Solid electrolyte, method for producing solid electrolyte, and battery

Abstract

This solid electrolyte includes Li, M, Si, and F, where M is an element that forms cations. Preferably, M is an element that forms trivalent positive ions, the solid electrolyte includes a component represented by the compositional formula LiaMbSicFd, and the relationships 0.9(3-x)≤a≤1.1(3-x), 0.9(1-x)≤b≤1.1(1-x), 0.9x≤c≤1.1x, 5.4≤d≤6.6, and 0<x<1 are satisfied.

Description

Technical Field

[0001] The present invention relates to a solid electrolyte and a battery.

Background Art

[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 increased significantly. In batteries used for such applications, an organic electrolyte solution in which an electrolyte is dissolved in an organic solvent has been conventionally used as a medium for moving ions. In a battery containing this organic electrolyte solution, problems related to safety may occur.

[0003] In order to solve such problems, in order to ensure essential safety, the development of all-solid-state batteries using a solid electrolyte instead of an organic electrolyte solution has been promoted. Since solid electrolytes are generally difficult to burn, a highly safe lithium (Li)-ion battery has been realized.

[0004] In addition, among solid electrolytes, materials such as sulfide-based ones that react with moisture to generate hydrogen sulfide gas are widely known. On the other hand, although oxide-based solid electrolytes that do not generate gases such as hydrogen sulfide are also widely being developed, since the lithium ion conductivity of the materials is lower than that of sulfides, it is difficult to improve the battery output (extraction of a large current). Therefore, in "Unlocking the Potential of Fluoride-Based Solid Electrolytes for Solid-State Lithium Batteries" by Max Feinauer et al. (ACS Appl. Energy Mater., 2019, Vol. 2, pp. 7196 - 7203) (Reference 1), it has been shown that the lithium ion conductivity is improved by adding Al2O3 to Li3AlF6 (see Table S1 in Reference 1).

[0005] However, in the solid electrolyte of Reference 1, the lithium ion conductivity at 100 °C is at most 1.8×10 -5 S / cm, which is not sufficient.

Summary of the Invention

[0006] The present invention is directed to a solid electrolyte, and an object thereof is to provide a solid electrolyte having high lithium ion conductivity.

[0007] The solid electrolyte according to a preferred form of the present invention contains Li, M, Si, and F, where M is trivalent an element that becomes a cation wherein the solid electrolyte contains a component represented by the composition formula Li a M b Si c F d and satisfies 0.9(3-x)≦a≦1.1(3-x), 0.9(1-x)≦b≦1.1(1-x), 0.9x≦c≦1.1x, 5.4≦d≦6.6, and 0<x<1 .

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

[0010] Preferably, M is an aluminum element.

[0012] Another preferred solid electrolyte according to the present invention contains Li, M, Si, and F, M is an element that becomes a tetravalent cation other than Si, and the solid electrolyte has a composition formula of Li a M b Si c F d and contains components represented by 1.8 ≦ a ≦ 2.2, 0.9(1 - x) ≦ b ≦ 1.1(1 - x), 0.9x ≦ c ≦ 1.1x, 5.4 ≦ d ≦ 6.6, and 0 < x < 1 are satisfied.

[0013] Preferably, in the composition formula, 0.05 ≦ x ≦ 0.6 is satisfied.

[0014] Preferably, the X-ray diffraction pattern obtained by X-ray diffraction measurement using CuKα rays for the solid electrolyte has peaks in both the range of diffraction angle 2θ of 19 to 23° and the range of diffraction angle 2θ of 40 to 44°.

[0015] Preferably, in the X-ray diffraction pattern obtained by X-ray diffraction measurement using CuKα rays with respect to the solid electrolyte, the full width at half maximum of the strongest peak is 0.4° or more.

