Electrode sheet and preparation method thereof, and energy storage device

Abstract

The present invention discloses a method for preparing an electrode sheet, an electrode sheet prepared by the method for preparing the electrode sheet, and an energy storage device including the electrode sheet. The method for preparing the electrode sheet of the present invention adds a pore former and a block copolymer polystyrene-b-polyethylene glycol (PS-b-PEO) when preparing a primer layer, and self-assembles the block copolymer PS-b-PEO by steam annealing technology to form uniform nanoscale pores, and then decomposes the pore former by heat treatment to achieve pore formation of the pore former, and the pore formation of the pore former and the pore formation of the block copolymer PS-b-PEO form a network-like pore structure, which increases the specific surface area of ​​the primer layer, thereby increasing the electrochemical activity, energy density and power density of the prepared electrode sheet. In combination with a specific embodiment, the conductivity and ionic conductivity of the electrode sheet prepared by the method for preparing the electrode sheet of the present invention are significantly higher than those of the electrode sheet using a traditional primer layer.

Description

Technical Field

[0001] The present invention relates to the field of energy storage devices, and in particular to an electrode sheet and a preparation method thereof, and an energy storage device comprising the electrode sheet. Background Art

[0002] Supercapacitors are new energy storage devices that store energy through the interfacial double layer formed between the electrode sheet and the electrolyte. Due to their high power density and long cycle life, they have broad application prospects in the field of energy storage devices. The electrode sheet is the core part of the supercapacitor. The traditional electrode sheet includes a current collector and an active material layer. The active material is prepared into an active slurry, coated on the current collector, and dried. However, this method has low production efficiency.

[0003] In order to improve the production efficiency of electrode sheets, the industry has developed a dry process for producing electrode sheets, that is, the electrode material is prepared into a dry film sheet, a primer is set on the current collector, and then the current collector, primer and dry film are stacked and hot pressed to bond the three together to obtain an electrode sheet. In order to ensure the bonding strength and conductive performance, the main materials of the primer include adhesive and conductive agent.

[0004] Since the amount of the binder used in the primer layer is relatively high, the electrical conductivity and ion conductivity of the electrode sheet including the primer layer are lower than those of the conventional electrode sheet. Summary of the invention

[0005] Based on this, it is necessary to provide a method for preparing an electrode sheet with higher electrical conductivity and ion conductivity.

[0006] In addition, it is also necessary to provide an electrode sheet prepared by the above-mentioned method for preparing the electrode sheet and an energy storage device including the electrode sheet.

[0007] A method for preparing an electrode sheet comprises the following steps:

[0008] A conductive agent, a binder, a flow aid, a wetting agent, a pore-forming agent, a dispersant and a solvent are mixed to obtain a mixed slurry, and polystyrene-b-polyethylene glycol and an aqueous antioxidant are added to the mixed slurry, and mixed evenly to obtain a primer slurry, wherein the mass percentage of the polystyrene-b-polyethylene glycol in the primer slurry is 5% to 15%, and the mass percentage of the aqueous antioxidant in the primer slurry is 0.1% to 0.5%;

[0009] The primer slurry is evenly dispersed on the current collector, and dried so that the primer slurry forms a primer layer to obtain a first semi-finished product;

[0010] Performing steam annealing treatment on the first semi-finished product so that the polystyrene-b-polyethylene glycol in the primer layer self-assembles to form pores, and then performing heat treatment on the first semi-finished product so that the pore-forming agent decomposes to obtain a second semi-finished product;

[0011] The dry film sheet is stacked on the second semi-finished product so that the current collector, the primer layer and the dry film sheet are stacked in sequence, and then thermally compounded to fix the current collector, the primer layer and the dry film sheet together to obtain the required electrode sheet, wherein the material of the dry film sheet is the electrode material.

[0012] In one embodiment, the pore-forming agent is selected from at least one of sodium bicarbonate, urea hydrogen peroxide and hydrazine p-toluenesulfonate, and the particle size of the pore-forming agent is 10 nm to 50 μm.

[0013] In one embodiment, in the primer slurry, the mass ratio of the conductive agent, the binder, the flow aid, the wetting agent, the pore former, the dispersant, the solvent and the polystyrene-b-polyethylene glycol is 10-20:5-10:0.5-1:0.5-1:3-7:1-5:70-80:1-5.

[0014] In one embodiment, the conductive agent is selected from at least one of conductive carbon black, conductive graphite, carbon nanotubes, carbon fibers, acetylene black and Ketjen black, and the particle size of the conductive agent is 30 nm to 20 μm;

[0015] The adhesive is a hot melt adhesive, the hot melt adhesive is selected from at least one of EVA, TPU, and HDPE, and the particle size of the hot melt adhesive is 70 μm to 300 μm;

[0016] The glidant is selected from at least one of silicon dioxide, fumed silicon dioxide and talc, and the particle size of the glidant is 10 nm to 10 μm;

[0017] The wetting agent is selected from at least one of polyethylene glycol wetting agents, polyoxyethylene alkyl ether wetting agents, alkyl phosphate wetting agents and silicone wetting agents, and the particle size of the wetting agent is 5nm to 0.2μm;

[0018] The dispersant is a block copolymer, the block copolymer is selected from at least one of Pluronic F127, polyethylene glycol, polyacrylic acid, polyvinyl pyrrolidone and styrene-acrylate copolymer, and the particle size of the dispersant is 10nm to 20μm;

[0019] The solvent is selected from at least one of ethanol, water and dimethyl sulfoxide.

