Current collector, battery pole piece, battery and electric equipment

Abstract

The invention provides a current collector, a battery pole piece, a battery and electric equipment. The current collector is used for preparing a battery pole piece, and the conductivity of the part, covered by the active material layer, of the current collector in the first direction of the battery pole piece is specially differentiated. The current collector provided by the invention is specially designed through the electronic conductivity, so that the reaction current in the active material layer is more uniform in the charging and discharging process of the battery, and the problems of potential generation, non-uniform SOC and the like in the first direction of a battery pole piece are effectively avoided; the fast charging capacity, the cycling stability, the battery capacity and the service life of the battery are improved.

Description

Technical Field

[0001] The embodiments of the present application relate to the field of battery technology, and specifically to a current collector, a battery pole piece, a battery, and an electrical device. Background Art

[0002] The active material layer of existing battery pole pieces is generally designed to be uniform, that is, the active materials in the active material layer of the battery pole piece are evenly distributed. However, during the actual use of the battery, this causes the current density, potential, lithium extraction / insertion and SOC at different positions of the battery pole piece to be unevenly distributed, thereby affecting the normal performance of important electrochemical properties of the battery, such as fast charging performance and cycle storage life. In extreme cases, it will also have a negative impact on the reliability and safety of the battery. Summary of the invention

[0003] In view of this, the present application provides a current collector, a battery pole piece, a battery, and an electrical device. The current collector is used to prepare a battery pole piece, and the conductivity of the portion of the current collector covered by the active material layer in the first direction of the battery pole piece is specially designed for differentiation. The current collector provided in the present application is specially designed through its electronic conductivity, so that the reaction current inside the active material layer is more uniform during the battery charging and discharging process, thereby effectively avoiding the problems of potential and SOC unevenness in the first direction of the battery pole piece, and improving the fast charging capability, cycle stability, battery capacity and service life of the battery.

[0004] In a first aspect, an embodiment of the present application provides a current collector, which is used to prepare a battery electrode sheet, wherein the battery electrode sheet comprises a current collector, an active material layer arranged on the surface of the current collector, and a pole ear arranged at one end of the battery electrode sheet in a first direction; the first direction is the length direction or the width direction of the battery electrode sheet;

[0005] The portion of the current collector covered by the active material layer is composed of a first region S1 and a second region S2 which are arranged side by side in sequence from close to the pole tab to away from the pole tab; the conductivity of the portion of the current collector covered by the active material layer increases from the side close to the pole tab to the side away from the pole tab, the conductivity of the second region S2 is greater than or equal to the maximum value of the conductivity of the first region S1, and the conductivity of the second region S2 is equal everywhere in the first direction of the battery electrode.

[0006] In the implementation manner of the present application, the conductivity of the measuring point in the first area S1 is denoted as A1, and the conductivity of the second area S2 is denoted as A2. Let y=A1 / A2, and the y corresponding to any measuring point in the first area S1 satisfies: 1.55*x+0.66-0.2*t≤y≤0.4*x+0.9625-0.0225*t, wherein t is the sum of the lengths of the first area S1 and the second area S2 in the first direction of the battery electrode, and the unit of t is meter; x is the ratio of s to t, s is the distance of the measuring point from the edge of the first area S1 away from the second area S2 on one side, and the unit of s is meter.

[0007] In the implementation manner of the present application, the value of t is greater than or equal to 0.2 and less than or equal to 1.5.

[0008] In the embodiment of the present application, the electrical conductivity of the portion of the current collector covered by the active material layer changes in a step-like gradient.

[0009] In the embodiment of the present application, the conductivity of the first region S1 increases from a side close to the electrode tab to a side away from the electrode tab.

[0010] In the implementation manner of the present application, the battery electrode is a positive electrode, and the current collector is a composite aluminum foil.

[0011] In an embodiment of the present application, the composite aluminum foil is a doped metal composite aluminum foil, and the doped metal composite aluminum foil includes a first doped metal element, and the first doped metal element includes one or more of Ag, Al, As, Au, B, Bi, C, Cd, Co, Cr, Fe, Mn, Ni, P, Pb, S, Sb, Se, Sn, Si, Zn, Zr and rare earth metal elements.

[0012] In the implementation manner of the present application, the battery electrode is a negative electrode, and the current collector is a composite copper foil.

