Electrode plate manufacturing method, electrode plate and energy storage device

Abstract

The invention relates to an electrode plate manufacturing method, an electrode plate and an energy storage device. The method comprises the following steps: obtaining a first binder emulsion; the first binder emulsion is a non-fibrillated binder emulsion; carrying out spray drying on the first binder emulsion to obtain binder micro-powder, and enabling the binder micro-powder to coat the surface of the negative electrode active material in a turning state to obtain a negative electrode active material of which the surface is coated with a binder dry coating; mixing the negative electrode active material coated with the binder dry coating on the surface with an electrode matrix material to obtain an electrode mixture; calendering the electrode mixture to obtain a negative electrode membrane; and carrying out thermal compounding on the negative electrode diaphragm and the current collector to obtain the electrode plate. The electrode plate manufactured by the electrode plate manufacturing method provided by the embodiment of the invention is subjected to battery assembly, so that a battery with relatively high battery capacity can be obtained.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrode sheet manufacturing, in particular to an electrode sheet manufacturing method, an electrode sheet and an energy storage device. BACKGROUND

[0002] From consumer electronics to electric vehicles to grid storage, demand for energy storage solutions is growing across industries, and as a result, demand for efficient, sustainable and cost-effective batteries is also rapidly increasing. In the field of electrode sheet manufacturing technology of batteries, due to the advantages of environmental protection and simplicity of dry electrode technology, it has become the main way of electrode sheet manufacturing.

[0003] In the process of manufacturing electrode sheets based on dry electrode technology, it is necessary to mix the binder and the battery active material to obtain an electrode mixture, and further to heat-composite the electrode mixture and the current collector to manufacture the electrode sheet. The commonly used binder at present is polytetrafluoroethylene (PTFE) which can form fibrils to produce adhesion and has various excellent material properties. However, due to the low energy level of the lowest unoccupied molecular orbital (LUMO) of PTFE, PTFE will show instability at the low potential of the negative electrode. Specifically, during the charging and discharging process of lithium batteries, PTFE will chemically react with lithium ions on the surface of the negative electrode to form lithium fluoride, which will weaken the adhesion effect of PTFE as a binder and affect the cycle performance of the battery assembled based on the manufactured electrode sheet. SUMMARY

[0004] Therefore, it is necessary to provide an electrode sheet manufacturing method, an electrode sheet and an energy storage device which can ensure that the battery assembled based on the manufactured electrode sheet has better cycle performance in view of the above technical problems.

[0005] In a first aspect, the present application provides an electrode sheet manufacturing method, comprising:

[0006] obtaining a first binder emulsion; the first binder emulsion is a non-fibrillated binder emulsion;

[0007] spray drying the first binder emulsion to obtain binder micro-powder, so that the binder micro-powder is coated on the surface of the negative electrode active material in the turbulent state to obtain the negative electrode active material coated with a binder dry coating layer on the surface;

[0008] mixing the negative electrode active material coated with the binder dry coating layer on the surface and the electrode matrix material to obtain an electrode mixture;

[0009] calendering the electrode mixture to obtain a negative electrode film;

[0010] The negative electrode film and the current collector are heat-combined to obtain an electrode sheet.

[0011] In an exemplary embodiment, the spray drying of the first binder emulsion to obtain the binder micropowder is performed such that the binder micropowder is coated on the surface of the negative electrode active material in the tumbling state to obtain the negative electrode active material coated with the dry coating layer of the binder, comprising:

[0012] The hot air at the preset drying temperature is fed into a mixing chamber of a coating machine in which the negative electrode active material is placed, so that the negative electrode active material is in the tumbling state under the action of the hot air;

[0013] The first binder emulsion in the form of mist droplets is sprayed into the mixing chamber by a spray gun of the coating machine at a preset feeding rate, so that the water in the first binder emulsion in the form of mist droplets is evaporated to obtain the binder micropowder, and then the binder micropowder is coated on the surface of the negative electrode active material in the tumbling state to obtain the negative electrode active material coated with the dry coating layer of the binder.

[0014] In an exemplary embodiment, the latex particle size in the first binder emulsion is 100 nm to 400 nm.

[0015] In an exemplary embodiment, the calendering of the electrode mixture to obtain the negative electrode film comprises:

[0016] The electrode mixture is calendered based on a preset calendering number and a preset calendering temperature to obtain the negative electrode film;

[0017] The negative electrode film and the current collector are heat-combined to obtain an electrode sheet, comprising:

[0018] The negative electrode film and the current collector are heat-combined based on a preset heat-combining temperature to obtain the electrode sheet;

[0019] The preset calendering number is 2 to 10, the preset calendering temperature is 50°C to 250°C, and the preset heat-combining temperature is 80°C to 250°C.

[0020] In an exemplary embodiment, the first binder emulsion comprises at least one of a polyvinylidene fluoride emulsion, a styrene-butadiene rubber emulsion, a polyacrylic emulsion, a terpolymer emulsion, a polyurethane emulsion, and a benzene and propylene emulsion.

