Preparation method and application of a high-strength electrolyte applicable to a structural battery

Abstract

The present invention discloses a preparation method and application of a high-strength electrolyte for a structural battery. The preparation method of the high-strength electrolyte comprises the following steps: Step 1, preparation of an epoxy resin-based precursor; Step 2, preparation of a composite pore former; Step 3, preparation of a liquid electrolyte; Step 4, preparation of an electrolyte containing the composite pore former; Step 5, preparation of a porous epoxy resin-based electrolyte template; Step 6, preparation of the high-strength electrolyte. The epoxy resin-based electrolyte prepared by the present invention has both high tensile strength and high elastic modulus at the same time. When compounded with a high-strength carbon-based material, it can endow the battery with the performance of bearing tensile force and shear force, and can be used for structural batteries and lithium-ion solid-state batteries.

Description

Technical Field

[0001] The present invention belongs to the technical field of new energy materials, and relates to a preparation method of a solid electrolyte, in particular to a preparation method and application of an epoxy resin-based electrolyte with both high tensile strength and high elastic modulus. Background Art

[0002] The development of lightweight batteries has great potential value for fully electrified devices and applications, including electric vehicles and electric aircraft, intelligent equipment, robots, etc. As the energy density of batteries gets closer and closer to the upper limit, another strategy to reduce the battery weight is to create energy storage devices that can withstand structural loads and serve as substitutes for structural components, thereby reducing the weight of the entire system. This type of battery is usually called a "structural battery", and its basic requirement is that the battery itself has a certain mechanical strength. The structured battery as a structural component can increase the cruising range of spacecraft and new energy vehicles, and improve the combat mobility and flexibility of intelligent equipment and military equipment.

[0003] At present, structural energy storage devices have been demonstrated experimentally and numerically, which can improve the mass efficiency of systems such as electric vehicles and aircraft to a certain extent and extend their operating time. Different from conventional lithium-ion batteries, the current process and battery structure of structured batteries cannot be simply physically stacked. One of the most important components is an electrolyte with high mechanical strength to support the whole battery and at the same time have ion-conducting ability to obtain electrical performance. In addition, the electrolyte with high mechanical strength can also largely inhibit the formation of lithium metal dendrites, making the lithium-ion battery obtain higher safety. Summary of the Invention

[0004] The purpose of the present invention is to provide a preparation method and application of a high-strength electrolyte for structural batteries. The epoxy resin-based electrolyte prepared by this method has both high tensile strength and high elastic modulus. When compounded with high-strength carbon-based materials, it can endow the battery with the performance of bearing tensile force and shear force, and can be used in structural batteries and lithium-ion solid-state batteries.

[0005] The purpose of the present invention is achieved by the following technical solutions:

[0006] A preparation method of a high-strength electrolyte for structural batteries, comprising the following steps:

[0007] Step 1: Preparation of an epoxy resin-based precursor:

[0008] Take epoxy resin, an organic compound containing a metal element, and a curing agent, mix them evenly according to a mass ratio of 60-90:5-40:10-30, and store them in a low-temperature and light-shielded environment for later use, where:

[0009] It is carried out entirely in a glove box filled with argon gas;

[0010] The epoxy resin type can be one or a mixture of several of E-44, E-51, E54, E57, etc.;

[0011] The organic compound containing a metal element is one or several of titanium acetylacetonate, bis(acetylacetonato)diisopropyl titanate, molybdenum acetylacetonate, aluminum acetylacetonate, cobalt acetylacetonate;

[0012] The curing agent can be one or several of bisphenol A, isopropanol, polycarbonate, and polyamide;

[0013] Step 2: Preparation of the composite pore former: Take a small molecule liquid organic ester solvent and a low-degree polymer containing an ether oxygen group, mix them evenly according to the mass ratio of 40~70:20~30, and store them in a low-temperature and light-proof environment for later use, where:

[0014] It is carried out entirely in a glove box filled with argon gas;

[0015] The small molecule liquid organic ester solvent can be one or several of ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, propylene carbonate, ethyl acetate, methyl propionate, isoamyl formate, and butyl benzoate;

[0016] The low-degree polymer containing an ether oxygen group can be one or several of polyethylene glycol 400, polyethylene glycol 600, polyethylene glycol 1000, polyethylene glycol diacrylate 2000, polyethylene glycol diacrylate 4000, poly(ethylene glycol) dimethacrylate;

