Three-dimensional crosslinked protective coating for lithium metal battery negative electrode and lithium metal battery negative electrode based thereon

Abstract

The application discloses a three-dimensional cross-linking protective coating for a lithium metal battery negative electrode and a lithium metal battery negative electrode based on the same, a preparation method of the coating, which comprises the following steps: dissolving PVA in water, stirring and dissolving, and adding glycerol after the solution is cooled to room temperature, stirring at room temperature to prepare solution A; adding reaction monomers SBMA and MBA and an initiator into water, stirring and dissolving to obtain solution B; adding solution B into solution A, stirring at room temperature to prepare the three-dimensional cross-linking protective coating for the lithium metal battery negative electrode. + The three-dimensional cross-linking structure protective coating designed through molecular chain cross-linking has excellent ion conductivity, high Li + transfer number, low resistance and long cycle life, effectively inhibits the extension of lithium dendrites formed by lithium ions in an electrochemical process and prolongs the service life of the lithium metal battery.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of lithium battery material development, and relates to a three-dimensional cross-linked protective coating for a lithium metal battery negative electrode and a lithium metal battery negative electrode based on the same. BACKGROUND

[0002] Lithium metal anode, as a key component of the next generation of high energy density battery technology, has the advantages of high energy density (3860 mA hg -1 ) and low redox potential (-3.04 V vs. reference hydrogen electrode), making it widely concerned and applied in the fields of electric vehicles, portable electronic devices and energy storage systems. However, lithium metal batteries face the following key challenges during charging and discharging cycles: (1) Formation and growth of lithium dendrites: During charging, the deposition of lithium metal is often uneven, leading to the formation of lithium dendrites. These dendrites not only grow continuously on the electrode surface, further increasing their volume, but also can penetrate the separator, causing internal short circuits in the battery, thus causing safety hazards such as fire and explosion. This phenomenon is called the formation of "dead lithium", which seriously affects the safety and service life of the battery. (2) Instability of solid electrolyte interface (SEI): Lithium metal batteries are prone to form a fragile and uneven solid electrolyte interface (SEI) during charging and discharging. The instability of this interface makes it vulnerable to damage during plating and stripping cycles, leading to rapid consumption of lithium ions and electrolyte. With the damage of SEI, the interface impedance increases significantly, and the cycle performance and capacity decay rate of the battery accelerate, ultimately affecting the overall performance and life of the battery.

[0003] To address these challenges, researchers are actively exploring various strategies to improve the performance and safety of lithium metal anodes, including but not limited to: electrolyte formulation optimization; advanced separator material design; application of coating technology; interface engineering. In the existing reported patents, such as patent US 5342710A, a composite of poly(2-vinylpyridine) is used as a passivation layer, but the interface formed by this method is unstable and can introduce impurities to reduce the interface ion conductivity. Patent CN201510005152 uses an in-situ treatment method to form a protective layer of silicon dioxide on the metal surface, which is simple but the protective layer is easy to fall off. Patent CN 107123788B uses an organic-inorganic double protective layer to physically isolate the contact between lithium metal and electrolyte and prevent the uneven deposition of lithium ions, but the small molecule organic used in this method is easy to dissolve and fall off, and the effect is not ideal. Therefore, further efforts are urgently needed to overcome the above challenges of lithium metal batteries, and to develop a lithium metal negative electrode that not only enables uniform lithium deposition, thereby effectively inhibiting the generation of lithium dendrites, but also avoids adverse reactions with electrolyte during battery operation. This new type of lithium metal negative electrode should have the following characteristics to ensure its feasibility and safety in practical applications in the new energy field. SUMMARY

[0004] In view of the problems in the prior art, the present application provides a three-dimensional cross-linked protective coating for a lithium metal battery negative electrode and a lithium metal battery negative electrode based thereon, thereby solving the technical problems of lithium dendrite growth and limited service life of lithium metal batteries in the prior art.

[0005] The present application is realized by the following technical solutions:

[0006] A preparation method of a three-dimensional cross-linked protective coating for a lithium metal battery negative electrode, comprising the following steps:

[0007] S1: dissolve PVA in water, stir and dissolve, and after the solution cools to room temperature, add glycerol, stir at room temperature to obtain solution A; add reaction monomers SBMA and MBA and an initiator to water, stir and dissolve to obtain solution B;

[0008] S2: add solution B to solution A, stir at room temperature to obtain the three-dimensional cross-linked protective coating for a lithium metal battery negative electrode.

