Al-Nb Co-Doped Lithium Lanthanum Zirconium Oxide, Its Preparation Method and Lithium-Ion Battery

Abstract

The present invention provides an Al-Nb co-doped lithium lanthanum zirconium oxide, a preparation method thereof, and a lithium ion battery. The chemical formula of the Al-Nb co-doped lithium lanthanum zirconium oxide is Li<subgt;7-y-3x< / subgt;Al<subgt;x< / subgt>La<subgt;3< / subgt>Zr<subgt;2-y< / subgt>Nb<subgt;y< / subgt>O<subgt;12; wherein: 0.05 ≤ x ≤ 0.10, 0.30 ≤ y ≤ 0.50; the Al-Nb co-doped lithium lanthanum zirconium oxide has a cubic phase structure; among them, Nb<supgt;5+ is doped by substituting an inequivalent cation at the Zr<supgt;4+ site; Al<supgt;3+ is concentrated at the grain boundaries of the cubic phase structure, substituting an inequivalent cation for Li<supgt;+, and also forms an amorphous Li-Al-O glass phase with Li<supgt;+. The present invention adopts a modification method of Nb-Al co-doping. By designing the doping ratios of Nb and Al, a pure cubic phase lithium lanthanum zirconium oxide powder is prepared, improving the ionic conductivity and stability of the lithium lanthanum zirconium oxide material.

Description

Technical Field

[0001] The present invention relates to the technical field of battery materials, specifically to a lithium lanthanum zirconium oxide material, and particularly to Al-Nb co-doped lithium lanthanum zirconium oxide and its preparation method and lithium-ion battery. Background Art

[0002] As an efficient secondary energy storage device, lithium-ion batteries have the advantages of high energy density, high output power, high voltage, low self-discharge, wide operating temperature range, no memory effect, and environmental friendliness, and have been widely used in fields such as electric vehicles, communication equipment, transportation tracks, and aerospace. However, most of the lithium-ion batteries widely used in the current market use flammable and explosive organic substances, bringing serious safety hazards. Solid electrolytes are an effective way to solve the safety hazards of lithium-ion batteries. Among them, lithium lanthanum zirconium oxide is the solid electrolyte material with the best comprehensive performance and the widest application at present. It has the advantages of high ionic conductivity, stable electrochemical performance, good thermal stability, wide electrochemical window, non-toxic and pollution-free, and stable contact with metallic lithium, so it has broad application prospects and research value in the future field of all-solid-state lithium batteries.

[0003] Cubic-phase lithium lanthanum zirconium oxide has a highly disordered Li + distribution and has high ionic conductivity. However, cubic-phase lithium lanthanum zirconium oxide is only stable at high temperatures and tends to transform into Li + with an ordered tetragonal-phase lithium lanthanum zirconium oxide at room temperature. The ionic conductivity of the tetragonal-phase lithium lanthanum zirconium oxide is only 10 -6 S / cm - 10 -5 S / cm, which is 1 - 2 orders of magnitude lower than that of cubic-phase lithium lanthanum zirconium oxide. Moreover, LiOH and Li2CO3 generated by the reaction of the surface of the cubic-phase lithium lanthanum zirconium oxide material with air induce a high interfacial resistance, thereby reducing the ionic conductivity.

[0004] CN114605152A discloses a cubic-phase lithium lanthanum zirconium oxide and its preparation method, including: by weight, mixing 10 - 30 parts of a zirconium-containing compound, 1 - 5 parts of an aluminum-containing compound, 6 - 17 parts of a lanthanum-containing compound, 1 - 20 parts of a polymerization inhibitor, 10 - 150 parts of urea, and 400 - 600 parts of water and stirring to obtain a first mixture; heating and holding the first mixture for a preset time, filtering, washing, and drying to obtain a precursor; mixing the precursor and a lithium salt, and then obtaining a mixed powder after grinding; sintering the mixed powder to obtain a finished product. The impedance value of the lithium lanthanum zirconium oxide prepared by this invention is relatively high.

[0005] CN113912120A discloses a method for improving the stability of the cubic phase of lithium lanthanum zirconium oxide, which includes using MoO3 as a doping source and preparing a lithium lanthanum zirconium oxide-based electrolyte by doping a small amount of Mo, so as to broaden the temperature range of the stable cubic phase, thereby improving the stability of the cubic phase. However, it is still impossible to prepare pure cubic phase lithium lanthanum zirconium oxide.

[0006] CN117756175A discloses a method for preparing nano lithium lanthanum zirconium oxide-based powder, which includes the steps of: S1 respectively weighing a lithium source and a lanthanum source and dissolving them in a first solvent, and stirring to obtain a first solution; S2 respectively weighing a zirconium source, a doped metal source, and an organic acid chelating agent and dissolving them in a second solvent, and stirring to obtain a second solution; S3 mixing the first solution and the second solution and stirring until a gel is formed, and aging to obtain an aged product; S4 subjecting the aged product to debinding, sintering, and grinding. The process steps of this invention are cumbersome and not suitable for industrial application.

