Solid-state electrolyte material, preparation method thereof, battery and electric device

Abstract

The application belongs to the technical field of new energy, and discloses a solid-state electrolyte material, a preparation method thereof, a battery and an electric device. The solid-state electrolyte material comprises an oxide solid-state electrolyte and a metal oxide, the metal oxide is distributed at the grain boundary of the oxide solid-state electrolyte, and the content of the metal oxide accounts for less than 0.01% of the mass percentage of the oxide solid-state electrolyte. The lower content of the metal oxide prevents the metal oxide from agglomerating and forming grains at the grain boundary of the oxide solid-state electrolyte, improves the strength, density and electrical conductivity of the solid-state electrolyte material, and the metal oxide can reduce the sintering temperature of the solid-state electrolyte material, reduce energy consumption, and improve the adhesion problem caused by the reaction between the solid-state electrolyte material and the container due to high-temperature reaction.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of new energy, and particularly relates to a solid-state electrolyte material, a preparation method thereof, a battery and an electric device. BACKGROUND

[0002] As a material different from the traditional liquid electrolyte, the solid-state electrolyte material can greatly improve the safety and performance of the battery. The existing solid-state electrolyte ceramic material includes a lithium lanthanum zirconium oxygen (LLZO) oxide sintered body having a garnet type or similar garnet type crystal structure and composed of at least Li (lithium), La (lanthanum), Zr (zirconium) and O (oxygen). In the preparation process, magnesium oxide (MgO) is generally added as a sintering aid to reduce the defects of the LLZO material. However, due to the hindering of MgO grains at the grain boundaries, and the excessive pursuit of the density and strength performance of the material, and the excessive growth of LLZO grains, the conductivity of the formed LLZO solid-state electrolyte is reduced and is far lower than the conductivity order of magnitude of the normal LLZO solid-state electrolyte. SUMMARY

[0003] In view of the above defects or deficiencies in the prior art, it is desirable to provide a solid-state electrolyte material, a preparation method thereof, a battery and an electric device.

[0004] In a first aspect of the present application, a solid-state electrolyte material is provided, including an oxide solid-state electrolyte and a metal oxide, the metal oxide being distributed at grain boundaries of the oxide solid-state electrolyte, and the content of the metal oxide accounting for less than 0.01% of the mass percentage of the oxide solid-state electrolyte.

[0005] In addition, the solid-state electrolyte material of the present application can also have the following additional technical features:

[0006] In some embodiments, the content of the metal oxide accounts for 0.002-0.008% of the mass percentage of the oxide solid-state electrolyte.

[0007] In some embodiments, the metal oxide includes magnesium oxide or / and yttrium oxide.

[0008] In some embodiments, the molecular formula of the oxide solid-state electrolyte is Li 7-x A x La3Zr 2-x O 12 , wherein A is Nb, Ga or Ta, and 0≤x≤0.5.

[0009] In some embodiments, the solid-state electrolyte material is sintered by a one-step sintering method from the oxide solid-state electrolyte and the additive; the additive comprises a metal oxide or / and a metal hydroxide, preferably, the additive comprises at least one of magnesium oxide, magnesium hydroxide, and yttrium oxide.

[0010] In some embodiments, the metal oxide is distributed at the grain boundaries of the oxide solid-state electrolyte and makes the solid-state electrolyte material have a cubic phase structure.

[0011] In some embodiments, the solid-state electrolyte material has an ionic conductivity of greater than 1×10 -4 S / cm, preferably greater than 0.4×10 -3 S / cm.

[0012] In some embodiments, the solid-state electrolyte material has an average particle size of 0.1-30 μm, preferably 15-20 μm.

[0013] In a second aspect, the present application provides a method for preparing a solid-state electrolyte material, comprising:

[0014] S130: mixing the oxide solid-state electrolyte with an additive, and sintering by a one-step sintering method to obtain a solid-state electrolyte powder; wherein the content of the additive accounts for less than 0.01% of the mass percentage of the oxide solid-state electrolyte.

[0015] In some embodiments, the content of the additive accounts for 0.002-0.008% of the mass percentage of the oxide solid-state electrolyte.

[0016] In some embodiments, the additive comprises at least one of magnesium oxide, magnesium hydroxide, and yttrium oxide.

[0017] In some embodiments, in step S130, the sintering temperature of the one-step sintering method is 800-1000°C, preferably 850-950°C; and the sintering time is 4-9 h, preferably 4-6 h.

[0018] In some embodiments, before step S130, the method further comprises:

[0019] S110: obtain the feeding amount of raw materials of the oxide solid-state electrolyte according to the molar ratio corresponding to the molecular formula of the oxide solid-state electrolyte; wherein the raw materials of the oxide solid-state electrolyte at least include a Li compound, a La compound and a Zr compound, and preferably further include at least one of a Nb compound, a Ga compound or a Ta compound; wherein the feeding amount of the Li compound exceeds 10% to 30% of the mass of the Li compound defined in the molecular formula of the oxide solid-state electrolyte, and preferably the feeding amount of the Li compound exceeds 15% to 25%.

[0020] Then, the raw materials of the oxide solid-state electrolyte are mixed with the additive to obtain a mixture.

[0021] In some embodiments, between step S110 and step S130, the method further comprises:

[0022] S120: put the mixture into a ball mill tank, then add a solvent, grind and mix uniformly to obtain a mixed slurry;

[0023] The mixed slurry is sequentially subjected to suction filtration, drying, crushing and sieving.

[0024] In some embodiments, after step S130, the method further comprises:

[0025] S140: tablet the solid-state electrolyte powder to obtain a green body;

[0026] Sinter the green body to obtain a solid-state electrolyte ceramic sheet.

[0027] In some embodiments, in step S140, the sintering temperature of the green body is 900 to 1200℃, and the sintering time is 3 to 5h.

