Metal lithium composite material with interface stabilizing function as well as preparation method and application of metal lithium composite material

Abstract

The invention discloses a metal lithium composite material with an interface stabilizing function as well as a preparation method and application of the metal lithium composite material. The metal lithium composite material comprises a lithium-containing core, an interface stabilizing layer is arranged on the surface of the lithium-containing core, the interface stabilizing layer comprises a porous elastic framework and an interface stabilizer, the porous elastic framework is integrally formed by single-walled carbon nanotubes and multi-walled carbon nanotubes, and the interface stabilizer comprises a carbon fluoride material. The carbon fluoride material exists on at least one of the surface of the lithium-containing inner core, the outer surface, the inner surface and pores of the porous elastic framework. By utilizing an in-situ synthesis technology, lithium fluoride is generated in situ at the interface of the lithium-containing core and the carbon fluoride material, so that the interface stability is improved, and meanwhile, the conductivity between the lithium-containing cores is improved. The flexibility of the single-walled carbon nanotubes and the rigidity of the multi-walled carbon nanotubes are utilized to construct an integrally formed porous elastic skeleton, so that the problem of volume expansion of the lithium-containing core is effectively relieved. The metal lithium composite material has good interface stability and cycle performance.

Description

Technical Field

[0001] The present invention relates to the technical field of secondary batteries, and in particular to a metal lithium composite material with an interface stabilization function, a preparation method thereof, and uses thereof. Background Art

[0002] Lithium-ion batteries are rechargeable secondary batteries with advantages such as high voltage and large capacity. While lithium metal anodes are widely used in lithium batteries due to their low potential and high theoretical specific capacity, their use is limited by their susceptibility to side reactions and the formation of dendrites during charge and discharge, resulting in poor cycling performance. Therefore, improving the interfacial stability of lithium metal is a hot topic in current research.

[0003] At present, the methods used to improve the interfacial stability of metallic lithium negative electrodes are mainly the following: (1) inhibiting the corrosion of the electrolyte on the surface of the lithium negative electrode through a surface protective layer, such as CN116565210A; (2) using conductive carbon nanotubes as a carrier of the lithium negative electrode to alleviate the volume expansion problem of metallic lithium, such as CN116504973A; (3) constructing a multi-level pore structure to build a multi-level electrolyte and metallic lithium contact interface, while dividing and confining the metallic lithium in a micron-scale space, which is conducive to the full reaction and deposition of metallic lithium; the multi-level structure provides a three-dimensional path for the conduction of electrons, inhibiting the growth of metallic lithium dendrites, such as CN107732204A.

[0004] Each of these methods has its advantages and disadvantages. For example, a surface protective layer alone cannot effectively address the volume expansion of metallic lithium. Untreated conductive carbon nanotubes hinder the uniform deposition of metallic lithium, leading to the formation and growth of lithium dendrites. Furthermore, the construction of a multi-level pore structure requires complex manufacturing processes and is costly.

[0005] Based on this, how to solve the problems of volume expansion of metallic lithium powder and uneven deposition of metallic lithium, while enhancing the interface stability between metallic lithium powder particles, has become an urgent problem to be solved. Summary of the Invention

[0006] To address the above technical issues, the present invention provides a metal lithium composite material, its preparation method, and its use. The composite material comprises an interfacial stabilization layer on the surface of a lithium-containing core. The interfacial stabilization layer comprises a porous elastic framework integrally formed of single-walled carbon nanotubes and multi-walled carbon nanotubes and an interfacial stabilizer. This layer can simultaneously address the volume expansion, uneven deposition, and interfacial instability between powder particles of powdered lithium-containing materials such as metal lithium powder, significantly improving the cycling stability of the metal lithium composite material.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is:

[0008] In a first aspect, the present invention provides a metal lithium composite material, which includes a lithium-containing core, and an interface stabilization layer is provided on the surface of the lithium-containing core, wherein the interface stabilization layer includes a porous elastic skeleton integrally formed of single-walled carbon nanotubes and multi-walled carbon nanotubes and an interface stabilizer; the interface stabilizer includes a fluorinated carbon material, and the fluorinated carbon material is present on the surface of the lithium-containing core, the outer surface, the inner surface and at least one location in the pores of the porous elastic skeleton.

