Quick-charging type lithium ion battery negative pole piece and preparation method thereof, lithium ion battery and electric equipment

Abstract

The invention relates to the technical field of lithium ion batteries, in particular to a negative pole piece of a fast-charging type lithium ion battery, a preparation method of the negative pole piece, the lithium ion battery and electric equipment. The negative pole piece of the quick-charge type lithium ion battery comprises a negative current collector with a tab, and a first active layer and a second active layer which are arranged on the surface of the negative current collector and are connected with each other; the first active layer is arranged on one side close to the tab, the second active layer is arranged on one side far away from the tab, and the fast charging capacity of the first active layer is greater than that of the second active layer. According to the lithium ion battery, the first active layer with better fast charging capacity is arranged on the side close to the tab, so that the problem that lithium is separated out from an interface close to the tab of the pole piece during charging due to non-uniform current density distribution of the pole piece caused by tab arrangement can be solved, the service life of the lithium ion battery is prolonged, and the safety performance of the lithium ion battery is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion batteries, and in particular, to a negative electrode sheet for a fast-charging lithium-ion battery, a preparation method thereof, a lithium-ion battery, and an electrical device. Background Art

[0002] Existing lithium-ion batteries are composed of a positive electrode, a negative electrode, a separator, and an electrolyte. Among them, the two electrodes play the role of storing and accepting lithium ions, namely a positive electrode composed of a positive electrode active material and an aluminum foil current collector, and a negative electrode composed of a negative electrode active material and a copper foil current collector. In the manufacturing process of the two electrode sheets, the electrode active material is generally uniformly coated on the current collector to obtain the electrode sheet. The active material parts in the X, Y, and Z directions of the electrode sheet are uniform, and their lithium deintercalation and intercalation capabilities are also the same. However, the performance of the electrode sheet does not necessarily show homogeneity during actual operation. The working principle of the electrode sheet generally starts with the transmission of current through the tab set on the electrode sheet. During charging, electrons are transmitted to the negative electrode sheet through the tab, which will cause the electrode sheet near the tab side to obtain electrons first and then transmit them to the side far from the tab. In this way, the side that obtains electrons first often needs to bear a greater current density, so that lithium ions are more likely to obtain electrons in this area to form lithium. When the active material on this side is not enough to accept so much lithium in a short time, lithium metal is likely to precipitate on the surface of the negative electrode, thus affecting the fast-charging use experience, the service life, and safety of the battery.

[0003] The prior art adopts the method of double-layer coating, setting different properties of active materials in the upper and lower layers to optimize the electrode performance. This method aims to solve the problem of the transmission and diffusion of lithium ions from the surface to the inside, but cannot solve the problem of lithium precipitation caused by uneven distribution of current density in different regions.

[0004] In view of this, the present invention is specifically proposed. Summary of the Invention

[0005] The first object of the present invention is to provide a negative electrode sheet for a fast-charging lithium-ion battery. By setting a first active layer with better fast-charging ability near the tab side, it can solve the problem of uneven current density distribution of the electrode sheet caused by the tab arrangement, thereby causing lithium precipitation at the interface near the tab during charging, and improving the service life and safety performance of the lithium-ion battery.

[0006] The second object of the present invention is to provide a method for preparing a negative electrode sheet of a fast-charging lithium-ion battery. By means of zoned coating, a first negative electrode slurry with strong high-power fast-charging ability is coated on the side close to the tab, and a second negative electrode slurry that meets the requirements of normal charging ability is arranged on the side far from the tab, so that the fast-charging ability of the first active layer is greater than that of the second active layer. Through the design of the charging ability of each region to adapt to the performance requirements of different regions of the electrode sheet, a reasonable design and utilization of the performance of the fast-charging negative electrode sheet can be achieved, and the problem of lithium deposition caused by a larger current on the tab side of the electrode sheet can be solved.

[0007] The third object of the present invention is to provide a lithium-ion battery with excellent cycle performance and good safety performance.

