Metallic lithium negative electrode with composite polymer electrolyte protective layer and method for manufacturing the same

Abstract

This invention discloses a lithium metal anode with a composite polymer electrolyte protective layer and its preparation method, relating to the field of lithium battery technology. First, graphene nanomaterials, such as nano-ZnO and ZnS, are pre-coated onto the surface of a cellulose membrane. These materials are sprayed onto the cellulose membrane using an aqueous solution to ensure uniform distribution. Then, the treated cellulose membrane is dried and pressed onto the surface of a lithium foil (or lithium metal alloy foil) anode. Subsequently, during roll-to-roll processing, a liquid precursor that can solidify in situ is sprayed onto the lithium metal surface. Finally, photo-initiated polymerization is used to form a uniform polymer electrolyte protective layer. The presence of the cellulose membrane allows the liquid precursor to disperse rapidly and uniformly, avoiding slippage and local aggregation, thus ensuring a smooth and uniform polymer electrolyte protective layer formed after photo-initiated polymerization.

Description

Technical Field

[0001] This invention relates to the field of lithium battery technology, and in particular to a lithium metal anode with a composite polymer electrolyte protective layer and its preparation method, aiming to significantly improve the interfacial cycle stability of the lithium metal anode and the overall performance of the battery. Background Technology

[0002] Lithium metal has attracted much attention as an anode material due to its high theoretical specific capacity and low potential, but it faces many challenges in practical applications, such as lithium dendrite formation and interface instability. These problems lead to decreased battery safety and shortened lifespan.

[0003] CN202211432565.8 discloses a method for modifying the interface of a lithium metal anode and a lithium metal battery using a double-layer protective layer. The method involves simply immersing a lithium foil in a solution containing a fluorine metal salt, drying it, and then using it as the anode during a charge / discharge process to spontaneously form the layer in situ. This simple preparation method creates a double-layer interface containing lithium fluoride and a lithium alloy on the lithium metal surface. This double-layer interface provides uniformly distributed lithiophilic sites, promotes uniform lithium nucleation and deposition, improves the stability of the lithium metal anode, facilitates rapid lithium-ion diffusion, effectively suppresses lithium dendrite growth, and enhances the safety and cycle stability of the lithium metal battery.

[0004] However, the above method is difficult to make the fluorine-containing metal salts evenly distributed on the lithium foil surface by soaking alone. Traditional protection methods cannot solve the problems of uniform lithium deposition and interface stability at the same time. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a lithium metal anode with a composite polymer electrolyte protective layer and its preparation method, which stabilizes the interface of the lithium metal anode and provides a new approach to improving the performance of the lithium metal anode.

[0006] This invention is achieved by a method for preparing a lithium metal anode with a composite polymer electrolyte protective layer, comprising the following steps:

[0007] (1) Spray a layer of ZnO-graphene nanocomposite aqueous solution or ZnS-graphene nanocomposite aqueous solution onto the surface of the cellulose membrane.

[0008] (2) A cellulose membrane prepared in step (1) is laminated onto the surface of a lithium foil or lithium metal alloy foil negative electrode;

[0009] (3) A liquid precursor that can be cured in situ is sprayed onto the cellulose membrane and a uniform composite polymer electrolyte protective layer is formed on the lithium metal anode by photo-initiated polymerization.

[0010] The thickness of the lithium foil or lithium alloy foil ranges from 10 to 80 micrometers.

[0011] The thickness of the cellulose membrane ranges from 0.5 to 5 micrometers.

[0012] The concentration of the aqueous solution of ZnO-graphene nanocomposite material or ZnS-graphene nanocomposite material is 0.1 mg / ml-1 mg / ml, and the spraying amount is controlled at 0.002-0.05 mg / cm³. 2 .

[0013] The ZnO-graphene nanocomposite material or ZnS-graphene nanocomposite material is prepared by heating a graphene oxide solution containing 2%-10% by mass of nano-ZnO or nano-ZnS in an autoclave via a hydrothermal method.

