A microcrystalline / amorphous halide solid electrolyte, its preparation method and application

Abstract

This invention relates to a microcrystalline / amorphous halide solid electrolyte, which is a doped and modified lithium zirconium halide with the chemical formula Li. x Zr 1‑y‑z Ta y M1 z X u O δ In the formula, M1 is any one of Nb, Hf, Mo, and W, X is at least one of Cl, Br, and I, 1.4≤x≤4, 0.3≤y≤0.7, 0.1≤z≤0.2, 4<u≤5, and 0.7≤δ≤2. The two high-valence cations and the anion O in this invention... 2‑ The synergistic effect of doping makes it easier for lithium ions to migrate in the crystal lattice, reduces the migration distance, and transforms the original trigonal lithium zirconium-based halide into an amorphous structure with a small amount of microcrystals, thereby improving its ionic conductivity. The resulting microcrystalline / amorphous halide solid electrolyte has a room temperature ionic conductivity of over 2.5 mS / cm.

Description

Technical Field

[0001] This invention belongs to the field of solid-state battery technology, specifically relating to a microcrystalline / amorphous halide solid electrolyte, its preparation method, and its application. Background Technology

[0002] All-solid-state batteries, as the next-generation energy storage technology, hold promise for solving the safety issues of commercial lithium-ion batteries and further improving their energy density. As the core of all-solid-state batteries, the performance of the solid electrolyte directly affects their electrochemical performance. Amorphous solid electrolytes possess good flexibility, are easy to manufacture, and exhibit isotropic ionic conductivity; however, their conductivity above ground is typically low. Crystalline solid electrolytes with long-range ordered structures demonstrate continuous and rapid lithium-ion conduction capabilities, but suffer from low oxidation stability and poor interfacial compatibility with anode (lithium metal) and cathode materials (lithium iron phosphate, lithium cobalt oxide). Combining the advantages of both solid electrolytes would be a promising strategy for preparing high-performance solid electrolytes. Among common crystalline solid electrolytes, lithium zirconium chloride (Li₂ZrCl₆) has attracted considerable attention due to its low price and high oxidation resistance; however, its room-temperature ionic conductivity of less than 1 mS / cm limits its application. Therefore, improving the ionic conductivity of lithium zirconium halides is of great significance.

[0003] To effectively improve the ionic conductivity of zirconium-based halide electrolytes, heterovalent cation doping strategies are widely used. Existing technologies generally employ cations with valences lower than +4 for doping because cations with valences higher than +4 replace Zr. 4+ This will cause the lithium concentration in the lattice to decrease, which will be detrimental to electrochemical performance. Tian et al. (J. Energy Chem. 79(2023) 348-356) reported that by appropriately increasing the Mg content... 2+ and Zn 2+ Heterovalent doping of Li₂ZrCl₆ can effectively improve ionic conductivity, among which Li 2.1 Zr 0.95 Mg 0.05 Cl6 exhibits a value of 0.62 mS / cm. Similarly, Jung et al. (Adv. Energy Mater. 11(2021) 2003 190) used Fe 3+ Doping of zirconium-based halides with elements effectively increased the ionic conductivity from 0.4 mS / cm to 0.98 mS / cm. Xie et al. (Chin. Chem. Lett. 33(2022) 4635-4639) successfully modified In... 3+ Doping was performed on the Li₂ZrCl₆ crystal structure, and the highest ionic conductivity (1.08 mS / cm) was obtained at a doping level of 0.25. Previous studies have used cation doping with valence states lower than Zr. 4+Research on high-valence cation doping is relatively limited. Furthermore, the anion F... -1 Doped and modified zirconium-based halide electrolytes have also been studied, but their low ionic conductivity remains unsatisfactory. Summary of the Invention

[0004] In view of the problem that the room temperature ionic conductivity of solid electrolytes in the prior art is low, the present invention provides a microcrystalline / amorphous halide solid electrolyte and its preparation method to solve the above problems.

