Lithium supplement agent, preparation method thereof, negative electrode material, negative electrode pole piece, lithium battery and electric device

Abstract

The invention relates to the field of lithium ion batteries, and discloses a lithium supplement agent, a preparation method thereof, a negative electrode material, a negative electrode plate, a lithium battery and an electric device. Graphene secondary particles with the surfaces modified with a carbon source, an aluminum source and a lithium source are subjected to high-temperature treatment in the subsequent reducing atmosphere, a porous structure formed by self-assembly of carbon nanowires formed through heat treatment and graphene is obtained, lithium intercalation exists in a graphene layer and / or deposited lithium exists in the porous structure, and the lithium-ion battery can be used for preparing the lithium-ion battery. The surface of the lithium-intercalated graphene and the surface of the lithium-deposited porous structure are modified with nanometer lithium aluminum oxide and lithium carbonate. Through multiple protection of a distribution medium and the surface of metal lithium, the air stability and the conductivity of the lithium battery are remarkably improved, and the first efficiency and the energy density of the battery can be effectively improved; in addition, the battery containing the lithium supplementing agent is low in manufacturing process requirement and low in cost, the process is easy to control, and large-scale preparation in the later period is facilitated.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of lithium ion batteries, in particular to a lithium supplementing agent, a preparation method thereof, a negative electrode material, a negative electrode sheet, a lithium battery and an electric device. BACKGROUND

[0002] Silicon-based negative electrode materials are considered to be the next generation of negative electrode materials for lithium ion batteries, mainly because they have a theoretical specific capacity of up to 4200 mAh / g, corresponding to the formation of an alloy Li x Si (0 < x < 4.4). Even at room temperature, the alloying of silicon negative electrodes with lithium produces a lithium-rich product Li 3.75 Si phase, with a capacity of up to 3572 mAh / g, which is much higher than that of traditional graphite negative electrode materials (the theoretical specific capacity of which is 372 mAh / g) and lithium titanate materials (the theoretical specific capacity of which is 175 mAh / g). However, the alloying of Si with Li 3.75 Si phase transition can produce a huge volume expansion of up to 270%, and the SEI film formed on the surface is destroyed, and in subsequent charging and discharging, the SEI film will continue to be formed, thereby continuously consuming capacity. After nanotechnology and various surface protection technologies such as carbon coating treatment, the volume expansion of silicon has been inhibited to some extent, but even the first formed surface SEI film will consume a lot of active lithium, and the phenomenon is low first efficiency and low battery energy density, and supplementing lithium is an effective method to improve the first efficiency and energy density.

[0003] Supplementing lithium includes positive electrode supplementing lithium and negative electrode supplementing lithium. Negative electrode supplementing lithium generally includes three types, one is to directly add lithium-containing metal particles to the negative electrode, or to fuse lithium foil to the surface of the negative electrode; the second is to pre-embed lithium in the negative electrode through an electrochemical reaction; and the third is to spontaneously supplement lithium in the negative electrode by soaking in a lithium-containing organic complex solution (i.e., chemical supplementing lithium). Generally, negative electrode pre-lithiation needs to strictly control moisture, and even the oxygen content also needs to be strictly controlled, and the process requirements are high, and the cost is high, such as the method of pressing metal lithium sheet to the surface of the negative electrode. A negative electrode supplementing lithium agent with inherent stability can reduce the humidity requirements for the environment, and is a prerequisite for large-scale application of negative electrode supplementing lithium agents

