A negative electrode protective film for a lithium metal battery with a self-healing composite nuclear seed and its application

Abstract

The present invention discloses a negative electrode protective film for a lithium metal battery with a self-healing composite nuclear seed and its application. The protective film is a polymer film, which is prepared by a one-step polymer mixed solution casting process, has a layered and tightly cross-linked structure, has grooves formed on the upper surface, and GaIn nanoparticles are modified in the polymer film. The GaIn nanoparticles are deposited at the bottom of the film under the influence of their own gravity, so that the polymer film presents a layered structure. The preparation method of the present invention is simple and convenient, and the battery assembled with the obtained composite film has excellent electrochemical performance, showing excellent lithium ion storage capacity, rate performance and stable lithium metal negative electrode cycling performance.

Description

Technical Field

[0001] The present invention relates to a preparation method of a negative electrode protective film for a lithium metal battery with self-healing synthetic nuclear seeds, belonging to the field of organic polymer materials. Background Art

[0002] Lithium metal has attracted wide attention due to its advantages of ultra-high theoretical capacity (3860 mAh·g -1 ) and low redox potential (3.04 V vs. standard hydrogen electrode), and is regarded as one of the most promising candidate negative electrodes for the next generation of high specific energy secondary batteries. However, due to the interfacial reaction of organic electrolytes, dendrite growth, uncontrolled volume change, and side reactions between lithium metal and electrolytes, the lithium metal battery has poor cycle life and safety problems, which hinder its application expansion. In previous studies, researchers have tried to solve the above problems through various strategies, such as functional electrolyte additives, constructing artificial SEI layers, solid-state electrolytes (SSEs), and designing three-dimensional current collectors. However, the lithium metal negative electrode modified with artificial SEI has limited deposition area and is difficult to induce uniform lithium deposition at high current density, and will face serious dendrite growth problems. Therefore, through a synergistic strategy combining artificial interface design and inducing uniform lithium nucleation host, it is expected to effectively address the problems faced by the lithium metal negative electrode. In addition, for the long cycle process, inhibiting the formation of lithium dendrites and constructing a composite structure lithium negative electrode are of great significance for high energy density batteries. Summary of the Invention

[0003] The present invention aims to provide a multifunctional lithium metal battery negative electrode protective film with self-healing synthetic nuclear seeds and its preparation method, which is convenient in preparation method, low in cost, novel in concept, and unique in morphology, so as to enhance the safety performance and stability of the lithium metal negative electrode, and the long-cycle stability and rate performance of the lithium metal battery.

[0004] In order to solve the technical problems, the present invention adopts the following technical solutions:

[0005] The present invention discloses a negative electrode protective film for a lithium metal battery with self-healing synthetic nuclear seeds, which is characterized in that: the negative electrode protective film for the lithium metal battery is a polymer film, grooves are formed on the upper surface of the polymer film, and GaIn nanoparticles are modified in the polymer film; the GaIn nanoparticles are deposited at the bottom of the film under the influence of their own gravity, so that the polymer film presents a layered structure.

[0006] The preparation method of the negative electrode protective film for the lithium metal battery with self-healing synthetic nuclear seeds of the present invention includes the following steps:

[0007] Step 1: Mix gallium and indium, heat and stir until evenly mixed to obtain a gallium-indium eutectic (GaIn);

[0008] Step 2: Add lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) to N-methylpyrrolidone (NMP), heat and stir until dissolved, then add poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), and continue to heat and stir until dissolved to obtain a homogeneous solution;

[0009] Step 3: Add the gallium-indium eutectic obtained in Step 1 to the homogeneous solution obtained in Step 2, after ultrasonic treatment, stir at room temperature until evenly dispersed, and then perform defoaming treatment to obtain a mixed solution; Pour the mixed solution onto a mold and dry it under vacuum to obtain a lithium metal battery negative electrode protective film with self-healing synthetic nuclear seeds.

[0010] Preferably, in Step 1, the weight ratio of gallium to indium is 70.5 - 79.5:29.5 - 20.5.

