Glass and solid electrolyte

Abstract

The present invention relates to a glass wherein: the cation content, expressed in terms of cation%, is 61.6% to 85.0% Li+, more than 0.0% but not more than 25.0% Si4+, and 0.0% to 20.0% B3+; O2- is included as an anion; and the anion content, expressed in terms of anion%, is more than 0.0% but not more than 10.0% SO4 2- and 0.0% to 9.5% Cl-.

Description

Glass, solid electrolyte

[0001] The present invention relates to a glass and a solid electrolyte containing a component derived from the glass.

[0002] Lithium ion secondary batteries are widely used as batteries for mobility devices such as automobiles, as well as batteries for small electronic devices such as personal computers and mobile phones.

[0003] In lithium-ion secondary batteries, lithium ions move between the positive and negative electrodes to charge and discharge, and an electrolyte is required to facilitate this movement of lithium ions. Conventional lithium-ion secondary batteries use liquid electrolytes, primarily organic solvents, but the use of solid electrolytes has been considered due to their potential window and safety.

[0004] As solid electrolytes, for example, sulfide-based solid electrolytes and oxide-based solid electrolytes have been mainly studied. In general, oxide-based solid electrolytes are more stable in the usage environment than sulfide-based solid electrolytes, and materials have been studied for a wide range of applications.

[0005] Glass materials are also being considered as oxide-based solid electrolytes. For example, in the following Patent Document 1, Li ＋ and Si ４＋ And B ３＋ And, O ２－ And Cl － and a glass containing the above in a predetermined ratio.

[0006] International Publication No. 2018 / 034271

[0007] Glass has superior fluidity at low temperatures compared to crystalline materials, and therefore can easily form a dense solid electrolyte when manufacturing a lithium-ion secondary battery. Therefore, glass is required to contain a small proportion of crystals. That is, glass is required to have a high vitrification ratio. Furthermore, glass used in lithium-ion secondary batteries is required to have high ionic conductivity in order to improve the performance of lithium-ion secondary batteries. High ionic conductivity may also be required for other applications. The present inventors have studied the glass described in Patent Document 1 and found that there is room for improvement in the vitrification ratio.

[0008] The present invention has been made in view of the above problems, and an object of the present invention is to provide a glass having a high vitrification rate and high ionic conductivity, and a solid electrolyte containing a component derived from such a glass.

[0009] As a result of extensive research into the above-mentioned problems, the present inventors have found that Li ＋ and Si ４＋ And B ３＋ and in a predetermined ratio, and SO ４ ２－ and Cl － The present inventors have found that by making the glass contain a predetermined proportion of the above, it is possible to achieve both a high vitrification rate and high ionic conductivity, and have thus completed the present invention.

[0010] That is, the inventors have found that the above-mentioned problems can be solved by the following configuration: [1] The content of cations, expressed as cation %, is: Li ＋ is 61.6% or more and 85.0% or less, Si ４＋ is more than 0.0% and 25.0% or less, and B ３＋ is 0.0 to 20.0%, and O is used as an anion. ２－ and the anion content is, in anion % notation, SO ４ ２－ is more than 0.0% and not more than 10.0%, and Cl －[2] A glass in which the cation content, expressed in cation %, is: Li ＋ is more than 67.0% and not more than 85.0%; ４＋ is more than 0.0% and 25.0% or less, and B ３＋ is 0.0 to 20.0%, and O is used as an anion. ２－ and the anion content is, in anion % notation, SO ４ ２－ is more than 0.0% and not more than 7.0%, and Cl － [3] The glass according to [1], wherein Y is 0.0% or more and 4.0% or less. ３＋ , Zr ４＋ , and La ３＋ and Y ３＋ , Zr ４＋ , and La ３＋ [4] The glass according to [1] or [2], wherein the total content of P is more than 0% and 10% or less in terms of cation %. ５＋ and Ge ４＋ [5] The glass according to any one of [1] to [3], further containing at least one cation of the following: [5] The content of the cation is expressed as cation % and is: ＋ is more than 67.0% and not more than 85.0%; ４＋ is more than 0.0% and 10.0% or less, and B ３＋ [6] The glass according to any one of [1] to [4], wherein the cation contents are, in cation %, 10.0 to 20.0%. ＋ is more than 67.0% and not more than 85.0%; ４＋ is 10.0 to 25.0%, and B ３＋ [7] The glass according to any one of [1] to [4], wherein the anion content is, in anion %, 0.0 to 11.0%. ２－ [8] The glass according to any one of [1] to [6], wherein the anion content is, in anion %, 75.0% or more. ２－ , S.O. ４ ２－, and Cl － [9] The glass according to any one of [1] to [8], which is a glass frit.

[10] A solid electrolyte comprising a component derived from the glass according to any one of [1] to [9].

[0011] According to the present invention, it is possible to provide a glass having a high vitrification rate and high ionic conductivity, and also to provide a solid electrolyte that is dense and capable of realizing high ionic conductivity.

[0012] Fig. 1 is a cross-sectional schematic diagram of an all-solid-state lithium-ion secondary battery having a solid electrolyte according to this embodiment. Fig. 2 is a cross-sectional schematic diagram showing an example of the configuration of a multilayer ceramic capacitor. Fig. 3 is a cross-sectional schematic diagram showing an example of the configuration of a ceramic multilayer substrate.

[0013] Hereinafter, embodiments of the present invention will be described in detail. The following description of the constituent elements may be based on a representative embodiment of the present invention, but the present invention is not limited to such an embodiment. In this specification, the term "to" indicating a range of numerical values ​​is used to mean that the numerical values ​​before and after it are included as the lower and upper limits.

[0014] As used herein, "cation %" refers to a unit in which the constituent components of glass are divided into cationic components and anionic components, and the molar amount of each cationic component is expressed as a percentage relative to the total molar amount of all cationic components contained in the glass. In this specification, when the content of cationic components is expressed as a percentage, this refers to cationic % unless otherwise specified. The content of each cationic component contained in glass is determined from the results of inductively coupled plasma atomic emission spectroscopy (ICP-AES) of the obtained glass. For inductively coupled plasma atomic emission spectroscopy, for example, an Agilent 5800 ICP-OES can be used.

