CN111682262B

CN111682262B - Three-dimensional cross-linked network gel polymer electrolyte membrane and preparation method and application thereof

Info

Publication number: CN111682262B
Application number: CN202010656610.2A
Authority: CN
Inventors: 吴丁财; 李始美; 刘绍鸿; 符若文
Original assignee: Sun Yat Sen University
Current assignee: Sun Yat Sen University
Priority date: 2020-07-09
Filing date: 2020-07-09
Publication date: 2021-07-09
Anticipated expiration: 2040-07-09
Also published as: CN111682262A

Abstract

The invention discloses a three-dimensional cross-linked network gel polymer electrolyte membrane and a preparation method and application thereof, firstly, synthesizing polychloromethyl styrene nanospheres by an emulsion polymerization method, and then carrying out a hypercrosslinked reaction to obtain hypercrosslinked microporous polychloromethyl styrene nanospheres (xPCMS); then, taking benzyl chloride of xPCMS as an active grafting site, and grafting poly glycidyl methacrylate on the surface of the xPCMS to prepare the hair-like microporous macromolecular nanospheres; secondly, crosslinking reaction is carried out on the nanospheres serving as a crosslinking agent, polyoxyethylene diamine and polyethylene glycol diglycidyl ether to prepare a three-dimensional crosslinking network gel polymer film; and finally, soaking the obtained polymer membrane in a liquid electrolyte for adsorption saturation to obtain the three-dimensional cross-linked network gel polymer electrolyte membrane. The electrolyte membrane has excellent mechanical property, higher room-temperature ionic conductivity and good thermal stability, and the assembled lithium ion battery has excellent electrochemical property.

Description

Three-dimensional cross-linked network gel polymer electrolyte membrane and preparation method and application thereof

Technical Field

The invention relates to the field of polymer gel electrolyte materials for lithium secondary batteries, in particular to a three-dimensional cross-linked network gel polymer electrolyte membrane based on hair-shaped microporous polymer nanospheres, a preparation method thereof and a lithium ion battery using the three-dimensional cross-linked network gel polymer electrolyte membrane.

Background

With the rapid development of industries such as electric vehicles, smart grids, portable electronic devices and the like, people increasingly demand energy storage devices with high energy density and high safety. Lithium metal has the highest theoretical specific capacity (3860mAh g) among various battery systems^-1) And the lowest redox electrode potential (-3.040V vs. standard hydrogen electrode), and therefore is widely regarded as a "holy cup" in the energy field and is expected to become a negative electrode material of the next-generation lithium secondary battery. However, lithium metal negative electrodes tend to form acicular or dendritic lithium dendrites during charge and discharge. The formation and growth of lithium dendrites will not bring about the battery systemReversible capacity loss can pierce through the diaphragm when serious, and causes short circuit in the battery to cause combustion and explosion, thereby greatly limiting the practical application of the lithium metal battery. In recent years, many strategies for inhibiting the growth of lithium dendrites in lithium metal batteries have been reported, such as the construction of a three-dimensional support skeleton of a lithium negative electrode, an electrolyte additive, the formation of an artificial SEI protective film on the lithium surface, the modification of a separator, the replacement of a liquid electrolyte with a solid electrolyte, and the like. Among them, the replacement of the liquid electrolyte with the solid electrolyte is considered to be the key to realize a safe and durable lithium metal battery because the mechanical rigidity of the solid electrolyte can inhibit the growth of lithium dendrites, and the low flammability and high thermal stability thereof can solve potential safety problems such as leakage, combustion, explosion and the like of the liquid electrolyte faced by the lithium metal battery.

Solid electrolytes are mainly classified into two major categories, inorganic ceramic electrolytes and polymer electrolytes. Inorganic ceramic solid electrolytes, such as perovskite type, garnet type, NASICON, sulfide and the like, generally have higher ionic conductivity and good flame retardant property, but have higher density compared with liquid electrolyte, and the specific energy capacity of the battery is seriously reduced; it is difficult to be in close contact with the electrode, and the interface impedance is large; the narrow electrochemical stability window leads to easy side reaction with the electrode and poor interface stability. The above disadvantages largely limit the practical application of the inorganic ceramic electrolyte. In comparison, the polymer electrolyte has unique advantages of flexible processing, low flammability, strong mechanical deformation resistance, superior electrode/electrolyte interface performance to inorganic solid electrolytes, and the like, and is widely concerned. At present, two types of polymer electrolytes, all Solid Polymer Electrolytes (SPEs) and Gel Polymer Electrolytes (GPEs), are often reported for lithium metal batteries. However, the conventional SPEs generally have a problem of low ionic conductivity (<10^-5S cm^-125 c) limit their use in lithium metal batteries. In contrast, GPEs exhibit satisfactory ionic conductivity values due to the presence of organic solvents as plasticizers (a)>10^-4

S cm

^-125 ℃ C.) and a lower electrode/electrolyte interfacial resistance; but the mechanical properties are generally weak and difficult to effectively inhibitAnd (5) making the lithium dendrite grow.

