Methods for controlled nucleation growth of lithium metal, lithium metal composite materials and applications

Abstract

This invention discloses a method for controllable nucleation growth of lithium metal, a lithium metal composite material, and its applications. The method includes the following steps: depositing a nucleation layer on the surface of a lithium metal layer, the nucleation layer containing transition metal carbides (MXenes); and nucleating and growing lithium metal based on the two-dimensional sheets of the MXenes to form a passivated lithium metal. The method of this invention is simple and easy to implement, starting from the concept of nucleation on the surface of lithium metal, avoiding the complex design and preparation of lithium metal microstructures, and has excellent practicality. The resulting lithium metal composite material, as a negative electrode for lithium metal-based batteries, exhibits excellent cycle performance; after multiple charge-discharge cycles, the surface remains smooth without obvious dendrite formation.

Description

[0001] This application is a divisional application, the parent application being the invention patent application filed on June 20, 2019, with application number 201910536478.9 and invention title "Lithium Metal Composite Electrode with Controllable Nucleation and Growth of Lithium Metal and Preparation Method Thereof". Technical Field

[0002] This invention belongs to the field of lithium metal materials, specifically relating to a method for controllable nucleation growth of lithium metal, lithium metal composite materials, and their applications. Background Technology

[0003] Lithium metal batteries, as one of the most widely used and promising batteries in the world today, have advantages such as high specific energy and discharge performance, long operating and storage life, high safety performance, and low cost. With the emergence of new high-capacity lithium batteries such as Li-S batteries, Li-air batteries, and Li-carbon dioxide batteries, the safe application of lithium metal anodes has become a decisive factor in the next generation of energy storage systems.

[0004] Lithium metal has long been considered the ideal negative electrode material for rechargeable lithium batteries, possessing an extremely high theoretical specific capacity (3860 mAh·g). -1 Low density (0.59 g·cm³) -3 It possesses excellent properties such as a negative electrochemical potential (approximately -3.04V compared to a standard hydrogen electrode). However, due to uncontrollable deposition during the charging and discharging process of lithium metal anodes, it suffers from dendrite growth and low coulombic efficiency (CE) during repeated charging / discharging, which has prevented the commercialization of rechargeable batteries based on lithium metal anodes to date.

[0005] Recently, research focus has shifted to controlling the deposition and growth of lithium metal to suppress lithium dendrite growth and regulate lithium cycling behavior. Controlling lithium nucleation with noble metals has become a new research direction. However, the cost of noble metals and the materials required for designing nanostructures limit their practical applications. Therefore, developing simple strategies for lithium metal design and designing and synthesizing possible composite electrodes to control lithium nucleation and growth behavior, thereby achieving superior electrochemical performance and cost-effectiveness, is essential for the further industrialization of lithium metal. Summary of the Invention

[0006] To address the scientific and technological problem of uncontrolled deposition during the charging and discharging of lithium metal anodes, which leads to disordered dendrite growth during repeated charging / discharging, this invention proposes a method for controllable nucleation growth of lithium metal and a lithium metal composite material.

[0007] The first aspect of the present invention provides a method for controllable nucleation growth of lithium metal, the steps of which include: setting a nucleation layer on the surface of a lithium metal layer, the nucleation layer containing transition metal carbides MXenes, wherein lithium metal can nucleate and grow based on two-dimensional sheets of the transition metal carbides MXenes to deposit and form passivated lithium metal.

[0008] In some embodiments, the more specific steps of forming a nucleation layer on the surface of the lithium metal layer include: configuring the transition metal carbide MXenes into a dispersion, dispersing it on the surface of the medium layer, drying it to form a nucleation layer containing the transition metal carbide MXenes; and then contacting and combining the nucleation layer with lithium metal to form the lithium metal layer on the surface of the nucleation layer.

[0009] In some embodiments, the solvent in the dispersion is selected from ethanol and / or aqueous solution.

[0010] In some embodiments, the method of dispersing the above-mentioned dispersion on the surface of the medium layer includes one or more of the following: Langmuir-Blodgett method, spraying, dip coating, spin coating, pressure filtration, vacuum filtration, 3D printing, or self-assembly.

[0011] In some embodiments, the method of dispersing the above-mentioned dispersion on the surface of the medium layer is the Langmuir-Blodgett method, which includes immersing the medium layer in the dispersion and lifting it several times to disperse the transition metal carbides MXenes in the dispersion on the surface of the medium layer.

[0012] In some embodiments, the method of contacting and bonding the nucleation layer with the lithium metal includes: rolling, 3D printing, or electroplating.

[0013] In some embodiments, the method further includes the step of: after forming a lithium metal layer on the surface of the nucleation layer, peeling off the dielectric layer.

[0014] In some embodiments, the dielectric layer is selected from a metal foil or a polymer film; preferably, the metal foil is selected from copper foil; and the polymer film is selected from polyethylene terephthalate (PET).

[0015] In some embodiments, the morphology of the lithium metal layer includes one or more of the following: lithium metal strip, lithium metal sheet, lithium metal wire, lithium metal foil, lithium metal micro / nanoparticles, or composite materials containing lithium metal.

[0016] In some embodiments, the thickness of the lithium metal layer is between 0.1 nanometers and 500 micrometers; and / or, the thickness of the nucleation layer is between 0.3 nanometers and 500 micrometers; and / or, the thickness of the transition metal carbide MXenes is between 0.3 nanometers and 100 nanometers, and the sheet diameter is between 100 nanometers and 100 micrometers.

