Lithium composite negative electrode with tabs as well as preparation method and application of lithium composite negative electrode

Abstract

The invention provides a lithium composite negative electrode with a tab as well as a preparation method and application of the lithium composite negative electrode. The lithium composite negative electrode with the tabs comprises an upper negative electrode layer and a lower negative electrode layer, wherein the negative electrode layers are metal lithium layers or lithium alloy layers; the flexible current collector layer is clamped between the two negative electrode layers, and the current collector layer is formed by a carbonaceous membrane material or a membrane material formed by depositing a conductive substance on non-conductive fiber cloth; the tab is combined with the current collector layer through a tab combination part, or the tab is formed by a metal deposition layer located on the part, exposed out of the negative electrode layer, of the current collector layer.

Description

Technical Field

[0001] The present invention relates to the technical field of electrochemical energy storage, and in particular to a method and application of leading out a lithium negative electrode tab for a lithium ion battery. Background Art

[0002] As society's demand for lithium-ion battery energy density becomes higher and higher, current research directions are turning to negative electrode materials with higher specific capacity. Metallic lithium is considered to be the optimal negative electrode material due to its capacity of 3860mAh / g and low potential of -3.04V. In addition, to improve the energy density of the battery, it is necessary to reduce the proportion of inactive substances. For the current collector, although the weight of the current collector copper foil can be reduced by continuously thinning the thickness of the copper current collector, the density of metallic copper is 8.96g / cm 3 The thinnest copper foil at present is 3.5um thick (3.5um thick copper foil is easy to break) which is still equivalent to 60um thick lithium metal. Carbon film materials or other flexible conductive film materials with certain conductivity are currently being developed to replace the current collector copper foil. The density of carbon film materials is 1g / cm 3 It can be a good substitute for the traditional current collector; but the problem is that after the relevant film materials are composited with the metal lithium negative electrode, the carbon film materials or other conductive film materials cannot be used directly as the tabs, and the tabs of the metal foil materials need to be led out before they can be welded and used; and how to lead out the tabs in batches, and how the led-out tabs and the carbon film materials can form a current collector as a whole, and at the same time, the thickness fluctuation at the junction of the current collecting film material and the tabs is small, this requires special design. Summary of the Invention

[0003] In order to solve the above problems, the present invention provides a lithium composite negative electrode with a built-in tab, a preparation method thereof, and an application thereof.

[0004] One aspect of the present invention relates to a lithium composite negative electrode with a built-in tab, the lithium composite electrode comprising:

[0005] Two upper and lower negative electrode layers, wherein the negative electrode layers are metallic lithium layers or lithium alloy layers;

[0006] A flexible current collector layer sandwiched between two negative electrode layers, wherein the current collector layer is formed of a carbonaceous film material, or a film material formed by depositing a conductive material on a non-conductive fiber cloth; and

[0007] Extreme ears,

[0008] The tab is connected to the current collector layer via a tab connection portion, and the tab connection portion includes any one of the following:

[0009] (1) A complementary structure, wherein the complementary structure is located between the upper and lower negative electrode layers and is composed of a tab junction at one end of the current collector layer and a current collector layer junction on the tab, wherein the tab junction and the current collector layer junction are complementary in structure;

[0010] (2) an overlapping region, the overlapping region consisting of the overlapping portion of the current collector and the tab, located between the upper and lower negative electrode layers, and the non-overlapping portion of the tab extending beyond the edge of the negative electrode layer; and

[0011] (3) a tab bonding portion, the tab bonding portion being located outside the upper and lower negative electrode layers and being formed by an adhesive layer on a portion of the current collector layer exposed from the negative electrode layer, or by an adhesive layer on the tab;

[0012] Alternatively, the tab is formed by a metal deposition layer located on a portion of the current collector layer exposed from the negative electrode layer.

[0013] In certain embodiments, the carbonaceous film material comprises at least one of the following film materials:

[0014] A film material formed by a vapor deposition process of at least one material selected from carbon nanotubes, carbon fibers, graphene, acetylene black, activated carbon materials, and graphite;

[0015] A carbon-containing film material formed from at least one polymer selected from polypropylene, polyethylene, polyimide, and polyurethane and at least one conductive carbon selected from conductive carbon black, graphene, and carbon nanotubes;

[0016] A carbon-containing film material formed by a papermaking process from a slurry of at least one conductive carbon material selected from conductive carbon black, carbon nanotubes, carbon fibers, and graphene and a binder in a solvent;

[0017] Film material formed by sintering a polyimide film; and

[0018] A film material formed by coating a slurry of carbon nanotubes or graphene on a release film.

[0019] In certain embodiments, the release film comprises a plastic film, such as a polypropylene film.

[0020] In certain embodiments, the non-conductive fiber cloth is formed by electrospinning, such as a non-woven fabric.

[0021] In certain embodiments, the tab joints are complementary structures, wherein the tab joints of the current collector layer have continuously distributed rectangular, triangular, or arcuate shapes, or the tab joints have comb-shaped or zigzag shapes.

[0022] In some embodiments, the tab joint of the current collector layer has a regularly distributed columnar protrusion or arc-shaped depression structure, and the top of the columnar protrusion or arc-shaped depression has a flange extending in a direction perpendicular to the thickness direction of the current collector layer (for example, forming a "T"-shaped structure).

[0023] In some embodiments, the tab joint is an overlapping area, wherein the width of the overlapping area is 0-5 mm. Preferably, one side of the current collector and / or one side of the tab has a mark for guiding the current collector and the tab to form an overlapping area, and the mark includes a marking line formed by multiple small holes arranged along the edge of the current collector or the tab.

