Solid-state electrolyte and preparation method and application thereof

Abstract

The application provides a solid-state electrolyte, the chemical formula of the solid-state electrolyte is: A(Li (3+x+2y) Zr (2‑x‑2y) M x N y Si2PO 12 )B(Li3La(PO4)2), wherein A+B=1, 0<=x<=0.5, 0.1<=y<=0.3, M is a trivalent metal ion, and N is a divalent metal ion. The application has the beneficial effects that the solid-state electrolyte has high ionic conductivity, and the battery prepared from the solid-state electrolyte has high battery capacity and service life.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium batteries, and in particular relates to a solid electrolyte and a preparation method and application thereof. Background Art

[0002] In the battery energy sector, lithium-ion secondary batteries (Li-ion batteries) dominate the mobile electronics and electric vehicles market due to their high energy density, wide operating temperature range, and long service life. Traditional Li-ion batteries use organic solvent electrolytes for lithium ion transmission. These volatile organic solvents have a low flash point and can easily cause leakage, flatulence, and even serious battery combustion and explosion problems, posing safety risks. Using solid-state electrolytes to replace electrolytes effectively avoids these safety risks caused by organic solvents. Furthermore, the use of higher-energy lithium metal in the negative electrode significantly increases the battery's energy density.

[0003] Solid-state lithium-ion electrolyte Li (3+x+2y) Zr (2-x-2y) M x N y Si2PO 12 It has very high room temperature lithium ion conductivity, and its conductivity can reach more than 10mS / cm. It is a very excellent lithium ion solid electrolyte material. This material is a high entropy material composed of multivalent divalent (Mg, Zn), trivalent (La, Fe, Al), and tetravalent (Zr, Si) metal oxides to form LSZP+LLZO+LLPO and other multi-phases. It has multidimensional lithium ion channels. This structure enables the material to have high room temperature lithium ion conductivity (>10mS / cm), but this material contains LZSP phase. The synthesis method is to carry out ion replacement at a high temperature of 180°C, that is, to replace the sodium ions in NZSP with lithium salts in a high-temperature organic solvent. Because this material has a metastable structure, its layered structure will be destroyed when the temperature exceeds 700°C. That is, the existing synthesis method cannot effectively solve the problem of the uniform distribution of Li, Mg, Zn, La, Fe, Al, Zr, Si, and PO4 ions in the solution, nor can it be synthesized below 700°C and make the crystals develop perfectly without amorphous powder, which seriously hinders its performance improvement and application prospects. Summary of the Invention

[0004] The present application provides a solid electrolyte and its preparation method and application, aiming to solve the problem of low conductivity of existing oxide solid lithium ion electrolytes.

[0005] The first aspect of the present application provides a solid electrolyte, the chemical formula of which is A(Li (3+x+2y) Zr (2-x-2y) M x N y Si2PO 12)B(Li3La(PO4)2), wherein A+B=1, 0≤x≤0.5, 0.1≤y≤0.3, M is a trivalent metal ion, and N is a divalent metal ion. The solid electrolyte described in the present application is a high-entropy material with a complex locally disordered structure including layered, cubic, and fluorite structures formed by a variety of divalent, trivalent, and tetravalent oxides and phosphates. This structure facilitates the generation of overlapping site energy distributions for lithium ions, resulting in a percolation network of connection points with reduced energy differences, and correspondingly accelerated lithium ion transport. The changes in ion paths generated by the different elemental compositions in the high-entropy material open up percolation paths for rapid lithium ion movement in the low-mobility lattice, thereby forming ultra-high lithium ion conductivity.

[0006] According to some embodiments of the solid electrolyte described herein, M includes La 3+ 、Fe 3+ and Al 3+ One or more of N including Mg 2+ and / or Zn 2+ .

[0007] The second aspect of the present application provides a composition for preparing the solid electrolyte described in the first aspect of the present application, comprising a lithium source, a zirconium source, a silicon source, a phosphorus source, an M source and a N source.

