Deep eutectic-based polymer semi-solid electrolyte as well as preparation method and application thereof

Abstract

The invention discloses a deep eutectic-based polymer semi-solid electrolyte as well as a preparation method and application thereof, and belongs to the technical field of solid-state lithium metal batteries. The method comprises the following steps: mixing and melting lithium salt and succinonitrile to obtain a deep eutectic solution; dissolving a polymer monomer and a thermal initiator in the deep eutectic solution at normal temperature to obtain a precursor solution; the method comprises the following steps: soaking a lithium metal negative electrode in fluoroethylene carbonate, and airing to obtain a pretreated negative electrode; and assembling the battery according to the sequence of the negative electrode shell, the pretreated negative electrode, the cellulose membrane, the positive electrode and the positive electrode shell, and performing in-situ polymerization reaction in a heating state to obtain the lithium ion battery. The semi-solid electrolyte obtained through in-situ polymerization has relatively good interfacial compatibility with the lithium metal negative electrode, so that the battery performance is remarkably improved; the addition of a small amount of polyester containing a plurality of urea groups not only retains the high electrochemical performance of a liquid electrolyte, but also has the high safety of a solid electrolyte.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid-state lithium metal batteries and relates to a flame-retardant deep eutectic-based polymer semi-solid electrolyte and a preparation method and application thereof. Background Art

[0002] With the vigorous development of the new energy industry, people's requirements for battery energy density are getting higher and higher. At the same time, the safety issues in battery use are also receiving more and more attention. At present, lithium-ion batteries usually use flammable organic electrolytes. Once abnormal heat is generated, they will catch fire or even explode, causing serious safety hazards. Therefore, the use of safe non-flammable electrolytes can greatly reduce this risk.

[0003] Typical prior art, such as Chinese patent CN111193070A, discloses a method for preparing a flame-retardant electrolyte for lithium-ion batteries containing a polyphosphazene main chain. The electrolyte uses a lithium phosphate salt containing a polyphosphazene main chain - poly (lithium diphosphate phosphazene) (LiPDPP) as a main component, and is compounded with an intermediate poly (bis (dialkoxy phosphate) phosphazene) (PBPP), an organic solvent and other electrolyte additives to obtain a flame-retardant electrolyte for lithium-ion batteries.

[0004] For example, Chinese patent CN111205322A discloses a method for preparing a flame-retardant electrolyte for lithium-ion batteries obtained by compounding a high-phosphoric acid lithium-containing 2,4,6-trioxo-1,3,5-triazine-triphosphate lithium salt with a solvent, an additive, etc. The electrolyte has a high phosphate group and lithium ion content. While achieving a flame retardant effect, it can provide multiple lithium ion attachment sites, increase the lithium ion concentration in the electrolyte, and reduce the use of flame retardant additives.

[0005] The existing technology mainly relies on nitrogen-phosphorus polymers with strong main chain flexibility to increase the conductivity of lithium ions and provide flame retardancy for electrolytes. However, this type of polymer needs to undergo a complex polymerization reaction before being compounded with organic solvents and corresponding additives, and a variety of flame retardant additives are also introduced. Organic solvents and various additives will have a certain negative impact on battery performance. Summary of the invention

[0006] In order to solve the above problems, the first object of the present invention is to provide a deep eutectic polymer semi-solid electrolyte, which not only maintains the excellent performance of the electrolyte by adding a small amount of polyurea polyester to the deep eutectic solution, but also has the advantages of a semi-solid electrolyte, can prevent electrolyte leakage, improve interface stability, and has excellent flame retardancy. In addition, the added polyurea polyester can utilize multiple urea groups and tertiary amine polar groups to cooperate with the molecular structure to promote the rapid migration of lithium ions and improve the cycle performance of the battery.