[0021] In an exemplary embodiment, the preset drying temperature is 80°C to 150°C, and the preset feeding rate is 4 kg / h to 10 kg / h.

[0022] In an exemplary embodiment, the solid content of the first binder emulsion is 10% to 60%.

[0023] In one exemplary embodiment, the electrode matrix material includes the conductive agent and the second binder;

[0024] In the electrode mixture, the mass percentage of the binder fine powder is 1% to 5%, the mass percentage of the second binder is 0.5% to 5%, the mass percentage of the negative electrode active material is 80% to 98%, and the mass percentage of the conductive agent is 0.5% to 10%.

[0025] In one exemplary embodiment, the negative electrode active material with the surface coated with the dry coating layer of the binder is mixed with the electrode matrix material to obtain an electrode mixture, including:

[0026] The electrode mixture is obtained by mixing the negative electrode active material with the surface coated with the dry coating layer of the binder with the electrode matrix material for a preset time based on the stirring component;

[0027] The end speed of the stirring component is 2 m / s to 30 m / s, and the preset time is 5 min to 60 min.

[0028] In one exemplary embodiment, the negative electrode active material includes at least one of natural graphite, synthetic graphite, hard carbon, soft carbon, activated carbon, silicon, silicon oxide, silicon-carbon, tin, tin oxide, and lithium titanate.

[0029] In one exemplary embodiment, the conductive agent includes at least one of conductive carbon black, graphene, carbon nanotube, carbon fiber, acetylene black, and ketjen black.

[0030] In one exemplary embodiment, the current collector is at least one of an aluminum foil coated with a conductive carbon layer, a copper foil coated with a conductive carbon layer, a nickel foil coated with a conductive carbon layer, a stainless steel foil coated with a conductive carbon layer, a porous aluminum foil coated with a conductive carbon layer, a porous copper foil coated with a conductive carbon layer, a porous nickel foil coated with a conductive carbon layer, a porous stainless steel foil coated with a conductive carbon layer, and a corrosion aluminum foil coated with a conductive carbon layer.

[0031] In a second aspect, the present application further provides an electrode sheet, which is manufactured by the electrode sheet manufacturing method according to any one of the first aspect of the present application.

[0032] In a third aspect, the present application further provides an energy storage device, which includes the electrode sheet according to the second aspect of the present application.

[0033] The electrode sheet manufacturing method, the electrode sheet and the energy storage device provided by the above-mentioned embodiment, the first binder emulsion is obtained; the first binder emulsion is a non-fibrillated binder emulsion; the first binder emulsion is spray-dried to obtain binder micro-powder, so that the binder micro-powder is coated on the surface of the negative electrode active material in the tumbling state to obtain the negative electrode active material coated with the binder dry coating layer; the negative electrode active material coated with the binder dry coating layer is mixed with the electrode matrix material to obtain an electrode mixture; the electrode mixture is calendered to obtain a negative electrode film; and the negative electrode film is hot-composited with the current collector to obtain the electrode sheet. The electrode sheet manufacturing method provided by the above-mentioned embodiment is based on the use of the non-fibrillated first binder emulsion with high LUMO energy level, and the spray-drying method is used to make the binder micro-powder obtained after the water in the first binder emulsion is evaporated to be coated on the surface of the negative electrode active material. Therefore, in the electrode sheet obtained by using the electrode sheet manufacturing method provided by the above-mentioned embodiment, the binder dry coating layer coated on the surface of the negative electrode active material is not easy to react with lithium ions in the charging and discharging process of the battery. Therefore, on the one hand, the stability of the binder dry coating layer can be ensured to ensure that the negative electrode film and the current collector have high bonding force, and the electrode sheet has high cohesion; on the other hand, the consumption of lithium ions can be avoided to ensure that the battery assembled based on the electrode sheet has excellent cycle performance. BRIEF DESCRIPTION OF DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the related art, the drawings needed to be used in the description of the embodiments of the present application or the related art will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other related drawings can be obtained by those skilled in the art without creative labor.

[0035] Figure 1 It is a flowchart of the electrode sheet manufacturing method in one embodiment;

[0036] Figure 2 It is a structural schematic diagram of the negative electrode active material coated with the binder dry coating layer in one embodiment;

[0037] Figure 3 It is a flowchart of the electrode sheet manufacturing method in another embodiment;

[0038] Figure 4 It is a structural schematic diagram of the rolling device in another embodiment;

[0039] Figure 5 It is a structural block diagram of the electrode sheet manufacturing system in one embodiment. DETAILED DESCRIPTION

[0040] In order to make the purposes, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and not to limit the present application.

[0041] The present application is made by the inventors based on the recognition and research of the following problems:

[0042] The LUMO energy level of the binder emulsion refers to the energy level of the lowest unoccupied molecular orbital (LUMO) in its molecular orbital, which can reflect the ability of the binder molecule to accept electrons, that is, the lower the LUMO energy level of a binder, the easier it is for the binder to accept electrons at low potential and undergo reduction.