[0008] The fourth object of the present invention is to provide an electrical equipment.

[0009] In order to achieve the above objects of the present invention, the following technical solutions are specifically adopted:

[0010] The present invention first provides a negative electrode sheet of a fast-charging lithium-ion battery, which includes a negative electrode current collector with a tab, and a first active layer and a second active layer that are connected and arranged on the surface of the negative electrode current collector; wherein, the first active layer is arranged on the side close to the tab, the second active layer is arranged on the side far from the tab, and the fast-charging ability of the first active layer is greater than that of the second active layer.

[0011] Furthermore, the median particle size of the first negative electrode active material in the first active layer is smaller than the median particle size of the second negative electrode active material in the second active layer.

[0012] Furthermore, the median particle size of the second negative electrode active material is 9-16 μm;

[0013] Furthermore, the median particle size of the first negative electrode active material is 0.5-5 μm smaller than the median particle size of the second negative electrode active material.

[0014] Furthermore, the first negative electrode active material in the first active layer has a first carbon coating layer, and the percentage of the mass of the first carbon coating layer in the mass of the first negative electrode active material is C 1 ; the second negative electrode active material in the second active layer has a second carbon coating layer, and the percentage of the mass of the second carbon coating layer in the mass of the second negative electrode active material is C 2 ; the C 1 is greater than the C 2 .

[0015] Furthermore, the C 2 is 0-2%.

[0016] Furthermore, the C1 higher than the C 2 by 0.5% to 2%.

[0017] Furthermore, the mass fraction of the first conductive agent in the first active layer is greater than the mass fraction of the second conductive agent in the second active layer.

[0018] Furthermore, the mass fraction of the second conductive agent is 0.5% to 1%.

[0019] Furthermore, the mass fraction of the first conductive agent is 0.01% to 1% higher than the mass fraction of the second conductive agent.

[0020] Furthermore, the first negative electrode active material in the first active layer includes at least one of graphite, hard carbon, and soft carbon.

[0021] Furthermore, the second negative electrode active material in the second active layer includes one of graphite, hard carbon, and soft carbon.

[0022] Furthermore, the width of the first active layer is 5% to 30% of the total width of the negative electrode tab of the fast-charging lithium-ion battery along the current transmission direction.

[0023] The present invention further provides a method for preparing the negative electrode tab of the fast-charging lithium-ion battery, including the following steps: coating a first negative electrode slurry containing a first negative electrode active material and a second negative electrode slurry containing a second negative electrode active material on the surface of a negative electrode current collector having a tab, wherein the first negative electrode slurry is coated on the side close to the tab, and the second negative electrode slurry is coated on the side far from the tab, and then drying to form a first active layer and a second active layer with adjacent boundaries, obtaining the negative electrode tab of the fast-charging lithium-ion battery; wherein, the fast-charging ability of the first active layer is greater than that of the second active layer.

[0024] The present invention also provides a lithium-ion battery including the negative electrode tab of the fast-charging lithium-ion battery.

[0025] The present invention further provides an electrical device including the lithium-ion battery.

[0026] Compared with the prior art, the beneficial effects of the present invention are:

[0027] The fast-charging lithium-ion battery negative electrode sheet provided by the present invention has a first active layer with strong high-power fast-charging ability arranged near the tab side, and a second active layer that meets the requirements of normal charging ability arranged on the side far from the tab side. That is, by controlling the fast-charging ability of the first active layer to be greater than that of the second active layer, the performance of each area of the electrode sheet can be optimally utilized, solving the problem of uneven current density distribution on the electrode sheet caused by the arrangement of the tabs, which in turn causes lithium deposition at the interface near the tab of the electrode sheet during charging, and improving the service life and safety performance of the lithium-ion battery. Description of the Drawings

[0028] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0029] Figure 1 It is a top view of the fast-charging lithium-ion battery negative electrode sheet provided by the present invention;

[0030] Figure 2 It is a left view of the fast-charging lithium-ion battery negative electrode sheet provided by the present invention. Detailed Embodiments

[0031] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the drawings and specific embodiments. However, those skilled in the art will understand that the following described embodiments are some embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention. Those not specified in the embodiments are carried out under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments not specified by the manufacturer can all be obtained as conventional products through commercial purchase.

