Rare earth halide solid electrolyte and preparation method and application thereof

Abstract

The invention relates to a rare earth halide solid electrolyte and a preparation method and application thereof, the rare earth halide solid electrolyte has a crystal phase structure, and the composition general formula of the rare earth halide solid electrolyte is Li < 3 + y > MX < 6-y > Oy. ZLi2O, wherein M is a rare earth element, and X is a halogen element, 0 lt; y is less than or equal to 0.4, 0lt; and z < = 0.6. The rare earth halide solid electrolyte disclosed by the invention has relatively high room-temperature ionic conductivity and relatively good electrochemical stability, can be compatible with a lithium metal negative electrode, and has a relatively great application prospect in an all-solid-state lithium metal solid-state battery.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion batteries, and in particular to a rare earth halide solid electrolyte and a preparation method and application thereof. Background Art

[0002] Lithium-ion battery technology, due to its high energy density, long cycle life, and low self-discharge rate, has become a core energy technology for portable electronics, electric vehicles, and energy storage systems. However, with the increasing demand for applications, traditional liquid lithium-ion batteries face numerous challenges in terms of safety and energy density. All-solid-state lithium batteries, as the next generation of battery technology, have gradually become a research hotspot. They offer improved safety and can be directly paired with lithium metal anodes, resulting in higher energy density in the assembled battery.

[0003] Developing solid-state electrolytes that combine good lithium-ion conductivity, high chemical stability, suitable mechanical strength, and excellent interfacial compatibility is key to advancing the practical application of all-solid-state batteries. Among the many types of solid-state electrolytes (such as oxide solid electrolytes, sulfide solid electrolytes, and polymer solid electrolytes), halide solid electrolytes exhibit excellent room-temperature ionic conductivity, compatibility with high-voltage cathodes, and good mechanical properties, demonstrating great development potential and practical application prospects.

[0004] However, compared with other electrolytes such as sulfide solid electrolytes, halide solid electrolytes have more serious instability problems towards lithium metal on the negative electrode side, which limits the large-scale practical application of halide solid electrolytes.

[0005] CN119092804A discloses a rare earth oxyhalide solid electrolyte and its preparation method and application. The rare earth oxyhalide solid electrolyte has an amorphous structure and a general chemical formula of Li 3-y MOX 4-y Wherein: M includes any one or a combination of at least two of Sc, Y, or a lanthanide element; X includes any one or a combination of at least two of F, Cl, Br, and I; 0≤y≤1. The method for preparing the rare earth oxyhalide solid electrolyte comprises the following steps: heat-treating a hydrated rare earth halide to obtain an MOX precursor; mixing the obtained MOX precursor with LiX, and ball-milling the mixture to obtain the rare earth oxyhalide solid electrolyte. The rare earth oxyhalide solid electrolyte in this patent has a maximum ionic conductivity of 4.1×10 -5 S / cm.

[0006] Therefore, there is an urgent need to develop a solid electrolyte with a simple preparation process, stable to lithium metal electrodes, and with an ionic conductivity that can be increased to the mS level. Summary of the Invention

[0007] To solve the above technical problems, the present invention provides a rare earth halide solid electrolyte, a preparation method thereof and an application thereof. By using rare earth halides as raw materials and introducing Li2O into the solid electrolyte, the rare earth halide solid electrolyte has a high room temperature ionic conductivity, good electrochemical stability, and can be compatible with a lithium metal negative electrode, and has great application prospects in all-solid-state lithium metal solid batteries.

[0008] To achieve this purpose, the present invention adopts the following technical solutions:

[0009] In the first aspect, the present invention provides a rare earth halide solid electrolyte, the rare earth halide solid electrolyte has a crystalline phase structure, and the general formula of the composition of the rare earth halide solid electrolyte is Li 3+y MX 6-y O y ·zLi2O;

[0010] where M is a rare earth element, X is a halogen element, 0 < y ≤ 0.4, 0 < z ≤ 0.6.

