Composite negative electrode sheet, composite positive electrode sheet, separator-free battery, and preparation method

Abstract

The present application relates to the technical field of lithium battery, and especially relates to a composite negative electrode sheet, a composite positive electrode sheet, a diaphragm-free battery and a preparation method. The composite negative electrode sheet comprises necessary component layers and can comprise or not comprise unnecessary component layers. The composite positive electrode sheet comprises necessary component layers and can comprise or not comprise unnecessary component layers. The diaphragm-free battery comprises the composite negative electrode sheet, the composite positive electrode sheet, an electrolyte and structural components. The present application sets an insulation layer on the negative electrode sheet and the positive electrode sheet, effectively prevents the side reaction of active lithium ions and the lithium-removing layer, and guarantees the service life of the battery. The battery assembly no longer needs a diaphragm, can effectively improve the energy density of the battery, and eliminates the large-area short circuit of the positive electrode sheet and the negative electrode sheet caused by the thermal shrinkage and melting of the diaphragm, and improves the safety performance of the battery. The lithium-removing layer set on the negative electrode sheet is beneficial to the improvement of the electrical performance of the negative electrode sheet, can effectively remove the lithium dendrites precipitated from the negative electrode sheet, and further improves the safety performance of the battery.

Description

Technical Field

[0001] This invention relates to the field of lithium battery technology, and in particular to a composite negative electrode, a composite positive electrode, a membrane-free battery, and a method for their preparation. Background Technology

[0002] Lithium-ion batteries are now widely used in computers, communications, consumer electronics, automobiles, ships, energy storage, and industrial machinery. Traditional positive and negative electrodes mainly consist of current collectors and active material layers, forming a lithium-ion battery together with the separator, electrolyte, and structural components. The separator is one of the essential materials for lithium-ion batteries, physically isolating the positive and negative electrodes and playing a crucial role in preventing internal short circuits caused by contact between the positive and negative electrodes. However, firstly, the separator is an inactive material and cannot contribute to battery capacity and energy; therefore, reducing the separator thickness is one way to improve battery energy density. Secondly, the current mainstream separator material is polyolefin (polyethylene, polypropylene), which undergoes significant physical thermal shrinkage at high temperatures (>120℃), causing direct contact between the positive and negative electrodes, leading to large-area internal short circuits and greatly increasing the likelihood of battery thermal runaway. Third, when the temperature reaches the melting point of polyolefin materials (PE about 130°C, PP about 160°C), they will melt and the membrane will break. Once the membrane melts, the physical isolation between the positive and negative electrodes is lost, causing a large-area internal short circuit, which is also very likely to lead to the occurrence of battery thermal runaway.

[0003] Due to long-term cyclic use, lithium dendrites will inevitably precipitate on the negative electrode in the battery, especially in the center, corners, and overhang areas of the negative electrode corresponding to the edge of the positive electrode in wound battery electrode packs. This will seriously damage the battery performance, leading to capacity decay and shortened life. More dangerously, the precipitated lithium dendrites may puncture the separator, causing internal short circuits, thermal runaway, or even fire and explosion. Summary of the Invention

[0004] The purpose of this invention is to address the technical deficiencies of existing technologies by providing a composite negative electrode, a composite positive electrode, a membrane-free battery, and a method for their preparation.

[0005] Therefore, the present invention provides a composite negative electrode sheet, which includes necessary constituent layers and may or may not include non-essential constituent layers; Preferably, the composite negative electrode does not include unnecessary constituent layers; The necessary components include a current collector, an active material layer, an insulating layer, and a lithium removal layer. The upper and lower surfaces of the current collector are each coated with a layer of active material. An insulating layer is coated on the upper and lower surfaces of the active material layer, respectively; The upper and lower surfaces of the insulating layer are each coated with a lithium removal layer; Preferably, the current collector is copper foil; Among them, copper foil includes at least one of double-sided copper foil, carbon-coated copper foil, and perforated copper foil; Preferably, the active material layer includes an active material, a conductive agent, a thickener, a binder, and additives; The active material includes at least one of artificial graphite, natural graphite, hard carbon, soft carbon, silicon anode, and lithium titanate. The conductive agent includes at least one of carbon black, carbon nanotubes, and graphene; Thickeners include at least one of sodium carboxymethyl cellulose and lithium carboxymethyl cellulose; The adhesive includes at least one of styrene-butadiene rubber, polyvinylidene fluoride, and acrylic (ester) polymers; Additives include at least one of wetting agents, liquid retaining agents, defoamers, and crack-resistant agents; Preferably, the insulating layer comprises inorganic material particles, binder, dispersant, thickener, and wetting agent; Preferably, the thickness of the single-sided insulating layer is (1~4) μm, and the areal density is (0.1~0.3) mg / cm³. 2 ; Among them, the inorganic material particles include at least one of alumina, boehmite, magnesium oxide, aluminum hydroxide, and magnesium hydroxide; The adhesive is an acrylic (ester) polymer; The dispersant is sodium polyacrylate polymer; The thickener is sodium carboxymethyl cellulose polymer; The wetting agent is a polyether-modified polysiloxane polymer; Preferably, the lithium-free layer comprises silica powder, binder, dispersant, thickener, wetting agent, and crosslinking agent; Preferably, the thickness of the lithium removal layer on one side is (1~4) μm, and the areal density is (0.1~0.3) mg / cm³. 2 ; Among them, the silica powder is a solid particle or a hollow particle, and the surface is modified with a silane coupling agent, which contains epoxy groups. The adhesive is an acrylic (ester) polymer containing epoxy groups; The dispersant is sodium polyacrylate polymer; The thickener is sodium carboxymethyl cellulose polymer; The wetting agent is a polyether-modified polysiloxane polymer; The crosslinking agent is an amine compound.