The nano composite electrolyte prepared by filling the polymer electrolyte with the nano particles can obtain higher modulus under the condition of lower content of the reinforcing material, and an effective way is provided for obtaining the polymer electrolyte with good mechanical property and high room temperature ionic conductivity. Uniform dispersion of the filler in the polymer matrix is considered a prerequisite to prevent particle agglomeration and local inhomogeneity in the electrolyte medium. However, due to the higher specific surface energy of the nanoparticles, the filler is easily attracted by strong van der waals forces to undergo aggregation and phase separation. The agglomeration of particles not only hinders the rapid transport of lithium ions, but also causes defects in the polymer electrolyte, resulting in deterioration of mechanical properties thereof. In addition, the filler is typically a dense, non-porous, non-lithium ion-conducting inorganic nanoparticle. Especially inorganic components having a greater density than the polymer, their introduction reduces the specific energy density of the battery while increasing the interfacial resistance between the polymer electrolyte and the electrode; the characteristics of non-porous and non-conductive lithium ions can block the transmission of the lithium ions to a certain extent and reduce the ionic conductivity of the lithium ions. Therefore, there remains a significant challenge to produce polymer electrolyte materials that combine high ionic conductivity with high mechanical properties.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provides a three-dimensional cross-linked network gel polymer electrolyte membrane based on hair-shaped microporous polymer nanospheres, a preparation method and application thereof.

In order to achieve the above purpose, the present application provides the following technical solutions:

a preparation method of a three-dimensional cross-linked network gel polymer electrolyte membrane,

firstly, synthesizing a polychloromethylstyrene nanosphere (PCMS) by an emulsion polymerization method, and then carrying out a hypercrosslinking reaction to obtain a hypercrosslinked microporous polychloromethylstyrene nanosphere (xPCMS); then, taking benzyl chloride of xPCMS as an active grafting site, and grafting Poly Glycidyl Methacrylate (PGMA) on the surface of the xPCMS by an electron transfer activation regeneration catalyst-atom transfer radical polymerization (ARGET-ATRP) technology to prepare a hair-shaped microporous polymer nanosphere (xPCMS-g-PGMA);

secondly, the hair-shaped microporous polymer nanospheres are used as a cross-linking agent to perform cross-linking reaction with polyoxyethylene diamine and polyethylene glycol diglycidyl ether to prepare a three-dimensional cross-linked network gel polymer membrane;

and finally, soaking the obtained polymer membrane in a liquid electrolyte for adsorption saturation to obtain the three-dimensional cross-linked network gel polymer electrolyte membrane.

Preferably, the method comprises the following steps:

(1) mixing 4-chloromethyl styrene with a cross-linking agent, and then dropwise adding the mixture into an aqueous solution (the sampling speed is 4-5 mL. h)^-1) Heating to 60-80 ℃, adding an initiator, carrying out reflux reaction for 4-8 h under an inert atmosphere, carrying out centrifugal separation, washing with ethanol and water, and carrying out vacuum drying to obtain an intermediate product I;

(2) dispersing the intermediate product I prepared in the step (1) in a solvent I, slowly stirring for overnight swelling, adding a catalyst at 65-85 ℃, stirring for reflux reaction for 12-48 h, adding an acetone/hydrochloric acid/water mixed solvent for termination of the reaction, filtering, washing and drying in vacuum to obtain an intermediate product II;

(3) uniformly dispersing the intermediate product II prepared in the step (2) in a solvent II, adding an acrylic ester polymerization monomer containing an epoxy group, N, N, N' -pentamethyldiethylenetriamine, copper bromide and vitamin C, heating to 50-80 ℃, sealing and reacting for 12-48 h in an inert atmosphere, washing with absolute ethyl alcohol, centrifugally separating, and drying in vacuum to obtain an intermediate product III;

(4) adding the intermediate product III prepared in the step (3), a linear polymer, polyoxyethylene diamine and polyethylene glycol diglycidyl ether into a solvent III, mixing and dispersing uniformly to prepare a precursor solution, pouring the precursor solution on a carrier mold, and heating to 60-100 ℃ to react for 12-48 h to obtain a three-dimensional cross-linked network polymer film;

(5) and (4) immersing the three-dimensional cross-linked network polymer membrane prepared in the step (4) into liquid electrolyte, and absorbing the electrolyte until the electrolyte is saturated to obtain the three-dimensional cross-linked network gel polymer electrolyte membrane.

Preferably, the crosslinking agent in step (1) is divinylbenzene; the initiator comprises one or more of azodiisobutyramidine hydrochloride, azodiisobutyronitrile, azodiisoheptonitrile and azodiisobutyronitrile.

Preferably, the catalyst in the step (2) is one or more of anhydrous ferric trichloride, anhydrous aluminum trichloride, boron fluoride, sulfuric acid, anhydrous stannic chloride or anhydrous zinc chloride.

