Solid-state electrolytes and lithium-ion batteries

Abstract

A solid electrolyte is provided that has high conductivity due to the content of Br, exhibits high stability in a dry room controlled to a dew point of -40°C, and furthermore, can significantly recover reduced conductivity by heat treatment. This solid electrolyte comprises Li, Mα, Mβ, Mγ, Cl, and Br, wherein Mα is at least one element selected from the group consisting of Zr and Hf, Mβ is at least one element selected from the group consisting of Ta, Nb, and Mo, and Mγ is at least one element selected from the group consisting of Gd, Yb, Dy, Er, Ho, Eu, Sc, and Al.

Description

Technology Field

[0001] The present disclosure relates to a solid electrolyte and a lithium-ion battery. Background Technology

[0002] Recently, there has been a strong demand for miniaturization and improved reliability (safety) for batteries that serve as power sources for electronic devices. For this reason, all-solid-state batteries that use solid electrolytes instead of liquid electrolytes are attracting attention. One representative type of solid electrolyte is the sulfide-based solid electrolyte. However, since sulfide-based solid electrolytes can generate toxic hydrogen sulfide, there is a demand for solid electrolytes that do not belong to the sulfide-based solid electrolyte category from a safety perspective.

[0003] Halides have been proposed as solid electrolytes that do not contain sulfur. For example, in Patent Document 1 (Japanese Patent Publication No. 7316571), Li 3-3δ-a Y 1+δ-a M a Cl 6-x-y Br x I y A solid electrolyte represented by the compositional formula (wherein M is Zr and / or Hf, and -1<δ<1, 0.1≤a≤0.9, 0<(3-3δ-a), 0<(1+δ-a), 0≤x≤6, 0≤y≤6, and (x+y)≤6) is disclosed. In this document, Li 2.5 Y 0.5 Zr 0.5 A solid electrolyte with the composition Cl6 exhibits high lithium ion conductivity at room temperature, and furthermore, Li doped with Br at some of the Cl sites 2.5 Y 0.5 Zr 0.5 It has been disclosed that a solid electrolyte with the composition of Cl5Br exhibits higher conductivity.

[0004] In addition, Patent Document 2 (WO 2024 / 010065) discloses a solid electrolyte comprising A, Mα, Mβ, Mγ, and Cl, wherein A is at least one element selected from the group consisting of Li and Na, Mα is at least one element selected from the group consisting of Zr and Hf, Mβ is at least one element selected from the group consisting of Ta and Nb, Mγ is at least one element selected from the group consisting of Gd, Yb, Dy, Er, Ho, Eu, and Sc, and the amount of Cl is greater than the amount of A. Prior art literature

[0005] Patent Document 1: Japanese Patent No. 7316571 Publication Patent Document 2: WO 2024 / 010065

[0006] As mentioned above, Li 2.5 Y 0.5 Zr 0.5 Cl6, Li 2.5 Y 0.5 Zr 0.5 Although it is known that chloride electrolytes such as Cl5Br (see Patent Document 1) exhibit high conductivity at room temperature, there have been no reports regarding the stability of these electrolytes. Therefore, the inventors prepared the chloride electrolyte powder disclosed in Patent Document 1 and placed it in a dry room controlled to a dew point of -40°C; it was found that the electrolyte decomposed and could not maintain its initial conductivity. Furthermore, it was found that in a composition in which Br was doped into a portion of the Cl sites, conductivity improved, while stability in a dry room controlled to a dew point of -40°C decreased.

[0007] The inventors of the present invention, this time, Li, M α , M β , M γ In a solid electrolyte containing , Cl and Br, M α , M β and M γIt was discovered that by employing a specific metal element, it is possible to provide a solid electrolyte that has high conductivity due to the Br content, exhibits high stability in a dry room controlled to a dew point of -40°C, and furthermore, can significantly recover reduced conductivity through heat treatment.

[0008] Accordingly, the objective of the present invention is to provide a solid electrolyte that has high conductivity due to the content of Br, exhibits high stability in a dry room controlled to a dew point of -40°C, and furthermore, can significantly recover reduced conductivity through heat treatment.

[0009] According to the present disclosure, the following aspects are provided.

