JP6425450B2 - Glass electrolyte - Google Patents

Description

  The present invention relates to a glass electrolyte having lithium ion conductivity.

  In recent years, the use of clean energy by solar power generation and wind power generation has been promoted as a solution to the energy problem caused by the exhaustion of energy resources. As a result, not only home electric appliances typified by conventional personal computers and televisions but also products for using electric energy in automobiles and ships are being studied, and the demand for large-capacity, high-safety batteries is increasing. ing.

  An all-solid-type lithium ion secondary battery is being studied as a large-capacity and safe next-generation lithium ion secondary battery that does not use a flammable organic solvent. In all solid lithium secondary batteries, it is the solid electrolyte that is responsible for lithium ion conduction instead of the non-aqueous electrolyte. However, since the ion conductivity of the solid electrolyte is inferior to that of the non-aqueous electrolyte, improvement of lithium ion conductivity of the solid electrolyte has been a problem.

  As a solid electrolyte exhibiting high ion conductivity having lithium ion conductivity, a chalcogenide glass containing lithium ion described in Non-Patent Document 1 has been proposed. It has high lithium ion conductivity, but its decomposition voltage is as low as 0.7 V, and its practical application as a component of a lithium ion secondary battery is not easy.

Although the oxide glass based on P ₂ O ₅ containing lithium ions as described in Non-Patent Document 2 is generally stable in the atmosphere and has a high decomposition voltage, the melting temperature of the glass is very high at 1450 ° C., It is not industrially practical. Further, for example, in order to realize an all solid lithium ion secondary battery as described in Patent Document 1, a reduction in Tg is required for a glass used as a battery member, as described in Non-Patent Document 2. Glass does not satisfy this.

JP, 2012-89406, A

H. Wada et al, "Preparation and ionic conductivity of new B2S3-Li2S-LiI glasses" Mat. Res. Bull, February, 1983, Vol. 18, Issue 2, p. 189-193 B. V. R. Chowdari, K. et al. Radhakrishnan, "IONIC CONDUCTIVITY STUDIES OF THE VITREOUS Li2O: P2O5: Ta2O5 SYSTEM" Journal of Non-Crystalline Solids, North-Holland, Amsterdam, April, 1989, Vol. 108, Issue 3, p.323-332

  The object of the present invention is to solve the above-mentioned drawbacks in solid electrolyte glass and to provide a glass which can be melted at a relatively low temperature in the atmosphere and which is suitable for an all solid lithium ion secondary battery member I assume.

As a result of intensive studies to solve the above problems, the present inventor has found that P ₂ O ₅ -B ₂ O ₃ -M ₂ O ₅ (where M is one or more selected from Ta, Nb, and V). ) -GeO 2 _-Li 2 discovered _{that O-based} vitrification range in the glass is present, it is found to exhibit a high lithium ion conductivity, the present invention has been accomplished. Specifically, it is as follows.