[0032] If there is no special description, in the present invention, "the first aspect", "the second aspect", "the third aspect", "the fourth aspect", etc. are only for descriptive purposes, and cannot be understood as indicating or implying relative importance or quantity, nor can they be understood as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "the first", "the second", "the third", "the fourth", etc. only serve the purpose of non-exhaustive list description and should be understood not to constitute a closed limitation on quantity.

[0033] Unless otherwise specified, the terms "comprising" and "including" mentioned in the present invention are open-ended and can also be closed-ended. For example, the terms "comprising" and "including" can mean that other components not listed can also be included or contained, or that only the listed components are included or contained.

[0034] Unless otherwise specified, in the present invention, "one or more" or "at least one" refers to any one, any two, or any two or more of the listed items. Among them, "several" refers to any two or more.

[0035] In a first aspect, the present invention provides a negative electrode sheet for a fast-charging lithium-ion battery, comprising a negative electrode current collector having a tab, and a first active layer and a second active layer which are in contact and arranged on the surface of the negative electrode current collector.

[0036] Figure 1 The figure shows a top view of the negative electrode sheet for a fast-charging lithium-ion battery provided by the present invention.

[0037] Figure 2 The figure shows a left view of the negative electrode sheet for a fast-charging lithium-ion battery provided by the present invention.

[0038] It can be understood that the first active layer and the second active layer are arranged in parallel, rather than in a stacked manner. Moreover, the first active layer and the second active layer are closely connected and their boundaries are in contact. That is to say, the negative electrode active layer on the surface of the negative electrode current collector includes two regions, namely the region corresponding to the first active layer and the region corresponding to the second active layer.

[0039] It can be understood that the first active layer and the second active layer are arranged on one side surface of the negative electrode current collector, or on two surface of the negative electrode current collector.

[0040] Among them, as shown in Figure 1 and Figure 2 the figure, the first active layer is arranged at one end close to the tab, the second active layer is arranged at one end far from the tab, and the fast-charging ability of the first active layer is greater than that of the second active layer.

[0041] Among them, the fast-charging ability refers to the ability to charge using a larger fast-charging rate that can be satisfied, that is, the charging rate is larger; generally speaking, the larger the charging rate, the larger the charging power will be.

[0042] That is, the maximum charging rate or charging power of the first active layer is greater than that of the second active layer.

[0043] Or rather, the fast-charging ability of the first negative electrode paste used to form the first active layer is superior to that of the second negative electrode paste used to form the second active layer.

[0044] The present invention designs a new type of negative electrode sheet for a lithium-ion battery suitable for fast charging to address the problem of lithium plating in the battery caused by uneven current in the electrode sheet. By providing a first active layer with strong fast charging ability near the tab side and a second active layer that meets the requirements of normal charging ability far from the tab side, that is, controlling the fast charging ability of the first active layer to be greater than that of the second active layer, the performance of each region of the electrode sheet can be optimally utilized, improving the service life and safety performance of the lithium-ion battery. It improves the problem of uneven current density distribution in the electrode sheet caused by the tab arrangement, which in turn causes lithium plating at the interface near the tab during charging, and solves the problem of easy failure of the negative electrode sheet of the lithium-ion battery due to uneven current distribution.

[0045] In some specific embodiments, the main components of the first active layer and the second active layer include a negative electrode active material, a binder, and a conductive agent, and the types of the negative electrode active material, the binder, and the conductive agent in the first active layer and the second active layer may be the same or different. Among them, any negative electrode material commonly used in the art can be used as the negative electrode active material, any binding material commonly used in the art can be used as the binder, and any conductive material commonly used in the art can be used as the conductive agent, and the present invention does not limit this.

