A halide solid electrolyte and its preparation method

Abstract

This invention relates to a halide solid electrolyte with the chemical formula [Li 3‑(z‑3)x M 1‑x N x ] 6+ [A a B b ] 6‑ Where M is Y 3+ V 3+ Cr 3+ At least one of them, N is selected from Hf 4+ Ta 5+ At least one of the following, A is selected from halogens, B is selected from halogens different from A, or N 3‑ , 0 < x < 1, 0 < a ≤ 6, 0 ≤ b < 6, the values ​​of a and b satisfy the condition that the anion [A a B b The oxidation state is -6; when B is a different halogen than A, b = 6 - a; when B is N... 3‑ When b = 6 - a / 3. This invention successfully prepares halide electrolytes doped with different valence elements through a simple mechanochemical method, exhibiting high lithium-ion conductivity, reducing the synthesis process and increasing energy efficiency; transition metal ions are relatively inexpensive, effectively lowering the raw material cost for synthesizing halide electrolytes.

Description

Technical Field

[0001] This invention belongs to the field of solid electrolytes, specifically relating to a halide solid electrolyte and its preparation method. Background Technology

[0002] The energy shortage and environmental damage caused by the overexploitation of fossil fuels are becoming increasingly prominent. Achieving efficient storage and utilization of renewable and environmentally friendly new energy sources is a crucial way to solve current energy and environmental problems. All-solid-state lithium batteries, due to their high safety and high energy density, are considered the next-generation battery technology to replace traditional lithium-ion batteries, and are expected to meet the demand for large-scale, efficient, and safe energy storage applications. Solid electrolytes are the core component of all-solid-state batteries, and their ionic conductivity, mechanical deformability, and electrochemical stability directly affect the overall performance of the battery. Currently, common solid electrolytes are mainly of two types: oxides and sulfides. While oxide electrolytes have good electrochemical stability, their poor compatibility with metallic lithium leads to high interfacial impedance. Sulfide electrolytes, although having high ionic conductivity, are prone to reacting with air to generate toxic hydrogen sulfide gas, resulting in failure. Therefore, there is an urgent need to develop new solid electrolytes with excellent overall performance.

[0003] Emerging halide solid electrolytes have garnered significant attention in recent years as a research hotspot in the field of all-solid-state batteries due to their advantages, including excellent deformability, high-voltage cathode stability, and high lithium-ion conductivity. However, to date, only a few rare-earth metal-containing halide electrolytes (such as Li3ScCl6, Li3YCl6, Li3InCl6, and Li3HoBr6) have achieved conductivity exceeding 10... - 3 The low room-temperature ionic conductivity (S / cm), high raw material costs, and generally low room-temperature ionic conductivity of halide electrolytes severely limit their large-scale practical application. Therefore, developing novel halide electrolytes with high lithium-ion conductivity and relatively low cost is of great value. Utilizing low-cost heterovalent transition metal ions to substitute cation sites in halide electrolytes can effectively improve the bottleneck size of lithium-ion migration channels, thereby enhancing the lithium-ion conductivity of halide electrolytes. Screening for inexpensive transition metal ions that can improve the ionic conductivity of halide electrolytes through doping, while further optimizing the synthesis process conditions of halide electrolytes, is of great significance for the successful preparation of novel halide electrolytes with high ionic conductivity and low cost.

[0004] CN112136184A discloses a halide solid electrolyte material doped with Zr and metallic M, where M is selected from at least one of Al, Ga, Bi, Sc, Sm, and Sb. However, its ionic conductivity remains low, with the highest being that of the halide solid electrolyte Li. 2.1 Zr 0.9 Sc0.1 The ionic conductivity of Cl6 is only 87.4 × 10⁻⁶. -5 S / cm is still insufficient to meet the current demand for all-solid-state batteries.

