High-strength conductive three-dimensional nanofiber coating for lithium metal electrodes and methods of making and using the same

Abstract

This invention discloses a high-strength conductive three-dimensional nanofiber coating for lithium metal electrodes, its preparation method, and its application. The preparation method includes: polymerizing a mixed reaction system comprising polyethylene glycol, dicyclohexane 4,4'-diisocyanate, a catalyst, and a solvent to obtain polyurethane; adding a halogen-containing heterocyclic compound to the polyurethane and stirring the reaction to obtain a halogen-containing hybrid polyurethane; mixing the halogen-containing hybrid polyurethane with a conductive material and then applying the resulting blend to the surface of lithium metal using electrospinning technology, thereby obtaining a high-strength conductive three-dimensional nanofiber coating. The high-strength conductive three-dimensional nanofiber coating of this invention can effectively improve the cycle life of lithium metal batteries and enhance their electrochemical performance, showing good application potential for high-energy-density lithium metal battery systems.

Description

Technical Field

[0001] This invention belongs to the field of lithium metal anode interface layer modification technology, specifically relating to a high-strength conductive three-dimensional nanofiber coating for lithium metal electrodes, its preparation method and application. Background Technology

[0002] During battery charging and discharging, the active lithium and electrolyte come into direct contact. Due to the uneven distribution of the electric field, the non-uniform deposition of lithium ions and the large-scale growth of lithium dendrites are aggravated, which puncture the separator and cause internal short circuits in the battery. The huge volume change of the metallic lithium anode makes it impossible for the SEI film to stably cover its surface, resulting in the continuous consumption of electrolyte and causing problems such as reduced coulombic efficiency and cycle life of the battery.

[0003] Therefore, artificial interface layer modification of lithium metal anodes is a promising solution. Patent application CN116417572A describes porous glass layers that can significantly improve the deposition morphology of lithium metal. However, this requires the preparation of high-purity glass precursors and acid etching, making the process complex and costly compared to polymer modification. Furthermore, the modified layer surface is brittle, making it unsuitable for the fabrication of wound cells. In contrast, polymer modification is applicable to existing battery types. Polyurethane is commonly used in lithium batteries due to its good support, conductivity, and interface optimization, making it suitable for use in solid electrolyte layers and separators. Currently, the process is mature and can easily produce large-area, ultra-thin, and defect-free flexible films. However, the polar functional groups in polyurethane molecules readily react with the lithium metal anode, forming a thick interface layer that leads to a decrease in coulombic efficiency, making direct modification of lithium metal difficult. Patent application CN120137130A describes a process where linear polyurethane compounds and bismaleimide are dissolved in a third solvent, heated and stirred until homogeneous to obtain an artificial SEI layer precursor solution. This precursor solution is then dropped onto the surface of a lithium metal anode. After the solvent evaporates, a dynamically adaptive protective layer modified lithium metal anode is obtained. The precursor solution reacts at 120°C for 36 hours, resulting in a long reaction cycle. Furthermore, the subsequent dropping onto the lithium metal battery makes the process unquantifiable and uncontrollable. Patent application CN120709380A describes a process where carbon nanotubes with hydroxyl groups on their surface, isocyanate raw materials, glycol, water, and a second organic solvent are mixed and heated under reflux. This mixture is then polymerized with an organic solvent and ammonium salt. After precipitation, washing and drying, the modified anode is deposited via electrochemical reaction. This process is extremely complex and hinders the promotion and commercial application of lithium metal batteries. Therefore, designing a high-strength conductive three-dimensional nanofiber coating for lithium metal electrodes that can be rapidly sprayed and formed, which can create a uniform electric field and promote uniform deposition of lithium metal batteries, while suppressing lithium dendrite growth and ultimately improving the cycle stability of lithium metal batteries, is a key step in promoting the development of lithium metal batteries. Summary of the Invention

[0004] The main objective of this invention is to provide a high-strength conductive three-dimensional nanofiber coating for lithium metal electrodes, its preparation method and application, in order to overcome the shortcomings of the prior art.

[0005] To achieve the aforementioned objectives, the technical solution adopted by this invention includes:

[0006] This invention provides a method for preparing a high-strength conductive three-dimensional nanofiber coating for lithium metal electrodes, comprising:

[0007] Polyurethane is prepared by polymerizing a mixed reaction system containing polyethylene glycol, dicyclohexane 4,4'-diisocyanate, catalyst, and solvent.