[0009] Preferably, in the step of dissolving PVA in water, stirring and dissolving, and after the solution cools to room temperature, adding glycerol, stirring at room temperature to obtain solution A, the temperature during stirring and dissolving is 80-120°C, and the time is 0.5-3h.

[0010] Preferably, in solution A, the ratio of PVA to water is (0.1-10)g:(10-50)mL; and the ratio of PVA to glycerol is (0.1-10)g:(1-5)mL.

[0011] Preferably, the molar ratio of SBMA to MBA is (1-10):1.

[0012] Preferably, the initiator accounts for 1%-10% of the total mass of SBMA and MBA.

[0013] Preferably, the volume ratio of solution B to solution A is (1-10):(11-55).

[0014] A three-dimensional cross-linked protective coating for a lithium metal battery negative electrode is prepared by the above method.

[0015] A preparation method of a lithium metal battery negative electrode containing a three-dimensional cross-linked protective coating, the three-dimensional cross-linked protective coating for a lithium metal battery negative electrode described above is coated on one side of an electrode sheet, and then dried in an oven at 30-100°C for 3-12h to obtain the lithium metal battery negative electrode containing a three-dimensional cross-linked protective coating.

[0016] A lithium metal battery negative electrode containing a three-dimensional cross-linked protective coating is prepared by the above method.

[0017] A lithium metal battery comprising the lithium metal battery negative electrode with three-dimensional cross-linked protective coating described above; the lithium metal battery has a capacity of 130-140 mA h / g and a capacity retention rate of 90-95% after 300 cycles of discharge at 1C.

[0018] Compared with the prior art, the present application has the following beneficial technical effects:

[0019] The present application provides a preparation method of a three-dimensional cross-linked protective coating for a lithium metal battery negative electrode. In the preparation process of the coating, PVA introduces a large number of polar functional groups (-OH), significantly enhancing its affinity for Li + ions; in addition, the sulfonic acid groups and quaternary ammonium groups introduced by SBMA construct a conductive path in the three-dimensional cross-linked molecular chain. This structural feature makes the film have excellent ion conductivity and high Li + ion transference number; the introduction of glycerol forms hydrogen bonds, increasing the density of the physical cross-linked network, so that the cross-linked network has high mechanical strength; this network structure not only has good flexibility, but also can effectively prevent the penetration of lithium dendrites to the film. After the coating is coated on the electrode sheet and heat polymerized, a three-dimensional cross-linked network coating with stable structure is formed. Since PVA introduces a large number of polar functional groups (-OH), its affinity for Li + ions is significantly enhanced, SBMA introduces sulfonic acid groups and quaternary ammonium groups to construct a conductive path in the three-dimensional cross-linked molecular chain, thereby improving the ion conductivity, reducing the impedance of the battery during the cycle process, improving the electrochemical performance, and the electrode modified by the three-dimensional cross-linked network coating can make lithium ions uniformly nucleate on the electrode surface, thereby effectively inhibiting the formation of lithium ion dendrites in the electrochemical process, effectively improving the performance and safety of the lithium metal battery.

[0020] Further, the PVA is dissolved in water, stirred and dissolved, and glycerol is added after the solution is cooled to room temperature, and the solution A is prepared by stirring at room temperature. When stirring and dissolving, the temperature is 80-120 DEG C, and the time is 0.5-3h, which can make PVA quickly dissolve in water to form a clear solution.

[0021] Further, in the solution A, the ratio of PVA to water is (0.1-10) g:(10-50) mL; the ratio of PVA to glycerol is (0.1-10) g:(1-5) mL, which can enhance the three-dimensional cross-linking strength of hydrogen bonds.

[0022] Further, the molar ratio of SBMA to MBA is (1-10):1, which can polymerize into a high molecular polymer containing zwitterions.

[0023] Further, the initiator accounts for 1% to 10% of the total mass of the SBMA and the MBA, so that the monomers can be subjected to polymerization.

[0024] Further, the volume ratio of the solution B to the solution A is (1-10):(11-55), so that the two polymer chains can form a three-dimensional crosslinking of physical and chemical bonds.

