A method for preparing a high-voltage lithium metal battery based on in-situ solidification

Abstract

The application relates to a preparation method of a high-voltage lithium metal battery based on in-situ solidification, and the specific steps comprise the following steps: step 1, a high-voltage positive electrode is prepared by adopting a casting method; step 2, preparation of a modified high-voltage positive electrode containing a ceramic composite polymer protective layer; step 3, preparation of an in-situ solid-state polymer electrolyte; and step 4, preparation of a high-voltage lithium metal soft package battery. The application solves the defect that an in-situ solid-state polymer electrolyte system cannot match a high-voltage positive electrode, and realizes low impedance, high coulomb efficiency, high energy density and long cycle life of an in-situ solid-state lithium metal battery using a modified high-voltage positive electrode.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of solid-state lithium metal batteries, and particularly relates to a preparation method of a high-voltage lithium metal battery based on in-situ solidification. BACKGROUND

[0002] With the development of society, lithium batteries are widely used in various portable electronic products, electric vehicles, and large-scale energy storage devices. In order to improve the safety and energy density of lithium batteries, solid-state lithium metal batteries are considered as the key technology of the next generation of lithium batteries. The solid-state lithium metal battery is mainly composed of a lithium metal negative electrode, a solid-state electrolyte, and a positive electrode material. The solid-state electrolyte is divided into inorganic ceramic solid-state electrolyte and organic polymer solid-state electrolyte. Although the inorganic ceramic solid-state electrolyte has high ionic conductivity and an electrochemical stability window, it is brittle, not easy to mass-produce, and has serious interface problems, which restrict its large-scale commercial application. The organic polymer electrolyte is divided into in-situ solid-state polymer electrolyte and non-in-situ solid-state polymer electrolyte. The in-situ solid-state polymer electrolyte is widely studied and applied due to its simple preparation process, good interface compatibility with the electrode, and excellent long cycle capacity.

[0003] In order to improve the energy density of the in-situ solid-state lithium metal battery, high-voltage positive electrode materials (such as lithium cobaltate and high-nickel ternary positive electrode) are matched with lithium metal batteries. However, due to the low electrochemical stability window of the in-situ solid-state polymer electrolyte, it is easy to oxidize and decompose in the high-voltage lithium metal battery, thereby reducing the coulomb efficiency of the lithium metal battery and shortening the cycle life. Therefore, solving the problem of easy decomposition of the electrolyte in the in-situ solid-state lithium metal battery under high pressure is a key technology to realize high-energy-density in-situ solid-state lithium metal batteries. SUMMARY

[0004] The purpose of the present application is to solve the problem of easy oxidation and decomposition of the electrolyte in the high-voltage in-situ solid-state lithium metal battery. A preparation method of a high-voltage lithium metal battery based on in-situ solidification is proposed. A composite polymer high-voltage protective layer containing inorganic ceramic powder fillers is generated in-situ on the surface of the high-voltage positive electrode. A modified high-voltage positive electrode is prepared, which has excellent compatibility with the in-situ solid-state polymer electrolyte and protects the electrolyte from oxidation and decomposition on the surface of the high-voltage positive electrode. The in-situ solid-state lithium metal battery using the modified high-voltage positive electrode realizes low impedance, high coulomb efficiency, high energy density, and long cycle life.

[0005] The purpose of the present application is achieved by the following technical solution: a preparation method of a high-voltage lithium metal battery based on in-situ solidification, comprising the following steps:

[0006] Step 1: preparing a high-voltage positive electrode by using a casting method:

[0007] 1.1, 180-200 parts by weight of N-methyl pyrrolidone, 8-10 parts of polyvinylidene fluoride binder are weighed into a stirrer, the stirring rate is 1500-2000 r / min, and stirring is carried out for 1-2 h to obtain a PVDF solution;

[0008] 1.2, 8-10 parts of conductive carbon black are added to the solution obtained in step 1.1, and stirring is continued at a speed of 1500-2000 r / min for 1-2 h;

[0009] 1.3, 60-80 parts of high-voltage positive active material are added to the mixture obtained in step 1.2, and stirring is continued at a speed of 1500-2000 r / min for 2-3 h to obtain a slurry;

[0010] 1.4, the slurry obtained in step 1.3 is vacuum degassed and filtered through gauze, then coated on an aluminum foil by a coating machine, the coating thickness is 60-200 μm, the drying temperature is 100-140 ℃, after coating, drying is carried out in a vacuum oven at 70-90 ℃ for 18-30 h, and then rolling is carried out to obtain a high-voltage positive electrode, which is cut to obtain a positive electrode when used;

[0011] Step 2, preparation of modified high-voltage positive electrode with ceramic composite polymer protective layer:

[0012] 2.1, the first lithium salt is dissolved in the first monomer, stirring at 450-550 r / min for 1.5-3 h to form a 0.8-2 M lithium salt solution;

[0013] 2.2, 5-20 parts of sieved nano ceramic particles are added to the lithium salt solution, first stirred at 450-550 r / min for 1.5-3 h, then ultrasonically dispersed for 1-3 times, each time for 20-40 min, to obtain a suspension; then, 0.2-1 part of a thermal initiator is added and stirred for 20-40 min to obtain a homogeneous precursor solidification liquid;

