Foil, pole piece and battery

Abstract

The utility model provides a foil material, pole piece and battery, the electrode comprises the foil material, the foil material comprises a main body part and a part to be cut, the main body part is located in the coating area, the part to be cut is located in the non-coating area, and the minimum thickness of the part to be cut is set to be greater than or equal to the thickness of the main body part. The thickness of the side, away from the main body part, of the to-be-cut part is larger than that of the side, close to the main body part, of the to-be-cut part, so that the thickness distribution of the foil can be effectively controlled, and it is ensured that the energy density of the thinned foil is improved, and meanwhile the battery performance is prevented from being affected by internal resistance increase.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to a foil, a pole piece and a battery. BACKGROUND

[0002] Lithium ion batteries have become the mainstream product of secondary batteries due to their high energy density and excellent cycle performance; as consumers continue to demand higher performance, efficiency and service life from batteries, improving the energy density of battery monomers has become one of the main indicators for battery manufacturers to improve their competitiveness.

[0003] Currently, the battery cell includes a plurality of pole pieces, and the pole piece is usually composed of a current collector and a coating layer covering the surface of the current collector. In the process of manufacturing the battery cell, the current collector is generally made of a foil. By reducing the thickness of the foil, the volume and mass energy density of the battery cell can be improved. However, the reduction of the thickness of the foil will increase the resistance, thereby adversely affecting the internal resistance and performance stability of the battery. UTILITY MODEL CONTENT

[0004] The embodiments of the utility model provide a kind of foil, pole piece and battery, to solve or at least partially solve the deficiency of the background art described above.

[0005] In a first aspect, the embodiments of the utility model provide a kind of foil, comprising coating area and the non-coating area located at at least one side of the coating area, the foil includes:

[0006] Main body part, in the coating area;

[0007] To be cut part, in the non-coating area;

[0008] Wherein, the minimum thickness of the to-be-cut part is greater than or equal to the thickness of the main body part, and the thickness of the to-be-cut part away from the side of the main body part is greater than the thickness of the to-be-cut part close to the side of the main body part.

[0009] In an embodiment, the relationship between the thickness of the to-be-cut part and the thickness of the to-be-cut part is: h2=(1.5-2)h1;

[0010] Wherein, h1 is the thickness of the main body part, and h2 is the thickness of the to-be-cut part.

[0011] In an embodiment, the thickness of the main body part is greater than or equal to 4 microns and less than or equal to 5 microns, and the thickness of the to-be-cut part is greater than or equal to 5 microns and less than or equal to 7 microns.

[0012] In an embodiment, the thickness of the to-be-cut part gradually increases in the direction from the main body part to the to-be-cut part.

[0013] In an embodiment, the to-be-cut part includes a to-be-cut sub-part, and a relationship among a parameter of the to-be-cut sub-part, a parameter of the to-be-cut part, and a parameter of the main part is (D1-d) / w1=(D-d) / W.

[0014] D1 is the thickness of the to-be-cut sub-part, D is the maximum thickness of the to-be-cut part, d is the thickness of the main part, W is the width of the to-be-cut part, and w1 is the width of the to-be-cut sub-part.

[0015] In an embodiment, the main part includes oppositely arranged first and second surfaces.

[0016] The foil further includes first and second protective films, the first protective film is arranged on the first surface, and the second protective film is arranged on the second surface.

[0017] The sum of the thickness of the first protective film, the thickness of the second protective film, and the thickness of the main part is equal to the maximum thickness of the to-be-cut part.

[0018] In an embodiment, the first protective film has a projection on the foil that coincides with a projection of the main part on the foil, and the second protective film has a projection on the foil that coincides with a projection of the main part on the foil.

[0019] In an embodiment, the first protective film and the second protective film are made of polypropylene, polyethylene, or one of polyethylene.

[0020] In a second aspect, the embodiments of the utility model provide a pole piece, including the foil of any one of the above embodiments; wherein the foil is provided with an active substance layer in the coating area, and the foil is provided with a pole lug in the non-coating area.