[0025] In addition, the application further discloses a preparation method of a lithium metal battery negative electrode with a three-dimensional crosslinking protective coating, specifically, the three-dimensional crosslinking protective coating for the lithium metal battery negative electrode in the application is coated on one side of an electrode sheet, and then dried in an oven at 30-100 DEG C for 3-12 hours, so that the three-dimensional crosslinking protective coating can be dried into a film on the electrode surface. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some of the embodiments of the application, and therefore should not be regarded as a limitation to the scope. For those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0027] Figure 1 A schematic diagram for preparing a PSM film on a bare copper foil in the application;

[0028] Figure 2 A Raman spectrum of a PSM film;

[0029] Figure 3 A graph of ion conductivity in a SS|PSM|SS battery assembled by using a PSM film prepared in the application example

[0030] Figure 4 Graphs of charge-discharge curves of a Li@PSM-Cu|LFP battery and a Li@Cu|LFP battery respectively under a constant current density of 0.2C, 0.5C, 1C, 2C and 5C, the Li@PSM-Cu electrode being assembled by using a Li@PSM-Cu electrode prepared in the application example;

[0031] Figure 5 A cycle charge-discharge curve of a Li@PSM-Cu|LFP battery and a Li@Cu|LFP battery under a current density of 1C, the Li@PSM-Cu electrode being assembled by using a Li@PSM-Cu electrode prepared in the application example;

[0032] Figure 6 A schematic diagram of a mechanism of a PSM coating avoiding lithium dendrites in the application. DETAILED DESCRIPTION

[0033] To enable persons skilled in the art to understand the features and effects of the present application, the following is a general description and definition of the terms and phrases mentioned in the specification and claims. Unless otherwise specified, all technical and scientific words used herein have their usual meanings to those skilled in the art of the present application, and in the event of conflict, the definitions in the present specification shall prevail.

[0034] Theories or mechanisms described and disclosed herein, whether correct or not, should not be considered limiting on the scope of the present application, i.e., the present application can be implemented without regard to any particular theory or mechanism.

[0035] Herein, all features defined in the form of numerical ranges or percentage ranges, such as numerical values, amounts, contents and concentrations, are for the sake of brevity and convenience only. Accordingly, the description of numerical ranges or percentage ranges should be considered to have encompassed and specifically disclosed all possible sub-ranges and individual numerical values within the range (including integers and fractions).

[0036] Herein, unless otherwise specified, "comprise", "include", "contain", "have" or similar words encompass the meaning of "consist of" and "consist essentially of", for example, "A comprises a" encompasses the meaning of "A comprises a and other" and "A comprises only a".

[0037] Herein, for the sake of brevity, all possible combinations of the technical features in each embodiment or example are not described. Therefore, as long as there is no contradiction in the combination of the technical features, each technical feature in each embodiment or example can be combined arbitrarily, and all possible combinations should be considered as the scope of the present specification.

[0038] The present application provides a preparation method of a three-dimensional cross-linked protective coating for a lithium metal battery negative electrode, comprising the following steps: S1: dissolving 0.1-10 g of polyvinyl alcohol (PVA) in 10-50 mL of water, stirring at 80-120°C for 0.5-3 h, and after the solution is cooled to room temperature, adding 1-5 mL of glycerol, and stirring at room temperature to obtain solution A; adding reaction monomer 3-[N,N-dimethyl-[2-(2-methylprop-2-enoyloxy)ethyl]ammonium]propane-1-sulfonic acid inner salt (SBMA) and N,N'-methylenebisacrylamide (MBA) and initiator (ammonium persulfate, APS) to water, stirring and dissolving to obtain solution B;

[0039] The molar ratio of SBMA to MBA is (1-10):1, and the initiator accounts for 1-10% of the total mass of SBMA and MBA. The molecular weight of PVA is 75,000-150,000, and the alcoholysis degree of PVA includes but is not limited to complete alcoholysis (98-100%) and partial alcoholysis (87-89%). The water used in this step can be ultrapure water, distilled water or deionized water. Glycerol includes but is not limited to natural glycerol, crude glycerol or refined glycerol.

[0040] S2: Add solution B to solution A, stir at room temperature for 0.5-3 h, and then ultrasonically treat the mixed system for 0.1-1 h to make solution A and solution B mix more uniformly and eliminate air bubbles formed during stirring to prepare the three-dimensional cross-linked protective coating for the negative electrode of a lithium metal battery. The volume ratio of solution B to solution A is (1-10):(11-55).