[0014] 2.3, the solidification liquid in step 2.2 is dropped on the surface of the high-voltage positive electrode at a rate of 0.67-4 μL / cm 2 After standing for 1-5 min, in-situ solidification is carried out at 100-140 ℃ for 0.5-2 h, the thermal initiator forms free radicals to initiate the in-situ polymerization of the first monomer, and finally a composite polymer protective layer containing nano ceramic particles is formed, i.e. a modified high-voltage positive electrode is obtained;

[0015] Step 3, preparation of in-situ solid-state polymer electrolyte:

[0016] 3.1, 20-40 parts of the second monomer and 5-10 parts of the crosslinking agent are mixed and stirred for 20-40 min to obtain a mixed liquid A;

[0017] 3.2, 5-10 parts of the second lithium salt is added in the mixed solution A, stirring for 20-40 min, and the obtained mixed solution B is stored at 2-8℃;

[0018] 3.3, 0.1-0.5 parts of the thermal initiator and 39.5-69.9 parts of the plasticizer are added in the mixed solution B, and stirring for 20-40 min, to obtain the solid-state electrolyte in-situ solidification precursor solution;

[0019] Step 4, preparation of high-pressure lithium metal soft-pack battery:

[0020] 4.1, the lithium foil is cut into a predetermined size, and the nickel tab is welded; the modified high-pressure positive electrode is cut into a predetermined size, and the aluminum tab is welded, and the insulation tape is wound around the welding position for insulation;

[0021] 4.2, the lithium metal negative electrode obtained in step 4.1 is stacked with the porous framework film and the modified high-pressure positive electrode obtained in step 2 in sequence, and the aluminum plastic film is packaged, and the packaging temperature is 160-180℃, to obtain a dry cell;

[0022] 4.3, the in-situ solidification precursor solution obtained in step 3 is injected into the dry cell obtained in step 4.2, and the injection amount is 32-50μL per 1-1.5cm 2 of the porous framework film, and then vacuumizing, sealing, and sealing at a temperature of 160-180℃, to obtain the cell after injection;

[0023] 4.4, the cell after injection is placed at room temperature for 10-12 h, and then in-situ solidification is carried out at 40-80℃ for 5h-24 h, to generate the solid-state polymer electrolyte in-situ, and finally the high-pressure lithium metal battery based on in-situ solidification is obtained.

[0024] Further improvement of the application is that in step 1.3, the high-pressure positive electrode active material is lithium cobaltate or ternary positive electrode.

[0025] Further improvement of the application is that in step 2.2, the sieved nano ceramic particles are Li7La3Zr2O 12 , Li 6.4 La3Zr 1.4 Ta 0.6 O 12 , Li5La3M2O 12 (M=Ta or Nb), Li 10 GeP2S 12 , In 0.25 O 12 , Li3N, Li 14One or more of Zn(GeO4)4, LiZr2(PO4)3, LiPON nanoparticles, and the powder particle size is less than 200 nm.

[0026] The further improvement of the application is that the first lithium salt and the second lithium salt are one of LiTFSI, LiFSI, LiClO4, LiPF6, LiDFOB and LiBOB.

[0027] The further improvement of the application is that the first monomer and the second monomer are one of methyl methacrylate, ethyl methacrylate, methyl acrylate, ethyl acrylate, ethylene carbonate, and vinylene carbonate.

[0028] The further improvement of the application is that the crosslinking agent is one of polyethylene glycol dimethacrylate, ethylene glycol diacrylate, pentaerythritol tetramethyl acrylate, pentaerythritol tetraacrylate, tripropylene glycol diacrylate, and trimethylolpropane triacrylate.

[0029] The further improvement of the application is that the thermal initiator is one of azobisisobutyronitrile, azobisisopentyl nitrile, and azobisisoheptyl nitrile. The plasticizer is a lithium salt solution of 0.8-5 M, the solute is one or two of LiTFSI, LiFSI, LiPF6, LiDFOB and LiBOB, and the solvent is one or more of ethylene carbonate, propylene carbonate, 1,3-dioxolane, ethylene glycol dimethyl ether, diethyl carbonate, and methyl ethyl carbonate.

[0030] The further improvement of the application is that the porous framework film is one of lignocellulose film, electrospun polyimide film, glass fiber film, and electrospun polyvinylidene fluoride film, and the thickness is less than 100 μm.

[0031] Compared with the prior art, the application has the following advantages:

[0032] The application provides a preparation method of a high-voltage lithium metal battery based on in-situ solidification. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 The high-voltage protective layer of the lithium metal battery obtained by all the examples and all the comparative examples of the application has the action principle shown in the schematic diagram.

