Preparation method and application of LiaMXb-based composite solid electrolyte membrane

Abstract

The invention belongs to the technical field of new energy, and discloses a preparation method and application of a LiaMXb-based composite solid electrolyte membrane, and the preparation method comprises the following steps: S1, carrying out spray drying on a mixed solution in which a Li source, an M source and an ammonium salt are dissolved, placing the mixed solution in a crucible of which the bottom is paved with the ammonium salt, and annealing for 2-10 hours at 350-800 DEG C in an inert atmosphere to obtain a LiaMXb solid electrolyte; s2, mixing the LiaMXb solid electrolyte with a fluorine-containing monomer A and a dispersing agent, and performing spray drying to obtain electrolyte powder wrapped by the fluorine-containing monomer A; s3, ball-milling and uniformly mixing the electrolyte powder wrapped by the fluorine-containing monomer A, a lithium salt, a thermal curing agent and a monomer B in an inert atmosphere to obtain composite electrolyte powder; and S4, carrying out cold isostatic pressing and hot pressing curing on the composite electrolyte powder to prepare the LiaMXb-based composite solid electrolyte membrane. The prepared LiaMXb-based composite solid electrolyte membrane not only has excellent air stability, flexibility and machinability, but also has a continuous three-dimensional ion conduction path, and the assembled all-solid-state lithium battery has good electrochemical performance.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy batteries, and in particular to a Li a MX b Preparation method and application of composite solid electrolyte membrane. Background Art

[0002] Traditional lithium-ion batteries have safety risks such as flammability and explosion due to the use of flammable organic liquid electrolytes, which makes it difficult to meet the growing requirements of high energy density and high safety. All-solid-state lithium batteries that use non-flammable inorganic solid electrolytes and match them with metal lithium negative electrodes can show outstanding energy density and safety, and thus have huge application potential. As a key component of all-solid-state lithium batteries, halide solid electrolytes stand out from many inorganic solid electrolytes due to their high ionic conductivity, wide electrochemical stability window and excellent mechanical properties. However, all-solid-state lithium batteries generally use thicker solid electrolyte layers to inhibit the penetration of lithium dendrites, which also leads to low energy density. Therefore, it is of great significance to improve the energy density of all-solid-state lithium batteries by thinning the solid electrolyte layer through film making process. However, thinner solid electrolyte layers are not enough to inhibit the penetration of lithium dendrites. In addition, most electrolyte membranes have defects such as poor density, low ionic conductivity and poor electrochemical performance. Therefore, it is necessary to develop a simple and feasible process to prepare Li-ion batteries that have excellent electrochemical properties, density and excellent lithium ion transmission paths. a MX b Composite solid electrolyte membranes are crucial for the development of all-solid-state lithium batteries with high energy density and long cycle life. Summary of the Invention

[0003] The purpose of the present invention is to overcome the above technical deficiencies and provide a Li a MX b The invention discloses a preparation method of a composite solid electrolyte membrane and its application, which solves the technical problems of poor density, low ion conductivity and poor electrochemical performance of the halide solid electrolyte membrane prepared in the prior art.

[0004] In order to achieve the above technical purpose, the technical solution of the present invention provides a Li a MX b Preparation method of composite solid electrolyte membrane and its application.

[0005] The present invention proposes a Li a MX b A method for preparing a composite solid electrolyte membrane comprises the following steps:

[0006] S1. The precursor powder obtained by spray drying a mixed aqueous solution containing a certain molar ratio of Li source, metal M source and ammonium salt is placed in a crucible with ammonium salt on the bottom, and annealed at 350-800 ° C for 2-10 hours (preferably heated to 400-500 ° C at a rate of 2 ° C / min and then kept warm for 4-5 hours) in an inert atmosphere, and then cooled in the furnace to obtain Li a MX b solid electrolytes;

[0007] S2, the Li obtained in step S1 a MX b The solid electrolyte is mixed with the fluorinated monomer A and the dispersant, and spray-dried to obtain the electrolyte powder coated with the fluorinated monomer A;

[0008] S3, mixing the electrolyte powder coated with the fluorinated monomer A obtained in step S2 with a lithium salt, a thermal curing agent, and monomer B in a certain proportion in an inert atmosphere and ball milling (preferably at a speed of 300 rpm for 1 hour) to obtain a composite electrolyte powder;

[0009] S4, the composite electrolyte powder obtained in step S3 is subjected to cold isostatic pressing (preferably cold isostatic pressing at 100 MPa) to obtain an electrolyte primary membrane, which is then hot-pressed and solidified to obtain the target Li a MX b A composite solid electrolyte membrane, wherein X is a halogen element, a is 2-3, b is 4-6, and at least one of the Li source, metal M source, and ammonium salt compound contains X;

[0010] The metal M is one of scandium, yttrium, hafnium, holmium, zirconium, tantalum, aluminum, gallium, iron, indium and lanthanide metal elements.

