A method for producing lithium metal strips containing lithium-loving carbon materials

Abstract

A method for producing lithium metal strips containing a lithiophilic carbon material is provided. The lithium metal strips prepared by this method exhibit superior tensile strength compared to pure lithium metal strips, making them suitable for use in unwinding and winding systems in industrial production. The lithium metal strip possesses a three-dimensional framework structure, providing space for lithium metal deposition and preventing drastic physical deformation of the electrode during cycling. The inclusion of a lithiophilic carbon material in this three-dimensional framework structure provides excellent wettability with lithium. When lithium metal is deposited on the surface of the lithiophilic carbon material, the required nucleation energy is lower, promoting uniform lithium nucleation and suppressing the formation and growth of lithium dendrites. Furthermore, the ratio of lithium metal to lithiophilic carbon material in this lithium metal strip is adjustable, allowing for adaptation to cathodes with different areal capacities and avoiding excessive lithium usage and waste.

Description

Technical Field

[0001] This invention belongs to the field of new materials technology, and particularly relates to the field of lithium metal processing, specifically a method for producing lithium metal strips containing lithium-loving carbon materials.

[0002] Background Introduction

[0003] Lithium metal, as an anode material, possesses a high theoretical specific capacity (3860 mAh / g) and the lowest electrochemical potential (-3.04 V relative to the hydrogen standard electrode). However, during battery cycling, the dendrite formation and volume expansion of lithium metal can cause electrode failure, hindering the large-scale application of lithium metal strips. Furthermore, the high viscosity of lithium metal makes it difficult to process into strips during production, especially for ultrathin lithium metal strips (strips with a thickness of less than 50 micrometers).

[0004] To address the issues of lithium dendrite formation and volume expansion, current solutions primarily involve constructing a three-dimensional framework structure. This framework serves two main purposes: first, its large specific surface area reduces local current density, thereby suppressing lithium dendrite formation and growth; second, the porosity within the three-dimensional framework provides storage space for lithium deposition, thus preventing electrode volume expansion. However, limitations in technology and materials result in low structural strength, inability to produce continuously, and significant issues with the wettability of the three-dimensional framework material to lithium.

[0005] In conclusion, it is indeed necessary to provide a method for producing lithium metal strips that can continuously produce lithium metal strips with a three-dimensional lithium-loving framework. Summary of the Invention

[0006] To address the above problems, the inventors of this application provide a continuous production method for lithium metal strips containing a lithiophilic carbon material. The lithium metal strips prepared by this method exhibit superior tensile strength compared to pure lithium metal strips and can be applied to unwinding and winding systems in industrial production scenarios. This lithium metal strip has a three-dimensional framework structure, providing space for lithium metal deposition and preventing drastic physical deformation of the electrodes during cycling. The three-dimensional framework structure of the lithium metal strip contains a lithiophilic carbon material, which has excellent wettability with lithium. When lithium metal is deposited on the surface of the lithiophilic carbon material, the required nucleation energy is relatively low, which is beneficial for uniform lithium nucleation and can suppress the generation and growth of lithium dendrites. Furthermore, the ratio of lithium metal to lithiophilic carbon material in this lithium metal strip is adjustable, adaptable to electrodes with different areal capacities, and avoids excessive use and waste of lithium metal.

[0007] To achieve the above-mentioned objectives, this invention provides a method for producing lithium metal strips containing a lithiophilic carbon material, comprising the following steps:

[0008] Step 1: Mix the first binder, filler containing carbon crystal material, crosslinking agent and first solvent to obtain a homogeneous mixture. After pre-drying, treat the mixture at a temperature range of 300℃-2000℃ under an inert atmosphere. After cooling, obtain a lithium-loving carbon material.

[0009] Step 2: Crush the lithium-loving carbon material into powder, mix it evenly with the second binder and the second solvent to prepare a slurry containing lithium-loving carbon material, coat the prepared slurry on a porous substrate, and dry it to obtain a tape containing lithium-loving carbon material.

