Solid electrolyte, production method for solid electrolyte, and battery

Abstract

A solid electrolyte according to the present invention includes a first element group that is one or more alkali metal elements selected from the group that consists of Li, Na, and K, a second element group that is one or more elements that become a trivalent positive ion selected from among metal elements and metalloid elements, a third element group that is one or more halogen elements selected from the group that consists of F, Cl, Br, and I, and hydroxyl groups.

Description

Solid electrolyte, method for producing solid electrolyte, and battery

[0001] This application claims the benefit of priority from International Patent Application PCT / JP2023 / 045959, filed December 21, 2023, the entire disclosure of which is incorporated herein by reference.

[0002] In recent years, with the development of portable devices such as personal computers and mobile phones, the demand for batteries as their power sources has expanded significantly. Batteries used for such applications have traditionally used organic electrolytes, in which electrolytes are dissolved in flammable organic solvents, as a medium for ion migration. Such batteries require a structure to ensure the safety of the organic electrolyte, which increases manufacturing costs.

[0003] To address these issues and ensure essential safety, development of all-solid-state batteries is underway, which use non-flammable solid electrolytes instead of organic electrolytes. Among these solid electrolytes, sulfide-based ones are known. However, sulfide-based solid electrolytes generate hydrogen sulfide gas when they react with water. Meanwhile, oxide-based solid electrolytes, which do not generate gases like hydrogen sulfide, are also being widely developed. However, the lithium ion conductivity of these materials is lower than that of sulfides, making it difficult to improve battery output (capacity for large current extraction).

[0004] R. Miyazaki and H. Maekawa, "Li + "Ion Conduction of Li3AlF6 Mechanically Milled with LiCl" (ECS Electrochemistry Letters, 2012, Vol. 1, No. 6, pp. A87-A89) (Reference 1) ３ AlF ６ A solid electrolyte with improved lithium ion conductivity has been proposed by mechanically milling LiCl. ２ ZrOHCl ５ A solid electrolyte is disclosed in which

[0005] There is a constant demand for improved ionic conductivity of solid electrolytes, and there is a need to propose new solid electrolytes with high ionic conductivity.

[0006] The present invention is directed to a solid electrolyte, and has as its main object to provide a solid electrolyte having high ionic conductivity.

[0007] A first aspect of the present invention is a solid electrolyte comprising a first element group consisting of one or more alkali metal elements selected from the group consisting of Li, Na, and K; a second element group consisting of one or more elements that become trivalent cations selected from metal elements and metalloid elements; a third element group consisting of one or more halogen elements selected from the group consisting of F, Cl, Br, and I; and a hydroxyl group.

[0008] According to the present invention, a solid electrolyte having high ionic conductivity can be provided.

[0009] A second aspect of the present invention is the solid electrolyte of the first aspect, wherein the second element group includes Al or Ga.

[0010] Aspect 3 of the present invention is the solid electrolyte of Aspect 1 (which may be Aspect 1 or 2), in which the elements included in the second element group among the metal elements and metalloid elements excluding alkali metal elements are 50 mol % or more.

[0011] A fourth aspect of the present invention is the solid electrolyte of the second aspect, wherein the second element group includes Al.

[0012] A fifth aspect of the present invention is the solid electrolyte of the first aspect (which may be any one of the first to fourth aspects), in which the third element group includes F or Cl.

[0013] Aspect 6 of the present invention is the solid electrolyte of aspect 1 (which may be any one of aspects 1 to 5), wherein when the first element group is expressed as Mα, the second element group is expressed as Mβ, and the third element group is expressed as X, the composition formula is Mα ａ Mβ ｂ X ｃ (OH) ｄ where a+3×b=c+d, 2.7<a<3.3, 0<b<1, 0<c<6, and 0<d<6 are satisfied.

[0014] A seventh aspect of the present invention is the solid electrolyte of Aspect 1 (which may be any one of Aspects 1 to 6), wherein a diffraction pattern measured with an X-ray diffractometer using CuKα radiation has peaks in the 2θ ranges of 21 to 24°, 32 to 34°, and 35.5 to 37.5°.

[0015] An eighth aspect of the present invention is the solid electrolyte of the fourth aspect, wherein a diffraction pattern measured with an X-ray diffractometer using CuKα radiation does not have a peak in the 2θ range of 24 to 26°.

[0016] A ninth aspect of the present invention is the solid electrolyte of the fourth aspect (which may be either the fourth or eighth aspect), wherein the solid electrolyte has a Raman spectrum of 470 cm －１ More than 570cm －１ and 720 cm －１ 820cm or more －１ The peak appears below.

[0017] A tenth aspect of the present invention is the solid electrolyte of the fourth aspect (which may be the fourth, eighth or ninth aspect), in which 60 mol % or more of Al has a coordination number of four.

[0018] The present invention is also directed to a battery.

[0019] Aspect 11 of the present invention is a battery comprising a positive electrode, a negative electrode, and a solid electrolyte layer provided between the positive electrode and the negative electrode, wherein the solid electrolyte according to any one of Aspects 1 to 10 is contained in at least one of the positive electrode, the negative electrode, and the solid electrolyte layer.

[0020] The present invention is also directed to a method for producing a solid electrolyte.

[0021] A twelfth aspect of the present invention is a method for producing a solid electrolyte, comprising the steps of: a) preparing a first material which is a compound of a group of elements which is one or more trivalent elements selected from metal elements and metalloid elements and a group of elements which is one or more halogen elements selected from the group consisting of F, Cl, Br, and I; b) preparing a second material which is a hydroxide of a group of elements which is one or more alkali metal elements selected from the group consisting of Li, Na, and K; c) mechanochemically treating a mixture containing the first material and the second material; and d) heating the mechanochemically treated mixture at 40° C. or higher for 30 minutes to 24 hours to obtain a solid electrolyte.

[0022] A thirteenth aspect of the present invention is the method for producing a solid electrolyte according to the twelfth aspect, further comprising, prior to the step c), a step d) of preparing a third material which is a compound of an element group which is one or more alkali metal elements selected from the group consisting of Li, Na, and K and an element group which is one or more halogen elements selected from the group consisting of F, Cl, Br, and I, and in the step c), a mixture containing the first material, the second material, and the third material is mechanochemically treated.

[0023] A fourteenth aspect of the present invention is the method for producing a solid electrolyte according to the twelfth or thirteenth aspect, wherein in the step d), the mixture subjected to the mechanochemical treatment is pressurized at a pressure of 1 MPa or more and 500 MPa or less.

[0024] The above and other objects, features, aspects and advantages will become more apparent from the following detailed description of the invention which proceeds with reference to the accompanying drawings.