[0011] Preferably, in Step 1, the temperature of heating and stirring is 145 - 175 °C.

[0012] Preferably, the dosage ratio of LiTFSI, NMP, PVDF-HFP in Step 2 and the gallium-indium eutectic in Step 3 is 0.05 - 0.25 g:1.0 - 8.0 mL:0.25 - 1.5 g:0.1 - 1.0 mL.

[0013] Preferably, in Step 2, the temperature of heating and stirring is 60 - 80 °C.

[0014] Preferably, in Step 3, the defoaming treatment is to mix and defoam in a planetary mixer under the conditions of self-rotation at 300 - 500 rpm and revolution at 500 - 2000 rpm for 60 - 600 s.

[0015] Preferably, in Step 3, the temperature of the vacuum drying is 60 - 80 °C and the drying time is 12 - 24 h.

[0016] The lithium metal battery negative electrode protective film with self-healing synthetic nuclear seeds prepared by the present invention can be used between the negative electrode lithium sheet and the separator of a lithium metal battery as a protective film for the negative electrode lithium sheet. During specific application, the protective film can be covered on the outer surface of one side of the lithium sheet and rolled with a polytetrafluoroethylene roller to form a film-modified negative electrode lithium sheet, and then the separator is closely attached to the protective film.

[0017] The beneficial effects of the present invention are reflected in:

[0018] The lithium metal battery anode protective film with self-healing composite nuclear seeds of the present invention is prepared by a one-step polymer mixed solution casting process. The method is convenient. The obtained multifunctional protective film has a layered and tightly cross-linked network structure, with grooves on the upper surface. Gallium indium (GaIn) nanoparticles are uniformly deposited at the bottom of the multifunctional film under the action of their own gravity. When applied in a lithium metal battery, the protective film with self-healing composite nuclear seeds is closely attached between the negative lithium sheet and the separator, which can effectively enhance the conductivity of lithium ions and inhibit the unlimited growth of lithium dendrites during the lithium metal cycle. At the same time, the groove structure on the upper surface can enhance the penetration of the electrolyte and quickly reach a steady state, enabling the lithium metal battery protected by this composite film to have excellent electrochemical performance, as well as excellent lithium ion storage capacity, cycle stability and rate performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 SEM photograph of SPF-1 obtained in Example 1 of the present invention.

[0020] Figure 2 SEM photograph of SPF-1 obtained in Example 1 of the present invention ( Figure 2 (a)) and distribution maps of C, F, Ga, and In elements ( Figure 2 (b) to (e))

[0021] Figure 3 Optical photograph of SPF-1 obtained in Example 1 of the present invention ( Figure 3 (a)) and X-ray diffraction pattern ( Figure 3 (b)).

[0022] Figure 4 Nyquist comparison diagram of SPF-1 and SPF-2 obtained in Example 1 of the present invention ( Figure 4 (a)) and Arrhenius comparison diagram ( Figure 4 (b)).

[0023] Figure 5 Current-time curve of SPF-1 obtained in Example 1 of the present invention ( Figure 5 (a), the inset is the EIS impedance test diagram of SPF-1), and stress-strain comparison curve with SPF-2 ( Figure 5 (b)).

[0024] Figure 6 SPF-1 obtained in Example 1 of the present invention ( Figure 6 (a)) and penetration angle test of polypropylene separator as a control group ( Figure 6 (b)).

[0025] Figure 7Electrochemical performance comparison of symmetric cells assembled with SPF-1@Li, SPF-2@Li and bare lithium (BareLi) obtained in Example 1 of the present invention.

[0026] Figure 8 Electrochemical performance comparison of symmetric cells assembled with SPF-1@Li, SPF-2@Li and bare lithium obtained in Example 1 of the present invention at a high current density of 20 mA cm -2 -2.

[0027] Figure 9 Rate performance comparison of full cells assembled with SPF-1@Li, SPF-2@Li and bare lithium obtained in Example 1 of the present invention. The test rates are 0.1, 0.2, 0.5, 1, 1.5, 2, 3, 0.1C respectively.