[0010] Step 3: Under an inert atmosphere, lithium metal is combined with the strip containing lithophile carbon material obtained in Step 2 to obtain a lithium metal strip containing lithophile carbon material.

[0011] In some embodiments, the mass ratio of the first binder, filler, crosslinking agent and first solvent in step one is (4-15 parts): (10-30 parts): (0.1-15 parts): (20-400 parts); the mass proportion of the carbon-containing crystalline material in the filler is 15% to 100%.

[0012] In some implementations, in step one,

[0013] The first adhesive is selected from the group consisting of polyethylene and its modified polymers (including polyvinylidene fluoride, polybutene styrene, polystyrene, polyvinyl chloride, etc.), organic alcohol polymers (including polyvinyl alcohol, polyethylene glycol, monosaccharide or polysaccharide polymers, etc.), glycerol, organic acid polymers (including polyacrylic acid, etc.), polyester organics (including cyanoacrylate, polyurethane, methacrylate, etc.), and organosiloxanes.

[0014] The filler comprises carbon-containing crystalline materials and optionally other fillers selected from the group consisting of plastic microparticles (polypropylene, polyethylene terephthalate, polystyrene), metal nanoparticles, metal oxides, metal nitrides, calcium carbonate, hydrated magnesium silicate, mica, hydrated silica, and silica.

[0015] The carbon-containing crystalline material includes at least one of carbon nanotubes, graphene, carbon fibers, carbon-based metal oxide fibers, and carbon-based covalent organic fibers.

[0016] The crosslinking agent is selected from one or more of the following: acrylic acid-bonded allyl sucrose or pentaerythritol allyl ether polymer, benzoyl peroxide, diethylenetriamine, sodium borate hydrate, cellulose derivatives, and isothiazolinone.

[0017] The first solvent is selected from the group consisting of water, tetrachloroethylene, toluene, turpentine, acetone, methyl acetate, ethyl acetate, pentane, n-hexane, cyclohexane, octane, limonene, alcohol, xylene, toluenecyclohexanone, isopropanol, diethyl ether, propylene oxide, methyl ethyl ketone, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, acetonitrile, pyridine, phenol, and ethylenediamine.

[0018] In some embodiments, the pre-drying in step one includes low-temperature drying (temperature range of -196°C to -10°C) and high-temperature drying (temperature range of 25°C to 125°C).

[0019] In some embodiments, the average particle size of the lithiophilic carbon material powder in step two is 0.1 micrometers to 25 micrometers.

[0020] In some embodiments, the porous substrate in step two includes a porous carbon fiber substrate.

[0021] In some embodiments, the mass ratio of adhesive to solvent in step two ranges from 0.35:1 to 0.65:1.

[0022] In some embodiments, the lithiophilic carbon material in step two has a mass content of 45% to 98% based on the solid content in the slurry.

[0023] In some embodiments, the second adhesive and the second solvent are selected from the group consisting of the first adhesive and the first solvent described above.

[0024] In some embodiments, the porous substrate in step two is in rolls.

[0025] In some embodiments, step two involves applying the slurry to both sides of the porous substrate.

[0026] In some embodiments, the composite method of lithium metal and strip containing lithium-bearing carbon material in step three includes at least one of coating, vapor deposition, and electroplating.

[0027] In some embodiments, the mass ratio of metallic lithium to the strip containing lithium-bearing carbon material in step three is [value missing].

[0028] In some embodiments, step three further includes post-processing after lamination, the post-processing including at least one of rolling, corona treatment, and surface treatment.

[0029] In some embodiments, the mass ratio of lithium metal to the strip containing lithium-bearing carbon material in step three is 0.3:1 to 5:1.

[0030] In some embodiments, the resulting lithium metal strip containing lithophile carbon material is a self-supporting lithium strip with a thickness ranging from 3 to 100 μm and a width ranging from 1 cm to 1 m.

[0031] The method for producing self-supporting lithium strips provided by this invention has at least the following advantages:

[0032] 1. The lithium metal strip of the present invention has a substrate that has a tensile strength superior to that of pure lithium metal strip, enabling continuous production and application. The substrate is heat-resistant and retains a certain degree of mechanical strength even after high-temperature treatment.

