A metal lithium battery

Abstract

This invention provides a lithium metal battery using a lithium-carbon composite anode. The lithium-carbon composite anode comprises a bulk material layer and a carbon material layer. The carbon skeleton in the bulk material layer homogenizes the current density, prevents "hot spots" on the surface of the bulk material layer, and suppresses the formation of lithium dendrites. The lithium and / or lithium alloy in the bulk material provides reserve active lithium for the lithium metal battery, significantly extending its cycle life. Furthermore, the carbon material layer on the surface of the bulk material layer is elastically variable, providing space for newly deposited lithium metal while effectively preventing volume changes in the lithium-carbon composite anode. The lithium-carbon composite anode utilizes lightweight carbon materials for a refined multi-layered electrode structure, effectively improving the defects of lithium metal anodes and enabling the lithium metal battery to achieve high energy density while also possessing longer cycle life and higher safety.

Description

Technical Field

[0001] This invention belongs to the field of lithium batteries, and specifically relates to a metallic lithium battery. Background Technology

[0002] With continuous technological advancements, rechargeable lithium-ion batteries have reached their energy density limit (250Wh / kg-300Wh / kg), necessitating the development of higher energy density lithium batteries to meet the demand for longer battery life in electronic devices. To improve battery energy density, researchers have begun using lithium metal, which has a higher specific capacity, as the negative electrode, and have developed lithium metal batteries with even higher energy densities (450 Wh / kg-550 Wh / kg). However, these high-energy-density batteries are still in the research stage or applied in some specialized fields, and have not yet entered people's daily lives on a large scale. Ultimately, this is due to the significant safety hazards inherent in lithium metal batteries. The lithium metal negative electrode used in batteries is prone to lithium dendrite formation. With cycling, lithium dendrites can easily lead to short circuits, resulting in thermal runaway, battery explosions, and other safety issues. Simply using surface protection or lithium metal modification cannot effectively improve the performance of the lithium metal negative electrode or eliminate safety hazards. A comprehensive and meticulous design of the lithium metal negative electrode is required to enable the large-scale application of lithium metal batteries.

[0003] In conclusion, it is indeed necessary to provide a lithium metal battery with high energy density, long cycle life, and high safety, which includes a finely designed negative electrode. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a lithium metal battery with a finely designed lithium-carbon composite anode. This anode comprises a bulk material layer and a carbon material layer, optionally with a surface protective layer on the surface of the carbon material layer. The bulk material layer contains a carbon skeleton, lithium, and / or a lithium alloy. The carbon skeleton helps to homogenize the current density, prevents "hot spots" from appearing on the surface of the bulk material layer, and suppresses the formation of lithium dendrites. The lithium and / or lithium alloy in the bulk material provides reserve active lithium for the lithium metal battery, significantly extending its cycle life. Furthermore, the elastic variable carbon material layer on the surface of the bulk material layer provides space for newly deposited lithium metal while effectively preventing volume changes in the lithium-carbon composite anode. The protective layer on the surface of the carbon material layer effectively reduces side reactions between active lithium and the electrolyte, improving the coulombic efficiency of the lithium metal battery during cycling. The lithium-carbon composite anode uses lightweight carbon materials for a refined multilayer design of the electrode structure, effectively improving the defects of the lithium metal anode, enabling the lithium metal battery to achieve high energy density while also possessing longer cycle life and high safety. In addition, by adjusting the mass of the nucleating agent and its binding energy with lithium in the bulk material layer and carbon material layer, uniform and orderly deposition of lithium metal can be achieved within the lithium-carbon composite anode.

[0005] To achieve the above-mentioned objectives, the present invention provides a lithium metal battery, the battery having one or more battery cells, each battery cell including a lithium-carbon composite negative electrode, a separator, a positive electrode, and a current collector arranged sequentially, and a liquid electrolyte, wherein the lithium-carbon composite negative electrode includes a current collector and a bulk material layer and a carbon material layer arranged sequentially on at least one side of the current collector; or the lithium-carbon composite negative electrode includes a bulk material layer and a carbon material layer arranged on at least one side of the bulk material layer, wherein the bulk material layer contains lithium and / or lithium alloy, a carbon skeleton, and a nucleating agent, and the carbon material layer includes a carbon skeleton and a nucleating agent, and the carbon skeleton and nucleating agent in the bulk material layer and the carbon material layer may be the same or different, the mass a of the nucleating agent in the bulk material layer and the mass b of the nucleating agent in the carbon material layer satisfying: a≥b, or the bonding bond energy Ea between the nucleating agent and lithium in the bulk material layer is higher than the bonding bond energy Eb between the nucleating agent and lithium in the carbon material layer, optionally, the lithium-carbon composite negative electrode further includes a surface protective layer disposed on the surface of the carbon material layer.

[0006] In some embodiments, the carbonaceous framework in the bulk material layer is at least one of micro / nano carbon material framework or composite framework of micro / nano carbon material and metal material.

[0007] The micro / nano carbon material is at least one of the following: multi-walled carbon nanotubes, few-walled carbon nanotubes, single-walled carbon nanotubes, graphene, ordered mesoporous carbon, whisker carbon nanotubes, graphite, carbon black, and carbon fiber.

