Pole piece processing system and pole piece processing method

Abstract

The invention belongs to the technical field of batteries, and particularly relates to a pole piece processing system and a pole piece processing method. The pole piece treatment system comprises an electromagnetic induction heating unit, wherein the electromagnetic induction heating unit is used for carrying out electromagnetic induction heating treatment on a pole piece. According to the present invention, the binder floating on the surface of the pole piece can be reduced, and the pores are left in the active layer, such that the porosity of the pole piece is improved, and the infiltration rate of the electrolyte on the pole piece is improved; various burrs and particles on the edge of the active layer can be improved, so that the surface of the active layer becomes smoother, the sharpness of the surface of the pole piece is reduced, and the risk that the pole piece pierces an isolating membrane is reduced. Moreover, the conductive agent in the pole piece tends to be consistent in direction under the influence of magnetic lines generated in the electromagnetic induction process, so that the diaphragm resistance of the pole piece is further reduced.

Description

Pole piece processing system and pole piece processing method Technical Field

[0001] The present application belongs to the field of battery technology, and in particular relates to a pole piece processing system and a pole piece processing method. Background Art

[0002] With the continuous deepening of battery research and the continuous increase in market demand, higher requirements are being placed on various battery performance. The pole piece is a key component in the battery, used to provide the active material for the battery chemical reaction and transmit electrons. The performance of the pole piece, such as wettability and internal resistance, not only affects the production efficiency of the battery (low wettability affects the time of the liquid injection process during battery production, thereby affecting production efficiency), but also affects the battery's impedance, self-discharge and other performance. Therefore, improving the pole piece is a key to improving battery performance.

[0003] Summary of the Invention

[0004] In view of the above problems, the present application provides a pole piece processing system and a pole piece processing method, which can improve the electrochemical performance of the pole piece.

[0005] In a first aspect, the present application provides a pole piece processing system, comprising: an electromagnetic induction heating unit, wherein the electromagnetic induction heating unit is used to perform electromagnetic induction heating treatment on the pole piece.

[0006] The embodiment of the present application provides a pole piece processing system, which performs electromagnetic induction heating on the pole piece by setting an electromagnetic induction heating unit, and softens (melts) or ablates the adhesive that floats to the pole piece surface during the drying process. This can reduce the adhesive floating on the pole piece surface and leave pores in the active layer, thereby increasing the pole piece porosity and further increasing the electrolyte infiltration rate of the pole piece; at the same time, after softening (melting) or ablating the adhesive, various burrs and particles on the edge of the active layer can be improved, making the surface of the active layer smoother, reducing the sharpness of the pole piece surface, and thus reducing the risk of the pole piece piercing the isolation membrane, which is beneficial to improving the battery DCR (direct current resistance), K value (voltage drop), and self-discharge. Moreover, the conductive agent in the pole piece is affected by the magnetic lines of force generated by the electromagnetic induction process, and the direction tends to be consistent, which is beneficial to further reduce the membrane resistance of the pole piece.

[0007] In some embodiments, the electrode has a dry active layer. A dry active layer refers to an active layer that is solvent-free, or has a very low solvent content, with the mass concentration of the solvent in the active layer being as low as ppm, such as less than 1000 ppm. There is floating binder on the surface of the dry active layer. The electromagnetic induction heating unit of the embodiment of the present application is used to perform electromagnetic induction heating on the electrode having the dry active layer, thereby treating the floating binder and improving the performance of the electrode.

[0008] In some embodiments, the electromagnetic induction heating unit includes an induction coil; the induction coil is used to generate alternating magnetic flux lines parallel to the pole piece.

[0009] The induction coil of the embodiment of the present application generates alternating magnetic flux lines parallel to the pole piece, which can generate an induced alternating current of the same frequency in the pole piece. When the induced alternating current passes through the pole piece, these alternating currents will tend to flow through the surface of the pole piece when passing through the pole piece. The current density at the surface of the pole piece is relatively large, and the current density inside the pole piece is relatively small. The current is mainly concentrated on the surface of the pole piece. The closer to the surface of the pole piece, the greater the current density, resulting in a "skin effect". Through this skin effect, the surface of the pole piece can be quickly heated, and the surface temperature of the pole piece can be rapidly increased, which can ablate the floating adhesive, edge burrs, and edge particles. At the same time, since the pole piece is less affected by the magnetic lines of force of the alternating magnetic field and the current density is relatively small, the temperature rise of the current collector inside the pole piece is relatively small, which can improve the softening and deformation of the current collector due to high temperature and improve the bonding force between the active material in the pole piece and the current collector.

[0010] In some embodiments, the electrode processing system further includes a temperature measuring unit for measuring the temperature of the electrode. By providing the temperature measuring unit, the electrode temperature can be timely and accurately understood and the electrode status can be monitored.

[0011] In some embodiments, the temperature measurement unit includes an infrared temperature measurement module. By means of infrared temperature measurement, non-contact temperature measurement of the electrode can be achieved.

[0012] In some embodiments, the electrode processing system further includes an automatic temperature control unit, which is used to control the heating parameters of the electromagnetic induction heating unit.

[0013] In the electrode processing system of the embodiment of the present application, by setting an automatic temperature control unit, the heating parameters (such as temperature, frequency, current, etc.) of the electromagnetic induction heating unit can be controlled according to the temperature of the electrode. When the temperature of the electrode is too low, the heating power (or temperature, current) of the electromagnetic induction heating unit can be controlled to increase, thereby increasing the temperature of the electrode; when the temperature of the electrode is too high, the heating power (or temperature, current) of the electromagnetic induction heating unit can be controlled to decrease, thereby reducing the temperature of the electrode. In some cases, a high-precision infrared temperature measurement module is used as the temperature measurement component of the temperature measurement unit. Under the control of a high-precision automatic control unit, precise control of the temperature accuracy between ±3°C can be met. Therefore, the use of an automatic temperature control unit can accurately and flexibly control the temperature of the electrode, so that the temperature of the electrode is within a suitable range, thereby effectively softening and decomposing excess adhesive in the electrode.

[0014] In second aspect, the present application provides a method for processing an electrode, wherein the electrode comprises a current collector and an active layer, the active layer being arranged on at least one side of the current collector, and the active layer comprising a binder. The method for processing the electrode comprises: performing electromagnetic induction heating treatment on the electrode, so that the surface temperature of the active layer is greater than or equal to the softening temperature or melting temperature of the binder, and the temperature of the current collector is lower than the deformation temperature of the current collector.

[0015] In the method of the embodiment of the present application, the electrode is treated by electromagnetic induction heating. The active layer usually contains a conductive agent. When the conductive agent in the active layer is subjected to electromagnetic induction, heat is generated, thereby achieving electromagnetic induction heating of the active layer. During electromagnetic induction heating, the surface temperature of the active layer is greater than or equal to the softening temperature or melting temperature of the binder. At this temperature, the binder that floats to the surface of the active layer during the drying process of the electrode softens or melts, or even ablates. By softening (melting) and ablating, the binder floating on the surface of the active layer can be reduced. After the binder is ablated, pores are left in the active layer, thereby increasing the porosity of the electrode and thus increasing the electrolyte infiltration rate. At the same time, after softening (melting) and ablating the binder, various burrs and particles on the edge of the active layer can be improved, making the surface of the active layer smoother, reducing the sharpness of the electrode surface, and thus reducing the risk of the electrode piercing the isolation membrane, which is beneficial to improving the battery DCR (DC resistance), K value (voltage drop), and self-discharge. At the same time, the conductive agent contained in the active layer is affected by the magnetic lines of force generated by the electromagnetic induction process, and its direction tends to be consistent, which is beneficial to further reduce the diaphragm resistance of the pole piece.

[0016] In addition, after electromagnetic induction heating treatment, the temperature of the current collector is lower than the deformation temperature of the current collector, so it can improve the softening and deformation of the current collector due to high temperature, and maintain good adhesion and conductivity between the current collector and the active layer, which is beneficial to reduce the diaphragm resistance of the electrode and improve problems such as electrode burning and powder loss.

[0017] In some embodiments, the electromagnetic induction heating treatment step includes: passing the pole piece through the interior of an induction coil and applying an alternating current to the induction coil.

[0018] The embodiment of the present application makes the pole piece pass through the inside of the induction coil, and generates an alternating magnetic field after the induction coil passes through the alternating current, and the alternating magnetic field generates an induced alternating current of corresponding frequency in the pole piece. When the induced alternating current passes through the pole piece, these alternating currents will tend to flow through the surface of the pole piece when passing through the pole piece. The current density at the surface of the pole piece is relatively large, and the current density inside the pole piece is relatively small. The current is mainly concentrated on the surface of the pole piece. The closer to the surface of the pole piece, the greater the current density, resulting in a "skin effect". This skin effect can rapidly heat the surface of the pole piece, causing the surface temperature of the pole piece to rise rapidly, and can burn off the floating adhesive, edge burrs, and edge particles. At the same time, since the current density inside the pole piece is relatively small, the problem of softening, deformation, and stress of the current collector inside the pole piece caused by high temperature can be improved, thereby improving the bonding force between the active layer of the pole piece and the current collector.

[0019] In some embodiments, the induction frequency of the electromagnetic induction heating treatment is greater than or equal to 5 KHz; optionally, the induction frequency of the electromagnetic induction heating treatment is 10 to 50 KHz; optionally, the induction frequency of the electromagnetic induction heating treatment is 10 to 20 kHz.

[0020] The induction frequency of the electromagnetic induction heating treatment can be considered as the output frequency after the alternating current is loaded in the induction coil. The induction coil generates an alternating magnetic field after the alternating current passes through it, and the alternating magnetic field generates the frequency of the induced alternating current in the pole piece. The induction frequency of the electromagnetic induction heating treatment affects the depth of action on the pole piece. Under the induction frequency of the embodiment of the present application, the induction heating of the active layer of the pole piece can be satisfied while the heating effect on the current collector inside the pole piece is very small, which is beneficial to maintaining the adhesion and conductivity between the current collector and the active layer. The active layer is tightly combined with the current collector, which is beneficial to the stability during the charge and discharge cycle (not easy to separate from the current collector), while improving the dynamic performance.

[0021] In some embodiments, the induction coil has 2 to 10 turns; optionally, the induction coil has 2 to 5 turns. The number of turns of an induction coil is a significant factor influencing its performance. Generally, for the same current, the greater the number of turns, the greater the induced magnetic field generated by the induction coil. Using an appropriate number of turns in the induction coil can meet induction strength requirements while saving equipment costs and reducing resource waste.

[0022] In some embodiments, the pole piece moves relative to the induction coil; optionally, the pole piece moves relative to the induction coil at a speed of 10 to 100 m / min; optionally, the pole piece moves relative to the induction coil at a speed of 40 to 80 m / min. By controlling the movement of the pole piece relative to the induction coil, the duration of electromagnetic induction heating of the pole piece can be adjusted, thereby regulating the pole piece's temperature; and the pole pieces can be processed in batches, improving processing efficiency.

