A current collector, a battery pole piece, a battery, and an electric device

Abstract

The application provides a current collector, a battery pole piece, a battery and an electric device. The current collector is used for preparing the battery pole piece, and the conductivity of the current collector covered by an active material layer in a first direction of the battery pole piece is specially designed in a differential manner. The current collector provided by the application is specially designed in terms of electronic conductivity, so that the internal reaction current of the active material layer is more uniform during the charging and discharging of the battery, and in turn, problems such as uneven electric potential and SOC in the first direction of the battery pole piece are effectively avoided, and the fast charging capability, cycle stability, battery capacity and service life of the battery are improved.

Description

TECHNICAL FIELD

[0001] Embodiments of the present application relate to the technical field of batteries, in particular to a current collector, a battery pole piece, a battery and an electric device. BACKGROUND

[0002] The active material layer of the existing battery pole piece is generally uniformly designed, that is, the active material in the active material layer of the battery pole piece is uniformly distributed, but in the actual use process 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 play of important electrochemical properties such as fast charging performance and cycle storage life of the battery, and in extreme cases, it also has a negative impact on the reliability and safety of the battery. SUMMARY

[0003] In view of this, the present application provides a current collector, a battery pole piece, a battery and an electric device. The current collector is used to prepare a battery pole piece, and the conductivity of the current collector covered by the active material layer in the first direction of the battery pole piece is specially designed. The current collector provided by the present application is specially designed by its electronic conductivity, so that the internal reaction current of the active material layer is more uniform during the charging and discharging process of the battery, thereby effectively avoiding problems such as uneven potential and SOC 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] The first aspect of the embodiments of the present application provides a current collector, which is used to prepare a battery pole piece, the battery pole piece comprising a current collector, an active material layer arranged on the surface of the current collector, and a tab 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.

[0005] The current collector covered by the active material layer is composed of a first region S1 and a second region S2 arranged side by side in turn from the tab to the direction away from the tab; the conductivity of the current collector covered by the active material layer increases from the side close to the tab to the side away from the 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 pole piece.

[0006] In the embodiment of the present application, the conductivity of the measurement point in the first area S1 is A1, the conductivity of the second area S2 is A2, y=A1 / A2, and the y corresponding to any measurement 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 pole piece, the unit of t is meter; x is the ratio of s to t, s is the distance of the measurement point from the edge of the first area S1 away from the second area S2, the unit of s is meter.

[0007] 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.

[0008] In the embodiment of the present application, the conductivity of the part of the current collector covered by the active material layer changes in a stepwise gradient.

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

[0010] In the embodiment of the present application, the battery pole piece is a positive pole piece, and the current collector is a composite aluminum foil.

[0011] 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 comprises a first doped metal element, and the first doped metal element comprises 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 embodiment of the present application, the battery pole piece is a negative pole piece, and the current collector is a composite copper foil.

[0013] In the embodiment of the present application, the composite copper foil is a doped metal composite copper foil, and the doped metal composite copper foil comprises a second doped metal element, and the second doped metal element comprises 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] The second aspect of the embodiment of the present application provides a battery pole piece, which comprises the current collector provided by the first aspect of the embodiment of the present application.

[0015] The third aspect of the embodiments of the present application provides a battery, which comprises the battery pole piece provided by the second aspect of the embodiments of the present application.

[0016] The fourth aspect of the embodiments of the present application provides a power consumption device, which comprises the battery provided by the third aspect of the embodiments of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 A relationship diagram of reaction current in the negative active material layer close to the diaphragm side and the distance from the side tab for a stacked type blade battery during fast charging;

[0018] Figure 2 A function relationship diagram of the electronic conductance of the current collector of the battery pole piece provided by an embodiment of the present application in the first direction of the battery pole piece and the position.

[0019] REFERENCE SIGNS

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

[0021] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application will be further described in detail below in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and do not limit the present application.

[0022] The existing battery pole piece is generally uniformly designed, i.e., the active material in the pole piece is uniformly distributed at the same thickness position. However, in the actual use process of the battery, the distribution of the current is not uniform due to the conduction of the electrons through the tab, thus leading to different degrees of de-intercalation / intercalation of the pole piece at different positions. Generally speaking, the active material layer close to the tab side has a higher potential and a higher SOC (State Of Charge), and is more likely to cause lithium precipitation and other phenomena, thus affecting the normal play of the electrochemical performance of the battery, such as fast charging performance, cycle storage life, etc. In the extreme case, it also has a negative impact on the reliability and safety of the battery.

