Negative current collector, negative plate, battery and electric device

Abstract

The invention provides a negative current collector, a negative plate, a battery and an electric device, the negative current collector comprises a current collector body and an alloying film layer, the current collector body comprises a pole piece area and a tab area, one side, close to the tab area, of the pole piece area is provided with a pole piece allowance area, and the pole piece allowance area is connected with the tab area; and the alloying film layer is arranged on at least one surface of the current collector body and covers at least part of the tab region and at least part of the pole piece allowance region. The negative electrode current collector is provided with the alloying film layer, so that the connection strength of the connection parts of the tab region, the pole piece region and the tab region of the negative electrode current collector is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a negative electrode current collector, a negative electrode sheet, a battery and an electrical device. Background Art

[0002] As an important auxiliary material of the battery, the current collector plays an important role in supporting the active material and conducting the current. Since the current collector does not contribute to the capacity of the battery, it is also called inactive weight. If you want to increase the energy density of the battery, you need to minimize the proportion of inactive weight.

[0003] In the prior art, reducing the thickness of the current collector has a significant effect on improving the energy density of the battery, but the current collector with insufficient mechanical strength or the design without a current collector is prone to bending and breaking during the subsequent welding of external pole ears, hot pressing, and testing. In addition, the thinned negative electrode current collector needs to undergo an isostatic pressing process when used in solid-state batteries, and the pole ears are easily separated from the pole pieces. Summary of the invention

[0004] In order to solve the problem of poor mechanical strength of the connection between the tabs, pole pieces and tabs in existing ultra-thin copper current collectors and current collector-free designs in battery applications, the present invention provides a negative current collector, a negative electrode sheet, a battery and an electrical device.

[0005] In a first aspect, the present invention provides a negative electrode current collector, comprising a current collector body and an alloyed film layer, wherein the current collector body comprises a pole piece region and a pole lug region, a pole piece surplus region is arranged on one side of the pole piece region close to the pole lug region, and the pole piece surplus region is connected to the pole lug region;

[0006] The alloyed film layer is arranged on at least one side of the current collector body and covers at least a portion of the pole lug region and at least a portion of the pole piece surplus region.

[0007] Optionally, the alloyed film layer covers the electrode margin area with a length L1 and a width L2, L1≤the width of the electrode area close to the electrode ear area, L2 <L1,L2≥0.5mm。

[0008] Optionally, the height of the alloyed film layer covering the pole lug region is less than or equal to the height of the pole lug region, and the width of the alloyed film layer covering the pole lug region is less than or equal to the width of the pole lug region.

[0009] Optionally, a weld mark area for welding an external pole lug is provided at one end of the pole lug area away from the pole piece surplus area, and the alloyed film layer covers the weld mark area.

[0010] Optionally, the alloyed film layer has a thickness of 0.05 to 5 μm.

[0011] Optionally, the alloyed film layer is made of alloying elements, the current collector body is a copper-based current collector, and the alloying elements are elements that can form an alloy with copper;

[0012] Or, the current collector body is a pure lithium strip, and the alloying element is an element that can form an alloy with lithium;

[0013] Or, the current collector body is a lithium alloy strip, the lithium alloy strip is a Li-M strip, M is selected from one or more of gold, indium, magnesium, zinc, chromium, nickel, molybdenum, tungsten, vanadium, titanium, niobium, zirconium, cobalt, manganese, aluminum, copper, boron, silver, tin, silicon, carbon, phosphorus, and bismuth; the alloying element is an element that can form an alloy with lithium and M at the same time.

[0014] Optionally, the current collector body is a copper-based current collector, and the alloying element is selected from one or more of zinc, tin, lead, phosphorus, silver, aluminum, nickel, and silicon;

[0015] Or, the current collector body is a pure lithium strip, and the alloying element is selected from one or more of gold, indium, magnesium, zinc, chromium, nickel, molybdenum, tungsten, vanadium, titanium, niobium, zirconium, cobalt, manganese, aluminum, copper, boron, silver, tin, silicon, carbon, phosphorus, and bismuth;

[0016] Alternatively, the current collector body is a lithium alloy strip, and the alloying element is selected from one or more of gold, indium, magnesium, zinc, chromium, nickel, molybdenum, tungsten, vanadium, titanium, niobium, zirconium, cobalt, manganese, aluminum, copper, boron, silver, tin, silicon, carbon, phosphorus, and bismuth.