[0016] The present invention is also directed to a method for producing a solid electrolyte. The method for producing a solid electrolyte according to a preferred embodiment of the present invention includes: a) obtaining a mixture obtained by mixing a compound composed of Li, M, and F (where M is an element that becomes a cation) and Li2SiF6, or a mixture obtained by mixing a compound composed of M and F, LiF, and Li2SiF6; and b) mechanically milling the mixture.

[0017] Preferably, M is an element that becomes a trivalent cation. The compound composed of Li, M, and F is Li3MF6, or the compound composed of M and F is MF3.

[0018] Preferably, M is an element that becomes a tetravalent cation other than Si. The compound composed of Li, M, and F is Li2MF6, or the compound composed of M and F is MF4.

[0019] The present invention is also directed to a battery. A battery according to a preferred embodiment of the present invention includes a positive electrode, a negative electrode, and an electrolyte layer provided between the positive electrode and the negative electrode. The above solid electrolyte is included in at least one of the positive electrode, the negative electrode, and the electrolyte layer.

[0020] The above objects and other objects, features, aspects, and advantages will be clarified by the following detailed description of the present invention with reference to the attached drawings.

Brief Description of the Drawings

[0021]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0022] FIG. 1 is a longitudinal sectional view showing an all-solid-state lithium ion secondary battery 1 (hereinafter simply referred to as "all-solid-state secondary battery 1"). The all-solid-state secondary battery 1 has, in order from the top in FIG. 1, a positive electrode 11, an electrolyte layer 13, and a negative electrode 12. That is, the electrolyte layer 13 is provided between the positive electrode 11 and the negative electrode 12. The electrolyte layer 13 is a solid electrolyte layer and 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 contains 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 contains a negative electrode active material.

[0023] 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, for example, NCM (Li(Ni,Co,Mn)O2). The positive electrode active material may be other lithium composite oxides, for example, NCA (Li(Ni,Co,Al)O2), LCO (LiCoO2) having a layered rock salt structure, LNMO (LiNi 0.5 Mn 1.5 O4) having a spinel-type structure, LFP (LiFePO4) having an olivine-type structure, etc. The positive electrode layer 112 further contains, in addition to the positive electrode active material, a solid electrolyte and an electron conduction assistant (such as carbon black) described later. The positive electrode layer 112 in the present embodiment is an integration of these substances by pressure or heating.

[0024] As the negative electrode active material of the negative electrode layer 122, for example, LTO (Li4Ti5O 12) Compounds such as NTO (Nb2TiO7), TiO2 (titanium oxide), graphite, SiO (silicon monoxide), etc. can be mentioned. The negative electrode layer 122 includes, in addition to the negative electrode active material, the solid electrolyte described later. The negative electrode layer 122 may further include an electron conduction assistant (such as carbon black). The negative electrode layer 122 in the present embodiment is an integrated body of these substances by pressurization or heating.

[0025] 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.

[0026] The electrolyte layer 13 is made of the solid electrolyte according to the present invention (hereinafter also referred to as "the present solid electrolyte") or includes the solid electrolyte. The solid electrolyte is a lithium (Li) ion conductive material. The solid electrolyte includes a lithium element (Li), an element (M) that becomes a cation, a silicon element (Si), and a fluorine element (F). M is typically a metal element. As will be described later, high lithium ion conductivity is achieved in the solid electrolyte. Further, the solid electrolyte is incombustible and chemically stable, and there is no generation of hydrogen sulfide gas, so the all-solid-state secondary battery 1 that is essentially safe is provided.

[0027] The present solid electrolyte is obtained, for example, by mixing a compound containing Li, M, and F with Li2SiF6. In one example, M is an element that becomes a trivalent cation, and the solid electrolyte is obtained by mixing Li3MF6 and Li2SiF6. When Li3MF6 and Li2SiF6 are mixed so that the molar ratio is (1 - x):x (where 0 < x < 1), the present solid electrolyte has a composition formula of Li 3-x M 1-x Si xIt is represented by F6. Considering measurement errors and the like, components with the molar ratios a:b:c:d of Li, M, Si, and F satisfying 0.9(3 - x) ≤ a ≤ 1.1(3 - x), 0.9(1 - x) ≤ b ≤ 1.1(1 - x), 0.9x ≤ c ≤ 1.1x, and 5.4 ≤ d ≤ 6.6 can be regarded as components represented by the above composition formula. In the above composition formula, it is preferably satisfied that 0.05 ≤ x ≤ 0.8, and more preferably satisfied that 0.05 ≤ x ≤ 0.6. Thereby, the lithium ion conductivity can be further improved.

