Electrode assembly and preparation method therefor, battery cell, battery and electrical apparatus

Abstract

The application discloses an electrode assembly and a preparation method therefor, a battery cell, a battery and an electrical apparatus. The electrode assembly comprises: a negative pole piece. The negative pole piece comprises a bend area. The bend area comprises a first negative electrode active material layer. The first negative electrode active material layer comprises first dielectric material particles, wherein the volume average particle size Dv50 of the first dielectric material particles is D 1 , and D 1 is 200 nm -2000 nm. The relative dielectric constant of the first dielectric material particles is 1000-10000. On the basis of the total mass of the first negative electrode active material layer, the proportion of the first dielectric material particles is W 1 , and W 1 is 0.5% -10%. Therefore, the first negative electrode active material layer on the bend area of the negative pole piece of the electrode assembly comprises the first dielectric material particles having the described particle size, content and relative dielectric constant, such that the cycle performance in the quick charging process of the battery containing same can be improved.

Description

Electrode assembly and preparation method thereof, battery cell, battery and electrical device Technical Field

[0001] The present application belongs to the field of batteries, and specifically relates to an electrode assembly and a preparation method thereof, a battery cell, 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, when the battery cell has a wound structure, metal dendrites are easily generated in the corners of the negative electrode during fast charging, resulting in reduced battery cycle performance. Summary of the Invention

[0003] In view of the technical problems existing in the background technology, the present application provides an electrode assembly, aiming to improve the cycle performance of the battery containing the electrode assembly during the fast charging process.

[0004] In order to achieve the above-mentioned objectives, the first aspect of the present application proposes an electrode assembly, including a negative electrode plate, the negative electrode plate including a corner area, the corner area including a first negative electrode active material layer, the first negative electrode active material layer including first dielectric material particles, the volume average particle size Dv50 of the first dielectric material particles is D1, D1 is 200nm-2000nm, the relative dielectric constant of the first dielectric material particles is 1000-10000, and based on the total mass of the first negative electrode active material layer, the proportion of the first dielectric material particles is W1, W1 is 0.5%-10%.

[0005] The present application includes at least the following beneficial effects: the first negative electrode active material layer on the corner area of ​​the negative electrode plate of the electrode assembly of the present application includes first dielectric material particles with the above-mentioned particle size, content and relative dielectric constant, which can improve the cycle performance of the battery containing it during the fast charging process.

[0006] In some embodiments, W1 is 1%-3%, thereby improving the cycle performance of the battery during fast charging.

[0007] In some embodiments, D1 is 600 nm to 1000 nm, thereby improving the cycle performance of the battery during fast charging.

[0008] In some embodiments, the relative dielectric constant of the first dielectric material particles is 1500-5000. This can improve the cycle performance of the battery during fast charging.

[0009] In some embodiments, the first dielectric material particles include at least one of barium titanate, lead titanate, lithium niobate, lead zirconate titanate, lead metaniobate, or lithium lead barium niobate, thereby improving the cycling performance of the battery during fast charging.

[0010] In some embodiments, the first 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 cycle performance of the battery during the fast charging process can be improved.

[0011] In some embodiments, the first 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. This can improve the cycling performance of the battery during fast charging.

[0012] In some embodiments, the trivalent rare earth metal ion comprises Sc 3+ 、Y 3+ or Yb 3+ Thus, the cycle performance of the battery during the fast charging process can be improved.

[0013] In some embodiments, the BET specific surface area of ​​the first dielectric material particles is 0.8 m 2 / g-7m 2 / g, optional 1.8m 2 / g-2m 2 / g. Thus, the cycle performance of the battery during the fast charging process can be improved.

[0014] In some embodiments, the barium titanate comprises a tetragonal crystal structure, thereby improving the cycle performance of the battery during fast charging.

[0015] In some embodiments, the first negative electrode active material layer includes a first negative electrode active material, and the volume average particle size Dv50 of the first negative electrode active material is D2, D1≤D2, and optionally D1<D2. This can improve the cycle performance of the battery during fast charging.

[0016] In some embodiments, D2 is 2 μm-20 μm, and optionally 8 μm-13 μm, thereby improving the cycle performance of the battery during fast charging.

[0017] In some embodiments, the length of the corner area is 5 mm to 30 mm, and optionally 6 mm to 15 mm, thereby improving the cycle performance of the battery during fast charging.

[0018] In some embodiments, the negative electrode plate also includes a straight area, the corner areas are arranged at both ends of the straight area, the straight area is provided with a second negative electrode active material layer, the second negative electrode active material layer includes second dielectric material particles, based on the total mass of the second negative electrode active material layer, the proportion of the second dielectric material particles is W2, W1 ≥ W2.

[0019] In some embodiments, W2 is 0-5%, and can be optionally 0-1%, thereby improving the cycle performance of the battery during fast charging.

[0020] In some embodiments, based on the total mass of the first negative electrode active material layer, the mass proportion of the first negative electrode active material is K1, the second negative electrode active material layer includes a second negative electrode active material, and based on the total mass of the second negative electrode active material layer, the mass proportion of the second negative electrode active material is K2, and K1≤K2.

[0021] In some embodiments, K1 is 90-98%, optionally 93%-97%.

[0022] In some embodiments, K2 is 90-98%, optionally 95%-98%.

[0023] In some embodiments, the negative electrode sheet further includes a negative electrode current collector and a third negative electrode active material layer, the third negative electrode active material layer is arranged on at least one side of the negative electrode current collector, and the first negative electrode active material layer and the second negative electrode active material layer are arranged on a side of the third negative electrode active material layer away from the negative electrode current collector.

[0024] In some embodiments, the thickness of the first negative electrode active material layer is H1, the thickness of the third negative electrode active material layer is H3, and H1 / H3 is 4%-30%, and can be optionally 10%-20%.

[0025] In some embodiments, the thickness of the first negative electrode active material layer is not greater than the thickness of the second negative electrode active material layer.

[0026] In some embodiments, at least one of the following conditions is met: the thickness of the first negative electrode active material layer is 20μm-100μm, optionally 40μm-80μm; the thickness of the second negative electrode active material layer is 20μm-100μm, optionally 40μm-80μm; the thickness of the third negative electrode active material layer is 40μm-200μm, optionally 60μm-150μm.

[0027] In some embodiments, at least a portion of the surface of the first negative electrode active material is provided with a first coating layer, the first coating layer comprising the first dielectric material particles; and / or at least a portion of the surface of the second negative electrode active material is provided with a second coating layer, the second coating layer comprising the second dielectric material particles.

[0028] In some embodiments, the first negative electrode active material, the second negative electrode active material, and the third negative electrode active material in the third negative electrode active material layer each independently include at least one of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based material, tin-based material, or titanate.

