Method for manufacturing pole piece, pole piece, battery, and electric device

Abstract

This application belongs to the field of battery technology, and particularly relates to a method for preparing an electrode, the electrode itself, a battery, and an electrical device. The method for preparing the electrode includes: preparing an active layer comprising an active material and a binder on at least one side of a current collector; heating the active layer to raise its surface temperature to a heating temperature; and holding the active layer at a holding temperature; wherein the heating temperature and the holding temperature are independently greater than or equal to the melting point or softening point of the binder, and less than the decomposition temperature of the binder. Using the method of this application to prepare the electrode enables batteries using this electrode to have excellent cycle performance.

Description

Technical Field

[0001] This application belongs to the field of battery technology, and in particular relates to methods for preparing electrodes, electrodes, batteries, and electrical devices. Background Technology

[0002] As batteries are used in more and more scenarios, the market is placing increasingly higher demands on their performance, and battery life is one of the key performance indicators affecting the user experience of various electrical devices. Therefore, extending battery life is crucial for promoting further battery development.

[0003] Electrodes are a crucial component of batteries and have a significant impact on battery life. Therefore, improving electrodes can enhance battery life. However, during battery cycling, electrodes often experience performance degradation, resulting in poor cycle performance and consequently shortened battery life. Summary of the Invention

[0004] In view of the above problems, this application provides a method for preparing an electrode, an electrode, a battery, and an electrical device, which can solve the problem of poor battery cycle performance.

[0005] In a first aspect, this application provides a method for preparing an electrode sheet, comprising:

[0006] An active layer comprising an active substance and a binder is prepared on at least one side of the current collector;

[0007] The active layer is subjected to a heat treatment, which raises the surface temperature of the active layer to the heating temperature.

[0008] The active layer is subjected to heat preservation treatment so that the surface of the active layer is at the heat preservation temperature;

[0009] The heating temperature and the heat preservation temperature are each independently greater than or equal to the melting point or softening point of the adhesive, and less than the decomposition temperature of the adhesive.

[0010] The method for preparing the electrode using the embodiments of this application enables the battery using the electrode to have excellent cycle performance, which is mainly due to:

[0011] (1) In the preparation method of this application embodiment, the active layer is heated to raise the surface temperature of the active layer to or above the melting point or softening point of the binder, causing the binder to become molten or softened. At the same time, heat preservation treatment is performed at the same temperature range, which can promote the re-movement of the binder molecular chains in the molten or softened state, thereby facilitating the uniform distribution of the binder in the active layer, facilitating the release of internal stress in the electrode, and increasing the cohesion and adhesion of the electrode, ultimately improving the cycle performance of the battery.

[0012] (2) The redistribution of binder includes the infiltration of binder from the surface of the active layer into the interior of the active layer. This helps to reduce the amount of binder on the surface of the active layer, thereby helping to increase the porosity of the surface of the active layer, accelerate the absorption rate of electrolyte by the electrode, and enable the electrode to fully contact the electrolyte, thereby effectively participating in the electrochemical reaction, reducing the internal resistance of the battery during the charge and discharge cycle, and thus improving the cycle performance of the battery.

[0013] (3) The temperature during heating and heat preservation is lower than the decomposition temperature of the binder. The binder will not decompose (ablation) during heating and heat preservation, which is beneficial to maintaining the total amount of binder in the active layer, improving the cohesion and adhesion of the electrode. At the same time, the active material will not be affected by the decomposition products of the binder during heating and heat preservation, which is further beneficial to improving the cycle performance of the battery.

[0014] (4) During the heating and heat preservation process, the moisture and residual impurities adsorbed in the active layer volatilize, which helps to reduce the reaction between the moisture in the electrode and the lithium salt in the electrolyte, thereby improving the interface stability of the electrode and improving the battery cycle performance.

[0015] In some embodiments, the heating temperature and the holding temperature are each independently less than or equal to the average of the melting point or softening point of the binder and the decomposition temperature of the binder. Thus, the binder does not decompose (ablate) during heating and holding, which helps maintain the total amount of binder in the active layer, improves the cohesion and adhesion of the electrode, and prevents binder decomposition residues from affecting the active material. Furthermore, at this temperature, the binder can maintain a high viscosity, preventing excessive flow and thus contributing to the stability of the electrode structure.

[0016] In some embodiments, the heat preservation treatment time is greater than or equal to 0.1 s, optionally 0.1 to 2.5 s. Through heat preservation for a certain period, the adhesive in a molten or softened state on the surface has sufficient time to penetrate into the active layer, thereby balancing the distribution of the adhesive in the active layer.

[0017] In some embodiments, the heat preservation temperature is less than or equal to the heating temperature. Having a heat preservation temperature equal to or lower than the heating temperature not only maintains the molten or softened state of the binder, keeping it in a flowable state with high viscosity, but also prevents excessive flow of the binder, which helps maintain the stability of the electrode structure and avoids powder shedding.

[0018] In some embodiments, the melting point or softening point of the binder is 140–180°C, and the decomposition temperature of the binder is 300–350°C; the heating temperature and the holding temperature are each independently 170–230°C, optionally 190–230°C. For different binders, the heating temperature and holding temperature can be set within suitable ranges. Within the above-mentioned heating and holding temperature ranges, the binder can melt or soften without decomposition, and the active material is free from binder residue interference, which is beneficial for maintaining the structural and performance stability of the active material.

[0019] In some embodiments, the active material includes lithium nickel cobalt manganese oxide; optionally, the molar ratio of Ni, Co, and Mn in the lithium nickel cobalt manganese oxide is (1-8):(1-2):(1-3). The method of this application embodiment can be used to prepare different lithium nickel cobalt manganese oxide cathode sheets, and can maintain the stability of lithium nickel cobalt manganese oxide during the preparation process, resulting in a battery with excellent cycle performance.

[0020] In some embodiments, the number-average molecular weight of the adhesive is (35–150) × 10⁻⁶. 4 The optional configuration is (45~150)×10 4 Typically, the melting point or softening point of an adhesive is related to its molecular weight. Within this number-average molecular weight range, adhesives with lower melting or softening points facilitate the implementation of the heating and heat preservation steps of the embodiments of this application at low temperatures.

[0021] In some embodiments, the heating treatment and the heat preservation treatment each independently include laser irradiation. Using a laser as a heat source offers advantages such as high energy density in a short time and high heating efficiency, enabling rapid heating of the active layer to the desired temperature. Furthermore, laser irradiation features controllable power, controllable wavelength, and high stability, effectively controlling the active layer temperature within the required range.

[0022] In some embodiments, the laser includes one or more of infrared wavelength lasers and near-infrared wavelength lasers. Optionally, the wavelength of the laser is 1000 nm to 15 μm. The electrode has strong absorption of infrared and near-infrared light. Irradiation with a laser in this wavelength range has a high photothermal conversion efficiency, which can heat the active layer to the required temperature in a short time.

[0023] In some embodiments, the laser power in the heat treatment step is 2000–4500 W, optionally 2000–4000 W. Performing heat treatment under high-power laser light is beneficial for rapidly raising the temperature of the active layer.

[0024] In some embodiments, the laser power in the heat preservation step is 80–200W, optionally 100–150W. Performing the heat preservation process under low-power laser can maintain the surface temperature of the active layer within the required temperature range without overheating.

[0025] In some embodiments, the method for preparing the electrode further includes a step of compacting the electrode after heat preservation treatment. During the heat treatment and heat preservation steps, the binder in the active layer is redistributed, and the moisture and impurities absorbed in the active layer evaporate, which may cause changes in the electrode thickness. Therefore, compaction after heat preservation treatment is beneficial for controlling the electrode thickness, for example, ensuring that the electrode thickness remains consistent before and after the heating and heat preservation treatments.

[0026] Secondly, this application provides an electrode sheet, which is obtained according to the preparation method of the first aspect mentioned above.

[0027] In the electrode of this application embodiment, the binder is uniformly distributed, which makes the electrode have high adhesion, high porosity and low water content. It can still maintain good structural stability after long-term charge and discharge cycles, which is beneficial to improving the cycle performance of the battery using this electrode.