[0046] In some specific embodiments, the median particle size of the first negative electrode active material in the first active layer is smaller than the median particle size of the second negative electrode active material in the second active layer. This can shorten the lithium ion diffusion path, thereby ensuring that the fast charging ability of the first active layer is greater than that of the second active layer.

[0047] In some specific embodiments, the median particle size of the second negative electrode active material is 9 - 16 μm, such as 10 μm, 12 μm, 13 μm, or 15 μm.

[0048] In some specific embodiments, the median particle size of the first negative electrode active material is 0.5 - 5 μm smaller than the median particle size of the second negative electrode active material, that is, the difference between the median particle sizes of the second negative electrode active material and the first negative electrode active material is 0.5 - 5 μm, such as 1 μm, 2 μm, 3 μm, or 4 μm.

[0049] In some specific embodiments, the first negative electrode active material in the first active layer has a first carbon coating layer, and the percentage of the mass of the first carbon coating layer in the mass of the first negative electrode active material is C 1 ; the second negative electrode active material in the second active layer has a second carbon coating layer, and the percentage of the mass of the second carbon coating layer in the mass of the second negative electrode active material is C 2 ; the C 1 is greater than the C 2 . This can increase the lithium intercalation channels, thereby ensuring that the fast charging ability of the first active layer is greater than that of the second active layer.

[0050] In some specific embodiments, the C 2 is 0 to 2%, such as 0.01%, 0.1%, 0.5%, 1% or 1.5%.

[0051] In some specific embodiments, the C 1 is 0.5% to 2% higher than the C 2 , that is, C 1 - C 2 = 0.5% to 2%, such as 0.8%, 1%, 1.2%, 1.5% or 1.8%.

[0052] In some specific embodiments, the mass fraction of the first conductive agent in the first active layer is greater than the mass fraction of the second conductive agent in the second active layer. This can improve the electrode conductivity, and further ensure that the fast charging ability of the first active layer is greater than that of the second active layer.

[0053] In some specific embodiments, the mass fraction of the second conductive agent is 0.5% to 1%, such as 0.6%, 0.7%, 0.8% or 0.9%.

[0054] In some specific embodiments, the mass fraction of the first conductive agent is 0.01% to 1% higher than the mass fraction of the second conductive agent, that is, the difference between the mass percentage content of the first conductive agent and the mass percentage content of the second conductive agent is 0.01% to 1%, such as 0.1%, 0.3%, 0.5% or 0.8%.

[0055] In some specific embodiments, the first negative electrode active material in the first active layer includes at least one of graphite, hard carbon and soft carbon, preferably at least two, and more preferably at least three.

[0056] In some specific embodiments, the outer surface of the graphite has a carbon coating layer.

[0057] In some specific embodiments, the second negative electrode active material in the second active layer includes one of graphite, hard carbon and soft carbon.

[0058] That is, the first negative electrode active material in the first active layer is one or more, preferably more than three, while the second negative electrode active material in the second active layer is one, which can further optimize the problem of current transmission in the electrode sheet, ensure that the fast charging ability of the first active layer is greater than that of the second active layer, and avoid the problem of lithium plating.

[0059] In some specific embodiments, the median particle size of the first negative electrode active material can be reduced, the proportion of the first carbon coating layer of the first negative electrode active material can be increased, the proportion of the first conductive agent can be increased, and a variety of first negative electrode active materials can be used simultaneously to improve the fast charging ability of the first active layer; alternatively, one of these methods can be selected to improve the fast charging ability of the first active layer.

[0060] In some specific embodiments, the areal density of the first active layer is the same as that of the second active layer. The width of the first active layer is 5% to 30% of the total width of the negative electrode tab of the fast charging lithium-ion battery along the current transmission direction, such as 10%, 15%, 20%, or 25%.