[0029] In a second aspect of the present application, the present application proposes a method for preparing an electrode assembly, comprising:

[0030] The positive electrode sheet and the negative electrode sheet are stacked and wound along a winding direction to form the electrode assembly, the negative electrode sheet includes a corner area, the corner area includes a first negative electrode active material layer, the first negative electrode active material layer includes first dielectric material particles, the volume average particle size Dv50 of the first dielectric material particles is D1, D1 is 200nm-2000nm, the relative dielectric constant of the first dielectric material particles is 1000-10000, and based on the total mass of the first negative electrode active material layer, the proportion of the first dielectric material particles is W1, and W1 is 0.5%-10%.

[0031] Therefore, the battery with the electrode assembly obtained by this method has excellent cycle performance during the fast charging process.

[0032] In a third aspect of the present application, the present application proposes a battery cell, comprising the electrode assembly described in the first aspect of the present application or the electrode assembly obtained by the method described in the second aspect of the present application.

[0033] In a fourth aspect of the present application, a battery is provided, comprising the electrode assembly described in the first aspect of the present application, the electrode assembly obtained by the method described in the second aspect of the present application, or the battery cell described in the third aspect of the present application. Thus, the battery has excellent cycle performance.

[0034] In some embodiments, the battery comprises a lithium-ion battery or a sodium-ion battery.

[0035] In the fifth aspect of the present application, the present application proposes an electrical device comprising the battery described in the fourth aspect of the present application.

[0036] 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

[0037] 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:

[0038] FIG1 is a schematic structural diagram of an electrode assembly according to an embodiment of the present application.

[0039] FIG. 2 is an XRD pattern of barium titanate according to one embodiment of the present application.

[0040] FIG3 is a schematic structural diagram of an electrode assembly according to another embodiment of the present application.

[0041] FIG4 is a schematic structural diagram of an electrode assembly according to another embodiment of the present application.

[0042] FIG5 is a schematic structural diagram of an electrode assembly according to another embodiment of the present application.

[0043] FIG6 is a schematic diagram of a battery cell according to an embodiment of the present application.

[0044] FIG. 7 is an exploded view of the battery cell shown in FIG. 6 according to an embodiment of the present application.

[0045] FIG8 is a schematic diagram of a battery module according to an embodiment of the present application.

[0046] FIG9 is a schematic diagram of a battery pack according to an embodiment of the present application.

[0047] FIG10 is an exploded view of the battery pack shown in FIG9 according to an embodiment of the present application.

[0048] FIG11 is a schematic diagram of an electrical device using a battery as a power source according to an embodiment of the present application.

[0049] FIG12 is a picture of the negative electrode sheet of the battery obtained in Example 1 after disassembly after cycling.

[0050] FIG13 is a picture of the negative electrode sheet of the battery obtained in Comparative Example 5 after disassembly after cycling.

[0051] Explanation of the reference numerals: 10 electrode assembly; 100 positive electrode sheet; 200 negative electrode sheet; 21 corner area; 210 first negative electrode active material layer; 22 straight area; 220 second negative electrode active material layer; 23 third negative electrode active material layer; 24 negative electrode current collector; 300 separator; 1 battery cell; 11 housing; 13 cover plate; 2 battery module; 3 battery pack; 31 upper case; 32 lower case. DETAILED DESCRIPTION

[0052] 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.

[0053] 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.

[0054] " 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.

[0055] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] As secondary batteries become increasingly widely used, performance requirements are becoming increasingly stringent, such as the requirement for fast charging capabilities. When the battery cell has a wound structure, the gap between the positive and negative electrodes in the corners is large, which spatially prolongs the transmission path of active ions. This can easily lead to increased polarization in the corners, resulting in large areas of metal lithium deposition. This is more pronounced during fast charging.

[0060] The electrode assembly disclosed in the embodiments of the present application is applicable to lithium-ion batteries and sodium-ion batteries, and the battery disclosed in the embodiments of the present application can be used in electrical equipment that uses the battery as a power source or various energy storage systems that use the battery as an energy storage element. Electrical equipment may include, but is not limited to, mobile phones, tablets, laptops, electric toys, power tools, battery cars, electric cars, ships, spacecraft, and the like. Among them, electric toys may include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, and the like, and spacecraft may include airplanes, rockets, space shuttles, and spacecraft, and the like.

[0061] In a first aspect, the present application proposes a negative electrode sheet. Referring to Figure 1, the electrode assembly 10 includes a negative electrode sheet 200, the negative electrode sheet 200 includes a corner area 21, the corner area 21 includes a first negative electrode active material layer 210, the first negative electrode active material layer 210 includes first dielectric material particles, the volume average particle size Dv50 of the first dielectric material particles is D1, D1 is 200nm-2000nm, the relative dielectric constant of the first dielectric material particles is 1000-10000, and based on the total mass of the first negative electrode active material layer 210, the proportion of the first dielectric material particles is W1, and W1 is 0.5%-10%.

[0062] In the present application, referring to FIG1 , the “corner region 21 ” refers to a region having a bent structure in the negative electrode sheet 200 of the electrode assembly 10 obtained by stacking the positive electrode sheet 100 , the separator 300 , and the negative electrode sheet 200 and winding them, that is, the negative electrode sheets 200 in the corner region 21 are all bent, that is, the surface of each layer of the negative electrode sheet 200 of the electrode assembly 10 in the corner region 21 is a curved surface.

[0063] The first negative active material layer 210 on the corner area 21 of the negative electrode plate 200 of the electrode assembly 10 of the present application includes first dielectric material particles with the above-mentioned particle size, content and relative dielectric constant, which can improve the cycle performance of the battery containing it during the fast charging process.

[0064] The process by which the above-mentioned first dielectric material particles exert their performance is speculated as follows: the first dielectric material particles with the above-mentioned particle size, content and relative dielectric constant are added to the first negative electrode active material layer 210 corresponding to the corner area 21 of the negative electrode plate 200 on the electrode assembly 10 of the present application. During the charging process of the battery containing the electrode assembly 10, the positive and negative charge centers in the material of the first dielectric material particles will be separated under the action of the electric field, and a reverse electric field will be generated inside. The reverse electric field generated by the first dielectric material particles on the surface of the first negative electrode active material layer 210 corresponding to the corner area 21 of the electrode assembly 10 is negatively charged, and therefore may attract the active ions gathered on the surface of the first negative electrode active material layer 210 corresponding to the corner area 21 to be evenly distributed, thereby reducing the risk of active ions gathering on the surface of the first negative electrode active material layer 210 corresponding to the corner area 21 and generating metal dendrites, thereby improving the cycle performance of the battery containing it during the fast charging process.

[0065] In some embodiments of the present application, based on the total mass of the first negative electrode active material layer 210, the proportion of the first dielectric material particles is 0.5%-10%, for example, 0.5%-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 first negative electrode active material layer 210, the proportion of the first dielectric material particles is 1%-3%.

[0066] In some embodiments of the present application, the volume average particle size Dv50 of the first dielectric material particles is D1, and D1 is 200 nm-2000 nm, for example, 300 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 first dielectric material particles is 600 nm-1000 nm.