[0006] This invention also provides a method for preparing a composite negative electrode, comprising the following steps: Step 1, negative electrode slurry preparation: Mix the active material, conductive agent, thickener, binder and additives according to the preset mass ratio, stir evenly, and then dissolve them in a solvent for dispersion to obtain the active material layer slurry; The second step, negative electrode slurry preparation 2: Inorganic material particles, binder, dispersant, thickener and wetting agent are mixed according to the preset mass ratio and stirred evenly. Then they are dissolved in a solvent for dispersion to obtain the insulating layer slurry. The third step, negative electrode slurry preparation 3: Mix silica powder, binder, dispersant, thickener, wetting agent and crosslinking agent according to the preset mass ratio, stir evenly, and then dissolve them in a solvent for dispersion to obtain lithium-free slurry. Step 4, Negative electrode coating and drying 1: The active material layer slurry is uniformly coated on the surface of the negative electrode current collector and dried to obtain a negative electrode sheet 1 with an active material layer on the surface of the current collector; Step 5, negative electrode rolling: The dried negative electrode sheet 1 with an active material layer on its surface is rolled to obtain negative electrode sheet 2; Step 6, Negative electrode coating and drying 2: The insulating layer slurry is evenly coated on the surface of the rolled negative electrode sheet 2 and dried to obtain a negative electrode sheet 3 with an insulating layer on the surface of the negative electrode sheet 2. Step 7, Negative electrode coating and drying 3: The lithium removal layer slurry is uniformly coated on the surface of the negative electrode sheet 3 and dried to obtain a negative electrode sheet 4 with a lithium removal layer on the surface of the negative electrode sheet 3, which is a composite negative electrode sheet.

[0007] The present invention also provides a composite positive electrode sheet, including necessary constituent layers, and may include or exclude non-essential constituent layers; Preferably, the composite positive electrode includes a non-essential layer; The necessary components include a current collector, an active material layer, and an insulating layer. The upper and lower surfaces of the current collector are each coated with a layer of active material. An insulating layer is coated on the upper and lower surfaces of the active material layer, respectively; Preferably, the current collector is aluminum foil; Among them, aluminum foil includes at least one of double-sided aluminum foil, carbon-coated aluminum foil, and perforated aluminum foil; Preferably, the active material layer includes an active material, a conductive agent, a binder, and additives; The active material includes at least one of lithium iron phosphate, lithium manganese iron phosphate, lithium nickel cobalt manganese oxide, lithium nickel oxide, lithium manganese oxide, lithium cobalt oxide, lithium nickel manganese oxide, and lithium-rich manganese-based oxide. The conductive agent includes at least one of carbon black, carbon nanotubes, and graphene; The adhesive includes at least one of polyvinylidene fluoride, acrylic (ester) polymers, and acrylonitrile polymers; Additives include at least one of wetting agents, liquid retaining agents, defoamers, and crack-resistant agents; Preferably, the insulating layer comprises inorganic material particles, binder, dispersant, thickener, and wetting agent; Preferably, the thickness of the single-sided insulating layer is (1~4) μm, and the areal density is (0.1~0.3) mg / cm³. 2 ; Among them, the inorganic material particles include at least one of alumina, boehmite, magnesium oxide, aluminum hydroxide, and magnesium hydroxide; The adhesive is an acrylic (ester) polymer; The dispersant is sodium polyacrylate polymer; The thickener is sodium carboxymethyl cellulose polymer; The wetting agent is a polyether-modified polysiloxane polymer; Preferably, the unnecessary layer is an adhesive layer; Preferably, the amount of adhesive applied to a single-sided adhesive layer is (0.3~1.0) g / m. 2 ; The dispensing layer includes an adhesive and a dispersant; The adhesive is at least one of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, and acrylic (ester) polymers; The dispersant is sodium polyacrylate polymer; This invention also provides a method for preparing a composite positive electrode, comprising the following steps: Step 1, Positive electrode slurry preparation: Mix the active material, conductive agent, binder and additives according to the preset mass ratio, stir evenly, and then dissolve them in a solvent for dispersion to obtain the active material layer slurry; The second step, positive electrode slurry preparation 2: Inorganic material particles, binder, dispersant, thickener and wetting agent are mixed according to the preset mass ratio and stirred evenly. Then, they are dissolved in a solvent for dispersion to obtain the insulating layer slurry. The third step, positive electrode slurry preparation 3: Mix the binder and dispersant according to the preset mass ratio, stir evenly, and then dissolve them in a solvent to disperse them and obtain the dispensing layer slurry; Step 4, Positive electrode coating and drying 1: The active material layer slurry is uniformly coated on the surface of the positive electrode current collector and dried to obtain a positive electrode sheet 1 with an active material layer on the surface of the current collector; Step 5, positive electrode rolling: The dried positive electrode sheet 1 with an active material layer on its surface is rolled to obtain positive electrode sheet 2; Step 6, Positive electrode coating and drying 2: The insulating layer slurry is evenly coated on the surface of the rolled positive electrode sheet 2 and dried to obtain a positive electrode sheet 3 with an insulating layer on the surface of the positive electrode sheet 2; Step 7, Positive electrode coating and drying 3: The adhesive layer slurry is evenly sprayed onto the surface of the positive electrode sheet 3 and dried to obtain a positive electrode sheet 4 with an adhesive layer on the surface of the positive electrode sheet 3, which is a composite positive electrode sheet.

[0008] The present invention also provides a membrane-free battery, comprising a composite negative electrode, a composite positive electrode, an electrolyte, and structural components; In this case, there is no separator between the composite positive electrode and the composite negative electrode. They are insulated by the insulating layer on the composite negative electrode and the composite positive electrode, and are fixedly bonded by the adhesive layer on the composite positive electrode. Furthermore, the present invention also provides a method for preparing a membrane-free battery, comprising the following steps: The first step is electrode sheet forming: the composite negative electrode sheet and composite positive electrode sheet are cut into strips and laser-cut to obtain the electrode sheets to be assembled; The second step is electrode assembly forming: the electrode sheets are wound or stacked by punching, cold pressing, and hot pressing to obtain the electrode assembly. The third step is the semi-finished battery forming process: the electrode assembly is assembled with structural components (positive electrode adapter, negative electrode adapter, Mylar film, lower pad, battery cover plate, and battery case) through conventional battery manufacturing processes such as ultrasonic welding, laser welding, film coating, casing, and peripheral welding. The fourth step is the forming of finished batteries: the dry batteries are processed through conventional battery manufacturing processes such as drying, electrolyte injection, formation, capacity testing, aging, and inspection, and then assembled with structural components (rubber stopper, pin, top gasket, blue film) to form finished batteries.

[0009] As can be seen from the technical solutions provided by the present invention above, compared with the prior art, the present invention provides a composite negative electrode, a composite positive electrode, a membrane-free battery and a preparation method, which are scientifically and rationally designed. The membrane-free battery prepared by the composite negative electrode and the composite positive electrode can effectively improve the energy density and safety performance of the battery, especially in terms of thermal runaway protection, which has great practical significance. Attached Figure Description

[0010] Figure 1 A schematic diagram illustrating a method for preparing a composite negative electrode sheet provided by the present invention; Figure 2 A schematic diagram illustrating a method for preparing a composite positive electrode sheet provided by the present invention; Figure 3 This is a cross-sectional schematic diagram of a composite negative electrode and a composite positive electrode. Detailed Implementation

[0011] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0012] It should be noted that the active material layer, insulating layer and lithium removal layer of the negative electrode are first prepared into slurry, and then composite negative electrode and composite positive electrode are prepared respectively, and then assembled into a membrane-free battery.