[0061] In a second aspect, the present invention provides a method for preparing a negative electrode tab of a fast charging lithium-ion battery, comprising the following steps:

[0062] Coat a first negative electrode slurry containing a first negative electrode active material and a second negative electrode slurry containing a second negative electrode active material on the surface of a negative electrode current collector having a tab, respectively. Among them, the first negative electrode slurry and the second negative electrode slurry have different kinetic properties. The first negative electrode slurry is coated on the side close to the tab, and the second negative electrode slurry is coated on the side far from the tab, and the coating areas of the first negative electrode slurry and the second negative electrode slurry are connected.

[0063] After the coating is completed, dry it to form a first active layer and a second active layer with connected boundaries, and obtain the negative electrode tab of the fast charging lithium-ion battery.

[0064] Among them, the fast charging ability of the first active layer is greater than that of the second active layer.

[0065] The present invention coats a first negative electrode slurry with strong high-power fast charging ability on the side close to the tab and sets a second negative electrode slurry that meets the requirements of normal charging ability on the side far from the tab by means of partition coating, so that the fast charging ability of the first active layer is greater than that of the second active layer. By designing the charging ability of each area to adapt to the performance requirements of different areas of the electrode tab, a reasonable design and utilization of the performance of the fast charging negative electrode tab can be achieved, which can improve the cycle and safety performance of the lithium-ion battery. This method can solve the problem of lithium deposition caused by the larger current on the tab side of the electrode tab, and this method is applicable to all types of lithium-ion batteries.

[0066] In some specific embodiments, the first negative electrode slurry mainly consists of a first negative electrode active material, a first conductive agent, a first binder, and a solvent.

[0067] In some specific embodiments, the second negative electrode slurry mainly consists of a second negative electrode active material, a second conductive agent, a second binder, and a solvent.

[0068] In a third aspect, the present invention provides a lithium-ion battery including the above-mentioned fast-charging lithium-ion battery negative electrode sheet.

[0069] The lithium-ion battery has good cycle performance and high safety performance.

[0070] In some specific embodiments, the lithium-ion battery further includes a positive electrode sheet, a separator, and an electrolyte.

[0071] In a fourth aspect, the present invention provides an electrical device including the above-mentioned lithium-ion battery.

[0072] Among them, the electrical device includes any device or equipment containing the above-mentioned lithium-ion battery, such as electric vehicles, electric motorcycles, electric bicycles, electric tools, starting power supplies, energy storage systems, electronic products, office equipment, etc., but not limited thereto.

[0073] Hereinafter, the embodiments of the present invention will be described in detail in conjunction with the examples. However, those skilled in the art will understand that the following examples are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention. For those not specified in the examples, they are carried out under conventional conditions or conditions recommended by the manufacturer. For reagents or instruments not specified in the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0074] Example 1

[0075] The preparation method of the fast-charging lithium-ion battery negative electrode sheet provided in this example includes the following steps:

[0076] The first negative electrode active material is graphite with a carbon coating layer and a median particle size of 10 μm, and the carbon coating amount on its surface (i.e., C 1 ) is 2%; the conductive agent is SP and CNTS; the binder is SBR (styrene-butadiene rubber) and CMC (carboxymethyl cellulose); among them, the ratio of graphite with a carbon coating layer, SP, CNTS, SBR, and CMC is 96%, 0.8%, 0.2%, 2%, and 1% by mass percentage. The graphite with a carbon coating layer, SP, CNTS, SBR, and CMC with the above ratio are mixed evenly with deionized water to obtain the first negative electrode slurry, and the first negative electrode slurry is coated on one side near the tab on both surfaces of the negative electrode current collector (i.e., double-sided coating), and then dried to form the first active layer, and its electrode charging capacity can maximally meet the 4C rate.

