Preparation method of DES / polyurethane-based self-repairing solid electrolyte membrane

Abstract

The invention belongs to the field of polymer electrolyte. Polyurethane (PU) which is high in strength, good in elasticity, convenient to form and capable of being self-repaired is selected as a substrate of the solid electrolyte. A deep eutectic solvent (DES) which can be copolymerized with the lithium salt is selected to enhance the polarity of the system and promote dissociation of the lithium salt, so that the conductivity of the solid electrolyte is improved. The invention provides a preparation method of a DES copolymerization modified self-repairing polyurethane-based solid electrolyte. The preparation method comprises the following steps: preparing a long-chain polyurethane prepolymer; preparing a self-repairing prepolymer; performing double-bond modification on the self-repairing prepolymer; preparing DES containing lithium salt and double bonds; uniformly mixing the self-repairing polyurethane prepolymer with the end capped by double bonds and DES (diethylbenzene sulfonate); pouring into a mold and curing to obtain the DES / polyurethane-based solid electrolyte membrane; and preparing the solid-state lithium battery. The solid electrolyte disclosed by the invention is free from slag falling and liquid leakage, capable of self-repairing, high in ion mobility, simple in preparation process, low in cost and outstanding in performance, and has a wide market application prospect.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of polymer electrolytes, and particularly relates to a preparation method of a deep eutectic solvent copolymer modified polyurethane-based self-healing solid electrolyte, and application of the solid electrolyte in a lithium ion battery. BACKGROUND

[0002] Rechargeable lithium metal batteries (LMB) show great potential as next-generation energy storage devices due to their high energy density. However, lithium dendrite growth in liquid organic electrolytes leads to poor cycle life and high safety risks, and the development of solid electrolytes is an effective strategy to address this challenge. It has attracted widespread attention due to its low cost, simple manufacturing, good flexibility and electrochemical stability to lithium metal.

[0003] Self-healing materials have the built-in ability to repair and restore their functions after fatigue or damage without any external or artificial intervention. The self-healing property of materials is usually based on the action of non-covalent bonds or dynamic covalent bonds, among which the disulfide bond, which has good self-healing performance and mild healing conditions, has attracted widespread attention. Disulfide bond is a dynamic covalent bond, which can realize the self-healing performance of materials due to the lower bond energy than traditional covalent bond. Disulfide-based self-healing polyurethane-based solid electrolyte can improve the cycle stability after cracks or deformation and prolong the service life of the battery.

[0004] Deep eutectic solvent (DES) is a low transition temperature mixture, which is formed by simple mixing and heating of two components containing hydrogen bonding, which is convenient and fast. DES has been widely used in the field of electrochemistry due to its non-flammability, wide electrochemical stability window and ion conductivity comparable to organic electrolytes. In addition, the selection of DES components is highly diversified. By selecting a hydrogen bond donor containing a polymerizable double bond functional group, it can be introduced into the polyurethane system with strong mechanical properties through copolymerization, providing the possibility for the preparation of high-performance solid electrolytes. SUMMARY

[0005] The purpose of the present application is to provide a preparation method of DES / polyurethane-based self-healing solid electrolyte which is simple to operate and can be mass-produced. In order to make the polyurethane which has excellent mechanical properties but is not conductive itself have strong electrical properties, the purpose of the present application can be achieved by the following technical scheme: A preparation method of DES / polyurethane-based self-healing solid electrolyte, the preparation steps are as follows: Step 1: preparing a long-chain polyurethane prepolymer; Step 2: preparing a disulfide-based polyurethane prepolymer; Step 3: grafting double bond groups on both sides of the disulfide-based polyurethane prepolymer prepared in step 2; Step 4 to prepare a deep eutectic solvent containing double bond group and lithium salt; Step 5 to mix the two components prepared in step 3 and step 4 in the solvent and stir uniformly; Step 6 to deoxygenate the mixture prepared in step 5 by aeration; Step 7 to add the initiator to the deoxygenated mixture, place it in a mold and heat to polymerize to obtain the DES / polyurethane-based self-repairing solid-state electrolyte film; Step 8 to prepare a DES / polyurethane-based self-repairing solid-state lithium ion battery.

[0006] The preparation formula and operation method of the DES / polyurethane-based solid-state electrolyte are as follows: In step 1, polypropylene glycol (PPG1000) is selected as the polyol component of the prepolymer; isophorone diisocyanate (IPDI) is selected as the isocyanate; and the catalyst is dibutyltin dilaurate (DBTDL).