[0011] In the general formula of the composition of the rare earth halide solid electrolyte, 0 < y ≤ 0.4, for example, it can be 0.05, 0.1, 0.2, 0.3 or 0.4. In the general formula of the composition of the rare earth halide solid electrolyte, 0 < z ≤ 0.6, for example, it can be 0.05, 0.1, 0.2, 0.3, 0.4, 0.5 or 0.6, but is not limited to the listed values, and other unlisted values within the above value range are equally applicable.

[0012] The rare earth halide solid electrolyte of the present invention has a crystalline phase structure, and has a high room temperature ionic conductivity, excellent electrochemical stability and lithium stability. The introduction of Li2O can realize the bulk oxygen anion doping of the ternary Li-M-X solid electrolyte matrix material, and can form a Li2O protective layer on the surface of the doped material, improving the interfacial stability when the composite electrolyte directly contacts the lithium metal.

[0013] As a preferred technical solution of the present invention, the rare earth element includes any one or at least two combinations of lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, scandium or yttrium. Among them, typical but non-limiting combinations include: the combination of lanthanum and cerium, the combination of lanthanum and praseodymium, the combination of lanthanum and neodymium, the combination of lanthanum and promethium, the combination of lanthanum and gadolinium, the combination of lanthanum and erbium, the combination of lanthanum, cerium and praseodymium, the combination of lanthanum, cerium and neodymium, the combination of lanthanum, cerium and samarium, the combination of lanthanum, cerium and gadolinium, the combination of lanthanum, cerium and erbium, the combination of lanthanum, cerium, praseodymium and neodymium.

[0014] Preferably, the halogen element includes any one or a combination of at least two of F, Cl, Br, or I. Typical but non-limiting combinations include: a combination of F and Cl, a combination of F and Br, a combination of F and I, a combination of Cl and Br, a combination of Cl and I, a combination of Br and I, a combination of F, Cl, and Br, a combination of F, Cl, and I, a combination of Cl, Br, and I, a combination of F, Br, and I, and a combination of F, Cl, Br, and I.

[0015] As a preferred technical solution of the present invention, in the general formula of the composition of the rare earth halide solid electrolyte, 0.2 ≤ y ≤ 0.4 and 0 < z ≤ 0.2. The value of y can be 0.2, 0.25, 0.3, 0.35, or 0.4, and the value of z can be 0.05, 0.07, 0.1, 0.12, 0.15, 0.17, or 0.2, but is not limited to the listed values. Other unlisted values within the above numerical range are equally applicable.

[0016] By defining the composition of each element in the general formula of the composition of the rare earth halide solid electrolyte, the present invention can not only achieve the bulk oxygen anion doping of the ternary Li-M-X solid electrolyte matrix material in the rare earth halide solid electrolyte, but also form a Li2O protective layer on the surface of the doped material, improving the interfacial stability when the composite electrolyte directly contacts lithium metal.

[0017] Preferably, the diffraction peaks in the XRD pattern of the rare earth halide solid electrolyte correspond to the diffraction peaks of Li3MX6.

[0018] As a preferred technical solution of the present invention, the rare earth halide solid electrolyte has a coated structure; the rare earth halide solid electrolyte includes a core and a coating layer coated outside the core.

[0019] Preferably, the general formula of the composition of the core is Li 3+y MX 6-y O y .

[0020] Preferably, the material of the coating layer is Li2O.

[0021] In a second aspect, the present invention provides a preparation method of the rare earth halide solid electrolyte described in the first aspect. The preparation method includes: mixing LiX, MX3, and Li2O to obtain a mixed material, and ball-milling the mixed material to obtain the rare earth halide solid electrolyte.

[0022] The rare earth halide solid electrolyte of the present invention uses rare earth halide as the matrix material. At the same time, with lithium oxide as the oxygen source, it can simultaneously achieve bulk anion doping and surface coating of the material. The corresponding rare earth halide solid electrolyte can be obtained by only one-step ball milling in the present invention. The preparation method is simple and the cost is low, which is suitable for large-scale production applications.