[0008] The metal material mentioned is a metal that does not react with lithium metal at room temperature or exists in a stable compound with lithium metal at room temperature, such as beryllium, chromium, cesium, iron, hafnium, potassium, manganese, molybdenum, sodium, nickel, titanium, vanadium, zirconium, copper, etc.

[0009] As used in this article, a carbonaceous framework refers to a component with a certain structure that is mainly or entirely formed of carbon materials. The structure of this component remains basically unchanged during electrode preparation and use, hence the name carbonaceous "framework".

[0010] In some embodiments, the carbonaceous skeleton is configured as linear, coiled, network, spherical, ellipsoidal, quasi-spherical, sheet-like, petal-like, spherical-architecture-like, spiny-spherical, pomegranate-like, or cactus-like.

[0011] In some implementations, the carbon material and metal material in the micro / nano carbon material and metal material composite framework can be combined in the form of through-through, embedded, coated, or entangled.

[0012] In some embodiments, the lithium alloy is one or more of the following: lithium-aluminum alloy, lithium-gold alloy, lithium-barium alloy, lithium-bismuth alloy, lithium-calcium alloy, lithium-gallium alloy, lithium-germanium alloy, lithium-mercury alloy, lithium-indium alloy, lithium-platinum alloy, lithium-silicon alloy, lithium-tin alloy, lithium-zinc alloy, lithium-lead alloy, lithium-antimony alloy, lithium-boron alloy, lithium-silver alloy, lithium-cadmium alloy, lithium-cobalt alloy, and lithium-magnesium alloy.

[0013] In some embodiments, the mass ratio of carbon material skeleton: lithium and / or lithium alloy: metal nucleating agent in the bulk lithium-carbon material ranges from (5-85):(15-95):(0.1-5).

[0014] In some embodiments, the carbon skeleton in the carbon material layer is a skeleton formed by at least one micro / nano carbon material selected from multi-walled carbon nanotubes, few-walled carbon nanotubes, single-walled carbon nanotubes, graphene, ordered mesoporous carbon, whisker carbon tubes, graphite, carbon black, and carbon fiber.

[0015] In some embodiments, the mass ratio of carbonaceous skeleton to nucleating agent in the carbon material layer ranges from (85-99):(1-15).

[0016] In some embodiments, the nucleating agent includes at least one of the following micron- or nano-sized particles: silver, aluminum, gold, barium, indium, bismuth, copper, tin, zinc, magnesium, silicon, germanium, lead, gallium, calcium, platinum, antimony, boron, chromium, cobalt, beryllium, cesium, iron, hafnium, potassium, manganese, molybdenum, sodium, nickel, titanium, vanadium, and zirconium. Preferred nucleating agents are micron- or nano-sized particles of silver, aluminum, indium, silicon, zinc, boron, and nickel. Micron- or nano-sized particles refer to particles with a micron or nanometer size.

[0017] In some embodiments, the surface protective layer is an electronic insulating layer, comprising a metal oxide and an adhesive, wherein the metal oxide is at least one selected from aluminum oxide, magnesium oxide, silicon oxide, zinc oxide, tin oxide, and copper oxide; and the adhesive is at least one selected from polyvinyl alcohol, polyvinylidene fluoride, polybutene styrene, polystyrene, polycarboxylic cellulose, cyanoacrylate, cyclodextrin, cyclic ether derivatives, polyurethane, methacrylate, epoxy resin, vinyl acetate polymer, polyimide, organofluoropolymer, organosiloxane, polyethylene glycol, polyethylene, polyvinyl chloride, polypropylene, glycerol, ethylparaben, and their derivatives.

[0018] In some embodiments, the thickness of the bulk material layer is from 3 micrometers to 500 micrometers, with a preferred thickness range of 10 micrometers to 170 micrometers.

[0019] In some embodiments, the thickness of the carbon material layer is from 1 micrometer to 50 micrometers, preferably from 5 micrometers to 25 micrometers.

[0020] In some embodiments, the thickness of the surface protective layer is from 1 micrometer to 50 micrometers, preferably from 3 micrometers to 20 micrometers.

[0021] In some embodiments, the current collector is at least one of copper foil, aluminum foil, stainless steel foil, nickel foil, tin foil, carbon nanotube paper, carbon fiber paper, copper mesh, aluminum mesh, stainless steel mesh, nickel foam, and organic fiber membranes with metal plating (such as copper-plated polyimide fiber membranes, silver-plated polyacrylonitrile membranes, etc.).

[0022] In some embodiments, the liquid electrolyte includes a solvent, a lithium salt, and additives, wherein,

[0023] The solvent includes esters, aliphatic hydrocarbons, ethers, aromatic hydrocarbons, and mixtures thereof; preferably, the solvent is at least one of ethylene carbonate, propylene carbonate, butenyl carbonate, pentenyl carbonate, fluoroethylene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl ethyl carbonate, and dioxolane.

[0024] The lithium salts include at least one of LiPF6 (lithium hexafluorophosphate), LiBF4 (lithium tetrafluoroborate), LiBOB (lithium dioxolaneborate), LiDFOB (lithium difluoroborate oxalate), LiFSI (lithium bis(fluorosulfonyl)imide), LiTFSI (lithium bis(trifluoromethylsulfonyl)imide), LiPF2O2 (lithium difluorophosphate), and LiDTI (lithium 4,5-dicyano-2-trifluoromethylimidazolium).

