阅读说明：本技术 一种复合固态电解质及制备方法 (Composite solid electrolyte and preparation method thereof ) 是由 邬佳杰 周晶晶 郭炳焜 于 2020-05-14 设计创作，主要内容包括：一种复合固态电解质及制备方法,所述复合固态电解质具有连续锂离子快速传导通路,包括：无机固态电解质多孔微球、聚合物和锂盐,所述复合固态电解质以无机固态电解质多孔微球为填料,所述无机固态电解质多孔微球利用喷雾干燥法制备；所述聚合物具有导锂离子能力。以及复合固态电解质的制备方法。本发明针对目前高陶瓷含量的复合固态电解质中因纳米陶瓷颗粒团聚导致的锂离子电导率低以及机械性能较差的问题,提供一种具有连续锂离子快速传导通路的复合固态电解质及制备方法,目的在于提高固态电解质的锂离子电导率的同时,改善电解质的机械性能和界面问题,为全固态电池的制备奠定基础。(A composite solid electrolyte and a preparation method thereof, the composite solid electrolyte has a continuous lithium ion rapid conduction path and comprises: the composite solid electrolyte comprises inorganic solid electrolyte porous microspheres, a polymer and lithium salt, wherein the inorganic solid electrolyte porous microspheres are used as a filler, and the inorganic solid electrolyte porous microspheres are prepared by a spray drying method; the polymer has the capability of conducting lithium ions. And a method for preparing the composite solid electrolyte. The invention provides a composite solid electrolyte with a continuous lithium ion rapid conduction path and a preparation method thereof, aiming at solving the problems of low lithium ion conductivity and poor mechanical property caused by the agglomeration of nano ceramic particles in the conventional composite solid electrolyte with high ceramic content, aiming at improving the lithium ion conductivity of the solid electrolyte and simultaneously improving the mechanical property and interface problem of the electrolyte and laying a foundation for the preparation of an all-solid-state battery.)

1. A composite solid state electrolyte having a continuous lithium ion fast conduction path, comprising: inorganic solid electrolyte porous microspheres, a polymer and a lithium salt;

the composite solid electrolyte takes inorganic solid electrolyte porous microspheres as a filler, and the inorganic solid electrolyte porous microspheres are prepared by a spray drying method;

the polymer has the capability of conducting lithium ions;

the mass percentage of the inorganic solid electrolyte porous microspheres in the composite solid electrolyte is 45-80%, the mass percentage of the polymer in the composite solid electrolyte is 10-45%, and the mass percentage of the lithium salt in the composite solid electrolyte is 5-40%.

2. The composite solid electrolyte according to claim 1, wherein the inorganic solid electrolyte porous microspheres are at least one of garnet-type, NASICON-type, LISICON-type, perovskite-type, anti-perovskite-type, or sulfide inorganic solid electrolyte porous microspheres.

3. The composite solid electrolyte according to claim 2, wherein the inorganic solid electrolyte porous microspheres have a particle size of 1 to 50 μm.

4. The composite solid-state electrolyte of claim 3, wherein the polymer is at least one of a polyethylene oxide-based polymer, a polysiloxane-based polymer, a polycarbonate-based polymer, polyvinylidene fluoride, or polyacrylonitrile.

5. The composite solid electrolyte of claim 4, wherein the lithium salt is lithium perchlorate (LiClO)₄) Lithium hexafluorophosphate (LiPF)₆) Lithium bistrifluoromethylsulfonyl imide (LiTFSI), lithium bistrifluorosulfonimide (LiFSI), lithium trifluoromethanesulfonate (LiCF)₃SO₃) At least one of lithium bis (oxalato) borate (LiBOB) or lithium difluoro (oxalato) borate (lidob).

6. A method of producing a composite solid electrolyte according to any one of claims 1 to 5, comprising the steps of:

step S100, preparing inorganic solid electrolyte porous microspheres by using a spray drying method, and calcining the inorganic solid electrolyte porous microspheres in air at a controlled temperature to obtain calcined inorganic solid electrolyte porous microspheres;

step S200, adding a polymer with lithium ion conductivity and a lithium salt into a solvent, wherein the mass ratio of a solute to the solvent is 5-50%, and uniformly stirring at a certain temperature to obtain a uniform and viscous solution;

step S300, adding the calcined inorganic solid electrolyte porous microspheres into the solution, and fully stirring for a certain time to obtain a uniform suspension;

and S400, pouring or casting the suspension into a substrate or a mold, standing for a certain time to enable the suspension to be leveled, quickly transferring the suspension into a vacuum drying oven, drying the suspension in the vacuum drying oven, stripping the composite solid electrolyte membrane from the substrate or the mold, and cutting the composite solid electrolyte membrane into a wafer to obtain the composite solid electrolyte.