[0005] CN110970667A discloses a Y-containing halide solid electrolyte Li3YCl x Br 6-x The anions include Cl and Br. In Li3YCl6, the hexagonal close-packed anions facilitate lithium-ion conduction through octahedral sites. Since Br has a larger radius than Cl, it can also form tetrahedral conduction sites. The Br and Cl composite in Li3YCl6... x Br 6-x It exhibits higher ionic conductivity, reaching a maximum of 0.81 mS / cm, but its poor intrinsic electrochemical oxidation stability is not conducive to the direct application of 4V class positive electrode active materials.

[0006] CN113889662A discloses a halide solid electrolyte Li a A 1-x-y M x N y X 3+a+x+y It is a ternary doped halide solid electrolyte. However, after doping, the ionic conductivity of most halides is still below 1 mS / cm, and the extensive use of expensive rare earth metals seriously hinders its mass production and commercial application. Summary of the Invention

[0007] This invention focuses on solving the problem of low ionic conductivity in halide electrolytes, based on the transition metal ion Hf. 4+ Heterovalent substitution of non-lithium metal sites in halide electrolytes can enrich the lithium vacancies in the halide electrolyte lattice structure and improve the bottleneck size of lithium-ion transport channels, thereby enabling the preparation of novel halide electrolytes with high lithium-ion conductivity and high electrochemical stability. This invention screened inexpensive transition metal ions that can improve halide ion conductivity through heterovalent doping, and further optimized the synthesis process conditions of the halide electrolytes, obtaining over 10... -3 A novel halide electrolyte with a conductivity of S / cm has been successfully applied to high-performance all-solid-state batteries. Furthermore, this invention utilizes a mechanochemical and annealing method to synthesize a halide electrolyte based on tetravalent transition metal ions, effectively reducing material synthesis costs compared to traditional halide electrolytes containing rare earth metals. Compared to most reported halide solid electrolytes, the halide solid electrolyte prepared by heterovalent ion doping in this invention exhibits significantly improved lithium-ion conductivity.

[0008] The objective of this invention is achieved through the following technical solution:

[0009] A halide solid electrolyte with the chemical formula [Li 3-(z-3)x M 1-x N x ] 6+ [A a B b ] 6- Where M is Y 3+ V 3 + Cr 3+ At least one of them, N is selected from Hf 4+ Ta 5+ At least one of the following, A is selected from halogens, B is selected from halogens different from A, or N 3- , 0 < x < 1, 0 < a ≤ 6, 0 ≤ b < 6, the values ​​of a and b satisfy the condition that the anion [A a B b The oxidation state is -6.

[0010] When B is a different halogen than A, b = 6 - a; when B is N... 3- At that time, b = 6 - a / 3.

[0011] This invention utilizes the tetravalent state of Hf 4+ and / or pentavalent Ta 5+ By replacing the central metal element in the trivalent state of halide, the lithium ion / vacancy ratio in the crystal structure can be effectively adjusted while optimizing the diffusion path of lithium ions in the crystal lattice, thereby obtaining a halide electrolyte with high lithium ion conductivity.

[0012] The halogen is selected from F. - Cl - ,Br - Or I - .

[0013] Preferably, 0.1≤x≤0.9, 1≤a≤5; more preferably, 0.5≤x≤0.7, 2≤a≤3.

[0014] More preferably, A is selected from F. - Cl - ,Br - Or I - B is selected from N 3- And 2≤a≤3.

[0015] A second objective of this invention is to provide a method for preparing the above-mentioned halide solid electrolyte, comprising the following steps:

[0016] The lithium source, M source, and N source are weighed according to the stoichiometric ratio, mixed, and the mixture is put into a ball mill jar and ball milled under an inert atmosphere. The product is a halide solid electrolyte.

[0017] Furthermore, the lithium source is selected from at least one of lithium halide and lithium nitride, and the M source is selected from Y. 3+ Cr 3+ V 3+ At least one of the halide salts and nitrides; the N source is selected from Hf 4+ Ta 5+ At least one of the following: a halide salt, a nitride, and a fluoride. The halide is a fluoride, a chloride, a bromide, or an iodide.