[0025] 1 is a longitudinal sectional view showing an all-solid-state secondary battery; FIG. 2 is a diagram showing a flow of manufacturing a solid electrolyte; FIG. 3 is a diagram showing press-molding of a solid electrolyte; FIG. 4 is a diagram showing XRD patterns in Experimental Examples 1, 2, and 5; FIG. 5 is a diagram showing the results of infrared spectroscopy measurements in Experimental Examples 1 and 2; FIG. 6 is a diagram showing how a potential window is measured; FIG. 7 is a diagram showing measurement results by cyclic voltammetry; FIG. 8 is a diagram showing a Raman spectrum; FIG. 9 is a diagram showing an NMR spectrum; FIG. 10 is a diagram showing a discharge curve of an all-solid-state battery (1); FIG. 11 is a diagram showing a discharge curve of an all-solid-state battery (2);

[0026] FIG. 1 is a longitudinal cross-sectional view showing an all-solid-state secondary battery 1. The all-solid-state secondary battery 1 has, from top to bottom in FIG. 1 , a positive electrode 11, a solid electrolyte layer 13, and a negative electrode 12. That is, the solid electrolyte layer 13 is located between the positive electrode 11 and the negative electrode 12. The solid electrolyte layer 13 also serves as a separator layer. The positive electrode 11 includes a current collector 111 and a positive electrode layer 112. The positive electrode layer 112 includes a positive electrode active material. The negative electrode 12 includes a current collector 121 and a negative electrode layer 122. The negative electrode layer 122 includes a negative electrode active material.

[0027] The positive electrode active material of the positive electrode layer 112 preferably contains a lithium composite oxide. A preferred positive electrode active material is a lithium composite oxide having a layered rock salt structure, such as NCM (Li(Ni, Co, Mn)O ２ The positive electrode active material may be other lithium composite oxides, for example, NCA (Li(Ni, Co, Al)O) having a layered rock salt structure. ２ ), LCO (LiCoO ２ ), LNMO (LiNi) having a spinel structure ０．５ Mn １．５ O ４ ), LFP (LiFePO ) having an olivine structure ４ The positive electrode layer 112 further contains a solid electrolyte and an electron-conducting additive (carbon black or the like) described below in addition to the positive electrode active material. The positive electrode layer 112 in this embodiment is formed by integrating these materials by applying pressure or heat.

[0028] The negative electrode active material of the negative electrode layer 122 is, for example, LTO (Li ４ Ti ５ O １２ ), NTO(Nb ２ TiO ７ ), TiO ２ Examples of the negative electrode layer 122 include compounds such as titanium oxide (TiO 2 ), graphite, and silicon monoxide (SiO 2 ). The negative electrode layer 122 includes a solid electrolyte, which will be described later, in addition to the negative electrode active material. The negative electrode layer 122 may further include an electron conduction aid (carbon black, etc.). The negative electrode layer 122 in this embodiment is formed by integrating these materials by applying pressure or heat.

[0029] The configurations and materials of the positive electrode 11 and the negative electrode 12 of the all-solid-state secondary battery 1 are not limited to those described above, and various other configurations and materials can be adopted.

[0030] The solid electrolyte layer 13 is made of or includes an ion-conductive material that is a solid electrolyte. The solid electrolyte includes a first element group consisting of one or more alkali metal elements selected from the group consisting of Li (lithium), Na (sodium), and K (potassium); a second element group consisting of one or more elements selected from metal elements and metalloid elements excluding Li, Na, K, Zr (zirconium), and Mg (magnesium); a third element group consisting of one or more halogen elements selected from the group consisting of F (fluorine), Cl (chlorine), Br (bromine), and I (iodine); and OH (hydroxyl group). This provides a novel solid electrolyte with high ionic conductivity. Specifically, the solid electrolyte has a ionic conductivity of 1.0×10 at room temperature. －５ In addition, the potential window of the solid electrolyte is wide and the moisture resistance is good.

[0031] Preferably, the second element group is an element selected from metal elements and metalloid elements that can form one or more trivalent cations, and more preferably, the second element group includes Al. Preferably, in the solid electrolyte, the elements included in the second element group are 50 mol % or more of the metal elements and metalloid elements excluding alkali metal elements.

[0032] In this specification, metalloid elements are boron (B), silicon (Si), germanium (Ge), arsenic (As), antimony (Sb), and tellurium (Te). Metal elements are elements included in Groups 1 to 12 of the periodic table excluding hydrogen, and elements included in Groups 13 to 16 of the periodic table excluding the above-mentioned metalloids and C, N, P, O, S, and Se. In other words, metal elements are a group of elements that can become cations when forming an inorganic compound with a halogen compound.

[0033] Preferably, when the first element group is represented by Mα, the second element group is represented by Mβ, and the third element group is represented by X, the composition formula is Mα ａ Mβ ｂ X ｃ (OH) ｄIn this case, where n is the valence of Mβ, the following conditions are satisfied: a + n × b = c + d, 2.7 < a < 3.3, 0 < b < 1, 0 < c < 6, and 0 < d < 6. More preferably, 2.7 < a < 3.3, 0.4 < b < 0.8, 2.0 < c < 2.8, and 1.5 < d < 3.3.

[0034] When the second element group is composed only of elements that become trivalent cations and the solid electrolyte is composed only of the first element group, the second element group, the third element group, and a hydroxyl group, the above composition formula Mα ａ Mβ ｂ X ｃ (OH) ｄ In the formula, the following conditions are satisfied: a+3×b=c+d, 2.7<a<3.3, 0<b<1, 0<c<6, and 0<d<6. More preferably, 2.7<a<3.3, 0.4<b<0.8, 2.0<c<2.8, and 1.5<d<3.3.

[0035] In a preferred example, the first element group consists solely of Li. The second element group preferably includes an element that forms a trivalent cation. A preferred example of an element that forms a trivalent cation is Al (aluminum) or Ga (gallium). In a preferred example, the second element group consists solely of at least one of Al and Ga. The third element group preferably includes F or Cl. More preferably, the third element group consists solely of at least one of F and Cl.

[0036] Preferably, the diffraction pattern of the solid electrolyte measured with an X-ray diffractometer using CuKα radiation has peaks in the 2θ ranges of 21 to 24°, 32 to 34°, and 35.5 to 37.5°. More preferably, the second element group includes Al, and the diffraction pattern has no peaks in the 2θ range of 24 to 26°. This is because AlF ３ means that there is virtually no

[0037] When the second element group includes Al, the Raman spectrum of the solid electrolyte shows a peak at 470 cm －１ More than 570cm －１ and 720 cm －１ 820cm or more －１It is preferable that the following peaks appear. The Raman spectrum reveals a certain degree of structural uniformity, which is thought to be one of the factors that contribute to the high ionic conductivity. Furthermore, the fact that Al has tetracoordination is thought to be one of the factors that contribute to the high ionic conductivity, and when the second element group of the solid electrolyte contains Al, preferably, 60 mol% or more of the Al has a coordination number of 4.

[0038] The solid electrolyte is non-flammable and chemically stable, and does not generate hydrogen sulfide gas, making it possible to provide an essentially safe all-solid-state secondary battery 1. Furthermore, the solid electrolyte can be densified by press molding rather than sintering, and does not react with the active material during battery production.

[0039] A preferred example of the solid electrolyte contains lithium, aluminum, chlorine, fluorine, and a hydroxyl group. Another preferred example contains lithium, aluminum, fluorine, and a hydroxyl group. Another preferred example contains lithium, gallium, fluorine, and a hydroxyl group.

[0040] 2 is a diagram showing the flow of manufacturing a solid electrolyte. In manufacturing a solid electrolyte, first, a compound of an alkali metal element and a halogen element is prepared (step S11). The group of alkali metal elements (i.e., one or more elements) is one or more elements selected from the group consisting of Li, Na, and K. The group of halogen elements is one or more elements selected from the group consisting of F, Cl, Br, and I. In one example of the compound, at least one of LiF and LiCl is prepared in step S11. Note that step S11 can be omitted.