[0023] Figure 1 A relationship diagram of reaction current in the negative active material layer close to the diaphragm side and the distance from the side tab for a stacked type blade battery during fast charging. From Figure 1As can be seen, in the process of battery charging and discharging, the initial reaction current of the active material layer in the length direction of the battery pole piece is larger at the positions close to the positive and negative pole tabs at both ends of the battery, and smaller at the middle part away from the positive and negative pole tabs at both ends of the battery. The non-uniformity of such current density distribution will gradually deepen during the use of the battery, and will affect the subsequent electrode reaction, causing the non-uniformity of the potential, the degree of deintercalation / intercalation and the SOC distribution of the battery pole piece, and further affecting the normal performance of important electrochemical properties of the battery such as fast charging performance, cycle storage life and the like.

[0024] In view of this, the application provides a current collector for preparing a battery pole piece, the conductivity of the current collector covered by the active material layer in the first direction of the battery pole piece is specially designed to be different. The current collector provided by the application is specially designed in terms of electronic conductivity, so that the internal reaction current of the active material layer is more uniform during the charging and discharging process of the battery, thereby effectively avoiding the problems of non-uniform potential and SOC 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] As shown in Figure 2 The application embodiment provides a current collector 101 for preparing a battery pole piece 100, the battery pole piece 100 comprising the current collector 101, an active material layer 102 arranged on the surface of the current collector 101, and a pole tab 103 arranged at one end of the battery pole piece 100 in the first direction. In the application embodiment, the first direction is the length direction or the width direction of the battery pole piece 100. In the application embodiment, 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 from the side close to the pole tab 103 to the side away from the pole tab 103, and the conductivity of the current collector 101 covered by the active material layer 102 increases from the side close to the pole tab 103 to the side away from the pole tab 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 pole piece. The conductivity of the current collector 101 provided by the application embodiment in the first direction of the battery pole piece 100 increases from the side close to the pole tab 103 to the side away from the pole tab 103, and remains unchanged after increasing to a certain value. In the application embodiment, the case that the conductivity of the second region S2 is equal everywhere is allowed to exist within a range of unavoidable errors in the actual production process.

[0026] In some embodiments of the application, the conductivity of the portion of the current collector 101 covered by the active material layer 102 gradually increases from the side close to the tab 103 to the side away from the tab 103. In some embodiments of the application, the conductivity of the portion of the current collector 101 covered by the active material layer 102 gradually increases from the side close to the tab 103 to the side away from the tab 103, and 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 tab, and is equal to the maximum value of the conductivity of the first region S1. In some other embodiments of the application, the conductivity of the portion of the current collector 101 covered by the active material layer 102 gradually increases from the side close to the tab 103 to the side away from the tab 103, and 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 application, the conductivity of the first region S1 gradually increases from the side close to the tab 103 to the side away from the tab 103. In some embodiments of the application, the conductivity of the first region S1 gradually increases from the side close to the tab 103 to the side away from the tab 103, and 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 tab, and is equal to the maximum value of the conductivity of the first region S1. In some other embodiments of the application, the conductivity of the first region S1 gradually increases from the side close to the tab 103 to the side away from the tab 103, and the conductivity of the second region S2 is greater than the maximum value of the conductivity of the first region S1.

[0028] In some embodiments of the application, the sum of the first region S1 and the second region S2 of the current collector 101 is completely coincident with the orthographic projection of the active material layer 102 in the thickness direction of the battery tab 100, i.e. the active material layer 102 completely covers the first region S1 and the second region S2 of the current collector. In some embodiments of the application, the boundary line between the first region S1 and the second region S2 is parallel to the edge of the first region close to the tab and the edge of the second region away from the tab.

[0029] In some embodiments of the present application, the active material layer 102 can partially cover the surface of the current collector 101, or can fully cover the surface of the current collector 101. In some embodiments of the present application, the active material layer 102 can be distributed on one side of the current collector 101, or can be distributed on both sides of the current collector 101. 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 101 can 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 101 is the same. Since the chemical environment on both sides of the current collector is the same, controlling the conductivity distribution of the active material layer on both sides of the current collector to be the same can further improve the cycle stability of the battery.

[0030] In some embodiments of the present application, the conductivity of the measurement point in the first region S1 is denoted as A1, the conductivity of the second region S2 is denoted as A2, and y = A1 / A2. The y corresponding to any measurement point in the first region S1 satisfies: 1.55*x+0.66-0.2*t≤y≤0.4*x+0.9625-0.0225*t, where 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 sheet 100, and the unit of t is meter; x is the ratio of s to t, and s is the distance from the measurement point to the edge of the first region S1 away from the second region S2, and the unit of s is meter. In some embodiments of the present application, the measurement point is any position point in the first region S1. In some embodiments 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 0.2, 0.3, 0.5, 0.6, 0.8, 1.0, 1.2, 1.5, for example.

