CN111342123A - Selective wetting polymer electrolyte and preparation and application thereof - Google Patents

Selective wetting polymer electrolyte and preparation and application thereof Download PDF

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CN111342123A
CN111342123A CN202010155436.3A CN202010155436A CN111342123A CN 111342123 A CN111342123 A CN 111342123A CN 202010155436 A CN202010155436 A CN 202010155436A CN 111342123 A CN111342123 A CN 111342123A
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lithium
polymer electrolyte
sulfone
solid
polyvinylidene fluoride
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CN111342123B (en
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崔光磊
马君
虞鑫润
王龙龙
徐红霞
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Qingdao Institute of Bioenergy and Bioprocess Technology of CAS
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Abstract

The invention relates to a polymer electrolyte, in particular to a polymer electrolyte of a polycarboxylate material containing a polyvinylidene fluoride material and a selective absorption sulfone micromolecule additive, a preparation method thereof and application thereof in a quasi-solid lithium battery. The polymer electrolyte is composed of 30-80% of polyvinylidene fluoride material, 10-40% of polycarboxylate material, 5-50% of lithium salt, 1-20% of sulfone small molecular additive and 1-50% of inorganic fast ion conductor by mass percentage. The electrolyte is prepared by adopting a solution pouring method, and is easy to prepare and simple to form; the selective wetting polymer electrolyte can be used in a high-safety secondary lithium battery at room temperature; the electrochemical oxidation-reduction composite material has excellent electrochemical oxidation-reduction stability and thermal stability, can infiltrate the interface between an electrolyte and an electrode, and also has higher room-temperature conductivity and excellent mechanical properties.

Description

Selective wetting polymer electrolyte and preparation and application thereof
Technical Field
The invention relates to a polymer electrolyte, in particular to a polymer electrolyte of a polycarboxylate material containing a polyvinylidene fluoride material and a selective absorption sulfone micromolecule additive, a preparation method thereof and application thereof in a quasi-solid lithium battery.
Background
Because of the safety problem caused by the adoption of liquid organic electrolyte in the traditional commercial lithium battery, the solid-state lithium battery adopting the solid electrolyte has become a research hotspot in recent years, and the solid-state battery can fundamentally solve the safety problem existing in the traditional commercial lithium battery. Common all-solid electrolytes are classified into inorganic solid electrolytes and polymer all-solid electrolytes. The inorganic solid electrolyte has the advantages of high ionic conductivity, wide electrochemical window, high mechanical strength and stable interface, but the preparation process of the inorganic solid electrolyte is complex, the contact with an electrode interface is poor, the machining performance is poor, and the large-scale application of the inorganic solid electrolyte is restricted due to sensitivity to water, oxygen and the like. The polymer all-solid-state electrolyte has the advantages of flexibility, easy processing and preparation, good thermal stability, high stability to lithium and the like; however, the development and application of the high energy density polymer solid-state lithium battery are hindered by low ionic conductivity, poor interface compatibility and limited working voltage. Compared with the polymer all-solid electrolyte, the polymer gel electrolyte has higher ionic conductivity and good electrode wettability, but still contains a large amount of flammable and combustible organic electrolyte (accounting for more than fifty percent of the mass of the whole gel electrolyte), so that the mechanical property of the polymer gel electrolyte is poor, and the safety problem still exists.
Disclosure of Invention
The invention aims to overcome the defects and provide a selectively-infiltrated polymer electrolyte, a simple and efficient preparation method of a selectively-infiltrated rigid-flexible polymer electrolyte film and application of the polymer electrolyte in a quasi-solid lithium battery.
In order to achieve the purpose, the invention adopts the technical scheme that:
the selectively infiltrated polymer electrolyte is prepared with polyvinylidene fluoride material 30-80 wt%, polycarboxylate material 10-40 wt%, lithium salt 5-50 wt%, sulfone small molecular additive 1-20 wt% and fast inorganic ion conductor 1-50 wt%.
The electrolyte has room temperature ionic conductivity of 5 × 10-5～1×10-3S/cm, initial decomposition voltage greater than 4.7V (vs. Li)+/Li)。
Preferably, the polymer electrolyte is composed of, by mass, 35-50% of polyvinylidene fluoride materials, 20-30% of polycarboxylate materials, 10-30% of lithium salt, 5-15% of sulfone small molecular additives and 5-15% of inorganic fast ion conductors.
