KR20170084912A - Fabricating mehtod of solid electrolyte - Google Patents

Abstract

The method for producing a solid electrolyte according to the present invention comprises the steps of preparing lithium polysulfide (Li2S8) by mixing lithium sulfide and sulfur with TEGDME (tetraethylene glycol dimethyl ether) as a solvent S110); A lithium salt addition step (S120) of adding LiTFSI (lithium trifluoromethanesulfonimide) lithium salt (LiTFSI) and LiClO4 (Lithium perchlorate) to the lithium polysulfide (Li2S8) obtained from the lithium polysulfide production step (S110) and mixing them; A semi-solid phase forming step (S130) in which silica (SiO2) is added to the mixture of the lithium salt addition step (S120) to form a quasi-solid-state (QS) intermediate between the gel and the solid state; The mixture of PEO (S140), which is a mixture of PEO (ethylene oxide) in a weight ratio of 1: 1, to the quasi-solid mixture obtained in the quasi-solid phase forming step (S130) And a step (S150) of obtaining a solid electrolyte by pressurization to form a solid electrolyte in the form of a film.
Also, a method of manufacturing a solid electrolyte using electrospinning according to the present invention includes a PEO stirring step (E110) in which PEO (poly (ethylene oxide)) is added to a solvent ACN (acetonitrile, Aldrich) and stirred; A PEO web preparation step E100 including PEO electrospinning step E120 for electrospinning the mixture obtained in the PEO stirring step E110 and a PEO web preparation step E100 for electropolishing the mixture obtained in the PEO stirring step E110 by mixing PANO which mixes SiO2 and PAN (polyacrylonitrile) Mixing step (E210); A PAN electrospinning step (E220) for electrospinning the mixture obtained in said PAN mixing step (E210); A PAN nanofiber loading step (E230) in which a hydrogen fluoride (HF) diluent solution is supported to remove SiO2 in the PAN nanofiber strands obtained by electrospinning in the PAN electrification step (E220); PAN web fabrication step (E200) including PAN nanofiber drying step (E230), followed by PAN nanofiber drying step (E240) in which the supported PAN nanofibers are washed with fresh water and dried, and TEGDME (Tetraethylene glycol dimethyl ether A lithium polysulfide production step (S110) of producing lithium polysulfide (Li2S8) by mixing lithium sulfide and sulfur with a solvent as a solvent; A lithium salt addition step (S120) of adding LiTFSI (lithium trifluoromethanesulfonimide) lithium salt (LiTFSI) and LiClO4 (Lithium perchlorate) to the lithium polysulfide (Li2S8) obtained from the lithium polysulfide production step (S110) and mixing them; Semi-solid form further comprising: to form an intermediate form of a semi-solid state (Quasi-solid-state, QS ) and the mixture was added to silica (SiO ₂₎ in the gel and the solid state of the lithium salt added to step (S120) (S130) (PE) web and PAN web obtained in the PEO web preparation step (E100) and the PAN web manufacturing step (E200) were mixed with the product obtained in the semi-solid phase preparation step (S100) and the semi-solid phase preparation step (E300) of obtaining an electrospinning solid electrolyte obtained by heating and pressing to obtain a solid electrolyte in the form of a film.

Description

TECHNICAL FIELD [0001] The present invention relates to a method of manufacturing a solid electrolyte,

The present invention relates to a solid electrolyte production method, and more particularly, to a solid electrolyte which is capable of improving the safety of a battery and improving shuttle phenomenon by applying a solid electrolyte instead of a liquid electrolyte used in a general lithium / And a method for producing an electrolyte.

The electrolyte is one of the main components of the secondary cell, and serves as a path for ion movement in the cell during charging and discharging.

Ion is the medium that stores the electric energy in the electrode by neutralizing the electrons inserted into the electrode and determines the amount of electric energy that can be stored. It is also the amount of ions inserted into the electrode to achieve charge neutrality.

In addition, the faster the moving speed of the ion between the electrolyte and the electrode, the faster the reaction rate in the electrode. That is, the moving speed of phosphorus in the electrolyte and the electrode region greatly affects the overall reaction rate of the battery.

There are several properties required for such electrolytes. First, the ion conductivity must be excellent in order to facilitate the transfer of lithium ions into / out of the cathode and the anode and the lithium ion in the electrolyte solution even during rapid charging / discharging of the battery.