[0028] In a third aspect, the application provides a battery comprising the solid-state electrolyte material according to any of the embodiments of the application, or the solid-state electrolyte material obtained by the preparation method according to any of the embodiments of the application.

[0029] In a fourth aspect, the application provides an electrical equipment comprising the battery according to any of the embodiments of the application.

[0030] The solid electrolyte material and the preparation method thereof, the battery and the electric device provided by the application are two-phase composite materials of oxide solid electrolyte and metal oxide. The additive is used as a sintering inhibitor. After sintering, the metal oxide is dispersed at the grain boundary of the solid electrolyte for a long time, and the high-temperature stability is good, and the solid electrolyte material will not react with Li2O during sintering. The additive can control the mass transfer between the solid electrolyte grains in the reaction, inhibit the excessive growth of single crystals, and make the oxide solid electrolyte grains form uniform small-size polyhedral grains, thereby reducing the internal porosity. The sintering temperature of the solid electrolyte material is reduced by using a small amount of additive, so that the cubic phase solid electrolyte material can be sintered at low temperature and for a short time. The adhesion problem caused by the reaction between the solid electrolyte material and the container due to high-temperature reaction is reduced and improved. BRIEF DESCRIPTION OF DRAWINGS

[0031] Other features, objects, and advantages of the application will become more apparent from the following detailed description of non-limiting embodiments made with reference to the drawings:

[0032] Figure 1 SEM images of the solid electrolyte ceramic sheet provided in Examples 1-3 of the application;

[0033] Figure 2 Impedance test graphs of the solid electrolyte material provided in Examples 1-8 and Comparative Examples 1-4 of the application. DETAILED DESCRIPTION

[0034] The following describes embodiments of the application, but the application is not limited thereto. The application is not limited to the respective configurations described below, and various modifications can be made within the scope of the application claimed, and embodiments obtained by appropriately combining different embodiments and appropriately combining the respective disclosed technical means in the embodiments are also included in the technical scope of the application.

[0035] In addition, the documents described in the specification are all incorporated by reference in the specification.

[0036] Unless otherwise defined, the technical and scientific terms used in the application have the same meanings as those commonly understood by those skilled in the art to which the application belongs.

[0037] In the specification, the numerical range represented by "numerical value A to numerical value B" means a range including the end point values A and B.

[0038] In the specification, "multiple", "a plurality of", "a plurality of" and the like mean a value of 2 or more, unless otherwise stated.

[0039] In the present specification, "substantially", "generally" or "essentially" means that the error is below 5%, or below 3%, or below 1% compared with the relevant perfect standard or theoretical standard.

[0040] In the present specification, "%" means mass percent unless otherwise specified.

[0041] In the present specification, "room temperature", "normal temperature" and the like, if any, generally means 10-37°C, or 15-35°C.

[0042] In the present specification, "may" or "can" means both the existence and the non-existence, and both the performance of a certain treatment and the non-performance of a certain treatment.

[0043] In the present specification, "optional" and "optionally" mean that the event or circumstance described next can or can not occur, and the description includes both the case where the event occurs and the case where the event does not occur.

[0044] The term "comprising", and variations thereof, as used in enlisting the claims and specification of the present application and the above-described drawings, are intended to cover both the inclusive and exclusive aspects of the term. For example, a process, method, product, or apparatus that comprises a list of steps or elements is not necessarily limited to only those steps or elements that are listed, but can also optionally include additional steps or elements not expressly listed or inherent to such process, method, product, or apparatus.

[0045] In the present specification, the phrases "some / certain / preferred embodiments", "embodiments", and the like mean that the particular feature (e.g., characteristic, structure, property, and / or characteristic) being described can be included in at least one embodiment described herein, and can or can not be present in other embodiments. In addition, it is to be understood that the described elements can be combined in any suitable manner in the various embodiments.

[0046] In the existing preparation method of solid-state electrolyte material, an excess of magnesium (Mg) compound such as MgO is added, and the excess MgO will agglomerate at the grain boundary of lithium lanthanum zirconium oxide (LLZO) solid-state electrolyte and further crystallize to finally form grains, resulting in that the conductivity of the LLZO solid-state electrolyte is reduced to far below the order of magnitude of normal LLZO due to the obstruction of MgO at the grain boundary, although the strength and density are improved, but the characteristics that an electrolyte material should have are lost. And too long sintering time will cause excessive growth of solid-state electrolyte grains, and the formation of giant size grains will cause the increase of porosity, and then reduce the grain boundary bonding strength. Too high sintering temperature, too long sintering time and step sintering will all cause the volatilization of lithium (Li) ions, thereby affecting the purity and material performance of the solid-state electrolyte.

[0047] To solve the above problems, the first aspect of the embodiments of the present application provides a solid-state electrolyte material, comprising an oxide solid-state electrolyte and a metal oxide, the metal oxide being distributed at the grain boundaries of the oxide solid-state electrolyte, and the content of the metal oxide being less than 0.01% of the mass percentage of the oxide solid-state electrolyte.

[0048] The solid-state electrolyte material provided by the present application is a two-phase composite material of an oxide solid-state electrolyte and a metal oxide. The raw material of the metal oxide can act as a sintering inhibitor. After sintering, the metal oxide is dispersed at the grain boundaries of the solid-state electrolyte for a long time, and has good high-temperature stability and will not react with Li2O during sintering. The low content of the added metal oxide can control the mass transfer between the solid-state electrolyte grains during the reaction, inhibit the excessive growth of single crystals, and make the oxide solid-state electrolyte grains form uniform small-size polyhedral grains, thereby reducing the internal porosity, improving the density, strength, and electrical conductivity of the solid-state electrolyte material. The raw material of the metal oxide can reduce the sintering temperature of the solid-state electrolyte material, reduce energy consumption, and improve the problem of adhesion caused by the reaction between the solid-state electrolyte material and the container due to high-temperature reaction.