[0028] Figure 10 Cycling performance comparison chart of full cells assembled with SPF-1@Li, SPF-2@Li and bare lithium obtained in Example 1 of the present invention at a high current density of 2C.

[0029] Figure 11 Electrochemical performance comparison of symmetric cells assembled with SPF-1@Li, SPF-2@Li and bare lithium obtained in Example 2 of the present invention.

[0030] Figure 12 Electrochemical performance comparison of symmetric cells assembled with SPF-1@Li, SPF-2@Li and bare lithium obtained in Example 3 of the present invention. Detailed implementation manners

[0031] To make the above objects, features and advantages of the present invention more comprehensible, the following detailed description of the specific implementation manners of the present invention is provided in conjunction with the accompanying drawings. The following content is only an example and illustration of the concept of the present invention. Those skilled in the art of the present technology can make various modifications or supplements to the described specific implementation cases or use similar methods to replace them, as long as they do not deviate from the concept of the invention or exceed the scope defined by the claims of the present invention, they should all fall within the protection scope of the present invention.

[0032] Unless otherwise specified, the experimental methods used in the following examples are all conventional methods.

[0033] Unless otherwise specified, the reagents, materials, etc. used in the following examples can all be obtained from commercial channels.

[0034] The electrochemical performance tests of the lithium metal batteries in the following examples were all completed by the NEWARE battery test system (test voltage 2.5V - 3.9V vs. Li + + / Li).

[0035] Example 1

[0036] The negative electrode protective film of the multifunctional lithium metal battery with self-healing synthetic nuclear seeds was prepared in the following steps in this embodiment:

[0037] Step 1: Mix gallium and indium at a weight ratio of 70.5:29.5. Subsequently, heat and stir the mixture at 175 °C for 0.5 h on a magnetic stirrer to make them evenly mixed, obtaining a gallium-indium eutectic (GaIn).

[0038] Step 2: Weigh 0.05 g of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI, MW = 5800, Aladdin) and add it to 1.0 mL of N-methylpyrrolidone (NMP, ≥99.9%, Macklin). Heat and stir at 60 °C until dissolved. Subsequently, add 0.25 g of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP, MW = 150,000, Macklin), and continue to heat and stir until dissolved to obtain a homogeneous solution.

[0039] Step 3: Add 100 μL of the gallium-indium eutectic obtained in Step 1 to the homogeneous solution obtained in Step 2, perform ultrasonic treatment for 20 min, then stir at room temperature until evenly dispersed. Then, perform defoaming treatment with a planetary mixer (rotation speed 300 rpm, revolution speed 500 rpm, time 60 s) to obtain a mixed solution. Pour the mixed solution onto a polytetrafluoroethylene mold and vacuum dry it at 60 °C for 12 h in a vacuum drying oven to obtain the negative electrode protective film of the multifunctional lithium metal battery with self-healing synthetic nuclear seeds (denoted as SPF-1).

[0040] For comparison, a pure-phase film without self-healing synthetic nuclear seeds (GaIn) (denoted as SPF-2) was also prepared in this embodiment. The method is the same as the preparation method of the above-mentioned multifunctional protective film (SPF-1), except that: directly perform defoaming treatment on the homogeneous solution obtained in Step 2 under the same conditions and then pour it onto a polytetrafluoroethylene mold, and then vacuum dry it at 60 °C for 12 h to obtain a pure-phase negative electrode protective film for lithium-ion batteries (SPF-2).

[0041] Morphology and structure characterization: Observe the morphology of SPF-1 prepared in this embodiment by SEM (scanning electron microscope), take optical images of the samples, analyze the structural components of the samples by XRD (X-ray diffraction), perform simulation analysis of ionic conductivity and activation energy on the samples with an electrochemical workstation, perform stress-strain tests on the samples with a stress tester, and perform penetration angle tests on the samples with a water contact angle tester.