[0005] The present invention achieves the above objectives using the following technical solutions:

[0006] A microcrystalline / amorphous halide solid electrolyte, which is a doped and modified lithium zirconium halide with the chemical formula Li. x Zr 1-y- z Ta y M1 z X u O δ In the formula, M1 is any one of Nb, Hf, Mo, and W, X is at least one of Cl, Br, and I, 1.4≤x≤4, 0.3≤y≤0.7, 0.1≤z≤0.2, 4<u≤5, and 0.7≤δ≤2.

[0007] Preferably, M1 is Nb or Hf; X is Cl.

[0008] Preferably, 2.4≤x≤3.2, 0.3≤y≤0.5, and 1.2≤δ≤1.6.

[0009] In a preferred embodiment of the present invention, the microcrystalline / amorphous halide solid electrolyte is Li. 3.2 Zr 0.4 Ta 0.5 Nb 0.1 Cl 4.6 O 1.6 .

[0010] Furthermore, the mass fraction of the microcrystalline portion in the microcrystalline / amorphous halide solid electrolyte is 5% to 10%.

[0011] Furthermore, the grain size of the microcrystalline portion in the microcrystalline / amorphous halide solid electrolyte is 10 nm to 200 nm.

[0012] This invention also provides a method for preparing the above-mentioned microcrystalline / amorphous halide solid electrolyte, which is a high-energy ball milling method, including the following steps:

[0013] (S1) Press Li x Zr 1-y-z Ta y M1 z Xu O δ According to the stoichiometric ratio, a certain amount of lithium source, zirconium source, tantalum source and M1 source are mixed to obtain a mixture;

[0014] (S2) The mixture and grinding balls were placed in a ball mill jar and subjected to high-energy ball milling under an inert atmosphere to obtain Li. x Zr 1-y-z Ta y M1 z X u O δ Microcrystalline / amorphous halide solid electrolytes.

[0015] Further, in step (S1), the lithium source is lithium oxide or lithium halide; the zirconium source is zirconium halide; the tantalum source is tantalum halide; and the M1 source is a halide of M1.

[0016] Further, in step (S1), the mixing is done by manual grinding for 5 to 20 minutes.

[0017] Further, in step (S2), the grinding balls are zirconia grinding balls with a diameter of 4-8 mm; the mass ratio of the mixture to the grinding balls is 1:(10-30), preferably 1:(20-30); the inert atmosphere is nitrogen and / or argon; the conditions for the high-energy ball milling treatment are: ball milling jar speed 300-800 rpm; ball milling time 12-36 h.

[0018] Furthermore, after high-energy ball milling, step (S2) also includes: annealing the material after high-energy ball milling under an inert atmosphere, wherein the annealing conditions are: temperature 100-200℃, time 2-5h.

[0019] The present invention also provides the application of the aforementioned microcrystalline / amorphous halide solid electrolyte in all-solid-state lithium batteries.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] (1) In this invention, two types of cation and anion co-doped modified lithium zirconium halide are used, with the anion being O 2- One of the two cations is Ta 5+ Another one is Hf 4+ 、Nb 5+ Mo 5+ or W 6+In this invention, both cations used as dopants have a valence state higher than or equal to +4. The higher valence cations bind more strongly to the more electronegative anions, weakening the binding energy between lithium ions and anions, which facilitates better lithium ion migration within the crystal lattice. Furthermore, the higher valence cations selected in this invention have smaller ionic radii, which, when doped into zirconium-based halide crystal structures, reduce the lithium ion migration distance, thereby improving the ionic conductivity of the material. In addition, typically, cations with a valence higher than +4 replace Zr... 4+ This would adjust the lithium concentration in the crystal lattice towards a lower level, but the inventors unexpectedly discovered that the simultaneous co-doping of two cations with a valence of +4 or higher in this invention, along with the simultaneous generation of anions (O),... 2- Doping does not shift the lithium concentration in the crystal lattice towards lower levels. That is, the two cations and the anion O in higher valence states... 2- The synergistic effect of doping makes lithium ions migrate more easily in the crystal lattice, reduces the migration distance, and does not reduce the lithium concentration in the crystal lattice, thereby improving its ionic conductivity. Meanwhile, the two cations and anions of this invention, O... 2- Co-doping transforms the originally trigonal lithium zirconium-based halide into an amorphous structure with a small amount of microcrystals, reducing its crystallinity and further improving the ionic conductivity of the material. The final product has the chemical formula Li. x Zr 1-y-z Ta y M1 z X u O δ The room temperature ionic conductivity of the microcrystalline-amorphous halide solid electrolyte is above 2.5 mS / cm.

