A semi-dry method for producing a half-dry type diaphragm-free full-solid lithium battery

Abstract

The application belongs to the technical field of electrochemical energy storage batteries, and particularly relates to a semi-dry method piece-type separator-free full-solid-state lithium battery production method. Positive electrode slurry including molten salt electrolyte and negative electrode slurry including solvent water are respectively extruded into films by a screw, and the formed films are respectively hot-rolled and compounded with current collectors, and punched into positive electrode unit pieces and negative electrode unit pieces. Solid electrolyte is extruded into a film by a screw and punched into a solid electrolyte film unit piece after being extruded into a film, and assembled to obtain a semi-dry method piece-type separator-free full-solid-state lithium battery. The application not only guarantees slurry uniformity and film formability, but also greatly reduces the use of toxic and harmful solvents. Meanwhile, the solid electrolyte film piece technology is adopted, which avoids the problem of edge cracking of conventional laminates, further reduces the battery production cost, and improves the energy density, cycle performance, large-rate charge and discharge and safety performance of the battery.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electrochemical energy storage batteries, and particularly relates to a semi-dry method for producing a full-solid-state lithium battery without a diaphragm. BACKGROUND

[0002] In recent years, new energy as a national strategic emerging industry has developed rapidly. As an important support and auxiliary technology of new energy industry, electrochemical energy storage devices have become a global research and development hotspot. New type of electrochemical energy storage devices are developing towards high specific energy, high safety, long cycle life and low cost. In recent years, solid-state lithium batteries using solid electrolyte are one of the key technical directions of new generation high-performance lithium batteries. They have obvious advantages such as high specific energy, high safety and long life, and are widely used in important fields such as electric power, transportation, industry, communication, building and military. They are also one of the key supports to achieve the goal of carbon peak and carbon neutral.

[0003] At present, solid-state lithium batteries have not really formed a commercial market scale. In addition to the problems existing in the batteries such as the structural stability of electrode active materials, solid-solid interface electron transfer and ion conduction, which need to be solved, the production process of solid-state lithium batteries is also an important factor restricting their development.

[0004] (1) In the electrode sheet production process, in the existing traditional process, the positive electrode is generally prepared by dispersing positive electrode dry powder, including positive electrode active material dry powder, binder dry powder and conductive agent dry powder, in a positive electrode solvent. The total weight ratio of the positive electrode solvent is up to 40%. The use of a large amount of positive electrode solvent N-methyl pyrrolidone brings great pressure to environmental protection. The more solvents used, the more energy is consumed for recovery. If no solvent is used, a pure dry process can be adopted. There are two ways: ① The binder dry powder (such as polyvinylidene fluoride and polytetrafluoroethylene) is melted and mixed with the positive electrode active material dry powder and the conductive agent dry powder at high temperature (above 300°C) and then extruded. This will bring two adverse results: the structure of the positive electrode material changes at high temperature, and the film cannot be formed due to poor flowability during extrusion; ② If the binder dry powder is filamentized by high-speed hot air and then mixed with the positive electrode active material dry powder and the conductive agent dry powder, the mixture is not uniform due to the large density difference between the positive electrode dry powders. Therefore, if the positive electrode solvent can be omitted without sacrificing the uniformity and film-forming property of the slurry, it will be an economical and efficient solution. After repeated research, it is found that a solid material containing a cyano functional group can be used as a co-melting solvent. When mixed with a metal lithium salt material, it has good mutual solubility and forms a liquid molten salt electrolyte, which can replace the positive electrode solvent. Thus, the solvent recovery cost and production cost are greatly reduced. At the same time, the solid material containing a cyano functional group as a solvent system has a high potential window, is not flammable, has a high flash point, a wide liquid range and is not easy to produce gas, which can greatly improve the safety of the battery. In addition, for the negative electrode, even the aqueous system slurry also needs to consume energy and time to dry, and reduce the water content of the negative electrode slurry, which is also meaningful.

[0005] (2) In the combination process between the solid electrolyte membrane and the electrode, generally speaking, the solid electrolyte usually has polymer solid electrolyte and inorganic solid electrolyte. ① For the polymer solid electrolyte, the polymer is usually dissolved in an organic solvent, mixed with a lithium salt, coated on a skeleton separator, and then used between the positive electrode and the negative electrode. The process is complex and still needs a separator material. The pure polymer solid electrolyte has a low room temperature ionic conductivity (~10 -6 S / cm), and when applied to a solid-state lithium battery, the battery has poor rate performance (<0.1C) and needs to be operated at a high temperature (~60°C); the in-situ polymerization process using a small-molecule monomer with unsaturated bonds and an initiator also needs a separator material as a skeleton support body; ② For the inorganic solid electrolyte, its film-forming property is worse. Even if the film is formed, it has problems such as high brittleness and poor mechanical properties; ③ The combination of the polymer solid electrolyte and the inorganic solid electrolyte can solve the film-forming problem and improve the ionic conductivity (>10 -4 S / cm), but when the "Z" type lamination process is adopted, the connection of the composite electrolyte membrane at the edge of the electrode sheet has a cracking problem. SUMMARY

[0006] To solve the above problems, the application provides a semi-dry method split diaphragm-free full solid-state lithium battery production method.

