A lithium composite material and its preparation method and application

Abstract

The present invention provides a lithium composite material and its preparation method and application. It uses a three-dimensional porous lithiophilic material as a skeleton. It can not only use the three-dimensional porous structure of the lithiophilic material to increase the contact area with lithium and composite lithium, but also make the area of ​​lithium exposed to the outside much smaller than that of pure lithium powder, thus avoiding the problem of instability of single lithium powder. It can also use the lithiophilic property of the lithiophilic material to induce lithium deposition, adsorb lithium into smaller pores to avoid the problem that the pores of ordinary skeletons are too small for lithium to enter or enter less, which easily causes lithium to be coated outside the skeleton and cause instability and uneven deposition, while obtaining a smaller and finer lithium composite material. It solves the problem of limited preparation of lithium powder at the micron level, especially not more than 50 microns, and avoids the problem that when the general pole piece is dried, the pole piece thickness is about 70μm, and the material particles are too large to bulge on the pole piece surface. When rolling, there will be a granular feeling, which makes it difficult to ensure the uniformity of the pole piece, and may cause the particles to be crushed by rolling, and the structural damage affects the battery performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of negative electrode material preparation, and specifically relates to a lithium composite material and a preparation method and application thereof. Background Art

[0002] At present, the whole society has an increasingly strong demand for high-energy-density batteries, and an important means to improve the specific energy of lithium batteries is to supplement lithium. Lithium powder, as an important material for lithium supplementation of lithium negative electrodes, has received widespread attention in the industry. However, the stability of lithium powder and the high equipment requirements required in the preparation process have seriously restricted its development. At present, the emulsification method is commonly used to prepare lithium powder. The lithium powder can reach a minimum diameter of 50 microns, which is smaller and more uniform than other methods. However, the preparation of lithium powder with smaller particle size is limited by the surface tension of lithium metal and cannot be achieved. In addition, the speed requirement for the emulsifier is higher, which does not meet actual production needs.

[0003] Patent publication number CN107732170B discloses a high-efficiency lithium metal composite material, its preparation method, and its application as a negative electrode. A TiC / C three-dimensional porous skeleton layer is synthesized by chemical vapor deposition (CVD) over a reaction time of 1 to 5 hours. This layer is then used as a carrier and infiltrated with molten lithium to prepare the high-efficiency lithium metal composite material. The high-efficiency lithium metal composite material comprises a Ti6Al4V substrate, a TiC / C three-dimensional porous skeleton layer grown on the substrate, and a lithium metal phase adsorbed within the skeleton layer. The TiC / C three-dimensional porous skeleton layer comprises titanium carbide nanotubes and amorphous carbon encapsulated within the titanium carbide nanotubes. This lithium metal composite material exhibits high Coulombic efficiency and significantly inhibits dendrite growth. When paired with lithium iron phosphate or sulfur cathode materials, it can significantly improve the energy density and cycling stability of full batteries. However, the TiC / C three-dimensional porous skeleton layer is composed of nanotube fibers and has very large pores, making it unsuitable for preparing micron-sized structures. Even if micron-sized structures are achieved, their mechanical properties are suboptimal.

[0004] The patent with announcement number CN111725513A discloses a composite shape memory alloy negative electrode, its preparation method and lithium battery. The composite shape memory alloy negative electrode has a three-dimensional shape memory alloy skeleton, at least part of the surface of the skeleton is coated with a lithium-philic substance, and the three-dimensional pores are filled with a lithium-containing material. This composite shape memory alloy negative electrode, by coating the surface of the three-dimensional shape memory alloy with a lithium-philic substance, not only suppresses the volume expansion of the negative electrode, but also further solves the problem of poor wettability of the three-dimensional shape memory alloy skeleton, which is conducive to suppressing the formation of lithium dendrites and achieving high rate performance and long cycle life of the lithium battery. However, the combination of its porous structure and lithium alloy is only ordinary fusion, which is only suitable for porous structures with large pores. This type of structure cannot be achieved at the micron level, and if the pore size is small, it cannot be effectively fused with the lithium alloy.

[0005] Therefore, how to obtain lithium powder or lithium composite materials at the micron level, especially no more than 50 microns, to avoid the situation when the electrode is generally dry and the thickness of the electrode is about 70μm. The lithium powder or lithium composite material particles are too large and will bulge on the surface of the electrode. When rolling, there will be a granular feeling, which makes it difficult to ensure the uniformity of the electrode, and may cause the particles to break when rolling, and the structural damage will affect the battery performance. Summary of the Invention

[0006] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a lithium composite material and its preparation method and application, so as to solve the problem of limited preparation of lithium powder or lithium composite materials with smaller particle size (micron level, especially not more than 50 microns), and further avoid the problem that when the electrode is generally dried, the thickness of the electrode is about 70μm, and the lithium powder or lithium composite material particles are too large and will bulge on the surface of the electrode. When rolling, there will be a granular feeling, which makes it difficult to ensure the uniformity of the electrode, and may cause the particles to be crushed by rolling, and the structural damage affects the battery performance.

[0007] The first object of the present invention is to provide a lithium composite material, comprising a lithiophilic three-dimensional porous skeleton loaded with lithium metal, wherein the lithiophilic three-dimensional porous skeleton loaded with lithium metal comprises a lithiophilic three-dimensional porous skeleton and lithium metal loaded in the pores of the lithiophilic three-dimensional porous skeleton, wherein the particle size of the lithium composite material is 5μm-50μm (such as 6μm, 10μm, 15μm, 20μm, 25μm, 30μm, 40μm, 45μm, 48μm).

[0008] In lithium composite materials, the lithium metal is substantially or entirely located within the pores of the framework. The lithium metal can be metallurgically bonded or chemically bonded to the framework. The lithium metal includes one or more of elemental lithium metal, lithium metal alloys, and lithium salts.

[0009] Furthermore, the lithium composite material further includes a first coating layer and / or a second coating layer coated on the outside of the lithiophilic three-dimensional porous framework loaded with lithium metal.

[0010] Furthermore, the first coating layer is a SEI film.

[0011] Preferably, the raw materials of the SEI film include one or more of chloroethylene carbonate, ethylene sulfite, propylene sulfite, diethyl sulfite, dimethyl sulfite, anisole, lithium nitrate, fluoroethylene carbonate, vinylene carbonate, antimony fluoride, magnesium fluoride, tin fluoride, aluminum fluoride, and diethyl nitrite.

[0012] Furthermore, the second coating layer is an ultra-thin polymer protective layer or a carbon coating layer.

[0013] Preferably, the high molecular weight polymer in the ultra-thin polymer protective layer is one or more of polyacrylonitrile, polyethylene oxide, polypropylene oxide, polyvinyl chloride, polyvinylidene fluoride, polycaprolactone, octadecanedioic acid, hexadecanedioic acid, tetradecanedioic acid, and dodecanedioic acid.

[0014] Preferably, the thickness of the polymer ultra-thin protective layer is 0.1 μm-1 μm (such as 0.15 μm, 0.2 μm, 0.25 μm, 0.5 μm, 0.75 μm, 0.9 μm, 0.95 μm).

[0015] Preferably, the lithiophilic three-dimensional porous skeleton loaded with lithium metal is coated with a SEI film on the outside, and the SEI film is coated with an ultra-thin polymer protective layer on the outside.

[0016] Furthermore, the mass percentage of lithium metal in the lithium composite material is 5%-40% (such as 6%, 10%, 15%, 20%, 25%, 30%, 35%, 38%).

[0017] Furthermore, the compacted density of the lithium composite material is 1 g / cm 3 -3g / cm 3 (such as 1.2g / cm 3 , 1.5g / cm 3 , 1.8g / cm 3 , 2g / cm 3 , 2.5g / cm 3 , 2.8g / cm 3 ).

[0018] Furthermore, the particle size of the lithiophilic three-dimensional porous framework is 5 μm-50 μm (such as 6 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 40 μm, 45 μm, 48 μm).

[0019] Furthermore, the porosity of the lithiophilic three-dimensional porous framework is 20% to 80% (such as 25%, 30%, 35%, 40%, 45%, 50%, 60%, 70%, 75%).

[0020] Furthermore, the lithiophilic three-dimensional porous skeleton is one or more of zinc oxide, silver oxide, tin oxide, aluminum oxide, lithium oxide, zirconium oxide, cobalt oxide, copper oxide, silicon oxide, germanium oxide, magnesium oxide, antimony oxide, zinc fluoride, silver fluoride, tin fluoride, aluminum fluoride, lithium fluoride, zirconium fluoride, cobalt fluoride, copper fluoride, silicon fluoride, germanium fluoride, magnesium fluoride and antimony fluoride after pore-forming treatment, and porous zinc, porous silver, porous tin, porous aluminum, porous lithium, porous zirconium, porous cobalt, porous copper, porous silicon, porous germanium, porous magnesium and porous antimony without pore-forming treatment.

[0021] Furthermore, the lithium composite material deteriorates at a rate of 0.1% to 0.8% (eg, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%) per hour in an environment with a dew point of -40°C.

[0022] The second object of the present invention is to provide a method for preparing the above-mentioned lithium composite material, which is as follows:

[0023] A method for preparing a lithium composite material, specifically prepared by emulsion polymerization, comprises the following steps:

[0024] S110: mixing the lithiophilic three-dimensional porous framework and molten lithium metal, and biaxially emulsifying and stirring to obtain a mixture;

[0025] S220: adding a first organic solvent to the mixture obtained in step S110, uniaxially emulsifying and stirring, and then removing unreacted molten lithium metal and the first organic solvent, respectively, to obtain a lithium composite material without a coating layer.

[0026] Further, in step S110, the lithiophilic three-dimensional porous skeleton is one or more of zinc oxide, silver oxide, tin oxide, aluminum oxide, lithium oxide, zirconium oxide, cobalt oxide, copper oxide, silicon oxide, germanium oxide, magnesium oxide, antimony oxide, zinc fluoride, silver fluoride, tin fluoride, aluminum fluoride, lithium fluoride, zirconium fluoride, cobalt fluoride, copper fluoride, silicon fluoride, germanium fluoride, magnesium fluoride and antimony fluoride after pore-forming treatment, and porous zinc, porous silver, porous tin, porous aluminum, porous lithium, porous zirconium, porous cobalt, porous copper, porous silicon, porous germanium, porous magnesium and porous antimony that do not require pore-forming treatment.

[0027] Furthermore, in step S110, the mass ratio of the molten lithium metal to the lithiophilic three-dimensional porous framework is not less than 2 (such as 2:1, 2.3:1, 2.5:1, 2.8:1, 3:1, 4:1).

[0028] Furthermore, in step S110, the particle size of the lithiophilic three-dimensional porous framework is 5 μm-50 μm (such as 6 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 40 μm, 45 μm, 48 μm).

[0029] Furthermore, in step S110, the porosity of the lithiophilic three-dimensional porous framework is 20% to 80% (such as 25%, 30%, 35%, 40%, 45%, 50%, 60%, 70%, 75%).

[0030] Furthermore, in step S110, the melting temperature of the molten lithium metal is not less than 180°C, preferably 180-220°C (such as 185°C, 190°C, 200°C, 205°C, 210°C, 215°C).

[0031] Furthermore, in step S110, during the biaxial emulsification stirring, the rotation speed of the emulsification shear is 5000-20000 rpm (such as 6000 rpm, 8000 rpm, 10000 rpm, 15000 rpm, 19500 rpm).

[0032] Furthermore, in step S110, during the biaxial emulsification stirring, the mass-to-time ratio of the emulsification shear is 1-10 mg / s (such as 1.5 mg / s, 2 mg / s, 4 mg / s, 6 mg / s, 8 mg / s, 9.5 mg / s).

[0033] Furthermore, in step S110, during the biaxial emulsification stirring, the ratio of the mass of the emulsified shear to the operating volume of the stirring paddle is 1-100 mg / mm 3 (such as 2mg / mm 3 , 5mg / mm 3 , 10mg / mm 3 , 30mg / mm 3 , 60mg / mm 3 , 90mg / mm 3 , 95mg / mm 3 ).

[0034] Further, in step S220, the first organic solvent is a high temperature resistant organic solvent.

