An oxide-based solid electrolyte material and its preparation method and application

Abstract

The application relates to an oxide-based solid-state electrolyte and a preparation method and application thereof, and belongs to the technical field of methods or devices for directly converting chemical energy into electric energy. The preparation method of the oxide-based solid-state electrolyte comprises the following steps: uniformly mixing raw materials and additives of the oxide-based solid-state electrolyte by means of a dry mixing method to obtain a precursor; and performing calcination treatment on the precursor to obtain the oxide-based solid-state electrolyte; the additives comprise additive I and additive II; the additive I comprises at least one of magnesium oxide, silicon oxide and a silicate compound; and the additive II is a high polymer material. The preparation method can not only effectively reduce the expansion rate of the raw materials of the oxide-based solid-state electrolyte in a sintering process, but also effectively inhibit wall sticking of the oxide-based solid-state electrolyte, and the prepared oxide-based solid-state electrolyte has high phase purity and high fluidity.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of methods or devices for directly converting chemical energy into electrical energy, in particular to an oxide-based solid-state electrolyte material and a preparation method and application thereof. BACKGROUND

[0002] Inorganic solid-state electrolytes are a class of ceramic materials with high ionic conductivity for lithium (Li), sodium (Na), or other alkali metal ions, which can provide a stable and efficient transport medium for ion flow between the positive and negative electrodes in batteries. According to the chemical properties of the anions, inorganic solid-state electrolytes are mainly divided into oxide-based solid-state electrolytes, sulfide-based solid-state electrolytes, and halide-based solid-state electrolytes. Among them, oxide-based solid-state electrolytes can be further divided into NASICON type, garnet, and perovskite type according to their structural characteristics. These materials are inherently non-flammable, have a wider electrochemical stability window, and better thermal stability, making them an effective alternative to organic liquid electrolytes in high-energy-density lithium batteries or sodium batteries.

[0003] Currently, the preparation methods of oxide-based solid-state electrolytes include solid-phase method, sol-gel method, and co-precipitation method. These preparation methods mostly use wet mixing of raw materials. However, in actual application, it is found that wet-mixed raw materials have serious expansion and overflow problems during high-temperature calcination, as well as material sticking to the wall, resulting in low production efficiency and low material utilization. To solve this problem, a dry method for preparing solid-state electrolytes is disclosed in the prior art (CN114824452A), which adds organic additives to the raw materials and combines with dry mixing and stirring of the mixed raw materials. The organic additives improve the flowability and moisture retention of the materials to avoid sticking to the crucible during calcination, and the high moisture retention effectively alleviates the problem of material expansion caused by gas discharge. Although this method can reduce the volume expansion of the material during sintering and reduce sticking to some extent, the improvement is limited. In addition, the oxide-based solid-state electrolytes prepared by the existing preparation methods are mostly irregularly shaped particles, resulting in low tap density of the corresponding materials. SUMMARY

[0004] The present application aims to overcome the shortcomings of the prior art and provide an oxide-based solid-state electrolyte and a preparation method and application thereof.

[0005] To achieve the above-mentioned purposes, the technical solutions adopted by the present application are as follows:

[0006] In a first aspect, the present application provides a preparation method of an oxide-based solid-state electrolyte. The raw materials and additives of the oxide-based solid-state electrolyte are uniformly mixed by dry mixing to obtain a precursor. Then, the precursor is calcined to obtain the oxide-based solid-state electrolyte.

[0007] The auxiliary agent includes auxiliary agent I and auxiliary agent II, the auxiliary agent I includes at least one of magnesium oxide, silicon oxide, silicate compound, and the auxiliary agent II is a high polymer material.

[0008] The application combines specific auxiliary agent I and auxiliary agent II, which can not only improve the hydrophobicity of the material surface to reduce the carrying moisture, improve the fluidity of the material in the sintering process to reduce the material wall sticking, but also effectively absorb the water vapor generated in the calcination process to inhibit the gas production rate and reduce the volume expansion of the material, and make the prepared oxide-based solid electrolyte maintain high phase purity and give the oxide-based solid electrolyte high fluidity, so as to improve the tap density when the oxide-based solid electrolyte is used as a composite positive electrode material component, and further improve the safety performance of the battery.

[0009] Optionally, the silicate compound can be at least one of methyl silicate, ethyl silicate and tetraethyl silicate.

[0010] As a preferred embodiment of the preparation method of the oxide-based solid electrolyte, the mass fraction of the auxiliary agent I relative to the total mass of the raw materials of the oxide-based solid electrolyte is 0.1% to 10%. Optionally, the mass fraction of the auxiliary agent I relative to the total mass of the raw materials of the oxide-based solid electrolyte can be 0.5%, 0.9%, 1.2%, 1.5%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%.