[0007] To achieve the above object, the application adopts the technical scheme of:

[0008] A semi-dry method split diaphragm-free full solid-state lithium battery production method, wherein positive electrode slurry including molten salt electrolyte and negative electrode slurry including solvent water are respectively extruded into films by a screw, and the formed films are respectively hot-rolled and compounded with current collectors, and then punched into positive electrode unit pieces and negative electrode unit pieces; solid electrolyte is extruded into a film by a screw and then punched into a solid electrolyte film unit piece; and the negative electrode unit piece, the solid electrolyte film unit piece and the positive electrode unit piece are stacked in a repeated unit type, so as to obtain a semi-dry method split diaphragm-free full solid-state lithium battery.

[0009] Specifically,

[0010] (1) Positive electrode slurry film preparation: positive electrode dry powder is fully mixed and uniformly placed in a double-screw extruder, and then extruded into a film-shaped positive electrode slurry film through a rectangular extrusion port; wherein, according to the weight ratio, the positive electrode active material dry powder, the binder dry powder, the conductive agent dry powder and the molten salt electrolyte are (85-95) : (1-5) : (1-5) : (0.5-3) ;

[0011] (2) Negative electrode slurry film preparation: negative electrode dry powder is placed in a double-screw extruder, and then negative electrode solvent water is added and fully mixed and uniformly, and then extruded into a film-shaped negative electrode slurry film through a rectangular extrusion port; wherein, according to the weight ratio, the negative electrode active material dry powder, the binder dry powder and the conductive agent dry powder are (85-95) : (1-5) : (1-5) ; the mass ratio of the negative electrode dry powder to the negative electrode solvent water is (80-95) : (5-20) ;

[0012] (3) The positive electrode slurry film obtained in step (1) and the negative electrode slurry film obtained in step (2) are respectively adhered to the positive electrode current collector and the negative electrode current collector by hot rolling through a hot roller pressing mechanism, so as to respectively form a positive electrode piece and a negative electrode piece;

[0013] (4) The positive electrode piece and the negative electrode piece are respectively punched into a square positive electrode unit piece and a square negative electrode unit piece by a die cutting mechanism;

[0014] (5) Preparation of solid electrolyte membrane: Preheat the twin-screw extruder, then put the polymer solid electrolyte dry powder, inorganic solid electrolyte dry powder, and molten salt electrolyte into the twin-screw extruder in a mass ratio of (1~30): (70~80): (0.5~10), mix them thoroughly and evenly, and extrude them into a film through the U-shaped extrusion nozzle. Then, through the hot roller pressing structure, solid electrolyte membrane is formed by hot roller pressing. After passing through the die-cutting mechanism, it is punched into square solid electrolyte membrane unit sheets.

[0015] (6) The battery cell is constructed according to the repeating structure of negative electrode unit piece / / solid electrolyte membrane unit piece / / positive electrode unit piece / / solid electrolyte membrane unit piece / / negative electrode unit piece / / solid electrolyte membrane unit piece / / positive electrode unit piece ... negative electrode unit piece. The two sides of the battery cell are always negative electrode unit pieces.

[0016] (7) Weld the battery cell to the tabs and encapsulate it in the casing to obtain a solid-state lithium battery.

[0017] The dew point of the environment before packaging is controlled at -25℃ to -65℃, and the solid-state lithium battery is formed by heating and pressurizing.

[0018] The battery formation pressure is 0.3MPa~2MPa. If the pressure is <0.3MPa, the interface contact between the positive or negative electrode and the solid electrolyte membrane is not tight during formation, affecting the battery's rate performance and cycle performance. If the pressure is >2MPa, the internal structure of the battery is easily damaged. The heating temperature is 40℃~80℃. If the temperature is <40℃, the battery cannot quickly form a good interface film, requiring a reduction in the formation current rate and extending the formation time, affecting formation efficiency. If the temperature is >80℃, the stability of the interface film decreases, and the battery's cycle performance deteriorates. The formation current rate is 0.02C~0.2C. If the current rate is <0.02C, the charging time is long, affecting production efficiency. If the current rate is >0.2C, a uniform electrolyte film cannot be formed on the electrode surface, and the battery's cycle performance decreases.

[0019] The square negative electrode unit is 2-5 mm longer than the square positive electrode unit in both the horizontal and vertical directions; the square solid electrolyte membrane unit is 2-5 mm longer than the square negative electrode unit in both the horizontal and vertical directions.

[0020] The molten salt electrolyte is composed of lithium salt and a solid material containing cyano functional groups, wherein the mass percentage of lithium salt in the molten salt electrolyte is 35-65%.

[0021] The lithium salt is one or more of lithium borate, lithium fluorine sulfonyl imide, and lithium fluorine phosphate.

[0022] The solid material containing cyano functional group is one or more of malononitrile, succinonitrile, polyacrylonitrile, azobisisobutyronitrile, azobisisoheptylnitrile, hexachlorotriphosphazene.