[0010] [Mode 1]

[0011] Li, M α , M β , M γ As a solid electrolyte containing , Cl and Br,

[0012] M α is at least one element selected from the group consisting of Zr and Hf, and

[0013] M β is at least one element selected from the group consisting of Ta, Nb and Mo, and

[0014] M γ A solid electrolyte in which at least one element selected from the group consisting of Gd, Yb, Dy, Er, Ho, Eu, Sc, and Al.

[0015] [Mode 2]

[0016] M α A solid electrolyte described in Embodiment 1, comprising Zr.

[0017] [Mode 3]

[0018] M β A solid electrolyte described in embodiment 1 or 2 comprising Ta.

[0019] [Mode 4]

[0020] M γ A solid electrolyte described in any one of embodiments 1 to 3, comprising at least one element selected from the group consisting of Gd, Yb, and Er.

[0021] [Mode 5]

[0022] Jo Seong-sik Ha:

[0023] Li 6-(4+a-b)(1+c) (M α (1-a-b) M β a M γ b ) 1+c Cl 6-2d-e-f O d F e Br f

[0024] A solid electrolyte described in any one of embodiments 1 to 3, comprising a composition represented as such and satisfying 0<a, 0<b, a+b<1, -0.2≤c≤0.2, 0≤d<3, 0≤e<6, and 0<f<6.

[0025] [Mode 6]

[0026] A lithium-ion battery comprising a solid electrolyte described in any one of embodiments 1 to 5. Brief explanation of the drawing

[0027] FIG. 1 is a schematic cross-sectional view showing an example of an all-solid-state battery according to the present invention. Specific details for implementing the invention

[0028] solid electrolyte

[0029] The solid electrolyte according to the present invention is Li, M α , M β , M γ It includes , Cl, and Br. M α is at least one element selected from the group consisting of Zr and Hf. M β is at least one element selected from the group consisting of Ta, Nb, and Mo. M γis at least one element selected from the group consisting of Gd, Yb, Dy, Er, Eu, Sc, and Al. As such, Li, M α , M β , M γ By employing specific constituent elements in a solid electrolyte containing Cl and Br, it is possible to provide a solid electrolyte that has high conductivity due to the Br content, exhibits high stability in a dry room controlled to a dew point of -40°C, and furthermore, can significantly recover reduced conductivity through heat treatment.

[0030] As previously stated, when the inventors prepared the chloride electrolyte powder disclosed in Patent Document 1 and placed it in a dry room controlled to a dew point of -40°C, it was found that the electrolyte decomposed and could not maintain its initial conductivity. Furthermore, it was found that in a composition in which Br was doped into a portion of the Cl sites, conductivity improved, while stability in a dry room controlled to a dew point of -40°C decreased. Therefore, in order to improve the stability of the chloride electrolyte, the inventors [prescribed] Li x MCl y Br z In the compositional system (where M is a cation), materials were fabricated using various cations to explore cations with good stability and their combinations. Furthermore, as a result of examining various cations and diverse combinations, M α As Zr, M β As Ta, M γ Li comprising a combination of Gd and / or Yb as x (M α ,M β ,M γ )Cl y Br z A solid electrolyte represented by the compositional formula, despite containing Br, exhibits high initial conductivity (10 at room temperature) -4 S / cm) and high stability (conductivity at room temperature is 10 after standing in a dry room for 16 hours) -4It was found that it is possible to achieve a conductivity of S / cm or higher. Furthermore, the same trend as above was confirmed for combinations of elements other than those mentioned above. In addition, it was confirmed that the conductivity, which had decreased, is restored by heat-treating the solid electrolyte of the above composition at 150°C after settling in a dry room. The present invention is based on these findings and can smoothly resolve the aforementioned problems, and as a result, provide a high conductivity solid electrolyte material that can be handled in a dry room environment with a dew point of -40°C and has high applicability to battery manufacturing processes.

