Negative pole piece and preparation method therefor, battery, and electrical apparatus

Abstract

The application discloses a negative pole piece and a preparation method therefor, a battery, and an electrical apparatus. The negative pole piece comprises: a negative electrode current collector and a negative electrode active material layer. The negative electrode active material layer is arranged on at least one side of the negative electrode current collector. The negative electrode active material layer comprises dielectric material particles, and the volume average particle size Dv50 of the dielectric material particles is D 1 , wherein D 1 is 400 nm -2000 nm. On the basis of the total mass of the negative electrode active material layer, the proportion of the dielectric material particles is 0.1% -10%. Therefore, the negative pole piece in the present application uses the dielectric material particles having the described particle size and content, such that the quick charging performance of the battery can be improved.

Description

Negative electrode sheet and preparation method thereof, battery and electrical device Technical Field

[0001] The present application belongs to the field of batteries, and specifically relates to a negative electrode plate and a preparation method thereof, a battery and an electrical device. Background Art

[0002] Secondary batteries are widely used in energy storage systems such as hydropower, thermal, wind, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, and other fields. As battery applications expand, the performance requirements for secondary batteries are becoming increasingly stringent, such as the requirement for fast charging capabilities. However, the performance of the battery's negative electrode has a certain impact on fast charging capabilities, making it imperative to improve the performance of the negative electrode. Summary of the Invention

[0003] In view of the technical problems existing in the background technology, the present application provides a negative electrode plate, aiming to improve the fast charging performance of the battery containing the negative electrode plate.

[0004] In order to achieve the above objectives, the first aspect of the present application provides a negative electrode sheet, comprising:

[0005] negative electrode current collector;

[0006] A negative electrode active material layer, wherein the negative electrode active material layer is disposed on at least one side of the negative electrode current collector, the negative electrode active material layer includes dielectric material particles, the volume average particle size Dv50 of the dielectric material particles is D1, D1 is 400nm-2000nm, and based on the total mass of the negative electrode active material layer, the proportion of the dielectric material particles is 0.1%-10%.

[0007] The present application includes at least the following beneficial effects: the use of dielectric material particles with the above-mentioned particle size and content in the negative electrode plate of the present application can improve the fast charging performance of the battery.

[0008] In some embodiments, D1 is 600 nm to 1000 nm, thereby improving the fast charging performance of the battery.

[0009] In some embodiments, the dielectric material particles account for 0.5% to 3% of the total mass of the negative electrode active material layer, thereby improving the fast charging performance of the battery.

[0010] In some embodiments, the relative dielectric constant of the dielectric material particles is 1000-10000, and can be optionally 1500-5000. This can improve the fast charging performance of the battery.

[0011] In some embodiments, the dielectric material particles include at least one of barium titanate, lead titanate, lithium niobate, lead zirconate titanate, lead metaniobate, or lithium barium lead niobate, thereby improving the fast charging performance of the battery.

[0012] In some embodiments, the dielectric material particles include dopant ions, and the dopant ions include trivalent rare earth metal ions, Nb 5+ 、W 5+ 、Mo 5+ 、Al 3+ 、Ga 3+ Cr 3+ 、Mn 3+ Mg 2+ 、Si 4+ or Ca 2+ Thus, the fast charging performance of the battery can be improved.

[0013] In some embodiments, the dielectric material particles include at least one of trivalent rare earth metal ion-doped barium titanate, pentavalent ion-doped barium titanate, pentavalent ion-doped lead titanate, or pentavalent ion-doped lead zirconate titanate, wherein the pentavalent ion includes Nb 5+ 、W 5+ Or Mo 5+ Thus, the fast charging performance of the battery can be improved.

[0014] In some embodiments, the trivalent rare earth metal ion comprises Sc 3+ 、Y 3+ or Yb 3+ Thus, the fast charging performance of the battery can be improved.

[0015] In some embodiments, the barium titanate comprises a tetragonal crystal structure, thereby improving the fast charging performance of the battery.

[0016] In some embodiments, the BET specific surface area of ​​the dielectric material particles is 0.8 m 2 / g-7m 2 / g, optional 1.8m 2 / g-2m 2 / g. Thus, the fast charging performance of the battery can be improved.

[0017] In some embodiments, the negative electrode active material layer includes a negative electrode active material, and the volume average particle size Dv50 of the negative electrode active material is D2, D1≤D2, and optionally D1<D2. This can improve the fast charging performance of the battery.

[0018] In some embodiments, D2 is 2 μm-20 μm, and optionally 8 μm-13 μm, thereby improving the fast charging performance of the battery.

[0019] In some embodiments, the negative electrode active material layer includes: a first negative electrode active material layer, the first negative electrode active material layer being disposed on at least one side of the negative electrode current collector; and a second negative electrode active material layer, the second negative electrode active material layer being disposed on a side of the first negative electrode active material layer away from the negative electrode current collector, wherein the first negative electrode active material layer and / or the second negative electrode active material layer include the dielectric material particles. This can improve the fast charging performance of the battery.

[0020] In some embodiments, at least a portion of the surface of the negative electrode active material is provided with a coating layer, wherein the coating layer includes the dielectric material particles, thereby improving the fast charging performance and cycle performance of the battery.

[0021] In some embodiments, the negative electrode active material includes at least one of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, or titanate.

[0022] In a second aspect of the present application, the present application proposes a method for preparing a negative electrode sheet, comprising:

[0023] A negative electrode active material layer is formed on at least one side of the negative electrode current collector, wherein the negative electrode active material layer includes dielectric material particles, wherein the volume average particle size Dv50 of the dielectric material particles is D1, D1 is 400nm-2000nm, and based on the total mass of the negative electrode active material layer, the proportion of the dielectric material particles is 0.1%-10%.

[0024] As a result, the battery containing the negative electrode sheet obtained by this method has excellent fast charging performance.

[0025] In a third aspect of the present application, the present application provides a battery comprising the negative electrode sheet described in the first aspect of the present application or the negative electrode sheet obtained by the method described in the second aspect of the present application. Thus, the battery has excellent fast charging performance.

[0026] In some embodiments, the battery comprises a lithium-ion battery or a sodium-ion battery.

[0027] In the fourth aspect of the present application, the present application proposes an electrical device comprising the battery described in the third aspect of the present application.

[0028] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become obvious from the description below, or will be learned through practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present application. The same reference numerals are used throughout the drawings to represent the same components. In the drawings:

[0030] FIG1 is a schematic structural diagram of a negative electrode sheet according to an embodiment of the present application.

[0031] FIG. 2 is an XRD pattern of barium titanate according to one embodiment of the present application.

[0032] FIG3 is a schematic structural diagram of a negative electrode sheet according to another embodiment of the present application.

[0033] FIG. 4 is a schematic diagram of a battery cell according to an embodiment of the present application.

[0034] FIG. 5 is an exploded view of the battery cell shown in FIG. 4 according to an embodiment of the present application.

[0035] FIG6 is a schematic diagram of a battery module according to an embodiment of the present application.