Preferably, the acrylic polymer monomer containing epoxy groups in step (3) is one or more of glycidyl methacrylate, glycidyl acrylate and allyl glycidyl ether.

Preferably, the linear polymer in step (4) includes one or more of polymethyl methacrylate, polyacrylonitrile, polyvinylidene fluoride, polystyrene, polyvinylidene fluoride-hexafluoropropylene, polyoxyethylene, polyurethane or polysulfone.

Preferably, the volume ratio of the 4-chloromethyl styrene to the cross-linking agent in the step (1) is 10-150: 1; the volume ratio of the 4-chloromethyl styrene to the water is 1: 12-24; the volume mass ratio of the 4-chloromethyl styrene to the initiator is 1: 0.015-0.03 mL/g.

Preferably, the mass-to-volume ratio of the intermediate product I to the solvent I in the step (2) is 1: 12-36 g/mL; the mass ratio of the intermediate product I to the catalyst is 1: 1-1.5.

Preferably, the mass-to-volume ratio of the intermediate product II to the solvent II in the step (3) is 1: 75-125 g/mL; the mass-volume ratio of the intermediate product II to the polymer monomer is 1: 35-75 g/mL; the mass-volume ratio of the intermediate product II to N, N, N' -pentamethyldiethylenetriamine is 1-1.5: 1 g/mL; the mass ratio of the intermediate product II to the copper bromide is 1: 0.5-0.8; the mass ratio of the intermediate product II to the vitamin C is 1: 0.3-0.6.

Preferably, the intermediate product III in the step (4) accounts for 0.3 to 2 percent of the mass of the precursor solution; the linear polymer, the polyoxyethylene diamine and the polyethylene glycol diglycidyl ether respectively account for 0.5-2 percent, 1-3 percent and 2-8 percent of the precursor solution by mass percent; the thickness of the three-dimensional cross-linked network polymer film is 70-200 um.

Preferably, the number average molecular weight (Mn) of the polyoxyethylene diamine in the step (4) is 500-2000, and the number average molecular weight (Mn) of the polyethylene glycol diglycidyl ether is 300-1000; the mass ratio of the polyoxyethylene diamine to the polyethylene glycol diglycidyl ether is 1: 2-3.

Preferably, the liquid electrolyte in step (5) is composed of a lithium salt and an organic solvent, the lithium salt being dissolved in the solvent; the lithium salt is one or more of lithium bistrifluoromethanesulfonimide, lithium hexafluorophosphate or lithium tetrafluoroborate; the concentration of the lithium salt is 0.6-1.2 mol/L; the organic solvent is one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, 1, 3-dioxolane and ethylene glycol dimethyl ether.

Preferably, the solvent I is one or more of 1, 2-dichloroethane, dichloromethane, chloroform and carbon tetrachloride.

Preferably, the solvent II is a mixed solvent of N, N-dimethylformamide and toluene, and the volume ratio of the N, N-dimethylformamide to the toluene is 4-6: 1.

preferably, the solvent III comprises one or more of N, N-dimethylformamide, N-dimethylacetamide, N-methylpyrrolidone, acetonitrile and tetrahydrofuran.

Preferably, the inert atmosphere in step (1) comprises one or more of nitrogen, argon and helium.

Preferably, the reflux temperature in step (2) is 80 ℃ and the reaction time is 24 h.

Preferably, the volume ratio of the hydrochloric acid to the water to the acetone in the acetone/hydrochloric acid/water mixed solvent in the step (2) is 1:9: 27.

Preferably, the reaction temperature in the step (3) is 60 ℃ and the reaction time is 24 h.

Preferably, the carrier mold in the step (4) is a polytetrafluoroethylene culture dish with the diameter of 6-12 cm.

Preferably, the reaction temperature in the step (4) is 80 ℃, and the reaction time is 24 h.

Preferably, before the three-dimensional crosslinked network polymer membrane is immersed in the liquid electrolyte in the step (5), the thermally crosslinked three-dimensional crosslinked network polymer membrane is washed with methanol three times to remove the residual monomers and solvent in the membrane, and the washed polymer membrane is dried in vacuum at 60 ℃ for 12 hours.

The three-dimensional cross-linked network gel polymer electrolyte membrane prepared by the method can be applied to lithium ion batteries.

The invention provides a lithium ion battery, which comprises a positive electrode, a negative electrode and a three-dimensional cross-linked network gel polymer electrolyte membrane prepared by assembling.

