KR20150088131A - Polyaniline nanopaste and preparation method thereof - Google Patents

Abstract

The present invention relates to a conductive composition comprising polyaniline particles, a preparation method thereof, a flexible electrode manufactured therefrom and all-solid flexible lithium secondary battery including the same. The conductive composition comprising polyaniline particles according to the present invention has excellent solubility in a low-boiling-point solvent and contains high density of polyaniline particles with improved crystallinity and doping level, thereby allowing a solution process in manufacturing a large area of a flexible electrode so to facilitate work processes and gain economic benefits. In addition, the flexible electrode manufactured therefrom has excellent electrical conductivity and the flexible lithium secondary battery including the flexible electrode and a solid-phase polymer electrolyte has improved stability for electrolytic solution leaks.

Description

Polyaniline nanopaste and preparation method thereof < RTI ID = 0.0 >

The present invention relates to a conductive composition comprising polyaniline particles which are excellent in solubility in a low-boiling solvent such as N-methylpyrrolidone (NMP) and chloroform, excellent in crystallinity and can be subjected to a solution process, To a flexible lithium secondary battery including a flexible electrode and a flexible electrode manufactured by using the same.

2. Description of the Related Art In recent years, research and industries for implementing portable devices with flexible characteristics have been actively conducted in the field of displays. Since the trend of such a change requires a flexible characteristic also in an energy supply device, functionalization of a lithium secondary battery, which is an energy supply device, is essential. For this purpose, development of an electrolyte suitable for a flexible electrode and a flexible battery characteristic It is desperately required.

In this regard, attention has been focused on conjugated polymers in the field of lithium secondary batteries and organic semiconductors. Particularly, among the conjugated polymers, polyaniline is characterized in that it is relatively simply polymerized by chemical oxidation and is stable in air even in a state showing high conductivity. In addition, polyaniline has a different chemical structure in a state of oxidation-reduction, doping-dedoping, and such a structural change is stable and has various electrochemical characteristics. Accordingly, various researches related to the structure, synthesis and application for using polyaniline for lithium secondary batteries and the like are under way.

As a result, Patent Document 1 discloses a method for producing soluble polyaniline using iron sulfate as a catalyst, and Patent Documents 2 and 3 disclose a method of dispersing polyaniline by mixing an additive material with a phenol-based solvent, Respectively.

However, in the case of Patent Document 1, only polyaniline to be prepared is soluble only in N-methylpyrrolidone (NMP) and N, N-dimethyl formamide (DMP) , Toluene used mainly as a resin coating agent has a problem in that the solubility thereof is remarkably low. In Patent Documents 2 and 3, an excessive amount of carcinogenic organic solvent must be used in order to produce polyaniline. Therefore, there is a great risk in the work, and due to the heat treatment (150-200 DEG C) for removing high boiling point solvent, And there is a problem that the performance is deteriorated.

Therefore, efforts to improve the solubility, conductivity, and other physical properties of polyaniline have been required for commercialization in the field of lithium secondary batteries and organic semiconductors.

In addition, when a flexible movement is applied to a lithium secondary battery, development and application of a polymer electrolyte capable of greatly improving the safety of the battery have been actively pursued in relation to leakage of the electrolyte. As a result, a gel type polymer electrolyte has been commercialized as an electrolyte of a lithium secondary battery. However, the gel-type polymer electrolyte also contains a large amount of liquid electrolytic solution, and thus is not suitable for use in a flexible battery.

Therefore, along with studies related to the improvement of the physical properties of polyaniline, there is a further demand for research on a flexible lithium secondary battery in which safety of a battery related to electrolyte leakage is ensured.

Japanese Patent Publication No. 06-200017; Korean Patent Publication No. 10-2005-0110911; Korean Patent Publication No. 10-2013-0017336.

An object of the present invention is to provide a polyaniline nanopaste which is excellent in solubility in a low-boiling solvent, excellent in crystallinity, and can be subjected to a solution process.

Another object of the present invention is to provide a method for producing the polyaniline nanopaste.

It is still another object of the present invention to provide a flexible electrode manufactured using the polyaniline nanopaste.

It is still another object of the present invention to provide a flexible lithium secondary battery including the flexible electrode.

In order to achieve the above object,

The present invention provides, in one embodiment, a polyaniline particle; And

An organic solvent,

In X-ray diffraction measurements on polyaniline particles,

A conductive composition which satisfies the following formula (1) is provided:

[Equation 1]

P ₁ ≤ P ₂

Here, P ₁ is a diffraction peak intensity of 22 to 23 ° expressed by 2 ?

P ₂ is a diffraction peak intensity of 26 to 27 ° expressed by 2 ?.

The present invention also provides, in one embodiment, a method comprising: fabricating a polyaniline (ES) doped with a first dopant;

Doping the doped polyaniline by mixing the doped polyaniline and the reducing agent;

Mixing undoped polyaniline (EB) and an organic solvent to prepare a undoped polyaniline solution; And

And doping the polyaniline by mixing the undoped polyaniline solution and the second dopant.

Further, in one embodiment, the present invention relates to a flexible substrate; Cathode collector; And a polyaniline nanopaste layer comprising the conductive composition.

In addition, the present invention, in one embodiment,

The flexible electrode;

Solid polymer electrolyte; And

There is provided a flexible lithium secondary battery including a counter electrode.

The conductive composition comprising the polyaniline particles according to the present invention has high solubility in the low-boiling solvent and high-density polyaniline particles with improved crystallinity and doping level, so that it is possible to perform a solution process in the production of a large- There is an economic advantage. Also, the flexible electrode manufactured using the flexible electrode has an excellent electrical conductivity, and the flexible lithium secondary battery including the flexible electrode and the solid polymer electrolyte has an advantage of improving the stability against electrolyte leakage.