[0017] Step 3: Preparation of the liquid electrolyte: Take an ionic liquid, a lithium salt, and an organic solvent, mix them evenly according to the mass ratio of 90~110:40~60:1~10, and store them for later use, where:

[0018] It is carried out entirely in a glove box filled with argon gas;

[0019] The ionic liquid is 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (EMIM-TFSI), 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF 6 ), 1-butyl-3-methylimidazolium hexafluorophosphate [C 4 mim][PF 6 , tetradecyltrihexylphosphonium 2-(methylthio)benzoate ([P66614][MTBA]), tetradecyltrihexylphosphonium thiosalicylate ([P66614][Ts]);

[0020] The lithium salt is lithium perchlorate (LiClO4 ), lithium tetrafluoroborate (LiBF 4 ), lithium hexafluoroarsenate (LiAsF 6 ), lithium hexafluorophosphate (LiPF 6 ), lithium bis(oxalato)borate (LiBOB), lithium difluoro(oxalato)borate (LiDFOB), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethylsulfonyl)imide (LiTFSI);

[0021] The organic solvent is one of propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC);

[0022] Step Four: Preparation of the electrolyte containing the composite pore former:

[0023] Step Four - One: Mix the epoxy resin - based precursor in Step One and the composite pore former in Step Two at a mass ratio of 10 - 40:50 - 90, and under the action of vigorous stirring at 1000 - 1500 r / min, conduct the first high - temperature curing for 10 - 45 min at 40 - 70 °C to obtain a mixed solution;

[0024] Step Four - Two: Add the nitrile - based binder to the epoxy resin - based precursor after the first high - temperature curing in Step Four - One, stir for 10 - 15 h, and after fully stirring evenly, conduct a suction filtration operation to form a filter cake. Then, conduct the second high - temperature curing for 5 - 45 min at 40 - 70 °C to obtain the electrolyte containing the composite pore former, where:

[0025] The mass of the nitrile - based binder accounts for 1 - 10% of the mass of the epoxy resin - based precursor;

[0026] The nitrile - based binder is one of methyl α - cyanoacrylate, ethyl cyanoacrylate, and methyl methacrylate - acrylonitrile copolymer;

[0027] Step Five: Preparation of the porous epoxy resin - based electrolyte template;

[0028] Step Five - One: High - temperature primary pore formation: Place the electrolyte containing the composite pore former obtained in Step Four under a high - temperature condition of 55 - 95 °C and vacuum dry for 1 - 6 h to obtain an electrolyte with micron - scale continuous pores;

[0029] Step Five - Two: High - temperature secondary pore formation: Place the electrolyte with micron - scale continuous pores under a high - temperature condition of 100 - 150 °C and vacuum dry for 1 - 6 h to obtain a porous epoxy resin - based electrolyte template with both micron - scale continuous pores and nano - scale continuous pores;

[0030] Step Six: Preparation of the high - strength electrolyte

[0031] Step 6.1: Drop the liquid electrolyte obtained in Step 3 onto the porous epoxy resin-based electrolyte template obtained in Step 5, with the mass ratio of the two being 50-100:30-80. Then, vacuum stand for 30-60 min to extract the gas in the pores of the template, so that the liquid electrolyte infiltrates;

[0032] Step 6.2: Stand at a temperature of 40-60 °C for 24-36 hours to make the liquid electrolyte fully infiltrate the template, and finally obtain an electrolyte with both high tensile strength and high elastic modulus. This electrolyte can be applied in structural batteries or solid-state lithium-ion batteries.

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

[0034] 1. The high-strength structural electrolyte prepared by the present invention combines the high elastic modulus of epoxy resin and the high tensile strength of nitrile binder, so that the electrolyte has both high elastic modulus and tensile resistance. Its tensile strength exceeds 17.9 MPa (as Figure 3 shown), far exceeding the strength of conventional lithium-ion battery separators and traditional polymer-based solid electrolytes (less than 2 MPa). Its elastic modulus is higher than 5.4 GPa (as Figure 4 shown), while traditional separators and polymer-based electrolytes hardly have elastic modulus strength. Therefore, it can endow the structural battery with high load capacity.