[0013] In an embodiment of the present application, the composite copper foil is a doped metal composite copper foil, and the doped metal composite copper foil includes a second doped metal element, and the second doped metal element includes one or more of Ag, As, Au, B, Ba, Be, Bi, C, Ca, Ce, Co, Cr, Cu, Fe, Ga, Ge, Hf, Hg, In, La, Li, Mg, Mn, Mo, Nb, Nd, Ni, Np, Pb, Pd, Pr, Pt, Pu, Sb, Se, Si, Sn, Sr, Ta, Te, Th, Ti, Tl, U, V, W, Zn and Zr.

[0014] A second aspect of an embodiment of the present application provides a battery pole piece, and the battery pole piece includes the current collector provided in the first aspect of an embodiment of the present application.

[0015] A third aspect of an embodiment of the present application provides a battery, comprising the battery electrode provided in the second aspect of an embodiment of the present application.

[0016] A fourth aspect of the embodiments of the present application provides an electrical device, wherein the electrical device includes the battery provided in the third aspect of the embodiments of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a graph showing the relationship between the reaction current in the negative electrode active material layer close to the diaphragm side and the distance from the electrode ear on one side during fast charging of a laminated blade battery;

[0018] Figure 2 A functional relationship diagram of the electronic conductivity and position of the current collector of the battery electrode in the first direction of the battery electrode provided in one embodiment of the present application.

[0019] Description of Figure Numbers

[0020] 100 - battery pole piece; 101 - current collector; 102 - active material layer; 103 - pole ear. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0022] Existing battery cell pole pieces are generally designed to be uniform, that is, the active materials in the pole pieces are evenly distributed at the same thickness position. However, during the actual use of the battery, since electrons are conducted through the pole ears, the current distribution is not uniform, resulting in different degrees of de-embedding / embedding of the pole pieces at different positions. Generally speaking, the active material layer close to the pole ear has a higher potential and a higher SOC (State Of Charge), and is more prone to lithium deposition, which in turn affects the normal performance of the battery's electrochemical properties such as fast charging performance and cycle storage life. In extreme cases, it will also have a negative impact on the reliability and safety of the battery.

[0023] Figure 1 This is a graph showing the relationship between the reaction current in the negative electrode active material layer near the diaphragm side and the distance from the electrode ear on one side during fast charging of a stacked blade battery. Figure 1It can be seen that during the battery charging and discharging process, the initial reaction current of the active material layer in the length direction of the battery electrode is larger at the position of the positive and negative electrode ears close to the two ends of the battery, and the initial reaction current is smaller in the middle part of the positive and negative electrode ears far away from the two ends of the battery. This uneven current density distribution will gradually deepen with the use of the battery and affect the subsequent electrode reactions, resulting in uneven distribution of the battery electrode potential, de- / embedding degree and SOC, thereby affecting the normal performance of important electrochemical properties such as the battery's fast charging performance and cycle storage life.

[0024] In view of this, the present application provides a current collector, which is used to prepare a battery pole piece, and the conductivity of the portion of the current collector covered by the active material layer in the first direction of the battery pole piece is specially designed for differentiation. The current collector provided in the present application is specially designed through its electronic conductivity, so that the reaction current inside the active material layer is more uniform during the battery charging and discharging process, thereby effectively avoiding the problems of potential and SOC unevenness in the first direction of the battery pole piece, and improving the fast charging capability, cycle stability, battery capacity and service life of the battery.

[0025] like Figure 2 As shown, the embodiment of the present application provides a current collector 101, the current collector 101 is used to prepare a battery electrode 100, and the battery electrode 100 includes the current collector 101, an active material layer 102 arranged on the surface of the current collector 101, and a pole ear 103 arranged at one end of the battery electrode 100 in the first direction. In the embodiment of the present application, the first direction is the length direction or the width direction of the battery electrode 100. In the embodiment of the present application, the portion of the current collector 101 covered by the active material layer 102 is composed of a first region S1 and a second region S2 arranged side by side in sequence from the direction close to the pole ear 103 to the direction away from the pole ear 103, and the conductivity of the portion of the current collector 101 covered by the active material layer 102 increases from the side close to the pole ear 103 to the side away from the pole ear 103, the conductivity of the second region S2 is greater than or equal to the maximum value of the conductivity of the first region S1, and the conductivity of the second region S2 is equal everywhere in the first direction of the battery electrode. The conductivity of the current collector 101 provided in the embodiment of the present application in the first direction of the battery electrode 100 increases from the side close to the electrode tab 103 to the side away from the electrode tab 103, and remains unchanged after increasing to a certain value. In the embodiment of the present application, the situation that the conductivity of the second region S2 is equal everywhere is within the range of error that cannot be avoided in the process in the actual production process.

