Preparation method of lithium metal negative electrode modified by multifunctional interfacial layer based on nanosheet layer and application thereof

Abstract

The application belongs to the technical field of batteries, and specifically provides a preparation method of a multifunctional interface layer modified lithium metal negative electrode based on nanosheet layers and application thereof. In the method, a nanosheet layer material with rich hydroxyl groups is peeled off, a binder is added into a nanosheet dispersion liquid obtained after peeling, and a lithium metal negative electrode with a functional interface layer is prepared by a simple blade coating method. The nanosheet material in the functional interface layer can effectively inhibit the lithium dendrite growth of the lithium metal battery during the cycle process, promote the efficient transmission of lithium ions in the solid-state battery system, regulate the uniform deposition / detachment of lithium, reduce the occurrence of side reactions, and thus improve the rate performance and cycle life of the solid-state lithium metal battery.

Description

Technical Field

[0001] This invention relates to the field of lithium battery technology, specifically a method for preparing a multifunctional interface layer modified lithium metal anode based on nanosheets and its application. Background Technology

[0002] With the rapid development of the new energy industry, the demand for rechargeable batteries with higher energy density and high safety is becoming increasingly urgent. Solid-state lithium metal batteries use lithium metal as the negative electrode, possessing a high theoretical specific capacity (3860 mAh / g), and use a solid electrolyte instead of an organic liquid electrolyte, fundamentally solving the safety hazards caused by liquid electrolyte leakage, thus offering high safety. Therefore, solid-state lithium metal batteries are considered a strong competitor for next-generation energy storage devices. However, even with solid electrolytes possessing high mechanical strength, it is still impossible to effectively suppress the growth of lithium dendrites. In solid-state battery systems, the irregular growth of lithium dendrites is the primary cause of short-circuit failure. Effectively suppressing lithium dendrite growth is key to achieving excellent cycle performance in solid-state batteries.

[0003] The uneven surface of lithium metal, its susceptibility to side reactions, and its significant volume changes during charging and discharging further limit the practical application of lithium metal anodes. Coating lithium metal is a simple and effective modification method with commercial potential. Forming an electronically insulating and ionically conductive protective layer on the surface of the lithium metal anode can effectively promote the deposition of lithium... + Uniform deposition and stripping are achieved, and direct contact between the solid electrolyte and the lithium metal anode is avoided, thus reducing the occurrence of side reactions. Furthermore, the protective layer effectively inhibits lithium dendrite formation, improving the rate performance and cycle life of lithium metal batteries. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings and deficiencies of existing technologies and to provide a method for preparing a multifunctional interface layer modified lithium metal anode based on nanosheets and its application. The technical solution adopted by this invention is as follows:

[0005] In a first aspect, a method for preparing a multifunctional interface layer modified lithium metal anode based on nanosheets is provided, comprising the following steps:

[0006] S1. A nanosheet material rich in hydroxyl groups is prepared by hydrothermal synthesis, and then a peeling agent is added to fully peel off the nanosheet material and ultrasonically disperse it to obtain a single-layer or few-layer nanosheet dispersion.

[0007] S2. Add a binder to the nanosheet dispersion prepared in S1, stir to obtain a slurry, uniformly coat the slurry onto the lithium metal surface, and evaporate the solvent in an argon atmosphere to obtain a lithium metal anode with a functional interface layer.

[0008] Preferably, in step S1, the nanosheet material is one or more of the following layered compounds: nickel cobalt oxide, graphene oxide, hydroxylated boron nitride, zirconium hydrogen phosphate (ZrP), cobalt hydroxyoxide, montmorillonite, and hydrotalcite.

[0009] In this technical solution, "ZrP" refers to "zirconium hydrogen phosphate".

[0010] Preferably, in step S1, the stripping agent is one or more of tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide.

[0011] Preferably, in step S1, the solvent used for the dispersion is one or more of tetrahydrofuran (THF), N-methylpyrrolidone (NMP), ethylene glycol dimethyl ether (DME), dimethyl carbonate (DMC), acetone, dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAC), acetonitrile, and cyclohexane.