[0036] FIG7 is a schematic diagram of a battery pack according to an embodiment of the present application.

[0037] FIG8 is an exploded view of the battery pack shown in FIG7 according to an embodiment of the present application.

[0038] FIG9 is a schematic diagram of an electrical device using a battery as a power source according to an embodiment of the present application.

[0039] FIG10 is a picture of the negative electrode sheet of the battery obtained in Comparative Example 4 after disassembly after cycling.

[0040] FIG11 is a SEM image of the negative electrode sheet of the battery obtained in Comparative Example 4 after cycle disassembly.

[0041] Explanation of the reference numerals: 10 negative electrode sheet; 100 negative electrode current collector; 200 negative electrode active material layer; 21 first negative electrode active material layer; 22 second negative electrode active material layer; 1 battery cell; 11 housing; 12 electrode assembly; 13 cover plate; 2 battery module; 3 battery pack; 31 upper case; 32 lower case. DETAILED DESCRIPTION

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

[0043] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0044] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0045] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0046] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0047] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0048] Currently, judging by market developments, the application of secondary batteries is becoming increasingly widespread. They are not only used in energy storage systems such as hydropower, thermal power, wind power, and solar power stations, but are also widely used in electric vehicles such as electric bicycles, electric motorcycles, and electric vehicles, as well as in military equipment and aerospace, among other fields.

[0049] As secondary batteries become increasingly widely used, performance requirements are becoming increasingly stringent, such as the requirement for fast charging capabilities. Currently, dielectric material particles are added to the negative electrode to improve fast charging performance. However, due to their small particle size, dielectric material particles tend to agglomerate during the slurrying process, which affects their performance.

[0050] The negative electrode sheet disclosed in the embodiment of the present application is suitable for lithium-ion batteries and sodium-ion batteries, and the battery disclosed in the embodiment of the present application can be used in electrical equipment that uses batteries as power sources or various energy storage systems that use batteries as energy storage elements. Electrical equipment may include but is not limited to mobile phones, tablets, laptops, electric toys, power tools, battery cars, electric cars, ships, spacecraft, etc. Among them, electric toys may include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc., and spacecraft may include airplanes, rockets, space shuttles, and spacecraft, etc.

[0051] In a first aspect, the present application proposes a negative electrode plate. Referring to Figure 1, the negative electrode plate 10 includes a negative electrode current collector 100 and a negative electrode active material layer 200. The negative electrode active material layer 200 is arranged on at least one side of the negative electrode current collector 100. The negative electrode active material layer 200 includes dielectric material particles. The volume average particle size Dv50 of the dielectric material particles is D1, and D1 is 400nm-2000nm. Based on the total mass of the negative electrode active material layer 200, the proportion of the dielectric material particles is 0.1%-10%.

[0052] In this application, "dielectric material particles" refer to materials that exhibit excellent insulating properties in an electric field, which can separate charges and store electrical energy without losing charge.

[0053] The addition of dielectric material particles of the aforementioned particle size and content to the negative electrode plate 10 of the present application can improve the fast-charging performance of the battery. This may be because the dielectric material particles of the aforementioned particle size added to the negative electrode plate 10 are less likely to agglomerate due to their larger particle size, and no additional dispersant is required, thereby allowing the performance of the dielectric material particles to be fully utilized. Furthermore, the aforementioned content can improve the fast-charging performance of the battery.

[0054] The process by which the above-mentioned dielectric material particles exert their performance is speculated as follows: During the charging process of a battery containing the negative electrode plate 10 of the present application, the dielectric material particles are subjected to the action of an electric field, and the positive and negative charge centers in the material will separate, generating a reverse electric field inside. Under the action of this reverse electric field, the electron concentration on the surface of the negative electrode active material may decrease. Since the SEI film (solid electrolyte interface film) formed on the surface of the negative electrode active material is formed by the electrolyte solvent obtaining electrons at the negative electrode active material and reducing the electron concentration on the surface of the negative electrode active material, the decrease in the electron concentration on the surface of the negative electrode active material will result in a thinner SEI film at the three-phase interface of the dielectric material particles, the negative electrode active material and the electrolyte solvent, reducing the loss of active ions and the SEI film impedance, shortening the migration path of active ions in the SEI film, thereby improving the fast charging performance of the battery and reducing electrolyte consumption. At the same time, the reverse electric field generated by the dielectric material particles on the surface of the negative electrode active material is negatively charged, so it may attract the active ions accumulated on the surface of the negative electrode active material to be evenly distributed, thereby reducing the risk of active ions aggregating on the local surface of the negative electrode plate and generating dendrites. In addition, the reverse electric field generated by the above-mentioned dielectric material particles may reduce the desolvation barrier of active ions, thereby increasing the desolvation rate of active ions and the diffusion rate of active ions in the SEI film, further improving the fast charging performance of the battery.

[0055] In some embodiments of the present application, the volume average particle size Dv50 of the dielectric material particles is D1, and D1 is 400 nm-2000 nm, for example, 400 nm-1900 nm, 400 nm-1800 nm, 500 nm-1700 nm, 600 nm-1600 nm, 700 nm-1500 nm, 800 nm-1400 nm, 900 nm-1300 nm, 1000 nm-1200 nm, 1000 nm-1100 nm, etc. In other embodiments of the present application, the volume average particle size Dv50 of the dielectric material particles is 600 nm-1000 nm.

[0056] In some embodiments of the present application, based on the total mass of the negative electrode active material layer 200, the proportion of the dielectric material particles is 0.1%-10%, for example, 0.3%-9.8%, 0.5%-9.5%, 0.6%-9.2%, 0.7%-9%, 0.8%-8.8%, 0.9%-8.5%, 1%-8%, 1.1%-7.8%, 1.2%-7.5%, 1.3%-7.2%, 1.5%-7%, 1.8%-6.5%, 2%-6%, 2.5%-5.5%, 2.8%-5%, 3%-4.5%, 3.5%-4%, etc. In other embodiments, based on the total mass of the negative electrode active material layer 200, the proportion of the dielectric material particles is 0.5%-3%. This can improve the fast charging performance and cycle performance of the battery.

[0057] In this application, the volume average particle size Dv50 of the dielectric material particles refers to the particle size corresponding to when the cumulative volume distribution percentage reaches 50%. The test method for the volume average particle size Dv50 of the dielectric material particles in the negative electrode sheet 10 is as follows:

[0058] (1) Scrape the negative electrode sheet 10, take a sample and calcine it to 600°C to complete the sintering of the binder and the negative electrode active material (for the system of silicon-containing negative electrode active material, sinter it and then mix it with sodium hydroxide solution for reaction), add water and filter;

[0059] (2) Referring to the standard GB / T 19077-2016, the volume average particle size Dv50 of the dielectric material particles of the filtered material is tested using a laser particle size analyzer (such as Malvern Master Size 3000).

