CN111244536A - Three-dimensional framework structure ceramic-polymer composite solid electrolyte and preparation method and application thereof - Google Patents

Three-dimensional framework structure ceramic-polymer composite solid electrolyte and preparation method and application thereof Download PDF

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CN111244536A
CN111244536A CN202010044314.7A CN202010044314A CN111244536A CN 111244536 A CN111244536 A CN 111244536A CN 202010044314 A CN202010044314 A CN 202010044314A CN 111244536 A CN111244536 A CN 111244536A
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llto
solid electrolyte
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吴勇军
林东良
黄玉辉
顾钰婷
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Zhejiang University ZJU
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Abstract

The invention discloses a three-dimensional framework structure ceramic-polymer composite solid electrolyte which comprises the following components in parts by weight: the three-dimensional skeleton structure ceramic is lithium lanthanum titanium oxygen ceramic LLTO, and the polymer comprises LiTFSI and PVDF-HFP. The invention also discloses a preparation method of the composite solid electrolyte, which comprises the following steps: preparing LLTO ceramic precursor slurry by a sol-gel method; preparing LLTO ceramic precursor fiber by an electrostatic spinning method; annealing and sintering to obtain a LLTO ceramic three-dimensional skeleton structure; and pouring the polymer sol dissolved with the bis (trifluoromethyl) sulfonyl imide lithium and the poly (vinylidene fluoride-hexafluoropropylene) into a LLTO ceramic three-dimensional skeleton structure to obtain the ceramic-polymer composite solid electrolyte with the three-dimensional skeleton structure. The invention also discloses application of the composite solid electrolyte in lithium ion batteries, lithium sulfur batteries and lithium air batteries. The composite electrolyte improves the conductivity of the electrolyte, can inhibit the generation of lithium dendrites, and ensures the safety performance of the solid-state battery.

Description

Three-dimensional framework structure ceramic-polymer composite solid electrolyte and preparation method and application thereof
Technical Field
The invention relates to the technical field of solid electrolyte materials for energy storage lithium ion batteries, in particular to a ceramic-polymer composite solid electrolyte with a three-dimensional framework structure and a preparation method and application thereof.
Background
Among various energy storage devices, lithium ion batteries have higher energy density and good power density, and lithium ions also have the characteristics of high working voltage, low self-discharge, long cycle life, greenness, no pollution and the like, and become an important direction in energy storage research. Commercial batteries on the market today are mainly liquid electrolyte lithium batteries. Since the liquid electrolyte is flammable and the diaphragm is easily pierced by lithium dendrites generated in the battery cycle process, the safety problem of the liquid electrolyte lithium battery is still very prominent, and thermal runaway is difficult to completely avoid. The solid lithium ion electrolyte is stable in chemical property and can not burn, so that the lithium ion battery can effectively avoid safety accidents.
The polymer solid electrolyte is generally formed by complexing polar macromolecules and metal salts, and is considered to be one of the most potential electrolytes for next-generation high-energy storage devices due to the advantages of high safety, mechanical flexibility, viscoelasticity, easiness in film formation and the like. Compared with a pure polymer solid electrolyte, the composite solid electrolyte has lower melting temperature (Tm) and glass transition temperature (Tg), so that the polymer chain segment has stronger moving capability, more lithium ion transmission channels and lower impedance. The partial oxide ceramic has larger lithium ion conductivity and has promotion effect on improving the dissociation degree of lithium salt in the composite solid electrolyte. In the aspect of solid electrolytes of lithium batteries, high lithium ion conductivity, high lithium ion mobility and high mechanical strength also make the oxide ceramic-polymer composite solid electrolytes get important attention.
Chinese patent application No. 201811635413.1 discloses a method for preparing an oxide ceramic-polymer composite solid electrolyte, which comprises the following steps: (1) preparing tantalum-doped garnet type oxide ceramic particles; (2) pomegranateThe stone-type ceramic particles are mixed with polymer electrolyte and lithium salt to prepare the composite solid electrolyte. The ionic conductivity of the particle composite electrolyte prepared by the method is up to 1.58 multiplied by 10 when measured at room temperature-4S/cm。
The above patent obtains a composite solid electrolyte by compounding garnet ceramic particles with a polymer electrolyte, and obtains a higher lithium ion conductivity because the added oxide ceramic reduces the crystallinity of the polymer electrolyte, increasing the active sites available for lithium ion conduction. However, the composite solid electrolyte added with oxide ceramic particles is too dense or too dispersed among the ceramic particles, and still cannot effectively form a large number of continuous and rapid lithium ion transmission channels, so how to construct a large number of continuous and rapid channels for lithium ions in a polymer through structural design and process improvement is a key for preparing the composite solid electrolyte with high lithium ion conductivity and low battery impedance.