[0008] According to some embodiments of the composition described herein, the lithium source includes one or more of lithium nitrate, lithium carbonate, and lithium chloride.

[0009] According to some embodiments of the composition described herein, the zirconium source includes one or more of zirconium oxychloride, zirconium nitrate, zirconium carbonate, and zirconium ammonia carbonate.

[0010] According to some embodiments of the composition described herein, the silicon source includes one or more of sodium silicate nonahydrate, ethyl silicate, and silica sol.

[0011] According to some embodiments of the composition described herein, the phosphorus source includes triethyl phosphate and / or butyl phosphate.

[0012] According to some embodiments of the composition described herein, the M source includes one or more of lanthanum carbonate, lanthanum nitrate, iron nitrate and aluminum nitrate.

[0013] According to some embodiments of the composition described herein, the N source includes magnesium acetate and / or zinc nitrate.

[0014] According to some embodiments of the composition described herein, the molar ratio of the lithium source to the zirconium source is: 3:(0.3-2), for example, 3:0.3, 3:0.5, 3:1.0, 3:1.2, 3:1.5, 3:1.7, 3:2, etc.

[0015] The molar ratio of the lithium source to the silicon source is (3-8):2, for example, 3:2, 3.3:2, 3.5:2, 5:2, 7:2, 8:2, etc.

[0016] The molar ratio of the lithium source to the phosphorus source is (1-3.5):1, for example, 1:1, 2:1, 3:1, 3.2:1, 3.3:1, 3.5:1, etc.

[0017] The molar ratio of the lithium source to the M source is: (3-3.6): (0.1-0.5).

[0018] The molar ratio of the lithium source to the nitrogen source is: (3-3.6): (0.1-0.3).

[0019] The third aspect of the present application provides a method for preparing the solid electrolyte described in the first aspect of the present application, which is prepared using the composition described in the second aspect of the present application.

[0020] According to some embodiments of the method for preparing the solid electrolyte described in this application, the following steps are included:

[0021] (1) mixing a lithium source, a zirconium source, a silicon source, a M source, a N source, and a solvent to obtain a mixed solution;

[0022] (2) mixing the mixed solution and a phosphorus source to react to obtain a gel;

[0023] (3) heating the gel to obtain a precursor material;

[0024] (4) calcining the precursor material to obtain the solid electrolyte.

[0025] According to some embodiments of the solid electrolyte preparation method described in the present application, in step (1), the solvent includes ethanol and / or acetic acid.

[0026] According to some embodiments of the solid electrolyte preparation method described in the present application, the mixing temperature is: 20-30°C, for example, 20°C, 25°C, 28°C, 30°C, etc., and the mixing time is 1-2h, for example, 1h, 1.2h, 1.5h, 1.8h, 2h, etc.

[0027] According to some embodiments of the solid electrolyte preparation method described in the present application, in step (2), the reaction temperature is 50-60°C, for example, 50°C, 52°C, 55°C, 58°C, 60°C, etc., and the reaction time is 3-5h, for example, 3h, 4h, 5h, etc.

[0028] According to some embodiments of the solid electrolyte preparation method described in the present application, in step (3), the heating is microwave heating.

[0029] According to some embodiments of the solid electrolyte preparation method described in the present application, the temperature of the microwave heating is 90-110°C, for example, 90°C, 95°C, 100°C, 105°C, 110°C, etc., and the time of the microwave heating is 1-2h, for example, 1h, 1.2h, 1.5h, 1.8h, etc.

[0030] According to some embodiments of the solid electrolyte preparation method described in the present application, in step (4), the calcination temperature is 450-700°C, for example, 450°C, 480°C, 500°C, 550°C, 580°C, 620°C, 650°C, 680°C, 700°C, etc., and the calcination time is 5-8h, for example, 5h, 6h, 7h, 8h, etc.

[0031] According to some embodiments of the solid electrolyte preparation method described in the present application, the solid electrolyte preparation method further includes cleaning, grinding and drying the calcined product.