[0007] Therefore, it is of great significance to provide a pure cubic phase lithium lanthanum zirconium oxide with simple preparation process, high ionic conductivity and high density. Summary of the Invention

[0008] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide an Al-Nb co-doped lithium lanthanum zirconium oxide, its preparation method and a lithium ion battery. The present invention adopts a modification method of Nb-Al co-doping. By designing the doping ratios of Nb and Al, pure cubic phase lithium lanthanum zirconium oxide is prepared, and the ionic conductivity and stability of the lithium lanthanum zirconium oxide material are improved. To achieve the purpose of this invention, the following technical solutions are adopted by the present invention:

[0009] In the first aspect, the present invention provides an Al-Nb co-doped lithium lanthanum zirconium oxide, and the chemical formula of the Al-Nb co-doped lithium lanthanum zirconium oxide is Li 7-y-3x Al x La3Zr 2-y Nb y O 12 ; wherein: 0.05 ≤ x ≤ 0.10, 0.30 ≤ y ≤ 0.50; the Al-Nb co-doped lithium lanthanum zirconium oxide has a cubic phase structure; wherein, Nb 5+ undergoes doping of inequivalent cation substitution at the Zr 4+ site; Al 3+ is concentrated at the grain boundaries of the cubic phase structure, undergoes doping of inequivalent cation substitution for Li + , and also forms an amorphous Li-Al-O glass phase with Li + .

[0010] The present invention adopts a modification method of Nb-Al co-doping. By designing the doping ratios of Nb and Al, pure cubic-phase Al-Nb co-doped lithium lanthanum zirconium oxide is obtained, improving the ionic conductivity and stability of the material. In the Al-Nb co-doped lithium lanthanum zirconium oxide provided by the present invention, Al 3+ is concentrated at the grain boundaries of the cubic-phase structure. On the one hand, through Al 3+ substituting for Li + , a large number of lithium vacancies are generated, forming stable cubic-phase lithium lanthanum zirconium oxide; on the other hand, through Al 3+ forming an amorphous Li-Al-O glass phase with Li + at the grain boundaries, improving the crystal density of lithium lanthanum zirconium oxide, reducing the content of surface LiOH and Li2CO3, and enhancing the ionic conductivity. Meanwhile, Nb 5+ substitutes for Zr 4+ , further reducing the content of lithium ions inside the lattice, increasing lithium vacancies, stabilizing the cubic-phase lattice, and enhancing the ionic conductivity.

[0011] Secondly, the present invention provides a preparation method of the Al-Nb co-doped lithium lanthanum zirconium oxide as described in the first aspect. The preparation method includes:

[0012] Performing a first mixing of a lanthanum source, a zirconium source, a niobium source, and an aluminum source according to a stoichiometric ratio, and pre-sintering to obtain a pre-sintered material; according to a stoichiometric ratio, performing a second mixing of the pre-sintered material and an excessive lithium source, and performing a solid-phase reaction to prepare the Al-Nb co-doped lithium lanthanum zirconium oxide.

[0013] The present invention prepares Al-Nb co-doped lithium lanthanum zirconium oxide through a solid-phase process. Nb 5+ performs doping of substituting an inequivalent cation at the Zr 4+ site; Al 3+ is concentrated at the grain boundaries of the cubic-phase structure. A small amount of Al 3+ performs doping of substituting an inequivalent cation at the Li + site at the grain boundaries, jointly promoting the formation of a low-melting-point phase during the sintering process, generating more lithium vacancies, reducing the grain boundary resistance, forming a stable cubic phase, and the remaining Al 3+ forms an amorphous Li-Al-O glass phase with Li + , improving the crystal density of lithium lanthanum zirconium oxide, reducing the content of surface LiOH and Li2CO3, and jointly enhancing the ionic conductivity. The present invention successfully prepares a pure cubic-phase lithium lanthanum zirconium oxide solid electrolyte by adjusting the doping ratios of Nb and Al and the preparation process, reducing the content of surface LiOH and Li2CO3, and improving the stability and ionic conductivity of the material.

[0014] Preferably, according to a stoichiometric ratio, the lithium source is excessive by 10wt%-25wt%.

[0015] Preferably, the mixing methods of the first mixing and the second mixing each independently include dry mixing.

[0016] Preferably, the temperature of the pre-sintering is 800°C - 900°C.

[0017] Preferably, the time of the pre-sintering is 8.0 h - 9.0 h.

[0018] Preferably, the temperature of the solid-phase reaction is 1000°C - 1100°C.

