Oxy halides, methods for producing the same, and all-solid-state lithium batteries

Abstract

This invention provides oxyhalides, a method for producing the same, and an all-solid-state lithium battery. The production method includes step 1, in which a mixture of lithium and boron sources weighed in stoichiometric ratios is polished, sheeted, placed in a reaction tube, the reaction tube is vacuumed and sealed, and a first firing is performed at a temperature of 300-450°C for a duration of 4-20 hours; and step 2, after the first firing, the mixture is cooled to room temperature, the intermediate product in the reaction tube is removed, further polished, sheet-pressed, placed in the reaction tube, the reaction tube is vacuumed and sealed, a second firing is performed, and then the mixture is cooled to room temperature. The production method of this invention is simple, has a high utilization rate of raw materials, and does not contain by-products, making it advantageous for industrial production. The oxyhalides produced have high ionic conductivity and stability, and good interfacial stability with metallic lithium. The all-solid-state lithium batteries produced have excellent electrochemical performance.

Description

Technical Field

[0001] The present invention relates to an oxyhalide, a method for producing the same, and a all-solid-state lithium battery.

Background Art

[0002] All-solid-state lithium batteries have attracted attention because of their simple structure, high safety, and large energy density. Since a solid electrolyte is used instead of an electrolytic solution and a separator, they are thinner and smaller in volume, improving the energy density of the battery and enhancing the safety performance of the battery. Therefore, the research and development of all-solid-state lithium batteries to replace conventional lithium-ion batteries is of great significance. However, all-solid-state lithium batteries have the following problems: (1) On the electrode surface, how to satisfy the transport problems of positive and negative electrodes and electrolyte ions; (2) During the cycling process, the positive and negative electrodes cannot maintain very good contact like liquids; (3) Dendritic crystals are likely to occur in metallic lithium during the charge and discharge process. Due to the existence of these problems, the electrochemical performance of all-solid-state lithium batteries is inferior, which is disadvantageous for their practical use and development.

[0003] The core part of an all-solid-state lithium battery lies in a compound as a solid electrolyte. At present, it has been reported that both organic and inorganic compounds can be used as excellent electrolytes. Compared with organic solid electrolytes, inorganic solid electrolytes have higher ionic conductivity and stability. So far, the materials of inorganic solid electrolytes are divided into sulfides, oxides, and halides. Sulfide solid electrolytes have a high ionic conductivity (>10 -3 S·cm -1 ), but are affected by moisture in the surrounding atmosphere, often causing harmful hydrolysis reactions and significantly reducing the ionic conductivity. In addition, sulfides have poor oxidation stability, greatly limiting the direct use of high-voltage cathode materials. Oxide solid electrolytes have high air stability and thermal stability, low manufacturing costs, and are easy for mass production. However, due to their mechanical rigidity, they lead to poor contact at the interface with electrode materials, and an inflow of a liquid electrolyte is required for high-temperature processes or battery assembly. Halide solid electrolytes have a high ionic conductivity (>10-3 S·cm -1 Although it possesses these properties, it still faces the problem of being prone to deliquescence and having poor stability.

[0004] In oxyhalide materials, the bonding of divalent oxygen ions and halogen ions maintains both the polarity of the halogen and the high bonding energy of oxygen, offering greater potential for the future exploration of new electrolyte materials. And Li4B7O 12 It has been reported that Cl has high ionic conductivity at 300°C. However, previous reports have shown that Li4B7O 12 During the synthesis of Cl, a series of byproducts, such as Li2B4O7, may be produced to some extent, hence the presence of Li4B7O. 12 It reduces the conductivity and electrochemical properties of Cl.

[0005] Therefore, research and development of oxyhalide materials that are in a pure phase and possess excellent conductivity and electrochemical properties is of great significance to the field of batteries. [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] The technical problem that this invention aims to solve is to overcome the drawback of existing technologies, namely the difficulty in producing oxyhalides that are in a pure phase and have excellent conductivity and electrochemical properties, and to provide oxyhalides, a method for producing them, and an all-solid-state lithium battery. The manufacturing method of this invention is simple, has a high utilization rate of raw materials, and does not contain by-products, making it advantageous for industrial production. The produced oxyhalides have high ionic conductivity and stability, good interfacial stability with metallic lithium, and the all-solid-state lithium batteries produced have excellent electrochemical performance.

[0007] To produce a pure-phase oxyhalide, the inventor manufactured it by a solid-phase reaction method. During the manufacturing process, by grinding and sheet-pressing the raw materials, the contact between each raw material becomes closer, and the occurrence of side reactions between the raw materials and the reaction tube can be reduced. By firing in a vacuum environment, the occurrence of side reactions can be further avoided. By means of firing that combines low-temperature pre-firing and high-temperature firing, each raw material component reacts more uniformly and sufficiently, and the generation of by-products is avoided to the maximum extent. Due to the synergistic effect between each technical feature, a pure-phase oxyhalide could finally be produced.

Means for Solving the Problems

[0008] The present invention solves the above technical problems by the following technical solutions.