[0011] Further, in step S1, the Li source is one or more of lithium chloride, lithium bromide, lithium fluoride, lithium iodide, lithium carbonate, lithium oxide, lithium hydroxide, lithium nitrate, lithium lactate, lithium oxalate, lithium formate, lithium hydrogen phosphate, lithium dihydrogen phosphate, lithium ammonium phosphate, and lithium diammonium phosphate; and / or

[0012] The metal M source is one or more of an oxide, anhydrous halide, and halide containing crystal water of metal M; and / or

[0013] The ammonium salt is one or more of ammonium chloride, ammonium fluoride, ammonium iodide, ammonium bromide, ammonium nitrate, ammonium carbonate, ammonium sulfate, ammonium bifluoride, and ammonium bicarbonate; and / or

[0014] In step S1, the molar ratio of the Li source, the metal M source and the ammonium salt in the mixed aqueous solution before spray drying is (2-3):1:6; and / or

[0015] The mass ratio of the ammonium salt to the precursor powder at the bottom of the crucible is (1-10):1.

[0016] Furthermore, in step S2, the fluorine-containing monomer A is one or more of vinyl fluoride, tetrafluoroethylene, hexafluoropropylene, vinylidene fluoride, chlorotrifluoroethylene, hexafluoropropylene oxide, hexafluoroisobutylene, perfluoroalkyl vinyl ether, perfluorobutylethylene, perfluoromethyl vinyl ether, perfluoropropyl vinyl ether, and perfluoro-n-propyl vinyl ether.

[0017] Further, in step S2, the Li a MX b The mass ratio of the halide solid electrolyte to the fluorinated monomer A is 100:(0.1-10);

[0018] Furthermore, in step S2, the dispersant is one or more non-polar or low-polar solvents such as piperidine, n-heptane, n-octane, n-decane, toluene, p-xylene, dichloroethane, dichloropropane, ester solvents, acetonitrile, etc.

[0019] Furthermore, in step S3, the lithium salt is one or more of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium bis(oxalatoborate), lithium oxalatodifluoroborate, lithium hexafluoroarsenate, lithium chloride, and lithium bromide.

[0020] Furthermore, in step S3, the thermal curing agent is one or more of tert-butyl perbenzoate, tert-butyl peroctoate, benzoyl peroxide, peroxyketal, dicumyl peroxide, dibenzoyl peroxide, azobisisobutyronitrile, azobisisoheptanenitrile, dimethyl azobisisobutyrate, ethylenediaminetetraacetic acid, benzoin dimethyl ether, and 4-dimethylamino-ethyl benzoate.

[0021] Furthermore, in step S3, the polymer monomer B is one or more of acrylate, acrylonitrile, methoxyacrylate, acrylamide, vinyl sulfonic acid, 2-acrylamide-2-methylpropanesulfonic acid, methyl methacrylate, glycidyl methacrylate, ethylene carbonate, propylene carbonate, ethylene oxide, acrylic acid, styrene, siloxane, and acetate.

[0022] Furthermore, in step S3, the mass ratio of the electrolyte powder wrapped by the fluorine-containing monomer A, the lithium salt, the thermal curing agent and the polymer monomer B is 100:(0.01-0.1):(0.002-0.03):(0.1-15).

[0023] Furthermore, in step S4, the hot pressing temperature is 20-200°C, the hot pressing pressure is 1-20 MPa, and the hot pressing time is 0.1-6 hours, preferably at 70-100°C for 2 hours under 1-7 MPa.

[0024] In addition, the present invention also includes the above-mentioned Li a MX b Application of composite solid electrolyte membrane in all-solid-state lithium batteries.

[0025] The present invention also proposes an all-solid-state lithium battery, comprising a dry composite positive electrode sheet, the above-mentioned Li a MX b The dry composite positive electrode plate is composed of the above-mentioned Li a MX b Based composite solid electrolyte, LiNi 0.83 Co 0.11 Mn 0.06 O2 is mixed with carbon black and pressed.

