A processing method of an electrode plate

Abstract

The application belongs to the technical field of secondary batteries, and particularly relates to a processing method of an electrode sheet. The electrode sheet comprises an active layer, and the active layer comprises an active material and a binder. The processing method comprises the following steps: performing a heating treatment on the electrode sheet, so that the active layer is heated to a processing temperature; the processing temperature is greater than or equal to a softening temperature or a melting temperature of the binder, and the processing temperature is less than the lowest temperature among a decomposition temperature, an oxidation temperature and an ignition temperature of the active material. The method can reduce the internal resistance of a battery, improve the rate performance of the battery and improve the kinetic performance of the battery.

Description

Technical Field

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

[0002] With the continuous deepening of secondary battery research and the continuous increase in market demand, higher requirements are being placed on battery fast-charging performance. Fast charging, or rapid charging, generally enables a battery to reach or near a fully charged state in a relatively short period of time. However, current battery fast-charging performance is often limited by poor kinetic properties such as high internal resistance and low rate capability. Therefore, reducing internal resistance, improving rate capability, and improving the kinetic performance of secondary batteries have become top priorities. Summary of the Invention

[0003] In view of the above problems, the present application provides a method for processing a pole piece, which can reduce the internal resistance of the battery, enhance the battery rate performance, and improve the battery dynamic performance.

[0004] In the first aspect, the present application provides a method for processing an electrode, wherein the electrode includes an active layer, and the active layer includes an active substance and a binder. The processing method includes: heating the electrode to raise the temperature of the active layer to a processing temperature; the processing temperature is greater than or equal to the softening temperature or melting temperature of the binder, and the processing temperature is less than the lowest temperature among the decomposition temperature, oxidation temperature, and ignition temperature of the active substance.

[0005] In the electrode processing method of the embodiment of the present application, the electrode is heated so that the temperature of the active layer is greater than or equal to the softening temperature or melting temperature of the binder, and the binder re-melts and penetrates into the active layer of the electrode, which plays a role in balancing the distribution of the binder in the upper and lower layers of the electrode, helping to improve the electrode resistance of the electrode and enhance the dynamic performance; the balanced distribution of the binder in the electrode helps to improve the bonding strength and cohesion of the electrode. Moreover, the high heat generated during heating can remove part of the binder on the surface of the electrode, and then form pores on the surface of the electrode; due to thermal expansion and contraction and the softening and fluidity of the binder, a small amount of pores are also regenerated inside the electrode after cooling. The generation of a small amount of pores constructs capillary channels, which can increase the infiltration rate with the electrolyte, accelerate the transmission of lithium ions between the electrodes and the electrolyte, reduce the internal resistance of the battery, improve the battery rate performance, and improve the battery dynamic performance.

[0006] At the same time, the processing temperature is lower than the lowest temperature among the decomposition temperature, oxidation temperature and ignition temperature of the active material. Therefore, during the electrode processing process, the etching or decomposition of the active material can be improved, which is beneficial for the active material in the electrode to maintain the integrity of the lattice, and thus is beneficial to maintaining the capacity of the electrode.

[0007] In some embodiments, the electrode is a positive electrode, and the processing temperature is less than or equal to the decomposition temperature of the binder.

[0008] According to the electron gain and loss of the active material in the electrode in the battery chemical reaction, the electrode can be divided into positive electrode and negative electrode. The active material in the positive electrode loses electrons in the battery chemical reaction during charging, and the active material in the negative electrode gains electrons in the battery chemical reaction during charging. Since the active materials in the positive and negative electrodes are different, the solubility of the active materials in the solvent is different, and the solubility of the binder in the solvent is different. Therefore, different types of solvents and binders are usually used in the production process of the active layer of the positive electrode and the negative electrode. Usually, oily solvents and oily binders are used in the production process of the active layer of the positive electrode, while aqueous solvents and aqueous binders are used for the negative electrode. The different volatilization rates of oily solvents and oily solvents make the migration of the binder different during the drying process of the slurry. Therefore, the distribution of the binder in the positive electrode is usually different from that of the negative electrode.

[0009] In practice, it has been found that the binder in the positive electrode sheet floats less. Therefore, for the positive electrode sheet, the treatment temperature is greater than or equal to the softening temperature or melting temperature of the binder, and less than or equal to the decomposition temperature of the binder. This allows the binder to re-infiltrate the electrode sheet in a molten manner, while the binder does not decompose or only decomposes minimally. This balances the adhesive distribution between different layers of the electrode sheet, helping to improve the bonding strength and cohesion of the positive electrode sheet.

[0010] For the negative electrode, the processing temperature is controlled to be greater than or equal to the softening temperature or melting temperature of the binder, and the processing temperature is less than the lowest temperature of the decomposition temperature, oxidation temperature, and ignition temperature of the active material. Considering that the decomposition temperature of the binder is usually higher than the softening temperature or melting temperature of the binder, and lower than the decomposition temperature of the active material, the processing temperature of the negative electrode can be greater than or equal to the decomposition temperature of the binder, or it can be less than the decomposition temperature of the binder. When the processing temperature of the negative electrode is greater than or equal to the decomposition temperature of the binder, the excess binder on the surface can be removed, the bonding force can be balanced, and the negative electrode is not prone to cracking or powdering during the cold pressing process. When the processing temperature of the negative electrode is less than the decomposition temperature of the binder, the binder can be re-infiltrated into the electrode in a molten manner, and at the same time, the binder does not decompose or only decomposes very little, so that the distribution of the adhesive between different layers of the electrode is balanced, which helps to improve the bonding force and cohesion of the positive electrode.

[0011] In some embodiments, the processing temperature is 160-400° C.; in other embodiments, the processing temperature is 180-370° C. This temperature range is greater than or equal to the softening temperature or melting temperature of common binders, and less than the decomposition temperature of common active substances. Therefore, for ease of operation, the processing temperature can be set within this temperature range.

[0012] In some embodiments, the electrode is a positive electrode, and the treatment temperature is 160-260°C, or 280-400°C. Depending on the type of binder used in the positive electrode, a suitable treatment temperature can be used. For example, the melting temperature of polyvinylidene fluoride (PVDF), a commonly used binder for positive electrode sheets, is 166-170°C, and the thermal decomposition temperature is greater than 310°C, so a treatment temperature of 160-260°C can be used; polyimide (PI) softens at ≥300°C, and the thermal decomposition temperature is greater than 500°C, so a treatment temperature of 280-400°C can be used; selecting a suitable treatment temperature within this temperature range for different binders can enable the binder to re-infiltrate the electrode in a molten manner, while the binder does not decompose or only decomposes very little, so that the adhesive distribution between different layers of the electrode is balanced, which helps to improve the bonding strength and cohesion of the positive electrode.

[0013] In some embodiments, the electrode is a negative electrode, and the treatment temperature is 180-350° C., optionally 200-350° C. This temperature is greater than or equal to the decomposition temperature of a common binder for negative electrode electrodes. For example, styrene-butadiene rubber (SBR), a common binder for negative electrode electrodes, will gradually decompose at temperatures above 220° C. At this treatment temperature, excess binder on the surface can be removed, balancing the bonding force and improving the problem of cracking and powdering of the negative electrode during the cold pressing process.

[0014] In some embodiments, the heating time is 0.02 to 0.3 seconds, and optionally 0.02 to 0.2 seconds. The treatment method of the present invention has a high heating rate, which can quickly bring the surface and internal temperatures of the active layer to the treatment temperature. The binder absorbs heat in a short period of time, which not only makes the binder more evenly distributed in the active layer, but also has a high treatment efficiency.

[0015] In some embodiments, the heating treatment method includes laser irradiation treatment. Laser irradiation treatment uses a laser to generate a laser beam and irradiates with the laser beam. Laser has the characteristics of excellent monochromaticity, extremely small divergence, and extremely high brightness, and can make the temperature of the active layer reach the required temperature in a very short time. Moreover, the pole piece processing method of the embodiment of the present application can quickly complete the processing of the pole piece at one time by using a laser on one side or both sides of the pole piece, and can be integrated on existing equipment without adding a lot of extra time and equipment. It can maintain the original pole piece production capacity and has low cost.

[0016] In some embodiments, the pole piece comprises a first surface and a second surface arranged oppositely; the laser irradiation processing step comprises: using a first laser beam to perform laser irradiation processing on the first surface, and using a second laser beam to perform laser irradiation processing on the second surface; the first laser beam and the second laser beam have a spacing in a direction parallel to the first surface and the second surface.

