Negative electrode sheet for lithium metal battery, electrode assembly, lithium metal battery and electronic device

Abstract

The present application provides a negative electrode sheet for a lithium metal battery, an electrode assembly, a lithium metal battery, and an electronic device. The negative electrode sheet comprises a carbon-based current collector, and a first metal lithium-replenishing layer and a second metal lithium-replenishing layer which are respectively provided on two sides of the carbon-based current collector. Compared with a conventional metal negative electrode sheet, the carbon-based current collector comprised in the negative electrode sheet can significantly reduce the weight of the negative electrode sheet, thereby significantly improving the gravimetric energy density of the lithium metal battery. The first metal lithium-replenishing layer and the second metal lithium-replenishing layer are respectively provided on the two sides of the carbon-based current collector; when tabs are welded to the negative electrode sheet, due to the existence of the carbon-based current collector, the negative electrode sheet will not be burned through, avoiding non-uniform current distribution between the negative electrode sheet and other parts of the battery, avoiding slowing down the electrochemical reaction rate in certain areas, avoiding reduction of the capacity of the lithium metal battery.

Description

Negative electrode sheets, electrode assemblies, lithium metal batteries and electronic devices for lithium metal batteries Technical Field

[0001] The present application relates to the field of electrochemical technology, and in particular to a negative electrode sheet, an electrode assembly, a lithium metal battery, and an electronic device for a lithium metal battery. Background Art

[0002] With the rapid development of electronic products, lithium secondary batteries are widely used in portable devices, power devices and energy storage systems due to their advantages such as high energy density, miniaturization and lightweight, such as mobile phones, laptops, tablets, drones, electric vehicles, power tools, power storage systems, etc.

[0003] Lithium secondary batteries include lithium metal batteries that use lithium metal as their negative electrode. Lithium metal negative electrodes have a high capacitance per unit weight, which gives lithium metal batteries a high capacitance. When using such a lithium metal negative electrode as the negative electrode, the lithium metal electrode can react with the electrolyte during charging and discharging. This reaction can easily cause the overall volume of the battery cell containing the lithium metal negative electrode to expand significantly. The lithium metal negative electrode near the tab area of ​​the battery cell is susceptible to fracture during repeated stretching, resulting in a reduction in the capacity of the lithium metal battery containing such a lithium metal negative electrode. Therefore, improvements are needed.

[0004] Summary of the Invention

[0005] In view of the above problems, the present application aims to provide a negative electrode plate, an electrode assembly, a lithium metal battery and an electronic device for a lithium metal battery, wherein the negative electrode plate can improve the problem of easy cracking during welding of the negative electrode plate and the breakage of the tab during the charge and discharge cycle of the battery, as well as the problem of reduced capacity caused thereby; the electrode assembly, lithium metal battery and electronic device containing the negative electrode plate also have the above advantages.

[0006] To this end, in a first aspect, an embodiment of the present application provides a negative electrode sheet for a lithium metal battery, comprising:

[0007] Carbon-based current collectors,

[0008] A first metal lithium replenishing layer and a second metal lithium replenishing layer are respectively arranged on both sides of the carbon-based current collector.

[0009] According to an embodiment of the present application, the negative electrode comprises a first metal lithium replenishing layer and a second metal lithium replenishing layer respectively disposed on both sides of the carbon-based current collector, wherein the density of lithium metal at room temperature is about 0.534 g / cm 3 Compared with traditional metal negative electrode sheets (such as copper foil), it can significantly reduce the weight of the negative electrode sheets, thereby significantly improving the mass energy density of lithium metal batteries.

[0010] The first metal lithium replenishing layer and the second metal lithium replenishing layer are respectively arranged on both sides of the carbon-based current collector. When welding the electrode tab on the negative electrode plate, due to the presence of the carbon-based current collector, the negative electrode plate of the present application will not be welded through, which is beneficial to avoiding the short circuit between the negative electrode plate and other electrodes or the battery shell or the increase of hot spots inside the battery due to welding, thereby improving the safety of the lithium metal battery; the negative electrode plate of the present application will not be welded through, which is beneficial to avoiding interference or interruption of the current path between the negative electrode plate and other parts, which is beneficial to the internal resistance of the lithium metal battery; the negative electrode plate will not be welded through, which is beneficial to avoiding uneven current distribution between the negative electrode plate and other parts of the battery, and is beneficial to avoiding the slowdown of the electrochemical reaction rate in certain areas, thereby avoiding a reduction in the capacity of the lithium metal battery.

[0011] Furthermore, during the electrochemical cycle of a lithium metal battery containing this negative electrode sheet, the lithium metal exhibits excellent electrical conductivity and current collection properties, resulting in a low impedance and minimal polarization of the lithium metal battery, thereby providing the lithium metal battery with high electrochemical performance. As the electrochemical cycle of the lithium metal battery progresses, the first and second metal lithium replenishing layers react with the electrolyte in the lithium metal battery, respectively, causing the precipitation and dissolution of metallic lithium in the first and second metal lithium replenishing layers, providing more active lithium ions for the lithium metal battery, thereby comprehensively improving the cycle life of the lithium metal battery.

[0012] In any embodiment of the present application, the carbon-based current collector includes one or more of graphene and carbon nanotubes.

[0013] According to the embodiments of the present application, graphene and carbon nanotubes have good electrical conductivity. Compared with the design without current collector, the rate at which active lithium ions in lithium metal batteries containing carbon-based current collectors are converted into "dead lithium" or loose lithium is significantly reduced, and the electrolyte consumption rate is slowed down, which can improve the cycle performance of lithium metal batteries.

[0014] In addition, the carbon-based current collector can support and strengthen the first metal lithium replenishing layer and the second metal lithium replenishing layer, improve the reliability of welding, and solve the problem of tab breakage during the cycle.

[0015] In any embodiment of the present application, the density of the carbon-based current collector is 1.9 to 2.3 g / cm 3 .

[0016] According to the embodiments of the present application, graphene and carbon nanotubes have good electrical conductivity. When the density of graphene and carbon nanotubes is within the above range, while maintaining uniform electronic conductivity, the energy density of lithium metal batteries is greatly improved compared to copper current collectors.

[0017] In any embodiment of the present application, the first metal lithium-replenishing layer and the second metal lithium-replenishing layer respectively include one or more of metallic lithium and lithium alloys.

[0018] According to the embodiments of the present application, the first and second metal lithium-replenishing layers comprise elemental lithium and a lithium alloy, respectively, significantly reducing the weight of the negative electrode sheet and thereby significantly improving the mass energy density of the lithium metal battery. The elemental lithium and lithium alloy react with the electrolyte in the lithium metal battery, causing the lithium metal in the first and second metal lithium-replenishing layers to precipitate and dissolve, providing more active lithium ions for the lithium metal battery, thereby comprehensively improving the energy density and cycle life of the lithium metal battery.

[0019] In any embodiment of the present application, the lithium alloy includes one or more of lithium silver alloy, lithium aluminum alloy, lithium magnesium alloy, lithium gold alloy, lithium sodium alloy, lithium tin alloy, lithium zinc alloy, lithium barium alloy, lithium bismuth alloy, lithium calcium alloy, lithium germanium alloy, lithium cesium alloy, lithium gallium alloy, lithium potassium alloy, lithium lead alloy, lithium antimony alloy, lithium boron alloy, lithium silicon alloy, lithium carbon alloy, lithium phosphorus alloy, lithium boron magnesium alloy, and lithium silicon magnesium alloy.

[0020] According to the embodiments of the present application, the mass content of metallic lithium in the above-mentioned lithium alloy is relatively large, so the advantage of metallic lithium in improving the energy density of lithium metal batteries can be fully utilized; metallic lithium reacts with the electrolyte to achieve lithium precipitation and dissolution, providing more active lithium ions for the lithium metal battery, thereby comprehensively improving the cycle life of the lithium metal battery.

[0021] In any embodiment of the present application, the negative electrode plate satisfies at least one of the following conditions:

[0022] 1) The ratio of the thickness H1 of the carbon-based current collector to the thickness H2 of the first metal lithium replenishing layer and the thickness H3 of the second metal lithium replenishing layer is 1:(0.5-50):(0.5-50), and can be 1:(2-10):(2-10); optionally, the thickness H2 of the first metal lithium replenishing layer and the thickness H3 of the second metal lithium replenishing layer are the same;

[0023] 2) The thickness of the carbon-based current collector can be 1 micron to 10 microns;

[0024] 3) The thickness of the first metal lithium replenishing layer and the second metal lithium replenishing layer are 5 microns to 50 microns respectively;

[0025] 4) The thickness of the negative electrode sheet is 11 microns to 110 microns.

