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

Abstract

A negative electrode sheet (10) and a preparation method therefor, a battery, and an electric device. The negative electrode sheet (10) comprises a negative electrode current collector (100) and a negative electrode active material layer (200); the negative electrode active material layer (200) is provided on at least one side of the negative electrode current collector (100), the negative electrode active material layer (200) comprises a thinned region (21), and the thinned region (21) comprises first dielectric material particles; the average particle size by volume Dv50 of the first dielectric material particles is D1, D1 being 400 nm-2000 nm; and with respect to the total mass of the thinned region (21), the proportion of the first dielectric material particles is W1, W1 being 0.5%-10%.

Description

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

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the priority benefit of Chinese patent application No. 202410007438.6 filed on January 3, 2024, and incorporates the entirety of the application into this document. Technical Field

[0003] The present application belongs to the field of batteries, and specifically relates to a negative electrode plate and a preparation method thereof, a battery and an electrical device. Background Art

[0004] 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, during fast charging, metal dendrites are easily formed in the thinned area of ​​the negative electrode, resulting in reduced battery cycle performance. Summary of the Invention

[0005] In view of the technical problems existing in the background technology, the present application provides a negative electrode plate, aiming to improve the cycle performance of the battery containing the negative electrode plate during the fast charging process.

[0006] In order to achieve the above objectives, the first aspect of the present application provides a negative electrode sheet, comprising:

[0007] negative electrode current collector;

[0008] A negative electrode active material layer, wherein the negative electrode active material layer is disposed on at least one side of the negative electrode current collector, the negative electrode active material layer includes a thinned area, the thinned area includes first dielectric material particles, the volume average particle size Dv50 of the first dielectric material particles is D1, D1 is 400nm-2000nm, and based on the total mass of the thinned area, the proportion of the first dielectric material particles is W1, and W1 is 0.5%-10%.

[0009] The present application includes at least the following beneficial effects: the thinned area of ​​the negative electrode plate of the present application includes the first dielectric material particles with the above-mentioned particle size and content, which can improve the cycle performance of the battery containing it during the fast charging process.

[0010] In some embodiments, W1 is 1%-5%, thereby improving the cycle performance of the battery during fast charging.

[0011] In some embodiments, D1 is 600 nm to 1000 nm, thereby improving the cycle performance of the battery during fast charging.

[0012] In some embodiments, the width of the thinned zone is H1, which is less than or equal to 20 mm, and can be optionally 2 mm-15 mm.

[0013] In some embodiments, the relative dielectric constant of the first dielectric material particles is 1000-10000, and can be optionally 1500-5000. This can improve the cycle performance of the battery.

[0014] 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.

[0015] 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 can be improved.

[0016] 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, wherein the pentavalent ion includes Nb 5+ 、W 5+ Or Mo 5+ Thus, the cycle performance of the battery can be improved.

[0017] In some embodiments, the trivalent rare earth metal ion comprises Sc 3+ 、Y 3+ or Yb 3+ Thus, the cycle performance of the battery can be improved.

[0018] 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 can be improved.

[0019] In some embodiments, the barium titanate comprises a tetragonal crystal structure, thereby improving the cycle performance of the battery.

[0020] In some embodiments, the skived region 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.

[0021] In some embodiments, D2 is 2 μm-20 μm, and optionally 8 μm-13 μm, thereby improving the cycle performance of the battery.

[0022] In some embodiments, the negative electrode active material layer further includes a main body region, the skived region and the main body region are adjacently disposed, and the thickness of the skived region is smaller than that of the main body region.

[0023] In some embodiments, the thickness of the thinned region decreases in a direction away from the main region.

[0024] In some embodiments, the width of the main region is H2, where H1<H2.

[0025] In some embodiments, H2 is 40 mm-250 mm, optionally 80 mm-150 mm.

[0026] In some embodiments, the main body region includes second dielectric material particles, and based on the total mass of the main body region, the second dielectric material particles account for W2, where W1≥W2. This can improve the cycle performance of the battery.

[0027] In some embodiments, W2 is 0-10%, and optionally 0-3%, thereby improving the cycle performance of the battery.

[0028] In some embodiments, based on the total mass of the thinned area, the mass proportion of the first negative electrode active material is K1, the main area includes a second negative electrode active material, based on the total mass of the main area, the mass proportion of the second negative electrode active material is K2, and K1≤K2.

[0029] In some embodiments, K1 is 90-97%, optionally 92%-95%.

[0030] In some embodiments, K2 is 90-98%, optionally 95%-97%.

[0031] 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.

[0032] In some embodiments, the first negative electrode active material and the second negative electrode active material each independently include at least one of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based material, tin-based material, or titanate.

[0033] In a second aspect of the present application, the present application proposes a method for preparing a negative electrode sheet, comprising:

[0034] A negative electrode active material layer is formed on at least one side of the negative electrode current collector, wherein the negative electrode active material layer includes a thinned area, the thinned area includes first dielectric material particles, and the volume average particle size Dv50 of the first dielectric material particles is D1, D1 is 400nm-2000nm, and based on the total mass of the thinned area, the proportion of the first dielectric material particles is W1, and W1 is 0.5%-10%.

