WO2023108322A1 - Solid electrolyte having mechanical gradient and preparation method therefor and application thereof - Google Patents

Abstract

Disclosed in the present invention are a solid electrolyte having a mechanical gradient and a preparation method therefor and an application thereof. The solid electrolyte comprises a solid polymer electrolyte precursor solution and initiator having high Young's modulus, a gel polymer electrolyte precursor solution and initiator having certain elasticity and adhesive property, and an electrolyte lithium salt. The mechanical property of the solid electrolyte having the mechanical gradient is that the Young's modulus is gradually increased from a positive electrode to a negative electrode. The electrolyte is regulated by means of the concentration of the lithium salt and the concentration of the initiators. A solid polymer electrolyte having high Young's modulus can decrease the height of the tips of lithium dendrites on the negative electrode side, inhibit the growth of the lithium dendrites, and prevent the short circuit of a battery. A solid electrolyte having certain elastic strain and adhesive property can relieve the problem of interface mechanical stress caused by volume expansion of the positive electrode in a circulation process. In addition, an in-situ polymerization process is used in an interface contact layer, such that a closely-combined interface is formed, and gaps and holes at the interface are prevented from being formed.

Description

A kind of solid electrolyte with mechanical gradient and its preparation method and application technical field

The invention belongs to the technical field of batteries, in particular to the technical field of solid electrolytes, in particular to a solid electrolyte with a mechanical gradient and a preparation method and application thereof.

Background technique

At present, the successful commercial application of electrolytes represented by liquid ethylene carbonate (EC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC) and other organic solvents has made lithium iron phosphate represented by lithium iron phosphate It has been widely recognized and accepted by the market. However, due to the intrinsic characteristics of liquid organic electrolyte systems, it is difficult to meet the requirements of high energy density scenarios and high safety scenarios. Therefore, the development of solid-state batteries is imminent. The energy density of traditional lithium-ion batteries has reached the bottleneck, and liquid organic electrolytes are prone to safety hazards such as leakage, volatility, and combustion. In comparison, the intrinsic characteristics of solid electrolytes that are non-leaking and non-volatile can significantly improve the safety of batteries, and at the same time avoid the problem of short battery life caused by electrolyte drying. In addition, the high mechanical strength of the solid electrolyte helps to inhibit the growth of lithium dendrites, which not only further ensures the safety of the battery, but also makes it possible to use lithium metal as the negative electrode, which is conducive to greatly improving the energy density of the battery. However, solid-state lithium metal batteries face problems such as lithium dendrite growth, interface mechanical failure, and poor interface compatibility: (1) the nucleation and growth of lithium dendrites on the negative electrode side penetrate the solid electrolyte, resulting in a short circuit in the solid-state battery; (2) The repeated volume change of the positive electrode material during the charge and discharge process produces mechanical stress, which destroys the physical contact performance of the electrode/electrolyte interface, resulting in mechanical failure of the interface, thereby reducing the cycle efficiency and stability of the battery.

The research on solid-state electrolytes mainly focuses on inorganic solid-state electrolytes and polymer solid-state electrolytes. Inorganic solid electrolytes not only have high ionic conductivity, such as Li10GeP2S12 ionic conductivity can reach 10mS/cm (Journal of the Electrochemical Society, 2015; 163(2):A67-A74.), Li6.5La3Zr1.5Ta0.5O12 The ionic conductivity can reach 1mS/cm (Chemistry of Materials, 2016; 28(1):197-206.), however, in the long cycle test, these inorganic solid electrolytes are difficult to maintain stability, and the interface problems gradually accumulate during the cycle and worsened. As an electrolyte, the production process of polymer is simple, and it can effectively alleviate the interface problem, so it has gradually attracted the attention of researchers. Usually, researchers reduce polymer crystallinity and improve ionic conductivity by cross-linking, grafting, blending, and doping. At the same time, the volume expansion of the positive electrode during cycling may also cause battery failure. Combining the characteristics of polymer solid electrolytes, researchers have designed various types of multilayer heterostructures: Goodenough et al. constructed an organic/inorganic/organic multilayer The solid electrolyte with layer structure, the inorganic layer can limit the transmission of lithium salt anions in the polymer electrolyte, and increase the number of ion transfer; the organic layer with good flexibility can enhance the contact performance with the positive and negative interfaces (Journal of the American Chemical Society, 2016;138(30):9385-9388.). Guo et al. designed an asymmetric multilayer electrolyte: the middle layer is a dense Li7La3Zr2O12 inorganic solid electrolyte, and the side facing the lithium metal negative electrode is a 7.5nm ultra-thin polymer electrolyte layer. The two synergistically enhance the interface contact performance and effectively Prevent lithium dendrites from penetrating the electrolyte; facing the positive side is a thicker polymer solid electrolyte, which helps maintain the close physical contact between the electrolyte and the positive electrode during charge and discharge, ensuring stable interfacial ion transport (Journal of the American Chemical Society, 2018; 140(1):82-85.). The construction of double-layer/multi-layer structures such as inorganic solid electrolyte layer/organic solid electrolyte layer, organic solid electrolyte layer/inorganic solid electrolyte layer/organic solid electrolyte layer can alleviate the mechanical failure problem of the interface on the positive electrode side and limit the negative electrode side. The growth of lithium dendrites, on the other hand, can improve the chemical/electrochemical compatibility of the interface. However, due to problems such as crystal phase mismatch and chemical potential difference on both sides of the heterointerface, Li-ion transport across the interface needs to overcome a higher diffusion energy barrier, which limits the diffusion kinetics of Li-ions in solid-state electrolytes, resulting in the current report. The bilayer/multilayer heterostructure solid electrolytes all exhibit low ionic conductivity (not more than 0.1mS/cm order).

