Polymer protective film, metal lithium negative electrode, lithium battery and vehicle

Abstract

The present application discloses a polymer protective film, a metallic lithium negative electrode, a lithium battery and a vehicle. The structural formula of the polymer protective film is as follows: #imgabs0# The nitrogen-containing polymer chain segment in the polymer protective film of the present application can react with metallic lithium continuously and slowly, which is conducive to the formation of a stable SEI; the ethoxy chain segment has a strong effect on metallic lithium, which is conducive to reducing the interface impedance between the polymer and metallic lithium, and at the same time is conducive to promoting lithium ion transmission and making lithium ions evenly distributed, reducing concentration polarization, and preventing the formation of lithium dendrites, thereby improving the safety performance and cycle performance of the battery.

Description

Technical Field

[0001] The present invention generally relates to the technical field of lithium batteries, and in particular to a polymer protective film, a metal lithium negative electrode, a lithium battery and a vehicle. Background Art

[0002] With the widespread application of smart electronic devices, electric vehicles, and large-scale energy storage devices, there is an urgent need for lithium secondary batteries with higher energy density and cycle life. Lithium metal has a high theoretical specific capacity (3860mAh / g) and a low electrochemical potential (-3.040V vs standard hydrogen electrode), making it the most ideal negative electrode material for next-generation lithium secondary batteries.

[0003] However, lithium metal will inevitably react with the electrolyte to form a solid-liquid interface (SEI). SEI is easily broken during the cycle, resulting in the consumption of electrolyte, lithium salt and active lithium, forming lithium dendrites, thereby shortening the cycle life of the battery and limiting the application of metal lithium negative electrodes. Summary of the Invention

[0004] In view of the above-mentioned defects or deficiencies in the prior art, it is desired to provide a polymer protective film, a metal lithium negative electrode, a lithium battery and a vehicle. The polymer protective film is conducive to the formation of a stable SEI, reduces the impedance between the polymer and metal lithium, promotes lithium ion transmission, inhibits the formation of lithium dendrites, and thereby improves the safety performance and cycle life of the battery.

[0005] In a first aspect, the present invention provides a polymer protective film having the following structural formula:

[0006]

[0007] Wherein, R1 and R3 are each independently selected from substituents substituted or unsubstituted wherein k1, k2, k3, k4, k5, k6, k7, and k8 are each independently an integer of 1 to 50, and K and L are each independently selected from substituted or unsubstituted

[0008] R2 is selected from the group consisting of a C0-C6 methylene group, a C6-C 12 Aryl, C6-C 12 Cycloalkyl, Wherein, M and Q are each independently selected from a substituted or unsubstituted C0-C6 methylene, phenyl, or cyclohexyl group;

[0009] m and x both represent the molar ratio of the ethoxy segments to the polymer, n and y represent the molar ratio of the nitrogen-containing segments to the polymer, m and n are each independently any decimal between 0 and 1, and m+n equals 1.0; x and y are each independently any decimal between 0 and 1, and x+y equals 1.0;

[0010] z represents the number of repeating units of the ethoxy structural unit, and z is an integer of 1 to 100.

[0011] As an optional solution, 0.5≤m≤0.95, 0.05≤n≤0.5; 0.5≤x≤0.95, 0.05≤y≤0.5.

[0012] As an optional solution, 0.7≤m≤0.9, 0.1≤n≤0.3; 0.7≤x≤0.9, 0.1≤y≤0.3.

[0013] As an optional scheme, the substituent is selected from halogen, hydroxyl, amino, carbonyl, cyano, C1-C6 alkoxy, C1-C6 alkyl, C6-C 12 Aryl or C6-C 12 of a cycloalkyl group.