[0020] In one embodiment, the operation of mixing the conductive agent, the binder, the flow aid, the wetting agent, the pore-forming agent, the dispersant and the solvent to obtain the mixed slurry is as follows: the conductive agent, the binder, the flow aid, the wetting agent and the pore-forming agent are ball-milled to obtain a mixed dry powder, the mixed dry powder is added to a solution containing a dispersant and a solvent, and the mixed slurry is obtained after high-speed shear mixing, wherein the ball milling speed is 30rpm to 100rpm, the ball milling time is 15min to 60min, the high-speed shearing speed is 1200rpm to 3000rpm, and the high-speed shearing time is 20min to 45min;

[0021] The aqueous antioxidant is selected from at least one of gallic acid, ascorbic acid, sodium hypophosphite and EDTA.

[0022] In one embodiment, the first semi-finished product is subjected to steam annealing treatment so that the polystyrene-b-polyethylene glycol in the primer layer self-assembles to form pores, and the steam annealing treatment is selected from at least one of oxygen, acetone, and dichloromethane.

[0023] In one embodiment, the steam annealing treatment is performed for 0.5 h to 2 h, and the steam annealing treatment is performed at a temperature of 120° C. to 150° C.

[0024] Then, the first semi-finished product is subjected to heat treatment to decompose the pore-forming agent, wherein the heat treatment is performed under vacuum or protective gas atmosphere, the heat treatment time is 0.5 h to 2 h, and the heat treatment temperature is 120° C. to 150° C.;

[0025] In the operation of laminating the dry film sheet on the second semi-finished product so that the current collector, the primer layer and the dry film sheet are laminated in sequence, and then thermally compounding the current collector, the primer layer and the dry film sheet to fix them together to obtain the required electrode sheet, the temperature of the thermal compounding is 160° C. to 200° C., the time of the thermal compounding is 10s to 30s, and the pressure of the thermal compounding is 1t to 10t.

[0026] An electrode sheet is prepared by the above-mentioned method for preparing the electrode sheet.

[0027] An energy storage device comprises the above-mentioned electrode sheet.

[0028] In one embodiment, the energy storage device is a secondary battery or a supercapacitor.

[0029] The preparation method of the electrode sheet of the present invention comprises the following steps: adding a pore former and a block copolymer polystyrene-b-polyethylene glycol (PS-b-PEO) when preparing a base coating layer, self-assembling the block copolymer PS-b-PEO through a steam annealing technique, thereby forming uniform nanoscale pores, and then decomposing the pore former through a heat treatment to achieve pore formation by the pore former. The pore formation by the pore former and the pore formation by the block copolymer PS-b-PEO form a network-like pore structure, thereby increasing the specific surface area of ​​the base coating layer, thereby increasing the electrochemical activity, energy density and power density of the prepared electrode sheet.

[0030] Compared with the electrode sheet using the traditional primer layer, the primer layer of the electrode sheet prepared by the preparation method of the electrode sheet of the present invention has a network pore structure, thereby providing more channels for electrolyte ions, reducing the ion diffusion path, and thus improving the conductivity and ion conductivity of the electrode sheet. In combination with the specific embodiment, the conductivity and ion conductivity of the electrode sheet prepared by the preparation method of the electrode sheet of the present invention are significantly higher than those of the electrode sheet using the traditional primer layer.

[0031] The network-like pore structure of the bottom coating layer of the electrode sheet prepared by the preparation method of the electrode sheet of the present invention also helps to buffer the volume change of the electrode material during the charge and discharge process, reduce mechanical stress, and improve the cycle stability and life of the electrode sheet.

[0032] The network-like pore structure of the bottom coating layer of the electrode sheet prepared by the preparation method of the electrode sheet of the present invention also helps the electrolyte to better penetrate into the interior of the electrode material, thereby improving the utilization rate of the electrode material and the overall battery performance.

[0033] The preparation method of the electrode sheet of the present invention can realize a nanometer-level microporous structure and directional uniform pore formation through steam annealing technology, and combine pore formation with a pore-forming agent to form a uniform network pore structure between the current collector and the dry film sheet, thereby significantly improving the electrochemical performance of the electrode sheet.

[0034] In the present invention, hot melt adhesive is used as a binder, combined with the application of a pore-forming agent, and the production process is simplified by optimizing the dry process and the wet process, thereby improving the production efficiency and material utilization rate.

[0035] In the present invention, an aqueous antioxidant is introduced during the preparation of the primer slurry to enhance the antioxidant performance of the primer layer having a network-like pore structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0037] in:

[0038] Figure 1 The present invention is a flow chart of a method for preparing an electrode sheet according to one embodiment.

[0039] Figure 2 This is a CV graph of a test battery using the electrode sheet prepared in Example 1 obtained in the test example.

[0040] Figure 3 This is a CV graph of a test battery using the electrode sheet prepared in Example 2 obtained in the test example.

[0041] Figure 4 This is a CV graph of a test battery using the electrode sheet prepared in Example 3 obtained in the test example.

[0042] Figure 5 This is a CV graph of a test battery obtained by using the electrode sheet prepared in Comparative Example 1.

