A garnet-type oxide solid electrolyte, a preparation method thereof, and a lithium-ion battery

Abstract

The present application discloses a garnet-type oxide solid electrolyte, a preparation method thereof, and a lithium-ion battery, relating to the technical field of lithium batteries. The chemical formula of the oxide solid electrolyte is Li<subgt;(6.4~6.6)< / subgt;MLa<subgt;3< / subgt>Zr<subgt;2< / subgt>O<subgt;12< / subgt>; wherein, M includes at least two elements of Fe, B, Be, Ga, Al, and Zn, and the molar amount of each element in M is greater than 0 and less than or equal to 0.1. In the present application, the Li sites are doped with equimolar amounts of at least two elements of Fe, B, Be, Ga, Al, and Zn, and the stoichiometric number of Li is between 6.4 and 6.6, so that the garnet-type oxide solid electrolyte in the present application has a high Li<supgt;+< / supgt> conductivity.

Description

Technical Field

[0001] The present application relates to the technical field of lithium-ion batteries, and particularly relates to a garnet-type oxide solid electrolyte, a preparation method thereof, and a lithium-ion battery. Background Art

[0002] At present, lithium-ion batteries have attracted wide attention from various energy storage systems due to their high voltage, high specific capacity, green and pollution-free characteristics. The development of new energy vehicles has also put forward higher requirements for lithium-ion batteries. Lithium-ion batteries with higher energy density, longer service life and higher safety have become the key to the technological innovation of new energy vehicles. Traditional lithium-ion batteries use organic electrolytes, and their flammable and leaky characteristics can lead to safety accidents. Solid-state lithium metal batteries using non-flammable solid electrolytes instead of organic electrolytes and directly matching with lithium metal anodes have broad prospects.

[0003] The core of a solid-state battery is a solid electrolyte. Solid electrolytes are mainly divided into several categories: organic, inorganic and composite solid electrolytes. Among them, inorganic solid electrolytes mainly include oxides, sulfides, halides and various new lithium ion conductors. Garnet-type Li7La3Zr2O 12 Solid electrolyte (LLZO) is a typical oxide solid electrolyte, which has many advantages such as high ionic conductivity, wide electrochemical window, and stability to lithium metal anodes.

[0004] Li + Ionic conductivity is an important parameter for evaluating the performance of solid electrolytes. Therefore, how to improve the Li + ionic conductivity of LLZO at room temperature is one of the key issues in the study of LLZO. There have been a large number of studies on the doping of LLZO, but the existing doping schemes are not ideal for improving the ionic conductivity of LLZO. Summary of the Invention

[0005] In view of this, the present application provides a garnet-type oxide solid electrolyte, a preparation method thereof, and a lithium-ion battery, aiming to improve the problem of low Li + ionic conductivity existing in existing solid electrolytes.

[0006] In a first aspect, an embodiment of the present application provides a garnet-type oxide solid electrolyte, and the chemical formula of the oxide solid electrolyte is Li (6.4~6.6) MLa3Zr2O 12 ; wherein, M is a doping element, and M includes at least two elements among Fe, B, Be, Ga, Al, and Zn. The molar amount of each element in M is greater than 0 and less than or equal to 0.1.

[0007] In some embodiments of the present application, M includes at least three elements among Fe, B, Be, Ga, Al, and Zn; and / or,

[0008] The elements in M are in equimolar ratio.

[0009] In some embodiments of the present application, M is selected from at least four elements among Fe, B, Be, Ga, Al, and Zn; or,

[0010] M includes Ga, Al, Zn, and Be; or,

[0011] M includes Ga, Fe, Al, and B; or M includes Ga, Fe, Al, Be, and Zn.

[0012] In some embodiments of the present application, the chemical formula of the oxide solid electrolyte is Li 6.4 Ga 0.1 Al 0.1 La3Zr2O 12、 Li 6.6 Ga 0.05 Al 0.05 Zn 0.05 La3Zr2O 12、 Li 6.5 Ga 0.05 Al 0.05 Zn 0.05 Be 0.05 La3Zr2O 12 、Li 6.4 Ga 0.05 Fe 0.05 Al 0.05 B 0.05 La3Zr2O 12 、Li 6.48 Ga 0.04 Fe 0.04 Al 0.04 Be 0.04 Zn 0.04 La3Zr2O 12 at least one of.

[0013] In some embodiments of the present application, the molar amount of each element in M is 0.03 to 0.06.

[0014] On the other hand, the present application provides a method for preparing an oxide solid electrolyte material, and the preparation method includes the following steps:

[0015] Weigh the lithium source, lanthanum source, zirconium source, and dopant according to the stoichiometric ratio, and the dopant includes dopant elements Fe, B, Be, Ga, Al, and Zn;

[0016] Ball-mill the mixture composed of the lithium source, the lanthanum source, the zirconium source, the dopant and the solvent to obtain a slurry;

[0017] After calcining the dried slurry at 900 °C - 950 °C for 6 h - 12 h, then grind it to obtain a powder;

[0018] Press the powder into a sheet and sinter it at a pressure of 10 MPa - 20 MPa and a temperature of 1000 °C - 1200 °C for 1 h - 2 h to obtain an oxide solid electrolyte;

[0019] Among them, the chemical formula of the oxide solid electrolyte is Li (6.4~6.6) MLa3Zr2O 12 ; M includes at least two elements among Fe, B, Be, Ga, Al, Zn, and the molar amount of each element in M is greater than 0 and less than or equal to 0.1.

