NASICON Solid Electrolyte Material, Its Preparation Method, Solid-State Battery and Application

Abstract

The present invention relates to a NASICON solid electrolyte material, a preparation method thereof, a solid-state battery, and an application. The preparation method of the NASICON solid electrolyte material may include the following steps: ball-milling and mixing a phosphate salt, an A-containing oxide, and a B-containing oxide, sintering at a relatively high temperature, granulating, preparing a solid electrolyte precursor, then adding a lithium salt, sintering at a relatively low temperature, granulating, and preparing a Li x A y B z (PO4)3 NASICON solid electrolyte material; wherein, the A element is one or more of Mg, Al, and Si, and the B element is one or more of Ca, Ti, and V. This preparation method can avoid excessive loss of lithium, and there is no need to additionally add a sintering aid, and a NASICON solid electrolyte material with good electrochemical stability and high lithium ion conductivity can be obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of solid electrolytes, and particularly to a NASICON solid electrolyte material, a preparation method thereof, a solid-state battery, and an application thereof. Background Art

[0002] Traditional lithium-ion batteries use liquid electrolytes for lithium-ion transport, and the organic liquid components therein pose double challenges in terms of safety and performance during battery cycling. Lithium-ion batteries based on liquid electrolytes generally have problems such as cyclic capacity decay, dissolution of electrode active materials, and even gradual failure. During this process, the liquid electrolyte is prone to leakage, gas swelling, and even cause the battery to catch fire and explode, presenting significant safety hazards while the performance fails. The solid electrolytes used in solid-state batteries can not only replace the liquid electrolytes in traditional batteries but also act as the separator components in traditional batteries, ensuring the performance stability of the battery system while realizing lithium-ion transport and greatly reducing the safety risk. As one of the mainstream routes of solid electrolytes, oxide electrolytes have attracted attention in scientific research and industrial applications because they are stable in air, do not require air isolation, which is conducive to simplifying production, reducing costs, and maintaining performance. However, the lithium-ion conductivity level of oxide electrolytes is generally lower than that of liquid electrolytes, which to a certain extent hinders the application of oxide electrolytes in solid-state batteries. Summary of the Invention

[0003] Based on this, the objectives of the present invention include providing a preparation method of a NASICON solid electrolyte material, which can effectively improve the lithium-ion conductivity of the obtained solid electrolyte material, and also providing a NASICON solid electrolyte material, a solid-state battery, and the application of the aforementioned NASICON solid electrolyte material in the preparation of solid-state batteries.

[0004] In the first aspect of the present invention, there is provided a preparation method of a NASICON solid electrolyte material, including the following steps:

[0005] Ball-mill and mix a phosphate salt, an A-containing oxide, and a B-containing oxide raw material to obtain a mixture I; wherein, the A element in the A-containing oxide is one or more of Mg, Al, and Si, and the B element in the B-containing oxide is one or more of Ca, Ti, and V; the molar ratio of the phosphorus element in the phosphate salt, the A element in the A-containing oxide, and the B element in the B-containing oxide is 3:(0-1):(1-4);

[0006] Heat the mixture I at a heating rate of 8 - 12 °C / min to 800 - 1000 °C, hold for 1 - 3 h, then cool at a cooling rate of 8 - 12 °C / min to 200 - 400 °C, and then cool in the furnace to 20 - 35 °C to prepare a NASICON solid electrolyte precursor;

[0007] Crush and grind the NASICON solid electrolyte precursor to a preset particle size;

[0008] Ball-mill and mix the crushed and ground NASICON solid electrolyte precursor with a lithium salt raw material to obtain a mixture II; wherein, the molar ratio of phosphorus element in the NASICON solid electrolyte precursor to lithium element in the lithium salt is 3:(1.1 - 1.5);

[0009] Heat the mixture II at a heating rate of 8 - 12 °C / min to 500 - 700 °C, hold for 1 - 3 h, then cool at a cooling rate of 8 - 12 °C / min to 200 - 400 °C, and then cool in the furnace to 20 - 35 °C to prepare a NASICON solid electrolyte crude material;

[0010] Crush and grind the NASICON solid electrolyte crude material to a preset particle size to prepare the NASICON solid electrolyte material.

[0011] In some embodiments, the phosphate salt is NH4H2PO4; the A-containing oxide is one or more of MgO, Al2O3, and SiO2; the B-containing oxide is one or more of TiO2, CaO, and V2O5; the lithium salt is Li2CO3.

[0012] In the step of ball-milling and mixing the phosphate salt, A-containing oxide, and B-containing oxide raw materials, the D50 of the phosphate salt raw material is 5 - 15 μm, the D50 of the A-containing oxide raw material is 200 - 600 nm, and the D50 of the B-containing oxide raw material is 0.5 - 2 μm; the ball-milling speed is 200 - 600 r / min, and the ball-milling time is 1 - 5 h;

[0013] In the step of crushing and grinding the NASICON solid electrolyte precursor to a preset particle size, the D50 of the material after crushing and grinding is 10 μm ± 2 μm;

[0014] In the step of ball-milling and mixing the crushed and ground NASICON solid electrolyte precursor with the lithium salt, the ball-milling speed is 200 - 600 r / min, and the ball-milling time is 1 - 5 h;

[0015] In the step of crushing and pulverizing the NASICON solid electrolyte rough material to a preset particle size, the D50 of the material after crushing and pulverizing is 10 μm ± 2 μm.

[0016] In some embodiments, the D50 of the raw material of the phosphate salt is 9.5 - 10.5 μm, the D50 of the raw material of the A-containing oxide is 450 - 550 nm, the D50 of the raw material of the B-containing oxide is 0.9 - 1.1 μm, and the D50 of the raw material of the lithium salt is 0.9 - 1.1 μm.

[0017] In some embodiments, in the step of ball-milling and mixing the phosphate salt, the A-containing oxide, and the B-containing oxide raw materials, the molar ratio of the phosphorus element in the phosphate salt, the A element in the A-containing oxide, and the B element in the B-containing oxide is 3:(0.1 - 0.55):(1.15 - 3.6);

[0018] In the step of ball-milling and mixing the crushed and pulverized NASICON solid electrolyte precursor with the lithium salt, the molar ratio of the phosphorus element in the crushed and pulverized NASICON solid electrolyte precursor to the lithium element in the lithium salt is 3:(1.2 - 1.4).

[0019] In a second aspect of the present invention, a NASICON solid electrolyte material is provided, which can be prepared by using the preparation method described in the first aspect of the present invention.

[0020] In a third aspect of the present invention, a NASICON solid electrolyte material is provided, which has the following chemical formula composition:

[0021] Li x A y B z (PO4)3,

[0022] wherein, x is a value selected from 1.1 - 1.5,

[0023] y is a value selected from 0 - 1,

[0024] z is a value selected from 1 - 4;

[0025] The A element is Si, and the B element is one or more of V, Ti, and Ca;

[0026] Or,

[0027] The A element is Al, and the B element is one of V and Ca, or at least two of Ti, V, and Ca;

[0028] Or,

[0029] Element A is Mg, element B is one of V and Ca, or at least two of Ti, V, and Ca.

[0030] In some embodiments, the Li x A y B z (PO4)3 is Li 1.1～1.5 Si 0.125～0.325 V 1.16～1.56 (PO4)3, Li 1.1～1.5 Si 0.125～0.325 Ti 1.5～1.9 (PO4)3, Li 1.1～1.5 Si 0.125～0.325 Ca 3.2～3.6 (PO4)3, Li 1.1～1.5 Al 0.2～ 0.4 V 1.16～1.56 (PO4)3, Li 1.1～1.5 Al 0.2～0.4 Ca 3.2～3.6 (PO4)3, Li 1.1～1.5 Mg 0.35～0.55 V 1.16～1.56 (PO4)3 and Li 1.1～1.5 Mg 0.35～0.55 Ca 3.2～3.6 (PO4)3, or one or more of them.

[0031] In some embodiments, the Li x A y B z (PO4)3 is Li 1.3 Si 0.225 V 1.36 (PO4)3, Li 1.3 Si 0.225 Ti 1.7 (PO4)3, Li 1.3 Si 0.225 Ca 3.4 (PO4)3, Li 1.3 Al 0.3 V 1.36 (PO4)3, Li 1.3 Al 0.3 Ca 3.4 (PO4)3, Li 1.3 Mg 0.45 V 1.36 (PO4)3 and Li 1.3 Mg 0.45 Ca 3.4 (PO4)3, or one or more of them.