[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 sheet 100 is 1 meter, that is, the length of the active material layer 102 in the first direction of the battery electrode sheet 100 is 1 meter. At this time, the function relationship between the electronic conductivity of the current collector 101 of the battery electrode sheet 100 in the first direction of the battery electrode sheet 100 and the position is as shown in FIG. 6. Figure 2 Figure 2 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, which corresponds to Figure 2 ​In the middle, that is, the function of the x and y of the measurement point Y(X) 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 point of the first area S1 is certainly less than or equal to the conductivity A2 of the second area S2, y <= 1, so in the first area S1, the curve of the function Y(X) of the x and y of the measurement point is located in the shadow area surrounded by the four straight lines: (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 area S1 is the area of 0 <= x <= 0.35, and the second area S2 is the area of 0.35 < x <= 1. In the embodiment of the application, the function Y(X) in the shadow area is a monotonically increasing function, 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 step type, a smooth curve, a polyline, etc. In the shadow area, the curve of the function Y(X) is monotonically increasing, and when the function value increases to 1, the function value Y does not change with the increase of the independent variable X and continues to remain 1.

[0032] By specially designing the gradient of the electronic conductivity of the first area S1 and the second area S2 of the current collector 101 in the first direction, the electronic conductivity of the battery tab in the first direction is gradiently increased from the side close to the tab 103 to the side far from the tab 103, so that the electronic conductivity of the area of the current collector covered by the active material layer is smaller on the side close to the tab and larger on the side far from the tab, which is further matched with 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 charging and discharging process of the battery, so that the non-uniformity of the electronic conductivity of the current collector and the non-uniformity of the current density distribution in the active material layer are mutually compensated, the reaction current in the active material layer in the first direction of the battery tab is more uniform, the electrochemical reaction occurs at the same rate, and the battery tab as a whole presents uniform potential and SOC in the first direction, effectively avoiding the non-uniformity of the deintercalation / lithiation degree of the battery tab in the first direction, and improving the fast charging capability, cycle stability, battery capacity and service life of the battery.

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

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

[0035] In the embodiments of the present application, the resistivity of the first doped metal element is less than that of aluminum. In some embodiments of the present application, the first doped 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 embodiments of the present application, in the first direction of the battery pole piece 100, the electrical conductivity of the part of the composite aluminum foil covered by the active material layer 102 increases from the side close to the tab 103 to the side away from the tab 103. In the embodiments of the present application, the electrical conductivity of the composite aluminum foil is equal everywhere in the thickness direction of the battery pole piece 100.

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

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

[0039] In the embodiments of the present application, the resistivity of the second doped metal element is less than that of copper. In some embodiments of the present application, the second doped 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 embodiments of the present application, in the first direction of the battery pole piece 100, the electrical conductivity of the part of the composite copper foil covered by the active material layer 102 increases from the side close to the tab 103 to the side away from the tab 103. In the embodiments of the present application, the electrical conductivity of the composite copper foil is equal everywhere in the thickness direction of the battery pole piece 100.

[0041] The application realizes the gradient change of the electronic conductivity of the current collector in the first direction of the battery electrode sheet by doping different metal elements into the current collector and controlling the addition amount of the doped metal elements to further regulate the electronic conductivity of the current collector, thereby improving the cycle performance of the battery and prolonging the service life of the battery.

[0042] In some embodiments of the application, the preparation of the current collector 101 can be performed by PVD (Physical Vapor Deposition) to deposit the first doped element onto the surface of the aluminum foil and / or deposit the second doped element onto the surface of the copper foil, and control the addition amount of the deposited doped metal to further control the electronic conductivity of the current collector according to a special design, and then obtain the current collector by rolling, so that the finally obtained current collector satisfies the function relationship described above.

[0043] The application also provides a battery electrode sheet comprising the current collector provided above.