[0035] Furthermore, in step S220, during the uniaxial emulsification stirring, the rotation speed of the emulsification shear is 8000-20000 rpm (such as 8500 rpm, 9000 rpm, 10000 rpm, 15000 rpm, 19500 rpm).

[0036] Furthermore, in step S220, during the uniaxial emulsification stirring, the mass-to-time ratio of emulsification shear is 1-10 mg / s (such as 1.5 mg / s, 2 mg / s, 4 mg / s, 6 mg / s, 8 mg / s, 9.5 mg / s).

[0037] Furthermore, in step S220, during the uniaxial emulsification stirring, the ratio of the mass of the emulsification shear to the operating volume of the stirring paddle is 1-100 mg / mm 3 (such as 2mg / mm 3 , 5mg / mm 3 , 10mg / mm 3 、30mg / mm 3 、60mg / mm 3 , 90mg / mm 3 , 95mg / mm 3 ).

[0038] Furthermore, in step S220, the removal method is one or more of centrifugation, sedimentation and filtration.

[0039] Furthermore, when the lithiophilic three-dimensional porous skeleton is a lithiophilic material after pore-forming treatment, the preparation method further includes step S100 of pore-forming: mixing the lithiophilic material to be pore-formed with a pore-forming agent, pressing, sintering the pores, and crushing to obtain the lithiophilic three-dimensional porous skeleton after pore-forming treatment.

[0040] Furthermore, in step S100, the lithiophilic material to be pore-formed includes one or more of zinc oxide, silver oxide, tin oxide, aluminum oxide, lithium oxide, zirconium oxide, cobalt oxide, copper oxide, silicon dioxide, germanium oxide, magnesium oxide, antimony oxide, zinc fluoride, silver fluoride, tin fluoride, aluminum fluoride, lithium fluoride, zirconium fluoride, cobalt fluoride, copper fluoride, silicon fluoride, germanium fluoride, magnesium fluoride and antimony fluoride.

[0041] Furthermore, in step S100, the pore-forming agent includes one or more of graphite, glucose, starch, polystyrene, grains, elemental sulfur, and pore-forming agent PL-05.

[0042] Furthermore, in step S100, the particle size of the pore-forming agent is 0.02-3.00 μm (such as 0.05 μm, 0.2 μm, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 2.8 μm).

[0043] Furthermore, in step S100, the mixing further includes adding a conductive agent, wherein the conductive agent comprises one or more of mesophase carbon, artificial graphite, natural graphite, expanded graphite, single-walled carbon nanotubes, multi-walled carbon nanotubes, amorphous carbon, hard carbon, activated carbon, MAX phase compounds, graphene, and Super P. Preferably, the conductive agent comprises one or more of single-walled carbon nanotubes, multi-walled carbon nanotubes, amorphous carbon, and graphene.

[0044] Furthermore, in step S100, the mass ratio of the lithiophilic material to be pore-formed, the pore-forming agent and the conductive agent is 1:(0.2-1.5):(0.03-0.1) (such as 1:0.25:0.04, 1:0.4:0.05, 1:0.6:0.06, 1:0.8:0.07, 1:1:0.08, 1:1.2:0.085, 1:1.4:0.09).

[0045] Furthermore, in step S100, the mixing further includes adding a solvent, and the solvent includes one or more of water, NMP, ethanol, ethyl acetate, glycerol, propanol, diethyl carbonate, and tetrahydrofuran.

[0046] Furthermore, in step S100, the mass ratio of the solvent to the total amount of solids is (2-5):1 (such as 2.2:1, 2.5:1, 3:1, 3.8:1, 4:1, 4.2:1, 4.8:1).

[0047] Furthermore, in step S100, the pressing pressure is 1.0-15.0 MPa (such as 1.5 MPa, 2 MPa, 5 MPa, 7 MPa, 9 MPa, 11 MPa, 12 MPa, 14 MPa).

[0048] Furthermore, in step S100, the pore-forming sintering is first pre-fired at 150-500°C (such as 180°C, 220°C, 250°C, 300°C, 350°C, 380°C, 420°C, 480°C) for 1-10h (such as 1.5h, 2h, 4h, 6h, 8h, 9h, 9.5h), and then sintered at 600-900°C (such as 650°C, 700°C, 750°C, 780°C, 800°C, 880°C) under a protective atmosphere for 5-20h (such as 5.5h, 7h, 9h, 11h, 14h, 16h, 18h, 19.5h).

[0049] Furthermore, in step S100, the particle size after crushing is required to be 5 μm-50 μm (such as 6 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 40 μm, 45 μm, 48 μm).

[0050] Furthermore, the preparation method further includes step S330 and / or step S440, wherein:

[0051] Step S330: adding a second organic solvent containing an SEI film additive to the lithium composite material without a coating layer obtained in step S220, stirring to coat the SEI film, and separating to remove the second organic solvent to obtain a lithium composite material with an SEI film;

[0052] Step S440: Add a third organic solvent containing a high molecular weight polymer to the lithium composite material without a coating layer obtained in step S220 or the lithium composite material with a SEI film obtained in step S330, stir, and coat the ultra-thin polymer protective layer to obtain a lithium composite material with a protective layer.

[0053] Furthermore, in step S330, the second organic solvent is one or more of ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, ethylene glycol dimethyl ether (DME), tetrahydrofuran (THF), dioxolane (DOL), acetonitrile, N-methylpyrrolidone (NMP), N,N-dimethylformamide (DMF), and dimethyl sulfoxide (DMSO).

[0054] Furthermore, in step S330, the SEI film additive is one or more of chloroethylene carbonate, ethylene sulfite, propylene sulfite, diethyl sulfite, dimethyl sulfite, anisole, lithium nitrate, fluoroethylene carbonate, vinylene carbonate, antimony fluoride, magnesium fluoride, tin fluoride, aluminum fluoride, and diethyl nitrite.

[0055] Furthermore, in step S330, the mass ratio of the lithium composite material without the coating layer to the SEI film additive is 1:(0.05-0.5) (such as 1:0.08, 1:0.1, 1:0.2, 1:0.3, 1:0.35, 1:0.04, 1:0.48).

[0056] Furthermore, in step S330, during the stirring, the stirring time is 0.5h-6h (such as 0.7h, 1h, 2h, 3h, 4h, 5.5h), and the heating temperature is 25-40℃ (such as 28℃, 30℃, 33℃, 35℃, 38℃, 39℃).

[0057] Furthermore, in step S440, the third organic solvent is one or more of ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, ethylene glycol dimethyl ether (DME), tetrahydrofuran (THF), dioxolane (DOL), acetonitrile, N-methylpyrrolidone (NMP), N,N-dimethylformamide (DMF), and dimethyl sulfoxide (DMSO).

[0058] Furthermore, in step S440, the high molecular polymer is a high molecular polymer that has ion conductivity or swelling property and is hydrophobic.

[0059] Preferably, in step S440, the high molecular polymer is one or more of polyacrylonitrile, polyethylene oxide, polypropylene oxide, polyvinyl chloride, polyvinylidene fluoride, polycaprolactone, octadecanedioic acid, hexadecanedioic acid, tetradecanedioic acid, and dodecanedioic acid.

[0060] Furthermore, in step S440, the coating method is one or more of solution coating, in-situ polymerization, melt coating, and spray drying.

[0061] Furthermore, in step S440, the thickness of the polymer ultra-thin protective layer is 0.1 μm-1 μm (such as 0.15 μm, 0.2 μm, 0.25 μm, 0.5 μm, 0.75 μm, 0.9 μm, 0.95 μm).

[0062] The third object of the present invention is to provide an application of a lithium composite material, which is as follows:

[0063] A negative electrode sheet comprises the above lithium composite material or the lithium composite material prepared by the above preparation method as a negative electrode active material.

[0064] A lithium battery comprises a negative electrode sheet using the above lithium composite material or the lithium composite material prepared by the above preparation method as a negative electrode active material.

[0065] Compared with the prior art, the present invention has the following beneficial effects:

[0066] 1. The lithium composite material of the present invention utilizes a three-dimensional porous lithiophilic material as a framework. This not only utilizes the lithiophilic material's three-dimensional porous structure to increase the contact area with lithium, thereby complexing lithium and significantly reducing the exposed area of ​​lithium compared to pure lithium powder, thus avoiding the instability of pure lithium powder. Furthermore, the lithiophilic properties of the lithiophilic material can be used to induce lithium deposition, allowing lithium to adsorb into smaller pores, thereby avoiding the problems of conventional frameworks where the pores are too small for lithium to enter, or where lithium can enter only minimally, resulting in lithium being encapsulated outside the framework and causing instability and uneven deposition. This results in a smaller and finer lithium composite material. Furthermore, the particle size of the lithium composite material is not only less than 50 microns, surpassing the 50-micron minimum particle size limit of lithium powder prepared by the emulsion method in the prior art, but also smaller than the typical dry thickness of a negative electrode sheet of approximately 70 microns. This prevents the negative electrode active material from being crushed during roller compression, leading to structural damage or uneven sheet formation that could affect battery performance. Furthermore, the particle size is no less than 5 microns, allowing for a large amount of lithium metal to be loaded without exposure, resulting in excellent stability.

[0067] 2. In the lithium composite material of the present invention, lithium metal can be combined with a lithiophilic material to be converted into a lithium alloy or lithium salt. The addition of an external modification layer such as an SEI film or an ultra-thin polymer coating can further enhance the stability, thereby avoiding the instability and uneven deposition problems of lithium powder alone.

[0068] 3. The lithium composite material of the present invention, wherein the mass percentage of lithium metal is 5%-40% and the compacted density is 1g / cm 3 -3g / cm 3 , the deterioration rate per hour is 0.1%-0.8% in an environment with a dew point of -40℃.

[0069] 4. The preparation method of the present invention comprises the following steps: after mixing molten lithium with a lithiophilic three-dimensional porous framework having a particle size of 5 μm-50 μm, biaxial emulsification shear stirring is used to increase the mutual collision and friction between the molten lithium and the lithiophilic three-dimensional porous framework, allowing the molten lithium to fully enter the lithiophilic three-dimensional porous framework and fully fuse and react. Then, uniaxial emulsification shear stirring is used to separate the excess unreacted molten lithium from the lithium composite material generated by the reaction, ultimately obtaining a micron-scale lithium composite material. This avoids the problem that conventional fusion is only applicable to porous structures with large pores, and that the particle size of the lithium composite material after fusion with lithium metal cannot reach the micron level, especially not greater than 50 μm, which cannot meet the requirements for preparing lithium composite materials with smaller particle sizes. In addition, the emulsification shear stirring method can continuously carry out the mixing reaction of lithium metal and the lithiophilic three-dimensional porous framework, the separation of lithium liquid and lithium-rich composite, and the polymer coating in the same container by adding different solvents, forming an integrated preparation, which is convenient and efficient. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] Figure 1 Scanning electron microscope (SEM) image of the lithiophilic three-dimensional porous framework in Example 2;

[0071] Figure 2 Scanning electron microscope (SEM) image of the lithium composite material in Example 2;

[0072] Figure 3 XRD patterns of the lithiophilic three-dimensional porous framework MgO (bottom) and the lithium composite material (top) in Example 2;

[0073] Figure 4 Figure 2 shows the rate performance test of the lithium composite material in Example 2;

[0074] Figure 5 Cycling performance test diagram of the lithium composite material in Example 2;

[0075] Figure 6 Figure 2 shows the first performance test of the lithium composite material in Example 2. DETAILED DESCRIPTION

[0076] In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention.

[0077] The embodiments of the present invention are implemented on the premise of the technical solution of the present invention, and detailed implementation methods and processes are given. However, the protection scope of the present invention is not limited to the following embodiments. The process parameters in the following embodiments that do not specify specific conditions are generally based on conventional conditions.

[0078] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to form one or more new numerical ranges, and these numerical ranges should be considered to be specifically disclosed in the present invention.

[0079] In the present invention, unless otherwise specified and / or explained, all numerical values ​​involving the amounts of components are "parts by weight or mass percentages". The process parameters in the following examples that are not specified in specific conditions are generally based on conventional conditions.