[0024] In certain embodiments, the tab joint is a tab adhesive portion, wherein the width of the adhesive layer is 2-10 mm, and the tensile strength at the tab adhesive portion is greater than or close to the tensile strength of the current collector.

[0025] In certain embodiments, the tab is formed of a metal deposition layer, wherein the metal deposition layer is continuously or spaced apart on a portion of the current collector layer exposed from the negative electrode layer and along a length direction of the current collector layer.

[0026] In certain embodiments, the lithium composite negative electrode is a continuous web having a length of 1-2000 m.

[0027] In some embodiments, the thickness of the negative electrode layer is 1-100 μm and the width is 50-1400 μm; the thickness of the current collector layer is 5-50 μm.

[0028] Another aspect of the present invention provides a method for preparing the above-mentioned lithium composite electrode, the method comprising:

[0029] One side edge of the current collector film material and one side edge of the metal foil material are formed into complementary structures respectively by using 3D printing technology, mold punching technology, and laser etching technology;

[0030] First, unwind the current collector film and metal foil in the middle position so that the edge of one side of the current collector film and the edge of one side of the metal foil are completely aligned with each other; then unwind the upper and lower rolls of lithium ribbon or lithium alloy ribbon, and unwind the current collector film, metal foil and metal lithium ribbon or lithium alloy ribbon at the same speed, which is 5-50 meters / min;

[0031] The upper and lower rolls of metal lithium strips or lithium alloy strips, the current collector film material and metal foil material in the middle position are pressure-compounded to obtain a composite negative electrode with its own tabs.

[0032] or

[0033] The current collector film material and the metal foil material at the middle position of the unwinding are overlapped with one side edge of the current collector film material and one side edge of the metal foil material;

[0034] At the same time, two rolls of lithium metal ribbon or lithium alloy ribbon are unwound and laminated under pressure to obtain a composite negative electrode with its own tabs.

[0035] or,

[0036] First, the current collector film and the tab foil are unwound, and at least one of the edge regions of the rolled current collector film and the tab foil is provided with a conductive adhesive. After the adhesive positions of one side edge region of the current collector film and one side edge region of the tab are adjusted, the one side edge of the current collector film and one side edge of the tab are formed into a complete whole by rolling pressure and the adhesion between the materials;

[0037] Then unwind the upper and lower rolls of lithium metal ribbon or lithium alloy ribbon, and press them together to obtain a lithium composite negative electrode with its own tabs.

[0038] or,

[0039] First, a metal layer is deposited on the edge area of the current collector film material to obtain a substrate with a current collector lead-out portion;

[0040] The upper and lower rolls of metal lithium strips or lithium alloy strips and the substrate of the middle layer are unwound and pressure-compounded to obtain a lithium composite negative electrode with its own tabs.

[0041] Another aspect of the present invention provides a lithium battery, comprising the above-mentioned lithium composite negative electrode with a built-in tab. The present invention has at least one of the following advantages:

[0042] (1) The lithium composite negative electrode with its own tabs of the present invention solves the problem of tabs being drawn out in the industrial production of current collector film materials (except metal current collectors).

[0043] (2) The lithium composite negative electrode with its own tabs has a simple production process and can be mass-produced.

[0044] (3) The lithium composite negative electrode with its own tabs of the present invention can make the thickness of the current collector film material and the lead tab foil material consistent, thereby obtaining a composite negative electrode with a smooth surface and good overall thickness uniformity of the negative electrode. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figures 1-1 to 1-4 This is a schematic diagram of a current collector film and a tab being combined with each other through a complementary structure according to a first embodiment of the present invention. Figure 1-1 It shows that rectangular regular shapes are complementary; Figure 1-2 Shown are semicircular regular shapes complementing each other; Figure 1-3 Shows the complementation of regular shapes close to circles; Figure 1-4 It shows that the triangle regular shape is complementary;

[0046] 101 - current collector layer, 102 - pole tab.

[0047] Figure 2-1 to Figure 2-2 This is a schematic diagram of a current collector film and a tab being coupled to each other via an overlap region according to a second embodiment of the present invention. Figure 2-1 shows the structure when the width of the overlap area is 0, Figure 2-2 It shows the structure when the width of the overlapping area 4 is greater than 0;

[0048] 201 - negative electrode layer, 202 - current collector layer, 203 - tab.

[0049] Figure 3 Schematic diagram of a current collector film and a tab being bonded to each other via a tab bonding portion according to a third embodiment of the present invention;

[0050] 301 - negative electrode layer, 302 - current collector layer, 303 - tab, 304 - tab bonding portion.

[0051] Figure 4 Schematic diagram of a composite negative electrode with a tab formed by a metal deposition layer according to a fourth embodiment of the present invention;

[0052] 401-negative electrode layer, 402-substrate layer, 403-metal deposition layer

[0053] Figure 5 A physical diagram of a lithium composite negative electrode with a tab according to one embodiment of the present invention is shown. DETAILED DESCRIPTION

[0054] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only intended to illustrate the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0055] The present invention addresses the problem of difficulty in mass-producing the tabs when using carbonaceous film materials or other conductive film materials as flexible current collectors. It proposes the idea of providing a tab joint or depositing a metal layer on the film material, thereby realizing large-scale batch production of lithium composite negative electrodes with built-in tabs.

[0056] The flexible current collector that can be used in the present invention can be formed of a carbonaceous film material, or a film material formed by depositing a conductive material on a non-conductive fiber cloth.

