WO2019221456A1 - Electrolyte and lithium secondary battery comprising same - Google Patents

Electrolyte and lithium secondary battery comprising same Download PDF

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Publication number
WO2019221456A1
WO2019221456A1 PCT/KR2019/005637 KR2019005637W WO2019221456A1 WO 2019221456 A1 WO2019221456 A1 WO 2019221456A1 KR 2019005637 W KR2019005637 W KR 2019005637W WO 2019221456 A1 WO2019221456 A1 WO 2019221456A1
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Prior art keywords
lithium
electrolyte
secondary battery
lithium secondary
battery
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PCT/KR2019/005637
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French (fr)
Korean (ko)
Inventor
하예영
김기현
양두경
Original Assignee
주식회사 엘지화학
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Priority claimed from KR1020190054060A external-priority patent/KR102229461B1/en
Application filed by 주식회사 엘지화학 filed Critical 주식회사 엘지화학
Priority to JP2020530953A priority Critical patent/JP7062171B2/en
Priority to US16/768,982 priority patent/US11539076B2/en
Priority to CN201980006381.5A priority patent/CN111492525B/en
Publication of WO2019221456A1 publication Critical patent/WO2019221456A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0567—Liquid materials characterised by the additives
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present invention relates to an electrolyte capable of improving the performance of a battery by inhibiting the growth of lithium dendrites in a lithium secondary battery including lithium metal as a negative electrode, and a lithium secondary battery including the same.
  • the lithium secondary battery has a structure in which an electrode assembly including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode is laminated or wound, and the electrode assembly is built in a battery case and a nonaqueous electrolyte is injected into the lithium secondary battery. .
  • the capacity of the lithium secondary battery is different depending on the type of electrode active material, and it is not commercialized because sufficient capacity is not secured as much as theoretical capacity during actual driving.
  • metal materials such as silicon (4,200 mAh / g) and tin (990 mAh / g), which exhibit high storage capacity characteristics by alloying with lithium, are used as the negative electrode active material.
  • silicon 4,200 mAh / g
  • tin 990 mAh / g
  • the volume expands to about four times in the charging process of alloying with lithium and shrinks during discharge. Due to such a large volume change of the electrode repeatedly generated during charging and discharging, the active material gradually becomes micronized and dropped from the electrode, thereby rapidly decreasing its capacity. As a result, it is difficult to secure stability and reliability, thereby preventing commercialization.
  • lithium metal has a high theoretical capacity of 3860 mAh / g and a very low standard hydrogen potential (SHE) of -3.045 V, which enables the implementation of a high capacity, high energy density battery.
  • SHE standard hydrogen potential
  • Many studies have been conducted on lithium metal batteries (LMB) using lithium metal as a negative electrode active material of a lithium secondary battery.
  • lithium metal batteries due to the high chemical / electrochemical reactivity of lithium metal, lithium metal batteries easily react with electrolytes, impurities, lithium salts, etc. to form a solid electrolyte interphase (SEI) on the surface of the electrode. Density is caused to form dendritic dendrite on the lithium metal surface. The lithium dendrites not only shorten the life of the lithium secondary battery, but also cause internal short circuits and dead lithium of the battery, thereby increasing physical and chemical instability of the lithium secondary battery, reducing battery capacity, and reducing cycle life. Adversely affects its stability.
  • SEI solid electrolyte interphase
  • the passivation layer is thermally unstable, so that charging and discharging of the battery may be continuously progressed, or, in particular, during high temperature storage in a fully charged state, the passivation layer may be gradually collapsed by increased electrochemical energy and thermal energy. Due to the collapse of the passivation layer, side reactions in which the exposed lithium metal surface reacts directly with the electrolyte solvent and decompose continuously occur, thereby increasing the resistance of the negative electrode and decreasing the charge and discharge efficiency of the battery. In addition, the solvent of the electrolyte is consumed when the passivation layer is formed, and the life of the battery is reduced due to by-products, gases, etc. generated during various side reactions such as formation and collapse of the passivation layer and decomposition of the electrolyte.
  • lithium metal batteries using lithium metal as a negative electrode Due to such high instability of lithium metal, lithium metal batteries using lithium metal as a negative electrode have not been commercialized.
  • Korean Patent Laid-Open Publication No. 2014-0027206 relates to an electrolyte composition in the form of a colloidal dispersion including a binder such as poly (ethylene glycol) dithiol to reduce the mobility of the electrolyte in the electrolyte.
  • a binder such as poly (ethylene glycol) dithiol
  • it has the effect of reducing the mobility of and improving the ionic conductivity and / or circulation performance
  • a large amount of binder must be included in the electrolyte composition to be used for all-solid-state batteries.
  • Patent Document 1 Korean Patent Publication No. 2014-0027206
  • Patent Document 2 Chinese Unexamined Patent Publication No. 106099181
  • the inventors of the present invention have conducted various studies to solve the above problems, and as an electrolyte for lithium secondary batteries, an electrolyte including polyethylene glycol as an additive is used, and a thiol group formed at one end of the polyethylene glycol is lithium. It was confirmed that the formation of a bond with a metal and the polyethylene oxide chain of the polyethylene glycol interacted with lithium ions, thereby suppressing the rapid change in lithium ion concentration on the surface of the lithium metal negative electrode, thereby inhibiting the growth of lithium dendrites.
  • an object of the present invention is to provide a lithium secondary battery electrolyte capable of maintaining a uniform lithium ion concentration on the surface of a lithium metal negative electrode, thereby suppressing growth of lithium dendrites and improving battery performance.
  • Still another object of the present invention is to provide a lithium secondary battery including the lithium secondary battery electrolyte.
  • the present invention provides an electrolyte for a lithium secondary battery
  • the electrolyte may include an additive represented by the following formula (1).
  • X is methyl or thiol and n is an integer from 5 to 45.
  • the content of the additive represented by Formula 1 may be more than 0 wt%, 1.0 wt% or less, preferably 0.05 to 0.5 wt%, based on the total weight of the electrolyte.
  • Thiol (-SH) in the additive represented by Formula 1 may be included in 1 to 30% by weight.
  • the electrolyte may further include an organic solvent and a lithium salt.
  • the organic solvent may be at least one selected from the group consisting of ether solvents, ester solvents, amide solvents, linear carbonate solvents and cyclic carbonate solvents.
  • the lithium salt is LiFSI, LiPF 6 , LiCl, LiBr, LiI, LiClO 4 , LiBF 4 , LiB 10 Cl 10 , LiPF 6 , LiCF 3 SO 3 , LiCF 3 CO 2 , LiAsF 6 , LiSbF 6 , LiPF 6 , LiAlCl 4 And CH 3 SO 3 Li, CF 3 SO 3 Li, (CF 3 SO 2 ) 2 NLi, chloroborane lithium, and 4-phenyl lithium borate.
  • the present invention also provides a lithium secondary battery comprising the electrolyte.
  • the lithium secondary battery may include a lithium metal negative electrode.
  • the electrolyte for a lithium secondary battery according to the present invention includes a polyethylene glycol functionalized at the terminal, it is possible to maintain a uniform lithium ion concentration on the surface of the lithium metal anode, thereby preventing the growth of lithium dendrites.
  • the thiol group forms a bond with lithium metal, and the polyethylene oxide chain of the polyethylene glycol interacts with lithium ions, thereby Sudden change in lithium ion concentration can be suppressed.
  • the functionalized polyethylene glycol is included in the lithium secondary battery electrolyte, it is excellent in the lithium dendrite growth inhibitory effect, it is possible to improve the overvoltage during charging and discharging of lithium metal and increase the capacity expressed.
  • Figure 1 shows the charge and discharge test results for the lithium-sulfur battery prepared in Example 1 and Comparative Example 1, respectively.
  • Figure 2 shows the discharge capacity measurement test results for the lithium-sulfur battery prepared in Example 3 and Comparative Examples 3,4, respectively.
  • Figure 3 shows the discharge capacity measurement test results for the lithium-sulfur battery prepared in Example 4 and Comparative Example 5, respectively.
  • FIG. 4 is a photograph of a surface of a lithium metal negative electrode after charging and discharging a lithium metal battery prepared in Example 2.
  • FIG. 4 is a photograph of a surface of a lithium metal negative electrode after charging and discharging a lithium metal battery prepared in Example 2.
  • Example 5 shows discharge capacity and coulombic efficiency measurement results of charging and discharging cycles of lithium-sulfur batteries prepared in Example 3 and Comparative Example 3, respectively.
  • the present invention relates to an electrolyte for a lithium secondary battery, wherein the electrolyte for a lithium secondary battery capable of controlling the growth of lithium dendrites by controlling the configuration of an additive included in the electrolyte and maintaining a uniform lithium ion concentration on the surface of the lithium metal anode. It is about.
  • the configuration of the additive included in the electrolyte may mean the kind, mole fraction and structure of the functional group formed in the additive material.
  • the electrolyte for a lithium secondary battery according to the present invention may include polyethylene glycol having a functional group bonded as an additive.
  • the additive of the lithium secondary battery electrolyte may be represented by the following formula (1).
  • X is methyl (methyl, CH 3 ) or thiol (SH) and n is an integer from 5 to 45.
  • the content of the additive represented by Formula 1 may be more than 0 wt%, 1.0 wt% or less, preferably 0.05 to 0.5 wt%, based on the total weight of the electrolyte.
  • the content of the additive represented by Formula 1 is less than the above range, lithium dendrite grows due to uneven lithium ion concentration on the surface of the lithium metal negative electrode.
  • the thiol (-SH) may be included in 1 to 30% by weight, preferably 1 to 20% by weight in the additive represented by the formula (1).
