WO2024021162A1 - Solid electrolyte material and preparation method therefor, and battery - Google Patents

Abstract

The present invention relates to a solid electrolyte material and a preparation method therefor, and a battery. The solid electrolyte material of the present invention comprises a doped or undoped oxide solid electrolyte inner core and a coating layer covering the surface of the oxide solid electrolyte inner core, the coating layer comprising one or two of tantalate and niobate. The solid electrolyte material is prepared by means of a one-step sintering solid-phase reaction method. The solid electrolyte material prepared by the present invention has a very high lithium ion conductivity and a very low impedance value, and surface side reactions of the solid electrolyte material in air are greatly reduced, so that the stability is higher. The solid electrolyte material of the present invention involves a simple and convenient preparation process and achieves high production efficiency, thus being very suitable for large-batch industrial production.

Description

Solid electrolyte material and preparation method thereof and battery

This application is filed based on a Chinese patent application with application number 202210908789.5 and a filing date of July 29, 2022, and claims the priority of the Chinese patent application. The entire content of the Chinese patent application is hereby incorporated into this application as a reference.

Technical field

The invention belongs to the field of new energy technology, and specifically relates to a solid electrolyte material, a preparation method thereof and a battery.

Background technique

The safety of traditional lithium-ion batteries cannot be guaranteed due to the use of electrolytes, and the energy density of lithium-ion batteries has also reached a bottleneck. All-solid-state batteries use lithium metal instead of graphite as the negative electrode, which greatly improves the energy density of the battery. And using solid electrolytes instead of traditional electrolytes can fundamentally solve battery safety problems, so they have received widespread attention from academia and industry.

One of the core technologies of all-solid-state batteries is solid electrolyte. Solid electrolytes include oxide solid electrolytes, sulfide solid electrolytes and polymer solid electrolytes. Among them, oxide solid electrolytes are favored because of their high conductivity (10 ^-4 S/cm), good thermal stability, and wide electrochemical window.

The all-solid-state battery corresponding to the oxide solid-state electrolyte prepared by existing methods will cause a significant decrease in conductivity when exposed to air, thus limiting its practical application.

Attention has been paid to the problem that oxide solid electrolytes are prone to side reactions in air. In the prior art, there are materials that coat the surface of the oxide solid electrolyte with coating layers such as lithium titanate, lithium metaaluminate, lithium lanthanum titanium oxide, lithium phosphate, and lithium halide. There are also materials that use two coating layers. However, these coating layers will cause the conductivity of lithium ions to decrease, and most of their coating methods are carried out using liquid phase methods, which has the problem of complicated steps and difficulty in practical application.

Contents of the invention

Invent the problem to be solved

The process corresponding to the solid electrolyte obtained by the existing preparation method is very complex, cumbersome, and unsuitable for scale-up. At the same time, exposure of the solid electrolyte to the air will cause a significant decrease in conductivity. However, the existing coating layer will cause the conductivity of lithium ions to decrease, and the coating method has complicated steps and is difficult to apply in practice.

Therefore, the object of the present invention is to provide a solid electrolyte material with high stability in air, high lithium ion conductivity and low impedance value, and a simple method for preparing the same.

solutions to problems

In the present invention, the oxide solid electrolyte powder is prepared by a one-step sintering solid phase method and the doped or undoped oxide solid electrolyte powder is coated with tantalate and/or niobate, which can significantly improve the oxide Conductivity stability of solid electrolytes in air. Moreover, in the present invention, the oxide solid electrolyte powder is prepared by a one-step sintering solid phase method and the oxide solid electrolyte material with a coating layer is prepared by a solid phase reaction method. Therefore, the preparation process can be simplified and the preparation efficiency can be significantly improved, which is very suitable Large-scale production and use.

Specifically, the present invention provides a solid electrolyte material, which includes a doped or undoped oxide solid electrolyte core and a coating layer coating the surface of the oxide solid electrolyte core,

The doping element in the doped oxide solid electrolyte is selected from at least one of Ta, Nb, Ca, Sr, Ba, Mo, and W;

The coating layer includes one or both of tantalate and niobate.

According to the above solid electrolyte material, the thickness of the coating layer is 0.01-1.0 μm, preferably 0.05-0.5 μm.

According to the above solid electrolyte material, the particle size of the oxide solid electrolyte core is 0.01 to 10 μm, preferably 0.1 to 5 μm.

According to the above solid electrolyte material, the oxide solid electrolyte is selected from at least one of a perovskite oxide solid electrolyte and a garnet oxide solid electrolyte.

According to the above solid electrolyte material, the chemical composition of the garnet type oxide solid electrolyte is Li _7-x La ₃ Zr _2-x A _x O ₁₂ , and the doping element A is Ta, Nb, Ca, Sr, One or more of Ba, Mo and W, 0≤x≤1,

The perovskite oxide solid electrolyte is LLTO.

According to the above solid electrolyte material, wherein the tantalate includes a lithium ion conductor tantalate, preferably lithium tantalate.

The invention also provides a preparation method of solid electrolyte material, which preparation method includes:

Step S1: Mix the raw materials of doped or undoped oxide solid electrolyte and then sinter them to obtain doped or undoped oxide solid electrolyte powder;

Step S2: Mix, coat and heat-treat the doped or undoped oxide solid electrolyte powder obtained in step S1 with the coating material to obtain a doped or undoped oxide solid electrolyte core and coating. The solid electrolyte material of the coating layer covering the surface of the oxide solid electrolyte core.

According to the above preparation method, in step S1, the sintering is one-step sintering.

According to the above preparation method, in step S1, when the oxide solid electrolyte is a garnet type oxide solid electrolyte, the sintering includes continuous sintering at the first temperature and the second temperature, and The conditions for sintering at the first temperature are: sintering at a first temperature of 800 to 1000°C, preferably 850 to 950°C for 3 to 12 hours, preferably 5 to 10 hours, and the sintering conditions at the second temperature are: The first temperature is raised to a second temperature of 1050-1250°C, preferably 1100-1200°C, and sintering is performed at the second temperature for 3-18h, preferably 6-12h;

When the oxide solid electrolyte is a perovskite oxide solid electrolyte, the sintering includes continuous sintering at a first temperature and a second temperature, and the conditions for sintering at the first temperature are: between 900 and 1100 ° C, preferably 950 ~ 1050 ° C, sintering at a first temperature of 3 to 18 hours, preferably 6 to 12 hours, the sintering conditions at the second temperature are: raising the first temperature to 1150 ~ 1350 ° C, preferably 1200 ~ A second temperature of 1300° C. and sintering at the second temperature for 3 to 18 hours, preferably 6 to 12 hours.

According to the above preparation method, in step S1, the particle size of the raw material is ≤5 microns.

According to the above preparation method, wherein in step S1, the raw materials are weighed according to the molar ratio of the chemical formula of the doped or undoped oxide solid electrolyte, or the lithium compound in the raw materials is excessive by 5 to 30 mass% .

According to the above preparation method, in step S2, the mass ratio of the coating material to the oxide solid electrolyte powder is (0.1-20):100, preferably (1-10):100.