Disclosure of Invention
The invention aims to provide a ceramic-polymer composite solid electrolyte with a three-dimensional skeleton structure and a preparation method thereof, which achieve the aim of increasing continuous lithium ion channels in the composite electrolyte, thereby improving the conductivity and safety performance of the composite solid electrolyte.
The invention provides the following technical scheme:
a three-dimensional framework structure ceramic-polymer composite solid electrolyte, wherein the three-dimensional framework structure ceramic is a lithium lanthanum titanium oxygen ceramic LLTO, and the polymer comprises LiTFSI and PVDF-HFP.
Preferably, the chemical composition of the lithium lanthanum titanium oxygen ceramic LLTO is Li3xLa2/3-xTiO3，0<x<0.16, x is the weight content; the chemical composition of the polymer is yLiTFSI + (1-y) PVDF-HFP, 0<y<0.5, and y is the weight content.
Further preferably, the LLTO ceramic has a chemical composition of Li0.33La0.557TiO3The chemical composition of the polymer electrolyte was 28.5 wt.% LiTFSI +71.5 wt.% PVDF-HFP.
The invention also provides a preparation method of the three-dimensional skeleton structure ceramic-polymer composite solid electrolyte, which comprises the following steps:
(1) preparing LLTO ceramic precursor slurry by a sol-gel method; the LLTO ceramic precursor slurry comprises Ti (C)4H9O)4Solution, LiAc and La (Ac)3Mixing the solution with a transparent sol of an organic polymer;
(2) preparing the LLTO ceramic precursor slurry obtained in the step (1) into LLTO ceramic precursor fibers with a three-dimensional network structure by using an electrostatic spinning method; the LLTO ceramic precursor fiber is a composite fiber of a LLTO ceramic precursor with a three-dimensional skeleton structure and an organic polymer;
(3) annealing and sintering the LLTO ceramic precursor fiber obtained in the step (2) to obtain a LLTO ceramic three-dimensional skeleton structure;
(4) and (3) pouring the polymer sol dissolved with lithium bis (trifluoromethyl sulfonyl imide) (LiTFSI) and poly (vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) in a LLTO ceramic three-dimensional skeleton structure, and drying in vacuum to obtain the ceramic-polymer composite solid electrolyte with the three-dimensional skeleton structure.
In the step (1), the method for preparing the LLTO ceramic precursor slurry by the sol-gel method comprises the following steps: mixing Ti (C)4H9O)4Dissolving in the mixture of ethylene glycol monomethyl ether and acetylacetone to obtain Ti (C)4H9O)4A solution; mixing LiAc and La (Ac)3Dissolved in water and CH3In the mixture of COOH, LiAc and La (Ac) were obtained3Mixing the solution; mixing Ti (C)4H9O)4Solution and LiAc and La (Ac)3Mixing the mixed solution, and simultaneously adding organic polymers of polyvinylpyrrolidone and polyether polyol to obtain mixed gel; and (3) placing the mixed sol in a water bath, stirring, heating and aging to obtain milky transparent sol which is LLTO precursor slurry.
Preferably, in the step (1), the volume ratio of ethylene glycol monomethyl ether to acetylacetone in the mixed solution of ethylene glycol methyl Ether (EM) and acetylacetone is 1:1 to 1: 3. Further preferably, the volume ratio of acetylacetone to ethylene glycol methyl Ether (EM) in the mixed solvent is 1: 2.
Preferably, in step (1), the real use mass of the LiAc is 5 wt.% to 30 wt.% more than the mass calculated from the target. Further preferably, the real use mass of the LiAc is 10 wt.% more than the mass calculated from the target.
Preferably, in step (1), the amount of PVP is 1.5-3.0 g and the amount of polyether F127 is 0.4-1.2 g per 40mL of LLTO precursor slurry. Further preferably, the amount of PVP used is 2.4g and the amount of polyether F127 used is 0.8g per 40mL of LLTO precursor slurry. By limiting the consumption of PVP in the precursor slurry, the viscosity of the precursor slurry can be controlled, so that the LLTO ceramic precursor fiber with more appropriate morphology can be obtained in the next step of electrostatic spinning.