[0028] Thirdly, this application provides a battery comprising the electrode sheet described in the second aspect.

[0029] The aforementioned electrode has high adhesion, high porosity, low water content, and good structural stability. Batteries containing this electrode will also exhibit excellent cycle performance and long battery life.

[0030] Fourthly, this application provides an electrical device, which includes the battery described in the third aspect.

[0031] The battery disclosed in this application can be used in electrical devices that use batteries as a power source, or in various energy storage systems that use batteries as energy storage elements, to provide electrical energy. The battery exhibits advantages such as good cycle performance and long lifespan; therefore, applying this battery to various electrical devices will improve the user experience of these devices. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1This is a schematic diagram of a battery cell according to one embodiment of this application;

[0034] Figure 2 for Figure 1 An exploded view of a battery cell according to one embodiment of this application is shown.

[0035] Figure 3 This is a schematic diagram of a battery module according to one embodiment of this application;

[0036] Figure 4 This is a schematic diagram of a battery pack according to one embodiment of this application;

[0037] Figure 5 for Figure 4 An exploded view of a battery pack according to one embodiment of this application is shown;

[0038] Figure 6 This is a schematic diagram of an electrical device that uses a battery as a power source according to one embodiment of this application;

[0039] Figure 7 The results are the cycle performance test results of the lithium-ion batteries in Example 1 and Comparative Example 1 of this application;

[0040] Figure 8 The XRD patterns of the lithium nickel cobalt manganese oxide cathode sheet of Example 1 of this application before and after heat treatment and heat preservation treatment are shown.

[0041] Figure 9 These are SEM images of the lithium nickel cobalt manganese oxide cathode sheet of Example 1 of this application before and after heat treatment and heat preservation treatment;

[0042] Figure 8 and Figure 9 In this context, "before treatment" refers to the period before heat treatment and heat preservation treatment, while "after treatment" refers to the period after heat treatment and heat preservation treatment.

[0043] Figure label:

[0044] 01-Housing, 02-Cover plate, 03-Electrode assembly, 04-Battery cell, 05-Battery module, 06-Upper housing, 07-Lower housing. Detailed Implementation

[0045] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0046] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0047] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0048] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0049] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0050] In the description of the embodiments of this application, the term "at least one" refers to one or more, and "more than one" refers to two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0051] It should be understood that in the various embodiments of this application, the order of the above processes does not imply the order of execution. Some or all steps may 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 this application.

[0052] The weights of the relevant components mentioned in the embodiments of this application can refer not only to the specific content of each component, but also to the proportional relationship between the weights of the components. Therefore, any scaling up or down of the content of the relevant components according to the embodiments of this application is within the scope disclosed in the embodiments of this application. Specifically, the mass described in the embodiments of this application can be a mass unit known in the chemical industry, such as μg, mg, g, or kg.

[0053] Electrodes are a crucial component of batteries and have a significant impact on battery life. However, during battery cycling, electrode performance often deteriorates, resulting in poor battery cycle performance.

[0054] Electrodes are composed of important components such as active materials and binders, which significantly influence their performance. For example, lithium nickel manganese cobalt oxide (LiCoMnO), as a superior positive electrode active material for lithium-ion batteries, has been widely used in passenger and commercial vehicles in recent years. Compared to lithium iron phosphate, lithium-ion batteries using LiCoMnO as the positive electrode have higher energy density and better fast-charging and low-temperature performance. However, in practice, it has been found that due to the influence of the synthesis process, such as the use of excessive lithium source in the synthesis of LiCoMnO, a significant amount of residual alkali, such as lithium oxide and lithium carbonate, is present in the LiCoMnO. The presence of residual alkali makes LiCoMnO easily absorb moisture from the air. After being assembled into a secondary battery, this moisture reacts with the lithium salts in the electrolyte, causing gas generation and deteriorating the battery's cycle performance.

[0055] Meanwhile, when active materials and binders are used together to form the active layer of the electrode, there are often problems such as poor binder distribution, uneven porosity distribution, or excessively low porosity, which also affect the battery cycle performance.

[0056] To improve battery cycle performance, various technical approaches have been researched. For example, forming a coating layer on the surface of the active material can improve interfacial interactions during battery cycling, thereby enhancing cycle performance. However, the presence of the coating layer may negatively impact the electronic or ion conductivity of the electrode, leading to higher internal resistance and reduced cycle performance. Another approach involves using radiation irradiation to prepare the electrode, reducing binder aging and improving electrode stability, thus enhancing cycle performance. However, radiation irradiation can cause crystal distortion of the active material and react with organic matter in the electrode to form residual free radicals, degrading electrode capacity and hindering effective improvement in battery cycle performance.

[0057] To address the aforementioned issues, embodiments of this application involve heating and heat preservation treatment of the electrode during electrode preparation, while controlling the heating and heat preservation temperatures within a certain range. This improves the electrode structure, including balancing the distribution of binder in the electrode, improving electrode porosity, reducing electrode moisture, and maintaining the stability of the active material, thereby improving battery cycle performance.

[0058] The electrode sheets processed by the above method can be used to manufacture batteries, and then applied to various electrical devices, including but not limited to mobile phones, tablets, laptops, electric toys, power tools, electric vehicles, electric cars, ships, spacecraft, etc.

[0059] The present application is further illustrated below with reference to embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the present application.

[0060] [Preparation methods for electrode sheets]

[0061] The first aspect of this application provides a method for preparing an electrode sheet, comprising:

[0062] An active layer comprising an active substance and a binder is prepared on at least one side of the current collector;

[0063] The active layer is heated to the heating temperature.

[0064] The active layer is insulated to keep its surface at the insulated temperature.

[0065] The heating temperature and the holding temperature are each independently greater than or equal to the melting point or softening point of the adhesive, and less than the decomposition temperature of the adhesive.

[0066] In the electrode preparation method of this application embodiment, the surface layer of the active layer refers to the outermost layer of the active layer that is in contact with the outside world. Generally, the electrode includes a current collector and an active layer disposed on at least one side of the current collector; therefore, the surface layer of the active layer is usually also the surface layer of the electrode. Generally, the area within 40% of the electrode thickness along the electrode thickness direction from the outside to the inside can be regarded as the surface layer of the electrode.

[0067] The softening point is the temperature at which the three-dimensional long-range ordered state of the macromolecular chain structure of an amorphous polymer transforms into a disordered viscous flow state. The melting point is the temperature at which the three-dimensional long-range ordered state of the macromolecular chain structure of a crystalline polymer transforms into a disordered viscous flow state; it represents the lower limit of the molding and processing temperature for crystalline polymers. Generally, the melting point range is relatively narrow, while the softening point range is relatively wide. The decomposition temperature refers to the temperature at which, with further increases in temperature, the degradation of the polymer molecular chains in the viscous flow state intensifies, and may even lead to significant degradation of the polymer molecular chains.

[0068] The method for preparing the electrode using the embodiments of this application enables the battery using the electrode to have excellent cycle performance, which is mainly due to:

[0069] (1) In the preparation method of this application embodiment, the active layer is heated to raise the surface temperature of the active layer to or above the melting point or softening point of the binder, causing the binder to become molten or softened. At the same time, heat preservation treatment is performed at the same temperature range, which can promote the re-movement of the binder molecular chains in the molten or softened state, thereby facilitating the uniform distribution of the binder in the active layer, facilitating the release of internal stress in the electrode, and increasing the cohesion and adhesion of the electrode, ultimately improving the cycle performance of the battery.

[0070] (2) The redistribution of binder includes the infiltration of binder from the surface of the active layer into the interior of the active layer. This helps to reduce the amount of binder on the surface of the active layer, thereby helping to increase the porosity of the surface of the active layer, accelerate the absorption rate of electrolyte by the electrode, and enable the electrode to fully contact the electrolyte, thereby effectively participating in the electrochemical reaction, reducing the internal resistance of the battery during the charge and discharge cycle, and thus improving the cycle performance of the battery.