[0011] Research shows that the addition amount of the auxiliary agent I affects the fluidity of the material in the calcination process and the phase purity of the oxide solid electrolyte; the auxiliary agent I in the above addition amount range can not only maintain high phase purity of the oxide solid electrolyte, but also be more uniformly distributed on the surface of the raw material particles, enhance the fluidity of the material in the calcination process to more effectively reduce the material wall sticking, and better inhibit the volume expansion. In addition, the auxiliary agent I can be mixed with one or more raw materials of the oxide-based solid electrolyte first, and then mixed with the remaining raw materials; or the auxiliary agent I can be directly mixed with all the raw materials of the oxide-based solid electrolyte.

[0012] As a preferred embodiment of the preparation method of the oxide-based solid electrolyte, the mass fraction of the auxiliary agent II relative to the total mass of the raw materials of the oxide-based solid electrolyte is 0.1% to 5%. Optionally, the mass fraction of the auxiliary agent II relative to the total mass of the raw materials of the oxide-based solid electrolyte can be 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%.

[0013] The study found that the amount of additive II added affects the volume expansion rate of the material during calcination and the phase purity of the oxide solid electrolyte; additive II in the above-mentioned addition range can maintain the high phase purity of the oxide solid electrolyte while also fully absorbing water vapor and slowing down gas production during the calcination process to better inhibit material expansion.

[0014] As a preferred embodiment of the method for preparing the oxide-based solid electrolyte of the present invention, the polymer material includes at least one of polyethylene glycol, polyethylene oxide, polyvinyl alcohol, polyvinyl butyral, methyl cellulose, ethyl cellulose, carboxymethyl cellulose, microcrystalline cellulose, and glucose.

[0015] As a preferred embodiment of the method for preparing the oxide-based solid electrolyte described herein, the precursor is a spherical or quasi-spherical particle. Studies have found that when the precursor is a spherical or quasi-spherical particle, the spherical morphology can provide more venting space during sintering, allowing the generated gas to be fully discharged, thereby further reducing volume expansion. Furthermore, the spherical morphology can further reduce adhesion between materials and adhesion to the wall.

[0016] Optionally, the spherical or quasi-spherical precursor particles can be obtained by a drum granulator, wherein the rotation speed of the drum granulator is 3 to 7 rpm, the slope is 3% to 4%, and the granulation time is 24 to 26 h; preferably, the rotation speed of the drum granulator is 5 rpm, the slope is 3.5%, and the granulation time is 26 h.

[0017] As a preferred embodiment of the method for preparing the oxide-based solid electrolyte of the present invention, the particle size D of the spherical particles or quasi-spherical particles is 50 Optionally, the particle size D of the spherical particles or quasi-spherical particles is 50 Specifically, it can be 1μm, 3μm, 5μm, 7μm, 9μm, 11μm, 13μm, 15μm, 17μm, and 19μm.

[0018] As a preferred embodiment of the method for preparing the oxide-based solid electrolyte of the present invention, the calcination treatment comprises: calcining at 700-1500° C. for 5-20 h (i.e., the calcination treatment is performed only once);

[0019] Alternatively, first calcinate at 200-800°C (primary calcination) for 2-15h, take out and grind, and then continue calcining at 600-1500°C (secondary calcination) for 5-20h (i.e., the calcination treatment is performed twice).

[0020] At the same time, nitrogen, oxygen, argon or dry compressed air can be introduced during the calcination process to quickly remove the waste gas and water vapor generated during the sintering process, further slowing down the expansion of the material and reducing the material sticking to the wall.

[0021] Optionally, the main function of the above-mentioned primary calcination is to discharge waste gas and water vapor, and the temperature can be specifically 300℃, 400℃, 500℃, 600℃, 700℃, and the time can be specifically 4h, 6h, 8h, 10h, 12h, 14h; the main function of the secondary calcination is to sinter the powder into a solid solution, and the temperature can be specifically 700℃, 800℃, 900℃, 1000℃, 1100℃, 1200℃, 1300℃, 1400℃, and the time can be specifically 6h, 8h, 10h, 12h, 14h, 16h, 18h.

[0022] As a preferred embodiment of the preparation method of the oxide-based solid electrolyte of the present invention, the oxide-based solid electrolyte is one of garnet-type solid electrolyte materials, NASCION-type solid electrolyte materials, LISCION-type solid electrolyte materials, perovskite-type solid electrolyte materials and their derivative materials. Optionally, the oxide-based solid electrolyte can be specifically Li 1+x Al x Ti 2-X P3O 12 、Li 6+x La3Zr 2-x Ta x O 12 、Li 0.33 La 0.56 TiO3、Li 14 Zn(GeO4)4, Li2PO2N, etc.