[0032] The fourth aspect of the present application provides an application of the solid electrolyte described in the first aspect of the present application or the solid electrolyte obtained by the preparation method described in the third aspect of the present application in lithium batteries.

[0033] The beneficial effects of the present application include: the solid electrolyte described in the present application has high ionic conductivity; and the battery prepared using the solid electrolyte described in the present application has high battery capacity and service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is the XRD spectrum of the solid electrolyte prepared in Example 1 of the present application;

[0035] Figure 2 This is the XRD spectrum of the solid electrolyte prepared in Example 2 of the present application;

[0036] Figure 3 This is the XRD spectrum of the solid electrolyte prepared in Example 3 of the present application;

[0037] Figure 4 This is the XRD spectrum of the solid electrolyte prepared in Example 4 of the present application. DETAILED DESCRIPTION

[0038] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to be used to explain the present invention, but should not be understood as limiting the present invention.

[0039] In the present invention, the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" mean that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and the features of different embodiments or examples without contradiction.

[0040] Example 1

[0041] A method for preparing a solid electrolyte comprises the following steps:

[0042] (1) 220.8 g of anhydrous lithium nitrate (3.2 mol), 481.09 g of zirconium nitrate (1.8 mol), 429.14 g of ethyl silicate (SiO2 content 28%), 64.98 g of lanthanum nitrate, 14.2 g of magnesium acetate, and 2000 g of ethanol were mixed and reacted at 20° C. for 1 h to obtain a mixed solution; wherein the molar ratio of lithium nitrate, zirconium nitrate, ethyl silicate, lanthanum nitrate, and magnesium acetate was 3.2:1.8:0.3:0.2:0.1;

[0043] (2) The mixed solution obtained in step (1) and 182.16 g of triethyl phosphate were reacted at 50° C. under vacuum conditions for 3 h to obtain a gel;

[0044] (3) The gel obtained in step (2) was subjected to microwave heating at a temperature of 100° C. for 1 h to obtain a powdered precursor, which was then calcined at a temperature of 700° C. for 8 h. The precursor was naturally cooled to room temperature, and the calcined product was washed with deionized water and anhydrous ethanol in sequence, ground, and then spray-dried to obtain a product having the chemical formula Li 3.2 Zr 1.8 La 0.2 Mg 0.1 Si2PO 12 of solid electrolytes.

[0045] Example 2

[0046] The only difference between Example 2 and Example 1 is that the amount of lanthanum nitrate added during the preparation of the solid electrolyte in Example 2 is different from that in Example 1.

[0047] The specific steps include:

[0048] (1) 220.8 g of anhydrous lithium nitrate (3.2 mol), 481.09 g of zirconium nitrate (1.8 mol), 429.14 g of ethyl silicate (SiO2 content 28%), 97.48 g of lanthanum nitrate, 14.2 g of magnesium acetate, and 2000 g of ethanol were mixed and reacted at 20° C. for 1 h to obtain a mixed solution; wherein the molar ratio of lithium nitrate, zirconium nitrate, ethyl silicate, lanthanum nitrate, and magnesium acetate was 3.2:1.8:0.3:0.3:0.1;

[0049] (2) The mixed solution obtained in step (1) and 182.16 g of triethyl phosphate were reacted at 50° C. under vacuum conditions for 3 h to obtain a gel;

[0050] (3) The gel obtained in step (2) was subjected to microwave heating at a temperature of 100° C. for 1 h to obtain a powdered precursor, which was then calcined at a temperature of 700° C. for 8 h. The precursor was naturally cooled to room temperature, and the calcined product was washed with deionized water and anhydrous ethanol in sequence, ground, and then spray-dried to obtain a product having the chemical formula Li 3.2 Zr 1.8 La 0.3 Mg 0.1 Si2PO 12 of solid electrolytes.