[0023] The positive active material dry powder is one or more of LiMn2O4, LiCoO2, LiFePO4, LiNi x Co y Mn z O2, LiNi x Co y Al z O2 and lithium-rich compounds, wherein x+y+z=1, 0<x, y, z<1.

[0024] The negative active material dry powder is one or more of metallic lithium, alloy material, graphite, amorphous carbon, mesocarbon microbead, nano-silicon, silicon-carbon material, lithium titanate and SiO n , wherein 0<n<2.

[0025] The positive current collector is aluminum foil, carbon-coated aluminum foil or perforated aluminum foil, wherein the thickness of the aluminum foil, carbon-coated aluminum foil or perforated aluminum foil is 8-25 microns, when the thickness of the foil is <8 microns, the positive slurry film is easily broken when passing through the hot-pressing mechanism, and when the thickness of the foil is >25 microns, the weight of the battery is increased, and the energy density of the battery is reduced; the hole diameter of the perforated aluminum foil is 30-100 microns, and when the hole diameter is >100 microns, the mechanical properties of the foil are poor, and the foil is easily broken.

[0026] The negative current collector is copper foil or perforated copper foil, wherein the thickness of the copper foil or perforated copper foil is 6-15 microns, the negative slurry film is easily broken when passing through the hot-pressing mechanism, and when the thickness of the foil is >15 microns, the weight of the battery is increased, and the energy density of the battery is reduced; the hole diameter of the perforated aluminum foil is 30-100 microns, and when the hole diameter is >100 microns, the mechanical properties of the foil are poor, and the foil is easily broken.

[0027] The inorganic solid electrolyte dry powder includes but is not limited to Li 10 SiP2S 12 , Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 , Li 10 GeP2S 12 , Li 1.3 Al 0.3 Ti 1.7 (PO4)3, Li7La3Zr2O 12 , Li 1.5 Al 0.5 Ge 1.5(PO4)3, Li 6.4 La3Zr 1.4 Ta 0.6 O 12 One or more of the following;

[0028] The solid polymer powder includes, but is not limited to, one or more of the following: polyethylene oxide, polyimide, polyvinylidene fluoride, polytetrafluoroethylene, polysiloxane, polytrimethylene carbonate, polyvinyl carbonate, polypropylene carbonate, polyvinyl carbonate, polyvinylidene fluoride-hexafluoropropylene, polymethacrylate, and polyacrylonitrile.

[0029] The adhesive powder includes, but is not limited to, one or more of the following: polyvinylidene fluoride, polyvinylidene chloride-hexafluoropropylene, polytetrafluoroethylene, polyethylene oxide, polyester, polyamide, polyamide-imide, polymethyl methacrylate, polycarbonate, carboxymethyl cellulose, styrene-butadiene copolymer, polyacrylonitrile, sodium carboxymethyl cellulose, or styrene-butadiene rubber;

[0030] Conductive agent dry powder includes, but is not limited to, one or more of carbon black, acetylene black, carbon nanotubes, carbon fibers, graphene or graphene oxide;

[0031] The pressure of hot rolling in step (3) is 5~20MPa. When the pressure is <5MPa, the positive electrode slurry film and the positive electrode current collector or the negative electrode slurry film and the negative electrode current collector are not tightly bonded, which reduces the battery cycle performance and rate performance. When the pressure is >20MPa, the current collector is easily torn due to excessive pressure. At this time, the contact between the dry powder particles of the positive electrode active material or the dry powder particles of the negative electrode active material is too tight, which will result in poor ion diffusion performance, which will also reduce the battery cycle performance and rate performance. The temperature is 50~200℃. If the temperature is <50℃, the hot pressing effect will not be achieved, and the battery energy density and cycle performance will decrease. If the temperature is >200℃, the physical properties of the dry powder of the positive electrode active material will be damaged, and the battery energy density and cycle performance will decrease.

[0032] The square negative electrode unit is 2-5 mm longer than the square positive electrode unit in both the horizontal and vertical directions. If the length is less than 2 mm, when misalignment occurs between the electrodes, lithium ions extracted from the positive electrode will have no place to be received in the negative electrode, easily forming lithium dendrites, causing safety problems, and potentially leading to battery fire or explosion. If the length is greater than 5 mm, the negative electrode unit is too large, reducing the battery's energy density. Similarly, the square solid electrolyte membrane unit is 2-5 mm longer than the square negative electrode unit in both the horizontal and vertical directions. If the length is less than 2 mm, when misalignment occurs between the electrodes and the separator, it can easily cause a short circuit between the positive and negative electrodes, leading to fire or explosion. If the length is greater than 5 mm, the solid electrolyte is too large, reducing the battery's energy density.