1 is an image showing an FT-IR spectrum of polyaniline contained in a polyaniline nanopaste in one embodiment;
Figure 2 is an image showing the UV spectrum of polyaniline in one embodiment, wherein (a) is the spectrum of the doped polyaniline, (b) is the spectrum of the doped polyaniline, and (c) The spectrum of the nanopaste;
3 is an image showing the X-ray diffraction spectrum of doped polyaniline in one embodiment: wherein (a) is the spectrum of the doped polyaniline and (b) the spectrum of the polyaniline nanopaste;
4 is an SEM image of a polyaniline, in one embodiment, wherein (a) is an image of a doped polyaniline, (b) is an image of a doped polyaniline, and c) is an image of a polyaniline nanopaste;
Figure 5 is an image of a result of a painting test of doped polyaniline in one embodiment: (a) is an image using a doped polyaniline solution, and (b) is an image using a polyaniline nanopaste;
FIG. 6 is an image of the result of coating using a screen printing technique of polyaniline nanopaste in one embodiment; FIG.
7 is an image of the manufactured flexible electrode in one embodiment;
8 is an image of a manufactured flexible lithium secondary battery in one embodiment;
9 is an image photographed, in one embodiment, of a resultant voltage result for the manufactured flexible lithium secondary battery;
10 is an image showing a structure of a flexible lithium secondary battery according to the present invention;
FIG. 11 is a graph showing charge / discharge curves for each flexible lithium secondary battery manufactured using a doped polyaniline solution and a doped polyaniline nano paste in one embodiment. Here, (a) is a graph showing the charge / discharge curve of the doped polyaniline nano (B) is a flexible lithium secondary battery made from a doped polyaniline solution;
FIG. 12 is a graph showing charge / discharge cycles for each flexible lithium secondary battery manufactured using a doped polyaniline solution and a doped polyaniline nano paste in one embodiment: (a) (B) is a flexible lithium secondary battery made from a doped polyaniline solution.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail.

It should be understood, however, that the invention is not intended to be limited to the particular embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

In the present invention, the terms "comprising" or "having ", and the like, specify that the presence of a feature, a number, a step, an operation, an element, a component, But do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.

Hereinafter, the present invention will be described in detail with reference to the drawings, and the same or corresponding components are denoted by the same reference numerals regardless of the reference numerals, and a duplicate description thereof will be omitted.

The present invention provides a conductive composition comprising polyaniline particles, a method for producing the same, a flexible electrode manufactured using the same, and a flexible electrode.

2. Description of the Related Art In recent years, research and industries for implementing portable devices with flexible characteristics have been actively conducted in the field of displays. Since the trend of such a change requires a flexible characteristic also in an energy supply device, functionalization of a lithium secondary battery, which is an energy supply device, is essential. For this purpose, development of an electrolyte suitable for a flexible electrode and a flexible battery characteristic It is desperately required.

Accordingly, the present invention proposes a conductive solid composition comprising polyaniline particles, a method for producing the same, a flexible electrode manufactured using the same, and a flexible electrode.

The conductive composition comprising the polyaniline particles according to the present invention has high solubility in the low-boiling solvent and high-density polyaniline particles with improved crystallinity and doping level, so that it is possible to perform a solution process in the production of a large- There is an economic advantage. In addition, the flexible electrode manufactured using the flexible electrode has an excellent electrical conductivity, and the flexible lithium secondary battery including the flexible electrode and the pre-solid electrolyte has an advantage that the stability against electrolyte leakage is improved.

Hereinafter, the present invention will be described in more detail.

The present invention provides, in one embodiment, a polyaniline particle; And

An organic solvent,

In X-ray diffraction measurements on polyaniline particles,

A conductive composition which satisfies the following formula (1) is provided:

[Equation 1]

P ₁ ≤ P ₂

Here, P ₁ is a diffraction peak intensity of 22 to 23 ° expressed by 2 ?

P ₂ is a diffraction peak intensity of 26 to 27 ° expressed by 2 ?.

The polyaniline particles contained in the conductive composition according to the present invention have diffraction peaks at 22 to 23 ° and 26 to 27 ° expressed by 2 ? In the X-ray diffraction measurement. The 22 to 23 ° peak (P ₁ ) represented by the 2 θ is a peak having a surface index [100], which is related to the periodicity to the vertical plane, and the 26 to 27 ° peak (P ₂ ) , Which is a peak reflecting the local crystallinity of the polyaniline itself.

At this time, looking at the intensity of 22 to 23 ° peak (P ₁₎ and 26 to 27 ° peak (P ₂₎ represented by the 2 θ for polyaniline particles according to the present invention compared to 26 to 27 ° is represented by 2 θ It can be seen that the intensity of the peak P ₂ is stronger than the 22 to 23 ° peak (P ₁ ). This means that the ratio of [Cl] / [N] has reached a level of about 0.5. That is, the crystallinity and doping level of the polyaniline particles are high.

From this, it can be seen that the conductive composition according to the present invention includes polyaniline particles having excellent crystallinity and doping level.

Also, the conductive composition according to the present invention is characterized in that,

In X-ray diffraction measurements on polyaniline particles,

22.4, 26.5, 27.5, and 30.2 degrees of diffraction peak value, expressed as 2 &thetas;.

FIG. 3 is a graph showing the X-ray diffraction pattern of (a) doped polyaniline and (b) doped polyaniline nanopaste, which is a conductive composition according to the present invention, in one embodiment.

Referring to FIG. 3 (b), in the X-ray diffraction measurement of the conductive composition comprising the polyaniline particles and the organic solvent according to the present invention, the diffraction peaks expressed by 2 ? Were 16.7, 22.4, 26.5, At 27.5 [deg.] And 30.2 [deg.], Interference between relatively peaks was less pronounced and clear. At this time, the fact that each peak is less interference and clear means that the region having amorphous is decreased.

Accordingly, it can be seen that the conductive composition according to the present invention includes polyaniline particles having excellent crystallinity and doping level, and electric conductivity is also improved due to improved crystallinity and doping level.

The conductive composition according to the present invention,

Particles having an average particle size of 40 to 60 nm account for 70% or more of the total particles,

And the particles having an average particle diameter of 30 to 80 nm are at least 95% of the total particles.

In addition, the shape of the polyaniline particle is not particularly limited, but specifically, it may be a hexahedron having a maximum angle of 90 to 120 degrees inside the hexahedron.

FIG. 4 is an image obtained by scanning electron microscopy of (a) doped polyaniline, (b) doped polyaniline, and (c) doped polyaniline nanopaste, which is a conductive composition according to the present invention, in one embodiment.

