Negative electrode sheet and preparation method therefor, battery and electric device

Abstract

A negative electrode sheet and a preparation method therefor, a battery and an electric device. The negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer, wherein the negative electrode active material layer is located on at least one side of the negative electrode current collector, and the negative electrode active material layer contains an active material and a porous ceramic.

Description

Negative electrode sheet and its preparation method, battery and electrical equipment

[0001] Priority information

[0002] This application claims priority and benefits to patent application No. 202411745712.6, filed with the China National Intellectual Property Administration on November 29, 2024, the entire contents of which are incorporated herein by reference.

[0003] Technical Field

[0004] This application relates to the field of battery technology, specifically to negative electrode sheets and their preparation methods, batteries, and electrical devices. Background Technology

[0005] With the rapid development of new energy vehicles in China, safety, driving range, and fast charging technologies have become priority indicators for consumers when purchasing new energy vehicles. Currently, the main method to improve energy density is to increase the areal density of battery electrodes, while improving fast charging capability mainly involves reducing the areal density of electrodes. Energy density and fast charging performance have become two mutually restrictive performance indicators. How to obtain batteries with high energy density and good fast charging performance is an urgent problem to be solved. Summary of the Invention

[0006] This invention aims to at least partially solve one of the technical problems in related technologies. To this end, this invention proposes a negative electrode sheet with high energy density and superior fast-charging performance, its preparation method, a battery, and an electrical device thereof.

[0007] A first aspect of this application provides a negative electrode sheet. According to an embodiment of this application, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer located on at least one side of the negative electrode current collector. The negative electrode active material layer contains an active material and porous ceramic. By adding a certain proportion of porous ceramic material to this negative electrode sheet, the diffusion rate of the electrolyte in the negative electrode sheet can be effectively increased, improving the electrolyte's wetting and liquid retention capabilities, and increasing the diffusion rate of lithium ions in the negative electrode sheet. Under high areal density conditions, fast charging capability can be significantly improved.

[0008] According to embodiments of this application, the porous ceramic is uniformly distributed in the negative electrode active material layer. This ensures that the electrolyte wetting and retention capabilities are essentially consistent at all locations within the negative electrode, and the lithium-ion diffusion rate is also essentially consistent, avoiding problems such as localized electrolyte depletion and poor wetting, thereby improving the electrochemical performance of the battery using this negative electrode.

[0009] According to embodiments of this application, based on the total mass of the negative electrode active material layer, the mass percentage content of the porous ceramic is 0.1% to 2%, specifically 0.2% to 1%. Within the above content range, the negative electrode sheet can have suitable porosity, improving its electrolyte wettability and liquid retention performance, thereby improving the fast-charging performance of the battery using this negative electrode sheet, while essentially not reducing the areal density of the negative electrode sheet, thus ensuring that the battery using this negative electrode sheet has a high energy density.

[0010] According to embodiments of this application, the D50 particle size D1 of the porous ceramic is 0.5 to 5 times the D50 particle size D2 of the negative electrode active material. With the particle size of the porous ceramic within this range, the negative electrode sheet can have a high areal density while significantly improving electrolyte wettability and electrolyte retention. Consequently, batteries using this negative electrode sheet can have higher energy density and better fast-charging performance.

[0011] According to embodiments of this application, the porous ceramic satisfies at least one of the following conditions:

[0012] The D50 particle size D1 of the porous ceramic is 1~40 micrometers, specifically 10~40 micrometers;

[0013] The porous ceramic has a pore size of 1 nm to 0.5 D1;

[0014] The porosity of the porous ceramic is 10%~50%;

[0015] The compressive strength of the porous ceramic is 0.2 MPa to 2 MPa, preferably 0.5 MPa to 1 MPa.

[0016] Within the above parameter range, the energy density and fast charging performance of batteries using this negative electrode can be further improved.

[0017] According to an embodiment of this application, the negative electrode active material layer includes a plurality of sub-active material layers stacked sequentially, with the direction closer to the negative electrode current collector defined as the inner side and the direction farther from the negative electrode current collector defined as the outer side, and the plurality of sub-active material layers satisfying at least one of the following conditions:

[0018] The D50 particle size of the porous ceramic in the outer sub-active material layer is greater than or equal to the D50 particle size of the porous ceramic in the inner sub-active material layer.

[0019] The content of porous ceramics in the outer sub-active material layer is greater than or equal to the content of porous ceramics in the inner sub-active material layer.