[0035] As a result, the battery containing the negative electrode plate obtained by this method has a lower risk of dendrites during fast charging, thereby improving the cycle performance of the battery.

[0036] In a third aspect of the present application, the present application provides a battery comprising the negative electrode sheet described in the first aspect of the present application or the negative electrode sheet obtained by the method described in the second aspect of the present application. Thus, the battery has excellent cycle performance.

[0037] In some embodiments, the battery comprises a lithium-ion battery or a sodium-ion battery.

[0038] In the fourth aspect of the present application, the present application proposes an electrical device comprising the battery described in the third aspect of the present application.

[0039] 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

[0040] 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:

[0041] FIG1 is a schematic structural diagram of a negative electrode sheet according to an embodiment of the present application.

[0042] FIG2 is a schematic structural diagram of a negative electrode sheet according to another embodiment of the present application.

[0043] FIG. 3 is an XRD pattern of barium titanate according to one embodiment of the present application.

[0044] FIG. 4 is a schematic diagram of a battery cell according to an embodiment of the present application.

[0045] FIG. 5 is an exploded view of the battery cell shown in FIG. 4 according to an embodiment of the present application.

[0046] FIG6 is a schematic diagram of a battery module according to an embodiment of the present application.

[0047] FIG7 is a schematic diagram of a battery pack according to an embodiment of the present application.

[0048] FIG8 is an exploded view of the battery pack shown in FIG7 according to an embodiment of the present application.

[0049] FIG9 is a schematic diagram of an electrical device using a battery as a power source according to an embodiment of the present application.

[0050] FIG10 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 negative electrode sheet; 100 negative electrode current collector; 200 negative electrode active material layer; 21 thinning area; 22 main body area; 300 negative electrode tab; 1 battery cell; 11 housing; 12 electrode assembly; 13 cover plate; 2 battery module; 3 battery pack; 31 upper case; 32 lower case. DETAILED DESCRIPTION

[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] During fast charging, the desolvation rate of solvated active ions and the diffusion rate of active ions in the SEI film (solid electrolyte interface film) affect the fast charging performance of the battery. Especially during high-current charging, the difference in active ion concentration between the bulk and surface phases of the negative electrode active material may lead to an increase in the local active ion concentration. When the active ions break through the nucleation barrier on the surface of the negative electrode active material, metal dendrites will be generated. This situation will be more serious in the thinned area of ​​the negative electrode sheet. Due to the excellent conductivity of metals, active ions will preferentially gather near the dendrites and be reduced to form metal dendrites. The formation of such metal dendrites is accompanied by the rupture of the SEI film, and new SEI films will continue to form, resulting in a decrease in battery cycle performance.

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

[0061] In a first aspect, the present application proposes a negative electrode sheet. Referring to Figure 1, the negative electrode sheet 10 includes a negative electrode current collector 100 and a negative electrode active material layer 200. The negative electrode active material layer 200 is provided on at least one side of the negative electrode current collector 100. The negative electrode active material layer 200 includes a thinning area 21. The thinning area 21 includes first dielectric material particles. The volume average particle size Dv50 of the first dielectric material particles is D1, and D1 is 400nm-2000nm. Based on the total mass of the thinning area 21, the proportion of the first dielectric material particles is W1, and W1 is 0.5%-10%.

[0062] In this application, "dielectric material particles" refer to materials that exhibit excellent insulating properties in an electric field. They are a type of material that can separate charges and store electrical energy without losing charge.

[0063] The thinned area 21 on the negative electrode plate 10 of the present application is added with first dielectric material particles of the above-mentioned particle size and content. The performance of the first dielectric material particles of this particle size can be fully exerted. At the same time, combined with the above-mentioned content, the cycle performance of the battery during fast charging can be improved.

[0064] The process by which the above-mentioned dielectric material particles exert their performance is speculated as follows: during the charging process of the battery containing the negative electrode plate 10, the positive and negative charge centers in the first dielectric material particles will separate 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 in the thinned area 21 on the negative electrode plate 10 is negatively charged, and therefore may attract the active ions gathered in the thinned area 21 on the negative electrode plate 10 to be evenly distributed, thereby reducing the risk of active ions gathering in the thinned area 21 and generating metal dendrites, thereby improving the cycle performance of the battery containing it during the fast charging process.

[0065] In this application, in order to facilitate the understanding of the thinning zone 21, referring to Figure 2, one end of the negative electrode sheet 10 is connected to the negative electrode tab 300, and the negative electrode active material layer 200 on the negative electrode sheet 10 is divided into a thinning zone 21 and a main zone 22. The thinning zone 21 is arranged on the edge area of ​​the negative electrode active material layer 200 close to the negative electrode tab 300, and the main zone 22 is arranged adjacent to the thinning zone 21. The main zone 22 is arranged on the side of the thinning zone 21 away from the negative electrode tab 300, and the thickness of the thinning zone 21 is less than the thickness of the main zone 22.