In view of this, the present invention provides a mechanical gradient solid electrolyte designed for the problem of lithium dendrites on the negative electrode side and the failure of interface mechanics caused by volume changes in positive electrode materials such as lithium iron phosphate during cycling. The mechanical properties of the gradient electrolyte show that the Young's modulus gradually increases from the positive electrode to the negative electrode; at the same time, the implementation of the mechanical gradient electrolyte is regulated by the concentration of lithium salt and the concentration of the initiator; in addition, the solid electrolyte with high Young's modulus can reduce The height of the tip of lithium dendrites on the negative side can inhibit the growth of lithium dendrites and prevent battery short circuit; and it has a certain elastic strain and bonding performance solid electrolyte, which can alleviate the interface mechanical stress problem caused by volume expansion of the positive electrode during cycling ; In addition, the in-situ polymerization process is adopted for the interface contact layer, which is conducive to the formation of a closely bonded interface and avoids the formation of voids and holes at the interface. In addition, the invention also discloses the solid electrolyte with the strength gradient structure and its preparation method and application.

Contents of the invention

In order to solve the problem of lithium dendrites on the negative electrode side and the interface mechanical failure caused by the volume change of positive electrode materials such as lithium iron phosphate during the cycle, the present invention designs a solid electrolyte with a mechanical gradient, which meets the requirements on the positive and negative electrodes of solid-state batteries. Achieving high ionic conductivity with contradictory demands on the mechanical properties of solid-state electrolytes. Therefore, the present application provides a solid electrolyte with mechanical gradient, its preparation method and application in battery.

The invention provides a solid electrolyte with a mechanical gradient and a preparation method thereof. The mechanical gradient electrolyte includes: (1) a solid polymer electrolyte precursor solution and an initiator with a high Young's modulus; Gel polymer electrolyte precursor solution and initiator with certain elasticity and bonding properties, (3) electrolyte salt; wherein (1) the gradient electrolyte shows that the Young's modulus gradually increases from the positive electrode to the negative electrode in terms of mechanical properties; (2) ) The implementation of the mechanical gradient electrolyte is regulated by the lithium salt concentration and the initiator concentration; (3) The solid polymer electrolyte with high Young's modulus can reduce the height of the lithium dendrite tip on the negative electrode side, inhibit the growth of lithium dendrites, and prevent the battery Short circuit; (4) solid electrolyte with certain elastic strain and bonding performance, which can alleviate the interface mechanical stress problem caused by volume expansion of the positive electrode during cycling; (5) In addition, the interface contact layer adopts in-situ polymerization process , which is conducive to the formation of a closely bonded interface and avoids the formation of voids and holes at the interface.

The (1) solid polymer electrolyte precursor solution and initiator with high Young's modulus, the precursor solution is selected from methyl methacrylate (MMA), methacrylate (VMA), vinylene carbonate (VC), vinylene carbonate (VEC), acrylonitrile (AN), vinyl acetate (VAC), styrene (ST), polyethylene oxide (PEO), polyethylene oxide (PPO), polyoxymethylene (POM), polyvinyl acetate (PVA), polyethyleneimine (PEI), polyethylene succinate, polyoxetane, poly-β-propiolactone, polyepichlorohydrin, polyN -Propyl aziridine, polyalkylene polysulfide, polyvinylidene fluoride (PVDF), methyl acrylate (MA), acrylamide (AM), 2-hydroxymethyl acrylate, trifluoroethyl acrylate (TFMA ), polyethylene glycol phenylene ether acrylate (PEGEA), polyethylene glycol diacrylate (PEGDA), polyethylene glycol diglycidyl ether (PEGDE), ethoxylated trimethylpropane triacrylate (ETPTA) , polycyanopolyvinyl alcohol (PVA-CN), 1,3-dioxolane (DOL), 1,3,5-trioxane, 1,4-dioxane, tetrahydrofuran (THF), One or more of polyvinyl formal (PVFM) and the like.