[0034] Figure 2 AC impedance plots for lithium metal batteries of Example 2 and Comparative Example 1;

[0035] Figure 3 Capacity vs. voltage plots for the 1st cycle for button lithium metal batteries of Example 2 and Comparative Example 1;

[0036] Figure 4 Capacity vs. voltage plots for the 2nd cycle for button lithium metal batteries of Example 2 and Comparative Example 1;

[0037] Figure 5 Capacity vs. voltage plots for the 3rd cycle for button lithium metal batteries of Example 2 and Comparative Example 1;

[0038] Figure 6 Coulombic efficiency vs. cycle number plots for 3 cycles for button lithium metal batteries of Example 2 and Comparative Example 1. DETAILED DESCRIPTION

[0039] In order to deepen the understanding of the present application, the present application will be further described in conjunction with the embodiments and drawings, which are only used to explain the present application and do not constitute a limitation on the protection scope of the present application.

[0040] In the description of the present application, it should be understood that the terms indicating the orientation or positional relationship, such as the orientation or positional relationship based on the drawings, are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the structure or unit referred to must have a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0041] In the present application, unless otherwise explicitly specified and limited, the terms such as “connection”, “provided with”, “have” and the like should be understood in a broad sense, for example, it can be fixed connection, detachable connection, or integral connection, which can be mechanical connection, or direct connection, or connection through intermediate medium, and for those skilled in the art, the basic meaning of the above terms in the present application can be understood according to the specific circumstances.

[0042] A preparation method of a high-voltage lithium metal battery based on in-situ solidification, comprising the following steps:

[0043] Step 1, using a casting method to prepare a high-voltage positive electrode:

[0044] 1.1, according to the weight fraction, 180-200 parts of N-methyl pyrrolidone, 8-10 parts of polyvinylidene fluoride binder are weighed into a blender, the stirring rate is 1500-2000 r / min, and the stirring time is 1-2 h to obtain a PVDF solution;

[0045] 1.2, 8-10 parts of conductive carbon black is added to the solution obtained in step 1.1, and stirring is continued at a speed of 1500-2000 r / min for 1-2 h;

[0046] 1.3, 60-80 parts of high-voltage positive active material is added to the mixed solution obtained in step 1.2, and stirring is continued at a speed of 1500-2000 r / min for 2-3 h to obtain a slurry;

[0047] 1.4, the slurry obtained in step 1.3 is vacuum degassed and filtered through gauze, then coated on an aluminum foil by a coating machine, the coating thickness is 60-200 μm, the drying temperature is 100-140 ℃, after coating, drying is carried out in a vacuum oven at 70-90 ℃ for 18-30 h, and then rolling is carried out to obtain a high-voltage positive electrode, which is cut to obtain a positive electrode when used;

[0048] Step 2, preparation of modified high-voltage positive electrode with ceramic composite polymer protective layer:

[0049] 2.1, the first lithium salt is dissolved in the first monomer, stirring at 450-550 r / min for 1.5-3 h to form a 0.8-2 M lithium salt solution;

[0050] 2.2, 5-20 parts of sieved nano ceramic particles is added to the lithium salt solution, first stirring at 450-550 r / min for 1.5-3 h, then ultrasonic dispersion for 1-3 times, each time for 20-40 min, to obtain a suspension; then, 0.2-1 parts of thermal initiator is added and stirred for 20-40 min to obtain a homogeneous precursor solidification liquid;

[0051] 2.3, the solidification liquid in step 2.2 is dropped on the surface of the high-voltage positive electrode at a rate of 0.67-4 μL / cm 2 , and after standing for 1-5 min, in-situ solidification is carried out at 100-140 ℃ for 0.5-2 h, the thermal initiator forms free radicals to initiate the in-situ polymerization of the first monomer, and finally a composite polymer protective layer containing nano ceramic particles is formed, i.e. a modified high-voltage positive electrode is obtained;

[0052] Step 3, preparation of in-situ solid-state polymer electrolyte:

[0053] 3.1, 20-40 parts of the second monomer and 5-10 parts of the crosslinking agent are mixed and stirred for 20-40 min to obtain a mixed liquid A;

[0054] 3.2, 5-10 parts of the second lithium salt is added to the mixed liquid A, and stirring is continued for 20-40 min to obtain a homogeneous mixture, and the obtained mixed liquid B is stored at 2-8 ℃;

[0055] 3.3, add 0.1-0.5 parts of thermal initiator and 39.5-69.9 parts of plasticizer to the mixed solution B, and stir for 20-40 min to obtain a solid-state electrolyte in-situ solidification precursor solution;

[0056] Step 4, preparation of high-voltage lithium metal soft-pack battery:

[0057] 4.1, cut the lithium foil into a predetermined size and weld the nickel tab; cut the modified high-voltage positive electrode into a predetermined size, weld the aluminum tab, and wrap the welding with insulating tape;

[0058] 4.2, stack the lithium metal negative electrode obtained in step 4.1 with the porous framework film and the modified high-voltage positive electrode obtained in step 2, and then perform aluminum plastic film packaging at a packaging temperature of 160-180 ℃ to obtain a dry cell;

[0059] 4.3, inject the in-situ solidification precursor solution obtained in step 3 into the dry cell obtained in step 4.2, and the injection amount is 32-50 μL per 1-1.5 cm 2 The porous framework film is injected with 32-50 μL, and then vacuumed, sealed, and sealed at a temperature of 160-180 ℃ to obtain the cell after injection;

[0060] 4.4, place the cell after injection at room temperature for 10-12 h, and then in-situ solidify at 40-80 ℃ for 5 h-24 h to generate a solid-state polymer electrolyte in-situ, and finally obtain a high-voltage lithium metal battery based on in-situ solidification.