[0013] To prepare the composite negative electrode sheet provided by this invention, see [link to relevant documentation]. Figure 1 This invention provides a method for preparing a composite negative electrode, comprising the following steps: The first step, negative electrode slurry preparation 1, is to obtain the active material layer slurry.

[0014] In this invention, specifically, the active material artificial graphite, the conductive agent carbon black, the thickener sodium carboxymethyl cellulose, and the auxiliary agent butanediol are mixed according to a preset mass ratio.

[0015] In this invention, specifically, the active material artificial graphite, the conductive agent carbon black, the thickener sodium carboxymethyl cellulose, and the auxiliary agent butanediol are mixed in a mass ratio of (0.955~0.974):(0.5~1.0):(1.0~1.5):(0.1~0.5).

[0016] In this invention, specifically, the active material artificial graphite, the conductive agent carbon black, the thickener sodium carboxymethyl cellulose, and the auxiliary agent butanediol are mixed and stirred evenly.

[0017] In this invention, specifically, artificial graphite (active material), carbon black (conductive agent), sodium carboxymethyl cellulose (thickener), and butanediol (auxiliary agent) are mixed and stirred evenly, then dissolved in water to disperse them. Before discharge, styrene-butadiene rubber (1.0~1.5) of binder is added to obtain an active material layer slurry.

[0018] In this invention, specifically, the solid content of the active material layer slurry is 45% to 55%.

[0019] The second step, negative electrode slurry preparation 2, is to obtain the insulating layer slurry.

[0020] In this invention, specifically, boehmite particles, acrylate polymer binder, sodium polyacrylate dispersant, sodium carboxymethyl cellulose thickener, and polyether-modified polysiloxane wetting agent are mixed according to a preset mass ratio.

[0021] In this invention, specifically, boehmite particles, acrylate polymer binder, sodium polyacrylate dispersant, sodium carboxymethyl cellulose thickener, and polyether-modified polysiloxane wetting agent are mixed in a mass ratio of (73.5~84.7):(15~25):(0.1~0.5):(0.1~0.5):(0.1~0.5).

[0022] In this invention, specifically, boehmite particles, acrylate polymer binder, sodium polyacrylate dispersant, sodium carboxymethyl cellulose thickener, and polyether-modified polysiloxane wetting agent are mixed and stirred evenly.

[0023] In this invention, specifically, boehmite particles, acrylate polymer binder, sodium polyacrylate dispersant, sodium carboxymethyl cellulose thickener, and polyether-modified polysiloxane wetting agent are mixed and stirred evenly, and then dissolved in water to disperse them, thereby obtaining an insulating layer slurry.

[0024] In this invention, specifically, the solid content of the insulating layer slurry is 15% to 35%.

[0025] The third step, negative electrode slurry preparation 3, is to obtain lithium-free slurry.

[0026] In this invention, specifically, silica powder, acrylic (ester) polymer binder, sodium polyacrylate dispersant, sodium carboxymethyl cellulose thickener, polyether-modified polysiloxane wetting agent, and polyamide crosslinking agent are mixed according to a preset mass ratio.

[0027] In this invention, specifically, silica powder, acrylic (ester) polymer binder, sodium polyacrylate dispersant, sodium carboxymethyl cellulose thickener, polyether-modified polysiloxane wetting agent, and polyamide crosslinking agent are mixed in a mass ratio of (71.5~84.5):(15~25):(0.1~0.5):(0.1~0.5):(0.1~0.5):(0.2~2.0).

[0028] In this invention, specifically, silica powder, acrylic (ester) polymer binder, sodium polyacrylate dispersant, sodium carboxymethyl cellulose thickener, polyether-modified polysiloxane wetting agent, and polyamide crosslinking agent are mixed and stirred evenly.

[0029] In this invention, specifically, silica powder, acrylic (ester) polymer binder, sodium polyacrylate dispersant, sodium carboxymethyl cellulose thickener, polyether-modified polysiloxane wetting agent, and polyamide crosslinking agent are mixed and stirred evenly, and then dissolved in water to disperse them to obtain a lithium-free slurry.

[0030] In this invention, specifically, the solid content of the lithium layer slurry is 15% to 35%.

[0031] The fourth step, negative electrode coating and drying 1, is to obtain negative electrode sheet 1.

[0032] In this invention, specifically, the active material layer slurry is uniformly coated on the upper and lower surfaces of the negative electrode current collector 1 and then dried to obtain a negative electrode sheet 1 with an active material layer 2' disposed on the upper and lower surfaces of the current collector.

[0033] The fifth step, negative electrode rolling, is to obtain negative electrode sheet 2.

[0034] In this invention, specifically, the negative electrode sheet 1, which has been dried and has active material layers 2' on the upper and lower surfaces of the current collector 1, is rolled to increase the compaction density of the active material layers, so as to reduce impedance and increase battery energy density. After rolling, the negative electrode sheet 2 is obtained, and the active material layers 2 are provided on the upper and lower surfaces of the current collector 1.

[0035] Step 6, negative electrode coating and drying 2, is to obtain negative electrode sheet 3.

[0036] In this invention, specifically, an insulating layer slurry is uniformly coated on the upper and lower surfaces of the rolled negative electrode sheet 2 and then dried to obtain a negative electrode sheet 3 with an insulating layer 3 on the upper and lower surfaces of the negative electrode sheet 2.

[0037] Step 7, the negative electrode coating and drying 3, is to obtain the negative electrode sheet 4, i.e., the composite negative electrode sheet 5.

[0038] In this invention, specifically, a lithium removal layer slurry is uniformly coated on the upper and lower surfaces of the negative electrode 3 and then dried to obtain a negative electrode 4 with a lithium removal layer 4 on the upper and lower surfaces of the negative electrode 3, which is a composite negative electrode 5.

[0039] To prepare the composite positive electrode sheet provided by this invention, see [link to relevant documentation]. Figure 2 This invention provides a method for preparing a composite positive electrode, comprising the following steps: The first step, positive electrode slurry preparation 1, is to obtain the active material layer slurry.

