KR101994879B1 - Non-aqueous liquid electrolye for lithium-sulfur battery and lithium-sulfur battery comprising the same - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrolyte solution for improving the capacity retention rate of a lithium-sulfur battery, and more particularly, to an electrolyte solution for stabilizing a lithium electrode by suppressing lithium dendrite growth and a lithium-sulfur battery including the same. The lithium-sulfur battery including the non-aqueous liquid electrolyte according to the present invention has the effect of stabilizing the lithium electrode, exhibiting excellent capacity retention according to the cycle, and improving battery life characteristics.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-aqueous electrolyte for a lithium-sulfur battery, and a lithium-sulfur battery including the same. BACKGROUND ART [0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrolyte solution for improving the capacity retention rate of a lithium-sulfur battery, and more particularly, to an electrolyte solution for stabilizing a lithium electrode by stabilizing lithium metal to suppress lithium dendrite growth, and a lithium- .

In recent years, miniaturization and weight reduction of electronic products, electronic devices, and communication devices are rapidly proceeding. As the necessity of electric automobiles has been greatly increased with respect to environmental problems, there has been an increase in demand for performance improvement of secondary batteries used as power sources for these products . Among them, lithium secondary batteries are attracting considerable attention as high performance batteries due to high energy density and high standard electrode potential.

In particular, a lithium-sulfur (Li-S) battery is a secondary battery in which a sulfur-based material having a sulfur-sulfur bond is used as a cathode active material and lithium metal is used as an anode active material. Sulfur, the main material of the cathode active material, is very rich in resources, has no toxicity, and has a low atomic weight. The theoretical energy density of the lithium-sulfur battery is 1672 mAh / g-sulfur and the theoretical energy density is 2,600 Wh / kg. The theoretical energy density (Ni-MH battery: 450 Wh / , Which is the most promising among the batteries that have been developed to date, because it is much higher than the FeS battery (480Wh / kg), Li-MnO ₂ battery (1,000Wh / kg) and Na-S battery (800Wh / kg).

During the discharge reaction of the lithium-sulfur battery, the oxidation reaction of lithium occurs at the cathode and the reduction reaction of sulfur occurs at the anode. Sulfur before discharging has an annular S ₈ structure. When the SS bond is cut off during the reduction reaction (discharging), the oxidation number of S decreases, and when the oxidation reaction (charging) The reduction reaction is used to store and generate electrical energy. During this reaction, the sulfur is converted to a linear polysulfide (Li ₂ S _x , x = 8, 6, 4, 2) by the reduction reaction at the cyclic S ₈ , When it is reduced, lithium sulfide (Li ₂ S) is finally produced. The discharge behavior of the lithium-sulfur battery by the process of reducing to each lithium polysulfide characterizes the discharge voltage stepwise unlike the lithium ion battery.

Among lithium polysulfides such as Li ₂ S ₈ , Li ₂ S ₆ , Li ₂ S ₄ and Li ₂ S ₂ , lithium polysulfide (Li ₂ S _x , usually x> 4) having a high oxidation number of sulfur is used in a hydrophilic electrolytic solution It melts easily. The lithium polysulfide dissolved in the electrolytic solution diffuses away from the anode where the lithium polysulfide is generated due to the difference in the concentration. Thus, the lithium polysulfide eluted from the anode is lost outside the positive electrode reaction region, and it is impossible to perform the stepwise reduction to lithium sulfide (Li ₂ S). That is, since the lithium polysulfide existing in a dissolved state from the anode and the cathode is not able to participate in the charge-discharge reaction of the battery, the amount of the sulfur material participating in the electrochemical reaction at the anode is reduced, Which is a major factor in reducing the charge capacity and energy of the battery.

In addition to being suspended or precipitated in the electrolyte solution, the lithium polysulfide diffused into the cathode causes a problem of corrosion of the lithium metal cathode because it reacts directly with lithium and is fixed in the form of Li ₂ S on the surface of the cathode.

Li + Li ₂ S _x → Li ₂ S

Due to the reaction according to the above reaction formula, lithium metal particles and lithium sulfide produced by precipitation and dissolution of lithium metal are mixed in the surface of the lithium metal cathode during charge and discharge. As a result, the surface of the lithium negative electrode is changed to a porous structure, and a part of the lithium negative electrode is dendritic to form a lithium dendrite. Due to the porous structure and lithium dendrite formed in this manner, the loss of lithium metal accelerates, resulting in irreversible capacity and a reduction in the lifetime of the lithium-sulfur battery. In addition, lithium dendrites are highly reactive and lead to short-circuit, heat, ignition and explosion of lithium-sulfur batteries, thus causing serious problems in stability.