According to the above preparation method, in the step S2, the heat treatment conditions are: heat treatment at 500-750°C, preferably 600-700°C for 6-18 hours, preferably 8-12 hours.

The present invention further provides a battery, which includes the above-mentioned solid electrolyte material and/or the solid electrolyte material obtained by the above-mentioned preparation method.

Effect of invention

The above technical solution of the present invention has the following beneficial effects:

(1) Since the solid electrolyte material of the present invention has a tantalate and/or niobate coating layer on the surface, it can avoid excessive contact between the oxide solid electrolyte and the air, inhibit side reactions between the oxide solid electrolyte and the air, and make the It maintains as high an ionic conductivity as possible. Compared with other coating layers that are not lithium ion conductors, the coating layer in this application has good ion diffusion performance and high conductivity.

(2) The solid electrolyte material of the present invention can effectively improve its lithium ion conductivity because the oxide solid electrolyte is doped.

(3) The solid electrolyte material of the present invention is easy to process into a solid electrolyte film. Due to its high stability in air, it can significantly improve the conductivity stability of all-solid-state batteries in air, and is very suitable for large-scale production and use.

(4) Further preferably, in the present invention, a one-step sintering solid-state reaction method is used to prepare the solid electrolyte powder and the surface coating layer is also prepared by the solid-phase method. Therefore, the preparation process of the solid electrolyte material is simple and the production efficiency is high. , and the raw materials used are cheap and very suitable for large-scale industrial production.

(5) Further preferably, the one-step sintering solid-state reaction method is used to prepare the solid electrolyte material, which can avoid excessive contact with air and suppress side reactions between the solid electrolyte material and the air.

Description of drawings

Figure 1 is an SEM image of the lithium lanthanum zirconium oxygen powder obtained in Example 2;

Figure 2 is a surface SEM image of lithium tantalate coating lithium lanthanum zirconium oxygen obtained in Example 2;

Figure 3 is the XRD pattern of lithium lanthanum zirconium oxygen obtained in Examples 1 to 4 and Comparative Examples 1 to 3;

Figure 4 is the impedance spectrum EIS diagram of the tableting test of Examples 1 to 4 and Comparative Examples 1 to 3;

Figure 5 is a process flow chart for preparing solid electrolyte materials according to the present invention.

Detailed ways

Embodiments of the present invention will be described below, but the present invention is not limited thereto. The present invention is not limited to each configuration described below, and various changes can be made within the scope of the claimed invention. Embodiments obtained by appropriately combining different embodiments and appropriately combining technical means disclosed in the examples are also included in the present invention. within the technical scope. In addition, all documents described in this specification are cited in this specification as references.

Unless otherwise defined, technical and scientific terms used herein have the same meanings commonly understood by one of ordinary skill in the art to which this invention belongs.

In this specification, the numerical range represented by "numeric value A to numerical value B" refers to the range including the endpoint values A and B.

In this specification, unless otherwise stated, "many" in "many", "many", "plurality", etc. means a numerical value of 2 or more.

In this specification, "basically", "substantially" or "substantially" means that compared with the relevant perfect standard or theoretical standard, the error is less than 5%, or less than 3%, or less than 1%.

In this specification, unless otherwise specified, "%" means mass percentage.

In this manual, if "room temperature", "normal temperature", etc. appear, the temperature can generally be 10 to 37°C, or 15 to 35°C.

In this specification, the meaning of "can" or "can" includes both the meaning of existence or non-existence, and the two meanings of performing certain processing and not performing certain processing.

In this specification, "optional" and "optionally" mean that the next described event or situation may or may not occur, and the description includes situations where the event occurs and situations where the event does not occur.

The term "comprising" and any variations thereof in the description and claims of the present invention and the above drawings are intended to cover non-exclusive inclusion. For example, a process, method or system, product or device that includes a series of steps or units is not limited to the listed steps or units, but optionally also includes steps or units that are not listed, or optionally also includes Other steps or units inherent in such processes, methods, products or devices.

In this specification, references to "some/certain/preferred embodiments", "embodiments", etc. refer to the specific elements (for example, features, structures, properties and/or characteristics) described in relation to the embodiments. is included in at least one embodiment described herein and may or may not be present in other embodiments. Additionally, it is to be understood that the described elements may be combined in various embodiments in any suitable manner.

<First aspect>

A first aspect of the present invention provides a solid electrolyte material, which includes a doped or undoped oxide solid electrolyte core and a coating layer coating the surface of the oxide solid electrolyte core. The doping element in the doped oxide solid electrolyte may be selected from at least one of Ta, Nb, Ca, Sr, Ba, Mo, and W. Among them, Ta and Nb are preferred.

In the present invention, the oxide solid electrolyte is selected from at least one of a perovskite oxide solid electrolyte and a garnet oxide solid electrolyte.

In the present invention, the garnet-type oxide solid electrolyte is lithium lanthanum zirconium oxide LLZO, and its chemical composition is Li _7-x La ₃ Zr _2-x A _x O ₁₂ . The doping element A is one or more of Ta, Nb, Ca, Sr, Ba, Mo, and W. Among them, Ta and Nb are preferred.

In the above formula, x is any number from 0 to 1.0, and preferably x is 0 to 0.75. For example, x can be 0, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1.0, etc.

In some preferred embodiments of the present invention, x is not 0 and the doping element A is one or both of Ta and Nb. In some more preferred embodiments, x is not 0 and doping element A is Ta. When tantalum and/or niobium are used to dope lithium lanthanum zirconium oxygen, the tantalum and/or niobium doping can more effectively promote the formation of the lithium lanthanum zirconium oxygen cubic phase (the cubic phase lithium ion conductivity is as high as 8×10 ^{- 4} S/cm), thereby improving the lithium ion conductivity of lithium lanthanum zirconium oxygen.

In the present invention, the perovskite-type oxide solid-state electrolyte is lithium lanthanum titanium oxide LLTO, and its doping element can be one or more of Ta, Nb, Ca, Sr, Ba, Mo, and W. Among them, Ta and Nb are preferred. When tantalum and/or niobium are used to dope lithium lanthanum titanium oxide LLTO, tantalum and/or niobium doping can more effectively promote the uniformity of lithium lanthanum titanium oxide particles and significantly increase their density, thereby improving the lithium Lithium ion conductivity of lanthanum titanium oxide.

When double doped, the chemical formula of lithium lanthanum titanium oxide LLTO can be Li _0.33+xy La _0.56-x M _x Ti _1-y N _y O ₃ , where M and N are doping elements, 0≤x≤0.1, 0 ≤y≤0.1. When single-doped, the chemical formula of lithium lanthanum titanium oxide LLTO can vary depending on the valence state of the doping element. For example, when the doping element is Ta, the chemical formula of lithium lanthanum titanium oxide LLTO can be Li _0.33-y La _0.56 Ti _1-y Ta _y O ₃ , where 0≤y≤0.1.

The existing garnet-type solid electrolyte material LLZO and the perovskite-type solid electrolyte material LLTO are prone to side reactions in the air, making the surfaces of LLZO and LLTO unstable. There are studies on forming coating materials on the surfaces of LLZO and LLTO. , to prevent LLZO and LLTO from contacting the air, but when forming the coating material, the ionic conductivity of the solid electrolyte is greatly reduced, which greatly limits its practical application.

