A positive electrode sheet, a battery and a method for manufacturing the same

Abstract

The application discloses a positive pole piece and a battery and a preparation method thereof, and belongs to the technical field of battery materials. The preparation of the positive pole piece comprises the following steps: coating positive pole slurry containing a positive pole active material, a binder, a conductive agent, a first solvent and IL on a current collector and drying; the IL is an imidazole ionic liquid; the amount of the IL is 0.15% to 3% of the preset volume of the positive pole piece. By pre-mixing the ionic liquid into the inside of the positive pole piece, the problem that the high-viscosity ionic liquid electrolyte has poor impregnation effect on the positive pole piece during the later assembly of the battery can be solved; the IL cannot dissolve the binder, which is beneficial to ensuring the stability of the structure of the positive pole piece, and the IL can be effectively preserved in the inside of the positive pole piece during the drying process and is basically not lost by volatilization. The battery prepared from the positive pole piece, the second electrolyte and the first electrolyte can have high initial efficiency and discharge specific capacity.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of battery materials, in particular to a positive electrode sheet, a battery and a preparation method thereof. BACKGROUND

[0002] With the rapid development of new energy technology, high safety, high specific energy and low temperature resistance battery has become an important direction for future development. As a core component in battery manufacturing, the importance and application value of electrolyte are increasingly prominent. However, the current ester-based electrolyte still has problems such as poor low-temperature performance, flammability, and difficulty in adapting to high-voltage cathodes, and liquid lithium-ion batteries have the risk of leakage.

[0003] Ionic liquid is a kind of liquid composed of cations and anions. They can form a variety of compounds through different combinations. The ionic liquid-based electrolyte currently used in batteries has the problem of high viscosity, which can easily lead to incomplete wetting of the positive electrode sheet by the electrolyte. In addition, due to the long wetting process, polymerization of the monomers is likely to occur during the wetting process, further deteriorating the wettability. Therefore, the rapid wetting of the positive electrode sheet by the ionic liquid-based electrolyte is a key to improving the performance of the battery.

[0004] In view of this, the present application is proposed. SUMMARY

[0005] The present application aims to provide a positive electrode sheet, a battery and a preparation method thereof to solve or improve the above technical problems.

[0006] The present application can be achieved as follows:

[0007] In a first aspect, the present application provides a preparation method of a positive electrode sheet, comprising the following steps: coating a positive electrode slurry containing a positive electrode active material, a binder, a conductive agent, a first solvent and IL on a current collector, and drying to remove the first solvent;

[0008] wherein the IL is an imidazole ionic liquid;

[0009] The mass ratio of the positive electrode active material, the binder and the conductive agent is (76-84):(8-12):(8-12); the solid content of the positive electrode slurry is 50%-80%; and the amount of IL is 0.15%-3% of the preset volume of the positive electrode sheet.

[0010] In an optional embodiment, the imidazole ionic liquid includes at least one of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide salt and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide salt;

[0011] And / or, the positive electrode active material includes at least one of a ternary positive electrode material, a lithium iron phosphate positive electrode material, a lithium manganate positive electrode material and a lithium cobaltate positive electrode material.

[0012] and / or, the binder comprises polyvinylidene fluoride;

[0013] and / or, the conductive agent comprises at least one of Super-P, KS-6, conductive graphite, carbon nanotube, graphene and carbon fiber;

[0014] and / or, the first solvent comprises N-methyl pyrrolidone.

[0015] In an optional embodiment, the drying temperature is 60-90°C, and the drying time is 1-5h.

[0016] In a second aspect, the present application provides a positive electrode sheet prepared by the preparation method of any one of the preceding embodiments.