[0007] The second object of the present invention is to provide a method for preparing a deep eutectic-based polymer semi-solid electrolyte. This method adds a small amount of polyurea-based polyester to a safe and environmentally friendly deep eutectic solvent by an in-situ polymerization method, which greatly improves the interface compatibility between the electrolyte and the lithium metal negative electrode, thereby significantly improving the cycle stability of the electrode.

[0008] The third object of the present invention is to provide an application of a deep eutectic-based polymer semi-solid electrolyte, which is applied to solid-state batteries to significantly increase the number of lithium ion migration and further improve the cycle stability and service life of the battery. No additional flame retardant is required, and the purpose of flame retardancy is directly achieved.

[0009] In order to achieve the above technical objectives, the present invention provides a deep eutectic-based polymer semi-solid electrolyte, the material comprising a polyurea-based polyester and a deep eutectic solution;

[0010] The polyurea polyester has the following chemical structure of Formula I or Formula II:

[0011]

[0012] wherein n is independently selected from 200 to 500;

[0013] The deep eutectic solution is obtained by melting lithium salt and succinonitrile.

[0014] The key to the semi-solid electrolyte of the present invention is to add a small amount of polyurea polyester to the deep eutectic solvent, so that it has good flame retardant properties and good battery cycle performance. Specifically, by mixing the deep eutectic solution and the polyurea polyester, the long-chain molecular structure of the present invention or the symmetrical molecular structure of formula II can be used to form a polymer network, which is more conducive to encapsulating the deep eutectic solution, thereby forming a gel-like semi-solid electrolyte, which effectively combines the high electrochemical properties of the liquid electrolyte and the flame retardancy of the solid electrolyte. In addition, the structural formula of the polyester of the present invention has multiple urea polar groups that can coordinate with lithium ions, so that lithium ions are continuously complexed and dissociated, thereby achieving rapid conduction of lithium ions; especially when the chemical structure of formula II of the present invention is adopted, the structure not only has more urea polar groups, but also has tertiary amine nitrogen that can cooperate with urea to provide a stronger polarity for the polymer and promote the conduction of lithium ions. In addition, tertiary amine nitrogen can cooperate with intermolecular hydrogen bonds to make the electrolyte have excellent mechanical elasticity. When the volume of the electrode material changes during the charge and discharge process, it can ensure that the electrolyte and the electrode maintain good adaptive contact, thereby improving the interface compatibility between the electrolyte and the lithium metal negative electrode. More preferably, the polyurea polyester has the structural formula II.

[0015] As a preferred solution, the volume fraction of the polyurea-based polyester in the electrolyte is 3-4%. The presence of trace amounts of polyester is the key to ensuring that the electrolyte of the present invention exhibits excellent electrochemical properties at room temperature when applied to solid-state batteries. The inventors have found that only at this volume fraction will the electrolyte of the present invention be a gel-like semi-solid electrolyte, and can it achieve a flame retardant effect without adding a flame retardant. When polyester is not added, due to the poor compatibility of the deep eutectic solution with lithium metal, side reactions will occur with lithium metal; and when the polyester content is too high, the formed polymer network will hinder ion migration, thereby affecting the performance of the battery.

[0016] The present invention also provides a method for preparing a deep eutectic-based polymer semi-solid electrolyte, comprising the following steps:

[0017] 1) mixing and melting lithium salt and succinonitrile to obtain a deep eutectic solution;

[0018] 2) dissolving a polymer monomer and a thermal initiator in a deep eutectic solution at room temperature in sequence to obtain a precursor solution; the polymer monomer is composed of a polyamine compound and isocyanoethyl methacrylate; the polyamine compound is ethylenediamine or tri(2-aminoethyl)amine;

[0019] 3) immersing the lithium metal negative electrode in fluoroethylene carbonate and drying it to obtain a pretreated negative electrode;

[0020] 4) After assembling the battery in the order of the negative electrode shell, the pretreated negative electrode, the cellulose membrane, the positive electrode and the positive electrode shell, an in-situ polymerization reaction is carried out under heating to obtain; the precursor solution is evenly dripped on both sides of the cellulose membrane.