In the present invention, the coating layer existing on the surface of the oxide solid electrolyte core includes one or both of tantalate and niobate. Tantalate and/or niobate can prevent the oxide solid electrolyte from excessive contact with air, inhibit side reactions between the oxide solid electrolyte and air, and maintain as high an ionic conductivity as possible.

In addition, this application selects the coating layer of the lithium ion conductor to make the ion diffusion performance of the coating layer good, thereby making the lithium ion conductivity of the oxide solid electrolyte high, and the effect is better than that of a solid electrolyte whose coating layer is not a lithium ion conductor. Material.

In specific embodiments of the present invention, the tantalate may include a lithium ion conductor tantalate, preferably lithium tantalate. The niobate may preferably be lithium niobate. This is because when lithium tantalate or lithium niobate is used, it can provide part of the lithium source during high-temperature sintering, preventing lithium deficiency during the synthesis process from causing the production of lanthanum zirconate or lanthanum titanate by-products, thereby preventing conductivity decline.

In the present invention, the thickness of the coating layer may be 0.01 to 1.0 μm, preferably 0.05 to 0.5 μm, and more preferably 0.08 to 0.4 μm. For example, the thickness of the cladding layer may be 0.01 μm, 0.03 μm, 0.05 μm, 0.08 μm, 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1.0 μm. wait. If the thickness of the coating layer is too thin, it may not function as a protective layer, and if the thickness of the coating layer is too thick, it will adversely affect the lithium ion conductivity of the oxide solid electrolyte.

In the present invention, the particle size of the oxide solid electrolyte core may be 0.01 to 10 μm, preferably 0.1 to 5 μm, and more preferably 0.1 to 3 μm. For example, the particle size of the oxide solid electrolyte core can be 0.01 μm, 0.03 μm, 0.05 μm, 0.1 μm, 0.3 μm, 0.5 μm, 0.8 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, etc.

<Second aspect>

A second aspect of the invention provides a method for preparing solid electrolyte materials. The preparation method of the present invention is a one-step sintering solid phase reaction method.

Figure 5 shows a process flow chart for preparing solid electrolyte materials according to the present invention. Specifically, the preparation method of the present invention includes:

Step S1: Mix doped or undoped oxide solid electrolyte raw materials and then sinter them to obtain doped or undoped oxide solid electrolyte powder;

Step S2: Mix, coat and heat-treat the doped or undoped oxide solid electrolyte powder obtained in step S1 with the coating material to obtain a doped or undoped oxide solid electrolyte core and coating. The solid electrolyte material of the coating layer covering the surface of the oxide solid electrolyte core.

Each step is explained in detail below.

Step S1

At present, most reports on the preparation of oxide solid electrolyte powders rely on liquid phase methods (such as co-precipitation methods, sol-gel methods, etc.). However, most of these methods are limited to laboratory techniques and are difficult to industrialize. The oxide solid electrolyte powder of the present invention is prepared by a one-step sintering solid phase method, thereby making the entire preparation process including preparing the oxide solid electrolyte powder and subsequently forming a coating layer on the surface simple and greatly improving production efficiency. Very conducive to batch industrial applications. Moreover, in the present invention, the oxide solid electrolyte powder is prepared through a one-step sintering solid phase method, which can avoid excessive contact with air and reduce the occurrence of surface side reactions.

"One-step sintering" in this specification refers to sintering that is performed without removing the solid electrolyte material from the sintering furnace in the middle of sintering. "One-step sintering" here includes one stage of sintering performed at the same temperature, and also includes multi-stage sintering performed in stages at different temperatures, such as two-stage sintering.

In this aspect, the doped or undoped oxide solid electrolyte is the same as in the above <first aspect>, that is, at least one selected from the group consisting of perovskite type oxide solid state electrolyte and garnet type oxide solid state electrolyte . The garnet-type oxide solid-state electrolyte is lithium lanthanum zirconium oxide LLZO, and its chemical composition is Li _7-x La ₃ Zr _2-x A _x O ₁₂ , in which the doping elements A and x are both the same as the above <first aspect> The same as in. The perovskite-type oxide solid-state electrolyte is lithium lanthanum titanium oxide LLTO, and its doping elements and chemical formula are also the same as those in the above-mentioned "first aspect".

The method for preparing oxide solid electrolyte powder through a one-step sintering solid-state reaction method is described in detail below.

The oxide solid electrolyte powder of the present invention is obtained by mixing, ball milling, sintering, crushing, and sieving raw materials.

raw material

In the present invention, the raw materials are not particularly limited. When the oxide solid electrolyte is the garnet type oxide solid electrolyte LLZO, for the Li compound, La compound, Zr compound as the raw material, and optional A compound as the doping compound, their salts and oxides can be used , hydroxide, etc. Wherein, the salt may include carbonate, nitrate, acetate, halide, etc. For the Li compound, lithium salt or lithium hydroxide monohydrate can be used. From the viewpoint of the ease of obtaining raw materials and cost, it is preferable to use salts thereof, such as lithium carbonate, lithium nitrate, lithium acetate, lithium chloride, and the like. Regarding La compounds and Zr compounds, from the viewpoint of production cost, it is preferred to use their oxides, that is, lanthanum oxide and zirconium oxide.

Compound A as the doping compound can be appropriately selected depending on the type of doping element. For example, when the doping element includes Ta, tantalates such as lithium tantalate and the like may be preferably used. When the doping element includes Nb, niobate, such as lithium niobate, etc. may be preferably used. Furthermore, from the viewpoint of supplementing the lithium element, it is also preferable to use lithium tantalate or lithium niobate. When the doping element includes Ca, Sr, Ba, Mo or W, their oxides or hydroxides may be used, such as calcium oxide, calcium hydroxide, strontium oxide, strontium hydroxide, barium oxide, barium hydroxide, oxide Molybdenum, molybdenum hydroxide, tungsten oxide, tungsten hydroxide.

When the oxide solid electrolyte is a perovskite oxide solid electrolyte LLTO, the Li compound, La compound, Ti compound and optional doping compound as raw materials are not particularly limited, and their salts, Oxides, hydroxides, etc. Wherein, the salt may include carbonate, nitrate, acetate, halide, etc. For the Li compound, lithium salt or lithium hydroxide monohydrate can be used. From the viewpoint of the ease of obtaining raw materials and cost, it is preferable to use salts thereof, such as lithium carbonate, lithium nitrate, lithium acetate, lithium chloride, and the like. Regarding La compounds and Ti compounds, from the viewpoint of production cost, it is preferable to use their oxides, that is, lanthanum oxide and titanium oxide. As for the doping compound, it can be appropriately selected according to the specific doping elements, and specific examples are the same as those in the above-mentioned garnet-type oxide solid electrolyte.