[0009] The present invention relates to a method for manufacturing an oxyhalide, wherein the chemical formula of the oxyhalide is Li3B7O 12 ·(LiX) a where X is Cl and / or Br, 0 < a ≤ 1, After grinding and sheet-pressing a mixture of a lithium source and a boron source weighed in a stoichiometric ratio, it is placed in a reaction tube. After evacuating and sealing the reaction tube, the first firing is carried out. The temperature of the first firing is 300 - 450°C, and the time of the first firing is 4 - 20 h, step 1. After the first firing, it is cooled to room temperature. The intermediate product in the reaction tube is taken out, further ground and sheet-pressed, then placed in the reaction tube. After evacuating and sealing the reaction tube, the second firing is carried out, and then cooled to room temperature to obtain the oxyhalide. When the lithium source is lithium halide and lithium oxide, and the boron source is boron oxide, the temperature of the second firing is 810 - 860°C, and the time of the second firing is 12 - 30 h. When the lithium source is lithium halide and lithium borate, and the boron source is boron oxide, the temperature of the second firing is 450 - 800°C, and the time of the second firing is 12 - 30 h, step 2. Provided is a method including

[0010] In the present invention, in the oxyhalide, LiX is Li3B7O 12 It is distributed in the void structure of the skeleton.

[0011] In the present invention, the lithium halide may be lithium chloride or lithium bromide.

[0012] When X is Cl, the lithium halide is lithium chloride.

[0013] When X is Br, the lithium halide is lithium bromide.

[0014] In the present invention, in the chemical formula of the oxyhalide, preferably 0 < a < 1 or a = 1, for example, a = 0.4, 0.5 or 0.9, and more preferably 0.8 < a < 0.98.

[0015] In step 2, when the lithium source is lithium chloride and lithium oxide, and the boron source is boron oxide, the molar ratio of the lithium chloride, the lithium oxide and the boron oxide is (0 to 2):3:7 and does not include 0:3:7. For example, it may be 2:3:7, 1.8:3:7, 1:3:7 or 0.8:3:7, and preferably (1.6 to 1.96):3:7.

[0016] In step 2, when the lithium source is lithium chloride and lithium metaborate, the boron source is boron oxide and the lithium metaborate is lithium metaborate, the molar ratio of the lithium chloride, the lithium metaborate and the boron oxide is (0 to 1):3:2 and does not include 0:3:2. For example, it may be 0.4:3:2, 0.5:3:2, 0.9:3:2 or 1:3:2, and preferably (0.8 to 0.98):3:2.

[0017] In the present invention, the lithium borate may be lithium metaborate (LiBO2), lithium tetraborate (Li2B4O7), or lithium pentaborate (LiB5O8).

[0018] In step 1 and / or step 2, the polishing operation and conditions may be those common in the art, for example, carried out in a mortar. In step 1 and / or step 2, the sheet press equipment may be of the usual type in the art, for example, a sheet press machine. The pressure of the sheet press is preferably 5 to 15 MPa, for example, 10 MPa.

[0019] In step 1 and / or step 2, the reaction tube is preferably a quartz tube.

[0020] In step 1 and / or step 2, after vacuum suction, the vacuum level of the reaction tube is preferably 10 -3 It is below Pa.

[0021] In step 1 and / or step 2, the sealing is generally performed on both ends of the reaction tube by heating and melting.

[0022] In the present invention, the first firing and the second firing are generally performed in a muffle furnace.

[0023] In step 1, the rate at which the temperature is raised to the temperature for the first firing may be 30 to 90°C / hour, for example, 60°C / hour.

[0024] In step 1, the temperature of the first firing is preferably 350 to 450°C, for example, 400°C.

[0025] In step 1, the duration of the first firing is preferably 10 to 15 hours, for example, 12 hours.

[0026] In step 2, the cooling rate after the first firing may be 10°C / h to 80°C / h, for example, 50°C / h.

[0027] In step 2, the rate at which the temperature is raised to the second firing temperature may be 30 to 90°C / hour, for example, 60°C / hour.

[0028] In step 2, the cooling rate after the second firing may be 10°C / h to 80°C / h, for example, 50°C / h.

[0029] In step 2, if the lithium source is lithium chloride and lithium oxide, and the boron source is boron oxide, the temperature of the second firing is, for example, 830°C, 840°C, 845°C, or 850°C, preferably 835-855°C.

[0030] In step 2, if the lithium source is lithium chloride and lithium oxide, and the boron source is boron oxide, the time for the second calcination is preferably 15 to 26 hours. Yes, for example, 20 hours or 24 hours.

[0031] In step 2, if the lithium source is lithium chloride and lithium borate, and the boron source is boron oxide, the temperature of the second firing is, for example, 500°C, 600°C, or 700°C, preferably 480-610°C.

[0032] In step 2, if the lithium source is lithium chloride and lithium borate, and the boron source is boron oxide, the duration of the second calcination is preferably 15 to 26 hours, for example, 20 hours or 24 hours. Furthermore, the present invention relates to an ionic conductivity of 0.2 to 2 mS·cm at 25°C. -1 The present invention provides oxyhalides produced by the aforementioned manufacturing method. In the present invention, the particle size of the oxyhalide crystalline granules is preferably 0.6 to 5 μm, more preferably 0.8 to 1.5 μm, and for example, 1 μm.