[0022] (2) The room temperature ionic conductivity of the microcrystalline-amorphous halide solid electrolyte of the present invention is significantly improved. When the metal lithium battery is assembled with the existing 4V-level cathode material, it shows higher discharge specific capacity and excellent rate performance. At the same time, the solid electrolyte supports the battery to charge and discharge normally at -20℃. Attached Figure Description

[0023] Figure 1 The XRD patterns are of the solid electrolytes prepared in Examples 1-3 and Comparative Example 1.

[0024] Figure 2 The solid electrolyte Li prepared in Example 1 3.2 Zr 0.4 Ta 0.5 Nb 0.1 Cl 4.6 O 1.6 The discharge curves of the assembled battery at different rates at room temperature and -20°C are shown. Figure 2(a) shows the discharge curves at different rates at room temperature, and (b) shows the discharge curves at different rates at -20℃.

[0025] Figure 3 To obtain the discharge curves of the solid electrolyte-assembled battery for Comparative Example 1 at different rates at room temperature and -20°C, the following data were obtained. Figure 3 (a) shows the discharge curves at different rates at room temperature, and (b) shows the discharge curves at different rates at -20℃. Detailed Implementation

[0026] The present invention will be further described below with reference to specific embodiments, but the present invention is not limited to the following embodiments.

[0027] Unless otherwise specified, the experimental methods described in the following examples are conventional methods; unless otherwise specified, the reagents and materials are commercially available.

[0028] Example 1---Preparation of microcrystalline / amorphous halide solid electrolyte Li 3.2 Zr 0.4 Ta 0.5 Nb 0.1 Cl 4.6 O 1.6 (x=3.2, y=0.5, z=0.1, u=4.6, δ=1.6)

[0029] (S1) Press Li 3.2 Zr 0.4 Ta 0.5 Nb 0.1 Cl 4.6 O 1.6 According to the stoichiometric ratio of each element, a certain amount of Li2O, ZrCl4, TaCl5 and NbCl5 were placed in a mortar and manually ground for 10 minutes to obtain a mixture;

[0030] (S2) The mixture and 5mm diameter zirconium grinding balls were placed in a ball mill jar at a mass ratio of 1:25. High-energy ball milling was performed in a planetary ball mill under nitrogen protection. The ball mill jar rotated at 500 rpm, using alternating forward and reverse rotation. For every 15 minutes of forward ball milling, followed by 15 minutes of reverse ball milling, this cycle was repeated, controlling the total ball milling time to 24 hours. The resulting product had the chemical formula Li. 3.2 Zr 0.4 Ta 0.5 Nb 0.1 Cl 4.6 O 1.6 Microcrystalline / amorphous halide solid electrolytes.

[0031] Example 2---Preparation of microcrystalline / amorphous halide solid electrolyte Li 1.4 Zr0.6 Ta 0.3 Nb 0.1 Cl 4.4 O 0.7

[0032] The rest is the same as in Example 1, except that the proportions of Li, Zr, Ta, MI (Nb), and X (Cl) in the chemical formula are different: x = 1.4, y = 0.3, z = 0.1, u = 4.4, and δ = 0.7. The final product is a compound with the chemical formula Li. 1.4 Zr 0.6 Ta 0.3 Nb 0.1 Cl 4.4 O 0.7 Microcrystalline / amorphous halide solid electrolytes.