[0041] Next, a compound of a group of elements selected from metal elements and metalloid elements and a group of halogen elements is prepared (step S12). However, the group of elements selected from metal elements and metalloid elements is preferably an element that becomes a trivalent cation. The group of elements may be defined as a group of elements selected from metal elements and metalloid elements excluding Li, Na, K, Zr, and Mg. The group of halogen elements is one or more elements selected from the group consisting of F, Cl, Br, and I. An example of the compound is AlF ３and GaF ３ At least one of the above is prepared in step S12.

[0042] Further, hydroxides of one or more alkali metal elements are prepared (step S13). The alkali metal elements are one or more elements selected from the group consisting of Li, Na, and K. In one example of the compound, LiOH is prepared in step S13. Steps S11 to S13 may be performed in any order.

[0043] Next, the materials prepared in steps S11 to S13 (or steps S12 to S13 if step S11 is not performed) are mixed, and the mixture is subjected to mechanochemical processing (step S14). The mechanochemical processing activates or reacts the particles of the mixture. As a specific example, in step S14, the mixture is subjected to mechanical milling using a planetary mill. During mixing, only the materials prepared in steps S11 to S13 (or steps S12 to S13) may be mixed, or other materials may be added.

[0044] In the mechanical milling process, for example, a planetary ball mill is used. In a planetary ball mill, the pot rotates on its axis while the stage on which the pot is placed revolves, making it possible to generate very high impact energy. The mechanical milling process may also be performed using other types of grinders. The mechanical milling process produces a powder (hereinafter also referred to as "processed powder") that will be the basis for the solid electrolyte used in the positive electrode layer 112, the negative electrode layer 122, or the solid electrolyte layer 13. In this processing example, the mechanical milling process is performed at room temperature, but conditions such as temperature may be changed as appropriate.

[0045] The mechanochemically treated mixture (treated powder) is then heated at 40° C. or higher for 30 minutes to 24 hours to obtain a solid electrolyte (step S15). At this time, the treated powder may be pressurized at 1 MPa to 500 MPa.

[0046] Next, experimental examples of solid electrolytes will be described. The following experimental examples were carried out in a glove box or a dry room with a dew point of −40° C. or lower.

[0047] (Experimental Example 1) As raw materials, commercially available LiF (lithium fluoride) powder (High Purity Chemical Laboratory Co., Ltd., LIH20XB), commercially available LiCl powder (High Purity Chemical Laboratory Co., Ltd., LIH09XB), and commercially available AlF ３ (Aluminum fluoride) powder (AlH17PB) was prepared. LiF, LiCl, AlF ３ were weighed out to give mole percentages of 25.0, 50.0, and 25.0, respectively, and then crushed and mixed in a mortar. The mixture was then subjected to mechanical milling using a planetary ball mill to obtain treated powders.

[0048] In mechanical milling, ZrO ２ (Zirconia) 100 pieces of 10 mm diameter ZrO ２ The balls and 12 g of the mixed powder were added, and mechanical milling was performed at 400 rpm for 20 hours to obtain a treated powder. Then, as shown in Fig. 3, 200 mg of the treated powder was sandwiched between an upper punch 92 and a lower punch 93 made of SUS (stainless steel) in a PEEK resin sleeve 91, and the solid electrolyte 2 was press-molded by heating to 150°C while applying a pressure of 150 MPa for 1 hour.

[0049] <Measurement of Ion Conductivity> After the solid electrolyte 2 sandwiched between the upper and lower punches 92, 93 was returned to room temperature, impedance was measured via the leads connected to the upper and lower punches 92, 93, and the ion conductivity was calculated. The impedance measurement was performed at a voltage of 10 mV and a frequency of 0.1 Hz to 1 MHz. The ion conductivity was 1.6 × 10 －７ S / cm (represented as 1.6E-07 in Table 1, the same applies below).

[0050] <XRD Measurement> A powder of solid electrolyte was obtained, and an X-ray diffraction pattern (hereinafter also referred to as "XRD pattern") was obtained for this powder using an X-ray diffraction (XRD) device. A sealed tube X-ray diffractometer (D8-ADVANCE manufactured by Bruker AXS K.K.) was used. Measurement was performed at 40 kV and 40 mA using CuKα radiation. The measurement step width was 0.02°.

[0051] The upper row indicated by reference numeral 31 in Fig. 4 shows the XRD pattern of Experimental Example 1. The peaks appearing at positions 301 from 29 to 31°, 34 to 36°, and 49.5 to 50.5° are LiCl, and the peak appearing at position 303 from 24 to 26° is AlF ３ The peak appearing at the position of reference 304 between 20 and 23° is Li ３ AlF ６ Corresponds to.

[0052] <Infrared Spectroscopic Measurement> Infrared spectroscopy was obtained for the solid electrolyte by the attenuated total reflectance (ATR) method. The measurement device used was an FT-IR VERTEX 70v (manufactured by Bruker), with SiC as the light source and DTGS (deuterated triglycine sulfate) as the detector. The resolution was 4 cm. －１ The number of integrations was set to 256, and a Platinum ATR (single reflection ATR, incident angle 45°, diamond prism used) was used as an accessory device.

[0053] 5 show the results of two measurements performed on the solid electrolyte of Experimental Example 1. The absorbance on the vertical axis indicates the relative value in one measurement, and the results of the two measurements are shown shifted up and down.

[0054] (Experimental Example 2) As raw materials, commercially available LiF powder, commercially available LiCl powder, and commercially available AlF ３ LiF, LiCl, and AlF were also prepared using commercially available LiOH (lithium hydroxide) powder (Sigma-Aldrich Co., 442410). ３ LiOH and LiOH were weighed to have mole percentages of 12.5, 25.0, 12.5, and 50.0, respectively, and then crushed and mixed in a mortar. The mixture was then subjected to mechanical milling using a planetary ball mill to obtain a treated powder. A solid electrolyte was then press-molded under the same conditions as in Experimental Example 1.

[0055] The ionic conductivity measured in the same manner as in Experimental Example 1 was 4.1 × 10 －４In Experimental Example 2, the ionic conductivity was measured during heating, and it was observed that the ionic conductivity increased with heating, and then decreased only to the above-mentioned value when the temperature was returned to room temperature.

[0056] XRD measurement was carried out in the same manner as in Experimental Example 1. The middle row indicated by reference numeral 32 in Fig. 4 shows the XRD pattern of Experimental Example 2. The peaks appearing at positions 301 of 29.5 to 30.5°, 34 to 35°, and 49.5 to 50.5° correspond to LiCl, and the peaks appearing at positions 302 of 38 to 39° and 44 to 46° correspond to LiF.

[0057] Infrared spectroscopy was performed under the same conditions as in Experimental Example 1. The curves denoted by reference numerals 421 and 422 in Fig. 5 show the results of two measurements performed on the solid electrolyte of Experimental Example 2. The two measurement results are shown shifted vertically in Fig. 5. The presence of OH groups can be confirmed.

[0058] (Experimental Example 3) In Experimental Example 3, commercially available AlF was used as a raw material. ３ AlF powder and commercially available LiOH powder were prepared. ３ LiOH and LiOH were weighed to be 20.0 and 80.0 mole percent, respectively, and then crushed and mixed in a mortar. The mixture was then subjected to mechanical milling using a planetary ball mill to obtain a treated powder. A solid electrolyte was then press-molded under the same conditions as in Experimental Example 1.

