Double-halogen-doped halide electrolyte and preparation method thereof

Abstract

The invention discloses a double-halogen-doped halide solid electrolyte and a preparation method thereof, and relates to the technical field of lithium ion batteries. The chemical formula of the double-halogen-doped halide electrolyte is Li3YBraCl6-a-bXb, X is at least one of F or I, a is more than 0 and less than 3, b is more than 0 and less than 3, a + b is less than or equal to 3, and a and b meet the condition that the valence of [BraCl6-a-bNb] is-6. According to the invention, Li3YBr2Cl4 is prepared by adopting a wet chemical method, so that the ionic conductivity of the electrolyte is greatly improved, and lithium ions have richer migration paths in the material; the Li3YBr2Cl4 is subjected to fluorine or iodine doping modification, so that on the premise of maintaining high ionic conductivity, the compatibility of the electrolyte and a lithium metal negative electrode interface is greatly improved, and the reaction between the lithium metal negative electrode and the interface is effectively inhibited, so that the electrolyte can be applied to an all-solid-state battery taking high-energy-density lithium metal as the negative electrode; the method has important significance in improving the energy density of the all-solid-state battery and ensuring the chemical stability and excellent electrical property of the all-solid-state secondary battery.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion batteries, and in particular to a double halogen-doped halide solid electrolyte and a preparation method thereof. Background Art

[0002] Driven by the continuous innovation of global new energy, lithium-ion batteries are widely used in energy storage for electric vehicles and social public utilities based on lithium batteries, but they still face development challenges such as insufficient energy density, safety and stability. All-solid-state batteries are realized by combining non-flammable solid electrolytes with high-voltage positive electrodes such as LiCoO2 and NCM series or high-capacity lithium metal electrodes, and achieve high energy density and good thermal stability in energy storage, thus becoming the focus of research. Solid electrolytes are the core components of all-solid-state batteries, and their ionic conductivity, mechanical deformability and electrochemical stability can directly affect the comprehensive performance of all-solid-state batteries.

[0003] At present, common solid electrolytes are mainly oxides and sulfides. Although oxide electrolytes have good electrochemical stability, they have poor compatibility with metallic lithium, resulting in large interfacial impedance. Although sulfide electrolytes have high ionic conductivity, they easily react with air to generate toxic hydrogen sulfide gas. Halide solid electrolytes have the advantages of excellent deformability, high-voltage positive electrode stability and high lithium ion conductivity and are widely concerned. Considering the high cost-effectiveness of halide solid electrolytes, rare earth elements with abundant stocks, simple preparation and low cost are preferred. Compared with the mechanical ball milling method, the wet chemical method for preparing halide solid electrolytes provides a more efficient, more uniform and more practical possibility for its future industrialization. Therefore, the study of the wet chemical method for preparing Li3YX6 (X=F, Cl, Br and I) halide system has good application prospects. However, there are two problems: First, the ionic conductivity of the halide electrolyte in this system is not high. For example, the ionic conductivity of LYC is 0.345mS cm -1 ; Second, the poor interface between yttrium-based halides and lithium metal electrolytes remains a challenge. Patent CN113363567A discloses a method for preparing halide solid electrolytes by wet chemical method, and improves the halide ion conductivity to a certain extent. Yu et al. (Yu, et al. Superionic Fluorinated Halide Solid Electrolytes for Highly Stable Li-Metal in All-Solid-State Li Batteries. Advanced Energy Materials 2021, 11 (36)) discloses Li3YBr prepared by mechanical ball milling 5.7 F 0.3It has excellent stability to lithium. Unfortunately, there is no wet chemical method to prepare the electrolyte, nor experimental research reports on the conductivity of yttrium-based halide electrolytes and their stability to lithium metal.

[0004] In summary, there is an urgent need to design an electrolyte that can be prepared by wet chemical methods and has the advantages of high ionic conductivity and enhanced stability to lithium metal, so that it can solve the problems of poor compatibility with lithium metal, complex preparation and high cost. Summary of the invention

[0005] The purpose of the present invention is to propose a double halogen-doped halide electrolyte and a preparation method thereof in view of the problems existing in the background technology. The halide electrolyte of the present invention has a high room temperature ionic conductivity (≥2.38mS / cm), so that lithium ions have a richer migration path in the material; and the electrolyte interface has excellent lithium metal negative electrode interface compatibility, which can inhibit the reaction between the lithium metal negative electrode and the interface. In addition, the double halogen-doped halide solid electrolyte has good economy and environmental friendliness, and can be mass-produced by wet chemical method without the use of high-cost and low-abundance metal materials. It is expected to promote the large-scale preparation of low-cost solid electrolytes and high-capacity all-solid-state batteries, and promote the commercial application of all-solid-state battery technology.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0007] A double halogen-doped halide electrolyte with the chemical formula Li3YBr a Cl 6-a-b X b , wherein X is at least one of F or I, 0<a<3, 0<b<3, a+b≤3, a and b satisfy [Br a Cl 6-a-b N b ]The chemical valence is -6.