[0057] According to one embodiment, the carbonaceous film material includes at least one of the following film materials: a film material formed by a vapor deposition process of at least one material selected from carbon nanotubes, carbon fibers, graphene, acetylene black, activated carbon materials, and graphite; a carbon-containing film material formed by a papermaking process by coating a slurry of at least one conductive carbon material selected from conductive carbon black, carbon nanotubes, carbon fibers, and graphene and a binder in a solvent; a carbon-containing film material formed by sintering a polyimide film; and a film material formed by coating a slurry of carbon nanotubes or graphene.

[0058] According to one embodiment, the non-conductive fiber cloth can be formed by electrospinning. The non-conductive membrane material can be selected from non-woven fabrics, polyester fiber materials, etc.

[0059] For the above-mentioned flexible current collector, the present invention mainly adopts two strategies for leading out the tabs. One is to position the tab joint between the upper and lower negative electrode layers, and use pressure compounding to fix the tab joint; the other is to use a current collector film material with a width greater than the negative electrode layer, and form an adhesive layer on the part of the current collector layer exposed to the negative electrode layer to bond the tab, or form a metal deposition layer directly as the tab.

[0060] Figures 1-1 to 1-4 A schematic diagram of a lead-out tab according to a first embodiment of the present invention is shown, wherein the tab junction adopts a complementary structure. Specifically, a lithium composite negative electrode with a tab according to one embodiment of the present invention includes: two upper and lower negative electrode layers; a current collector layer and a tab sandwiched between the two negative electrode layers, wherein the width of the current collector layer is smaller than the width of the negative electrode layer, one end is aligned with the negative electrode layer in the width direction, and a tab junction is formed at the other end; the tab has a current collector layer junction, the current collector layer junction and the tab junction form a complementary structure, and the tab is seamlessly connected to the current collector layer through the complementary structure. Figure 1-1 The tab joint portion of the current collector layer 101 has a rectangular regular shape (comb-like structure), and the tab 102 has a structure complementary thereto; Figure 1-2 、 Figure 1-3 The tab joint portion of the current collector layer 101 has an arc shape (semicircular or nearly circular structure), and the tab 102 has a complementary structure thereto; Figure 1-4 The tab joint portion of the current collector layer 101 has a triangular regular shape (a sawtooth structure), and the tab 102 has a structure complementary thereto. Figure 5 A physical diagram of a lithium composite negative electrode with a tab according to one embodiment of the present invention is shown.

[0061] In the lithium composite negative electrode of the present invention, the negative electrode layer (active material) is made of metallic lithium or lithium alloy, the current collector layer is made of carbonaceous film or other flexible conductive film; and the tab is made of metal foil.

[0062] According to one embodiment, the active material can be distributed on the current collector layer and a portion of the tab area through coating, pressure lamination, and vapor deposition processes to obtain a double-sided lithium composite negative electrode with its own tabs.

[0063] According to one embodiment, the thickness of the active material metal lithium or lithium alloy (thickness of the negative electrode layer) can be 1-100 um, preferably 1-20 um; the width is 50-1400 mm, preferably 200-700 mm.

[0064] According to one embodiment, the lithium alloy is formed by a combination of metallic lithium and any one or at least two elements of Ag, Au, Sn, Si, Zn, Al, Mg, In, Ga, B, Mn, Sb, Bi, Cr, C, V, Cu, Fe or Ti.

[0065] According to one embodiment, the thickness of the current collector layer is 5-50 μm, preferably 5-20 μm.

[0066] According to one embodiment, the tabs are made of metal foil, including copper foil, nickel foil, or stainless steel foil; the thickness of the metal foil is 5-50 μm, preferably 5-20 μm, and the thickness of the lead tab matches or is consistent with the thickness of the current collector film. The tab width can be 10-40 mm.

[0067] According to one embodiment, the edge region of the current collector layer and the edge region of the tab can be respectively formed into a continuous, regular, complementary pattern using 3D printing, die punching, laser etching, etc. The width of the complementary region can be 2-15 mm.

[0068] According to one embodiment, the complementary shapes of the edge of one side of the current collector layer and the edge of one side of the tab may include: arc-like, semicircular-like, rectangular or square-like, triangular-like, and S-like.

[0069] According to one embodiment, the lithium composite negative electrode with its own tab can be in the form of a continuous web (rolled), wherein the edge area on one side of the current collector layer and the edge area on one side of the tab are respectively formed into complementary structures using laser etching technology, and then the current collector film material and the tab are continuously unwound. After the initial debugging of several meters to more than ten meters, the edge of one side of the current collector film material and the edge of one side of the tab can be well matched together, and there is no gap between the two materials. In addition, the thickness of the current collector film material and the tab foil material is consistent. In this way, the current collector film material and the tab become one.

[0070] The lithium composite electrode can be prepared by the following method, which comprises:

[0071] One side edge of the current collector film material and one side edge of the metal foil material of the lead-out tab are formed into complementary patterns respectively with the help of 3D printing technology, specific mold punching technology, and laser etching technology.

[0072] First, unwind the current collector film material in the middle position and the metal foil material for the lead-out tab. Through debugging, the edge of one side of the current collector film material and the edge of one side of the metal foil material for the lead-out tab are completely aligned together; then unwind the upper and lower rolls of lithium ribbon or lithium alloy ribbon. The unwinding speed of the current collector film material, metal foil and metal lithium ribbon or lithium alloy ribbon is consistent, and the unwinding speed is 5-50 meters / min.

[0073] The upper and lower rolls of metal lithium strips or lithium alloy strips, the current collector film material and metal foil material in the middle position are pressure-compounded to obtain a composite negative electrode with its own tabs.