[0059] The ionic conductivity measured in the same manner as in Experimental Example 1 was 1.0 × 10 －５ S / cm.

[0060] (Experimental Examples 4 to 8) In Experimental Examples 4 to 8, as in Experimental Example 2, commercially available LiF powder, commercially available LiCl powder, and commercially available AlF ３ In Experimental Example 4, LiF, LiCl, and AlF were used as the starting material. ３ , and LiOH were weighed out in mole percentages of 4.3, 8.7, 17.4, and 69.6, respectively, and then crushed and mixed in a mortar. Further, mechanical milling was performed using a planetary ball mill to obtain a treated powder. Thereafter, a solid electrolyte was press-molded under the same conditions as in Experimental Example 1. The ionic conductivity measured in the same manner as in Experimental Example 1 was 6.2 × 10－４ The viscosity was S / cm.

[0061] In Experimental Example 5, LiF, LiCl, and AlF ３ , and LiOH were weighed out in mole percentages of 7.7, 15.4, 15.4, and 61.5, respectively, and then crushed and mixed in a mortar. Further, mechanical milling was performed using a planetary ball mill to obtain a treated powder. Thereafter, a solid electrolyte was press-molded under the same conditions as in Experimental Example 1. The ionic conductivity measured in the same manner as in Experimental Example 1 was 1.0 × 10 －３ The viscosity was S / cm.

[0062] XRD measurement was carried out in the same manner as in Experimental Example 1. The lower row indicated by reference numeral 33 in Fig. 4 shows the XRD pattern of Experimental Example 3. The peaks appearing at positions indicated by reference numeral 302, 38 to 39° and 44 to 46°, correspond to LiF.

[0063] In Experimental Example 6, LiF, LiCl, and AlF ３ , and LiOH were weighed out in mole percentages of 13.3, 20.0, 13.3, and 53.3 (the total may not be 100 due to rounding; the same applies below), respectively, and then pulverized and mixed in a mortar. Further, mechanical milling was performed using a planetary ball mill to obtain a treated powder. Thereafter, a solid electrolyte was press-molded under the same conditions as in Experimental Example 1. The ionic conductivity measured in the same manner as in Experimental Example 1 was 2.1 × 10 －４ The viscosity was S / cm.

[0064] In Experimental Example 7, LiF, LiCl, and AlF ３ , and LiOH were weighed out in mole percentages of 14.3, 14.3, 14.3, and 57.1, respectively, and then crushed and mixed in a mortar. Further, mechanical milling was performed using a planetary ball mill to obtain a treated powder. Thereafter, a solid electrolyte was press-molded under the same conditions as in Experimental Example 1. The ionic conductivity measured in the same manner as in Experimental Example 1 was 5.0 × 10 －４ The viscosity was S / cm.

[0065] In Experimental Example 8, LiF, LiCl, and AlF ３, and LiOH were weighed out in mole percentages of 15.4, 7.7, 15.4, and 61.5, respectively, and then crushed and mixed in a mortar. Further, mechanical milling was performed using a planetary ball mill to obtain a treated powder. Thereafter, a solid electrolyte was press-molded under the same conditions as in Experimental Example 1. The ionic conductivity measured in the same manner as in Experimental Example 1 was 1.2 × 10 －４ S / cm.

[0066] (Experimental Example 9) In Experimental Example 9, the AlF ３ Instead of commercially available GaF ３ Gallium (III) fluoride (Alfa Aesar (catalog name), 32112) was prepared. LiF, LiCl, GaF ３ , and LiOH were weighed out in mole percentages of 12.5, 25.0, 12.5, and 50.0, respectively, and then crushed and mixed in a mortar. Further, mechanical milling was performed using a planetary ball mill to obtain a treated powder. Thereafter, a solid electrolyte was press-molded under the same conditions as in Experimental Example 1. The ionic conductivity measured in the same manner as in Experimental Example 1 was 7.1 × 10 －５ S / cm.

[0067] (Experimental Example 10) In Experimental Example 10, the AlF ３ Instead of commercially available ZrF ４ Zirconium (IV) fluoride (Strem Chemicals, 232-018-1) was prepared. LiF, LiCl, ZrF ４ , and LiOH were weighed out in mole percentages of 12.5, 25.0, 12.5, and 50.0, respectively, and then crushed and mixed in a mortar. Further, mechanical milling was performed using a planetary ball mill to obtain a treated powder. Thereafter, a solid electrolyte was press-molded under the same conditions as in Experimental Example 1. The ionic conductivity measured in the same manner as in Experimental Example 1 was 4.2 × 10 －７ S / cm.

[0068] (Experimental Example 11) In Experimental Example 11, the AlF ３ Instead of commercially available MgF ２ Magnesium fluoride (MGH18XB, High Purity Chemical Laboratory Co., Ltd.) was prepared. LiF, LiCl, MgF ２, and LiOH were weighed out in mole percentages of 12.5, 25.0, 12.5, and 50.0, respectively, and then crushed and mixed in a mortar. Further, mechanical milling was performed using a planetary ball mill to obtain a treated powder. Thereafter, a solid electrolyte was press-molded under the same conditions as in Experimental Example 1. The ionic conductivity measured in the same manner as in Experimental Example 1 was 1.0 × 10 －９ The viscosity was S / cm.

[0069] (Experimental Example 12) In Experimental Example 12, the same materials as in Experimental Example 2 were weighed out in the same molar percentages, pulverized in a mortar, and mixed. Further, mechanical milling using a planetary ball mill was performed to obtain a treated powder. Thereafter, as in Experimental Example 1, the treated powder was sandwiched between an upper punch 92 and a lower punch 93 in a sleeve 91 as shown in FIG. 3 , and press-molded at room temperature for 15 minutes under a pressure of 150 MPa. Subsequently, after the pressure was released, the powder was heat-treated at 150°C for 1 hour. After cooling, impedance measurement was performed via the leads connected to the upper and lower punches 92 and 93 in the same manner as in Experimental Example 1 to calculate the ionic conductivity. The ionic conductivity was 5.3 × 10 －５ The viscosity was S / cm.

[0070] (Experimental Example 13) In Experimental Example 13, the same materials as in Experimental Example 5 were weighed out in the same molar percentages, pulverized in a mortar, and mixed. Further, mechanical milling using a planetary ball mill was performed to obtain a treated powder. Thereafter, similar to Experimental Example 12, the treated powder was press-molded without heating. Subsequently, after the pressure was released, the powder was heat-treated at 150°C for 1 hour. After cooling, impedance measurement was performed similar to Experimental Example 1 to calculate the ionic conductivity. The ionic conductivity was 1.3 x 10 －４ The viscosity was S / cm.

[0071] (Experimental Example 14) In Experimental Example 14, commercially available LiCl powder and commercially available AlF were used as raw materials. ３ LiCl, AlF powder and commercially available LiOH powder were prepared. ３, and LiOH were weighed out in mole percentages of 16.7, 16.7, and 66.7, respectively, and then crushed and mixed in a mortar. Further, mechanical milling was performed using a planetary ball mill to obtain a treated powder. Thereafter, a solid electrolyte was press-molded under the same conditions as in Experimental Example 1. The ionic conductivity measured in the same manner as in Experimental Example 1 was 1.6 × 10 －３ The viscosity was S / cm.