[0066] In some embodiments of the present application, based on the total mass of the skived area 21, 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 skived area 21, the proportion of the first dielectric material particles is 1%-5%.

[0067] In some embodiments of the present application, the volume average particle size Dv50 of the first dielectric material particles is D1, and D1 is 400 nm-2000 nm, for example, 400 nm-1900 nm, 400 nm-1800 nm, 500 nm-1700 nm, 600 nm-1600 nm, 700 nm-1500 nm, 800 nm-1400 nm, 900 nm-1300 nm, 1000 nm-1200 nm, 1000 nm-1100 nm, etc. In other embodiments of the present application, the volume average particle size Dv50 of the first dielectric material particles is 600 nm-1000 nm.

[0068] In the present application, the volume average particle size Dv50 of the first dielectric material particles refers to the particle size corresponding to when the cumulative volume distribution percentage reaches 50%. The test method for the volume average particle size Dv50 of the dielectric material particles in the negative electrode sheet 10 is as follows:

[0069] (1) Scrape the thinned area 21 corresponding to the negative electrode sheet 10, take a sample and calcine it to 600°C to complete the sintering of the binder and the negative electrode active material (for the system of silicon-containing negative electrode active material, sinter it and then mix it with sodium hydroxide solution for reaction), add water and filter;

[0070] (2) Referring to the standard GB / T 19077-2016, the volume average particle size Dv50 of the dielectric material particles of the filtered material is tested using a laser particle size analyzer (such as Malvern Master Size 3000).

[0071] In the present application, the method for testing the mass proportion of the first dielectric material particles in the thinned area 21 of the negative electrode sheet 10 includes: scraping the thinned area 21 of the negative electrode sheet 10, 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 thinned area 21.

[0072] As an example, the negative electrode current collector 100 has two surfaces facing each other in its thickness direction, and the negative electrode active material layer 200 is provided on either or both of the two facing surfaces of the negative electrode current collector 100 .

[0073] In some embodiments of the present application, the negative electrode current collector 100 may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base layer. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer base layer (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0074] In some embodiments of the present application, the width of the thinned area 21 is H1, which is less than or equal to 20 mm, such as 1 mm-20 mm, 2 mm-18 mm, 5 mm-15 mm, 7 mm-12 mm, 9 mm-10 mm, etc. In other embodiments of the present application, the width H1 of the thinned area 21 is 2 mm-15 mm.

[0075] In the present application, referring to FIG. 2 , the “width H1 of the thinned region 21 ” may be understood as the minimum distance between the end of the main region 22 close to the negative electrode tab 300 and the negative electrode tab 300 .

[0076] 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. Therefore, the present application uses the first dielectric material particles meeting the relative dielectric constant in the negative electrode plate 10, which can further improve the cycle performance of the battery containing the first dielectric material particles during the fast charging process.

[0077] The process by which the dielectric material particles with the above relative dielectric constant exert their performance is speculated as follows: Dielectric material particles that meet this relative dielectric constant can form an excellent reverse electric field effect during the charging process, which may further evenly distribute the active ions accumulated in the thinned area 21 of the negative electrode plate 10, thereby reducing the risk of active ions agglomerating in the thinned area 21 and generating metal dendrites, thereby improving the cycle performance of the battery containing the dielectric material particles during the fast charging process. In other embodiments of the present application, the relative dielectric constant of the first dielectric material particles is 1500-5000.

[0078] 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 thinned area 21 corresponding to the negative electrode plate 10 can be scraped, and a sample can be 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 materials, the system is 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 binder (the binder is composed of acrylic acid (PAA) emulsion and The raw material is mixed with an alcohol amine plasticizer, and its decomposition temperature is less than 300 ° C), and after being fully stirred, it is slowly added into an 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 material 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 material porcelain cake is then placed on a sheet punching machine (the pressing plate of the sheet punching machine is round and the size is Under the pressure plate (made of stainless steel with a polished surface), 10 thin circular ceramic pieces with a diameter of 11±1 mm are punched out; (2) debinding: the thin circular ceramic piece obtained in step (1) is placed on a clean and flat zirconia or alumina support plate, and placed in a muffle furnace together with the support plate, and debinding is performed by heating the ceramic piece to 300°C at a heating rate of 0.3°C / min and then keeping the temperature for 6 hours; after the front debinding is completed, the thin circular ceramic piece is taken out and replaced with the back side facing up, and the above operation is repeated for the back debinding; (3) silver coating: the thin circular ceramic piece after debinding in step (2) is placed on a clean and flat zirconia or alumina support plate, and the silver paste is evenly applied to the front of the thin circular ceramic piece using a fine brush, The silver paste is a high-temperature sintering conductive silver paste. The silver paste is applied in a one-way manner for 2-3 times, with a thickness of 80μm to 100μm. (4) Silver burning: first, the silver layer on the side of the thin circular porcelain piece after silver coating in step (3) is gently scraped off with a blade, and then the thin circular porcelain piece after silver coating is placed in a muffle furnace together with a firing plate. Silver burning is performed at a heating rate of 5℃ / min and after heating to 800℃ and keeping warm for 2h. After the front side silver burning is completed, the thin circular porcelain piece and the firing plate are taken out, and steps (3) and (4) are repeated to silver burn the back side. After that, the capacitance C is tested by an LCR meter and calculated according to the formula: relative dielectric constant ε=(C×d) / (ε0×A). C represents capacitance, in farads (F); d represents sample thickness, in cm; A represents sample area, in cm 2 ;ε0 represents the dielectric constant of vacuum, ε0=8.854×10 -14F / 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.