[0043] Figure 6 This is a CV graph of a test battery obtained by using the electrode sheet prepared in Comparative Example 2.

[0044] Figure 7 The EIS spectra of the test battery obtained by the test example are obtained by using the electrode sheets prepared by Examples 1 to 3 and Comparative Examples 1 to 2.

[0045] Figure 8 This is a partial enlarged view of the EIS spectrum of the test battery obtained by using the electrode sheets prepared in Examples 1 to 3. DETAILED DESCRIPTION

[0046] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0047] Combination Figure 1 The present invention discloses a method for preparing an electrode sheet according to an embodiment of the present invention, comprising the following steps:

[0048] S10, mixing a conductive agent, a binder, a flow aid, a wetting agent, a pore-forming agent, a dispersant and a solvent to obtain a mixed slurry, adding polystyrene-b-polyethylene glycol and an aqueous antioxidant to the mixed slurry, and mixing them evenly to obtain a primer slurry.

[0049] The mass percentage of polystyrene-b-polyethylene glycol (PS-b-PEO) in the primer slurry is 5% to 15%, and the mass percentage of the aqueous antioxidant in the primer slurry is 0.1% to 0.5%.

[0050] The conductive agent, the binder, the flow aid, the wetting agent, the pore former, the dispersant and the solvent are mixed to obtain a mixed slurry, and then the polystyrene-b-polyethylene glycol and the aqueous antioxidant are added to the mixed slurry. The uniformity of the mixing can be improved by mixing in steps.

[0051] Specifically, in this embodiment, the aqueous antioxidant is selected from at least one of gallic acid, ascorbic acid, sodium hypophosphite and EDTA.

[0052] Specifically, in this embodiment, the pore-forming agent is selected from at least one of sodium bicarbonate, urea hydrogen peroxide and hydrazine p-toluenesulfonate, and the particle size of the pore-forming agent is 10 nm to 50 μm.

[0053] Preferably, in the primer slurry prepared in S10, the mass ratio of the conductive agent, the binder, the flow aid, the wetting agent, the pore former, the dispersant, the solvent and the polystyrene-b-polyethylene glycol is 10-20:5-10:0.5-1:0.5-1:3-7:1-5:70-80:1:5.

[0054] Specifically, in the present embodiment, the conductive agent is selected from at least one of conductive carbon black, conductive graphite, carbon nanotubes, carbon fibers, acetylene black and Ketjen black, and the particle size of the conductive agent is 30 nm to 20 μm.

[0055] Particularly preferably, in this embodiment, the conductive agent is selected from at least two of conductive carbon black, conductive graphite, carbon nanotubes, carbon fibers, acetylene black and Ketjen black.

[0056] Specifically, in this embodiment, the adhesive is a hot melt adhesive, the hot melt adhesive is selected from at least one of EVA, TPU, and HDPE, and the particle size of the hot melt adhesive is 70 μm to 300 μm.

[0057] Specifically, in this embodiment, the glidant is selected from at least one of silicon dioxide, fumed silica and talc, and the particle size of the glidant is 10 nm to 10 μm.

[0058] Preferably, in this embodiment, the wetting agent is selected from at least one of polyethylene glycol wetting agents, polyoxyethylene alkyl ether wetting agents, alkyl phosphate wetting agents and silicone wetting agents, and the particle size of the wetting agent is 5 nm to 0.2 μm.

[0059] Specifically, the wetting agent may be polyoxyethylene alkyl ether or polyethylene glycol (PEG).

[0060] Specifically, in this embodiment, the dispersant can be a block copolymer, the block copolymer is selected from at least one of Pluronic F127, polyethylene glycol (PEG), polyacrylic acid (PAA), polyvinyl pyrrolidone (PVP) and styrene-acrylate copolymer (SAA), and the particle size of the dispersant is 10nm to 20μm.

[0061] Specifically, in this embodiment, the solvent is selected from at least one of ethanol, water and dimethyl sulfoxide.

[0062] Particularly preferably, the solvent may be ethanol and water in a volume ratio of 1:1.

[0063] Specifically, in this embodiment, the conductive agent, binder, flow aid, wetting agent, pore-forming agent, dispersant and solvent are mixed to obtain a mixed slurry by ball-milling to obtain a mixed dry powder, adding the mixed dry powder to a solution containing a dispersant and a solvent, and obtaining a mixed slurry after high-speed shear mixing, wherein the ball milling speed is 30rpm~100rpm, the ball milling time is 15min~60min, the high-speed shearing speed is 1200rpm~3000rpm, and the high-speed shearing time is 20min~45min.

[0064] Among them, ball milling can be performed by a ball mill, and high-speed shearing can be performed by a high-shear mixing device.

[0065] The conductive agent, binder, flow aid, wetting agent and pore former are ball-milled and mixed to obtain a mixed dry powder, which is then added to a solution containing a dispersant and a solvent, and mixed at high speed to obtain a mixed slurry. The uniformity of the mixing can be improved by mixing in steps.

[0066] S20, uniformly dispersing the primer slurry on the current collector, and drying the primer slurry to form a primer layer, thereby obtaining a first semi-finished product.

[0067] The operation of uniformly dispersing the primer slurry onto the current collector can be accomplished by a coating device, for example, a micro-concave coater can be used.

