Oxide, method for preparing the same, solid electrolyte including the oxide, and electrochemical device including the oxide

Abstract

The present invention relates to an oxide, a method for preparing the same, a solid electrolyte including the oxide, and an electrochemical device including the oxide. The oxide includes a compound represented by Formula 1, a compound represented by Formula 2, or a combination thereof, wherein, in Formula 1, M is an element having an oxidation number of 5+ or 6+, Q is an element having an oxidation number of 4+, X is a halogen atom, a pseudohalogen, or a combination thereof, 0 ≤ x < 0.6, 0 ≤ y < 1, and 0 ≤ z < 1, where x and y are not simultaneously 0, and wherein, in Formula 2, M is an element having an oxidation number of 5+ or 6+, Q is an element having an oxidation number of 4+, X is a halogen atom, a pseudohalogen, or a combination thereof, 0 ≤ x < 0.6, 0 ≤ y < 1, and 0 ≤ z < 1, where x and y are not simultaneously 0, and wherein in Formulas 1 and 2, M, Q, x, y, and z are independently selected. Formula 1 Li 1‑x+y‑z Ta 2‑x M x P 1‑y Q y O 8‑z X z Formula 2 Li 1‑x+y Ta 2‑ x M x P 1‑y Q y O8·zLiX.

Description

[0001] Cross - reference to related applications

[0002] This application claims the priority and benefit of, and all rights arising from, U.S. Patent Application No. 16 / 914,859, filed on June 29, 2020, the content of which is incorporated herein by reference in its entirety. Technical field

[0003] The present disclosure relates to oxides, methods of preparing the oxides, and solid electrolytes and electrochemical devices each including the oxides. Background art

[0004] Lithium secondary batteries have high electrochemical capacity, high working potential, and excellent charge and discharge cycle characteristics, and thus there is an increasing use of such batteries in portable information terminals, portable electronic devices, small household power storage devices, motorcycles, electric vehicles, and hybrid electric vehicles. With the expansion of the use of lithium secondary batteries, improved safety and high performance are desired.

[0005] Because lithium secondary batteries of the prior art use liquid electrolytes, ignition may occur when exposed to moisture in the air, which raises safety concerns. Due to the use of lithium secondary batteries in electric vehicles, such safety concerns are becoming more prominent. Therefore, in recent years, there has been active research on all - solid - state secondary batteries using solid electrolytes including inorganic materials to improve safety. All - solid - state secondary batteries have attracted attention as next - generation secondary batteries in terms of safety, high energy density, high power output, long life, simplification of manufacturing processes, larger battery size, compact size, and lower cost.

[0006] However, there is still a need for improved solid electrolytes that exhibit high ionic conductivity at room temperature. Summary of the invention

[0007] Provide oxides having high ionic conductivity at room temperature and improved lithium stability.

[0008] Provide a method of preparing the oxides.

[0009] Provide a solid electrolyte including the oxides.

[0010] Provide an electrochemical device including the oxides.

[0011] Additional aspects will be set forth in part in the following description and in part will be apparent from the description.

[0012] According to one aspect, there is provided an oxide including a compound represented by Formula 1, a compound represented by Formula 2, or a combination thereof:

[0013] Formula 1

[0014] Li 1-x+y-z Ta 2-x M x P 1-y Q y O 8-z X z

[0015] wherein, in Formula 1,

[0016] M is an element with an oxidation number of 5+ or 6+;

[0017] Q is an element with an oxidation number of 4+;

[0018] X is a halogen atom, pseudohalogen, or a combination thereof;

[0019] 0 ≤ x < 0.6, 0 ≤ y < 1, and 0 ≤ z < 1, where x and y are not both 0;

[0020] Formula 2

[0021] Li 1-x+y Ta 2-x M x P 1-y Q y O 8 ·zLiX

[0022] wherein, in Formula 2,

[0023] M is an element with an oxidation number of 5+ or 6+;

[0024] Q is an element with an oxidation number of 4+;

[0025] X is a halogen atom, pseudohalogen, or a combination thereof;

[0026] 0 ≤ x < 0.6, 0 ≤ y < 1, and 0 ≤ z < 1, where x and y are not both 0, and where in Formulas 1 and 2, M, Q, x, y, and z are independently selected.

[0027] According to one aspect, a method for preparing the oxide includes:

[0028] contacting a lithium precursor, a tantalum precursor, an M precursor, a Q precursor, a phosphorus precursor, and optionally an X precursor to obtain a precursor mixture; and

[0029] thermally treating the precursor mixture in an oxidizing gas atmosphere to prepare the oxide,

[0030] wherein the oxide is a compound represented by Formula 1, a compound represented by Formula 2, or a combination thereof

[0031] Formula 1

[0032] Li 1-x+y-z Ta 2-x M x P 1-y Q y O 8-z X z

[0033] Among them, in Formula 1,

[0034] M is an element with an oxidation number of 5+ or 6+,

[0035] Q is an element with an oxidation number of 4+,

[0036] X is a halogen atom, pseudohalogen, or a combination thereof,

[0037] 0≤x<0.6, 0≤y<1, and 0≤z<1, where x and y are not both 0,

[0038] Formula 2

[0039] Li 1-x+y Ta 2-x M x P 1-y Q y O 8 ·zLiX

[0040] Among them, in Formula 2,

[0041] M is an element with an oxidation number of 5+ or 6+,

[0042] Q is an element with an oxidation number of 4+,

[0043] X is a halogen atom, pseudohalogen, or a combination thereof,

[0044] 0≤x<0.6, 0≤y<1, and 0≤z<1, where x and y are not both 0.

[0045] According to one aspect, a solid electrolyte is provided, which includes the oxide and a binder.

[0046] According to one aspect, an electrochemical device is provided, which includes a positive electrode, a negative electrode, and a solid electrolyte disposed between the positive electrode and the negative electrode, wherein at least one of the positive electrode, the negative electrode, or the solid electrolyte includes the oxide.

[0047] In an embodiment, the electrochemical device may be an electrochemical cell. Description of the Drawings

[0048] The above and other aspects, features, and advantages of some embodiments of the present disclosure will become more apparent from the following description taken in conjunction with the accompanying drawings, in which:

[0049] Figure 1 Graph of the intensity in arbitrary units (a.u.) versus the diffraction angle (°, 2θ) of the oxides prepared in Example 5, Example 6, Example 8, Example 9, Comparative Example 1, and Comparative Example 2 when analyzed by X-ray diffraction using Cu Kα radiation;

[0050] Figures 2A to 2D Graphs of the diffusivity (square centimeters per second, (cm 2 / s)) versus the temperature (1000 / T (K -1 )) of the oxides of Example 9, Example 10, Comparative Example 1, and Comparative Example 2, respectively, and each is an Arrhenius plot for illustrating the diffusion of lithium ions before and after introducing a dopant into each oxide;

[0051] Figures 3A to 3C Graphs of the mean square displacement versus the time step (picoseconds (ps)) of the oxides of Example 11 and 9 and Comparative Example 1, respectively, and illustrate the diffusion of Li ions before and after introducing a dopant into each oxide;

[0052] Figure 4A Graph of the imaginary impedance (Z 虚 / Ω) versus the real impedance (Z 实 / Ω) and illustrates the ionic conductivity characteristics of the oxides of Example 1, 2, 4, 5, 6, 8, and 9 and Comparative Example 1 and 2 when analyzed using electrochemical impedance spectroscopy;

[0053] Figure 4B Graph of the imaginary impedance (Z 虚 / Ω) versus the real impedance (Z 实 / Ω) and illustrates Figure 4A An enlarged view of a part of;

[0054] Figure 5 Graph of the conductivity (lnσ, Siemens per centimeter (S / cm)) versus the temperature (1000 / K (K -1 )) and shows the activation energy of the oxide of Example 1 and the oxides of Comparative Example 1 and 2;

[0055] Figure 6 Graph of the imaginary impedance (Z 虚 / Ω) versus the real impedance (Z 实 / Ω) and shows the lithium stability of lithium symmetric cells containing the oxides of Example 1, Example 5, and Comparative Example 1, respectively;

[0056] Figure 7A An image showing the state change of the lithium symmetric cell using the oxide of Example 1 after being placed for 3 days;

[0057] Figure 7B An image showing the state change of the lithium symmetric cell using the oxide of Comparative Example 1 after being placed for 3 days;

[0058] Figure 8A and 8B are scanning electron microscope (SEM) images of the oxides of Example 1 and Example 2, respectively;

[0059] Figure 9A and 9B are SEM images of the oxides of Example 5 and Example 6, respectively; and

[0060] Figures 10 to 12 is a cross-sectional view illustrating the structure of the all-solid-state battery. Detailed Description

[0061] The present invention will now be described more fully hereinafter with reference to the accompanying drawings in which various embodiments are shown. However, the present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like reference numerals always refer to like elements.

[0062] It will be understood that when an element is referred to as being "on" another element, it can be directly on the other element or intervening elements may be present therebetween. In contrast, when an element is referred to as being "directly on" another element, there are no intervening elements.

[0063] It will be understood that although the terms "first", "second", "third", etc. may be used herein to describe various elements, components, regions, layers and / or portions, these elements, components, regions, layers and / or portions should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or portion from another element, component, region, layer or portion. Thus, without departing from the teachings herein, the "first element", "component", "region", "layer" or "portion" discussed below may be referred to as a second element, component, region, layer or portion.

[0064] The terms used in this document are for the purpose of describing specific embodiments only and are not intended to be limiting. As used herein, the indefinite articles "a", "an", the definite article "the", and "at least one" do not denote a limitation of quantity and are intended to include both the singular and the plural, unless the context clearly indicates otherwise. For example, "an element" has the same meaning as "at least one element", unless the context clearly indicates otherwise. "At least one" will not be construed as limiting "one". "Or" means "and / or". As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items. It will be further understood that the terms "comprising" or "including", when used in this specification, indicate the presence of the stated features, regions, wholes, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more additional features, regions, wholes, steps, operations, elements, components, and / or their groups.

