Composite material and preparation method thereof, negative-electrode-free coating slurry, negative-electrode-free current collector and lithium ion battery

Abstract

The invention relates to the technical field of lithium ion batteries, and discloses a composite material, a preparation method of the composite material, negative-electrode-free coating slurry, a negative-electrode-free current collector and a lithium ion battery. The composite material comprises lithium aluminum oxide, aluminum oxide, carbon nanowires, a carbon coating layer and a porous structure which is self-assembled by a conductive pore-forming agent, carbon nanowires are loaded in the porous structure, and lithium aluminum oxide and aluminum oxide are loaded on the surface of the porous structure; the carbon coating layer is coated on at least part of the surfaces of the lithium aluminum oxide and the aluminum oxide. The composite material is integrally of a porous structure, has irregular secondary particle characteristics, can improve the metal lithium deposition uniformity and conductivity of a negative-electrode-free current collector, can further form a negative-electrode-free coating with uniformly distributed pores with an electrolyte lithium salt and a polymer film-forming agent, prevents excessive SEI films from being formed on the surface in the lithium deposition process, and improves the service life of the negative-electrode-free current collector. The surface stability of lithium metal is facilitated, and the first effect of the non-cathode lithium ion battery can be remarkably improved.

Description

Technical Field

[0001] This application relates to the field of lithium-ion battery technology, and in particular to a composite material and its preparation method, as well as a negative electrode-free coating slurry, a negative electrode-free current collector, and a lithium-ion battery. Background Technology

[0002] Current development of lithium-ion batteries is primarily focused on increasing energy density. The energy density of a lithium-ion battery is mainly determined by the specific capacity of the positive and negative electrode materials. Currently, graphite is the primary negative electrode material, with a theoretical specific capacity of 372 mAh / g. When combined with high-nickel positive electrode materials, the overall energy density limit is around 280 Wh / kg. Batteries requiring higher energy densities necessitate the use of new materials with even higher specific capacity for the negative electrode. At room temperature, the lithium-rich product Li-Si produced by the alloying of silicon and lithium in the negative electrode... 3.75 The silicon phase boasts a specific capacity as high as 3572 mAh / g. To prevent material failure caused by excessive volume expansion of silicon-based materials, it is generally used in combination with graphite. Currently, practical silicon-graphite hybrid composite materials have a total specific capacity of up to approximately 650 mAh / g, supporting a total energy density of around 350 Wh / kg. To further improve battery energy density, lithium metal has been reintroduced into lithium-ion battery anode materials, paired with high-nickel cathodes, achieving a total energy density exceeding 400 Wh / kg. With increasing research and development of solid-state batteries, lithium metal anodes are also undergoing extensive practical exploration.

[0003] There are two main applications of lithium metal anodes. One is to mix them with graphite, which can improve the overall stability of the anode. The higher the proportion of lithium metal in the mixture, the higher the specific capacity of the overall material, but the stability decreases accordingly. This application method offers limited improvement in the overall energy density. The other method is to directly use lithium metal as the anode, which can significantly improve the energy density of the entire battery. However, lithium metal is highly reactive, and directly using lithium metal places very high demands on the battery manufacturing process environment and poses safety hazards. Using anode-free coating technology to fabricate electrodeless lithium metal batteries (IFLMBs) is one way to solve this problem. Summary of the Invention

[0004] In view of this, the purpose of this application is to provide a composite material and a method for preparing the same, so that the composite material can significantly improve the first-stage efficiency of lithium-ion batteries when used without a negative electrode coating.

[0005] Another objective of this application is to provide a negative electrode-free coating slurry, a negative electrode-free current collector, and a lithium-ion battery based on the composite material described in this application.

[0006] To achieve all or part of the above objectives, as a first aspect of this application, a composite material is provided, comprising lithium alumina, alumina, carbon nanowires, a carbon coating layer, and a porous structure self-assembled by a conductive pore-forming agent; the porous structure is loaded with carbon nanowires and has lithium alumina and alumina loaded on its surface; the carbon coating layer coats at least a portion of the surfaces of the lithium alumina and alumina.

[0007] Optionally, the mass ratio of the conductive pore-forming agent, lithium alumina, alumina, and carbon nanowires is 2~8:20~90:30~80:3~10.

[0008] Optionally, the conductive pore-forming agent includes one or more of graphene, carbon nanotubes, one-dimensional silver nanowires, one-dimensional copper nanowires, one-dimensional zinc oxide nanowires, one-dimensional copper oxide nanowires, one-dimensional titanium dioxide nanowires, one-dimensional boron nitride nanowires, and one-dimensional silicon dioxide nanowires.