[0068] Preferably, in this embodiment, the thickness of the primer layer is 1 μm to 5 μm.

[0069] Specifically, in this embodiment, the current collector can be aluminum foil, copper foil, etched foil or nickel foil.

[0070] Specifically, in this embodiment, the drying process to form the primer layer from the primer slurry may be: treating at 60° C. to 70° C. for 5 min to 30 min.

[0071] S30, steam annealing the first semi-finished product so that the polystyrene-b-polyethylene glycol in the primer layer self-assembles to form pores, and then heat-treating the first semi-finished product so that the pore-forming agent decomposes to obtain a second semi-finished product.

[0072] Through steam annealing technology, the block copolymer PS-b-PEO can be self-assembled to form uniform nano-scale pores.

[0073] Preferably, in this embodiment, the first semi-finished product is subjected to steam annealing treatment so that the polystyrene-b-polyethylene glycol in the primer layer self-assembles to form pores, and the steam annealing treatment is performed by at least one selected from oxygen, acetone, and dichloromethane.

[0074] Specifically, in this embodiment, the steam annealing treatment time is 0.5 h to 2 h, and the steam annealing treatment temperature is 120° C. to 150° C.

[0075] Specifically, in this embodiment, the heat treatment is performed in a vacuum or protective gas atmosphere, the heat treatment time is 0.5 h to 2 h, and the heat treatment temperature is 120° C. to 150° C.

[0076] S40, stacking the dry film sheet on the second semi-finished product so that the current collector, the primer layer and the dry film sheet are stacked in sequence, and then thermally compounding the current collector, the primer layer and the dry film sheet to fix them together to obtain the required electrode sheet.

[0077] The material of the dry film is the electrode material.

[0078] Dry film sheets can be purchased directly or prepared by yourself.

[0079] In this embodiment, the dry film can be purchased from Guangdong Qingyan Electronics Co., Ltd., with a thickness of 100 μm to 140 μm, and its materials are activated carbon, conductive agent SP, binder PTFE and pore-forming agent anhydrous citric acid in a mass ratio of 80:10:8:2.

[0080] Specifically, in the present embodiment, the temperature of the thermal bonding is 160° C. to 200° C., the time of the thermal bonding is 10 s to 30 s, and the pressure of the thermal bonding is 1 t to 10 t.

[0081] The preparation method of the electrode sheet of the present invention comprises the following steps: adding a pore former and a block copolymer polystyrene-b-polyethylene glycol (PS-b-PEO) when preparing a base coating layer, self-assembling the block copolymer PS-b-PEO through a steam annealing technique, thereby forming uniform nanoscale pores, and then decomposing the pore former through a heat treatment to achieve pore formation by the pore former. The pore formation by the pore former and the pore formation by the block copolymer PS-b-PEO form a network-like pore structure, thereby increasing the specific surface area of ​​the base coating layer, thereby increasing the electrochemical activity, energy density and power density of the prepared electrode sheet.

[0082] Compared with the electrode sheet using the traditional primer layer, the primer layer of the electrode sheet prepared by the preparation method of the electrode sheet of the present invention has a network pore structure, thereby providing more channels for electrolyte ions, reducing the ion diffusion path, and thus improving the conductivity and ion conductivity of the electrode sheet. In combination with the specific embodiment, the conductivity and ion conductivity of the electrode sheet prepared by the preparation method of the electrode sheet of the present invention are significantly higher than those of the electrode sheet using the traditional primer layer.

[0083] The network-like pore structure of the bottom coating layer of the electrode sheet prepared by the preparation method of the electrode sheet of the present invention also helps to buffer the volume change of the electrode material during the charge and discharge process, reduce mechanical stress, and improve the cycle stability and life of the electrode sheet.

[0084] The network-like pore structure of the bottom coating layer of the electrode sheet prepared by the preparation method of the electrode sheet of the present invention also helps the electrolyte to better penetrate into the interior of the electrode material, thereby improving the utilization rate of the electrode material and the overall battery performance.

[0085] The preparation method of the electrode sheet of the present invention can realize a nanometer-level microporous structure and directional uniform pore formation through steam annealing technology, and combine pore formation with a pore-forming agent to form a uniform network pore structure between the current collector and the dry film sheet, thereby significantly improving the electrochemical performance of the electrode sheet.

[0086] In the present invention, hot melt adhesive is used as a binder, combined with the application of a pore-forming agent, and the production process is simplified by optimizing the dry process and the wet process, thereby improving the production efficiency and material utilization rate.

[0087] In the present invention, an aqueous antioxidant is introduced during the preparation of the primer slurry to enhance the antioxidant performance of the primer layer having a network-like pore structure.

[0088] The present invention also discloses an embodiment of an electrode sheet prepared by the above-mentioned method for preparing the electrode sheet.

[0089] The electrode sheet prepared by the method for preparing the electrode sheet of the present invention can be applied to various fields, for example, in the field of energy storage.

[0090] The present invention also discloses an energy storage device according to an embodiment, comprising the electrode sheet mentioned above.

[0091] Specifically, the energy storage device may be a secondary battery or a supercapacitor.

[0092] When the electrode sheet prepared by the method for preparing the electrode sheet of the present invention is applied to a supercapacitor, the overall performance of the supercapacitor can be improved.