[0028] Preferably, M is an aluminum element (Al), and Li3MF6 is Li3AlF6 (hereinafter also referred to as "LAF"). In a solid electrolyte containing LAF and Li2SiF6 (hereinafter also referred to as "LSF"), the lithium ion conductivity is higher than that of LAF alone. The reason for this is not necessarily clear, but one reason is considered to be that Al and Si are mixed in the crystal structure containing Li (for example, Al 3+ with respect to Si 4+ is solid-solved). The same applies when M is an element that is a trivalent cation other than Al.

[0029] As described later, for this solid electrolyte, the X-ray diffraction pattern obtained by X-ray diffraction measurement using CuKα radiation preferably has peaks in both the range of diffraction angle 2θ of 19 - 23° and the range of diffraction angle 2θ of 40 - 44°. Also, the full width at half maximum of the strongest peak in the X-ray diffraction pattern is preferably 0.4° or more. In such a solid electrolyte, the crystallinity is moderately low, and high lithium ion conductivity is realized. Note that this solid electrolyte may be amorphous.

[0030] Figure 2 is a diagram showing the manufacturing process of the present solid electrolyte. In the following description, the process of manufacturing the present solid electrolyte by mixing LAF and LSF will be described. First, LAF powder is prepared. In the preparation of LAF powder, for example, commercially available LiF (lithium fluoride) powder and commercially available AlF3 (aluminum fluoride) powder are weighed and mixed so that the ratio is 3:1 (molar ratio). Subsequently, the obtained mixture is heat-treated (for example, at 900°C), and then pulverized to obtain LAF powder. The LAF powder may be produced by other methods.

[0031] Also, LSF powder is prepared. Commercially available LSF powder is used. Of course, the LSF powder may be produced by a well-known method. Then, a mixture is obtained by mixing the LAF powder and the LSF powder (step S11). In the mixture, the ratio of the amount of substance of LSF to the total of the amount of substance of LAF and the amount of substance of LSF is greater than 0% and less than 100%. The ratio is preferably 5% or more and 80% or less, and more preferably 5% or more and 60% or less.

[0032] Subsequently, the mixture is subjected to mechanical milling treatment (step S12). Here, in an example of the mechanical milling treatment, a planetary ball mill is used. In a planetary ball mill, since the pot rotates while the stage on which the pot is placed revolves, it is possible to generate very high impact energy. The mechanical milling treatment may be performed using other types of grinders. By the above mechanical milling treatment, the powder of the present solid electrolyte used for the positive electrode layer 112, the negative electrode layer 122, or the electrolyte layer 13 is obtained. In this processing example, the mechanical milling treatment is performed at room temperature, but conditions such as temperature may be appropriately changed.

[0033] FIG. 3 is a diagram showing an X-ray diffraction (XRD) pattern obtained by measurement by the powder X-ray diffraction method for this solid electrolyte. In this measurement, CuKα rays are used as the radiation source of the X-ray diffractometer. In FIG. 3, the X-ray diffraction pattern of the solid electrolyte (Experimental Example 3 described later) obtained with the molar ratio of LSF being 20% is labeled with the symbol L11, the X-ray diffraction pattern of the solid electrolyte (Experimental Example 4 described later) obtained with the molar ratio being 50% is labeled with the symbol L12, and the X-ray diffraction pattern of the solid electrolyte (Experimental Example 5 described later) obtained with the molar ratio being 80% is labeled with the symbol L13. Further, the X-ray diffraction pattern of the solid electrolyte of the comparative example obtained by subjecting only LAF to mechanical milling treatment is labeled with the symbol L21. Furthermore, the X-ray diffraction pattern of the LAF powder without mechanical milling treatment is labeled with the symbol L31, and the X-ray diffraction pattern of the LSF powder without mechanical milling treatment is labeled with the symbol L32. Note that in the X-ray diffraction patterns of the lines L11 to L13 and L21, the change in the vertical axis direction (intensity) is enlarged compared to the lines L31 and L32.

