Pole piece, preparation method thereof, battery and electric device

Abstract

This application discloses an electrode sheet, its preparation method, a battery, and an electrical device. The electrode sheet includes: a current collector; and an active material layer disposed on at least a portion of the surface of the current collector. The active material layer includes a cellulose ether polymer, which is located in the voids contained within the active material layer. The cellulose ether polymer in the active material layer of this application can form pores in situ within the active material layer, effectively improving the porosity and electrolyte wettability of the electrode sheet without altering the electrode design or causing mechanical damage. Furthermore, after the electrode sheet is immersed in the electrolyte, the cellulose ether polymer can transform into a gel state, further enhancing the electrolyte's wettability and the electrode's liquid retention rate. Additionally, the cellulose ether polymer in the electrode sheet consumes trace amounts of water during immersion in the electrolyte and initiates grafting reactions on its side chains, effectively improving the electrolyte's affinity and ionic conductivity while suppressing side reactions caused by moisture.

Description

Technical Field

[0001] This application belongs to the field of battery technology, specifically relating to an electrode sheet and its preparation method, a battery, and an electrical device. Background Technology

[0002] The wetting of the electrode by the electrolyte and the electrical properties of the battery cell during long-cycle operation are greatly affected by the porosity of the electrode. Currently, the conventional approach is to adjust the overall porosity of the electrode by regulating its areal density and compaction density. However, high porosity is mainly achieved through low compaction density, resulting in energy density loss, uneven pore distribution, and poor pore structure integrity. Another approach is to create pores using mechanical needle punching. The advantage is that the size and distribution of the pores are uniform and controllable, but the disadvantage is that it can easily damage the electrode. The compressed coating may fall off or accumulate at the pore edges, affecting the uniformity of the electrode surface and potentially causing interface problems in severe cases. Summary of the Invention

[0003] This application aims to at least partially address one of the technical problems in related technologies. Therefore, the purpose of this application is to provide an electrode, its preparation method, a battery, and an electrical device. The cellulose ether polymer in the active material layer of this application can form pores in situ within the active material layer, effectively improving the porosity and electrolyte wettability of the electrode without altering the electrode design or causing mechanical damage. Furthermore, after the electrode is immersed in the electrolyte, the cellulose ether polymer can transform into a gel state, further enhancing the electrolyte's wettability and the electrode's liquid retention rate. Additionally, the cellulose ether polymer in the electrode consumes trace amounts of water during immersion in the electrolyte and initiates grafting reactions on its side chains, effectively improving the electrolyte's affinity and ionic conductivity while suppressing side reactions caused by moisture.

[0004] In one aspect of this application, an electrode is provided. According to an embodiment of this application, the electrode comprises:

[0005] current collector;

[0006] An active material layer is disposed on at least a portion of the surface of the current collector, the active material layer comprising a cellulose ether polymer located in the voids contained in the active material layer.

[0007] According to the electrode of this application embodiment, the active material layer includes a cellulose ether polymer. This cellulose ether polymer can form pores in situ within the active material layer, thus effectively increasing the porosity of the electrode without altering its design or causing mechanical damage. Simultaneously, the formed pores have advantages such as uniform distribution and good pore structure integrity; the uniform and abundant pores significantly improve electrolyte wettability. Furthermore, after the electrode is immersed in the electrolyte, the cellulose ether polymer in the active material layer can transform into a gel state, restricting the fluidity of the electrolyte and further enhancing the electrolyte's wettability and electrolyte retention rate. Additionally, the cellulose ether polymer in the electrode consumes trace amounts of water during immersion in the electrolyte and initiates grafting reactions on its side chains. This not only effectively improves the electrolyte's affinity and ionic conductivity but also acts as a moisture absorbent, capturing residual moisture from baking within the battery cell and suppressing side reactions caused by moisture.

[0008] In addition, the electrode sheet according to the above embodiments of this application may also have the following additional technical features:

[0009] In some embodiments of this application, the weight-average molecular weight of the cellulose ether polymer is 20,000 to 200,000.

[0010] In some embodiments of this application, the cellulose ether polymer includes at least one of hydroxypropyl methylcellulose, hydroxyethyl methylcellulose, and hydroxypropyl ethylcellulose.

[0011] In some embodiments of this application, the cellulose ether polymer accounts for 1% to 5% of the mass of the active material layer.

[0012] In some embodiments of this application, the electrode is a positive electrode with a porosity of 36.5% to 40%.

[0013] In some embodiments of this application, the electrode is a negative electrode, and the porosity of the negative electrode is 38.5% to 42%.

[0014] In a second aspect of this application, a method for preparing the electrode sheet of the first aspect is provided. According to an embodiment of this application, the method includes:

[0015] A cellulose ether polymer solution is formed on at least a portion of the surface of the active material layer away from the current collector, and then dried to obtain an electrode.