[0008] A halogen-containing heterocyclic compound is added to the polyurethane and the mixture is stirred to react, thereby obtaining a halogen-containing hybrid polyurethane; wherein the halogen-containing heterocyclic compound includes 3,3-bis(bromomethyl)oxetane and / or 3,3-bis(chloromethyl)oxetane.

[0009] The halogen-containing hybrid polyurethane is stirred and mixed with a conductive material, and the resulting blend is then electrospinned to form a high-strength conductive three-dimensional nanofiber coating.

[0010] The present invention also provides a high-strength conductive three-dimensional nanofiber coating prepared by the aforementioned preparation method.

[0011] This invention also provides a high-strength conductive polyurethane composite lithium metal anode, comprising: a lithium metal anode, and the aforementioned high-strength conductive three-dimensional nanofiber coating modified on the surface of the lithium metal anode.

[0012] The present invention also provides a method for preparing the aforementioned high-strength conductive polyurethane composite lithium metal anode, which includes: preparing a high-strength conductive three-dimensional nanofiber coating on the surface of a lithium metal anode using the aforementioned preparation method, thereby obtaining a high-strength conductive polyurethane composite lithium metal anode.

[0013] The embodiments of the present invention also provide the application of the aforementioned high-strength conductive three-dimensional nanofiber coating or high-strength conductive polyurethane composite lithium metal anode in the preparation of high-energy-density lithium metal battery systems.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0015] (1) The preparation method provided by the present invention has the advantages of simple raw materials, high preparation efficiency and easy control; specifically, it only requires simple mixing reaction and blending to form a blend, and then modification by electrospinning technology to prepare a high-strength conductive polyurethane composite lithium metal anode.

[0016] (2) This invention effectively develops a high mechanical strength, ion-conducting polyurethane modified layer; on the one hand, thanks to the design of the molecular chain structural domains, heterocyclic groups containing halogen elements are introduced into the long polyurethane molecular chain as propellants, and the state of local hydrogen bonds in the polyurethane is changed by heat treatment. The strongly polar hydrogen bonds can dissociate lithium salts in the electrolyte, and the dissociated Li + Through the loosely distributed Li within the soft-chain domain of the polyethylene glycol backbone + The -O complex facilitates uniform transport, promoting microphase separation between polyol microdomains (soft segments) and urethane microdomains (hard segments). After the polymer chains are rearranged, they exhibit excellent mechanical properties. Bromine and chlorohalogen elements are released from the main chain and combine with some lithium ions to form an SEI component rich in lithium chloride and lithium bromide on the electrode surface. Furthermore, the halogen elements enhance the oxidation resistance of the polyurethane. The polymer-inorganic complex SEI formed by these inorganic components and the outer organic coating is beneficial for improving the stability of the electrode-electrolyte interface.

[0017] (3) Traditional polyurethane is an insulating material and does not possess conductivity. To obtain a high-performance polyurethane conductive composite material, this invention incorporates conductive fillers to impart electronic conductivity to the polyurethane. High-strength conductive organic molecules are then modified onto the surface of metallic lithium via electrostatic spraying, forming a three-dimensional nanofiber conductive network structure with high mechanical strength. This structure can effectively suppress the growth of lithium dendrites during battery cycling. The nanofiber channels in this structure can also ensure uniform Li + transmission. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a scanning electron microscope image of the surface of the high-strength conductive polyurethane composite lithium metal anode prepared in Example 1 of this invention;

[0020] Figure 2 The diagram shows the full-cell cycle performance of the high-strength conductive polyurethane composite lithium metal anode prepared in Example 1 of this invention and the pure lithium metal matched nickel cobalt manganese oxide (NCM 811) cathode in Comparative Example 1.

[0021] Figure 3 In a typical embodiment of this invention, a high-strength conductive polyurethane composite lithium metal anode suppresses lithium dendrite growth and ensures Li... +A schematic diagram illustrating the principle of transmission. Detailed Implementation

[0022] In view of the deficiencies of the prior art, this invention, through long-term research and extensive practice, has yielded the technical solution of the present invention. The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0023] Specifically, as one aspect of the technical solution of this invention, a method for preparing a high-strength conductive three-dimensional nanofiber coating for lithium metal electrodes includes:

[0024] Polyurethane is prepared by polymerizing a mixed reaction system containing polyethylene glycol, dicyclohexane 4,4'-diisocyanate, catalyst, and solvent.

[0025] A halogen-containing heterocyclic compound is added to the polyurethane and the mixture is stirred to react, thereby obtaining a halogen-containing hybrid polyurethane; wherein the halogen-containing heterocyclic compound includes 3,3-bis(bromomethyl)oxetane and / or 3,3-bis(chloromethyl)oxetane.

