Modifying Structure for Lithium Metal Anode, Lithium Metal Anode and Preparation Method and Application Thereof

Abstract

The present invention provides a modified structure for a lithium metal anode, a lithium metal anode, and a preparation method and application thereof. The modified structure includes a lithiumophilic amido acid modified layer, and the raw materials of the lithiumophilic amido acid modified layer include a polymer, an amido acid, and a lithiumophilic material; the adsorption energy between the lithiumophilic material and a lithium metal atom is lower than -2.0 eV, and it can at least reduce the nucleation overpotential of the lithium metal. The amido acid therein can in-situ form Li3N with high thermodynamic stability, high Li+ conductivity, and inhibition of lithium dendrite growth after the first charge of the lithium metal battery, thereby accelerating lithium ion transport and protecting the lithium metal surface in the lithium metal battery; moreover, the added lithiumophilic material can combine with lithium during the charge and discharge process of the battery to increase the lithium diffusion rate and ensure uniform interfacial contact and good wettability on the anode surface.

Description

Technical Field

[0001] The present invention belongs to the technical field of new energy, and particularly relates to a modified structure for a lithium metal anode, a lithium metal anode, a preparation method thereof, and an application thereof. Background Art

[0002] Lithium metal is considered to be one of the most ideal anode materials due to its high theoretical capacity (e.g., up to 3860 mAh g -1 ) and low standard redox potential (-3.040 V). However, due to the uneven current distribution during the deposition process of lithium metal batteries, and the easy occurrence of irreversible side reactions with the electrolyte, it is easy to cause the problem of disordered growth of lithium dendrites, and it is easy to form a relatively thick solid electrolyte interphase (SEI) film. In addition, the repeated deposition and stripping process of lithium metal will cause battery volume expansion and increase in battery internal resistance, which will all lead to shortened battery life and increased battery safety hazards.

[0003] Currently, the main strategies to solve the above technical problems include constructing an artificial solid electrolyte interface, modifying the current collector, improving the separator, and improving electrolyte additives, etc. Among them, the artificial solid electrolyte interface refers to artificially constructing a stable and functional solid layer on the electrode surface through specific process means to simulate and optimize the naturally formed solid electrolyte interface. Existing artificial solid electrolyte interfaces usually have problems of insufficient thermodynamic stability and low conductivity, and still need to be improved in inhibiting the growth of lithium dendrites and reducing side reactions. Summary of the Invention

[0004] To solve all or part of the above technical problems, the present invention provides the following technical solutions:

[0005] One object of the present invention is to provide a modified structure for a lithium metal anode, the modified structure includes a lithiumophilic amide acid modified layer, and the raw materials of the lithiumophilic amide acid modified layer include a polymer, an amide acid, and a lithiumophilic material; the adsorption energy between the lithiumophilic material and a lithium atom is lower than -2.0 eV, and the lithiumophilic material can at least reduce the nucleation overpotential of lithium metal.

[0006] The amide acid is an amide organic compound formed by the reaction of reactants containing amide and carboxylic acid, and it can in-situ form a solid with high thermodynamic stability and high Li +The present invention can improve the conductivity and inhibit the growth of lithium dendrites of Li3N, thereby promoting ion transmission and protecting the lithium metal surface in the lithium metal battery; and, by adding a lithium-philic material, a lithium-philic site is formed during the charge and discharge process of the lithium metal battery, thereby improving the lithium diffusion rate and ensuring uniform interface contact and good wettability on the negative electrode surface; wherein, the role of the polymer is to increase the Young's modulus of the modified layer, forming a stable structure to resist the volume expansion of the lithium metal negative electrode during the charge and discharge process; and there is a synergistic effect between the raw materials of the lithium-philic amic acid modification layer. When the lithium-philic material and the amic acid are used at the same time, the lithium ion migration number can be increased, the adsorption energy of lithium metal and amic acid can be enhanced, and the lithium ion diffusion rate and transmission speed can be improved.

[0007] In some embodiments, the mass ratio of the polymer, amic acid, and lithium-philic material in the raw materials is 1-10:1-5:1-5. If the amic acid content is too low, the amount of Li3N in the generated SEI film is small, which cannot accelerate the migration of lithium ions. If the amic acid content is too high, the SEI film is brittle and cannot resist the volume expansion of the lithium metal battery during the charge and discharge process. If the lithium-philic material content is too low, the overpotential of the lithium metal battery is not significantly reduced. If the lithium-philic material content is too high, the first cycle will consume excessive lithium metal and electrolyte, reducing the first cycle coulombic efficiency and discharge capacity.

[0008] In some embodiments, the polymer includes one or more of polyethylene terephthalate (PET), polyacrylonitrile (PAN), polyetheretherketone (PEEK), polymethyl methacrylate (PMMA), polyvinylidene fluoride (PVDF), polyethylene oxide (PEO), polyvinylpyrrolidone (PVP), polyhydroxyalkanoate (PHA), cellulose, and protein, but is not limited thereto. The cellulose includes but is not limited to cellulose acetate (CA).

[0009] In some embodiments, the weight average molecular weight of the polymer is greater than 200,000.

[0010] In some embodiments, the amide acid includes one or more of asparagine, alaninamide, phenylalaninamide, malonylglutamine, tryptophanamide, valinamide, phenylmalonamide, and arabinamide. The amide acid has good chemical stability and is not easily affected by reactions such as hydrolysis and oxidation. The modified layer formed has high thermodynamic stability and high Li + conductivity and good performance in inhibiting lithium dendrite growth.

[0011] In some embodiments, the lithium-philic material includes one or a combination of metal elements, alloys, metal oxides, and carbon materials.

[0012] In some preferred embodiments, the elemental metal includes one or more of gold, silver, and antimony, the alloy includes lithium aluminum alloy, the carbon material includes graphene oxide and / or three-dimensional carbon nanotubes, and the metal oxide includes antimony tin oxide, zinc oxide, and / or copper oxide.