[0014] The liquid precursor comprises the following components:

[0015] Polymer monomers: One of epoxy resin monomers, acrylonitrile (AN), vinyl ether monomers, and acrylate monomers;

[0016] Solvents include one of dimethyl carbonate (DMC), ethylene glycol dimethyl ether (G2), and propylene glycol dimethyl ether (G3);

[0017] Electrolyte salts include one of lithium hexafluorophosphate (LiPF6), lithium difluorooxalate borate (LiDFOB), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and lithium bis(difluorosulfonyl)imide (LiFSI);

[0018] Photoinitiator: One of benzoin ether (BPOE), benzoin dimethyl ether (DBM), or 2,2-dimethoxy-2-phenylacetophenone (DMPA).

[0019] The liquid precursor is sprayed during roll-to-roll travel, and the liquid precursor has a mass percentage of 10%-40% and a density of 0.5-3 g / cm³. 3 The coating thickness is 5-20 micrometers, and a uniform protective layer is formed by photo-initiated polymerization.

[0020] The method for preparing the lithium metal anode with the composite polymer electrolyte protective layer further includes further processing the treated lithium metal anode and cutting it into a specific size.

[0021] The lithium metal anode with a composite polymer electrolyte protective layer prepared by the above method.

[0022] The advantages and technical effects of this invention are as follows:

[0023] 1. Promotes uniform lithium deposition: Lithophilic nanoparticles on cellulose films help guide the uniform deposition of lithium ions and reduce the risk of lithium dendrite formation.

[0024] 2. Enhanced interfacial stability: The cellulose membrane and the nanomaterials on it work together to enhance the interfacial stability of the lithium metal anode and improve the cycle life of the battery.

[0025] 3. Ensure coating uniformity: The presence of the cellulose membrane enables the liquid precursor to disperse rapidly and uniformly, avoiding unevenness caused by liquid sliding and local aggregation, ensuring that the final polymer electrolyte protective layer is flat and uniform, which is beneficial to the uniform transport of lithium ions.

[0026] 4. Simplified manufacturing process: The entire process is simple and easy to implement, suitable for large-scale industrial production, and reduces manufacturing costs. Attached Figure Description

[0027] Figure 1 This is the charge / discharge curve of the INP05 / 110 / 150 lithium metal battery obtained in Example 1 of the present invention.

[0028] Figure 2 This is the room temperature cycling curve of the INP05 / 110 / 150 lithium metal battery obtained in Example 1 of the present invention.

[0029] Figure 3 This is the rate discharge curve of the INP05 / 110 / 150 lithium metal battery obtained in Example 1 of the present invention.

[0030] Figure 4 This is the low-temperature discharge curve of the INP05 / 110 / 150 lithium metal battery obtained in Example 1 of the present invention. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0032] The method for preparing the composite polymer electrolyte protective layer of the lithium metal anode of the present invention includes the following steps in sequence:

[0033] (1) Spray a layer of ZnO-graphene nanocomposite aqueous solution or ZnS-graphene nanocomposite aqueous solution onto the surface of the cellulose membrane.

[0034] (2) A cellulose membrane prepared in step (1) is laminated onto the surface of a lithium foil or lithium metal alloy foil negative electrode;

[0035] (3) A liquid precursor that can be cured in situ is sprayed onto the cellulose membrane and a uniform composite polymer electrolyte protective layer is formed on the lithium metal anode by photo-initiated polymerization.

[0036] The thickness of the lithium foil or lithium alloy foil ranges from 10 to 80 micrometers.

[0037] The thickness of the cellulose membrane ranges from 0.5 to 5 micrometers.

[0038] The concentration of the aqueous solution of ZnO-graphene nanocomposite material or ZnS-graphene nanocomposite material is 0.1 mg / ml-1 mg / ml, and the spraying amount is controlled at 0.002-0.05 mg / cm³. 2 .

[0039] The ZnO-graphene nanocomposite material or ZnS-graphene nanocomposite material is prepared by heating a graphene oxide solution containing 2%-10% by mass of nano-ZnO or nano-ZnS in an autoclave via a hydrothermal method.