[0016] According to the method for preparing the electrode according to the embodiments of this application, a cellulose ether polymer solution is sprayed onto the coated electrode. After drying, the cellulose ether polymer solution evaporates, and the cellulose ether polymer matrix shrinks, forming pores in situ. The method of this application is simple and effectively improves the porosity of the electrode without changing the electrode design or damaging the electrode. At the same time, the created pores have the advantages of uniform distribution and good pore structure integrity. The uniform and abundant pores can significantly improve the electrolyte wettability. The rapidly shrinking sprayed cellulose ether polymer can also slowly absorb a large amount of electrolyte and gel, which can limit the fluidity of the electrolyte and effectively improve the electrolyte retention capacity of the electrode. In addition, the cellulose ether polymer in the electrode, when wetted in the electrolyte, consumes a small amount of water and initiates a grafting reaction on its side chains. This not only effectively improves the affinity and ionic conductivity of the electrolyte, but also acts as a moisture absorbent, capturing residual moisture in the battery cell during baking and inhibiting side reactions caused by moisture.

[0017] In addition, the method according to the above embodiments of this application may also have the following additional technical features:

[0018] In some embodiments of this application, the mass concentration of the cellulose ether polymer solution is 0.5 wt% to 15 wt%.

[0019] In some embodiments of this application, the viscosity of the cellulose ether polymer solution is 200 mPa·s to 1500 mPa·s.

[0020] In some embodiments of this application, the solvent in the cellulose ether polymer solution includes at least one of N,N-dimethylformamide, N-methylpyrrolidone, and dimethyl sulfoxide.

[0021] In some embodiments of this application, the cellulose ether polymer solution is atomized and sprayed onto at least a portion of the surface of the active material layer away from the current collector, and then dried to obtain an electrode sheet.

[0022] In a third aspect, this application proposes a battery. According to embodiments of this application, the battery has the electrodes described above or electrodes manufactured using the methods described above. This effectively improves the battery's high-rate performance, energy density, cycle stability, and safety.

[0023] In a fourth aspect, this application proposes an electrical device. According to an embodiment of this application, the electrical device has a battery as described above. Thus, the electrical device possesses all the advantages of the battery, which will not be elaborated further here.

[0024] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0025] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0026] Figure 1 This is a schematic diagram of the process for preparing electrode sheets according to some embodiments of this application;

[0027] Figure 2 This is a schematic diagram of the positive electrode hole formation in some embodiments of this application;

[0028] Figure 3 This is a schematic diagram of the hole formation of the negative electrode sheet in some embodiments of this application.

[0029] The attached figures are labeled as follows: 201 - Positive electrode active material layer dressing; 202 - Positive electrode polymer droplets; 203 - Polymer layer that has shrunk after drying; 204 - Pores left after polymer shrinkage; 301 - Negative electrode active material layer dressing; 302 - Negative electrode polymer droplets; 303 - Polymer skeleton after phase transfer; 304 - Dried polymer particles; 305 - Dried polymer skeleton; 306 - Finger-shaped pores. Detailed Implementation

[0030] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application.

[0031] In one aspect of this application, an electrode is provided. According to an embodiment of this application, the electrode includes: a current collector; an active material layer disposed on at least a portion of the surface of the current collector, the active material layer including a cellulose ether polymer located in the voids contained in the active material layer.

[0032] The beneficial effects that the electrode proposed in this application can achieve are described in detail below:

[0033] The active material layer of this application includes cellulose ether polymers, which can form pores in situ within the active material layer. This effectively increases the porosity of the electrode without altering its design or causing mechanical damage. Furthermore, the created pores are uniformly distributed and have good structural integrity; the uniform and abundant pores significantly improve electrolyte wettability. Moreover, after the electrode is immersed in the electrolyte, the cellulose ether polymers in the active material layer transform into a gel state, restricting the electrolyte's flowability and further enhancing the electrolyte's wettability and electrolyte retention rate.

[0034] In addition, when LiPF6 and trace amounts of water are present in the electrolyte, the side chains of cellulose ether polymers can be grafted with the ring-opening polymerization products of ethylene carbonate (EC) in the electrolyte through transesterification under the action of trace amounts of water, which can effectively improve the affinity and ionic conductivity of the electrolyte. At the same time, the reaction process consumes trace amounts of water, which can effectively remove trace amounts of water from the electrodes or electrolyte in the battery cell and effectively inhibit the occurrence of side reactions.

[0035] However, synthetic polymers such as polyacrylonitrile, polymethyl methacrylate, and polyethylene oxide cannot achieve the technical effects of this application. These polymers are limited by their high crystallinity and preparation methods, resulting in low porosity, limited electrolyte plasticizing effect, poor absorption of electrolyte (generally 100wt% to 300wt%), and poor affinity for electrolyte.