[0015] In this specification, "anion %" is a unit that divides the constituent components of glass into cationic components and anionic components, and expresses the molar amount of each anionic component as a percentage relative to the total molar amount of all anionic components contained in the glass. In this specification, when the content of anionic components is expressed in %, it means anionic % unless otherwise specified. O contained in glass ２－ The content of anion components other than O is determined from the results of quartz tube combustion ion chromatography. ２－ The molar amount of anionic components other than the above is determined. Also, the molar amount of each cationic component in the measurement sample is determined by the above method. Here, the molar amount of oxygen atoms contained in the glass is calculated assuming that each cationic component contained in the glass is the most stable oxide in the standard state. From the above value of the molar amount of oxygen atoms, the above O ２－ The molar amount obtained by subtracting the content of anion components other than O in the measurement sample is ２－ The molar amount of O in the measurement sample calculated above is ２－ and the molar amount of O in the measurement sample. ２－ The molar amount of anion components other than O in the measurement sample relative to the total value ２－ The molar ratio of anion % is expressed as O ２－ The molar ratio of each anion component in the measurement sample to the total value is expressed as O in anion % notation. ２－ The quartz tube combustion ion chromatography can be performed using, for example, a Dionex ICS-2100 manufactured by Thermo Fisher Scientific.

[0016] In this specification, "mol %" is a unit that expresses the molar amount of each component relative to the total molar amount of all components of the glass as a percentage.

[0017] In this specification, the phrase "not containing or substantially not containing" a cationic component specifically means that the content relative to the total molar amount of all cationic components contained in the glass is preferably 0.3% or less (e.g., 0.0 to 0.3%), more preferably 0.2% or less (e.g., 0.0 to 0.2%), even more preferably 0.1% or less (e.g., 0.0 to 0.1%), and particularly preferably 0.01% or less (e.g., 0.0 to 0.01%).

[0018] In this specification, the expression "not containing or substantially not containing" an anionic component specifically means that the content relative to the total molar amount of all anionic components contained in the glass is preferably 0.3% or less (e.g., 0.0 to 0.3%), more preferably 0.2% or less (e.g., 0.0 to 0.2%), even more preferably 0.1% or less (e.g., 0.0 to 0.1%), and particularly preferably 0.01% or less (e.g., 0 to 0.01%).

[0019] In this specification, when the glass is glass flakes, the vitrification ratio refers to the proportion of flakes in which no diffraction peaks derived from crystals are observed in an X-ray diffraction chart obtained by X-ray diffraction. That is, the vitrification ratio refers to the proportion of the mass of flakes in which no diffraction peaks derived from crystals are observed in an X-ray diffraction chart to the mass of the entire glass flakes. The absence of diffraction peaks derived from crystals in an X-ray diffraction chart means that only a halo pattern is observed. The glass transition temperature (Tg) of the glass flakes can be confirmed by differential thermal analysis (DTA).

[0020] <Glass> The glass according to this embodiment has a cation content expressed in cation % of Li, ＋ is 61.6% or more and 85.0% or less, Si ４＋ is more than 0.0% and 25.0% or less, and B ３＋ The glass according to this embodiment contains O as an anion. ２－ and the anion content is expressed as anion % and ４ ２－ is more than 0.0% and not more than 10.0%, and Cl－ is 0.0% or more and 9.5% or less.

[0021] The mechanism by which the glass according to this embodiment has a high vitrification rate and high ionic conductivity is not entirely clear, but the present inventors speculate as follows. ＋ The content of is within the above range, and B ３＋ Since the content of is within the above range, Li, which is responsible for ion conduction, ＋ This is thought to increase the proportion of B in the glass, resulting in high ionic conductivity. ３＋ Is O ２－ This is thought to be because the Li in the glass tends to bond with the Li to form a network. ＋ The proportion of B is large ３＋ If the ratio of is small, B ３＋ O that is likely to exist around ２－ NiLi ＋ is less likely to be trapped, resulting in Li ＋ It is considered that this is because SO 3 easily contributes to ion conduction. ４ ２－ and Cl － It is thought that the vitrification rate is likely to be high when the content is equal to or less than a predetermined value.

[0022] The glass according to this embodiment will be described in detail below.

[0023] (Cation component) The glass according to this embodiment has a cation content expressed in cation % of Li, ＋ is 61.6% or more and 85.0% or less, Si ４＋ is more than 0.0% and 25.0% or less, and B ３＋ The cation component of the glass according to this embodiment will be described below.

[0024] Li ＋ is a component that improves the ionic conductivity of the glass and also tends to lower the glass transition temperature (Tg). ＋The content of Li is 61.6% or more and 85.0% or less. ＋ The content of Li is preferably more than 67.0%, more preferably 69.0% or more, even more preferably 71.0% or more, particularly preferably 73.0% or more, particularly preferably 74.0% or more, and most preferably 75.0% or more, in that ionic conductivity is likely to be higher. ＋ The content of is preferably 85.0% or less, more preferably 84.0% or less, and even more preferably 83.0% or less, in that the vitrification rate is likely to be higher.

[0025] Si ４＋ is a glass-forming component that contributes to the stability of the glass. ４＋ The content of Si is more than 0.0% and not more than 25.0%. ４＋ If the content of Si exceeds 0.0%, the stability of the glass tends to be high. ４＋ In one preferred aspect of the glass according to this embodiment (hereinafter, aspect 1), Si ４＋ The content of Si is more than 0.0%, may be more than 0.3%, may be 1.0% or more, is preferably 2.5% or more, more preferably 5.0% or more, further preferably 6.0% or more, and particularly preferably 7.0% or more. ４＋ The content of Si is preferably 10.0% or less, more preferably 9.0% or less, and even more preferably 8.0% or less. ４＋ The content of Si is preferably 10.0% or more, more preferably 11.0% or more, further preferably 15.0% or more, and particularly preferably 17.0% or more. ４＋ The content is 25.0% or less, preferably 23.0% or less, and more preferably 21.0% or less.

[0026] B ３＋ is a glass-forming component that contributes to improving the stability of the glass. ３＋In the above-mentioned aspect 1, which is one of the preferred aspects of the glass according to the present embodiment, the content of B is 0.0 to 20.0%. ３＋ The content of B is preferably 10.0% or more, more preferably 11.0% or more, and even more preferably 12.0% or more. ３＋ The content of B is 20.0% or less, preferably 18.0% or less, and more preferably 16.0% or less. ３＋ The content of B is preferably 0.0% or more, and may be more than 0.3% in that the vitrification rate is likely to be higher, more preferably 0.5% or more, more preferably 1% or more, and even more preferably 2.0% or more. ３＋ The content is preferably 11.0% or less, more preferably 7.0% or less, and still more preferably 6.5% or less.

