂ O ₅ —P ₂ O ₅ —MoO ₃ based as one aspect. Since such an inorganic composition appropriately contains the MoO ₃ component, it is easy to vitrify, and the glass electrolyte formed from the inorganic composition is excellent in lithium ion conductivity.

The above inorganic composition, on an oxide basis, the content _C Li of Li ₂ O component, the content of _Nb 2 _{O 5} component _{C Nb,} P 2 _{O 5} component content _{C P,} and MoO ₃ ingredients The content C _Mo preferably satisfies the following relationship:
50 mol% ≦ C _Li ≦ 60 mol%,
5 mol% ≦ C _Nb ≦ 30 mol%,
15 mol% ≦ C _P ≦ 30 mol% and 0 mol% <C _Mo ≦ 30 mol%.

  By satisfying the above relationship, facilitating vitrification of the inorganic composition and improving the lithium ion conductivity of the glass electrolyte made of the inorganic composition are more stably realized.

From the viewpoint of more stably realizing vitrification of the inorganic composition, it may be preferable that the first ratio R1 defined by C _Mo / (C _Nb + C _Mo ) satisfies the following relationship: is there.
0 <R1 ≦ 0.75

  Another aspect of the present invention is a glass electrolyte made of the inorganic composition according to the present invention and having Li ion conductivity.

  Another aspect of the present invention is a secondary battery including the glass electrolyte according to the present invention as a solid electrolyte.

  It should be noted that the above summary of the invention does not enumerate all the necessary features of the present invention. In addition, a sub-combination of these feature groups can also be an invention.

According to the present invention, an inorganic composition capable of forming a glass electrolyte excellent in lithium ion conductivity is provided without containing a GeO ₂ component. Moreover, according to this invention, a secondary battery provided with the glass electrolyte which consists of said inorganic type composition, and the glass electrolyte is also provided.

It is sectional drawing which shows the secondary battery which concerns on one Embodiment of this invention. 2 is an X-ray diffraction spectrum of an inorganic composition of Example 1. FIG. 2 is an X-ray diffraction spectrum of an inorganic composition of Example 2. FIG. 2 is an X-ray diffraction spectrum of an inorganic composition of Example 3. FIG. 4 is an X-ray diffraction spectrum of an inorganic composition of Example 4. 3 is an X-ray diffraction spectrum of an inorganic composition of Example 5. FIG. It is a graph which shows the differential thermal analysis (DTA) result of the inorganic type composition of Example 1, and the inorganic type composition of Example 2. FIG. 2 is an X-ray diffraction spectrum of an inorganic composition of Example 7. FIG.

  Hereinafter, the present invention will be described through embodiments of the invention, but the following embodiments do not limit the invention according to the claims. In addition, not all the combinations of features described in the embodiments are essential for the solving means of the invention.

The inorganic composition according to an embodiment of the present invention is a Li ₂ O—Nb ₂ O ₅ —P ₂ O ₅ —MoO ₃ system.

The Li ₂ O component is a component that provides lithium ions as a carrier and imparts lithium ion conductivity to a glass electrolyte made of an inorganic composition according to an embodiment of the present invention. From the viewpoint of appropriately imparting lithium ion conductivity to the glass electrolyte, the content C _Li of the Li ₂ O component in the inorganic composition according to one embodiment of the present invention is 50 mol% or more based on the oxide. It is preferable that it is 51.5 mol% or more, and it is especially preferable that it is 53 mol% or more. From the viewpoint of reducing the possibility of increasing the crystallinity of the glass electrolyte, the content C _Li of the Li ₂ O component in the inorganic composition according to an embodiment of the present invention is 60 mol% or less based on the oxide. It is preferable that it is 58.5 mol% or less, and it is especially preferable that it is 57 mol% or less.

The Nb ₂ O ₅ component imparts weather resistance, particularly moisture resistance, to the inorganic composition. From the viewpoint of appropriately imparting such weather resistance, the content C _Nb of the Nb ₂ O ₅ component in the inorganic composition according to an embodiment of the present invention is preferably 5 mol% or more based on the oxide, It is more preferably 10 mol% or more, and particularly preferably 15 mol% or more. From the viewpoint of facilitating vitrification of an inorganic composition according to an embodiment of the present invention, the content C _Nb of the Nb ₂ O ₅ component in the inorganic composition according to an embodiment of the present invention is based on an oxide. , Preferably 30 mol% or less, more preferably 25 mol% or less, and particularly preferably 20 mol% or less.