[0040] In this invention, specifically, the active material lithium nickel cobalt manganese oxide, the conductive agent carbon black, the conductive agent carbon nanotubes, the binder polyvinylidene fluoride, and the additives are mixed according to a preset mass ratio.

[0041] In this invention, specifically, the active material lithium nickel cobalt manganese oxide, the conductive agent carbon black, the conductive agent carbon nanotube, the binder polyvinylidene fluoride, and the additives are mixed in a mass ratio of (0.950~0.978):(0.5~1.0):(0.1~1.0):(1.5:2.5):(0.1~0.5).

[0042] In this invention, specifically, the active material lithium nickel cobalt manganese oxide, the conductive agent carbon black, the conductive agent carbon nanotubes, the binder polyvinylidene fluoride, and the additives are mixed and stirred evenly.

[0043] In this invention, specifically, the active material lithium nickel cobalt manganese oxide, the conductive agent carbon black, the conductive agent carbon nanotubes, the binder polyvinylidene fluoride, and the additives are mixed and stirred evenly, and then dissolved in the solvent N-methylpyrrolidone for dispersion to obtain an active material layer slurry.

[0044] In this invention, specifically, the solid content of the active material layer slurry is 55% to 75%.

[0045] The second step, positive electrode slurry preparation 2, is to obtain the insulating layer slurry.

[0046] In this invention, specifically, boehmite particles, acrylate polymer binder, sodium polyacrylate dispersant, sodium carboxymethyl cellulose thickener, and polyether-modified polysiloxane wetting agent are mixed according to a preset mass ratio.

[0047] In this invention, specifically, boehmite particles, acrylate polymer binder, sodium polyacrylate dispersant, sodium carboxymethyl cellulose thickener, and polyether-modified polysiloxane wetting agent are mixed in a mass ratio of (73.5~84.7):(15~25):(0.1~0.5):(0.1~0.5):(0.1~0.5).

[0048] In this invention, specifically, boehmite particles, acrylate polymer binder, sodium polyacrylate dispersant, sodium carboxymethyl cellulose thickener, and polyether-modified polysiloxane wetting agent are mixed and stirred evenly.

[0049] In this invention, specifically, boehmite particles, acrylate polymer binder, sodium polyacrylate dispersant, sodium carboxymethyl cellulose thickener, and polyether-modified polysiloxane wetting agent are mixed and stirred evenly, and then dissolved in water to disperse them, thereby obtaining an insulating layer slurry.

[0050] In this invention, specifically, the solid content of the insulating layer slurry is 15% to 35%.

[0051] The third step, positive electrode slurry preparation 3, is to obtain the dispensing layer slurry.

[0052] In this invention, specifically, the binder polyvinylidene fluoride-hexafluoropropylene copolymer and the dispersant acrylic (ester) polymer are mixed according to a preset mass ratio.

[0053] In this invention, specifically, the binder polyvinylidene fluoride-hexafluoropropylene copolymer and the dispersant acrylic (ester) polymer are mixed in a mass ratio of (95~99):(1~5).

[0054] In this invention, specifically, the binder polyvinylidene fluoride-hexafluoropropylene copolymer and the dispersant acrylic (ester) polymer are mixed and stirred evenly.

[0055] In this invention, specifically, the binder polyvinylidene fluoride-hexafluoropropylene copolymer and the dispersant acrylic (ester) polymer are mixed and stirred evenly, and then dissolved in water to disperse them, thereby obtaining the dispensing layer slurry.

[0056] In this invention, specifically, the solid content of the dispensing layer slurry is 10% to 30%.

[0057] The fourth step, drying the positive electrode coating, is to obtain the positive electrode sheet 1.

[0058] In this invention, specifically, the active material layer slurry is uniformly coated on the upper and lower surfaces of the positive electrode current collector 6 and then dried to obtain a positive electrode sheet 1 with an active material layer 7' disposed on the upper and lower surfaces of the current collector.

[0059] The fifth step, positive electrode crushing, is to obtain positive electrode plate 2.

[0060] In this invention, specifically, the positive electrode sheet 1, which has been dried and has active material layers 7' on the upper and lower surfaces of the current collector 6, is rolled to increase the compaction density of the active material layers, so as to reduce impedance and increase battery energy density. After rolling, a positive electrode sheet 2 is obtained, with active material layers 7' on the upper and lower surfaces of the current collector 6.

[0061] Step 6, drying the positive electrode coating 2, is to obtain the positive electrode sheet 3.

[0062] In this invention, specifically, an insulating layer slurry is uniformly coated on the upper and lower surfaces of the rolled positive electrode sheet 2 and then dried to obtain a positive electrode sheet 3 with an insulating layer 8 on the upper and lower surfaces of the positive electrode sheet 2.

[0063] Step 7, the positive electrode coating and drying step 3, is to obtain the positive electrode sheet 4, namely the composite positive electrode sheet 10.

[0064] In this invention, specifically, the adhesive layer slurry is uniformly sprayed onto the upper and lower surfaces of the positive electrode sheet 3 and dried to obtain a positive electrode sheet 4 with an adhesive layer 9 on the upper and lower surfaces of the positive electrode sheet 3, which is a composite positive electrode sheet 10.

[0065] To prepare the membrane-free battery provided by this invention, this invention provides a method for preparing a membrane-free battery, comprising the following steps: The first step is electrode sheet forming: the composite negative electrode sheet and composite positive electrode sheet are cut into strips and laser-cut to obtain the positive and negative electrode sheets to be assembled.

[0066] The second step is electrode assembly: a positive electrode and a negative electrode are wound or stacked, cold-pressed, short-circuited, hot-pressed, and short-circuited to obtain an electrode assembly.

[0067] The third step is the semi-finished battery forming: the foil tabs of the two electrode groups are ultrasonically welded to the positive and negative electrode adapters, and the ultrasonic welding area is protected with tape. Then, the positive and negative electrode adapters are laser welded to the electrode posts of the battery cover plate. After that, the two electrode groups are assembled into a semi-finished battery by conventional battery manufacturing processes such as core forming, wrapping with Mylar film and lower pad, inserting into the battery case, and welding the battery case and battery cover around the perimeter.

[0068] The fourth step is the assembly of finished batteries: the dry cell batteries are assembled into finished batteries through conventional battery manufacturing processes such as short-circuit testing, drying in an oven, moisture content testing, initial electrolyte injection, soaking, negative pressure formation, secondary electrolyte replenishment, sealing with rubber stoppers, soldering pins, capacity testing, aging, coating with blue film, attaching top gaskets, and inspection.