(Configuration 1)
Containing Li ₂ O component, P ₂ O ₅ component, GeO ₂ component and M ₂ O ₅ component (M is one or more selected from Ta, Nb, V) on an oxide basis, and the content of Li ₂ O component is Glass electrolyte which is 30-65 mol%.
(Configuration 2)
In mol% based on oxide,
The content of P ₂ O ₅ component is 5% to 40%,
The content of GeO ₂ component is 0.2% to 7%,
The glass electrolyte according to Configuration 1, wherein the content of the M ₂ O ₅ component (M is one or more selected from Ta, Nb, and V) is 0.2% to 20%.
(Configuration 3)
The ratio of the content of Li ₂ O component to the total content of Ta ₂ O ₅ component, Nb ₂ O ₅ component, V ₂ O ₅ component, and GeO ₂ component in mol% based on oxide: Li ₂ O / ( The glass electrolyte according to configuration 1 or 2, wherein Ta ₂ O ₅ + Nb ₂ O ₅ + V ₂ O ₅ + GeO ₂ ) is 2.0 or more.
(Configuration 4)
In mol% based on oxide,
0 to 20% of Ta ₂ O ₅ ingredients,
0 to 20% of Nb ₂ O ₅ component, or 0 to 15% of V ₂ O ₅ component
The glass electrolyte in any one of the structures 1 to 3 containing.
(Configuration 5)
In mol% based on oxide,
0 to 25% of B ₂ O ₃ ingredient
The glass electrolyte in any one of the structures 1-4 containing.
(Configuration 6)
In mol% based on oxide,
0 to 5% of SiO ₂ component,
0 to 10% of Al ₂ O ₃ ingredients,
0 to 5% of K ₂ O component,
0 to 5% of the Cs ₂ O component,
0 to 5% of MgO component,
0-5% CaO ingredient,
0 to 5% of BaO ingredient,
0 to 5% of ZnO component,
0-5% of SnO component,
0 to 5% of Y ₂ O ₃ component,
0 to 5% of Bi ₂ O ₃ component,
0-5% of TeO ₂ component or 0-5% of Sb ₂ O ₃ component
The glass electrolyte in any one of the structures 1 to 5 containing.
(Configuration 7)
The glass electrolyte in any one of the structures 1-6 whose melting temperature is 1350 degrees C or less.
(Configuration 8)
The glass electrolyte in any one of the structures 1-7 whose lithium ion conductivity in 25 degreeC is 5.00 * 10 < ^-8 > Scm < ^-1 > or more.

According to the present invention, it is possible to obtain a glass electrolyte having a lithium ion conductivity of 5.00 × 10 ⁻⁸ Scm ⁻¹ or more at 25 ° C. The glass electrolyte of the present invention can be melted at a low temperature of 1350 ° C. or less in the atmosphere.

Next, each composition component which comprises the glass electrolyte of this invention is described. In addition, content of each component is shown by mol% on the basis of an oxide. Here, "mol% on the basis of oxide" means oxides, hydroxides, carbonates, nitrates, fluorides, chlorides, ammonium salts, metaphosphates used as raw materials of components of the glass electrolyte of the present invention. It is a method of describing the composition of each component contained in a glass electrolyte on the assumption that an acid compound etc. is completely decomposed at the time of melting and changes to an oxide state. The ratio of the substance mass of each component contained in the glass electrolyte is represented, where the total of the substances of the formed oxide is 100 mol%.
Hereinafter, in the present specification, unless otherwise specified, the contents of the components of the glass electrolyte are represented by mol% based on the oxide.

The Li ₂ O component is a component essential for providing a carrier and imparting lithium ion conductivity. When the content of the Li ₂ O component is less than 30%, lithium ion conductivity does not appear, or lithium ion conductivity significantly decreases, so the lower limit of the content is preferably 30%, and more preferably 40%, 45% is most preferred. In addition, if the content of the Li ₂ O component exceeds 65%, it is difficult to obtain a glass electrolyte having high lithium ion conductivity, for example, by crystallization to precipitate Li ₃ PO ₄ having low lithium ion conductivity, The upper limit of the content is preferably 65%, more preferably 63%, and most preferably 59%.

The P ₂ O ₅ component is a glass-forming component suitable for obtaining a high ion conductor having a large difference in electronegativity and having lithium ions as mobile ions, and is a component essential to the formation of a glass electrolyte in the present invention. is there. If the content is less than 5%, vitrification is difficult, so the lower limit of the content is preferably 5%, more preferably 6%, and most preferably 7%. In addition, when the content of the P ₂ O ₅ component exceeds 40%, the chemical stability decreases and the melting temperature further rises, and thus it becomes difficult to obtain desired properties, so the upper limit of the content is 40% is preferred, 38.5% is more preferred, and 35% is most preferred.

The GeO ₂ component is a component that facilitates vitrification, and if the content is less than 0.2%, it is difficult to obtain glass because the thermal stability decreases, so the lower limit of the content is 0. It is preferably 0.2%, more preferably 0.3%, and most preferably 0.4%. However, if the content exceeds 7%, the melting temperature rises, and it is difficult to obtain a glass electrolyte containing lithium ions in a high concentration, and the lithium ion conductivity decreases, so the upper limit of the content is 7%. It is preferable to set it as 6%, it is more preferable to set it as 6%, and it is most preferable to set it as 5%.