[0072] (Experimental Example 15) In Experimental Example 15, in addition to the raw materials of Experimental Example 14, commercially available GaF ３ Powder was prepared, and LiCl, AlF ３ , GaF ３ , and LiOH were weighed out in mole percentages of 16.7, 13.3, 3.3, and 66.7, respectively, and then crushed and mixed in a mortar. Further, mechanical milling was performed using a planetary ball mill to obtain a treated powder. Then, a solid electrolyte was press-molded under the same conditions as in Experimental Example 1. The ionic conductivity measured in the same manner as in Experimental Example 1 was 1.4 × 10 －３ The viscosity was S / cm.

[0073] (Experimental Example 16) In Experimental Example 16, in addition to the raw materials of Experimental Example 14, commercially available Al ２ O ３ (Aluminum oxide) powder (Sumitomo Chemical Co., Ltd., AKP-20) was prepared, and LiCl, AlF ３ , Al ２ O ３ , and LiOH were weighed out in mole percentages of 16.7, 15.0, 1.7, and 66.7, respectively, and then crushed and mixed in a mortar. Further, mechanical milling was performed using a planetary ball mill to obtain a treated powder. Then, a solid electrolyte was press-molded under the same conditions as in Experimental Example 1. The ionic conductivity measured in the same manner as in Experimental Example 1 was 7.9 × 10 －４ The viscosity was S / cm.

[0074] (Experimental Example 17) In Experimental Example 17, in addition to the raw materials of Experimental Example 14, commercially available B ２ O ３ Boron oxide powder (BBO08PB, manufactured by Kojundo Chemical Laboratory Co., Ltd.) was prepared, and LiCl, AlF ３ , B ２ O ３, and LiOH were weighed out in mole percentages of 16.7, 15.0, 1.7, and 66.7, respectively, and then crushed and mixed in a mortar. Further, mechanical milling was performed using a planetary ball mill to obtain a treated powder. Then, a solid electrolyte was press-molded under the same conditions as in Experimental Example 1. The ionic conductivity measured in the same manner as in Experimental Example 1 was 5.0 × 10 －４ The viscosity was S / cm.

[0075] (Experimental Example 18) In Experimental Example 18, in addition to the raw materials of Experimental Example 1, commercially available ZrF ４ Powders were prepared, LiF, LiCl, and AlF ３ , ZrF ４ , and LiOH were weighed out in mole percentages of 7.7, 15.4, 13.8, 1.5, and 61.5, respectively, and then crushed and mixed in a mortar. Further, mechanical milling was performed using a planetary ball mill to obtain a treated powder. Then, a solid electrolyte was press-molded under the same conditions as in Experimental Example 1. The ionic conductivity measured in the same manner as in Experimental Example 1 was 2.5 × 10 －４ The viscosity was S / cm.

[0076] (Experimental Example 19) In Experimental Example 19, in addition to the raw materials of Experimental Example 1, commercially available MgF ２ Powders were prepared, LiF, LiCl, and AlF ３ , MgF ２ , and LiOH were weighed out in mole percentages of 1.6, 16.4, 14.8, 1.6, and 65.6, respectively, and then crushed and mixed in a mortar. Further, mechanical milling was performed using a planetary ball mill to obtain a treated powder. Thereafter, a solid electrolyte was press-molded under the same conditions as in Experimental Example 1. The ionic conductivity measured in the same manner as in Experimental Example 1 was 1.1 × 10 －４ The viscosity was S / cm.

[0077] (Experimental Example 20) In Experimental Example 20, in addition to the raw materials of Experimental Example 1, commercially available Li ２ SiF ６ Lithium hexafluorosilicate powder (SynQuest Laboratories, M003-2-X2) was prepared, and LiF, LiCl, and AlF ３ , Li ２ SiF ６, and LiOH were weighed out in mole percentages of 4.8, 15.9, 14.3, 1.6, and 63.5, respectively, and then crushed and mixed in a mortar. Further, mechanical milling was performed using a planetary ball mill to obtain a treated powder. Thereafter, a solid electrolyte was press-molded under the same conditions as in Experimental Example 1. The ionic conductivity measured in the same manner as in Experimental Example 1 was 1.8 × 10 －４ S / cm.

[0078] (Experimental Example 21) In Experimental Example 21, in addition to the raw materials of Experimental Example 1, commercially available TiF ４ Titanium (IV) fluoride powder (Alfa Aesar, no product number) was prepared, and LiF, LiCl, and AlF ３ , TiF ４ , and LiOH were weighed out in mole percentages of 7.7, 15.4, 13.8, 1.5, and 61.5, respectively, and then crushed and mixed in a mortar. Further, mechanical milling was performed using a planetary ball mill to obtain a treated powder. Then, a solid electrolyte was press-molded under the same conditions as in Experimental Example 1. The ionic conductivity measured in the same manner as in Experimental Example 1 was 2.0 × 10 －４ S / cm.

[0079] (Experimental Example 22) In Experimental Example 22, in addition to the raw materials of Experimental Example 14, commercially available ZnF ２ Zinc fluoride powder (ZNH14XB, manufactured by Kojundo Chemical Laboratory Co., Ltd.) was prepared, and LiCl, AlF ３ , ZnF ２ , and LiOH were weighed out in mole percentages of 19.4, 12.9, 3.2, and 64.5, respectively, and then crushed and mixed in a mortar. Further, mechanical milling was performed using a planetary ball mill to obtain a treated powder. Then, a solid electrolyte was press-molded under the same conditions as in Experimental Example 1. The ionic conductivity measured in the same manner as in Experimental Example 1 was 1.8 × 10 －４ S / cm.

[0080] (Experimental Example 23) In Experimental Example 23, in addition to the raw materials of Experimental Example 14, commercially available LiBr (lithium bromide) powder (Kojundo Chemical Laboratory Co., Ltd., LIH04XB) was prepared, and LiCl, AlF ３, LiBr, and LiOH were weighed out in mole percentages of 12.5, 16.7, 4.2, and 66.7, respectively, and then crushed and mixed in a mortar. Mechanical milling was then performed using a planetary ball mill to obtain a treated powder. A solid electrolyte was then press-molded under the same conditions as in Experimental Example 1. The ionic conductivity, measured in the same manner as in Experimental Example 1, was 5.3 × 10 －４ S / cm.

[0081] (Experimental Example 24) In Experimental Example 24, in addition to the raw materials of Experimental Example 3, commercially available LiBr powder was prepared, and AlF ３ , LiBr, and LiOH were weighed out in mole percentages of 16.7, 16.7, and 66.7, respectively, and then crushed and mixed in a mortar. Further, mechanical milling was performed using a planetary ball mill to obtain a treated powder. Thereafter, a solid electrolyte was press-molded under the same conditions as in Experimental Example 1. The ionic conductivity measured in the same manner as in Experimental Example 1 was 4.4 × 10 －４ S / cm.

[0082] (Experimental Example 25) In Experimental Example 25, commercially available NaCl (sodium chloride) powder (Sigma-Aldrich Co., 793566), commercially available AlF ３ powder and commercially available NaOH (sodium hydroxide) powder (Sigma-Aldrich, 757527) were prepared. ３ , and NaOH were weighed out in mole percentages of 16.7, 16.7, and 66.7, respectively, and then crushed and mixed in a mortar. Further, mechanical milling was performed using a planetary ball mill to obtain a treated powder. Thereafter, a solid electrolyte was press-molded under the same conditions as in Experimental Example 1. The ionic conductivity measured in the same manner as in Experimental Example 1 was 7.0 × 10 －５ S / cm.