[0017] In the embodiments of the present application, the first laser beam and the second laser beam have a spacing in a direction parallel to the first surface and the second surface, that is, the first laser beam and the second laser beam are irradiated in a staggered manner on both sides of the pole piece, and the laser head used to generate the laser beam is located on both sides of the pole piece but not directly opposite to the pole piece, and the two have a certain distance interval in the plane direction of the pole piece, which is beneficial to control the temperature of the pole piece and improve the problem of overheating of the pole piece in a short time.

[0018] In some embodiments, in the laser irradiation processing step, the maximum size of the laser spot falling on the surface of the pole piece is greater than or equal to the minimum size of the surface of the pole piece. In the embodiments of the present application, the maximum size of the laser spot is greater than or equal to the minimum size on the surface of the pole piece, and under this condition, the pole piece can be irradiated simultaneously and comprehensively in the direction of the minimum size on the surface of the pole piece in one laser irradiation processing, so that the adhesive in this direction is almost simultaneously melted, which helps to improve the uniformity of the redistributed adhesive.

[0019] In some embodiments, the laser irradiation processing step comprises: moving the pole piece relative to the laser spot falling on the surface of the pole piece, and the speed of the moving processing is 10-200 m / min, and optionally 30-200 m / min. In the embodiments of the present application, the processing process of the pole piece can be in a dynamic state, and the pole piece moves relative to the laser spot, and the laser performs a short heating treatment on the pole piece, which can make the temperature of the active layer in the pole piece rise, but the rising temperature will not be too high. In actual operation, the movement of the pole piece can be realized by placing the pole piece on a winding guide roller and a unwinding guide roller and using the winding guide roller to pull the pole piece. The speed of the movement of the pole piece can be controlled by the running speed of the winding guide roller. By controlling the movement of the pole piece, the laser irradiation processing of the whole roll of pole pieces can be completed in one winding and unwinding process, the processing speed is high, which helps to improve the production capacity and is convenient and easy to process.

[0020] In some embodiments, the power of the laser irradiation processing is 100-8000 W, and optionally 1000-7000 W. By changing the power, the heating speed can be adjusted. When the movement speed is high, the power of the laser is increased correspondingly to meet the rapid heating of the pole piece in a shorter residence time.

[0021] In some embodiments, before the heating step, a step of drying the electrode is included.

[0022] In some embodiments, before the heating treatment step, a step of forming the pole piece is included. Optionally, the forming treatment includes one or both of cold pressing treatment and hot pressing treatment.

[0023] In some embodiments, before the heating step, a step of cutting the pole piece is included.

[0024] In the manufacturing process of the electrode, the active material is generally mixed with a binder, a solvent and other necessary components to form a slurry. The slurry is coated on the current collector and dried to form a electrode including a current collector and an active layer. After drying, the electrode is usually subjected to a forming process such as cold pressing or hot pressing to increase the compaction density of the active layer and enhance the bonding force between the active layer and the current collector, and finally cut into the desired shape. The electrode processing method of the embodiment of the present application is applicable to each process of electrode production. This process can be performed after coating and drying, forming, and cutting. It can process a wide range of materials and has low requirements for the electrode. Moreover, after the electrode is cut, the electrode has residual stress and burrs are generated during cutting. After being treated by the method of the embodiment of the present application, the residual stress is released in advance and the burrs are softened.

[0025] In a second aspect, the present application provides a pole piece, which is obtained by processing according to the above processing method.

[0026] The electrode obtained by the above-mentioned treatment method has improved binder floating phenomenon, wherein the binder is redistributed and has good uniformity in the active layer, the bonding force and cohesion between the components in the active layer of the electrode are improved, and the stress between the components is released; at the same time, the electrode has a higher porosity, which helps to increase the absorption rate of the electrolyte; the possibility of electrons forming a conductive path increases, and the resistivity of the electrode decreases, resulting in a decrease in internal resistance, which helps to improve the battery dynamic performance.

[0027] In a third aspect, the present application provides a battery comprising the above-mentioned electrode.

[0028] The battery of the embodiment of the present application includes the above-mentioned electrode piece, which can be either a positive electrode piece or a negative electrode piece, or can include both positive and negative electrode pieces. Under the action of the treated electrode piece, the battery has excellent battery dynamic performance, such as rate performance, low K value (voltage drop per unit time of the battery), low DC impedance, etc.

[0029] In a fourth aspect, the present application provides an electrical device, which includes the above-mentioned battery.

[0030] The battery disclosed in the embodiments of the present application can be used in electrical devices that use the battery as a power source, or various energy storage systems that use the battery as an energy storage element. 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, such as 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] 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.

[0032] Figure 1 SEM images of the positive electrode sheet provided in Example 1 of the present application before (a) and after (b) laser treatment;

[0033] Figure 2 SEM images of the negative electrode provided in Example 1 of the present application before (a) and after (b) laser treatment;

[0034] Figure 3 A schematic diagram of a battery module according to an embodiment of the present application;

[0035] Figure 4 A schematic diagram of a battery pack according to an embodiment of the present application;

[0036] Figure 5 for Figure 4 An exploded view of a battery pack according to an embodiment of the present application is shown;

[0037] Figure 6 A schematic diagram of a battery according to one embodiment of the present application;

[0038] Figure 7 for Figure 6 An exploded view of a battery according to an embodiment of the present application is shown;

[0039] Figure 8 FIG2 is a schematic diagram of an electrical device using a battery as a power source according to an embodiment of the present application.

[0040] Description of reference numerals:

[0041] 1 battery pack; 2 upper box; 3 lower box; 4 battery module; 5 battery cell; 51 shell; 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 only for the purpose of describing specific embodiments 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] With the continuous deepening of lithium-ion battery research and the continuous increase in market demand, higher requirements are being placed on the battery's fast charging (fast charging) performance. The fast charging performance of a battery is closely related to its internal resistance, rate performance, and dynamic performance. Therefore, how to reduce internal resistance, improve rate performance, and improve dynamic performance has become a top priority.

[0051] To improve the aforementioned performance aspects, improvements can be made to the active materials, conductive agents, binders, electrolytes, and separators within the battery electrodes. For example, related techniques sequentially subject lithium-ion battery electrodes to microwave heating and radiation irradiation. However, the high-energy particles from the radiation can cause lattice distortion and rearrangement in some active materials with inherently less stable structures, such as lithium nickel cobalt manganese oxide, thereby affecting capacity. Residual free radicals resulting from crosslinking can also degrade electrode capacity. Another example involves micro-gravure coating of an aqueous solution of CMC (sodium carboxymethyl cellulose) or a solution of PVDF (polyvinylidene fluoride) in NMP (N-methylpyrrolidone) onto a rolled positive or negative electrode, followed by drying and a second roll-coating. During gravure coating, a slight rebound expansion occurs, causing the material particles within the electrode to "rotate" slightly, thereby alleviating stress within the electrode, facilitating lithium ion insertion, and improving dynamic performance. However, this method may cause long-term thickness rebound, affecting the stability of the electrode. Furthermore, because the electrode surface is coated with a layer of adhesive, the surface resistance is too high, which increases the electrode resistance and the DC internal resistance of the lithium-ion battery using this electrode. The need for secondary drying also prolongs the production cycle.

[0052] In addition, there are related technologies that use carbon coating structures in active materials, add high specific surface area conductive agents such as carbon nanotubes, graphene, etc. to the conductive agent, introduce conductive binders into the binder, introduce primers on the current collector, etc. These methods are all based on the raw materials of the electrode, and still have the following problems: during the preparation of the slurry, the rapid evaporation of the solvent causes the binder to easily migrate to the surface, causing the binder to float, thereby worsening the surface dynamics and affecting the wettability of the electrode. Currently, double-layer coating can be used to compensate for this problem, but this method requires the simultaneous preparation of two slurries, which consumes more equipment. Therefore, how to quickly and effectively improve the floating of the binder in the electrode and improve the dynamic performance of the battery at the same time has become a technical breakthrough.

[0053] To this end, by heating the surface of the electrode and controlling the heating temperature so that the temperature is greater than or equal to the softening temperature or melting temperature of the adhesive, the adhesive is removed or re-infiltrated into the electrode by ablation or melting, thereby balancing the distribution of adhesive in the upper and lower layers of the electrode, helping to improve the diaphragm resistance of the electrode and enhance the dynamic performance; the balanced distribution of the adhesive in the electrode helps to improve the bonding strength and cohesion of the electrode.

[0054] The high heat generated during heating can partially remove the binder on the electrode surface, forming pores on the electrode surface. Due to thermal expansion and contraction, as well as the softening and fluidity of the binder, a small amount of pores are also generated within the electrode after cooling. The formation of a small amount of pores creates capillary channels, which can increase the infiltration rate of the electrolyte, accelerate the transfer of lithium ions between the electrodes and the electrolyte, and improve battery dynamics.