[0025] The additives include at least one of lithium nitrate, carbonate compounds, phosphate compounds, borate compounds, sulfite compounds, sulfonyl lactone compounds, and fluorinated derivatives of the above compounds.

[0026] In some embodiments, the cathode material includes: organic cathode materials (including polypyrrole and its modified or composite, polyacrylonitrile and its modified or composite, anthraquinone and its modified or composite), and inorganic cathode materials (including lithium iron phosphate, lithium iron manganese phosphate, lithium titanate, lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, sulfur, carbon, and oxygen).

[0027] In some embodiments, the ratio of the capacity Cp of the positive electrode to the capacity Cn of the lithium-carbon composite negative electrode is in the range of 0.35≤Cn / Cp≤7, preferably 1≤Cn / Cp≤3.5.

[0028] In some embodiments, the volume expansion rate of the lithium-carbon composite negative electrode before and after cycling is less than 1%, and the volume expansion rate of the lithium metal battery is less than 5%.

[0029] Compared with the prior art, the present invention has at least one of the following advantages:

[0030] 1. The lithium-carbon composite anode uses lightweight carbon materials to carry out a refined multi-layer design of the electrode structure. The lithium-carbon composite anode includes a bulk material layer and a carbon material layer. Optionally, a surface protective layer is set on the surface of the carbon material layer. These designs effectively improve the defects of the lithium metal anode, enabling the lithium metal battery to achieve high energy density while also having a longer cycle life and high safety.

[0031] 2. The bulk material layer in the lithium-carbon composite anode has a carbon skeleton, lithium and / or lithium alloy. The carbon skeleton can homogenize the current density, avoid the appearance of "hot spots" on the surface of the bulk material layer, and suppress the formation of lithium dendrites. The lithium and / or lithium alloy in the bulk material provides reserve active lithium for the lithium metal battery, which can greatly extend the cycle life of the lithium metal battery.

[0032] 3. The carbon material layer on the surface of the bulk material layer is elastic and variable. While providing space for newly deposited metallic lithium, it can avoid volume changes in the lithium-carbon composite anode and maintain the stability of the anode structure.

[0033] 4. The nucleating agents inside the bulk material layer and the carbon material layer can guide the uniform, rapid and dense deposition of lithium metal inside the negative electrode structure, avoiding damage to the negative electrode structure caused by uneven lithium metal deposition.

[0034] 5. The protective layer on the surface of the carbon material layer can effectively reduce the side reactions between deposited lithium and the electrolyte, and improve the coulombic efficiency of the lithium metal battery during the cycle. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the structure of the first type of battery cell of a lithium metal battery according to the present invention.

[0036] Figure 2 This is a schematic diagram of the structure of a second type of battery cell in a lithium metal battery according to the present invention.

[0037] Figure 3 This is a schematic diagram of the bulk material layer of a lithium metal battery according to the present invention.

[0038] Figure 4 This is a schematic diagram of the carbon material layer of a lithium metal battery according to the present invention.

[0039] Figures 5 to 8 Here are scanning electron microscope (SEM) images of several carbonaceous frameworks used in this invention, wherein Figure 5 The image shows a spherical multi-walled carbon nanotube framework. Figure 6 The image shows the framework of a composite material consisting of multi-walled carbon nanotubes and carbon whisker nanotubes. Figure 7 The image shows the framework of a graphene-multi-walled carbon nanotube composite material. Figure 8 It is a network of multi-walled carbon nanotube framework.

[0040] Figure 9 The figures show the coulombic efficiency curves of the lithium metal batteries in various embodiments of the present invention during cycling.

[0041] Figure 10 The battery discharge capacity curves for Embodiment 1, Comparative Example 2, and Comparative Example 3 of this invention are shown. Detailed Implementation

[0042] The present invention will be further described in detail below with reference to embodiments. These embodiments are only for a better understanding of the principles of the invention and should not be construed as limiting the scope of protection of the invention. Any equivalent changes or substitutions made by those skilled in the art after reading the specification should be covered within the scope of the claims of this application.

[0043] The lithium-carbon composite anode uses lightweight carbon materials to modify metallic lithium, eliminating inherent defects such as lithium dendrite formation, volume expansion, and "dead lithium." The principle behind this invention is to alter the lithium deposition pattern. First, the constructed carbon framework increases the lithium deposition sites, enabling uniform and dense deposition of lithium ions within the lithium-carbon anode. The different bond energies between the nucleating agent and lithium metal provide favorable conditions for selective lithium deposition. The design of the carbon material layer provides space for lithium metal while mitigating volume expansion of the lithium-carbon anode.