[0012] Preferably, in step S2, the adhesive is one or more of polyvinylidene fluoride (PVDF), polyethylene oxide (PEO), polytetrafluoroethylene (PTFE), polyacrylic acid (PAA), styrene-butadiene rubber (SBR), and polyethylene glycol (PEG).

[0013] Preferably, the specific steps of the above method include:

[0014] S1. Prepare phosphorus source solution and zirconium source solution separately with distilled water and stir to mix evenly. Place the resulting mixed solution in a hydrothermal synthesis reactor and heat at 180~220 ℃ for 10~24 h. After the hydrothermal reaction is completed, centrifuge and wash the solution in the reactor with deionized water until weakly neutral. After drying, grind to obtain ZrP. Weigh the prepared ZrP and deionized water and place them in a beaker. Sonicate for 1~4 h. Then add the stripping agent and stir for 1~4 h under ice bath conditions (stirring temperature -10~0 ℃, speed 200~1000 r / min) to fully strip the ZrP. Then sonicate to obtain a transparent liquid.

[0015] Add hydrochloric acid solution, stir for 10-50 min and centrifuge to obtain exfoliated ZrP. Then, wash the exfoliated ZrP sample three times by centrifugation with water and organic solvent (one or more of acetone, toluene and tetrahydrofuran) to obtain exfoliated layered ZrP nanosheets and retain them in organic solvent.

[0016] S2. Measure the exfoliated ZrP dispersion into a serum bottle, add PEO as a binder to the ZrP dispersion in a certain proportion (e.g., the mass ratio of ZrP to PEO binder is 4~10:1, and the molecular weight of PEO is 300,000~1,000,000), stir thoroughly for 10~24 h, and then uniformly coat the prepared slurry onto the surface of the lithium strip with a scraper. Then, evaporate at room temperature under an argon atmosphere for 24~36 h to ensure that the solvent (tetrahydrofuran) of the dispersion is completely removed, resulting in lithium metal with a functionalized interface layer. Cut it into negative electrodes Li@ZrP for lithium metal batteries.

[0017] Preferably, in the above specific steps, the zirconium source is ZrOCl2·8H2O, the phosphorus source is an 85%wt phosphoric acid solution, and the stripping agent is tetrabutylammonium hydroxide.

[0018] In a second aspect, a lithium metal battery is provided, comprising a lithium metal anode material prepared by the above-mentioned preparation method of a multifunctional interface layer modified lithium metal anode based on nanosheets; specifically, the lithium metal anode material is prepared by matching the lithium metal anode material with a polymer solid electrolyte and a positive electrode sheet.

[0019] Furthermore, the polymer solid electrolyte matrix of the aforementioned lithium metal battery is one or more of the following: polyethylene oxide, polyacrylonitrile, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polyimide, polymethyl methacrylate, polycyanoacrylate, polyethylene carbonate, polypropylene carbonate, polytrimethylene carbonate, and polyvinyl carbonate.

[0020] Preferably, the conductive lithium salt used in the polymer solid electrolyte is one or more of LiPF6, LiBF4, LiClO4, LiFSI, LiTFSI, LiBOB, LiODFB, LiODFP, and LiPO2F2.

[0021] Furthermore, a method for preparing the electrolyte for the above-mentioned lithium metal battery is provided: in an argon-filled glove box, according to the formula "-EO" in PEO and "Li" in LiTFSI... +The molar ratio of PEO to lithium bis(trifluoromethane)sulfonylimide is (10~20):1. PEO and lithium bis(trifluoromethane)sulfonylimide are added and stirred for 12~20 h to ensure that PEO is fully dissolved in acetonitrile. The resulting solution is poured into a polytetrafluoroethylene mold and evaporated at room temperature under an argon atmosphere for 12~24 h to remove most of the acetonitrile solvent. Then the mold is transferred to a vacuum drying oven at 45~60 ℃ and dried for 12~24 h to remove residual acetonitrile solvent. After drying, an untreated polymer electrolyte membrane is obtained. The membrane is peeled off from the polytetrafluoroethylene mold, wrapped with clean and dust-free release paper or polytetrafluoroethylene film, and pressed in a flatbed hot press. After hot pressing, it is cooled to obtain a membrane with a thickness of 90~120μm. Then it is cut into circular electrolyte membranes by a punching machine and used as the electrolyte for lithium metal batteries.