[0004] The lithium-organic complex used for chemical lithium supplement has high stability, but when used on a silicon-based negative electrode, it generally only forms an SEI film and cannot supplement active lithium. The use of stabilized lithium metal powder (SLMP) has a high stability in a dry atmosphere due to the presence of a passivation layer (such as Li2CO3) on the surface thereof. When using the lithium supplement, the surface protective layer of the lithium supplement particles needs to be crushed in the rolling process to enable the lithium metal to contact the negative electrode active material, so that the lithium supplement effect can be achieved, but this process is difficult to ensure consistency. Patent CN202110833988.X directly uses metal lithium mixed with nano particles that can be alloyed with lithium, and coats an aluminum-based material on the outer layer to prepare a negative electrode lithium supplement additive. This method has a long process treatment time for lithium metal and high environmental requirements, and the aluminum-based material has poor electrical conductivity, which affects the lithium supplement effect of the lithium supplement. Therefore, it is necessary to develop a negative electrode lithium supplement with high surface stability and good electrical conductivity, which can reduce the difficulty of the manufacturing process of the battery containing the lithium supplement and effectively improve the initial efficiency and energy density of the battery. SUMMARY

[0005] Therefore, the purpose of the present application is to provide a lithium supplement and a preparation method thereof, so that the lithium supplement has high stability and good electrical conductivity, and can effectively improve the initial efficiency and energy density of the battery.

[0006] Another purpose of the present application is to provide a negative electrode material, a negative electrode sheet, a lithium ion battery and an electric device prepared based on the above-mentioned lithium supplement.

[0007] In order to solve the above technical problems / achieve the above purposes or at least partially solve the above technical problems / achieve the above purposes, as a first aspect of the present application, a lithium supplement is provided, which comprises graphene, carbon nanowires, metal lithium, lithium alumina and lithium carbonate; the graphene and carbon nanowires form a matrix with a porous structure, the metal lithium is embedded between graphene layers and / or deposited in the porous structure, the lithium alumina is coated on the surface of the porous structure, and the lithium carbonate is coated on the surface of the graphene.

[0008] Optionally, the mass ratio of the graphene, lithium alumina, carbon nanowires, metal lithium and lithium carbonate is (20-50):(45-75):(2-8):(20-50):(1-8).

[0009] As a second aspect of the present application, a preparation method of the lithium supplement as described in the present application is provided, which comprises:

[0010] An aluminum source, a lithium source, a carbon source and a dispersing agent are wet ball milled to obtain a slurry, graphene is added into the slurry, and after uniform dispersion, spray drying is performed to obtain secondary particles self-assembled by the graphene;

[0011] The lithium supplementing agent is obtained after the secondary particles are treated by calcination under a reducing atmosphere.

[0012] Optionally, the aluminum source comprises one or more of boehmite, aluminum oxide, and aluminum hydroxide; the lithium source comprises one or more of lithium oxalate, lithium acetate, and lithium hydroxide monohydrate; and the carbon source comprises one or more of citric acid, malic acid, glucose, sucrose, lactic acid, ascorbic acid, fruit acid, sorbic acid, tartaric acid, carboxymethyl cellulose, polyethylene, polypropylene, polystyrene, phenolic resin, epoxy resin, and asphalt.

[0013] Optionally, the calcination temperature is 400-1000°C.

[0014] Optionally, the reducing atmosphere comprises one or more of H2, CH4, C2H6, C2H4, C3H3, and CO.

[0015] As a third aspect of the present application, a negative electrode material is provided, comprising a negative electrode active material, a binder, a conductive agent, and the lithium supplementing agent described in the present application.

[0016] As a fourth aspect of the present application, a negative electrode sheet is provided, comprising a current collector and the negative electrode material described in the present application coated on the surface of the current collector.

[0017] As a fifth aspect of the present application, a lithium ion battery is provided, comprising a positive electrode sheet, the negative electrode sheet described in the present application, and a separator and electrolyte.

[0018] As a sixth aspect of the present application, an electrical device is provided, comprising the lithium ion battery described in the present application, which provides electrical energy for the electrical device.