The polyvinylidene fluoride-based material is a homopolymer of vinylidene fluoride (VDF) (i.e., polyvinylidene fluoride (PVDF)) or a copolymer of vinylidene fluoride (VDF) and a fluorine-containing vinyl monomer.
The copolymer of vinylidene fluoride (VDF) and fluorine-containing vinyl monomer is chlorotrifluoroethylene, tetrafluoroethylene, hexafluoropropylene, vinyl fluoride or fluorine-containing alkyl vinyl ether.
The polycarboxylate material is one or more of polyvinyl acetate, polymethyl methacrylate and polymethyl acrylate.
The lithium salt is one or more of lithium dioxalate borate, lithium tetrafluoroborate, lithium hexafluorophosphate, lithium dioxydifluorophosphate, lithium perchlorate, lithium hexafluoroarsenate, lithium trifluoromethylsulfonate, lithium bis (fluoromethanesulfonylimide), lithium bis (fluorosulfonimide) and lithium difluorooxalato borate.
The sulfone small molecular additive is R1-SO2-R2Or R1-SO-R2(ii) a wherein-S ═ O2-is sulfuryl, -S ═ O-is thionyl, R1、R2Identical or different from-CnH2n+1(n takes a value of 1-5) and-CnH2n-1(n takes a value of 2-5) and-CnH2n-3(n takes a value of 2-5) and-CnH2n- (n values 2-5), -C6H5，-C6H4-OH or CH ═ CH-C6H5。
Preferred small molecule additives of the sulfone type are dimethyl sulfone, phenethylsulfone, diethyl sulfone, diphenyl sulfone, sulfolane, bisphenol S or ethyl isopropyl sulfone.
The inorganic fast ion conductor is Li7La3Zr2O12(LLZO)，LixLa2/3-xTiO3(LLTO)，Li1+xAlxTi2-x(PO4)3(LATP)，LiAlO2(LAO)，Li7-xLa3Zr2-xMxO12(M＝Ta,Nb,W)(0.25<x<2)(LLZMO)，Li7+ xGexP3-xS11(LGPS)，xLi2S·(100-x)P2S5(LPS) one or more of them; the particle size is 50nm-3 μm.
A preparation method of a selective infiltration polymer electrolyte comprises the following steps:
the method comprises the following steps: mixing the polyvinylidene fluoride material, the polycarboxylate material and the lithium salt according to the proportion, adding the mixture into a volatile anhydrous organic solvent, and dissolving and mixing the mixture uniformly;
step two: adding a fast ion conductor into the mixed solution, and performing ultrasonic treatment and stirring to uniformly disperse the mixed solution;
step three: uniformly pouring or blade-coating the mixed solution by using a scraper to prepare an electrolyte membrane, and obtaining a self-supporting solid polymer electrolyte membrane after the volatile anhydrous organic solvent is completely volatilized; wherein the film thickness is 10 μm to 200 μm, preferably 20 μm to 100 μm.
Step four: and adding a sulfone small molecular additive into the obtained solid polymer electrolyte membrane, and obtaining the selectively infiltrated polymer electrolyte after the additive is fully absorbed by the polymer electrolyte.
In the first step, the polyvinylidene fluoride material and the polycarboxylate material have good compatibility; in the step four, the sulfone small molecular additive is only selectively combined with the polycarboxylate material, but is not absorbed by the polyvinylidene fluoride material insoluble with the sulfone small molecular additive.
The volatile anhydrous organic solvent is one or more of acetone, acetonitrile, tetrahydrofuran, N-dimethylformamide and N-methylpyrrolidone.
The mass ratio of the volatile anhydrous organic solvent to the solute is between 5:1 and 20: 1.
Use of a polymer electrolyte in a quasi-solid state secondary lithium battery (lithium ion battery, lithium metal battery, lithium sulphur battery). The quasi-solid lithium battery is formed by sequentially stacking a negative electrode, the polymer electrolyte and a positive electrode.
A quasi-solid secondary lithium battery comprises a positive electrode and a negative electrode, and the polymer electrolyte is arranged between the positive electrode and the negative electrode.
Further, the positive electrode comprises a positive electrode current collector, a positive electrode active material and a conductive agent. The positive active material comprises a ternary material, lithium cobaltate, lithium manganate, lithium iron phosphate, lithium cobalt phosphate, lithium iron silicate and a lithium-rich manganese-based solid solution material.
The negative electrode comprises a negative electrode current collector, a negative electrode active material, a conductive agent and a binder.