[0023] In some embodiments, the surface temperature of the active layer is 100-450°C; alternatively, the surface temperature of the active layer is 220-400°C. When the surface of the active layer reaches these temperatures, the adhesive on the surface of the electrode can soften (melt) or even ablate. At the same time, when heat reaches the internal current collector through heat transfer, the temperature of the current collector will be lower than its deformation temperature.

[0024] In a third aspect, the present application provides a pole piece, which is obtained by processing according to the method of the second aspect above.

[0025] In the pole piece obtained by the above method, the floating binder is softened (melted) and ablated, thereby reducing the floating binder; at the same time, the binder is softened (melted) and ablated, leaving pores in the active layer, thereby increasing the pole piece porosity, and then increasing the electrolyte infiltration rate; various burrs and particles on the edge of the pole piece are improved, and the pole piece surface becomes smoother and less sharp, thereby reducing the risk of the pole piece piercing the isolation membrane; in addition, the conductive agent in the active layer is affected by the magnetic lines of force generated by the electromagnetic induction process, and the direction tends to be consistent, which is conducive to further reducing the diaphragm resistance of the pole piece; the above properties are all conducive to improving the battery DCR, K value, and self-discharge.

[0026] In a fourth aspect, the present application provides a battery, comprising the electrode according to the third aspect.

[0027] The battery of the embodiment of the present application includes the above-mentioned pole piece, which can be either a positive pole piece or a negative pole piece, or can include both a positive pole piece and a negative pole piece. Since the floating binder in the pole piece of the battery is softened (melted) and ablated, the floating binder is reduced; the pores in the pole piece are enriched due to the softening (melting) and ablation of the binder, and the porosity is higher, which is beneficial to improving the electrolyte infiltration rate; the various burrs and particles on the edge of the pole piece are improved, and the surface of the pole piece becomes smoother and less sharp, thereby reducing the risk of the pole piece piercing the isolation membrane, which is beneficial to improving the battery DCR, K value, and self-discharge. In addition, the conductive agent in the active layer is affected by the magnetic lines of force generated by the electromagnetic induction process, and the direction tends to be consistent, which is beneficial to further reduce the membrane resistance of the pole piece. Therefore, the battery containing the above-mentioned pole piece has better DCR, K value, and self-discharge performance.

[0028] In a fifth aspect, the present application provides an electrical device, which includes the battery according to the fourth aspect.

[0029] The battery disclosed in the embodiments of the present application can be used in an electrical device using a battery as a power source, or in various energy storage systems using a battery as an energy storage element, for providing electrical energy. The electrical device may include, but is not limited to, a mobile phone, a tablet, a laptop computer, an electric toy, an electric tool, a battery car, an electric car, a ship, a spacecraft, and the like. Among them, the electric toy may include a fixed or mobile electric toy, for example, a game console, an electric car toy, an electric ship toy, and an electric airplane toy, and the like, and the spacecraft may include an airplane, a rocket, a space shuttle, and a spacecraft, and the like. As the electrical device, a battery cell, a battery module, or a battery pack in a secondary battery can be selected according to its usage requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments or descriptions of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0031] FIG1 is a schematic diagram of the structure of a pole piece passing through the interior of an induction coil in an embodiment of the present application;

[0032] FIG2 is a schematic structural diagram of the electrode processing system in Example 1 of the present application;

[0033] FIG3 is a schematic diagram showing the positional relationship between the pole piece and the induction coil in Comparative Example 5 of the present application;

[0034] FIG4 is a photograph of the electrode in Examples 2 to 4, Comparative Example 1 and Comparative Example 4 of the present application;

[0035] FIG5 is a schematic diagram of a battery module according to an embodiment of the present application;

[0036] FIG6 is a schematic diagram of a battery pack according to an embodiment of the present application;

[0037] FIG7 is an exploded view of the battery pack shown in FIG6 according to an embodiment of the present application;

[0038] FIG8 is a schematic diagram of a battery according to an embodiment of the present application;

[0039] FIG9 is an exploded view of the battery shown in FIG8 according to one embodiment of the present application;

[0040] FIG10 is a schematic diagram of an electrical device using a battery as a power source according to an embodiment of the present application.

[0041] Figure markings: 10-pole piece; 20-electromagnetic induction heating unit; 21-metal sleeve; 22-induction coil; 30-transmission unit; 31-unwinding guide roller; 32-winding guide roller; 40-temperature measuring unit; 50-purge unit; D-transmission direction of pole piece; 1-battery pack; 2-upper box; 3-lower box; 4-battery module; 5-battery cell; 51-housing; 52-electrode assembly; 53-cover plate. DETAILED DESCRIPTION

[0042] The following embodiments of the technical solution of the present application will be described in detail with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application and are therefore only examples and are not intended to limit the scope of protection of the present application.

[0043] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein are for the purpose of describing specific embodiments only and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned figure descriptions are intended to cover non-exclusive inclusions.

[0044] In the description of the embodiments of this application, the technical terms "first" and "second" are used only to distinguish different objects and should not be understood to indicate or imply relative importance or implicitly specify the quantity, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, the meaning of "plurality" is more than two, unless otherwise clearly and specifically defined.

[0045] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0046] In the description of the embodiments of this application, the term "and / or" is simply a description of the association relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent the following three situations: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0047] In the description of the embodiments of the present application, the term "at least one" refers to one or more, and "plurality" refers to two or more. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single items or plural items. For example, "at least one of a, b, or c", or "at least one of a, b, and c" can all represent: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple, respectively.

[0048] It should be understood that in the various embodiments of the present application, the size of the serial numbers of the above-mentioned processes does not mean the order of execution. Some or all of the steps can be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0049] The weights of the relevant components mentioned in the examples of this application may not only refer to the specific content of each component, but also represent the weight ratio between the components. Therefore, as long as the content of the relevant components is proportionally enlarged or reduced according to the examples of this application, it is within the scope disclosed in the examples of this application. Specifically, the mass described in the examples of this application may be a mass unit known in the chemical industry, such as μg, mg, g, kg, etc.

[0050] The electrode is a key component in a battery, providing the active material for the battery's chemical reactions and transporting electrons. The electrode preparation process typically involves mixing the electrode active material, conductive agent, binder, and solvent to form a slurry, applying the slurry to the current collector surface, and then drying and rolling. The drying process primarily removes the solvent from the slurry and enriches the pores of the electrode. During the drying process, the slurry solvent migrates and evaporates toward the electrode surface through capillary forces. Commonly used binders have a low density and a large specific surface area, making them susceptible to migration to the electrode surface as the solvent evaporates, leading to binder floating. After drying, rolling is performed. Once the electrode reaches the required compaction density and thickness, further electrode processing is typically not performed, and the electrode is directly cut and used for battery cell assembly. Therefore, the binder floating problem during the drying process has remained unresolved. The floating of the binder will lead to many problems, such as: the floating binder blocks the pores on the surface of the electrode, resulting in poor electrode wetting effect; the adhesion of the active material on the current collector is reduced, making the electrode prone to powder loss, resulting in increased internal resistance of the electrode; in the subsequent cutting process, the electrode is prone to edge burrs, particles, and electrode thickness rebound; these burrs and particles can easily pierce the isolation membrane in the battery cell, causing battery cell failure, increasing costs and causing hidden safety hazards during the use of subsequent electrical devices, etc.

[0051] To address the above issues, related technologies improve the uniformity of the binder in the slurry by controlling the slurry's rotation during the slurry preparation process, or by optimizing the baking temperature, or by reversing the electrode after baking for a period of time and performing reverse baking, or by using supercritical fluid drying technology to replace traditional high-temperature drying, or by surface treatment of the electrode through methods such as corona and laser pore making. However, from the dynamic analysis of the binder's floating, no matter how uniform the binder is dispersed in the slurry, how the drying temperature is controlled, how the baking direction is changed, and what drying method is used, the phenomenon of binder migration and redistribution will inevitably occur during the drying process; at the same time, corona and laser pore making only treat the surface of the electrode and cannot act on the inside of the electrode, and the improvement of the effects such as electrode wetting is limited.

[0052] In response to the phenomenon of adhesive floating, related technologies generally improve the drying method or the slurry itself. Since it is difficult to solve the problem of adhesive floating during the drying process, the electrode can be further processed to improve the distribution of the adhesive in the electrode when adhesive floating has occurred.

[0053] By subjecting the dried pole piece to electromagnetic induction heating, the adhesive that floats to the pole piece surface can be softened (melted) or ablated during the electromagnetic induction heating process. After the floated adhesive is softened (melted) or ablated, pores are left on the pole piece, which can increase the porosity of the pole piece and thus accelerate the absorption rate of the electrolyte by the pole piece; at the same time, the burrs and particles on the edge of the pole piece caused by the floated adhesive can also be improved. Moreover, the conductive agent in the active layer is affected by the magnetic lines of force generated by the electromagnetic induction process, and the direction tends to be consistent, which is conducive to further reducing the membrane resistance of the pole piece.

[0054] The present application will be further described below with reference to the following examples. It should be understood that these examples are only used to illustrate the present application and are not intended to limit the scope of the present application.

[0055] A first aspect of an embodiment of the present application provides a pole piece processing system, comprising: an electromagnetic induction heating unit, wherein the electromagnetic induction heating unit is used to perform electromagnetic induction heating treatment on the pole piece.

[0056] The embodiment of the present application provides a pole piece processing system, which performs electromagnetic induction heating on the pole piece by setting an electromagnetic induction heating unit, and softens (melts) or ablates the adhesive that floats to the pole piece surface during the drying process, which can reduce the adhesive floating on the pole piece surface and leave pores in the active layer, thereby increasing the pole piece porosity, and further increasing the electrolyte infiltration rate of the pole piece; at the same time, after softening (melting) or ablating the adhesive, various burrs and particles on the edge of the active layer can be improved, making the surface of the active layer smoother, reducing the sharpness of the pole piece surface, and thus reducing the risk of the pole piece piercing the isolation membrane, which is beneficial to improving the battery DCR (direct current resistance), K value (voltage drop), and self-discharge. Moreover, the conductive agent in the pole piece is affected by the magnetic lines of force generated by the electromagnetic induction process, and the direction tends to be consistent, which is beneficial to further reduce the membrane resistance of the pole piece.

[0057] In addition, the electrode processing system of the embodiment of the present application can be integrated into the existing electrode production line. It only requires adding an electromagnetic induction heating unit to the existing electrode production line, without requiring a large amount of additional time and equipment, and the cost is low.

[0058] In some embodiments, the electrode has a dry active layer. A dry active layer refers to an active layer that is solvent-free, or has a very low solvent content, with the mass concentration of the solvent in the active layer being as low as ppm, such as less than 1000 ppm. There is floating binder on the surface of the dry active layer. The electromagnetic induction heating unit of the embodiment of the present application is used to perform electromagnetic induction heating on the electrode having the dry active layer, thereby treating the floating binder and improving the performance of the electrode.

