CN115566264A

CN115566264A - Hollow nano-sphere-based composite solid electrolyte of lithium battery and preparation method thereof

Info

Publication number: CN115566264A
Application number: CN202211213688.2A
Authority: CN
Inventors: 王真; 白岩; 桂兴发
Original assignee: Liaoning Dengsai New Energy Co ltd
Current assignee: Liaoning Dengsai New Energy Co ltd
Priority date: 2022-09-30
Filing date: 2022-09-30
Publication date: 2023-01-03

Abstract

The invention discloses a hollow nano-sphere-based composite solid electrolyte of a lithium battery and a preparation method thereof, and particularly relates to the technical field of lithium batteries. The method comprises the following steps of synthesizing the hollow nanospheres: preparing SiO2 hollow nanospheres by adopting lauryl sodium sulfate, cetyl trimethyl ammonium bromide and tetraethoxysilane dissolved in a mixed solution of ammonia water and deionized water through a template method; siSE preparation: and (3) carrying out in-situ polymerization on the SiO2 hollow nanospheres and PVDF in an NMPP dispersing agent by using a precursor solution in the SiO2 hollow nanosphere layer to obtain SiSE. The use of SiSE in LFP/SiSE/Li batteries was found to exhibit good cycling performance due to a stable electrode/electrolyte interface and significant inhibition of lithium dendrite growth. The superior performance of the SiSE and its simple solid-state battery assembly process make it an electrolyte material for high energy density lithium metal batteries.

Description

Hollow nano-sphere-based composite solid electrolyte of lithium battery and preparation method thereof

Technical Field

The invention relates to the technical field of lithium batteries, in particular to a hollow nano-sphere-based composite solid electrolyte of a lithium battery and a preparation method thereof.

Background

Using a high energy density (3860 mAh/g) low density (0.59 g/cm) ³ ) The replacement of the traditional carbon-based negative electrode material by lithium metal with a cathode potential (-3.040V vs standard hydrogen electrode) is an effective way for improving the energy density of the conventional lithium ion battery。

However, the low coulombic efficiency and safety problems caused by the growth of lithium dendrites during electrochemical deposition/desorption greatly hinder the practical application of lithium metal, and the solid electrolyte has value in replacing the traditional organic electrolyte. The solid electrolyte can inhibit the growth of lithium dendrites and avoid the safety problems of ignition, explosion, liquid leakage and the like caused by the use of organic electrolyte in the lithium battery.

According to the theoretical model proposed by Newman et al, the shear modulus of the solid electrolyte should be more than twice that of lithium metal in order to suppress the growth of lithium dendrites, and therefore, a high-strength inorganic component is generally introduced into the solid electrolyte in the form of an inorganic/organic composite solid electrolyte or an inorganic all-solid electrolyte to obtain a solid electrolyte for a lithium metal battery.

However, the use of inorganic components often entails a series of problems such as low ionic conductivity, high electrode/solid electrolyte interfacial impedance, and the like, which approximately restrict the application of such solid electrolytes. It is a great challenge to prepare a solid electrolyte material that has both high ionic conductivity, good contact with the electrode, and a function of suppressing the growth of lithium dendrites.

Disclosure of Invention

Therefore, the invention provides a lithium battery hollow nano sphere-based composite solid electrolyte and a preparation method thereof, and aims to solve the problems that the conventional solid electrolyte cannot have high ionic conductivity, keeps good contact with an electrode, has a function of inhibiting the growth of lithium dendrites and the like.

As a new functional material, hollow nano-oxides with low density, high specific surface area and high loading have attracted much attention. When the hollow oxide nanospheres are applied to a solid electrolyte, the hollow oxide nanospheres show strong electrolyte adsorption capacity, so that lithium ion transmission is hardly hindered by the walls of the nanospheres. Based on these advantages, siO was designed ₂ Hollow nanosphere-based composite solid electrolytes (sises) to overcome many of the deficiencies of lithium metal electrolytes described above. The layer of the secondary electrolyte is prepared by mixing SiO ₂ The hollow nanospheres are compounded with a tripropylene glycol diacrylate (TPGDA) -based gel polymer electrolyte. Crosslinked TPGDA polymer backbones for SiSE retentionA quasi-solid state that does not leak at all. At the same time, siO ₂ The hollow nano-sphere layer compounds the TPGDA-based gel polymer electrolyte in a cavity of the hollow nano-sphere layer in a large amount, and forms a high-strength barrier structure for the growth of lithium dendrites. The resulting SiSE had high room temperature ionic conductivity (1.74X 10) ^-3 S/cm) good safety and low electrode/solid electrolyte interfacial resistance. It was applied to LFP/SiSE/Li batteries, which were found to exhibit good cycling performance due to a stable electrode/electrolyte interface and significant inhibition of lithium dendrite growth. The superior performance of the SiSE and its simple solid-state battery assembly process make it an electrolyte material for high energy density lithium metal batteries.

In order to achieve the above purpose, the invention provides the following technical scheme:

according to a first aspect of the present invention, there is provided a method for preparing a hollow nanosphere-based composite solid electrolyte for a lithium battery, comprising:

step one, synthesis of hollow nanospheres:

preparing SiO by using lauryl sodium sulfate, cetyl trimethyl ammonium bromide and ethyl orthosilicate which are dissolved in mixed solution of ammonia water and deionized water through a template method ₂ Hollow nanospheres;

step two, siSE preparation:

mixing SiO ₂ Hollow nanospheres and PVDF are prepared in NMPP dispersing agent by dissolving precursor solution in SiO ₂ And carrying out in-situ polymerization in the hollow nano-sphere layer to obtain SiSE.