[0014] As an optional scheme, the halogen is selected from one of fluorine, chlorine and bromine; the amine group is selected from a C1-C6 primary amine, a C1-C6 alkyl-substituted secondary amine or a tertiary amine; the C1-C6 alkoxy group is selected from a methoxy group or an ethoxy group; the C1-C6 alkyl group is selected from a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group or a tert-butyl group; the C6-C 12 The aryl group is selected from phenyl, naphthyl, or biphenyl; C6-C 12 The cycloalkyl group is selected from cyclohexyl or bicyclohexyl;

[0015] As an optional solution, the molecular weight of the polymer protective film is 10,000 to 500,000.

[0016] In a second aspect, the present invention provides a metal lithium negative electrode, comprising a metal lithium sheet and the polymer protective film of the first aspect, wherein the polymer protective film is disposed on the metal lithium sheet.

[0017] As an option, the polymer protective film has a thickness of 1 μm-10 μm.

[0018] In a third aspect, the present invention provides a lithium battery comprising the metallic lithium negative electrode of the second aspect.

[0019] In a fourth aspect, the present invention provides a vehicle comprising the lithium battery of the third aspect.

[0020] The polymer protective film of the present application includes nitrogen-containing segments and ethoxy segments. The nitrogen-containing segments can slowly and continuously react with metallic lithium to form lithium nitride in situ, which is conducive to the formation of a stable SEI. The ethoxy segments can form a strong interaction with metallic lithium, reducing the interfacial impedance between the polymer and metallic lithium, which is conducive to promoting lithium ion transport, ensuring uniform lithium ion distribution, reducing concentration polarization, and inhibiting the formation of lithium dendrites, thereby improving the safety and cycle performance of the battery. DETAILED DESCRIPTION

[0021] The present application will be further described in detail below with reference to the embodiments. It will be appreciated that the specific embodiments described herein are intended only to explain the invention and are not intended to limit the invention. Furthermore, it should be noted that, for ease of description, only portions relevant to the invention are shown in the embodiments.

[0022] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the embodiments.

[0023] An embodiment of the present invention provides a polymer protective film, the structural formula of the polymer protective film is as follows:

[0024]

[0025] Wherein, R1 and R3 are each independently selected from substituents substituted or unsubstituted wherein k1, k2, k3, k4, k5, k6, k7, and k8 are each independently an integer of 1 to 50, and K and L are each independently selected from substituted or unsubstituted

[0026] R2 is selected from the group consisting of a C0-C6 methylene group, a C6-C 12 Aryl, C6-C 12 Cycloalkyl, Wherein, M and Q are each independently selected from a substituted or unsubstituted C0-C6 methylene, phenyl, or cyclohexyl group;

[0027] m and x both represent the molar ratio of the ethoxy segments to the polymer, n and y represent the molar ratio of the nitrogen-containing segments to the polymer, m and n are each independently any decimal between 0 and 1, and m+n equals 1.0; x and y are each independently any decimal between 0 and 1, and x+y equals 1.0;

[0028] z represents the number of repeating units of the ethoxy structural unit, and z is an integer of 1 to 100.

[0029] Wherein, the nitrogen-containing segment comes from the R1 or R3 group, the nitrogen-containing group in the nitrogen-containing segment can be an amine group or an imidazole nitrogen or a triazole group, k1, k2, k3, k4, k5, k6, k7, k8 represent the number of repeating units in the polymer containing an amine group or an imidazole nitrogen or a triazole group, and the values ​​of k1, k2, k3, k4, k5, k6, k7, k8 affect the length of the nitrogen-containing segment and the molecular weight of the polymer;

[0030] Controlling the values ​​of m and n, or x and y, is beneficial to regulating the content of nitrogen-containing segments and ethoxy segments in the polymer protective film, and thus is beneficial to controlling the polymer protective film's ability to promote the stable formation of SEI, its interaction with metallic lithium, and its ability to conduct lithium ions.

[0031] Controlling the value of z is beneficial to adjusting the content of ethoxy groups, which can enhance the interaction between the polymer and metallic lithium, thereby reducing the interfacial impedance between the polymer and lithium metal. At the same time, it is also beneficial to promote lithium ion transmission and make lithium ions evenly distributed, reduce concentration polarization, and prevent the formation of lithium dendrites.

