Pole piece, battery cell and battery pack

Abstract

The utility model provides a pole piece, a battery cell and a battery pack, the pole piece comprises a current collector and an active substance, the current collector comprises a first central part and first edge parts, the first edge parts are arranged on two sides of the first central part in the width direction, and the thickness of the first edge parts is greater than that of the first central part; the active substance is arranged on at least one side of the current collector in the thickness direction, the part of the active substance arranged in the first central part is a second central part, the rest part is a second edge part, and the thickness of the second edge part is greater than that of the second central part. According to the pole piece provided by the embodiment of the invention, the quantity and probability of embedding lithium ions into the edge of the pole piece are improved, the uniformity of embedding the lithium ions into the pole piece is improved, and the quantity of the lithium ions aggregated on the outer surface of the second central part is reduced, so that the time of separating lithium in the middle of the pole piece is shortened, or the risk of separating lithium in the middle of the pole piece is eliminated; and meanwhile, the weight of the pole piece is relatively light, the energy density of the battery cell is improved, and the energy density of the battery pack is improved.

Description

Technical Field

[0001] The present disclosure relates to the field of battery technology, and in particular to a pole piece, a battery cell and a battery pack. Background Art

[0002] When charging a lithium-ion battery, if there is insufficient space for lithium embedding in the negative electrode, too high resistance for Li+ to embed in the negative electrode, or Li+ is de-embedded from the positive electrode too quickly but cannot be embedded in the negative electrode in equal amounts, the Li+ that cannot be embedded in the negative electrode can only obtain electrons on the surface of the negative electrode, thus forming a silvery-white metallic lithium single substance, and black spots appear on the pole piece. This phenomenon is called lithium deposition. During the cycle of the battery cell, the expansion force and temperature affect the uneven polarization distribution of the pole piece and the difficulty of the electrolyte to flow back to the middle of the pole piece, causing lithium deposition, which in turn affects the battery capacity, cycle life and safety performance. Utility Model Content

[0003] In order to solve the above technical problems or at least partially solve the above technical problems, the present disclosure provides a pole piece, a battery cell and a battery pack.

[0004] The present application discloses a pole piece, comprising: a current collector, comprising a first central portion and a first edge portion, the first edge portion being arranged on both sides of the first central portion in a width direction, and the thickness of the first edge portion being greater than the thickness of the first central portion; an active material being arranged on at least one side of the current collector in a thickness direction, the portion of the active material arranged on the first central portion being a second central portion, the portion of the active material arranged on the first edge portion being a second edge portion, and the thickness of the second edge portion being greater than the thickness of the second central portion.

[0005] Optionally, the first central portion includes a first reinforcement layer and a first conductive layer, and the first conductive layer is sandwiched between the first reinforcement layer and the active material layer.

[0006] Optionally, the thickness of the first reinforcement layer is greater than the thickness of the first conductive layer.

[0007] Optionally, the thickness of the first reinforcement layer is greater than or equal to 1 um and less than or equal to 16 um; and / or the thickness of the first conductive layer is greater than or equal to 0.1 um and less than or equal to 15 um.

[0008] Optionally, the first edge portion includes a second reinforcement layer and a second conductive layer, and the second conductive layer is sandwiched between the second reinforcement layer and the active material layer.

[0009] Optionally, in the width direction of the first central portion, the ratio of the width of the first central portion to the width of the current collector is less than or equal to 0.4; and / or the ratio of the width of the first edge portion to the width of the current collector is greater than or equal to 0.3 and less than or equal to 0.45.

[0010] Optionally, on the same side of the first central portion in the width direction, a distance between an outer surface of the first central portion and an outer surface of the first edge portion is greater than or equal to 1 um and less than or equal to 8 um.

[0011] Optionally, the pole piece is a positive pole piece, and the current collector is an aluminum foil; or, the pole piece is a negative pole piece, and the current collector is a copper foil.

[0012] The present application also discloses a battery cell, comprising: a pole piece provided according to the above disclosure.

[0013] The present application also discloses a battery pack, comprising: a battery cell provided according to the above disclosure.