Therefore, for the commercialization of lithium-sulfur battery, the problem of lithium polysulfide and lithium dendrite is the first priority to be solved.

Korean Patent Laid-Open Publication No. 2014-0138078 entitled "Lithium Secondary Battery Excellent in Output and Cycle Characteristics &

As described above, attempts have been made to design an anode structure or to apply a mediator or the like in order to inhibit the dissolution of lithium polysulfide, but the manufacturing process of the anode is complicated and the synthesis of the barrier layer component is difficult have. In addition, various techniques have been proposed to inhibit the growth of lithium dendrite, such as the use of various additives or the formation of a crosslinked structure of an electrolyte. However, such a technique has not been satisfactory to date.

Accordingly, the present inventors have continued research and experiment to solve the problem of dissolution of lithium polysulfide through the composition of the electrolytic solution and to enhance the stability of the lithium metal as a more effective method for solving the problem of the lithium-sulfur battery, .

Accordingly, an object of the present invention is to provide a non-aqueous liquid electrolyte for a lithium-sulfur battery.

Another object of the present invention is to provide a lithium-sulfur battery including the non-aqueous liquid electrolyte.

In order to accomplish the above object, the present invention provides a process for producing an organic solvent, Sulfonate-based solvents; Lithium bis (fluorosulfonyl) imide: LiFSI); And a non-aqueous liquid electrolyte for a lithium-sulfur battery including a nitric acid-based compound.

The present invention also provides a lithium-sulfur battery including the electrolyte.

The lithium-sulfur battery including the non-aqueous liquid electrolyte according to the present invention stabilizes the lithium electrode, suppressing the generation of lithium dendrite, preventing elution of the lithium polysulfide, and exhibiting excellent capacity retention ratio according to the cycle, The characteristics are improved.

1 is a graph showing the capacity retention rate according to the cycle of the embodiment and the comparative example according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

In the present specification, the numerical range indicated by using " ~ " indicates a range including numerical values before and after " ~ " as the minimum value and the maximum value, respectively. In the present specification, the term " combination thereof " is intended to include both of mixing two or more of them as a single element or applying each of them as a separate element, Any combination of these, regardless of their form, is regarded as one species.

The present invention relates to an ether-based solvent; Sulfonate-based solvents; Lithium salts; And a non-aqueous liquid electrolyte for a lithium secondary battery comprising a nitric acid-based additive. Hereinafter, the present invention will be described in detail.

Ether solvent

The ether solvent according to the present invention may be a non-cyclic ether, a cyclic ether, a polyether or a mixture thereof.

Examples of the linear ether include, but are not limited to, diethyl ether, dipropyl ether, dibutyl ether, dimethoxymethane (DMM), trimethoxyethane, (TM), dimethoxyethane (DME), diethoxyethane (DEE), and dimethoxypropane (DMP).

The cyclic ethers include, but are not limited to, Dioxolane (DOL), Methyldioxolane, Oxane, Dioxane, Trioxane, Tetrahydrofuran, Tetrahydrofuran (THF), dihydropyran (DHP), tetrahydropyran (THP) and methyltetrahydrofuran, furan and methyl furan.

Examples of the polyether include, but are not limited to, diethyleneglycol dimethyl ether, triethyleneglycol dimethyl ether, tetraethyleneglycol dimethyl ether, ethylene glycol divinyl ether ( Ethyleneglycol divinyl ether, diethyleneglycol divinyl ether, triethyleneglycol divinyl ether, dipropyleneglycol dimethylene ether and butyleneglycol ether groups. Lt; / RTI >

More specifically, the ether solvent may include 1,3-dioxolane (DOL), 1,2-dimethoxyethane (DME), furan, 2-methyl 2-Methylfuran, 2,5-Dimethylfuran, Tetrahydrofuran, Ethylene oxide, 1,4-Oxane, 4 Methyl-1,3-dioxolane, tetraethylene glycol dimethyl ether (TEGDME), or a mixture thereof.