Referring to FIG. 4 (c), it can be seen that the polyaniline nanopaste, which is a conductive composition according to the present invention, contains polyaniline particles having an average particle diameter of 40 to 60 nm of 70% or more of the total particles. It can also be seen that the particles having an average particle diameter of 30 to 80 nm comprise polyaniline particles which are 95% of the total particles. Further, it can be seen that the conductive composition contains a mixture of polyaniline particles in the form of a rectangular parallelepiped or a cuboid. This means that the polyaniline particle has a uniform size of 100 nm or less and its shape is also constant in a rectangular parallelepiped or a cuboid.

From this, it can be seen that the conductive composition including the uniform polyaniline particles is excellent in crystallinity as well as excellent in electric conductivity because of improved crystallinity.

Also, the conductive composition according to the present invention may be in the form of a paste, wherein the density (D) of the polyaniline particles contained in the conductive composition may satisfy the following formula (2)

&Quot; (2) "

40 mg / mL? D? 200 mg / mL.

Since the conductive composition contains polyaniline particles having excellent crystallinity in a minimum amount of organic solvent at a high density, it is possible to apply a solution process when manufacturing a large-area electrode, which is economically advantageous.

In this case, the polyaniline particles specifically include 40 mg / mL to 20 mg / mL; 40 mg / mL to 150 mg / mL; 40 mg / mL to 100 mg / mL; 50 mg / mL to 180 mg / mL; 50 mg / mL to 100 mg / mL; 50 mg / mL to 80 mg / mL; From 100 mg / mL to 200 mg / mL or from 100 mg / mL to 150 mg / mL.

5 is an image of a result of a painting test on a polyaniline solution and a polyaniline nanopaste in one embodiment.

Referring to FIG. 5, polyaniline (b) doped polyaniline nanopaste (density of polyaniline particles: 50 mg / mL) was painted as a conductive composition, and polyaniline was uniformly applied to the substrate. On the other hand, when the (a) conventional doped polyaniline solution is painted, the area where the polyaniline is applied to the substrate is remarkably small, and the polyaniline to be applied is not uniform.

From this, it can be seen that the conductive composition according to the present invention has excellent solution processability.

Furthermore, the organic solvent of the conductive composition according to the present invention is not particularly limited as long as it is a solvent in which polyaniline is dissolved. More specifically, for example, N-methylpyrrolidone, cnloroform, N, N-dimethylformamide, m-cresol m -cresol) can be used.

The use of an organic solvent having a low boiling point such as N-methylpyrrolidone or chloroform as the organic solvent of the conductive composition is effective in the structural modification of the polyaniline generated by the high temperature heat treatment for removing the organic solvent having a high boiling point Can be prevented.

In addition, the conductive composition according to the present invention may further include at least one of a binder and a conductive agent.

The binder may be used to bond the conductive composition to a flexible substrate in the production of a flexible electrode. Examples of the binder applicable to the present invention include polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), carboxymethylcellulose / styrene-butadiene rubber (CMC- SBR, carboxymethyl cellulose / styrene-butadiene rubber), polyolefin, polyimide, polyurethane, polyester or mixtures thereof.

In addition, the conductive agent can be used to improve the current flow in the flexible electrode manufactured using the conductive composition according to the present invention. Examples of the conductive agent applicable to the present invention include super-p, carbon black, acetylene black, denka black, ketjen black, Or a vapor-grown carbon fiber (VGCF); Silver (Ag); Aluminum (Al); Copper (Cu); Zinc (Zn), or mixtures thereof.

In addition, the present invention, in one embodiment,

Preparing a polyaniline (ES) doped with a first dopant;

Doping the doped polyaniline by mixing the doped polyaniline and the reducing agent;

Mixing undoped polyaniline (EB) and an organic solvent to prepare a undoped polyaniline solution; And

Doped polyaniline solution and a second dopant to form a polyaniline solution, thereby doping the polyaniline in the solution.

Hereinafter, the method for preparing the conductive composition according to the present invention will be described in detail for each step.

First, in the step of preparing the doped polyaniline (ES) according to the present invention, the first dopant dissolved in water and the aniline monomer are mixed and stirred. Then, an initiator is added to polymerize the aniline monomer, and the reaction mixture is filtered Polyaniline can be produced.

At this time, the polyaniline to be produced may be a doped emeraldine salt (ES).

In addition, the first dopant can be applied to the present invention, for example, hydrofluoric acid (HF), hydrochloric acid (HCl), perchloric acid (HClO _4), nitric acid (HNO _3), sulfuric acid (H ₂ SO _4), fluorine sulfonic acid ( FSO ₃ H), sulfonic acid (CH ₃ SO ₃ H), camphorsulfonic acid, polystyrenesulfonic acid (PSS), p-toluenesulfonic acid (p-TSA), dodecylbenzenesulfonic acid , dodecyl benzene sulfonic acid), or mixtures thereof, but are not limited thereto.

Further, the polymerization can be carried out by stirring at room temperature for 5 minutes to 1 hour. When polyaniline having a weight average molecular weight (M _w ) of about 50,000 is prepared, the polymerization can be carried out at 0 ° C for 24 hours with stirring.

Next, in the step of deodoping the doped polyaniline according to the present invention, the polyaniline prepared in the above step is mixed with a reducing agent to remove the protons of the polyaniline to obtain undoped polyaniline (EB, emeralide base) .

Examples of the reducing agent applicable to the present invention include ammonium hydroxide (NH ₄ OH), sodium hydroxide (NaOH), potassium hydroxide (KOH), calcium hydroxide (Ca (OH) ₂ ) , But is not limited thereto.

Next, in the step of preparing the undoped polyaniline solution according to the present invention, the undoped polyaniline solution may be prepared by dissolving the undoped polyaniline in the organic solvent contained in the conductive composition.

In this step, the size and shape of the doped polyaniline particles prepared according to the amount of the undoped polyaniline powder dissolved in the organic solvent, that is, the concentration of the dissolved solution, can be controlled.

At this time, the organic solvent according to the present invention is not particularly limited as long as it is a solvent in which polyaniline is dissolved. More specifically, for example, N-methylpyrrolidone, cnloroform, N, N-dimethylformamide, m-cresol m -cresol) can be used.

Next, in the step of doping the polyaniline, the doped polyaniline solution prepared in the above step may be mixed with the second dopant, and the doped polyaniline solution may be prepared by performing a reaction in a reactor having a mechanical external force.