[0033] In the present invention, the ionic conductivity of the oxyhalide at 25°C is, for example, 0.25 mS·cm. -1 , 0.44 mS·cm -1 , 0.52 mS·cm -1 , 0.72 mS·cm -1 , 0.81 mS·cm -1 , 0.83 mS·cm -1 , 0.92 mS·cm -1 , 1.01 mS·cm -1 Or 1.12 mS·cm -1 The coefficient of pressure is preferably 0.4 to 2 mS·cm. -1 That is the case.

[0034] In the present invention, the electronic conductivity of the oxyhalide at 25°C is preferably 1 × 10⁻⁶. -8 ~1 × 10 -6 S·cm -1 For example, 3.18 × 10 -7 S·cm -1 or 6.52 × 10 -7 S·cm -1 And more preferably 2.5 × 10 -7 ~5×10 -7 S·cm -1 That is the case.

[0035] In the present invention, the ionic conductivity of the oxyhalide at 30°C is preferably 0.4 to 5 mS·cm. -1 For example, 1.23 mS·cm -1 That is the case.

[0036] In the present invention, the ionic conductivity of the oxyhalide at 40°C is preferably 0.6 to 5 mS·cm. -1 For example, 1.17 mS·cm -1 That is the case.

[0037] In the present invention, the ionic conductivity of the oxyhalide at 50°C is preferably 1 to 5 mS·cm. -1 For example, 2.03 mS·cm -1 That is the case.

[0038] Furthermore, the present invention relates to an all-solid-state lithium battery comprising a positive electrode, a solid electrolyte layer, a buffer layer, and a negative electrode arranged in that order, The present invention provides a battery in which the positive electrode comprises a positive electrode current collector and a positive electrode active material layer located on the surface of the positive electrode current collector, the positive electrode active material layer comprises LiFePO4 and the aforementioned oxyhalide, the solid electrolyte layer comprises the aforementioned oxyhalide, the buffer layer comprises Li6PS5Cl, and the negative electrode comprises a negative electrode current collector and a negative electrode active material layer located on the surface of the negative electrode current collector.

[0039] In the present invention, the positive electrode current collector may be made of any material that does not undergo chemical changes and has high conductivity, without limitation. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, or "aluminum or stainless steel material surface-treated with carbon, nickel, titanium, silver, etc." may be used.

[0040] In the present invention, the thickness of the positive electrode current collector may be that which is common in the art, for example, 16 μm.

[0041] In the present invention, the positive electrode active material layer comprises the LiFePO4 and the oxyhalide The mass ratio may be (2-5):1, for example, 3:1.

[0042] In the present invention, the thickness of the positive electrode active material layer may be 50 to 500 μm, for example, 100 μm.

[0043] In the present invention, the thickness of the solid electrolyte layer may be 100 to 1000 μm, for example, 400 μm.

[0044] In the present invention, the thickness of the buffer layer may be 100 to 1000 μm, for example, 420 μm.

[0045] In the present invention, the negative electrode current collector may be made of any material that does not undergo chemical changes and is electrically conductive, without limitation. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, aluminum-cadmium alloy, or "copper, stainless steel material, or aluminum-cadmium alloy surface-treated with carbon, nickel, titanium, or silver" may be used.

[0046] In the present invention, the thickness of the negative electrode current collector may be 4.5 to 10 μm, for example, 6 μm.

[0047] In the present invention, the negative electrode active material layer comprises graphite and / or silicon carbon, for example, graphite.

[0048] In the present invention, the thickness of the negative electrode active material layer may be 50 to 500 μm, for example, 100 μm.

[0049] In the present invention, the all-solid-state lithium battery further includes a housing, wherein the positive electrode, the solid electrolyte layer, the buffer layer, and the negative electrode are packaged within the housing.

[0050] In the present invention, according to common knowledge in the art, the all-solid-state lithium battery is a lithium battery that does not contain any liquid.

[0051] Furthermore, the present invention relates to a method for manufacturing the all-solid-state lithium battery described above, A step of performing a first press on the material of the solid electrolyte layer to obtain the solid electrolyte layer, A step of adding the buffer layer material to one side of the solid electrolyte layer and performing a second press to obtain the buffer layer, A step of adding the material for the positive electrode active layer to the other side of the solid electrolyte layer and performing a third press to obtain the positive electrode active layer, A step of adding the material for the negative electrode active layer to one side of the buffer layer and performing a fourth press to obtain the all-solid-state lithium battery, This provides a method that includes this.

[0052] In the present invention, after the fourth pressing, preferably, the process further includes placing the positive electrode current collector on one side of the positive electrode active material layer and the negative electrode current collector on one side of the negative electrode active material layer, and then performing a fifth pressing.

[0053] In the present invention, the first press, the second press, the third press, the fourth press, and the fifth press are generally performed in a mold for a solid-state battery.