In a preferred embodiment of the present invention, the above-mentioned raw materials are pretreated. The pretreatment includes first pulverizing, and then roasting or drying, thereby reducing the particle size of the raw materials and reducing the moisture content in the raw materials, so that the raw material powders can be mixed more uniformly and reduce the impact of the moisture in the raw materials on the product properties. This adverse effect also makes it possible to implement one-step sintering. The particle size of the raw materials through this pretreatment is ≤5 microns, preferably ≤4 microns, more preferably ≤3 microns, still more preferably ≤2 microns, even more preferably ≤1 micron.

The raw materials used in the prior art are usually tens of microns, so they generally require two steps of sintering. After the first step of calcination is completed, they are taken out of the calcining furnace, crushed and ground, and then the second step of sintering is performed. In the present invention, since the raw materials have been pretreated to a smaller particle size, there is no need to take them out during sintering, and sintering can be performed in one step. Therefore, the present invention not only simplifies the preparation process, but also avoids excessive contact between the oxide solid electrolyte powder and air.

Regarding the pulverization process, a pulverizer commonly used in this field, such as a jet pulverizer, can be used. Roasting can be carried out at 800 to 1000°C for 5 to 10 hours. Drying can be performed at 100 to 150°C for 10 to 15 hours. Generally, a roasting treatment is used for La compounds; a drying treatment is used for Li compounds, Zr compounds, Ti compounds and optional doped compounds.

The raw materials are weighed according to the chemical formula of the doped or undoped oxide solid electrolyte. Typically, an excess of Li is required to compensate for the loss of lithium during the sintering process. The excess amount of Li compound is usually 5 to 30% by mass, preferably 10 to 15% by mass. For example, when the oxide solid electrolyte is Li _7-x La ₃ Zr _2-x A _x O ₁₂ (where x is 0 to 1.0), the ratio of Li compound, La compound, Zr compound, and A compound can be In terms of element content, the molar ratio of Li:La:Zr:A is 7-x:3:2-x:x (where x is 0 to 1.0), and the excess Li compound is 5 to 30% by mass. Weigh each raw material.

Ball milling steps

The pretreated raw materials are weighed according to the molar ratio of the chemical formula or preferably lithium excess of 5 to 30 mass%, and mixed and ball milled in a ball mill tank to obtain a mixture.

In the present invention, the ball milling conditions are not particularly limited and can be appropriately adjusted according to actual conditions. For example, the rotation speed of the ball mill can be 200 to 800 r/min, preferably 400 to 600 r/min, and the ball milling time can be 4 to 30 hours, preferably 10 to 24 hours. The mass ratio of the grinding balls in the ball mill tank to the raw materials, that is, the ball material mass ratio, can be (1-5):1, preferably (1-3):1.

In order to make the mixture uniform and the particle size of the mixture smaller, the grinding balls are preferably made by compounding balls of different diameters. For example, large balls with a diameter of approximately 7 to 9 mm, medium balls with a diameter of 4 to 6 mm, and small balls with a diameter of 1 to 3 mm can be mixed at a certain mass ratio. The mass ratio may be 1:(1~3):(1~5), preferably 1:(1~2):(2~3). The grinding balls are not particularly limited, and grinding balls commonly used in this field can be used, examples of which may include zirconia balls, silicon nitride balls, brown corundum balls, etc. Among them, zirconia balls are preferably used.

sintering step

After the ball milling step, the mixture obtained is subjected to one-step sintering. In the present invention, the one-step sintering may be one-stage sintering, but is more preferably two-stage sintering. When two-stage sintering is used, the purpose of the first stage of sintering is to decompose the raw materials, remove moisture and preliminarily synthesize an oxide solid electrolyte, and the purpose of the second stage of sintering is to synthesize a cubic phase, high crystallinity oxide solid electrolyte.

Specifically, when the oxide solid electrolyte is a garnet type oxide solid electrolyte, the sintering includes continuous sintering at a first temperature and a second temperature, and the conditions for sintering at the first temperature are: at 800 Sintering at a first temperature of ~1000°C, preferably 850~950°C, for 3 to 12 hours, preferably 5 to 10 hours, and the sintering conditions at the second temperature are: raising the first temperature to 1050~1250°C, preferably The second temperature is 1100-1200°C and sintered at the second temperature for 3-18h, preferably 6-12h.

When the oxide solid electrolyte is a perovskite oxide solid electrolyte, the sintering includes continuous sintering at a first temperature and a second temperature, and the conditions for sintering at the first temperature are: between 900 and 1100 °C, preferably 1000 °C, sintering for 3 to 18 hours, preferably 6 to 12 hours, and the sintering conditions at the second temperature are: raising the first temperature to 1150 to 1350 °C, preferably 1200 to 1300 °C the second temperature and sinter at the second temperature for 3 to 18 hours, preferably 6 to 12 hours. In the present invention, the oxide solid electrolyte powder is prepared through a one-step sintering method, which simplifies the production process, improves the production efficiency, and avoids excessive contact with air. Moreover, through two-stage sintering, the crystal form of the obtained product is not only more perfect, but also Can increase the relative density of the product.

Crushing and screening steps

The product obtained through the sintering step is crushed and sieved to obtain oxide solid electrolyte powder.

In the present invention, the oxide solid electrolyte powder obtained by crushing and sieving contains a small amount of primary particles, and most of the particles are secondary particles formed by agglomeration of primary particles. The primary particle size distribution is 0.01 to 2 microns, and the secondary particles are The secondary particle size is 1 to 10 microns.

There are no particular limitations on the crusher and crushing conditions in the present invention. A crusher commonly used in this field can be used and the crushing conditions can be appropriately adjusted as long as oxide solid electrolyte powder with a desired particle size can be obtained.

As described in [First Aspect] above, the particle size of the oxide solid electrolyte powder as the core may be 0.01 to 10 μm, preferably 0.1 to 5 μm, and more preferably 0.1 to 2 μm.

Step S2

In step S2, the doped or undoped oxide solid electrolyte powder obtained in step S1 and the coating material are mixed, coated and heat treated to obtain a doped or undoped oxide solid electrolyte core and a coating material. The solid electrolyte material of the coating layer coating the surface of the oxide solid electrolyte core.

In the present invention, the particle size of the oxide solid electrolyte powder obtained in step S1 is the particle size of the oxide solid electrolyte core in the final solid electrolyte material.

The coating material in this aspect is the same as the material used for the coating layer in the above-mentioned <First Aspect>, which includes one or both of tantalate and niobate.

In the present invention, the mass ratio of the coating material to the doped or undoped oxide solid electrolyte powder can be (0.1-20):100, preferably (1-10):100, more preferably (2-8) :100. For example, the mass ratio can be 0.1:100, 0.5:100, 1:100, 2:100, 3:100, 4:100, 5:100, 6:100, 7:100, 8:100, 9: 100, 10:100, 12:100, 15:100, 18:100, 20:100. Using the above-mentioned mass ratio of coating material and oxide solid electrolyte powder can not only better coat the coating material on the surface of the oxide solid electrolyte, but also avoid coating too much to affect the lithium ions of the oxide solid electrolyte. Conductivity.

In some embodiments of the present invention, it is preferred that the prepared oxide solid electrolyte powder is directly mixed with the coating material for mechanical fusion, so that the coating material coats the surface of the oxide solid electrolyte.