[0017] Optionally, the copper-based current collector comprises one of copper and a copper alloy, and the mass fraction of copper in the copper-based current collector is 80% to 99.5%;

[0018] And / or, the copper-based current collector has a thickness of 3 to 10 μm.

[0019] Optionally, the mass fraction of lithium in the pure lithium strip is ≥99%;

[0020] And / or, the thickness of the pure lithium strip is 1 to 50 μm;

[0021] And / or, at least one side of the pure lithium strip is provided with a passivation layer containing carbon or nitrogen elements.

[0022] Optionally, the mass fraction of lithium in the lithium alloy strip is 5% to 95%;

[0023] And / or, the thickness of the lithium alloy strip is 1 to 10 μm.

[0024] Optionally, the pole lug region is a single pole lug, multiple pole lugs or a full pole lug; when the pole lug region is multiple pole lugs, the distance between two adjacent pole lugs is ≥4 mm.

[0025] In a second aspect, the present invention further provides a negative electrode sheet, comprising the negative electrode current collector as described in any one of the above items.

[0026] Optionally, when the current collector body is a copper-based current collector, an active material layer is provided on at least one side of the copper-based current collector, and the active material layer covers the area where the alloyed film layer overlaps with the pole piece area.

[0027] Optionally, the active material layer includes an active substance, and the active substance includes one or more of metallic lithium, lithium alloy, graphite, silicon, silicon carbon, and silicon oxygen.

[0028] Optionally, the lithium alloy in the active material is an alloy formed by metallic lithium and one or more of gold, indium, magnesium, zinc, chromium, nickel, molybdenum, tungsten, vanadium, titanium, niobium, zirconium, cobalt, manganese, aluminum, copper, boron, silver, tin, silicon, carbon, phosphorus, and bismuth; the mass content of metallic lithium in the lithium alloy is 0.5% to 99.5%.

[0029] In a third aspect, the present invention further provides a battery, comprising a positive electrode sheet and a negative electrode sheet as described in any one of the above items.

[0030] Optionally, the battery is a liquid battery, a semi-solid battery or a solid battery.

[0031] In a fourth aspect, the present invention further provides an electrical device, comprising the battery described above.

[0032] In the present invention, by arranging an alloyed film layer covering at least part of the tab area and at least part of the pole piece surplus area on at least one side of the current collector body, the mechanical strength of the connection between the tab area, the pole piece area and the tab area can be effectively improved, and cracks and fractures in the tab area during welding, pressing, forming and testing can be prevented, which is beneficial to improving the cycle performance of the battery. The pole piece surplus area is the area where the negative electrode current collector pole piece area extends out of the positive electrode current collector pole piece area in the battery cell. The alloyed film layer covers at least part of the pole piece surplus area, but does not cover the overlapping area between the negative electrode current collector pole piece area and the positive electrode active material, effectively avoiding the change of lithium nucleation overpotential caused by the pole piece area of ​​the negative electrode current collector other than the pole piece surplus area covered by the alloyed film layer, and further avoiding the preferential deposition of lithium in the area of ​​the alloyed film layer of the negative electrode, resulting in the deposition and uneven stripping of lithium on the negative electrode side causing the growth of lithium dendrites, and causing short circuit in the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 is a schematic structural diagram of a negative electrode current collector provided by one embodiment of the present invention;

[0034] Figure 2 It is a schematic structural diagram of a negative electrode current collector provided by one embodiment of the present invention when the tab region is a single tab;

[0035] Figure 3 It is a schematic structural diagram of a negative electrode current collector provided by one embodiment of the present invention when the tab region is multi-tab;

[0036] Figure 4 It is a schematic structural diagram of a negative electrode current collector provided by one embodiment of the present invention when the tab region is a full tab;

[0037] Figure 5 yes Figure 4 Side view of.

[0038] The reference numerals in the drawings of the specification are as follows:

[0039] 1. Current collector body; 2. Alloyed film layer;

[0040] L1, the length of the alloyed film layer covering the residual area of ​​the pole piece; L2, the width of the alloyed film layer covering the residual area of ​​the pole piece; L3, the height of the alloyed film layer covering the pole lug area; L4, the width of the alloyed film layer covering the pole lug area. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention 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 invention and are not intended to limit the present invention.