[0009] As a second aspect of this application, a method for preparing the composite material described in this application is provided, comprising: Aluminum source, conductive pore-forming agent, lithium source, carbon source, dispersing solvent and binder are evenly dispersed, coated and dried to obtain secondary particles self-assembled by the pore-forming agent; The secondary particles are calcined in a protective gas atmosphere to obtain the composite material.

[0010] Optionally, the aluminum source includes one or more of boehmite, nano-alumina, and aluminum hydroxide; The conductive pore-forming agent includes one or more of the following: graphene, carbon nanotubes, one-dimensional silver nanowires, one-dimensional copper nanowires, one-dimensional zinc oxide nanowires, one-dimensional copper oxide nanowires, one-dimensional titanium dioxide nanowires, one-dimensional boron nitride nanowires, and one-dimensional silicon dioxide nanowires. The lithium source includes one or more of lithium oxalate, lithium acetate, and lithium hydroxide monohydrate. The carbon source includes one or more of the following: citric acid, malic acid, glucose, sucrose, lactic acid, ascorbic acid, fruit acid, sorbic acid, tartaric acid, polyethylene, polypropylene, polystyrene, phenolic resin, epoxy resin, and asphalt.

[0011] Optionally, the calcination treatment includes calcination at 400~1000℃ for 2~10 hours.

[0012] As a third aspect of this application, a negative electrode-free coating slurry is provided, comprising the composite material described in this application or the composite material prepared by the preparation method described in this application, as well as an electrolyte lithium salt, a polymer film-forming agent, and an organic solvent.

[0013] Optionally, the mass ratio of the composite material, the electrolyte lithium salt, and the polymer film-forming agent is 80~90:1~5:5~10.

[0014] As a fourth aspect of this application, a negative electrode-free current collector is provided, comprising a current collector and a coating disposed on at least one side surface of the current collector, including the composite material described in this application, or the composite material prepared by the preparation method described in this application, or the cured negative electrode-free coating slurry described in this application.

[0015] As a fifth aspect of this application, a lithium-ion battery is provided, including a positive electrode, a negative electrode-free current collector as described in this application, a separator, and an electrolyte.

[0016] The composite material of this application has a porous structure as a whole, mainly formed by the self-assembly of conductive nanoscale one-dimensional or two-dimensional pore-forming agents, carbon nanowires, nano-alumina, and nano-alumina lithium. The porous structure exhibits irregular secondary particle characteristics, which can improve the uniformity and conductivity of lithium metal deposition without a negative electrode current collector. Furthermore, it can form a uniformly pore-distributed coating without a negative electrode with electrolyte lithium salt and polymer film-forming agents, preventing the formation of too much SEI film on the surface during lithium deposition, which is beneficial to the surface stability of lithium metal and can significantly improve the first efficiency of the negative electrode-free lithium-ion battery. Attached Figure Description

[0017] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments of this application and their descriptions are used to explain this application and do not constitute an undue limitation of this application. Figure 1 The image shown is a planar SEM image of the powder after coating and drying (left image) and after calcination (right image) in Example 1; Figure 2 The image shown is a cross-sectional SEM image of the powder after coating and drying (left image) and after calcination (right image) in Example 1; Figure 3 The XRD pattern of the composite powder prepared in Example 1 is shown; the symbols represent the following substances: ●LiAlO2 (COD9009880), ◆Graphite (COD9012230), ▲Alumina (COD1101168), ■Lithium alumina intermediate. Detailed Implementation

[0018] This application discloses a composite material and its preparation method, as well as a negative electrode-free coating slurry, a negative electrode-free current collector, and a lithium-ion battery. Those skilled in the art can refer to the content of this application and appropriately modify the process parameters to achieve the desired results. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included in this application. The products and processes described in this application have been described through preferred embodiments. Those skilled in the art can obviously modify or appropriately change and combine the products and processes described herein without departing from the content, spirit, and scope of this application to realize and apply the technology of this application. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0019] It should be noted that, in this document, relational terms such as "first" and "second," "step 1" and "step 2," and "(1)" and "(2)" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element. Moreover, the embodiments and features described in this application can be combined with each other without conflict.