Preferably, the solid polymer precursor solution is 1,3-dioxolane (DOL).

The initiator is selected from common free radical initiators, cationic initiators, anionic initiators and coordination polymerization initiators. Free radical initiators are mainly azo initiators (azobisisobutyronitrile (AIBN), dimethyl azobisisobutyrate initiator, etc.), peroxygen initiators (dibenzamide peroxide (BPO ), etc.) and redox initiators, etc.; cationic polymerization initiators mainly include protonic acids and Lewis acids (mainly including BF ₃ , PF ₅ , AlCl ₃ , Al(CF ₃ SO ₃ ) ₃ , Sn(CF ₃ SO ₃ ) ₂ , etc.); anionic polymerization initiators (mainly organic compounds of alkali metals, alkali metals and alkaline earth metals, tertiary amines and other alkalis, electron donors or nucleophiles, etc.); coordination polymerization initiators (mainly One or more of Ziegler-Natta initiators, metallocene initiators, etc.).

Preferably, the solid polymer precursor solution initiator is a cationic initiator LiPF ₆ which can be decomposed to form PF ₅ .

The (2) gel polymer electrolyte precursor solution and initiator with certain elasticity and bonding properties, a typical but non-limiting precursor solution is selected from methyl methacrylate (MMA), methacrylate (VMA), vinylene carbonate (VC), acrylonitrile (AN), vinyl acetate (VAC), styrene (ST), polyethylene oxide (PEO), polyethylene oxide (PPO), polyoxymethylene (POM), polyvinyl acetate (PVA), polyethyleneimine (PEI), polyethylene succinate, polyoxetane, poly-β-propiolactone, polyepichlorohydrin, polyN -Propyl aziridine, polyalkylene polysulfide, polyvinylidene fluoride (PVDF), methyl acrylate (MA), acrylamide (AM), 2-hydroxymethyl acrylate, trifluoroethyl acrylate (TFMA ), polyethylene glycol phenylene ether acrylate (PEGEA), polyethylene glycol diacrylate (PEGDA), polyethylene glycol diglycidyl ether (PEGDE), ethoxylated trimethylpropane triacrylate (ETPTA) , polycyanopolyvinyl alcohol (PVA-CN), 1,3-dioxolane (DOL), 1,3,5-trioxane, 1,4-dioxane, tetrahydrofuran (THF), Polyvinyl formal (PVFM), propylene carbonate, ethylene carbonate, diethyl carbonate, fluoroethylene carbonate, dimethyl carbonate, ethyl methyl carbonate, ethylene glycol dimethyl ether, diethylene glycol di One or more of methyl ether, dimethyl sulfone, dimethyl ether, etc.

Preferably, the gel polymer precursor solution is 1,3-dioxolane (DOL).

The initiator of the gel polymer precursor solution is selected from common free radical initiators, cationic initiators, anionic initiators and coordination polymerization initiators. Free radical initiators are mainly azo initiators (azobisisobutyronitrile (AIBN), dimethyl azobisisobutyrate initiator, etc.), peroxygen initiators (dibenzamide peroxide (BPO ), etc.) and redox initiators, etc.; cationic polymerization initiators mainly include protonic acids and Lewis acids (mainly including BF ₃ , PF ₅ , AlCl ₃ , Al(CF ₃ SO ₃ ) ₃ , Sn(CF ₃ SO ₃ ) ₂ , etc.); anionic polymerization initiators (mainly organic compounds of alkali metals, alkali metals and alkaline earth metals, tertiary amines and other alkalis, electron donors or nucleophiles, etc.); coordination polymerization initiators (mainly One or more of Ziegler-Natta initiators, metallocene initiators, etc.).

Preferably, the gel polymer precursor solution initiator is a cationic initiator LiPF ₆ , which can be decomposed to form PF ₅ .