[0059] In some embodiments, the electromagnetic induction heating unit includes an induction coil configured to generate alternating magnetic flux lines parallel to the pole pieces.

[0060] Among them, the induction coil, also known as the inductor coil, is an electrical component consisting of one or more coils, each of which is wound by a conductor. When current passes through the coil, a magnetic field is generated around it. The conductor wound into the coil is usually a copper wire or aluminum wire with good conductivity and corrosion resistance, or other metal wire, or metal sheet. In operation, the induction coil can generate alternating magnetic flux lines parallel to the pole piece by passing the pole piece through the inside of the induction coil. The inside of the induction coil refers to the internal hollow area formed by one or more coils that make up the induction coil. The pole piece passes through the inside of the induction coil, that is, the pole piece is placed in the hollow area inside the induction coil. The schematic diagram is shown in Figure 1. In Figure 1, 10 represents the pole piece and 22 represents the induction coil.

[0061] The induction coil of the embodiment of the present application generates alternating magnetic flux lines parallel to the pole piece, which can generate an induced alternating current of the same frequency in the pole piece. When the induced alternating current passes through the pole piece, these alternating currents will tend to flow through the surface of the pole piece when passing through the pole piece. The current density at the surface of the pole piece is relatively large, and the current density inside the pole piece is relatively small. The current is mainly concentrated on the surface of the pole piece. The closer to the surface of the pole piece, the greater the current density, resulting in a "skin effect". Through this skin effect, the surface of the pole piece can be quickly heated, and the surface temperature of the pole piece can be rapidly increased, which can ablate the floating adhesive, edge burrs, and edge particles. At the same time, since the pole piece is less affected by the magnetic lines of force of the alternating magnetic field and the current density is relatively small, the temperature rise of the current collector inside the pole piece is relatively small, which can improve the softening and deformation of the current collector due to high temperature and improve the bonding force between the active material in the pole piece and the current collector.

[0062] In some embodiments, the shape of the induction coil includes, but is not limited to, circular, square, rectangular, or other shapes.

[0063] In some embodiments, the maximum dimension of the induction coil's cross-section perpendicular to the pole piece is greater than or equal to the minimum dimension of the pole piece's surface. The minimum dimension on the pole piece's surface refers to the shortest distance between the pole pieces on the surface. Since pole pieces are typically rectangular, the minimum dimension on the pole piece's surface refers to the pole piece's width. This dimensional relationship allows the pole piece to pass smoothly through the induction coil, facilitating the induction coil's generation of alternating magnetic flux lines parallel to the pole piece.

[0064] In some embodiments, the electromagnetic induction heating unit includes an induction heating power supply, a resonant tank module, and a cooling module. The resonant tank module includes an induction coil. The induction heating power supply is connected to the resonant tank module, and the cooling module is connected to the resonant tank module. Generally, in an induction circuit, a circuit consisting of an inductor, a load, and a resonant capacitor is called a resonant tank. The inductor typically includes an induction coil; the inductor may also include a metal sleeve, and the induction coil may be wound around the outer surface of the metal sleeve or around the inner wall of the metal sleeve. The induction heating power supply provides power to the resonant tank module, and the cooling module is used to cool the resonant tank module.

[0065] In some embodiments, the electromagnetic induction heating unit further comprises an operating table, which refers to a control panel (including a panel and knobs for controlling parameters such as temperature, frequency, and power) that can facilitate adjustment of the heating parameters of the electromagnetic induction unit.

[0066] In some embodiments, the electrode processing system further includes a temperature measurement unit for measuring the electrode temperature. By providing the temperature measurement unit, the electrode temperature can be promptly and accurately determined, and the electrode status can be monitored. The temperature measurement unit can be used to measure both the surface temperature and the internal temperature of the electrode, or both simultaneously.

[0067] In some embodiments, the temperature measurement unit includes an infrared temperature measurement module, which can be used to measure the temperature of the electrode in a non-contact manner.

[0068] In some embodiments, the electrode processing system further includes an automatic temperature control unit, which is used to control the heating parameters (such as temperature, frequency, current, etc.) of the electromagnetic induction heating unit. The automatic temperature control unit can receive the temperature data of the electrode measured by the temperature measuring unit and control the heating parameters of the electromagnetic induction heating unit based on the data. The automatic temperature control unit may include an automatic control module, which includes several types such as a temperature control component, a frequency control component, and a current control component. The feedback mechanism of the automatic control module is to automatically control the heating parameters of the electromagnetic induction heating unit through the temperature of the electrode measured by the temperature measuring unit. The automatic temperature control unit can be connected to other units in the electrode processing system through a PLC (programmable logic controller).

[0069] For the electrode, the slurry evenly coated on the current collector contains a variety of binders, conductive agents and other additives. Binders, conductive agents and other additives may all be polymers. Different polymers have different softening and decomposition temperatures. Therefore, more precise temperature control can most effectively soften and decompose excess polymers in the electrode (for example, excess floating binder).

[0070] In the electrode processing system of the embodiment of the present application, by setting an automatic temperature control unit, the heating parameters of the electromagnetic induction heating unit can be controlled according to the temperature of the electrode. When the temperature of the electrode is too low, the heating power (or temperature, current) of the electromagnetic induction heating unit can be controlled to increase, thereby increasing the temperature of the electrode; when the temperature of the electrode is too high, the heating power (or temperature, current) of the electromagnetic induction heating unit can be controlled to decrease, thereby reducing the temperature of the electrode. In some cases, a high-precision infrared temperature measurement module is used as the temperature measurement component of the temperature measurement unit. Under the control of a high-precision automatic control unit, precise control of the temperature accuracy between ±3°C can be achieved. Therefore, the use of an automatic temperature control unit can accurately and flexibly control the temperature of the electrode, so that the temperature of the electrode is within a suitable range, thereby effectively softening and decomposing the excess binder in the electrode.

[0071] In some embodiments, the electrode processing system further includes a conveying unit for conveying the electrode. Under the action of the conveying unit, the electrode enters the electromagnetic induction heating unit and other processes in an orderly manner for processing, allowing for continuous and uninterrupted operation. The conveying unit may include an arranged unwinding guide roller and a winding guide roller, respectively used to unwind and rewind the electrode. Placing the electrode on the unwinding guide roller and the winding guide roller and operating the winding guide roller allows the electrode to be moved under the traction of the winding guide rail and pass through the interior of the induction coil of the electromagnetic induction heating unit. The running speed of the winding guide roller can be set to 10-100 m / min, optionally 40-80 m / min. For example, the running speed can include but is not limited to any point value among 10 m / min, 15 m / min, 20 m / min, 25 m / min, 30 m / min, 35 m / min, 40 m / min, 45 m / min, 50 m / min, 55 m / min, 60 m / min, 65 m / min, 70 m / min, 75 m / min, 80 m / min, 85 m / min, 90 m / min, 95 m / min, and 100 m / min, or a range of values ​​between any two points, or can be set to other running speeds according to actual needs. By adjusting the running speed, the processing time and processing efficiency of the pole piece under the electromagnetic induction heating unit can be adjusted.

[0072] In some embodiments, the electrode processing system further includes a drying unit, which is used to dry the electrode coated with the electrode slurry, and the drying unit and the electromagnetic induction heating unit are arranged in sequence in the conveying direction of the electrode. Among them, the electrode coated with the electrode slurry refers to the electrode in the intermediate state of not forming a film formed by coating the electrode slurry on the current collector (usually one surface or two surfaces of the current collector). At this time, the electrode slurry has not been dried and still contains a solvent. The drying unit and the electromagnetic induction heating unit are arranged in sequence in the conveying direction of the electrode, which means that the electrode first passes through the drying unit and then passes through the electromagnetic induction heating unit. After being processed by the drying unit, the solvent in the electrode slurry evaporates and dries, and at the same time, the binder in the electrode slurry migrates with the volatilization of the solvent and floats to the surface of the electrode. In this regard, these floating binders can be softened (melted) or ablated after being processed by the electromagnetic induction heating unit.

[0073] In some embodiments, the electrode processing system further includes a rolling unit for rolling the electrode sheets. The rolling unit and the electromagnetic induction heating unit are arranged sequentially in the direction of conveyance of the electrode sheets. Alternatively, the drying unit, the rolling unit, and the electromagnetic induction heating unit are arranged sequentially in the direction of conveyance of the electrode sheets. Rolling methods generally include cold pressing and hot pressing. Rolling can enhance the internal bonding strength of the electrode sheets and achieve the desired compaction density.

[0074] In some embodiments, the electrode processing system further includes a purge unit for purging the electrode; the purge unit and the electromagnetic induction heating unit are arranged sequentially in the direction of conveyance of the electrode. Purging the electrode before entering the electromagnetic induction heating unit can remove impurities on the electrode surface and optimize the electromagnetic induction heating effect.

[0075] In some embodiments, the electrode processing system further includes a cooling unit for cooling the electrode. The electromagnetic induction heating unit and the cooling unit are arranged sequentially in the direction of electrode transport. After the electrode is processed by the electromagnetic induction heating unit, it is usually necessary to reel the electrode. Excessively high electrode temperature is not conducive to reeling. Therefore, cooling the electrode by the cooling unit can reduce the electrode temperature and facilitate subsequent reeling of the electrode.

[0076] A second aspect of an embodiment of the present application provides a method for processing an electrode, which includes a current collector and an active layer, the active layer being arranged on at least one side of the current collector, and the active layer including a binder. The method for processing the electrode in an embodiment of the present application includes: performing electromagnetic induction heating treatment on the electrode, so that the surface temperature of the active layer is greater than or equal to the softening temperature or melting temperature of the binder, and the temperature of the current collector is less than the deformation temperature of the current collector.

[0077] In the pole piece, the current collector on the pole piece is used as an attachment base for the active layer and transmits electrons in the battery chemical reaction. The binder is a polymer compound used to bind the various components in the active layer (such as active substances and other substances) and the current collector to each other. It mainly plays the role of bonding and maintaining the firmness of the active substance in the active layer, enhancing the contact between the active layer and the current collector, and enhancing the contact between the various substances in the active layer. The binder is mixed with the active substance, solvent and other necessary components to form a slurry and coated on at least one side of the current collector. After the solvent evaporates, the slurry dries to form an active layer. During the drying process, the evaporation of the solvent makes it easy for the binder to migrate to the surface of the active layer, causing the binder to float and affect the electrochemical properties of the pole piece.

[0078] The surface of the active layer refers to the outermost layer of the active layer that contacts the outside world. Typically, a pole piece includes a current collector and an active layer disposed on at least one side of the current collector. Therefore, the surface of the active layer is usually also the surface of the pole piece. Generally, the area within 40% of the pole piece thickness, from the outside inward, along the thickness of the pole piece can be considered the pole piece surface.