[0079] 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, such first dielectric material particles can further improve the cycling performance of batteries containing them during fast charging.

[0080] 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 in the thinned area 21 of the negative electrode plate 10 more evenly distributed, thereby reducing the risk of active ions gathering in the thinned area 21 and generating 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 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.

[0082] 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 first dielectric material particles can be adjusted, so that the active ions gathered in the thinned area 21 of the negative electrode plate 10 may be evenly distributed, thereby reducing the risk of active ions gathering in the thinned area 21 and generating metal dendrites, thereby improving the cycle performance of the battery containing it during the fast charging process.

[0083] 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.

[0084] In some embodiments of the present application, the first dielectric material particles are barium titanate, and the barium titanate includes a tetragonal crystal.

[0085] 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 is perpendicular to the other two axes. The tetragonal form of barium titanate can be determined by XRD testing. Figure 3 is an XRD pattern of tetragonal barium titanate, with the 2θ positions of its X-ray diffraction peaks at 22°, 31°, 38°, 45°, 56°, and 66°.

[0086] Therefore, the above-mentioned tetragonal barium titanate as the first dielectric material particle may further reduce the risk of active ions agglomerating in the thinned area 21 to generate metal dendrites, thereby improving the cycle performance of the battery containing it during the fast charging process.

[0087] 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.

[0088] As a result, the first dielectric material particles within the above-mentioned specific surface area range are more tightly bonded to the negative electrode active material, which is beneficial to the performance of the dielectric material particles and may further reduce the risk of active ions agglomerating in the thinned area 21 to generate metal dendrites, thereby improving the cycle performance of the battery containing the first dielectric material particles during the fast charging process. In other embodiments of the present application, the BET specific surface area of ​​the first dielectric material particles is 1.8 m 2 / g-2m 2 / g.

[0089] In the present application, the BET specific surface area of ​​the first dielectric material particles has a well-known meaning in the art and can be tested using instruments and methods well-known in the art. For example, first scrape the powder from the thinned area 21 corresponding to the negative electrode plate 10, take a sample and calcine it to 600°C, sinter all the binder and the negative electrode active material (for the system of silicon-containing negative electrode active materials, sinter them and then mix them with sodium hydroxide solution for reaction), add water and filter. Then, refer to GB / T 19587-2017, use the nitrogen adsorption specific surface area analysis test method to test the filtered sample, and calculate it 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 from Micromeritics, USA.

[0090] In some embodiments of the present application, the skived region 21 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 volume average particle size Dv50 of the first negative electrode active material is D2, where D1 < D2.

[0091] Therefore, the particle sizes of the first negative electrode active material and the first dielectric material satisfy 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 in the thinned area 21 of the negative electrode plate 10, thereby reducing the risk of active ions gathering in the thinned area 21 and generating metal dendrites, thereby improving the cycle performance of the battery containing it during the fast charging process; and can also make the thinned area 21 have a high compaction density, thereby improving the battery energy density.

[0092] 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.

[0093] 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 dielectric material particles, so that the active ions accumulated in the thinned area 21 of the negative electrode plate 10 are evenly distributed, thereby reducing the risk of active ions agglomerating in the thinned area 21 and generating metal dendrites, thereby improving the cycling performance of the battery containing it during the fast charging process; it can also make the thinned area 21 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.

[0094] In the present application, the method for testing the volume average particle size Dv50 of the first negative electrode active material in the negative electrode plate 10 includes: using a flame to ablate the surface of the thinned area 21 of the negative electrode plate 10 to remove the binder in the surface thinned area 21 (the flame temperature is 300° C.-500° C., and the negative electrode plate 10 is moved at a rate of 1 m / min-30 m / min), then scraping the surface of the thinned area 21 to remove powder, and sieving the resulting powder to separate the first negative electrode active material from the first dielectric material particles and the conductive agent. The resulting large-size particles 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 (e.g., Malvern Master Size 3000) to obtain the volume average particle size Dv50 of the first negative electrode active material.

[0095] In some embodiments of the present application, referring to FIG1 , the thickness of the thinned region 21 tends to decrease along a direction away from the main region 22 . For example, the thickness of the thinned region 21 gradually decreases along a direction away from the main region 22 .

[0096] In some embodiments of the present application, referring to FIG2 , the width of the main region 22 is H2, where H1<H2. Therefore, the present application controls the width of the thinned region 21 to be smaller than the width of the main region 22 to ensure the energy density of the negative electrode sheet 10.