[0055] Under the action of high temperature, the burrs on the electrode caused by cutting can be shrunk and softened, making them less sharp and reducing the risk of puncturing the isolation membrane, thereby improving the battery K value (voltage drop per unit time) and self-discharge rate.

[0056] At the same time, the temperature is controlled to be lower than the lowest temperature among the decomposition temperature, oxidation temperature and ignition temperature of the active material, so that the active material in the electrode can maintain the integrity of the lattice, which is beneficial to maintaining the capacity of the electrode.

[0057] In this way, by performing a specific heating treatment on the electrode, the dried electrode is reactivated, the binder is evenly distributed, and the stress between the components in the electrode is released, which helps to increase the porosity of the electrode and improve the absorption rate of the electrolyte; the possibility of electrons forming a conductive path is increased, which is beneficial to reduce the resistivity of the electrode, reduce the internal resistance of the battery, and help improve the battery dynamic performance.

[0058] 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.

[0059] The method for processing a pole piece provided by the embodiments of the present application includes an active layer, and the active layer includes an active substance and a binder. The method for processing a pole piece provided by the embodiments of the present application includes: heating the pole piece, so that the active layer is heated to a processing temperature; the processing temperature is greater than or equal to the softening temperature or the melting temperature of the binder, and the processing temperature is less than the lowest temperature among the decomposition temperature, the oxidation temperature and the ignition temperature of the active substance.

[0060] In the embodiments of the present application, the active substance on the pole piece is a medium for electron transfer in the process of battery chemical reaction. The active substance is usually formed into an active layer together with a binder and other materials, and is arranged on at least one side of the current collector of the pole piece. The binder is a high molecular compound for binding various components (for example, the active substance and other substances) in the active layer and the current collector, and mainly plays the roles of binding 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 substances in the active layer. The binder is mixed with the active substance, a solvent and other necessary components to form a slurry. After the solvent is evaporated, the slurry is dried to form the active layer. During the drying process, the evaporation of the solvent causes the binder to easily migrate to the surface of the active layer, resulting in the floating of the binder, and thus deteriorating the surface layer kinetics, affecting the wettability of the pole piece, and finally affecting the electrochemical performance of the pole piece.

[0061] Heating the active layer to the processing temperature means that at least the surface temperature of the active layer is heated to the processing temperature. The surface of the active layer refers to the outermost layer of the active layer in contact with the outside world. Generally, the pole piece includes a current collector and an active layer arranged on at least one side of the current collector, so the surface of the active layer is usually also the surface of the pole piece. Generally, the region within 40% of the thickness of the pole piece along the thickness direction of the pole piece and from the outside to the inside can be regarded as the surface of the pole piece. The active layer is usually thin in thickness, and the temperature of the surface of the active layer is usually close to or the same as the temperature of the inside of the active layer during the heating process, and the temperature difference is small. At this time, the temperature of the inside of the active layer can also reach the processing temperature.

[0062] The softening temperature is the temperature at which the three-dimensional long-range ordered state of the macromolecular chain structure of the non-crystalline polymer is converted into the 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 the crystalline polymer is converted into the disordered viscous flow state, also known as the melting point, and is the lower limit of the forming and processing temperature of the crystalline polymer. Generally, the melting temperature interval is relatively narrow, and the softening temperature interval is relatively wide.

[0063] For polymers, the decomposition temperature refers to the temperature at which, as the temperature of a polymer in a viscous flow state increases, its molecular chains begin to degrade rapidly, or even significantly. For inorganic materials, the decomposition temperature refers to the temperature at which, although combustion does not occur, the molecular structure is destroyed or the crystal lattice is distorted. The oxidation temperature is the minimum temperature at which oxidation reactions occur. The ignition temperature, also known as the ignition temperature, is the minimum temperature at which combustion occurs.

[0064] In the electrode processing method of the embodiment of the present application, the electrode is heated so that the temperature of the active layer is greater than or equal to the softening temperature or melting temperature of the binder, and the binder re-melts and penetrates into the active layer of the electrode, which plays a role in balancing the distribution of the binder in the upper and lower layers of the electrode, helping to improve the electrode resistance of the electrode and enhance the dynamic performance; the balanced distribution of the binder in the electrode helps to improve the bonding strength and cohesion of the electrode. Moreover, the high heat generated during heating can remove part of the binder on the surface of the electrode, and then form pores on the surface of the electrode; due to thermal expansion and contraction and the softening and fluidity of the binder, a small amount of pores are also regenerated inside the electrode after cooling. The generation of a small amount of pores constructs a capillary channel, which can increase the infiltration rate with the electrolyte, accelerate the transmission of lithium ions between the electrodes and the electrolyte, and improve the dynamic performance of the battery.

[0065] At the same time, the processing temperature is lower than the lowest temperature among the decomposition temperature, oxidation temperature and ignition temperature of the active material. Therefore, during the electrode processing process, the etching or decomposition of the active material can be improved, which is beneficial for the active material in the electrode to maintain the integrity of the lattice, and thus is beneficial to maintaining the capacity of the electrode.

[0066] In some embodiments, the electrode is a positive electrode, and the processing temperature is less than or equal to the decomposition temperature of the binder.

[0067] According to the electron gain and loss of the active material in the electrode in the battery chemical reaction, the electrode can be divided into positive electrode and negative electrode. The active material in the positive electrode loses electrons in the battery chemical reaction during charging, and the active material in the negative electrode gains electrons in the battery chemical reaction during charging. Since the active materials in the positive and negative electrodes are different, the solubility of the active materials in the solvent is different, and the solubility of the binder in the solvent is different. Therefore, different types of solvents and binders are usually used in the production process of the active layer of the positive electrode and the negative electrode. Usually, oily solvents and oily binders are used in the production process of the active layer of the positive electrode, while aqueous solvents and aqueous binders are used for the negative electrode. The different volatilization rates of oily solvents and oily solvents make the migration of the binder different during the drying process of the slurry. Therefore, the distribution of the binder in the positive electrode is usually different from that of the negative electrode.

[0068] In practice, it has been found that the binder in the positive electrode sheet floats less. Therefore, for the positive electrode sheet, the treatment temperature is greater than or equal to the softening temperature or melting temperature of the binder, and less than or equal to the decomposition temperature of the binder. This allows the binder to re-infiltrate the electrode sheet in a molten manner, while the binder does not decompose or only decomposes minimally. This balances the adhesive distribution between different layers of the electrode sheet, helping to improve the bonding strength and cohesion of the positive electrode sheet.

[0069] For the negative electrode, the processing temperature is controlled to be greater than or equal to the softening temperature or melting temperature of the binder, and the processing temperature is less than the lowest temperature of the decomposition temperature, oxidation temperature, and ignition temperature of the active material. Considering that the decomposition temperature of the binder is usually higher than the softening temperature or melting temperature of the binder, and lower than the decomposition temperature of the active material, the processing temperature of the negative electrode can be greater than or equal to the decomposition temperature of the binder, or it can be less than the decomposition temperature of the binder. When the processing temperature of the negative electrode is greater than or equal to the decomposition temperature of the binder, the excess binder on the surface can be removed, the bonding force can be balanced, and the negative electrode is not prone to cracking or powdering during the cold pressing process. When the processing temperature of the negative electrode is less than the decomposition temperature of the binder, the binder can be re-infiltrated into the electrode in a molten manner, and at the same time, the binder does not decompose or only decomposes very little, so that the distribution of the adhesive between different layers of the electrode is balanced, which helps to improve the bonding force and cohesion of the positive electrode.

[0070] In some embodiments, the treatment temperature is 160-400°C; in other embodiments, the treatment temperature is 180-370°C. For example, the treatment temperature includes but is 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, 370°C, 380°C, and 400°C, or a range of values ​​between any two of them. The treatment temperature can be measured by an infrared thermometer or other temperature tester. The treatment temperature can be measured by an infrared thermometer or other temperature tester. This temperature range is greater than or equal to the softening temperature or melting temperature of a common binder, and is less than the decomposition temperature of a common active substance. Therefore, for ease of operation, the treatment temperature can be set within this temperature range.