[0083] The mixing ratios of materials and the ionic conductivities in the above experimental examples are shown in Table 1. In Table 1, the numbers of experimental examples with relatively high ionic conductivities are marked with "*".

[0084]

[0085] As shown in Table 1, in Experimental Examples 2 to 9 and 12 to 25, the concentration of 1.0 × 10 －５A high ionic conductivity of 200 S / cm or more was obtained.

[0086] Comparing Experimental Example 1 with Experimental Examples 2, 4, and 8, it is clear that the addition of LiOH to the material dramatically improves ionic conductivity. Furthermore, infrared spectroscopy of Experimental Example 2 reveals that the presence of OH groups contributes to this improvement.

[0087] In Experimental Examples 2 and 5, the material was a metal fluoride (AlF ３ ), but the XRD pattern in FIG. 4 (curves 32 and 33) shows that AlF ３ There is no peak (peak around 2θ=25° marked with symbol 303) due to other compounds containing Al (Li ３ AlF ６ No peaks due to 2θ=21 to 24°, 32 to 34°, and 35.5 to 37.5° are observed. On the other hand, unspecified low-intensity peaks are observed at 2θ=21 to 24°, 32 to 34°, and 35.5 to 37.5°, which are designated by the reference symbol 305. That is, the above solid electrolyte is characterized in that, in the diffraction pattern measured by an X-ray diffractometer using CuKα radiation, peaks are present in the 2θ ranges of 21 to 24°, 32 to 34°, and 35.5 to 37.5°.

[0088] Although the detailed principle is not clear, it is believed that high ionic conductivity is obtained by Li, Al, OH (hydroxyl group), and halogen elements. In addition, when comparing the curve of Experimental Example 1 denoted by reference numeral 31 in FIG. 4 with the curves of Experimental Examples 2 and 5 denoted by reference numerals 32 and 33, it is found that AlF ３ Since no peak is observed, it is understood that it is preferable that no peak exists in the 2θ range of 24 to 26° in the diffraction pattern measured by an X-ray diffractometer using CuKα rays.

[0089] Furthermore, in the curve of Experimental Example 2 marked with reference numeral 32, there is a peak of LiCl marked with reference numeral 301, but in the curve of Experimental Example 5 marked with reference numeral 33, there is no peak of LiCl, and since Experimental Example 5 has a higher ionic conductivity, it can be seen that the absence of a peak of LiCl is more preferable.

[0090] Furthermore, since a relatively high ionic conductivity was obtained in Experimental Example 3 as well, it is understood that lithium halide is not essential as a material.

[0091] The composition formula of the solid electrolyte is Li ａ Al ｂ X ｃ (OH) ｄ (where X is at least one of F and Cl), a + 3 × b = c + d, and with 2.7 < a < 3.3, 0 < b < 1, 0 < c < 6, and 0 < d < 6. When a is fixed at 3, in Experimental Examples 2 to 8, b is 0.43 to 0.75, c is 2.25 to 2.57, and d is 1.71 to 3. When the above ranges for a to d are given a margin of about 10%, the preferred ranges are 2.7 < a < 3.3, 0.4 < b < 0.8, 2.0 < c < 2.8, and 1.5 < d < 3.3.

[0092] On the other hand, it is presumed that Li can be replaced with other alkali metal elements, Al can be replaced with other metal elements and / or metalloid elements (high ionic conductivity was obtained even when Al was replaced with Ga in Experimental Example 9), and F and Cl can be replaced with other halogen elements. Therefore, the composition formula of the solid electrolyte is Mα, where Mα is a first element group that is one or more alkali metal elements selected from the group consisting of Li, Na, and K, Mβ is a second element group that is one or more elements selected from metal elements and metalloid elements excluding Li, Na, and K, and X is a third element group that is one or more halogen elements selected from the group consisting of F, Cl, Br, and I. ａ Mβ ｂ X ｃ (OH) ｄ where a, b, c, and d satisfy the above conditions.

[0093] However, as shown in Experimental Examples 10 and 11, it is known that when Mβ is Zr or Mg, high ionic conductivity cannot be obtained, and therefore it is preferable to exclude these metal elements from Mβ.

[0094] In addition, in Experimental Examples 12 and 13, the same treated powders as in Experimental Examples 2 and 5 were heated without applying pressure after molding, which shows that applying pressure during heating is not an essential requirement for improving ionic conductivity. The preferred range of pressure when applying pressure depends on the degree of mechanochemical treatment, so it may be appropriately set within the range of 1 MPa to 500 MPa.

[0095] Furthermore, the heating temperature for the treated powder also depends on the degree of mechanochemical treatment and does not need to be high. Heating only needs to be performed at 40°C or higher for 30 minutes or more. It has been confirmed that high ionic conductivity can be obtained even at low temperatures. There is no need to specify an upper limit for the heating temperature, but for example, the heating temperature is 300°C or lower. There is also no need to specify an upper limit for the heating time, but for example, the heating time is 24 hours or less.

[0096] In Experimental Examples 15 to 17 and 22, the raw materials of Experimental Example 14, LiCl and AlF ３ , LiOH, other materials (GaF ３ , Al ２ O ３ , B ２ O ３ or ZnF ２ That is, in Experimental Example 15, the metal element Ga is added, in Experimental Example 17, the metalloid element B is added, and in Experimental Example 22, the metal element Zn is added. In Experimental Examples 18 to 21, the raw materials LiF, LiCl, and AlF, which are the raw materials in Experimental Examples 2 and 4 to 8, are added. ３ , LiOH, other materials (ZnF ４ , MgF ３ , Li ２ SiF ６ or TiF ４ That is, in Experimental Example 18, the metal element Zr was added, in Experimental Example 19, the metal element Mg was added, in Experimental Example 20, the metalloid element Si was added, and in Experimental Example 21, the metal element Ti was added.

[0097] Examples 15 to 22 show that other metal elements and metalloid elements may be present as long as the second element group includes at least one element selected from metal elements and metalloid elements that can form trivalent cations. Furthermore, it is preferable that the second element group includes at least one of Al and Ga.

[0098] The solid electrolyte of Experimental Example 23 contains Cl, F, and Br as halogen elements, and the solid electrolyte of Experimental Example 24 contains F and Br. From these Experimental Examples, it is inferred that the third element group is preferably one or more halogen elements selected from the group consisting of F, Cl, and Br, and more preferably one or more halogen elements selected from the group consisting of F, Cl, Br, and I.

[0099] Experimental Examples 14 to 24 show that, in general, solid electrolytes containing Li, Al, F, and OH, or solid electrolytes containing Li, Al, F, Cl, and OH, Ga, Al oxide, B, Zr, Mg, Si, Ti, Zn, and Br may be contained. Experimental Examples 10 and 11 show that the inclusion of large amounts of Zr or Mg is undesirable. Generally, among the metal elements and metalloid elements excluding alkali metal elements (first element group), it is preferable that the elements contained in the second element group be 50 mol% or more. Experimental Examples 18 to 22 show that, among the metal elements and metalloid elements excluding alkali metal elements, it is preferable that the elements contained in the second element group be 80 mol% or more, and more preferably 90 mol% or more. In this case, the preferred second element group is Al.