[0033] Compared with the prior art, the present application has the following beneficial effects:

[0034] (1) Compared with the traditional electrode preparation process, the present application uses a solid material containing a cyano functional group as a co-melting solvent. When mixed with lithium salt material, it has good mutual solubility, forms a liquid molten salt electrolyte, and can replace the positive electrode solvent N-methyl pyrrolidone to form a semi-dry electrode sheet production process. The solvent recovery device must be installed during the production process of the positive electrode, thereby greatly reducing the solvent recovery cost and production cost. At the same time, the lithium salt in the positive electrode molten salt electrolyte can not only conduct lithium ions, but also supplement the consumption of lithium ions in the positive electrode material during the cycle process, thereby improving the cycle performance. In addition, the solid material containing a cyano functional group in the molten salt electrolyte has a high potential window, is not flammable, has a high flash point, a wide liquid range, and is not easy to produce gas, and can be compatible with high specific energy solid-state lithium batteries, thereby greatly improving the safety of the battery.

[0035] (2) Compared with the pure dry electrode preparation process, a small amount of liquid molten salt electrolyte containing a cyano functional group as a co-melting solvent is added to the positive electrode, and a small amount of aqueous solvent is added to the negative electrode in the present application, which can improve the uniformity and film-forming property of the electrode slurry mixture. The stability of the electrode slurry can be realized under normal temperature conditions, thereby improving the cycle performance, coulombic efficiency, large-rate charge and discharge, and safety performance of the battery.

[0036] (3) Compared with the "Z" type stacking production process used in the traditional battery production, the present application uses a slicing type battery production process. The solid electrolyte film is pre-cut to form a solid electrolyte film unit piece, which is then placed between the positive electrode unit piece and the negative electrode unit piece, and the stacking is repeated, thereby effectively avoiding the cracking problem of the connection of the solid electrolyte film at the edge part of the electrode piece.

[0037] (4) Under the premise of ensuring ion conductivity and insulating the positive and negative electrodes, the present application uses a process of combining a polymer solid electrolyte, an inorganic solid electrolyte, and a lithium salt, thereby eliminating the use of a separator, reducing auxiliary materials, reducing costs, and improving the energy density of the battery. DETAILED DESCRIPTION

[0038] The present application will be further described below through examples.

[0039] Example 1

[0040] (1) Positive electrode slurry film preparation: 93 kg of positive electrode active material dry powder LiNi 0.8 Co 0.1 Mn 0.1O2, 2.5 g of binder dry powder polyvinylidene fluoride, 2.5 kg of conductive agent carbon black dry powder, are added into the twin-screw extruder through the feeding port, 10 kg of molten salt electrolyte (containing 6 kg of succinonitrile powder, 3.5 kg of LiTFSI powder, and 0.5 kg of LiDFOB powder in the molten salt electrolyte) is added, the screw rotation speed is adjusted to 250 rpm, the positive electrode slurry is formed, and then the positive electrode slurry is extruded into a film-shaped positive electrode slurry film through the rectangular extrusion port, and the whole process is controlled at an ambient dew point of -30°C.

[0041] (2) Negative electrode slurry film preparation: take 94 kg of negative electrode active material dry powder silicon-carbon material, 3 kg of binder polytetrafluoroethylene dry powder, and 3 kg of conductive agent carbon black dry powder, add them into the twin-screw extruder through the feeding port, add 15 kg of negative electrode solvent water, adjust the screw rotation speed to 230 rpm, form the negative electrode slurry, and then extrude the negative electrode slurry into a film-shaped negative electrode slurry film through the rectangular and outlet ports, and the whole process is controlled at an ambient dew point of -10°C.

[0042] (3) Take an aluminum foil with a thickness of 12 μm as the positive electrode current collector, and adhere the positive electrode slurry film prepared in (1) to the positive and negative surfaces of the positive electrode current collector by hot rolling, with a hot rolling pressure of 15 MPa and a heating temperature of 120°C, to form a positive electrode sheet; take a copper foil with a thickness of 8 μm, and adhere the negative electrode slurry film prepared in (2) to the positive and negative surfaces of the negative electrode current collector by hot rolling, with a hot rolling pressure of 15 MPa and a heating temperature of 120°C, to form a negative electrode sheet, and the whole process is controlled at an ambient dew point of -30°C.

[0043] (4) Use a die-cutting mechanism to punch the positive electrode sheet and the negative electrode sheet into square positive electrode unit sheets with tabs and square negative electrode unit sheets, respectively, wherein the square negative electrode unit sheets are 4 mm longer than the square positive electrode unit sheets in both the horizontal and vertical directions, and the whole process is controlled at an ambient dew point of -30°C.

[0044] (5) Solid electrolyte film preparation: preheat the twin-screw extruder to 150°C, take 5 kg of polymer solid electrolyte polyethylene oxide, 92 kg of inorganic solid electrolyte Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3, 3 kg of molten salt electrolyte (containing 1.75 kg of succinonitrile powder, 1.2 kg of LiTFSI powder, and 0.05 kg of LiDFOB powder in the molten salt electrolyte), which is added to the twin-screw extruder through the feeding port, and the screw rotation speed is adjusted to 250 rpm to form a solid electrolyte mixture. Then, it is extruded through the rectangular extrusion port and rolled into a solid electrolyte film through the hot roller mechanism with a rolling pressure of 15 MPa and a temperature of 120°C. Then, it is punched into a square solid electrolyte film unit piece through the die-cutting mechanism. The length of the square solid electrolyte film in the transverse and longitudinal directions is 4 mm longer than that of the square negative electrode unit piece. The entire process is controlled in an environment with a dew point of -30°C.