[0054] In the present invention, the pressure of the first press may be 300 to 500 MPa, for example, 380 MPa.

[0055] In the present invention, the pressure of the second press may be 200 to 400 MPa, for example, 250 MPa.

[0056] In the present invention, the pressure of the third press may be 200 to 400 MPa, for example, 250 MPa.

[0057] In the present invention, the pressure of the fourth press may be 200 to 400 MPa, for example, 250 MPa.

[0058] In the present invention, the pressure of the fifth press may be 60 to 180 MPa, for example, 100 MPa.

[0059] In the present invention, if the all-solid-state lithium battery further includes a housing, the positive electrode, the solid electrolyte layer, the buffer layer, and the negative electrode are packaged within the housing.

[0060] All raw materials and reagents used in this invention are commercially available. Assuming that they conform to common sense in this field, various suitable examples of the present invention can be obtained by arbitrarily combining the above suitable conditions.

[0061] All reagents and raw materials used in this invention are commercially available.

[0062] The positive advancements of this invention are as follows: (1) The method according to the present invention is advantageous for industrial production because the synthesis process is simple, the raw material utilization rate is high, and no by-products are produced. (2) The manufactured oxyhalides have high ionic conductivity, air stability and thermal stability, and good interfacial stability with metallic lithium. (3) The manufactured all-solid-state lithium battery has excellent electrochemical performance. [Brief explanation of the drawing]

[0063] [Figure 1] This is an SEM image of the oxyhalide Li4B7O12Cl produced in Example 1. [Figure 2] These are the XRD spectra of the oxyhalides produced in Examples 1-2 and Comparative Examples 5-7. [Figure 3] These are the XRD spectra of the oxyhalides produced in Examples 3-5 and Comparative Example 1. [Modes for carrying out the invention] [Examples]

[0064] The present invention will be further described below with reference to the embodiments, but this does not limit the present invention to the scope of the embodiments described. In the following embodiments, experimental methods for which specific conditions are not described are selected according to conventional methods and conditions or according to the product description.

[0065] Table 1 below shows the manufacturers and purities of the raw materials used in the following examples and comparative examples.

[0066] [Table 1]

[0067] [Example 1] (1) Weigh out 2 mmol of LiCl, 3 mmol of Li2O, and 7 mmol of B2O3 in stoichiometric ratios, perform normal polishing in a mortar, then press into thin sheets using a sheet press at a pressure of 10 MPa, place in a quartz tube, suction the quartz tube into a vacuum, and seal (seal both ends of the quartz tube by heating and melting) (vacuum degree < 10 -3 Pa) The material was then transferred to a muffle furnace for the first firing, with a heating rate of 60°C / hour, a firing temperature of 400°C, and a firing time of 12 hours.

[0068] (2) After the first firing, the mixture is cooled to room temperature at a cooling rate of 50°C / h, the intermediate product in the quartz tube is removed, further polished and sheet-pressed (the conditions for polishing and sheet-pressing are the same as in step 1), placed in the quartz tube, the quartz tube is vacuumed and sealed, then transferred to the muffle furnace for a second firing at a heating rate of 60°C / h, the temperature of the second firing is 845°C, the duration of the second firing is 22h, then the mixture is cooled to room temperature at a cooling rate of 50°C / h, and the pure phase oxyhalide Li4B7O 12 Cl was obtained.

[0069] [Example 2] Compared to Example 1, all other operations and conditions were the same as in Example 1, except that the temperature of the second firing in step 2 was adjusted to 830°C.

[0070] [Example 3] (1) Weigh out 1 mmol of LiCl, 3 mmol of LIBO2, and 2 mmol of B2O3 in stoichiometric ratios, perform normal polishing in a mortar, then press into thin sheets using a sheet press at a pressure of 10 MPa, place in a quartz tube, suction the quartz tube into a vacuum, and seal (seal both ends of the quartz tube by heating and melting) (vacuum degree < 10 -3Pa) The material was then transferred to a muffle furnace for the first firing, with a heating rate of 60°C / hour, a firing temperature of 400°C, and a firing time of 12 hours.

[0071] (2) After the first firing, the mixture is cooled to room temperature at a cooling rate of 50°C / h, the intermediate product in the quartz tube is removed, further polished and sheet-pressed (the conditions for polishing and sheet-pressing are the same as in step 1), placed in the quartz tube, the quartz tube is vacuumed and sealed, then transferred to the muffle furnace for a second firing at a heating rate of 60°C / h, the temperature of the second firing is 500°C, the duration of the second firing is 24 hours, then the mixture is cooled to room temperature at a cooling rate of 50°C / h, and the pure phase oxyhalide Li4B7O 12 Cl was obtained.

[0072] [Example 4] Compared to Example 3, all other operations and conditions were the same as in Example 3, except that the temperature of the second firing in step 2 was adjusted to 600°C.

[0073] [Example 5] Compared to Example 3, all other operations and conditions were the same as in Example 3, except that the temperature of the second firing in step 2 was adjusted to 700°C.