[0043] As described in the background section, since PTFE can form fibrils to generate adhesion and PTFE also has many excellent material properties, based on this, the binder used in the process of manufacturing electrode sheets based on the current dry electrode technology is usually PTFE, and the LUMO energy level of PTFE is low, which causes PTFE to chemically react with lithium ions on the surface of the negative electrode to generate lithium fluoride during the charging and discharging process of the lithium battery. Due to the chemical reaction of part of the PTFE, the mass percentage of PTFE decreases, thereby weakening the adhesion effect of PTFE on the electrode sheet, and further, causing the electrode sheet to be prone to peeling or cracking, which is not conducive to maintaining the battery capacity.

[0044] During the charging and discharging process of the lithium battery, single PTFE will consume about 1070 mAh of lithium, that is, the higher the PTFE content in the lithium battery, the more lithium will be consumed. Obviously, the cycle performance of the battery assembled by the electrode sheet manufactured by the current dry electrode technology cannot be guaranteed.

[0045] Based on the above technical problems, the inventors found that in order to improve the cycle performance of the battery assembled by the electrode sheet, it is necessary to avoid using PTFE, which has certain defects in the charging and discharging process of the lithium battery. Based on this, the inventors further researched and developed the technical solutions of the embodiments of the present application.

[0046] In an exemplary embodiment, as shown in Figure 1 An electrode sheet manufacturing method is provided, which is used as an example to illustrate the application of the method to an electrode sheet manufacturing system, including the following steps 102 to step 110. Among them:

[0047] Step 102, obtaining a first binder emulsion; the first binder emulsion is a non-fibrillated binder emulsion.

[0048] The binder emulsion is an emulsion-like substance formed by dispersing binder particles in a liquid medium, and is used to bind together the active material, conductive agent, and other components in the electrode material and fix them on the current collector to form an electrode sheet with sufficient stability.

[0049] The first binder emulsion is a binder emulsion obtained by mixing a first binder with water or other liquid solvents.

[0050] The non-fibrillated binder emulsion is a binder emulsion that does not form a fibrillated structure. The non-fibrillated binder emulsion has strong material compatibility and can be mixed with other binders to form a composite binder. Based on the composite binder, the cohesion of the battery assembled based on the electrode sheet can be improved to avoid adverse phenomena such as cracking or peeling of the electrode sheet, thereby significantly improving the cycle performance of the battery.

[0051] Optionally, the first binder emulsion is a binder emulsion with a LUMO energy level greater than or equal to a preset electron-volt value. Thus, due to the high LUMO energy level of the first binder emulsion, the first binder emulsion is less likely to react with lithium ions at the low potential of the negative electrode.

[0052] Since the polymer containing an aromatic ring or a conjugated double bond generally has a high LUMO energy level, in an exemplary embodiment, the first binder emulsion is a non-fibrillated binder emulsion of a polymer containing an aromatic ring or a conjugated double bond.

[0053] In step 104, the first binder emulsion is spray-dried to obtain binder micropowder, so that the binder micropowder is coated on the surface of the negative electrode active material in a tumbling state to obtain negative electrode active material coated with a dry binder coating on the surface.

[0054] The first binder emulsion is spray-dried to obtain binder micropowder, and the purpose is to remove water or other liquid solvents in the binder emulsion to obtain dry binder micropowder.

[0055] In the process of spray-drying the first binder emulsion to obtain binder micropowder, the first binder emulsion is first atomized into a large number of mist droplets. Then, under the drying action of hot air or other drying media, the water or other liquid solvents in the large number of mist droplets evaporate rapidly, and thus dry binder micropowder can be obtained.

[0056] The particle size of the mist droplets is 50-150 μm.

[0057] It is easy to understand that since the binder powder is obtained by spray-drying the first binder emulsion, the binder powder has a smaller particle size and a larger specific surface area, which helps to improve the dispersibility and binding performance of the binder powder in the negative electrode active material.

[0058] It is easy to understand that since the negative electrode active material is in a tumbling state, the contact area of ​​the binder powder relative to the negative electrode active material can be increased. Based on this, the binder powder can more fully contact the negative electrode active material, and further, it helps to improve the coating effect of the binder powder on the surface of the negative electrode active material, ensuring that a uniform dry binder coating can be formed on the surface of the negative electrode active material.

[0059] The negative electrode active material is a material in the battery's negative electrode that can undergo a reversible electrochemical reaction to insert and remove lithium ions. The surface of the negative electrode active material is coated with a dry binder coating, meaning the surface of the negative electrode active material is evenly covered with a layer of dry binder coating composed of a large amount of binder powder.

[0060] It is easy to understand that the negative electrode active material is coated by the binder powder, which means that the periphery of the negative electrode active material has been completely surrounded and covered by the binder powder, and the coated negative electrode active material is difficult to come into contact with the outside air or other substances.

[0061] For example, Figure 2 As shown, a large number of binder powders 202 are coated on the surface of the negative electrode active material 204 , forming a layer of dry binder coating on the surface of the negative electrode active material 204 .