For the above-mentioned "directly", the present invention refers to the absence of obvious unnecessary intermittent interference during operation, so as to avoid unnecessary reactions in the air of the obtained oxide solid electrolyte powder. Specifically, in some specific embodiments of the present invention, the "direct" time range may be 10 min or less, preferably 5 min or less, and more preferably 3 min or less from the time when the oxide solid electrolyte powder is prepared.

In the present invention, mechanical fusion is performed in a mechanical fusion machine. The specific fusion conditions are not particularly limited and can be adjusted according to the actual situation. In some specific embodiments of the present invention, the fusion conditions are: fusion at a low speed of 100 to 500 rpm/min, preferably 150 to 300 rpm/min for 3 to 10 min, preferably 5 to 8 min, and then at a low speed of 1500 to 3500 rpm/min, preferably 2000 Fusion is performed at a high speed of ~3000 rpm/min for 10 to 30 minutes, preferably 15 to 25 minutes.

After the fusion product is obtained through mechanical fusion, it is heat treated to obtain a solid electrolyte material including an oxide solid electrolyte core and a cladding layer. The temperature and time of heat treatment are not particularly limited and can be adjusted according to actual conditions. For example, the heat treatment temperature can be 500-750°C, preferably 600-700°C, and the heat treatment time can be 6-18 hours, preferably 8-12 hours. Heat treatment after tantalate or niobate coating is beneficial to promote the cubic phase structure of the oxide solid electrolyte, making the coating more uniform and making the bonding between the coating layer and the core stronger, which can improve the lithium ion conductivity.

In some preferred embodiments, the heat-treated solid electrolyte material can be screened to obtain a solid electrolyte material with a more uniform particle size.

Usually, a large excess of lithium salt is required during the preparation of oxide solid electrolytes through solid-phase sintering. This will result in lithium oxide remaining on the surface of the oxide solid electrolyte. If it comes into contact with air, it is easy to form lithium carbonate or lithium hydroxide, which will significantly increase The surface resistance of oxide solid electrolytes is not conducive to its application. In the present invention, the one-step sintering solid-state reaction method is used to prepare the oxide solid electrolyte material, which can avoid excessive contact with air. At the same time, coating the surface of the oxide solid electrolyte with a layer of tantalate or niobate can inhibit the formation of oxide solid electrolytes. The solid electrolyte undergoes side reactions with air to maintain high ionic conductivity and conductivity stability and reduce surface impedance.

<Third aspect>

A third aspect of the present invention provides a battery, which includes the above-mentioned solid electrolyte material including a doped or undoped oxide solid electrolyte core and a coating layer coating the surface of the oxide solid electrolyte core. .

Since the solid electrolyte material of the present invention has high ionic conductivity and can effectively reduce impedance, the battery containing the solid electrolyte material of the present invention has higher energy density and better safety performance.

Example

The present invention will be described in detail below through examples. The examples of embodiments are intended to explain the invention and are not to be construed as limitations of the invention. If the specific technology or conditions are not specified in the examples, the technology or conditions described in the literature in the field or the product instructions shall be followed. If the manufacturer of the reagents or instruments used is not indicated, they are all conventional products that can be purchased commercially.

Raw material pretreatment

First, the raw materials Li ₂ CO ₃ , La ₂ O ₃ , ZrO ₂ , and TiO ₂ used in the following examples and comparative examples were air-flow pulverized respectively, and then La ₂ O ₃ was put into a muffle furnace and roasted at 900°C for 8 hours. Li ₂ CO ₃ , ZrO ₂ , TiO ₂ , and Ta ₂ O ₅ were placed in an oven and dried at 120°C for 12 hours. After the roasting and drying are completed, they are vacuum sealed for later use.

Example 1

S1. Weigh 70.83g lithium carbonate (excess 15 mass%), 116.4g lanthanum oxide and 58.7g zirconium oxide according to the Li:La:Zr molar ratio of 7:3:2, and put them into the ball mill tank. Mix large zirconium balls (diameter 8mm), medium balls (diameter 5mm), and small balls (diameter 2mm) at a mass ratio of 1:2:3 to form mixed zirconium balls. Weigh 240g of mixed zirconia balls according to the ball mass ratio of about 1:1, and put it into the ball mill tank. Set the ball mill speed to 500r/min, rotate forward for 30 minutes, 30 minutes apart, and reverse for 30 minutes. After 24 hours of ball milling, take it out and screen it. A mixture is obtained. Put the mixture into a crucible and put it into a muffle furnace. First, raise the temperature to 950°C for pre-sintering for 6 hours, then raise the temperature to 1200°C and continue sintering for 12 hours. Afterwards, it is crushed and sieved to obtain lithium lanthanum with a particle size of 0.1 to 10 μm. Zirconium oxide powder, the main particle size of the primary particles is distributed between 0.1 and 1 μm, and the main particle size of the secondary particles formed by agglomeration of the primary particles is between 1 and 10 μm.

S2. Add 100g lithium lanthanum zirconium oxygen powder and 5g lithium tantalate nanopowder (the particle size distribution is 50-100nm) into the mechanical fusion machine, fuse at a low speed of 200rpm/min for 5 minutes, and at a high speed of 2500rpm/min for 20 minutes, and then fuse the obtained The powder is loaded into a sagger, placed in a muffle furnace and heat-treated at 650°C for 9 hours to obtain lithium tantalate-coated lithium lanthanum zirconium oxide, which includes a lithium lanthanum zirconium oxide core and tantalate coated on the surface of the lithium lanthanum zirconium oxide core. Lithium layer, the chemical composition of the lithium lanthanum zirconium oxygen core is Li ₇ La ₃ Zr ₂ O ₁₂ , and the surface is coated with a layer of lithium tantalate.

Example 2

S1. Weigh 62.68g lithium carbonate (excess 15%), 110.93g lanthanum oxide, 41.95g zirconium oxide and 26.77g lithium tantalate according to the Li:La:Zr:Ta molar ratio of 6.5:3:1.5:0.5, and put them in into the ball mill jar. Mix large zirconium balls (diameter 8mm), medium balls (diameter 5mm), and small balls (diameter 2mm) at a mass ratio of 1:2:3 to form mixed zirconium balls. Weigh 240g of mixed zirconia balls according to the ball mass ratio of about 1:1, and put it into the ball mill tank. Set the ball mill speed to 500r/min, rotate forward for 30 minutes, 30 minutes apart, and reverse for 30 minutes. After 24 hours of ball milling, take it out and screen it. A mixture is obtained. Put the mixture into a crucible and put it into a muffle furnace. First, raise the temperature to 950°C for pre-sintering for 6 hours, then raise the temperature to 1175°C and continue sintering for 6 hours. Afterwards, it is crushed and sieved to obtain lithium lanthanum with a particle size of 0.1 to 10 μm. Zirconium oxide powder. The scanning electron microscope SEM image of the surface of the lithium lanthanum zirconium oxygen precursor is shown in Figure 1. As can be seen from Figure 1, the main particle size distribution of the primary particles of lithium lanthanum zirconium oxygen is between 0.1 and 2 μm, and the main particle size distribution of the secondary particles formed by the agglomeration of primary particles is between 1 and 10 μm.