[0026] According to the embodiments of the present application, controlling the ratio of H1, H2 and H3 within the above range is beneficial to controlling the relative thickness of the carbon-based current collector, and on the basis of exerting the role of the carbon-based current collector, further improving the capacity density of the lithium metal battery and reducing its internal resistance.

[0027] Electrode assembly

[0028] In a second aspect, an embodiment of the present application provides an electrode assembly comprising the negative electrode sheet of the first aspect.

[0029] In any embodiment of the present application, the electrode assembly includes a positive electrode plate, the positive electrode plate includes a positive electrode active material film layer, the positive electrode active material film layer includes a first electrolyte and a positive electrode active material, and the first electrolyte is dispersed in the positive electrode active material film layer.

[0030] According to the embodiments of the present application, the solid electrolyte has excellent ion conductivity and provides ion conduction channels in the positive electrode sheet, allowing ions (such as lithium ions) in the positive electrode active material to migrate during the charge and discharge process. This enables the lithium ions in the positive electrode active material layer to move quickly and reliably, thereby achieving charge and discharge cycles. This helps to extend the cycle performance of lithium metal batteries.

[0031] In any embodiment of the present application, the positive electrode active material layer includes the first electrolyte in an amount of 1% to 5% by mass based on the total mass of the positive electrode active material layer.

[0032] According to the embodiment of the present application, the positive electrode active material film layer includes the first electrolyte with the above-mentioned mass content, which can enable the lithium ions in the positive electrode active material layer to move quickly and reliably, thereby realizing charge and discharge cycles and improving the charge and discharge performance and cycle performance of the lithium metal battery.

[0033] In any embodiment of the present application, the first electrolyte includes Li 0.33 La 0.56 TiO3、Li 1.3 Al 0.3 Ti 1.7 (PO4)3、Li7La3Zr2O 12 , undoped or containing doping elements Li 6.5 La3Zr 1.5 Ta 0.5 O 12 One or more of the following, wherein the doping elements include one or more of silicon, germanium and tin.

[0034] According to the embodiments of the present application, the above-mentioned type of first electrolyte has good chemical corrosion resistance, can resist the corrosion of the electrolyte by solvents and other components in the electrolyte, and stabilize the positive electrode active material film layer; the above-mentioned type of first electrolyte has high ionic conductivity, so that lithium ions can be quickly transmitted in the solid electrolyte, promoting high power output and fast charge and discharge performance of the battery; the above-mentioned type of first electrolyte has a wide electrochemical stability window, has good chemical stability under a wide range of voltages, can withstand higher potentials and polarization, and improve the safety risks of lithium metal batteries.

[0035] In any embodiment of the present application, the mass fraction W1 of the positive electrode active material in the positive electrode active material film layer is 85% to 99%, and optionally 90% to 97.9%. The mass fraction W1 of the positive electrode active material in the positive electrode active material film layer within the above range is beneficial for improving the capacity of the lithium metal battery and improving the cycling performance.

[0036] In any embodiment of the present application, the mass ratio of the positive electrode active material to the first electrolyte in the positive electrode active material film layer is 1:(0.025-5), and can be optionally 1:(0.06-0.75).

[0037] According to the embodiments of the present application, by controlling the mass ratio of the positive electrode active material to the first electrolyte in the positive electrode active material film layer within the above range, the first electrolyte is better dispersed around the positive electrode active material. The ionic conductivity of the first electrolyte enables rapid transport of lithium ions in the solid electrolyte, more effectively achieving lithium ion insertion and deinsertion, and improving charge and discharge efficiency. It is also beneficial to contain the positive electrode active material and improve cycle stability.

[0038] In any embodiment of the present application, the compaction density of the positive electrode active material film layer is 3.8 to 4.3 g / cm 3， Optional: 3.9~4.2g / cm 3 .

[0039] According to the embodiments of the present application, the compaction density of the positive electrode active material film layer is within the above range. On the one hand, it can improve the contact between the particles in the positive electrode active material layer, increase the electron conduction path, thereby reducing resistance loss and improving the conductivity and power output capacity of the battery. On the other hand, the appropriate compaction density helps to optimize the pore structure of the positive electrode active material layer, provide better ion transmission channels, reduce ionic impedance, and thus improve the charge and discharge rate and cycle stability of the battery.

[0040] Furthermore, a suitable compaction density of the positive electrode active material layer can improve its structural stability, reduce deformation of the positive electrode active material film layer and particle shedding, thereby improving the mechanical stability and cycle life of the battery. Furthermore, the above-mentioned compaction density of the embodiment of the present application, combined with the dispersion of the first electrolyte in the positive electrode active material film layer, can further improve the stability of the positive electrode active material film layer, which is beneficial to the stability of the lithium metal battery.

[0041] In some optional embodiments, the area capacity of the positive electrode active material film layer is 3 to 5 mAh / cm 2 , 3.5~4.8mAh / cm 2 .

[0042] The areal capacity of the positive electrode active material layer refers to the amount of charge or capacity that the positive electrode active material can store per unit area. Its size has a direct impact on the total capacity and performance of the battery. Increasing the positive electrode areal capacity can increase the battery's total capacity, thereby extending its service life. A larger positive electrode area provides more active material, increases the contact area between the battery's positive electrode and electrolyte, promotes ion transport and electron conduction, and improves battery performance indicators such as capacity, power, and cycle life.

[0043] A second aspect of the present invention provides a lithium metal battery comprising a positive electrode, a negative electrode, and the negative electrode plate of the first aspect. The lithium metal battery can alleviate the problems of cracking of the negative electrode plate during welding and tab breakage during the battery's charge and discharge cycles, as well as the resulting capacity reduction.

[0044] A third aspect of the present application provides an electronic device comprising the lithium metal battery of the second aspect. The lithium metal battery of the second aspect has at least the advantages of a lithium metal battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] FIG1 shows a schematic diagram of a lithium metal battery according to an embodiment of the present application;

[0046] FIG2 shows an exploded view of the lithium metal battery according to one embodiment of the present application shown in FIG1 ;

[0047] FIG3 shows a schematic diagram of an electronic device using a lithium metal battery as a power source according to an embodiment of the present application.

[0048] Description of reference numerals: 5 lithium metal battery; 51 housing; 52 electrode assembly; 53 cover plate.

[0049] The drawings in this application are not necessarily drawn to scale. DETAILED DESCRIPTION

[0050] Below, with appropriate reference to the accompanying drawings, the embodiments of the negative electrode sheet, electrode assembly, lithium metal battery and electronic device for the lithium metal battery of the present application are specifically disclosed in detail. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0051] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0052] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of the present application.

[0053] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form new technical solutions, and such technical solutions should be deemed to be included in the disclosure of this application.

[0054] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0055] Unless otherwise specified, the terms "include" and "comprising" used in this application may be open-ended or closed-ended. For example, "include" and "comprising" may mean that other components not listed may also be included or that only the listed components are included.

[0056] Unless otherwise specified, the term "or" is used in this application to be inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the condition "A or B" is satisfied if any of the following conditions are met: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0057] Unless otherwise specified, in this application, the terms "first", "second", "third", "fourth", etc. are used to distinguish different objects rather than to describe a specific order or a primary-secondary relationship.

[0058] Unless otherwise specified, in this application, the term "active ions" refers to ions that can be embedded and extracted back and forth between the positive and negative electrodes of lithium metal batteries, including but not limited to lithium ions, sodium ions, etc.

[0059] The term "plurality" used in this application refers to two or more (including two).

[0060] In this application, lithium metal batteries may include lithium-ion batteries, etc., and the embodiments of this application are not limited to this. Lithium metal batteries may be aqueous batteries or oil-based batteries, and the embodiments of this application are not limited to this. Lithium metal batteries may be flat, rectangular, or in other shapes, and the embodiments of this application are not limited to this.

[0061] As the application of lithium-ion batteries continues to expand, the requirements for their capacity and energy density are becoming increasingly higher. How to improve the capacity and energy density of lithium-ion batteries is an urgent problem that needs to be solved.

[0062] Lithium-ion batteries have a high energy density, typically greater than 200Wh / kg, a high operating voltage, typically greater than 3.5V, and advantages such as low self-discharge, compact size, and light weight. They are widely used in consumer electronics. However, with the development of society, people's demands for battery energy density, cycle life, and other related factors are increasing.

[0063] Lithium-ion batteries include a type of battery in which the positive electrode material is typically lithium cobalt oxide, lithium manganese oxide, etc. These positive electrode materials serve as a lithium ion source. During the charging process, lithium ions are deintercalated from the positive electrode material and move through the electrolyte to the negative electrode material (usually a carbon material) for intercalation. During the discharge process, lithium ions are deintercalated from the negative electrode material and move back through the electrolyte to the positive electrode material for intercalation, completing the battery cycle.