[0042] Electrochemical performance test: The SPF-1 and SPF-2 prepared in this example were stored in a glove box filled with Ar with the contents of water and oxygen both less than 0.01 ppm for standby. The film-modified lithium metal electrodes (SPF-1@Li and SPF-2@Li) were prepared by one-step rolling, that is, covering the film on the surface of the lithium metal and then rolling it with a polytetrafluoroethylene roller.

[0043] The symmetric cell used SPF-1@Li, SPF-2@Li or a bare lithium sheet as the counter electrode and the working electrode respectively, with a PP (polypropylene) separator and an electrolyte of 1.0 M LiPF6 in EC:DMC:EMC = 1:1:1 Vol% solution. Taking SPF-1 as an example, the CR2032 coin cell was assembled in the order of the negative electrode shell, lithium sheet, SPF-1, PP separator, electrolyte, SPF-1, lithium sheet, gasket, spring sheet, and positive electrode shell. Subsequently, the cell was left standing at room temperature for several hours before testing, and all relevant electrochemical performance tests were carried out on a Neware battery test system.

[0044] The full cell was paired with a lithium iron phosphate (LiFePO4) positive electrode. LiFePO4 was mixed and ground with Ketjen black and a binder (PVDF) in a weight ratio of 8:1:1 and evenly coated on the surface of the aluminum foil. After vacuum drying at 90 °C, it was sliced to be used as the working electrode of the lithium-ion battery. A PP (polypropylene) separator was used, with SPF-1@Li, SPF-2@Li or a bare lithium sheet as the counter electrode and an electrolyte of 1.0 M LiPF6 in EC:DMC:EMC = 1:1:1 Vol% solution. Taking SPF-1 as an example, the CR2032 coin cell was assembled in the order of the negative electrode shell, lithium sheet, SPF-1, PP separator, electrolyte, LiFePO4 electrode sheet, gasket, spring sheet, and positive electrode shell. Subsequently, the cell was left standing at room temperature for several hours before testing, and all relevant electrochemical performance tests were carried out on a Neware battery test system.

[0045] Figure 1 This is the SEM photograph of SPF-1 obtained in this example. It can be seen that SPF-1 as a whole presents a cross-linked network morphology, and grooves with a diameter of about 1.0 - 2.0 μm are formed on the surface.

[0046] Figure 2 This is the SEM photograph of SPF-1 obtained in this example ( Figure 2 (a)) and the distribution maps of C, F, Ga, and In elements ( Figure 2 (b) - (e)). It can be seen that GaIn nanoparticles are embedded in the polymer network of the protective film, and the GaIn nanoparticles are deposited at the bottom of the film.

[0047] Figure 3(a) The optical photograph of SPF-1 obtained in this example shows that SPF-1 has excellent flexibility. Figure 3 (b) The X-ray diffraction patterns of SPF-1 and SPF-2 show that the diffraction peaks of SPF-1 and SPF-2 correspond one by one, indicating that the composite protective film was successfully prepared in this example. In contrast, the diffraction peak intensity of SPF-1 weakens and broadens at 2θ = 19° and 40°, indicating that the introduction of GaIn nanoparticles reduces the crystallinity of PVDF-HFP and enhances the flexibility of the film.

[0048] Figure 4 The performance comparison of SPF-1, SPF-2 and PP separator obtained in this example is as follows: Figure 4 (a) The Nyquist comparison diagram shows that SPF-1 has a higher ionic conductivity; Figure 4 (b) The Arrhenius comparison diagram shows that the activation energy of SPF-1 is much lower than that of the other two groups, indicating its self-healing ability, and the introduction of hydrophilic GaIn seeds can effectively induce the deposition of lithium ions and inhibit the formation of "dead lithium".

[0049] Figure 5 The performance comparison of SPF-1 and SPF-2 obtained in this example is as follows Figure 5 (a) The current-time curve of SPF-1 (the inset is the EIS impedance test diagram of SPF-1), Figure 5 (b) The stress-strain comparison curve of SPF-1 and SPF-2 shows that SPF-1 has a higher lithium ion transference number and excellent tensile properties, indicating that it can effectively inhibit the growth of dendrites and thus improve the electrochemical performance of the symmetric battery.