[0008] Preferably, the chemical formula of the double halogen-doped halide electrolyte is Li3YBr a Cl 6-a-b F b 、Li3YBr a Cl 6-a-b I b or Li3YBr a Cl 6-a-b (FI) b .

[0009] Furthermore, the surface of the double halogen-doped halide electrolyte is a microstructure with non-oriented stripes, the stripe length is 1 μm to 2.4 μm, and the stripe spacing is 40 nm to 60 nm.

[0010] Furthermore, the anion arrangement of the double halogen-doped halide electrolyte is hexagonal close packing or cubic close packing.

[0011] A method for preparing a double halogen-doped halide electrolyte comprises the following steps:

[0012] S1. Add YCl3·6H2O to the ethanol solvent of NH4Cl, move to a magnetic heating stirring platform and mix them at 40-60°C and 500-800 rpm / min to obtain solution A;

[0013] S2. Add LiCl and LiBr to deionized water, move to a magnetic heating stirring platform and mix them at 40-60°C and 500-800 rpm / min to obtain solution B; mix solution A and solution B to obtain solution C;

[0014] S3. Add 10% NH4Cl to solution C. -5 mol / L LiOH solution, adjust the pH to 7-8, then add LiF or LiI, mix well, and obtain solution D;

[0015] S4. The solution D was moved to a vacuum drying oven and vacuum dried at 85°C to 120°C for 24 to 72 hours to obtain a precursor block;

[0016] S5. The precursor block is ground into powder and pressed into a disc under a pressure of 2 to 4 tons;

[0017] S6. Heat-treating the wafer in an argon environment at 350-600° C. for 5 hours to obtain the halide electrolyte.

[0018] Further, when NH4Cl, YCl3·6H2O, LiCl, LiBr, and LiF are used as raw materials, the molar ratio of NH4Cl, YCl3·6H2O, LiCl, LiBr, and LiF is 3:1:1-x:2:x, 0<x<1;

[0019] When NH4Cl, YCl3·6H2O, LiCl, LiBr and LiI are used as raw materials, the molar ratio of NH4Cl, YCl3·6H2O, LiCl, LiBr and LiI is 3:1:1-x:2:x, 0<x<1.

[0020] Furthermore, in step S3, LiF and LiI can be added simultaneously. In this case, the raw material in S2 is only LiBr, and the molar ratio of NH4Cl, YCl3·6H2O, LiBr, LiF and LiI is 3:1:y:x:3-xy, 0<x<1, 1<y<2.

[0021] The present invention also provides the use of the double halogen-doped halide electrolyte in an electrolyte or electrode interface additive in a solid-state secondary battery.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. The present invention provides a double halogen-doped halide electrolyte and a preparation method thereof, which uses a wet chemical method to prepare Li3YBr2Cl4, greatly improving the ionic conductivity of the electrolyte (3.04mS cm -1 ), so that lithium ions have more abundant migration paths in the material; Li3YBr2Cl4 was modified by fluorine or iodine doping, while maintaining high ionic conductivity (2.38mScm -1 ) under the premise of greatly improving the compatibility of the electrolyte with the lithium metal negative electrode interface, effectively inhibiting the reaction between the lithium metal negative electrode and the interface, so that it can be used in all-solid-state batteries with high energy density lithium metal as the negative electrode, which is of great significance for improving the energy density of all-solid-state batteries and ensuring the chemical stability and excellent electrical performance of all-solid-state secondary batteries.