[0036] According to some specific embodiments of this application, the weight-average molecular weight of the cellulose ether polymer is 20,000 to 200,000, for example, 20,000, 60,000, 80,000, 100,000, 120,000, 140,000, 160,000, 180,000, 200,000, etc. By limiting the weight-average molecular weight of the cellulose ether polymer to the above range, it is possible to further ensure that the cellulose ether polymer forms effective pores in situ in the active material layer, while also ensuring that the cellulose ether polymer has a high liquid absorption rate. For example, when the weight-average molecular weight of the cellulose ether polymer is 200,000, its liquid absorption rate is approximately 1700 wt%.

[0037] According to further specific embodiments of this application, the cellulose ether polymer includes at least one of hydroxypropyl methylcellulose, hydroxyethyl methylcellulose, and hydroxypropyl ethylcellulose. Therefore, the aforementioned cellulose ether polymers can form pores in situ within the active material layer, and the formed pores have advantages such as uniform distribution and good pore structure integrity. Furthermore, after the electrode is immersed in the electrolyte, the aforementioned cellulose ether polymers can transform into a gel state, further improving the wettability of the electrolyte on the electrode and further enhancing the electrolyte retention rate. In addition, the aforementioned cellulose ether polymers are low in cost, environmentally friendly, and have an extremely high electrolyte absorption rate.

[0038] According to some specific embodiments of this application, the mass percentage of cellulose ether polymer in the active material layer is 1% to 5%, for example, it can be 1%, 2%, 3%, 4%, 5%, etc. By limiting the mass percentage of cellulose ether polymer in the active material layer to the above range, the porosity of the electrode can be further improved, the wettability of the electrolyte to the electrode can be further improved, and the electrolyte retention rate of the electrode can be further improved.

[0039] The technical solution of this application is applicable not only to positive electrode sheets but also to negative electrode sheets. In the positive electrode sheet, the cellulose ether polymer shrinking at the edge of the pores provides a certain supporting effect, protecting the integrity of the pore structure to some extent. In the negative electrode sheet, the cellulose ether polymer itself has a good structure retention effect, with more extended molecular chains and more electrolyte contact and reaction sites, effectively improving the efficiency of electrolyte wetting. At the same time, the internal wrinkles and pores generated by the swelling of the cellulose ether polymer after absorbing electrolyte can absorb and store a large amount of electrolyte, further improving the wetting and electrolyte retention capacity of the negative electrode sheet.

[0040] According to some specific embodiments of this application, the electrode is a positive electrode with a porosity of 36.5% to 40%, such as 36.5%, 37%, 37.5%, 38%, 38.5%, 39%, 39.5%, 40%, etc., thereby further improving the wettability of the electrolyte to the positive electrode and further improving the electrolyte retention rate of the positive electrode.

[0041] According to some specific embodiments of this application, the electrode is a negative electrode with a porosity of 38.5% to 42%, such as 38.5%, 39%, 39.5%, 40%, 40.5%, 41%, 41.5%, 42%, etc., thereby further improving the wettability of the electrolyte to the negative electrode and further improving the electrolyte retention rate of the negative electrode.

[0042] When the aforementioned electrode is a positive electrode, the positive electrode includes: a positive current collector and a positive active material layer. The positive active material layer is disposed on at least a portion of the surface of the positive current collector, and includes a positive active material, a positive binder, and a positive conductive agent. In the embodiments of this application, the mass ratio of the positive active material, the positive conductive agent, and the positive binder in the positive active material layer is not particularly limited, and those skilled in the art can set it according to actual needs.

[0043] In the embodiments of this application, the positive current collector can be made of a material with good conductivity and mechanical strength, such as aluminum foil.

[0044] In the embodiments of this application, the specific types of positive electrode active materials are not particularly limited, and those skilled in the art can select them according to actual needs. As some specific examples, positive electrode active materials include at least one of lithium iron phosphate, ternary lithium, lithium cobalt oxide, lithium manganese oxide, lithium-rich nickel manganese oxide, and lithium manganese iron phosphate.

[0045] In the embodiments of this application, the specific type of positive electrode conductive agent is not particularly limited, and those skilled in the art can select it according to actual needs. As some specific examples, the positive electrode conductive agent includes at least one of carbon black, acetylene black, Ketjen black, graphene, and carbon nanotubes. Similarly, the specific type of positive electrode binder is not particularly limited, and those skilled in the art can select it according to actual needs. As some specific examples, the positive electrode binder includes at least one of polymers such as polyacrylic acid, polyimide, and polyvinylidene fluoride and their derivatives.

[0046] When the aforementioned electrode is a negative electrode, the negative electrode includes: a negative current collector and a negative active material layer. The negative active material layer is disposed on at least a portion of the surface of the negative current collector, and the negative active material layer includes a negative active material, a negative binder, and a negative conductive agent. In the embodiments of this application, the mass ratio of the negative active material, the negative conductive agent, and the negative binder in the negative active material layer is not particularly limited, and those skilled in the art can set it according to actual needs.