[0020] According to embodiments of this application, at least one of the plurality of said sub-active material layers satisfies:

[0021] In the direction from the inside to the outside, the D50 particle size of the porous ceramics in the multiple sub-active material layers gradually increases;

[0022] In the direction from the inside to the outside, the content of porous ceramics in the multiple sub-active material layers gradually increases.

[0023] According to an embodiment of this application, the negative electrode active material layer includes a first sub-active material layer and a second sub-active material layer stacked in a direction from the inside to the outside. The first sub-active material layer includes a first active material and a first porous ceramic, and the second sub-active material layer includes a second active material and a second porous ceramic.

[0024] According to an embodiment of this application, the D50 particle size of the first porous ceramic is 3~10μm.

[0025] According to an embodiment of this application, based on the total mass of the first sub-active material layer, the mass percentage of the first porous ceramic is 0% to 2%, specifically 0.2% to 1%.

[0026] According to an embodiment of this application, the D50 particle size of the second porous ceramic is 10~40μm.

[0027] According to an embodiment of this application, based on the total mass of the second sub-active material layer, the mass percentage of the second porous ceramic is 0.1% to 2%, specifically 0.5% to 1%.

[0028] According to an embodiment of this application, the ratio of the thickness of the first sub-active material layer to the thickness of the second sub-active material layer is 0.5~1:0.5~1, specifically 1:1.

[0029] According to an embodiment of this application, the D50 particle size of the first active material is 6μm~12μm.

[0030] According to an embodiment of this application, the D50 particle size of the second active material is 10 μm to 20 μm.

[0031] According to embodiments of this application, the porous ceramic comprises at least one of alumina, aluminum hydroxide, boehmite, and silicon dioxide.

[0032] According to an embodiment of this application, the negative electrode further includes a conductive layer located between the negative electrode current collector and the negative electrode active material layer.

[0033] A second aspect of this application provides a method for preparing the aforementioned negative electrode sheet. According to an embodiment of this application, the method includes: coating a negative electrode slurry containing a negative electrode active material and porous ceramic onto at least one side of a negative electrode current collector to form a negative electrode active material layer, thereby obtaining the negative electrode sheet. This method is simple and convenient, compatible with existing technologies, requires no additional equipment or processes, and is easy to scale up for production.

[0034] According to an embodiment of this application, the method may further include: coating a conductive slurry containing a conductive agent onto at least one side of the negative electrode current collector to form a conductive layer; coating the negative electrode slurry onto the surface of the conductive layer away from the negative electrode current collector to form the negative electrode active material layer, thereby obtaining the negative electrode sheet.

[0035] A third aspect of this application provides a battery. According to embodiments of this application, the battery includes the negative electrode sheet described above or prepared by the methods described above. This battery exhibits high energy density and superior fast-charging performance.

[0036] In a fourth aspect, this application provides an electrical device. According to an embodiment of this application, the electrical device includes the battery described above. The electrical device has superior battery life and superior fast-charging performance. Attached Figure Description

[0037] Figure 1 is a schematic diagram of the structure of a negative electrode sheet according to an embodiment of this application.

[0038] Figure 2 is a schematic diagram of the negative electrode sheet according to another embodiment of this application.

[0039] Figure 3 is a schematic diagram of the negative electrode sheet according to another embodiment of this application.

[0040] Figure 4 is a schematic diagram of the negative electrode sheet according to another embodiment of this application.

[0041] Figure 5 is a schematic diagram of the negative electrode sheet according to another embodiment of this application.

[0042] Figure 6 is a schematic diagram of the structure of a battery according to an embodiment of this application.

[0043] Figure 7 is a schematic diagram of the structure of an electrical device according to an embodiment of this application.

[0044] Figure label:

[0045] 100: Negative electrode sheet; 10: Negative electrode current collector; 20: Negative electrode active material layer; 21: Sub-active material layer; 201: First sub-active material layer; 202: Second sub-active material layer; 30: Conductive layer; 200: Battery; 300: Electrical equipment. Embodiments of the present invention

[0046] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0047] A first aspect of this application provides a negative electrode sheet. According to embodiments of this application, referring to Figures 1 and 2, the negative electrode sheet 100 includes: a negative electrode current collector 10; and a negative electrode active material layer 20, the negative electrode active material layer 20 being located on at least one side of the negative electrode current collector 10, the negative electrode active material layer 10 containing an active material and porous ceramic. In this negative electrode sheet 100, by adding a certain proportion of porous ceramic material, the diffusion rate of the electrolyte in the negative electrode sheet can be effectively improved, enhancing the electrolyte's wetting and liquid retention capabilities, increasing the diffusion rate of lithium ions in the negative electrode sheet, and significantly improving fast charging capability under high areal density conditions; for example, the charging speed can reach 5-10 minutes from 10% SOC to 80% SOC.