[0049] It can be understood that the content of the metal element in the metal oxide is also less than 0.01% of the mass percentage of the oxide solid-state electrolyte.

[0050] In some optional embodiments, the metal oxide comprises magnesium oxide or / and yttrium oxide. The addition amount of magnesium oxide or yttrium oxide is limited to a low content, or the total addition amount of magnesium oxide and yttrium oxide is limited to a low content, so as to prevent the metal oxide from agglomerating and eventually crystallizing at the grain boundaries of the oxide solid-state electrolyte when the content of the metal oxide is too high, forming large-size accumulated grains, affecting the conduction of Li ions in the oxide solid-state electrolyte, and improving the strength, density, and electrical conductivity of the solid-state electrolyte material. The content of the metal oxide is 0.002-0.008% of the mass percentage of the oxide solid-state electrolyte.

[0051] For example, when the metal oxide is MgO or yttrium oxide, the content of MgO or yttrium oxide is less than 0.01%, preferably 0.002-0.008%, further preferably 0.002-0.006%, more preferably 0.003-0.0045%, such as 0.002%, 0.0024%, 0.003%, 0.0032%, 0.0045%, 0.006, 0.0065%, 0.008%, 0.009%, etc. of the mass percentage of the oxide solid-state electrolyte.

[0052] For example, the metal oxide is magnesium oxide and yttrium oxide, and the total amount of the two is less than 0.01% of the mass percentage of the oxide solid electrolyte, such as 0.0025%, 0.0027%, 0.0033%, 0.0046, 0.0065%, 0.0072%, 0.0093%, etc. of the total mass percentage; and the mass ratio of magnesium oxide and yttrium oxide is 1:1, 1:2, 2:1, 3:1, 1:3, etc.

[0053] The solid electrolyte material of the present application is sintered from an oxide solid electrolyte and a metal oxide, and forms a structure with the oxide solid electrolyte as the core and the metal oxide dispersed on the surface of the oxide solid electrolyte. The use of a low content of metal oxide (especially MgO) can prevent the metal oxide from agglomerating and forming grains in the oxide solid electrolyte, thereby improving the strength and density of the solid electrolyte material while also improving the electrical conductivity of the solid electrolyte material. Moreover, the metal oxide can lower the sintering temperature, allowing the oxide solid electrolyte and the metal oxide to be sintered into a solid electrolyte material at a low temperature, thereby reducing energy consumption and improving the problem of adhesion caused by the reaction between the solid electrolyte material and the container due to high-temperature reaction.

[0054] The oxide solid electrolyte used as the raw material for the preparation of the solid electrolyte material is selected from a garnet-type oxide solid electrolyte, which has a chemical composition of Li 7-x A x La3Zr 2-x O 12 wherein A is Nb (niobium), Ga (gallium), or Ta (tantalum), and 0≤x≤0.5, x being any number within the range of 0-0.5, such as 0, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, etc.

[0055] When x is 0, the oxide solid electrolyte is an LLZO solid electrolyte; when x is not 0, A is any one or more of Nb, Ga, or Ta. That is, at least part of the Zr in the crystal structure of the LLZO solid electrolyte material is replaced by at least one of Nb, Ga, or Ta, further promoting the formation of a cubic phase of the LLZO solid electrolyte material and improving its lithium ion conductivity, thereby improving its ionic conductivity.

[0056] Further, in some optional embodiments, the solid electrolyte material is sintered from the oxide solid electrolyte and an additive by a one-step sintering method; the additive includes a metal oxide or / and a metal hydroxide, preferably, the additive includes at least one of magnesium oxide, magnesium hydroxide, and yttrium oxide.

[0057] The existing traditional two-step sintering method for preparing garnet-type oxide solid electrolyte includes high-temperature pre-sintering of precursor powder and high-temperature sintering to obtain solid electrolyte, such as Li7La3Zr2O 12 The research on various doped elements is relatively extensive.

[0058] The sintering time of the two-step sintering method is generally long, and the sintering temperature is high, which can cause volatilization of Li ions in the solid electrolyte, thereby affecting the purity and material performance of the solid electrolyte. In the present application, due to the addition of a low-content additive such as MgO, the oxide solid electrolyte and the additive can be sintered at a lower temperature by using a one-step sintering method, the sintering time is shorter, the energy consumption is reduced, the crystallization and accumulation of MgO are prevented, the electrical conductivity of the solid electrolyte material is avoided to be reduced, and the problem of adhesion caused by the reaction of the solid electrolyte material with the container due to high-temperature reaction can be reduced and improved. The sintering temperature of the one-step sintering method is 800-1000℃, preferably 850-950℃; the sintering time is 4-9h, preferably 4-6h. For example, the sintering temperature is 950℃ and the sintering time is 6h; for another example, the sintering temperature is 800℃ and the sintering time is 7.5h.

[0059] In the present application, the solid electrolyte material is sintered from two-phase materials of oxide solid electrolyte and additive, by controlling the sintering temperature and time parameters and the content of the additive, the size of the metal oxide accumulated at the grain boundary of the oxide solid electrolyte can be controlled, and the crystallization and gradual growth of the metal oxide to block the transport of Li ions in the oxide solid electrolyte is avoided; due to the existence of small-size polyhedral grains of LLZO and LLZTO solid electrolyte, the two-phase composite material effectively reduces the temperature required for sintering of the solid electrolyte, and cubic-phase LLZO and LLZTO solid electrolyte can be obtained. Therefore, cubic-phase LLZO and LLZTO solid electrolyte can also be obtained under low-temperature sintering conditions in the present application, and the electrical conductivity of the cubic-phase LLZO and LLZTO solid electrolyte is much higher than that of the tetragonal-phase LLZO and LLZTO solid electrolyte, which does not cause the reduction of ionic conductivity of the electrolyte, and effectively improves the various electrochemical properties and material properties of the solid electrolyte.