[0017] In some embodiments, the nucleation layer is composed of transition metal carbides MXenes.

[0018] In some embodiments, the aforementioned transition metal carbides MXenes include: Ti3C2T x One or more of the following: Ti5C4, Ti4C3, Ti2C, Cr2TiC2, Hf2C, Mo2C, Mo2Ti2C3, Mo2TiC2, Mo2ScC2, Nb2C, Nb4C3, Nb5C4, V4C3, V2C, V3C2, Ta2C, Ta3C2, Ta4C3, Ta2C2, Ta5C4, Zr3C2, Zr2C, Sc2C, Cr2TiC2, or MXenes with vacancies and defects.

[0019] A second aspect of the present invention provides a lithium metal composite material prepared by the above method, wherein the surface of the lithium metal has a nucleation layer, the nucleation layer comprising transition metal carbides MXenes.

[0020] A third aspect of the present invention provides the use of the above-mentioned lithium metal composite material in the negative electrode of a lithium metal battery.

[0021] In some embodiments, the lithium metal battery of the present invention includes: lithium-sulfur battery, lithium metal battery, lithium-sulfur battery, lithium-air battery, and lithium-carbon dioxide battery.

[0022] In some embodiments, the negative electrode includes the nucleation layer, the lithium metal layer, and the current collector layer, wherein the nucleation layer is between the lithium metal layer and the current collector layer, or the lithium metal layer is between the nucleation layer and the current collector layer; the current collector layer is a conductive material.

[0023] The outstanding advantages of this invention compared to the prior art are as follows:

[0024] (1) The method of controlled nucleation growth of lithium metal in this invention is simple and easy to implement. Starting from the idea of ​​nucleation on the surface of lithium metal, it avoids the complex design and preparation of lithium metal microstructure and has excellent practicality. The prepared lithium metal composite electrode is suitable for lithium metal-based batteries and has broad application prospects in communication equipment, mobile electronic equipment, transportation vehicles and spacecraft.

[0025] (2) The nucleation layer containing MXene in this invention acts as a nucleating agent for lithium metal. During the lithium deposition process, lithium metal is confined to the surface of the two-dimensional MXene sheet to nucleate and grow, and grows parallel and vertically along the sheet to form a passive lithium metal block, which effectively controls the formation of sharp lithium branches.

[0026] (3) The lithium metal composite material obtained by the method of this invention, as the negative electrode of a lithium metal battery, exhibits excellent cycle performance, good rate performance, excellent deep charge and discharge performance, and high coulombic efficiency. After multiple charge and discharge cycles, the surface remains smooth without obvious dendrite formation. This is because MXenes acts as a nucleating agent for lithium metal during the charge and discharge process. During lithium deposition, lithium metal can be controlled to nucleate and grow on the MXenes nanosheets on the surface of the negative electrode material, effectively controlling the formation of sharp lithium dendrites. This avoids the serious safety problem caused by lithium dendrite growth piercing the separator layer during charge and discharge, leading to a short circuit in the battery. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the structure of a lithium metal composite electrode with the nucleation layer between the lithium metal layer and the current collector layer, according to an embodiment of the present invention.

[0028] Figure 2 This is a schematic diagram of the structure of a lithium metal composite electrode between the nucleation layer and the current collector layer according to an embodiment of the present invention;

[0029] Figure 3 This is a schematic diagram of a method for preparing a lithium metal composite electrode structure according to an embodiment of the present invention;

[0030] Figure 4 This is a schematic diagram of another method for preparing the lithium metal composite electrode structure according to an embodiment of the present invention;

[0031] Figure 5 This is a schematic diagram illustrating the implementation process of the Langmuir-Blodgett method according to an embodiment of the present invention;

[0032] Figure 6 This is a schematic diagram of an internal structure of a lithium metal composite electrode used in battery assembly according to an embodiment of the present invention.

[0033] Figure 7 This is a schematic diagram of another internal structure of a lithium metal composite electrode used in battery assembly according to an embodiment of the present invention;

[0034] Figure 8 The electrochemical test results of the lithium metal composite electrode symmetrical battery in this embodiment of the invention are as follows: at a current of 1 mA per square centimeter and an areal capacity of 0.5 mA per square centimeter.

[0035] Figure 9The electrochemical test results of the lithium metal composite electrode symmetrical battery of the present invention are shown in the embodiment of the present invention at a current of 1 mA per square centimeter and an areal capacity of 35 mA per square centimeter.

[0036] Figure 10 The results of constant current charge-discharge tests conducted at a rate of 10C are shown for the lithium metal composite electrode full cell and the control sample cell of this invention.

[0037] Figure 11 The AC impedance test results of the lithium metal composite electrode full cell and the control sample cell of this invention after 1100 cycles of charge and discharge are shown.

[0038] Figure 12 Scanning electron microscope images of the lithium metal composite electrode of this invention under electrochemical deposition at a current of 1 mA per square centimeter and different areal capacities.

[0039] Figure 13 This is a schematic diagram of the nucleation growth of metallic lithium on the surface of the nucleation layer in a lithium metal composite electrode according to an embodiment of the present invention;

[0040] Figure 14 The lithium metal composite electrode of this embodiment of the invention has a current of 1 mA per square centimeter and a current of 5 mAh per square centimeter. -2 10mAh cm -2 20mAh cm -2 and 35mAh cm -2 Scanning electron microscope images of electrochemical deposition performed at a surface capacity.