The principle of the invention is as follows: the invention provides a three-dimensional cross-linked network gel polymer electrolyte membrane and a preparation method and application thereof. Then, benzyl chloride of xPCMS is used as an active grafting site, and Poly Glycidyl Methacrylate (PGMA) is grafted on the surface of the xPCMS through an electron transfer activation regeneration catalyst-atom transfer radical polymerization (ARGET-ATRP) technology to prepare the hair-shaped microporous polymer nanosphere (xPCMS-g-PGMA). Then, xPCMS-g-PGMA is used as a cross-linking agent to perform simple one-step cross-linking reaction with polyoxyethylene Diamine (DPEG) and polyethylene glycol diglycidyl ether (PEGDE) at high temperature, so that the three-dimensional cross-linked network polymer membrane can be prepared. And finally, soaking the membrane in a commercial liquid electrolyte for adsorption saturation to obtain the three-dimensional cross-linked network gel polymer electrolyte membrane with high ionic conductivity and high mechanical property.

Compared with the prior art, the invention has the following beneficial effects:

(1) the three-dimensional cross-linked network gel polymer electrolyte membrane prepared by the method can obviously improve the mechanical property of the polymer electrolyte by introducing rigid hair-shaped microporous polymer nanospheres as a cross-linking agent; the high porosity of the hair-shaped microporous polymer nanospheres is beneficial to absorbing more liquid electrolyte and ensuring the high-efficiency conduction of lithium ions, and the mutually communicated pore channel structures can promote the rapid transmission of the lithium ions and can effectively improve the ionic conductivity of the three-dimensional cross-linked network gel polymer electrolyte membrane; the PGMA grafted and modified hair-like microporous polymer nanospheres are beneficial to being uniformly dispersed in a polymer matrix, and the reduction of elasticity and flexibility of a polymer electrolyte caused by the agglomeration of nanoparticles is prevented.

(2) The three-dimensional cross-linked network gel polymer electrolyte membrane has excellent mechanical property, higher room-temperature ionic conductivity and good thermal stability, can be applied to a lithium ion battery, and the assembled lithium ion battery has excellent electrochemical property.

Drawings

In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below.

Fig. 1 is a scanning electron micrograph and a particle size histogram of an intermediate product i according to example 1 of the present invention.

Fig. 2 is a scanning electron micrograph and a particle size histogram of the intermediate product two provided in example 1 of the present invention.

Fig. 3 is a scanning electron micrograph and a particle size histogram of intermediate product three provided in example 1 of the present invention.

FIG. 4 shows N of intermediate III provided in example 1 of the present invention₂Adsorption-desorption isotherm plot and pore size distribution plot (inset).

Fig. 5 is a digital photograph (fig. 5a, b) and a scanning electron microscope image (fig. 5c, d) of the three-dimensional crosslinked network gel polymer electrolyte membrane provided in example 1 of the present invention.

Fig. 6 is a stress-strain curve of a tensile test of the three-dimensional crosslinked network gel polymer electrolyte membrane provided in example 1 of the present invention.

Fig. 7 is a thermal weight loss curve of the three-dimensional crosslinked network gel polymer electrolyte membrane provided in example 1 of the present invention.

Fig. 8 is a graph showing the relationship between the ion conductivity and the temperature of the three-dimensional crosslinked network gel polymer electrolyte membrane (3d GPEs) and the electrolyte solution matched polypropylene diaphragm (PP + LE) provided in example 1 of the present invention.

Fig. 9 is a linear sweep voltammogram of a three-dimensional cross-linked network gel polymer electrolyte membrane provided in example 1 of the present invention.

Fig. 10 shows the rate performance of CR2032 coin cell provided in example 1 of the present invention at 25 ℃.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention and the accompanying drawings.

It is understood that the steps of the sem test include: fixing the product sample on a sample table by using conductive adhesive, and placing the sample table in a vacuum drying oven for drying treatment for 12 h. After the metal spraying treatment, the structural morphology of the sample is observed by an S-4800 cold field emission scanning electron microscope produced by Hitachi high and new technology under the voltage of 10 kV.

It is understood that the steps of the specific surface area and pore size distribution test include: n of the sample was measured by using ASAP2020 adsorption apparatus manufactured by Micromeritics of USA₂Adsorption-desorption isotherms. A sample of 0.02g of the above product was weighed and degassed under vacuum at 90 ℃ for 6h before testing. Specific surface area S_BETCalculated by the BET method, the full pore size distribution is calculated using the DFT theory.

The invention is further illustrated by the following examples.

Example 1

A preparation method of a three-dimensional cross-linked network gel polymer electrolyte membrane comprises the following steps:

step (1): mixing 12.25mL of 4-chloromethylstyrene and 0.25mL of divinylbenzene, then slowly pushing and injecting the mixture into 248mL of deionized water by using a trace sample injection pump, heating the mixture to 75 ℃, weighing 0.21g of azodiisobutyl amidine hydrochloride (V50 initiator) to be dissolved in 2mL of deionized water, injecting the mixture into a reaction system by using a needle tube, carrying out reflux reaction for 4 hours at 75 ℃ under an inert atmosphere, carrying out centrifugal separation, then washing with ethanol and water, and carrying out vacuum drying at 40 ℃ to obtain an intermediate product I;