[0013] In some embodiments, the size of the lithiumophilic material is nanoscale, preferably 10 - 100 nm.

[0014] In some embodiments, the raw materials further include an organic solvent.

[0015] In some preferred embodiments, the organic solvent includes one or a combination of more of trifluoroacetic acid (TFA), dimethylformamide (DMF), dimethylacetamide (DMA), tetrahydrofuran, acetone, ethanol, acetic acid, and CH2Cl2.

[0016] In some embodiments, the thickness of the lithiumophilic amide acid modification layer is 2 μm - 10 μm.

[0017] In some embodiments, the modification structure further includes a substrate.

[0018] In some preferred embodiments, the substrate includes copper foil, aluminum foil, stainless steel foil, nickel foil, or lithium foil.

[0019] A second object of the present invention is to provide a lithium metal negative electrode, which includes a lithium metal substrate and a modification structure for the lithium metal negative electrode according to any one of the technical solutions, and the modification structure for the lithium metal negative electrode is combined with the lithium metal.

[0020] In some embodiments, the lithiumophilic amide acid modification layer and the lithium metal are arranged in a stacked manner; or, the metallic lithium is filled inside the lithiumophilic amide acid modification layer.

[0021] In embodiments containing a substrate, the substrate, the lithiumophilic amide acid modification layer, and the metallic lithium are arranged in a stacked manner in sequence; or, the substrate and the lithiumophilic amide acid modification layer are arranged in a stacked manner, and the lithiumophilic amide acid modification layer is filled with metallic lithium inside.

[0022] A third object of the present invention is to provide a method for preparing a lithiumophilic amide acid modified lithium metal negative electrode, including:

[0023] Providing a precursor solution containing a polymer, an amide acid, and a lithiumophilic material, wherein the adsorption energy between the lithiumophilic material and the lithium metal is lower than -2.0 eV, and it can at least reduce the nucleation overpotential of the lithium metal;

[0024] The precursor solution is prepared into a lithium-philic amide acid modification layer and combined with lithium metal to obtain a lithium-philic amide acid modified lithium metal negative electrode; or, the lithium-philic amide acid modification layer is directly formed on the lithium metal to obtain a lithium-philic amide acid modified lithium metal negative electrode.

[0025] In some embodiments, the mass ratio of the polymer, amic acid, and lithiophilic material in the precursor solution is 1 to 10: 1 to 5: 1 to 5. In a preferred embodiment, the mass ratio of the polymer, amic acid, and lithiophilic material is 8:1:1.

[0026] In some embodiments, the polymer includes one or a combination of polyethylene terephthalate, polyacrylonitrile, polyetheretherketone, polymethyl methacrylate, polyvinylidene fluoride, polyethylene oxide, polyvinylpyrrolidone, polyhydroxyalkanoate, cellulose acetate, protein, and cellulose.

[0027] In some embodiments, the weight average molecular weight of the polymer is greater than 200,000.

[0028] In some embodiments, the amidic acid comprises one or a combination of asparagine, alaninamide, phenylalaninamide, malonylglutamine, tryptophanamide, valinamide, phenylmalonamide, and arabinamide.

[0029] In some embodiments, the lithium-philic material includes one or a combination of metal elements, alloys, metal oxides, and carbon materials.

[0030] In some preferred embodiments, the metal element includes one or more of gold, silver, and antimony, the alloy includes lithium-aluminum alloy, the carbon material includes graphene oxide and / or three-dimensional carbon nanotubes, and the metal oxide includes zinc oxide and / or copper oxide.

[0031] In some embodiments, the lithium-philic material has a size of nanometer scale.

[0032] In some preferred embodiments, the size of the lithium-philic material is 10-100 nm.

[0033] In some embodiments, the thickness of the lithium-philic amic acid modification layer is 2 μm to 10 μm.

[0034] In some embodiments, the method for preparing the precursor solution includes: mixing and stirring the polymer, amic acid, lithium-philic material and organic solvent under inert atmosphere to obtain the precursor solution.

[0035] In some embodiments, the method for preparing the precursor solution specifically includes: adding the polymer, amic acid, and lithium-philic material into an organic solvent, and stirring uniformly to obtain the precursor solution.

[0036] In some embodiments, the stirring speed is 400 - 1000 rpm / min.

[0037] In some embodiments, the stirring time is 12 - 24 h.

[0038] In a typical embodiment, the precursor solution is obtained by stirring at a speed of 1000 rpm / min for 12 h.

[0039] In some embodiments, the organic solvent includes one or a combination of more of trifluoroacetic acid (TFA), dimethylformamide (DMF), dimethylacetamide (DMA), tetrahydrofuran, acetone, ethanol, acetic acid, CH2Cl2.

[0040] In some embodiments, the preparation of the lithium - amide - acid modified layer from the precursor solution specifically includes: coating the precursor solution on the surface of the substrate and drying to form the lithium - amide - acid modified layer; or, forming the lithium - amide - acid modified layer on the substrate by an electrospinning process.

[0041] In a typical embodiment, the coating speed is 15 m / min. In the electrospinning process, the feeding rate of the precursor solution is 1 mL / h -1 .

[0042] In some embodiments, the method of combining the lithium - amide - acid modified layer with lithium metal includes one or more of mechanical roll - pressing, injecting molten lithium metal, and electrochemical deposition.

[0043] In a typical embodiment, the roll - pressing pressure for combining the lithium - amide - acid modified layer with lithium metal by mechanical roll - pressing is 10 MPa.

[0044] In some embodiments, the method of directly forming the lithium - amide - acid modified layer on the lithium metal includes an electrospinning process.

[0045] In some embodiments, the substrate includes copper foil, aluminum foil, stainless - steel foil, nickel foil, or lithium foil, but is not limited thereto.

[0046] The fourth object of the present invention is to provide a lithium - metal negative electrode modified with lithium - amide - acid obtained by the preparation method of any one of the technical solutions.

[0047] The fifth object of the present invention is to provide the application of the modification structure for the lithium - metal negative electrode of any one of the technical solutions or the lithium - metal negative electrode in the preparation of a lithium - metal battery.