[0019] Preferably, the heating rate of the solid-phase reaction is 2.0°C / min - 5.0°C / min.

[0020] Preferably, the time of the solid-phase reaction is 10 h - 15 h.

[0021] Preferably, the pre-sintering and the solid-phase reaction each independently are carried out in an oxygen-containing atmosphere.

[0022] Preferably, the lanthanum source includes any one or a combination of at least two of lanthanum oxide, lanthanum nitrate, lanthanum chloride, or lanthanum fluoride.

[0023] Preferably, the zirconium source includes any one or a combination of at least two of zirconium oxide, zirconium nitrate, or zirconium acetate.

[0024] Preferably, the niobium source includes niobium oxide and / or niobium nitrate.

[0025] Preferably, the aluminum source includes aluminum oxide and / or aluminum hydroxide.

[0026] Preferably, the lithium source includes any one or a combination of at least two of lithium hydroxide, lithium carbonate, lithium nitrate, or lithium bis(trifluoromethanesulfonyl)imide.

[0027] Preferably, the preparation method further includes, after the solid-phase reaction, performing micronization treatment or nanometerization treatment on the Al-Nb co-doped lithium lanthanum zirconium oxide.

[0028] Preferably, the preparation method further includes, after the solid-phase reaction, performing micronization treatment and then nanometerization treatment on the Al-Nb co-doped lithium lanthanum zirconium oxide in sequence.

[0029] In a third aspect, the present invention provides a lithium-ion battery, and the lithium-ion battery includes the Al-Nb co-doped lithium lanthanum zirconium oxide as described in the first aspect.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] (1) The present invention adopts the modification method of Nb-Al co-doping. By designing the doping ratios of Nb and Al, pure cubic phase Al-Nb co-doped lithium lanthanum zirconium oxide is obtained, which improves the ionic conductivity and stability of the material.

[0032] (2) In the Al-Nb co-doped lithium lanthanum zirconium oxide provided by the present invention, Al 3+ is concentrated at the grain boundaries of the lithium lanthanum zirconium oxide material. By replacing Li 3+ at the grain boundaries, it helps to generate stable cubic phase lithium lanthanum zirconium oxide, and forms an amorphous Li-Al-O glass phase through Al + and Li 3+ and Li + , which improves the crystal density of lithium lanthanum zirconium oxide and reduces the content of surface LiOH and Li2CO3; Nb 5+ replaces Zr 4+ , reduces the content of lithium ions inside the lattice, increases lithium vacancies, further stabilizes the cubic phase lattice, and helps to improve the ionic conductivity of lithium lanthanum zirconium oxide.

[0033] (3) The Al-Nb co-doped lithium lanthanum zirconium oxide is prepared by a solid-phase process in the present invention. Nb 5+ performs substitution doping of inequivalent cations at the Zr 4+ site, and Al 3+ is concentrated at the grain boundaries of the cubic phase structure. A small amount of Al 3+ performs substitution doping of inequivalent cations at the Li + site, jointly promoting the formation of a low-melting-point phase during the sintering process, generating more lithium vacancies, reducing the grain boundary resistance, forming a stable cubic phase, and the remaining Al 3+ and Li + form an amorphous Li-Al-O glass phase, which improves the crystal density of lithium lanthanum zirconium oxide, reduces the content of surface LiOH and Li2CO3, and jointly improves the ionic conductivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 is the XRD pattern of the Al-Nb co-doped lithium lanthanum zirconium oxide in Example 1.

[0035] Figure 2 is the EIS pattern of the Al-Nb co-doped lithium lanthanum zirconium oxide in Example 1.

[0036] Figure 3 is the XRD pattern of the lithium lanthanum zirconium oxide in Comparative Example 1.

[0037] Figure 4 is the EIS pattern of the lithium lanthanum zirconium oxide in Comparative Example 1.

[0038] Figure 5 is the XRD pattern of the Nb-doped lithium lanthanum zirconium oxide in Comparative Example 2.

[0039] Figure 6 It is the EIS spectrum of Nb-doped lithium lanthanum zirconium oxide in Comparative Example 2. Specific embodiments

[0040] The technical solutions of the present invention will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations to the present invention.

[0041] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in this application are intended to cover non-exclusive inclusion.

[0042] In the description of this application, technical terms such as "first" and "second" are only used to distinguish different objects and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity, specific order or primary-secondary relationship of the indicated technical features. In the description of the embodiments of this application, "a plurality" means more than two unless otherwise specifically defined.