[0023] As a preferred technical solution of the present invention, the molar ratio of LiX, MX3 and Li2O is a:b:c, where 2.6 ≤ a < 3, b = 1, 0 < c ≤ 1. The value of a can be 2.6, 2.7, 2.8, 2.9 or 2.98, and the value of c can be 0.05, 0.1, 0.2, 0.4, 0.6, 0.8 or 1, but is not limited to the listed values. Other unlisted values within the above value ranges are equally applicable.

[0024] By limiting the addition ratio between the raw materials in the present invention, the rare earth halide solid electrolyte can have a high room temperature ionic conductivity and good electrochemical stability. If the content of Li2O is too much, it will be unfavorable for the transmission of Li + and ultimately reduce the ionic conductivity of the rare earth halide solid electrolyte.

[0025] Preferably, 2.6 ≤ a ≤ 2.8, 0.2 < c ≤ 0.6. The value of a can be 2.6, 2.65, 2.7, 2.75 or 2.8, and the value of c can be 0.25, 0.3, 0.4, 0.5 or 0.6, but is not limited to the listed values. Other unlisted values within the above value ranges are equally applicable.

[0026] As a preferred technical solution of the present invention, the mass ratio of the balls to the material in the ball milling is (10 - 50):1. For example, it can be 10:1, 20:1, 30:1, 40:1 or 50:1, but is not limited to the listed values. Other unlisted values within the above value ranges are equally applicable.

[0027] As a preferred technical solution of the present invention, the rotation speed of the ball milling is 200 - 550 rpm. For example, it can be 200 rpm, 250 rpm, 300 rpm, 350 rpm, 400 rpm, 450 rpm, 500 rpm or 550 rpm, but is not limited to the listed values. Other unlisted values within the above value ranges are equally applicable.

[0028] By limiting the ball milling speed to 200-550 rpm, the present invention not only enables the prepared rare earth halide solid electrolyte to have a crystalline structure, but also enables the rare earth halide solid electrolyte to have high room temperature ionic conductivity and good electrochemical stability. If the ball milling speed is lower than 200 rpm, insufficient reaction between the raw materials will occur, resulting in the presence of multiple heterogeneous phase structures in the prepared rare earth halide solid electrolyte. If the ball milling speed is higher than 550 rpm, a sharp increase in kinetic energy will occur, causing violent collisions between the raw materials, destroying the periodic arrangement of the crystal structure, and ultimately reducing the ionic conductivity of the rare earth halide solid electrolyte.

[0029] Preferably, the ball milling time is 6 to 40 hours, for example, 6 hours, 10 hours, 20 hours, 30 hours or 40 hours, but is not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable.

[0030] The present invention limits the ball milling time to 6 to 40 hours, thereby not only ensuring that the prepared rare earth halide solid electrolyte has a crystalline structure, but also ensuring that the rare earth halide solid electrolyte has higher room temperature ionic conductivity and better electrochemical stability. If the ball milling time is less than 6 hours, insufficient reaction between the raw materials will result, resulting in the presence of multiple heterogeneous phase structures in the prepared rare earth halide solid electrolyte. If the ball milling time is greater than 40 hours, powder agglomeration will be aggravated, ultimately reducing the ionic conductivity of the rare earth halide solid electrolyte.

[0031] The present invention synthesizes a target rare earth halide solid electrolyte material by coordinated regulation of ball milling speed and ball milling time, so that the prepared rare earth halide solid electrolyte has higher room temperature ionic conductivity and better electrochemical stability.

[0032] As a preferred technical solution of the present invention, the preparation method includes: mixing LiX, MX3 and Li2O according to the proportion of each substance to obtain a mixed material, and ball milling the mixed material for 6 to 40 hours at a ball material mass ratio of (10 to 50):1 and a rotation speed of 200 to 550 rpm to obtain the rare earth halide solid electrolyte.