[0026] Compared with the prior art, the advantages and beneficial effects of the present invention include:

[0027] The spray drying-crosslinking-hot pressing method used in the present invention is a Li a MX b The preparation method of the composite solid electrolyte membrane has the advantages of simple operation, scalable preparation, uniform product composition and stable properties. The presence of fluorinated monomer A helps to broaden the scope of Li a MX b The electrochemical stability window of the composite solid electrolyte membrane is improved, and a more stable electrode / solid electrolyte interface is achieved. In addition, the Li a MX b The composite solid electrolyte membrane not only exhibits excellent air stability, flexibility, and processability, but also possesses a continuous three-dimensional ion conduction path. The resulting Li2ZrCl6-based composite solid electrolyte membrane has an ionic conductivity of up to 4.31 mS / cm. An all-solid-state lithium battery assembled with this composite electrolyte membrane achieves an initial discharge capacity of 191.6 mAh / g at a current density of 0.1C, with a capacity retention rate of 93.6% after 50 cycles. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 : is the impedance spectrum of the SS / Li2ZrCl6-based composite solid electrolyte membrane / SS symmetrical battery in Example 1 of the present invention;

[0029] Figure 2 1 is a discharge specific capacity-efficiency cycle curve of an all-solid-state lithium battery composed of a Li2ZrCl6-based composite solid electrolyte membrane in Example 1 of the present invention;

[0030] Figure 3 This is an electron microscope image of the Li3YCl6 solid electrolyte in Example 2 of the present invention. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0032] The spray drying conditions in all examples were set as an inlet air temperature of 230° C., an outlet air temperature of 120° C., and a feed rate of 800 mL / h.

[0033] Example 1

[0034] This embodiment provides a Li2ZrCl6-based composite solid electrolyte membrane, which is prepared by the following steps:

[0035] S1. A precursor powder obtained by spray drying an aqueous solution containing LiCl, ZrCl4 and NH4Cl in a molar ratio of 2:1:6 is placed in a crucible with NH4Cl on the bottom, wherein the mass ratio of NH4Cl to the precursor powder on the bottom of the crucible is 1:1. The crucible is then placed in a nitrogen atmosphere tubular furnace, and the temperature is increased from room temperature to 400°C at a heating rate of 2°C / min, and the temperature is maintained for 4 hours for annealing. The Li2ZrCl6 solid electrolyte is obtained after cooling in the furnace;

[0036] S2, mixing the Li2ZrCl6 solid electrolyte obtained in step S1 with the fluorine-containing monomer A, vinylidene fluoride, in a mass ratio of 100:3, adding a dispersant, piperidine, and spray drying to obtain a vinylidene fluoride-coated Li2ZrCl6 solid electrolyte powder;

[0037] S3, mixing the vinylidene fluoride-coated Li2ZrCl6 solid electrolyte powder obtained in step S2 with lithium bis(trifluoromethylsulfonyl)imide, benzoyl peroxide, and monomer B methyl methacrylate in a mass ratio of 100:0.03:0.004:3, and ball milling at a speed of 300 rpm for 1 h to obtain a composite electrolyte powder;

[0038] S4. The composite electrolyte powder obtained in step S3 is cold isostatically pressed at 100 MPa to obtain an initial electrolyte membrane, which is then hot pressed at 100° C. and 7 MPa for 2 h to obtain a target Li2ZrCl6-based composite solid electrolyte membrane with a thickness of 57 μm.

[0039] The prepared Li2ZrCl6-based composite solid electrolyte membrane was cut into 10 mm-sized discs and assembled with stainless steel (SS) blocking electrodes to form SS / Li2ZrCl6-based composite solid electrolyte membrane / SS symmetric cells. 6 The impedance is measured in the Hz range to evaluate its ionic conductivity. Figure 1As shown in Figure 2, the ionic conductivity is calculated according to σ = L / (R * S), where σ is the ionic conductivity of the solid electrolyte membrane, L is the thickness of the solid electrolyte membrane, S is the area of the solid electrolyte membrane, and R is the resistance of the solid electrolyte membrane. Therefore, the Li2ZrCl6 solid electrolyte membrane has an excellent ionic conductivity of 4.31mS / cm.