[0043] In a specific embodiment, the present invention provides an Al-Nb co-doped lithium lanthanum zirconium oxide, and the chemical formula of the Al-Nb co-doped lithium lanthanum zirconium oxide is Li 7-y-3x Al x La3Zr 2-y Nb y O 12 ; wherein: 0.05 ≤ x ≤ 0.10, 0.30 ≤ y ≤ 0.50; the Al-Nb co-doped lithium lanthanum zirconium oxide has a cubic phase structure; wherein, Nb 5+ substitutes and dopes at the Zr 4+ site with an inequivalent cation; Al 3+ is concentrated at the grain boundaries of the cubic phase structure, substitutes and dopes Li + with an inequivalent cation, and also forms an amorphous Li-Al-O glass phase with Li +

[0044] The present invention adopts a modification method of Nb-Al co-doping. By designing the doping ratios of Nb and Al, a pure cubic phase Al-Nb co-doped lithium lanthanum zirconium oxide is obtained, which improves the ionic conductivity and stability of the material.

[0045] In the Al-Nb co-doped lithium lanthanum zirconium oxide provided by the present invention, Al 3+The doping amount of Al is 0.05 ≤ x ≤ 0.10, and for example, it can be 0.05, 0.06, 0.07, 0.08, 0.09 or 0.10. 3+ It is concentrated at the grain boundaries of the lithium lanthanum zirconium oxide material. On the one hand, through Al 3+ substitutes Li at the grain boundaries, helping to generate stable cubic-phase lithium lanthanum zirconium oxide. On the other hand, through Al + forms an amorphous Li-Al-O glass phase with Li, improving the density of the lithium lanthanum zirconium oxide crystal and reducing the content of surface LiOH and Li2CO3. 3+ with Li +

[0046] In the Al-Nb co-doped lithium lanthanum zirconium oxide provided by the present invention, the doping amount of Nb 5+ is 0.30 ≤ y ≤ 0.50, and for example, it can be 0.30, 0.35, 0.40, 0.45 or 0.50. Nb 5+ substitutes Zr 4+ , helping to improve the ionic conductivity of lithium lanthanum zirconium oxide.

[0047] In another specific embodiment, the present invention provides a preparation method of the Al-Nb co-doped lithium lanthanum zirconium oxide as described in the foregoing specific embodiment, and the preparation method includes:

[0048] Perform a first mixing of the lanthanum source, zirconium source, niobium source and aluminum source according to the stoichiometric ratio, and pre-burn to obtain a pre-burned material; according to the stoichiometric ratio, perform a second mixing of the pre-burned material and an excessive lithium source, and perform a solid-phase reaction to prepare the Al-Nb co-doped lithium lanthanum zirconium oxide.

[0049] The present invention prepares Al-Nb co-doped lithium lanthanum zirconium oxide through a solid-phase process. Nb 5+ performs substitution doping of inequivalent cations at the Zr 4+ site, and Al 3+ is concentrated at the grain boundaries of the cubic-phase structure and performs substitution doping of inequivalent cations at the Li + site at the grain boundaries, jointly promoting the formation of a low-melting-point phase during the sintering process, generating more lithium vacancies, reducing the grain boundary resistance, forming a stable cubic phase, and the remaining Al 3+ forms an amorphous Li-Al-O glass phase with Li + , improving the density of the lithium lanthanum zirconium oxide crystal and reducing the content of surface LiOH and Li2CO3, jointly improving the ionic conductivity. The present invention successfully prepares a pure cubic-phase lithium lanthanum zirconium oxide solid electrolyte by adjusting the doping ratios of Nb and Al and the preparation process, reducing the content of surface LiOH and Li2CO3 and improving the stability of the material.

[0050] ​In the present invention, first, a lanthanum source, a zirconium source, a niobium source, and an aluminum source are first mixed in a stoichiometric ratio to obtain a pre-sintered material, and then the pre-sintered material and an excessive lithium source are secondarily mixed and subjected to subsequent solid-phase reactions, which can compensate for the volatilization loss of lithium during high-temperature sintering, promote the formation of a lithium lanthanum zirconium oxide cubic phase structure (the cubic phase has a shorter Li⁺ migration path and higher conductivity), and at the same time reduce the cost and loss of lithium raw materials during the synthesis of Al-Nb co-doped lithium lanthanum zirconium oxide, facilitating the large-scale industrial preparation of the material.

[0051] In the present invention, when the pre-sintered material and the excessive lithium source are secondarily mixed, Al concentrated at the grain boundaries 3+ and Li + form an amorphous Li-Al-O glass phase, improving the density of the lithium lanthanum zirconium oxide crystal and reducing the content of surface LiOH and Li2CO3.

[0052] In some embodiments, according to the stoichiometric ratio, the lithium source is excessive by 10wt%-25wt%, for example, it can be 10wt%, 13wt%, 15wt%, 17wt%, 19wt%, 20wt%, 21wt%, 23wt% or 25wt%, including but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0053] In some embodiments, the mixing methods of the first mixing and the second mixing each independently include dry mixing.