[0033] In a third aspect, the present invention provides a solid-state battery, comprising the rare earth halide solid electrolyte described in the first aspect.

[0034] The rare earth halide solid electrolyte prepared by the present invention has high room temperature ionic conductivity and good electrochemical stability, and is compatible with lithium metal negative electrodes. The rare earth halide solid electrolyte provided by the present invention can be used for any component of the positive electrode, electrolyte, negative electrode, interface layer, modified layer or protective layer of a solid-state battery.

[0035] Compared with the prior art, the present invention has at least the following beneficial effects:

[0036] (1) The rare earth halide solid electrolyte provided by the present invention has high room temperature ionic conductivity and good electrochemical stability, wherein the room temperature ionic conductivity can reach 0.21mS·cm -1 Above, preferably up to 0.33mS·cm -1 Above, the stable cycle time can reach more than 180h, preferably more than 200h;

[0037] (2) The preparation method provided by the present invention is simple and convenient, and the target material can be synthesized by ball milling only once, which is suitable for large-scale production applications;

[0038] (3) The solid-state battery assembled using the rare earth halide solid electrolyte provided by the present invention has good stability to lithium and can be cycled for more than 180 hours when matched with lithium metal. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is the XRD spectrum of the rare earth halide solid electrolyte provided in Example 1.

[0040] Figure 2 This is the EIS spectrum of the rare earth halide solid electrolyte provided in Example 1.

[0041] Figure 3 This is the XRD spectrum of the rare earth halide solid electrolyte provided in Comparative Example 1.

[0042] Figure 4 This is the XRD spectrum of the rare earth halide solid electrolyte provided in Comparative Example 2. DETAILED DESCRIPTION

[0043] The technical solution of the present invention will be further described below with reference to the accompanying drawings and through specific embodiments. However, the following examples are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

[0044] Example 1

[0045] This embodiment provides a rare earth halide solid electrolyte, which has a crystalline structure and a general composition formula of Li 3.2 YCl 5.8 O 0.2 0.2Li2O; the rare earth halide solid electrolyte is a coated structure; the rare earth halide solid electrolyte comprises a core and a coating layer coated outside the core; the core composition formula is Li 3.2 YCl 5.8 O0.2 The coating material is Li2O, and the XRD spectrum of the rare earth halide solid electrolyte is as follows Figure 1 As shown, the diffraction peak in the XRD spectrum of the rare earth halide solid electrolyte is equivalent to the diffraction peak of Li3YCl6.

[0046] This embodiment also provides a preparation method of the rare earth halide solid electrolyte, which comprises: mixing LiCl, YCl3 and Li2O in a molar ratio of 2.8:1:0.4 in a glove box with an Ar atmosphere to obtain a mixture, and ball-milling the mixture for 12 hours at a ball-to-material mass ratio of 20:1 and a rotation speed of 400 rpm. After ball milling, separating the ball milling beads from the powder material in a glove box with an Ar atmosphere to obtain the powder material, which is the rare earth halide solid electrolyte.

[0047] Example 2

[0048] This embodiment provides a rare earth halide solid electrolyte, which has a crystalline structure and a general composition formula of Li 3.3 ScCl 5.7 O 0.3 0.1Li2O; the rare earth halide solid electrolyte is a coated structure; the rare earth halide solid electrolyte includes a core and a coating layer coated outside the core; the core composition formula is Li 3.3 ScCl 5.7 O 0.3 ; The material of the coating layer is Li2O, and the diffraction peak in the XRD spectrum of the rare earth halide solid electrolyte is equivalent to the diffraction peak of Li3ScCl6.

[0049] This embodiment also provides a preparation method of the rare earth halide solid electrolyte, which comprises: mixing LiCl, ScCl3 and Li2O in a molar ratio of 2.7:1:0.4 in a glove box with an Ar atmosphere to obtain a mixture, and ball-milling the mixture for 6 hours at a ball-to-material mass ratio of 10:1 and a rotation speed of 550 rpm. After ball milling, separating the ball milling beads from the powder material in a glove box with an Ar atmosphere to obtain the powder material, which is the rare earth halide solid electrolyte.