[0067] In this application, the volume average particle size Dv50 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 first dielectric material particles in the negative electrode sheet 200 is as follows:

[0068] (1) The electrode assembly 10 is disassembled, and the first negative electrode active material layer 210 on the corner area 21 corresponding to the negative electrode sheet 200 is scraped and calcined 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, the sintering is followed by mixing with sodium hydroxide solution for reaction), and then filtered with water;

[0069] (2) Referring to the standard GB / T 19077-2016, the filtered material is tested using a laser particle size analyzer (such as Malvern Master Size 3000) to measure the volume average particle size Dv50 of the first dielectric material particles.

[0070] In the present application, the method for testing the mass proportion of the first dielectric material particles in the negative electrode plate 200 includes: disassembling the electrode assembly 10, then scraping the first negative electrode active material layer 210 on the corresponding corner area 21 of the disassembled negative electrode plate 200, and subjecting the sample (for the system of silicon-containing negative electrode active materials, 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 first dielectric material particles in the first negative electrode active material layer.

[0071] In some embodiments of the present application, the relative dielectric constant of the first 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. In other embodiments of the present application, the relative dielectric constant of the first dielectric material particles is 1500-5000.

[0072] In the present application, the relative dielectric constant of the first 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 electrode assembly 10 can be disassembled first, and then the first negative electrode active material layer 210 of the corner area 21 of the negative electrode plate 200 can be scraped, and a sample can be 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 water is added to filter and separate to obtain the first dielectric material particles, and then the first dielectric material particles are prepared into a circular sample (the sample preparation process includes: adding 40g of adhesive (the adhesive) to 200g of the dielectric material particles to be tested The agent is compounded by acrylic acid (PAA) emulsion and alcohol amine plasticizer, and its decomposition temperature is less than 300℃), after being fully stirred, it is slowly added into the automatic roller press (the roller press is a roller press with stainless steel rollers and a polished surface; the gap between the two rollers is adjustable within the range of 0.5mm to 2mm), and rolled into a raw porcelain cake with a thickness of 1mm±0.15mm. The surface is free of color difference, the cross section is uniform, and there is no obvious stratification. The raw porcelain cake is then placed on the punching machine (the punching machine has a round platen with a size of 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.

[0073] In some embodiments of the present application, the first dielectric material particles include at least one of barium titanate, lead titanate, lithium niobate, lead zirconate titanate, lead metaniobate, or lithium lead barium niobate. Thus, using such first dielectric material particles in the first negative electrode active material layer 210 of the corner region 21 of the negative electrode sheet 200 can further improve the cycling performance of a battery containing such first dielectric material particles during fast charging.

[0074] The process by which the first dielectric material particles of the above composition exert their performance is speculated as follows: the first dielectric material particles of the above composition can exert an excellent reverse electric field effect, which may make the active ions gathered on the surface of the first negative electrode active material layer 210 corresponding to the corner area 21 of the negative electrode plate 200 evenly distributed, thereby reducing the risk of active ions gathering on the surface of the first negative electrode active material layer 210 corresponding to the corner area 21 and generating metal dendrites, thereby improving the cycle performance of the battery containing it during the fast charging process.

[0075] In some embodiments of the present application, the first dielectric material particles include doping ions, and the doping 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, by doping the first dielectric material particles of the present application with the above ions, the relative dielectric constant of the first dielectric material particles can be adjusted, thereby improving the cycle performance of the battery containing the first dielectric material particles during the fast charging process.

[0076] The process by which the above-mentioned doped first dielectric material particles exert their performance is speculated as follows: by doping the above-mentioned ions into the first dielectric material particles, the relative dielectric constant of the dielectric material particles can be adjusted, thereby making it possible to evenly distribute the active ions gathered on the surface of the first negative electrode active material layer 210 corresponding to the corner area 21 of the negative electrode plate 200, thereby reducing the risk of active ions gathering on the surface of the first negative electrode active material layer 210 corresponding to the corner area 21 and generating metal dendrites, thereby improving the cycle performance of the battery containing it during the fast charging process.

[0077] As an example, the first 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 ion includes 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 first 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.

[0078] In some embodiments of the present application, the first dielectric material particles are barium titanate, and the barium titanate includes a tetragonal crystal.

[0079] 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°.

[0080] Therefore, the above-mentioned tetragonal barium titanate as the first dielectric material particles can further reduce the risk of active ions agglomerating on the surface of the first negative electrode active material layer 210 corresponding to the corner area 21 of the negative electrode plate 200 to generate metal dendrites, thereby improving the cycle performance of the battery containing it during the fast charging process.

[0081] In some embodiments of the present application, the BET specific surface area of ​​the first 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.

[0082] Therefore, the first dielectric material particles with the above-mentioned specific surface area range are more tightly combined with the negative electrode active material, which is conducive to the performance of the dielectric material particles, and may further reduce the risk of active ions agglomerating on the surface of the first negative electrode active material layer 210 corresponding to the corner area 21 to generate metal dendrites, thereby improving the cycle performance of the battery containing it during the fast charging process. In other embodiments of the present application, the BET specific surface area of ​​the first dielectric material particles is 1.8m 2 / g-2m 2 / g.

[0083] In the present application, the BET specific surface area of ​​the first dielectric material particles has a meaning well known in the art and can be tested using instruments and methods well known in the art. For example, the electrode assembly 10 is first disassembled, and then the first negative electrode active material layer 210 corresponding to the corner area 21 of the negative electrode plate 200 is scraped, and a sample is 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 / T 19587-2017, 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.

[0084] In some embodiments of the present application, the first negative electrode active material layer 210 may be disposed on either or both of the two opposing surfaces of the corner region 21 of the negative electrode sheet 200 along the thickness direction. Furthermore, the first negative electrode active material layer 210 may be disposed on a portion of the corner region 21 or on the entire corner region 21. For example, the first negative electrode active material layer 210 may be disposed on the entire two opposing surfaces of the corner region 21 of the negative electrode sheet 200 along the thickness direction.

[0085] In some embodiments of the present application, the first negative electrode active material layer 210 includes a first negative electrode active material, and the volume average particle size Dv50 of the first negative electrode active material is D2, where D1 ≤ D2. In other embodiments of the present application, the first negative electrode active material layer 210 includes a first negative electrode active material, and the volume average particle size Dv50 of the first negative electrode active material is D2, where D1 < D2.

[0086] Therefore, the particle sizes of the first negative electrode active material and the first dielectric material particles meet the above conditions, which not only makes it possible to give full play to the reverse electric field effect of the first dielectric material particles, but also makes it possible to evenly distribute the active ions gathered on the surface of the first negative electrode active material layer 210 corresponding to the corner area 21 of the negative electrode plate 200, thereby reducing the risk of active ions gathering on the surface of the first negative electrode active material layer 210 corresponding to the corner area 21 and generating metal dendrites, thereby improving the cycle performance of the battery containing the first negative electrode active material layer 210 during the fast charging process; and can also make the first negative electrode active material layer 210 have a high compaction density, thereby improving the battery energy density.

[0087] In some embodiments of the present application, the volume average particle size Dv50 of the first 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.