In addition, since it causes an electrochemical reaction at the positive electrode and negative electrode of the battery, it must be electrochemically stable in the charging and discharging voltage range and chemically stable for various metals and materials in the electricity.

Types of such electrolytes include liquid electrolytes, ionic liquid electrolytes, gel polymer electrolytes, and solid electrolytes. Currently the most widely used liquid electrolyte is used by dissolving salts in organic solvents. The ionic conductivity is excellent, but when the battery is heated to a high temperature due to a short circuit or the like due to the use of an organic solvent which is a combustible material, there is a risk of combustion and explosion due to ignition or ignition. Therefore, the higher the flash point and the higher the flash point, the better the organic solvent should be, and the flame retardant nonflammable material should be used. In addition, toxicity should be low so that it does not have a large influence even if it is exposed to the outside when leakage or disposal.

  An ionic liquid is a liquid salt consisting of only ions. It maintains a liquid state in a wide temperature range as compared with general liquid electrolytes and has a low vapor pressure. It is flame retardant and has excellent heat resistance and chemical stability. However, it is disadvantageous in that it has a high viscosity due to ionic bonding and another cation is present, which interferes with the movement of lithium ions in the battery.

 The gel polymer electrolyte is a solid polymer film impregnated with a polymer electrolyte matrix, which serves to store the liquid component together with the mechanical strength of the film. However, the electrolyte polymer impregnated into the polymer matrix has ~ 10-3 S / cm It has high ionic conductivity.

Lithium / sulfur batteries with high energy densities and capacities are attracting attention as the batteries become larger and larger, but liquid electrolytes are one of the biggest causes of fatal problems. Therefore, research and development are being conducted in the direction of liquid-gel-solid instead of the liquid electrolyte causing various problems, and also aiming at flame retardancy and nonflammability.

JP 05311169 B2

KR 10-1557490 B1

JP 03677508 B2

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems of the prior art.

Specifically, the solid polymer electrolyte is composed of only a polymer and a salt. First, safety is secured because there is no concern about leakage. Secondly, it is possible to manufacture various shapes and ultra-thin batteries. Third, even when the battery temperature rises, no flammable gas is ejected. Fourth, since the separator and the protection circuit are not required, the battery can be manufactured at a lower cost.

Therefore, by utilizing the advantages of the solid electrolyte as described above, it is possible to secure the safety of the battery and improve the shuttle phenomenon by using a solid electrolyte in place of the liquid electrolyte in the lithium / sulfur battery.

In order to accomplish the above object, the present invention provides a method of producing a solid electrolyte comprising mixing lithium sulfide and sulfur with TEGDME (tetraethylene glycol dimethyl ether) as a solvent to produce lithium polysulfide (Li2S8) Lithium polysulfide production step (S110); A lithium salt addition step (S120) of adding LiTFSI (lithium trifluoromethanesulfonimide) lithium salt (LiTFSI) and LiClO4 (Lithium perchlorate) to the lithium polysulfide (Li2S8) obtained from the lithium polysulfide production step (S110) and mixing them; A semi-solid phase forming step (S130) in which silica (SiO2) is added to the mixture of the lithium salt addition step (S120) to form a quasi-solid-state (QS) intermediate between the gel and the solid state; The mixture of PEO (S140), which is a mixture of PEO (ethylene oxide) in a weight ratio of 1: 1, to the quasi-solid mixture obtained in the quasi-solid phase forming step (S130) And a step (S150) of obtaining a solid electrolyte by pressurization to form a solid electrolyte in the form of a film.

