Metal lithium negative electrode and preparation method therefor, solid-state lithium battery and electric device

Abstract

A metal lithium negative electrode and a preparation method therefor, a solid-state lithium battery and an electric device. The metal lithium negative electrode comprises a metal lithium layer and a protective layer arranged on the surface of the metal lithium layer, wherein the protective layer comprises LiF and a compound containing a -COOLi group. The preparation method for the metal lithium negative electrode comprises the following steps: soaking a metal lithium sheet in a solution containing a fluorinated acrylic monomer, taking out the metal lithium sheet, and drying same, wherein the fluorinated acrylic monomer comprises 2-fluoroacrylic acid and / or 2-trifluoromethacrylic acid. By means of a reaction between the fluorinated acrylic monomer and metal lithium, the protective layer comprising LiF and a compound containing a -COOLi group is formed on the surface of the negative electrode, such that a uniform deposition of Li can be effectively induced, and the formation of lithium dendrites is inhibited, thereby improving the cycling performance of the battery.

Description

A metal lithium negative electrode and its preparation method, solid-state lithium battery and electrical equipment

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to Chinese patent application number 2023107852622 filed with the State Intellectual Property Office of China on June 29, 2023, entitled “A metallic lithium negative electrode and its preparation method, solid-state lithium battery and electrical equipment”, the entire contents of which are incorporated by reference into this application. Technical Field

[0003] The present application relates to the field of solid-state battery technology, and in particular to a metal lithium negative electrode and a preparation method thereof, a solid-state lithium battery and electrical equipment. Background Art

[0004] Lithium metal anodes are considered the "holy grail" of secondary lithium batteries due to their high capacity (3860 mAh / g) and the most negative potential (-3.040 V vs. standard hydrogen electrode). While these anodes offer advantages such as high theoretical capacity and energy density, they also suffer from issues such as lithium dendrites, the formation of "dead lithium" powder, and stability against atmospheric oxygen.

[0005] Due to the high reactivity of metallic lithium, it easily reacts with the external air (water, oxygen, carbon dioxide, etc.) during the production process, forming an uneven impurity layer (such as Li2O, LiOH, Li2CO3, etc.) on the surface of the metallic lithium. After being prepared into a battery, as the battery cycle process increases, this uneven deposition is further aggravated, leading to the formation of lithium dendrites and the powdering of metallic lithium.

[0006] In view of this, this application is hereby filed.

[0007] Summary of the Invention

[0008] The present application discloses a metal lithium negative electrode, comprising a metal lithium layer and a protective layer arranged on the surface of the metal lithium layer;

[0009] The protective layer contains LiF and a compound containing a -COOLi group.

[0010] Optionally, the compound containing a -COOLi group includes at least one of lithium acrylate, lithium methacrylate, lithium polyacrylate and lithium polymethacrylate.

[0011] Optionally, the protective layer has a thickness of 5 to 25 μm.

[0012] Optionally, the weight percentage of LiF in the protective layer is 3.8 wt% to 10 wt%.

[0013] The present disclosure also provides a method for preparing a metallic lithium negative electrode, comprising the following steps:

[0014] Soaking the lithium metal sheet in a solution containing a fluorinated acrylic monomer, taking it out and drying it; or

[0015] The lithium metal sheets were coated with a solution containing a fluorinated acrylic monomer and dried.

[0016] Optionally, the fluorinated acrylic monomer includes 2-fluoroacrylic acid and / or 2-trifluoromethylacrylic acid.

[0017] The present application also discloses a method for preparing the metal lithium negative electrode as described above, comprising the following steps: immersing a metal lithium sheet in a solution containing a fluorinated acrylic monomer, taking it out and drying it;

[0018] The fluorinated acrylic monomer includes 2-fluoroacrylic acid and / or 2-trifluoromethylacrylic acid.

[0019] Optionally, in the solution containing the fluorinated acrylic monomer, the mass percentage of the fluorinated acrylic monomer is 1% to 20%.