[0054] The present invention prepares Al-Nb co-doped lithium lanthanum zirconium oxide by combining dry mixing with a solid-phase process. The preparation method is simple to operate, has a fast production speed, high atomic utilization rate, and is environmentally friendly, and has broad application prospects.

[0055] In the present invention, the equipment for dry mixing includes but is not limited to a high-speed mixer or a blender.

[0056] In some embodiments, the time for the dry mixing is 0.1h-4.0h, for example, it can be 0.1h, 0.5h, 1.0h, 1.5h, 2.0h, 2.5h, 3.0h, 3.5h or 4.0h, including but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0057] In some embodiments, the temperature for the pre-sintering is 800°C-900°C, for example, it can be 800°C, 820°C, 840°C, 860°C, 880°C or 900°C, including but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0058] In some embodiments, the pre-sintering time is 8.0 h - 9.0 h, for example, it can be 8.0 h, 8.2 h, 8.4 h, 8.6 h, 8.8 h or 9.0 h, including but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0059] In some embodiments, the temperature of the solid-phase reaction is 1000 °C - 1100 °C, for example, it can be 1000 °C, 1020 °C, 1040 °C, 1060 °C, 1080 °C or 1100 °C, including but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0060] In some embodiments, the heating rate of the solid-phase reaction is 2.0 °C / min - 5.0 °C / min, for example, it can be 2.0 °C / min, 2.5 °C / min, 3.0 °C / min, 3.5 °C / min, 4.0 °C / min, 4.5 °C / min or 5.0 °C / min, including but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0061] In some embodiments, the time of the solid-phase reaction is 10 h - 15 h, for example, it can be 10 h, 11 h, 12 h, 13 h, 14 h or 15 h, including but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0062] In some embodiments, the pre-sintering and the solid-phase reaction are each independently carried out in an oxygen-containing atmosphere. Exemplarily, the oxygen-containing atmosphere can be air.

[0063] In some embodiments, the lanthanum source includes any one or a combination of at least two of lanthanum oxide, lanthanum nitrate, lanthanum chloride or lanthanum fluoride.

[0064] In some embodiments, the zirconium source includes any one or a combination of at least two of zirconium oxide, zirconium nitrate or zirconium acetate.

[0065] In some embodiments, the niobium source includes niobium oxide and / or niobium nitrate.

[0066] In some embodiments, the aluminum source includes aluminum oxide and / or aluminum hydroxide.

[0067] In some embodiments, the lithium source includes any one or a combination of at least two of lithium hydroxide, lithium carbonate, lithium nitrate or lithium bis(trifluoromethanesulfonyl)imide.

[0068] The present invention successfully prepares Al-Nb co-doped lithium lanthanum zirconium oxide with a pure cubic phase through a solid-phase process, and the Al-Nb co-doped lithium lanthanum zirconium oxide obtained after the solid-phase reaction can be post-treated as needed to control the particle size.

[0069] In some embodiments, the preparation method further includes micronizing or nanonizing the Al-Nb co-doped lithium lanthanum zirconium oxide after the solid-phase reaction.

[0070] In some embodiments, the micronizing includes crushing the prepared Al-Nb co-doped lithium lanthanum zirconium oxide.

[0071] In some embodiments, the equipment used for the crushing includes a jaw crusher or a pair-roll crusher.

[0072] In some embodiments, the preparation method further includes nanonizing the Al-Nb co-doped lithium lanthanum zirconium oxide after the solid-phase reaction.

[0073] In some embodiments, prior to the nanonizing, micronizing the Al-Nb co-doped lithium lanthanum zirconium oxide after the solid-phase reaction is further included.

[0074] In some embodiments, the equipment used for the nanonizing includes a sand mill, a ball mill, a jet mill, etc.

[0075] In yet another specific embodiment, the present invention provides a lithium-ion battery, which includes the Al-Nb co-doped lithium lanthanum zirconium oxide as described in a foregoing specific embodiment.

[0076] Example 1

[0077] This example provides an Al-Nb co-doped lithium lanthanum zirconium oxide with the chemical formula Li 6.375 Al 0.075 La3Zr 1.6 Nb 0.4 O 12 .

[0078] This example also provides a preparation method for the Al-Nb co-doped lithium lanthanum zirconium oxide, and the preparation method includes:

[0079] Mixing lanthanum oxide, zirconium oxide, niobium oxide and aluminum oxide according to the stoichiometric ratio, mixing in a high-speed mixer for 0.5 h, pre-firing in an air atmosphere at 900 °C for 9 h, and naturally cooling to room temperature to obtain a pre-fired material. According to 20 wt% excess lithium, mixing the pre-fired material with lithium carbonate in a high-speed mixer for 0.5 h, heating to 1025 °C at a heating rate of 3 °C / min, holding for 15 h, and performing a solid-phase reaction to prepare Li 6.375 Al 0.075 La3Zr 1.6 Nb 0.4 O 12 .