[0044] Figure 1 A schematic diagram of the structure of a first type of battery cell for a lithium metal battery is shown. The battery cell includes a lithium-carbon composite negative electrode, a separator, a positive electrode, and a current collector arranged sequentially. The lithium-carbon composite negative electrode includes a current collector and a bulk material layer, a carbon material layer, and a surface protective layer arranged sequentially on the current collector. Figure 2 This shows a schematic diagram of the structure of a second type of battery cell for a lithium metal battery, and... Figure 1 Compared to the structure shown, the only difference is that the lithium-carbon composite anode does not include a current collector, while the bulk material layer can simultaneously act as a current collector. Figure 3 This is a schematic diagram of a bulk material layer. Figure 4 This is a schematic diagram of a carbon material layer. (Example) Figure 3 As shown, the bulk material layer contains lithium and / or lithium alloys as the host phase, and a carbonaceous framework and nucleating agent dispersed in the lithium and / or lithium alloys. The carbonaceous framework is formed by micro / nano carbon materials through entanglement or intercalation or by adhesion via metallic lithium / lithium alloys. Figure 4 As shown, the carbon material layer comprises a carbonaceous framework and a nucleating agent dispersed within the carbonaceous framework. The carbonaceous framework is formed by the intertwining or interlocking of micro- and nano-carbon materials. The lithium-carbon composite anode and its composition / structure are described in detail below.

[0045] Lithium-carbon composite anode

[0046] The lithium-carbon composite anode features a multilayer design, comprising at least a bulk material layer and a carbon material layer, and optionally, a current collector and a surface protective layer. The bulk material layer and the carbon material layer can use the same or different carbonaceous framework and nucleating agent. The mass 'a' of the nucleating agent in the bulk material layer and the mass 'b' of the nucleating agent in the carbon material layer satisfy: a ≥ b, or the bond energy Ea between the nucleating agent and lithium in the bulk material layer is higher than the bond energy Eb between the nucleating agent and lithium in the carbon material layer. This guides the orderly and uniform deposition of metallic lithium within the lithium-carbon composite anode. To ensure physical contact and electronic pathways between the layers of the lithium-carbon composite anode, the same carbonaceous framework is preferably used in both the bulk material layer and the carbon material layer.

[0047] Bulk material layer

[0048] The bulk material layer comprises a carbonaceous framework, lithium and / or lithium alloys, and a nucleating agent. The thickness of the bulk material layer is not specifically limited and can be 500 micrometers, 300 micrometers, 200 micrometers, 50 micrometers, 15 micrometers, or 3 micrometers, with a preferred thickness range of 10 micrometers to 170 micrometers.

[0049] The mass ratio of carbon skeleton to lithium and / or lithium alloy in the bulk material layer is not specifically limited. It can be 85:15, 90:10, 70:30, 50:50, or 15:85. The filling design can be based on the performance of lithium-carbon composite anode.

[0050] The carbon framework can be a pure carbon material framework, including single carbon material frameworks and composite frameworks of multiple carbon materials; it can also be a composite framework of carbon materials and metal materials. The carbon materials are micro / nano carbon materials, including at least one of multi-walled carbon nanotubes, few-walled carbon nanotubes, single-walled carbon nanotubes, graphene, ordered mesoporous carbon, whisker carbon nanotubes, graphite, carbon black, and carbon fibers. Carbon materials can undergo lithophilization treatment to achieve good wettability with lithium atoms. Lithophilization treatment includes surface modification and atomic doping of carbon materials. The carbon materials can be primary particles or aggregates prepared from combinations of primary particles.

[0051] Metallic materials are metals that do not react with lithium at room temperature or exist in stable compounds with lithium at room temperature, such as beryllium, chromium, cesium, iron, hafnium, potassium, manganese, molybdenum, sodium, nickel, titanium, vanadium, zirconium, copper, tantalum, tungsten, rhenium, osmium, niobium, ruthenium, and cobalt. The formation of a carbon-metal composite framework can be achieved using two methods. The first method involves first forming carbon particles and then depositing a metallic layer on the carbon surface using magnetron sputtering, physical vapor deposition, or similar techniques. The second method primarily uses metallic materials that do not react with lithium, which are melted and dispersed within a bulk matrix to form the carbon-metal composite framework.

[0052] The carbon skeleton can be linear, coiled, network-like, spherical, ellipsoidal, quasi-spherical, sheet-like, petal-like, spherical-architecture-like, spiky-spherical, pomegranate-like, cactus-like, or a combination of multiple configurations of carbon material skeletons. Figures 5 to 8 Scanning electron microscope (SEM) images of several carbonaceous frameworks in this invention are shown, wherein Figure 5 The image shows a spherical multi-walled carbon nanotube framework. Figure 6 The image shows the framework of a composite material consisting of multi-walled carbon nanotubes and carbon whisker nanotubes. Figure 7 The image shows the framework of a graphene-multi-walled carbon nanotube composite material. Figure 8 It is a network of multi-walled carbon nanotube framework.

[0053] The lithium in lithium and / or lithium alloys is pure metallic lithium, excluding any alloying elements or having an alloying element mass percentage of less than 0.001%. Lithium alloys refer to materials containing metallic lithium and alloying elements. The combination of lithium and alloying elements can be a compound, a mixture, or a solid solution. The types of alloying elements are not specifically limited, but can include one or more of the following: aluminum, gold, barium, bismuth, calcium, gallium, germanium, mercury, indium, platinum, silicon, tin, zinc, lead, antimony, boron, silver, cadmium, cobalt, magnesium, scandium, strontium, yttrium, rhodium, palladium, iridium, thallium, and arsenic.