[0024] 2. The present invention provides a double halogen-doped halide electrolyte and a preparation method thereof. The process is simple, and the wet chemical method is conducive to the large-scale preparation of materials, so that they are no longer limited to the glove box environment, and have good economy and environmental friendliness; only low-cost and high-abundance metal materials such as Y are used, and the cost is low. It is expected to promote the large-scale preparation of low-cost solid electrolytes and high-capacity all-solid-state batteries, and promote the commercial application of all-solid-state battery technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 For the preparation of Li3YBr2Cl 3.7 F 0.3 XRD pattern of Li3YBr2Cl4 halide solid electrolyte (a) and local magnification (b and c);

[0026] Figure 2 For the preparation of Li3YBr2Cl 3.7 F 0.3 SEM micromorphology of halide solid electrolyte;

[0027] Figure 3 For the preparation of Li3YBr2Cl 3.7 F 0.3 Lithium-ion battery with halide solid electrolyte 0.1 mA cm -2 Constant current cycle test diagram (a) and partial enlarged diagram (b);

[0028] Figure 4 Li3YBr2Cl obtained in Example 13.7 F 0.3 The impedance test curve obtained after sintering at annealing temperature with Li3YBr2Cl4 solid electrolyte material. DETAILED DESCRIPTION

[0029] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several variations and improvements may be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0030] Example 1

[0031] This embodiment provides a halide solid electrolyte, whose chemical formula is Li3YBr2Cl 3.7 F 0.3 , the preparation method is as follows:

[0032] S1: In a glove box, first weigh 1 mol YCl3·6H2O, 0.7 mol LiCl, 3 mol NH4Cl, 2 mol LiBr and 0.3 mol LiF in molar ratios for later use, transfer the weighed NH4Cl to a beaker and add anhydrous ethanol until it is fully dissolved, then add the weighed YCl3·6H2O to the beaker and move it to a magnetic heating stirring platform, stir at 40°C and 600 r / min for 30 minutes to obtain solution A;

[0033] S2: Add LiCl and LiBr to deionized water solvent, move to a magnetic heating stirring platform and mix them evenly at 40°C and 600 rpm / min to obtain solution B; add solution A to solution B and mix evenly to obtain solution C;

[0034] S3: Add a 10% solution into solution C. -5 mol / L LiOH solution, adjust the pH to 7-8, add weighed LiF, and stir at 600 r / min for 30 minutes until the mixture is uniformly mixed to obtain solution D;

[0035] S4: moving solution D to a vacuum drying oven and vacuum drying it at 120° C. for 48 hours to obtain a precursor block;

[0036] S5: grinding the precursor block into powder and pressing it into a block under a pressure of 2 tons;

[0037] S6: heat-treating the block at 450° C. for 5 hours to obtain the halide solid electrolyte.

[0038] Example 2

[0039] The difference between Example 2 and Example 1 is that the annealing temperature of step S6 is adjusted to 500° C., and the remaining steps are the same as those of Example 1.

[0040] Example 3

[0041] The difference between Example 3 and Example 1 is that the annealing temperature of step S6 is adjusted to 550° C., and the remaining steps are the same as those of Example 1.

[0042] Example 4

[0043] This embodiment provides a halide solid electrolyte, whose chemical formula is Li3YBr2Cl3I1, and the preparation method is as follows:

[0044] S1: In a glove box, weigh 1 mol YCl3·6H2O, 3 mol NH4Cl, 2 mol LiBr and 1 mol LiI in molar ratio for later use, transfer the weighed NH4Cl to a beaker and add anhydrous ethanol until it is fully dissolved, then add the weighed YCl3·6H2O to the beaker and move it to a magnetic heating stirring platform, stir at 40°C and 600 r / min for 30 minutes to obtain solution A;

[0045] S2: Add LiCl and LiBr to deionized water solvent, move to a magnetic heating stirring platform and mix them evenly at 40°C and 600 rpm / min to obtain solution B; add solution A to solution B and mix evenly to obtain solution C;

[0046] S3: Add a concentration of 10 -5 mol / L LiOH solution, adjust the pH to 7-8, add weighed LiI, and stir at 600 r / min for 30 minutes until the mixture is uniformly mixed to obtain solution D;

[0047] S4: moving solution D to a vacuum drying oven and vacuum drying it at 120° C. for 48 hours to obtain a precursor block;

[0048] S5: Grinding the precursor block into powder and pressing it into a block under a pressure of 2 tons;

[0049] S6: heat-treating the block at 450° C. for 5 hours to obtain the halide solid electrolyte.

[0050] Example 5

[0051] Compared with Example 4, Example 5 differs in that the annealing temperature of step S6 is adjusted to 500° C., and the remaining steps are the same as those of Example 4.