[0079] The softening temperature is the temperature at which the three-dimensional long-range ordered state of the macromolecular chain structure of a non-crystalline polymer is transformed into a disordered viscous flow state. The melting temperature is the temperature at which the three-dimensional long-range ordered state of the macromolecular chain structure of a crystalline polymer is transformed into a disordered viscous flow state. It is also called the melting point and is the lower limit of the molding processing temperature of crystalline polymers. Generally, the melting temperature range is relatively narrow, while the softening temperature range is relatively wide. The decomposition temperature refers to the temperature at which the degradation of the molecular chain of a polymer in a viscous flow state is aggravated when the temperature is further increased, and even the polymer molecular chain is significantly degraded. The deformation temperature refers to the temperature at which the material can deform (including but not limited to elongation, shortening, bending, etc.) when heated.

[0080] In the method of the embodiment of the present application, the electrode is treated by electromagnetic induction heating. The active layer usually contains a conductive agent. When the conductive agent in the active layer is subjected to electromagnetic induction, heat is generated, thereby achieving electromagnetic induction heating of the active layer. During electromagnetic induction heating, the surface temperature of the active layer is greater than or equal to the softening temperature or melting temperature of the binder. At this temperature, the binder that floats to the surface of the active layer during the drying process of the electrode softens or melts, or even ablates. By softening (melting) and ablating, the binder floating on the surface of the active layer can be reduced. After the binder is ablated, pores are left in the active layer, thereby increasing the porosity of the electrode and thus increasing the electrolyte infiltration rate. At the same time, after softening (melting) and ablating the binder, various burrs and particles on the edge of the active layer can be improved, making the surface of the active layer smoother, reducing the sharpness of the electrode surface, and thus reducing the risk of the electrode piercing the isolation membrane, which is beneficial to improving the battery DCR (DC resistance), K value (voltage drop), and self-discharge. At the same time, the conductive agent contained in the active layer is affected by the magnetic lines of force generated by the electromagnetic induction process, and its direction tends to be consistent, which is beneficial to further reduce the diaphragm resistance of the pole piece.

[0081] In addition, after electromagnetic induction heating treatment, the temperature of the current collector is lower than the deformation temperature of the current collector, so it can improve the softening and deformation of the current collector due to high temperature, and maintain good adhesion and conductivity between the current collector and the active layer, which is beneficial to reduce the diaphragm resistance of the electrode and improve problems such as electrode burning and powder loss.

[0082] In some embodiments, the active layer further includes an active substance, and the surface temperature of the active layer is lower than the lowest temperature among the decomposition temperature, oxidation temperature, and ignition temperature of the active substance. The treatment temperature is lower than the lowest temperature among the decomposition temperature, oxidation temperature, and ignition temperature of the active substance, so that the active substance is not etched or decomposed, oxidized, or ignited, so that the active substance in the electrode can maintain lattice integrity, thereby improving the capacity of the electrode. Typically, the decomposition temperature, oxidation temperature, and ignition temperature of the active substance are very high. During the electromagnetic induction heating process, under the condition that the temperature of the current collector is lower than the deformation temperature of the current collector, the surface temperature of the active layer will also be lower than the lowest temperature among the decomposition temperature, oxidation temperature, and ignition temperature of the active substance.

[0083] In some embodiments, the electromagnetic induction heating step includes: passing the pole piece through the interior of the induction coil and applying an alternating current to the induction coil.

[0084] Among them, alternating current, that is, alternating current, refers to the current whose direction changes periodically with time.

[0085] The embodiment of the present application allows the pole piece to pass through the interior of the induction coil, and generates an alternating magnetic field after the induction coil passes through the alternating current, which can cause the induction coil to generate alternating magnetic flux lines parallel to the pole piece, thereby generating an induced alternating current of the corresponding frequency in the pole piece. When the induced alternating current passes through the pole piece, these alternating currents will tend to flow through the surface of the pole piece when passing through the pole piece. The current density at the surface of the pole piece is large, and the current density inside the pole piece is small. The current is mainly concentrated on the surface of the pole piece. The closer to the surface of the pole piece, the greater the current density, resulting in a "skin effect". This skin effect can rapidly heat the surface of the pole piece, causing the surface temperature of the pole piece to rise rapidly, and can ablate the floating adhesive, edge burrs, and edge particles. At the same time, since the current density inside the pole piece is small, the problem of softening, deformation, and stress of the current collector inside the pole piece caused by high temperature can be improved, thereby improving the bonding force between the active layer of the pole piece and the current collector.

[0086] At the same time, the pole piece passes through the inside of the induction coil, and there is only one set of induction coils above and below the pole piece, which reduces space bloat and improves the safety factor.

[0087] In some embodiments, the induction frequency of the electromagnetic induction heating process is greater than or equal to 5 kHz; in some embodiments, the induction frequency of the electromagnetic induction heating process is between 10 and 50 kHz; and in some embodiments, the induction frequency of the electromagnetic induction heating process is between 10 and 20 kHz. For example, the induction frequency of the electromagnetic induction heating process may include, but is not limited to, any of 5 kHz, 10 kHz, 15 kHz, 20 kHz, 25 kHz, 30 kHz, 35 kHz, 40 kHz, 45 kHz, and 50 kHz, or any range therebetween. The induction frequency of the electromagnetic induction heating process can typically be set directly within the electromagnetic induction heating device. The induction frequency of the electromagnetic induction heating process can be considered the output frequency of the induction coil after alternating current is applied to the induction coil. The induction coil generates an alternating magnetic field after the alternating current passes through the induction coil, and the frequency of the alternating current induced in the pole piece by this alternating magnetic field. The induction frequency of the electromagnetic induction heating process affects the depth of the induction heating process on the pole piece. At the induction frequency of the embodiments of the present application, sufficient induction heating of the pole piece active layer is achieved while minimal heating of the current collector within the pole piece, which helps maintain the adhesion and conductivity of the current collector to the active layer. The active layer is tightly integrated with the current collector, which is beneficial to the stability during the charge and discharge cycle (not easy to separate from the current collector) and improves the dynamic performance.

[0088] In some embodiments, the waveform of the alternating current includes one or more of a sine wave, a triangle wave, and a square wave. In the embodiment of the present application, alternating currents of various waveforms can be loaded into the induction coil to achieve electromagnetic induction heating of the electrode.

[0089] In some embodiments, the number of turns of the induction coil is 2 to 10; in some embodiments, the number of turns of the induction coil is 2 to 5. For example, the number of turns of the induction coil may include, but is not limited to, any one of 2, 3, 4, 5, 6, 7, 8, 9, and 10, or a range of values ​​between any two of them. The number of turns of the induction coil is an important factor affecting its performance. Generally, when the same current flows through, the more turns the induction coil has, the greater the induced magnetic field generated by the induction coil. Using an appropriate number of turns of the induction coil can not only meet the induction intensity requirements, but also save equipment costs and reduce resource waste.

[0090] In some embodiments, the shape of the induction coil includes, but is not limited to, circular, square, rectangular, or other shapes.

[0091] In some embodiments, the maximum dimension of the induction coil's cross-section perpendicular to the pole piece is greater than or equal to the minimum dimension of the pole piece surface. The minimum dimension on the pole piece surface refers to the shortest distance between the pole pieces on the surface. Since pole pieces are typically rectangular, the minimum dimension on the pole piece surface refers to the width of the pole piece. This dimensional relationship allows the pole piece to pass smoothly through the interior of the induction coil.

[0092] In some embodiments, the pole piece moves relative to the induction coil. The movement speed can be flexibly set as needed. As an example, the movement speed of the pole piece relative to the induction coil is 10 to 100 m / min, optionally 40 to 80 m / min. For example, the operating speed may include but is not limited to any point value of 10 m / min, 15 m / min, 20 m / min, 25 m / min, 30 m / min, 35 m / min, 40 m / min, 45 m / min, 50 m / min, 55 m / min, 60 m / min, 65 m / min, 70 m / min, 75 m / min, 80 m / min, 85 m / min, 90 m / min, 95 m / min, 100 m / min or any range value between two points. The pole piece can be placed on the unwinding guide roller and the winding guide roller, and the winding guide rail is used to pull the pole piece, so as to achieve the movement of the pole piece relative to the induction coil. By controlling the rotational speed of the unwinding and winding guide rollers, the speed of the pole piece's movement relative to the induction coil can be adjusted. By controlling the pole piece's movement relative to the induction coil, the processing time of the pole piece in the electromagnetic induction heating unit can be adjusted, thereby regulating the pole piece's temperature. Furthermore, the pole pieces can be processed in batches, increasing processing efficiency.

[0093] In some embodiments, the surface temperature of the active layer is 100-450°C; in some embodiments, the surface temperature of the active layer is 220-400°C. For example, the surface temperature of the active layer includes, but is not limited to, any point value among 100°C, 120°C, 140°C, 160°C, 180°C, 200°C, 220°C, 240°C, 260°C, 280°C, 300°C, 320°C, 340°C, 360°C, 380°C, 400°C, 420°C, and 450°C, or a range of values ​​between any two of them. The surface temperature of the active layer can be measured by an infrared temperature measurement module or other temperature tester. When the surface of the active layer reaches these temperature ranges, the adhesive on the surface of the electrode can be softened (melted) or even ablated. At the same time, after the heat reaches the internal current collector through heat transfer, the temperature of the current collector will be lower than its deformation temperature.

[0094] In some embodiments, the thickness of the pole piece before electromagnetic induction heating is 50 to 300 μm; in other embodiments, the thickness of the pole piece before electromagnetic induction heating is 50 to 200 μm. For example, the thickness of the pole piece may include, but is not limited to, any one of 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 150 μm, 200 μm, 250 μm, and 300 μm, or a range of values ​​between any two of them. Generally, the thickness of the pole piece can be measured using a micrometer, a laser thickness gauge, a thickness scanning thickness gauge, or the like. The frequency and power of the alternating current applied to the induction coil, as well as the induction frequency of the electromagnetic induction heating treatment, affect the depth of action on the pole piece. The method of the embodiment of the present application can process pole pieces of different thicknesses, and can flexibly adjust electromagnetic induction conditions such as the alternating current frequency, power, and induction frequency to perform induction heating treatment on the active layer in pole pieces of different thicknesses without affecting the current collector inside the pole piece.

[0095] In some embodiments, before electromagnetic induction heating, the surface density of the active layer is 0.05 to 0.6 mg / mm 2 In some embodiments, before electromagnetic induction heating, the surface density of the active layer is 0.1 to 0.5 mg / mm 2 For example, the surface density of the active layer may include but is not limited to 0.05 mg / mm 2 , 0.1mg / mm 2 , 0.15mg / mm 2 , 0.2mg / mm 2 , 0.25mg / mm 2 , 0.3mg / mm 2 , 0.35mg / mm 2 , 0.4mg / mm 2 , 0.45mg / mm 2 , 0.5mg / mm 2 , 0.55mg / mm 2 , 0.6mg / mm 2 Any point value in or the range value between any two. Surface density refers to the mass of the active electrode coating per unit area, which can be obtained by testing with an X / β-ray surface density meter. Surface density mainly affects the internal resistance and capacity of the electrode. Generally, within a certain range, the internal resistance of the electrode decreases with the increase of surface density. Increasing the surface density of the electrode helps to reduce the internal resistance of the electrode, thereby improving the capacity of the electrode. The active layer of the embodiment of the present application has a suitable surface density, and the electrode has low internal resistance and high capacity.