[0047] In the embodiments of this application, the negative electrode current collector can be made of a material with good conductivity and mechanical strength, such as copper foil.

[0048] In the embodiments of this application, the specific types of negative electrode active materials are not particularly limited, and those skilled in the art can choose according to actual needs. As some specific examples, negative electrode active materials include at least one of graphite, mesophase micro carbon spheres (MCMB), hard carbon, and soft carbon.

[0049] In the embodiments of this application, the specific type of negative electrode conductive agent is not particularly limited, and those skilled in the art can select it according to actual needs. As some specific examples, the negative electrode conductive agent includes at least one of carbon black, acetylene black, Ketjen black, graphene, and carbon nanotubes.

[0050] Similarly, the specific type of negative electrode binder is not particularly limited, and those skilled in the art can choose according to actual needs. As some specific examples, negative electrode binders include at least one of water-based binders such as polyacrylic acid, styrene-butadiene rubber, polytetrafluoroethylene, and LA-123 series.

[0051] In a second aspect, this application proposes a method for preparing electrode sheets. According to embodiments of this application, the method includes:

[0052] A cellulose ether polymer solution is sprayed onto at least a portion of the surface of the active material layer away from the current collector, and then dried to obtain an electrode.

[0053] According to some specific embodiments of this application, a cellulose ether polymer solution is atomized and sprayed onto at least a portion of the surface of the active material layer away from the current collector, followed by drying to obtain an electrode. This application uses atomized spraying to apply the cellulose ether polymer solution to the coated electrode. After drying, the cellulose ether polymer solution evaporates, and the cellulose ether polymer matrix shrinks, forming pores in situ. This method is simple and effectively improves the porosity of the electrode without altering its design or damaging it. Simultaneously, the created pores have advantages such as uniform distribution and good pore structure integrity; the uniform and abundant pores significantly improve electrolyte wettability. Furthermore, the rapidly shrinking sprayed cellulose ether polymer can slowly absorb a large amount of electrolyte and gel, limiting electrolyte flow and effectively improving the electrode's electrolyte retention capacity.

[0054] Appendix Figure 1 The diagram below illustrates the process of preparing electrode sheets according to some embodiments of this application, including slurry preparation (i.e., preparation of active material layer slurry), coating (i.e., coating the active material layer slurry onto at least a portion of the surface of the current collector), atomizing and spraying a cellulose ether polymer solution, baking and drying, and rolling to obtain the electrode sheet.

[0055] The technical solution of this application is applicable not only to positive electrode sheets but also to negative electrode sheets. First, it should be noted that the solvent used to form the positive electrode active material layer slurry of the positive electrode sheet is an organic solvent, the solvent used to form the negative electrode active material layer slurry of the negative electrode sheet is water, and the solvent used to form the cellulose ether polymer solution is an organic solvent.

[0056] When the technical solution of this application is used in a positive electrode, refer to the appendix. Figure 2 In this method, atomized cellulose ether polymer solution particles are introduced into the positive electrode coating process. During the drying process of the positive electrode, because the cellulose ether polymer solution lacks skeletal support, the polymer matrix shrinks after the solvent evaporates, thus creating uniformly distributed and relatively consistent pore sizes in situ. Unlike existing methods, this method does not require changes to the electrode design and causes no mechanical damage to the electrode. Furthermore, after the positive electrode is rolled, the polymer shrinking at the pore edges provides some support, protecting the integrity of the pore structure to a certain extent. A schematic diagram of the positive electrode pore formation is shown below. Figure 2 As shown. In the appendix Figure 2 In the diagram, 201 represents the positive electrode active material layer dressing, 202 represents the positive electrode polymer droplet, 203 represents the polymer layer that shrinks after drying, and 204 represents the pores left after the polymer shrinks.

[0057] The preparation method of the above positive electrode is as follows:

[0058] The positive electrode active material, positive electrode binder, and positive electrode conductive agent are added to a mixing tank in a specific ratio to form a slurry. The resulting positive electrode slurry is then uniformly coated onto the positive electrode current collector. Atomized cellulose ether polymer solution is then sprayed onto the surface of the slurry, and the mixture is subsequently placed in an oven for drying. After the solvent evaporates, the cellulose ether polymer shrinks in volume, forming a non-uniform polymer film within the pores, which provides some support to the pores. Finally, the prepared positive electrode sheet is rolled using the same process as conventional electrode sheets.