[0020] In some embodiments of the present application, if the sum of the masses of the lithium source, the lanthanum source, the zirconium source and the dopant is M1, the mass of the ball-milling beads is M2, and the mass of the solvent is M3, then M1:M2:M3 is (1 - 5):(1 - 5):(5 - 20).

[0021] In some embodiments of the present application, the ball-milling speed during the ball-milling process is 250 r / min - 400 r / min; and / or,

[0022] The ball-milling time during the ball-milling process is 6 h - 12 h.

[0023] In some embodiments of the present application, the process of drying the slurry includes placing the slurry in a forced-air drying oven at 80 °C - 120 °C for 6 h - 12 h; and / or,

[0024] Before the sintering step, the preparation method further includes sieving the ground particles through sieves with 200 meshes, 400 meshes, and 500 meshes in sequence to obtain the powder; and / or,

[0025] Before the sintering step, the preparation method further includes dry-pressing the powder to obtain a precursor, and then hot-pressing and sintering the precursor to obtain the oxide solid electrolyte.

[0026] The present application also provides a lithium-ion battery, which includes the oxide solid electrolyte described above, or the oxide solid electrolyte prepared by the preparation method described above.

[0027] Beneficial effects:

[0028] In this application, at least two elements among Fe, B, Be, Ga, Al, and Zn are used to dope the Li sites in equimolar amounts, and the stoichiometric number of Li is between 6.4 and 6.6, so that the garnet-type oxide solid electrolyte in this application has a high Li + ionic conductivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of this application, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of this application. For those skilled in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0030] Figure 1 is the XRD pattern of the oxide solid electrolyte prepared in Example 1 of this application;

[0031] Figure 2 is the scanning electron micrograph of the oxide solid electrolyte prepared in Example 1 of this application;

[0032] Figure 3 is the XRD pattern of the oxide solid electrolyte prepared in Example 2 of this application;

[0033] Figure 4 is the XRD pattern of the oxide solid electrolyte prepared in Example 3 of this application;

[0034] Figure 5 is the XRD pattern of the oxide solid electrolyte prepared in Example 4 of this application;

[0035] Figure 6 is the XRD pattern of the oxide solid electrolyte prepared in Example 5 of this application;

[0036] Figure 7 is the XRD pattern of the oxide solid electrolyte prepared in Comparative Example 1 of this application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0037] The experimental examples described in this application are only a part of the embodiments of this application, rather than all embodiments. All other embodiments obtained by those skilled in the art without creative efforts fall within the scope of protection of this application. In addition, it should be understood that the specific embodiments described herein are only used to illustrate and explain this application, and are not used to limit this application.

[0038] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terms used in the description of the present invention herein are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0039] In the description of the present application, the term "comprising" means "including but not limited to". The terms first, second, third, etc. are used only as labels and do not impose a numerical requirement or establish an order.

[0040] In the present application, "and / or" describes the association relationship of associated objects and indicates that three relationships may exist. For example, A and / or B may represent: A exists alone, A and B exist simultaneously, or B exists alone. Wherein A and B may be singular or plural.

[0041] In the present application, "at least one" means one or more, and "a plurality" means two or more. "One or more", "at least one of the following (items)" or similar expressions refer to any combination of these items, including any combination of single (item) or plural items. For example, "at least one of (item) a, b, or c", or "at least one of (item) a, b, and c" can both represent: a, b, c, a - b (i.e., a and b), a - c, b - c, or a - b - c, where a, b, and c can be single or plural respectively.

[0042] The various embodiments of the present application may exist in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity and should not be construed as a rigid limitation on the scope of the present application; therefore, it should be considered that the range description has specifically disclosed all possible sub - ranges and the individual values within that range. For example, the range description from 1 to 6 should be considered to have specifically disclosed sub - ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and the individual numbers within the range, such as 1, 2, 3, 4, 5, and 6, and this applies regardless of the range. Additionally, whenever a numerical range is indicated herein, it means including any cited number (fraction or integer) within the indicated range.

[0043] At present, lithium-ion batteries have attracted extensive attention from various energy storage systems due to their high voltage, high specific capacity, green and pollution-free characteristics. The development of new energy vehicles has also put forward higher requirements for lithium-ion batteries. Lithium-ion batteries with higher energy density, longer service life and higher safety have become the key to the technological innovation of new energy vehicles. Traditional lithium-ion batteries use organic electrolytes, and their flammable and leaky characteristics can lead to safety accidents. Solid-state lithium-metal batteries that use non-flammable solid electrolytes instead of organic electrolytes and are directly matched with lithium-metal anodes have broad prospects.

[0044] The core of a solid-state battery is the solid electrolyte. Solid electrolytes are mainly divided into several categories: organic, inorganic and composite solid electrolytes. Among them, inorganic solid electrolytes mainly include oxides, sulfides, halides and various new lithium-ion conductors, etc. Garnet-type Li7La3Zr2O 12 Solid electrolyte (LLZO) is a typical oxide solid electrolyte, which has many advantages such as high ionic conductivity, wide electrochemical window and stability to lithium-metal anodes.