[0050] Example 3

[0051] This embodiment provides a rare earth halide solid electrolyte, which has a crystalline structure and a general composition formula of Li 3.4 YB 5.6 O 0.40.05Li2O; the rare earth halide solid electrolyte is a coated structure; the rare earth halide solid electrolyte includes a core and a coating layer coated outside the core; the core composition formula is Li 3.4 YB 5.6 O 0.4 ; The material of the coating layer is Li2O, and the diffraction peak in the XRD spectrum of the rare earth halide solid electrolyte is equivalent to the diffraction peak of Li3YBr6.

[0052] This embodiment also provides a preparation method of the rare earth halide solid electrolyte, which comprises: mixing LiBr, YBr3 and Li2O in a molar ratio of 2.6:1:0.45 in a glove box with an Ar atmosphere to obtain a mixture, and ball-milling the mixture for 30 hours at a ball-to-material mass ratio of 50:1 and a rotation speed of 200 rpm. After ball milling, separating the ball milling beads from the powder material in a glove box with an Ar atmosphere to obtain the powder material, which is the rare earth halide solid electrolyte.

[0053] Example 4

[0054] This embodiment provides a rare earth halide solid electrolyte, which has a crystalline structure and a general composition formula of Li 3.05 DyCl 5.95 O 0.05 0.2Li2O; the rare earth halide solid electrolyte is a coated structure; the rare earth halide solid electrolyte comprises a core and a coating layer coated outside the core; the core composition formula is Li 3.05 DyCl 5.95 O 0.05 ; The material of the coating layer is Li2O, and the diffraction peak in the XRD spectrum of the rare earth halide solid electrolyte is equivalent to the diffraction peak of Li3DyCl6.

[0055] This embodiment also provides a preparation method of the rare earth halide solid electrolyte, which comprises: mixing LiCl, DyCl3 and Li2O in a molar ratio of 2.95:1:0.25 in a glove box with an Ar atmosphere to obtain a mixture, and ball-milling the mixture for 40 hours at a ball-to-material mass ratio of 50:1 and a rotation speed of 200 rpm. After ball milling, separating the ball milling beads from the powder material in a glove box with an Ar atmosphere to obtain the powder material, which is the rare earth halide solid electrolyte.

[0056] Example 5

[0057] This embodiment provides a rare earth halide solid electrolyte, which differs from the embodiment 1 only in that the value of z in the general formula of the rare earth halide solid electrolyte is adjusted from 0.2 to 0.05, that is, the general formula is Li 3.2 YCl 5.8 O 0.2 0.05Li2O, that is, the molar ratio of LiCl, YCl3 and Li2O in the preparation method of the rare earth halide solid electrolyte is 2.8:1:0.25, and the rest is the same as in Example 1.

[0058] The rare earth halide solid electrolyte prepared in this embodiment has a crystalline structure, and the rare earth halide solid electrolyte is a coated structure.

[0059] Example 6

[0060] This embodiment provides a rare earth halide solid electrolyte, which differs from the embodiment 1 only in that the value of z in the general formula of the rare earth halide solid electrolyte is adjusted from 0.2 to 0.6, that is, the general formula is Li 3.2 YCl 5.8 O 0.2 0.6Li2O, that is, the molar ratio of LiCl, YCl3 and Li2O in the preparation method of the rare earth halide solid electrolyte is 2.8:1:0.8, and the rest is the same as in Example 1.

[0061] The rare earth halide solid electrolyte prepared in this embodiment has a crystalline structure, and the rare earth halide solid electrolyte is a coated structure.

[0062] Example 7

[0063] This embodiment provides a rare earth halide solid electrolyte, which is the same as Example 1 except that the rotation speed of the ball mill in the preparation method is adjusted from 400 rpm to 100 rpm.