[0009] In the present invention, the interfacial stabilization layer comprises a porous elastic framework integrally formed from single-walled carbon nanotubes and multi-walled carbon nanotubes. This porous elastic framework combines the flexibility of single-walled carbon nanotubes with the rigidity of multi-walled carbon nanotubes, providing a stable structure and space for the volume expansion of the lithium-containing core. Furthermore, the porous elastic framework allows for the transport of lithium ions and electrons simultaneously, providing dual regulation of current density and lithium ion transport, enabling the uniform deposition of metallic lithium.

[0010] In the present invention, the fluorine in the carbon fluoride material located on the surface of the lithium-containing core, in the portion directly in contact with the lithium-containing core surface, reacts with the active metallic lithium on the lithium-containing core surface to form lithium fluoride, thereby in-situ constructing a stable SEI film. Simultaneously, the carbon in the carbon fluoride material can conduct electrons, effectively regulating the interface state between the lithium-containing cores and the uniform distribution of current density. The carbon fluoride material located on the outer surface, inner surface, or pores of the porous elastic framework acts as a fluorine source, reacting with the active lithium during the charge and discharge process to continuously generate lithium fluoride, stabilizing the interface of the composite material. Furthermore, it can also form a conductive network with carbon nanotubes to regulate the uniform deposition of metallic lithium.

[0011] The interfacial stabilization layer, a composite of single-walled carbon nanotubes, multi-walled carbon nanotubes, and fluorinated carbon materials, simultaneously addresses uneven lithium metal deposition, volume expansion of lithium metal, and interface instability between the lithium-containing core and the lithium-containing core. The metal-lithium composite material exhibits excellent cycling performance and safety. The interfacial stabilization layer can be adjusted based on the size of the lithium-containing core, enabling modification of the lithium-containing core at nanometer, submicrometer, and micrometer scales.

[0012] Optionally, the fluorinated carbon material includes at least one of fluorinated graphite, fluorinated carbon, fluorinated carbon black, fluorinated nanocarbon fibers (VGCF), fluorinated graphene microsheets, fluorinated graphene oxide, or fluorinated carbon nanotubes.

[0013] Optionally, the atomic ratio of carbon to fluorine in the fluorinated carbon material is greater than 0 and less than 1.25, for example, it can be 0.1, 0.25, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2 or 1.25, including but not limited to the listed point values. The atomic ratio can take into account both the in situ construction of a complete SEI and the regulation of electron transport, and is preferably 0.5-1.

[0014] Optionally, the size of the carbon fluoride material is 1 nm to 50 μm, preferably a nanoscale carbon fluoride material with a size of 3 nm to 500 nm, more preferably 5 to 300 nm. It should be noted that the nanoscale in the nanoscale carbon fluoride material only requires that the size in at least one of the three-dimensional directions is nanoscale.

[0015] As a preferred technical solution of the present invention, the mass ratio of the single-walled carbon nanotubes, multi-walled carbon nanotubes and fluorinated carbon material is 1: (0.05-100): (0.05-100), and the interface stabilization layer constructed by the single-walled carbon nanotubes, multi-walled carbon nanotubes and fluorinated carbon material of the specific mass ratio has a stable structure and good interface contact, so that the metal lithium composite material has good cycle performance. The mass ratio can be 1: 0.05: 0.05, 1: 0.075: 0.05, 1: 0.1: 0.075, 1: 0.5: 0.5, 1: 1: 1, 1: 2: 5, 1: 5: 3, 1: 10: 5, 1: 20: 10, 1: 30: 50, 1: 40: 60, 1: 50: 50, 1: 60: 30, 1: 70: 80, 1: 90: 90 or 1: 100: 100, etc., including but not limited to the listed point values. Less fluorinated carbon material means less SEI formed on the surface of the lithium-containing core, which is effective for interface regulation but not conducive to improving the interface stability between the lithium-containing cores; less single-walled carbon nanotubes means a looser porous elastic skeleton, which has limited effect on alleviating the volume expansion of the lithium-containing core; more single-walled carbon nanotubes means that due to the greater flexibility of single-walled carbon nanotubes and the denser porous elastic skeleton, the effect of regulating lithium ions and current density uniformity is poor. The ratio is preferably 1:(0.1-50):(0.1-50), and more preferably 1:(0.5-20):(0.5-20).