[0032] In a fourth aspect of the present invention, there is provided a solid-state battery, which includes a positive electrode active material layer, a negative electrode active material layer, and a solid electrolyte layer formed between the positive electrode active material layer and the negative electrode active material layer. Among them, the solid electrolyte layer contains at least one of the NASICON solid electrolyte materials prepared by the preparation method described in the first aspect of the present invention and the NASICON solid electrolyte materials described in the second and third aspects of the present invention.

[0033] In a fifth aspect of the present invention, there is provided an application of the NASICON solid electrolyte material prepared by the preparation method described in the first aspect of the present invention or the NASICON solid electrolyte materials described in the second or third aspects of the present invention in preparing an electrolyte of a solid-state battery. Further, the solid electrolyte includes an oxide solid electrolyte, a polymer and an oxide mixed solid electrolyte, or an electrolyte solution and an oxide mixed semi-solid electrolyte, and the solid-state battery includes a battery with a lithium metal or a lithium alloy as the negative electrode.

[0034] In the preparation method of the NASICON solid electrolyte material provided by the present invention, a step-by-step sintering method is adopted. First, the lithium-free solid precursor is subjected to the first sintering at a high temperature (such as 800 - 1000 °C), and then the solid precursor subjected to the high-temperature sintering is mixed with a lithium salt, and then the second sintering is carried out at a low temperature (such as 500 - 700 °C) to prepare the NASICON solid electrolyte material. In this method, the means of step-by-step sintering is cleverly utilized, which can not only fully sinter the non-lithium material, but also avoid the high-temperature loss of lithium. In addition, this method can avoid adding a sintering aid additionally, which is beneficial to accurately adjusting the specific stoichiometric ratio of the NASICON solid electrolyte material. The process flow is simple and easy to scale up production. The NASICON solid electrolyte material provided by the present invention may have the following chemical formula Li x A y B z (PO4)3. The solid-state battery composed of the solid electrolyte material with a specific ratio of lithium element, A element, and B element has a relatively high room-temperature ionic conductivity and relatively stable electrochemical performance, which helps to maintain the capacity of the solid-state battery, improve the rate performance, and reduce the battery performance attenuation, battery failure, and risks such as fire and combustion.

[0035] By using the secondary sintering method to prepare the NASICON solid electrolyte material, it is prepared without adding a sintering aid, which is beneficial to simplifying the preparation process of the solid-state battery, improving the reliability, and broadening the application range of the NASICON solid electrolyte. Description of the Drawings

[0036] Figure 1Schematic diagram of the preparation method of the NASCION solid electrolyte material in an embodiment of the present invention. Detailed implementation manners

[0037] To facilitate the understanding of the present invention, the present invention will be described more comprehensively below with reference to the relevant attached drawings. Preferred embodiments of the present invention are shown in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided to make the understanding of the disclosure of the present invention more thorough and comprehensive.

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

[0039] Term

[0040] Unless otherwise stated or there is a contradiction, the terms or phrases used herein have the following meanings:

[0041] In the present invention, "a plurality of", "a variety of", "multiple times", etc. refer to a quantity greater than 2 or equal to 2 if not otherwise specified. For example, "one or more" means one or greater than or equal to two.

[0042] In this article, "preferred", "better", "more preferable", "it is advisable" are only used to describe embodiments or examples with better effects. It should be understood that they do not constitute a limitation on the protection scope of the present invention. If "preferred" appears in multiple places in a technical solution, unless otherwise specified and there is no contradiction or mutual restriction relationship, each "preferred" is independent.

[0043] In the present invention, "further", "even further", "especially", etc. are used for descriptive purposes and indicate differences in content, but should not be construed as a limitation on the protection scope of the present invention.

[0044] In the present invention, among the technical features described in an open-ended manner, it includes a closed technical solution composed of the listed features, and also includes an open technical solution containing the listed features.

[0045] In the present invention, when it comes to numerical intervals (i.e., numerical ranges), unless otherwise specified, the distribution of the selectable numerical values within the numerical interval is considered continuous, and includes the two numerical endpoints of the numerical interval (i.e., the minimum value and the maximum value), as well as each numerical value between these two numerical endpoints. Unless otherwise specified, when the numerical interval only refers to the integers within the numerical interval, it includes the two endpoint integers of the numerical range, as well as each integer between the two endpoints, which is equivalent to directly listing each integer. When multiple numerical ranges are provided to describe features or characteristics, these numerical ranges can be combined. In other words, unless otherwise specified, the numerical ranges disclosed herein should be understood to include any and all sub-ranges subsumed therein. The "numerical values" in the numerical interval can be any quantitative values, such as numbers, percentages, ratios, etc. The "numerical interval" allows for a broad inclusion of numerical interval types such as percentage intervals, ratio intervals, and ratio value intervals.

[0046] For the temperature parameters in the present invention, unless otherwise specified, both constant temperature treatment and variation within a certain temperature interval are allowed. It should be understood that the constant temperature treatment allows the temperature to fluctuate within the accuracy range controlled by the instrument. Fluctuations within ranges such as ±5°C, ±4°C, ±3°C, ±2°C, and ±1°C are allowed.

[0047] In the present invention, the term "room temperature" generally refers to 4°C to 35°C, preferably 20°C ± 5°C. In some embodiments of the present invention, room temperature refers to 20°C to 30°C.

[0048] In the present invention, regarding the units of data ranges, if the unit is only attached to the right endpoint, it means that the units of the left endpoint and the right endpoint are the same. For example, 3 to 5 h means that the units of the left endpoint "3" and the right endpoint "5" are both h (hours).

[0049] In the present invention, the lithium metal secondary battery, also known as the lithium metal battery, the negative electrode of the lithium metal secondary battery of the present invention contains at least one of lithium metal and lithium alloy.

[0050] In the present invention, D50, also known as the median diameter, median particle size, or average particle size, means the particle diameter corresponding to when the cumulative particle size distribution percentage of a sample reaches 50%. Its physical meaning is that 50% of the particles have a particle diameter smaller than this value, and 50% of the particles have a particle diameter larger than this value.

[0051] Sodium superionic conductor (NASICON) is an oxide electrolyte material that has been studied extensively. Its typical structure is LiM2(PO4)3, where M is a tetravalent cation. The three-dimensional framework structure of this typical structure is composed of octahedra MO6 and tetrahedra PO4. The interstitial positions between the tetrahedra and octahedra can accommodate lithium ions with a small radius and provide a three-dimensional transport channel for the transport of lithium ions.

[0052] Li 1.3 Al 0.3 Ti 1.7 (PO4)3, abbreviated as LATP, with Al 3+ substituting for Ti 4+ occupying specific sites, improving the lithium-ion transport channels and increasing the lithium-ion conductivity. The Li 1.3 Al 0.3 Ti 1.7 (PO4)3 conductivity obtained by assisted sintering can reach 10 -4 S cm -1 or even 10 -3 S cm -1 , but the lithium-ion conductivity is still relatively low and the preparation method is complex.

[0053] In traditional technologies, NASICON oxide solid electrolytes are usually prepared by methods with complex processes and even harsh conditions to obtain a relatively high lithium-ion conductivity. In order to achieve a lithium-ion conductivity of 10 -3 S cm -1 order of magnitude, one of the routes of traditional technologies is through liquid-phase synthesis: the initial raw materials are selected as soluble or dissolvable compounds containing the target elements, and the ions are uniformly dispersed into the reaction system solution through chelating agents, templating agents, dispersing agents, etc. Some technologies even require atomic-level uniform dispersion of elements to facilitate subsequent multi-step heat treatment and mechanical treatment processes to obtain a solid electrolyte with a lithium-ion conductivity of 10 -3 S cm -1 order of magnitude. Another route of traditional technologies is to prepare NASICON solid electrolytes with relatively high lithium-ion conductivity by using special solid-phase methods, but expensive heat treatment methods are required, such as reactive sintering, ultra-rapid high-temperature sintering (UHS), etc., or methods such as adding sintering aids, to achieve the purpose of reducing lithium loss in NASICON solid electrolytes and realizing uniform, dense and high lithium-ion conductivity of the electrolyte. Introducing sintering aids can help reduce the grain boundary resistance and make the total conductivity equivalent to the lattice conductivity. Common sintering aids such as Li3BO3 and Li3PO4, etc.

[0054] The inventors of the present application have conducted a large number of experimental studies and explorations and found a preparation method for NASICON solid electrolyte materials that can better overcome the above problems.