[0022] The beneficial effects of this invention are as follows: This invention prepares nanosheet materials (such as ZrP) through hydrothermal synthesis, and obtains a single-layer or few-layer nanosheet material dispersion through a stripping agent. After adding a binder to the dispersion, a lithium metal anode with a functional interface layer is prepared by a simple coating method. By utilizing the sheet-like structure of the nanosheet material, the purpose of inhibiting lithium dendrite growth, promoting efficient lithium-ion transport in the solid-state battery system, and regulating uniform lithium deposition / stripping is achieved. The solid-state lithium metal battery prepared by matching the lithium metal anode with the functional interface layer with a solid polymer electrolyte has significantly improved rate performance and cycle life compared to unprotected bare lithium metal batteries, enhancing the rate performance and long-cycle stability of solid-state lithium metal batteries, and solving the key problem of battery failure caused by the irregular growth of lithium dendrites during cycling. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention 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 of the present invention. For those skilled in the art, obtaining other drawings based on these drawings without creative effort still falls within the scope of the present invention.

[0024] Figure 1 Optical photographs of the lithium metal anodes used in Example 1 and Comparative Example 1;

[0025] Figure 2 A comparison chart of the rate performance of solid lithium metal batteries prepared in Example 1 and Comparative Example 1;

[0026] Figure 3 This is a comparison chart of the long-cycle performance of solid-state lithium metal batteries prepared in Example 1 and Comparative Example 1. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings.

[0028] (1) Preparation of positive electrode sheet

[0029] In the following embodiments, a positive electrode sheet for a secondary lithium battery, prepared by the following method, is used:

[0030] Lithium cobalt oxide (LCO) active material, polyvinylidene fluoride (PVDF) binder, and conductive carbon were uniformly dispersed in an N-methylpyrrolidone (NMP) solution at a mass ratio of 8:1:1 and stirred at a constant speed for 16 h. The resulting slurry was cast onto aluminum foil using a doctor blade and vacuum dried at 80–100 °C for 12 h to obtain a thin film. The film was then stamped into a disc with a diameter of 12–14 mm to obtain the positive electrode sheet.

[0031] Example 1

[0032] A method for preparing a multifunctional interface layer modified lithium metal anode based on nanosheets and a lithium battery using the same method are provided, comprising the following steps:

[0033] Step 1: Weigh a certain amount of ZrOCl2·8H2O at a molar ratio of 1:20 and add it to the H3PO4 solution. After stirring and mixing evenly, place the resulting mixture in a hydrothermal synthesis reactor and heat it at 180 °C for 24 h. After the hydrothermal reaction is complete, centrifuge and wash the solution in the reactor with deionized water until it is weakly neutral. After drying, grind it to obtain ZrP.

[0034] Step 2: Weigh 0.5 g of the prepared ZrP and 30 mL of deionized water into a beaker and sonicate for 1 h. Then, add tetrabutylammonium hydroxide (TBA) as a stripping agent at a molar ratio of 1:1 and stir for 1 h under ice bath conditions to fully strip the ZrP. After sonication, a transparent liquid is obtained. Finally, add hydrochloric acid solution at a molar ratio of TBA:HCl = 1:1 to further treat the ZrP. After stirring for 10 min, centrifuge to obtain the stripped ZrP. Subsequently, wash the ZrP sample three times by centrifugation with water and organic solvent to obtain the final stripped layered ZrP nanosheets, which are then retained in the organic solvent.

[0035] Step 3: Measure 3 mL of the exfoliated ZrP dispersion into a serum bottle, and add PEO (Mw=10) at a ZrP:PEO mass ratio of 10:1. 6Using 24 h as a binder, the prepared slurry was uniformly coated onto the surface of the lithium strip using a scraper. Then, under an argon atmosphere, it was volatilized at room temperature for 24 h to ensure that tetrahydrofuran was completely removed, thus obtaining lithium metal with a functionalized interface layer. Subsequently, it was cut into 15 mm diameter discs using a die-cutting machine and used as the negative electrode (Li@ZrP) of a lithium metal battery.

