Negative plate, lithium battery and vehicle

Abstract

The invention provides a negative electrode piece, a lithium battery and a vehicle, the negative electrode piece comprises a negative electrode current collector and a negative electrode lug, the negative electrode lug is connected with the negative electrode current collector, the negative electrode current collector comprises a first surface, the first surface is provided with a modified material layer, the modified material layer is located at the edge of the first surface, and the modified material layer is provided with a modified material. The modified material is used for chemical reaction with the lithium metal, and by limiting the setting position of the modified material, the consumption of the lithium metal by the modified material is reduced, the service life of the battery is prolonged, and the stability of the battery is improved.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a negative electrode sheet, a lithium battery and a vehicle. Background Art

[0002] As the third generation of lithium batteries, the "negative electrode-free" lithium battery abandons the traditional negative electrode active material, and lithium ions can be directly deposited and analyzed on the negative electrode current collector. Therefore, the "negative electrode-free" lithium battery has a higher energy density and has received widespread attention since its introduction.

[0003] However, during the charge and discharge process of the "negative electrode-free" lithium battery, lithium ions are excessively deposited on the current collector, causing the current collector surface to become powdery, forming a small amount of "dead lithium" that is separated from the negative electrode current collector. The "dead lithium" is free in the electrolyte, which not only causes the loss of metallic lithium, but also leads to internal short circuits in the battery cell, corrosion of the battery case or corrosion of the pole ears, thereby affecting the service life and safety and stability of the "negative electrode-free" lithium battery.

[0004] Therefore, it is of great significance to improve the service life, safety and stability of "negative electrode-free" lithium batteries. Summary of the invention

[0005] The purpose of the present application is to provide a negative electrode sheet, a lithium battery and a vehicle to solve the problem of large-scale consumption of lithium metal after the negative electrode current collector is modified.

[0006] To achieve the purpose of this application, this application provides the following technical solutions:

[0007] In a first aspect, the present application provides a negative electrode sheet, comprising a negative electrode collector and a negative electrode ear, wherein the negative electrode ear is connected to the negative electrode collector, the negative electrode collector comprises a first surface, the first surface is provided with a modified material layer, the modified material layer is located at the edge of the first surface, the modified material layer has a modified material, and the modified material is used to produce a chemical reaction with lithium metal.

[0008] In one embodiment, the first surface includes a first edge and a second edge opposite to each other, and at least one of the first edge and the second edge is provided with the modified material layer.

[0009] In one embodiment, the first surface further includes a third edge and a fourth edge opposite to each other, wherein the third edge and the fourth edge are both connected to the first edge and the second edge, and at least one of the third edge and the fourth edge is provided with the modified material layer.

[0010] In one embodiment, the negative electrode current collector further includes a second surface, the second surface and the first surface are arranged opposite to each other, and the second surface is provided with the modified material layer.

[0011] In one embodiment, the negative electrode tab extends from the first edge.

[0012] In one embodiment, the modified material includes M a T b , wherein M is selected from one or more of Cu, Si, Sn, Fe, Co, Ni, Ti, Zn, Ge, In and Ag, T is selected from one or more of O, N, P, F and S, 1≤a≤3, 1≤b≤4.

[0013] In one embodiment, M a T b It is one or more of CuO, SnO2, SnO, Fe2O3, Co3O4, ZnO, ZnS, CuS, Ni3S2, GeO2, CuF2, ZnF2, Ni2O3, TiO2, Cu3N2, SiO, In2O3 and Ag2O.

[0014] In one embodiment, the modified material includes A, and A is selected from one or more of Si, Sn, Al, Zn, Ge, In, Au and Ag.

[0015] In one embodiment, the width of the modified material layer on one side is 0.1 mm to 3 mm; and in the thickness direction of the negative electrode current collector, the thickness of the modified material layer is 0.02 μm to 50 μm.

[0016] In a second aspect, the present application further provides a lithium battery, comprising a shell and a negative electrode sheet as described in any one of the embodiments of the first aspect, wherein a negative electrode collector of the negative electrode sheet is accommodated inside the shell.

[0017] In a third aspect, the present application also provides a vehicle, comprising the lithium battery described in the second aspect.