[0054] Nucleating agents primarily lower the nucleation barrier of lithium atoms, guiding the uniform and dense deposition of metallic lithium. The shape of the nucleating agent can be spherical, plate-like, or linear. The size of the nucleating agent is not specifically limited; it can be nanoscale or micrometer-scale particles. There are many types of nucleating agents, not limited by the preparation process. Preferred nucleating agents can react with metallic lithium at room temperature or form a solid solution, such as at least one of the following: silver, aluminum, gold, barium, indium, bismuth, copper, tin, zinc, magnesium, silicon, germanium, lead, gallium, calcium, platinum, antimony, boron, chromium, cobalt, beryllium, cesium, iron, hafnium, potassium, manganese, molybdenum, sodium, nickel, titanium, vanadium, and zirconium. Preferred metallic nucleating agents are silver, aluminum, indium, silicon, zinc, boron, and nickel.

[0055] There are many ways in which nucleating agents can bond with carbonaceous frameworks. This can involve the carbon material physically coating the nucleating agent, or the nucleating agent coating or embedding itself on the surface of the carbon material. Bonding can occur through van der Waals forces and chemical bonds. Lithium and / or lithium alloys fill the gaps in the carbonaceous framework.

[0056] carbon material layer

[0057] The carbon material layer includes a carbon skeleton and a nucleating agent. The mass ratio of the carbon skeleton to the nucleating agent is not specifically limited and can be 90:10, 80:20, 95:5, or 70:30. The mass of the nucleating agent in the carbon material layer is less than or equal to the mass of the nucleating agent in the bulk material layer, or the bonding energy between the nucleating agent in the carbon material layer and the lithium atom is lower than the bonding energy between the nucleating agent in the bulk material layer and the lithium atom.

[0058] The carbon framework in the carbon material layer can be one or more of the following: multi-walled carbon nanotubes, few-walled carbon nanotubes, single-walled carbon nanotubes, graphene, ordered mesoporous carbon, whisker carbon nanotubes, graphite, carbon black, and carbon fiber. The carbon material can undergo lithophilization treatment, exhibiting excellent wettability with lithium atoms. Lithophilization treatment includes surface modification and atomic doping of the carbon material. There are no special requirements for the configuration of the carbon material. The thickness of the carbon material layer is not specifically limited; it can be 5 micrometers, 10 micrometers, or 25 micrometers, and can be designed and processed according to actual needs.

[0059] Nucleating agents are distributed inside the carbon material layer and can bind to the carbon skeleton in many ways. They can be physically coated with carbon materials, or the nucleating agents can be coated on or embedded on the surface of carbon materials. They can be bound by van der Waals forces and chemical bonds.

[0060] The carbon material layer may also contain other components such as a binder. The binder may be at least one of the following: polyvinyl alcohol, polyvinylidene fluoride, polybutene-styrene, polystyrene, polycarboxymethyl cellulose, cyanoacrylate, cyclodextrin, cyclic ether derivatives, polyurethane, methacrylate, epoxy resin, vinyl acetate polymer, polyimide, organofluoropolymer, organosiloxane, polyethylene glycol, polyethylene, polyvinyl chloride, polypropylene, glycerol, ethylparaben, and their derivatives.

[0061] There are two methods for preparing carbon material layers. The first method involves generating carbon nanotubes that are blown out of the reactor and electrostatically collected on a roller. Alcohol (e.g., an alcohol dispersion containing a nucleating agent) is then sprayed onto the rotating collection roller, and collection continues until the carbon material layer reaches a certain thickness. After drying, the carbon material layer is obtained. This method produces a carbon material layer containing only carbon material and a nucleating agent. The second method involves uniformly mixing carbon material, a binder, and a solvent, then coating the mixture onto a substrate. After drying and evaporating the solvent, a carbon material layer is formed. This method contains carbon material, a nucleating agent, and a binder.

[0062] Surface protective layer

[0063] The surface protective layer is an electronic insulating layer, composed of oxides and binders. The oxides are at least one selected from aluminum oxide, magnesium oxide, silicon oxide, zinc oxide, tin oxide, and copper oxide. The binder is one selected from polyvinyl alcohol, polyvinylidene fluoride, polybutene-styrene, polystyrene, polycarboxylic cellulose, cyanoacrylate, cyclodextrin, cyclic ether derivatives, polyurethane, methacrylate, epoxy resin, vinyl acetate polymer, polyimide, organofluoropolymer, organosiloxane, polyethylene glycol, polyethylene, polyvinyl chloride, polypropylene, glycerol, ethylparaben, and their derivatives. The thickness of the surface protective layer is not specifically limited and can be 3 micrometers, 7 micrometers, or 20 micrometers, and can be designed according to requirements.

[0064] current collector

[0065] The current collector primarily provides a good electron path. There are no special requirements for the material of the current collector; its thickness can be 2 micrometers, 15 micrometers, or 55 micrometers, without specific limitations. The current collector can be made of foil, mesh, or irregularly shaped materials, without specific limitations. The current collector can be one or more of the following: copper foil, aluminum foil, stainless steel foil, nickel foil, tin foil, carbon nanotube paper, carbon fiber paper, copper mesh, aluminum mesh, stainless steel mesh, nickel foam, or organic fiber films with metal-plated surfaces (such as copper-plated polyimide fiber films, silver-plated polyacrylonitrile films, etc.).

