KR20220099665A - Positive electrode additive for lithium secondary battery, positive electrode and lithium secondary battery comprising the same - Google Patents

Abstract

The present invention relates to a positive electrode additive for a lithium secondary battery, a positive electrode including the same, and a lithium secondary battery. More specifically, the positive electrode additive represented by chemical formula 1 is formed on the surface of a carbon material included in a positive electrode active material and is not soluble in an electrolyte to perform a function of electrically separating a positive electrode and a negative electrode, thereby improving battery performance by suppressing side reactions within a battery.

Description

Positive electrode additive for lithium secondary battery, positive electrode and lithium secondary battery containing same

The present invention relates to a positive electrode additive for a lithium secondary battery, a positive electrode comprising the same, and a lithium secondary battery.

Until recently, there has been considerable interest in developing high-energy-density batteries using lithium as an anode. Compared to other electrochemical systems with lithium intercalated carbon negative electrodes, for example, and nickel or cadmium electrodes, lithium metal, which increases the weight and volume of the negative electrode in the presence of a non-electroactive material, thereby reducing the energy density of the cell, lithium metal Since silver has low weight and high capacity characteristics, it is very interesting as an anode active material for an electrochemical cell. A lithium metal negative electrode, or a negative electrode mainly containing lithium metal, provides an opportunity to construct a battery having a higher energy density and lighter weight than a battery such as a lithium-ion, nickel metal hydride or nickel-cadmium battery. These features are highly desirable for batteries for portable electronic devices, such as cell phones and laptop computers, where the premium is paid at a low weight.

These types of positive electrode active materials for lithium batteries are known, and the positive electrode active materials include a sulfur-containing positive electrode active material containing a sulfur-sulfur bond, and are highly resistant from electrochemical cleavage (reduction) and reformation (oxidation) of the sulfur-sulfur bond. Energy capacity and rechargeability are achieved.

As described above, the lithium-sulfur secondary battery using lithium and alkali metal as the negative electrode active material and sulfur as the positive electrode active material has a theoretical energy density of 2,800 Wh/kg and a theoretical capacity of 1,675 mAh/g of sulfur, which is far superior to other battery systems. high. In addition, since sulfur is a resource-rich, inexpensive, and environmentally friendly material, lithium-sulfur secondary batteries are attracting attention as an energy source for portable electronic devices.

However, since sulfur used as a cathode active material of a lithium-sulfur secondary battery is an insulator, it is difficult to move electrons generated by an electrochemical reaction. In addition, polysulfide (Li ₂ S ₈ ~ Li ₂ S ₄ ) generated during the charging and discharging process of the lithium-sulfur secondary battery is eluted, and the lithium sulfide (Li ₂ S ₂ /Li ₂ S) and sulfur have electrical conductivity. It was not good, and the kinetics for the electrochemical reaction were slow, so there were problems that the battery life characteristics and speed characteristics were inhibited.

When benzo[ ghi ]peryleneimide (BPI) is introduced as an additive for a positive electrode in order to improve the problems in such lithium-sulfur secondary batteries, the BPI acts as a redox mediator, Research results have been reported that it can improve the kinetic of the electrochemical reaction and improve the performance and lifespan characteristics of the battery (Laura CHGerber et al. ; “Three-Dimensional Growth of Li ₂ S in Lithium-Sulfur Batteries Promoted by a Redox Mediator”; Nano Lett. 2016, 16, 1, 549-554).

However, the BPI has a property of being dissolved in an ether-based solvent or a carbonate-based solvent used in the electrolyte of a lithium-sulfur secondary battery, and when the BPI is dissolved in the electrolyte, electrons are transferred between the positive electrode and the negative electrode to be electrically separated Therefore, there is a problem in that the performance of the battery is reduced by causing an internal short circuit.

Therefore, it is necessary to develop an additive that does not dissolve in the electrolyte of a lithium secondary battery, including a lithium-sulfur secondary battery, and can serve as a catalyst for the reaction proceeding in the positive electrode.

Nano Lett. 2016, 16, 1, 549-554; Laura C. H. Gerber et al.; “Three-Dimensional Growth of Li2S in Lithium-Sulfur Batteries Promoted by a Redox Mediator”

An object of the present invention is to provide a positive electrode additive for a lithium secondary battery that is not soluble in an electrolyte for a lithium secondary battery and can serve as a catalyst as a redox mediator in a positive electrode, and a method for manufacturing the same.