[0018] Furthermore, in the ball milling process, the ball-to-material ratio is 20-40:1, the inert atmosphere is argon, the ball milling speed is 400-700 rpm, and the milling is in a forward and reverse rotation mode. After milling in the forward rotation for 10-20 minutes, stop for 3-5 minutes, then mill in the reverse rotation for 10-20 minutes, stop for 3-5 minutes, and then mill in the forward rotation again. This forward and reverse rotation is repeated continuously for 30-50 hours.

[0019] A third objective of this invention is to provide a lithium-ion battery in which the positive electrode material and / or electrolyte comprises the aforementioned halide solid electrolyte.

[0020] The superior effects of this invention are as follows:

[0021] I. The high-performance all-solid-state battery with novel halide solid electrolyte of the present invention can be used in electric vehicle power supply and stationary energy storage system, and is expected to have broad market prospects.

[0022] I. This invention utilizes transition metal ions Hf 4+ Or Ta 5+ By replacing the central metal ion in halide electrolytes, novel halides, Li, were obtained. 3-(z-3)x M 1-x N x z+ A a B 6-a Compared to previously reported halide electrolytes containing rare-earth metals, this novel halide electrolyte exhibits higher lithium-ion conductivity. Furthermore, by replacing non-lithium metal sites in the halide electrolyte with transition metal ions, the electronic conductivity of the prepared novel halide electrolyte can be reduced by an order of magnitude, suppressing short circuits between the positive and negative electrodes. This results in a longer cycle life for halide-based all-solid-state lithium batteries.

[0023] II. This invention successfully prepares aberrant element-doped halide electrolyte using a simple mechanochemical method. Compared to halide electrolytes prepared by high-temperature annealing, it exhibits higher lithium-ion conductivity and eliminates the need for subsequent high-temperature annealing, thus reducing the synthesis process and saving energy. Transition metal ions are relatively inexpensive, effectively lowering the raw material cost for synthesizing halide electrolytes. Attached Figure Description

[0024] Figure 1 Li was prepared in Example 1 2.4 Y 0.4 Hf 0.6 Cl6 and other different Hf 4+ XRD pattern of doped halides.

[0025] Figure 2 Li was prepared in Example 1 2.4 Y 0.4 Hf 0.6 Cl6 and other different Hf 4+ Electrochemical impedance spectroscopy of doped halides at room temperature.

[0026] Figure 3 Li was prepared in Example 1 2.4 Y 0.4 Hf 0.6 Cl6 and other different Hf 4+ Ionic conductivity diagram of doped halides.

[0027] Figure 4 Li was prepared in Example 1 2.4 Y 0.4 Hf 0.6 Cl6 and other different Hf 4+ Electron conductivity diagram of doped halides.

[0028] Figure 5 This is a scanning electron microscope image of the halide electrolyte of Example 1.

[0029] Figure 6 It is lithium cobalt oxide (a) and lithium cobalt oxide and halides Li 2.4 Y 0.4 Hf 0.6 Scanning electron microscope image of the Cl6 composite cathode (b).

[0030] Figure 7 The first charge-discharge curve of the all-solid-state battery prepared with the halide solid electrolyte of Example 1 at 0.1C is shown. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. The following embodiments are provided to better understand this invention, but do not limit the invention. Unless otherwise specified, the experimental methods in the following embodiments are conventional methods.

[0032] Example 1

[0033] Under the protection of high-purity argon, LiCl, YCl3, and HfCl4 were fed in a molar ratio of 2.4:0.4:0.6 and placed in an agate grinding bowl in an argon-filled glove box. The mixture was then manually ground for 30 minutes. The mixed precursor materials were then transferred to a zirconia ball mill jar with a ball-to-material ratio of 40:1. The high-energy ball mill was set to a speed of 550 rpm / min. The mill was rotated forward for 10 minutes, stopped for 5 minutes, then rotated backward for 10 minutes, stopped for 5 minutes, and so on, for a total of 50 hours. After high-energy ball milling, the product was removed from the argon-filled glove box to obtain the mechanochemically synthesized halide electrolyte powder Li. 2.4 Y 0.4 Hf 0.6 Cl6.