[0041] Explanation of symbols in the attached diagram:

[0042] A1 nucleation layer is a single-sided lithium metal composite electrode between the lithium metal layer and the current collector layer;

[0043] A2 nucleation layer is a double-sided lithium metal composite electrode between the lithium metal layer and the current collector layer;

[0044] B1 is a single-sided lithium metal composite electrode between the nucleation layer and the current collector layer;

[0045] B2 lithium metal layer is a double-sided lithium metal composite electrode between the nucleation layer and the current collector layer;

[0046] 1. Lithium metal layer;

[0047] 2 nucleation layers; 21 two-dimensional MXenes nanosheets; 24 composite dielectric layers;

[0048] 3. Current collector layer; 31. Current collector lithium metal layer; 32. Current collector composite layer;

[0049] 4. Dielectric layer;

[0050] 5. Positive electrode plate; 51. Positive current collector; 52. Positive electrode material;

[0051] 6. Diaphragm;

[0052] 7. Water. Detailed Implementation

[0053] The technical solution of the present invention is illustrated below through specific embodiments. It should be understood that one or more steps mentioned in the present invention do not preclude the existence of other methods and steps before or after the combined steps, or that other methods and steps may be inserted between these explicitly mentioned steps. It should also be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. Unless otherwise stated, the numbering of each method step is only for the purpose of identifying each method step, and not for limiting the order of each method or limiting the scope of the present invention. Changes or adjustments to their relative relationships, without substantial changes to the technical content, can also be considered as within the scope of the present invention.

[0054] The raw materials and instruments used in the examples are not subject to any specific restrictions on their source; they can be purchased from the market or prepared using conventional methods known to those skilled in the art.

[0055] Example 1

[0056] This embodiment provides a method for controlled nucleation and growth of lithium metal, a lithium metal composite electrode and its preparation method, using transition metal carbide (MXenes)₂₁ as Ti₃C₂T. X The preparation method of this lithium metal composite electrode is illustrated using an example where the current collector layer 3 is made of copper foil and the lithium metal layer 1 is made of lithium foil. The preparation method includes steps 1) to 3):

[0057] Step 1): Under an argon atmosphere, lithium metal foil is rolled onto the surface of copper metal foil to obtain a current collector lithium metal layer 31.

[0058] Step 2): Place Ti3C2T X The composite dielectric layer 24 was obtained by transferring and dispersing the composite dielectric layer onto the copper foil of dielectric layer 4 using the Langmuir-Blodgett method, and then drying it under vacuum at 60°C for 24 hours to remove residual moisture.

[0059] Step 3): Under an argon atmosphere, the Ti3C2T on the composite dielectric layer 24 is rolled using a rolling method. X The surface of the lithium metal on the current collector lithium metal layer 31 obtained in step 1) is prepared, while the copper foil of the dielectric layer 4 is removed.

[0060] "Ti3C2T" was prepared using the above method. XA lithium metal composite electrode with a "lithium metal-copper foil" structure.

[0061] The implementation process of the Langmuir-Blodgett method described in step 2) is as follows: Figure 5 As shown, the steps include: vertically immersing a copper foil into a beaker containing distilled water 7, and then adding 2 mg / ml of Ti3C2T X When a dispersion of nanosheets in ethanol is slowly added dropwise to water, it tends to diffuse instantaneously at the water surface due to the Marangoni effect. When uniformly distributed Ti3C2T... X When the nanosheets fill 2 / 3 of the water surface, the copper foil is slowly pulled out, at which point Ti3C2T X Nanosheets are transferred from the water surface and dispersed onto the copper foil surface.

[0062] In some embodiments, the number of times the copper foil is pulled up can be controlled to control the formation of the Ti3C2T nucleation layer. X The thickness of the nucleation layer 2 on the copper foil surface. The thickness of the nucleation layer 2 obtained in a single pull is 350 nm, and the thickness of the nucleation layer 2 can reach 500 micrometers when pulled repeatedly.

[0063] In some embodiments, the thickness of the lithium metal foil in step 1) can be selected from 50 nanometers to 500 micrometers according to design requirements.

[0064] In some embodiments, the thickness of the copper foil in the current collector layer 3 can be selected from 3 micrometers to 100 micrometers, depending on design requirements.

[0065] In some embodiments, the thickness of the two-dimensional MXenes nanosheet 21 is 0.3 nm to 100 nm, and the sheet diameter is 100 nm to 100 micrometers.

[0066] In some embodiments, the two-dimensional MXenes nanosheets 21 in the nucleation layer 2 may also be selected from two-dimensional materials, including one or more of graphene, boron nitride, molybdenum oxide, molybdenum disulfide, or transition metal carbides MXenes; wherein, the transition metal carbides MXenes include: Ti3C2T x One or more of the following: Ti5C4, Ti4C3, Ti2C, Cr2TiC2, Hf2C, Mo2C, Mo2Ti2C3, Mo2TiC2, Mo2ScC2, Nb2C, Nb4C3, Nb5C4, V4C3, V2C, V3C2, Ta2C, Ta3C2, Ta4C3, Ta2C2, Ta5C4, Zr3C2, Zr2C, Sc2C, Cr2TiC2, or MXenes with vacancies and defects.