[0021] Another key control point of the present invention is to generate polyurea polyester by in-situ polymerization during the preparation process. The principle is: at room temperature, two monomers are used to react between amine groups and isocyanate groups in a deep eutectic solution to form a polyester compound having multiple polar groups, urea groups and tertiary amine nitrogen. The key to forming a polymer network is to add a thermal initiator to the deep eutectic solvent, and to decompose the initiator under heating to become a free radical, thereby initiating an addition reaction of carbon-carbon double bonds to form a polymer network, and wrap the deep eutectic solution in the network to form a polymer semi-solid electrolyte. Due to the poor compatibility of the deep eutectic solution with lithium metal, it will have side reactions with lithium metal, and the preparation method of in-situ polymerization of the present invention can form a tight interface between the electrolyte and the electrode, which greatly enhances the interface compatibility between the electrolyte and the electrode. The polyurea polyester network formed at the same time can effectively slow down the interface reaction between the deep eutectic solution and lithium metal, which not only maintains the excellent performance of the deep eutectic solution as an electrolyte, but also does not have the risk of electrolyte leakage, and also improves the interface compatibility.

[0022] The two polyamine compounds selected in the present invention both have multiple amino groups that can react with isocyanoethyl methacrylate to form a polymer network structure, effectively slowing down the interfacial reaction between the electrolyte and the lithium negative electrode. Due to the influence of the polar groups in the polymer on the battery performance, tris(2-aminoethyl)amine is further preferred.

[0023] As a preferred solution, the molar ratio of the polyamine compound to isocyanoethyl methacrylate is 1:(2-3). Within the molar ratio range selected by the present invention, the two monomers can be fully polymerized while reducing the occurrence of side reactions.

[0024] As a preferred solution, the mass ratio of the lithium salt to succinonitrile is 1:(3-4), and the mixing conditions are: temperature of 60-65° C. and time of 1-2 h.

[0025] As a preferred solution, the lithium salt is lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). The mixing temperature of the present invention is slightly higher than the melting point of succinonitrile to ensure that the lithium salt and succinonitrile are eutectic.

[0026] As a preferred solution, the volume ratio of the polymer monomer and the deep eutectic solution is controlled within 1: (30-35) to form a gel state. Within the volume ratio range of the polymer monomer and the deep eutectic solution selected in the present invention, the volume fraction of the polymer in the deep eutectic solution can be controlled within 3-4 vol%. The presence of trace amounts of polymer is the key to ensuring that the electrolyte of the present invention exhibits excellent electrochemical properties at room temperature when applied to solid-state batteries. Gel polymer electrolytes combine the excellent properties of the polymer matrix (such as mechanical stability, flexibility, and non-leakage, etc.) with the excellent ionic conductivity of liquid organic electrolytes. This combination has both the cohesiveness of a solid and the diffusivity of a liquid, and has broad application prospects.

[0027] As a preferred solution, the thermal initiator is azobisisobutyronitrile, and the amount added is 0.5-1 mol% of the precursor solution. The thermal initiator selected in the present invention is a white crystalline powder, which can be dissolved in the deep eutectic solution formed by lithium salt and succinonitrile at room temperature.

[0028] As a preferred solution, in step 4, the volume of the precursor solution dripped on one side of the cellulose membrane is 10-20 μl. Too little dripping of the precursor solution will affect the density of the membrane and make the electrolyte membrane uneven, while too much dripping will make the electrolyte membrane too thick and affect the battery performance.

[0029] As a preferred solution, the in-situ polymerization reaction conditions are: temperature of 50-60°C and time of 1-2 hours. The temperature and time range selected in the present invention can ensure rapid and efficient polymerization and reduce the occurrence of side reactions.

[0030] As a preferred solution, the steps before assembling the battery are all carried out under an inert gas atmosphere in a glove box, which can effectively prevent the oxidation of lithium salts and lithium metals.