[0016] Optionally, the lithium-containing core comprises metallic lithium powder and / or lithium alloy powder, with an average particle size of 1-100 μm, preferably 10-50 μm.

[0017] Optionally, the alloying elements in the lithium alloy powder include at least one of tin, gold, barium, bismuth, calcium, germanium, platinum, lead, antimony, silver, boron, magnesium, indium, gallium, aluminum, or zinc. During lithium extraction from the metal-lithium composite material, the alloying elements remain in place and do not participate, thereby improving the stability of the core. The alloying elements have an affinity for lithium, which can regulate the uniform deposition of the metallic lithium during deposition.

[0018] Optionally, the length of the single-walled carbon nanotubes is 0.5 μm to 50 μm, preferably 1-20 μm. If the length of the single-walled carbon nanotubes is too short, it is difficult to form a continuous and stable interfacial stabilization layer. If the length of the single-walled carbon nanotubes is too long, it is difficult to disperse evenly, and the interfacial stabilization layer is unevenly distributed on the surface of the lithium-containing core.

[0019] Optionally, the outer diameter of the single-walled carbon nanotube is 1-2 nm.

[0020] Optionally, the number of layers of the multi-walled carbon nanolayer is greater than or equal to 2 and less than or equal to 15 layers, preferably 2-10 layers.

[0021] Optionally, the outer diameter of the multi-walled carbon nanotubes is less than 30 nm, preferably 4-20 nm.

[0022] Optionally, the multi-walled carbon nanotubes contain a lithium-phobic element, and the lithium-phobic element includes at least one of copper, nickel, titanium, chromium, vanadium, cobalt, manganese or iron. In the prior art, the regulation of the deposition of metallic lithium is concentrated on the deposition site where lithium affinity is introduced. In the present invention, the inventors found during the experiment that the use of multi-walled carbon nanotubes containing a lithium-phobic element modification layer can also achieve the regulation of metallic lithium deposition. The reason is speculated to be: the uneven deposition of metallic lithium is caused by the uneven current density on the surface of the material. Although the lithium-phobic element modification layer cannot induce uniform deposition of metallic lithium, it has good electronic conductivity, which makes the current density on the surface of the material more uniform, thereby solving the problem of uneven deposition of metallic lithium and the generation and growth of lithium dendrites.

[0023] Optionally, based on the mass of the multi-walled carbon nanotubes being 100%, the mass content of the lithium-phobic element is greater than 30%, preferably 50-80%. A lower mass content may limit the uniform deposition of metallic lithium, while a higher mass content may result in a lower gram capacity of the metallic lithium composite.

[0024] Optionally, the thickness of the interfacial stabilization layer is between 0.5 μm and 30 μm. A thicker thickness results in a lower metallic lithium content and a lower gram capacity of the metallic lithium composite material. A thinner thickness has a limited effect on mitigating core volume expansion, and is preferably between 3 and 20 μm. The thickness of the interfacial stabilization layer can be adjusted based on the mass ratio of the single-walled carbon nanotubes, multi-walled carbon nanotubes, and fluorinated carbon material, thereby simultaneously achieving effective control of ions and electrons and stabilizing the interface between the lithium-containing cores.

[0025] Optionally, based on the mass of the metal lithium composite material being 100%, the mass fraction of the core in the metal lithium composite material is greater than 50%, preferably greater than 70%, and more preferably greater than 85%.