S2. Add 100g lithium lanthanum zirconium oxygen powder and 5g lithium tantalate nanopowder into the mechanical fusion machine, fuse at a low speed of 200rpm/min for 5 minutes, and at a high speed of 2500rpm/min for 20 minutes. Then put the obtained powder into a crucible and place it in the muffle The lithium tantalate-coated lithium lanthanum zirconium oxide is obtained by sintering in the furnace at 650° C. for 9 hours, which includes a lithium lanthanum zirconium oxide core and a lithium tantalate layer coating the surface of the lithium lanthanum zirconium oxide core. The lithium lanthanum zirconium oxide core is The chemical composition is Li _6.5 La ₃ Zr _1.5 Ta _0.5 O ₁₂ , the particle size of the lithium lanthanum zirconium oxygen core is 0.1 to 10 μm, and the thickness of the lithium tantalate layer is 0.1 to 0.3 μm. The surface SEM image of the lithium tantalate-coated lithium lanthanum zirconium oxygen is shown in Figure 2. As can be seen from Figure 2, the particle size of the lithium lanthanum zirconium oxygen core particles is about 0.1 to 10 μm, and the surface is coated with a layer of lithium tantalate.

Example 3

S1. Weigh 66.66g lithium carbonate (excess 15%), 113.60g lanthanum oxide, 50.12g zirconium oxide and 13.71g lithium tantalate according to the Li:La:Zr:Ta molar ratio of 6.75:3:1.75:0.25, and put them in into the ball mill jar. Mix large zirconium balls (diameter 8mm), medium balls (diameter 5mm), and small balls (diameter 2mm) at a mass ratio of 1:2:3 to form mixed zirconium balls. Weigh 240g of mixed zirconia balls according to a mass ratio of 1:1, and put it into the ball milling tank. Set the ball milling speed to 500r/min, rotate forward for 30 minutes, 30 minutes apart, and reverse for 30 minutes. After 24 hours of ball milling, take it out and sift to obtain Mixture. Put the mixture into a crucible and put it into a muffle furnace. First, raise the temperature to 950°C for pre-sintering for 6 hours, then raise the temperature to 1175°C and continue sintering for 6 hours. Afterwards, it is crushed and sieved to obtain lithium lanthanum with a particle size of 0.05 to 10 μm. Zirconium oxide powder, the main particle size distribution of primary particles is 0.05-2 μm, and the main particle size distribution of secondary particles formed by agglomeration of primary particles is 1-10 μm.

S2. Add 100g lithium lanthanum zirconium oxygen powder and 5g lithium tantalate nanopowder into the mechanical fusion machine, fuse at a low speed of 200rpm/min for 5 minutes, and at a high speed of 2500rpm/min for 20 minutes. Then put the obtained powder into a sagger and place it on the horse. The lithium tantalate-coated lithium lanthanum zirconium oxide is obtained by sintering in a furnace at 650°C for 9 hours, which includes a lithium lanthanum zirconium oxide core and a lithium tantalate layer coating the surface of the lithium lanthanum zirconium oxide core. The lithium lanthanum zirconium oxide core is The chemical composition is Li _6.75 La ₃ Zr _1.75 Ta _0.25 O ₁₂ , and the surface is coated with a layer of lithium tantalate.

Example 4

S1. Weigh 58.89g lithium carbonate (excess 15%), 108.38g lanthanum oxide, 34.16g zirconium oxide and 36.75g lithium tantalate according to the Li:La:Zr:Ta molar ratio of 6.25:3:1.25:0.75, and put them in into the ball mill jar. Mix large zirconium balls (diameter 8mm), medium balls (diameter 5mm), and small balls (diameter 2mm) at a mass ratio of 1:2:3 to form mixed zirconium balls. Weigh 240g of mixed zirconia balls according to a mass ratio of 1:1, and put it into the ball milling tank. Set the ball milling speed to 500r/min, rotate forward for 30 minutes, 30 minutes apart, and reverse for 30 minutes. After 24 hours of ball milling, take it out and sift to obtain Mixture. Put the mixture into a crucible and put it into a muffle furnace. First, raise the temperature to 950°C for pre-sintering for 6 hours, then raise the temperature to 1175°C and continue sintering for 6 hours. Afterwards, it is crushed and sieved to obtain lithium lanthanum with a particle size of 0.05 to 10 μm. Zirconium oxide powder, the main particle size distribution of the primary particles is 0.05~2μm, and the main particle size distribution of the secondary particles formed by the agglomeration of the primary particles is 1~10μm.

S2. Add 100g lithium lanthanum zirconium oxygen powder and 5g lithium tantalate nanopowder into the mechanical fusion machine, fuse at a low speed of 200rpm/min for 5 minutes, and at a high speed of 2500rpm/min for 20 minutes. Then put the obtained powder into a sagger and place it on the horse. The lithium tantalate-coated lithium lanthanum zirconium oxide is obtained by sintering in a furnace at 650° C. for 9 hours, which includes a lithium lanthanum zirconium oxide core and a lithium tantalate layer coating the surface of the lithium lanthanum zirconium oxide core. The lithium lanthanum zirconium oxide core is The chemical composition is Li _6.25 La ₃ Zr _1.25 Ta _0.75 O ₁₂ , and the surface is coated with a layer of lithium tantalate.

Example 5

S1. Weigh 13.62g lithium carbonate (excess 20% by mass), 100.11g lanthanum oxide, 83.26g titanium oxide, and 12.12g tantalum oxide, and put them into a ball mill tank. Mix large zirconium balls (diameter 8mm), medium balls (diameter 5mm), and small balls (diameter 2mm) at a mass ratio of 1:2:3 to form mixed zirconium balls. Weigh 210g of mixed zirconia balls according to the mass ratio of the balls to about 1:1, and put them into the ball mill tank. Set the ball mill speed to 500r/min, rotate forward for 30 minutes, 30 minutes apart, and reverse for 30 minutes. After 24 hours of ball milling, take it out and screen it. A mixture is obtained. Put the mixture into a crucible and put it into a muffle furnace. First, raise the temperature to 950°C for pre-sintering for 6 hours, then raise the temperature to 1300°C and continue sintering for 12 hours. Afterwards, it is crushed and sieved to obtain lithium lanthanum with a particle size of 0.1 to 10 μm. Titanium oxide powder, the main particle size distribution of the primary particles is 0.1~1μm, and the main particle size distribution of the secondary particles formed by the agglomeration of the primary particles is 1~10μm.

S2. Add 100g lithium lanthanum titanium powder and 5g lithium tantalate nanopowder (the particle size distribution is 50-100nm) into the mechanical fusion machine, fuse at a low speed of 200rpm/min for 5 minutes, and at a high speed of 2500rpm/min for 20 minutes, and then fuse the obtained The powder is put into a sagger, placed in a muffle furnace and heat-treated at 650°C for 9 hours to obtain lithium tantalate-coated lithium lanthanum titanium oxide. The chemical composition of the lithium lanthanum titanium core is Li _0.28 La _0.56 Ti _0.95 Ta _0.05 O _3. The surface is coated with a layer of lithium tantalate.