[0026] In the embodiment of the present application, the portion of the current collector 101 covered by the active material layer 102 is composed of a first region S1 and a second region S2 arranged side by side in a direction from close to the pole lug 103 to away from the pole lug 103. In the embodiment of the present application, the conductivity of the portion of the current collector covered by the active material layer can be gradual or can be a step-like gradient change. In some embodiments of the present application, the conductivity of the portion of the current collector covered by the active material layer is gradual, at which time the conductivity of the second region S2 is equal to the maximum value of the conductivity of the first region S1, and the conductivity of the second region S2 is equal everywhere in the first direction of the battery electrode, and is equal to the maximum value of the conductivity of the first region S1. In other embodiments of the present application, the conductivity of the portion of the current collector covered by the active material layer changes in a step-like gradient, at which time the conductivity of the second region S2 is greater than the maximum value of the conductivity of the first region S1.

[0027] In some embodiments of the present application, the conductivity of the first region S1 increases from the side close to the pole lug 103 to the side away from the pole lug 103. In the embodiments of the present application, the conductivity of the first region S1 can be gradual or step-like gradient. In some embodiments of the present application, the conductivity of the first region S1 is gradual, at which time the conductivity of the second region S2 is equal to the maximum value of the conductivity of the first region S1, and the conductivity of the second region S2 is equal everywhere in the first direction of the battery electrode, and is equal to the maximum value of the conductivity of the first region S1. In other embodiments of the present application, the conductivity of the first region S1 changes in a step-like gradient, at which time the conductivity of the second region S2 is greater than the maximum value of the conductivity of the first region S1.

[0028] In the embodiment of the present application, the sum of the first region S1 and the second region S2 of the current collector 101 completely overlaps with the orthographic projection of the active material layer 102 in the thickness direction of the battery electrode 100, that is, the active material layer 102 just completely covers the first region S1 and the second region S2 of the current collector. In some embodiments of the present application, the boundary line of the first region S1 and the second region S2 is parallel to the edge of the first region close to the pole ear and the edge of the second region away from the pole ear.

[0029] In the embodiments of the present application, the active material layer 102 may partially cover the surface of the current collector 101, or may completely cover the surface of the current collector 101. In some embodiments of the present application, the active material layer 102 may be distributed on the surface of one side of the current collector 101, or may be distributed on the surfaces of both sides of the current collector. When the active material layer 102 is distributed on both sides of the current collector 101, the conductivity distribution of the first region S1 and the second region S2 in the active material layer 102 distributed on both sides of the current collector may be the same or different. In some specific embodiments of the present application, the conductivity distribution of the first region S1 and the second region S2 in the active material layer 102 distributed on both sides of the current collector is the same. Since the chemical environment on both sides of the current collector is the same, controlling the conductivity distribution in the active layer of the material on both sides of the current collector to be the same can further improve the cycle stability of the battery.

[0030] In the embodiment of the present application, the conductivity of the measuring point in the first region S1 is A1, and the conductivity of the second region S2 is A2. Let y=A1 / A2, and the y corresponding to any of the measuring points in the first region S1 satisfies: 1.55*x+0.66-0.2*t≤y≤0.4*x+0.9625-0.0225*t, wherein t is the sum of the lengths of the first region S1 and the second region S2 in the first direction of the battery electrode 100, and the unit of t is meter; x is the ratio of s to t, and s is the distance of the measuring point from the edge of the first region S1 away from the second region S2, and the unit of s is meter. In the embodiment of the present application, the measuring point is any position point in the first region S1. In the embodiment of the present application, the value of t is greater than or equal to 0.2 and less than or equal to 1.5. In some specific embodiments, t can be, for example, 0.2, 0.3, 0.5, 0.6, 0.8, 1.0, 1.2, 1.5.