[0061] Further, in step 1.3, the high-voltage positive active material is lithium cobaltate or a ternary positive electrode.

[0062] Further, in step 2.2, the sieved nano ceramic particles are one or more of Li7La3Zr2O 12 , Li 6.4 La3Zr 1.4 Ta 0.6 O 12 , Li5La3M2O 12 (M=Ta or Nb), Li 10 GeP2S 12 , In 0.25 O 12 , Li3N, Li 14 Zn(GeO4)4, LiZr2(PO4)3, LiPON nanoparticles, and the powder particle size is less than 200 nm.

[0063] Further, the first lithium salt and the second lithium salt are one of LiTFSI, LiFSI, LiClO4, LiPF6, LiDFOB, and LiBOB.

[0064] Further, the first monomer and the second monomer are one of methyl methacrylate, ethyl methacrylate, methyl acrylate, ethyl acrylate, ethylene carbonate, and vinylene carbonate.

[0065] Further, the crosslinking agent is one of polyethylene glycol dimethacrylate, ethylene glycol diacrylate, pentaerythritol tetramethyl acrylate, pentaerythritol tetraacrylate, tripropylene glycol diacrylate, and trimethylolpropane triacrylate.

[0066] Further, the thermal initiator is one of azobisisobutyronitrile, azobisisovaleronitrile, and azobisisoheptanonitrile. The plasticizer is a lithium salt solution of 0.8-5 M, the solute is one or two of LiTFSI, LiFSI, LiPF6, LiDFOB, and LiBOB, and the solvent is one or several of ethylene carbonate, propylene carbonate, 1,3-dioxolane, ethylene glycol dimethyl ether, diethyl carbonate, and methyl ethyl carbonate.

[0067] Further, the porous framework film is one of lignocellulose film, electrospun polyimide film, glass fiber film, and electrospun polyvinylidene fluoride film, and the thickness is less than 100 μm.

[0068] In the present application, if a high-voltage lithium metal battery is prepared, the lithium foil is cut into 48 mm*56 mm in step 4.1, the nickel tab is welded, the modified high-voltage positive electrode is cut into 46 mm*54 mm, the aluminum tab is welded, and the insulation tape is wound around the welding position for insulation. If a high-voltage lithium metal button cell is prepared, the difference lies in that the modified high-voltage positive electrode is a 14 mm diameter disc, the lithium metal negative electrode is a 15.4 mm diameter lithium sheet, a CR2025 type battery shell is used, and the button cell pressing pressure is 10 Mpa, and the remaining preparation steps are exactly the same.

[0069] Example 1

[0070] A preparation method of a high-voltage lithium metal battery based on in-situ curing, comprising the following steps:

[0071] Step 1, a high-voltage positive electrode is prepared by using a casting method:

[0072] 1.1, 180 parts of N-methyl pyrrolidone and 8 parts of polyvinylidene fluoride binder are weighed according to the weight fraction, added to a blender, and stirred at a stirring rate of 1500 r / min for 1 h to obtain a PVDF solution;

[0073] 1.2, 8 parts of conductive carbon black are added to the solution obtained in step 1.1, and stirring is continued at a rotation speed of 1500 r / min for 1 h;

[0074] 1.3, 60 parts of lithium cobalt oxide active material were added to the mixed solution obtained in step 1.2, and stirring was continued at a speed of 1500 r / min for 2 h to obtain a slurry;

[0075] 1.4, the slurry obtained in step 1.3 was vacuum degassed and filtered through gauze, then coated on an aluminum foil by a coating machine with a coating thickness of 60 μm, a drying temperature of 100°C, and dried in a vacuum oven at 70°C for 18 h after coating was completed, and then rolled to obtain a high-voltage positive electrode, which was cut to obtain a positive electrode for use;

[0076] Step 2, preparation of a modified high-voltage positive electrode with a ceramic composite polymer protective layer:

[0077] 2.1, LiTFSI was dissolved in methyl methacrylate, stirred at 450 r / min for 1.5 h to form a 0.8M lithium salt solution;

[0078] 2.2, 5 parts of sieved nano ceramic particles Li7La3Zr2O 12 (D 50 =200 nm) were added to the lithium salt solution, first stirred at 450 r / min for 1.5 h, then ultrasonically dispersed once for 20 min each time to obtain a suspension; then, 0.2 parts of azobisisobutyronitrile was added and stirred for 20 min to obtain a homogeneous precursor solidification liquid;

[0079] 2.3, the solidification liquid in step 2.2 was added dropwise to the surface of the high-voltage positive electrode at a rate of 0.67 μL / cm 2 , and immediately placed at 100°C for in-situ solidification for 0.5 h, and the thermal initiator formed free radicals to initiate the in-situ polymerization of the first monomer, and finally a composite polymer protective layer containing nano ceramic particles was formed, i.e. a modified high-voltage positive electrode was obtained;