[0096] In some embodiments, the binder includes one or more of an oil-soluble binder, a water-soluble binder, and an emulsion-type binder.

[0097] In some embodiments, the oil-soluble binder includes one or more of polyvinylidene fluoride, polyimide, polytetrafluoroethylene, polybutyl acrylate, and polyacrylonitrile.

[0098] In some embodiments, the water-soluble binder includes one or more of carboxymethyl cellulose, carboxymethyl cellulose salt, polyacrylic acid, polyacrylic acid salt, polyvinyl alcohol, sodium alginate, and cyclodextrin.

[0099] In some embodiments, the emulsion binder includes one or more of styrene-butadiene rubber, vinyl acetate resin, acrylic resin, and chlorinated rubber.

[0100] Depending on the type of active material in the electrode, different binders can be selected, and the appropriate treatment temperature can be determined based on the softening temperature or melting temperature, or decomposition temperature of the binder. For example, polyvinylidene fluoride (PVDF) or polyimide (PI) is selected as the binder, and the surface temperature of the active layer in the electromagnetic induction heating treatment can be set to 160-400°C, more specifically 300-400°C, including but not limited to any one of 160°C, 180°C, 200°C, 220°C, 240°C, 260°C, 280°C, 300°C, 320°C, 340°C, 360°C, 380°C, and 400°C. Or a range value between any two; for example, when styrene-butadiene rubber is selected as the binder, the surface temperature of the active layer in the electromagnetic induction heating treatment can be set to 180-350°C, more specifically to 250-300°C, including but not limited to any one of 180°C, 200°C, 220°C, 240°C, 250°C, 260°C, 280°C, 300°C, 320°C, 340°C, and 350°C, or a range value between any two.

[0101] In some embodiments, the mass content of the binder in the active layer includes but is not limited to 0.5% to 10%, such as 1% to 5%, for example, any one of 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10% or a range between any two of them, and can also be set to other contents as needed.

[0102] In some embodiments, the electrode sheet includes either or both of a positive electrode sheet and a negative electrode sheet. Both positive and negative electrode sheets experience the phenomenon of binder floating during drying. The methods of the present invention are applicable to both positive and negative electrode sheets.

[0103] In some embodiments, the electrode is a positive electrode, and the active material includes one or more of a metal inorganic active material and an organic active material.

[0104] In some embodiments, the metal inorganic active material includes one or more of lithium iron phosphate, lithium manganese iron phosphate, lithium cobalt oxide, lithium manganese oxide, nickel cobalt lithium manganese iron, and lithium nickel cobalt aluminum oxide.

[0105] In some embodiments, the organic active material includes one or more of quinone compounds, carboxylate compounds, anhydride compounds, and amide compounds.

[0106] In some embodiments, the electrode is a negative electrode, and the active material includes one or more of a carbon-based active material, a titanium-based active material, a silicon-based active material, a nitride, and metallic lithium.

[0107] In some embodiments, the carbon-based material includes one or more of graphite, hard carbon, soft carbon, mesocarbon microbeads, and graphene.

[0108] In some embodiments, the titanium-based active material includes one or more of lithium titanate and titanium dioxide.

[0109] In some embodiments, the silicon-based active material includes one or more of silicon, silicon dioxide.

[0110] In some embodiments, the nitride comprises lithium nitride.

[0111] In some embodiments, the mass content of the active substance in the active layer includes but is not limited to 90% to 98%, such as 95% to 98%, for example, any point value of 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or a range value between any two of them, and can also be set to other contents as needed.

[0112] In some embodiments, the active layer also includes a conductive agent. This agent is used to collect microcurrents between the active materials and between the active materials and the current collector, improving electronic conductivity. It also promotes electrolyte wetting of the positive electrode. The conductive agent is influenced by the magnetic lines of force generated by electromagnetic induction, aligning their direction and further reducing the electrode sheet resistance.

[0113] In some embodiments, the conductive agent includes one or more of acetylene black (SP), carbon nanotubes, conductive carbon black (super-P), Ketjen black, carbon fiber, and graphene. The conductive agent is influenced by the magnetic lines of force generated by the electromagnetic induction process and tends to align in direction, which helps further reduce the diaphragm resistance of the electrode.

[0114] In some embodiments, the mass content of the conductive agent in the active layer includes but is not limited to 0.5% to 10%, such as 1% to 5%, for example, any one of 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10% or a range between any two of them, and can also be set to other contents as needed.

[0115] In some embodiments, the current collector includes, but is not limited to, a metal current collector, a carbon current collector, a conductive resin current collector, a metal-resin composite current collector, and more specifically, copper, nickel, titanium, iron, and their respective alloys, stainless steel, carbon fiber, carbon nanotubes (CNTs), graphite, etc. During the electromagnetic induction heating process, due to the skin effect and the control of the electromagnetic induction heating conditions, the current collector is not or is rarely subjected to electromagnetic induction, and its temperature change is small, so that the current collector can maintain good adhesion and conductivity with the active layer.

[0116] In some embodiments, the active layer may further include a thickener, such as carboxymethyl cellulose (CMC). The mass content of the thickener in the active layer includes, but is not limited to, 0.5% to 5%, such as 1% to 5%, including but not limited to any one of 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, and 5%, or a range between any two of these, and may also be set to other content as needed.

[0117] In some embodiments, the step of drying the active layer is included before the electromagnetic induction heating step. In the manufacturing process of the pole piece, the active material is generally mixed with a binder, a conductive agent, a solvent and other necessary components to form a slurry, and the slurry is coated on the current collector and dried to form an active layer. Usually, after the drying process, a molding step is also included, such as cold pressing the pole piece. During the drying process, the solvent evaporates, and the binder will also migrate to the surface of the active layer, resulting in the phenomenon of binder floating, which in turn leads to various problems that are not conducive to the electrochemical performance of the pole piece. The method of the embodiment of the present application performs electromagnetic induction heating on the pole piece after drying, which can solve the problem of binder floating during the drying process and improve the electrochemical performance of the pole piece.

[0118] In some embodiments, the electrode sheet is subjected to a roll pressing step prior to the electromagnetic induction heating step. Roll pressing methods typically include cold pressing and hot pressing. Roll pressing can enhance the internal bonding strength of the electrode sheet and achieve the desired compaction density. The roll pressing step can be performed after the drying step and before the electromagnetic induction heating step.

[0119] In some embodiments, after the electromagnetic induction heating step, a cooling step is included for the electrode. Cooling methods include, but are not limited to, air cooling and circulating water cooling. After the electrode is heated by the electromagnetic induction heating unit, it is usually necessary to reel the electrode. Excessively high electrode temperature is not conducive to reeling. Therefore, cooling the electrode by the cooling unit can reduce the electrode temperature and facilitate subsequent reeling.

[0120] A third aspect of an embodiment of the present application provides a pole piece, which is obtained by processing according to the above method.

[0121] In the pole piece obtained by the above-mentioned treatment method, the floating binder is softened (melted) and ablated, thereby reducing the floating binder; at the same time, the binder is softened (melted) and ablated, leaving pores in the active layer, thereby increasing the pole piece porosity, and then increasing the electrolyte infiltration rate; various burrs and particles on the edge of the pole piece are improved, and the pole piece surface becomes smoother and less sharp, thereby reducing the risk of the pole piece piercing the isolation membrane; in addition, the conductive agent in the active layer is affected by the magnetic lines of force generated by the electromagnetic induction process, and the direction tends to be consistent, which is conducive to further reducing the diaphragm resistance of the pole piece; the above properties are all conducive to improving the battery DCR, K value, and self-discharge.

[0122] In some embodiments, after using a 0.3 mm capillary to absorb 3 mm high electrolyte, it is vertically contacted with the electrode of the embodiment of the present application so that the electrode absorbs the electrolyte. The time for the electrode to absorb the electrolyte is less than 20 seconds, optionally 3 to 15 seconds, including but not limited to any one of 1s, 2s, 3s, 4s, 5s, 6s, 7s, 8s, 9s, 10s, 11s, 12s, 13s, 14s, 15s, 16s, 17s, 18s, 19s, and 19.8s, or a range of values ​​between any two of them. Alternatively, after using a 0.3mm capillary to absorb 3mm of electrolyte, it is brought into vertical contact with the electrode of the embodiment of the present application, so that the electrode absorbs the electrolyte. The time for the electrode to absorb the electrolyte is shortened by 15% or more compared to before the electromagnetic induction heating treatment, optionally shortened by 45% or more, optionally shortened by 45% to 90%, and optionally shortened by 47% to 87%, including but not limited to any one of 15%, 20%, 25%, 30%, 35%, 40%, 45%, 47%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 87%, and 90%, or a range of values ​​between any two of them. The electrode of the embodiment of the present application has a high porosity, which makes it have a fast absorption rate for the electrolyte and a short absorption time.

[0123] In some embodiments, the electrode sheet of the embodiments of the present application has a sheet resistance reduced by 20% or more, and optionally by 20% to 60%, compared to before electromagnetic induction heating treatment, including but not limited to any of 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, and 60%, or any range therebetween. After electromagnetic induction heating, the conductive agent in the active layer is affected by the magnetic lines of force generated by the electromagnetic induction process, and their direction tends to be consistent, which helps further reduce the sheet resistance of the electrode sheet.

[0124] In some embodiments, the K value of the pole piece of the embodiment of the present application is reduced compared to that before the electromagnetic induction heating treatment; optionally, the K value of the pole piece is reduced by 5% or more compared to that before the electromagnetic induction heating treatment; optionally, it is reduced by 10% or more, including but not limited to any point value of 5%, 15%, 20%, 25%, 30% or any range value between two of them. The K value is the voltage drop of the battery per unit time, which represents the self-discharge performance of the battery. After the pole piece of the embodiment of the present application is subjected to electromagnetic induction heating treatment, its infiltration speed into the electrolyte is increased, the membrane resistance is reduced, and the pole piece surface becomes smooth, thereby reducing the risk of the pole piece piercing the isolation membrane, and ultimately reducing the K value of the battery and improving the self-discharge performance of the battery.

[0125] A fourth aspect of an embodiment of the present application provides a battery, which includes the above-mentioned electrode.