[0048] Specifically, during battery use, the active materials exhibit expansion and contraction, causing the porosity of the negative electrode to constantly change. Electrolyte is continuously squeezed out and absorbed into the negative electrode. Porous ceramics, due to their inherent toughness, do not undergo volume changes during charging and discharging. The electrolyte can be stored within the ceramic's pores, allowing the negative electrode to hold more electrolyte and improving fast-charging performance.

[0049] According to embodiments of this application, the porous ceramic is uniformly distributed within the negative electrode active material layer. It is understood that ideally, the porous ceramic is completely uniformly distributed within the negative electrode active material layer. However, due to various factors such as process limitations and errors, a completely uniform distribution of porous ceramic is generally impossible. The term "uniformly distributed" used herein includes both completely uniform distribution and distributions within a reasonable range due to process limitations and errors. This arrangement ensures that the electrolyte wetting and retention capabilities at various locations within the negative electrode are essentially consistent, as are the lithium-ion diffusion rates, avoiding problems such as localized electrolyte depletion and poor wetting, thereby improving the electrochemical performance of the battery using this negative electrode.

[0050] It is understood that porous ceramics are ceramic materials with a large number of pores, which can be interconnected or closed. As an example, some embodiments of this application use porous ceramics with an open porous structure, which is beneficial for improving the electrolyte wetting and liquid retention performance of the negative electrode. In other embodiments, the porous ceramic can be a solid structure or a hollow structure. As an example, the porous ceramic has a hollow structure, which can further improve the electrolyte wetting and liquid retention performance of the negative electrode.

[0051] According to embodiments of this application, a larger particle size of porous ceramics allows for the formation of more pores in the negative electrode sheet, but also reduces the areal density of the negative electrode active material layer, thereby lowering the energy density of the battery using this negative electrode sheet. Considering both the fast-charging performance and energy density of the battery, the D50 particle size D1 of the porous ceramics is 0.5 to 5 times the D50 particle size D2 of the negative electrode active material, specifically such as 0.5 times, 1 time, 1.5 times, 2 times, 2.5 times, 3 times, 3.5 times, 4 times, 4.5 times, and 5 times. With the particle size of the porous ceramics within the above range, the negative electrode sheet can have a higher areal density while significantly improving electrolyte wettability and electrolyte retention, thus enabling the battery using this negative electrode sheet to have higher energy density and better fast-charging performance.

[0052] According to embodiments of this application, the D50 particle size D1 of the porous ceramic can be 1~40 micrometers, specifically 10~40 micrometers, and more specifically 1 micrometer, 2 micrometers, 5 micrometers, 8 micrometers, 10 micrometers, 12 micrometers, 15 micrometers, 20 micrometers, 25 micrometers, 30 micrometers, 35 micrometers, 40 micrometers, etc. Within the above range, the energy density and fast charging performance of the battery using this negative electrode can be further improved.

[0053] In this article, the D50 particle size, also known as the median particle size or volume average particle size, is the particle size corresponding to 50% of the material volume. Its physical meaning is that the sum of the volumes of all particles smaller than D50 is equal to the sum of the volumes of all particles larger than D50. It can be detected by conventional methods in this field, such as by a laser particle size analyzer.

[0054] According to embodiments of this application, the pore size of the porous ceramic is 1 nm to 0.5 μm, specifically such as 1 nm, 5 nm, 10 nm, 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, etc. Having the above-mentioned pore size is beneficial for increasing the porosity of the negative electrode active material layer, thereby improving the electrolyte wetting and liquid retention performance of the negative electrode sheet. When this negative electrode sheet is used in a battery, it can effectively improve fast charging performance without significantly reducing energy density. In some embodiments, the pore size of the porous ceramic is 1 nm to 0.5 μm or 1 nm to 20 μm, for example, 1 nm, 5 nm, 10 nm, 50 nm, 100 nm, 0.5 μm, 1 μm, 5 μm, 10 μm, 15 μm, or 20 μm.

[0055] In this article, the pore size of porous ceramics refers to the diameter of the pores within the porous ceramic, typically the maximum diameter of the pores. It can be detected using conventional methods in the field, such as gas adsorption, scanning electron microscopy, and transmission electron microscopy.

[0056] According to embodiments of this application, the porosity of the porous ceramic is 10% to 50%, specifically 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, etc. Having the above porosity can effectively improve the porosity of the negative electrode sheet, thereby improving the electrolyte wettability and electrolyte retention of the negative electrode sheet, while maintaining a certain mechanical strength of the porous ceramic.