[0018] The negative electrode sheet provided in the present application includes a negative electrode collector and a negative electrode ear, which is connected to the negative electrode collector. The negative electrode collector is provided with a modified material layer, which is located at the edge of the negative electrode collector so that the edge of the negative electrode collector is locally modified. The modified material layer has a modified material, and the modified material can chemically react with lithium metal. By setting the modified material layer on the path where "dead lithium" is freed to the inside of the battery cell, the modified material reacts with the "dead lithium" to consume the free "dead lithium" in the electrolyte to prevent it from affecting the safety and stability of the battery; at the same time, the product of the reaction with the "dead lithium" remains at the edge of the negative electrode sheet, and can also form a physical barrier to prevent the "dead lithium" formed during the cycle from continuously floating out with the electrolyte and affecting the service life of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the implementation methods of the present application or the technical solutions in the prior art, the drawings required for use in the implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0020] Figure 1 is a schematic structural diagram of a wound negative electrode sheet according to an embodiment;

[0021] Figure 2 is a schematic structural diagram of a stacked negative electrode sheet according to an embodiment;

[0022] Figure 3 It is a schematic diagram of the structure of a rewinding device, a modification device and a negative electrode sheet according to an implementation mode;

[0023] Figure 4 is a flow chart of preparing a negative electrode sheet according to an embodiment;

[0024] Figure 5 The present invention is a schematic diagram of the structure of the negative electrode current collector after the battery is disassembled according to an embodiment.

[0025] Description of reference numerals:

[0026] 10-negative electrode sheet, 20-rewinding equipment, 30-modification equipment;

[0027] 11 - negative electrode current collector, 111 - first edge, 112 - second edge, 113 - third edge, 114 - fourth edge, 12 - negative electrode ear, 13 - modified material layer. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0029] It should be noted that when a component is said to be "fixed to" another component, it can be directly on the other component or there can be a central component. When a component is said to be "connected to" another component, it can be directly connected to the other component or there can be a central component at the same time.

[0030] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used in this application and in the specification are only for the purpose of describing specific embodiments and are not intended to limit this application. The term "and / or" used in this application includes any and all combinations of one or more of the related listed items.

[0031] In conjunction with the accompanying drawings, some embodiments of the present application are described in detail below. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0032] The present application embodiment provides a negative electrode sheet 10, see Figure 1 and Figure 2 The negative electrode sheet 10 includes a negative electrode current collector 11 and a negative electrode ear 12. The negative electrode ear 12 is connected to the negative electrode current collector 11. The negative electrode current collector 11 includes a first surface. The first surface is provided with a modified material layer 13. The modified material layer 13 is located at the edge of the first surface.

[0033] The negative electrode current collector 11 may be made of copper foil or copper alloy. The modified material layer 13 has a modified material that is different from the material of the negative electrode current collector 11 . The modified material can chemically react with lithium ions, while the copper foil or copper alloy does not chemically react with lithium ions.

[0034] The negative electrode current collector 11 further includes a second surface, which is disposed opposite to the first surface and is also provided with a modified material layer 13 .

[0035] Optionally, the modified material layer 13 at the second surface is arranged in the same manner as the modified material layer 13 at the first surface, and the arrangement position of the modified material layer 13 at the second surface corresponds to the arrangement position of the modified material layer 13 at the first surface, that is, the orthographic projection of the modified material layer 13 at the second surface on the first surface completely overlaps with the modified material layer 13 at the first surface.

[0036] Optionally, the negative electrode tab 12 is connected to the second surface.

[0037] The negative electrode current collector 11 can be wound, and in the wound negative electrode current collector 11, its first surface is located on the outside of the wound negative electrode current collector 11, and its second surface is located on the inside of the wound negative electrode current collector 11, so that the modified material layer 13 is located on the outer surface of the wound negative electrode current collector 11, and the modified material layer 13 is arranged in a circumferential direction of the wound negative electrode current collector 11.

[0038] The negative electrode current collector 11 may also be stacked, and a plurality of negative electrode current collectors 11 are stacked to form a multilayer structure. The stacked negative electrode current collector 11 includes two outer surfaces opposite to each other in its stacking direction, and the two outer surfaces may both be the first surface of the negative electrode current collector 11; or one may be the first surface of the negative electrode current collector 11 and the other may be the second surface of the negative electrode current collector 11. The first surface of the negative electrode current collector 11 is provided with a modified material layer 13, so that at least one surface of the stacked negative electrode current collector 11 is provided with a modified material layer 13.

