Solid-state polymer electrolyte, preparation method thereof and solid-state lithium metal battery

Abstract

The application discloses a preparation method of a solid-state polymer electrolyte, comprising the following steps: dissolving polyimide containing a trifluoromethyl group and a lithium salt into an organic solvent to form a uniform polymer solution; coating the polymer solution on a substrate, and drying to obtain a solid-state polymer electrolyte film. The application further discloses the solid-state polymer electrolyte obtained by the preparation method and a solid-state lithium metal battery comprising the solid-state polymer electrolyte. The preparation method of the solid-state polymer electrolyte is simple, the prepared solid-state polymer electrolyte has a high oxidation stable potential, can match a high-voltage positive electrode material, has a high ion transference number and good mechanical properties, and the prepared solid-state lithium metal battery has a long service life and high safety.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium battery, in particular to a solid-state polymer electrolyte, a preparation method thereof and a solid-state lithium metal battery. BACKGROUND

[0002] Currently, commercial batteries use liquid electrolytes, which are flammable, and their high reactivity with positive and negative electrodes makes it difficult to match high-energy-density high-voltage positive materials and lithium metal negative electrodes. Polymer solid-state electrolytes, which can be designed through molecular structure, have the potential to meet the requirements of the next generation of lithium batteries for electrolytes in terms of ionic conductivity, electrochemical stability window, interface stability with electrodes, thermal stability, and processability.

[0003] Current research on polymer electrolyte materials includes polyethylene oxide, polyester, polyvinylidene fluoride, and polyacrylonitrile. However, it is still challenging to develop polymer electrolyte materials that simultaneously meet high ionic conductivity, high mechanical properties, high oxidation resistance, and low film thickness. Polyethylene oxide in a molten state has high ionic conductivity, but poor mechanical properties and poor oxidation resistance. Cui et al. used a porous polyimide film to fill polyethylene oxide / bistrifluoromethanesulfonimide lithium (PEO / LiTFSI) to prepare an electrolyte film with good mechanical properties and a thickness of less than 10 um, but it cannot match high-voltage positive materials. (Wan J, Xie J, Kong X, et al. Ultrathin, flexible, solid polymer composite electrolyte enabled with aligned nanoporous host for lithium batteries [J]. Nature Nano Technology, 2019, 14(7): 705.) Although polyacrylonitrile (PAN) has high oxidation resistance and mechanical properties, it is a semi-crystalline polymer at room temperature with low ionic conductivity. Zhang et al. prepared a PAN film with composite silica particles (SiO2) with a thickness of about 30 um, which has high ionic conductivity at room temperature and can match high-voltage positive materials. (Yao M, Ruan Q, Yu T, et al. Solid polymer electrolyte with in-situ generated fast Li +conductive network enable high voltage and dendrite-free lithium metal battery[J]. Energy Storage Materials, 2022, 44:93-103.) Zhang et al. reported that the room temperature ionic conductivity of poly(vinylidene difluoride)-based polymer electrolyte is in the order of 10 -4 S cm -1 and has good mechanical properties, strong oxidation resistance and large thickness (about 90 um). (Zhang X., Wang S., Xue C., et al. Self-Suppression of lithium dendrite in All-Solid-State lithium metal batteries with poly(vinylidene difluoride)-Based solid electrolytes[J]. Advanced Materials, 2019, 31(11): 1-9.) Therefore, the polymer electrolyte material in the prior art does not really solve the problem of poor comprehensive performance of the polymer electrolyte, and the preparation process is complex. SUMMARY

[0004] In order to overcome the above-mentioned defects and deficiencies of the prior art, the purpose of the present application is to provide a preparation method of a solid-state polymer electrolyte, which has a simple preparation process and excellent mechanical properties, a high oxidation stable potential, and can match high-voltage positive electrode materials.

[0005] Another purpose of the present application is to provide a solid-state polymer electrolyte prepared by the above-mentioned preparation method of a solid-state polymer electrolyte.