[0071] In some embodiments, the pole piece is a positive pole piece, and the processing temperature is 160-260°C, including but not limited to any one of 160°C, 180°C, 200°C, 220°C, 240°C, 260°C or a range value between any two of them. In other embodiments, the pole piece is a positive pole piece, and the processing temperature is 280-400°C, including but not limited to any one of 280°C, 300°C, 320°C, 340°C, 360°C, 370°C, 380°C, 400°C or a range value between any two of them. Depending on the type of binder used in the positive pole piece, a suitable processing temperature can be used. For example, the melting temperature of the commonly used binder polyvinylidene fluoride (PVDF) for positive pole pieces is 166-170°C, and the thermal decomposition temperature is >310°C, so a processing temperature of 160-260°C can be used; polyimide (PI) will soften at ≥300°C, and the thermal decomposition temperature is >500°C, so a processing temperature of 280-400°C can be used; according to different binders, a suitable processing temperature can be selected in this temperature range, so that the binder can re-penetrate into the pole piece in a molten state, and at the same time, the binder does not decompose or only a small amount of the binder decomposes, so that the distribution of the binder between different layers of the pole piece is balanced, which helps to improve the adhesion and cohesion of the positive pole piece.

[0072] In some embodiments, the pole piece is a negative pole piece, and the processing temperature is 180-350°C, optionally 200-350°C, including but not limited to any one of 180°C, 200°C, 220°C, 240°C, 260°C, 280°C, 300°C, 320°C, 340°C, 350°C or a range value between any two of them. The temperature is greater than or equal to the decomposition temperature of the commonly used binder for negative pole pieces, for example, the commonly used binder styrene-butadiene rubber (SBR) for negative pole pieces will gradually decompose at a temperature of >220°C, so at this processing temperature, the excess binder on the surface can be removed, the adhesion can be balanced, and the problem of easy cracking and powdering of the negative pole piece during cold pressing can be improved.

[0073] In some embodiments, the time for heating is 0.02-0.3s, optionally 0.02-0.2s, including but not limited to any one of 0.02s, 0.04s, 0.06s, 0.08s, 0.1s, 0.12s, 0.14s, 0.16s, 0.18s, 0.2s, 0.22s, 0.24s, 0.26s, 0.28s, 0.3s or a range value between any two of them.

[0074] In the embodiments of the present application, the heating time refers to the time it takes for the surface of the active layer to heat up to the processing temperature. The shorter the heating time, the faster the heating rate. The heating time can be recorded by a temperature sensor. The treatment method in the embodiments of the present application has a high heating rate, which can quickly bring the surface and internal temperatures of the active layer to the processing temperature. The binder absorbs heat in a short period of time, which not only makes the binder more evenly distributed in the active layer, but also has a high treatment efficiency.

[0075] In some embodiments, the thickness of the active layer before heat treatment is 50 to 300 μm; in other embodiments, the thickness of the active layer before heat treatment is 50 to 200 μm. For example, the thickness of the pole piece may include, but is not limited to, any 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 ​​therebetween. Typically, the thickness of the pole piece can be measured using a micrometer, a laser thickness gauge, a scanning thickness gauge, or the like.

[0076] Due to the influence of heat conduction and diffusion, the method of the embodiment of the present application can process various single-sided or double-sided pole pieces with an actual coating thickness of 50 to 300 μm. At the appropriate thickness, it can make the surface and interior of the active layer reach the required processing temperature under rapid heating, reducing the temperature difference between the surface and interior of the active layer. When the surface and interior of the active layer have similar or the same processing temperatures, the melting and flow of the adhesive are more uniform, thereby improving the uniformity of the distribution of the adhesive in the pole piece. The method of the embodiment of the present application can process a wide range of materials and has low requirements for pole pieces.

[0077] Furthermore, in terms of thickness, the electrode processing method of the embodiment of the present application has little effect on the thickness of the electrode due to the small number of newly generated pores. That is, after the processing, the thickness of the electrode changes little.

[0078] In some embodiments, before heat treatment, the surface density of the active layer is 0.05 to 0.6 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 / mm2 , 0.6mg / mm 2 Any point value or any range value between the two. Surface density refers to the mass of the sheet coating per unit surface area, which can be obtained by testing with an X / β-ray surface density meter. Due to the influence of heat conduction and diffusion, the method of the embodiment of the present application can handle an actual coating thickness of 0.05 to 0.6 mg / mm 2 At an appropriate surface density, the binder in the active layer can be effectively heated, ablated, or melted into the electrode. At the same time, surface density primarily affects the internal resistance and capacity of the electrode. Generally, within a certain range, the internal resistance of the electrode decreases with increasing surface density. Increasing the surface density of the electrode helps reduce the internal resistance of the electrode, thereby improving the electrode capacity. The active layer of the embodiment of the present application has an appropriate surface density, and the electrode has low internal resistance and high capacity.

[0079] In some embodiments, the electrode is a positive electrode, and before heat treatment, the surface density of the active layer is 0.08 to 0.6 mg / mm 2 , optionally 0.1 to 0.5 mg / mm 2 For example, the surface density of the active layer may include but is not limited to 0.08 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 any range of values ​​between them.

[0080] In some embodiments, the electrode is a negative electrode, and before heat treatment, the surface density of the active layer is 0.05 to 0.3 mg / mm 2 , optionally 0.05 to 0.2 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 2Any point value in or any range of values ​​between them.

[0081] Generally, the active materials of the positive and negative electrodes have different densities, and many positive electrode active materials have higher densities than negative electrode active materials; and the positive and negative electrodes usually have different gram capacities. Under the same surface density, the negative electrode capacity is larger than the positive electrode capacity. In order to make the positive and negative electrode capacities roughly the same, the surface density of the negative electrode is usually set to be slightly smaller than the surface density of the positive electrode.

[0082] In some embodiments, the heating treatment method includes laser irradiation treatment. Laser irradiation treatment uses a laser to generate a laser beam and irradiates with the laser beam. Laser has the characteristics of excellent monochromaticity, extremely small divergence, and extremely high brightness, and can make the temperature of the active layer reach the required temperature in a very short time. Moreover, the electrode processing method of the embodiment of the present application can quickly complete the processing of the electrode at one time by using a laser on one side or both sides of the electrode, and can be integrated on existing equipment without adding a lot of extra time and equipment. The original electrode production capacity can be maintained at a low cost.

[0083] In some embodiments, the pole piece includes a first surface and a second surface arranged opposite to each other; the laser irradiation treatment step includes: using a first laser beam to perform laser irradiation treatment on the first surface, and using a second laser beam to perform laser irradiation treatment on the second surface; there is a spacing between the first laser beam and the second laser beam in a direction parallel to the first surface and the second surface.

[0084] In the embodiment of the present application, there is a distance between the first laser beam and the second laser beam in the direction parallel to the first surface and the second surface, that is, the first laser beam and the second laser beam are staggered for irradiation on both sides of the pole piece, and the laser heads for generating the laser beams are located on both sides of the pole piece but not directly facing each other. The two are separated by a certain distance in the plane direction of the pole piece, which is beneficial to control the temperature of the pole piece and improve the problem of overheating of the pole piece in a short time.

[0085] In some embodiments, in the laser irradiation treatment step, the maximum size of the laser spot falling on the surface of the pole piece is greater than or equal to the minimum size on the surface of the pole piece. The laser spot is the area (usually circular or rectangular) formed at the focal point after the laser beam is focused, and the laser power density is most concentrated at the laser spot. The maximum size of the laser spot is also usually called the laser spot width, which is usually the diameter (circular) or diagonal size (rectangular) of the area. The maximum size of the laser spot can usually be set directly in the laser generator. The minimum size on the surface of the pole piece refers to the shortest distance of the pole piece on the surface. The pole piece is usually rectangular, and the minimum size on the surface of the pole piece refers to the width of the pole piece, which is also usually called the membrane area width. In the embodiment of the present application, the maximum size of the laser spot is greater than or equal to the minimum size on the surface of the pole piece. Under this condition, the pole piece can be simultaneously and comprehensively irradiated in the direction of the minimum size on the surface of the pole piece in one laser irradiation treatment, so that the adhesive in this direction is melted almost at the same time, which helps to improve the uniformity of the adhesive after it is fully distributed. For example, the maximum size of the laser spot falling on the surface of the pole piece can be adjusted to 50-220 mm, including but not limited to any point value of 50 mm, 60 mm, 70 mm, 80 mm, 90 mm, 100 mm, 120 mm, 140 mm, 160 mm, 180 mm, 200 mm, 220 mm or any range value between two of them. This size can meet the processing requirements of most pole pieces.

[0086] In some embodiments, during the laser irradiation step, the distance between the laser used to generate the laser beam and the surface of the pole piece is 10 to 50 cm, including but not limited to any one of 10 cm, 15 cm, 20 cm, 25 cm, 30 cm, 35 cm, 40 cm, 45 cm, and 50 cm, or any range therebetween. A suitable distance effectively utilizes laser irradiation to heat the pole piece, while also facilitating temperature control of the pole piece, thereby reducing the cost of pole piece overheating and the need for higher-power, longer-duration laser irradiation.