[0020] Optionally, in the solution containing the fluorinated acrylic monomer, the solvent includes at least one of THF, DMSO, toluene, benzene, xylene and ethyl acetate.

[0021] Optionally, the soaking time is 8 to 30 hours.

[0022] Optionally, the drying temperature is 80 to 178° C., and the drying time is 0.5 to 24 hours.

[0023] The present application also discloses a solid-state lithium battery, comprising the metal lithium negative electrode as described above or the metal lithium negative electrode prepared by the preparation method of the metal lithium negative electrode as described above.

[0024] Optionally, the solid-state lithium battery is a sulfide solid-state lithium battery.

[0025] The present application also provides an electrical device comprising the solid-state lithium battery described above. DETAILED DESCRIPTION

[0026] The technical scheme of the present application will be clearly and completely described below in conjunction with specific embodiments, but it will be understood by those skilled in the art that the following described embodiments are part of the present application's embodiments, rather than all of the embodiments, and are only used to illustrate the present application, and should not be considered as limiting the scope of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present application. Those who do not specify specific conditions in the embodiments are carried out according to conventional conditions or the conditions recommended by the manufacturer. Those whose reagents or instruments are not specified as manufacturers are conventional products that can be purchased commercially.

[0027] The following is a detailed description of a metal lithium negative electrode, a preparation method thereof, and an electrical device according to an embodiment of the present application.

[0028] The present application provides a metallic lithium negative electrode, which can effectively induce uniform deposition of Li and inhibit the formation of lithium dendrites by forming a protective layer containing LiF and a compound containing a -COOLi group on the negative electrode surface, thereby improving the cycle performance of the battery.

[0029] The present application provides a method for preparing a metallic lithium negative electrode as described above, which utilizes a fluorinated acrylic monomer to react with metallic lithium to generate a compound containing a -COOLi group and LiF with excellent ionic conductivity, thereby protecting the metallic lithium negative electrode.

[0030] The present application provides a solid-state lithium battery with excellent cycle stability.

[0031] The present application provides an electrical device.

[0032] In some embodiments of the present application, a metal lithium negative electrode is provided, comprising a metal lithium layer and a protective layer disposed on a surface of the metal lithium layer;

[0033] The protective layer includes LiF and a compound containing a -COOLi group.

[0034] The metallic lithium negative electrode of the present application, by forming a protective layer including LiF and a compound containing a -COOLi group on the surface of the metallic lithium layer, can effectively induce the uniform deposition of Li, inhibit the formation of lithium dendrites, and improve the conductivity of lithium ions, thereby improving the cycle performance of the battery.

[0035] In some embodiments of the present application, the compound containing a -COOLi group includes at least one of lithium acrylate, lithium methacrylate, lithium polyacrylate, and lithium polymethacrylate.

[0036] Wherein, when using a metallic lithium negative electrode, the lithium acrylate and / or lithium methacrylate is polymerized to form lithium polyacrylate and / or lithium polymethacrylate.

[0037] In some embodiments of the present application, the thickness of the protective layer is 5 to 25 μm. Typically, but not limited to, for example, the thickness of the protective layer is 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm, or a range consisting of any two of the above values, such as 6 to 20 μm, 10 to 18 μm, 15 to 25 μm, 5 to 15 μm, etc. Without being bound by theory, the thickness of the protective layer within the above range can further improve the cycle performance of the battery.

[0038] In some embodiments of the present application, the weight percentage of LiF in the protective layer is 3.8 wt % to 10 wt %; typically, but not limited to, for example, the weight percentage of LiF in the protective layer is 3.8 wt %, 4.5 wt %, 5.0 wt %, 5.5 wt %, 6.5 wt %, 7.0 wt %, 7.5 wt %, 8.0 wt %, 8.5 wt %, 9.0 wt %, 9.5 wt %, 10 wt %, or a range consisting of any two of the above values, such as 4.5 wt % to 9.5 wt %, 5.5 wt % to 9.0 wt %, 6.5 wt % to 8.5 wt %, 7.0 wt % to 10 wt %, 3.8 wt % to 7 wt %, etc. Without being bound by theory, the weight percentage of LiF in the protective layer within the above range can further improve the cycle performance of the battery.