[0039] During the charge and discharge process of the lithium battery, lithium metal will be deposited on the surface of the negative electrode current collector 11. The modified material layer 13 is arranged at the edge of the first surface of the negative electrode current collector 11, so that the modified material at the modified material layer 13 has little or almost no contact with the lithium metal deposited on the negative electrode current collector 11, thereby avoiding excessive consumption of active lithium.

[0040] When lithium metal is pulverized on the surface of the negative electrode current collector 11, a small amount of "dead lithium" separated from the negative electrode current collector 11 will be formed. The "dead lithium" will be freed to the inside of the battery cell, which will cause short circuit, corrosion of the battery shell or corrosion of the pole ear. The modified material layer 13 is set at the edge of the first surface of the negative electrode current collector 11. The "dead lithium" will pass through the modified material layer 13 in the process of being freed to the inside of the battery cell. The modified material at the modified material layer 13 can react with the "dead lithium", thereby consuming the "dead lithium" in the electrolyte. The product of the reaction with the "dead lithium" remains at the edge of the negative electrode sheet, and can also form a physical barrier to prevent the "dead lithium" formed during the cycle from continuously floating out with the electrolyte and affecting the performance of the battery.

[0041] The negative electrode sheet 10 includes a negative electrode collector 11 and a negative electrode ear 12. The negative electrode collector 11 is made of a copper alloy foil such as pure copper foil, brass or red copper. The negative electrode ear 12 is connected to the negative electrode collector 11. The negative electrode collector 11 is provided with a modified material layer 13. The modified material layer 13 is located at the edge of the negative electrode collector 11, so that the edge of the negative electrode collector 11 is locally modified. The modified material layer 13 has a modified material. The modified material can react chemically with lithium metal. By arranging the modified material layer on the path where "dead lithium" is freed to the inside of the battery cell, the modified material reacts with the "dead lithium" to consume the free "dead lithium" in the electrolyte to avoid affecting the safety and stability of the battery. At the same time, the product of the reaction with the "dead lithium" remains at the edge of the negative electrode sheet, and can also form a physical barrier to prevent the "dead lithium" formed during the cycle from continuously floating out with the electrolyte and affecting the service life of the battery.

[0042] In one implementation, see Figure 1 The first surface of the negative electrode current collector 11 includes a first edge 111 and a second edge 112 opposite to each other, and at least one of the first edge 111 and the second edge 112 is provided with a modified material layer 13 .

[0043] Taking the direction from the first edge 111 to the second edge 112 as the width direction, the width and extension length of the modified material layer 13 at the first edge 111 and the modified material layer 13 at the second edge 112 can be equal, so that the area of ​​the modified material layer 13 at the first edge 111 is equal to the area of ​​the modified material layer 13 at the second edge 112.

[0044] The first surface further includes a third edge 113 and a fourth edge 114 opposite to each other. The third edge 113 and the fourth edge 114 are both connected to the first edge 111 and the second edge 112 . At least one of the third edge 113 and the fourth edge 114 is provided with a modified material layer 13 .

[0045] Taking the direction from the third edge 113 to the fourth edge 114 as the length direction, the modified material layer 13 at the first edge 111 to the second edge 112 extends along the length direction, and the modified material layer 13 from the third edge 113 to the fourth edge 114 extends along the width direction.

[0046] Similarly, the length and width of the modified material layer 13 at the third edge 113 and the modified material layer 13 at the fourth edge 114 may be equal, so that the area of ​​the modified material layer 13 at the third edge 113 is equal to the area of ​​the modified material layer 13 at the fourth edge 114 .

[0047] Optionally, the length of the modified material layer 13 at the third edge 113 is equal to the width of the modified material layer 13 at the first edge 111 .

[0048] In one implementation, see Figure 1 , the negative electrode ear 12 extends from the first edge 111 .

[0049] When the negative electrode current collector 11 is wound or stacked, the modified material layer 13 can be located on the outer surface of the negative electrode current collector 11. This avoids the situation where the modified material layer 13 is located at both ends of the negative electrode current collector 11 in the winding direction when the negative electrode current collector 11 is wound, so that part of the modified material layer 13 is wound inside, affecting the performance.