[0097] In some embodiments of the present application, the width H2 of the main body region 22 is 40 mm to 250 mm, for example, 50 mm to 240 mm, 70 mm to 220 mm, 80 mm to 210 mm, 100 mm to 200 mm, 120 mm to 180 mm, 130 mm to 160 mm, or 140 mm to 150 mm. Thus, by controlling the width of the main body region 22 within this range, the energy density of the negative electrode sheet 10 can be ensured. In other embodiments of the present application, the width H2 of the main body region 22 is 80 mm to 150 mm.

[0098] In some embodiments of the present application, the main body region 22 includes second dielectric material particles. Based on the total mass of the main body region 22, the proportion of the second dielectric material particles is W2, where W1 ≥ W2. Therefore, by adding the second dielectric material particles to the main body region 22, and ensuring that the content of the second dielectric material particles in the main body region 22 is less than or equal to the content of the first dielectric material particles in the skived region 21, not only can the risk of metal dendrites forming in the skived region 21 of the negative electrode sheet 10 be reduced, but also material costs can be reduced.

[0099] In the present application, the “second dielectric material particles” are the same as the “first dielectric material particles” mentioned above, and the “first dielectric material particle composition” and the “second dielectric material particle composition” may be the same or different.

[0100] In some embodiments of the present application, based on the total mass of the main body region 22, the proportion W2 of the second dielectric material particles is 0-10%, for example, 1%-10%, 3%-7%, 5%-6%, etc. In some embodiments of the present application, based on the total mass of the main body region 22, the proportion W2 of the second dielectric material particles is 0-3%.

[0101] In the present application, the method for testing the mass proportion of the second dielectric material particles in the main area 22 of the negative electrode plate 10 includes: drying the negative electrode plate 10, then scraping the powder from the main area 22, and then subjecting the powder obtained from the main area 22 (for a system of silicon-containing negative electrode active materials, the powder is sintered and then mixed with a 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 vertical coordinate on the thermal gravimetric curve corresponding to 1000°C is the mass proportion of the second dielectric material particles in the main area 22.

[0102] In some embodiments of the present application, the skived region 21 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 skived region 21. The main body region 22 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 main body region 22, where K2 ≥ K1. Thus, the first negative electrode active material content K1 in the skived region 21 is less than or equal to the second negative electrode active material content K2 in the main body region 22, thereby reducing the risk of metal dendrites forming in the skived region 21 during fast charging while improving the energy density of the battery.

[0103] In some embodiments of the present application, the mass proportion K1 of the first negative electrode active material in the thinned area 21 is 90-97%, 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 thinned area 21 is 92%-95%. As a result, the energy density of the battery can be improved while reducing the risk of metal dendrites in the thinned area 21 during fast charging.

[0104] In some embodiments of the present application, the mass proportion K2 of the second negative electrode active material in the main body region 22 is 90-98%, for example, 91%-97%, 92%-96%, 93%-95%, 94%-95%, etc. In other embodiments of the present application, the mass proportion K2 of the second negative electrode active material in the main body region 22 is 95%-97%. This can improve the energy density of the battery.

[0105] In some embodiments of the present application, the negative electrode plate 10 is provided with the thinning area 21 on both sides of the thickness thereof, and the thinning area 21 on one side of the negative electrode plate 10 and the thinning area 21 on the other side are symmetrically arranged relative to the negative electrode current collector 100; at the same time, the negative electrode plate 10 is provided with the main body area 22 on both sides of the thickness thereof, and the main body area 22 on one side of the negative electrode plate 10 and the main body area 22 on the other side are symmetrically arranged relative to the negative electrode current collector.

[0106] 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. As a result, 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. Furthermore, the counter-electric field generated by the first dielectric material particles in the thinned region 21 of the negative electrode plate 10 is negatively charged, thereby attracting active ions accumulated in the thinned region 21 of the negative electrode plate 10 to be evenly distributed, thereby reducing the risk of active ions agglomerating in the thinned region 21 of the negative electrode plate 10 and generating metal dendrites.

[0107] 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.

[0108] In some embodiments of the present application, the first negative electrode active material and the second negative electrode active material may be negative electrode active materials for batteries that are well known in the art. As an example, the first negative electrode active material and the second negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and titanates. The silicon-based material may include at least one of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, or silicon alloys. The tin-based material may include at least one of elemental tin, tin oxides, or tin alloys. When the battery is a lithium-ion battery, lithium titanate is used as the titanate; when the battery is a sodium-ion battery, sodium titanate is used as the titanate. However, the present application is not limited to these materials, and other traditional materials that can be used as battery negative electrode active materials may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0109] In some embodiments of the present application, the skived region 21 and the main body region 22 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).

[0110] In some embodiments of the present application, the skived region 21 and the main region 22 may further include a conductive agent. The conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, or carbon nanofibers.