[0020] In a battery without a negative electrode coating, the negative electrode active material is directly derived from lithium ions migrating from the positive electrode during charging, resulting in lithium deposition. To improve the uniformity of deposition, the negative electrode current collector typically requires lithiophilic modification, and the modifying material must also possess good electrolyte wettability, such as metal oxides. However, metal oxides have poor conductivity, necessitating the introduction of additives with good conductivity. After lithium metal deposition, the surface exhibits high activity and forms an SEI film. Without special protection and the addition of functional additives, the SEI film will continue to form, leading to capacity loss and decreased battery stability. A conventional method to improve the surface stability after lithium deposition is to pre-add film-forming additives to the electrolyte. However, since lithium deposition occurs repeatedly during charging and discharging, film-forming additives cannot guarantee the subsequent stability of the lithium metal surface. Furthermore, the lithium deposition process is also a volume expansion process; the battery interior must reserve sufficient space for the volume changes required for lithium deposition. Otherwise, the battery may expand, potentially leading to lithium dendrite formation and posing safety hazards.

[0021] To address the various shortcomings of the aforementioned electrodeless lithium metal batteries, the first aspect of this application provides a composite material comprising lithium alumina, alumina, carbon nanowires, a carbon coating layer, and a porous structure self-assembled by a conductive pore-forming agent; the porous structure contains carbon nanowires, and its surface is loaded with lithium alumina and alumina; the carbon coating layer covers at least a portion of the surfaces of the lithium alumina and alumina. The carbon nanowires have a diameter between 10 and 150 nm and a length between 0.5 and 10 μm.

[0022] This composite material is primarily used for lithium metal deposition to fabricate lithium-ion batteries without a negative electrode coating, thereby improving the overall energy density. The composite material mainly consists of a porous structure formed by the self-assembly of nano-sized alumina, nano-sized lithium alumina, nano-sized one-dimensional or two-dimensional conductive pore-forming agents, and carbon nanowires. This porous structure is a random secondary particle powder, which, after being formulated into a slurry and coated, forms a uniform porous structure distribution. The composite material contains the metal oxide alumina and the lithium-containing substance lithium alumina, both of which are lithiophilic and can promote the lithium metal deposition process, solving the problem of uneven lithium metal deposition. Furthermore, alumina and lithium alumina have good electrolyte wetting properties, and their nano-sized form further promotes electrolyte wetting, solving the problem of insufficient lithium metal deposition across the entire electrode. The conductive one-dimensional or two-dimensional pore-forming agent, carbon nanowires, and carbon coating on the oxide surface form a three-dimensional conductive network, promoting the overall conductivity of the material and solving the problem of uneven deposition caused by high impedance during the lithium deposition process. Simultaneously, no additional conductive agent needs to be added when formulating the slurry. In addition, the composite material has a porous structure, which provides deposition space for lithium deposition and solves the problem of electrode expansion caused by lithium deposition.

[0023] In some embodiments of this application, the mass ratio of the conductive pore-forming agent, lithium alumina, alumina, and carbon nanowires is 2~8:20~90:30~80:3~10. The mass ratio parameter of the conductive pore-forming agent can be selected from 2, 3, 4, 5, 6, 7, 8, or any value between any two. The mass ratio parameter of the lithium alumina can be selected from 20, 30, 40, 50, 60, 70, 80, 90, or any value between any two. The mass ratio parameter of the alumina can be selected from 30, 40, 50, 60, 70, 80, or any value between any two. The mass ratio parameter of the carbon nanowires can be selected from 3, 4, 5, 6, 7, 8, 9, 10, or any value between any two. If the proportion of the pore-forming agent is too low, it will reduce the porous structure of the material, which is detrimental to lithium deposition; if the proportion is too high, the improvement on the porous structure is limited. If the proportion of lithium alumina is too low, it will affect the lithium-ion migration rate, which is detrimental to lithium deposition; if the proportion is too high, it will lead to a decrease in the porous structure. If the proportion of alumina is too low, it will affect the electrolyte wettability; if the proportion is too high, it will affect the conductivity. If the proportion of carbon nanowires is too low, it will affect the conductivity; if the proportion is too high, it will affect the lithium-ion conductivity. By controlling the amount of each raw material during the preparation process to achieve the above-mentioned proportions, the overall performance of the composite material can be optimized.

[0024] In some embodiments of this application, the conductive pore-forming agent includes one or more of graphene, carbon nanotubes, one-dimensional silver nanowires, one-dimensional copper nanowires, one-dimensional zinc oxide nanowires, one-dimensional copper oxide nanowires, one-dimensional titanium dioxide nanowires, one-dimensional boron nitride nanowires, and one-dimensional silicon dioxide nanowires. Graphene is present in a solid content of 2-6%, with a particle size of 0.5-5 μm and a thickness of 1-50 nm; carbon nanotubes have a diameter of 10-20 nm and a length of 1-20 μm; other one-dimensional nanomaterials have a diameter of 10 nm-100 nm and a length of 0.5 μm-50 μm.