[0017] In a third aspect, the present application provides a preparation method of a battery, comprising the following steps: adding a second electrolyte to the positive electrode sheet of the preceding embodiments; then adding a first electrolyte, placing a separator, adding the first electrolyte, placing a negative electrode sheet, standing, packaging, and thermal polymerization;

[0018] wherein the first electrolyte comprises a monomer, a crosslinking agent, an initiator, an IL and an electrolyte, and the second electrolyte is the first electrolyte without IL;

[0019] The first electrolyte contains 10-30wt% of the monomer, 10-50wt% of the IL and 30-60wt% of the electrolyte; the mass ratio of the crosslinking agent to the monomer is 0.01:1 to 0.05:1, and the mass ratio of the initiator to the monomer is 0.001:1 to 0.01:1; the electrolyte comprises a second solvent, a lithium salt and an additive in a mass ratio of (7.4-8.6):(1-2):(0.4-0.6).

[0020] In an optional embodiment, the monomer comprises an acrylate monomer;

[0021] and / or, the crosslinking agent comprises at least one of polyethylene glycol diacrylate and 1,6-bis(acryloyloxy)-2,2,3,3,4,4,5,5-octafluorohexane;

[0022] and / or, the initiator comprises azobisisobutyronitrile;

[0023] and / or, the second solvent comprises at least one of dimethyl carbonate, methyl ethyl carbonate and diethyl carbonate, and at least one of ethylene carbonate and propylene carbonate;

[0024] and / or, the IL in the first electrolyte comprises an imidazole ionic liquid;

[0025] And / or, the lithium salt includes at least one of LiTFSI, LFSI, LiClO4, LiBF4, LIPF6, LiDFOB and LiBOB;

[0026] And / or, the additives include at least one of vinylene carbonate, fluoroethylene carbonate, and at least one of trimethylsilyl phosphate and trimethylsilyl borate.

[0027] In an optional embodiment, the acrylate monomer includes at least one of butyl acrylate and hexafluorobutyl acrylate;

[0028] And / or, the imidazole ionic liquid in the first electrolyte includes at least one of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt and 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt.

[0029] In an optional embodiment, the amount of the second electrolyte added is 18% to 45% of the preset volume of the positive electrode sheet;

[0030] The amount of the first electrolyte added before placing the diaphragm is 5 μL / cm. 2 ~10μL / cm 2 The amount of the first electrolyte added after placing the diaphragm was 5 μL / cm. 2 ~10μL / cm 2 .

[0031] In an optional implementation, the settling time is 0.5h to 2h;

[0032] And / or, the temperature of thermal polymerization is 50℃~80℃, and the time of thermal polymerization is 5h~10h.

[0033] Fourthly, the present invention provides a battery prepared by any of the preparation methods described in the foregoing embodiments.

[0034] The beneficial effects of this invention include:

[0035] The method provided by this invention solves the problem of poor wetting effect of high-viscosity ionic liquid electrolytes on the positive electrode by pre-mixing imidazole ionic liquid into the interior of the positive electrode sheet at a specific volume. Furthermore, the imidazole ionic liquid can be effectively preserved inside the positive electrode sheet during the drying process with minimal evaporation loss. Moreover, the imidazole ionic liquid does not dissolve the binder, which helps ensure the stability of the positive electrode sheet structure. A battery prepared from this positive electrode sheet in combination with a second electrolyte and a first electrolyte can achieve high initial efficiency and high discharge specific capacity. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0037] The positive electrode sheet and battery provided by the present invention and their preparation method are described in detail below.

[0038] The present invention provides a method for preparing a positive electrode sheet, comprising the following steps: coating a positive electrode slurry containing a positive electrode active material, a binder, a conductive agent, a first solvent and 1L onto a current collector, and drying to remove the first solvent.

[0039] The positive electrode active material may, by way of example, include at least one of ternary positive electrode materials, lithium iron phosphate positive electrode materials, lithium manganese oxide positive electrode materials, and lithium cobalt oxide positive electrode materials.

[0040] The adhesive may include polyvinylidene fluoride (PVDF).

[0041] The conductive agent may include at least one of Super-P, KS-6, conductive graphite, carbon nanotubes, graphene, and carbon fiber.

[0042] The first solvent may include N-methylpyrrolidone (NMP).

[0043] The IL is an imidazole ionic liquid, and may exemplary include at least one of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt and 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt. The aforementioned IL does not dissolve the binder PVDF, which helps ensure the stability of the positive electrode structure.