[0042] In the description of the present invention, it should be understood that the terms "longitudinal", "radial", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element 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 invention. In the description of the present invention, unless otherwise specified, "plurality" means two or more. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0043] In order to illustrate the technical solution of the present invention, specific embodiments are provided below for illustration.

[0044] like Figure 1 to Figure 5 As shown, a negative electrode current collector according to an embodiment of the present invention comprises a current collector body 1 and an alloyed film layer 2, wherein the current collector body 1 comprises a pole piece region and a pole lug region, a pole piece surplus region is arranged on one side of the pole piece region close to the pole lug region, and the pole piece surplus region is connected to the pole lug region;

[0045] The alloying film layer 2 is disposed on at least one surface of the current collector body 1 and covers at least a part of the tab area and at least a part of the tab margin area of the electrode sheet.

[0046] In this embodiment, by disposing the alloying film layer 2 covering at least a part of the tab area and at least a part of the tab margin area of the electrode sheet on at least one surface of the current collector body 1, the mechanical strength of the tab area, the electrode sheet area, and the connection part between the tab areas can be effectively improved, preventing cracks and fractures from occurring in the tab area during welding, pressing, formation, and testing, which is beneficial to improving the cycle performance of the battery. The tab margin area is the area where the negative current collector electrode sheet area extends beyond the positive current collector electrode sheet area in the battery cell. The alloying film layer 2 covers at least a part of the tab margin area and does not cover the overlapping area between the negative current collector electrode sheet area and the positive active material, effectively avoiding the change in the lithium nucleation overpotential caused by covering the alloying film layer 2 on the electrode sheet area other than the tab margin area of the negative current collector, and further avoiding the preferential deposition of lithium in the area of the alloying film layer 2 on the negative electrode, resulting in uneven deposition and stripping of lithium on the negative electrode side, causing lithium dendrite growth and triggering an internal short circuit in the battery.

[0047] Specifically, the length range of the electrode sheet area is 6 - 1000 mm, and the width range is 4 - 600 mm. Figure 1 The area shown by the dashed box in the figure is the electrode sheet area of the positive current collector.

[0048] As Figure 1 shown, in some embodiments of the present invention, the length of the alloying film layer 2 covering the tab margin area is L1, and the width is L2. L1 ≤ the width of the electrode sheet area near the tab area, L2 < L1, and L2 ≥ 0.5 mm. By restricting the size of the alloying film layer 2, it is effectively avoided that the significant increase in the mass of the negative electrode due to the introduction of alloying elements with a large atomic weight affects the battery energy density.

[0049] As Figure 1 shown, in one embodiment, the height of the alloying film layer 2 covering the tab area is less than or equal to the height of the tab area, and the width of the alloying film layer 2 covering the tab area is less than or equal to the width of the tab area. By defining the size of the alloying film layer 2, the strength of the tab area is effectively enhanced, preventing cracks and fractures from occurring in the tab area during welding, pressing, formation, and testing.

[0050] In some embodiments of the present invention, a welding mark area for welding an external tab is provided at one end of the tab area away from the tab margin area, and the alloying film layer 2 covers the welding mark area. By defining the size of the alloying film layer 2, the mechanical strength of the welding mark area is enhanced, and further effectively enhances the connection strength between the tab area and the external tab.

[0051] In some embodiments of the present invention, the thickness of the alloying film layer 2 is 0.05-5 μm. By limiting the thickness of the alloying film layer 2, it is effectively avoided that the negative electrode mass is significantly increased due to the introduction of alloying elements with a large atomic weight, thereby affecting the battery energy density.

[0052] Specifically, the preparation methods of the alloyed film layer 2 include rolling, melt coating, and masked physical vapor deposition (magnetron sputtering or evaporation). Masked physical vapor deposition refers to a method of masking the area that does not need to be coated, thereby obtaining coating of a partial area.

[0053] In some embodiments of the present invention, the alloyed film layer 2 is made of alloying elements, the current collector body 1 is a copper-based current collector, and the alloying elements are elements that can form an alloy with copper;

[0054] Or, the current collector body 1 is a pure lithium strip, and the alloying element is an element that can form an alloy with lithium;

[0055] Or, the current collector body 1 is a lithium alloy strip, the lithium alloy strip is a Li-M strip, M is selected from one or more of gold, indium, magnesium, zinc, chromium, nickel, molybdenum, tungsten, vanadium, titanium, niobium, zirconium, cobalt, manganese, aluminum, copper, boron, silver, tin, silicon, carbon, phosphorus, and bismuth; the alloying element is an element that can form an alloy with lithium and M at the same time.