Further, the template method comprises:

dissolving sodium dodecyl sulfate and hexadecyl trimethyl ammonium bromide in a mixed solution of ammonia water and deionized water to obtain a mixed solution;

adding tetraethoxysilane into the mixed solution, stirring and heating for continuous reaction to obtain suspension;

filtering and separating white precipitate from the suspension, repeatedly washing and precipitating with ethanol and concentrated hydrochloric acid, and then carrying out air drying to obtain white powder;

step four, calcining the white powder in air to obtain SiO ₂ Hollow nanospheres.

Further, in the first step, the dissolving condition is magnetic stirring at 68 ℃.

Further, in the second step, the conditions of stirring and heating for continuous reaction are that stirring is continuously carried out for 2 hours at 68 ℃, and then the temperature is increased to 80 ℃ for continuous reaction for 2 hours.

Further, in the third step, the air drying condition is that the air drying is carried out for 12 hours at the temperature of 80 ℃.

Further, in the fourth step, the calcination in air is performed for 2 hours at 500 ℃ in air. To remove the organic template.

As an example, siO is produced by a templating method ₂ The method of the hollow nanosphere comprises the following steps: 0.665g dodecyl sodium sulfate (SDS) and 1.335g hexadecyl trimethyl ammonium bromide (CTAB) are dissolved in the mixed solution of 210mL ammonia water and 270mL deionized water by magnetic stirring at 68 ℃ to prepare a mixed solution; then 20mL of Tetraethoxysilane (TEOS) is slowly added into the mixed solution, the mixture is continuously stirred for 2h at 68 ℃, then the temperature is raised to 80 ℃ for continuous reaction for 2h, then white precipitate is filtered and separated from the suspension, the precipitate is repeatedly washed with 450mL of ethanol and 20mL of concentrated hydrochloric acid for three times, and then air drying is carried out for 12h at 80 ℃; finally obtaining white powder, calcining the white powder for 2 hours at 500 ℃ in the air to remove the organic template, thus obtaining SiO ₂ Hollow nanospheres.

Further, the in situ polymerization comprises:

preparing SiO2 hollow nanospheres and PVDF into slurry in an NMP dispersant; then pouring the slurry on a polytetrafluoroethylene mold, and drying under vacuum to obtain the hollow nanospheres;

separating the hollow nanospheres from the die, and then punching to obtain SiO2 hollow nanosphere wafers;

injecting the precursor into the SiO2 hollow nanosphere wafer; then heating in vacuum to obtain transparent SiSE; mashing SiSE, adding the smashed SiSE into a large amount of acetone, centrifuging to obtain white precipitate, adding acetone into the precipitate, centrifuging again, repeating for multiple times, and fully drying the white precipitate; and putting the dried powder into a dialysis bag, and dialyzing in deionized water to obtain the SiSE without the electrolyte.

Further, in the third step, the precursor is composed of 5wt% of TPGDA monomer and 0.1wt% of AIBN initiator dissolved in 1M of LiPF6-EC/EMC/DMC in a volume ratio of 1.

By way of example, by reducing 80wt% SiO ₂ Preparing the hollow nanospheres and 20% of PVDF into slurry in an NMP dispersing agent, then pouring the slurry on a polytetrafluoroethylene mold, and placing the polytetrafluoroethylene mold at 120 ℃ for vacuum drying for 24 hours to prepare the hollow nanospheres; separating the obtained hollow nanospheres from the die, and then punching into round pieces for later use;

the precursor consists of 5wt% of TPGDA monomer and 0.1wt% of AIBN initiator dissolved in 1M LiPF6-EC/EMC/DMC (volume ratio 1;

injecting the precursor into SiO ₂ The hollow nanosphere wafer is uniformly cast; then placing the mixture at 60 ℃ and heating the mixture in vacuum for 6 hours to ensure that TPDGA is fully polymerized to obtain transparent SiSE; the above operation was carried out in a glove box (moisture and oxygen less than 1 ppm); in order to remove the electrolyte in the SiSE for FTIR analysis, the SiSE is smashed and added into a large amount of acetone, the mixture is centrifuged for 15min at 10000rpm to obtain white precipitate, the precipitate is added into the acetone and then centrifuged again, the operation is repeated for 3 times, and then the white precipitate is placed at 120 ℃ for full drying; and (3) putting the dried powder into a dialysis bag, and dialyzing in deionized water for three days to remove ions, thereby obtaining the SiSE (SiSE) with electrolyte removed, namely the TPGDA polymer skeleton/SiO 2 hollow nanosphere compound.

According to a second aspect of the invention, a hollow nanosphere-based composite solid electrolyte for a lithium battery is provided, which is prepared by the method.

According to a third aspect of the present invention, there is provided a lithium battery comprising a positive electrode, a separator, a negative electrode and an electrolyte, wherein the negative electrode material of the negative electrode is the hollow nanosphere-based composite solid electrolyte as described above.