  • the weight percent is based on the mass ratio of thiol (-SH) contained in the additive. If the content of the thiol is less than 1% by weight, it is difficult to form a bond with the lithium metal, making it difficult to maintain the concentration of lithium ions uniformly on the surface of the lithium metal anode, and when the content of more than 30% by weight is relatively excessive, This accelerates the decomposition of additives and side reactions with lithium metal.
  • the polyethylene oxide chain (-(CH 2 -CH 2 -O) n- ) may be linear or branched (baranched).
  • n means the length of the polyethylene oxide chain (-(CH 2 -CH 2 -O) n- ), if less than the above range of n to form an effective complex with lithium ions There is a problem that it does not, if there is a problem that the additive is difficult to reach the surface of the lithium metal electrode.
  • the electrolyte for a lithium secondary battery may include an organic solvent.
  • the organic solvent may be used alone or in combination of two or more of ether, ester, amide, linear carbonate, cyclic carbonate and the like.
  • the ether compound is dimethyl ether, diethyl ether, dipropyl ether, methylethyl ether, methylpropyl ether, ethylpropyl ether, dimethoxyethane, diethoxyethane, methoxyethoxyethane, ethylene glycol monomethyl ether, diethylene Glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol methylethyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, triethylene glycol methylethyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol diethyl ether , Tetraethylene glycol methylethyl ether, polyethylene glycol dimethyl ether, polyethylene glycol diethyl ether, polyethylene glycol methylethyl ether, 1,3-dioxolane, tetrahydrofuran, 2-methyltetrahydrofur
  • the esters include methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, ⁇ -butyrolactone, ⁇ -valerolactone, ⁇ -caprolactone, ⁇ -valerolactone And ⁇ -caprolactone, but any one selected from the group consisting of, or a mixture of two or more thereof may be used, but is not limited thereto.
  • linear carbonate compounds include any one selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethylmethyl carbonate (EMC), methylpropyl carbonate and ethylpropyl carbonate. Two or more kinds of mixtures and the like may be representatively used, but are not limited thereto.
  • cyclic carbonate compound examples include ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate , 2,3-pentylene carbonate, vinylene carbonate, vinylethylene carbonate, and any one selected from the group consisting of halides thereof or mixtures of two or more thereof.
  • halides include, for example, fluoroethylene carbonate (FEC), but are not limited thereto.
  • N-methylpyrrolidone dimethyl sulfoxide, sulfolane and the like.
  • the electrolyte for a lithium secondary battery of the present invention may further include a nitrate-based compound commonly used in the art in addition to the above composition.
  • a nitrate-based compound commonly used in the art in addition to the above composition.
  • the electrolyte for a lithium secondary battery may include a lithium salt as an electrolyte salt.
  • the lithium salt is not particularly limited in the present invention, and any lithium salt may be used without limitation as long as it can be commonly used in the electrolyte for lithium secondary batteries.
  • the lithium salt is 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, (SO 2 F) 2 NLi, (CF 3 SO 2 ) 3 CLi It may include one or more selected from the group consisting of lithium chloroborane, lower aliphatic carboxylic acid having 4 or less carbon atoms, lithium 4-phenyl borate and lithium imide.
  • the lithium salt may be lithium bis (trifluoromethanesulfonyl) imide (LiTFSI), (CF 3 SO 2 ) 2 NLi.
  • the concentration of the lithium salt may be appropriately determined in consideration of ionic conductivity, solubility, and the like, and may be, for example, 0.1 to 4.0 M, preferably 0.5 to 2.0 M.
  • concentration of the lithium salt is less than the above range, it is difficult to secure ionic conductivity suitable for driving the battery.On the contrary, when the concentration of the lithium salt exceeds the above range, the viscosity of the electrolyte increases to decrease the mobility of the lithium ions and the decomposition reaction of the lithium salt itself increases. Since the performance of the battery may be degraded, it is appropriately adjusted within the above range.
  • the present invention provides a lithium secondary battery comprising the electrolyte for a lithium secondary battery.
  • the lithium secondary battery according to the present invention may include a lithium metal negative electrode, and may be, for example, a lithium metal battery, a lithium-sulfur battery, or the like.
  • the lithium secondary battery includes a positive electrode, a negative electrode, and an electrolyte interposed between the positive electrode and the negative electrode, and includes the lithium metal battery electrolyte according to the present invention as the electrolyte.
  • the positive electrode may include a positive electrode current collector and a positive electrode active material coated on one or both surfaces of the positive electrode current collector.
  • the positive electrode current collector supports the positive electrode active material, and is not particularly limited as long as it has high conductivity without causing chemical change in the battery.
  • copper, stainless steel, aluminum, nickel, titanium, palladium, calcined carbon, surface treated with carbon, nickel, silver, etc. on the surface of copper or stainless steel, aluminum-cadmium alloy, and the like can be used.
  • the positive electrode current collector may form fine concavities and convexities on its surface to enhance bonding strength with the positive electrode active material, and may be used in various forms such as a film, a sheet, a foil, a mesh, a net, a porous body, a foam, and a nonwoven fabric.
  • the cathode active material may include a cathode active material, and optionally a conductive material and a binder.
  • the cathode active material may be an oxide formed of lithium and a transition metal having a structure capable of intercalating lithium, and for example, may be represented by the following Chemical Formula 2.
  • a 1, 0.1 ⁇ x ⁇ 0.3, 0.15 ⁇ y ⁇ 0.25, 0 ⁇ b ⁇ 0.05
  • M is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, Zn and It may be any one selected from a transition metal or a lanthanide element selected from the group consisting of a combination thereof.
  • inorganic sulfur (S 8 ) can be used.
  • the positive electrode may further include one or more additives selected from transition metal elements, group IIIA elements, group IVA elements, sulfur compounds of these elements, and alloys of these elements and sulfur, in addition to the positive electrode active material.
  • the transition metal element may be Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Os, Ir, Pt, Au or Hg and the like
  • the Group IIIA element may include Al, Ga, In, Ti, and the like
  • the Group IVA element may include Ge, Sn, Pb and the like.
  • the conductive material is to improve electrical conductivity, and there is no particular limitation as long as it is an electronic conductive material that does not cause chemical change in a lithium secondary battery.
  • carbon black, graphite, carbon fiber, carbon nanotubes, metal powder, conductive metal oxide, organic conductive materials, and the like can be used, and currently commercially available as a conductive material acetylene black series (Chevron Chemical) Chevron Chemical Company or Gulf Oil Company, etc., Ketjen Black EC series (Armak Company), Vulcan XC-72 (Cabot Company) (Cabot Company) and Super P (MMM).
  • acetylene black, carbon black, graphite, etc. are mentioned.
  • the cathode active material may further include a binder having a function of maintaining the cathode current collector and connecting the active materials.
  • a binder for example, polyvinylidene fluoride-hexafluorofluoropropylene (PVDF-co-HFP), polyvinylidene fluoride (PVDF), polyacrylonitrile, poly Methyl methacrylate, styrene butadiene rubber (SBR), carboxyl methyl cellulose (CMC), poly (acrylic acid, PAA), polyvinyl alcohol
  • binders such as (vinyl alcohol) and PVA may be used.
  • the negative electrode may include a negative electrode current collector and a negative electrode active material positioned on the negative electrode current collector.
  • the negative electrode may be a lithium metal plate.
  • the negative electrode current collector is for supporting the negative electrode active material, and is not particularly limited as long as it has excellent conductivity and is electrochemically stable in the voltage range of the lithium secondary battery.
  • copper, stainless steel, aluminum, nickel, titanium, Palladium, calcined carbon, surface treated with carbon, nickel, silver or the like on the surface of copper or stainless steel, aluminum-cadmium alloy, or the like may be used.
  • the negative electrode current collector may form fine irregularities on its surface to enhance bonding strength with the negative electrode active material, and may be used in various forms such as film, sheet, foil, mesh, net, porous body, foam, and nonwoven fabric.
  • the anode active material includes a material capable of reversibly intercalating or deintercalating lithium (Li + ), a material capable of reacting with lithium ions to reversibly form a lithium-containing compound, a lithium metal or a lithium alloy can do.
  • Substance capable of reversibly occluding or emitting in the lithium ion (Li +) may be, for example, crystalline carbon, amorphous carbon, or a mixture thereof.
  • the material capable of reacting with the lithium ions (Li + ) to form a lithium-containing compound reversibly may be, for example, tin oxide, titanium nitrate or silicon.
  • the lithium alloy is, for example, lithium (Li) and sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), francium (Fr), beryllium (Be), magnesium (Mg), calcium ( It may be an alloy of a metal selected from the group consisting of Ca), strontium (Sr), barium (Ba), radium (Ra), aluminum (Al) and tin (Sn).
  • the negative electrode active material may be lithium metal, and specifically, may be in the form of a lithium metal thin film or lithium metal powder.
  • the method of forming the negative electrode active material is not particularly limited, and a method of forming a layer or a film commonly used in the art may be used. For example, a method such as pressing, coating or vapor deposition can be used.
  • the negative electrode of the present invention also includes a case where a metal lithium thin film is formed on a metal plate by initial charging after assembling a battery without a lithium thin film in a current collector.
  • the electrolyte includes lithium ions, and is used for causing an electrochemical oxidation or reduction reaction at the positive electrode and the negative electrode through the above, as described above.
  • the injection of the electrolyte may be performed at an appropriate step in the manufacturing process of the electrochemical device, depending on the manufacturing process and the required physical properties of the final product. That is, it may be applied before the electrochemical device assembly or the final step of the electrochemical device assembly.
  • the separator may be additionally included between the positive electrode and the negative electrode.
  • the separator is used to physically separate both electrodes in the lithium secondary battery of the present invention. If the separator is used as a separator in a lithium secondary battery, the separator may be used without particular limitation. It is desirable that the capability is excellent.
  • the separator may be made of a porous substrate, and the porous substrate may be used as long as it is a porous substrate commonly used in an electrochemical device.