[0126] The battery of the embodiment of the present application includes the above-mentioned pole piece, which can be either a positive pole piece or a negative pole piece, or can include both a positive pole piece and a negative pole piece. Since the floating binder in the pole piece of the battery is softened (melted) and ablated, the floating binder is reduced; the pores in the pole piece are enriched due to the softening (melting) and ablation of the binder, and the porosity is higher, which is beneficial to improving the electrolyte infiltration rate; the various burrs and particles on the edge of the pole piece are improved, and the surface of the pole piece becomes smoother and less sharp, thereby reducing the risk of the pole piece piercing the isolation membrane, which is beneficial to improving the battery DCR, K value, and self-discharge. In addition, the conductive agent in the active layer is affected by the magnetic lines of force generated by the electromagnetic induction process, and the direction tends to be consistent, which is beneficial to further reduce the membrane resistance of the pole piece. Therefore, the battery containing the above-mentioned pole piece has better DCR, K value, and self-discharge performance.

[0127] In some embodiments, the battery of the present invention includes one or more primary batteries and secondary batteries. Batteries can be divided into primary batteries and secondary batteries based on whether they can be recharged and reused. Primary batteries cannot be recharged to restore their original state after discharge, while secondary batteries can be recharged to activate their active materials and continue to be used after discharge. The electrode of the present invention can be applied to both primary and secondary batteries, thus having a wide range of applications.

[0128] In some embodiments, the battery of the embodiments of the present application includes one or more of a battery cell, a battery module, and a battery pack. In the case where the battery is a secondary battery, the secondary battery is divided into a battery cell, a battery module, and a battery pack according to the different packaging forms. Among them, the battery cell is the most basic unit of a secondary battery, including an electrode assembly and an electrolyte. The electrode assembly is usually composed of a positive electrode sheet, a negative electrode sheet, and an insulator. The battery cell mainly relies on the movement of metal ions in the electrolyte between the positive electrode sheet and the negative electrode sheet to work. In some battery packaging technologies, one or more battery cells can be integrated into a battery module first, and then one or more battery modules can be installed in the battery box to form a battery pack. In other battery packaging technologies, one or more battery cells can also be directly installed in the box to form a battery pack, eliminating the intermediate state of the battery module, thereby reducing the mass of the battery pack and increasing the energy density of the battery.

[0129] In some embodiments, the battery further comprises an electrolyte, which can serve as a carrier for ion transport in the battery.

[0130] In some embodiments, the electrolyte may be an electrolyte solution, which may include a solvent and a lithium salt dissolved in the solvent. The electrolyte may also include a solid electrolyte, such as a polymer electrolyte, an inorganic solid electrolyte, etc., but is not limited thereto.

[0131] The solvent in the electrolyte may be a non-aqueous organic solvent, such as one or more of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB) and ethyl butyrate (EB).

[0132] The lithium salt may be one or more of LiPF6 (lithium hexafluorophosphate), LiBF4 (lithium tetrafluoroborate), LiClO4 (lithium perchlorate), LiAsF6 (lithium hexafluoroarsenate), LiFSI (lithium bis(fluorosulfonyl imide), LiTFSI (lithium bis(trifluoromethanesulfonyl imide), LiTFS (lithium trifluoromethanesulfonyl imide), LiDFOB (lithium difluorooxalatoborate), LiBOB (lithium bis(oxalatoborate), LiPO2F2 (lithium difluorophosphate), LiDFOP (lithium difluorooxalatophosphate) and LiTFOP (lithium tetrafluorooxalatophosphate), for example, one or more of LiPF6 (lithium hexafluorophosphate), LiBF4 (lithium tetrafluoroborate), LiBOB (lithium bis(oxalatoborate), LiDFOB (lithium difluorooxalatoborate), LiTFSI (lithium bis(trifluoromethanesulfonyl imide)) and LiFSI (lithium bis(fluorosulfonyl imide).

[0133] The electrolyte may also optionally contain other additives, such as vinylene carbonate (VC), vinyl ethylene carbonate (VEC), fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), trifluoromethylethylene carbonate (TFPC), succinonitrile (SN), adiponitrile (ADN), glutaronitrile (GLN), hexanetrinitrile (HTN), 1,3-propane sultone (1,3-PS), vinyl sulfate (DTD), methylene disulfonate (MMDS), 1-propylene-1,3-sultone (PST), 4-methylethylene sulfate (PCS), 4-ethylethylene sulfate (PES), 4-propylethylene sulfate (PEGLST), propylene sulfate (TS), 1,4-butane sultone (1,4-BS), ethylene sulfite (DTO), dimethyl sulfite (DMS), diethyl sulfite (DES), sulfonate cyclic quaternary ammonium salt, tris(trimethylsilyl) phosphate (TMSP) and tris(trimethylsilyl) borate (TMSB), but are not limited thereto.

[0134] In some embodiments, the battery further includes a separator stacked between the positive electrode and the negative electrode. In some batteries, a separator is required to separate the positive and negative electrodes, preventing electrons from freely passing through the battery and short-circuiting the electrodes while allowing ions in the electrolyte to pass freely between the positive and negative electrodes.

[0135] The diaphragm can be any known porous structure separator with electrochemical stability and mechanical stability, such as single-layer or multi-layer films of one or more of glass fiber, non-woven fabric, polyethylene (PE), polypropylene (PP) and polyvinylidene fluoride (PVDF).

[0136] The positive and negative electrode sheets are alternately stacked, and a separator is placed between the positive and negative electrode sheets to act as an isolation film to obtain a bare cell, or a bare cell obtained by winding. The cell is placed in a casing, injected with electrolyte, and sealed to obtain a battery cell. Multiple battery cells are first integrated to form a battery module, which can provide higher voltage and capacity and have a specific functional output; the battery module is then installed in the battery box, and a battery management system is usually added to form a battery pack, which is usually a product provided to users. Alternatively, multiple battery cells can be directly installed in the box to form a battery pack.

[0137] Referring to Figure 5 , an example battery module 4 is shown. Within the battery module 4 , multiple battery cells 5 may be arranged sequentially along the length of the battery module 4 . Alternatively, the arrangement may be arranged in any other manner. Furthermore, the multiple battery cells 5 may be secured together using fasteners.

[0138] Optionally, the battery module 4 may further include a housing having an accommodation space, and the plurality of battery cells 5 are accommodated in the accommodation space.

[0139] Refer to Figures 6 and 7 , which illustrate an example battery pack 1. The battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box comprises an upper case 2 and a lower case 3. The upper case 2 can be positioned over the lower case 3 to form an enclosed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0140] In some embodiments, the battery may include an outer packaging that can be used to encapsulate the electrode assembly consisting of the positive electrode sheet, the negative electrode sheet, the separator, and the electrolyte.

[0141] The battery outer packaging can be a hard shell, such as a hard plastic shell, aluminum shell, or steel shell; or a soft shell, such as a pouch-type soft shell. The soft shell can be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0142] The shape of the battery can be cylindrical, square or any other shape. For example, FIG8 is an example of a square battery.

[0143] In some embodiments, referring to FIG9 , the outer packaging may include a housing 51 and a cover plate 53 . The housing 51 may include a bottom plate and side plates connected to the bottom plate, which together form a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 can be positioned over the opening to seal the receiving cavity. The positive electrode sheet, the negative electrode sheet, and the separator may be wound or laminated to form an electrode assembly 52 . One or more electrode assemblies 52 are encapsulated within the receiving cavity. Electrolyte is infiltrated into the electrode assembly 52 .

[0144] An embodiment of the present application further provides an electrical device, which includes the above-mentioned battery.

[0145] The battery disclosed in the embodiments of the present application can be used in electrical devices that use batteries as power sources, or various energy storage systems that use batteries as energy storage elements to provide electrical energy. Electrical devices may include but are not limited to mobile phones, tablets, laptops, electric toys, power tools, battery cars, electric cars, ships, spacecraft, and the like. Among them, electric toys may include fixed or mobile electric toys, for example, game consoles, electric car toys, electric ship toys, and electric airplane toys, and the like, and spacecraft may include airplanes, rockets, space shuttles, and spacecraft, and the like. As the electrical device, a battery cell, a battery module, or a battery pack in the battery can be selected according to its usage requirements.

[0146] Figure 10 shows an example of an electric device. This device can be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the battery, a battery pack or battery module can be used.

[0147] The following describes the details in conjunction with specific embodiments.

[0148] Example 1

[0149] This embodiment provides a pole piece processing system. Referring to FIG2 , the pole piece processing system of this embodiment includes: a drying unit for drying the pole piece 10 (the drying unit is not shown in FIG2 ); an electromagnetic induction heating unit 20 for performing electromagnetic induction heating on the pole piece 10; and a conveying unit 30 for conveying the pole piece 10. The conveying unit 30 includes an unwinding guide roller 31 and a winding guide roller 32. The drying unit and the electromagnetic induction heating unit 20 are arranged sequentially in the conveying direction of the pole piece 10 (direction D in FIG2 ).

[0150] The electromagnetic induction heating unit 20 includes an induction heating power supply (not shown in FIG2 ), a resonant tank module (not shown in FIG2 ), and a cooling unit (not shown in FIG2 ). The resonant tank module includes a metal sleeve 21 and an induction coil 22 wound around the outer surface of the metal sleeve 21. The induction coil 22 has three turns. The pole piece 10 passes through the interior of the induction coil 22. The induction heating power supply is connected to the resonant tank module to provide electrical energy to the resonant tank module. The cooling unit is connected to the resonant tank module to cool the resonant tank module.

[0151] In this embodiment, the electrode processing system further includes a temperature measuring unit 40 for measuring the temperature of the electrode 10. The temperature measuring unit 40 in this embodiment includes an infrared temperature measuring module, which implements non-contact temperature measurement of the electrode 10 by means of infrared temperature measurement.

[0152] In this embodiment, the electrode processing system further includes an automatic temperature control unit (not shown in FIG. 2 ), which is used to control the heating power of the electromagnetic induction heating unit 20 according to the temperature of the electrode 10 measured by the temperature measuring unit 40 .

[0153] In this embodiment, the pole piece processing system further includes a purge unit 50 , which is used to purge the pole piece 10 before the pole piece 10 enters the electromagnetic induction heating unit 20 to remove impurities on the surface of the pole piece 10 .

[0154] The working process of the electrode processing system of this embodiment is as follows:

[0155] The electrode slurry is applied to the current collector and dried in a drying unit (which may also undergo a cold pressing process after drying), forming a pole piece 10 having a dried active layer. The pole piece 10 is then transported by a transport unit 30 and passed through the interior of the induction coil 22 in the electromagnetic induction heating unit 20. An induction heating power supply applies an alternating current to the induction coil 22, thereby electromagnetically heating the pole piece 10. During the electromagnetic induction heating process, the temperature measurement unit 40 monitors the temperature of the pole piece 10 in real time. Simultaneously, the automatic temperature control unit receives the temperature data of the pole piece 10 measured by the temperature measurement unit 40 and, based on this data, adjusts the heating power of the electromagnetic induction heating unit 20 to the pole piece 10, maintaining the temperature of the pole piece 10 within the desired temperature range.

[0156] Example 2

[0157] This embodiment provides a method for processing a negative electrode plate, specifically, processing the negative electrode plate in the plate processing system in embodiment 1.