7. The method of producing a composite solid electrolyte of claim 6, wherein the substrate is a polyester resin (PET) substrate and the mold is a Polytetrafluoroethylene (PTFE) mold.

8. The method according to claim 7, wherein in step S200, the solvent is one or more selected from dimethylformamide, ethanol, acetone, tetrahydrofuran, and acetonitrile.

9. The method for preparing a composite solid electrolyte according to claim 8, wherein in step S100, the calcination temperature is 500 ℃ to 1000 ℃ and the calcination time is 0.5h to 5 h; in step S200, the temperature is 50-80 ℃; in step S300, fully stirring for 3 hours to obtain a uniform suspension; in the step S400, the standing time is 8min-12min, the drying temperature is-20-80 ℃, and the diameter of the wafer is 18 mm.

10. A method of manufacturing a battery using the composite solid electrolyte according to any one of claims 1 to 5, comprising the steps of: and assembling the composite solid electrolyte and a positive and negative electrode shell of the battery into the battery.

Technical Field

The invention relates to the technical field of solid electrolytes of lithium ion batteries, in particular to a composite solid electrolyte with a continuous lithium ion rapid conduction path and a preparation method thereof.

Background

The lithium ion battery has the advantages of high energy density, long service life, light weight and the like, and is widely applied to portable electronic equipment and new energy automobiles. However, the flammable organic electrolyte used in the current commercial lithium ion battery has a great safety hazard, and the battery can be burnt or even exploded under the condition of thermal runaway. Although the safety can be improved to some extent by adding flame retardants, electrode materials, membrane optimization and the like, the potential safety hazard cannot be completely eliminated. The inflammable liquid electrolyte is replaced by the solid electrolyte which is not easy to burn and volatilize, so that the safety can be fundamentally ensured. Meanwhile, the solid electrolyte has higher stability, can be matched with high-energy-density electrode materials such as a high-voltage anode, a lithium metal cathode and the like, and improves the energy density of the battery.

However, the lithium ion conductivity of the solid electrolyte and the interface problem between the solid electrolyte and the electrode limit the stable operation of the solid-state battery. The inorganic/polymer composite electrolyte has the flexibility of polymer and the stability of inorganic matters, and is one of the most promising solid electrolyte materials at present. Particularly, the inorganic solid electrolyte ensures that the composite solid electrolyte has better mechanical stability and thermal stability, and the safety performance and the interface stability of the composite solid electrolyte are higher. In addition, in the high ceramic content composite solid electrolyte, lithium ions tend to be transported at the inorganic solid electrolyte phase and the polymer-inorganic interface, but the high content of inorganic solid electrolyte nano particles directly added into the composite solid electrolyte easily causes non-uniform agglomeration of particles, so that the transportation of lithium ions is hindered, and the lithium ion conductivity of the composite solid electrolyte is reduced.

Disclosure of Invention

Aiming at the problems of low lithium ion conductivity and poor mechanical property caused by the agglomeration of nano ceramic particles in the conventional high-ceramic-content composite solid electrolyte, the invention provides the composite solid electrolyte with the continuous lithium ion rapid conduction path and a preparation method thereof, aiming at improving the lithium ion conductivity of the solid electrolyte and simultaneously improving the mechanical property and the interface problem of the electrolyte and laying a foundation for the preparation of an all-solid-state battery.

The invention is realized by adopting the following technical scheme:

a first aspect of the invention provides a composite solid-state electrolyte having a continuous lithium ion fast conduction path, comprising: inorganic solid electrolyte porous microspheres, a polymer and a lithium salt;

the composite solid electrolyte takes inorganic solid electrolyte porous microspheres as a filler, and the inorganic solid electrolyte porous microspheres are prepared by a spray drying method;

the polymer has the capability of conducting lithium ions;

the mass percentage of the inorganic solid electrolyte porous microspheres in the composite solid electrolyte is 45-80%, the mass percentage of the polymer in the composite solid electrolyte is 10-45%, and the mass percentage of the lithium salt in the composite solid electrolyte is 5-40%.