Preferably, in the step (1), the water bath heating temperature of the mixed sol is 30-80 ℃, and the aging time is 6-48 h. Further preferably, the heating temperature of the mixed sol water bath is 50 ℃ and the aging time is 24 h.
In the step (2), the electrostatic spinning method comprises the following steps: stably injecting the precursor sol at a set rate by using an injector; the injected sol forms a Taylor cone at the needle mouth; and under the action of an electric field, stretching and drying by strong light irradiation, spinning into filaments and solidifying on a collecting substrate to prepare the LLTO ceramic precursor fiber with the three-dimensional network structure.
Wherein the rate of the injector for injecting the sol is 0.15 mL/h-0.50 mL/h. Preferably, the rate of sol injection from the syringe is 0.24 mL/h.
Preferably, the distance between the needle opening of the injector and the wire mesh collecting substrate is 5 cm-20 cm; the voltage between the needle opening of the injector and the wire netting collecting substrate is 15 kV-25 kV. Further preferably, the distance between the needle opening of the injector and the wire mesh collecting substrate is 10cm and 15 cm; the voltage between the syringe needle port and the wire netting collecting substrate is 17kV and 20 kV. By limiting the distance and the voltage, the LLTO ceramic precursor fibers with different morphologies can be obtained, and meanwhile, the LLTO ceramic three-dimensional skeleton structure with more proper morphology can be obtained in the next annealing and sintering step.
Preferably, in the step (3), the LLTO ceramic precursor fiber is annealed in the air atmosphere at the annealing temperature of 500-600 ℃ and sintered at 800-1100 ℃. Further preferably, the LLTO ceramic precursor fiber is annealed in air atmosphere at 600 deg.C and sintered at 800 deg.C, 900 deg.C, 1000 deg.C, 1100 deg.C. By adjusting the conditions, a more appropriate LLTO ceramic three-dimensional skeleton structure can be obtained and the skeleton structure has specific pores, so that the finally prepared composite solid electrolyte has better conductivity.
In the step (4), after the LiTFSI is dissolved in the N-methylpyrrolidone, the PVDF-HFP is added and stirred under the heating of a water bath, and a transparent light brown solution is obtained after complete dissolution and is used as the composite solid electrolyte slurry.
Preferably, in the step (4), PVDF-HFP is used as the polymer electrolyte, the mass ratio of LiTFSI to PVDF-HFP is 1: 5-1: 1, the solvent is NMP, the water bath heating temperature is 30-80 ℃, and the stirring time is 6-24 h. Further preferably, the mass ratio of the LiTFSI to the PVDF-HFP is 2:5, the water bath heating temperature is 60 ℃, and the stirring time is 12 h.
Preferably, in the step (5), the LLTO three-dimensional framework is compounded with the composite solid electrolyte slurry by using a casting method, and the drying temperature is 60 ℃ and the drying time is 12h under the vacuum condition.
The invention also provides application of the three-dimensional skeleton structure ceramic-polymer composite solid electrolyte in lithium ion batteries, lithium sulfur batteries and lithium air batteries.
Compared with the prior art, the invention has the beneficial effects that: the composite solid electrolyte with a three-dimensional skeleton structure comprises perovskite type oxide ceramics, polymer electrolyte and lithium salt. The preparation method realizes the preparation of the ceramic-polymer composite solid electrolyte with the three-dimensional framework structure by an electrostatic spinning method and a casting method, utilizes the distribution uniformity and continuity of ceramic fibers in the three-dimensional structure, and constructs a large number of continuous lithium ion rapid transmission channels on the polymer part of the composite electrolyte, thereby not only improving the conductivity of the electrolyte, but also inhibiting the generation of lithium dendrites.
Drawings
FIG. 1 is a schematic diagram of electrospinning;
FIG. 2 is a scanning electron microscope picture of ceramics obtained by electrostatic spinning under different PVP contents and different electric field conditions and sintering under different temperature conditions in examples 1-4: (a) PVP content 1.8g/40mL, collection distance 15cm, voltage between two poles 20kV (example 3); (b) PVP content 2.4g/40mL, collection distance 15cm, voltage between two poles 20kV (example 2); (c) PVP content 2.4g/40mL, collection distance 10cm, voltage between two poles 17kV (example 1); (d) the resulting ceramic skeleton was sintered at 1100 ℃ (example 4); (e) and (f) different regions of the three-dimensional ceramic skeleton obtained by sintering at 1000 ℃ (example 1).