[0027] The glass according to the above-mentioned aspect 1 is preferable from the viewpoint of vitrification rate, and the glass according to the above-mentioned aspect 2 is preferable from the viewpoint of ionic conductivity.

[0028] The Si content of the glass according to this embodiment ４＋ and B ３＋ From the viewpoint of glass stability, the total content of Si is preferably 10.0% or more, more preferably 20.0% or more, even more preferably 25.0% or more, and most preferably 29.0% or more. ４＋ and B ３＋ The total content is preferably 36.0% or less, more preferably 35.0% or less, and even more preferably 30.0% or less.

[0029] In addition, the glass according to this embodiment is Y ３＋ , Zr ４＋ , and La ３＋ Preferably, the compound further contains one or more cations selected from the group consisting of: ３＋ , Zr ４＋ , and La ３＋ It is more preferable that the total content of Y is more than 0% and 10% or less in terms of cation %. ３＋ , Zr ４＋ , and La ３＋The total content of Y is more preferably 0.1% or more, further preferably 0.4% or more, particularly preferably 0.6% or more, particularly preferably 0.8% or more, and most preferably 1.0% or more. ３＋ , Zr ４＋ , and La ３＋ The total content of Y is more preferably 8.0% or less, further preferably 7.0% or less, particularly preferably 6.0% or less, and particularly preferably 5.0% or less. ３＋ , Zr ４＋ , and La ３＋ The total content of Y is preferably 0.3% or more, more preferably 0.5% or more, and even more preferably 0.7% or more. ３＋ , Zr ４＋ , and La ３＋ The total content of Y is preferably 1.8% or less, more preferably 1.6% or less, and even more preferably 1.4% or less. ３＋ , Zr ４＋ , and La ３＋ The total content of Y is preferably 1.0% or more, more preferably 1.5% or more, even more preferably 1.8% or more, and particularly preferably 2.0% or more. ３＋ , Zr ４＋ , and La ３＋ The total content of Zr in the glass is preferably 10.0% or less, more preferably 9.0% or less, even more preferably 8.0% or less, particularly preferably 7.0% or less, particularly preferably 6.0% or less, and most preferably 5.0% or less. ２＋ When Zr is contained, ２＋ is Zr ４＋ The content in cation % is calculated assuming this.

[0030] In the glass according to this embodiment, Y ３＋ If it contains, Y ３＋The content of Y is preferably 0.1% or more, more preferably 0.2% or more, even more preferably 0.5% or more, particularly preferably 0.8% or more, and particularly preferably 1.0% or more. ３＋ If it contains, Y ３＋ The content of Y is preferably 5.0% or less, more preferably 4.0% or less, even more preferably 3.0% or less, and particularly preferably 2.0% or less. ３＋ In the above-mentioned aspect 2, which is one of the preferred aspects of the glass according to the present embodiment, Y ３＋ may be contained within the above range, ３＋ It is also preferred that it does not contain

[0031] In the glass according to this embodiment, Zr ４＋ When containing Zr ４＋ The content of Zr is preferably 0.1% or more, more preferably 0.5% or more, further preferably 1.0% or more, and particularly preferably 2.0% or more. ４＋ When containing Zr ４＋ The content of Zr is preferably 7.0% or less, more preferably 5.0% or less, even more preferably 4.0% or less, particularly preferably 3.0% or less, and particularly preferably 2.0% or less. ４＋ In addition, in the above-mentioned aspect 2, which is one of the preferred aspects of the glass according to the present embodiment, Zr ４＋ is preferably within the above range.

[0032] In the glass according to this embodiment, La ３＋ If it contains ３＋ The content of La is preferably 0.1% or more, more preferably 0.2% or more, even more preferably 0.5% or more, particularly preferably 1.0% or more, and particularly preferably 1.5% or more. ３＋ If it contains ３＋The content of La is preferably 6.0% or less, more preferably 5.0% or less, even more preferably 4.0% or more, particularly preferably 3.0% or less, and especially preferably 2.0% or less. In the above-mentioned aspect 1 which is one of the preferred aspects of the glass according to this embodiment, ３＋ In addition, in the above-mentioned aspect 2, which is one of the preferred aspects of the glass according to the present embodiment, La ３＋ is preferably within the above range.

[0033] The glass according to this embodiment is P ５＋ and Ge ４＋ In particular, in the above-mentioned aspect 2, which is one of the preferred aspects of the glass according to this embodiment, P ５＋ and Ge ４＋ The compound may contain at least one cation of the above.

[0034] In the glass according to this embodiment, ５＋ If it contains, P ５＋ The content of is preferably 0.2% or more, more preferably 0.4% or more, even more preferably 0.6% or more, particularly preferably 0.8% or more, and particularly preferably 1.0% or more. ５＋ If it contains, P ５＋ The content of is preferably 4.0% or less, more preferably 3.0% or less, even more preferably 2.5% or less, particularly preferably 2.0% or less, and particularly preferably 1.5% or less. ５＋ The glass may be substantially free of P. ３＋ If it contains such P ３＋ Is P ５＋ The content in cation % is calculated assuming this.

[0035] In the glass according to this embodiment, Ge ４＋ When containing Ge ４＋ The content of is preferably 0.1% or more, more preferably 0.2% or more, even more preferably 0.4% or more, particularly preferably 0.6% or more, and particularly preferably 0.8% or more.４＋ When containing Ge ４＋ The content of is preferably 4.0% or less, more preferably 3.0% or less, even more preferably 2.5% or less, particularly preferably 2.0% or less, and particularly preferably 1.5% or less. ４＋ The glass may be substantially free of Ge. ２＋ When such Ge is contained, ２＋ is Ge ４＋ The content in cation % is calculated assuming this.