[0014] Compared with the prior art, the technical solution provided by the embodiments of the present disclosure has the following advantages:

[0015] The pole piece provided in the embodiment of the present disclosure can make the impedance of the first center portion greater than that of the first edge portion by setting the thickness of the first center portion greater than that of the first center portion, and setting the thickness of the second edge portion of the active material greater than that of the second center portion, so that the current collector exerts a greater tendency force on the lithium ions enriched in the middle position of the pole piece to move toward the first edge portion, thereby increasing the amount and probability of lithium ions embedded in the edge of the pole piece, improving the consistency of the polarity of the pole piece, and improving the uniformity of lithium ions embedded in the pole piece; and can make the second center portion of the active material have more sufficient expansion space, reduce the amount of electrolyte squeezed out of the second center portion of the active material, so that the second center portion can better absorb lithium ions, reduce the amount of lithium ions accumulated on the outer surface of the second center portion, effectively reduce or eliminate the risk of lithium deposition caused by the accumulation of lithium ions on the outer surface of the second center portion, thereby reducing the time for lithium deposition in the middle portion of the pole piece, or eliminating the risk of lithium deposition in the middle portion of the pole piece; at the same time, the weight of the pole piece can be made smaller, the energy density of the battery cell can be increased, and the energy density of the battery pack can be increased.

[0016] The battery cell provided in the embodiment of the present disclosure can effectively delay or avoid lithium precipitation caused by the enrichment of lithium ions in the central area of ​​the electrode plate by setting the above-mentioned electrode plate, thereby improving the reliability of battery cell charging and discharging, extending the service life of the battery cell, and extending the service life of the battery pack.

[0017] The battery pack provided in the embodiment of the present disclosure can ensure the reliability of charging and discharging of the battery pack, extend the service life of the battery pack, and improve the overall performance of the battery pack by providing the above-mentioned battery cells. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present disclosure and, together with the description, serve to explain the principles of the present disclosure.

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0020] Figure 1 A front view of a pole piece of some embodiments provided by the present disclosure;

[0021] Figure 2 for Figure 1 A cross-sectional view of the pole piece in FIG.

[0022] Figure 3 Cross-sectional views of pole pieces according to other embodiments of the present disclosure.

[0023] Among them, 100, pole piece;

[0024] 10. current collector; 1. first central portion; 11. first reinforcement layer; 12. first conductive layer; 2. first edge portion; 21. second reinforcement layer; 22. second conductive layer;

[0025] 30. Active material; 31. Second central portion; 32. Second edge portion. DETAILED DESCRIPTION

[0026] In order to more clearly understand the above-mentioned objectives, features and advantages of the present disclosure, the scheme of the present disclosure will be further described below. It should be noted that the embodiments of the present disclosure and the features in the embodiments can be combined with each other without conflict.

[0027] In the following description, many specific details are set forth to facilitate a full understanding of the present disclosure, but the present disclosure may also be implemented in other ways different from those described herein; it is obvious that the embodiments in the specification are only part of the embodiments of the present disclosure, rather than all of the embodiments.

[0028] Reference Figure 1-Figure 3 The present application discloses a pole piece 100, including a current collector 10 and an active material 30, wherein the current collector 10 includes a first central portion 1 and a first edge portion 2, wherein the first edge portion 2 is disposed on both sides of the first central portion 1 in a width direction, and the thickness of the first edge portion 2 is greater than the thickness of the first central portion 1.

[0029] For example, the material of the current collector 10 can be selected from at least one of Ni, Ti, Cu, Ag, Au, Pt, Fe, Co, Cr, W, Mo, Al, Mg, K, Na, Ca, Sr, Ba, Si, Ge, Sb, Pb, In, Zn and their combinations (alloys); specifically, when the pole piece 100 is a positive pole piece, the current collector 10 is aluminum foil; specifically, when the pole piece 100 is a negative pole piece, the current collector 10 is copper foil.