[0040] The liquid precursor comprises the following components:

[0041] Polymer monomers: One of epoxy resin monomers, acrylonitrile (AN), vinyl ether monomers, and acrylate monomers;

[0042] Solvents include one of dimethyl carbonate (DMC), ethylene glycol dimethyl ether (G2), and propylene glycol dimethyl ether (G3);

[0043] Electrolyte salts include one of lithium hexafluorophosphate (LiPF6), lithium difluorooxalate borate (LiDFOB), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and lithium bis(difluorosulfonyl)imide (LiFSI);

[0044] Photoinitiator: One of benzoin ether (BPOE), benzoin dimethyl ether (DBM), or 2,2-dimethoxy-2-phenylacetophenone (DMPA).

[0045] The liquid precursor is sprayed during roll-to-roll travel, with a mass percentage of 10%-40%, a density of 0.5-3 g / cm3, a spray thickness of 5-20 micrometers, and a uniform protective layer formed by photo-initiated polymerization.

[0046] The method for preparing the lithium metal anode with the composite polymer electrolyte protective layer further includes further processing the treated lithium metal anode and cutting it into a specific size.

[0047] The lithium metal anode with a composite polymer electrolyte protective layer prepared by the above method.

[0048] Specifically, it includes:

[0049] S1 Prepare the substrate: Select lithium foil or lithium metal alloy foil of appropriate thickness and size as the base material.

[0050] S2 Nanomaterial Pretreatment: Graphene nanomaterials of ZnO or ZnS are prepared into an aqueous solution. The nanomaterials are then uniformly coated onto the surface of the cellulose membrane using a spraying technique, ensuring uniform distribution and firm adhesion of the nanomaterials.

[0051] S3 Cellulose Membrane Pressing: A cellulose membrane containing pre-formed nanomaterials is tightly pressed onto the surface of a lithium foil or lithium alloy foil, ensuring that there are no bubbles or other defects between them.

[0052] S4 Liquid Precursor Spraying and Curing: During roll-to-roll travel, a liquid precursor that can be cured in situ is sprayed onto the surface of metallic lithium. Due to the good wettability of the cellulose membrane, the droplets can be rapidly and uniformly dispersed. Subsequently, photo-initiated polymerization is used to form a uniform polymer electrolyte protective layer.

[0053] S5 Post-processing: The lithium metal anode that has undergone the above treatment is further processed as needed, such as being cut into specific sizes, to adapt to different battery design requirements.

[0054] The following are some specific examples:

[0055] Example 1

[0056] S1 Substrate Preparation: Select a 20-micron thick lithium foil as the base material.

[0057] S2 Nanomaterial Pretreatment: ZnO-graphene nanocomposite material was prepared into an aqueous solution with a concentration of 0.2 mg / ml. This nanomaterial was then uniformly coated onto the surface of a 2-micron cellulose membrane using a spraying technique, with the coating amount controlled at 0.005 mg / cm². 2 This ensures that the nanomaterials are evenly distributed and firmly adhered.

[0058] S3 Cellulose Membrane Lamination: A cellulose membrane containing pre-formed nanomaterials is tightly laminated onto the surface of a lithium foil, ensuring that there are no air bubbles or other defects between the two.

[0059] S4 Liquid Precursor Spraying and Curing: During roll-to-roll travel, a liquid precursor (PETDA+EOEOEA+LiFSi) that can be cured in situ is sprayed onto the surface of metallic lithium. The density of the liquid precursor is 1.2 g / cm³. 3 The coating thickness is 10 micrometers. Due to the good wettability of the cellulose membrane, the droplets can be rapidly and uniformly dispersed. Subsequently, photo-initiated polymerization is used to form a uniform polymer electrolyte protective layer.

[0060] S5 Post-processing: The lithium metal anode that has undergone the above processing is further processed as needed, cut into specific sizes, and assembled with specific positive electrode sheets to form a model cell, and then subjected to corresponding tests.