Comparative example 1

Weigh 70.83g lithium carbonate (excess 15%), 116.4g lanthanum oxide and 58.7g zirconium oxide according to the Li:La:Zr molar ratio of 7:3:2, and put them into the ball mill tank. Mix large zirconium balls (diameter 8mm), medium balls (diameter 5mm), and small balls (diameter 2mm) at a mass ratio of 1:2:3 to form mixed zirconium balls. Weigh 240g of mixed zirconia balls according to the ball mass ratio of about 1:1, and put it into the ball mill tank. Set the ball mill speed to 500r/min, rotate forward for 30 minutes, 30 minutes apart, and reverse for 30 minutes. After 24 hours of ball milling, take it out and screen it. A mixture is obtained. Put the mixture into a crucible and put it into a muffle furnace. First, raise the temperature to 950°C for pre-sintering for 6 hours, then raise the temperature to 1200°C and continue sintering for 12 hours. Afterwards, it is crushed and sieved to obtain lithium lanthanum with a particle size of 0.1 to 10 μm. Zirconium oxide powder, the main particle size of the primary particles is distributed between 0.1 and 1 μm, and the main particle size of the secondary particles formed by agglomeration of the primary particles is between 1 and 10 μm.

Comparative example 2

S1. Weigh 62.28g lithium carbonate (excess 15%), 110.93g lanthanum oxide, 41.95g zirconium oxide and 26.77g lithium tantalate according to the Li:La:Zr:Ta molar ratio of 6.5:3:1.5:0.5, and put them in into the ball mill jar. Mix large zirconium balls (diameter 8mm), medium balls (diameter 5mm), and small balls (diameter 2mm) at a mass ratio of 1:2:3 to form mixed zirconium balls. Weigh 240g of mixed zirconia balls according to the ball mass ratio of about 1:1, and put it into the ball mill tank. Set the ball mill speed to 500r/min, rotate forward for 30 minutes, 30 minutes apart, and reverse for 30 minutes. After 24 hours of ball milling, take it out and screen it. A mixture is obtained. Put the mixture into a crucible and put it into a muffle furnace. First, raise the temperature to 950°C for pre-sintering for 18 hours, then raise the temperature to 1175°C and continue sintering for 6 hours. Afterwards, it is crushed and sieved to obtain lithium lanthanum with a particle size of 0.1 to 10 μm. Zirconium oxide powder, in which the main particle size of the primary particles of lithium lanthanum and zirconium oxide is distributed in 0.1 to 2 μm, and the main particle size of the secondary particles formed by agglomeration of the primary particles is in the range of 1 to 10 μm.

Comparative example 3

S1. Weigh 62.68g lithium carbonate (excess 15%), 110.93g lanthanum oxide, 41.95g zirconium oxide and 26.77g lithium tantalate according to the Li:La:Zr:Ta molar ratio of 6.5:3:1.5:0.5, and put them in into the ball mill jar. Mix large zirconium balls (diameter 8mm), medium balls (diameter 5mm), and small balls (diameter 2mm) at a mass ratio of 1:2:3 to form mixed zirconium balls. Weigh 240g of mixed zirconia balls according to the ball mass ratio of 1:1 and put it into the ball mill tank. Set the ball mill speed to 500r/min, rotate forward for 30 minutes, 30 minutes apart, reverse for 30 minutes. After 24 hours of ball milling, take it out and sieve to obtain Mixture. Put the mixture into a crucible and put it into a muffle furnace. First, raise the temperature to 950°C for pre-sintering for 6 hours, then raise the temperature to 1175°C and continue sintering for 6 hours. Afterwards, it is crushed and sieved to obtain lithium lanthanum with a particle size of 0.1 to 10 μm. For zirconium oxide powder, the main particle size distribution of primary particles is 0.1-2 μm, and the main particle size distribution of secondary particles formed by agglomeration of primary particles is 1-10 μm.

S2. Add 100g lithium lanthanum zirconium oxygen powder and 5g aluminum oxide nanopowder into the mechanical fusion machine, fuse at a low speed of 200rpm/min for 5 minutes, and at a high speed of 2500rpm/min for 20 minutes. Then put the obtained powder into a sagger and place it Alumina-coated lithium lanthanum zirconium oxygen was obtained by sintering in a muffle furnace at 350°C for 6 hours. The chemical composition of the lithium lanthanum zirconium oxygen core is Li _6.5 La ₃ Zr _1.5 Ta _0.5 O ₁₂ , and the surface is coated with a layer of alumina. .

It can be seen from Figure 3 that the lithium lanthanum zirconium oxygen prepared in Example 2-4 and Comparative Example 2-3 has a pure cubic phase structure. Since the lithium lanthanum zirconium oxygen prepared in Example 1 and Comparative Example 1 was not doped, a mixed phase of cubic phase and tetragonal phase was obtained.

test case

Preparation of samples for electrical performance testing

Tablet pressing: Weigh 2g of the lithium tantalate-coated lithium lanthanum zirconium oxygen solid electrolyte powder obtained in the above-mentioned Examples 1 to 4 or the lithium lanthanum zirconium oxygen powder obtained in Comparative Examples 1 to 3 respectively, and press 20 to 30% Mass ratio: Add the pre-prepared aqueous solution of polyvinyl alcohol (PVA) binder (containing 10 mass% PVA) to the sample powder, and grind it in an agate mortar to mix the powder and PVA solution evenly. After complete drying, the powder is placed in the mold and held under a pressure of 200MPa for 10 minutes to obtain a formed wafer with a diameter of 17mm;

Debinding: Place the pressed molded sheet in an oven at 50°C to remove the solvent in the adhesive. The molded piece was then placed upright in an open crucible, heated to 450°C at a heating rate of 2°C/min in a muffle furnace and kept for 4 hours to remove the glue, thereby obtaining a ceramic piece;

Polishing paste: Polish and polish the debonded ceramic piece on both sides, apply a layer of silver paste, and then dry it to obtain a sample for testing.

Impedance value test

The impedance values of the test samples of Examples 1 to 4 and Comparative Examples 1 to 3 prepared by the above method were measured using the AC impedance testing method. Specifically, the test sample was placed on the Chenhua electrochemical workstation to test the AC impedance. The frequency was set to 0.1~10MHZ and the voltage amplitude was set to 5mV. The test results are shown in Figure 4.

Lithium ion conductivity calculation

The lithium ion conductivity of the test samples of Examples 1 to 4 and Comparative Examples 1 to 3 was obtained as follows:

Ion conductivityσ=h/RA

In the formula: h-sample thickness (cm);

R-sample impedance (Ω);

A-sample circular cross-sectional area (cm ² )

The test results are shown in Figure 4: It can be seen from Figure 4 that the impedance spectrum of Comparative Example 1 has the largest semicircle, the highest impedance, and the lowest lithium ion conductivity; followed by Example 1, the impedance is relatively large, that is, the lithium ion conductivity Lower; the semicircles of the impedance spectra of Examples 2, 3, 4 and Comparative Example 2 are smaller, and Example 3 is the smallest, indicating that Example 3 has the lowest impedance value and the highest lithium ion conductivity. Among Example 2-4 and Comparative Example 3, Example 2-4 has the highest initial lithium ion conductivity, and Comparative Example 3 has the lowest.