[0048] A sixth object of the present invention is to provide a lithium metal battery, comprising a positive electrode, a negative electrode, an electrolyte, and a separator, wherein the negative electrode comprises the modified structure for lithium metal negative electrode described in any one of the technical solutions, or the negative electrode is the lithium metal negative electrode described in any one of the technical solutions.

[0049] Compared with the prior art, the present invention has at least the following technical effects:

[0050] (1) The raw material of the modified structure provided by the present invention contains amido acid, which has good chemical stability and is not easily affected by reactions such as hydrolysis and oxidation. And during the first charging process of the lithium metal battery, this amido acid can in-situ form Li3N with high thermodynamic stability, high Li + ionic conductivity and capable of inhibiting the growth of lithium dendrites on the surface of the negative electrode, so that during the operation of the lithium metal battery, it can play a role in promoting ion transport and protecting the surface of the lithium metal;

[0051] (2) The raw material of the modified structure provided by the present invention contains lithiumophilic materials, which are easy to form alloys or lithium-carbon composite materials with lithium during the charge and discharge process of the lithium metal battery, thereby improving the lithium diffusion rate and ensuring uniform interfacial contact and good wettability of the negative electrode;

[0052] (3) The lithium metal battery provided by the present invention has good battery cycle stability, high energy density, Coulomb efficiency, and low impedance. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments recorded in the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0054] Figure 1 It is a scanning electron microscope image of the lithiumophilic amido acid modified layer in Example 1 of the present invention;

[0055] Figure 2 It is a comparison chart of the Coulomb efficiency curves of the lithium metal batteries in Example 1 and Comparative Example 1 of the present invention;

[0056] Figure 3 It is a comparison chart of the cycle performance curves of the lithium metal batteries in Examples 1-5 and Comparative Examples 1-4 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0057] The technical solution of the present invention will be described in detail below in conjunction with specific embodiments, so that those skilled in the art can better understand and implement the technical solution of the present invention. The specific functional details disclosed herein should not be construed as restrictive, but only as the basis of the claims and as a representative basis for teaching those skilled in the art to adopt the present invention in any appropriate detailed embodiment in different ways.

[0058] Unless otherwise specified, the raw materials and reagents used in the specific embodiments of the present invention are obtained commercially.

[0059] Example 1

[0060] This example provides a lithium metal anode modified with lithiophilic amide acid and its preparation method, which is as follows:

[0061] In an argon glove box (with water and oxygen content both <0.1 ppm), a precursor solution with a solid content of 13% was prepared: polyvinylidene fluoride (PVDF, weight-average molecular weight of 400000), asparagine (purchased from Aladdin), and silver nanoparticles with a particle size of 5 nm were added to a dimethylformamide (DMF) solution in a mass ratio of 8:1:1, and stirred at a rotation speed of 2000 r / min for 12 h to obtain a uniform precursor solution after complete dissolution.

[0062] The above-obtained uniform precursor solution was transferred to an electrospinning syringe, and electrospinning was carried out on a copper foil substrate, where the solution feeding rate was 1 mL h -1 , the applied voltage was 23 kV, the distance between the spinneret tip and the copper foil substrate was 10 cm, the temperature was 35 °C, and the relative humidity was 30%, to obtain a lithiophilic asparagine modification layer with a thickness of 3 μm loaded on the copper foil substrate. Figure 1 is the scanning electron microscope image of this lithiophilic amide acid modification layer.

[0063] The obtained lithiophilic asparagine modification layer was mechanically roll-pressed with a 100-μm lithium sheet at a mechanical roll-pressing pressure of 10 MPa to obtain a lithium metal anode containing the lithiophilic asparagine modification layer.

[0064] In this example, the above-obtained lithium metal anode containing the lithiophilic asparagine modification layer was assembled into a lithium metal battery for electrochemical performance testing. The specific process of making the lithium metal battery is as follows:

[0065] Preparation of the positive electrode sheet: Use a vacuum mixer to mix LiNi 0.8 Co 0.1 Mn 0.1O2, conductive agent (sp), and binder (PVDF) materials are mixed in a ratio of 98:1:1, and then a solvent is added and stirred into a slurry; the stirred slurry is then evenly coated on a copper foil using a coater and dried to form a positive electrode sheet, which is then baked in a dryer at 85°C to remove moisture and keep the electrode sheet dry; after drying, the electrode sheet is compacted using a roller press and a roller press, and finally cut into the specifications required for the battery of this embodiment for use;

[0066] Preparation of negative electrode sheet: In a glove box filled with argon (water and oxygen content <0.1 ppm), the lithium metal negative electrode sheet containing the lithium-philic amic acid modified layer prepared above was punched out using a die-cutting machine to the specifications required for the battery of this embodiment;

[0067] Electrolyte preparation: 1 M lithium bis(fluorosulfonyl)imide (LiFSI) was dissolved in equal volumes of 1,3-dioxolane (DOL) and ethylene glycol dimethyl ether (DME) to obtain a lithium metal battery electrolyte.

[0068] Battery cell preparation: The prepared positive electrode sheet, negative electrode sheet and 16μm thick polyethylene separator are prepared into a battery cell through a lamination process, and the battery cell is placed in an aluminum-plastic film shell, and the tab welding and side sealing operations are performed. Then, the electrolyte is injected in a glove box filled with argon (water and oxygen content are both <0.1ppm). After packaging, the battery cell is left to stand, formed, degassed, aged and capacity divided to finally obtain a lithium metal battery.

[0069] The lithium metal battery has an energy density of 400wh / kg at 25°C, a coulombic efficiency greater than 98.5%, a cycle number greater than 280 at a 0.3 / 0.5C rate, and a battery internal resistance less than 16mΩ.