[0041] The application also discloses a three-dimensional cross-linked protective coating for the negative electrode of a lithium metal battery prepared by the above method. Meanwhile, the application also discloses a preparation method of a lithium metal battery negative electrode containing a three-dimensional cross-linked protective coating, wherein the three-dimensional cross-linked protective coating for the negative electrode of a lithium metal battery is coated on one side of an electrode sheet, and then dried in an oven at 30-100℃ for 3-12 h, and the obtained electrode sheet is cut into a desired shape to prepare the lithium metal battery negative electrode containing the three-dimensional cross-linked protective coating. The thickness of the three-dimensional cross-linked protective coating after drying is 5 μm.

[0042] Preferably, the electrode sheet can be pretreated between coating the three-dimensional cross-linked protective coating for the negative electrode of a lithium metal battery, and the pretreatment specifically comprises: cleaning the electrode sheet with water and ethanol for 1-5 times to remove surface impurities and improve the adhesion of the subsequent coating, and then coating the three-dimensional cross-linked protective coating for the negative electrode of a lithium metal battery on the cleaned electrode sheet by using a doctor blade with a thickness in the range of 10-100 μm to ensure the uniformity and consistency of the coating. The electrode sheet can be a copper foil.

[0043] In the cutting process, the obtained electrode sheet can be punched into a circular electrode sheet with a diameter of 10-30 mm, and then assembled into a button cell.

[0044] The application also discloses a lithium metal battery negative electrode containing a three-dimensional cross-linked protective coating prepared by the above method. Meanwhile, the application also discloses a lithium metal battery containing the lithium metal battery negative electrode containing a three-dimensional cross-linked protective coating, and the lithium metal battery has a capacity of 130-140 mA h / g and a capacity retention rate of 90-95% after 300 cycles of discharge at 1C.

[0045] The present application reports a simple strategy for the synthesis of a three-dimensional cross-linked network coating with excellent flexibility and ionic conductivity to construct a stable artificial protective layer for lithium metal anode. Specifically, the zwitterionic polymer molecular chain formed by radical polymerization of 3-[N,N-dimethyl-[2-(2-methylprop-2-enoyloxy)ethyl]ammonium]propane-1-sulfonic acid inner salt (SBMA) and N,N'-methylene bisacrylamide (MBA) constructs a conductive path in the three-dimensional cross-linked molecular chain. This structural feature makes the film have excellent ionic conductivity and high Li + ion transfer number; the introduction of polyvinyl alcohol (PVA) introduces a large number of polar functional groups (-OH), which significantly enhances its affinity for Li + ions; glycerol provides hydrogen bonds, increasing the density of the physical cross-linked network, so that the cross-linked network has high mechanical strength, thereby constructing a three-dimensional cross-linked network artificial solid electrolyte interface (SEI) layer. This network structure improves the affinity for Li + , so that Li + can be uniformly deposited and nucleated on the electrode surface, effectively avoiding the formation of lithium dendrites. This interface layer has good flexibility and mechanical strength, can meet the irregular deformation of lithium ion deposition, and can also effectively prevent lithium dendrites from penetrating the film. The three-dimensional cross-linked network coating effectively improves the thermal stability and toughness, so that the electrode surface protective coating will not easily decompose under high temperature conditions, while reducing the impedance of the battery during the cycle process, improving the ionic conductivity, and improving the electrochemical performance, so that the present application has shown significant advantages in improving the performance and safety of lithium metal batteries.

[0046] As Figure 6 shown, the present application discloses a lithium metal battery negative electrode three-dimensional cross-linked structure protective coating and a preparation method thereof. The preparation method comprises the following steps: dissolving polyvinyl alcohol in water, then mixing the polyvinyl alcohol solution with a small amount of glycerol, and stirring uniformly at room temperature. Then, [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl) ammonium hydroxide and N,N'-methylene bisacrylamide are added to water for dissolution, and a polymer long chain is obtained after adding an initiator APS. The two solutions are stirred and mixed together and then ultrasonically treated, and then the mixed solution is coated on bare copper using a scraper, and then dried to form a surface protective film, and then punched into a circular electrode sheet. The polyvinyl alcohol in the protective layer introduces a large number of polar functional groups (-OH) to enhance its affinity for Li+ions, and the sulfonic acid groups and quaternary ammonium groups introduced by the polymer long chain construct a conductive path in the three-dimensional cross-linked molecular chain. The three-dimensional cross-linked structure protective coating designed by the molecular chain cross-linking of the present application has excellent ionic conductivity and high Li +The transfer number, low resistance, and long cycle life effectively inhibit the extension of lithium dendrites formed by lithium ions in the electrochemical process, thereby prolonging the service life of the lithium metal battery.