This proves that by doping lithium lanthanum zirconium oxygen powder with tantalum element, the impedance value is reduced and the lithium ion conductivity is improved, and when the surface of lithium lanthanum zirconium oxygen is coated with lithium tantalate, its surface is more stable and in the air There was no significant decrease in ionic conductivity after three days of storage. By doping and coating lithium lanthanum and zirconium oxygen at the same time, the performance of the oxide solid electrolyte can be significantly improved. It is more stable in the air, and the ion conductivity does not decrease significantly after being placed in the air. As shown in Table 1, in The lithium ion conductivity after being left in the air for 3 days (Examples 2-4) is higher than the ion conductivity of only coating without doping (Example 1) and only doping without coating (Comparative Example 2).

In addition, it can be seen from the data of Examples 2-4 and Comparative Example 3 that this application selects the coating layer of the lithium ion conductor to make the ion diffusion performance of the coating layer good, thereby making the lithium ion conductivity of the oxide solid electrolyte The efficiency is high and the effect is better than the solid electrolyte material whose coating layer is not a lithium ion conductor. The resistance value and lithium ion conductivity of the lithium tantalate-coated lithium lanthanum zirconium oxygen obtained in Examples 1 to 4 and the lithium lanthanum zirconium oxygen powder obtained in Comparative Examples 1-3 were calculated using the fitting method. The fitting software used Zview 2. The results are shown in Table 1 below.

Table 1 Impedance fitting values and corresponding lithium ion conductivity

It can be seen from the results in Table 1 that the initial powder lithium ion conductivity is highest in Example 3 and Comparative Example 2 doped with tantalum, followed by Examples 2 and 4. Since aluminum oxide will hinder lithium ion transport, Comparative Example 3 The conductivity is poor, and the lithium ion conductivity of undoped Example 1 and Comparative Example 1 is the worst. After being exposed to air for 3 days, the lithium ion conductivity of the samples without lithium tantalate coating (Comparative Examples 1 and 2) decreased significantly. However, in Examples 1 to 4, due to the coating effect of lithium tantalate, the lithium ion conductivity did not significantly decrease. This result further proves the effect of improving lithium ion conductivity through the lithium tantalate coating layer and tantalum doping.

Although the embodiments of the present invention have been shown and described above, it can be understood that the above-mentioned embodiments are illustrative and should not be construed as limitations of the present invention. Those of ordinary skill in the art will not deviate from the principles and purposes of the present invention. Under the circumstances, the above-described embodiments can be changed, modified, replaced and modified within the scope of the present invention.

Industrial availability

The solid electrolyte material prepared by the present invention not only has high lithium ion conductivity and low impedance value, but also has significantly reduced surface side reactions in the air and higher stability. The solid electrolyte material of the present invention has a simple preparation process and high production efficiency, and is very suitable for large-scale industrial production.

Claims (14)

1. A solid electrolyte material, characterized in that it includes a doped or undoped oxide solid electrolyte core and a coating layer covering the surface of the oxide solid electrolyte core,

   The doping element in the doped oxide solid electrolyte is selected from at least one of Ta, Nb, Ca, Sr, Ba, Mo, and W;

   The coating layer includes one or both of tantalate and niobate.
2. The solid electrolyte material according to claim 1, wherein the thickness of the coating layer is 0.01-1.0 μm, preferably 0.05-0.5 μm.
3. The solid electrolyte material according to claim 1 or 2, wherein the particle size of the oxide solid electrolyte core is 0.01 to 10 μm, preferably 0.1 to 5 μm.
4. The solid electrolyte material according to any one of claims 1 to 3, wherein the oxide solid electrolyte is selected from at least one of a perovskite type oxide solid electrolyte and a garnet type oxide solid electrolyte.
5. The solid electrolyte material according to claim 4, wherein the chemical composition of the garnet type oxide solid electrolyte is Li _7-x La ₃ Zr _2-x A _x O ₁₂ , wherein the doping element A is Ta, Nb, One or more of Ca, Sr, Ba, Mo and W, 0≤x≤1,

   The perovskite oxide solid electrolyte is LLTO.
6. The solid electrolyte material according to any one of claims 1 to 5, wherein the tantalate includes a lithium ion conductor tantalate, preferably lithium tantalate.
7. A method for preparing solid electrolyte materials, characterized in that the preparation method includes:

   Step S1: Mix the raw materials of doped or undoped oxide solid electrolyte and then sinter them to obtain doped or undoped oxide solid electrolyte powder;

   Step S2: Mix, coat and heat-treat the doped or undoped oxide solid electrolyte powder obtained in step S1 with the coating material to obtain a doped or undoped oxide solid electrolyte core and coating. The solid electrolyte material of the coating layer covering the surface of the oxide solid electrolyte core.
8. The preparation method according to claim 7, wherein in step S1, the sintering is one-step sintering.
9. The preparation method according to claim 7 or 8, wherein in the step S1, when the oxide solid electrolyte is a garnet type oxide solid electrolyte, the sintering includes heating at the first temperature and the second temperature. Continuous sintering, the conditions for sintering at the first temperature are: sintering at a first temperature of 800 to 1000°C, preferably 850 to 950°C for 3 to 12 hours, preferably 5 to 10 hours, and the sintering at the second temperature The conditions are: raising the first temperature to a second temperature of 1050-1250°C, preferably 1100-1200°C, and sintering at the second temperature for 3-18 hours, preferably 6-12 hours;

   When the oxide solid electrolyte is a perovskite oxide solid electrolyte, the sintering includes continuous sintering at a first temperature and a second temperature, and the conditions for sintering at the first temperature are: between 900 and 1100 ° C, preferably 950 ~ 1050 ° C, sintering at a first temperature of 3 to 18 hours, preferably 6 to 12 hours, the sintering conditions at the second temperature are: raising the first temperature to 1150 ~ 1350 ° C, preferably 1200 ~ A second temperature of 1300° C. and sintering at the second temperature for 3 to 18 hours, preferably 6 to 12 hours.
10. The preparation method according to any one of claims 7-9, wherein in step S1, the particle size of the raw material is ≤5 microns.
11. The preparation method according to any one of claims 7 to 10, wherein in the step S1, the raw materials are weighed according to the molar ratio of the chemical formula of the doped or undoped oxide solid electrolyte, or the raw materials are The excess amount of lithium compound is 5 to 30% by mass.
12. The preparation method according to any one of claims 7-11, wherein in the step S2, the mass ratio of the coating material and the oxide solid electrolyte powder is (0.1~20):100, preferably (1～10):100.
13. The preparation method according to any one of claims 7-12, wherein in the step S2, the heat treatment conditions are: heat treatment at 500-750°C, preferably 600-700°C for 6-18 hours, preferably 8 hours ~12 hours.
14. A battery, characterized in that it includes the solid electrolyte material according to any one of claims 1 to 6 and/or the solid electrolyte material obtained by the preparation method according to any one of claims 7 to 13.

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