Also, a method of manufacturing a solid electrolyte using electrospinning according to the present invention includes a PEO stirring step (E110) in which PEO (poly (ethylene oxide)) is added to a solvent ACN (acetonitrile, Aldrich) and stirred; A PEO web preparation step E100 including PEO electrospinning step E120 for electrospinning the mixture obtained in the PEO stirring step E110 and a PEO web preparation step E100 for electropolishing the mixture obtained in the PEO stirring step E110 by mixing PANO which mixes SiO2 and PAN (polyacrylonitrile) Mixing step (E210); A PAN electrospinning step (E220) for electrospinning the mixture obtained in said PAN mixing step (E210); A PAN nanofiber loading step (E230) in which a hydrogen fluoride (HF) diluent solution is supported to remove SiO2 in the PAN nanofiber strands obtained by electrospinning in the PAN electrification step (E220); PAN web fabrication step (E200) including PAN nanofiber drying step (E230), followed by PAN nanofiber drying step (E240) in which the supported PAN nanofibers are washed with fresh water and dried, and TEGDME (Tetraethylene glycol dimethyl ether A lithium polysulfide production step (S110) of producing lithium polysulfide (Li2S8) by mixing lithium sulfide and sulfur with a solvent as a solvent; A lithium salt addition step (S120) of adding LiTFSI (lithium trifluoromethanesulfonimide) lithium salt (LiTFSI) and LiClO4 (Lithium perchlorate) to the lithium polysulfide (Li2S8) obtained from the lithium polysulfide production step (S110) and mixing them; Semi-solid form further comprising: to form an intermediate form of a semi-solid state (Quasi-solid-state, QS ) and the mixture was added to silica (SiO ₂₎ in the gel and the solid state of the lithium salt added to step (S120) (S130) (PE) web and PAN web obtained in the PEO web preparation step (E100) and the PAN web manufacturing step (E200) were mixed with the product obtained in the semi-solid phase preparation step (S100) and the semi-solid phase preparation step (E300) of obtaining an electrospinning solid electrolyte obtained by heating and pressing to obtain a solid electrolyte in the form of a film.

As described above, the present invention uses the solid electrolyte in place of the liquid electrolyte in the lithium / sulfur battery to secure the safety of the battery and to improve the shuttle phenomenon.

That is, by using a solid electrolyte in place of the liquid organic electrolyte, the shuttle phenomenon does not occur originally. Particularly, by preparing lithium polysulfide, the inside of the electrolyte is preliminarily saturated with lithium polysulfide to prevent further dissolution of polysulfide, and since an organic solvent having no risk of explosion and combustion is not used, safety can be secured Effect.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a solid electrolyte photograph data prepared according to an embodiment of the present invention; FIG.
FIG. 2 is a flowchart showing a method for producing a solid electrolyte using PEO according to an embodiment of the present invention; FIG.
3 is a flowchart showing a method of manufacturing a solid electrolyte using electrospinning according to an embodiment of the present invention;
FIG. 4 is surface characteristic data of nanofibers prepared by electrospinning; FIG.
5 is a view showing the surface and cross-section of the pores of the fiber strand and the solid electrolyte of the nano web manufactured by electrospinning;
6 is an EDS mapping data of surface properties of nanofibers prepared using electrospinning;
FIG. 7 shows data obtained by observing the surface characteristics of the solid electrolyte according to the molar concentration of Li2S8;
FIG. 8 is the data of the EDS mapping surface analysis of the surface characteristics of the solid electrolyte according to the molar concentration of Li2S8;
9 is an electrochemical characteristic data at room temperature of a solid electrolyte prepared by mixing LiTFSI with different concentrations of Li2S8;
10 is an electrochemical characteristic data of a solid electrolyte at a high temperature;
11 is an electrochemical characteristic data of a solid electrolyte prepared by adding LiClO4 and each of 0.2, 0.5, and 1 M Li2S8 at room temperature;
12 is an electrochemical characteristic data of a solid electrolyte prepared by adding LiClO4 and each of 0.2, 0.5, and 1 M Li2S8 at a high temperature;
13 is an electrochemical characteristic data of a lithium / sulfur battery using PEO as a nanofiber matrix of a solid electrolyte by electrospinning at room temperature and high temperature;
14 is an electrochemical characteristic data of a lithium / sulfur battery using PAN as a nanofiber matrix of a solid electrolyte at normal temperature and high temperature;

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings, but the present invention is not limited by the scope of the present invention.

Polymers used as solid polymer electrolytes should have an amorphous structure including a polar element capable of dissociating salts because the polymer chain has a low glass transition temperature and thus the polymer chains move even at room temperature.

(PEO), poly (propylene oxide), polyphosphazene, and polysiloxane have been mainly studied. Among them, studies on electrolytes using PEO as a basic skeleton have been actively conducted.

The present invention also uses PEO as a matrix as a solid polymer electrolyte polymer. When PEO alone is used, SiO2 is added to improve the amorphization of the PEO polymer because it tends to be crystallized at 60 DEG C or less. In general, adding a liquid plasticizer improves the ionic conductivity while decreasing the crystallization tendency, but the mechanical properties of the electrolyte are weakened and the reactivity with lithium is increased. Therefore, ceramic fine particles, which are not a plasticizer in a liquid state, are added as a filler to serve as a solid plasticizer to inhibit the crystallization of PEO.