Preferably, one of the linear ether and the cyclic ether can be selected and mixed. More preferably, 1,3-dioxolane (DOL) and 1,2-dimethoxyethane (1, 2-dimethoxyethane: DME) in a predetermined volume ratio. For example, the mixed solution may be mixed at a volume ratio of 1: 1.

The ether solvent can reduce the viscosity of the electrolytic solution and chelate the lithium cation by the ether symmetric structure to increase the dissociation degree of the lithium salt and greatly improve the ionic conductivity of the electrolytic solution. Since ionic conductivity is generally determined by the mobility of ions within the electrolyte, the factors affecting ionic conductivity are the viscosity of the electrolyte and the concentration of ions in the solution. The lower the viscosity of the solution, the more the ions move in the solution and the ionic conductivity increases. The higher the concentration of ions in the solution, the higher the ionic conductivity of the charge transport chain.

In the non-aqueous liquid electrolyte for a lithium-sulfur battery of the present invention, the content of the ether-based solvent may be adjusted according to the goal of improving the performance of the battery, but is applied within the range of 50 to 95% based on the total volume of the electrolyte . If less than 50% is used, the desired performance improvement is insignificant, and at least 5% can not exceed 95%, since the sulfonate-based solvent described below must be used.

Sulfonate system  menstruum

Non-limiting examples of the sulfonate-based solvent according to the present invention include methyl methanesulfonate, ethyl methanesulfonate, methyl ethanesulfonate, propyl methanesulfonate, Methyl propanesulfonate, ethyl propanesulfonate, Ethenyl methanesulfonate, propenyl methanesulfonate, Ethenyl benzenesulfonate, propenylsulfonate, But are not limited to, propenyl propensulfonate, propenyl cyanoethanesulfonate, and the like. These may be used alone or in combination of two or more.

In the sulfonate-based solvent, lithium ions are coordinated to the oxygen of the sulfonate group and the bond between the sulfur of the sulfonate group and the substituent is broken, and a lithium sulfonate radical (-SO ₃ ^- Li ⁺ ) and a substituent radical . The sulfonate-based solvent of the present invention includes a substituent of a sulfonate group. Therefore, in the present invention, the substituent radical (for example, an allyl radical) formed in the above may have a chemically stable resonance structure, which may be advantageous in reduction of a sulfonate-based solvent.

The lithium-sulfur battery is charged and discharged while intercalating and deintercalating lithium ions into the carbon electrode. Since lithium is highly reactive, it reacts with the carbon electrode to generate Li ₂ CO ₃ , LiO ₂ , LiOH, and the like to form a film on the surface of the negative electrode. Such a film is called a solid electrolyte interface (SEI) film. These SEI membranes, once formed during the initial charge, prevent the reaction between lithium ions and the negative electrode or other materials during repetition of charging and discharging by using batteries, and serve as ion tunnels for passing only lithium ions between the electrolyte and the negative electrode .

The sulfonate-based solvent used in the present invention is dissociated into a sulfonate anion in the electrolyte solution, which is highly reactive with lithium ions and other ions (NO ₃ anion, sulfonate anion in the lithium salt) in the electrolyte, The SEI film is formed on the surface of the negative electrode through bonding. The SEI film contains a polar group such as S and O in the film structure and thus has excellent lithium ion conductivity. In addition, the SEI film is excellent in lithium ion conductivity and is comparable to SEI film formed when a carbonate-based solvent is used as a solvent of a conventional electrolyte solution or when an ether- So that it has more dense and stable film characteristics. As a result, it is possible to secure an effect of improving the capacity and life characteristic of the finally produced battery.

In the nonaqueous electrolyte solution for a lithium-sulfur battery of the present invention, the content of the sulfonate solvent may be adjusted according to the aim of improving the performance of the battery, but it is applied within the range of 5 to 50% based on the total volume of the electrolyte solution . If less than 5% is used, the desired performance improvement is insignificant, and if it exceeds 50%, the resistance of the battery may be increased. Therefore, the ether solvent and the sulfatoate solvent are preferably mixed in a volume ratio of 50:50 to 95: 5.

Lithium salt

LiFSI ((FSO ₂ ) ₂ NLi), which is a lithium salt contained in the nonaqueous electrolyte solution for a lithium-sulfur battery of the present invention, has a melting point of 145 캜 and is thermally stable up to 200 캜. LiFSI not only exhibits higher electrical conductivity than LiPF ₆ , LiTFSI ((CF ₃ SO ₂ ) ₂ NLi), but also exhibits higher electrical conductivity than LiPF ₆ More stable and less corrosive than LiTFSI, LiPF ₆ Or LiTFSI as a lithium salt, problems such as current collecting corrosion may be solved.