  • a porous substrate commonly used in an electrochemical device.
  • a polyolefin-based porous membrane or a nonwoven fabric may be used, but is not particularly limited thereto. .
  • polyolefin-based porous membrane examples include polyethylene, polypropylene, polybutylene, polypentene, such as high density polyethylene, linear low density polyethylene, low density polyethylene, ultra high molecular weight polyethylene, respectively, or a mixture thereof
  • polyolefin-based polymers such as polyethylene, polypropylene, polybutylene, polypentene, such as high density polyethylene, linear low density polyethylene, low density polyethylene, ultra high molecular weight polyethylene, respectively, or a mixture thereof
  • polyethylene such as polyethylene, polypropylene, polybutylene, polypentene, such as high density polyethylene, linear low density polyethylene, low density polyethylene, ultra high molecular weight polyethylene, respectively, or a mixture thereof
  • polypentene such as high density polyethylene, linear low density polyethylene, low density polyethylene, ultra high molecular weight polyethylene, respectively, or a mixture thereof
  • the nonwoven fabric may be, for example, polyethylene terephthalate, polybutylene terephthalate, polyester, polyacetal, polyamide, polycarbonate, or polycarbonate. ), Polyimide, polyetheretherketone, polyethersulfone, polyphenyleneoxide, polyphenylenesulfide and polyethylenenaphthalate alone Or the nonwoven fabric formed from the polymer which mixed these is mentioned.
  • the structure of the nonwoven fabric may be a spunbond nonwoven fabric or a melt blown nonwoven fabric composed of long fibers.
  • the thickness of the porous substrate is not particularly limited, but may be 1 to 100 ⁇ m, preferably 5 to 50 ⁇ m.
  • the pore size and pore present in the porous substrate are also not particularly limited, but may be 0.001 to 50 ⁇ m and 10 to 95%, respectively.
  • the lithium secondary battery according to the present invention may be a lamination (stacking) and folding (folding) process of the separator and the electrode in addition to the winding (winding) which is a general process.
  • the shape of the lithium secondary battery is not particularly limited and may be in various shapes such as cylindrical, stacked, coin type.
  • the present invention provides a battery module comprising the lithium secondary battery as a unit cell.
  • the battery module may be used as a power source for medium and large devices requiring high temperature stability, long cycle characteristics, and high capacity characteristics.
  • Examples of the medium-to-large device include a power tool that is driven by an electric motor; Electric vehicles including electric vehicles (EVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and the like; Electric motorcycles including electric bicycles (E-bikes) and electric scooters (E-scooters); Electric golf carts; Power storage systems and the like, but is not limited thereto.
  • Electric vehicles including electric vehicles (EVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and the like
  • Electric motorcycles including electric bicycles (E-bikes) and electric scooters (E-scooters); Electric golf carts; Power storage systems and the like, but is not limited thereto.
  • the lithium metal negative electrode and the S / C positive electrode were positioned to face each other, and a PE (polyethylene) separator was placed therebetween, and 70 ⁇ l of the electrolyte was injected to prepare a coin-cell lithium-sulfur battery.
  • PE polyethylene
  • a lithium-sulfur battery in the form of a coin cell was prepared in the same manner as in Example 1, but using an electrolyte solution E1 containing no additive as the electrolyte.
  • a lithium metal anode and a lithium metal anode were positioned to face each other, a PE (polyethylene) separator was placed therebetween, and 100 ⁇ l of an electrolyte was injected to prepare a coin-cell lithium-lithium battery.
  • PE polyethylene
  • an electrolyte solution (E2) containing 0.1 wt% of an additive was used, and the additive is polyethylene glycol methyl ether thiol (mPEG-SH, molecular weight: 800).
  • the electrolyte solution (E2) is an electrolyte solution containing 1 M LiTFSI using DOL / DME (1: 1, v / v) as a solvent (DOL: Dioxolane, DME: Dimethoxyethane).
  • a lithium-lithium battery of the coin cell type was prepared in the same manner as in Example 2, but using an electrolyte solution E2 containing no additive as the electrolyte.
  • an electrolyte (E1) containing 0.1 wt% of an additive was used, and the additive is polyethylene glycol methyl ether thiol (mPEG-SH, molecular weight: 2,000).
  • a lithium-sulfur battery in the form of a coin cell was prepared in the same manner as in Example 3, but using an electrolyte solution E1 containing no additive as the electrolyte.
  • Example 3 a lithium-sulfur battery in the form of a coin cell was manufactured using an electrolyte solution (E1) having an additive content of 1.5 wt% as the electrolyte.
  • a lithium-sulfur battery in the form of a coin cell was prepared in the same manner as in Example 4 but using an electrolyte solution E1 containing no additive as the electrolyte.
  • Figure 1 shows the charge and discharge test results for the lithium-sulfur battery prepared in Example 1 and Comparative Example 1, respectively.
  • Example 1 including mPEG-SH as an electrolyte additive improves overvoltage and increases expressed capacity when charging and discharging.
  • the discharge capacity and the coulombic efficiency of the lithium-sulfur battery prepared in Example 3 and Comparative Examples 3 and 4, respectively, according to the charge and discharge cycles was measured and battery performance evaluation was performed.
  • the test conditions were 0.6 mA cm -2 charge / 0.6 mA cm -2 discharge and 1.2 mA cm -2 charge / 1.2 mA cm -2 discharge conditions.
  • Figure 2 shows the discharge capacity measurement test results for the lithium-sulfur battery prepared in Example 3 and Comparative Examples 3,4, respectively.
  • Figure 3 shows the discharge capacity measurement test results for the lithium-sulfur battery prepared in Example 4 and Comparative Example 5, respectively.
  • 4arm-PEG5k-SH (molecular weight: 5,000) is used as an additive of an electrolyte
  • Example 4 in which the mass ratio of thiol is 3 wt% in the additive, does not include an additive and thus the content of thiol is 0. It can be seen that the discharge capacity is higher than that in Comparative Example 5, which is% by weight.
  • the lithium metal battery prepared in Example 2 was observed by comparing the surface of the lithium metal negative electrode after the charge and discharge cycle progress.
  • the experimental conditions were 1.3 mA ⁇ cm ⁇ 2 charge / 1.3 mA ⁇ cm ⁇ 2 discharge conditions, and the DOD was 83%. After charging and discharging for 10 cycles, the coin cell was decomposed to observe the surface of the lithium metal negative electrode.
  • Figure 4 is a photograph of the surface of the lithium metal negative electrode after charging and discharging the lithium metal battery prepared in Example 2 (photograph taken after performing the same charge and discharge experiment twice).
  • FIG. 5 shows discharge capacity and coulombic efficiency measurement results of charging and discharging cycles of lithium-sulfur batteries prepared in Example 3 and Comparative Example 3, respectively.
  • Example 3 including mPEG-SH as an electrolyte additive exhibits increased cycle life compared to Comparative Example 3.

Abstract

The present invention relates to an electrolyte for a lithium secondary battery and a lithium secondary battery comprising same. More specifically, the present invention relates to an electrolyte for a lithium secondary battery which maintains a uniform concentration of lithium ions on the surface of a lithium metal anode even if the electrolyte contains only a small amount of an additive comprising a functional group forming a bond with a lithium metal and a polyethylene oxide chain interacting with lithium ions, such that growth of lithium dendrites can be suppressed.

Description

전해질 및 이를 포함하는 리튬 이차전지Electrolyte and lithium secondary battery comprising same
본 출원은 2018년 5월 14일자 한국 특허 출원 제10-2018-0054612호 및 2019년 5월 9일자 한국 특허 출원 제10-2019-0054060호에 기초한 우선권의 이익을 주장하며, 해당 한국 특허 출원의 문헌에 개시된 모든 내용은 본 명세서의 일부로서 포함한다.This application claims the benefit of priority based on Korean Patent Application No. 10-2018-0054612 dated May 14, 2018 and Korean Patent Application No. 10-2019-0054060 dated May 9, 2019. All content disclosed in the literature is included as part of this specification.
본 발명은 리튬 금속을 음극으로 포함하는 리튬 이차전지에서 리튬 덴드라이트의 성장을 억제하여 전지의 성능을 향상시킬 수 있는 전해질 및 이를 포함하는 리튬 이차전지에 관한 것이다.The present invention relates to an electrolyte capable of improving the performance of a battery by inhibiting the growth of lithium dendrites in a lithium secondary battery including lithium metal as a negative electrode, and a lithium secondary battery including the same.
전기, 전자, 통신 및 컴퓨터 산업이 급속히 발전함에 따라 고성능 및 고안정성의 이차전지에 대한 수요가 최근 급격히 증가하고 있다. 특히, 전지, 전자 제품의 경량화, 박형화, 소형화 및 휴대화 추세에 따라 핵심 부품인 이차전지도 경량화 및 소형화가 요구되고 있다. 또한, 환경 공해 문제 및 석류 고갈에 따른 새로운 형태의 에너지 수급원의 필요성이 대두됨에 따라 이를 해결할 수 있는 전기 자동차의 개발 필요성이 증가되어 왔다. 여러 이차전지 중에서 가볍고, 높은 에너지 밀도와 작동 전위를 나타내고, 사이클 수명이 긴 리튬 이차전지가 최근 각광받고 있다.With the rapid development of the electric, electronic, communication and computer industries, the demand for high performance and high stability secondary batteries has recently increased rapidly. In particular, secondary batteries, which are key components, are required to be lighter and smaller in size, due to the trend toward lighter, thinner, smaller, and more portable batteries and electronic products. In addition, as the necessity of a new type of energy supply and demand due to environmental pollution and the depletion of pomegranate has emerged, the necessity of developing an electric vehicle that can solve this problem has increased. Among various secondary batteries, lithium secondary batteries that are light in weight, exhibit high energy density and operating potential, and have long cycle life have recently been in the spotlight.