Further, the inorganic solid electrolyte porous microspheres are at least one of garnet type, NASICON type, LISICON type, perovskite type, anti-perovskite type or sulfide inorganic solid electrolyte porous microspheres.

Further, the particle size of the inorganic solid electrolyte porous microspheres is 1-50 μm.

Further, the polymer is at least one of polyethylene oxide-based polymer, polysiloxane-based polymer, polycarbonate-based polymer, polyvinylidene fluoride, or polyacrylonitrile.

Further, the lithium salt is lithium perchlorate (LiClO)₄) Lithium hexafluorophosphate (LiPF)₆) Lithium bistrifluoromethylsulfonyl imide (LiTFSI), lithium bistrifluorosulfonimide (LiFSI), lithium trifluoromethanesulfonate (LiCF)₃SO₃) At least one of lithium bis (oxalato) borate (LiBOB) or lithium difluoro (oxalato) borate (lidob).

A second aspect of the present invention provides a method for preparing the composite solid electrolyte as described above, comprising the steps of:

step S100, preparing inorganic solid electrolyte porous microspheres by using a spray drying method, and calcining the inorganic solid electrolyte porous microspheres in air at a controlled temperature to obtain calcined inorganic solid electrolyte porous microspheres;

step S200, adding a polymer with lithium ion conductivity and a lithium salt into a solvent, wherein the mass ratio of a solute to the solvent is 5-50%, and uniformly stirring at a certain temperature to obtain a uniform and viscous solution;

step S300, adding the calcined inorganic solid electrolyte porous microspheres into the solution, and fully stirring for a certain time to obtain a uniform suspension;

and S400, pouring or casting the suspension into a substrate or a mold, standing for a certain time to enable the suspension to be leveled, quickly transferring the suspension into a vacuum drying oven, drying the suspension in the vacuum drying oven, stripping the composite solid electrolyte membrane from the substrate or the mold, and cutting the composite solid electrolyte membrane into a wafer to obtain the composite solid electrolyte.

Further, the substrate is a polyester resin (PET) substrate and the mold is a Polytetrafluoroethylene (PTFE) mold.

Further, in step S200, the solvent is one or more of dimethylformamide, ethanol, acetone, tetrahydrofuran, and acetonitrile.

Further, in step S100, the calcining temperature is 500-1000 ℃, and the calcining time is 0.5-5 h; in step S200, the temperature is 50-80 ℃; in step S300, fully stirring for 3 hours to obtain a uniform suspension; in the step S400, the standing time is 8min-12min, the drying temperature is-20-80 ℃, and the diameter of the wafer is 18 mm.

The invention also provides a method for preparing a battery by applying the composite solid electrolyte, and the composite solid electrolyte and a positive and negative electrode shell of the battery are assembled into the battery.

In summary, the present invention provides a composite solid electrolyte and a preparation method thereof, wherein the composite solid electrolyte has a continuous lithium ion fast conduction path, and the preparation method comprises: the composite solid electrolyte comprises inorganic solid electrolyte porous microspheres, a polymer and lithium salt, wherein the inorganic solid electrolyte porous microspheres are used as a filler, and the inorganic solid electrolyte porous microspheres are prepared by a spray drying method; the polymer has the capability of conducting lithium ions. And a method for preparing the composite solid electrolyte. The invention provides a composite solid electrolyte with a continuous lithium ion rapid conduction path and a preparation method thereof, aiming at solving the problems of low lithium ion conductivity and poor mechanical property caused by the agglomeration of nano ceramic particles in the conventional composite solid electrolyte with high ceramic content, aiming at improving the lithium ion conductivity of the solid electrolyte and simultaneously improving the mechanical property and interface problem of the electrolyte and laying a foundation for the preparation of an all-solid-state battery.