[0047] The application will be further described in conjunction with specific examples. It should be understood that these examples are only used to illustrate the application and not used to limit the scope of the application. Furthermore, it should be understood that after reading the content taught by the application, those skilled in the art can make various modifications or changes to the application, and these equivalent forms also fall within the scope defined by the appended claims. In the following examples, conventional instruments and equipment in the art are used. In the following examples, the experimental methods not specified in the specific conditions are usually carried out according to the conventional conditions or according to the conditions recommended by the manufacturer. In the following examples, various raw materials are used, unless otherwise specified, and the conventional commercially available products are used, which are of the conventional specifications in the art. In the specification of the application and the following examples, unless otherwise specified, “%” means weight percent, “parts” means weight parts, and the ratio means weight ratio.

[0048] Example 1

[0049] A preparation method of a three-dimensional cross-linked structure protective coating for a lithium metal battery negative electrode, characterized in that it comprises the following steps:

[0050] Step 1: First, 10 parts of polyvinyl alcohol powder (PVA) (1 g) is dissolved in 150 parts of water (15 mL), and after heating and stirring at 80°C to dissolve, 10 parts of glycerol (Gly) (2 mL) solution is added after the solution is cooled to room temperature, and the solution is stirred at room temperature for 1 h to obtain solution A;

[0051] Step 2: 10 parts of 3-[N,N-dimethyl-[2-(2-methylprop-2-enoyloxy)ethyl]ammonium] propane-1-sulfonic acid inner salt (SBMA) and 0.5 parts of N,N'-methylenebisacrylamide (MBA) are added as reaction monomers, and ammonium persulfate (APS) (5 wt% of the weight of the monomers) is added as an initiator to 20 parts of water solvent, and the solution is stirred until all components are dissolved to obtain solution B;

[0052] Step 3: Then 10 parts of solution B is added to the above uniform solution A, and stirred at room temperature for 1 h to obtain the lithium metal battery negative electrode three-dimensional cross-linked structure protective coating.

[0053] Further, the lithium metal battery negative electrode three-dimensional cross-linked structure protective coating is coated on the electrode sheet, and after drying, the electrode sheet containing the lithium metal battery negative electrode three-dimensional cross-linked structure protective coating is prepared.

[0054] In this embodiment, the process of preparing the electrode sheet containing the lithium metal battery negative electrode three-dimensional cross-linked structure protective coating is specifically as follows: a copper foil is pasted on a glass sheet, only one side is exposed, and washed with water and ethanol; then the lithium metal battery negative electrode three-dimensional cross-linked structure protective coating is coated on the copper foil washed with ethanol by using a doctor blade, and placed in a 50℃ oven for drying for 5h, and finally the electrode sheet containing the lithium metal battery negative electrode three-dimensional cross-linked structure protective coating is obtained, which can be marked as electrode sheet PSM-Cu.

[0055] Further, in order to verify the excellent effect of the lithium metal battery negative electrode three-dimensional cross-linked structure protective coating in the application, the following four batteries are assembled for testing, which are Li@PSM-Cu|LFP, Li@Cu|LFP, SS|PSM|SS and SS|PVA|SS.

[0056] The assembly process of the above five batteries is as follows:

[0057] (1) Li@PSM-Cu|LFP (Li@PSM-Cu / separator / lithium iron phosphate) battery:

[0058] The positive electrode of the lithium ion battery uses a mixture of 50wt% lithium iron phosphate (as an active material), 5wt% binder (polyvinylidene fluoride, PVDF) and 5wt% ketchen black. After mixing, grind in a grinder for 1h, and then load into a container. Then, add an appropriate amount of N-methyl-2-pyrrolidone (NMP) as a solvent in the container, and place it on a magnetic stirrer for uniform stirring for 5h to ensure that the mixture reaches a viscous fluid state. In this process, carbon-coated aluminum foil is used as a current collector, and the mixed slurry is uniformly coated on its surface. Then, the carbon-coated aluminum foil coated with the mixture is placed in a vacuum drying oven, the temperature is set to 100℃, and after 6h of drying, it is taken out for use. Next, use a special slicing machine to cut the prepared carbon-coated aluminum foil into several electrode round sheets to obtain the lithium positive electrode material.