The invention has the following advantages:

the invention synthesizes SiO with abundant surface pore structure and high pore volume by utilizing a template method ₂ Hollow nanospheres, and in turn SiO ₂ Coating of hollow nanospheresForming a uniform coating on the LFP surface, and compounding the uniform coating with TPGDA-based gel electrolyte in situ to obtain the SiO of the long-life lithium metal battery ₂ The hollow nanosphere is compounded with a solid electrolyte. On the basis, the comprehensive performance of the electrolyte material is examined in detail and the inhibition effect of the electrolyte material on the growth of lithium dendrites is verified; CTAB and SDS are used as soft templates, TEOS is used as a silicon source, and SiO with high specific surface area, high pore volume, rich mesopores on the surface of the spherical wall and high absorption rate to electrolyte can be obtained by hydrolysis under alkaline conditions ₂ Hollow nanospheres.

In the construction of the SiSE, the crosslinked TPGDA polymer backbone allows the SiSE to remain in a liquid-tight quasi-solid state, whereas SiO ₂ The hollow nanospheres then act as a high strength membrane.

Due to SiO ₂ High washing rate of hollow nanosphere, and the prepared SiSE shows high room temperature ionic conductivity (1.74 multiplied by 10) ^-3 S/cm). The SiSE also has good safety (basically no electrolyte volatilization under 100 ℃) and high electrochemical stability (4.91V vs Li/Li) ⁺ ). Compared with the traditional electrolyte diaphragm, the SiSE has good interface compatibility with lithium metal, and SiO with high shear modulus in the SiSE ₂ The hollow nanospheres can effectively inhibit the growth of lithium dendrites in the charge-discharge cycle process.

When the SiSE is applied to the lithium metal battery, the obtained LFP/SiSE/Li shows good cycle stability (the capacity retention rate is 100.2 percent after 200 cycles under 0.2 ℃ C.) mainly due to the low-impedance and high-stability electrode/SiSE interface and the obvious inhibition effect of the SiSE on the production of lithium dendrites.

The electrolyte of the invention is prepared by mixing SiO ₂ The hollow nanospheres are compounded with tripropylene glycol diacrylate (TPGDA) based gel polymer electrolyte; the crosslinked TPGDA polymer backbone keeps the SiSE in a safe, leak-free quasi-solid state; at the same time, siO ₂ The hollow nano-sphere layer compounds a large amount of TPGDA-based gel polymer electrolyte in the cavity of the hollow nano-sphere layer, and forms a high-strength barrier structure for the growth of lithium dendrites; the resulting SiSE had high room temperature ionic conductivity (1.74X 10) ^-3 S/cm), good safety and low electrode/solid electrolyte interfacial impedance. It was applied to LFP/SiSE/Li battery, and the battery was foundGood cycling performance is exhibited due to a stable electrode/electrolyte interface and significant inhibition of lithium dendrite growth. The superior performance of the SiSE and its simple solid-state battery assembly process make it an electrolyte material for high energy density lithium metal batteries.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below. It should be apparent that the drawings in the following description are merely exemplary, and that other embodiments can be derived from the drawings provided by those of ordinary skill in the art without inventive effort.

The structures, ratios, sizes, and the like shown in the present specification are only used for matching with the contents disclosed in the specification, so as to be understood and read by those skilled in the art, and are not used to limit the conditions that the present invention can be implemented, so that the present invention has no technical significance, and any structural modifications, changes in the ratio relationship, or adjustments of the sizes, without affecting the effects and the achievable by the present invention, should still fall within the range that the technical contents disclosed in the present invention can cover.

FIG. 1 is a SiSE synthesis route diagram according to the present invention;

FIG. 2 is a schematic diagram of the polymerization mechanism of TPGDA monomer provided by the present invention;

FIG. 3 shows SiO provided by the present invention ₂ Hollow nanospheres, TPGDA monomer and SiSE (after removal of electrode solution) FIRT spectra;

wherein, A-SiSE (after removing electrode solution) FIRT spectrum; FIRT spectrum of B-TPGDA monomer; C-SiSE (after removal of electrode solution) FIRT spectra;

FIG. 4 shows the FIRT spectra of TPGDA monomer and SiSE (after removing electrode solution) provided by the present invention;

wherein, C-SiSE (after removing electrode solution) FIRT spectrum; D-TPGDA monomer FIRT spectrum;

FIG. 5 shows SiO provided in example 1 of the present invention ₂ Hollow nanosphere/PVDF mixture map;

FIG. 6 shows an embodiment of the present invention80wt% SiO as provided in example 1 ₂ Mixing hollow nanospheres with 20wt% PVDF in NMP dispersant to prepare slurry;

FIG. 7 shows SiO provided in example 1 of the present invention ₂ A sheet of hollow nanospheres;

FIG. 8 shows the precursor solution in SiO according to example 1 of the present invention ₂ The wetting effect of the surface of the hollow nanospheres;

FIG. 9 shows SiSE and TPGDA-based gel polymer electrolytes provided in example 1 of the present invention;

FIG. 10 shows SiO provided in example 1 of the present invention ₂ Coating the hollow nanosphere slurry on the surface of the LPF pole piece;

FIG. 11 is SiO that is provided in example 2 of the present invention ₂ TEM images of hollow nanospheres;

FIG. 12 is a SiO solid provided in example 2 of the present invention ₂ A SEAD map of hollow nanospheres;

FIG. 13 is a schematic representation of SiO provided in example 2 of the present invention ₂ A nitrogen isothermal adsorption curve and a BJH pore size distribution diagram of the hollow nanospheres;

wherein, A-is adsorbed; b-desorption;