[0019] The present application utilizes graphene secondary particles modified with a carbon source, an aluminum source, and a lithium source, which are subsequently treated at high temperature under a reducing atmosphere to obtain a composite negative electrode lithium supplementing agent with a porous structure formed by self-assembly of carbon nanowires and graphene formed by heat treatment, lithium intercalated in the graphene layer and / or lithium deposited in the porous structure, and the surface of the lithium intercalated graphene and lithium deposited porous structure modified with nano-aluminum lithium oxide and lithium carbonate. Through multiple protection of the distribution medium and surface of metallic lithium, the air stability and electrical conductivity of the lithium supplementing agent are significantly improved, which can effectively improve the initial efficiency and energy density of the battery. In addition, the battery manufacturing process with the lithium supplementing agent has low requirements, low cost, and easy process control, which is convenient for large-scale production in the later stage. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 SEM images (1000x magnification) of the lithium supplementing agent prepared in the present application are shown.

[0021] Figure 2 Shown is a SEM image of the lithium supplement prepared in this application (magnification 50000×);

[0022] Figure 3 The figure shows the XRD pattern of the lithium supplement agent prepared in the present application; wherein, the solid line represents the XRD pattern of the lithium supplement agent of the present application, the dotted line represents the XRD pattern of nano-alumina, and the dotted line represents the XRD pattern after boehmite and lithium hydroxide are calcined at a high temperature of 600°C in an inert atmosphere. DETAILED DESCRIPTION

[0023] The present application discloses a lithium supplement and a preparation method thereof, as well as a negative electrode material, a negative electrode plate, a lithium battery and an electrical device. Those skilled in the art can refer to the contents of this article and appropriately improve the process parameters to achieve the desired effect. It should be noted in particular that all similar replacements and modifications are obvious to those skilled in the art, and they are all deemed to be included in this application. The products, processes and applications described in this application have been described through preferred embodiments. Relevant personnel can obviously modify or appropriately change and combine the preparation methods described herein without departing from the content, spirit and scope of this application to implement and apply the technology of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0024] It should be noted that, in this document, if relational terms such as "first" and "second", "step 1" and "step 2", and "(1)" and "(2)" appear, they are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "including a..." do not exclude the presence of other identical elements in the process, method, article or device comprising the elements. At the same time, the embodiments in this application and the features in the embodiments can be combined with each other in the absence of conflict.

[0025] The interlayer distance of graphene is 0.335nm, which can accommodate lithium ions and exert its capacity. In addition, graphene is light and thin, which has little effect on the specific capacity of the material. Graphene in a lithium-embedded state is more stable than metallic lithium, and graphene has good conductivity, which can promote the release of the capacity of the lithium supplement. Based on these properties of graphene, in the first aspect of the present application, a lithium supplement is provided, comprising graphene, carbon nanowires, metallic lithium, lithium aluminum oxide and lithium carbonate; the graphene and carbon nanowires form a matrix with a porous structure, the metallic lithium is embedded in the graphene layers and / or deposited in the porous structure, the lithium aluminum oxide is coated on the surface of the porous structure, and the lithium carbonate is coated on the surface of the graphene.

[0026] The lithium supplement agent of the present application is a porous structure as a whole, which is mainly a porous structure matrix composed of graphene and carbon nanowires. Metallic lithium is distributed between the graphene layers and / or in the porous structure. There is nano-lithium alumina modification between the porous structures, and lithium carbonate is also modified on the surface of the porous structure. Due to the small size of metallic lithium, it can exist in a state of being embedded in graphene, and at the same time it can exist in the form of a deposited layer in the porous structure. Compared with the large-sized block lithium (micrometer level, such as lithium metal sheets) in conventional lithium supplementation methods, the small-sized metallic lithium has a relatively low activity and is not prone to ignition in the event of loss of control, thereby solving the safety problem caused by the high activity of the negative electrode lithium supplement agent. Metallic lithium is embedded in graphene or coated in lithium alumina and the outer layer of lithium carbonate, isolating it from contact with the outside air, further improving its air stability, and solving the stability problem of the negative electrode lithium supplement agent.

[0027] The lithium-intercalated graphene and the porous structure matrix (graphene and carbon nanowires) used to deposit the metallic lithium layer are both highly conductive substrates that prevent the generation of dead lithium. This allows for lithium replenishment without the need for a subsequent rolling process, addressing the issues of ineffective and inefficient lithium replenishers due to poor conductivity. The metallic lithium is contained within a porous structure composed of graphene and carbon nanofibers and modified with lithium alumina nanoparticles, a fast-acting lithium-ion conductor. This facilitates contact between the lithium replenisher and the electrolyte, promoting lithium ion diffusion and addressing the high impedance of the lithium replenisher.