[0026] The halogen-containing hybrid polyurethane is stirred and mixed with a conductive material, and the resulting blend is then electrospinned to form a high-strength conductive three-dimensional nanofiber coating.

[0027] In some preferred embodiments, the preparation method specifically includes:

[0028] Polyethylene glycol and dicyclohexane 4,4'-diisocyanate were dissolved in a solvent and a catalyst was added to form the mixed reaction system. Then, the polymerization reaction was carried out at 60~80℃ for 2~5h to obtain polyurethane.

[0029] Furthermore, a halogen-containing heterocyclic compound is added to the polyurethane and polymerized at 80-120°C for 6-8 hours to obtain a halogen-containing hybrid polyurethane.

[0030] Furthermore, the molar ratio of polyethylene glycol to dicyclohexane 4,4'-diisocyanate is 1:1 to 1:3.

[0031] Furthermore, the molar ratio of the catalyst to polyethylene glycol is 0.001 to 0.1:1.

[0032] Furthermore, the molar ratio of the halogen-containing heterocyclic compound to the polyurethane is 1:1 to 3.

[0033] Furthermore, the molecular weight of the polyethylene glycol is 1000~20000.

[0034] Furthermore, the catalyst comprises any one or more combinations of di-n-butyltin diisooctanoate, dibutyltin dilaurate, stannous octanoate, bismuth neodecanoate, and bismuth 2-ethylhexanoate, and is not limited thereto.

[0035] Furthermore, the solvent includes, but is not limited to, N,N-dimethylformamide and / or N,N-dimethylacetamide.

[0036] In some preferred embodiments, the preparation method specifically includes:

[0037] The halogen-containing hybrid polyurethane is mixed with a conductive material and stirred at 80-120°C for 8-12 hours to obtain a blend with a three-dimensional nanofiber conductive network structure.

[0038] Furthermore, the blend is electrospinned to form a high-strength conductive three-dimensional nanofiber coating; wherein the voltage used in the electrospinning technology is 5~15KV and the flow rate is 0.5~1.5ml / h.

[0039] In some preferred embodiments, the conductive material includes any one or more combinations of metals, non-metallic materials, and polymers encapsulated in transition metal oxides, but is not limited thereto.

[0040] Furthermore, the metal includes any one or more combinations of nano-copper-zinc alloy powder, gold nanoparticles, and silver nanoparticles, and is not limited thereto.

[0041] Furthermore, the non-metallic material includes any one or more combinations of carbon nanotubes, graphene, conductive carbon black, acetylene black, and graphite, and is not limited thereto.

[0042] Furthermore, the transition metal oxide in the polymer encapsulated by the transition metal oxide includes any one or more combinations of manganese dioxide, zinc oxide, and molybdenum trioxide, and the polymer in the polymer encapsulated by the transition metal oxide includes any one or more combinations of polyaniline, polypyrrole, and polythiophene.

[0043] Furthermore, the polymer encapsulated with the transition metal oxide is obtained by encapsulating the transition metal oxide on the polymer using microencapsulation technology.

[0044] Furthermore, the method for preparing the polymer encapsulated by the transition metal oxide specifically includes: mixing the transition metal oxide with the polymer in an air or oxygen atmosphere by at least one of stirring, sonication, or oscillation, and then filtering, washing, and drying overnight to obtain the polymer encapsulated by the transition metal oxide.

[0045] Another aspect of the present invention provides a high-strength conductive three-dimensional nanofiber coating prepared by the aforementioned preparation method.

[0046] Another aspect of the present invention provides a high-strength conductive polyurethane composite lithium metal anode, comprising: a lithium metal anode, and the aforementioned high-strength conductive three-dimensional nanofiber coating modified on the surface of the lithium metal anode.

[0047] Another aspect of the present invention provides a method for preparing the aforementioned high-strength conductive polyurethane composite lithium metal anode, which includes: preparing a high-strength conductive three-dimensional nanofiber coating on the surface of a lithium metal anode using the aforementioned preparation method, thereby obtaining a high-strength conductive polyurethane composite lithium metal anode.

[0048] In this invention, the high-strength conductive polyurethane composite lithium metal anode suppresses lithium dendrite growth and ensures Li metal integrity during battery cycling. + A schematic diagram of the transmission principle is shown below. Figure 3 As shown.