[0065] In addition, relative terms such as "lower" or "bottom" and "upper" or "top" may be used herein to describe the relationship of one element to another as shown in the figures. It will be understood that relative terms are also intended to include different orientations of the device in addition to the orientation depicted in the figures. For example, if the device in one of the figures is flipped over, an element described as on the "lower" side of other elements will then be oriented on the "upper" side of said other elements. Thus, depending on the specific orientation of the figure, the exemplary term "lower" may include both the "lower" and "upper" orientations. Similarly, if the device in one of the figures is flipped over, an element described as "beneath" or "under" other elements will then be oriented "above" said other elements. Thus, the exemplary terms "beneath" or "under" may include both the "above" and "beneath" orientations.

[0066] As used herein, "about" or "approximately" includes the stated value and means within an acceptable deviation range for the specific value as determined by one of ordinary skill in the art in view of the measurements discussed and the errors associated with the measurement of a particular quantity (i.e., the limitations of the measurement system). For example, "about" may mean within one or more standard deviations of the stated value, or within ±30%, 20%, 10%, or 5%.

[0067] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and this disclosure, and will not be interpreted in an idealized or overly formal sense unless clearly so defined herein.

[0068] Exemplary embodiments are described herein with reference to cross-sectional views that are schematic illustrations of idealized embodiments. As such, deviations from the shapes of the figures can be expected as a result of, for example, manufacturing techniques and / or tolerances. Accordingly, the embodiments described herein should not be construed as limited to the specific shapes of regions as shown herein, but include deviations in shape resulting from, for example, manufacturing. For example, regions illustrated or described as flat may typically have rough and / or non-linear features. Additionally, sharp corners shown may be rounded. Thus, the regions shown in the figures are schematic in nature, and their shapes are not intended to illustrate the exact shape of the regions and are not intended to limit the scope of the claims.

[0069] Embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings, where like reference numerals always refer to like elements. In this regard, the present embodiments may have different forms and should not be construed as limited to the description set forth herein. Accordingly, the embodiments are described below only by way of example with reference to the accompanying drawings. As used herein, the term “and / or” includes any and all combinations of one or more of the associated listed items. The phrase such as “at least one (kind) of” when before or after a list of elements modifies the entire list of elements and not individual elements of the list.

[0070] As used herein, “pseudohalogen” includes two or more electronegative atoms that, like free (uncombined) halogen, can provide anions similar to halide ions. Examples of pseudohalogens are cyanide (CN), cyanate (OCN), thiocyanate (SCN), azide (N 3 ), or combinations thereof.

[0071] As used herein, if the particles are spherical, the term “particle size” may refer to the diameter, or if the particles are non-spherical, it may refer to the length of the major axis. The particle size can be determined by light scattering or by scanning electron microscopy (SEM).

[0072] The all-solid-state secondary battery includes a positive electrode, a solid electrolyte, and a negative electrode, wherein the solid electrolyte has high ionic conductivity and low electronic conductivity. The solid electrolytes for all-solid-state secondary batteries include sulfide-based solid electrolytes and oxide-based solid electrolytes. Among these solid electrolytes, oxide-based solid electrolytes do not produce toxic substances during preparation and have excellent stability, but are limited because they have lower room-temperature ionic conductivity compared to sulfide-based solid electrolytes.

[0073] Hereinafter, embodiments of the oxide, its preparation method, and the solid electrolyte and electrochemical device each including the oxide will be described in more detail.

[0074] The oxide includes a compound represented by Formula 1, a compound represented by Formula 2, or a combination thereof.

[0075] Formula 1

[0076] Li 1-x+y-z Ta 2-x M x P 1-y Q y O 8-z X z

[0077] In Formula 1, M is an element with an oxidation number of 5+ or 6+, Q is an element with an oxidation number of 4+, X is a halogen atom, pseudohalogen, or a combination thereof, and 0 ≤ x < 0.6, 0 ≤ y < 1, and 0 ≤ z < 1, where x and y are not both 0.

[0078] Formula 2

[0079] Li 1-x+y Ta 2-x M x P 1-y Q y O 8 ·zLiX

[0080] In Formula 2, M is an element with an oxidation number of 5+ or 6+, Q is an element with an oxidation number of 4+, X is a halogen atom, pseudohalogen, or a combination thereof, and 0 ≤ x < 0.6, 0 ≤ y < 1, and 0 ≤ z < 1, where x and y are not both 0.

[0081] In Formulas 1 and 2, M, Q, x, y, and z are independently selected. In Formulas 1 and 2, each M is independently an element for substituting tantalum with an oxidation number of 5+, and may have, for example, an oxidation number of 5+ or 6+ and a coordination number of 6.

[0082] In Formulas 1 and 2, each Q may independently have, for example, a coordination number of 4.

[0083] The compound of Formula 1 may have the following form: where X in Formula 1 substitutes for oxygen and is present at the oxygen position in the crystal structure of the compound. The compound of Formula 2 may have the following complex form: where LiX such as LiCl is added as an additive to Li 1-x+y Ta 2-x M x P 1-y Q y O 8 。

[0084] As used herein, with respect to the expression "a compound represented by Formula 1, a compound represented by Formula 2, or a combination thereof", the expression "a combination thereof" may refer to, for example, a compound represented by Formula 1 alone, a compound represented by Formula 2 alone, a mixture of a compound represented by Formula 1 and a compound represented by Formula 2, or a complex of a compound represented by Formula 1 and a compound represented by Formula 2.

[0085] In Formulas 1 and 2, each M may independently be, for example, tungsten (W), tellurium (Te), selenium (Se), niobium (Nb), vanadium (V), antimony (Sb), chromium (Cr), molybdenum (Mo), neodymium (Nd), technetium (Tc), bismuth (Bi), or a combination thereof.

[0086] In Formulas 1 and 2, x may be, for example, greater than 0 and about 0.5 or less, such as greater than 0 and less than about 0.5, such as about 0.1 or greater and less than 0.5, or such as about 0.1 to about 0.2.

[0087] In Formula 1, Q may be an element having an oxidation number of 4+. In one aspect, Q may substitute for phosphorus (P) and may be present at the P position in the crystal structure of the compound. In one aspect, Q may be, for example, silicon (Si), tin (Sn), titanium (Ti), germanium (Ge), niobium (Nb), selenium (Se), palladium (Pd), rhodium (Rh), cobalt (Co), molybdenum (Mo), chromium (Cr), ruthenium (Ru), nickel (Ni), manganese (Mn), vanadium (V), molybdenum (Mo), or a combination thereof. Silicon (Si), tin (Sn), titanium (Ti), germanium (Ge), and niobium (Nb) may have an oxidation number of 4+, and selenium (Se) may have an oxidation number of 4+ or 6+. In Formula 1, y may be about 0 and about 0.5 or less, such as about 0.1 to about 0.5, or such as about 0.1 to about 0.2. Q in Formulas 1 and 2 may be independently selected.

[0088] In Formulas 1 and 2, X may substitute for oxygen, and in the crystal structure of the compound of Formula 1 or 2, X may be present at the oxygen position. In one aspect, X may be, for example, chlorine (Cl), bromine (Br), fluorine (F), cyanide (CN), cyanate (OCN), thiocyanate (SCN), azide (N 3 )), or a combination thereof. In Formulas 1 and 2, z may be greater than 0 and about 0.9 or less, such as about 0.01 to about 0.8, such as about 0.01 to about 0.7, such as about 0.01 to about 0.6, such as about 0.01 to about 0.5, such as about 0.01 to about 0.2, or such as about 0.05 to about 0.15. X in Formulas 1 and 2 may be independently selected.

[0089] As a lithium phosphate-based lithium ion conductor, LiTa 2 PO 8 has been considered.

[0090] However, LiTa 2 PO 8 is not satisfactory in terms of room temperature ionic conductivity or lithium stability. Therefore, compounds with improved ionic conductivity and lithium stability are desired.

[0091] In this regard, the present inventors have surprisingly found an oxide having improved ionic conductivity at room temperature and improved lithium stability. The oxide can be provided as follows: by introducing an M element having an oxidation number of 5+ or 6+ at the tantalum (Ta) octahedral position of LiTa 2 PO 8 , by introducing an element having an oxidation number of 4+ and a coordination number of 4 at the phosphorus (P) tetrahedral position, or by simultaneously introducing an M element having an oxidation number of 5+ or 6+ and an element having an oxidation number of 4+ and a coordination number of 4 at the phosphorus (P) tetrahedral position. The oxide can be a lithium ion conductor.

[0092] In addition, a halogen such as chlorine (Cl) or fluorine (F), and / or a pseudohalogen can be introduced into the oxygen (O) position of the oxide. Although not wishing to be bound by theory, it is understood that when the oxide in which a halogen and / or a pseudohalogen is introduced is used in the preparation of a solid electrolyte, a passivation layer including fluorine (F) can be formed between the lithium metal electrode and the solid electrolyte including the oxide. When the passivation layer is provided, the solid electrolyte can have improved lithium stability and, due to the presence of LiF or LiCl at the grain boundary region, can have improved Li ion conductivity at the grain boundaries of the solid electrolyte.

[0093] The oxide according to an embodiment can be a lithium ion conductor and, like LiTa 2 PO 8 , can have: a monoclinic structure, for example, having a space group of C2 / c; or a pseudo-monoclinic structure; or a structure in which two [MO 6 octahedra and one [PO 4 tetrahedron share corners.

[0094] The oxide can be electrically neutral. To satisfy the electrical neutrality of the oxide, Li + vacancies can be introduced. Here, the introduced vacancies can be used as Li + hopping sites to reduce the activation energy required for Li migration.

[0095] In one aspect, when Q is Si, the compound represented by Formula 1 can be the compound represented by Formula 3.

[0096] Formula 3

[0097] Li 1-x+y-z Ta 2-x Wx P 1-y Si y O 8-z X z

[0098] In Formula 3, X is a halogen, a pseudohalogen, or a combination thereof, and

[0099] 0 ≤ x < 0.6, 0 ≤ y < 1, and 0 ≤ z < 1, where x and y are not both 0.

[0100] In Formula 3, x can be, for example, greater than 0 and about 0.5 or less, such as greater than 0 and less than about 0.5, such as about 0.1 or greater and less than about 0.5, or such as about 0.1 to about 0.2; y can be greater than 0 and about 0.5 or less, such as about 0.1 to about 0.5, or such as about 0.1 to about 0.2; and z can be greater than 0 and about 0.9 or less, such as about 0.01 to about 0.8, such as about 0.01 to about 0.7, such as about 0.01 to about 0.6, such as about 0.01 to about 0.5, such as about 0.01 to about 0.2, or such as about 0.05 to about 0.15.