[0088] Therefore, using a first negative electrode active material with this particle size in combination with the first dielectric material particles can not only fully utilize the reverse electric field effect of the first dielectric material particles, but also evenly distribute the active ions accumulated on the surface of the first negative electrode active material layer 210 corresponding to the corner area 21 of the negative electrode plate 200, thereby reducing the risk of active ions agglomerating on the surface of the first negative electrode active material layer 210 corresponding to the corner area 21 and generating metal dendrites, thereby improving the cycle performance of the battery containing it during the fast charging process; it can also make the first negative electrode active material layer 210 have a high compaction density, thereby improving the battery energy density. In other embodiments of the present application, the volume average particle size Dv50 of the first negative electrode active material is D2, and D2 is 8μm-13μm.

[0089] In the present application, the method for testing the volume average particle size Dv50 of the first negative electrode active material includes: first, disassembling the electrode assembly 10, then using a flame to ablate the surface of the first negative electrode active material layer 210 on the negative electrode plate 200 to remove the binder in the surface first negative electrode active material layer 210 (the flame temperature is 300°C-500°C, and the negative electrode plate 200 is moved at a speed of 1m / min-30m / min), then scraping the surface layer to remove powder, and sieving the obtained powder (for example, the mesh size is 6250 mesh) to separate the negative electrode active material from the dielectric material and the conductive agent. The obtained particles on the sieve are the first negative electrode active material. Then, referring to the standard GB / T 19077-2016, the first negative electrode active material is tested using a laser particle size analyzer (for example, Malvern Master Size 3000) to obtain the volume average particle size Dv50 of the first negative electrode active material.

[0090] In the present application, the “length of the corner region 21 ” may be defined as half the length of the negative electrode sheet 200 located in the corner region 21 on the outermost negative electrode sheet 200 along the winding direction of the electrode assembly 10 .

[0091] In some embodiments of the present application, referring to FIG3 , the length L of the corner area 21 may be 5 mm to 30 mm, such as 6 mm to 28 mm, 7 mm to 25 mm, 8 mm to 23 mm, 10 mm to 20 mm, 12 mm to 18 mm, 13 mm to 16 mm, or 14 mm to 15 mm. In other embodiments of the present application, the length L of the corner area 21 may be 6 mm to 15 mm.

[0092] In some embodiments of the present application, referring to Figure 4, the negative electrode plate 200 further includes a straight area 22, and the straight area 22 and the corner area 21 are alternately arranged along the winding direction of the negative electrode plate 200. The straight area 22 is provided with a second negative electrode active material layer 220, and the second negative electrode active material layer 220 includes second dielectric material particles. Based on the total mass of the second negative electrode active material layer 220, the proportion of the second dielectric material particles is W2, and W1 ≥ W2.

[0093] Therefore, by adding second dielectric material particles to the second negative electrode active material layer 220 in the straight area 22, and the content of the second dielectric material particles in the second negative electrode active material layer 220 is lower than or equal to the first dielectric material particles in the first negative electrode active material layer 210, not only can the risk of metal dendrites being generated on the surface of the first negative electrode active material layer 210 corresponding to the corner area 21 of the negative electrode sheet 200 be reduced, but also the material cost can be reduced.

[0094] In the present application, the "flat region 22" refers to the region of the negative electrode sheet 200 of the electrode assembly 10 having a planar structure, obtained by stacking and winding the positive electrode sheet 100, the separator 300, and the negative electrode sheet 200. That is, the surface of the negative electrode sheet 200 within the flat region 22 is flat, and the corner regions 21 are located at both ends of the flat region 22. Furthermore, the Dv50, BET specific surface area, and relative dielectric constant of the "second dielectric material particles" are the same as those of the "first dielectric material particles" described above. It should be noted that the composition of the "second dielectric material particles" of the present application may be the same as or different from that of the "first dielectric material particles." For example, the first dielectric material particles may be barium titanate, and the second dielectric material particles may be lead titanate.

[0095] In some embodiments of the present application, the second negative electrode active material layer 220 may be disposed on either or both of the two opposing surfaces of the flat region 22 of the negative electrode sheet 200 along the thickness direction. Furthermore, the second negative electrode active material layer 220 may be disposed on a portion of the flat region 22 or on the entire flat region 22. As an example, the second negative electrode active material layer 220 may be disposed on the entirety of the two opposing surfaces of the flat region 22 of the negative electrode sheet 200 along the thickness direction.

[0096] In some embodiments of the present application, based on the total mass of the second negative electrode active material layer 220, the proportion W2 of the second dielectric material particles is 0-5%, for example, 1%-5%, 2%-4%, 2%-3%, etc. In some embodiments of the present application, based on the total mass of the second negative electrode active material layer 220, the proportion W2 of the second dielectric material particles is 0-1%.

[0097] In the present application, the method for testing the mass proportion of the second dielectric material particles in the second negative electrode active material layer 220 includes: first disassembling the electrode assembly 10, then drying the disassembled negative electrode plate 200, then scraping the powder corresponding to the second negative electrode active material layer 220 in the flat area 22, and then performing a thermal gravimetric test on the powder obtained from the second negative electrode active material layer 220 (for the system of silicon-containing negative electrode active materials, the powder is sintered and then mixed with sodium hydroxide solution for reaction, and the filtered powder is the sample). The test conditions are: oxygen atmosphere, heating from 25°C to 1000°C, and the heating rate is 5° / min. The corresponding vertical coordinate on the weight loss curve corresponding to 1000°C is the mass proportion of the second dielectric material particles in the second negative electrode active material layer 220.

[0098] In some embodiments of the present application, the first negative electrode active material layer 210 includes a first negative electrode active material, the mass fraction of the first negative electrode active material being K1 based on the total mass of the first negative electrode active material layer 210. The second negative electrode active material layer 220 includes a second negative electrode active material, the mass fraction of the second negative electrode active material being K2 based on the total mass of the second negative electrode active material layer 220, where K2 ≥ K1. Thus, the first negative electrode active material content K1 in the first negative electrode active material layer 210 is less than or equal to the second negative electrode active material content K2 in the second negative electrode active material layer 220. This can reduce the risk of metal dendrites forming in the corner region 21 corresponding to the first negative electrode active material layer 210 during fast charging of the battery while improving the energy density of the battery.

[0099] In some embodiments of the present application, the mass proportion K1 of the first negative electrode active material in the first negative electrode active material layer 210 is 90-98%, for example, 91%-97%, 92%-96%, 93%-95%, 94%-95%, etc. In other embodiments of the present application, the mass proportion K1 of the first negative electrode active material in the first negative electrode active material layer 210 is 93%-97%. As a result, the energy density of the battery can be improved while reducing the risk of metal dendrites forming in the first negative electrode active material layer 210 corresponding to the corner region 21 during fast charging of the battery.

[0100] In some embodiments of the present application, the mass percentage K2 of the second negative electrode active material in the second negative electrode active material layer 220 is 90-98%, for example, 91%-97%, 92%-96%, 93%-95%, 94%-95%, etc. In other embodiments of the present application, the mass percentage K2 of the second negative electrode active material in the second negative electrode active material layer 220 is 95%-98%. This can improve the energy density of the battery.