[0057] In this article, the porosity of porous ceramics refers to the proportion of pore volume to the total volume in porous ceramics. It can be detected using conventional methods in the field, such as density methods, gas adsorption methods, and fluid filling methods.

[0058] According to embodiments of this application, the compressive strength of the porous ceramic is 0.2 MPa to 2 MPa, specifically 0.5 MPa to 1 MPa, and more specifically 0.2 MPa, 0.5 MPa, 0.8 MPa, 1 MPa, 1.2 MPa, 1.5 MPa, 1.8 MPa, 2 MPa, etc. Having the above-mentioned compressive strength allows for better maintenance of the pore structure, meeting the performance requirements of processes such as rolling during the preparation of the negative electrode sheet, and preventing breakage.

[0059] In this article, the compressive strength of porous ceramics is an important indicator of its mechanical properties. It refers to the ability of porous ceramics to resist failure under stress. Specifically, it can be expressed as the force when porous ceramics break under pressure divided by the surface area of ​​the ceramic material. It can be tested by methods such as a pressure testing machine or a universal testing machine.

[0060] According to embodiments of this application, the shape of the porous ceramic is not particularly limited, and it can be spherical, polygonal, scalene, regular or irregular geometric shape, etc., without any particular limitation. The shape of the pores in the porous ceramic is also not particularly limited, as long as it can accommodate the electrolyte.

[0061] According to embodiments of this application, the porous ceramic comprises at least one of alumina, aluminum hydroxide, boehmite, and silicon dioxide. Therefore, the material is widely available, readily accessible, low in cost, and has good compatibility with other substances in the negative electrode active material layer.

[0062] According to embodiments of this application, based on the total mass of the negative electrode active material layer, the mass percentage content of the porous ceramic is 0.1% to 2%, specifically 0.2% to 1%, and more specifically 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 0.2%, 0.3%, 0.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, etc. Within the above content range, the negative electrode sheet can have suitable porosity, improving its electrolyte wettability and electrolyte retention performance, thereby improving the fast-charging performance of the battery using this negative electrode sheet, while essentially not reducing the areal density of the negative electrode sheet, thus ensuring that the battery using this negative electrode sheet has a high energy density.

[0063] According to embodiments of this application, the negative electrode active material layer can be a single-layer structure or a multi-layer structure. It is understood that in a negative electrode sheet with a single-layer negative electrode active material layer, the same or different ceramic sizes can be used to increase the porosity of the electrode and enhance its liquid absorption performance. In a negative electrode sheet with a multi-layer negative electrode active material layer, based on the particle size of the active material in each sub-active material layer, the porous ceramic particle size can be distributed in a gradient along the electrode thickness direction. That is, different pore gradients are formed on the inner and outer sides of the apparent electrode distribution. Furthermore, by adjusting the content of porous ceramics in different sub-active material layers, multi-layer negative electrode sheets with different pore sizes can be obtained.

[0064] In some embodiments, referring to FIG3, the negative electrode active material layer 20 includes a plurality of sub-active material layers 21 stacked sequentially. The direction closer to the negative electrode current collector 10 is defined as the inner side, and the direction farther from the negative electrode current collector 10 is defined as the outer side. The plurality of sub-active material layers 21 satisfy at least one of the following conditions: the D50 particle size of the porous ceramic in the outer sub-active material layer is greater than or equal to the D50 particle size of the porous ceramic in the inner sub-active material layer; the content of porous ceramic in the outer sub-active material layer is greater than or equal to the content of porous ceramic in the inner sub-active material layer. Therefore, the porosity of the outer negative electrode active material layer is larger, making it easier for the electrolyte to wet the negative electrode sheet, improving the electrolyte wettability and liquid retention of the negative electrode sheet, and thus improving the fast-charging performance of the battery using this negative electrode sheet.

[0065] In some embodiments, the plurality of sub-active material layers satisfy at least one of the following conditions: the D50 particle size of the porous ceramics in the plurality of sub-active material layers gradually increases in the direction from the inside to the outside; and the content of porous ceramics in the plurality of sub-active material layers gradually increases in the direction from the inside to the outside. This further improves the electrolyte wettability and liquid retention of the negative electrode, thereby improving the fast-charging performance of the battery using this negative electrode.

[0066] According to an embodiment of this application, referring to FIG4, the negative electrode active material layer 20 includes a first sub-active material layer 201 and a second sub-active material layer 202 stacked in a direction from the inside to the outside. The first sub-active material layer 201 includes a first active material and a first porous ceramic, and the second sub-active material layer 202 includes a second active material and a second porous ceramic.