[0064] This embodiment cannot synthesize the corresponding rare earth halide solid electrolyte.

[0065] Example 8

[0066] This embodiment provides a rare earth halide solid electrolyte, which is the same as Example 1 except that the rotation speed of the ball mill in the preparation method is adjusted from 400 rpm to 600 rpm.

[0067] The rare earth halide solid electrolyte prepared in this embodiment has a crystalline structure, and the rare earth halide solid electrolyte is a coated structure.

[0068] Example 9

[0069] This embodiment provides a rare earth halide solid electrolyte, which is the same as Example 1 except that the ball milling time in the preparation method is adjusted from 12 hours to 2 hours.

[0070] This embodiment cannot synthesize the corresponding rare earth halide solid electrolyte.

[0071] Example 10

[0072] This embodiment provides a rare earth halide solid electrolyte, which is the same as Example 1 except that the ball milling time in the preparation method is adjusted from 12 hours to 50 hours.

[0073] The rare earth halide solid electrolyte prepared in this embodiment has a crystalline structure, and the rare earth halide solid electrolyte is a coated structure.

[0074] Comparative Example 1

[0075] This comparative example provides a rare earth halide solid electrolyte, which differs from Example 1 only in that the raw materials of the rare earth halide solid electrolyte are adjusted to LiCl and YCl3, and the molar ratio of LiCl and YCl3 is 3:1, that is, the preparation method of the rare earth halide solid electrolyte is adjusted to: mixing LiCl and YCl3 in a molar ratio of 3:1 to obtain the corresponding rare earth halide solid electrolyte. The rest is the same as Example 1.

[0076] The general formula of the rare earth halide solid electrolyte prepared in this comparative example is Li3YCl6.

[0077] The XRD spectrum of the rare earth halide solid electrolyte prepared in this comparative example is as follows: Figure 3 As shown, the diffraction peak in the XRD spectrum of the rare earth halide solid electrolyte is equivalent to the diffraction peak of Li3YCl6, that is, the rare earth halide solid electrolyte prepared in this comparative example has a crystalline structure, but the rare earth halide solid electrolyte is not a coated structure.

[0078] Comparative Example 2

[0079] This comparative example provides a rare earth halide solid electrolyte, which differs from Example 1 only in that the raw materials of the rare earth halide solid electrolyte are adjusted to LiCl, YCl3 and YOCl, and the molar ratio of LiCl, YCl3 and YOCl is 3.4:0.6:0.4, that is, the preparation method of the rare earth halide solid electrolyte is adjusted to: mixing LiCl, YCl3 and YOCl according to a molar ratio of 3.4:0.6:0.4 to obtain the corresponding rare earth halide solid electrolyte. The rest is the same as Example 1.

[0080] The general formula of the rare earth halide solid electrolyte prepared in this comparative example is Li 3.4 YCl 5.6 O 0.4 .

[0081] The XRD spectrum of the rare earth halide solid electrolyte prepared in this comparative example is as follows: Figure 4 As shown, the XRD spectrum of the rare earth halide solid electrolyte shows that it has an amorphous structure, and the rare earth halide solid electrolyte is not a coated structure.

[0082] Test method: (1) Test method for ionic conductivity: Weigh 150 mg of rare earth halide solid electrolyte into a solid-state battery mold with a diameter of 10 mm, apply 4t pressure to press into shape, and then perform AC impedance test at room temperature; the impedance value (R, in Ω) obtained from the impedance (EIS) spectrum is shown in the following figure: Figure 2 As shown, the thickness (L, in cm) and area (S, in cm) of the electrolyte sheet are combined. 2 ), and the ionic conductivity of the corresponding rare earth halide solid electrolyte is calculated by the formula σ=L / (R×S).