[0101] In some embodiments of the present application, referring to FIG5 , the electrode assembly 10 further includes a third negative electrode active material layer 23 and a negative electrode current collector 24. The third negative electrode active material layer 23 is disposed on at least one side of the negative electrode current collector 24, and the first negative electrode active material layer 210 and the second negative electrode active material layer 220 are disposed on a side of the third negative electrode active material layer 23 away from the negative electrode current collector 24. Thus, by first disposing the third negative electrode active material layer 23 on the negative electrode current collector 24, and then disposing the first negative electrode active material layer 210 on the third negative electrode active material layer 23 corresponding to the corner region 21, and disposing the second negative electrode active material layer 220 on the third negative electrode active material layer 23 corresponding to the straight region 22, the risk of metal dendrites forming in the first negative electrode active material layer 210 corresponding to the corner region 21 during fast charging of the battery can be reduced, and the battery energy density can be improved.

[0102] In some embodiments of the present application, the thickness of the first negative electrode active material layer 210 is H1, the thickness of the third negative electrode active material layer 23 is H3, and H1 / H3 is 4%-30%, for example, 5%-25%, 10%-20%, 15%-20%, etc. Thus, the thickness ratio of the first negative electrode active material layer 210 containing the first dielectric material particles to the thickness of the third negative electrode active material layer 23 is within this range, which can further reduce the risk of metal dendrites in the first negative electrode active material layer 210 corresponding to the corner area 21 during fast charging of the battery while improving the battery energy density. In other embodiments of the present application, H1 / H3 is 10%-20%.

[0103] In some embodiments of the present application, the thickness of the first negative electrode active material layer 210 is not greater than the thickness of the second negative electrode active material layer 220 .

[0104] As an example, the thickness of the first negative electrode active material layer 210 is 20μm-100μm, for example, 30μm-90μm, 40μm-80μm, 50μm-70μm, 50μm-60μm, etc. In some embodiments of the present application, the thickness of the first negative electrode active material layer 210 is 40μm-80μm.

[0105] As an example, the thickness of the second negative electrode active material layer 220 is 20 μm-100 μm, such as 30 μm-90 μm, 40 μm-80 μm, 50 μm-70 μm, 50 μm-60 μm, etc. In some embodiments of the present application, the thickness of the second negative electrode active material layer 220 is 40 μm-80 μm.

[0106] As an example, the thickness of the third negative electrode active material layer 23 is 40 μm-200 μm, such as 50 μm-180 μm, 60 μm-160 μm, 70 μm-150 μm, 80 μm-130 μm, 90 μm-120 μm, 100 μm-110 μm, etc. In some embodiments of the present application, the thickness of the third negative electrode active material layer 23 is 60 μm-150 μm.

[0107] In some embodiments of the present application, a first coating layer is provided on at least a portion of the surface of the first negative electrode active material, and the first coating layer includes particles of the first dielectric material. Thus, the first dielectric material particles can be in close contact with the first negative electrode active material, which may facilitate the first dielectric material particles to exert their counter-electric field effect during the charging process. The counter-electric field generated by the first dielectric material particles on the surface of the first negative electrode active material layer 210 corresponding to the corner region 21 of the negative electrode plate 200 is negatively charged, and thus may attract active ions accumulated on the surface of the first negative electrode active material layer 210 corresponding to the corner region 21 to be evenly distributed, thereby reducing the risk of active ions agglomerating on the surface of the first negative electrode active material layer 210 corresponding to the corner region 21 and generating metal dendrites, thereby improving the cycle performance of the battery containing the first dielectric material particles during the fast charging process.

[0108] In some embodiments of the present application, a second coating layer is provided on at least a portion of the surface of the second negative electrode active material, and the second coating layer includes particles of the second dielectric material. As a result, the second dielectric material particles can be in close contact with the second negative electrode active material, which may facilitate the second dielectric material particles to exert their counter-electric field effect during charging. Furthermore, the counter-electric field generated by the second dielectric material particles on the surface of the negative electrode plate 200 is negatively charged, thereby attracting active ions accumulated on the surface of the negative electrode plate 200 and evenly distributing them, thereby reducing the risk of active ions accumulating on the surface of the negative electrode plate 200 and forming metal dendrites.

[0109] In some embodiments of the present application, the negative electrode current collector 24 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.).

[0110] In some embodiments of the present application, the first negative electrode active material, the second negative electrode active material, and the third negative electrode active material in the third negative electrode active material layer may be negative electrode active materials commonly known in the art for use in batteries. By way of example, the first, second, and third negative electrode active materials may include at least one of the following: 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, a silicon-oxygen compound, a silicon-carbon complex, a silicon-nitrogen complex, or a silicon alloy. The tin-based material may include at least one of elemental tin, a tin-oxygen compound, or a tin alloy. When the battery is a lithium-ion battery, the titanate is lithium titanate; when the battery is a sodium-ion battery, the titanate is sodium titanate. However, the present application is not limited to these materials; other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used singly or in combination.

[0111] In some embodiments of the present application, the first negative electrode active material layer 210, the second negative electrode active material layer 220, and the third negative electrode active material layer 23 may further optionally 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).

[0112] In some embodiments of the present application, the first negative electrode active material layer 210, the second negative electrode active material layer 220, and the third negative electrode active material layer 23 may further optionally 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.

[0113] In some embodiments of the present application, the first negative electrode active material layer 210 , the second negative electrode active material layer 220 and the third negative electrode active material layer 23 may further optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0114] In some embodiments of the present application, the negative electrode sheet can be prepared in the following manner: 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) in proportion to form a first negative electrode slurry and a second negative electrode slurry, respectively; the first negative electrode slurry is then coated on the negative electrode collector and wound into a battery cell, on two opposite sides or one side of the corner area along the thickness direction of the negative electrode slurry; the second negative electrode slurry is coated on the negative electrode collector and wound into a battery cell, on two opposite sides or one side of the straight area along the thickness direction of the negative electrode slurry; after drying, cold pressing and other processes, a negative electrode sheet including the first negative electrode active material layer and the second negative electrode active material layer can be obtained.

[0115] In some embodiments of the present application, the negative electrode sheet can also be prepared in the following manner: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as deionized water) in proportion to form a third negative electrode slurry, and the third negative electrode slurry is coated on the negative electrode current collector on two opposite sides or one side along its thickness direction, and then the negative electrode active material, the dielectric material particles, the conductive agent, the binder and any other components are dispersed in a solvent (such as deionized water) in proportion to form a first negative electrode slurry and a second negative electrode slurry respectively; then the first negative electrode slurry is coated on the third negative electrode active material layer on two opposite sides or one side along its thickness direction at the corner area after being wound into a battery cell, and the second negative electrode slurry is coated on the third negative electrode active material layer on two opposite sides or one side along its thickness direction at the straight area after being wound into a battery cell. After drying, cold pressing and other processes, a negative electrode sheet including the first negative electrode active material layer, the second negative electrode active material layer and the third negative electrode active material layer can be obtained.