[0080] Step 3, preparation of an in-situ solid-state polymer electrolyte:

[0081] 3.1, 20 parts of vinylene carbonate and 5 parts of pentaerythritol tetraacrylate were mixed and stirred for 20 min to obtain a mixed solution A;

[0082] 3.2, 5 parts of LiTFSI was added to the mixed solution A and stirred for 20 min to obtain a mixed solution B, which was stored at 2°C;

[0083] 3.3, 0.1 parts of azobisisobutyronitrile and 39.5 parts of plasticizer (1 M LiTFSI dissolved in DOL / DME = 1: 1) were added to the mixed solution B and stirred for 20 min to obtain a solid-state electrolyte in-situ solidification precursor liquid;

[0084] Step 4, preparation of a high-voltage lithium metal soft pack battery:

[0085] 4.1, cut the lithium foil into a predetermined size and weld the nickel tab; cut the modified high-voltage positive electrode into a predetermined size, weld the aluminum tab, and wrap the welding with insulating tape;

[0086] 4.2, stack the lithium metal negative electrode obtained in step 4.1 with the polyimide film (22 um thick) and the modified high-voltage positive electrode obtained in step 2 in sequence, and then perform aluminum plastic film packaging at a packaging temperature of 160°C to obtain a dry battery;

[0087] 4.3, inject the in-situ cured precursor liquid obtained in step 3 into the dry battery obtained in step 4.2, and the injection amount is 32 μL per 1 cm 2 The polyimide film is injected with 32 μL, and then vacuum is drawn, sealed, and sealed at a temperature of 160°C to obtain the battery after liquid injection;

[0088] 4.4, the battery after liquid injection is placed at room temperature for 10 h, and then in-situ cured at 40°C for 5 h to generate a solid-state polymer electrolyte, and finally a high-voltage lithium metal battery based on in-situ curing is obtained.

[0089] Step 5, the obtained high-voltage lithium metal battery is subjected to charge-discharge test on a LAND charge-discharge instrument at a rate of 0.1 C for 3 cycles.

[0090] Example 2

[0091] A preparation method of a high-voltage lithium metal battery based on in-situ curing, comprising the following steps:

[0092] Step 1, a high-voltage positive electrode is prepared by a casting method:

[0093] 1.1, 200 parts of N-methyl pyrrolidone and 10 parts of polyvinylidene fluoride binder are weighed according to the weight fraction and added to a blender, and stirred at a stirring rate of 2000 r / min for 2 h to obtain a PVDF solution;

[0094] 1.2, 10 parts of conductive carbon black is added to the solution obtained in step 1.1 and stirred at a speed of 2000 r / min for 2 h;

[0095] 1.3, 80 parts of lithium cobaltate active material is added to the mixed liquid obtained in step 1.2, and stirring is continued at a speed of 2000 r / min for 3 h to obtain a slurry;

[0096] 1.4, the slurry obtained in step 1.3 is vacuum degassed and filtered through gauze, then coated on an aluminum foil by a coating machine with a coating thickness of 200 μm, and dried at a temperature of 140°C. After coating, dry in a vacuum oven at 90°C for 30 h, and then roll to obtain a high-voltage positive electrode, which is cut to obtain a positive electrode when used;

[0097] Step 2, preparation of modified high-voltage cathode with ceramic composite polymer protective layer:

[0098] 2.1, LiTFSI was dissolved in vinyl carbonate, stirred at 550 r / min for 3 h to form a 2M lithium salt solution;

[0099] 2.2, 20 parts of sieved ceramic particles Li7La3Zr2O 12 (D 50 =200 nm) were added to the lithium salt solution, first stirred at 550 r / min for 3 h, then ultrasonically dispersed for 3 times, 40 min each time, to obtain a suspension; then, 1 part of azobisisobutyronitrile was added and stirred for 40 min to obtain a homogeneous precursor curing liquid;

[0100] 2.3, the curing liquid in step 2.2 was dropped on the surface of the high-voltage cathode at a rate of 4 μL / cm 2 , and after standing for 5 min, in-situ curing was immediately carried out at 140 ℃ for 2 h, the thermal initiator formed free radicals to initiate the in-situ polymerization of the first monomer, and finally a composite polymer protective layer containing nano ceramic particles was formed, i.e. a modified high-voltage cathode was obtained;

[0101] Step 3, preparation of in-situ solid-state polymer electrolyte:

[0102] 3.1, 40 parts of vinyl carbonate and 10 parts of pentaerythritol tetraacrylate were mixed and stirred for 40 min to obtain a mixed liquid A;

[0103] 3.2, 10 parts of LiTFSI was added to the mixed liquid A, stirred for 40 min to mix evenly, and the obtained mixed liquid B was stored at 8 ℃;

[0104] 3.3, 0.5 parts of azobisisobutyronitrile and 69.9 parts of plasticizer (1 M LiTFSI dissolved in DOL / DME=1:1) were added to the mixed liquid B, and then stirred for 40 min to obtain a solid electrolyte in-situ curing precursor liquid;