[0101] In Formula 3, tungsten (W 6+ ) can replace tantalum and be present at the tantalum position in the crystal structure of the compound. In this regard, since the radius of tungsten (W 6+ ) is and that of Ta 5+ is so this replacement can be easy.

[0102] In addition, when Si with an oxidation number of 4 + is introduced into the [PO 4 tetrahedron in place of P with an oxidation number of 5+, excess Li + ions can be introduced to provide the electrical neutrality of the compound, such that the amount of mobile Li + ions can be increased, resulting in increased lithium ion conductivity.

[0103] When some oxygen positions are replaced by X anions, a passivation layer including elements such as F or Cl can be formed, so that improved lithium stability and increased Li ion conductivity at grain boundaries due to the presence of LiF or LiCl at grain boundaries can occur.

[0104] In the compound of Formula 2, M can be W and Q can be Si, and the compound represented by Formula 2 can be, for example, the compound represented by Formula 4.

[0105] Formula 4

[0106] Li 1-x+y Ta 2-x Wx P 1-y Si y O 8 ·zLiX

[0107] In Formula 4, X can be a halogen atom, a pseudohalogen, or a combination thereof, and 0 ≤ x < 0.6, 0 ≤ y < 1, and 0 ≤ z < 1, where x and y are not both 0.

[0108] In Formula 4, x can be, for example, greater than 0 and about 0.5 or less, such as greater than 0 and about 0.5 or less, such as about 0.1 or greater and less than about 0.5, or such as about 0.1 to about 0.2;

[0109] In Formula 4, y can be greater than 0 and about 0.5 or less, such as about 0.1 to about 0.5, or such as about 0.1 to about 0.2; and z can be greater than 0 and about 0.9 or less, such as about 0.01 to about 0.8, such as about 0.01 to about 0.7, such as about 0.01 to about 0.6, such as about 0.01 to about 0.5, such as about 0.01 to about 0.2, or such as about 0.05 to about 0.15.

[0110] The compound represented by Formula 1, the compound represented by Formula 2, or a combination thereof can be, for example, the compound represented by Formula 3, the compound represented by Formula 4, or a combination thereof.

[0111] In an embodiment, the oxide can be, for example, Li 0.9 Ta 1.9 W 0.1 PO 8 , Li 0.8 Ta 1.8 W 0.2 PO 8 , Li 0.7 Ta 1.7 W 0.3 PO 8 , Li 0.75 Ta 1.75 W 0.25 PO 8 , Li 0.6 Ta 1.6 W 0.4 PO 8 , Li 0.5 Ta 1.5 W 0.5 PO 8 ;

[0112] Li 0.9 Ta 1.9 Te 0.1 PO 8 , Li 0.8 Ta 1.8 Te0.2 PO 8 ,Li 0.75 Ta 1.75 Te 0.25 PO 8 ,Li 0.7 Ta 1.7 Te 0.3 PO 8 ,Li 0.6 Ta 1.6 Te 0.4 PO 8 ,Li 0.6 Ta 1.5 Te 0.5 PO 8 ;

[0113] Li 0.9 Ta 1.9 Se 0.1 PO 8 ,Li 0.8 Ta 1.8 Se 0.2 PO 8 ,Li 0.75 Ta 1.75 Se 0.25 PO 8 ,Li 0.7 Ta 1.7 Se 0.3 PO 8 ,Li 0.6 Ta 1.6 Se 0.4 PO 8 ,Li 0.5 Ta 1.5 Se 0.5 PO 8 ;

[0114] Li 0.8 Ta 1.9 W 0.1 PO 7.9 Cl 0.1 (Li 0.9 Ta 1.9 W 0.1 PO 8 ·0.1LiCl),Li 0.7 Ta 1.8 W 0.2 PO 7.9 Cl 0.1 (Li 0.8 Ta 1.8 W 0.2 PO 8 ·0.1LiCl),Li 0.65 Ta1.75 W 0.25 PO 7.9 Cl 0.1 ,

[0115] Li 0.6 Ta 1.7 W 0.3 PO 7.9 Cl 0.1 ,Li 0.5 Ta 1.6 W 0.4 PO 7.9 Cl 0.1 ,Li 0.4 Ta 1.5 W 0.5 P 7.9 O 7.9 Cl 0.1 ;

[0116] Li 0.85 Ta 1.9 W 0.1 PO 7.95 Cl 0.05 ,Li 0.75 Ta 1.8 W 0.2 PO 7.95 Cl 0.05 ,Li 0.7 Ta 1.75 W 0.25 PO 7.95 Cl 0.05 ,Li 0.65 Ta 1.7 W 0.3 PO 7.95 Cl 0.05 ,Li 0.55 Ta 1.6 W 0.4 PO 7.95 Cl 0.05 ,Li 0.45 Ta 1.5 W 0.5 PO 7.95 Cl 0.05 ;

[0117] Li 0.8 Ta 1.9 Nb 0.1 PO 7.9 Cl 0.1 ,Li 0.7 Ta 1.8 Nb 0.2 PO 7.9 Cl 0.1 ,Li 0.65 Ta1.75 Nb 0.25 PO 7.9 Cl 0.1 ,Li 0.6 Ta 1.7 Nb 0.3 PO 7.9 Cl 0.1 ,Li 0.5 Ta 1.6 Nb 0.4 PO 7.9 Cl 0.1 ,Li 0.4 Ta 1.5 Nb 0.5 P 7.9 Cl 0.1 ;

[0118] Li 0.85 Ta 1.9 Nb 0.1 PO 7.95 Cl 0.05 ,Li 0.75 Ta 1.8 Nb 0.2 PO 7.95 Cl 0.05 ,Li 0.7 Ta 1.75 Nb 0.25 PO 7.95 Cl 0.05 ,Li 0.65 Ta 1.7 Nb 0.3 PO 7.95 Cl 0.05 ,Li 0.55 Ta 1.6 Nb 0.4 PO 7.95 Cl 0.05 ,Li 0.45 Ta 1.5 Nb 0.5 PO 7.95 Cl 0.05 ;

[0119] Li 1.1 Ta 2 P 0.9 Si 0.1 O 8 ,Li 1.2 Ta 2 P 0.8 Si 0.2 O 8 ,Li 1.3 Ta 2 P 0.7 Si 0.3 O8 ,Li 1.4 Ta 2 P 0.6 Si 0.4 O 8 ,Li 1.5 Ta 2 P 0.5 Si 0.5 O 8 ;

[0120] Li 1 Ta 2 P 0.9 Si 0.1 PO 7.9 Cl 0.1 ,Li 1.1 Ta 2 P 0.8 Si 0.2 PO 7.9 Cl 0.1 ,Li 1.2 Ta 2 P 0.7 Si 0.3 PO 7.9 Cl 0.1 ,Li 1.3 Ta 2 P 0.6 Si 0.4 PO 7.9 Cl 0.1 ,Li 1.4 Ta 2 P 0.5 Si 0.5 PO 7.9 Cl 0.1 ;

[0121] Li 1.05 Ta 2 P 0.9 Si 0.1 PO 7.95 Cl 0.05 ,Li 1.15 Ta 2 P 0.8 Si 0.2 PO 7.95 Cl 0.05 ,Li 1.25 Ta 2 P 0.7 Si 0.3 PO 7.95 Cl 0.05 ,Li 1.35 Ta 2 P 0.6 Si 0.4 PO7.95 Cl 0.05 ,Li 1.45 Ta 2 P 0.5 Si 0.5 PO 7.95 Cl 0.05 ;

[0122] Li 1.1 Ta 2 P 0.9 Sn 0.1 O 8 ,Li 1.2 Ta 2 P 0.8 Sn 0.2 O 8 ,Li 1.3 Ta 2 P 0.7 Sn 0.3 O 8 ,Li 1.4 Ta 2 P 0.6 Sn 0.4 O 8 ,Li 1.5 Ta 2 P 0.5 Sn 0.5 O 8 ;

[0123] Li 1.0 Ta 2 P 0.9 Sn 0.1 O 7.9 Cl 0.1 ,Li 1.1 Ta 2 P 0.8 Sn 0.2 O 7.9 Cl 0.1 ,Li 1.2 Ta 2 P 0.7 Sn 0.3 O 7.9 Cl 0.1 ,Li 1.3 Ta 2 P 0.6 Sn 0.4 O 7.9 Cl 0.1 ,Li 1.4 Ta 2 P 0.5 Sn 0.5 O 7.9 Cl 0.1 ;

[0124] Li 1.05 Ta 2 P 0.9 Sn 0.1 O 7.95 Cl 0.05 ,Li 1.15 Ta 2 P 0.8 Sn 0.2 O 7.95 Cl 0.05 ,Li 1.25 Ta 2 P 0.7 Sn 0.3 O 7.95 Cl 0.05 ,Li 1.35 Ta 2 P 0.6 Sn 0.4 O 7.95 Cl 0.05 ,Li 1.45 Ta 2 P 0.5 Sn 0.5 O 7.95 Cl 0.05 ;

[0125] Li 1.0 Ta 1.9 W 0.1 P 0.9 Si 0.1 O 8 ,Li 0.9 Ta 1.8 W 0.2 P 0.9 Si 0.1 O 8 ,Li 0.8 Ta 1.7 W 0.3 P 0.9 Si 0.1 O 8 ,Li 0.85 Ta 1.75 W 0.25 P 0.9 Si 0.1 O 8 ,Li 0.7 Ta 1.6 W 0.4 P 0.9 Si 0.1 O 8 ,Li 0.6 Ta 1.5 W 0.5 P 0.9 Si 0.1 O8 ;

[0126] Li 1.1 Ta 1.9 W 0.1 P 0.8 Si 0.2 O 8 ,Li 1.0 Ta 1.8 W 0.2 P 0.8 Si 0.2 O 8 ,Li 0.9 Ta 1.7 W 0.3 P 0.8 Si 0.2 O 8 ,Li 0.95 Ta 1.75 W 0.25 P 0.8 Si 0.2 O 8 ,Li 0.8 Ta 1.6 W 0.4 P 0.8 Si 0.2 O 8 ,Li 0.7 Ta 1.5 W 0.5 P 0.8 Si 0.2 O 8 ;

[0127] Li 1.0 Ta 1.9 Nb 0.1 P 0.9 Si 0.1 O 8 ,Li 0.9 Ta 1.8 Nb 0.2 P 0.9 Si 0.1 O 8 ,Li 0.8 Ta 1.7 Nb 0.3 P 0.9 Si 0.1 O 8 ,Li 0.85 Ta 1.75 Nb 0.25 P 0.9 Si 0.1 O 8 ,Li 0.7 Ta 1.6 Nb 0.4 P0.9 Si 0.1 O 8 ,Li 0.6 Ta 1.5 Nb 0.5 P 0.9 Si 0.1 O 8 ;

[0128] Li 1.1 Ta 1.9 Nb 0.1 P 0.8 Si 0.2 O 8 ,Li 1.0 Ta 1.8 Nb 0.2 P 0.8 Si 0.2 O 8 ,Li 0.9 Ta 1.7 Nb 0.3 P 0.8 Si 0.2 O 8 ,Li 0.95 Ta 1.75 Nb 0.25 P 0.8 Si 0.2 O 8 ,Li 0.8 Ta 1.6 Nb 0.4 P 0.8 Si 0.2 O 8 ,Li 0.7 Ta 1.5 Nb 0.5 P 0.8 Si 0.2 O 8 ;Li 1.05 Ta 2 P 0.9 Si 0.1 O 7.95 Cl 0.05 ,Li 1.0 Ta 2 P 0.9 Si 0.1 O 7.9 Cl 0.1 ,Li 0.9 Ta 1.75 W 0.25 PO 8 , or a combination thereof.