[0055] In the first aspect of the present invention, a preparation method for NASICON solid electrolyte materials is provided. The method may include the following steps: ball-milling and mixing a phosphate salt, an A-containing oxide and a B-containing oxide, sintering at a relatively high temperature, granulating to prepare a solid electrolyte precursor, then adding a lithium salt, sintering at a relatively low temperature, granulating, and preparing to obtain Li x Ay B z (PO4)3NASICON solid electrolyte material; wherein, element A is one or more of Mg, Al, and Si, and element B is one or more of Ca, Ti, and V. This preparation method can avoid excessive loss of lithium, does not require additional addition of sintering aids, and can obtain a NASICON solid electrolyte material with good electrochemical stability and high lithium ion conductivity.

[0056] According to an embodiment of the present invention, a method for preparing a NASICON solid electrolyte material is provided, which includes the following steps:

[0057] S100: Ball-mill and mix phosphate salt, A-containing oxide, and B-containing oxide raw materials to obtain mixture I; wherein, element A in the A-containing oxide is one or more of Mg, Al, and Si, and element B in the B-containing oxide is one or more of Ca, Ti, and V; further, the molar ratio of phosphorus element in the phosphate salt, element A in the A-containing oxide, and element B in the B-containing oxide is 3:(0-1):(1-4);

[0058] S200: Heat mixture I to 800-1000 °C, keep warm, then cool down to 200-400 °C, and then cool down to room temperature (such as 20-35 °C) in the furnace to prepare a NASICON solid electrolyte precursor;

[0059] S300: Crush and pulverize the NASICON solid electrolyte precursor to a preset particle size;

[0060] S400: Ball-mill and mix the crushed and pulverized NASICON solid electrolyte precursor with lithium salt raw materials to obtain mixture II; further, the molar ratio of phosphorus element in the NASICON solid electrolyte precursor to lithium element in the lithium salt is 3:(1.1-1.5);

[0061] S500: Heat mixture II to 500-700 °C, keep warm, then cool down to 200-400 °C, and then cool down to room temperature (such as 20-35 °C) in the furnace to prepare a NASICON solid electrolyte rough material;

[0062] S600: Crush and pulverize the NASICON solid electrolyte rough material to a preset particle size to prepare the NASICON solid electrolyte material.

[0063] According to an embodiment of the present invention, a method for preparing a NASICON solid electrolyte material includes the following steps:

[0064] S100: Ball-mill and mix a phosphate salt, an A-containing oxide, and a B-containing oxide according to the molar ratio to obtain Mixture I; wherein, the A element in the A-containing oxide is one or more of Mg, Al, and Si, and the B element in the B-containing oxide is one or more of Ca, Ti, and V;

[0065] S200: Heat the Mixture I to 800 - 1000 °C at a suitable heating rate (such as 8 - 12 °C / min), hold for a period of time (such as 1 - 3 h), then cool to 200 - 400 °C at a suitable cooling rate (such as 8 - 12 °C / min), and then cool to room temperature (such as 20 - 35 °C) in the furnace to prepare a NASICON solid electrolyte precursor;

[0066] S300: Crush and pulverize the NASICON solid electrolyte precursor to a preset particle size;

[0067] S400: Ball-mill and mix the crushed and pulverized NASICON solid electrolyte precursor with a lithium salt according to the molar ratio to obtain Mixture II;

[0068] S500: Heat the Mixture II to 500 - 700 °C at a suitable heating rate (such as 8 - 12 °C / min), hold for a period of time (such as 1 - 3 h), then cool to 200 - 400 °C at a suitable cooling rate (such as 8 - 12 °C / min), and then cool to room temperature (such as 20 - 35 °C) in the furnace to prepare a NASICON solid electrolyte rough material;

[0069] S600: Crush and pulverize the NASICON solid electrolyte rough material to a preset particle size to prepare the NASICON solid electrolyte material.

[0070] In the present invention, a two-step sintering method can be adopted. After mixing a phosphate salt, an A-containing oxide, and a B-containing oxide, first sinter at a higher temperature without adding a lithium salt to prepare a NASICON solid electrolyte precursor, and then mix with a lithium salt and sinter at a lower temperature to prepare a NASICON solid electrolyte material. Compared with the traditional one-step high-temperature sintering, lithium loss can be avoided or significantly reduced, and there is no need to additionally add a sintering aid. Further, on the basis of finely controlling the two-stage sintering process (including but not limited to the program temperature, heating rate of high-temperature sintering, program temperature, cooling rate of low-temperature sintering, holding time of each sintering process, etc.), further synergistically controlling parameters such as the material ratio and particle size in each step, a NASICON solid electrolyte material with excellent performance can be prepared, which can give precise element ratio control and high lithium ion conductivity to the solid electrolyte, and can further prepare a solid-state battery with good electrochemical stability and high lithium ion conductivity.

[0071] Adopt a two-step sintering method. First, according to the required molar ratio of substances, mix phosphate salt, A-containing oxide, and B-containing oxide, then sinter at a relatively high temperature to obtain a NASICON solid electrolyte precursor, and crush it to obtain a uniform powder with a certain D50 (such as 10μm ± 2μm). Then mix a lithium salt with a specific particle size with the aforementioned NASICON oxide solid electrolyte precursor powder and sinter at a relatively low temperature to obtain a NASICON solid electrolyte material. Through the two-stage sintering method of high-temperature sintering (without adding lithium salt) and low-temperature sintering (adding lithium salt), it is possible to avoid lithium loss caused by one-time high-temperature sintering of raw materials such as phosphate salt, A-containing oxide, B-containing oxide, and lithium salt in the traditional technology, and there is no need to additionally add a sintering aid, which is beneficial to precisely adjusting the specific stoichiometric ratio of the NASICON solid electrolyte material. Further, by finely controlling the raw material particle size, the process powder particle size, and the reasonable control of heat treatment parameters, a NASICON solid electrolyte material can be prepared, which can endow the solid electrolyte with precise element ratio control and a relatively high lithium ion conductivity, and further a solid battery with good electrochemical stability and a relatively high lithium ion conductivity can be prepared. Further, the raw materials used are stable in air, and the process flow is simple, which is beneficial to large-scale production.

[0072] In some embodiments, the phosphate salt is NH4H2PO4.

[0073] In some embodiments, the A-containing oxide is one or more of MgO, Al2O3, and SiO2.

[0074] In some embodiments, the B-containing oxide is one or more of TiO2, CaO, and V2O5.

[0075] In some embodiments, the lithium salt is Li2CO3.

[0076] In some embodiments, the phosphate salt is NH4H2PO4; the A-containing oxide is one or more of MgO, Al2O3, and SiO2; the B-containing oxide is one or more of TiO2, CaO, and V2O5; the lithium salt is Li2CO3. At this time, the chemical stabilities of raw materials such as NH4H2PO4, MgO, Al2O3, SiO2, TiO2, CaO, V2O5, and Li2CO3 involved are relatively strong, and they are not easily deteriorated in an air atmosphere. The process flow is simple and the cost is relatively low, which is beneficial to large-scale production.

[0077] In some embodiments, in step S100, the D50 of the raw material of the phosphate salt is 5 - 15 μm, further it can be 6 - 14 μm, 7 - 13 μm, 8 - 12 μm, 9 - 11 μm, 9.5 - 10.5 μm. It can also be selected from any one of the following particle sizes or the intervals formed by any two of them: 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, 13.5 μm, 14 μm, 14.5 μm, and 15 μm. The size of the raw material particles affects the uniformity of ball milling and mixing and the final particle size of the raw materials. If the particle size of the raw material is too small, it may cause the raw materials to agglomerate or adhere to the gaps of the ball milling tank or the ball milling medium. If the particle size of the raw material is too large, it may be difficult to pulverize, thus affecting the mixing uniformity of different raw materials.

[0078] In some embodiments, in step S100, the D50 of the raw material of the oxide containing A is 200 - 600 nm, further it can be 250 - 550 nm, 300 - 500 nm, 350 - 450 nm, 375 - 425 nm. It can also be selected from any one of the following particle sizes or the intervals formed by any two of them: 200 μm, 225 μm, 250 μm, 275 μm, 300 μm, 325 μm, 350 μm, 375 μm, 400 μm, 425 μm, 450 μm, 475 μm, 500 μm, 525 μm, 550 μm, 575 μm, and 600 μm.

[0079] In some embodiments, in step S100, the D50 of the raw material of the oxide containing B is 0.5 - 2 nm, further it can be 0.75 - 1.75 nm, and further it can be 1 - 1.5 nm. It can also be selected from any one of the following particle sizes or the intervals formed by any two of them: 0.5 nm, 0.6 nm, 0.7 nm, 0.8 nm, 0.9 nm, 1.0 nm, 1.1 nm, 1.2 nm, 1.3 nm, 1.4 nm, 1.5 nm, 1.6 nm, 1.7 nm, 1.8 nm, 1.9 nm, and 2 nm.