[0007] In step 2, bis(2-hydroxyethyl)disulfide (HEDS) is selected as the dynamic covalent bond system providing self-repairing performance; and the catalyst is dibutyltin dilaurate (DBTDL).

[0008] In step 3, hydroxyethyl methacrylate (HEMA) is selected to cap the double bonds on both sides of the disulfide-based polyurethane prepolymer (SPU-HEMA); the reaction solvent is acetone; and the catalyst is DBTDL.

[0009] In step 4, the substances used to prepare the deep eutectic solvent containing double bond group and lithium salt are acetylcholine chloride (ACH), lithium bis(trifluoromethanesulfonimide) (LiTFSI), and hydroxyethyl methacrylate HEMA.

[0010] In step 5, anhydrous ethanol is selected as the solvent.

[0011] In step 6, argon is used as the gas for deoxygenation by aeration.

[0012] In step 7, azobisisobutyronitrile (AIBN) is selected as the initiator.

[0013] In step 1, the preferred molar ratio for preparing the polyurethane prepolymer is PPG1000:IPDI = 1:2.05; the amount of catalyst DBTDL is 0.1 mL / 100 g of prepolymer; the reaction temperature is 70°C, and the reaction time is 4 hours.

[0014] In step 2, the molar ratio of the two is HEDS:prepolymer = 1:2.05; the amount of catalyst DBTDL is 0.1 mL / 100 g of prepolymer; the reaction solvent is acetone, the reaction temperature is 45°C, and the reaction is refluxed for not less than 12 hours.

[0015] The preferred molar ratio in step 3 for preparing the double bond capped bis-sulfur polyurethane prepolymer (SPU-HEMA) is HEMA: bis-sulfur polyurethane prepolymer = 2.05:1; the amount of acetone solvent added is 10 mL / 100 g mixture; the amount of catalyst DBTDL used is 0.1 mL / 100 g prepolymer; the reaction temperature is 45°C, condensing reflux, and the reaction time is 80 hours.

[0016] The preferred molar ratio of lithium salt based DES in step 4 is ACH:LiTFSI:HEMA = 1:1:3 ~ 1:1:6, the reaction temperature is 90°C, and the reaction time is 4 hours.

[0017] The preferred mass ratio in step 5 is anhydrous ethanol: SPU-HEMA: DES = 2:1:0.5 ~ 2:1:2, and it is necessary to fully stir uniformly.

[0018] The argon purging time in step 6 is 10 minutes.

[0019] The initiator AIBN in step 7 is configured as an ethanol solution of 0.01 g / mL; the amount added is 100 μL / 10 g mixture, and it needs to be fully stirred uniformly; the polymerization temperature is 75°C, and the polymerization time is 4 hours.

[0020] Preferably, the preparation time of the lithium salt deep eutectic solvent cannot exceed 6 hours, and the temperature cannot be higher than 90°C, otherwise it is easy to self-polymerize.

[0021] Preferably, in step 8, the positive electrode is at least one of lithium iron phosphate, spinel lithium nickel manganese oxide, lithium cobaltate, and high-nickel ternary material; and the negative electrode is at least one of graphite, metallic lithium, tin-based material, lithium titanate, and silicon-based material negative electrode.

[0022] Preferably, in step 8, the lithium ion solid-state battery is one or more of a button cell, a soft-packaged battery, and a cylindrical battery.

[0023] Compared with existing materials, the present application has the following characteristics: 1) The functional filler added to the DES / polyurethane-based self-repairing solid-state electrolyte prepared by the present application is introduced in the form of a liquid small molecule, solving the problem of poor compatibility with the matrix resin, no phase separation, and greatly improving the overall stability of the solid-state electrolyte.

[0024] 2) The DES / polyurethane-based self-repairing solid-state electrolyte prepared by the present application is completely polymerized on the polyurethane segment by copolymerization, and the liquid system does not have the problems of easy evaporation and leakage, greatly improving the stability of the solid-state electrolyte and the cycle stability during use.

[0025] 3) The prepared DES / polyurethane-based self-repairing solid electrolyte has a simple preparation method, and after obtaining a double bond-terminated prepolymer, only a free radical reaction is needed for one-step curing, without a complicated post-curing process, which is more simple and convenient, and can be mass-produced.