[0083] The test method for lithium stability is as follows: 120 mg of rare earth halide solid electrolyte is weighed and placed in a solid-state battery mold with a diameter of 10 mm. A pressure of 4 tons is applied to press the mold. Then a lithium metal sheet is placed on the upper and lower sides of the electrolyte sheet. After the mold is assembled, a pressure of 0.5 tons is applied and maintained at this pressure at a current density of 0.1 mA cm -2 The cycle stability test was carried out under the condition of stable polarization voltage to record the cycle time of the solid electrolyte.

[0084] The performance test results are shown in Table 1.

[0085] Table 1

[0086] Ionic conductivity (mS / cm) Stable cycle time of lithium symmetric battery (h) Example 1 0.33 280 Example 2 0.38 200 Example 3 0.28 180 Example 4 0.24 200 Example 5 0.35 220 Example 6 0.21 190 Example 8 0.26 200 Example 10 0.22 210 Comparative Example 1 0.37 120 Comparative Example 2 0.08 90

[0087] The test results show that:

[0088] (1) It can be seen from Examples 1 to 6 that the rare earth halide solid electrolyte of the present invention has high room temperature ionic conductivity and good electrochemical stability, wherein the ionic conductivity can reach above 0.21 mS / cm, preferably above 0.33 mS / cm, and is compatible with the lithium metal negative electrode, and the stable cycle time of the lithium symmetric battery can reach above 180 h, preferably above 200 h. The concentration of lithium oxide coated on the surface of the rare earth halide solid electrolyte of the present invention has an optimal value, and the stability to lithium can be better improved by determining the optimal coating concentration value; if the coating concentration is too low, the interface side reaction when the solid electrolyte contacts with metallic lithium cannot be effectively suppressed; if the coating concentration is too high, the ionic conductivity of the target product will be reduced.

[0089] (2) It can be seen from Examples 1 and 7-10 that in Example 1, the ball milling speed is 400 rpm and the time is 12 h, and the ionic conductivity of the rare earth halide solid electrolyte prepared therefrom is 0.33 mS / cm, and the stable cycle time of the lithium symmetrical battery is 280 h; while in Example 7, the ball milling speed is 100 rpm and the time is 12 h. Since the ball milling speed is too low, the reaction between the raw materials is insufficient, resulting in the presence of multiple heterogeneous phase structures in the prepared rare earth halide solid electrolyte, which cannot be tested; in Example 8, the ball milling speed is 600 rpm and the time is 12 h, and the ionic conductivity of the rare earth halide solid electrolyte prepared therefrom is 0.26 mS / cm, and the stable cycle time of the lithium symmetrical battery is 2 00h; in Example 9, the ball milling speed is 400rpm and the time is 2h. Since the ball milling time is too short, the reaction between the raw materials is insufficient, resulting in the presence of multiple heterogeneous phase structures in the prepared rare earth halide solid electrolyte, which cannot be tested; in Example 10, the ball milling speed is 400rpm and the time is 50h. The ionic conductivity of the prepared rare earth halide solid electrolyte is 0.22mS / cm, and the stable cycle time of the lithium symmetric battery is 210h. This shows that the present invention, by controlling the ball milling speed and time, can not only make the prepared rare earth halide solid electrolyte have a crystalline phase structure, but also make the rare earth halide solid electrolyte have higher room temperature ionic conductivity and better electrochemical stability.

[0090] (3) It can be seen from Example 1 and Comparative Example 1 that the crystal structure of the rare earth halide solid electrolyte material prepared by the present invention can accommodate a certain amount of lithium oxide, that is, a certain concentration of oxygen doping can be achieved. With the incorporation of oxygen elements, the ionic conductivity of the doped solid electrolyte material decreases slightly. When the lithium oxide reaches a certain concentration, the amount of oxygen accommodated in the crystal structure of the rare earth halide solid electrolyte reaches saturation, and the lithium oxide will be evenly distributed on the surface of the synthesized rare earth halide oxide solid electrolyte particles, that is, forming a surface coating layer; the lithium oxide surface layer will play a certain degree of protective role on the rare earth halide solid electrolyte during the lithium symmetric battery cycle, and can inhibit the adverse reactions that may occur when the solid electrolyte directly contacts lithium metal.