The (3) electrolyte lithium salt is selected from lithium trifluoromethanesulfonate (LiCF ₃ SO ₃ ), lithium bis(trifluoromethylsulfonate)imide [LiN(CF ₃ SO ₂ ) ₂ , LiTFSI] and Derivatives, lithium perfluoroalkyl phosphate [LiPF ³ (C2F ₅ ) ₃ , LiFAP], lithium tetrafluorooxalate phosphate [LiPF ⁴ (C ² O ⁴ )], lithium bisoxalate borate (LiBOB), tris(phthalic di Lithium phenophosphate (LTBP) and lithium sulfonated polysulfonamide salt, lithium hexafluorophosphate (LiPF ⁶ ), aluminum perchlorate (LiClO ⁴ ), lithium tetrafluoroborate (LiBF ⁴ ), lithium hexafluoroarsenate (LiAsF ⁶ ), etc. one or more of.

Preferably, the electrolyte lithium salt is lithium bis(trifluoromethanesulfonate)imide LiTFSI, and the concentration range is 0.01-10 mol/L (preferably 0.25-1 mol/L).

In the second aspect, the present invention provides a method for preparing a continuous mechanical gradient solid electrolyte controlled by lithium salt concentration, the method comprising:

(1) Preparation of a solid polymer electrolyte precursor solution with high Young's modulus: first, take a certain amount of solid polymer monomer solvent; then take an appropriate amount of lithium salt and dissolve it in the precursor solution, stir well; The above obtained solution was dewatered with lithiated molecular sieves for 24 hours, and finally an appropriate amount of initiator was added to the above solution while stirring, fully stirred until the solution was completely uniform, and the above operations were all carried out in an argon glove box (the water and oxygen content were all less than 0.1ppm).

(2) Preparation of gel polymer electrolyte precursor solution with certain elasticity and cohesiveness, weighing a certain amount of gel polymer monomer solvent, adding an appropriate amount of lithium salt, fully stirring until dissolved; Use lithiated molecular sieves to remove water for 24 hours, and finally take an appropriate amount of initiator and add it to the above solution while stirring, and fully stir until the solution is completely uniform. The above operations are all carried out in an argon glove box (the water and oxygen content are both less than 0.1ppm) .

(3) For the preparation of button cells, drop the solid polymer electrolyte precursor solution controlled by the low lithium salt concentration on the surface of the negative electrode, keep the sample for observation, and proceed to the next step when the precursor solution in the glass bottle is solidified. This step is Pre-curing: drop a gel polymer electrolyte precursor solution controlled by a high lithium salt concentration on the surface of the cured gel polymer, and stack lithium iron phosphate or a ternary positive electrode on top to assemble a button battery. The above operations are all carried out in an argon glove box (the water and oxygen content are all less than 0.1ppm); the reverse order of the above operations is also within the technical application scope.

Or (4) Assemble the soft pack battery, cut a lithium strip of a certain shape, drop a solid polymer electrolyte precursor solution regulated by a low lithium salt concentration on the surface of the negative electrode, keep a sample for observation, and wait until the precursor solution in the glass bottle solidifies , proceed to the next step, this step is pre-curing; the separator is wound between the lithium ribbon and the lithium iron phosphate positive electrode or the ternary positive electrode, and the gel polymer electrolyte precursor solution controlled by the high lithium salt concentration is injected, and after vacuum pumping Encapsulation, compaction and curing, and assembly of pouch batteries. The above operations are all carried out in an argon glove box (the water and oxygen content are all less than 0.1ppm); the reverse order of the above operations is also within the technical application scope.

In addition, the present invention also provides a secondary battery structure based on the mechanically gradient solid electrolyte, including a positive electrode collector 1, a positive electrode 2, a negative electrode 4, a solid electrolyte 3 with a mechanical gradient, and a battery case for packaging.

The positive current collector 1 is selected from one of aluminum, vanadium, copper, iron, tin, zinc, nickel, titanium, manganese, or an alloy thereof, or a composite of any one of these metals, or an alloy of any one of them. Preferably, the positive electrode current collector is aluminum foil.

The positive electrode 2 material of the lithium ion battery is one or several composite materials in positive electrode compound materials (such as lithium cobaltate, lithium iron phosphate, nickel-cobalt-manganese ternary materials, etc.). Preferably, the positive electrode active material is lithium iron phosphate.

The material of the negative electrode 4 of the lithium-ion battery includes alloyed materials such as lithium, lithium-aluminum alloy, lithium-magnesium alloy, and other lithiated composite materials. Preferably, the negative electrode active material is lithium.

The negative electrode, the solid electrolyte with mechanical gradient, the positive electrode, the positive electrode current collector, and the battery case are used for assembly, and then in-situ polymerization is carried out by thermal initiation or other initiation methods to form a solid-state battery.