[0087] In some embodiments, the laser irradiation processing step includes: moving the pole piece relative to the laser spot falling on the surface of the pole piece, and the moving processing speed is 10 to 200 m / min; in some embodiments, the moving processing speed is 30 to 200 m / min. For example, the speed of the moving process includes but is not limited to any one of 10m / min, 15m / min, 20m / min, 25m / min, 30m / min, 35m / min, 40m / min, 45m / min, 50m / min, 55m / min, 60m / min, 65m / min, 70m / min, 75m / min, 80m / min, 85m / min, 90m / min, 95m / min, 100m / min, 110m / min, 120m / min, 130m / min, 140m / min, 150m / min, 160m / min, 170m / min, 180m / min, 190m / min, and 200m / min, or a range of values ​​between any two of them. In the embodiment of the present application, the processing process of the electrode can be in a dynamic state, the electrode moves relative to the laser spot, and the laser briefly heats the electrode, which can increase the temperature of the active layer in the electrode, but the temperature rise will not be too high. In actual operation, the movement of the electrode can be achieved by placing the electrode on the winding guide roller and the unwinding guide roller, and using the winding guide roller to pull the electrode. The speed of the movement of the electrode can be controlled by the operating speed of the winding guide roller. By controlling the movement of the electrode, the laser irradiation treatment of the entire roll of electrode can be completed in one winding and unwinding process, with a high processing speed, which helps to improve production capacity and is convenient and easy to process. During the movement, the time the electrode passes through the laser light source is usually less than 0.2s, which is enough time to redistribute the adhesive in the active layer, while reducing heat accumulation and unnecessary side reactions.

[0088] In some embodiments, the power of the laser irradiation treatment is 100 to 8000 W, optionally 1000 to 7000 W, and further optionally 2000 to 6500 W. For example, the power of the laser irradiation treatment includes but is not limited to any one of 100 W, 500 W, 1000 W, 1500 W, 2000 W, 2500 W, 3000 W, 3500 W, 4000 W, 4500 W, 5000 W, 5500 W, 6000 W, 6500 W, 7000 W, 7500 W, and 8000 W, or a range of values ​​therebetween. The heating speed can be adjusted by changing the power. At high movement speeds, the laser power is increased accordingly to meet the requirements for rapid heating of the electrode in a shorter dwell time.

[0089] In some embodiments, the laser irradiation treatment includes one or both of pulsed laser irradiation and continuous laser irradiation. Pulsed laser refers to a single light pulse emitted by a laser operating in a pulsed mode, with a certain interval between two adjacent light pulses. Continuous laser, on the other hand, is continuous, uninterrupted laser light emitted by a continuous laser. Whether pulsed or continuous laser irradiation is used on the electrode plate, the active layer can reach the desired processing temperature in a short period of time.

[0090] In some embodiments, the binder includes one or more of an oil-soluble binder, a water-soluble binder, and an emulsion-type binder.

[0091] In some embodiments, the oil-soluble binder includes one or more of polyvinylidene fluoride, polyimide, polytetrafluoroethylene, polybutyl acrylate, and polyacrylonitrile.

[0092] 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.

[0093] In some embodiments, the emulsion binder includes one or more of styrene-butadiene rubber, vinyl acetate resin, acrylic resin, and chlorinated rubber.

[0094] Depending on the type of active material in the electrode, different binders can be selected, and the appropriate processing temperature can be determined based on the softening temperature or melting temperature, or decomposition temperature of the binder. For example, in the case where the electrode is a positive electrode, polyvinylidene fluoride can usually be used as a binder, and its processing temperature can be set to 160-260°C, more specifically 180-250°C, including but not limited to any point value of 160°C, 180°C, 200°C, 220°C, 240°C, 250°C, 260°C or a range between any two of them; if polyimide is used as a binder, its processing temperature can be set to 280-400°C, more specifically 300-380°C, including but not limited to any point value of 280°C, 300°C, 320°C, 340°C, 360°C, 370°C, 380°C, 400°C or a range between any two of them. For example, in the case where the electrode is a negative electrode, styrene-butadiene rubber can usually be selected as the binder, and the processing temperature can be set to 180-350°C, more specifically 200-350°C, such as 200-300°C, including but not limited to any one of 180°C, 200°C, 220°C, 240°C, 260°C, 280°C, 300°C, 320°C, 340°C, 350°C or a range between any two of them.

[0095] 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.

[0096] 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.

[0097] In some embodiments, the metal inorganic active material includes one or more of lithium iron phosphate, lithium manganese iron phosphate, lithium cobaltate, lithium manganese oxide, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide.

[0098] In some embodiments, the organic active material includes one or more of quinone compounds, carboxylate compounds, anhydride compounds, and amide compounds.

[0099] 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.

[0100] In some embodiments, the carbon-based material includes one or more of graphite, hard carbon, soft carbon, mesocarbon microbeads, and graphene.

[0101] In some embodiments, the titanium-based active material includes one or more of lithium titanate and titanium dioxide.

[0102] In some embodiments, the silicon-based active material includes one or more of silicon, silicon dioxide.

[0103] In some embodiments, the nitride comprises lithium nitride.

[0104] 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.

[0105] In some embodiments, the step of drying the electrode sheet is included before the heating step.

[0106] In some embodiments, the step of forming the electrode piece is included before the heating step. In some embodiments, the forming step includes one or both of cold pressing and hot pressing.

[0107] In some embodiments, before the heating step, a step of cutting the electrode piece is included.

[0108] In the manufacturing process of the electrode, the active material is generally mixed with a binder, a solvent and other necessary components to form a slurry. The slurry is coated on the current collector and dried to form a electrode including a current collector and an active layer. After drying, the electrode is usually subjected to a forming process such as cold pressing or hot pressing to increase the compaction density of the active layer and enhance the bonding force between the active layer and the current collector, and finally cut into the required shape. The electrode processing method of the embodiment of the present application is applicable to each process of electrode production. This process can be performed after coating and drying, forming, and cutting. It can process a wide range of materials and has low requirements for the electrode. Moreover, after the electrode is cut, the electrode has residual stress and burrs are generated during cutting. After being treated by the method of the embodiment of the present application, the residual stress is released in advance and the burrs are softened.

[0109] In some embodiments, the pole piece further includes a current collector, with the active layer disposed on at least one side of the current collector. The current collector on the pole piece serves as a substrate for the active layer to attach to and transports electrons during the battery's chemical reactions. Current collectors include, but are not limited to, metal current collectors, carbon current collectors, conductive resin current collectors, and composite current collectors of metal and resin. More specifically, examples include copper, nickel, titanium, iron, and their respective alloys, stainless steel, carbon fiber, carbon nanotubes (CNTs), and graphite.

[0110] In some embodiments, the active layer further includes a conductive agent. The conductive agent collects microcurrents between the active materials and between the active materials and the current collector, thereby improving electronic conductivity. At the same time, the conductive agent can also promote the infiltration of the electrolyte into the positive electrode. Conductive agents include but are not limited to acetylene black (SP), carbon nanotubes, conductive carbon black (super-P), Ketjen black, carbon fiber, graphene, etc. Due to the softening flow of the binder, the conductive agent will also produce related movement during the electrode processing. The conductive agents have good affinity with each other and a large specific surface area. At the moment of movement, it is easier to form a conductive path, which can significantly improve the conductivity of the electrode and improve the battery DCR (direct current resistance).

[0111] 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.

[0112] 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.

[0113] An embodiment of the present application also provides a pole piece, which is obtained by processing according to the above-mentioned processing method.

[0114] The electrode obtained by the above-mentioned treatment method has a redistributed binder and has good uniformity in the active layer. The bonding force and cohesion between the components in the active layer of the electrode are improved, and the stress between the components is released. At the same time, the electrode has a higher porosity, which helps to increase the absorption rate of the electrolyte; the possibility of electrons forming a conductive path increases, and the resistivity of the electrode decreases, resulting in a decrease in internal resistance, which helps to improve the battery dynamic performance.

[0115] The embodiment of the present application further provides a battery comprising the above-mentioned electrode.

[0116] The battery of the embodiment of the present application includes the above-mentioned electrode piece, which can be either a positive electrode piece or a negative electrode piece, or can include both positive and negative electrode pieces. Under the action of the treated electrode piece, the battery has excellent battery dynamic performance, such as high rate performance, low K value (voltage drop per unit time of the battery), and low DC impedance.

[0117] 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.

[0118] 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 assembled into a battery pack. In other battery packaging technologies, one or more battery cells can also be directly installed in a 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.