[0060] Further, the particle size of the solid electrolyte material can be observed by SEM, and the average particle size of the solid electrolyte material is 0.1-30μm, preferably 15-20μm, so as to improve the density and strength of the solid electrolyte material; wherein the metal oxide is preferably MgO, so as not to hinder the transport path of lithium ions, and finally the electrochemical performance of the solid electrolyte material can be significantly improved, such as the ionic conductivity of the solid electrolyte material is greater than 1×10 -4 S / cm, preferably greater than 0.4×10 -3 S / cm.

[0061] In a second aspect, the present application provides a method for preparing a solid-state electrolyte material, comprising:

[0062] S130: mixing the oxide solid-state electrolyte with an additive, and sintering by one-step sintering method to obtain a solid-state electrolyte powder; wherein the content of the additive accounts for less than 0.01% of the mass percentage of the oxide solid-state electrolyte.

[0063] Specifically, the oxide solid-state electrolyte is mixed with the additive in a sealed container which does not react with the solid-state electrolyte material and its raw materials for preparation, such as a platinum crucible or a high-purity magnesium oxide crucible, which can be obtained by commercial purchase. The magnesium oxide crucible has good thermal stability and does not react with the raw materials for preparation of the solid-state electrolyte material, nor does it enter the finished solid-state electrolyte material to affect its purity.

[0064] In this example, a low content of additive is used to sinter the oxide solid-state electrolyte into a solid-state electrolyte powder by one-step sintering method, which can be used in film forming process. Due to the presence of trace amounts of metal oxides, they can promote the formation of cubic phase grains of the solid-state electrolyte at a low content level, prevent the agglomeration of metal oxides at the grain boundaries of the oxide solid-state electrolyte and form grains, improve the strength and density of the solid-state electrolyte material, and at the same time, improve the electrical conductivity of the solid-state electrolyte material; in addition, the sintering temperature can be reduced, so that the oxide solid-state electrolyte and the additive can be sintered into a solid-state electrolyte material at a low temperature, reducing energy consumption and improving the sticking problem caused by the reaction of the solid-state electrolyte material with the container due to high temperature reaction.

[0065] In some embodiments, the content of the additive accounts for 0.002-0.008% of the mass percentage of the oxide solid-state electrolyte. Preferably, 0.002-0.006%, more preferably, 0.003-0.0045%.

[0066] Specifically, a low content of additive is used to prevent the agglomeration of metal oxides at the grain boundaries of the oxide solid-state electrolyte and form grains, improve the strength, density and electrical conductivity of the solid-state electrolyte material, and the additive can reduce the sintering temperature of the solid-state electrolyte material, reduce energy consumption, and improve the sticking problem caused by the reaction of the solid-state electrolyte material with the container due to high temperature reaction.

[0067] In some embodiments, the additive includes at least one of magnesium oxide, magnesium hydroxide, and yttrium oxide.

[0068] Specifically, the additive includes at least one of magnesium oxide (MgO), magnesium hydroxide (MgOH2) and yttrium oxide (Y2O3), preferably MgO, to prevent the metal oxide from agglomerating and forming grains in the oxide solid electrolyte, and to improve the strength, density and electrical conductivity of the solid electrolyte material.

[0069] In some embodiments, in step S130, the sintering temperature of the one-step sintering method is 800-1000℃, preferably 850-950℃; the sintering time is 4-9h, preferably 4-6h; and the heating rate of sintering is 1-5℃ / min, preferably 2-3℃ / min. Too fast heating rate can cause problems such as porosity of the ceramic body, affecting the density, causing excessive stress cracking, bending, etc.; and too slow heating rate can cause too long preparation time, but is beneficial to the growth of the ceramic.

[0070] The addition of trace amounts of magnesium oxide can enable the oxide solid electrolyte and magnesium oxide to be sintered into a cubic phase solid electrolyte material at a lower temperature, avoiding the gradual growth of oxide solid electrolyte grains and the accumulation and gradual growth and crystallization of MgO at the triple-junction grain boundaries due to the excessively long sintering time. In the present application, the sintering parameters of the one-step sintering method are limited to the above range, which can reduce energy consumption, prevent the crystallization and accumulation of MgO, avoid the reduction of electrolyte conductivity, and avoid the reaction between the solid electrolyte material and the reaction container and the resulting adhesion.

[0071] The present application can control the size of the solid electrolyte material grains by controlling the amount of added magnesium oxide and the temperature and time parameters of the one-step sintering method, enabling the preparation of a solid electrolyte material with low-temperature short-time sintering and high lithium ion conductivity and high strength, which has an oxide solid electrolyte as the core and magnesium oxide dispersed at the grain boundaries of the oxide solid electrolyte; and the ionic conductivity of the final product solid electrolyte material is greater than 1×10 -4 S / cm, preferably greater than 0.4×10 -3 S / cm, has excellent properties such as high ionic conductivity, and can be applied in lithium ion batteries. The present application limits the average particle size of the solid electrolyte material to the above range, which can significantly improve the electrochemical performance of the solid electrolyte material.

[0072] In some embodiments, before step S130, the method further comprises:

[0073] S110: obtaining the raw material amount of the oxide solid-state electrolyte according to the molar ratio corresponding to the molecular formula of the oxide solid-state electrolyte; wherein the raw material of the oxide solid-state electrolyte at least includes a Li compound, a La compound and a Zr compound, and preferably further includes at least one of a Nb compound, a Ga compound or a Ta compound; wherein the raw material amount of the Li compound exceeds 10% to 30% of the mass of the Li compound defined in the molecular formula of the oxide solid-state electrolyte, and preferably the raw material amount of the Li compound exceeds 15% to 25%;

[0074] The raw material of the oxide solid-state electrolyte is mixed with the additive to obtain a mixture.