[0034] By changing the molar ratio of LiCl, YCl3, and HfCl4, Li was prepared. 3-x Y 1-x Hf x Cl6, where x is 1, 0.8, 0.6, 0.4, 0.2 and 0 respectively.

[0035] Figure 1 Li was prepared in Example 1 2.4 Y 0.4 Hf 0.6 Cl6 and other different Hf 4+ The XRD patterns of doped halides show that the characteristic peaks shift to higher angles after doping, which is attributed to Hf. 4+ Compared to Y 3+ Smaller ionic radius.

[0036] Figure 2 Li was prepared in Example 1 2.4 Y 0.4 Hf 0.6 Cl6 and other different Hf 4+ Electrochemical impedance spectroscopy of doped halides at room temperature can reveal heterovalent Hf. 4+ Doping can significantly reduce the impedance of the original halide electrolyte, thereby effectively enhancing the rapid migration of lithium ions in the halide lattice.

[0037] Figure 3 Li was prepared in Example 1 2.4 Y 0.4 Hf 0.6 Cl6 and other different Hf 4+ The ionic conductivity diagram of the doped halides shows that the ionic conductivity first increases and then decreases with increasing Hf doping concentration. At an Hf doping concentration of x = 0.6, the prepared Li... 2.4 Y 0.4 Hf 0.6Cl6 has the highest ionic conductivity of 1.49 mS / cm.

[0038] Figure 4 Li was prepared in Example 1 2.4 Y 0.4 Hf 0.6 Cl6 and other different Hf 4+ The electronic conductivity diagram of doped halides shows that the electronic conductivity decreases by an order of magnitude as the Hf doping concentration increases.

[0039] Figure 5 These are scanning electron microscope (SEM) images of the halide electrolyte of Example 1, where (a) and (b) are SEM images of the halide electrolyte Li3YCl6 at different magnifications; (c) and (d) are SEM images of the halide electrolyte Li 2.4 Y 0.4 Hf 0.6 Scanning electron microscope images of Cl6 at different magnifications show that the surface morphology of the halide electrolyte is not significantly different before and after Hf doping.

[0040] Example 2

[0041] Under the protection of high-purity argon, LiCl, VCl3, and HfCl4 were fed in a molar ratio of 2.25:0.25:0.75 and placed in an agate grinding bowl in an argon-filled glove box. The mixture was then manually ground for 30 minutes. The mixed precursor materials were then transferred to a zirconia ball mill jar with a ball-to-material ratio of 40:1. The high-energy ball mill was set to a speed of 550 rpm / min. High-energy ball milling was performed in the forward direction for 10 minutes, then stopped for 5 minutes, followed by reverse high-energy ball milling for 10 minutes, then stopped for 5 minutes. This process was repeated for 50 hours. After high-energy ball milling, the product was removed from the argon-filled glove box to obtain the mechanochemically synthesized halide electrolyte powder Li. 2.25 V 0.25 Hf 0.75 Cl6.

[0042] Example 3

[0043] Under the protection of high-purity argon, LiCl, CrCl3, and HfCl4 were fed in a molar ratio of 2.1:0.1:0.9 and placed in an agate grinding bowl in an argon-filled glove box. The mixture was then manually ground for 30 minutes. The mixed precursor materials were then transferred to a zirconia ball mill jar with a ball-to-material ratio of 40:1. The high-energy ball mill was set to a speed of 550 rpm / min. The mill was rotated forward for 10 minutes, stopped for 5 minutes, then rotated backward for 10 minutes, stopped for 5 minutes, and so on, for a total of 50 hours. After high-energy ball milling, the product was removed from the argon-filled glove box to obtain the mechanochemically synthesized halide electrolyte powder Li. 2.1 Cr0.1 Hf 0.9 Cl6.

