A ceramic oxide solid electrolyte and its preparation method

Abstract

This invention discloses a ceramic oxide solid electrolyte and its preparation method, relating to the field of electrolyte technology. The preparation method of the ceramic oxide solid electrolyte involves using main raw materials and additives, including: mixing and calcining the main raw materials to obtain an intermediate powder; mixing the intermediate powder with an additive and sintering it; wherein the additive is a fluoride, and the mass ratio of the additive to the intermediate powder is 0.1-10:100. By introducing the additive after calcining the main raw materials and then sintering, the requirements for the accuracy of raw material weighing and the process cost of ball milling are reduced. More importantly, by selecting the type of additive and adjusting its dosage, a significant improvement in ionic conductivity can be achieved with a very small proportion of fluoride added, making it a simple and efficient process.

Description

Technical Field

[0001] This invention relates to the field of electrolyte technology, and more specifically, to a ceramic oxide solid electrolyte and its preparation method. Background Technology

[0002] Batteries play a crucial role in energy storage and electric vehicles, but incidents of fires and explosions caused by traditional batteries frequently result in injuries and fatalities. Improving battery safety has become one of the most pressing tasks in battery development. Solid-state batteries are currently one of the most important directions in battery development. Solid-state batteries use non-flammable solid electrolytes, which inherently possess extremely high safety. Combined with a metal anode, they can simultaneously achieve high energy density and safety.

[0003] Besides the problem of ineffective interface integration, the low ionic conductivity of the electrolyte itself is another major bottleneck hindering the development of solid-state batteries. High ionic conductivity can significantly reduce internal resistance and enhance rate capability and cycle performance. However, the ionic conductivity of most solid-state electrolytes is currently still limited to 1×10⁻⁶. -4 In the S / cm range, the overall resistance of the electrolyte is approximately 200-300 ohms, and non-mainstream electrolytes can even reach the kiloohm level. Electrolytes with this performance are difficult to use as components in commercial batteries.

[0004] Currently, there are limited technologies for improving the performance of solid electrolytes, with most methods using doping to enhance the intrinsic ionic conductivity. However, doping places high demands on the process. The dopant material needs to be precisely weighed before mixing with the raw material. Some processes require pre-ball milling of the dopant and the substituted material to form a solid solution, which increases the complexity and time cost of the synthesis process.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] The purpose of this invention is to provide a ceramic oxide solid electrolyte and its preparation method, which aims to simplify the synthesis and doping process and significantly reduce the resistance of the electrolyte with a lower amount of additives.

[0007] This invention is implemented as follows:

[0008] In a first aspect, the present invention provides a method for preparing a ceramic oxide solid electrolyte, which is prepared by using main raw materials and additives, including: mixing and calcining the main raw materials to obtain an intermediate powder, and mixing and sintering the intermediate powder with additives;

[0009] The additive is a fluoride, and the mass ratio of the additive to the intermediate powder is 0.1-10:100.

[0010] In optional embodiments, the additive is selected from at least one of magnesium fluoride, calcium fluoride, sodium fluoride, and potassium fluoride; preferably magnesium fluoride.

[0011] In an optional embodiment, the mass ratio of additive to intermediate powder is 1-3:100; preferably 1-2:100.

[0012] In an optional embodiment, the intermediate powder and additives are mixed and ball-milled, then pressed into shape and sintered.

[0013] In an optional embodiment, the sintering temperature is 1100-1300℃ and the sintering time is 10-15h;

[0014] Preferably, the sintering temperature is 1150-1250℃ and the sintering time is 11-13h.

[0015] In an optional embodiment, the preparation process of the intermediate powder includes: mixing the main raw materials, ball milling and calcining, and then ball milling again;

[0016] Preferably, the particle size of the intermediate powder is 2-20 micrometers.

[0017] In an optional embodiment, the calcination temperature is 1000-1200℃ and the calcination time is 10-15h;

[0018] Preferably, the calcination temperature is 1050-1150℃ and the calcination time is 11-13h.

[0019] In an optional implementation, the main raw materials are mixed by ball milling for 0.5-2 hours.

[0020] In an optional implementation, the main raw materials are selected according to the type of ceramic oxide solid electrolyte being prepared;

[0021] Preferably, the ceramic oxide solid electrolyte is at least one of NASICON-type solid electrolyte and garnet-type LLZO;

[0022] More preferably, by mass parts, the main raw materials include 31.5-33.1 parts of sodium phosphate dodecahydrate, 18.0-20.0 parts of silicon dioxide, 33.6-34.1 parts of zirconium dioxide and 11.6-12.8 parts of sodium carbonate.

[0023] Secondly, the present invention provides a ceramic oxide solid electrolyte, which is prepared by any of the preparation methods described in the foregoing embodiments.