[0044] Using other conventional ionic liquids, such as pyrrolidine ionic liquids, pyridine ionic liquids, or quaternary ammonium salt ionic liquids, is not conducive to broadening the electrochemical stability window of the electrolyte.

[0045] The current collector may, by way of example, include aluminum foil, etc.

[0046] In this invention, the mass ratio of the positive electrode active material, binder, and conductive agent can be (76~84):(8~12):(8~12), such as 76:12:12, 80:10:10, or 84:8:8, or other values ​​within the range of (76~84):(8~12):(8~12). In some typical embodiments, the mass ratio of the positive electrode active material, binder, and conductive agent is 80:10:10.

[0047] The solid content of the positive electrode slurry can be 50% to 80%, such as 50%, 55%, 60%, 65%, 70%, 75% or 80%, or other values ​​within the range of 50% to 80%.

[0048] The amount of IL can be 0.15% to 3% of the preset volume of the positive electrode, such as 0.15%, 0.5%, 1%, 1.5%, 2%, 2.5%, or 3%, or other values ​​within the range of 0.15% to 3%. In some other embodiments, it can also be added at 1% to 10% of the internal pore volume of the positive electrode, which is typically 15% to 30% of the preset volume of the positive electrode.

[0049] If the amount of IL is too small, it will not be conducive to the performance at low temperatures; if the amount of IL is too large, it will easily lead to an increase in the electronic conductivity of the electrolyte.

[0050] In some alternative embodiments, the drying temperature can be 60°C to 90°C, such as 60°C, 65°C, 70°C, 75°C, 80°C, 85°C or 90°C, or other values ​​within the range of 60°C to 90°C.

[0051] The drying time can be 1h to 5h, such as 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h or 5h, or other values ​​within the range of 1h to 5h.

[0052] Under the aforementioned dry conditions, IL can be effectively preserved inside the positive electrode plate with virtually no volatilization loss.

[0053] In conclusion, this invention solves the problem of poor wetting effect of high-viscosity ionic liquid electrolyte on the positive electrode sheet during later battery assembly by pre-mixing a specific ionic liquid into the interior of the positive electrode sheet.

[0054] Accordingly, the present invention provides a positive electrode sheet, which is prepared by the above-described preparation method.

[0055] In addition, the present invention also provides a method for preparing a battery, comprising the following steps: adding a second electrolyte to the above-mentioned positive electrode sheet; subsequently adding a first electrolyte, placing a separator, adding another first electrolyte, placing a negative electrode sheet, allowing it to stand, encapsulating, and thermally polymerizing.

[0056] The first electrolyte comprises a monomer, a crosslinking agent, an initiator, an electrolyte solvent (IL), and an electrolyte solution. The second electrolyte is the first electrolyte that does not contain IL. In other words, the first electrolyte can be understood as the second electrolyte plus the IL pre-mixed into the interior of the positive electrode.

[0057] In this invention, the first electrolyte contains 10wt% to 30wt% of monomer, 10wt% to 50wt% of IL and 30wt% to 60wt% of electrolyte.

[0058] In some alternative embodiments, the amount of monomer contained in the first electrolyte may be 10wt%, 15wt%, 20wt%, 25wt%, or 30wt%, or other values ​​in the range of 10wt% to 30wt%.

[0059] The amount of IL contained in the first electrolyte can be 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, 35wt%, 40wt%, 45wt%, or 50wt%, or other values ​​within the range of 10wt% to 50wt%.

[0060] The amount of electrolyte contained in the first electrolyte can be 30wt%, 35wt%, 40wt%, 45wt%, 50wt%, 55wt%, or 60wt%, or other values ​​within the range of 30wt% to 60wt%.

[0061] In some alternative embodiments, the mass ratio of crosslinking agent to monomer is 0.01:1 to 0.05:1, such as 0.01:1, 0.02:1, 0.03:1, 0.04:1 or 0.05:1, or other values ​​in the range of 0.01:1 to 0.05:1.