[0031] As a preferred solution, the lithium metal negative electrode is immersed in fluoroethylene carbonate for 4 to 5 hours and then used after being dried.

[0032] Finally, the present invention also provides an application of a deep eutectic-based polymer semi-solid electrolyte, which is applied to solid-state batteries. Since the polyurea-based polyester is introduced by an in-situ polymerization method, the interface impedance of the electrode / electrolyte is reduced and the transmission flux of lithium ions at the interface is increased. The formed stable electrode / electrolyte interface film ensures the rapid migration of lithium ions, prevents the continuous decomposition of electrolyte components, and prevents the co-embedding of solvent molecules from causing irreversible damage to the electrode material, thereby significantly improving the cycle stability and service life of the battery.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] 1) The electrolyte provided by the present invention not only maintains the excellent performance of the electrolyte by adding a small amount of polyurea polyester to the deep eutectic solution, but also has the advantages of a semi-solid electrolyte, can prevent electrolyte leakage, improve interface stability, and has excellent flame retardancy. In addition, the added polyurea polyester can utilize multiple urea groups and tertiary amine polar groups to coordinate the molecular structure to promote the rapid migration of lithium ions and improve the cycle performance of the battery.

[0035] 2) When the chemical structure of formula II is adopted in the present invention, the structure not only has more urea polar groups, but also has tertiary amine nitrogen that can cooperate with the urea group to provide a stronger polarity for the polymer and promote the conduction of lithium ions. In addition, the tertiary amine nitrogen can cooperate with the intermolecular hydrogen bonds to make the electrolyte have excellent mechanical elasticity. When the volume of the electrode material changes during the charge and discharge process, it can ensure that the electrolyte and the electrode maintain good adaptive contact, thereby improving the interface compatibility between the electrolyte and the lithium metal negative electrode.

[0036] 3) The present invention adopts an in-situ polymerization method to thermally polymerize a layer of semi-solid electrolyte on the surface of the cellulose membrane, which effectively improves the interface compatibility between the electrolyte and the lithium metal negative electrode, and at the same time improves the cycle stability of the lithium metal electrode.

[0037] 4) The in-situ polymerization method provided by the present invention avoids the cumbersome process of using a complex polymerization reaction and then compounding with an organic solvent and corresponding additives in the prior art, and has a simple process and is more conducive to industrial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The present invention will be further described below in conjunction with the accompanying drawings.

[0039] Figure 1 Schematic diagram of the preparation of the deep eutectic solution of Example 1 of the present invention.

[0040] Figure 2 This is a gel electrolyte obtained by heating the two precursor solutions in Example 1 of the present invention.

[0041] Figure 3 This is the constant current polarization curve of the symmetrical battery cycle of the D-EDA electrolyte of Example 1 of the present invention.

[0042] Figure 4 This is the constant current polarization curve of the symmetrical battery cycle of the D-TAEA electrolyte of Example 1 of the present invention.

[0043] Figure 5 This is a scanning electron microscope image of the electrode surface of the symmetrical battery using DES electrolyte after cycling in Comparative Example 1 of the present invention.

[0044] Figure 6 This is a scanning electron microscope image of the electrode surface of the symmetrical battery using D-EDA electrolyte after cycling in Example 1 of the present invention.

[0045] Figure 7 This is a scanning electron microscope image of the electrode surface of the symmetrical battery using D-TAEA electrolyte after cycling in Example 1 of the present invention.

[0046] Figure 8 Schematic diagram of full battery cycle using different electrolytes in Example 1 of the present invention and Comparative Example 1.

[0047] Fig. 9 This is a schematic diagram of flame retardancy of different electrolytes in Example 1 of the present invention.

[0048] Fig.10 This is a schematic diagram of the deep eutectic solution after adding 2 vol % of polymer and heating in Comparative Example 2 of the present invention.

[0049] Fig.11 This is the constant current polarization curve of the symmetrical battery cycle of the D-TAEA electrolyte prepared by dropping 20 μl of the precursor solution when assembling the battery in Example 3 of the present invention.