[0045] Li + Ionic conductivity is an important parameter for evaluating the performance of solid electrolytes. Therefore, how to improve the Li + ionic conductivity of LLZO at room temperature is one of the key issues in the study of LLZO. There have been a large number of studies on the doping of LLZO, but the existing doping schemes are not ideal for improving the ionic conductivity of LLZO.

[0046] In view of this, the present application provides a garnet-type oxide solid electrolyte, which has a high ionic conductivity.

[0047] The chemical formula of the oxide solid electrolyte provided by the embodiment of the present application is Li (6.4~6.6) MLa3Zr2O 12 ; where M is a doping element, and M includes at least two elements among Fe, B, Be, Ga, Al, and Zn. The molar amount of each element in M is greater than 0 and less than or equal to 0.1.

[0048] Taking M including two of these elements as an example, exemplarily, M can include at least one of Fe and B, Fe and Be, Fe and Ga, Fe and Al, Fe and Zn, B and Be, B and Ga, B and Al, B and Zn, Be and Ga, Be and Al, Be and Zn, Ga and Al, Ga and Zn, and Al and Zn. Of course, in some embodiments of the present application, in addition to including two elements among Fe, B, Be, Ga, Al, and Zn, M can also include other elements (other doping elements except Fe, B, Be, Ga, Al, and Zn), which are not limited herein.

[0049] Taking the case where M includes three of these elements as an example, illustratively, M may include Fe, B, and Be; or, M may include Fe, B, and Ga; or, M may include Fe, B, and Al; or, M may include Fe, B, and Zn; or, M may include Fe, Be, and Ga; or, M may include Fe, Be, and Al; or, M may include Fe, Be, and Zn; or, M may include Fe, Ga, and Al; or, M may include Fe, Ga, and Zn; or, M may include B, Be, and Ga; or, M may include B, Be, and Al; or, M may include B, Be, and Zn; or, M may include Be, Ga, and Al; or, M may include Be, Ga, and Zn; or, M may include Ga, Al, and Zn. Of course, in some embodiments of the present application, in addition to including three elements among Fe, B, Be, Ga, Al, and Zn, M may further include other elements (other doping elements except Fe, B, Be, Ga, Al, and Zn), which are not limited herein.

[0050] Illustratively, taking the case where M includes four of these elements as an example, in one embodiment, M may include

[0051] the four elements Fe, B, Be, and Ga. In another example, M may include the four elements B, Be, Ga, and Al. In another example, M may include the four elements B, Be, Ga, and Al.

[0052] In another example, M may include the four elements Fe, Be, Al, and Zn. Of course, in some embodiments of the present application, in addition to including at least four elements among Fe, B, Be, Ga, Al, and Zn, M may further include other elements, which are not limited herein.

[0053] Illustratively, taking the case where M includes five of these elements as an example, in one example, M may include the five elements Fe, B, Be, Ga, and Al. In another example, the five elements B, Be, Ga, Al, and Zn. In another example, the five elements B, Be, Ga, Al, and Zn. Of course, in some embodiments of the present application, in addition to including at least four elements among Fe, B, Be, Ga, Al, and Zn, M may further include other elements, which are not limited herein.

[0054] Of course, M may also include six of these elements. For example, M includes Fe, B, Be, Ga, Al, and Zn. Of course, in some embodiments of the present application, in addition to including six elements among Fe, B, Be, Ga, Al, and Zn, M may further include other elements, which are not limited herein.

[0055] Exemplarily, the stoichiometric number of Li can be 6.4, 6.45, 6.5, 6.55, 6.6, and interval values between any two of the above values. It should be emphasized that in the present application, by introducing a doping element M at the Li site, the stoichiometric number of Li in the present application is below 7, and a stable cubic phase solid electrolyte can be obtained. At the same time, in the present application, at least four elements among Fe, B, Be, Ga, Al, and Zn are used to dope the Li site, and the stoichiometric number of Li is between 6.4 and 6.6, so that the garnet-type oxide solid electrolyte in the present application has a high Li + ionic conductivity.

[0056] Exemplarily, the molar amount of each element in M can be 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, and interval values between any two of the above values.

[0057] It should be noted that the related art discloses single doping of the Li site, La site, and Zr site, as well as double doping and multi-doping of multiple sites of the Li site, La site, and Zr site simultaneously. The doping elements at the Zr site of LLZO are usually some relatively precious rare earth elements, and the ionic conductivity is extremely susceptible to the influence of the doping cation radius; while the improvement of the ionic conductivity by La site doping is far less than that of the Li site and Zr site. Li site doping improves the LLZO ionic conductivity by directly adjusting the lithium concentration and increasing lithium vacancies, and the doping elements are usually relatively inexpensive. The Li + ionic conductivity of the garnet-type oxide solid electrolyte provided by the solution of the present application can reach about 0.9 mS / cm. Compared with the solution of single doping at the Li site, its Li + ionic conductivity is increased by more than 1 time, showing an unexpected effect.