[0026] 4) The DES / polyurethane-based self-repairing solid electrolyte prepared in the application has good mechanical properties, self-repairing performance, and can exhibit higher compression resistance, wear resistance, and deformation resistance in the later use process, and greatly improves the service life of the battery. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 SEM image of the surface of the DES / polyurethane-based self-repairing solid electrolyte film of Example 1.

[0028] Figure 2 Optical microscope photos of the DES / polyurethane-based self-repairing solid electrolyte film of Example 1 before and after self-repairing DETAILED DESCRIPTION

[0029] The application will be described in detail below with reference to specific embodiments. The embodiments are implemented on the premise of the technical solution of the application, and detailed implementation modes and specific operation processes are given, but the protection scope of the application is not limited to the following embodiments.

[0030] Example 1: A preparation method of a DES / polyurethane-based self-repairing solid electrolyte, the preparation steps of which are as follows: Step 1, preparation of long-chain polyurethane prepolymer. Polypropylene glycol (PPG1000) is selected as the polyol component of the prepolymer; isophorone diisocyanate (IPDI) is selected as the isocyanate, and the molar ratio of PPG1000:IPDI is 1:2.05; the catalyst is dibutyltin dilaurate (DBTDL), and the amount is 0.1 mL / 100 g of prepolymer; the reaction temperature is 70°C, and the reaction time is 4 hours.

[0031] Step 2, bis(2-hydroxyethyl)disulfide (HEDS) is selected as a dynamic covalent bond system providing self-repairing performance, and the molar ratio of HEDS:prepolymer is 1:2.05. The catalyst is dibutyltin dilaurate (DBTDL), and the amount is 0.1 mL / 100 g of prepolymer; the reaction solvent is acetone, the reaction temperature is 45°C, and the reaction is refluxed and condensed for not less than 12 hours.

[0032] Step 3, grafting double bond groups on both sides of the dithio polyurethane prepolymer prepared in step 2. Selecting hydroxyethyl methacrylate (HEMA) to cap the double bond on both sides of the polyurethane prepolymer (SPU-HEMA), the molar ratio of HEMA: polyurethane prepolymer is 2.05:1; the reaction solvent is acetone, the amount added is 10 mL / 100 g of mixture; the catalyst is DBTDL, the amount used is 0.1 mL / 100 g of prepolymer; the reaction temperature is 45°C, condensation reflux, and the reaction time is 80 hours.

[0033] Step 4, preparing a deep eutectic solvent containing double bond groups and lithium salt. The substances used to prepare the deep eutectic solvent containing double bond groups and lithium salt are acetylcholine chloride (ACH), lithium bis(trifluoromethanesulfonimide) (LiTFSI), and hydroxyethyl methacrylate HEMA, the molar ratio of lithium salt-based DES is ACH:LiTFSI:HEMA = 1:1:4, the reaction temperature is 90°C, which cannot exceed 90°C, and the reaction time is 4 hours, which cannot exceed 6 hours.

[0034] Step 5, mixing the two components prepared in steps 3 and 4 in a solvent and stirring uniformly. The solvent selected is anhydrous ethanol, the mass ratio is anhydrous ethanol: SPU-HEMA: DES = 2:1:1, and it is necessary to stir uniformly.

[0035] Step 6, passing the mixture prepared in step 5 through argon for 10 minutes to remove oxygen.

[0036] Step 7, adding initiator azobisisobutyronitrile (AIBN) to the mixture after removing oxygen, the concentration of the ethanol solution is 0.01 g / mL, the amount added is 100 μL / 10 g of mixture, and it is necessary to stir uniformly; placing in a mold to polymerize at a temperature of 75°C for 4 hours, thereby obtaining the DES / polyurethane-based self-repairing solid-state electrolyte film with a thickness of 0.05 mm.

[0037] Step 8, preparing a DES / polyurethane-based self-repairing solid-state lithium ion battery. Using a puncher to cut the metal lithium sheet and lithium iron phosphate positive electrode sheet into circular sheets with a diameter of 14 mm; cutting the DES / polyurethane-based self-repairing solid-state electrolyte film into a circular sheet with a diameter of 16 mm; using a CR2032 type button cell, assembling it into a lithium ion battery in the glove box in the order of negative electrode shell, spring, gasket, metal lithium sheet, electrolyte film, lithium iron phosphate positive electrode sheet, and positive electrode shell.