[0025] In a second aspect of this application, a method for preparing the composite material described in this application is provided, comprising: Weigh out the corresponding aluminum source, conductive pore-forming agent, lithium source, and carbon source according to the proportions in the composite material, mix them with a dispersing solvent and an appropriate amount of binder, disperse them evenly, coat and dry them to obtain secondary particles that are self-assembled by the pore-forming agent. The secondary particles are calcined in a protective gas atmosphere to obtain the composite material.

[0026] In some embodiments of this application, the dispersion solvent includes one or more of the following: ethanol, acetone, N-methylpyrrolidone (NMP), N,N-dimethylformamide (DMF), isopropanol, ethyl acetate, propylene carbonate, ethylene carbonate, methyl ethyl carbonate, dimethyl carbonate, diethyl carbonate, butyrolactone, dimethyl sulfoxide, deionized water, chloroform, toluene, xylene, tetrahydrofuran, and acetonitrile. In other embodiments of this application, the aluminum source and dispersion solvent can be mixed and wet-milled first, and then a conductive pore-forming agent, lithium source, carbon source, and binder can be added and dispersed uniformly. This method can reduce the particle size of the aluminum source and promote subsequent material reactions.

[0027] In some embodiments of this application, the aluminum source includes one or more of boehmite, nano-alumina, and aluminum hydroxide; The conductive pore-forming agent includes one or more of the following: graphene, carbon nanotubes, one-dimensional silver nanowires, one-dimensional copper nanowires, one-dimensional zinc oxide nanowires, one-dimensional copper oxide nanowires, one-dimensional titanium dioxide nanowires, one-dimensional boron nitride nanowires, and one-dimensional silicon dioxide nanowires. The lithium source includes one or more of lithium oxalate, lithium acetate, and lithium hydroxide monohydrate. The carbon source includes one or more of the following: citric acid, malic acid, glucose, sucrose, lactic acid, ascorbic acid, fruit acid, sorbic acid, tartaric acid, polyethylene, polypropylene, polystyrene, phenolic resin, epoxy resin, and asphalt.

[0028] In some embodiments of this application, the calcination treatment includes calcination at 400~1000℃ for 2~10 hours. The calcination temperature can be selected from 400℃, 450℃, 500℃, 550℃, 600℃, 650℃, 700℃, 750℃, 800℃, 850℃, 900℃, 950℃, 1000℃, or any value between two of these. The calcination time can be selected from 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, or any value between two of these, depending on the calcination temperature.

[0029] In some embodiments of this application, the protective gas includes nitrogen and an inert gas.

[0030] In a third aspect of this application, a negative electrode-free coating slurry is provided, comprising the composite material described in this application or the composite material prepared by the preparation method described in this application, as well as an electrolyte lithium salt, a polymer film-forming agent, and an organic solvent. The addition of a polymer film-forming agent to the negative electrode-free coating slurry allows for the formation of a polymer protective film on the coating surface after the negative electrode-free coating is formed, preventing excessive SEI film formation during lithium deposition and thus improving the surface stability of the lithium metal. The added electrolyte lithium salt provides conductive lithium ions.

[0031] In some embodiments of this application, the mass ratio of the composite material, the lithium electrolyte salt, and the polymer film-forming agent is 80-90:1-5:5-10. The mass ratio parameter of the composite material can be selected from 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, or any value between any two; the mass ratio parameter of the lithium electrolyte salt can be selected from 1, 2, 3, 4, 5, or any value between any two; and the mass ratio parameter of the polymer film-forming agent can be selected from 5, 6, 7, 8, 9, 10, or any value between any two.

[0032] In some embodiments of this application, the electrolyte includes one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium bis(oxalate-borate) (LiBOB), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorooxalate-borate) (LiODFB), lithium perchlorate (LiClO4), and lithium chloride (LiCl). The polymer film-forming agent includes one or more of polyacrylic acid (PAA), polyimide (PI), polyurethane (PU), polyvinylpyrrolidone (PVP), polyvinylidene fluoride (PVDF), polyvinyl butyral (PVB), polythiourea, styrene-butadiene rubber (SBR), cis-butadiene rubber (BR), and nitrile rubber (NBR). The organic solvent may be selected from the aforementioned dispersion solvents, and will not be elaborated further here.