[0052] Example 6

[0053] Compared with Example 4, Example 6 differs in that the annealing temperature of step S6 is adjusted to 550° C., and the remaining steps are the same as those of Example 4.

[0054] Example 7

[0055] This embodiment provides a halide solid electrolyte, whose chemical formula is Li3YBr2Cl 3.9 F 0.1 , the preparation method is as follows:

[0056] S1: In a glove box, weigh 1 mol YCl3·6H2O, 0.9 mol LiCl, 3 mol NH4Cl, 2 mol LiBr and 0.1 mol LiF in molar ratios for later use, transfer the weighed NH4Cl to a beaker and add anhydrous ethanol until it is fully dissolved, then add the weighed YCl3·6H2O to the beaker and move it to a magnetic heating stirring platform, stir at 40°C and 600 r / min for 30 minutes to obtain solution A;

[0057] S2: Add LiCl and LiBr to deionized water solvent, move to a magnetic heating stirring platform and mix them evenly at 40°C and 600 rpm / min to obtain solution B; add solution A to solution B and mix evenly to obtain solution C;

[0058] S3: Add a concentration of 10 -5 mol / L LiOH solution, adjust the pH to 7-8, add weighed LiF, and stir at 600 r / min for 30 minutes until the mixture is uniformly mixed to obtain solution D;

[0059] S4: moving solution D to a vacuum drying oven and vacuum drying it at 120° C. for 48 hours to obtain a precursor block;

[0060] S5: Grinding the precursor block into powder and pressing it into a block under a pressure of 2 tons;

[0061] S6: heat-treating the block at 450° C. for 5 hours to obtain the halide solid electrolyte.

[0062] Example 8

[0063] This embodiment provides a halide solid electrolyte, whose chemical formula is Li3YBr2Cl 3.5 F 0.5 , the preparation method is as follows:

[0064] S1: In a glove box, first weigh 1 mol YCl3·6H2O, 0.5 mol LiCl, 3 mol NH4Cl, 2 mol LiBr and 0.5 mol LiF in molar ratios for later use, transfer the weighed NH4Cl to a beaker and add anhydrous ethanol until it is fully dissolved, then add the weighed YCl3·6H2O to the beaker and move it to a magnetic heating stirring platform, stir at 40°C and 600 r / min for 30 minutes to obtain solution A;

[0065] S2: Add LiCl and LiBr to deionized water solvent, move to a magnetic heating stirring platform and mix them evenly at 40°C and 600 rpm / min to obtain solution B; add solution A to solution B and mix evenly to obtain solution C;

[0066] S3: Add a concentration of 10 -5 mol / L LiOH solution, adjust the pH to 7-8, add weighed LiF, and stir at 600 r / min for 30 minutes until the mixture is uniformly mixed to obtain solution D;

[0067] S4: moving solution D to a vacuum drying oven and vacuum drying it at 120° C. for 48 hours to obtain a precursor block;

[0068] S5: Grinding the precursor block into powder and pressing it into a block under a pressure of 2 tons;

[0069] S6: heat-treating the block at 450° C. for 5 hours to obtain the halide solid electrolyte.

[0070] Example 9

[0071] This embodiment provides a halide solid electrolyte, whose chemical formula is Li3YBr2Cl 3.3 F 0.7 , the preparation method is as follows:

[0072] S1: In a glove box, first weigh 1 mol YCl3·6H2O, 0.3 mol LiCl, 3 mol NH4Cl, 2 mol LiBr and 0.7 mol LiF in molar ratios for later use, transfer the weighed NH4Cl to a beaker and add anhydrous ethanol until it is fully dissolved, then add the weighed YCl3·6H2O to the beaker and move it to a magnetic heating stirring platform, stir at 40°C and 600 r / min for 30 minutes to obtain solution A;

[0073] S2: Add LiCl and LiBr to deionized water solvent, move to a magnetic heating stirring platform and mix them evenly at 40°C and 600 rpm / min to obtain solution B; add solution A to solution B and mix evenly to obtain solution C;

[0074] S3: Add a concentration of 10 -5 mol / L LiOH solution, adjust the pH to 7-8, add weighed LiF, and stir at 600 r / min for 30 minutes until the mixture is uniformly mixed to obtain solution D;

[0075] S4: moving solution D to a vacuum drying oven and vacuum drying it at 120° C. for 48 hours to obtain a precursor block;

[0076] S5: Grinding the precursor block into powder and pressing it into a block under a pressure of 2 tons;

[0077] S6: heat-treating the block at 450° C. for 5 hours to obtain the halide solid electrolyte.