[0033] 2. The lithium metal strip prepared by this method has a three-dimensional framework structure, which can effectively suppress the volume expansion of the electrode during battery cycling.

[0034] 3. The lithium metal strip of the present invention contains a lithium-loving carbon material. During electrode cycling, lithium metal has a very small nucleation energy when deposited on the surface of the lithium-loving carbon material, which is conducive to the uniform deposition of lithium metal and can effectively suppress the formation and growth of lithium dendrites.

[0035] 4. The ratio of lithium metal to lithophile carbon material in this lithium metal strip is adjustable, which can be adapted to cathodes with different areal capacities, avoiding the use and waste of excessive lithium metal. Attached Figure Description

[0036] Figure 1 Cycling profiles of electrodes prepared using the lithium metal strip in Example 1;

[0037] Figure 2 Cycling profiles of the counter electrode were prepared using the lithium metal strip in Comparative Example 1. Detailed Implementation

[0038] The present invention will be illustrated below with reference to specific embodiments.

[0039] Example 1

[0040] Polyvinyl alcohol (Aladdin Reagent (Shanghai) Co., Ltd.), carbon nanotubes (Shandong Dazhan), diethylenetriamine (Shanghai Yantai Industrial Co., Ltd.), isothiazolinone (Aladdin Reagent (Shanghai) Co., Ltd.), and deionized water were uniformly mixed in a mass ratio of 6:8:5:5:60 to obtain a paste. The prepared paste was pre-dried at 85°C for 5 hours.

[0041] The pre-dried matrix material was placed in a crucible and subjected to high-temperature treatment under an inert atmosphere to obtain a lithium-loving carbon material. The high-temperature treatment temperature was 1000℃ for 5 hours.

[0042] The prepared lithiophilic carbon material was crushed into powder with a D50 of 10 micrometers. The obtained powder was uniformly dispersed with polyvinyl alcohol in deionized water at a mass ratio of 1:1 to prepare a stable slurry. The slurry was then coated onto a carbon fiber cloth roll. The roll was placed in a vacuum oven for drying at 105°C for 8 hours. The thickness of the dried roll was 50 micrometers.

[0043] Under an inert atmosphere, molten lithium metal is coated onto the surface of a dried roll material, and the lithium metal is impregnated into the carbon material. After cooling, a lithium metal strip with a three-dimensional lithium-loving carbon skeleton is obtained.

[0044] After rolling and leveling, a lithium metal strip containing lithophile carbon material with a thickness of 50 micrometers is obtained.

[0045] Example 2

[0046] Polyvinyl alcohol (Aladdin Reagent (Shanghai) Co., Ltd.), carbon nanotubes (Shandong Dazhan), sodium borate hydrate (Aladdin Reagent (Shanghai) Co., Ltd.), and deionized water were uniformly mixed in a mass ratio of 1:1:1:1:200 to obtain a paste. The prepared paste was pre-dried at 105°C for 3 hours.

[0047] The pre-dried matrix material was placed in a crucible and subjected to high-temperature treatment under an inert atmosphere to obtain a lithium-loving carbon material. The high-temperature treatment temperature was 800℃ for 5 hours.

[0048] The prepared lithiophilic carbon material was crushed into powder with a D50 of 15 micrometers. The powder was then uniformly dispersed in deionized water at a mass ratio of 0.8:1 to prepare a stable slurry. This slurry was then coated onto a carbon fiber fabric roll. The roll was placed in a vacuum oven for drying at 105°C for 8 hours. The dried roll had a thickness of 50 micrometers.

[0049] Atomic deposition was performed on the surface of a roll containing a lithophile carbon material under vacuum conditions, with a working chamber vacuum of -1.0 MPa and a lithium metal generator temperature of 300°C. After cooling, a lithium metal strip with a three-dimensional lithophile carbon framework was obtained.