[0059] The negative electrode of the lithium ion battery is the Li@PSM-Cu electrode sheet, and the above positive electrode, negative electrode and PP separator are assembled into an LFP battery, i.e. Li@PSM-Cu|LFP battery, for subsequent testing.

[0060] The preparation process of the Li@PSM-Cu electrode is as follows: Li is deposited on the PSM-Cu by electroplating, specifically: the PSM-Cu electrode sheet is used as the positive electrode, Li is used as the negative electrode, the battery liquid is a mixed solution of 1M lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), 1,3-dioxolane (DOL) and dimethoxyethane (DME), the volume ratio of DOL to DME is 1:1, the amount of LiNO3 added is 2wt%, and the single charging cycle is 10h under the condition of 0.5mAh / h, at this time, Li ions move to the positive electrode direction through the diaphragm and undergo reduction reaction on the PSM-Cu electrode sheet, deposit on the surface of the PSM-Cu electrode sheet, and form 5mAh capacity of Li on the PSM-Cu electrode sheet, the deposited Li will penetrate the PSM coating film and pre-deposit on the surface of the copper foil to form the Li@PSM-Cu electrode.

[0061] (2) Li@Cu|LFP (Li@Cu / diaphragm / lithium iron phosphate) battery:

[0062] The positive electrode of the lithium ion battery is Li@Cu, and the negative electrode is lithium iron phosphate; the Li@Cu electrode is lithium deposited on the surface of the copper foil.

[0063] (3) SS|PSM|SS (SS / PSM / SS) battery:

[0064] The positive and negative electrodes of the lithium ion battery are both gaskets (SS), and the above-mentioned positive and negative electrodes and PSM film are assembled into a SS|PSM|SS battery for subsequent testing. The PSM film serves as a diaphragm.

[0065] The preparation process of the above-mentioned PSM film is as follows: the slurry, i.e. the precursor C solution, is poured onto a polytetrafluoroethylene plate to dry into a film, taken off, and cut into the size of a battery diaphragm to obtain.

[0066] (4) SS|PVA|SS (SS / PVA / SS) battery:

[0067] The positive and negative electrodes of the lithium ion battery are both gaskets (SS), and the above-mentioned positive and negative electrodes and PVA film are assembled into a SS|PVA|SS battery for subsequent testing. The PVA film serves as a diaphragm.

[0068] Figure 1A schematic diagram of preparing PSM film on bare copper foil in the application, from the figure, a first network is constructed by using rigid PVA clusters, a second network is constructed by radical polymerization of SBMA and MBA monomers, namely P(SBMA-MBA), which can act as a soft network, and the hydroxyl groups of Gly can interact with the functional groups of PVA and P(SBMA-MBA) molecular chains through hydrogen bonds to enhance the physical crosslinking network of the coating. In this process, due to the addition of initiator, a polymerization reaction is initiated during the drying process of the coating.

[0069] Figure 2 A Raman spectrum of the PSM film prepared in the application, from the figure, the stretching vibration of S=O at 1039 cm -1 and the stretching vibration of -N + (CH3)2 at 2978 cm -1 , which is a sign of electrostatic interaction, and the stretching vibration of O-H at 3422 to 3467 cm -1 . The results show that there are hydrogen bonds and electrostatic interactions in the PSM, and a crosslinked structural network coating is successfully synthesized.

[0070] Figure 3 Impedance test results of the SS|PSM|SS battery and the SS|PVA|SS battery in the application, and the ionic conductivity in the battery is calculated using the impedance test results of the figure, from the figure, due to the interaction of ionic dipoles, the ionic conductivity in the battery using PSM as the separator is 1.14×10 -4 Scm -1 , which is much higher than the ionic conductivity in the battery using PVA as the separator, which is 0.42×10 -4 Scm -1 .