[0058] It should be emphasized that the doping elements at the Li site in the present application include Fe, B, Be, Ga, Al, and Zn. These elements are in line with the first-principles calculation, and the ionic radius is similar to that of Li. Thus, it is beneficial to improve the ionic conductivity of the oxide solid electrolyte in the present application.

[0059] In addition, the stoichiometric number of Li in the present application is between 6.4 and 6.6. The inventors have found through research that the stoichiometric number of Li affects the disorder degree of Li and the Li + transport space. When the stoichiometric number of Li is between 6.4 and 6.6, it is beneficial to improve the ionic conductivity of the oxide solid electrolyte in the present application.

[0060] In some embodiments of the present application, M is selected from at least four of Fe, B, Be, Ga, Al, and Zn, and the elements in M have an equimolar ratio. For example, M is selected from four elements or five elements or six elements of Fe, B, Be, Ga, Al, and Zn. In this way, a high-entropy LLZO solid electrolyte material can be prepared, which is beneficial to further improving the ionic conductivity of the oxide solid electrolyte in the present application.

[0061] It should be noted that the equimolar ratio of the elements in M means that the doping amounts of the elements in M at the Li site are the same. Taking M including four elements of Fe, B, Be, and Ga as an example, the molar contents of Fe, B, Be, and Ga in M are the same. For example, M is Fe 0.05 B 0.05 Be 0.05 Ga 0.05。

[0062] In some embodiments of the present application, the molar amount of each element in M is from 0.03 to 0.06. Exemplarily, the molar amount of each element in M is 0.03, 0.04, 0.05, 0.06, and values between any two of the above.

[0063] In some embodiments of the present application, the chemical formula of the oxide solid electrolyte is Li 6.4 Ga 0.1 Al 0.1 La3Zr2O 12、 Li 6.6 Ga 0.05 Al 0.05 Zn 0.05 La3Zr2O 12、 Li 6.5 Ga 0.05 Al 0.05 Zn 0.05 Be 0.05 La3Zr2O 12 、Li 6.4 Ga 0.05 Fe 0.05 Al 0.05 B 0.05 La3Zr2O 12 、Li 6.48 Ga 0.04 Fe 0.04 Al 0.04 Be 0.04 Zn 0.04 La3Zr2O 12 at least one of.

[0064] On the other hand, the present application provides a method for preparing an oxide solid electrolyte material, and the preparation method includes the following steps:

[0065] S10 Weigh the lithium source, lanthanum source, zirconium source and dopant according to the stoichiometric ratio. The dopant includes dopant elements Fe, B, Be, Ga, and Al.

[0066] Exemplarily, the lithium salt can be lithium carbonate. The lanthanum source can be lanthanum oxide. The zirconium source can be zirconium oxide. Taking the dopant elements as Ga, Al, Zn and Be as an example, the dopant includes gallium oxide, aluminum oxide, zinc oxide and beryllium oxide. Further, calculated according to the stoichiometric ratio, the addition amount of the lithium salt is about 10% in excess.

[0067] S20 Ball-mill the mixture composed of the lithium source, the lanthanum source, the zirconium source, the dopant and the solvent to obtain a slurry.

[0068] In some embodiments of the present application, if the sum of the masses of the lithium source, the lanthanum source, the zirconium source and the dopant is M1, the mass of the ball-milling beads is M2, and the mass of the solvent is M3, then M1:M2:M3 is (1 - 5):(1 - 5):(5 - 20).

[0069] Exemplarily, M1 can be 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5 and values between any two of the above.

[0070] Exemplarily, M2 can be 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5 and values between any two of the above.

[0071] Exemplarily, M3 can be 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 and values between any two of the above. Exemplarily, the solvent can be isopropyl alcohol. The mass ratio of the powder (i.e., the powder formed by the lithium source, lanthanum source, zirconium source and dopant), zirconia ball-milling beads and the solvent is 1:1:10.

[0072] Exemplarily, the ball-milling speed in the ball-milling process is 250 r / min - 400 r / min, and the ball-milling time in the ball-milling process is 6 h - 12 h. Specifically, the ball-milling speed is 250 r / min and the ball-milling time is 12 h to obtain a slurry.

[0073] S30 After drying the slurry, calcine it at 900°C - 950°C for 6 h - 12 h, and then grind it to obtain a powder.

[0074] Exemplarily, the slurry after ball milling in step S20 is placed in a forced air drying oven at 80°C - 120°C for 6h - 12h to obtain a powder. Then, the powder is placed in an alumina crucible and calcined in a muffle furnace at a heating rate of 5°C / min, a calcination temperature of 900°C, and a calcination time of 12h, and then cooled to room temperature. Then, the calcined powder is taken out, ground fine with a mortar, and sieved successively through 200-mesh, 400-mesh, and 500-mesh sieves to obtain a fine and uniform powder.

[0075] S40 Sinter the powder at a pressure of 10 MPa - 20 MPa and a temperature of 1000°C - 1200°C for 1h - 2h to obtain an oxide solid electrolyte; wherein, the chemical formula of the oxide solid electrolyte is Li (6.4~6.6) MLa3Zr2O 12 ; M includes at least two elements of Fe, B, Be, Ga, Al, and Zn, and the molar amount of each element in M is greater than 0 and less than or equal to 0.1.