[0071] (3) The temperature during heating and heat preservation is lower than the decomposition temperature of the binder. The binder will not decompose (ablation) during heating and heat preservation, which is beneficial to maintaining the total amount of binder in the active layer, improving the cohesion and adhesion of the electrode. At the same time, the active material will not be affected by the decomposition products of the binder during heating and heat preservation, which is further beneficial to improving the cycle performance of the battery.

[0072] (4) During the heating and heat preservation process, the moisture and residual impurities adsorbed in the active layer volatilize, which helps to reduce the reaction between the moisture in the electrode and the lithium salt in the electrolyte, thereby improving the interface stability of the electrode and improving the battery cycle performance.

[0073] In some embodiments, the heating temperature and the holding temperature are each independently less than or equal to the average of the melting point or softening point of the binder and the decomposition temperature of the binder. Thus, the binder does not decompose (ablate) during heating and holding, which helps maintain the total amount of binder in the active layer, improves the cohesion and adhesion of the electrode, and prevents binder decomposition residues from affecting the active material. Furthermore, at this temperature, the binder can maintain a high viscosity, preventing excessive flow and thus contributing to the stability of the electrode structure.

[0074] In some embodiments, the heat preservation time is greater than or equal to 0.1 s, optionally between 0.1 and 2.5 s, for example, it can be any one of 0.1 s, 0.2 s, 0.4 s, 0.6 s, 0.8 s, 1 s, 1.2 s, 1.4 s, 1.6 s, 1.8 s, 2 s, 2.2 s, 2.5 s, or a range between any two. Through heat preservation for a certain period, the adhesive in the molten or softened state on the surface has sufficient time to penetrate into the active layer, thereby balancing the distribution of the adhesive in the active layer.

[0075] In some embodiments, the heat treatment time is 0.05 to 0.3 seconds, for example, any one of 0.05 seconds, 0.1 seconds, 0.15 seconds, 0.2 seconds, 0.25 seconds, or 0.3 seconds, or a range between any two. The heat treatment time is the time it takes for the surface of the active layer to heat up to the heating temperature. The heating rate affects the uniformity of the material. In the embodiments of this application, rapid heating enables the adhesive on the surface of the active layer to quickly change from a solid state to a molten or softened state; it also facilitates the rapid transfer of heat to the interior of the active layer, causing the adhesive inside the active layer to melt or soften rapidly as well, thereby forming an integral whole with the adhesive on the surface and promoting the uniform distribution of the adhesive in the active layer.

[0076] In some embodiments, the holding temperature is less than or equal to the heating temperature; alternatively, the holding temperature is less than the heating temperature. Holding the temperature to be equal to or lower than the heating temperature not only maintains the molten or softened state of the binder, keeping it in a flowable state with high viscosity, but also prevents excessive flow of the binder, which helps maintain the stability of the electrode structure and avoids powder shedding.

[0077] In some embodiments, the adhesive has a melting point or softening point of 140–180°C and a decomposition temperature of 300–350°C; the heating temperature and holding temperature are independently set to 170–230°C, optionally 190–230°C, for example, any one of 170°C, 180°C, 190°C, 200°C, 210°C, 220°C, or 230°C, or a range between any two. Optionally, the heating temperature can be set to 180–230°C, and the holding temperature can be set to 180–200°C.

[0078] The heating and holding temperatures can be measured using infrared thermometers or other temperature testing instruments. For different binders, the heating and holding temperatures can be set within appropriate ranges. Within these ranges, the binder can melt or soften without decomposition, and the active material is free from binder residue interference, which helps maintain the structural and performance stability of the active material.

[0079] In some embodiments, the active material includes lithium nickel cobalt manganese oxide; optionally, the molar ratio of Ni, Co, and Mn in the lithium nickel cobalt manganese oxide is (1-8):(1-2):(1-3), for example, it can be any one of 8:1:1, 8:1.5:0.5, 6:2:2, 5:2:3, 5:3:2, 1:1:1, or any range between two of these values. The method of this application embodiment can be used to prepare different lithium nickel cobalt manganese oxide cathode sheets, and can maintain the stability of lithium nickel cobalt manganese oxide during the preparation process, resulting in a battery with excellent cycle performance.

[0080] In some embodiments, the melting point or softening point of the binder is 140–180°C, optionally 150–180°C, for example, any one of 140°C, 150°C, 160°C, 170°C, or 180°C, or a range between any two. Using a low-melting-point or low-softening-point binder allows the binder to melt or soften by heating and holding the active layer at a lower temperature, thereby achieving binder redistribution. This helps to reduce the temperature during the heating and holding process, thus reducing the probability of lithium nickel cobalt manganese oxide structural damage and consequently improving the cycle stability of the electrode.

[0081] In some embodiments, the decomposition temperature of the binder is 300–350°C, optionally 300–320°C, for example, any one of 3000°C, 310°C, 320°C, 330°C, 340°C, or 350°C, or a range between any two. Both the heating temperature and the holding temperature are lower than the decomposition temperature of the binder. Heating and holding the active layer below this decomposition temperature can melt or soften the binder, thereby achieving binder redistribution, and can also reduce the probability of lithium nickel cobalt manganese oxide structural damage, thus improving the cycle stability of the electrode.

[0082] In some embodiments, the number-average molecular weight of the adhesive can be set to (35–150) × 10⁻⁶. 4 The optional configuration is (45~150)×10 4 For example, 35×10 4 40×10 4 45×10 4 50×10 4 60×10 4 70×10 4 80×10 4 90×10 4 100×10 4 120×10 4 140×10 4 150×10 4The number-average molecular weight (NMR) is any one of the point values ​​or any range between the two. NMR is a characterization of molecular size, calculated as the total weight of all molecules in a polymer sample divided by the total number of molecules. Gel permeation chromatography (GPC) can be used, with polystyrene (PS) as a standard, to test the NMR of the binder. Typically, the melting point or softening point of an binder is related to its molecular weight; within this NMR range, the binder has a lower melting point or softening point, which facilitates the implementation of the heating and holding steps of the embodiments of this application at low temperatures.

[0083] As an example, the adhesive may include one or more of polyvinylidene fluoride, polyvinylidene fluoride, polyimide, polytetrafluoroethylene, polybutyl acrylate, and polyacrylonitrile, optionally including polyvinylidene fluoride.

[0084] In some embodiments, the active layer further includes a conductive agent, which may include one or more of conductive carbon black, carbon nanotubes, and graphene. Such conductive agents can transfer heat from the surface of the active layer to its interior via electrons, ensuring uniform heating of the positive electrode and promoting the uniform distribution of the binder throughout the active layer.

[0085] The mass content of each substance in the active layer can be set as needed.

[0086] For example, the mass content of the active substance in the active layer may include, but is not limited to, 90% to 98%, or 95% to 98%, such as any one of 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or any range between two.

[0087] The mass content of the adhesive and the conductive agent in the active layer can be independently, but not limited to, 0.5% to 5%, or 1% to 5%, for example, any one of the following values ​​or any range between the two: 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%.

[0088] In some embodiments, the heating treatment and heat preservation treatment each independently include laser irradiation treatment.

[0089] Laser irradiation treatment uses a laser to generate a laser beam and then irradiates the active layer. Using a laser as a heating source offers advantages such as high energy density in a short time and high heating efficiency, enabling rapid heating of the active layer to the required temperature. Furthermore, laser irradiation features controllable power, controllable wavelength, and high stability, effectively controlling the active layer temperature within the desired range.

[0090] Both the heating and heat preservation processes utilize laser irradiation. In practice, at least one set of lasers can be used to heat the active layer, and at least another set of lasers can be used for heat preservation. During the heating or heat preservation process, lasers can be optionally positioned on one or both sides of the electrode to heat or preserve the two surfaces of the active layer.