[0033] In some embodiments of this application, the electrodeless coating slurry may optionally contain a binder, such as PVDF.

[0034] In a fourth aspect of this application, a negative electrode-free current collector is provided, comprising a current collector and a coating disposed on at least one surface of the current collector, including the composite material described in this application, or the composite material prepared by the preparation method described in this application, or the cured negative electrode-free coating slurry described in this application. The curing includes, but is not limited to, drying.

[0035] The statement that the coating can be disposed on at least one surface of the current collector means that the coating can be disposed on one surface of the current collector along its own thickness direction, or on two surfaces of the current collector along its own thickness direction. Here, "surface" can be the entire area of ​​the current collector or a part of the current collector.

[0036] In some embodiments of this application, the current collector may be a metal foil or a composite current collector. For example, copper foil or aluminum foil may be used as the metal foil. The composite current collector may include a carbon substrate or a polymer substrate, and a metal layer formed on at least one surface of the substrate coating. The composite current collector may be formed by forming a metal material (copper, aluminum, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a carbon substrate or a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0037] In a fifth aspect of this application, a lithium-ion battery is provided, comprising a positive electrode, a negative electrode-free current collector as described in this application, a separator, and an electrolyte, belonging to a negative electrode-free battery. Initially, only the positive electrode side has positive electrode active material, while the negative electrode side only has a negative electrode-free current collector, without any pre-existing coating of negative electrode active material such as lithium or graphite. Therefore, in the initial state, the negative electrode is "missing".

[0038] When an external power source begins charging the battery, lithium ions are released from the positive electrode material. These lithium ions pass through the electrolyte and separator, reaching the surface of the negative electrode current collector. Driven by an electric field, the lithium ions gain electrons, are reduced to metallic lithium atoms, and are deposited layer by layer on the surface of the negative electrode current collector. This process is equivalent to "creating" a lithium metal negative electrode on-site. Because lithium deposition occurs after battery assembly, the initial fabrication of the negative electrode current collector does not require excessively demanding environmental conditions; conventional battery manufacturing environments are sufficient. Furthermore, there are no safety hazards, which helps reduce manufacturing costs and allows for large-scale production.

[0039] When discharge begins, lithium metal atoms deposited on the current collector without a negative electrode lose electrons and are oxidized into lithium ions. These lithium ions pass through the separator and electrolyte and re-enter the positive electrode material. Electrons flow from the negative electrode to the positive electrode through the external circuit, doing work and generating current. After discharge, theoretically, the lithium metal on the surface of the current collector without a negative electrode will completely dissolve. However, there is usually some loss during the first cycle. The degree of loss determines the first-cycle efficiency (also known as the first coulombic efficiency, which is the ratio of the discharge capacity to the charge capacity in the first charge-discharge cycle, usually expressed as a percentage) of the battery without a negative electrode. The lithium-ion battery provided in this application has a higher first-cycle efficiency than batteries prepared by other comparative processes, avoiding excessive lithium loss and improving the actual usable capacity and energy density of the battery.

[0040] In some embodiments of this application, the positive electrode material is stirred evenly with an organic solvent such as N-methylpyrrolidone to the required solid content, then uniformly coated on at least one surface of the current collector, and then dried, rolled, and cut to obtain a positive electrode sheet, or the positive electrode sheet is directly made of lithium metal sheet.

[0041] The cathode material includes cathode active materials, such as various ternary cathode materials (including NCM523, NCM622, NCM811, Ni90, Ni95), lithium-rich manganese-based materials, as well as binders and conductive agents, with their weight percentages being 90-98%:1-5%:1-5% respectively.

[0042] The conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, SP conductive agent, Ketjen black, carbon fiber, carbon nanotube, graphene or carbon nanofiber.

[0043] The adhesive includes oil-based and / or water-based adhesives, such as at least one of polyvinylidene fluoride (PVDF), polyvinylpyrrolidone (PVP), sodium carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), and polyacrylic acid (PAA).

[0044] This application does not impose specific limitations on the type of electrolyte, which can be selected according to requirements. For example, the electrolyte can be liquid, gel, or all-solid. In some embodiments of this application, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent. In other embodiments of this application, the electrolyte salt may include at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, or lithium tetrafluorooxalate phosphate. In other embodiments of this application, the solvent may include at least one selected from ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, ethylene glycol dimethyl ether, methyl ethyl sulfone, or diethyl sulfone.

[0045] In some embodiments of this application, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0046] In some embodiments of this application, the positive electrode sheet, the current collector without a negative electrode, and the separator can be fabricated into an electrode assembly by a winding process or a stacking process.