[0040] Li2ZrCl6, LiNi 0.83 Co 0.11 Mn 0.06 O2 and carbon black were uniformly mixed in a mass ratio of 30:65:5 and pressed into a composite positive electrode sheet, which was then assembled with a Li2ZrCl6-based composite solid electrolyte membrane and metallic lithium to form an all-solid-state lithium battery. The battery performance was investigated at a current density of 0.1C and a voltage range of 2.8-4.3V. The electrochemical performance at room temperature is shown in Figure 2. Figure 2 As shown, the first discharge specific capacity of the all-solid-state lithium battery composed of Li2ZrCl6-based composite solid electrolyte membrane is as high as 191.6mAh / g, and the capacity retention rate after 50 cycles is as high as 93.6%.

[0041] Example 2

[0042] This embodiment provides a Li3YCl6-based composite solid electrolyte membrane, which is prepared by the following steps:

[0043] S1. A precursor powder obtained by spray drying an aqueous solution containing LiCl, YCl3·6H2O, and NH4Cl in a molar ratio of 3:1:6 is placed in a crucible with NH4Cl on the bottom, wherein the mass ratio of NH4Cl to the precursor powder on the bottom of the crucible is 2:1. The crucible is then placed in a nitrogen atmosphere tubular furnace and heated from room temperature to 500°C at a heating rate of 2°C / min for 5 hours for annealing. The solid electrolyte Li3YCl6 is obtained after cooling in the furnace.

[0044] S2, mixing the Li3YCl6 solid electrolyte obtained in step S1 with the fluorinated monomer A hexafluoropropylene at a mass ratio of 100:2, 100:4, 100:6 and 100:8, adding acetonitrile, and obtaining a hexafluoropropylene-coated Li3YCl6 solid electrolyte powder by spray drying technology;

[0045] S3, mixing the hexafluoropropylene-coated Li3YCl6 solid electrolyte powder obtained in step S2 with lithium perchlorate, dibenzoyl peroxide, and monomer B acrylate in a mass ratio of 100:0.05:0.004:2, and ball milling at a rotation speed of 300 rpm for 1 hour to obtain a composite electrolyte powder;

[0046] S4. The composite electrolyte powder obtained in step S3 is cold isostatically pressed at 100 MPa to obtain an initial electrolyte membrane, which is then hot pressed at 70° C. and 1 MPa for 2 h to obtain a target Li3YCl6-based composite solid electrolyte membrane with a thickness of 48 μm.

[0047] Figure 3 It can be seen that the prepared Li3YCl6 solid electrolyte is nanoscale spherical particles.

[0048] The prepared Li3YCl6-based composite solid electrolyte membrane was cut into 10 mm-sized discs and assembled into SS / Li3YCl6-based composite solid electrolyte membrane / SS symmetrical cells. 6 The impedance and linear voltammetric scanning curves were measured in the Hz range to evaluate the ionic conductivity. The specific performance is shown in Table 1.

[0049] The prepared composite electrolyte powder and carbon black were uniformly mixed in a mass ratio of 70:30 and pressed into sheets. The mixed sheets were then assembled with a Li3YCl6-based composite solid electrolyte membrane and metallic lithium into an all-solid-state battery. The cyclic voltammetry curves were tested in the voltage range of -0.5-6.0 V at a scan rate of 0.1 mV / s to investigate the electrochemical stability window. The specific performance is shown in Table 1.

[0050] Li3YCl6、LiNi 0.83 Co 0.11 Mn 0.06 O2 and carbon black were uniformly mixed in a mass ratio of 30:65:5 and pressed into a composite positive electrode sheet, which was then assembled with a Li3YCl6-based composite solid electrolyte membrane and metallic lithium into an all-solid-state lithium battery. The battery performance was investigated at a current density of 0.1C and a voltage range of 2.8-4.3V. The specific performance is shown in Table 1.

[0051] Table 1 Experimental conditions and results of Example 2

[0052]

[0053]

[0054] Note: The capacity retention rates in the specific embodiments of the present invention are all the capacity retention rates after 50 cycles.

[0055] As can be seen from Table 1, under the same conditions, increasing the hexafluoropropylene content affects the ionic conductivity and electrochemical stability window of the Li3YCl6-based composite solid electrolyte membrane, as well as the electrochemical performance of its all-solid-state lithium battery. Among them, the Li3YCl6-based composite solid electrolyte membrane with a mass ratio of 100:4 exhibits the best performance, with an ionic conductivity of up to 3.40mS / cm, an electrochemical stability window of up to 4.77V, an initial discharge specific capacity of up to 190.5mAh / g, and a capacity retention rate of 90.7%.