The present invention also provides a method for preparing a secondary battery structure based on the mechanical gradient solid electrolyte, comprising the following steps:

Step 101: Prepare the positive electrode: Weigh the positive electrode active material, conductive agent and binder in a certain proportion, add them into an appropriate solvent and mix them well to form a uniform slurry to form a positive electrode active material layer; clean the positive electrode current collector, and then put the The positive electrode active material layer is evenly coated on the surface of the positive electrode current collector, and then cut after the positive electrode active material layer is completely dried to obtain a battery positive electrode of a desired size. Wherein, the ratio of positive electrode active material, conductive agent and binder is preferably weighed in a mass ratio of 8:1:1 or 7:2:1.

Step 102: Prepare the negative electrode: cut the negative electrode into discs with a diameter of 14 mm, and put them in a vacuum drying oven for later use.

Step 103: Preparation of a solid polymer electrolyte precursor solution with high Young's modulus: First, take a certain amount of solid polymer monomer solvent; then take an appropriate amount of lithium salt and dissolve it in the precursor solution, and stir well; The above-mentioned obtained solution was dewatered with lithiated molecular sieves for 24 hours, and finally an appropriate amount of initiator was added to the above-mentioned solution while stirring, and fully stirred until the solution was completely uniform. less than 0.1ppm). spare.

Step 104: Preparation of a gel polymer electrolyte precursor solution with certain elasticity and cohesiveness, weighing a certain amount of gel polymer monomer solvent, adding an appropriate amount of lithium salt, and fully stirring until dissolved; the above obtained solution Use lithiated molecular sieves to remove water for 24 hours, and finally take an appropriate amount of initiator and add it to the above solution while stirring, and fully stir until the solution is completely uniform. The above operations are all carried out in an argon glove box (the water and oxygen content are both less than 0.1ppm) . spare.

Step 105: To prepare the button battery, drop the solid polymer electrolyte precursor solution with high Young’s modulus on the surface of the negative electrode, keep the sample for observation, and proceed to the next step when the precursor solution in the glass bottle is solidified. This step For pre-curing; drop a gel polymer electrolyte precursor solution with certain elasticity and cohesiveness on the surface of the cured gel polymer, and stack lithium iron phosphate or ternary positive electrode on top to assemble the button battery. The above operations are all carried out in an argon glove box (the water and oxygen content are all less than 0.1ppm); the reverse order of the above operations is also within the technical application scope.

Step 106: Assemble the soft-pack battery, cut out a lithium strip of a certain shape, drop a solid polymer electrolyte precursor solution with high Young’s modulus on the surface of the negative electrode, keep the sample for observation, and wait for the precursor solution in the glass bottle to solidify , proceed to the next step, this step is pre-curing; wrap the separator between the lithium ribbon and the lithium iron phosphate positive electrode or the ternary positive electrode, inject the gel polymer electrolyte precursor solution with certain elasticity and cohesiveness, and vacuum Seal after gas, compact and solidify, and assemble the pouch battery. The above operations are all carried out in an argon glove box (water and oxygen content are all less than 0.1ppm); the reverse order of the above operations is also within the technical application scope.

The preparation method of the above-mentioned solid-state battery is further illustrated by specific examples below, but it should be understood that these examples are only used for more detailed description, and should not be construed as limiting the present invention in any form.

It should be noted that although the above steps 101 to 104 describe the operations of the preparation method of the present invention in a specific order, this does not require or imply that these operations must be performed in this specific order. The preparations of step 101-step 104 can be performed simultaneously or in any sequence.

In this application, the formation of the mechanical gradient is regulated by the concentration gradient of lithium salt/initiator for the gradient single-layer solid electrolyte of positive and negative target modification, and the in-situ polymerization process is used to construct the polymer solid electrolyte in situ inside the battery, This design of controlling the lithium salt/initiator concentration gradient in a certain degree of freedom to achieve a mechanical gradient can simultaneously inhibit the growth of lithium dendrites and alleviate the positive electrode caused by volume expansion without additionally introducing a solid phase interface. The interface mechanical stress failure problem, and the in-situ polymerization process effectively improves the interface contact and wettability between the solid electrolyte and the electrolysis, and improves the cycle stability, rate performance and safety performance of the battery. Compared with the prior art, the key of the solid electrolyte with mechanical gradient prepared by the present invention lies in the control of the lithium salt concentration gradient and the control of the initiator concentration. (2) The implementation of the mechanical gradient electrolyte is regulated by the concentration of lithium salt and the concentration of the initiator; (3) The solid electrolyte with high Young's modulus can reduce the height of the lithium dendrite tip on the negative electrode side and inhibit the lithium dendrite. crystal growth to prevent battery short circuit; (4) solid electrolyte with certain elastic strain and bonding performance can alleviate the interface mechanical stress problem caused by volume expansion of the positive electrode during cycling; (5) in addition, the interface contact layer is The in-situ polymerization process is adopted, which is conducive to the formation of a closely bonded interface and avoids the formation of voids and holes at the interface.