[0047] In some embodiments of this application, the lithium-ion battery may include an outer packaging. This outer packaging can be used to encapsulate the aforementioned electrode components and electrolyte. In other embodiments of this application, the outer packaging of the lithium-ion battery may be a hard shell, such as a hard plastic shell, aluminum shell, or steel shell. The outer packaging of the lithium-ion battery may also be a soft pack, such as a pouch.

[0048] Furthermore, this application provides an electrical device including the lithium-ion battery described in this application. The lithium-ion battery provides electrical energy to the electrical device and can also be used as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0049] In the comparative experiments provided in this application, unless otherwise specified, all experimental conditions and materials remain consistent to ensure comparability. Furthermore, all materials used in this application are commercially available.

[0050] The following provides further details regarding a composite material and its preparation method, as well as a negative electrode-free coating slurry, a negative electrode-free current collector, and a lithium-ion battery.

[0051] Example 1: First, 740g of boehmite with a D50 of 3μm and 4000g of deionized water as the dispersion solvent were added to a mixing tank and ball-milled at 2000 rpm for 24 hours to obtain a slurry. The slurry was then transferred to a grinding and dispersion transfer tank, where 185g of glucose, 267g of lithium salt (LiOH·H2O), 750g of graphene (4% content), and 1925g of CMC adhesive (2% content) were added. The mixture was then ground at 3500 rpm for 5 hours. The resulting slurry was then coated and dried at 180°C. The powder was then scraped off, yielding 1054g of dried powder. Finally, a calcination process was performed at 650°C for 3 hours under a nitrogen inert atmosphere. During calcination, some boehmite and lithium salt were converted to lithium alumina, and the remaining boehmite was converted to alumina. The carbon source underwent carbonization, forming carbon nanowires and carbon coating. 702g of powder was obtained after calcination. This completes the preparation of the composite material. The mass ratio of graphene, lithium alumina, alumina, and carbon nanowires in this composite material is 5:70:50:8.

[0052] The powder obtained after coating, drying, and calcination was observed in planar and cross-sectional morphology to investigate the formation of porous structures. Planar SEM images are shown below. Figure 1 See cross-sectional SEM image. Figure 2 In the planar SEM images, after coating and drying, the surface exhibits flocculent nanoparticles with a diameter of approximately 20 nm, nanowires with a diameter less than 100 nm, and typical sheet-like graphene, all mixed together to form a porous surface structure. After calcination, the porous structure produces a new nanosheet morphology, identified as lithium alumina formed by the combination of boehmite and lithium salt (subsequently verified by XRD). The reduction in flocculent nanoparticles is mainly due to the combination reaction of boehmite and lithium salt, and the decomposition reaction of boehmite itself. Furthermore, the number of nanowires increases after calcination, indicating the formation of carbon nanowires from a carbon source. Calcination further loosens the porous structure on the surface, facilitating subsequent lithium metal deposition. Cross-sectional SEM images further demonstrate the significant improvement in the internal porous structure of the material after calcination. After calcination, the material is generally grayish-black, rather than exhibiting the white characteristics of oxides, indicating a carbon coating on the surface of the aluminum-based nanoparticles. Thus, carbon nanowires, graphene, and carbon-coated nanoparticles intertwine to form a three-dimensional conductive network, which is beneficial to improving the conductivity of the material.

[0053] To verify the composition, XRD analysis was performed, and the results are shown below. Figure 3Among them, the peaks marked with circles at 18.7°, 37.6°, 45.2°, 59.4°, 65.0°, 66.8°, and 70.0° are typical diffraction peaks of LiAlO2 (COD9009880), indicating that boehmite and lithium salt combined to form LiAlO2 during the material preparation process. Furthermore, the peaks marked with triangles at 32.0°, 39.4°, 45.6°, 60.6°, and 66.8° are characteristic peaks of alumina (COD1101168), indicating that some boehmite directly decomposed into alumina after calcination. In addition, comparative analysis revealed that the peaks marked with boxes at 22.0°, 22.8°, 33.1°, 34.0°, and 36.2° are lithium alumina intermediates. This is mainly due to the presence of a carbon source and the porous structure, which facilitates localized reactions between boehmite and lithium salt. These intermediates generally possess high surface activity, promoting lithium-ion diffusion. Furthermore, the peak at 26.6° for graphite mainly consists of graphene and peaks generated after carbonization of the carbon source. Overall, XRD analysis indicates that after calcination, a composite structure of lithium alumina (including intermediates), alumina, carbon nanowires, and graphene is formed.