[0080] In some embodiments, in step S100, the D50 of the raw material of the phosphate salt is 5 - 15 μm, the D50 of the raw material of the oxide containing A is 200 - 600 nm, and the D50 of the raw material of the oxide containing B is 0.5 - 2 μm.

[0081] In some embodiments, in step S100, the D50 of the raw material of the phosphate salt is 7.5 - 13 μm, the D50 of the raw material of the oxide containing A is 300 - 575 nm, and the D50 of the raw material of the oxide containing B is 0.7 - 1.5 μm.

[0082] In some embodiments, in step S100, the D50 of the raw material of the phosphate salt is 9.5 - 10.5 μm, the D50 of the raw material of the A-containing oxide is 450 - 550 nm, and the D50 of the raw material of the B-containing oxide is 0.9 - 1.1 μm.

[0083] In some embodiments, in step S100, the ball milling speed is 200 - 600 r / min and the ball milling time is 1 - 5 h. Further, the ball milling speed is 300 - 500 r / min and the ball milling time is 1.5 - 4 h. Even further, the ball milling speed is 350 - 450 r / min and the ball milling time is 2 - 3 h. The speed can also be selected from any one of the following speeds or the intervals formed by any two of them: 200 r / min, 250 r / min, 300 r / min, 350 r / min, 400 r / min, 450 r / min, 500 r / min, 550 r / min, and 600 r / min. The ball milling time can also be selected from any one of the following durations or the intervals formed by any two of them: 1 h, 1.5 h, 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h, and 5 h.

[0084] When performing ball milling and mixing in step S100, the ball milling method can be dry method. Further, the ball milling medium can be zirconia balls.

[0085] In some embodiments, in step S100, the D50 of the raw material of the phosphate salt is 5 - 15 μm; the D50 of the raw material of the A-containing oxide is 200 - 600 nm, and the D50 of the raw material of the B-containing oxide is 0.5 - 2 μm; the ball milling speed is 200 - 600 r / min and the ball milling time is 1 - 5 h; in step S300, the D50 of the material after crushing and pulverizing is 10 μm ± 2 μm.

[0086] In some embodiments, in step S100, the D50 of the raw material of the phosphate salt is 7.5 - 13 μm, the D50 of the raw material of the A-containing oxide is 300 - 575 nm, and the D50 of the raw material of the B-containing oxide is 0.7 - 1.5 μm; the ball milling speed is 300 - 500 r / min and the ball milling time is 1.5 - 4 h; in step S300, the D50 of the material after crushing and pulverizing is 10 μm ± 1 μm.

[0087] In some embodiments, in step S100, the D50 of the raw material of the phosphate salt is 9.5 - 10.5 μm, the D50 of the raw material of the A-containing oxide is 350 - 450 nm, and the D50 of the raw material of the B-containing oxide is 0.9 - 1.1 μm; the ball milling speed is 200 - 600 r / min and the ball milling time is 2 - 3 h; in step S300, the D50 of the material after crushing and pulverizing is 10 μm ± 0.5 μm.

[0088] In some embodiments, in step S400, the ball milling rotation speed is 200 - 600 r / min, and the ball milling time is 1 - 5 h. Examples of the ball milling rotation speed include 200 r / min, 250 r / min, 300 r / min, 350 r / min, 400 r / min, 450 r / min, 500 r / min, 550 r / min, or 600 r / min. Examples of the ball milling time include 1 h, 1.5 h, 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h, or 5 h.

[0089] In some embodiments, in step S600, the D50 of the material after crushing and pulverizing is 10 μm ± 2 μm. Examples of the D50 of the material after crushing and pulverizing include 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, or 12 μm, etc.

[0090] In some embodiments, the D50 of the raw material of the phosphate salt is 9.5 - 10.5 μm, the D50 of the raw material of the A-containing oxide is 450 - 550 nm, the D50 of the raw material of the B-containing oxide is 0.9 - 1.1 μm, and the D50 of the raw material of the lithium salt is 0.9 - 1.1 μm.

[0091] Preferably, the D50 of the raw material of the phosphate salt is 9.75 - 10.25 μm, the D50 of the raw material of the A-containing oxide is 475 - 525 nm, the D50 of the raw material of the B-containing oxide is 0.95 - 1.05 μm, and the D50 of the raw material of the lithium salt is 0.95 - 1.05 μm.

[0092] In some embodiments, in step S100, the molar ratio of the phosphate salt, the A-containing oxide, and the B-containing oxide satisfies 3:(0-1):(1-4); further, it can be 3:(0.1-0.55):(1.15-3.6). Some non-limiting examples include but are not limited to (3:0.125:1.16), (3:0.225:1.36), (3:0.325:1.56), (3:0.125:1.56), (3:0.125:1.5), (3:0.225:5.1), (3:0.325:1.9), (3:0.125:1.9), (3:0.125:3.2), (3:0.225:3.4), (3:0.325:3.6), (3:0.125:3.6), (3:0.2:1.16), (3:0.3:1.36), (3:0.4:1.56), (3:0.2:1.56), (3:0.2:3), (3:0.3:3.4), (3:0.4:3.8), (3:0.2:3.8), (3:0.35:1.16), (3:1.35:1.36), (3:0.55:1.56), (3:0.35:1.56), (3:0.35:3), (3:0.45:3.4), (3:0.55:3.8), and (3:0.35:3.8).

[0093] In some embodiments, in step S400, the molar ratio of the phosphorus element in the NASICON solid electrolyte precursor to the lithium element in the lithium salt is 3:(1.1-1.5); further, it can be 3:(1.2-1.4). Some non-limiting examples include but are not limited to (3:1.1), (3:1.2), (3:1.3), (3:1.4), (3:1.5), etc.

[0094] Regarding the typical NASICON structure of LiM2(PO4)3, some research has explored the selection of element M. It involves NASICON systems where M is a single element and those containing more than one element. However, there is no unified conclusion regarding the influence of the selection of element M and the element ratio. Some theories suggest that when M contains elements with tetravalent cations and is in a non-stoichiometric situation, especially when the molar ratio of M is between 2.0 and 2.2, a high ionic conduction phase can be formed. In another case, when M contains monovalent to trivalent cations and the molar ratio of M to Li is within a certain range, a high ionic conduction phase can be formed. The basis of the aforementioned theories is that a suitable valence state of element M and non-stoichiometry can inhibit the reduction of the amount of Li participating in ionic conduction, which can be explained from the perspective of charge compensation. Some research has compared the changes in conductivity with partial substitution of trivalent cations for M. Within a certain range and under stoichiometric conditions, as the substitution ratio of trivalent cations increases, the delocalization degree of lithium atoms is higher, the ionic activation energy of LiM2(PO4)3 decreases, and the total lithium ion conductivity and grain boundary lithium ion conductivity of the system increase. Therefore, the research and theories on the influence of the atomic radius, ionic radius, and doping ratio of element M on the framework structure of LiM2(PO4)3 and the lithium ion transport channels are still evolving.

[0095] In the second aspect of the present invention, a NASICON solid electrolyte material is provided, which can be prepared by using the preparation method described in the first aspect of the present invention.

[0096] In the third aspect of the present invention, according to an embodiment of the present invention, a NASICON solid electrolyte material is further provided, which may have the following chemical formula composition:

[0097] Li x A y B z (PO4)3,

[0098] where x is a value selected from 1.1 to 1.5,

[0099] y is a value selected from 0 to 1,

[0100] z is a value selected from 1 to 4;

[0101] Element A is Si, and element B is one or more of V, Ti, and Ca;

[0102] Or,

[0103] Element A is Al, and element B is one of V and Ca, or at least two of Ti, V, and Ca;

[0104] Or,

[0105] Element A is Mg, and element B is one of V and Ca, or at least two of Ti, V, and Ca.

[0106] In some embodiments, x is a value selected from 1.2 to 1.4, y is a value selected from 0.1 to 0.6, and z is a value selected from 1.2 to 3.6.

[0107] The electrolyte material Li x A y B z (PO4)3 of the NASICON solid electrolyte system provided by the above embodiments has good electrochemical stability and high lithium ion conductivity. Ions with a large atomic radius and a low valence state are beneficial to expanding the three-dimensional channels for lithium ion transport, and a specific molar ratio range can maintain a relatively stable Li x A y B z (PO4)3 framework structure, so as to achieve high lithium ion conductivity while having good electrochemical stability.