[0129] In an embodiment, the ionic conductivity of the oxide may have improved isotropy.

[0130] In many lithium ion conductors, the ionic conductivity in the z-axis direction is very fast compared to the ionic conductivity in the x-axis and y-axis directions (c(z-axis) >> b(y-axis) and a(x-axis)).

[0131] In the oxide according to the embodiment, the ionic conduction paths that are only faster in c(z-axis) among other lithium ion conductors and the anisotropy of the ionic conductivity can be relaxed to the level of c(z-axis) > b(y-axis) > a(x-axis). That is, due to the reduction or relaxation of the anisotropy, the isotropy of the ionic conductivity can be improved.

[0132] As used herein, the expression "isotropy of ionic conductivity" means that the diffusion paths of lithium ions decrease in the order of the c(z-axis) direction, the b(y-axis) direction, and the a(x-axis) direction, so that the difference between the directions decreases, thereby reducing the anisotropy of the ionic conductivity and improving the isotropy of the ionic conductivity.

[0133] The improved isotropy of the ionic conductivity of the oxide according to the embodiment can be shown by the results of calculating the diffusion rate (D, unit: cm 2 / s) and the mean square displacement (MSD) of the diffusion of lithium (Li) ions before and after introducing dopants into the oxide using the nudged elastic band (NEB) model. According to the calculation, the oxide shows a total increase in the lithium ion conductivity value due to the reduction of the anisotropy of the diffusion path (the mobility increases on the a-axis and b-axis), indicating that the oxide exhibits an isotropic ionic conductivity characteristic.

[0134] In the embodiment, the oxide may have a monoclinic structure with a space group of C2 / c. In the embodiment, when measured by X-ray diffraction spectrometry using Cu K α radiation, the oxide may exhibit peaks at diffraction angles (2θ) of 17.5° ± 0.5°, 24.8° ± 0.5°, 24.9° ± 0.5°, 25.4° ± 0.5°, and 27.8° ± 0.5°, for example, 17.5° ± 0.2°, 24.8° ± 0.2°, 24.9° ± 0.2°, 25.4° ± 0.2°, and 27.8° ± 0.2°.

[0135] Compared with an oxide that does not contain LiX such as LiCl (where z = 0 in Formula 1), an oxide that contains LiX such as LiCl as in Formula 2 may exhibit shifted X-ray diffraction peak characteristics. From the shifted X-ray diffraction peak characteristics, it can be understood that X in LiX substitutes some oxygen (O) positions.

[0136] In an embodiment, the oxide as the lithium conductor may have about 1×10 -2 mS / cm or greater, for example about 1.0×10 -1 S / cm or greater, for example about 2.4×10 -1 S / cm or greater, for example about 2.6×10 -1 S / cm or greater, or for example about 2.8×10 -1 S / cm or greater ionic conductivity at room temperature (25 °C). The ionic conductivity may be, for example, about 1×10 -2 mS / cm to about 10 mS / cm, or about 5×10 -2 mS / cm to about 1 mS / cm, or about 1×10 -1 mS / cm to about 8×10 -1 mS / cm. When the oxide has an ionic conductivity at room temperature within these ranges, an electrochemical device including the oxide, such as an electrochemical cell, may have a reduced internal resistance.

[0137] The oxide may have an electronic conductivity of about 1×10 -5 mS / cm or less, for example 1×10 -6 mS / cm or less at room temperature (25 °C). The electronic conductivity may be, for example, about 1×10 -9 mS / cm to about 1×10 -5 mS / cm, or about 1×10 -8 mS / cm to about 1×10 -6 mS / cm.

[0138] When the oxide is used in a solid electrolyte according to an embodiment, the solid electrolyte has a high ionic conductivity and a low electronic conductivity at room temperature.

[0139] When the oxide according to an embodiment is used as an electrode additive, the oxide may exhibit an electronic conductivity of about 1×10 -5 mS / cm or higher compared to when used as a solid electrolyte.

[0140] The oxide according to an embodiment may be electrochemically stable, for example, at a voltage of about 2 V to about 4 V with respect to lithium metal (Li / Li + ).

[0141] In an embodiment, the oxide may have an activation energy of about 0.44 electron volts per atom (eV / atom) or less, for example about 0.41 eV / atom or less, for example about 0.37 eV / atom or less, for example about 0.35 eV / atom or less, for example about 0.32 eV / atom or less, or for example about 0.29 to about 0.41 eV / atom.

[0142] The oxide may have a grain size in the range of about 5 nm to about 500 μm. When the compound of Formula 1 includes X, the oxide may have a reduced grain size and improved stability and adhesion between the grains.

[0143] In an embodiment, the oxide may be in particulate form. In an embodiment, the oxide may have an average particle diameter of about 5 nm to about 500 μm, such as about 100 nm to about 100 μm, or such as about 1 μm to about 50 μm, and a specific surface area of about 0.01 square meters per gram (m 2 / g) to about 1000 m 2 / g, such as about 0.5 m 2 / g to about 100 m 2 / g.

[0144] According to an embodiment, a method for preparing the oxide includes:

[0145] contacting a lithium precursor, a tantalum precursor, an M precursor, a Q precursor, a phosphorus precursor, and optionally an X precursor to obtain a precursor mixture, and heat-treating the precursor mixture in an oxidizing gas atmosphere to prepare the oxide.

[0146] The precursor mixture may include a suitable solvent. Any solvent may be used as long as it can dissolve or disperse the lithium precursor, the tantalum precursor, the M precursor, the Q precursor, and the phosphorus precursor. The solvent may be, for example, acetone, ethanol, water, ethylene glycol, isopropanol, or a combination thereof. The amount of the solvent may be in the range of about 50 parts by weight to 1,000 parts by weight, such as 100 to 300 parts by weight, relative to the total weight of 100 parts by weight of the precursor mixture.

[0147] The mixing may be carried out using, for example, grinding, blending, or sputtering. The grinding may be carried out using, for example, a ball mill, a jet mill, a bead mill, a roll mill, or a planetary mill.

[0148] The heat-treatment of the mixture may be carried out at a temperature increase rate of about 1 °C / minute to 10 °C / minute and a heat-treatment temperature (T 1 ) of about 500 °C to about 1200 °C, such as about 600 °C to about 1000 °C. When the temperature increase rate in the heat-treatment step is within this range, the heat-treatment may be sufficient.

[0149] The heat-treatment may be carried out in an oxidizing gas atmosphere. The oxidizing gas atmosphere may contain, for example, air or oxygen. The heat-treatment time may vary depending on the heat-treatment temperature and may be, for example, about 1 to about 20 hours, such as about 1 to about 10 hours, or such as about 2 to about 8 hours.

[0150] The heat treatment may be performed in two steps, including a first heat treatment at a first temperature and a second heat treatment at a second temperature, wherein the second heat treatment is performed at a temperature greater than that of the first heat treatment. The first heat treatment may be performed at about 500° C. to about 1000° C., and the second heat treatment may be performed at about 600° C. to about 1200° C. When the heat treatment is performed in two steps as described above, an oxide having a high density may be obtained.

[0151] After the first heat treatment step, before the second heat treatment step, an additional step of grinding the heat treated product may be performed. Here, the grinding may be, for example, planetary grinding or manual grinding. By performing such additional grinding, the particle size of the heat treated product may be controlled. By performing grinding, the particle size of the heat treated product may be controlled, for example, to about 1 μm or less. By controlling the particle size to about 1 μm or less, the oxide finally obtained may have an improved density.

[0152] The lithium precursor may be, for example, lithium oxide, lithium carbonate, lithium chloride, lithium sulfide, lithium nitrate, lithium phosphate, lithium hydroxide, or a combination thereof.

[0153] The tantalum precursor may be, for example, tantalum hydroxide, tantalum carbonate, tantalum chloride, tantalum sulfate, tantalum nitrate, tantalum oxide, or a combination thereof.

[0154] The phosphorus precursor may be, for example, (NH 4 ) 2 HPO 4 NH 4 )H 2 PO 4 、Na 2 HPO 4 , or Na 3 PO 4 .

[0155] The M precursor may be, for example, an oxide containing the M element, a carbonate containing the M element, a chloride containing the M element, a phosphate containing the M element, a hydroxide containing the M element, a nitrate containing the M element, or a combination thereof, for example, tungsten oxide, tungsten hydroxide, tungsten chloride, tellurium oxide, tellurium hydroxide, tellurium chloride, selenium oxide, selenium hydroxide, selenium chloride, niobium oxide, niobium hydroxide, or niobium chloride.

[0156] The Q precursor may be, for example, an oxide containing a Q element, a carbonate containing a Q element, a chloride containing a Q element, a phosphate containing a Q element, a hydroxide containing a Q element, a nitrate containing a Q element, or a combination thereof, for example, silicon oxide, tin oxide, or tin chloride.