[0067] In some embodiments, the D50 particle size of the first porous ceramic is 1~5μm, specifically such as 1μm, 1.5μm, 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm, 5μm, etc.

[0068] In some embodiments, based on the total mass of the first sub-active material layer, the mass percentage of the first porous ceramic is 0% to 2%, specifically 0.2% to 1%, and more specifically 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, etc.

[0069] In some embodiments, the D50 particle size of the second porous ceramic is 5~20μm, specifically 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 19μm, 20μm, etc.

[0070] In some embodiments, based on the total mass of the second sub-active material layer, the mass percentage of the second porous ceramic is 0.1% to 2%, specifically 0.5% to 1%, and more specifically 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, etc.

[0071] In some embodiments, the D50 particle size of the first active material is 0.5 μm to 2 μm, specifically 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1.0 μm, 0.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2.0 μm, etc.

[0072] In some embodiments, the D50 particle size of the second active material is 1μm to 4μm, specifically 1μm, 1.5μm, 2μm, 2.5μm, 3μm, 3.5μm, 4μm, etc.

[0073] The porous ceramics and active materials in the first and second active material layers meet the above conditions, which allows the negative electrode sheet to have good electrolyte wettability and liquid retention while having a high areal density. This, in turn, enables the battery using this negative electrode sheet to have high energy density and better fast charging performance.

[0074] In some embodiments, the ratio of the thickness of the first sub-active material layer to the thickness of the second sub-active material layer is 0.5~1:0.5~1, specifically 0.5:1, 0.6:1, 0.8:1, 1:1, 1.2:1, 1.5:1, 2:1, etc., and can specifically be 1:1. This can further improve the energy density and fast-charging performance of batteries using this negative electrode.

[0075] According to embodiments of this application, the specific type of negative electrode active material in the negative electrode active material layer can be selected according to actual needs. In some embodiments, the negative electrode active material may include one or more of carbon-based materials, silicon-based materials, tin-based materials, and lithium titanate. Carbon-based materials may include one or more of graphite (e.g., artificial graphite, natural graphite, etc.), soft carbon, and hard carbon. Silicon-based materials may include one or more of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may include one or more of elemental tin, tin oxide compounds, and tin alloys.

[0076] In some embodiments, the negative electrode active material layer may include a negative electrode binder. As an example, the negative electrode binder may include one or more of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS), and the embodiments of this application are not limited thereto.

[0077] In some embodiments, the negative electrode active material layer may further include a negative electrode conductive agent. As an example, the negative electrode conductive agent may include one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers, and the embodiments of this application are not limited thereto.

[0078] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymeric material substrate and a metal layer formed on at least one surface of the polymeric material substrate. The composite current collector may be formed by forming a metal material (such as copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys) on a polymeric material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0079] According to an embodiment of this application, referring to FIG5, the negative electrode further includes a conductive layer 30, which is located between the negative electrode current collector 10 and the negative electrode active material layer 20. This effectively improves the conductivity of the negative electrode, thereby enhancing the electrochemical performance of the battery using this negative electrode.

[0080] According to embodiments of this application, the conductive layer may include a conductive agent and a binder. As an example, the conductive agent may include, but is not limited to, graphite or other carbon materials, specifically one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. As an example, the binder may include one or more of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0081] A second aspect of this application provides a method for preparing the aforementioned negative electrode sheet. According to an embodiment of this application, the method includes: coating a negative electrode slurry containing a negative electrode active material and porous ceramic onto at least one side of a negative electrode current collector to form a negative electrode active material layer, thereby obtaining the negative electrode sheet. This method is simple and convenient, compatible with existing technologies, requires no additional equipment or processes, and is easy to scale up for production.

[0082] According to embodiments of this application, a negative electrode active material, porous ceramic, conductive agent and binder can be added to a solvent to obtain a negative electrode slurry, which is then coated on at least one side of the negative electrode current collector, and then dried and rolled to obtain a negative electrode sheet.

[0083] It is understandable that when the negative electrode active material layer has a single-layer structure, only one slurry needs to be prepared and coated sequentially. When the negative electrode active material layer has a multi-layer structure, one slurry can be prepared and coated multiple times to form the negative electrode active material layer; alternatively, multiple slurries can be prepared according to the formula of different sub-active material layers, and multiple coatings can be performed (e.g., one slurry can be coated each time) to form the negative electrode active material layer.