[0093] The following are specific embodiments.

[0094] In a specific embodiment, the dry active membrane is purchased from Guangdong Qingyan Electronics Co., Ltd., has a thickness of 120 μm, and its materials are activated carbon, conductive agent SP, binder PTFE and pore-forming agent anhydrous citric acid in a mass ratio of 80:10:8:2.

[0095] Example 1

[0096] Carbon black powder (Termical, SUPER P Li, 40nm) and carbon nanotubes (Jiangsu Tiannai, FT700) were mixed in a mass ratio of 8:2 as a conductive agent. Conductive agent, binder EVA (Wenzhou Huate, HT-9260), flow agent fumed silica (Cabot, M5), wetting agent PEG (Dow Chemical, CARBOWAX TM 200) and pore-forming agent sodium bicarbonate (Henan Zhongyuan Chemical), and then placed in a ball mill and mixed at a speed of 50rpm for 30min. Add solvent deionized water and dispersant polyacrylic acid (Aksu 602N) to the ball-milled mixture, and use a high shear mixer to mix at a speed of 2000rpm for 30min to obtain a mixed slurry. Add polystyrene-b-polyethylene glycol (Xi'an Qiyue Biological, Q series) and aqueous antioxidant ascorbic acid to the mixed slurry to obtain a primer slurry. Among them, the mass ratio of the conductive agent, binder, flow aid, wetting agent, pore-forming agent, dispersant, solvent, polystyrene-b-polyethylene glycol and aqueous antioxidant is 15:8:0.8:0.8:5:3:75:3:0.3.

[0097] The primer slurry was evenly coated on an aluminum foil with a thickness of 20 μm (Japan JCC, 20CB) using a gravure printing device, and the coating thickness was 2 μm to obtain a first semi-finished double-sided coated aluminum foil. The coated aluminum foil was treated at 130° C. for 1 h in a saturated atmosphere of dichloromethane to allow the block copolymer PS-b-PEO to self-assemble to form pores, and then the first semi-finished product was placed at 130° C. for 1 h to allow the pore-forming agent to decompose and form pores, and the second semi-finished double-sided coated aluminum foil was obtained after heat treatment.

[0098] The dry active membrane was placed on both sides of the second semi-finished double-sided coated aluminum foil, and put into a thermal composite machine for rolling so that the membrane and the current collector were tightly and evenly bonded together to prepare an electrode sheet. The thermal composite temperature was 180°C, the thermal composite pressure was 5.5t, and the thermal composite time was 15s.

[0099] Example 2

[0100] Carbon black powder (Termical, SUPER P Li, 40nm) and carbon nanotubes (Jiangsu Tiannai, FT700) were mixed in a mass ratio of 8:2 as a conductive agent. Conductive agent, binder EVA (Wenzhou Huate, HT-9260), flow agent fumed silica (Cabot, M5), wetting agent PEG (Dow Chemical, CARBOWAX TM 200) and pore-forming agent sodium bicarbonate (Henan Zhongyuan Chemical), and then placed in a ball mill and mixed at a speed of 100rpm for 15min. Add solvent deionized water and dispersant polyacrylic acid (Aksu 602N) to the ball-milled mixture, and use a high shear mixer to mix at a speed of 3000rpm for 20min to obtain a mixed slurry. Add polystyrene-b-polyethylene glycol (Xi'an Qiyue Biological, Q series) and aqueous antioxidant ascorbic acid to the mixed slurry to obtain a primer slurry. Among them, the mass ratio of the conductive agent, binder, flow aid, wetting agent, pore-forming agent, dispersant, solvent, polystyrene-b-polyethylene glycol and aqueous antioxidant is 20:5:1:0.5:7:1:80:1:0.1.

[0101] The primer slurry was uniformly coated on an aluminum foil with a thickness of 20 μm (Japan JCC, 20CB) using a gravure printing device, and the coating thickness was 5 μm to obtain a first semi-finished double-sided coated aluminum foil. The coated aluminum foil was treated at 120° C. for 2 h in a saturated atmosphere of dichloromethane to allow the block copolymer PS-b-PEO to self-assemble to form pores, and then the first semi-finished product was placed at 150° C. for a heat treatment of 0.5 h to decompose the pore-forming agent to form pores, and the second semi-finished double-sided coated aluminum foil was obtained after the heat treatment.

[0102] The dry active membrane is placed on both sides of the second semi-finished double-sided coated aluminum foil, and is placed in a thermal composite machine for rolling so that the membrane and the current collector are tightly and evenly bonded together to prepare an electrode sheet. The thermal composite temperature is 200°C, the thermal composite pressure is 1t, and the thermal composite time is 30s.

[0103] Example 3

[0104] Carbon black powder (Termical, SUPER P Li, 40nm) and carbon nanotubes (Jiangsu Tiannai, FT700) were mixed in a mass ratio of 8:2 as a conductive agent. Conductive agent, binder EVA (Wenzhou Huate, HT-9260), flow agent fumed silica (Cabot, M5), wetting agent PEG (Dow Chemical, CARBOWAX TM 200) and pore-forming agent sodium bicarbonate (Henan Zhongyuan Chemical), and then placed in a ball mill and mixed at a speed of 30rpm for 60min. Add solvent deionized water and dispersant polyacrylic acid (Aksu 602N) to the ball-milled mixture, and use a high shear mixer to mix at a speed of 1200rpm for 45min to obtain a mixed slurry. Add polystyrene-b-polyethylene glycol (Xi'an Qiyue Biological, Q series) and aqueous antioxidant ascorbic acid to the mixed slurry to obtain a primer slurry. Among them, the mass ratio of the conductive agent, binder, flow aid, wetting agent, pore-forming agent, dispersant, solvent, polystyrene-b-polyethylene glycol and aqueous antioxidant is 10:10:0.5:1:3:5:70:5:0.5.