In addition, SiO2 itself does not have ionic conductivity, but ionic conductivity of electrolyte is remarkably improved when added in small amount to PEO. When PEO is mixed with a lithium salt and used as an electrolyte, it usually has an ion conductivity of 10-4 S / cm at a temperature of 60 ° C or higher.

(1) Production of solid electrolyte using PEO

Referring to FIG. 2, the solid electrolyte according to the present invention is prepared by mixing lithium sulfide and sulfur in the presence of TEGDME (tetraethylene glycol dimethyl ether) A lithium polysulfide production step (S110) for producing sulfide (Li2S8); A lithium salt addition step (S120) of adding LiTFSI (lithium trifluoromethanesulfonimide) lithium salt (LiTFSI) and LiClO4 (Lithium perchlorate) to the lithium polysulfide (Li2S8) obtained from the lithium polysulfide production step (S110) and mixing them; A quasi-solid-state (QS) state in which 15 wt% of silica (SiO ₂ ) is added to the mixture of the lithium salt addition step (S120) to form an intermediate form of gel and a solid state Step S130; The mixture of PEO (S140), which is a mixture of PEO (ethylene oxide) in a weight ratio of 1: 1, to the quasi-solid mixture obtained in the quasi-solid phase forming step (S130) And a step (S150) of obtaining a solid electrolyte by pressurization to form a solid electrolyte in the form of a film.

Specifically, all the raw materials are vacuum dried in a glove box filled with argon to remove water and impurities before preparing the solid electrolyte.

Lithium sulfide (Aldrich) and sulfur (100 mesh, Aldrich) were mixed with TEGDME (Tetraethylene glycol dimethyl ether, Aldrich) as a solvent to prepare lithium polysulfide (Li2S8) of 0.2, 0.5, .

Two kinds of lithium salt LiTFSI (Bis (trifluoromethanesulfonimide) lithium salt, Aldrich) and LiClO4 (Lithium perchlorate, Aldrich) Aldrich) is added to each concentration.

The TEGDME-lithium polysulfide-lithium salt in liquid state is adsorbed to SiO2 in a comparable amount to the solid state. It is in the form of gel and solid state, called quasi-solid-state (QS).

PEO (Poly (ethylene oxide), Mv 600,000, Aldrich) is added to quasi-solid-state electrolyte (QSE) at a weight ratio of 1: 1 and mixed for at least 3 hours in a stirrer.

After sufficiently mixing, applying a pressure of 0.8 MPa at 100 DEG C for 60 minutes can produce a film-like solid electrolyte as shown in Fig. It is ~ 100 μm thick, very flexible and elastic.

The results of observing the surface characteristics of the solid electrolyte according to the molar concentration of lithium polysulfide (Li2S8) in the step of producing lithium polysulfide (S110) are shown in FIG. The surface of the solid electrolyte to which 0.2 M of Li 2 S 8 was added at the time of manufacture shows that the PEO matrix was not formed as a whole and that the materials added during the production were not mixed evenly. On the other hand, when 0.5 M of Li 2 S 8 is added, the solid electrolyte has a smooth surface evenly mixed with PEO, SiO 2 and lithium salt. When a larger amount of Li2S8 is added, it is confirmed that the particles are precipitated on the surface of the PEO matrix.

Figure 8 shows the positional information of each element through the EDS mapping surface analysis in order to more precisely confirm the component distribution of the surface. The solid electrolyte added with 0.5 M Li2S8 has a uniform mixture of all the elements (Fig. 8 (a)), but when 1 M is added, the particles observed on the surface are excessively added with sulfur through EDS mapping analysis, (Fig. 8 (b)). As a result of FE-SEM and EDS analysis, 0.5 M of Li2S8 was the most suitable ratio and showed the most uniform surface shape.

Next, FIG. 9 shows the electrochemical characteristics at room temperature of the solid electrolyte prepared by mixing LiTFSI selected with Li salt with different concentrations of Li2S8. LiTFSI and 0.2, 0.5, and 1 M Li2S8 were added to the solid electrolytes. The initial discharge capacities of the batteries were 1308, 95, and 721 mAhg-1 at 0.1 C and 30 ° C, respectively. Are 314, 164, and 149 mAhg-1, respectively.