[0050] Figure 6 The wetting angle test of SPF-1 obtained in this example Figure 6 (a)) and the polypropylene separator as the control group Figure 6 (b)). During the test, a drop of 1.0 M LiPF6 in EC:DMC:EMC = 1:1:1 Vol% solution was dropped on the SPF-1 protective film and the polypropylene separator respectively. After 3 seconds, it can be seen that the wettability of SPF-1 with a unique structure to the electrolyte is much greater than that of the control group, indicating that the lithium metal anode modified with SPF-1 can quickly reach the interface steady state.

[0051] Figure 7 The symmetric batteries assembled with SPF-1@Li, SPF-2@Li and bare lithium obtained in this example at 0.25 mA cm -2Comparing the electrochemical performance at a current density, it can be seen that the voltage hysteresis of SPF-1@Li is much smaller than that of the control group. After stable cycling for 4000 hours, it still has a low overpotential (~16.8 mV). Compared with the overpotential (~85.3 mV) of the SPF-2@Li symmetric battery after 500 hours of cycling and the overpotential (~227.1 mV) of the bare lithium symmetric battery after 100 hours of cycling, it shows excellent electrochemical performance.

[0052] Figure 8 For the symmetric batteries assembled with SPF-1@Li, SPF-2@Li and bare lithium obtained in this example at a current density of 20 mA cm -2 Comparing the electrochemical performance, it can be seen that even at a large current density of 20 mA cm -2 , compared with the overpotential (~303.8 mV) of the SPF-2@Li symmetric battery and the overpotential (~480.5 mV) of the bare lithium symmetric battery, SPF-1@Li still has a smaller overpotential (~50.4 mV), and its cycle life is much longer than that of the control group, indicating that faster mass transfer can inhibit the growth of lithium dendrites and shows more excellent electrochemical performance.

[0053] Figure 9 For the rate performance comparison of the full batteries assembled with SPF-1@Li, SPF-2@Li and bare lithium obtained in this example, the test rates are 0.1, 0.2, 0.5, 1, 2, 3, 0.1 C respectively. As shown in the figure, the full battery assembled with SPF-1@Li still shows a high reversible specific capacity of lithium storage (120 mAh g –1 ) at a large current density of 3 C. Compared with the reversible specific capacity of lithium storage (60 mAh g –1 ) of the full battery assembled with SPF-2@Li and the reversible specific capacity of lithium storage (30 mAh g –1 ) of the full battery assembled with bare lithium, it shows more excellent rate performance.

[0054] Figure 10 For the comparison chart of the cycle performance of the full batteries assembled with SPF-1@Li, SPF-2@Li and bare lithium obtained in this example at a large current density of 2 C. As shown in the figure, after 1000 charge-discharge cycles, the reversible specific capacity of SPF-1@Li still remains at 128 mAh g –1 . Compared with the reversible specific capacity (70 mAh g –1 ) of the full battery assembled with SPF-2@Li after 1000 charge-discharge cycles and the reversible specific capacity (25 mAh g –1 ) of the full battery assembled with bare lithium after 200 charge-discharge cycles, it shows more excellent cycle stability performance.

[0055] Example 2

[0056] The negative electrode protective film of the multifunctional lithium metal battery with self-healing synthetic nuclear seeds is prepared according to the following steps:

[0057] Step 1: Mix gallium and indium at a weight ratio of 79.5:20.5. Subsequently, heat and stir the mixture on a magnetic stirrer at 145 °C for 0.5 h to make them evenly mixed, obtaining a gallium-indium eutectic (GaIn).

[0058] Step 2: Weigh 0.25 g of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI, MW = 5800, Aladdin) and add it to 8.0 mL of N-methylpyrrolidone (NMP, ≥99.9%, Macklin). Heat and stir at 80 °C until dissolved. Subsequently, add 1.5 g of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP, MW = 150,000, Macklin), and continue to heat and stir until dissolved to obtain a homogeneous solution.