Another object of the present invention is to provide a positive electrode and a lithium secondary battery including the positive electrode additive for a lithium secondary battery.

In order to achieve the above object, the present invention provides a positive electrode additive for a lithium secondary battery represented by the following formula (1):

<Formula 1>

In Formula 1, R is a carbon chain.

The present invention also provides a method for producing a positive electrode additive for a lithium secondary battery comprising reacting benzoperylene anhydride (BPA) with a linear carbon molecule containing an amine group at at least one terminal.

The present invention also provides a positive electrode for a lithium secondary battery comprising the positive electrode additive.

The present invention also provides a lithium secondary battery comprising the positive electrode, the negative electrode, a separator interposed therebetween, and an electrolyte.

Since the positive electrode additive for a lithium secondary battery according to the present invention does not dissolve in the electrolyte, it is possible to prevent deterioration of battery performance due to an internal short circuit that occurs when the positive electrode additive is dissolved in the electrolyte.

In addition, the positive electrode additive for the lithium secondary battery exhibits electrochemical activity in a state of being adsorbed to the carbon material contained in the positive electrode of the lithium secondary battery, and serves as a catalyst for the reaction proceeding in the positive electrode, thereby improving the electrochemical activity of the battery. can

1 is a schematic diagram showing raw materials used to synthesize a positive electrode additive in Examples and Comparative Examples.
FIG. 2 is a graph showing Fourier-transform infrared spectroscopy (FT-IR) measurement results for a mixed solution including the positive electrode additive of Example 1 and Comparative Example 1. FIG.
3 is a photograph showing the color change over time of a mixed solution containing the positive electrode additive and carbon material (MWCNT) of Example 1;
4 is a graph showing the electrochemical activity of the coin cell according to the presence or absence of adsorption of the positive electrode additive of Example 1.

Hereinafter, the present invention will be described in more detail to help the understanding of the present invention.

The terms or words used in the present specification and claims should not be construed as being limited to their ordinary or dictionary meanings, and the inventor may properly define the concept of the term in order to best describe his invention. Based on the principle that there is, it should be interpreted as meaning and concept consistent with the technical idea of the present invention.

Cathode Additive for Lithium Secondary Battery

The present invention relates to a positive electrode additive for a lithium secondary battery, which is adsorbed to a carbon material used in a general positive electrode for a lithium secondary battery, has physical properties that do not dissolve in an electrolyte, and has electrochemical activity while adsorbed on the surface of the carbon material. It relates to a positive electrode additive.

In the present invention, the positive electrode additive for a lithium secondary battery may be one represented by the following Chemical Formula 1:

<Formula 1>

In Formula 1, R is a carbon chain.

The additive of Formula 1 has a structure in which a carbon chain is introduced into benzo[ghi]peryleneimide (BPI). The form of the carbon chain is not particularly limited, and may be, for example, a linear, cyclic or branched carbon chain.

In addition, when the carbon chain is a linear carbon chain, compared to a cyclic or branched carbon chain, the adsorption process for the carbon material may be easily performed, thereby improving process efficiency. For example, the linear carbon chain may be an aliphatic carbon chain.

The BPI is an imide compound synthesized by dehydration condensation of a molecule containing benzoperylene anhydride (BPA) and an amine, and is used as a cathode additive for a lithium secondary battery. However, since the BPI has a property of being soluble in the electrolyte, electrons may be transferred between the positive electrode and the negative electrode to be electrically separated in a state of being dissolved in the electrolyte, thereby causing an internal short circuit, thereby reducing the performance of the battery.

However, when a carbon chain is introduced into the BPI as shown in Chemical Formula 1, the carbon chain does not dissolve in the electrolyte due to the property that it does not dissolve well in a conventional electrolyte solvent. In this case, the electrolyte means an electrolyte for a lithium secondary battery, and for example, may mean an electrolyte including a carbonate-based solvent and/or an ether-based solvent.

In the carbon chain, if the number of carbon atoms is small, solubility in the electrolyte is not controlled, so it is difficult to give a function to prevent it from being dissolved in the electrolyte, and if the number of carbon atoms is large, benzophenylene capable of electrochemical reaction Since the proportion of anhydride (BPA) is relatively reduced, the effect per mass of the additive may decrease, and may also unnecessarily increase the cell weight. Accordingly, R may preferably be an alkyl group having 8 to 12 carbon atoms.