[0084] This application innovatively applies porous ceramics to negative electrode sheets. The porous ceramics are dispersed together with active materials, binders, and conductive agents during electrode slurry preparation, and the required negative electrode sheets are formed through a coating process, which is suitable for high energy density and fast-charging batteries.

[0085] According to an embodiment of this application, the method may further include: coating a conductive slurry containing a conductive agent onto at least one side of the negative electrode current collector to form a conductive layer; coating the negative electrode slurry onto the surface of the conductive layer away from the negative electrode current collector to form the negative electrode active material layer, thereby obtaining the negative electrode sheet.

[0086] Specifically, conductive agents and binders can be added to a solvent to prepare a conductive slurry. The conductive slurry is then coated on at least one side of the negative electrode current collector. A negative electrode active material layer is then coated on the surface of the conductive layer away from the negative electrode current collector. The coating of the negative electrode active material layer is the same as described above and will not be elaborated further here.

[0087] A third aspect of this application provides a battery 200, the structural schematic of which is shown in Figure 6. According to an embodiment of this application, the battery 200 includes the negative electrode sheet described above or prepared by the method described above. This battery has high energy density and good fast-charging performance.

[0088] It is understood that there are no other restrictions on the specific type of battery, such as including but not limited to lithium-ion batteries, sodium-ion batteries, etc., and the battery can be a prismatic battery, a pouch battery, a cylindrical battery, etc., and can be in different forms such as a battery cell, a battery module, or a battery pack.

[0089] It can also be understood that, in addition to the aforementioned negative electrode, the battery may include other structures and components necessary for conventional batteries. Taking a lithium-ion battery as an example, it may include an outer packaging, and an electrode assembly and electrolyte contained within the outer packaging. The electrode assembly may include a positive electrode, a negative electrode, and a separator located between the positive and negative electrodes.

[0090] In some embodiments, the positive electrode film layer may include a positive electrode current collector and a positive electrode active material layer disposed on at least one side surface of the positive electrode current collector. The positive electrode active material layer may include a positive electrode active material, a positive electrode conductive agent, and a positive electrode binder.

[0091] In some embodiments, the positive electrode active material includes, but is not limited to, lithium transition metal oxides and / or lithium-containing phosphates with olivine structures. Specifically, the lithium transition metal oxides include lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, lithium nickel cobalt manganese oxides (such as NCM333, NCM523, NCM211, NCM622, NCM811), and lithium nickel cobalt aluminum oxides (such as LiNi). 0.85 Co 0.15 Al 0.05 O2) or combinations thereof; lithium phosphates with olivine structures, including but not limited to lithium iron phosphate (such as LiFePO4), lithium manganese iron phosphate, composites of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), composites of lithium manganese phosphate and carbon, lithium manganese iron phosphate (such as LiMn) x Fe 1-x At least one of PO4 (0 < x < 1) and a composite material of lithium manganese iron phosphate and carbon.

[0092] In some embodiments, the positive electrode conductive agent may include one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers, but this application embodiment does not limit this.

[0093] In some embodiments, the positive electrode binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyacrylic acid (PAA), polyvinyl alcohol (PVA), ethylene-vinyl acetate copolymer (EVA), styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC), sodium alginate (SA), polymethacrylic acid (PMA), and carboxymethyl chitosan (CMCS).

[0094] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0095] In some embodiments, the electrolyte may include an electrolyte salt, which may include at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium perchlorate, lithium difluorooxalate borate, lithium bis(oxalate borate), lithium difluorophosphate, lithium difluorodioxalate phosphate, and lithium tetrafluoroborate.

[0096] In some embodiments, the organic solvent in the electrolyte may include one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, ethyl formate, ethyl acetate, methyl acetate, fluoroethylene carbonate, difluoroethylene carbonate, methyl methyl fluorocarbonate, diethyl fluorocarbonate, ethyl fluoroformate, ethyl fluoroacetate, and methyl fluoroacetate.

[0097] In some embodiments, the diaphragm may include, but is not limited to, single-layer or multi-layer polymer diaphragms, such as polyethylene diaphragms, polypropylene diaphragms, polyethylene-polypropylene composite diaphragms, etc.

[0098] In a fourth aspect, this application provides an electrical device 300, the structural schematic of which is shown in Figure 7. According to an embodiment of this application, the electrical device 300 includes the aforementioned battery. This electrical device has superior battery life and fast-charging performance.

[0099] According to embodiments of this application, the electrical equipment may include mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but is not limited thereto. The battery may be used as a power source for the electrical equipment or as an energy storage unit for the electrical equipment.