[0074] [Example 6] Compared to Example 4, the only difference was that the amount of LiCl charged in step 1 was adjusted to 0.9 mmol; all other operations and conditions were the same as in Example 4, and oxyhalide Li3B7O 12 (LiCl) 0.9 I obtained it.

[0075] [Example 7] Compared to Example 4, the only difference was that LiCl in step 1 was changed to LiBr; all other operations and conditions were the same as in Example 4, and oxyhalide Li4B7O 12 I obtained Br.

[0076] [Example 8] Compared to Example 4, the only difference was that the amount of LiCl charged in step 1 was adjusted to 0.4 mmol; all other operations and conditions were the same as in Example 4, and oxyhalide Li3B7O 12 (LiCl) 0.4 I obtained it.

[0077] [Example 9] Compared to Example 4, the only difference was that 1 mmol of LiCl in step 1 was changed to 0.25 mmol of LiCl and 0.25 mmol of LiBr; all other operations and conditions were the same as in Example 4, and oxyhalide Li3B7O 12 (LiCl) 0.25 (LiBr) 0.25 I obtained it.

[0078] [Example 10] Manufacturing of all-solid-state lithium batteries LiFePO4 and the fabricated oxyhalide were mixed in a mass ratio of 7.5:2.5 using a sand mill for 20 minutes to obtain the material for the positive electrode active layer. The positive electrode current collector was aluminum foil with a thickness of 16 μm.

[0079] The manufactured oxyhalide was used as the solid electrolyte material. Li6PS5Cl was used as the buffer layer material. Graphite was used as the negative electrode active material layer material. The negative electrode current collector was copper foil with a thickness of 6 μm.

[0080] First, 40 mg of oxyhalide powder was placed in a mold, and a first press was performed using a sheet press machine at a pressure of 380 MPa to obtain a solid electrolyte layer. 42 mg of Li6PS5Cl was added to one side of the solid electrolyte layer, and a second press was performed using a sheet press machine at a pressure of 250 MPa to obtain a buffer layer. 10 mg of positive electrode active material was added to the other side of the solid electrolyte layer, and a third press was performed using a sheet press machine at a pressure of 250 MPa to obtain a positive electrode active material layer. 10 mg of negative electrode active material was added to one side of the buffer layer, and a fourth press was performed using a sheet press machine at a pressure of 250 MPa to obtain a negative electrode active material layer. Finally, a positive electrode current collector was placed on one side of the positive electrode active material layer, and a negative electrode current collector was placed on one side of the negative electrode active material layer, and a fifth press was performed using a sheet press machine at a pressure of 100 MPa to obtain an all-solid-state lithium battery. In this all-solid-state lithium battery, the thickness of the solid electrolyte layer was 400 μm, the thickness of the buffer layer was 420 μm, the thickness of the positive electrode active material layer was 100 μm, and the thickness of the negative electrode active material layer was 100 μm.

[0081] [Comparative Example 1] (1) 1 mmol LiCl, 3 mmol LIBO2, and 2 mmol B2O3 were weighed in stoichiometric ratios, polished in a mortar as usual, and then pressed into thin sheets at a pressure of 10 MPa using a sheet press machine. These sheets were then placed in a quartz tube (without vacuum suction or sealing) and transferred to a muffle furnace for the first firing. The heating rate was 60°C / hour, the temperature of the first firing was 400°C, and the duration of the first firing was 12 hours.

[0082] (2) After the first firing, the material was cooled to room temperature at a cooling rate of 50°C / h, the intermediate product in the quartz tube was removed, further polished and sheet-pressed (the conditions for polishing and sheet-pressing were the same as in step 1), placed back into the quartz tube, and transferred to a muffle furnace for a second firing at a heating rate of 60°C / h, with a second firing temperature of 500°C and a second firing duration of 24 hours. After that, it was cooled to room temperature at a cooling rate of 50°C / h to obtain an oxyhalide with an impurity phase.

[0083] [Comparative Example 2] (1) Weigh out 2 mmol LiCl, 3 mmol Li2O, and 7 mmol B2O3 in stoichiometric ratios, polish them in a mortar as usual, place them in a quartz tube, suction the quartz tube into a vacuum, and seal it (vacuum < 10°C). -3 Pa) The material was then transferred to a muffle furnace for the first firing, with a heating rate of 60°C / hour, a firing temperature of 400°C, and a firing time of 12 hours.

[0084] (2) After the first firing, the material was cooled to room temperature at a cooling rate of 50°C / h. The intermediate product in the quartz tube was removed, polished further, and placed back into the quartz tube. The quartz tube was then vacuumed and sealed, and transferred to a muffle furnace for a second firing at a heating rate of 60°C / h. The temperature of the second firing was 845°C, and the duration of the second firing was 22 hours. After that, the material was cooled to room temperature at a cooling rate of 50°C / h to obtain an oxyhalide with an impurity phase.