[0026] In a second aspect, the present invention provides a method for preparing the metal lithium composite material as described in the first aspect, the preparation method comprising the following steps:

[0027] (1) mixing an organic solvent, single-walled carbon nanotubes, multi-walled carbon nanotubes, and a fluorinated carbon material to obtain a mixture;

[0028] (2) mixing the mixture with a lithium-containing powder material and spray drying the mixture to obtain the metal lithium composite material;

[0029] Alternatively, the mixture and the lithium-containing powder material are entangled at a high speed at a rotation speed of 5000 rpm or more to remove the organic solvent to obtain the metal lithium composite material; the organic solvent is inert to the lithium-containing powder material.

[0030] In the present invention, the organic solvent is not specifically limited, as long as it is inert to the lithium metal powder and / or lithium alloy powder, does not undergo violent chemical reactions, and can be used as a solvent. For example, it can be any one of liquid alkanes having 4 to 20 carbon atoms, liquid halogenated hydrocarbons having 4 to 20 carbon atoms, toluene, xylene, liquid paraffin, tetrahydrofuran, N,N-dimethylformamide, or silicone oil, or a combination of at least two thereof.

[0031] Optionally, the step (1) includes the following operations: pre-dispersing the single-walled carbon nanotubes in an organic solvent, and then adding multi-walled carbon nanotubes and fluorinated carbon materials to mix to obtain a mixture; pre-dispersing the carbon nanotubes makes the single-walled carbon nanotubes more evenly dispersed, and can better form a stable and uniform interface stabilization layer with the multi-walled carbon nanotubes and fluorinated carbon materials.

[0032] Optionally, the mixing method in step (2) includes at least one of mechanical stirring, ultrasonic dispersion or high-speed winding at a rotation speed of 5000 rpm or above.

[0033] In a third aspect, the present invention provides an electrode comprising the metal lithium composite material as described in the first aspect. The electrode may be an electrode made of pure metal lithium composite material, or a composite electrode comprising the metal lithium composite material and graphite or silicon-based materials.

[0034] Compared with the prior art, the present invention has at least the following beneficial effects:

[0035] 1. By constructing a porous elastic skeleton formed by single-walled carbon nanotubes and multi-walled carbon nanotubes, the volume expansion problem of metallic lithium during charging and discharging is alleviated, and the effect is better than that of the porous skeleton formed by single-walled carbon nanotubes or multi-walled carbon nanotubes;

[0036] 2. The porous elastic skeleton can conduct electrons and ions simultaneously, regulate lithium ion transmission and current density, effectively solve the problem of uneven deposition of metallic lithium, avoid the growth of lithium dendrites, and thus improve the safety and service life of the battery;

[0037] 3. The fluorine in the fluorinated carbon material can react with metallic lithium or lithium alloy to generate lithium fluoride to construct a stable SEI film in situ. At the same time, the carbon in the fluorinated carbon material can improve electron conduction, solve the problem of lithium dendrite generation and growth, and solve the problem of unstable interface between lithium-containing cores.

[0038] 4. The cyclic stability of the lithium metal composite material modified by single-walled carbon nanotubes, multi-walled carbon nanotubes and fluorinated carbon materials is better than that of the lithium metal composite material modified by any two of single-walled carbon nanotubes, multi-walled carbon nanotubes or fluorinated carbon materials;

[0039] 5. By designing the mass ratio of single-walled carbon nanotubes, multi-walled carbon nanotubes and fluorinated carbon materials, the thickness of the interface stabilization layer can be adjusted. The thickness and composition of the interface stabilization layer of the metal lithium composite material can be adjusted and customized. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 These are the symmetrical battery test curves of Example 2, Example 3, and Example 5;

[0041] Figure 2 These are the symmetrical battery test curves of Example 2, Example 6, and Example 7;

[0042] Figure 3 These are the symmetrical battery test curves of Example 2, Comparative Example 1, Comparative Example 2, and Comparative Example 3.

[0043] Note: Some discontinuous areas in the test curve are caused by different sampling parameter settings of the test equipment. DETAILED DESCRIPTION

[0044] The present invention will be further described in detail below with reference to the examples. The following examples are only used to explain the principle of the present invention and are not to be construed as limiting the present invention.