[0108] In some embodiments, the Li x A y B z (PO4)3 is Li 1.1～1.5 Si 0.125～0.325 V 1.16～1.56 (PO4)3, Li 1.1～1.5 Si 0.125～0.325 Ti 1.5～1.9 (PO4)3, Li 1.1～1.5 Si 0.125～0.325 Ca 3.2～3.6 (PO4)3, Li 1.1～1.5 Al 0.2～ 0.4 V 1.16～1.56 (PO4)3, Li 1.1～1.5 Al 0.2～0.4 Ca 3.2～3.6 (PO4)3, Li 1.1～1.5 Mg 0.35～0.55 V 1.16～1.56 (PO4)3 or Li 1.1～1.5 Mg 0.35～0.55 Ca 3.2～3.6 (PO4)3, one or more of them.

[0109] In some embodiments, the Li x A y B z (PO4)3 is Li 1.3 Si 0.225 V 1.36 (PO4)3, Li 1.3 Si0.225 Ti 1.7 (PO4)3, Li 1.3 Si 0.225 Ca 3.4 (PO4)3, Li 1.3 Al 0.3 V 1.36 (PO4)3, Li 1.3 Al 0.3 Ca 3.4 (PO4)3, Li 1.3 Mg 0.45 V 1.36 (PO4)3 or Li 1.3 Mg 0.45 Ca 3.4 Any one of (PO4)3.

[0110] In the fourth aspect of the present invention, according to an embodiment of the present invention, a solid-state battery is further provided, including a positive electrode active material layer, a negative electrode active material layer, and a solid electrolyte layer formed between the positive electrode active material layer and the negative electrode active material layer. Further, the solid electrolyte layer includes at least one of the NASICON solid electrolyte materials prepared by the preparation method described in the first aspect of the present invention and the NASICON solid electrolyte materials described in the third aspect of the present invention.

[0111] In the fifth aspect of the present invention, an application of the NASICON solid electrolyte material prepared by the preparation method described in the first aspect of the present invention or the NASICON solid electrolyte materials described in the second or third aspect of the present invention in the preparation of the electrolyte of a solid-state battery is provided.

[0112] In some embodiments, the solid electrolyte includes an oxide solid electrolyte, a polymer, and an oxide mixed solid electrolyte or an electrolyte and an oxide mixed semi-solid electrolyte.

[0113] In some embodiments, the solid-state battery includes a battery with a lithium metal or lithium alloy as the negative electrode.

[0114] For easier understanding and implementation of the present invention, the following relatively easy-to-implement, more specific and detailed examples and comparative examples are also provided for reference.

[0115] Unless otherwise specified, the raw materials used in the following tests can be conventionally purchased from the market.

[0116] Unless otherwise specifically limited, the instrument models involved in the following examples are:

[0117] Ball mill: Changsha Tianchuang Powder Technology Co., Ltd., planetary ball mill, XQM-1L;

[0118] Crusher: Tangyin Longhui Mingyuan Experimental Instrument Manufacturing Company, environmentally friendly double roll crusher, LHMY-200x75(H);

[0119] Pulverizer: Shandong Fengli Heavy Industry Co., Ltd., air flow pulverizer, FQ02;

[0120] Muffle furnace: Hefei Fischer Thermal Equipment Co., Ltd., tube furnace, FGL-50 / 11 / 1;

[0121] Laser particle size analyzer: Shanghai Precision Instrument and Meter Co., Ltd., laser particle size analyzer, CLPA-1500.

[0122] Conductivity tester: Membrane resistance meter, Hangzhou Chuanyuan Technology Co., Ltd., TT-ACCF-G1.

[0123] Method for preparing electrolyte substrate: Press NASICON solid electrolyte material into a NASICON solid electrolyte embryo sheet with a radius of 16 mm and a thickness of 2 mm at a pressure of 0.4 MPa to 0.8 MPa, and obtain the electrolyte substrate through heat treatment at 600 to 900 °C for 0.5 h to 2 h.

[0124] Method for testing conductivity of electrolyte substrate: Use a membrane conductivity tester to test the conductivity of the electrolyte substrate. The test method is to place the electrolyte electrode sheet in the middle between the two electrode posts of the membrane conductivity tester, and the pressure between the electrode posts is 0.6 MPa.

[0125] Example 1

[0126] Prepare NASCION type solid electrolyte Li 1.3 Si 0.225 V 1.36 (PO4)3.

[0127] S100: Weigh 1867.68 g of NH4H2PO4 with D50 of 10 μm (16.24 mol), 669.52 g of V2O5 with D50 of 1 μm (3.68 mol), and 73.17 g of SiO2 with D50 of 500 nm (1.22 mol), place them in a ball mill mixing blender, with a stirring speed of 400 r / min and a stirring time of 2 h to obtain mixture I;

[0128] S200: Heat mixture I to 900 °C at a heating rate of 10 °C / min, hold for 2 h, then cool to 300 °C at a cooling rate of 10 °C / min, and then cool to 25 °C in the furnace to prepare the NASICON solid electrolyte precursor;

[0129] S300: Crush the NASICON solid electrolyte precursor with a roll crusher and grind it with a fluidized bed jet mill to a powder with a D50 of 2 μm;

[0130] S400: Weigh 259.94 g of Li2CO3 (3.52 mol) with a D50 of 1 μm and the above-mentioned NASICON solid electrolyte precursor that has been crushed and ground, and place them in a ball mill mixing blender. Stir at a speed of 400 r / min for 2 h to obtain Mixture II;

[0131] S500: Heat Mixture II at a heating rate of 10 °C / min to 600 °C, hold for 2 h, then cool at a cooling rate of 10 °C / min to 300 °C, and then cool in the furnace to 25 °C to prepare the NASICON solid electrolyte rough material Li 1.3 Si 0.225 V 1.36 (PO4)3.

[0132] S600: After crushing and grinding the NASICON solid electrolyte rough material, obtain the NASICON solid electrolyte material Li 1.3 Si 0.225 V 1.36 (PO4)3;

[0133] Press the NASICON solid electrolyte material into a NASICON solid electrolyte green sheet with a radius of 16 mm and a thickness of 2 mm at a pressure of 0.4 MPa to 0.8 MPa, and heat-treat it at 900 °C for 1 h to obtain the electrolyte substrate.

[0134] After 10 tests, the average conductivity of the Li 1.3 Si 0.225 V 1.36 (PO4)3 electrolyte substrate is measured to be 5.12×10 - 3 S / cm.

[0135] Example 2

[0136] Prepare the NASCION-type solid electrolyte Li 1.3 Si 0.225 Ti 1.7 (PO4)3.

[0137] S100: Weigh 1808.38 g of NH4H2PO4 with a D50 of 10 μm (15.72 mol), 711.62 g of TiO2 with a D50 of 1 μm (8.91 mol), and 70.85 g of SiO2 with a D50 of 500 nm (1.18 mol), and place them in a ball mill mixing blender. Stir at a speed of 400 r / min for 2 h to obtain Mixture I;

[0138] S200: Treat Mixture I with the same heat treatment steps as in Example 1 to obtain a NASCION-type solid electrolyte precursor;

[0139] S300: Crush the NASICON solid electrolyte precursor with a roll crusher and grind it with a fluidized bed jet mill to obtain a powder with a D50 of 2 μm;

[0140] S400: Weigh 251.69 g of Li2CO3 with a D50 of 1 μm (3.41 mol) and the above-mentioned NASICON solid electrolyte precursor that has been crushed and ground, and place them in a ball mill mixing blender. Stir at a speed of 400 r / min for 2 h to obtain Mixture II;

[0141] S500: Treat Mixture II with the same heat treatment steps as in Example 1 to obtain the NASICON solid electrolyte crude material Li 1.3 Si 0.225 Ti 1.7 (PO4)3.

[0142] S600: After crushing and grinding the NASICON solid electrolyte crude material, obtain the NASICON solid electrolyte material Li 1.3 Si 0.225 Ti 1.7 (PO4)3.

[0143] Press the NASICON solid electrolyte material into a NASICON solid electrolyte green sheet with a radius of 16 mm and a thickness of 2 mm at a pressure of 0.4 MPa to 0.8 MPa, and heat-treat it at 900 °C for 1 h to obtain an electrolyte substrate.

[0144] After 10 tests, the average conductivity of the Li 1.3 Si 0.225 Ti 1.7 (PO4)3 electrolyte substrate was measured to be 4.51×10 - 3 S / cm.