At this time, the mechanical external force used in this step plays a role of maintaining the uniform size and shape of the polyaniline particles.

In this step, similarly to the step of preparing the undoped polyaniline solution, the size and shape of the doped polyaniline particles produced according to the concentration of the second dopant mixed in the undoped polyaniline solution can be controlled.

The second dopant can be applied to the present invention, for example, hydrofluoric acid (HF), hydrochloric acid (HCl), perchloric acid (HClO _4), nitric acid (HNO _3), sulfuric acid (H ₂ SO _4), fluorine sulfonic acid (FSO ₃ H), sulfonic acid (CH ₃ SO ₃ H), camphorsulfonic acid, polystyrenesulfonic acid (PSS), p-toluenesulfonic acid (p-TSA), dodecylbenzenesulfonic acid benzene sulfonic acid, or mixtures thereof, but are not limited thereto.

Further, the reactor in which a mechanical external force acts is not particularly limited as long as it is a device capable of pulverizing simultaneously with stirring of the reactants. Specifically, for example, a ball mill may be used.

The method for producing the conductive composition according to the present invention comprises:

Prior to the step of preparing the undoped polyaniline solution,

Pulverizing the undoped polyaniline;

After the step of doping polyaniline,

Mixing an additive in a doped polyaniline solution; And

After the step of doping polyaniline,

And removing the excess solvent by centrifugation.

The step of pulverizing the undoped polyaniline according to the present invention serves to homogenize polyaniline particles by pulverizing polyaniline with an external force before dissolving the polyaniline in the organic solvent contained in the conductive composition. The polyaniline particles that have been made uniform by this step can have improved electrical conductivity with better crystallinity.

In addition, the step of mixing the additive with the doped polyaniline solution according to the present invention can improve the adhesion of the polyaniline solution to the flexible substrate by mixing the doped polyaniline solution with a binder or a conductive agent, The current flow of the flexible electrode to be manufactured can be improved.

In addition, the step of centrifuging the excess solvent according to the present invention can increase the polyaniline density of the polyaniline solution. In this step, when the density of the polyaniline solution is low, it is difficult to manufacture a flexible electrode having a large area. Therefore, after performing the centrifugation of the doped polyaniline solution, the supernatant which is the surplus solvent is removed and the density of the polyaniline in the polyaniline solution is 40 mg / mL To 200 mg / mL.

Further, the present invention, in one embodiment,

A flexible substrate; Cathode collector; And a polyaniline nanopaste layer comprising the conductive composition.

The flexible electrode is advantageous in that it has excellent electrical conductivity as compared with a flexible electrode manufactured using a conventional polyaniline solution by preparing the flexible electrode using the polyaniline nanopaste according to the present invention.

Hereinafter, each component of the flexible electrode according to the present invention will be described in detail.

First, the flexible substrate according to the present invention is a substrate serving as a base of a flexible electrode, and has a characteristic that flexibility acts when an external force is applied from the outside.

The flexible substrate applicable to the present invention is not particularly limited as long as it is a flexible substrate. Examples of the flexible substrate include polyethylene terephthalate (PET), polyethyleneterephthalate (PEN), poly (ethylene naphthalate) , Polyethersulfone (PES), or a mixed resin thereof.

Next, the negative electrode collector according to the present invention is not particularly limited as long as it has a thickness of 3 to 500 탆 and has high conductivity without causing chemical changes in the battery. For example, copper, stainless steel Aluminum, nickel, titanium, sintered carbon, or aluminum or stainless steel whose surface is treated with carbon, nickel, titanium, silver, or the like. More specifically, nickel can be used.

At this time, the negative electrode current collector may have fine irregularities on the surface thereof to increase the adhesive force of the negative electrode active material, and various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric are possible.

Next, the polyaniline nano-paste layer according to the present invention is a layer containing a conductive composition comprising the polyaniline particles according to the present invention. By using the conductive composition, it is possible to perform a solution process at the time of manufacturing a flexible electrode having a large area It is easy to work and has an economical advantage. In addition, the polyaniline particles contained in the conductive composition have an improved electrical conductivity because of their improved crystallinity and doping level.

The flexible electrode according to the present invention can be manufactured by the following manufacturing method:

Printing an anode current collector on one surface of a flexible substrate;

Coating a conductive composition according to the present invention on one side of a flexible substrate on which an anode current collector is printed; And

Heat-treating and drying the coated flexible substrate.

In the method of manufacturing the flexible electrode, the step of coating the conductive composition may be performed by a solution process. Examples of the applicable solution process include a dip coating method, a spin coating method, a meniscus coating method, a printing method, and a spray coating method. More specifically, a printing method can be used.

The solution processes are simple in process, low in equipment cost and manufacturing cost, and can be deposited in a desired pattern position, so that in principle, there is no loss of material, so there is no waste of raw material and environmental load is small. In addition, there is an advantage that the characteristics of the substrate and the material are not deteriorated due to a chemical effect because processes such as development and etching are not required like photolithography.

In addition, in the method of manufacturing the flexible electrode, the step of heat-treating and drying may be performed at a temperature of 50 to 100 ° C for 5 to 48 hours.

The flexible electrode according to the present invention can be manufactured by the above-described manufacturing method, but the present invention is not limited thereto, and can be manufactured by various manufacturing methods conventionally used in the art.

In addition, the present invention, in one embodiment,

The flexible electrode;

Solid polymer electrolyte; And

There is provided a flexible lithium secondary battery including a counter electrode.

Since the flexible lithium secondary battery includes the flexible electrode according to the present invention, it has an excellent electrical conductivity as compared with an electrode including a common polyaniline, and also has an advantage of improving the safety against leakage of an electrolytic solution because it includes a solid polymer electrolyte have. 11 and 12, the flexible lithium secondary battery according to the present invention has a discharge capacity of about 1.5 times as much as that of a flexible lithium secondary battery manufactured by a conventionally produced polyaniline solution at the time of charge / It is not only superior but also has an excellent charge / discharge cycle of 100 times or more.

10, the flexible lithium secondary battery 100 according to the present invention has a structure in which a flexible electrode 103, a solid polymer electrolyte 102, and a counter electrode 101 are sequentially stacked.

Hereinafter, each component of the flexible lithium secondary battery according to the present invention will be described in detail with reference to FIG.