[0064] Lithium-ion batteries include another type of battery: the lithium metal battery. The negative electrode of a lithium metal battery can contain metallic lithium itself. During the charge and discharge process of a lithium metal battery, the lithium metal anode undergoes lithium precipitation and dissolution reactions.

[0065] In the related art, lithium metal cells in lithium metal batteries usually use lithium-coated copper strips as negative electrodes. The density of copper in the current collector is about 8.96 g / cm 3 , typically 5-10 μm thick. The lithium metal in lithium-ion batteries has the smallest relative atomic mass (6.94) and the lowest standard electrode potential (-3.045 V) of all metal elements, with a theoretical gram capacity of 3860 mAh / g. This results in the gravimetric energy density (GED) advantage of lithium metal batteries not being maximized.

[0066] Lithium ribbons can be used as current collectors in lithium metal batteries containing them, further improving the gravimetric energy density (GED). However, directly using pure lithium ribbons as negative electrode sheets will bring many problems. For example, when preparing lithium-ion batteries, pure lithium ribbons are easily welded through when welding the tabs. This is because lithium metal is soft and has low hardness, and it is easy to weld through it at high temperatures during welding. In addition, this type of lithium metal battery containing only lithium ribbons expands significantly during the charge and discharge process, and the lithium metal pole sheet near the tab area is easily broken during repeated stretching, which can easily cause the capacity of the lithium metal battery to drop rapidly.

[0067] Secondly, the negative electrode plate in lithium metal batteries uses a current collector-free design. Compared to designs using copper foil as a current collector, lithium stripping is uneven and easily corroded by the electrolyte, forming perforations. Uneven lithium deposition and stripping increases the rate at which lithium metal is converted into loose lithium / dead lithium, accelerating electrolyte consumption. Finally, when a large amount of lithium is converted, the electronic contact between the tab and the plate is lost, and the battery cell fails.

[0068] Compared to traditional graphite anodes, active lithium ions do not embed into the graphite lamellar structure of the negative electrode when they reach it, but are deposited directly on the surface. Consequently, they experience significant volume changes during repeated cycling. This volume change can cause the tab area, where welding defects already exist, to desolder or break during repeated stretching, further reducing the capacity of the lithium metal cell.

[0069] In view of this, the present application provides a negative electrode plate for a lithium metal battery, which can improve the energy density of the lithium metal battery containing the negative electrode plate while avoiding the tabs from being welded through during the welding of the negative electrode plate, thereby making the capacity of the lithium metal battery containing the negative electrode plate more stable.

[0070] Anode plates for lithium metal batteries

[0071] In a first aspect, an embodiment of the present application provides a negative electrode sheet for a lithium metal battery, comprising:

[0072] Carbon-based current collectors,

[0073] A first metal lithium replenishing layer and a second metal lithium replenishing layer are respectively arranged on both sides of the carbon-based current collector.

[0074] According to an embodiment of the present application, the negative electrode comprises a first metal lithium replenishing layer and a second metal lithium replenishing layer respectively disposed on both sides of the carbon-based current collector, wherein the density of lithium metal at room temperature is about 0.534 g / cm 3 Compared with traditional metal negative electrode sheets (such as copper foil, the density is about 8.96g / cm 3 ), it can significantly reduce the weight of the negative electrode sheet, thereby significantly improving the mass energy density of the lithium metal battery.

[0075] The first metal lithium replenishing layer and the second metal lithium replenishing layer are respectively arranged on both sides of the carbon-based current collector. When welding the electrode tab on the negative electrode plate, due to the presence of the carbon-based current collector, the negative electrode plate of the present application will not be welded through, which is beneficial to avoiding the short circuit between the negative electrode plate and other electrodes or the battery shell or the increase of hot spots inside the battery due to welding, thereby improving the safety of the lithium metal battery; the negative electrode plate of the present application will not be welded through, which is beneficial to avoiding interference or interruption of the current path between the negative electrode plate and other parts, which is beneficial to the internal resistance of the lithium metal battery; the negative electrode plate will not be welded through, which is beneficial to avoiding uneven current distribution between the negative electrode plate and other parts of the battery, and is beneficial to avoiding the slowdown of the electrochemical reaction rate in certain areas, thereby avoiding a reduction in the capacity of the lithium metal battery.

[0076] Furthermore, during the electrochemical cycle of a lithium metal battery containing this negative electrode sheet, the lithium metal exhibits excellent electrical conductivity and current collection properties, resulting in a low impedance and minimal polarization of the lithium metal battery, thereby providing the lithium metal battery with high electrochemical performance. As the electrochemical cycle of the lithium metal battery progresses, the first and second metal lithium replenishing layers react with the electrolyte in the lithium metal battery, respectively, causing the precipitation and dissolution of metallic lithium in the first and second metal lithium replenishing layers, providing more active lithium ions for the lithium metal battery, thereby comprehensively improving the cycle life of the lithium metal battery.

[0077] In some optional embodiments, the carbon-based current collector includes one or more of graphene and carbon nanotubes.

[0078] According to the embodiments of the present application, graphene and carbon nanotubes have good electrical conductivity. Compared with the design without current collector, the rate at which active lithium ions in lithium metal batteries containing carbon-based current collectors are converted into "dead lithium" or loose lithium is significantly reduced, and the electrolyte consumption rate is slowed down, which can improve the cycle performance of lithium metal batteries.

[0079] In addition, the carbon-based current collector can support and strengthen the first metal lithium replenishing layer and the second metal lithium replenishing layer, improve the reliability of welding, and solve the problem of tab breakage during the cycle.

[0080] In some optional embodiments, the density of the carbon-based current collector is 1.9 to 2.3 g / cm 3 .

[0081] Optionally, the density of the carbon-based current collector is 1.9 g / cm 3 , 1.95g / cm 3 , 2.00g / cm 3 , 2.05g / cm 3 , 2.1g / cm 3 , 2.15g / cm 3 , 2.2g / cm 3 , 2.25g / cm 3 , 2.3g / cm 3 Any numerical value or range thereof.

[0082] According to the embodiments of the present application, graphene and carbon nanotubes have good electrical conductivity. When the density of graphene and carbon nanotubes is within the above range, while maintaining uniform electronic conductivity, the energy density of lithium metal batteries is greatly improved compared to copper current collectors.

[0083] Method for measuring the density of carbon-based current collectors: crush the carbon-based current collector to 0.15 mm and then use the boiling method to vacuum degas the material; after vacuum degassing, test it using the standard YB4091-92 method.

[0084] In some optional embodiments, the first metal lithium-replenishing layer and the second metal lithium-replenishing layer respectively include one or more of metallic lithium and lithium alloys.

[0085] According to the embodiments of the present application, the first and second metal lithium-replenishing layers comprise elemental lithium and a lithium alloy, respectively, significantly reducing the weight of the negative electrode sheet and thereby significantly improving the mass energy density of the lithium metal battery. The elemental lithium and lithium alloy react with the electrolyte in the lithium metal battery, causing the lithium metal in the first and second metal lithium-replenishing layers to precipitate and dissolve, providing more active lithium ions for the lithium metal battery, thereby comprehensively improving the energy density and cycle life of the lithium metal battery.

[0086] In some optional embodiments, the lithium alloy includes one or more of lithium silver alloy, lithium aluminum alloy, lithium magnesium alloy, lithium gold alloy, lithium sodium alloy, lithium tin alloy, lithium zinc alloy, lithium barium alloy, lithium bismuth alloy, lithium calcium alloy, lithium germanium alloy, lithium cesium alloy, lithium gallium alloy, lithium potassium alloy, lithium lead alloy, lithium antimony alloy, lithium boron alloy, lithium silicon alloy, lithium carbon alloy, lithium phosphorus alloy, lithium boron magnesium alloy, and lithium silicon magnesium alloy.

[0087] According to the embodiments of the present application, the mass content of metallic lithium in the above-mentioned lithium alloy is relatively large, so the advantage of metallic lithium in improving the energy density of lithium metal batteries can be fully utilized; metallic lithium reacts with the electrolyte to achieve lithium precipitation and dissolution, providing more active lithium ions for the lithium metal battery, thereby comprehensively improving the cycle life of the lithium metal battery.

[0088] In some optional embodiments, the first metal lithium replenishing layer and the second metal lithium replenishing layer are made of the same material.