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

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

[0046] The technical solutions of the application are further described below through specific examples:

[0047] Example 1

[0048] (1) An aluminum foil with a width of 1050 mm and a thickness of 15 μm is selected, and from one end to the other end, it is sequentially: 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, 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. The non-sputtering area is covered and protected during unwinding. Through a magnetron sputtering device, the first doped element is deposited onto the surface of the aluminum foil at a temperature of 200 ℃ and a pressure of 5 × 10 -4The Si element is sputtered to the surface of the aluminum foil under the pressure of Pa, so that the electrical conductivity of the first sputtering area and the second sputtering area is reduced to 95% of that of the non-sputtering area, then the second sputtering area which has been sputtered on the surface is protected, and the first sputtering area is sputtered with the Si element again, so that the electrical conductivity of the first sputtering area is reduced to 90% of that of the non-sputtering area, thereby obtaining the aluminum foil current collector;

[0049] (2) The copper foil with a width of 1052 mm and a thickness of 8 μm is selected, and from one end to the other end, the copper foil is sequentially provided with a blank area with a width of 50 mm, a first sputtering area with a width of 151 mm, a second sputtering area with a width of 150 mm, and a non-sputtering area with a width of 701 mm. 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. The non-sputtering area is protected during unwinding. The Ag element is sputtered to the surface of the copper foil by a magnetron sputtering device at a temperature of 190 ℃ and a pressure of 5×10 -4 Pa, so that the electrical conductivity of the first sputtering area and the second sputtering area is reduced to 95% of that of the non-sputtering area, then the second sputtering area which has been sputtered on the surface is protected, and the first sputtering area is sputtered with the Si element again, so that the electrical conductivity of the first sputtering area is reduced to 90% of that of the non-sputtering area, thereby obtaining the aluminum 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-methyl pyrrolidone (NMP) are mixed to obtain a positive electrode active paste. The positive electrode active paste is coated on the treated aluminum foil current collector, and the coating width is 1000 mm. The blank area is not coated. After drying and rolling, a positive electrode sheet is obtained. The thickness of the positive electrode active material layer is 150 μm.

[0051] (4) 2 kg of a conductive agent carbon black and carbon nanotube mixture, 2 kg of a binder styrene butadiene rubber (SBR), 100 kg of a negative electrode active material graphite, and 100 kg of a solvent water are mixed to obtain a negative electrode active paste. The negative electrode active paste is coated on the treated copper foil current collector, and the coating width is 1002 mm. The blank area is not coated. After drying and rolling, a negative electrode sheet is obtained. The thickness of the negative electrode active material layer is 120 μm.

[0052] (5) The positive electrode sheet and the negative electrode sheet are respectively cut and die-cut. The positive electrode sheet, a separator, and the negative electrode sheet are sequentially stacked to obtain a core. The core is a double-sided tab lead-out type. The tab lead-out position is the blank area. The part of the negative electrode sheet in the first direction that exceeds the positive electrode sheet is 1 mm. The core is packaged, injected, formed, aged, and filled to obtain a battery core.

[0053] Example 2

[0054] The preparation method is the same as that of Example 1, with the exception that in step (1), the conductivity of the first sputtered region of the aluminum foil current collector is 94% of that of the non-sputtered region, and the conductivity of the second sputtered region is 99% of that of the non-sputtered region; in step (2), the conductivity of the first sputtered region of the copper foil current collector is 94% of that of the non-sputtered region, and the conductivity of the second sputtered region is 99% of that of the non-sputtered region.

[0055] Example 3

[0056] The preparation method is the same as that of Example 1, with the exception that in step (1), the conductivity of the first sputtered region of the aluminum foil current collector is 86% of that of the non-sputtered region, and the conductivity of the second sputtered region is 93% of that of the non-sputtered region; in step (2), the conductivity of the first sputtered region of the copper foil current collector is 86% of that of the non-sputtered region, and the conductivity of the second sputtered region is 93% of that of the non-sputtered region.

[0057] Example 4

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

[0059] Example 5

[0060] The preparation method is the same as that of Example 1, except that in step (1), the aluminum foil is sequentially from one end to the other end: 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 region S1, and the non-sputtering area corresponds to the second region S2; and in step (2), the copper foil is sequentially from one end to the other end: 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 region S1, and the non-sputtering area corresponds to the second region S2.

[0061] Example 6

[0062] The preparation method is the same as that of Example 1, except that in step (2), the copper foil is directly used as the copper foil current collector without sputtering treatment.

[0063] Example 7

[0064] The preparation method is the same as that of Example 1, except that in step (1), the aluminum foil is directly used as the aluminum foil current collector without sputtering treatment.

[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 directly used as the aluminum foil current collector without sputtering treatment; and in step (2), the copper foil is directly used as the copper foil current collector without sputtering treatment.

[0067] Comparative Example 2

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

[0069] In step (2), the copper foil is sequentially from one end to the other end: 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 Test

[0071] Conductivity Test:

[0072] The current collector prepared by the examples and the comparative examples is measured by the four-probe method vertically to the starting line, a smooth sample surface is prepared, four probes are fixed on the surface of the current collector according to a specific spacing, a current is applied to the sample by two current probes to form a detection area, and the voltage difference in the detection area is measured by the other two voltage probes, and the conductivity of the current collector is calculated according to the measured current and voltage values.