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

1. the invention solves the problem that a large amount of nano particles can be agglomerated in a composite solid electrolyte in a disordered way, the three-dimensional framework formed by the secondary particles has better mechanical strength and electrochemical stability, the continuity of a lithium ion transmission channel can be still kept in the bending process, and the invention can be well applied to flexible batteries. The composite solid electrolyte with the optimal lithium ion conductivity is obtained by regulating and controlling the content of the inorganic solid electrolyte porous microspheres, and a solid lithium ion battery prepared by utilizing the composite solid electrolyte has the characteristics of high capacity and good cycle performance;

2. the invention prepares inorganic solid electrolyte porous microspheres by spray drying, and prepares the composite solid electrolyte with continuous lithium ion rapid conduction paths by using a solvent evaporation method. The inorganic solid electrolyte porous microspheres form a continuous lithium ion rapid conduction path in the composite solid electrolyte through a seepage model, so that lithium ions can be transmitted through an inorganic solid electrolyte phase and a polymer-inorganic interface, and the lithium ion conductivity of the composite electrolyte is obviously improved;

3. compared with nano inorganic electrolyte particles, the inorganic solid electrolyte porous microspheres prepared by spray drying have larger specific surface area and particle size, can form a three-dimensional framework in the composite solid electrolyte, and can effectively prevent the reduction of lithium ion conductivity and mechanical property caused by the nonuniform agglomeration of nano particles;

4. the continuous lithium ion rapid conduction channel formed by the inorganic solid electrolyte porous microspheres and the interface can keep the continuity of the channel under the deformation action of bending and the like, and has good mechanical stability;

5. the composite solid electrolyte has the advantages of simple raw materials, multiple varieties, strong selectivity and controllable cost;

6. the composite solid electrolyte has controllable size and thickness, good flexibility and mechanical stability;

7. the preparation method of the composite solid electrolyte has strong universality, simple used equipment and environmental friendliness, and is suitable for industrial and large-scale commercial application.

Drawings

FIG. 1 is a schematic structural view of a composite solid electrolyte having a continuous lithium ion fast conduction path;

FIG. 2 is a view showing the LLZTO porous microsphere prepared by spray drying in example 1 of the present invention;

FIG. 3 is an SEM photograph of a composite solid electrolyte according to example 1 of the present invention;

FIG. 4 is an SEM photograph of a composite solid electrolyte according to example 2 of the present invention;

fig. 5 is an XRD pattern of the composite solid electrolyte according to examples 1 and 2 of the present invention;

fig. 6 is a temperature swing lithium ion conductivity curve of the composite solid state electrolyte according to examples 1 and 2 of the present invention;

fig. 7 is a temperature swing lithium ion conductivity curve of the composite solid state electrolytes described in comparative example 1 and comparative example 2 of the present invention;

fig. 8 is a flow chart of a method for preparing the composite solid electrolyte having a continuous lithium ion rapid conduction path according to the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the accompanying drawings in conjunction with the following detailed description. It should be understood that the description is intended to be exemplary only, and is not intended to limit the scope of the present invention. Moreover, in the following description, descriptions of well-known structures and techniques are omitted so as to not unnecessarily obscure the concepts of the present invention.

A first aspect of the present invention provides a composite solid-state electrolyte having a continuous lithium ion rapid conduction path, the composite solid-state electrolyte comprising: inorganic solid electrolyte porous microspheres, polymer with lithium ion conducting capacity and lithium salt. The inorganic solid electrolyte porous microspheres are prepared by a spray drying method, the composite solid electrolyte takes the inorganic solid electrolyte porous microspheres as a filler, the mass percentage of the inorganic solid electrolyte porous microspheres in the composite solid electrolyte is 45-80%, the mass percentage of a polymer with the lithium ion conducting capacity in the composite solid electrolyte is 10-45%, and the mass percentage of lithium salt in the composite solid electrolyte is 5-40%. As shown in fig. 3 and 4.

The inorganic solid electrolyte porous microspheres are prepared by a spray drying method, nano inorganic solid electrolyte particles are prepared into secondary particles with a porous structure by the spray drying method, and by utilizing the characteristics of large specific surface area and continuous crystal grains of the secondary particles, a continuous lithium ion rapid conduction path of a bulk phase and a polymer-inorganic interface is formed in the composite electrolyte, so that the lithium ion conductivity of the composite solid electrolyte is obviously improved.

Specifically, the inorganic solid electrolyte porous microspheres are at least one of garnet type, NASICON type, LISICON type, perovskite type, anti-perovskite type or sulfide inorganic solid electrolyte porous microspheres.

The particle size of the inorganic solid electrolyte porous microspheres is 1-50 μm.