[0030] By setting the thickness of the first edge portion 2 to be greater than the thickness of the first center portion 1, the impedance of the first center portion 1 can be made greater than that of the first edge portion 2, so that the current collector 10 exerts a greater tendency on the lithium ions enriched in the middle position of the pole piece 100 to move toward the first edge portion 2, thereby reducing the amount of lithium ions accumulated in the middle position of the pole piece 100, and increasing the amount of lithium ions embedded in the active material 30 corresponding to the first edge portion 2, so that the lithium ions are distributed more evenly in the second center portion 31 and the second edge portion 32 of the active material 30, thereby improving the consistency of the polarity of the pole piece 100, and improving the uniformity of the lithium ions embedded in the pole piece 100, thereby reducing the time for lithium deposition in the middle of the pole piece 100, or eliminating the risk of lithium deposition in the middle of the pole piece 100.

[0031] The active material 30 is disposed on at least one side in the thickness direction of the current collector 10, the portion of the active material 30 disposed on the first central portion 1 is the second central portion 31, and the remaining portion is the second edge portion 32, and the thickness of the second edge portion 32 is greater than the thickness of the second central portion 31. For example, the active material 30 can be disposed on both sides in the width direction of the first central portion 1 to increase the amount of lithium ions that can be absorbed by the pole piece 100 and improve the energy density of the battery cell.

[0032] For example, when the pole piece 100 is a positive pole piece, the active material 30 may be a composite material in which NCM, conductive carbon black and polyvinylidene fluoride are uniformly mixed in a mass ratio of 96.5:1.5:2. For example, when the pole piece 100 is a positive pole piece, the active material 30 may be a composite material in which active material (graphite), conductive carbon black, styrene-butadiene rubber and sodium hydroxycellulose (CMC) are uniformly mixed in a mass ratio of 96:1:1.8:1.2.

[0033] By setting the thickness of the second edge portion 32 of the active material 30 to be greater than the thickness of the second center portion 31 , the outer surface of the second center portion 31 of the active material 30 is lower than the outer surface of the second edge portion 32 , so that the active material 30 forms a space for accommodating the electrolyte at the position of the second center portion 31 .

[0034] During the charge and discharge cycle of the battery cell, the second central portion 31 of the active material 30 can have sufficient expansion space, reducing the amount of electrolyte squeezed out of the second central portion 31 of the active material 30, so that the amount of electrolyte immersed in the second central portion 31 of the negative electrode plate increases, and the second central portion 31 can better absorb lithium ions, so that the lithium ions can be better embedded in the second central portion 31 of the active material 30, thereby reducing the amount of lithium ions gathered on the outer surface of the second central portion 31, effectively reducing or eliminating the risk of lithium deposition caused by the accumulation of lithium ions on the outer surface of the second central portion 31, thereby slowing down the time for lithium deposition in the middle of the pole piece 100, or eliminating the risk of lithium deposition in the middle of the pole piece 100;

[0035] Moreover, setting the thickness of the second edge portion 32 of the active material 30 to be greater than the thickness of the second center portion 31 can improve the ability of the second edge portion 32 to absorb lithium ions, so that the second edge portion 32 can reliably absorb and accommodate lithium ions, effectively avoiding the risk of lithium ions precipitating on the outer surface of the second edge portion 32, improving the reliability of the electrode 100, and improving the reliability of the battery cell.

[0036] The pole piece 100 provided in the embodiment of the present disclosure can make the impedance of the first center portion 1 greater than the first edge portion 2 by setting the thickness of the first edge portion 2 to be greater than the thickness of the first center portion 1, and setting the thickness of the second edge portion 32 of the active material 30 to be greater than the thickness of the second center portion 31, so that the current collector 10 exerts a greater tendency force on the lithium ions to move toward the first edge portion 2, thereby increasing the amount and probability of lithium ions embedded in the edge of the pole piece 100, improving the consistency of the polarity of the pole piece 100, and improving the uniformity of lithium ions embedded in the pole piece 100; making the second center portion 32 of the active material 30 thicker than the second center portion 31. The core portion 31 has a relatively sufficient expansion space, which reduces the amount of electrolyte squeezed out of the second center portion 31 of the active material 30, so that the second center portion 31 can better absorb lithium ions, and reduce the amount of lithium ions gathered on the outer surface of the second center portion 31, effectively reducing or eliminating the risk of lithium deposition caused by the accumulation of lithium ions on the outer surface of the second center portion 31, thereby reducing the time for lithium deposition in the middle of the electrode 100, or eliminating the risk of lithium deposition in the middle of the electrode 100; at the same time, the weight of the electrode 100 can be reduced, the energy density of the battery cell can be improved, and the energy density of the battery pack can be improved.