Fig. 3 is a photograph of the composite solid electrolyte prepared in example 1: (a) an electron photograph of the composite solid electrolyte; (b) a surface micro-topography of the composite solid electrolyte; (c) a composite solid electrolyte cross-sectional morphology map; (d) the micro-morphology of the cross section of the composite solid electrolyte;
FIG. 4 is the XRD diffraction patterns of the ceramics obtained by sintering in example 4 under different temperature conditions (800 deg.C, 900 deg.C) and in example 1 under different temperature conditions (1000 deg.C);
fig. 5 is a polarization current curve and an ac impedance profile measured after assembling the three-dimensional skeleton-structured ceramic-polymer composite solid electrolyte prepared in example 1 into an S | CPE | S symmetric cell.
Detailed Description
The invention is further illustrated below with reference to specific examples.
Example 1
(1) Preparation of Li by sol-gel method0.33La0.557TiO3Precursor slurry: 3.404g of Ti (C) was weighed in accordance with the designed LLTO ceramic chemical formula4H9O)40.244g LiAc (10 wt.% excess) and 1.770g La (Ac)3(ii) a Mixing Ti (C)4H9O)4Dissolving in the mixed solution prepared by glycol methyl Ether (EM) and acetylacetone according to a specific proportion,stirring to be uniform to obtain Ti (C)4H9O)4A solution; mixing LiAc and La (Ac)3Dissolved in water and CH3COOH is mixed into the mixed liquid according to the specific proportion and stirred evenly to obtain LiAc and La (Ac)3Mixing the solution; mixing the two solutions, and simultaneously adding 2.4g of polyvinylpyrrolidone (PVP) and 0.8g of polyether polyol (polyether F127) to obtain a mixed sol; and (3) placing the mixed sol in a water bath, heating and stirring at 50 ℃, and aging for 24h to obtain 40mL of milky white transparent sol.
(2) Preparation of Li by electrostatic spinning method0.33La0.557TiO3Precursor fiber: subjecting the Li obtained in step (1)0.33La0.557TiO3And spinning and forming the precursor slurry under a proper condition through an electrostatic spinning device to obtain the precursor fiber. The schematic diagram of electrospinning is shown in fig. 1. The method specifically comprises the following steps: stably injecting the precursor sol at a set rate by using an injector; the injected sol forms a Taylor cone at the needle mouth; under the action of an electric field, polymer sol in the Taylor cone is stretched, dried by strong light irradiation, spun into filaments and solidified on a collecting substrate to prepare Li with a three-dimensional network structure0.33La0.557TiO3Precursor fiber. The electric field intensity is determined by the distance between the needle head and the collecting substrate and the voltage, the collecting distance is 10cm, and the voltage between the two poles is 17 kV. Li with three-dimensional network structure0.33La0.557TiO3The scanning electron microscope image of the precursor fiber is shown in fig. 2 (c).
(3) Pressing the precursor fiber prepared in the step (2) to a thickness by using a mold, annealing at 600 ℃ in a muffle furnace air atmosphere, and sintering at 1000 ℃ to prepare Li0.33La0.557TiO3And (3) a three-dimensional framework. Li after sintering at 1000 DEG C0.33La0.557TiO3Scanning electron micrographs of the three-dimensional skeleton are shown in (e) and (f) of FIG. 2.
(4) And preparing the composite solid electrolyte slurry. After 2.0g of LiTFSI was dissolved in 45ml of NMP, 5.0g of PVDF-HFP was added and stirred at 50 ℃ for 12 hours to obtain a clear pale brown solution after complete dissolution.
(5) The step (3) is to preparePrepared Li0.33La0.557TiO3And (4) fully compounding the three-dimensional framework and the composite solid electrolyte slurry prepared in the step (4) by a pouring method, and heating the mixture in a vacuum drying oven at 60 ℃ for 12 hours under a vacuum condition to obtain the high-lithium-ion-conductivity composite solid electrolyte with the three-dimensional framework structure.