[0049] The high-mechanical-strength three-dimensional nanofiber conductive network structure rapidly formed on the lithium metal anode in this invention can effectively suppress the growth of lithium dendrites during battery cycling. The nanofiber channels in this structure ensure uniform Li+ transport. The introduction of halogen elements enables the formation of a polymer-inorganic composite SEI layer, which is beneficial for uniform Li deposition. Furthermore, the preparation of the polyurethane conductive mixture is simple: polyethylene glycol and polyisocyanate are polymerized to form a polyurethane polymer; then, heterocyclic groups containing halogen elements are introduced into the polyurethane molecules as propellants; finally, conductive fillers are added to the modified polyurethane to form a conductive mixture. The high-strength conductive three-dimensional nanofiber coating can effectively improve the cycle life of lithium metal batteries and enhance their electrochemical performance, showing potential application in high-energy-density lithium metal battery systems.

[0050] Another aspect of the present invention provides the application of the aforementioned high-strength conductive three-dimensional nanofiber coating or high-strength conductive polyurethane composite lithium metal anode in the preparation of high-energy-density lithium metal battery systems.

[0051] The technical solution of the present invention will be further described in detail below with reference to several preferred embodiments and accompanying drawings. This embodiment is implemented on the premise of the technical solution of the invention, and provides detailed implementation methods and specific operation processes. However, the protection scope of the present invention is not limited to the following embodiments.

[0052] Unless otherwise specified, the experimental materials used in the examples below can be purchased from conventional biochemical reagent companies.

[0053] Example 1

[0054] Add 10 mmol of polyethylene glycol to a Schllenk flask, heat to 110°C, evacuate and circulate the solution three times to remove residual moisture, then cool to 60°C. Dissolve 20 mmol of dicyclohexane 4,4'-diisocyanate in a certain amount of N,N-dimethylformamide, mix well, and add to the Schllenk flask. Then add 0.1 mol of catalyst di-n-butyl diisooctanoate and stir the reaction for 5 h. Next, the temperature was raised to 80°C, and 10 mmol of 3,3-bis(bromomethyl)oxetane and 10 mmol of 3,3-bis(chloromethyl)oxetane were slowly added to a Schllenk flask. The mixture was stirred for 8 hours to obtain the hybrid polyurethane. 50 mg of manganese dioxide and 80 mg of polyaniline were dispersed in 5 mL of distilled water by stirring and sonication. This solution was then added to a solution containing 200 mL of (3 mol / L sodium chloride / 1 mol / L hydrochloric acid / 0.1 mol / L aniline monomer) and mechanically stirred for 2 hours. The mixture was then stored in an ice bath at -10°C for 4 hours. The conductive mixture coated with transition metal oxides was filtered, washed with hydrochloric acid, and dried overnight at 60°C to obtain the conductive mixture coated with transition metal oxides. 50 mg of manganese dioxide and 80 mg of polyaniline were weighed... A conductive mixture coated with mg transition metal oxides was added to a Schllenk flask and mixed with the hybridized polyurethane at 80°C for 12 hours. The resulting blend was then modified onto a 100 μm lithium metal foil using an electrospinning device. The voltage was set to 5 kV and the flow rate to 0.5 ml / h to obtain a high-strength conductive polyurethane composite lithium metal anode.

[0055] Example 2

[0056] Add 10 mmol of polyethylene glycol to a Schllenk flask, heat to 110°C, evacuate and circulate the solution three times to remove residual moisture, then cool to 80°C. Dissolve 30 mmol of dicyclohexane 4,4'-diisocyanate in a mixture of N,N-dimethylformamide and N,N-dimethylacetamide (molar ratio 3:1), mix well, and add to the Schllenk flask. Then add 0.001 mol of dibutyltin dilaurate catalyst and stir for 4 h. Next, the temperature was raised to 120°C, and 10 mmol of 3,3-bis(chloromethyl)oxetane was slowly added to a Schllenk flask. The mixture was stirred for 6 hours to obtain the hybrid polyurethane. 50 mg of molybdenum trioxide, 10 mg of zinc oxide, 10 mg of manganese dioxide, 20 mg of polypyrrole, and 80 mg of polythiophene were dispersed in 5 mL of distilled water by stirring and sonication. This solution was then added to a solution containing 200 mL of (3 mol / L sodium chloride / 1 mol / L hydrochloric acid / 0.1 mol / L aniline monomer) and mechanically stirred for 2 hours. The mixture was then stored in an ice bath at -10°C for 4 hours. The conductive mixture coated with transition metal oxides was filtered, washed with hydrochloric acid, and dried overnight at 60°C to obtain the conductive mixture coated with transition metal oxides. 50 mg of molybdenum trioxide, 10 mg of zinc oxide, 10 mg of manganese dioxide, 20 mg of polypyrrole, and 80 mg of polythiophene were weighed... A conductive mixture coated with mg transition metal oxides was added to a Schllenk flask and mixed with hybrid polyurethane at 120°C for 8 hours. The resulting blend was then modified onto a 100 μm lithium metal foil using an electrospinning device. The voltage was set to 15 kV and the flow rate to 1.5 ml / h to obtain a high-strength conductive polyurethane composite lithium metal anode.