[0006] Still another purpose of the present application is to provide a solid-state lithium metal battery comprising the above-mentioned solid-state polymer electrolyte.

[0007] The purpose of the present application is achieved by the following technical solutions:

[0008] A preparation method of a solid-state polymer electrolyte, comprising the following steps:

[0009] dissolving a polyimide and a lithium salt into an organic solvent to form a uniform polymer solution;

[0010] The polyimide has any one of the following structures:

[0011]

[0012] wherein n is (0.1-10)*105 ;

[0013] The polymer solution is coated on a substrate, dried, and a solid-state polymer electrolyte film is prepared.

[0014] Preferably, the lithium salt accounts for 10% to 60% of the total mass of the polyimide and the lithium salt.

[0015] Preferably, the lithium salt is at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium trifluoromethanesulfonate, lithium hexafluorophosphate, and lithium tetrafluoroborate.

[0016] Preferably, the organic solvent is at least one of N,N-dimethylacetamide, N,N-dimethylformamide, dimethyl sulfoxide, and N-methyl pyrrolidone.

[0017] Preferably, the thickness of the solid-state polymer electrolyte film is 5 to 40 microns.

[0018] A solid-state polymer electrolyte is prepared by the method for preparing a solid-state polymer electrolyte.

[0019] A solid-state lithium metal battery comprises the solid-state polymer electrolyte, a working electrode, and a reference electrode; the solid-state polymer electrolyte is located between the working electrode and the reference electrode; and the reference electrode is a metal lithium electrode.

[0020] Preferably, a liquid electrolyte for wetting the interface is provided between the solid-state polymer electrolyte and the metal lithium electrode.

[0021] Preferably, the liquid electrolyte for wetting the interface comprises a solvent and a lithium salt; the solvent is at least one of 1,3-dioxolane, ethylene glycol dimethyl ether, dimethyl carbonate, methyl ethyl carbonate, ethylene carbonate, propylene carbonate, and diethyl carbonate; and the lithium salt is at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium trifluoromethanesulfonate, lithium hexafluorophosphate, and lithium tetrafluoroborate.

[0022] Preferably, the concentration of the lithium salt in the liquid electrolyte for wetting the interface is 0.1 to 1 mol / L.

[0023] Preferably, the amount of the liquid electrolyte for wetting the interface is 1 to 4 uL per square centimeter of the interface.

[0024] Compared with the prior art, the present application has the following advantages and beneficial effects:

[0025] (1) The method for preparing a solid-state polymer electrolyte of the present application has a simple preparation process and good repeatability, and can match the existing polyimide film industrial production system.

[0026] (2) The solid-state polymer electrolyte of the present application has a high oxidation stable potential and can match high-voltage positive electrode materials.

[0027] (3) The solid-state polymer electrolyte of the present application reduces the reactivity of anions on the surface of lithium metal through the attraction of polyimide molecular chains to lithium salt anions, induces the formation of a uniform interface layer of anions at the interface between the electrolyte and lithium metal, and has good interface stability with lithium metal.

[0028] (4) The solid-state polymer electrolyte of the present application has a high lithium ion transference number, low concentration polarization in application, and is conducive to achieving higher power density.

[0029] (5) The solid-state polymer electrolyte of the present application has good mechanical properties, can prepare ultra-light and thin electrolyte membranes, and enables the battery to have higher energy / volume density.

[0030] (6) The solid-state polymer electrolyte of the present application has good mechanical properties, good film-forming properties, can achieve a smooth and flat polymer film surface, greatly reduces the electrical damage of the battery interface caused by defects on the surface of the electrolyte membrane, and enables the battery to have a longer service life.

[0031] (7) The solid-state polymer electrolyte of the present application has high mechanical properties, can prevent short circuits caused by lithium dendrite growth, and has higher safety.