The M ₂ O ₅ component (M is one or more selected from Ta, Nb, and V) increases the thermal stability of the glass and facilitates the formation of the glass by the function of the network modification oxide, and further, the lithium ion conductivity Is a necessary ingredient to raise In the present invention, lithium ions are trapped in the network structure of the network-forming oxide P ₂ O ₅ in the M ₂ O ₅ component (M is one or more selected from Ta, Nb, and V) in the glass electrolyte. The effect of securing the lithium ion conduction path is exhibited. In order to obtain these effects sufficiently, the lower limit of the content of the M ₂ O ₅ component (M is one or more selected from Ta, Nb, and V) is preferably 0.2% and 0.3%. Is more preferably 0.4%. From the viewpoint of enhancing these effects, the lower limit of the M ₂ O ₅ component may be 1% or 2.5%. However, if the content exceeds 20%, the stability of the glass is reduced to promote crystallization and the melting temperature is increased, so the upper limit of the content is preferably 20%, and 18.5%. It is more preferable to set it as 17.5%, and it is most preferable to set it as 17.5%.

In the glass electrolyte of the present invention, from the viewpoint of increasing the lithium ion _{conductivity,} among M 2 _{O 5} component, a _Ta 2 _{O 5} component or _Nb 2 _{O 5} either component alone as _M 2 _{O 5} component It is preferable to contain.

In the glass electrolyte of the present invention, the ratio of the content of the Li ₂ O component to the total content of the M ₂ O ₅ component (M is one or more selected from Ta, Nb, and V) and the GeO ₂ component Li ₂ O / (Ta ₂ O ₅ + Nb ₂ O ₅ + V ₂ O ₅ + GeO ₂ ) is preferably 2.0 or more. By setting the ratio to 2.0 or more, lithium is contained in a high concentration, and the effects of the M ₂ O ₅ component and the GeO ₂ component can be maximized, so a glass electrolyte having high lithium ion conductivity is obtained. be able to. Accordingly, the ratio of the content of the Li ₂ O component to the total content of the M ₂ O ₅ component (M is one or more selected from Ta, Nb, and V) and the GeO ₂ component Li ₂ O / (Ta ₂ O ₅ + Nb ₂ O ₅ + V ₂ O ₅ + GeO ₂ ) is preferably 2.0 or more, more preferably 2.3 or more, still more preferably 2.5 or more, and 3.0 or more Is most preferred. However, when the value of Li ₂ O / (Ta ₂ O ₅ + Nb ₂ O ₅ + V ₂ O ₅ + GeO ₂ ) becomes larger than 15, the M ₂ O ₅ component (M is one or more selected from Ta, Nb, V) The content is extremely reduced, and the effect of the M ₂ O ₅ component can not be sufficiently obtained, and the lithium ion conductivity is extremely reduced. Therefore, 15 or less is preferable, 14.5 or less is more preferable, and 14 or less is most preferable.

The Ta ₂ O ₅ component is an optional component having the effect of increasing the lithium ion conductivity while increasing the thermal stability of the glass. It is speculated that the lithium-oxygen bond that occurs when bonds are broken by alkali ions (e.g. lithium ions) in the network structure in the glass prevents lithium ion migration in the glass. By including the Ta ₂ O ₅ component, a TaO _6/2 octahedral structure without lithium-oxygen bond is formed in the glass, and as a result, the lithium-oxygen bond is reduced, and thus such an effect is obtained. it is conceivable that. In order to sufficiently obtain these effects, the lower limit of the content of the Ta ₂ O ₅ component is more preferably 1%, and most preferably 2.5%. However, if the content exceeds 20%, the stability of the glass is reduced to promote crystallization, and the cost of raw materials for the glass is significantly increased, so the upper limit of the content is preferably 20%. It is more preferably 18.5%, most preferably 17.5%.