The polymer with the lithium ion conducting capacity is at least one of polyethylene oxide-based polymer, polysiloxane-based polymer, polycarbonate-based polymer, polyvinylidene fluoride or polyacrylonitrile.

The lithium salt is lithium perchlorate (LiClO)₄) Lithium hexafluorophosphate (LiPF)₆) Lithium bistrifluoromethylsulfonyl imide (LiTFSI), lithium bistrifluorosulfonimide (LiFSI), lithium trifluoromethanesulfonate (LiCF)₃SO₃) At least one of lithium bis (oxalato) borate (LiBOB) or lithium difluoro (oxalato) borate (lidob).

A second aspect of the present invention provides a method for preparing a composite solid electrolyte having a continuous rapid lithium ion conduction path, as shown in fig. 8, the method comprising the steps of:

and S100, preparing inorganic solid electrolyte porous microspheres by using a spray drying method, and calcining the inorganic solid electrolyte porous microspheres in air at a controlled temperature to obtain the calcined inorganic solid electrolyte porous microspheres.

Specifically, the calcining temperature is 500-1000 ℃, and the calcining time is 0.5-5 h;

step S200, adding a polymer with lithium ion conductivity and a lithium salt into a solvent, wherein the mass ratio of a solute to the solvent is 5% -50%, and uniformly stirring at a certain temperature to obtain a uniform and viscous solution.

Specifically, the temperature is 50-80 ℃.

Specifically, the solvent is one or more of dimethylformamide, ethanol, acetone, tetrahydrofuran and acetonitrile.

And step S300, adding the calcined inorganic solid electrolyte porous microspheres into the solution, and fully stirring for a certain time to obtain uniform suspension.

Specifically, the mixture was stirred sufficiently for 3 hours to obtain a uniform suspension.

And S400, pouring or casting the suspension into a substrate or a mold, standing for a certain time to enable the suspension to be leveled, quickly transferring the suspension into a vacuum drying oven, drying the suspension in the vacuum drying oven, stripping the composite solid electrolyte membrane from the substrate or the mold, and cutting the composite solid electrolyte membrane into a wafer to obtain the composite solid electrolyte.

Specifically, the composite solid electrolyte membrane is peeled off from the substrate or the mold.

Specifically, the substrate is a polyester resin (PET) substrate and the mold is a Polytetrafluoroethylene (PTFE) mold.

Specifically, the standing time is 8min-12 min.

Specifically, the drying treatment mode is one or two of vacuum drying or glove box drying methods, and the drying temperature is-20-80 ℃.

Specifically, the diameter of the circular plate is 18 mm.

A third aspect of the invention provides a method of making a battery using a composite solid electrolyte made by the above method, the method comprising the steps of:

and assembling the cut composite solid electrolyte and the positive and negative electrode shells of the battery into the battery.

Specifically, the cell is a CR2302 coin cell, and the cut composite solid electrolyte and the positive and negative electrode shells of the CR2302 coin cell are assembled into the coin cell.

And (3) performing impedance test on the composite solid electrolyte at a certain temperature by using an alternating current impedance method to obtain a variable temperature lithium ion conductivity curve, wherein the temperature is 25-80 ℃.

The purpose and technical solution of the present invention will be further described in detail with reference to the following examples.

Example 1

Step S1: spray drying of nano Li_6.4La₃Zr_1.4Ta_0.6O₁₂(LLZTO) preparing inorganic solid electrolyte porous microsphere precursor with particle size of 2-10 μm, and calcining in air at 800 deg.C for 3 hr. The sodium carboxymethyl cellulose in the inorganic solid electrolyte porous microsphere precursor is removed by calcination, and the LLZTO crystal grains are bonded more tightly by recrystallization.

Step S2: 0.5g of polyethylene oxide (PEO) with a molecular weight of 300000 and 0.41g of LiTFSI were added to 2mL of acetonitrile and stirred well at 60 ℃ to give a homogeneous viscous solution.

Step S3: and (3) mixing the LLZTO porous microspheres obtained in the step (S1) and the solution obtained in the step (S2) according to the mass ratio of 3:2, and stirring for 3 hours at 60 ℃ to obtain a uniform suspension.