Example 2
(1) Preparation of Li by sol-gel method0.33La0.557TiO3Precursor slurry: 3.404g of Ti (C) was weighed in accordance with the designed LLTO ceramic chemical formula4H9O)40.244g LiAc (10 wt.% excess) and 1.770g La (Ac)3(ii) a Mixing Ti (C)4H9O)4Dissolving in mixed solution prepared by ethylene glycol monomethyl Ether (EM) and acetylacetone according to a specific proportion, and stirring to be uniform to obtain Ti (C)4H9O)4A solution; mixing LiAc and La (Ac)3Dissolved in water and CH3COOH is mixed into the mixed liquid according to the specific proportion and stirred evenly to obtain LiAc and La (Ac)3Mixing the solution; mixing the two solutions, and simultaneously adding 2.4g of polyvinylpyrrolidone (PVP) and 0.8g of polyether polyol (polyether F127) to obtain a mixed sol; and (3) placing the mixed sol in a water bath, heating and stirring at 50 ℃, and aging for 24h to obtain 40mL of milky white transparent sol.
(2) Preparation of Li by electrostatic spinning method0.33La0.557TiO3Precursor fiber: subjecting the Li obtained in step (1)0.33La0.557TiO3And spinning and forming the precursor slurry under a proper condition through an electrostatic spinning device to obtain the precursor fiber. The method specifically comprises the following steps: stably injecting the precursor sol at a set rate by using an injector; the injected sol forms a Taylor cone at the needle mouth; under the action of an electric field, polymer sol in the Taylor cone is stretched, dried by strong light irradiation, spun into filaments and solidified on a collecting substrate to prepare Li with a three-dimensional network structure0.33La0.557TiO3Precursor fiber. The electric field intensity is determined by the distance between the needle head and the collecting substrate and the voltage, the collecting distance is 15cm, and the voltage between the two poles is 20 kV. Li with three-dimensional network structure0.33La0.557TiO3A scanning electron micrograph of the precursor fiber is shown in fig. 2 (b).
(3) Pressing the precursor fiber prepared in the step (2) to a thickness by using a mold, annealing at 600 ℃ in a muffle furnace air atmosphere, and sintering at 1000 ℃ to prepare Li0.33La0.557TiO3And (3) a three-dimensional framework.
(4) And preparing the composite solid electrolyte slurry. After 2.0g of LiTFSI was dissolved in 45ml of NMP, 5.0g of PVDF-HFP was added and stirred at 50 ℃ for 12 hours to obtain a clear pale brown solution after complete dissolution.
(5) Li prepared in the step (3)0.33La0.557TiO3And (4) fully compounding the three-dimensional framework and the composite solid electrolyte slurry prepared in the step (4) by a pouring method, and heating the mixture in a vacuum drying oven at 60 ℃ for 12 hours under a vacuum condition to obtain the high-lithium-ion-conductivity composite solid electrolyte with the three-dimensional framework structure.
Example 3
(1) Preparation of Li by sol-gel method0.33La0.557TiO3Precursor slurry: 3.404g of Ti (C) was weighed in accordance with the designed LLTO ceramic chemical formula4H9O)40.244g LiAc (10 wt.% excess) and 1.770g La (Ac)3(ii) a Mixing Ti (C)4H9O)4Dissolving in mixed solution prepared by ethylene glycol monomethyl Ether (EM) and acetylacetone according to a specific proportion, and stirring to be uniform to obtain Ti (C)4H9O)4A solution; mixing LiAc and La (Ac)3Dissolved in water and CH3COOH is mixed into the mixed liquid according to the specific proportion and stirred evenly to obtain LiAc and La (Ac)3Mixing the solution; mixing the two solutions, and simultaneously adding 1.6g of polyvinylpyrrolidone (PVP) and 0.8g of polyether polyol (polyether F127) to obtain a mixed sol; and (3) placing the mixed sol in a water bath, heating and stirring at 50 ℃, and aging for 24h to obtain 40mL of milky white transparent sol.