[0031] As mentioned above, the solid electrolyte of the present invention is Li, M α , M β , M γ It includes Cl and Br. The solid electrolyte contains these elements, and is not particularly limited as long as it is a halide having the characteristics of a solid electrolyte, but Li x (M α ,M β M γ )Cl y Br z In the basic composition, it may be a composition in which Br is doped into some of the Cl sites, or in which O and / or F is doped as well as Br. Specifically, such a solid electrolyte is given by the following compositional formula:

[0032] Li 6-(4+a-b)(1+c) (M α (1-a-b) M β a M γ b ) 1+c Cl 6-2d-e-f O d F e Br f

[0033] It is preferable that the composition includes the formula represented by 0<a, 0<b, a+b<1, -0.2≤c≤0.2, 0≤d<3, 0≤e<6 and 0<f<6). In addition, the solid electrolyte may be crystalline or amorphous.

[0034] M α is an element that becomes a tetravalent cation. M α is at least one element selected from the group consisting of Zr and Hf, and typically includes Zr.

[0035] M β is an element that becomes a pentavalent cation. M β is at least one element selected from the group consisting of Ta, Nb, and Mo, and typically includes Ta. M β The coefficient a multiplied by satisfies 0 < a (where a+b < 1), preferably 0 < a ≤ 0.8, and more preferably 0.1 ≤ a ≤ 0.5.

[0036] M γ is an element that becomes a trivalent cation. M γ is at least one element selected from the group consisting of Gd, Yb, Dy, Er, Ho, Eu, Sc, and Al, and typically comprises at least one element selected from the group consisting of Gd, Yb, and Er. γ The coefficient b multiplied by satisfies 0 < b (where a+b < 1), preferably 0 < b ≤ 0.8, and more preferably 0.25 ≤ b ≤ 0.75.

[0037] The coefficient c is -0.2 ≤ c ≤ 0.2, preferably -0.15 ≤ c ≤ 0.15, more preferably -0.1 ≤ c ≤ 0.1, and typically c = 0.

[0038] As can be seen from the above compositional formula, at the Cl site, not only Cl, but also Br, optionally O, and optionally F may be present. The coefficient f multiplied by Br is 0 < f < 6, preferably 0 < f ≤ 2.0, more preferably 0.3 ≤ f ≤ 1.0. O is any element, and the coefficient d multiplied by O is 0 ≤ d < 3, preferably 0 ≤ d < 0.5, more preferably 0 ≤ d ≤ 0.4. F is also any element, and the coefficient e multiplied by F is 0 ≤ e < 6, preferably 0 ≤ e ≤ 2, more preferably 0 ≤ e ≤ 1.

[0039] When determining whether the unknown solid electrolyte is the said solid electrolyte, chemical analysis is performed on the said unknown solid electrolyte and the constituent elements are Li, M α , M β , M γ It is advisable to check whether it is Cl, O, F, or Br. In addition, when verifying whether an unknown solid electrolyte meets the above compositional formula, for example, Li, M α , M β and M γ Regarding [it], it can be quantified by an ICP-emission spectroscopic analyzer. Cl, F, and Br can be quantified by an ion chromatograph. O can be quantified by ONH analysis using an oxygen, nitrogen, and hydrogen analyzer.

[0040] lithium-ion battery

[0041] According to a preferred embodiment of the present invention, a lithium-ion battery comprising a solid electrolyte of the present invention is provided. The lithium-ion battery is preferably a lithium-ion secondary battery, and more preferably an all-solid-state lithium-ion secondary battery. Particularly preferably, it is an all-solid-state lithium-ion secondary battery. FIG. 1 schematically illustrates an example of a lithium-ion battery (10) according to the present invention.

[0042] The positive electrode (12) includes a positive electrode active material. The positive electrode active material preferably includes a lithium composite oxide. Examples of lithium composite oxides include lithium nickel manganese oxide (LNMO) (typically LiNi 0.5 Mn 1.5 Examples include lithium nickel cobalt manganese oxide (NCM) (typically Li(Ni,Co,Mn)O2), lithium cobaltate (LCO) (typically LiCoO2), lithium nickel cobalt aluminum oxide (NCA) (typically Li(Ni,Co,Al)O2), and lithium iron phosphate (LFP) (typically LiFePO4), and combinations thereof. NCM, LCO, and NCA have a layered rock salt structure. LNMO has a spinel-type structure. LFP has an olivine-type structure. Preferably, it is a lithium composite oxide having a layered rock salt structure, such as NCM. The positive electrode (12) preferably further comprises a solid electrolyte and / or an electron conductivity aid (such as carbon black) in addition to the positive electrode active material. In the present embodiment, the positive electrode (12) is formed by integrating these materials by pressurization or heating. Accordingly, as shown in FIG. 1, the positive electrode (12) is typically in the form of a positive electrode layer. When the positive electrode (12) includes a solid electrolyte, it is preferable to use the solid electrolyte described below.