[0070] Example 2

[0071] This embodiment provides a lithium metal anode modified with a lithium-philic amic acid and a preparation method thereof, as follows:

[0072] In an argon glove box (water and oxygen contents were <0.1 ppm), a precursor solution with a solid content of 13% was prepared: polyethylene terephthalate (PET, weight-average molecular weight of 250,000), alanine amide (purchased from MacLean), and nano-zinc oxide powder with a particle size of 10 nm were added to a tetrahydrofuran solution in this order at a mass ratio of 1:8:1. The mixture was stirred at 2000 rpm for 12 h to fully dissolve the precursor solution to obtain a uniform precursor solution.

[0073] The precursor solution obtained above was evenly coated on a 12 μm copper foil using a spin coating process to form a 3 μm thick lithium-philic alanine amide modification layer;

[0074] The obtained lithiumophilic propylamido-modified layer was mechanically roll-pressed with an 80-μm lithium sheet at a mechanical roll-pressing pressure of 15 MPa to obtain a lithium metal negative electrode containing the lithiumophilic propylamido-modified layer.

[0075] In this example, the above-obtained lithium metal negative electrode containing the lithiumophilic propylamido-modified layer was assembled into a lithium metal battery for electrochemical performance testing. The specific manufacturing process of the lithium metal battery was the same as that in Example 1.

[0076] The lithium metal battery obtained in this example had an energy density of 400 Wh / kg at 25 °C, a Coulombic efficiency > 98.8%, a cycle life > 290 cycles at a 0.3 / 0.5 C rate, a cycle life > 200 cycles at a 1 C rate, and a battery internal resistance < 16 mΩ.

[0077] Example 3

[0078] This example provides a lithiumophilic amide acid-modified lithium metal negative electrode and its preparation method, which are as follows:

[0079] In an argon glove box (with water and oxygen contents both < 0.1 ppm), a precursor solution with a solid content of 13% was prepared: polymethyl methacrylate (PMMA, weight-average molecular weight of 200,000), phenylalanine amide (purchased from Macklin), and nanometer zinc oxide with a particle size of 10 nm were sequentially added to a dimethylformamide (DMF) solution and stirred at a rotation speed of 2000 r / min for 12 h. After being fully dissolved, a uniform precursor solution was obtained.

[0080] The above-obtained uniform precursor solution was transferred to an electrospinning syringe and electrospun onto a copper foil substrate. The solution feeding rate was 0.5 mL / h -1 , the applied voltage was 23 kV, the distance between the spinneret tip and the copper foil substrate was 10 cm, the temperature was 35 °C, and the relative humidity was 30%. A lithiumophilic phenylalanine amide-modified layer with a thickness of 5 μm and loaded on the copper foil substrate was obtained.

[0081] Under an inert gas atmosphere, molten lithium operation was carried out to prevent lithium from reacting with oxygen in the air. The molten lithium was injected into the lithiumophilic phenylalanine amide-modified layer and allowed to stand for shaping to obtain a modified composite lithium metal negative electrode.

[0082] In this example, the composite lithium metal negative electrode prepared by the above method was also assembled into a lithium metal battery for electrochemical performance testing. The specific manufacturing process of the lithium metal battery was the same as that in Example 1.

[0083] The lithium metal battery had an energy density of 400 Wh / kg at 25 °C, a Coulombic efficiency > 98.8%, a cycle life > 280 cycles at a 0.3 / 0.5 C rate, and a battery internal resistance < 15 mΩ.

[0084] Example 4

[0085] This example provides a lithium metal anode modified with lithiophilic bisamide acid and its preparation method, which is as follows

[0086] In an argon glove box (with water and oxygen content both < 0.1 ppm), a precursor solution with a solid content of 15% was prepared: Polyethylene oxide (PEO, weight-average molecular weight of 200,000), asparagine (purchased from Macklin), phenylalanine amide (purchased from Macklin), and silver nanoparticles with a particle size of 5 nm were added to a dimethylformamide (DMF) solution in the mass ratio of 1:8:0.5:0.5, and stirred at a rotation speed of 2000 r / min for 12 h. After being fully dissolved, a uniform precursor solution was obtained;

[0087] Using a doctor blade coating process, the above precursor solution was uniformly coated on a 12-μm copper foil to form a lithiophilic bisamide acid modification layer with a thickness of 5 μm;

[0088] Using the method of electrochemically depositing metallic lithium, the modification layer containing the copper foil current collector obtained in the above step was paired with a pure lithium electrode sheet. An electrolyte of 1 M lithium bis(fluorosulfonyl)imide (LiFSI) dissolved in an equal volume of 1,3-dioxolane (DOL) and dimethoxyethane (DME) was used, and lithium was deposited into the modification layer by a constant current charge-discharge method to obtain a lithium metal anode sheet containing a lithiophilic bisamide acid modification layer.

[0089] This example also assembled the lithium metal anode sheet containing a lithiophilic bisamide acid modification layer into a lithium metal battery for electrochemical performance testing. The specific manufacturing process of the lithium metal battery was the same as that in Example 1.

[0090] The energy density of the lithium metal battery at 25 °C was 400 wh / kg, the Coulomb efficiency > 98.5%, the number of cycles at 0.3 / 0.5 C rate > 270 cycles, and the battery internal resistance < 16 mΩ.

[0091] Example 5

[0092] This example provides a lithium metal anode modified with lithiophilic amide acid and its preparation method, which is as follows:

[0093] In an argon glove box (with water and oxygen content both < 0.1 ppm), a precursor solution with a solid content of 15% was prepared: Polyether ether ketone (PEEK, weight-average molecular weight of 200,000), alanyl glutamine (purchased from Macklin), and tin antimony oxide nanoparticles with a particle size of 15 nm were added to a dimethylacetamide (DMA) solution in the mass ratio of 9:1:0.5, and stirred at a rotation speed of 2000 r / min for 12 h. After being fully dissolved, a uniform precursor solution was obtained;

[0094] Transfer the obtained uniform precursor solution to an electrospinning syringe and perform electrospinning on a stainless-steel foil substrate. The solution feeding rate is 1 mL / h -1 , with an applied voltage of 23 kV, a distance of 10 cm between the spinneret tip and the stainless-steel foil substrate, a temperature of 35 °C, and a relative humidity of 30%, to obtain a 5-μm-thick N-malonylglutamine modified layer loaded on the substrate.