[0074] Figure 2-1 to Figure 2-2 Schematic diagram of a current collector film and a tab being coupled to each other via an overlap region according to a second embodiment of the present invention, wherein the lithium composite electrode comprises two negative electrode layers 201 , a current collector 202 sandwiched between the two negative electrode layers, and a tab 203 overlapping the current collector 202 . Figure 2-1 shows the structure when the width of the overlap area is 0, Figure 2-2 The structure is shown when the width of the overlapping region 4 is greater than 0.

[0075] According to one embodiment, one side edge of the current collector film overlaps with one side edge of the lead-out tab by 0-5 mm, and the metal foil area not composited with lithium is used as the tab.

[0076] According to one embodiment, the thickness of the tab may match or be consistent with the thickness of the current collector film.

[0077] According to one embodiment, one side of the current collector and / or one side of the tab has a mark for guiding the current collector and the tab to form an overlapping area, and the mark includes a marking line formed by multiple small holes arranged along the edge of the current collector or the tab.

[0078] Other structural features are the same as those of the first embodiment.

[0079] The lithium composite electrode according to the second embodiment can be prepared by the following method, which includes:

[0080] Simultaneously unwind the upper and lower rolls of lithium metal ribbon or lithium alloy ribbon, and simultaneously unwind the conductive carbon film and conductive metal foil in the middle position. The thickness of the carbon film and the metal foil are consistent. The unwinding speed of the carbon film, metal foil and lithium metal ribbon or lithium alloy ribbon is consistent, and the unwinding speed is 5-50 m / min.

[0081] The upper and lower rolls of metal lithium ribbon or lithium alloy ribbon, the carbon film material and the metal foil material in the middle are overlapped by 0-5mm, and are pressure-compounded to obtain a composite negative electrode with its own tabs.

[0082] Figure 3 This is a schematic diagram of the current collector film and the tab being bonded to each other via the tab bonding portion according to the third embodiment of the present invention. Figure 3 As shown, the lithium composite negative electrode of the present invention includes two negative electrode layers 301, a current collector layer 302 sandwiched between the two negative electrode layers, and a tab 303 located outside the negative electrode layer. The tab 303 and the portion of the current collector layer 302 exposed from the negative electrode layer are bonded by a tab bonding portion 304.

[0083] According to one embodiment, the width of the tab bonding portion is 2-10 mm, which can be formed by first bonding the conductive adhesive to the edge area of the tab or first bonding it to the edge area on the width of the current collector.

[0084] According to one embodiment, the adhesive layer is formed of a conductive adhesive. The adhesive layer can be pre-formed on the portion of the current collector layer that is exposed to the negative electrode layer, or pre-formed on the tab. The adhesive properties of the conductive adhesive layer can effectively bond the portion of the current collector layer to the portion of the tab.

[0085] According to one embodiment, the tensile strength at the tab bonding portion is greater than or close to the tensile strength of the current collector. For example, if the tensile strength of the current collector is 80 MPa and the tensile strength of the tab is 200 MPa, the tensile strength at the tab bonding portion is approximately equal to or close to 80 MPa.

[0086] Other structural features are the same as those of the first embodiment.

[0087] The lithium composite electrode according to the third embodiment may be prepared by the following method, which includes:

[0088] First, the current collector layer and the tab foil are unwound. The edge area of at least one of the rolled current collector layer and the tab foil is provided with a conductive glue. After adjusting the gluing position of one side edge area of the current collector and one side edge area of the tab, the one side edge of the current collector and one side edge of the tab are formed into a complete whole by rolling pressure and the adhesion between the materials. Then, the upper and lower rolls of the metallic lithium product are unwound, and after pressure compounding, a lithium composite negative electrode with its own tab is obtained.

[0089] Figure 4 Schematic diagram of a composite negative electrode with a tab formed by a metal deposition layer according to a fourth embodiment of the present invention. Figure 4As shown, the lithium composite negative electrode with a built-in tab of the present invention includes two negative electrode layers 401, an upper and a lower negative electrode layer, and a substrate layer 402 sandwiched between the two negative electrode layers. The substrate layer is wider than the negative electrode layer, one end of the substrate layer is aligned with the negative electrode layer in the width direction, and the other end has a current collecting and leading portion 403 that exposes the negative electrode layer. The current collecting and leading portion is a metal deposited layer that can serve as a tab.

[0090] According to one embodiment, a metal layer is first deposited on an edge region of the substrate layer or on the entire substrate region to form a current collecting and leading portion.

[0091] According to one embodiment, the active material can be distributed to most areas of the substrate layer (excluding the current collecting lead-out portion) through coating, pressure compounding, and vapor deposition processes, with one end of the active material aligned with the substrate layer in the width direction and the other end being smaller than the width of the negative electrode substrate layer.

[0092] According to one embodiment, the metal layer of the current collecting and leading portion is at least one of copper, nickel, tin, silver, and gold.

[0093] According to one embodiment, the width of the current collecting and leading portion is 10-30 mm.

[0094] Other structural features are the same as those of the first embodiment.

[0095] The lithium composite electrode according to the fourth embodiment may be prepared by the following method, which includes:

[0096] The substrate is first cleaned with a mixture of ethanol and water, then washed with water, and dried after washing. A metal layer is then deposited on the edge area of the substrate (conductive substrate) or the upper and lower surface areas of the entire substrate (non-conductive substrate) to obtain a substrate with a current collecting and leading portion.

[0097] The upper and lower rolls of metallic lithium products and the intermediate substrate layer are unwound and pressure-compounded to obtain a lithium composite negative electrode with its own tabs.