The counter electrode 101 according to the present invention refers to a lithium electrode and includes a positive electrode collector 105 and a positive electrode collector 105 which is supported on one or both surfaces of the positive electrode collector 105, .

The positive electrode active material 104 may be formed using a lithium metal sheet or a mixture of LiCoO ₂ , LiClO ₄ , LiNiO ₂ , LiCF ₃ SO ₃ , LiBF ₄ , LiPF ₆ , LiAsF ₆ , Li (CF ₃ SO ₂ ) ₂ N , And the like, but the present invention is not limited thereto.

As the cathode current collector 105, a conductive substrate having a porous structure or a non-porous conductive substrate can be used. These conductive substrates include, for example, copper, stainless steel, aluminum, nickel, titanium, sintered carbon, or aluminum or stainless steel whose surface is treated with carbon, nickel, titanium, silver or the like.

Further, the counter electrode 101 may include a binder for joining the cathode active material 104 and the cathode current collector 105, or for connecting the cathode active material 104; And the conductive agent for improving the current flow of the counter electrode (101).

Next, examples of the solid polymer electrolyte 102 according to the present invention include polyethylene resin, polyethylene oxide resin, polypropylene oxide resin, phosphate ester polymer, aging lysine, Based resins, polyvinyl alcohol-based resins, polyvinylidene fluoride-based resins, resins containing ionic dissociation groups, and the like, but the present invention is not limited thereto.

The flexible lithium secondary battery 100 according to the present invention can improve the safety of leakage of the lithium secondary battery 100 which has been caused by the use of the electrolyte in the related art by using the solid polymer electrolyte 102.

Next, the flexible electrode 103 according to the present invention functions as a cathode and includes a flexible substrate 108; An anode current collector 107; And a polyaniline nano-paste layer 106 comprising the conductive composition. The electrode according to the present invention is advantageous in that it has excellent electrical conductivity as compared with an electrode manufactured using a polyaniline solution by using a polyaniline nanopaste containing uniform polyaniline particles.

The flexible lithium secondary battery according to the present invention can be manufactured by the following manufacturing method:

Impregnating a material such as polyethylene, polypropylene, non-woven fabric, etc. with a solid phase pre-solid polymer electrolyte;

Introducing the impregnated solid polyelectrolyte solid polymer electrolyte between the flexible electrode and the counter electrode;

Solidifying the solid polyelectrolyte solid polymer electrolyte; And

The step of finishing the flexible cell in which the electrolyte is solidified with vinyl acetate resin and drying.

In the method of manufacturing the flexible electrode, the step of impregnating the solid phase pre-solid polymer electrolyte may be performed by impregnating a solid polyelectrolyte to a material such as polyethylene, polypropylene, non-woven fabric, or the like.

In the method of manufacturing the flexible electrode, the step of solidifying the solid phase pre-polymerization solid polymer electrolyte can be performed by solidifying the impregnated solid phase pre-solid polymer electrolyte at 80 to 100 DEG C in an oven.

The flexible lithium secondary battery according to the present invention can be manufactured by the above-described manufacturing method, but is not limited thereto, and can be manufactured by various manufacturing methods conventionally used in the related art.

Hereinafter, the present invention will be described in more detail with reference to Examples and Experimental Examples.

However, the following Examples and Experimental Examples are merely illustrative of the present invention, and the present invention is not limited to the following Examples and Experimental Examples.

Example  1. Preparation of conductive compositions

Aniline monomer (10 mL, 10.22 g, 0.1 mol) was added to 1 M HCl (320 mL), and the mixture was stirred for 20 minutes using a stirrer. Ammonium persulfate ((NH ₄ ) ₂ S ₂ O ₈ , 5.75 g) as an initiator was dissolved in 20 mL of 1 M HCl and then added dropwise over 5 minutes to the solution containing the aniline monomer at 300 rpm while stirring. Subsequently, the precipitate was filtered using a filter paper and an aspirator, and the filtered filtrate was washed with 500 mL of 1 M HCl until the filtrate became completely colorless to generate a protonated emeraldine salt (ES) .

The emeraldine salt (ES) was added to 300 mL of a 1 M aqueous solution of NH ₄ OH, followed by dehydration for 1 hour with stirring. The precipitate was filtered using a filter paper and an aspirator. The filtered filtrate was washed with 500 mL of 1 M NH ₄ OH and dried in a vacuum oven at 60 ° C for 48 hours. The filtrate was homogeneously pulverized with a mortar to prepare an emeraldine base (EB) powder Respectively.

The emeraldine base (10.330 g) was dropped and dissolved in N-methyl-2-pyrrolidone (500 mL, NMP) stirred at room temperature over 2 hours to prepare an emeraldine base ) Solution. The solution (60 mL) was poured into a zirconia container and 1 M HCl (1 mL) was added and mixed with eight zirconia balls to prepare an emeraldine base (EB) (emeraldine salt, ES).

The doped emeraldine salt solution was centrifuged at 5,000 rpm for 30 minutes and the excess supernatant liquid was removed. The precipitate was again injected into a zirconia container and mixed with eight zirconia balls at 300 rpm to prepare a doped polyaniline nano- Paste.

In order to confirm the synthesis of doped polyaniline, FT-IR spectroscopic analysis was performed on a dried powder obtained by collecting a small amount of polyaniline nanopaste, and the result is shown in FIG.

As shown in Fig. 1, the polyaniline according to the present invention had peaks at 1588, 1492, 1302, 1142, 832 and 677 cm ^-1 .

At this time, the peaks at 1588 and 1492 cm ^-1 are stretching vibration modes of C = N constituting a quinoid ring of polyaniline, and stretching vibration modes of C = C constituting a benznoid ring Mode. The peak due to the benzonoid ring is stronger than the peak due to the quinoid ring, which means that the synthesized polyaniline is doped with emeraldine.

From these results, it was confirmed that doped polyaniline was synthesized.