[0080] Example 2

[0081] This embodiment provides an Al-Nb co-doped lithium lanthanum zirconium oxide with the chemical formula Li 6.2 Al 0.1 La3Zr 1.5 Nb 0.5 O 12 。

[0082] This embodiment also provides a preparation method for the Al-Nb co-doped lithium lanthanum zirconium oxide, and the preparation method includes:

[0083] Mix lanthanum nitrate, zirconium nitrate, niobium nitrate and aluminum hydroxide according to the stoichiometric ratio. After mixing in a blender for 2 h, pre-calcine in an air atmosphere at 800 °C for 8 h, and naturally cool to room temperature to obtain a pre-calcined material. According to 10 wt% excess lithium, mix the pre-calcined material with lithium hydroxide, mix in a blender for 3 h, heat up to 1000 °C at a heating rate of 2 °C / min, hold for 10 h, and carry out a solid-phase reaction to prepare Li 6.2 Al 0.1 La3Zr 1.5 Nb 0.5 O 12 。

[0084] Example 3

[0085] This embodiment provides an Al-Nb co-doped lithium lanthanum zirconium oxide with the chemical formula Li 6.55 Al 0.05 La3Zr 1.7 Nb 0.3 O 12 。

[0086] This embodiment also provides a preparation method for the Al-Nb co-doped lithium lanthanum zirconium oxide, and the preparation method includes:

[0087] Mix lanthanum oxide, zirconium oxide, niobium oxide and aluminum oxide according to the stoichiometric ratio. After mixing in a blender for 4 h, pre-calcine in an air atmosphere at 850 °C for 5.5 h, and naturally cool to room temperature to obtain a pre-calcined material. According to 25 wt% excess lithium, mix the pre-calcined material with lithium carbonate, mix in a blender for 4 h, heat up to 1100 °C at a heating rate of 5 °C / min, hold for 12 h, and carry out a solid-phase reaction to prepare Li 6.55 Al 0.05 La3Zr 1.7 Nb 0.3 O 12 。

[0088] Example 4

[0089] This embodiment provides an Al-Nb co-doped lithium lanthanum zirconium oxide with the chemical formula Li 6.375 Al0.075 La3Zr 1.6 Nb 0.4 O 12 。

[0090] This example also provides a preparation method of Al-Nb co-doped lithium lanthanum zirconium oxide. Except for mixing the pre-sintered material with lithium carbonate according to 5 wt% excess lithium, the rest are the same as in Example 1.

[0091] Example 5

[0092] This example provides an Al-Nb co-doped lithium lanthanum zirconium oxide with the chemical formula Li 6.375 Al 0.075 La3Zr 1.6 Nb 0.4 O 12 。

[0093] This example also provides a preparation method of Al-Nb co-doped lithium lanthanum zirconium oxide. Except for mixing the pre-sintered material with lithium carbonate according to 30 wt% excess lithium, the rest are the same as in Example 1.

[0094] Comparative Example 1

[0095] This comparative example provides a lithium lanthanum zirconium oxide with the chemical formula Li7La3Zr2O 12 。

[0096] This comparative example also provides a preparation method of lithium lanthanum zirconium oxide. Except for mixing lanthanum oxide and zirconium oxide to obtain the pre-sintered material according to the stoichiometric ratio, the rest are the same as in Example 1.

[0097] Comparative Example 2

[0098] This comparative example provides a Nb-doped lithium lanthanum zirconium oxide with the chemical formula Li 6.6 La3Zr 1.6 Nb 0.4 O 12 。

[0099] This comparative example also provides a preparation method of Nb-doped lithium lanthanum zirconium oxide. Except for mixing lanthanum oxide, niobium oxide and zirconium oxide to obtain the pre-sintered material according to the stoichiometric ratio, the rest are the same as in Example 1.

[0100] Comparative Example 3

[0101] This comparative example provides an Al-doped lithium lanthanum zirconium oxide with the chemical formula Li 6.775 La3Zr2Al 0.075 O 12 。

[0102] This comparative example also provides a method for preparing Al-doped lithium lanthanum zirconium oxide. Except for mixing lanthanum oxide, zirconium oxide, and aluminum oxide according to the stoichiometric ratio to obtain a pre-sintered material, the rest are the same as in Example 1.

[0103] Comparative Example 4

[0104] This comparative example provides an Al-Nb co-doped lithium lanthanum zirconium oxide with the chemical formula Li 6.1 La3Zr 1.55 Al 0.15 Nb 0.45 O 12 。

[0105] This comparative example also provides a method for preparing Al-Nb co-doped lithium lanthanum zirconium oxide. Except for mixing lanthanum oxide, zirconium oxide, niobium oxide, and aluminum oxide according to the stoichiometric ratio in this comparative example to obtain a pre-sintered material, the rest are the same as in Example 2.