[0038] Example 2: A method for preparing a DES / polyurethane-based self-repairing solid-state electrolyte, the preparation steps of which are as follows: Step 1, preparation of long-chain polyurethane prepolymer. Polypropylene glycol (PPG1000) is selected as the polyol component of the prepolymer; isophorone diisocyanate (IPDI) is selected as the isocyanate, and the molar ratio of PPG1000:IPDI is 1:2.05; the catalyst is dibutyltin dilaurate (DBTDL), and the amount used is 0.1 mL / 100 g of prepolymer; the reaction temperature is 70°C, and the reaction time is 4 hours.

[0039] Step 2, bis(2-hydroxyethyl)disulfide (HEDS) is selected as the dynamic covalent bond system to provide self-repairing performance, and the molar ratio of HEDS:prepolymer is 1:2.05. The catalyst is dibutyltin dilaurate (DBTDL), and the amount used is 0.1 mL / 100 g of prepolymer; the reaction solvent is acetone, the reaction temperature is 45°C, and the reaction is refluxed for not less than 12 hours.

[0040] Step 3, grafting double bond groups on both sides of the disulfide-based polyurethane prepolymer prepared in step 2. Hydroxyethyl methacrylate (HEMA) is selected to cap the double bond groups on both sides of the polyurethane prepolymer (SPU-HEMA), and the molar ratio of HEMA:polyurethane prepolymer is 2.05:1; the reaction solvent is acetone, and the amount added is 10 mL / 100 g of mixture; the catalyst is DBTDL, and the amount used is 0.1 mL / 100 g of prepolymer; the reaction temperature is 45°C, and the reaction is refluxed for 80 hours.

[0041] Step 4, preparation of a deep eutectic solvent containing double bond groups and lithium salt. The substances used to prepare the deep eutectic solvent containing double bond groups and lithium salt are acetylcholine chloride (ACH), lithium bis(trifluoromethanesulfonimide) (LiTFSI), and hydroxyethyl methacrylate HEMA, and the molar ratio of ACH:LiTFSI:HEMA is 1:1:5; the reaction temperature is 90°C, and it must not exceed 90°C; the reaction time is 4 hours, and it must not exceed 6 hours.

[0042] Step 5, mix the two components prepared in steps 3 and 4 in a solvent and stir until uniform. Anhydrous ethanol is selected as the solvent, and the mass ratio of anhydrous ethanol:SPU-HEMA:DES is 2:1:1.5, and it must be stirred until uniform.

[0043] Step 6, pass the mixture prepared in step 5 through argon for 10 minutes to remove oxygen.

[0044] Step 7, the mixture without peroxide was added to initiator azobisisobutyronitrile (AIBN) in ethanol solution with a concentration of 0.01 g / mL, the amount of addition was 100 μL / 10 g of mixture, and it needed to be fully stirred evenly; it was placed in a mold to polymerize at a temperature of 75°C for 4 hours, thereby obtaining the DES / polyurethane-based self-repairing solid-state electrolyte film with a thickness of 0.06 mm.

[0045] Step 8, preparation of DES / polyurethane-based self-repairing solid-state lithium ion battery. A puncher was used to cut the metal lithium sheet and lithium iron phosphate anode sheet into a circular sheet with a diameter of 14 mm, respectively; the DES / polyurethane-based self-repairing solid-state electrolyte film was cut into a circular sheet with a diameter of 16 mm; a CR2032 type button cell was used, and the lithium ion battery was assembled in the glove box in the order of negative electrode shell, spring, gasket, metal lithium sheet, electrolyte film, lithium iron phosphate anode sheet, and positive electrode shell.

[0046] The above examples are only examples of the present application, although the best embodiments and drawings of the present application are disclosed for the purpose of showing, however, the present application is not limited by the above examples, any person skilled in the art, without departing from the spirit and scope of the present application and the appended claims, various alternatives, changes and modifications are possible. Therefore, the present application should not be limited to the content disclosed by the best embodiments and drawings.