[0060] In the present application, the method for testing the mass proportion of dielectric material particles in the negative electrode plate 10 includes: drying the negative electrode plate 10, then scraping the powder to take a sample, and subjecting the sample (for the system of silicon-containing negative electrode active material, the system is sintered and then mixed with sodium hydroxide solution for reaction, and the filtered powder is the sample) to a thermal gravimetric test. The test conditions are: oxygen atmosphere, heating from 25°C to 1000°C, and a heating rate of 5° / min. The corresponding ordinate on the thermal gravimetric curve corresponding to 1000°C (thermal gravimetric (TG) curve, where the ordinate is weight percentage and the abscissa is temperature) is the mass proportion of the dielectric material particles in the negative electrode active material layer.

[0061] In some embodiments of the present application, the relative dielectric constant of the dielectric material particles is 1000-10000, for example, 1000-9500, 1200-9000, 1300-8500, 1500-8000, 1600-7500, 1700-7000, 1800-6500, 1900-6000, 2000-5500, 2100-5000, 2200-4500, 2300-4000, 2400-3500, 2500-3000, 2600-2900, 2700-2800, etc. Therefore, the present application uses dielectric material particles that meet this relative dielectric constant in the negative electrode sheet 10 to further improve the fast charging performance of the battery.

[0062] The process by which the dielectric material particles with the above relative dielectric constant exert their performance is speculated as follows: Dielectric material particles that meet the relative dielectric constant can form an excellent reverse electric field effect during the charging process, and may form a thinner SEI film on the surface of the negative electrode active material, shortening the migration path of active ions in the SEI film, thereby improving the fast charging performance of the battery and reducing electrolyte consumption. At the same time, the reverse electric field generated by the dielectric material particles may reduce the desolvation barrier of the active ions, thereby increasing the desolvation rate of the active ions and the diffusion rate of the active ions in the SEI film, further improving the fast charging performance of the battery. In other embodiments of the present application, the relative dielectric constant of the dielectric material particles is 1500-5000.

[0063] In the present application, the relative dielectric constant of the dielectric material particles refers to the relative dielectric constant at room temperature (25±5° C.), which has a well-known meaning in the art and can be tested using instruments and methods known in the art. For example, the negative electrode plate 10 can be scraped and powdered first, and a sample is taken and calcined to 600°C, and the binder and the negative electrode active material are completely sintered (for the system of silicon-containing negative electrode active materials, they are sintered and then mixed with sodium hydroxide solution for reaction), and water is added to filter and separate to obtain dielectric material particles, and then the dielectric material particles are prepared into circular samples (the sample preparation process includes: adding 40g of binder (the binder is compounded by acrylic acid (PAA) emulsion and alcohol amine plasticizer, and its decomposition temperature is less than 300°C) to 200g of dielectric material particles to be tested, and after fully stirring, slowly adding it to an automatic roller press (the roller press is a double-roll roller press, the rollers are made of stainless steel and the surface is polished; the gap between the two rollers is adjustable within the range of 0.5mm to 2mm), and rolling it into a raw porcelain cake with a thickness of 1mm±0.15mm, and it is qualified if there is no color difference on the surface, uniform cross-section, and no obvious stratification; then the raw porcelain cake is placed on a sheet punching machine (the pressing plate of the sheet punching machine is circular and the size is Under the pressure plate (made of stainless steel with a polished surface), 10 thin circular ceramic pieces with a diameter of 11±1 mm are punched out; (2) debinding: the thin circular ceramic piece obtained in step (1) is placed on a clean and flat zirconia or alumina support plate, and placed in a muffle furnace together with the support plate, and debinding is performed by heating the ceramic piece to 300°C at a heating rate of 0.3°C / min and then keeping the temperature for 6 hours; after the front debinding is completed, the thin circular ceramic piece is taken out and replaced with the back side facing up, and the above operation is repeated for the back debinding; (3) silver coating: the thin circular ceramic piece after debinding in step (2) is placed on a clean and flat zirconia or alumina support plate, and the silver paste is evenly applied to the front of the thin circular ceramic piece using a fine brush, The silver paste is a high-temperature sintering conductive silver paste. The silver paste is applied in a one-way manner for 2-3 times, with a thickness of 80μm to 100μm. (4) Silver burning: first, the silver layer on the side of the thin circular porcelain piece after silver coating in step (3) is gently scraped off with a blade, and then the thin circular porcelain piece after silver coating is placed in a muffle furnace together with a firing plate. Silver burning is performed at a heating rate of 5℃ / min and after heating to 800℃ and keeping warm for 2h. After the front side silver burning is completed, the thin circular porcelain piece and the firing plate are taken out, and steps (3) and (4) are repeated to silver burn the back side. After that, the capacitance C is tested by an LCR meter and calculated according to the formula: relative dielectric constant ε=(C×d) / (ε0×A). C represents capacitance, in farads (F); d represents sample thickness, in cm; A represents sample area, in cm 2 ;ε0 represents the dielectric constant of vacuum, ε0=8.854×10 -14 F / cm. In this application, the test conditions may be 1 kHz, 1.0 V, and 25 ± 5°C. The test standard may be in accordance with GB / T 11297.11-2015.

[0064] In some embodiments of the present application, the dielectric material particles include at least one of barium titanate, lead titanate, lithium niobate, lead zirconate titanate, lead metaniobate, or lithium barium lead niobate. Thus, such dielectric material particles can further improve the fast charging performance of the battery.

[0065] The process by which the dielectric material particles of the above composition exert their performance is speculated as follows: the dielectric material particles of the above composition can exert excellent reverse electric field effects, which may reduce the desolvation barrier of active ions, thereby increasing the desolvation rate of active ions and the diffusion rate of active ions in the SEI film, and improving the fast charging performance of the battery.

[0066] In some embodiments of the present application, the dielectric material particles include doping ions, and the doping ions include trivalent rare earth metal ions, Nb 5+ 、W 5+ 、Mo 5+ 、Al 3+ 、Ga3+ Cr 3+ 、Mn 3+ Mg 2+ 、Si 4+ or Ca 2+ Thus, by doping the dielectric material particles of the present application with the above ions, the relative dielectric constant of the dielectric material particles can be adjusted, thereby improving the fast charging performance of the battery.

[0067] The process by which the above-mentioned doped dielectric material particles exert their performance is speculated as follows: by doping the above-mentioned ions into the dielectric material particles, the relative dielectric constant of the dielectric material particles can be adjusted, which may enable the dielectric material particles to exert an excellent reverse electric field and reduce the desolvation barrier of the active ions, thereby increasing the desolvation rate of the active ions and the diffusion rate of the active ions in the SEI film, and improving the fast charging performance of the battery.

[0068] As an example, the dielectric material particles may include at least one of trivalent rare earth metal ion-doped barium titanate, pentavalent ion-doped barium titanate, pentavalent ion-doped lead titanate, or pentavalent ion-doped lead zirconate titanate, for example, the trivalent rare earth metal ions include Sc 3+ 、Y 3+ or Yb 3+ At least one of the pentavalent ions, wherein the pentavalent ions include Nb 5+ 、W 5+ Or Mo 5+ For example, the dielectric material particles may include Ba x Ti y Al z O3(x+y+z=1), Ba a Y b Ti c O3(a+b+c=1), Pb m Ti n Nb p O3(m+n+p=1), etc.