(2) Preparation of Li by electrostatic spinning method0.33La0.557TiO3Precursor fiber: subjecting the Li obtained in step (1)0.33La0.557TiO3The precursor slurry is passed through an electrostatic spinning device, and then the precursor slurry is properly mixed with the slurrySpinning and forming under the condition to obtain precursor fiber. The method specifically comprises the following steps: stably injecting the precursor sol at a set rate by using an injector; the injected sol forms a Taylor cone at the needle mouth; under the action of an electric field, polymer sol in the Taylor cone is stretched, dried by strong light irradiation, spun into filaments and solidified on a collecting substrate to prepare Li with a three-dimensional network structure0.33La0.557TiO3Precursor fiber. The electric field intensity is determined by the distance between the needle head and the collecting substrate and the voltage, the collecting distance is 10cm, and the voltage between the two poles is 17 kV. Li with three-dimensional network structure0.33La0.557TiO3A scanning electron micrograph of the precursor fiber is shown in fig. 2 (a).
(3) Pressing the precursor fiber prepared in the step (2) to a thickness by using a mold, annealing at 600 ℃ in a muffle furnace air atmosphere, and sintering at 900 ℃ to prepare Li0.33La0.557TiO3And (3) a three-dimensional framework.
(4) And preparing the composite solid electrolyte slurry. After 2.0g of LiTFSI was dissolved in 45ml of NMP, 5.0g of PVDF-HFP was added and stirred at 50 ℃ for 12 hours to obtain a clear pale brown solution after complete dissolution.
(5) Li prepared in the step (3)0.33La0.557TiO3And (4) fully compounding the three-dimensional framework and the composite solid electrolyte slurry prepared in the step (4) by a pouring method, and heating the mixture in a vacuum drying oven at 60 ℃ for 12 hours under a vacuum condition to obtain the high-lithium-ion-conductivity composite solid electrolyte with the three-dimensional framework structure.
Example 4
(1) Preparation of Li by sol-gel method0.33La0.557TiO3Precursor slurry: 3.404g of Ti (C) was weighed in accordance with the designed LLTO ceramic chemical formula4H9O)40.244g LiAc (10 wt.% excess) and 1.770g La (Ac)3(ii) a Mixing Ti (C)4H9O)4Dissolving in mixed solution prepared by ethylene glycol monomethyl Ether (EM) and acetylacetone according to a specific proportion, and stirring to be uniform to obtain Ti (C)4H9O)4A solution; mixing LiAc and La (Ac)3Dissolved in water and CH3COOH is oneStirring the mixture in a certain proportion until the mixture is uniform to obtain LiAc and La (Ac)3Mixing the solution; mixing the two solutions, and simultaneously adding 2.4g of polyvinylpyrrolidone (PVP) and polyether polyol (polyether F127) to obtain mixed sol; and (3) placing the mixed sol in a water bath, heating and stirring at 50 ℃, and aging for 24h to obtain 40mL of milky white transparent sol.
(2) Preparation of Li by electrostatic spinning method0.33La0.557TiO3Precursor fiber: subjecting the Li obtained in step 10.33La0.557TiO3And spinning and forming the precursor slurry under a proper condition through an electrostatic spinning device to obtain the precursor fiber. The method specifically comprises the following steps: stably injecting the precursor sol at a set rate by using an injector; the injected sol forms a Taylor cone at the needle mouth; under the action of an electric field, polymer sol in the Taylor cone is stretched, dried by strong light irradiation, spun into filaments and solidified on a collecting substrate to prepare Li with a three-dimensional network structure0.33La0.557TiO3Precursor fiber. The electric field intensity is determined by the distance between the needle head and the collecting substrate and the voltage, the collecting distance is 10cm, and the voltage between the two poles is 17 kV.
(3) Pressing the precursor fiber prepared in the step (2) to a thickness by using a mould, annealing at 600 ℃ in a muffle furnace air atmosphere, and sintering at 800 ℃, 900 ℃ and 1100 ℃ to prepare Li0.33La0.557TiO3And (3) a three-dimensional framework. Wherein Li is obtained by sintering at 800 ℃ and 900 DEG C0.33La0.557TiO3The XRD diffraction pattern of the three-dimensional framework is shown in FIG. 4 (the ordinate is intensity), Li obtained by sintering at 1100 ℃0.33La0.557TiO3The scanning electron micrograph of the three-dimensional skeleton is shown in fig. 2 (d).
(4) And preparing the composite solid electrolyte slurry. After 2.0g of LiTFSI was dissolved in 45ml of NMP, 5.0g of PVDF-HFP was added and stirred at 50 ℃ for 12 hours to obtain a clear pale brown solution after complete dissolution.