[0043] The negative electrode (14) is 0.1 V (pair Li / Li + It includes a negative electrode active material capable of inserting and extracting lithium ions above. Examples of negative electrode active materials include lithium titanate (LTO) (typically Li4Ti5O). 12 Examples include ), SiO, Si or Si alloys, and TiO2, and combinations thereof. Preferably, the negative electrode active material is LTO, SiO, or TiO2 in terms of non-flammability, and particularly preferably LTO in terms of cyclability. LTO is typically known to have a spinel-type structure, but other structures may also be adopted during charging and discharging. For example, LTO is Li4Ti5O during charging and discharging 12(Spinel structure) and Li7Ti5O 12 The reaction proceeds through the coexistence of two phases (rock salt structure). Therefore, LTO is not limited to a spinel structure. It is desirable for the negative electrode (14) to further include a solid electrolyte in addition to the negative electrode active material for the improvement of ion conductivity. The negative electrode (14) may further include an electron conductivity aid (such as carbon black). In this embodiment, the negative electrode (14) is formed by integrating these materials by pressurization or heating. Therefore, as shown in FIG. 1, the negative electrode (14) is typically in the form of a negative electrode layer. When the negative electrode (14) includes a solid electrolyte, it is desirable to use the solid electrolyte according to the present invention described above as such a solid electrolyte.

[0044] The electrolyte layer (16) is a layer containing an electrolyte disposed between the positive electrode (12) and the negative electrode (14). Typically, the electrolyte layer (16) contains a solid electrolyte, and preferably consists of a solid electrolyte. In this case, the electrolyte layer (16) can be said to also serve as a separator. As the solid electrolyte included in the electrolyte layer (16), it is preferable to use the solid electrolyte according to the present invention described above.

[0045] At least one of the positive electrode (12), the negative electrode (14), and the electrolyte layer (16) comprises a solid electrolyte according to the present invention. The solid electrolyte exhibits high ionic conductivity (e.g., lithium ion conductivity). Furthermore, since this solid electrolyte is non-flammable, chemically stable, and does not generate hydrogen sulfide gas, it is possible to realize an inherently safe lithium-ion battery (10). However, it is not necessary for all of the positive electrode (12), the negative electrode (14), and the electrolyte layer (16) to comprise the solid electrolyte, and at least one of them may comprise the solid electrolyte.

[0046] The solid electrolyte according to the present invention may be mixed with other materials and used as an electrolyte material. In this case, the solid electrolyte is preferably the component with the largest mass ratio among the components included in the electrolyte material, that is, the main component. The mass ratio of the main component in the electrolyte material is preferably 50 weight% or more, more preferably 60 weight% or more, and even more preferably 70 weight% or more.

[0047] As described above, in the lithium-ion battery (10) of the present invention, materials that do not contain sulfides can be used as the positive electrode (12), the negative electrode (14), and the electrolyte layer (16). That is, it is preferable that no part of the positive electrode (12), the negative electrode (14), and the electrolyte layer (16) contains sulfides. By doing so, toxic gases such as hydrogen sulfide are not generated, and an essentially safe lithium-ion battery (10) can be provided.

[0048] It is preferable that the lithium-ion battery (10) further comprises a positive electrode current collector (18) and a negative electrode current collector (20). It is preferable that the positive electrode current collector (18) be provided on the side opposite to the electrolyte layer (16) of the positive electrode (12), and it is preferable that the negative electrode current collector (20) be provided on the side opposite to the electrolyte layer (16) of the negative electrode (14). Examples of materials constituting the positive electrode current collector (18) and the negative electrode current collector (20) include aluminum (Al), copper (Cu), titanium (Ti), nickel (Ni), stainless steel (SUS), carbon, platinum (Pt), platinum (Pt) / palladium (Pd), gold (Au), silver (Ag), ITO (indium-tin oxide), etc.