[0066] Example

[0067] Positive electrode preparation

[0068] LiNi 0.8 Co 0.1 Mn 0.1 Using O2 as the positive electrode active material, polyvinylidene fluoride (PVDF) as a binder, and conductive carbon (SP) as a conductive agent, a positive electrode slurry was prepared by dissolving PVDF in N-methylpyrrolidone (NMP) at a mass ratio of 96:2:2 (PVDF:SP). The slurry was then uniformly coated onto aluminum foil and dried to obtain a positive electrode sheet with a thickness of 120 micrometers. The resulting positive electrode was cut to a size of 4.1 cm × 5.6 cm, with an on-area capacity of 3 mAh / cm². 2 .

[0069] Preparation of lithium-carbon composite anode

[0070] Step 1: Carbon nanotubes (GTC-304 from Shandong Dazhan Materials Co., Ltd.), serving as the carbonaceous framework material, are uniformly dispersed in molten lithium containing a silver nucleating agent (secondary particle D50 of 10 micrometers). The mass ratio of carbonaceous framework:silver nucleating agent:lithium is 3:1:17. After uniform dispersion, the melt is cast and rolled into a bulk material film with a thickness of 50 micrometers, or the film is rolled into a single unit with a current collector on both sides.

[0071] It is particularly important to emphasize that the carbon material framework used in this step can be finely designed by changing the configuration of the carbon material to give the bulk material layer different structural strengths and electrochemical properties. Figures 5 to 8 These are carbon materials with different configurations prepared in the experiment. Figure 5 The particles were prepared by spray granulation of carbon nanotube materials. Figure 6 It was prepared by ball milling carbon nanotubes and carbon whisker tubes; Figure 7 It is prepared by combining carbon nanotubes and graphene materials; Figure 8 It is prepared by dispersing carbon nanotube materials. The carbon material used in the examples is... Figure 5 The materials shown.

[0072] Step 2: Single-walled carbon nanotubes (Miaosika (Shenzhen) Technology Co., Ltd.) and metallic silver particles (Suzhou Nofi Nanotechnology Co., Ltd., particle size 80nm) are uniformly dispersed in N-methylpyrrolidone containing polyvinylidene fluoride, with a mass ratio of single-walled carbon nanotubes: metallic silver particles: polyvinylidene fluoride of 10:2:5. The above-dispersed slurry is uniformly coated on the surface of the bulk material layer to a thickness of 100 micrometers. After drying, it is rolled to obtain a film with a carbon material layer on the surface of the bulk material layer.

[0073] Step 3: α-Alumina (Aladdin) is uniformly dispersed in N-methylpyrrolidone containing polyvinylidene fluoride (PVDF), with a mass ratio of α-alumina to PVDF of 2:1. The dispersed slurry is then uniformly coated onto the surface of the membrane to a thickness of 50 micrometers. After drying, it is rolled flat to obtain a lithium-carbon composite anode membrane. The membrane is then punched to obtain a lithium-carbon composite anode with dimensions of 4.3 cm × 5.8 cm.

[0074] Preparation of lithium metal anodes

[0075] Commercially available 50-micron lithium metal strips were punched to prepare lithium metal anodes with dimensions of 4.3cm × 5.8cm.

[0076] Example 1

[0077] Using the above-mentioned positive electrode, lithium-carbon composite negative electrode, polyethylene separator and electrolyte (lithium salt LiPF6 concentration of 1mol / L, solvent ratio of EC:DME:DEC=1:1:1) to assemble a lithium metal battery, the Cn / Cp of the battery is 3.

[0078] Example 2

[0079] Other conditions remained the same as in Example 1, except that α-alumina was not coated during the preparation of the lithium-carbon composite anode.

[0080] Example 3

[0081] Other conditions remained the same as in Example 1, except that no carbon material layer was applied during the preparation of the lithium-carbon composite anode.

[0082] Example 4

[0083] Other conditions remained the same as in Example 1, except that no carbon material layer was applied and no α-alumina was coated during the preparation of the lithium-carbon composite anode.

[0084] Example 5

[0085] All other conditions remained the same as in Example 1, except that α-alumina was replaced with fumed nano-silicon oxide during the preparation of the lithium-carbon composite anode.

[0086] Example 6

[0087] All other conditions remained the same as in Example 1, except that single-walled carbon nanotubes were changed to multi-walled carbon nanotubes during the preparation of the lithium-carbon composite anode.

[0088] Example 7

[0089] All other conditions remained the same as in Example 1, except that silver particles were not used in step two of the preparation of the lithium-carbon composite anode.

[0090] Example 8

[0091] All other conditions remain the same as in Example 1, except that the thickness of the positive electrode coating is changed and Cn / Cp is adjusted to 5.

[0092] Example 9

[0093] All other conditions remained the same as in Example 1, except that the thickness of the bulk material layer film was changed, and the Cn / Cp ratio was adjusted to 0.8.