[0119] In some embodiments, the battery further comprises an electrolyte, which can serve as a carrier for ion transport in the battery.

[0120] In some embodiments, the electrolyte may be a solid electrolyte, such as a polymer electrolyte, an inorganic solid electrolyte, etc., but is not limited thereto. The electrolyte may also be an electrolyte solution. The electrolyte solution includes a solvent and a lithium salt dissolved in the solvent.

[0121] The solvent 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), preferably two or more.

[0122] 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).

[0123] 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.

[0124] 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.

[0125] The isolation membrane can be any known porous structure isolation membrane with electrochemical stability and mechanical stability, such as a single-layer or multi-layer film of one or more of glass fiber, non-woven fabric, polyethylene (PE), polypropylene (PP) and polyvinylidene fluoride (PVDF).

[0126] The positive and negative electrode sheets are alternately stacked, and a separator is placed between the positive and negative electrode sheets to provide isolation, resulting in a battery cell. Alternatively, the battery cell can be wound and wound. The battery cell is placed in a casing, injected with electrolyte, and sealed to form a battery cell. Multiple battery cells are first integrated to form a battery module, which can provide higher voltage and capacity, and has a specific functional output. The battery module is then installed in a battery casing, and a battery management system is usually added to form a battery pack, which is usually provided to users. Alternatively, multiple battery cells can be directly installed in the casing to form a battery pack.

[0127] refer to Figure 3 , which is an example of a battery module 4. In the battery module 4, multiple battery cells 5 can be arranged in sequence along the length of the battery module 4. Of course, they can also be arranged in any other manner. Further, the multiple battery cells 5 can be fixed using fasteners.

[0128] 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.

[0129] refer to Figure 4 and Figure 5 , which is used as an example battery pack 1. The battery pack 1 may include a battery box and multiple battery modules 4 disposed in the battery box. The battery box includes an upper box body 2 and a lower box body 3. The upper box body 2 can be placed on the lower box body 3 to form an enclosed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner in the battery box.

[0130] 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.

[0131] The battery's outer packaging can be a hard shell, such as a hard plastic shell, aluminum shell, or steel shell. Alternatively, the battery's outer packaging can be 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.

[0132] The shape of the battery can be cylindrical, square or any other shape. For example, Figure 6 This is a square-structured battery as an example.

[0133] In some embodiments, reference Figure 7The outer packaging may include a shell 51 and a cover plate 53. The shell 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates together form a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to seal the receiving cavity. The positive electrode sheet, the negative electrode sheet and the separator can be formed into an electrode assembly 52 through a winding process or a lamination process. One or more electrode assemblies 52 are encapsulated in the receiving cavity. The electrolyte is impregnated in the electrode assembly 52.

[0134] The embodiment of the present application also provides an electric device, which includes the above-mentioned battery. The battery disclosed in the embodiment of the present application can be used for an electric device using a battery as a power source, or various energy storage systems using a battery as an energy storage element. The electric device may include but is not limited to mobile phones, tablets, laptops, electric toys, electric tools, battery cars, electric cars, ships, spacecraft, and the like. Among them, electric toys may include fixed or mobile electric toys, such as 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 electric device, the battery cell, battery module, or battery pack in the battery can be selected according to its usage requirements.

[0135] Figure 8 This is an example of an electric device. This device is 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.

[0136] The following describes the details in conjunction with specific embodiments.

[0137] Example 1

[0138] 1) Preparation of positive electrode sheet

[0139] Lithium iron phosphate was selected as the positive electrode active material, and was dispersed in NMP (N-methylpyrrolidone) with conductive carbon black and PI (polyimide) at a mass ratio of 97wt%, 1wt%, and 2wt% respectively. The mixture was then coated on both sides of aluminum foil and dried. The surface density (CW) was 360mg / 1540.25mm by cold pressing. 2 , the positive electrode sheet has a total thickness of 97μm and a membrane area width of 100mm.

[0140] 2) Laser treatment of the positive electrode surface

[0141] The positive electrode sheet was heated by laser irradiation between two lasers at a constant speed of 180 m / min. The distance between the lasers and the electrode sheet was 10 cm, and the two lasers were offset on either side of the positive electrode sheet. The laser spot width was 200 mm, the continuous laser heating power was 6500 W, and the heating time was 0.067 seconds. The final temperature (i.e., the treatment temperature) of the positive electrode sheet after laser irradiation and heating was 340°C.

[0142] SEM images of the positive electrode before and after laser treatment Figure 1 As shown in the figure, it can be seen that after laser treatment, the positive electrode plate has not been etched.

[0143] 3) Preparation of negative electrode sheet

[0144] 95 wt% of the negative electrode active material artificial graphite, 1.0 wt% of conductive carbon black, 2.0 wt% of the binder styrene-butadiene rubber (SBR), and 2.0 wt% of the thickener sodium carboxymethyl cellulose (CMC) were mixed, added with deionized water, stirred, and dispersed to form a negative electrode slurry. The negative electrode slurry was then coated on Cu foil, and after both sides were completed, it was dried and cold pressed to obtain a total CW = 160 mg / 1540.25 mm 2 , the negative electrode sheet has a thickness of 67μm and a membrane area width of 105mm.

[0145] 4) Laser treatment of the negative electrode surface

[0146] The negative electrode plate was heated by laser irradiation at a constant speed of 120 m / min between two lasers. The distance between the lasers and the negative electrode plate was 20 cm, and the two lasers were offset on either side of the negative electrode plate. The laser spot width was 105 mm, the continuous laser heating power was 6000 W, and the heating time was 0.053 seconds. The final surface temperature of the negative electrode plate after laser irradiation and heating was 300°C.

[0147] SEM images of the negative electrode before and after laser treatment are as follows: Figure 2 As shown in the figure, it can be seen that after laser treatment, the negative electrode plate has not been etched.

[0148] Example 2

[0149] 1) Preparation of positive electrode sheet

[0150] Lithium nickel cobalt manganese oxide with a nickel-cobalt-manganese molar ratio of 8:1:1 was selected as the positive electrode active material, and was dispersed in NMP (N-methylpyrrolidone) with conductive carbon black and PVDF at a mass ratio of 96wt%, 2wt%, and 2wt% respectively. The mixture was then coated on both sides of aluminum foil and dried to obtain a CW=660mg / 1540.25mm 2The positive electrode sheet is then cold-pressed to obtain a positive electrode sheet with a total thickness of 130 μm and a film area width of 200 mm.

[0151] 2) Laser treatment of the surface of the positive electrode sheet

[0152] The positive electrode sheet is uniformly moved at a speed of 80 m / min through the space between the two lasers for laser irradiation and heating. The continuous heating power of the lasers is 3000 W, and the heating time (warming-up time) is 0.075 s. The distance between each laser and the positive electrode sheet is 15 cm, and the two lasers are misaligned on the two sides of the positive electrode sheet. The width of the laser spot is 100 mm. The final temperature of the surface of the positive electrode sheet after laser irradiation and heating is 250 °C.

[0153] 3) Preparation of the negative electrode sheet

[0154] 95 wt% of artificial graphite as the negative active material, 1 wt% of silicon, 0.5 wt% of conductive carbon black, 2.0 wt% of binder styrene-butadiene rubber (SBR), and 1.5 wt% of thickening agent sodium carboxymethyl cellulose (CMC) are mixed, deionized water is added and stirred, and dispersed to prepare a negative electrode slurry. The negative electrode slurry is then coated on a Cu foil, both sides are completed, and then dried and cold-pressed to obtain a negative electrode sheet with CW = 420 mg / 1540.25 mm 2 , a thickness of 190 μm, and a film area width of 210 mm.

[0155] 4) Laser treatment of the surface of the negative electrode sheet

[0156] The negative electrode sheet is uniformly moved at a speed of 200 m / min through the space between the two lasers for laser irradiation and heating. The distance between the lasers and the electrode sheet is 35 cm, and the two lasers are misaligned on the two sides of the positive electrode sheet. The width of the laser spot is 210 mm, the continuous heating power of the lasers is 2000 W, and the heating time is 0.063 s. The final temperature of the surface of the negative electrode sheet after laser irradiation and heating is 275 °C.

[0157] Example 3

[0158] The same as Example 1, except that the final heating temperature of the positive and negative electrode sheets is 370 °C and 260 °C, respectively, the corresponding continuous heating power of the lasers is 4500 W and 4000 W, respectively, the movement speed of the positive electrode sheet is 60 m / min, the movement speed of the negative electrode sheet is 80 m / min, and the heating time of the positive electrode sheet and the negative electrode sheet is 0.2 s and 0.079 s, respectively.