The Nb ₂ O ₅ component is an optional component that contributes to the formation of glass, increases the stability of the glass, lowers the melting temperature and at the same time increases the lithium ion conductivity. By including the Nb ₂ O ₅ component, a lithium-oxygen bond-free NbO _6/2 octahedral structure is formed in the glass, and as a result, the lithium-oxygen bond is reduced, and such an effect is obtained. it is conceivable that. In order to sufficiently obtain these effects, the lower limit of the content of Nb ₂ O ₅ is more preferably 1%, and most preferably 2.5%. However, if the content exceeds 20%, the stability of the glass is lowered to promote crystallization, so the upper limit of the content is preferably 20%, more preferably 18%, and more preferably 17. It is more preferably 5%, still more preferably 15%, still more preferably 14%, and most preferably 13%.

The V ₂ O ₅ component is an optional component having the effect of lowering the melting temperature of the glass, suppressing crystallization, and further enhancing the lithium ion conductivity. In order to sufficiently obtain these effects, the lower limit of the content of V ₂ O ₅ is more preferably 1%, and most preferably 2.5%. However, if the content of V ₂ O ₅ component exceeds 15%, the chemical stability of the glass is reduced, crystallization is promoted, it becomes weak to moisture, and the conductivity of lithium ions is further reduced, so that the desired characteristics are obtained. The upper limit of the content is preferably 15%, more preferably 14%, and most preferably 13%.

The B ₂ O ₃ component is an optional component useful for forming glass, and is a component that lowers the melting temperature of the glass, increases the chemical stability, and lowers the viscosity. In order to sufficiently obtain these effects, the lower limit of the content of the B ₂ O ₃ component is more preferably 3%, and most preferably 5%. However, if the content exceeds 25%, crystallization is promoted, and it becomes difficult to obtain a glass electrolyte containing lithium ions in a high concentration, and the lithium ion conductivity decreases, so the upper limit of the content is 25%. Preferably 24.5%, and most preferably 24%.

Besides these components, SiO ₂ , K ₂ O, Cs ₂ O, MgO, CaO, BaO, ZnO, SnO, Y ₂ O ₃ , Bi ₂ O ₃ , TeO ₂ , Sb ₂ O ₃ , Co ₂ O ₃ Although components such as CuO and Fe ₂ O ₃ can be added, if the amount exceeds 5 mol%, it becomes difficult to obtain a glass electrolyte having high lithium ion conductivity containing lithium ions in a high concentration. Therefore, the content of each should be 5% or less. 10% or less is preferable and, as for the total amount of these components added, 5% or less is more preferable. Al ₂ O ₃ can also be added, but should be 10% or less for the same reason.

It is desirable that the composition of the glass electrolyte does not contain the Na ₂ O component as much as possible. When this component is present in the glass, the mixing effect of the alkali ions tends to inhibit the conduction of lithium ions and to lower the conductivity. Further, if sulfur or chlorine is contained in the composition of the glass electrolyte, although lithium ion conductivity is slightly improved, chemical durability and stability deteriorate, so it is desirable not to contain as much as possible. In the composition of the glass electrolyte, it is preferable not to contain as much as possible components such as Pb, As, Cd and Hg which may harm the environment and the human body. Furthermore, lanthanoids represented by rare metal oxides such as La, actinides represented by Ac, Ru, Co, Ir, In, Se, Hf and other components avoid high cost from the aspect of industrial use. Therefore, it is desirable not to contain as much as possible. In the glass electrolyte of the present invention, crystallization is promoted from the nature thereof, and therefore, it is desirable not to contain components such as Sr, Mn, Ni, Zr, etc. as much as possible.

  The glass electrolyte of the present invention is produced, for example, as follows. That is, the above raw materials are uniformly mixed so that each component is within a predetermined content range, and the prepared mixture is placed in a quartz crucible, an alumina crucible or a platinum crucible, and the temperature range of 1000 ° C. to 1450 ° C. 5. Melt for 5 to 4 hours, perform stirring and homogenization, cast into a mold and slowly cool, or press-mold with a mold, or cast into water at 5 to 25 ° C.