[0057] Example 3

[0058] Add 10 mmol of polyethylene glycol to a Schllenk flask, heat to 110 °C, evacuate and circulate three times to remove residual moisture in the Schllenk flask, cool to 60 °C, dissolve 10 mmol of dicyclohexane 4,4'-diisocyanate in a certain amount of N,N-dimethylformamide, mix well and add to the Schllenk flask, then add 0.05 mol of di-n-butyl diisooctanoate catalyst and 0.001 mol of bismuth 2-ethylhexanoate, and stir the reaction for 4 h. Next, the temperature was raised to 80℃, and 10 mmol of 3,3-bis(bromomethyl)oxetane and 10 mmol of 3,3-bis(chloromethyl)oxetane were slowly added to a Schllenk flask. The mixture was stirred for 8 hours to obtain the hybrid polyurethane. 50 mg of a mixture of carbon nanotubes / graphene / conductive carbon black / acetylene black / graphite (mass ratio 1:1:1:1:1) was added to the Schllenk flask and mixed with the hybrid polyurethane at 80℃ for 8 hours. The resulting blend was then modified onto a 100 μm lithium metal foil using an electrospinning device. The voltage was set to 10 kV and the flow rate to 0.5 ml / h to obtain a high-strength conductive polyurethane composite lithium metal anode.

[0059] Example 4

[0060] Add 10 mmol of polyethylene glycol to a Schllenk flask, heat to 110°C, evacuate and circulate the mixture three times to remove residual moisture, then cool to 60°C. Dissolve 30 mmol of dicyclohexane 4,4'-diisocyanate in a certain amount of N,N-dimethylformamide, mix well, and add to the Schllenk flask. Then add 0.05 mol of bismuth neodecanoate catalyst and stir the reaction for 4 h. Next, the temperature was raised to 80°C, and 10 mmol of 3,3-bis(bromomethyl)oxetane and 10 mmol of 3,3-bis(chloromethyl)oxetane were slowly added to a Schllenk flask. The mixture was stirred for 8 hours to obtain the hybrid polyurethane. 50 mg of zinc oxide and 80 mg of polyaniline were dispersed in 5 mL of distilled water by stirring and sonication. This solution was then added to a solution containing 200 mL of (3 mol / L sodium chloride / 1 mol / L hydrochloric acid / 0.1 mol / L aniline monomer) and mechanically stirred for 2 hours. The mixture was then stored in an ice bath at -10°C for 4 hours. The conductive mixture coated with transition metal oxides was filtered, washed with hydrochloric acid, and dried overnight at 60°C to obtain the conductive mixture coated with transition metal oxides. 50 mg of zinc oxide and 80 mg of polyaniline were weighed... A conductive mixture coated with mg transition metal oxides was added to a Schllenk flask and mixed with the hybridized polyurethane at 80°C for 12 hours. The resulting blend was then modified onto a 100 μm lithium metal foil using an electrospinning device. The voltage was set to 5 kV and the flow rate to 0.5 ml / h to obtain a high-strength conductive polyurethane composite lithium metal anode.

[0061] Example 5

[0062] Add 10 mmol of polyethylene glycol to a Schllenk flask, heat to 110°C, evacuate and circulate the solution three times to remove residual moisture, then cool to 60°C. Dissolve 20 mmol of dicyclohexane 4,4'-diisocyanate in a certain amount of N,N-dimethylformamide, mix well, and add to the Schllenk flask. Then add 0.1 mol of catalyst di-n-butyl diisooctanoate and stir the reaction for 4 hours. Next, the temperature was raised to 80°C, and 10 mmol of 3,3-bis(bromomethyl)oxetane was slowly added to a Schllenk flask. The mixture was stirred for 8 hours to obtain the hybrid polyurethane. 50 mg of molybdenum trioxide and 80 mg of polypyrrole were dispersed in 5 mL of distilled water by stirring and sonication. This solution was then added to a solution containing 200 mL of (3 mol / L sodium chloride / 1 mol / L hydrochloric acid / 0.1 mol / L aniline monomer) and mechanically stirred for 2 hours. The mixture was then stored in an ice bath at -10°C for 4 hours. The conductive mixture coated with transition metal oxides was filtered, washed with hydrochloric acid, and dried overnight at 60°C to obtain the conductive mixture coated with transition metal oxides. 50 mg of molybdenum trioxide and 80 mg of polypyrrole were weighed... A conductive mixture coated with mg transition metal oxides was added to a Schllenk flask and mixed with hybrid polyurethane at 80°C for 12 h. The resulting blend was then modified onto a 100 μm lithium metal foil using an electrospinning device. The voltage was set to 10 kV and the flow rate to 1 ml / h to obtain a high-strength conductive polyurethane composite lithium metal anode.