[0061] The preparation method of ZnO-graphene nanocomposite materials is as follows:

[0062] 1) Dispersion: Graphene oxide (GO) is dispersed in deionized water and ultrasonically treated for 1 hour to ensure that the GO sheets are fully exfoliated and uniformly dispersed.

[0063] 2) Dissolution: Dissolve the ZnO precursor Zn(NO3)2·6H2O in deionized water and stir until homogeneous to form transparent ZnO. 2+ Solution.

[0064] 3) Mixing: Mix the well dispersed GO solution with Zn 2+ The solutions were mixed, with a ZnO precursor to graphene oxide mass ratio of 4:100, stirred until homogeneous, and then 1% by mass of ascorbic acid, a reducing agent, was added.

[0065] 4) Hydrothermal reaction: Transfer the mixed solution to an autoclave, seal it, and place it in an oven for hydrothermal reaction. The reaction temperature is usually between 170℃ and the reaction time is 10 hours.

[0066] 5) Washing: After the reaction is complete, the product is centrifuged and washed repeatedly with deionized water and ethanol to remove unreacted precursors and other impurities.

[0067] 6) Drying: The washed product is dried in a vacuum drying oven to obtain the final ZnO-graphene nanocomposite material.

[0068] The INP05 / 110 / 150 lithium metal battery obtained in this embodiment has the following appearance: Figure 1 As shown in Figure 2-4, the battery was subsequently subjected to electrical performance tests. The test results are shown in Figure 2-4. The battery has a nominal capacity of 14.6 Ah, dimensions of 4.5 × 110 × 150 mm, an energy density of up to 455 Wh / kg (0.1C), an operating voltage of 3-4.35 V, a capacity retention rate of 82.69% after 200 cycles at room temperature, 95.8% at 1C, 91% at 3C, a low-temperature capacity retention rate of 82.1% (-20℃, 0.2C), and a high-temperature capacity retention rate of 103.7% (80℃, 0.2C).

[0069] Example 2

[0070] S1 Substrate Preparation: Select a 20-micron thick lithium foil as the base material.

[0071] S2 Nanomaterial Pretreatment: ZnO-graphene nanocomposite material was prepared into an aqueous solution with a concentration of 0.2 mg / ml. This nanomaterial was then uniformly coated onto the surface of a 2-micron cellulose membrane using a spraying technique, with the coating amount controlled at 0.005 mg / cm². 2 This ensures that the nanomaterials are evenly distributed and firmly adhered.

[0072] S3 Cellulose Membrane Lamination: A cellulose membrane containing pre-formed nanomaterials is tightly laminated onto the surface of a lithium foil, ensuring that there are no air bubbles or other defects between the two.

[0073] S4 Liquid Precursor Spraying and Curing: During roll-to-roll travel, a liquid precursor (TEGDMA+EOEOEA+LiFSi) that can be cured in situ is sprayed onto the surface of metallic lithium. The density of the liquid precursor is 1.2 g / cm³. 3 The coating thickness is 10 micrometers. Due to the good wettability of the cellulose membrane, the droplets can be rapidly and uniformly dispersed. Subsequently, photo-initiated polymerization is used to form a uniform polymer electrolyte protective layer.

[0074] S5 Post-processing: The lithium metal anode that has undergone the above processing is further processed as needed, cut into specific sizes, and assembled with specific positive electrode sheets to form a model cell, and then subjected to corresponding tests.

[0075] The INP05 / 110 / 150 lithium metal battery obtained in this embodiment was subsequently subjected to electrical performance testing. The battery has a nominal capacity of 14.6 Ah and dimensions of 4.5×110×150 mm. The energy density is lower than that of Example 1. This is mainly due to the longer TEGDMA monomer molecular chain and the reduced ionic conductivity of the polymer electrolyte, which in turn leads to a decrease in energy density.

[0076] Example 3

[0077] Compared with Example 1, replacing the 2-micron cellulose membrane with a 4-micron cellulose membrane while keeping other conditions unchanged, the energy density of the resulting INP05 / 110 / 150 lithium metal battery decreased compared with Example 1. This is mainly because as the thickness of the cellulose membrane increases, the ionic conductivity of the battery decreases, and the weight increases, thus reducing the energy density.