[0059] Step 3: Add 1.0 mL of the gallium-indium eutectic obtained in Step 1 to the homogeneous solution obtained in Step 2, perform ultrasonic treatment for 30 min, then stir at room temperature until evenly dispersed. Next, perform defoaming treatment with a planetary mixer (rotation speed 500 rpm, revolution speed 2000 rpm, time 600 s) to obtain a mixed solution. Pour the mixed solution onto a polytetrafluoroethylene mold and vacuum dry it in a vacuum drying oven at 80 °C for 24 h to obtain the negative electrode protective film of the multifunctional lithium metal battery with self-healing synthetic nuclear seeds (denoted as SPF-1).

[0060] For comparison, a pure-phase film without self-healing synthetic nuclear seeds (GaIn) (denoted as SPF-2) was also prepared in this example. Its preparation method is the same as that of the above-mentioned multifunctional protective film (SPF-1), except that: directly perform defoaming treatment on the homogeneous solution obtained in Step 2 under the same conditions and then pour it onto a polytetrafluoroethylene mold, and then vacuum dry it at 80 °C for 24 h to obtain a pure-phase negative electrode protective film for lithium-ion batteries (SPF-2).

[0061] Figure 11 For the comparison of the electrochemical performance of the symmetric batteries assembled with SPF-1@Li, SPF-2@Li and bare lithium in this example at a current density of 0.25 mA cm -2 It can be seen that the voltage hysteresis of SPF-1@Li is much smaller than that of the control group. After stable cycling for 4000 hours, it still has a low overpotential (~18.2 mV). Compared with the overpotential (~88.2 mV) of the SPF-2@Li symmetric battery after 500 hours of cycling and the overpotential (~229.7 mV) of the bare lithium symmetric battery after 100 hours of cycling, it shows excellent electrochemical performance.

[0062] Example 3

[0063] The negative electrode protective film of the multifunctional lithium metal battery with self-healing synthetic nuclear seeds was prepared according to the following steps in this example:

[0064] Step 1: Mix gallium and indium at a weight ratio of 72.5:27.5. Subsequently, heat and stir the mixture at 155 °C for 0.5 h on a magnetic stirrer to make them evenly mixed, obtaining a gallium-indium eutectic (GaIn).

[0065] Step 2: Weigh 0.15 g of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI, MW = 5800, Aladdin) and add it to 3.0 mL of N-methylpyrrolidone (NMP, ≥99.9%, Macklin). Heat and stir at 70 °C until dissolved. Subsequently, add 0.75 g of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP, MW = 150,000, Macklin), and continue to heat and stir until dissolved to obtain a homogeneous solution.

[0066] Step 3: Add 300 μL of the gallium-indium eutectic obtained in Step 1 to the homogeneous solution obtained in Step 2, perform ultrasonic treatment for 24 min, then stir at room temperature until evenly dispersed. Next, perform defoaming treatment with a planetary mixer (rotating at 400 rpm, revolving at 900 rpm, for 180 s) to obtain a mixed solution. Pour the mixed solution onto a polytetrafluoroethylene mold and vacuum dry it at 70 °C for 16 h in a vacuum drying oven, thus obtaining the negative electrode protective film of the multifunctional lithium metal battery with self-healing synthetic nuclear seeds (denoted as SPF-1).

[0067] For comparison, a pure-phase film without self-healing synthetic nuclear seeds (GaIn) (denoted as SPF-2) was also prepared in this example. Its preparation method is the same as that of the above-mentioned multifunctional protective film (SPF-1), except that: directly perform defoaming treatment on the homogeneous solution obtained in Step 2 under the same conditions and then pour it onto a polytetrafluoroethylene mold, and then vacuum dry it at 70 °C for 16 h to obtain a pure-phase negative electrode protective film for lithium-ion batteries (SPF-2).