[0067] Figure 3 and 4A schematic diagram of the method for preparing the lithium metal composite electrode structure of the present invention is provided, wherein the conductive nanosheets are transition metal carbides MXenes (i.e., two-dimensional MXenes nanosheets in nucleation layer 2), and the dispersion methods include: Langmuir-Blodgett method, spraying, electrochemical deposition, chemical vapor deposition, electroplating, dip coating, spin coating, pressure filtration, vacuum filtration, 3D printing, and self-assembly; the physical methods include: rolling, Langmuir-Blodgett method, spraying, dip coating, spin coating, pressure filtration, vacuum filtration, and 3D printing; and the chemical methods include: chemical vapor deposition, electroplating, and self-assembly.

[0068] Example 2

[0069] This embodiment provides a method for preparing Ti3C2T in transition metal carbides (MXenes). X Ti3C2T was prepared by nanosheet method. X Nanosheets can be used in Example 1 to prepare "lithium metal-Ti3C2T". X A lithium metal composite electrode with a "copper foil" structure. The steps include steps 1) and 2):

[0070] Step 1): Immerse 1g of Ti3AlC2 powder in 20ml of 5mol / L HCl solution and stir for 40h in a water bath at 35℃ to completely etch the Al layer in Ti3AlC2 with HCl.

[0071] Step 2): The suspension obtained in Step 1) is filtered, repeatedly washed with deionized water, and then freeze-dried at -40℃ to obtain a black powder, which is Ti3C2T. X Nanosheets.

[0072] Ti3C2T obtained by this method X The nanosheets have a single-layer thickness of 0.5 nm and a sheet diameter between 1 and 10 micrometers.

[0073] In this embodiment, the raw material Ti3AlC2 in step 1) can be replaced with other types of MXenes two-dimensional materials. After etching reaction, two-dimensional MXenes nanosheets 21 are obtained and applied to the nucleation layer 2 in the lithium metal composite electrode of the present invention.

[0074] Example 3

[0075] This embodiment provides a lithium metal composite electrode with controllable nucleation and growth of lithium metal and its preparation method. Taking two-dimensional MXenes nanosheets 21 as transition metal carbides (MXenes), current collector layer 3 as copper foil, and lithium metal layer 1 as lithium foil as an example, the method of this embodiment is illustrated. Taking Nb2C in MXenes as an example, the method includes steps 1) to 2):

[0076] Step 1): Nb2C is transferred and dispersed onto a copper foil using the Langmuir-Blodgett method, and then dried under vacuum at 60°C for 24 hours to remove residual moisture, resulting in a current collector composite layer 32.

[0077] Step 2): Under an argon atmosphere, lithium metal foil is rolled onto the surface of Nb2C on the current collector composite layer 32 obtained in step 1) by a rolling method.

[0078] The lithium metal composite electrode with a "lithium metal-Nb2C-copper foil" structure was prepared by the above method.

[0079] The implementation process of the Langmuir-Blodgett method in step 1) is similar to that in Example 1, except that Ti3C2T is used instead of Ti3C2T. X The nanosheets were replaced with Nb2C nanosheets.

[0080] Example 4

[0081] This embodiment provides a method for controlled nucleation and growth of lithium metal, a lithium metal composite electrode, and its preparation method. Taking the two-dimensional MXenes nanosheet 21 as Mo2C in transition metal carbides (MXenes), the current collector layer 3 as a 25-micrometer-thick copper foil, and the lithium metal layer 1 as a 500-nm-thick lithium foil as an example, the method of this embodiment is illustrated. The preparation method includes steps 1) to 3).

[0082] Step 1): Mo2C nanosheets were uniformly dispersed in an ethanol solution to obtain a 5 mg / ml Mo2C dispersion.

[0083] Step 2): The suspension obtained in Step 1) is dispersed onto the copper foil by spraying, and then dried under vacuum at 60°C for 24 hours to remove residual moisture, thus obtaining the current collector composite layer 32.

[0084] Step 3): Under an argon atmosphere, lithium metal foil is rolled onto the surface of Mo2C on the current collector composite layer 32 obtained in step 2) by a rolling method.

[0085] A lithium metal composite electrode with a "lithium metal-Mo2C-copper foil" structure was prepared by the above method.

[0086] In step 2), by controlling the mass fraction of the Mo2C dispersion and the number of spraying times, the thickness of the nucleation layer Mo2C on the copper foil surface can be controlled to be between 1 micrometer and 500 micrometers.

[0087] Example 5

[0088] This embodiment provides a method for controllable nucleation and growth of lithium metal, a lithium metal composite electrode, and its preparation method. Taking the two-dimensional MXenes nanosheet 21 as Nb2C in the transition metal carbide (MXenes), the current collector layer 3 as a 100-micrometer-thick nickel foil, and the lithium metal layer 1 as a 500-micrometer-thick lithium foil as an example, the method of this embodiment is illustrated. The preparation method includes steps 1) to 3).

[0089] Step 1): Nb2C nanosheets were uniformly dispersed in an ethanol solution to obtain a 2 mg / ml Nb2C dispersion;

[0090] Step 2): The suspension obtained in Step 1) is dispersed onto the nickel foil by spraying, and then dried under vacuum at 60°C for 24 hours to remove residual moisture, thus obtaining the current collector composite layer 32.

[0091] Step 3): Under an argon atmosphere, lithium metal foil is rolled onto the surface of Nb2C on the current collector composite layer 32 obtained in step 2) by a rolling method.

[0092] The lithium metal composite electrode with a "lithium metal-Nb2C-nickel foil" structure was prepared by the above method.