[0033] Example 3---Preparation of microcrystalline / amorphous halide solid electrolyte Li 2.4 Zr 0.5 Ta 0.3 Nb 0.2 Cl 4.5 O 1.2

[0034] The rest is the same as in Example 1, except that the proportions of Li, Zr, Ta, MI (Nb), and X (Cl) in the chemical formula are different: x = 2.4, y = 0.3, z = 0.2, u = 4.5, and δ = 1.2. The final product is a compound with the chemical formula Li. 2.4 Zr 0.5 Ta 0.3 Nb 0.2 Cl 4.5 O 1.2 Microcrystalline / amorphous halide solid electrolytes.

[0035] Example 4---Preparation of microcrystalline / amorphous halide solid electrolyte Li 3.2 Zr 0.3 Ta 0.5 Nb 0.2 Cl 4.7 O 1.6

[0036] The rest is the same as in Example 1, except that the proportions of Li, Zr, Ta, MI (Nb), and X (Cl) in the chemical formula are different: x = 3.2, y = 0.5, z = 0.2, u = 4.7, and δ = 1.6. The final product is a compound with the chemical formula Li. 3.2 Zr 0.3 Ta 0.5 Nb 0.2 Cl 4.7 O 1.6 Microcrystalline / amorphous halide solid electrolytes.

[0037] Example 5---Preparation of microcrystalline / amorphous halide solid electrolyte Li4Zr 0.1 Ta 0.7 Nb 0.2 Cl 4.9 O2

[0038] The rest is the same as in Example 1, except that the proportions of Li, Zr, MI (Nb), and X (Cl) in the chemical formula are different: x = 4, y = 0.7, z = 0.2, u = 4.9, and δ = 2. The final product has the chemical formula Li4Zr. 0.1 Ta 0.7 Nb 0.2 Cl 4.9 O2 microcrystalline / amorphous halide solid electrolyte.

[0039] Example 6---Preparation of microcrystalline / amorphous halide solid electrolyte Li 3.2 Zr 0.4 Ta 0.5 Hf 0.1 Cl 4.5 O 1.6

[0040] The rest is the same as in Example 1, except that the type of M1 in the chemical formula is different; M1 is Hf. Accordingly, in step (S1), HfCl4 is used instead of NbCl5, and the final product is Li. 3.2 Zr 0.4 Ta 0.5 Hf 0.1 Cl 4.5 O 1.6 Microcrystalline / amorphous halide solid electrolytes.

[0041] Example 7---Preparation of microcrystalline / amorphous halide solid electrolyte Li 3.2 Zr 0.4 Ta 0.5 Mo 0.1 Cl 4.6 O 1.6

[0042] The rest is the same as in Example 1, except that the type of M1 in the chemical formula is different. M1 is Mo, and correspondingly, MoCl5 is used instead of NbCl5 in step (S1), ultimately yielding a product with the chemical formula Li. 3.2 Zr 0.4 Ta 0.5 Mo 0.1 Cl 4.6 O 1.6 Microcrystalline / amorphous halide solid electrolytes.

[0043] Example 8---Preparation of microcrystalline / amorphous halide solid electrolyte Li3.2 Zr 0.4 Ta 0.5 W 0.1 Br 4.7 O 1.6

[0044] The rest is the same as in Example 1, except that the types of M1 and X in the chemical formula are different. M1 is W and X is Br. Accordingly, in step (S1), ZrBr4 is used instead of ZrCl4 and TaBr5 is used instead of TaCl. 5， By replacing NbCl5 with WBr6, the final product with the chemical formula Li was obtained. 3.2 Zr 0.4 Ta 0.5 W 0.1 Br 4.7 O 1.6 Microcrystalline / amorphous halide solid electrolytes.

[0045] Comparative Example 1

[0046] The rest is the same as in Example 1. In step (S1), according to the stoichiometric ratio of each element corresponding to the chemical formula Li2ZrCl6, a certain amount of LiCl and ZrCl4 are put into a mortar and manually ground for 10 minutes to obtain a mixture. Step (S2) is the same as in Example 1, and the solid electrolyte with the chemical formula Li2ZrCl6 is obtained.