[0076] Exemplarily, weigh the powder obtained in step S30, place it in a graphite mold for dry pressing into a shape, and then transfer it to a hot pressing furnace filled with Ar. Sinter it at 1000°C for 1h, with a pressing pressure of 10 MPa and a heating rate of 3°C / min. After sintering, slowly cool it to room temperature at a rate of 2°C / min to obtain an oxide solid electrolyte.

[0077] In this embodiment, the technology adopts a hot pressing sintering method of pressing while sintering. Compared with ordinary pressureless sintering, the sintering time is shorter and the sintering temperature is lower, which is beneficial to reducing energy consumption. At the same time, the density and ionic conductivity of the electrolyte are also significantly improved.

[0078] Further, M is selected from at least four elements of Fe, B, Be, Ga, Al, and Zn. It should be noted that in this embodiment, there are more doping elements M. Using hot pressing sintering can effectively control the vapor change of the high-pressure component system, avoiding problems such as easy formation of impurities due to numerous components in traditional atmospheric pressure solid-phase sintering, and better obtaining a high-entropy LLZO solid electrolyte material with higher density and ionic conductivity. In some embodiments of the present application, the sum of the masses of the lithium source, the lanthanum source, the zirconium source, and the dopant is M1, the mass of the ball milling beads is M2, and the mass of the solvent is M3, then M1:M2:M3 is 1:1:10. In some embodiments of the present application, the ball milling speed during the ball milling process is 250 r / min; and / or,

[0079] the ball milling time during the ball milling process is 12h.

[0080] In some embodiments of the present application, the process of drying the slurry includes placing the slurry in a forced air drying oven at 120°C for 6h; and / or,

[0081] Before the sintering step, the preparation method further includes sieving the milled particles through sieves with 200 meshes, 400 meshes, and 500 meshes in sequence to obtain the powder; and / or,

[0082] Before the sintering step, the preparation method further includes dry-pressing the powder to obtain a precursor, and then hot-pressing and sintering the precursor to obtain the oxide solid electrolyte.

[0083] This application also provides a lithium-ion battery, which includes the oxide solid electrolyte described above, or the oxide solid electrolyte prepared by the preparation method described above.

[0084] Example 1: Preparation of Li 6.5 Ga 0.05 Al 0.05 Zn 0.05 Be 0.05 La3Zr2O 12 Preparation.

[0085] (1) According to the stoichiometric ratio, weigh lithium carbonate (10% in excess), gallium oxide, aluminum oxide, zinc oxide, beryllium oxide, lanthanum oxide, and zirconium oxide respectively, place them in a zirconia ball milling tank, and use isopropanol as a solvent for ball milling. Among them, the mass ratio of the powder, zirconia ball milling beads, and the solvent is 1:1:10, the ball milling speed is 250 r / min, and the ball milling time is 12 h.

[0086] (2) Place the above-mentioned ball-milled powder slurry in a forced-air drying oven at 120 °C for 6 h to dry.

[0087] (3) Place the dried powder in an alumina crucible and calcine it in a muffle furnace. The calcination temperature is 900 °C, the calcination time is 12 h, and the heating rate is 5 °C / min.

[0088] (4) Grind the calcined powder finely with a mortar and sieve it through sieves with 200 meshes, 400 meshes, and 500 meshes in sequence. The purpose of sieving is to obtain fine and uniform powder particles. Weigh 150 g of the sieved powder, place it in a graphite mold for dry pressing and forming, then transfer it to a hot pressing furnace filled with Ar, sinter at 1000 °C for 1 h, the pressing pressure is 10 MPa, the heating rate is 3 °C / min, and after sintering, slowly cool to room temperature at a rate of 2 °C / min. Cut and process the sintered electrolyte sheet according to requirements to obtain the final required square ceramic sheet with a size of 5 mm × 5 mm × 1 mm. Its XRD pattern is as Figure 1 shown, and the scanning electron microscope photo is as Figure 2 shown.

[0089] Example 2: Li 6.4 Ga 0.05 Fe0.05 Al 0.05 B 0.05 La3Zr2O 12 Preparation of

[0090] (1) According to the stoichiometric ratio, weigh lithium carbonate (10% in excess), gallium oxide, aluminum oxide, iron oxide, boron oxide, lanthanum oxide, and zirconium oxide respectively, place them in a zirconia ball milling jar, and use isopropanol as the solvent for ball milling. Among them, the mass ratio of the powder, zirconia ball milling beads, and the solvent is 1:1:10, the ball milling speed is 250 r / min, and the ball milling time is 12 h;

[0091] (2) Place the above-mentioned ball-milled powder slurry in a forced-air drying oven at 120 °C for 6 h to dry;

[0092] (3) Place the dried powder in an alumina crucible and calcine it in a muffle furnace. The calcination temperature is 900 °C, the calcination time is 12 h, and the heating rate is 5 °C / min.