[0089] In some optional embodiments, the negative electrode plate satisfies at least one of the following conditions:

[0090] 1) The ratio of the thickness H1 of the carbon-based current collector to the thickness H2 of the first metal lithium replenishing layer and the thickness H3 of the second metal lithium replenishing layer is 1:(0.5-50):(0.5-50), which can be optionally 1:(2-10):(2-10); Optionally, the ratio of the thickness H1 of the carbon-based current collector to the thickness H2 of the first metal lithium replenishing layer and the thickness H3 of the second metal lithium replenishing layer can be 1:0.5:0.5, 1:0 .5:1,1:1:0.5,1:1:1,1:2:2,1:2:1,1:1:2,1:3:3,1:4:4,1:5:5,1:6:6,1:7:7,1:8:8,1:9:9,1:10:10,1:11:11,1:12:12,1:13:13,1:14:14,1:15:15,1:16:16,1:17: 17,1:18:18,1:19:19,1:20:20,1:21:21,1:22:22,1:23:23,1:24:24,1:25:25,1:26:26,1:27:27,1:28:28,1:29:29,1:30:30,1:31:31,1:32:32,1:33:33,1:34:34,1 In some embodiments, the thickness H2 of the first metal lithium-replenishing layer and the thickness H3 of the second metal lithium-replenishing layer are the same as each other.

[0091] 2) The thickness of the carbon-based current collector can be 1 micron to 10 microns; optionally, the thickness of the carbon-based current collector is any value among 1 micron, 2 microns, 3 microns, 4 microns, 5 microns, 6 microns, 7 microns, 8 microns, 9 microns, 10 microns or a range of their compositions.

[0092] 3) The thickness of the first metal lithium replenishing layer and the second metal lithium replenishing layer are 5 microns to 50 microns respectively;

[0093] Optionally, the thickness of the first metal lithium replenishing layer and the second metal lithium replenishing layer can be 5 microns, 6 microns, 7 microns, 8 microns, 9 microns, 10 microns, 11 microns, 12 microns, 13 microns, 14 microns, 15 microns, 16 microns, 17 microns, 18 microns, 19 microns, 20 microns, 21 microns, 22 microns, 23 microns, 24 microns, 25 microns, 26 microns, 27 microns, 28 microns, 29 microns, 30 microns, 31 microns, 32 microns, 33 microns, 34 microns, 35 microns, 36 microns, 37 microns, 38 microns, 39 microns, 40 microns, 41 microns, 42 microns, 43 microns, 44 microns, 45 microns, 46 microns, 47 microns, 48 ​​microns, 49 microns, and 50 microns respectively.

[0094] 4) The thickness of the negative electrode sheet is 11 microns to 110 microns. Optionally, the thickness of the negative electrode sheet can be 11 microns, 12 microns, 13 microns, 14 microns, 15 microns, 16 microns, 17 microns, 18 microns, 19 microns, 20 microns, 21 microns, 22 microns, 23 microns, 24 microns, 25 microns, 26 microns, 27 microns, 28 microns, 29 microns, 30 microns, 31 microns, 32 microns, 33 microns, 34 microns, 35 microns, 36 microns, 37 microns, 38 microns, 39 microns, 40 microns, 41 microns, 42 microns, 43 microns, 44 microns, 45 microns, 46 microns, 47 microns, 48 ​​microns, 49 microns, 50 microns, 51 microns, 52 microns, 53 microns, 54 microns, 55 microns, 56 microns, 57 microns, 58 microns, 59 microns, 60 microns, 61 microns, 62 μm, 63 μm, 64 μm, 65 μm, 66 μm, 67 μm, 68 μm, 69 μm, 70 μm, 71 μm, 72 μm, 73 μm, 74 μm, 75 μm, 76 μm, 77 μm, 78 μm, 79 μm, 80 μm, 81 μm, 82 μm, 83 μm, 84 μm, 85 μm, 86 μm, 87 μm, 88 μm, 89 μm, 90 μm, 91 μm, 92 μm, 93 μm, 94 μm, 95 μm, 96 μm, 97 μm, 98 μm, 99 μm, 100 μm, 101 μm, 102 μm, 103 μm, 104 μm, 105 μm, 106 μm, 107 μm, 108 μm, 109 μm, and 110 μm.

[0095] According to the embodiments of the present application, controlling the ratio of H1, H2 and H3 within the above range is beneficial to controlling the relative thickness of the carbon-based current collector, and on the basis of exerting the role of the carbon-based current collector, further improving the capacity density of the lithium metal battery and reducing its internal resistance.

[0096] In some optional embodiments, the mass fraction of the carbon-based current collector in the negative electrode sheet is 5% to 40%, and optionally 10%-35%.

[0097] Optionally, the mass fraction of the carbon-based current collector in the negative electrode sheet can be any value or its composition range of 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39% and 40%.

[0098] Method for measuring the mass fraction of carbon-based current collector in the negative electrode sheet:

[0099] The negative electrode sheet was tested under safe conditions: ① Take an 18mm small disc of negative electrode sheet and weigh it as weight m1; ② Place the small disc in 100ml of deionized water and allow it to react for 10 minutes; ③ Take it out and dry it, then weigh the remaining carbon-based current collector weight m2; W1 = m2 / m1.

[0100] Electrode assembly

[0101] In a second aspect, an embodiment of the present application provides an electrode assembly comprising the negative electrode sheet of the first aspect.

[0102] The present application has no particular limitation on the type of electrode assembly. For example, the electrode assembly can be used in lithium-ion batteries.

[0103] In some optional embodiments, the electrode assembly includes a positive electrode plate, the positive electrode plate includes a positive electrode active material film layer, the positive electrode active material film layer includes a first electrolyte and a positive electrode active material, and the first electrolyte is dispersed in the positive electrode active material film layer.

[0104] According to the embodiments of the present application, the solid electrolyte has excellent ion conductivity and provides ion conduction channels in the positive electrode sheet, allowing ions (such as lithium ions) in the positive electrode active material to migrate during the charge and discharge process. This enables the lithium ions in the positive electrode active material layer to move quickly and reliably, thereby achieving charge and discharge cycles. This helps to extend the cycle performance of lithium metal batteries.

[0105] The presence of solid electrolyte in the cathode active material film layer not only creates an embedding site for active lithium ions in the electrolyte, but also prevents some harmful substances in the electrolyte from directly contacting the cathode active material, thereby improving the stability of the cathode active material. This helps to extend the life and cycle performance of lithium metal batteries.

[0106] In some optional embodiments, the positive electrode active material film layer includes a first electrolyte in an amount of 1% to 5% by mass based on the total mass of the positive electrode active material film layer. Alternatively, the positive electrode active material film layer includes the first electrolyte in an amount of 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, or 5% by mass, or any range thereof.

[0107] According to the embodiment of the present application, the positive electrode active material film layer includes the first electrolyte with the above-mentioned mass content, which can enable the lithium ions in the positive electrode active material layer to move quickly and reliably, thereby realizing charge and discharge cycles and improving the charge and discharge performance and cycle performance of the lithium metal battery.

[0108] The method for detecting the content of the first electrolyte as a percentage of the content of the positive electrode active material film layer can be controlled by applying the positive electrode coating slurry. During the slurry stirring process, a solid electrolyte is added at a weight ratio of 1% to 5% of the positive electrode material. The method for detecting the content of the first electrolyte as a percentage of the content of the positive electrode active material film layer can be as follows: the negative electrode plate after metal battery cycling is disassembled, and after being thoroughly soaked and rinsed with dimethyl ether (DME) solvent; the plate is then thoroughly digested with aqua regia; after digestion, it is tested using ICP; the test elements contain characteristic elements such as La, Ti, Al, and Ta; the plate is simultaneously tested using XRD, corresponding to the solid electrolyte peak position standard card; and the added substance and amount in the plate are determined by combining the ICP and XRD results.

[0109] In some optional embodiments, the first electrolyte includes Li 0.33 La 0.56 TiO3、Li 1.3 Al 0.3 Ti 1.7 (PO4)3、Li7La3Zr2O 12 , undoped or containing doping elements Li 6.5 La3Zr 1.5 Ta 0.5 O 12 One or more of the following, wherein the doping elements include one or more of silicon, germanium and tin.

[0110] According to the embodiments of the present application, the above-mentioned type of first electrolyte has good chemical corrosion resistance, can resist the corrosion of the electrolyte by solvents and other components in the electrolyte, and stabilize the positive electrode active material film layer; the above-mentioned type of first electrolyte has high ionic conductivity, so that lithium ions can be quickly transmitted in the solid electrolyte, promoting high power output and fast charge and discharge performance of the battery; the above-mentioned type of first electrolyte has a wide electrochemical stability window, has good chemical stability under a wide range of voltages, can withstand higher potentials and polarization, and improve the safety risks of lithium metal batteries.