[0032] (8) The solid-state polymer electrolyte of the present application has high thermal stability, can maintain dimensional stability up to 200℃, can effectively prevent short circuits caused by battery thermal runaway, and has higher safety. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 SEM image of the solid-state polymer electrolyte of Example 1 of the present application.

[0034] Figure 2 Temperature dependence curve of ionic conductivity of the solid-state polymer electrolytes of Example 1 and Example 2 of the present application.

[0035] Figure 3 Linear sweep voltammetry curve of the lithium-steel plate asymmetric battery assembled by the solid-state polymer electrolyte in Example 1 and Example 2 of the present application.

[0036] Figure 4 Cycle performance test diagram of the solid-state lithium metal battery assembled by the solid-state polymer electrolyte in Example 1 of the present application at different rates within the voltage range of 75℃, 2.5V-3.8V.

[0037] Figure 5The long-cycle performance of the solid-state lithium metal battery assembled with the solid polymer electrolyte in Example 1 of the present invention at 75°C and 0.5C rate is shown in the figure.

[0038] Figure 6 This is a chronopotential graph showing the lithium-lithium symmetric battery assembled with a solid polymer electrolyte in Example 1 of the present invention during constant current cycling tests at different current densities at 75°C.

[0039] Figure 7(a) is a chronoamperometry diagram of the lithium-lithium symmetric battery assembled with solid polymer electrolyte in Example 1 of the present invention, under polarization test at 75°C.

[0040] Figure 7(b) shows the impedance diagrams before and after polarization testing of the lithium-lithium symmetric battery assembled with solid polymer electrolyte in Example 1 of the present invention.

[0041] Figure 8 Stress-strain curve of the solid polymer electrolyte in Example 1 of the present invention.

[0042] Figure 9 The graph shows the cycle performance of the solid-state lithium battery assembled in Example 2 of the present invention at a temperature of 75°C and at different rates.

[0043] Figure 10 The graph shows the cycle performance of the solid-state lithium battery assembled in Example 2 of the present invention at a temperature of 75°C and a rate of 0.2C.

[0044] Figure 11 The lithium-lithium symmetric battery assembled with the solid polymer electrolyte in Example 2 of the present invention was tested at 75°C and 0.02 mA cm⁻¹. -2 Timing potential diagram during constant current cycling test at current density.

[0045] Figure 12 This is a stress-strain curve of the solid polymer electrolyte in Example 2 of the present invention. Detailed Implementation

[0046] The present invention will be further described in detail below with reference to the embodiments, but the implementation of the present invention is not limited thereto.

[0047] Example 1

[0048] The preparation process of the solid polymer electrolyte in this embodiment is as follows:

[0049] 1.0 g of polyimide (PI-2CN-2CF3) and 1.0 g of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI, 99.9%) were dissolved in N,N-dimethylacetamide, stirred well to obtain a uniform polymer solution, then coated on a glass plate, dried in a blast oven at 80°C for 10 hours, and then transferred to a vacuum oven for drying at 90°C for 48 hours to remove the organic solvent and obtain a polymer electrolyte film. The solid-state polymer electrolyte prepared in this example is transparent, with a smooth and flat surface and a film thickness of 27 um.

[0050] The polyimide of this example has the following structural formula:

[0051]

[0052] wherein n is (0.1-10)*10 5 .

[0053] Performance test:

[0054] The scanning electron microscope (SEM) image of the polymer electrolyte prepared in this example is shown in Figure 1 . It can be seen from Figure 1 that the solid-state polymer electrolyte prepared in this example is transparent, with a smooth and flat surface and no pores, which is conducive to forming an interface-free contact surface with the positive and negative electrodes of the battery and conducive to the conduction of lithium ions.