[0045] (6) According to the repeating structure type of negative electrode unit piece / / solid electrolyte film unit piece / / positive electrode unit piece / / solid electrolyte film unit piece / / negative electrode unit piece / / solid electrolyte film unit piece / / positive electrode unit piece, an electric core is formed with a capacity of 20 Ah. The entire process is controlled in an environment with a dew point of -30°C.

[0046] (7) The electric core is welded with tabs and packaged in a shell to prepare a solid-state lithium battery. The entire process is controlled in an environment with a dew point of -30°C.

[0047] (8) Battery formation: The solid-state lithium battery is formed by heating and pressing. The heating temperature is 60°C, the pressure is 0.6 MPa, and the current rate is 0.1C.

[0048] Test results: The battery has an energy density of 367.9 Wh / kg at 0.5C rate current and an energy density of 346.7 Wh / kg at 1C rate current. The capacity retention rate is 93.6% after 1000 cycles at 0.5C, and the coulombic efficiency is 99.7%. According to the nail safety test according to the national standard GBT 31485-2015, the battery does not smoke, does not catch fire, and does not explode.

[0049] Comparative Example 1

[0050] In the preparation of the positive electrode slurry film in Example 1, the weight of the molten salt electrolyte was changed to 30 kg. It was found that the flowability of the positive electrode slurry was too high, and it could not be formed into a film after passing through the rectangular extrusion port.

[0051] Comparative Example 2

[0052] In the preparation of the positive electrode slurry film in Example 1, the weight of the molten salt electrolyte was changed to 0 kg. It was found that the viscosity of the positive electrode slurry was too high, and the positive electrode slurry could not be formed into a film.

[0053] Comparative Example 3

[0054] The negative electrode solvent water in the negative electrode slurry film preparation in Example 1 is changed to 45 kg, and it is found that the negative electrode slurry has too high fluidity and cannot form a film after passing through the square extrusion port. The amount of solvent used is 3 times that in Example 1, and the battery production cost is increased.

[0055] Comparative Example 4

[0056] The negative electrode solvent water in the negative electrode slurry film preparation in Example 1 is changed to 0 kg, and it is found that the negative electrode slurry has too high viscosity and cannot form a film.

[0057] Comparative Example 5

[0058] In the solid electrolyte film preparation in Example 1, the sheeting process is not used, that is, the square solid electrolyte film unit sheet is not punched using the die cutting mechanism, but is directly wound after rolling. In the preparation of the battery cell, the "Z" type lamination process is used, and it is found that the solid electrolyte film cracks at the edge of the positive and negative electrodes, causing short circuit of the positive and negative electrodes during charging and discharging, and the battery catches fire and explodes, with poor safety.

[0059] Comparative Example 6

[0060] The thickness of the positive electrode current collector aluminum foil in Example 1 is changed to 6 μm, and the rest is the same as in Example 1. Under the above hot pressing conditions, it is found that the positive electrode slurry film and the current collector aluminum foil are broken when passing through the hot pressing mechanism.

[0061] Comparative Example 7

[0062] The thickness of the positive electrode current collector aluminum foil in Example 1 is changed to 35 μm, and the rest is the same as in Example 1.

[0063] Test: The battery has an energy density of 285.6 Wh / kg at 0.5C rate current, an energy density of 235.6 Wh / kg at 1C rate current, a capacity retention rate of 93.5% at 0.5C for 1000 cycles, a coulomb efficiency of 99.6%, and the battery does not smoke, catch fire, or explode during the nail penetration safety test.

[0064] Example 2

[0065] The positive electrode current collector in Example 1 is changed to a perforated aluminum foil with a hole diameter of 50 μm, and the rest is the same as in Example 1.

[0066] Test: The battery has an energy density of 374.6 Wh / kg at 0.5C rate current, an energy density of 336.8 Wh / kg at 1C rate current, a capacity retention rate of 93.7% at 0.5C for 1000 cycles, a coulomb efficiency of 99.7%, and the battery does not smoke, catch fire, or explode during the nail penetration safety test.

[0067] Comparative Example 8

[0068] The hole diameter of the punched aluminum foil in Example 2 was changed to 150 micrometers, and the rest was the same as in Example 2. It was found that the positive electrode slurry film and the current collector aluminum foil were broken when passing through the hot-pressing mechanism under the hot-pressing conditions described in the above examples.

[0069] Comparative Example 9

[0070] The thickness of the negative electrode current collector aluminum foil in Example 1 was changed to 4 micrometers, and the rest was the same as in Example 1. It was found that the negative electrode slurry film and the current collector copper foil were broken when passing through the hot-pressing mechanism under the hot-pressing conditions described in the above examples.

[0071] Comparative Example 10

[0072] The thickness of the negative electrode current collector aluminum foil in Example 1 was changed to 20 micrometers, and the rest was the same as in Example 1.