[0032] The SEI is rich in lithium nitride, which helps improve lithium ion transport and SEI stability. However, lithium nitride has poor solubility in the electrolyte and cannot be added directly to the electrolyte. The lithium nitride in the SEI is usually formed by the reaction of lithium metal and lithium salts, but this consumes the lithium salt, reducing the lithium salt concentration and affecting the battery's rate performance and cycle performance.

[0033] The nitrogen-containing segments in the polymer protective film of the embodiment of the present application can continuously and slowly form lithium nitride in situ with lithium metal, which is conducive to forming a stable SEI and improving the cycle performance of the battery. In addition, the lithium nitride formed in situ is more evenly distributed in the SEI film than the lithium nitride formed non-in situ, which is conducive to forming a more stable SEI with better performance. The ethoxy segments in the polymer protective film can form a strong effect with lithium metal, reduce the interfacial impedance between the polymer and lithium metal, and at the same time promote lithium ion transmission, make the lithium ion distribution uniform, reduce concentration polarization, prevent the generation of lithium dendrites, and improve the safety and cycle performance of the battery.

[0034] The polymer of the present application contains two different segments at the same time, a nitrogen-containing segment and an ethoxy segment, which is beneficial to reducing the crystallinity of the polymer and improving the effect of each segment.

[0035] Furthermore, 0.5≤m≤0.95, 0.05≤n≤0.5; 0.5≤x≤0.95, 0.05≤y≤0.5. For example, m is 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.9, and 0.95; n is 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.4, and 0.5; x is 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.9, and 0.95; y is 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.4, and 0.5. The value ranges of m and n, or x and y disclosed in the embodiments of the present application are beneficial to the content of nitrogen-containing segments and ethoxy segments, so that the nitrogen-containing segments and ethoxy segments have a suitable ratio, thereby promoting the stable formation of SEI, the interaction between the polymer and metallic lithium, and the ability to conduct lithium ions.

[0036] In a preferred embodiment, 0.7≤m≤0.9, 0.1≤n≤0.3; 0.7≤x≤0.9, 0.1≤y≤0.3. For example, m is 0.7, 0.75, 0.8, 0.9, and 0.95; n is 0.1, 0.15, 0.2, 0.25, and 0.3; x is 0.7, 0.75, 0.8, 0.9, and 0.95; and y is 0.1, 0.15, 0.2, 0.25, and 0.3.

[0037] Furthermore, the substituent is selected from halogen, hydroxyl, amino, carbonyl, cyano, C1-C6 alkoxy, C1-C6 alkyl, C6-C 12 Aryl or C6-C 12 The substituent is beneficial to improving the lithium ion conductivity of the polymer protective film, increasing the lithium ion migration number, making the lithium ions evenly distributed, and thus more effectively preventing the formation of lithium dendrites.

[0038] Furthermore, the halogen is selected from one of fluorine, chlorine and bromine; the amine group is selected from a C1-C6 primary amine, a C1-C6 alkyl-substituted secondary amine or a tertiary amine; the C1-C6 alkoxy group is selected from a methoxy group or an ethoxy group; the C1-C6 alkyl group is selected from a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group or a tert-butyl group; the C6-C 12 The aryl group is selected from phenyl, naphthyl, or biphenyl; C6-C 12 The cycloalkyl group is selected from cyclohexyl or bicyclohexyl.

[0039] Furthermore, the molecular weight of the polymer protective film is 10,000 to 500,000. For example, the molecular weight of the polymer protective film can be 10,000, 15,000, 20,000, 30,000, 50,000, 100,000, 180,000, 250,000, 30,000, 360,000, 400,000, 430,000, 480,000, 500,000, etc. The embodiment of the present invention does not limit the specific molecular weight. The polymer disclosed in the embodiment of the present invention can form lithium nitride with lithium metal, which is conducive to the formation of a stable SEI, and can form a strong interaction with lithium metal, effectively conduct lithium ions, prevent the formation of lithium dendrites, and thus help improve the cycle performance of the lithium battery.