[0069] In some embodiments of the present application, the dielectric material particles are barium titanate, and the barium titanate includes a tetragonal crystal.

[0070] In this application, "tetragonal" refers to a crystal structure having a unit cell with three axes, two of which are of equal length and at right angles to each other, and the third axis is perpendicular to the other two axes. The tetragonal form of barium titanate can be determined by XRD testing. Figure 2 is an XRD pattern of tetragonal barium titanate, with X-ray diffraction peaks at 2θ positions of 22°, 31°, 38°, 45°, 56°, and 66°.

[0071] Therefore, using the above-mentioned tetragonal barium titanate as the dielectric material particles may further increase the desolvation rate of active ions and the diffusion rate of active ions in the SEI film, further reduce the thickness of the SEI film, and improve the cycle performance and fast charging performance of the secondary battery.

[0072] In some embodiments of the present application, the BET specific surface area of ​​the dielectric material particles is 0.8 m 2 / g-7m 2 / g, for example 0.9m 2 / g-6.5m 2 / g,1m 2 / g-6m 2 / g,1.5m 2 / g-5.5m 2 / g,1.8m 2 / g-5m 2 / g,0.8m 2 / g-7m 2 / g.

[0073] As a result, the dielectric material particles within the above specific surface area range are more closely integrated with the negative electrode active material, which is beneficial to the performance of the dielectric material particles, and may further improve the desolvation effect of active ions and reduce the thickness of the SEI film, thereby further improving the cycle performance and fast charging performance of the battery. In other embodiments of the present application, the BET specific surface area of ​​the dielectric material particles is 1.8 m 2 / g-2m 2 / g.

[0074] In this application, the BET specific surface area of ​​the dielectric material particles has a well-known meaning in the art and can be tested using instruments and methods well-known in the art. For example, the negative electrode sheet is first scraped and powdered, a sample is taken and calcined to 600°C, and the binder and the negative electrode active material are all sintered (for the system of silicon-containing negative electrode active materials, they are sintered and then mixed with sodium hydroxide solution for reaction), and then filtered with water. Then, referring to GB / T19587-2017, the filtered sample is tested using the nitrogen adsorption specific surface area analysis test method, and calculated using the BET (Brunauer Emmett Teller) method. The nitrogen adsorption specific surface area analysis test can be performed by the Tri-Star 3020 specific surface area pore size analyzer of Micromeritics, USA.

[0075] As an example, the negative electrode current collector 100 has two surfaces facing each other in its thickness direction, and the negative electrode active material layer 200 is provided on either or both of the two facing surfaces of the negative electrode current collector 100 .

[0076] In some embodiments of the present application, the negative electrode current collector 100 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 polymer base layer and a metal layer formed on at least one surface of the polymer base layer. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer base layer (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0077] In some embodiments of the present application, the negative electrode active material layer 200 includes a negative electrode active material, and the volume average particle size Dv50 of the negative electrode active material is D2, and D1 ≤ D2. In other embodiments of the present application, the negative electrode active material layer 200 includes a negative electrode active material, and the volume average particle size Dv50 of the negative electrode active material is D2, and D1 < D2.

[0078] Therefore, when the particle sizes of the negative electrode active material and the dielectric material particles meet the above conditions, it is not only possible to give full play to the role of the dielectric material particles in reducing the desolvation barrier, thereby increasing the desolvation rate of the active ions and the diffusion rate of the active ions in the SEI film, and improving the fast charging performance of the battery; but also it can make the negative electrode active material layer 200 have a high compaction density, thereby improving the battery energy density.

[0079] In some embodiments of the present application, the volume average particle size Dv50 of the negative electrode active material is D2, and D2 is 2 μm-20 μm, for example, 5 μm-18 μm, 8 μm-15 μm, 10 μm-12 μm, etc.

[0080] Therefore, using negative electrode active material with this particle size in combination with dielectric material particles can not only fully utilize the dielectric material particles' ability to reduce the desolvation barrier, thereby increasing the desolvation rate of active ions and the diffusion rate of active ions in the SEI membrane, improving the battery's fast-charging performance; it can also provide the negative electrode active material layer 200 with a high compaction density, thereby increasing the battery's energy density. In other embodiments of the present application, the negative electrode active material has a volume average particle size Dv50 of D2, and D2 is 8μm-13μm.

[0081] In the present application, the method for testing the volume average particle size Dv50 of the negative electrode active material in the negative electrode plate includes: using a flame to ablate the surface of the negative electrode plate to remove the binder in the surface negative electrode active material layer (the flame temperature is 300°C-500°C, and the negative electrode plate line speed is 1m-30m / min), then scraping the surface layer, and sieving the resulting powder to separate the negative electrode active material from the dielectric material and the conductive agent. The resulting large-size particles are the negative electrode active material, and then referring to the standard GB / T 19077-2016, using a laser particle size analyzer (such as Malvern Master Size 3000) to test the negative electrode active material to obtain the volume average particle size Dv50 of the negative electrode active material.

[0082] In some embodiments of the present application, referring to Figure 3, the negative electrode active material layer 200 may include a first negative electrode active material layer 21 and a second negative electrode active material layer 22, the first negative electrode active material layer 21 is arranged on at least one side of the negative electrode current collector 100, and the second negative electrode active material layer 22 is arranged on the side of the first negative electrode active material layer 21 away from the negative electrode current collector 100, and the first negative electrode active material layer 21 and / or the second negative electrode active material layer 22 include the dielectric material particles.

[0083] In the present application, the "dielectric material particles" can be dispersed in the above-mentioned first negative electrode active material layer 21 or the second negative electrode active material layer 22 or dispersed in the first negative electrode active material layer 21 and the second negative electrode active material layer 22 at the same time, and the content of the dielectric material particles in the first negative electrode active material layer 21 and the second negative electrode active material layer 22 is not limited, as long as it satisfies the requirement that the proportion of the dielectric material particles based on the total mass of the negative electrode active material layer is 0.1%-10%.

[0084] In some embodiments of the present application, a coating layer is provided on at least a portion of the surface of the negative electrode active material, and the coating layer includes the dielectric material particles.

[0085] As a result, the dielectric material particles can be in close contact with the negative electrode active material, which may be beneficial for the dielectric material particles to exert their counter-electric field effect during the charging process, thereby forming a thinner SEI film on the surface of the negative electrode, reducing the loss of active ions and the SEI film impedance, shortening the migration path of active ions in the SEI film, thereby improving the battery's fast charging performance and reducing electrolyte consumption. At the same time, it may reduce the active ion desolvation barrier, thereby increasing the desolvation rate of active ions and the diffusion rate of active ions in the SEI film, further improving the battery's fast charging performance.

[0086] In some embodiments of the present application, the negative electrode active material may be a negative electrode active material for a battery that is well known in the art. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and titanates. The silicon-based material may include at least one of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, or silicon alloys. The tin-based material may include at least one of elemental tin, tin oxides, or tin alloys. When the battery is a lithium-ion battery, lithium titanate is used as the titanate; when the battery is a sodium-ion battery, sodium titanate is used as the titanate. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0087] In some embodiments of the present application, the negative electrode active material layer 200 may further include a binder. The binder may include at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), or carboxymethyl chitosan (CMCS).