[0159] Example 4

[0160] The rest is the same as Example 2, with the only difference being that the final heating temperatures of the positive and negative electrode sheets are 180° C. and 200° C., respectively, and the corresponding laser continuous heating powers are 1800W and 1300W, respectively.

[0161] Comparative Example 1

[0162] The difference from Example 1 is that the positive and negative electrode plates are not laser treated, that is, steps 2) and 4) of Example 1 are not performed.

[0163] Comparative Example 2

[0164] The difference from Example 2 is that the positive and negative electrode plates are not laser treated, that is, steps 2) and 4) of Example 2 are not performed.

[0165] Comparative Example 3

[0166] The difference from Example 1 is that the heating temperature of the positive electrode is higher than the decomposition temperature of the active material therein, and the surface laser treatment of the negative electrode is not performed. Specifically, step 2) in Example 1 is replaced by the following steps:

[0167] The laser was adjusted to 10 side-by-side rectangular spots acting perpendicularly on the surface of the positive electrode. The width of these 10 side-by-side rectangular spots was 10 mm perpendicular to the direction of movement of the positive electrode, and the length was 15 mm parallel to the direction of movement of the positive electrode. The laser was 5 cm away from the electrode, the laser instantaneous pulse power was 8000 W, the laser pulse time was 0.005 s, the pulse time interval was 0.008 s, the movement speed of the positive electrode was 35 m / min, the heating time was 0.025 s, and the instantaneous temperature of the surface of the positive electrode after laser irradiation and heating was 600 ° C, resulting in etching and forming holes on the surface of the positive electrode.

[0168] Other implementation conditions and methods are consistent with those in Example 1.

[0169] Comparative Example 4

[0170] The difference from Example 2 is that the heating temperature of the negative electrode is higher than the decomposition temperature of the active material therein, and the surface laser treatment of the positive electrode is not performed. Specifically, step 4) in Example 2 is replaced by the following steps:

[0171] The laser was adjusted to 8 side-by-side rectangular spots acting perpendicularly on the surface of the negative electrode. The width of these 8 side-by-side rectangular spots was 25 mm perpendicular to the direction of movement of the negative electrode, and the length was 30 mm parallel to the direction of movement of the negative electrode. The laser was 6 cm away from the electrode, the movement speed of the negative electrode was 30 m / min, the instantaneous pulse power of the laser was 7500 W, the laser pulse time was 0.005 s, the pulse time interval was 0.005 s, the total heating time was 0.030 s, and the instantaneous temperature of the surface of the negative electrode after laser irradiation and heating was 550 ° C, resulting in etching and forming holes on the surface of the negative electrode.

[0172] Other implementation conditions and methods are consistent with those of Example 2.

[0173] The surface treatment conditions of the electrode pieces of various embodiments and comparative examples are shown in Tables 1 and 2 below.

[0174] Table 1. Surface treatment conditions of the electrode in Example 1, Example 3, Comparative Example 1, and Comparative Example 3

[0175]

[0176]

[0177] Table 2. Surface treatment conditions of the electrode in Example 2, Example 4, Comparative Example 2, and Comparative Example 4

[0178]

[0179]

[0180] The performance tests were conducted on the positive and negative electrode sheets after treatment in the embodiments and comparative examples, and the results are shown in Tables 3 and 4 below.

[0181] Table 3. Pole performance test results in Example 1, Example 3, Comparative Example 1, and Comparative Example 3

[0182]

[0183]

[0184] Table 4. Pole performance test results in Example 2, Example 4, Comparative Example 2, and Comparative Example 4

[0185]

[0186]

[0187] The data in Tables 3 and 4 were processed to obtain the electrode performance change rates of Example 1, Example 3, and Comparative Example 3 compared to Comparative Example 1, as well as the electrode performance change rates of Example 2, Example 4, and Comparative Example 4 compared to Comparative Example 2. The results are shown in Tables 5 and 6 below.

[0188] Table 5. Change rate of electrode performance of Example 1, Example 3, and Comparative Example 3 compared with Comparative Example 1

[0189]

[0190]

[0191] Table 6. Changes in electrode performance of Example 2, Example 4, and Comparative Example 4 compared to Comparative Example 2

[0192]

[0193] From the test results of Examples 1 to 4 and Comparative Examples 1 to 2 in Tables 3 to 6 above, it can be seen that after heat treatment, the resistance of the electrode decreased significantly, among which the negative electrode decreased more than the positive electrode; the adhesion and cohesion of the electrode were slightly improved; the absorption rate of the electrolyte by the electrode was greatly improved, and the porosity of the electrode was slightly improved; and after heat treatment, the gram capacity of the electrode did not decrease. In addition, after heat treatment, no significant change in the thickness of the electrode of Examples 1 to 4 was found. The results show that appropriate heat treatment of the electrode can effectively improve the performance of the electrode, with little side effects, and will not cause significant capacity loss and potential risk of lithium dendrites.

[0194] At the same time, it can be seen from the test results of Comparative Examples 3 to 4 that after the heating treatment, if the electrode temperature is too high and etching occurs, not only will the adhesion and cohesion of the electrode fail to be effectively improved, but the gram capacity of the electrode will also drop significantly, indicating that the heating temperature has a great influence on the electrochemical properties of the electrode, and inappropriate heating temperature will bring side effects to the electrode.

[0195] The positive and negative electrode sheets of the above embodiments and comparative examples were cut into pieces, and the sheets were separated from the three-layer separator of polyethylene / polypropylene / polyethylene and 1 mol·L containing vinylene carbonate (VC), tris(trimethylsilyl) phosphate (TMSP), ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC). -1 Lithium hexafluorophosphate (LiPF6) electrolyte solution is assembled into a lithium-ion battery with paired positive and negative electrodes. The corresponding performance is shown in the table below.

[0196] Table 7. Lithium-ion battery performance test results

[0197]

[0198] The data in Table 7 were processed to obtain the performance change rates of the lithium-ion batteries of Example 1, Example 3, and Comparative Example 3 compared with Comparative Example 1, as well as the performance change rates of the lithium-ion batteries of Example 2, Example 4, and Comparative Example 4 compared with Comparative Example 2. The results are shown in the following table.

[0199] Table 8. Lithium-ion battery performance change rate

[0200]

[0201]

[0202] In Table 7, “4C discharge rate retention” indicates the retention rate of the discharge capacity of the lithium-ion battery at a 4C rate compared to the discharge capacity at a 1C rate;

[0203] "SOC" is the state of charge, which is used to reflect the remaining capacity of the battery. Its numerical value is defined as the ratio of the remaining capacity to the battery capacity;

[0204] "K value" represents the voltage drop of the battery per unit time.

[0205] As can be seen from the above table: the lithium ion positive and negative electrode plates treated by the methods of Examples 1 to 4, after being assembled into lithium ion batteries, are compared with the untreated group (Comparative Examples 1 to 2), and compared with Comparative Examples 3 to 4 in which the plate is etched due to excessively high plate temperatures after heat treatment. Under the same system, their rate performance, K value, and DC impedance are all improved. This shows that the plate treatment methods of Examples 1 to 4 reduce the plate resistance and improve the electrolyte infiltration rate, thereby significantly improving the kinetic performance of lithium ion batteries while ensuring good bonding strength. At the same time, the treatment method is simple, less time-consuming and energy-consuming, and can be used in large-scale production.

[0206] Appendix: The relevant performance test methods in Table 3 and Table 4 above are as follows:

[0207] (1) Electrode resistance

[0208] Use a Yuanneng Technology Sheet Resistor Tester to test the sheet resistance. Cut small discs with a diameter of 10 mm from the left, center, and right sides of the electrode. Turn on the Yuanneng Technology Sheet Resistor Tester indicator, place the small disc in the appropriate position on the probe, click the "Start" button, and wait for the display to stabilize before reading. Test two positions on each disc. Calculate the average of the six measurements to obtain the sheet resistance for that electrode.

[0209] (2) Adhesion test

[0210] Cut the pole piece into 20*100mm 2The 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 to ensure 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.

[0211] (3) Electrode electrolyte absorption rate

[0212] 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, and then make vertical contact with the electrode to allow the electrode to absorb the electrolyte. Measure the time it takes to absorb the electrolyte and obtain the electrolyte absorption rate by conversion.

[0213] (4) Pole cohesion test

[0214] Cut the pole piece into 20*100mm 2 The test specimens are of different sizes and are kept aside. The specimens are attached to the surface of stainless steel with double-sided tape, and the single-sided tape is attached to the surface of the specimen, with the excess part being bent at an 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. The angle of the specimen is adjusted to ensure that the upper and lower ends are in a vertical position. The specimen is then stretched at a speed of 50 mm / min until the tape is completely peeled off from the specimen. The displacement and force during the process are recorded. It is generally believed that the force when the force is balanced is the cohesive force of the electrode.