[0085] [Comparative Example 3] Weigh out 2 mmol LiCl, 3 mmol Li2O, and 7 mmol B2O3 in stoichiometric ratios, perform normal polishing in a mortar, then press into thin sheets at a pressure of 10 MPa using a sheet press machine, place in a quartz tube, suction the quartz tube into a vacuum, and seal (vacuum degree < 10°C). -3 Pa) The material was then transferred to a muffle furnace for firing at a heating rate of 60°C / hour, a firing temperature of 845°C, and a firing time of 22 hours. After that, it was cooled to room temperature at a cooling rate of 50°C / h, yielding an oxyhalide with an impurity phase.

[0086] [Comparative Example 4] Compared to Example 1, all other operations and conditions were the same as in Example 1, except that the temperature of the first firing in step 1 was adjusted to 200°C.

[0087] [Comparative Example 5] Compared to Example 1, all other operations and conditions were the same as in Example 1, except that the temperature of the second firing in step 2 was adjusted to 780°C.

[0088] [Comparative Example 6] Compared to Example 1, all other operations and conditions were the same as in Example 1, except that the temperature of the second firing in step 2 was adjusted to 870°C.

[0089] [Comparative Example 7] Compared to Example 1, all other operations and conditions were the same as in Example 1, except that the temperature of the second firing in step 2 was adjusted to 890°C.

[0090] [Comparative Example 8] Compared to Example 3, all other operations and conditions were the same as in Example 3, except that the temperature of the second firing in step 2 was adjusted to 400°C.

[0091] [Comparative Example 9] Compared to Example 3, all other operations and conditions were the same as in Example 3, except that the temperature of the second firing in step 2 was adjusted to 900°C.

[0092] [Examples of effects] (1) Analysis of structure and profile Figure 1 shows the oxyhalide Li4B7O produced in Example 1. 12 This is an SEM image of Cl. From the image, Li4B7O 12 It can be seen that the particle size of the Cl crystal granules is approximately 1 μm.

[0093] (2) Characterization using XRD Figures 2 and 3 show the XRD spectra of the oxyhalides produced in the examples and comparative examples, and Table 2 shows the peaks that appeared in the XRD of the samples produced in the examples and comparative examples. From the test results, no impurity phase substances were detected in the oxyhalides produced in Examples 1 to 9, and there were no clear differences in the XRD spectra. However, the oxyhalides produced in the comparative examples showed the presence of a Li2B4O7 impurity peak. From the figures, it can be seen that the oxyhalides produced in Examples 1 to 9 exhibit a crystal structure similar to the cubic lithium borate structure (space group F43c), and that it matches PDF#34-0742 well. From the experimental results of the above examples and comparative examples, it can be seen that in the process of producing oxyhalides, if the firing environment is not a vacuum, or if the raw materials are not sheet-pressed, or if the first low-temperature firing is not performed, or if the temperature of the first firing is not within the range of 350-450°C, or if the temperature of the second firing is not within the range of 810-860°C or 450-800°C, the produced oxyhalides will contain an impurity phase rather than a pure phase. The peak positions listed in Table 2 indicate that the peak intensity at the corresponding position is greater than 100 particles / second. " / " indicates that the peak intensity at the corresponding position for that substance is less than 100 particles / second, meaning that no peak corresponding to that position is observed. Here, "particles / second" represents the number of X-ray particles received by the detector per second.

[0094] [Table 2]

[0095] (3) Ionic conductivity test At room temperature (25°C), 300 mg of the oxyhalide powder produced in Examples 1-9 and Comparative Examples 1-9 was first pressed into thin flakes at 380 MPa, then placed in a sealed vacuum quartz tube, and fired at 600°C for 20 hours. After firing, the granules were transferred to a PEEK jacket in a mold, and an electrochemical resistance test was performed using an electrochemical workstation (CHI, 650E) with an applied voltage of 0.05 V and a frequency range of 10 -1 Hz to 10 6 It is Hz, and the test results This is shown in Table 3.

[0096] The formula for calculating the lithium ion conductivity of an oxyhalide solid electrolyte is ionic conductivity ρ = L / RS, where L is 3 mm, S represents the area of ​​a circle with a radius of 5 mm, and R is resistance.

[0097] [Table 3]

[0098] Table 4 shows the lithium ion conductivity of the oxyhalide solid electrolyte produced in Example 1 at different temperatures.

[0099] [Table 4]

[0100] (4) Electronic conductivity test At room temperature (25°C), the solid electrolyte powders of oxyhalides prepared in Examples 1-2 and Comparative Examples 6-7 were placed in a PEEK jacket, two ion-blocking electrodes were placed at both ends of the powder, and a pressure of 380 MPa was applied. DC polarization measurements were then performed using an electrochemical workstation (CHI, 650E), and the electron conductivity at different polarization voltages was measured. The formula for calculating electron conductivity is σ e =LI / SE, σ e is the electronic conductivity, and L is Li4B7O 12 The thickness of the Cl electrolyte is 0.3 cm, and S is Li4B7O 12 Area of ​​Cl electrolyte (0.785 cm²)2 ) where E is the polarization voltage (1V) and I is the current in the stable state. The test results are shown in Table 5.