[0095] Adopt the method of electrochemically depositing metallic lithium to composite the N-malonylglutamine modified layer with lithium metal, and obtain a lithium metal negative electrode sheet containing the N-malonylglutamine modified layer.

[0096] In this example, a lithium metal battery assembled with the composite lithium metal negative electrode prepared by the above method is also used for electrochemical performance testing, and the specific manufacturing process of the lithium metal battery is the same as that in Example 1.

[0097] The lithium metal battery has an energy density of 400 Wh / kg at 25 °C, a Coulomb efficiency > 99%, a cycle life > 290 cycles at a 0.3 / 0.5 C rate, and a battery internal resistance < 16 mΩ.

[0098] Example 6

[0099] This example provides a lithium metal negative electrode modified with a lithiumophilic amide acid and its preparation method, which are as follows:

[0100] In an argon glove box (with water and oxygen contents both < 0.1 ppm), prepare a precursor solution with a solid content of 13%: Add polyethylene terephthalate (PET, weight-average molecular weight of 250,000), tryptophan amide (purchased from Aladdin), and graphene oxide in a mass ratio of 2:7:1 to a dimethylformamide (DMF) solution in sequence, and stir at a rotation speed of 2000 r / min for 12 h until it is fully dissolved to obtain a uniform precursor solution;

[0101] Adopt a spraying process to uniformly coat the obtained precursor solution on a 12-μm copper foil to obtain a lithiumophilic tryptophan amide modified layer with a thickness of?;

[0102] Mechanically roll-press the obtained lithiumophilic tryptophan amide modified layer with an 80-μm lithium sheet, and the mechanical roll-pressing pressure is 105 MPa to obtain a lithium metal negative electrode containing the lithiumophilic tryptophan amide modified layer.

[0103] In this example, a lithium metal battery assembled with the composite lithium metal negative electrode prepared by the above method is also used for electrochemical performance testing, and the specific manufacturing process of the lithium metal battery is the same as that in Example 1.

[0104] The energy density of the lithium metal battery at 25 °C is 400 wh / kg, the Coulomb efficiency > 98.5%, the number of cycles at 0.3 / 0.5 C rate > 280 cycles, and the internal resistance of the battery < 16 mΩ.

[0105] Example 7

[0106] This example provides a lithium metal negative electrode modified with lithophilic amide acid and its preparation method, which is as follows:

[0107] In an argon glove box (with water and oxygen content both < 0.1 ppm), a precursor solution with a solid content of 13% was prepared: Polyvinylpyrrolidone (PVP, weight-average molecular weight of 250,000), polyvinylidene fluoride (PVDF), valine amide (purchased from Macklin), and nano-copper oxide with a particle size of 5 nm were added to the dimethylformamide (DMF) solution in a mass ratio of 4:4:1:1, and stirred at a speed of 2000 r / min for 12 h to obtain a uniform precursor solution after complete dissolution.

[0108] The above uniform precursor solution was transferred to an electrospinning syringe and electrospun on a copper foil substrate, where the solution feeding rate was 1 mL / h -1 , the applied voltage was 23 kV, the distance between the spinneret tip and the current collector was 12 cm, the temperature was 35 °C, and the relative humidity was 30%, to obtain a lithophilic valine amide modified layer with a thickness of 3 μm loaded on the substrate.

[0109] The obtained lithophilic valine amide modified layer was mechanically roll-pressed with a 50-μm lithium sheet under a mechanical roll-pressing pressure of 10 MPa to obtain a lithium metal negative electrode containing the lithophilic valine amide modified layer.

[0110] This example also assembled the composite lithium metal negative electrode prepared by the above method into a lithium metal battery for electrochemical performance testing. The specific process of fabricating the lithium metal battery was the same as that in Example 1.

[0111] The energy density of the lithium metal battery at 25 °C is 400 wh / kg, the Coulomb efficiency > 99%, the number of cycles at 0.3 / 0.5 C rate > 270 cycles, and the internal resistance of the battery < 16 mΩ.

[0112] Example 8

[0113] This example provides a lithium metal negative electrode modified with lithophilic amide acid and its preparation method, which is as follows:

[0114] In an argon glove box (water and oxygen contents were <0.1 ppm), a precursor solution with a solid content of 13% was prepared: cellulose acetate (CA, weight-average molecular weight 600,000), phenylmalonamide (purchased from MacLean), and nano-tin antimony oxide with a particle size of 15 nm were added to an acetone solution in this order at a mass ratio of 9:1:1:1, and stirred at 2000 rpm for 12 h to fully dissolve them to obtain a uniform precursor solution.

[0115] The uniform precursor solution obtained above was transferred to the electrospinning needle tube and electrospun on a copper foil substrate, wherein the solution feed rate was 0.8 mL / h. -1 , the applied voltage was 23 kV, the distance between the spinneret tip and the current collector was 10 cm, the temperature was 35°C, and the relative humidity was 30%, obtaining a lithiophilic phenylmalonamide modified layer with a thickness of 5 μm supported on the substrate.

[0116] The obtained lithiophilic phenylmalonamide modified layer was mechanically rolled with a 100 μm lithium sheet at a mechanical rolling pressure of 10 MPa to obtain a lithium metal negative electrode containing the lithiophilic phenylmalonamide modified layer.

[0117] In this example, the composite lithium metal negative electrode prepared by the above method is assembled into a lithium metal battery to perform electrochemical performance testing. The specific lithium metal battery production process is the same as that of Example 1.

[0118] The lithium metal battery has an energy density of 400wh / kg at 25°C, a coulombic efficiency greater than 98.5%, a cycle number greater than 280 at a 0.3 / 0.5C rate, and a battery internal resistance less than 16mΩ.