[0036] The glass according to this embodiment may contain a cation component other than those mentioned above. For example, the glass according to this embodiment may contain Mg ２＋ , Ca ２＋ , Sr ２＋ , Ba ２＋ , Fe ２＋ , Fe ３＋ , Sc ３＋ , Ce ３＋ , Ce ４＋ , Nd ２＋ , Nd ３＋ , Gd ３＋ , Dy ２＋ , Dy ３＋ , Yb ２＋ , Yb ３＋ , Ti ４＋ , Nb ２＋ , Nb ３＋ , Nb ４＋ , Nb ５＋ , Ta ５＋ , Cr ３＋ , W ６＋ , Mn ２＋ , Mn ３＋ , Mn ４＋ , Co ２＋ , Co ３＋ , Ni ２＋ , Ni ３＋ , Cu ２＋ , Zn ２＋ , Al ３＋ , Ga ３＋ , In ３＋ , Sn ２＋ , Sn ４＋ , Sb ３＋ , Sb ５＋ , and Bi ３＋and the like.

[0037] (Anion Component) The glass according to this embodiment contains O as an anion. ２－ and the anion content is expressed as anion % and ４ ２－ is more than 0.0% and not more than 10.0%, and Cl － The anionic components contained in the glass according to this embodiment and the anionic components that may be contained in the glass according to this embodiment will be described below.

[0038] O ２－ is an anion component mainly contained in the glass according to this embodiment. ２－ The content of is preferably 75.0% or more, more preferably 85.0% or more, even more preferably 90.0% or more, and particularly preferably 92.0% or more. ２－ The content of is less than 100.0%, preferably 99.8% or less, and more preferably 99.6% or less.

[0039] SO ４ ２－ is one of the components that increases the vitrification rate. ４ ２－ In the glass according to this embodiment, the content of SO ４ ２－ The content of SO is preferably 0.05% or more, more preferably 0.1% or more, and from the viewpoint that the vitrification rate is likely to be higher, is further preferably 0.3% or more, and particularly preferably 0.5% or more. ４ ２－ The content is preferably 8.0% or less, more preferably 7.0% or less, even more preferably 6.0% or less, particularly preferably 4.0% or less, and is particularly preferably 3.0% or less in that the ionic conductivity is likely to be higher, and may be 2.0% or less.

[0040] Cl － is one of the components that can easily increase the vitrification rate.－ Yes, O ２－ It has a lower electronegativity than Li ＋ Therefore, the glass according to this embodiment is less likely to trap Cl. － In the glass according to this embodiment, the ionic conductivity is likely to be higher. － In the glass according to this embodiment, the content of Cl is 0.0% or more and 9.5% or less. － When it contains Cl － The content of Cl is preferably 0.5% or more, more preferably 1.0% or more, even more preferably 1.5% or more, particularly preferably 2.0% or more, and may be 2.5% or more, in that ionic conductivity is likely to be higher. － When it contains Cl － The content of Cl is preferably 7.0% or less, more preferably 4.0% or less, further preferably 3.5% or less, particularly preferably 3.0% or less, and may be 2.5% or less, in that the vitrification rate is likely to be higher. － In particular, in the above-mentioned embodiment 2, Cl － may not be included.

[0041] The glass according to this embodiment may contain an anion component other than those mentioned above. For example, the glass according to this embodiment may contain F － , I － , and S ２－ and the like.

[0042] In the glass according to this embodiment, O ２－ , S.O. ４ ２－ , and Cl － The total content of O is preferably 90.0% or more, more preferably 95.0% or more, and even more preferably 99.0% or more. ２－ , S.O. ４ ２－ , and Cl － The total content of O may be 100.0%. ２－ , S.O.４ ２－ , and Cl － It may be substantially free of anionic components other than the above.

[0043] (Glass Properties) The glass according to this embodiment has high ionic conductivity. In this specification, the ionic conductivity refers to lithium ion conductivity. The ionic conductivity of the glass according to this embodiment at 25° C. is 1.0×10 －６ S / cm or more is preferable, and 2.0 × 10 －６ S / cm or more is more preferable, and 3.0 × 10 －６ S / cm or more is more preferable. In this specification, the ionic conductivity of glass is measured by an AC impedance method. Specifically, the ionic conductivity is measured by an AC impedance method using an impedance / gain phase analyzer SI-1260 manufactured by Solartron Analytical. The glass according to this embodiment is cut into an appropriate shape (for example, a diameter of 6 mm or more) in a dry air atmosphere with a dew point of −50 to −70°C, and gold electrodes with a diameter of 4 mm are formed on both sides by a vapor deposition method in a dry air atmosphere with a dew point of −30 to −50°C to obtain a measurement sample. Using the obtained measurement sample, a measurement is performed in an environment with a temperature of 25°C and a dew point of −30°C or less, with an applied voltage of 10 mV and a frequency of 1 to 10 ７ The ionic conductivity is calculated from the electrical resistance obtained from the Nyquist plot, the electrode area, and the thickness of the measurement sample excluding the gold electrode.

[0044] The glass transition point (Tg) of the glass according to this embodiment is preferably 500° C. or lower, and more preferably 450° C. or lower. The Tg of the glass according to this embodiment is often 200° C. or higher, and may be 300° C. or higher. When the Tg of the glass according to this embodiment is in the above range, it is easily sintered at a low temperature.

[0045] When the crystallization onset temperature of the glass according to this embodiment is Tc1-on, the value of (Tc1-on)-Tg is preferably 50°C or higher. If the value is 50°C or higher, dense and stable glass is likely to be obtained when sintered by heat treatment. Furthermore, the value of (Tc1-on)-Tg is preferably 100°C or lower. If the value is 90°C or lower, it is preferable from the viewpoint of suppressing crystallization during glass melting and molding.

[0046] The values ​​of Tg and Tc1-on are determined by differential thermal analysis (DTA) of the glass, using the inflection point of the DTA curve showing the amount of heat generation and endotherm, the intersection point between the peak and the baseline, and the like. More specifically, Tc1-on can be determined by the following method. First, the region of the DTA curve where an exothermic reaction due to crystallization of the glass occurred is identified. Then, from the low-temperature side of that region, a straight line is drawn by extrapolating the range showing monotonous change to the high-temperature side, using the baseline as the range, and a tangent line to the inflection point (the peak point in the differential curve) is drawn from the high-temperature side, and the temperature at the intersection point of these lines can be determined as the crystallization onset temperature (Tc1-on).

[0047] The vitrification rate of the glass according to this embodiment is preferably 15% or more, more preferably 20% or more, even more preferably 30% or more, even more preferably 60% or more, particularly preferably 70% or more, and most preferably 80% or more. The vitrification rate of the glass according to this embodiment may be 100%. A method for measuring the vitrification rate will be described in the Examples section below.