[0101] [Table 5]

[0102] (5) Li4B7O 12 Stability study of Cl Oxyhalide Li4B7O produced in Example 1 12 Cl was exposed to air for 6 months (room temperature), then calcined in a muffle furnace at 300°C in air for 12 hours, and subsequently characterized by XRD. The test results showed that after 6 months of exposure to air or calcination in air, all peak values ​​matched the peak values ​​of the initial sample, indicating Li4B7O 12 Cl has been shown to have high air and thermal stability.

[0103] (6) Li4B7O 12 Study of interfacial stability between Cl and metallic lithium Oxyhalide Li4B7O produced in Example 1 12 I conducted research using Cl.

[0104] The ion transition number negatively affects concentration polarization during the charge-discharge process, thereby improving the battery's power density and limiting anion movement in the lithium salt.

[0105] Li|Li4B7O 12 By assembling a Cl|Li symmetrical half-cell, Li4B7O 12 We studied the lithium-ion transition rate of Cl, and the assembly process of the half-cell is as follows. A lithium metal sheet was pressed into thin slices and cut into circular sheets using a 1mm diameter circular cutter. 40mg of Li4B7O 12 Cl powder is placed in a mold and pressed at a pressure of 380 MPa using a sheet press machine, then Li4B7O 12Place the cut circular sheets on both sides of the Cl, and press them further with a pressure of 100 MPa to form Li|Li4B7O 12 A Cl|Li control half-cell was obtained. Li|Li4B7O 12 Cl|Li electrons used in Li4B7O 12 Li electrolyte of Cl + Number of transitions (T Li+ The following measurements were taken: Initial electrical resistance (R0) before the constant potential test and electrical resistance (R0) after the measurement. s ) is obtained by AC resistance measurement, and the frequency is 10 -1 Hz to 10 6 The value was Hz. The electrolyte transition number can be obtained by the following formula. [ka]

[0106] Here, ΔV(0.01V) is the DC polarization voltage applied to the sample, I0 is the initial current, and I s This is a stable current.

[0107] From the experimental results, the calculated Li4B7O 12 The lithium ion transition number of Cl was 0.74. A higher lithium ion transition number indicates a lower transition number for the corresponding anion and smaller concentration polarization, which inhibits the growth of resinous lithium crystals and the occurrence of some side reactions.

[0108] Li4B7O 12 To evaluate the electrochemical stability of the Cl solid electrolyte with respect to metallic lithium, a multi-channel battery test system (LAND, CT3002A) was used. Li|Li4B7O 12 For a Cl|Li symmetrical half-cell, the current was 0.01 mA·cm at 50°C. -2 and 0.05 mA·cm -2 Constant current charge-discharge cycles were performed at the following current densities. The symmetrical half-cell had a current of 0.05 mA·cm². -2and 0.01 mA·cm -2 After 40 cycles (80 hours) and 200 cycles (400 hours) respectively at a current density of -2 , a polarization voltage of 5 V was reached.

[0109] (7) Research on the electrochemical performance of all-solid-state lithium batteries (ASSLB) Based on Li4B7O 12 Cl produced in Example 1, an ASSLB was assembled and studied by the above method. The constant-current charge-discharge characteristics of LiFePO4@Li4B7O 12 Cl|Li4B7O 12 Cl|Li6PS5Cl|graphite ASSLB were tested at 50 °C in a battery test system (LAND, CT3002A).

[0110] From the test results, it can be seen that the initial discharge capacity and the 100th discharge capacity of the assembled all-solid-state lithium battery were 75 mAh·g -1 and 88 mAh·g[[ID=2①]] -1 respectively. The initial Coulomb efficiency of the ASSLB was 78%. The ASSLB has high cycle stability and reversible capacity. After 180 cycles, the specific discharge capacity was 83.6 mAh·g -1 and the Coulomb efficiency was 76%.

[0111] As described above, specific embodiments of the present invention have been described. It can be understood by those skilled in the art that these are merely exemplary descriptions, and the protection scope of the present invention is limited by the appended claims. Those skilled in the art can make various changes and modifications to these embodiments on the premise of not violating the principle and essence of the present invention, and all these changes and modifications fall within the protection scope of the present invention.

Claims

1. A method for producing oxyhalides, The chemical formula of the oxyhalide is Li ３ B ７ O １２ ・(LiX) ａ And, However, X is Cl and / or Br, and 0 < a ≤ 1, Step 1 involves polishing and sheet-pressing a mixture of lithium and boron sources weighed in stoichiometric ratios, placing it in a reaction tube, suctioning the reaction tube into a vacuum, sealing it, and then performing a first firing, with the temperature of the first firing being 300-450°C and the duration of the first firing being 4-20 hours. After the first firing, the reaction tube is cooled to room temperature, the intermediate product in the reaction tube is removed, further polished and sheet-pressed, then placed back into the reaction tube, the reaction tube is vacuumed and sealed, and a second firing is performed. After this, the tube is cooled to room temperature to obtain the oxyhalide. When the lithium source is lithium halide and lithium oxide, and the boron source is boron oxide, the temperature of the second firing is 810 to 860°C, and the duration of the second firing is 12 to 30 hours. In step 2, if the lithium source is lithium halide and lithium borate, and the boron source is boron oxide, the temperature of the second firing is 450 to 800°C, and the duration of the second firing is 12 to 30 hours. A method characterized by including the following.