In addition, in the additive of Formula 1, if an ether chain other than a carbon chain is included, the affinity with the electrolyte solvent having a polarity is improved by an atom such as oxygen having a high electronegativity, so it is easily dissolved in the electrolyte solution, Accordingly, electron transfer between the positive electrode and the negative electrode may cause an internal short circuit, thereby reducing the performance of the battery.

Manufacturing method of positive electrode additive for lithium secondary battery

The present invention also relates to a method for preparing a positive electrode additive for a lithium secondary battery, which may include reacting (i) benzoperylene or a derivative thereof, and (ii) a carbon molecule containing an amine group at at least one terminal. .

In the present invention, the benzoperylene derivative may be benzoperylene anhydride (BPA), amine group-containing benzoperylene or carboxyl group-containing benzoperylene, preferably with carbon molecules. In consideration of reactivity, the derivative of benzoperylene may be benzoperylene anhydride (BPA).

Further, in the present invention, the carbon molecule including an amine group at at least one terminal may be an alkylamine having 8 to 12 carbon atoms. For example, the alkylamine having 8 to 12 carbon atoms may be octylamine (C ₈ H ₁₉ N), aminodecane (1-aminodecane, C10), or dodecylamine (C12).

In addition, the reaction may be a dehydration condensation reaction comprising the step of dissolving a reactant in an organic solvent, refluxing the reactant at a temperature of 100° C. to 200° C., and then cooling. In this case, the organic solvent is not particularly limited as long as it is an organic solvent that can be generally used in the anode reaction of a lithium secondary battery, and may be, for example, dimethylformamide (DMF).

The reaction temperature may be 100 °C or higher, 120 °C or higher, or 140 °C or higher, and 160 °C or lower, 170 °C or lower, or 200 °C or lower. If the reaction temperature is less than 100 ℃, the reaction rate is slow, so the desired compound cannot be obtained.

In addition, the reflux may be carried out for 5 hours to 30 hours in consideration of the degree to which the additive of Formula 1 is sufficiently synthesized, specifically, for 5 hours or more or 10 hours or more, or for 20 hours or less or 30 hours or less may be carried out. If the reflux time is less than 10 hours, the reaction may not be terminated and thus a desired reaction product may not be obtained.

In addition, the cooling may be cooling to room temperature, in this case, the room temperature may be 20 ℃ or more or 23 ℃ or more, 27 ℃ or less or 30 ℃ or less, for example, may be 25 ℃. If the cooling temperature is less than 20 ℃, the cooling time is long and the process time is unnecessarily long, and if it exceeds 30 ℃, it is not sufficiently cooled, and the yield of the precipitation step may be reduced.

In addition, after the cooling, the step of stirring to precipitate the reaction product in solution by adding methanol may be further included. The stirring time may be 30 minutes to 3 hours. For example, the stirring time may be 30 minutes or more or 1 hour or more, and may be 2 hours or less or 3 hours or less. If the stirring time is less than 30 minutes, the precipitation time is not sufficiently secured, resulting in a lower yield, and if it exceeds 3 hours, the process efficiency may be reduced.

In addition, after the stirring step, the step of filtering and washing the mixture under reduced pressure may be further included, and the purity may be improved.

Positive electrode for lithium secondary battery

The present invention also relates to a positive electrode for a lithium secondary battery comprising the additive of Formula 1 above.

In the present invention, the positive electrode is not particularly limited as long as it contains a carbon material as the positive electrode active material. That is, the electrode may be a positive electrode or a negative electrode including a carbon material as an active material.

Preferably, since the additive of Formula 1 does not dissolve in carbonate-based solvents and/or ether-based solvents generally used as electrolytes for lithium secondary batteries, it may be suitable as a cathode material for lithium secondary batteries. In addition, since the additive of Formula 1 has electrochemical activity within the voltage range of the electrochemical reaction of sulfur, it may be suitable as an additive for a cathode of a lithium-sulfur secondary battery including a sulfur-carbon composite as a cathode active material.

In the present invention, the additive of Formula 1 may be adsorbed on the surface of the carbon material included in the electrode. Due to the strong bonding force due to adsorption, the additive of Chemical Formula 1 may not dissolve in the electrolyte even when the battery is driven, and accordingly, a phenomenon such as a short circuit of the battery resulting from the dissolution of the additive of Chemical Formula 1 in the electrolyte may be prevented. In addition, since the additive of Chemical Formula 1 can be attached to the surface of the carbon material without chemical bonding, chemical/electrochemical intervention that may occur when other chemicals necessary for chemical bonding are added can be prevented. In addition, since the adsorption occurs within a short time, the surface adhesion reaction can be completed within a few minutes.