[0049] The container (22) is not particularly limited to a container capable of accommodating a lithium-ion battery (10) alone, or a container capable of accommodating a stack of multiple lithium-ion batteries (10) stacked in series or parallel. In particular, when the lithium-ion battery (10) is a solid-state battery, there is no concern about leakage of the electrolyte, so the container (22) can adopt a relatively simple container shape. For example, a chip shape for mounting on an electronic circuit or a laminate cell shape for thin and wide space applications (e.g., a multilayer aluminum (Al) / polypropylene (PP)) can be adopted.

[0050] Examples

[0051] The present invention will be explained in more detail by the following examples. However, the present invention is not limited to the following examples.

[0052] Example 1

[0053] (1) Preparation of electrolyte

[0054] In an argon atmosphere having a dew point of -60°C or lower, each raw material powder of LiCl, LiBr, ZrCl4, ZrF4, HfCl4, TaCl5, MoCl5, Gd2O3, YbCl3, DyCl3, ErCl3, and HoCl3 was weighed in a molar ratio of LiCl:LiBr:ZrCl4:ZrF4:HfCl4:TaCl5:MoCl5:Gd2O3:YbCl3:DyCl3:ErCl3:HoCl3 = 1.8:0.5:0.125:0.075:0.2:0.1:0.05:0.025:0.05:0.1:0.2:0.05, and these raw material powders were ground and mixed in a mortar. The obtained mixed powder was placed in a zirconia pot and milled using a planetary ball mill at 300 rpm for 20 hours to obtain a solid electrolyte powder.

[0055] (2) Conductivity measurement

[0056] Solid electrolyte powder was introduced into a mold consisting of a resin sleeve and upper and lower punches made of stainless steel, and uniaxial press molding was performed by applying pressure of 150 MPa. Wires were connected to the upper and lower punches to perform impedance measurements at room temperature, and the lithium ion conductivity (hereinafter referred to as initial conductivity C1) was calculated from the obtained measurement results. The results are as shown in Table 1.

[0057] (3) Exposure test

[0058] The solid electrolyte powder was placed in a petri dish and left to stand for 16 hours in a dry room controlled to a dew point of -40℃.

[0059] (4) Heat treatment

[0060] Solid electrolyte powder that had been left in a dry room for 16 hours was heat-treated at 150°C.

[0061] (5) Stability evaluation

[0062] For each of the solid electrolyte powder set in a dry room in (3) above and the solid electrolyte powder heat-treated in (4) above, impedance measurements were performed at room temperature in the same manner as in (2) above to calculate the lithium ion conductivity of each powder. In this way, the conductivity retention rate of each powder was calculated by dividing the conductivity C2 after the exposure test and the conductivity C3 after the exposure test and heat treatment by the initial conductivity C1 and multiplying by 100. These results were as shown in Table 1.

[0063] Example 2

[0064] In the preparation of the electrolyte of Example 1, the raw material powders of LiCl, LiBr, ZrCl4, ZrF4, HfCl4, TaCl5, MoCl5, Gd2O3, YbCl3, DyCl3, ErCl3, and HoCl3 were weighed in a molar ratio of LiCl:LiBr:ZrCl4:ZrF4:HfCl4:TaCl5:MoCl5:Gd2O3:YbCl3:DyCl3:ErCl3:HoCl3 = 1.3:1.0:0.125:0.075:0.2:0.1:0.05:0.025:0.05:0.1:0.2:0.05, except that the electrolyte was prepared and evaluated in the same manner as in Example 1.

[0065] Example 3

[0066] In the preparation of the electrolyte of Example 1, the electrolyte was prepared and evaluated in the same manner as in Example 1, except that each raw material powder of LiCl, LiBr, ZrCl4, TaCl5, and ErCl3 was weighed in a molar ratio of LiCl:LiBr:ZrCl4:TaCl5:ErCl3 = 1.25:0.5:0.25:0.5:0.25.

[0067] Example 4

[0068] In the preparation of the electrolyte of Example 1, the electrolyte was prepared and evaluated in the same manner as in Example 1, except that each raw material powder of LiCl, LiBr, ZrCl4, TaCl5, and ErCl3 was weighed in a molar ratio of LiCl:LiBr:ZrCl4:TaCl5:ErCl3 = 0.75:1.0:0.25:0.5:0.25.