[0039] In some embodiments of the present application, a method for preparing a metallic lithium negative electrode is further provided, comprising the following steps:

[0040] Soaking the lithium metal sheet in a solution containing a fluorinated acrylic monomer, taking it out and drying it; or

[0041] A solution containing a fluorinated acrylic monomer is used to coat the lithium metal sheet and then dried. In some embodiments of the present application, a method for preparing the lithium metal negative electrode is also provided, comprising the following steps: immersing the lithium metal sheet in a solution containing a fluorinated acrylic monomer, removing the sheet, and drying the sheet;

[0042] Fluorinated acrylic monomers include 2-fluoroacrylic acid and / or 2-trifluoromethylacrylic acid.

[0043] Metallic lithium has a high reactivity. In addition to reacting with air, it also reacts with polar solvents. Therefore, in the process of surface modification of metallic lithium, it is difficult to use acids for polar solvents. For example, hydrochloric acid, nitric acid, phosphoric acid, sulfuric acid and other aqueous acids. The present application utilizes the weak acidity of fluorinated acrylic monomers to react with metallic lithium to generate monomers containing -COOLi groups and LiF with excellent ionic conductivity. During battery cycling and high-temperature formation, the monomers containing -COOLi groups can self-polymerize to form polymers due to the double bonds they contain, thereby constructing a protective layer rich in LiF and compounds containing -COOLi groups on the surface of metallic lithium. The compounds containing -COOLi groups can protect the metallic lithium negative electrode, and LiF can further induce uniform deposition of metallic lithium and inhibit the formation of lithium dendrites, thereby improving the cycle stability of metallic lithium batteries.

[0044] In some embodiments of the present application, the thickness of the lithium metal sheet is 3 μm to 600 μm; typically but not limited to, for example, the thickness of the lithium metal sheet is 3 μm, 30 μm, 50 μm, 70 μm, 100 μm, 120 μm, 150 μm, 170 μm, 600 μm, or a range consisting of any two of the above values.

[0045] In some embodiments of the present application, the solvent in the solution containing the fluorinated acrylic monomer includes at least one of THF, DMSO, toluene, benzene, xylene and ethyl acetate.

[0046] In some embodiments of the present application, in the solution containing the fluorinated acrylic monomer, the mass percentage of the fluorinated acrylic monomer is 1% to 20%; typically but not limitatively, for example, in the solution containing the fluorinated acrylic monomer, the mass percentage of the fluorinated acrylic monomer is 1%, 2%, 4%, 6%, 8%, 10%, 12%, 14%, 16%, 18%, 20% or a range consisting of any two of the above values, such as 2% to 18%, 4% to 16%, 6% to 14%, 8% to 12%, 1% to 12%, 8% to 20%, and the like.

[0047] In some embodiments of the present application, the soaking time is 8 to 30 hours; typically but not limitatively, for example, the soaking time is 8 hours, 12 hours, 14 hours, 16 hours, 18 hours, 20 hours, 22 hours, 24 hours, 30 hours or a range consisting of any two of the above values, such as 12 to 24 hours, 14 to 22 hours, 16 to 20 hours, 8 to 18 hours, 18 to 30 hours, etc.

[0048] The thickness of the protective layer can be controlled by controlling the concentration of the fluorinated acrylic monomer in the solution and the immersion time. A higher concentration of the fluorinated acrylic monomer and a longer immersion time in the solution results in a thicker protective layer, poorer electronic conductivity, and reduced battery specific capacity. A lower concentration of the fluorinated acrylic monomer and a shorter immersion time in the solution results in an inability to form a uniform protective layer.