[0028] In certain embodiments of the present application, the mass ratio of the graphene, lithium aluminum oxide, carbon nanowires, metallic lithium, and lithium carbonate is (20-50):(45-75):(2-8):(20-50):(1-8). wherein, the mass ratio of the graphene may be selected as 20, 25, 30, 35, 40, 45, 50 or any value therebetween; the mass ratio of the lithium aluminum oxide may be selected as 45, 50, 55, 60, 65, 70, 75 or any value therebetween; the mass ratio of the carbon nanowire may be selected as 2, 3, 4, 5, 6, 7, 8 or any value therebetween; the mass ratio of the metallic lithium may be selected as 20, 25, 30, 35, 40, 45, 50 or any value therebetween; the mass ratio of the lithium carbonate may be selected as 1, 2, 3, 4, 5, 6, 7, 8 or any value therebetween; in some other embodiments of the present application, the mass ratio of the graphene, lithium aluminum oxide, carbon nanowire, metallic lithium and lithium carbonate is 30:50:5:25:2.5, 25:65:7:40:5 or 45:65:7:45:7.

[0029] In a second aspect of the present application, a method for preparing the lithium supplement agent as described in the present application is provided, comprising:

[0030] An aluminum source, a lithium source, a carbon source, and a dispersant are wet ball-milled to obtain a slurry, graphene is added to the slurry, dispersed uniformly, and then spray-dried to obtain secondary particles self-assembled by the graphene;

[0031] The secondary particles are calcined under a reducing atmosphere to obtain the lithium supplement agent.

[0032] During the material preparation process, the aluminum source, lithium source, carbon source, and dispersant are wet-ball milled. Graphene slurry is then added to the slurry. After grinding and dispersion, the slurry is spray-dried to obtain secondary particles self-assembled from graphene, whose surface is loaded with nanoscale aluminum source, molecular-level lithium source, and molecular-level carbon source. The particles are then calcined in a reducing atmosphere to reduce the lithium source loaded on the graphene surface and embed it between the graphene layers. The additional lithium source is reduced and deposited between the porous structure. The mixture of aluminum and lithium sources is converted into lithium aluminum oxide and modified on the surface of the porous structure. The carbon source on the graphene surface is carbonized and converted into a lithium carbonate modification layer, which, together with the lithium aluminum oxide, protects the lithium-intercalated graphene and the metallic lithium deposition layer in the porous structure.

[0033] In certain embodiments of the present application, the graphene is a graphene slurry with a solid content of 2-6%, a particle size of 0.5-5 μm, and a thickness of 1-50 nm.

[0034] In certain embodiments of the present application, the aluminum source includes one or more of boehmite, alumina, and aluminum hydroxide; the lithium source includes one or more of lithium oxalate, lithium acetate, and lithium hydroxide monohydrate; and the carbon source includes one or more of citric acid, malic acid, glucose, sucrose, lactic acid, ascorbic acid, fruit acid, sorbic acid, tartaric acid, carboxymethyl cellulose, polyethylene, polypropylene, polystyrene, phenolic resin, epoxy resin, and asphalt.

[0035] In certain embodiments of the present application, the inlet temperature of the spray drying is 300-400°C, for example, 300°C, 325°C, 350°C, 375°C, 400°C or any value therebetween; the outlet temperature of the spray drying is 90-120°C, for example, 90°C, 100°C, 110°C, 120°C or any value therebetween.

[0036] In certain embodiments of the present application, the calcination temperature is 400-1000° C., for example, 400° C., 450° C., 500° C., 550° C., 600° C., 650° C., 700° C., 750° C., 800° C., 850° C., 900° C., 950° C., 1000° C., or any value therebetween. The calcination time is 2-10 h, for example, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, or any value therebetween.