[0080] A specific embodiment of the present invention provides a lithium composite material, comprising a lithiophilic three-dimensional porous skeleton loaded with lithium metal, wherein the lithiophilic three-dimensional porous skeleton loaded with lithium metal comprises a lithiophilic three-dimensional porous skeleton and lithium metal loaded in the pores of the lithiophilic three-dimensional porous skeleton; wherein the particle size of the lithium composite material is 5 μm-50 μm (such as 6 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 40 μm, 45 μm, 48 μm).

[0081] In lithium composite materials, the lithium metal is substantially or entirely located within the pores of the framework. The lithium metal can be metallurgically bonded or chemically bonded to the framework. The lithium metal includes one or more of elemental lithium metal, lithium metal alloys, and lithium salts.

[0082] The lithium composite material of the present invention uses a three-dimensional porous lithiophilic material as a skeleton. It can not only utilize the three-dimensional porous structure of the lithiophilic material to increase the contact area with lithium, composite lithium, and make the area of ​​lithium exposed to the outside much smaller than that of pure lithium powder, thus avoiding the instability problem of single lithium powder. It can also utilize the lithiophilic property of the lithiophilic material to induce lithium deposition, adsorbing lithium into smaller pores to avoid the problem that the pores of ordinary skeletons are too small for lithium to enter or enter less, which easily causes lithium to be coated outside the skeleton, causing instability and uneven deposition, and at the same time obtain a smaller and finer lithium composite material. The particle size of the lithium composite material of the present invention is no more than 50 microns, which can avoid being crushed during roller pressing as a negative electrode active material, resulting in structural damage and affecting performance. Because the thickness of the negative electrode plate is generally about 70 microns when dry, in order to ensure the uniformity of the plate, the particles cannot be too large. The particles are too large and will bulge on the surface of the plate, resulting in a grainy feeling during rolling. The particles are easily crushed by the roller, resulting in structural damage. In addition, the particle size of the lithium composite material of the present invention is not less than 5 microns, so that the amount of lithium metal loaded is large and not exposed, and both the structural stability and lithium stability are excellent.

[0083] In some embodiments, the lithium composite material further comprises a first coating layer and / or a second coating layer coated on the exterior of the lithiophilic three-dimensional porous framework-supported lithium metal. Preferably, the first coating layer is coated on the exterior of the lithiophilic three-dimensional porous framework-supported lithium metal, and the second coating layer is coated on the exterior of the first coating layer.

[0084] The outer coating layer of the lithium composite material of the present invention can further enhance stability and avoid the instability of lithium powder alone.

[0085] In some embodiments, the first coating layer is an SEI film. Preferably, the raw materials of the SEI film include one or more of chloroethylene carbonate, ethylene sulfite, propylene sulfite, diethyl sulfite, dimethyl sulfite, anisole, lithium nitrate, fluoroethylene carbonate, vinylene carbonate, antimony fluoride, magnesium fluoride, tin fluoride, aluminum fluoride, and diethyl nitrite.

[0086] In some embodiments, the second coating layer is an ultra-thin polymer protective layer or a carbon coating layer. Preferably, the polymer in the ultra-thin polymer protective layer is one or more of polyacrylonitrile, polyethylene oxide, polypropylene oxide, polyvinyl chloride, polyvinylidene fluoride, polycaprolactone, octadecanedioic acid, hexadecanedioic acid, tetradecanedioic acid, and dodecanedioic acid. The carbon coating layer can be made of fine lithium-philic powder, such as ultrafine graphite powder.

[0087] In some embodiments, the thickness of the polymer ultra-thin protective layer is 0.1 μm-1 μm (eg, 0.15 μm, 0.2 μm, 0.25 μm, 0.5 μm, 0.75 μm, 0.9 μm, 0.95 μm).

[0088] In some embodiments, the lithiophilic three-dimensional porous skeleton is loaded with lithium metal and coated with a SEI film on the outside, and the SEI film is coated with an ultra-thin polymer protective layer on the outside.

[0089] In some embodiments, the mass percentage of lithium metal in the lithium composite material is 5%-40% (eg, 6%, 10%, 15%, 20%, 25%, 30%, 35%, 38%).

[0090] In the present invention, the mass percentage of lithium metal in the lithium composite material can reach 40%, which has the advantages that more active materials lead to higher battery energy and greater rate.

[0091] In some embodiments, the compacted density of the lithium composite material is 1 g / cm 3 -3g / cm 3 (such as 1.2g / cm 3 , 1.5g / cm 3 , 1.8g / cm 3 , 2g / cm 3 , 2.5g / cm 3 , 2.8g / cm 3 ).

[0092] The compacted density of the lithium metal composite material of the present invention can reach 3g / cm 3 The greater the compaction density of the composite material, the more mass of active material can be accommodated per unit volume, the higher the battery energy and the higher the discharge power performance per unit volume.

[0093] In some embodiments, the lithiophilic three-dimensional porous framework has a particle size of 5 μm to 50 μm (eg, 6 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 40 μm, 45 μm, 48 μm).

[0094] In some embodiments, the porosity of the lithiophilic three-dimensional porous framework is 20% to 80% (eg, 25%, 30%, 35%, 40%, 45%, 50%, 60%, 70%, 75%).

[0095] In some embodiments, the lithiophilic three-dimensional porous skeleton is one or more of zinc oxide, silver oxide, tin oxide, aluminum oxide, lithium oxide, zirconium oxide, cobalt oxide, copper oxide, silicon oxide, germanium oxide, magnesium oxide, antimony oxide, zinc fluoride, silver fluoride, tin fluoride, aluminum fluoride, lithium fluoride, zirconium fluoride, cobalt fluoride, copper fluoride, silicon fluoride, germanium fluoride, magnesium fluoride and antimony fluoride that have been subjected to pore-forming treatment, and porous zinc, porous silver, porous tin, porous aluminum, porous lithium, porous zirconium, porous cobalt, porous copper, porous silicon, porous germanium, porous magnesium and porous antimony that do not require pore-forming treatment.

[0096] In the present invention, the differences between the lithiophilic three-dimensional porous frameworks in the lithium composite material lie in the number of lithiophilic sites they can provide. Fluoride, a lithiophilic three-dimensional porous framework, reacts with elemental metallic lithium droplets to generate lithium fluoride, which can improve the initial efficiency and cycle performance of lithium batteries. Because lithium fluoride is tougher, it can better adapt to the volume changes of the negative electrode sheet than oxides, and its ionic conductivity is also higher than that of oxides.

[0097] In some embodiments, the lithium composite material deteriorates at a rate of 0.1%-0.8% (eg, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%) per hour in an environment with a dew point of -40°C.

[0098] In some embodiments, the preparation method of the lithium composite material is specifically prepared by emulsion polymerization, comprising the following steps:

[0099] S110: mixing the lithiophilic three-dimensional porous framework and molten lithium metal, and biaxially emulsifying and stirring to obtain a mixture;

[0100] S220: adding a first organic solvent to the mixture obtained in step S110, uniaxially emulsifying and stirring, and then removing unreacted molten lithium metal and the first organic solvent, respectively, to obtain a lithium composite material without a coating layer.

[0101] The preparation method of the present invention firstly mixes molten lithium metal and a lithiophilic three-dimensional porous skeleton, controls the temperature so that the lithiophilic three-dimensional porous skeleton remains in a solid state and the molten lithium metal is in a liquid state, and when the elemental metallic lithium droplets react with the lithiophilic three-dimensional porous skeleton, a lithium salt or lithium alloy with a higher melting point is formed and loaded into the pores of the lithiophilic three-dimensional porous skeleton, and the newly formed lithium salt or lithium alloy maintains a solid form together with the lithiophilic three-dimensional porous skeleton; the contact between the elemental metallic lithium droplets and the solid lithiophilic three-dimensional porous skeleton can be further accelerated by biaxial emulsification, because the elemental metallic lithium droplets react at high speed. In the state, it will collide and rub with the solid lithium-philic three-dimensional porous skeleton and fully diffuse into the pores. Due to the limitations of the pores and the lithium-philic properties, it will react at the surface interface of the pores to form a solid lithium salt or lithium alloy; then add a high-temperature resistant first organic solvent such as tetramethylsilane and perform uniaxial high-speed emulsification shearing. Due to the different resistance caused by density and specific surface area, centrifugation is performed through different densities and phase differences to separate the unreacted elemental metal lithium droplets and the porous lithium-rich microparticles generated by the reaction, so that the unreacted elemental metal lithium droplets enriched in the pores of the lithium-rich microparticles are thrown out to obtain porous lithium-rich microparticles, that is, lithium composite materials without a coating layer. The thrown elemental metal lithium droplets will form microspheres by themselves according to different tensions, and form solids after cooling, which can be reused. In addition, the elemental metal lithium droplets can be removed by one or more methods of centrifugation, sedimentation and filtration to obtain porous lithium-rich microparticles.

[0102] At present, emulsification shearing is generally only used for the preparation of lithium powder, and there is no precedent for the preparation of lithium composites. When emulsification shearing is used to prepare lithium powder, the minimum particle size of the lithium powder is 50 microns and cannot be smaller. Research has found that this is mainly due to the surface tension of the elemental metal lithium droplets. Based on this, the present application combines the use of a lithiophilic three-dimensional porous skeleton material with a biaxial emulsification process to allow the elemental metal lithium droplets to fully enter the pores of the lithiophilic three-dimensional porous skeleton. At the same time, the elemental metal lithium droplets in contact with the pores of the lithiophilic three-dimensional porous skeleton are basically or completely combined with the lithiophilic three-dimensional porous skeleton on the pore surface to form a lithium alloy or lithium salt, so as to reduce the surface tension to form smaller particles, and finally obtain smaller and finer composite lithium powder (lithium composite material).

[0103] Preferably, in step S110, after mixing the lithiophilic three-dimensional porous framework and molten lithium metal, the mixture is allowed to stand for a certain period of time before biaxial emulsification and stirring, so that the molten lithium metal can enter the pores of the framework due to the lithiophilic effect of the framework or its own flow. The standing time is preferably 1-4 hours.

[0104] In some embodiments, in step S110, the lithiophilic three-dimensional porous skeleton is one or more of zinc oxide, silver oxide, tin oxide, aluminum oxide, lithium oxide, zirconium oxide, cobalt oxide, copper oxide, silicon oxide, germanium oxide, magnesium oxide, antimony oxide, zinc fluoride, silver fluoride, tin fluoride, aluminum fluoride, lithium fluoride, zirconium fluoride, cobalt fluoride, copper fluoride, silicon fluoride, germanium fluoride, magnesium fluoride and antimony fluoride after pore-forming treatment, and porous zinc, porous silver, porous tin, porous aluminum, porous lithium, porous zirconium, porous cobalt, porous copper, porous silicon, porous germanium, porous magnesium and porous antimony that do not require pore-forming treatment.

[0105] In the present invention, the lithiophilic three-dimensional porous skeleton is both a lithiophilic material that can induce lithium deposition and a three-dimensional skeleton that can increase the contact area with lithium and reduce the area of ​​lithium powder exposure. In addition, the difference between the above-mentioned lithiophilic three-dimensional porous skeletons lies in the number of lithiophilic sites they can provide. Among them, fluoride is used as a lithiophilic three-dimensional porous skeleton. The lithium fluoride generated by its reaction with elemental metallic lithium droplets can improve the initial efficiency and cycle performance of lithium batteries. Because lithium fluoride is tough, it can adapt to the volume change of the negative electrode sheet better than oxides, and its ion conductivity is also higher than that of oxides.

[0106] In some embodiments, in step S110 , the particle size of the lithiophilic three-dimensional porous framework is 5 μm-50 μm (eg, 6 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 40 μm, 45 μm, 48 μm).

[0107] The present invention further limits the particle size of the lithiophilic three-dimensional porous framework to 5 μm-50 μm, thereby ensuring that the particle size of the lithium composite material is no larger than 50 microns, and that the structure has good mechanical properties while facilitating the deposition and loading of lithium. If the particle size of the lithiophilic three-dimensional porous framework is too small, smaller than the size determined by the minimum tension of the elemental metallic lithium droplet, it will be unable to load lithium metal and ultimately cause the lithium metal to be deposited outside the framework as pure lithium powder. If the particle size of the lithiophilic three-dimensional porous framework is too large, it will be detrimental to the release of lithium in the battery.