The P ₂ O ₅ component is a glass forming component and is also a preferable component from the viewpoint of increasing the lithium ion conductivity of the glass electrolyte made of the inorganic composition according to one embodiment of the present invention. From the viewpoint of reducing the possibility that the crystallinity of the glass electrolyte increases, the content C _P of P ₂ O ₅ component in the inorganic composition according to one embodiment of the present invention, on an oxide basis, 15 mol% or more It is preferable that it is 17.5 mol% or more, and it is especially preferable that it is 20 mol% or more. From the viewpoint of properly securing a lithium ion conductive glass electrolyte of the content C _P of P ₂ O ₅ component in the inorganic composition according to one embodiment of the present invention, on an oxide basis, 30 mol% It is preferably at most 27.5 mol%, more preferably at most 25 mol%.

The MoO ₃ component improves the lithium ion conductivity of the glass electrolyte made of the inorganic composition according to one embodiment of the present invention. Further, by containing the MoO ₃ ingredients, it is possible to lower the glass transition temperature of the glass electrolyte above. From the viewpoint of stably realizing an increase in lithium ion conductivity and a reduction in glass transition temperature in the glass electrolyte, the content C _Mo of the MoO ₃ component in the inorganic composition according to an embodiment of the present invention is: In terms of oxide, it is preferably 0.1 mol% or more, more preferably 0.5 mol% or more, and particularly preferably 1 mol% or more. From the viewpoint of reducing the possibility of increasing the crystallinity of the glass electrolyte, the viewpoint of appropriately ensuring lithium ion conductivity in the glass electrolyte, and the like, the inclusion of the MoO ₃ component in the inorganic composition according to an embodiment of the present invention The amount C _Mo is preferably 30 mol% or less, more preferably 25 mol% or less, and particularly preferably 20 mol% or less, based on the oxide.

From the viewpoint of more stably realizing vitrification of the inorganic composition, it may be preferable that the first ratio R1 defined by C _Mo / (C _Nb + C _Mo ) satisfies the following relationship: is there.
0 <R1 ≦ 0.75

  R1 may be more preferably 0.5 or less.

An inorganic composition according to an embodiment of the present invention includes Al ₂ O ₃ , SiO ₂ , K ₂ O, Cs ₂ O, MgO, CaO, BaO, ZnO, SnO, Y ₂ O ₃ , Bi ₂ O ₃ , Components such as TeO ₂ , Sb ₂ O ₃ , Co ₂ O ₃ , CuO, and Fe ₂ O ₃ can be contained as optional additional components. From the viewpoint of facilitating the formation of a glass electrolyte excellent in lithium ion conductivity, the total content of these optional additives is preferably 5 mol% or less, preferably 1 mol% or less, based on the oxide. More preferably.

  Since the inorganic composition according to one embodiment of the present invention is easily vitrified, the glass electrolyte formed from the inorganic composition is less likely to increase the crystallinity in the glass electrolyte. In the present specification, the “glass electrolyte” is a glass having a glass phase as a main phase, and includes a structure in which crystal phases are scattered in the glass phase. Since the glass electrolyte which concerns on one Embodiment of this invention contains Mo ion from which an ion radius differs from Nb ion with Nb ion, it is excellent in lithium ion conductivity.

As described above, when the inorganic composition according to the embodiment of the present invention contains the MoO ₃ component, the glass transition temperature of the glass electrolyte formed from the inorganic composition is lowered. A decrease in the glass transition temperature is preferable because the melting temperature decreases.

The manufacturing method of the glass electrolyte which concerns on one Embodiment of this invention is not limited. An example is as follows. First, raw materials are prepared, and the raw materials are pretreated as necessary. A specific example of the pretreatment includes removing volatile components (for example, carbon dioxide) contained in the raw material by heating. Next, the blended raw materials (pretreated if necessary) are melted to produce a frit. Since the inorganic composition according to an embodiment of the present invention contains the MoO ₃ component, the melting temperature is relatively low, about 900 ° C. to 1200 ° C., and excellent in productivity. By rapidly cooling the melted frit, a glass electrolyte made of the inorganic composition according to one embodiment of the present invention can be obtained. In addition, a glass electrolyte can be obtained by subjecting the frit to a ball milling method.

  The glass electrolyte which concerns on one Embodiment of this invention can be used as a solid electrolyte of a secondary battery. An example of such a secondary battery is an all-solid secondary battery. FIG. 1 is a diagram conceptually showing a cross section of an example of an all-solid secondary battery. As shown in FIG. 1, in the secondary battery 100, a current collector 104, a positive electrode layer 106, an electrolyte layer 108, and a negative electrode layer 110 are sequentially stacked on a substrate 102.