[0078] Example 4

[0079] Compared to Example 1, the amount of graphene nanomaterials sprayed was controlled at 0.005 mg / cm³. 2 The coating amount of graphene nanomaterials was controlled at 0.01 mg / cm³. 2 With other conditions remaining unchanged, the energy density of the final INP05 / 110 / 150 lithium metal battery decreased compared to Example 1. This is mainly because as the thickness of the cellulose membrane increases, the ionic conductivity of the battery decreases, and the weight increases, resulting in a decrease in energy density.

[0080] Replacing the ZnO-graphene nanocomposite material with the ZnS-graphene nanocomposite material yields the same result, so no further examples will be given here.

[0081] The embodiments of the present invention have been described in detail above, but the content described is only a preferred embodiment of the present invention and should not be considered as limiting the scope of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the patent coverage of the present invention.

Claims

1. A method for preparing a lithium metal anode with a composite polymer electrolyte protective layer, characterized in that, The steps are as follows: (1) Spray a layer of ZnO-graphene nanocomposite aqueous solution or ZnS-graphene nanocomposite aqueous solution onto the surface of the cellulose membrane; (2) A layer of cellulose membrane prepared in step (1) is laminated onto the surface of a lithium foil or lithium alloy foil negative electrode; (3) A liquid precursor that can be cured in situ is sprayed onto the cellulose membrane and a uniform composite polymer electrolyte protective layer is formed on the lithium metal anode by photo-initiated polymerization.

2. The method for preparing the lithium metal anode with the composite polymer electrolyte protective layer according to claim 1, characterized in that, The thickness of the lithium foil or lithium alloy foil ranges from 10 to 80 micrometers.

3. The method for preparing the lithium metal anode with the composite polymer electrolyte protective layer according to claim 1, wherein the thickness of the cellulose membrane is in the range of 0.5-5 micrometers.

4. The method for preparing the lithium metal anode with the composite polymer electrolyte protective layer according to claim 1, characterized in that, The concentration of the aqueous solution of ZnO-graphene nanocomposite material or ZnS-graphene nanocomposite material is 0.1 mg / ml-1 mg / ml, and the spraying amount is controlled at 0.002-0.05 mg / cm³. 2 .

5. The method for preparing the lithium metal anode with the composite polymer electrolyte protective layer according to claim 1, characterized in that, The ZnO-graphene nanocomposite material or ZnS-graphene nanocomposite material is prepared by heating a graphene oxide solution containing 2%-10% by mass of nano-ZnO or nano-ZnS in an autoclave via a hydrothermal method.

6. The method for preparing the lithium metal anode with the composite polymer electrolyte protective layer according to claim 1, characterized in that, The liquid precursor comprises the following components: Polymer monomers: One of epoxy resin monomers, acrylonitrile, vinyl ether monomers, and acrylate monomers; Solvents include one of dimethyl carbonate, ethylene glycol dimethyl ether, and propylene glycol dimethyl ether; Electrolyte salts include one of lithium hexafluorophosphate, lithium difluorooxalate borate, lithium bis(trifluoromethanesulfonyl)imide, and lithium bis(difluorosulfonyl)imide; Photoinitiator: one of benzoin ether and 2,2-dimethoxy-2-phenylacetophenone.

7. The method for preparing the lithium metal anode with the composite polymer electrolyte protective layer according to claim 1, characterized in that, The liquid precursor is sprayed during roll-to-roll travel, and the liquid precursor has a mass percentage of 10%-40% and a density of 0.5-3 g / cm³. 3 The coating thickness is 5-20 micrometers, and a uniform protective layer is formed by photo-initiated polymerization.

8. The method for preparing the lithium metal anode with the composite polymer electrolyte protective layer according to claim 1, characterized in that, It also includes further processing of the treated lithium metal anode, cutting it into specific sizes.

9. The lithium metal anode with a composite polymer electrolyte protective layer prepared by the preparation method according to any one of claims 1-8.

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