The negative active material comprises one or more of graphite, silicon oxide, tin oxide, a silicon-carbon composite material, a tin-nickel alloy, lithium titanate or metal lithium foil and a lithium metal alloy.
Compared with the prior art, the invention achieves the technical effects that:
the polymer electrolyte is compounded by polyvinylidene fluoride materials, polycarboxylate materials, lithium salts, inorganic fast ion conductors and sulfone micromolecule additives, the thickness of the polymer electrolyte is 10-200 mu m, and the room-temperature ionic conductivity is 5 × 10-5-1×10-3S/cm, electrochemical window greater than 4.7V (vs. Li)+Li), does not contain a large amount of organic electrolyte, mechanical strength is obviously superior to gel electrolyte, wettability and interface compatibility between polymer electrolyte and electrodes are obviously improved, the electrolyte has good flexibility, stretchability and easy processability, excellent electrochemical redox stability, a wide electrochemical window, a simple preparation method and high production efficiency, the assembled quasi-solid lithium battery has lower impedance and higher capacity exertion, and meanwhile, the polymer electrolyte can be matched with a higher-voltage anode material, a lithium metal battery assembled by the polymer electrolyte not only has good interface stability and long cycle performance, but also effectively inhibits the growth of lithium dendrite, so that the safety performance is greatly improvedIt is good.
Drawings
Fig. 1 is a charge and discharge curve of a lithium cobaltate/lithium metal battery assembled with a polymer electrolyte according to an embodiment of the present invention;
fig. 2 shows a stable long-cycle performance charge-discharge curve of a lithium cobaltate/lithium metal battery assembled with the polymer electrolyte according to an embodiment of the present invention.
Fig. 3 is a charge and discharge curve of a ternary material/lithium metal battery assembled with a polymer electrolyte according to an embodiment of the present invention;
fig. 4 is a ternary material/lithium metal battery assembled with the polymer electrolyte according to an embodiment of the present invention, which has a stable long-cycle performance charge and discharge curve.
Fig. 5 shows a stable long-cycle performance charge-discharge curve of a lithium cobaltate/graphite full cell assembled by the polymer electrolyte provided by the embodiment of the invention.
Detailed Description
The following examples are presented to further illustrate embodiments of the present invention, and it should be understood that the embodiments described herein are for purposes of illustration and explanation only and are not intended to limit the invention.
According to the invention, a small amount (the mass fraction in the whole polymer electrolyte is less than twenty percent) of non-flammable, high-thermal stability and wide electrochemical window micromolecular solvent is used for selectively infiltrating the polymer in the polymer electrolyte to form a rigid-flexible quasi-solid polymer electrolyte; further, the electrode has high safety, high ionic conductivity, high electrochemical stability, good electrode wettability and mechanical properties. The rigid part forms a rigid skeleton by a polymer insoluble in the small molecule additive to maintain better mechanical properties, and the flexible polymer part selectively absorbing the small molecule additive can provide faster ion transmission and good interface contact. And the quasi-solid lithium battery assembled by the quasi-solid lithium battery has good cycle performance and capacity retention rate, and the safety performance is greatly improved.
Furthermore, the interface compatibility between the electrolyte and the electrode can be effectively improved through the selective interaction of the polycarboxylate material and the sulfone small molecular additive, the problem of high solid-solid interface impedance of the polymer solid-state battery is solved, and meanwhile, the polymer solid-state battery and the sulfone solvent insoluble polyvinylidene fluoride material provide mechanical properties required by the solid-state battery. The electrolyte is prepared by adopting a solution pouring method, and is easy to prepare and simple to form; the selective wetting polymer electrolyte can be used in a high-safety secondary lithium battery at room temperature; the electrochemical oxidation-reduction electrolyte has excellent electrochemical oxidation-reduction stability and thermal stability, can infiltrate the interface between the electrolyte and the electrodes, and also has higher room-temperature conductivity.
Example 1
Selectively infiltrating a polymer electrolyte, wherein the polymer electrolyte comprises, by mass, 40% of polyvinylidene fluoride, 25% of polyvinyl acetate, 15% of lithium salt, 7% of a fast ion conductor and 13% of a sulfone small molecular additive. Wherein the lithium salt is lithium perchlorate, and the fast ion conductor is Li7La3Zr2O12(LLZO) the sulfone additive is sulfolane.