Example  2. flexible  Manufacture of electrodes

Except that the tab portion of the polyimide substrate was cut so as to have a size of 5 cm in width and 5 cm in length and was coated by a printing method using silver (Ag) paste. Thereafter, the masking tape was removed from the substrate coated with silver (Ag) paste and dried in an oven at 150 ° C for 15 minutes. N-methyl-2-pyrrolidone (0.3 mL, NMP) and polyvinylidene fluoride (0.01 g, PVdF) were added to the vessel and then mixed with eight zirconia balls at 120 rpm for 20 minutes. Then, a conductive agent, Super-P (0.02 g, super-p), was added and mixed for 30 minutes, and the doped polyaniline nanopaste prepared in Example 1 at a solid content density of about 50 mg / mL (1.5 mL, Weight 0.07 g) was poured into a container and mixed at 320 rpm for 2 hours to prepare a polyaniline nano-paste containing a binder and a conductive agent. At this time, the mixing ratio of doped polyaniline, polyvinylidene fluoride (PVdF) as a binder and super-p as a conductive agent is 70:10:20 (wt./wt.). The remainder was masked with tape to expose the silver paste area 3 cm in width and 3 cm in width on the polyimide substrate on which silver paste was printed, and the exposed part was coated with polyaniline nanopaste using a screen printing technique. Then, the masking tape was removed and dried in an oven at 60 DEG C for 24 hours to prepare a flexible electrode having a thickness of 60 mu m. The coated substrate coated with the screen printing technique and the flexible electrode thus manufactured are shown in FIGS. 6 and 7. FIG.

Example  3. flexible  Manufacture of lithium secondary battery

The nonwoven fabric was impregnated with a liquid polymer electrolyte of a liquid state, and the nonwoven fabric was laminated on the flexible electrode prepared in Example 2. At this time, the nonwoven fabric has a size of 3.8 cm by 3.8 cm and 14 μm by height. Then, a lithium sheet having a width of 3.2 cm and a length of 3.2 cm was laminated on a nickel mesh as a negative electrode collector, and the lithium sheet and the nickel mesh were compressed to a thickness of 0.2 mm. The pressed lithium sheet and nickel mesh were laminated on the nonwoven fabric and then heat-treated in an oven at 80 ° C for 30 minutes. The heat-treated laminate was fixed to the flexible electrode and the counter electrode with a polyimide tape, the remaining portion except the tab was coated using a polyvinyl acetate resin, and then dried for 24 hours to produce a flexible lithium secondary battery . A flexible lithium secondary battery thus manufactured is shown in Fig.

In order to confirm whether or not the voltage of the flexible lithium secondary battery fabricated above was generated, the voltage of the flexible lithium secondary battery was measured by using a detector. The results are shown in FIG.

As shown in Fig. 9, it can be seen that the open circuit voltage of the flexible lithium secondary battery according to the present invention is about 3.1 V.

Comparative Example  One. Dedoped Polyaniline  Produce

Aniline monomer (10 mL, 10.22 g, 0.1 mol) was added to 1 M HCl (320 mL), and the mixture was stirred for 20 minutes using a stirrer. Ammonium persulfate ((NH ₄ ) ₂ S ₂ O ₈ , 5.75 g) as an initiator was dissolved in 20 mL of 1 M HCl and then added dropwise over 5 minutes to the solution containing the aniline monomer at 300 rpm while stirring. Subsequently, the precipitate was filtered using a filter paper and an aspirator, and the filtered filtrate was washed with 500 mL of 1 M HCl until the filtrate became completely colorless to generate a protonated emeraldine salt (ES) .

The emeraldine salt (ES) was added to 300 mL of a 1 M aqueous solution of NH ₄ OH, followed by dehydration for 1 hour with stirring. The precipitate was filtered using a filter paper and an aspirator. The filtered filtrate was washed with 500 mL of 1 M NH ₄ OH, dried in a vacuum oven at 60 ° C for 48 hours and then dissolved in N-methyl-2-pyrrolidone (500 mL, NMP) (EB).

Comparative Example  2. Doped Polyaniline  Preparation of solution

The emeraldine salt was deodoped and dried in the step of deodoping the doped emeraldine salt (ES) with an aqueous solution of NH ₄ OH, and then the emeraldine base was dissolved in N-methyl -2-pyrrolidone (500 mL, NMP) to prepare an emeraldine base solution (EB). Then, 1 M HCl was added to the solution, and the solution was reacted with a general stirrer to prepare a doped emeraldine salt (ES) solution.

Experimental Example  1. Evaluation of doping level of conductive composition

The following experiment was conducted to evaluate the doping level of the conductive composition according to the present invention.

(A) a doped polyaniline solution, (b) a doped polyaniline solution, and (c) a UV-Vis for the doped polyaniline nanopaste prepared in Comparative Example 1, Comparative Example 2 and Example 1, respectively. The spectra were measured at 25 캜 in the range of 200-1000 nm using a UV-Vis analyzer (Optizen analyzer, Mecasys co.), And the results are shown in FIG.

As shown in FIG. 2, it can be seen that the polyaniline particles of the conductive composition (c) polyaniline nanopaste according to the present invention have an excellent doping level.

More specifically, referring to FIG. 2, a peak near 327 nm was observed in all the polyanilines. This peak is a peak attributed to the transition of the polyaniline to the π → π *. The polyaniline has a tendency to be oxidized because the band gap is as high as 4.0 eV and the ionization energy is as small as 5.1 eV. That is, when the polyaniline is doped by the dopant, a part of the valence band is deficient. (B) doped polyaniline solution of Comparative Example 2 and (c) the doped polyaniline nanopaste of Example 1 at the same wavelength, since the electrons can be transferred to the generated conduction band, The transition is more actively generated and (a) the peak of the doped polyaniline solution of Comparative Example 1 is shown.

In addition, (c) the peak of the doped polyaniline nanopaste is higher than that of the doped polyaniline solution (b) and shifted toward the longer wavelength side. This indicates that (c) the π → π * transition of the doped polyaniline nanopaste is more active and easier to generate, and (c) the doped polyaniline nanopaste shows a high doping effect and the highest conductivity have.

Further, (b) the doped polyaniline solution and (c) the doped polyaniline nanopaste can confirm the absorption peak even at around 450 nm. This is due to the protonation of the doped polyaniline.

In addition, it can be confirmed that (b) the doped polyaniline solution and (c) the doped polyaniline nanopaste have a near infrared absorption peak over 500 nm to 1000 nm. This peak is a phenomenon due to delignification of the charge carriers commonly found in materials with high electrical conductivity, and (c) the charge carrier of the doped polyaniline nanopaste is more specific.