In the present invention, the weight ratio of the additive of Formula 1 and the carbon material may be 0.01:1 to 0.1:1, specifically, 0.01:1 or more, 0.02:1 or more, 0.03:1 or more, or 0.04:1 or more. and may be 0.06:1 or less, 0.08:1 or less, or 0.1:1 or less. If the weight ratio is less than 0.01:1, a significant change may not occur because the additive content of Formula 1 is small, and if it exceeds 0.1:1, the adsorption limit of the carbon material is exceeded, and a part of the additive is eluted in the electrolyte to cause self-discharge or , it is possible to decrease the energy density of the battery by increasing the weight.

lithium secondary battery

The present invention also relates to a lithium secondary battery comprising a positive electrode, a negative electrode, a separator interposed therebetween, and an electrolyte, wherein the positive electrode or the negative electrode includes the additive of Formula 1 above. The additive of Formula 1 may be included in the positive active material layer and/or the negative active material layer to be described later.

The electrolyte of the present invention may include an organic solvent and a lithium salt.

The organic solvent may be used without any particular limitation as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move.

Specifically, as the organic solvent, ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, ε-caprolactone; ether-based solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; dimethylcarbonate (DMC), diethylcarbonate (DEC), methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), propylene carbonate, carbonate-based solvents such as PC); alcohol solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (R is a C2 to C20 linear, branched or cyclic hydrocarbon group, which may include a double bond aromatic ring or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; Or sulfolane may be used. Among them, a carbonate-based solvent is preferable, and a cyclic carbonate (eg, ethylene carbonate or propylene carbonate, etc.) having high ionic conductivity and high dielectric constant capable of increasing the charge/discharge performance of the battery, and a low-viscosity linear carbonate-based compound ( For example, a mixture of ethylmethyl carbonate, dimethyl carbonate or diethyl carbonate, etc.) is more preferable. In this case, when the cyclic carbonate and the chain carbonate are mixed in a volume ratio of about 1:1 to about 1:9, the electrolyte may exhibit excellent performance.

The lithium salt may be used without particular limitation as long as it is a compound capable of providing lithium ions used in a lithium secondary battery. Specifically, the lithium salt is LiPF ₆ , LiClO ₄ , LiAsF ₆ , LiBF ₄ , LiSbF ₆ , LiAl0 ₄ , LiAlCl ₄ , LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , LiN(C ₂ F ₅ SO ₃ ) ₂ , LiN(C ₂ F ₅ SO ₂ ) ₂ , LiN(CF ₃ SO ₂ ) ₂ . LiCl, LiI, or LiB(C ₂ O ₄ ) ₂ and the like may be used. The concentration of the lithium salt is preferably used within the range of 0.1 to 2.0M. When the concentration of the lithium salt is included in the above range, since the electrolyte has an appropriate conductivity and viscosity, excellent electrolyte performance may be exhibited, and lithium ions may move effectively.

In the electrolyte, in addition to the electrolyte components, for the purpose of improving battery life characteristics, suppressing battery capacity reduction, and improving battery discharge capacity, for example, haloalkylene carbonate-based compounds such as difluoroethylene carbonate, pyridine, tri Ethyl phosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivative, sulfur, quinone imine dye, N-substituted oxazolidinone, N,N-substituted imida One or more additives such as jolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol or aluminum trichloride may be further included. In this case, the additive may be included in an amount of 0.1 to 5% by weight based on the total weight of the electrolyte.

In the present invention, the positive electrode includes a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector and including the above-described positive electrode active material.

In the positive electrode, the positive electrode current collector is not particularly limited as long as it has conductivity without causing a chemical change in the battery, for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or carbon on the surface of aluminum or stainless steel. , nickel, titanium, silver or the like surface-treated may be used. In addition, the positive electrode current collector may typically have a thickness of 3 to 500 μm, and may increase the adhesion of the positive electrode active material by forming fine irregularities on the surface of the positive electrode current collector. For example, it may be used in various forms, such as a film, a sheet, a foil, a net, a porous body, a foam, a non-woven body.

The positive active material layer may include a conductive material and a binder together with the above-described positive active material.