The preparation method of the polymer electrolyte comprises the following steps:
the method comprises the following steps: in a drying room, adding 4.0g of polyvinylidene fluoride, 2.5g of polyvinyl acetate and 1.5g of lithium perchlorate into 100ml of a mixed solvent of anhydrous N, N-dimethylformamide and tetrahydrofuran (N, N-dimethylformamide accounts for 20% of the volume fraction of the mixed solvent) according to the dosage recorded above, stirring, dissolving and uniformly mixing;
step two: adding 0.7g of LLZO into the mixed solution, and performing ultrasonic treatment and stirring to uniformly disperse the mixed solution;
step three: uniformly pouring the mixed solution obtained in the step two or preparing an electrolyte membrane by using a scraper blade, and forming a self-supporting solid polymer electrolyte membrane (the thickness is about 40 mu m) after the mixed solvent is completely volatilized;
step four: 1.3g of sulfolane is added into the solid polymer electrolyte membrane obtained in the above, the sulfolane is uniformly dispersed on the surface of the polymer electrolyte, and the final polymer electrolyte is obtained after the solvent and the polymer matrix are fully soaked and absorbed.
The prepared polymer electrolyte membrane is thickThe electrolyte membrane prepared by sandwiching the electrolyte membrane with stainless steel in a glove box filled with argon gas was assembled into a symmetrical blocking-type cell measurement system, room temperature ac impedance r was measured with an electrochemical workstation, and the ion conductivity at room temperature was measured to be 4.7 × 10 by calculation with the formula ion conductivity σ ═ d/(r · s) (s is the area of the membrane)-4S/cm. And (3) taking stainless steel as a working positive electrode and metallic lithium as a counter electrode and a reference electrode, clamping the prepared electrolyte membrane in the middle to assemble the cell, standing the cell at room temperature for more than 6 hours, and performing linear sweep voltammetry test through an electrochemical workstation. The test voltage range of the linear sweep voltammetry test is 3-6.0V (vsLi)+/Li), scan rate of 0.1mVs-1The initial decomposition voltage was measured to be 4.8V (vs. Li)+/Li)。
The electrolyte assembly quasi-solid lithium battery obtained by the above examples was formed by stacking a negative electrode, a prepared polymer electrolyte, and a positive electrode in this order.
In the above technical solution, the positive electrode further includes a positive current collector, a positive active material, a conductive agent, and a binder. The positive active material comprises a ternary material, lithium cobaltate, lithium manganate, lithium iron phosphate, lithium cobalt phosphate, lithium iron silicate and a lithium-rich manganese-based solid solution material.
The negative electrode comprises a negative electrode current collector, a negative electrode active material, a conductive agent and a binder.
The negative active material comprises one or more of graphite, silicon oxide, tin oxide, a silicon-carbon composite material, a tin-nickel alloy, lithium titanate or metal lithium foil and a lithium metal alloy.
Performance testing of the assembled cells:
the charge-discharge curves and the long cycle performance of different batteries assembled according to the records are tested by using a LAND battery program-controlled tester, and the specific test method comprises the following steps:
1) lithium cobaltate/lithium metal batteries were assembled with the polymer electrolyte of example 1 in an argon-filled glove box using lithium cobaltate as the positive electrode and lithium metal as the negative electrode, and charge and discharge tests were performed at 30 ℃ and 0.5C rate between 3-4.5V (see FIGS. 1 and 2)
As can be seen from figure 1, at 30 ℃, under the multiplying power of 0.5C, the charging and discharging interval is 3-4.5V, the charging and discharging curve of the battery is stable, and the discharging capacity reaches 189 mAh/g;
as can be seen from FIG. 2, the battery has stable long-cycle performance at 30 ℃ and 0.5C multiplying power and in a charging and discharging interval of 3-4.5V.
2) Ternary material/lithium metal batteries were assembled with the polymer electrolyte of example 1 in an argon-filled glove box using ternary material as the positive electrode and lithium metal as the negative electrode, and charge and discharge tests were performed at 30 ℃ and 0.5C rate between 3-4.4V (see FIGS. 3 and 4)
As can be seen from FIG. 3, at 30 ℃ and 0.5C multiplying power, the charging and discharging interval is 3-4.4V, the charging and discharging curve of the battery is stable, and the discharging capacity reaches 165 mAh/g;
as can be seen from FIG. 4, the battery has stable long-cycle performance in the charge-discharge interval of 3-4.4V at 30 ℃ and 0.5C multiplying power.