[0054] To verify lithium deposition experiments, the prepared composite material was slurry-prepared and coated. First, 6g of film-forming agent PI was dissolved in 90g of acetonitrile solvent, followed by the addition of 2.4g of electrolyte LiTFSI. Separately, 1.8g of PVDF was dissolved in 90g of NMP. The two solutions were then mixed thoroughly, and finally, 50g of the composite material was added and stirred to disperse. After coating and drying, a negative electrode current collector was obtained. The electrode composition ratio was: coating material:LiTFSI:PI:PVDF = 83%:4%:10%:3%. The coating thickness was controlled at 40μm ± 3μm, and the electrode was not rolled. It was then assembled with lithium metal into a coin cell, and coin half-cell testing was conducted. The charge / discharge voltage range was 0.005-2.0V, and the surface capacity was controlled at 3mAh / cm². 2 The first-efficacy rate was 84.1%.

[0055] Example 2: First, 1006g of aluminum hydroxide with a D50 of 5μm and 5000g of deionized water as the dispersion solvent were added to a mixing tank and ball-milled at 2000 rpm for 24 hours to obtain a slurry. The slurry was then transferred to a grinding and dispersion transfer tank, where 140g of sucrose, 212g of lithium salt LiOH·H2O, 20g of boron nitride nanowires (40nm diameter, 10μm length), and 2014g of PAA adhesive solution (2% concentration) were added. The mixture was then ground at 4000 rpm for 4 hours. The resulting slurry was then coated and dried at 150°C. The powder was then scraped off, yielding 1221g of dried powder. Finally, a calcination process was performed at 600°C for 3 hours under a nitrogen inert atmosphere. During calcination, some aluminum hydroxide and lithium salt were converted to lithium alumina, and the remaining aluminum hydroxide was converted to alumina. The carbon source underwent carbonization, forming carbon nanowires and carbon coating. 660g of powder was obtained after calcination. This completes the preparation of the composite material. The mass ratio of boron nitride, lithium alumina, alumina, and carbon nanowires in this material is 3:50:60:8.

[0056] To verify lithium deposition experiments, the prepared composite material was slurry-prepared and coated. First, 4.6g of film-forming agent PVB was dissolved in 86g of isopropanol solvent, and 2.9g of electrolyte LiBF4 was dissolved in 86g of tetrahydrofuran. Additionally, 1.6g of PVDF adhesive was dissolved in 90g of NMP. The two solutions were then mixed thoroughly, and finally, 50g of functional coating material was added and stirred to disperse. After coating and drying, a current collector without a negative electrode was obtained. The electrode composition ratio was coating material:LiBF4:PVB = 87%:5%:8%. The coating thickness was controlled at 40μm ± 3μm, and the electrode was not rolled. It was then assembled with lithium metal into a coin cell, and coin half-cell testing was conducted. The charge / discharge voltage range was 0.005-2.0V, and the surface capacity was controlled at 3mAh / cm². 2 The first-efficacy rate was 83.3%.

[0057] Example 3: First, 784g of boehmite with a D50 of 3μm and 4000g of deionized water as the dispersion solvent were added to a mixing tank and ball-milled at 2000 rpm for 24 hours to obtain a slurry. The slurry was then transferred to a grinding and dispersion transfer tank, where 155g of citric acid, 136g of lithium salt LiOH·H2O, 50g of titanium dioxide nanowires with a diameter of 30nm and a length of 5μm, and 1179g of sodium alginate solution at a 2% concentration were added. The mixture was then ground at 3500 rpm for 4 hours. The resulting slurry was then coated and dried at 165°C. Finally, 1004g of dried powder was scraped off. Finally, a calcination process was performed at 550°C for 3 hours under a nitrogen inert atmosphere. During calcination, some boehmite and lithium salt were converted to lithium alumina, and the remaining boehmite was converted to alumina. The carbon source underwent carbonization, forming carbon nanowires and carbon coating. 669g of powder was obtained after calcination. This completes the preparation of the composite material. The mass ratio of titanium dioxide nanowires, lithium alumina, alumina, and carbon nanowires in this material is 7:30:70:5.