[0062] The mass ratio of initiator to monomer can be from 0.001:1 to 0.01:1, such as 0.001:1, 0.002:1, 0.005:1, 0.008:1 or 0.01:1, or other values ​​in the range of 0.001:1 to 0.01:1.

[0063] In some optional embodiments, the electrolyte may include a second solvent, a lithium salt, and an additive in a mass ratio of (7.4~8.6):(1~2):(0.4~0.6). For example, the mass ratio of the second solvent, lithium salt, and additive in the electrolyte may be 7.4:2:0.6, 8:1.5:0.5, or 8.6:1:0.4, etc.

[0064] In this invention, the monomer may include acrylate monomers, such as at least one of butyl acrylate and hexafluorobutyl acrylate.

[0065] Crosslinking agents may, by way of example, include at least one of polyethylene glycol diacrylate (PEGDA) and 1,6-bis(acryloyloxy)-2,2,3,3,4,4,5,5-octafluorohexane (OFHDODA).

[0066] The initiator is a thermally initiated initiator, such as azobisisobutyronitrile (AIBN).

[0067] The second solvent may, by way of example, include at least one of dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC), and at least one of ethylene carbonate (EC) and propylene carbonate (PC).

[0068] The IL in the first electrolyte includes imidazole ionic liquids, and the specific types are the same as those in the positive electrode.

[0069] Lithium salts may, by way of example, include at least one of LiTFSI, LFSI, LiClO4, LiBF4, LIPF6, LiDFOB, and LiBOB.

[0070] The additive may, by way of example, include at least one of vinylene carbonate (VC), fluoroethylene carbonate (FEC), and at least one of trimethylsilyl phosphate (TMSB) and trimethylsilyl borate (TMSP).

[0071] In some optional embodiments, the amount of the second electrolyte added is 18% to 45% of the preset volume of the positive electrode, such as 18%, 20%, 25%, 30%, 35%, 40%, or 45%, or other values ​​within the range of 18% to 45%. In other embodiments, it can also be added at 1.2 to 1.5 times the internal pore volume of the positive electrode, which is typically 15% to 30% of the preset volume of the positive electrode.

[0072] If the amount of the second electrolyte added is too small, it will not be conducive to the full wetting of the positive electrode plate; if the amount of the second electrolyte added is too large, it will interfere with the subsequent addition of the first electrolyte and will not be conducive to maintaining the proportion of each component of the first electrolyte.

[0073] In some optional embodiments, taking a single-layer battery as an example, the amount of the first electrolyte added before placing the separator is 5 μL / cm. 2 ~10μL / cm 2 such as 5μL / cm 2 6μL / cm 2 7μL / cm 2 8μL / cm 2 9μL / cm 2 or 10 μL / cm 2 etc., can also be 5μL / cm 2 ~10μL / cm 2 Other values ​​within the range. The amount of the first electrolyte added after placing the diaphragm can also be 5 μL / cm. 2~10μL / cm 2 such as 5μL / cm 2 6μL / cm 2 7μL / cm 2 8μL / cm 2 9μL / cm 2 or 10 μL / cm 2 And so on, it can also be 5μL / cm 2 ~10μL / cm 2 Other values ​​within the range.

[0074] If too little of the first electrolyte is added, it will not be conducive to the wetting of the battery separator; if too much of the first electrolyte is added, it will lead to electrolyte waste.

[0075] In some alternative implementations, the negative electrode can be a negative electrode made of lithium metal.

[0076] The diaphragm can be a PE diaphragm coated with 2μm of alumina on both sides.

[0077] In some optional implementations, the settling time can be 0.5h to 2h, such as 0.5h, 1h, 1.5h, or 2h, or other values ​​within the range of 0.5h to 2h. The settling temperature can be room temperature.

[0078] In some alternative embodiments, the temperature of thermal polymerization can be 50°C to 80°C, such as 50°C, 55°C, 60°C, 65°C, 70°C, 75°C or 80°C, or other values ​​within the range of 50°C to 80°C.

[0079] The time for thermal polymerization can be 5h to 10h, such as 5h, 6h, 7h, 8h, 9h or 10h, or other values ​​within the range of 5h to 10h.