[0045] Example 1

[0046] This embodiment provides a metal lithium composite material, the metal lithium composite material comprising metal lithium powder, an interfacial stabilization layer of single-walled carbon nanotubes, multi-walled carbon nanotubes, and fluorinated carbon black in a mass ratio of 1:0.05:0.05 provided on the surface of the metal lithium powder, the interfacial stabilization layer having a thickness of 30 μm, and a mass fraction of the metal lithium powder of approximately 50%;

[0047] The preparation method of the metal lithium composite material comprises the following steps:

[0048] (1) 2 g of single-walled carbon nanotubes (Article No. 104477, outer diameter 1-2 nm, length 5-30 μm, Jiangsu Xianfeng Nanomaterial Technology Co., Ltd.), 0.1 g of multi-walled carbon nanotubes (GT-400, outer diameter 20-30 nm, length 3-12 μm, Shandong Dazhan Nanomaterial Co., Ltd.) and 0.1 g of fluorinated carbon black (Shanghai Furui Fine Chemical Co., Ltd., fluorine-carbon ratio 1.0, particle size 50-100 nm) were added to 200 L of heptane, ultrasonically dispersed, and mixed uniformly to obtain a first mixture;

[0049] (2) adding 2.2 g of metallic lithium powder having an average particle size of 10 μm to the first mixture and mixing at a rotation speed of 9000 rpm for 30 min to obtain a second mixture;

[0050] (3) The second mixture is filtered to remove heptane, and then dried at 100° C. for 24 hours under vacuum conditions to obtain the metal lithium composite material.

[0051] Example 2

[0052] This embodiment provides a metal lithium composite material, the metal lithium composite material comprising metal lithium powder, an interface stabilization layer of single-walled carbon nanotubes, multi-walled carbon nanotubes, and graphite fluoride in a mass ratio of 1:100:100 provided on the surface of the metal lithium powder, the thickness of the interface stabilization layer being 1 μm, and the mass fraction of the metal lithium powder being approximately 90%;

[0053] The preparation method of the metal lithium composite material comprises the following steps:

[0054] (1) adding 0.01 g of single-walled carbon nanotubes (Article No. 104477, outer diameter 1-2 nm, length 5-30 μm, Jiangsu Xianfeng Nanomaterial Technology Co., Ltd.), 1 g of multi-walled carbon nanotubes (GT-400, outer diameter 20-30 nm, length 3-12 μm, Shandong Dazhan Nanomaterial Co., Ltd.) and 1 g of fluorinated graphite (Aladdin, F302204, specification or purity: ≥56 wt% F, D90 ≤8 μm) to 150 L of p-xylene, dispersing at a high speed of 9000 rpm, and mixing uniformly to obtain a first mixture;

[0055] (2) adding 20.1 g of metallic lithium powder having an average particle size of 50 μm to the first mixture, and mechanically stirring the mixture at a speed of 3000 rpm for 60 min to obtain a second mixture;

[0056] (3) The second mixture was spray-dried at an air inlet temperature of 220° C., an air outlet temperature of 90° C., an atomization pressure of 1.2 MPa, and an injection volume of 150 mL / min to obtain the metal lithium composite material.

[0057] Example 3

[0058] Compared with Example 2, the only difference is that the mass ratio of single-walled carbon nanotubes, multi-walled carbon nanotubes and graphite fluoride is replaced with 1:0.5:0.5, and the other conditions are the same.

[0059] Example 4

[0060] Compared with Example 2, the only difference is that the mass ratio of single-walled carbon nanotubes, multi-walled carbon nanotubes and graphite fluoride is replaced with 1:20:20, and the other conditions are the same.

[0061] Example 5

[0062] Compared with Example 2, the only difference is that the mass ratio of single-walled carbon nanotubes, multi-walled carbon nanotubes and graphite fluoride is replaced with 1:50:50, and the other conditions are the same.

[0063] Example 6

[0064] Compared with Example 2, the only difference is that the mass ratio of single-walled carbon nanotubes, multi-walled carbon nanotubes and fluorinated graphite is replaced with 1:0.01:0.01, and the other conditions are the same.