[0073] Tested: The battery had an energy density of 265.6 Wh / kg at a 0.5C rate current, an energy density of 236.6 Wh / kg at a 1C rate current, a capacity retention rate of 93.6% at 0.5C for 1000 cycles, a coulombic efficiency of 99.7%, and the battery passed the nail penetration safety test, showing that the battery did not smoke, catch fire, or explode.

[0074] Example 3

[0075] The negative electrode current collector in Example 1 was changed to a punched copper foil with a hole diameter of 50 micrometers, and the rest was the same as in Example 1.

[0076] Tested: The battery had an energy density of 378.8 Wh / kg at a 0.5C rate current, an energy density of 325.7 Wh / kg at a 1C rate current, a capacity retention rate of 93.8% at 0.5C for 1000 cycles, a coulombic efficiency of 99.8%, and the battery passed the nail penetration safety test, showing that the battery did not smoke, catch fire, or explode.

[0077] Comparative Example 11

[0078] The hole diameter of the punched copper foil in Example 3 was changed to 150 micrometers, and the rest was the same as in Example 3. It was found that the negative electrode slurry film and the current collector copper foil were broken when passing through the hot-pressing mechanism under the hot-pressing conditions described in the above examples.

[0079] Example 4

[0080] The inorganic solid electrolyte in Example 1 was changed to Li 6.4 La3Zr 1.4 Ta 0.6 O 12 , and the rest was the same as in Example 1.

[0081] Tested: the battery has an energy density of 328.8 Wh / kg at 0.5C rate current, an energy density of 293.7 Wh / kg at 1C rate current, a capacity retention of 86.8% at 0.5C for 1000 cycles, a coulombic efficiency of 99.2%, and the nail penetration safety test shows that the battery does not smoke, does not catch fire, and does not explode.

[0082] Example 5

[0083] In Example 1, the polymer solid electrolyte is replaced by polyacrylonitrile, 4 kg in weight, and the inorganic solid electrolyte is replaced by Li 1.3 Al 0.3 Ti 1.7 (PO4)3, 93 kg in weight, and the rest is the same as Example 1.

[0084] Tested: the battery has an energy density of 325.8 Wh / kg at 0.5C rate current, an energy density of 263.8 Wh / kg at 1C rate current, a capacity retention of 83.5% at 0.5C for 1000 cycles, a coulombic efficiency of 99.1%, and the nail penetration safety test shows that the battery does not smoke, does not catch fire, and does not explode.

[0085] Example 6

[0086] In Example 1, the positive electrode active material dry powder is replaced by LiFePO4, and the rest is the same as Example 1.

[0087] Tested: the battery has an energy density of 190.8 Wh / kg at 0.5C rate current, an energy density of 175.6 Wh / kg at 1C rate current, a capacity retention of 94.6% at 0.5C for 1000 cycles, a coulombic efficiency of 99.8%, and the nail penetration safety test shows that the battery does not smoke, does not catch fire, and does not explode.

[0088] Example 7

[0089] In Example 1, the composition of the molten salt electrolyte in the preparation of the positive electrode slurry film is changed to succinonitrile powder 5 kg, LiDFOB powder 1 kg, and Li(C2F5SO2)2N powder 4 kg, and the rest is the same as Example 1.

[0090] Tested: the battery has an energy density of 365.7 Wh / kg at 0.5C rate current, an energy density of 336.8 Wh / kg at 1C rate current, a capacity retention of 91.4% at 0.5C for 1000 cycles, a coulombic efficiency of 99.5%, and the nail penetration safety test shows that the battery does not smoke, does not catch fire, and does not explode.

[0091] Example 8

[0092] The composition of the molten salt electrolyte in the preparation of the positive electrode slurry film of Example 1 is changed to 4.5 g of malononitrile solid, 2.5 kg of LiBOB powder, and 3 kg of LiFSI powder, and the rest is the same as in Example 1.

[0093] Tested: The battery has an energy density of 364.7 Wh / kg at a 0.5C rate current, an energy density of 348.6 Wh / kg at a 1C rate current, a capacity retention rate of 93.8% at 0.5C for 1000 cycles, a coulombic efficiency of 99.7%, and the nail penetration safety test shows that the battery does not smoke, does not catch fire, and does not explode.

[0094] Example 9

[0095] The composition of the molten salt electrolyte in the preparation of the positive electrode slurry film of Example 1 is changed to 6 kg of polyacrylonitrile solid, 3 kg of LiDFOB powder, and 1 kg of LiBF4 powder, and the rest is the same as in Example 1.

[0096] Tested: The battery has an energy density of 360.9 Wh / kg at a 0.5C rate current, an energy density of 328.7 Wh / kg at a 1C rate current, a capacity retention rate of 91.4% at 0.5C for 1000 cycles, a coulombic efficiency of 99.5%, and the nail penetration safety test shows that the battery does not smoke, does not catch fire, and does not explode.

[0097] Example 10

[0098] The composition of the molten salt electrolyte in the preparation of the positive electrode slurry film of Example 1 is changed to 5 kg of azobisdiisopropyl cyanide solid, 3 kg of LiBF4 powder, and 2 g of LiPF6 powder, and the rest is the same as in Example 1.