[0075] Specifically, the preparation raw material of the solid-state electrolyte material is not particularly limited in the embodiments of the present application, and can be set according to actual needs by those skilled in the art, and each preparation raw material can use its salt, oxide or hydroxide. For example, the preparation raw material of the oxide solid-state electrolyte can include a Li compound, a La compound and a Zr compound, and further preferably includes at least one of a doping compound such as a Nb compound, a Ga compound or a Ta compound. The final product solid-state electrolyte material can be an LLZO series solid-state electrolyte, or a doped solid-state electrolyte, such as an LLZO series solid-state electrolyte in which at least part of Zr is replaced by one, two or three of Nb, Ga or Ta.

[0076] The Li compound can use lithium salt or lithium hydroxide, and from the perspective of ease of obtaining raw materials and cost, the salt is preferably used, for example, lithium carbonate, lithium hydroxide, lithium nitrate, lithium acetate, lithium chloride, etc., and more preferably lithium carbonate is selected. For the La compound, lanthanum hydroxide, lanthanum oxide, lanthanum nitrate, etc. can be used. For the Zr compound, zirconium oxide, zirconium carbonate, zirconium nitrate, etc. can be used.

[0077] When the doping element includes Ta, tantalum salt or tantalum oxide can be preferably used, for example, lithium tantalate, tantalum pentoxide, etc. When the doping element includes Nb, niobium salt can be preferably used, for example, lithium niobate, etc.; and from the perspective of supplementing lithium elements, lithium tantalate or lithium niobate is also preferably used. When the doping element is Ga, gallium oxide or gallium chloride can be used. When lithium lanthanum titanium oxide LLTO is doped, at least one of Ta, Ga or Ta can more effectively promote the uniformity of lithium lanthanum titanium oxide particles and significantly improve the density, so as to improve the lithium ion conductivity of lithium lanthanum titanium oxide.

[0078] According to the molecular formula Li 7-x A x La3Zr 2-x O 12The corresponding molar ratio is used to obtain the raw material of the oxide solid electrolyte, including the amount of Li compound, La compound and Zr compound, preferably further including at least one of Nb compound, Ga compound or Ta compound; the content of the Li compound in the solid electrolyte powder raw material needs to exceed the amount of the molar ratio defined in the molecular formula of the oxide solid electrolyte to ensure that there is no Li deficiency to form a mixed phase during sintering, and the excess of the Li compound is limited to 10% to 30%, more preferably 15% to 25%. Then, at least one of the metal oxides such as magnesium oxide, magnesium hydroxide and yttrium oxide is weighed.

[0079] In some embodiments, before the raw material of the oxide solid electrolyte is mixed with the metal oxide, the raw material of the oxide solid electrolyte and the metal oxide are pretreated respectively, and the pretreatment includes a crushing treatment and then a calcination or drying treatment, so that the raw material powder is more uniformly mixed and the adverse effects of water in the raw material on the performance of the product solid electrolyte material are reduced. The particle size D10 of the raw material is 5.05 μm, the particle size D50 is 22.16 μm, and the particle size D90 is 50.54 μm.

[0080] The crushing treatment can be performed using a common crusher in the art, such as an air jet crusher. The calcination can be performed at 800 to 1000℃ for 5 to 10 hours, preferably at 800 to 900℃ for 6 to 8 hours. The drying can be performed at 100 to 150℃ for 5 to 15 hours, preferably at 110 to 130℃ for 8 to 12 hours. Preferably, the La compound is subjected to the calcination treatment; and the Li compound, the Zr compound and the optional doped compound such as the Nb compound, the Ga compound or the Ta compound are subjected to the drying treatment.

[0081] In some embodiments, between step S110 and step S130, the following steps are further included:

[0082] S120: The mixture is placed in a ball mill tank, a solvent is added, and the mixture is ground and mixed uniformly to obtain a mixed slurry;

[0083] The mixed slurry is sequentially subjected to suction filtration, drying, crushing and sieving treatment.

[0084] Specifically, the ball milling conditions of the present application are not particularly limited and can be appropriately adjusted according to the actual situation. For example, the rotation speed of the ball mill can be 100 to 800 r / min, preferably 200 to 600 r / min, and the ball milling time can be 4 to 30 h, preferably 10 to 24 h. The mass ratio of the grinding balls to the raw material in the ball mill tank, i.e. the ball-to-material mass ratio, can be (1 to 5):1, preferably (1 to 3):1.

[0085] In order to make the mixture uniform and make the particle size of the mixture smaller, the grinding balls are preferably mixed by mixing balls of different diameters. For example, large balls of about 7-9 mm, medium balls of 4-6 mm, and small balls of 1-3 mm can be mixed in a certain mass ratio, which can be 1:(1-3):(1-5), preferably 1:(1-2):(2-3). There is no particular limitation on the grinding balls, and grinding balls commonly used in the art can be used, such as zirconia balls, silicon nitride balls, brown corundum balls, etc. Among them, zirconia balls are preferably used.

[0086] In addition, an appropriate amount of solvent can be added to the mixture. The solvent can be an organic solvent such as methanol, ethanol, isopropanol, acetonitrile, hexane, etc., and isopropanol is preferred, so that the mixture can be better dispersed. When adding the solvent, the mass ratio of the solvent to the material can be (1-3):1.