[0119] Example 9

[0120] This embodiment provides a lithium metal anode modified with a lithium-philic amic acid and a preparation method thereof, as follows:

[0121] In an argon glove box (water and oxygen contents were <0.1 ppm), a precursor solution with a solid content of 13% was prepared: polyacrylonitrile (PAN, weight-average molecular weight of 150,000), arabinamide (purchased from Aladdin), and lithium aluminum alloy were added to a dimethylformamide (DMF) solution in a mass ratio of 2:7:1 in sequence, and stirred at 2000 rpm for 12 h to fully dissolve them to obtain a uniform precursor solution;

[0122] The precursor solution obtained above was evenly coated on a 12 μm copper foil using a doctor blade coating process to obtain a lithium-philic tryptophan amide modified layer with a thickness of 5 μm.

[0123] The obtained lithiumophilic tryptophan amide modified layer was mechanically roll-pressed with an 80-μm lithium sheet at a mechanical roll-pressing pressure of 100 MPa to obtain a lithium metal anode containing a lithiumophilic arabinamide modified layer.

[0124] In this example, the composite lithium metal anode prepared by the above method was also assembled into a lithium metal battery for electrochemical performance testing. The specific manufacturing process of the lithium metal battery was the same as that in Example 1.

[0125] The lithium metal battery had an energy density of 400 wh / kg at 25 °C, a Coulombic efficiency > 98.8%, a cycle life > 265 cycles at a 0.3 / 0.5 C rate, and a battery internal resistance < 16 mΩ.

[0126] Example 10

[0127] This example provides a lithiumophilic amide acid modified lithium metal anode and its preparation method, which are as follows:

[0128] In an argon glove box (with water and oxygen contents both < 0.1 ppm), a precursor solution with a solid content of 12% was prepared: silk fibroin (weight-average molecular weight of 25,000), arabinamide (purchased from Aladdin), and three-dimensional carbon nanotubes were added to a dimethylformamide (DMF) solution in a mass ratio of 2:7:1 in sequence, and stirred at a rotation speed of 2000 r / min for 12 h to obtain a uniform precursor solution after complete dissolution.

[0129] Using a coating process, the above-obtained precursor solution was uniformly coated on a 12-μm copper foil to obtain a lithiumophilic tryptophan amide modified layer with a thickness of 5 μm.

[0130] The obtained lithiumophilic tryptophan amide modified layer was mechanically roll-pressed with an 80-μm lithium sheet at a mechanical roll-pressing pressure of 105 MPa to obtain a lithium metal anode containing a lithiumophilic arabinamide modified layer.

[0131] In this example, the composite lithium metal anode prepared by the above method was also assembled into a lithium metal battery for electrochemical performance testing. The specific manufacturing process of the lithium metal battery was the same as that in Example 1.

[0132] The lithium metal battery had an energy density of 400 wh / kg at 25 °C, a Coulombic efficiency > 98.5%, a cycle life > 280 cycles at a 0.3 / 0.5 C rate, and a battery internal resistance < 16 mΩ.

[0133] Comparative Example 1

[0134] In an argon glove box (both the water and oxygen contents are < 0.1 ppm), a precursor solution with a solid content of 13% was prepared: polyvinylidene fluoride was added to a dimethylformamide (DMF) solution, and the mixture was stirred at 2000 r / min for 12 h until it was fully dissolved to obtain a uniform precursor solution;

[0135] The above-mentioned uniform precursor solution was transferred to an electrospinning syringe, and electrospinning was carried out on a copper foil substrate. The solution feeding rate was 1 mL / h -1 , the applied voltage was 23 kV, the distance between the spinneret tip and the current collector was 10 cm, the temperature was 35 °C, and the relative humidity was 30%, to obtain a polymer modification layer with a thickness of 5 μm;

[0136] The obtained polymer modification layer was mechanically roll-pressed with a 100-μm lithium sheet under a mechanical roll-pressing pressure of 10 MPa to obtain a modified composite lithium metal negative electrode. The negative electrode sheet was assembled into a lithium metal battery according to the battery assembly method in Example 1 above.

[0137] Comparative Example 2

[0138] In an argon glove box (both the water and oxygen contents are < 0.1 ppm), a precursor solution with a solid content of 13% was prepared: polyacrylonitrile was added to a dimethylformamide (DMF) solution, and the mixture was stirred at 2000 r / min for 12 h until it was fully dissolved to obtain a uniform precursor solution;

[0139] Using a doctor blade coating process, the precursor solution was uniformly coated on a 12-μm copper foil to prepare a polymer modification layer with a thickness of 5 μm;

[0140] The obtained polymer modification layer was mechanically roll-pressed with a 100-μm lithium sheet under a mechanical roll-pressing pressure of 10 MPa to obtain a modified composite lithium metal negative electrode. This negative electrode sheet was assembled into a lithium metal battery according to the battery assembly method in Example 1 above.

[0141] Comparative Example 3

[0142] In an argon glove box (both the water and oxygen contents are < 0.1 ppm), a precursor solution with a solid content of 15% was prepared: polyethylene oxide (PEO) was added to a dimethylformamide solution, and the mixture was stirred at 2000 r / min for 12 h until it was fully dissolved to obtain a uniform precursor solution;

[0143] Using a doctor blade coating process, the precursor solution was uniformly coated on a 12-μm copper foil to form a polymer modification layer with a thickness of 5 μm.

[0144] The modification layer was combined with lithium metal using an electrochemical deposition method to obtain a composite lithium metal negative electrode. This negative electrode sheet was assembled into a lithium metal battery according to the battery assembly method in Example 1 above.

[0145] Comparative Example 4

[0146] Step 1: In an argon glove box (with water and oxygen content both < 0.1 ppm), prepare a precursor solution with a solid content of 16%: Add polyetheretherketone (PEEK) to a dimethylacetamide (DMA) solution, stir at a rotation speed of 2000 r / min for 12 h, and obtain a uniform precursor solution after it is fully dissolved;

[0147] Step 2: Transfer the uniform precursor solution in Step 1 to an electrospinning syringe, and perform electrospinning on a copper foil substrate, where the solution feeding rate is 1.2 mL / h -1 ; the applied voltage is 25 kV; the distance between the spinneret tip and the current collector is 10 cm; the temperature is 35 °C; the relative humidity is 30%.