[0098] The present invention also provides the use of the above-mentioned composite negative electrode with a tab in a lithium-ion battery. According to one embodiment, the present invention provides a lithium battery comprising the above-mentioned lithium composite negative electrode, wherein the positive electrode material is selected from a ternary nickel-cobalt-manganese material, a ternary nickel-cobalt-aluminum material, a lithium-rich manganese-based positive electrode material, lithium cobalt oxide, lithium iron phosphate, and a sulfur-based positive electrode material.

[0099] According to one embodiment, the electrolyte of the lithium battery can be a liquid electrolyte or a solid electrolyte; the liquid electrolyte can be an ester or an ether; the solid electrolyte can be a halide solid electrolyte, an oxide solid electrolyte, a sulfide solid electrolyte, a polymer electrolyte or an organic-inorganic mixed electrolyte, such as a polyethylene oxide (mixed oxide, halide or sulfide powder) electrolyte.

[0100] For liquid batteries, the separator can be made of polypropylene (PP), polyethylene (PE), or a PP and PE composite. The separator can be coated with ceramic or polyvinylidene fluoride. The battery can be prismatic, soft-pack, or cylindrical.

[0101] The present invention is illustrated below by way of examples. The various product structural parameters, various reaction participants and process conditions used in the following examples are all relatively typical examples. However, after a large number of experiments and verifications by the inventors of this case, other different structural parameters, other types of reaction participants and other process conditions listed above are also applicable and can also achieve the technical effects claimed in the present invention.

[0102] Example 1

[0103] Using 3D printing technology, a semicircular shape is first printed on one edge of the rolled carbon nanotube film as the current collector, and then a semicircular shape is printed on one edge of another roll of copper foil used as the tab. The diameter of the semicircle is 0.6 cm, and the shapes of the two edges can complement each other to form a complete whole.

[0104] First, unroll the carbon nanotube film (thickness 10um) of the current collector film in the middle position and the copper foil (thickness 10um) of the metal foil for the pole ear. Wait until the edges of the carbon nanotube film and the copper foil overlap into a whole, and then unroll the upper and lower rolls of metal lithium tape. The thickness of the lithium tape is 20um, the widest width of the carbon nanotube film is 150mm, the widest part of the copper foil is 20mm, and the width of the lithium tape is 152mm. The semicircular depression on one edge of the carbon nanotube film and the semicircular protrusion on one edge of the copper foil complement each other to form a complete whole. The unwinding speed of the carbon nanotube film, copper foil and metal lithium tape is consistent, and the unwinding speed is 10 meters / min. The three layers of tape are pressure-compounded to obtain a lithium composite negative electrode with its own pole ear. The thickness consistency of the lithium composite negative electrode is good, and the thickness deviation of the entire negative electrode surface is less than or equal to 3um.

[0105] Example 2

[0106] Using 3D printing technology, an equilateral triangle shape is first printed on one edge of the rolled current collector graphite film, and then an equilateral triangle shape is printed on one edge of another roll of the tab copper foil. The height of the equilateral triangle is 0.4 cm, and the shapes of the two edges can complement each other to form a complete whole.

[0107] First, unwind the current collector graphite film (thickness 15um) in the middle position and the metal foil copper foil (thickness 15um) for the pole ear. Wait until the edges of the graphite film and the copper foil overlap as a whole. Unwind the upper and lower rolls of lithium-magnesium alloy strips (magnesium content is 5%). The thickness of the lithium alloy strip is 20um, the widest width of the graphite film is 120mm, the widest part of the copper foil is 20mm, and the width of the lithium strip is 122mm. The triangle on one edge of the graphite film and the triangle on one edge of the copper foil complement each other to form a complete whole. The unwinding speed of the graphite film, copper foil and lithium-magnesium alloy strip is consistent, and the unwinding speed is 8 meters / min. The three layers of strips are pressure-compounded to obtain a lithium composite negative electrode with its own pole ear. The thickness consistency of the lithium composite negative electrode is good, and the thickness deviation of the entire negative electrode surface is less than or equal to 3um.

[0108] Comparative Example 1:

[0109] At the same time, the upper and lower rolls of metal lithium ribbons are unwound, and the thickness of the lithium ribbon is 20um. At the same time, the current collector copper foil (thickness 10um) in the middle position is unwound. The width of the copper foil is 167mm, and the width of the lithium ribbon is 152mm. The unwinding speed of the copper foil and the metal lithium ribbon is the same, which is 8 meters / min. The three layers of strips are pressure-compounded to obtain a lithium composite negative electrode with copper foil tabs.

[0110] Example 3:

[0111] The negative electrode used the lithium composite negative electrode prepared in Example 1, and the positive electrode used NCM (811 nickel-cobalt-manganese ternary positive electrode) with a coating surface density of 50 mg / cm 2 The positive electrode sheet measures 43*56mm, the negative electrode sheet measures 45*58mm, and a PE separator is used. A four-positive, five-negative soft-pack battery is assembled, and the electrolyte is 1M LiPF6 with an EC (ethylene carbonate) to EMC (ethyl methyl carbonate) ratio of 3:7 (vol / vol). The negative electrode sheet, NCM ternary positive electrode sheet, and separator are assembled into a soft-pack battery using a lamination machine. The test voltage range is 2.8-4.4V, the charge current is 0.1C, and the discharge current is 0.5C.

[0112] Comparative Example 2:

[0113] The negative electrode used was the lithium composite negative electrode of Comparative Example 1, and the assembly and testing of the positive electrode, separator, electrolyte and soft-pack battery were the same as those in Example 3.

[0114] Table 1 Data comparison

[0115] Group Specific energy of battery cell (wh / kg) Number of cycles (capacity decay 80%) Example 3 428.9 128 Comparative Example 2 392.6 109

[0116] It can be seen from Table 1 that the specific energy of the battery cell using copper foil as the current collector is 392.6wh / kg due to the high specific gravity of copper; Example 3 uses a carbon film material as the current collector, and because the current collector is light in weight, the specific energy of the battery cell can exceed 400wh / kg.