[0069] To better understand the technical solution of the present invention, the following specific embodiments will be used to illustrate the technical solution of the present invention.

[0070] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0071] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0072] The existing methods for preparing positive and negative electrodes, as well as the methods for preparing batteries, are described in detail below: I. Preparation of negative electrode active material layer slurry, by weight ratio (parts) Add 96.3 parts of active material artificial graphite, 0.7 parts of conductive agent carbon black, 1.3 parts of thickener sodium carboxymethyl cellulose (solid content 92.5%), and 0.3 parts of additive butylene glycol to the pulping tank, mix and stir evenly, then dissolve in water to disperse. Before discharge, add 3.75 parts of binder styrene-butadiene rubber (solid content 40%) to adjust the solid content of the slurry in the pulping tank to 52% to obtain the active material layer slurry, and then discharge.

[0073] II. Negative Electrode Preparation 1. Negative Electrode Coating: The negative electrode active material slurry prepared in the above steps is coated onto a 6μm double-sided copper foil current collector. The active material layer is distributed on both the upper and lower sides of the copper foil, with a double-sided areal density of 18.02 mg / cm³. 2 The negative electrode sheet is obtained by drying in an oven and then pressing.

[0074] 2. Negative electrode compaction: At room temperature, the negative electrode sheet is compacted to increase the compaction density of the active material layer to 1.7 g / cm³. 3This is to reduce impedance and increase battery energy density.

[0075] 3. Negative electrode cutting and slitting: The rolled negative electrode sheet is cut and slitting into negative electrode sheets of the required size for battery production.

[0076] 4. Laser cutting of tabs for negative electrode: The foil edges of the slit negative electrode sheet are cut into tabs using a laser cutting device.

[0077] III. Preparation of the positive electrode active material layer slurry, by weight ratio (parts) Add 96.3 parts of active material lithium nickel cobalt manganese oxide, 1.0 part of conductive agent carbon black, 12.5 parts of conductive agent carbon nanotubes (solid content of 4%), 2.0 parts of binder polyvinylidene fluoride, and 0.2 parts of additives to the pulping tank, mix and stir evenly, then dissolve it in the solvent N-methylpyrrolidone for dispersion, adjust the solid content of the slurry in the pulping tank to 65%, obtain the active material layer slurry, and then discharge it.

[0078] IV. Preparation of Positive Electrode 1. Positive Electrode Coating: The positive electrode active material slurry prepared in the above steps is coated onto a 13μm double-sided aluminum foil current collector. The active material layer is distributed on both the upper and lower sides of the aluminum foil, with a double-sided areal density of 37.0 mg / cm³. 2 After being dried in an oven, the positive electrode sheet is obtained and ready to be rolled.

[0079] 2. Positive electrode compaction: At room temperature, the positive electrode sheet is compacted to increase the compaction density of the active material layer to 3.5 g / cm³. 3 This is to reduce impedance and increase battery energy density.

[0080] 3. Positive electrode cutting and slitting: The rolled positive electrode sheet is cut and slitting into positive electrode sheets of the required size for battery manufacturing.

[0081] 4. Positive electrode laser cutting tabs: The foil edges of the cut positive electrode sheet are cut into foil tabs using a laser cutting device.

[0082] V. Battery Manufacturing 1. Winding: A positive electrode, a negative electrode, and two separators are wound, cold-pressed, short-circuited, hot-pressed, and short-circuited to obtain an electrode assembly to be assembled.

[0083] 2. Semi-finished battery forming: The aluminum foil tabs of the two electrode groups mentioned above are ultrasonically welded to the positive electrode adapter and the copper foil tabs to the negative electrode adapter. The ultrasonic welding area is protected with tape. Then, the positive electrode adapter and the negative electrode adapter are laser welded to the positive electrode post and the negative electrode post of the battery cover plate, respectively. After that, the two electrode groups are assembled into a semi-finished battery by conventional battery manufacturing processes such as core forming, wrapping with Mylar film and lower pad, inserting into the battery case, and welding the battery case and the battery cover around the perimeter.

[0084] 3. Finished battery forming: The dry cell batteries are assembled into finished batteries through conventional battery manufacturing processes such as short circuit testing, oven drying, moisture content testing, primary electrolyte injection, soaking, negative pressure formation, secondary electrolyte replenishment, sealing with rubber stoppers, soldering pins, capacity testing, aging, coating with blue film, attaching top gaskets, and inspection. Example

[0085] I. Preparation of negative electrode active material layer slurry, by weight ratio (parts) Add 96.3 parts of active material artificial graphite, 0.7 parts of conductive agent carbon black, 1.3 parts of thickener sodium carboxymethyl cellulose (solid content 92.5%), and 0.3 parts of additive butylene glycol to the pulping tank, mix and stir evenly, then dissolve in water to disperse. Before discharge, add 3.75 parts of binder styrene-butadiene rubber (solid content 40%) to adjust the solid content of the slurry in the pulping tank to 52% to obtain the active material layer slurry, and then discharge.

[0086] II. Preparation of negative electrode insulating layer slurry, by weight ratio (parts) Add 79.2 parts of boehmite particles, 20 parts of acrylic (ester) polymer binder, 0.3 parts of sodium polyacrylate dispersant, 0.22 parts of sodium carboxymethyl cellulose thickener (solid content of 92.5%), and 0.3 parts of polyether modified polysiloxane wetting agent to the pulping tank, mix and stir evenly, then dissolve in water to disperse, adjust the solid content of the slurry in the pulping tank to 25%, obtain the insulating layer slurry, and then discharge.

[0087] III. Preparation of lithium removal slurry for negative electrode, by weight ratio (parts) Add 78.9 parts of silica powder, 20 parts of acrylic (ester) polymer binder, 0.3 parts of sodium polyacrylate dispersant, 0.22 parts of sodium carboxymethyl cellulose thickener (solid content of 92.5%), 0.3 parts of polyether-modified polysiloxane wetting agent, and 0.3 parts of polyamide crosslinking agent to the pulping tank, mix and stir evenly, then dissolve in water to disperse, adjust the solid content of the slurry in the pulping tank to 20%, obtain lithium-free slurry, and then discharge.

[0088] IV. Preparation of Composite Anode Sheets 1. Negative Electrode Coating and Drying: The negative electrode active material layer slurry prepared in the above steps is coated onto the upper and lower surfaces of a 6μm double-sided copper foil current collector and dried to obtain a negative electrode sheet 1 with active material layers on the upper and lower surfaces of the current collector. The double-sided areal density of the active material layer is 18.02 mg / cm³. 2 .