[0093] In step 2), by controlling the mass fraction of the Nb2C dispersion and the number of spraying times, the thickness of the nucleation layer Nb2C nanosheets on the nickel foil surface can be controlled to be between 1 micrometer and 500 micrometers.

[0094] Example 6

[0095] The lithium metal composite electrode with controllable nucleation and growth of lithium metal described in this invention includes two structures: one in which the nucleation layer 2 is located between the lithium metal layer 1 and the current collector layer 3, forming a "lithium metal layer 1-nucleation layer 2-current collector layer 3" structure, as shown below. Figure 1 As shown. When the lithium metal layer 1 and the nucleation layer 2 are sequentially distributed on one side of the current collector, its structure is as follows. Figure 1 As shown in A1, when the lithium metal layer 1 and the nucleation layer 2 are sequentially distributed on both sides of the current collector layer 3, the structure is as follows. Figure 1 As shown in A2 of the diagram.

[0096] Another configuration has a lithium metal layer 1 located between the nucleation layer 2 and the current collector layer 3, forming a structure of "nucleation layer 2 - lithium metal layer 1 - current collector layer 3", as shown below. Figure 2As shown. When the nucleation layer 2 and the lithium metal layer 1 are sequentially distributed on one side of the current collector layer 3, the structure is as follows. Figure 2 As shown in B1, when the nucleation layer 2 and the lithium metal layer 1 are sequentially distributed on both sides of the current collector layer 3, the structure is as follows. Figure 2 As shown in B2 of the diagram.

[0097] Both of the above structures can be prepared by processing one or both sides of the current collector layer 3 using the preparation methods described in Examples 1 to 5.

[0098] Example 7

[0099] This embodiment provides a lithium metal-based battery, comprising: a lithium metal composite electrode as described in this invention, a positive electrode 5, a separator 6, an aluminum-plastic film, an electrolyte, etc. This embodiment uses a lithium metal composite electrode with a "nucleation layer 2-lithium metal layer 1-current collector layer 3" structure and a ternary positive electrode material (LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 The structure of the lithium metal-based battery is illustrated using O2 as an example.

[0100] The structure of the lithium metal composite electrode is as follows: Figure 2 As shown in the structure of B1 (hereinafter referred to as lithium metal composite electrode B1), the nucleation layer 2 and the lithium metal layer 1 are sequentially located on one side of the current collector layer 3.

[0101] The positive electrode 5 includes a positive electrode material 52 and a positive electrode current collector aluminum foil 51. Its preparation method includes: [The text abruptly ends here, so the translation also ends here.] 1 / 3 Co 1 / 3 Mn 1 / 3 O, conductive agent carbon black, and binder PVDF are added in a mass ratio of 8:1:1 to prepare a slurry, which is then coated on one side of the positive electrode current collector aluminum foil 51. After conventional rolling and drying processes in the art, the positive electrode sheet 5 is obtained.

[0102] The side of the positive electrode 5 coated with the positive electrode material 52 faces the nucleation layer 2 on the lithium metal composite electrode B1, separated by a separator 6, as shown in the diagram. Figure 6 As shown, the battery cell, composed of a lithium metal composite electrode B1, a positive electrode 5, and a separator 6, is encapsulated in an aluminum-plastic film, with the interior of the film filled with electrolyte. The separator 6 is a polypropylene (PP) microporous membrane, and the electrolyte is 1M LiPF6 dissolved in a solution of ethylene carbonate (EC), diethyl carbonate (DEC), and methyl ethyl carbonate (EMC), with a solvent volume ratio of EC:DEC:EMC = 1:1:1.

[0103] In some embodiments, the lithium metal composite electrode can also be replaced with the structure shown in lithium metal composite electrode A1.

[0104] In some embodiments, the cathode material can also be replaced with compounds such as olivine-structured LiMPO4 (M = Co, Ni, Mn, Fe, etc.), spinel-structured LiMn2O4, layered LiMO2 (M = Co, Ni, Mn), and lithium titanate Li2TiO3.

[0105] This embodiment provides a lithium metal pouch battery that is both ultra-thin and flexible.

[0106] Example 8

[0107] This embodiment provides a lithium metal-based battery, comprising: the lithium metal composite electrode described in this invention, a positive electrode 5, a separator 6, an aluminum-plastic film, an electrolyte, etc. This embodiment uses a lithium metal composite electrode with a "nucleation layer 2-lithium metal layer 1-current collector layer 3" structure and lithium cobalt oxide (LiCoO2) as an example to illustrate the structure of the lithium metal-based battery.

[0108] The structure of the lithium metal composite electrode is as follows: Figure 2 As shown in B2, the nucleation layer 2 and the lithium metal layer 1 are located on both sides of the current collector layer 3.

[0109] The positive electrode 5 includes a positive electrode material 52 and a positive electrode current collector aluminum foil 51. Its preparation method includes: preparing a slurry by adding N-methylpyrrolidone (NMP) to LiCoO2, conductive agent carbon black, and binder PVDF in a mass ratio of 8:1:1; coating the slurry on both sides of the positive electrode current collector aluminum foil 51; and then preparing the positive electrode 5 through conventional processes such as rolling and drying.