(5) Li prepared in the step (3)0.33La0.557TiO3Fully compounding the three-dimensional framework and the composite solid electrolyte slurry prepared in the step (4) by a casting methodAnd (3) after the combination, heating the mixture for 12 hours in a vacuum drying oven at the temperature of 60 ℃ under the vacuum condition to obtain the high-lithium-ion-conductivity composite solid electrolyte with the three-dimensional framework structure.
Comparative example 1
(1) Preparation of Li by common solid phase method0.33La0.557TiO3Ceramic particles: adding a proper amount of Li2CO3、La2O3、TiO2Adding into a ball milling tank, and ball milling for 24h by taking deionized water as a ball milling medium to obtain Li with sufficient uniformity and smaller granularity0.33La0.557TiO3Precursor powder; pre-sintering at 1150 ℃ in a muffle furnace, and preserving heat for 3h to obtain Li0.33La0.557TiO3A single phase ceramic powder; fully grinding the single-phase powder, and sieving the powder with a 300-mesh sieve to obtain Li with the particle size of about 10-50 mu m0.33La0.557TiO3A single phase powder;
(2) and preparing the composite solid electrolyte slurry. After 2.0g of LiTFSI was dissolved in 45ml of NMP, 5.0g of PVDF-HFP was added and stirred at 50 ℃ for 12 hours to obtain a clear pale brown solution after complete dissolution.
(3) And (3) fully stirring and mixing the micron-sized ceramic powder prepared in the step (1) and the composite solid electrolyte slurry prepared in the step (2) to obtain the ceramic-polymer composite solid electrolyte slurry.
(4) And (3) preparing the ceramic-polymer composite solid electrolyte slurry prepared in the step (3) into a composite solid electrolyte membrane by a tape casting method, and heating the composite solid electrolyte membrane in a vacuum drying oven at the temperature of 60 ℃ for 12 hours under a vacuum condition to obtain a dried ceramic particle composite solid electrolyte membrane.
Comparative example 2
(1) And preparing the polymer solid electrolyte slurry. After 2.0g of LiTFSI was dissolved in 45ml of NMP, 5.0g of PVDF-HFP was added and stirred at 50 ℃ for 12 hours to obtain a clear pale brown solution after complete dissolution.
(2) And (2) preparing the polymer solid electrolyte slurry prepared in the step (1) into a polymer solid electrolyte membrane by a tape casting method, and heating the polymer solid electrolyte membrane in a vacuum drying oven at 60 ℃ for 12h under a vacuum condition to obtain a dried polymer solid electrolyte membrane.
The microstructure and chemical composition of examples 1 to 4 were analyzed by SEM and XRD, respectively, to analyze the influence on the performance of the composite solid electrolyte. The composite solid electrolyte prepared in the examples 1-4 and the comparative examples 1-2 is assembled with a stainless steel sheet to form an S | CPE | S symmetrical battery, the alternating current impedance performance and the electrochemical polarization curve of the battery are tested by an Ivium electrochemical workstation in the Netherlands, and the lithium ion conductivity and the lithium ion mobility of the composite electrolyte are obtained through calculation. The polarization current curve and the ac impedance obtained by the test after the three-dimensional framework structure ceramic-polymer composite solid electrolyte prepared in example 1 is assembled into a Li | CPE | Li symmetric battery are shown in fig. 5 (the ordinate is current, the abscissa is time, and before polarization and after polarization refer to pre-polarization and post-polarization, respectively).
Table 1 is a table comparing the properties of the ceramic-polymer composite solid electrolyte having a three-dimensional skeleton structure prepared in example 1 with those of the ceramic particle composite solid electrolyte prepared in comparative example 1 and the polymer solid electrolyte prepared in comparative example 2. The three-dimensional framework structure ceramic-polymer composite solid electrolyte prepared in the embodiment 1 is improved in lithium ion migration number and lithium ion conductivity, and the expected effect of a large number of designed continuous lithium ion rapid transmission channels is achieved.
As can be seen from Table 1, the lithium ion conductivity of the ceramic-polymer composite solid electrolyte with the three-dimensional framework structure prepared in example 1 can reach more than 1.71 multiplied by 10 < -4 > S/cm at room temperature, and compared with a pure PVDF-HFP polymer electrolyte without adding LLTO ceramic, the lithium ion conductivity at room temperature is improved by 77.7 percent; compared with PVDF-HFP polymer electrolyte added with similar LLTO ceramic particles, the lithium ion conductivity at room temperature is improved by 23.9 percent.