[0111] [Positive electrode]

[0112] The positive electrode sheet includes a positive electrode current collector and a positive electrode material layer disposed on at least one surface of the positive electrode current collector. This application does not specifically limit the positive electrode current collector, as long as it can achieve the objectives of this application. For example, the positive electrode current collector may comprise aluminum foil, aluminum alloy foil, or a composite current collector. The positive electrode material layer of this application comprises a positive electrode active material.

[0113] In some optional embodiments, the mass fraction W1 of the positive electrode active material in the positive electrode active material film layer is 85% to 99%, and optionally 90% to 97.9%.

[0114] Optionally, the mass fraction W1 of the positive electrode active material in the positive electrode active material film layer can be any value or its composition range among 85.0%, 85.5%, 86.0%, 86.5%, 87.0%, 87.5%, 88.0%, 88.5%, 89.0%, 89.5%, 0.0%, 90.5%, 91.0%, 91.5%, 92.0%, 92.5%, 93.0%, 93.5%, 94.0%, 94.5%, 95.0%, 95.5%, 96.0%, 96.5%, 97.0%, 97.5%, 98.0%, 98.5% and 99.0%.

[0115] The mass fraction W1 of the positive electrode active material in the positive electrode active material film layer can be measured using methods commonly used in the art. As an example, the mass fraction W1 of the positive electrode active material in the positive electrode active material film layer can be calculated using elemental analysis: an elemental analyzer can be used to determine the content of each element in the sample, thereby calculating the mass fraction of the positive electrode active material. This method is suitable for cases where the positive electrode active material contains specific elements (such as lithium, cobalt, nickel, etc.).

[0116] In some optional embodiments, the mass ratio of the positive electrode active material to the first electrolyte in the positive electrode active material film layer is 1:(0.025-5), or 1:(0.06-0.75). Alternatively, the mass ratio of the positive electrode active material to the first electrolyte in the positive electrode active material film layer may be 1:0.05, 1:0.1, 1:0.15, 1:0.2, 1:0.25, 1:0.3, 1:0.35, 1:0.4, 1:0.45, 1:0.5, 1:0.55, 1:0.6, 1:0.65, 1:0.7, 1:0.75, 1:0.8, 1:0.85, 1:0.9, 1:0.95, 1:1, 1:1.05, 1:1.1. 1:1, 1:1.15, 1:1.2, 1:1.25, 1:1.3, 1:1.35, 1:1.4, 1:1.45, 1:1.5, 1:1.55, 1:1.6, 1:1.65, 1:1.7, 1:1.75, 1:1.8, 1:1.85, 1:1.9, 1:1.95, 1:2, 1:2.05, 1:2.1, 1:2.15, 1:2.2, 1:2.25, 1:2.3, 1:2.35, 1:2.4, 1 :2.45, 1:2.5, 1:2.55, 1:2.6, 1:2.65, 1:2.7, 1:2.75, 1:2.8, 1:2.85, 1:2.9, 1:2.95, 1:3, 1:3.05, 1:3.1, 1:3.15, 1:3.2, 1:3.25, 1:3.3, 1:3.35, 1:3.4, 1:3.45, 1:3.5, 1:3.55, 1:3.6, 1:3.65, 1:3.7, 1:3.7 5, 1:3.8, 1:3.85, 1:3.9, 1:3.95, 1:4, 1:4.05, 1:4.1, 1:4.15, 1:4.2, 1:4.25, 1:4.3, 1:4.35, 1:4.4, 1:4.45, 1:4.5, 1:4.55, 1:4.6, 1:4.65, 1:4.7, 1:4.75, 1:4.8, 1:4.85, 1:4.9, 1:4.95, and 1:5.

[0117] According to the embodiments of the present application, by controlling the mass ratio of the positive electrode active material to the first electrolyte in the positive electrode active material film layer within the above range, the first electrolyte is better dispersed around the positive electrode active material. The ionic conductivity of the first electrolyte enables rapid transport of lithium ions in the solid electrolyte, more effectively achieving lithium ion insertion and deinsertion, and improving charge and discharge efficiency. It is also beneficial to contain the positive electrode active material and improve cycle stability.

[0118] In some optional embodiments, the compaction density of the positive electrode active material layer is 3.8 to 4.3 g / cm 3，Optional: 3.9~4.2g / cm 3 .

[0119] According to the embodiment of the present application, the compaction density of the positive electrode active material film layer is within the above range.

[0120] It can improve the contact between particles in the positive electrode active material layer, increase the electron conduction path, thereby reducing resistance loss and improving the battery's conductivity and power output capacity. On the other hand, appropriate compaction density helps optimize the pore structure of the positive electrode active material layer, providing better ion transmission channels, reducing ionic impedance, and thus improving the battery's charge and discharge rate and cycle stability.

[0121] Furthermore, a suitable compaction density of the positive electrode active material layer can improve its structural stability, reduce deformation of the positive electrode active material film layer and particle shedding, thereby improving the mechanical stability and cycle life of the battery. Furthermore, the above-mentioned compaction density of the embodiment of the present application, combined with the dispersion of the first electrolyte in the positive electrode active material film layer, can further improve the stability of the positive electrode active material film layer, which is beneficial to the stability of the lithium metal battery.

[0122] The compaction density of the positive electrode sheet can be tested using common methods in the field. As an example, the compaction density test method of the positive electrode active material film layer is: cut the positive electrode sheet into 18mm 2 Weigh the weight m of the positive electrode sheet, and measure the thickness h of the positive electrode sheet, the type A1 of the positive electrode collector, and the thickness d of the positive electrode collector. The compaction density = (m1-Al) / ((hd)*18mm 2 ).

[0123] In some optional embodiments, the area capacity of the positive electrode active material film layer is 3 to 5 mAh / cm 2 , 3.5~4.8mAh / cm 2 .

[0124] The areal capacity of the positive electrode active material layer refers to the amount of charge or capacity that the positive electrode active material can store per unit area. Its size has a direct impact on the total capacity and performance of the battery. Increasing the positive electrode areal capacity can increase the battery's total capacity, thereby extending its service life. A larger positive electrode area provides more active material, increases the contact area between the battery's positive electrode and electrolyte, promotes ion transport and electron conduction, and improves battery performance indicators such as capacity, power, and cycle life.

[0125] The areal capacity of the cathode active material layer depends on the type, composition, and structure of the cathode active material, as well as the battery design. Common cathode active materials include lithium cobalt oxide (LiCoO2), lithium nickel cobalt manganese oxide (Li(NiCoMn)O2), and lithium iron phosphate (LiFePO4). These materials have different specific capacities, or the amount of charge they can store per unit mass.

[0126] The present application does not particularly limit the type of positive electrode active material, as long as the purpose of the present application can be achieved. For example, the positive electrode active material may include at least one of lithium nickel cobalt manganese oxide (811, 622, 523, 111), lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium-rich manganese-based materials, lithium cobalt oxide, lithium manganese oxide, lithium iron manganese phosphate or lithium titanate. In the present application, the positive electrode active material may also include non-metallic elements, for example, non-metallic elements include at least one of fluorine, phosphorus, boron, chlorine, silicon or sulfur, etc. These elements can further improve the stability of the positive electrode active material.

[0127] In the present application, there is no particular restriction on the thickness of the positive electrode current collector and the positive electrode active material layer, as long as the purpose of the present application can be achieved. For example, the thickness of the positive electrode current collector is 5μm to 20μm, preferably 6μm to 18μm. The thickness of the single-sided positive electrode active material layer is 30μm to 120μm. In the present application, the positive electrode active material layer can be arranged on one surface in the thickness direction of the positive electrode current collector, or on two surfaces in the thickness direction of the positive electrode current collector. It should be noted that the "surface" here can be the entire area of ​​the positive electrode current collector or a partial area of ​​the positive electrode current collector. There is no particular restriction in the present application, as long as the purpose of the present application can be achieved. Optionally, the positive electrode sheet may further include a conductive layer, which is located between the positive electrode current collector and the positive electrode active material layer.

[0128] The above-mentioned conductive agent and binder are not particularly limited, as long as the purpose of the present application can be achieved. In some embodiments, the positive electrode material layer may also optionally include a binder. For example, the binder may include polypropylene alcohol, sodium polyacrylate, potassium polyacrylate, lithium polyacrylate, polyimide, polyimide, polyamide-imide, styrene-butadiene rubber (SBR), polyvinyl alcohol (PVA), polyvinylidene fluoride, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl butyral (PVB), water-based acrylic resin, carboxymethyl cellulose (CMC) or sodium carboxymethyl cellulose (CMC-Na) etc. At least one.