[0021] In a third aspect, the embodiments of the utility model provide a battery, including a battery core, and the battery core includes the pole piece of any one of the above embodiments.

[0022] The embodiments of the utility model have the beneficial effects that the embodiments of the utility model provide a foil, a pole piece, and a battery, the electrode includes the foil, the foil includes a main part and a to-be-cut part, the main part is located in the coating area, and the to-be-cut part is located in the non-coating area, by setting the minimum thickness of the to-be-cut part to be greater than or equal to the thickness of the main part and the thickness of the side of the to-be-cut part away from the main part to be greater than the thickness of the side of the to-be-cut part close to the main part, the thickness distribution of the foil can be effectively controlled, and the thinned foil can improve the energy density while avoiding the influence of the increased internal resistance on the battery performance. BRIEF DESCRIPTION OF DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments, the following will briefly introduce the drawings needed to be used in the embodiments. Obviously, the drawings in the following description only some of the embodiments of the present application, and for those skilled in the art, other drawings can also be obtained from these drawings without creative labor.

[0024] Figure 1 The structural schematic diagram of the battery provided by the embodiment of the present application;

[0025] Figure 2 The structural schematic diagram of the battery provided by the embodiment of the present application;

[0026] Figure 3 The structural schematic diagram of the battery provided by the embodiment of the present application;

[0027] Figure 4 The structural schematic diagram of the battery provided by the embodiment of the present application;

[0028] Figure 5 The structural schematic diagram of the battery provided by the embodiment of the present application; Figure 4 The sectional structure schematic diagram of the A-A` in the above figure;

[0029] Figure 6 The relationship curve diagram between the parameters of the to-be-cut sub-portion, the parameters of the to-be-cut portion and the parameters of the main portion provided by the embodiment of the present application;

[0030] Figure 7 The assembly schematic diagram of the foil winding provided by the embodiment of the present application;

[0031] Figure 8 The structural schematic diagram of the foil after winding provided by the embodiment of the present application;

[0032] Figure 9 The sectional structure schematic diagram of the B-B` in the above figure provided by the embodiment of the present application. Figure 8

[0033] Explanation of reference signs:

[0034] 1-battery; 11-battery cell; 111-pole piece; 112-isolation film; 111A-positive pole lug; 111B-negative pole lug; 1111-foil; 1111A-coating area; 1111B-non-coating area; 11111-main portion; 11112-to-be-cut portion; 11113-first protective film; 11114-second protective film; 111121-to-be-cut sub-portion. DETAILED DESCRIPTION

[0035] ​Clearly and completely describe the technical scheme in the embodiments of the utility model with reference to the drawings in the embodiments of the utility model, obviously, the described embodiment is only a part of the embodiment of the utility model, and is not all the embodiment. Based on the embodiment in the utility model, all other embodiments obtained by the person skilled in the art without making creative labor belong to the range of protection of the utility model. In addition, it should be understood that the specific implementation described herein is only used to illustrate and explain the utility model, and is not used to limit the utility model. In the utility model, the orientation words such as "up" and "down" are generally used to indicate the up and down of the device in the actual use or working state, and the specific is the drawing direction in the drawing. And "inner" and "outer" are relative to the outline of the device.

[0036] Please combine Figure 1 , Figure 2 and Figure 3 ; wherein, Figure 1 It is the structural schematic diagram of the battery provided by the embodiment of the utility model; Figure 2 It is the structural schematic diagram of the battery provided by the embodiment of the utility model; Figure 3 It is the structural schematic diagram of the battery provided by the embodiment of the utility model.

[0037] The embodiment provides a kind of battery 1, the battery 1 includes but is not limited to square battery, the battery 1 includes at least one battery 11, the battery 11 can be laminated battery 11, the battery 11 includes multiple pole pieces 111 and multiple isolation films 112, the pole piece 111 includes positive pole piece and negative pole piece, one described positive pole piece is provided with one described positive ear 111A, the positive pole piece and the positive ear 111A can be integrally formed, or can be connected into a whole by welding etc.;One described negative pole piece is provided with one described negative ear, multiple described negative ears are arranged on the same side of the negative pole piece, the negative pole piece and the negative ear can also be integrally formed, or can be connected into a whole by welding etc., so that the structure of the battery 11 is compact and stable.