[0116] 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.

[0117] 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.

[0118] 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.).

[0119] 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.

[0120] 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 NCM 211 ), 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 Co0.15 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.

[0121] 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.

[0122] Examples of the layered transition metal oxides include:

[0123] 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;

[0124] 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;

[0125] Na a Li b Ni c Mn d Fe e O2, of which 0.67 <a≤1,0<b<0.2,0<c<0.3,0.67<d+e<0.8,b+c+d+e=1。

[0126] Examples of the polyanionic compound include:

[0127] A1 f M 3 g (PO4) i O j X 1 3-j , wherein 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;

[0128] Na n M 4 PO4X 2 , wherein 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;

[0129] Na p M 5 q (SO4)3, wherein M​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​+ , 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.

[0133] The battery's charge and discharge processes are accompanied by the intercalation and deintercalation of Li or Na, and the molar content of Li or Na varies when the battery is discharged to different states. The molar content of Li or Na in the positive electrode active materials listed in this application refers to the material's initial state, i.e., the state before the materials are added. When the positive electrode active materials are used in a battery system, the molar content of Li or Na will change after charge and discharge cycles.

[0134] In the list of positive electrode active materials in this application, the molar content of oxygen is only a theoretical value. Lattice oxygen release will cause the molar content of oxygen to change, and the actual molar content of oxygen will fluctuate.

[0135] In some embodiments of the present application, the positive electrode active material layer may further optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, or a fluorine-containing acrylate resin.

[0136] In some embodiments of the present application, based on the total mass of the positive electrode active material layer, the mass proportion of the binder is 0.5%-3%, for example, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, etc.

[0137] 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.

[0138] 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.

[0139] 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.

[0140] 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.

[0141] In some embodiments of the present application, 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.

[0142] In some embodiments of the present application, the positive electrode sheet, the separator and the negative electrode sheet are stacked in sequence and then wound to form the above-mentioned electrode assembly.

[0143] In a second aspect of the present application, the present application proposes a method for preparing an electrode assembly, comprising:

[0144] The positive electrode sheet and the negative electrode sheet are stacked and wound along a winding direction to form the electrode assembly, the negative electrode sheet includes a corner area, the corner area includes a first negative electrode active material layer, the first negative electrode active material layer includes first dielectric material particles, the volume average particle size Dv50 of the first dielectric material particles is D1, D1 is 200nm-2000nm, the relative dielectric constant of the first dielectric material particles is 1000-10000, and based on the total mass of the first negative electrode active material layer, the proportion of the first dielectric material particles is W1, and W1 is 0.5%-10%.

[0145] The first negative electrode active material layer on the corner area of ​​the negative electrode plate of the electrode assembly obtained by the method of the present application includes first dielectric material particles with the above-mentioned particle size, content and relative dielectric constant, which can improve the cycle performance of the battery containing it during the fast charging process.

[0146] The process by which the above-mentioned first dielectric material particles exert their performance is speculated as follows: the first dielectric material particles with the above-mentioned particle size, content and relative dielectric constant are added to the first negative electrode active material layer corresponding to the corner area of ​​the negative electrode plate on the electrode assembly obtained in this application. During the charging process of the battery containing the electrode assembly, the first dielectric material particles are under the action of the electric field, and the positive and negative charge centers in the material will be separated, generating a reverse electric field inside. The reverse electric field generated by the first dielectric material particles on the surface of the first negative electrode active material layer corresponding to the corner area of ​​the electrode assembly is negatively charged, and therefore may attract the active ions gathered on the surface of the first negative electrode active material layer corresponding to the corner area to be evenly distributed, thereby reducing the risk of active ions gathering on the surface of the first negative electrode active material layer corresponding to the corner area to generate metal dendrites, thereby improving the cycle performance of the battery containing it during the fast charging process.

[0147] In a third aspect of the present application, the present application proposes a battery cell, comprising the electrode assembly described in the first aspect of the present application or the electrode assembly obtained by the method described in the second aspect of the present application.

[0148] As an example, the battery cell includes an electrode assembly and an electrolyte. The present application does not specifically limit the type of electrolyte, and the electrolyte can be selected according to needs. For example, the electrolyte can be liquid, gel, or fully solid.

[0149] In some embodiments of the present application, the electrolyte is an electrolyte solution comprising an electrolyte salt and a solvent.

[0150] 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.

[0151] 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.

[0152] 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.

[0153] 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.

[0154] In some embodiments of the present application, the positive electrode sheet, the negative electrode sheet and the separator can be made into a wound battery cell through a winding process.

[0155] In some embodiments, the battery cell may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0156] 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.

[0157] 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, FIG6 shows a battery cell 1 with a square structure as an example.

[0158] In some embodiments, referring to Figure 7, 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 separator and the negative electrode sheet can be formed into an electrode assembly 10 through a lamination and winding process. The electrode assembly 10 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 10. The number of electrode assemblies 10 contained in the battery cell 1 can be one or more, and those skilled in the art can select according to specific actual needs.

[0159] In the fourth aspect of the present application, the present application proposes a battery, comprising the electrode assembly described in the first aspect of the present application or the electrode assembly obtained by the method described in the second aspect of the present application or the battery cell described in the third aspect of the present application.

[0160] In some embodiments, the battery comprises a lithium-ion battery or a sodium-ion battery. The battery can be in the form of a battery cell, a battery module, or a battery pack.

[0161] In some embodiments, battery cells may be assembled into a battery module. The number of batteries contained in the battery module may be one or more. The specific number may be selected by those skilled in the art based on the application and capacity of the battery module.

[0162] Figure 8 shows an example battery module 2. Referring to Figure 8 , 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.

[0163] 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.

[0164] 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.

[0165] Figures 9 and 10 illustrate an example battery pack 3. Referring to Figures 9 and 10 , 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.

[0166] 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, or 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.

[0167] As the electrical device, a battery cell, a battery module or a battery pack can be selected according to its usage requirements.

[0168] Figure 11 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 secondary battery, a battery pack or battery module can be used.

[0169] 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.

[0170] 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.

[0171] Example 1

[0172] 1. Preparation of positive electrode sheet

[0173] 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), dielectric material particles barium titanate are mixed in a weight ratio of 98:1:1:0, N-methylpyrrolidone (NMP) is added as a solvent, the slurry is stirred in a vacuum state until it is uniform to obtain a positive electrode slurry, and then the obtained positive electrode slurry is 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.