[0037] In certain embodiments of the present application, the reducing atmosphere includes one or more of H2, CH4, C2H6, C2H4, C3H3, and CO. In other embodiments of the present application, the reducing atmosphere includes N2 as a reducing gas diluent and a mixed gas of one or more of H2, CH4, C2H6, C2H4, C3H3, and CO reducing gases, and the volume ratio of N2 to these reducing gases is any ratio, for example, 1:1, 1:2, 2:1, or any specific ratio therebetween.

[0038] In a third aspect of the present application, a negative electrode material is provided, comprising a negative electrode active material, a binder, a conductive agent, and the lithium supplement described herein, wherein the mass ratio of the components is (90-95):(1.5-5):(1.5-5):(2-10). The negative electrode active material is at least one of artificial graphite, natural graphite, mesophase carbon microbeads, silicon-carbon materials, silicon-oxygen materials, and tin oxide materials. The binder is at least one of PVDF, polyurethane, polyacrylic acid, cyclodextrin, and spandex. The conductive agent is at least one of conductive carbon black SP, Ketjen black, carbon nanotubes, graphene, and conductive graphite KS-6.

[0039] As a fourth aspect of the present application, a negative electrode plate is provided, comprising a current collector and the negative electrode material described in the present application coated on the surface of the current collector.

[0040] In certain embodiments of the present application, the current collector includes a metal foil, such as aluminum foil, copper foil, etc.; the negative electrode material is slurried by NMP and then coated on the metal foil and rolled and sheeted to obtain the negative electrode sheet.

[0041] In a fifth aspect of the present application, a lithium-ion battery is provided, comprising a positive electrode plate, the negative electrode plate described in the present application, a separator, and an electrolyte.

[0042] The present application does not specifically limit the type of electrolyte, and it can be selected according to needs. For example, the electrolyte can be liquid, gel or all-solid. In certain embodiments of the present application, the electrolyte adopts an electrolyte. The electrolyte includes an electrolyte salt and a solvent. In some other embodiments of the present 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 difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate or lithium tetrafluorooxalatophosphate. In some other embodiments of the present application, the solvent may include at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane sulfone, dimethyl sulfone, ethylene glycol dimethyl ether, methyl ethyl sulfone or diethyl sulfone.

[0043] In certain embodiments of the present application, the electrolyte may optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, and additives that improve battery high or low temperature performance.

[0044] In certain embodiments of the present application, the positive electrode sheet, the negative electrode sheet, and the separator may be formed into an electrode assembly through a winding process or a lamination process.

[0045] In certain embodiments of the present application, a lithium-ion battery may include an outer packaging. This outer packaging may be used to encapsulate the electrode assembly and electrolyte. In other embodiments of the present application, the outer packaging of the lithium-ion battery may be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the lithium-ion battery may also be a soft package, such as a pouch-type soft package.

[0046] In certain embodiments of the present application, the positive electrode plate includes a current collector and a positive electrode material coated on the surface of the current collector. The positive electrode material is composed of an active material (e.g., a high-nickel ternary material, including NCM8 series (e.g., NCM811, Ni85) and NCM9 series (e.g., Ni90, Ni92, Ni96), high-voltage NCM622, lithium-rich manganese-based materials), a conductive agent, and a binder. The mass ratio can be 96.5:2:1.5. In the positive electrode plate, the conductive agent and the binder can be conventional materials in the art. For example, the conductive agent can be conductive carbon black SP, Ketjen black, carbon nanotubes, graphene, etc., and the binder can be PVDF, SBR, CMC, etc.

[0047] In a sixth aspect of the present application, an electrical device is provided, comprising the lithium-ion battery described herein, wherein the lithium-ion battery provides electrical energy to the electrical device and can also serve 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, satellites, energy storage systems, and the like.

[0048] In the comparative experiments provided in this application, unless otherwise specified, other experimental conditions, materials, etc. were kept consistent except for the differences noted in each group, so as to provide comparability. The experimental materials and reagents used in the examples were all available from commercial sources unless otherwise specified.