[0063] Comparative Example 1

[0064] A 100μm lithium metal foil was used, and the electrolyte was a commercially available ester electrolyte, 1 M LiPF6 in EC / EMC / DMC (solvent volume ratio 1:1:1).

[0065] Comparative Example 2

[0066] 10 mmol of polyethylene glycol was added to a Schllenk flask, heated to 110 °C, and circulated under vacuum for three cycles to remove residual moisture. The mixture was then cooled to 80 °C. 20 mmol of dicyclohexane 4,4'-diisocyanate was dissolved in a mixture of N,N-dimethylformamide and N,N-dimethylacetamide (molar ratio 3:1), mixed thoroughly, and added to the Schllenk flask. Subsequently, 0.001 mol of dibutyltin dilaurate catalyst was added, and the mixture was stirred for 4 h. Next, the temperature was raised to 120 °C, and 10 mmol of 3,3-bis(chloromethyl)oxetane was slowly added to the Schllenk flask, and the mixture was stirred for 6 h. The resulting hybrid polyurethane was then modified onto a 100 μm lithium foil using an electrospinning apparatus with a voltage of 10 kV and a flow rate of 1 ml / h.

[0067] Comparative Example 3

[0068] Add 10 mmol of polyethylene glycol to a Schllenk flask, heat to 110°C, evacuate and circulate the solution three times to remove residual moisture, then cool to 60°C. Dissolve 50 mmol of dicyclohexane 4,4'-diisocyanate in a certain amount of N,N-dimethylformamide, mix well, and add to the Schllenk flask. Then add 0.1 mol of catalyst di-n-butyl diisooctanoate and stir the reaction for 4 hours. Next, the temperature was raised to 80°C, and 10 mmol of 3,3-bis(bromomethyl)oxetane and 10 mmol of 3,3-bis(chloromethyl)oxetane were slowly added to a Schllenk flask and stirred for 8 hours. 50 mg of carbon nanotubes were added to the Schllenk flask and mixed with the hybrid polyurethane at 80°C and stirred for 8 hours. The resulting blend was then modified onto a 100 μm lithium foil using an electrospinning device with a voltage of 10 kV and a flow rate of 0.5 ml / h.

[0069] Comparative Example 4

[0070] The method is the same as in Example 3, except that 3,3-bis(bromomethyl)oxetane and 3,3-bis(chloromethyl)oxetane are missing.

[0071] 10 mmol of polyethylene glycol was added to a Schllenk flask, heated to 110 °C, and evacuated and circulated three times to remove residual moisture. The temperature was then lowered to 60 °C. 10 mmol of dicyclohexane 4,4'-diisocyanate was dissolved in a certain amount of N,N-dimethylformamide, mixed, and added to the Schllenk flask. Subsequently, 0.05 mol of di-n-butyl diisooctanoate catalyst and 0.001 mol of bismuth 2-ethylhexanoate were added, and the mixture was stirred for 4 h to obtain polyurethane. Next, the temperature was raised to 80℃; 50 mg of a mixture of carbon nanotubes / graphene / conductive carbon black / acetylene black / graphite (mass ratio 1:1:1:1:1) was added to a Schllenk flask and mixed with polyurethane at 80℃ for 8 h. The resulting blend was then modified onto a 100 μm lithium metal foil using an electrospinning device. The voltage was set to 10 kV and the flow rate to 0.5 ml / h to obtain a high-strength conductive polyurethane composite lithium metal anode.