[0129] In some implementations, the weight percentage of the conductive agent in the positive electrode material layer is greater than or equal to 0.5 wt %, which is beneficial for constructing a better electronic conductive network.

[0130] In some implementations, the weight percentage of the binder in the positive electrode material layer is greater than or equal to 0.5 wt %, which is beneficial for obtaining good bonding performance.

[0131] In some embodiments, the positive electrode material layer may further include a conductive agent. For example, the conductive agent may include at least one of conductive carbon black (Super P), carbon nanotubes (CNTs), carbon nanofibers, flake graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, or graphene.

[0132] In some embodiments, the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, such as the positive electrode material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0133] [Isolation film]

[0134] The separator is placed between the positive electrode and the negative electrode to prevent short circuits between the positive and negative electrodes. This application does not limit the type of separator, and any known porous separator with good chemical and mechanical stability can be used.

[0135] The diaphragm of the present application is used to separate the positive electrode and the negative electrode, prevent the internal short circuit of the battery, allow the electrolyte ions to pass freely, and complete the electrochemical charge and discharge process. The diaphragm in the present application is not particularly limited, as long as the purpose of the present application can be achieved. For example, polyethylene (PE), polypropylene (PP)-based polyolefin (PO)-based diaphragms, polyester films (such as polyethylene terephthalate (PET) films), cellulose films, polyimide films (PI), polyamide films (PA), spandex, aramid films, woven films, non-woven films (non-woven fabrics), microporous membranes, composite membranes, diaphragm paper, rolled membranes or spinning membranes, etc. At least one.

[0136] In some embodiments, the material of the isolation membrane can include one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The isolation membrane can be a single-layer film or a multi-layer composite film. When the isolation membrane is a multi-layer composite film, the materials of each layer can be the same or different.

[0137] For example, the diaphragm may include a substrate layer and a surface treatment layer. The substrate layer may be a non-woven fabric, a film or a composite film having a porous structure, and the material of the substrate layer may include at least one of polyethylene, polypropylene, polyethylene terephthalate or polyimide. Optionally, at least one of a polypropylene porous film, a polyethylene porous film, a polypropylene non-woven fabric, a polyethylene non-woven fabric or a polypropylene-polyethylene-polypropylene porous composite film may be used. Optionally, a surface treatment layer is provided on at least one surface of the substrate layer, and the surface treatment layer may be a polymer layer or an inorganic layer, or a layer formed by a mixed polymer and an inorganic material. For example, the inorganic layer includes inorganic particles and a binder, and the inorganic particles are not particularly limited, and may, for example, be selected from at least one of aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide or barium sulfate.

[0138] The binder is not particularly limited, and can be, for example, at least one selected from polyvinylidene fluoride, a copolymer of vinylidene fluoride and hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyvinyl pyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, or polyhexafluoropropylene. The polymer layer includes a polymer, and the polymer material includes at least one selected from polyamide, polyacrylonitrile, an acrylate polymer, polyacrylic acid, polyacrylate, polyvinyl pyrrolidone, polyvinyl ether, polyvinylidene fluoride, or poly(vinylidene fluoride-hexafluoropropylene).

[0139] In some embodiments, the positive electrode sheet, the negative electrode sheet and the separator can be made into an electrode assembly by a winding process or a lamination process. Typically, the electrode assembly includes a positive electrode sheet, a negative electrode sheet, a second electrolyte and a separator. During the charge and discharge process of the battery, active ions are embedded and released back and forth between the positive electrode sheet and the negative electrode sheet. The electrolyte plays the role of conducting ions between the positive electrode sheet and the negative electrode sheet. The separator is arranged between the positive electrode sheet and the negative electrode sheet, mainly to prevent the positive and negative electrodes from short-circuiting, while allowing active lithium ions to pass through.

[0140] lithium metal batteries

[0141] In a third aspect, an embodiment of the present application provides a lithium metal battery, comprising the electrode assembly of the second aspect.

[0142] In some optional embodiments, the lithium metal battery includes a second electrolyte, and the second electrolyte includes the first electrolyte. The second electrolyte may include Li 0.33 La 0.56 TiO3、Li 1.3 Al 0.3 Ti 1.7(PO4)3、Li7La3Zr2O 12 , undoped or containing doping elements Li 6.5 La3Zr 1.5 Ta 0.5 O 12 One or more of the following, wherein the doping elements include one or more of silicon, germanium and tin.

[0143] The second electrolyte is usually located between the positive electrode and the negative electrode in lithium metal batteries, acting as an ion transport medium between the positive and negative electrodes. It not only provides an ion conduction channel to maintain the battery's charge and discharge reactions, but also protects the battery's interface stability and improves safety performance.

[0144] In some embodiments, a lithium metal battery includes an electrolyte. The electrolyte functions as a conductor of active ions between the positive and negative electrodes. This application does not specifically limit the type of electrolyte, and the electrolyte may be selected based on specific needs. For example, the electrolyte may be selected from at least one of a solid electrolyte and a liquid electrolyte (i.e., an electrolyte solution).

[0145] In some embodiments, the second electrolyte may be an electrolyte solution comprising an electrolyte salt and a solvent.

[0146] The type of electrolyte salt is not specifically limited and can be selected according to actual needs. For example, the electrolyte salt includes one or more selected from lithium salts for lithium ion batteries and sodium salts for sodium ion batteries. As an example, the lithium salt includes one or more selected from lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB), lithium dioxalatoborate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorobis(oxalatophosphate) (LiDFOP), lithium tetrafluorooxalatophosphate (LiTFOP). As an example, the sodium salt includes one or more selected from NaPF6, NaClO4, NaBCl4, NaSO3CF3, Na(CH3)C6H4SO3.

[0147] The type of solvent is not specifically limited and can be selected according to actual needs. In some embodiments, as an example, the solvent may include one or more selected from ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), ethyl methyl sulfone (EMS) and diethyl sulfone (ESE).

[0148] In some embodiments, the electrolyte may optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, or additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high-temperature performance, and additives that improve battery low-temperature power performance.

[0149] The lithium metal battery of the present application is not particularly limited and may include any battery containing lithium and undergoing an electrochemical reaction. In some embodiments, the lithium metal battery may include, but is not limited to, a lithium ion lithium metal battery (lithium ion battery), a lithium polymer lithium metal battery, or a lithium ion polymer lithium metal battery.

[0150] The preparation process of a lithium metal battery is well known to those skilled in the art and is not particularly limited in this application. For example, it may include but is not limited to the following steps: stacking the positive electrode, separator, and negative electrode in order, and winding, folding, and other operations as needed to obtain a wound electrode assembly, placing the electrode assembly in a packaging shell, injecting the negative electrode sheet into the packaging shell and sealing it to obtain a lithium metal battery; or stacking the positive electrode, separator, and negative electrode in order, and then fixing the four corners of the entire stacked structure with tape to obtain a stacked electrode assembly, placing the electrode assembly in a packaging shell, injecting the negative electrode sheet into the packaging shell and sealing it to obtain a lithium metal battery. In addition, overcurrent protection elements, guide plates, etc. may also be placed in the packaging shell as needed to prevent pressure rise and overcharging and discharging inside the lithium metal battery.

[0151] In some embodiments, the lithium metal battery may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0152] In some embodiments, the outer packaging of the lithium metal battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. Alternatively, the outer packaging of the lithium metal battery can be a soft shell, such as a pouch-type soft shell. The soft shell can be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0153] The present application has no particular limitation on the shape of the lithium metal battery, which can be cylindrical, square, or any other shape. For example, FIG1 shows a lithium metal battery 5 with a square structure as an example.

[0154] In some embodiments, referring to Figure 2, the outer packaging may include a shell 51 and a cover plate 53. The shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can form an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The negative electrode sheet is immersed in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the lithium metal battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0155] In some embodiments, lithium metal batteries can be assembled into a battery module. The number of lithium metal batteries contained in the battery module can be one or more. The specific number can be selected by those skilled in the art based on the application and capacity of the battery module.

[0156] electronic devices

[0157] In a fourth aspect, an embodiment of the present application provides an electronic device comprising the lithium metal battery of the third aspect.

[0158] The electronic device of the embodiment of the present application includes at least one of the lithium metal battery, battery module, or battery pack provided in the present application. The lithium metal battery, battery module, or battery pack can be used as a power source for the electronic device, and can also be used as an energy storage unit for the electronic device. The electronic device may include a mobile device (such as a mobile phone, a laptop computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc., but is not limited thereto.

[0159] As the electronic device, a lithium metal battery, a battery module or a battery pack can be selected according to its usage requirements.