In addition, LiFSI improves the initial output characteristics, low temperature and high temperature output characteristics by forming a solid and stable SEI film on the surface of the anode, inhibits decomposition of the anode surface which may occur during operation at a high temperature of 45 ° C or more, It is possible to improve the capacity characteristics of the secondary battery at the same time.

According to an embodiment of the present invention, the concentration of LiFSI in the electrolytic solution is in the range of 0.05 to 5 M, preferably 0.1 to 1 M. If the concentration is less than the above range, the improvement of the output and cycle characteristics of the lithium-sulfur battery is insignificant. If the concentration exceeds the above range, a side reaction in the electrolyte is excessively generated during charging and discharging of the battery, A swelling phenomenon may occur in which gas is continuously generated to increase the thickness of the battery.

The lithium salt according to the invention LiFSI solely used or, or industry conventionally used in the art as _{LiCl, LiBr, LiI, LiClO 4} , LiBF 4, LiB 10 Cl 10, LiPF 6, LiCF 3 SO 3, LiCF 3 CO 2 _{, LiC 4 BO 8, LiAsF 6} , LiSbF 6, LiAlCl 4, CH 3 SO 3 Li, CF 3 SO 3 Li, (CF 3 SO 2) 2 NLi, (C 2 F 5 SO 2) 2 NLi, (CF 3 SO ₂ ) ₃ CLi, chloroborane lithium, lower aliphatic carboxylate lithium, lithium tetraphenylborate, imide, and the like. For example, LiFSI may be used with LiPF _6. In this case, there is an effect of suppressing the corrosion of the positive electrode current collector, and it is possible to stabilize the negative electrode interface and to improve the capacity retention ratio at room temperature and low temperature.

The molar ratio of LiFSI to the auxiliary lithium salt is preferably 1: 1 to 9: 1. When the mixing ratio of the LiFSI and the auxiliary lithium salt is out of the range of the molar ratio, a side reaction in the electrolytic solution occurs excessively during charging / discharging of the battery, and swelling phenomenon may occur.

additive

The nonaqueous electrolyte solution for a lithium-sulfur battery of the present invention uses a nitric acid compound as an additive. The nitric acid compound has the effect of forming a stable film on the lithium electrode and greatly improving the charge / discharge efficiency. Examples of such nitric acid compounds include, but are not limited to, inorganic nitric acid compounds such as lithium nitrate (LiNO ₃ ) and lithium nitrite (LiNO ₂ ); Organic nitrate compounds such as nitromethane (CH ₃ NO ₂ ) and methyl nitrate (CH ₃ NO ₃ ); And a combination thereof. Lithium nitrate (LiNO ₃ ) is preferably used.

The nitric acid compound is used in an amount of 0.01 to 10% by weight, preferably 0.1 to 5% by weight within 100% by weight of the total electrolyte composition. If the content is less than the above range, the above-mentioned effect can not be ensured. On the other hand, if the content exceeds the above range, resistance may increase due to the coating film.

As described above, the electrolyte according to the present invention can enhance the stability of the lithium metal when the four kinds of components of the ether type solvent, the sulfonate type solvent, the LiFSI lithium salt and the nitric acid type compound are combined, and more preferably the Li- The problem of dissolving lithium polysulfide can be solved.

The method for producing the electrolytic solution according to the present invention is not particularly limited and can be produced by a conventional method known in the art.

Lithium-sulfur battery

The nonaqueous electrolyte solution for a lithium-sulfur battery of the present invention described above is applied to a conventional lithium-sulfur battery having a negative electrode and a positive electrode. The lithium-sulfur battery according to the present invention comprises a positive electrode and a negative electrode arranged opposite to each other; A separator interposed between the anode and the cathode; And a lithium-sulfur battery impregnated with the positive electrode, the negative electrode, and the separator, and having an ionic conductivity. One embodiment of the present invention may be a lithium-sulfur battery.

anode

The positive electrode according to the present invention may include a positive electrode active material layer and a positive electrode collector for supporting the positive electrode active material layer as a positive electrode of a lithium-sulfur battery.