step (2): adding 3.5g of the intermediate product I prepared in the step (1) into 112mL of 1, 2-dichloroethane, slowly stirring overnight to fully swell the intermediate product I, heating to 80 ℃, adding 3.7g of anhydrous ferric trichloride, refluxing for reaction for 24 hours, adding an acetone/hydrochloric acid/water mixed solvent to stop the reaction, filtering, washing, and drying in vacuum to obtain an intermediate product II;

and (3): uniformly dispersing 0.2g of the intermediate product II prepared in the step (2) in 20mL of dimethylformamide and 5mL of toluene, sequentially adding 7mL of glycidyl methacrylate, 212 mu L N, N, N' -pentamethyldiethylenetriamine, 113mg of copper bromide and 89mg of vitamin C, heating to 60 ℃, sealing and reacting for 24 hours in an inert atmosphere, washing with absolute ethyl alcohol, centrifuging, and then drying in vacuum to obtain an intermediate product III;

and (4): adding 0.12g of the intermediate product prepared in the step (3), 0.2g of polyvinylidene fluoride-hexafluoropropylene, 0.3g of polyoxyethylene diamine and 0.7g of polyethylene glycol diglycidyl ether into 10mL of dimethylformamide, uniformly mixing and dispersing to obtain a precursor solution, pouring 3.5mL of the precursor solution on a polytetrafluoroethylene culture dish mould with the diameter of 6cm, heating to 80 ℃ for reaction for 24 hours, washing with methanol for 3 times, and drying at 60 ℃ in vacuum to obtain the three-dimensional cross-linked network polymer membrane I.

And (5): and (4) immersing the three-dimensional cross-linked network polymer membrane I prepared in the step (4) into liquid electrolyte, and absorbing the electrolyte until the electrolyte is saturated to obtain the three-dimensional cross-linked network gel polymer electrolyte membrane I. The electrolyte is prepared by dissolving lithium hexafluorophosphate in a mixed solvent consisting of ethylene carbonate and dimethyl carbonate in a volume ratio of 1: 1. In the electrolyte, the concentration of the lithium hexafluorophosphate is 1 mol/L.

The three-dimensional cross-linked network gel polymer electrolyte membrane is applied to a lithium ion battery, wherein a lithium plate is used as a negative electrode, a lithium iron phosphate plate is used as a positive electrode, and the three-dimensional cross-linked network gel polymer electrolyte membrane is used as an electrolyte. The lithium iron phosphate pole piece is prepared by mixing and coating active substances, conductive carbon black (Super P) and polyvinylidene fluoride (PVDF) with the mass ratio of 7:2:1 on an aluminum foil to form a film, putting the film into an oven at 80 ℃ for drying, and punching the film into a pole piece with the diameter of 12 mm. The lithium ion battery is assembled in a glove box under argon atmosphere, and the content of moisture and oxygen in the glove box needs to be kept lower than 0.1 ppm. The assembled button cell is CR 2032.

The lithium ion battery is subjected to constant-current charge and discharge performance test on an LAND battery test system (provided by Wuhan blue electronics Co., Ltd.), the charge and discharge multiplying power is 1C, and the charge and discharge cutoff voltage is 2V-4V vs Li/Li⁺。

To further illustrate the effects of the three-dimensional cross-linked network gel polymer electrolyte membrane one prepared in example 1, the following characterization was performed.

FIG. 1 is a scanning electron micrograph and a particle size histogram of the first intermediate obtained in example 1. As can be seen from FIG. 1, the intermediate product has a good morphology of nanospheres, and the particle size is about 650 nm.

FIG. 2 is a scanning electron micrograph and a particle size histogram of the second intermediate obtained in example 1. As can be seen from FIG. 2, the intermediate product II still maintains a good morphology of nanospheres after undergoing a hypercrosslinking reaction from the intermediate product I, and the particle size of the intermediate product II is increased to about 713 nm.

Fig. 3 is a scanning electron micrograph and a particle size histogram of intermediate iii obtained in example 1. As can be seen from fig. 3, the intermediate product three also has a good nanosphere morphology after the intermediate product two is grafted with the polymer on the surface, and the particle size of the intermediate product three is increased to about 780nm, which indicates that the polymer has been successfully grafted on the surface of the intermediate product two, and the thickness of the polymer nanoparticle layer is about 33 nm.

FIG. 4 shows N of intermediate III obtained in example 1₂Adsorption-desorption isotherm plot and pore size distribution plot (inset). As can be seen from FIG. 4, the third intermediate product has interconnected multi-level porous junctionsStructure, calculated to have a BET specific surface area of 330m²/g。

FIG. 5 is a digital photograph and a scanning electron microscope image of the three-dimensional crosslinked network gel polymer electrolyte membrane prepared in example 1. As can be seen from fig. 5a and b, the three-dimensional crosslinked network gel polymer electrolyte membrane has good membrane morphology, can be bent and deformed, and has good flexibility and mechanical stability. As can be seen from FIGS. 5c and d, the structure of the three-dimensional crosslinked network gel polymer electrolyte has a flat and uniform surface and a thickness of about 136 μm.