[0034] As shown in Fig. 3, the X-ray diffraction pattern of the solid electrolyte produced by mechanical milling has broad peaks in both the range of diffraction angle 2θ of 19 to 23° and the range of diffraction angle 2θ of 40 to 44°. From Fig. 3, due to the extremely high impact energy by mechanical milling, it is considered that LAF and LSF particles are refined or partially amorphized, and the crystal structure is disrupted by strain and dislocations within the crystal, etc. In particular, since this phenomenon occurs remarkably at the particle interface, it is considered that the lithium ion conductivity of this solid electrolyte is high. Therefore, this solid electrolyte may be further or completely amorphous. In order to more surely improve the lithium ion conductivity of this solid electrolyte, the half-value width of the strongest peak (for example, the peak within the range of 19 to 23°) in the X-ray diffraction pattern is preferably in a state of 0.4° or more, and more preferably in a state of 0.6° or more. In the X-ray diffraction pattern of line L11, the half-value width of the strongest peak is 1.08°. The upper limit of the half-value width is not particularly limited, but is, for example, 3.0°. The half-value width of the peak is obtained by performing fitting with a pseudo-Voigt peak function (type 1) using data analysis software Origin Pro 2020b for the X-ray diffraction pattern.

[0035] Also, as shown by the arrow marked with symbol A1 in Fig. 3, the peak in the range of 40 to 44° shifts to the high-angle side as the ratio of the molar amount of LSF increases. Therefore, in this solid electrolyte, in the crystal structure of LAF, Al with an ionic radius of 0.54 Å 3+ is considered to be solid-solved with Si having an ionic radius of 0.40 Å 4+ and the unit cell is considered to be smaller. Depending on the manufacturing method, etc. of the solid electrolyte, this solid electrolyte may be amorphous.

[0036] Next, experimental examples of the solid electrolyte will be described. The following experiments were conducted in a glove box with a dew point of -40°C or lower, or in a dry room.

[0037] (Experimental Example 1) As raw materials, commercially available LiF (lithium fluoride) powder and commercially available AlF3 (aluminum fluoride) powder were prepared. Each raw material was weighed and mixed so that LiF:AlF3 was 3:1 (molar ratio). The obtained mixture was heat-treated at 900 °C and then ground in a mortar to obtain Li3AlF6 (i.e., LAF) powder. Thereby, a solid electrolyte powder containing only LAF powder was obtained.

[0038] (Experimental Example 2) In addition to the above LAF powder, commercially available Li2SiF6 (i.e., LSF) powder was prepared. It was weighed so that LAF:LSF was 90:10 (molar ratio), and mechanical milling treatment was performed using a planetary ball mill to obtain a solid electrolyte powder containing LAF and LSF.

[0039] (Experimental Example 3) A solid electrolyte powder was obtained by performing the same treatment as in Experimental Example 2, except that it was weighed so that LAF:LSF was 80:20 (molar ratio).

[0040] (Experimental Example 4) A solid electrolyte powder was obtained by performing the same treatment as in Experimental Example 2, except that it was weighed so that LAF:LSF was 50:50 (molar ratio).

[0041] (Experimental Example 5) A solid electrolyte powder was obtained by performing the same treatment as in Experimental Example 2, except that it was weighed so that LAF:LSF was 20:80 (molar ratio).