[0055] The solid-state polymer electrolyte prepared in this example was placed between two stainless steel electrodes, and the ion conductivity of the solid-state polymer electrolyte was tested using a Chenhua electrochemical workstation. The ion conductivity-temperature curve obtained is shown in Figure 2 . It can be seen from Figure 2 that as the temperature increases, the ion conductivity of the solid-state polymer electrolyte also increases, and the ion conductivity at 75°C is 0.11 mS / cm.

[0056] A piece of lithium metal was used as a reference electrode, a stainless steel sheet was used as a working electrode, and the solid-state polymer electrolyte prepared in this example was used as an electrolyte. The 2025 type button cell shell was packaged, and the electrochemical stability of the solid-state polymer electrolyte was tested by linear voltammetry (LSV). The scanning range was 2.5V-6V, and the scanning speed was 1mV / s. The LSV curve obtained is shown in Figure 3 . It can be seen from Figure 3 that the solid-state polymer electrolyte has high electrochemical stability, and the stable voltage can reach 4.5V, which can meet the actual application under a wide electrochemical window.

[0057] LiFePO4 was used as the positive electrode of the battery (the active material loading was about 1mg / cm 2, the mass ratio of each component in the positive electrode is LiFePO4: binder: conductive carbon black = 8: 1: 1), lithium metal as the negative electrode of the battery, the solid-state polymer electrolyte prepared in this embodiment as the separator and electrolyte, and the solid-state lithium metal battery is assembled. When assembling, 3uL of liquid electrolyte is added on the surface of the positive electrode sheet, the electrolyte film prepared in this embodiment is placed on the positive electrode sheet, 3uL of liquid electrolyte is added on the surface of the film, the lithium metal sheet is placed on the film, and then the battery is placed on a hot stage at 80°C for 10h to remove the residual solvent at the interface, and then the battery shell is packaged. The electrolyte used is a DME / DOL solution (DME is ethylene glycol dimethyl ether, and DOL is 1,3-dioxolane) with a volume ratio of 1:1 and a LiTFSI concentration of 1mol / L. The assembled battery is subjected to cycle performance test at 75°C and in the voltage range of 2.5V-4.0V, and the cycle performance curves at different rates (as shown in Figure 4 ) and the cycle performance graph at 75°C and 0.5C (as shown in Figure 5 ) are obtained. As shown in Figure 4 and Figure 5 , the solid-state lithium metal battery has high cycle capacity and retention rate, and the coulombic efficiency is higher than 99.5%. At 0.5C, the initial capacity is 96.6mAh / g, and after 250 cycles, the capacity retention rate is still 88%.

[0058] The solid-state polymer electrolyte prepared in this embodiment is placed between two lithium metal sheets, and a 2025 type button cell box is used for packaging to obtain a lithium-lithium symmetric battery. The assembly method of the lithium-lithium symmetric battery is as follows: 3uL of liquid electrolyte is added on the surface of one lithium metal sheet, the electrolyte film prepared in this embodiment is placed thereon, 3uL of liquid electrolyte is added on the surface of the film, the lithium metal sheet is placed on the film, and then the battery is placed on a hot stage at 80°C for 10h to remove the residual solvent at the interface, and then the battery shell is packaged. The liquid electrolyte used is a DME / DOL solution (DME is ethylene glycol dimethyl ether, and DOL is 1,3-dioxolane) with a volume ratio of 1:1 and a LiTFSI concentration of 1mol / L. The solid-state polymer electrolyte prepared in this embodiment is assembled into a lithium-lithium symmetric battery, and is subjected to constant current cycle test at 75°C and at current densities of 0.01mA / cm 2 , 0.02mA / cm 2 , and 0.05mA / cm 2 , respectively, and each cycle is subjected to 1h charging and 1h discharging, and the chronopotentiogram obtained is as shown in Figure 6 . As shown in Figure 6It can be seen that the voltage of the lithium-lithium symmetric battery is relatively stable in each constant current cycle, indicating that lithium ions can be uniformly reduced and deposited on the surface of the metal lithium electrode at this current density. The voltage change between different cycles is small, indicating that the solid-state polymer electrolyte has good stability to metal lithium. In addition, during the constant current cycle process, even after running for 300 h, there is no sudden large drop in voltage (short circuit) of the lithium-lithium symmetric battery, indicating that the solid-state polymer electrolyte has excellent ability to inhibit the growth of lithium dendrites, and the lithium-lithium symmetric battery does not have a short circuit caused by lithium dendrites piercing the separator during long-term operation.