[0050] In one implementation, see Figure 2 The modified material layer 13 is disposed on all four edges of the first surface, so that the modified material layer 13 is disposed around the edge of the first surface of the negative electrode current collector 11 .

[0051] The negative electrode current collectors 11 are stacked. When the negative electrode current collectors 11 form a stacked structure, the modified material layers 13 are located on two opposite outer surfaces in the stacking direction of the negative electrode current collectors 11. Both of the two opposite outer surfaces are provided with modified material layers 13 arranged around the surface edges.

[0052] When the negative electrode current collector 11 is wound, the modified material layers 13 at both ends of the negative electrode current collector 11 in the winding direction will be covered during the winding process.

[0053] By providing the modified material layer 13 on all four edges of the first surface, the modified material layer 13 is evenly distributed on the edge of the first surface of the negative electrode current collector 11. The modified material layer 13 is arranged on the path where the "dead lithium" that falls off the surface of the negative electrode current collector 11 is freed to the inside of the battery cell. The modified material reacts with the "dead lithium" to consume the "dead lithium" in the electrolyte to prevent it from affecting the performance of the battery.

[0054] In one embodiment, the modified material comprises a chemical formula M a T b The metal compound is selected from one or more of Cu, Si, Sn, Fe, Co, Ni, Ti, Zn, Ge, In and Ag, T is selected from one or more of O, N, P, F and S, 1≤a≤3, 1≤b≤4. Specifically, the lithium metal reacts with the modified material, and the lithium metal replaces the M ions in the modified material to generate a lithium-containing compound and M metal. The chemical reaction formula of the reaction is: M a T b +aLi→Li a T b +aM.

[0055] Optionally, the modified material includes a metal compound of a single chemical formula; or, the modified material includes a combination of metal compounds of multiple chemical formulas, and the combination ratio of the metal salt materials of the multiple chemical formulas is adjusted according to actual conditions.

[0056] By making the modified material include a chemical formula M a T b The metal compound, M element is selected from metal elements with lower activity than lithium element, and T element is selected from nitrogen element, oxygen element or halogen element with oxidizing property, which is beneficial to the reaction between lithium metal and M element. a T b The replacement reaction occurs smoothly, and the “dead lithium” passing through the modified material layer 13 of the negative electrode current collector 11 is absorbed.

[0057] In one embodiment, M a T b It is one or more of CuO, SnO2, SnO, Fe2O3, Co3O4, ZnO, ZnS, CuS, Ni3S2, GeO2, CuF2, ZnF2, Ni2O3, TiO2, Cu3N2, SiO, In2O3 and Ag2O.

[0058] In one embodiment, the modified material includes A, and A is selected from one or more metal elements selected from Si, Sn, Al, Zn, Ge, In, Au and Ag. Specifically, when the modified material is a metal element, the lithium metal and the metal element undergo an alloying reaction, and the electrons of the lithium metal are captured by the metal of the metal element to generate positive lithium ions and negative metal ions. The chemical reaction formula of the reaction is: A+cLi→Li c A.

[0059] Optionally, the modified material is a metal material of a single element; or, the modified material is a combination of metal materials of multiple elements, and the combination ratio of the metal materials of multiple elements is adjusted according to actual conditions; or, the modified material includes a combination of a metal material and the above-mentioned metal salt materials, the modified material undergoes a substitution reaction and an alloying reaction with lithium metal at the same time, and the combination ratio of the metal element and the metal compound is adjusted according to actual conditions.

[0060] The modified material layer 13 may further include a binder, and the modified material layer 13 may be bonded to the negative electrode current collector 11 by the binder.

[0061] By making the modified material include a metal element with lower activity than lithium, the metal element in the modified material reacts with lithium metal to form an alloy at a low potential, thereby absorbing the "dead lithium" passing through the modified material layer 13 of the negative electrode current collector 11. In one embodiment, please refer to Figure 1 and Figure 2 The width of the single-sided modified material layer 13 is 0.1 mm to 3 mm in the direction from the first edge 111 to the second edge 112 , and the thickness of the modified material layer 13 is 0.02 μm to 50 μm in the thickness direction of the negative electrode current collector 11 .