[0031] In some embodiments of the present application, t=1, that is, the sum of the lengths of the first region S1 and the second region S2 in the first direction of the battery electrode 100 is 1 meter, that is, the length of the active material layer 102 in the first direction of the battery electrode 100 is 1 meter. At this time, the functional relationship between the electronic conductivity and the position of the current collector 101 of the battery electrode 100 in the first direction of the battery electrode 100 is as follows: Figure 2 shown. Figure 2 In the figure, the horizontal axis is the ratio of the distance of the measuring point from the edge of the first region S1 close to the pole lug 103 to 1 meter, and the vertical axis is the ratio of the conductivity of the measuring point to the conductivity of the second region S2. Let the function of x and y of the measuring point be Y(X). In some embodiments of the present application, when t=1, 1.55*x+0.66-0.2*t≤y≤0.4*x+0.9625-0.0225*t is 1.55*x+0.4575≤y≤0.4*x+0.94, corresponding to Figure 2Among them, that is, the function formed by x and y of the measurement point is Y(X), which is located between the function y = 0.4*x + 0.94 and the function y = 1.55*x + 0.4575. And since the conductivity A1 of the measurement points in the first region S1 must be less than or equal to the conductivity A2 of the second region S2, so y ≤ 1. Therefore, in the first region S1, the curve of the function Y(X) formed by x and y of the measurement points is located within the shaded area enclosed by: (1) x = 0; (2) y = 1; (3) y = 0.4*x + 0.94; (4) y = 1.55*x + 0.4575. At this time, the first region S1 is the region of 0 ≤ x ≤ 0.35, and the second region S2 is the region of 0.35 < x ≤ 1. In the embodiment of the present application, the function Y(X) is a monotonically increasing function in the shaded area, and the shape of the curve of the function Y(X) is not limited. In some specific embodiments, the curve of the function Y(X) includes but is not limited to a stepped shape, a smooth curve, a broken line, etc. In the shaded area, the curve of the function Y(X) is monotonically increasing. When the function value increases to 1, as the independent variable X increases, the function value Y remains unchanged and continues to be 1.

[0032] In the present application, by performing a special gradient design on the electronic conductivity in the first direction of the first region S1 and the second region S2 of the current collector 101, it is possible to make the electronic conductivity of the battery electrode in the first direction increase gradually from the side close to the tab 103 to the side far from the tab 103, so that the electronic conductivity of the region where the current collector is covered by the active material layer is smaller on the side close to the tab and larger on the side far from the tab. Furthermore, it matches the characteristics that the initial reaction current in the active material layer is larger on the side close to the tab and smaller on the side far from the tab during the charge and discharge process of the battery. The non-uniformity of the electronic conductivity of the current collector compensates for the non-uniformity of the current density distribution in the active material layer, making the reaction current in the active material layer more uniform in the first direction of the battery electrode, and the electrochemical reaction occurs simultaneously at a more identical rate. As a result, the overall battery electrode shows a uniform electric potential and SOC in the first direction, effectively avoiding the uneven degree of lithium deintercalation / insertion in the first direction of the battery electrode, and improving the fast charging ability, cycle stability, battery capacity and service life of the battery.

[0033] In some embodiments of the present application, the battery electrode 100 is a positive electrode sheet. At this time, the current collector 101 is a composite aluminum foil. In the embodiment of the present application, the composite aluminum foil is a doped metal composite aluminum foil, and the doped metal composite aluminum foil includes a first doped metal element, and the first doped metal element is uniformly distributed in the thickness direction of the battery electrode 100. In the embodiment of the present application, the method of using the doped metal composite aluminum foil as the current collector includes but is not limited to forming an alloy with aluminum.

[0034] In the embodiment of the present application, in the first direction of the battery electrode 100 , the mass percentage of the first doped metal element in the composite aluminum foil covered by the active material layer 102 increases from the side close to the electrode tab 103 to the side away from the electrode tab 103 .

[0035] In an embodiment of the present application, the resistivity of the first doping metal element is less than that of aluminum. In some embodiments of the present application, the first doping metal element includes, but is not limited to, one or more of Ag, Al, As, Au, B, Bi, C, Cd, Co, Cr, Fe, Mn, Ni, P, Pb, S, Sb, Se, Sn, Si, Zn, Zr and rare earth metal elements.