[0056] Example 3

[0057] This embodiment proposes a Li3YCl 5.2 F 0.8 The composite solid electrolyte membrane is prepared by the following steps:

[0058] S1. The precursor powder obtained by spray drying an aqueous solution containing LiCl, YCl3·6H2O, YF3 and NH4Cl in a molar ratio of 3:0.733:0.267:6 was placed in a crucible with NH4Cl on the bottom, wherein the mass ratio of NH4Cl to the precursor powder on the bottom of the crucible was 2:1. The crucible was then placed in a nitrogen atmosphere tube furnace and heated from room temperature to 500℃ at a heating rate of 2℃ / min for 5h for annealing. Li3YCl was obtained after cooling in the furnace. 5.2 F 0.8 solid electrolytes;

[0059] S2, the Li3YCl obtained in step S1 5.2 F 0.8 The solid electrolyte and the fluorinated monomer A hexafluoropropylene were mixed at a mass ratio of 100:4, and acetonitrile was added. The hexafluoropropylene-coated Li3YCl was obtained by spray drying technology. 5.2 F 0.8 Solid electrolyte powder;

[0060] S3, the hexafluoropropylene-wrapped Li3YCl 5.2 F 0.8 The solid electrolyte powder was mixed with lithium perchlorate, azobisisobutyronitrile, and monomer B acrylate in a mass ratio of 100:0.05:0.004:2, and then ball-milled at a speed of 300 rpm for 1 h to obtain a composite electrolyte powder.

[0061] S4, the composite electrolyte powder obtained in step S3 was subjected to cold isostatic pressing at 100 MPa to obtain an electrolyte primary film, and then hot pressed at 70°C for 2 h under the conditions of 2 MPa, 3 MPa, 4 MPa and 5 MPa to obtain the target Li3YCl 5.2 F 0.8 Composite solid electrolyte membrane.

[0062] The prepared Li3YCl 5.2 F 0.8 The composite solid electrolyte membrane was cut into 10 mm discs and assembled with stainless steel (SS) blocking electrodes to form SS / Li3YCl 5.2 F 0.8 Composite solid electrolyte membrane / SS symmetrical battery, at 25℃, amplitude 50mV and 0.1-10 6 Its impedance was measured in the Hz range to evaluate its ionic conductivity. The specific performance is shown in Table 2.

[0063] The prepared composite electrolyte powder and carbon black were uniformly mixed in a mass ratio of 70:30 and pressed into tablets, and then mixed with Li3YCl 5.2 F 0.8 The all-solid-state battery was assembled with a composite solid electrolyte membrane and metallic lithium. The cyclic voltammetry curve was tested in the voltage range of -0.5-6.0 V at a scan rate of 0.1 mV / s to investigate its electrochemical stability window. The specific performance is shown in Table 2.

[0064] Li3YCl 5.2 F 0.8 、LiNi 0.83 Co 0.11 Mn 0.06 O2 and carbon black are uniformly mixed in a mass ratio of 30:65:5 and pressed into a composite positive electrode sheet, and then mixed with Li3YCl 5.2 F 0.8 The all-solid-state lithium battery was assembled with a composite solid electrolyte membrane and metallic lithium, and its battery performance was investigated at a current density of 0.1C and a voltage range of 2.8-4.3V. The specific performance is shown in Table 2.

[0065] Table 2 Experimental conditions and results of Example 3

[0066]

[0067] It can be seen from Table 2 that under the same conditions, the increase of hot pressing pressure will affect its ionic conductivity and electrochemical performance of all-solid-state lithium batteries, but will have little effect on the electrochemical stability window. 5.2 F 0.8 The composite solid electrolyte membrane exhibits optimal performance, with an ionic conductivity of up to 3.28mS / cm, an electrochemical stability window of up to 5.08V, a first discharge specific capacity of up to 188.8mAh / g, and a capacity retention rate of 95.5%.

[0068] Example 4

[0069] A Li2ZrCl6-based composite solid electrolyte membrane was prepared according to the method of Example 1, except that lithium bis(trifluoromethylsulfonyl)imide was replaced with lithium hexafluorophosphate. All other aspects were the same as in Example 1. The prepared Li2ZrCl6-based composite solid electrolyte membrane still had excellent ionic conductivity of 4.22 mS / cm. The all-solid-state lithium battery constructed with the membrane exhibited an initial discharge capacity of 191.1 mAh / g, and a capacity retention rate of 90.6% after 50 cycles.