[0108] In some embodiments, in step S110 , the porosity of the lithiophilic three-dimensional porous framework is 20% to 80% (eg, 25%, 30%, 35%, 40%, 45%, 50%, 60%, 70%, 75%).

[0109] In the present invention, the skeleton porosity is further limited to ensure good structural mechanical properties and good lithium loading of the lithium composite material.

[0110] In some embodiments, in step S110, the mass ratio of the molten lithium metal to the lithiophilic three-dimensional porous framework is not less than 2 (e.g., 2:1, 2.3:1, 2.5:1, 2.8:1, 3:1, 4:1). The mass of the molten lithium metal is appropriately increased to ensure that the molten lithium metal can fully react with the lithiophilic three-dimensional porous framework, resulting in a lithium composite material with a high lithium content.

[0111] In some embodiments, in step S110, the melting temperature of the molten lithium metal is not less than 180°C, preferably 180-220°C (such as 185°C, 190°C, 200°C, 205°C, 210°C, 215°C).

[0112] In some embodiments, in step S110, during biaxial emulsification stirring, the rotation speed of the emulsification shear is 5000-20000 rpm (e.g., 6000 rpm, 8000 rpm, 10000 rpm, 15000 rpm, 19500 rpm). Biaxial emulsification increases the collision force compared to uniaxial emulsification, which is conducive to the mutual fusion of molten lithium metal and the lithiophilic three-dimensional porous framework.

[0113] In some embodiments, in step S110, during biaxial emulsification stirring, the mass-to-time ratio of emulsification shear is 1-10 mg / s (e.g., 1.5 mg / s, 2 mg / s, 4 mg / s, 6 mg / s, 8 mg / s, 9.5 mg / s).

[0114] In some embodiments, in step S110, during biaxial emulsification stirring, the ratio of the mass of the emulsified shear to the operating volume of the stirring paddle is 1-100 mg / mm 3 (such as 2mg / mm 3 , 5mg / mm 3, 10mg / mm 3 、30mg / mm 3 、60mg / mm 3 , 90mg / mm 3 , 95mg / mm 3 ).

[0115] In some embodiments, in step S220, the first organic solvent is a high-temperature resistant organic solvent, such as tetramethyl silicone oil. It should be noted that the temperature set in step S220 cannot be higher than the temperature tolerance of the high-temperature resistant organic solvent. For example, tetramethyl silicone oil cannot tolerate temperatures above 800°C, resulting in the production of a large amount of byproducts that could affect the purity of the lithium composite material and lead to poor performance.

[0116] In some embodiments, in step S220, during uniaxial emulsification stirring, the rotation speed of the emulsification shear is 8000-20000 rpm (e.g., 8500 rpm, 9000 rpm, 10000 rpm, 15000 rpm, 19500 rpm). Compared with biaxial emulsification, uniaxial emulsification can avoid collisions between porous lithium-rich particles, thereby avoiding damage to the structure of the porous lithium-rich particles and reducing the lithium loading capacity.

[0117] In some embodiments, in step S220, during uniaxial emulsification stirring, the mass-to-time ratio of emulsification shear is 1-10 mg / s (e.g., 1.5 mg / s, 2 mg / s, 4 mg / s, 6 mg / s, 8 mg / s, 9.5 mg / s).

[0118] In some embodiments, when the lithiophilic three-dimensional porous skeleton is a lithiophilic material after pore-forming treatment, step S100 is further included: mixing the lithiophilic material to be pore-formed and a pore-forming agent, pressing, sintering the pores, and crushing to obtain the lithiophilic three-dimensional porous skeleton after pore-forming treatment.

[0119] In some embodiments, in step S100, the lithiophilic material to be pore-formed includes one or more of zinc oxide, silver oxide, tin oxide, aluminum oxide, lithium oxide, zirconium oxide, cobalt oxide, copper oxide, silicon dioxide, germanium oxide, magnesium oxide, antimony oxide, zinc fluoride, silver fluoride, tin fluoride, aluminum fluoride, lithium fluoride, zirconium fluoride, cobalt fluoride, copper fluoride, silicon fluoride, germanium fluoride, magnesium fluoride, and antimony fluoride.

[0120] In some embodiments, in step S100, the pore-forming agent comprises one or more of graphite, glucose, starch, polystyrene, grains, elemental sulfur, and pore-forming agent PL-05.

[0121] In some embodiments, in step S100, the particle size of the pore-forming agent is 0.02-3.00 μm (e.g., 0.05 μm, 0.2 μm, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 2.8 μm). The pore-forming agent determines the size of the pores in the lithiophilic three-dimensional porous framework. If the pore size is too small, it cannot fuse with the elemental metallic lithium droplets, and if it is too large, it cannot lock the elemental metallic lithium droplets. At the same time, the structure of the lithiophilic three-dimensional porous framework is fragile, so the particle size of the pore-forming agent is crucial. The particle size of the pore-forming agent is preferably such that the pores after sintering can be continuously connected, avoiding dead holes and hindering the entry of elemental metallic lithium droplets.

[0122] In some embodiments, in step S100, the mixing further includes adding a conductive agent, wherein the conductive agent comprises one or more of mesophase carbon, artificial graphite, natural graphite, expanded graphite, single-walled carbon nanotubes, multi-walled carbon nanotubes, amorphous carbon, hard carbon, activated carbon, MAX phase compounds, graphene, and Super P. Preferably, the conductive agent comprises one or more of single-walled carbon nanotubes, multi-walled carbon nanotubes, amorphous carbon, and graphene. The conductive agent is selected based on the conductivity of the lithiophilic material. For example, when the lithiophilic material is a compound, a conductive agent is preferably added to enhance the compound's conductivity. However, when the lithiophilic material is a metal, a conductive agent is not required because the metal itself has excellent conductivity.

[0123] In some embodiments, in step S100, the mass ratio of the lithiophilic material to be pore-formed, the pore-forming agent, and the conductive agent is 1:(0.2-1.5):(0.03-0.1) (e.g., 1:0.25:0.04, 1:0.4:0.05, 1:0.6:0.06, 1:0.8:0.07, 1:1:0.08, 1:1.2:0.085, 1:1.4:0.09). The ratio of the lithiophilic material to be pore-formed, the pore-forming agent, and the conductive agent determines the porosity, pore size, and lithium metal loading of the lithiophilic material structure. If the pore size of the lithiophilic three-dimensional porous framework is small, then the corresponding crushed particle size should also be small, and the corresponding biaxial emulsification speed should be high, and the mass-to-time ratio and mass-to-volume ratio should be small, because the difficulty of lithium metal integration during compounding and the release of lithium ions during charging and discharging should be considered.

[0124] In some embodiments, in step S100, the mixing further comprises adding a solvent, wherein the solvent comprises one or more of water, NMP, ethanol, ethyl acetate, glycerol, propanol, diethyl carbonate, and tetrahydrofuran.

[0125] In some embodiments, in step S100, the mass ratio of the solvent to the total amount of solids is (2-5):1 (e.g., 2.2:1, 2.5:1, 3:1, 3.8:1, 4:1, 4.2:1, 4.8:1).

[0126] In some embodiments, in step S100 , the pressing pressure is 1.0-15.0 MPa (eg, 1.5 MPa, 2 MPa, 5 MPa, 7 MPa, 9 MPa, 11 MPa, 12 MPa, 14 MPa).

[0127] In some embodiments, in step S100, pore-forming sintering is performed by pre-calcining at 150-500°C (e.g., 180°C, 220°C, 250°C, 300°C, 350°C, 380°C, 420°C, 480°C) for 1-10 hours (e.g., 1.5 hours, 2 hours, 4 hours, 6 hours, 8 hours, 9 hours, 9.5 hours), and then sintering at 600-900°C (e.g., 650°C, 700°C, 750°C, 780°C, 800°C, 880°C) for 5-20 hours (e.g., 5.5 hours, 7 hours, 9 hours, 11 hours, 14 hours, 16 hours, 18 hours, 19.5 hours) under a protective atmosphere. The purpose of pre-calcining is to remove the pore-forming agent. It should be noted that oxygen is required in this process. The purpose of sintering by heating under a protective atmosphere (such as an inert gas, such as nitrogen) is to avoid oxidation and decomposition of the conductive agent and to ensure that the inorganic material can be sintered, crystallized and densified, so as to finally obtain a skeleton structure with three-dimensional continuous pores inside.

[0128] In some embodiments, in step S100, the particle size requirement after crushing is 5-50 μm (such as 6 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 40 μm, 45 μm, 48 μm). The crushing operation can lay the foundation for obtaining porous lithium-rich particles of 50 μm and below, ensuring that the particle size of the lithiophilic three-dimensional porous skeleton meets the application requirements and avoids being too small or too large. If the particle size of the lithiophilic three-dimensional porous skeleton is too small, smaller than the size determined by the minimum tension of the elemental metallic lithium droplet, it will not be able to load lithium metal, and will eventually cause the lithium metal to be deposited outside the skeleton and exist as pure lithium powder. If the particle size of the lithiophilic three-dimensional porous skeleton is too large, it will be detrimental to the release of lithium in the battery.

[0129] In some embodiments, the emulsion polymerization method for preparing an inert lithium composite material further includes step S330: adding a second organic solvent containing an SEI film additive to the lithium composite material without a coating layer obtained in step S220, stirring to coat the SEI film, and separating to remove the second organic solvent to obtain a lithium composite material with an SEI film.

[0130] The preparation method of the present invention obtains a lithium composite material with a SEI film through step S330, further improves the porous lithium-rich particles (lithium composite material without a coating layer), forms a SEI film on the outside, and can reduce the side reaction of lithium metal in the porous lithium-rich particles with the electrolyte. The SEI film additive is added here in advance to form a SEI film on the surface of the porous lithium-rich particles. Compared with adding the SEI film additive to the electrolyte, the material selection of the second organic solvent can be expanded. Conventional SEI film additives are limited in variety and all contain lithium elements. They can only be dissolved in a small amount of ester organic solvents. The preparation process is cumbersome, the cost is high, there are safety risks in production, and usually ordinary contact with the electrolyte cannot generate an SEI film. The generation of the SEI film can only be completed in the electrochemical process. However, due to the presence of lithium metal in the porous lithium-rich particles of the present application, a variety of SEI film additives that do not contain lithium elements can be directly used, and in a chemical solvent that is not limited to ester organic solvents, they are directly reacted with lithium metal to form a SEI film containing fluorine or other elements. According to the stability of the second organic solvent and lithium metal and the solubility of the SEI membrane additive, the types of selectable second organic solvents and SEI membrane additives have been greatly increased, which greatly reduces the cost of raw materials. At the same time, preparing the SEI membrane outside the battery helps to simplify the complexity of the battery system and reduce factors that interfere with other electrochemical processes. The SEI membrane additive itself does not enter the battery system, which has a positive effect on factors such as the viscosity of the electrolyte. In addition, the amount of SEI membrane additive is selected according to the pore size of the lithiophilic three-dimensional porous skeleton. If the pore size of the lithiophilic three-dimensional porous skeleton is small, the amount of SEI membrane additive is also relatively small. In addition, general stirring can be used for stirring in step S330, and care should be taken to avoid using ultrasonic stirring to destroy or damage the structure of the porous lithium-rich particles.

[0131] In some embodiments, in step S330, the second organic solvent is one or more of ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, ethylene glycol dimethyl ether (DME), tetrahydrofuran (THF), dioxolane (DOL), acetonitrile, N-methylpyrrolidone (NMP), N,N-dimethylformamide (DMF), and dimethyl sulfoxide (DMSO).

[0132] In some embodiments, in step S330, the SEI film additive is one or more of chloroethylene carbonate, ethylene sulfite, propylene sulfite, diethyl sulfite, dimethyl sulfite, anisole, lithium nitrate, fluoroethylene carbonate, vinylene carbonate, antimony fluoride, magnesium fluoride, tin fluoride, aluminum fluoride, and diethyl nitrite.

[0133] In some embodiments, in step S330, the mass ratio of the lithium composite material without the coating layer to the SEI film additive is 1:(0.05-0.5) (e.g., 1:0.08, 1:0.1, 1:0.2, 1:0.3, 1:0.35, 1:0.04, 1:0.48).