리튬 이차전지는 양극, 음극 및 상기 양극과 음극 사이에 개재된 분리막을 포함하는 전극조립체가 적층 또는 권취된 구조를 가지며, 이 전극조립체가 전지케이스에 내장되고 그 내부에 비수 전해액이 주입됨으로써 구성된다. 이때 리튬 이차전지의 용량은 전극 활물질의 종류에 따라 차이가 있으며, 실제 구동시 이론 용량만큼 충분한 용량이 확보되지 않기 때문에 상용화되고 있지 못한 실정이다. The lithium secondary battery has a structure in which an electrode assembly including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode is laminated or wound, and the electrode assembly is built in a battery case and a nonaqueous electrolyte is injected into the lithium secondary battery. . At this time, the capacity of the lithium secondary battery is different depending on the type of electrode active material, and it is not commercialized because sufficient capacity is not secured as much as theoretical capacity during actual driving.
리튬 이차전지의 고용량화를 위해 리튬과의 합금화 반응에 통해 높은 저장용량 특성을 나타내는 규소(4,200 mAh/g), 주석(990 mAh/g) 등의 금속계 물질이 음극 활물질로 이용되고 있다. 그러나 규소, 주석 등의 금속을 음극 활물질로 사용하는 경우, 리튬과 합금화하는 충전 과정에서 체적이 4배 정도로 크게 팽창하고 방전 시에는 수축한다. 이러한 충·방전시 반복적으로 발생하는 전극의 큰 체적 변화에 의해 활물질이 서서히 미분화되어 전극으로부터 탈락함으로써 용량이 급격하게 감소하며 이로 인해 안정성, 신뢰성의 확보가 어려워 상용화에 이르지 못하였다.In order to increase the capacity of the lithium secondary battery, metal materials such as silicon (4,200 mAh / g) and tin (990 mAh / g), which exhibit high storage capacity characteristics by alloying with lithium, are used as the negative electrode active material. However, when a metal such as silicon or tin is used as the negative electrode active material, the volume expands to about four times in the charging process of alloying with lithium and shrinks during discharge. Due to such a large volume change of the electrode repeatedly generated during charging and discharging, the active material gradually becomes micronized and dropped from the electrode, thereby rapidly decreasing its capacity. As a result, it is difficult to secure stability and reliability, thereby preventing commercialization.
앞서 언급한 음극 활물질과 비교하여 리튬 금속은 이론 용량이 3,860 mAh/g로 우수하고 표준 환원 전위(Standard Hydrogen Electrode; SHE)도 -3.045 V로 매우 낮아 고용량, 고에너지 밀도 전지의 구현이 가능하기 때문에, 리튬 이차전지의 음극 활물질로 리튬 금속을 사용하는 리튬 금속 전지(Lithium Metal Battery; LMB)에 대한 많은 연구가 진행되고 있다.Compared to the negative electrode active material mentioned above, lithium metal has a high theoretical capacity of 3860 mAh / g and a very low standard hydrogen potential (SHE) of -3.045 V, which enables the implementation of a high capacity, high energy density battery. Many studies have been conducted on lithium metal batteries (LMB) using lithium metal as a negative electrode active material of a lithium secondary battery.
그러나 리튬 금속 전지는 리튬 금속의 높은 화학적/전기화학적 반응성으로 인해 전해질, 불순물, 리튬염 등과 쉽게 반응하여 전극 표면에 부동태층(Solid Electrolyte Interphase; SEI)을 형성하고, 이와 같은 부동태층은 국부상의 전류밀도 차이를 초래하여 리튬 금속 표면에 수지상의 덴드라이트를 형성시킨다. 상기 리튬 덴드라이트는 리튬 이차전지의 수명 단축은 물론이고 전지 내부단락과 불활성 리튬(dead lithium)을 야기하여 리튬 이차전지의 물리적, 화학적 불안정성을 가중시키고 전지의 용량을 감소시키고 사이클 수명을 단축시키며, 전지의 안정성에 좋지 않은 영향을 미친다. 이에 더해서, 상기 부동태층은 열적으로 불안정하여 전지의 충·방전이 지속적으로 진행되거나, 특히, 완전충전 상태에서의 고온 저장시, 증가된 전기 화학적 에너지와 열 에너지에 의해 서서히 붕괴될 수 있다. 이러한 부동태층의 붕괴로 인해 노출된 리튬 금속 표면이 전해질 용매와 직접 반응하여 분해되는 부반응이 지속적으로 발생하게 되며, 이로 인해 음극의 저항이 증가하고, 전지의 충방전 효율이 저하된다. 또한, 상기 부동태층 형성시 전해질의 용매가 소모되며 부동태층의 형성과 붕괴, 전해질의 분해 등의 각종 부반응시 발생하는 부산물, 가스 등으로 인해 전지의 수명이 줄어드는 문제가 발생한다.However, due to the high chemical / electrochemical reactivity of lithium metal, lithium metal batteries easily react with electrolytes, impurities, lithium salts, etc. to form a solid electrolyte interphase (SEI) on the surface of the electrode. Density is caused to form dendritic dendrite on the lithium metal surface. The lithium dendrites not only shorten the life of the lithium secondary battery, but also cause internal short circuits and dead lithium of the battery, thereby increasing physical and chemical instability of the lithium secondary battery, reducing battery capacity, and reducing cycle life. Adversely affects its stability. In addition, the passivation layer is thermally unstable, so that charging and discharging of the battery may be continuously progressed, or, in particular, during high temperature storage in a fully charged state, the passivation layer may be gradually collapsed by increased electrochemical energy and thermal energy. Due to the collapse of the passivation layer, side reactions in which the exposed lithium metal surface reacts directly with the electrolyte solvent and decompose continuously occur, thereby increasing the resistance of the negative electrode and decreasing the charge and discharge efficiency of the battery. In addition, the solvent of the electrolyte is consumed when the passivation layer is formed, and the life of the battery is reduced due to by-products, gases, etc. generated during various side reactions such as formation and collapse of the passivation layer and decomposition of the electrolyte.
이와 같은 리튬 금속의 높은 불안정성 때문에 리튬 금속을 음극으로 사용하는 리튬 금속 전지는 상용화되지 못하고 있다.Due to such high instability of lithium metal, lithium metal batteries using lithium metal as a negative electrode have not been commercialized.
이를 해결하기 위하여 리튬 금속 표면에 보호층을 도입하거나, 전해질의 조성을 달리하는 등의 다양한 방법들이 연구되고 있다.In order to solve this problem, various methods such as introducing a protective layer on the lithium metal surface or changing the composition of the electrolyte have been studied.
일례로, 한국 공개특허 제2014-0027206호는 전해질 내에서 전해질의 이동성을 감소시키기 위해 폴리(에틸렌 글리콜) 디티올 등의 바인더를 포함하는 콜로이드 분산액 형태의 전해질 조성물에 관한 것으로, 상기 바인더로 인하여 전해질의 이동성을 감소시키고, 이온 전도율 및/또는 순환 성능을 향상시키는 효과가 있으나, 전고체 전지용으로 사용되어 많은 양의 바인더가 전해질 조성물에 포함되어야 한다는 단점이 있다.As an example, Korean Patent Laid-Open Publication No. 2014-0027206 relates to an electrolyte composition in the form of a colloidal dispersion including a binder such as poly (ethylene glycol) dithiol to reduce the mobility of the electrolyte in the electrolyte. Although it has the effect of reducing the mobility of and improving the ionic conductivity and / or circulation performance, there is a disadvantage that a large amount of binder must be included in the electrolyte composition to be used for all-solid-state batteries.
이에, 리튬 금속전지의 전해질에 소량만 첨가하여도 리튬 금속 음극 표면에서 균일한 리튬 이온농도를 유지시켜 리튬 덴드라이트의 성장을 방지할 수 있는 전해질의 개발이 요구되고 있다.Accordingly, there is a demand for the development of an electrolyte capable of preventing the growth of lithium dendrites by maintaining a uniform lithium ion concentration on the surface of the lithium metal anode even when only a small amount is added to the electrolyte of the lithium metal battery.
[선행기술문헌][Preceding technical literature]
[특허문헌][Patent Documents]
(특허문헌 1) 한국 공개특허 제2014-0027206호(Patent Document 1) Korean Patent Publication No. 2014-0027206
(특허문헌 2) 중국 공개특허 제106099181호(Patent Document 2) Chinese Unexamined Patent Publication No. 106099181
본 발명자들은 상기 문제점을 해결하기 위해 다각적으로 연구를 수행한 결과, 리튬 이차전지용 전해질로서, 첨가제인 폴리에틸렌 글리콜을 포함하는 전해질을 사용하되, 상기 폴리에틸렌 글리콜의 일 말단에 형성된 티올기(thiol)는 리튬 금속과 결합을 형성하고, 상기 폴리에틸렌 글리콜의 폴리에틸렌 옥사이드 사슬은 리튬 이온과 상호 작용함으로써, 리튬 금속 음극 표면에서 리튬 이온 농도의 급격한 변화를 억제하여 리튬 덴드라이트의 성장을 억제한다는 것을 확인하였다. The inventors of the present invention have conducted various studies to solve the above problems, and as an electrolyte for lithium secondary batteries, an electrolyte including polyethylene glycol as an additive is used, and a thiol group formed at one end of the polyethylene glycol is lithium. It was confirmed that the formation of a bond with a metal and the polyethylene oxide chain of the polyethylene glycol interacted with lithium ions, thereby suppressing the rapid change in lithium ion concentration on the surface of the lithium metal negative electrode, thereby inhibiting the growth of lithium dendrites.