Description of drawings

FIG. 1 is a schematic structural diagram of a secondary battery with a gradient solid electrolyte, including a positive electrode collector 1, a positive electrode 2, a gradient polymer solid electrolyte/solid electrolyte with a mechanical gradient 3, and a negative electrode 4.

Figure 2(a) is the time-voltage curve of Li/GSPE/Li symmetric battery at 0.5mA/cm ² areal current density (GSPE stands for gradient structure solid electrolyte).

Figure 2(b) is the specific capacity-voltage diagram of the 1st, 50th, 100th, 150th, and 200th cycle of the LFP/GSPE/Li battery.

Figure 2(c) is the cycle performance graph of LFP/GSPE/Li.

Detailed ways

The present invention will be described in further detail below in conjunction with the accompanying drawings and specific embodiments. The following description is a preferred embodiment of the present invention. It should be pointed out that for those skilled in the art, some improvements and modifications can be made without departing from the principles of the embodiments of the present invention. These improvements and modifications It is also regarded as the protection scope of the present invention.

Example 1

Prepare a solid polymer electrolyte precursor solution with high Young's modulus: dissolve lithium salt 0.25mol/L LiTFSI and an appropriate amount of initiator LiPF ₆ in 5mL1,3-dioxolane (DOL), fully stir to dissolve, and set aside .

Preparation of gel polymer electrolyte precursor solution with certain elasticity and cohesiveness: dissolve lithium salt 1mol/L LiTFSI and appropriate amount of initiator LiPF ₆ in 5mL 1,3-dioxolane (DOL), stir well to dissolve ,spare.

Preparation of lithium iron phosphate positive electrode: Weigh the positive electrode active material, conductive agent, and binder respectively according to the mass ratio of 8:1:1 or 7:2:1, add appropriate amount of N-methylpyrrolidone (NMP) fully, mix and grind it into Uniform slurry: clean the aluminum foil of the positive electrode collector, and then uniformly coat the lithium iron phosphate positive electrode slurry on the surface of the positive electrode collector to form a positive electrode active material layer, place it at room temperature for 8 hours, and then put it in a vacuum drying oven for drying at 60°C After 24 hours, after the positive electrode active material layer is completely dried, take out the discs cut into 10 mm, and put them in a vacuum drying oven for later use.

Preparation of lithium negative electrode: cut the lithium sheet into a disc with a diameter of 14mm, and put it in an argon-filled glove box (both water and oxygen content are less than 0.1ppm) for later use.

Assembling polymer solid electrolyte button batteries with gradient structure: drop a solid polymer electrolyte precursor solution with high Young’s modulus on the surface of the negative electrode, keep the sample for observation, and proceed to the next step when the precursor solution in the glass bottle is solidified Operation: Drop a gel polymer electrolyte precursor solution with certain elasticity and cohesiveness on the surface of the cured gel polymer, and stack lithium iron phosphate or ternary positive electrode on top to assemble the button battery. The above operations were all carried out in an argon glove box (both water and oxygen content were less than 0.1ppm).

Specific embodiments 2 to 6 adopt the same process steps as in embodiment 1, and the specific positive and negative electrode materials, monomers, lithium salts, initiators, etc. used and the corresponding results of the full battery are shown in Table 1 below:

Table 1, the specific materials used in Examples 2-6 and the corresponding results of the full battery

The above-mentioned specific embodiments have further described the purpose, technical solutions and beneficial effects of the present invention in detail. Obviously, the above-mentioned embodiments are only examples for clearly illustrating, rather than limiting the implementation. For those of ordinary skill in the art, other changes or changes in different forms can be made on the basis of the above description. It is not necessary and impossible to exhaustively list all the implementation manners here. And the obvious changes or changes derived therefrom are still within the scope of protection of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (10)