[0134] In some embodiments, in step S330, during stirring, the stirring time is 0.5h-6h (such as 0.7h, 1h, 2h, 3h, 4h, 5.5h), and the heating temperature is 25-40°C (such as 28°C, 30°C, 33°C, 35°C, 38°C, 39°C).

[0135] In some embodiments, the emulsion polymerization method for preparing an inert lithium composite material further includes step S440: adding a third organic solvent containing a high molecular weight polymer to the lithium composite material without a coating layer obtained in step S220, or the lithium composite material with an SEI film obtained in step S330, stirring, and coating the ultra-thin protective layer of the polymer to obtain a lithium composite material with a protective layer. The lithium composite material with a protective layer is a porous lithium-rich particle with an ultra-thin protective layer of a polymer or a porous lithium-rich particle with both an ultra-thin protective layer of a polymer and an SEI film, which further improves the stability of the porous lithium-rich particle (lithium composite material without a coating layer). In addition, the polymer coating can also be replaced by carbon coating in a solution system, and the carbon coating can use fine lithium-philic powder, such as ultra-fine graphite powder.

[0136] In some embodiments, in step S440, the third organic solvent is one or more of ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, ethylene glycol dimethyl ether (DME), tetrahydrofuran (THF), dioxolane (DOL), acetonitrile, N-methylpyrrolidone (NMP), N,N-dimethylformamide (DMF), and dimethyl sulfoxide (DMSO).

[0137] In some embodiments, in step S440, the polymer is an ion-conducting or swellable polymer that is also hydrophobic. The polymer should be soluble in the electrolyte or have a relatively large swelling capacity to avoid interfering with ion transport in the battery. Furthermore, the amount of polymer used is selected based on the pore size of the lithiophilic three-dimensional porous framework. If the pore size of the lithiophilic three-dimensional porous framework is small, the amount of polymer used can be relatively small.

[0138] In some embodiments, in step S440, the high molecular polymer is one or more of polyacrylonitrile, polyethylene oxide (PEO), polyoxypropylene, polyvinyl chloride, polyvinylidene fluoride, polycaprolactone, octadecanedioic acid, hexadecanedioic acid, tetradecanedioic acid, and dodecanedioic acid.

[0139] In some embodiments, in step S440, the coating method is one or more of solution coating, in-situ polymerization, melt coating, and spray drying.

[0140] In some embodiments, in step S440 , the thickness of the polymer ultra-thin protective layer is 0.1 μm-1 μm (eg, 0.15 μm, 0.2 μm, 0.25 μm, 0.5 μm, 0.75 μm, 0.9 μm, 0.95 μm).

[0141] In some embodiments, a negative electrode sheet comprises the above-mentioned lithium composite material or the lithium composite material prepared by the above-mentioned preparation method as a negative electrode active material.

[0142] In some embodiments, a lithium battery includes a negative electrode sheet using the above lithium composite material or the lithium composite material prepared by the above preparation method as a negative electrode active material.

[0143] The following is a detailed description using some embodiments.

[0144] Example 1

[0145] A lithium composite material is prepared by emulsion polymerization, comprising the following steps:

[0146] S100: tin fluoride, PL-05, and single-walled carbon nanotubes in a mass ratio of 1:1.5:0.1 were wet-milled in water for 6 h, and then dried in a forced air oven at 100° C. for 5 h;

[0147] The mixed material was then pressed into a pellet at a pressure of 15 MPa, and the pellet was placed in an air furnace at 400°C for 1 hour to form pores, and then sintered in an Ar gas atmosphere at 800°C in a vacuum furnace for 12 hours.

[0148] Finally, the material was crushed and granulated to control the particle size to 5 μm-50 μm, thereby obtaining a lithiophilic three-dimensional porous skeleton. The porosity was measured to be 70.1% by the BET test method, and the particle size D50 was 30 μm by the laser method.

[0149] S110: The lithiophilic three-dimensional porous framework obtained in step S100 is placed in molten lithium metal for mixing, wherein the mass ratio of the lithiophilic three-dimensional porous framework to the molten lithium metal is 1:3, and then high-speed biaxial emulsification shearing is performed at a speed of 15000 rpm, a temperature of 180°C, a mass-time ratio of 1 mg / s, and a mass-volume ratio of 1 mg / mm 3 , mixing time is 1h to obtain a mixture;

[0150] S220: Add tetramethylsilane to the mixture obtained in step S110 and perform high-speed uniaxial emulsification shearing at a speed of 20,000 rpm, a temperature of 180°C, a mass-time ratio of 1 mg / s, and a mass-volume ratio of 1 mg / mm 3 After the emulsification and stirring are stopped, unreacted elemental metallic lithium is removed by filtration to obtain porous lithium-rich particles coated with tetramethylsilane, and the obtained porous lithium-rich particles coated with tetramethylsilane are dispersed in an ethylene carbonate solvent and centrifuged. Different deposition areas are formed according to different specific gravities to obtain porous lithium-rich particles with the tetramethylsilane removed, i.e., a lithium composite material without a coating layer.

[0151] S330: adding an ethylene carbonate solvent containing fluoroethylene carbonate to the lithium composite material without a coating layer obtained in step S220, wherein the mass ratio of fluoroethylene carbonate to the lithium composite material without a coating layer is 0.5:1, stirring at a constant speed to coat the SEI film for 4 hours at a temperature of 40° C., and separating to obtain a lithium composite material with a SEI film;

[0152] S440: Add acetonitrile solvent to the lithium composite material with SEI membrane obtained in step S330, wherein the acetonitrile solvent contains PEO powder whose mass is 4% of the mass of the lithium composite material with SEI membrane, stir at room temperature for 5 hours, and then spray dry and granulate to obtain porous lithium-rich particles coated with a 1 μm polymer ultra-thin protective layer, that is, a lithium composite material having both a polymer ultra-thin protective layer and a SEI membrane.

[0153] The specific process parameters in the above preparation method are shown in Table 1.

[0154] The lithium composite material obtained in this embodiment has a lithium metal mass percentage of 39.5%; a particle size D50 of 30 μm; and a compacted density of 1.63 g / cm 3 The deterioration rate of lithium composite materials in an environment with a dew point of -40°C is 0.35% per hour.

[0155] Examples 2-8

[0156] A lithium composite material is prepared by emulsion polymerization, comprising the following steps:

[0157] S100: The lithiophilic material, pore-forming agent and conductive agent in different mass ratios were wet-milled in water for 6 h, and then dried in a blast oven at 100° C. for 5 h;

[0158] The mixed material was then pressed into a pellet at a pressure of 15 MPa, and the pellet was placed in an air furnace at 400°C for 1 hour to form pores, and then sintered in an Ar gas atmosphere at 800°C in a vacuum furnace for 12 hours.

[0159] Finally, the granulation was performed to obtain lithiophilic three-dimensional porous frameworks with different porosities and particle sizes. The porosities and particle sizes are shown in Table 1.

[0160] S110: placing the lithiophilic three-dimensional porous framework obtained in step S100 into molten lithium metal and mixing, wherein the mass ratio of the lithiophilic three-dimensional porous framework to the molten lithium metal is 1:3, and then performing high-speed biaxial emulsification shearing with different parameter settings for a mixing time of 1 hour to obtain a mixture;

[0161] S220: adding tetramethylsilane to the mixture obtained in step S110, performing high-speed uniaxial emulsification shearing with different parameter settings, filtering to remove unreacted elemental metallic lithium after stopping the emulsification stirring, and obtaining porous lithium-rich microparticles coated with tetramethylsilane. The obtained porous lithium-rich microparticles coated with tetramethylsilane are dispersed in an ethylene carbonate solvent and centrifuged. Different specific gravities lead to different sedimentation areas, thereby obtaining porous lithium-rich microparticles with the tetramethylsilane removed, i.e., a lithium composite material without a coating layer.

[0162] S330: adding a second organic solvent containing a SEI film additive to the lithium composite material without a coating layer obtained in step S220, wherein the SEI film additive and the second organic solvent are different, and the mass ratio of the lithium composite material without a coating layer to the SEI film additive is different, stirring at a uniform speed to coat the SEI film for 4 hours at a temperature of 40° C., and separating to obtain a lithium composite material with a SEI film;

[0163] S440: Add different third organic solvents to the lithium composite material with SEI film obtained in step S330, where the third organic solvent contains different polymer powders with a mass of 4% of the mass of the lithium composite material with SEI film, stir at room temperature for 5 hours, and then spray dry and granulate to obtain lithium composite materials coated with ultra-thin polymer protective layers of different thicknesses.

[0164] The specific process parameters in the above preparation method are shown in Table 1.

[0165] The lithium composite material obtained in the above embodiment, wherein the mass percentage of lithium metal is 25%-40%; the particle size D50 is 10-45 μm; the compacted density is 1.5 g / cm 3 -2g / cm 3 The deterioration rate of lithium composite materials in an environment with a dew point of -40°C is 0.2%-0.8% per hour, see Table 1.

[0166] Example 9

[0167] A lithium composite material is prepared by emulsion polymerization, comprising the following steps:

[0168] S110: Porous silver with a D50 particle size of 30 μm and a porosity of 24.3% was used as a lithiophilic three-dimensional porous framework and placed in molten lithium metal for mixing, wherein the mass ratio of porous silver to molten lithium metal was 1:2.5, followed by high-speed biaxial emulsification shearing at a speed of 20,000 rpm, a temperature of 220°C, a mass-to-time ratio of 1 mg / s, and a mass-to-volume ratio of 50 mg / mm 3 , mixing time is 1h to obtain a mixture;

[0169] S220: Add tetramethylsilane to the mixture obtained in step S110 and perform high-speed uniaxial emulsification shearing at a speed of 20,000 rpm, a temperature of 220°C, a mass-time ratio of 1 mg / s, and a mass-volume ratio of 50 mg / mm 3 After the emulsification and stirring are stopped, unreacted elemental metallic lithium is removed by filtration to obtain porous lithium-rich particles coated with tetramethylsilane, and the obtained porous lithium-rich particles coated with tetramethylsilane are dispersed in an ethylene carbonate solvent and centrifuged. Different deposition areas are formed according to different specific gravities to obtain porous lithium-rich particles with the tetramethylsilane removed, i.e., a lithium composite material without a coating layer.

[0170] S330: Adding a tetrahydrofuran solvent containing lithium nitrate to the lithium composite material without a coating layer obtained in step S220, wherein the mass ratio of lithium nitrate to the lithium composite material without a coating layer is 0.5:1, stirring at a constant speed to coat the SEI film for 4 hours at a temperature of 40° C., and separating to obtain a lithium composite material with a SEI film;

[0171] S440: Adding tetrahydrofuran solvent to the lithium composite material with SEI film obtained in step S330, wherein the tetrahydrofuran solvent contains dodecanedioic acid in an amount of 4% by mass of the lithium composite material with SEI film, stirring at room temperature for 5 hours, and then spray drying and granulating to obtain a lithium composite material coated with a 1 μm polymer ultra-thin protective layer.

[0172] The specific process parameters in the above preparation method are shown in Table 1.

[0173] The lithium composite material obtained in this embodiment has a lithium metal mass percentage of 12.5%; a particle size D50 of 30 μm; and a compacted density of 2.91 g / cm 3 The deterioration rate of lithium composite materials in an environment with a dew point of -40°C is 0.26% per hour.

[0174] Table 1 Process parameters of the preparation method of Examples 1-9

[0175]

[0176]

[0177] Examples 10-15

[0178] A lithium composite material is prepared by emulsion polymerization, comprising the following steps:

[0179] S100: tin fluoride, PL-05, and single-walled carbon nanotubes at different mass ratios (see Table 2 for specific mass ratios) were wet-milled in water for 6 h, and then dried in a forced air oven at 100° C. for 5 h;

[0180] The mixed material was then pressed into a pellet at a pressure of 15 MPa, and the pellet was placed in an air furnace at 400°C for 1 hour to form pores, and then sintered in an Ar gas atmosphere at 800°C in a vacuum furnace for 12 hours.

[0181] Finally, the granulation was performed to obtain lithiophilic three-dimensional porous frameworks with different porosities and particle sizes. The porosities and particle sizes are shown in Table 2.