[0024] The present invention has the following beneficial effects: by introducing additives for sintering after the main raw materials are calcined, the requirements for the accuracy of raw material weighing and the process cost of ball milling are reduced. More importantly, by selecting the type of additive and adjusting the amount, the total impedance can be significantly reduced with a very small proportion of fluoride added. It is a simple and efficient process. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 A comparison chart of EIS test results between NASICON electrolyte with added magnesium fluoride and commercial NASICON electrolyte;

[0027] Figure 2 Scanning electron microscope image of a NASICON sample with added magnesium fluoride;

[0028] Figure 3 This is a scanning electron microscope image of a commercially available electrolyte. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0030] In existing technologies, dopant materials are generally mixed and calcined together with the main raw materials. This requires precise calculation of the dopant material's mass before the weighing stage, and involves multiple ball milling steps, making the synthesis process cumbersome and time-consuming. To address these problems, the inventors have modified the timing of additive addition, optimized the types and amounts of additives, and provided a simple and efficient preparation process.

[0031] This invention provides a method for preparing a ceramic oxide solid electrolyte, which involves using main raw materials and additives, and includes the following steps:

[0032] S1, calcination

[0033] The main raw materials are mixed and calcined to obtain intermediate powder. Calcination decomposes the raw materials to obtain the corresponding oxides. In actual operation, the preparation process of intermediate powder includes: after mixing and calcining the main raw materials, ball milling is performed to obtain powder with a particle size that meets the requirements. The particle size of the intermediate powder can be 2-20 micrometers.

[0034] The main raw materials are selected according to the type of ceramic oxide solid electrolyte being prepared. Different types of ceramic oxide solid electrolytes require different main raw materials. Generally, the preparation process of ceramic oxide solid electrolytes is suitable for the preparation method provided in the embodiments of this invention. The composition of the main raw materials for different types of ceramic oxide solid electrolytes is based on existing technology and is not limited here.

[0035] In some embodiments, the ceramic oxide solid electrolyte can be a NASICON-type solid electrolyte; by mass parts, the main raw materials include 31.5-33.1 parts of sodium phosphate dodecahydrate, 18.0-20.0 parts of silicon dioxide, 33.6-34.1 parts of zirconium dioxide, and 11.6-12.8 parts of sodium carbonate. Using the main raw materials of the NASICON-type solid electrolyte, the resulting electrolyte product exhibits excellent performance, with a significant reduction in total impedance.

[0036] In some embodiments, the calcination temperature is 1000-1200℃ and the calcination time is 10-15h; preferably, the calcination temperature is 1050-1150℃ and the calcination time is 11-13h. By controlling the calcination temperature and calcination time, the raw materials can be fully decomposed to obtain the corresponding oxides.

[0037] Specifically, the calcination temperature can be 1000℃, 1050℃, 1100℃, 1150℃, 1200℃, etc., or any value between adjacent temperature values; the calcination time can be 10h, 11h, 12h, 13h, 14h, 15h, etc., or any value between adjacent time values.

[0038] In some embodiments, the main raw materials are mixed by ball milling for a time of 0.5-2 hours, such as 0.5 hours, 1 hour, 1.5 hours, 2 hours, etc., or any value between the above adjacent time values. Large ball mills can be used and the amplitude can be controlled to be about 0.1 mm.

[0039] S2, sintering

[0040] Intermediate powder and additives are mixed and sintered; wherein the additives are fluorides, and the mass ratio of additives to intermediate powders is 0.1-10:100. By selecting specific types of additives and controlling their dosage, the performance of oxide ceramic electrolytes can be further improved.

[0041] Specifically, the mass ratio of additives to intermediate powders can be 0.1:100, 0.5:100, 1.0:100, 2.0:100, 3.0:100, 4.0:100, 5.0:100, 6.0:100, 7.0:100, 8.0:100, 9.0:100, 10:100, etc., or any value between the above adjacent ratios.

[0042] In a preferred embodiment, the mass ratio of the additive to the intermediate powder is 1-3:100; more preferably, it is 1-2:100.

[0043] The additive can be any common fluoride, all of which can significantly improve the performance of the electrolyte. In some embodiments, the additive is selected from at least one of magnesium fluoride, calcium fluoride, sodium fluoride, and potassium fluoride; preferably magnesium fluoride. Using magnesium fluoride as an additive can significantly improve the performance of the electrolyte with very small amounts.

[0044] In actual operation, the intermediate powder and additives are mixed and ball-milled, then pressed and sintered to obtain an electrolytic sheet of a specific shape with the required density.