[0158] The negative electrode plate of this embodiment is a graphite plate, and its preparation method includes: mixing 95wt% of the negative electrode active material artificial graphite, 1.0wt% of conductive carbon black, 2.0wt% of styrene-butadiene rubber (SBR), and 2.0wt% of sodium carboxymethyl cellulose (CMC), adding deionized water, stirring, and dispersing to form a negative electrode slurry. Then, the negative electrode slurry is coated on Cu foil, and after both sides are completed, it is dried at 90-110℃ and cold pressed to obtain a total CW = 160mg / 1540.25mm 2 , a dry negative electrode sheet with a thickness of 70μm and a membrane area width of 105mm. The active layer of the negative electrode sheet is formed after the negative electrode slurry is dried.

[0159] The method for processing the negative electrode sheet in this embodiment includes:

[0160] (1) Place the cold-pressed negative electrode sheet on the unwinding guide roller 31 and the winding guide roller 32 of the electrode sheet processing system of Example 1 as shown in FIG2 , and pass the negative electrode sheet through the interior of the induction coil 22 ;

[0161] (2) The speed of the winding guide roller 32 is set to 80 m / min. The negative electrode plate passes through the induction coil under the traction of the winding guide roller 32. The induction coil is loaded with an alternating current to start electromagnetic induction heating of the negative electrode plate. The induction frequency of the electromagnetic induction heating process is 15 kHz. During the electromagnetic induction heating process, the automatic temperature control unit of the plate processing system is used to control the static temperature monitoring to 450°C (by controlling the current knob), and the power remains unchanged thereafter. The static temperature refers to the surface temperature of the plate when it is stationary (i.e., the temperature of the plate surface when the winding guide roller speed is 0).

[0162] During the treatment process, the surface temperature of the active layer of the negative electrode plate and the internal temperature of the plate (i.e., the temperature of the current collector) under stable operation are shown in Table 1.

[0163] Example 3

[0164] This embodiment provides a method for processing a negative electrode sheet. The only difference from Embodiment 2 is that the speed of the winding guide roller 32 is 60 m / min, and the remaining steps are the same as those in Embodiment 2.

[0165] During the treatment process, the surface temperature of the active layer of the negative electrode sheet and the temperature of the current collector under the stable operation state are shown in Table 1.

[0166] Example 4

[0167] This embodiment provides a method for processing a negative electrode sheet. The only difference from Embodiment 2 is that the speed of the winding guide roller 32 is 40 m / min, and the remaining steps are the same as those in Embodiment 2.

[0168] During the treatment process, the surface temperature of the active layer of the negative electrode sheet and the temperature of the current collector under the stable operation state are shown in Table 1.

[0169] Example 5

[0170] This comparative example provides a method for treating a negative electrode sheet, the only difference from Example 2 being that the induction frequency of the electromagnetic induction heating treatment is changed to 5 kHz. The remaining steps are the same as in Example 2.

[0171] During the treatment process, the surface temperature of the active layer of the negative electrode sheet and the temperature of the current collector under the stable operation state are shown in Table 1.

[0172] Example 6

[0173] This embodiment provides a method for processing a negative electrode sheet. The only difference from Example 2 is that the induction frequency of the electromagnetic induction heating treatment is 10 kHz, and the remaining steps are the same as those in Example 2.

[0174] During the treatment process, the surface temperature of the active layer of the negative electrode sheet and the temperature of the current collector under the stable operation state are shown in Table 1.

[0175] Example 7

[0176] This embodiment provides a method for processing a positive electrode sheet, which differs from embodiment 2 in that:

[0177] 1) Replace the negative electrode with a positive electrode. The positive electrode of this embodiment is a lithium iron phosphate battery electrode. The preparation method includes: selecting lithium iron phosphate as the positive electrode active material, dispersing it with conductive carbon black SP and polyvinylidene fluoride PVDF in a mass ratio of 96wt%, 2wt%, and 2wt% in N-methylpyrrolidone NMP, and coating it on both sides of aluminum foil in sequence, and then drying and cold pressing at 100-120℃ to finally obtain CW=324mg / 1540.25mm 2 , a dry positive electrode sheet with a thickness of 100μm and a membrane area width of 100mm.

[0178] 2) The induction frequency of the electromagnetic induction heating treatment was adjusted to 20 kHz.

[0179] 3) Adjust the static temperature to 500°C.

[0180] During the treatment process, the surface temperature of the active layer of the positive electrode sheet and the temperature of the current collector under the stable operation state are shown in Table 1.

[0181] Example 8

[0182] This embodiment provides a method for processing a positive electrode sheet. The only difference from Embodiment 7 is that the speed of the winding guide roller 32 is 60 m / min, and the remaining steps are the same as those in Embodiment 7.

[0183] During the treatment process, the surface temperature of the active layer of the positive electrode sheet and the temperature of the current collector under the stable operation state are shown in Table 1.

[0184] Example 9

[0185] This embodiment provides a method for processing a positive electrode sheet. The only difference from Example 7 is that the speed of the winding guide roller 32 is 40 m / min, and the remaining steps are the same as Example 7.

[0186] During the treatment process, the surface temperature of the active layer of the positive electrode sheet and the temperature of the current collector under the stable operation state are shown in Table 1.

[0187] Comparative Example 1

[0188] This comparative example provides a negative electrode sheet, which is produced using a normal process and obtained by cold pressing. Specifically, the preparation method of the negative electrode sheet of this comparative example includes: mixing 95wt% of the negative electrode active material artificial graphite, 1.0wt% of conductive carbon black, 2.0wt% of styrene-butadiene rubber SBR and 2.0wt% of sodium carboxymethyl cellulose CMC, adding deionized water and stirring, and dispersing to form a negative electrode slurry. Then, the negative electrode slurry is coated on Cu foil. After both sides are completed, it is dried and cold pressed to obtain a total CW = 160mg / 1540.25mm 2 , a negative electrode sheet with a thickness of 70μm and a membrane area width of 105mm.

[0189] Comparative Example 2

[0190] This comparative example provides a positive electrode sheet, which is produced by a normal process and obtained by cold pressing. Specifically, the preparation method of the positive electrode sheet of this comparative example includes: selecting lithium iron phosphate as the positive electrode active material, dispersing it with conductive carbon black SP and polyvinylidene fluoride PVDF in a mass ratio of 96wt%, 2wt%, and 2wt% in N-methylpyrrolidone NMP, and coating it on both sides of aluminum foil in sequence, and then drying and cold pressing, finally obtaining CW=324mg / 1540.25mm 2 , the positive electrode sheet has a thickness of 100μm and a membrane area width of 100mm.

[0191] Comparative Example 3

[0192] This comparative example provides a method for processing a negative electrode sheet. The only difference from Example 2 is that the induction frequency of the electromagnetic induction heating treatment is 25 kHz, and the remaining steps are the same as those in Example 2.

[0193] During the treatment process, the surface temperature of the active layer of the negative electrode sheet and the temperature of the current collector under the stable operation state are shown in Table 1.

[0194] Comparative Example 4

[0195] This comparative example provides a method for treating a negative electrode sheet, the only difference from Example 2 being that the induction frequency of the electromagnetic induction heating treatment is changed to 30 kHz. The remaining steps are the same as in Example 2.

[0196] During the treatment process, the surface temperature of the active layer of the negative electrode plate and the temperature of the current collector under stable operation are shown in Table 1. During the treatment, it was found that the electrode was burned and powdered, and could not be used for battery assembly or electrochemical performance testing.

[0197] Comparative Example 5

[0198] This comparative example provides a method for processing a negative electrode pole piece. This method differs from Example 2 in that the negative electrode pole piece does not pass through the interior of the induction coil 22. Instead, the induction coil 22 is placed on top of the negative electrode pole piece, with the negative electrode pole piece and the induction coil 22 positioned perpendicular to each other, as shown in FIG3 . In this case, the magnetic lines of force generated by the alternating current applied to the negative electrode pole piece and the induction coil 22 are perpendicular.

[0199] The other steps are the same as those in Example 2.

[0200] During the treatment process, the surface temperature of the active layer of the negative electrode plate and the temperature of the current collector under stable operation are shown in Table 1. During the treatment, it was found that the electrode was burned and powdered, and could not be used for battery assembly or electrochemical performance testing.

[0201] Comparative Example 6

[0202] This comparative example provides a method for treating a negative electrode sheet. The difference from Example 2 is that this comparative example uses corona treatment to treat the surface of the negative electrode sheet. The specific steps are as follows:

[0203] The cold-pressed negative electrode sheet is placed on the unwinding guide roller 31 and the winding guide roller 32 of the electrode sheet processing system as shown in Figure 2. The electromagnetic induction heating unit 20 is removed, and the negative electrode sheet is surface treated using an inductively coupled plasma device. The surface treatment parameters are: voltage of 50V, current of 100mA, reaction chamber pressure of 20Pa, gas flow rate of 1L / min, treatment atmospheres of oxygen and methyl methacrylate, and treatment speed of 80m / min (speed of the winding guide roller).

[0204] The electrode processing conditions of Examples 2 to 9 and Comparative Examples 1 to 6 are shown in Table 1. The electrode processing conditions of Examples 2 to 9 and Comparative Examples 1 to 6 were shown in Table 1. The electrode processing conditions of Examples 2 to 9 and Comparative Examples 1 to 6 were shown in Table 2. The electrode processing conditions of Examples 2 to 9 and Comparative Examples 1 to 6 were shown in Table 2.

[0205] Table 1. Pole processing conditions of various embodiments and comparative examples

[0206] Table 2. Pole performance test results of various embodiments and comparative examples

[0207] The data in Table 2 were processed to obtain the change rates of the liquid absorption rate, membrane resistance, K value, etc. of the electrode pieces after treatment in each embodiment and comparative example compared with the electrode pieces without treatment, as shown in Table 3.

[0208] Table 3. Change rate of pole piece performance of each embodiment and comparative example

[0209] In Table 1, "Active Layer Surface Temperature" and "Current Collector Temperature" refer to the surface temperature of the active layer and current collector, respectively, when the electrode is pulled by the winding guide rollers in the operating state. Typically, the surface temperature of the active layer is equivalent to the surface temperature of the electrode. During operation, the surface temperature of the active layer is lower than the static temperature. "Pole Plate Positioning" indicates the position of the electrode relative to the induction coil. "Through" indicates that the electrode passes through the interior of the induction coil; "Perpendicular" indicates that the electrode is perpendicular to the induction coil, rather than passing through it.

[0210] In Table 3, the change rates of Examples 2 to 6 and Comparative Examples 3 and 6 are the change rates compared with Comparative Example 1, and the change rates of Examples 7 to 9 are the change rates compared with Comparative Example 2.