0.2, and 1 M Li2S8 was added to the surface of the solid electrolyte. As a result, the internal electrode resistance was increased due to poor electrolyte and electrode interface characteristics, and the cycle characteristics were also affected.

The solid electrolyte prepared by adding 0.2 and 1 M of Li2S8, respectively, showed a second flat region not observed in the discharge curves of the lithium / sulfur battery, unlike the solid electrolyte containing 0.5 M of Li2S8, The flattening period is observed during the process of lithium ions moving through the electrolyte and reacting with the sulfur of the anode and reacting with a high-dimensional lithium polysulfide to a low-level lithium polysulfide. Due to the excess of Li 2 S 8 added between the sulfur electrode and the lithium ion Of the respondents said they did not have any further progress. In addition, due to the characteristics of Li2S8 and the solid polymer added in an excessive amount, the lithium ion reaches the sulfur by the low ionic conductivity at room temperature, and therefore, it takes more time to eventually slow the electric reaction in the battery, This is a major cause.

The electrochemical characteristics at a high temperature of the solid electrolyte prepared under the same conditions are shown in FIG. The initial discharge capacity of LiTFSI and 0.2, 0.5, and 1 M Li2S8 was 685, 1439 and 527 mAhg-1 at 0.1 C and 80 ℃, respectively. Discharge capacity in the 25th cycle was 461 mAhg-1 and 1.0 M Li2S8 in the 20th cycle, the discharge capacity was 147 mAhg-1, and the discharge capacity was 147 mAhg-1. The results can be confirmed. The addition of SiO2 prevents the aggregation of the polymer chain of PEO, thereby reducing the crystallization tendency and securing the amorphous region and improving the ionic conductivity. However, since the interaction between O-Li + is strong as PEO is used as a matrix, It is judged that sufficient ionic conductivity does not appear.

The electrochemical characteristics at room temperature of solid electrolytes prepared by adding LiClO4 and 0.2, 0.5, and 1 M Li2S8, which are superior in ionic conductivity when bound to PEO, are shown in FIG. 11 to improve ionic conductivity and improve cycle characteristics . The initial discharge capacities of 375, 590 and 206 mAhg-1 were observed at 0.1 C, respectively. In the 20th cycle, discharge capacities of 138, 394 and 136 mAhg-1 were better than solid electrolytes containing LiTFSI at room temperature. Do.

FIG. 12 shows electrochemical characteristics at a high temperature of a solid electrolyte prepared by mixing LiClO4 selected with Li salt and Li2S8 at different concentrations. The cells using Li2S8 with 0.2, 0.5, and 1 M of LiClO4 showed an initial discharge capacity of 422, 230, and 1027 mAhg-1 at 0.1 C and 80 ° C, respectively. The discharge capacity is 318 mAhg-1 in the cycle, 0.5 M Li2S8 is 659 mAhg-1 in the 12th cycle, and the discharge capacity is 108 mAhg-1 in the 15th cycle of 1.0 M Li2S8. The initial discharge capacity of 1.0 M Li2S8 was the highest, but the capacity was drastically decreased during the cycle, while 0.5 M Li2S8 was gradually stabilized as the cycle progressed and the cycle holding characteristics were the best.

The SiO2 added during the production of the solid electrolyte inhibits the crystallization of the polymer and promotes dissociation of the salt due to the ferroelectricity of the inorganic substance by allowing the residual water or impurities in the electrolyte to be adsorbed on the surface of the inorganic particles. As a result, ionic conductivity, mechanical strength, and electrode and electrolyte interface characteristics can be expected to be improved. As confirmed by the surface shape results, SiO2 is evenly dispersed in the solid electrolyte to which 0.5 M of Li2S8 is added, and thus the interface stabilizing action is obtained.

Therefore, the molar concentration of lithium polysulfide (Li2S8) in the lithium polysulfide production step (S110) is preferably 0.5M.

(2) Solid electrolytes according to the type of matrix prepared by electrospinning

① Electrospinning

In the above-described solid electrolyte production method, PEO in powder state and [TEGDME-lithium polysulfide-lithium salt-SiO 2] in quasi-solid state were simply mixed and heat-treated and compressed to obtain a film form. In another manufacturing method, electrospinning is used to more easily transfer lithium ions into the solid electrolyte matrix.