3) Lithium cobaltate/graphite full cell was assembled with the polymer electrolyte of example 1 using lithium cobaltate as the positive electrode and graphite as the negative electrode in a glove box filled with argon gas, and charge and discharge tests were performed at 30 ℃ and 0.5C rate between 3-4.5V cells (see FIG. 5)
As can be seen from FIG. 5, the battery has stable long-cycle performance in the charge-discharge interval of 3-4.5V at 30 ℃ and 0.5C rate.
Example 2
Selectively infiltrating a polymer electrolyte, wherein the polymer electrolyte comprises 45% of polyvinylidene fluoride-hexafluoropropylene copolymer, 25% of polyvinyl acetate, 10% of lithium salt, 6% of fast ion conductor and 14% of sulfone small molecule additive in percentage by mass. Wherein the lithium salt is lithium hexafluorophosphate, and the fast ion conductor is Li6.4La3Zr1.4Ta0.6O12(LLZTO), the sulfone additive is ethyl isopropyl sulfone.
The preparation method of the polymer electrolyte comprises the following steps:
the method comprises the following steps: in a drying room, 4.5g of polyvinylidene fluoride-hexafluoropropylene copolymer, 2.5g of polyvinyl acetate and 1.0g of lithium hexafluorophosphate are added into 100ml of a mixed solvent of anhydrous N, N-dimethylformamide and tetrahydrofuran (N, N-dimethylformamide accounts for 20% of the volume fraction of the mixed solvent) according to the above-mentioned dosage, stirred, dissolved and mixed uniformly;
step two: adding 0.6g of LLZTO into the mixed solution, performing ultrasonic treatment and stirring to uniformly disperse the mixed solution;
step three: uniformly pouring the mixed solution obtained in the step two or preparing an electrolyte membrane by using a scraper blade coating, and forming a self-supporting solid polymer electrolyte membrane after the mixed solvent is completely volatilized;
step four: adding 1.4g of ethyl isopropyl sulfone into the solid polymer electrolyte membrane obtained above, uniformly dispersing the ethyl isopropyl sulfone on the surface of the polymer electrolyte, and obtaining the final polymer electrolyte after the solvent and the polymer matrix are fully soaked and absorbed.
The thickness of the prepared polymer electrolyte membrane was about d 64 μm, and the prepared electrolyte membrane was sandwiched with stainless steel in an argon-filled glove box to assemble a symmetrical blocking-type cell measurement system, and the room-temperature ac impedance r was measured with an electrochemical workstation, and the ion conductivity at room temperature was determined to be 4.2 × 10 by calculation with the formula ion conductivity σ ═ d/(r · s) (s is the area of the membrane)-4S/cm. And (3) taking stainless steel as a working positive electrode and metallic lithium as a counter electrode and a reference electrode, clamping the prepared electrolyte membrane in the middle to assemble the cell, standing the cell at room temperature for more than 6 hours, and performing linear sweep voltammetry test through an electrochemical workstation. The test voltage range of the linear sweep voltammetry test is 3-6.0V (vsLi)+/Li), scan rate of 0.1mVs-1The initial decomposition voltage was measured to be 4.7V (vs. Li)+/Li)。
The electrolyte assembly quasi-solid lithium battery obtained by the above examples was formed by stacking a negative electrode, a prepared polymer electrolyte, and a positive electrode in this order.
In the above technical solution, the positive electrode further includes a positive current collector, a positive active material, a conductive agent, and a binder. The positive active material comprises a ternary material, lithium cobaltate, lithium manganate, lithium iron phosphate, lithium cobalt phosphate, lithium iron silicate and a lithium-rich manganese-based solid solution material.
The negative electrode comprises a negative electrode current collector, a negative electrode active material, a conductive agent and a binder. The negative active material comprises one or more of graphite, silicon oxide, tin oxide, a silicon-carbon composite material, a tin-nickel alloy, lithium titanate or metal lithium foil and a lithium metal alloy.
Example 3
The selective wetting polymer electrolyte comprises, by mass, 35% of polyvinylidene fluoride-hexafluoropropylene copolymer, 25% of polypropylene acetate, 20% of lithium salt, 6% of fast ion conductor and 14% of sulfone small molecule additive. Wherein the lithium salt is lithium tetrafluoroborate, the fast ion conductor is LLZO, and the sulfone additive is ethyl isopropyl sulfone.