[0077] The second negative electrode active material is graphite with a carbon coating layer and a median particle size of 12 μm, and the carbon coating amount on its surface (i.e., C 2) is 1%; the conductive agent is SP; the binder is SBR (styrene-butadiene rubber) and CMC (carboxymethyl cellulose); among them, the ratio of graphite with a carbon coating layer, SP, SBR, and CMC is 96%, 1%, 2%, and 1% by mass percentage. After mixing the graphite with a carbon coating layer, SP, SBR, and CMC in this ratio evenly with deionized water, a second negative electrode slurry is obtained, and the second negative electrode slurry is coated on one side of the negative electrode current collector surface away from the tab, and then dried to form a second active layer, whose electrode charging capacity can maximally meet the 3C rate. Among them, the second active layer is closely connected to and bordered with the first active layer. The areal density of the second active layer is the same as that of the first active layer, and the width of the first active layer is 15% of the total width of the fast-charging type lithium-ion battery negative electrode along the current transmission direction. The fast-charging capacity of the first active layer is greater than that of the second active layer.

[0078] Example 2

[0079] The preparation method of the fast-charging type lithium-ion battery negative electrode provided in this example is basically the same as that in Example 1, except that: the median particle size of the first negative electrode active material (graphite with a carbon coating layer) is replaced with 7 μm.

[0080] Example 3

[0081] The preparation method of the fast-charging type lithium-ion battery negative electrode provided in this example is basically the same as that in Example 2, except that: the carbon coating amount of the first negative electrode active material (graphite with a carbon coating layer) (i.e., C 1 ) is replaced with 3%.

[0082] Example 4

[0083] The preparation method of the fast-charging type lithium-ion battery negative electrode provided in this example is basically the same as that in Example 3, except that: the ratio of graphite with a carbon coating layer, SP, CNTS, SBR, and CMC in the first negative electrode slurry is replaced with 95%, 1.6%, 0.4%, 2%, and 1% (by mass percentage).

[0084] Example 5

[0085] The preparation method of the fast-charging type lithium-ion battery negative electrode provided in this example is basically the same as that in Example 4, except that: the first negative electrode active material is graphite with a carbon coating layer, hard carbon, and soft carbon with a mass ratio of 2:1:1 (the percentage of the first negative electrode active material remains unchanged, still 96%).

[0086] Example 6

[0087] The preparation method of the fast - charging lithium - ion battery negative electrode sheet provided in this embodiment is basically the same as that in Embodiment 1, except that the width of the first active layer is 25% of the total width of the fast - charging lithium - ion battery negative electrode sheet along the current transmission direction.

[0088] Comparative Example 1

[0089] Using the second negative electrode slurry prepared in Embodiment 1, the second negative electrode slurry was coated on the surface of the negative electrode current collector (with the same areal density as in Embodiment 1), and then dried to obtain a negative electrode sheet, whose electrode charging ability can satisfy a maximum of 3C rate.

[0090] Comparative Example 2

[0091] The preparation method of the fast - charging lithium - ion battery negative electrode sheet provided in this comparative example is basically the same as that in Embodiment 1, except that the first negative electrode slurry was coated on the side of the negative electrode current collector surface far from the tab, and the second negative electrode slurry was coated on the side of the negative electrode current collector surface close to the tab.

[0092] Experimental Example

[0093] The negative electrode sheets prepared in each embodiment and each comparative example were respectively assembled with the positive electrode sheet, separator, and electrolyte into lithium - ion batteries, and each lithium - ion battery was subjected to a cycle test of 1000 cls by the method of charging at 25°C, 3C, and discharging at 1C. The test results are shown in Table 1.

[0094] Table 1 Cycle test results of each battery

[0095]

[0096]

[0097] Among them, the larger the value of the negative electrode vs. lithium potential, the better the fast - charging ability.

[0098] It can be seen from Table 1 that compared with Comparative Example 1 and Comparative Example 2, the lithium - ion batteries prepared from the negative electrode sheets of each embodiment have better cycle performance and no lithium - plating problem.