[0157] The amounts of the lithium precursor, M precursor, tantalum precursor, Q precursor, phosphorus precursor, and X precursor can be selected stoichiometrically to obtain the oxide represented by Formula 1.

[0158] Then, the heat-treated product can be pulverized to obtain a pulverized product. The pulverized product can be in the form of a powder including particles, for example. The pulverized product obtained by pulverization can have a size of about 10 μm or less. When the size of the pulverized particles is within this range, the particle size can be small enough to allow sufficient pulverization and mixing, thereby promoting the formation of a layered crystal phase.

[0159] Subsequently, the pulverized product can be heat-treated. In the heat treatment of the pulverized product, the rate of temperature increase can be about 1 °C / minute to about 10 °C / minute. The heat treatment of the pulverized product can be carried out at about 600 °C to about 1100 °C, for example, about 1000 °C to about 1100 °C. The heat treatment temperature (T 2 ) of the pulverized product can be greater than the temperature (T 1 ) of the heat treatment carried out before obtaining the pulverized product.

[0160] In an embodiment, before the heat treatment, the pulverized product can be processed into a sheet (wafer) form by pressing. When the pulverized product in sheet form is heat-treated, the diffusion distance of the material to be heat-treated can be shortened, thereby promoting the preparation of the desired oxide.

[0161] The heat treatment of the pulverized product can be carried out, for example, in an oxidizing gas atmosphere, a reducing gas atmosphere, or an inert gas atmosphere. The oxidizing gas atmosphere includes air or oxygen. The inert gas atmosphere can include an inert gas such as argon or helium. For example, the reducing gas atmosphere can include a reducing gas such as hydrogen and an inert gas such as argon or helium.

[0162] The heat treatment time of the pulverized product can vary depending on the heat treatment temperature (T 2 ) of the pulverized product, and can be, for example, about 1 to about 50 hours, or for example, about 6 to about 48 hours.

[0163] According to one aspect, there is provided an electrochemical device including the oxide. The electrochemical device can be, for example, one selected from the following: an electrochemical cell, a storage battery, a supercapacitor, a fuel cell, a sensor, or an electrochromic device.

[0164] According to one aspect, there is provided an electrochemical cell including a positive electrode, a negative electrode, and a solid electrolyte disposed between the positive electrode and the negative electrode, wherein the solid electrolyte contains the oxide. The electrochemical cell can include: a positive electrode, a negative electrode including lithium, and a solid electrolyte disposed between the positive electrode and the negative electrode, wherein the solid electrolyte contains the oxide.

[0165] The electrochemical cell may be a lithium secondary battery, a metal-air battery such as a lithium-air battery, or an all-solid-state battery. The electrochemical cell can be used in both primary and secondary batteries. The shape of the electrochemical cell is not limited. The electrochemical cell can have any shape such as, for example, coin, button, sheet, stack, cylinder, flat, or angular. The electrochemical cell according to an embodiment can be used as a medium to large-sized battery for an electric vehicle.

[0166] The electrochemical cell may be, for example, an all-solid-state battery using a deposited negative electrode. The deposited negative electrode may refer to a negative electrode that has a negative electrode coating without a negative electrode active material during the assembly of the electrochemical cell, but on which a negative electrode material such as lithium metal is deposited after the electrochemical cell is charged.

[0167] The solid electrolyte may be an electrolyte protective film, a positive electrode protective film, a negative electrode protective film, or a combination thereof.

[0168] In an embodiment, the solid electrolyte can be used as a positive electrode protective film in a battery using a sulfide-based solid electrolyte to effectively suppress the reaction between the sulfide-based solid electrolyte and the positive electrode. In an embodiment, the solid electrolyte can be used as a positive electrode coating material and a positive electrode protective film. In an embodiment, due to its high oxidation potential, the solid electrolyte can be used as a positive electrode electrolyte (cathode electrolyte), for example, as a positive electrode electrolyte of an all-solid-state battery.

[0169] In an embodiment, the electrochemical cell may be an all-solid-state battery. The all-solid-state battery may be an all-solid-state secondary battery.

[0170] Reference will be made to Figure 10 Describe the structure of the all-solid-state secondary battery 1 according to an embodiment. Referring to Figure 10 , the all-solid-state secondary battery 1 may include a positive electrode 10, a negative electrode 20, and a solid electrolyte 30 containing the oxide.

[0171] The positive electrode 10 may include a positive electrode current collector 11 and a positive electrode active material layer 12. The positive electrode current collector 11 may have a main body in the form of a plate or foil composed of, for example, indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or a combination thereof. The positive electrode current collector 11 may be omitted.

[0172] The positive electrode active material layer 12 may include a positive electrode active material and a solid electrolyte. The solid electrolyte included in the positive electrode 10 may be similar (the same) or different from the solid electrolyte included in the solid electrolyte 30.

[0173] The positive electrode active material may be a positive electrode active material capable of reversibly absorbing and desorbing lithium ions.

[0174] For example, the positive electrode active material may be obtained, for example, as follows: lithium transition metal oxides such as lithium cobalt oxide (LCO), lithium nickel oxide, lithium nickel cobalt oxide, lithium nickel cobalt aluminum oxide (NCA), lithium nickel cobalt manganese oxide (NCM), lithium manganate, or lithium iron phosphate; nickel sulfide; copper sulfide; lithium sulfide; iron oxide; or vanadium oxide. These positive electrode active materials may be used alone or in combination of at least two thereof.

[0175] The positive electrode active material may be, for example, a lithium salt of a ternary transition metal oxide such as LiNi x Co y Al z O 2 (NCA) or LiNi x Co y Mn z O 2 (NCM) (where 0 < x < 1, 0 < y < 1, 0 < z < 1, and x + y + z = 1).

[0176] The positive electrode active material may be covered with a coating layer. In an embodiment, the coating layer of the positive electrode active material may be any suitable coating layer for the positive electrode active material of an all-solid-state secondary battery. For example, the coating layer may be, for example, Li 2 O-ZrO 2 .

[0177] When the positive electrode active material is a ternary lithium transition metal oxide such as NCA or NCM and includes nickel (Ni), the all-solid-state secondary battery 1 may have an increased capacity density, and the release of metals in the positive electrode active material may be reduced in the charged state of the all-solid-state secondary battery 1. Therefore, the long-term reliability and cycle characteristics in the charged state of the all-solid-state secondary battery 1 may be improved.

[0178] The positive electrode active material may be in the form of particles having, for example, a true spherical particle shape or an ellipsoidal particle shape. The particle diameter of the positive electrode active material is not limited and may be within a suitable range for the positive electrode active material of an all-solid-state secondary battery. The amount of the positive electrode active material in the positive electrode 10 is not limited and may be within a suitable range applicable to the positive electrode active material of an all-solid-state secondary battery.

[0179] In addition to the positive electrode active material and the solid electrolyte as described above, the positive electrode 10 may further include additives such as a conductive agent, a binder, a filler, a dispersant, or an auxiliary ion conductor.

[0180] The conductive agent that can be added to the positive electrode 10 can be, for example, graphite, carbon black, acetylene black, Ketjen black, carbon fiber, or metal powder. The binder that can be added to the positive electrode 10 can be, for example, styrene-butadiene rubber (SBR), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), or polyethylene. The additives that can be added to the positive electrode 10, such as fillers, dispersants, or auxiliary ion conductors, can be any suitable materials used in the positive electrode of an all-solid-state secondary battery.

[0181] The negative electrode 20 can include a negative electrode current collector 21 and a negative electrode coating-free layer 22. Although the negative electrode coating-free layer 22 is shown in Figure 10 , it can include a normal negative electrode active material layer.

[0182] The negative electrode coating-free layer 22 can contain, for example, a semi-metal such as silicon and carbon, and can have a structure in which a conductive binder surrounds the metal and carbon.

[0183] The negative electrode coating-free layer 22 can have a thickness of about 1 μm to about 20 μm. The negative electrode current collector 21 can include a material that does not react with lithium, that is, does not form an alloy or compound with lithium. The material of the negative electrode current collector 21 can be, for example, copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), or nickel (Ni). The negative electrode current collector 21 can include a single metal, or an alloy or coating material of at least two metals. The negative electrode current collector 21 can be formed, for example, in the form of a plate or foil,

[0184] as Figure 11 shown, a thin film 24 can be formed on the surface of the negative electrode current collector 21. The thin film 24 can include an element that can form an alloy with lithium. The element that can form an alloy with lithium can be, for example, gold (Au), silver (Ag), zinc (Zn), tin (Sn), indium (In), silicon (Si), aluminum (Al), or bismuth (Bi). The thin film 24 can include at least one of the aforementioned metals or an alloy of two or more of the metals. When the thin film 24 is present, the metal layer 23 can be deposited in a flat form, as Figure 12 shown, so that the all-solid-state secondary battery 1a can have improved characteristics.

[0185] Although the thickness of the thin film 24 is not limited, it can be, for example, about 1 nm to about 500 nm. When the thickness of the thin film 24 is within this range, the thin film 24 can function sufficiently to allow an appropriate amount of lithium to be deposited on the negative electrode, so that the all-solid-state secondary battery 1 can have improved characteristics. The thin film 24 can be formed on the negative electrode current collector 21, for example, by vacuum deposition, sputtering, or plating.

[0186] The negative electrode coating-free layer 22 can include a negative electrode active material that can form an alloy or compound with lithium.

[0187] The negative electrode active material may be, for example, amorphous carbon, gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), or zinc (Zn). For example, the amorphous carbon may be carbon black (CB), acetylene black (AB), furnace black (FB), Ketjen black (KB), or graphene.

[0188] The non-negative electrode coating 22 may include one or at least two of the negative electrode active materials. For example, the non-negative electrode coating 22 may include only amorphous carbon, or gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), zinc (Zn), or a combination thereof as the negative electrode active material. The non-negative electrode coating 22 may include a mixture of amorphous carbon and gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), zinc (Zn), or a combination thereof. The mixing weight ratio of amorphous carbon and, for example, gold may be, for example, about 10:1 to about 1:2. When the negative electrode active material includes these materials, the all-solid secondary battery 1 may have improved characteristics.