[0069] Example 5

[0070] In the preparation of the electrolyte of Example 1, the raw material powders of LiCl, LiBr, ZrCl4, TaCl5, DyCl3, ErCl3, HoCl3, and AlCl3 were weighed in a molar ratio of LiCl:LiBr:ZrCl4:TaCl5:DyCl3:ErCl3:HoCl3:AlCl3 = 2.3:0.3:0.2:0.1:0.3:0.1:0.2:0.1, except that the electrolyte was prepared and evaluated in the same manner as in Example 1.

[0071] Example 6

[0072] In the preparation of the electrolyte of Example 1, the raw material powders of LiCl, LiBr, ZrCl4, TaCl5, MoCl5, Gd2O3, YbCl3, DyCl3, ErCl3, HoCl3, and AlCl3 were weighed in a molar ratio of LiCl:LiBr:ZrCl4:TaCl5:MoCl5:Gd2O3:YbCl3:DyCl3:ErCl3:HoCl3:AlCl3 = 2.2:0.45:0.15:0.05:0.05:0.025:0.05:0.35:0.15:0.05:0.1, and the preparation and evaluation of the electrolyte were carried out in the same manner as in Example 1.

[0073] Example 7 (comparison)

[0074] In the preparation of the electrolyte of Example 1, the electrolyte was prepared and evaluated in the same manner as in Example 1, except that each raw material powder of LiCl, LiBr, YCl3, and ZrCl4 was weighed in a molar ratio of LiCl:LiBr:YCl3:ZrCl4 = 2.0:0.5:0.5:0.5.

[0075] Example 8 (comparison)

[0076] In the preparation of the electrolyte of Example 1, the electrolyte was prepared and evaluated in the same manner as in Example 1, except that each raw material powder of LiCl, LiBr, YCl3, and ZrCl4 was weighed in a molar ratio of LiCl:LiBr:YCl3:ZrCl4 = 1.5:1.0:0.5:0.5.

[0077] Example 9 (comparison)

[0078] In the preparation of the electrolyte of Example 1, the electrolyte was prepared and evaluated in the same manner as in Example 1, except that each raw material powder of LiCl, LiBr, YCl3, and ZrCl4 was weighed in a molar ratio of LiCl:LiBr:YCl3:ZrCl4 = 0.5:2.0:0.5:0.5.

[0079] Example 10 (reference)

[0080] In the preparation of the electrolyte of Example 1, the raw material powders of LiCl, ZrCl4, ZrF4, HfCl4, TaCl5, MoCl5, Gd2O3, YbCl3, DyCl3, ErCl3, and HoCl3 were weighed in a molar ratio of LiCl:ZrCl4:ZrF4:HfCl4:TaCl5:MoCl5:Gd2O3:YbCl3:DyCl3:ErCl3:HoCl3 = 2.3:0.125:0.075:0.2:0.1:0.05:0.025:0.05:0.1:0.2:0.05, except that the electrolyte was prepared and evaluated in the same manner as in Example 1.

[0081] Example 11 (reference)

[0082] In the preparation of the electrolyte of Example 1, the electrolyte was prepared and evaluated in the same manner as in Example 1, except that each raw material powder of LiCl, ZrCl4, TaCl5, and ErCl3 was weighed in a molar ratio of LiCl:ZrCl4:TaCl5:ErCl3 = 1.75:0.25:0.5:0.25.

[0083] Example 12 (reference)

[0084] In the preparation of the electrolyte of Example 1, the raw material powders of LiCl, ZrCl4, TaCl5, DyCl3, ErCl3, HoCl3, and AlCl3 were weighed in a molar ratio of LiCl:ZrCl4:TaCl5:DyCl3:ErCl3:HoCl3:AlCl3 = 2.6:0.2:0.1:0.3:0.1:0.2:0.1, except that the electrolyte was prepared and evaluated in the same manner as in Example 1.