[0087] In the present application, the pre-weighed raw materials of the oxide solid-state electrolyte and the metal oxide are placed in a ball mill tank, a solvent is added, and the mixture is ground and mixed uniformly, the ball mill balls are filtered out, and a mixed slurry is obtained; the mixed slurry is then sequentially subjected to suction filtration to obtain a filter cake, wherein suction filtration can be performed using a suction filter machine, then the filter cake is placed in an oven and dried at 70-90°C for 12-24 hours, after drying, the mixture is crushed, granulated, and passed through a 200-800 mesh sieve, preferably a 300-500 mesh sieve, and the mixture powder is obtained. The mixture powder is then placed in a sealed container and placed in a muffle furnace, heated at a rate of 2-10°C / min to 800-1000°C and sintered for 5-9h, then the obtained sintered product is crushed and passed through a 200-800 mesh sieve to obtain the two-phase solid-state electrolyte powder.

[0088] In some embodiments, step S130 is followed by:

[0089] S140: tabletting the solid-state electrolyte powder to obtain a green body;

[0090] sintering the green body to obtain a solid-state electrolyte ceramic sheet.

[0091] Specifically, 1-5g of solid-state electrolyte powder is placed in a φ17mm mold and tabletted under a pressure of 100-300MPa, the tabletted green body is placed in a sealed container and then placed in a muffle furnace and heated to 900-1200°C and sintered for 3-5h, preferably sintered at 1000-1100°C for 4-5h, to obtain a densified solid-state electrolyte material.

[0092] Alternatively, the binder is added to the solid electrolyte powder before tabletting, and then the tablet is sintered to remove the binder, and finally sintered to densify the solid electrolyte ceramic sheet. For example, the binder is added to 1-5 g of the solid electrolyte powder and ground uniformly, the ground powder is introduced into a mold, and a green body is prepared by pressing in a hydraulic press. The green body is placed in a sealed container and heated to 400-600°C for 3-5 h to remove the binder, and then heated to 900-1100°C for 3-5 h to densify the ceramic sheet. In the present application, the type of binder is not particularly limited, and can be an organic binder such as PEO or PVA. The amount of binder added is 0.01-0.02% by mass of the solid electrolyte powder.

[0093] The present application will be described in detail below by way of examples. The examples are intended to illustrate the present application and should not be construed as limiting the present application. If a specific technique or condition is not mentioned in the examples, the technique or condition described in the literature in the art or according to the product manual is used. If the manufacturer of the reagent or instrument is not mentioned, it is a conventional product that can be obtained commercially.

[0094] The raw materials for preparing the oxide solid electrolyte and the metal oxide are pretreated. Li2CO3, La2O3, ZrO2, and MgO are separately subjected to jet milling. La2O3 is calcined in a muffle furnace at 900°C for 8 h, and Li2CO3 and ZrO2 are dried in an oven at 120°C for 12 h. After calcination and drying, the materials are vacuum-sealed for use.

[0095] Example 1

[0096] A method for preparing a solid electrolyte ceramic sheet, comprising:

[0097] S110: 43.23 g of lithium carbonate (20% excess by mass), 16.57 g of tantalum pentoxide, 73.31 g of lanthanum oxide, and 27.73 g of zirconium oxide are weighed according to the molar ratio of Li:Ta:La:Zr of 6.5:0.5:3:1.5, 0.008 wt% of MgO is weighed, mixed, and a mixed material is obtained.

[0098] S120: The mixed material and 160 g of isopropanol are introduced into a ball mill tank together, and mixed zirconium balls (8 mm in diameter), medium balls (5 mm in diameter), and small balls (1 mm in diameter) are prepared in a mass ratio of 1:2:3. 320 g of mixed zirconium oxide balls are weighed according to a ball-to-material mass ratio of about 1:1, introduced into the ball mill tank, set to a rotation speed of 500 r / min, rotated forward for 30 min, reversed for 30 min at intervals of 20 min, and ball-milled for 24 h. After being taken out, the mixed slurry is sieved to obtain a mixed slurry. The mixed slurry is suction-filtered, the filter cake is dried in an oven, and the dried material is crushed, granulated, and sieved through a 400-mesh sieve to obtain a mixed powder.

[0099] S130: 100 g of the mixed powder is weighed into a zirconia airtight container, and then placed into a muffle furnace to sinter at a rate of 3℃ / min to 950℃ for 6 h. After crushing and sieving through a 400 mesh sieve, a solid electrolyte powder is obtained.

[0100] S140: 1.5 g of the solid electrolyte powder is taken and 3 drops of a 1 wt% PEO solution are added. The mixture is stirred and ground into a powder. The ground powder is placed into a φ17 mm mold and pressed into a tablet under a pressure of 200 MPa. The green body is placed into an airtight container and placed into a muffle furnace. The temperature is first raised to 500℃ to remove the binder for 4 h, and then raised to 1100℃ for 4 h to densify the green body, thereby obtaining a solid electrolyte ceramic sheet.

[0101] Figure 1 FIG. 1 is an SEM image of a solid electrolyte ceramic sheet according to an embodiment of the present application. FIG. 1(a) is an SEM image of a ceramic cross-section with 0.008% Mg addition, FIG. 1(b) is an SEM image of a ceramic cross-section with 0.005% Mg addition, and FIG. 1(c) is an SEM image of a ceramic cross-section with 0.002% Mg addition. As can be seen from the figures, as the Mg content increases, the sintering morphology becomes more uniform, and when the addition is 0.008%, the overall ceramic particle size is less than 10 microns.

[0102] Examples 2-8

[0103] The preparation method of the solid electrolyte ceramic sheet of this embodiment is the same as that of Example 1, except that the type and content of the metal oxide and the parameters of the one-step sintering method of Examples 2-8 are different from those of Example 1, as shown in Table 1. In Table 1, "-" indicates that the parameter is the same as that of Example 1.