[0049] In some embodiments of the present application, the drying temperature is 80-178°C, and the drying time is 0.5-24 hours. Typically, but not limiting, for example, the drying temperature is 80°C, 100°C, 120°C, 140°C, 160°C, 178°C, or a range consisting of any two of the above values, such as 80-160°C, 100-178°C, 120-160°C, etc. The drying time is 0.5 h, 5 h, 10 h, 15 h, 20 h, 24 h, or a range consisting of any two of the above values, such as 0.5-20 h, 5-15 h, 5-10 h, 0.5-15 h, 15-24 h, etc.

[0050] Since metallic lithium is highly reactive, it is prone to side reactions with residual solvents. After soaking, the metallic lithium sheets are removed and dried under an inert atmosphere to remove the residual solvent.

[0051] In some embodiments of the present application, the metallic lithium may be metallic lithium element and / or metallic lithium alloy.

[0052] In some embodiments of the present application, the metal lithium alloy is selected from at least one of Li-Al alloy, Li-In alloy, Li-Mg alloy, Li-Si alloy, Li-Ag alloy, Li-Ga alloy, Li-Ca alloy and Li-Bi alloy.

[0053] In some embodiments of the present application, a solid-state lithium battery is further provided, comprising the above-mentioned metal lithium negative electrode or the metal lithium negative electrode prepared by the above-mentioned method for preparing the metal lithium negative electrode.

[0054] In some embodiments of the present application, the solid-state lithium battery includes a sulfide solid-state lithium battery.

[0055] In some embodiments of the present application, an electrical device is also provided, comprising the above-mentioned solid-state lithium battery.

[0056] The following describes a metal lithium negative electrode, a preparation method thereof, a solid-state lithium battery, and an electrical device provided by the present application in conjunction with specific embodiments.

[0057] The beneficial effects of this application are:

[0058] The metallic lithium negative electrode of the present application, by forming a protective layer including LiF and a compound containing a -COOLi group on the surface of the metallic lithium layer, can effectively induce the uniform deposition of Li, inhibit the formation of lithium dendrites, and improve the conductivity of lithium ions, thereby improving the cycle performance of the battery.

[0059] This application utilizes fluorinated acrylic monomers to react with metallic lithium to generate monomers containing double bonds and -COOLi groups and LiF with excellent ionic conductivity. During battery cycling and high-temperature formation, the monomers containing double bonds and -COOLi groups self-polymerize to form polymers, thereby constructing a protective layer rich in LiF and compounds containing -COOLi groups on the surface of metallic lithium to protect the metallic lithium negative electrode; using it in solid-state batteries is beneficial to improving the electrochemical performance of solid-state batteries.

[0060] Example 1 provides a method for preparing a metallic lithium negative electrode, comprising the following steps:

[0061] 5 parts (by mass) of 2-fluoroacrylic acid, 50 parts (by mass) of THF, and 50 parts (by mass) of DMSO were mixed and stirred for 30 minutes to obtain a mixed solution; a metal lithium sheet with a thickness of 600 μm was immersed in the above mixed solution for 16 hours, then taken out and dried in an oven at 160°C under an argon atmosphere for 24 hours to obtain a metal lithium negative electrode with a protective layer thickness of 12 μm and a LiF content of 6.5 wt% in the protective layer.

[0062] The preparation methods of the metal lithium negative electrodes provided in Examples 2 to 6 refer to Example 1, except that the immersion time is adjusted to 8 h, 12 h, 20 h, 24 h, and 30 h, respectively, to obtain protective layers of different thicknesses, as shown in Table 1.

[0063] Comparative Example 1 provides a metal lithium negative electrode, which is the untreated metal lithium sheet in Example 1.

[0064] Table 1

[0065] The lithium metal negative electrodes of Examples 1 to 6 and Comparative Example 1 were used, and 0.1 g of LPSC sulfide electrolyte was taken and pressed into 10 mm discs at 70 MPa. The symmetrical cells were assembled. The current density was 0.1 mA / cm 2 , test the cycle performance, and the results are shown in Table 2.