[0035] 2. The high-strength structural electrolyte prepared by the present invention adopts a composite pore-forming technology. By creatively utilizing the viscosity, fluidity and compatibility differences of organic molecules with epoxy resin, a hierarchical pore-forming strategy is realized, and an electrolyte template with both micron pores and nano pores is prepared, greatly improving the ionic conductivity of the electrolyte. As Figure 5 shown, its ionic conductivity exceeds 0.8×10 ‒4 S / cm, higher than the conductivity of traditional polymer-based electrolytes.

[0036] 3. The preparation process of the high-strength electrolyte for structural batteries of the present invention introduces a structural electrolyte process on the basis of the existing lithium-ion battery electrode process, is compatible with the existing lithium-ion battery production process, realizes the high strength of the positive and negative electrodes of the battery, and the prepared high-strength structural battery can be charged and discharged normally. As Figure 6 shown, the charge-discharge efficiency of the structural battery with lithium iron phosphate as the positive electrode is close to 100%, demonstrating the good electrochemical performance of the structural electrolyte.

[0037] 4. The high-strength structural electrolyte prepared by the present invention for structural batteries can replace existing equipment structural parts, such as robotic arms, casings, chassis, etc., improving the overall energy utilization rate and endurance of the equipment.

[0038] 5. The high-strength structural electrolyte prepared by the present invention reduces the occurrence of lithium deposition and lithium dendrites at the negative electrode due to its high elastic modulus, further improving the safety of the battery, and can endow lithium-ion batteries or solid-state lithium-metal batteries with long cycle stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 is a schematic diagram of the preparation process of the high-strength electrolyte;

[0040] Figure 2 is a scanning electron microscope image of the high-strength electrolyte;

[0041] Figure 3 is the tensile strength test result of the high-strength electrolyte;

[0042] Figure 4 is the elastic modulus test result of the high-strength electrolyte;

[0043] Figure 5 is the electrochemical impedance spectroscopy test result of the high-strength electrolyte;

[0044] Figure 6 is the charge-discharge test result of the battery assembled with the high-strength electrolyte. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0045] The technical solutions of the present invention will be further described below with reference to the accompanying drawings, but are not limited thereto. Any modification or equivalent replacement of the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention shall be covered by the protection scope of the present invention.

[0046] The present invention provides a method for preparing a high-strength electrolyte that can be used in structural batteries, as Figure 1 shown, the method includes the following steps:

[0047] Step 1. Preparation of an epoxy resin-based precursor:

[0048] Take epoxy resin, an organic compound containing a metal element, and a curing agent, mix them evenly according to a mass ratio of 60-90:5-40:10-30, and store them in a low-temperature and light-shielded environment for later use, where:

[0049] The whole process is carried out in a glove box filled with argon;

[0050] The epoxy resin model can be one or a mixture of several of E-44, E-51, E54, E57, etc., which has a high elastic modulus after high-temperature curing;

[0051] The organometallic compound containing a metal element is one or more of titanium acetylacetonate, bis(acetylacetonato)diisopropyl titanate, molybdenum acetylacetonate, aluminum acetylacetonate, and cobalt acetylacetonate. Its function is to further enhance the mechanical strength of the epoxy resin and be compatible with the epoxy resin, forming a homogeneous phase;

[0052] The curing agent can be one or more of bisphenol A, isopropyl alcohol, polycarbonate, and polyamide. Its function is to cure the epoxy resin-based precursor into a single solid phase at high temperature;

[0053] Step 2: Preparation of the composite pore former: Take a small molecule liquid organic ester solvent and a low-degree polymer containing ether oxygen groups, mix them evenly according to a mass ratio of 40-70:20-30, and store them in a low-temperature and light-proof environment for later use. Among them:

[0054] The whole process is carried out in a glove box filled with argon;

[0055] The small molecule liquid organic ester solvent can be one or more of ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, propylene carbonate, ethyl acetate, methyl propionate, isoamyl formate, and butyl benzoate. Its function is to have poor compatibility with the epoxy resin-based precursor and is volatile during high-temperature pore formation, easily forming micron-sized large pores and forming micron-sized continuous pores;