[0088] In some embodiments of the present application, the negative electrode active material layer 200 may further include a conductive agent. The conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, or carbon nanofibers.

[0089] In some embodiments of the present application, the negative electrode active material layer 200 may further optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0090] On the other hand, the present application provides a negative electrode active material, wherein at least part of the surface of the negative electrode active material is provided with a coating layer, and the coating layer includes dielectric material particles, and the volume average particle size Dv50 of the dielectric material particles is D1, and D1 is 400nm-2000nm, for example, 400nm-1900nm, 400nm-1800nm, 500nm-1700nm, 600nm-1600nm, 700nm-1500nm, 800nm-1400nm, 900nm-1300nm, 1000nm-1200nm, 1000nm-1100nm, etc.

[0091] As a result, the dielectric material particles can be in close contact with the negative electrode active material, which may be beneficial for the dielectric material particles to exert their reverse electric field effect during the charging process, thereby forming a thinner SEI film on the surface of the negative electrode plate, reducing the loss of active ions and the SEI film impedance, shortening the migration path of active ions in the SEI film, thereby improving the fast charging performance of the battery and reducing electrolyte consumption. At the same time, the reverse electric field generated by the dielectric material particles on the surface of the negative electrode plate is negatively charged, so it may attract the active ions gathered on the surface of the negative electrode plate to be evenly distributed, thereby reducing the risk of active ions gathering on the local surface of the negative electrode plate and generating dendrites. In addition, the reverse electric field generated by the above-mentioned dielectric material particles may reduce the active ion desolvation barrier, thereby increasing the desolvation rate of the active ions and the diffusion rate of the active ions in the SEI film, further improving the fast charging performance of the battery. In other embodiments of the present application, the volume average particle size Dv50 of the dielectric material particles is 600nm-1000nm.

[0092] It should be noted that the relative dielectric constant, composition, and content of the dielectric material particles in the negative electrode sheet are the same as those described above and will not be repeated here.

[0093] In the second aspect of the present application, the present application proposes a method for preparing a negative electrode plate, including forming a negative electrode active material layer on at least one side of a negative electrode current collector, wherein the negative electrode active material layer includes dielectric material particles, and the volume average particle size Dv50 of the dielectric material particles is D1, D1 is 400nm-2000nm, and based on the total mass of the negative electrode active material layer, the proportion of the dielectric material particles is 0.1%-10%.

[0094] Therefore, the addition of dielectric material particles of the aforementioned particle size and content to the negative electrode plate 10 of the present application can improve the fast charging performance of the battery. This may be because the dielectric material particles of the aforementioned particle size added to the negative electrode plate 10 are less likely to agglomerate due to their larger particle size, and no additional dispersant needs to be added, thereby allowing the performance of the dielectric material particles to be fully utilized. At the same time, the aforementioned content can improve the fast charging performance of the battery.

[0095] The process by which the above-mentioned dielectric material particles exert their performance is speculated as follows: During the charging process of a battery containing the negative electrode plate 10 of the present application, the dielectric material particles are subjected to the action of an electric field, and the positive and negative charge centers in the material will separate, generating a reverse electric field inside. Under the action of this reverse electric field, the electron concentration on the surface of the negative electrode active material may decrease. Since the SEI film (solid electrolyte interface film) formed on the surface of the negative electrode active material is formed by the electrolyte solvent obtaining electrons at the negative electrode active material and reducing the electron concentration on the surface of the negative electrode active material, the decrease in the electron concentration on the surface of the negative electrode active material will result in a thinner SEI film at the three-phase interface of the dielectric material particles, the negative electrode active material and the electrolyte solvent, reducing the loss of active ions and the SEI film impedance, shortening the migration path of active ions in the SEI film, thereby improving the fast charging performance of the battery and reducing electrolyte consumption. At the same time, the reverse electric field generated by the dielectric material particles on the surface of the negative electrode active material is negatively charged, so it may attract the active ions accumulated on the surface of the negative electrode active material to be evenly distributed, thereby reducing the risk of active ions aggregating on the local surface of the negative electrode plate and generating dendrites. In addition, the reverse electric field generated by the above-mentioned dielectric material particles may reduce the desolvation barrier of active ions, thereby increasing the desolvation rate of active ions and the diffusion rate of active ions in the SEI film, further improving the fast charging performance of the battery.

[0096] In some embodiments of the present application, the negative electrode sheet can be prepared by the following method: the components for preparing the negative electrode sheet, such as the negative electrode active material, dielectric material particles, conductive agent, binder and any other components are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is then coated on the negative electrode collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0097] In a third aspect of the present application, a battery is provided, comprising the negative electrode sheet described in the first aspect of the present application or the negative electrode sheet obtained by the method described in the second aspect of the present application. Thus, the battery has excellent fast charging performance and cycle performance.

[0098] In some embodiments of the present application, the battery comprises a lithium-ion battery or a sodium-ion battery. The battery of the present application includes a battery cell form, a battery module form and a battery pack form.

[0099] Typically, a battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During the battery's charge and discharge processes, active ions are inserted and removed between the positive and negative electrodes. The electrolyte conducts ions between the positive and negative electrodes. The separator, located between the positive and negative electrodes, primarily prevents short circuits between the positive and negative electrodes while allowing ions to pass through.

[0100] In some embodiments of the present application, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer, the positive electrode active material layer is provided on at least one side of the positive electrode current collector, and the positive electrode active material layer includes the positive electrode active material.

[0101] As an example, the positive electrode current collector has two surfaces facing each other in its thickness direction, and the positive electrode active material layer is provided on either or both of the two facing surfaces of the positive electrode current collector.

[0102] In some embodiments of the present application, the positive electrode 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 material base layer and a metal layer formed on at least one surface of the polymer material base layer. 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 material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0103] In some embodiments of the present application, the positive electrode active material layer may further include a positive electrode active material. The positive electrode active material may be a positive electrode active material for batteries known in the art.

[0104] As an example, when the positive electrode plate is used in a lithium-ion battery, the positive electrode active material may adopt a positive electrode active material for lithium-ion batteries that is well known in the art. As an example, the positive electrode active material may include at least one of the following materials: lithium-containing phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as battery positive electrode active materials may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also referred to as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.8 Co 0.15 Al 0.05 O2) or at least one of its modified compounds. Examples of olivine-structured lithium-containing phosphates may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, or a composite material of lithium iron manganese phosphate and carbon.

[0105] For example, when the positive electrode plate is used in a sodium ion battery, the positive electrode active material may be a positive electrode active material known in the art for use in sodium ion batteries. For example, the positive electrode active material may include, but is not limited to, at least one of a layered transition metal oxide, a polyanion compound, and a Prussian blue analog.