[0040] In summary, the nitrogen-containing segments in the polymer protective film provided in the present application can continuously and slowly form lithium nitride in situ with metallic lithium, which is conducive to the formation of a stable SEI; the ethoxy segments can form a strong interaction with metallic lithium, reducing the interfacial impedance between the polymer and metallic lithium, which is conducive to promoting lithium ion transmission, making lithium ions evenly distributed, reducing concentration polarization, and inhibiting the generation of lithium dendrites, thereby improving the safety and cycle performance of the battery.

[0041] Moreover, by adjusting the content of nitrogen-containing segments and ethoxy groups, the performance of the metal lithium negative electrode is optimized, thereby improving the safety and cycle performance of the battery.

[0042] In a second aspect, the present invention provides a lithium metal anode comprising a lithium metal sheet and the polymer protective film of the first aspect, the polymer protective film being disposed on the lithium metal sheet. Those skilled in the art will appreciate that this lithium battery anode possesses all the features and advantages of the polymer protective film described above, and further details will not be given here.

[0043] In a specific embodiment, the metallic lithium negative electrode is prepared by the following process:

[0044] dissolving the polymer in an organic solvent to obtain a mixed solution;

[0045] The mixed solution is coated on a metal lithium sheet, dried at room temperature, and then placed in a vacuum oven for drying to obtain a metal lithium negative electrode.

[0046] Among them, the organic solvent can be selected from any one of toluene, xylene, trimethylbenzene, n-pentane, n-hexane, n-heptane, tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, ethyl ether, propyl ether, butyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol methyl ethyl ether, acetone, butanone, ethyl acetate, butyl acetate, ethyl propionate, butyl propionate, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, and N-methylpyrrolidone.

[0047] The coating methods include drop coating, blade coating, spin coating or spray coating, as long as it can ensure that the polymer protective film is evenly coated on the lithium metal sheet. This embodiment does not make specific limitations on this.

[0048] The thickness of the protective film is 1 μm - 10 μm. For example, it can be 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm. In a preferred embodiment, the thickness of the protective film is 2 μm - 5 μm. The thickness of the protective film in this embodiment is beneficial to ensuring that the lithium metal negative electrode has high activity, while avoiding direct contact between lithium metal and the electrolyte, thereby avoiding the generation of lithium dendrites and improving the cycle performance of the battery.

[0049] To ensure that the polymer protective film can be firmly bonded to the lithium metal sheet, the drying temperature is 25°C - 50°C and the time is 0.5 h - 4 h. This embodiment of the present invention does not limit the specific reaction temperature and time. The temperature and time ranges disclosed in this embodiment of the present invention are beneficial to ensuring that the polymer is firmly bonded to the lithium metal sheet while avoiding affecting the activity of the lithium metal negative electrode and causing problems such as polymer decomposition.

[0050] In a third aspect, the present invention provides a lithium battery, including the lithium metal negative electrode of the second aspect. Those skilled in the art can understand that this lithium secondary battery has all the characteristics and advantages of the aforementioned polymer protective film, and will not be elaborated here too much. Generally speaking, the lithium battery of this embodiment of the present invention has good specific capacity and cycle stability performance.

[0051] In a specific embodiment, the lithium battery further includes: a positive electrode, a separator, and an electrolyte. Among them, the positive electrode includes a positive electrode current collector and an active material layer located on the positive electrode current collector. The active material layer includes a positive electrode active material, a binder, and a conductive agent. The positive electrode active material can be selected from lithium cobaltate (LiCoO2), lithium nickelate (LiNiO2), lithium iron phosphate (LiFePO4), lithium cobalt phosphate (LiCoPO4), lithium manganese phosphate (LiMnPO4), lithium nickel phosphate (LiNiPO4), lithium manganate (LiMnO2), binary material LiNi x A (1-x) O2 (where A is selected from one of Co and Mn, 0 < x < 1), ternary material LiNimBnC (1-m-n) O2 (where B and C are independently selected from at least one of Co, Al, and Mn, and B and C are different, 0 < m < 1, 0 < n < 1).