FIG. 14 shows SiO production process in example 2 of the present invention ₂ Nitrogen isothermal adsorption and desorption curve and BJH pore size distribution and SiO of hollow nano-sphere layer ₂ A nitrogen isothermal adsorption curve graph of the hollow nano-sphere layer;

wherein, A-SiO ₂ Hollow nano-sphere particles, adsorbing; B-SiO ₂ Desorbing the hollow nano-sphere particles; C-SiO ₂ Coating-adsorbing the hollow nanospheres; D-SiO ₂ Coating the hollow nanospheres, and desorbing;

FIG. 15 shows SiO coated on the surface of an LFP electrode plate according to embodiment 2 of the present invention ₂ FE-SEM images of the surface and the longitudinal section of the hollow nanosphere coating;

wherein, A-SiO ₂ (ii) a B-LFP; c-aluminum current collector;

fig. 16 is a stress-strain curve of the TPGDA-based gel electrolyte and SiSE provided in example 2 of the present invention;

wherein, the stress-strain curve of the A-TPGDA-based gel electrolyte; stress-strain curves for B-SiSE;

FIG. 17 is a graph of the combustion phenomena of 1M LiPF6-EC/EMC/DMC electrolyte, TPGDA-based gel polymer electrolyte (5 wt% TPGDA monomer polymerized in situ in 1M Li PF6-EC/EMC/DMC electrolyte) and SiSE provided in test example 1 of the present invention;

wherein, a-LiPF 6-EC/EMC/DMC electrolyte combustion diagram of highly combustible electrolyte 1M; b-mild burn gel polymer electrolyte TPGDA-based gel polymer electrolyte burn profile; a combustion phenomenon map of c-SiSE; d-electrolyte @ SD216 diaphragm, TPGDA-based gel polymer electrolyte @ SD216 diaphragm and SiSE air at 10 ℃ for min ^-1 TGA profile at ramp rate;

FIG. 18 shows the 1M LiPF6-EC/EMC/DMC electrolyte, TPGDA-based gel polymer electrolyte, electrolyte @ SD216 diaphragm, electrolyte @ hollow SiO solid provided in test example 1 of the present invention ₂ Graph of conductivity-temperature relationship between nanosphere coating and SiSE at-20 deg.C to 90 deg.C;

wherein, the A-electrolyte has a relation graph of conductivity and temperature at-20 ℃ to 90 ℃; a graph of the conductivity-temperature relationship of B-GPE at-20 ℃ to 90 ℃; a graph of conductivity versus temperature for the C-electrolyte @ membrane at-20 ℃ to 90 ℃; d-electrolyte @ hollow SiO ₂ A graph of conductivity versus temperature at-20 ℃ to 90 ℃; a graph of the conductivity-temperature relationship of E-SiSE at-20 ℃ to 90 ℃;

FIG. 19 is a graph showing measured data with discrete points and VTF fitting results with solid lines, which are provided in test example 2 of the present invention; stainless steel is used as a working electrode, a lithium sheet is used as a reference electrode and a counter electrode, and electrolyte @ hollow SiO are adopted ₂ The nano-ball layer and the SiSE are in 1mVs ^-1 LSV curve at sweep speed;

wherein, the A-electrolyte is 1mVs ^-1 LSV curve at sweep speed; the layer of B-electrolyte @ hollow SiO2 is at 1mVs ^-1 LSV curve at sweep speed; C-SiSE at 1mVs ^-1 LSV curve at sweep speed;

FIG. 20 is a chronoamperometric curve of a Li/1M LiPF6-EC/EMC/DMC electrolyte/Li symmetrical cell provided in test example 2 of the present invention at a polarization voltage of 10 mV;

wherein, A-initial state; b-steady state;

FIG. 21 is a chronoamperometric curve of a Li/SiSE/Li symmetric cell provided in test example 2 of the present invention at a polarization voltage of 10 mV;

wherein, A-initial state; b-steady state;

FIG. 22 shows that the Li/1M LiPF6-EC/EMC/DMC/Li and Li/SiSE/Li symmetrical battery provided in test example 2 of the present invention has a density of 0.5mAcm ^-2 Constant current cycle curve at current density;

wherein the A-electrolyte is 0.5mAcm ^-2 Constant current cycle curve at current density; B-SiSE is 0.5mAcm ^-2 Constant current cycle curve at current density;

FIG. 23 shows that the Li/1M LiPF6-EC/EMC/DMC/Li and Li/SiSE/Li symmetrical battery provided in test example 2 of the present invention has a density of 1.0mAcm ^-2 Constant current cycle curve at current density;

wherein, the A-electrolyte is 1.0mAcm ^-2 Constant current cycle curve at current density; B-SiSE at 1.0mAcm ^-2 Constant current cycling profile at current density.

Detailed Description

The present invention is described in terms of particular embodiments, other advantages and features of the invention will become apparent to those skilled in the art from the following disclosure, and it is to be understood that the described embodiments are merely exemplary of the invention and that it is not intended to limit the invention to the particular embodiments disclosed. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

PVDF-polyvinylidene chloride

NMP-N-methylpyrrolidone

TPGDA-tripropylene glycol diacrylate

AIBN-azobisisobutyronitrile

LiPF 6-EC/EMC/DMC-lithium hexafluorophosphate-lithium carbonate ethylene ester/ethyl methyl carbonate/dimethyl carbonate

SiSE--SiO ₂ Hollow nano ball based composite solid electrolyte

PETEA-pentaerythritol tetraacrylate

LFP-lithium iron phosphate

Super-P-conductive carbon black

Analysis of the synthesis mechanism of SiSE:

the SiSE synthesis scheme is shown in fig. 1.