Step S4: and (4) vacuumizing the suspension obtained in the step S3 for 3min to remove air bubbles in the suspension, pouring the suspension into a PTFE (polytetrafluoroethylene) mold, and controlling the quality of the suspension in the mold to control the thickness of the composite solid electrolyte. Standing for 10min to level the suspension, quickly transferring to a vacuum drying oven, and vacuum drying at 60 deg.C for 24 hr. And (3) removing the composite solid electrolyte from the PTFE mold, and cutting the composite solid electrolyte into round pieces with the diameter of 18mm to obtain the composite solid electrolyte added with 60 wt% of LLZTO porous microspheres.

Step S5: and assembling the cut composite solid electrolyte and the positive and negative electrode shells of the CR2302 button cell to form the button cell. Impedance testing of the composite solid electrolyte at 25-80 deg.C by AC impedance method to obtain temperature-variable lithium ion conductivity curve shown in FIG. 6, wherein the conductivity at 60 deg.C is 1.99 × 10^-4S cm^-1。

As shown in fig. 3, is an SEM image of the composite solid electrolyte of example 1.

Example 2

Step S1: spray drying of nano Li_6.4La₃Zr_1.4Ta_0.6O₁₂(LLZTO) preparing inorganic solid electrolyte porous microsphere precursor with particle size of 2-10 μm, and calcining in air at 800 deg.C for 3 hr. The sodium carboxymethyl cellulose in the inorganic solid electrolyte porous microsphere precursor is removed by calcination, and the LLZTO crystal grains are bonded more tightly by recrystallization.

Step S2: 0.5g of polyethylene oxide (PEO) with a molecular weight of 300000 and 0.15g of LiClO were taken₄Added to 2mL of acetonitrile and stirred well at 60 ℃ to obtain a homogeneous viscous solution.

Step S3: and (3) mixing the LLZTO porous microspheres obtained in the step (S1) and the solution obtained in the step (S2) according to the mass ratio of 1:1, and stirring for 3 hours at 60 ℃ to obtain a uniform suspension.

Step S4: and (4) vacuumizing the suspension obtained in the step S3 for 3min to remove air bubbles in the suspension, pouring the suspension into a PTFE (polytetrafluoroethylene) mold, and controlling the quality of the suspension in the mold to control the thickness of the composite solid electrolyte. Standing for 10min to level the suspension, quickly transferring to a vacuum drying oven, and vacuum drying at 60 deg.C for 24 hr. And (3) tearing the composite solid electrolyte from the PTFE mold, and then cutting the composite solid electrolyte into wafers with the diameter of 18mm to obtain the composite solid electrolyte added with 50 wt% of LLZTO porous microspheres.

Step S5: and assembling the cut composite solid electrolyte and the positive and negative electrode shells of the CR2302 button cell to form the button cell. The composite solid electrolyte was subjected to impedance measurement at 25-80 deg.C by AC impedance method, and the measured temperature-variable lithium ion conductivity curve is shown in FIG. 6, in which the conductivity at 60 deg.C is 2.65X 10^-5S cm^-1

As shown in fig. 4, is an SEM image of the composite solid electrolyte of example 2;

as shown in fig. 5, XRD patterns of the composite solid electrolytes of example 1 and example 2 are shown.

Comparative example 1

Step S1: 0.5g of polyethylene oxide (PEO) with a molecular weight of 300000 and 0.41g of LiTFSI were added to 2mL of acetonitrile and stirred well at 60 ℃ to give a homogeneous viscous solution.

Step S2: the LLZTO nanoparticles and the solution obtained in step S1 were mixed at a mass ratio of 3:2, and stirred at 60 deg.C for 3h to obtain a uniform suspension.

Step S3: and (4) vacuumizing the suspension obtained in the step S2 for 3min to remove air bubbles in the suspension, pouring the suspension into a PTFE (polytetrafluoroethylene) mold, and controlling the quality of the suspension in the mold to control the thickness of the composite solid electrolyte. Standing for 10min to level the suspension, quickly transferring to a vacuum drying oven, and vacuum drying at 60 deg.C for 24 hr. And (3) removing the composite solid electrolyte from the PTFE mold, and cutting the composite solid electrolyte into round pieces with the diameter of 18mm to obtain the composite solid electrolyte added with 60 wt% of LLZTO porous microspheres.