[0189] When the negative electrode active material is gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), zinc (Zn), or a combination thereof, the particle size (e.g., average particle diameter) of the negative electrode active material may be about 4 μm or less. The all-solid secondary battery 1 may have improved characteristics. The particle diameter of the negative electrode active material may be, for example, the median diameter (D50) measured using a laser particle size distribution analyzer. In the examples and comparative examples, the particle diameter was measured using this method. Although there is no limitation on the lower limit of the particle diameter, it may be about 10 nm.

[0190] The negative electrode active material may include a mixture of first particles of amorphous carbon and second particles of a metal or semiconductor. The metal or semiconductor may include, for example, gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), zinc (Zn), or a combination thereof. The amount of the second particles may be about 8 weight percent (wt%) to about 60 wt%, or about 10 wt% to about 50 wt%, based on the total weight of the mixture. When the amount of the second particles is within this range, the all-solid secondary battery 1 may have improved characteristics.

[0191] The thickness of the non-negative electrode coating 22 is not particularly limited and may be about 1 μm to about 20 μm. When the thickness of the non-negative electrode coating 22 is within this range, the all-solid secondary battery 1 may have improved characteristics. When a binder is used, the thickness of the non-negative electrode coating 22 can be easily within the aforementioned range.

[0192] The non-negative electrode coating 22 may include additives at an appropriate ratio, such as a mixture of fillers, dispersants, or ion conductors suitable for all-solid-state batteries.

[0193] The solid electrolyte may include such solid electrolytes that contain the separate oxide or contain the oxide and a commercially available solid electrolyte.

[0194] The commercially available solid electrolyte may include, for example, a sulfide-based solid electrolyte material. The sulfide-based solid electrolyte material may be, for example, Li 2 S-P 2 S 5 、Li 2 S-P 2 S 5 -LiX (where X is a halogen such as I or Cl), Li 2 S-P 2 S 5 -Li 2 O, Li 2 S-P 2 S 5 -Li 2 O-LiI, Li 2 S-SiS 2 、Li 2 S-SiS 2 -LiI, Li 2 S-SiS 2 -LiBr, Li 2 S-SiS 2 -LiCl, Li 2 S-SiS 2 -B 2 S 3 -LiI, Li 2 S-SiS 2 -P 2 S 5 -LiI, Li 2 S-B 2 S 3 、Li 2 S-P 2 S 5 -Z m S n (where m and n may be integers, and Z may be Ge, Zn, Ga, or a combination thereof), or Li 2 S-GeS 2 、Li 2 S-SiS 2 -Li 3 PO 4 、Li2 S-SiS 2 -Li p MO q (where p and q are integers, and M can be one of P, Si, Ge, B, Al, Ga, and In). The sulfide-based solid electrolyte material can be prepared as follows: starting materials (e.g., Li 2 S or P 2 S 5 ) are processed, for example, by melt quenching or mechanical grinding. Heat treatment can be carried out after the processing. The solid electrolyte can be in an amorphous state, a crystalline state, or a mixed state of both.

[0195] As the solid electrolyte, a sulfide-based solid electrolyte material including at least sulfur (S), phosphorus (P), and lithium (Li) among the sulfide-based solid electrolyte materials can be used. For example, a sulfide-based solid electrolyte material including Li 2 S-P 2 S 5 can be used. When a sulfide-based solid electrolyte material including Li 2 S-P 2 S 5 is used as the solid electrolyte, the mixed molar ratio of Li 2 S and P 2 S 5 (Li 2 S:P 2 S 5 ) can be in the range of about 50:50 to about 90:10. The solid electrolyte 30 can further include a binder. The binder that can be included in the solid electrolyte 30 can be, for example, styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, or polyethylene. The binder of the solid electrolyte 30 can be the same as or different from the binder of the positive electrode active material layer 12 and the negative electrode-free coating 22.

[0196] The embodiments of the present disclosure will now be described in detail with reference to the following examples and comparative examples. However, these examples are for illustrative purposes only and are not intended to limit the scope of the embodiments of the present disclosure.

[0197] Examples

[0198] Example 1

[0199] LiOH as a lithium precursor, Ta 2 O 5 as a tantalum precursor, WO 3 , and (NH 4 ) 2 HPO 4Mix in stoichiometric ratio according to the composition shown in Table 1, and then simultaneously grind with an acetone mixture using a planetary mill containing zirconia balls for about 2 hours to thereby obtain a precursor mixture. The amount of acetone is about 100 parts by weight, relative to the total weight of 100 parts by weight of the precursor mixture, and LiOH is used in an excess of about 10 wt% during the preparation of the precursor mixture to pre-compensate for losses during subsequent heat treatment of the precursor mixture.

[0200] Heat the precursor mixture to about 600 °C at a temperature increase rate of about 5 °C / min, and then subject it to a first heat treatment in an air atmosphere at the same temperature for about 8 hours.

[0201] Subject the powder after the first heat treatment to planetary grinding for about 10 minutes.

[0202] Heat the resulting product to 1000 °C at a temperature increase rate of about 5 °C / min, and then subject it to a second heat treatment in an air atmosphere at the same temperature for about 8 hours to thereby obtain an oxide powder having the composition shown in Table 1.

[0203] Example 2 - 3

[0204] Prepare an oxide powder having the composition shown in Table 1 in the same manner as in Example 1, except that: lithium chloride (LiCl) is further added during the preparation of the precursor mixture. The amount of lithium chloride in Examples 2 and 3 is selected in stoichiometric ratio according to the corresponding composition in Table 1.

[0205] Example 4

[0206] Prepare an oxide powder having the composition shown in Table 1 in the same manner as in Example 1, except that: the amount of tungsten precursor WO 3 is selected in stoichiometric ratio to obtain an oxide powder having the corresponding composition in Table 1.

[0207] Example 5

[0208] LiOH as the lithium precursor, Ta as the tantalum precursor 2 O 5 , (NH 4 ) 2 HPO 4 , and SiO as the silicon precursor 2Mix in stoichiometric ratio according to the composition shown in Table 1, and then mix with acetone while pulverizing with a planetary mill containing zirconia balls for about 2 hours to thereby obtain a precursor mixture. The amount of acetone is about 100 parts by weight, relative to the total weight of 100 parts by weight of the precursor mixture, and LiOH is used in an excess of about 10 wt% during the preparation of the precursor mixture to pre-compensate for the loss during the subsequent heat treatment of the precursor mixture.

[0209] Heat the precursor mixture to about 600 °C at a temperature increase rate of about 5 °C / min, and then subject it to a first heat treatment in an air atmosphere at the same temperature for about 8 hours.

[0210] Subject the powder after the first heat treatment to planetary grinding for about 10 minutes.

[0211] Heat the resulting product to 1000 °C at a temperature increase rate of about 5 °C / min, and then subject it to a second heat treatment in an air atmosphere at the same temperature for about 8 hours to thereby obtain an oxide powder having the composition shown in Table 1.

[0212] Examples 6 - 7

[0213] Prepare an oxide powder having the composition shown in Table 1 in the same manner as in Example 5, except that: lithium chloride (LiCl) is further added during the preparation of the precursor mixture. The amount of lithium chloride in Examples 6 and 7 is selected in stoichiometric ratio according to the corresponding composition in Table 1.

[0214] Examples 8 - 9

[0215] Prepare an oxide powder in the same manner as in Example 5, except that: the amount of the silicon precursor SiO 2 is selected to obtain an oxide powder having the corresponding composition in Table 1.

[0216] Example 10

[0217] Prepare an oxide powder (Li 0.75 Ta 1.75 W 0.25 PO 8 ) in the same manner as in Example 1, except that: the amount of the tungsten precursor (WO 3 ) is selected to obtain an oxide powder having the composition in Table 1.

[0218] Example 11

[0219] Prepare an oxide powder (Li 0.5 Ta 2 W 0.5 P 0.5 O8 ), except as follows: the amounts of the lithium precursor, tantalum precursor, tungsten precursor, and phosphorus precursor are selected to obtain an oxide powder having the composition of Table 1.

[0220] Comparative Example 1

[0221] An oxide powder was prepared in the same manner as in Example 1, except as follows: LiOH was used as the lithium precursor, Ta 2 O 5 , and (NH 4 ) 2 HPO 4 was used as the phosphorus precursor, and the amounts of the lithium precursor, tantalum precursor, and phosphorus precursor were selected to obtain an oxide powder having the composition of Table 1.

[0222] Comparative Example 2

[0223] An oxide powder was prepared in the same manner as in Comparative Example 1, except as follows: SiO 2 was further used as the silicon precursor, and the amounts of the lithium precursor, tantalum precursor, and silicon precursor were selected to obtain an oxide powder having the composition of Table 1.

[0224] Comparative Example 3

[0225] An oxide powder was prepared in the same manner as in Comparative Example 2, except as follows: WO 3 was further used as the tungsten precursor, and the amounts of the lithium precursor, tantalum precursor, silicon precursor, and tungsten precursor were selected to obtain an oxide powder having the composition of Table 1.

[0226] Table 1

[0227]

[0228]

[0229] Example 12: Preparation of Oxide

[0230] LiOH as the lithium precursor, Ta 2 O 5 , WO 3 as the tungsten precursor, (NH 4 ) 2 HPO 4 as the phosphorus precursor, and SiO 2Mix in stoichiometric ratio according to the composition shown in Table 2, and then mix with acetone while pulverizing with a planetary mill containing zirconia balls for about 2 hours to thereby obtain a precursor mixture. The amount of acetone is about 100 parts by weight, relative to the total weight of 100 parts by weight of the precursor mixture, and LiOH is used in an excess of about 10% by weight in the preparation of each precursor mixture to pre-compensate for losses during subsequent heat treatment of the precursor mixture.

[0231] Heat the precursor mixture to about 600 °C at a temperature increase rate of about 5 °C / minute, and then subject it to a first heat treatment in an air atmosphere at the same temperature for about 8 hours.

[0232] Subject the powder after the first heat treatment performed as described above to planetary grinding for about 10 minutes.

[0233] Heat the resulting product to 1000 °C at a temperature increase rate of about 5 °C / minute, and then subject it to a second heat treatment in an air atmosphere at the same temperature for about 8 hours to thereby obtain an oxide powder having the composition shown in Table 2.

[0234] Table 2

[0235]

[0236]

[0237] Evaluation Example 1: Evaluation of XRD Spectrum

[0238] Evaluate the X-ray diffraction (XRD) spectra of the oxides according to Example 5, Example 6, Example 8, Example 9, Comparative Example 1, and Comparative Example 2. The results are shown in Figure 1 . The XRD analysis was performed using Bruker's D8 Advance with Cu Kα radiation to obtain the XRD spectrum.