Fig. 6 is a stress-strain curve of the three-dimensional crosslinked network gel polymer electrolyte membrane prepared in example 1 subjected to a tensile test. It can be seen that the three-dimensional crosslinked network gel polymer electrolyte membrane has excellent mechanical strength and flexibility. Compared with the traditional linear polymer, the three-dimensional cross-linked network structure of the three-dimensional cross-linked network gel polymer electrolyte membrane can effectively enhance the rigidity of the polymer membrane, and meanwhile, the hair-shaped micro-porous polymer nanospheres xPCMS-g-PGMA with certain rigidity, which play a role of a cross-linking agent, can also improve the overall mechanical property and flexibility of the polymer membrane by cross-linking the relatively soft high-molecular-chain PGMA and the PEO-based polymer.

Fig. 7 is a thermogravimetric curve of the three-dimensional crosslinked network gel polymer electrolyte membrane prepared in this example 1. As can be seen from fig. 7, the initial decomposition temperature of the polymer film is about 300 ℃, which indicates that the polymer film has high thermal stability and can meet the practical application requirements of the lithium secondary battery.

Fig. 8 is a graph showing the relationship between the ion conductivity and the temperature of the three-dimensional crosslinked network gel polymer electrolyte membrane (3d GPEs) prepared in this example 1 and the electrolyte solution in combination with the polypropylene separator (PP + LE). The ionic conductivity of the three-dimensional crosslinked network gel polymer electrolyte membrane at room temperature is 4.61 multiplied by 10 according to the data calculation of the graph^-3S/cm, which is obviously higher than the room-temperature ionic conductivity (3.12 multiplied by 10) of the electrolyte matched with the polypropylene diaphragm^-4S/cm). The dense three-dimensional cross-linked network structure of the gel polymer electrolyte membrane can prevent a large volume to some extentThe migration of lithium salt cations improves the migration number of lithium ions, the flexibility of polymer chain segments is enhanced due to the introduction of the hair-shaped microporous polymer nanospheres, and the mutually communicated pore channel structures are favorable for promoting the transmission of the lithium ions, so that the ionic conductivity of the three-dimensional cross-linked network gel polymer electrolyte membrane is about 10 times that of an electrolyte matched with a polypropylene diaphragm.

Fig. 9 is a linear sweep voltammogram of the three-dimensional crosslinked network gel polymer electrolyte membrane prepared in this example 1. The stainless steel gasket is used as a working electrode, the metal lithium sheet is used as a counter electrode and a reference electrode, and the three-dimensional cross-linked network gel polymer electrolyte membrane is clamped in the middle, so that the electrochemical stability window is 4.5V, and the practical application requirement of the lithium secondary battery can be met as can be seen from figure 9.

FIG. 10 shows the rate performance at 25 ℃ of CR2032 coin cells prepared in example 1. Compared with an electrolyte matched polypropylene diaphragm (PP + LE), the LFP full cell assembled by the three-dimensional cross-linked network gel polymer electrolyte membrane (3d GPEs) has higher specific capacity and shows excellent rate performance under the current density of 0.2, 0.5, 1,2, 3 and 5C.

Example 2

and (4): adding 0.06g of the intermediate product prepared in the step (3), 0.2g of polyvinylidene fluoride-hexafluoropropylene, 0.3g of polyoxyethylene diamine and 0.7g of polyethylene glycol diglycidyl ether into 10mL of dimethylformamide, uniformly mixing and dispersing to obtain a precursor solution, pouring 3.5mL of the precursor solution on a polytetrafluoroethylene culture dish mould with the diameter of 6cm, heating to 120 ℃, reacting for 12h, washing for 3 times with methanol, and drying in vacuum at 60 ℃ to obtain the three-dimensional cross-linked network polymer membrane I.

And (5): and (5) immersing the three-dimensional cross-linked network polymer membrane I prepared in the step (4) into liquid electrolyte, and absorbing the electrolyte until the electrolyte is saturated to obtain a three-dimensional cross-linked network gel polymer electrolyte membrane II. The electrolyte is prepared by dissolving lithium hexafluorophosphate in a mixed solvent consisting of ethylene carbonate and dimethyl carbonate in a volume ratio of 1: 1. In the electrolyte, the concentration of the lithium hexafluorophosphate is 1 mol/L.

Example 3

and (4): adding 0.18g of the intermediate product prepared in the step (3), 0.2g of polyvinylidene fluoride-hexafluoropropylene, 0.3g of polyoxyethylene diamine and 0.7g of polyethylene glycol diglycidyl ether into 10mL of dimethylformamide, uniformly mixing and dispersing to obtain a precursor solution, pouring 3.5mL of the precursor solution on a polytetrafluoroethylene culture dish mould with the diameter of 6cm, heating to 80 ℃ for reaction for 24 hours, washing with methanol for 3 times, and drying at 60 ℃ in vacuum to obtain the three-dimensional cross-linked network polymer membrane I.