[0037] Reference Figure 3 According to some embodiments disclosed, the first central portion 1 includes a first reinforcement layer 11 and a first conductive layer 12, and the first conductive layer 12 is sandwiched between the first reinforcement layer 11 and the active material layer 30. For example, the thickness of the first reinforcement layer 11 is greater than the thickness of the first conductive layer 12.

[0038] For example, the material of the first conductive layer 12 can be selected from at least one of Ni, Ti, Cu, Ag, Au, Pt, Fe, Co, Cr, W, Mo, Al, Mg, K, Na, Ca, Sr, Ba, Si, Ge, Sb, Pb, In, Zn and their combinations (or alloys).

[0039] For example, the material of the first reinforcement layer 11 can be selected from at least one of polyethylene terephthalate, polyimide, polybutylene terephthalate, polyetheretherketone, polyamide, polycarbonate, cyclic polyolefin, polyphenylene sulfide, polyethylene naphthalate, polypropylene carbonate, polyvinylidene fluoride-hexafluoropropylene, polyvinyl acetate, polytetrafluoroethylene, polymethylene naphthalene, polyvinylidene fluoride, polyethylene glycol, polyamideimide, polyethylene naphthalate, poly(vinylidene fluoride-co-chlorotrifluoroethylene), silicone, vinylon, polypropylene, polyethylene, polyvinyl chloride, polystyrene, polyether nitrile, polyurethane, polyphenylene ether, polyester, polysulfone and their derivatives.

[0040] In this way, the first reinforcing layer 11 can strengthen the first conductive layer 12, so that the thickness of the first conductive layer 12 is set to be smaller, the material usage of the first conductive layer 12 is reduced, and the production cost of the pole piece 100 is reduced. Moreover, in this way, the weight of the first reinforcing layer 11 can be lowered, and the weight of the pole piece 100 can be lowered, thereby improving the energy density of the battery cell.

[0041] Reference Figure 3 According to some publicly provided embodiments, the thickness of the first reinforcement layer 11 is greater than or equal to 1um and less than or equal to 16um; for example, the thickness of the first reinforcement layer 11 can be 1um, 2um, 3um, 4um, 5um, 6um, 7um, 8um, 9um, 10um, 11um, 12um, 13um, 14um, 15um, or 16um.

[0042] The smaller the thickness of the first reinforcement layer 11, the lower the production cost of the pole piece 100; the larger the thickness of the first reinforcement layer 11, the more reliable the structure of the first reinforcement layer 11. Setting the thickness of the first reinforcement layer 11 to be greater than or equal to 1 um and less than or equal to 16 um can take into account both the structural strength of the first reinforcement layer 11 and the production cost of the pole piece 100, thereby improving the overall performance of the battery cell.

[0043] Reference Figure 3According to some embodiments disclosed, the thickness of the first conductive layer 12 is greater than or equal to 0.1um and less than or equal to 15um. For example, the thickness of the first conductive layer 12 can be 0.1um, 0.2um, 0.3um, 0.4um, 0.5um, 0.6um, 0.7um, 0.8um, 0.9um, 1um, 2um, 3um, 4um, 5um, 6um, 7um, 8um, 9um, 10um, 11um, 12um, 13um, 14um, 15um, 16um.

[0044] Specifically, the thickness of the first conductive layer 12 and the thickness of the first reinforcement layer 11 can be adjusted according to design requirements. The thickness of the first conductive layer 12 and the thickness of the first reinforcement layer 11 can be set to be the same, or the thickness of the first conductive layer 12 can be set to be greater than the thickness of the first reinforcement layer 11, or the thickness of the first conductive layer 12 can be set to be less than the thickness of the first reinforcement layer 11.