[0091] In some embodiments, the laser includes one or more of infrared wavelength lasers and near-infrared wavelength lasers. Optionally, the laser wavelength is 1000 nm to 15 μm, or optionally 1000 nm to 3000 nm, for example, any one of 1000 nm, 1200 nm, 1400 nm, 1600 nm, 1800 nm, 2000 nm, 2200 nm, 2400 nm, 2600 nm, 2800 nm, 3000 nm, 5000 nm, 1 μm, 5 μm, 10 μm, and 15 μm, or a range between any two. The laser wavelength is mainly related to the type of laser excitation medium; therefore, different laser wavelengths can be obtained by selecting different laser excitation media. Infrared wavelength lasers refer to lasers with wavelengths between 0.76 and 100 μm, while near-infrared wavelength lasers refer to lasers with wavelengths between 780 and 3000 nm. The electrode has strong absorption of infrared and near-infrared light. When irradiated with lasers in this wavelength range, it has a high photothermal conversion efficiency and can heat the active layer to the required temperature in a short time.

[0092] In some embodiments, the laser generating laser includes one or more of neodymium-doped yttrium aluminum garnet (Nd:YAG) lasers, ytterbium-doped yttrium aluminum garnet (Yb:YAG) lasers, fiber lasers, CO2 lasers, and antimony arsenide lasers. These lasers can generate infrared or near-infrared wavelength lasers; for example, an Nd:YAG laser can emit laser light with a wavelength of 1064 nm, a Yb:YAG laser can emit laser light with a wavelength of 1030 nm, and a fiber laser can emit laser light with a wavelength of 1080 nm.

[0093] In some embodiments, the laser power in the heat treatment step is 2000–4500 W, optionally 2000–4000 W, for example, any one of 2000 W, 2200 W, 2400 W, 2600 W, 2800 W, 3000 W, 3200 W, 3400 W, 3600 W, 3800 W, 4000 W, 4200 W, or 4500 W, or a range between any two. The laser power can be set directly in the laser. Heating under a high-power laser is beneficial for rapidly raising the temperature of the active layer.

[0094] In some embodiments, the laser power in the heat preservation step is 80–200W, optionally 100–150W, for example, any one of 80W, 100W, 120W, 140W, 150W, 160W, 180W, or 200W, or a range between any two. Performing the heat preservation process under low-power laser power can maintain the surface temperature of the active layer within the required temperature range without overheating.

[0095] In some embodiments, the heating and holding steps each independently include a step of moving the electrode relative to the laser. Optionally, the moving speed is 20–200 m / min, more preferably 20–60 m / min, for example, any one of 20 m / min, 30 m / min, 40 m / min, 50 m / min, 60 m / min, 70 m / min, 80 m / min, 90 m / min, 100 m / min, 120 m / min, 140 m / min, 160 m / min, 180 m / min, 200 m / min, or a range between any two. In the preparation method of this application embodiment, the heating and holding processes can be dynamic, with the electrode moving relative to the laser. The laser performs brief heating and brief holding processes on the electrode, which can raise the temperature of the active layer while reducing heat accumulation and unnecessary side reactions.

[0096] In some implementations, laser irradiation treatment includes one or both of pulsed laser irradiation treatment and continuous laser irradiation treatment. Pulsed laser refers to a single light pulse emitted by a laser operating in pulsed mode, with a certain interval between adjacent light pulses. Continuous laser, on the other hand, is a continuous, uninterrupted laser emitted by a continuous laser. Whether pulsed or continuous laser irradiation is used, the active layer can reach the required temperature within a short time and maintain that temperature.

[0097] In some embodiments, the electrode preparation method further includes a compaction step of the electrode after heat preservation treatment. During the heat treatment and heat preservation steps, the binder in the active layer is redistributed, and the moisture and impurities absorbed in the active layer evaporate, which may cause changes in the electrode thickness. Therefore, performing compaction after heat preservation treatment is beneficial for controlling the electrode thickness, for example, ensuring that the electrode thickness remains consistent before and after the heat and heat preservation treatments. This compaction treatment can be performed at room temperature or at high temperature; for example, the compaction temperature can be 25–130°C, such as any one of the values ​​of 25°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, 120°C, and 130°C, or a range between any two.

[0098] In addition, in the preparation method of the electrode, the preparation method of the active layer containing the active material and the binder can be carried out according to the following steps: mixing the active material, the binder and the solvent to obtain a slurry; coating the slurry on at least one surface of the current collector, and drying and compacting it to obtain the active layer.

[0099] [Extreme Film]

[0100] The second aspect of this application provides an electrode sheet, which is obtained according to the preparation method of the first aspect described above.

[0101] In the electrode of this application embodiment, the binder is uniformly distributed, which makes the electrode have high adhesion, high porosity and low water content. It can still maintain good structural stability after long-term charge and discharge cycles, which is beneficial to improving the cycle performance of the battery using this electrode.

[0102] Understandably, structurally, the electrode may include a current collector and an active layer disposed on at least one surface of the current collector, the active layer comprising an active material and a binder. Furthermore, the electrode may be prepared by the method of the first aspect.

[0103] In some embodiments, the adhesion strength of the electrode is greater than or equal to 25 N / m, optionally between 25 and 28 N / m, for example, any one of 25 N / m, 26 N / m, 27 N / m, or 28 N / m, or a range between any two. The adhesion strength of the electrode can be obtained by testing with a high-speed rail tensile testing machine. The electrode of the embodiments of this application has high adhesion strength, which is beneficial to maintaining the stability of the electrode during battery cycling, thereby improving the cycle performance of the battery.

[0104] In some embodiments, the water content of the electrode is ≤60ppm, optionally 25-60ppm, for example, any one of 25ppm, 30ppm, 35ppm, 40ppm, 45ppm, 50ppm, 55ppm, 60ppm or a range between any two. The water content of the electrode refers to the mass content of water in the electrode, which can be measured by a moisture analyzer. A low water content helps reduce the reaction between water in the electrode and lithium salts in the electrolyte, thereby improving the interfacial stability of the electrode and enhancing battery cycle performance.

[0105]

Battery

[0106] A third aspect of this application provides a battery that includes the electrodes described in the second aspect.

[0107] The aforementioned electrode has high adhesion, high porosity, low water content, and good structural stability. Batteries containing this electrode will also exhibit excellent cycle performance and long battery life.

[0108] The active material in the aforementioned electrode may include lithium nickel cobalt manganese oxide cathode material, therefore the electrode can be used as the cathode of a battery.

[0109] Typically, a battery may also include a negative electrode, an electrolyte, a separator, and outer packaging. Furthermore, the battery in this application embodiment may include one or more of the following: a battery cell, a battery module, and a battery pack.

[0110] 1. Negative electrode plate

[0111] The negative electrode sheet may include a negative current collector and a negative active layer containing a negative active material, a binder, and a conductive agent disposed on at least one side of the negative current collector.

[0112] The negative electrode current collector can include, but is not limited to, metal current collectors, carbon current collectors, conductive resin current collectors, and composite current collectors of metal and resin, and more specifically, copper, nickel, titanium, iron and their respective alloys, stainless steel, carbon fiber, carbon nanotubes (CNTs), graphite, etc.

[0113] The negative electrode active material may include one or more of graphite, hard carbon, soft carbon, mesophase carbon microspheres, graphene, silicon, and silicon dioxide. The mass content of the negative electrode active material in the negative electrode active layer may include, but is not limited to, 90% to 98%, such as 95% to 98%, for example, any one of 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, and 98%, or any range between two.

[0114] The conductive agent in the negative electrode sheet may include, but is not limited to, acetylene black (SP), carbon nanotubes, conductive carbon black (super-P), Ketjen black, carbon fiber, graphene, etc. The mass content of the conductive agent in the active layer of the negative electrode sheet is, but is not limited to, 0.5% to 10%, or 1% to 5%, for example, any one of the following values ​​or any range between two: 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%.

[0115] The negative electrode active layer may optionally 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%, or, for example, 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%, 5%, or a range between any two.

[0116] 2. Electrolytes

[0117] Electrolytes can serve as carriers for ion transport in batteries. In the batteries of this application embodiment, the electrolyte used can be a solid electrolyte, such as a polymer electrolyte or an inorganic solid electrolyte, but is not limited to these; the electrolyte can also be a liquid electrolyte. The aforementioned liquid electrolyte includes a solvent and a lithium salt dissolved in the solvent.