[0105] Step 4, preparation of high-voltage lithium metal soft-pack battery:

[0106] 4.1, lithium foil was cut into a predetermined size and nickel tabs were welded; the modified high-voltage cathode was cut into a predetermined size, aluminum tabs were welded, and insulation tape was wrapped around the welding part for insulation;

[0107] 4.2, the lithium metal anode obtained in step 4.1 was laminated with a polyimide film (22 um thick) and the modified high-voltage cathode obtained in step 2 in sequence, and then aluminum plastic film packaging was carried out, with a packaging temperature of 180 ℃, to obtain a dry cell;

[0108] 4.3, inject the in-situ cured precursor solution obtained in step 3 into the dry cell obtained in step 4.2, the injection amount is 50 μL per 1.5 cm 2 Polyimide film injection 50 μL, then vacuum, sealing, sealing temperature is 180 ℃, the injection of the cell;

[0109] 4.4, the injection of the cell, at room temperature for 12 h, and then in-situ curing at 80 ℃ for 24 h, in-situ generation of solid-state polymer electrolyte, finally get in-situ curing based on high pressure lithium metal battery.

[0110] Step 5, the high pressure lithium metal battery obtained is subjected to charge-discharge test on LAND charge-discharge instrument, rate 0.1 C cycle 3 times.

[0111] Example 3

[0112] A preparation method of a high pressure lithium metal battery based on in-situ curing, comprising the following steps:

[0113] Step 1, using casting method to prepare high pressure positive electrode:

[0114] 1.1, according to the weight fraction, 190 parts of N-methyl pyrrolidone, 9 parts of polyvinylidene fluoride binder are weighed into a blender, the stirring rate is 1800 r / min, and the stirring time is 1.5 h to obtain a PVDF solution;

[0115] 1.2, 9 parts of conductive carbon black is added to the solution obtained in step 1.1, and the stirring speed is 1800 r / min, and the stirring time is 1.5 h;

[0116] 1.3, 70 parts of lithium cobalt oxide active material is added to the mixed solution obtained in step 1.2, and the stirring speed is 1800 r / min, and the stirring time is 2.5 h, to obtain a slurry;

[0117] 1.4, the slurry obtained in step 1.3 is vacuum degassed and filtered through gauze, and then coated on an aluminum foil by a coating machine, the coating thickness is 80 μm, the drying temperature is 120 ℃, and after coating, the coated aluminum foil is dried in a vacuum oven at 80 ℃ for 24 h, and then rolled to obtain a high pressure positive electrode, which is cut to obtain a positive electrode when used;

[0118] Step 2, preparation of modified high pressure positive electrode with ceramic composite polymer protective layer:

[0119] 2.1, LiTFSI is dissolved in vinylene carbonate, stirred at 500 r / min for 2 h to form a 1M lithium salt solution;

[0120] 2.2, 10 parts of sieved Li 6.4 La3Zr 1.4 Ta 0.6 O12 , stirring at 500 r / min for 2 h, and then ultrasonic dispersion for 3 times, each for 30 min, to obtain a suspension; then, 0.8 parts of azobisisobutyronitrile was added and stirred for 30 min to obtain a homogeneous precursor curing solution;

[0121] 2.3, the curing solution in step 2.2 was dropped on the surface of the high-voltage positive electrode at a rate of 2 μL / cm 2 , and then in-situ cured at 120 °C for 1 h immediately after standing for 3 min, the thermal initiator formed free radicals to initiate the in-situ polymerization of the first monomer, and finally a composite polymer protective layer containing nano ceramic particles was formed, that is, the modified high-voltage positive electrode was obtained;

[0122] Step 3, preparation of in-situ solid-state polymer electrolyte:

[0123] 3.1, 30 parts of vinylene carbonate and 8 parts of pentaerythritol tetraacrylate were mixed and stirred for 30 min to obtain a mixed solution A;

[0124] 3.2, 8 parts of LiTFSI was added to the mixed solution A and stirred for 30 min to obtain a homogeneous mixture, and the obtained mixed solution B was stored at 5 °C;

[0125] 3.3, 0.3 parts of azobisisobutyronitrile and 50 parts of plasticizer (1 M LiTFSI dissolved in DOL / DME=1:1) were added to the mixed solution B, and then stirred for 30 min to obtain a solid-state electrolyte in-situ curing precursor solution;

[0126] Step 4, preparation of high-voltage lithium metal soft-pack battery:

[0127] 4.1, cut the lithium foil into a predetermined size and weld the nickel tab; cut the modified high-voltage positive electrode into a predetermined size, weld the aluminum tab, and wrap the insulation with insulation tape at the welding position;

[0128] 4.2, stack the lithium metal negative electrode obtained in step 4.1 with a polyimide film (22 um thick) and the modified high-voltage positive electrode obtained in step 2 in sequence, and then perform aluminum plastic film packaging at a packaging temperature of 170 °C to obtain a dry cell;

[0129] 4.3, inject the in-situ curing precursor solution obtained in step 3 into the dry cell obtained in step 4.2, and the injection amount is 40 μL per 1.2 cm 2 of the porous skeleton film, and then perform vacuum pumping, sealing, and sealing at a temperature of 170 °C to obtain the liquid-injected cell;

[0130] 4.4, place the liquid-injected cell at room temperature for 10 h, and then in-situ cure at 60 °C for 15 h to generate a solid-state polymer electrolyte in-situ, and finally obtain a high-voltage lithium metal battery based on in-situ curing;

[0131] Step 5, the obtained high-voltage lithium metal battery was subjected to charge-discharge test on a LAND charge-discharge instrument, and the rate was 0.1 C and the cycle was 3 cycles.