[0117] Example 4

[0118] At the same time, two rolls of metal lithium ribbons are unwound, and the thickness of the lithium ribbon is 20um. At the same time, the carbon nanotube film (thickness 8um) of the current collector film in the middle position and the copper foil (thickness 8um) of the lead-out tab are unwound. The width of the carbon nanotube film is 100mm, the width of the copper foil is 15mm, and the width of the lithium ribbon is 102mm. The edge of one side of the carbon nanotube film and the edge of one side of the copper foil are close together, and the overlapping area is 0mm; the unwinding speed of the carbon nanotube film, copper foil and metal lithium ribbon is consistent, and the unwinding speed is 6 meters / min. The three layers of ribbons are pressure-compounded to obtain a lithium composite negative electrode with its own tabs.

[0119] Example 5

[0120] At the same time, two rolls of lithium-magnesium alloy strips (magnesium content is 10%) are unwound, and the thickness of the lithium alloy strip is 10um. At the same time, the current collector graphite film (thickness 15um) in the middle position and the metal foil copper foil (thickness 15um) for the lead-out tab are unwound. The width of the graphite film is 100mm, the width of the copper foil is 15mm, and the width of the lithium-magnesium alloy strip is 102mm. The edge of one side of the graphite film and the edge of one side of the copper foil overlap together, and the overlapping area is 2mm. The unwinding speed of the graphite film, copper foil and lithium-magnesium alloy strip is consistent, and the unwinding speed is 10 meters / min. The three layers of strips are pressure-compounded to obtain a lithium composite negative electrode with its own tabs.

[0121] Comparative Example 3:

[0122] At the same time, the upper and lower rolls of metal lithium ribbons are unwound, and the thickness of the lithium ribbon is 20um. At the same time, the current collector copper foil (thickness 8um) in the middle position is unwound. The width of the copper foil is 115mm, and the width of the lithium ribbon is 102mm. The unwinding speed of the copper foil and the metal lithium ribbon is the same, which is 8 meters / min. The three layers of ribbons are pressure-compounded to obtain a lithium composite negative electrode with copper foil tabs.

[0123] Example 6: The negative electrode used the lithium composite negative electrode prepared in Example 4, and the positive electrode used NCM (811 nickel-cobalt-manganese ternary positive electrode), with a coating surface density of 52 mg / cm 2 The positive electrode sheet measures 43*56mm, the negative electrode sheet measures 45*58mm, and a PE separator is used to assemble a 4-positive, 5-negative soft-pack battery. The electrolyte is 1M LiPF6 with an EC:EMC ratio of 3:7 (vol / vol). The negative electrode sheet, NCM ternary positive electrode sheet, and separator are assembled into a soft-pack battery using a lamination machine. The test voltage range is 2.8-4.4V, the charge current is 0.1C, and the discharge current is 0.5C.

[0124] Example 7: The lithium composite negative electrode prepared in Example 5 was used as the negative electrode, and the assembly test of the positive electrode, separator, electrolyte and soft-pack battery was consistent with that in Example 6.

[0125] Comparative Example 4: The lithium composite negative electrode of Comparative Example 3 was used as the negative electrode, and the assembly test of the positive electrode, separator, electrolyte and soft-pack battery was consistent with that of Example 6.

[0126] Table 2 Data comparison

[0127]

[0128]

[0129] It can be seen from Table 2 that the specific energy of the battery cell using copper foil as the current collector is 398.8wh / kg due to the high specific gravity of copper; Examples 6 and 7 use carbon film materials as current collectors, and because the current collectors are light in weight, the specific energy of the battery cell can be increased by about 5%; the cycle performance of Example 7 is better than that of Example 6 because magnesium in the lithium-magnesium alloy is a good deposition site, and the presence of magnesium is conducive to the uniform deposition of metallic lithium.

[0130] Example 8

[0131] The tab uses 10um thick copper foil with a width of 30mm and a length of 1000 meters. A 5mm wide conductive adhesive layer is applied to the edge area of one side of the copper foil, and no conductive adhesive is applied to the other areas of the copper foil.

[0132] At the same time, a 150mm wide carbon nanotube film (8um thickness) and a 30mm wide copper foil coated with conductive adhesive are unwound. After the 5mm wide conductive adhesive layer area of the copper foil and the 5mm wide area at the edge of the carbon nanotube film are completely aligned, the carbon nanotube film and copper foil are rolled together through a rolling device to form an integrated film material.

[0133] At the same time, two rolls of lithium film (lithium with plastic film support, lithium thickness 10um, width 145mm) and the integrated film material in the middle are unwound, and after rolling, a lithium composite negative electrode with its own tabs is obtained.

[0134] Example 9

[0135] The current collector layer is selected to be a carbon nanotube film (8um thickness), with a width of 150mm and a length of 1000 meters. A 3mm wide conductive adhesive layer is coated on the edge area of one side of the carbon nanotube film, and no conductive adhesive is coated on the other areas of the carbon nanotube film.

[0136] A 150mm wide carbon nanotube film and a 20mm wide copper foil (10um thick) are unwound at the same time. After the 3mm wide conductive adhesive layer area of the carbon nanotube film and the 3mm wide area at the edge of the copper foil are completely aligned, the carbon nanotube film and the copper foil are rolled into one film material through a rolling device.

[0137] At the same time, two rolls of metal lithium ribbon (lithium thickness 20um, width 147mm) and the integrated film material in the middle are unwound and rolled to obtain a lithium composite negative electrode with its own tabs.