The conductive material is used to impart conductivity to the positive electrode, and in the configured battery, it can be used without any particular limitation as long as it has electronic conductivity without causing chemical change. Specific examples include graphite such as natural graphite and artificial graphite; carbon-based materials such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, summer black, and carbon fiber; metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or a conductive polymer such as a polyphenylene derivative, and the like, and any one of them or a mixture of two or more thereof may be used. The conductive material may be included in an amount of 1 to 30 wt% based on the total weight of the positive active material layer.

The binder serves to improve adhesion between the positive active material particles and adhesion between the positive active material and the positive electrode current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC) ), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluororubber, or various copolymers thereof, and any one of them or a mixture of two or more thereof may be used. The binder may be included in an amount of 1 to 30% by weight based on the total weight of the positive active material layer.

The positive electrode may be manufactured according to a conventional positive electrode manufacturing method except for using the above-described positive electrode active material. Specifically, it may be prepared by applying the above-described positive active material and, optionally, a composition for forming a positive electrode active material layer including a binder and a conductive material on a positive electrode current collector, followed by drying and rolling. In this case, the types and contents of the positive electrode active material, the binder, and the conductive material are as described above.

The solvent may be a solvent generally used in the art, dimethyl sulfoxide (DMSO), isopropyl alcohol (isopropyl alcohol), N-methylpyrrolidone (NMP), acetone (acetone) or water and the like, and any one of them or a mixture of two or more thereof may be used. The amount of the solvent used is enough to dissolve or disperse the positive electrode active material, the conductive material and the binder in consideration of the application thickness of the slurry and the production yield, and to have a viscosity capable of exhibiting excellent thickness uniformity during application for the production of the positive electrode thereafter. do.

Alternatively, the positive electrode may be prepared by casting the composition for forming the positive electrode active material layer on a separate support, and then laminating a film obtained by peeling it from the support on the positive electrode current collector.

In the present invention, the negative electrode includes a negative electrode current collector and a negative electrode active material layer positioned on the negative electrode current collector.

The anode active material layer optionally includes a binder and a conductive material together with the anode active material.

As the anode active material, a compound capable of reversible intercalation and deintercalation of lithium may be used. Specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloy, Sn alloy, or Al alloy; metal oxides capable of doping and dedoping lithium, such as SiO _β (0<β<2), SnO ₂ , vanadium oxide, and lithium vanadium oxide; or a composite including the above-mentioned metallic compound and a carbonaceous material, such as a Si-C composite or a Sn-C composite, and the like, and any one or a mixture of two or more thereof may be used. In addition, a metal lithium thin film may be used as the negative active material. In addition, as the carbon material, both low crystalline carbon and high crystalline carbon may be used. As low crystalline carbon, soft carbon and hard carbon are representative, and as high crystalline carbon, natural or artificial graphite of amorphous, plate-like, flaky, spherical or fibrous shape, and Kish graphite (Kish) graphite), pyrolytic carbon, mesophase pitch based carbon fiber, meso-carbon microbeads, liquid crystal pitches (Mesophase pitches), and petroleum and coal tar pitch (petroleum or coal tar pitch) High-temperature calcined carbon such as derived cokes) is a representative example.

The binder, the conductive material, and the negative electrode current collector may be selected with reference to the above-described configuration of the positive electrode, but is not limited thereto. In addition, the method of forming the negative electrode active material layer on the negative electrode current collector is similar to the positive electrode by a known coating method and is not particularly limited.

In the present invention, the separator separates the negative electrode and the positive electrode and provides a passage for lithium ions to move, and can be used without any particular limitation as long as it is used as a separator in a lithium secondary battery, and in particular, low resistance to ion movement of the electrolyte It is preferable that the electrolyte solution is excellent in moisture content. Specifically, a porous polymer film, for example, a porous polymer film made of a polyolefin-based polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene/butene copolymer, an ethylene/hexene copolymer, and an ethylene/methacrylate copolymer, or these A laminated structure of two or more layers of may be used. In addition, a conventional porous nonwoven fabric, for example, a nonwoven fabric made of high melting point glass fiber, polyethylene terephthalate fiber, etc. may be used. In addition, in order to secure heat resistance or mechanical strength, a coated separator containing a ceramic component or a polymer material may be used, and may optionally be used in a single-layer or multi-layer structure.