[0038] Multiple described positive pole pieces and multiple described negative pole pieces are sequentially stacked along the width direction of the battery 11, one described isolation film 112 is arranged between one described positive pole piece and one described negative pole piece, multiple described positive ears 111A are aligned and arranged along the width direction of the battery 11, multiple described negative ears are aligned and arranged along the width direction of the battery 11;Wherein, the positive ear 111A and the negative ear can be arranged on the same side of the battery 11, the positive ear 111A and the negative ear are sequentially arranged along the length direction of the battery 11.

[0039] The length direction of the battery cell can be the X direction in Figure 2 The width direction of the battery cell can be the Y direction in Figure 2 The height direction of the battery cell is the Z direction in Figure 2 The length direction of the battery cell, the width direction of the battery cell 11, and the height direction of the battery cell are perpendicular to each other.

[0040] It should be noted that the shape of the battery 1, the number of the battery cells 11, the structure of the battery cells 11, and the position of the tabs are not specifically limited in the embodiment; for the convenience of describing the technical scheme of the utility model, the battery 1 is a square battery, the battery cell 11 is a laminated battery cell, and the positive tab 111A and the negative tab are arranged on the same side of the battery cell 11 in the embodiment; it should be emphasized that the technical scheme of the embodiment is also applicable to other types of battery shapes, battery cell structures, and tab position combinations, and has strong applicability and flexibility.

[0041] Please refer to Figure 1 , Figure 2 , Figure 3 , Figure 4 and Figure 5 ; wherein, Figure 4 is a structure diagram of a foil provided by the embodiment of the utility model; Figure 5 is a cross-sectional structure diagram of A-A` in Figure 4 It should be noted that, Figure 4 The foil shown in the drawing is in an initial state before die cutting, and the foil can be processed by die cutting to obtain a tab as shown in Figure 3 , and finally applied to a battery cell as shown in Figure 2 .

[0042] Continue to refer to Figures 1 to 5 In an embodiment, the tab 111 includes a foil 1111, and the foil 1111 can be selected from any one of an aluminum foil, a copper foil, a nickel foil, or an iron foil; the surface of the foil 1111 includes a coated area 1111A and a non-coated area 1111B located on at least one side of the coated area 1111A.

[0043] Before the die-cutting process is performed on the foil 1111, the foil 1111 includes a main body part 11111 and a part to be cut 11112, wherein the main body part 11111 is located in the coating area 1111A, and the part to be cut 11112 is located in the non-coating area 1111B; specifically, the main body part 11111 includes oppositely arranged first and second surfaces, by coating the first and second surfaces with active substances, and performing die-cutting processing on the part to be cut 11112 located in the non-coating area 1111B, the excess part can be effectively removed, thereby obtaining the pole piece 111 and the tab (positive tab 111A and negative tab) meeting the design requirements.

[0044] It should be noted that the active substance can be one of a positive active substance and / or a negative active substance, and the material of the foil 1111 and the specific type, composition and content of the active substance are not specifically required or specially limited in the embodiment. In order to describe the technical solutions of the present application in detail, the surface of the foil 1111 includes the coating area 1111A and the non-coating area 1111B located on the opposite sides of the coating area 1111A as an example.

[0045] Further, the minimum thickness of the part to be cut 11112 is greater than or equal to the thickness of the main body part 11111, and the thickness of the part to be cut 11112 away from the main body part 11111 is greater than the thickness of the part to be cut 11112 close to the main body part 11111; the thickness of the main body part 11111 away from the part to be cut 11112 is equal to the thickness of the main body part 11111 close to the part to be cut 11112, that is, the main body part 11111 can be flat, and the cross-sectional shape of the main body part 11111 can be rectangular.