[0111] In some embodiments of the present application, the skived region 21 and the main region 22 may optionally further include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0112] In a second aspect of the present application, the present application proposes a method for preparing a negative electrode sheet, comprising:

[0113] A negative electrode active material layer is formed on at least one side of the negative electrode current collector, the negative electrode active material layer includes a thinned area, the thinned area includes first dielectric material particles, the volume average particle size Dv50 of the first dielectric material particles is D1, D1 is 400nm-2000nm, and based on the total mass of the thinned area, the proportion of the first dielectric material particles is W1, and W1 is 0.5%-10%.

[0114] The thinned area on the negative electrode plate of the present application is added with first dielectric material particles of the above-mentioned particle size and content. The performance of the first dielectric material particles of this particle size can be fully exerted. At the same time, combined with the above-mentioned content, the cycle performance of the battery during fast charging can be improved.

[0115] The process by which the above-mentioned dielectric material particles exert their performance is speculated as follows: during the charging process of the battery containing the negative electrode plate, the positive and negative charge centers in the first dielectric material particles will separate 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 in the thinned area on the negative electrode plate is negatively charged, and therefore may attract the active ions gathered in the thinned area on the negative electrode plate to be evenly distributed, thereby reducing the risk of active ions gathering in the thinned area and generating metal dendrites, thereby improving the cycle performance of the battery containing it during the fast charging process.

[0116] 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 applied to the edge area of ​​the negative electrode collector close to the negative electrode tab, and the second negative electrode slurry is applied to other areas of the negative electrode collector. After drying, cold pressing and other processes, the negative electrode active material layer on the edge area is thinned so that its thickness is less than that of the main area, and the above-mentioned negative electrode sheet can be obtained.

[0117] In a third aspect of the present application, the present application provides a battery comprising the negative electrode sheet described in the first aspect of the present application or the negative electrode sheet obtained by the method described in the second aspect of the present application. Thus, the battery has excellent cycle performance.

[0118] 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.

[0119] Typically, a battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During the battery's charge and discharge processes, active ions are inserted and removed between the positive and negative electrodes. The electrolyte conducts ions between the positive and negative electrodes. The separator, located between the positive and negative electrodes, primarily prevents short circuits between the positive and negative electrodes while allowing ions to pass through.

[0120] 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.

[0121] 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.

[0122] 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.).

[0123] 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.

[0124] 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.

[0125] 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.

[0126] Examples of the layered transition metal oxides include:

[0127] 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;

[0128] 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;

[0129] 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。

[0130] Examples of the polyanionic compound include:

[0131] 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;

[0132] 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;

[0133] Na p M 5 q (SO4)3, wherein M 5 includes at least one of Mn, Fe, Co, Ni, Cu or Zn, 0 < p ≤ 2, 0 < q ≤ 2;

[0134] Na s Mn t Fe 3-t (PO4)2(P2O7), wherein 0 < s ≤ 4, 0 ≤ t ≤ 3, for example t is 0, 1, 1.5, 2 or 3.

[0135] As an example of the above Prussian blue analogs, for example, the following can be listed:

[0136] A u M 6 v [M 7 (CN)6] w ·xH2O, wherein A includes H + , NH4 + , an alkali metal cation or an alkaline earth metal cation, M 6 and M 7 each independently include at least one of transition metal cations, 0 < u ≤ 2, 0 < v ≤ 1, 0 < w ≤ 1, 0 < x < 6. For example, A includes H + , Li + , Na + , K + , NH4+ , Rb + 、Cs + 、Fr + 、Be 2+ Mg 2+ , Ca 2+ 、Sr 2+ 、Ba 2+ or Ra 2+ At least one of M 6 and M 7 Each independently includes at least a cation of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sn, or W.

[0137] 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.

[0138] 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.

[0139] 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.

[0140] In some embodiments of the present application, based on the total mass of the 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.

[0141] 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.

[0142] In some embodiments of the present application, based on the total mass of the 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.

[0143] 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.

[0144] The present application has no specific restrictions on the type of electrolyte, which can be selected according to needs. For example, the electrolyte can be liquid, gel or solid.

[0145] In some embodiments of the present application, the electrolyte is an electrolyte solution comprising an electrolyte salt and a solvent.

[0146] 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.

[0147] 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.

[0148] 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.

[0149] 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.

[0150] 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.

[0151] In some embodiments, the material of the separator may include at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, or polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer may be the same or different, without particular limitation.

[0152] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly through a winding process or a lamination process.

[0153] In some embodiments, the battery cell may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0154] 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.

[0155] The present application has no particular limitation on the shape of the battery cell, which can be cylindrical, square, or any other shape. For example, FIG4 shows a battery cell 1 with a square structure as an example.

[0156] In some embodiments, referring to Figure 5, the outer packaging may include a shell 11 and a cover plate 13. The shell 11 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 11 has an opening connected to the receiving cavity, and the cover plate 13 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can form an electrode assembly 12 through a winding process or a lamination process. The electrode assembly 12 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 12. The number of electrode assemblies 12 contained in the battery cell 1 can be one or more, and those skilled in the art can select according to specific actual needs.