[0052] The separator can be any separator material used in existing lithium secondary batteries. Specifically, it can be polyethylene, polypropylene, polyvinylidene fluoride, and their multi-layer composite films.

[0053] The electrolyte includes an organic solvent, a lithium salt and an additive. Among them, the organic solvent can be selected from ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol methyl ethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane, 1,4-dioxane, tetrahydrofuran, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, methyl formate, ethyl formate, ethyl propionate, propyl propionate, methyl butyrate, ethyl acetate, acid anhydride, N-methylpyrrolidone, N-methylformamide, N-methylacetamide, acetonitrile, sulfolane, dimethyl sulfoxide, ethylene sulfite, propylene sulfite, methyl sulfide, diethyl sulfite, dimethyl sulfite, At least one of a fluorinated cyclic organic ester and a sulfur-containing cyclic organic ester; the lithium salt is selected from at least one of an organic lithium salt and an inorganic lithium salt, such as LiPF6, LiBF4, LiTFSI, LiFSI, LiClO4, LiAsF6, LiBOB, LiDFOB, and LiTFOP; the additive may be selected from at least one of vinylene carbonate, fluorocarbonate, bisfluoroethylene carbonate, fluoroethylene carbonate, vinyl ethylene carbonate, vinyl sulfite, methylene methanedisulfonate, 1,3-propane sultone, 1,3-propylene sultone, vinyl sulfate, lithium difluorophosphate, lithium difluorobisoxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0054] In a fourth aspect, the present invention provides a vehicle comprising the lithium battery of the third aspect. For example, the vehicle may include a battery pack comprising multiple lithium batteries as described above. Thus, the vehicle possesses all the features and advantages of the lithium batteries described above, which will not be further elaborated here.

[0055] The present invention is described below by means of specific examples. It should be noted that the following specific examples are only for illustrative purposes and are not intended to limit the scope of the present invention in any way.

[0056] Example 1

[0057] (1) Preparation of metallic lithium negative electrode:

[0058] Polymer I was dissolved in tetrahydrofuran to obtain a solution with a concentration of 2 wt%. The structural formula of polymer I is as follows:

[0059]

[0060] The mixed liquid was coated on a metal lithium sheet, dried at room temperature, and then placed in a vacuum oven at 50°C for 2 hours to obtain a lithium metal negative electrode with a protective film having a thickness of 3 μm.

[0061] (2) Half-cell preparation

[0062] CR2025 button cells were assembled in an argon-filled glove box (content O2≤0.5ppm, H2O≤0.5ppm), wherein the positive electrode was a lithium iron phosphate electrode, the negative electrode was the above-mentioned lithium metal negative electrode with a protective film, the electrolyte was a 1 mol / L solution of lithium bis(fluorosulfonyl)imide in 1,3-dioxolane and ethylene glycol dimethyl ether (DOL / DME, v / v 1:1), and the separator was a 14 μm PE separator.

[0063] Example 2

[0064] The difference between this embodiment and embodiment 1 is that the structural formula of the polymer protective film II is:

[0065]

[0066] Example 3

[0067] The difference between this embodiment and embodiment 1 is that the structural formula of the polymer protective film III is:

[0068]

[0069] Example 4

[0070] The difference between this embodiment and embodiment 1 is that the structural formula of the polymer protective film IV is:

[0071]

[0072] Example 5

[0073] The difference between this embodiment and embodiment 1 is that the structural formula of the polymer protective film V is:

[0074]

[0075] Example 6

[0076] The difference between this embodiment and embodiment 1 is that the thickness of the protective film is 1 μm.