[0046] In a lithium ion battery, the foil serves as a conductor, connecting the positive and negative electrodes and transmitting current. In the related art, a relatively thin foil is usually used to improve the energy density of the battery, that is, to reduce the volume and weight of the battery cell, thereby improving the energy density of the battery. However, as the thickness of the foil decreases, it can be known from the resistance formula R = pL / S, where R is the resistance of the foil, p is the resistivity of the foil material, L is the length of the foil, and S is the cross-sectional area of the foil, that the smaller the cross-sectional area of the foil, the greater the resistance when the current passes through, thereby affecting the performance of the battery.

[0047] It can be understood that the embodiment can improve the volume and mass energy density of the battery 1 by thinning the thickness of the foil 1111; at the same time, by setting the minimum thickness of the to-be-cut part 11112 to be greater than or equal to the thickness of the main body part 11111, and the thickness of the to-be-cut part 11112 away from the main body part 11111 is greater than the thickness of the to-be-cut part 11112 close to the main body part 11111, thereby increasing the thickness of the to-be-cut part 11112, reducing the resistance of the to-be-cut part 11112, and thereby avoiding the problem of increased internal resistance caused by excessive thinning of the thickness of the foil 1111; in this way, the foil 1111 design proposed in the embodiment can increase the thickness of the to-be-cut part 11112 on the basis of using a thinner main body part 11111, thereby improving the energy density of the battery 1.

[0048] Please continue to combine Figures 1 to 5 In an embodiment, the relationship between the thickness of the to-be-cut part 11112 and the thickness of the to-be-cut part 11112 is: h2 = (1.5-2) h1; wherein h1 is the thickness of the main body part 11111, h2 is the thickness of the to-be-cut part 11112, by limiting the relationship between the thickness of the to-be-cut part 11112 and the thickness of the to-be-cut part 11112, thereby improving the mechanical reliability and assembly compatibility of the battery 1.

[0049] Specifically, the thickness of the main body part 11111 is greater than or equal to 4 microns and less than or equal to 5 microns; the thickness of the to-be-cut part 11112 is greater than or equal to 5 microns and less than or equal to 7 microns; by setting the minimum thickness of the to-be-cut part 11112 to be greater than or equal to the thickness of the main body part 11111, the thickening of the to-be-cut part 11112 is realized, thereby effectively avoiding the problems of bending and wrinkling of the tab during use, improving the mechanical reliability and assembly compatibility of the battery 1; at the same time, the thickness of the main body part 11111 can be thinned without increasing the internal resistance of the foil 1111, thereby improving the volume energy density and mass energy density of the battery 1, and realizing the lightweight design of the battery 1.

[0050] It can be understood that during the production and assembly of the electrode, the foil 1111 needs a certain mechanical strength to avoid breaking or deforming, by adjusting the thickness of the to-be-cut part 11112, the strength of the tab can be improved while meeting the resistance performance, the adaptability to processing and cutting is enhanced, the damage problem caused by the foil 1111 being too thin during production and use is avoided, and the feasibility and stability of production are ensured.

[0051] Meanwhile, by limiting the relationship between the thickness of the to-be-cut part 11112 and the thickness of the to-be-cut part 11112 as h2 = (1.5-2) h1, the thickness range of the main body part 11111 and the thickness of the to-be-cut part 11112 can be regulated, so that the foil 1111 can be adapted to different types of battery cells 11 and design requirements, ensuring electrical performance, and balancing structural strength and manufacturing cost.

[0052] It should be noted that in the present embodiment, the thickness of the main body part 11111 and the thickness of the to-be-cut part 11112 are not specifically limited, and the thickness can be designed and adjusted according to specific application requirements to meet the requirements of different battery 1 structures, performance optimization and manufacturing process.

[0053] Further, the orthogonal projection of the foil 1111 in the length direction is an I-shaped or T-shaped, that is, along the length direction of the foil 1111, the projection of the main body part 11111 is a symmetrical structure, thereby enhancing the mechanical strength and stability of the foil 1111.