[0132] Comparative Example 1

[0133] This comparative example is compared with Example 2, the difference is that the preparation of the modified high-voltage positive electrode in Step 2 is omitted, that is, the high-voltage positive electrode prepared in Step 1 is not subjected to any treatment for battery assembly, and the remaining steps are exactly the same as Example 2.

[0134] The purpose of setting Comparative Example 1 is to illustrate that the composite polymer high-voltage protective layer of the application can protect the electrolyte from oxidative decomposition reaction on the surface of the high-voltage positive electrode in the in-situ solid-state polymer electrolyte system, and the high-voltage lithium metal battery can work normally.

[0135] The application successively tests Example 1, Example 2, Example 3 and Comparative Example 1 on a LAND tester at 0.1 C cycle, the first cycle coulombic efficiency of Example 1 is 85.3%, the first cycle coulombic efficiency of Example 2 is 90.21%, the first cycle coulombic efficiency of Example 3 is 87.96%, and the first cycle coulombic efficiency of Comparative Example 1 is 81.10%, so Example 2 is the best example.

[0136] Figure 1 It is a schematic diagram of the action principle of the high-voltage protective layer, which shows that the high-voltage protective layer can effectively avoid the oxidative decomposition of the in-situ solid-state polymer electrolyte on the surface of the high-voltage positive electrode. Figure 2 It is the AC impedance spectrum of the high-voltage lithium metal button cell of Example 1 and Comparative Example 1, which shows that the protective layer has no obvious effect on the interface impedance, that is, the interface compatibility of the protective layer with the electrolyte and the high-voltage positive electrode is relatively good. Figure 3 、 Figure 4 、 Figure 5 It is the capacity-voltage curve of the first 3 cycles of the high-voltage lithium metal button cell, which shows that during the cycle process, the lithium metal battery without high-voltage protective layer will have obvious overcharging phenomenon, and the capacity will also rapidly decay. Figure 6 It is Figure 3 、 Figure 4 、 Figure 5 It is a comparative bar chart of the coulombic efficiency, which shows that the high-voltage protective layer can effectively avoid the decomposition of the electrolyte and improve the coulombic efficiency of the high-voltage lithium metal battery.

[0137] The application provides a preparation method of a high-voltage lithium metal battery based on in-situ solidification, a dense ceramic-containing composite polymer protective layer is generated on the surface of a high-voltage positive electrode in a high-temperature in-situ solidification mode (100-140 DEG C, ensuring no small molecule residue), and a solid-state polymer electrolyte is prepared in the in-situ solidification mode, so that a safe and high-energy-density lithium metal battery is prepared by matching a lithium metal negative electrode with high theoretical specific capacity and low chemical potential. The application provides a fundamentally effective strategy, solves the defect that an in-situ solid-state polymer electrolyte system cannot match a high-voltage positive electrode, and improves the energy density of the lithium metal battery.