[0044] Example 4

[0045] Under the protection of high-purity argon, LiCl, YCl3, and TaCl5 were fed in a molar ratio of 2.0:0.5:0.5 and placed in an agate grinding bowl in an argon-filled glove box. The mixture was then manually ground for 30 minutes. The mixed precursor materials were then transferred to a zirconia ball mill jar with a ball-to-material ratio of 40:1. The high-energy ball mill was set to a speed of 550 rpm / min. The mill was rotated forward for 10 minutes, stopped for 5 minutes, then rotated backward for 10 minutes, stopped for 5 minutes, and so on, for a total of 50 hours. After high-energy ball milling, the product was removed from the argon-filled glove box to obtain the mechanochemically synthesized halide electrolyte powder Li2Y. 0.5 Ta 0.5 Cl6.

[0046] Example 5

[0047] Under the protection of high-purity argon, LiCl, LiBr, CrCl3, and HfBr4 were fed in a molar ratio of 1.8:0.6:0.4:0.6 and placed in an agate grinding bowl in an argon-filled glove box. The mixture was then manually ground for 30 minutes. The mixed precursor materials were then transferred to a zirconia ball mill jar with a ball-to-material ratio of 40:1. The high-energy ball mill was set to a speed of 550 rpm / min. The mill was rotated forward for 10 minutes, stopped for 5 minutes, then rotated backward for 10 minutes, stopped for 5 minutes, and so on, for a total of 50 hours. After high-energy ball milling, the product was removed from the argon-filled glove box to obtain the mechanochemically synthesized halide electrolyte powder Li. 2.4 Cr 0.4 Hf 0.6 Cl3Br3.

[0048] Example 6

[0049] Under the protection of high-purity argon, LiCl, Li3N, VN, and TaCl5 were fed in a molar ratio of 0.5:0.5:0.5:0.5 and placed in an agate grinding bowl in an argon-filled glove box. The mixture was then manually ground for 30 minutes. The mixed precursor materials were then transferred to a zirconia ball mill jar with a ball-to-material ratio of 40:1. The high-energy ball mill was set to a speed of 550 rpm / min. The mill was rotated forward for 10 minutes, stopped for 5 minutes, then rotated backward for 10 minutes, stopped for 5 minutes, and so on, for a total of 50 hours. After high-energy ball milling, the product was removed from the argon-filled glove box to obtain the mechanochemically synthesized halide electrolyte powder Li2V. 0.5 Ta 0.5 Cl3N.

[0050] Comparative Example 1

[0051] Under the protection of high-purity argon, LiCl and YCl3 were fed in a molar ratio of 3:1 and placed in an agate grinding bowl in an argon-filled glove box. The mixture was then manually ground for 30 minutes. The mixed precursor materials were then transferred to a zirconia ball mill jar with a ball-to-material ratio of 40:1. The high-energy ball mill was set to a speed of 550 rpm / min. The high-energy ball mill was rotated forward for 10 minutes and then stopped for 5 minutes. The high-energy ball mill was then rotated in reverse for 10 minutes and then stopped for 5 minutes. The process was repeated for 50 hours. After the high-energy ball milling was completed, the product was removed from the argon-filled glove box to obtain the mechanochemically synthesized halide electrolyte powder Li3YCl6.

[0052] Example of effect

[0053] 1. All-solid-state battery The composite cathode was prepared by mixing lithium cobalt oxide (LiCoO2) and the halide solid electrolyte prepared in the example at a mass ratio of 7:3 in an agate grinding mortar, and then manually grinding for 30 min. The assembly steps of the all-solid-state battery are as follows: 40 mg of Li6PS5Cl powder was placed in a polyetheretherketone mold with a diameter of 10 mm, and then held at 1 ton pressure for 1 min; then 75 mg of halide solid electrolyte powder was uniformly dispersed on the Li6PS5Cl electrolyte sheet, and then held at 1 ton pressure for 1 min; then 4.5 mg of composite cathode powder was uniformly dispersed on one side of the halide electrolyte, and then held at 3 ton pressure for 5 min; finally, 100 μm thick In foil was attached to one side of the Li6PS5Cl electrolyte sheet. and Li foil Finally, a stainless steel column was placed in the battery to complete the assembly of the all-solid-state battery. The entire battery was then subjected to constant current charge-discharge testing on a battery tester (LANDCT2001A).