[0036] In the embodiment of the present application, in the first direction of the battery electrode 100, the conductivity of the portion of the composite aluminum foil covered by the active material layer 102 increases from the side close to the electrode tab 103 to the side away from the electrode tab 103. In the embodiment of the present application, in the thickness direction of the battery electrode 100, the conductivity of the composite aluminum foil is equal everywhere.

[0037] In some embodiments of the present application, the battery pole piece 100 is a negative pole piece, and in this case, the current collector 101 is a composite copper foil. In the embodiments of the present application, the composite copper foil is a doped metal composite copper foil, and the doped metal composite copper foil includes a second doped metal element, and the second doped metal element is uniformly distributed in the thickness direction of the battery pole piece 100. In the embodiments of the present application, the doped metal composite copper foil current collector includes, but is not limited to, forming an alloy with copper.

[0038] In the embodiment of the present application, in the first direction of the battery electrode 100 , the mass percentage of the second doped metal element in the composite copper foil covered by the active material layer 102 increases from the side close to the electrode tab 103 to the side away from the electrode tab 103 .

[0039] In an embodiment of the present application, the resistivity of the second doping metal element is less than that of copper. In some embodiments of the present application, the second doping metal element includes, but is not limited to, one or more of Ag, As, Au, B, Ba, Be, Bi, C, Ca, Ce, Co, Cr, Cu, Fe, Ga, Ge, Hf, Hg, In, La, Li, Mg, Mn, Mo, Nb, Nd, Ni, Np, Pb, Pd, Pr, Pt, Pu, Sb, Se, Si, Sn, Sr, Ta, Te, Th, Ti, Tl, U, V, W, Zn and Zr.

[0040] In the embodiment of the present application, in the first direction of the battery electrode 100, the conductivity of the portion of the composite copper foil covered by the active material layer 102 increases from the side close to the electrode tab 103 to the side away from the electrode tab 103. In the embodiment of the present application, in the thickness direction of the battery electrode 100, the conductivity of the composite copper foil is equal everywhere.

[0041] The present application achieves the purpose of changing the electronic conductivity gradient of the current collector in the first direction of the battery electrode by doping and compounding the current collector with different metal elements and controlling the amount of added doped metal elements to regulate the electronic conductivity of the current collector, thereby improving the battery's cycle performance and extending the battery's service life.

[0042] In some embodiments of the present application, the preparation of the current collector 101 can be achieved by depositing the first doping element onto the surface of the aluminum foil and / or depositing the second doping element onto the surface of the copper foil by PVD (Physical Vapor Deposition), and controlling the amount of deposited doping metal added according to a special design to control the electronic conductivity of the current collector, and then preparing the current collector by rolling, so that the final current collector satisfies the functional relationship described above.

[0043] The present application also provides a battery pole piece, which includes the current collector provided above.

[0044] The present application also provides a battery, the battery comprising a positive electrode sheet, a negative electrode sheet, and a separator and an electrolyte located between the positive electrode sheet and the negative electrode sheet, the battery comprising the battery electrode sheet provided above. In some embodiments of the present application, the positive electrode sheet comprises the battery electrode sheet provided above. In some embodiments of the present application, the negative electrode sheet comprises the battery electrode sheet provided above. In some embodiments of the present application, both the positive electrode sheet and the negative electrode sheet comprise the battery electrode sheet provided above.

[0045] The present application also provides an electrical device, including the battery provided above. The electrical device may be, for example, an electric car, a mobile phone, a tablet computer, a laptop computer, a wearable device (a watch, a bracelet), a digital camera, etc.

[0046] The technical solution of the present application is further described below through specific embodiments:

[0047] Example 1

[0048] (1) An aluminum foil with a width of 1050 mm and a thickness of 15 μm was selected. From one end to the other, there was a blank area of ​​50 mm, a first sputtering area of ​​150 mm, a second sputtering area of ​​150 mm, and a non-sputtering area of ​​700 mm. The first sputtering area and the second sputtering area corresponded to the first area S1, and the non-sputtering area corresponded to the second area S2. When unwinding, the non-sputtering area was covered and protected. The aluminum foil was sputtered at a temperature of 200 °C and 5×10 -4The Si element is continuously sputtered onto the surface of the aluminum foil under a pressure of 1.5 Pa, so that the conductivity of the first sputtering area and the second sputtering area are both reduced to 95% of the non-sputtering area, and then the second sputtering area on which the surface has been sputtered is covered and protected, and the remaining first sputtering area is sputtered with the Si element for the second time, so that the conductivity is reduced to 90% of the non-sputtering area, thereby obtaining an aluminum foil current collector;