The synthesis of the SiSE was first to synthesize SiO by using a vesicle soft template ₂ Hollow nanospheres. Mixing surfactants CTAB and SDS in ammonia water (adjusting PH value) and deionized water uniformly, and forming vesicles by CTAB and SDS spontaneously. Then, a silicon source TEOS is dripped into the solution, the TEOS is hydrolyzed on the surface of the ionic surfactant vesicle under the action of coulomb force, and SiO is generated on the surface of the vesicle ₂ And (5) shell layer. Removing the organic template after calcining to obtain SiO ₂ Mixing the hollow nanospheres with the PVDF binder according to the mass ratio of 1:5, adding a proper amount of NMP to prepare slurry, coating the slurry on the surface of the LFP pole piece, and drying at 120 ℃ for 24 hours. Subsequently preparing a precursor solution from 5wt% of TPGDA monomer and 0.1wt% of AIBN initiator and 1MLiPF6-EC/EMC/DMC electrolyte, injecting the precursor into SiO ₂ And (4) assembling the battery after coating the hollow nanospheres, and placing the packaged battery at 60 ℃ for 12 hours. During this heating, the C = C double bond on the TPGDA monomer is radical polymerized by AIBN (the primary radicals generated by AIBN thermal decomposition generate two radicals in total for the C = C double bond on the TPGDA monomer, and then chain propagation occurs by continued addition of PETEA monomer at the ends of the two radicals, eventually generating a three-dimensionally crosslinked TPGDA polymer backbone in the electrolyte, as shown in fig. 2). In SiO ₂ A transparent TPGDA-based gel electrolyte is formed in the hollow nanospheres to obtain SiSE in situ in the lithium metal battery.

FIRT was used to study the mechanism of monomer polymerization during the preparation of SiSE:

SiO as shown in FIGS. 3 and 4 ₂ 3450cm in FTIR spectra of hollow nanospheres ^-1 ，1650cm ^-1 ，1100cm ^-1 The peak at (A) corresponds to upsilon OH, δ NH ₂ And upsilon Si-O-Si, and TPGDA monomer has an FTIR spectrum of 2840-3050cm ^-1 (υC-H)1735cm ^-1 (υC＝O)1460cm ^-1 ，1407cm ^-1 ，(υCH ₂ )1270cm ^-1 And 1090cm ^-1 Each peak at (. Nu.C-O-C) is consistent with literature reports when taken aloneAfter bulk polymerization, from the FIRT spectrum of SiSE (after removal of electrolyte), 1620cm ^-1 The absorption peak at C = C stretching vibration almost disappeared, indicating a high conversion of TPGDA monomer. The FTIR results indicate that the TPGDA monomer can absorb SiO ₂ The electrolyte in the hollow cavities of the hollow nanospheres was successfully polymerized to form quasi-solid SiSE.

Example 1

The embodiment provides a preparation method of a hollow nano-sphere-based composite solid electrolyte of a lithium battery, which comprises the following steps:

synthesis of hollow nanospheres: the SiO2 hollow nanospheres are prepared by a template method.

Specifically, siO is prepared by a template method ₂ The method of the hollow nanosphere comprises the following steps: 0.665g dodecyl sodium sulfate (SDS) and 1.335g hexadecyl trimethyl ammonium bromide (CTAB) are dissolved in the mixed solution of 210mL ammonia water and 270mL deionized water by magnetic stirring at 68 ℃ to prepare a mixed solution; then 20mL of Tetraethoxysilane (TEOS) is slowly added into the mixed solution, the mixture is continuously stirred for 2h at 68 ℃, then the temperature is raised to 80 ℃ for continuous reaction for 2h, then white precipitate is filtered and separated from the suspension, the precipitate is repeatedly washed with 450mL of ethanol and 20mL of concentrated hydrochloric acid for three times, and then air drying is carried out for 12h at 80 ℃; finally obtaining white powder, calcining the white powder for 2 hours at 500 ℃ in the air to remove the organic template, thus obtaining SiO ₂ Hollow nanospheres.

Preparation of SiSE: by dissolving the precursor in SiO ₂ And carrying out in-situ polymerization in the hollow nano-sphere layer to obtain SiSE.

Specifically, by mixing 80wt% of SiO ₂ Hollow nanospheres and 20% PVDF (as shown in fig. 5) were slurried in NMP dispersant as shown in fig. 6; then pouring the slurry on a polytetrafluoroethylene mold, and placing the polytetrafluoroethylene mold at 120 ℃ for vacuum drying for 24 hours to prepare hollow nanospheres; the resulting hollow nanospheres are separated from the mold and then punched into disks for use, as shown in fig. 7;

injecting the precursor into SiO ₂ Uniform casting in hollow nanosphere disks as shown in FIG. 8Shown in the specification; then placing the mixture at 60 ℃ and heating the mixture in vacuum for 6h to ensure that the TPDGA is fully polymerized to obtain transparent SiSE, as shown in figure 9; the above operation was carried out in a glove box (moisture and oxygen less than 1 ppm); in order to remove the electrolyte in the SiSE for FTIR analysis, the SiSE is smashed and added into a large amount of acetone, the mixture is centrifuged for 15min at 10000rpm to obtain white precipitate, the precipitate is added into the acetone and then centrifuged again, the operation is repeated for 3 times, and then the white precipitate is placed at 120 ℃ for full drying; placing the dried powder in a dialysis bag, dialyzing in deionized water for three days to remove ions to obtain electrolyte-removed SiSE (SiO) ₂ Hollow nanosphere-based composite solid electrolyte), i.e., TPGDA polymer backbone/SiO ₂ A hollow nanosphere composite.