[0062] It can be understood that the width of the single-sided modified material layer 13 refers to the width of the modified material layer 13 at the first edge 111 or the width of the modified material layer 13 at the second edge 112, rather than the sum of the widths of the modified material layer 13 at the first edge 111 and the modified material layer 13 at the second edge 112. That is, in the extension direction perpendicular to the modified material layer 13 at the first edge 111, the width of the modified material layer 13 at the first edge 111 is 0.1 mm to 3 mm; the modified material layer 13 at the second edge 112 is similar to the modified material layer 13 at the first edge 111.

[0063] Optionally, the width of the single-sided modified material layer 13 is 0.5 mm to 3 mm; the thickness of the modified material layer 13 is 0.1 μm to 40 μm.

[0064] When the width of the single-sided modified material layer 13 meets the above range, the single-sided area of ​​the modified material layer 13 is within a reasonable range, so that the single-sided area of ​​the modified material layer 13 is smaller, thereby avoiding the problem of excessive consumption of active lithium due to excessive modified material in the modified material layer 13; when the single-sided width of the modified material layer 13 is smaller than the above range, the single-sided area of ​​the modified material layer 13 is too small, and the absorption of "dead lithium" of the modified material layer 13 passing through the negative electrode current collector 11 is poor; when the single-sided width of the modified material layer 13 is greater than the above range, the single-sided area of ​​the modified material layer 13 is too large, and there are too many modified materials, which easily consumes too much active lithium, reduces the content of active lithium in the battery, and affects the energy density and cycle life of the battery.

[0065] When the thickness of the modified material layer 13 satisfies the above range, the thickness of the modified material layer 13 is within a reasonable range, avoiding the thickness of the modified material layer 13 being too thick or too thin, reducing the uniformity of the surface of the negative electrode collector 11, and further affecting the uniformity of lithium metal deposition on the surface of the negative electrode collector 11.

[0066] By making the width and thickness of the modified material layer 13 meet the above ranges, the area of ​​the modified material layer 13 is within a reasonable range, thereby ensuring the modification effect on the negative electrode current collector 11, and also making the area of ​​the modified material layer 13 smaller, thereby avoiding the problem of excessive consumption of active lithium due to excessive modified material in the modified material layer 13. At the same time, the thickness of the modified material is also made within a reasonable range, thereby ensuring the uniformity of the surface of the negative electrode current collector 11.

[0067] The present application also provides a method for preparing the negative electrode sheet 10, see Figure 1 , Figure 3 and Figure 4 The preparation method of the negative electrode sheet 10 includes:

[0068] Step S10: fixing the negative electrode current collector 11 on the rewinding device 20;

[0069] Step S20: starting the rewinding device 20 to drive the negative electrode current collector 11 to move;

[0070] Step S30: starting the modification device 30, the modification device 30 processes at least one side of the negative electrode current collector 11, so that a modified material layer 13 is formed on the surface of the negative electrode current collector 11, and the modified material layer 13 includes a modified material, and the modified material is used to produce a chemical reaction with lithium metal;

[0071] Step S40 : connecting the negative electrode tab 12 to one side of the negative electrode current collector 11 .

[0072] Specifically, the negative electrode current collector 11 fixed on the rewinding device 20 is in sheet shape. The rewinding device 20 includes a guide member and a traction member. The negative electrode current collector 11 contacts the guide member and moves under the action of the traction member. Optionally, the guide member and the traction member are both rollers. There are multiple guide members, which are arranged at intervals to jointly support and guide the negative electrode current collector 11.

[0073] Optionally, in the above step S20, the rewinding device 20 drives the negative electrode current collector 11 to move at a speed of 0.05 m / s.

[0074] Optionally, in the above step S30, the modification device 30 includes any one of a laser device or a coating device, without limitation.

[0075] When the modification device 30 is a laser device, the frequency of the laser emitted by the laser device is 100 kHz to 450 kHz, and the residence time of the laser emitted by the laser device on the surface of the negative electrode current collector 11 is 60 ns to 100 ns.

[0076] Optionally, in the above step S30 , the single-side width of the modified material layer 13 formed by the modifying device 30 on the surface of the negative electrode current collector 11 is 0.1 mm to 3 mm, and the single-side thickness of the modified material layer 13 is 20 nm to 50 μm.