[0148] Step 3: Inject molten lithium into the above polymer modified layer to obtain a composite lithium metal negative electrode, and assemble this negative electrode sheet into a lithium metal battery according to the battery assembly method in Example 1 above.

[0149] Comparative Example 5

[0150] In an argon glove box (with water and oxygen content both < 0.1 ppm), prepare a precursor solution with a solid content of 14%: Add polyethylene terephthalate (PET) to a tetrahydrofuran (THF) solution, stir at a rotation speed of 2000 r / min for -1 12 h, and obtain a uniform precursor solution after it is fully dissolved;

[0151] Adopt a spin coating process to uniformly coat the obtained precursor solution on a 12-μm copper foil to form a modified layer with a thickness of 3 μm;

[0152] Mechanically roll press the obtained polymer modified layer and a 100-μm lithium sheet, with a mechanical roll pressing pressure of 10 MPa, to obtain a modified composite lithium metal negative electrode, and assemble this negative electrode sheet into a lithium metal battery according to the battery assembly method in Example 1 above.

[0153] Comparative Example 6

[0154] The difference between Comparative Example 6 and Example 1 is only that the precursor solution does not contain asparagine, and the rest is the same as that in Example 1.

[0155] Comparative Example 7

[0156] The difference between Comparative Example 7 and Example 1 is only that the precursor solution does not contain nano silver, and the rest is the same as that in Example 1.

[0157] Figure 2 It is a comparative diagram of the Coulomb efficiency curves of the lithium metal batteries in Example 1 and Comparative Example 1;Figure 3 It is a comparative graph of the cycling performance curves of the lithium metal batteries of Examples 1-5 and Comparative Examples 1-4 of the present invention. It can be seen that the Coulombic efficiency and cycling performance of the lithium metal battery containing the lithiumophilic amido acid modification layer are significantly improved.

[0158] Detection method

[0159] The soft-pack lithium metal batteries prepared by the above-mentioned examples and comparative examples were respectively compared for cycling ability and internal resistance detection, and the detection methods are as follows:

[0160] 1) Cycling ability detection: At 25 °C, the soft-pack battery was charged at a constant current and constant voltage of 0.2C to 4.3V, with a cut-off current of 0.05C; then it was left to stand for 10 minutes; then it was discharged at a constant current of 0.5C to 3.0V, and the number of cycles was recorded when the capacity decayed to 80% of the nominal capacity;

[0161] 2) Internal resistance detection: At 25 °C, the internal resistance of the soft-pack lithium metal batteries prepared by Example 1 and Comparative Example 1 was measured with an internal resistance tester, and the internal resistance data was recorded.

[0162] Result analysis

[0163] The electrochemical performances of the soft-pack lithium metal batteries prepared by the above-mentioned examples and comparative examples are shown in Table 1:

[0164] Table 1 Comparison of the electrochemical performances of lithium metal batteries

[0165]

[0166]

[0167] In summary, the lithiumophilic amido acid-modified lithium metal negative electrode provided by the present invention can inhibit the growth of lithium dendrites, reduce the side reactions between the electrolyte and the metal negative electrode, and effectively extend the cycle life of the lithium metal battery. The amido acid selected in the present invention has good chemical stability, is not easily affected by reactions such as hydrolysis and oxidation, and can in-situ form Li3N with high thermodynamic stability, high Li + ionic conductivity and inhibition of lithium dendrite growth after the first charge of the lithium metal battery, which can play a role in promoting ion transport and protecting the surface of the lithium metal in the lithium metal battery; at the same time, the lithiumophilic substance is extremely easy to form an alloy with lithium during the charge and discharge process of the lithium metal battery, providing a high lithium diffusion rate to ensure uniform interfacial contact and good wettability.

[0168] All aspects, embodiments, features and examples of the present invention should be considered illustrative in all respects and are not intended to limit the present invention, the scope of which is only defined by the claims. Without departing from the spirit and scope of the claimed invention, those skilled in the art will appreciate other embodiments, modifications and uses.

[0169] In addition, with reference to the foregoing embodiments, the inventors of the present case also conducted tests using other raw materials, process operations, and process conditions described in this specification, and all obtained relatively ideal results.

[0170] Although the present invention has been described with reference to illustrative embodiments, those skilled in the art will understand that various other changes, omissions, and / or additions can be made without departing from the spirit and scope of the present invention, and elements of the embodiments can be replaced with substantially equivalent ones. Additionally, many modifications can be made to adapt a particular situation or material to the teachings of the present invention without departing from its scope. Therefore, the present invention is not intended to be limited to the specific embodiments disclosed for carrying out the present invention, but is intended to cover all embodiments falling within the scope of the appended claims. Moreover, unless specifically stated, any use of the terms first, second, etc. does not denote any order or importance, but the terms first, second, etc. are used to distinguish one element from another.

Claims

1. A modified structure for a lithium metal anode, characterized in that: The modification structure includes a lithiophilic amic acid modification layer, and the raw materials of the lithiophilic amic acid modification layer include a polymer, an amic acid, and a lithiophilic material in a mass ratio of 1-10:1-5:1-5; The adsorption energy between the lithiophilic material and a lithium atom is lower than -2.0 eV. The lithiophilic material can at least reduce the nucleation overpotential of lithium metal, and is selected from one or more combinations of a metal element, an alloy, a metal oxide, or a carbon material; The polymer is used to increase the Young's modulus of the lithiophilic amic acid modification layer, and is selected from one or more combinations of polyethylene terephthalate, polyacrylonitrile, polyether ether ketone, polymethyl methacrylate, polyvinylidene fluoride, polyethylene oxide, polyvinylpyrrolidone, polyhydroxyalkanoate, cellulose, and protein, and the weight-average molecular weight is above 200,000; The amic acid can in-situ form Li3N after the first charge of the lithium metal battery, and is selected from one or more combinations of asparagine, propionamide, phenylalanine amide, malonyl glutamine, tryptophan amide, valine amide, phenyl succinamide, and arabinamide; 2. The modification structure for a lithium metal negative electrode according to claim 1, characterized in that: The metal element includes one or more of gold, silver, or antimony, the alloy includes a lithium-aluminum alloy, the carbon material includes graphene oxide and / or three-dimensional carbon nanotubes, and the metal oxide includes zinc oxide and / or copper oxide; 3. The modification structure for a lithium metal anode according to claim 1, wherein: The size of the lithiophilic material is nanoscale.