Example 2

This example provides a TPGDA Polymer backbone/SiO utilizing example 1 ₂ Application of the hollow nanosphere composite in the battery:

SiSE lithium metal battery assembly and standard

The CR2032 type LFP/SiSE/Li button cell is assembled in a glove box, the cell takes an LFP pole piece as a positive electrode, a lithium piece as a negative electrode and SiSE as a solid electrolyte without a diaphragm.

(ii) sizing the super-P,10wt% PVDF in NMP by 80% wtLFP,10wt%, followed by coating on carbon-coated aluminum foil and vacuum drying at 120 ℃ for 24h; the SiO obtained in example 1 is subsequently ₂ Coating the hollow nanosphere-based composite solid electrolyte to form a coating with the thickness of 60um on the surface of the electrode, as shown in fig. 10; the above precursor (5wt% TPGDA and 0.1wt% AIBN initiator solution dissolved in 1MLiPF6-EC/EMC/DMC (volume ratio = 1) ₂ And (3) filling the LFP pole piece coated by the hollow nanospheres into a battery, and standing the assembled battery for 2 hours at room temperature to ensure that the precursor solution fully infiltrates the electrode.

Prior to electrochemical testing, the cells were placed under vacuum at 60 ℃ for 12h to ensure adequate polymerization of the monomers. The prepared LFP/SiSE/Li battery is subjected to cycle test at 25 ℃ and under different current densities of 2.4-4.2V. Transferring the battery subjected to specific cycle to a glove box for disassembly, taking out the lithium cathode, repeatedly washing by using DMC, then carrying out vacuum drying at 60 ℃ for 2h, and taking out residual solvent. The morphology of the lithium negative electrode was characterized by FE-SEM (5 kv).

SiSE performance characterization:

TEM was used to observe SiO ₂ Microstructure of hollow nanospheres, as shown in FIG. 11, siO ₂ The hollow nanospheres are microscopically hollow vesicles with the diameter of 80-200 nm.

As shown in FIG. 12, the SAED pattern indicates SiO ₂ The hollow nanospheres exhibit an amorphous structure.

High magnification TEM photographs further reveal SIO ₂ The wall thickness of the hollow nanosphere is about 10nm, and the hollow nanosphere shows a porous structure. This porous structure of the sphere wall plays a crucial role for electrolyte absorption. Notably, siO ₂ The tap density of the hollow nanospheres is only 0.13g/cm ³ Significantly lower than the apparent density (0.46 g/cm) of SD216 diaphragm ³ ) This reduction in density helps to reduce the overall quality of the cell and increases the energy density of the device.

The nitrogen isothermal adsorption and desorption experiment is used for researching SiO ₂ Pore structure of hollow nanospheres. As shown in FIG. 13, siO ₂ Hollow nanospheres exhibit a typical type IV isothermal adsorption curve. At a relative pressure (P/P) ₀ ) The occurrence of an H3-type hysteresis loop at about 0.5 indicates N ₂ Molecule in SiO ₂ The pores of the hollow nanospheres are adsorbed. The pore size distribution calculated by the BJH method clearly shows SiO ₂ Two types of pores with pore diameters of 2.5nm and 90nm exist in the hollow nanosphere, as shown in fig. 14. In conjunction with TEM photographic analysis, the smaller pores of 2.5nm can be considered to be mesoporous structures on the sphere wall, while the larger pores of 90nm can be considered to be SiO ₂ Hollow cavities of hollow nanospheres. SiO2 ₂ The specific surface area of the hollow nanosphere can reach 400.19m ² g ^-1 The pore volume can reach 1.49cm ³ g ^-1 . It is noted that when SiO ₂ After the hollow nanosphere powder is mixed with the PVDF binder to form a coating, siO ₂ Hollow nanosphere powder and SiO ₂ No obvious difference is observed in the nitrogen isothermal adsorption and desorption curves of the hollow nano-sphere layers as shown in FIG. 15, which indicates that SiO is ₂ The hollow nano-sphere layer completely keeps SiO ₂ Pore structure of hollow nanospheresIs destroyed. Compared with SiO ₂ Hollow nanosphere powder, siO ₂ The specific surface area and the pore volume of the hollow nano-sphere layer are respectively slightly reduced to 349.10m ² g ^-1 And 1.26cm ³ g ^-1 Mainly due to SiO ₂ The mesoporous pores on the wall of the hollow nanosphere sphere are partially blocked by the PVDF binder.

This high pore volume imparts SiO ₂ The liquid absorption rate of the hollow nanosphere layer is extremely high at 298.8%, and is far higher than 87.6% of a commercial diaphragm for an electrolyte solution, 90.7% of the electrolyte solution and 90.7% of the precursor solution for an electrolyte solution, wherein the electrolyte solution is 311.5% of the precursor solution. Such a high imbibition rate can significantly enhance the ion conductivity of the SiSE.