[0118] The solvent may be a non-aqueous organic solvent, such as one or more of ethylene carbonate (EC), propylene carbonate (PC), methyl ethyl 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.

[0119] Lithium salts may include 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 trifluoromethanesulfonate), LiDFOB (lithium difluorooxalate borate), LiBOB (lithium bis(oxalate borate), LiPO2F2 (lithium difluorophosphate), LiDFOP (lithium difluorooxalate phosphate), and LiTFOP (lithium tetrafluorooxalate phosphate), for example, one or more of LiPF6 (lithium hexafluorophosphate), LiBF4 (lithium tetrafluoroborate), LiBOB (lithium bis(oxalate borate), LiDFOB (lithium difluorooxalate borate), LiTFSI (lithium bis(trifluoromethanesulfonyl)imide), and LiFSI (lithium bis(fluorosulfonyl)imide).

[0120] The electrolyte may also optionally contain other additives, such as vinylene carbonate (VC), ethylene ethylene carbonate (VEC), fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), trifluoromethyl ethylene carbonate (TFPC), succinic anionyl (SN), adiponitrile (ADN), glutaronitrile (GLN), hexanetrionitrile (HTN), 1,3-propanesulfonyl lactone (1,3-PS), vinyl sulfate (DTD), methylene disulfonate (MMDS), and 1-propene-1,3-sulfonyl lactone. One or more of the following, but not limited to: (PST), 4-methyl ethylene sulfate (PCS), 4-ethyl ethylene sulfate (PES), 4-propyl ethylene sulfate (PEGLST), propylene sulfate (TS), 1,4-butane sulpholactone (1,4-BS), ethylene sulfite (DTO), dimethyl sulfite (DMS), diethyl sulfite (DES), sulfonate cyclic quaternary ammonium salts, tris(trimethylsilane) phosphate (TMSP), and tris(trimethylsilane) borate (TMSB).

[0121] 3. Separating membrane

[0122] The battery also includes a separator membrane stacked between the positive and negative electrodes to separate the positive and negative electrodes, preventing electrons in the battery from passing freely and preventing short circuits between the two electrodes, while allowing ions in the electrolyte to pass freely between the positive and negative electrodes.

[0123] The separator can be any porous structure separator with electrochemical and mechanical stability, such as one or more single-layer or multi-layer films made of glass fiber, non-woven fabric, polyethylene (PE), polypropylene (PP) and polyvinylidene fluoride (PVDF).

[0124] 4. Outer packaging

[0125] The battery may include an outer packaging. This outer packaging may be used to encapsulate an electrode assembly containing a positive electrode, a negative electrode, a separator, and an electrolyte.

[0126] The outer packaging of batteries can be a hard shell, such as a hard plastic shell, aluminum shell, or steel shell; or it can be a soft pack, such as a pouch. The material of the soft pack can be plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0127] The outer packaging can be cylindrical, square, or any other shape. For example, Figure 1 The battery cell, as an example, has a square outer packaging shape.

[0128] Reference Figure 2The outer packaging may include a housing 01 and a cover plate 02. The housing 01 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 01 has an opening communicating with the receiving cavity, and the cover plate 02 can be placed over the opening to close the receiving cavity. A positive electrode, a negative electrode, and a separator can be formed into an electrode assembly 03 via a winding or stacking process. One or more electrode assemblies 03 are encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 03.

[0129] 5. Battery cells, battery modules, and battery packs

[0130] The battery in this application embodiment can be at least one of a battery cell, a battery module, or a battery pack. Depending on the packaging form, batteries are classified as battery cells, battery modules, and battery packs. A battery cell is the most basic unit of a secondary battery, including an electrode assembly and an electrolyte. The electrode assembly typically consists of a positive electrode, a negative electrode, and a separator. A bare cell is obtained by alternately stacking the positive and negative electrodes and placing a separator between them for isolation; alternatively, a bare cell can be obtained by winding the electrodes. The cell is placed in a casing, injected with electrolyte, and sealed to obtain a battery cell. A battery cell primarily functions by the movement of metal ions in the electrolyte between the positive and negative electrodes.

[0131] In some battery packaging technologies, one or more individual battery cells can be integrated into a battery module, and then one or more battery modules can be assembled into a battery pack. In other battery packaging technologies, one or more individual battery cells can be directly installed in a housing to form a battery pack, eliminating the intermediate state of battery modules, thereby reducing the weight of the battery pack and increasing the energy density of the battery.

[0132] refer to Figure 3 This is an example battery module. In the battery module, multiple battery cells 04 can be arranged sequentially along the length of the battery module. Of course, they can also be arranged in any other arbitrary way. Furthermore, these multiple battery cells 04 can be secured using fasteners.

[0133] Optionally, the battery module may also include a housing with a receiving space in which multiple battery cells 04 are received.

[0134] refer to Figure 4 and Figure 5 This is an example of a battery pack. The battery pack may include a battery compartment and multiple battery modules 05 disposed within the battery compartment. The battery compartment includes an upper body 06 and a lower body 07, with the upper body 06 covering the lower body 07 to form a closed space for accommodating the battery modules 05. The multiple battery modules 05 can be arranged in any manner within the battery compartment.

[0135] Electrical appliances

[0136] This application also provides an electrical device that includes the battery described in the third aspect above.

[0137] The battery disclosed in this application can be used in electrical devices that use batteries as a power source, or in various energy storage systems that use batteries as energy storage elements, to provide electrical energy. The battery exhibits advantages such as good cycle performance and long lifespan; therefore, applying this battery to various electrical devices will improve the user experience of these devices.

[0138] Electrical devices can include, but are not limited to, mobile phones, tablets, laptops, electric toys, power tools, electric vehicles, electric cars, ships, spacecraft, etc. Electric toys can include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Spacecraft can include airplanes, rockets, space shuttles, and spacecraft, etc. As for the aforementioned electrical devices, battery cells, battery modules, or battery packs can be selected according to their usage requirements.

[0139] Figure 6 This is an example of an electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the device's requirements for high power and high energy density, a battery pack or battery module can be used.

[0140] The embodiments of this application are described in detail below. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0141]

Example

[0142] Example 1

[0143] 1) Lithium nickel cobalt manganese oxide cathode sheet

[0144] This embodiment provides a lithium nickel cobalt manganese oxide positive electrode sheet and its preparation method. The lithium nickel cobalt manganese oxide positive electrode sheet includes an aluminum foil and a positive electrode active layer disposed on two surfaces of the aluminum foil. The positive electrode active layer contains lithium nickel cobalt manganese oxide, conductive carbon black, carbon nanotubes and PVDF.

[0145] The preparation method of lithium nickel cobalt manganese oxide cathode sheet includes the following steps:

[0146] The mixture consists of 96 wt% lithium nickel cobalt manganese oxide (molar ratio Ni:Co:Mn = 8:1:1), 1.0 wt% conductive carbon black, 0.5 wt% carbon nanotubes, and 2.5 wt% PVDF (number average molecular weight 600,000, i.e., 60 × 10⁻⁶). 4 The following materials were mixed (melting point 172℃, decomposition temperature 310℃), then N-methylpyrrolidone was added and stirred to disperse, thus preparing a positive electrode slurry containing lithium nickel cobalt manganese oxide. This positive electrode slurry was coated onto aluminum foil, dried, and cold-pressed to obtain a double-sided loading of 0.6 g / 1540.25 mm. 2 The compacted density is 3.5 g / cm³. 3 Lithium nickel cobalt manganese oxide cathode sheet.

[0147] The cold-pressed products are then subjected to heating and heat preservation treatments in sequence.

[0148] Heat treatment: The lithium nickel cobalt manganese oxide (LCO) cathode sheet is moved at a constant speed of 20 m / min under the influence of a laser. A 2000W Nd:YAG laser is placed on each side of the LCO cathode sheet. The laser heats the surface temperature of the active layer of the LCO cathode sheet to 200℃ (heating temperature).