[0105] The primer slurry was evenly coated on an aluminum foil with a thickness of 20 μm (Japan JCC, 20CB) using a gravure printing device, and the coating thickness was 2 μm to obtain a first semi-finished double-sided coated aluminum foil. The coated aluminum foil was treated at 150° C. in a saturated atmosphere of dichloromethane for 0.5 h, so that the block copolymer PS-b-PEO self-assembled to form pores, and then the first semi-finished product was placed at 120° C. for 2 h to decompose the pore-forming agent to form pores, and the second semi-finished double-sided coated aluminum foil was obtained after heat treatment.

[0106] The dry active membrane is placed on both sides of the second semi-finished double-sided coated aluminum foil, and is put into a thermal composite machine for rolling so that the membrane and the current collector are tightly and evenly bonded together to prepare an electrode sheet. The thermal composite temperature is 160°C, the thermal composite pressure is 10t, and the thermal composite time is 10s.

[0107] Comparative Example 1

[0108] Comparative Example 1 is substantially the same as Example 1, except that: in Comparative Example 1, pore-forming agents sodium bicarbonate and polystyrene-b-polyethylene glycol are not added.

[0109] Comparative Example 1 is as follows:

[0110] Carbon black powder (Termical, SUPER P Li, 40 nm) and carbon nanotubes (Jiangsu Tiannai, FT700) were mixed in a mass ratio of 8:2 as a conductive agent. Conductive agent, binder EVA (Wenzhou Huate, HT-9260), flow agent fumed silica (Cabot, M5) and wetting agent PEG (Dow Chemical, CARBOWAX TM 200), and then placed in a ball mill and mixed at a speed of 50rpm for 30min. Add solvent deionized water and dispersant polyacrylic acid (Aksu 602N) to the ball-milled mixture, and use a high shear mixer to mix at a speed of 2000rpm for 30min to obtain a mixed slurry. Add an aqueous antioxidant ascorbic acid to the mixed slurry to obtain a primer slurry. Among them, the mass ratio of the conductive agent, binder, flow aid, wetting agent, dispersant, solvent and aqueous antioxidant is 15:8:0.8:0.8:3:75:0.3.

[0111] The primer slurry was evenly coated on an aluminum foil with a thickness of 20 μm (Japan JCC, 20CB) using a gravure printing device, and the coating thickness was 2 μm to obtain a first semi-finished double-sided coated aluminum foil. The first semi-finished product was heat treated at 130° C. for 1 h to obtain a second semi-finished double-sided coated aluminum foil.

[0112] The dry active membrane was placed on both sides of the second semi-finished double-sided coated aluminum foil, and put into a thermal composite machine for rolling so that the membrane and the current collector were tightly and evenly bonded together to prepare an electrode sheet. The thermal composite temperature was 180°C, the thermal composite pressure was 5.5t, and the thermal composite time was 15s.

[0113] Comparative Example 2

[0114] Comparative Example 2 is substantially the same as Example 1, except that the pore-forming agent sodium bicarbonate is not added in Comparative Example 2.

[0115] Carbon black powder (Termical, SUPER P Li, 40nm) and carbon nanotubes (Jiangsu Tiannai, FT700) were mixed in a mass ratio of 8:2 as a conductive agent. Conductive agent, binder EVA (Wenzhou Huate, HT-9260), flow agent fumed silica (Cabot, M5), wetting agent PEG (Dow Chemical, CARBOWAX TM200) and pore-forming agent sodium bicarbonate (Henan Zhongyuan Chemical) were mixed and placed in a ball mill at a speed of 50rpm for 30min. Solvent deionized water and dispersant polyacrylic acid (Aksu 602N) were added to the ball-milled mixture, and mixed at a speed of 2000rpm for 30min using a high shear mixer to obtain a mixed slurry. A water-based antioxidant ascorbic acid was added to the mixed slurry to obtain a primer slurry. Among them, the mass ratio of the conductive agent, binder, flow aid, wetting agent, pore-forming agent, dispersant, solvent and water-based antioxidant is 15:8:0.8:0.8:5:3:75:0.3.

[0116] The primer slurry was evenly coated on an aluminum foil with a thickness of 20 μm (Japan JCC, 20CB) using a gravure printing device, and the coating thickness was 2 μm to obtain a first semi-finished double-sided coated aluminum foil. The first semi-finished product was heat treated at 130° C. for 1 h to decompose the pore-forming agent to form pores, and a second semi-finished double-sided coated aluminum foil was obtained after heat treatment.

[0117] The dry active membrane was placed on both sides of the second semi-finished double-sided coated aluminum foil, and put into a thermal composite machine for rolling so that the membrane and the current collector were tightly and evenly bonded together to prepare an electrode sheet. The thermal composite temperature was 180°C, the thermal composite pressure was 5.5t, and the thermal composite time was 15s.