2. (1) In step 1 and / or step 2, the pressure of the sheet press is 5 to 15 MPa, (2) In step 1 and / or step 2, the condition is that the reaction tube is a quartz tube, (3) In step 1 and / or step 2, after vacuum suction, the vacuum level of the reaction tube is 10 －３ The condition is that Pa is less than or equal to, (4) The lithium borate is lithium metaborate, lithium tetraborate, or lithium pentaborate. (5) The lithium halide is lithium chloride or lithium bromide, (6) The chemical formula of the oxyhalide is such that 0.8 < a < 0.98, A method for producing oxyhalides according to claim 1, characterized by satisfying one or more of the following.

3. In step 1, the temperature of the first firing is 350 to 450°C. and / or, the method for producing oxyhalides according to claim 1 or 2, characterized in that the time of the first firing in step 1 is 10 to 15 hours.

4. In step 2, if the lithium source is lithium chloride and lithium oxide, and the boron source is boron oxide, the temperature of the second firing is 835 to 855°C. Furthermore / or, in step 2, if the lithium source is lithium chloride and lithium oxide, and the boron source is boron oxide, the time for the second calcination is 15 to 26 hours. Furthermore / or, in step 2, the lithium source is lithium chloride and lithium oxide, and the boron source is boron oxide, the molar ratio of lithium chloride, lithium oxide and boron oxide is (1.6 to 1.96):3:7, characterized in that the method for producing oxyhalides according to claim 1 or 2.

5. In step 2, if the lithium source is lithium chloride and lithium borate, and the boron source is boron oxide, the temperature of the second firing is 480 to 610°C. Furthermore / or, in step 2, the lithium source is lithium chloride and lithium borate If the boron source is boron oxide, the duration of the second firing is 15 to 26 hours. Furthermore / or, in step 2, the lithium source is lithium chloride and lithium borate, the boron source is boron oxide, and the lithium borate is lithium metaborate, characterized in that the molar ratio of lithium chloride, lithium borate and boron oxide is (0.8 to 0.98):3:2, as described in claim 1 or 2.

6. Produced by the method for producing oxyhalides described in any one of claims 1 to 5, with an ionic conductivity of 0.2 to 2 mS·cm at 25°C. －１ An oxyhalide characterized by the following:

7. An all-solid-state lithium battery comprising, in order, a positive electrode, a solid electrolyte layer, a buffer layer, and a negative electrode, The positive electrode includes a positive electrode current collector and a positive electrode active material layer located on the surface of the positive electrode current collector, and the positive electrode active material layer contains LiFePO ４ and the oxyhalide according to claim 6, the solid electrolyte layer contains the oxyhalide according to claim 6, and the buffer layer contains Li ６ PS ５ Cl, and the negative electrode includes a negative electrode current collector and a negative electrode active material layer located on the surface of the negative electrode current collector. A battery characterized by this.

8. (1) In the positive electrode active material layer, the LiFePO ４ And the condition that the mass ratio of the oxyhalide is (2-5):1, (2) The condition that the thickness of the positive electrode active material layer is 50 to 500 μm, (3) The condition that the thickness of the solid electrolyte layer is 100 to 1000 μm, (4) The condition that the thickness of the buffer layer is 100 to 1000 μm, (5) The condition that the thickness of the negative electrode active material layer is 50 to 500 μm, The all-solid-state lithium battery according to claim 7, characterized in that it satisfies one or more of the following conditions.

9. A method for manufacturing an all-solid-state lithium battery according to claim 7 or 8, A step of performing a first press on the material of the solid electrolyte layer of the all-solid-state lithium battery to obtain the solid electrolyte layer, A step of adding the buffer layer material of the all-solid-state lithium battery to one side of the solid electrolyte layer and performing a second press to obtain the buffer layer, A step of adding the material for the positive electrode active layer of the all-solid-state lithium battery to the other side of the solid electrolyte layer and performing a third press to obtain the positive electrode active layer, A step to obtain the all-solid-state lithium battery by adding the material for the negative electrode active layer of the all-solid-state lithium battery to one side of the buffer layer and performing a fourth press, A method characterized by including the following.

10. (1) Conditions including the process of performing a fifth press after the fourth press, by placing the positive electrode current collector on one side of the positive electrode active material layer and the negative electrode current collector on one side of the negative electrode active material layer, (2) Under the condition that the pressure of the first press is 300 to 500 MPa, (3) The condition that the pressure of the second press is 200 to 400 MPa, (4) The condition that the pressure of the third press is 200 to 400 MPa, (5) The condition that the pressure of the fourth press is 200 to 400 MPa, (6) Under the condition that the pressure of the fifth press is 60 to 180 MPa, A method for manufacturing an all-solid-state lithium battery according to claim 9, characterized in that it satisfies one or more of the following conditions.

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