[0099] It can be seen that by setting the first active layer with better fast - charging ability on the side close to the tab in the present invention, the problem of uneven current density distribution of the electrode sheet caused by the tab arrangement, which in turn causes lithium - plating at the interface near the tab of the electrode sheet during charging, can be solved, and the service life and safety performance of the lithium - ion battery can be improved.

[0100] Although the present invention has been illustrated and described with reference to specific embodiments, it should be understood that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it; those of ordinary skill in the art should understand that: without departing from the spirit and scope of the present invention, the technical solutions described in the foregoing embodiments may be modified, or some or all of the technical features may be equivalently replaced; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention; therefore, this means that all such replacements and modifications that fall within the scope of the present invention are included in the appended claims.

Claims

1. A fast-chargeable lithium-ion battery negative electrode plate, characterized in that: The invention comprises a negative electrode current collector having a tab, and a first active layer and a second active layer connected to each other and arranged on the surface of the negative electrode current collector; The first active layer is arranged on a side close to the pole ear, and the second active layer is arranged on a side away from the pole ear. The fast charging capability of the first active layer is greater than the fast charging capability of the second active layer.

2. The fast-chargeable lithium-ion battery negative electrode according to claim 1, characterized in that: The median particle size of the first negative electrode active material in the first active layer is smaller than the median particle size of the second negative electrode active material in the second active layer; Preferably, the median particle size of the second negative electrode active material is 9 to 16 μm; Preferably, the median particle size of the first negative electrode active material is 0.5 to 5 μm smaller than the median particle size of the second negative electrode active material.

3. The fast-chargeable lithium-ion battery negative electrode according to claim 1, characterized in that: The first negative electrode active material in the first active layer has a first carbon coating layer, and the mass of the first carbon coating layer accounts for a percentage of the mass of the first negative electrode active material of C1; the second negative electrode active material in the second active layer has a second carbon coating layer, and the mass of the second carbon coating layer accounts for a percentage of the mass of the second negative electrode active material of C2; C1 is greater than C2; Preferably, the C2 is 0-2%; Preferably, the C1 is 0.5% to 2% higher than the C2.

4. The fast-chargeable lithium-ion battery negative electrode according to claim 1, characterized in that: The mass fraction of the first conductive agent in the first active layer is greater than the mass fraction of the second conductive agent in the second active layer; Preferably, the mass fraction of the second conductive agent is 0.5% to 1%; Preferably, the mass fraction of the first conductive agent is 0.01% to 1% higher than the mass fraction of the second conductive agent.

5. The fast-chargeable lithium-ion battery negative electrode according to claim 1, characterized in that: The first negative electrode active material in the first active layer includes at least one of graphite, hard carbon and soft carbon.

6. The negative electrode plate of a fast-chargeable lithium-ion battery according to claim 5, characterized in that: The second negative electrode active material in the second active layer includes one of graphite, hard carbon and soft carbon.

7. The fast-chargeable lithium-ion battery negative electrode according to claim 1, characterized in that: The width of the first active layer is 5% to 30% of the total width of the negative electrode plate of the fast-chargeable lithium-ion battery along the current transmission direction.

8. The method for preparing a negative electrode sheet for a fast-chargeable lithium-ion battery according to any one of claims 1 to 7, characterized in that: The steps include: The first negative electrode slurry containing the first negative electrode active material and the second negative electrode slurry containing the second negative electrode active material are respectively coated on the surface of the negative electrode current collector having the tab, wherein the first negative electrode slurry is coated on the side close to the tab, and the second negative electrode slurry is coated on the side away from the tab, and then dried to form a first active layer and a second active layer with their boundaries connected, thereby obtaining the negative electrode sheet of the fast-charging lithium-ion battery; The fast charging capability of the first active layer is greater than the fast charging capability of the second active layer.

9. A lithium ion battery, characterized in that: It comprises a negative electrode plate of a fast-charging lithium-ion battery as claimed in any one of claims 1 to 7.

10. An electrical device, characterized in that: Comprising the lithium ion battery as claimed in claim 9.

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