[0110] Multiple lithium metal composite electrodes B2 are alternately stacked with positive electrode 5, separated by a separator 6. The assembly structure is as follows: Figure 7 As shown, the battery cell, composed of a lithium metal composite electrode B2, a positive electrode 5, and a separator 6, is encapsulated in an aluminum-plastic film, with the interior of the film filled with electrolyte. The separator 6 is a polypropylene (PP) microporous membrane, and the electrolyte is 1M LiPF6 dissolved in a solution of ethylene carbonate (EC), diethyl carbonate (DEC), and methyl ethyl carbonate (EMC), with a solvent volume ratio of EC:DEC:EMC = 1:1:1.

[0111] In some embodiments, the lithium metal composite electrode can also be replaced with the structure shown in lithium metal composite electrode A1.

[0112] In some embodiments, the cathode material can also be replaced with compounds such as olivine-structured LiMPO4 (M = Co, Ni, Mn, Fe, etc.), spinel-structured LiMn2O4, layered LiMO2 (M = Co, Ni, Mn), and lithium titanate Li2TiO3.

[0113] This embodiment provides a lithium metal pouch battery with high specific capacity and high performance.

[0114] Example 9

[0115] This embodiment provides a lithium-sulfur metal battery, comprising: a lithium metal composite electrode as described in this invention, a positive electrode 5, a separator 6, an aluminum-plastic film, an electrolyte, etc. This embodiment uses a lithium metal composite electrode with a "nucleation layer 2-lithium metal layer 1-current collector layer 3" structure and elemental sulfur as an example to illustrate the structure of the lithium-based metal battery.

[0116] The structure of the lithium metal composite electrode is as follows: Figure 2 As shown in B2, the nucleation layer 2 and the lithium metal layer 1 are located on both sides of the current collector layer 3.

[0117] The positive electrode material is elemental sulfur. Elemental sulfur or composite materials containing elemental sulfur, conductive agent carbon black, binder PVDF, etc., are mixed with NMP in a mass ratio of 7.5:1.5:1 to prepare a slurry. This slurry is coated on both sides of the positive electrode current collector aluminum foil and then processed through conventional rolling, drying, and other processes to obtain the positive electrode sheet.

[0118] Multiple lithium metal composite electrodes B2 are alternately stacked with positive electrode 5, separated by a separator 6. The assembly structure is as follows: Figure 7 As shown, the battery cell, consisting of a lithium metal composite electrode B2, a positive electrode 5, and a separator 4, is encapsulated in an aluminum-plastic film, with the interior of the film filled with electrolyte. The separator is a polypropylene (PP) microporous membrane, and the electrolyte is a mixed solution of 1M LiTFSI dissolved in DOL and DME, with a solvent volume ratio of DOL:DME = 1:1. The electrolyte additive is 1 wt.% LiNO3.

[0119] In some embodiments, the lithium metal composite electrode can also be replaced with the structure shown in lithium metal composite electrode A1.

[0120] This embodiment provides a metal-based soft-pack lithium-sulfur battery with high specific capacity and high performance.

[0121] Example 10

[0122] This embodiment provides a lithium metal-based battery, comprising: the lithium metal composite electrode described in this invention, a positive electrode 5, a separator 6, an aluminum-plastic film, an electrolyte, etc. This embodiment uses a lithium metal composite electrode with a "nucleation layer 2-lithium metal layer 1-current collector layer 3" structure and lithium iron phosphate (LiFePO4) as examples to illustrate the structure of the lithium metal-based battery.

[0123] The structure of the lithium metal composite electrode is as follows: Figure 2As shown in B2, nucleation layer 2 and lithium metal layer 1 are sequentially located on both sides of the current collector layer. The current collector layer is made of copper foil with a thickness of 20 micrometers, and lithium metal layer 1 has a thickness of 10 micrometers. The nucleation layer is Ti3C2T from MXenes. X The thickness is 50nm, and the resulting lithium metal composite electrode is 700mm long, 57mm wide and 0.05mm thick.

[0124] The positive electrode material is lithium iron phosphate (LiFePO4). LiFePO4, conductive agent carbon black, binder PVDF, etc. are mixed in a mass ratio of 8.4:0.6:1 and NMP is added to prepare a slurry. The slurry is coated on both sides of a 20-micron thick positive electrode current collector aluminum foil. After conventional rolling, drying and cutting processes in this field, a long strip positive electrode sheet with a length of 660 mm, a width of 55 mm and a thickness of 0.168 mm is prepared.

[0125] The lithium metal composite electrode and the positive electrode sheet are separated by a separator, and then wound into a battery cell in a battery winding machine. The cell is then placed in an 18650 steel shell, electrolyte is placed in the steel shell, and then it is sealed to obtain a cylindrical 18650 steel shell lithium metal battery.

[0126] In some embodiments, the lithium metal composite electrode can also be replaced by the structure shown in lithium metal composite electrode A2.

[0127] In some embodiments, the cylindrical 18650 steel casing can be changed to other sizes of cylindrical batteries, such as 20700, 16650, 14500, etc., depending on the battery design.

[0128] This embodiment provides a cylindrical lithium metal-based battery with high specific capacity and high performance.

[0129] Example 11

[0130] To illustrate the beneficial technical effects of the controllable nucleation and growth of lithium metal in the lithium metal composite electrode of the present invention, this embodiment uses the preparation method described in Example 1 to obtain "lithium metal-Ti3C2T". X Taking a lithium metal composite electrode with a "copper foil" structure as an example, the lithium metal layer 1 used for testing is a lithium metal foil with a thickness of 1.7 micrometers, the current collector layer 3 is a copper metal foil with a thickness of 25 micrometers, and the nucleation layer Ti3C2T X The thickness is 350nm.