[0047] Comparative Example 2

[0048] The rest is the same as in Example 1, except that Zn is used instead of Ta, that is, ZnCl2 is used instead of TaCl5 in step (S1) to finally obtain Li 3.2 Zr 0.4 Zn 0.5 Nb 0.1 Cl 3.1 O 1.6 Solid electrolyte.

[0049] Comparative Example 3

[0050] The rest is the same as in Example 1, except that Nb is not included in the chemical formula, and correspondingly, in step (S1) the chemical formula Li is used instead. 3.2 Zr 0.5 Ta 0.5 Cl 7.7 A certain amount of LiCl, ZrCl4, and TaCl5 were placed in a mortar and manually ground for 10 minutes to obtain a mixture; finally, a compound with the chemical formula Li was obtained. 3.2 Zr 0.5 Ta 0.5 Cl 7.7 Solid electrolyte.

[0051] Testing and Analysis

[0052] I. Structural Performance

[0053] X-ray diffraction tests were performed on the solid electrolytes prepared in the examples and comparative examples. The XRD patterns of the solid electrolytes prepared in Examples 1-3 and Comparative Example 1 are shown below. Figure 1 As shown in the figure, Comparative Example 1 exhibits a clear trigonal structure (hcp), with the space group being... In Examples 1-3, through co-doping with two cations and anions, the original trigonal structure diffraction peaks essentially disappeared without the appearance of any new, stronger diffraction peaks, instead exhibiting the characteristics of an amorphous structure. Furthermore, at 30... o and 35 o Weak diffraction peaks are observed to varying degrees on both sides. Comparison with the PDF standard card confirms that these are diffraction peaks of LiCl microcrystals. Similarly, at 32... o Weak diffraction peaks also appeared on the left and right sides, which are diffraction peaks of Li2O microcrystals. This indicates that the anion and cation co-doping strategy of the present invention can transform the original hcp structure of Li2ZrCl6 material into a near-amorphous structure, and the amorphous structure contains trace amounts of LiCl and Li2O crystals. The mass fraction of microcrystals in Examples 1-3 was calculated to be between 5% and 10% by the external standard method. This halide electrolyte with a special structure may improve its electrochemical performance.

[0054] II. Electrochemical Performance

[0055] (1) Conductivity test: The conductivity of the solid electrolytes prepared in the examples and comparative examples was tested. The method was as follows: under an environment with a water content of less than 50 ppm, 60 mg of the above solid electrolyte powder was accurately weighed and placed into a solid electrolyte test mold. A pressure of 250 MPa was applied externally for tableting. Electrochemical impedance spectroscopy was performed using an electrochemical workstation by cold pressing. The test results are shown in Table 1.

[0056] Table 1 Conductivity Test

[0057]

[0058]

[0059] As can be seen from Table 1, the microcrystalline / amorphous halide solid electrolyte Li prepared in the embodiments of the present invention... x Zr 1-y- z Ta y M1 z X u O δThe room temperature ionic conductivity of the sample was significantly higher than that of the control sample, both exceeding 2.5 mS / cm.

[0060] (2) Rate Performance Test: The solid electrolytes prepared in the examples and comparative examples were used in lithium batteries. The assembly process was as follows: In an environment with a water content of less than 50 ppm, 60 mg of solid electrolyte was accurately weighed and placed into a solid battery mold with a diameter of 10 mm. The mold was pressed with a pressure of 1 ton for 2 minutes. Then, 5 mg of composite positive electrode was evenly spread on one side of the solid electrolyte and pressed with a pressure of 2 tons for 2 minutes. The composite positive electrode material was obtained by uniformly mixing single-crystal NCM811 and solid electrolyte at a mass ratio of 7:3. The solid battery mold was then inverted, and a layer of 40 mg of Li6PS5Cl electrolyte was spread on the other side of the solid electrolyte and pressed with a pressure of 2 tons for 10 minutes. Finally, indium foil and lithium foil with diameters of 10 mm and thicknesses of 100 μm and 30 μm, respectively, were attached to one side of the Li6PS5Cl electrolyte and pressed with a pressure of 0.5 tons. The resulting battery underwent a rate performance test at a pressure of 100 MPa, with a charge / discharge voltage range of 2.3-3.7 V vs. Li. + / LiIn.