Claims

1. A method of preparing a DES / polyurethane-based self-healing solid-state electrolyte, characterized by, The method comprises the following steps: (1) preparing a long-chain polyurethane prepolymer; (2) preparing a disulfide-based polyurethane prepolymer; (3) grafting double bond groups on both sides of the disulfide-based polyurethane prepolymer prepared in step (2); (4) preparing a deep eutectic solvent containing double bond groups and lithium salt; (5) mixing the two components prepared in steps (3) and (4) in a solvent and stirring uniformly; (6) aerating the mixture prepared in step (5) to remove oxygen; (7) adding an initiator to the mixture from which oxygen has been removed, placing the mixture in a mold, and heating to polymerize to obtain the DES / polyurethane-based self-repairing solid-state electrolyte film; (8) preparing a DES / polyurethane-based self-repairing solid-state lithium ion battery.

2. The method of making a DES / polyurethane-based self-healing solid-state electrolyte of claim 1, wherein, In step (1), polypropylene glycol (PPG1000) is selected as the polyol component of the prepolymer; isophorone diisocyanate (IPDI) is selected as the isocyanate, and the molar ratio of PPG1000:IPDI is 1:2.05; the catalyst is dibutyltin dilaurate (DBTDL), and the amount used is 0.1 mL / 100 g of prepolymer; the reaction temperature is 80°C, and the reaction time is not less than 2 hours.

3. The method of making a DES / polyurethane-based self-healing solid-state electrolyte of claim 1, wherein, In step (2), bis(2-hydroxyethyl)disulfide (HEDS) is selected as the dynamic covalent bond system providing self-repairing performance, and the molar ratio of HEDS:prepolymer is 1:2.

05. The catalyst is dibutyltin dilaurate (DBTDL), and the amount used is 0.1 mL / 100 g of prepolymer; the reaction solvent is acetone, the reaction temperature is 45°C, and the reaction is refluxed and condensed for not less than 12 hours.

4. The method of making a DES / polyurethane-based self-healing solid-state electrolyte of claim 1, wherein, In step (3), hydroxyethyl methacrylate (HEMA) is selected to cap the double bonds on both sides of the disulfide-based polyurethane prepolymer, and the molar ratio of HEMA:polyurethane prepolymer is 2.05:1; the reaction solvent is acetone, and the amount added is 10 mL / 100 g of mixture; the catalyst is DBTDL, and the amount used is 0.1 mL / 100 g of prepolymer; the reaction temperature is 45°C, and the reaction is refluxed and condensed for 80 hours.

5. The method of making a DES / polyurethane-based self-healing solid-state electrolyte of claim 1, wherein, In step (4), the substances used to prepare the deep eutectic solvent containing double bond groups and lithium salt are acetylcholine chloride (ACH), lithium bis(trifluoromethanesulfonimide) (LiTFSI), and hydroxyethyl methacrylate HEMA, and the molar ratio of lithium salt-based DES is ACH:LiTFSI:HEMA = 1:1:3 ~ 1:1:6; the reaction temperature is 90°C, and the reaction time is 4 hours.

6. The method of making a DES / polyurethane-based self-healing solid-state electrolyte of claim 1, wherein, In step (5), the solvent is anhydrous ethanol, and the mass ratio of anhydrous ethanol:SPU-HEMA:DES is 2:1:0.5 ~ 2:1:2, and it is necessary to stir uniformly.

7. The method of making a DES / polyurethane-based self-healing solid-state electrolyte of claim 1, wherein, In step (6), the oxygen removal gas is argon, and the aeration time is 10 minutes.

8. The method of making a DES / polyurethane-based self-healing solid-state electrolyte of claim 1, wherein, In step (7), the initiator selected is azobisisobutyronitrile (AIBN), the concentration is 0.01 g / mL of ethanol solution, the amount added is 100 μL / 10 g of mixture, and it needs to be fully stirred and uniform; placed in the mold to polymerize, the temperature is 75°C, and the polymerization time is 4 hours, to obtain the DES / polyurethane-based self-repairing solid electrolyte membrane with a thickness of 0.04-0.07 mm.

9. The method of making a DES / polyurethane-based self-healing solid-state lithium battery of claim 1, wherein, In step (8), the composite solid electrolyte, and one of lithium iron phosphate, lithium manganate, lithium cobaltate, nickel-cobalt-manganese positive electrode; at least one of metal lithium, graphite, lithium alloy, lithium titanate, silicon negative electrode. The lithium ion solid-state battery is one or more of a button cell, a soft package cell, and a cylindrical cell.

Images