Referring to FIG. 3, a method of preparing a solid electrolyte using the electrospinning method according to the present invention will be described. A PEO stirring step (E110 (1)) in which 1.8 g of PEO (poly (ethylene oxide)) is added to 45 ml of solvent ACN (acetonitrile, Aldrich) ); The mixture obtained in the PEO stirring step E110 was applied at an applied voltage of 16 kV, the distance from the nozzle to the collector was 18 cm, the current collecting speed was 180 rpm, the nozzle diameter was 21 gauge (ID: 0.51 mm) a PEO web preparation step (E100) including a PEO electrospinning step (E120) in which electrospinning is carried out in an electrospinning step (E120) Step E210; The mixture obtained in the PAN mixing step E210 was applied at an applied voltage of 20 kV, the distance from the nozzle to the collector was 18 cm, the current collecting speed was 180 rpm, the nozzle diameter was 21 gauge (ID: 0.51 mm) a PAN electrospinning step (E 220) of electrospinning at a rate of 1 ml / min; In order to remove SiO2 in the PAN nanofiber strands obtained by electrospinning in the PAN electrospinning step (E220), HF (hydrogen fluoride: Advantor performance materials, Inc 50%) was supported on a 1: 1 diluted solution in distilled water PAN nanofiber supporting step (E230); PAN web fabrication step (E200) including PAN nanofiber drying step (E230), followed by PAN nanofiber drying step (E240) in which the supported PAN nanofibers are washed with fresh water and dried, and TEGDME (Tetraethylene glycol dimethyl ether A lithium polysulfide production step (S110) of producing lithium polysulfide (Li2S8) by mixing lithium sulfide and sulfur with a solvent as a solvent; A lithium salt addition step (S120) of adding LiTFSI (lithium trifluoromethanesulfonimide) lithium salt (LiTFSI) and LiClO4 (Lithium perchlorate) to the lithium polysulfide (Li2S8) obtained from the lithium polysulfide production step (S110) and mixing them; A quasi-solid-state (QS) state in which 15 wt% of silica (SiO ₂ ) is added to the mixture of the lithium salt addition step (S120) to form an intermediate form of the gel and a solid state PEO web production step (E100) and PAN web production step (E200) obtained in the semi-solid phase production step (S100) and the quasi solid phase production step (S100) including step (S130) And a step (E300) of obtaining an electrospinning solid electrolyte by mixing and heating the PAN web to obtain a solid electrolyte in the form of a film.

Specifically, electrospinning is a technique of obtaining a nonwoven web made of fibers of several hundreds of nm in diameter by using an electrostatic repulsion between the polymer chains and an electric field generated between the cathode and the anode by applying a high voltage to the polymer solution or melt to be.

That is, a high-voltage electric field is applied to discharge the polymer melt or the polymer solution charged with (+) from the spinneret and collect it in the charged current collector.

When a specific threshold voltage is applied, one jet is formed from the polymer solution or molten material in the nozzle, and is split into several fibers having a diameter of nanometer together with evaporation of the solvent.

These cracked fibers are irregularly collected on the (-) charged collecting body to form a nonwoven fabric.

② PEO web manufacture

1.8 g of PEO (poly (ethylene oxide)) is added to 45 ml of solvent ACN (acetonitrile, Aldrich), stirred for 24 hours, and the mixed solution is transferred into a 60 ml syringe and electrospun. At this time, the applied voltage was 16 kV, the distance from the syringe to the current collector was 18 cm, the current collecting speed was 180 rpm, the nozzle diameter was 21 gauge (ID: 0.51 mm) Radiation.

③ PAN web manufacturing

7 g of SiO2 (Aldrich, Particle size: 7 nm) and PAN (polyacrylonitrile: Polysciences, Inc. Mw: 150,000) were added to 54.6 ml of a solvent DMF (dimethylformamide: Samchun Pure Chemical Co., And mixed for 1 hour using a high energy ball mill. The mixture solution is transferred into a 60 ml syringe and electrospun. At this time, the applied voltage is 20 kV, the distance from the syringe to the current collector is 18 cm, the current collecting speed is 180 rpm, the nozzle diameter is 21 gauge (ID: 0.51 mm) and the scanning speed is 0.1 ml / min. The PAN nanofibers produced by the electrospinning were spun onto a dried aluminum foil on a stainless steel rotary drum placed on the bottom, and HF (hydrogen fluoride: Advantor performance materials. %) Is diluted to 1: 1 with distilled water. PAN nanofibers are added to the solution for 24 hours at room temperature, washed with distilled water, and dried in an oven at 50 ° C for 24 hours.