[0023] In a second aspect, the present invention provides an oxide-based solid electrolyte prepared by the above preparation method.

[0024] In a third aspect, the present invention provides the use of the above-mentioned oxide-based solid electrolyte in batteries or capacitors.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] The present invention combines specific additives I and II, which can not only improve the hydrophobicity of the material surface to reduce water carryover, and improve the fluidity of the material during the sintering process to reduce material wall adhesion, but also effectively absorb water vapor generated during the calcination process to inhibit the gas production rate and reduce the volume expansion of the material; at the same time, it can also enable the prepared oxide-based solid electrolyte to maintain a high physical purity, and impart high fluidity to the oxide-based solid electrolyte to increase its tap density when used as a component of the composite positive electrode material, thereby improving the safety performance of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a SEM image of the oxide-based solid electrolyte prepared in Example 1 (magnified 10,000 times);

[0028] Figure 2 This is a SEM image of the oxide-based solid electrolyte prepared in Example 1 (magnified 20,000 times);

[0029] Figure 3 This is a physical photo of the oxide solid electrolyte prepared in Example 1 (unbroken);

[0030] Figure 4 This is a physical photo of the oxide solid electrolyte prepared in Comparative Example 3 (not broken). DETAILED DESCRIPTION

[0031] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0032] Unless otherwise specified, other materials and reagents used in the examples can be obtained from commercial sources.

[0033] Examples 1 to 8 and Comparative Examples 1 to 4

[0034] The method for preparing the oxide-based solid electrolyte of the present invention comprises the following steps:

[0035] S1. Based on the total mass of the raw materials of the oxide-based solid electrolyte being 100%, 9.7 wt% of lithium carbonate, 3.7 wt% of aluminum oxide, 23.4 wt% of titanium oxide, and 63.2 wt% of ammonium dihydrogen phosphate were added together with the additives into a VC mixing device and mixed for 40 minutes;

[0036] S2. The uniformly mixed materials in S1 are added to a turbine and rotated at high speed to form a precursor. The precursor is then calcined at 400°C for 10 hours and then at 800°C for 12 hours to obtain an oxide-based solid electrolyte.

[0037] Table 1 Additives in Examples 1 to 8 and Comparative Examples 1 to 4 and their addition amounts relative to the total mass of the raw materials of the oxide-based solid electrolyte

[0038]

[0039] The addition amounts of additive I and additive II in Table 1 refer to the mass fraction of additive I or additive II relative to the total mass of the raw materials of the oxide-based solid electrolyte.

[0040] Example 9

[0041] An embodiment of a method for preparing an oxide-based solid electrolyte of the present invention is basically the same as Example 1, except that in step S1, the raw materials of the oxide-based solid electrolyte and their mass fractions are: 6.6wt% Li2CO3, 50.0wt% La2O3 and 43.4wt% TiO2; auxiliary agent I is tetraethyl silicate, and its addition amount relative to the total mass of the raw materials of the oxide-based solid electrolyte is 2wt%; auxiliary agent II is polyvinyl butyral, and its addition amount relative to the total mass of the raw materials of the oxide-based solid electrolyte is 0.5wt%.

[0042] Performance Testing

[0043] 1. Phase purity: The oxide-based solid electrolytes prepared in each embodiment and comparative example were subjected to XRD testing to obtain the XRD diffraction pattern of the oxide-based solid electrolyte. The intensities of the diffraction peaks of the main phase and the impurity phase in the XRD diffraction pattern were then analyzed and statistically analyzed, and the phase purity was calculated using the following formula;

[0044] Phase purity (%) = main phase diffraction peak intensity / (main phase diffraction peak intensity + impurity phase diffraction peak intensity) × 100%.

[0045] 2. Expansion rate: Under the conditions of a temperature of 25° C. and an air pressure of 101 kPa, the volume of the precursor before sintering and the volume of the oxide-based solid electrolyte after sintering in each embodiment and comparative example were measured, and the volume expansion rate was calculated using the following formula. During production, the height of the sagger input for each batch was about 40 mm;

[0046] Expansion rate (T) = (V2-V1) / V1×100%; where V1 is the volume of the precursor in cm 3 ; V2 is the volume of the oxide-based solid electrolyte, in cm 3 .

[0047] 3. Angle of repose: Measured according to the standard "GB 6521-1986 Determination of angle of repose of alumina powder".