[0068] Figure 12 For the comparison of the electrochemical performance of the symmetric batteries assembled with SPF-1@Li, SPF-2@Li and bare lithium in this example at a current density of 0.25 mA cm -2 It can be seen that the voltage hysteresis of SPF-1@Li is much smaller than that of the control group. After stable cycling for 4000 hours, it still has a low overpotential (~17.4 mV). Compared with the overpotential (~82.8 mV) of the SPF-2@Li symmetric battery after cycling for 500 hours and the overpotential (~223 mV) of the bare lithium symmetric battery after cycling for 100 hours, it shows excellent electrochemical performance;

[0069] Example 4

[0070] In this embodiment, the multifunctional lithium metal battery anode protective film with self-healing synthetic nuclear seeds is prepared according to the following steps:

[0071] Step 1: Mix gallium and indium in a weight ratio of 74.5:25.5. Subsequently, heat and stir the mixture at 160 °C for 0.5 h on a magnetic stirrer to make them evenly mixed and obtain gallium-indium eutectic (GaIn).

[0072] Step 2: Weigh 0.20 g of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI, MW = 5800, Aladdin) and add it to 4.0 mL of N-methylpyrrolidone (NMP, ≥99.9%, Macklin). Heat and stir at 75 °C until dissolved; then, add 1.00 g of poly(vinylidene-co-hexafluoropropylene) (PVDF-HFP, MW = 150,000, Macklin) and continue to heat and stir until dissolved to obtain a homogeneous solution.

[0073] Step 3: Add 400 μL of the gallium-indium eutectic obtained in Step 1 to the homogeneous solution obtained in Step 2, perform ultrasonic treatment for 26 min, then stir at room temperature until evenly dispersed. Next, perform defoaming treatment with a planetary mixer (rotation speed 450 rpm, revolution speed 1100 rpm, time 240 s) to obtain a mixed solution. Pour the mixed solution onto a polytetrafluoroethylene mold and vacuum dry it at 75 °C for 18 h in a vacuum drying oven to obtain the multifunctional lithium metal battery anode protective film with self-healing synthetic nuclear seeds.

[0074] Example 5

[0075] In this embodiment, the multifunctional lithium metal battery anode protective film with self-healing synthetic nuclear seeds is prepared according to the following steps:

[0076] Step 1: Mix gallium and indium in a weight ratio of 76.5:23.5. Subsequently, heat and stir the mixture at 160 °C for 0.5 h on a magnetic stirrer to make them evenly mixed and obtain gallium-indium eutectic (GaIn).

[0077] Step 2: Weigh 0.08 g of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI, MW = 5800, Aladdin) and add it to 5.0 mL of N-methylpyrrolidone (NMP, ≥99.9%, Macklin). Heat and stir at 80 °C until dissolved; then, add 1.25 g of poly(vinylidene-co-hexafluoropropylene) (PVDF-HFP, MW = 150,000, Macklin) and continue to heat and stir until dissolved to obtain a homogeneous solution.

[0078] Step 3: Add 500 μL of the eutectic gallium-indium obtained in Step 1 into the homogeneous solution obtained in Step 2, perform ultrasonic treatment for 28 min, then stir at room temperature until evenly dispersed. Next, perform defoaming treatment with a planetary mixer (rotation speed of 500 rpm, revolution speed of 1300 rpm, time of 300 s) to obtain a mixed solution. Pour the mixed solution onto a polytetrafluoroethylene mold and dry it in a vacuum drying oven at 80 °C under vacuum for 20 h to obtain a multifunctional lithium metal battery negative electrode protective film with self-healing synthetic nuclear seeds.

[0079] Example 6

[0080] In this example, a multifunctional lithium metal battery negative electrode protective film with self-healing synthetic nuclear seeds was prepared according to the following steps:

[0081] Step 1: Mix gallium and indium at a weight ratio of 78.5:21.5. Subsequently, heat and stir at 170 °C for 0.5 h on a magnetic stirrer to make the two evenly mixed and obtain eutectic gallium-indium (GaIn).