[0054] It can be understood that the I-shaped or T-shaped structure can make the foil 1111 have better strength and stability when bearing current and mechanical pressure, and can avoid deformation, bending or breaking of the foil 1111 due to external force, thereby enhancing the overall structural stability of the battery 1.

[0055] Meanwhile, the I-shaped or T-shaped structure is also beneficial to heat conduction, avoiding hot spot problems caused by heat concentration, further improving the performance and safety of the battery 1; and the I-shaped or T-shaped design can also simplify the manufacturing and cutting process of the foil 1111; in the manufacturing process, the I-shaped or T-shaped structure can be conveniently cut into appropriate size and shape, and is easy to match with other battery 1 components (such as electrodes, current collectors, etc.) in the subsequent battery 1 assembly process, which has good production adaptability in actual application, and can improve production efficiency.

[0056] Please continue to combine Figures 1 to 5 ; in an embodiment, the thickness of the to-be-cut part 11112 gradually increases in the direction from the main body part 11111 to the to-be-cut part 11112, thereby reducing the risk of local stress concentration or unstable mechanical performance.

[0057] Specifically, the thickness of the to-be-cut part 11112 linearly increases in the direction from the main body part 11111 to the to-be-cut part 11112, avoiding the stress concentration problem caused by too sharp thickness change, so that the foil 1111 will not be broken, bent or deformed due to uneven stress during processing, effectively improving the structural stability and mechanical strength of the battery 1.

[0058] It can be understood that if the thickness of the to-be-cut part 11112 changes sharply (for example, suddenly thickens or thins), stress concentration may be generated at the joint (transition) of the to-be-cut part 11112 and the main body part 11111, thereby causing deformation, cracking and other problems of the foil 1111 during processing or use; the embodiment can make the thickness change of the to-be-cut part 11112 more smooth and gradual, and reduce the risk of local stress concentration or unstable mechanical properties, by linearly increasing the thickness of the to-be-cut part 11112 in the direction from the main body part 11111 to the to-be-cut part 11112.

[0059] Please refer to Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 and Figure 6 ; wherein, Figure 6 is a relationship curve between the parameters of the to-be-cut sub-part, the parameters of the to-be-cut part and the parameters of the main body part provided by the embodiment of the utility model.

[0060] In an embodiment, the to-be-cut part 11112 includes a to-be-cut sub-part 111121, and the parameters of the to-be-cut sub-part 111121, the parameters of the to-be-cut part 11112 and the parameters of the main body part 11111 satisfy the relationship formula: (D1-d) / w1=(D-d) / W; wherein D1 is the thickness of the to-be-cut sub-part 111121, D is the maximum thickness of the to-be-cut part 11112, d is the thickness of the main body part 11111, W is the width of the to-be-cut part 11112, and w1 is the width of the to-be-cut sub-part 111121.

[0061] It should be noted that, please refer to Figure 4 and Figure 5 , the thickness D1 of the to-be-cut sub-part 111121 is the length of the to-be-cut sub-part 111121 in the Y direction; the maximum thickness D of the to-be-cut part 11112 is the length of the to-be-cut part 11112 in the Y direction; the thickness d of the main body part 11111 is the length of the main body part 11111 in the Y direction; the width W of the to-be-cut part 11112 is the length of the to-be-cut part 11112 in the Z direction, and the width w1 of the to-be-cut sub-part 111121 is the length of the to-be-cut sub-part 111121 in the Z direction.

[0062] In the design of the foil 1111, by limiting the parameters of the to-be-cut sub-portion 111121, the parameters of the to-be-cut portion 11112 and the parameters of the main body portion 11111 to satisfy the above relationship, the uniformity of the thickness change of the transition area between the to-be-cut portion 11112 and the main body portion 11111 can be ensured, the local weak area caused by sharp change can be effectively reduced, and the overall mechanical performance of the battery 1 can be improved.