The lithium ion conductivity of the glass electrolyte of the present invention is preferably 5.00 × 10 ⁻⁸ (S / cm), more preferably 6.40 × 10 ⁻⁸ (S / cm), most preferably 7.00 × The lower limit is 10 ^-8 (S / cm). Thereby, for example, it becomes applicable to the all-solid-type lithium ion secondary battery member. Here, the higher the lithium ion conductivity, the better the performance of the battery.

  The melting temperature of the glass electrolyte of the present invention is 1350 ° C. or less, 1325 ° C. or less in a more preferable embodiment, and 1300 ° C. or less in a most preferable embodiment. The melting temperature of the glass electrolyte of the present invention can be obtained up to 950 ° C. Here, "the melting temperature of glass" means that when the raw material powder of glass is heated, the raw material powder becomes a melt, and is generated from the unmelted raw material powder and the raw material powder on the melt surface and inside the melt. It is a temperature at which solid matter (hereinafter referred to as "unmelted") disappears. Even if solids adhere to the inner wall of the crucible above the melt surface, they are ignored. However, in the present invention, since direct measurement of the melting temperature is difficult, the raw material powder is heated while being heated, and observed at 50 ° C. or 25 ° C. intervals, and the melt surface and melt interior visually The temperature at which no melting residue is observed is taken as the melting temperature.

  The glass electrolyte of the present invention contains a high concentration of lithium, has high lithium ion conductivity, is chemically and thermally stable, and notices remarkable deterioration of glass visually in the air and in water. I can not.

  The composition of Examples 1 to 43 of the present invention, the composition of Comparative Example 1, and the results of melting temperature and lithium ion conductivity are shown in Tables 1 to 7. The following examples are for the purpose of illustration only and are not limited to these examples.

  In Examples 1 to 43 of the present invention and Comparative Example 1 shown in Tables 1 to 7, oxides, hydroxides, carbonates, nitrates, fluorides, chlorides, and ammonium corresponding to each as raw materials of the respective components are all used. Raw materials with high purity used for ordinary glass such as salts and metaphosphoric acid compounds were selected. Predetermined glass material powders were prepared and uniformly mixed so as to have the compositions of the respective examples shown in Tables 1 to 7 and the compositions of the comparative examples. The uniformly mixed glass raw material powder was charged into a platinum crucible, and was melted for 0.5 to 4 hours in a temperature range of 1000 to 1450 ° C. in an electric furnace according to the melting difficulty of the glass composition to perform stirring and homogenization. Thereafter, the molten glass was cast on a cast iron plate and annealed, or poured into a mold and quenched by a press to obtain a glass.

  Measurement of lithium ion conductivity according to Examples 1 to 43 and Comparative Example 1 was performed as follows. Using a quick coater manufactured by Sanyu Electronics Co., Ltd., sputtering was performed on both sides of the glass using gold as a target, and gold electrodes were attached. In this regard, lithium ion conductivity at 25 ° C. in a range of 0.1 Hz to 10 MHz was calculated by complex impedance measurement by an alternating current two-terminal method using an impedance analyzer SI-1260 manufactured by Solartron.

  The measurement of the melting temperature which concerns on Examples 1-43 and the comparative example 1 was performed as follows. The raw material powder prepared to be glass of each composition component is put in a platinum crucible of about 50 cc and heated in an electric furnace, 50 ° C. interval from 1000 ° C. to 1300 ° C., 25 ° C. interval from 1300 ° C. The temperature was maintained at different temperatures for 30 minutes, removed from the furnace, and observed in the crucible. In the case where no melt residue was observed in the melt surface in the crucible and in the melt, the temperature was taken as a temporary melt temperature. Thereafter, the raw material powder of the same composition is heated again, heated to a temperature 25 ° C. lower than the temporary melting temperature, and kept warm for 30 minutes, and when there is no melting residue, the temperature 25 ° C. lower than the temporary melting temperature is taken as the melting temperature When melting residue was observed, the temporary melting temperature was taken as the melting temperature.