[0149] Heat preservation treatment: Then, under the irradiation of two 100W fiber lasers arranged along the direction of movement of the lithium nickel cobalt manganese oxide positive electrode sheet and set on both sides of the lithium nickel cobalt manganese oxide positive electrode sheet, the surface of the active layer contained in the lithium nickel cobalt manganese oxide positive electrode sheet is kept at 190℃ (heat preservation temperature) for 1 second (heat preservation time).

[0150] Then it is cooled to 25°C and rolled.

[0151] 2) Lithium-ion batteries

[0152] This embodiment also provides a lithium-ion battery, which includes an electrode assembly (bare cell) composed of the above-mentioned lithium nickel cobalt manganese oxide positive electrode, graphite negative electrode, and separator, as well as electrolyte and outer packaging. The bare cell is placed in the outer packaging, and the electrolyte wets the bare cell.

[0153] Lithium-ion batteries can be assembled as follows:

[0154] A mixture of 95 wt% artificial graphite, 1.0 wt% conductive carbon black, 2.0 wt% styrene-butadiene rubber (SBR), and 2.0 wt% sodium carboxymethyl cellulose (CMC) was prepared by mixing, adding deionized water, and stirring to disperse the mixture into a negative electrode slurry. The negative electrode slurry was then coated onto a Cu foil. After coating both sides, the foil was dried, cold-pressed, slit, and sheeted to obtain a graphite negative electrode sheet.

[0155] The graphite negative electrode sheet, separator, and lithium nickel cobalt manganese oxide positive electrode sheet are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. The resulting bare cell is then wound up. The bare cell is placed in outer packaging, injected with prepared electrolyte, and then subjected to processes such as encapsulation, electrolyte injection, formation, and venting to obtain a lithium-ion battery (cell).

[0156] Example 2

[0157] The only difference between this embodiment and Embodiment 1 is that in the preparation method of the lithium nickel cobalt manganese oxide positive electrode, the electrode movement speed is 60 m / min, the heating laser power is 3000 W, the heating temperature is 190℃, and the holding time is 0.33 s. Everything else is the same as in Embodiment 1.

[0158] Example 3

[0159] The only difference between this embodiment and Embodiment 1 is that in the preparation method of the lithium nickel cobalt manganese oxide positive electrode, the electrode movement speed is 200 m / min, the heating laser power is 4000 W, the heating temperature is 180℃, and the holding time is 0.1 s. Everything else is the same as in Embodiment 1.

[0160] Example 4

[0161] The only difference between this embodiment and Embodiment 3 is that the heat preservation time in the preparation method of the lithium nickel cobalt manganese oxide positive electrode is 0.5 s. Everything else is the same as in Embodiment 3.

[0162] Example 5

[0163] The only difference between this embodiment and Embodiment 3 is that the heat preservation time in the preparation method of the lithium nickel cobalt manganese oxide positive electrode is 2 seconds. Everything else is the same as in Embodiment 3.

[0164] Example 6

[0165] The only difference between this embodiment and Embodiment 1 is that in the preparation method of the lithium nickel cobalt manganese oxide cathode, the molar ratio of Ni:Co:Mn in the lithium nickel cobalt manganese oxide is 6:2:2, the heating laser power is 3500W, and the heating temperature is 210℃. Everything else is the same as in Embodiment 1.

[0166] Example 7

[0167] The only difference between this embodiment and Embodiment 1 is that in the preparation method of the lithium nickel cobalt manganese oxide cathode, the molar ratio of Ni:Co:Mn in the lithium nickel cobalt manganese oxide is 5:2:3, the heating laser power is 4000W, and the heating temperature is 220℃. Everything else is the same as in Embodiment 1.

[0168] Example 8

[0169] The only difference between this embodiment and Embodiment 1 is that in the preparation method of the lithium nickel cobalt manganese oxide cathode, the molar ratio of Ni:Co:Mn in the lithium nickel cobalt manganese oxide is 1:1:1, the heating laser power is 4500W, and the heating temperature is 230℃. Everything else is the same as in Embodiment 1.

[0170] Example 9

[0171] The only difference between this embodiment and Embodiment 1 is that in the preparation method of the lithium nickel cobalt manganese oxide cathode, the PVDF molecular weight is 1 million and the PVDF melting point is 175℃. Everything else is the same as in Embodiment 1.

[0172] Example 10

[0173] The only difference between this embodiment and Embodiment 1 is that in the preparation method of the lithium nickel cobalt manganese oxide cathode, the PVDF molecular weight is 1.5 million and the PVDF melting point is 180°C. Everything else is the same as in Embodiment 1.

[0174] Example 11

[0175] The only difference between this embodiment and Embodiment 1 is that in the preparation method of the lithium nickel cobalt manganese oxide cathode, the PVDF molecular weight is 450,000 and the PVDF melting point is 150°C. Everything else is the same as in Embodiment 1.

[0176] Example 12

[0177] The only difference between this embodiment and Embodiment 1 is that in the preparation method of the lithium nickel cobalt manganese oxide cathode, the laser in the laser heating step is a Yb:YAG laser, and the laser in the laser heat preservation step is a CO2 laser. Everything else is the same as in Embodiment 1.

[0178] Example 13

[0179] The only difference between this embodiment and Embodiment 1 is that in the preparation method of the lithium nickel cobalt manganese oxide cathode, the laser in the laser heating step is a fiber laser, and the laser in the laser heat preservation step is an antimony arsenide laser. Everything else is the same as in Embodiment 1.

[0180] [Comparative Example]

[0181] Comparative Example 1

[0182] The only difference between this comparative example and Example 1 is that the preparation method of the lithium nickel cobalt manganese oxide cathode does not involve heating or heat preservation. Everything else is the same as in Example 1.

[0183] Comparative Example 2

[0184] The only difference between this comparative example and Example 1 is that the heat preservation treatment is not performed in the preparation method of the lithium nickel cobalt manganese oxide positive electrode. Everything else is the same as in Example 1.

[0185] Comparative Example 3

[0186] The only difference between this comparative example and Example 1 is that in the preparation method of the lithium nickel cobalt manganese oxide cathode, the heating temperature is 320°C and the heating laser power is 5500W. Everything else is the same as in Example 1.

[0187] Comparative Example 4

[0188] The only difference between this comparative example and Example 6 is that the preparation method of the lithium nickel cobalt manganese oxide cathode does not involve heating or heat preservation. Everything else is the same as in Example 6.

[0189] Comparative Example 5

[0190] The only difference between this comparative example and Example 7 is that the preparation method of the lithium nickel cobalt manganese oxide cathode does not involve heating or heat preservation. Everything else is the same as in Example 7.

[0191] Comparative Example 6

[0192] The only difference between this comparative example and Example 8 is that the preparation method of the lithium nickel cobalt manganese oxide cathode does not involve heating or heat preservation. Everything else is the same as in Example 8.

[0193] Electrochemical performance and structural testing

[0194] The positive electrode sheets and lithium-ion batteries of each embodiment and comparative example were tested, and the relevant test results were obtained.

[0195] 1. Heating temperature, holding temperature, and holding time

[0196] Table 1. Electrochemical performance test results of batteries in Examples 1-5 and Comparative Examples 1-3 (PVDF melting point 172℃, decomposition temperature 310℃; Ni:Co:Mn = 8:1:1)

[0197]

[0198] Table 2. Performance test results of the positive electrode sheets in Examples 1-5 and Comparative Examples 1-3

[0199]

[0200] Table 1 shows that, without heating and heat preservation treatment of the positive electrode (Comparative Example 1), the battery retained 96.63% of its capacity after 500 cycles at 1C after applying the positive electrode. However, adding a heating step without heat preservation treatment (Comparative Example 2) resulted in less improvement in battery cycle performance, with a capacity retention of 96.97% after 500 cycles at 1C. Analysis of the results in Table 2 suggests that simply applying heating treatment may not be sufficient to improve the electrode's performance; the bonding strength within the positive electrode does not change significantly, thus offering little improvement in cycle performance.