[0174] 2. Preparation of negative electrode sheet

[0175] The first negative electrode active material artificial graphite, conductive agent acetylene black, composite binder SBR (styrene butadiene rubber), dispersant sodium carboxymethyl cellulose (CMC-Na), and the first dielectric material particle barium titanate were dissolved in deionized water according to a weight ratio of 94:1:1:1:3, and stirred and mixed to prepare the first negative electrode slurry. The second negative electrode active material artificial graphite (Dv50 is 10.2μm), conductive agent acetylene black, composite binder SBR (styrene butadiene rubber), dispersant sodium carboxymethyl cellulose (CMC-Na) and the first dielectric material particle barium titanate were mixed to prepare the first negative electrode slurry. MC-Na), the second dielectric material particles of barium titanate are dissolved in a solvent of deionized water in a weight ratio of 97:1:1:1:0, stirred and mixed evenly to prepare a second negative electrode slurry, the first negative electrode slurry is coated on the negative electrode collector after winding into a battery core at the corner position along the entire area of ​​the thickness direction of the opposite sides, the second negative electrode slurry is coated on the negative electrode collector after winding into a battery core at the straight position along the entire area of ​​the thickness direction of the opposite sides (coating density is 9.6 mg / cm 2 ), and after drying, cold pressing, and slitting, a negative electrode sheet is obtained (the thickness of the first negative electrode active material layer and the second negative electrode active material layer are equal and both are 60 μm).

[0176] 3. Preparation of electrolyte

[0177] 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.

[0178] 4. Isolation film

[0179] 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.

[0180] 5. Preparation of secondary batteries

[0181] 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.

[0182] The preparation methods of the lithium-ion batteries of Examples 2-19 and Comparative Examples 1-5 are the same as those of Example 1, except that the processes for preparing the negative electrode sheets are different, as shown in Table 1.

[0183] The preparation method of the lithium-ion battery of Example 20 is the same as that of Example 1, except that the process of preparing the negative electrode plate is different, specifically comprising: dissolving the negative electrode active material artificial graphite, the conductive agent acetylene black, the composite binder SBR (styrene butadiene rubber), the dispersant sodium carboxymethyl cellulose (CMC-Na), and the first dielectric material particle barium titanate in a weight ratio of 94:1:1:1:3 in the solvent deionized water, stirring and mixing them uniformly to prepare a first negative electrode slurry; dissolving the negative electrode active material artificial graphite (Dv50 is 10.2 μm), the conductive agent acetylene black, the composite binder SBR (styrene butadiene rubber), the dispersant sodium carboxymethyl cellulose (CMC-Na), and the second dielectric material particle barium titanate in a weight ratio of 97:1:1:1:0 in the solvent deionized water, stirring and mixing them uniformly to prepare a second negative electrode slurry; dissolving the negative electrode active material artificial graphite (Dv50 is 10.2 μm), the conductive agent acetylene black, the composite binder SBR (styrene butadiene rubber), the dispersant sodium carboxymethyl cellulose (CMC-Na), and the second dielectric material particle barium titanate in a weight ratio of 97:1:1:1:0 in the solvent deionized water, stirring and mixing them uniformly to prepare a second negative electrode slurry; 50 is 10.2 μm), conductive agent acetylene black, composite binder SBR (styrene-butadiene rubber), and dispersant sodium carboxymethyl cellulose (CMC-Na) are dissolved in solvent deionized water in a weight ratio of 97:1:1:1, and the mixture is stirred and evenly mixed to prepare a third negative electrode slurry, and the third negative electrode slurry is coated on the opposite sides of the negative electrode current collector along the thickness direction, and then the first negative electrode slurry is coated on the third negative electrode slurry and wound into a battery cell, and the entire area is located at the corner area along the thickness direction after the first negative electrode slurry is coated on the third negative electrode slurry. The entire area is located at the opposite sides of the thickness direction of the straight area after the second negative electrode slurry is coated on the third negative electrode slurry and wound into a battery cell. After drying, cold pressing, and slitting, negative electrode sheets are obtained (the thickness of the third negative electrode active material layer is 60 μm; the thickness of the first negative electrode active material layer is 40 μm and the thickness of the second negative electrode active material layer is 60 μm).

[0184] The lithium plating and cycle performance of the batteries of Examples 1-20 and Comparative Examples 1-5 were characterized, and the characterization results are shown in Table 3.

[0185] (1) Test of lithium deposition on negative electrode:

[0186] 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 backscattered electron diffraction technique (EBSD) was used to scan the surface of the corner area of ​​the disassembled negative electrode under vacuum conditions (the scanning angle of the scanning electron microscope (SEM) used was 70 degrees), and the lithium deposition area signal of the corner area and the non-lithium deposition area signal of the corner area were collected respectively. The proportion of lithium deposition area in the corner area = the intensity of the lithium deposition area signal in the corner area / (the intensity of the lithium deposition area signal in the corner area + the signal intensity of the non-lithium deposition area in the corner area).

[0187] (2) Cyclic performance test:

[0188] 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.

[0189] Table 2

[0190] Figure 12 is a picture of the negative electrode sheet disassembled after the battery obtained in Example 1 was cycled (cycled 300 times according to the cycle conditions of the above-mentioned cycle performance test), and Figure 13 is a picture of the negative electrode sheet disassembled after the battery obtained in Comparative Example 5 was cycled (cycled 300 times according to the cycle conditions of the above-mentioned cycle performance test). Comparing Figures 12 and 13, no lithium dendrites were generated on the surface of the corner area of ​​the negative electrode sheet disassembled after the battery obtained in Example 1 was cycled, while obvious lithium dendrites were generated on the surface of the corner area of ​​the negative electrode sheet disassembled after the battery obtained in Comparative Example 5. This shows that in Example 1, the addition of dielectric material particles with a volume average particle size of 210 nm, a mass proportion of 3% in the first negative electrode active material layer, and a relative dielectric constant of 1610 to the first negative electrode active material layer in the corner area can reduce the risk of metal dendrites generated by surface aggregation in the corner area.

[0191] Table 3

[0192] Conclusion, compared with Comparative Examples 1-5, the volume average particle size Dv50 of the first dielectric material particles in the first negative electrode active material layer in the corner area of ​​the negative electrode sheet of the battery of Example 1-20 is 200nm-2000nm, and based on the total mass of the first negative electrode active material layer, the proportion of the first dielectric material particles is 0.5%-10%. The volume average particle size Dv50 of the first dielectric material in the first negative electrode active material layer in the corner area of ​​the negative electrode sheet of the battery of Comparative Example 1 is 101nm, the relative dielectric constant is 817, and based on the total mass of the first negative electrode active material layer, the proportion of the first dielectric material particles is 3%; the volume average particle size Dv50 of the first dielectric material in the first negative electrode active material layer in the corner area of ​​the negative electrode sheet of the battery of Comparative Example 2 is 2530nm, the relative dielectric constant is 817, and based on the total mass of the first negative electrode active material layer, the proportion of the first dielectric material particles is 3%. The dielectric constant is 4803, and the first dielectric material particles account for 3% of the total mass of the first negative electrode active material layer. The volume average particle size Dv50 of the first dielectric material in the first negative electrode active material layer in the corner area of ​​the negative electrode sheet of the battery of Comparative Example 3 is 820nm, the relative dielectric constant is 2213, and the first dielectric material particles account for 0.2% of the total mass of the first negative electrode active material layer. The volume average particle size Dv50 of the first dielectric material in the first negative electrode active material layer in the corner area of ​​the negative electrode sheet of the battery of Comparative Example 4 is 820nm, the relative dielectric constant is 2213, and the first dielectric material particles account for 13% of the total mass of the first negative electrode active material layer. No dielectric material particles are added to the first negative electrode active material layer of the negative electrode sheet of the battery of Comparative Example 5. As shown in Table 3, the lithium plating area of ​​the negative electrode sheet of the battery of Example 1-20 after cycle disassembly is significantly smaller than that of Comparative Example 1-5, and the cycle performance of the battery of Example 1-20 is also higher than that of Comparative Example 1-5. This shows that the first negative electrode active material layer on the corner area of ​​the negative electrode plate of the present application uses first dielectric material particles (the volume average particle size Dv50 of the first dielectric material particles is 200nm-2000nm, the relative dielectric constant of the first dielectric material particles is 1000-10000, and based on the total mass of the first negative electrode active material layer, the proportion of the first dielectric material particles is 0.5%-10%), which can not only reduce the risk of lithium plating in the corner area of ​​the negative electrode plate, but also improve the cycle performance of the battery during the fast charging process.