From this, it can be seen that the conductive composition according to the present invention contains polyaniline particles having a high doping level, compared with the conventionally prepared doped polyaniline solution and the doped polyaniline solution.

Experimental Example  2. Evaluation of doping level and crystallinity of conductive composition

The following experiment was conducted to evaluate the doping level and crystallinity of the conductive composition according to the present invention.

X-ray diffraction spectra of (a) doped polyaniline solution prepared in Comparative Example 2 and Example 1 and (b) doped polyaniline nanopaste were measured. The polyaniline sample was prepared by thoroughly drying (a) the doped polyaniline solution and (b) the doped polyaniline nanopaste in an oven at 60 ° C for 48 hours, finely ground into a powder form in a mortar. Each of the samples was uniformly distributed on a sample holder, and the amount of the sample distributed on the holder was used to uniformly fill a diameter of about 1 cm. The X-ray diffraction pattern was obtained at a scanning speed of 0.02 ° / sec in the range of 10-80 ° in 2θ by scanning with 1.5406 Å wavelength using Rigaku ultra-X (Cu Ka radiation, 40 kV, 120 mA). The results are shown in Fig. The results are shown in Fig.

As shown in FIG. 3, the polyaniline particles of the polyaniline nanopaste, which is a conductive composition according to the present invention, have not only excellent crystallinity and doping level, but also have excellent electrical conductivity.

More specifically, referring to FIG. 3, the (a) doped polyaniline solution of Comparative Example 2 was measured in the form that the peaks represented by 2 ? At 16.7 ° 22.4 ° and 26.5 ° were highly interfering between peaks. The other hand, in Example 1 (b) doping the polyaniline nano-paste is 16.7 ° 22.4 ° 26.5 ° 27.5 °, and the peak was less interference between the relatively peak that appears at 30.2 ° to the 2 θ measured in clear form. As for each peak, a peak of 16.7 DEG is a peak whose surface index is [0 1 0] and reflects the periodicity in parallel, and the peak of 22.4 DEG is a surface index of [1 0 0] It is a performance-related peak. Also, a peak at 26.5 DEG is a peak whose surface index is [1 1 0] and reflects the local crystallinity of the polyaniline itself.

It can be seen that the 22.4 ° and 26.5 ° peaks of the doped polyaniline solution (a) have a similar size because the degree of doping of the polyaniline is proportional to the ratio of dopant to nitrogen atom, ie, [Cl] / [N] Is less than or equal to 0.5. On the other hand, in the case of the doped polyaniline nanopaste (b), it can be seen that the 26.5 ° peak has a larger relative ratio than the 22.4 ° peak, from which the ratio of [Cl] / [N] Able to know.

Further, a peak of 27.5 ° with a surface index of [1 1 1] and a peak of 30.2 ° with a surface index of [0 2 0] are also peaks indicating a high doping level.

From this, it can be seen that the conductive composition according to the present invention has excellent crystallinity and doping level. Further, the pattern of the polyaniline nanopaste (b) having less interference between the peaks as a whole and having a less amorphous portion means that the conductive composition is more excellent in electric conductivity as compared with a general polyaniline solution.

Experimental Example  3. Evaluation of Crystallinity of Conductive Composition

The following experiment was conducted to evaluate the crystallinity of the conductive composition according to the present invention.

Scanning electron microscopy (SEM) photographs of the doped polyaniline solution (a) prepared in Comparative Example 2 and Example 1 and (b) the polyaniline crystal form of the doped polyaniline nanopaste were performed. Respectively.

As shown in FIG. 4, the polyaniline nanopaste, which is a conductive composition according to the present invention, includes polyaniline particles having excellent crystallinity.

More specifically, referring to FIG. 4, the doped polyaniline nanopaste of Example 1 (b) has particles having an average particle diameter of 40 to 60 nm of not less than 70% of the total particles and an average particle diameter of 30 to 80 nm The particles having a particle size of 95% or more of the total particles are uniform in size as a whole. In addition, the polyaniline particles were found to have a rectangular parallelepiped or cubic shape.

On the other hand, in the doped polyaniline solution of Comparative Example 2 (a), it was confirmed that primary particles having a size of 20 to 50 nm such as skeins were combined with each other to form secondary particles having a size of 10 to 100 μm. Further, although the shape has a spherical granular structure, it has been confirmed that the granularity is remarkably low.

From this, it can be seen that (b) the doped polyaniline nanopaste has excellent crystallinity.

Experimental Example  4. Evaluation of solution fairness of conductive compositions

In order to evaluate the solution processability of the conductive composition according to the present invention, the following experiment was conducted.

(A) doped polyaniline solution prepared in Comparative Example 2 and Example 1 and (b) doped polyaniline nanopaste were subjected to a painting test. The results are shown in FIG.

As shown in FIG. 5, the conductive composition according to the present invention has excellent solution processability.

More specifically, referring to FIG. 5, the doped polyaniline nanopaste of Example 1, which is a conductive composition, was painted, and it was found that polyaniline was uniformly applied to the substrate. On the other hand, when (a) the doped polyaniline solution of Comparative Example 2 was painted, the area of the substrate coated with polyaniline was considerably small and the polyaniline applied was not uniform.

From this, it can be seen that the conductive composition according to the present invention is excellent in the solution processability by containing the polyaniline particles having excellent crystallinity in the minimum organic solvent at a high density.

Experimental Example  5. Evaluation of electrical conductivity of conductive compositions

The following experiment was conducted to evaluate the electrical conductivity of the conductive composition according to the present invention.

(A) doped polyaniline solution prepared in Comparative Example 2 and Example 1 and (b) doped polyaniline nanopaste were coated on a substrate, and then electrical conductivity was measured using a four-point terminal method on each of the coated substrates Respectively.

As a result, it can be seen that the conductive composition according to the present invention has improved electric conductivity.

More specifically, the substrate using the doped polyaniline nanopaste (b) of Example 1, which is a conductive composition according to the present invention, exhibited an electrical conductivity of 1.70 × 10 ^-1 S / cm. On the other hand, conventionally, a substrate using the doped polyaniline solution of (a) of Comparative Example 2 which is generally manufactured has an electrical conductivity of 1.09 x 10 ^-1 S / cm.