[0100] The solid electrolyte of Experimental Example 25 contains Na instead of Li in Experimental Example 14. Therefore, it is presumed that the first element group is preferably one or more alkali metal elements selected from the group consisting of Li and Na, and more preferably one or more alkali metal elements selected from the group consisting of Li, Na, and K.

[0101] In Experimental Examples 14 to 24, the composition formula of the solid electrolyte was Li ａ Al ｂ X ｃ (OH) ｄ(where X is at least one of F and Cl), a + 3 × b = c + d, where 2.7 < a < 3.3, 0 < b < 1, 0 < c < 6, and 0 < d < 6. Furthermore, the preferred ranges of 2.7 < a < 3.3, 0.4 < b < 0.8, 2.0 < c < 2.8, and 1.5 < d < 3.3, which were obtained with reference to Experimental Examples 2 to 8, are also satisfied in Experimental Examples 14 to 24.

[0102] <Potential Window Evaluation> Next, the evaluation of the potential window performed on Experimental Example 2 will be described. The treated powder of Experimental Example 2 was sandwiched between upper and lower punches 92 and 93 made of SUS (stainless steel) in a resin sleeve 91 similar to that shown in FIG. 3 , pressurized to 150 MPa, heated to 150°C, and press-molded. One of the punches was then removed, and a Li metal foil 94 with a diameter of 8 mm and a thickness of 0.2 mm was placed under the solid electrolyte 2, as shown in FIG. 6 . Cyclic voltammetry measurement was performed via wiring connected to the upper and lower punches 92 and 93. The measurement conditions were a voltage range of +4.1 V to −0.5 V and a sweep rate of 10 mV / sec.

[0103] Figure 7 shows the results of measurements by cyclic voltammetry. The horizontal axis represents the potential (-0.5 to 4.0 V (vs. Li / Li+)) and the vertical axis represents the current density (-0.3 to 0.3 mA / cm ２ ) is observed. A redox current associated with the deposition and dissolution of Li is observed near 0 V, and it is believed to have Li ion conduction. Moreover, no significant redox current other than that associated with the deposition and dissolution of Li is observed over a wide voltage range of 0 to 4 V, and it is believed to have high redox resistance (i.e., a wide potential window).

[0104] <Raman Spectrum Measurement> Next, the results of Raman spectrum measurement performed on Experimental Example 14 will be described. Fig. 8 is a diagram showing the Raman spectrum obtained by measurement. The measurement was performed using an "HR Evoluiton" (manufactured by Horiba Jobin Yvon) under the following conditions: measurement mode: microscopic Raman, beam diameter: 2 µm, light source: 532 nm (YAG laser, 2nd Harmonic), laser power: 25 mW, diffraction grating: Single 1800 gr / mm, slit: 100 µm, cross slit: 100 µm, and detector (CCD (Symphony II)).

[0105] The solid electrolyte is a material close to amorphous because no significant peak is observed in XRD, but it has been found to have a certain degree of structural uniformity in the Raman spectrum. This structural uniformity is thought to be one of the factors that results in high ionic conductivity. From the conditions of Experimental Example 14, when the first element group includes Li and the second element group includes Al, a peak at 470 cm in the Raman spectrum was observed. －１ More than 570cm －１ and 720 cm －１ 820cm or more －１ The peak appears as follows:

[0106] <NMR Spectrum Measurement> Next, the solid NMR spectrum measurement performed on Experimental Example 14 was 27 The measurement results of Al NMR (nuclear magnetic resonance) spectrum will be described. Figure 9 shows the NMR spectrum obtained by the measurement. The measurement was performed using "ECA 600" (manufactured by JOEL RESONANCE), with the measurement atmosphere being dry nitrogen, the temperature being room temperature (up to 22°C), the chemical shift reference being an aqueous solution of aluminum nitrate (external reference: 0 ppm), and the observed frequency being 27 The conditions were as follows: Al: 156.38565 MHz, observation width: 806 kHz, pulse width: 30° pulse: 1 μs, pulse repetition time: ACQTM=10.158 ms: PD=16 s, data points: POINT=16384: SAMPO=8192, pulse mode: DD / MAS method, sample rotation speed: 25 kHz.

[0107] The coordination number (chemical bonding state) of Al was determined from the measurement results of the solid-state NMR spectrum, and in the case of Experimental Example 14, 94 mol % of the Al, i.e., 90 mol % or more of the Al had a coordination number of 4. From this, it is considered that one of the factors for achieving high ionic conductivity is to contain a large amount of Al with 4-coordination, and that it is preferable for 60 mol % or more of the Al to have a coordination number of 4.

[0108] <Fabrication of All-Solid-State Battery (1)> The treated powder of Experimental Example 2 and Li(Ni,CO,Mn)O, which is a positive electrode active material, were mixed. ２ The treated powder, positive electrode active material powder, and conductive additive carbon powder were weighed and mixed in a weight ratio of 50:50:1 to obtain a positive electrode blend powder.

[0109] 200 mg of the treated powder of Experimental Example 2 was placed into a PEEK resin sleeve 91 with a hole of 10 mm inner diameter similar to that shown in Figure 3, and uniaxially pressed at 150 MPa with upper and lower punches 92, 93. One side of the punch was removed, and 30 mg of the above-mentioned positive electrode blend powder was weighed out and placed on the pressed treated powder, followed by uniaxial pressing at 150 MPa and 150°C with the upper and lower punches 92, 93. After returning to room temperature, the punch on the side opposite the positive electrode was removed, and a Li metal foil with a diameter of 8 mm and a thickness of 0.2 mm was placed on the solid electrolyte, and the punch was returned.

[0110] <Evaluation of All-Solid-State Battery (1)> A charge / discharge test of the all-solid-state battery was carried out at room temperature via conductors connected to a pair of upper and lower metal punches as follows.

[0111] First, the charge cut-off voltage was set to 4.0 V and the CC charge current was set to 150 μA / cm ２ , CV charging current 30 μA / cm ２ The all-solid-state battery was charged at 150 μA / cm ２ The battery was charged at a constant current (CC) until the voltage reached 4.0 V, and then the current value was increased to 30 μA / cm ２ The battery was charged at a constant voltage (CV) until

[0112] Next, the charged all-solid-state battery was subjected to a discharge cut-off voltage of 2.1 V and a CC discharge current of 150 μA / cm ２ CV discharge current was 30 μA / cm２ That is, the discharge operation was carried out at 150 μA / cm ２ Discharge was performed at a constant current (CC) until the voltage reached 2.1 V, and then the current value was increased to 30 μA / cm ２ Discharge was carried out at a constant voltage (CV) until

[0113] Figure 10 shows the resulting discharge curve. The horizontal axis represents the capacity (0 to 1.4 mAh), and the vertical axis represents the cell potential (1.5 to 4.0 V). The discharge capacity was 1.3 mAh. This experiment demonstrates that the solid electrolyte can be used in the solid electrolyte layer and positive electrode layer of all-solid-state batteries.

[0114] <Fabrication of All-Solid-State Battery (2)> The treated powder of Experimental Example 2 and LiFePO 4 as a positive electrode active material were mixed. ４ powder and the negative electrode active material Li ４ Ti ５ O １２ The treated powder, positive electrode active material powder, and conductive additive powder were weighed and mixed in a weight ratio of 50:50:1 to obtain a positive electrode blended powder. The treated powder, negative electrode active material powder, and conductive additive powder were weighed and mixed in a weight ratio of 50:50:1 to obtain a negative electrode blended powder.