[0106] Examples of the layered transition metal oxides include:

[0107] Na 1-x Cu h Fe k Mn l M 1 m O 2-y , where M 1 Including at least one of Li, Be, B, Mg, Al, K, Ca, Ti, Co, Ni, Zn, Ga, Sr, Y, Nb, Mo, In, Sn or Ba, 0 <x≤0.33,0<h≤0.24,0≤k≤0.32,0<l≤0.68,0≤m<0.1,h+k+l+m=1,0≤y<0.2;

[0108] Na 0.67 Mn 0.7 Ni z M 2 0.3-z O2, where M 2 including at least one of Li, Mg, Al, Ca, Ti, Fe, Cu, Zn or Ba, 0 <z≤0.1;

[0109] Na a Lib Ni c Mn d Fe e O₂, where 0.67 < a ≤ 1, 0 < b < 0.2, 0 < c < 0.3, 0.67 < d + e < 0.8, and b + c + d + e = 1.

[0110] As an example of the above polyanion compound, for example, the following can be listed:

[0111] A 1 f M 3 g (PO₄) i O j X 1 3-j , where A 1 includes at least one of H, Li, Na, K, or NH₄, M 3 includes at least one of Ti, Cr, Mn, Fe, Co, Ni, V, Cu, or Zn, X 1 is at least one of F, Cl, or Br, 0 < f ≤ 4, 0 < g ≤ 2, 1 ≤ i ≤ 3, 0 ≤ j ≤ 2;

[0112] Na n M 4 PO₄X 2 , where M 4 includes at least one of Mn, Fe, Co, Ni, Cu, or Zn, X 2 is at least one of F, Cl, or Br, 0 < n ≤ 2;

[0113] Na p M 5 q (SO₄)₃, where M 5 includes at least one of Mn, Fe, Co, Ni, Cu, or Zn, 0 < p ≤ 2, 0 < q ≤ 2;

[0114] Na s Mn t Fe 3-t (PO₄)₂(P₂O₇), where 0 < s ≤ 4, 0 ≤ t ≤ 3, for example, t is 0, 1, 1.5, 2, or 3.

[0115] As an example of the above Prussian blue analog, for example, the following can be listed:

[0116] A u M 6 v [M 7 (CN)₆] w ·xH₂O, where A includes H+ 、 NH4 + 、 at least one of an alkali metal cation or an alkaline earth metal cation, M 6 and M 7 each independently includes at least one of transition metal cations, 0 < u ≤ 2, 0 < v ≤ 1, 0 < w ≤ 1, 0 < x < 6. For example, A includes H + 、 Li + 、 Na + 、 K + 、 NH4 + 、 Rb + 、 Cs + 、 Fr + 、 Be 2+ 、 Mg 2+ 、 Ca 2+ 、 Sr 2+ 、 Ba 2+ or Ra 2+ at least one of, M 6 and M 7 each independently includes at least a cation of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sn or W.

[0117] During the charge and discharge process of the battery, the insertion and extraction and consumption of Li or Na will occur, and the molar content of Li or Na is different when the battery is discharged to different states. In the listing of the positive electrode active material in this application, the molar content of Li or Na is the initial state of the material, that is, the state before feeding. When the positive electrode active material is applied to the battery system, after charge and discharge cycles, the molar content of Li or Na will change.

[0118] In the listing of the positive electrode active material in this application, the molar content of oxygen is only the theoretical state value, and the release of oxygen from the lattice will cause the molar content of oxygen to change, and the actual molar content of oxygen will fluctuate.

[0119] In some embodiments of this application, the positive electrode active material layer may also optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer or fluorinated acrylate resin.

[0120] In some embodiments of this application, based on the total mass of the active material layer, the mass ratio of the binder is 0.5% - 3%, such as 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, etc.

[0121] In some embodiments of the present application, the positive electrode active material layer may further optionally include a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, or carbon nanofibers.

[0122] In some embodiments of the present application, based on the total mass of the positive electrode active material layer, the mass proportion of the conductive agent is 0.8%-4%, for example, 0.8%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, etc.

[0123] In some embodiments of the present application, the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0124] The present application has no specific restrictions on the type of electrolyte, which can be selected according to needs. For example, the electrolyte can be liquid, gel or solid.

[0125] In some embodiments of the present application, the electrolyte is an electrolyte solution comprising an electrolyte salt and a solvent.

[0126] In some embodiments of the present application, when the battery is a lithium ion battery, the electrolyte salt may include at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate or lithium tetrafluorooxalatophosphate.

[0127] In some embodiments of the present application, when the battery is a sodium ion battery, the electrolyte salt may include at least one of sodium hexafluorophosphate, sodium difluorooxalatoborate, sodium tetrafluoroborate, sodium bisoxalatoborate, sodium perchlorate, sodium hexafluoroarsenate, sodium bis(fluorosulfonyl)imide, sodium trifluoromethylsulfonate or sodium bis(trifluoromethylsulfonyl)imide.

[0128] In some embodiments of the present application, the solvent may include at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane, dimethyl sulfone, ethylene glycol dimethyl ether, methyl ethyl sulfone or diethyl sulfone.

[0129] In some embodiments of the present application, the electrolyte may optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, and additives that improve battery high or low temperature performance.

[0130] The present application has no particular limitation on the type of isolation membrane, and any known isolation membrane with a porous structure having good chemical stability and mechanical stability can be selected.

[0131] In some embodiments, the material of the separator may include at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, or polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer may be the same or different, without particular limitation.

[0132] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly through a winding process or a lamination process.

[0133] In some embodiments, the battery cell may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0134] In some embodiments, the outer packaging of the battery cell may be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. Alternatively, the outer packaging of the battery cell may be a soft shell, such as a pouch-type soft shell. The soft shell may be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0135] The present application has no particular limitation on the shape of the battery cell, which can be cylindrical, square, or any other shape. For example, FIG4 shows a battery cell 1 with a square structure as an example.

[0136] In some embodiments, referring to Figure 5, the outer packaging may include a shell 11 and a cover plate 13. The shell 11 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 11 has an opening connected to the receiving cavity, and the cover plate 13 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can form an electrode assembly 12 through a winding process or a lamination process. The electrode assembly 12 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 12. The number of electrode assemblies 12 contained in the battery cell 1 can be one or more, and those skilled in the art can select according to specific actual needs.

[0137] In some embodiments, battery cells may be assembled into a battery module. The battery module may contain one or more battery cells. The specific number may be selected by those skilled in the art based on the application and capacity of the battery module.

[0138] Figure 6 shows an example battery module 2. Referring to Figure 6 , within the battery module 2, multiple battery cells 1 may be arranged sequentially along the length of the battery module 2. Of course, they may also be arranged in any other manner. Furthermore, the multiple battery cells 1 may be secured together using fasteners.

[0139] Optionally, the battery module 2 may further include a housing having an accommodation space, and the plurality of battery cells 1 are accommodated in the accommodation space.

[0140] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art based on the application and capacity of the battery pack.