[0036] Step 4: In a glove box filled with argon (moisture content <0.01ppm, oxygen content <0.01ppm), follow the instructions for PEO ("-EO") and LiTFSI ("Li")... + The molar ratio of PEO (Mw = 1,000,000) and LiTFSI was 18:1. The mixture was stirred for 24 h to ensure complete dissolution of PEO in acetonitrile. The resulting solution was poured into a polytetrafluoroethylene (PTFE) mold and evaporated at room temperature under an argon atmosphere for 24 h to remove most of the acetonitrile solvent. The mold was then transferred to a 50 °C vacuum drying oven for 24 h to remove residual acetonitrile solvent. After drying, an untreated polymer electrolyte membrane was obtained. The membrane was removed from the PTFE mold, wrapped with clean, dust-free release paper, and pressed in a flatbed hot press. After hot pressing and cooling, a membrane with a thickness of 90–120 μm was obtained. This membrane was then cut into 16.5 mm diameter circular electrolyte membranes using a die-cutting machine and used as the electrolyte in lithium metal batteries.

[0037] Step 5: Assemble the lithium metal anode with functional interface layer, polymer electrolyte membrane, and positive electrode obtained in the above steps into a lithium metal coin cell, and perform relevant electrochemical performance tests on it.

[0038] Comparative Example 1

[0039] Bare lithium without functional interface layer protection was used as the negative electrode of the solid lithium metal battery, and the rest of the operation was the same as in Example 1.

[0040] Optical photographs of the lithium metal anodes used in Example 1 and Comparative Example 1 are shown below. Figure 1 As shown, Figure a is an optical photograph of the uncoated lithium metal anode surface, which has a metallic luster under light; Figure b is an optical photograph of the lithium anode surface with a functional interface layer, showing that the exfoliated ZrP is uniformly coated on the lithium anode surface.

[0041] Example 2

[0042] 600,000 molecular weight PEO was used instead of 1,000,000 molecular weight PEO as the polymer matrix and binder, and the rest of the operation was the same as in Example 1.

[0043] Example 3

[0044] PVDF was used instead of PEO as the binder, and the rest of the operation was the same as in Example 1.

[0045] Example 4

[0046] Tetramethylammonium hydroxide was used instead of tetrabutylammonium hydroxide as the stripping agent, and the rest of the operation was the same as in Example 1.

[0047] Example 5

[0048] Replace EO:Li = 18:1 with 16:1, and perform the remaining operations as in Example 1.

[0049] Example 6

[0050] LiPF6 was used instead of LiTFSI as the conductive lithium salt, and the rest of the operation was the same as in Example 1.

[0051] Example 7

[0052] DMC was used instead of THF as the dispersant, and the rest of the operation was the same as in Example 1.

[0053] Example 8

[0054] DME was used instead of THF as the dispersant, and the rest of the operation was the same as in Example 1.

[0055] Example 9

[0056] NMP was used instead of THF as the dispersant, and the rest of the operation was the same as in Example 1.

[0057] Example 10

[0058] Nickel cobalt oxide was used instead of ZrP as nanosheets, and the rest of the operation was the same as in Example 1.

[0059] Example 11

[0060] Graphene oxide was used instead of ZrP as nanosheets, and the rest of the operation was the same as in Example 1.

[0061] Example 12

[0062] Montmorillonite was used instead of ZrP as nanosheets, and the rest of the operation was the same as in Example 1.

[0063] Example 13

[0064] Cobalt hydroxyoxide was used instead of ZrP as nanosheets, and the rest of the operation was the same as in Example 1.

[0065] Example 14

[0066] Hydroxylated boron nitride was used instead of ZrP as nanosheets, and the rest of the operation was the same as in Example 1.

[0067]

[0068] As can be seen from Table 1, the all-solid-state lithium metal battery assembled with a lithium metal-matched polymer electrolyte with a functional interface layer and a lithium cobalt oxide cathode prepared by the present invention has a higher discharge specific capacity and a better capacity retention rate compared with the comparative example.