[0093] (4) Grind the calcined powder finely with a mortar and sieve it successively through 200-mesh, 400-mesh, and 500-mesh sieves. The purpose of sieving is to obtain fine and uniform powder particles. Weigh 150 g of the sieved powder, place it in a graphite mold for dry pressing into a shape, and then transfer it to a hot pressing furnace filled with Ar. Sinter it at 1000 °C for 1 h, the pressing pressure is 10 MPa, the heating rate is 3 °C / min, and after sintering, slowly cool it to room temperature at a rate of 2 °C / min. Cut and process the sintered electrolyte sheet according to requirements to obtain the final required square ceramic sheet of 5 mm × 5 mm × 1 mm. Its XRD pattern is as Figure 3 shown.

[0094] Example 3: Li 6.48 Ga 0.04 Fe 0.04 Al 0.04 Be 0.04 Zn 0.04 La3Zr2O 12 Preparation of

[0095] (1) According to the stoichiometric ratio, weigh lithium carbonate (10% in excess), gallium oxide, aluminum oxide, iron oxide, beryllium oxide, zinc oxide, lanthanum oxide, and zirconium oxide respectively, place them in a zirconia ball milling jar, and use isopropanol as the solvent for ball milling. Among them, the mass ratio of the powder, zirconia ball milling beads, and the solvent is 1:1:10, the ball milling speed is 250 r / min, and the ball milling time is 12 h;

[0096] (2) Place the above-mentioned ball-milled powder slurry in a forced-air drying oven at 120 °C for 6 h to dry;

[0097] (3) The dried powder was placed in an alumina crucible and calcined in a muffle furnace at a calcination temperature of 900 °C for 12 h with a heating rate of 5 °C / min.

[0098] (4) The calcined powder was ground fine with a mortar and then sieved successively through 200-mesh, 400-mesh, and 500-mesh sieves. The purpose of sieving was to obtain fine and uniform powder particles. 150 g of the sieved powder was weighed and dry-pressed into a mold in a graphite mold, and then transferred into a hot-pressing furnace filled with Ar. It was sintered at 1000 °C for 40 min with a pressing pressure of 20 MPa and a heating rate of 3 °C / min. After sintering, it was slowly cooled to room temperature at a rate of 2 °C / min. The sintered electrolyte sheet was cut and processed according to requirements to obtain the final required square ceramic sheet of 5 mm × 5 mm × 1 mm. Its XRD pattern is as Figure 4 shown.

[0099] Example 4: Preparation of Li 6.4 Ga 0.1 Al 0.1 La3Zr2O 12 .

[0100] (1) According to the stoichiometric ratio, lithium carbonate (10% in excess), gallium oxide, aluminum oxide, lanthanum oxide, and zirconium oxide were weighed respectively and placed in a zirconia ball-milling tank. Isopropyl alcohol was used as a solvent for ball milling. Among them, the mass ratio of the powder, zirconia ball-milling beads, and the solvent was 1:1:10, the ball-milling speed was 300 r / min, and the ball-milling time was 10 h;

[0101] (2) The above-mentioned ball-milled powder slurry was placed in a forced-air drying oven at 120 °C for 6 h to dry;

[0102] (3) The dried powder was placed in an alumina crucible and calcined in a muffle furnace at a calcination temperature of 950 °C for 12 h with a heating rate of 5 °C / min.

[0103] (4) The calcined powder was ground fine with a mortar and then sieved successively through 200-mesh, 400-mesh, and 500-mesh sieves. The purpose of sieving was to obtain fine and uniform powder particles. 150 g of the sieved powder was weighed and dry-pressed into a mold in a graphite mold, and then transferred into a hot-pressing furnace filled with Ar. It was sintered at 1100 °C for 30 min with a pressing pressure of 15 MPa and a heating rate of 3 °C / min. After sintering, it was slowly cooled to room temperature at a rate of 2 °C / min. The sintered electrolyte sheet was cut and processed according to requirements to obtain the final required square ceramic sheet of 5 mm × 5 mm × 1 mm. Its XRD pattern is as Figure 5 shown.

[0104] Example 5: Li 6.6 Ga0.05 Al 0.05 Zn 0.05 La3Zr2O 12 Preparation of

[0105] (1) Weigh lithium carbonate (10% in excess), gallium oxide, aluminum oxide, zinc oxide, lanthanum oxide, and zirconium oxide respectively according to the stoichiometric ratio, place them in a zirconia ball milling tank, and use isopropanol as the solvent for ball milling. Among them, the mass ratio of the powder, zirconia ball milling beads, and the solvent is 1:1:10, the ball milling speed is 300 r / min, and the ball milling time is 8 h;

[0106] (2) Place the ball milled powder slurry in a forced air drying oven at 120 °C for 6 h to dry;

[0107] (3) Place the dried powder in an alumina crucible and calcine it in a muffle furnace. The calcination temperature is 950 °C, the calcination time is 6 h, and the heating rate is 5 °C / min.

[0108] (4) Grind the calcined powder finely with a mortar and sieve it successively through 200-mesh, 400-mesh, and 500-mesh sieves. The purpose of sieving is to obtain fine and uniform powder particles. Weigh 150 g of the sieved powder, place it in a graphite mold for dry pressing into a shape, and then transfer it to a hot pressing furnace filled with Ar. Sinter it at 1100 °C for 30 min, with a pressing pressure of 15 MPa and a heating rate of 3 °C / min. After sintering, slowly cool it to room temperature at a rate of 2 °C / min. Cut and process the sintered electrolyte sheet according to requirements to obtain the final required square ceramic sheet of 5 mm × 5 mm × 1 mm. Its XRD pattern is as Figure 6 shown.