[0061] Solid electrolyte Li prepared in Example 1 3.2 Zr 0.4 Ta 0.5 Nb 0.1 Cl 4.6 O 1.6 The discharge curves of the assembled battery at different rates at room temperature and -20°C are shown below. Figure 2 As shown, where Figure 2 (a) shows the discharge curves at different discharge rates at room temperature. Figure 2 (b) Discharge curves at different rates at -20°C. The discharge curves of the solid electrolyte-assembled battery obtained in Comparative Example 1 at different rates at room temperature and -20°C are shown below. Figure 3 As shown, where Figure 3 (a) shows the discharge curves at different discharge rates at room temperature. Figure 3 (b) shows the discharge curves at different rates at -20℃.

[0062] The discharge specific capacity of each embodiment and comparative example at different rates at room temperature and -20°C is shown in Table 2.

[0063] Table 2 Discharge capacity at different rates

[0064]

[0065] As can be seen from Table 2, the chemical formula Li obtained using the examples is... x Zr 1-y-z Ta yM1 z X u O δ Solid-state mold batteries assembled with microcrystalline-amorphous halide solid electrolytes exhibit higher discharge specific capacity and excellent rate performance; at the same time, the solid electrolyte supports normal charging and discharging of the battery at -20℃.

[0066] The above specific embodiments are merely illustrative of the invention and do not represent a limitation thereof. Those skilled in the art will recognize that other variations of the specific structure of this invention are possible.

Claims

1. A microcrystalline / amorphous halide solid electrolyte, which is a doped and modified lithium zirconium halide, characterized in that, Its chemical formula is Li 3.2 Zr 0.4 Ta 0.5 Nb 0.1 Cl 4.6 O 1.6 Or Li 3.2 Zr 0.3 Ta 0.5 Nb 0.2 Cl 4.7 O 1.6 The mass fraction of the microcrystalline portion in the microcrystalline / amorphous halide solid electrolyte is 5% to 10%.

2. The method for preparing the microcrystalline / amorphous halide solid electrolyte according to claim 1, characterized in that, The high-energy ball milling method includes the following steps: (S1) According to Li 3.2 Zr 0.4 Ta 0.5 Nb 0.1 Cl 4.6 O 1.6 Or Li 3.2 Zr 0.3 Ta 0.5 Nb 0.2 Cl 4.7 O 1.6 By using stoichiometric ratios, a certain amount of lithium source, zirconium source, niobium source, and tantalum source are mixed to obtain a mixture; (S2) The mixture and grinding balls are placed in a ball mill jar and subjected to high-energy ball milling under an inert atmosphere to obtain the microcrystalline / amorphous halide solid electrolyte.

3. The preparation method according to claim 2, characterized in that, In step (S1), the lithium source is Li2O; the zirconium source is ZrCl4; the tantalum source is TaCl5; and the niobium source is NbCl5.

4. The preparation method according to claim 2, characterized in that, In step (S1), the mixing is performed by manual grinding for 5-20 minutes; and / or In step (S2), the grinding balls are zirconia grinding balls with a diameter of 4-8 mm; the mass ratio of the mixture to the grinding balls is 1:10-30; the inert atmosphere is nitrogen and / or argon; the conditions for the high-energy ball milling treatment are: ball milling jar speed 300-800 rpm; ball milling time 12-36 h.

5. The application of the microcrystalline / amorphous halide solid electrolyte as described in claim 1 in all-solid-state lithium batteries.

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