The preparation method of the polymer electrolyte comprises the following steps:
the method comprises the following steps: in a drying room, 3.5g of polyvinylidene fluoride-hexafluoropropylene copolymer, 2.5g of polypropylene acetate and 2.0g of lithium tetrafluoroborate are added into 100ml of a mixed solvent of anhydrous N, N-dimethylformamide and tetrahydrofuran (N, N-dimethylformamide accounts for 20% of the volume fraction of the mixed solvent) according to the above-mentioned dosage, stirred, dissolved and mixed uniformly;
step two: adding 0.6g of LLZO into the mixed solution, and performing ultrasonic treatment and stirring to uniformly disperse the mixed solution;
step three: uniformly pouring the mixed solution obtained in the step two or preparing an electrolyte membrane by using a scraper blade coating, and forming a self-supporting solid polymer electrolyte membrane after the mixed solvent is completely volatilized;
step four: adding 1.4g of ethyl isopropyl sulfone into the solid polymer electrolyte membrane obtained above, uniformly dispersing the ethyl isopropyl sulfone on the surface of the polymer electrolyte, and obtaining the final polymer electrolyte after the solvent and the polymer matrix are fully soaked and absorbed.
The thickness of the prepared polymer electrolyte membrane was about d 59 μm, and the prepared electrolyte membrane was sandwiched with stainless steel in an argon-filled glove box to assemble a symmetrical blocking-type cell measurement system, and the room-temperature ac impedance r was measured with an electrochemical workstation, and the ion conductivity at room temperature was determined to be 4.6 × 10 by calculation with the formula ion conductivity σ d/(r · s) (s is the area of the membrane)-4S/cm. Using stainless steel as working anode and goldThe prepared electrolyte membrane is clamped between a middle assembled battery, the battery is stood for more than 6 hours at room temperature, and linear sweep voltammetry test is carried out through an electrochemical workstation. The test voltage range of the linear sweep voltammetry test is 3-6.0V (vsLi)+/Li), scan rate of 0.1mVs-1The initial decomposition voltage was measured to be 4.9V (vs. Li)+/Li)。
The electrolyte assembly quasi-solid lithium battery obtained by the above examples was formed by stacking a negative electrode, a prepared polymer electrolyte, and a positive electrode in this order.
In the above technical solution, the positive electrode further includes a positive current collector, a positive active material, a conductive agent, and a binder. The positive active material comprises a ternary material, lithium cobaltate, lithium manganate, lithium iron phosphate, lithium cobalt phosphate, lithium iron silicate and a lithium-rich manganese-based solid solution material.
The negative electrode comprises a negative electrode current collector, a negative electrode active material, a conductive agent and a binder. The negative active material comprises one or more of graphite, silicon oxide, tin oxide, a silicon-carbon composite material, a tin-nickel alloy, lithium titanate or metal lithium foil and a lithium metal alloy.
Example 4
Selectively infiltrating a polymer electrolyte, wherein the polymer electrolyte comprises, by mass, 40% of polyvinylidene fluoride, 20% of allyl acetate, 20% of lithium salt, 6% of a fast ion conductor and 14% of a sulfone small molecular additive. Wherein the lithium salt is lithium trifluoromethanesulfonate, the fast ion conductor is LLZTO, and the sulfone additive is ethyl isopropyl sulfone.
The preparation method of the polymer electrolyte comprises the following steps:
the method comprises the following steps: in a drying room, adding 4.0g of polyvinylidene fluoride, 2.0g of allyl acetate and 2.0g of lithium trifluoromethanesulfonate into 100ml of a mixed solvent of anhydrous N, N-dimethylformamide and tetrahydrofuran (N, N-dimethylformamide accounts for 20% of the volume fraction of the mixed solvent) according to the above-mentioned dosage, stirring, dissolving and uniformly mixing;
step two: adding 0.6g of LLZTO into the mixed solution, performing ultrasonic treatment and stirring to uniformly disperse the mixed solution;
step three: uniformly pouring the mixed solution obtained in the step two or preparing an electrolyte membrane by using a scraper blade coating, and forming a self-supporting solid polymer electrolyte membrane after the mixed solvent is completely volatilized;
step four: adding 1.4g of ethyl isopropyl sulfone into the solid polymer electrolyte membrane obtained above, uniformly dispersing the ethyl isopropyl sulfone on the surface of the polymer electrolyte, and obtaining the final polymer electrolyte after the solvent and the polymer matrix are fully soaked and absorbed.