[0085] Example 13 (reference)

[0086] In the preparation of the electrolyte of Example 1, the raw material powders of LiCl, ZrCl4, TaCl5, MoCl5, Gd2O3, YbCl3, DyCl3, ErCl3, HoCl3, and AlCl3 were weighed in a molar ratio of LiCl:ZrCl4:TaCl5:MoCl5:Gd2O3:YbCl3:DyCl3:ErCl3:HoCl3:AlCl3 = 2.65:0.15:0.05:0.05:0.025:0.05:0.35:0.15:0.05:0.1, and the preparation and evaluation of the electrolyte were carried out in the same manner as in Example 1, except that each of the raw material powders of LiCl, ZrCl4:TaCl5:MoCl5:Gd2O3:YbCl3:DyCl3:ErCl3:HoCl3:AlCl3 = 2.65:0.15:0.05:0.05:0.025:0.05:0.35:0.15:0.05:0.1.

[0087] Example 14 (reference)

[0088] In the preparation of the electrolyte of Example 1, the electrolyte was prepared and evaluated in the same manner as in Example 1, except that each raw material powder of LiCl, YCl3, and ZrCl4 was weighed so that the molar ratio of LiCl:YCl3:ZrCl4 was 2.5:0.5:0.5.

[0089] result

[0090] Table 1 shows the composition and measurement results of the solid electrolytes prepared in Examples 1 to 15. In addition, the compositional formulas of Examples 1 to 6 are Li 6-(4+a-b)(1+c) (M α (1-a-b) M β a M γ b ) 1+c Cl 6-2d-e-f O d F eBr f To verify that the equations (where a > 0, b > 0, a + b < 1, -0.2 ≤ c ≤ 0.2, 0 ≤ d < 3, 0 ≤ e < 6, and 0 ≤ f < 6) are satisfied, Table 2 shows the composition formula and each coefficient applied to the above general formula.

[0091]

[0092]

[0093] From the results shown in Table 1, the following can be seen. From the comparison of Examples 1 and 2 (containing Br) and Reference Example 10 (not containing Br), Examples 3 and 4 (containing Br) and Reference Example 11 (not containing Br), Example 5 (containing Br) and Reference Example 12 (not containing Br), and Example 6 (containing Br) and Reference Example 13 (not containing Br), in which the composition ratios other than Cl and Br are common among the comparison subjects, it can be seen that by adding Br, high initial conductivity is exhibited, and that conductivity can be maintained at a high retention rate (although it decreases to some extent) even after exposure to a dry room controlled to a dew point of -40°C for 16 hours, and furthermore, the conductivity that decreased due to the exposure can be significantly recovered by heat treatment.

[0094] In this regard, Li according to the prior art as disclosed in Patent Document 1 x (Y,Zr)Cl y Br zRegarding the compositional system, from a comparison of Comparative Examples 7 to 9 (containing Br) and Reference Example 14 (not containing Br), in which the compositional ratios other than Cl and Br are common, it was observed that the addition of Br improved the initial conductivity, but after exposure for 16 hours in a dry room controlled to a dew point of -40°C, the conductivity decreased drastically, and furthermore, the conductivity reduced by the exposure could not be recovered by heat treatment. From these results, it can be said that the effect of the solid electrolyte according to the present invention is unexpectedly excellent.

Claims

Claim 1 Li, M α , M β , M γ As a solid electrolyte containing , Cl and Br, M α is at least one element selected from the group consisting of Zr and Hf, and M β is at least one element selected from the group consisting of Ta, Nb, and Mo, and M γ A solid electrolyte that is at least one element selected from the group consisting of Gd, Yb, Dy, Er, Ho, Eu, Sc, and Al. Claim 2 In paragraph 1, M α is a solid electrolyte containing Zr. Claim 3 In paragraph 1 or 2, M β is a solid electrolyte containing Ta. Claim 4 In paragraph 1 or 2, M γ A solid electrolyte comprising at least one element selected from the group consisting of Gd, Yb, and Er. Claim 5 In Paragraph 1 or 2, the following composition formula: Li 6-(4+a-b)(1+c) (M α (1-a-b) M β a M γ b ) 1+c Cl 6-2d-e-f O d F e Br f A solid electrolyte represented as such, comprising a composition satisfying 0<a, 0<b, a+b<1, -0.2≤c≤0.2, 0≤d<3, 0≤e<6 and 0<f<6. Claim 6 A lithium-ion battery comprising the solid electrolyte described in paragraph 1 or 2.

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