[0049] The following further describes a lithium supplement agent and a preparation method thereof, as well as a negative electrode material, a negative electrode plate, a lithium battery, and an electrical device provided in this application.

[0050] Example 1:

[0051] 185g of boehmite with a D50 of 4μm and 1000g of deionized water as a dispersant were added to a mixing tank. A solution of 83g of glucose dissolved in 500g of deionized water was also added, along with a solution of 740g of lithium salt LiOH.H2O dissolved in 2000g of deionized water. The pre-dispersion process was carried out at a stirring rate of 30Hz for 1h. After discharging, 1500g of deionized water was added to clean the equipment, and the cleaning solution was incorporated into the slurry. The slurry was then transferred to a ball mill transfer tank for ball milling at a speed of 2000r / min for 24h to obtain a milled slurry. The resulting slurry was transferred to a grinding and dispersion transfer tank, where 3000g of 4% graphene was added. The grinding and dispersion process was then carried out at a speed of 3500r / min for 5h. The resulting slurry was transferred to a spray drying feed tank for spray drying, with inlet and outlet temperatures at 350°C and 100°C, respectively, to obtain 1025g of powder. Afterwards, the powder was subjected to a calcination process at a temperature of 650° C. for 4 hours in a mixed atmosphere of CO (50%) and nitrogen (50%). After calcination, 402 g of lithium supplement powder was obtained.

[0052] The morphology of the prepared lithium supplement powder was observed, and the results are shown in Figure 1 and Figure 2 The lithium supplement particles are spherical in shape, with a size distribution between 5 and 20 μm. High-magnification images clearly show that the lithium supplement particles form a porous matrix, with the flakes representing graphene and the linear carbon nanowires. The carbon nanowires have diameters ranging from 10 to 150 nm, more preferably 10 to 50 nm, and lengths greater than 0.5 to 10 μm, but no greater than the diameter of the lithium supplement particles they contain, more preferably greater than 1 μm, but no greater than the diameter of the lithium supplement particles they contain, for example, ranging from 1 to 20 μm. The carbon nanowires are primarily formed by the spontaneous conversion of the carbon source in the feed during the calcination process, and they enhance the conductivity of the porous matrix.

[0053] Between the porous structure and the interwoven carbon nanowires, there are numerous nanoparticles with a primary particle size of less than 20nm. These are fine particles converted from the added boehmite through ball milling. After calcination, they combine with the lithium salt to form a combination of aluminum oxide and lithium salt, namely lithium aluminum oxide. To verify the composition, XRD analysis was performed. To illustrate the generation of the reaction products, the XRD pattern of aluminum oxide was compared with the XRD pattern of the sample obtained by mixing aluminum oxide with the lithium salt LiOH in liquid phase, drying, and calcining at 650℃. The XRD patterns of the three are compared as shown in Figure 2. Figure 3, wherein, the peak of aluminum oxide with dotted lines is wider, corresponding to nano-scale aluminum oxide (its original particle size is less than 20nm). After mixing and calcining with lithium salts, the new peaks produced are mainly lithium aluminum oxide and a small amount of lithium carbonate (the position of the peak corresponding to the triangle symbol). The original wide peak of aluminum oxide becomes stronger and the peak width becomes narrower after combining with lithium salts, which also shows that the changes produced after combining with lithium salts correspond to the characteristic peaks of lithium aluminum oxide, rather than the structural characteristics of aluminum oxide. The XRD spectrum of the sample of this embodiment, compared with the peak of the dotted line, clearly has the characteristic peak of lithium aluminum oxide, but the peak intensity is low, mainly because the oxide is nano-scale. In addition, there are characteristic peaks of carbon at 26.5°, 42.3°, and 54.6° (the ellipse conforms to the corresponding peak, the COD number of the carbon XRD peak is 9012230), corresponding to the peaks of graphene and carbon nanowires. The peak at 25.6°, slightly ahead of carbon at 26.5° (marked by a circular symbol), is a peak that does not correspond to lithium aluminum oxide, lithium carbonate, and aluminum oxide. It is slightly forward of the main peak of carbon, and the corresponding interplanar spacing becomes larger. It is a peak produced after carbon is embedded with lithium, indicating that metallic lithium is produced and embedded in the carbon after calcination in a reducing atmosphere. Since the interlayers of graphene can store lithium, the metallic lithium produced is mainly embedded in the graphene. If a lot of lithium metal is deposited, it can be deposited between the porous structure. The peaks at 20.2° and 40.6° (marked by a square symbol) are also produced on oxide-free and lithium-containing carbon materials, verifying that they are peaks produced by the combination of lithium and carbon. Stronger peaks are produced at 48.0° and 50.2° (marked by a diamond symbol), which are even stronger than the XRD peak intensity corresponding to the main component of lithium aluminum oxide. It can be judged that metallic lithium is produced, affecting the crystal structure of lithium aluminum oxide, that is, more lithium components are embedded in the lithium aluminum oxide particles. In addition, the lithium supplement material clearly produces XRD peaks of lithium carbonate (indicated by triangle symbols), indicating that the surface of the lithium supplement material is protected by lithium carbonate. Therefore, XRD pattern analysis verifies the negative electrode lithium supplement structure: metallic lithium is embedded in the graphene interlayers, metallic lithium is encapsulated within the nano-alumina, and there is a lithium carbonate protective layer on the surface.