[0182] S110: The lithiophilic three-dimensional porous framework obtained in step S100 is placed in molten lithium metal for mixing, wherein the mass ratio of the lithiophilic three-dimensional porous framework to the molten lithium metal is 1:2, and then high-speed biaxial emulsification shearing is performed at a speed of 15000 rpm, a temperature of 180°C, a mass-time ratio of 1 mg / s, and a mass-volume ratio of 1 mg / mm 3 , mixing time is 1h to obtain a mixture;

[0183] S220: Add tetramethylsilane to the mixture obtained in step S110 and perform high-speed uniaxial emulsification shearing at a speed of 20,000 rpm, a temperature of 180°C, a mass-time ratio of 1 mg / s, and a mass-volume ratio of 1 mg / mm 3 After the emulsification and stirring are stopped, unreacted elemental metallic lithium is removed by filtration to obtain porous lithium-rich particles coated with tetramethylsilane, and the obtained porous lithium-rich particles coated with tetramethylsilane are dispersed in an ethylene carbonate solvent and centrifuged. Different deposition areas are formed according to different specific gravities to obtain porous lithium-rich particles with the tetramethylsilane removed, i.e., a lithium composite material without a coating layer.

[0184] S330: adding an ethylene carbonate solvent containing fluoroethylene carbonate to the lithium composite material without a coating layer obtained in step S220, wherein the mass ratio of fluoroethylene carbonate to the lithium composite material without a coating layer is 0.5:1, stirring at a constant speed to coat the SEI film for 4 hours at a temperature of 40° C., and separating to obtain a lithium composite material with a SEI film;

[0185] S440: Add acetonitrile solvent to the lithium composite material with SEI film obtained in step S330, wherein the acetonitrile solvent contains PEO powder with a mass of 4% of the mass of the lithium composite material with SEI film, stir at room temperature for 5 hours, and then spray dry and granulate to obtain a lithium composite material coated with a 1 μm polymer ultra-thin protective layer.

[0186] The specific process parameters in the above preparation method are shown in Table 2.

[0187] The lithium composite material obtained in this embodiment has a lithium metal mass percentage of 8%-40%; a particle size D50 of 8-48 μm; and a compacted density of 1 g / cm 3 -2g / cm 3 The deterioration rate of lithium composite materials in an environment with a dew point of -40°C is 0.15%-0.7% per hour, see Table 2.

[0188] Table 2 Process parameters of the preparation method of Examples 10-15

[0189]

[0190]

[0191] Example 16

[0192] A lithium composite material is specifically prepared by an emulsion polymerization method. The difference from Example 1 is that step S330 is not included, and step S440 is directly performed after the lithium composite material without a coating layer obtained in step S220: an acetonitrile solvent is added to the lithium composite material without a coating layer obtained in step S220, wherein the acetonitrile solvent contains PEO powder with a mass that is 4% of the mass of the lithium composite material without a coating layer, and the mixture is stirred at room temperature for 5 hours, followed by spray drying and granulation to obtain a lithium composite material coated with a 1 μm polymer ultra-thin protective layer.

[0193] The lithium composite material obtained in this embodiment has a lithium metal mass percentage of 39.5%; a particle size D50 of 30 μm; and a compacted density of 1.61 g / cm 3 The deterioration rate of lithium composite materials in an environment with a dew point of -40°C is 0.38% per hour.

[0194] Example 17

[0195] A lithium composite material is different from embodiment 1 in that step S440 is not included, and step S330 is to obtain a lithium composite material having a SEI film.

[0196] The lithium composite material obtained in this embodiment has a lithium metal mass percentage of 39.5%; a particle size D50 of 30 μm; and a compacted density of 1.64 g / cm 3The deterioration rate of lithium composite materials in an environment with a dew point of -40°C is 0.36% per hour.

[0197] Example 18

[0198] A lithium composite material is different from Example 1 in that step S330 and step S440 are not included, and step S220 obtains a lithium composite material without a coating layer.

[0199] The lithium composite material obtained in this embodiment has a lithium metal mass percentage of 39.5%; a particle size D50 of 30 μm; and a compacted density of 1.75 g / cm 3 The deterioration rate of lithium composite materials in an environment with a dew point of -40°C is 0.73% per hour.

[0200] Comparative Example 1

[0201] A lithium composite material is prepared by emulsion polymerization. The difference from Example 7 is that iron oxide is used instead of a lithiophilic material as the three-dimensional porous framework. The specific preparation is as follows:

[0202] S100: Iron oxide, elemental sulfur, and MAX in a mass ratio of 1:1.5:0.03 were wet-milled in water for 6 h, and then dried in a forced air oven at 100° C. for 5 h;

[0203] The mixed material was then pressed into a pellet at a pressure of 15 MPa, and the pellet was placed in an air furnace at 400°C for 1 hour to form pores, and then sintered in an Ar gas atmosphere at 800°C in a vacuum furnace for 12 hours.

[0204] Finally, crushing and granulation were carried out, and the crushing particle size was controlled to be 5μm-50μm to obtain a three-dimensional porous skeleton. The porosity was measured by BET test method to be 70.9%, and the particle size D50 was measured by laser method to be 30μm.

[0205] S110: The three-dimensional porous framework obtained in step S100 is placed in molten lithium metal for mixing, wherein the mass ratio of the three-dimensional porous framework to the molten lithium metal is 1:3, and then high-speed biaxial emulsification shearing is performed at a speed of 20,000 rpm, a temperature of 200°C, a mass-time ratio of 1 mg / s, and a mass-volume ratio of 1 mg / mm 3 , mixing time is 1h to obtain a mixture;

[0206] S220: Add tetramethylsilane to the mixture obtained in step S110 and perform high-speed uniaxial emulsification shearing at a speed of 20,000 rpm, a temperature of 200°C, a mass-to-time ratio of 1 mg / s, and a mass-to-volume ratio of 1 mg / mm 3After the emulsification and stirring are stopped, unreacted elemental metallic lithium is removed by filtration to obtain porous lithium-containing microparticles coated with tetramethylsilane, and the obtained porous lithium-containing microparticles coated with tetramethylsilane are dispersed in an ethylene carbonate solvent and centrifuged. Different specific gravities lead to different sedimentation areas, thereby obtaining porous lithium-containing microparticles with the tetramethylsilane removed.

[0207] S330: adding ethyl methyl carbonate solvent containing diethyl sulfite to the porous lithium-containing microparticles obtained in step S220, wherein the mass ratio of diethyl sulfite to the porous lithium-containing microparticles is 0.5:1, stirring at a constant speed to coat the SEI film for 4 hours at a temperature of 40° C., and separating to obtain SEI film-coated porous lithium-containing microparticles;

[0208] S440: Add ethyl methyl carbonate solvent to the SEI membrane-coated porous lithium-containing microparticles obtained in step S330, where the ethyl methyl carbonate solvent contains hexadecanedioic acid at a mass of 4% of the mass of the SEI membrane-coated porous lithium-containing microparticles, stir at room temperature for 5 hours, and then spray dry and granulate to obtain porous lithium-containing microparticles coated with a 1 μm ultra-thin polymer protective layer, i.e., a lithium composite material.

[0209] The specific process parameters in the above preparation method are shown in Table 3.

[0210] The lithium composite material obtained in this comparative example has a lithium metal mass percentage of 12.5%; a particle size D50 of 30 μm; and a compacted density of 1.53 g / cm 3 The deterioration rate of lithium composite materials in an environment with a dew point of -40°C is 2.08% per hour.

[0211] Comparative Example 2

[0212] A lithium composite material is prepared by emulsion polymerization. The difference from Example 1 is that large particles of a lithiophilic material, zinc oxide, are used as a raw material. A carbon powder pore former accounting for only 0.2 of the mass ratio of zinc oxide is used. A lithiophilic three-dimensional porous framework with a particle size D50 of 100 μm and a porosity of 22.1% is obtained. In addition, the stirring conditions in S110, biaxial emulsification, and S220, uniaxial emulsification are controlled. The specific preparation is as follows:

[0213] S100: Zinc oxide, carbon powder, and Super P in a mass ratio of 1:0.2:0.05 were wet-milled in water for 6 h, and then dried in a forced air oven at 100°C for 5 h;

[0214] The mixed material was then pressed into a pellet at a pressure of 15 MPa, and the pellet was placed in an air furnace at 400°C for 1 hour to form pores, and then sintered in an Ar gas atmosphere at 800°C in a vacuum furnace for 12 hours.

[0215] Finally, the material was crushed and granulated to obtain a lithiophilic three-dimensional porous framework with a particle size D50 of 100 μm and a porosity of 22.1%.

[0216] S110: The lithiophilic three-dimensional porous framework obtained in step S100 is placed in molten lithium metal for mixing, wherein the mass ratio of the lithiophilic three-dimensional porous framework to the molten lithium metal is 1:3, and then biaxial emulsification shearing is performed at a speed of 1000 rpm, a temperature of 200°C, a mass-time ratio of 100 mg / s, and a mass-volume ratio of 500 mg / mm 3 , mixing time is 1h to obtain a mixture;

[0217] S220: Add tetramethylsilane to the mixture obtained in step S110 and perform uniaxial emulsification shearing at a speed of 1000 rpm, a temperature of 200°C, a mass time ratio of 100 mg / s, and a mass volume ratio of 500 mg / mm 3 After the emulsification and stirring are stopped, unreacted elemental metallic lithium is removed by filtration to obtain porous lithium-containing microparticles coated with tetramethylsilane, and the obtained porous lithium-containing microparticles coated with tetramethylsilane are dispersed in an ethylene carbonate solvent and centrifuged. Different specific gravities lead to different sedimentation areas, thereby obtaining porous lithium-containing microparticles with the tetramethylsilane removed.

[0218] S330: Adding an ethylene carbonate solvent containing fluoroethylene carbonate to the porous lithium-containing microparticles obtained in step S220, wherein the mass ratio of fluoroethylene carbonate to the porous lithium-containing microparticles is 0.5:1, stirring at a constant speed to coat the SEI film for 4 hours at a temperature of 40° C., and separating to obtain SEI-film-coated porous lithium-containing microparticles;

[0219] S440: Add acetonitrile solvent to the SEI membrane-coated porous lithium-containing microparticles obtained in step S330, wherein the acetonitrile solvent contains PEO powder with a mass of 4% of the mass of the SEI membrane-coated porous lithium-containing microparticles, stir at room temperature for 5 hours, and then spray dry and granulate to obtain porous lithium-containing microparticles coated with a 1 μm polymer ultra-thin protective layer, i.e., a lithium composite material.

[0220] The specific process parameters in the above preparation method are shown in Table 3.

[0221] The lithium composite material obtained in this comparative example has a lithium metal mass percentage of 8.7%; a particle size D50 of 100 μm; and a compacted density of 3.66 g / cm 3 The deterioration rate of lithium composite materials in an environment with a dew point of -40°C is 1.71% per hour.

[0222] Comparative Example 3

[0223] A lithium composite material is prepared by emulsion polymerization. The difference from Example 1 is that the temperature in S110, biaxial emulsification, and S220, uniaxial emulsification are controlled to be 100° C., and the other settings are the same as those in Example 1.

[0224] The specific process parameters in the above preparation method are shown in Table 3, and the specific parameters of the obtained lithium composite material are also shown in Table 3.

[0225] Comparative Examples 4 and 5

[0226] A lithium composite material is specifically prepared by emulsion polymerization. The difference from Example 1 is that the particle size of the crushing and granulation in S100 is controlled, and the other settings are the same as those in Example 1.

[0227] The specific process parameters in the above preparation method are shown in Table 3, and the specific parameters of the obtained lithium composite material are also shown in Table 3.

[0228] Comparative Examples 6 and 7

[0229] A lithium composite material is specifically prepared by emulsion polymerization. The difference from Example 1 is that the mass ratio of the lithiophilic material to be pore-formed, the pore-forming agent, and the conductive agent in S100 is controlled, especially the mass of the pore-forming agent. The other settings are the same as those in Example 1.

[0230] The specific process parameters in the above preparation method are shown in Table 3, and the specific parameters of the obtained lithium composite material are also shown in Table 3.