[0045] The smaller the thickness of the first conductive layer 12, the lower the production cost of the pole piece 100; the larger the thickness of the first conductive layer 12, the more reliable the structure of the first conductive layer 12. Setting the thickness of the first conductive layer 12 to be greater than or equal to 1 um and less than or equal to 16 um can take into account both the structural strength of the first reinforcement layer 11 and the production cost of the pole piece 100, thereby improving the overall performance of the battery cell.

[0046] Reference Figure 3 According to some embodiments disclosed, the first edge portion 2 includes a second reinforcement layer 21 and a second conductive layer 22, and the second conductive layer 22 is sandwiched between the second reinforcement layer 21 and the active material 30 layer. For example, the thickness of the second reinforcement layer 21 is greater than the thickness of the second conductive layer 22.

[0047] For example, the material of the second conductive layer 22 can be selected from at least one of Ni, Ti, Cu, Ag, Au, Pt, Fe, Co, Cr, W, Mo, Al, Mg, K, Na, Ca, Sr, Ba, Si, Ge, Sb, Pb, In, Zn and their combinations (or alloys).

[0048] For example, the material of the second reinforcement layer 21 can be selected from at least one of polyethylene terephthalate, polyimide, polybutylene terephthalate, polyetheretherketone, polyamide, polycarbonate, cyclic polyolefin, polyphenylene sulfide, polyethylene naphthalate, polypropylene carbonate, polyvinylidene fluoride-hexafluoropropylene, polyvinyl acetate, polytetrafluoroethylene, polymethylene naphthalene, polyvinylidene fluoride, polyethylene glycol, polyamideimide, polyethylene naphthalate, poly(vinylidene fluoride-co-chlorotrifluoroethylene), silicone, vinylon, polypropylene, polyethylene, polyvinyl chloride, polystyrene, polyether nitrile, polyurethane, polyphenylene ether, polyester, polysulfone and their derivatives.

[0049] In this way, the second reinforcing layer 21 can strengthen the second conductive layer 22, so that the thickness of the second conductive layer 22 is set to be smaller, the material usage of the second conductive layer 22 is reduced, and the production cost of the pole piece 100 is reduced. Moreover, in this way, the weight of the second reinforcing layer 21 can be lowered, and the weight of the pole piece 100 can be lowered, thereby improving the energy density of the battery cell.

[0050] For example, the first conductive layer 12 and the second conductive layer 22 may be two regions of the same metal foil, and the first reinforcement layer 11 and the second reinforcement layer 21 may be two regions of the same polymer layer. This facilitates the production of the pole piece 100 and reduces the production cost of the pole piece 100.

[0051] Reference Figure 1-Figure 3 According to some embodiments disclosed, in the width direction of the first central portion 1, the ratio of the width of the first central portion 1 to the width of the current collector 10 is greater than or equal to 0.1 and less than or equal to 0.4; and / or, in the width direction of the first central portion 1, the ratio of the width of the first edge portion 2 to the width of the current collector 10 is greater than or equal to 0.3 and less than or equal to 0.45. That is, the ratio of the area of ​​the first central portion 1 to the area of ​​the current collector 10 is greater than or equal to 0.1 and less than or equal to 0.4.

[0052] For example, the ratio of the width of the first central portion 1 to the width of the current collector 10 can be 0.1, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.2, 0.21, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, 0.3, 0.3, 0.31, 0.32, 0.33, 0.34, 0.35, 0.36, 0.37, 0.38, 0.39, or 0.4.

[0053] The larger the area ratio of the first central portion 1, the greater the impedance of the pole piece 100 to lithium ions at the first central portion 1, and the more effectively the lithium deposition phenomenon of the pole piece 100 at the central portion can be delayed or eliminated; the smaller the area ratio of the first central portion 1, the greater the total amount of active material 30, and the higher the energy density of the battery cell. Setting the ratio of the width of the first central portion 1 to the width of the current collector 10 to be greater than or equal to 0.1 and less than or equal to 0.4 can solve the lithium deposition phenomenon while making the battery cell have a higher energy density.