The cathode active material may include elemental sulfur (S8), a sulfur-based compound, or a mixture thereof. Specifically, the sulfur-based compound may be Li ₂ S _n ( _n ? 1), an organic sulfur compound or a carbon-sulfur polymer ((C ₂ S _x ) _n : x = 2.5 to 50, n? They are applied in combination with the conductive material since the sulfur alone does not have electrical conductivity.

The conductive material may be porous. Therefore, any conductive material having porosity and conductivity may be used without limitation, and for example, a carbon-based material having porosity may be used. Examples of such carbon-based materials include carbon black, graphite, graphene, activated carbon, carbon fiber, and the like. Further, metallic fibers such as metal mesh; Metallic powder such as copper, silver, nickel, and aluminum; Or an organic conductive material such as a polyphenylene derivative can also be used. The conductive materials may be used alone or in combination.

The binder may include a thermoplastic resin or a thermosetting resin. For example, it is possible to use polyethylene, polypropylene, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), styrene-butadiene rubber, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, vinylidene fluoride- Vinylidene fluoride copolymer, fluoropropylene copolymer, vinylidene fluoride-chlorotrifluoroethylene copolymer, ethylene-tetrafluoroethylene copolymer, polychlorotrifluoroethylene, vinylidene fluoride-pentafluoropropylene copolymer, propylene-tetrafluoro Ethylene-chlorotrifluoroethylene copolymers, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymers, vinylidene fluoride-perfluoromethyl vinyl ether-tetrafluoroethylene copolymers, ethylene -Acrylic acid copolymer or the like may be used alone or in combination, but not always limited thereto, Anything that can be used as a binder in the technical field is possible.

The positive electrode current collector may be any as long as it can be used as a current collector in the technical field. Specifically, it may be preferable to use foamed aluminum or foamed nickel having excellent conductivity.

The positive electrode may be prepared by a conventional method. Specifically, a composition for forming a positive electrode active material layer prepared by mixing a positive electrode active material, a conductive material, and a binder in an organic solvent is applied on a current collector, And then compression molding the current collector to improve the electrode density. At this time, it is preferable that the organic solvent, the cathode active material, the binder and the conductive material can be uniformly dispersed and easily evaporated. Specific examples thereof include acetonitrile, methanol, ethanol, tetrahydrofuran, water, isopropyl alcohol and the like.

cathode

The negative electrode according to the present invention may further include a negative electrode active material layer and a negative electrode current collector for supporting the negative electrode active material layer as a negative electrode of a lithium-sulfur battery.

Examples of the negative electrode include a material capable of reversibly intercalating or deintercalating lithium ions (Li ⁺ ) as a negative electrode active material, a material capable of reversibly forming a lithium-containing compound by reacting with lithium ions, Lithium alloy may be used. The material capable of reversibly storing or releasing lithium ions (Li ^< ^{+ &} gt ^; ) may be, for example, crystalline carbon, amorphous carbon, or a mixture thereof. The material capable of reacting with the lithium ion (Li ^< ^{+ &} gt ^; ) to reversibly form a lithium-containing compound may be, for example, tin oxide, titanium nitride or silicon. The lithium alloy includes, for example, lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), francium (Fr), beryllium (Be), magnesium (Mg) Ca, strontium (Sr), barium (Ba), radium (Ra), aluminum (Al), and tin (Sn).

The binder acts as a paste for the anode active material, mutual adhesion between the active materials, adhesion between the active material and the current collector, buffering effect on expansion and contraction of the active material, and the like. Specifically, the binder is the same as that described above for the positive electrode binder.

The negative electrode may be a lithium metal or a lithium alloy. As a non-limiting example, the negative electrode may be a thin film of lithium metal, and may include one or more metals selected from the group consisting of lithium, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, / RTI >

The negative electrode current collector may be specifically selected from the group consisting of copper, stainless steel, titanium, silver, palladium, nickel, alloys thereof, and combinations thereof. The stainless steel may be surface-treated with carbon, nickel, titanium or silver, and an aluminum-cadmium alloy may be used as the alloy. In addition, fired carbon, a nonconductive polymer surface treated with a conductive agent, or a conductive polymer may be used.

Membrane

A conventional separator may be interposed between the anode and the cathode. The separation membrane is a physical separation membrane having a function of physically separating the electrode. Any separator membrane can be used without any particular limitations as long as it is used as a conventional separation membrane. Particularly, it is preferable that the separator membrane is low in resistance against ion movement of the electrolyte solution and excellent in electrolyte wettability.