LFP electrode surface SiO ₂ FE-SEM photograph of hollow nanosphere coating is shown in FIG. 15, indicating SiO ₂ SiO in hollow nanosphere coating ₂ The hollow nanospheres adhere tightly together to form dense SiO ₂ And (5) surface film. Due to SiO ₂ Has a higher shear modulus than lithium metal, so this high strength structure helps to act as a barrier to lithium dendrite growth. The profile in longitudinal section, as shown in FIG. 15, shows SiO about 60 μm thick ₂ The hollow nanosphere coating adheres tightly to the LFP electrode surface, helping to reduce the electrode/electrolyte contact impedance. In addition, when the SiO is brittle ₂ After the hollow nano-sphere layer is compounded with the TPGDA-based gel polymer electrolyte with high elasticity, the strength of SiSE is obviously improved. As shown in FIG. 16, siO ₂ The hollow nanospheres exhibit very low mechanical strength to withstand the pressure of the fixture and fail tensile testing. This is mainly composed of SiO ₂ Limited adhesion between the layers of the hollow nanospheres. However, when SiO ₂ After the hollow nano-sphere layer is compounded with the TPGDA-based gel polymer electrolyte (the maximum tensile stress is 0.31MPa, and the elongation at break is 71.9 percent), the maximum tensile stress and the elongation at break of the SiSE film respectively reach 0.49MPa and 2.9 percent. In conclusion, the SiSE prepared in situ can construct a robust electrode/electrolyte integrated structure with low interface resistance, and is expected to greatly improve the electrochemical performance of the solid-state lithium metal battery.

Test example 1

It is known that the use of the conventional carbonate-based electrolyte is liable to cause safety hazards such as ignition, explosion and the like to the battery, and is particularly serious when the battery is placed under abuse conditions such as short circuit, overcharge, high-temperature environment and the like. Therefore, the thermal safety of the electrolyte is critical to the lithium metal battery.

This test example provides a safety comparison, and the burning phenomena of 1M LiPF6-EC/EMC/DMC electrolyte, TPGDA-based gel polymer electrolyte (5 wt% TPGDA monomer polymerized in situ in 1M Li PF6-EC/EMC/DMC electrolyte) and SiSE are shown in FIG. 17. Compared to highly flammable electrolytes (FIG. 17-a) and mildly burning gel polymer electrolytes (FIG. 17-b), siSE exhibited significantly lower flammability so as to be less prone to ignition by a fire source (FIG. 17-c).

FIG. 17-d shows electrolyte @ SD216 separator, TPGDA-based gel polymer electrolyte @ SD216 separator and SiSE air at 10 deg.C for min ^-1 TGA profile at ramp rate. The electrolyte @ membrane sample rapidly volatilizes and loses weight even at room temperature due to the low boiling point of the carbonate solution, while the gel polymer electrolyte @ membrane begins to undergo significant thermal weight loss at about 40 ℃. By contrast, siSE shows good thermal stability with little solvent evaporation at 100 ℃, which is mainly benefited by mesoporous SiO ₂ Liquid confinement and heat resistance of the ball wall. The good non-flammability and thermal stability of the SiSE are critical to improve the safety performance of the lithium metal battery.

Ionic conductivity is a key performance parameter that determines the application of solid-state electrolytes in energy storage devices. FIG. 18 shows 1M LiPF6-EC/EMC/DMC electrolyte, TPGDA-based gel polymer electrolyte, electrolyte @ SD216 separator, electrolyte @ hollow SiO ₂ The nanosphere coating and the SiSE have a conductivity-temperature relationship at-20 to 90 ℃. The Ea value of SiSE (2.63X 10) can be seen ^-2 eV) is very close to (2.04X 10) that of the electrolyte ^-2 eV). Since Ea represents an energy barrier for ion conduction, this result indicates that the TPGDA polymer backbone and SiO ₂ The hollow nanospheres have weak effect on inhibiting lithium ion conduction. Further, it can be seen from FIG. 18 that the ion conductivity of SiSE at 25 ℃ can be 1.74X 10 ^-3 S·cm ^-1 (ii) a Due to TPGDA polymer boneShelf and SiO ₂ The hollow nanospheres are non-ionic conductors, and the value is slightly lower than that of electrolyte (9.06 multiplied by 10- ³ Scm ^-1 ). However, considering the use of separators in conventional lithium batteries, the conductivity values of the SiSE are much higher than that of 1MLiPF6-EC/EMC/DMC electrolyte @ separator systems (5.75X 10 at 25 ℃ C.) ^-4 Scm ^-1 ). This is mainly due to SiO ₂ The hollow nanospheres have a higher imbibition rate than the membrane. The high ionic conductivity of the SiSE helps to reduce ohmic polarization, thus improving the electrochemical performance of the solid-state lithium metal battery.

Test example 2

Electrochemical stability is another important performance parameter of solid-state electrolytes. The electrochemical stability of the SiSE was characterized by LSV. As shown in fig. 19, at up to 4.91Vvs. No oxidation peak or obvious oxidation current is observed on the voltammetry curve of the SiSE in the voltage interval of Li/Li +, which indicates that the SiSE can keep electrochemical stability at 4.91V. This electrochemical stability window is higher than that of TPGDA-based gel polymer electrolyte (4.85V) and electrolyte (4.77V), mainly due to SiO which is resistant to electrochemical oxidation ₂ Hollow nanospheres and TPGDA-based polymer backbones, and the electrolyte. The good electrochemical stability of the SiSE can meet the practical requirements of high energy density lithium batteries. The lithium ion transport number (tLi +) is also important for solid state electrolytes because low tLi + means excess anions that increase electrode polarization and cause undesirable side reactions at the electrode. As shown in FIG. 20, it can be seen that tLi + of LiPF6-EC/EMC/DMC electrolyte (@ diaphragm) is only 0.35. In contrast, siSE's tLi + is as high as 0.44 (fig. 21). The rise of siseltli + can be attributed to that the SiO2 hollow nanospheres and the polyacrylate derivative backbone can restrict the movement of anions. This high tLi + helps to reduce cell polarization and thus improve the rate performance of the SiSE-based solid-state cell.