[0231] Comparative Examples 8 and 9

[0232] A lithium composite material is specifically prepared by emulsion polymerization. The difference from Example 1 is that the mass ratio of the lithiophilic material to be pore-formed, the pore-forming agent, and the conductive agent in S100 is controlled, especially the mass of the conductive agent. The other settings are the same as those in Example 1.

[0233] The specific process parameters in the above preparation method are shown in Table 3, and the specific parameters of the obtained lithium composite material are also shown in Table 3.

[0234] Table 3 Process parameters of the preparation method of comparative examples 1-10

[0235]

[0236]

[0237] test

[0238] All porosities in the present invention were measured using the BET test method, and all particle sizes were measured using a laser method. Furthermore, the lithium composite materials obtained in Examples 1-18 and Comparative Examples 1-9 were subjected to performance testing, including stability testing and electrochemical performance testing. The specific test settings are as follows:

[0239] (1) Air stability test

[0240] A) Place 100 mg of the test sample in a 10 cm diameter watch glass, spread it evenly, and leave it open in an ambient dew point of -40°C.

[0241] B) After standing for 24 h, the sample was poured into 1 L of anhydrous ethanol solution and stirred at 300 rpm for 10 min. The unreacted solid was filtered to obtain the supernatant. 1 ml of the supernatant was taken for ICP testing to calculate the total lithium metal content of the sample: stability residual amount = total lithium metal content × 100%; deterioration ratio = (1-stability residual amount) / 24.

[0242] (2) Electrochemical testing

[0243] A) The active material lithium titanate, the conductive agent Super P, the carbon nanotubes, the binder polyvinylidene fluoride (PVDF) were mixed and stirred uniformly with N-methylpyrrolidone (NMP) in a mass ratio of 97.0:1.0:0.5:1.5 to prepare a positive electrode slurry (solid content of 70%), which was coated on the current collector aluminum foil with a thickness of 160 μm, dried at 70°C, and rolled at 4 MPa at room temperature, then punched and cut into The disc is made into a positive electrode;

[0244] B) The sample in the embodiment or comparative example, the conductive agent Super P, the carbon nanotubes, the binder polyvinylidene fluoride (PVDF) and N-methylpyrrolidone (NMP) were mixed and stirred uniformly in a mass ratio of 97.0:1.0:0.5:1.5 to prepare a negative electrode slurry (solid content of 70%), which was coated on a current collector aluminum foil with a thickness of 10 μm, dried at 70°C, and rolled at 4 MPa at room temperature, then punched and cut into The disc is made into a negative electrode;

[0245] C) Coin cells were assembled in a glove box in the following order: negative electrode cap - nickel foam - negative electrode sheet - separator - positive electrode sheet - gasket - spring - positive electrode cap. After placing the separator, three drops of electrolyte were added onto the separator. The electrolyte consisted of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) (EC:EMC:DEC volume ratio = 1:1:1), containing 1.0 M LiPF6.

[0246] The diameter of the positive electrode sheet is 10mm, the diameter of the negative electrode sheet is 12mm, the diameter of the diaphragm is 19mm, and the size of the battery case (positive and negative electrode covers) is 20mm. The diaphragm is a 12μm thick ceramic-coated isolating membrane. Place the assembled button cell in the mold of the hydraulic sealing machine, lock it, and shake the handle to apply pressure >500kg / cm 2 , then unlock and remove the sealed button battery. Test the button battery as follows:

[0247] 1) First coulombic efficiency and capacity retention test:

[0248] At 25°C, the charge and discharge cycle characteristics of the button battery were tested using a blue electric test cabinet. The battery was charged and discharged at a charge and discharge rate of 0.1C in the voltage range of 0.1V-3V. Specifically, the battery was discharged at a constant current of 0.1C to 0.1V, and then discharged at a constant voltage of 0.1V to 0.1V, with a cut-off current of 0.02C and left for 5 minutes. The battery was then charged at 0.1C to 3V and left for 5 minutes. The charge and discharge capacity after the first cycle was recorded.

[0249] Again, discharge at a constant current of 0.1C to 0.1V, then charge at a constant voltage at 0.1V to a cutoff current of 0.02C, let it sit for 5 minutes, charge at 0.1C to 3V, let it sit for 5 minutes, and repeat this cycle. After 200 charge / discharge cycles, record the charge and discharge capacity after the 200th cycle, and determine the battery's first coulombic efficiency (first efficiency) and the capacity retention rate after 200 cycles.

[0250] 2) Rate discharge performance test:

[0251] At 25°C, discharge the button cell at 0.33C constant current and constant voltage to 0.1V, set the cutoff current to 0.02C, and wait for 5 minutes. Then charge it at 0.33C to 3V, record the 0.33C discharge capacity, and wait for 5 minutes. Then discharge it at 0.33C constant current and constant voltage to 0.1V, set the cutoff current to 0.02C, and wait for 5 minutes. Then charge it at 3C to 3V, record the 3C discharge capacity.

[0252] 3C discharge capacity retention rate (ie, 3C rate, %) = 3C discharge capacity / 0.33C discharge capacity × 100%.

[0253] The test results are recorded in Table 4.

[0254] Table 4 Performance test results of lithium composite materials obtained from Examples 1-18 and Comparative Examples 1-9

[0255]

[0256] The particle size of the lithium composite material obtained in Example 1 is smaller than that in Example 2. Under the same pore-forming agent ratio, the area of ​​lithium metal exposed to the surface of the lithium composite material particles filled in the pores of the lithiophilic three-dimensional porous framework accounts for the same proportion of the particle surface. The larger the particle size, the smaller the specific surface area of ​​the lithium composite material particles formed, the relatively small amount of lithium exposed to the outside, and the better the stability. In addition, the pore-forming agent glucose forms a small amount of amorphous carbon relative to PL-05 during the removal process, which further reduces the pore width and lowers the specific surface area. At the same time, Example 2 has a faster rotation speed and more stirring per unit time, which facilitates the full contact reaction between the lithium metal and the framework. The remaining unembedded space inside the three-dimensional framework is less, and the resulting capacity also has certain advantages. In contrast, Example 1 has a larger specific surface area due to its small particle size and more chemical reactions with the external environment. Therefore, the sample prepared in Example 2 has fewer side reactions with the outside world, thereby making the first effect, cycle performance, and deterioration ratio better than Example 1, while the 3C rate is lower than Example 1.

[0257] Figure 1 The surface morphology of the lithiophilic three-dimensional porous skeleton of Example 2 is shown, and it can be observed that the pore size is about 1-2 microns. Figure 2 This is the surface morphology of the lithiophilic three-dimensional porous skeleton after being compounded with lithium metal, SEI membrane and polymer ultra-thin protective layer. It can be seen that the pores on the surface have been basically evenly filled with lithium metal, SEI membrane and polymer ultra-thin protective layer. Due to the centrifugal treatment, the surface of the lithium composite material is slightly lower than the surface of the lithiophilic three-dimensional porous skeleton, that is, it is slightly concave. Figure 3 This is the XRD result of the lithium composite material of Example 2, in which lithium metal, magnesium oxide, and the alloy phase formed by the two can be clearly detected. Figure 4 This is a rate performance test diagram of the lithium composite material of Example 2, which can reach 74.1% of the capacity at a 3C rate. Figure 5 This is a test chart of the cycle performance of the lithium composite material in Example 2. After 200 cycles at 0.1C, 88% of the original capacity is still retained. Figure 6 This is the first cycle charge and discharge curve of the lithium composite material in Example 2. The first efficiency obtained by dividing the two is 89.9%.

[0258] By comparison, the particle size of the lithium composite material obtained in Example 1 is larger than that of Example 3. It is found that the 3C rate performance of Example 1 is lower than that of Example 3. At the same time, the rotation speed of Example 1 is faster and more stirring is carried out per unit time, which facilitates the full contact and reaction between the elemental metallic lithium and the lithiophilic three-dimensional porous skeleton, and the obtained capacity also has certain advantages. In addition, the thickness of the polymer protective layer of Example 3 is less than that of Example 1, which results in its stability being lower than that of Example 1.

[0259] By comparing the lithium composite material obtained in Example 1 with that in Example 4, it was found that the mass-to-volume ratio in the uniaxial and biaxial emulsification stirring of Example 1 was much smaller than that in Example 4, which resulted in more complete mixing of the substances in Example 1 during high-speed stirring. Because the frequency of contact between the unit substance and the stirring head was higher under the same stirring head conditions, the stirring in Example 1 was more complete, and the remaining pore space in the lithiophilic three-dimensional porous skeleton was smaller, so the lithium content was higher than that in Example 4. At the same time, the SEI membrane in Example 1 had more additives and a thicker coating layer, so the battery electrolyte consumed less surface metal lithium. Therefore, the capacity, stability and cycle performance of Example 1 were all higher than those of Example 4, while the rate performance was lower than that of Example 4.

[0260] By comparing the lithium composite material obtained in Example 1 with Examples 5 and 6, it was found that the biaxial emulsification speed of Examples 5 and 6 was relatively low, resulting in a low degree of reaction between elemental metallic lithium and the lithiophilic three-dimensional porous skeleton during high-speed stirring, and the presence of more unfilled space. Therefore, the lithium content was somewhat lower than that of Example 1. In addition, the SEI membrane additive in Example 5 was smaller than that in Example 1, and the generated SEI membrane was less, and the cycle performance was lower than that of Example 1, but the rate performance was the same as that of Example 1 or was somewhat improved.

[0261] By comparing the lithium composite material obtained in Example 1 with that in Example 7, it is found that Example 7 contains less conductive agent than Example 1, and the interface impedance is significantly higher than that of Example 1 when working at a high rate during the cycle, so its rate performance is lower than that of Example 1.

[0262] By comparing the lithium composite material obtained in Example 1 with Examples 8 and 9, it was found that the proportion of pore-forming agent in Example 8 was lower, the space left for filling with elemental metallic lithium to form lithium metal was smaller, and the porosity was lower. Similarly, the porosity of Example 9 itself was relatively low. Therefore, the lithium content, i.e., the capacity, of Examples 8 and 9 was lower than that of Example 1, so the capacity and cycle performance were lower than that of Example 1. However, due to the small pore size, the area of ​​lithium metal exposed on the outer surface was smaller, and the deterioration rate was lower, so the stability was improved and the initial effect was also improved.

[0263] By comparing the lithium composite material obtained in Example 1 with the lithium composite materials obtained in Examples 16, 17, and 18, it was found that the lithium composite material of Example 16 did not have an ultra-thin polymer protective layer, the lithium composite material of Example 17 did not have an SEI film coating, and the lithium composite material of Example 18 had neither an ultra-thin polymer protective layer nor an SEI film coating, resulting in their stability being inferior to that of Example 1. In addition, the absence of an ultra-thin polymer protective layer in the lithium composite material of Example 16 resulted in poor air stability and slightly poor cycle stability; the absence of an SEI film coating in the lithium composite material of Example 17 resulted in poor cycle stability but essentially unchanged air stability, because the lithium metal in the battery composed of the lithium composite material of Example 17 was continuously consumed by the electrolyte during the cycle, and therefore the cycle performance was much lower than that of Example 1; the lithium composite material of Example 18 had neither an ultra-thin polymer protective layer nor an SEI film coating, and had a better rate capability, but both air stability and cycle stability were inferior to those of Example 1.

[0264] Comparison of the lithium composite material obtained in Example 7 with Comparative Example 1 reveals that Comparative Example 1 uses non-lithium-philic iron oxide. During uniaxial stirring, the molten elemental lithium metal cannot fully fuse with it. During biaxial stirring, the lack of binding force causes the elemental lithium metal and the three-dimensional porous framework to easily separate. Therefore, at the same porosity as Example 7, the lithium content is very low, and the lithium replenishment performance is greatly reduced, resulting in poor cycle and rate performance. Furthermore, since the elemental lithium metal cannot completely fill the pores of the three-dimensional porous framework, the exposed lithium metal specific surface area is also large and cannot be fully protected. Therefore, the initial efficiency and stability are also lower than those of Example 1.

[0265] By comparing the lithium composite material obtained in Example 1 with that in Comparative Example 2, it was found that Comparative Example 2 used a large-particle lithiophilic three-dimensional porous skeleton with a small amount of pore-forming agent, resulting in an excessively long and thin pore size, and the pore size was smaller than the lower limit of the surface tension of elemental metallic lithium. The molten elemental metallic lithium microspheres could not enter the pores of the lithiophilic three-dimensional porous skeleton, resulting in a low lithium content. The lithium metal contained was basically distributed on the surface of the particles and in shallow pores. Therefore, the stability, cycle, first effect and rate performance were poor.