[0065] Example 7

[0066] Compared with Example 2, the only difference is that the mass ratio of single-walled carbon nanotubes, multi-walled carbon nanotubes and graphite fluoride is replaced with 1:200:200, and the other conditions are the same.

[0067] Example 8

[0068] Compared with Example 2, the only difference is that the multi-walled carbon nanotubes are replaced with nickel-plated multi-walled carbon nanotubes (Beike Nano, HQNANO-CNTs-009-6A, nickel content greater than 60% by mass, outer diameter 8-15 nm, length 50 μm), and the other conditions are the same.

[0069] Example 9

[0070] Compared with Example 2, the only difference is that the metallic lithium powder is replaced by lithium-zinc alloy powder (the mass fraction of zinc is 10 wt %), and the other conditions are the same.

[0071] Example 10

[0072] Compared with Example 2, the only difference is that the metallic lithium powder is replaced by lithium magnesium zinc alloy powder (the mass fraction of magnesium is 2 wt %, and the mass fraction of zinc is 3%), and the other conditions are the same.

[0073] Comparative Example 1

[0074] Compared with Example 2, the only difference is that the interface stabilization layer contains only single-walled carbon nanotubes and multi-walled carbon nanotubes, and does not contain fluorinated graphite.

[0075] Comparative Example 2

[0076] Compared with Example 2, the only difference is that the interface stabilization layer contains only fluorinated graphite and multi-walled carbon nanotubes, and does not contain single-walled carbon nanotubes.

[0077] Comparative Example 3

[0078] Compared with Example 2, the only difference is that the interface stabilization layer contains only fluorinated graphite and single-walled carbon nanotubes, but does not contain multi-walled carbon nanotubes.

[0079] Comparative Example 4

[0080] Compared with Example 2, the only difference is that the fluorinated graphite in the interface stabilization layer is replaced by ordinary graphite.

[0081] Comparative Example 5

[0082] Compared with Example 2, the only difference is that the metal lithium composite material does not include an interface stabilizing layer, but only contains metal lithium powder.

[0083] Comparative Example 6

[0084] Compared with Example 2, the only difference is that the interface stabilization layer contains only fluorinated graphite and does not contain single-walled carbon nanotubes and multi-walled carbon nanotubes.

[0085] Comparative Example 7

[0086] Compared with Example 2, the only difference is that the interface stabilization layer contains only single-walled carbon nanotubes and does not contain fluorinated graphite and multi-walled carbon nanotubes.

[0087] Comparative Example 8

[0088] Compared with Example 2, the only difference is that the interface stabilization layer contains only multi-walled carbon nanotubes and does not contain fluorinated graphite and single-walled carbon nanotubes.

[0089] Testing of the performance of metal lithium composite materials:

[0090] The lithium metal composite materials in Examples 1-10 and Comparative Examples 1-8 were pressed onto copper foam to make electrodes, and then assembled into symmetrical cells. The electrolyte was 1M LiTFSIDOL / DME (volume ratio 1:1), and the cycling performance was tested. 2 and 1mAh / cm 2 Under the conditions of , the test results are shown in Table 1. The test cutoff condition is that the overpotential exceeds 1V or a short circuit occurs.

[0091] Table 1

[0092] Sources Number of cycles Example 1 783 Example 2 851 Example 3 975 Example 4 1086 Example 5 1016 Example 6 496 Example 7 683 Example 8 882 Example 9 1180 Example 10 1225 Comparative Example 1 531 Comparative Example 2 535 Comparative Example 3 560 Comparative Example 4 596 Comparative Example 5 205 Comparative Example 6 300 Comparative Example 7 337 Comparative Example 8 263

[0093] From Table 1 we can see that:

[0094] (1) The cycling performance of the lithium metal composite material of Example 2 is poorer than that of Examples 3 to 5 (the test curves of Examples 2, 3 and 5 are shown in FIG. Figure 1This is because the mass ratio of single-walled carbon nanotubes, multi-walled carbon nanotubes and graphite fluoride in Examples 3 to 5 is more conducive to constructing a stable interface modification layer, and the effect of regulating the volume expansion of metal lithium powder during charge and discharge, uniform deposition and interface stability between metal lithium powder particles is better than that in Example 2;

[0095] (2) The cycle performance of the lithium metal composite materials in Examples 6 and 7 is worse than that in Example 2 (test curves as shown in FIG. Figure 2 This is because the mass ratios of single-walled carbon nanotubes, multi-walled carbon nanotubes, and graphite fluoride in Examples 6 and 7 are not within the preferred range of the present invention, and are therefore limited in their effectiveness in solving the problems of volume expansion of metallic lithium, uneven deposition, generation and growth of lithium dendrites, and interface stability between metallic lithium powder particles.