[0089] 2. Negative electrode compaction: At room temperature, the dried negative electrode sheet 1, on the upper and lower surfaces of the current collector, with active material layers, is compacted to increase the compaction density of the active material layer to 1.7 g / cm³. 3In order to reduce impedance and increase battery energy density, negative electrode sheet 2 is obtained after rolling.

[0090] 3. Negative Electrode Coating and Drying 2: The insulating slurry is evenly coated on the upper and lower surfaces of the rolled negative electrode sheet and then dried to obtain a negative electrode sheet 3 with an insulating layer on the upper and lower surfaces of the negative electrode sheet 2. The double-sided areal density of the insulating layer is 0.3 mg / cm³. 2 .

[0091] 4. Negative Electrode Coating and Drying 3: The lithium removal layer slurry is uniformly coated on the upper and lower surfaces of the negative electrode sheet 3 and then dried to obtain a negative electrode sheet 4 with a lithium removal layer on the upper and lower surfaces of the negative electrode sheet 3, which is a composite negative electrode sheet. The double-sided areal density of the lithium removal layer is 0.22 mg / cm³. 2 .

[0092] 5. Cutting and slitting: Cut the composite negative electrode sheet into positive electrode sheets of the required size for battery production.

[0093] 6. Laser cutting of tabs: The foil edges of the cut composite negative electrode sheet are cut into tabs using a laser cutting device.

[0094] V. Preparation of positive electrode active material layer slurry, by weight ratio (parts) Add 96.3 parts of active material lithium nickel cobalt manganese oxide (NCM811), 1.0 part of conductive agent carbon black, 12.5 parts of conductive agent carbon nanotubes (solid content of 4%), 2.0 parts of binder polyvinylidene fluoride, and 0.2 parts of additives to the pulping tank, mix and stir evenly, then dissolve it in the solvent N-methylpyrrolidone for dispersion, adjust the solid content of the slurry in the pulping tank to 65%, obtain the active material layer slurry, and then discharge it.

[0095] VI. Preparation of positive electrode insulating layer slurry, by weight ratio (parts) Add 79.2 parts of boehmite particles, 20 parts of acrylic (ester) polymer binder, 0.3 parts of sodium polyacrylate dispersant, 0.22 parts of sodium carboxymethyl cellulose thickener (solid content of 92.5%), and 0.3 parts of polyether modified polysiloxane wetting agent to the pulping tank, mix and stir evenly, then dissolve in water to disperse, adjust the solid content of the slurry in the pulping tank to 25%, obtain the insulating layer slurry, and then discharge.

[0096] VII. Preparation of positive electrode adhesive layer slurry, by weight ratio (parts) Add 95 parts of the binder polyvinylidene fluoride-hexafluoropropylene copolymer and 5 parts of the dispersant acrylic (ester) polymer to the pulping tank, mix and stir evenly, then dissolve it in water to disperse it. Adjust the solid content of the slurry in the pulping tank to 20% to obtain the dispensing layer slurry, and then discharge it.

[0097] VIII. Preparation of Composite Cathode Sheets 1. Positive Electrode Coating and Drying: The positive electrode active material layer slurry prepared in the above steps is coated onto the upper and lower surfaces of a 13μm double-sided aluminum foil current collector and dried to obtain a positive electrode sheet 1 with an active material layer on the upper and lower surfaces of the current collector. The double-sided areal density of the active material layer is 37 mg / cm³. 2 .

[0098] 2. Positive electrode compaction: At room temperature, the dried positive electrode sheet 1, on the upper and lower surfaces of the current collector, with active material layers, is compacted to increase the compaction density of the active material layer to 3.5 g / cm³. 3 In order to reduce impedance and increase battery energy density, positive electrode sheet 2 is obtained after rolling.

[0099] 3. Positive Electrode Coating and Drying 2: The insulating layer slurry is uniformly coated on the upper and lower surfaces of the rolled positive electrode sheet and then dried to obtain a positive electrode sheet 3 with an insulating layer on the upper and lower surfaces of the positive electrode sheet 2. The double-sided areal density of the insulating layer is 0.3 mg / cm³. 2 .

[0100] 4. Positive Electrode Coating and Drying 3: The dispensing slurry is evenly sprayed onto the upper and lower surfaces of the positive electrode sheet 3 and dried to obtain a positive electrode sheet 4 with a dispensing layer on the upper and lower surfaces of the positive electrode sheet 3, which is a composite positive electrode sheet. The double-sided areal density of the dispensing layer is 0.8 mg / cm³. 2 .

[0101] 5. Cutting and slitting: Cut the composite positive electrode sheet into positive electrode sheets of the required size for battery manufacturing.

[0102] 6. Laser cutting of tabs: The foil edges of the slit composite positive electrode sheet are cut into tabs using a laser cutting device.

[0103] IX. Preparation of Membrane-less Batteries 1. Winding: A positive electrode and a negative electrode are wound, cold-pressed, short-circuited, hot-pressed, and short-circuited to obtain an electrode assembly to be assembled.

[0104] 2. Semi-finished battery forming: The aluminum foil tabs of the two electrode groups mentioned above are ultrasonically welded to the positive electrode adapter and the copper foil tabs to the negative electrode adapter. The ultrasonic welding area is protected with tape. Then, the positive electrode adapter and the negative electrode adapter are laser welded to the positive electrode post and the negative electrode post of the battery cover plate, respectively. After that, the two electrode groups are assembled into a semi-finished battery by conventional battery manufacturing processes such as core forming, wrapping with Mylar film and lower pad, inserting into the battery case, and welding the battery case and the battery cover around the perimeter.

[0105] 3. Finished battery forming: The dry cell batteries are assembled into finished batteries through conventional battery manufacturing processes such as short circuit testing, oven drying, moisture content testing, primary electrolyte injection, soaking, negative pressure formation, secondary electrolyte replenishment, sealing with rubber stoppers, soldering pins, capacity testing, aging, coating with blue film, attaching top gaskets, and inspection.