[0077] Optionally, in the above step S30, the modification device 30 causes the modified material layer 13 of the negative electrode current collector 11 to form an oxide. The specific oxide depends on the selection of the current collector. For example, when the current collector is copper foil, the generated oxide is copper oxide or cuprous oxide. When other substances (such as nitrides, sulfides or fluorides) are formed in the modified material layer 13, the modified material layer 13 can be treated by magnetron sputtering or slurry coating; when the slurry coating method is adopted, the modified material layer also includes a binder. Specifically, the modified material, the binder and the solvent are mixed to prepare a slurry, and the slurry is applied to a specific area of ​​the current collector and dried to form a modified material layer 13.

[0078] In one implementation, see Figure 1 and Figure 4 The modifying device 30 emits laser light to irradiate the side where the negative electrode current collector 11 is connected to the negative electrode tab 12 and the side where the negative electrode current collector 11 is opposite to the negative electrode tab 12 .

[0079] In one implementation, see Figure 3 and Figure 4 After the modification device 30 irradiates the two opposite sides of the negative electrode current collector 11 with a laser, the negative electrode current collector 11 is cut, and then the cut negative electrode current collector 11 is fixed on the rewinding device 20. The modification device 30 emits a laser to irradiate the two sides adjacent to the side where the negative electrode current collector 11 is connected to the negative electrode ear 12.

[0080] Optionally, the width of the negative electrode current collector 11 after trimming is 63 mm, and the length of the negative electrode current collector 11 after trimming is 74 mm. The specific electrode sheet size can be further limited according to the use requirements.

[0081] This application also provides a lithium battery, see Figure 1 and Figure 2 , comprising a shell and the negative electrode sheet 10 provided in any one of the above embodiments, wherein the negative electrode collector 11 of the negative electrode sheet 10 is accommodated inside the shell, and the negative electrode ear 12 of the negative electrode sheet 10 is located outside the shell.

[0082] The lithium battery of the present application also includes a positive electrode sheet and a diaphragm, wherein the diaphragm is disposed between the positive electrode sheet and the negative electrode sheet. The auxiliary material area of ​​the positive electrode sheet is smaller than that of the negative electrode sheet; preferably, the auxiliary material area of ​​the positive electrode sheet is smaller than the area of ​​the negative electrode sheet (negative electrode current collector) where no material layer is disposed.

[0083] It can be understood that the lithium battery in this embodiment has the negative electrode sheet 10 in the above embodiment. Therefore, the lithium battery in this embodiment has all the technical effects of the negative electrode sheet 10 in the above embodiment. Since the technical effects of the negative electrode sheet 10 have been fully explained in the above embodiment, they will not be repeated here.

[0084] The present application also provides a vehicle, comprising the lithium battery provided in the above embodiment.

[0085] It can be understood that the vehicle in this embodiment has the lithium battery in the above embodiment. Therefore, the vehicle in this embodiment has all the technical effects of the lithium battery in the above embodiment. Since the technical effects of the lithium battery have been fully explained in the above embodiment, they will not be repeated here.

[0086] The technical solution of the present invention is described in detail below through specific embodiments.

[0087] Example 1

[0088] This embodiment provides a negative electrode sheet with a thickness of 10 μm, a width of 63 mm, and a length of 74 mm. The negative electrode sheet is provided with a modified region, the modified region is provided at the edges of the current collector, and the modified region has a modified material layer, the width of the single-side modified material layer is 1 mm, the thickness of the single-side modified material layer of the electrode sheet is 2 μm, and the modified material layer includes CuO.

[0089] Example 2

[0090] The negative electrode sheet provided in this embodiment is different from that in Embodiment 1 in that the modified material layer includes SnO2.

[0091] Example 3

[0092] The negative electrode sheet provided in this embodiment is different from that in Embodiment 1 in that the modified material layer includes CuS.

[0093] Example 4

[0094] The negative electrode sheet provided in this embodiment is different from that in Embodiment 1 in that the modified material layer includes Ni3S2.

[0095] Example 5

[0096] The negative electrode sheet provided in this embodiment is different from that in Embodiment 1 in that the modified material layer includes ZnS.

[0097] Example 6

[0098] The negative electrode sheet provided in this embodiment is different from that in Embodiment 1 in that the modified material layer includes Zn.

[0099] Example 7

[0100] The negative electrode sheet provided in this embodiment is different from that in Embodiment 1 in that the modified material layer includes Sn.

[0101] Example 8

[0102] The negative electrode sheet provided in this embodiment is different from that in Embodiment 1 in that the modified material layer includes Al.