[0080] It should be noted that other steps in the battery manufacturing process not described in this invention can be referred to in the prior art, and will not be elaborated or limited here.

[0081] Continuing from the above, in the process of preparing the battery, by first adding a second electrolyte without IL to the positive electrode sheet that already contains IL, the second electrolyte without IL has a lower viscosity, which can quickly wet the positive electrode sheet and dissolve the IL that is already present in the positive electrode sheet. The dissolved IL and the second electrolyte together form an electrolyte system with the same composition as the first electrolyte. Then, the first electrolyte is added. Under the same wetting system, the battery can obtain a better wetting effect, which is beneficial to improving the electrochemical performance of the battery.

[0082] Accordingly, the present invention also provides a battery prepared by the above-described preparation method, which can have high initial efficiency and discharge specific capacity.

[0083] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0084] Example 1

[0085] This embodiment provides a battery, the preparation method of which is as follows:

[0086] S1: Prepare the positive electrode sheet.

[0087] A positive electrode slurry containing positive active material, binder, conductive agent, first solvent and IL is coated onto aluminum foil, dried at 80°C for 3 hours, then rolled and cut to obtain a positive electrode sheet.

[0088] The positive electrode active material is a nickel-cobalt-manganese ternary positive electrode material, the binder is polyvinylidene fluoride, the conductive agent is Super-P, the first solvent is N-methylpyrrolidone, and the IL is 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt. The mass ratio of the positive electrode active material, binder, and conductive agent is 80:10:10, the solid content of the positive electrode slurry is 65%, and the amount of IL can be 1% of the preset volume of the positive electrode sheet. The volume of the internal pores of the positive electrode sheet accounts for 20% of the total volume of the positive electrode sheet (the amount of IL is 5% of the internal pore volume of the positive electrode sheet).

[0089] S2: Install battery.

[0090] The second electrolyte was added dropwise to the positive electrode obtained in S1; then the first electrolyte was added dropwise, a separator (PE separator coated with 2μm alumina on both sides) was placed, the first electrolyte was added dropwise again, a lithium metal negative electrode was placed, it was left to stand for 1 hour, sealed, and thermally polymerized at 75℃ for 8 hours.

[0091] The first electrolyte contains 20 wt% monomer, 10 wt% lithium salt, and 50 wt% electrolyte solution. The mass ratio of crosslinking agent to monomer is 0.03:1, and the mass ratio of initiator to monomer is 0.005:1. The electrolyte solution consists of a second solvent, lithium salt, and additives in a mass ratio of 8:1.5:0.5.

[0092] The monomers are butyl acrylate, IL is 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt, the second solvent is obtained by mixing ethylene carbonate and diethyl carbonate in a volume ratio of 1:1, the lithium salt is LIPF6, the additive is obtained by mixing vinylene carbonate and tris(trimethylsilyl) phosphate in a volume ratio of 2:1, the crosslinking agent is polyethylene glycol diacrylate, and the initiator is azobisisobutyronitrile. The second electrolyte is the first electrolyte without IL.

[0093] The amount of the second electrolyte added is 30% of the preset volume of the positive electrode (the amount of the second electrolyte added is 1.5 times the internal pore volume of the positive electrode). The amount of the first electrolyte added before placing the separator is 10 μL / cm. 2 The amount of the first electrolyte added after placing the diaphragm was also 10 μL / cm. 2 .

[0094] Example 2

[0095] The difference between this embodiment and Embodiment 1 is that the amount of IL contained in the first electrolyte is 20wt%.

[0096] Example 3

[0097] The difference between this embodiment and Embodiment 1 is that the amount of IL contained in the first electrolyte is 30wt%.

[0098] Example 4

[0099] The difference between this embodiment and Embodiment 1 is that the amount of IL contained in the first electrolyte is 40 wt%.

[0100] Example 5

[0101] The difference between this embodiment and Embodiment 1 is that the amount of IL contained in the first electrolyte is 50 wt%.

[0102] Example 6

[0103] This embodiment provides a battery, the preparation method of which is as follows:

[0104] S1: Prepare the positive electrode sheet.