[0106] Comparative Example 5

[0107] This comparative example provides an Al-Nb co-doped lithium lanthanum zirconium oxide with the chemical formula Li 6.3 La3Zr 1.45 Al 0.05 Nb 0.55 O 12 。

[0108] This comparative example also provides a method for preparing Al-Nb co-doped lithium lanthanum zirconium oxide. Except for mixing lanthanum oxide, zirconium oxide, niobium oxide, and aluminum oxide according to the stoichiometric ratio in this comparative example to obtain a pre-sintered material, the rest are the same as in Example 2.

[0109] Comparative Example 6

[0110] This comparative example provides an Al-Nb co-doped lithium lanthanum zirconium oxide with the chemical formula Li 6.59 La3Zr 1.68 Al 0.03 Nb 0.32 O 12 。

[0111] This comparative example also provides a method for preparing Al-Nb co-doped lithium lanthanum zirconium oxide. Except for mixing lanthanum oxide, zirconium oxide, niobium oxide, and aluminum oxide according to the stoichiometric ratio in this comparative example to obtain a pre-sintered material, the rest are the same as in Example 3.

[0112] Comparative Example 7

[0113] This comparative example provides an Al-Nb co-doped lithium lanthanum zirconium oxide with the chemical formula Li 6.45 La3Zr 1.75 Al0.1 Nb 0.25 O 12 。

[0114] This comparative example also provides a preparation method of Al-Nb co-doped lithium lanthanum zirconium oxide. Except that the pre-sintered material is obtained by mixing lanthanum oxide, zirconium oxide, niobium oxide and aluminum oxide according to the stoichiometric ratio in this comparative example, the rest are the same as in Example 3.

[0115] Performance test:

[0116] XRD tests were respectively carried out on the lithium lanthanum zirconium oxide provided in Example 1, Comparative Example 1 and Comparative Example 2, and the obtained XRD patterns are respectively shown in Figure 1 、 Figure 3 and Figure 5 。

[0117] The lithium lanthanum zirconium oxide provided by all the above examples and comparative examples was pressed into tablets at a pressure of 15-20 MPa, and then sintered into dense sheet samples. After gold spraying treatment on both sides of the sheet samples, EIS tests were carried out with an electrochemical workstation to obtain its resistance value R, and then according to the formula: σ = L / (R×S), the ionic conductivity of the solid electrolyte material can be calculated:

[0118] where L is the thickness of the electrolyte sheet during testing (cm); S is the area of the electrolyte sheet during testing (cm 2 ), and three samples were tested for each example or comparative example, and the average value was calculated. The test results are shown in Table 1.

[0119] The EIS test patterns of the lithium lanthanum zirconium oxide provided by Example 1, Comparative Example 1 and Comparative Example 2 are respectively shown in Figure 2 、 Figure 4 and Figure 6 。

[0120] Table 1

[0121]

[0122] According to Figure 1 the XRD pattern of the Al-Nb co-doped lithium lanthanum zirconium oxide provided by Example 1 as shown, it can be determined that through the design of the doping ratios of Nb and Al in the present invention, a pure-phase cubic Al-Nb co-doped lithium lanthanum zirconium oxide is obtained. For lithium lanthanum zirconium oxide without Nb and Al doping, as Figure 3 shown, the lithium lanthanum zirconium oxide provided in Comparative Example 1 does not have a cubic phase structure and has many impurity peaks. For only Nb doping, as Figure 5 shown, compared with the pattern of the standard cubic phase lithium lanthanum zirconium oxide, the XRD pattern of the Nb-doped lithium lanthanum zirconium oxide in Comparative Example 2 has a shift of some diffraction peaks, and a pure-phase cubic lithium lanthanum zirconium oxide cannot be obtained.

[0123] According to the ionic conductivities of lithium lanthanum zirconium oxide provided in Examples 1 to 3 in Table 1, compared with the undoped lithium lanthanum zirconium oxide in Comparative Example 1, after doping according to the Nb and Al ratios defined in the present invention, the ionic conductivity of lithium lanthanum zirconium oxide is significantly improved and can reach 4.8×10 -4 S / cm or more. If Nb and Al are not doped, the ionic conductivity is only 2.4×10 -5 S / cm. If only Nb is doped, the ionic conductivity can only be increased to 3.0×10 -4 S / cm. If only Al is doped, the ionic conductivity can only be increased to 2.0×10 -4 S / cm.

[0124] According to the ionic conductivity test results of Example 2 and Comparative Examples 4 to 5, and Example 3 and Comparative Examples 6 to 7, it can be determined that when the total doping amount of Nb and Al remains unchanged, if the doping amount of any one of the elements Nb or Al does not meet the range defined in the present invention, the ionic conductivity will decrease.