[0054] The mass ratio of graphene, lithium aluminum oxide, carbon nanowires, metallic lithium, and lithium carbonate in the above product is 30:50:5:25:2.5. The resulting negative electrode lithium supplement was used to fabricate a button half-cell with a formula of 80:10:10 for the lithium supplement: conductive agent SP: binder PVDF. NMP was used as a dispersant. The slurry was then coated onto copper foil, dried, rolled, cut, and packaged with liquid injection. The counter electrode was lithium metal, resulting in a 2016-model button cell. Charge and discharge tests were conducted over a voltage range of 0.005-2.0V, with a gram capacity of 738mAh / g and an initial efficiency of 1538.3%.

[0055] Example 2:

[0056] 300g of boehmite with a D50 of 4μm and 1000g of deionized water as a dispersant were added to a stirring tank. At the same time, an aqueous solution of 390g of citric acid dissolved in 1000g of deionized water was added. A solution of 2255g of lithium salt lithium acetate was added to 4000g of deionized water for a pre-dispersion process. The stirring rate was 30Hz and the stirring time was 1h. After discharging, 1500g of deionized water was added to clean the equipment, and the cleaning liquid was incorporated into the slurry. The slurry was then transferred to a ball mill transfer tank for a ball milling process at a ball milling speed of 2000r / min for 24h to obtain a ball-milled slurry. The resulting slurry was transferred to a grinding and dispersion transfer tank, 3000g of 4% graphene was added, and then a grinding and dispersion process was carried out at a grinding speed of 3500r / min for 5h. The resulting slurry was transferred to a spray drying feed tank and spray-dried at inlet and outlet temperatures of 350°C and 100°C, respectively, to obtain 2865g of powder. The powder was then calcined at 550°C for 5 hours in a 50% CH4-50% nitrogen mixture to obtain 624g of lithium supplement powder.

[0057] The mass ratio of graphene, lithium aluminum oxide, carbon nanowires, metallic lithium, and lithium carbonate in the above product is 25:65:7:40:5. The resulting negative electrode lithium supplement was tested in a half-cell, showing a charge and discharge voltage range of 0.005-2.0V, a gram capacity of 934mAh / g, and an initial efficiency of 1671%.