[0091] (4) It can be seen from Example 1 and Comparative Example 2 that the present invention, by controlling the type of oxygen source, can not only make the prepared rare earth halide solid electrolyte have a crystalline structure, but also make the rare earth halide solid electrolyte have a coated structure, forming oxygen doping in the core of the rare earth halide solid electrolyte, and its coating layer is a Li2O coating layer, which can improve the stability of the rare earth halide solid electrolyte to lithium.

[0092] In summary, the present invention uses rare earth halides as raw materials to prepare rare earth halide solid electrolytes. At the same time, lithium oxide is used as an oxygen source to simultaneously achieve bulk anion doping and surface coating of the material. The preparation method provided by the present invention only requires one step of ball milling to obtain the corresponding rare earth halide solid electrolyte. The preparation method is simple and low-cost. The room temperature ionic conductivity of the prepared rare earth halide solid electrolyte can reach 0.21mS·cm -1 The above results show that the stable cycle time can reach 180h and it is compatible with lithium metal negative electrode, which has great application prospects in all-solid-state lithium metal solid-state batteries.

[0093] The applicant declares that the above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the scope of protection and disclosure of the present invention.

Claims

1. A rare earth halide solid electrolyte, characterized in that: The rare earth halide solid electrolyte has a crystalline structure, and the composition formula of the rare earth halide solid electrolyte is Li 3+y MX 6-y O y zLi2O; Wherein, M is a rare earth element, X is a halogen element, <y≤0.4,0<z≤0.6。 2. The rare earth halide solid electrolyte according to claim 1, characterized in that The rare earth element includes any one of lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, scandium or yttrium, or a combination of at least two thereof; Preferably, the halogen element includes any one of F, Cl, Br or I, or a combination of at least two of them.

3. The rare earth halide solid electrolyte according to claim 1 or 2, characterized in that The composition formula of the rare earth halide solid electrolyte is 0.2≤y≤0.4, 0 <z≤0.2; Preferably, the diffraction peak in the XRD spectrum of the rare earth halide solid electrolyte is equivalent to the diffraction peak of Li3MX6.

4. The rare earth halide solid electrolyte according to any one of claims 1 to 3, characterized in that The rare earth halide solid electrolyte is a coated structure; the rare earth halide solid electrolyte comprises a core and a coating layer coated outside the core; Preferably, the core has the general formula Li 3+y MX 6-y O y ; Preferably, the material of the coating layer is Li2O.

5. A method for preparing a rare earth halide solid electrolyte according to any one of claims 1 to 4, characterized in that: The preparation method comprises: mixing LiX, MX3 and Li2O to obtain a mixed material, and ball-milling the mixed material to obtain the rare earth halide solid electrolyte.

6. The preparation method according to claim 5, characterized in that The molar ratio of LiX, MX3 and Li2O is a:b:c, wherein 2.6≤a<3, b=1, 0 <c≤1; Preferably, 2.6≤a≤2.8, 0.2 <c≤0.6。 7. The preparation method according to claim 5 or 6, characterized in that: The mass ratio of the balls to the materials in the ball mill is (10-50):

1.

8. The preparation method according to any one of claims 5 to 7, characterized in that The ball mill has a rotation speed of 200 to 550 rpm; Preferably, the ball milling time is 6 to 40 hours.

9. The preparation method according to any one of claims 5 to 8, characterized in that The preparation method comprises: mixing LiX, MX3 and Li2O according to the proportion of each substance to obtain a mixed material, and ball milling the mixed material for 6 to 40 hours at a ball material mass ratio of (10 to 50):1 and a rotation speed of 200 to 550 rpm to obtain the rare earth halide solid electrolyte.

10. A solid-state battery, characterized in that: The solid-state battery comprises the rare earth halide solid electrolyte according to any one of claims 1 to 4.

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