[0103] Example 9

[0104] The negative electrode sheet provided in this embodiment is different from that in Embodiment 1 in that the modified material layer includes Cu and CuO.

[0105] Example 10

[0106] The negative electrode sheet provided in this embodiment is different from that in Embodiment 1 in that the modified material layer includes Zn and ZnS.

[0107] Embodiment 11

[0108] The negative electrode sheet provided in this embodiment is different from that in Embodiment 1 in that the single-side width of the modified material layer is 0.5 mm.

[0109] Example 12

[0110] The negative electrode sheet provided in this embodiment is different from that in Embodiment 1 in that the single-side width of the modified material layer is 1.5 mm.

[0111] Example 13

[0112] The negative electrode sheet provided in this embodiment is different from that in Embodiment 1 in that the single-side width of the modified material layer is 0.1 mm.

[0113] Embodiment 14

[0114] The negative electrode sheet provided in this embodiment is different from that in Embodiment 1 in that the single-side width of the modified material layer is 3 mm.

[0115] Embodiment 15

[0116] The negative electrode sheet provided in this embodiment is different from that in Embodiment 1 in that the thickness of the modified material layer on one side is 0.1 μm.

[0117] Example 16

[0118] The negative electrode sheet provided in this embodiment is different from that in Embodiment 1 in that the thickness of the modified material layer on one side is 40 μm.

[0119] Embodiment 17

[0120] The negative electrode sheet provided in this embodiment is different from that in Embodiment 1 in that the thickness of the modified material layer on one side is 0.02 μm.

[0121] Embodiment 18

[0122] The negative electrode sheet provided in this embodiment is different from that in Embodiment 1 in that the thickness of the modified material layer on one side is 50 μm.

[0123] Embodiment 19

[0124] The negative electrode sheet provided in this embodiment is different from that in Embodiment 1 in that the modified region is arranged on one side of the electrode ear.

[0125] Comparative Example 1

[0126] The difference between the negative electrode sheet provided in this comparative example and the negative electrode sheet provided in Example 19 is that no modified material layer is provided in the modified area.

[0127] Comparative Example 2

[0128] The difference between the negative electrode sheet provided in this comparative example and the negative electrode sheet provided in Example 1 is that a modified material layer is provided on the surface of the current collector.

[0129] In order to illustrate the electrochemical performance of the negative electrode sheet provided in Example 1, the following test steps were performed:

[0130] (1) The positive electrode active material (LiNi 0.70 Co 0.10 Mn 0.20O2) 48.5g, conductive agent (acetylene black) 1.0g and binder (polyvinylidene fluoride, PVDF) 0.5g are mixed in N-methylpyrrolidone (NMP) to form a stable and uniform slurry, wherein the stirring speed of the vacuum mixer is 1000rpm and the stirring time is 12h; then the obtained slurry is coated on the current collector aluminum sheet, the surface density is controlled to be 395g / m2, and then dried at 80°C, and then cut into positive electrode sheets with a size of 57×68mm; then the cut positive electrode sheets are dried at 80°C, and a flat positive electrode sheet is obtained after being pressed by a roller press, and one of the sheets is cut into sheets with a diameter of 13mm to assemble button batteries for capacity calibration, and the calibrated capacity is 7.5mAh / cm 2 .

[0131] (2) The negative electrode current collectors Z1-19, DZ1, and DZ2 of the above-mentioned Examples 1-19, Comparative Examples 1 and 2 are directly used as negative electrodes, and are stacked layer by layer with the separator and the positive electrode sheet to assemble into batteries, and 2.2 mL / Ah electrolyte is added dropwise, and the electrolyte is 1 wt% LiNO3 dissolved in 4 MLiFSI ethylene glycol dimethyl ether (DME), and then packaged to obtain batteries S1-19 and DS1-DS2, respectively.

[0132] Five batteries each of S1-19 and DS1-DS2 were taken and the batteries were subjected to charge and discharge cycle tests at 0.2C at 25°C on a secondary battery performance testing device.