[0066] Table 2

[0067] From the above examples and comparative examples, it can be seen that by using fluorinated acrylic acid to modify the surface of metallic lithium, a protective layer rich in LiF and compounds containing -COOLi groups can be constructed, which can effectively induce uniform deposition of lithium and improve the cycle capacity of the battery.

[0068] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application. Industrial Applicability

[0069] The present application discloses a metal lithium negative electrode, comprising a metal lithium layer and a protective layer disposed on the surface of the metal lithium layer; the protective layer comprises LiF and a compound containing a -COOLi group. The preparation method of the metal lithium negative electrode comprises the following steps: immersing a metal lithium sheet in a solution containing a fluorinated acrylic monomer, taking it out and drying it; the fluorinated acrylic monomer comprises 2-fluoroacrylic acid and / or 2-trifluoromethylacrylic acid. The present application utilizes a fluorinated acrylic monomer to react with metal lithium to form a protective layer comprising LiF and a compound containing a -COOLi group on the surface of the negative electrode, which can effectively induce uniform deposition of Li and inhibit the formation of lithium dendrites, thereby improving the cycle performance of the battery and having excellent industrial applicability.

Claims

1. A metal lithium negative electrode, comprising a metal lithium layer and a protective layer disposed on the surface of the metal lithium layer; The protective layer includes LiF and a compound containing a -COOLi group.

2. The metallic lithium negative electrode according to claim 1, wherein The compound containing a -COOLi group includes at least one of lithium acrylate, lithium methacrylate, lithium polyacrylate and lithium polymethacrylate.

3. The metallic lithium negative electrode according to claim 1, wherein The thickness of the protective layer is 5 to 25 μm.

4. The metallic lithium negative electrode according to claim 1, wherein The weight percentage of LiF in the protective layer is 3.8 wt % to 10 wt %.

5. A method for preparing a metallic lithium negative electrode, comprising the following steps: Soaking the lithium metal sheet in a solution containing a fluorinated acrylic monomer, taking it out and drying it; or The lithium metal sheet was coated with a solution containing a fluorinated acrylic monomer and dried.

6. The preparation method according to claim 5, wherein: The fluorinated acrylic monomer includes 2-fluoroacrylic acid and / or 2-trifluoromethylacrylic acid.

7. The method for preparing a metal lithium negative electrode according to any one of claims 1 to 4, comprising the following steps: immersing a metal lithium sheet in a solution containing a fluorinated acrylic monomer, taking it out and drying it; The fluorinated acrylic monomer includes 2-fluoroacrylic acid and / or 2-trifluoromethylacrylic acid.

8. The method for preparing a metallic lithium negative electrode according to claim 5 or 7, wherein: In the solution containing fluorinated acrylic monomers, the mass percentage of fluorinated acrylic monomers is 1% to 20%.

9. The method for preparing a metallic lithium negative electrode according to claim 5 or 7, wherein: In the solution containing the fluorinated acrylic monomer, the solvent includes at least one of THF, DMSO, toluene, benzene, xylene and ethyl acetate.

10. The method for preparing a metallic lithium negative electrode according to claim 7, wherein: The soaking time is 8 to 30 hours.

11. The method for preparing a metallic lithium negative electrode according to claim 5 or 7, wherein: The drying temperature is 80-178° C., and the drying time is 0.5-24 hours.

12. A solid-state lithium battery, wherein: A metal lithium negative electrode comprising the metal lithium negative electrode as described in any one of claims 1 to 4 or a metal lithium negative electrode prepared by the preparation method of the metal lithium negative electrode as described in any one of claims 5 to 11. The solid-state lithium battery according to claim 12 , which is a sulfide solid-state lithium battery.

14. An electrical device, wherein: Including the solid-state lithium battery as described in claim 9.

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