[0050] Fig.12 1 is the chronoamperometric curve at a polarization voltage of 10 mV in Example 4, and the corresponding electrochemical impedance spectroscopy (EIS) spectra before and after polarization.

[0051] Fig.13 are the HOMO and LUMO energy levels of different electrolyte components in Example 4.

[0052] Fig.14This is the constant current polarization curve of the symmetrical battery cycle using DES as the electrolyte in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0053] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0054] In order to further illustrate the present invention, the specific implementation of the present invention is further described below in conjunction with specific embodiments and drawings, but the implementation of the present invention is not limited thereto.

[0055] In the examples and comparative examples of the present invention, when the polymer monomers are ethylenediamine and isocyanoethyl methacrylate, the structural formula of the formed polymer is:

[0056]

[0057] Among them, n is 299.

[0058] In the examples and comparative examples of the present invention, when the polymer monomers are tris(2-aminoethyl)amine and isocyanoethyl methacrylate, the structural formula of the formed polymer is:

[0059]

[0060] Among them, n is 412.

[0061] Example 1

[0062] Add 3 vol% of polyurea polyester to the deep eutectic solution:

[0063] 1) 4.78 g of succinonitrile (SN) and 1.39 g of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) were mixed, heated and stirred at 60 °C for 1 h to obtain a colorless, transparent, clear deep eutectic solution, such as Figure 1 .

[0064] 2) 17 μl of ethylenediamine and 71 μl of isocyanatoethyl methacrylate were added to 2845 μl of the deep eutectic solution obtained in step 1) respectively, and stirred evenly to obtain a homogeneous solution (D-EDA).

[0065] 3) 15 μl of tris(2-aminoethyl)amine and 43 μl of isocyanatoethyl methacrylate were added to 1875 μl of the deep eutectic solution obtained in step 1) respectively, and stirred evenly to obtain a homogeneous solution (D-TAEA).

[0066] 4) Azobisisobutyronitrile (AIBN) accounting for 0.5 mol% of the precursor solution is added to step 2) and step 3) respectively, and stirred to uniformly dissolve to obtain a homogeneous precursor solution.

[0067] 5) Soak the lithium metal negative electrode in fluoroethylene carbonate for 5 hours, then take it out and dry it. Assemble the battery in the order of negative electrode shell, lithium metal negative electrode, precursor solution, cellulose membrane, precursor solution, lithium iron phosphate positive electrode, and positive electrode shell, and drip the two precursor solutions obtained in step 4) on both sides of the cellulose diaphragm of two different assembled batteries (the volume dripped on one side is 10μl), and heat the two assembled symmetrical batteries at 60°C to make the homogeneous mixture composed of SN, LiTFSI and polymer monomers in situ polymerize for 1 hour, and test the flame retardancy of the electrolyte by igniting them respectively.

[0068] At 0.05mAcm -2 At the current density, the charge and discharge time was 120 min. Electrochemical tests were carried out on the two symmetrical batteries respectively. SEM analysis was performed on the lithium metal surface of the symmetrical battery after cycling. The full battery was subjected to a long cycle test at 0.1C.

[0069] pass Figure 1 It can be seen that the deep eutectic solution is obtained by mixing succinonitrile and lithium bis(trifluoromethanesulfonyl)imide to obtain a clear colorless liquid.

[0070] pass Figure 2 It can be seen that after heating the two precursor solutions, a colorless and transparent gel was obtained.

[0071] pass Figure 3 and Figure 4 It can be seen that at 0.05mAcm -2 Under the current density and charge and discharge time of 120 min, the D-EDA electrolyte short-circuited after about 200 h of cycling, while the D-TAEA electrolyte cycled for nearly 800 h, which was more stable.