[0105] A positive electrode slurry containing positive active material, binder, conductive agent, first solvent and IL is coated onto aluminum foil, dried at 60°C for 5 hours, then rolled and cut into sheets to obtain positive electrode sheets.

[0106] The positive electrode active material is a nickel-cobalt-manganese ternary positive electrode material, the binder is polyvinylidene fluoride, the conductive agent is Super-P, the first solvent is N-methylpyrrolidone, and the IL is 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt. The mass ratio of the positive electrode active material, binder, and conductive agent is 76:12:12, the solid content of the positive electrode slurry is 50%, and the amount of IL can be 0.15% of the preset volume of the positive electrode sheet.

[0107] S2: Install battery.

[0108] The second electrolyte was added dropwise to the positive electrode obtained in S1; then the first electrolyte was added dropwise, a separator (PE separator coated with 2μm alumina on both sides) was placed, the first electrolyte was added dropwise again, a lithium metal negative electrode was placed, it was left to stand for 0.5h, sealed, and thermally polymerized at 80℃ for 8h.

[0109] The first electrolyte contains 10 wt% monomer, 50 wt% lithium salt, and 40 wt% electrolyte solution. The mass ratio of crosslinking agent to monomer is 0.01:1, and the mass ratio of initiator to monomer is 0.001:1. The electrolyte solution consists of a second solvent, lithium salt, and additives in a mass ratio of 7.4:2:0.6.

[0110] The monomers are hexafluorobutyl acrylate, IL is 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt, the second solvent is a mixture of propylene carbonate and ethyl methyl carbonate in a volume ratio of 1:1, the lithium salt is LiTFSI, the additive is a mixture of fluoroethylene carbonate and tris(trimethylsilyl) borate in a volume ratio of 3:1, the crosslinking agent is 1,6-bis(acryloyloxy)-2,2,3,3,4,4,5,5-octafluorohexane, and the initiator is azobisisobutyronitrile. The second electrolyte is the first electrolyte without IL.

[0111] The amount of the second electrolyte added is 18% of the preset volume of the positive electrode. The amount of the first electrolyte added before placing the separator is 5 μL / cm³. 2 The amount of the first electrolyte added after placing the diaphragm is also 5 μL / cm. 2 .

[0112] Example 7

[0113] This embodiment provides a battery, the preparation method of which is as follows:

[0114] S1: Prepare the positive electrode sheet.

[0115] A positive electrode slurry containing positive active material, binder, conductive agent, first solvent and IL is coated onto aluminum foil, dried at 90°C for 1 hour, then rolled and cut into sheets to obtain positive electrode sheets.

[0116] The positive electrode active material is a nickel-cobalt-manganese ternary positive electrode material, the binder is polyvinylidene fluoride, the conductive agent is Super-P, the first solvent is N-methylpyrrolidone, and the IL is 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt. The mass ratio of the positive electrode active material, binder, and conductive agent is 84:8:8, the solid content of the positive electrode slurry is 80%, and the amount of IL can be 3% of the preset volume of the positive electrode sheet.

[0117] S2: Install battery.

[0118] The second electrolyte was added dropwise to the positive electrode obtained in S1; then the first electrolyte was added dropwise, a separator (a PE separator coated with 2μm alumina on both sides) was placed, the first electrolyte was added dropwise again, a lithium metal negative electrode was placed, it was left to stand for 2 hours, sealed, and thermally polymerized at 80℃ for 8 hours.

[0119] The first electrolyte contains 30 wt% monomer, 10 wt% lithium salt, and 60 wt% electrolyte solution. The mass ratio of crosslinking agent to monomer is 0.05:1, and the mass ratio of initiator to monomer is 0.01:1. The electrolyte solution consists of a second solvent, lithium salt, and additives in a mass ratio of 8.6:1:0.4.