From this, it can be seen that the conductive composition according to the present invention contains polyaniline particles having excellent crystallinity and doping level, and thus has an electric conductivity about 1.6 times higher than that of a conventionally prepared doped polyaniline solution.

Experimental Example  6. flexible  The lithium secondary battery Charging and discharging  evaluation

The following experiments were conducted to evaluate charge / discharge of the flexible lithium secondary battery according to the present invention.

The charging / discharging curve of the flexible lithium secondary battery (a) prepared in Example 3 was measured. Also, a flexible lithium secondary battery (b) was prepared by using the doped polyaniline solution of Comparative Example 2 in the same manner as in Example 3, and its charging / discharging curve and charge / discharge cycle were measured. At this time, the measurement was performed at a room temperature of 25 ° C in a voltage range of 2.5 V to 4.1 V, and the current density was fixed to 5 μA / cm ² . The measured results are shown in Figs. 11 and 12. Fig.

As shown in Fig. 11 and Fig. 12, it can be seen that the flexible lithium secondary battery according to the present invention has excellent charge and discharge capacities.

More specifically, referring to FIG. 11, the charging / discharging curve of the flexible lithium secondary battery (a) produced in Example 3 shows typical charging / discharging characteristics of polyaniline, and discharge capacity was found to be about 112 mAh / g. On the other hand, in the case of the flexible lithium secondary battery (b) prepared using the doped polyaniline solution of Comparative Example 2, the charging / discharging curve shows typical charging / discharging characteristics of polyaniline, but the discharging capacity is about 75 mAh / g Respectively.

Referring to FIG. 12, it can be seen that the flexible lithium secondary battery (a) according to the present invention can be charged and discharged 100 times or more at a high discharge capacity.

It can be seen from the above that the flexible lithium secondary battery according to the present invention has an excellent discharge capacity of about 1.5 times as much as that of a conventional flexible lithium secondary battery manufactured by a commonly used polyaniline solution and has a superior charge / discharge cycle.

100: Flexible lithium secondary battery
101: opposing electrode
102: Solid polymer electrolyte
103: Flexible electrode
104: cathode active material
105: positive electrode collector
106: polyaniline nanopaste layer
107: cathode collector
108: Flexible substrate

Claims (17)

Polyaniline particles; And
An organic solvent,
In X-ray diffraction measurements on polyaniline particles,
A conductive composition satisfying the following formula:
[Equation 1]
P ₁ ≤ P ₂
Here, P ₁ is a diffraction peak intensity of 22 to 23 ° expressed by 2 ?
P ₂ is a diffraction peak intensity of 26 to 27 ° expressed by 2 ?.
The method according to claim 1,
In X-ray diffraction measurements on polyaniline particles,
2 < / RTI >&thetas; of 16.7 DEG, 22.4 DEG, 26.5 DEG, 27.5 DEG and 30.2 DEG.
The method according to claim 1,
Wherein the particles having an average particle diameter of 40 to 60 nm are 70% or more of the total particles,
Wherein the particles having an average particle diameter of 30 to 80 nm comprise at least 95% of the total particles of the polyaniline particles.
The method according to claim 1,
The shape of the polyaniline particles is hexahedral,
Wherein the maximum angle inside the cube is 90 to 120 DEG.
The method according to claim 1,
Wherein the conductive composition has a paste form.
The method according to claim 1,
The density (D) of the polyaniline particles contained in the conductive composition satisfies the following formula:
&Quot; (2) "
40 mg / mL? D? 200 mg / mL.
The method according to claim 1,
The organic solvent may be selected from the group consisting of N-methylpyrrolidone (NMP), N, N-dimethylformamide, m-cresol and cnloroform. Lt; RTI ID = 0.0 > 1, < / RTI >
The method according to claim 1,
Wherein the conductive composition further comprises at least one of a binder and a conductive agent.
9. The method of claim 8,
The binder may be selected from the group consisting of polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), carboxymethylcellulose / styrene-butadiene rubber (CMC-SBR) , A polyimide, a polyurethane, and a polyester.
9. The method of claim 8,
The conductive agent may be selected from the group consisting of super-p, carbon black, acetylene black, denka black, ketjen black or vapor grown carbon (VGCF) based conductive agent; Silver (Ag); Aluminum (Al); Copper (Cu); And zinc (Zn).
Preparing a polyaniline (ES) doped with a first dopant;
Doping the doped polyaniline by mixing the doped polyaniline and the reducing agent;
Mixing undoped polyaniline (EB) and an organic solvent to prepare a undoped polyaniline solution; And
And doping the polyaniline by mixing the undoped polyaniline solution and the second dopant.
12. The method of claim 11,
The reducing agent is ammonium hydroxide (NH ₄ OH), sodium hydroxide (NaOH), potassium hydroxide (KOH), calcium hydroxide (Ca (OH) ₂₎ as a method for producing at least one member selected from the group consisting of conductive composition.
12. The method of claim 11,
The organic solvent may be selected from the group consisting of N-methylpyrrolidone (NMP), N, N-dimethylformamide, m-cresol and cnloroform. Lt; RTI ID = 0.0 > 1, < / RTI >
12. The method of claim 11,
The first dopant and the second dopant are independently selected from the group consisting of hydrofluoric acid (HF), hydrochloric acid (HCl), perchloric acid (HClO ₄ ), nitric acid (HNO ₃ ), sulfuric acid (H ₂ SO ₄ ), fluorosulfonic acid (FSO ₃ H) (CH ₃ SO ₃ H), camphorsulfonic acid, polystyrenesulfonic acid (PSS), p-toluenesulfonic acid (p-TSA) and dodecyl benzene sulfonic acid ). ≪ / RTI >
12. The method of claim 11,
Prior to the step of preparing the undoped polyaniline solution,
Pulverizing the undoped polyaniline;
After the step of doping polyaniline,
Mixing an additive in a doped polyaniline solution; And
After the step of doping polyaniline,
And removing the surplus solvent by centrifugation to remove excess solvent.
A flexible substrate; An anode current collector layer; And a polyaniline nano-paste layer comprising the conductive composition according to claim 1.
A flexible electrode according to claim 16;
Solid polymer electrolyte; And
A flexible lithium secondary battery comprising a counter electrode.

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