Pole piece and spraying device

Abstract

The utility model discloses a pole piece which comprises a current collector, an active substance layer and a functional layer, the active substance layer is arranged on the surface of the current collector, the functional layer is arranged on the surface of the active substance layer, and the functional layer has wettability and is beneficial to electrolyte infiltration; the pole piece has a width direction, and along the width direction of the pole piece, the surface density of the middle part of the functional layer is greater than that of the two sides of the functional layer. The utility model solves the problem that the electrolyte in the middle of the pole piece is infiltrated slowly, and improves the speed of infiltrating the pole piece by the electrolyte. The utility model further discloses a spraying device.

Description

Technical Field

[0001] The utility model relates to the technical field of batteries, in particular to an electrode sheet and a spraying device. Background Art

[0002] For electrolytes with high viscosity or easily variable viscosity, such as the precursor liquid of in-situ solidified electrolyte, before solidification, both temperature and time have an impact on its viscosity. The viscosity of the precursor liquid will increase with the extension of time and with the increase of temperature. The increase in viscosity is not conducive to the infiltration of the electrolyte inside the battery cell, and the closer to the middle area of the battery cell, the more difficult the infiltration becomes over time. If the infiltration is insufficient or solidification occurs prematurely under the condition of insufficient infiltration, it will affect the performance of the battery cell. Therefore, for electrolytes with high viscosity or easily variable viscosity, it is particularly important to design an electrode sheet that can enable the electrolyte to infiltrate quickly. Summary of the Utility Model

[0003] In order to overcome the deficiencies in the prior art, the purpose of the utility model is to provide an electrode sheet and a spraying device, which solve the problem of slow infiltration in the middle part of the electrode sheet and improve the infiltration speed of the electrolyte into the electrode sheet.

[0004] The purpose of the utility model is achieved by the following technical solutions:

[0005] An electrode sheet includes a current collector, an active material layer, and a functional layer. The active material layer is disposed on the surface of the current collector, and the functional layer is disposed on the surface of the active material layer. The functional layer has wettability assistance, which is conducive to the infiltration of the electrolyte. The electrode sheet has a width direction. Along the width direction of the electrode sheet, the areal density of the middle part of the functional layer is greater than that of its two sides.

[0006] In one embodiment, along the width direction of the electrode sheet, the areal density of the functional layer decreases from the middle to both sides.

[0007] In one embodiment, along the width direction of the electrode sheet, the functional layer includes at least three sub-functional layers arranged adjacent to each other in sequence, including a second sub-functional layer located in the middle and a first sub-functional layer and a third sub-functional layer located on both sides.

[0008] In one embodiment, the areal density of the first sub-functional layer and / or the areal density of the third sub-functional layer is 10%-90% of the areal density of the second sub-functional layer.

[0009] In one embodiment, the width of the second sub-functional layer is W1, and the width of the electrode sheet is W3, where 1 / 10 ≤ W1 / W3 ≤ 9 / 10.

[0010] In one embodiment, a transition layer is provided between adjacent sub-functional layers, and the areal density of the transition layer is between the areal densities of the adjacent sub-functional layers.

[0011] In one embodiment, the width of the second sub-functional layer is W1, the width of the transition layer is W2, and the width of the electrode tab is W3, where 1 / 10 ≤ W1 / W3 ≤ 1 / 2 and 1 / 10 ≤ W2 / W1 ≤ 1.

[0012] In one embodiment, the thickness of the functional layer is 1 - 10 μm.

[0013] In one embodiment, the functional layer is an acrylate copolymer coating, a carbonate coating, a sulfate coating, or a phosphate coating.

[0014] In one embodiment, the functional layer is provided on the electrode tab by spraying, coating, printing, or transfer printing.

[0015] The present utility model further provides a spraying device for preparing the electrode tab as described above.

[0016] In one embodiment, the spraying device includes a nozzle, the nozzle is flat, and the width of the nozzle matches the width of the electrode tab.

[0017] In one embodiment, the nozzle includes a liquid outlet, the nozzle has a thickness direction and a width direction, and along the width direction of the nozzle, the dimension of the middle part of the liquid outlet in the thickness direction is greater than the dimensions of its two sides in the thickness direction;

[0018] Alternatively, the nozzle includes a plurality of liquid outlets, and along the width direction of the nozzle, the dimension of the liquid outlet located in the middle is greater than the dimensions of the liquid outlets located on both sides.