[0056] The low-degree polymer containing ether oxygen groups can be one or more of polyethylene glycol 400, polyethylene glycol 600, polyethylene glycol 1000, polyethylene glycol diacrylate 2000, polyethylene glycol diacrylate 4000, and poly(ethylene glycol) dimethacrylate. Its characteristics are poor fluidity, high viscosity, moderate compatibility with the epoxy resin-based precursor but not easily flowing during high-temperature curing, easily forming an integrated template with the precursor, requiring higher temperature for pore formation, and the formed pores are smaller, being nanometer-sized continuous pores;

[0057] Step 3: Preparation of the liquid electrolyte: Take an ionic liquid, a lithium salt, and an organic solvent, mix them evenly according to a mass ratio of 90-110:40-60:1-10, and store them for later use. Among them:

[0058] The whole process is carried out in a glove box filled with argon;

[0059] The ionic liquid is 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (EMIM-TFSI), 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF 6 ), 1-butyl-3-methylimidazolium hexafluorophosphate [C 4 mim][PF 6One of tetrahexyl(tetradecyl)phosphonium 2-(methylthio)benzoate ([P66614][MTBA]), tetrahexyl(tetradecyl)phosphonium thiosalicylic acid ([P66614][Ts]);

[0060] The lithium salt is lithium perchlorate (LiClO 4 ), lithium tetrafluoroborate (LiBF 4 ), lithium hexafluoroarsenate (LiAsF 6 ), lithium hexafluorophosphate (LiPF 6 ), lithium bis(oxalato)borate (LiBOB), lithium difluoro(oxalato)borate (LiDFOB), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethylsulfonyl)imide (LiTFSI);

[0061] The organic solvent is one of propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC);

[0062] The liquid electrolyte is finally poured into the porous epoxy-based electrolyte template to form an ion-conducting network for transporting lithium ions to ensure the normal operation of the battery;

[0063] Step Four: Preparation of the electrolyte containing the composite pore former:

[0064] Step Four One: Mix the epoxy resin-based precursor in Step One and the composite pore former in Step Two at a mass ratio of 10~40:50~90, and under the action of vigorous stirring at 1000~1500 r / min, conduct the first high-temperature curing for 10~45 min at 40~70 °C to obtain a mixed solution. The epoxy resin-based precursor is cured into micron-sized spheres. The epoxy resin micron spheres contain a small amount of polymers with ether oxy groups and low degrees of polymerization. This is because the polymer has a high viscosity, poor fluidity, and better compatibility with epoxy resin than small-molecule liquid organic ester solvents;

[0065] Step Four Two: Add an appropriate amount of nitrile binder to the epoxy resin-based precursor after the first high-temperature curing in Step Four One, stir for 10~15 h, and after fully stirring evenly, conduct a filtration operation to remove most of the composite pore former to form a filter cake. Further, conduct the second high-temperature curing for 5~45 min at 40~70 °C. At this time, the nitrile binder undergoes self-polymerization to form a high-strength binder network, thereby obtaining the electrolyte containing the composite pore former. At this time, the nitrile binder is further cured, enhancing the adhesion between the epoxy resin micron spheres. In addition, the nitrile binder itself has a high mechanical strength after curing, thereby improving the tensile mechanical strength of the entire electrolyte skeleton; where:

[0066] The mass of the nitrile-based binder accounts for 1-10% of the mass of the epoxy resin-based precursor;

[0067] The nitrile-based binder is one of methyl α-cyanoacrylate, ethyl cyanoacrylate, and methyl methacrylate-acrylonitrile copolymer;

[0068] Step Five: Preparation of the porous epoxy resin-based electrolyte template;

[0069] Step Five One: High-temperature primary pore formation: The electrolyte containing the composite pore former obtained in Step Four is vacuum dried at a high temperature of 55-95 °C for 1-6 h to obtain an electrolyte with micron-scale continuous pores;

[0070] Step Five Two: High-temperature secondary pore formation: The electrolyte with micron-scale continuous pores is vacuum dried at a high temperature of 100-150 °C for 1-6 h to obtain a porous epoxy resin-based electrolyte template with both micron-scale continuous pores and nano-scale continuous pores, and its morphology is as Figure 2 shown, where the nano-pores are distributed in the epoxy resin microspheres;

[0071] Step Six: Preparation of the high-strength electrolyte

[0072] Step Six One: Drop the liquid electrolyte obtained in Step Three onto the porous epoxy resin-based electrolyte template obtained in Step Five, and the mass ratio of the two is 50-100:30-80. Then, vacuum stand for 30-60 min to extract the gas in the pores of the template, so that the liquid electrolyte infiltrates;

[0073] Step Six Two: Stand at a temperature of 40-60 °C for 24-36 hours to make the liquid electrolyte fully infiltrate the template, and finally obtain an electrolyte with both high tensile strength and high elastic modulus, and at the same time having ionic conductivity.