[0201] In contrast, in Examples 1-5, by sequentially performing heating and heat preservation treatments during the preparation of the positive electrode sheet, the capacity retention rate of the corresponding battery after 500 cycles at 1C can be increased to 97.2% or higher. Figure 7 As shown, the cycle performance was improved. This is mainly because the binder was fully balanced after the heat treatment and heat preservation treatment, which increased the adhesion of the positive electrode sheet. Furthermore, during the heat preservation process, moisture evaporated, increasing the porosity of the positive electrode sheet (the increased liquid absorption rate reflects the increased porosity of the positive electrode sheet, which improves its wettability). Also, during the heat treatment and heat preservation treatment, both the heating and heat preservation temperatures were lower than the decomposition temperature of the binder, allowing the lithium nickel cobalt manganese oxide to remain stable and unaffected by impurities generated during the decomposition of the binder during heating. Figure 8 XRD patterns of the positive electrode sheet in Example 1 before and after heat treatment and heat preservation treatment, and Figure 9 The SEM images of the positive electrode sheet in Example 1 before and after heat treatment and heat preservation treatment show that the crystal form, structure, and degree of crystallinity of lithium nickel cobalt manganese oxide did not change significantly after the heat treatment and heat preservation treatment. Under the combined effect of these phenomena, the interfacial performance of the positive electrode sheet is greatly improved, and the impedance of the positive electrode sheet is reduced, thereby improving the battery cycle performance.

[0202] During the heat treatment and heat preservation processes, both the heating temperature and the heat preservation temperature can be set within a temperature range greater than or equal to the binder's melting point and less than its decomposition temperature. More specifically, they can be set within the first 50% of this range (i.e., greater than or equal to the binder's melting point and less than or equal to the average of its melting point and decomposition temperature). The heating and heat preservation temperatures can be the same or different (the heat preservation temperature can be higher or lower than the heating temperature), both of which improve battery cycle performance, as seen in Examples 1-3. Specifically, when the heat preservation temperature is lower than the heating temperature, the battery exhibits better cycle performance. However, if either the heating or heat preservation temperature is too high, such as in Comparative Example 3 where the heating temperature is set at 320°C, the battery cycle performance will decrease. According to the test results in Table 2, this is mainly due to the excessively high temperature causing the binder to decompose, which reduces the adhesion of the positive electrode sheet; in addition, the decomposition products of the binder react with the active material lithium nickel cobalt manganese oxide, and the decomposition residue remains in the electrode sheet without being removed, which increases the side reactions between the positive electrode sheet and the electrolyte, causing the interface performance of the positive electrode sheet to deteriorate.

[0203] Meanwhile, the battery's cycle performance is related to the holding time. As shown in Examples 3-5, within the holding time range of 0.1-2 seconds, the battery's capacity retention rate after 500 cycles at 1C initially increased and then decreased with increasing holding time. Therefore, a suitable holding time can be selected to achieve better battery cycle performance.

[0204] In addition, the test results also showed that, compared with Comparative Examples 1 to 3, the positive electrode sheets of Examples 1 to 5 had higher specific capacity and better rate performance (higher 3C capacity retention rate), indicating that heating and heat preservation treatment can not only improve battery cycle performance, but also improve specific capacity and rate performance.

[0205] 2. Ni:Co:Mn molar ratio

[0206] Table 3. Electrochemical performance test results of batteries with different Ni:Co:Mn molar ratios (PVDF melting point 172℃, decomposition temperature 310℃)

[0207]

[0208] Table 4. Performance test results of cathode sheets with different Ni:Co:Mn molar ratios

[0209]

[0210] According to the test results in Table 3, the method of sequentially performing heat treatment and heat preservation treatment during the preparation process is applicable to the preparation of positive electrode sheets with different Ni:Co:Mn molar ratios, and can improve the cycle performance of the battery. For example, Example 6 showed a higher capacity retention rate after 500 cycles at 1C than Comparative Example 4, which used the same Ni:Co:Mn molar ratio but did not undergo heat treatment and heat preservation treatment; Example 7 showed a higher capacity retention rate after 500 cycles at 1C than Comparative Example 5, which used the same Ni:Co:Mn molar ratio but did not undergo heat treatment and heat preservation treatment; Example 8 showed a higher capacity retention rate after 500 cycles at 1C than Comparative Example 6, which used the same Ni:Co:Mn molar ratio but did not undergo heat treatment and heat preservation treatment. Similarly, this is mainly because after heat treatment and heat preservation treatment, the binder is fully balanced, increasing the bonding force of the positive electrode sheet. Furthermore, during the heat preservation process, moisture evaporates, increasing the porosity of the positive electrode sheet, thereby greatly improving the interfacial performance of the positive electrode sheet. Simultaneously, the impedance of the positive electrode sheet decreases, ultimately improving the cycle performance of the battery.

[0211] Similar to Examples 1-5, for cathodes with different Ni:Co:Mn molar ratios, after heat treatment and heat preservation treatment, in addition to excellent battery cycle performance, they also exhibit high cathode specific capacity and rate performance.

[0212] 3. Molecular weight and melting point of the binder

[0213] Table 5. Electrochemical performance test results of batteries with different binders (PVDF decomposition temperature 310℃; Ni:Co:Mn = 8:1:1)

[0214]

[0215] The test results in Table 5 show that, with PVDF of different molecular weights and melting points, the batteries exhibit excellent cycle performance and rate performance after the positive electrode sheet is heated and kept warm.

[0216] 4. Laser

[0217] Table 6. Electrochemical performance test results of the battery under different lasers (PVDF melting point 172℃, decomposition temperature 310℃; Ni:Co:Mn=8:1:1)

[0218]

[0219]

[0220] As shown in Table 6, using a laser that can emit infrared or near-infrared wavelength lasers to heat and heat-preserve the positive electrode can improve the cycle performance and rate performance of the battery.

[0221] [Performance Testing Methods]

[0222] (1) Adhesion of positive electrode sheet

[0223] Cut the positive electrode sheet to 20*100mm. 2 Prepare test specimens of the desired dimensions; adhere the test specimen to the side to be tested with double-sided tape and press it firmly with a roller to ensure complete adhesion between the double-sided tape and the specimen; attach the other side of the double-sided tape to the stainless steel surface, bend one end of the specimen in the opposite direction at a bending angle of 180°; use a high-speed rail tensile testing machine, fix one end of the stainless steel specimen to the lower clamp of the tensile testing machine, fix the bent end of the specimen to the upper clamp, adjust the specimen angle to ensure that the upper and lower ends are in a vertical position, and then stretch the specimen at a speed of 50 mm / min until the specimen is completely peeled off from the substrate, record the displacement and force during the process, and generally consider the force when the forces are balanced to be the bonding force of the positive electrode sheet.

[0224] (2) Positive electrode liquid absorption rate

[0225] Fix the positive electrode plate onto a clean glass plate, and use a 0.3 mm capillary tube to draw 3 mm of electrolyte (1 mol·L⁻¹). - 1After LiPF6 (EC:DMC:EMC mass ratio = 1:1:1) is brought into vertical contact with the positive electrode to allow the electrode to absorb the electrolyte. The time it takes for the electrolyte to be completely absorbed is measured, and the electrolyte absorption rate is obtained by calculation.

[0226] (3) Positive electrode specific capacity and 1C capacity retention

[0227] After cleaning one side of the positive electrode with N-methylpyrrolidone or deionized water, it is punched into a single-sided circular electrode with a diameter of 14 mm and weighed. At the same time, the weight of the corresponding current collector substrate under the 14 mm diameter circular electrode is weighed to obtain the total loading. The active material loading is calculated according to the electrode formulation.

[0228] The 2032 coin cell is equipped with a negative electrode casing, nickel foam, a 16mm diameter lithium sheet, an 18mm diameter Celgard 2325 separator, and 0.1g 1mol·L⁻¹. -1 A 2032 coin cell was assembled using a LiPF6 EC:DMC:EMC (mass ratio 1:1:1) electrolyte, a 14mm diameter single-sided circular electrode (active material side facing the separator), and a 2032 coin cell positive electrode case. After the assembled coin cell was allowed to stand for 12 hours, it was tested: at 25℃, it was charged at 0.1C to the upper limit of the positive electrode active material voltage, then charged at the upper limit voltage until the current was less than 0.05C, at which point charging was stopped. After standing for 5 minutes, it was discharged at 0.1C to the lower limit of the positive electrode active material voltage, and the discharge capacity (i.e., the initial discharge capacity C0) was recorded. The initial discharge capacity was divided by the positive electrode active material loading to obtain the specific capacity of the positive electrode.