[0050] After rolling and leveling, a lithium metal strip containing lithophile carbon material with a thickness of 50 micrometers is obtained.

[0051] Comparative Example 1

[0052] Commercially available lithium-copper composite tape with a thickness of 50 micrometers or more.

[0053] Material tensile strength test

[0054] The tensile strength of the lithium metal strip was measured using the following method: test strips of the same width were prepared using the lithium metal strips from each embodiment, with five strips in each embodiment. Tensile tests were performed on a tensile strength testing machine. The tensile strength of the lithium metal strips in Example 1 and Comparative Example 1 is the average of the tensile strengths at break of the five strips. The test results are shown in Table 1.

[0055] Table 1. Tensile strength (MPa) test results of Example 1 and Comparative Example 1

[0056]

[0057] Electrode Cyclic Performance Testing

[0058] The lithium metal strips from Example 1 and Comparative Example 1 were punched into wafers and assembled into coin cells. The cells were subjected to charge-discharge cycles under the following conditions: the electrolyte contained 1 mol / L LiPF6 and a two-component mixed solvent EC:EMC = 1:1 (volume ratio v / v); the separator was a dry-stretched biaxially oriented polypropylene membrane; the test temperature was 25°C; and the cycling steps were: 12 hours of rest, 1 hour of constant current charging, 1 hour of constant current discharging, and a cycling current of 1 mA / cm². 2 Cyclic capacity is 1mAh / cm³ 2 Record the voltage and cycle time during the cycle and plot the results as follows. Figure 1 and Figure 2 As shown.

[0059] from Figure 1 As can be seen, the electrode prepared by the material in Example 1 exhibits stable polarization voltage during cycling. Even after 375 cycles, the polarization voltage remains less than 100mV, and there is no trend of increasing polarization voltage. Figure 2 As can be seen, the polarization voltage of the electrode prepared using the material of Comparative Example 1 is stable for about 200 cycles. After 200 cycles, the polarization voltage tends to increase, indicating that the electrode surface structure changes, leading to an increase in the battery internal resistance. The direct cause is the generation and growth of lithium dendrites.

[0060] It is understood that, although the method for producing a lithium metal strip with a lithiophilic carbon material has been described in detail in the embodiments of the present invention with reference to specific examples, the above description is merely for the purpose of meeting legal requirements, and the present invention is not limited to the given embodiments. Those skilled in the art can replicate the lithium metal strip containing the lithiophilic carbon material through appropriate operations based on the disclosure and teachings of the specification.

[0061] Based on the disclosure and teachings of the foregoing specification, those skilled in the art can make appropriate changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some modifications and changes to the present invention should also fall within the protection scope of the claims of the present invention. Furthermore, although some specific terms are used in this specification, these terms are only for convenience of explanation and do not constitute any limitation on the present invention.

Claims

1. A method for producing a metal lithium ribbon containing a lithiophilic carbon material, characterized by, The method comprises the following steps: Step one: mixing the first binder, the filler containing carbon crystal material, the cross-linking agent and the first solvent to obtain a uniform mixture, pre-drying, and then treating the mixture at a temperature ranging from 300℃ to 2000℃ under the protection of inert atmosphere to obtain a lithium-philic carbon material after cooling; Step two: crushing the lithium-philic carbon material into powder, mixing the lithium-philic carbon material powder with the second binder and the second solvent to obtain a slurry containing the lithium-philic carbon material, coating the slurry on a porous substrate, and drying to obtain a lithium-philic carbon material-containing strip; Step three: compounding the lithium metal with the lithium-philic carbon material-containing strip obtained in step two under the protection of inert atmosphere to obtain a lithium metal strip containing the lithium-philic carbon material. In the step two, the average particle size of the lithium-philic carbon material powder ranges from 0.1 microns to 25 microns, the porous substrate comprises a porous carbon fiber substrate, and the mass ratio of the lithium-philic carbon material to the porous substrate after drying of the coating slurry ranges from 0.15 to 0.

75.