[0062] In an exemplary embodiment, the negative electrode active material includes at least one of natural graphite, synthetic graphite, hard carbon, soft carbon, activated carbon, silicon, silicon oxide, silicon carbon, tin, tin oxide, and lithium titanate.

[0063] It is easy to understand that, under normal circumstances, the first binder emulsion contains a certain amount of water or other liquid solvents, and therefore, the first binder emulsion is usually the material used in the wet electrode sheet manufacturing process. The embodiment of the present application innovatively spray-dries the first binder emulsion to obtain binder powder, so that the non-fibrillated first binder emulsion can also be used in the dry electrode sheet manufacturing process to improve the cycle performance of the battery after the manufactured battery sheet is assembled.

[0064] Step 106 : Mix the negative electrode active material with the binder dry coating on its surface with the electrode matrix material to obtain an electrode mixture.

[0065] Among them, the electrode matrix material is a material used to provide mechanical support for the negative electrode active material and realize the conductivity of the negative electrode active material.

[0066] In one exemplary embodiment, the electrode matrix material comprises the conductive agent and the second binder.

[0067] wherein, in the electrode mixture, the mass percentage of the binder fine powder is 1% to 5%, the mass percentage of the second binder is 0.5% to 5%, the mass percentage of the negative electrode active material is 80% to 98%, and the mass percentage of the conductive agent is 0.5% to 10%.

[0068] Optionally, the second binder can comprise PTFE.

[0069] In the present embodiment, since the first binder emulsion is a non-fibrillated binder emulsion, and the non-fibrillated binder emulsion lacks a fiber network structure, it is difficult to ensure the stability between the negative electrode active material and the first binder emulsion in the dry process only by relying on the first binder emulsion. Therefore, the second binder included in the electrode matrix material can form a composite binder with the first binder emulsion, and further, based on the composite binder, the cohesion of the battery assembled based on the electrode sheet can be improved to avoid adverse phenomena such as cracking or peeling of the electrode sheet, so as to significantly improve the cycle performance of the battery.

[0070] In one exemplary embodiment, the conductive agent comprises at least one of conductive carbon black, graphene, carbon nanotubes, carbon fibers, acetylene black, and Ketjen black.

[0071] Optionally, the components that can constitute the electrode matrix material can be mixed to prepare the electrode matrix material, and then the electrode matrix material and the negative electrode active material coated with the dry binder coating layer on the surface are mixed to obtain the electrode mixture; alternatively, the components that can constitute the electrode matrix material and the negative electrode active material coated with the dry binder coating layer on the surface can be mixed at the same time to obtain the electrode mixture.

[0072] As can be easily understood, the quality of the electrode mixture directly affects the capacity, cycle life, charge-discharge rate, and safety performance of the battery. Therefore, during the mixing of the negative electrode active material coated with the dry binder coating layer on the surface and the electrode matrix material, the uniformity of the mixing should be ensured, that is, the obtained electrode mixture should have mixing uniformity.

[0073] It should be noted that the mixing process of the negative electrode active material coated with the dry binder coating layer on the surface and the electrode matrix material is a dry mixing process.

[0074] In step 108, the electrode mixture is calendered to obtain a negative electrode film sheet.

[0075] The calendering is a processing method for providing multiple rollings of the electrode mixture by a roll pressing device so that the electrode mixture is shaped into the negative electrode film.

[0076] The negative electrode film is a film used as a negative electrode part in the electrode sheet.

[0077] As can be easily understood, since the electrode mixture contains only the negative electrode active material but no positive electrode active material, the film obtained after the calendering of the electrode mixture is the negative electrode film.

[0078] In step 110, the negative electrode film is hot-combined with the current collector to obtain the electrode sheet.

[0079] The current collector is a material used to collect and conduct electric current to ensure that the negative electrode active material in the negative electrode film can effectively participate in the electrochemical reaction, and at the same time, the current collector can also provide mechanical support for the negative electrode film.

[0080] The hot-combining is a processing method for tightly combining the negative electrode film and the current collector by applying pressure while heating to obtain the electrode sheet.

[0081] As can be easily understood, the electrode sheet in the embodiment is a negative electrode sheet. Further, based on the electrode sheet obtained in the embodiment, a battery can be obtained by further combining a positive electrode sheet, a separator, an electrolyte and the like.

[0082] Exemplarily, as shown in Figure 3 In the case where the electrode matrix material includes the conductive agent and the second binder, the process flow of the electrode sheet manufacturing is specifically as follows: first, a non-fibrillated first binder emulsion is obtained, the first binder emulsion is spray-dried to obtain binder micropowder, the binder micropowder is coated on the surface of the negative electrode active material in a turbulent state, so that the negative electrode active material coated with a binder dry coating layer is obtained, then the negative electrode active material coated with the binder dry coating layer, the conductive agent and the second binder are mixed to obtain the electrode mixture, further, the electrode mixture is calendered to obtain the negative electrode film, and then the negative electrode film is hot-combined with the current collector to obtain the electrode sheet. It should be noted that after the electrode sheet is obtained, a conventional battery assembly method can be used to obtain a battery, and therefore the specific process flow of the battery assembly will not be described herein.