To investigate the compatibility of SiSE with lithium metal electrodes, the current density was 0.5mAcm for Li/SiSE/Li cells ^-2 The 3h charge/3 h discharge cross-flow cycling test was performed at current density. As shown in fig. 22, the negative voltage value indicates deposition of lithium, and the positive voltage value indicates extraction of lithium. It can be seen that Li/SiSE/Li battery cycles at 300h as compared with Li/1M LiPF6-EC/EMC/DMC (@ diaphragm)/Li batteryThe ring exhibits a smaller overpotential, mainly due to the high ionic conductivity of the SiSE and the good interfacial contact between the SiSE and the lithium electrode. Further, for Li/1M lippf 6-EC/EMC/DMC/Li batteries, the voltage difference between lithium deposition/deintercalation increases with increasing cycle number, mainly due to the progressively thicker SEI film and deterioration of the electrode/electrolyte interface caused by non-uniform lithium deposition and dendrite growth. By contrast, the voltage fluctuation during cycling of the Li/SiSE/Li cell was small, indicating a stable Li/SiSE interface and uniform lithium deposition, and SiO was verified ₂ The hollow nanosphere coating has the function of inhibiting dendritic crystal growth. When the current density is increased to 1.0mAcm ^-2 The voltage difference between the Li/1M lipff 6-EC/EMC/DMC/Li cell lithium deposition/extraction increased rapidly with increasing cycle time, and the voltage dropped abruptly to about 0.2V at about 195h, indicating that the cell was short circuited by dendrite growth piercing the separator (fig. 23). While the Li/SiSE/Li battery maintains a stable voltage difference, and no drastic voltage fluctuation caused by micro-short circuit is observed. The good compatibility between the above-mentioned SiSE and the lithium metal electrode ensures the long-time cycle of the lithium metal battery, and also avoids the short circuit risk caused by the growth of dendrites.

Although the invention has been described in detail with respect to the general description and the specific embodiments, it will be apparent to those skilled in the art that modifications and improvements may be made based on the invention. Accordingly, such modifications and improvements are intended to be within the scope of the invention as claimed.

Claims

1. A preparation method of a hollow nano-sphere-based composite solid electrolyte of a lithium battery is characterized by comprising the following steps:

step one, synthesis of hollow nanospheres:

step two, siSE preparation:

mixing SiO ₂ Hollow nanospheres and PVDF are prepared by dissolving precursor solution in SiO in NMPP dispersing agent ₂ And carrying out in-situ polymerization in the hollow nano-sphere layer to obtain SiSE.

2. The method for preparing the hollow nanosphere-based composite solid electrolyte for lithium battery as claimed in claim 1, wherein the template method comprises:

step four, calcining the white powder in the air to obtain SiO ₂ Hollow nanospheres.

3. The method for preparing the hollow nanoparticle-based composite solid electrolyte for a lithium battery as claimed in claim 2, wherein the dissolving condition in the first step is magnetic stirring at 68 ℃.

4. The method for preparing the hollow nanosphere-based composite solid electrolyte of the lithium battery as claimed in claim 2, wherein in the second step, the conditions of stirring and temperature rising for continuous reaction are that stirring is continued for 2h at 68 ℃ and then temperature rising to 80 ℃ for continuous reaction for 2h.

5. The method for preparing the hollow nanosphere-based composite solid electrolyte for the lithium battery as claimed in claim 2, wherein the air drying condition in the third step is air drying at 80 ℃ for 12h.

6. The method for preparing the hollow nanosphere-based composite solid electrolyte for the lithium battery as claimed in claim 2, wherein in the fourth step, the calcination in air is performed under the condition of calcination at 500 ℃ in air for 2 hours.

7. The method for preparing the hollow nanoparticle-based composite solid electrolyte for a lithium battery as claimed in claim 1, wherein the in-situ polymerization comprises:

step one, siO ₂ Preparing hollow nanospheres and PVDF into slurry in an NMP dispersant; then pouring the slurry on a polytetrafluoroethylene mold, and drying under vacuum to obtain the hollow nanospheres;

step two, separating the hollow nanospheres from the mold, and then punching to obtain the SiO ₂ A hollow nanosphere wafer;

step three, injecting the precursor into SiO ₂ Hollow nanosphere wafers; then heating in vacuum to obtain transparent SiSE; mashing SiSE, adding the smashed SiSE into a large amount of acetone, centrifuging to obtain white precipitate, adding acetone into the precipitate, centrifuging again, repeating for multiple times, and fully drying the white precipitate; and putting the dried powder into a dialysis bag, and dialyzing in deionized water to obtain the SiSE with the electrolyte removed.

8. The method for preparing the hollow nanosphere-based composite solid electrolyte of the lithium battery of claim 7, wherein in the third step, the precursor is a mixture of 5wt% of TPGDA monomer and 0.1wt% of AIBN initiator dissolved in 1M LiPF6-EC/EMC/DMC in a volume ratio of 1.

9. A hollow nanosphere-based composite solid electrolyte for a lithium battery, characterized by being prepared by the method of any one of claims 1 to 8.

10. A lithium battery comprising a positive electrode, a negative electrode and an electrolyte, wherein the electrolyte is the hollow nanosphere-based composite solid electrolyte of claim 9.