As shown in Tables 1 to 7, the glasses of Examples 1 to 43 had lithium ion conductivity of 7.00 × 10 ⁻⁸ (S / cm) or more and a melting temperature of 1300 ° C. or less. On the other hand, the glass of Comparative Example 1 had unmelted even when it was melted at 1350 ° C., and was not in the melted state. Furthermore, when lithium ion conductivity was measured about the sample acquired by casting only the fuse | melted part about the comparative example 1, it was 2.12 * 10 < ^-9 > (S / cm). Therefore, it was revealed that the glass of the example has a low melting temperature while having the desired lithium ion conductivity.

From the above, in the glass of the example, the content of the Li ₂ O component, the content of the B ₂ O ₃ component, the content of the P ₂ O ₅ component, and the M ₂ O ₅ component (M is Ta, Nb, V (1) or (2) or more) and GeO ₂ component content within a predetermined range, even when using industrially practical melting temperature and glass preparation method, lithium ion conduction It became clear that the degree could be improved.

Industrial application field

The glass electrolyte of the present invention comprises a P ₂ O ₅ -B ₂ O ₃ -M ₂ O ₅ component (M is one or more selected from Ta, Nb, and V) -GeO containing lithium ions in a high concentration. _{A 2-} Li ₂ O-based glass with high lithium ion conductivity of 5.00 × 10 ^-8 Scm ^-1 or more at room temperature, so all solid lithium ion secondary batteries, capacitors, solid electrochemical devices, etc. Available to

Claims (8)

Containing Li ₂ O component, P ₂ O ₅ component, GeO ₂ component and M ₂ O ₅ component (M is one or more selected from Ta, Nb, V) on an oxide basis, and the content of Li ₂ O component is Glass electrolyte which is 30-65 mol%. In mol% based on oxide,
The content of P ₂ O ₅ component is 5% to 40%,
The content of GeO ₂ component is 0.2% to 7%,
The glass electrolyte according to claim 1, wherein the content of the M ₂ O ₅ component (M is one or more selected from Ta, Nb, and V) is 0.2% to 20%. The ratio of the content of Li ₂ O component to the total content of Ta ₂ O ₅ component, Nb ₂ O ₅ component, V ₂ O ₅ component, and GeO ₂ component in mol% based on oxide: Li ₂ O / ( The glass electrolyte according to claim 1, wherein Ta ₂ O ₅ + Nb ₂ O ₅ + V ₂ O ₅ + GeO ₂ ) is 2.0 or more. In mol% based on oxide,
0 to 20% of Ta ₂ O ₅ ingredients,
0 to 20% of Nb ₂ O ₅ component, or 0 to 15% of V ₂ O ₅ component
The glass electrolyte in any one of the Claims 1 to 3 containing. In mol% based on oxide,
0 to 25% of B ₂ O ₃ ingredient
The glass electrolyte in any one of the Claims 1 to 4 containing. In mol% based on oxide,
0 to 5% of SiO ₂ component,
0 to 10% of Al ₂ O ₃ ingredients,
0 to 5% of K ₂ O component,
0 to 5% of the Cs ₂ O component,
0 to 5% of MgO component,
0-5% CaO ingredient,
0 to 5% of BaO ingredient,
0 to 5% of ZnO component,
0-5% of SnO component,
0 to 5% of Y ₂ O ₃ component,
0 to 5% of Bi ₂ O ₃ component,
0-5% of TeO ₂ component or 0-5% of Sb ₂ O ₃ component
The glass electrolyte according to any one of claims 1 to 5, which contains it.   The glass electrolyte according to any one of claims 1 to 6, which has a melting temperature of 1350 ° C or less. The lithium ion conductivity at 25 ° C. in a frequency range of 0.1 Hz to 10 MHz measured by complex impedance measurement by an alternating current two-terminal method is 5.00 × 10 ⁻⁸ Scm ⁻¹ or more. The glass electrolyte as described in any one.