[0054] Figure 6 It is lithium cobalt oxide (a) and lithium cobalt oxide and halides Li 2.4 Y 0.4 Hf 0.6 Scanning electron microscope (SEM) image of the composite cathode (b) after manual grinding and mixing of Cl6. It can be seen that a relatively uniform, semi-coated halide thin layer on the surface of lithium cobalt oxide can be obtained through simple grinding, attributed to the Li halide. 2.4 Y 0.4 Hf 0.6 Cl6 exhibits excellent deformation properties.

[0055] Figure 7 The first charge-discharge curve of the all-solid-state battery prepared with the halide solid electrolyte in Example 1 at 0.1C shows that, based on Li 2.4 Y 0.4 Hf0.6 The first-cycle charge-discharge capacity (over 120 mAh / g) and coulombic efficiency (close to 100%) of the Cl6-based full cell are significantly higher than those of the Li3YCl6-based full cell.

[0056] 2. Assemble symmetrical stainless steel / electrolyte sheet / stainless steel mold batteries 100 mg of halide solid electrolyte powder was weighed and placed in a 10 mm diameter polyetheretherketone mold. A stainless steel column was then placed inside and the mixture was pressed into a pellet under a pressure of approximately 3 tons. The AC impedance spectroscopy of the halide electrolyte was then measured. The mold cell was tested using an electrochemical workstation (Zahner).

[0057] The electrochemical performance of the halide electrolytes prepared in the above examples was tested, and the results are shown in Table 1 below:

[0058] Table 1

[0059]

[0060] It can be seen that the transition metal ion-substituted halide electrolyte prepared in this invention exhibits significantly improved lithium-ion conductivity and decreased electronic conductivity at room temperature, thus possessing beneficial electrochemical performance. When fabricated into an all-solid-state battery, its cycle stability is significantly improved. The inventors also discovered that, in addition to the transition metal Hf... 4+ / Ta 5+ Doping non-lithium metal sites in halide electrolytes can improve their electrochemical performance by modulating the anions, such as using two different halogen atoms, like Cl and Br, or halide anions and N. 3- Together, they act as anions, which can further improve the electrochemical performance of halide solid electrolytes.

[0061] This invention utilizes a simple mechanochemical method, namely high-energy ball milling, to obtain high-performance halide solid electrolyte materials, demonstrating excellent prospects for industrial transformation. The mechanochemical method for doping transition metal ions to enhance the ionic conductivity of halides can also be applied to the following halide electrolytes: Li3ScCl6, Li3HoCl6, Li3ErCl6, and Li3InCl6, but is not limited to these.

Claims

1. A halide solid electrolyte, characterized in that, The chemical formula is Li₂V 0.5 Ta 0.5 Cl3N.

2. The method for preparing the halide solid electrolyte according to claim 1, characterized in that, The process includes the following steps: weighing and mixing lithium source, M source, and N source according to stoichiometric ratio; placing the mixture into a ball mill jar and ball milling under an inert atmosphere; the product is a halide solid electrolyte; the lithium source is selected from at least one of lithium halide and lithium nitride, and the M source is selected from V... 3+ At least one of the halide salts and nitrides; the N source is selected from Ta. 5+ The halide salt, at least one of the nitrides; the halide salt is a chloride.

3. The preparation method according to claim 2, characterized in that, The ball milling process uses a ball-to-material ratio of 20-40:1, an inert atmosphere of argon, and a ball milling speed of 400-700 rpm. The process is carried out in a forward and reverse rotation mode. After milling in the forward rotation for 10-20 minutes, the milling is stopped for 3-5 minutes, then the milling is reversed for 10-20 minutes, stopped for 3-5 minutes, and then the milling is repeated in the forward and reverse rotation mode for 30-50 hours.

4. A lithium-ion battery, wherein the positive electrode material and / or electrolyte comprises the halide solid electrolyte of claim 1.

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