[0106] Table 1. Differences in battery heating and overcharge safety test results between the comparative example and the embodiment. Comparative Example The 120℃ explosion-proof valve opened, producing a large amount of smoke. 105% SOC explosion-proof valve opens to produce a large amount of smoke. 265Wh / kg 650Wh / L Example 160℃ explosion-proof valve opens, producing a small amount of smoke. 130% SOC explosion-proof valve opens to produce a small amount of smoke. 270Wh / kg 705Wh / L The differences in battery heating and overcharge safety test results between the comparative example and the embodiment are shown in Table 1. As can be seen from Table 1, because the battery in the embodiment does not contain a polymer separator, the insulation between the positive and negative electrodes no longer relies on the polymer separator. Instead, it is isolated by inorganic material insulating layers on the surfaces of the positive and negative electrodes. This prevents large-area internal short circuits between the positive and negative electrodes caused by thermal shrinkage and melting of the polymer separator. Consequently, the thermal runaway temperature in the heating test is increased by 40°C, and the amount of smoke after thermal runaway is significantly reduced, effectively improving the battery's thermal safety performance. Furthermore, because a lithium removal layer is provided on the surface of the negative electrode insulating layer, it effectively removes lithium dendrites deposited on the negative electrode surface, preventing internal short circuits between the positive and negative electrodes caused by lithium deposition. Consequently, the thermal runaway SOC in the overcharge test is increased by 25%, and the amount of smoke after thermal runaway is significantly reduced, improving battery safety performance. Additionally, the energy density of the separatorless battery is increased, with a 5Wh / kg increase in gravimetric energy density and a 55Wh / L increase in volumetric energy density.

[0107] Compared with existing technologies, the composite negative electrode, composite positive electrode, membrane-free battery, and preparation method provided by the present invention have the following beneficial technical effects: By setting insulating layers on the upper and lower surfaces of the negative electrode active material layer, on the one hand, the transfer of electrons from the negative electrode to the lithium removal layer along the current collector → active material layer path is effectively prevented, effectively preventing side reactions between the reversibly cyclic active lithium ions in the battery and the lithium removal layer of the negative electrode, thus ensuring the battery's lifespan; on the other hand, because insulating layers are set on the upper and lower surfaces of the negative electrode active material layer, and further, lithium removal layers are set on the upper and lower surfaces of the insulating layers, and insulating layers are set on the upper and lower surfaces of the positive electrode active material layer, the battery assembly no longer requires polymer separator materials. This effectively improves the battery's energy density and effectively prevents large-area short circuits between the positive and negative electrodes caused by thermal shrinkage and melting of the polymer separator, thereby improving the battery's safety performance.

[0108] Furthermore, the silica powder, binder, and crosslinking agent in the lithium removal layer form a three-dimensional crosslinked network, which improves the mechanical strength and thermal stability of the lithium removal layer, thus enhancing battery safety. The lithium removal layer is insulated from the negative electrode active material layer by an insulating layer on the negative electrode, and from the positive electrode active material layer by an insulating layer on the positive electrode. This prevents the lithium removal layer from contacting electrons on the negative and positive electrodes, fundamentally eliminating side reactions between the lithium removal layer and the reversibly recyclable active lithium ions in the battery. Consequently, the lithium removal layer only reacts with lithium dendrites deposited on the negative electrode, preventing the dendrites from growing and extending towards the positive electrode, thus avoiding internal short circuits caused by lithium deposition on the negative electrode and further improving battery safety.

[0109] Furthermore, the insulating layer on the positive and negative electrodes is mainly composed of boehmite inorganic material particles, and the lithium removal layer on the negative electrode is mainly composed of silicon dioxide inorganic material particles. The surfaces of both inorganic material particles have a large number of hydroxyl groups, which have good compatibility with the electrolyte and excellent electrolyte wettability and liquid retention, which is beneficial to improving the electrochemical performance of the battery.

[0110] As can be seen from the technical solutions provided by the present invention above, compared with the prior art, the present invention provides a composite negative electrode, a composite positive electrode, a membrane-free battery and a preparation method, which are scientifically and rationally designed. The membrane-free battery prepared by the composite negative electrode and the composite positive electrode can effectively improve the safety performance and energy density of the battery, and has significant practical significance, especially in thermal runaway protection.

[0111] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A composite negative electrode, characterized in that, The composite negative electrode sheet includes necessary constituent layers and may or may not include non-essential constituent layers. Preferably, the composite negative electrode does not include an unnecessary layer, which is a dispensing layer; the dispensing layer includes a binder and a dispersant; Preferably, the adhesive is at least one of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, and acrylic (ester) polymers; Preferably, the dispersant is a sodium polyacrylate polymer; The necessary constituent layers include a current collector, an active material layer, an insulating layer, and a lithium removal layer; Current collectors include at least one of double-sided copper foil, carbon-coated copper foil, and perforated copper foil; The active material layer includes active materials, conductive agents, thickeners, binders, and additives; Preferably, the active material includes at least one of artificial graphite, natural graphite, hard carbon, soft carbon, silicon anode, and lithium titanate; Preferably, the conductive agent includes at least one of carbon black, carbon nanotubes, and graphene; Preferably, the thickener includes at least one of sodium carboxymethyl cellulose and lithium carboxymethyl cellulose; Preferably, the adhesive comprises at least one of styrene-butadiene rubber, polyvinylidene fluoride, and acrylic (ester) polymers; Preferably, the additives include at least one of wetting agents, liquid retaining agents, defoamers, and anti-cracking agents.

2. The composite negative electrode sheet according to claim 1, characterized in that, The insulating layer comprises inorganic material particles, binder, dispersant, thickener, and wetting agent; the lithium removal layer comprises silica powder, binder, dispersant, thickener, wetting agent, and crosslinking agent. Preferably, the inorganic material particles include at least one of alumina, boehmite, magnesium oxide, aluminum hydroxide, and magnesium hydroxide; Preferably, the adhesive is an acrylic (ester) polymer; Preferably, the dispersant is a sodium polyacrylate polymer; Preferably, the thickener is a sodium carboxymethyl cellulose polymer; Preferably, the wetting agent is a polyether-modified polysiloxane polymer; Preferably, the thickness of the single-sided insulating layer is (1~4) μm, and the areal density is (0.1~0.3) mg / cm³. 2 ; Preferably, the silica powder is a solid particle or a hollow particle, and its surface is modified with a silane coupling agent; the silane coupling agent contains epoxy groups; Preferably, the adhesive is an acrylic (ester) polymer containing epoxy groups; Preferably, the dispersant is a sodium polyacrylate polymer; Preferably, the thickener is a sodium carboxymethyl cellulose polymer; Preferably, the wetting agent is a polyether-modified polysiloxane polymer; Preferably, the crosslinking agent is an amine compound; Preferably, the thickness of the lithium removal layer on one side is (1~4) μm, and the areal density is (0.1~0.3) mg / cm³. 2 .