The thickness of the prepared polymer electrolyte membrane was about d 70 μm, and the prepared electrolyte membrane was sandwiched with stainless steel in an argon-filled glove box to assemble a symmetrical blocking-type cell measurement system, and the room-temperature ac impedance r was measured with an electrochemical workstation, and the ion conductivity at room temperature was determined to be 4.6 × 10 by calculation with the formula ion conductivity σ ═ d/(r · s) (s is the area of the membrane)-4S/cm. And (3) taking stainless steel as a working positive electrode and metallic lithium as a counter electrode and a reference electrode, clamping the prepared electrolyte membrane in the middle to assemble the cell, standing the cell at room temperature for more than 6 hours, and performing linear sweep voltammetry test through an electrochemical workstation. The test voltage range of the linear sweep voltammetry test is 3-6.0V (vsLi)+/Li), scan rate of 0.1mVs-1The initial decomposition voltage was measured to be 4.8V (vs. Li)+/Li)。
The electrolyte assembly quasi-solid lithium battery obtained by the above examples was formed by stacking a negative electrode, a prepared polymer electrolyte, and a positive electrode in this order.
In the above technical solution, the positive electrode further includes a positive current collector, a positive active material, a conductive agent, and a binder. The positive active material comprises a ternary material, lithium cobaltate, lithium manganate, lithium iron phosphate, lithium cobalt phosphate, lithium iron silicate and a lithium-rich manganese-based solid solution material.
The negative electrode comprises a negative electrode current collector, a negative electrode active material, a conductive agent and a binder.
The negative active material comprises one or more of graphite, silicon oxide, tin oxide, a silicon-carbon composite material, a tin-nickel alloy, lithium titanate or metal lithium foil and a lithium metal alloy.
Example 5:
selectively infiltrating a polymer electrolyte, wherein the polymer electrolyte comprises 40% of polyvinylidene fluoride-chlorotrifluoroethylene copolymer, 25% of polymethyl methacrylate, 15% of lithium salt, 6% of fast ion conductor and 14% of sulfone small molecule additive in percentage by mass. Wherein the lithium salt is lithium trifluoromethanesulfonate, the fast ion conductor is LLZO, and the sulfone additive is sulfolane.
The preparation method of the polymer electrolyte comprises the following steps:
the method comprises the following steps: in a drying room, adding 4.0g of polyvinylidene fluoride-chlorotrifluoroethylene copolymer, 2.5g of polymethyl methacrylate and 1.5g of lithium trifluoromethanesulfonate into 100ml of a mixed solvent of anhydrous N, N-dimethylformamide and tetrahydrofuran (N, N-dimethylformamide accounts for 20% of the volume fraction of the mixed solvent) according to the above-mentioned dosage, stirring, dissolving and uniformly mixing;
step two: adding 0.6g of LLZO into the mixed solution, and performing ultrasonic treatment and stirring to uniformly disperse the mixed solution;
step three: uniformly pouring the mixed solution obtained in the step two or preparing an electrolyte membrane by using a scraper blade coating, and forming a self-supporting solid polymer electrolyte membrane after the mixed solvent is completely volatilized;
step four: 1.4g of sulfolane is added into the solid polymer electrolyte membrane obtained in the above way, the sulfolane is uniformly dispersed on the surface of the polymer electrolyte, and the final polymer electrolyte is obtained after the solvent and the polymer matrix are fully soaked and absorbed.
The thickness of the prepared polymer electrolyte membrane was about d 64 μm, and the prepared electrolyte membrane was sandwiched with stainless steel in an argon-filled glove box to assemble a symmetrical blocking-type cell measurement system, and the room-temperature ac impedance r was measured with an electrochemical workstation, and the ion conductivity at room temperature was determined to be 4.3 × 10 by calculation with the formula ion conductivity σ ═ d/(r · s) (s is the area of the membrane)-4S/cm. And (3) taking stainless steel as a working positive electrode and metallic lithium as a counter electrode and a reference electrode, clamping the prepared electrolyte membrane in the middle to assemble the cell, standing the cell at room temperature for more than 6 hours, and performing linear sweep voltammetry test through an electrochemical workstation. Line scanThe test voltage range of the voltammetry test is 3-6.0V (vsLi)+/Li), scan rate of 0.1mVs-1The initial decomposition voltage was measured to be 4.9V (vs. Li)+/Li)。
The electrolyte assembly quasi-solid lithium battery obtained by the above examples was formed by stacking a negative electrode, a prepared polymer electrolyte, and a positive electrode in this order.
In the above technical solution, the positive electrode further includes a positive current collector, a positive active material, a conductive agent, and a binder. The positive active material comprises a ternary material, lithium cobaltate, lithium manganate, lithium iron phosphate, lithium cobalt phosphate, lithium iron silicate and a lithium-rich manganese-based solid solution material.