[0074] The high-strength electrolyte prepared by the above method can be applied in structural batteries or solid-state lithium-ion batteries, where:

[0075] The specific preparation method of the solid-state lithium-ion battery is as follows:

[0076] Step 1. Mix an appropriate amount of nitrile binder, epoxy resin-based precursor after the first high-temperature curing, battery cathode active material, binder, and solvent to form an electrode slurry. Mix in a planetary stirrer for 30 - 60 min at a rotation speed of 400 - 1200 r / min to obtain a structural battery cathode slurry. After repeating the steps of secondary high-temperature curing, primary pore formation, and secondary pore formation, coat the electrode slurry on carbon-coated aluminum foil, dry it, and roll it to obtain a battery cathode electrode sheet. Control the mass ratio of the epoxy resin-based precursor, nitrile binder, battery cathode active material, binder, and solvent to be 70 - 90:5 - 10:60 - 85:0.5 - 2:100 - 150; prepare the anode in the same way, or use lithium metal / sodium metal foil as the anode; the battery cathode active material is one of lithium iron phosphate, lithium cobaltate, lithium nickel cobalt manganese oxide (such as LiNi 0.8 Co 0.1 Mn 0.1 O 2 ,LiNi 0.83 Co 0.08 Mn 0.09 O 2 ,LiNi 0.90 Co 0.05 Mn 0.05 O 2 ), sodium vanadium phosphate, sodium nickel iron manganese oxide materials, etc., and the battery anode active material is graphite, hard carbon material, lithium metal anode, sodium metal anode, etc.;

[0077] Step 2. Stack the positive electrode sheet, porous epoxy resin-based electrolyte template, and negative electrode together in sequence, inject liquid electrolyte, and after standing in vacuum for 30 min, stand at a temperature of 40 - 60 °C for 24 - 36 hours to allow the liquid electrolyte to fully infiltrate the battery, and obtain a structural battery after encapsulation.

[0078] The specific preparation method of the structural battery is as follows:

[0079] Step 1. Mix an appropriate amount of nitrile binder, epoxy resin-based precursor after the first high-temperature curing, battery cathode active material, binder, and solvent to form an electrode slurry. Mix in a planetary stirrer for 30 - 60 min at a rotation speed of 400 - 1200 r / min to obtain a structural battery cathode slurry. After repeating the steps of secondary high-temperature curing, primary pore formation, and secondary pore formation, coat the electrode slurry on a high-strength carbon-based material, dry it, and roll it to obtain a battery cathode electrode sheet. Control the mass ratio of the epoxy resin-based precursor, nitrile binder, battery cathode active material, binder, and solvent to be 70 - 90:5 - 10:60 - 85:0.5 - 2:100 - 150; and directly use the high-strength carbon-based material as the negative electrode; the battery cathode active material is lithium iron phosphate, lithium cobaltate, lithium nickel cobalt manganese oxide (such as LiNi 0.8 Co0.1 Mn 0.1 O 2 ,LiNi 0.83 Co 0.08 Mn 0.09 O 2 ,LiNi 0.90 Co 0.05 Mn 0.05 O 2 ), sodium vanadium phosphate, sodium nickel iron manganese oxide material, etc., and the high-strength carbon-based material is one of carbon fiber, graphene fiber, carbon cloth, and carbon paper;

[0080] Step 2: Stack the positive electrode sheet, porous epoxy resin-based electrolyte template, and negative electrode together in sequence, inject the liquid electrolyte, let it stand still in vacuum for 30 min, and then let it stand still at a temperature of 40-60 °C for 24-36 hours to make the liquid electrolyte fully infiltrate the battery, and obtain a structural battery after encapsulation.