따라서, 본 발명의 목적은 리튬 금속 음극의 표면에서 리튬 이온 농도를 균일하게 유지시켜, 리튬 덴드라이트의 성장을 억제하고 전지 성능을 향상시킬 수 있는 리튬 이차전지용 전해질을 제공하는 것이다.Accordingly, an object of the present invention is to provide a lithium secondary battery electrolyte capable of maintaining a uniform lithium ion concentration on the surface of a lithium metal negative electrode, thereby suppressing growth of lithium dendrites and improving battery performance.
본 발명의 또 다른 목적은 상기 리튬 이차전지용 전해질을 포함하는 리튬 이차전지를 제공하는 것이다.Still another object of the present invention is to provide a lithium secondary battery including the lithium secondary battery electrolyte.
상기 목적을 달성하기 위해, 본 발명은 리튬 이차전지용 전해질을 제공하되, 상기 전해질은 하기 화학식 1로 표시되는 첨가제를 포함할 수 있다.In order to achieve the above object, the present invention provides an electrolyte for a lithium secondary battery, the electrolyte may include an additive represented by the following formula (1).
[화학식 1][Formula 1]
X-(CH2-CH2-O)n-SHX- (CH 2 -CH 2 -O) n -SH
상기 식에서, X는 메틸(methyl) 또는 티올(thiol)이고, n은 5 내지 45인 정수임.Wherein X is methyl or thiol and n is an integer from 5 to 45.
상기 화학식 1로 표시되는 첨가제의 함량은 상기 전해질의 전체 중량을 기준으로 0 중량% 초과, 1.0 중량% 이하, 바람직하게는 0.05 내지 0.5 중량%일 수 있다.The content of the additive represented by Formula 1 may be more than 0 wt%, 1.0 wt% or less, preferably 0.05 to 0.5 wt%, based on the total weight of the electrolyte.
상기 화학식 1로 표시되는 첨가제에서 티올(-SH)은 1 내지 30 중량%로 포함된 것일 수 있다. Thiol (-SH) in the additive represented by Formula 1 may be included in 1 to 30% by weight.
상기 화학식 1에서 -(CH2-CH2-O)n- 은 선형 또는 분지형일 수 있다.In Formula 1,-(CH 2 -CH 2 -O) n -may be linear or branched.
상기 전해질은 유기용매 및 리튬염을 더 포함할 수 있다.The electrolyte may further include an organic solvent and a lithium salt.
상기 유기용매는 에테르계 용매, 에스테르계 용매, 아미드계 용매, 선형 카보네이트계 용매 및 환형 카보네이트계 용매로 이루어진 군에서 선택되는 1종 이상일 수 있다.The organic solvent may be at least one selected from the group consisting of ether solvents, ester solvents, amide solvents, linear carbonate solvents and cyclic carbonate solvents.
상기 리튬염은 LiFSI, LiPF6, LiCl, LiBr, LiI, LiClO4, LiBF4, LiB10Cl10, LiPF6, LiCF3SO3, LiCF3CO2, LiAsF6, LiSbF6, LiPF6, LiAlCl4, CH3SO3Li, CF3SO3Li, (CF3SO2)2NLi, 클로로 보란 리튬 및 4-페닐 붕산 리튬으로 이루어진 군에서 선택되는 1종 이상일 수 있다.The lithium salt is LiFSI, LiPF 6 , LiCl, LiBr, LiI, LiClO 4 , LiBF 4 , LiB 10 Cl 10 , LiPF 6 , LiCF 3 SO 3 , LiCF 3 CO 2 , LiAsF 6 , LiSbF 6 , LiPF 6 , LiAlCl 4 And CH 3 SO 3 Li, CF 3 SO 3 Li, (CF 3 SO 2 ) 2 NLi, chloroborane lithium, and 4-phenyl lithium borate.
본 발명은 또한, 상기 전해질을 포함하는 리튬 이차전지를 제공한다.The present invention also provides a lithium secondary battery comprising the electrolyte.
상기 리튬 이차전지는 리튬 금속 음극을 포함하는 것일 수 있다.The lithium secondary battery may include a lithium metal negative electrode.
본 발명에 따른 리튬 이차전지용 전해질은 말단이 기능화된 폴리에틸렌 글리콜을 포함함으로써, 리튬 금속 음극 표면에서 균일한 리튬 이온 농도를 유지시킬 수 있어, 리튬 덴드라이트의 성장을 방지할 수 있다.Since the electrolyte for a lithium secondary battery according to the present invention includes a polyethylene glycol functionalized at the terminal, it is possible to maintain a uniform lithium ion concentration on the surface of the lithium metal anode, thereby preventing the growth of lithium dendrites.
구체적으로, 상기 폴리에틸렌 글리콜의 일 말단에 티올기(thiol)가 형성된 경우, 상기 티올기는 리튬 금속과 결합을 형성하고, 상기 폴리에틸렌 글리콜의 폴리에틸렌 옥사이드 사슬은 리튬 이온과 상호 작용하여, 리튬 금속 음극 표면에서 리튬 이온 농도의 급격한 변화를 억제할 수 있다.Specifically, in the case where a thiol group is formed at one end of the polyethylene glycol, the thiol group forms a bond with lithium metal, and the polyethylene oxide chain of the polyethylene glycol interacts with lithium ions, thereby Sudden change in lithium ion concentration can be suppressed.
또한, 상기 말단이 기능화된 폴리에틸렌 글리콜은 소량만 리튬 이차전지용 전해질에 포함되더라도, 리튬 덴드라이트 성장 억제 효과가 우수하여, 리튬 금속의 충방전시 과전압이 개선되고 발현되는 용량을 증가시킬 수 있다.In addition, even if only a small amount of the functionalized polyethylene glycol is included in the lithium secondary battery electrolyte, it is excellent in the lithium dendrite growth inhibitory effect, it is possible to improve the overvoltage during charging and discharging of lithium metal and increase the capacity expressed.
도 1은 실시예 1 및 비교예 1에서 각각 제조된 리튬-황 전지에 대한 충방전 실험 결과를 나타낸 것이다.Figure 1 shows the charge and discharge test results for the lithium-sulfur battery prepared in Example 1 and Comparative Example 1, respectively.
도 2는 실시예 3 및 비교예 3,4에서 각각 제조된 리튬-황 전지에 대한 방전 용량 측정 실험 결과를 나타낸 것이다.Figure 2 shows the discharge capacity measurement test results for the lithium-sulfur battery prepared in Example 3 and Comparative Examples 3,4, respectively.
도 3은 실시예 4 및 비교예 5에서 각각 제조된 리튬-황 전지에 대한 방전 용량 측정 실험 결과를 나타낸 것이다.Figure 3 shows the discharge capacity measurement test results for the lithium-sulfur battery prepared in Example 4 and Comparative Example 5, respectively.
도 4 는 실시예 2에서 제조된 리튬 금속전지를 충방전시킨 후 리튬 금속 음극 표면의 사진이다.4 is a photograph of a surface of a lithium metal negative electrode after charging and discharging a lithium metal battery prepared in Example 2. FIG.
도 5는 실시예 3 및 비교예 3에서 각각 제조된 리튬-황 전지에 대한 충방전 사이클 진행에 따른 방전 용량 및 쿨롱 효율 측정 결과를 나타낸 것이다.5 shows discharge capacity and coulombic efficiency measurement results of charging and discharging cycles of lithium-sulfur batteries prepared in Example 3 and Comparative Example 3, respectively.
이하, 본 발명에 대한 이해를 돕기 위하여 본 발명을 더욱 상세하게 설명한다.Hereinafter, the present invention will be described in more detail to aid in understanding the present invention.
본 명세서 및 청구범위에서 사용된 용어나 단어는 통상적이거나 사전적인 의미로 한정해서 해석되어서는 아니 되며, 발명자는 그 자신의 발명을 가장 최선의 방법으로 설명하기 위해 용어의 개념을 적절하게 정의할 수 있다는 원칙에 입각하여 본 발명의 기술적 사상에 부합하는 의미와 개념으로 해석되어야만 한다.The terms or words used in this specification and claims are not to be construed as limiting in their usual or dictionary meanings, and the inventors may appropriately define the concept of terms in order to best describe their invention. It should be interpreted as meaning and concept corresponding to the technical idea of the present invention based on the principle that the present invention.
리튬 이차전지용 전해질Electrolyte for Lithium Secondary Battery
본 발명은 리튬 이차전지용 전해질에 관한 것으로, 전해질에 포함되는 첨가제의 구성을 제어하여, 리튬 금속 음극의 표면에서 리튬 이온 농도를 균일하게 유지시킴으로써 리튬 덴드라이트의 성장을 제어할 수 있는 리튬 이차전지용 전해질에 관한 것이다.BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrolyte for a lithium secondary battery, wherein the electrolyte for a lithium secondary battery capable of controlling the growth of lithium dendrites by controlling the configuration of an additive included in the electrolyte and maintaining a uniform lithium ion concentration on the surface of the lithium metal anode. It is about.
이때, 상기 전해질에 포함되는 첨가제의 구성이란, 첨가제 물질에 형성된 기능기의 종류와 몰분율 및 구조를 의미하는 것일 수 있다.In this case, the configuration of the additive included in the electrolyte may mean the kind, mole fraction and structure of the functional group formed in the additive material.
본 발명에 따른 리튬 이차전지용 전해질은 첨가제로서 기능기가 결합된 폴리에틸렌 글리콜을 포함할 수 있다.The electrolyte for a lithium secondary battery according to the present invention may include polyethylene glycol having a functional group bonded as an additive.
구체적으로, 상기 리튬 이차전지용 전해질의 첨가제는 하기 화학식 1로 표시될 수 있다.Specifically, the additive of the lithium secondary battery electrolyte may be represented by the following formula (1).