[0019] In one embodiment, the spraying device further includes a storage tank, a compressor, and a spraying device. The storage tank is used for storing liquid materials, and the storage tank, the compressor, and the nozzle are all connected to the spraying device; the spraying device introduces the liquid materials in the storage tank through the compressor and then sprays the liquid materials through the nozzle to form the functional layer.

[0020] In one embodiment, the spraying device is an atomizing device, and the atomizing device introduces the liquid materials in the storage tank through the compressor, atomizes them, and sprays the atomized materials through the nozzle to form the functional layer.

[0021] The beneficial effects of the present utility model are as follows: A functional layer with enhanced wettability is provided on the electrode sheet, and in the width direction of the electrode sheet, the areal density in the middle of the functional layer is greater than that on both sides, that is, the areal density in the middle of the functional layer is larger. Utilizing the areal density difference, after injecting the electrolyte, the electrolyte can quickly wet the electrode sheet, solving the problem that when the electrolyte with a relatively high viscosity or an easily variable viscosity is being wetted, the wetting of the middle part of the electrode sheet is slow, difficult, or even incomplete wetting cannot be achieved. This ensures good wetting in the middle region, reduces or eliminates the subsequent process of further improving wetting, and shortens the wetting cycle. The middle part of the electrode sheet in this application does not specifically refer to the central part of the electrode sheet. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present utility model, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present utility model and should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other relevant drawings can also be obtained based on these drawings.

[0023] Figure 1 is a schematic structural diagram of the electrode sheet of the present utility model;

[0024] Figure 2 is a plan view of the electrode sheet of an embodiment of the present utility model;

[0025] Figure 3 is a plan view of the electrode sheet of another embodiment of the present utility model;

[0026] Figure 4 is a schematic structural diagram of the spraying device of the present utility model;

[0027] Figure 5 is a schematic structural diagram of the nozzle of an embodiment of the present utility model;

[0028] Figure 6 is a schematic structural diagram of the nozzle of another embodiment of the present utility model;

[0029] Figure 7 is a schematic structural diagram of the nozzle of another embodiment of the present utility model;

[0030] Figure 8 is a schematic cross-sectional view of the nozzle of another embodiment of the present utility model.

[0031] In the figure: 100, electrode; 11, current collector; 12, active material layer; 13, functional layer; 131, first sub-functional layer; 132, second sub-functional layer; 133, third sub-functional layer; 134, transition layer; 2, storage tank; 3, compressor; 4, ejection device; 5, nozzle; 51, liquid outlet; 6, sealed housing; 61, gas filtration device; 7, collection box; 8, baking device; 91, conveyor roller; 92, rolling roller. Detailed implementation manners

[0032] The following will describe in detail specific embodiments of the present utility model in conjunction with the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present utility model, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the description of the present utility model without creative efforts shall fall within the scope of protection of the present utility model.

[0033] In the description of the present utility model, unless otherwise clearly defined and limited, terms such as "set", "installed", "connected", etc. shall be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected, or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to specific circumstances.

[0034] The orientation or positional relationship indicated by terms such as "upper", "lower", "left", "right", "front", "rear", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of the present utility model is usually placed during use. It is only for the convenience of description and simplification of the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present utility model.

[0035] Terms such as "first", "second", "third", etc. are only used to distinguish elements with similar attributes, rather than indicating or implying relative importance or a specific order.

[0036] The term "comprises", "comprising" or any other variant thereof is intended to cover a non-exclusive inclusion. In addition to the elements listed, it may also include other elements not specifically listed.

[0037] The present utility model provides an electrode 100, such as Figure 1 and Figure 2As shown in the figure, it includes a current collector 11, an active material layer 12, and a functional layer 13. The active material layer 12 is disposed on the surface of the current collector 11, and the functional layer 13 is disposed on the surface of the active material layer 12. The functional layer 13 has wettability assistance, which is conducive to the infiltration of the electrolyte; the electrode sheet 100 has a width direction W. Along the width direction W of the electrode sheet 100, the areal density of the middle part of the functional layer 13 is greater than that of its two sides. In this embodiment, the active material layer 12 and the functional layer 13 are sequentially coated on the surface of the current collector 11, and the functional layer 13 has wettability assistance. Along the width direction W of the electrode sheet 100, the areal density of the middle part of the functional layer 13 is greater than that of its two sides, that is, the areal density of the middle part of the functional layer 13 is larger. By using the areal density difference, the electrolyte can quickly infiltrate the electrode sheet 100 after injecting the liquid, solving the problem that when the electrolyte with a large viscosity or an easily variable viscosity infiltrates, the infiltration of the middle part of the electrode sheet 100 is slow, difficult, or even cannot be completely infiltrated, ensuring that the area that is difficult to infiltrate in the middle is well infiltrated, reducing or eliminating the subsequent process of further improving infiltration, and shortening the infiltration cycle. Among them, the middle part of the electrode sheet in this application does not specifically refer to the central part of the electrode sheet.