[0069] Figure 2 The figure shows a comparison of the rate performance of the solid-state lithium metal batteries prepared in Example 1 and Comparative Example 1. As can be seen from the figure, the Li@ZrP / PEO / LCO all-solid-state battery exhibits a higher discharge specific capacity than the Bare Li / PEO / LCO battery in the 0.1~2 C rate range. The discharge specific capacity reaches 119 mAh / g and 91 mAh / g at 0.5 C and 1 C rates, respectively. This is due to the presence of the functional interface layer, which effectively suppresses the formation of lithium dendrites and reduces the occurrence of side reactions, thereby improving the rate performance of the solid-state lithium metal battery.

[0070] Figure 3 The figure compares the long-term cycling performance of the solid-state lithium metal batteries prepared in Example 1 and Comparative Example 1 at a rate of 0.5 C. As shown in the figure, the bare Li||LCO battery exhibits a low coulombic efficiency at the beginning of the cycle, reaching 98% only after 40 cycles, while the specific capacity has already dropped sharply from 108 mAh / g to 19 mAh / g. Conversely, the Li@ZrP||LCO battery with a functional interface layer still has a discharge specific capacity of 87 mAh / g after 100 cycles, and the coulombic efficiency remains around 99% throughout the cycle. This test result indicates that the functional interface layer plays an important role in the Li||LCO cycling process, effectively suppressing lithium dendrite growth, reducing side reactions, and improving the cycling stability when matched with high-voltage LCO cathode materials.

[0071] The above description discloses only preferred embodiments of the present invention and should not be construed as limiting the scope of the present invention. Therefore, equivalent variations made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. A method for preparing a multifunctional interface layer modified lithium metal anode based on nanosheets, characterized in that, Includes the following steps: S1. Prepare phosphorus source solution and zirconium source solution separately with distilled water and stir to mix evenly. Place the resulting mixed solution in a hydrothermal synthesis reactor and heat at 180~220 ℃ for 10~24 h. After the hydrothermal reaction is completed, centrifuge and wash the solution in the reactor with deionized water until weakly neutral. After drying, grind to obtain ZrP. Weigh the prepared ZrP and deionized water and place them in a beaker for sonication for 1~4 h. Then add the stripping agent and stir under ice bath conditions for 1~4 h to fully strip the ZrP. After sonication, a transparent liquid is obtained. Then add hydrochloric acid solution, stir for 10~50 min, centrifuge and wash to obtain stripped ZrP. S2. PEO is added to the ZrP dispersion as a binder in proportion. After stirring thoroughly for 10-24 h, the prepared slurry is uniformly coated onto the surface of the lithium strip using a scraper. Then, under an argon atmosphere, it is evaporated at room temperature for 24-36 h to ensure that the solvent in the dispersion is fully removed, resulting in lithium metal with a functionalized interface layer. This is then cut into pieces to serve as the negative electrode Li@ZrP for lithium metal batteries.

2. The method for preparing a multifunctional interface layer modified lithium metal anode based on nanosheets according to claim 1, characterized in that: The zirconium source is ZrOCl2·8H2O, the phosphorus source is 85%wt phosphoric acid solution, and the stripping agent is tetrabutylammonium hydroxide.

3. A lithium metal battery comprising a lithium metal anode material prepared by the preparation method of the multifunctional interface layer modified lithium metal anode based on nanosheets as described in claim 1 or 2, a polymer solid electrolyte, and a positive electrode sheet.

4. The lithium metal battery according to claim 3, characterized in that: Its polymer solid electrolyte matrix is ​​one or more of the following: polyethylene oxide, polyacrylonitrile, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polyimide, polymethyl methacrylate, polycyanoacrylate, polyethylene carbonate, polypropylene carbonate, polytrimethylene carbonate, and polyvinyl carbonate.

5. The lithium metal battery according to claim 3, characterized in that: The conductive lithium salt used in the polymer solid electrolyte is one or more of LiPF6, LiBF4, LiClO4, LiFSI, LiTFSI, LiBOB, LiODFB, LiODFP, and LiPO2F2.

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