[0160] Figure 3 shows an example electronic device. This electronic device is a pure electric vehicle, hybrid electric vehicle, or plug-in hybrid electric vehicle. To meet the electronic device's requirements for high power and high energy density of lithium metal batteries, a battery pack or battery module can be used.

[0161] Another example device may be a mobile phone, a tablet computer, a laptop computer, etc. Such a device is usually required to be lightweight and thin, and may use a lithium metal battery as a power source.

[0162] Example

[0163] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0164] Comparative Example 1

[0165] Preparation of negative electrode: Cut 20um thick pure lithium strip into (40mm×60mm) specifications for use.

[0166] Preparation of positive electrode sheet: LiNi 0.8 Mn 0.1 Co 0.1 O2 (NMC811), conductive carbon black (Super P), and polyvinylidene fluoride (PVDF) were mixed in a weight ratio of 96:2:2, and N-methylpyrrolidone (NMP) was added as a solvent to prepare a slurry with a solid content of 0.75, which was then stirred evenly. The slurry was evenly coated on the positive electrode current collector aluminum foil and dried at 90°C to obtain a positive electrode sheet with a surface capacity of 3.75 mAh / cm 2 After coating, cold pressing is completed, and the compaction density is 3.38g / cm 3 , then cut the electrode into specifications of (38mm×58mm) for use.

[0167] Separator film: polyethylene (PE), thickness 9 μm.

[0168] Preparation of the electrolyte: In a dry argon atmosphere, the organic solvents ethylene carbonate (EC) and 1,1,2,2-tetrafluoro-3-(1,1,2,2-tetrafluoroethoxy)propane (TTE) were first mixed at a mass ratio of EC:TTE = 2:3. Fluorinated ethylene carbonate (FEC), fluorodimethyl carbonate (FEMC), and lithium hexafluorophosphate (LiPF6) were then added to the organic solvent, dissolved, and mixed uniformly to obtain an electrolyte with a lithium salt concentration of 1.0 M. The electrolyte contained a molar concentration of 1 M LiPF6 and mass concentrations of 20% FEC, 30% FEMC, 20% EC, and 30% TTE.

[0169] Preparation of a lithium-ion battery: A 15μm-thick polyethylene (PE) separator is used, and the battery is stacked in a Z-shaped pattern. The positive and negative electrodes are placed on either side of the separator, with the separator between them. After stacking, the tabs are welded. After welding, the battery is placed in an aluminum-plastic film. After top and side sealing, liquid injection, and packaging, the resulting lithium metal stack battery is completed.

[0170] Comparative Example 2

[0171] The difference between Comparative Example 2 and Comparative Example 1 is: Preparation of the negative electrode sheet: a 30 μm thick pure lithium strip is cut into a size of (40 mm×60 mm) for use.

[0172] Comparative Example 3

[0173] The difference between Comparative Example 3 and Comparative Example 1 is: Preparation of the negative electrode sheet: a 50 μm thick pure lithium strip is cut into a size of (40 mm×60 mm) for use.

[0174] Example 1

[0175] The difference between Example 1 and Comparative Example 1 is that the negative electrode sheet was prepared by rolling a 10 μm thick pure lithium ribbon, a 10 μm thick graphene sheet (from Wuhan Roudian Technology), and a 10 μm thick pure lithium ribbon together to form a lithium-graphene-lithium three-layer structure. The composite ribbon was cut into 40 mm × 60 mm sheets for later use.

[0176] Example 2-12

[0177] The difference between this embodiment and Example 1 is that the thickness ratio of the lithium-graphene-lithium three-layer structure in the preparation of the negative electrode plate is different.

[0178] Examples 13-19

[0179] The difference between this embodiment and Example 1 is that the materials of the first metal lithium-replenishing layer and the second metal lithium-replenishing layer in the preparation of the negative electrode plate are different from those in Example 1. Among them, the lithium-magnesium alloy, lithium-silver alloy, lithium-indium alloy, lithium-tin alloy, lithium-carbon alloy, lithium-silicon alloy, and lithium-boron alloy in the first metal lithium-replenishing layer and the second metal lithium-replenishing layer are 99% respectively, and the remaining 1% is magnesium, silver, indium, etc. in different embodiments. For example, in Example 13, the first metal lithium-replenishing layer contains 99% metal lithium and 1% metal magnesium by mass. The second metal lithium-replenishing layer contains 99% metal lithium and 1% metal magnesium by mass.

[0180] Example 20

[0181] The difference between this embodiment and Example 1 is that the material of the current collector in the preparation of the negative electrode plate is different.

[0182] Examples 21-33

[0183] The difference between this embodiment and Example 1 is that the first metal lithium replenishing layer and the second metal lithium replenishing layer of the negative electrode plate include a first electrolyte, and the type and content of the first electrolyte are different.

[0184] Comparative Example 4

[0185] The difference between this comparative example and comparative example 1 is that:

[0186] Preparation of negative electrode: Cut the lithium-coated copper strip into 40mm x 60mm dimensions for later use. The lithium layer of the lithium-coated copper strip is 20μm thick, and the copper foil is 5μm thick.

[0187] Preparation of positive electrode

[0188] The positive electrode ternary active materials NMC811, LATP, conductive carbon black (Super P), and polyvinylidene fluoride (PVDF) were mixed in a weight ratio of 94:2:2:2, and N-methylpyrrolidone (NMP) was added as a solvent to prepare a slurry with a solid content of 0.75, and stirred evenly. The slurry was evenly coated on the positive electrode current collector aluminum foil and dried at 90°C to obtain a positive electrode sheet with an area capacity of 4.5 mAh / cm 2 After coating, cold pressing is completed, and the compaction density is 3.55g / cm 3 , then cut the electrode into specifications of (38mm×58mm) for use.

[0189] Comparative Example 5

[0190] This comparative example differs from comparative example 1 in that: Preparation of the negative electrode: The lithium-coated porous copper strip was cut into a size of 40 mm x 60 mm for use. The lithium layer of the lithium-coated porous copper strip had a thickness of 20 μm, the copper foil had a thickness of 5 μm, and an open porosity of 50%.

[0191] Preparation of positive electrode

[0192] The positive electrode ternary active materials NMC811, LATP, conductive carbon black (Super P), and polyvinylidene fluoride (PVDF) were mixed in a weight ratio of 94:2:2:2, and N-methylpyrrolidone (NMP) was added as a solvent to prepare a slurry with a solid content of 0.75, and stirred evenly. The slurry was evenly coated on the positive electrode current collector aluminum foil and dried at 90°C to obtain a positive electrode sheet with an area capacity of 4.5 mAh / cm 2 After coating, cold pressing is completed, and the compaction density is 3.55g / cm 3 , then cut the electrode into specifications of (38mm×58mm) for use.

[0193] Comparative Example 6

[0194] This comparative example differs from comparative example 1 in that: Preparation of the negative electrode: The lithium-coated porous copper strip was cut into a size of 40 mm x 60 mm for use. The lithium layer of the lithium-coated porous copper strip had a thickness of 20 μm, the copper foil had a thickness of 5 μm, and an open porosity of 75%.

[0195] Preparation of positive electrode

[0196] The positive electrode ternary active materials NMC811, LATP, conductive carbon black (Super P), and polyvinylidene fluoride (PVDF) were mixed in a weight ratio of 94:2:2:2, and N-methylpyrrolidone (NMP) was added as a solvent to prepare a slurry with a solid content of 0.75, and stirred evenly. The slurry was evenly coated on the positive electrode current collector aluminum foil and dried at 90°C to obtain a positive electrode sheet with an area capacity of 4.5 mAh / cm 2 After coating, cold pressing is completed, and the compaction density is 3.55g / cm 3 , then cut the electrode into specifications of (38mm×58mm) for use.

[0197] Test section

[0198] The data from the comparative examples and examples demonstrate the effectiveness of this solution using the capacity density and cycling performance of a 2.2Ah laminated battery. Cycling performance of the laminated battery was measured using a 9th-generation Neware battery with a cutoff voltage of 2.8-4.3V and a cycle rate of 0.2 / 0.5C. Specific data are shown in the table below.