[0049] (2) A copper foil with a width of 1052 mm and a thickness of 8 μm was selected, and from one end to the other, there was a blank area of ​​50 mm, a first sputtering area of ​​151 mm, a second sputtering area of ​​150 mm, and a non-sputtering area of ​​701 mm, wherein the first sputtering area and the second sputtering area corresponded to the first area S1, and the non-sputtering area corresponded to the second area S2. When unwinding, the non-sputtering area was covered and protected. The copper foil was sputtered at a temperature of 190 °C and 5×10 -4 Ag element is continuously sputtered onto the surface of the copper foil under a pressure of 1.3 Pa, so that the conductivity of the first sputtering area and the second sputtering area are both reduced to 95% of the non-sputtering area, and then the second sputtering area on which the surface has been sputtered is covered and protected, and the remaining first sputtering area is sputtered for the second time, so that the conductivity is reduced to 90% of the non-sputtering area, thereby obtaining a copper foil current collector;

[0050] (3) 2 kg of a conductive agent carbon black and carbon nanotube mixture, 2 kg of a binder polyvinylidene fluoride (PVDF), 100 kg of a positive electrode active material lithium iron phosphate and 75 kg of a solvent N-methylpyrrolidone (NMP) were mixed to obtain a positive electrode active slurry, and the positive electrode active slurry was coated on the treated aluminum foil current collector with a coating width of 1000 mm, leaving the blank area uncoated, and a positive electrode sheet was obtained after drying and rolling, and the thickness of the positive electrode active material layer was 150 μm;

[0051] (4) 2 kg of a conductive agent carbon black and carbon nanotube mixture, 2 kg of a binder styrene butadiene latex (SBR), 100 kg of a negative electrode active material graphite and 100 kg of solvent water were mixed to obtain a negative electrode active slurry, and the negative electrode active slurry was coated on the treated copper foil current collector with a coating width of 1002 mm, leaving the blank area uncoated, and a negative electrode sheet was obtained after drying and rolling, and the thickness of the negative electrode active material layer was 120 μm;

[0052] (5) The positive electrode sheet and the negative electrode sheet are cut and die-cut respectively, and the positive electrode sheet, the separator and the negative electrode sheet are stacked in sequence to obtain a pole core, wherein the pole core has pole ears led out on both sides, and the pole ears are led out at a blank area, and the portion of the negative electrode sheet that exceeds the positive electrode sheet in the first direction is 1 mm, and the pole core is packaged, injected, formed, aged and divided into different capacities to obtain a battery pole core.

[0053] Example 2

[0054] The preparation method is the same as that of Example 1, except that: in step (1), the conductivity of the first sputtering area of ​​the aluminum foil collector is 94% of that of the non-sputtering area, and the conductivity of the second sputtering area is 99% of that of the non-sputtering area; in step (2), the conductivity of the first sputtering area of ​​the copper foil collector is 94% of that of the non-sputtering area, and the conductivity of the second sputtering area is 99% of that of the non-sputtering area.

[0055] Example 3

[0056] The preparation method is the same as that of Example 1, except that: in step (1), the conductivity of the first sputtering area of ​​the aluminum foil collector is 86% of that of the non-sputtering area, and the conductivity of the second sputtering area is 93% of that of the non-sputtering area; in step (2), the conductivity of the first sputtering area of ​​the copper foil collector is 86% of that of the non-sputtering area, and the conductivity of the second sputtering area is 93% of that of the non-sputtering area.