[0059] When the technical solution of this application is used in a negative electrode, refer to the appendix. Figure 3 Since the solvent for forming the negative electrode active material layer slurry is water, and the solvent for forming the cellulose ether polymer solution is an organic solvent, the cellulose ether polymer dissolved in the organic solvent undergoes a phase transfer process upon contact with water. After drying, the cellulose ether polymer particles themselves have good structure retention, with more extended molecular chains and more contact sites, improving the efficiency of electrolyte wetting. Simultaneously, the internal wrinkles and pores created by the swelling of the cellulose ether polymer after absorbing the electrolyte can absorb and store a large amount of electrolyte, further enhancing the wetting and electrolyte retention capacity of the negative electrode. A schematic diagram of the pore formation process for the negative electrode is shown below. Figure 3 As shown. In the appendix Figure 3 In the diagram, 301 represents the negative electrode active material layer dressing, 302 represents the negative electrode polymer droplets, 303 represents the polymer skeleton after phase transfer, 304 represents the dried polymer particles, 305 represents the dried polymer skeleton, and 306 represents the finger pores.

[0060] In addition, cellulose ether polymer electrolytes consume trace amounts of water during the reaction process and initiate grafting reactions on their side chains. This not only effectively improves the affinity and ion conductivity of the electrolyte, but also acts as a moisture absorbent to capture residual moisture in the battery cell during baking and inhibit side reactions caused by moisture. Synthetic polymers such as polyacrylonitrile do not have this effect.

[0061] The preparation method of the above negative electrode is as follows:

[0062] The negative electrode active material, negative electrode binder, and negative electrode conductive agent are added to a mixing tank in a specific ratio to form a slurry. The resulting negative electrode slurry is uniformly coated onto the negative electrode current collector, and then an atomized cellulose ether polymer solution is sprayed onto its surface. During the contact of the polymer solution with water, a phase transfer process occurs, and the polymer matrix changes from a liquid phase to a solid phase. The substrate is then placed in an oven for drying. After baking, the solvent evaporates, and the resulting polymer skeleton exhibits good dimensional stability, limited volume shrinkage, and a porous structure dominated by finger-like pores. Finally, the prepared negative electrode sheet is rolled using the same process as conventional electrode sheets.

[0063] According to some specific embodiments of this application, the mass concentration of the cellulose ether polymer solution is 0.5wt% to 15wt%, for example, it can be 0.5wt%, 2wt%, 4wt%, 6wt%, 8wt%, 0wt%, 12wt%, 15wt%, etc. By limiting the mass concentration of the cellulose ether polymer solution within the above range, it can be effectively ensured that a solution with a reasonable viscosity is formed, which can be sprayed onto the surface of the electrode by atomization spraying. At the same time, it can ensure that the active material layer contains a certain amount of cellulose ether polymer, further improving the porosity of the electrode, further improving the wettability of the electrolyte on the electrode, and further improving the electrolyte retention rate of the electrode.

[0064] According to some specific embodiments of this application, the viscosity of the cellulose ether polymer solution is 200 mPa·s to 1500 mPa·s, for example, it can be 200 mPa·s, 500 mPa·s, 700 mPa·s, 1000 mPa·s, 1200 mPa·s, 1500 mPa·s, etc. By limiting the viscosity of the cellulose ether polymer solution within the above range, it is possible to ensure that the cellulose ether polymer solution is sprayed onto the surface of the electrode by atomization spraying, and at the same time, it is possible to further improve the porosity of the electrode, further improve the wettability of the electrolyte on the electrode, and further improve the electrolyte retention rate of the electrode.

[0065] In the embodiments of this application, the solvent in the cellulose ether polymer solution is not particularly limited, and those skilled in the art can choose according to actual needs. As some preferred embodiments, the solvent in the cellulose ether polymer solution includes at least one of N,N-dimethylformamide, N-methylpyrrolidone, and dimethyl sulfoxide. All of the above solvents can effectively dissolve cellulose ether polymers.

[0066] According to some specific embodiments of this application, the drying temperature is 60℃~80℃ (e.g., 60℃, 65℃, 70℃, 75℃, 80℃, etc.), and the drying time is 6h~12h (e.g., 6h, 7h, 8h, 9h, 10h, 11h, 12h, etc.). This effectively removes the solvent from the active material layer while ensuring that the organic solvent in the cellulose ether polymer solution evaporates, the cellulose ether polymer matrix shrinks, and pores are formed in situ.

[0067] According to some specific embodiments of this application, the dissolution temperature of the cellulose ether polymer solution is 60℃~100℃, for example, it can be 60℃, 70℃, 80℃, 90℃, 100℃, etc., thereby effectively dissolving the cellulose ether polymer to form a cellulose ether polymer solution.