[0120] The monomers are butyl acrylate, IL is 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt, the second solvent is obtained by mixing ethylene carbonate and dimethyl carbonate at a volume ratio of 1:1.5, the lithium salt is LiBOB, the additive is obtained by mixing vinylene carbonate and tris(trimethylsilyl) borate at a volume ratio of 2:1, the crosslinking agent is polyethylene glycol diacrylate, and the initiator is azobisisobutyronitrile. The second electrolyte is the first electrolyte without IL.

[0121] The amount of the second electrolyte added is 45% of the preset volume of the positive electrode. The amount of the first electrolyte added before placing the separator is 8 μL / cm³. 2 The amount of the first electrolyte added after placing the diaphragm was also 8 μL / cm. 2 .

[0122] Comparative Example 1

[0123] The difference between this comparative example and Example 1 is that IL was not used in S1; in S2, the positive electrode obtained in S1 was directly added dropwise to the first electrolyte, a separator was placed, the first electrolyte was added dropwise again, a lithium metal negative electrode was placed, it was left to stand for 1 hour, encapsulated, and thermally polymerized at 80°C for 8 hours.

[0124] Comparative Example 2

[0125] The difference between this comparative example and Example 2 is that IL was not used in S1; in S2, the positive electrode obtained in S1 was directly added dropwise to the first electrolyte, a separator was placed, the first electrolyte was added dropwise again, a lithium metal negative electrode was placed, it was left to stand for 1 hour, encapsulated, and thermally polymerized at 80°C for 8 hours.

[0126] Comparative Example 3

[0127] The difference between this comparative example and Example 3 is that IL was not used in S1; in S2, the positive electrode obtained in S1 was directly added dropwise to the first electrolyte, a separator was placed, the first electrolyte was added dropwise again, a lithium metal negative electrode was placed, it was left to stand for 1 hour, encapsulated, and thermally polymerized at 80°C for 8 hours.

[0128] Comparative Example 4

[0129] The difference between this comparative example and Example 4 is that IL was not used in S1; in S2, the positive electrode obtained in S1 was directly added dropwise to the first electrolyte, a separator was placed, the first electrolyte was added dropwise again, a lithium metal negative electrode was placed, it was left to stand for 1 hour, encapsulated, and thermally polymerized at 80°C for 8 hours.

[0130] Comparative Example 5

[0131] The difference between this comparative example and Example 5 is that IL was not used in S1; in S2, the positive electrode obtained in S1 was directly added dropwise to the first electrolyte, a separator was placed, the first electrolyte was added dropwise again, a lithium metal negative electrode was placed, it was left to stand for 1 hour, encapsulated, and thermally polymerized at 80°C for 8 hours.

[0132] Comparative Example 6

[0133] The difference between this comparative example and Example 1 is that N-butylpyridine tetrafluoroborate is used in an equal amount instead of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide.

[0134] Comparative Example 7

[0135] The difference between this comparative example and Example 1 is that 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt is replaced with an equal amount of tetramethylammonium tetrafluoroborate.

[0136] Comparative Example 8

[0137] The difference between this comparative example and Example 1 is that 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt is replaced with an equal amount of N-butyl-N-methylpiperidine bromide.

[0138] Comparative Example 9

[0139] The difference between this comparative example and Example 1 is that the amount of IL used is 0.1% of the preset volume of the positive electrode sheet.

[0140] Comparative Example 10

[0141] The difference between this comparative example and Example 1 is that the amount of IL used is 5% of the preset volume of the positive electrode sheet.

[0142] Test case

[0143] The batteries obtained in Examples 1-7 and Comparative Examples 1-10 were tested at 25°C, 3V-4.3V, and 0.1C. The results are shown in Table 1.

[0144] Table 1 Test Results

[0145]

[0146] As can be seen from Table 1, the batteries prepared in the embodiments of the present invention can have high initial efficiency and high discharge specific capacity.

[0147] In summary, the method provided by this invention solves the problem of poor wetting effect of high-viscosity ionic liquid electrolytes on the positive electrode by pre-mixing imidazole ionic liquids into the interior of the positive electrode sheet. Furthermore, the aforementioned imidazole ionic liquids can be effectively preserved inside the positive electrode sheet during the drying process, with virtually no volatilization loss. Moreover, the imidazole ionic liquids do not dissolve the binder polyvinylidene fluoride, which helps ensure the stability of the positive electrode sheet structure. Batteries prepared from these positive electrode sheets in combination with a second electrolyte and a first electrolyte can achieve high initial efficiency and high discharge specific capacity.