[0094] Comparative Example 1

[0095] A lithium metal battery is assembled using a positive electrode, a lithium metal negative electrode, a polyethylene separator, and an electrolyte (lithium salt LiPF6 concentration of 1 mol / L, solvent ratio of EC:DME:DEC=1:1:1).

[0096] Comparative Example 2

[0097] Other conditions remain the same as in Example 1, except that the mass of the nucleating agent in the bulk material layer is reduced so that the mass ratio of carbonaceous framework: metallic silver nucleating agent: lithium is 10:1:56.

[0098] Comparative Example 3

[0099] Other conditions remained the same as in Example 1, with zinc, which has a low binding bond energy with lithium, used as a nucleating agent in the bulk material layer.

[0100] The assembled lithium metal battery was formed and subjected to charge-discharge tests. Battery charge-discharge efficiency data were collected and plotted. The battery charge-discharge process was as follows: rest for 5 minutes, charge to 4.3V at 0.5C, rest for 5 minutes, discharge to 2.85V at 0.5C, and repeat the above process until the end of the cycle.

[0101] Figure 9 The figures show the charge-discharge efficiency curves of the lithium metal batteries in various embodiments of the present invention during cycling (data with charge-discharge efficiencies below 95% are discarded). As can be seen from the figures, during cycling, the lithium metal battery assembled in Example 1 achieved a charge-discharge efficiency of 95% after 158 cycles, while the battery assembled in Comparative Example 1 had a charge-discharge efficiency below 95% after 62 cycles. The cycle life of the lithium metal battery of the present invention is 2.5 times that of a conventional lithium metal battery. The figures also show that without coating with α-alumina and without implementing a carbon material layer (Examples 2 to 4 and Example 7), the performance of the battery of the present invention is poor, but it still has higher charge-discharge efficiency and cycle life than the conventional lithium metal battery in Comparative Example 1. Changing the type of coating material and the type of carbon material will affect the performance of the lithium metal battery of the present invention, but compared to the conventional lithium metal battery in Comparative Example 1, the lithium metal battery of the present invention still has a significant advantage. Adjusting Cn / Cp affects battery cycle efficiency. Overall, Cn / Cp values ​​of 5 and 0.8 are not conducive to improving battery charge and discharge efficiency. There is an optimal value for Cn / Cp (preferred range 1≤Cn / Cp≤3.5).

[0102] High-rate charge-discharge tests were conducted on batteries from Example 1, Comparative Example 2, and Comparative Example 3. The test procedure was as follows: after resting for 5 minutes, the batteries were charged to 4.35V at a 3C current; after resting for 5 minutes, the batteries were discharged to 2.85V at a 3C current; this process was repeated until the discharge was complete. The battery discharge capacity data were then statistically analyzed and plotted. Figure 10As shown in the figure, the discharge capacity of the battery in Example 1 is stable. When the battery is cycled to 140 cycles, the discharge capacity does not show a significant decay trend. However, the batteries in Comparative Example 2 and Comparative Example 3 begin to show a capacity decay trend after 72 and 44 cycles, respectively. The battery capacity decay is significantly affected by the quality and type of nucleating agent in the phase material layer. High nucleating agent content and nucleating agent types with high lithium binding bond energy are beneficial to extending the battery cycle life.

[0103] Based on the disclosure and teachings of the foregoing specification, those skilled in the art can make appropriate changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some modifications and changes to the present invention should also fall within the protection scope of the claims of the present invention. Furthermore, although some specific terms are used in this specification, these terms are only for convenience of explanation and do not constitute any limitation on the present invention.

Claims

1. A metal lithium battery, characterized by, The battery has one or more battery cells, each battery cell including a lithium-carbon composite negative electrode, a separator, a positive electrode, and a current collector arranged sequentially, as well as a liquid electrolyte. The lithium-carbon composite anode includes a current collector and a bulk material layer and a carbon material layer sequentially disposed on at least one side of the current collector; or The lithium-carbon composite anode includes a bulk material layer and a carbon material layer disposed on at least one side of the bulk material layer. The bulk material layer comprises lithium and / or lithium alloys, a carbonaceous framework, and a nucleating agent; the carbon material layer comprises a carbonaceous framework and a nucleating agent. The carbonaceous framework and nucleating agent in the bulk material layer and the carbon material layer can be the same or different. The mass 'a' of the nucleating agent in the bulk material layer and the mass 'b' of the nucleating agent in the carbon material layer satisfy: a ≥ b, or the bonding bond energy Ea between the nucleating agent and lithium in the bulk material layer is higher than the bonding bond energy Eb between the nucleating agent and lithium in the carbon material layer. Optionally, the lithium-carbon composite anode further includes a surface protective layer disposed on the surface of the carbon material layer.