[0239] Reference Figure 1 , it was found that the oxides of Example 5, Example 6, Example 8, and Example 9 exhibited the same XRD peak characteristics as those of the oxides of Comparative Example 1 and 2. From these results, it was understood that the oxides of Example 5, Example 6, Example 8, and Example 9 had a crystal structure substantially the same as that of the oxides of Comparative Example 1 and 2.

[0240] Evaluation Example 2: Measurement of Ionic Conductivity and Activation Energy

[0241] The oxide powders of Example 1, Example 2, Example 4, Example 5, Example 6, Example 8, Example 9, Comparative Example 1 and Comparative Example 2 were made into tablets as follows: They were pressed at a pressure of about 6 tons for about 5 minutes to thereby form tablets of each oxide (having a thickness: about 500 μm). The surfaces of the obtained oxide tablets were completely covered with mother powder having the same composition as the tablets of each oxide to minimize the compositional change caused by the volatilization of lithium during heat treatment, and then heat-treated at about 1100 °C for about 12 hours. Both sides of the heat-treated tablets were polished using SiC sandpaper to adjust the thickness of the tablets to about 500 μm, and then Au electrodes were deposited on both sides of the tablets by sputtering to thereby fabricate Au / oxide tablet / Au structures.

[0242] The Au / oxide tablet / Au structures were analyzed using electrochemical impedance spectroscopy (EIS). This EIS analysis was performed at an amplitude of about 10 mV and a frequency of about 0.1 hertz (Hz) to 10 6 Hz. The results of the EIS analysis are shown in Figure 4A and 4B and Table 3. From the impedance measurement results, the total resistance value (R 总 ) was obtained. Using this value, the electrode area and tablet thickness were corrected to thereby calculate the conductivity value. From the results of the EIS analysis performed while changing the temperature of the chamber in which each oxide sample was loaded, the activation energy (Ea) for the conduction of lithium ions was calculated. An Arrhenius plot (ln(σT) vs. 1 / T) of Equation 1 was obtained using the conductivity values measured at different temperatures in the range of 298 K to 378 K to thereby calculate the activation energy (Ea) from the slope.

[0243] Equation 1

[0244] σT = A (Ea / RT)

[0245] In Equation 1, Ea represents the activation energy, T represents the absolute temperature, A represents the pre-exponential factor, σ represents the conductivity, and R represents the gas constant.

[0246] The obtained activation energy analysis results are shown in Figure 5 and Table 3.

[0247]

[0248] In Table 3, Li + , bulk represents the lithium ion bulk conductivity, Li + , grain boundary represents the lithium ion grain boundary conductivity, and Li + , total represents the total lithium ion conductivity. The oxides of Example 8 and Example 9 include LiTaO having a perovskite phase 3When the oxide has this phase, the lithium stability can be improved.

[0249] Referring to Table 3, it was found that the oxides of Examples 1 to 9 had improved room temperature (25 °C) ionic conductivity compared to the oxides of Comparative Examples 1 to 3. The ionic conductivity of the oxide of Comparative Example 3 was outside the measurable range and was not available.

[0250] Compared to the activation energies of the oxides of Comparative Examples 1 to 3, the oxides of Examples 1 to 2, 4, and 6 to 9 exhibited smaller activation energies. The activation energies of Examples 3 and 5 were equal to or greater than that of Comparative Example 2. The oxides of Examples 1 to 9 exhibited an activation energy of about 0.41 eV / atom or less, and such a reduced activation energy of the oxide could result in improved ionic conductivity at low temperatures.

[0251] Evaluation of Example 3: Lithium stability

[0252] The oxide powders of Example 1, Example 5, and Comparative Example 1 were made into pellets as follows: pressed at a pressure of about 6 tons for about 5 minutes to thereby obtain pellets of each oxide (having a thickness of about 500 μm). The surfaces of the oxide pellets obtained by the above process were completely covered with a mother powder having the same composition as the pellets of each oxide to minimize the compositional change caused by the volatilization of lithium during heat treatment, and then heat-treated at about 1100 °C for about 12 hours. The two sides of the heat-treated pellet were polished using SiC sandpaper to adjust the thickness of the pellet to about 500 μm, and then lithium metal was disposed on each side of the pellet, and then subjected to cold isostatic pressing (CIP) to thereby fabricate a lithium (Li) symmetric cell.

[0253] After the fabrication of the lithium symmetric cell, the lithium symmetric cell was placed at room temperature for 3 days, and the impedance characteristics of each cell were evaluated. The results are shown in Figure 6 .

[0254] Referring to Figure 6 , it was found that compared to the lithium symmetric cell using the oxide of Comparative Example 1, after being placed at room temperature for 3 days, the lithium symmetric cells using the oxides of Examples 1 and 5 exhibited smaller resistance changes due to significantly suppressed reactions with lithium metal.

[0255] The state changes of the lithium symmetric cell using the oxide of Example 1 and the lithium symmetric cell using the oxide of Comparative Example 1 after being placed for 3 days are shown in Figure 7A and 7B . Figure 7A and 7B respectively show the state changes of the lithium symmetric cell using the oxide of Example 1 and the lithium symmetric cell using the oxide of Comparative Example 1.

[0256] Reference Figure 7A and 7B it was found that, compared with the lithium symmetric cell using the oxide of Comparative Example 1, the lithium symmetric cell using the oxide of Example 1 showed less lithium discoloration.

[0257] From Figure 6 、 7A and the above results of 7B, it was found that the oxides of Example 1 and Example 5 showed improved lithium stability compared with the oxide of Comparative Example 1.

[0258] Evaluation of Example 4: Calculation of activation energy and mean square displacement (MSD) (calculated value)

[0259] The diffusivity (D, unit: cm 2 / s) of each oxide through the diffusion of lithium ions was calculated using the nudged elastic band (NEB) method before and after introducing dopants into the oxides of Example 9, Example 10, Comparative Example 1 and Comparative Example 2. The results are shown in Figures 2A to 2D respectively.

[0260] It was found that the oxides of Example 9 and Example 10 showed a greatly increased ionic conductivity compared with those of the oxides of Comparative Example 1 and Comparative Example 2 as shown in Figure 2C and 2D respectively, as shown in Figure 2A and 2B respectively. From these results, it was found that, unlike the oxides of Comparative Example 1 and 2, the oxides of Example 9 and Example 10 had an increased isotropy of the ionic conduction path.

[0261] The mean square displacement (MSD) of the diffusion of lithium ions through the oxides of Example 9 and 11 and Comparative Example 1 before and after introducing dopants into each oxide was calculated using the nudged elastic band (NEB) calculation method, and the results are shown in Figures 3A to 3C respectively. In Figures 3A to 3C “a” represents the MSD in the x-axis, “b” represents the MSD in the y-axis, “c” represents the MSD in the z-axis, and “total” represents the net MSD.

[0262] It was found that the oxides of Example 9 and 11 had a reduced anisotropy of the diffusion path (increased mobility in the a-axis and b-axis) compared with the oxide of Comparative Example 1, resulting in a total increase in ionic conductivity. From these results, it was found that the oxides of Example 9 and 11 had an increased isotropy of the ionic conduction path.

[0263] Evaluation of Example 5: Scanning electron microscope analysis

[0264] The oxides of Example 1, Example 2, Example 5, and Example 6 were analyzed by scanning electron microscopy (SEM). The scanning electron microscopy was performed using FE-SEM (Hitachi SU 8030).

[0265] The SEM images of the oxides of Example 1 and Example 2 are shown in Figure 8A and 8B respectively. The SEM images of the oxides of Example 5 and Example 6 are shown in Figure 9A and 9B respectively.

[0266] Referring to Figure 8B , it was found that the oxide of Example 2 has a reduced grain size compared to the grain size of the oxide of Example 1 as shown in Figure 8A . Referring to Figure 9B , it was found that the oxide of Example 6 has a reduced grain size compared to the grain size of the oxide of Example 5 as shown in Figure 9A . Such a reduced grain size can result in improved interfacial stability of the grains.

[0267] As described above, according to the embodiment, the oxide can be used as a lithium ion conductor. Such a lithium ion conductor can have excellent room temperature ionic conductivity and improved lithium stability, and can also be used as a positive electrode electrolyte due to its high oxidation potential. An electrochemical device having improved performance can be manufactured using such a lithium ion conductor.

[0268] It should be understood that the embodiments described herein should be considered only in a descriptive sense and not for purposes of limitation. The description of features, aspects, or advantages in each embodiment should be considered applicable to other similar features, aspects, or advantages in other embodiments. Although the embodiments have been described with reference to the accompanying drawings, those of ordinary skill in the art will understand that various changes in form and detail can be made therein without departing from the spirit and scope as defined by the appended claims.

Claims

1. An oxide, comprising: a compound represented by Formula 1, a compound represented by Formula 2, or a combination thereof Formula 1 Li 1-x+y-z Ta 2-x M x P 1-y Q y O 8-z X z wherein, in Formula 1, M is an element having an oxidation number of 6+ and is tungsten, tellurium, selenium, chromium, molybdenum, technetium, or a combination thereof, Q is an element having an oxidation number of 4+ and is silicon, tin, titanium, germanium, selenium, palladium, rhodium, cobalt, molybdenum, chromium, ruthenium, nickel, manganese, vanadium, or a combination thereof, X is a halogen atom, pseudohalogen, or a combination thereof, 0 ≤ x < 0.6, 0 ≤ y < 1, and 0 ≤ z < 1, where x and y are not both 0, Formula 2 Li 1-x+y Ta 2-x M x P 1-y Q y O 8 ·zLiX wherein, in Formula 2, M is an element having an oxidation number of 6+ and is tungsten, tellurium, selenium, chromium, molybdenum, technetium, or a combination thereof, Q is an element having an oxidation number of 4+ and is silicon, tin, titanium, germanium, selenium, palladium, rhodium, cobalt, molybdenum, chromium, ruthenium, nickel, manganese, vanadium, or a combination thereof, X is a halogen atom, pseudohalogen, or a combination thereof, 0 ≤ x < 0.6, 0 ≤ y < 1, and 0 ≤ z < 1, where x and y are not both 0, and wherein in Formulas 1 and 2, M, Q, x, y, and z are independently selected.