[0211] From Table 2 and Table 3 we can see that:

[0212] (1) The electrode pieces after electromagnetic induction heating treatment in Examples 2 to 9 have a very high liquid absorption rate. The liquid absorption time of the negative electrode pieces in Examples 2 to 6 can be reduced by 77.22% compared to the comparative example 1 that has not been subjected to electromagnetic induction heating treatment, that is, the liquid absorption rate can be increased by 77.22% compared to the comparative example 1 that has not been subjected to electromagnetic induction heating treatment; and the liquid absorption time of the positive electrode pieces in Examples 7 to 9 can be reduced by 83.89% compared to the comparative example 2 that has not been subjected to electromagnetic induction heating treatment, that is, the liquid absorption rate can be increased by 83.89% compared to the comparative example 2 that has not been subjected to electromagnetic induction heating treatment. Moreover, it can be seen from Examples 2 and Examples 5 to 6 that, within a certain range, as the electromagnetic induction heating frequency increases, the liquid absorption rate shortens, that is, the liquid absorption rate also increases. Combined with the analysis of the surface temperature of the active layer in Table 1, it can be seen that the improvement in the liquid absorption rate is mainly due to the fact that after the electrode is subjected to electromagnetic induction heating, the surface temperature of the active layer is increased, which softens and even ablates the binder in the active layer, thereby removing the floating binder, increasing the porosity of the electrode, and thus improving the electrolyte infiltration rate. It should be noted that an inappropriate electromagnetic induction heating frequency can cause the electrode temperature to be too high, resulting in the electrode being burned and causing powder loss (as shown in Comparative Example 4 and Figure 4).

[0213] (2) The electrode pieces in Examples 2 to 9 that have undergone electromagnetic induction heating treatment have lower diaphragm resistance than the electrode pieces that have not undergone electromagnetic induction heating treatment. This is mainly due to the fact that during the electromagnetic induction heating process, the conductive agent in the electrode piece is affected by the magnetic lines of force and tends to be in the same direction, which is conducive to reducing the diaphragm resistance of the electrode piece. At the same time, an inappropriate electromagnetic induction heating frequency will cause the temperature of the electrode collector to be too high, resulting in deformation of the electrode collector, excessive pores between the current collector and the active material, and a state close to powdering, which ultimately causes the electrode sheet resistance to increase instead of decrease (as shown in Comparative Example 3).

[0214] (3) After the pole piece is subjected to electromagnetic induction heating treatment, the corresponding battery K value is reduced. This is not only due to the increase in the pole piece porosity mentioned above and the change in the direction of the conductive agent in the pole piece, but also due to the softening (melting) and ablation of the binder, which can also improve the various burrs and particles on the edge of the active layer, making the surface of the active layer smoother, reducing the sharpness of the pole piece surface, and thus reducing the risk of the pole piece piercing the isolation membrane. As shown in Figure 4, the pole piece in Comparative Example 1 that has not been subjected to electromagnetic induction heating treatment has more edge burrs, while the pole piece edges after electromagnetic induction heating treatment in Examples 2 to 4 have no burrs or particles and are smooth.

[0215] (4) The electrode pieces in Examples 2 to 9, after electromagnetic induction heating treatment, have high adhesion and shear strength. Their adhesion is above 15 N / m, and their shear strength is greater than 0.5 MPa, meeting the market requirements for electrode adhesion and shear strength. This also shows that after appropriate electromagnetic induction heating treatment, the active layer and the current collector can still maintain a close bond, which is beneficial to stability during the charge and discharge cycle (the active layer is not easily separated from the current collector).

[0216] (5) The electrode is treated by electromagnetic induction heating. Compared with the traditional corona treatment method (Comparative Example 6), it can better improve the liquid absorption rate of the electrode, reduce the membrane resistance of the electrode, and improve the K value of the battery.

[0217] Appendix: The relevant performance test methods in Table 2 above are as follows:

[0218] (1) Diaphragm resistance test method

[0219] Use a Yuanneng Technology chip resistor meter to test the sheet resistance. Cut small 10mm diameter discs from the left, center, and right sides of the electrode. Turn on the Yuanneng Technology chip resistor meter's indicator light, place the disc in the appropriate position on the meter's "probe," click "Start," and wait for the display to stabilize before reading. Test each disc in two locations. Calculate the average of these six measurements to determine the sheet resistance for that electrode.

[0220] (2) Adhesion test method

[0221] Cut the pole piece into 20*100mm 2 The test specimens of different sizes are kept aside; the double-sided tape is used to stick to the side of the specimen that needs to be tested, and it is compacted with a pressure roller to make the double-sided tape fit the specimen completely; the other side of the double-sided tape of the specimen is stuck to the stainless steel surface, and one end of the specimen is bent in the opposite direction with a bending angle of 180°; a high-speed rail tensile testing machine is used for testing, one end of the stainless steel is fixed to the lower fixture of the tensile testing machine, and the bent end of the specimen is fixed to the upper fixture, and the angle of the specimen is adjusted so that the upper and lower ends are in a vertical position, and then the specimen is stretched at a speed of 50 mm / min until the specimen is completely peeled off from the substrate, and the displacement and force in the process are recorded. It is generally believed that the force when the force is balanced is the bonding force of the electrode.

[0222] (3) Electrolyte absorption rate of the electrode

[0223] Fix the electrode on a clean glass plate, use a capillary with an inner diameter of 0.3mm to absorb the electrolyte at a height of 3mm (the electrolyte composition includes EC, DMC and EMC with a volume ratio of 3:2:1, and 1mol / L lithium salt LiPF6), then bring the capillary into vertical contact with the electrode to allow the electrode to absorb the electrolyte, measure the time it takes for the electrode to absorb the electrolyte (absorption time), and use the absorption time to reflect the absorption rate of the electrolyte by the electrode.

[0224] (4) Shear strength test

[0225] Cut a double-sided tape about 60 mm long, stick the tape along the MD direction (longitudinal) of the electrode, and use a blade to cut the electrode along the edge of the double-sided tape; select a steel plate with a smooth appearance, polish the surface of the steel plate with sandpaper, wipe the surface of the steel plate with cotton gauze dipped in alcohol, and dry it; stick the adhesive paper to the steel plate, and the distance between the bottom edge of the tape and the bottom edge of the steel plate is greater than 1 cm. Place the steel plate in a 60-80℃ oven for 5 minutes, take out the steel plate, and gently scrape off the release paper on the tape with a blade; place the cut electrode on the double-sided tape with the test side facing down. Use a 2kg roller to roll back and forth 3 times; turn on the power of the tensile testing machine, the indicator light will light up, and adjust the limit block to the appropriate position; fix the end of the steel plate without the electrode with the lower clamp, and clamp the upper clamp on the unbonded end of the electrode; turn on the dedicated computer connected to the tensile testing machine, double-click the "U60" software icon on the desktop; set the tensile testing machine parameters and the test speed to 10mm / min; after adjusting the position of the upper and lower clamps, click the "clear" icon for displacement and force values ​​in the test software. After the parameters are reset to zero, click the "test" icon; when the test curve shows a peak, the electrode and the steel plate are completely separated, and the test stops automatically. Export the raw data; record the fracture mode of the electrode and take a photo, measure the length and width of the electrode damage area, and calculate the actual bonding area S (mm2); select the peak of the curve as the maximum shear force Fs (N) of the electrode, and calculate the shear strength of the electrode according to Q = Fs / S, in MPa; after repeating the test on all samples, turn off the power of the tensile testing machine; clean the table.

[0226] (5) K value test

[0227] The K value is tested using a self-discharge test system. Model: Auto-OCV / IMP-21173 / 26148 (Purpose: for lithium battery performance testing).

[0228] Working Principle: The self-discharge test system consists of an automatic transport cart, a docking platform, a static (aging) shelf, and battery voltage and internal resistance testing equipment. The automatic transport cart transports batteries from the docking platform at the front of the system to the static (aging) shelf. After the set static (aging) time, the automatic transport cart transports the batteries to the voltage and internal resistance testing equipment for voltage and internal resistance testing, and records the corresponding test data. Batteries that have completed all tests are transported by a conveyor to the discharge position at the back end of the system. The system automatically sorts out defective batteries and transfers them to shipping status.

[0229] K value = [OCVB (voltage after static state) - OCV1 (voltage before static state)] / static state time.

[0230] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application 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 or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A pole piece processing system, characterized in that: include: An electromagnetic induction heating unit, wherein the electromagnetic induction heating unit is used to perform electromagnetic induction heating treatment on the pole piece; Optionally, the pole piece has a dry active layer.

2. The electrode processing system according to claim 1, characterized in that: The electromagnetic induction heating unit comprises an induction coil, and the induction coil is used to generate alternating magnetic flux lines parallel to the pole piece.

3. The electrode processing system according to claim 1 or 2, characterized in that: The pole piece processing system further comprises a temperature measuring unit, and the temperature measuring unit is used to measure the temperature of the pole piece.

4. The electrode processing system according to claim 3, characterized in that: The temperature measuring unit includes an infrared temperature measuring module.

5. The electrode processing system according to claim 3 or 4, characterized in that: The electrode processing system further comprises an automatic temperature control unit, and the automatic temperature control unit is used to control the heating parameters of the electromagnetic induction heating unit.

6. A method for processing a pole piece, characterized in that: The pole piece includes a current collector and an active layer, the active layer is arranged on at least one side of the current collector, and the active layer includes a binder. The method for processing the pole piece includes: performing electromagnetic induction heating treatment on the pole piece so that the surface temperature of the active layer is greater than or equal to the softening temperature or melting temperature of the binder, and the temperature of the current collector is lower than the deformation temperature of the current collector.

7. The method for processing a pole piece according to claim 6, characterized in that: The step of the electromagnetic induction heating treatment includes: passing the pole piece through the interior of the induction coil and applying an alternating current to the induction coil.

8. The method for processing a pole piece according to claim 6 or 7, characterized in that: The induction frequency of the electromagnetic induction heating treatment is greater than or equal to 5 kHz; optionally, the induction frequency of the electromagnetic induction heating treatment is 10 to 50 kHz; optionally, the induction frequency of the electromagnetic induction heating treatment is 10 to 20 kHz.

9. The method for processing a pole piece according to claim 7, characterized in that: The number of turns of the induction coil is 2 to 10; optionally, the number of turns of the induction coil is 2 to 5.

10. The method for processing a pole piece according to claim 7 or 9, characterized in that: The pole piece moves relative to the induction coil; optionally, the pole piece moves at a speed of 10 to 100 m / min relative to the induction coil; optionally, the pole piece moves at a speed of 40 to 80 m / min relative to the induction coil.

11. The method for processing a pole piece according to any one of claims 6 to 10, characterized in that: The surface temperature of the active layer is 100-450°C; optionally, the surface temperature of the active layer is 220-400°C.

12. A pole piece, characterized in that: The pole piece is obtained by processing according to any one of claims 6 to 11.

13. A battery, characterized in that: The battery comprises the electrode sheet according to claim 12.

14. An electrical device, characterized in that: The electrical device comprises the battery according to claim 13.

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