[0054] Reference Figure 1-Figure 3According to some embodiments disclosed, on the same side in the width direction of the first central portion 1, the spacing between the outer surface of the first central portion 1 and the outer surface of the first edge portion 2 is greater than or equal to 1um and less than or equal to 8um. For example, the spacing between the outer surface of the first central portion 1 and the outer surface of the first edge portion 2 can be 1um, 1.5um, 2um, 2.5um, 3um, 3.5um, 4um, 4.5um, 5um, 5.5um, 6um, 6.5um, 7um, 7.5um, 8um.

[0055] The larger the distance between the outer surface of the first central portion 1 and the outer surface of the first edge portion 2, the more effectively the thickness of the second edge portion 32 can be ensured to be greater than the thickness of the second central portion 31, and the more effectively the lithium deposition in the middle of the pole piece 100 can be eliminated; the smaller the distance between the outer surface of the first central portion 1 and the outer surface of the first edge portion 2, the more the total amount of active material 30, and the higher the energy density of the battery cell. Setting the distance between the outer surface of the first central portion 1 and the outer surface of the first edge portion 2 to be greater than or equal to 1um and less than or equal to 8um can effectively solve the lithium deposition phenomenon while making the battery cell have a higher energy density.

[0056] The present application also discloses a battery cell, comprising: a pole piece 100 provided according to the above disclosure.

[0057] The battery cell provided in the embodiment of the present disclosure can effectively delay or avoid lithium plating caused by the enrichment of lithium ions in the central area of ​​the electrode piece 100 by setting the above-mentioned electrode piece 100, thereby improving the reliability of charging and discharging of the battery cell, extending the service life of the battery cell, and extending the service life of the battery pack.

[0058] The present application also discloses a battery pack, comprising: a battery cell provided according to the above disclosure.

[0059] The battery pack provided in the embodiment of the present disclosure can ensure the reliability of charging and discharging of the battery pack, extend the service life of the battery pack, and improve the overall performance of the battery pack by providing the above-mentioned battery cells.

[0060] It should be noted that, in this article, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0061] The above description is only a specific embodiment of the present disclosure, so that those skilled in the art can understand or implement the present disclosure. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present disclosure. Therefore, the present disclosure will not be limited to the embodiments described herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A pole piece, characterized in that: include: A current collector, comprising a first central portion and a first edge portion, wherein the first edge portion is disposed on both sides of the first central portion in a width direction, and the thickness of the first edge portion is greater than the thickness of the first central portion; The active material is arranged on at least one side in the thickness direction of the current collector, the portion of the active material arranged on the first central portion is the second central portion, the portion of the active material arranged on the first edge portion is the second edge portion, and the thickness of the second edge portion is greater than the thickness of the second central portion.

2. The pole piece according to claim 1, characterized in that: The first central portion includes a first reinforcement layer and a first conductive layer, and the first conductive layer is interposed between the first reinforcement layer and the active material layer.

3. The pole piece according to claim 2, characterized in that: The thickness of the first reinforcement layer is greater than the thickness of the first conductive layer.

4. The pole piece according to claim 2 or 3, characterized in that: The thickness of the first reinforcement layer is greater than or equal to 1 um and less than or equal to 16 um; and / or the thickness of the first conductive layer is greater than or equal to 0.1 um and less than or equal to 15 um.

5. The pole piece according to claim 1, characterized in that: The first edge portion includes a second reinforcement layer and a second conductive layer, and the second conductive layer is interposed between the second reinforcement layer and the active material layer.

6. The pole piece according to claim 1, characterized in that: In the width direction of the first central portion, a ratio of a width of the first central portion to a width of the current collector is less than or equal to 0.4; and / or a ratio of a width of the first edge portion to a width of the current collector is greater than or equal to 0.3 and less than or equal to 0.

45.

7. The pole piece according to claim 1, characterized in that: On the same side of the first central portion in the width direction, a distance between an outer surface of the first central portion and an outer surface of the first edge portion is greater than or equal to 1 um and less than or equal to 8 um.

8. The pole piece according to claim 1, characterized in that: The pole piece is a positive pole piece, and the current collector is an aluminum foil; or, the pole piece is a negative pole piece, and the current collector is a copper foil.

9. A battery cell, characterized in that: include: A pole piece according to any one of claims 1 to 8.

10. A battery pack, characterized in that: include: The battery cell according to claim 9.

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