[0099] Tested: The battery has an energy density of 362.7 Wh / kg at a 0.5C rate current, an energy density of 341.6 Wh / kg at a 1C rate current, a capacity retention rate of 92.3% at 0.5C for 1000 cycles, a coulombic efficiency of 99.6%, and the nail penetration safety test shows that the battery does not smoke, does not catch fire, and does not explode.

[0100] Comparative Example 12

[0101] The pressure of the hot roller pressing of the positive electrode slurry film and the positive electrode current collector or the negative electrode slurry film and the negative electrode current collector in Example 1 is changed to 3 MPa, and the rest is the same as in Example 1.

[0102] Tested: The battery has an energy density of 362.5 Wh / kg at a 0.5C rate current, an energy density of 325.6 Wh / kg at a 1C rate current, a capacity retention rate of 79.4% at 0.5C for 1000 cycles, a coulombic efficiency of 98.5%, and the nail penetration safety test shows that the battery does not smoke, does not catch fire, and does not explode.

[0103] Comparative Example 13

[0104] The pressure of the hot rolling of the positive electrode slurry film and the positive electrode current collector or the negative electrode slurry film and the negative electrode current collector in Example 1 was changed to 25 MPa, and the rest was the same as in Example 1.

[0105] Tested: The battery had an energy density of 322.5 Wh / kg at a 0.5C rate current, an energy density of 253.9 Wh / kg at a 1C rate current, a capacity retention rate of 72.3% at 0.5C for 1000 cycles, a coulombic efficiency of 98.0%, and the battery passed the nail penetration safety test, showing that the battery did not smoke, catch fire, or explode.

[0106] Comparative Example 14

[0107] The temperature of the hot rolling of the positive electrode slurry film and the positive electrode current collector or the negative electrode slurry film and the negative electrode current collector in Example 1 was changed to 25°C, and the rest was the same as in Example 1.

[0108] Tested: The battery had an energy density of 365.7.5 Wh / kg at a 0.5C rate current, an energy density of 312.6 Wh / kg at a 1C rate current, a capacity retention rate of 76.6% at 0.5C for 1000 cycles, a coulombic efficiency of 98.3%, and the battery passed the nail penetration safety test, showing that the battery did not smoke, catch fire, or explode.

[0109] Comparative Example 15

[0110] The temperature of the hot rolling of the positive electrode slurry film and the positive electrode current collector or the negative electrode slurry film and the negative electrode current collector in Example 1 was changed to 230°C, and the rest was the same as in Example 1.

[0111] Tested: The battery had an energy density of 348.3 Wh / kg at a 0.5C rate current, an energy density of 293.6 Wh / kg at a 1C rate current, a capacity retention rate of 81.0% at 0.5C for 1000 cycles, a coulombic efficiency of 98.0%, and the battery passed the nail penetration safety test, showing that the battery did not smoke, catch fire, or explode.

[0112] Comparative Example 16

[0113] The length of the square negative electrode unit piece in the transverse and longitudinal directions in Example 1 was changed to be 1 mm longer than the length of the square positive electrode unit piece, and the rest was the same as in Example 1.

[0114] It was found through testing that the square negative electrode unit piece and the square positive electrode unit piece were easily misaligned, causing the lithium ions that were deintercalated from the positive electrode during charging to not be fully intercalated into the negative electrode, and lithium dendrites were present. In the long-term charging and discharging cycle process, the battery short-circuited, caught fire, and exploded.