[0157] In some embodiments, battery cells may be assembled into a battery module. The battery module may contain one or more battery cells. The specific number may be selected by those skilled in the art based on the application and capacity of the battery module.

[0158] Figure 6 shows an example battery module 2. Referring to Figure 6 , within the battery module 2, multiple battery cells 1 may be arranged sequentially along the length of the battery module 2. Of course, they may also be arranged in any other manner. Furthermore, the multiple battery cells 1 may be secured together using fasteners.

[0159] 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.

[0160] 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.

[0161] Figures 7 and 8 illustrate an example battery pack 3. Referring to Figures 7 and 8 , the battery pack 3 may include a battery box and multiple battery modules 2 disposed within the battery box. The battery box comprises an upper case 31 and a lower case 32. The upper case 31 can be positioned over the lower case 32 to form an enclosed space for accommodating the battery modules 2. The multiple battery modules 2 can be arranged in any manner within the battery box.

[0162] In addition, the present application also provides an electrical device, which includes the battery provided in the present application. The battery cell, battery module, or battery pack can be used as a power source for the electrical device, and can also be used as an energy storage unit for the electrical device. The electrical device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but is not limited thereto.

[0163] As the electrical device, a battery cell, a battery module or a battery pack can be selected according to its usage requirements.

[0164] Figure 9 shows an example of an electric device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the secondary battery, a battery pack or battery module can be used.

[0165] 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.

[0166] 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.

[0167] Example 1

[0168] 1. Preparation of positive electrode sheet

[0169] The positive electrode active material is lithium nickel cobalt manganese oxide (NCM523, namely LiNi0.5 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.

[0170] 2. Preparation of negative electrode sheet

[0171] The first negative electrode active material artificial graphite secondary particles, conductive agent acetylene black, composite binder SBR (styrene butadiene rubber), dispersant sodium carboxymethyl cellulose (CMC), and the first dielectric material particles barium titanate are dissolved in solvent deionized water in a weight ratio of 94:1:1:1:3, stirred and mixed evenly to prepare a first negative electrode slurry, the second negative electrode active material artificial graphite (Dv50 is 10.3 μm), conductive agent acetylene black, composite binder SBR (styrene butadiene rubber), and dispersant sodium carboxymethyl cellulose (CMC) are dissolved in solvent deionized water in a weight ratio of 97:1:1:1, stirred and mixed evenly to prepare a second negative electrode slurry, and the first negative electrode slurry is coated on the negative electrode collector copper foil (thickness 6 μm) along the edge area near the negative electrode tab on both sides of its thickness, and the second negative electrode slurry is coated on the negative electrode collector along the other areas outside the first slurry on both sides of its thickness (coating density is 9.6 mg / cm 2 ), after drying, cold pressing, and slitting, the negative electrode active material layer in the edge area is thinned to obtain a thinned area (the thickness of the thinned area gradually decreases in the direction away from the main area, and the thickness of the thinned area close to one end of the negative electrode tab is 0 and the width is 5 mm), and a negative electrode sheet (the width of the main area is 100 mm) is obtained.

[0172] 3. Preparation of electrolyte

[0173] 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.

[0174] 4. Isolation film

[0175] 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.

[0176] 5. Preparation of secondary batteries

[0177] 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.

[0178] 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.

[0179] The lithium deposition and cycle performance of the batteries of Examples 1-19 and Comparative Examples 1-5 were characterized, and the characterization results are shown in Table 3.

[0180] (1) Test of lithium deposition on negative electrode:

[0181] 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, 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 thinned area on the surface 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 thinned area and the non-lithium deposition area signal of the thinned area were collected respectively. The proportion of lithium deposition area in the thinned area = the intensity of the lithium deposition area signal in the thinned area / (the intensity of the lithium deposition area signal in the thinned area + the signal intensity of the non-lithium deposition area in the thinned area).

[0182] (2) Cyclic performance test:

[0183] 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.

[0184] Table 2

[0185] Figure 10 shows a disassembled negative electrode sheet from the battery obtained in Comparative Example 5 after cycling (300 cycles according to the cycling performance test conditions described above). Obvious lithium dendrites are observed on the surface of the negative electrode sheet corresponding to the thinned area of ​​the negative current collector in the disassembled negative electrode sheet from the battery obtained in Comparative Example 5. This indicates that in Comparative Example 5, since the aforementioned dielectric material particles were not added to the thinned area of ​​the negative electrode sheet, there is a risk of metal dendrites forming on the surface of the negative electrode active material layer corresponding to the thinned area.