TABLE 1 Properties of solid electrolytes prepared in example 1 and comparative examples 1 to 2
Figure BDA0002368832310000121

Claims (9)

1. The ceramic-polymer composite solid electrolyte with the three-dimensional framework structure is characterized in that the ceramic with the three-dimensional framework structure is lithium lanthanum titanium oxygen ceramic LLTO, and the polymer comprises LiTFSI and PVDF-HFP.
2. The three-dimensional skeletal structure ceramic-polymer composite solid-state electrolyte of claim 1, wherein the chemical composition of the lithium lanthanum titanium oxygen ceramic LLTO is Li3xLa2/3-xTiO3，0<x<0.16, x is the weight content; the chemical composition of the polymer is yLiTFSI + (1-y) PVDF-HFP, 0<y<0.5, and y is the weight content.
3. A method for producing the three-dimensional skeleton-structured ceramic-polymer composite solid-state electrolyte according to claim 1 or 2, characterized by comprising the steps of:
(1) preparing LLTO ceramic precursor slurry by a sol-gel method; the LLTO ceramic precursor slurry comprises Ti (C)4H9O)4Solution, LiAc and La (Ac)3Mixing the solution with a transparent sol of an organic polymer;
(2) preparing the LLTO ceramic precursor slurry obtained in the step (1) into LLTO ceramic precursor fibers with a three-dimensional network structure by using an electrostatic spinning method; the LLTO ceramic precursor fiber is a composite fiber of a LLTO ceramic precursor with a three-dimensional skeleton structure and an organic polymer;
(3) annealing and sintering the LLTO ceramic precursor fiber obtained in the step (2) to obtain a LLTO ceramic three-dimensional skeleton structure;
(4) and (3) pouring the polymer sol dissolved with the bis (trifluoromethyl) sulfonyl imide lithium and the poly (vinylidene fluoride-hexafluoropropylene) into a LLTO ceramic three-dimensional skeleton structure, and drying in vacuum to obtain the ceramic-polymer composite solid electrolyte with the three-dimensional skeleton structure.
4. The method for preparing the ceramic-polymer composite solid electrolyte having a three-dimensional skeletal structure according to claim 3, wherein the LLTO ceramic precursor slurry is prepared by a sol-gel method in the step (1) by: mixing Ti (C)4H9O)4Soluble in glycol methyl ether and acetyl acetoneObtaining Ti (C) in the mixed solution4H9O)4A solution; mixing LiAc and La (Ac)3Dissolved in water and CH3In the mixture of COOH, LiAc and La (Ac) were obtained3Mixing the solution; mixing Ti (C)4H9O)4Solution and LiAc and La (Ac)3Mixing the mixed solution, and simultaneously adding organic polymers of polyvinylpyrrolidone and polyether polyol to obtain mixed gel; and (3) placing the mixed sol in a water bath, stirring, heating and aging to obtain milky transparent sol which is LLTO precursor slurry.
5. The method of claim 4, wherein the PVP is 1.5-3.0 g and the polyether F127 is 0.4-1.2 g per 40mL of the LLTO precursor slurry in the step (1).
6. The method for preparing a ceramic-polymer composite solid electrolyte with a three-dimensional skeleton structure according to claim 3, wherein in the step (2), the electrospinning method comprises: stably injecting the precursor sol at a set rate by using an injector; the injected sol forms a Taylor cone at the needle mouth; and under the action of an electric field, stretching and drying by strong light irradiation, spinning into filaments and solidifying on a collecting substrate to prepare the LLTO ceramic precursor fiber with the three-dimensional network structure.
7. The method for preparing the ceramic-polymer composite solid electrolyte with the three-dimensional framework structure according to claim 6, wherein the distance between the needle opening of the injector and the wire collecting substrate is 5 cm-20 cm; the voltage between the needle opening of the injector and the wire netting collecting substrate is 15 kV-25 kV.
8. The method of claim 3, wherein in the step (3), the LLTO ceramic precursor fiber is annealed in an air atmosphere at an annealing temperature of 500 to 600 ℃ and sintered at 800 to 1100 ℃.
9. Use of the three-dimensional skeletal structure ceramic-polymer composite solid electrolyte according to any one of claims 1 to 8 in lithium ion batteries, lithium sulfur batteries and lithium air batteries.
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