[0096] (3) The cycling performance of the lithium metal composite material of Example 8 is better than that of Example 2. This is because the nickel-plated multi-walled carbon nanotubes used in Example 8 as one of the components of the interface stabilization layer have good conductivity, making the current density on the surface of the material more uniform than that in Example 2, thus solving the problem of uneven deposition of lithium metal and the generation and growth of lithium dendrites.

[0097] (4) The cycle performance of the metal lithium composite materials of Examples 9 and 10 is better than that of Example 2. This is because the core of Examples 9 and 10 is lithium alloy powder. When the metal lithium is stripped, the alloy elements do not participate in the lithium extraction and remain in place, playing a role in stabilizing the core; when the metal lithium is deposited, the alloy elements have an affinity for lithium and regulate the uniform deposition of the metal lithium;

[0098] (5) The cycle performance of the lithium metal composite material of Example 2 is better than that of Comparative Examples 1-8 (the symmetrical battery test curves of Example 2, Comparative Example 1, Comparative Example 2 and Comparative Example 3 are as follows) Figure 3 As shown), this is because the interface stabilization layer in Comparative Examples 1-3 and Comparative Examples 6-8 is composed of any one or two of single-walled carbon nanotubes, multi-walled carbon nanotubes and fluorinated graphite, and the interface stabilization layer in the present invention is not formed (the interface stabilization layer in the present invention includes a porous elastic skeleton and an interface stabilizer integrally formed by single-walled carbon nanotubes and multi-walled carbon nanotubes, and the interface stabilizer includes a fluorinated carbon material, and the fluorinated carbon material is present on the surface of the lithium-containing core, the outer surface, the inner surface and at least one position in the pores of the porous elastic skeleton), the structural stability and the interface stability between the metal lithium powder particles are worse than those in Example 2, and the effects of alleviating the volume expansion of metal lithium, regulating the uniform deposition of metal lithium and inhibiting the growth of lithium dendrites are worse than those of the present invention; in Comparative Example 5, there is only metal lithium powder and no interface stabilization layer, which characterizes the performance of the metal lithium powder itself.

[0099] In summary, the metal lithium composite material provided by the present invention is provided with an interface stabilization layer on the surface of the lithium-containing core, and the interface stabilization layer includes a porous elastic skeleton and an interface stabilizer integrally formed by single-walled carbon nanotubes and multi-walled carbon nanotubes, and the interface stabilizer includes a fluorinated carbon material, and the fluorinated carbon material is present on the surface of the lithium-containing core, the outer surface, the inner surface and the pores of the porous elastic skeleton. The fluorinated carbon material reacts with the lithium-containing core to generate lithium fluoride, thereby realizing in situ construction of the SEI film, so that the interface between the lithium-containing core particles is relatively stable; the porous elastic skeleton integrally formed by single-walled carbon nanotubes and multi-walled carbon nanotubes alleviates the problem of volume expansion of metal lithium during charging and discharging; the porous elastic skeleton can conduct electrons and ions at the same time, regulate lithium ion transmission and current density, effectively solve the problem of uneven deposition of metal lithium, and avoid the growth of lithium dendrites; single-walled carbon nanotubes, multi-walled carbon nanotubes and fluorinated carbon materials cooperate with each other to simultaneously regulate lithium ion transmission and electron transmission, effectively solving the problems of volume expansion of the lithium-containing core, uneven deposition of metal lithium, and generation and growth of lithium dendrites.