[0048] (Glass Form) The form of the glass according to this embodiment is not particularly limited, and may be a block of glass, a plate of glass, a cullet-like form, a flake-like form (thin plate-like form), or a powder-like form. That is, the glass according to this embodiment may be glass frit, which is powdered glass. The volume-based median diameter (D50) of the glass frit is not particularly limited, and may be, for example, 0.1 to 100 μm.

[0049] (Method for Producing Glass) The method for producing the glass according to this embodiment is not particularly limited, but the glass can be produced, for example, by the following method.

[0050] First, raw materials are mixed to prepare a raw material mixture. The raw materials are not particularly limited as long as they are raw materials used in the manufacture of ordinary oxide-based glasses, and oxides, carbonates, etc. are used. However, the raw materials include SO ４ ２－ Contains source. ４ ２－ Examples of the source include sulfates of the elements contained in the above cationic components, such as Li ２ SO ４ , Y ２ (SO ４ ) ３ , Zr(SO ４ ) ２ , or La ２ (SO ４ ) ３ The resulting glass may contain Cl as an anion component. － When the raw material contains Cl － Contains a source of Cl － Examples of the source include chlorides of the elements contained in the above-mentioned cationic components, such as LiCl and YCl. ３ , ZrCl ４ , LaCl ３ , PCl ５ or GeCl ４ may be.

[0051] Next, the raw material mixture is heated by a known method to obtain a melt. The heating temperature (melting temperature) can be set appropriately, but is preferably 800°C or higher, and more preferably 900°C or higher. The melting temperature is often 1600°C or lower. The heating time is not particularly limited, but is often 10 minutes or longer, and preferably 20 minutes or longer. The heating time is often 10 hours or shorter, and preferably 4 hours or shorter.

[0052] The resulting melt is then cooled and solidified to obtain the glass according to this embodiment. The cooling method is not particularly limited, and any known cooling method can be applied. Examples of the cooling method include a method using a roll-out machine or a press machine. Alternatively, the melt may be dropped into a cooling liquid for rapid cooling.

[0053] The glass obtained is preferably amorphous. The vitrification rate of the glass obtained is 100% when the glass is amorphous. The method for measuring the vitrification rate in this specification will be described later.

[0054] The obtained glass may be processed into a desired shape. For example, to obtain glass frit, the obtained glass may be crushed. The crushing method is not particularly limited, and known methods can be applied.

[0055] <Solid Electrolyte> The solid electrolyte according to this embodiment contains a component derived from the glass according to this embodiment described above. For example, the solid electrolyte according to this embodiment can be obtained by sintering glass frit, which is the glass according to this embodiment. Furthermore, the plate-shaped glass according to this embodiment may be used as is as the solid electrolyte. The solid electrolyte according to this embodiment exhibits high ionic conductivity and can be applied to various applications. Furthermore, since glass with a high vitrification rate is used, a dense solid electrolyte can be obtained.

[0056] The solid electrolyte according to this embodiment may contain a crystalline component. The crystalline component may be a crystalline component added to a material other than the glass according to this embodiment when obtaining the solid electrolyte, or may be a crystalline component precipitated by heat treating the glass according to this embodiment. Examples of crystalline components other than the glass according to this embodiment include ion-conductive crystals.

[0057] The solid electrolyte according to this embodiment preferably contains 40% by volume or more, preferably 70% by volume or more, and more preferably 80% by volume or more of a component derived from the glass according to this embodiment. Furthermore, the solid electrolyte according to this embodiment may contain 100% by volume of a component derived from the glass according to this embodiment, i.e., may be made of the glass according to this embodiment. The component derived from the glass according to this embodiment includes the glass according to this embodiment, a sintered body obtained by sintering the glass, or a mixture thereof.

[0058] <Applications> The glass according to this embodiment and the solid electrolyte containing a component derived from the glass according to this embodiment can be used in a variety of applications. For example, the solid electrolyte containing a component derived from the glass according to this embodiment exhibits high ionic conductivity and is therefore suitable for use in the solid electrolyte layer of an all-solid-state lithium-ion secondary battery. An all-solid-state lithium-ion secondary battery containing the solid electrolyte according to this embodiment will be described below.

[0059] (All-Solid-State Lithium-Ion Secondary Battery) FIG. 1 shows a cross-sectional schematic diagram of an all-solid-state lithium-ion secondary battery having a solid electrolyte according to this embodiment. The all-solid-state lithium-ion secondary battery 10 shown in FIG. 1 has three laminate units 20 arranged between a positive electrode current collector 24 and a negative electrode current collector 26, with an electron conductor layer 22 arranged between the laminate units 20. Each laminate unit 20 has a positive electrode layer 12, a solid electrolyte layer 16, and a negative electrode layer 14, in this order. Note that in each laminate unit 20, the positive electrode layer 12 is arranged on the upper side of the drawing. The positive electrode current collector 24 is electrically connected to the adjacent positive electrode layer 12, and the negative electrode current collector 26 is electrically connected to the adjacent negative electrode layer 14. The electron conductor layer 22 electrically connects the positive electrode layer 12 and the negative electrode layer 14, enabling electrons to be exchanged between the laminate units 20. The positive electrode layer 12 is made of Li ＋ The negative electrode layer 14 contains a positive electrode active material that absorbs and releases Li. ＋ The all-solid-state lithium-ion secondary battery 10 shown in Fig. 1 is charged or discharged when electrodes are connected to the positive electrode current collector 24 and the negative electrode current collector 26.

[0060] In the laminate unit 20, Li in the positive electrode active material contained in the positive electrode layer 12 ＋ and the standard electrode potentials of the desorption and absorption reactions of Li in the negative electrode active material contained in the negative electrode layer 14. ＋ A voltage corresponding to the difference between the standard electrode potential of the desorption reaction and the standard electrode potential of the absorption reaction of Li is generated. ＋ By conducting electrons and blocking electrons, it is possible to charge and discharge the laminated unit 20. Furthermore, by stacking a plurality of laminated units 20 with an electron conductor layer 22 interposed therebetween as necessary, it is possible to increase the voltage that can be extracted.

[0061] The positive electrode active material contained in the positive electrode layer 12 is not particularly limited, and known positive electrode active materials can be used. Examples of the positive electrode active material include LiCoO ２ , LiNiO ２ , LiMn ２ O ４ , and LiFePO ４ In addition, active materials in which some of the elements of the above active materials are substituted with other elements can also be used.