[0059] The solid-state polymer electrolyte prepared in this example was assembled into a lithium-lithium symmetric battery, and the lithium ion transference number test was carried out at 75°C. The test results are shown in FIGS. 7(a)-(b). The lithium ion transference number obtained by the test is 0.41.

[0060] The polymer electrolyte film prepared in this example was prepared into a long rectangular thin film sample with a length of 50 mm and a width of 10 mm, and a thickness of 27 um. The mechanical properties were tested using a Zwick universal testing machine at a stretching speed of 20 mm / min, and the results are shown in FIGS. 8(a)-(b). Figure 8 Figure 8 It can be seen that the tensile strength of the polymer electrolyte film prepared in this example reaches 20 MPa, and the elongation at break is 51%.

[0061] The polyimide structural unit used in this example contains a trifluoromethyl group, which induces the uniform deposition of lithium salt anions on the surface of lithium metal to form a stable interfacial layer and improve the interfacial stability. The polyimide used in this application is strong and tough, which can inhibit the growth of lithium dendrites and can prepare ultra-thin electrolyte films with low bulk resistance. The polyimide of the present application has strong oxidation resistance and good interfacial stability with the positive electrode.

[0062] Example 2

[0063] The preparation process of the solid-state polymer electrolyte of this example is as follows:

[0064] 1.0 g of polyimide (PI-4CF3) and 1.0 g of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI, 99.9%) were dissolved in N,N-dimethylacetamide, stirred thoroughly, and a uniform polymer solution was obtained. Then, the solution was coated on a glass plate using a doctor blade, dried in a blast oven at 80°C for 10 hours, and then transferred to a vacuum oven for drying at 90°C for 48 hours to remove the organic solvent and obtain a polymer electrolyte film. The solid-state polymer electrolyte film prepared in this example is transparent, with a smooth and flat surface, and has a thickness of 25 um.

[0065] The polyimide of this example has the following structural formula:

[0066] ​

[0067] wherein n is (0.1-10)*10 5 .

[0068] Performance test:

[0069] The solid-state polymer electrolyte prepared in this embodiment was placed between two stainless steel electrodes, and the ion conductivity of the solid-state polymer electrolyte was tested by a Chenhua electrochemical workstation. The ion conductivity-temperature curve obtained is shown in FIG. 6. The ion conductivity of the solid-state polymer electrolyte at 75°C was 0.086 mS / cm. Figure 2

[0070] A lithium metal sheet was used as a reference electrode, a stainless steel sheet was used as a working electrode, and the solid-state polymer electrolyte prepared in this embodiment was used as an electrolyte. The electrochemical stability of the solid-state polymer electrolyte was tested by linear voltammetry (LSV) with a 2025 type button cell box for packaging. The scanning range was 2.5 V to 6 V, and the scanning speed was 1 mV / s. The LSV curve obtained is shown in FIG. 7. It can be seen from FIG. 7 that the solid-state polymer electrolyte has high electrochemical stability, and the stable voltage can reach 4.5 V, which can meet the actual application under a wide electrochemical window. Figure 3 Figure 3