[0083] The electrode sheet manufacturing method comprises the following steps: obtaining a first binder emulsion; the first binder emulsion is a non-fibrillated binder emulsion; spray drying the first binder emulsion to obtain binder micropowder, so that the binder micropowder is coated on the surface of the negative active material in a turbulent state to obtain negative active material coated with a binder dry coating; mixing the negative active material coated with the binder dry coating with an electrode matrix material to obtain an electrode mixture; calendering the electrode mixture to obtain a negative electrode film; and hot-compositing the negative electrode film with a current collector to obtain an electrode sheet. The electrode sheet manufacturing method provided in the embodiment is based on the use of a non-fibrillated first binder emulsion with a high LUMO energy level, and the first binder emulsion is spray dried, so that the water in the first binder emulsion is evaporated to obtain binder micropowder which is coated on the surface of the negative active material. Therefore, in the electrode sheet obtained by using the electrode sheet manufacturing method provided in the embodiment, the binder dry coating coated on the surface of the negative active material is not prone to react with lithium ions during the charging and discharging process of the battery. On the one hand, the stability of the binder dry coating can be ensured to ensure that the negative electrode film and the current collector have high bonding force, and the electrode sheet has high cohesion. On the other hand, the consumption of lithium ions can be avoided to ensure that the battery assembled based on the electrode sheet has excellent cycle performance.

[0084] In one exemplary embodiment, the spray drying of the first binder emulsion to obtain binder micropowder, so that the binder micropowder is coated on the surface of the negative active material in a turbulent state to obtain negative active material coated with a binder dry coating, comprises:

[0085] The hot air at the preset drying temperature is sent into the mixing chamber of the coating machine containing the negative active material, so that the negative active material is in a turbulent state under the action of the hot air.

[0086] The first binder emulsion in the form of mist droplets is sprayed into the mixing chamber at a preset feeding rate through the spray gun of the coating machine, so that the water in the first binder emulsion in the form of mist droplets is evaporated to obtain binder micropowder, and the binder micropowder is coated on the surface of the negative active material in a turbulent state to obtain negative active material coated with a binder dry coating.

[0087] The mist droplets are small droplets of the first binder emulsion formed in the mixing chamber after being atomized by the spray gun.

[0088] Hot air refers to air heated to a specific preset drying temperature. Since the hot air corresponds to a higher temperature condition, on the one hand, the hot air can blow the negative active material so that the negative active material is in a state of turbulence, and on the other hand, the hot air can make the water in the first binder emulsion in the form of mist droplets evaporate under heat to obtain binder fines.

[0089] Turbulence refers to a state of violent rolling and stirring of the negative active material under the blowing action of the hot air. In the case where the negative active material is in a state of turbulence, since the particles of the negative active material will constantly turn over, move and collide, the negative active material has high dispersibility and a large contact area with the hot air or the binder fines. Therefore, it is easy to understand that in the case where the negative active material is in a state of turbulence, it helps to improve the coating effect of the first binder emulsion on the negative active material, and thus the subsequent manufactured electrode sheet has high cohesion.

[0090] The coating machine is an industrial equipment for uniformly coating a coating layer (i.e. a binder dry coating layer) on the surface of the negative active material in the embodiment. The coating machine forms a binder dry coating layer on the surface of the negative active material as a protective layer of the negative active material through processes such as spraying, drying and mixing.

[0091] The mixing chamber of the coating machine is a chamber inside the coating machine for containing the negative active material and enabling the negative active material to be fully mixed with the binder fines to coat the binder dry coating layer on the surface of the negative active material. Alternatively, the mixing chamber of the coating machine can be a drum-type chamber, so that the negative active material constantly rolls and stirs in the rotating drum to ensure that the binder fines can be uniformly and comprehensively coated on the surface of the negative active material.

[0092] The spray gun is a component of the coating machine for atomizing the first binder and spraying the mist droplets obtained by atomization into the mixing chamber of the coating machine. The water in the mist droplets is rapidly evaporated under the drying action of the hot air in the mixing chamber, so that the binder fines left after the water in the mist droplets evaporates can be coated on the surface of the negative active material. Obviously, the atomization of the first binder emulsion by the spray gun can ensure the coating effect of the binder fines on the negative active material.

[0093] In an exemplary embodiment, the preset drying temperature is 80°C to 150°C, and the preset feeding rate is 4 kg / h to 10 kg / h.

[0094] The preset feeding rate is a rate at which the first binder emulsion enters the mixing chamber under the spraying action of the spray gun. If the preset feeding rate is too low, the coating efficiency of the coating machine on the negative active material will be low. If the preset feeding rate is too high, the content of water or other liquid solvents brought by the first binder emulsion in the mixing chamber will be too large, which will make it difficult for the water or other liquid solvents to be fully evaporated, thereby affecting the coating effect of the coating machine on the negative active material. Therefore, when the preset feeding rate is 4 kg / h to 10 kg / h, a balance between the coating efficiency and the coating effect can be achieved, that is, a better coating efficiency and coating effect can be achieved.