[0063] Specifically, by limiting the parameters of the to-be-cut sub-portion 111121, the parameters of the to-be-cut portion 11112 and the parameters of the main body portion 11111 to satisfy the relationship (D1-d) / w1=(D-d) / W, the ratio between each parameter restricts the speed of the thickness increase of the to-be-cut sub-portion 111121, the thickness change of the joint (transition) is smoother, and the stress concentration problem caused by the thickness mutation is avoided.

[0064] It can be understood that, by setting the gradation of the thickness of the foil 1111 at different positions, i.e., the thickness of the to-be-cut portion 11112 gradually transitions from the main body portion 11111 to the to-be-cut sub-portion 111121, and then to the maximum thickness of the to-be-cut portion 11112, the thickness change of the joint (transition) is smoother, the stress concentration problem caused by the thickness mutation is avoided, and the performance and life of the battery 1 are improved; at the same time, the uniform thickness transition ensures the smooth distribution of the current between the to-be-cut portion 11112 and the main body portion 11111, reduces the abruptness of the resistance, and improves the stability of the electrode performance.

[0065] Please refer to Figure 4 , Figure 5 , Figure 7 , Figure 8 and Figure 9 ; wherein, Figure 7 is an assembly schematic diagram of the foil during winding provided by the embodiment of the utility model; Figure 8 is a structure schematic diagram of the foil after winding provided by the embodiment of the utility model; Figure 9 is a sectional structure schematic diagram of B-B` in Figure 8 provided by the embodiment of the utility model.

[0066] In an embodiment, the foil 1111 further comprises a first protective film 11113 and a second protective film 11114, the first protective film 11113 is arranged on the first surface of the foil 1111, and the second protective film 11114 is arranged on the second surface of the foil 1111; wherein the sum of the thickness of the first protective film 11113, the thickness of the second protective film 11114 and the thickness of the main body portion 11111 is equal to the maximum thickness of the to-be-cut portion 11112.

[0067] It should be noted that, in the process of winding the foil 1111, if the thickness of the to-be-cut part 11112 is significantly greater than the thickness of the main body part 11111, the uneven thickness can cause the foil 1111 to not closely fit when winding, thereby forming a "drum edge" phenomenon, resulting in uneven surface of the foil 1111 after winding, affecting the consistency of subsequent processes (such as coating, lamination or winding).

[0068] It can be understood that, in the embodiment, the first protective film 11113 is arranged on the first surface of the foil 1111, and the second protective film 11114 is arranged on the second surface of the foil 1111; wherein the sum of the thickness of the first protective film 11113, the thickness of the second protective film 11114 and the thickness of the main body part 11111 is equal to the maximum thickness of the to-be-cut part 11112, so that the overall thickness of the main body part 11111 which is fitted with the first protective film 11113 and the second protective film 11114 is adjusted to be similar or consistent with the maximum thickness of the to-be-cut part 11112, thereby eliminating the thickness difference and ensuring that the foil 1111 is tightly and smoothly wound.

[0069] Further, the material of the first protective film 11113 and the material of the second protective film 11114 can both be flexible materials, and the material of the first protective film 11113 and the material of the second protective film 11114 include but are not limited to one of polypropylene, polyethylene or polyethylene.

[0070] It can be understood that the flexible material has the advantages of low rigidity and high elastic modulus, and by setting the material of the first protective film 11113 and the material of the second protective film 11114 to be flexible materials, the first protective film 11113 and the second protective film 11114 can adapt to the bending or deformation of the main body part 11111 and the to-be-cut part 11112 during the processing of the foil 1111, without exerting excessive stress on the foil 1111 or causing local hard contact, thereby avoiding the problem of surface damage or delamination of the foil 1111 caused by excessive rigidity of the protective film, that is, enhancing the anti-deformation ability of the foil 1111 during winding.

[0071] At the same time, during the transportation and subsequent processing (such as coating and winding) of the foil 1111, the flexible material can disperse local stress and absorb deformation, thereby effectively avoiding the problem of surface indentation, cracking or rupture of the foil 1111 caused by excessive hardness or insufficient ductility of the protective film material.