Step S4: and assembling the cut composite solid electrolyte and the positive and negative electrode shells of the CR2302 button cell to form the button cell. Subjecting the composite solid electrolyte to impedance test at 25-80 deg.C by AC impedance method, wherein the conductivity at 60 deg.C is 2.47 × 10^-6S cm^-1。

Comparative example 2

Step S1: 0.5g of polyethylene oxide (PEO) with a molecular weight of 300000 and 0.15g of LiClO were taken₄Added to 2mL of acetonitrile and stirred well at 60 ℃ to obtain a homogeneous viscous solution.

Step S2: and (3) mixing the LLZTO nanoparticles with the solution obtained in the step S1 according to the mass ratio of 3:2, and stirring at 60 ℃ for 3 hours to obtain a uniform suspension.

Step S3: and (4) vacuumizing the suspension obtained in the step S2 for 3min to remove air bubbles in the suspension, pouring the suspension into a PTFE (polytetrafluoroethylene) mold, and controlling the quality of the suspension in the mold to control the thickness of the composite solid electrolyte. Standing for 10min to level the suspension, quickly transferring to a vacuum drying oven, and vacuum drying at 60 deg.C for 24 hr. And (3) tearing the composite solid electrolyte from the PTFE mold, and then cutting the composite solid electrolyte into wafers with the diameter of 18mm to obtain the composite solid electrolyte added with 50 wt% of LLZTO porous microspheres.

Step S4: and assembling the cut composite solid electrolyte and the positive and negative electrode shells of the CR2302 button cell to form the button cell. Subjecting the composite solid electrolyte to impedance test at 25-80 deg.C by AC impedance method, wherein the conductivity at 60 deg.C is 1.89 × 10^-6S cm^-1。

Fig. 7 shows temperature-variable lithium ion conductivity curves of the composite solid electrolytes of comparative example 1 and comparative example 2 according to the present invention.

In the composite solid electrolyte, the rapid transmission channel of lithium ions is mainly an inorganic solid electrolyte phase and a polymer-inorganic interface, and the high-content nano inorganic solid electrolyte particles are compounded with the polymer, so that the particles are easy to agglomerate unevenly in the polymer, and the transmission of the lithium ions in the composite solid electrolyte is limited. The nano inorganic solid electrolyte particles are prepared into secondary particles with a porous structure by a spray drying method, and the lithium ion conductivity of the composite electrolyte can be effectively improved by utilizing a continuous lithium ion rapid conduction path of a bulk phase and a polymer-inorganic interface formed by the secondary particles in the composite electrolyte. According to the invention, the inorganic solid electrolyte porous microspheres with large specific surface area are prepared by spray drying, and after the inorganic solid electrolyte porous microspheres are compounded with the polymer with low mass ratio, the problem of disordered agglomeration of nano particles is solved, and the obtained composite solid electrolyte can efficiently transmit lithium ions through an inorganic solid electrolyte phase and a polymer-inorganic interface. In addition, different from a solid electrolyte prepared by compounding nano fibers and polymers, the lithium ion continuous channel can not be broken and the like in the deformation process such as bending, and the lithium ion continuous channel can be effectively applied to flexible electronic wearable equipment.

In summary, the present invention provides a composite solid electrolyte and a preparation method thereof, wherein the composite solid electrolyte has a continuous lithium ion fast conduction path, and the preparation method comprises: the composite solid electrolyte comprises inorganic solid electrolyte porous microspheres, a polymer and lithium salt, wherein the inorganic solid electrolyte porous microspheres are used as a filler, and the inorganic solid electrolyte porous microspheres are prepared by a spray drying method; the polymer has the capability of conducting lithium ions. And a method for preparing the composite solid electrolyte. The invention provides a composite solid electrolyte with a continuous lithium ion rapid conduction path and a preparation method thereof, aiming at solving the problems of low lithium ion conductivity and poor mechanical property caused by the agglomeration of nano ceramic particles in the conventional composite solid electrolyte with high ceramic content, aiming at improving the lithium ion conductivity of the solid electrolyte and simultaneously improving the mechanical property and interface problem of the electrolyte and laying a foundation for the preparation of an all-solid-state battery.

It is to be understood that the above-described embodiments of the present invention are merely illustrative of or explaining the principles of the invention and are not to be construed as limiting the invention. Therefore, any modification, equivalent replacement, improvement and the like made without departing from the spirit and scope of the present invention should be included in the protection scope of the present invention. Further, it is intended that the appended claims cover all such variations and modifications as fall within the scope and boundaries of the appended claims or the equivalents of such scope and boundaries.