[0056] In this embodiment, the alloying elements are limited to elements that can form an alloy with the current collector body 1 , so as to enhance the bonding force between the alloyed film layer 2 and the current collector body 1 .

[0057] In some embodiments of the present invention, the current collector body 1 is a copper-based current collector, and the alloying element is selected from one or more of zinc, tin, lead, phosphorus, silver, aluminum, nickel, and silicon;

[0058] Or, the current collector body 1 is a pure lithium strip, and the alloying element is selected from one or more of gold, indium, magnesium, zinc, chromium, nickel, molybdenum, tungsten, vanadium, titanium, niobium, zirconium, cobalt, manganese, aluminum, copper, boron, silver, tin, silicon, carbon, phosphorus, and bismuth;

[0059] Alternatively, the current collector body 1 is a lithium alloy strip, and the alloying element is selected from one or more of gold, indium, magnesium, zinc, chromium, nickel, molybdenum, tungsten, vanadium, titanium, niobium, zirconium, cobalt, manganese, aluminum, copper, boron, silver, tin, silicon, carbon, phosphorus, and bismuth.

[0060] By selecting the above alloying elements, it is convenient to enhance the bonding force between the alloyed film layer 2 and the current collector body 1 .

[0061] In some embodiments of the present invention, the copper-based current collector comprises one of copper and a copper alloy, and the mass fraction of copper in the copper-based current collector is 80% to 99.5%;

[0062] And / or, the copper-based current collector has a thickness of 3 to 10 μm to form an ultra-thin copper-based current collector.

[0063] In some embodiments of the present invention, the mass fraction of lithium in the pure lithium strip is ≥ 99%;

[0064] And / or, the thickness of the pure lithium strip is 1 to 50 μm;

[0065] And / or, at least one side of the pure lithium strip is provided with a passivation layer containing carbon or nitrogen. Specifically, the passivation layer is an organic artificial SEI, an inorganic artificial SEI or an organic-inorganic composite artificial SEI layer.

[0066] In some embodiments of the present invention, the mass fraction of lithium in the lithium alloy strip is 5% to 95%;

[0067] And / or, the thickness of the lithium alloy strip is 1 to 10 μm.

[0068] In some embodiments of the present invention, the pole lug region is a single pole lug, multiple pole lugs or a full pole lug. When the pole lug region is multiple pole lugs, the distance between two adjacent pole lugs is ≥4 mm.

[0069] On the other hand, an embodiment of the present invention further provides a negative electrode sheet, comprising the negative electrode current collector as described in any one of the above embodiments.

[0070] In some embodiments of the present invention, when the current collector body 1 is a copper-based current collector, at least one side of the copper-based current collector is provided with an active material layer, and the active material layer covers the area where the alloyed film layer 2 overlaps with the pole piece area.

[0071] In some embodiments of the present invention, the active material layer includes an active substance, and the active substance includes one or more of metallic lithium, lithium alloy, graphite, silicon, silicon carbon, and silicon oxygen.

[0072] In some embodiments of the present invention, the lithium alloy in the active material is an alloy formed by metallic lithium and one or more of gold, indium, magnesium, zinc, chromium, nickel, molybdenum, tungsten, vanadium, titanium, niobium, zirconium, cobalt, manganese, aluminum, copper, boron, silver, tin, silicon, carbon, phosphorus, and bismuth; the mass content of metallic lithium in the lithium alloy is 0.5% to 99.5%.

[0073] It should be noted that the thickness of the negative electrode active material layer is 0-100 μm. When the thickness of the negative electrode active material layer is 0, the current collector body 1 is a pure lithium strip or a lithium alloy strip. The negative electrode active material layer can be prepared by rolling, physical vapor deposition PVD, coating and other methods.

[0074] On the other hand, an embodiment of the present invention further provides a battery, comprising a positive electrode sheet and a negative electrode sheet as described in any one of the above embodiments.