[0193] 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. An electrode assembly, wherein, It includes a negative electrode plate, the negative electrode plate includes a corner area, the corner area includes a first negative electrode active material layer, the first negative electrode active material layer includes first dielectric material particles, the volume average particle size Dv50 of the first dielectric material particles is D1, D1 is 200 nm - 2000 nm, the relative dielectric constant of the first dielectric material particles is 1000 - 10000, and based on the total mass of the first negative electrode active material layer, the proportion of the first dielectric material particles is W1, W1 is 0.5% - 10%.

2. The electrode assembly according to claim 1, wherein, W1 is 1% - 3%.

3. The electrode assembly according to claim 1 or 2, wherein D1 is 600 nm - 1000 nm.

4. The electrode assembly according to any one of claims 1-3, wherein, The relative dielectric constant of the first dielectric material particles is 1500 - 5000.

5. The electrode assembly according to any one of claims 1-4, wherein, The first dielectric material particles include at least one of barium titanate, lead titanate, lithium niobate, lead zirconate titanate, lead metaniobate or barium lithium lead niobate.

6. The electrode assembly according to claim 5, wherein, The first dielectric material particles include doped ions, and the doped ions include at least one of 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+ .

7. The electrode assembly according to any one of claims 1-6, wherein, The first 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.

8. The electrode assembly according to claim 6 or 7, wherein, The trivalent rare earth metal ions include Sc 3+ , Y 3+ or Yb 3+ and at least one of them.

9. The electrode assembly according to any one of claims 1-8, wherein, The BET specific surface area of the first dielectric material particles is 0.8 m 2 / g - 7 m 2 / g.

10. The electrode assembly according to any one of claims 5-7, wherein, The barium titanate includes a tetragonal crystal form.

11. The electrode assembly according to any one of claims 1-10, wherein, The first negative electrode active material layer further includes a first negative electrode active material, the volume average particle size Dv50 of the first negative electrode active material is D2, and D1 ≤ D2.

12. The electrode assembly according to claim 11, wherein, D2 is 2 μm - 20 μm.

13. The electrode assembly according to claim 11 or 12, wherein, D2 is 8 μm - 13 μm.

14. The electrode assembly according to any one of claims 1-13, wherein, The length of the corner area is 5 mm - 30 mm.

15. The electrode assembly according to any one of claims 1-14, wherein, The negative electrode plate further includes a straight area, the corner area is provided at both ends of the straight area, the straight area is provided with a second negative electrode active material layer, the second negative electrode active material layer includes second dielectric material particles, and based on the total mass of the second negative electrode active material layer, the proportion of the second dielectric material particles is W2, and W1 ≥ W2.

16. The electrode assembly according to claim 15, wherein, W2 is 0 - 5%.

17. The electrode assembly according to claim 15 or 16, wherein, Based on the total mass of the first negative electrode active material layer, the mass proportion of the first negative electrode active material is K1; The second negative electrode active material layer includes a second negative electrode active material, and based on the total mass of the second negative electrode active material layer, the mass proportion of the second negative electrode active material is K2, and K1 ≤ K2.

18. The electrode assembly according to claim 17, wherein, K1 is 90% - 98%.

19. The electrode assembly according to claim 17 or 18, wherein, K2 is 90% - 98%.

20. The electrode assembly according to claim 15, wherein The negative electrode plate further includes a negative electrode current collector and a third negative electrode active material layer, the third negative electrode active material layer is provided on at least one side of the negative electrode current collector, and the first negative electrode active material layer and the second negative electrode active material layer are provided on the side of the third negative electrode active material layer away from the negative electrode current collector.

21. The electrode assembly according to claim 20, wherein, The thickness of the first negative electrode active material layer is H1, the thickness of the third negative electrode active material layer is H3, and H1 / H3 is 4% - 30%.

22. The electrode assembly according to claim 20 or 21, wherein, The thickness of the first negative electrode active material layer is not higher than the thickness of the second negative electrode active material layer.

23. The electrode assembly according to any one of claims 20-22, wherein, Meet one or more of the following conditions: The thickness of the first negative electrode active material layer is 20 μm - 100 μm; The thickness of the second negative electrode active material layer is 20 μm - 100 μm; The thickness of the third negative electrode active material layer is 40 μm - 200 μm.

24. The electrode assembly according to claim 17, wherein, At least a part of the surface of the first negative electrode active material is provided with a first coating layer, and the first coating layer includes the first dielectric material particles; and / or At least a part of the surface of the second negative electrode active material is provided with a second coating layer, and the second coating layer includes the second dielectric material particles.

25. The electrode assembly according to claim 20, wherein, The first negative electrode active material, the second negative electrode active material, and the third negative electrode active material in the third negative electrode active material layer independently include at least one of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, or titanates.

26. A method for preparing an electrode assembly, wherein, Comprising: Stacking the positive electrode plate and the negative electrode plate and winding them in the winding direction to form the electrode assembly. The negative electrode plate includes a corner area, and the corner area includes a first negative electrode active material layer. The first negative electrode active material layer includes first dielectric material particles. The volume average particle diameter Dv50 of the first dielectric material particles is D1, D1 is 200 nm - 2000 nm, the relative dielectric constant of the first dielectric material particles is 1000 - 10000, and based on the total mass of the first negative electrode active material layer, the proportion of the first dielectric material particles is W1, and W1 is 0.5% - 10%.

27. A battery cell, wherein, Comprising the electrode assembly according to any one of claims 1 - 25 or the electrode assembly obtained by the method according to claim 26.

28. A battery, wherein, Comprising the electrode assembly according to any one of claims 1 - 25, or the electrode assembly obtained by the method according to claim 26, or the battery cell according to claim 27.

29. The battery according to claim 28, wherein, The battery includes a lithium-ion battery or a sodium-ion battery.

30. An electrical device, wherein, Comprising the battery according to claim 28 or 29.

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