[0109] Comparative Example 1: Preparation of Li 6.4 Al 0.2 La3Zr2O 12

[0110] (1) Weigh lithium carbonate (10% in excess), aluminum oxide, lanthanum oxide, and zirconium oxide respectively according to the stoichiometric ratio, place them in a zirconia ball milling tank, and use isopropanol as the solvent for ball milling. Among them, the mass ratio of the powder, zirconia ball milling beads, and the solvent is 1:1:10, the ball milling speed is 250 r / min, and the ball milling time is 12 h;

[0111] (2) Place the ball milled powder slurry in a forced air drying oven at 120 °C for 6 h to dry;

[0112] (3) Place the dried powder in an alumina crucible and calcine it in a muffle furnace. The calcination temperature is 900 °C, the calcination time is 12 h, and the heating rate is 5 °C / min.

[0113] (4) The calcined powder is ground fine with a mortar and sieved successively through sieves of 200 mesh, 400 mesh, and 500 mesh. The purpose of sieving is to obtain fine and uniform powder particles. Each time, 1 g of the powder is placed in a mold with a diameter of 10 mm, and using an axial press, it is kept under pressure for 2 min at a pressure of 20 MPa to obtain a disk with a diameter of 10 mm.

[0114] (5) Seal multiple disks in multiple balloons, and place the multiple balloons in a hydraulic press. Keep under pressure for 3 min at a pressure of 20 KN to eliminate uneven internal stress in the disks.

[0115] (6) Lay a layer of LLZO mother powder on an alumina crucible, place the disk on the mother powder (the purpose of laying the mother powder is to prevent lithium loss at high temperatures), and cover it with a thick layer of mother powder. Cover the crucible with a magnesia crucible lid and sinter it in a high-temperature muffle furnace at 1200 °C for 12 h with a heating rate of 5 °C / min. Its XRD pattern is as Figure 7 shown.

[0116] Experimental tests:

[0117] Perform XRD pattern and scanning electron microscope tests on the garnet-type oxide solid electrolyte prepared in the above Experimental Example 1. Figure 1 For the XRD pattern of the garnet-structured high-entropy oxide solid electrolyte Li 6.5 Ga 0.05 Al 0.05 Zn 0.05 Be 0.05 La3Zr2O 12 It can be seen that its peaks correspond one by one to the cubic garnet phase LLZO, without impurity peaks, Figure 1 and there are only peaks corresponding to the cubic phase without other impurity phases, indicating the successful incorporation of Li-site elements. Figure 1

[0118] Figure 2 For the scanning electron microscope photo of Li 6.5 Ga 0.05 Al 0.05 Zn 0.05 Be 0.05 12 La3Zr2O 12 La3Zr2O, it can be found that the grain size is about 1 - 5 μm, the grains are in close contact with each other, and there are no obvious voids or holes, indicating its high densification.

[0119] Perform XRD pattern tests on the garnet-type oxide solid electrolyte prepared in the above Experimental Example 2. It can be seen from Figure 3 this that Figure 3 there are only peaks corresponding to the cubic phase without other impurity phases, indicating the successful incorporation of Li-site elements.

[0120] The garnet-type oxide solid electrolyte prepared in Experimental Example 3 above was tested by XRD pattern. It can be seen from Figure 4 that Figure 4 there are only peaks corresponding to the cubic phase and no other impurity phases, indicating the successful incorporation of Li-site elements. Similarly, it can be seen from Figure 5 and Figure 6 the successful incorporation of Li-site elements in Example 4 and Example 5.

[0121] The garnet-type oxide solid electrolyte prepared in Comparative Example 1 above was tested by XRD pattern. It was found from Figure 7 that there is a peak at about 2θ = 25°, corresponding to LaAlO3 impurity; at the same time, it can be observed that multiple main peaks on the pattern are split, indicating the existence of partially untransformed tetragonal phase; the existence of impurities etc. causes the lattice constant of LLZO to increase, manifested as the peak shifting to the left; in addition, the existence of impurities will cause the grain boundary impedance of LLZO to increase, and then cause the total impedance of the material to increase, and finally manifested as a decrease in ionic conductivity.

[0122] The impedance of the examples and comparative examples was analyzed by EIS, and calculated using the conductivity formula. The ionic conductivities of each electrolyte are summarized in Table 1.

[0123] Table 1

[0124]

[0125] The difference between Examples 1 to 5 and Comparative Example 1 is that the Li site is doped with at least two elements such as Fe, B, Be, Ga, Al, Zn in equimolar amounts. It can be seen from Table 1 that doping at least two elements of Fe, B, Be, Ga, Al, Zn at the Li site can significantly improve the conductivity of the garnet-type oxide solid electrolyte.