[0070] Example 5

[0071] A Li2ZrCl6-based composite solid electrolyte membrane was prepared according to the method of Example 1, except that ZrCl4 was replaced with ZrO2. All other aspects were the same as in Example 1. The resulting Li2ZrCl6-based composite solid electrolyte membrane still had excellent ionic conductivity of 4.13 mS / cm. The all-solid-state lithium battery constructed with the membrane exhibited an initial discharge capacity of 190.8 mAh / g, and a capacity retention rate of 91.4% after 50 cycles.

[0072] Example 6

[0073] A Li3YF6-based composite solid electrolyte membrane was prepared according to the method of Example 2, except that YCl3·6H2O and NH4Cl were replaced with YF3 and NH4F. All other components were the same as in Example 2. The resulting Li3YF6-based composite solid electrolyte membrane still had excellent ionic conductivity of 2.13 mS / cm. The all-solid-state lithium battery constructed with the membrane exhibited an initial discharge capacity of 181.4 mAh / g, and a capacity retention rate of 92.6% after 50 cycles.

[0074] Comparative Example 1

[0075] A Li2ZrCl6-based composite solid electrolyte membrane was prepared according to the method of Example 1, except that the fluorinated monomer A, vinylidene fluoride, was not added. All other conditions were the same as in Example 1. The resulting Li2ZrCl6-based composite solid electrolyte membrane still had excellent ionic conductivity of 4.43 mS / cm. An all-solid-state lithium battery constructed using the membrane exhibited an initial discharge capacity of 192.1 mAh / g, and a capacity retention rate of 61.2% after 50 cycles.

[0076] Comparative Example 2

[0077] A Li2ZrCl6-based composite solid electrolyte membrane was prepared according to the method of Example 1, except that the composite electrolyte powder was not cold isostatically pressed but only cured by hot pressing at 100°C and 7 MPa for 2 hours. All other procedures were the same as in Example 1. The resulting Li2ZrCl6-based composite solid electrolyte membrane still had an excellent ionic conductivity of 3.18 mS / cm. The all-solid-state lithium battery constructed from the membrane exhibited an initial discharge capacity of 189.1 mAh / g, and a capacity retention rate of 69.8% after 50 cycles.

[0078] Comparative Example 3

[0079] A Li2ZrCl6-based composite solid electrolyte membrane was prepared according to the method of Example 1, except that the molar ratio of LiCl, ZrCl4, and NH4Cl was 2:1:20, and NH4Cl was not laid on the bottom of the crucible. All other conditions were the same as in Example 1. The prepared Li2ZrCl6-based composite solid electrolyte membrane still had excellent ionic conductivity of 3.27 mS / cm. The all-solid-state lithium battery constructed with the membrane exhibited an initial discharge capacity of 189.4 mAh / g, and a capacity retention rate of 74.2% after 50 cycles.

[0080] Comparative Example 4

[0081] A Li2ZrCl6-based composite solid electrolyte membrane was prepared according to the method of Example 1, except that the aqueous solution of LiCl, ZrCl4, and NH4Cl was dried in a water bath. All other procedures were the same as in Example 1. The resulting Li2ZrCl6-based composite solid electrolyte membrane still had excellent ionic conductivity of 3.34 mS / cm. The all-solid-state lithium battery constructed with the membrane exhibited an initial discharge capacity of 189.8 mAh / g, and a capacity retention rate of 76.5% after 50 cycles.

[0082] The present invention adopts spray drying-chemical crosslinking-hot pressing process to prepare Li a MX b The precursor powder obtained by drying the mixed solution containing Li source, M source and ammonium salt is placed in a crucible with ammonium salt on the bottom, annealed in an inert atmosphere, and cooled in the furnace to obtain Li a MX b Solid electrolyte, mixed with fluorinated monomer A and non-polar solvent, spray drying technology to obtain solid electrolyte powder coated with fluorinated monomer A, and then ball milled with lithium salt, thermal curing agent and monomer B to obtain composite electrolyte powder, which was successively cold isostatically pressed and hot pressed to obtain the target Li a MX b Based on a composite solid electrolyte membrane, it has excellent air stability and electrochemical performance.