[0145] Example 3

[0146] Preparation of NASCION-type solid electrolyte Li1.3 Si 0.225 Ca 3.4 (PO4)3。

[0147] S100: Weigh 1581.04 g of NH4H2PO4 with a D50 of 10 μm (13.74 mol), 873.58 g of CaO with a D50 of 1 μm (15.58 mol), and 61.94 g of SiO2 with a D50 of 500 nm (1.03 mol), and place them in a ball milling and mixing blender. Stir at a speed of 400 r / min for 2 h to obtain Mixture I;

[0148] S200: Treat Mixture I with the same heat treatment steps as in Example 1 to obtain a NASCION-type solid electrolyte precursor;

[0149] S300: Crush the NASICON solid electrolyte precursor with a roll crusher and pulverize it with a fluidized bed jet mill to obtain a powder with a D50 of 2 μm;

[0150] S400: Weigh 220.05 g of Li2CO3 with a D50 of 1 μm (2.98 mol) and the above-mentioned NASICON solid electrolyte precursor that has been crushed and pulverized, and place them in a ball milling and mixing blender. Stir at a speed of 400 r / min for 2 h to obtain Mixture II;

[0151] S500: Treat Mixture II with the same heat treatment steps as in Example 1 to obtain a NASICON solid electrolyte rough material Li 1.3 Si 0.225 Ca 3.4 (PO4)3。

[0152] S600: After crushing and pulverizing the NASICON solid electrolyte rough material, a NASICON solid electrolyte material Li with a D50 of 10 μm is obtained 1.3 Si 0.225 Ca 3.4 (PO4)3。

[0153] Press the NASICON solid electrolyte material into a NASICON solid electrolyte green sheet with a radius of 16 mm and a thickness of 2 mm at a pressure of 0.4 MPa to 0.8 MPa, and heat-treat it at 900 °C for 1 h to obtain an electrolyte substrate.

[0154] After 10 tests, it is measured that the average conductivity of the Li 1.3 Si 0.225 Ca 3.4 (PO4)3 electrolyte substrate is 4.12×10 - 3 S / cm.

[0155] Example 4

[0156] Preparation of NASICON-type solid electrolyte Li 1.3 Si 0.45 V 1.18 (PO4)3.

[0157] S100: Weigh 1882.19 g of NH4H2PO4 with a D50 of 10 μm (16.37 mol), 585.42 g of V2O5 with a D50 of 1 μm (3.22 mol), and 147.48 g of SiO2 with a D50 of 500 nm (2.45 mol), and place them in a ball mill mixing and stirring machine. Stir at a speed of 400 r / min for 2 h to obtain mixture I;

[0158] S200: Treat mixture I with the same heat treatment steps as in Example 1 to obtain a NASICON-type solid electrolyte precursor;

[0159] S300: Crush the NASICON solid electrolyte precursor with a roll crusher and pulverize it with a fluidized bed jet mill to obtain a powder with a D50 of 2 μm;

[0160] S400: Weigh 261.97 g of Li2CO3 with a D50 of 1 μm (3.55 mol) and the above-mentioned NASICON solid electrolyte precursor that has been crushed and pulverized, and place them in a ball mill mixing and stirring machine. Stir at a speed of 400 r / min for 2 h to obtain mixture II;

[0161] S500: Treat mixture II with the same heat treatment steps as in Example 1 to obtain a NASICON solid electrolyte rough material Li 1.3 Si 0.45 V 1.18 (PO4)3.

[0162] S600: After crushing and pulverizing the NASICON solid electrolyte rough material, obtain a NASICON solid electrolyte material Li 1.3 Si 0.45 V 1.18 (PO4)3.

[0163] Press the NASICON solid electrolyte material into a NASICON solid electrolyte green sheet with a radius of 16 mm and a thickness of 2 mm at a pressure of 0.4 MPa to 0.8 MPa, and heat-treat it at 900 °C for 1 h to obtain an electrolyte substrate.

[0164] After 10 tests, it was measured that Li 1.3 Si 0.45 V1.18 (PO4)3 electrolyte substrate has an average conductivity of 4.33×10 - 3 S / cm.

[0165] Example 5

[0166] Prepare NASCION-type solid electrolyte Li 1.3 Mg 0.45 Ca 3.4 (PO4)3.

[0167] S100: Weigh 1564.49 g of NH4H2PO4 with D50 of 10 μm, 864.44 g of CaO with D50 of 1 μm, and 82.23 g of MgO with D50 of 500 nm, and place them in a ball milling and mixing blender. Stir at a speed of 400 r / min for 2 h to obtain mixture I;

[0168] S200: Treat mixture I with the same heat treatment steps as in Example 1 to obtain a NASCION-type solid electrolyte precursor;

[0169] S300: Crush the NASICON solid electrolyte precursor with a roll crusher and pulverize it with a fluidized bed air classifier to obtain a powder with D50 of 2 μm;

[0170] S400: Weigh 217.75 g of Li2CO3 with D50 of 1 μm and the above-mentioned NASICON solid electrolyte precursor that has been crushed and pulverized, and place them in a ball milling and mixing blender. Stir at a speed of 400 r / min for 2 h to obtain mixture II;

[0171] S500: Treat mixture II with the same heat treatment steps as in Example 1 to obtain NASICON solid electrolyte rough material Li 1.3 Mg 0.45 Ti 1.7 (PO4)3.

[0172] S600: After crushing and pulverizing the NASICON solid electrolyte rough material, obtain NASICON solid electrolyte material Li 1.3 Mg 0.45 Ca 3.4 (PO4)3.

[0173] Press the NASICON solid electrolyte material into a NASICON solid electrolyte embryo with a radius of 16 mm and a thickness of 2 mm under a pressure of 0.4 MPa to 0.8 MPa, and heat-treat it at 900 °C for 1 h to obtain an electrolyte substrate.

[0174] After 10 tests, the measured conductivity mean of the Li 1.3 Mg 0.45 Ca 3.4 (PO4)3 electrolyte substrate is 2.24×10 - 3 S / cm.

[0175] Example 6

[0176] Prepare the NASCION-type solid electrolyte Li 1.3 Al 0.3 Ca 3.4 (PO4)3.

[0177] S100: Weigh 1574.65 g of NH4H2PO4 with a D50 of 10 μm, 870.05 g of CaO with a D50 of 1 μm, and 69.78 g of Al2O3 with a D50 of 500 nm and place them in a ball mill mixing and stirring machine. Stir at a speed of 400 r / min for 2 h to obtain mixture I;

[0178] S200: Treat mixture I with the same heat treatment steps as in Example 1 to obtain the NASCION-type solid electrolyte precursor;

[0179] S300: Crush the NASICON solid electrolyte precursor with a roll crusher and crush it with a fluidized bed air classifier to a powder with a D50 of 2 μm;

[0180] S400: Weigh 219.16 g of Li2CO3 with a D50 of 1 μm and the above-mentioned NASICON solid electrolyte precursor that has been crushed and pulverized and place them in a ball mill mixing and stirring machine. Stir at a speed of 400 r / min for 2 h to obtain mixture II;

[0181] S500: Treat mixture II with the same heat treatment steps as in Example 1 to obtain the NASICON solid electrolyte rough material Li 1.3 Al 0.3 Ca 3.4 (PO4)3.

[0182] S600: After crushing and pulverizing the NASICON solid electrolyte rough material, obtain the NASICON solid electrolyte material Li 1.3 Al 0.3 Ca 3.4 (PO4)3.

[0183] The NASICON solid electrolyte material is pressed into a NASICON solid electrolyte blank with a radius of 16 mm and a thickness of 2 mm under a pressure of 0.4 MPa to 0.8 MPa, and then heat-treated at 900 °C for 1 h to obtain an electrolyte substrate.

[0184] After 10 tests, the average conductivity of the Li 1.3 Al 0.3 Ca 3.4 (PO4)3 electrolyte substrate is 2.84×10 - 3 S / cm.

[0185] Comparative Example 1

[0186] The preparation method of Comparative Example 1 is basically the same as that of Example 1, except that: in step S500, the holding temperature of the mixture II is 900 °C. The average conductivity of the measured electrolyte substrate is 4.37×10 -3 S / cm.

[0187] Comparative Example 2

[0188] The preparation method of Comparative Example 2 is basically the same as that of Example 1, except that: in step S200, the holding temperature of the mixture I is 600 °C. The average conductivity of the measured electrolyte substrate is 4.43×10 -3 S / cm.

[0189] Comparative Example 3

[0190] The preparation method of Comparative Example 3 is basically the same as that of Example 1, except that: after ball-milling and mixing in S100 to obtain mixture I, there is no S200 heat treatment step. After ball-milling and mixing in S300 to obtain mixture II, mixture II is heated to 900 °C at a heating rate of 10 °C / min, held for 2 h; then cooled to 600 °C at a cooling rate of 10 °C / min and held for 2 h; then cooled to 300 °C at a cooling rate of 10 °C / min, and then cooled to 25 °C in the furnace to prepare a NASICON solid electrolyte crude material.