[0131] (1) It was assembled into a 2032 type coin cell symmetric battery, wherein the electrolyte was 1M LiPF6 dissolved in ethylene carbonate (EC), diethyl carbonate (DEC), and methyl ethyl carbonate (EMC) solution, with a solvent volume ratio of EC:DEC:EMC = 1:1:1, and the separator was a PP polypropylene microporous membrane. A pure lithium symmetric battery assembled by replacing the lithium metal composite electrode with pure lithium metal sheet was used as a control battery.

[0132] Electrochemical tests were conducted on a lithium metal composite electrode symmetrical cell and a control cell at a current of 1 mA / cm² and an areal capacity of 0.5 mA / cm². The test results are as follows: Figure 8 As shown, the lithium metal composite electrode symmetric battery has a long cycle stability of up to 900 hours, while the pure lithium symmetric battery shows an increase in overpotential after 200 hours and battery failure after 350 hours.

[0133] Electrochemical tests were conducted on a lithium metal composite electrode symmetrical cell at a current of 1 mA / cm² and an areal capacity of 35 mA / cm². The test results are as follows: Figure 9 As shown, it can stably perform deep charge-discharge for 420 hours at a current of 1 mA per square centimeter and a surface capacity of 35 mA per square centimeter.

[0134] (2) The above-mentioned lithium metal composite electrode and lithium iron phosphate (LiFePO4) positive electrode are paired and assembled into a 2032 coin cell. The preparation method of the LiFePO4 positive electrode is as follows: LiFePO4, conductive agent carbon black, binder PVDF, etc. are mixed in a mass ratio of 8:1:1, and N-methylpyrrolidone (NMP) is added to prepare a slurry. The slurry is coated on one side of the positive electrode current collector aluminum foil, and the positive electrode sheet is prepared by conventional rolling and drying processes in the art. The circular LiFePO4 positive electrode sheet is prepared by a stamping machine. The mass loading of LiFePO4 in the obtained positive electrode sheet is 2.5 mg·cm³. -2 The electrolyte consisted of 1M LiPF6 dissolved in ethylene carbonate (EC), diethyl carbonate (DEC), and methyl ethyl carbonate (EMC) solutions, with a solvent volume ratio of EC:DEC:EMC = 1:1:1. A PP polypropylene membrane was used as the separator. A control cell was constructed by replacing the lithium metal composite electrode with a pure lithium metal sheet.

[0135] The lithium metal composite electrode full cell and the control cell were subjected to constant current charge-discharge tests at a rate of 10C. The test results are as follows: Figure 10 As shown in the figure, the lithium metal composite electrode full cell exhibits excellent cycle stability, maintaining a capacity of 100 mAh·g after 1100 charge-discharge cycles. -1That's all. In contrast, the full battery begins to experience capacity decay after 450 cycles, and after 1100 charge-discharge cycles, its capacity decreases to 20 mAh·g. -1 The following shows the AC impedance spectroscopy of the lithium metal composite electrode full cell that has completed 1100 charge-discharge cycles and the control full cell, performed on an electrochemical workstation. Their Nyquist spectra are shown below. Figure 11 As shown in the figure, their spectral shapes are basically similar, both consisting of a semicircle and a diagonal line. It is generally believed that the diameter of the semicircle is related to the contact resistance of the solid electrolyte interphase (SEI) film and the resistance of the charge transfer reaction. Figure 11 It is evident that the semi-circular diameter of the lithium metal composite electrode full cell is smaller than that of the control full cell, indicating that the lithium metal composite electrode exhibits lower internal resistance after multiple cycles. This demonstrates that the addition of the nucleation layer can improve the cycle life of the battery, reduce the internal resistance of the electrode, and positively promote the electrochemical performance of the battery.

[0136] Figure 12 A comparison chart of the rate performance of the lithium metal composite electrode full cell and the control cell is presented. Figure 12 As can be seen, when the charge / discharge rate increases to 20C, the lithium metal composite electrode full cell has a significantly higher capacity, indicating that the lithium metal composite electrode can enable the battery to exhibit excellent high-rate performance.

[0137] The superior performance of lithium metal composite electrodes compared to lithium metal electrodes is related to the nucleation layer within them. Figure 13 Figure b shows a schematic diagram of the nucleation growth of lithium metal on the surface of the nucleation layer in a lithium metal composite electrode. Figure 13 Figure b shows a schematic diagram of a uniformly dispersed, multilayered MXene nanosheet structure. It can be seen that nucleation layer 2 is located on the surface of lithium metal layer 1. When the battery is in a charging state, Li... + Ti3C2T, which is extracted from the positive electrode material LiFePO4, passes through the electrolyte, and is deposited onto the nucleation layer 2 of the lithium metal composite electrode. X On the nanosheet, Ti3C2T X It acted as a nucleating agent, Li + In Ti3C2T X The surface of the lithium metal exhibits vertical deposition in a layered lithium morphology, forming passive, bulk lithium metal and thus preventing the formation of sharp lithium metal branches. When the battery is in a discharged state, Li... + Ti3C2T capable of nucleating layer 2 from lithium metal composite electrodes XThe lithium metal layer 1 on the upper and lower surfaces is extracted, passes through the electrolyte, and embeds into the positive electrode material. Furthermore, the nucleation layer 2 acts as a framework, suppressing the volume expansion of the lithium metal to some extent, which is beneficial to improving the coulombic efficiency of the lithium metal composite electrode during charging and discharging. For lithium metal electrodes without the nucleation layer 2, its Li... + The deposition process is as follows Figure 13 As shown in figure a, when Li is deposited on the surface of metallic lithium, disordered lithium particles are first formed. When Li... + As deposition continues, these lithium particles continue to grow into sharp lithium branches. It should be noted that... Figure 13 The schematic diagram shows a lithium metal composite electrode with lithium metal layer 1 between nucleation layer 2 and current collector layer 3, which is a schematic diagram of a lithium metal composite electrode with structure B1 and B2. Similarly, a lithium metal composite electrode with nucleation layer 2 between lithium metal layer 1 and current collector layer 3 is a lithium metal composite electrode with structure A1 and A2. Because the battery undergoes repeated dissolution and deposition of lithium metal during charging and discharging, the nucleation process is also applicable to... Figure 13 The process is illustrated in diagram b.