[0073] Electrochemical performance test:

[0074] The battery pole core prepared by example 1 to example 7 and comparative example 1 to comparative example 2 is tested by the following method:

[0075] 40 batteries prepared by each example and the comparative example are taken, and the batteries are subjected to charge-discharge cycle test at 1C rate under the condition of 318±1K on a secondary battery performance detection device. The steps are as follows: standing for 30 min; constant voltage charging to 3.8V / 0.1C cut-off; standing for 30 min; constant current discharging to 2.0V, which is 1 cycle. The steps are repeated for 500 times, and the cycle is terminated, the initial capacity ratio (taking example 1 as the denominator, i.e. the initial capacity of each example and the comparative example / the initial capacity of example 1) and the capacity retention rate of the comparative pole core are taken, and the average value of each group is taken, and 2 batteries are taken out every 50 cycles to be disassembled to confirm whether the edge lithium precipitation problem occurs, and the data of the cycle life and the lithium precipitation are shown in table 1.

[0076] Table 1

[0077]

[0078] As can be seen from table 1, the electronic conductivity of the current collector is specially designed in the examples, so that the cycle performance of the prepared battery pole core is better, and the lithium precipitation problem is less likely to occur, and the service life and safety performance of the battery are effectively improved. And from the data of example 1, example 5 and example 6, it can be seen that compared with the special design of the electronic conductivity of the current collector of a single pole piece, the special design of the electronic conductivity of the current collector of the positive and negative pole pieces of the battery has better cycle performance.

[0079] The above is an exemplary embodiment of the present application, and it should be noted that those skilled in the art can make some improvements and refinements without departing from the principles of the present application, and these improvements and refinements are also considered within the protection scope of the present application.

Claims

1. A current collector characterized by comprising: The current collector is used to prepare a battery pole piece, the battery pole piece comprising a current collector, an active material layer arranged on the surface of the current collector, and a tab arranged at one end of the battery pole piece in a first direction of the battery pole piece; the first direction is a length direction or a width direction of the battery pole piece; The current collector covered by the active material layer is composed of a first region S1 and a second region S2 arranged side by side in turn from the side close to the tab to the side away from the tab; the electrical conductivity of the current collector covered by the active material layer increases from the side close to the tab to the side away from the tab, the electrical conductivity of the second region S2 is greater than or equal to the maximum value of the electrical conductivity of the first region S1, and the electrical conductivity of the second region S2 is equal everywhere in the first direction of the battery pole piece; the electrical conductivity of the measuring point in the first region S1 is denoted as A1, the electrical conductivity of the second region S2 is denoted as A2, and y=A1 / A2, the y corresponding to any measuring point 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 pole piece, the unit of t is meter, the value of t is greater than or equal to 0.2 and less than or equal to 1.5; x is the ratio of s to t, s is the distance of the measuring point from the edge of the first region S1 away from the second region S2, the unit of s is meter.

2. The current collector of claim 1, wherein The electrical conductivity of the current collector covered by the active material layer changes in a stepwise gradient.

3. The current collector of claim 1, wherein The electrical conductivity of the first region S1 increases from the side close to the tab to the side away from the tab.

4. The current collector of any one of claims 1-3, wherein The battery pole piece is a positive pole piece, and the current collector is a composite aluminum foil.

5. The current collector of claim 4, wherein The composite aluminum foil is a doped metal composite aluminum foil, and the doped metal composite aluminum foil comprises a first doped metal element, and the first doped metal element comprises one or more of Ag, Au, Bi, Cd, Co, Cr, Fe, Mn, Ni, Pb, Sb, Sn, Zn, Zr, and rare earth metal elements.

6. The current collector of any one of claims 1-3, wherein The battery pole piece is a negative pole piece, and the current collector is a composite copper foil.

7. The current collector of claim 6, wherein The composite copper foil is a doped metal composite copper foil, and the doped metal composite copper foil comprises a second doped metal element, and the second doped metal element comprises one or more of Ag, Au, Ba, Be, Bi, Ca, Ce, Co, Cr, Fe, Ga, Ge, Hf, Hg, In, La, Li, Mg, Mn, Mo, Nb, Nd, Ni, Np, Pb, Pd, Pr, Pt, Pu, Sb, Sn, Sr, Ta, Th, Ti, Tl, U, V, W, Zn, and Zr.

8. A battery electrode sheet, characterized by, The battery pole piece comprises the current collector according to any one of claims 1-7.

9. A battery, characterized by The battery comprises the battery pole piece according to claim 8.

10. An electric device, characterized by The electrical equipment comprises the battery according to claim 9.

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