[0118] Test Case

[0119] 1) Conductivity test

[0120] The resistivity of the electrode sheet was measured using a four-probe test method to calculate its conductivity. The specific steps are as follows: the electrode sheets prepared in Examples 1 to 3 and Comparative Examples 1 to 2 were cut into small discs with a diameter of 14 mm, and then the following tests were performed: randomly selected points were used to measure the electrode sheet resistance using a resistance tester. The test results are shown in Table 1 below.

[0121] 2. Mechanical properties test

[0122] Test the peel strength of the electrode. The specific steps are as follows: Cut the electrode sheets prepared in Examples 1 to 3 and Comparative Examples 1 to 2 into 25mm*200mm strips, and use 3M double-sided tape to stick the 25mm*100mm electrode sheets to a smooth stainless steel plate. Use a tensile testing machine to clamp the stainless steel plate end at one end and the non-stick end of the sample at the other end. Stretch at a constant speed, record the 180° peel strength force, calculate the peel strength index, and test

[0123] The results are shown in Table 1 below.

[0124] Table 1: Test results of conductivity and mechanical properties of electrode sheets

[0125] factor <![CDATA[Pole piece resistance (mΩ / mm 2 )]]> Peel strength (N / cm) Example 1 0.039 0.798 Example 2 0.041 0.785 Example 3 0.045 0.755 Comparative Example 1 0.054 0.608 Comparative Example 2 0.057 0.602

[0126] 3. Electrochemical performance test

[0127] The electrochemical performance of the electrode was tested by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The specific steps are as follows:

[0128] 1) The electrode sheets prepared in Examples 1 to 3 and Comparative Examples 1 to 2 were cut into small discs with a diameter of 14 mm, vacuum dried for 12 h, and assembled into symmetrical test cells in a glove box. The electrolyte used was Xinzhoubang DLC301. 2) CV test was performed using a PARSTAT2273 electrochemical workstation with a voltage range of -1.75 V to 1.75 V and a scan rate of 1 mV / s. Figure 2 to Figure 6 3) Use PARSTAT 2273 electrochemical workstation to perform EIS test in the test range of 10mHz to 100kHz, and obtain Figure 7 and Figure 8 .

[0129] Combination Figure 2 to Figure 6 , it can be seen that under the same scan rate and electrolyte conditions, Figure 2 to Figure 4 The peak current of the curve is significantly higher than Figure 5-6 , with a greater current response. The area under the curve reflects the amount of charge passing through, Figure 2 to Figure 4 Compare Figure 5-6 Having a larger area means that the electrode sheets prepared in Examples 1 to 3 have better electrochemical performance. Therefore, the electrode sheets prepared in Examples 1 to 3 have stronger conductivity, ions migrate more smoothly in the electrode, and the charge transfer impedance is reduced.

[0130] Combination Figure 7 and Figure 8 It can be seen that the AC impedance of the test battery using the electrode sheets prepared in Examples 1 to 3 at 1 kHz is smaller than that of Comparative Examples 1 to 2. This proves again that the present invention is effective in reducing the electrode sheet resistance.

[0131] 4. Thermal stability test

[0132] Test the stability of the electrode sheet in a high temperature environment. The specific steps are as follows: 1) Place the sample in a high temperature oven, set the temperature to 130°C, and the time is 1 hour. 2) Take out the sample, observe the changes in appearance, and test its resistance changes.

[0133] Table 2: Conductivity of the electrode sheet after 1h at 130℃

[0134] factor Appearance <![CDATA[Pole piece resistance (mΩ / mm 2 )]]> Example 1 No change 0.061 Example 2 No change 0.073 Example 3 No change 0.086 Comparative Example 1 No change 0.132 Comparative Example 2 No change 0.215

[0135] Combined with Table 2, it can be seen that the thermal stability of the electrode sheets prepared in Examples 1 to 3 is significantly higher than that of the electrode sheets prepared in Comparative Examples 1 to 2, and the conductivity of the electrode sheets prepared in Examples 1 to 3 after heat treatment is significantly higher than that of the electrode sheets prepared in Comparative Examples 1 to 2.

[0136] Through the above implementation methods and testing methods, the performance of the prepared electrode can be comprehensively evaluated and its application potential in capacitors and lithium batteries can be verified.

[0137] In the description of the embodiments of the present invention, it should be noted that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limitations on the embodiments of the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0138] In the description of the embodiments of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "connected" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of the present invention can be understood according to specific circumstances.