[0072] Performance testing

[0073] The pure lithium electrode sheets from Example 1 and Comparative Example 1 were used as negative electrode materials for lithium metal batteries. According to... Figure 1 The surface scanning electron microscope (SEM) image of Example 1 shows that a highly elastic conductive polyurethane layer is smoothly and uniformly distributed on the lithium sheet surface above the negative electrode, exhibiting a nanofiber structure. This layer is stably bonded to the lithium metal, effectively inhibiting lithium dendrite growth. The rich polymer and inorganic SEI components help guide uniform lithium deposition. In an argon glove box with a water-oxygen concentration of less than 0.1 ppm, the battery assembly consisted of the positive and negative electrode sheets of a single-cell pouch cell, namely, lithium nickel cobalt manganese oxide (NCM 811) positive electrode, lithium metal composite negative electrode (or pure lithium), commercial ester electrolyte, separator, and aluminum-plastic film. The cells were sealed using a fully automated sealing machine. After battery aging, formation and testing were performed using a Xinwei battery testing system. Electrochemical tests were conducted in an explosion-proof cabinet at approximately 25 °C. The full-cell cycle performance diagrams of the high-strength conductive polyurethane composite lithium metal negative electrode prepared in Example 1 and the pure lithium metal matched lithium nickel cobalt manganese oxide (NCM 811) positive electrode in Comparative Example 1 are shown below. Figure 2 As shown.

[0074] The performance test results are shown in Table 1 below: Examples 1-5 and Comparative Examples 1-4 are the impedance test, four-probe conductivity test and capacity retention rate recorded after 200 cycles after the battery is assembled.

[0075] Table 1

[0076]

[0077] As shown in Table 1, the battery assembled using a high-strength conductive polyurethane composite lithium metal anode as the artificial polymer solid electrolyte interphase layer exhibits lower cycle impedance and higher capacity retention. Example 1 demonstrates the best performance, exhibiting superior mechanical properties, uniform electronic and ionic conductivity, and strong interfacial stability compared to Comparative Example 1, resulting in better electrochemical performance. Examples 2-5 show improved electrochemical performance in the full-cell batteries matched with this high-strength conductive polyurethane composite lithium metal anode. Examples 3 and 4 reveal that the combined effect of 3,3-bis(bromomethyl)oxetane and 3,3-bis(chloromethyl)oxetane significantly enhances the battery's electrochemical performance. This is likely due to the formation of a richer SEI layer at the electrode interface by the two halogen atoms, promoting interface stability and improving cycle stability. Comparisons with other examples also indicate that using transition metal oxide-encapsulated organic materials to enhance polyurethane conductivity is superior to directly using conductive metals and carbon-based materials. This is likely because conductive polymers have better compatibility with polyurethane.

[0078] Furthermore, comparing Comparative Example 2 and Example 2, the polyurethane polymer modification layer also improves the electrochemical performance of lithium metal batteries, indicating that the polymer has a certain mechanical strength, which can suppress the uneven deposition and stripping of lithium during cycling, thereby extending the cycle life of the battery. The sudden increase in impedance is due to the lack of conductive filler in this layer, which hinders the effective transport of ions and electrons. Comparative Example 3 and Example 5 show that the polymerization reaction of polyethylene glycol and dicyclohexane 4,4'-diisocyanate during the preparation of polyurethane requires a ratio controlled between 1:1 and 1:3. If this range is exceeded, the polymerization reaction is insufficient, and excess alcohols or esters affect the degree to which heterocyclic groups promote the separation of the soft and hard chain ends of the polymer, resulting in a lower Young's modulus for the prepared polymer modification layer. This is insufficient to completely suppress lithium dendrite formation during battery cycling, thus affecting the electrochemical performance. Comparative Example 4 and Example 3 show that halogen-containing heterocyclic compounds can react better with Li metal to achieve the formation of a polymer-inorganic composite SEI layer, which is beneficial for uniform Li deposition, reduces interfacial impedance, and thus improves the cycle life of lithium metal batteries.

[0079] In summary, the high-strength conductive polyurethane composite lithium metal anode prepared by this invention has advantages such as inhibiting dendrite growth, high ionic conductivity, and long cycle life. Its mechanism of action is as follows: On the one hand, the introduction of heterocyclic groups into the long polyurethane molecular chain promotes microphase separation between the polyol microdomains (soft segments) and the urethane microdomains (hard segments), resulting in excellent mechanical properties after the polymer chains are rearranged. The polymer-inorganic composite SEI formed by the inorganic components rich in lithium chloride and lithium bromide and the outer organic coating is beneficial to improving the stability of the electrode-electrolyte interface. On the other hand, the conductive mixture imparts conductivity to the polyurethane, and a three-dimensional nanofiber conductive network structure with high mechanical strength is prepared by electrostatic spraying, providing a fast and uniform ion channel.