3. A composite positive electrode, characterized in that, It includes essential component layers, and may or may not include non-essential component layers; Preferably, the composite positive electrode includes a non-essential component layer, which is a dispensing layer; The necessary constituent layers include a current collector, an active material layer, and an insulating layer; The current collector includes at least one of double-sided aluminum foil, carbon-coated aluminum foil, and perforated aluminum foil; the active material layer includes an active material, a conductive agent, a binder, and an additive. Preferably, the active material includes at least one of lithium iron phosphate, lithium manganese iron phosphate, lithium nickel cobalt manganese oxide, lithium nickel oxide, lithium manganese oxide, lithium cobalt oxide, lithium nickel manganese oxide, and lithium-rich manganese-based oxide. Preferably, the conductive agent includes at least one of carbon black, carbon nanotubes, and graphene; Preferably, the adhesive comprises at least one of polyvinylidene fluoride, acrylic (ester) polymers, and acrylonitrile polymers; Preferably, the additives include at least one of wetting agents, liquid retaining agents, defoamers, and anti-cracking agents.

4. The composite positive electrode sheet according to claim 3, characterized in that, The insulating layer includes inorganic material particles, binders, dispersants, thickeners, and wetting agents; the dispensing layer includes binders and dispersants. Preferably, the inorganic material particles include at least one of alumina, boehmite, magnesium oxide, aluminum hydroxide, and magnesium hydroxide; Preferably, the adhesive is an acrylic (ester) polymer; Preferably, the dispersant is a sodium polyacrylate polymer; Preferably, the thickener is a sodium carboxymethyl cellulose polymer; Preferably, the wetting agent is a polyether-modified polysiloxane polymer; Preferably, the thickness of the single-sided insulating layer is (1~4) μm, and the areal density is (0.1~0.3) mg / cm³. 2 ; Preferably, the adhesive is at least one of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, and acrylic (ester) polymers; Preferably, the dispersant is a sodium polyacrylate polymer; Preferably, the amount of adhesive applied to a single-sided adhesive layer is (0.3~1.0) g / m. 2 .

5. A separatorless battery, characterized in that, The negative electrode included is the composite negative electrode as described in claims 1-2, and the positive electrode included is the composite positive electrode as described in claims 3-4. There is no separator between the positive electrode and the negative electrode. In addition to the composite negative electrode and the composite positive electrode, it also includes an electrolyte and structural components.

6. A method for preparing a composite negative electrode sheet as described in claims 1-2, characterized in that, Includes the following steps: Step 1, negative electrode slurry preparation: Mix the active material, conductive agent, thickener, binder and additives according to the preset mass ratio, stir evenly, and then dissolve them in a solvent for dispersion to obtain the active material layer slurry; The second step, negative electrode slurry preparation 2: Inorganic material particles, binder, dispersant, thickener and wetting agent are mixed according to the preset mass ratio and stirred evenly. Then they are dissolved in a solvent for dispersion to obtain the insulating layer slurry. The third step, negative electrode slurry preparation 3: Mix silica powder, binder, dispersant, thickener, wetting agent and crosslinking agent according to the preset mass ratio, stir evenly, and then dissolve them in a solvent for dispersion to obtain lithium-free slurry. Step 4, Negative electrode coating and drying 1: The active material layer slurry is uniformly coated on the surface of the negative electrode current collector and dried to obtain a negative electrode sheet 1 with an active material layer on the surface of the current collector; Step 5, negative electrode rolling: The dried negative electrode sheet 1 with an active material layer on its surface is rolled to obtain negative electrode sheet 2; Step 6, Negative electrode coating and drying 2: The insulating layer slurry is evenly coated on the surface of the rolled negative electrode sheet 2 and dried to obtain a negative electrode sheet 3 with an insulating layer on the surface of the negative electrode sheet 2. Step 7, Negative electrode coating and drying 3: The lithium removal layer slurry is uniformly coated on the surface of the negative electrode sheet 3 and dried to obtain a negative electrode sheet 4 with a lithium removal layer on the surface of the negative electrode sheet 3, which is a composite negative electrode sheet.

7. A method for preparing a composite positive electrode sheet as described in claims 3-4, characterized in that, Includes the following steps: Step 1, Positive electrode slurry preparation: Mix the active material, conductive agent, binder and additives according to the preset mass ratio, stir evenly, and then dissolve them in a solvent for dispersion to obtain the active material layer slurry; The second step, positive electrode slurry preparation 2: Inorganic material particles, binder, dispersant, thickener and wetting agent are mixed according to the preset mass ratio and stirred evenly. Then, they are dissolved in a solvent for dispersion to obtain the insulating layer slurry. The third step, positive electrode slurry preparation 3: Mix the binder and dispersant according to the preset mass ratio, stir evenly, and then dissolve them in a solvent to disperse them and obtain the dispensing layer slurry; Step 4, Positive electrode coating and drying 1: The active material layer slurry is uniformly coated on the surface of the positive electrode current collector and dried to obtain a positive electrode sheet 1 with an active material layer on the surface of the current collector; Step 5, positive electrode rolling: The dried positive electrode sheet 1 with an active material layer on its surface is rolled to obtain positive electrode sheet 2; Step 6, Positive electrode coating and drying 2: The insulating layer slurry is evenly coated on the surface of the rolled positive electrode sheet 2 and dried to obtain a positive electrode sheet 3 with an insulating layer on the surface of the positive electrode sheet 2; Step 7, Positive electrode coating and drying 3: The adhesive layer slurry is evenly sprayed onto the surface of the positive electrode sheet 3 and dried to obtain a positive electrode sheet 4 with an adhesive layer on the surface of the positive electrode sheet 3, which is a composite positive electrode sheet.

8. A method for preparing a membrane-free battery as described in claims 16-19, characterized in that, Includes the following steps: Step 1, Electrode sheet forming: The composite negative electrode sheet and the composite positive electrode sheet are cut into strips and laser-cut electrode tabs to obtain the electrode sheets to be assembled; The second step is electrode assembly forming: the electrode sheets are wound or stacked by punching to obtain an electrode assembly. The third step is the semi-finished battery forming process: the electrode assembly is assembled with structural components (positive electrode adapter, negative electrode adapter, Mylar film, lower pad, battery cover plate, and battery case) through conventional battery manufacturing processes such as ultrasonic welding, laser welding, film coating, casing, and peripheral welding. The fourth step is the forming of finished batteries: the dry batteries are processed through conventional battery manufacturing processes such as drying, electrolyte injection, formation, capacity testing, aging, and inspection, and then assembled with structural components (rubber stopper, pin, top gasket, blue film) to form finished batteries.

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