[0139] In the embodiments of the present invention, unless otherwise clearly specified and limited, the first feature being "above" or "below" the second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature being "above", "above" and "above" the second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. The first feature being "below", "below" and "below" the second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0140] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the embodiment of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0141] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing an electrode sheet, characterized in that: The steps include: A conductive agent, a binder, a flow aid, a wetting agent, a pore former, a dispersant and a solvent are mixed to obtain a mixed slurry, and polystyrene-b-polyethylene glycol and an aqueous antioxidant are added to the mixed slurry, and mixed evenly to obtain a primer slurry, wherein the mass percentage of the polystyrene-b-polyethylene glycol in the primer slurry is 1% to 5%, the mass percentage of the aqueous antioxidant in the primer slurry is 0.1% to 0.5%, and the particle size of the pore former is 10 nm to 50 μm; The primer slurry is evenly dispersed on the current collector, and dried so that the primer slurry forms a primer layer to obtain a first semi-finished product; Performing steam annealing treatment on the first semi-finished product so that the polystyrene-b-polyethylene glycol in the primer layer self-assembles to form pores, and then performing heat treatment on the first semi-finished product so that the pore-forming agent decomposes to obtain a second semi-finished product; The dry film sheet is stacked on the second semi-finished product so that the current collector, the primer layer and the dry film sheet are stacked in sequence, and then thermally compounded to fix the current collector, the primer layer and the dry film sheet together to obtain the required electrode sheet, wherein the material of the dry film sheet is the electrode material, and a pore former and a block copolymer polystyrene-b-polyethylene glycol are added when preparing the primer layer. The block copolymer polystyrene-b-polyethylene glycol is self-assembled through steam annealing technology to form uniform nanoscale pores, and then the pore former is decomposed through heat treatment to achieve pore formation of the pore former, and the pore formation of the pore former and the pore formation of the block copolymer polystyrene-b-polyethylene glycol form a network pore structure.

2. The method for preparing an electrode sheet according to claim 1, characterized in that: The pore-forming agent is selected from at least one of sodium bicarbonate, hydrogen peroxide, urea and hydrazine p-toluenesulfonate.

3. The method for preparing an electrode sheet according to claim 1, characterized in that: In the primer slurry, the mass ratio of the conductive agent, the binder, the flow aid, the wetting agent, the pore former, the dispersant, the solvent and the polystyrene-b-polyethylene glycol is 10-20:5-10:0.5-1:0.5-1:3-7:1-5:70-80:1-5.

4. The method for preparing an electrode sheet according to claim 2, characterized in that: The conductive agent is selected from at least one of conductive carbon black, conductive graphite, carbon nanotubes, carbon fibers, acetylene black and Ketjen black, and the particle size of the conductive agent is 30 nm to 20 μm; The adhesive is a hot melt adhesive, the hot melt adhesive is selected from at least one of EVA, TPU and HDPE, and the particle size of the hot melt adhesive is 70 μm to 300 μm; The glidant is selected from at least one of silicon dioxide and talc, and the particle size of the glidant is 10 nm to 10 μm; The wetting agent is selected from at least one of polyethylene glycol wetting agents, polyoxyethylene alkyl ether wetting agents, alkyl phosphate wetting agents and silicone wetting agents, and the particle size of the wetting agent is 5nm~0.2μm; The dispersant is a block copolymer, the block copolymer is selected from at least one of Pluronic F127, polyethylene glycol, polyacrylic acid, polyvinyl pyrrolidone and styrene-acrylate copolymer, and the particle size of the dispersant is 10nm~20μm; The solvent is selected from at least one of ethanol, water and dimethyl sulfoxide.

5. The method for preparing an electrode sheet according to claim 2, characterized in that: The operation of mixing the conductive agent, the binder, the flow aid, the wetting agent, the pore-forming agent, the dispersant and the solvent to obtain the mixed slurry is as follows: the conductive agent, the binder, the flow aid, the wetting agent and the pore-forming agent are ball-milled to obtain a mixed dry powder, the mixed dry powder is added to a solution containing a dispersant and a solvent, and the mixed slurry is obtained after high-speed shear mixing, wherein the rotation speed of the ball mill is 30 rpm to 100 rpm, the time of the ball mill is 15 min to 60 min, the rotation speed of the high-speed shear is 1200 rpm to 3000 rpm, and the time of the high-speed shear is 20 min to 45 min; The aqueous antioxidant is selected from at least one of gallic acid, ascorbic acid, sodium hypophosphite and EDTA.

6. The method for preparing an electrode sheet according to any one of claims 1 to 5, characterized in that: The first semi-finished product is subjected to steam annealing treatment so that the polystyrene-b-polyethylene glycol in the primer layer self-assembles to form pores, and the steam annealing treatment is performed with at least one selected from oxygen, acetone, and dichloromethane.

7. The method for preparing an electrode sheet according to claim 6, characterized in that: The steam annealing treatment time is 0.5h~2h, and the steam annealing treatment temperature is 120℃~150℃; Then, the first semi-finished product is subjected to heat treatment to decompose the pore-forming agent, wherein the heat treatment is performed under vacuum or protective gas atmosphere, the heat treatment time is 0.5 h to 2 h, and the heat treatment temperature is 120° C. to 150° C.; In the operation of laminating the dry film sheet on the second semi-finished product so that the current collector, the primer layer and the dry film sheet are laminated in sequence, and then thermally compounding the current collector, the primer layer and the dry film sheet to fix them together to obtain the required electrode sheet, the temperature of the thermal compounding is 160° C. to 200° C., the time of the thermal compounding is 10s to 30s, and the pressure of the thermal compounding is 1t to 10t.

8. An electrode sheet, characterized in that: The electrode sheet is prepared by the method for preparing the electrode sheet according to any one of claims 1 to 7.

9. An energy storage device, characterized in that: Comprising the electrode sheet as claimed in claim 8.

10. The energy storage device according to claim 9, characterized in that: The energy storage device is a secondary battery or a supercapacitor.

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