[0071] Figure 4 Charging and discharging curve diagrams of Li@PSM-Cu|LFP batteries and Li@Cu|LFP batteries respectively assembled using Li@PSM-Cu electrodes prepared in the application at a constant current density of 0.2C, 0.5C, 1C, 2C, and 5C, from the figure, after 120 cycles at 1C (1C=170mA g -1 ), the initial capacity of Li@Cu|LFP is 135.1mA h / g, which decreases sharply, and the battery begins to gradually fail. While the initial discharge capacity of the Li@PSM-Cu|LFP full cell is 139.3mA h / g, and after 300 stable discharges, the capacity decreases to 133.5mA h / g, and the capacity retention rate is 93.8%, which significantly improves the cycle performance.

[0072] Figure 5The cycle charge-discharge curves of Li@PSM-Cu|LFP batteries and Li@Cu|LFP batteries prepared by using the Li@PSM-Cu electrode prepared in the application example are shown in the figure, and it can be seen from the figure that the discharge capacity of the Li@PSM-Cu|LFP battery is always much higher than that of the Li@Cu|LFP battery at a current density of 0.2, 0.5, 1, 2 and 5C, which means that the PSM can significantly improve the utilization rate of LFP.

[0073] The application discloses a lithium metal battery negative electrode three-dimensional cross-linking structure protective coating and a preparation method thereof. + The application discloses a lithium metal battery negative electrode three-dimensional cross-linking structure protective coating and a preparation method thereof.

[0074] Embodiment 2

[0075] A preparation method of a three-dimensional cross-linking protective coating for a lithium metal battery negative electrode, comprising the following steps:

[0076] S1: 0.1g of PVA is dissolved in 10mL of water, stirred at 80℃ for 3h, and after the solution is cooled to room temperature, 1mL of glycerol is added, and the solution A is prepared by stirring at room temperature; the reaction monomers SBMA and MBA and APS are added to water, stirred and dissolved, and then solution B is obtained;

[0077] The molar ratio of SBMA to MBA is 1:1, and the initiator accounts for 1% of the total mass of SBMA and MBA.

[0078] S2: solution B is added to solution A, stirred at room temperature for 0.5h, and then the mixed system is ultrasonically treated for 0.1h, so that the mixture of solution A and solution B is more uniform and the air bubbles formed during stirring are eliminated, and the three-dimensional cross-linking protective coating for the lithium metal battery negative electrode is prepared.

[0079] The three-dimensional cross-linked protective coating prepared above for the lithium metal battery negative electrode is coated on one side of an electrode sheet, which is then dried in an oven at 30°C for 12 h. The obtained electrode sheet is cut into a desired shape to prepare the lithium metal battery negative electrode containing a three-dimensional cross-linked protective coating. The thickness of the three-dimensional cross-linked protective coating after drying is 5 pm. The lithium metal battery negative electrode is cut and assembled into a lithium metal battery. After 300 cycles of discharge at 1C, the capacity of the lithium metal battery is 130 mA h / g, and the capacity retention rate is 90%.

[0080] Example 3

[0081] A preparation method of a three-dimensional cross-linked protective coating for a lithium metal battery negative electrode, comprising the following steps:

[0082] S1: 10 g of PVA is dissolved in 50 mL of water, stirred at 120°C for 0.5 h, and 5 mL of glycerol is added after the solution is cooled to room temperature. The solution A is prepared by stirring at room temperature. The reaction monomers SBMA and MBA and APS are added to water, and after stirring and dissolving, solution B is obtained;

[0083] The molar ratio of SBMA to MBA is 10:1, and the initiator accounts for 10% of the total mass of SBMA and MBA.

[0084] S2: Solution B is added to solution A, stirred at room temperature for 3 h, and then the mixed system is ultrasonically treated for 1 h to make the mixture of solution A and solution B more uniform and eliminate the air bubbles formed during stirring. The three-dimensional cross-linked protective coating for the lithium metal battery negative electrode is prepared. The volume ratio of solution B to solution A is 10:55.