[0075] Specifically, the positive electrode sheet can be a positive electrode sheet using a conventional metal foil current collector, or a positive electrode sheet using a composite current collector; the positive electrode active material of the positive electrode sheet includes but is not limited to lithium nickel cobalt manganese oxide (N x M y C z ,x+y+z=1), lithium iron manganese phosphate (LiFe x Mn y PO4, x+y=1), lithium iron phosphate, lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide, lithium-rich manganese base, lithium nickel manganese oxide (LMNO), lithium vanadium phosphate (Li3V2(PO4)3, LiVOPO4), which is not limited in this embodiment.

[0076] The lug area schemes for the positive and negative electrodes include but are not limited to: 1) The positive and negative electrodes are respectively provided with single lugs, and the lugs of the positive and negative electrodes are on the same side; 2) The positive and negative electrodes are respectively provided with single lugs, and the lugs of the positive and negative electrodes are on opposite sides; 3) The positive electrode is provided with a single lug, and the negative electrode is provided with multiple lugs, and the lugs of the positive and negative electrodes are on opposite sides; 4) The positive electrode is provided with multiple lugs, and the negative electrode is provided with a single lug, and the lugs of the positive and negative electrodes are on opposite sides; 5) The positive electrode is provided with multiple lugs, and the negative electrode is provided with multiple lugs, and the lugs of the positive and negative electrodes are on opposite sides. If at least one polarity of the positive and negative electrodes adopts the full lug scheme, the positive and negative electrodes need to be on opposite sides.

[0077] In some embodiments of the present invention, the battery is a liquid battery, a semi-solid battery or a solid battery. The semi-solid battery includes a positive electrode sheet, a negative electrode sheet and a gel electrolyte, or the semi-solid battery includes a positive electrode sheet, a negative electrode sheet, a solid electrolyte and 0.5% to 50% electrolyte.

[0078] Furthermore, the battery may be a laminated soft-pack battery, a wound battery or a cylindrical battery.

[0079] When the battery is a liquid battery, the liquid battery further includes a separator and an electrolyte.

[0080] The diaphragm includes polypropylene PP, polyethylene PE and composite films thereof. Furthermore, at least one side of the diaphragm is provided with a ceramic coating.

[0081] The electrolyte includes a lithium salt, a solvent and an additive, wherein the solvent includes one or more of a carbonate compound, an ether compound and a nitrile compound. The lithium salt includes one or more of LiPF6, LiClO4, LiBF4, LiAsF6, LiCF3SO, LiTFSI, LiFSI, LiTNFSI, LiFNFSI, LiBOB, LiN(CF3SO2)2 and LiC(SO2CF3)3. The additives include film-forming additives, conductive additives, flame retardant additives and overcharge protection additives, additives for controlling the water and HF content in the electrolyte, and general additives for improving low-temperature performance. It can also be an additive for improving the interface stability of the metal lithium negative electrode, such as fluoroethylene carbonate FEC and lithium nitrate LiNO3.

[0082] Specifically, the carbonate compound includes one or more of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate and γ-butyrolactone.

[0083] The ether compound includes one or more of tetrahydrofuran, 2-methyltetrahydrofuran, dimethoxydimethyl ether and 1,2-dimethoxyethane.

[0084] The nitrile compound includes acetonitrile.

[0085] When the battery is a solid-state battery, the solid-state battery further includes a solid electrolyte, and the solid electrolyte includes one of an inorganic solid electrolyte, a polymer solid electrolyte and a composite solid electrolyte. Specifically, the composite solid electrolyte is an electrolyte based on a polymer matrix and an inorganic filler.

[0086] The inorganic solid electrolyte includes one or more of an oxide solid electrolyte, a sulfide solid electrolyte and a halide solid electrolyte.

[0087] The polymer solid electrolyte includes a polymer matrix and a lithium salt.

[0088] The composite solid electrolyte comprises a polymer matrix and an inorganic filler. Specifically, the composite method of the polymer matrix and the inorganic filler includes but is not limited to dispersion and mixing, or the inorganic filler is filled in the gap of the polymer matrix.

[0089] Specifically, the oxide solid electrolyte includes one or more of a NASICON electrolyte, a perovskite electrolyte, and a Garnet garnet electrolyte. Specifically, the NASICON electrolyte includes LATP (Li 1.3 Al 0.3 Ti 1.7 (PO4)3), LAGP(Li 1.5 Al 0.5 Ge 1.5P3O 12 Garnet garnet electrolytes include lithium lanthanum zirconium oxide LLZO, with a conductivity of 10- 3 S / cm, and has good stability to lithium metal.