[0077] Example 7

[0078] The difference between this embodiment and embodiment 1 is that the thickness of the protective film is 8 μm.

[0079] Example 8

[0080] The difference between this embodiment and embodiment 1 is that the structural formula of the polymer protective film VI is:

[0081]

[0082] Example 9

[0083] The difference between this embodiment and embodiment 1 is that the structural formula of the polymer protective film VII is:

[0084]

[0085] Example 10

[0086] The difference between this embodiment and embodiment 1 is that the structural formula of the polymer protective film VIII is:

[0087]

[0088] Example 11

[0089] The difference between this embodiment and embodiment 1 is that the structural formula of the polymer protective film IX is:

[0090]

[0091] Example 12

[0092] The difference between this embodiment and embodiment 1 is that the structural formula of the polymer protective film X is:

[0093]

[0094] Comparative Example 1

[0095] The difference between this comparative example and Example 1 is that the polymer is PEO (polyethylene oxide) with a molecular weight of 600,000;

[0096] Comparative Example 2

[0097] The difference between this comparative example and Example 1 is that the polymer is The value of i is such that the molecular weight of the polymer is 10,000-500,000;

[0098] Comparative Example 3

[0099] The difference between this comparative example and Example 1 is that the polymer is The value of j is chosen so that the molecular weight of the polymer is 10,000-500,000;

[0100] Comparative Example 4

[0101] The difference between this comparative example and Example 1 is that there is no protective film on the surface of the lithium metal negative electrode.

[0102] The lithium batteries prepared in the above examples and comparative examples were subjected to the following performance tests to characterize the electrochemical properties of the polymer protective films.

[0103] The test procedure was as follows: 10 batteries prepared in each example and comparative example were subjected to charge-discharge cycling at 0.5C on a LAND CT 2001C secondary battery performance tester at 25±1°C. The procedure was as follows: 1 cycle was defined as: 5 minutes of rest; constant current charging to 3.8V; 5 minutes of rest; and constant current discharge to 2.7V. This cycle was repeated until the battery capacity fell below 80% of the initial discharge capacity. This number of cycles was considered the battery's cycle life. The test results are shown in Table 1.

[0104] Table 1 Performance test results of half-cells prepared in Examples 1-12 and Comparative Examples 1-4

[0105]

[0106]

[0107] From the results shown in Table 1, we can briefly analyze the test results.

[0108] According to the test results of Examples 1-12 and Comparative Example 4, it can be seen that the cycle life of the half-cells assembled with the polymer protective films of Examples 1-12 is better than that of the half-cell of Comparative Example 4. In the half-cell of Comparative Example 4, the metallic lithium negative electrode is not coated with a polymer protective film. Therefore, the polymer protective films of the embodiments of the present application are beneficial for improving the cycle life of the battery.

[0109] According to the test results of Examples 1, 4-5, 8 and 11-12, it can be concluded that different R groups have little effect on the performance of the polymer, and the polymer structures disclosed in the examples of this application can effectively improve the performance of the battery.

[0110] The test results of Examples 1 and 6-7 indicate that the thickness ranges of the polymer protective films disclosed herein are all beneficial for improving the cycle life of half-cells. These protective films, while possessing suitable strength, effectively protect lithium metal and inhibit the formation of lithium dendrites. Furthermore, they facilitate lithium ion transport and in-situ lithium nitride formation, contributing to the formation of a stable SEI.