④ Solid electrolyte production

Two kinds of matrices were obtained through the above-mentioned electrospinning, and then the pressure was applied at a pressure of 0.6 MPa at 30 DEG C for 5 minutes together with QSE prepared according to the PEO-based solid electrolyte production method described above, By uniformly penetrating between the strands, it is possible to obtain a solid electrolyte in the form of a film having a thickness of 80 μm or less.

The surface properties of the nanofibers produced by such electrospinning are shown in FIG. The nanofiber webs, which are spun using PEO and PAN, have a smooth surface and have a structure in which the fiber strands can penetrate the QSE in a well-porous form.

In particular, PAN nanofibers have more pores than PEO nanofibers by removing SiO2 in the strands. That is, the PAN nanofibers can fill the pores within the strands as well as the pores between the strands. Thus, a larger amount of QSE can be made more evenly filled with a solid electrolyte. This can be confirmed from FIG. 5 and FIG. 5 shows the surface (Fig. 5 (c)) of the solid electrolyte made by filling QSE (Fig. 5 (b)) between the inner pores and the strands of the fiber strand (Fig. 5 Sectional view (Fig. 5 (d)). PAN-QSE EDS mapping analysis also shows that QSE is well dispersed and evenly distributed on the surface and cross-section of PAN nanofibers.

Next, FIG. 13 shows electrochemical characteristics at room temperature and high temperature of a lithium / sulfur battery using PEO as a nanofiber matrix of a solid electrolyte by electrospinning. The initial discharge capacity of 95 mAhg-1 at 0.1 ° C and 30 ° C is shown. The discharge rate is maintained at 190 mAhg-1 in the 30th cycle as the reaction rate increases and stabilizes after the first discharge. At 80 deg. C, the initial discharge capacity is 485 mAhg-1, and the discharge capacity in the 30th cycle is 126 mAhg-1. When the powdered PEO is used as the matrix, the high temperature characteristics are remarkably excellent. However, when the electrospun PEO nanofiber is used as the matrix, the electrochemical characteristics at room temperature are better in terms of the discharge capacity retention ratio. The nanofiber matrix prepared by electrospinning is thinner than the powder form, and the QSE is evenly dispersed, so it is easier to transport lithium ions at room temperature.

FIG. 14 is an electrochemical characteristic of a lithium / sulfur battery using PAN as a nanofiber matrix of a solid electrolyte at normal temperature and high temperature. The initial discharge capacity was shown to be 1887 mAhg-1 at 0.1 ° C and 30 ° C, and the discharge capacity at 160th mAh-1 was 1603 mAhg-1. At 80 ° C, the initial discharge capacity is 924 mAhg-1, the discharge capacity in the seventh cycle is 1072 mAhg-1, stabilized after the first discharge, and the capacity is gradually decreased.

Regardless of the type of the matrix of the lithium salt and the solid polymer electrolyte comparing the electrochemical characteristics, when 0.5 M of Li2S8 was added, the discharge capacity and the capacity retention were better than those of Li2S8 having different concentrations.

That is, in the case of the solid electrolyte, the addition of LiClO4 to Li salt is superior to the addition of LiTFSI to the cycle characteristics, and the proper concentration of added Li2S8 is 0.5M. By adding Li2S8 in the solid electrolyte, the shuttle phenomenon, which is a chronic problem of lithium / sulfur due to the use of a liquid electrolyte, is blocked and the stability of the electrode, Is obtained.

In addition, when using PEO as a matrix, it was better to use a powdery matrix than a nanofiber matrix using electrospinning, and the electrochemical properties of PAN nanofiber matrix were better than that of PEO. Since the thickness of the solid polymer electrolyte prepared using the PAN nanofiber matrix is thin and many pores are distributed in the nanofiber strands, the QSE is more uniformly dispersed than the nanofiber matrix using the PEO, It is easy.

While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments.