[0042] (Measurement of Lithium Ion Conductivity) The solid electrolyte powder was put into a mold consisting of a resin sleeve and upper and lower punches made of SUS (stainless steel), and uniaxially press-molded under a pressure of 150 MPa. Conductive wires were connected to the upper and lower punches, and impedance measurement was performed at room temperature to 100 °C to calculate the lithium ion conductivity.

[0043] Table 1 shows the composition formulas of the solid electrolytes in Experimental Examples 1 to 5, the lithium ion conductivity at 100 °C, and the full width at half maximum of each peak calculated by the above-described method for the XRD pattern. The composition formula Li 3-x Al 1-x Si x F6 is for the case where Li3AlF6 which is LAF and Li2SiF6 which is LSF are mixed at a molar ratio of (1 - x):x. Experimental Examples 2 to 5 are examples of the present invention where 0 < x < 1 is satisfied, and Experimental Example 1 is a comparative example where x = 0. Further, FIG. 4 shows the relationship between the value of x (that is, the molar ratio of LSF) in the composition formula Li 3-x Al 1-x Si x F6 and the lithium ion conductivity at 100 °C.

[0044]

Table 1

[0045] In the solid electrolyte powders of Experimental Examples 2 to 5 containing LSF, the lithium ion conductivity at 100 °C was higher than that of the solid electrolyte powder of Experimental Example 1 not containing LSF. Specifically, as the molar ratio of LSF increased from 0% to 20%, the lithium ion conductivity increased. When the ratio of LSF further increased, the lithium ion conductivity decreased. Even in Experimental Example 5 where the ratio of LSF was 80%, the lithium ion conductivity was 2.4×10 -5 S / cm, which is sufficiently higher than the lithium ion conductivity of 7.6×10 -6 S / cm of Experimental Example 1 not containing LSF. Therefore, it is considered that when the ratio of LSF is greater than 0% and less than 100% (that is, 0 < x < 1), a higher lithium ion conductivity than that of the solid electrolyte powder of Experimental Example 1 is ensured.

[0046] Also, in Experimental Example 2 where the molar ratio of LSF was 10%, the lithium ion conductivity was 8.9×10 -5Since it was S / cm, it is considered that if the ratio of LSF is 5% or more, the lithium ion conductivity will be sufficiently high. The upper limit of the ratio of LSF is preferably 80%, more preferably 60%. Thereby, it becomes possible to more surely realize a sufficiently high lithium ion conductivity.

[0047] In step S11 of FIG. 2, Li3AlF6 (i.e., LAF) generated from LiF and AlF3 is mixed with LSF, but LiF and AlF3 may be directly mixed with LSF without generating Li3AlF6. Also in this case, by subjecting the mixture to mechanical milling treatment in step S12, it becomes possible to produce a solid electrolyte having a high lithium ion conductivity. Further, in step S11, an element that becomes a trivalent cation is represented by M, and Li3MF6 other than Li3AlF6 may be mixed with LSF. Li3MF6 is, for example, Li3GaF6, Li3CrF6, Li3LaF6, etc. Furthermore, MF3 other than AlF3 and LiF may be directly mixed with LSF. MF3 is, for example, GaF3, CrF3, LaF3, BiF3, YF3, etc.

[0048] M in this solid electrolyte may be an element that becomes a tetravalent cation other than Si. Such a solid electrolyte is obtained, for example, by mixing Li2MF6 and LSF (i.e., Li2SiF6). Also in this case, a solid electrolyte having a high lithium ion conductivity is realized. When Li2MF6 and Li2SiF6 are mixed in step S11 of FIG. 2 so that the molar ratio is (1 - x):x (where 0 < x < 1), this solid electrolyte has a composition formula of Li2M 1-x Si x represented by F6.