[0081] Example 1:

[0082] This example provides a preparation method of a high-strength electrolyte for a structural battery, and the method includes the following steps:

[0083] Step 1: Preparation of epoxy resin-based precursor: Take epoxy resin E-51, titanium acetylacetonate, and bisphenol A, mix them evenly according to the mass ratio of 70:20:10, and store them in a low-temperature and light-proof environment for later use;

[0084] Step 2: Preparation of composite pore-forming agent: Take propylene carbonate and polyethylene glycol 400, mix them evenly according to the mass ratio of 60:20, and store them in a low-temperature and light-proof environment for later use;

[0085] Step 3: Preparation of liquid electrolyte: Take 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (EMIM-TFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and propylene carbonate (PC), mix them evenly according to the mass ratio of 100:55:5, and store them for later use;

[0086] Step 4: Preparation of electrolyte containing composite pore-forming agent:

[0087] Step 4-1: Mix the epoxy resin-based precursor in Step 1 and the composite pore-forming agent in Step 2 according to the mass ratio of 20:70, and under the action of intense stirring at 1200 r / min, carry out the first high-temperature curing at 60 °C for 15 min;

[0088] Step 4-2: Add ethyl cyanoacrylate to the epoxy resin-based precursor after the first high-temperature curing in Step 4-1, stir for 12 h, and after fully stirring evenly, perform suction filtration to form a filter cake. Cure the filter cake at 60 °C for the first high-temperature curing for 15 min to obtain an electrolyte containing a composite pore former, where the mass of ethyl cyanoacrylate accounts for 3.4% of the mass of the epoxy resin-based precursor;

[0089] Step 5: Preparation of a porous epoxy resin-based electrolyte template;

[0090] Step 5-1: High-temperature primary pore formation: Place the electrolyte containing the composite pore former obtained in Step 4 in a high-temperature condition of 70 °C and vacuum dry it for 4 h to obtain an electrolyte with micron-scale continuous pores;

[0091] Step 5-2: High-temperature secondary pore formation: Place the electrolyte with micron-scale continuous pores in a high-temperature condition of 110 °C and vacuum dry it for 3 h to obtain a porous epoxy resin-based electrolyte template with both micron-scale continuous pores and nano-scale continuous pores;

[0092] Step 6: Preparation of a high-strength electrolyte

[0093] Step 6-1: Drop the liquid electrolyte obtained in Step 3 onto the porous epoxy resin-based electrolyte template obtained in Step 5, with a mass ratio of 55:45 between the two. Then, vacuum stand for 30 min to extract the gas in the pores of the template, so that the liquid electrolyte infiltrates;

[0094] Step 6-2: Stand at 40 °C for 24 h to make the liquid electrolyte fully infiltrate the template, and finally obtain an electrolyte with both high tensile strength and high elastic modulus, and at the same time has ionic conductivity and can be used in a solid-state lithium battery. The specific preparation method of the solid-state lithium battery is as follows:

[0095] Step 1: Mix ethyl cyanoacrylate, the epoxy resin-based precursor after the first high-temperature curing, lithium iron phosphate, a binder, and a solvent in a mass ratio of 70:5:85:1.5:120 to form an electrode slurry, and mix it in a planetary stirrer for 45 min at a rotation speed of 1000 r / min to obtain a structural battery positive electrode slurry. After repeating the steps of secondary high-temperature curing, primary pore formation, and secondary pore formation, coat the electrode slurry on carbon-coated aluminum foil, dry it, and roll it to obtain a battery positive electrode plate; use lithium metal as the negative electrode for the negative electrode;

[0096] Step 2: Stack the positive electrode plate, the porous epoxy resin-based electrolyte template, and the negative electrode together in sequence, inject the liquid electrolyte, vacuum stand for 30 min, and then further stand at 40 °C for 24 h to make the liquid electrolyte fully infiltrate the battery. After encapsulation, a solid-state lithium battery is obtained, and its charge and discharge performance is as Figure 6 shown.

[0097] Example 2:

[0098] This example provides a method for preparing a high-strength electrolyte for a structural battery, and the method includes the following steps:

[0099] Step 1. Preparation of an epoxy resin-based precursor: Take epoxy resin E-57, aluminum acetylacetonate, and polyamide, mix them evenly according to a mass ratio of 70:20:10, and store them in a low-temperature and light-shielded environment for later use;

[0100] Step 2. Preparation of a composite pore former: Take propylene carbonate and polyethylene glycol 400, mix them evenly according to a mass ratio of 60:20, and store them in a low-temperature and light-shielded environment for later use;