[0083] In the above embodiment, the added Li source can also be selected from one or more of lithium chloride, lithium bromide, lithium fluoride, lithium iodide, lithium carbonate, lithium oxide, lithium hydroxide, lithium nitrate, lithium lactate, lithium oxalate, lithium formate, lithium hydrogen phosphate, lithium dihydrogen phosphate, lithium ammonium phosphate or lithium diammonium phosphate; the M source can also be selected from one or more of scandium, yttrium, hafnium, holmium, zirconium, tantalum, aluminum, gallium, iron, indium and lanthanide metal elements oxides, anhydrous halides, and halides containing crystal water; the ammonium salt can also be one or more of ammonium chloride, ammonium fluoride, ammonium iodide, ammonium bromide, ammonium nitrate, ammonium carbonate, ammonium sulfate, ammonium bifluoride, and ammonium bicarbonate.

[0084] In the above embodiment, the added dispersant may also be one or more non-polar or low-polar solvents such as piperidine, n-heptane, n-octane, n-decane, toluene, p-xylene, dichloroethane, dichloropropane, ester solvents, acetonitrile, etc. In the above embodiment, the added fluorinated monomer A may be one or more of vinyl fluoride, tetrafluoroethylene, hexafluoropropylene, vinylidene fluoride, chlorotrifluoroethylene, hexafluoropropylene oxide, hexafluoroisobutylene, perfluoroalkyl vinyl ether, perfluorobutylethylene, perfluoromethyl vinyl ether, perfluoropropyl vinyl ether, and perfluoro-n-propyl vinyl ether.

[0085] In the above embodiment, the added lithium salt can also be one or more of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium bis(oxalatoborate), lithium oxalatodifluoroborate, lithium hexafluoroarsenate, lithium chloride, and lithium bromide.

[0086] In the above embodiment, the added thermal curing agent can also be one or more of tert-butyl perbenzoate, tert-butyl peroctoate, benzoyl peroxide, peroxyketal, dicumyl peroxide, dibenzoyl peroxide, azobisisobutyronitrile, azobisisoheptanenitrile, dimethyl azobisisobutyrate, ethylenediaminetetraacetic acid, benzoin dimethyl ether, and 4-dimethylamino-ethyl benzoate.

[0087] In the above embodiment, the added monomer B may also be a monomer containing a carboxyl group, a xanthyl group, a thiol group, an amino group, an alkenyl group, or an epoxy group functional group, such as one or more of acrylate, acrylonitrile, methoxyacrylate, acrylamide, vinyl sulfonic acid, 2-acrylamide-2-methylpropanesulfonic acid, methyl methacrylate, glycidyl methacrylate, ethylene carbonate, propylene carbonate, ethylene oxide, acrylic acid, styrene, fluoride, siloxane, and acetate.

[0088] The key points of the present invention are: first, a high-purity nano-scale halide solid electrolyte is prepared by a liquid phase-layer method based on ammonium salt, and the reactants are mixed at the molecular or atomic level in the solution, which helps to prepare nano-scale halide solid electrolyte particles of uniform size; second, a non-polar or low-polarity solvent is used as a dispersant, a fluorine-containing monomer A is used as a coating material, and the halide solid electrolyte is uniformly functionalized and coated by spray drying technology to improve the moisture resistance of the halide solid electrolyte and broaden the electrochemical stability window; third, a continuous three-dimensional conductive network is formed by the homopolymerization and copolymerization reaction of fluorine-containing monomer A and monomer B to assist the migration of lithium ions, while improving the flexibility and processability of the electrolyte membrane; fourth, the composite electrolyte powder is pressed into a dense electrolyte film by cold isostatic pressing and hot pressing in succession to improve the energy density of the all-solid-state electrolyte and inhibit the penetration of lithium dendrites. This method is not only suitable for the preparation of a variety of halide solid electrolyte membranes, but also can achieve its large-scale preparation.

[0089] The specific embodiments of the present invention described above do not limit the scope of protection of the present invention. Any other corresponding changes and modifications made based on the technical concept of the present invention should be included in the scope of protection of the claims of the present invention.