[0085] The three-dimensional cross-linked protective coating prepared above for the lithium metal battery negative electrode is coated on one side of an electrode sheet, which is then dried in an oven at 100°C for 3 h. The obtained electrode sheet is cut into a desired shape to prepare the lithium metal battery negative electrode containing a three-dimensional cross-linked protective coating. The thickness of the three-dimensional cross-linked protective coating after drying is 5 pm. The lithium metal battery negative electrode is cut and assembled into a lithium metal battery. After 300 cycles of discharge at 1C, the capacity of the lithium metal battery is 141 mA h / g, and the capacity retention rate is 94.8%.

[0086] Example 4

[0087] A preparation method of a three-dimensional cross-linked protective coating for a lithium metal battery negative electrode, comprising the following steps:

[0088] S1: 5 g of PVA was dissolved in 25 mL of water, stirred at 100°C for 2 h, and after the solution was cooled to room temperature, 2 mL of glycerol was added, and the solution was prepared by stirring at room temperature; the reaction monomers SBMA and MBA and APS were added to water, and after stirring and dissolving, solution B was obtained;

[0089] The molar ratio of SBMA to MBA is 5:1, and the initiator accounts for 5% of the total mass of SBMA and MBA.

[0090] S2: Solution B was added to solution A, stirred at room temperature for 2 h, and then the mixed system was ultrasonically treated for 0.5 h, which can make the mixing of solution A and solution B more uniform and eliminate the air bubbles formed during stirring, and the three-dimensional cross-linked protective coating for the negative electrode of lithium metal battery was prepared. The volume ratio of solution B to solution A is 5:20.

[0091] In this embodiment, the three-dimensional cross-linked protective coating for the negative electrode of lithium metal battery prepared above was coated on one side of the electrode sheet, and then dried in a 70°C oven for 10 h, and the obtained electrode sheet was cut into the required shape to prepare the lithium metal battery negative electrode containing a three-dimensional cross-linked protective coating. The thickness of the three-dimensional cross-linked protective coating after drying is 5 μm. After cutting the lithium metal battery negative electrode, the lithium metal battery was assembled, and the capacity of the lithium metal battery was 133 mA h / g after 300 cycles of discharge at 1C, and the capacity retention rate was 92.5%.

[0092] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application and not to limit the protection scope of the present application. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present application.

Claims

1. A method for preparing a three-dimensional cross-linked protective coating for a lithium metal battery anode, characterized in that, The method comprises the following steps: S1: dissolving PVA in water, stirring and dissolving, and adding glycerol after the solution is cooled to room temperature, and stirring at room temperature to prepare solution A; adding reaction monomers SBMA and MBA and an initiator into water, stirring and dissolving to obtain solution B; S2: adding solution B into solution A, stirring at room temperature to prepare the three-dimensional cross-linked protective coating for a lithium metal battery negative electrode; In the solution A, the ratio of PVA to water is (0.1-10) g:(10-50) mL; the ratio of PVA to glycerol is (0.1-10) g:(1-5) mL; The molar ratio of SBMA to MBA is (1-10):1; The initiator accounts for 1%-10% of the total mass of SBMA and MBA; The volume ratio of solution B to solution A is (1-10):(11-55).

2. The method of claim 1, wherein the method is characterized by: In the preparation of solution A, the temperature during stirring and dissolving is 80-120℃, and the time is 0.5-3h.

3. A three-dimensional cross-linked protective coating for lithium metal battery negative electrode, characterized in that, The three-dimensional cross-linked protective coating for a lithium metal battery negative electrode is prepared by the method of any one of claims 1-2.

4. A method of making a lithium metal battery anode containing a three- dimensional cross-linked protective coating, characterized in that, The three-dimensional cross-linked protective coating for a lithium metal battery negative electrode is coated on one side of an electrode sheet, and then dried in an oven at 30-100℃ for 3-12h to prepare the lithium metal battery negative electrode containing a three-dimensional cross-linked protective coating.

5. A lithium metal battery anode comprising a three-dimensional crosslinked protective coating, characterized in that, The lithium metal battery negative electrode containing a three-dimensional cross-linked protective coating is prepared by the method of claim 4.

6. A lithium metal battery characterized in that, The lithium metal battery negative electrode containing a three-dimensional cross-linked protective coating is prepared by the method of claim 4. The lithium metal battery negative electrode containing a three-dimensional cross-linked protective coating is prepared by the method of claim 4. The lithium metal battery negative electrode containing a three-dimensional cross-linked protective coating is prepared by the method of claim 4.

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