[0104] Table 1

[0105]

[0106] Comparative Example 1

[0107] A conventional method for preparing a solid electrolyte ceramic sheet includes:

[0108] Take 67.75 g of lithium carbonate (10% excess), 116.4 g of lanthanum oxide and 58.7 g of zirconium oxide according to the molar ratio of Li:La:Zr 7:3:2, and put them into the ball mill tank. Mix the zirconium balls of large balls (diameter 8 mm) and medium balls (diameter 5 mm), and small balls (diameter 1 mm) according to the mass ratio of 1:2:3. Take 240 g of mixed zirconium oxide balls according to the ball-to-material mass ratio of about 1:2, and put them into the ball mill tank. Set the ball milling speed to 500 r / min, forward rotation for 30 min, interval for 30 min, reverse rotation for 30 min, and ball milling for 24 h. After taking out, sieve to get the mixed material. Take 1.5 g of the mixed material and put it into the crucible. Add 2 g of mother powder (i.e. the mixed material laid as a base to prevent impurities generated during the sintering process of the solid-state electrolyte) to bury the material, and then put it into the muffle furnace. First, heat to 900℃ and pre-sinter for 6 h, and then heat to 1200℃ and continue to sinter for 12 h to obtain the solid-state electrolyte ceramic sheet.

[0109] Comparative Example 2

[0110] A preparation method of a solid-state electrolyte ceramic sheet, comprising:

[0111] Take 59.96 g of lithium carbonate (20% excess), 110.93 g of lanthanum oxide, 41.95 g of zirconium oxide and 26.77 g of tantalum pentoxide according to the molar ratio of Li:La:Zr:Ta 6.5:3:1.5:0.5, and put them into the ball mill tank. Mix the zirconium balls of large balls (diameter 8 mm) and medium balls (diameter 5 mm), and small balls (diameter 1 mm) according to the mass ratio of 1:2:3. Take 240 g of mixed zirconium oxide balls according to the ball-to-material mass ratio of about 1:1, and put them into the ball mill tank. Set the ball milling speed to 500 r / min, forward rotation for 30 min, interval for 30 min, reverse rotation for 30 min, and ball milling for 24 h. After taking out, sieve to get the mixed material. Take 1.5 g of the mixed material and put it into the crucible. Add 2 g of mother powder (i.e. the mixed material laid as a base to prevent impurities generated during the sintering process of the solid-state electrolyte) to bury the material, and then put it into the muffle furnace. First, heat to 950℃ and pre-sinter for 6 h, and then heat to 1100℃ and continue to sinter for 4 h to obtain the solid-state electrolyte ceramic sheet.

[0112] Comparative Example 3

[0113] The preparation method of the solid-state electrolyte ceramic sheet of the present embodiment is the same as that of Example 1, except that the mass percentage of MgO in the oxide solid-state electrolyte is 0.08% in the present embodiment.

[0114] Comparative Example 4

[0115] The preparation method of the solid-state electrolyte ceramic sheet of the present embodiment is the same as that of Example 1, except that the sintering time in S130 is 24 h in the present embodiment.

[0116] It should be noted that the solid electrolyte ceramic sheets obtained in Examples 1-8 and Comparative Examples 1-4 all have cubic phase structure.

[0117] Test

[0118] The products obtained in Examples 1-8 and Comparative Examples 1-4 were pressed into sheets by adding a binder for solid electrolyte powders, and were sintered to remove the binder, densified, and subjected to EIS (electrochemical impedance spectroscopy) test, and the results are shown in Table 2. Figure 2 For solid electrolyte ceramic sheets, after being directly polished, both sides were coated with conductive silver paste, and then placed in an electrochemical workstation for impedance (EIS) test, and the material conductivity was calculated.

[0119] (1) Impedance value test method

[0120] Among them, the impedance value is determined by the test method of alternating current impedance, the ceramic sheet is placed in an electrochemical workstation to test the alternating current impedance, the frequency is set to 1-1 MHz, the amplitude is 5 mV, and the results are as follows:

[0121] (2) Conductivity test method

[0122] The impedance value of the solid electrolyte ceramic sheet obtained in Examples 1-8 and Comparative Examples 1-4 is replaced by the real part value of the inflection point of the impedance diagram, and the test of lithium ion conductivity is calculated using the formula σ=L / SR.

[0123] (3) Purity test method

[0124] The content of the second phase element (i.e. the metal element in the metal oxide) in the bulk phase is tested by ICP (inductively coupled plasma).

[0125] (4) Strength test method

[0126] According to the national standard GB / T 4741-1999, the bending strength of the ceramic material is tested, and the bending strength of the ceramic sheet is tested by three-point load method.

[0127] The test results are shown in Table 2.

[0128] Table 2

[0129]

[0130] According to Table 2 and the comparison of Examples 1-8 and Comparative Examples 1-4 in Figure 2 It can be seen that the solid electrolyte material in the present application can balance the strength and conductivity.

[0131] In a third aspect, the application provides a battery comprising the solid electrolyte material according to any of the embodiments of the application, or the solid electrolyte material obtained by the preparation method according to any of the embodiments of the application.

[0132] In particular, the battery provided by the embodiments of the application can be a lithium battery, and the specific technical effects are the same as those of the solid electrolyte material and the preparation method thereof, which will not be repeated here.

[0133] In a fourth aspect, the application provides an electrical device comprising the battery according to any of the embodiments of the application.

[0134] The electrical device provided by the embodiments of the application has the same specific technical effects as those of the solid electrolyte material and the preparation method thereof, which will not be repeated here.