[0058] To verify lithium deposition experiments, the prepared composite material was slurry-prepared and coated. First, 4.5g of the film-forming agent polythiourea and 1.7g of the electrolyte LiClO4 were dissolved in 168g of dimethyl sulfoxide solvent, and 1.8g of PVDF was dissolved in 90g of NMP. The two solutions were then mixed thoroughly, and finally 50g of the functional coating material was added and stirred to disperse. After coating and drying, a current collector without a negative electrode was obtained. The electrode composition ratio was coating material: LiClO4: polythiourea = 89%: 3%: 8%. The coating thickness was controlled at 40μm ± 3μm, and the electrode was not rolled. It was then assembled with lithium metal into a coin cell, and coin half-cell testing was conducted. The charge / discharge voltage range was 0.005-2.0V, the surface capacity was controlled at 3mAh / cm², and the initial efficiency was 85.6%.

[0059] Comparative Example 1: In Example 1, except that lithium salt was not added in the grinding and dispersion process, everything else was the same as in Example 1. The resulting composite material contained only aluminum oxide and no lithium aluminum oxide. This material was then used to prepare electrodes with the same formulation as in Example 1. Button cell tests were performed, with a charge / discharge voltage range of 0.005-2.0V and an areal capacity controlled at 3mAh / cm². 2 The first-efficacy rate was 76.4%.

[0060] Comparative Example 2: In Example 1, the process was identical to Example 1 except that no polymer film-forming agent was added during electrode fabrication. The electrode was tested as a coin cell, with a charge / discharge voltage range of 0.005-2.0V and a facet capacity controlled at 3mAh / cm². 2 The first-efficacy rate was 68.5%.

[0061] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A composite material, characterized in that, The invention comprises lithium alumina, alumina, carbon nanowires, a carbon coating layer, and a porous structure self-assembled by a conductive pore-forming agent; the porous structure is loaded with carbon nanowires and has lithium alumina and alumina loaded on its surface; the carbon coating layer covers at least a portion of the surfaces of the lithium alumina and alumina.

2. The composite material according to claim 1, characterized in that, The mass ratio of the conductive pore-forming agent, lithium alumina, alumina, and carbon nanowires is 2~8:20~90:30~80:3~10.

3. The composite material according to claim 1 or 2, characterized in that, The conductive pore-forming agent includes one or more of the following: graphene, carbon nanotubes, one-dimensional silver nanowires, one-dimensional copper nanowires, one-dimensional zinc oxide nanowires, one-dimensional copper oxide nanowires, one-dimensional titanium dioxide nanowires, one-dimensional boron nitride nanowires, and one-dimensional silicon dioxide nanowires.

4. A method for preparing the composite material as described in claim 1, characterized in that, include: Aluminum source, conductive pore-forming agent, lithium source, carbon source, dispersing solvent and binder are evenly dispersed, coated and dried to obtain secondary particles self-assembled by the pore-forming agent; The secondary particles are calcined in a protective gas atmosphere to obtain the composite material.

5. The preparation method according to claim 4, characterized in that, The aluminum source includes one or more of boehmite, nano-alumina, and aluminum hydroxide. The conductive pore-forming agent includes one or more of the following: graphene, carbon nanotubes, one-dimensional silver nanowires, one-dimensional copper nanowires, one-dimensional zinc oxide nanowires, one-dimensional copper oxide nanowires, one-dimensional titanium dioxide nanowires, one-dimensional boron nitride nanowires, and one-dimensional silicon dioxide nanowires. The lithium source includes one or more of lithium oxalate, lithium acetate, and lithium hydroxide monohydrate. The carbon source includes one or more of the following: citric acid, malic acid, glucose, sucrose, lactic acid, ascorbic acid, fruit acid, sorbic acid, tartaric acid, polyethylene, polypropylene, polystyrene, phenolic resin, epoxy resin, and asphalt.

6. The preparation method according to claim 4, characterized in that, The calcination treatment includes calcination at 400~1000℃ for 2~10 hours.

7. A negative electrode-free coating slurry, characterized in that, The composite material includes the composite material according to any one of claims 1-3 or the composite material prepared by the preparation method according to any one of claims 4-6, as well as the electrolyte lithium salt, the polymer film-forming agent and the organic solvent.

8. The electrodeless coating slurry according to claim 7, characterized in that, The mass ratio of the composite material, the electrolyte lithium salt, and the polymer film-forming agent is 80~90:1~5:5~10.

9. A current collector without a negative electrode, characterized in that, Includes a current collector and a coating disposed on at least one side surface of the current collector, including the composite material according to any one of claims 1-3, or the composite material prepared by the preparation method according to any one of claims 4-6, or the non-anode coating slurry according to claim 7 or 8 after curing.

10. A lithium-ion battery, characterized in that, It includes a positive electrode, a negative electrode-free current collector as described in claim 9, a separator, and an electrolyte.

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