[0048] Table 2 Properties of oxide-based solid electrolytes in various embodiments and comparative examples

[0049] serial number Phase purity / % Expansion rate / % Whether it sticks to the wall Angle of repose / ° Example 1 98％ -22.5％ no 30 Example 2 94％ 3.7％ no 32 Example 3 92％ -19.6％ no 33 Example 4 85％ -17.8％ no 35 Example 5 96％ -20.5％ no 32 Example 6 95％ -15.3％ no 33 Example 7 98％ -14.6％ no 32 Example 8 96％ -13.7％ no 31 Example 9 96％ -18.0％ no 31 Comparative Example 1 95％ 12％ yes 55 Comparative Example 2 96％ 47％ no 36 Comparative Example 3 81％ 33％ no 38 Comparative Example 4 67％ 53％ no 36

[0050] According to the data in Table 2, the phase purity of the oxide-based solid electrolytes in Examples 1 to 9 reaches more than 85%, the expansion rate is less than or equal to 3.7%, and no wall sticking occurs during the calcination process, and the angle of repose is less than or equal to 35°, indicating that the preparation method of the oxide-based solid electrolyte of the present invention can effectively improve the wall sticking of the material during the sintering process and reduce the volume expansion of the material, while making the obtained oxide-based solid electrolyte have high phase purity and high fluidity. In addition, according to Comparative Examples 1 and 2, it can be seen that using auxiliary agent I (magnesium oxide) or auxiliary agent II (polyethylene oxide) alone is difficult to simultaneously improve the wall sticking and volume expansion problems of the material during the sintering process; and from Comparative Examples 3 and 4, it can be found that when calcium stearate or calcium oxide is used as auxiliary agent I and auxiliary agent II (polyethylene oxide), it is not only difficult to effectively reduce the volume expansion of the material, but also the phase purity of the obtained oxide-based solid electrolyte is reduced.

[0051] In addition, according to Figure 3 It can be seen that compared with the volume of the precursor before sintering, the volume of the oxide-based solid electrolyte after sintering in Example 1 did not expand, but shrunk; Figure 4 It can be found that compared with the volume of the precursor before sintering, the volume of the oxide-based solid electrolyte after sintering in Comparative Example 3 expanded significantly, further proving that the preparation method of the oxide-based solid electrolyte of the present invention can effectively reduce the volume expansion of the material during the sintering process.

[0052] 4. SEM test: The oxide-based solid electrolytes prepared in each embodiment were subjected to SEM (scanning electron microscope) test, wherein the SEM image of the oxide-based solid electrolyte in Example 1 is as follows: Figure 1 and Figure 2 As shown, according to Figure 1 and Figure 2 It can be seen that the secondary particles of the oxide-based solid electrolyte are spherical or quasi-spherical. The secondary particles of the oxide-based solid electrolyte in Examples 2 to 9 are basically the same as those in Example 1, which are all spherical or quasi-spherical. Oxide-based solid electrolyte particles of this morphology can be more densely stacked due to their regular geometric shape, thereby improving the volume energy density of the battery. Moreover, the spherical or quasi-spherical particles have better fluidity during mixing and coating, which helps to improve the efficiency and consistency of battery production.

[0053] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing an oxide-based solid electrolyte, characterized in that: The raw materials and additives of the oxide-based solid electrolyte are mixed evenly by dry mixing to obtain a precursor; the precursor is then calcined to obtain the oxide-based solid electrolyte; The auxiliary agent includes auxiliary agent I and auxiliary agent II, wherein the auxiliary agent I includes at least one of magnesium oxide, silicon oxide, and silicate compounds, and the auxiliary agent II is a polymer material; The mass fraction of the auxiliary agent I relative to the total mass of the raw materials of the oxide-based solid electrolyte is 0.1% to 6%; the mass fraction of the auxiliary agent II relative to the total mass of the raw materials of the oxide-based solid electrolyte is 0.1% to 5%.

2. The preparation method according to claim 1, wherein The polymer material includes at least one of polyethylene glycol, polyethylene oxide, polyvinyl alcohol, polyvinyl butyral, methyl cellulose, ethyl cellulose, carboxymethyl cellulose, microcrystalline cellulose, and glucose.

3. The preparation method according to claim 1, wherein The precursor is spherical particles or quasi-spherical particles.

4. The preparation method according to claim 3, wherein The particle size D50 of the spherical particles or quasi-spherical particles is 0.5 to 20 μm.

5. The preparation method according to claim 1, wherein The calcination treatment includes: calcining at 700-1500° C. for 5-20 hours.

6. The preparation method according to claim 1, wherein The calcination treatment comprises: first calcining at 200-800° C. for 2-15 hours, taking out and grinding and crushing, and then continuing to calcine at 600-1500° C. for 5-20 hours.

7. The preparation method according to claim 1, wherein The oxide-based solid electrolyte is one of garnet-type solid electrolyte materials, NASCION-type solid electrolyte materials, LISCION-type solid electrolyte materials, perovskite-type solid electrolyte materials and derivative materials thereof.

8. An oxide-based solid electrolyte prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the oxide-based solid electrolyte according to claim 8 in batteries or capacitors.

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