[0095] The preset drying temperature is a temperature of hot air in the mixing chamber of the coating machine, which is preset to achieve a specific drying effect. On the one hand, the preset drying temperature of the hot air will affect the evaporation efficiency of water or other liquid solvents in the mist droplets of the first binder emulsion. On the other hand, the preset drying temperature of the hot air will also affect the degree of tumbling of the negative active material in the mixing chamber. Therefore, the preset drying temperature can be determined based on the material properties of the negative active material and the material properties of the first binder emulsion.

[0096] If the preset drying temperature is too high, the evaporation efficiency of the hot air on the water or other liquid solvents will be too fast, which will cause the first binder emulsion to be evaporated before it has had time to fully disperse into mist droplets, thereby making it difficult to form binder micropowder with high dispersibility. Even worse, multiple binder particles may form a large block. Obviously, if the binder micropowder particles are not small enough, the coating effect on the negative active material will be poor. If the preset drying temperature is too low, the evaporation efficiency of the hot air on the water or other liquid solvents will be too low, and the flow rate of the hot air will be low, which will result in a low degree of tumbling of the negative active material in the mixing chamber. Similarly, this is also not conducive to improving the coating effect of the binder micropowder on the negative active material. Therefore, the preset drying temperature is 80°C to 150°C, which is conducive to ensuring that the binder micropowder can fully and uniformly coat the surface of the negative active material, thereby improving the coating effect of the binder micropowder on the negative active material.

[0097] In an exemplary embodiment, the size of the latex particles in the first binder emulsion is 100 nm to 400 nm.

[0098] The latex particles are microscopic colloidal particles dispersed in water or other liquid solvents in the first binder emulsion.

[0099] A small amount of water or other liquid solvents in the latex particles can be obtained as binder micropowder after spray drying. Therefore, it can be understood that the latex particles are a precursor form of the binder micropowder.

[0100] The size of latex particles is much smaller than that of the negative electrode active material particles.

[0101] In this embodiment, since the latex particles in the first binder emulsion have an extremely small size, after the first binder emulsion is spray-dried, the binder powder, which also has an extremely small size, can be evenly coated on the surface of the negative electrode active material in a tumbling state, so as to form a uniform dry binder coating on the surface of the negative electrode active material. The dry binder coating is beneficial to reducing the volume change and structural damage that may occur in the negative electrode active material during the battery charging and discharging process, thereby improving the cycle performance of the battery.

[0102] In an exemplary embodiment, the electrode mixture is rolled to obtain a negative electrode film, comprising:

[0103] The electrode mixture is rolled based on a preset rolling number and a preset rolling temperature to obtain a negative electrode membrane.

[0104] The above-mentioned process of thermally combining the negative electrode film and the current collector to obtain the electrode sheet includes:

[0105] The negative electrode film and the current collector are thermally composited based on a preset thermal composite temperature to obtain an electrode sheet.

[0106] Among them, the preset calendering times are 2 to 10 times, the preset calendering temperature is 50°C to 250°C, and the preset thermal composite temperature is 80°C to 250°C.

[0107] The number of rolling cycles refers to the number of times the electrode mixture is shaped by the rolling action of the rollers during the multi-roll rolling process. This number of rolling cycles affects the shaping of the electrode mixture and the electrical properties of the resulting electrode membrane. The number of rolling cycles is positively correlated with the uniformity and flatness of the electrode membrane, and negatively correlated with its thickness.

[0108] It is easy to understand that the number of calendering times corresponds to the number of rollers in the rolling device.

[0109] The preset calendering times are 2 to 10 times, which can ensure that the negative electrode membrane obtained by calendering has high uniformity and flatness. At the same time, it can avoid the undesirable situation of low manufacturing efficiency of the negative electrode membrane due to too many calendering times.

[0110] Calendering temperature refers to the temperature experienced by the electrode mixture during the multi-roll calendering process as it is rolled into the negative electrode membrane. Calendering temperature affects the shaping of the electrode mixture. Calendering temperature is positively correlated with the degree of deformation of the electrode membrane.

[0111] The preset calendering temperature is 50℃~250℃, which can ensure that the electrode mixture can undergo a certain degree of deformation under appropriate temperature conditions to form a negative electrode membrane with high flatness. At the same time, the calendering efficiency is improved by avoiding the calendering temperature being too low, and the material properties of the electrode mixture are changed under high temperature by avoiding the calendering temperature being too high.

[0112] The thermal bonding temperature refers to the temperature experienced by the negative electrode membrane during the multi-roll calendering process as it is tightly bonded to the current collector in the rolling device to form the electrode sheet. To allow the composite binder in the negative electrode membrane to flow better and fill the tiny gap between the negative electrode membrane and the current collector, achieving a strong bond between the negative electrode membrane and the current collector, the thermal bonding temperature generally needs to be higher than the calendering temperature. Therefore, the preset calendering temperature is within the preset thermal bonding temperature range.