[0100] It is understandable that, in addition to the battery mentioned above, the electrical equipment may also include the necessary structures and components of conventional electrical equipment. Taking electric vehicles as an example, it may include the body, windows, chassis, engine, seats, tires, and other necessary structures and components, which will not be elaborated here.

[0101] The embodiments of this application are described in detail below.

[0102] Example 1:

[0103] Coating the current collector surface with a conductive coating: The negative electrode conductive paste (the mass ratio of carbon black, CMC and binder SBR in the paste is 100:6:20) is uniformly coated on the aluminum foil to form a conductive layer with a thickness of 2μm.

[0104] Negative electrode preparation: Artificial graphite (anode active material), conductive agent, thickener CMC, binder SBR, and porous ceramic are dispersed in deionized water in a certain proportion to obtain a uniformly mixed negative electrode slurry. The negative electrode slurry is uniformly coated onto the conductive layer, and after baking and slitting, a negative electrode sheet is obtained. The coating amount is 205 g / m². 2 The electrode thickness is 140μm.

[0105] Positive electrode preparation: Lithium iron phosphate (PFP), carbon black (CSI), and PVDF (PVDF) binder were dispersed in NMP solvent at a mass ratio of 96.2:1.8:2. After thorough mixing, a positive electrode slurry was obtained. The slurry was uniformly coated onto carbon-coated aluminum foil, and after baking and slitting, a positive electrode sheet was obtained; the coating amount was 450 g / m². 2 The electrode thickness is 186μm.

[0106] Battery assembly: The negative electrode, separator (PE single-sided adhesive separator (9μm base film, 2μm adhesive coating)), and positive electrode are stacked sequentially in a stacking manner to produce a soft-pack battery. After injecting the electrolyte (solvent EC+EMC+DEC, lithium hexafluorophosphate, 1.0mol / L), formation activation is performed, followed by testing.

[0107] Examples 2, 5-8, 10-15

[0108] Same as Example 1, the differences are shown in Table 1.

[0109] Example 3

[0110] Same as Example 1, except that:

[0111] Negative electrode sheet preparation: A certain proportion of artificial graphite (negative electrode active material), conductive agent, CMC (thickening agent), SBR (binder), and porous ceramic are dispersed in deionized water to obtain a uniformly mixed first negative electrode slurry. The first negative electrode slurry is uniformly coated onto the conductive layer and baked. The same composition is then dispersed in deionized water to obtain a uniformly mixed second negative electrode slurry. The second negative electrode slurry is uniformly coated onto the coating formed by the first negative electrode slurry. After baking and slitting, the negative electrode sheet is obtained. The coating amount is 205 g / m². 2 The electrode thickness is 140μm.

[0112] Examples 4, 9, and 16

[0113] Same as Example 3, the differences are shown in Table 1.

[0114] Comparative Examples 1-2

[0115] Same as Example 1, the differences are shown in Table 1.

[0116] Table 1

[0117]

[0118] Note: In Examples 3, 4, 9 and 16 in Table 1, the negative electrode sheet has a double layer of negative electrode active material. In the description “94.8:1:2:2:0.2 / 94.5:1:2:2:0.5”, the data before and after “ / ” represent the corresponding data in the two negative electrode active material layers along the direction away from the negative electrode current collector. Other similar descriptions have the same meaning.

[0119] Performance testing:

[0120] 1. Energy density test: At 25℃, charge to 3.8V with C / 3 constant current, charge to 3.8V with 0.1C, and let stand for 5 minutes; discharge to 2.0V with C / 3 constant current. Energy density = discharge energy / cell weight. The test results are shown in Table 2.

[0121] 2. Fast charging time: The lithium deposition potential was measured using a three-electrode method (lithium sheet as the three electrodes), and the fast charging time was calculated based on the lithium deposition potential. The test results are shown in Table 2.

[0122] 3. D50 particle size: Tested using a laser particle size analyzer, referring to GB / T19077-2016.

[0123] 4. Pore size and porosity of porous ceramics: The pore size was measured by SEM and the porosity was measured by mercury intrusion porosimetry, in accordance with GB / T21650.

[0124] 5. Compressive strength of porous ceramics: Tested in accordance with GB / T 8489-2006.

[0125] Table 2

[0126]

[0127] The data above clearly shows that adding porous ceramics has almost no impact on the battery's energy density, but significantly improves fast charging performance.

[0128] In the description of this invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0129] 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 the present invention. 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.

[0130] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A negative electrode (100), characterized in that, include: Negative current collector (10); A negative electrode active material layer (20) is located on at least one side of the negative electrode current collector (10), and the negative electrode active material layer (20) contains active materials and porous ceramics.