[0115] 200 mg of the treated powder of Experimental Example 2 was placed in a PEEK resin sleeve 91 having a hole with an inner diameter of 10 mm similar to that shown in Fig. 3, and uniaxially pressed at 150 MPa using upper and lower punches 92 and 93. One of the punches was removed, and 30 mg of the above-mentioned positive electrode mixed powder was weighed out and placed on the treated powder after pressing, followed by uniaxial pressing again at 150 MPa.

[0116] The punch on the side opposite to the positive electrode was removed, and 30 mg of the negative electrode mixed powder was weighed out and placed on the pressed and treated powder, followed by uniaxial pressing at 150 MPa and 150° C. using upper and lower punches 92 and 93. The mixture was then returned to room temperature.

[0117] <Evaluation of All-Solid-State Battery (2)> A charge / discharge test of the all-solid-state battery was carried out at room temperature via conductors connected to a pair of upper and lower metal punches, respectively, as follows.

[0118] First, the charge cut-off voltage was set to 2.2 V, and the CC charge current was set to 150 μA / cm ２, CV charging current 30 μA / cm ２ The all-solid-state battery was charged at 150 μA / cm ２ The battery was charged at a constant current (CC) until the voltage reached 2.2 V, and then the current value was increased to 30 μA / cm ２ The battery was charged at a constant voltage (CV) until

[0119] Next, the charged all-solid-state battery was subjected to a discharge cut-off voltage of 1.0 V and a CC discharge current of 150 μA / cm ２ CV discharge current was 30 μA / cm ２ That is, the discharge operation was carried out at 150 μA / cm ２ The battery was discharged at a constant current (CC) until the voltage reached 1.0 V, and then the current value was increased to 30 μA / cm ２ Discharge was carried out at a constant voltage (CV) until

[0120] Figure 11 shows the resulting discharge curve. The horizontal axis represents the capacity (0 to 1.2 mAh), and the vertical axis represents the cell potential (0.0 to 2.5 V). The discharge capacity was 1.0 mAh. This experiment demonstrates that the solid electrolyte can be used in the solid electrolyte layer, positive electrode layer, and negative electrode layer of an all-solid-state battery.

[0121] The above-described solid electrolyte, its manufacturing method, and battery can be modified in various ways.

[0122] The solid electrolyte may contain impurities and may be a solid electrolyte having the above composition formula Mα ａ Mβ ｂ X ｃ (OH) ｄ The substance represented by the formula (I) may be contained as a main component. The main component is the component having the largest mass ratio among the components contained in the solid electrolyte. The mass ratio of the main component in the solid electrolyte is preferably 80 mass% or more, more preferably 90 mass% or more. The solid electrolyte may be mixed with other substances and used as an electrolyte material. The mass ratio of the solid electrolyte in the electrolyte material is preferably 50 mass% or more, more preferably 60 mass% or more, and even more preferably 70 mass% or more.

[0123] The solid electrolyte layer 13 in Fig. 1 may contain a material other than the solid electrolyte. The solid electrolyte used in the all-solid-state secondary battery 1 does not necessarily need to be contained in all of the positive electrode 11, the negative electrode 12, and the solid electrolyte layer 13, but may be contained in at least one of the positive electrode 11, the negative electrode 12, and the solid electrolyte layer 13. The solid electrolyte may be used in batteries other than all-solid-state secondary batteries and for applications other than batteries. In producing the solid electrolyte, a mechanochemical process other than mechanical milling may be performed.

[0124] The configurations in the above-described embodiment and each modification may be combined as appropriate as long as they are not mutually contradictory.

[0125] While the invention has been particularly illustrated and described, it should be understood that the foregoing description is illustrative and not restrictive, and that numerous modifications and variations are possible without departing from the scope of the invention.

[0126] 1 All-solid-state secondary battery 2 Solid electrolyte 11 Positive electrode 12 Negative electrode 13 Solid electrolyte layer S11 to S14 Steps

Claims

1. A solid electrolyte comprising: a first element group consisting of one or more alkali metal elements selected from the group consisting of Li, Na, and K; a second element group consisting of one or more elements that become trivalent cations selected from metal elements and metalloid elements; a third element group consisting of one or more halogen elements selected from the group consisting of F, Cl, Br, and I; and a hydroxyl group.

2. A solid electrolyte according to claim 1, wherein the second element group includes Al or Ga.

3. A solid electrolyte according to claim 1, wherein the content of elements included in said second element group among metal elements and metalloid elements excluding alkali metal elements is 50 mol % or more.

4. A solid electrolyte according to claim 2, wherein the second element group includes Al.

5. The solid electrolyte according to claim 1, wherein the third element group includes F or Cl.

6. The solid electrolyte according to claim 1, wherein the first element group is represented by Mα, the second element group is represented by Mβ, and the third element group is represented by X, and the composition formula is Mα ａ Mβ ｂ X ｃ (OH) ｄ a+3×b=c+d, 2.7<a<3.3, 0<b<1, 0<c<6, and 0<d<6.

7. A solid electrolyte as claimed in claim 1, in which a diffraction pattern measured with an X-ray diffractometer using CuKα radiation has peaks in the 2θ ranges of 21 to 24°, 32 to 34°, and 35.5 to 37.5°.

8. A solid electrolyte according to claim 4, in which a diffraction pattern measured with an X-ray diffractometer using CuKα radiation has no peak in the 2θ range of 24 to 26°.

9. The solid electrolyte according to claim 4, wherein the first element group includes Li, and the Raman spectrum shows a peak at 470 cm －１ More than 570cm －１ Below 720cm －１ 820cm or more －１ The solid electrolyte shows the peaks below.

10. The solid electrolyte according to claim 4, wherein 60 mol % or more of Al has a coordination number of 4.

11. A battery comprising: a positive electrode; a negative electrode; and a solid electrolyte layer provided between the positive electrode and the negative electrode, wherein the solid electrolyte according to any one of claims 1 to 10 is contained in at least one of the positive electrode, the negative electrode, and the solid electrolyte layer.

12. A method for producing a solid electrolyte, comprising the steps of: a) preparing a first material which is a compound of an element group which is one or more elements selected from metal elements and metalloid elements that can become trivalent cations, and an element group which is one or more halogen elements selected from the group consisting of F, Cl, Br, and I; b) preparing a second material which is a hydroxide of an element group which is one or more alkali metal elements selected from the group consisting of Li, Na, and K; c) mechanochemically treating a mixture containing the first material and the second material; and d) heating the mechanochemically treated mixture at 40°C or higher for 30 minutes to 24 hours to obtain a solid electrolyte.

13. A method for producing a solid electrolyte as described in claim 12, further comprising, prior to step c), a step e) of preparing a third material which is a compound of a group of elements which are one or more alkali metal elements selected from the group consisting of Li, Na, and K, and a group of elements which are one or more halogen elements selected from the group consisting of F, Cl, Br, and I, wherein in step c), a mixture containing the first material, the second material, and the third material is mechanochemically treated.

14. A method for producing a solid electrolyte according to claim 12 or 13, wherein in step d), the mixture that has been subjected to the mechanochemical treatment is pressurized at a pressure of 1 MPa or more and 500 MPa or less.

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