2. The oxide according to claim 1, wherein M in Formula 1 and Formula 2 each independently has an oxidation number of 6+ and a coordination number of 6.

3. The oxide according to claim 1, wherein X in Formula 1 and Formula 2 each independently is chlorine, bromine, fluorine, cyanide, cyanate, thiocyanate, azide, or a combination thereof.

4. The oxide according to claim 1, wherein the oxide has a monoclinic structure.

5. The oxide according to claim 1, wherein when analyzed by X-ray diffraction spectroscopy using Cu Kα radiation, the oxide exhibits peaks at diffraction angles of 17.5° ± 0.5°, 24.8° ± 0.5°, 24.9° ± 0.5°, 25.4° ± 0.5°, and 27.8° ± 0.5° 2θ.

6. The oxide according to claim 1, wherein the oxide has a lithium ion conductivity of about 1×10 -2 mS / cm or greater at room temperature (25 °C).

7. The oxide according to claim 1, wherein the oxide has an electronic conductivity of about 1×10 -5 milliSiemens / cm or less at room temperature (25 °C).

8. The oxide according to claim 1, wherein the compound represented by Formula 1 is a compound represented by Formula 3: <Formula 3> Li 1-x+y-z Ta 2-x W x P 1-y Si y O 8-z X z wherein, in Formula 3, X is a halogen atom, pseudohalogen, or a combination thereof, 0 ≤ x < 0.6, 0 ≤ y < 1, and 0 ≤ z < 1, except when x and y are both 0.

9. The oxide according to claim 1, wherein the compound represented by Formula 2 is a compound represented by Formula 4: <Formula 4> Li 1-x+y Ta 2-x W x P 1-y Si y O 8 ·zLiX wherein, in Formula 4, X is a halogen, 0 ≤ x < 0.6, 0 ≤ y < 1, and 0 ≤ z < 1, except when x and y are both 0.

10. The oxide according to claim 1, wherein the oxide is Li 0.9 Ta 1.9 W 0.1 PO 8 , Li 0.8 Ta 1.8 W 0.2 PO 8 , Li 0.7 Ta 1.7 W 0.3 PO 8 , Li 0.75 Ta 1.75 W 0.25 PO 8 , Li 0.6 Ta 1.6 W 0.4 PO 8 , Li 0.5 Ta 1.5 W 0.5 PO 8 ; Li 0.9 Ta 1.9 Te 0.1 PO 8 ,Li 0.8 Ta 1.8 Te 0.2 PO 8 ,Li 0.75 Ta 1.75 Te 0.25 PO 8 ,Li 0.7 Ta 1.7 Te 0.3 PO 8 ,Li 0.6 Ta 1.6 Te 0.4 PO 8 ,Li 0.6 Ta 1.5 Te 0.5 PO 8 ; Li 0.9 Ta 1.9 Se 0.1 PO 8 ,Li 0.8 Ta 1.8 Se 0.2 PO 8 ,Li 0.75 Ta 1.75 Se 0.25 PO 8 ,Li 0.7 Ta 1.7 Se 0.3 PO 8 ,Li 0.6 Ta 1.6 Se 0.4 PO 8 ,Li 0.5 Ta 1.5 Se 0.5 PO 8 ; Li 0.8 Ta 1.9 W 0.1 PO 7.9 Cl 0.1 ,Li 0.7 Ta 1.8 W 0.2 PO 7.9 Cl 0.1 ,Li 0.65 Ta 1.75 W 0.25 PO 7.9 Cl 0.1 , Li 0.6 Ta 1.7 W 0.3 PO 7.9 Cl 0.1 ,Li 0.5 Ta 1.6 W 0.4 PO 7.9 Cl 0.1 ,Li 0.4 Ta 1.5 W 0.5 P 7.9 O 7.9 Cl 0.1 ; Li 0.85 Ta 1.9 W 0.1 PO 7.95 Cl 0.05 ,Li 0.75 Ta 1.8 W 0.2 PO 7.95 Cl 0.05 ,Li 0.7 Ta 1.75 W 0.25 PO 7.95 Cl 0.05 ,Li 0.65 Ta 1.7 W 0.3 PO 7.95 Cl 0.05 ,Li 0.55 Ta 1.6 W 0.4 PO 7.95 Cl 0.05 ,Li 0.45 Ta 1.5 W 0.5 PO 7.95 Cl 0.05 ; Li 1.1 Ta 2 P 0.9 Si 0.1 O 8 ,Li 1.2 Ta 2 P 0.8 Si 0.2 O 8 ,Li 1.3 Ta 2 P 0.7 Si 0.3 O 8 ,Li 1.4 Ta 2 P 0.6 Si 0.4 O 8 ,Li 1.5 Ta 2 P 0.5 Si 0.5 O 8 ; Li 1 Ta 2 P 0.9 Si 0.1 PO 7.9 Cl 0.1 ,Li 1.1 Ta 2 P 0.8 Si 0.2 PO 7.9 Cl 0.1 ,Li 1.2 Ta 2 P 0.7 Si 0.3 PO 7.9 Cl 0.1 ,Li 1.3 Ta 2 P 0.6 Si 0.4 PO 7.9 Cl 0.1 ,Li 1.4 Ta 2 P 0.5 Si 0.5 PO 7.9 Cl 0.1 ; Li 1.05 Ta 2 P 0.9 Si 0.1 PO 7.95 Cl 0.05 ,Li 1.15 Ta 2 P 0.8 Si 0.2 PO 7.95 Cl 0.05 ,Li 1.25 Ta 2 P 0.7 Si 0.3 PO 7.95 Cl 0.05 ,Li 1.35 Ta 2 P 0.6 Si 0.4 PO 7.95 Cl 0.05 ,Li 1.45 Ta 2 P 0.5 Si 0.5 PO 7.95 Cl 0.05 ; Li 1.1 Ta 2 P 0.9 Sn 0.1 O 8 ,Li 1.2 Ta 2 P 0.8 Sn 0.2 O 8 ,Li 1.3 Ta 2 P 0.7 Sn 0.3 O 8 ,Li 1.4 Ta 2 P 0.6 Sn 0.4 O 8 ,Li 1.5 Ta 2 P 0.5 Sn 0.5 O 8 ; Li 1.0 Ta 2 P 0.9 Sn 0.1 O 7.9 Cl 0.1 ,Li 1.1 Ta 2 P 0.8 Sn 0.2 O 7.9 Cl 0.1 ,Li 1.2 Ta 2 P 0.7 Sn 0.3 O 7.9 Cl 0.1 ,Li 1.3 Ta 2 P 0.6 Sn 0.4 O 7.9 Cl 0.1 ,Li 1.4 Ta 2 P 0.5 Sn 0.5 O 7.9 Cl 0.1 ; Li 1.05 Ta 2 P 0.9 Sn 0.1 O 7.95 Cl 0.05 ,Li 1.15 Ta 2 P 0.8 Sn 0.2 O 7.95 Cl 0.05 ,Li 1.25 Ta 2 P 0.7 Sn 0.3 O 7.95 Cl 0.05 ,Li 1.35 Ta 2 P 0.6 Sn 0.4 O 7.95 Cl 0.05 ,Li 1.45 Ta 2 P 0.5 Sn 0.5 O 7.95 Cl 0.05 ; Li 1.0 Ta 1.9 W 0.1 P 0.9 Si 0.1 O 8 ,Li 0.9 Ta 1.8 W 0.2 P 0.9 Si 0.1 O 8 ,Li 0.8 Ta 1.7 W 0.3 P 0.9 Si 0.1 O 8 ,Li 0.85 Ta 1.75 W 0.25 P 0.9 Si 0.1 O 8 ,Li 0.7 Ta 1.6 W 0.4 P 0.9 Si 0.1 O 8 ,Li 0.6 Ta 1.5 W 0.5 P 0.9 Si 0.1 O 8 ; Li 1.1 Ta 1.9 W 0.1 P 0.8 Si 0.2 O 8 ,Li 1.0 Ta 1.8 W 0.2 P 0.8 Si 0.2 O 8 ,Li 0.9 Ta 1.7 W 0.3 P 0.8 Si 0.2 O 8 ,Li 0.95 Ta 1.75 W 0.25 P 0.8 Si 0.2 O 8 ,Li 0.8 Ta 1.6 W 0.4 P 0.8 Si 0.2 O 8 ,Li 0.7 Ta 1.5 W 0.5 P 0.8 Si 0.2 O 8 ; Li 1.05 Ta 2 P 0.9 Si 0.1 O 7.95 Cl 0.05 ,Li 1.0 Ta 2 P 0.9 Si 0.1 O 7.9 Cl 0.1 ,Li 0.9 Ta 1.75 W 0.25 PO 8 , or a combination thereof.

11. The oxide according to claim 1, wherein the oxide has an activation energy of 0.29 electron volts / atom to about 0.44 electron volts / atom.

12. A method for preparing the oxide according to any one of claims 1-11, the method comprising: contacting a lithium precursor, a tantalum precursor, an M precursor, a Q precursor, a phosphorus precursor, and optionally an X precursor to obtain a precursor mixture; and thermally treating the precursor mixture in an oxidizing gas atmosphere to prepare the oxide.

13. The method according to claim 12, wherein thermally treating the precursor mixture comprises thermally treating at about 500 °C to about 1200 °C.

14. The method according to claim 12, wherein the heat treatment includes a first heat treatment at a first temperature and a second heat treatment at a second temperature, wherein the second temperature is greater than the first temperature, wherein the first temperature is between about 500 °C and about 1000 °C, and the second temperature is between about 600 °C and about 1200 °C.

15. A solid electrolyte, comprising: an oxide according to any one of claims 1-11.

16. An electrochemical device, comprising: a positive electrode; a negative electrode; and a solid electrolyte disposed between the positive electrode and the negative electrode, wherein at least one of the positive electrode, the negative electrode or the solid electrolyte comprises an oxide according to any one of claims 1-11.

17. The electrochemical device according to claim 16, wherein the solid electrolyte comprises an oxide according to any one of claims 1-11.

18. The electrochemical device according to claim 16, wherein the solid electrolyte is an electrolyte protective film, a positive electrode protective film, a negative electrode protective film, or a combination thereof.

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