[0038] As an implementation manner, along the width direction W of the electrode sheet 100, the areal density of the functional layer 13 decreases from the middle to both sides, that is, the areal density of the middle part of the functional layer 13 is large. During the process of the electrolyte quickly infiltrating the electrode sheet 100, it is ensured that the area that is difficult to infiltrate in the middle of the electrode sheet 100 is well infiltrated.

[0039] As an implementation manner, as Figure 2 shown, along the width direction W of the electrode sheet 100, the functional layer 13 includes at least three sub-functional layers arranged adjacent to each other in sequence, including a second sub-functional layer 132 in the middle and first sub-functional layers 131 and third sub-functional layers 133 on both sides.

[0040] As an implementation manner, the areal density of the first sub-functional layer 131 and / or the areal density of the third sub-functional layer 133 is 10%-90%, or 20%-80%, or 25%-75%, or 30%-70%, or 35%-65%, or 40%-60% of the areal density of the second sub-functional layer 132.

[0041] As an implementation manner, as Figure 2 shown, the width of the second sub-functional layer 132 is W1, and the width of the electrode sheet 100 is W3. Among them, 1 / 10 ≤ W1 / W3 ≤ 9 / 10, or 1 / 5 ≤ W1 / W3 ≤ 4 / 5, or 3 / 10 ≤ W1 / W3 ≤ 7 / 10, or 2 / 5 ≤ W1 / W3 ≤ 3 / 5.

[0042] As an implementation manner, as Figure 3As shown, a transition layer 134 is provided between adjacent sub-functional layers, and the areal density of the transition layer 134 is between the areal densities of the adjacent sub-functional layers. If there are multiple transition layers 134, the areal densities of the transition layers 134 are not necessarily the same, that is, the transition layers 134 adjacent to the second sub-functional layer 132 (on both sides in the width direction of the second sub-functional layer 132) can have different areal densities.

[0043] As an implementation manner, as Figure 3 shown, the width of the second sub-functional layer 132 is W1, the width of the transition layer 134 is W2, and the width of the electrode tab 100 is W3, where 1 / 10 ≤ W1 / W3 ≤ 1 / 2, or 1 / 5 ≤ W1 / W3 ≤ 2 / 5; where 1 / 10 ≤ W2 / W1 ≤ 1, or 1 / 5 ≤ W2 / W1 ≤ 9 / 10, or 3 / 10 ≤ W2 / W1 ≤ 4 / 5.

[0044] As an implementation manner, the thickness of the functional layer 13 is 1 - 10 μm, or 2 - 9 μm, or 3 - 8 μm, or 4 - 7 μm.

[0045] As an implementation manner, the functional layer 13 is an acrylate copolymer coating, a carbonate coating, a sulfate coating, or a phosphate coating.

[0046] As an implementation manner, the functional layer 13 is disposed on the electrode tab 100 by spraying, coating, printing, or transfer printing.

[0047] The present utility model further provides a spraying device for preparing the above-mentioned electrode tab 100. This device can be conveniently installed on the existing coating equipment process, is easy to operate, and has high compatibility. When the spraying device sprays the electrode tab 100, an electrode tab 100 with an areal density in the middle of the above-mentioned functional layer 13 being greater than the areal densities on both sides thereof can be obtained.

[0048] As an implementation manner, as Figure 5 shown, the spraying device includes a nozzle 5, the nozzle 5 can be set to be flat, and the width of the nozzle 5 matches the width of the electrode tab 100. So that the width of the material sprayed by the nozzle 5 matches the width of the electrode tab 100, improving the atomization spraying efficiency.