[0186] Table 3

[0187] Conclusion: Compared with Comparative Examples 1-5, the volume average particle size Dv50 of the first dielectric material particles in the thinned area of ​​the negative electrode sheet of the battery of Example 1-20 is 400nm-2000nm, and based on the total mass of the thinned area, 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 thinned area of ​​the negative electrode sheet of the battery of Comparative Example 1 is 110nm, and based on the total mass of the thinned area, the proportion of the first dielectric material particles is 3%; the volume average particle size Dv50 of the first dielectric material in the first active material layer of the thinned area of ​​the negative electrode sheet of the battery of Comparative Example 2 is 110nm. The particle size Dv50 is 2530nm, and the first dielectric material particles account for 3% of the total mass of the thinned area. The volume average particle size Dv50 of the first dielectric material particles in the thinned area of ​​the negative electrode sheet of the battery of Comparative Example 3 is 816nm, and the first dielectric material particles account for 0.2% of the total mass of the thinned area. The volume average particle size Dv50 of the first dielectric material particles in the thinned area of ​​the negative electrode sheet of the battery of Comparative Example 4 is 816nm, and the first dielectric material particles account for 13% of the total mass of the thinned area. No dielectric material particles are added to the thinned area 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 1-19 after cycle disassembly is significantly smaller than that of Comparative Example 1-5, and the cycle performance of the battery of Example 1-19 is also higher than that of Comparative Example 1-5. This shows that the thinning area of ​​the negative electrode sheet of the present application adopts a thinning area including first dielectric material particles (the volume average particle size Dv50 of the first dielectric material particles is 400nm-2000nm, and based on the total mass of the thinning area, the proportion of the first dielectric material particles is 0.5%-10%), which can not only reduce the risk of lithium plating in the thinning area of ​​the negative electrode sheet, but also improve the cycle performance of the battery during the fast charging process.

[0188] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A negative electrode plate, wherein, Comprising: A negative electrode current collector; A negative electrode active material layer provided on at least one side of the negative electrode current collector. The negative electrode active material layer includes a thinned region, and the thinned region includes first dielectric material particles. The volume average particle diameter Dv50 of the first dielectric material particles is D1, where D1 is 400 nm - 2000 nm. Based on the total mass of the thinned region, the proportion of the first dielectric material particles is W1, and W1 is 0.5% - 10%.

2. The negative electrode sheet according to claim 1, wherein, W1 is 1% - 5%.

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

4. The negative electrode sheet according to any one of claims 1-3, wherein, The width of the thinned region is H1, and H1 is less than or equal to 20 mm.

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

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

7. The negative electrode sheet according to any one of claims 1-6, 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 niobate lead.

8. The negative electrode sheet according to claim 7, 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+ .

9. The negative electrode sheet according to claim 8, 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, and the pentavalent ions include Nb 5+ , W 5+ , or Mo 5+ and at least one of them.

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

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

12. The negative electrode sheet according to any one of claims 7-9, wherein, The barium titanate includes a tetragonal crystal form.

13. The negative electrode electrode sheet according to claim 3, wherein, The thinned region includes a first negative electrode active material. The volume average particle diameter Dv50 of the first negative electrode active material is D2, and D1 ≤ D2.

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

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

16. The negative electrode sheet according to any one of claims 13-15, wherein, The negative electrode active material layer further includes a main body region. The thinned region and the main body region are adjacent to each other, and the thickness of the thinned region is less than the thickness of the main body region.

17. The negative electrode sheet according to claim 16, wherein, Along the direction away from the main body region, the thickness of the thinned region shows a decreasing trend.

18. The negative electrode sheet according to claim 16 or 17, wherein, The width of the main body region is H2, and H1 < H2.

19. The negative electrode sheet according to claim 18, wherein, H2 is 40 mm - 250 mm.

20. The negative electrode sheet according to any one of claims 16-19, wherein, The main body region includes second dielectric material particles. Based on the total mass of the main body region, the proportion of the second dielectric material particles is W2, and W1 ≥ W2.

21. The negative electrode tab according to claim 20, wherein, W2 is 0 - 10%.

22. The negative electrode sheet according to claim 20 or 21, wherein, Based on the total mass of the thinned region, the mass proportion of the first negative electrode active material is K1. The main body region includes a second negative electrode active material. Based on the total mass of the main body region, the mass proportion of the second negative electrode active material is K2, and K1 ≤ K2.

23. The negative electrode sheet according to claim 22, wherein, K1 is 90 - 97%.

24. The negative electrode sheet according to claim 22 or 23, wherein, K2 is 90 - 98%.

25. The negative electrode sheet according to any one of claims 22-24, wherein, At least 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 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.

26. The negative electrode sheet according to any one of claims 22-25, wherein, The first negative electrode active material and the second negative electrode active material each independently include at least one of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, or titanates.

27. A method for preparing a negative electrode sheet according to any one of claims 1-26, wherein, Comprising: Forming a negative electrode active material layer on at least one side of a negative electrode current collector. The negative electrode active material layer includes a thinned region, and the thinned region includes first dielectric material particles. The volume average particle diameter Dv50 of the first dielectric material particles is D1, where D1 is 400 nm - 2000 nm. Based on the total mass of the thinned region, the proportion of the first dielectric material particles is W1, and W1 is 0.5% - 10%.

28. A battery, wherein, Comprising the negative electrode tab according to any one of claims 1 - 26 or the negative electrode tab obtained by the method 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, Includes the battery according to claim 28 or 29.

Images