2. The production method according to claim 1, characterized by, In the step one, the mass ratio of the first binder, the filler, the cross-linking agent and the first solvent ranges from (4-15): (10-30): (0.1-15): (20-400), wherein the mass ratio of the carbon crystal material in the filler ranges from 15% to 100%. The first binder is selected from the group consisting of polyethylene and modified polymers thereof, organic alcohol polymers, glycerol, organic acid polymers, polyester organic matter and organosiloxane. The filler comprises the carbon crystal material and other fillers selected from the group consisting of plastic microparticles, metal nanoparticles, metal oxides, metal nitrides, calcium carbonate, hydrous magnesium silicate, mica, hydrated silicon dioxide and silicon dioxide. The carbon crystal material comprises at least one of carbon nanotubes, graphene, carbon fibers, carbon-based metal oxide fibers and carbon-based covalent organic fibers. The cross-linking agent is selected from one or more of high-molecular polymers of acrylate bonding allyl sucrose or pentaerythritol allyl ether, benzoyl peroxide, diethylenetriamine, hydrated sodium borate, cellulose derivatives and isothiazolinone. The first solvent is selected from the group consisting of water, tetrachloroethylene, toluene, turpentine, acetone, methyl acetate, ethyl acetate, pentane, n-hexane, cyclohexane, octane, lemon essence, alcohol, dimethylbenzene, toluene cyclohexanone, isopropyl alcohol, diethyl ether, propylene oxide, methyl butanone, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, acetonitrile, pyridine, phenol and ethylenediamine.

3. The production method according to claim 2, characterized by, The polyethylene and modified polymers thereof comprise polyvinylidene fluoride, polybutylene styrene, polystyrene and polyvinyl chloride. The organic alcohol polymers comprise polyvinyl alcohol, polyethylene glycol, monosaccharide or polysaccharide polymers. The organic acid polymers comprise polyacrylic acid. The polyester organic matter comprises cyanoacrylate, polyurethane and methacrylate. The plastic microparticles comprise polypropylene, polyethylene terephthalate and polystyrene.

4. The production method according to claim 1, characterized by, The pre-drying in the step one comprises low-temperature drying and high-temperature drying.

5. The production method according to claim 1, characterized by, In the step two, the mass ratio of the binder to the solvent ranges from 0.35:1 to 0.65:

1. The mass content of the lithiumophilic carbon material is 45% to 98% based on the solid content in the slurry; The second binder is selected from the group consisting of polyethylene and modified polymers thereof, organic alcohol polymers, glycerol, organic acid polymers, polyester organic matter, organosiloxane; The second solvent is selected from the group consisting of water, tetrachloroethylene, toluene, turpentine, acetone, methyl acetate, ethyl acetate, pentane, n-hexane, cyclohexane, octane, lemon essence, alcohol, xylene, toluene cyclohexanone, isopropyl alcohol, diethyl ether, propylene oxide, methyl butanone, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, acetonitrile, pyridine, phenol, ethylenediamine.

6. The production method according to claim 5, characterized by, The polyethylene and modified polymers thereof include polyvinylidene fluoride, polybutylene styrene, polystyrene, polyvinyl chloride; The organic alcohol polymers include polyvinyl alcohol, polyethylene glycol, monosaccharide or polysaccharide polymers; The organic acid polymers include polyacrylic acid; The polyester organic matter includes cyanoacrylate, polyurethane, methacrylate.

7. The production method according to claim 1, characterized by, The compounding method in step three includes at least one of coating, atomic deposition, and electroplating.

8. The production method according to claim 1, characterized by, The mass ratio of metallic lithium to the ribbon containing lithiumophilic carbon material in step three is 0.3:1 to 5:

1.

9. The production method according to claim 1, characterized by, Step three further includes post-treatment after compounding, and the post-treatment includes at least one of rolling, corona, and surface chemical treatment.

10. The production method according to claim 1, characterized by, The prepared metallic lithium ribbon containing lithiumophilic carbon material is a self-supporting lithium ribbon, with a thickness ranging from 3 to 100 um and a width ranging from 1 centimeter to 1 meter.

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