[0071] LiFePO4 was used as a battery positive electrode (active material loading was about 1 mg / cm 2 , the mass ratio of each component in the positive electrode was LiFePO4: binder: conductive carbon black = 8: 1: 1), lithium metal was used as a battery negative electrode, and the solid-state polymer electrolyte prepared in this embodiment was used as a separator and an electrolyte to assemble a solid-state lithium metal battery. During assembly, 3 uL of liquid electrolyte was added to the surface of the positive electrode sheet, and then the electrolyte film prepared in this embodiment was placed on the positive electrode sheet. Then 3 uL of liquid electrolyte was added to the film, and then the lithium metal sheet was placed on the film. Then the sample was placed on a hot stage at 80°C for 10 h to remove the residual solvent at the interface, and then the battery shell was packaged. The liquid electrolyte used was a DME / DOL solution (DME was ethylene glycol dimethyl ether, and DOL was 1,3-dioxolane) with a volume ratio of 1:1 and a LiTFSI concentration of 1 mol / L. The assembled battery was subjected to cycle performance test at 75°C and a voltage range of 2.5 V to 4.0 V. The cycle performance curves at different rates (as shown in FIG. 8) and the cycle performance graph at 75°C and 0.5C (as shown in FIG. 9) were obtained. From FIGS. 8 and 9, it can be seen that the solid-state lithium metal battery prepared in this embodiment has good cycle performance. Figure 9 Figure 10 Figure 9 Figure 10 ​​​​​​It can be seen that the solid-state lithium metal battery assembled in the embodiment has high cycle capacity and excellent capacity retention rate, and the coulombic efficiency is higher than 99.5%; at 0.5C, the initial specific discharge capacity is 117 mAh / g, and after 200 cycles, the specific discharge capacity is 100 mAh / g, and the capacity retention rate is 85.5%.

[0072] The solid-state polymer electrolyte prepared in the embodiment was placed between two lithium metal sheets, and a 2025 type button cell box was used for packaging to obtain a lithium-lithium symmetric battery. The solid-state polymer electrolyte prepared in the embodiment was placed between two lithium metal sheets, and a 2025 type button cell box was used for packaging to obtain a lithium-lithium symmetric battery. The assembly method of the lithium-lithium symmetric battery is: adding 3uL of liquid electrolyte on the surface of one lithium metal sheet, then placing the electrolyte film prepared in the embodiment on it, then adding 3uL of electrolyte on the surface of the film, then placing the lithium metal sheet on the film, and then placing it on a hot stage at 80℃ for 10h to remove the residual solvent at the interface, and then packaging the battery shell. The assembled lithium-lithium symmetric battery was subjected to constant current cycle test at 75℃ and a current density of 0.02mA / cm 2 Figure 11 Figure 11 It can be seen that the voltage of the lithium-lithium symmetric battery is relatively stable in each constant current cycle, indicating that lithium ions can be uniformly reduced and deposited on the surface of the metal lithium electrode at this current density. The voltage change between different cycles is small, indicating that the solid-state polymer electrolyte is stable to metal lithium. In addition, even if the lithium-lithium symmetric battery runs for more than 850h during the constant current cycle, there is no case of sudden large decrease in voltage (short circuit), indicating that the solid-state polymer electrolyte has excellent ability to inhibit the growth of lithium dendrites, and the lithium-lithium symmetric battery does not have battery short circuit caused by lithium dendrite piercing the separator during long-term operation.

[0073] The polymer electrolyte film prepared in the embodiment was prepared into a rectangular thin film sample with a length of 50mm and a width of 10mm, and a thickness of 25um. The mechanical properties were tested using a Zwick universal testing machine at a stretching speed of 10mm / min, and the results are shown in Figure 12 Figure 12 It can be seen that the tensile strength of the polymer electrolyte film prepared in the embodiment reaches 40MPa, and the elongation at break is 65%.

[0074] The polyimide structural unit used in the embodiment contains trifluoromethyl and cyano groups, which induce uniform deposition of lithium salt on the surface of lithium metal to form a stable interfacial layer and inhibit the growth of lithium dendrites. The polyimide used in the present application is strong and tough, and can prepare an ultra-thin electrolyte film with low bulk resistance. The polyimide of the present application has strong oxidation resistance and good interface stability with the positive electrode. ​​​

[0075] In the above embodiments, the lithium salt compounded with the polyurethane can also be at least one of lithium bistrifluoromethanesulfonimide, lithium bisfluorosulfonimide, lithium triflate, lithium hexafluorophosphate, and lithium tetrafluoroborate.