[0045] Further, the sintering temperature is 1100-1300℃, and the sintering time is 10-15h; in a preferred embodiment, the sintering temperature is 1150-1250℃, and the sintering time is 11-13h. Specifically, the sintering temperature can be 1100℃, 1150℃, 1200℃, 1250℃, 1300℃, etc., and the sintering time can be 10h, 11h, 12h, 13h, 14h, 15h, etc.

[0046] It should be noted that magnesium fluoride is a flux used in the manufacture of ceramics, metals, and glass. Its melting point is 1261℃, close to the sintering temperature range of ceramic solid electrolytes. During sintering, it can act as a liquid-phase assisted sintering agent, enhancing ceramic density and reducing grain boundary resistivity. Simultaneously, the diffusion of magnesium ions within the electrolyte lattice contributes to heterovalent doping. The inventors' research indicates that these two aspects are the main reasons why magnesium fluoride can enhance the performance of oxide ceramic electrolytes.

[0047] This invention provides a ceramic oxide solid electrolyte, prepared by the above-described method, which has advantages such as low cost and low total impedance.

[0048] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0049] Example 1

[0050] This embodiment provides a method for preparing a ceramic oxide solid electrolyte, using the main raw material of NASICON solid electrolyte and magnesium fluoride additive, including the following steps:

[0051] Weigh out 3.5570g of sodium phosphate dodecahydrate, 2.1418g of silicon dioxide, 3.6605g of zirconium dioxide, and 1.3853g of sodium carbonate. Mix the above main raw materials and grind them for 1 hour using a large ball mill with an amplitude of 0.1mm. Place the uniformly ground powder into an alumina crucible and calcine it at 1100℃ for 12 hours. Grind the obtained product with a large ball mill with the same amplitude for 30 minutes to obtain a white master powder with uniform particles.

[0052] Weigh a certain amount of white master powder, add magnesium fluoride powder at a ratio of 1 wt%, ball mill for 30 minutes, and press the uniformly mixed master powder into a disc shape using an axial pressure of 700 MPa through a mold. Place it in a crucible and sinter at 1200℃ for 12 hours to obtain an electrolyte sheet of white ceramic oxide.

[0053] Example 2

[0054] This embodiment provides a method for preparing a ceramic oxide solid electrolyte, using Na3Zr2Si2PO4. 12 The preparation of solid electrolytes involves the following steps, using the main raw materials and magnesium fluoride additive:

[0055] Weigh out 8.2393g of sodium phosphate dodecahydrate, 4.64508g of zirconium dioxide, and 2.2649g of silicon dioxide. Mix the above main raw materials and grind them for 1 hour using a large ball mill with an amplitude of 0.1mm. Place the uniformly ground powder into an alumina crucible and calcine it at 1100℃ for 12 hours. Grind the obtained product with a large ball mill with the same amplitude for 30 minutes to obtain a white master powder with uniform particles.

[0056] Weigh a certain amount of white master powder, add magnesium fluoride powder at a ratio of 1 wt%, ball mill for 30 minutes, and press the uniformly mixed master powder into a disc shape using an axial pressure of 700 MPa through a mold. Place it in a crucible and sinter at 1200℃ for 12 hours to obtain an electrolyte sheet of white ceramic oxide.

[0057] Example 3

[0058] This embodiment provides a method for preparing a ceramic oxide solid electrolyte, which differs from Embodiment 1 only in that magnesium fluoride is replaced with calcium fluoride.

[0059] Example 4

[0060] This embodiment provides a method for preparing a ceramic oxide solid electrolyte, which differs from Example 1 only in that magnesium fluoride is added at a mass ratio of 1 wt%.

[0061] Example 5

[0062] This embodiment provides a method for preparing a ceramic oxide solid electrolyte, which differs from Example 1 only in that magnesium fluoride is added at a mass ratio of 3 wt%.

[0063] Example 6

[0064] This embodiment provides a method for preparing a ceramic oxide solid electrolyte, which differs from Example 1 only in that magnesium fluoride is added at a mass ratio of 0.1 wt%.

[0065] Comparative Example 1

[0066] This comparative example provides a method for preparing a ceramic oxide solid electrolyte, which differs from Example 1 only in that magnesium fluoride is not added.

[0067] Comparative Example 2

[0068] This comparative example provides a method for preparing a ceramic oxide solid electrolyte, which differs from Example 1 only in that magnesium fluoride is replaced with sodium silicate.

[0069] Comparative Example 3

[0070] This comparative example provides a method for preparing a ceramic oxide solid electrolyte, which differs from Example 1 only in that magnesium fluoride is added at a mass ratio of 5 wt%.

[0071] Comparative Example 4

[0072] This comparative example provides a method for preparing a ceramic oxide solid electrolyte, which differs from Example 1 only in that magnesium fluoride is added at a mass ratio of 20 wt%.