[0072] pass Figure 5 , Figure 6 and Figure 7 It can be seen that the surface of the battery with D-TAEA as the electrolyte is the smoothest and flattest, the surface of the battery with DES as the electrolyte has the most side reaction products, and the surface of the battery with D-EDA as the electrolyte is relatively flat, indicating that the existence of the polymer network effectively slows down the interfacial reaction between the electrolyte and the lithium negative electrode.

[0073] pass Figure 8 It can be seen that at a rate of 0.1C and a cut-off voltage of 2.5V-4.2V, D-TAEA has the largest number of cycles and is the most stable.

[0074] pass Fig. 9It can be seen that neither of these two electrolytes is flammable upon ignition.

[0075] Example 2

[0076] Add 4 vol% of polyurea polyester to the deep eutectic solution:

[0077] The difference from Example 1 is that the volumes of the deep eutectic solutions in step 2) and step 3) are 2112 μl and 1392 μl respectively. Other than that, the remaining operation steps and conditions are the same as those in Example 1. It was found through experiments that 4 vol% of polyurea polyester can also form a gel in a deep eutectic solution, but since too much polymer forms a denser network, which affects battery performance, 3 vol% of the polymer is the best.

[0078] Example 3

[0079] 1) 5.24 g of succinonitrile (SN) and 1.53 g of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) were mixed, and heated with stirring at 60° C. to obtain a colorless, transparent, clear deep eutectic solution.

[0080] 2) 15 μl of tri(2-aminoethyl)amine and 43 μl of isocyanatoethyl methacrylate were added to 1875 μl of the deep eutectic solution obtained in step 1), respectively, and stirred evenly to obtain a homogeneous solution (D-TAEA).

[0081] 3) Azobisisobutyronitrile (AIBN) accounting for 0.5 mol% of the precursor solution is added to step 2), and the mixture is stirred and dissolved to obtain a homogeneous precursor solution.

[0082] 4) Soak the lithium metal negative electrode in fluoroethylene carbonate for 5 hours, then take it out and dry it. Assemble the battery in the order of negative electrode shell, lithium metal negative electrode, precursor solution, cellulose membrane, precursor solution, lithium iron phosphate positive electrode, and positive electrode shell, and drip the precursor solution obtained in step 3) on both sides of the cellulose separator (the volume dripped on one side is 20μl), and heat the assembled battery at 60°C to allow the homogeneous mixture composed of SN, LiTFSI and polymer to polymerize in situ for 1 hour.

[0083] At 0.05mAcm -2 At the current density, the charge and discharge time is 120min, and the electrochemical test of the symmetrical battery is carried out. Fig.11 It can be seen that when the electrolyte membrane thickness is doubled, the battery cycle performance decreases, but within the range of 10μl-20μl, the cycle is still stable.

[0084] Example 4

[0085] To verify the effect of polar groups on battery performance, two symmetrical batteries in Example 1 were tested. The chronoamperometric curves at a polarization voltage of 10 mV and the corresponding electrochemical impedance spectroscopy (EIS) spectra before and after polarization were tested. The HOMO and LUMO energy levels of the electrolyte components were also calculated to analyze the reaction order of different components during the battery cycle.

[0086] pass Fig.12 It can be seen that the ion migration number of the polyester containing multiple urea groups prepared by tri(2-aminoethyl)amine and having more polar groups, such as urea groups and tertiary amine groups, is much higher than that prepared by ethylenediamine.

[0087] pass Fig.13 It can be seen that the HOMO energy level of tri(2-aminoethyl)amine is much higher than that of other electrolyte components, so it will react preferentially at the positive electrode to form oxides at the interface that are beneficial to battery cycling, thereby improving the performance of the battery.

[0088] Comparative Example 1

[0089] The deep eutectic solution obtained in step 1) of Example 1 was used as the electrolyte to assemble the battery. 2 At the current density, the charge and discharge time is 120min, and the symmetric battery is electrochemically tested, and the lithium metal surface after the symmetric battery cycle is analyzed by SEM. The flame retardancy of the electrolyte is tested by ignition. The full battery is subjected to a long cycle test at 0.1C.