[0141] Figures 7 and 8 illustrate an example battery pack 3. Referring to Figures 7 and 8 , the battery pack 3 may include a battery box and multiple battery modules 2 disposed within the battery box. The battery box comprises an upper case 31 and a lower case 32. The upper case 31 can be positioned over the lower case 32 to form an enclosed space for accommodating the battery modules 2. The multiple battery modules 2 can be arranged in any manner within the battery box.

[0142] In addition, the present application also provides an electrical device, which includes the battery provided in the present application. The battery cell, battery module, or battery pack can be used as a power source for the electrical device, and can also be used as an energy storage unit for the electrical device. The electrical device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as 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.

[0143] As the electrical device, a battery cell, a battery module or a battery pack can be selected according to its usage requirements.

[0144] Figure 9 shows an example of an electric device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the battery, a battery pack or battery module can be used.

[0145] Another example device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is usually required to be lightweight and thin, and may use a battery cell as a power source.

[0146] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0147] Example 1

[0148] 1. Preparation of positive electrode sheet

[0149] The positive electrode active material is lithium nickel cobalt manganese oxide (NCM523, namely LiNi 0.5 Co 0.2 Mn 0.3 O2), binder polyvinylidene fluoride PVDF, conductive agent acetylene black (Super P) were mixed in a weight ratio of 98:1:1, N-methylpyrrolidone (NMP) was added as a solvent, and the slurry was stirred in a vacuum state until it was uniform to obtain a positive electrode slurry. The obtained positive electrode slurry was then heated at 13.7 mg / cm 2 The surface density of the film was coated on both sides of the 13μm aluminum foil with a doctor blade, and then dried at 140℃, cold pressed, and cut to obtain the positive electrode sheet.

[0150] 2. Preparation of negative electrode sheet

[0151] The negative electrode active material artificial graphite secondary particles, conductive agent acetylene black, composite binder SBR (styrene-butadiene rubber), dispersant sodium carboxymethyl cellulose (CMC-Na), and dielectric material particles barium titanate are dissolved in solvent deionized water in a weight ratio of 96:1:1:1:1, stirred and mixed evenly to prepare a negative electrode slurry, and the negative electrode slurry is evenly coated on the double-sided surface of the 7μm negative electrode current collector copper foil. After drying, cold pressing, and slitting, the negative electrode sheet (the thickness of the single-sided negative electrode active material layer is 120μm) is obtained.

[0152] 3. Preparation of electrolyte

[0153] In an argon atmosphere glove box (H2O <0.1ppm, O2 <0.1ppm), organic solvents ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed in a volume ratio of 3:7 to obtain an organic solvent, LiPF6 was dissolved in the above solvent, and stirred evenly to obtain an electrolyte with a concentration of 1 mol / L.

[0154] 4. Isolation film

[0155] A commercially available PP-PE copolymer microporous film (from Zhuogao Electronic Technology Co., Ltd., Model 20) with a thickness of 20 μm and an average pore size of 80 nm was used.

[0156] 5. Preparation of secondary batteries

[0157] The positive electrode sheet, separator, and negative electrode sheet are stacked in order, with the separator positioned between the positive and negative electrodes to provide isolation. The cells are then wound to form a bare cell. The bare cell is then placed in an outer packaging, injected with the aforementioned electrolyte, and packaged to form a lithium-ion battery.

[0158] The preparation methods of the lithium-ion batteries of Examples 2-18 and Comparative Examples 1-4 are the same as those of Example 1, except that the process of preparing the negative electrode sheets is different, as shown in Table 1.

[0159] The lithium plating, first-cycle coulombic efficiency, fast charging performance, and cycle performance of the batteries of Examples 1-18 and Comparative Examples 1-4 were characterized. The characterization results are shown in Table 3.

[0160] (1) Test of lithium deposition on negative electrode:

[0161] The battery was charged to 4.4V at 4C conditions, allowed to stand for 5 minutes, and then discharged to 2.8V at 1C conditions and allowed to stand for 5 minutes. The above charge and discharge process was cycled for 500 cycles, and then the negative electrode was disassembled. The surface of the disassembled negative electrode was scanned under vacuum conditions using backscattered electron diffraction (EBSD) technology (the scanning angle of the scanning electron microscope (SEM) used was 70 degrees), and the lithium deposition area signal and the non-lithium deposition area signal were collected respectively. The lithium deposition area ratio = the intensity of the lithium deposition area signal / (the intensity of the lithium deposition area signal + the signal intensity of the non-lithium deposition area).

[0162] (2) First week Coulomb efficiency test:

[0163] The unformed secondary battery was first charged to 3.4V at 25°C and 0.02C, then charged to 3.8V at 0.1C, and then charged to 4.4V at a constant current of 0.5C. Then, it was charged to 0.05C at a constant voltage of 4.4V. After standing for 10 minutes, it was discharged at a constant current of 0.5C to a cut-off voltage of 2.8V (5 batteries per group). After obtaining the first-week charging capacity and the first-week discharge capacity of the secondary battery, the first coulombic efficiency of the secondary battery was calculated according to the following formula.

[0164] First-cycle coulombic efficiency (%) = (first-cycle discharge capacity / first-cycle charge capacity) × 100%.

[0165] (3) Fast charging performance test:

[0166] At 25°C, the battery was charged at a constant current of 4C to a charge cut-off voltage of 4.4V, then charged at a constant voltage to a current of 0.05C, allowed to stand for 5 minutes, and then discharged at a constant current of 0.33C to a discharge cut-off voltage of 2.8V. The actual capacity was recorded as C0.

[0167] Then the battery is charged with a constant current of 0.5C0, 1C0, 1.5C0, 2C0, 2.5C0, 3C0, 3.5C0, 4C0, and 4.5C0 in sequence to the full battery charge cut-off voltage of 4.4V or the negative electrode cut-off potential of 0V (whichever is reached first). After each charge is completed, it is necessary to discharge with 1C0 to the full battery discharge cut-off voltage of 2.8V. Record the state of charge (SOC) at different charge rates to 10%, 20%, 30%...80%. The negative electrode potential corresponding to the state of charge (SOC) is plotted, and the rate-negative electrode potential curves under different SOC states are drawn. After linear fitting, the charge rate corresponding to the negative electrode potential of 0V under different SOC states is obtained. The charge rate is the charging window under that SOC state, which is recorded as C10% SOC, C20% SOC, C30% SOC, C40% SOC, C50% SOC, C60% SOC, C70% SOC, and C80% SOC respectively. The charging time T for the battery from 10% SOC to 80% SOC is calculated according to the formula (60 / C20% SOC + 60 / C30% SOC + 60 / C40% SOC + 60 / C50% SOC + 60 / C60% SOC + 60 / C70% SOC + 60 / C80% SOC) × 10%. The shorter the charging time T, the better the fast charging performance of the secondary battery.

[0168] (4) Cyclic performance test:

[0169] At 25°C, the battery was charged at a constant current rate of 4C to a cut-off voltage of 4V, and then discharged at a rate of 1C to a cut-off voltage of 2.8V. The initial capacity was recorded as C0. Then, the battery was charged according to the strategy shown in Table 2 and discharged at a rate of 1C. The discharge capacity of each cycle was recorded as C0. n , until the battery capacity retention rate (capacity retention rate = C n The cycle number is recorded. The greater the number of cycles, the better the cycle performance of the secondary battery.