And (5): and (5) immersing the three-dimensional cross-linked network polymer membrane I prepared in the step (4) into liquid electrolyte, and absorbing the electrolyte until the electrolyte is saturated to obtain a three-dimensional cross-linked network gel polymer electrolyte membrane III. The electrolyte is prepared by dissolving lithium hexafluorophosphate in a mixed solvent consisting of ethylene carbonate and dimethyl carbonate in a volume ratio of 1: 1. In the electrolyte, the concentration of the lithium hexafluorophosphate is 1 mol/L.

To further illustrate the advantageous effects of the present invention, mechanical properties and room temperature conductivity of the three-dimensional crosslinked network gel polymer electrolyte membranes prepared in examples 1 to 3 were measured, and the results are shown in table 1.

TABLE 1 mechanical Properties and Room temperature Ionic conductivities of three-dimensional crosslinked network gel Polymer electrolyte membranes

The results show that: the influence of the dosage of the intermediate product III in the step (4) on the mechanical property and the ionic conductivity of the product is large. With the increase of the amount of the intermediate product III, the tensile strength of the product is increased, and the elongation at break and the room-temperature ionic conductivity are reduced.

Example 4

and (4): adding 0.12g of the intermediate product prepared in the step (3), 0.2g of polyvinylidene fluoride-hexafluoropropylene, 0.3g of polyoxyethylene diamine and 0.7g of polyethylene glycol diglycidyl ether into 10mL of dimethylformamide, uniformly mixing and dispersing to obtain a precursor solution, pouring 2.5mL of the precursor solution on a polytetrafluoroethylene culture dish mould with the diameter of 6cm, heating to 80 ℃ for reaction for 48 hours, washing with methanol for 3 times, and drying at 60 ℃ in vacuum to obtain the three-dimensional cross-linked network polymer membrane I.

And (5): and (5) immersing the three-dimensional cross-linked network polymer membrane I prepared in the step (4) into liquid electrolyte, and absorbing the electrolyte until the electrolyte is saturated to obtain a three-dimensional cross-linked network gel polymer electrolyte membrane IV. The electrolyte is prepared by dissolving lithium hexafluorophosphate in a mixed solvent consisting of ethylene carbonate and dimethyl carbonate in a volume ratio of 1: 1. In the electrolyte, the concentration of the lithium hexafluorophosphate is 1 mol/L.

Example 5

and (4): adding 0.12g of the intermediate product prepared in the step (3), 0.2g of polyvinylidene fluoride-hexafluoropropylene, 0.3g of polyoxyethylene diamine and 0.7g of polyethylene glycol diglycidyl ether into 10mL of dimethylformamide, uniformly mixing and dispersing to obtain a precursor solution, pouring 5mL of the precursor solution on a polytetrafluoroethylene culture dish mould with the diameter of 6cm, heating to 80 ℃, reacting for 24h, washing for 3 times by using methanol, and drying in vacuum at 60 ℃ to obtain the three-dimensional cross-linked network polymer membrane I.

And (5): and (5) immersing the three-dimensional cross-linked network polymer membrane I prepared in the step (4) into liquid electrolyte, and absorbing the electrolyte until the electrolyte is saturated to obtain a three-dimensional cross-linked network gel polymer electrolyte membrane V. The electrolyte is prepared by dissolving lithium hexafluorophosphate in a mixed solvent consisting of ethylene carbonate and dimethyl carbonate in a volume ratio of 1: 1. In the electrolyte, the concentration of the lithium hexafluorophosphate is 1 mol/L.

The three-dimensional crosslinked network gel polymer electrolyte membranes prepared in examples 1, 4 and 5 were subjected to mechanical properties and room temperature conductivity tests, and the results are shown in table 2.

TABLE 2 mechanical properties and Room temperature Ionic conductivities of three-dimensional crosslinked network gel Polymer electrolyte membranes

The results show that: the dosage of the precursor solution in the step (4) has great influence on the mechanical property and the ionic conductivity of the product. With the increase of the dosage of the precursor solution, the tensile strength and the elongation at break of the product are increased and then slightly reduced, and the room-temperature ionic conductivity is increased and then reduced.

Finally, it should be noted that: it should be understood that the above examples are only for clearly illustrating the present application and are not intended to limit the embodiments. Other variations and modifications in light of the above teachings may occur to those skilled in the art. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications of this invention may be made without departing from the spirit or scope of the invention.