[0078] Example 10

[0079] This embodiment provides a halide solid electrolyte, whose chemical formula is Li3YBr2Cl3F1, and the preparation method is as follows:

[0080] S1: In a glove box, weigh 1 mol YCl3·6H2O, 3 mol NH4Cl, 2 mol LiBr and 1 mol LiF in molar ratios for later use, transfer the weighed NH4Cl to a beaker and add anhydrous ethanol until it is fully dissolved, then add the weighed YCl3·6H2O to the beaker and move it to a magnetic heating stirring platform, stir at 40°C and 600 r / min for 30 minutes to obtain solution A;

[0081] S2: Add LiCl and LiBr to deionized water solvent, move to a magnetic heating stirring platform and mix them evenly at 40°C and 600 rpm / min to obtain solution B; add solution A to solution B and mix evenly to obtain solution C;

[0082] S3: Add a concentration of 10 -5 mol / L LiOH solution, adjust the pH to 7-8, add weighed LiF, and stir at 600 r / min for 30 minutes until the mixture is uniformly mixed to obtain solution D;

[0083] S4: moving solution D to a vacuum drying oven and vacuum drying it at 120° C. for 48 hours to obtain a precursor block;

[0084] S5: Grinding the precursor block into powder and pressing it into a block under a pressure of 2 tons;

[0085] S6: heat-treating the block at 450° C. for 5 hours to obtain the halide solid electrolyte.

[0086] Other embodiments will not be described in detail.

[0087] It should be noted that the present invention is not limited to the above-mentioned specific embodiments, and those skilled in the art may make various variations or modifications within the scope of the claims, which will not affect the essential content of the present invention.

Claims

1. A double halogen-doped halide electrolyte, characterized in that: The chemical formula of the halide electrolyte is Li3YBr a Cl 6-a-b X b , wherein X is at least one of F or I, 0<a<3, 0<b<3, a+b≤3.

2. The double halogen-doped halide electrolyte according to claim 1, characterized in that: The surface of the double halogen-doped halide electrolyte is a microstructure with non-oriented stripe arrangement, the stripe length is 1 μm to 2.4 μm, and the stripe spacing is 40 nm to 60 nm.

3. The double halogen-doped halide electrolyte according to claim 1, characterized in that: The anion arrangement mode of the double halogen-doped halide electrolyte is hexagonal close packing or cubic close packing.

4. A method for preparing a double halogen-doped halide electrolyte, characterized in that: The following steps are involved: S1. Add YCl3·6H2O to the ethanol solvent of NH4Cl, stir and mix well to obtain solution A; S2. Add LiCl and LiBr to deionized water, stir and mix well to obtain solution B; mix solution A and solution B well to obtain solution C; S3. LiOH solution was added dropwise to solution C, the pH was adjusted to 7-8, and then LiF or LiI was added and mixed to obtain solution D; S4. The solution D is vacuum dried at 85°C to 120°C to obtain a precursor block; S5. Grinding the precursor block into powder and pressing into a mold; S6. heat-treating the formed blank at 350-600° C. in an argon environment to obtain the halide electrolyte.

5. The method for preparing a double halogen-doped halide electrolyte according to claim 4, characterized in that: When NH4Cl, YCl3·6H2O, LiCl, LiBr, and LiF are used as raw materials, the molar ratio of NH4Cl, YCl3·6H2O, LiCl, LiBr, and LiF is 3:1:1-x:2:x, 0<x<1; When NH4Cl, YCl3·6H2O, LiCl, LiBr and LiI are used as raw materials, the molar ratio of NH4Cl, YCl3·6H2O, LiCl, LiBr and LiI is 3:1:1-x:2:x, 0<x<1.

6. The method for preparing a double halogen-doped halide electrolyte according to claim 4, characterized in that: In step S3, LiF and LiI are added simultaneously. At this time, the raw material in S2 is only LiBr, and the molar ratio of NH4Cl, YCl3·6H2O, LiBr, LiF and LiI is 3:1:y:x:3-xy, 0<x<1, 1<y<2.

7. Use of the double halogen-doped halide electrolyte according to any one of claims 1 to 3 as an electrolyte or electrode interface additive in a solid-state secondary battery.

8. Use of the double halogen-doped halide electrolyte prepared by the method according to any one of claims 4 to 6 as an electrolyte or electrode interface additive in a solid-state secondary battery.

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