[0051] Example 3

[0052] The only difference between Example 3 and Example 1 is that the amount of lanthanum nitrate added during the preparation of the solid electrolyte in Example 3 is different from that in Example 1.

[0053] The specific steps include:

[0054] (1) 220.8 g of anhydrous lithium nitrate (3.2 mol), 481.09 g of zirconium nitrate (1.8 mol), 429.14 g of ethyl silicate (SiO2 content 28%), 129.97 g of lanthanum nitrate, 14.2 g of magnesium acetate, and 2000 g of ethanol were mixed and reacted at 20° C. for 1 h to obtain a mixed solution; wherein the molar ratio of lithium nitrate, zirconium nitrate, ethyl silicate, lanthanum nitrate, and magnesium acetate was 3.2:1.8:0.3:0.4:0.1;

[0055] (2) The mixed solution obtained in step (1) and 182.16 g of triethyl phosphate were reacted at 50° C. under vacuum conditions for 3 h to obtain a gel;

[0056] (3) The gel obtained in step (2) was subjected to microwave heating at a temperature of 100° C. for 1 h to obtain a powdered precursor, which was then calcined at a temperature of 700° C. for 8 h. The precursor was naturally cooled to room temperature, and the calcined product was washed with deionized water and anhydrous ethanol in sequence, ground, and then spray-dried to obtain a product having the chemical formula Li 3.2 Zr 1.8 La 0.4 Mg 0.1 Si2PO 12 of solid electrolytes.

[0057] Example 4

[0058] The only difference between Example 4 and Example 1 is that the amount of magnesium acetate added during the preparation of the solid electrolyte described in Example 4 is different from that in Example 1.

[0059] The specific steps include:

[0060] (1) 220.8 g of anhydrous lithium nitrate (3.2 mol), 481.09 g of zirconium nitrate (1.8 mol), 429.14 g of ethyl silicate (SiO2 content 28%), 64.98 g of lanthanum nitrate, 28.4 g of magnesium acetate, and 2000 g of ethanol were mixed and reacted at 20° C. for 1 h to obtain a mixed solution; wherein the molar ratio of lithium nitrate, zirconium nitrate, ethyl silicate, lanthanum nitrate, and magnesium acetate was 3.2:1.8:0.3:0.2:0.2;

[0061] (2) The mixed solution obtained in step (1) and 182.16 g of triethyl phosphate were reacted at 50° C. under vacuum conditions for 3 h to obtain a gel;

[0062] (3) The gel obtained in step (2) was subjected to microwave heating at a temperature of 100° C. for 1 h to obtain a powdered precursor, which was then calcined at a temperature of 700° C. for 8 h. The precursor was naturally cooled to room temperature, and the calcined product was washed with deionized water and anhydrous ethanol in sequence, ground, and then spray-dried to obtain a product having the chemical formula Li 3.2 Zr 1.8 La 0.2 Mg 0.2 Si2PO 12 of solid electrolytes.

[0063] Comparative Example 1

[0064] The only difference between Comparative Example 1 and Example 1 is that no lanthanum nitrate as a raw material is added during the preparation of the solid electrolyte in Comparative Example 1, and the remaining operations are the same as those in Example 1.

[0065] Comparative Example 2

[0066] Comparative Example 2 is different from Example 1 only in that no raw material magnesium acetate is added in the preparation process of the solid-state electrolyte of Comparative Example 2, and the rest of the operations are the same as those of Example 1.

[0067] Comparative Example 3

[0068] Comparative Example 3 is different from Example 1 only in that no raw material lanthanum nitrate and magnesium acetate is added in the preparation process of the solid-state electrolyte of Comparative Example 3, and the rest of the operations are the same as those of Example 1.

[0069] Comparative Example 4

[0070] The solid-state electrolyte of Comparative Example 4 is a LATP oxide electrolyte.

[0071] Comparative Example 5

[0072] The solid-state electrolyte of Comparative Example 5 is an oxide solid-state electrolyte LLZO.