In addition, the separator separates or insulates the positive electrode and the negative electrode from each other, and enables transport of lithium ions between the positive electrode and the negative electrode. Such a separator may be made of a porous, nonconductive or insulating material. The separator may be an independent member such as a film, or a coating layer added to the anode and / or the cathode.

Specifically, 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 may be used alone Or they may be laminated. Alternatively, nonwoven fabrics made of conventional porous nonwoven fabrics such as glass fibers of high melting point, polyethylene terephthalate fibers and the like may be used, but the present invention is not limited thereto.

The anode, the cathode, and the separator included in the lithium-sulfur battery may be prepared according to a common component and a manufacturing method, respectively. In addition, the external shape of the lithium-sulfur battery is not particularly limited, but a cylindrical, square, A pouch type, a coin type, or the like.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to examples. However, the embodiments according to the present invention can be modified into various other forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. The embodiments of the present invention are provided to enable those skilled in the art to more fully understand the present invention.

≪ Example 1 > Preparation of non-aqueous liquid electrolyte

Aqueous organic solvent having a volume ratio of 1,3-dioxolane (DOL), 1,2-dimethoxyethane (DME) and methyl methane sulfonate (MMS) of 40:40:20 and 1.0M LiFSI ( FSO ₂ ) ₂ NLi) was added to 1 wt% of LiNO ₃ based on the total amount of the electrolytic solution to prepare a nonaqueous electrolyte solution.

≪ Comparative Example 1 > Preparation of non-aqueous liquid electrolyte

Aqueous electrolytic solution containing a nonaqueous organic solvent having a composition ratio of ethylene carbonate (EC) and dimethyl carbonate (DMC) of 1: 1 and 1.0 M of LiTFSI ((CF ₃ SO ₂ ) ₂ NLi) 1 wt% of LiNO ₃ was added to prepare a non-aqueous liquid electrolyte.

≪ Comparative Example 2 > Preparation of non-aqueous liquid electrolyte

A nonaqueous organic solvent having a composition of 1: 1 by volume of 1,3-dioxolane (DOL) and 1,2-dimethoxyethane (DME) and 1.0 M LiTFSI ((CF ₃ SO ₂ ) ₂ NLi) , 1 wt% of LiNO ₃ was added based on the total amount of the electrolytic solution to prepare a nonaqueous electrolytic solution.

≪ Comparative Example 3 > Preparation of non-aqueous liquid electrolyte

Aqueous organic solvent having a composition ratio of 1: 3 dioxolane (DOL), 1,2-dimethoxyethane (DME) and methyl methanesulfonate (MMS) of 40:40:20, and 1.0 M LiTFSI ( CF ₃ SO ₂ ) ₂ NLi) was added to 1 wt% of LiNO ₃ based on the total amount of the electrolytic solution to prepare a non-aqueous electrolytic solution.

<Experimental Example 1> Preparation of lithium-sulfur battery and analysis of charge / discharge characteristics

(1) Manufacture of lithium-sulfur battery

65 wt% sulfur, 25 wt% carbon black, and 10 wt% polyether oxide were mixed with acetonitrile to prepare a cathode active material. The positive electrode active material was coated on an aluminum current collector and dried to prepare a positive electrode. Lithium metal having a thickness of 150 mu m was used as a negative electrode.

The prepared positive electrode and negative electrode were positioned to face each other, and a polyethylene separator was interposed therebetween, and then filled with the electrolytic solution of Example 1 and Comparative Examples 1 to 3.

(2) Measurement of charging and discharging characteristics by cycle

The charge and discharge characteristics of the lithium-sulfur battery were measured, and the results are shown in Table 1 and FIG.

menstruum Lithium salt additive Capacity retention rate (50 times)
Example 1 DOL: DME: MMS
(40:40:20, v / v) 1.0M LiFSI 1 wt% LiNO ₃ 90.5% Comparative Example 1 EC: DEC
(50:50, v / v) 1.0M LiTFSI 1 wt% LiNO ₃ 15.0% Comparative Example 2 DOL: DME
(50:50, v / v) 1.0M LiTFSI 1 wt% LiNO ₃ 46.5% Comparative Example 3 DOL: DME: MMS
(40:40:20, v / v) 1.0M LiTFSI 1 wt% LiNO ₃ 76.1% week)
DOL: 1,3-Dioxolane
DME: 1,2-Dimethoxyethane
MMS: Methyl methansulfonate
EC: Ethylene carbonate
DEC: Dimethyl carbonate

1 and Comparative Example 1, which is a simple combination of a carbonate-based solvent and a lithium salt (LiTFSI) used as a conventional electrolytic solution, the capacity retention ratio was about 15.0% Which was about 6 times lower than that of the previous study.