[0138] Those skilled in the art should understand that the application is not limited to the above-mentioned embodiments, and the above-mentioned embodiments and descriptions in the specification are only to illustrate the principles of the application, and various changes and improvements can be made without departing from the spirit and scope of the application, and these changes and improvements all fall within the scope of the application. The scope of protection of the application is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a high-voltage lithium metal battery based on in-situ solidification, comprising the following steps: Step 1: Prepare the high-voltage cathode using the casting method: 1.1 Weigh 180-200 parts by weight of N-methylpyrrolidone and 8-10 parts by weight of polyvinylidene fluoride binder and add them to a mixer. Stir at a speed of 1500-2000 r / min for 1-2 hours to obtain a PVDF solution. 1.2 Add 8-10 parts of conductive carbon black to the solution obtained in step 1.1 and continue stirring at a speed of 1500-2000 r / min for 1-2 h; 1.3 Add 60-80 parts of high-voltage positive electrode active material to the mixture obtained in step 1.2, and continue to stir at a speed of 1500-2000 r / min for 2-3 hours to obtain a slurry; 1.4 After vacuum degassing and gauze filtration, the slurry obtained in step 1.3 is coated on aluminum foil using a coating machine with a coating thickness of 60-200μm and a drying temperature of 100-140℃. After coating, it is dried in a vacuum oven at 70-90℃ for 18-30h, and then rolled to obtain a high-voltage positive electrode. When in use, it is cut to obtain the positive electrode. Step 2: Preparation of the modified high-voltage cathode containing a ceramic composite polymer protective layer: 2.1 Dissolve the first lithium salt in the first monomer and stir at 450-550 r / min for 1.5-3 h to form a 0.8-2 M lithium salt solution; 2.2 Add 5-20 parts of sieved nano-ceramic particles to the lithium salt solution, stir at 450-550 r / min for 1.5-3 h, then ultrasonically disperse 1-3 times, 20-40 min each time, to obtain a suspension; Then, add 0.2-1 parts of thermal initiator and stir for 20-40 minutes to obtain a homogeneous precursor curing liquid; 2.3, the solidification liquid in step 2.2 is 0.67-4 μL / cm 2 Dropped on the surface of the high-voltage positive electrode, and after standing for 1-5 min, in-situ solidification at 100-140 ℃ for 0.5-2 h, the thermal initiator forms free radicals to initiate the in-situ polymerization of the first monomer, and finally forms a composite polymer protective layer containing nano ceramic particles, that is, a modified high-voltage positive electrode; Step 3: Preparation of in-situ solid polymer electrolyte: 3.1 Mix 20-40 parts of the second monomer and 5-10 parts of the crosslinking agent and stir for 20-40 minutes to obtain mixture A; 3.2 Add 5-10 parts of the second lithium salt to mixture A, stir for 20-40 min to mix evenly, and store the resulting mixture B at 2-8℃. 3.3 Add 0.1-0.5 parts of thermal initiator and 39.5-69.9 parts of plasticizer to mixture B, and stir for 20-40 minutes to obtain the in-situ solidification precursor solution of solid electrolyte; Step 4: Fabrication of high-voltage lithium metal pouch cells: 4.1 Cut the lithium foil to the predetermined size and weld the nickel tabs; cut the modified high-voltage positive electrode to the predetermined size and weld the aluminum tabs, and wrap the weld joint with insulating tape for insulation; 4.2 The lithium metal anode obtained in step 4.1 is sequentially stacked with a porous framework membrane and the modified high voltage cathode obtained in step 2, and then encapsulated with an aluminum-plastic film at a temperature of 160-180 ℃ to obtain a dry cell. 4.3, inject the in-situ solidified precursor solution obtained in step 3 into the dry cell obtained in step 4.2, the injection amount is 1-1.5 cm 2 Porous skeleton film injection 32-50 μL, and then vacuum, sealing, sealing temperature is 160-180 ℃, the injection of the cell; 4.4 After the electrolyte is injected, the cell is left to stand at room temperature for 10-12 hours, and then cured in situ at 40-80 ℃ for 5-24 hours to generate a solid polymer electrolyte in situ, thus obtaining a high-voltage lithium metal battery based on in-situ curing.

2. The method for preparing a high-voltage lithium metal battery based on in-situ solidification according to claim 1, characterized in that, The high-voltage positive active material in step 1.3 is lithium cobaltate or a ternary positive electrode.

3. The method for preparing a high-voltage lithium metal battery based on in-situ solidification according to claim 2, characterized in that, In step 2.2, the sieved nanoceramic particles are Li7La3Zr2O 12 , Li 6.4 La3Zr 1.4 Ta 0.6 O 12 , Li5La3M2O 12 , wherein M = Ta or Nb, Li 10 GeP2S 12 , In 0.25 O 12 , Li3N, Li 14 Zn(GeO4)4, LiZr2(PO4)3, LiPON nanoparticles, and the powder particle size is less than 200 nm.

4. The method for preparing a high-voltage lithium metal battery based on in-situ solidification according to claim 3, characterized in that, The first lithium salt and the second lithium salt are each one of LiTFSI, LiFSI, LiClO4, LiPF6, LiDFOB, and LiBOB.

5. The method for preparing a high-voltage lithium metal battery based on in-situ solidification according to claim 4, characterized in that, The first monomer and the second monomer are each one of methyl methacrylate, ethyl methacrylate, methyl acrylate, ethyl acrylate, ethylene carbonate, and vinylene carbonate.

6. The method for preparing a high-voltage lithium metal battery based on in-situ solidification according to claim 5, characterized in that, The crosslinking agent is one of polyethylene glycol dimethacrylate, ethylene glycol diacrylate, pentaerythritol tetramethyl acrylate, pentaerythritol tetraacrylate, tripropylene glycol diacrylate, and trimethylolpropane triacrylate.

7. The method for preparing a high-voltage lithium metal battery based on in-situ solidification according to claim 6, characterized in that, The thermal initiator is one of azobisisobutyronitrile, azobisisopentyl nitrile, and azobisisoheptyl nitrile; the plasticizer is a lithium salt solution with a concentration of 0.8-5 M, the solute is one or two of LiTFSI, LiFSI, LiPF6, LiDFOB, and LiBOB, and the solvent is one or more of ethylene carbonate, propylene carbonate, 1,3-dioxolane, ethylene glycol dimethyl ether, diethyl carbonate, and methyl ethyl carbonate.

8. The method for preparing a high-voltage lithium metal battery based on in-situ solidification according to claim 7, characterized in that, The porous framework film is one of a lignocellulose film, an electrospun polyimide film, a glass fiber film, and an electrospun polyvinylidene fluoride film, and has a thickness of less than 100 μm.

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