[0135] It should be noted that the electrical device can be a vehicle, a mobile phone, a portable device, a notebook computer, a ship, a spacecraft, an electric toy, an electric tool, etc. The vehicle can be a fuel automobile, a gas automobile or a new energy automobile, and the new energy automobile can be a pure electric automobile, a hybrid electric automobile or a range extended automobile, etc. The spacecraft includes an airplane, a rocket, a space shuttle and a spacecraft, etc. The electric toy includes a fixed or mobile electric toy, such as a game console, an electric automobile toy, an electric ship toy and an electric airplane toy, etc. The electric tool includes a metal cutting electric tool, a grinding electric tool, an assembling electric tool and a railway electric tool, such as an electric drill, an electric grinder, an electric wrench, an electric screwdriver, an electric hammer, an impact drill, a concrete vibrator and an electric planer, etc. The embodiments of the application do not specially limit the above electrical devices.

[0136] The above description is merely preferred embodiments of the application and a description of the principles of the technology used. Those skilled in the art should understand that the scope of the application disclosed in the application is not limited to the technical solutions formed by the specific combinations of the above technical features, and also covers other technical solutions formed by any combination of the above technical features or equivalent features without departing from the inventive concept. For example, the above features are replaced with the technical features disclosed in the application (but not limited to) having similar functions to form technical solutions.

Claims

1. A solid electrolyte material, characterized in that, The solid electrolyte material includes an oxide solid electrolyte and a metal oxide, wherein the metal oxide is distributed at the grain boundaries of the oxide solid electrolyte, and the content of the metal oxide accounts for 0.002 to 0.008% of the mass of the oxide solid electrolyte; the metal oxide includes magnesium oxide and / or yttrium oxide.

2. The solid electrolyte material according to claim 1, characterized in that, The molecular formula of the oxide solid electrolyte is Li 7-x A x La3Zr 2-x O 12 , where A is Nb, Ga or Ta, and 0≤x≤0.

5.

3. The solid electrolyte material according to claim 1, characterized in that, The solid electrolyte material is produced by a one-step sintering process using raw materials and additives from the oxide solid electrolyte; the additives include metal oxides and / or metal hydroxides.

4. The solid electrolyte material according to claim 3, characterized in that, The additives include at least one of magnesium oxide, magnesium hydroxide, and yttrium oxide.

5. The solid electrolyte material according to claim 3, characterized in that, The metal oxide is distributed at the grain boundaries of the oxide solid electrolyte and gives the solid electrolyte material a cubic phase structure.

6. The solid electrolyte material according to any one of claims 1-5, characterized in that, The ionic conductivity of the solid electrolyte material is greater than 1×10⁻⁶. -4 S / cm.

7. The solid electrolyte material according to claim 6, characterized in that, The ionic conductivity of the solid electrolyte material is greater than 0.4 × 10⁻⁶. -3 S / cm.

8. The solid electrolyte material according to any one of claims 1-5, characterized in that, The average particle size of the solid electrolyte material is 0.1–30 μm.

9. The solid electrolyte material according to claim 8, characterized in that, The average particle size of the solid electrolyte material is 15–20 μm.

10. A method for preparing a solid electrolyte material, characterized in that, The method is used to obtain the solid electrolyte material according to any one of claims 1-9, the method comprising: The raw materials of the oxide solid electrolyte are mixed with additives and sintered using a one-step sintering method to obtain solid electrolyte powder; wherein the content of the additives accounts for 0.002 to 0.008% of the mass percentage of the oxide solid electrolyte, and the additives include at least one of magnesium oxide, magnesium hydroxide, and yttrium oxide.

11. The method for preparing the solid electrolyte material according to claim 10, characterized in that, The sintering temperature of the one-step sintering method is 800-1000℃, and the sintering time is 4-9h.

12. The method for preparing the solid electrolyte material according to claim 11, characterized in that, The sintering temperature of the one-step sintering method is 850–950℃, and the sintering time is 4–6 hours.

13. The method for preparing the solid electrolyte material according to claim 10, characterized in that, The process of mixing the raw materials of the oxide solid electrolyte with additives includes: The feed amounts of the raw materials for the oxide solid electrolyte are obtained according to the molar ratio corresponding to the molecular formula of the oxide solid electrolyte; wherein, the raw materials for the oxide solid electrolyte include at least Li compound, La compound and Zr compound; wherein, the feed amount of the Li compound exceeds 10% to 30% of the mass of the Li compound defined in the molecular formula of the oxide solid electrolyte; The raw materials of the oxide solid electrolyte are then mixed with the additives to obtain a mixture.

14. The method for preparing the solid electrolyte material according to claim 13, characterized in that, The amount of the Li compound fed into the feed exceeds 15% to 25%.

15. The method for preparing the solid electrolyte material according to claim 13, characterized in that, The raw materials for the oxide solid electrolyte further include at least one of Nb compound, Ga compound, or Ta compound.

16. The method for preparing the solid electrolyte material according to any one of claims 13-15, characterized in that, The process of mixing the raw materials of the oxide solid electrolyte with the additives to obtain a mixture, and before sintering, further includes: The mixture is placed in a ball mill jar, a solvent is added, and the mixture is ground and mixed evenly to obtain a slurry. The mixed slurry is subjected to sequential processes of filtration, drying, pulverization, and sieving.

17. The method for preparing the solid electrolyte material according to any one of claims 10-15, characterized in that, After obtaining the solid electrolyte powder, the process further includes: The solid electrolyte powder is compressed into tablets to obtain a raw embryo; The raw embryo is sintered to obtain a solid electrolyte ceramic sheet.

18. The method for preparing the solid electrolyte material according to claim 17, characterized in that, The sintering temperature of the green embryo is 900-1200℃, and the time is 3-5 hours.

19. A battery, characterized in that, The battery comprises the solid electrolyte material according to any one of claims 1-9, or the solid electrolyte material obtained by the preparation method of the solid electrolyte material according to any one of claims 10-18.

20. An electrical appliance, characterized in that, The electrical device includes the battery as described in claim 19.

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