[0229] The aforementioned coin cell was charged at 25°C with a current of 1C to the upper limit of the positive electrode active material voltage. Then, it was charged at a constant voltage until the current was less than 0.05C, at which point charging was stopped. After resting for 5 minutes, it was discharged again with a current of 1C to the lower limit of the positive electrode active material voltage. The discharge capacity of this discharge was recorded as C1. This test method was repeated 500 times, and the discharge capacity C at this point was recorded. 500 According to C 500 The capacity retention rate at 1C calculated using C1 is @500cls = (C1 - C1) / (C1 - C1) 500 ) / C1*100%.

[0230] (4) Moisture content of the positive electrode

[0231] Cut the positive electrode sheet to be tested into fragments less than 5 mm in length and width. Place 0.6–1 g of the cut positive electrode sheet fragments in a dry vial. Add Karl Fischer anolyte and Karl Fischer catholyte to a titration vessel at a volume ratio of 20:1. Connect the generating electrode, indicating electrode, and gas delivery tube in the titration vessel to a Karl Fischer moisture analyzer. Set the test temperature to 170℃, the actual weight of the electrode sheet, the inlet flow rate to 40 mL / min, the initial drift rate to 10 μg / min, the stop drift rate to 20 μg / min, and the stabilization time to 20 s. The moisture content of the positive electrode sheet can then be obtained.

[0232] (5) Discharge rate (3C capacity retention rate)

[0233] The battery cell was left to stand at 25°C for 30 minutes; then discharged at a constant current of 0.33C to 2.8V, and then discharged again at a constant current of 0.33C to 2.8V; left to stand at 25°C for 1 hour; then charged at a constant current of 0.33C to the cutoff voltage (the charging cutoff voltage for Examples 6-8 and Comparative Examples 4-6 was 4.35V, and the charging cutoff voltage for other examples and comparative examples was 4.25V); and then charged at a constant voltage at the cutoff voltage with a cutoff current of 0.05C.

[0234] Repeat the above steps once more. Record the discharge capacity C at 0.33C. 0.33 .

[0235] The sample was left to stand at 25°C for 30 minutes; then discharged at 3C to 2.8V, and left to stand at 25°C for 1 hour. The discharge capacity C3 at 3C was recorded. Based on C... 0.33 The capacity retention rate of 3C is calculated from C3 = (C 0.33 -C3) / C 0.33 *100%.

[0236] (6) DC impedance (25℃ DCR@50% SOC)

[0237] The battery cell was left to stand at 25°C for 30 minutes, and then charged at a constant current of 0.33C to the cutoff voltage (the charging cutoff voltage for Examples 6-8 and Comparative Examples 4-6 was 4.35V, and the charging cutoff voltage for other examples and comparative examples was 4.25V). It was then charged at a constant voltage at the cutoff voltage with a cutoff current of 0.05C. At this time, the state of charge (SOC) of the battery was 100%.

[0238] After standing at 25℃ for 5 minutes, discharge at 0.33C with a cutoff current of 0.5C, and adjust the SOC to 50%. After standing at 25℃ for 1 hour, record the voltage V1.

[0239] Record the voltage V2 and the current I during the 5C constant current discharge for 30 seconds.

[0240] After standing at 25°C for 40 seconds, charge at a constant current of 3.75C for 30 seconds. After standing at 25°C for 1 hour, charge at a constant current of 0.33C to the cutoff voltage (the charging cutoff voltage for Examples 6-8 and Comparative Examples 4-6 is 4.35V, and the charging cutoff voltage for other examples and comparative examples is 4.25V). Charge at a constant voltage at the cutoff voltage with a cutoff current of 0.05C. After standing at 25°C for 5 minutes, record the voltage V1'.

[0241] Then discharge at 0.33C with a cutoff current of 0.9C and adjust the SOC to 50%. Let it stand at 25℃ for 1 hour, discharge at 5C for 30 seconds, and record the voltage V2' and the current I' of the 5C constant current discharge.

[0242] Let it stand at 25℃ for 40 seconds, charge it at a constant current of 3.75C for 30 seconds, and let it stand at 25℃ for 5 minutes. The above steps can be repeated multiple times.

[0243] The DC resistance of the battery cell at 25℃, 50% SOC, and 5C constant current discharge for 30s is, i.e., 25℃ DCR@50% SOC=(V2-V1) / I=(V2'-V1') / I'.

[0244] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and they should all be covered within the scope of the claims and specification of this application. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A method for preparing an electrode sheet, characterized in that, include: An active layer comprising an active substance and a binder is prepared on at least one side of the current collector; The active layer is subjected to a heat treatment, which raises the surface temperature of the active layer to the heating temperature. The active layer is subjected to heat preservation treatment so that the surface of the active layer is at the heat preservation temperature; The heating temperature and the heat preservation temperature are each independently greater than or equal to the melting point or softening point of the adhesive, and less than the decomposition temperature of the adhesive. The heating treatment and the heat preservation treatment each independently include laser irradiation treatment.

2. The method for preparing the electrode according to claim 1, characterized in that, The heating temperature and the heat preservation temperature are each independently less than or equal to the average of the melting point or softening point of the adhesive and the decomposition temperature of the adhesive.

3. The method for preparing the electrode according to claim 1, characterized in that, The heat preservation treatment time is greater than or equal to 0.1s.

4. The method for preparing the electrode according to claim 3, characterized in that, The heat preservation treatment time is 0.1~2.5s.

5. The method for preparing the electrode according to claim 1, characterized in that, The heat preservation temperature is less than or equal to the heating temperature.

6. The method for preparing the electrode according to claim 5, characterized in that, The adhesive has a melting point or softening point of 140~180℃ and a decomposition temperature of 300~350℃; the heating temperature and the heat preservation temperature are each independently 170~230℃.

7. The method for preparing the electrode according to claim 6, characterized in that, The heating temperature and the heat preservation temperature are each independently 190~230℃.

8. The method for preparing the electrode according to any one of claims 1 to 7, characterized in that, The active material includes lithium nickel cobalt manganese oxide.

9. The method for preparing the electrode according to claim 8, characterized in that, In the lithium nickel cobalt manganese oxide, the molar ratio of Ni, Co, and Mn is (1~8):(1~2):(1~3).

10. The method for preparing the electrode according to any one of claims 1 to 7, characterized in that, The number average molecular weight of the adhesive is (35~150)×10 4 .

11. The method for preparing the electrode according to claim 10, characterized in that, The number average molecular weight of the adhesive is (45~150)×10 4 .

12. The method for preparing the electrode according to any one of claims 1 to 7, characterized in that, The laser includes one or more of infrared wavelength lasers and near-infrared wavelength lasers.

13. The method for preparing the electrode according to claim 12, characterized in that, The wavelength of the laser is 1000nm~15μm.

14. The method for preparing the electrode according to claim 12, characterized in that, The laser power in the heat treatment step is 2000~4500W.

15. The method for preparing the electrode according to claim 14, characterized in that, The laser power in the heat treatment step is 2000~4000W.

16. The method for preparing the electrode according to claim 12, characterized in that, The laser power in the heat preservation process is 80~200W.

17. The method for preparing the electrode according to claim 16, characterized in that, The laser power in the heat preservation process is 100~150W.

18. The method for preparing the electrode according to any one of claims 1 to 7, characterized in that, The method for preparing the electrode sheet also includes a step of compacting the electrode sheet after heat preservation treatment.

19. An electrode sheet, characterized in that, The electrode is obtained by the preparation method according to any one of claims 1 to 18.

20. A battery, characterized in that, The battery comprises the electrode as described in claim 19.

21. An electrical appliance, characterized in that, The electrical device includes the battery of claim 20.

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