[0068] According to the method for preparing the electrode according to the embodiments of this application, a cellulose ether polymer solution is sprayed onto the coated electrode. After drying, the cellulose ether polymer solution evaporates, and the cellulose ether polymer matrix shrinks, forming pores in situ. The method of this application is simple and effectively improves the porosity of the electrode without changing the electrode design or damaging the electrode. At the same time, the created pores have the advantages of uniform distribution and good pore structure integrity. The uniform and abundant pores can significantly improve the electrolyte wettability. The rapidly shrinking sprayed cellulose ether polymer can also slowly absorb a large amount of electrolyte and gel, which can limit the fluidity of the electrolyte and effectively improve the electrolyte retention capacity of the electrode. In addition, the cellulose ether polymer in the electrode, when wetted in the electrolyte, consumes a small amount of water and initiates a grafting reaction on its side chains. This not only effectively improves the affinity and ionic conductivity of the electrolyte, but also acts as a moisture absorbent, capturing residual moisture in the battery cell during baking and inhibiting side reactions caused by moisture.

[0069] In a third aspect, this application proposes a battery. According to embodiments of this application, the battery has the electrodes described above or electrodes manufactured using the methods described above. This effectively improves the battery's high-rate performance, energy density, cycle stability, and safety.

[0070] Specifically, the aforementioned battery can be a single cell, a battery module, or a battery pack. When the battery is a single cell, it includes a positive electrode, a negative electrode, and a separator, with the separator disposed between the electrode and the negative electrode. The positive electrode of the single cell adopts the electrode structure of the embodiments of this application, or the negative electrode of the single cell adopts the electrode structure of the embodiments of this application, or both the positive and negative electrodes of the single cell adopt the electrode structure of the embodiments of this application.

[0071] In a fourth aspect, this application proposes an electrical device. According to an embodiment of this application, the electrical device has a battery as described above, which provides electrical energy to the electrical device. Thus, the electrical device possesses all the advantages of a battery, which will not be elaborated further here.

[0072] Specifically, the aforementioned electrical equipment can include, but is not limited to, mobile phones, tablets, laptops, electric toys, power tools, electric vehicles, electric cars, ships, spacecraft, etc. Among them, electric toys can include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc., and spacecraft can include airplanes, rockets, space shuttles, and spacecraft, etc.

[0073] The embodiments of this application are described in detail below. It should be noted that the embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. In addition, unless otherwise specified, all reagents used in the following embodiments are commercially available or can be synthesized according to the methods described herein or known methods. For reaction conditions not listed, they are also readily available to those skilled in the art.

[0074] Example 1

[0075] This embodiment provides a positive electrode sheet, the preparation method of which includes:

[0076] (1) Preparation of the positive electrode:

[0077] Take the weight-average molecular weight M w A quantitative amount of hydroxypropyl methylcellulose of 100,000 was dissolved in N,N-dimethylformamide at 80°C to prepare a polymer solution with a mass fraction of 5 wt%. The solution with a viscosity of 600 mPa·s was then added to the atomizing device for later use.

[0078] (2) The positive electrode slurry was prepared by mixing lithium iron phosphate, carbon nanotubes and polyvinylidene fluoride in a mass ratio of 8:1:1. The positive electrode slurry was evenly coated on carbon-coated aluminum foil. Then the above atomized polymerization solution was evenly sprayed onto the coating. The solution was then sent to an 80°C oven for solvent evaporation for 8 hours to obtain a dried positive electrode sheet. The positive electrode sheet was then rolled to obtain the final positive electrode sheet.

[0079] Example 2

[0080] This embodiment provides a positive electrode sheet. The preparation method of this embodiment is basically the same as that of Embodiment 1, with the only difference being:

[0081] Hydroxypropyl methylcellulose was replaced with hydroxyethyl methylcellulose, whose weight-average molecular weight M w It is 200,000.

[0082] Example 3

[0083] This embodiment provides a positive electrode sheet. The preparation method of this embodiment is basically the same as that of Embodiment 1, with the only difference being:

[0084] Hydroxypropyl methylcellulose was replaced with hydroxypropyl ethylcellulose, whose weight-average molecular weight M w It is 20,000.

[0085] Example 4

[0086] This embodiment provides a positive electrode sheet. The preparation method of this embodiment is basically the same as that of Embodiment 1, with the only difference being:

[0087] Prepare a polymer solution with a mass fraction of 0.5 wt%, where the polymer's weight-average molecular weight M is... w When the concentration is 20000 and the solution viscosity is 200 mPa·s, add it to the atomizing device for later use.

[0088] Example 5

[0089] This embodiment provides a positive electrode sheet. The preparation method of this embodiment is basically the same as that of Embodiment 1, with the only difference being:

[0090] Prepare a polymer solution with a mass fraction of 10 wt%, wherein the weight-average molecular weight M of the polymer is... w Add the solution to the atomizing device when the concentration is 20000 and the solution viscosity is 500 mPa·s.

[0091] Example 6

[0092] This embodiment provides a positive electrode sheet. The preparation method of this embodiment is basically the same as that of Embodiment 1, with the only difference being:

[0093] Prepare a polymer solution with a mass fraction of 15 wt%, where the polymer's weight-average molecular weight M is... w Add the solution to the atomizing device when the concentration is 200,000 and the solution viscosity is 1500 mPa·s.