[0090] The sulfide solid electrolyte includes binary compounds and ternary compounds. The binary compounds include Li2S-SiS2, Li2S-P2S5, and Li2S-GeS2. The ternary compounds include one or more of Li2S-MS2-P2S5 and Li6PS5X, wherein X is selected from at least one of F, Cl, Br and I, and M is selected from at least one of Si, Ge, Sn and Al.

[0091] The halide solid electrolyte includes Li a MX4, Li a MX6 and Li a MX8 type, M is a divalent metal ion, a trivalent metal ion or other valent metal ion, and X is a halogen. Specifically, the halide solid electrolyte includes one or more of Li2MnCl4, Li2ZnCl4, LiYbF4, LiAlF4, Li3YCl6, Li3BrCl6 and Li6CoCl8.

[0092] The polymer matrix includes one or more of polyethylene oxide, polycarbonate, polytrimethylene carbonate, polymethyl methacrylate, polyacrylonitrile, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoroethylene copolymer and lithium polyacrylate.

[0093] The lithium salt includes one or more of LiAsF6, LiPF6, LiClO4, LiTFSI, LiFSI and LiBF4.

[0094] The inorganic filler includes one or more of LATP, LLZO, Al2O3 and metal organic framework.

[0095] The gel electrolyte includes at least one solid electrolyte in the above embodiments and at least one electrolyte solution in the above embodiments.

[0096] An embodiment of the present invention further provides an electrical device, comprising the battery described in the above embodiment.

[0097] The negative electrode current collector of the present invention is further described below in conjunction with specific embodiments.

[0098] Example 1

[0099] This embodiment is used to illustrate the negative electrode current collector and the negative electrode sheet disclosed in the present invention.

[0100] Preparation of negative electrode:

[0101] 3.5μm pure copper is used as the current collector, the size of the alloyed film layer 2 is: L1=20mm, L2=1mm, the height of the alloyed film layer 2 covering the pole ear area L3=12mm, the width of the alloyed film layer 2 covering the pole ear area L4=10mm, the alloyed film layer 2 is 0.5μm tin, and is prepared by melt coating. On this basis, 20μm lithium metal is rolled in the pole piece area of ​​the negative current collector as an active material.

[0102] Example 2

[0103] This embodiment is used to illustrate the negative electrode current collector and the negative electrode sheet disclosed in the present invention.

[0104] The design without current collector is adopted; the negative electrode active material is 20μm pure lithium strip. The size of alloying film layer 2 is: L1=60mm, L2=1mm, L3=12mm, L4=10mm, alloying film layer 2 is 1μm magnesium, and is prepared by mask magnetron sputtering.

[0105] Example 3

[0106] This embodiment is used to illustrate the negative electrode current collector and the negative electrode sheet disclosed in the present invention.

[0107] The design is without current collector; the negative electrode active material is 5μm lithium-magnesium alloy strip, in which the mass fraction of lithium is 85%. The alloying area size is: L1=15mm, L2=1mm, L3=12mm, L4=10mm, and the alloying film layer 2 is 1μm zinc, which is prepared by mask magnetron sputtering.

[0108] Comparative Example 1

[0109] This comparative example is used to illustrate the negative electrode current collector and the negative electrode sheet disclosed in the present invention.

[0110] 3.5μm pure copper is used as the current collector, on this basis, 20μm lithium metal is rolled on the pole piece area of ​​the negative electrode current collector as the active material.

[0111] Comparative Example 2

[0112] This comparative example is used to illustrate the negative electrode current collector and the negative electrode sheet disclosed in the present invention.

[0113] 3.5μm pure copper is used as the current collector, and a 1μm tin coating is magnetron sputtered over the entire range of the pole piece and the pole ear area. On this basis, 20μm lithium metal is rolled on the pole piece area of ​​the negative current collector as the active material.

[0114] Comparative Example 3

[0115] This comparative example is used to illustrate the negative electrode current collector and the negative electrode sheet disclosed in the present invention.

[0116] It adopts a current collector-free design and a 20μm pure lithium strip as the negative electrode.