[0090] pass Figure 5 It can be seen that there are many side reaction products between the deep eutectic solution and the lithium metal surface;

[0091] pass Figure 8 It can be seen that the battery cycling performance of deep eutectic solution as electrolyte is poor;

[0092] pass Fig.14 It can be seen that the deep eutectic solution without polymer can only circulate for less than 100 hours.

[0093] Comparative Example 2

[0094] Add 2 vol% of polyurea polyester to the deep eutectic solution:

[0095] The difference between this comparative example and Example 1 is that the volumes of the deep eutectic solutions in step 2) and step 3) are 4312 μl and 2812 μl respectively. Other than this, the remaining operating steps and conditions are the same as those in Example 1. The results are shown in FIG. Fig.10 .

[0096] pass Fig.10 It can be seen that adding 2 vol% of polyurea polyester into the deep eutectic solution cannot form a gel.

[0097] The above are only a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the present application. Any technician familiar with the profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A deep eutectic-based polymer semi-solid electrolyte, characterized in that: Contains polyurea polyester and deep eutectic solution; The polyurea polyester has the following chemical structure of Formula I or Formula II: wherein n is independently selected from 200 to 500; The deep eutectic solution is obtained by melting lithium salt and succinonitrile.

2. A deep eutectic-based polymer semi-solid electrolyte according to claim 1, characterized in that: The volume fraction of the polyurea-based polyester in the electrolyte is 3-4%.

3. The method for preparing a deep eutectic-based polymer semi-solid electrolyte according to claim 1 or 2, characterized in that: The steps include: 1) mixing and melting lithium salt and succinonitrile to obtain a deep eutectic solution; 2) dissolving a polymer monomer and a thermal initiator in a deep eutectic solution at room temperature in sequence to obtain a precursor solution; the polymer monomer is composed of a polyamine compound and isocyanoethyl methacrylate; the polyamine compound is ethylenediamine or tri(2-aminoethyl)amine; 3) immersing the lithium metal negative electrode in fluoroethylene carbonate and drying it to obtain a pretreated negative electrode; 4) After assembling the battery in the order of the negative electrode shell, the pretreated negative electrode, the cellulose membrane, the positive electrode and the positive electrode shell, an in-situ polymerization reaction is carried out under heating to obtain; the precursor solution is evenly dripped on both sides of the cellulose membrane.

4. The method for preparing a deep eutectic-based polymer semi-solid electrolyte according to claim 3, characterized in that: The molar ratio of the polyamine compound to isocyanoethyl methacrylate is 1:(2-3).

5. The method for preparing a deep eutectic-based polymer semi-solid electrolyte according to claim 3, characterized in that: The mass ratio of the lithium salt to succinonitrile is 1:(3-4), and the mixing conditions are: temperature of 60-65° C. and time of 1-2 hours.

6. The method for preparing a deep eutectic-based polymer semi-solid electrolyte according to claim 5, characterized in that: The volume ratio of the polymer monomer to the deep eutectic solution is controlled within 1:(30-35); The thermal initiator is azobisisobutyronitrile, and the added amount is 0.5-1 mol% of the precursor solution.

7. The method for preparing a deep eutectic-based polymer semi-solid electrolyte according to claim 6, characterized in that: In step 4, the volume of the precursor solution dripped onto one side of the cellulose membrane is 10-20 μl.

8. The method for preparing a deep eutectic-based polymer semi-solid electrolyte according to claim 3 or 7, characterized in that: The in-situ polymerization reaction conditions are: temperature of 50-60° C. and time of 1-2 hours.

9. The method for preparing a deep eutectic-based polymer semi-solid electrolyte according to claim 3, characterized in that: The steps before assembling the battery are all carried out under an inert gas atmosphere in a glove box.

10. The use of a deep eutectic-based polymer semi-solid electrolyte according to claim 1 or 2, characterized in that: Application in solid-state batteries.

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