Hereinafter, preferred examples are presented to aid the understanding of the present invention, but the following examples are merely illustrative of the present invention, and it will be apparent to those skilled in the art that various changes and modifications are possible within the scope and spirit of the present invention, It goes without saying that changes and modifications fall within the scope of the appended claims.

1 is a schematic diagram showing raw materials used to synthesize a positive electrode additive in Examples and Comparative Examples. Hereinafter, in Examples and Comparative Examples, additives were synthesized using raw materials as shown in FIG. 1 .

Preparation Example 1: Benzoperylene anhydride (BPA)

A glass topper, thermos-couple, and reflux condenser were installed in a three-neck flask, respectively, and placed in a heating mentle.

123.0 g of maleic anhydride was added and dissolved at 75°C, followed by adding 8.04 g of perylene and heating to 240°C.

16.5 g of chloranil was added, refluxed for 10 minutes, cooled to 140 °C, and 160 ml of xylene heated to 60 °C was added to obtain a mixture.

The mixture was cooled to 90° C., filtered, and the filtered mixture was placed in an ethyl acetate/chloroform (2:1 (v/v)) solution, and the washing process of heating and heating to 65° C. was repeated twice for purification.

Thereafter, the purified mixture was vacuum dried at 70° C. to prepare BPA.

Example 1

8 g of BPA prepared in Preparation Example 1 and 45 mmol of octylamine (C8) were added, refluxed at 160° C. overnight, and then cooled to room temperature to obtain a synthesized compound.

300 ml of methanol was added to the compound and stirred at room temperature for 1 hour.

Thereafter, the stirred mixture was filtered under reduced pressure, washed several times with methanol and dried to prepare an additive for an electrode of a lithium secondary battery (C8 A-BPI).

Example 2

An additive for an electrode of a lithium secondary battery was prepared in the same manner as in Example 1, except that aminodecane (1-aminodecane, C10) was used instead of octylamine (C10 A-BPI).

Example 3

An additive for an electrode of a lithium secondary battery was prepared in the same manner as in Example 1, except that dodecylamine (C12) was used instead of octylamine (C12 A-BPI).

Comparative Example 1

An additive for an electrode of a lithium secondary battery was prepared in the same manner as in Example 1, except that tetraethyleneglycol monoamine was used instead of octylamine.

Experimental Example 1: Solubility test for electrolyte solvent for lithium secondary battery

A solubility test was conducted on whether the additives prepared in Example 1 and Comparative Example 1 were dissolved in the electrolyte solvent (Example 1: C8 linear carbon chain, Comparative Example 1: C8 linear ether chain).

For the solubility test, dimethoxyethan (DME), which is commonly used in lithium-sulfur secondary batteries, was used as a solvent.

0.1 g of the positive electrode additive of Example 1 and Comparative Example 1 was added to 10 g of a dimethoxyethane solvent and mixed for 1 day, and then FT-IR (Fourier-transform infrared spectroscopy) was measured to confirm whether there was a solute in the mixed solution. . At this time, the FT-IR was measured using Nicolet iS5 (Thermo Fisher Scientific).

FIG. 2 is a graph showing FT-IR measurement results for a mixed solution including the positive electrode additive of Example 1 and Comparative Example 1. FIG.

As shown in FIG. 2 , in the mixed solution containing the positive electrode additive of Example 1, the C=O peak, which is characteristic of the positive electrode additive material, did not appear, and in the mixed solution containing the positive electrode additive of Comparative Example 1, the C=O peak did not appear. appeared to be confirmed.

From these results, it can be seen that the additive of Example 1 does not dissolve in the DME solvent, and the additive of Comparative Example 1 has a property of being soluble in the DME solvent.

Experimental Example 2: Carbon Adsorption Test

A carbon adsorption test was conducted to determine whether the additive for electrodes of the lithium secondary battery prepared in Example 1 exhibits adsorption to carbon material.

The additive for electrodes of the lithium secondary battery prepared in Example 1 and the carbon material were mixed in a tetrahydrofuran (THF) solvent, and the mixed solution was visually observed immediately after mixing and 1 day after mixing. In this case, as the carbon material, multi-walled carbon nanotubes (MWCNT, multi-walled CNT, CNano) were used. In addition, the additive and the carbon material were mixed to be 1 wt% and 25 wt%, respectively, based on the total weight of the mixed solution (the weight ratio of the additive to the carbon material was 0.04:1).