[0138] Figure 14 The current of the lithium metal composite electrode of this invention at 1 mA per square centimeter and 5 mAh per square centimeter are given. -2 10mAhcm -2 20mAh cm -2 and 35mAh cm -2 Scanning electron microscope images of electrochemical deposition under the areal capacity show the formation of lithium metal blocks with blunt edges, further proving that lithium metal is controlled to nucleate on the MXene sheet and grow in parallel and vertical directions along the sheet.

[0139] The above description is merely illustrative of preferred embodiments of the present invention and is not intended to limit the patent scope of the present invention. Other equivalent variations made using the ideas of the present invention should fall within the patent scope of the present invention.

Claims

1. A method for controllable nucleation and growth of metallic lithium, characterized in that the steps include... include: A nucleation layer containing transition metal carbides MXenes is provided on the surface of the lithium metal layer, so that during the lithium deposition process, lithium metal can nucleate and grow based on the two-dimensional sheets of the transition metal carbides MXenes to form passivated lithium metal.

2. The method as described in claim 1, characterized in that, More specific steps include: preparing the transition metal carbide MXenes into a dispersion, dispersing it on the surface of the medium layer, drying it to form a nucleation layer containing the transition metal carbide MXenes; then contacting and combining the nucleation layer with lithium metal to form the lithium metal layer on the surface of the nucleation layer.

3. The method as described in claim 2, characterized in that, The solvent in the dispersion is selected from ethanol and / or aqueous solution.

4. The method as described in claim 2 or 3, characterized in that, The method of dispersing on the surface of the medium layer includes one or more of the following: Langmuir-Blodgett method, spraying, dip coating, spin coating, pressure filtration, vacuum filtration, 3D printing, or self-assembly; And / or, the method of contacting and bonding the nucleation layer with the lithium metal includes: rolling, 3D printing, or electroplating.

5. The method as described in claim 4, characterized in that, The Langmuir-Blodgett process includes immersing the medium layer in the dispersion and lifting it several times to disperse the transition metal carbides MXenes in the dispersion on the surface of the medium layer.

6. The method according to any one of claims 2 to 5, characterized in that, It also includes the step of: after forming a lithium metal layer on the surface of the nucleation layer, peeling off the dielectric layer; And / or, the dielectric layer is selected from metal foil or polymer film.

7. The method as described in claim 6, characterized in that, The metal foil is selected from copper foil; the polymer film is selected from polyethylene terephthalate (PET).

8. The method according to any one of claims 1 to 7, characterized in that, The morphology of the lithium metal layer includes one or more of the following: lithium metal strip, lithium metal sheet, lithium metal wire, lithium metal foil, lithium metal micro / nano particles, or composite materials containing lithium metal.

9. The method according to any one of claims 1 to 8, characterized in that, The thickness of the lithium metal layer is between 0.1 nanometers and 500 micrometers; And / or, the thickness of the nucleation layer is between 0.3 nanometers and 500 micrometers; And / or, the thickness of the transition metal carbide MXenes is from 0.3 nm to 100 nm, and the sheet diameter is from 100 nm to 100 μm.

10. The method according to any one of claims 1 to 9, characterized in that, The nucleation layer is composed of transition metal carbides MXenes; And / or, transition metal carbides MXenes include: Ti3C2T x One or more of the following: Ti5C4, Ti4C3, Ti2C, Cr2TiC2, Hf2C, Mo2C, Mo2Ti2C3, Mo2TiC2, Mo2ScC2, Nb2C, Nb4C3, Nb5C4, V4C3, V2C, V3C2, Ta2C, Ta3C2, Ta4C3, Ta2C2, Ta5C4, Zr3C2, Zr2C, Sc2C, Cr2TiC2, or MXenes with vacancies and defects.

11. A lithium metal composite material prepared by the method according to any one of claims 1 to 10, characterized in that, The surface of the lithium metal has a nucleation layer comprising transition metal carbides MXenes.

12. Use of the lithium metal composite material as described in claim 11 as the negative electrode of a lithium metal battery.

13. The use as described in claim 12, characterized in that, The lithium metal batteries include: lithium-sulfur batteries, lithium metal batteries, lithium-sulfur batteries, lithium-air batteries, and lithium-carbon dioxide batteries. And / or, the negative electrode includes the nucleation layer, the lithium metal layer and the current collector layer, wherein the nucleation layer is between the lithium metal layer and the current collector layer, or the lithium metal layer is between the nucleation layer and the current collector layer; the current collector layer is a conductive material.

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