[0191] After 10 tests, the average conductivity of the measured electrolyte substrate is 4.06×10 -3 S / cm.

[0192] Comparative Example 4

[0193] The preparation method of Comparative Example 4 is basically the same as that of Example 1, except that: in step S100, the amount of V2O5 is different. Weigh 1883.25 g of NH4H2PO4 with a D50 of 10 μm (16.37 mol), 546.04 g of V2O5 with a D50 of 1 μm (3.00 mol), 73.78 g of SiO2 with a D50 of 500 nm (1.23 mol), and 262.11 g of Li2CO3 with a D50 of 1 μm (3.55 mol). The remaining steps are the same as those in Example 1, and the average conductivity of the electrolyte substrate is measured to be 5.06×10 -3 S / cm.

[0194] Comparative Example 5

[0195] Preparation of NASICON-type solid electrolyte Li 1.3 Mg 0.45 Ti 1.7 (PO4)3.

[0196] S100: Weigh 1786.75 g of NH4H2PO4 with a D50 of 10 μm, 708.33 g of TiO2 with a D50 of 1 μm, and 93.92 g of MgO with a D50 of 500 nm and place them in a ball mill mixing blender. Stir at a speed of 400 r / min for 2 h to obtain mixture I;

[0197] S200: Treat mixture I with the same heat treatment steps as in Example 1 to obtain a NASICON-type solid electrolyte precursor;

[0198] S300: Crush the NASICON solid electrolyte precursor with a roll crusher and pulverize it with a fluidized bed jet mill to obtain a powder with a D50 of 2 μm;

[0199] S400: Weigh 248.68 g of Li2CO3 with a D50 of 1 μm and the above-mentioned NASICON solid electrolyte precursor that has been crushed and pulverized and place them in a ball mill mixing blender. Stir at a speed of 400 r / min for 2 h to obtain mixture II;

[0200] S500: Treat mixture II with the same heat treatment steps as in Example 1 to obtain a NASICON solid electrolyte rough material Li 1.3 Mg 0.45 Ti 1.7 (PO4)3.

[0201] S600: After crushing and pulverizing the NASICON solid electrolyte rough material, a NASICON solid electrolyte material with a D50 of 10 μm is obtained, Li 1.3 Mg 0.45 Ti1.7 (PO4)3。

[0202] The NASICON solid electrolyte material is pressed into a NASICON solid electrolyte embryo sheet with a radius of 16 mm and a thickness of 2 mm at a pressure of 0.4 MPa to 0.8 MPa, and is heat-treated at 900 °C for 1 h to obtain an electrolyte substrate.

[0203] After 10 tests, the measured Li 1.3 Mg 0.45 Ti 1.7 (PO4)3 electrolyte substrate has an average conductivity of 2.52×10 - 3 S / cm.

[0204] Comparative Example 6

[0205] Prepare NASCION-type solid electrolyte Li 1.3 Al 0.3 Ti 1.7 (PO4)3.

[0206] S100: Weigh 1800.02 g of NH4H2PO4 with a D50 of 10 μm, 708.33 g of TiO2 with a D50 of 1 μm, and 79.78 g of Al2O3 with a D50 of 500 nm and place them in a ball mill mixing blender. Stir at a speed of 400 r / min for 2 h to obtain Mixture I;

[0207] S200: Treat Mixture I with the same heat treatment steps as in Example 1 to obtain a NASCION-type solid electrolyte precursor;

[0208] S300: Crush the NASICON solid electrolyte precursor with a roll crusher and pulverize it with a fluidized bed air classifier to a powder with a D50 of 2 μm;

[0209] S400: Weigh 250.53 g of Li2CO3 with a D50 of 1 μm and the above-mentioned NASICON solid electrolyte precursor that has been crushed and pulverized and place them in a ball mill mixing blender. Stir at a speed of 400 r / min for 2 h to obtain Mixture II;

[0210] S500: Treat Mixture II with the same heat treatment steps as in Example 1 to obtain NASICON solid electrolyte crude material Li 1.3 Al 0.3 Ti 1.7 (PO4)3.

[0211] S600: The NASICON solid electrolyte coarse material is crushed and pulverized to obtain the NASICON solid electrolyte material Li 1.3 Al 0.3 Ti 1.7 (PO4)3.

[0212] The NASICON solid electrolyte material is pressed into a NASICON solid electrolyte green sheet with a radius of 16 mm and a thickness of 2 mm at a pressure of 0.4 MPa to 0.8 MPa, and is heat-treated at 900 °C for 1 h to obtain an electrolyte substrate.

[0213] After 10 tests, the average conductivity of the Li 1.3 Al 0.3 Ti 1.7 (PO4)3 electrolyte substrate is measured to be 3.12×10 - 3 S / cm.

[0214] From the relevant data in Table 3 and Table 4, it can be seen that the theoretical raw material ratios of Comparative Examples 1, 2, and 3 are the same as those of the Examples.

[0215] Compared with Example 1, in Comparative Example 1, the mixture II was heat-insulated at a higher temperature (900 °C) for 2 h, and it was found that the average conductivity of the prepared NASICON solid electrolyte substrate was 4.37×10 -3 S / cm, which is lower than 5.12×10 - 3 S / cm of Example 1. It is speculated that after mixing Li2CO3 with the NASCION-type solid electrolyte precursor powder, the heat treatment temperature (900 °C) of the mixture II is relatively high, resulting in an increase in lithium loss, changing the crystal phase structure of the NASCION-type solid electrolyte material, and thus having an adverse effect on the conductivity of the prepared NASICON solid electrolyte substrate.

[0216] Compared with Example 1, in Comparative Example 2, the mixture I was heat-insulated at a lower temperature (600 °C), and it was found that the average conductivity of the prepared NASICON solid electrolyte substrate was 4.43×10 -3 S / cm, which is lower than 5.12×10 -3 S / cm of Example 1. It is speculated that due to the relatively low heat treatment temperature (600 °C) of the mixture I after mixing NH4H2PO4, V2O5, and SiO2, the grains in the precursor become inferior, affecting the crystal phase structure of the preset-composition NASCION-type solid electrolyte material, and thus having an adverse effect on the conductivity of the prepared NASICON solid electrolyte substrate.

[0217] Compared with Example 1, in Comparative Example 3, the mixture I was not heat-treated, and stepped heat treatment was carried out after secondary mixing with the lithium salt. As a result, it was found that the average conductivity of the NASICON solid electrolyte substrate prepared was 4.06×10 -3 S / cm, which was lower than 5.12×10 -3 S / cm of Example 1. The NASICON solid electrolyte material prepared in Comparative Example 3 showed an uneven appearance color of the powder. It is speculated that after NH4H2PO4, V2O5 and SiO2 were mixed and then mixed with Li2CO3, and kept at 900 °C and 600 °C for 2 h respectively, the heat accumulation and diffusion were poor during this period, resulting in uneven powder. At the same time, Li2CO3 underwent high-temperature treatment, causing a large loss of lithium, which ultimately had an adverse effect on the conductivity of the prepared NASICON solid electrolyte substrate.

[0218] The chemical formulas of the materials synthesized in Comparative Example 4 were Li 1.3 Si 0.225 V 1.10 (PO4)3, and the V content was lower than that of Li 1.3 Si 0.225 V 1.36 (PO4)3 in Example 1. The average conductivity of the NASICON solid electrolyte substrate prepared was 5.06×10 -3 S / cm, slightly lower than 5.12×10 -3 S / cm of Example 1. It is speculated that due to the lower amount of substance of V than the stoichiometric ratio, there are more defects in the crystal phase of the NASICON solid electrolyte material, which is not conducive to the construction of the lithium ion transport channel, and thus has an adverse effect on the conductivity of the prepared NASICON solid electrolyte substrate.

[0219] Comparative Examples 5 and 6 were Li 1.3 Mg 0.45 Ti 1.7 (PO4)3 and Li 1.3 Al 0.3 Ti 1.7 (PO4)3 respectively. The Li 1.3 Mg 0.45 Ti 1.7 (PO4)3 and Li 1.3 Al 0.3 Ti 1.7 (PO4)3 materials obtained by the preparation method disclosed in this application, and the average conductivities of the prepared NASICON solid electrolyte substrates were relatively high, reaching 2.52×10 -3 S / cm and 3.12×10 -3 S / cm respectively, but less than 4.12×10 -3S / cm. Among them, the ionic radii of Mg, Al, and Si are different. It is speculated that Li 1.3 Mg 0.45 Ti 1.7 (PO4)3 and Li 1.3 Al 0.3 Ti 1.7 (PO4)3, the substitution of Mg and Al for Ti results in a transformation of the crystal phase structure and a lithium-ion transport channel that is inferior to the lithium-ion channel caused by the substitution of Si for Ti in Example 2, thereby having an adverse effect on the conductivity of the prepared NASICON solid electrolyte material and the prepared substrate.