[0117] Comparative Example 4

[0118] This comparative example is used to illustrate the negative electrode current collector and the negative electrode sheet disclosed in the present invention.

[0119] A current collector-free design is adopted; a 20μm pure lithium strip is used as the negative electrode, and a 1μm magnesium coating is magnetron sputtered on the surface of the negative electrode.

[0120] Comparative Example 5

[0121] This comparative example is used to illustrate the negative electrode current collector and the negative electrode sheet disclosed in the present invention.

[0122] A current collector-free design is adopted, and a 5μm lithium-magnesium alloy strip is used as the negative electrode, in which the mass fraction of lithium is 85%.

[0123] Comparative Example 6

[0124] This comparative example is used to illustrate the negative electrode current collector and the negative electrode sheet disclosed in the present invention.

[0125] A current collector-free design is adopted, a 5μm lithium-magnesium alloy strip is used as the negative electrode, in which the mass fraction of lithium is 85%, and a 1μm zinc coating is evaporated on the surface of the negative electrode.

[0126] Performance Testing

[0127] In the above embodiments and comparative examples, lithium batteries were prepared according to the contents of this application and the disclosed schemes, and performance tests were carried out. For all embodiments and comparative examples, the pole piece size is fixed: the size of the negative pole piece area is 60*80mm, the size of the pole lug area is 10*12mm, and the short side of the pole piece is connected to the short side of the pole lug; the size of the positive pole piece area is 58*78mm, the size of the pole lug area is 10*12mm, and the short side of the pole piece is connected to the short side of the pole lug. The positive electrode active material is high nickel ternary NCM811, with a surface capacity of 4mAh / cm 2 . The electrolyte is 1 mol LiTFSI, 50% DOL + 50% DME. The injection volume is 2.5g / Ah; the diaphragm is a 10μm uncoated PP diaphragm; the thickness of the aluminum-plastic film is 113μm. The above positive electrode, diaphragm, electrolyte, and aluminum-plastic film are respectively assembled with the negative electrode sheets in the above embodiments and comparative examples into soft-pack laminated batteries with 5 positive electrodes and 6 negative electrodes, and a 1C / 1D room temperature cycle performance test is carried out. The specific test data are shown in Table 1.

[0128] Table 1

[0129]

[0130]

[0131] It can be seen from the test results of Examples 1-3 and Comparative Examples 1, 3 and 5 that, compared with Comparative Examples 1, 3 and 5 in which the alloyed film layer 2 is not introduced, the introduction of the alloyed film layer 2 has less effect on the energy density, but is more significant in improving the cycle water diving problem caused by the low mechanical strength of the tab area.

[0132] It can be seen from the test results of Examples 1-3 and Comparative Examples 2, 4 and 6 that since the full alloying film layer 2 on the negative electrode can reduce the nucleation overpotential of lithium, it is beneficial to the uniform deposition of lithium on the negative electrode side. Therefore, the cycle performance of Examples 1-3 is slightly worse than that of Comparative Examples 2, 4 and 6, but the energy density of Comparative Example 2 is lower than that of Example 1. It can be seen that although the fully alloyed negative electrode can enhance the mechanical strength, it is not conducive to the improvement of the energy density of the negative electrode sheet.

[0133] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them. Although the present invention has been described in detail with reference to the above embodiments, it should be understood by those skilled in the art that the technical solutions described in the above embodiments can still be modified, or some of the technical features can be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention, and should be included in the protection scope of the present invention.

Claims

1. A negative electrode current collector, characterized in that The current collector comprises a current collector body and an alloyed film layer, wherein the current collector body comprises a pole piece region and a pole tab region, a pole piece margin region is provided on a side of the pole piece region close to the pole tab region, and the pole piece margin region is connected to the pole tab region; The alloyed film layer is arranged on at least one side of the current collector body and covers at least a portion of the tab area and at least a portion of the pole piece margin area.

2. The negative electrode current collector according to claim 1, characterized in that The length of the alloyed film layer covering the electrode margin area is L1, and the width is L2, L1≤the width of the electrode area close to the electrode ear area, L2 <L1,L2≥0.5mm。 3. The negative electrode current collector according to claim 1, characterized in that The height of the tab region covered by the alloyed film layer is less than or equal to the height of the tab region, and the width of the tab region covered by the alloyed film layer is less than or equal to the width of the tab region.