[0073] Experimental Example 1

[0074] The electrolyte sheet prepared in Example 1 was vacuum-deposited with silver electrodes on both sides. The impedance curves of the electrolyte were measured using electrochemical impedance spectroscopy (EIS) at frequencies of 1 Hz–1 MHz. The obtained data were fitted using Zview software and compared with commercially available powdered electrolytes. The results are as follows: Figure 1 As shown.

[0075] from Figure 1 It can be seen that the addition of 1 wt% magnesium fluoride reduced the grain resistance of the sample to 33.49 ohms, the grain boundary resistance to 20.04 ohms, and the total resistance to 53.53 ohms. The total resistance of a commercially available powdered electrolyte, after the same testing procedure, was 256.64 ohms. The resistance of the sample with added magnesium fluoride was only 20.85% of that of the ordinary commercial powder.

[0076] It should be added that the composition of commercially available powdered electrolytes is Na3Zr2Si2PO4. 12 .

[0077] Experimental Example 2

[0078] The cross-section of the electrolyte sample obtained in Example 1 was observed by scanning electron microscopy, and the fracture surface was a cleavage plane. Figure 2 The sample containing magnesium fluoride has relatively large particles with close contact between them and no obvious pores, which provides the material with relatively low grain boundary resistance. The fracture surface has dimples, indicating that the material has good plasticity and high mechanical strength.

[0079] The scanning electron microscope (SEM) image of the commercially available electrolyte sample in Test Example 1 is shown below. Figure 3 As shown, the commercially available product has small grains, insufficient contact between particles, and many pores, resulting in high grain boundary resistance and low ionic conductivity. The fracture surface lacks obvious dimples, indicating poor toughness and brittleness when processed into batteries.

[0080] Based on the calculation using the ionic conductivity formula σ=(1 / R)×(L / S), the electrolyte ionic conductivity of the magnesium fluoride-added electrolyte in Example 1 can reach 1.8×10⁻⁶. -3 S / cm, while the conductivity of commercially available electrolytes is only 3×10. -4 Its S / cm performance is six times that of commercially available electrolytes.

[0081] Experimental Example 3

[0082] The performance of the electrolyte products was tested in Examples 2-6 and Comparative Examples 1-3. The impedance data obtained in Examples 4-6 were 61.69 ohms, 79.67 ohms, and 92.82 ohms, respectively. The impedance data obtained in Comparative Examples 1-4 were 460.9 ohms, 392 ohms, 275.3 ohms, and 1185 ohms, respectively.

[0083] In summary, this invention provides a ceramic oxide solid electrolyte and its preparation method. In the preparation process of the solid electrolyte, the addition time of the additives, the types of additives, and the dosage of additives are changed. By introducing additives after the main raw materials are calcined and then sintering, the requirements for the accuracy of raw material weighing and the process cost of ball milling are reduced. More importantly, by selecting the type of additives and adjusting the dosage, the goal of significantly reducing the total impedance can be achieved with a very small proportion of fluoride added.

[0084] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for producing a ceramic oxide solid state electrolyte, characterized by, Prepared by main raw materials and additives, including: mixing and calcining main raw materials to obtain intermediate powder, mixing and sintering intermediate powder and additives; The additive is magnesium fluoride, and the mass ratio of the additive to the intermediate powder is (0.1-0.5):

100. The main raw materials are selected according to the type of the ceramic oxide solid electrolyte prepared; the type of the ceramic oxide solid electrolyte is NASICON, and the main raw materials include, in mass fraction, sodium phosphate dodecahydrate 31.5-33.1 parts, silicon dioxide 18.0-20.0 parts, zirconium dioxide 33.6-34.1 parts and sodium carbonate 11.6-12.8 parts; The preparation process of the intermediate powder includes: mixing, ball milling and calcining the main raw materials, and then ball milling again.

2. The production method according to claim 1, characterized by, The intermediate powder and the additive are mixed and ball milled, and then sintered after being pressed into shape.

3. The production method according to claim 2, characterized by, The sintering temperature is 1100-1300 ℃, and the sintering time is 10-15 h.

4. The production method according to claim 3, characterized by, The sintering temperature is 1150-1250 ℃, and the sintering time is 11-13 h.

5. The preparation method according to claim 1, characterized in that, The particle size of the intermediate powder is 2-20 microns.

6. The production method according to claim 1, characterized by, The calcining temperature is 1000-1200 ℃, and the calcining time is 10-15 h.

7. The production method according to claim 6, characterized by, The calcining temperature is 1050-1150 ℃, and the calcining time is 11-13 h.

8. The production method according to claim 1, characterized by, The main raw materials are mixed by ball milling, and the ball milling time is 0.5-2 h.

9. A ceramic oxide solid state electrolyte, characterized by, Prepared by the preparation method in any one of claims 1-8.

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