[0073] Performance research of the solid-state electrolytes of Examples 1-4 and Comparative Examples 1-5 of the present application

[0074] The solid-state electrolytes of Examples 1-4 and Comparative Examples 1-5 of the present application were weighed respectively, and were hot-pressed at 30 MPa and 700°C. Then the above samples were repeatedly sputtered with gold using an ion sputtering instrument, and were tested for room temperature conductivity using SP-300 under the conditions of 0.1 Hz-7 MHz and ±1 V (10 pieces were tested for each group, and the average value was obtained), and the test results are shown in Table 1.

[0075] Table 1

[0076]

[0077] As can be seen from Table 1, the solid-state electrolyte of the present application can be stably prepared in large quantities at a lower cost through multi-element doping, and a very high ionic conductivity oxide solid-state electrolyte can be obtained. At present, most oxide solid-state electrolytes have a high Young's modulus, and the interface matching problem in the solid-state battery when the positive electrode material is used seriously affects the performance. The solid-state electrolyte A(Li (3+x+2y) Zr (2-x-2y) M x N y Si2PO 12 )B(Li3La(PO4)2) of the present application can be prepared into a solid-state electrolyte with high ionic conductivity and low Young's modulus by adjusting the ratio of A and B.

[0078] This application describes the above embodiments. It is understandable that the above embodiments are illustrative and cannot be understood as limitations of the present invention. Changes, modifications, replacements and variations of the above embodiments made by ordinary technicians in this field are all within the scope of protection of the present invention.

Claims

1. A solid electrolyte, characterized in that The chemical formula of the solid electrolyte is: A(Li (3+x+2y) Zr (2-x-2y) M x N y Si2PO 12 )B(Li3La(PO4)2), where A+B=1, 0≤x≤0.5, 0.1≤y≤0.3, and M is La 3+ , N is Mg 2+ ; The preparation method of the solid electrolyte comprises the following steps: (1) mixing a lithium source, a zirconium source, a silicon source, a lanthanum source, a magnesium source, and a solvent to obtain a mixed solution; (2) mixing the mixed solution and a phosphorus source to react to obtain a gel; (3) subjecting the gel to microwave heating treatment, and setting the microwave heating temperature to 90-110° C. to obtain a precursor material; (4) calcining the precursor material at 700° C. for 5-8 hours to obtain the solid electrolyte; The molar ratio of the lithium source to the lanthanum source is 3.2:(0.2-0.4), and the molar ratio of the lithium source to the magnesium source is 3.2:0.

1.

2. The solid electrolyte according to claim 1, characterized in that The lithium source includes one or more of lithium nitrate, lithium carbonate and lithium chloride; The zirconium source includes one or more of zirconium oxychloride, zirconium nitrate, zirconium carbonate and zirconium ammonia carbonate; The silicon source includes one or more of sodium silicate nonahydrate, ethyl silicate and silica sol; The phosphorus source includes triethyl phosphate and / or butyl phosphate; The lanthanum source includes lanthanum carbonate and / or lanthanum nitrate; The magnesium source includes magnesium acetate.

3. The solid electrolyte according to claim 2, characterized in that The molar ratio of the lithium source to the zirconium source is 3:(0.3-2); The molar ratio of the lithium source to the silicon source is: (3-8):2; The molar ratio of the lithium source to the phosphorus source is (1-3.5):

1.

4. The solid electrolyte according to claim 1, characterized in that In step (1), the solvent includes ethanol and / or acetic acid; And / or, the mixing temperature is 20-30° C., and the mixing time is 1-2 h.

5. The solid electrolyte according to claim 1, characterized in that In step (2), the reaction temperature is 50-60° C., and the reaction time is 3-5 h; And / or, in step (3), the microwave heating time is 1-2 hours.

6. The solid electrolyte according to claim 1, characterized in that The method for preparing the solid electrolyte further comprises cleaning, grinding and drying the calcined product.

7. Use of the solid electrolyte according to claim 1 in lithium batteries.

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