[0138] Example 10: The negative electrode used was the lithium composite negative electrode prepared in Example 8, and the positive electrode used was NCM (811 nickel-cobalt-manganese ternary positive electrode), with a coating surface density of 50 mg / cm 2 The positive electrode sheet measures 43*56mm, the negative electrode sheet measures 45*58mm, and a PE separator is used to assemble a 4-positive, 5-negative soft-pack battery. The electrolyte is 1M LiPF6 with an EC:EMC ratio of 3:7 (vol / vol). The negative electrode sheet, NCM ternary positive electrode sheet, and separator are assembled into a soft-pack battery using a lamination machine. The test voltage range is 2.8-4.35V, the charge current is 0.2C, and the discharge current is 0.5C.

[0139] Comparative Example 5:

[0140] The upper and lower rolls of lithium film are unwound at the same time. The thickness of the lithium film is 10um. At the same time, the current collector copper foil (thickness 8um) in the middle position is unwound. The width of the copper foil is 175mm and the width of the lithium film is 145mm. The unwinding speed of the copper foil and the metallic lithium film is the same. The three layers of strips are pressure-compounded to obtain a lithium composite negative electrode with copper foil tabs.

[0141] Comparative Example 6: The lithium composite negative electrode of Comparative Example 5 was used as the negative electrode, and the assembly test of the positive electrode, separator, electrolyte and soft-pack battery was consistent with that of Example 10.

[0142] Table 3 Tensile strength values of the junction between the current collector and the tab

[0143] name Tensile strength of conductive adhesive joint material / MPa Example 8 80.3 Example 9 80.1

[0144] The tensile strength of the carbon nanotube film material tested is 78.9 MPa, and the tensile strength of the 10 μm thick copper foil is 210.3 MPa. From the data in Table 3, it can be seen that the tensile strength of the material at the conductive adhesive joint is very strong and can be used in actual production.

[0145] Table 4 Data comparison

[0146] Group Specific energy of battery cell (wh / kg) Number of cycles (capacity decay 80%) Example 10 429.6 125 Comparative Example 6 396.3 103

[0147] From the data in Table 4, it can be seen that the specific energy of the battery cell using copper foil as the current collector is 396.3wh / kg due to the high specific gravity of copper. In Example 10, a carbon film material is used as the current collector. Due to the light weight of the current collector, the specific energy of the battery cell is increased by 8.4%.

[0148] Example 11

[0149] A rolled conductive carbon nanotube film (10µm thick) was used as the substrate. The substrate was 200mm wide and 200 meters long. The carbon nanotube film was cleaned with a mixture of ethanol and water, then rinsed with water and dried in a forced air oven at 100°C for 12 hours before use. A copper layer was deposited on the edge (20mm wide) of one side of the substrate. The copper layer was deposited on both sides of the edge, with a thickness of 3µm on each side, resulting in a substrate with a built-in current collector and lead-out section.

[0150] At the same time, two rolls of lithium film (lithium with plastic film support, lithium thickness 10um, width 179mm) and the middle layer substrate with its own current collecting lead-out part are unwound, and after rolling, a lithium composite negative electrode with its own tabs is obtained.

[0151] The size of the die-cut negative electrode sheet is 45*58mm, and the tab size is 8mm wide*10mm long. Customize the corresponding die, determine the position of the tab on the sheet, and directly die-cut the negative electrode sheet with a small tab. The area of the negative electrode sheet is lithium layer + substrate layer + lithium layer, and the tab area is copper layer + substrate layer + copper layer.

[0152] Example 12: The negative electrode used was the lithium composite negative electrode prepared in Example 11, and the positive electrode used was NCM (811 nickel-cobalt-manganese ternary positive electrode), with a coating surface density of 50 mg / cm 2 The positive electrode sheet measures 43*56mm, the negative electrode sheet measures 45*58mm, and a PE separator is used to assemble a 4-positive, 5-negative soft-pack battery. The electrolyte is 1M LiPF6 with an EC:EMC ratio of 3:7 (vol / vol). The negative electrode sheet, NCM ternary positive electrode sheet, and separator are assembled into a soft-pack battery using a lamination machine. The test voltage range is 2.8-4.35V, the charge current is 0.2C, and the discharge current is 0.5C.

[0153] Comparative Example 7:

[0154] The upper and lower rolls of lithium film are unwound at the same time. The thickness of the lithium film is 10um. At the same time, the current collector copper foil (thickness 6um) in the middle position is unwound. The width of the copper foil is 200mm and the width of the lithium film is 179mm. The unwinding speed of the copper foil and the metallic lithium film is the same. The three layers of strips are pressure-compounded to obtain a lithium composite negative electrode with its own copper foil tabs.

[0155] Comparative Example 8: The lithium composite negative electrode of Comparative Example 7 was used as the negative electrode, and the assembly of the positive electrode, separator, electrolyte and soft-pack battery was the same as that of Example 12.

[0156] Table 5 Comparison of battery specific energy

[0157] Group Specific energy of battery cell (wh / kg) Number of cycles (capacity decay 80%) Example 12 426.5 128 Comparative Example 8 399.7 103

[0158] The specific energy of the battery in Example 12 is increased by 6.7% compared with the specific energy of the battery in Comparative Example 8.