Claims

1. A kind of Li a MX b A method for preparing a composite solid electrolyte membrane comprises the following steps: S1. Place the precursor powder obtained by spray drying a mixed aqueous solution containing a certain molar ratio of Li source, metal M source and ammonium salt in a container with ammonium salt on the bottom, anneal at 350-800℃ for 2-10h in an inert atmosphere, and cool it in the furnace to obtain Li a MX b solid electrolytes; S2, the Li obtained in step S1 a MX b The solid electrolyte is mixed with the fluorinated monomer A and the dispersant, and spray-dried to obtain the electrolyte powder coated with the fluorinated monomer A; S3, mixing the electrolyte powder coated with the fluorinated monomer A obtained in step S2 with a lithium salt, a thermal curing agent, and monomer B in a certain proportion in an inert atmosphere and ball milling to obtain a composite electrolyte powder; S4, the composite electrolyte powder obtained in step S3 is subjected to cold isostatic pressing to obtain an electrolyte primary film, and then hot pressing and curing to obtain the target Li a MX b A composite solid electrolyte membrane, wherein X is a halogen element, a is 2-3, b is 4-6, and at least one of the Li source, metal M source, and ammonium salt compound contains X; The metal M is one of scandium, yttrium, hafnium, holmium, zirconium, tantalum, aluminum, gallium, iron, indium and lanthanide metal elements; Monomer B is an organic substance containing a carboxyl group, an ester group, an amide group, a cyano group, an epoxy group, an alkenyl group or a siloxane bond.

2. The preparation method according to claim 1, characterized in that In step S1, the Li source is one or more of lithium chloride, lithium bromide, lithium fluoride, lithium iodide, lithium carbonate, lithium oxide, lithium hydroxide, lithium nitrate, lithium lactate, lithium oxalate, lithium formate, lithium hydrogen phosphate, lithium dihydrogen phosphate, lithium ammonium phosphate, and lithium diammonium phosphate; and / or The metal M source is one or more of an oxide, anhydrous halide, and halide containing crystal water of metal M; and / or The ammonium salt is one or more of ammonium chloride, ammonium fluoride, ammonium iodide, ammonium bromide, ammonium nitrate, ammonium carbonate, ammonium sulfate, ammonium bifluoride, and ammonium bicarbonate.

3. The preparation method according to claim 2, characterized in that In step S1, the molar ratio of the Li source, the metal M source and the ammonium salt in the mixed aqueous solution before spray drying is (2-3):1:6; and / or The mass ratio of the ammonium salt to the precursor powder at the bottom of the crucible is (1-10):

1.

4. The preparation method according to claim 1, characterized in that In step S2, the fluorinated monomer A is one or more of vinyl fluoride, tetrafluoroethylene, hexafluoropropylene, vinylidene fluoride, chlorotrifluoroethylene, hexafluoropropylene oxide, hexafluoroisobutylene, perfluoroalkyl vinyl ether, perfluorobutylethylene, perfluoromethyl vinyl ether, perfluoropropyl vinyl ether, and perfluoro-n-propyl vinyl ether; and / or In step S2, the Li a MX b The mass ratio of the halide solid electrolyte to the fluorinated monomer A is 100:(0.1-10); and / or The dispersant is one or more of piperidine, n-heptane, n-octane, n-decane, toluene, p-xylene, dichloroethane, dichloropropane, ester solvents and acetonitrile.

5. The preparation method according to claim 1, characterized in that In step S3, the lithium salt is one or more of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium bis(oxalatoborate), lithium oxalatodifluoroborate, lithium hexafluoroarsenate, lithium chloride, and lithium bromide.

6. The preparation method according to claim 1, characterized in that In step S3, the thermal curing agent is one or more of tert-butyl perbenzoate, tert-butyl peroctoate, benzoyl peroxide, peroxyketal, dicumyl peroxide, dibenzoyl peroxide, azobisisobutyronitrile, azobisisoheptanenitrile, dimethyl azobisisobutyrate, ethylenediaminetetraacetic acid, benzoin dimethyl ether, and 4-dimethylamino-ethyl benzoate.

7. The preparation method according to claim 1, characterized in that In step S3, the polymer monomer B is one or more of acrylate, acrylonitrile, methoxyacrylate, acrylamide, vinyl sulfonic acid, 2-acrylamide-2-methylpropanesulfonic acid, methyl methacrylate, glycidyl methacrylate, ethylene carbonate, propylene carbonate, ethylene oxide, acrylic acid, styrene, siloxane, and acetate.

8. The preparation method according to claim 1, characterized in that In step S3, the mass ratio of the electrolyte powder coated with the fluorine-containing monomer A, the lithium salt, the thermal curing agent and the monomer B is 100: (0.01-0.1): (0.002-0.03): (0.1-15).

9. The preparation method according to claim 1, characterized in that In step S4, the hot pressing temperature is 20-200° C., the hot pressing pressure is 1-20 MPa, and the hot pressing time is 0.1-6 h.

10. Li obtained by the preparation method according to any one of claims 1 to 9 a MX b Application of composite solid electrolyte membrane in the preparation of all-solid-state lithium batteries.

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