[0049] As an implementation manner, as Figure 6 and Figure 7 shown, the nozzle 5 includes a liquid outlet 51, the nozzle 5 has a thickness direction D0 and a width direction W0, along the width direction W0 of the nozzle 5, the size of the middle part of the liquid outlet 51 in the thickness direction D0 is greater than the sizes of both sides thereof in the thickness direction D0; for example, the liquid outlet 51 can be set to be olive-shaped (as Figure 6 shown) or crescent arc-shaped (as Figure 7As shown, the middle part of the liquid outlet 51 has a convex arc, which is beneficial for more material to be ejected from the middle part and less material to be ejected from both sides. Or, as Figure 8 shown, the nozzle 5 includes a plurality of liquid outlets 51. Along the width direction W0 of the nozzle 5, the size of the liquid outlet 51 located in the middle is larger than that of the liquid outlets 51 located on both sides, which is beneficial for more material to be ejected from the middle part and less material to be ejected from both sides, forming a functional layer 13 with a large surface density in the middle and a small surface density on both sides in the width direction W of the electrode sheet 100. Of course, the spraying device can also control the atomizing ejection flow through a control system (not shown). There are a plurality of pipes (not shown) in the nozzle 5, and the control system controls the flow rate into different pipes, so that the flow rate of the pipes located in the middle of the nozzle 5 is greater than that of the pipes located on both sides of the nozzle 5, so that more material (i.e., surface density) is sprayed in the middle part of the electrode sheet 100 in the width direction W, and less on both sides (i.e., surface density), solving the problem that the middle part of the original electrode sheet 100 is slowly infiltrated.

[0050] As an implementation manner, as Figure 4 shown, the spraying device further includes a storage tank 2, a compressor 3 and an ejection device 4. The storage tank 2 is used to store the liquid material. The storage tank 2, the compressor 3 and the nozzle 5 are all connected to the ejection device 4; the ejection device 4 introduces the liquid material in the storage tank 2 through the compressor 3, and then sprays the liquid material through the nozzle 5 to form the functional layer 13.

[0051] As an implementation manner, the ejection device 4 is an atomizing device. The atomizing device introduces and atomizes the liquid material in the storage tank 2 through the compressor 3, and sprays the atomized material through the nozzle 5 to form the functional layer 13; by setting the atomizing device, a more uniform and thinner functional layer 13 is formed during spraying.

[0052] As an implementation manner, as Figure 4 shown, the spraying device further includes a sealed housing 6. The sealed housing 6 surrounds the nozzle 5 and the electrode sheet 100 to be sprayed, preventing the atomized droplets from affecting the surrounding environment and ensuring the safety of the operator.

[0053] As an implementation manner, as Figure 4 shown, the spraying device further includes a gas filtering device 61. The gas filtering device 61 is installed at the bottom of the sealed housing 6. The inside of the sealed housing 6 is communicated with the outside through the gas filtering device 61, so that a relatively stable pressure is maintained inside the sealed housing 6.

[0054] As an implementation manner, as Figure 4 shown, the spraying device further includes a collection box 7. The collection box 7 is connected to the gas filtering device 61. During the atomizing spraying process of the material, the excess droplets carried converge on the gas filtering device 61 and then converge in the collection box 7 to avoid the influence of the droplets on the surrounding environment.

[0055] The use of the spraying device is as follows Figure 4 As shown, the spraying device performs a spraying operation on the moving electrode sheet 100. The conveying roller 91 is used to convey the electrode sheet 100, so that the electrode sheet 100 continuously passes through the spraying area of the nozzle 5, enabling the nozzle 5 to continuously spray the atomized material on the electrode sheet 100, and then forming a functional layer 13 on the entire surface of the electrode sheet 100.

[0056] As Figure 4 shown, along the conveying direction S of the electrode sheet 100, there is also a baking device 8. The baking device 8 is arranged downstream of the sealed housing 6 and is used to heat-treat the electrode sheet 100 after spraying, so that the material can be quickly dried to form a stable functional layer 13.

[0057] As Figure 4 shown, along the conveying direction S of the electrode sheet 100, there is also a rolling roller 92. The rolling roller 92 is installed downstream of the baking device 8. The rolling roller 92 is used to roll the baked electrode sheet 100 to tightly press the functional layer 13, the active material layer 12, and the current collector 11 together to improve the spraying effect. Among them, the number of rolling rollers 92 is two. The two rolling rollers 92 are arranged in parallel and rotate towards each other. The electrode sheet 100 passes through between the two rolling rollers 92, and the two rolling rollers 92 can simultaneously roll the electrode sheet 100 to ensure that the functional layer 13 is tightly attached to the active material layer 12.