[0062] The negative electrode active material contained in the negative electrode layer 14 is not particularly limited, and any known negative electrode active material can be used. Examples of the negative electrode active material include metallic Li, Li alloys, graphite, metallic Si, and lithium titanate. Note that materials other than those exemplified above as the positive electrode active material and the negative electrode active material can also be used as appropriate.

[0063] The laminate unit 20 of the all-solid-state lithium-ion secondary battery 10 shown in FIG. 1 may have layers other than the positive electrode layer 12, the negative electrode layer 14, and the solid electrolyte layer 16. The all-solid-state lithium-ion secondary battery 10 shown in FIG. 1 may have layers other than the laminate unit 20 and the electron conductor layer 22. The number of laminate units 20 in the all-solid-state lithium-ion secondary battery 10 may be one or two, three, or four or more. The all-solid-state lithium-ion secondary battery 10 is a series type in which a plurality of laminate units 20 are stacked with the electron conductor layer 22 interposed therebetween, but it may also be a parallel type. To achieve a parallel type, the positive electrode layers 12 and the negative electrode layers 14 in the laminate units 20 may be connected to each other via wiring.

[0064] The method for producing the all-solid-state lithium ion secondary battery shown in FIG. 1 is not particularly limited, but it can be produced, for example, by the following method.

[0065] First, a positive electrode green sheet containing a positive electrode active material and the glass according to this embodiment, a solid electrolyte green sheet containing the glass according to this embodiment, and a negative electrode green sheet containing a negative electrode active material and the glass according to this embodiment are each prepared. Examples of methods for producing each green sheet include preparing a paste or slurry containing each material, applying it to a substrate, and drying it. The paste or slurry can be prepared by a known method, such as mixing each material with a solvent. The method for applying the paste or slurry is not particularly limited, and known methods such as die coating, screen printing, blade coating, slit coating, and roll coating can be used. The paste or slurry may also be applied in a pattern.

[0066] The substrate used in producing the green sheet is preferably a resin substrate, for example, a polyethylene terephthalate resin substrate. The paste or slurry may contain a binder resin, which will be described later.

[0067] Next, the obtained green sheets are stacked in order, and if necessary, alignment and cutting are performed to produce a laminate. If necessary, alignment may be performed so that the end face of the positive electrode green sheet does not coincide with the end face of the negative electrode green sheet, and then the sheets may be stacked.

[0068] Next, the resulting laminates are pressed together and fired to obtain an all-solid-state lithium-ion secondary battery. The laminates may be pressed together while being heated, and the heating temperature may be 40 to 80°C. The firing is preferably carried out in an air atmosphere, and the firing temperature is preferably 20°C or more higher than the Tg of the glass according to this embodiment and lower than the Tc1-on of the glass according to this embodiment. Specifically, the firing temperature is preferably 280 to 600°C, and more preferably 280 to 550°C. The firing time may be, for example, 1 to 3 hours.

[0069] An all-solid-state lithium-ion secondary battery can be obtained by the above-described procedure. Note that the above-described procedure may include a step of providing the above-described configuration that the all-solid-state lithium-ion secondary battery may have.

[0070] Although the above procedure describes a method of heating the laminate, other methods may be used. For example, the laminates may be heated individually and then stacked to obtain an all-solid-state lithium-ion secondary battery. Also, for example, the positive electrode green sheet, the solid electrolyte green sheet, and the negative electrode green sheet may be heated individually and then stacked to obtain an all-solid-state lithium-ion secondary battery.

[0071] (Multilayer Ceramic Capacitor) The glass according to this embodiment is also useful as a binder for bonding when manufacturing a multilayer ceramic capacitor. Hereinafter, a multilayer ceramic capacitor manufactured using the glass according to this embodiment will be described.

[0072] FIG. 2 is a cross-sectional schematic diagram showing an example of the configuration of a multilayer ceramic capacitor. The multilayer ceramic capacitor 30 shown in FIG. 2 includes dielectric layers 32, internal electrode layers 34, and external electrodes 36. Dielectric layers 32 are disposed between the internal electrode layers 34, and the internal electrode layers 34 are alternately connected to the external electrodes 36. In the multilayer ceramic capacitor 30, the glass according to this embodiment is included in the dielectric layers 32. Hereinafter, a green sheet method will be described as a method for manufacturing the multilayer ceramic capacitor 30. Note that the method for manufacturing the multilayer ceramic capacitor 30 is not limited to the green sheet method, and a printing method or the like may also be used.

[0073] First, a powder of the functional ceramic constituting the dielectric layer and the glass (glass frit) according to the present embodiment are mixed to obtain a mixed powder. The functional ceramic is appropriately selected, and for example, barium titanate (BaTiO ３ The content of the glass according to this embodiment relative to the total volume of the mixed powder is preferably, for example, 1 to 10% by volume.

[0074] Next, a dielectric paste or dielectric slurry containing the mixed powder, a solvent, and the binder resin described below is prepared. The dielectric paste or dielectric slurry may contain at least one of a plasticizer and a dispersant. The prepared dielectric paste or dielectric slurry is applied to a substrate and dried to form a green sheet. The substrate and application method are the same as those for the all-solid-state lithium-ion secondary battery described above, and therefore a description thereof will be omitted.

[0075] Examples of the binder resin include polyvinyl butyral, acrylic resin, polyvinyl alcohol, ethyl cellulose, methyl cellulose, nitrocellulose, butyl cellulose acetate, propyl cellulose acetate, poly-α-methylstyrene, polypropylene carbonate, polyethylene carbonate, etc. The binder resin can be appropriately selected depending on the firing temperature, which will be described later, etc.

[0076] Next, to form internal electrode layers on the necessary portions of the green sheets, a conductive paste containing particles of one or more metals selected from the group consisting of copper, silver, nickel, etc. is applied. The glass (glass frit) according to this embodiment may also be added to the conductive paste. Adding the glass according to this embodiment to the conductive paste facilitates the production of a multilayer ceramic capacitor with excellent adhesion between layers, dielectric performance, and stability over time. Then, multiple green sheets coated with the conductive paste are stacked and integrated by applying heat and pressure to obtain a laminated sheet. The method for applying the conductive paste is not particularly limited, and examples include screen printing and gravure printing. The heating temperature during the compression bonding is, for example, 40 to 80°C.