2. The lithium metal battery of claim 1, wherein, The carbonaceous framework in the bulk material layer is at least one of micro / nano carbon material framework or composite framework of micro / nano carbon material and metal material; the carbon framework in the carbon material layer is a micro / nano carbon material framework. The micro / nano carbon material is at least one of the following: multi-walled carbon nanotubes, few-walled carbon nanotubes, single-walled carbon nanotubes, graphene, ordered mesoporous carbon, whisker carbon nanotubes, graphite, carbon black, and carbon fiber. The metal material mentioned is a metal that does not react with lithium metal at room temperature or exists in a stable compound with lithium metal at room temperature, including: beryllium, chromium, cesium, iron, hafnium, potassium, manganese, molybdenum, sodium, nickel, titanium, vanadium, zirconium, and copper; The composite framework incorporates micro / nano carbon materials and metallic materials in various ways, including through-penetration, embedding, coating, and entanglement. The carbon material skeleton has the following configurations: linear, coiled, net-like, spherical, ellipsoidal, quasi-spherical, sheet-like, petal-like, spherical-segmented, spiky-spherical, pomegranate-like, and cactus-like.

3. The lithium metal battery of claim 1, wherein, The lithium alloy is one or more of the following: lithium-aluminum alloy, lithium-gold alloy, lithium-barium alloy, lithium-bismuth alloy, lithium-calcium alloy, lithium-gallium alloy, lithium-germanium alloy, lithium-mercury alloy, lithium-indium alloy, lithium-platinum alloy, lithium-silicon alloy, lithium-tin alloy, lithium-zinc alloy, lithium-lead alloy, lithium-antimony alloy, lithium-boron alloy, lithium-silver alloy, lithium-cadmium alloy, lithium-cobalt alloy, and lithium-magnesium alloy.

4. The lithium metal battery of claim 1, wherein, The mass ratio of carbonaceous framework: lithium and / or lithium alloy: nucleating agent in the bulk material layer ranges from (5-85):(15-95):(0.1-5); and / or The mass ratio of carbon skeleton to nucleating agent in the carbon material layer is (85-99):(1-15).

5. The lithium metal battery of claim 1, wherein, The nucleating agent includes at least one of the following: silver, aluminum, gold, barium, indium, bismuth, copper, tin, zinc, magnesium, silicon, germanium, lead, gallium, calcium, platinum, antimony, boron, chromium, cobalt, beryllium, cesium, iron, hafnium, potassium, manganese, molybdenum, sodium, nickel, titanium, vanadium, and zirconium micro / nano particles. The preferred metal nucleating agent is silver, aluminum, indium, silicon, zinc, boron, or nickel micro / nano particles.

6. The lithium metal battery of claim 1, wherein, The surface protective layer is an electronic insulating layer, comprising a metal oxide and a binder. The metal oxide is at least one of aluminum oxide, magnesium oxide, silicon oxide, zinc oxide, tin oxide, and copper oxide. The binder is at least one of polyvinyl alcohol, polyvinylidene fluoride, polybutene-styrene, polystyrene, polycarboxylic cellulose, cyanoacrylate, cyclodextrin, cyclic ether derivatives, polyurethane, methacrylate, epoxy resin, vinyl acetate polymer, polyimide, organofluoropolymer, organosiloxane, polyethylene glycol, polyethylene, polyvinyl chloride, polypropylene, glycerol, ethylparaben, and their derivatives.

7. The lithium metal battery of claim 1, wherein, The current collector is at least one of copper foil, aluminum foil, stainless steel foil, nickel foil, tin foil, carbon nanotube paper, carbon fiber paper, copper mesh, aluminum mesh, stainless steel mesh, nickel foam, and organic fiber membranes with metal plating (including polyimide fiber membranes with copper plating and polyacrylonitrile membranes with silver plating).

8. The lithium metal battery of claim 1, wherein, The liquid electrolyte comprises a solvent, a lithium salt, and additives, wherein, The solvent includes esters, aliphatic hydrocarbons, ethers, aromatic hydrocarbons, and mixtures thereof; preferably, the solvent is at least one of ethylene carbonate, propylene carbonate, butenyl carbonate, pentenyl carbonate, fluoroethylene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl ethyl carbonate, and dioxolane. The lithium salts mentioned include at least one of LiPF6 (lithium hexafluorophosphate), LiBF4 (lithium tetrafluoroborate), LiBOB (lithium dioxolaneborate), LiDFOB (lithium difluoroborate oxalate), LiFSI (lithium bis(fluorosulfonyl)imide), LiTFSI (lithium bis(trifluoromethylsulfonyl)imide), LiPF2O2 (lithium difluorophosphate), and LiDTI (lithium 4,5-dicyano-2-trifluoromethylimidazolium). The additives include at least one of lithium nitrate, carbonate compounds, phosphate compounds, borate compounds, sulfite compounds, sulfonyl lactone compounds, and fluorinated derivatives of the above compounds.

9. The lithium metal battery of claim 1, wherein, The cathode materials include: organic cathode materials (including polypyrrole and its modified or composite materials, polyacrylonitrile and its modified or composite materials, anthraquinone and its modified or composite materials), and inorganic cathode materials (including lithium iron phosphate, lithium iron manganese phosphate, lithium titanate, lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, sulfur, and oxygen).

10. The lithium metal battery of claim 1, wherein, The ratio of the capacity Cp of the positive electrode to the capacity Cn of the lithium-carbon composite negative electrode is in the range of: 0.35 ≤ Cn / Cp ≤ 7; and / or The volume expansion rate of the lithium-carbon composite negative electrode before and after cycling is less than 1%, and the volume expansion rate of the lithium metal battery is less than 5%.

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