[0199] 1) Compaction density test method of positive electrode active material film layer: Cut the positive electrode sheet into 18mm 2 Weigh the weight m of the positive electrode sheet, and measure the thickness h of the positive electrode sheet, the type A1 of the positive electrode collector, and the thickness d of the positive electrode collector. The compaction density = (m1-Al) / ((hd)*18mm 2 )

[0200] 2) Area capacity test of positive electrode active material layer:

[0201] ① Cut the positive electrode material into 18mm small discs and weigh the weight m1;

[0202] ② Assemble the positive electrode material into a button battery for Li;

[0203] ③ Test the gram capacity C1 of the battery cell at 2.8-4.3V at 0.2C;

[0204] ④ Area capacity of positive electrode active material layer = C1 / (m1 / 18mm)

[0205] 3) Energy density test: In an environment of 25°C, the lithium metal battery prepared in the embodiment or comparative example is charged according to the following operating procedure, and then discharged to obtain the discharge capacity of the lithium metal battery. The lithium metal battery is charged to 4.3V at a constant current of 0.7C, and then charged to 0.025C at a constant voltage of 4.3V. After standing for 5 minutes, it is discharged to 3.0V at a constant current of 1C, and the discharge capacity Cap of the lithium metal battery in the first cycle is recorded. After the above-mentioned lithium metal battery is charged to 3.85V at a constant current of 0.7C, it is then charged to 0.025C at a constant voltage of 3.85V, and the weight of the battery cell is weighed to obtain the weight W of the lithium metal battery. Its energy density (ED) = Cap / W, in units of Wh / kg.

[0206] 4) Cycle rate test: The lithium-ion batteries of the examples and comparative examples were tested. The battery was placed in a constant temperature box at 25°C for 120 minutes, then charged to 4.3V at a constant current of 0.7C, then charged to 0.025C at a constant voltage, allowed to stand for 5 minutes, then discharged to 3V at 1C, and the 0.7C discharge capacity C2 was recorded, and allowed to stand for 5 minutes. After being charged to 4.3V at a constant current of 0.7C again, then charged to 0.025C at a constant voltage, allowed to stand for 5 minutes, then discharged to 3V at 1C, and the 1C discharge capacity C3 was recorded. The capacity retention rate is C3 / C2*100%, and the number of cycles is the number of cycles when the capacity retention rate drops to 80%.

[0207] Note: “\” in Table 1 indicates no relevant preparation parameters.

[0208] From the results in Table 1, it can be seen that the comparison between the embodiment and the comparative example shows that using pure lithium ribbon as the negative electrode sheet, or using a carbon current collector instead of a Cu current collector, can greatly improve the GED of the lithium metal battery.

[0209] Comparative Examples 1-3 demonstrate that using pure lithium ribbon as the negative electrode plate can easily lead to tab cracking during cycling, resulting in a drop in battery capacity. Using copper as the current collector reduces the battery's energy density. Examples 2 and 3 demonstrate that increasing the thickness of the lithium ribbon can mitigate tab cracking, but this results in a significant loss in energy density.

[0210] Examples 1-20 show that using a carbon current collector can achieve a higher GED. When the graphene thickness is reduced to 5 μm, the cell GED is greater than 500 Wh / kg.

[0211] Comparison between Examples 5 and 6 shows that the negative electrode active material film layer uses CNTs, which have 10-20% pores and are lighter in weight. Therefore, the battery cell using CNTs as the current collector can achieve a higher GED.

[0212] Examples 7-9 illustrate that using thick electrodes and increasing cathode compaction density can compensate for the ED loss caused by increased thickness of the carbon current collector and pre-supplemented lithium. However, due to the electrolyte infiltration problem caused by the thick electrodes and increased compaction density, the battery cell cycle deteriorates.

[0213] Comparative Examples 5-6 demonstrate that using perforated copper foil as a current collector significantly improves cell ED. However, perforated copper foil affects the current collector's uniformity, which in turn affects the uniformity of lithium deposition and stripping. Furthermore, free electrolyte can penetrate the underlying electrode through the perforations, accelerating the conversion of loose lithium and "dead lithium" and deteriorating cell performance.

[0214] From the results in Table 2, it can be seen that, compared with Example 1, and Example 21 and Example 22, adding the first electrolyte, i.e., pre-replenishing lithium, can improve the cycle performance of the battery cell, but it will also cause GED loss.

[0215] As shown in Table 2, Examples 23-33 demonstrate that by incorporating solid electrolyte particles into the cathode to create a 3D ion-conductive network, ion transport issues caused by electrolyte wetting can be resolved, with a doping level of 2 wt% being optimal. Examples 23-33 demonstrate that varying solid electrolyte doping levels have a certain impact on the cycling performance of the battery cell, primarily due to the volume fraction and ionic conductivity of the solid electrolyte.

[0216] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and within the scope of the technical solution of the present application, embodiments having substantially the same structure as the technical concept and performing the same function are all included in the technical scope of the present application. In addition, without departing from the scope of the subject matter of the present application, other methods of constructing the embodiments by applying various modifications that can be conceived by those skilled in the art and combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A negative electrode sheet for a lithium metal battery, wherein: include: Carbon-based current collector, A first metal lithium replenishing layer and a second metal lithium replenishing layer are respectively arranged on both sides of the carbon-based current collector.

2. The negative electrode sheet according to claim 1, wherein: The carbon-based current collector includes one or more of graphene and carbon nanotubes; and / or, The density of the carbon-based current collector is 1.9 to 2.3 g / cm 3 .

3. The negative electrode sheet according to claim 1 or 2, wherein: The first metal lithium-replenishing layer and the second metal lithium-replenishing layer respectively include one or more of metal lithium and lithium alloy.

4. The negative electrode sheet according to claim 3, wherein: The lithium alloy includes one or more of lithium silver alloy, lithium aluminum alloy, lithium magnesium alloy, lithium gold alloy, lithium sodium alloy, lithium tin alloy, lithium zinc alloy, lithium barium alloy, lithium bismuth alloy, lithium calcium alloy, lithium germanium alloy, lithium cesium alloy, lithium gallium alloy, lithium potassium alloy, lithium lead alloy, lithium antimony alloy, lithium boron alloy, lithium silicon alloy, lithium carbon alloy, lithium phosphorus alloy, lithium boron magnesium alloy, and lithium silicon magnesium alloy.

5. The negative electrode sheet according to any one of claims 1 to 4, wherein: The negative electrode sheet satisfies at least one of the following conditions: 1) The ratio of the thickness H1 of the carbon-based current collector to the thickness H2 of the first metal lithium replenishing layer and the thickness H3 of the second metal lithium replenishing layer is 1:(0.5-50):(0.5-50), which can be 1:(2-10):(2-10); Optionally, the thickness H2 of the first metal lithium replenishing layer and the thickness H3 of the second metal lithium replenishing layer are the same; 2) The thickness of the carbon-based current collector is 1 micron to 10 microns; 3) The thickness of the first metal lithium replenishing layer and the second metal lithium replenishing layer are 5 microns to 50 microns respectively; 4) The thickness of the negative electrode plate is 11 microns to 110 microns.

6. An electrode assembly, wherein: The negative electrode sheet comprises the negative electrode sheet as described in any one of claims 1 to 5.

7. The electrode assembly according to claim 6, wherein: The electrode assembly includes a positive electrode sheet, the positive electrode sheet includes a positive electrode active material film layer, the positive electrode active material film layer includes a first electrolyte and a positive electrode active material, and the first electrolyte is dispersed in the positive electrode active material film layer.

8. The electrode assembly according to claim 7, wherein: Based on the total mass of the positive electrode active material film layer, the positive electrode active material film layer includes a first electrolyte with a mass content of 1% to 5%; and / or, The first electrolyte includes Li 0.33 La 0.56 TiO3、Li 1.3 Al 0.3 Ti 1.7 (PO4)3, Li7La3Zr2O 12 , undoped or containing doping elements Li 6.5 Ln3Z 1.5 Ta 0.5 O 12 One or more of the following, wherein the doping elements include one or more of silicon, germanium and tin.

9. The electrode assembly according to claim 7 or 8, wherein: The mass fraction W1 of the positive electrode active material in the positive electrode active material film layer is 85% to 99%, and can be 90% to 97.9%.

10. The electrode assembly according to claim 7 or 8, wherein: The positive electrode sheet includes a positive electrode current collector, and the ratio of the thickness of the positive electrode current collector to the thickness of the positive electrode active material film layer is 1:(0.025-5), and can be optionally 1:(0.06-0.75); and / or, The compaction density of the positive electrode active material film layer is 3.8 to 4.3 g / cm 3 , can be selected as 3.9~4.2g / cm 3 and / or, The area capacity of the positive electrode active material film layer is 3 to 5 mAh / cm 2 , 3.5~4.8mAh / cm 2 .

11. A lithium metal battery, wherein: An electrode assembly comprising any one of claims 6 to 10.

12. The lithium metal battery according to claim 11, wherein The lithium metal battery includes a second electrolyte, and the second electrolyte includes the first electrolyte.

13. An electronic device, wherein: Including the lithium metal battery as described in claim 11 or 12.

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