[0077] The resulting laminate sheet is then cut into individual pieces (chips), heated to remove the binder resin, and the dielectric layers and conductive paste are sintered to obtain a fired laminate. Forming a multilayer ceramic capacitor by co-firing the laminate sheet in this manner results in a multilayer ceramic capacitor with excellent adhesion between the layers, dielectric performance, and stability over time.

[0078] Heating and sintering are carried out using a firing furnace in a predetermined atmosphere, such as air, an inert gas, or a reduced pressure environment. The heating temperature is preferably 20°C or more higher than the Tg of the glass according to this embodiment and lower than the Tc1-on of the glass according to this embodiment. Specific temperatures are preferably, for example, 280 to 600°C, and more preferably 280 to 550°C. The firing time is, for example, 1 to 3 hours.

[0079] Thereafter, a conductive paste that will become external electrodes is applied to the fired laminate, followed by drying and firing, and if necessary, plating layers of Ni, Sn, etc. are formed. Through the above procedure, a multilayer ceramic capacitor having dielectric layers containing components derived from the glass according to this embodiment is obtained.

[0080] (Low-temperature co-fired ceramic multilayer substrate) The glass according to this embodiment is also useful as a sintering binder when manufacturing a low-temperature co-fired ceramic multilayer substrate. Hereinafter, a low-temperature co-fired ceramic multilayer substrate (hereinafter simply referred to as a "ceramic multilayer substrate") manufactured using the glass according to this embodiment will be described.

[0081] The ceramic multilayer substrate is composed of a laminate (hereinafter also referred to as a "lamination unit") that forms three-dimensional wiring in which electrode wiring layers are separated by insulator layers. The ceramic multilayer substrate may have one or more of the above-mentioned laminate units.

[0082] FIG. 3 is a cross-sectional schematic diagram illustrating an example of the configuration of a ceramic multilayer substrate. The ceramic multilayer substrate 40 shown in FIG. 3 has a substrate body composed of a dielectric layer 42 and multiple planar electrodes 50 with main surfaces parallel to the main surfaces of the substrate body, both inside and outside the substrate body. Furthermore, the substrate body has internal vertical electrodes 52 extending along the thickness direction of the substrate, which are arranged to electrically connect certain planar electrodes 50 together. Furthermore, internally mounted components 46 are arranged inside the substrate body so as to contact the planar electrodes 50 arranged inside the substrate, and surface-mounted components 44 are arranged so as to contact the planar electrodes 50 arranged outside the substrate. The surface-mounted components 44 have electrodes, and these electrodes are electrically connected to other planar electrodes 50 via conductive wires 56. The ceramic multilayer substrate 40 has heat dissipation vias 54 penetrating the substrate body, and the surface-mounted components 44 are mounted directly above them.

[0083] In such a ceramic multilayer substrate 40, the glass according to this embodiment is used, for example, to form the dielectric layer 42. Methods for forming a ceramic multilayer substrate include a printing method and a green sheet method, but the green sheet method will be described below.

[0084] First, the glass (glass frit) according to the present embodiment is mixed with a powder of functional ceramic that constitutes the dielectric layer to obtain a mixed powder. The functional ceramic can be appropriately selected, and alumina is an example. The content of the glass according to the present embodiment relative to the total volume of the mixed powder is preferably, for example, 40 to 70 volume %.

[0085] Next, a green sheet is obtained in the same manner as in the manufacturing method of the multilayer ceramic capacitor described above.

[0086] Next, a conductive paste containing at least one of silver and copper is applied to the necessary portions of the green sheet to form internal wiring or planar electrodes. The glass according to this embodiment may also be added to the conductive paste. Adding the glass according to this embodiment to the conductive paste facilitates the production of a ceramic multilayer substrate with excellent adhesion between layers. To form a resistor layer, a method using a resistor paste primarily composed of ruthenium oxide is an example. Internal vertical electrodes can be formed by drilling holes in the green sheet in advance and then filling and applying the conductive paste. Heat dissipation vias can also be formed by drilling holes in the green sheet in the same manner and then filling and applying a paste containing a highly thermally conductive material. Internal components may also be mounted as needed. The method for applying the paste is not particularly limited; for example, it can be applied using screen printing or gravure printing. Then, multiple sheets are stacked and pressure-bonded together by applying appropriate heat and pressure to obtain a laminated sheet. The heating temperature during compression can be, for example, 40 to 80°C.

[0087] Next, the obtained laminate sheet is heated to remove the binder resin, etc., and then the functional ceramic contained in the green sheet, the glass according to the present embodiment, and the conductive paste, etc. are sintered to obtain a fired laminate. By firing the laminate sheet in this manner to produce a ceramic multilayer substrate, it is possible to obtain a ceramic multilayer substrate that has excellent adhesion between the layers, is highly reliable, and has excellent stability over time.

[0088] Heating and sintering are carried out using a firing furnace in a predetermined atmosphere, such as air, an inert gas, or a reduced pressure environment. The heating temperature is preferably 20°C or more higher than the Tg of the glass according to this embodiment and lower than the Tc1-on of the glass according to this embodiment. Specific temperatures are preferably, for example, 280 to 600°C, and more preferably 280 to 550°C. The firing time is, for example, 1 to 3 hours.

[0089] Thereafter, if necessary, plating treatment with Ni, Au, etc. is performed on the portions of the fired laminate that will become the external electrodes. If necessary, the laminate sheet can be half-cut before firing and then broken into chips after firing. Chips can also be formed using a dicing saw. Furthermore, surface-mounted components and conductive wires that connect the electrodes of the surface-mounted components to the external electrodes are provided on the external electrodes. Known methods can be applied to the above procedure. A ceramic multilayer substrate (low-temperature co-fired ceramic multilayer substrate) is obtained by the above procedure.

[0090] The present invention will be described in more detail below based on examples. The materials, amounts used, ratios, treatment details, treatment procedures, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be interpreted as being limited by the examples shown below. Note that Examples 1 to 9, 14 to 19, and 22 to 28 described below are working examples, and Examples 10 to 13, 20, and 21 are comparative examples.

[0091] <Production Method> For the glass of each example, the raw materials were weighed and mixed to obtain the composition shown in the table below. Next, the mixed raw materials were placed in a platinum crucible and placed in an electric furnace at 800 to 1600°C to melt for approximately 0.5 to 4 hours, and the melt was rapidly cooled using a roll-out machine to produce glass flakes. The roll was rotated at 10 to 20 rpm, and the flakes that had passed through the roll were collected in a dry air flow environment. Various conditions were adjusted so that the cooling rate in each example was a constant value. The glass of each example was obtained using the above procedure.