[0215] (5) Electrode porosity test

[0216] Cut the electrode into 20 circular double-sided electrodes with a diameter of 14mm. Record the electrode weight and thickness to calculate the volume density. Place the circular double-sided electrode into the sample cup of a true density porosity tester. Displace the electrode with helium and combine Archimedes' principle with Bohr's law to determine the electrode's true volume, from which the true density is calculated. Porosity is equal to (1 - volume density / true density) * 100%.

[0217] (6) Electrode gram capacity test

[0218] Wash one side of the positive or negative electrode with N-methylpyrrolidone or deionized water, punch out a single-sided circular electrode with a diameter of 14 mm and weigh it; at the same time, weigh the weight of the corresponding current collector substrate under the 14 mm diameter circular piece (circular current collector). The active layer loading is obtained based on the weight of the circular electrode and the corresponding circular current collector. The mass of the active material is calculated according to the formula. The 2032 button battery is equipped with a negative electrode shell, nickel foam, a 16 mm diameter lithium sheet, an 18 mm diameter Celgard2325 separator, 0.1 g 1 mol·L -1 A 2032 button cell was assembled using a LiPF6 electrolyte solution containing EC:DMC:EMC (mass ratio 1:1:1), a 14mm diameter single-sided circular electrode (active material side facing the separator), and a 2032 button cell positive electrode casing. The assembled button cells were allowed to rest for 12 hours before testing. For button cells with negative electrode plates, the cells were discharged at a current of 0.05C to the lower voltage limit of the material, then charged at a current of 0.1C to the upper voltage limit of the material. The charge capacity was recorded. The charge capacity was divided by the mass of the active material to obtain the gram capacity of the negative electrode plate. For button cells with positive electrode plates, the cells were charged at a current of 0.1C to the upper voltage limit of the material, then discharged at a current of 0.1C to the upper voltage limit of the material. The discharge capacity was recorded. The discharge capacity was divided by the mass of the active material to obtain the gram capacity of the positive electrode plate.

[0219] (7) Determination of K value

[0220] Charge the cell to 20% capacity, then record the cell voltage (OCV1). Then, place the cell at 25°C for 48 hours, and measure the cell voltage (OCV2). The K value is (OCV1 - OCV2) / 48, expressed in mV / h.

[0221] (8) Discharge rate test

[0222] Proceed as follows:

[0223] After the battery cell was left at rest for 30 minutes at 25°C, it was discharged at a constant current of 0.33C to 2.5V (Example 2, Example 4 and Comparative Example 2 were discharged at a constant current of 2.8V); after standing at 25°C for 1 hour, it was charged at a constant current of 0.33C to 3.65V (Example 2, Example 4 and Comparative Example 2 were charged at a constant current of 4.25V); and constant voltage charged at 3.65V (or 4.25V) to a cutoff current of 0.05C.

[0224] Repeat the above steps once, let it stand at 25°C for 30 minutes, and then discharge at 1C to 2.5V (Example 2, Example 4 and Comparative Example 2 discharge to 2.8V). After standing at 25°C for 1 hour, charge at a constant current of 0.33C to 3.65V (Example 2, Example 4 and Comparative Example 2 charge to 4.25V); charge at a constant voltage of 3.65V (or 4.25V) to a cutoff current of 0.05C. After standing at 25°C for 30 minutes, discharge at 4C to 2.5V (Example 2, Example 4 and Comparative Example 2 discharge to 2.8V). Finally, let it stand at 25°C for 30 minutes.

[0225] The discharge capacity during the test was recorded, and the 4C discharge rate retention rate was calculated based on the discharge capacity at 4C and 1C.

[0226] (9) DC impedance test

[0227] Proceed as follows:

[0228] After the cell was allowed to rest at 25°C for 30 minutes, it was charged at a constant current of 0.33C to 3.65V (Example 2, Example 4, and Comparative Example 2 were charged to 4.25V at a constant current). It was then charged at a constant voltage to a cutoff current of 0.05C, at which point the battery's state of charge (SOC) was 100%. After resting at 25°C for 5 minutes, it was discharged at a constant current of 0.33C with a cutoff current of 0.5C to adjust the SOC to 50%. After resting at 25°C for 1 hour, the voltage V1 was recorded. The cell was discharged at a constant current of 5C for 30 seconds, and the voltage V2 and the current I of the 5C constant current discharge were recorded.

[0229] Let it stand for 40 seconds at 25°C, and charge at a constant current of 3.75C for 30 seconds. After letting it stand for 1 hour at 25°C, charge at a constant current of 0.33C to 3.65V (Example 2, Example 4 and Comparative Example 2 are charged to 4.25V with a constant current); charge at a constant voltage of 3.65V (or 4.25V) with a cut-off current of 0.05C. Let it stand for 5 minutes at 25°C, and record the voltage V1'. Then discharge at 0.33C with a cut-off current of 0.9C, and adjust the SOC to 50%. After letting it stand for 1 hour at 25°C, discharge at 5C for 30 seconds, and record the voltage V2' and the current I' of the 5C constant current discharge.

[0230] Let it rest at 25°C for 40 seconds, then charge at 3.75C constant current for 30 seconds. After letting it rest at 25°C for 5 minutes, you can repeat the above steps multiple times.

[0231] The DC impedance of the battery cell at 25°C, 50% SOC, and 5C constant current discharge for 30s = (V2-V1) / I = (V2'-V1') / I'.

[0232] 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 method for processing a pole piece, wherein the pole piece comprises an active layer, wherein the active layer comprises an active material and a binder, wherein: The treatment method includes: heating the electrode to raise the temperature of the active layer to a treatment temperature; the treatment temperature is greater than or equal to the softening temperature or melting temperature of the binder, and is less than the lowest temperature among the decomposition temperature, oxidation temperature, and ignition temperature of the active material; The heating treatment method includes laser irradiation treatment; The surface of the pole piece includes a first surface and a second surface disposed opposite to each other; the laser irradiation treatment step includes: performing laser irradiation treatment on the first surface using a first laser beam, and performing laser irradiation treatment on the second surface using a second laser beam; the first laser beam and the second laser beam are spaced apart in a direction parallel to the first surface and the second surface; In the laser irradiation processing step, the maximum size of the laser spot falling on the surface of the pole piece is greater than or equal to the minimum size of the surface of the pole piece.

2. The electrode processing method according to claim 1, characterized in that: The electrode is a positive electrode, and the processing temperature is less than or equal to the decomposition temperature of the binder.

3. The electrode processing method according to claim 1 or 2, characterized in that: The processing temperature is 160-400°C.

4. The electrode processing method according to claim 3, characterized in that: The treatment temperature is 180-370°C.

5. The electrode processing method according to claim 3, characterized in that: The electrode is a positive electrode, and the processing temperature is 160-260°C or 280-400°C.

6. The electrode processing method according to claim 1, characterized in that: The electrode is a negative electrode, and the processing temperature is 180-350°C.

7. The electrode processing method according to claim 6, characterized in that: The treatment temperature is 200-350°C.

8. The electrode processing method according to claim 1, characterized in that: The heating time is 0.02-0.3s.

9. The electrode processing method according to claim 8, characterized in that: The heating time is 0.02-0.2s.

10. The electrode processing method according to claim 1, characterized in that: The laser irradiation processing step includes: moving the pole piece relative to the laser spot falling on the surface of the pole piece, and the speed of the moving processing is 10~200m / min.

11. The electrode processing method according to claim 10, characterized in that: The speed of the moving process is 30-200 m / min.

12. The electrode processing method according to any one of claims 1, 10 and 11, characterized in that: The power of the laser irradiation treatment is 100~8000W.

13. The electrode processing method according to claim 12, characterized in that: The power of the laser irradiation treatment is 1000~7000W.

14. The electrode processing method according to claim 1 or 2, characterized in that: Before the heating step, a step of drying the electrode is included.

15. The electrode processing method according to claim 1 or 2, characterized in that: Before the heating step, a step of forming the pole piece is included.

16. The electrode processing method according to claim 15, characterized in that: The forming process includes one or both of cold pressing and hot pressing.

17. The electrode processing method according to claim 1 or 2, characterized in that: Before the heating step, the step of cutting the electrode piece is included.

18. A pole piece, characterized in that: The pole piece is obtained by processing according to any one of claims 1 to 17.

19. A battery, characterized in that: The battery comprises the electrode as claimed in claim 18.

20. An electrical device, characterized in that: The electrical device comprises the battery as claimed in claim 19.

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