[0115] The above described embodiments only represent several implementation manners in the present application, which are described in a more specific and detailed manner, but cannot be understood as a limitation on the patent scope of the present application. It should be noted that, for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present application, which all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A semi-dry, segmented, membrane-free, all-solid-state lithium battery manufacturing method, characterized in that: The positive electrode slurry including molten salt electrolyte and the negative electrode slurry including solvent water are extruded into films by screw extrusion, and the films formed are respectively combined with current collectors by hot rolling and punching into positive electrode unit sheets and negative electrode unit sheets. The solid electrolyte is extruded into films by screw extrusion and extrusion into films and then punched into solid electrolyte membrane unit sheets. The films are stacked according to the repeating unit pattern of negative electrode unit sheet / / solid electrolyte membrane unit sheet / / positive electrode unit sheet to obtain a semi-dry segmented membrane-free all-solid-state lithium battery; (1) Preparation of positive electrode slurry film: The positive electrode dry powder is thoroughly mixed and placed in a twin-screw extruder. The positive electrode slurry film is extruded through the U-shaped extrusion nozzle; wherein, the positive electrode dry powder, by weight ratio, is (85~95): (1~5): (1~5): (0.5~3); (2) Preparation of negative electrode slurry film: Place the negative electrode dry powder in a twin-screw extruder, add negative electrode solvent water, mix thoroughly and evenly, and extrude the negative electrode slurry film into a film shape through a U-shaped extrusion nozzle; wherein, the negative electrode dry powder, by weight ratio, is (85~95): (1~5): (1~5); the mass ratio of negative electrode dry powder to negative electrode solvent water is (80~95): (5~20); (3) The positive electrode slurry film obtained in step (1) and the negative electrode slurry film obtained in step (2) are respectively bonded to the positive electrode current collector and the negative electrode current collector by hot rolling mechanism to form positive electrode sheet and negative electrode sheet respectively; (4) The positive electrode sheet and the negative electrode sheet are respectively punched into square positive electrode unit sheet and square negative electrode unit sheet by die cutting mechanism; (5) Solid electrolyte membrane preparation: The twin-screw extruder is preheated, and then polymer solid electrolyte dry powder, inorganic solid electrolyte dry powder and molten salt electrolyte are mixed in a mass ratio of (1~30): (70~80): (0.5~10) is placed in a twin-screw extruder, thoroughly mixed, and extruded into a film through a U-shaped extrusion nozzle. Then, it is formed into a solid electrolyte membrane by hot rolling through a hot rolling structure. After being die-cut by a die-cutting mechanism, it is punched into square solid electrolyte membrane unit sheets; (6) The battery cell is constructed according to the repeating structure of negative electrode unit sheet / / solid electrolyte membrane unit sheet / / positive electrode unit sheet / / solid electrolyte membrane unit sheet / / negative electrode unit sheet / / solid electrolyte membrane unit sheet / / positive electrode unit sheet... negative electrode unit sheet. It is always a negative electrode unit; (7) Weld the battery cell to the electrode tab and encapsulate it in the shell to obtain a solid lithium battery; The molten salt electrolyte is composed of lithium salt and solid material containing cyano functional groups, and the mass percentage of lithium salt in the molten salt electrolyte is 35~65%; The lithium salt is one or more of lithium borate, lithium fluorine sulfonamide, and lithium fluorine phosphate; The solid material containing cyano functional groups is one or more of malononitrile, succinic anionitrile, polyacrylonitrile, azobisisobutyronitrile, azobisisoheptanenitrile, and hexachlorocyclotriphosphazene.

2. The semi-dry process segmented membrane-free all-solid-state lithium battery production method according to claim 1, characterized in that: The dew point of the environment before packaging is controlled at -25℃ to -65℃, and the solid-state lithium battery is formed by heating and pressurizing.

3. The semi-dry process segmented membrane-free all-solid-state lithium battery production method according to claim 2, characterized in that: The battery formation pressure is 0.3MPa~2MPa, the heating temperature is 40℃~80℃, and the formation current ratio is 0.02C~0.2C.

4. The semi-dry process segmented membrane-free all-solid-state lithium battery production method according to claim 1, characterized in that: The square negative electrode unit is 2-5 mm longer than the square positive electrode unit in both the horizontal and vertical directions; the square solid electrolyte membrane unit is 2-5 mm longer than the square negative electrode unit in both the horizontal and vertical directions.

5. The semi-dry process segmented membrane-free all-solid-state lithium battery production method according to claim 1, characterized in that: The positive electrode active material dry powder is one or more of LiMn2O4, LiCoO2, LiFePO4, LiNi x Co y Mn z O2, LiNi x Co y Al z O2, and one or more of lithium-rich compounds, where x + y + z = 1, 0 < x, y, z < 1; the negative electrode active material dry powder is one or more of metallic lithium, alloy materials, graphite, amorphous carbon, mesocarbon microbeads, nanosilicon, silicon-carbon materials, lithium titanate, and SiO n where 0 < n < 2.

6. The semi-dry process segmented membrane-free all-solid-state lithium battery production method according to claim 1, characterized in that: The positive electrode current collector is aluminum foil, carbon-coated aluminum foil, or perforated aluminum foil, wherein the thickness of the aluminum foil, carbon-coated aluminum foil, or perforated aluminum foil is 8-25 micrometers, and the hole diameter of the perforated aluminum foil is 30-100 micrometers; the negative electrode current collector is copper foil or perforated copper foil, wherein the thickness of the copper foil or perforated copper foil is 6-15 micrometers, and the hole diameter of the perforated aluminum foil is 30-100 micrometers.

7. The semi-dry process segmented membrane-free all-solid-state lithium battery production method according to claim 1, characterized in that: The inorganic solid electrolyte dry powder includes Li 10 SiP2S 12 Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 Li 10 GeP2S 12 Li 1.3 Al 0.3 Ti 1.7 (PO4)3, Li7La3Zr2O 12 Li 1.5 Al 0.5 Ge 1.5 (PO4)3, Li 6.4 La3Zr 1.4 Ta 0.6 O 12 One or more of the following; the polymer solid electrolyte dry powder includes one or more of polyethylene oxide, polyimide, polyvinylidene fluoride, polytetrafluoroethylene, polysiloxane, polytrimethylene carbonate, polyvinyl carbonate, polypropylene carbonate, polyvinyl carbonate, polyvinylidene carbonate, polyvinylidene fluoride-hexafluoropropylene, polymethacrylate, and polyacrylonitrile.

8. The semi-dry process for producing a diaphragm-free, all-solid-state lithium battery according to claim 1, characterized in that: The pressure of the hot roller pressing in step (3) is 5~20MPa and the temperature is 50~200℃.