[화학식 1][Formula 1]
X-(CH2-CH2-O)n-SHX- (CH 2 -CH 2 -O) n -SH
상기 식에서, X는 메틸(methyl, CH3) 또는 티올(thiol, SH)이고, n은 5 내지 45인 정수이다.Wherein X is methyl (methyl, CH 3 ) or thiol (SH) and n is an integer from 5 to 45.
상기 화학식 1로 표시되는 첨가제의 함량은 상기 전해질의 전체 중량을 기준으로 0 중량% 초과, 1.0 중량% 이하, 바람직하게는 0.05 내지 0.5 중량%일 수 있다. 상기 화학식 1로 표시되는 첨가제의 함량이 상기 범위 미만이면 리튬 금속 음극의 표면에서 리튬 이온 농도가 균일하지 않아 리튬 덴드라이트가 성장하게 되고, 상기 범위 초과이면 첨가제 분해에 의한 부반응의 문제가 있다.The content of the additive represented by Formula 1 may be more than 0 wt%, 1.0 wt% or less, preferably 0.05 to 0.5 wt%, based on the total weight of the electrolyte. When the content of the additive represented by Formula 1 is less than the above range, lithium dendrite grows due to uneven lithium ion concentration on the surface of the lithium metal negative electrode.
상기 화학식 1로 표시되는 첨가제에서, 일 말단에 형성된 -SH는 리튬 금속과 결합을 형성하고, -(CH2-CH2-O)-는 리튬 이온과 상호작용(interact) 함으로써, 리튬 금속 음극의 표면에서 리튬 이온 농도를 균일하게 유지시킬 수 있다.In the additive represented by Chemical Formula 1, -SH formed at one end forms a bond with lithium metal, and-(CH 2 -CH 2 -O)-interacts with lithium ions, thereby The lithium ion concentration can be kept uniform at the surface.
여기서, 상기 티올(-SH)은 상기 화학식 1로 표시되는 첨가제에서 1 내지 30 중량%, 바람직하게는 1 내지 20 중량%로 포함될 수 있다. 이때, 상기 중량%는 상기 첨가제에 포함된 티올(-SH)의 질량비율을 기준으로 한 것이다. 상기 티올의 함량이 1 중량% 미만이면 리튬 금속과 결합을 형성하기가 어려워 리튬 금속 음극 표면에서 리튬 이온의 농도를 균일하게 유지하기가 힘들고, 30 중량% 초과이면 -SH의 함량이 상대적으로 과도하게 되어 첨가제의 분해 및 리튬 금속과의 부반응이 가속화 된다. Here, the thiol (-SH) may be included in 1 to 30% by weight, preferably 1 to 20% by weight in the additive represented by the formula (1). In this case, the weight percent is based on the mass ratio of thiol (-SH) contained in the additive. If the content of the thiol is less than 1% by weight, it is difficult to form a bond with the lithium metal, making it difficult to maintain the concentration of lithium ions uniformly on the surface of the lithium metal anode, and when the content of more than 30% by weight is relatively excessive, This accelerates the decomposition of additives and side reactions with lithium metal.
또한, 상기 화학식 1로 표시되는 첨가제에서, 폴리에틸렌 옥사이드 사슬(-(CH2-CH2-O)n-)은 선형(linear) 또는 분지형(baranched)일 수 있다.In addition, in the additive represented by Formula 1, the polyethylene oxide chain (-(CH 2 -CH 2 -O) n- ) may be linear or branched (baranched).
또한, 상기 화학식 1로 표시되는 첨가제에서, n은 폴리에틸렌 옥사이드 사슬(-(CH2-CH2-O)n-)의 길이를 의미하는 것으로, n의 상기 범위 미만이면 리튬 이온과 효과적인 complex를 형성하지 못한다는 문제점이 있고, 상기 범위 초과이면 리튬 금속 전극 표면에 첨가제가 도달하기 어렵다는 문제점이 있다.In addition, in the additive represented by Formula 1, n means the length of the polyethylene oxide chain (-(CH 2 -CH 2 -O) n- ), if less than the above range of n to form an effective complex with lithium ions There is a problem that it does not, if there is a problem that the additive is difficult to reach the surface of the lithium metal electrode.
본 발명에 있어서, 리튬 이차전지용 전해질은 유기용매를 포함할 수 있다. 상기 유기용매는 에테르, 에스테르, 아미드, 선형 카보네이트, 환형 카보네이트 등을 각각 단독으로 또는 2종 이상 혼합하여 사용할 수 있다. In the present invention, the electrolyte for a lithium secondary battery may include an organic solvent. The organic solvent may be used alone or in combination of two or more of ether, ester, amide, linear carbonate, cyclic carbonate and the like.
상기 에테르계 화합물은 디메틸 에테르, 디에틸 에테르, 디프로필 에테르, 메틸에틸 에테르, 메틸프로필 에테르, 에틸프로필 에테르, 디메톡시에탄, 디에톡시에탄, 메톡시에톡시에탄, 에틸렌 글리콜 모노메틸 에테르, 디에틸렌 글리콜 디메틸 에테르, 디에틸렌 글리콜 디에틸 에테르, 디에틸렌 글리콜 메틸에틸 에테르, 트리에틸렌 글리콜 디메틸 에테르, 트리에틸렌 글리콜 디에틸 에테르, 트리에틸렌 글리콜 메틸에틸 에테르, 테트라에틸렌 글리콜 디메틸 에테르, 테트라에틸렌 글리콜 디에틸 에테르, 테트라에틸렌 글리콜 메틸에틸 에테르, 폴리에틸렌 글리콜 디메틸 에테르, 폴리에틸렌 글리콜 디에틸 에테르, 폴리에틸렌 글리콜 메틸에틸 에테르, 1,3-디옥솔란, 테트라하이드로퓨란, 2-메틸테트라하이드로퓨란으로 이루어진 군에서 선택되는 1종 이상이 사용될 수 있으나, 이에 한정되는 것은 아니다.The ether compound is dimethyl ether, diethyl ether, dipropyl ether, methylethyl ether, methylpropyl ether, ethylpropyl ether, dimethoxyethane, diethoxyethane, methoxyethoxyethane, ethylene glycol monomethyl ether, diethylene Glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol methylethyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, triethylene glycol methylethyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol diethyl ether , Tetraethylene glycol methylethyl ether, polyethylene glycol dimethyl ether, polyethylene glycol diethyl ether, polyethylene glycol methylethyl ether, 1,3-dioxolane, tetrahydrofuran, 2-methyltetrahydrofuran More than It may be used, and the like.
상기 에스테르로는 메틸 아세테이트, 에틸 아세테이트, 프로필 아세테이트, 메틸 프로피오 네이트, 에틸 프로피오네이트, 프로필 프로피오네이트, γ-부티로락톤, γ-발레로락톤, γ-카프로락톤, σ-발레로락톤 및 ε-카프로락톤으로 이루어진 군에서 선택되는 어느 하나 또는 이들 중 2종 이상의 혼합물을 사용할 수 있으나, 이에 한정되는 것은 아니다.The esters include methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone And ε-caprolactone, but any one selected from the group consisting of, or a mixture of two or more thereof may be used, but is not limited thereto.
상기 선형 카보네이트 화합물의 구체적인 예로는 디메틸 카보네이트(DMC), 디에틸 카보네이트(DEC), 디프로필 카보네이트, 에틸메틸 카보네이트(EMC), 메틸프로필 카보네이트 및 에틸프로필 카보네이트로 이루어진 군에서 선택되는 어느 하나 또는 이들 중 2종 이상의 혼합물 등이 대표적으로 사용될 수 있으나, 이에 한정되는 것은 아니다.Specific examples of the linear carbonate compounds include any one selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethylmethyl carbonate (EMC), methylpropyl carbonate and ethylpropyl carbonate. Two or more kinds of mixtures and the like may be representatively used, but are not limited thereto.
또한 상기 환형 카보네이트 화합물의 구체적인 예로는 에틸렌 카보네이트(ethylene carbonate, EC), 프로필렌 카보네이트(propylene carbonate, PC), 1,2-부틸렌 카보네이트, 2,3-부틸렌 카보네이트, 1,2-펜틸렌 카보네이트, 2,3-펜틸렌 카보네이트, 비닐렌 카보네이트, 비닐에틸렌 카보네이트 및 이들의 할로겐화물로 이루어진 군에서 선택되는 어느 하나 또는 이들 중 2종 이상의 혼합물이 있다. 이들의 할로겐화물로는 예를 들면, 플루오로에틸렌 카보네이트(fluoroethylene carbonate, FEC) 등이 있으며, 이에 한정되는 것은 아니다.In addition, specific examples of the cyclic carbonate compound include ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate , 2,3-pentylene carbonate, vinylene carbonate, vinylethylene carbonate, and any one selected from the group consisting of halides thereof or mixtures of two or more thereof. These halides include, for example, fluoroethylene carbonate (FEC), but are not limited thereto.
또한, 상술한 유기용매 이외에 N-메틸피롤리돈, 디메틸설폭사이드, 설포란 등이 있다.In addition to the aforementioned organic solvents, there are N-methylpyrrolidone, dimethyl sulfoxide, sulfolane and the like.
본 발명의 리튬 이차전지용 전해질은 전술한 조성 이외에 해당 기술분야에서 통상적으로 사용되는 질산계 화합물을 추가로 포함할 수 있다. 일례로, 질산리튬(LiNO3), 질산칼륨(KNO3), 질산세슘(CsNO3), 질산마그네슘(MgNO3), 질산바륨(BaNO3), 아질산리튬(LiNO2), 아질산칼륨(KNO2), 아질산세슘(CsNO2) 등을 들 수 있다.The electrolyte for a lithium secondary battery of the present invention may further include a nitrate-based compound commonly used in the art in addition to the above composition. For example, lithium nitrate (LiNO 3 ), potassium nitrate (KNO 3 ), cesium nitrate (CsNO 3 ), magnesium nitrate (MgNO 3 ), barium nitrate (BaNO 3 ), lithium nitrite (LiNO 2 ), potassium nitrite (KNO 2) ), Cesium nitrite (CsNO 2 ), and the like.