[0094] Example 7

[0095] This embodiment provides a positive electrode sheet. The preparation method of this embodiment is basically the same as that of Embodiment 1, with the only difference being:

[0096] Replace N,N-dimethylformamide in the polymer solution with N-methylpyrrolidone.

[0097] Example 8

[0098] This embodiment provides a negative electrode sheet, the preparation method of which includes:

[0099] (1) Preparation of negative electrode:

[0100] Take the weight-average molecular weight M w A quantitative amount of hydroxypropyl methylcellulose of 100,000 was dissolved in N,N-dimethylformamide at 80°C to prepare a polymer solution with a mass fraction of 5 wt%. The solution with a viscosity of 600 mPa·s was then added to the atomizing device for later use.

[0101] (2) The graphite: carbon black: styrene-butadiene rubber was added into a mixing tank in a mass ratio of 8:1:1 to make a slurry. The negative electrode slurry was evenly coated on the carbon-coated copper foil. Then the above atomized polymerization solution was evenly sprayed onto the coating. Then it was sent into an 80°C oven for solvent evaporation for 8 hours to obtain a dried negative electrode sheet. The negative electrode sheet was rolled to obtain the final negative electrode sheet.

[0102] Example 9

[0103] This embodiment provides a negative electrode sheet. The preparation method of this embodiment is basically the same as that of Embodiment 1, except that:

[0104] Hydroxypropyl methylcellulose was replaced with hydroxyethyl methylcellulose, whose weight-average molecular weight M w It is 200,000.

[0105] Example 10

[0106] This embodiment provides a negative electrode sheet. The preparation method of this embodiment is basically the same as that of Embodiment 1, except that:

[0107] Hydroxypropyl methylcellulose was replaced with hydroxypropyl ethylcellulose, whose weight-average molecular weight M w It is 20,000.

[0108] Example 11

[0109] This embodiment provides a negative electrode sheet. The preparation method of this embodiment is basically the same as that of Embodiment 1, except that:

[0110] Prepare a polymer solution with a mass fraction of 0.5 wt%, where the polymer's weight-average molecular weight M is... w When the concentration is 20000 and the solution viscosity is 200 mPa·s, add it to the atomizing device for later use.

[0111] Example 12

[0112] This embodiment provides a negative electrode sheet. The preparation method of this embodiment is basically the same as that of Embodiment 1, except that:

[0113] Prepare a polymer solution with a mass fraction of 10 wt%, wherein the weight-average molecular weight M of the polymer is... w Add the solution to the atomizing device when the concentration is 20000 and the solution viscosity is 500 mPa·s.

[0114] Example 13

[0115] This embodiment provides a negative electrode sheet. The preparation method of this embodiment is basically the same as that of Embodiment 1, except that:

[0116] Prepare a polymer solution with a mass fraction of 15 wt%, where the polymer's weight-average molecular weight M is... w Add the solution to the atomizing device when the concentration is 200,000 and the solution viscosity is 1500 mPa·s.

[0117] Example 14

[0118] This embodiment provides a negative electrode sheet. The preparation method of this embodiment is basically the same as that of Embodiment 1, except that:

[0119] Replace N,N-dimethylformamide in the polymer solution with dimethyl sulfoxide.

[0120] Comparative Example 1

[0121] This comparative example provides a positive electrode sheet, the preparation method of which includes:

[0122] Lithium iron phosphate, carbon nanotubes, and polyvinylidene fluoride were added to a mixing tank in a mass ratio of 8:1:1 to prepare a slurry. The positive electrode slurry was then uniformly coated onto carbon-coated aluminum foil and sent to an 80°C oven for solvent evaporation for 8 hours to obtain a dried positive electrode sheet. The positive electrode sheet was then rolled to obtain the final positive electrode sheet.

[0123] Comparative Example 2

[0124] This comparative example provides a negative electrode sheet, the preparation method of which includes:

[0125] The graphite, carbon black, and styrene-butadiene rubber were added to a mixing tank in a mass ratio of 8:1:1 to prepare a slurry. The negative electrode slurry was then evenly coated onto a carbon-coated copper foil and sent to an 80°C oven for solvent evaporation for 8 hours to obtain a dried negative electrode sheet. The negative electrode sheet was then rolled to obtain the final negative electrode sheet.

[0126] The mass percentage of cellulose ether polymers in the active material layer of the electrodes prepared in Examples 1 to 14 was tested using the TGA method, and the results are shown in Table 1.

[0127] The contact angle, liquid retention rate and porosity of the electrodes prepared in Examples 1-14 and Comparative Examples 1-2 were tested respectively, and the results are shown in Table 1.