[0080] In addition, this case also referred to the foregoing embodiments and conducted experiments with other raw materials, process operations, and process conditions described in this specification, and all of them obtained relatively ideal results.

[0081] It should be understood that the technical solutions of the present invention are not limited to the specific embodiments described above. Any technical modifications made to the technical solutions of the present invention without departing from the spirit and scope of the claims are within the scope of protection of the present invention.

Claims

1. A method for the preparation of a high-strength conductive three-dimensional nanofiber coating for lithium metal electrodes, characterized by, include: Polyurethane is prepared by polymerizing a mixed reaction system containing polyethylene glycol, dicyclohexane 4,4'-diisocyanate, catalyst, and solvent. A halogen-containing heterocyclic compound is added to the polyurethane and the mixture is stirred to react, thereby obtaining a halogen-containing hybrid polyurethane; wherein the halogen-containing heterocyclic compound includes 3,3-bis(bromomethyl)oxetane and / or 3,3-bis(chloromethyl)oxetane. The halogen-containing hybrid polyurethane is stirred and mixed with a conductive material, and the resulting blend is then electrospinned to form a high-strength conductive three-dimensional nanofiber coating.

2. The production method according to claim 1, characterized by, Specifically, it includes: Polyethylene glycol and dicyclohexane 4,4'-diisocyanate were dissolved in a solvent and a catalyst was added to form the mixed reaction system. Then, the polymerization reaction was carried out at 60~80℃ for 2~5h to obtain polyurethane. Furthermore, a halogen-containing heterocyclic compound is added to the polyurethane and polymerized at 80-120°C for 6-8 hours to obtain a halogen-containing hybrid polyurethane.

3. The method of claim 2, wherein: The molar ratio of polyethylene glycol to dicyclohexane 4,4'-diisocyanate is 1:1 to 1:3; And / or, the molar ratio of the catalyst to polyethylene glycol is 0.001 to 0.1:1; And / or, the molar ratio of the halogen-containing heterocyclic compound to the polyurethane is 1:1~3; And / or, the molecular weight of the polyethylene glycol is 1000~20000; And / or, the catalyst comprises any one or more combinations of di-n-butyltin diisooctanoate, dibutyltin dilaurate, stannous octanoate, bismuth neodecanoate, and bismuth 2-ethylhexanoate; And / or, the solvent includes N,N-dimethylformamide and / or N,N-dimethylacetamide.

4. The method of claim 1, wherein, Specifically, it includes: The halogen-containing hybrid polyurethane is mixed with a conductive material and stirred at 80-120°C for 8-12 hours to obtain a blend with a three-dimensional nanofiber conductive network structure. Furthermore, the blend is electrospinned to form a high-strength conductive three-dimensional nanofiber coating; wherein the voltage used in the electrospinning technology is 5~15KV and the flow rate is 0.5~1.5ml / h.

5. The method of claim 4, wherein: The conductive material includes any one or more combinations of metals, non-metallic materials, and polymers encapsulated in transition metal oxides.

6. The method of claim 5, wherein: The metal includes any one or more combinations of nano-copper-zinc alloy powder, gold nanoparticles, and silver nanoparticles. And / or, the non-metallic material includes any one or more combinations of carbon nanotubes, graphene, conductive carbon black, acetylene black, and graphite; And / or, the transition metal oxide in the polymer encapsulated by the transition metal oxide includes any one or more combinations of manganese dioxide, zinc oxide, and molybdenum trioxide, and the polymer in the polymer encapsulated by the transition metal oxide includes any one or more combinations of polyaniline, polypyrrole, and polythiophene. And / or, the transition metal oxide-encapsulated polymer is obtained by encapsulating the transition metal oxide onto the polymer using microencapsulation technology.

7. A high-strength conductive three-dimensional nanofiber coating prepared by any one of claims 1-6.

8. A high strength conductive polyurethane composite lithium metal anode, characterized by, include: A lithium metal anode, and a high-strength conductive three-dimensional nanofiber coating of claim 7, which is applied to the surface of the lithium metal anode.

9. The method of making a high strength conductive polyurethane composite lithium metal anode of claim 8, wherein, include: A high-strength conductive three-dimensional nanofiber coating is prepared on the surface of a lithium metal anode using the preparation method described in any one of claims 1-6, thereby obtaining a high-strength conductive polyurethane composite lithium metal anode.

10. The application of the high-strength conductive three-dimensional nanofiber coating of claim 7 or the high-strength conductive polyurethane composite lithium metal anode of claim 8 in the preparation of high-energy-density lithium metal battery systems.

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