[0113] For example, Figure 4 As shown, the electrode mixture 402 is rolled by a rolling device 40 based on a preset rolling number and a preset rolling temperature to obtain a negative electrode film 404, and the negative electrode film 404 and the current collector 406 are thermally composited based on a preset thermal composite temperature to obtain an electrode sheet 408.

[0114] In an exemplary embodiment, the first binder emulsion includes at least one of polyvinylidene fluoride emulsion, styrene-butadiene rubber emulsion, polyacrylic emulsion, terpolymer emulsion, polyurethane emulsion, and styrene-acrylic emulsion.

[0115] Among them, polyvinylidene fluoride emulsion is an emulsion with polyvinylidene fluoride (PVDF) as the main component.

[0116] Styrene butadiene rubber emulsion is a synthetic rubber emulsion with styrene butadiene rubber (SBR) as the main component.

[0117] Polyacrylic acid emulsion is an aqueous emulsion with polyacrylic acid and its derivatives as the main components.

[0118] A terpolymer emulsion is an emulsion formed by copolymerizing three different monomers. Optionally, the terpolymer emulsion may be composed of styrene (St), methyl methacrylate (MMA), and butyl acrylate (BA).

[0119] Polyurethane emulsion is a water-based emulsion with polyurethane as the main component.

[0120] Styrene acrylic emulsion is a water-based emulsion copolymerized with styrene and acrylic ester monomers.

[0121] In an exemplary embodiment, the solid content of the first binder emulsion is 10% to 60%.

[0122] The solid content of the first binder emulsion refers to the percentage of the mass of the solid substance in the first binder emulsion in the total mass of the first binder emulsion.

[0123] In this embodiment, the solid content of the first binder emulsion is 10% to 60%, which can avoid the problem of high transportation cost caused by the excessive weight of water or other liquid solvents in the first binder emulsion due to the low solid content, and can also avoid the problem of poor coating effect on the negative active material due to the low solid content. At the same time, it can avoid the problem that the water or other liquid solvents in the first binder emulsion are difficult to be fully evaporated, and it is difficult to form a binder micro-powder with sufficient dryness due to the high solid content. That is, the solid content of the first binder emulsion is 10% to 60%, which can ensure that the corresponding binder micro-powder of the first binder emulsion has a good coating effect on the negative active material.

[0124] In one exemplary embodiment, the negative active material coated with the binder dry coating layer on the surface is mixed with the electrode matrix material to obtain an electrode mixture, comprising:

[0125] The negative active material coated with the binder dry coating layer on the surface is mixed with the electrode matrix material by the stirring component for a preset time to obtain an electrode mixture.

[0126] The end speed of the stirring component is 2 m / s to 30 m / s, and the preset time is 5 min to 60 min.

[0127] The stirring component is a key component in the stirring device for mixing the negative active material coated with the binder dry coating layer on the surface with the electrode matrix material to improve the uniformity of the obtained electrode mixture.

[0128] Optionally, the stirring device can be a high-speed mixer with a stirring component capable of high-speed rotation. The stirring component can be one of a spiral rotor, a paddle rotor, and a plow rotor.

[0129] Exemplarily, when the stirring component is a paddle rotor, the end speed of the stirring component refers to the end speed of the paddle rotor.

[0130] In this embodiment, in the process of stirring and mixing the negative electrode active material coated with a dry coating of binder on the surface and the electrode matrix material for a preset time based on the stirring component to obtain an electrode mixture, since the stirring component has an appropriate terminal speed, it is possible to ensure that the electrode mixture has sufficient uniformity while avoiding the damage of some materials in the electrode mixture due to excessive stirring force. At the same time, since the preset time spent on stirring is appropriate, it is possible to ensure that the rate of obtaining the electrode mixture is high, thereby ensuring that the electrode sheet manufacturing has a high efficiency.

[0131] In an exemplary embodiment, the current collector is at least one of an aluminum foil coated with a conductive carbon layer, a copper foil coated with a conductive carbon layer, a nickel foil coated with a conductive carbon layer, a stainless steel foil coated with a conductive carbon layer, a porous aluminum foil coated with a conductive carbon layer, a porous copper foil coated with a conductive carbon layer, a porous nickel foil coated with a conductive carbon layer, a porous stainless steel foil coated with a conductive carbon layer, and a corroded aluminum foil coated with a conductive carbon layer.

[0132] For example, Figure 5 As shown, the electrode sheet manufacturing system 50 includes a coating machine 502, a stirring device 504 and a roller pressing device 506. The process flow of the electrode sheet manufacturing method provided in this application based on the electrode sheet manufacturing system 50 is as follows:

[0133] (1) A negative electrode active material is placed in the mixing chamber of the coating machine 502, and the negative electrode active material is in a tumbling state under the blowing action of hot air sent into the mixing chamber of the coating machine 502; a first binder emulsion is obtained and sprayed into the coating machine through a spray gun of the coating machine 502, so that the coating machine 502 spray-dries the first binder emulsion in the mixing chamber to obtain a binder fine powder, and the binder fine powder is coated on the surface of the negative electrode active material in the tumbling state, so as to obtain a negative electrode active material with a surface coated with a dry binder coating.