[0058] Specifically, the spraying device includes a storage tank 2, a compressor 3, an atomizing device, and a nozzle 5. The atomizing device atomizes the liquid material in the storage tank 2 through the compressor 3 and sprays the atomized material through the nozzle 5 to form a functional layer 13. The spraying device also includes a sealed housing 6 to prevent the atomized droplets from affecting the surrounding environment and ensure the safety of the operators. At the same time, a gas filtering device 61 is equipped at the bottom of the sealed housing 6 to maintain a relatively stable pressure in the sealed cavity. As the gas is released, the excess droplets converge into the collection box 7. After the electrode sheet 100 is sprayed, it needs to be baked to remove the solvent on the surface of the electrode sheet 100. Finally, the rolling of the surface of the electrode sheet 100 is completed, and then it enters the subsequent process to finally complete the production of the battery cell.

[0059] The beneficial effects of the present utility model are as follows:

[0060] 1. Due to the electrolyte-friendly property of the functional layer 13, and in the width direction W of the electrode sheet 100, the areal density in the middle of the functional layer 13 is greater. After injecting the electrolyte, it can quickly wet the electrolyte, reducing the subsequent process of further improving wetting and shortening the wetting cycle.

[0061] 2. The spraying device is convenient to be installed on the existing coating equipment process, with simple operation and high compatibility.

[0062] The present utility model also provides a method for preparing an electrode sheet, comprising the following steps:

[0063] S1. Provide an electrode sheet 100 coated with an active material layer 12;

[0064] S2. Inject the material of the functional layer 13 into the storage tank 2 of the spraying device, atomize the material using the spraying device and spray it out through a flat nozzle to obtain an electrode sheet 100 with a surface density in the middle of the above functional layer 13 greater than that on both sides.

[0065] Example 1:

[0066] Prepare a positive electrode active paste by mixing a positive ternary nickel-cobalt-manganese active material, a conductive agent carbon black, and a binder polyvinylidene fluoride in a mass ratio of 97:2:1 with a solvent N-methylpyrrolidone (NMP), and coat it on an aluminum foil to make a positive electrode sheet;

[0067] Prepare a negative electrode active paste by mixing a negative electrode graphite active material, a conductive agent carbon black, and a binder styrene-butadiene rubber in a mass ratio of 96:2:2 with a solvent N-methylpyrrolidone (NMP), and coat it on a copper foil to make a negative electrode sheet;

[0068] Dissolve an acrylate copolymer in N-methylpyrrolidone (NMP) to prepare a wetting aid solution with a mass fraction of 5%; transfer the wetting aid solution to the storage tank 2 of the spraying device, adjust the control system, and set the discharge intensity of the atomizing nozzle so that the discharge flow rate at the middle position of the nozzle 5 is 20% greater than that at both sides.

[0069] Pass the above positive electrode sheet and negative electrode sheet through the spraying device at a constant speed respectively. The spraying device sprays the wetting aid paste on the surface of the electrode sheet, and then bake and roll the electrode sheet to obtain a positive electrode sheet and a negative electrode sheet with the wetting aid attached to the surface. In the width direction of the positive electrode sheet and the negative electrode sheet, the surface density at the middle part is 20% greater than that at both sides of the electrode sheet. Assemble the above electrode sheets with a separator to form a 50Ah bare electric core.

[0070] Comparative Example 1:

[0071] Adjust the control system of the spraying device, set the discharge intensity of the atomizing nozzle to the same intensity, and the other steps are the same as those in Example 1. The surface density at the middle of the obtained electrode sheet is the same as that at both sides of the electrode sheet.

[0072] The internal resistance test and capacity test were carried out on Example 1 and Comparative Example 1: Ethylene glycol dicyclopentenyl ether acrylate, acrylamide, polyethylene glycol dimethacrylate, azobisisobutyronitrile, and electrolyte (EC / EMC / DEC = 1:1:1, 1M LiPF6) were uniformly mixed in a ratio of 7:21:14:0.4:93 to obtain a precursor solution. Then, the precursor solution was injected into the bare battery cell and placed at room temperature of 25°C for infiltration. The first alternating current internal resistance test was carried out after 12 h, and then the alternating current internal resistance test was carried out every 4 h. After 24 h, the temperature was raised to 45°C and cured for 12 h, and then formation was carried out and constant volume test was carried out. The test data are shown in Table 1.

[0073] Table 1 Test data table of Example 1 and Comparative Example 1

[0074]

[0075] Through the above experiments, the results showed that after infiltration (12 h, 16 h, 20 h, and 24 h) of the electrode sheet of Example 1, the alternating current impedance measured at each infiltration time was less than that of Comparative Example 1, and the formation capacity of Example 1 was higher than that of Comparative Example 1. It was shown that by arranging the electrode sheet with the areal density in the middle of the functional layer 13 being greater than that on both sides along the width direction W of the electrode sheet 100, the infiltration speed would be faster, the infiltration would be more complete, the infiltration of the in-situ cured electrolyte could be significantly improved, and the infiltration cycle could be shortened.