[0082] Step 2: Weigh 0.18 g of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI, MW = 5800, Aladdin) and add it to 6.0 mL of N-methylpyrrolidone (NMP, ≥99.9%, Macklin). Heat and stir at 70 °C until dissolved. Subsequently, add 1.50 g of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP, MW = 150,000, Macklin) and continue to heat and stir until dissolved to obtain a homogeneous solution.

[0083] Step 3: Add 600 μL of the eutectic gallium-indium obtained in Step 1 into the homogeneous solution obtained in Step 2, perform ultrasonic treatment for 30 min, then stir at room temperature until evenly dispersed. Next, perform defoaming treatment with a planetary mixer (rotation speed of 350 rpm, revolution speed of 1500 rpm, time of 360 s) to obtain a mixed solution. Pour the mixed solution onto a polytetrafluoroethylene mold and dry it in a vacuum drying oven at 65 °C under vacuum for 22 h to obtain a multifunctional lithium metal battery negative electrode protective film with self-healing synthetic nuclear seeds.

[0084] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A lithium metal battery negative electrode protective film with a self-healing composite nuclear seed, characterized in that: The negative electrode protective film of the lithium metal battery is a polymer film. Grooves are formed on the upper surface of the polymer film, and GaIn nanoparticles are modified in the polymer film. The GaIn nanoparticles are deposited at the bottom of the film under the influence of their own gravity, so that the polymer film presents a layered structure. The preparation method of the negative electrode protective film of the lithium metal battery with self-healing synthesis nuclear seeds includes the following steps: Step 1: Mix gallium and indium, heat and stir until evenly mixed to obtain a gallium-indium eutectic. Step 2: Add lithium bis(trifluoromethanesulfonyl)imide LiTFSI to N-methylpyrrolidone NMP, heat and stir until dissolved, then add poly(vinylidene fluoride-co-hexafluoropropylene) PVDF-HFP, and continue to heat and stir until dissolved to obtain a homogeneous solution. Step 3: Add the gallium-indium eutectic obtained in Step 1 to the homogeneous solution obtained in Step 2, after ultrasonic treatment, stir at room temperature until evenly dispersed, and then perform defoaming treatment to obtain a mixed solution. Pour the mixed solution onto a mold and dry it in vacuum to obtain the negative electrode protective film of the lithium metal battery with self-healing synthesis nuclear seeds.

2. The negative electrode protective film of the lithium metal battery with a self-healing composite nuclear seed according to claim 1, characterized in that: In Step 1, the weight ratio of gallium to indium is 70.5-79.5:29.5-20.

5.

3. The negative electrode protective film of the lithium metal battery with a self-healing composite nuclear seed according to claim 1, characterized in that: In Step 1, the temperature of heating and stirring is 145-175 °C.

4. The lithium metal battery anode protective film with a self-healing synthetic nuclear seed according to claim 1, wherein: In Step 2, the dosage ratio of LiTFSI, NMP, PVDF-HFP and the gallium-indium eutectic in Step 3 is 0.05-0.25 g:1.0-8.0 mL:0.25-1.5 g:0.1-1.0 mL.

5. The negative electrode protective film of the lithium metal battery with a self-healing composite nuclear seed according to claim 1, characterized in that: In Step 2, the temperature of heating and stirring is 60-80 °C.

6. The negative electrode protective film of a lithium metal battery with a self-healing composite nuclear seed according to claim 1, characterized in that: In Step 3, the defoaming treatment is to mix and defoam in a planetary mixer under the conditions of self-rotation at 300-500 rpm and revolution at 500-2000 rpm for 60-600 s.

7. The negative electrode protective film of the lithium metal battery with a self-healing composite nuclear seed according to claim 1, characterized in that: In Step 3, the temperature of the vacuum drying is 60-80 °C and the drying time is 12-24 h.

8. Use of a negative electrode protective film of a lithium metal battery having a self-healing composite nuclear seed according to claim 1, characterized in that: It is used between the negative electrode lithium sheet and the separator of the lithium metal battery as a protective film for the negative electrode lithium sheet.

Images