[0076] In the above embodiments, the organic solvent can also be at least one of N,N-dimethylformamide, dimethyl sulfoxide, and N-methyl pyrrolidone.

[0077] In the above embodiments, the solvent in the liquid electrolyte for infiltrating the interface can also be at least one of 1,3-dioxolane, ethylene glycol dimethyl ether, dimethyl carbonate, ethyl methyl carbonate, ethylene carbonate, propylene carbonate, and diethyl carbonate.

[0078] In the above embodiments, the lithium salt in the liquid electrolyte for infiltrating the interface can also be at least one of lithium bistrifluoromethanesulfonimide, lithium bisfluorosulfonimide, lithium triflate, lithium hexafluorophosphate, and lithium tetrafluoroborate.

[0079] The above embodiments are preferred embodiments of the present application, but the embodiments of the present application are not limited by the above embodiments, and any changes, modifications, substitutions, combinations, simplifications, and the like made without departing from the spirit and principles of the present application are equivalent replacement manners and are included in the protection scope of the present application.

Claims

1. A solid-state lithium metal battery, characterized in that, It includes a solid polymer electrolyte membrane, a working electrode, and a reference electrode; the solid polymer electrolyte is located between the working electrode and the reference electrode; the reference electrode is a lithium metal electrode; The solid polymer electrolyte membrane is prepared by the following method: Polyimide and lithium salt are dissolved in an organic solvent to form a homogeneous polymer solution; the polymer solution is coated onto a substrate and dried to obtain a solid polymer electrolyte membrane; the lithium salt accounts for 50% of the total mass of polyimide and lithium salt. The polyimide has the following structure; Where n is (0.1-10)*10 5 ; The solid polymer electrolyte has an ionic conductivity of 0.11 mS / cm at 75 °C and a stable voltage of 4.5 V. The solid-state lithium metal battery is assembled as follows: The assembly method is as follows: liquid electrolyte is dropped onto the surface of a lithium metal sheet, then the solid polymer electrolyte membrane is placed on it, liquid electrolyte is dropped onto the surface of the solid polymer electrolyte membrane, then the lithium metal sheet is placed on it, and then it is left to stand on a hot table at 80 ℃ for 10 h to remove residual solvent at the interface, and then the battery case is encapsulated. The solid-state lithium metal battery retains 88% of its capacity after 250 cycles.

2. The solid-state lithium metal battery according to claim 1, characterized in that, A liquid electrolyte is provided between the solid polymer electrolyte and the lithium metal electrode for wetting the interface.

3. The solid-state lithium metal battery according to claim 2, characterized in that, The liquid electrolyte used for wetting the interface includes a solvent and a lithium salt; the solvent is at least one selected from 1,3-dioxane, ethylene glycol dimethyl ether, dimethyl carbonate, ethyl methyl carbonate, ethylene carbonate, propylene carbonate, and diethyl carbonate.

4. The solid-state lithium metal battery according to claim 3, characterized in that, The amount of liquid electrolyte used for wetting the interface is 1~4 uL per square centimeter of interface.

5. The solid-state lithium metal battery according to claim 1, characterized in that, The lithium salt is at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium trifluoromethanesulfonate, lithium hexafluorophosphate, and lithium tetrafluoroborate.

6. The solid-state lithium metal battery according to claim 1, characterized in that, The organic solvent is at least one of N,N-dimethylacetamide, N,N-dimethylformamide, dimethyl sulfoxide, or N-methylpyrrolidone.

7. The solid-state lithium metal battery according to claim 1, characterized in that, The thickness of the solid polymer electrolyte membrane is 5~200 μm.

Images