4. The modification structure for a lithium metal negative electrode according to claim 3, characterized in that: The size of the lithiophilic material is 10-100 nm.

5. The modified structure for a lithium metal negative electrode according to claim 1, characterized in that: The raw materials further include an organic solvent.

6. The modified structure for a lithium metal negative electrode according to claim 5, wherein: The organic solvent includes one or more combinations of trifluoroacetic acid, dimethylformamide, dimethylacetamide, tetrahydrofuran, acetone, ethanol, acetic acid, or CH2Cl2; 7. The modified structure for a lithium metal negative electrode according to claim 1, wherein: The thickness of the lithiophilic amic acid modification layer is 2 μm-10 μm.

8. The modified structure for a lithium metal negative electrode according to claim 1, characterized in that: The modification structure further includes a substrate, and the lithiophilic amic acid modification layer is formed on the substrate.

9. The modified structure for a lithium metal negative electrode according to claim 8, characterized in that: The substrate includes copper foil, aluminum foil, stainless steel foil, nickel foil, or lithium foil.

10. A lithium metal anode, comprising lithium metal, characterized in that, The lithium metal negative electrode further includes the modification structure for a lithium metal negative electrode according to any one of claims 1-9. The modification structure for a lithium metal negative electrode is combined with lithium metal; and the lithiophilic amic acid modification layer and lithium metal are arranged in a stacked manner; or, the lithium metal is filled inside the lithiophilic amic acid modification layer.

11. A preparation method of a lithiumophilic amide acid-modified lithium metal anode, characterized in that, Including: Providing a precursor solution containing a polymer, an amic acid, and a lithiophilic material in a mass ratio of 1-10:1-5:1-5; Coating the precursor solution on the surface of the substrate and drying to form a lithiophilic amic acid modification layer, thereby obtaining a modification structure, or forming a lithiophilic amic acid modification layer on the substrate by an electrospinning process to obtain a modification structure, and combining the modification structure with lithium metal to obtain a lithiophilic amic acid-modified lithium metal negative electrode; Or, directly forming a lithiophilic amic acid modification layer on lithium metal to obtain a lithiophilic amic acid-modified lithium metal negative electrode; Among them, the adsorption energy between the lithium-philic material and the lithium atom is lower than -2.0 eV, and the lithium-philic material can at least reduce the nucleation overpotential of lithium metal, including one or more combinations of metal elements, alloys, metal oxides or carbon materials; the polymer is used to increase the Young's modulus of the lithium-philic amic acid modified layer, including one or more combinations of polyethylene terephthalate, polyacrylonitrile, polyetheretherketone, polymethyl methacrylate, polyvinylidene fluoride, polyethylene oxide, polyvinylpyrrolidone, polyhydroxyalkanoate, cellulose acetate, protein, and cellulose, and the weight-average molecular weight is greater than 200,000; the amic acid can form Li3N in situ after the first charge of the lithium metal battery, and the amic acid includes one or more combinations of aspartamide, alaninamide, phenylalaninamide, malonylglutamine, tryptophanamide, valinamide, phenylmalonamide, and arabinamide.

12. The preparation method according to claim 11, characterized in that: The metal element includes one or more of gold, silver or antimony, the alloy includes lithium aluminum alloy, the carbon material includes graphene oxide and / or three-dimensional carbon nanotubes, and the metal oxide includes zinc oxide and / or copper oxide.

13. The preparation method according to claim 11, wherein: The size of the lithium-philic material is nanometer scale.

14. The preparation method according to claim 13, characterized in that: The size of the lithium-philic material is 10-100 nm.

15. The preparation method according to claim 14, characterized in that: The thickness of the lithium-philic amic acid modification layer is 2 μm to 10 μm.

16. The preparation method according to claim 11, characterized in that, The preparation method of the precursor solution comprises: mixing and stirring the polymer, amic acid, lithium-philic material and organic solvent under inert atmosphere to obtain the precursor solution.

17. The preparation method according to claim 16, characterized in that: The stirring speed is 400-1000 rpm / min.

18. The preparation method according to claim 16, characterized in that: The stirring time is 12 to 24 hours.

19. The preparation method according to claim 16, characterized in that: The organic solvent includes one or a combination of trifluoroacetic acid, dimethylformamide, dimethylacetamide, tetrahydrofuran, acetone, ethanol, acetic acid or CH2Cl2.

20. The preparation method according to claim 11, characterized in that: The method of combining the modified structure with lithium metal includes one or more of mechanical rolling, injecting molten lithium, and electrochemical deposition.

21. The preparation method according to claim 11, characterized in that: The method of directly forming the lithium-philic amic acid modification layer on the lithium metal includes electrospinning or coating.

22. A lithium metal negative electrode modified with a lithium-philic amic acid obtained according to the preparation method according to any one of claims 11 to 21.

23. Use of the modified structure for a lithium metal negative electrode according to any one of claims 1 to 9 or the lithium metal negative electrode according to claim 10 or 22 in the preparation of a lithium metal battery.

24. A lithium metal battery, comprising a positive electrode, a negative electrode, an electrolyte, and a separator, characterized in that: The negative electrode includes the modified structure for a lithium metal negative electrode according to any one of claims 1 to 9, or the negative electrode is the lithium metal negative electrode according to claim 10 or 22.

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