3 is a photograph showing the color change over time of a mixed solution containing the positive electrode additive and carbon material (MWCNT) of Example 1;

As shown in FIG. 3 , it was confirmed that the mixed solution showed a yellow color immediately after mixing the positive electrode additive and MWCNT of Example 1 in the THF solvent (before adsorption), whereas the yellow color disappeared when 1 day after mixing had elapsed. (after adsorption).

From these results, it was found that, in the mixed solution containing the MWCNT, the additive of Example 1 being a carbon material, the additive of Example 1 was adsorbed to the carbon material and not dissolved in the solvent.

Experimental Example 3: Relevance experiment with the electrochemical activity of the battery

In the same manner as in Experimental Example 2, the additive of Example 1 was adsorbed to MWCNT, and dried at 80° C. for 1 day to prepare MWCNT powder to which the additive of Example 1 was adsorbed.

An aqueous slurry was prepared by mixing the MWCNT powder adsorbed with the additive of Example 1 and a carboxymethyl cellulose (CMC) binder in 96:4 parts by weight. The aqueous slurry was coated and dried on aluminum foil, punched at 14 pi, used as a reference electrode, and a lithium electrode as a counter electrode to prepare a coin cell. In manufacturing the coin cell, a polyethylene separator (16 μm, Celgard) was used as the separator, and LiTFSI 1M electrolyte was used in a mixed solvent of DOL and DME (1:1 (v/v)) as the electrolyte.

In addition, a comparative coin cell was prepared in the same manner as above using the MWCNT to which the additive of Example 1 was not adsorbed.

For the coin cell and the comparative coin cell, the 1.8-2.9V section was reciprocated three times at a rate of 10 mV/sec to measure the current according to the voltage change during the third reciprocation (VMP3, Biologic).

4 is a graph showing the battery scientific activity of the coin cell according to the presence or absence of adsorption of the positive electrode additive of Example 1.

As shown in FIG. 4 , it was confirmed that the coin cell including the MWCNT to which the positive electrode additive of Example 1 was adsorbed had electrochemical activity within the range of 1.8V to 2.5V, which is the driving range of a general lithium-sulfur secondary battery. .

From these results, it can be seen that the additive of Example 1 will improve the electrochemical activity of lithium secondary batteries including lithium-sulfur secondary batteries.

In the above, although the present invention has been described with reference to limited examples and drawings, the present invention is not limited thereto, and it is described below with the technical idea of the present invention by those of ordinary skill in the art to which the present invention pertains. Of course, various modifications and variations are possible within the scope of equivalents of the claims to be made.

Claims (12)

A cathode additive for a lithium secondary battery represented by the following formula (1):
<Formula 1>

In Formula 1, R is a carbon chain. According to claim 1,
Wherein R is a linear carbon chain positive electrode additive for a lithium secondary battery. 3. The method of claim 2,
Wherein R is an alkyl group having 8 to 12 carbon atoms, a positive electrode additive for a lithium secondary battery. (i) benzoperylene or a derivative thereof, and (ii) a method for producing a positive electrode additive for a lithium secondary battery comprising the step of reacting a carbon molecule comprising an amine group at at least one terminal. 5. The method of claim 4,
The benzoperylene derivative is benzoperylene anhydride (BPA), amine group-containing benzoperylene or carboxyl group-containing benzoperylene, the method for producing a positive electrode additive for a lithium secondary battery. 5. The method of claim 4,
The carbon molecule comprising an amine group at the at least one terminal is an alkylamine having 8 to 12 carbon atoms, the method for producing a cathode additive for a lithium secondary battery. 5. The method of claim 4,
The reaction is a dehydration condensation reaction comprising the step of cooling after reflux at a temperature of 100 ℃ to 200 ℃, a method for producing a positive electrode additive for a lithium secondary battery. A positive electrode for a lithium secondary battery comprising the positive electrode additive of any one of claims 1 to 3. 9. The method of claim 8,
The positive electrode includes a carbon material as a positive electrode active material, a positive electrode for a lithium secondary battery. 9. The method of claim 8,
The additive is formed on the surface of the carbon material included in the positive electrode active material, a positive electrode for a lithium secondary battery. A lithium secondary battery comprising the positive electrode of claim 8, the negative electrode, a separator interposed therebetween, and an electrolyte. 12. The method of claim 11,
The electrolyte solution is a lithium secondary battery comprising at least one selected from an ether-based solvent and a carbonate-based solvent.

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