  The substrate 102 supports the constituent members of the secondary battery 100 such as the current collector 104. As long as the structural member has a mechanical strength that can be supported, the substrate 102 is not limited in material, size, shape, and the like. However, since heat treatment such as firing is performed in the manufacturing process of the secondary battery 100 described later, it is preferable that the battery has heat resistance enough to withstand the heat treatment. Moreover, it is preferable to have chemical stability with respect to the organic solvent, lithium salt, etc. which are used in the manufacturing process of the secondary battery 100. Examples of the substrate 102 include a glass substrate, a metal foil, and a film such as PET (polyethylene terephthalate).

  The current collector 104 is connected to the positive electrode layer 106 and the negative electrode layer 110, and collects and supplies charges from the positive electrode layer 106 and the negative electrode layer 110. The current collector 104 is preferably made of a conductor such as a metal that is chemically stable with respect to the polymer electrolyte contained in the electrolyte layer 108. Examples of the current collector 104 include aluminum, copper, and stainless steel. Note that aluminum and stainless steel are preferable for the current collector 104 connected to the positive electrode layer 106, and copper and stainless steel are preferable for the current collector 104 connected to the negative electrode layer 110.

The positive electrode layer 106 functions as the positive electrode of the secondary battery 100. The positive electrode layer 106 includes a positive electrode active material and a conductive material, and is fixed with a binder. The positive electrode active material is a particulate material (powder), and can be exemplified by a lithium-containing composite oxide such as lithium manganate (LiMn ₂ O ₄ ). Examples of the conductive material include acetylene black. Examples of the binder include polyethylene oxide (PEO) resin, ethylene / propylene oxide copolymer, and polyvinylidene fluoride (PVdF) resin. When a polyethylene oxide (PEO) resin or an ethylene / propylene oxide copolymer is used for the binder, a lithium salt such as lithium bis (trifluoromethanesulfonyl) imide (LiTFSI) may be added to the positive electrode layer 106. The positive electrode layer 106 may contain a solid electrolyte such as a glass electrolyte according to an embodiment of the present invention.

The electrolyte layer 108 functions as an electrolyte for the secondary battery 100. The electrolyte layer 108 includes a glass electrolyte and a binder according to an embodiment of the present invention. As the binder, a copolymer of ethylene oxide and propylene oxide can be exemplified. A supporting electrolyte that improves lithium ion conductivity may be added to the binder, and examples of the supporting electrolyte include lithium bis (trifluoromethanesulfonyl) imide (LiTFSI). The solid electrolyte having lithium ion conductivity may contain a material other than the glass electrolyte according to the embodiment of the present invention. Such _{materials, Li 4-2x Zn x GeO 4 (} LISICON) based solid _{electrolyte, Li-Al-Ti-PO} 4 (LATP) based solid _{electrolyte, Li 1 + X Ge 2-} y Al y P 3 O 12 (LAGP ) Based solid electrolytes.

  The negative electrode layer 110 functions as the negative electrode of the secondary battery 100. The negative electrode layer 110 is a layer in which a negative electrode active material is fixed with a binder, and may include a carbon-based material. An example of the negative electrode active material is hard carbon. Examples of the binder include polyethylene oxide (PEO) resin, ethylene / propylene oxide copolymer, and polyvinylidene fluoride (PVdF) resin. When a polyethylene oxide (PEO) resin or an ethylene / propylene oxide copolymer is used for the binder, a lithium salt such as lithium bis (trifluoromethanesulfonyl) imide (LiTFSI) may be added to the negative electrode layer 110. The negative electrode layer 110 may include a solid electrolyte such as a glass electrolyte according to an embodiment of the present invention.

  As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. It will be apparent to those skilled in the art that various modifications or improvements can be added to the above-described embodiment. It is apparent from the scope of the claims that the embodiments added with such changes or improvements can be included in the technical scope of the present invention.

  EXAMPLES Hereinafter, although an Example demonstrates this invention more concretely below, this invention is not limited to these.

(Example 1 to Example 7)
Raw materials containing each element of Li, Nb, Mo and P were prepared, and heated and cooled with a platinum crucible to obtain a frit. The frit was heated again to melt the frit (melting temperature: 900 ° C. to 1200 ° C.), and the melt was quenched to obtain an inorganic composition having the composition shown in Table 1.