[0076] The above is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed above with the preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications within the scope of the technical solution of the present invention by using the above-disclosed technical content, which are equivalent embodiments of equivalent changes. However, as long as it does not depart from the content of the technical solution of the present invention, any simple modification, equivalent change, and modification made to the above embodiment based on the technical essence of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A pole piece, characterized in that, It includes a current collector (11), an active material layer (12) and a functional layer (13). The active material layer (12) is disposed on the surface of the current collector (11), and the functional layer (13) is disposed on the surface of the active material layer (12). The functional layer (13) has wettability assistance, which is conducive to the infiltration of the electrolyte. The electrode sheet (100) has a width direction (W). Along the width direction (W) of the electrode sheet (100), the areal density in the middle of the functional layer (13) is greater than that on both sides thereof.

2. The electrode sheet according to claim 1, characterized in that, Along the width direction (W) of the electrode sheet (100), the areal density of the functional layer (13) decreases from the middle to both sides.

3. The pole piece according to claim 1, characterized in that, Along the width direction (W) of the electrode sheet (100), the functional layer (13) includes at least three sub-functional layers arranged adjacent to each other in sequence, including a second sub-functional layer (132) located in the middle and a first sub-functional layer (131) and a third sub-functional layer (133) located on both sides.

4. The pole piece according to claim 3, wherein The areal density of the first sub-functional layer (131) and / or the areal density of the third sub-functional layer (133) is 10%-90% of the areal density of the second sub-functional layer (132).

5. The electrode tab according to claim 3, wherein The width of the second sub-functional layer (132) is W1, and the width of the electrode sheet (100) is W3, where 1 / 10 ≤ W1 / W3 ≤ 9 / 10.

6. The electrode tab according to claim 3, wherein, A transition layer (134) is disposed between adjacent sub-functional layers, and the areal density of the transition layer (134) is between the areal densities of adjacent sub-functional layers.

7. The pole piece according to claim 6, wherein The width of the second sub-functional layer (132) is W1, the width of the transition layer (134) is W2, and the width of the electrode sheet (100) is W3, where 1 / 10 ≤ W1 / W3 ≤ 1 / 2 and 1 / 10 ≤ W2 / W1 ≤ 1.

8. The pole piece according to any one of claims 1-7, characterized in that, The thickness of the functional layer (13) is 1-10 μm.

9. The pole piece according to any one of claims 1-7, characterized in that The functional layer (13) is an acrylate copolymer coating, a carbonate coating, a sulfate coating or a phosphate coating.

10. The pole piece according to any one of claims 1-7, characterized in that, The functional layer (13) is disposed on the electrode sheet (100) by spraying, coating, printing or transferring.

11. A spraying device, characterized in that, It is used to prepare the electrode sheet (100) according to any one of claims 1-9.

12. The spraying device according to claim 11, characterized in that, The spraying device includes a nozzle (5), and the width of the nozzle (5) matches the width of the electrode sheet (100).

13. The spraying device according to claim 12, characterized in that, The nozzle (5) includes a liquid outlet (51). The nozzle (5) has a thickness direction (D0) and a width direction (W0). Along the width direction (W0) of the nozzle, the dimension of the middle of the liquid outlet (51) in the thickness direction (D0) is greater than the dimensions of both sides thereof in the thickness direction (D0); Alternatively, the nozzle (5) includes a plurality of liquid outlets (51). Along the width direction (W0) of the nozzle (5), the dimension of the liquid outlet (51) located in the middle is greater than the dimensions of the liquid outlets (51) located on both sides.

14. The spraying device according to claim 12 or 13, characterized in that, The spraying device further includes a storage tank (2), a compressor (3) and a spraying device (4). The storage tank (2) is used for storing liquid materials. The storage tank (2), the compressor (3) and the nozzle (5) are all connected to the spraying device (4). The spraying device (4) introduces the liquid materials in the storage tank (2) through the compressor (3), and then sprays the liquid materials through the nozzle (5) to form the functional layer (13).

15. The spraying device according to claim 14, characterized in that, The spraying device (4) is an atomizing device. The atomizing device introduces the liquid materials in the storage tank (2) through the compressor (3), atomizes the liquid materials, and sprays the atomized materials through the nozzle (5) to form the functional layer (13).

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