본 발명에 있어서, 리튬 이차전지용 전해질은 전해질염으로서 리튬염을 포함할 수 있다. 상기 리튬염은 본 발명에서 특별히 한정하지 않으며, 리튬 이차전지용 전해질에 통상적으로 사용 가능한 것이라면 제한없이 사용될 수 있다.In the present invention, the electrolyte for a lithium secondary battery may include a lithium salt as an electrolyte salt. The lithium salt is not particularly limited in the present invention, and any lithium salt may be used without limitation as long as it can be commonly used in the electrolyte for lithium secondary batteries.
예를 들어, 상기 리튬염은 LiCl, LiBr, LiI, LiClO4, LiBF4, LiB10Cl10, LiPF6, LiCF3SO3, LiCF3CO2, LiC4BO8, LiAsF6, LiSbF6, LiAlCl4, CH3SO3Li, CF3SO3Li, (CF3SO2)2NLi, (C2F5SO2)2NLi, (SO2F)2NLi, (CF3SO2)3CLi, 클로로 보란 리튬, 탄소수 4 이하의 저급지방족 카르본산 리튬, 4-페닐 붕산 리튬 및 리튬 이미드로 이루어진 군에서 선택되는 1종 이상을 포함할 수 있다. 바람직하기로 상기 리튬염은 리튬 비스(트리플루오로메탄설포닐)이미드(Lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), (CF3SO2)2NLi)일 수 있다.For example, the lithium salt is 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, (SO 2 F) 2 NLi, (CF 3 SO 2 ) 3 CLi It may include one or more selected from the group consisting of lithium chloroborane, lower aliphatic carboxylic acid having 4 or less carbon atoms, lithium 4-phenyl borate and lithium imide. Preferably, the lithium salt may be lithium bis (trifluoromethanesulfonyl) imide (LiTFSI), (CF 3 SO 2 ) 2 NLi.
상기 리튬염의 농도는 이온 전도도, 용해도 등을 고려하여 적절하게 결정될 수 있으며, 예를 들어 0.1 내지 4.0 M, 바람직하게는 0.5 내지 2.0 M 일 수 있다. 상기 리튬염의 농도가 상기 범위 미만인 경우 전지 구동에 적합한 이온 전도도의 확보가 어려우며, 이와 반대로 상기 범위를 초과하는 경우 전해액의 점도가 증가하여 리튬 이온의 이동성을 저하되며 리튬염 자체의 분해 반응이 증가하여 전지의 성능이 저하될 수 있으므로 상기 범위 내에서 적절히 조절한다.The concentration of the lithium salt may be appropriately determined in consideration of ionic conductivity, solubility, and the like, and may be, for example, 0.1 to 4.0 M, preferably 0.5 to 2.0 M. When the concentration of the lithium salt is less than the above range, it is difficult to secure ionic conductivity suitable for driving the battery.On the contrary, when the concentration of the lithium salt exceeds the above range, the viscosity of the electrolyte increases to decrease the mobility of the lithium ions and the decomposition reaction of the lithium salt itself increases. Since the performance of the battery may be degraded, it is appropriately adjusted within the above range.
리튬 이차전지Lithium secondary battery
본 발명은 상기 리튬 이차전지용 전해질을 포함하는 리튬 이차전지를 제공한다.The present invention provides a lithium secondary battery comprising the electrolyte for a lithium secondary battery.
본 발명에 따른 리튬 이차전지는 리튬 금속 음극을 포함하는 것일 수 있으며, 예를 들어, 리튬 금속전지, 리튬-황 전지 등일 수 있다.The lithium secondary battery according to the present invention may include a lithium metal negative electrode, and may be, for example, a lithium metal battery, a lithium-sulfur battery, or the like.
상기 리튬 이차전지는 양극, 음극 및 상기 양극과 음극 사이에 개재되는 전해질을 포함하며, 상기 전해질로서 본 발명에 따른 리튬 금속 전지용 전해질을 포함한다.The lithium secondary battery includes a positive electrode, a negative electrode, and an electrolyte interposed between the positive electrode and the negative electrode, and includes the lithium metal battery electrolyte according to the present invention as the electrolyte.
상기 양극은 양극 집전체와 상기 양극 집전체의 일면 또는 양면에 도포된 양극 활물질을 포함할 수 있다.The positive electrode may include a positive electrode current collector and a positive electrode active material coated on one or both surfaces of the positive electrode current collector.
상기 양극 집전체는 양극 활물질을 지지하며, 당해 전지에 화학적 변화를 유발하지 않으면서 높은 도전성을 가지는 것이라면 특별히 제한되는 것은 아니다. 예를 들어, 구리, 스테인리스 스틸, 알루미늄, 니켈, 티타늄, 팔라듐, 소성 탄소, 구리나 스테인리스 스틸 표면에 카본, 니켈, 은 등으로 표면 처리한 것, 알루미늄-카드뮴 합금 등이 사용될 수 있다.The positive electrode current collector supports the positive electrode active material, and is not particularly limited as long as it has high conductivity without causing chemical change in the battery. For example, copper, stainless steel, aluminum, nickel, titanium, palladium, calcined carbon, surface treated with carbon, nickel, silver, etc. on the surface of copper or stainless steel, aluminum-cadmium alloy, and the like can be used.
상기 양극 집전체는 그것의 표면에 미세한 요철을 형성하여 양극 활물질과의 결합력을 강화시킬 수 있으며, 필름, 시트, 호일, 메쉬, 네트, 다공질체, 발포체, 부직포체 등 다양한 형태를 사용할 수 있다.The positive electrode current collector may form fine concavities and convexities on its surface to enhance bonding strength with the positive electrode active material, and may be used in various forms such as a film, a sheet, a foil, a mesh, a net, a porous body, a foam, and a nonwoven fabric.
상기 양극 활물질은 양극 활물질과 선택적으로 도전재 및 바인더를 포함할 수 있다.The cathode active material may include a cathode active material, and optionally a conductive material and a binder.
상기 양극 활물질은 상기 양극 활물질은 리튬의 인터칼레이션이 가능한 구조를 가지는 리튬과 전이 금속으로 이루어진 산화물일 수 있으며, 예를 들어, 하기 화학식 2로 표시될 수 있다.The cathode active material may be an oxide formed of lithium and a transition metal having a structure capable of intercalating lithium, and for example, may be represented by the following Chemical Formula 2.
[화학식 2] [Formula 2]
LiaNi1 -x- yCoxMnyMbO2 Li a Ni 1 -x- y Co x Mn y M b O 2
상기 화학식 2에서, a=1, 0.1 ≤ x ≤ 0.3, 0.15 ≤ y ≤ 0.25, 0 ≤ b ≤ 0.05 이며, M은 Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, Zn 및 이들의 조합으로 이루어진 군에서 선택되는 전이 금속 또는 란탄족 원소에서 선택되는 어느 하나일 수 있다.In Formula 2, a = 1, 0.1 ≦ x ≦ 0.3, 0.15 ≦ y ≦ 0.25, 0 ≦ b ≦ 0.05, and M is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, Zn and It may be any one selected from a transition metal or a lanthanide element selected from the group consisting of a combination thereof.
특히, 리튬-황 전지의 경우, 양극 활물질은 황 원소(Elemental sulfur, S8); Li2Sn(n≥1), 2,5-디머캅토-1,3,4-티아디아졸(2,5-dimercapto-1,3,4-thiadiazole), 1,3,5-트리티오시아누익산(1,3,5-trithiocyanuic acid) 등과 같은 디설파이드 화합물, 유기황 화합물 또는 탄소-황 폴리머((C2Sx)n: x=2.5 ~ 50, n≥2) 등의 황 함유 화합물로 이루어진 군으로부터 선택된 1종 이상일 수 있다. 바람직하게는 무기 황(S8)을 사용할 수 있다.In particular, in the case of a lithium-sulfur battery, the positive electrode active material is elemental sulfur (S 8 ); Li 2 S n (n ≧ 1), 2,5-dimercapto-1,3,4-thiadiazole, 1,3,5-trithio Sulfur-containing compounds such as disulfide compounds such as cyanuric acid (1,3,5-trithiocyanuic acid), organosulfur compounds or carbon-sulfur polymers ((C 2 S x ) n : x = 2.5-50, n≥2) It may be one or more selected from the group consisting of. Preferably inorganic sulfur (S 8 ) can be used.
상기 양극은 상기 양극 활물질 이외에 전이금속 원소, ⅢA족 원소, ⅣA족 원소, 이들 원소들의 황 화합물, 및 이들 원소들과 황의 합금 중에서 선택되는 하나 이상의 첨가제를 더 포함할 수 있다.The positive electrode may further include one or more additives selected from transition metal elements, group IIIA elements, group IVA elements, sulfur compounds of these elements, and alloys of these elements and sulfur, in addition to the positive electrode active material.
상기 전이금속 원소로는 Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Os, Ir, Pt, Au 또는 Hg 등이 포함되고, 상기 ⅢA족 원소로는 Al, Ga, In, Ti 등이 포함되며, 상기 ⅣA족 원소로는 Ge, Sn, Pb 등이 포함될 수 있다.The transition metal element may be Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Os, Ir, Pt, Au or Hg and the like, the Group IIIA element may include Al, Ga, In, Ti, and the like, and the Group IVA element may include Ge, Sn, Pb and the like.
상기 도전재는 전기 전도성을 향상시키기 위한 것으로, 리튬 이차전지에서 화학변화를 일으키지 않는 전자 전도성 물질이면 특별한 제한이 없다.The conductive material is to improve electrical conductivity, and there is no particular limitation as long as it is an electronic conductive material that does not cause chemical change in a lithium secondary battery.