[0058] Example 3:

[0059] 260g of an Al(OH)3 aluminum source with a D50 of 3μm and 500g of ethanol as a dispersant were added to a stirring tank. A solution containing 52g of phenolic resin dissolved in 500g of ethanol and 1673g of lithium acetate dissolved in 5000g of ethanol were also added. Pre-dispersion step 1 was performed at a stirring rate of 30Hz for 1 hour. After discharge, the equipment was cleaned with 1500g of ethanol, and the cleaning solution was incorporated into the slurry. The slurry was then transferred to a ball mill transfer tank and ball milled at 2000r / min for 24 hours to obtain a milled slurry. The resulting slurry was then transferred to a grinding and dispersion transfer tank, where 3750g of 4% graphene was added. The grinding and dispersion step was then performed at a grinding speed of 3500r / min for 5 hours. The resulting slurry was then transferred to a spray drying feed tank for spray drying at inlet and outlet temperatures of 300°C and 90°C, respectively, yielding 1958g of powder. Afterwards, the powder was subjected to a calcination process at a calcination temperature of 600° C., a calcination time of 5 h, and an atmosphere of a H 2 (50%)-nitrogen (50%) mixed atmosphere. After calcination, 421 g of lithium supplement powder was obtained.

[0060] The mass ratio of graphene, lithium aluminum oxide, carbon nanowires, metallic lithium, and lithium carbonate in the above product is 45:65:7:45:7. The resulting negative electrode lithium supplement was tested in a half-cell, showing a charge and discharge voltage range of 0.005-2.0V, a gram capacity of 885mAh / g, and an initial efficiency of 1580%.

[0061] The foregoing is merely a list of specific embodiments of the present application, intended to enable those skilled in the art to understand or implement the present 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 the present application. Therefore, the present application is not limited to the embodiments shown herein, but is intended to conform to the broadest scope consistent with the principles and novel features of the present application.

Claims

1. A lithium supplement, characterized in that: The invention comprises graphene, carbon nanowires, metallic lithium, lithium aluminum oxide and lithium carbonate; the graphene and carbon nanowires form a matrix with a porous structure, the metallic lithium is embedded between graphene layers and / or deposited in the porous structure, the lithium aluminum oxide is coated on the surface of the porous structure, and the lithium carbonate is coated on the surface of the graphene.

2. The lithium supplement according to claim 1, characterized in that The mass ratio of the graphene, lithium aluminum oxide, carbon nanowires, metallic lithium and lithium carbonate is (20-50):(45-75):(2-8):(20-50):(1-8).

3. A method for preparing the lithium supplement according to claim 1, characterized in that: include: An aluminum source, a lithium source, a carbon source, and a dispersant are wet ball-milled to obtain a slurry, graphene is added to the slurry, dispersed uniformly, and then spray-dried to obtain secondary particles self-assembled by the graphene; The lithium supplement agent is obtained by calcining the secondary particles under a reducing atmosphere.

4. The preparation method according to claim 3, characterized in that The aluminum source includes one or more of boehmite, alumina, and aluminum hydroxide; the lithium source includes one or more of lithium oxalate, lithium acetate, and lithium hydroxide monohydrate; and the carbon source includes one or more of citric acid, malic acid, glucose, sucrose, lactic acid, ascorbic acid, fruit acid, sorbic acid, tartaric acid, carboxymethyl cellulose, polyethylene, polypropylene, polystyrene, phenolic resin, epoxy resin, and asphalt.

5. The preparation method according to claim 3, characterized in that The calcination temperature is 400-1000°C.

6. The preparation method according to claim 3, characterized in that The reducing atmosphere includes one or more of H2, CH4, C2H6, C2H4, C3H3, and CO.

7. A negative electrode material, characterized in that The invention comprises a negative electrode active material, a binder, a conductive agent, and the lithium supplement agent according to claim 1 or 2.

8. A negative electrode plate, characterized in that: The invention comprises a current collector and the negative electrode material according to claim 7 coated on the surface of the current collector.

9. A lithium-ion battery, characterized in that: The invention comprises a positive electrode sheet, a negative electrode sheet as claimed in claim 8, a separator and an electrolyte.

10. An electrical device, characterized in that: The lithium-ion battery according to claim 9 is included, and the lithium-ion battery provides electrical energy for the electrical device.

Images