[0133] The test steps are as follows: leave for 10 minutes; charge at 0.2C constant current to 4.3V, charge at constant voltage to 4.3V / 0.05C; leave for 10 minutes; discharge at 0.5C to 3.0V, which is the first cycle. Then charge at 0.2C constant current to 4.3V, charge at constant voltage to 4.3V / 0.05C; leave for 10 minutes; discharge at 0.5C to 3.6V, repeat this step, when the battery capacity is less than 80% of the second discharge capacity during the cycle, the cycle is terminated, and the number of cycles is the cycle life of the battery, and the average value is taken for each group. The mass energy density is calculated by multiplying the first discharge capacity by the average discharge voltage, and then dividing by the mass of the battery, that is, the mass energy density of the battery is obtained, in Wh / Kg.

[0134] See also Figure 5 The battery disassembly steps are as follows: discharge the cycled battery at 0.5C to 3.0V, then transfer the battery to the disassembly room for disassembly, disassemble the aluminum-plastic film, and then carefully take out the battery cell; then peel off the outermost diaphragm of the battery cell to expose the outer copper foil (i.e., the negative electrode current collector 11), observe the black matter in the T1-T4 area, and evaluate based on the presence or absence, more or less of black matter.

[0135] The results of the cell evaluation after testing and disassembly are shown in Table 1 below:

[0136] Table 1

[0137]

[0138]

[0139] It can be seen from the test results of Examples 1-19 and Comparative Examples 1-2 in Table 1 that the battery mass energy density and cycle life are effectively improved by forming a local modified region on the surface of the negative electrode current collector.

[0140] In the description of the embodiments of the present application, it should be noted that the orientation or positional relationship of terms such as "center", "up", "down", "left", "right", "vertical", "horizontal", "inside" and "outside" are based on the orientation or positional relationship of the accompanying drawings, which are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or original referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application.

[0141] What is disclosed above is only a preferred embodiment of the present application, and it certainly cannot be used to limit the scope of rights of the present application. Ordinary technicians in this field can understand that all or part of the processes of implementing the above embodiment and equivalent changes made according to the claims of the present application are still within the scope covered by the present application.

Claims

1. A negative electrode sheet, characterized in that: It includes a negative electrode current collector and a negative electrode ear, wherein the negative electrode ear is connected to the negative electrode current collector, the negative electrode current collector includes a first surface, the first surface is provided with a modified material layer, the modified material layer is located at the edge of the first surface, the modified material layer has a modified material, and the modified material is used to produce a chemical reaction with lithium metal.

2. The negative electrode sheet according to claim 1, characterized in that: The first surface includes a first edge and a second edge opposite to each other, and at least one of the first edge and the second edge is provided with the modified material layer.

3. The negative electrode sheet according to claim 2, characterized in that: The first surface further includes a third edge and a fourth edge opposite to each other, wherein the third edge and the fourth edge are both connected to the first edge and the second edge, and at least one of the third edge and the fourth edge is provided with the modified material layer.

4. The negative electrode sheet according to claim 2, characterized in that: The negative electrode current collector further includes a second surface, the second surface is arranged opposite to the first surface, and the second surface is provided with the modified material layer.

5. The negative electrode sheet according to claim 4, characterized in that: The negative electrode tab extends from the first edge.

6. The negative electrode sheet according to claim 1, characterized in that: The modified material includes M a T b , wherein M is selected from one or more of Cu, Si, Sn, Fe, Co, Ni, Ti, Zn, Ge, In and Ag, T is selected from one or more of O, N, P, F and S, 1≤a≤3, 1≤b≤4.

7. The negative electrode sheet according to claim 6, characterized in that: M a T b It is at least one of CuO, SnO2, SnO, Fe2O3, Co3O4, ZnO, ZnS, CuS, Ni3S2, GeO2, CuF2, ZnF2, Ni2O3, TiO2, Cu3N2, SiO, In2O3 and Ag2O.

8. The negative electrode sheet according to claim 1 or 6, characterized in that: The modified material includes A, and A is selected from one or more of Si, Sn, Al, Zn, Ge, In, Au and Ag.

9. The negative electrode sheet according to claim 2, characterized in that: The width of the modified material layer on one side is 0.1 mm to 3 mm; and in the thickness direction of the negative electrode current collector, the thickness of the modified material layer is 0.02 μm to 50 μm.

10. A lithium battery, characterized in that: The invention comprises a shell and the negative electrode sheet according to any one of claims 1 to 9, wherein the negative electrode collector of the negative electrode sheet is accommodated inside the shell.

11. A vehicle, characterized in that: Comprising the lithium battery as claimed in claim 10.

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