[0101] Step 3. Preparation of a liquid electrolyte: Take 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (EMIM-TFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and propylene carbonate (PC), mix them evenly according to a mass ratio of 100:55:5, and store them for later use;

[0102] Step 4. Preparation of an electrolyte containing a composite pore former:

[0103] Step 4-1. Mix the epoxy resin-based precursor in Step 1 and the composite pore former in Step 2 according to a mass ratio of 20:70, and under the action of intense stirring at 1200 r / min, perform the first high-temperature curing for 15 min at 60 °C;

[0104] Step 4-2. Add ethyl cyanoacrylate to the epoxy resin-based precursor after the first high-temperature curing in Step 4-1, stir for 12 h, stir evenly, perform a suction filtration operation to form a filter cake, and perform the first high-temperature curing for 15 min on the filter cake at 60 °C to obtain an electrolyte containing a composite pore former, where the mass of ethyl cyanoacrylate accounts for 3.4% of the mass of the epoxy resin-based precursor;

[0105] Step 5. Preparation of a porous epoxy resin-based electrolyte template;

[0106] Step 5-1. High-temperature primary pore formation: Place the electrolyte containing a composite pore former obtained in Step 4 in a high-temperature condition of 70 °C and vacuum dry it for 4 h to obtain an electrolyte with micron continuous pores;

[0107] Step 5-2. High-temperature secondary pore formation: Place the electrolyte with micron continuous pores in a high-temperature condition of 110 °C and vacuum dry it for 3 h to obtain a porous epoxy resin-based electrolyte template with both micron continuous pores and nano continuous pores;

[0108] Step 6. Preparation of high-strength electrolyte

[0109] Step 6-1. Drop the liquid electrolyte obtained in Step 3 onto the porous epoxy resin-based electrolyte template obtained in Step 5, with a mass ratio of 55:45 between the two. Then, vacuum stand for 30 min to extract the gas in the pores of the template, so that the liquid electrolyte infiltrates;

[0110] Step 6-2. Stand at 40 °C for 24 hours to make the liquid electrolyte completely infiltrate the template, and finally obtain an electrolyte with both high tensile strength and high elastic modulus, which also has ionic conductivity and can be used in a structural battery. The specific preparation method of the structural battery is as follows:

[0111] Step 1. Mix ethyl cyanoacrylate, the epoxy resin-based precursor after the first high-temperature curing, lithium iron phosphate, binder and solvent in a mass ratio of 70:5:85:1.5:120 to form an electrode slurry. Mix in a planetary stirrer for 45 min at a rotation speed of 1000 r / min to obtain the positive electrode slurry of the structural battery. After repeating the steps of the second high-temperature curing, the first pore-forming and the second pore-forming, coat the electrode slurry on carbon fiber, dry it, and roll it to obtain the positive electrode plate of the battery; The negative electrode directly uses carbon fiber as the active material;

[0112] Step 2. Stack the positive electrode plate, the porous epoxy resin-based electrolyte template, and the negative electrode together in sequence, inject the liquid electrolyte, vacuum stand for 30 min, and then further stand at 40 °C for 24 hours to make the liquid electrolyte completely infiltrate the battery. After encapsulation, the structural battery is obtained.

[0113] Example 3:

[0114] The difference between this example and Example 1 is that the temperature of the first pore-forming is adjusted to 85 °C and the time is controlled to be 1.5 h; the temperature of the second pore-forming is adjusted to 125 °C and the time is controlled to be 2 h.

Claims

1. A method for preparing a high-strength electrolyte that can be used in structural batteries, characterized in that The method comprises the following steps: Step 1: Preparation of epoxy resin-based precursor: Take epoxy resin, organic compound containing metal elements and curing agent, mix them evenly in a mass ratio of 60-90:5-40:10-30, store them in a low temperature and dark environment for later use; Step 2, preparation of composite pore-forming agent: taking a small molecule liquid organic ester solvent and a low polymerization degree ether group-containing polymer, mixing them evenly in a mass ratio of 40-70:20-30, and storing them in a low temperature and light-proof environment for standby use, wherein the small molecule liquid organic ester solvent is propylene carbonate, and the low polymerization degree ether group-containing polymer is polyethylene glycol 400; Step 3, preparation of liquid electrolyte: take ionic liquid, lithium salt and organic solvent, mix them evenly in a mass ratio of 90-110:40-60:1-10, and set aside; Step 4: Preparation of electrolyte containing composite pore-forming agent: Step 4:

1. Mix the epoxy resin-based precursor in step 1 and the composite pore-forming agent in step 2 in a mass ratio of 10-40:50-90, and perform a first high-temperature curing under vigorous stirring; Step 42: adding a nitrile-based adhesive to the epoxy resin-based precursor after the first high-temperature curing in step 41, fully stirring, filtering it to form a filter cake, and curing the filter cake at a second high temperature to obtain an electrolyte containing a composite pore-forming agent, wherein the mass of the nitrile-based adhesive accounts for 1-10% of the mass of the epoxy resin-based precursor; Step 5: Preparation of porous epoxy resin-based electrolyte template; Step 51: High-temperature one-time pore formation: the electrolyte containing the composite pore-forming agent obtained in step 4 is placed under vacuum drying at a high temperature of 55-95°C to obtain an electrolyte with micron-sized continuous pores; Step 52: High-temperature secondary pore formation: the electrolyte with micron continuous pores is placed under vacuum drying at a high temperature of 100-150°C to obtain a porous epoxy resin-based electrolyte template with both micron continuous pores and nanometer continuous pores; Step 6: Preparation of high-strength electrolyte Step 6: drip the liquid electrolyte obtained in step 3 onto the porous epoxy resin-based electrolyte template obtained in step 5, with the mass ratio of the two being 50-100:30-80, and then vacuum standing to extract the gas in the pores of the template to allow the liquid electrolyte to infiltrate; Step 62: Let the template stand at a temperature of 40-60°C to allow the liquid electrolyte to completely infiltrate the template, and finally obtain an electrolyte having both high tensile strength and high elastic modulus.

2. The method for preparing a high-strength electrolyte for structural batteries according to claim 1, characterized in that The entire process of step 1, step 2 and step 3 is carried out in a glove box filled with argon.

3. The method for preparing a high-strength electrolyte for structural batteries according to claim 1, characterized in that In the step 1, the epoxy resin model is one or a mixture of E-44, E-51, E54, and E57; the organic compound containing metal elements is one or more of acetylacetonate titanium oxide, bis(acetylacetonate) diisopropyl titanate, acetylacetonate molybdenum, acetylacetonate aluminum, and acetylacetonate cobalt; and the curing agent is one or more of bisphenol A, isopropyl alcohol, polycarbonate, and polyamide.

4. The method for preparing a high-strength electrolyte for structural batteries according to claim 1, characterized in that In the step 3, the ionic liquid is one of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (EMIM-TFSI), 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]), 1-butyl-3-methylimidazolium hexafluorophosphate [C4mim][PF6], tetradecyltrihexylphosphine 2-(methylthio)benzoic acid ([P66614][MTBA]), and tetradecyltrihexylphosphine thiosalicylic acid ([P66614][Ts]); the lithium salt is one of lithium perchlorate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium hexafluorophosphate, lithium bisoxalate borate, lithium difluorooxalate borate, bis(trifluorosulfonyl)imide lithium salt, and bis(trifluoromethylsulfonyl)imide lithium; and the organic solvent is one of propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, and ethyl methyl carbonate.

5. The method for preparing a high-strength electrolyte that can be used for structural batteries according to claim 1, characterized in that In the step 41, the stirring speed is 1000-1500 r / min, the temperature of the first high-temperature curing is 40-70°C, and the time is 10-45 min; in the step 42, the stirring time is 10-15 h, the nitrile-based adhesive is one of α-methyl cyanoacrylate, ethyl cyanoacrylate, and methyl methacrylate-acrylonitrile copolymer, and the temperature of the second high-temperature curing is 40-70°C, and the time is 5-45 min.

6. The method for preparing a high-strength electrolyte for structural batteries according to claim 1, characterized in that In the step 5, the vacuum drying time is 1 to 6 hours.

7. The method for preparing a high-strength electrolyte for structural batteries according to claim 1, characterized in that In the step 61, the vacuum standing time is 30 to 60 minutes; in the step 62, the standing time is 24 to 36 hours.

8. A high-strength electrolyte prepared by the method according to any one of claims 1 to 7.

9. Use of a high-strength electrolyte prepared by the method according to any one of claims 1 to 7 in a structural battery or a solid-state lithium-ion battery.

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