In the case of Comparative Example 2 using only an ether solvent as a solvent, the capacity retention rate was somewhat increased as compared with Comparative Example 1 using a carbonate solvent, but was about twice as low as that of Example 1.

In addition, the battery of Comparative Example 3 uses LiTFSI, which is not LiFSI, as the lithium salt. Even though the ether-based solvent and the sulfonate-based solvent and the additive, which are the three components of the present invention, are used together, the capacity retention ratio is about 70% Respectively.

From these results, it was found that when the lithium-sulfur battery contains both ether-based solvent, sulfonate-based solvent, LiFSI, and LiNO ₃ as a non-aqueous liquid electrolyte, stability of the lithium metal is enhanced and the problem of lithium polysulfide elution is solved, It can be seen that not only the charge / discharge capacity is increased but also the high capacity retention ratio of 90% or more can be secured.

Although the preferred embodiments of the present invention have been described in detail, the scope of the present invention is not limited thereto.

Claims (9)

Ether-based solvents;
Sulfonate-based solvents;
Lithium bis (fluorosulfonyl) imide: LiFSI); And
Nitrate compounds;
Aqueous electrolyte solution for a lithium-sulfur battery,
Examples of the sulfonate solvent include methyl methanesulfonate, ethyl methanesulfonate, methyl ethanesulfonate, propyl methanesulfonate, methyl propanesulfonate, ethyl propanesulfonate, ethenyl methanesulfonate, propenyl methanesulfonate, ethenyl Benzene sulfonate, propenyl propane sulfonate, propenyl cyanoethanesulfonate, and combinations thereof. 2. The nonaqueous electrolyte solution for a lithium-sulfur battery according to claim 1,
The method according to claim 1,
The ether solvent may be at least one selected from the group consisting of diethyl ether, dipropyl ether, dibutyl ether, dimethoxymethane, trimethoxymethane, dimethoxyethane, diethoxyethane, dimethoxypropane, dioxolane, methyl dioxolane, , Trioxane, tetrahydrofuran, dihydropyrane, tetrahydropyrane, methyltetrahydrofuran, furan, methylfuran, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, ethylene glycol divinyl ether , Diethylene glycol divinyl ether, triethylene glycol divinyl ether, dipropylene glycol dimethylene ether, butylene glycol ether, and combinations thereof. The nonaqueous system for a lithium-sulfur battery Electrolytic solution.
delete The method according to claim 1,
Wherein the volume ratio of the ether solvent to the sulfonate solvent is 50:50 to 95: 5.
The method according to claim 1,
Wherein the ether-based solvent is a mixed solvent of 1,3-dioxolane (DOL) and 1,2-dimethoxyethane (DME) Aqueous electrolyte.
The method according to claim 1,
The nonaqueous electrolyte solution for a lithium-sulfur battery according to claim 1, wherein the concentration of the lithium bis-fluorosulfonylimide is 0.05 to 5 M.
The method according to claim 1,
The nitric acid-based compound is an inorganic nitric acid compound including lithium nitrate (LiNO ₃ ) and lithium nitrite (LiNO ₂ ); Organic nitrate compounds including nitromethane (CH ₃ NO ₂ ), methyl nitrate (CH ₃ NO ₃ ); And a combination thereof. 2. The nonaqueous electrolyte solution for a lithium-sulfur battery according to claim 1,
The method according to claim 1,
The nonaqueous electrolyte solution for a lithium-sulfur battery according to claim 1, wherein the nitric acid compound is contained in the total electrolyte composition in an amount of 0.01 to 10 wt%.
An anode and a cathode arranged opposite to each other;
A separator interposed between the anode and the cathode; And
An electrolyte solution impregnated into the positive electrode, the negative electrode and the separation membrane and having ion conductivity;
&Lt; / RTI &gt;
The lithium-sulfur battery according to claim 1, wherein the electrolyte is a non-aqueous liquid electrolyte according to any one of claims 1, 2 and 4 to 8.

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