[0134] (2) The negative electrode active material with the surface coated with the dry binder coating is transferred from the coating machine 502 to the stirring device 504, so that the stirring device 504 mixes the negative electrode active material with the surface coated with the dry binder coating with the electrode matrix material to obtain an electrode mixture.

[0135] (3) The electrode mixture is transferred from the stirring device 504 to the roller pressing device 506, so that the roller pressing device 506 rolls the electrode mixture to obtain a negative electrode film, and thermally combines the negative electrode film with the current collector to obtain an electrode sheet.

[0136] It should be understood that, although the steps in the flowcharts involved in the embodiments described above are shown in sequence according to the arrows, the steps are not necessarily executed in the order indicated by the arrows. Unless otherwise specified herein, the execution of the steps is not strictly limited in sequence, and the steps can be executed in other sequences. Moreover, at least some of the steps in the flowcharts involved in the embodiments described above can include multiple steps or multiple stages, which are not necessarily executed at the same time, but can be executed at different times, and the execution sequence of the steps or stages is not necessarily sequential, but can be executed in rotation or alternation with at least some of the other steps or the steps or stages in the other steps.

[0137] In an exemplary embodiment, an electrode sheet is also provided, which is manufactured by the steps of any one of the electrode sheet manufacturing method embodiments described above.

[0138] In an exemplary embodiment, an energy storage device is also provided, which includes the electrode sheet.

[0139] The technical features of the above embodiments can be combined in any manner. To make the description concise, not all possible combinations of the technical features in the above embodiments are described, but as long as the combinations of the technical features do not contradict, they should be considered within the scope of the present application.

[0140] The above-described embodiments only express several implementation manners of the present application, which are described in detail and specifically, but should not be understood as limitations on the patent scope of the present application. It should be pointed out that, for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present application, which are all within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the appended claims.

Claims

1. A method for manufacturing an electrode sheet, characterized in that: The method comprises: Obtaining a first binder emulsion; wherein the first binder emulsion is a non-fibrillated binder emulsion; spray drying the first binder emulsion to obtain binder powder, so that the binder powder is coated on the surface of the negative electrode active material in a tumbling state, thereby obtaining a negative electrode active material with a surface coated with a dry binder coating; Mixing the negative electrode active material with the binder dry coating on the surface with an electrode matrix material to obtain an electrode mixture; rolling the electrode mixture to obtain a negative electrode film; The negative electrode film and the current collector are thermally combined to obtain an electrode sheet.

2. The method according to claim 1, characterized in that The method comprises spray drying the first binder emulsion to obtain a binder powder, so that the binder powder is coated on the surface of the negative electrode active material in a tumbling state to obtain a negative electrode active material with a surface coated with a dry binder coating, comprising: sending hot air of a preset drying temperature into a mixing chamber of a coating machine containing the negative electrode active material, so that the negative electrode active material is in a tumbling state under the action of the hot air; The first binder emulsion in the form of mist droplets is sprayed into the mixing chamber at a preset feed rate through the spray gun of the coating machine, so that the water in the first binder emulsion in the form of mist droplets is evaporated to obtain the binder fine powder, and then the binder fine powder is coated on the surface of the negative electrode active material in a tumbling state, thereby obtaining the negative electrode active material with the surface coated with a dry binder coating.

3. The method according to claim 1, characterized in that The latex particles in the first binder emulsion have a size of 100 nm to 400 nm.

4. The method according to claim 1, wherein The step of rolling the electrode mixture to obtain a negative electrode film comprises: Rolling the electrode mixture based on a preset rolling number and a preset rolling temperature to obtain the negative electrode film; The step of thermally combining the negative electrode film and the current collector to obtain an electrode sheet comprises: Thermally combining the negative electrode film and the current collector based on a preset thermal combination temperature to obtain the electrode sheet; Wherein, the preset calendering times are 2 to 10 times, the preset calendering temperature is 50°C to 250°C, and the preset thermal composite temperature is 80°C to 250°C.

5. The method according to claim 1, wherein The first binder emulsion includes at least one of polyvinylidene fluoride emulsion, styrene-butadiene rubber emulsion, polyacrylic emulsion, terpolymer emulsion, polyurethane emulsion and styrene-acrylic emulsion.

6. The method according to claim 2, characterized in that The preset drying temperature is 80° C. to 150° C., and the preset feeding rate is 4 kg / h to 10 kg / h.

7. The method according to claim 1, characterized in that The solid content of the first binder emulsion is 10% to 60%.

8. The method according to claim 1, characterized in that The electrode matrix material includes a conductive agent and a second binder; In the electrode mixture, the mass percentage of the binder powder is 1% to 5%, the mass percentage of the second binder is 0.5% to 5%, the mass percentage of the negative electrode active material is 80% to 98%, and the mass percentage of the conductive agent is 0.5% to 10%.

9. An electrode sheet, characterized in that: The electrode sheet is manufactured using the electrode sheet manufacturing method according to any one of claims 1 to 8.

10. An energy storage device, characterized in that: The energy storage device comprises the electrode sheet according to claim 9.

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