[0126] In Example 5, the Li site was doped with three elements such as Fe, B, Be, Ga, Al, Zn in equimolar amounts. It can be seen from Table 1 that the conductivity of the obtained garnet-type oxide solid electrolyte is increased by 10.7% compared with doping with the above two elements. In Examples 1 to 3, the Li site was doped with at least four elements such as Fe, B, Be, Ga, Al, Zn in equimolar amounts. It can be seen from Table 1 that the conductivity of the obtained garnet-type oxide solid electrolyte is increased by 42% compared with doping with the above three elements. Compared with the 10.7% increase in doping with the above three elements compared with two elements at the Li site, it has a surprising effect. Further, in the present application, the Li site is doped with at least four elements such as Fe, B, Be, Ga, Al, Zn in equimolar amounts, and the stoichiometric number of Li is between 6.4 and 6.6, so that the garnet-type oxide solid electrolyte in the present application has a high Li+ Conductivity. The possible reason is that doping the Li sites with equimolar amounts of at least four elements among Fe, B, Be, Ga, Al, Zn generates a certain amount of lithium vacancies, stabilizes the disordered cubic phase of LLZO, and promotes Li + ion conduction; moreover, the incorporation of multiple elements changes the adjacent atomic sizes and ionic bond energies, causing local lattice distortion and reducing the + migration activation energy of Li and improving the ionic conductivity; in addition, through the coordinated action of each element, the high-entropy effect unique to high-entropy materials also significantly improves the phase stability of the LLZO solid electrolyte, enhances its air stability, and reduces the possibility of the formation of insulating Li2CO3 having an adverse effect on the ionic conductivity.

[0127] The technical solutions provided by the embodiments of the present application have been introduced in detail above. Specific examples are used herein to elaborate on the principles and implementation manners of the present application. The description of the above embodiments is only used to help understand the method and its core idea of the present application; at the same time, for those skilled in the art, according to the idea of the present application, there will be changes in the specific implementation manners and application scopes. In summary, the content of this specification should not be construed as a limitation to the present application.

Claims

1. A garnet-type oxide solid electrolyte, characterized in that, The chemical formula of the oxide solid electrolyte is Li (6.4~6.6) MLa3Zr2O 12 ; wherein, M is a doping element, and M is selected from at least four elements of Fe, B, Be, Ga, Al, and Zn. The molar amount of each element in M is greater than 0 and less than or equal to 0.1; the elements in M have an equimolar ratio.

2. The oxide solid electrolyte according to claim 1, wherein M is Ga, Al, Zn, and Be; or M is Ga, Fe, Al, and B; or M is Ga, Fe, Al, Be, and Zn.

3. The oxide solid electrolyte according to claim 1 or 2, characterized in that, The chemical formula of the oxide solid electrolyte is Li 6.5 Ga 0.05 Al 0.05 Zn 0.05 Be 0.05 La3Zr2O 12 、Li 6.4 Ga 0.05 Fe 0.05 Al 0.05 B 0.05 La3Zr2O 12 、Li 6.48 Ga 0.04 Fe 0.04 Al 0.04 Be 0.04 Zn 0.04 La3Zr2O 12 and at least one of them.

4. The oxide solid electrolyte according to any one of claims 1 to 2, characterized in that, The molar amount of each element in M is from 0.03 to 0.

06.

5. A method for preparing a garnet-type oxide solid electrolyte according to any one of claims 1 to 4, characterized in that, The preparation method includes the following steps: Weigh a lithium source, a lanthanum source, a zirconium source, and a dopant according to stoichiometric ratios. The dopant is selected from at least four of the doping elements Fe, B, Be, Ga, Al, and Zn; Ball-mill the mixture composed of the lithium source, the lanthanum source, the zirconium source, the dopant, and a solvent to obtain a slurry; After drying the slurry, calcine it at 900°C - 950°C for 6 h - 12 h, and then grind it to obtain a powder; Sinter the powder at a pressure of 10 MPa - 20 MPa and a temperature of 1000°C - 1200°C for 1 h - 2 h to obtain an oxide solid electrolyte.

6. The preparation method according to claim 5, characterized in that, If the sum of the masses of the lithium source, the lanthanum source, the zirconium source, and the dopant is M1, the mass of the ball-milling beads is M2, and the mass of the solvent is M3, then M1:M2:M3 is (1 - 5):(1 - 5):(5 - 20).

7. The preparation method according to claim 5, characterized in that, The ball-milling speed during the ball-milling process is 250 r / min - 400 r / min; and / or The ball-milling time during the ball-milling process is 6 h - 12 h.

8. The preparation method according to claim 5, characterized in that, The process of drying the slurry includes placing the slurry in a forced-air drying oven at 80°C - 120°C for 6 h - 12 h; and / or Before the sintering step, the preparation method further includes sieving the milled particles through sieves with 200 meshes, 400 meshes, and 500 meshes in sequence to obtain the powder; and / or Before the sintering step, the preparation method further includes dry-pressing the powder to obtain a precursor, and then hot-pressing and sintering the precursor to obtain the oxide solid electrolyte.

9. A lithium-ion battery, characterized in that, The lithium-ion battery includes the oxide solid electrolyte according to any one of claims 1 to 4, or the oxide solid electrolyte prepared by the preparation method according to any one of claims 5 to 8.

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