The negative electrode comprises a negative electrode current collector, a negative electrode active material, a conductive agent and a binder. The negative active material comprises one or more of graphite, silicon oxide, tin oxide, a silicon-carbon composite material, a tin-nickel alloy, lithium titanate or metal lithium foil and a lithium metal alloy.
The above embodiments are merely illustrative of the technical ideas and features of the present invention, and the purpose thereof is to enable those skilled in the art to understand the contents of the present invention and implement the present invention, and not to limit the protection scope of the present invention. All equivalent changes and modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.

Claims (10)

1. A selectively infiltrated polymer electrolyte, characterized by: the polymer electrolyte is composed of 30-80% of polyvinylidene fluoride material, 10-40% of polycarboxylate material, 5-50% of lithium salt, 1-20% of sulfone small molecular additive and 1-50% of inorganic fast ion conductor by mass percentage.
2. The polymer electrolyte of claim 1, wherein: the polymer electrolyte comprises, by mass, 35-50% of a polyvinylidene fluoride material, 20-30% of a polycarboxylate material, 10-30% of a lithium salt, 5-15% of a sulfone small molecular additive and 5-15% of an inorganic fast ion conductor.
3. The polymer electrolyte according to claim 1 or 2, characterized in that: the polyvinylidene fluoride material is a homopolymer of vinylidene fluoride (VDF) or a copolymer of the vinylidene fluoride (VDF) and a fluorine-containing vinyl monomer.
4. The polymer electrolyte according to claim 1 or 2, characterized in that: the polycarboxylate material is one or more of polyvinyl acetate, polymethyl methacrylate and polymethyl acrylate.
5. The polymer electrolyte according to claim 1 or 2, characterized in that: the lithium salt is one or more of lithium dioxalate borate, lithium tetrafluoroborate, lithium hexafluorophosphate, lithium dioxydifluorophosphate, lithium perchlorate, lithium hexafluoroarsenate, lithium trifluoromethylsulfonate, lithium bis (fluoromethanesulfonylimide), lithium bis (fluorosulfonimide) and lithium difluorooxalato borate.
6. The polymer electrolyte according to claim 1 or 2, characterized in that: the sulfone small molecular additive is R1-SO2-R2Or R1-SO-R2(ii) a wherein-S ═ O2-is sulfuryl, -S ═ O-is thionyl, R1、R2Identical or different from-CnH2n+1(n takes a value of 1-5) and-CnH2n-1(n takes a value of 2-5) and-CnH2n-3(n takes a value of 2-5) and-CnH2n- (n values 2-5), -C6H5，-C6H4-OH or-CH ═ CH-C6H5。
7. The polymer electrolyte according to claim 1 or 2, characterized in that: the inorganic fast ion conductor is Li7La3Zr2O12(LLZO)，LixLa2/3-xTiO3(LLTO)，Li1+xAlxTi2-x(PO4)3(LATP)，LiAlO2(LAO)，Li7-xLa3Zr2-xMxO12(M＝Ta,Nb,W)(0.25<x<2)(LLZMO)，Li7+xGexP3-xS11(LGPS)，xLi2S·(100-x)P2S5(LPS) one or more of them.
8. A method of preparing the selectively infiltrated polymer electrolyte of claim 1, wherein:
the method comprises the following steps: mixing the polyvinylidene fluoride material, the polycarboxylate material and the lithium salt according to the proportion, adding the mixture into a volatile anhydrous organic solvent, and dissolving and mixing the mixture uniformly;
step two: adding a fast ion conductor into the mixed solution, and performing ultrasonic treatment and stirring to uniformly disperse the mixed solution;
step three: uniformly pouring or blade-coating the mixed solution by using a scraper to prepare an electrolyte membrane, and obtaining a self-supporting solid polymer electrolyte membrane after the volatile anhydrous organic solvent is completely volatilized;
step four: and adding a sulfone small molecular additive into the obtained solid polymer electrolyte membrane, and obtaining the selectively infiltrated polymer electrolyte after the additive is fully absorbed by the polymer electrolyte.
9. Use of the polymer electrolyte of claim 1, wherein: the polymer electrolyte is applied to quasi-solid secondary lithium batteries (lithium ion batteries, lithium metal batteries and lithium sulfur batteries).
10. A quasi-solid-state secondary lithium battery includes a positive electrode and a negative electrode, characterized in that: interposed between the positive and negative electrodes is the polymer electrolyte of claim 1.
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