[0159] It should be understood that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A lithium composite negative electrode with a built-in tab, characterized in that: The lithium composite electrode comprises: Two upper and lower negative electrode layers, wherein the negative electrode layers are metallic lithium layers or lithium alloy layers; A flexible current collector layer sandwiched between two negative electrode layers, wherein the current collector layer is formed of a carbonaceous film material, or a film material formed by depositing a conductive material on a non-conductive fiber cloth; and Extreme ears, The tab is connected to the current collector layer via a tab connection portion, and the tab connection portion includes any one of the following: (1) A complementary structure, wherein the complementary structure is located between the upper and lower negative electrode layers and is composed of a tab junction at one end of the current collector layer and a current collector layer junction on the tab, wherein the tab junction and the current collector layer junction are complementary in structure; (2) an overlapping region, the overlapping region consisting of the overlapping portion of the current collector and the tab, located between the upper and lower negative electrode layers, and the non-overlapping portion of the tab extending beyond the edge of the negative electrode layer; and (3) a tab bonding portion, the tab bonding portion being located outside the upper and lower negative electrode layers and being formed by an adhesive layer on a portion of the current collector layer exposed from the negative electrode layer, or by an adhesive layer on the tab; Alternatively, the tab is formed by a metal deposition layer located on a portion of the current collector layer exposed from the negative electrode layer.

2. The lithium composite electrode with a tab according to claim 1, characterized in that: The carbonaceous film material includes at least one of the following film materials: A film material formed by a vapor deposition process of at least one material selected from carbon nanotubes, carbon fibers, graphene, acetylene black, activated carbon materials, and graphite; A carbon-containing film material formed from at least one polymer selected from polypropylene, polyethylene, polyimide, and polyurethane and at least one conductive carbon selected from conductive carbon black, graphene, and carbon nanotubes; A carbon-containing film material is formed by forming a slurry from at least one conductive carbon material selected from conductive carbon black, carbon nanotubes, carbon fibers, and graphene and a binder in a solvent, and then using a papermaking process; Membrane material made by sintering polyimide film; and The film material is formed by coating a slurry of carbon nanotubes or graphene on a release film. The non-conductive fiber cloth is formed by electrostatic spinning.

3. The lithium composite electrode with a tab according to claim 1, wherein: The tab joints are complementary structures, wherein the tab joints of the current collector layer have continuously distributed rectangular, triangular, or arc shapes, or the tab joints have comb-shaped or zigzag shapes; Preferably, the tab joint portion of the current collector layer has a regularly distributed columnar protrusion or arc-shaped depression structure, and the top of the columnar protrusion or arc-shaped depression has a flange extending in a direction perpendicular to the thickness direction of the current collector layer.

4. The lithium composite electrode with a tab according to claim 1, characterized in that: The tab joint is an overlapping area, wherein the width of the overlapping area is 0-5 mm. Preferably, one side of the current collector and / or one side of the tab has a mark for guiding the current collector and the tab to form an overlapping area, and the mark includes a marking line formed by multiple small holes arranged along the edge of the current collector or the tab.

5. The lithium composite electrode with a tab according to claim 1, wherein: The tab joint portion is a tab adhesive portion, wherein the width of the adhesive layer is 2-10 mm, and the tensile strength at the tab adhesive portion is greater than or close to the tensile strength of the current collector.

6. The lithium composite electrode with a tab according to claim 1, characterized in that: The tab is formed by a metal deposition layer, wherein the metal deposition layer is continuously or intermittently distributed on a portion of the current collector layer exposed from the negative electrode layer and along a length direction of the current collector layer.

7. The lithium composite electrode with a tab according to claim 1, wherein: The lithium composite negative electrode is a continuous web with a length of 1-2000 m.

8. The lithium composite negative electrode with a tab according to claim 1, characterized in that: The thickness of the negative electrode layer is 1-100 μm and the width is 50-1400 mm; The thickness of the current collector layer is 5-50 μm.

9. A method for preparing the lithium composite electrode according to any one of claims 1 to 8, characterized in that: The method comprises: One side edge of the current collector film material and one side edge of the metal foil material are formed into complementary structures respectively by using 3D printing technology, mold punching technology, and laser etching technology; First, unwind the current collector film and metal foil in the middle position so that the edge of one side of the current collector film and the edge of one side of the metal foil are completely aligned with each other; then unwind the upper and lower rolls of lithium ribbon or lithium alloy ribbon, and unwind the current collector film, metal foil and metal lithium ribbon or lithium alloy ribbon at the same speed, which is 5-50 meters / min; The upper and lower rolls of metal lithium strips or lithium alloy strips, the current collector film material and metal foil material in the middle position are pressure-compounded to obtain a composite negative electrode with its own tabs. or The current collector film material and the metal foil material at the middle position of the unwinding are overlapped with one side edge of the current collector film material and one side edge of the metal foil material; At the same time, two rolls of lithium metal ribbon or lithium alloy ribbon are unwound and laminated under pressure to obtain a composite negative electrode with its own tabs. or, First, the current collector film and the tab foil are unwound, and at least one of the edge regions of the rolled current collector film and the tab foil is provided with a conductive adhesive. After the adhesive positions of one side edge region of the current collector film and one side edge region of the tab are adjusted, the one side edge of the current collector film and one side edge of the tab are formed into a complete whole by rolling pressure and the adhesion between the materials; Then unwind the upper and lower rolls of lithium metal ribbon or lithium alloy ribbon, and press them together to obtain a lithium composite negative electrode with its own tabs. or, First, a metal layer is deposited on the edge area of the current collector film material to obtain a substrate with a current collector lead-out portion; The upper and lower rolls of metal lithium strips or lithium alloy strips and the substrate of the middle layer are unwound and pressure-compounded to obtain a lithium composite negative electrode with its own tabs.

10. A lithium battery, characterized in that: The lithium battery comprises the lithium composite negative electrode with a tab according to any one of claims 1 to 8.

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