[0057] Example 4

[0058] The preparation method is the same as that of Example 1, and the difference from Example 1 is that: in step (1), the aluminum foil is sequentially arranged from one end to the other end: a blank area of ​​50 mm, a first sputtering area of ​​100 mm with a conductivity of 90% of the non-sputtering area, a second sputtering area of ​​100 mm with a conductivity of 92% of the non-sputtering area, a third sputtering area of ​​100 mm with a conductivity of 95% of the non-sputtering area, and a non-sputtering area of ​​700 mm, wherein the first sputtering area, the second sputtering area and the third sputtering area correspond to the first area S1, and the non-sputtering area The sputtering area corresponds to the second area S2; in step (2), the copper foil is, from one end to the other end: a blank area of ​​50 mm, a first sputtering area of ​​101 mm with a conductivity of 90% of the non-sputtering area, a second sputtering area of ​​100 mm with a conductivity of 92% of the non-sputtering area, a third sputtering area of ​​100 mm with a conductivity of 95% of the non-sputtering area, and a non-sputtering area of ​​701 mm, wherein the first sputtering area, the second sputtering area and the third sputtering area correspond to the first area S1, and the non-sputtering area corresponds to the second area S2.

[0059] Example 5

[0060] The preparation method is the same as that of Example 1, and the difference from Example 1 is that: in step (1), the aluminum foil is, from one end to the other, in sequence: a blank area of ​​50 mm, a first sputtering area of ​​250 mm, a second sputtering area of ​​250 mm, and a non-sputtering area of ​​500 mm, wherein the first sputtering area and the second sputtering area correspond to the first area S1, and the non-sputtering area corresponds to the second area S2; in step (2), the copper foil is, from one end to the other, in sequence: a blank area of ​​50 mm, a first sputtering area of ​​251 mm, a second sputtering area of ​​250 mm, and a non-sputtering area of ​​501 mm, wherein the first sputtering area and the second sputtering area correspond to the first area S1, and the non-sputtering area corresponds to the second area S2.

[0061] Example 6

[0062] The preparation method is the same as that of Example 1, and the difference from Example 1 is that in step (2), the copper foil is not subjected to sputtering treatment and is directly used as a copper foil current collector.

[0063] Example 7

[0064] The preparation method is the same as that of Example 1, and the difference from Example 1 is that in step (1), the aluminum foil is not subjected to sputtering treatment and is directly used as an aluminum foil current collector.

[0065] Comparative Example 1

[0066] The preparation method is the same as that of Example 1, except that in step (1), the aluminum foil is not subjected to sputtering treatment and is directly used as the aluminum foil current collector; in step (2), the copper foil is not subjected to sputtering treatment and is directly used as the copper foil current collector.

[0067] Comparative Example 2

[0068] The preparation method is the same as that of Example 1, and the difference from Example 1 is that: in step (1), the aluminum foil is composed of a blank area of ​​50 mm, a non-sputtering area of ​​150 mm, a first sputtering area of ​​150 mm with a conductivity of 95% of the non-sputtering area, and a second sputtering area of ​​700 mm with a conductivity of 90% of the non-sputtering area from one end to the other end;

[0069] In step (2), the copper foil is arranged from one end to the other in the following order: a blank area of ​​50 mm, a non-sputtering area of ​​151 mm, a first sputtering area of ​​150 mm having a conductivity of 95% of the non-sputtering area, and a second sputtering area of ​​701 mm having a conductivity of 90% of the non-sputtering area.

[0070] Related performance tests

[0071] Conductivity test:

[0072] The current collectors prepared in the embodiments and comparative examples were measured perpendicular to the starting line using the four-probe method. A flat sample surface was prepared, and four probes were fixed on the current collector surface at specific intervals. Current was applied to the sample through two current probes to form a detection area. The voltage difference in the detection area was measured through the other two voltage probes. The conductivity of the current collector was calculated based on the measured current and voltage values.

[0073] Electrochemical performance test:

[0074] The battery cores prepared in Examples 1 to 7 and Comparative Examples 1 to 2 were tested using the following method:

[0075] Take 40 batteries prepared in each embodiment and comparative example, and perform charge and discharge cycle test at 1C rate on secondary battery performance test device under 318±1K condition. The steps are as follows: leave for 30 minutes; charge at constant voltage until 3.8V / 0.1C is cut off; leave for 30 minutes; discharge at constant current until 2.0V, which is 1 cycle. Repeat this step 500 times, and the cycle is terminated. Compare the initial capacity ratio of the battery cells (with embodiment 1 as the denominator, that is, the initial capacity of each embodiment and comparative example / initial capacity of embodiment 1) and the capacity retention rate, take the average value for each group, and take out 2 batteries every 50 cycles for disassembly to confirm whether edge lithium plating occurs. The cycle life and lithium plating data are shown in Table 1.