2. The negative electrode (100) according to claim 1, characterized in that, The porous ceramic is uniformly distributed in the negative electrode active material layer (20).

3. The negative electrode (100) according to claim 1 or 2, characterized in that, Based on the total mass of the negative electrode active material layer (20), the mass percentage of the porous ceramic is 0.1% to 2%, preferably 0.2% to 1%.

4. The negative electrode sheet (100) according to any one of claims 1 to 3, characterized in that, The D50 particle size D1 of the porous ceramic is 0.5 to 5 times the D50 particle size D2 of the negative electrode active material.

5. The negative electrode sheet (100) according to any one of claims 1 to 4, characterized in that, The porous ceramic satisfies at least one of the following conditions: The D50 particle size D1 of the porous ceramic is 1~40 micrometers, preferably 10~40 micrometers; The porous ceramic has a pore size of 1 nm to 0.5 D1; The porosity of the porous ceramic is 10%~50%; The compressive strength of the porous ceramic is 0.2 MPa to 2 MPa, preferably 0.5 MPa to 1 MPa.

6. The negative electrode sheet (100) according to any one of claims 1 to 5, characterized in that, The negative electrode active material layer (20) includes a plurality of sub-active material layers (21) stacked sequentially. The direction closer to the negative electrode current collector (10) is defined as the inner side, and the direction farther from the negative electrode current collector (10) is defined as the outer side. The plurality of sub-active material layers (21) satisfy at least one of the following conditions: The D50 particle size of the porous ceramic in the outer sub-active material layer (21) is greater than or equal to the D50 particle size of the porous ceramic in the inner sub-active material layer (21). The content of porous ceramics in the outer sub-active material layer (21) is greater than or equal to the content of porous ceramics in the inner sub-active material layer (21).

7. The negative electrode (100) according to claim 6, characterized in that, The plurality of said sub-active material layers (21) satisfy at least one of the following conditions: In the direction from the inside to the outside, the D50 particle size of the porous ceramics in the multiple sub-active material layers (21) gradually increases; In the direction from the inside to the outside, the content of porous ceramics in the multiple sub-active material layers (21) gradually increases.

8. The negative electrode (100) according to claim 6, characterized in that, The negative electrode active material layer (20) includes a first sub-active material layer (201) and a second sub-active material layer (202) stacked in a direction from the inside to the outside. The first sub-active material layer (201) includes a first active material and a first porous ceramic, and the second sub-active material layer (202) includes a second active material and a second porous ceramic, and satisfies at least one of the following conditions: The D50 particle size of the first porous ceramic is 3~10μm; Based on the total mass of the first sub-active material layer (201), the mass percentage of the first porous ceramic is 0%~2%, preferably 0.2%~1%; The D50 particle size of the second porous ceramic is 10~40μm; Based on the total mass of the second sub-active material layer (202), the mass percentage of the second porous ceramic is 0.1% to 2%, preferably 0.5% to 1%; The ratio of the thickness of the first sub-active material layer (201) to the thickness of the second sub-active material layer (202) is 0.5~1:0.5~1, preferably 1:1; The D50 particle size of the first active material is 6μm~12μm; The D50 particle size of the second active material is 10μm~20μm.

9. The negative electrode sheet (100) according to any one of claims 1 to 8, characterized in that, The porous ceramic includes at least one of alumina, aluminum hydroxide, boehmite, and silicon dioxide.

10. The negative electrode sheet (100) according to any one of claims 1 to 9, characterized in that, It also includes a conductive layer (30) located between the negative electrode current collector (10) and the negative electrode active material layer (20).

11. A method for preparing the negative electrode sheet (100) according to any one of claims 1 to 10, characterized in that, include: A negative electrode slurry containing negative electrode active material and porous ceramic is coated on at least one side of the negative electrode current collector (10) to form a negative electrode active material layer (20) and obtain the negative electrode sheet (100).

12. The method according to claim 11, characterized in that, include: A conductive paste containing a conductive agent is coated on at least one side of the negative electrode current collector (10) to form a conductive layer (30). The negative electrode slurry is coated on the surface of the conductive layer (30) away from the negative electrode current collector (10) to form the negative electrode active material layer (20), thereby obtaining the negative electrode sheet (100).

13. A battery (200), characterized in that, The negative electrode (100) includes any one of claims 1 to 10 or the negative electrode (100) prepared by the method of claim 11 or 12.

14. An electrical appliance (300), characterized in that, Includes the battery as described in claim 13.

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