Claims

1. A metal lithium composite material with interface stabilization function, characterized in that: The metal lithium composite material comprises a lithium-containing core, an interface stabilization layer is provided on the surface of the lithium-containing core, and the interface stabilization layer comprises a porous elastic skeleton integrally formed of single-walled carbon nanotubes and multi-walled carbon nanotubes and an interface stabilizer; The interface stabilizer includes a fluorinated carbon material, and the fluorinated carbon material exists on the surface of the lithium-containing core, the outer surface, the inner surface and the pores of the porous elastic skeleton.

2. The lithium metal composite material according to claim 1, wherein: The fluorinated carbon material comprises at least one of fluorinated graphite, fluorinated activated carbon, fluorinated carbon black, fluorinated carbon nanofibers, fluorinated graphene, fluorinated graphene oxide or fluorinated carbon nanotubes; Preferably, the atomic ratio of carbon to fluorine in the fluorinated carbon material is greater than 0 and less than 1.25, preferably 0.5-1; Preferably, the mass ratio of the single-walled carbon nanotubes, multi-walled carbon nanotubes and fluorinated carbon material is 1:(0.05-100):(0.05-100), preferably 1:(0.1-50):(0.1-50), and more preferably 1:(0.5-20):(0.5-20).

3. The lithium metal composite material according to claim 1 or 2, characterized in that: The lithium-containing core comprises metallic lithium powder and / or lithium alloy powder, with an average particle size of 1-100 μm, preferably 10-50 μm; Preferably, the alloying elements in the lithium alloy powder include at least one of tin, gold, barium, bismuth, calcium, germanium, platinum, lead, antimony, silver, boron, magnesium, indium, gallium, aluminum or zinc.

4. The lithium metal composite material according to any one of claims 1 to 3, characterized in that: The length of the single-walled carbon nanotube is 0.5 μm to 50 μm, preferably 1-20 μm.

5. The lithium metal composite material according to any one of claims 1 to 4, characterized in that: The number of layers of the multi-walled carbon nanotubes is greater than or equal to 2 and less than or equal to 15 layers, preferably 2-10 layers; Preferably, the outer diameter of the multi-walled carbon nanotubes is less than 30 nm, preferably 4-20 nm.

6. The lithium metal composite material according to any one of claims 1 to 5, characterized in that: The multi-walled carbon nanotubes contain lithium-phobic elements, and the lithium-phobic elements include at least one of copper, nickel, titanium, chromium, vanadium, cobalt, manganese or iron; Preferably, based on 100% of the mass of the multi-walled carbon nanotubes, the mass content of the lithium-phobic element is above 30%, preferably 50-80%.

7. The lithium metal composite material according to any one of claims 1 to 6, characterized in that: The thickness of the interfacial stabilization layer is between 0.5 μm and 30 μm, preferably 3-20 μm; Preferably, based on the mass of the metal lithium composite material being 100%, the mass fraction of the lithium core in the metal lithium composite material is 50% or more, preferably 70% or more, and more preferably 85% or more.

8. A method for preparing the metal lithium composite material according to any one of claims 1 to 7, characterized in that: The preparation method comprises the following steps: (1) mixing an organic solvent, single-walled carbon nanotubes, multi-walled carbon nanotubes, and a fluorinated carbon material to obtain a mixture; (2) mixing the mixture with a lithium-containing powder material and spray drying the mixture to obtain the metal lithium composite material; Alternatively, the mixture and the lithium-containing powder material are entangled at a high speed at a rotation speed of 5000 rpm or more to remove the organic solvent to obtain the metal lithium composite material; the organic solvent is inert to the lithium-containing powder material.

9. The preparation method according to claim 8, characterized in that Step (1) includes the following operations: Pre-dispersing single-walled carbon nanotubes in an organic solvent, then adding multi-walled carbon nanotubes and a fluorinated carbon material to mix to obtain a mixture; Preferably, the mixing in step (2) comprises at least one of mechanical stirring, ultrasonic dispersion or high-speed winding at a rotation speed of 5000 rpm or above.

10. An electrode, characterized in that: The electrode comprises the metal lithium composite material according to any one of claims 1 to 8.

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