[0170] Table 2

[0171] Figure 10 is a picture of the negative electrode plate disassembled after the battery obtained in Comparative Example 4 was cycled (300 cycles according to the cycle conditions of the above-mentioned cycle performance test). It can be seen from the figure that the surface of the negative electrode plate disassembled after the battery obtained in Comparative Example 4 has obvious lithium dendrites. Figure 11 is an SEM image (scanning electron microscope image) of the dendrites of the negative electrode plate disassembled after the battery obtained in Comparative Example 1 was cycled. Referring to Figure 11, the surface of the negative active material in the negative electrode plate disassembled after the battery obtained in Comparative Example 1 was cycled has obvious lithium dendrites (the rod-shaped structures circled in the figure are lithium dendrites). This shows that the above-mentioned dielectric material particles are not added to Comparative Example 4, and its negative electrode plate has the risk of generating lithium dendrites.

[0172] Table 3

[0173] Conclusion: Compared with Comparative Examples 1-4, the volume average particle size Dv50 of the dielectric material particles in the active material layer of the negative electrode sheet of the battery of Examples 1-18 is 400nm-2000nm, and based on the total mass of the negative electrode active material layer, the proportion of the dielectric material particles is 0.1%-10%. The volume average particle size Dv50 of the dielectric material in the active material layer of the negative electrode sheet of the battery of Comparative Example 1 is 112nm, and the mass proportion in the negative electrode active material layer is 1%; the volume average particle size Dv50 of the dielectric material in the active material layer of the negative electrode sheet of the battery of Comparative Example 2 is 112nm. The volume average particle size Dv50 of the dielectric material in the active material layer of the negative electrode plate of the battery of Comparative Example 3 is 820 nm, and the content of the dielectric material in the negative electrode active material layer is 12%. No dielectric material particles are added to the active material layer of the negative electrode plate of the battery of Comparative Example 4. At the same time, the lithium deposition area of ​​the negative electrode plate of the battery of Example 1-18 after cycle disassembly is significantly smaller than that of Comparative Example 1-4, and the charging time of the battery of Example 1-18 is also significantly lower than that of Comparative Example 1-4, and the cycle performance of the battery of Example 1-18 is also higher than that of Comparative Example 1-4.

[0174] This shows that the use of dielectric material particles in the negative electrode plate of the present application (the volume average particle size Dv50 of the dielectric material particles is 400nm-2000nm, and based on the total mass of the negative electrode active material layer, the proportion of the dielectric material particles is 0.1%-10%) can not only reduce the loss of active ions and the risk of lithium plating, but also improve the cycle performance and fast charging performance of the battery.

[0175] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A negative electrode plate, wherein, Comprising: A negative electrode current collector; A negative electrode active material layer provided on at least one side of the negative electrode current collector, the negative electrode active material layer comprising dielectric material particles, the volume average particle diameter Dv50 of the dielectric material particles being D1, D1 being 400 nm - 2000 nm, and based on the total mass of the negative electrode active material layer, the proportion of the dielectric material particles being 0.1% - 10%.

2. The negative electrode sheet according to claim 1, wherein, D1 is 600 nm - 1000 nm.

3. The negative electrode sheet according to claim 1 or 2, wherein Based on the total mass of the negative electrode active material layer, the proportion of the dielectric material particles is 0.5% - 3%.

4. The negative electrode sheet according to any one of claims 1-3, wherein, The relative dielectric constant of the dielectric material particles is 1000 - 10000.

5. The negative electrode sheet according to any one of claims 1-4, wherein, The relative dielectric constant of the dielectric material particles is 1500 - 5000.

6. The negative electrode sheet according to any one of claims 1-5, wherein, The dielectric material particles include at least one of barium titanate, lead titanate, lithium niobate, lead zirconate titanate, lead metaniobate, or lithium barium lead niobate.

7. The negative electrode sheet according to any one of claims 1-6, wherein, The dielectric material particles include doped ions, and the doped ions include trivalent rare earth metal ions, Nb 5+ , W 5+ , Mo 5+ , Al 3+ , Ga 3+ , Cr 3+ , Mn 3+ , Mg 2+ , Si 4+ or Ca 2+ and at least one of them.

8. The negative electrode sheet according to any one of claims 1-7, wherein, The dielectric material particles include at least one of barium titanate doped with trivalent rare earth metal ions, barium titanate doped with pentavalent ions, lead titanate doped with pentavalent ions, or lead zirconate titanate doped with pentavalent ions, and the pentavalent ions include Nb 5+ , W 5+ or Mo 5+ and at least one of them.

9. The negative electrode sheet according to claim 7 or 8, wherein The trivalent rare earth metal ions include Sc 3+ , Y 3+ or Yb 3+ and at least one of them.

10. The negative electrode sheet according to claim 6 or 8, wherein, The barium titanate includes a tetragonal crystal form.

11. The negative electrode sheet according to any one of claims 1-10, wherein, The BET specific surface area of the dielectric material particles is 0.8 m 2 / g - 7 m 2 / g.

12. The negative electrode sheet according to any one of claims 1-11, wherein, The negative electrode active material layer includes a negative electrode active material, the volume average particle diameter Dv50 of the negative electrode active material being D2, D1 ≤ D2.

13. The negative electrode sheet according to claim 12, wherein, D2 is 2 μm - 20 μm.

14. The negative electrode sheet according to claim 12 or 13, wherein, D2 is 8 μm - 13 μm.

15. The negative electrode sheet according to any one of claims 1-14, wherein, The negative electrode active material layer comprises: A first negative electrode active material layer provided on at least one side of the negative electrode current collector; A second negative electrode active material layer provided on a side of the first negative electrode active material layer away from the negative electrode current collector, the first negative electrode active material layer and / or the second negative electrode active material layer including the dielectric material particles.

16. The negative electrode sheet according to any one of claims 12-14, wherein, At least a part of the surface of the negative electrode active material is provided with a coating layer, the coating layer including the dielectric material particles.

17. The negative electrode sheet according to any one of claims 12-14, wherein, The negative electrode active material includes at least one of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, or titanates.

18. A method for preparing a negative electrode plate, wherein, Comprising: Forming a negative electrode active material layer on at least one side of a negative electrode current collector, the negative electrode active material layer including dielectric material particles, the volume average particle diameter Dv50 of the dielectric material particles being D1, D1 being 400 nm - 2000 nm, and based on the total mass of the negative electrode active material layer, the proportion of the dielectric material particles being 0.1% - 10%.

19. A battery, wherein, Comprising the negative electrode tab according to any one of claims 1 - 17 or the negative electrode tab obtained by the method according to claim 18.

20. The battery according to claim 19, wherein, The battery includes a lithium-ion battery or a sodium-ion battery.

21. An electrical device, wherein, Comprising the battery according to claim 19 or 20.

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