1. A solid electrolyte with a mechanical gradient, characterized in that it includes: a solid polymer electrolyte precursor solution with a high Young's modulus and an initiator, a gel polymer electrolyte precursor solution with certain elasticity and bonding properties, and Initiator, electrolyte lithium salt; the mechanical properties of the solid electrolyte with a mechanical gradient show that the Young's modulus gradually increases from the positive electrode to the negative electrode and is prepared by an in-situ polymerization process.
2. The solid electrolyte with mechanical gradient according to claim 1, wherein said solid polymer electrolyte precursor solution with high Young's modulus is selected from methyl methacrylate (MMA), methacrylate (VMA), Vinylene carbonate (VC), acrylonitrile (AN), vinyl acetate (VAC), styrene (ST), polyethylene oxide (PEO), polyethylene oxide (PPO), polyoxymethylene (POM), Polyvinyl acetate (PVA), polyethyleneimine (PEI), polyethylene succinate, polyoxetane, polybeta-propiolactone, polyepichlorohydrin, polyN-propyl nitrogen Heterocyclopropane, polyalkylene polysulfide, polyvinylidene fluoride (PVDF), methyl acrylate (MA), acrylamide (AM), 2-hydroxymethyl acrylate, trifluoroethyl acrylate (TFMA), polyethylene Glycol Phenyl Ether Acrylate (PEGEA), Polyethylene Glycol Diacrylate (PEGDA), Polyethylene Glycol Diglycidyl Ether (PEGDE), Ethoxylated Trimethylpropane Triacrylate (ETPTA), Polycyano One or more of polyvinyl alcohol (PVA-CN), 1,3-dioxolane (DOL), tetrahydrofuran (THF), polyvinyl formal (PVFM), preferably 1,3-diox pentacycline (DOL).
3. The solid electrolyte with mechanical gradient according to any one of claims 1-2, wherein the solid polymer electrolyte precursor solution initiator with high Young's modulus is selected from commonly used initiators, including azo initiators One or more of the following types of catalysts, peroxide initiators, redox initiators, cationic polymerization initiators, anionic polymerization initiators, and coordination polymerization initiators.
4. The solid-state electrolyte with mechanical gradient according to any one of claims 1-3, wherein the azo initiator is selected from the group consisting of azobisisobutyronitrile (AIBN), dimethyl azobisisobutyrate initiator One or more; the peroxy initiator is selected from dibenzamide peroxide (BPO); the cationic polymerization initiator is selected from BF ₃ , PF ₅ , AlCl ₃ , Al(CF ₃ SO ₃ ) ₃ , Sn( One or more of CF3SO ₃ ) ₂ ; the initiator of anionic polymerization is selected from one or more of alkalis such as alkali metals, alkali metals and alkaline earth metals, tertiary amines, electron donors or nucleophiles Various; the coordination polymerization initiator is selected from one or more of Ziegler-Natta initiators and metallocene initiators; cationic initiator LiPF ₆ is preferred, which can be decomposed to form PF ₅ .
5. The solid electrolyte with mechanical gradient according to claim 1, wherein the gel polymer electrolyte precursor solution with certain elasticity and cohesiveness is selected from methyl methacrylate (MMA), methacrylate ( VMA), vinylene carbonate (VC), acrylonitrile (AN), vinyl acetate (VAC), styrene (ST), polyethylene oxide (PEO), polyethylene oxide (PPO), polyoxymethylene ( POM), polyvinyl acetate (PVA), polyethyleneimine (PEI), polyethylene succinate, polyoxetane, polyβ-propiolactone, polyepichlorohydrin, polyN- Propylaziridine, polyalkylene polysulfide, polyvinylidene fluoride (PVDF), methyl acrylate (MA), acrylamide (AM), 2-hydroxymethyl acrylate, trifluoroethyl acrylate (TFMA) , polyethylene glycol phenylene ether acrylate (PEGEA), polyethylene glycol diacrylate (PEGDA), polyethylene glycol diglycidyl ether (PEGDE), ethoxylated trimethylpropane triacrylic acid (ETPTA), Polycyanopolyvinyl alcohol (PVA-CN), 1,3-dioxolane (DOL), 1,3,5-trioxane, 1,4-dioxane, tetrahydrofuran (THF), poly Vinyl formal (PVFM), propylene carbonate, ethylene carbonate, diethyl carbonate, fluoroethylene carbonate, dimethyl carbonate, ethyl methyl carbonate, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, dimethyl sulfone, dimethyl ether), preferably 1,3-dioxolane (DOL).
6. The solid electrolyte with mechanical gradient according to claim 1, wherein the gel polymer electrolyte precursor solution initiator with certain elasticity and cohesiveness is selected from commonly used initiators, including azo initiators, peroxides One or more of oxygen initiators, redox initiators, cationic polymerization initiators, and anionic polymerization initiators.
7. The solid-state electrolyte with mechanical gradient according to any one of claims 5-6, wherein the azo initiator is selected from the group consisting of azobisisobutyronitrile (AIBN), dimethyl azobisisobutyrate initiator One or more of them; the peroxygen initiator is selected from dibenzamide peroxide (BPO); the cationic polymerization initiator is selected from BF ₃ , PF ₅ , AlCl ₃ , Al(CF ₃ SO ₃ ) ₃ , Sn One or more of (CF ₃ SO ₃ ) ₂ ; the initiator of anionic polymerization is selected from alkali metals, organic compounds of alkali metals and alkaline earth metals, bases such as tertiary amines, electron donors or nucleophiles One or more; cationic initiator LiPF ₆ is preferred, which can be decomposed to form PF ₅ .
8. The solid-state electrolyte with mechanical gradient according to claim 1, wherein the electrolyte lithium salt is selected from lithium trifluoromethanesulfonate (LiCF ₃ SO ₃ ), lithium bis(trifluoromethylsulfonate)imide[ LiN(CF ₃ SO ₂ ) ₂ , LiTFSI] and its derivatives, lithium perfluoroalkyl phosphate [LiPF ₃ (C ₂ F ₅ ) ₃ , LiFAP], lithium tetrafluorooxalate phosphate [LiPF ₄ (C ₂ O ₄ ) ], lithium bisoxalate borate (LiBOB), lithium tris(catechol)phosphate (LTBP) and sulfonated polysulfonamide lithium salt, lithium hexafluorophosphate (LiPF ₆ ), aluminum perchlorate (LiClO ₄ ), lithium tetrafluoroborate ( One or more of LiBF ₄ ), lithium hexafluoroarsenate (LiAsF ₆ ), preferably lithium bis(trifluoromethanesulfonate)imide LiTFSI, and the concentration range is 0.01-10mol/L, preferably 0.25 ~1mol/L.
9. A secondary battery based on a solid-state electrolyte with a mechanical gradient, comprising a positive electrode current collector, a positive electrode, a negative electrode, the solid-state electrolyte with a mechanical gradient according to any one of claims 1-8, and a battery casing for packaging.
10. A method for preparing a secondary battery containing any one of claims 1-8 having a solid electrolyte with a mechanical gradient, comprising:

    Step 101: Prepare the positive electrode: Weigh the positive electrode active material, conductive agent and binder in a certain proportion, add them into an appropriate solvent and mix them well to form a uniform slurry to form a positive electrode active material layer; clean the positive electrode current collector, and then put the The positive electrode active material layer is evenly coated on the surface of the positive electrode current collector, and then cut after the positive electrode active material layer is completely dry to obtain a battery positive electrode of the desired size;

    Step 102: Prepare the negative electrode: cut the negative electrode into discs with a diameter of 14 mm, and put them in a vacuum drying oven for standby;

    Step 103: Preparation of a solid polymer electrolyte precursor solution with high Young's modulus: First, take a certain amount of solid polymer monomer solvent; then take an appropriate amount of lithium salt and dissolve it in the precursor solution, and stir well; Use lithiated molecular sieves to remove water from the above solution for 24 hours, and finally take an appropriate amount of initiator and add it to the above solution while stirring, and fully stir until the solution is completely uniform. The above operations are all carried out in an argon glove box. All less than 0.1ppm, spare;

    Step 104: Preparation of a gel polymer electrolyte precursor solution with certain elasticity and cohesiveness, weighing a certain amount of gel polymer monomer solvent, adding an appropriate amount of lithium salt, and fully stirring until dissolved; the above obtained solution Use lithiated molecular sieves to remove water for 24 hours, and finally take an appropriate amount of initiator and add it to the above solution while stirring, and stir until the solution is completely uniform. The above operations are all carried out in an argon glove box, and the water and oxygen content are all less than 0.1ppm ;spare;

    Step 105: To prepare the button battery, drop the solid polymer electrolyte precursor solution with high Young’s modulus on the surface of the negative electrode, keep the sample for observation, and proceed to the next step when the precursor solution in the glass bottle is solidified. This step It is pre-cured; drop a gel polymer electrolyte precursor solution with certain elasticity and cohesiveness on the surface of the cured gel polymer, and stack lithium iron phosphate or ternary positive electrode on top to assemble the buckle battery; the above operations are all Carried out in an argon glove box, the water and oxygen content of which is less than 0.1ppm; or pouch battery assembly, cutting a lithium strip of a certain shape, and dropping a solid polymer electrolyte precursor with a high Young's modulus on the surface of the negative electrode Solution, keep a sample for observation, and when the precursor solution in the glass bottle is solidified, proceed to the next step, which is pre-curing; the diaphragm is wound between the lithium ribbon and the lithium iron phosphate positive electrode or the ternary positive electrode, and a certain elasticity and The adhesive gel polymer electrolyte precursor solution is packaged after vacuum pumping, compacted and solidified, and a pouch battery is assembled. The above operations were all carried out in an argon glove box, and the water and oxygen content were all less than 0.1ppm.

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