[0111] According to the test results of Examples 1-12 and Comparative Examples 2-4, it can be seen that the cycle life of the half-cell of Examples 1-12 is better than that of the half-cell of Comparative Examples 2-4. The polymer of Comparative Examples 2-4 only includes one of the segments. Therefore, it can be seen that the reason why the polymer disclosed in this application can improve the performance of the battery is that the coordinated effect of the nitrogen-containing segment and the ethoxy segment allows a stable SEI to be formed on the surface of the lithium metal. The polymer can form a strong interaction with metallic lithium, reduce the interfacial impedance between the polymer and metallic lithium, promote lithium ion transmission, make the lithium ion distribution uniform, reduce concentration polarization, and inhibit the generation of lithium dendrites, thereby improving the safety performance and cycle performance of the battery.

[0112] The above description is merely a preferred embodiment of the present application and an illustration of the technical principles employed. Those skilled in the art should understand that the scope of the invention herein is not limited to the technical solutions formed by the specific combination of the above-mentioned technical features, but also encompasses other technical solutions formed by any combination of the above-mentioned technical features or their equivalents without departing from the inventive concept. For example, a technical solution formed by replacing the above-mentioned features with (but not limited to) technical features having similar functions disclosed in this application.

Claims

1. A polymer protective film, characterized in that: The structural formula of the polymer protective film is as follows: ,or Wherein, R1 and R3 are each independently selected from substituents substituted or unsubstituted 、 、 、 、 、 、 、 、 ; wherein k1, k2, k3, k4, k5, k6, k7, k8 are each independently an integer of 1 to 50, and K and L are each independently selected from the substituents substituted or unsubstituted 、 、 、 、 、 、 ; R2 is selected from the group consisting of C0-C6 methylene, C6-C 12 Aryl, C6-C 12 Cycloalkyl, or ; Wherein, M and Q are each independently selected from C0-C6 methylene, phenyl, and cyclohexane substituted or unsubstituted by the substituent; m and x each represent the molar ratio of the ethoxy segments to the polymer, n and y represent the molar ratio of the nitrogen-containing segments to the polymer, m and n are each independently any decimal between 0 and 1, and m+n equals 1.0; x and y are each independently any decimal between 0 and 1, and x+y equals 1.0; z represents the number of repeating units of the ethoxy structural unit, and z is an integer of 1 to 100.

2. The polymer protective film according to claim 1, characterized in that 0.5≤m≤0.95, 0.05≤n≤0.5; 0.5≤x≤0.95, 0.05≤y≤0.

5.

3. The polymer protective film according to claim 2, characterized in that 0.7≤m≤0.9, 0.1≤n≤0.3; 0.7≤x≤0.9, 0.1≤y≤0.

3.

4. The polymer protective film according to any one of claims 1 to 3, characterized in that: The substituent is selected from halogen, hydroxyl, amino, carbonyl, cyano, C1-C6 alkoxy, C1-C6 alkyl, C6-C 12 Aryl or C6-C 12 of a cycloalkyl group.

5. The polymer protective film according to claim 4, characterized in that The halogen is selected from one of fluorine, chlorine and bromine; the amino group is selected from C1-C6 primary amine, C1-C6 alkyl-substituted secondary amine or tertiary amine; the C1-C6 alkoxy group is selected from methoxy or ethoxy; the C1-C6 alkyl group is selected from methyl, ethyl, propyl, isopropyl, butyl or tert-butyl; the C6-C 12 The aryl group is selected from phenyl, naphthyl, or biphenyl; the C6-C 12 The cycloalkyl group is selected from cyclohexyl or bicyclohexyl.

6. The polymer protective film according to any one of claims 1 to 3, characterized in that: The molecular weight of the polymer protective film is 10,000-500,000.

7. A metallic lithium negative electrode, characterized in that The invention comprises a metal lithium sheet and a polymer protective film according to any one of claims 1 to 6, wherein the polymer protective film is arranged on the metal lithium sheet.

8. The metallic lithium negative electrode according to claim 7, characterized in that The thickness of the polymer protective film is 1 μm-10 μm.

9. A lithium battery, characterized in that: Comprising the metallic lithium negative electrode according to claim 7 or 8.

10. A vehicle, characterized in that: Including the lithium battery according to claim 9.

Images