[0266] By comparing the lithium composite material obtained in Example 1 with Comparative Example 3, it was found that in Comparative Example 3, the elemental metallic lithium was not melted due to the low emulsification temperature, so the lithiophilic three-dimensional porous skeleton could not undergo alloying reaction with the elemental metallic lithium, and thus had no lithium capacity.

[0267] By comparing Examples 1, 10 and 11 and Comparative Examples 4 and 5, it can be seen that the particle size of the lithiophilic three-dimensional porous skeleton has a significant effect on the air stability and electrochemical properties of the prepared lithium composite material. Within a reasonable particle size range, a small particle size helps to improve the rate performance, but reduces the air stability, first effect and cycle stability. For a particle size that is too small, the lithiophilic three-dimensional porous skeleton cannot effectively protect the lithium metal, resulting in a significant decrease in air stability and first effect, and no application value. Although an excessively large pore size has a certain improvement on air stability and first effect, it has a great negative impact on rate performance and is also of no application value.

[0268] By comparing Example 1, Example 12 and Example 13 and Comparative Example 6 and Comparative Example 7, it can be seen that the ratio of pore-forming agent is closely related to the stability and electrochemical performance of lithium composite materials. Within a reasonable range, the lithium composite material prepared by the ratio is stable in structure and meets the application needs. The higher the pore-forming agent ratio, such as Example 1, the greater the lithium content accommodated, the more lithium can be supplemented, and the rate and cycle performance are significantly improved. The less the pore-forming agent ratio, such as Example 12, has a significant positive effect on stability improvement. Outside the reasonable range, too low a pore-forming agent ratio leads to too low a lithium content, and the pore size is too small, and the elemental metal lithium cannot enter, and has no use value. The excessively high pore-forming agent ratio weakens the stability of the structure and does not play a wrapping role for the lithium metal frame. The lithium metal is still mostly exposed to the external environment, so the stability and first effect are almost the same as those of ordinary lithium powder, and the purpose and effect of the present invention are not achieved. In addition, among the same type of pore-forming agent, the smaller the ratio, the more evenly it is dispersed in the mixed grinding with other substances, and the smaller the pore size formed after dispersion, the smaller the contact area between the lithium metal and the outside world. Microspheres with the same pore size but larger particle size have smaller specific surface area and are therefore more stable.

[0269] By comparing Example 1, Example 14 and Example 15 and Comparative Example 8 and Comparative Example 9, it can be seen that the ratio of the conductive agent is closely related to the rate performance of the lithium composite material. The content of the conductive agent has a certain degree of influence on the lithium capacity and stability, but has a significant impact on the rate performance. The content of the conductive agent within a reasonable range can ensure that the rate performance meets the application requirements. The less conductive agent, the lower the rate performance. Outside the reasonable range, a too low proportion of the conductive agent causes the lithium powder to be unable to meet the high rate requirements, generates a huge impedance under high current, and hinders the release and deposition of lithium. Excessive conductive agent content causes a waste of resources, cannot further improve the rate performance, and simultaneously reduces the lithium content, reduces the capacity, and has a negative effect on the cycle stability.

Claims

1. A lithium composite material, characterized in that The invention relates to a lithium-rich composite material comprising a lithiophilic three-dimensional porous skeleton loaded with lithium metal, wherein the lithiophilic three-dimensional porous skeleton loaded with lithium metal comprises a lithiophilic three-dimensional porous skeleton and lithium metal loaded in the pores of the lithiophilic three-dimensional porous skeleton; wherein the particle size of the lithium composite material is 5 μm-50 μm; The lithium metal is a lithium salt; Fluoride as a lithiophilic three-dimensional porous framework; The particle size of the lithiophilic three-dimensional porous skeleton is 5 μm-50 μm; the lithiophilic three-dimensional porous skeleton is a lithiophilic material after pore-forming treatment with a pore-forming agent, and the particle size of the pore-forming agent is 0.02-3.00 μm; Through a biaxial emulsification process, elemental metallic lithium droplets are allowed to enter the pores of the lithiophilic three-dimensional porous skeleton. At the same time, the elemental metallic lithium droplets in contact with the pores of the lithiophilic three-dimensional porous skeleton are combined with the lithiophilic three-dimensional porous skeleton on the pore surface to form lithium salts. Then, through uniaxial emulsification shear stirring, the excess unreacted molten lithium is separated from the lithium composite material generated by the reaction, and finally a micron-level lithium composite material is obtained.

2. The lithium composite material according to claim 1, wherein The lithium composite material further includes a first coating layer and / or a second coating layer coated on the outside of the lithiophilic three-dimensional porous skeleton loaded lithium metal; the first coating layer is a SEI film; the second coating layer is an ultra-thin polymer protective layer or a carbon coating layer.

3. The lithium composite material according to claim 2, wherein The lithiophilic three-dimensional porous framework is one or more of zinc fluoride, silver fluoride, tin fluoride, aluminum fluoride, lithium fluoride, zirconium fluoride, cobalt fluoride, copper fluoride, silicon fluoride, germanium fluoride, magnesium fluoride and antimony fluoride after pore formation treatment; And / or, the raw materials of the SEI film include one or more of chloroethylene carbonate, ethylene sulfite, propylene sulfite, diethyl sulfite, dimethyl sulfite, anisole, lithium nitrate, fluoroethylene carbonate, and vinylene carbonate; And / or, the high molecular weight polymer in the ultra-thin polymer protective layer is one or more of polyacrylonitrile, polyethylene oxide, polypropylene oxide, polyvinyl chloride, polyvinylidene fluoride, and polycaprolactone; And / or, the thickness of the ultra-thin polymer protective layer is 0.1 μm-1 μm.

4. The lithium composite material according to any one of claims 1 to 3, wherein The porosity of the lithiophilic three-dimensional porous framework is 20% to 80%; And / or, the mass percentage of lithium metal in the lithium composite material is 5%-40%; And / or, the compacted density of the lithium composite material is 1g / cm 3 -3g / cm 3 ; And / or, the lithium composite material deteriorates at a rate of 0.1% to 0.8% per hour in an environment with a dew point of -40°C.

5. A method for preparing the lithium composite material according to any one of claims 1 to 4, characterized in that: Prepared by emulsion polymerization, comprising the following steps: S110: mixing the lithiophilic three-dimensional porous framework and molten lithium metal, and biaxially emulsifying and stirring to obtain a mixture; S220: adding a first organic solvent to the mixture obtained in step S110, uniaxially emulsifying and stirring, and then removing unreacted molten lithium metal and the first organic solvent, respectively, to obtain a lithium composite material without a coating layer.

6. The preparation method according to claim 5, wherein In step S110, the mass ratio of the molten lithium metal to the lithiophilic three-dimensional porous framework is not less than 2; And / or, in step S110, the melting temperature of the molten lithium metal is 180-220°C; And / or, in step S110, during the biaxial emulsification stirring, the rotation speed of the emulsification shear is 5000-20000 rpm; and / or, in step S110, during the biaxial emulsification stirring, the mass-to-time ratio of the emulsification shear is 1-10 mg / s; And / or, in step S110, during the biaxial emulsification stirring, the ratio of the mass of the emulsified shear to the operating volume of the stirring paddle is 1-100 mg / mm 3 ; and / or, in step S220, the first organic solvent is a high temperature resistant organic solvent; And / or, in step S220, during the uniaxial emulsification stirring, the rotation speed of the emulsification shear is 8000-20000 rpm; and / or, in step S220, during the uniaxial emulsification stirring, the mass-to-time ratio of the emulsification shear is 1-10 mg / s; And / or, in step S220, during the uniaxial emulsification stirring, the ratio of the mass of the emulsification shear to the operating volume of the stirring paddle is 1-100 mg / mm 3 ; And / or, in step S220, the removal method is one or more of centrifugation, sedimentation and filtration.

7. The preparation method according to claim 5, wherein When the lithiophilic three-dimensional porous framework is a lithiophilic material that has been subjected to pore-forming treatment, the preparation method further comprises step S100 of pore-forming: mixing the lithiophilic material to be pore-formed with a pore-forming agent, pressing, sintering to form pores, and crushing to obtain the lithiophilic three-dimensional porous framework that has been subjected to pore-forming treatment; In step S100, the pore-forming agent comprises one or more of graphite, glucose, starch, polystyrene, grains, and elemental sulfur; in step S100, the mass ratio of the lithiophilic material to be pore-formed to the pore-forming agent is 1:(0.2-1.5); and / or, in step S100, the particle size of the pore-forming agent is 0.02-3.00 μm; And / or, in step S100, the mixing further includes adding a conductive agent, wherein the conductive agent comprises one or more of artificial graphite, natural graphite, single-walled carbon nanotubes, multi-walled carbon nanotubes, amorphous carbon, and graphene; in step S100, the mass ratio of the lithiophilic material to be pore-formed, the pore-forming agent, and the conductive agent is 1:(0.2-1.5):(0.03-0.1); And / or, in step S100, the mixing further comprises adding a solvent, wherein the solvent comprises one or more of water, NMP, ethanol, ethyl acetate, glycerol, propanol, diethyl carbonate, and tetrahydrofuran; in step S100, the mass ratio of the solvent to the total amount of solids is (2-5):1; in step S100, the pressing pressure is 1.0-15.0 MPa; And / or, in step S100, the pore-forming sintering is: first pre-sintered at 150-500°C for 1-10h, and then sintered at 600-900°C for 5-20h under a protective atmosphere; in step S100, the particle size after crushing is required to be 5-50μm.

8. The preparation method according to claim 5, wherein The preparation method further includes step S330 and / or step S440, wherein: Step S330: adding a second organic solvent containing an SEI film additive to the lithium composite material without a coating layer obtained in step S220, stirring to coat the SEI film, and separating to remove the second organic solvent to obtain a lithium composite material with an SEI film; Step S440: Add a third organic solvent containing a high molecular weight polymer to the lithium composite material without a coating layer obtained in step S220 or the lithium composite material with a SEI film obtained in step S330, stir, and coat the ultra-thin polymer protective layer to obtain a lithium composite material with a protective layer.

9. The preparation method according to claim 8, wherein In step S330, the second organic solvent is one or more of ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, ethylene glycol dimethyl ether, tetrahydrofuran, dioxolane, acetonitrile, N-methylpyrrolidone, N,N-dimethylformamide, and dimethyl sulfoxide; And / or, in step S330, the SEI film additive is one or more of chloroethylene carbonate, ethylene sulfite, propylene sulfite, diethyl sulfite, dimethyl sulfite, anisole, lithium nitrate, fluoroethylene carbonate, and vinylene carbonate; And / or, in step S330, the mass ratio of the lithium composite material without the coating layer to the SEI film additive is 1:(0.05-0.5); And / or, in step S330, during the stirring, the stirring time is 0.5h-6h and the heating temperature is 25-40°C; and / or, in step S440, the third organic solvent is one or more of ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, ethylene glycol dimethyl ether, tetrahydrofuran, dioxolane, acetonitrile, N-methylpyrrolidone, N,N-dimethylformamide, and dimethyl sulfoxide; And / or, in step S440, the polymer is a polymer that is ion conductive or swellable and hydrophobic; in step S440, the polymer is one or more of polyacrylonitrile, polyethylene oxide, polypropylene oxide, polyvinyl chloride, polyvinylidene fluoride, and polycaprolactone; And / or, in step S440, the coating method is one or more of solution coating, in-situ polymerization, melt coating, and spray drying.

10. An application of a lithium composite material, characterized in that: Applicable to a negative electrode sheet, the negative electrode sheet comprising the lithium composite material according to any one of claims 1 to 4 or the lithium composite material prepared by the preparation method according to any one of claims 5 to 9 as a negative electrode active material; Or: applied to a lithium battery, the lithium battery comprising a negative electrode sheet using the lithium composite material according to any one of claims 1 to 4 or the lithium composite material prepared by the preparation method according to any one of claims 5 to 9 as the negative electrode active material.

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