[0092] <Measurement> (Measurement of Vitrification Ratio) The vitrification ratio of the glass of each example obtained above was measured by the following method. At least 10 of the glass flakes were randomly selected and observed under an optical microscope. They were then separated into flakes in which crystals were observed and those in which no crystals were observed. The observation using the optical microscope was performed under the following conditions: Model: Nikon LV100; Magnification: 100x. Observation of crystals refers to the observation of five or more crystals formed from the glass within the observation field under the above observation conditions. Next, the remaining flakes in which no crystals were observed under the optical microscope were evaluated using X-ray diffraction. Specifically, as described above, the X-ray diffraction method was used to determine whether or not a diffraction peak derived from crystals was observed, and the number of flakes in which no diffraction peaks were observed was finally calculated. The vitrification ratio was defined as the percentage of flakes in which no crystals were observed and no diffraction peaks derived from crystals were observed by X-ray diffraction among the flakes observed under the optical microscope. That is, the number of flakes that did not show diffraction peaks derived from crystals by X-ray diffraction, relative to the number of flakes observed under the optical microscope, was taken as the vitrification rate (unit: %). Note that there is no significant difference in the mass of each glass flake, so the vitrification rate calculated from the number can be regarded as the vitrification rate value in mass ratio. The results are shown in the table below.

[0093] (Ionic Conductivity) The ionic conductivity of each glass example obtained was measured at 25° C. by the method described above. The method for measuring ionic conductivity was as described above. The results are shown in the table below.

[0094] (Tg and Tc1-on) For each example glass, Tg and Tc1-on were measured by the method described above. The results are shown in the table below.

[0095] <Results> The table shows the starting composition, cation composition, and anion composition of the glass of each example. The table also shows the measurement results of the glass of each example. In the table, the starting composition, cation composition, and anion composition are expressed in mol %. In the table, the notation "-" in the "Measurement" column indicates that no measurement was performed.

[0096]

[0097]

[0098]

[0099] From the results shown in the table, the cation contents, expressed as cation %, are Li, ＋ is 61.6% or more and 85.0% or less, Si ４＋ is more than 0.0% and 25.0% or less, and B ３＋ is 0.0 to 20.0%, and O is an anion ２－ and the anion content is expressed as anion % and ４ ２－ is more than 0.0% and not more than 10.0%, and Cl － It was confirmed that the glasses of Examples 1 to 9 and 14 to 19, in which the content of B is 0.0% or more and 9.5% or less, have a higher vitrification rate than the glasses of Examples 10 to 13, 20 and 21, which do not satisfy any of the above ranges. From a comparison of Examples 14, 18 and 19 with Examples 15 to 17, it can be seen that B ３＋ It was confirmed that when the content of SO was 2.0% or more, the vitrification rate was higher. ４ ２－ It was confirmed that when the content of SO is 0.05% or more, the vitrification rate becomes higher. ４ ２－ A tendency was observed in which the vitrification rate increased as the content of SO increased. ４ ２－ It was confirmed that when the content of SO was 3.0% or less, the ionic conductivity was higher. ４ ２－ It was confirmed that when the content was 0.3% or more, the vitrification rate was improved to 25% or more.

[0100] Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made thereto without departing from the spirit and scope of the present invention. This application is based on a Japanese patent application (Patent Application No. 2024-128879) filed on August 5, 2024, the contents of which are incorporated herein by reference.

[0101] REFERENCE SIGNS LIST 10 All-solid-state lithium-ion secondary battery 12 Positive electrode layer 14 Negative electrode layer 16 Solid electrolyte layer 20 Laminate unit 22 Electronic conductor layer 24 Positive electrode current collector 26 Negative electrode current collector 30 Multilayer ceramic capacitor 32 Dielectric layer 34 Internal electrode layer 36 External electrode 40 Ceramic multilayer substrate 42 Dielectric layer 44 Surface-mounted component 46 Internal-mounted component 50 Planar electrode 52 Internal vertical electrode 54 Heat dissipation via 56 Conductive wire

Claims

1. The cation content is expressed as cation %, and ＋ is 61.6% or more and 85.0% or less, Si ４＋ is more than 0.0% and 25.0% or less, and B ３＋ is 0.0 to 20.0%, and O is used as an anion. ２－ and the anion content is, in anion % notation, SO ４ ２－ is more than 0.0% and not more than 10.0%, and Cl － The glass having a content of 0.0% or more and 9.5% or less.

2. The cation content is expressed as cation %, and is Li ＋ is more than 67.0% and not more than 85.0%; ４＋ is more than 0.0% and 25.0% or less, and B ３＋ is 0.0 to 20.0%, and O is used as an anion. ２－ and the anion content is, in anion % notation, SO ４ ２－ is more than 0.0% and not more than 7.0%, and Cl － The glass according to claim 1, wherein the content of C is 0.0% or more and 4.0% or less.

3. Y ３＋ , Zr ４＋ , and La ３＋ and Y ３＋ , Zr ４＋ , and La ３＋ The glass according to claim 1 or 2, wherein the total content of is more than 0% and not more than 10% in terms of cation %.

4. P ５＋ and Ge ４＋ 3. The glass of claim 1, further comprising at least one cation selected from the group consisting of:

5. The cation content is expressed as cation %, respectively: Li ＋ is more than 67.0% and not more than 85.0%; ４＋ is more than 0.0% and 10.0% or less, and B ３＋ The glass according to claim 1 or 2, wherein the content of C is 10.0 to 20.0%.

6. The cation content is expressed as cation %, respectively: Li ＋ is more than 67.0% and not more than 85.0%; ４＋ is 10.0 to 25.0%, and B ３＋ The glass according to claim 1 or 2, wherein the content of C is 0.0 to 11.0%.

7. The anion content is expressed as anion % and is O ２－ The glass according to claim 1 or 2, wherein is 75.0% or more.

8. The anion content is expressed as anion % and is O ２－ , S.O. ４ ２－ , and Cl － The glass according to claim 1 or 2, wherein the total content of 9. The glass of claim 1 or 2, which is a glass frit.

10. A solid electrolyte comprising a component derived from the glass of claim 1 or 2.

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