[0125] According to the test results of Example 1 and Examples 4 to 5, during the preparation of Al-Nb co-doped lithium lanthanum zirconium oxide, when the lithium source is appropriately in excess, Al concentrated at the grain boundaries 3+ and Li + form an amorphous Li-Al-O glass phase, which improves the crystal density of lithium lanthanum zirconium oxide, reduces the content of surface LiOH and Li2CO3, and enhances the ionic conductivity of Al-Nb co-doped lithium lanthanum zirconium oxide. If the lithium source is in excess too little, pure cubic-phase lithium lanthanum zirconium oxide cannot be obtained and the ionic conductivity cannot be effectively improved; if the lithium source is in excess too much, by-products such as Li2ZrO3 will be generated, destroying the integrity of the garnet structure of cubic-phase lithium lanthanum zirconium oxide, which will also lead to a decrease in ionic conductivity.

[0126] The applicant declares that the above is only the specific implementation manner of the present invention, but the protection scope 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 protection scope and the disclosure scope of the present invention.

Claims

1. An Al-Nb co-doped lithium lanthanum zirconium oxide, characterized in that, The chemical formula of the Al-Nb co-doped lithium lanthanum zirconium oxide is Li 7-y-3x Al x La3Zr 2-y Nb y O 12 ; where: 0.05 < x < 0.10, 0.30 < y < 0.50; The Al-Nb co-doped lithium lanthanum zirconium oxide has a cubic phase structure; Among them, Nb 5+ substitute and dope with inequivalent cations at the 4+ Zr site; Al 3+ Concentrates at the grain boundaries of the cubic phase structure and dopes Li + by substituting with inequivalent cations, and also forms an amorphous Li-Al-O glass phase with Li + ; The Al-Nb co-doped lithium lanthanum zirconium oxide is prepared by the following preparation method, which includes: Mixing a lanthanum source, a zirconium source, a niobium source, and an aluminum source in a stoichiometric ratio for the first time, and pre-calcining to obtain a pre-calcined material; mixing the pre-calcined material and an excessive lithium source for the second time, and performing a solid-phase reaction to prepare the Al-Nb co-doped lithium lanthanum zirconium oxide; According to the stoichiometric ratio, the lithium source is excessive by 13wt%-25wt%.

2. A preparation method of Al-Nb co-doped lithium lanthanum zirconium oxide as described in claim 1, characterized in that, The preparation method includes: Mixing a lanthanum source, a zirconium source, a niobium source, and an aluminum source in a stoichiometric ratio for the first time, and pre-calcining to obtain a pre-calcined material; mixing the pre-calcined material and an excessive lithium source for the second time, and performing a solid-phase reaction to prepare the Al-Nb co-doped lithium lanthanum zirconium oxide; According to the stoichiometric ratio, the lithium source is excessive by 13wt%-25wt%.

3. The preparation method according to claim 2, characterized in that, The mixing methods of the first mixing and the second mixing each independently include dry mixing.

4. The preparation method according to claim 2, characterized in that, The temperature of the pre-calcining is 800°C - 900°C; and / or, the time of the pre-calcining is 8.0h - 9.0h.

5. The preparation method according to claim 2, characterized in that, The temperature of the solid-phase reaction is 1000°C - 1100°C; and / or, the heating rate of the solid-phase reaction is 2.0°C / min - 5.0°C / min; and / or, the time of the solid-phase reaction is 10h - 15h.

6. The preparation method according to claim 2, characterized in that, The pre-calcining and the solid-phase reaction are each independently carried out in an oxygen-containing atmosphere.

7. The preparation method according to claim 2, wherein, The lanthanum source includes any one or a combination of at least two of lanthanum oxide, lanthanum nitrate, lanthanum chloride, or lanthanum fluoride; and / or, the zirconium source includes any one or a combination of at least two of zirconium oxide, zirconium nitrate, or zirconium acetate; and / or, the niobium source includes niobium oxide and / or niobium nitrate; and / or, the aluminum source includes aluminum oxide and / or aluminum hydroxide; and / or, the lithium source includes any one or a combination of at least two of lithium hydroxide, lithium carbonate, lithium nitrate, or lithium bis(trifluoromethanesulfonyl)imide.

8. The preparation method according to any one of claims 2-7, characterized in that, The preparation method further includes performing micronization treatment or nanometerization treatment on the Al-Nb co-doped lithium lanthanum zirconium oxide after the solid-phase reaction; and / or, the preparation method further includes sequentially performing micronization treatment and nanometerization treatment on the Al-Nb co-doped lithium lanthanum zirconium oxide after the solid-phase reaction.

9. A lithium-ion battery, characterized in that, The lithium ion battery includes the Al-Nb co-doped lithium lanthanum zirconium oxide as described in claim 1.

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