[0072] Further, the width of the first protective film 11113, the width of the second protective film 11114 and the width of the main body 11111 are equal, the orthographic projection of the first protective film 11113 on the foil 1111 coincides with the orthographic projection of the main body 11111 on the foil 1111, and the orthographic projection of the second protective film 11114 on the foil 1111 coincides with the orthographic projection of the main body 11111 on the foil 1111, so that the first protective film 11113 can be uniformly covered on the first surface of the main body 11111, and the second protective film 11114 can be uniformly covered on the second surface of the main body 11111, so that the symmetry and balance of the foil 1111 structure can be ensured while the foil 1111 is protected, and local stress concentration or unevenness caused by width mismatch can be avoided.

[0073] The utility model embodiment provides a kind of electric equipment, and the electric equipment includes the battery described in any of the above embodiments.

[0074] It can be understood that the battery has been described in detail in the above embodiments, and will not be repeated here.

[0075] The electric equipment includes battery, and the battery module is used as the power supply of electric equipment, therefore, the electric equipment also has the advantages of the above battery, so as to help simplify the overall structure of electric equipment;The electric equipment can be a car, an aircraft, a mechanical production equipment, etc.

[0076] The above embodiments of the utility model are described in detail, and the principle and implementation mode of the utility model are described by applying specific examples in this paper, and the above embodiment is only used to help understand the method and core idea of the utility model;At the same time, for those skilled in the art, according to the idea of the utility model, the specific implementation mode and application range will be changed, and the above is described, and the content of the specification should not be understood as the limitation of the utility model.

Claims

1. A foil material, characterized by, The foil comprises a coated area and a non-coated area located at least one side of the coated area, and the foil comprises: a main body part located in the coated area; a to-be-cut part located in the non-coated area; wherein the minimum thickness of the to-be-cut part is greater than or equal to the thickness of the main body part, and the thickness of the to-be-cut part away from the main body part is greater than the thickness of the to-be-cut part close to the main body part.

2. The foil of claim 1, wherein The relationship between the thickness of the to-be-cut part and the thickness of the to-be-cut part is h2=(1.5-2)h1; wherein h1 is the thickness of the main body part, and h2 is the thickness of the to-be-cut part.

3. The foil of claim 2, wherein The thickness of the main body part is greater than or equal to 4 microns and less than or equal to 5 microns, and the thickness of the to-be-cut part is greater than or equal to 5 microns and less than or equal to 7 microns.

4. The foil according to any one of claims 1 to 3, characterized in that, The thickness of the to-be-cut part gradually increases in the direction from the main body part to the to-be-cut part.

5. The foil of claim 4, wherein The to-be-cut part comprises a to-be-cut sub-part, and the relationship between the parameters of the to-be-cut sub-part, the to-be-cut part and the main body part is (D1-d) / w1=(D-d) / W; wherein D1 is the thickness of the to-be-cut sub-part, D is the maximum thickness of the to-be-cut part, d is the thickness of the main body part, W is the width of the to-be-cut part, and w1 is the width of the to-be-cut sub-part.

6. The foil according to any one of claims 1 to 3, characterized in that The main body part comprises oppositely arranged first and second surfaces; The foil further comprises a first protective film and a second protective film, the first protective film is arranged on the first surface, and the second protective film is arranged on the second surface; wherein the sum of the thickness of the first protective film, the thickness of the second protective film and the thickness of the main body part is equal to the maximum thickness of the to-be-cut part.

7. The foil of claim 6, wherein The orthographic projection of the first protective film on the foil coincides with the orthographic projection of the main body part on the foil, and the orthographic projection of the second protective film on the foil coincides with the orthographic projection of the main body part on the foil.

8. The foil of claim 6, wherein The material of the first protective film and the material of the second protective film are both polypropylene, polyethylene or one of polyethylene.

9. A pole piece characterized by, The foil comprises an active substance layer in the coated area of the foil, and a tab is arranged in the non-coated area of the foil.

10. A battery, characterized by The electric core comprises the tab as claimed in claim 9.

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