Claims (8)

A step (S110) of preparing lithium polysulfide to produce lithium polysulfide (Li2S8) by mixing lithium sulfide and sulfur with TEGDME (tetraethylene glycol dimethyl ether) as a solvent;
A lithium salt addition step (S120) of adding LiTFSI (lithium trifluoromethanesulfonimide) lithium salt (LiTFSI) and LiClO4 (Lithium perchlorate) to the lithium polysulfide (Li2S8) obtained from the lithium polysulfide production step (S110) and mixing them;
Semi-solid form further comprising: to form an intermediate form of a semi-solid state (Quasi-solid-state, QS ) and the mixture was added to silica (SiO ₂₎ in the gel and the solid state of the lithium salt added to step (S120) (S130) ;
A PEO mixing step (S140) of mixing PEO (poly (ethylene oxide) at a weight ratio of 1: 1) to the semi-solid mixture obtained from the semi-solid phase forming step (S130);
And a solid electrolyte obtaining step (S150) of heating and pressurizing the mixture of the PEO mixing step (S140) to form a solid electrolyte in the form of a film. A PEO stirring step (E110) in which PEO (poly (ethylene oxide)) is added to a solvent ACN (acetonitrile, Aldrich) and stirred; A PEO web preparation step (E100) including a PEO electrospinning step (E120) for electrospinning the mixture obtained in the PEO stirring step (E110)
PAN mixing step (E210) in which SiO2 and PAN (polyacrylonitrile) are mixed with solvent DMF (dimethylformamide); A PAN electrospinning step (E220) for electrospinning the mixture obtained in said PAN mixing step (E210); A PAN nanofiber loading step (E230) in which a hydrogen fluoride (HF) diluent solution is supported to remove SiO2 in the PAN nanofiber strands obtained by electrospinning in the PAN electrification step (E220); (PAN) web fabrication step (E200) comprising a PAN nanofiber drying step (E240) for washing and drying the supported PAN nanofibers with fresh water after the PAN nanofiber supporting step (E230)
A step (S110) of preparing lithium polysulfide to produce lithium polysulfide (Li2S8) by mixing lithium sulfide and sulfur with TEGDME (tetraethylene glycol dimethyl ether) as a solvent; A lithium salt addition step (S120) of adding LiTFSI (lithium trifluoromethanesulfonimide) lithium salt (LiTFSI) and LiClO4 (Lithium perchlorate) to the lithium polysulfide (Li2S8) obtained from the lithium polysulfide production step (S110) and mixing them; Semi-solid form further comprising: to form an intermediate form of a semi-solid state (Quasi-solid-state, QS ) and the mixture was added to silica (SiO ₂₎ in the gel and the solid state of the lithium salt added to step (S120) (S130) ; A semi-solid phase preparation step (S100)
The PEO web and the PAN web obtained in the PEO web production step (E100) and the PAN web production step (E200) are mixed with the product obtained in the semi-solid phase production step (S100) and heated to pressurize the electric And a step (E300) of obtaining a spinning solid electrolyte. 3. The method of claim 2,
The PEO electrospunping step E120 is a step in which the mixture obtained in the PEO stirring step E110 is spun by a nozzle and the applied voltage is 16 kV, the distance from the nozzle to the collector is 18 cm, the current collecting speed is 180 rpm, Wherein the diameter is 21 gauge (ID: 0.51 mm) and the spraying speed is 0.05 ml / min. 3. The method of claim 2,
The PAN electrospun process (E220) is a process in which the mixture obtained in the PAN mixing process (E210) is spun by a nozzle, the applied voltage is 20 kV, the distance from the nozzle to the collector is 18 cm, the current collecting speed is 180 rpm, A diameter of 21 gauge (ID: 0.51 mm) and an injection speed of 0.1 ml / min. 3. The method of claim 2,
In the PEO stirring step (E110), 1.8 g of PEO (poly (ethylene oxide)) is added to 45 ml of solvent ACN (acetonitrile, Aldrich) and stirred. 3. The method of claim 2,
Wherein the PAN mixing step (E210) comprises mixing 54.6 ml of DMF (dimethylformamide) with 7 g of SiO2 and 4.6 g of PAN (polyacrylonitrile). 4. The method according to any one of claims 1 to 3,
The semi-solid phase forming step (S130), the solid electrolyte, production method further comprising a step of adding a silica (SiO ₂₎ 15 wt% of the mixture of the lithium salt added to step (S120). 4. The method according to any one of claims 1 to 3,
Wherein the lithium polysulfide production step (S110) comprises a molar concentration of lithium polysulfide (Li2S8) of 0.5M.

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