4. The negative electrode current collector according to claim 3, characterized in that: A weld mark area for welding an externally connected tab is provided at one end of the tab area away from the pole piece margin area, and the alloyed film layer covers the weld mark area.

5. The negative electrode current collector according to claim 1, characterized in that The thickness of the alloyed film layer is 0.05 to 5 μm.

6. The negative electrode current collector according to claim 1, characterized in that The alloyed film layer is made of alloying elements, the current collector body is a copper-based current collector, and the alloying elements are elements that can form an alloy with copper; Alternatively, the current collector body is a pure lithium ribbon, and the alloying element is an element that can form an alloy with lithium; Alternatively, the current collector body is a lithium alloy strip, the lithium alloy strip is a Li-M strip, M is selected from one or more of gold, indium, magnesium, zinc, chromium, nickel, molybdenum, tungsten, vanadium, titanium, niobium, zirconium, cobalt, manganese, aluminum, copper, boron, silver, tin, silicon, carbon, phosphorus, and bismuth; the alloying element is an element that can form an alloy with lithium and M at the same time.

7. The negative electrode current collector according to claim 6, characterized in that: The current collector body is a copper-based current collector, and the alloying element is selected from one or more of zinc, tin, lead, phosphorus, silver, aluminum, nickel, and silicon; Alternatively, the current collector body is a pure lithium ribbon, and the alloying element is selected from one or more of gold, indium, magnesium, zinc, chromium, nickel, molybdenum, tungsten, vanadium, titanium, niobium, zirconium, cobalt, manganese, aluminum, copper, boron, silver, tin, silicon, carbon, phosphorus, and bismuth; Alternatively, the current collector body is a lithium alloy strip, and the alloying element is selected from one or more of gold, indium, magnesium, zinc, chromium, nickel, molybdenum, tungsten, vanadium, titanium, niobium, zirconium, cobalt, manganese, aluminum, copper, boron, silver, tin, silicon, carbon, phosphorus, and bismuth.

8. The negative electrode current collector according to claim 6, characterized in that: The copper-based current collector comprises one of copper and a copper alloy, and the mass fraction of copper in the copper-based current collector is 80% to 99.5%; And / or, the copper-based current collector has a thickness of 3 to 10 μm.

9. The negative electrode current collector according to claim 6, characterized in that: The mass fraction of lithium in the pure lithium strip is ≥99%; and / or, the thickness of the pure lithium strip is 1 to 50 μm; And / or, a passivation layer containing carbon or nitrogen is provided on at least one side of the pure lithium ribbon.

10. The negative electrode current collector according to claim 6, characterized in that: The mass fraction of lithium in the lithium alloy strip is 5% to 95%; And / or, the thickness of the lithium alloy strip is 1 to 10 μm.

11. The negative electrode current collector according to claim 1, characterized in that: The tab area is a single tab, multiple tabs or a full tab; when the tab area is a multiple tab, the distance between two adjacent tabs is ≥4 mm.

12. A negative electrode sheet, characterized in that: The negative electrode current collector comprises the negative electrode current collector according to any one of claims 1 to 11.

13. The negative electrode sheet according to claim 12, characterized in that: When the current collector body is a copper-based current collector, an active material layer is provided on at least one side of the copper-based current collector, and the active material layer covers the area where the alloyed film layer overlaps with the pole piece area.

14. The negative electrode sheet according to claim 13, characterized in that: The active material layer includes an active substance, and the active substance includes one or more of metallic lithium, lithium alloy, graphite, silicon, silicon carbon, and silicon oxygen.

15. The negative electrode sheet according to claim 14, characterized in that: The lithium alloy in the active material is an alloy formed by metallic lithium and one or more of gold, indium, magnesium, zinc, chromium, nickel, molybdenum, tungsten, vanadium, titanium, niobium, zirconium, cobalt, manganese, aluminum, copper, boron, silver, tin, silicon, carbon, phosphorus, and bismuth; the mass content of metallic lithium in the lithium alloy is 0.5% to 99.5%.

16. A battery, characterized in that: The invention comprises a positive electrode sheet and the negative electrode sheet according to any one of claims 12 to 15.

17. The battery according to claim 16, characterized in that The battery is a liquid battery, a semi-solid battery or a solid battery.

18. An electrical device, characterized in that: A battery comprising the battery according to claim 16 or 17.

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