[0148] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method of producing a battery, characterized by, The method comprises the following steps: adding a second electrolyte to a positive electrode sheet; then adding a first electrolyte, placing a separator, adding the first electrolyte again, placing a negative electrode sheet, standing, packaging, and thermal polymerization; The first electrolyte comprises monomers, a crosslinking agent, an initiator, IL, and an electrolyte solution, and the second electrolyte is the first electrolyte without IL; The first electrolyte contains 10wt%-30wt% monomers, 10wt%-50wt% IL, and 30wt%-60wt% electrolyte solution; the mass ratio of the crosslinking agent to the monomers is 0.01:1-0.05:1, and the mass ratio of the initiator to the monomers is 0.001:1-0.01:1; the electrolyte solution comprises a second solvent, a lithium salt, and an additive, with a mass ratio of (7.4-8.6):(1-2):(0.4-0.6); The second electrolyte is added in an amount of 18%-45% of the preset volume of the positive electrode sheet; The amount of the first electrolyte to be added correspondingly before placing the separator is 5 μL / cm 2 ~10 μL / cm 2 The amount of the first electrolyte to be added correspondingly after placing the separator is 5 μL / cm 2 ~10 μL / cm 2 ; The method for preparing the positive electrode sheet comprises the following steps: coating positive electrode slurry containing a positive electrode active material, a binder, a conductive agent, a first solvent, and IL on a current collector, and drying to remove the first solvent. The IL is an imidazole-based ionic liquid. The mass ratio of the positive electrode active material, the binder, and the conductive agent is (76-84):(8-12):(8-12); the solid content of the positive electrode slurry is 50%-80%; and the amount of the IL is 0.15%-3% of the preset volume of the positive electrode sheet.

2. The production method according to claim 1, characterized by, The imidazole-based ionic liquid comprises at least one of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide; The positive electrode active material comprises at least one of a ternary positive electrode material, a lithium iron phosphate positive electrode material, a lithium manganate positive electrode material, and a lithium cobaltate positive electrode material; The binder comprises polyvinylidene fluoride; The conductive agent comprises at least one of Super-P, KS-6, conductive graphite, carbon nanotubes, graphene, and carbon fibers; The first solvent comprises N-methylpyrrolidone.

3. The production method according to claim 1 or 2, characterized by, The drying temperature is 60°C-90°C, and the drying time is 1h-5h.

4. The preparation method according to claim 1, characterized in that, The monomers comprise acrylate monomers; The crosslinking agent comprises at least one of polyethylene glycol diacrylate and 1,6-bis(acryloyloxy)-2,2,3,3,4,4,5,5-octafluorohexane; The initiator comprises azobisisobutyronitrile; The second solvent comprises at least one of dimethyl carbonate, methyl ethyl carbonate, and diethyl carbonate, and at least one of ethylene carbonate and propylene carbonate; The IL in the first electrolyte comprises an imidazole-based ionic liquid; The lithium salt comprises at least one of LiTFSI, LFSI, LiClO4, LiBF4, LIPF6, LiDFOB, and LiBOB. And / or, the additive comprises at least one of vinylene carbonate, fluoroethylene carbonate, and at least one of tris(trimethylsilyl) phosphate and tris(trimethylsilyl) borate.

5. The production method according to claim 4, characterized by, The acrylate monomer comprises at least one of butyl acrylate and hexafluorobutyl acrylate; And / or, the imidazole ionic liquid in the first electrolyte comprises at least one of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide.

6. The method of claim 1, wherein, The standing time is 0.5h~2h; And / or, the temperature of the thermal polymerization is 50℃~80℃, and the time of the thermal polymerization is 5h~10h.

7. A battery, characterized by The battery is prepared by the preparation method in any one of claims 1~6.

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