[0128] Contact angle testing method:

[0129] A contact angle tester was used to test the contact angle between the electrolyte and the rolled electrode. The smaller the angle, the stronger the wettability of the electrode to the electrolyte.

[0130] The electrolyte contains a solvent and a lithium salt. The solvent is a mixture of ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate in a mass ratio of 1:1:1. The lithium salt is LiPF6 with a concentration of 1 mol / L.

[0131] Liquid retention rate test method:

[0132] Take a 4cm*4cm electrode, weigh the mass m1 before soaking, soak it in electrolyte for 1 hour, remove the electrode, wipe the surface free electrolyte with lint-free paper, weigh the mass m2 after soaking, and calculate the electrolyte retention rate of the electrode using the formula: (m2-m1) / m1.

[0133] The electrolyte contains a solvent and a lithium salt. The solvent is a mixture of ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate in a mass ratio of 1:1:1. The lithium salt is LiPF6 with a concentration of 1 mol / L.

[0134] Porosity testing methods:

[0135] Take a 4cm*4cm electrode, measure its thickness d, and weigh it before immersion (m3). Immerse it in n-butanol for 1 hour. Remove the electrode, wipe off any remaining solution on the surface with lint-free paper, and weigh it after immersion (m4). Calculate the porosity using the formula: Porosity = (m4 - m3) / ρV, where ρ is the density of n-butanol = 0.8148 g / cm³. 3 Let V be the volume of the electrode, and calculate the porosity of the electrode.

[0136] Table 1

[0137]

[0138]

[0139] As can be seen from Table 1, compared with Comparative Example 1, the contact angle of the positive electrode sheets in Examples 1 to 7 is significantly reduced, and the liquid retention rate and porosity of the positive electrode sheets in Examples 1 to 7 are significantly improved. It can be seen that Examples 1 to 7 of this application use atomized spraying to spray the cellulose ether polymer solution onto the coated positive electrode sheet. After drying, the cellulose ether polymer solution evaporates, and the cellulose ether polymer matrix shrinks, forming pores in situ, thereby effectively improving the liquid retention rate and porosity of the positive electrode sheet and significantly reducing the contact angle of the positive electrode sheet.

[0140] As can be seen from Table 1, compared with Comparative Example 2, the contact angle of the negative electrode sheets in Examples 8-14 is significantly reduced, and the liquid retention rate and porosity of the negative electrode sheets in Examples 8-14 are significantly improved. It can be seen that Examples 8-14 of this application use atomized spraying to spray the cellulose ether polymer solution onto the coated negative electrode sheet. After drying, the cellulose ether polymer solution evaporates, and the cellulose ether polymer matrix shrinks, forming pores in situ, thereby effectively improving the liquid retention rate and porosity of the negative electrode sheet and significantly reducing the contact angle of the negative electrode sheet.

[0141] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0142] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A method of making a pole piece, characterized by, The electrode comprises: a current collector; and an active material layer, the active material layer being disposed on at least a portion of the surface of the current collector, the active material layer comprising a cellulose ether polymer located in the voids contained within the active material layer, the cellulose ether polymer having a weight-average molecular weight of 20,000 to 200,000, and the cellulose ether polymer comprising 1% to 5% of the mass of the active material layer. The electrode is a positive electrode, and the porosity of the positive electrode is 36.5%~40%; or The electrode is a negative electrode, and the porosity of the negative electrode is 38.5%~42%. The method includes: A cellulose ether polymer solution is atomized and sprayed onto at least a portion of the surface of the active material layer away from the current collector, and then dried to obtain an electrode. The mass concentration of the cellulose ether polymer solution is 0.5 wt% to 15 wt%; the viscosity of the cellulose ether polymer solution is 200 mPa·s to 1500 mPa·s; and the solvent in the cellulose ether polymer solution includes at least one of N,N-dimethylformamide, N-methylpyrrolidone, and dimethyl sulfoxide.

2. The pole piece prepared by the method of claim 1, characterized in that, include: current collector; An active material layer is disposed on at least a portion of the surface of the current collector. The active material layer includes a cellulose ether polymer, which is located in the voids contained within the active material layer. The weight-average molecular weight of the cellulose ether polymer is 20,000 to 200,000, and the mass percentage of the cellulose ether polymer in the active material layer is 1% to 5%. The electrode is a positive electrode, and the porosity of the positive electrode is 36.5%~40%; or The electrode is a negative electrode, and the porosity of the negative electrode is 38.5%~42%.

3. The pole piece of claim 2, wherein The cellulose ether polymers include at least one of hydroxypropyl methylcellulose, hydroxyethyl methylcellulose, and hydroxypropyl ethylcellulose.

4. A battery, characterized by An electrode having the electrode as described in claim 2 or 3, or an electrode prepared by the method described in claim 1.

5. An electric device, characterized by It has the battery as described in claim 4.

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