[0220] The raw material phosphate salts, A oxides, B oxides, lithium salts, as well as the heat treatment and machining parameters in the preparation methods of Examples 1 to 6 and Comparative Examples 1 to 6 are listed in Tables 1 and 2 below:

[0221] Table 1 Chemical composition and preparation parameters of NASICON solid electrolyte materials in Examples 1 to 6

[0222]

[0223] Table 2 Chemical composition and preparation parameters of NASICON solid electrolyte materials in Comparative Examples 1 to 6

[0224]

[0225]

[0226]

[0227] The conductivity of the NASCION-type solid electrolyte materials prepared in Examples 1 to 6 and Comparative Examples 1 to 6 was tested, and the test results can be referred to Tables 3 and 4.

[0228] Among them, a membrane conductivity tester was used to test the conductivity of the electrolyte substrate. The test method was to place the electrolyte electrode sheet in the middle between the two electrode posts of the membrane conductivity tester, and the pressure between the electrode posts was 0.6 MPa. After 10 tests, the average conductivity of the electrolyte substrate was measured. The measurement temperature was 25°C.

[0229] Table 3 Conductivity test results of NASICON electrolyte substrates in Examples 1 to 6

[0230]

[0231] Table 4 Conductivity test results of NASICON electrolyte substrates in Comparative Examples 1 to 6

[0232]

[0233]

[0234] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as falling within the scope described in this specification.

[0235] The above-described embodiments merely represent several implementation manners of the present invention. The description thereof is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the invention patent shall be subject to the appended claims, and the description and drawings can be used to explain the content of the claims.

Claims

1. A preparation method of a NASICON solid electrolyte material, characterized in that, It includes the following steps: Ball mill and mix the phosphate salt, A-containing oxide and B-containing oxide raw materials to obtain Mixture I; wherein, the A element in the A-containing oxide is one or more of Mg, Al and Si, and the B element in the B-containing oxide is one or more of Ca, Ti and V; the molar ratio of the phosphorus element in the phosphate salt, the A element in the A-containing oxide and the B element in the B-containing oxide is 3:(0-1):(1-4); Heat the Mixture I to 800-1000 °C at a heating rate of 8-12 °C / min, hold for 1-3 h, then cool to 200-400 °C at a cooling rate of 8-12 °C / min, and then cool to 20-35 °C in the furnace to prepare a NASICON solid electrolyte precursor; Crush and grind the NASICON solid electrolyte precursor to a preset particle size; Ball mill and mix the crushed and ground NASICON solid electrolyte precursor with the lithium salt raw material to obtain Mixture II; wherein, the molar ratio of the phosphorus element in the NASICON solid electrolyte precursor to the lithium element in the lithium salt is 3:(1.1-1.5); Heat the Mixture II to 500-700 °C at a heating rate of 8-12 °C / min, hold for 1-3 h, then cool to 200-400 °C at a cooling rate of 8-12 °C / min, and then cool to 20-35 °C in the furnace to prepare a NASICON solid electrolyte crude material; Crush and grind the NASICON solid electrolyte crude material to a preset particle size to prepare the NASICON solid electrolyte material.

2. The preparation method of the NASICON solid electrolyte material according to claim 1, characterized in that The phosphate salt is NH4H2PO4; the A-containing oxide is one or more of MgO, Al2O3 and SiO2; the B-containing oxide is one or more of TiO2, CaO and V2O5; the lithium salt is Li2CO3.

3. The preparation method of the NASICON solid electrolyte material according to claim 1 or 2, characterized in that In the step of ball mill mixing the phosphate salt, A-containing oxide and B-containing oxide raw materials, the D50 of the raw material of the phosphate salt is 5-15 μm, the D50 of the raw material of the A-containing oxide is 200-600 nm, and the D50 of the raw material of the B-containing oxide is 0.5-2 μm; the ball mill rotation speed is 200-600 r / min, and the ball mill time is 1-5 h; In the step of crushing and grinding the NASICON solid electrolyte precursor to a preset particle size, the D50 of the material after crushing and grinding is 10 μm ± 2 μm; In the step of ball mill mixing the crushed and ground NASICON solid electrolyte precursor with the lithium salt, the ball mill rotation speed is 200-600 r / min, and the ball mill time is 1-5 h; In the step of crushing and grinding the NASICON solid electrolyte crude material to a preset particle size, the D50 of the material after crushing and grinding is 10 μm ± 2 μm.

4. The preparation method of the NASICON solid electrolyte material according to claim 3, characterized in that, The raw material D50 of the phosphate salt is 9.5 - 10.5 μm, the raw material D50 of the A-containing oxide is 450 - 550 nm, the raw material D50 of the B-containing oxide is 0.9 - 1.1 μm, and the raw material D50 of the lithium salt is 0.9 - 1.1 μm.

5. The preparation method of the NASICON solid electrolyte material according to claim 3, characterized in that, In the step of ball-milling and mixing the phosphate salt, the A-containing oxide, and the B-containing oxide raw materials, the molar ratio of the phosphorus element in the phosphate salt, the A element in the A-containing oxide, and the B element in the B-containing oxide is 3:(0.1 - 0.55):(1.15 - 3.6); In the step of ball-milling and mixing the crushed and pulverized NASICON solid electrolyte precursor with the lithium salt, the molar ratio of the phosphorus element in the crushed and pulverized NASICON solid electrolyte precursor to the lithium element in the lithium salt is 3:(1.2 - 1.4).

6. A NASICON solid electrolyte material, characterized in that, Prepared by using the preparation method according to any one of claims 1 - 5.

7. The NASICON solid electrolyte material according to claim 6, characterized in that, The NASICON solid electrolyte material has the following chemical formula composition: Li x A y B z (PO4)3 wherein, x is a value selected from 1.1 - 1.5, y is a value selected from 0 - 1, z is a value selected from 1 - 4; The A element is Si, and the B element is one or more of V, Ti, and Ca; or, The A element is Al, and the B element is any one of V and Ca, or at least two of Ti, V, and Ca; or, The A element is Mg, and the B element is any one of V and Ca, or at least two of Ti, V, and Ca.

8. The NASICON solid electrolyte material according to claim 7, characterized in that, The Li x A y B z (PO4)3 is Li 1.1～1.5 Si 0.125～0.325 V 1.16～1.56 (PO4)3, Li 1.1～1.5 Si 0.125～0.325 Ti 1.5～1.9 (PO4)3, Li 1.1～1.5 Si 0.125～ 0.325 Ca 3.2～3.6 (PO4)3, Li 1.1～1.5 Al 0.2～0.4 V 1.16～1.56 (PO4)3, Li 1.1～1.5 Al 0.2～0.4 Ca 3.2～3.6 (PO4)3, Li 1.1～1.5 Mg 0.35～0.55 V 1.16～1.56 (PO4)3 and Li 1.1～1.5 Mg 0.35～0.55 Ca 3.2～3.6 One or more of them.

9. The NASICON solid electrolyte material according to claim 8, characterized in that, The Li x A y B z (PO4)3 is Li 1.3 Si 0.225 V 1.36 (PO4)3, Li 1.3 Si 0.225 Ti 1.7 (PO4)3, Li 1.3 Si 0.225 Ca 3.4 (PO4)3, Li 1.3 Al 0.3 V 1.36 (PO4)3, Li 1.3 Al 0.3 Ca 3.4 (PO4)3, Li 1.3 Mg 0.45 V 1.36 (PO4)3 and Li 1.3 Mg 0.45 Ca 3.4 One or more of 10. A solid-state battery, characterized in that, It includes a positive electrode active material layer, a negative electrode active material layer, and a solid electrolyte layer formed between the positive electrode active material layer and the negative electrode active material layer, wherein the solid electrolyte layer contains at least one of the NASICON solid electrolyte materials prepared by the preparation method according to any one of claims 1 - 5 and the NASICON solid electrolyte materials according to any one of claims 6 - 9.

11. Application of the NASICON solid electrolyte material prepared by the preparation method according to any one of claims 1 - 5 or the NASICON solid electrolyte material according to any one of claims 6 - 9 in preparing the solid electrolyte of a solid-state battery, wherein the solid electrolyte includes an oxide solid electrolyte, a polymer and an oxide mixed solid electrolyte, or an electrolyte solution and an oxide mixed semi-solid electrolyte.

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