X-ray diffraction measurement (X-ray source: CuKα) of the obtained inorganic composition was performed. The results are shown in Table 1 and FIGS. The meanings of symbols in the “X-ray measurement” column of Table 1 are as follows.
In the G: X-ray diffraction spectrum, a peak having an intensity sufficient to confirm the crystal structure is not recognized, and it is determined that the measurement target is a glassy material that does not substantially contain a crystal phase.
In the G + C: X-ray diffraction spectrum, a peak having an intensity sufficient to confirm the crystal structure is observed, but the peak intensity is weak, the main phase to be measured is a glass phase, and the crystal phase is scattered in the main phase. I guess that.

  FIG. 2 is an X-ray diffraction spectrum of the inorganic composition of Example 1. FIG. 3 is an X-ray diffraction spectrum of the inorganic composition of Example 2. 4 is an X-ray diffraction spectrum of the inorganic composition of Example 3. FIG. FIG. 5 is an X-ray diffraction spectrum of the inorganic composition of Example 4. 6 is an X-ray diffraction spectrum of the inorganic composition of Example 5. FIG.

  As shown in Table 1 and FIGS. 2 to 6, in the X-ray diffraction spectra of the inorganic compositions of Examples 1 to 3 and Example 6, there is substantially no peak having an intensity that can confirm the crystal structure. Was not recognized. Therefore, it was confirmed by X-ray diffraction spectrum that these inorganic compositions were vitreous substantially free of crystal phase.

On the other hand, peaks derived from Li ₃ PO ₄ were observed in the X-ray diffraction spectra of the inorganic compositions of Example 4 and Example 5.

Moreover, the lithium ion conductivity of each inorganic composition was measured. The measurement method was as follows. Each inorganic composition was pulverized in a mortar, and the powder was press-compressed with upper and lower bar-shaped stainless steel (SUS) materials. Using the upper and lower SUS materials as electrodes, a Cole-Cole plot was obtained and calculated using an impedance gain phase analyzer. The measurement results are shown in Table 1. As shown in Table 1, it was confirmed that the lithium ion conductivity of the glass electrolyte made of the inorganic composition can be improved by containing the MoO ₃ component.

Differential thermal analysis (DTA) was performed on the inorganic composition of Example 1 and the inorganic composition of Example 2. The result is shown in FIG. As shown in FIG. 7, the glass transition temperature estimated from the endothermic peak of the DTA curve of the inorganic composition of Example 2 is 435 ° C., and from the endothermic peak of the DTA curve of the inorganic composition of Example 1. The estimated glass transition temperature was 465 ° C. From these results, it was confirmed that the glass transition temperature can be lowered by containing the MoO ₃ component.

(Example 7)
A frit having the same composition as the frit manufactured in the inorganic composition of Example 2 was prepared. The frit was melted and then allowed to cool to obtain an inorganic composition having the same composition as the inorganic composition of Example 2.

With respect to the inorganic composition of Example 7, the X-ray diffraction spectrum and lithium ion conductivity were measured in the same manner as described above. As a result, as shown in FIG. 8, the inorganic composition of Example 7 was crystalline, and the lithium ion conductivity was 2 × 10 ⁻⁹ S / cm. From this result, it was confirmed that when the inorganic composition of Example 2 is glassy, lithium ion conductivity four times or more that of crystalline is obtained.

  As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. It will be apparent to those skilled in the art that various modifications or improvements can be added to the above-described embodiment. It is apparent from the scope of the claims that the embodiments added with such changes or improvements can be included in the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 100 ... Secondary battery 102 ... Board | substrate 104 ... Current collector 106 ... Positive electrode layer 108 ... Electrolyte layer 110 ... Negative electrode layer

Claims (5)

Inorganic composition which is a _{Li 2 O-Nb 2 O 5} -P 2 O 5 -MoO 3 system. On an oxide basis, the content _C Li of Li ₂ O component, the content _C Nb of _Nb 2 _{O 5 component,} the content _{C P} of P 2 _{O 5} component, and MoO ₃ ingredient content _{C Mo} of the following relationship The inorganic composition according to claim 1, wherein:
50 mol% ≦ C _Li ≦ 60 mol%,
5 mol% ≦ C _Nb ≦ 30 mol%,
15 mol% ≦ C _P ≦ 30 mol% and 0 mol% <C _Mo ≦ 30 mol%. 3. The inorganic composition according to claim 1, wherein the first ratio R < _b > 1 defined by C _Mo / (C _Nb + C _Mo ) satisfies the following relationship.
0 <R1 ≦ 0.75   The glass electrolyte which consists of an inorganic composition as described in any one of Claim 1 to 3, and has Li ion conductivity.   A secondary battery comprising the glass electrolyte according to claim 4 as a solid electrolyte.