[0049] Considering measurement errors and the like, components that satisfy the molar ratios a:b:c:d of Li, M, Si, and F as 1.8 ≦ a ≦ 2.2, 0.9(1 - x) ≦ b ≦ 1.1(1 - x), 0.9x ≦ c ≦ 1.1x, and 5.4 ≦ d ≦ 6.6 can be regarded as components represented by the above compositional formula. In the above compositional formula, it is preferably satisfied that 0.05 ≦ x ≦ 0.8, and more preferably satisfied that 0.05 ≦ x ≦ 0.6. Thereby, the lithium ion conductivity can be further improved. Li2MF6 is, for example, Li2TiF6, Li2ZrF6, Li2GeF6, etc. In step S11, LiF and MF4 may be directly mixed with Li2SiF6 without generating Li2MF6. MF4 is, for example, TiF4, ZrF4, etc.

[0050] As described above, this solid electrolyte contains Li, M, Si, and F, and M is an element that becomes a cation. Thereby, a solid electrolyte having high lithium ion conductivity can be provided.

[0051] Preferably, M is an element that becomes a trivalent cation. In this case, this solid electrolyte has a compositional formula of Li a M b Si c F d and preferably contains components represented by, 0.9(3 - x) ≦ a ≦ 1.1(3 - x), 0.9(1 - x) ≦ b ≦ 1.1(1 - x), 0.9x ≦ c ≦ 1.1x, 5.4 ≦ d ≦ 6.6, and 0 < x < 1 are satisfied. Thereby, high lithium ion conductivity can be more surely realized.

[0052] M may be an element that becomes a tetravalent cation other than Si. In this case, this solid electrolyte has a compositional formula of Li a M b Si c F d and preferably contains components represented by, 1.8 ≦ a ≦ 2.2, 0.9(1 - x) ≦ b ≦ 1.1(1 - x), 0.9x ≦ c ≦ 1.1x, 5.4 ≦ d ≦ 6.6, and 0 < x < 1 are satisfied. Thereby, high lithium ion conductivity can be more surely realized.

[0053] When confirming whether an unknown solid electrolyte is this solid electrolyte, chemical analysis is performed on the unknown solid electrolyte to confirm whether the constituent elements are Li, M, Si, and F. Also, in the confirmation of whether the unknown solid electrolyte has the above composition formula, for example, for Li, Al, and Si, quantification can be performed using an ICP-emission spectroscopic analyzer. For F, quantification can be performed using an ion chromatograph. When this solid electrolyte contains an element M other than Al, a measurement method capable of quantifying the element M is appropriately selected.

[0054] The manufacturing method of this solid electrolyte includes a step (step S11) of obtaining a mixture obtained by mixing a compound composed of Li, M, and F (where M is an element that becomes a cation) and Li2SiF6, or a mixture obtained by mixing a compound composed of M and F, LiF, and Li2SiF6, and a step (step S12) of subjecting the mixture to mechanical milling treatment. Thereby, a solid electrolyte having high lithium ion conductivity can be easily provided.

[0055] Preferably, M is an element that becomes a trivalent cation. In this case, it is preferable that the above compound composed of Li, M, and F is Li3MF6, or the above compound composed of M and F is MF3. Thereby, a solid electrolyte having high lithium ion conductivity can be more reliably manufactured.

[0056] M may be an element that becomes a tetravalent cation other than Si. In this case, it is preferable that the above compound composed of Li, M, and F is Li2MF6, or the above compound composed of M and F is MF4. Thereby, a solid electrolyte having high lithium ion conductivity can be more reliably manufactured.

[0057] Various modifications are possible for this solid electrolyte, the manufacturing method of this solid electrolyte, and the battery.

[0058] If M contained in the present solid electrolyte is an element that becomes a cation, it may be an element other than an element that becomes a trivalent cation and an element that becomes a tetravalent cation. Further, the X-ray diffraction pattern obtained from the solid electrolyte may not have peaks in the range of diffraction angle 2θ of 19 to 23° and / or in the range of diffraction angle 2θ of 40 to 44°. Furthermore, the full width at half maximum of the strongest peak in the X-ray diffraction pattern may be less than 0.4°.