[0076] Table 1

[0077]

[0078] As can be seen from Table 1, the embodiments of the present application make special designs for the electronic conductivity of the current collector, so that the prepared battery cell has better cycle performance and is not prone to lithium precipitation problems, effectively improving the service life and safety performance of the battery. And from the data of Example 1, Example 5, and Example 6, it can be seen that the special design of the electronic conductivity of the current collectors of the positive and negative electrodes of the battery at the same time is better than the special design of the electronic conductivity of the current collector of a single electrode. The cycle performance of the battery is better.

[0079] The above is an exemplary embodiment of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made thereto without departing from the principles of the present application. These improvements and modifications are also considered to be within the scope of protection of the present application.

Claims

1. A current collector, characterized in that: The current collector is used to prepare a battery pole piece, and the battery pole piece includes a current collector, an active material layer arranged on the surface of the current collector, and a pole ear arranged at one end of the battery pole piece in a first direction; the first direction is the length direction or the width direction of the battery pole piece; The portion of the current collector covered by the active material layer is composed of a first region S1 and a second region S2 which are arranged side by side in sequence from close to the pole tab to away from the pole tab; the conductivity of the portion of the current collector covered by the active material layer increases from the side close to the pole tab to the side away from the pole tab, the conductivity of the second region S2 is greater than or equal to the maximum value of the conductivity of the first region S1, and the conductivity of the second region S2 is equal everywhere in the first direction of the battery electrode.

2. The current collector according to claim 1, characterized in that Let the conductivity of the measuring point in the first area S1 be A1, and the conductivity of the second area S2 be A2. Let y=A1 / A2, and the y corresponding to any measuring point in the first area S1 satisfies: 1.55*x+0.66-0.2*t≤y≤0.4*x+0.9625-0.0225*t, wherein t is the sum of the lengths of the first area S1 and the second area S2 in the first direction of the battery electrode, and the unit of t is meter; x is the ratio of s to t, s is the distance of the measuring point from the edge of the first area S1 away from the second area S2, and the unit of s is meter.

3. The current collector according to claim 2, characterized in that: The value of t is greater than or equal to 0.2 and less than or equal to 1.

5.

4. The current collector according to any one of claims 1 to 3, characterized in that: The electrical conductivity of the portion of the current collector covered by the active material layer changes in a step-like gradient.

5. The current collector according to any one of claims 1 to 4, characterized in that: The electrical conductivity of the first region S1 increases from a side close to the electrode tab to a side away from the electrode tab.

6. The current collector according to any one of claims 1 to 5, characterized in that: The battery pole piece is a positive pole piece, and the current collector is a composite aluminum foil.

7. The current collector according to claim 6, characterized in that The composite aluminum foil is a doped metal composite aluminum foil, and the doped metal composite aluminum foil includes a first doped metal element, and the first doped metal element includes one or more of Ag, Al, As, Au, B, Bi, C, Cd, Co, Cr, Fe, Mn, Ni, P, Pb, S, Sb, Se, Sn, Si, Zn, Zr and rare earth metal elements.

8. The current collector according to any one of claims 1 to 5, characterized in that: The battery pole piece is a negative pole piece, and the current collector is a composite copper foil.

9. The current collector according to claim 8, characterized in that: The composite copper foil is a doped metal composite copper foil, and the doped metal composite copper foil includes a second doped metal element, and the second doped metal element includes one or more of Ag, As, Au, B, Ba, Be, Bi, C, Ca, Ce, Co, Cr, Cu, Fe, Ga, Ge, Hf, Hg, In, La, Li, Mg, Mn, Mo, Nb, Nd, Ni, Np, Pb, Pd, Pr, Pt, Pu, Sb, Se, Si, Sn, Sr, Ta, Te, Th, Ti, Tl, U, V, W, Zn and Zr.

10. A battery pole piece, characterized in that: The battery pole piece includes the current collector as described in any one of claims 1-9.

11. A battery, characterized in that: The battery comprises the battery pole piece as claimed in claim 10.

12. An electrical equipment, characterized in that: The electric device comprises the battery as claimed in claim 11.

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