Claims

1. A preparation method of a three-dimensional cross-linked network gel polymer electrolyte membrane is characterized in that,

firstly, synthesizing a polychloromethylstyrene nanosphere PCMS by an emulsion polymerization method, and then carrying out a hypercrosslinking reaction to obtain a hypercrosslinked microporous polychloromethylstyrene nanosphere xPCMS; then, taking benzyl chloride of xPCMS as an active grafting site, and grafting polyglycidyl methacrylate PGMA on the surface of the xPCMS by an electron transfer activation regeneration catalyst-atom transfer radical polymerization technology to prepare a hair-like microporous polymer nanosphere xPCMS-g-PGMA;

secondly, the hair-shaped microporous polymer nanospheres are used as a cross-linking agent to perform cross-linking reaction with linear polymers, polyoxyethylene diamine and polyethylene glycol diglycidyl ether to prepare a three-dimensional cross-linked network gel polymer membrane;

2. The method of claim 1, comprising the steps of:

(1) mixing 4-chloromethyl styrene with a cross-linking agent, dropwise adding the mixture into an aqueous solution, heating to 60-80 ℃, adding an initiator, carrying out reflux reaction for 4-8 hours under an inert atmosphere, carrying out centrifugal separation, washing with ethanol and water, and carrying out vacuum drying to obtain an intermediate product I;

3. The method according to claim 2, wherein the crosslinking agent in the step (1) is divinylbenzene; the initiator comprises one or more of azodiisobutyramidine hydrochloride, azodiisobutyronitrile, azodiisoheptonitrile and azodiisobutyronitrile;

the catalyst in the step (2) is one or more of anhydrous ferric trichloride, anhydrous aluminum trichloride, boron fluoride, sulfuric acid, anhydrous stannic chloride or anhydrous zinc chloride;

the acrylic ester polymer monomer containing the epoxy group in the step (3) is one or more of glycidyl methacrylate, glycidyl acrylate and allyl glycidyl ether;

the linear polymer in the step (4) comprises one or more of polymethyl methacrylate, polyacrylonitrile, polyvinylidene fluoride, polystyrene, polyvinylidene fluoride-hexafluoropropylene, polyoxyethylene, polyurethane or polysulfone.

4. The production method according to claim 3,

the volume ratio of the 4-chloromethyl styrene to the cross-linking agent in the step (1) is 10-150: 1; the volume ratio of the 4-chloromethyl styrene to the water is 1: 12-24; the volume mass ratio of the 4-chloromethyl styrene to the initiator is 1: 0.015-0.03 mL/g;

the mass-volume ratio of the intermediate product I to the solvent I in the step (2) is 1: 12-36 g/mL; the mass ratio of the intermediate product I to the catalyst is 1: 1-1.5;

the mass-volume ratio of the intermediate product II to the solvent II in the step (3) is 1: 75-125 g/mL; the mass-volume ratio of the intermediate product II to the polymer monomer is 1: 35-75 g/mL; the mass-volume ratio of the intermediate product II to N, N, N' -pentamethyldiethylenetriamine is 1-1.5: 1 g/mL; the mass ratio of the intermediate product II to the copper bromide is 1: 0.5-0.8; the mass ratio of the intermediate product II to the vitamin C is 1: 0.3-0.6.

5. The preparation method according to claim 4, wherein the intermediate product III in the step (4) accounts for 0.3-2% of the precursor solution by mass; the linear polymer, the polyoxyethylene diamine and the polyethylene glycol diglycidyl ether respectively account for 0.5-2 percent, 1-3 percent and 2-8 percent of the precursor solution by mass percent; the thickness of the three-dimensional cross-linked network polymer film is 70-200 μm.

6. The method according to claim 5, wherein the polyoxyethylene diamine in the step (4) has a number average molecular weight (Mn) of 500 to 2000, and the polyethylene glycol diglycidyl ether has a number average molecular weight (Mn) of 300 to 1000; the mass ratio of the polyoxyethylene diamine to the polyethylene glycol diglycidyl ether is 1: 2-3;

the liquid electrolyte in the step (5) is composed of lithium salt and an organic solvent, wherein the lithium salt is dissolved in the solvent; the lithium salt is one or more of lithium bistrifluoromethanesulfonimide, lithium hexafluorophosphate or lithium tetrafluoroborate; the concentration of the lithium salt is 0.6-1.2 mol/L; the organic solvent is one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, 1, 3-dioxolane and ethylene glycol dimethyl ether.

7. The preparation method according to claim 6, wherein the solvent I is one or more of 1, 2-dichloroethane, dichloromethane, chloroform and carbon tetrachloride;

the solvent II is a mixed solvent of N, N-dimethylformamide and toluene, and the volume ratio of the N, N-dimethylformamide to the toluene is 4-6: 1;

the solvent III comprises one or more of N, N-dimethylformamide, N-dimethylacetamide, N-methylpyrrolidone, acetonitrile and tetrahydrofuran.

8. The three-dimensional crosslinked network gel polymer electrolyte membrane prepared by the method of any one of claims 1 to 7.

9. Use of the three-dimensional cross-linked network gel polymer electrolyte membrane of claim 8 in a lithium ion battery.

10. A lithium ion battery comprising a positive electrode and a negative electrode, wherein the lithium ion battery further comprises the three-dimensional crosslinked network gel polymer electrolyte membrane of claim 8.