[0059] The present solid electrolyte may be mixed with other substances (which may contain Li) and used as an electrolyte material. In this case, the present solid electrolyte is preferably the component having the largest mass ratio among the components contained in the electrolyte material, that is, the main component. The mass ratio of the main component in the electrolyte material is preferably 50% by mass or more, more preferably 60% by mass or more, and still more preferably 70% by mass or more.

[0060] The present solid electrolyte used in the all-solid-state secondary battery 1 does not necessarily have to be contained in all of the positive electrode 11, the negative electrode 12, and the electrolyte layer 13, and it may be contained in at least one of the positive electrode 11, the negative electrode 12, and the electrolyte layer 13. Further, the present solid electrolyte may be used in batteries other than all-solid-state secondary batteries, and may also be used for applications other than batteries. The production of the present solid electrolyte may be carried out by means other than mechanical milling treatment.

[0061] The configurations in the above embodiments and each modification may be appropriately combined as long as they do not conflict with each other.

[0062] Although the invention has been described and explained in detail, the above description is illustrative and not restrictive. Therefore, it can be said that numerous modifications and aspects are possible without departing from the scope of the present invention.

Explanation of Reference Numerals

[0063] 1 All-solid-state lithium-ion secondary battery 11 Positive electrode 12 Negative electrode 13 Electrolyte layer S11, S12 Steps

Claims

1. A solid electrolyte, comprising Li, M, Si, and F, where M is an element that forms a trivalent cation, the solid electrolyte contains a component represented by the composition formula LiaMbSicFd, 0.9(3 - x) ≤ a ≤ 1.1(3 - x), 0.9(1 - x) ≤ b ≤ 1.1(1 - x), 0.9x ≤ c ≤ 1.1x, 5.4 ≤ d ≤ 6.6, and 0 < x < 1 are satisfied.

2. The solid electrolyte according to Claim 1, where M is an aluminum element.

3. A solid electrolyte, comprising Li, M, Si, and F, where M is an element that forms a tetravalent cation other than Si, wherein the solid electrolyte contains a component represented by the composition formula Li ａ M ｂ Si ｃ F ｄ and 1.8 ≤ a ≤ 2.2, 0.9(1 - x) ≤ b ≤ 1.1(1 - x), 0.9x ≤ c ≤ 1.1x, 5.4 ≤ d ≤ 6.6, and 0 < x < 1 are satisfied.

4. The solid electrolyte according to any one of Claims 1 to 3, where in the composition formula, 0.05 ≤ x ≤ 0.6 is satisfied.

5. The solid electrolyte according to any one of Claims 1 to 4, the X-ray diffraction pattern obtained by X-ray diffraction measurement using CuKα radiation has peaks in both the range of diffraction angle 2θ of 19 - 23° and the range of diffraction angle 2θ of 40 - 44°.

6. The solid electrolyte according to any one of Claims 1 to 5, in the X-ray diffraction pattern obtained by X-ray diffraction measurement using CuKα radiation, the full width at half maximum of the strongest peak is 0.4° or more.

7. A method for manufacturing a solid electrolyte, a) A compound composed of Li, M, and F (where M is an element that becomes a cation) and Li ２ SiF ６ to obtain a mixture, or a compound composed of M and F, LiF, and Li ２ SiF ６ to obtain a mixture, and b) a step of subjecting the mixture to mechanical milling treatment, is provided.

8. The method for manufacturing a solid electrolyte according to Claim 7, where M is an element that forms a trivalent cation, The compound consisting of Li, M, and F is Li ３ MF ６ or the compound consisting of M and F is MF ３ is.

9. The method for manufacturing a solid electrolyte according to Claim 7, where M is an element that forms a tetravalent cation other than Si, The compound consisting of Li, M, and F is Li ２ MF ６ or the compound consisting of M and F is MF ４ is the case.

10. A battery, comprising a positive electrode, a negative electrode, and an electrolyte layer provided between the positive electrode and the negative electrode, is provided, where the solid electrolyte according to any one of Claims 1 to 6 is included in at least one of the positive electrode, the negative electrode, and the electrolyte layer.

Images