일반적으로 카본블랙(carbon black), 흑연, 탄소섬유, 카본 나노튜브, 금속분말, 도전성 금속산화물, 유기 도전재 등을 사용할 수 있고, 현재 도전재로 시판되고 있는 상품으로는 아세틸렌 블랙계열(쉐브론 케미컬 컴퍼니(Chevron Chemical Company) 또는 걸프 오일 컴퍼니(Gulf Oil Company) 제품 등), 케트젠 블랙(Ketjen Black) EC 계열 (아르막 컴퍼니(Armak Company) 제품), 불칸(Vulcan) XC-72(캐보트 컴퍼니(Cabot Company) 제품) 및 수퍼 P(엠엠엠(MMM)사 제품) 등이 있다. 예를 들면 아세틸렌블랙, 카본블랙, 흑연 등을 들 수 있다.In general, carbon black, graphite, carbon fiber, carbon nanotubes, metal powder, conductive metal oxide, organic conductive materials, and the like can be used, and currently commercially available as a conductive material acetylene black series (Chevron Chemical) Chevron Chemical Company or Gulf Oil Company, etc., Ketjen Black EC series (Armak Company), Vulcan XC-72 (Cabot Company) (Cabot Company) and Super P (MMM). For example, acetylene black, carbon black, graphite, etc. are mentioned.
또한, 상기 양극 활물질은 양극 집전체에 유지시키고, 활물질 사이를 이어주는 기능을 갖는 바인더를 추가로 포함할 수 있다. 상기 바인더로서, 예를 들면, 폴리비닐리덴 풀루오라이드-헥사풀루오로프로필렌(PVDF-co-HFP), 폴리비닐리덴 풀루오라이드(polyvinylidene fluoride, PVDF), 폴리아크릴로니트릴 (polyacrylonitrile), 폴리메틸 메타크릴레이트(polymethyl methacrylate), 스티렌-부타디엔 고무(styrene butadiene rubber, SBR), 카르복실 메틸 셀룰로오스 (carboxyl methyl cellulose, CMC), 폴리 아크릴산(poly(acrylic acid), PAA), 폴리 비닐 알코올(poly(vinyl alcohol), PVA) 등의 다양한 종류의 바인더가 사용될 수 있다.In addition, the cathode active material may further include a binder having a function of maintaining the cathode current collector and connecting the active materials. As the binder, for example, polyvinylidene fluoride-hexafluorofluoropropylene (PVDF-co-HFP), polyvinylidene fluoride (PVDF), polyacrylonitrile, poly Methyl methacrylate, styrene butadiene rubber (SBR), carboxyl methyl cellulose (CMC), poly (acrylic acid, PAA), polyvinyl alcohol Various kinds of binders such as (vinyl alcohol) and PVA) may be used.
상기 음극은 음극 집전체 및 상기 음극 집전체 상에 위치하는 음극 활물질을 포함할 수 있다. 또는 상기 음극은 리튬 금속판일 수 있다.The negative electrode may include a negative electrode current collector and a negative electrode active material positioned on the negative electrode current collector. Alternatively, the negative electrode may be a lithium metal plate.
상기 음극 집전체는 음극 활물질의 지지를 위한 것으로, 우수한 도전성을 가지고 리튬 이차전지의 전압영역에서 전기화학적으로 안정한 것이라면 특별히 제한되는 것은 아니며, 예를 들어, 구리, 스테인리스 스틸, 알루미늄, 니켈, 티타늄, 팔라듐, 소성 탄소, 구리나 스테인리스 스틸 표면에 카본, 니켈, 은 등으로 표면 처리한 것, 알루미늄-카드뮴 합금 등이 사용될 수 있다. The negative electrode current collector is for supporting the negative electrode active material, and is not particularly limited as long as it has excellent conductivity and is electrochemically stable in the voltage range of the lithium secondary battery. For example, copper, stainless steel, aluminum, nickel, titanium, Palladium, calcined carbon, surface treated with carbon, nickel, silver or the like on the surface of copper or stainless steel, aluminum-cadmium alloy, or the like may be used.
상기 음극 집전체는 그것의 표면에 미세한 요철을 형성하여 음극 활물질과의 결합력을 강화시킬 수 있으며, 필름, 시트, 호일, 메쉬, 네트, 다공질체, 발포체, 부직포체 등 다양한 형태를 사용할 수 있다. The negative electrode current collector may form fine irregularities on its surface to enhance bonding strength with the negative electrode active material, and may be used in various forms such as film, sheet, foil, mesh, net, porous body, foam, and nonwoven fabric.
상기 음극 활물질은 리튬 (Li+)을 가역적으로 흡장(Intercalation) 또는 방출(Deintercalation)할 수 있는 물질, 리튬 이온과 반응하여 가역적으로 리튬 함유 화합물을 형성할 수 있는 물질, 리튬 금속 또는 리튬 합금을 포함할 수 있다. 상기 리튬 이온(Li+)을 가역적으로 흡장 또는 방출할 수 있는 물질은 예컨대 결정질 탄소, 비정질 탄소 또는 이들의 혼합물일 수 있다. 상기 리튬 이온(Li+)과 반응하여 가역적으로 리튬 함유 화합물을 형성할 수 있는 물질은 예를 들어, 산화주석, 티타늄나이트레이트 또는 실리콘일 수 있다. 상기 리튬 합금은 예를 들어, 리튬(Li)과 나트륨(Na), 칼륨(K), 루비듐(Rb), 세슘(Cs), 프랑슘(Fr), 베릴륨(Be), 마그네슘(Mg), 칼슘(Ca), 스트론튬(Sr), 바륨(Ba), 라듐(Ra), 알루미늄(Al) 및 주석(Sn)으로 이루어지는 군에서 선택되는 금속의 합금일 수 있다. 바람직하게 상기 음극 활물질은 리튬 금속일 수 있으며, 구체적으로, 리튬 금속 박막 또는 리튬 금속 분말의 형태일 수 있다.The anode active material includes a material capable of reversibly intercalating or deintercalating lithium (Li + ), a material capable of reacting with lithium ions to reversibly form a lithium-containing compound, a lithium metal or a lithium alloy can do. Substance capable of reversibly occluding or emitting in the lithium ion (Li +) may be, for example, crystalline carbon, amorphous carbon, or a mixture thereof. The material capable of reacting with the lithium ions (Li + ) to form a lithium-containing compound reversibly may be, for example, tin oxide, titanium nitrate or silicon. The lithium alloy is, for example, lithium (Li) and sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), francium (Fr), beryllium (Be), magnesium (Mg), calcium ( It may be an alloy of a metal selected from the group consisting of Ca), strontium (Sr), barium (Ba), radium (Ra), aluminum (Al) and tin (Sn). Preferably, the negative electrode active material may be lithium metal, and specifically, may be in the form of a lithium metal thin film or lithium metal powder.
상기 음극 활물질의 형성방법은 특별히 제한되지 않으며, 당업계에서 통상적으로 사용되는 층 또는 막의 형성방법을 이용할 수 있다. 예컨대 압착, 코팅, 증착 등의 방법을 이용할 수 있다. 또한, 집전체에 리튬 박막이 없는 상태로 전지를 조립한 후 초기 충전에 의해 금속판 상에 금속 리튬 박막이 형성되는 경우도 본 발명의 음극에 포함된다.The method of forming the negative electrode active material is not particularly limited, and a method of forming a layer or a film commonly used in the art may be used. For example, a method such as pressing, coating or vapor deposition can be used. The negative electrode of the present invention also includes a case where a metal lithium thin film is formed on a metal plate by initial charging after assembling a battery without a lithium thin film in a current collector.
상기 전해질은 리튬 이온을 포함하며, 이를 매개로 양극과 음극에서 전기 화학적인 산화 또는 환원 반응을 일으키기 위한 것으로, 전술한 바를 따른다.The electrolyte includes lithium ions, and is used for causing an electrochemical oxidation or reduction reaction at the positive electrode and the negative electrode through the above, as described above.
상기 전해액의 주입은 최종 제품의 제조 공정 및 요구 물성에 따라, 전기화학소자의 제조 공정 중 적절한 단계에서 행해질 수 있다. 즉, 전기화학소자 조립 전 또는 전기화학소자 조립 최종 단계 등에서 적용될 수 있다.The injection of the electrolyte may be performed at an appropriate step in the manufacturing process of the electrochemical device, depending on the manufacturing process and the required physical properties of the final product. That is, it may be applied before the electrochemical device assembly or the final step of the electrochemical device assembly.
전술한 양극과 음극 사이에는 추가적으로 분리막이 포함될 수 있다. 상기 분리막은 본 발명의 리튬 이차전지에 있어서 양 전극을 물리적으로 분리하기 위한 것으로, 통상 리튬 이자전지에서 분리막으로 사용되는 것이라면 특별한 제한없이 사용가능하며, 특히 전해질의 이온 이동에 대하여 저저항이면서 전해액 함습 능력이 우수한 것이 바람직하다.The separator may be additionally included between the positive electrode and the negative electrode. The separator is used to physically separate both electrodes in the lithium secondary battery of the present invention. If the separator is used as a separator in a lithium secondary battery, the separator may be used without particular limitation. It is desirable that the capability is excellent.
상기 분리막은 다공성 기재로 이루어질 수 있는데 상기 다공성 기재는 통상적으로 전기화학소자에 사용되는 다공성 기재라면 모두 사용이 가능하고, 예를 들면 폴리올레핀계 다공성 막 또는 부직포를 사용할 수 있으나, 이에 특별히 한정되는 것은 아니다.The separator may be made of a porous substrate, and the porous substrate may be used as long as it is a porous substrate commonly used in an electrochemical device. For example, a polyolefin-based porous membrane or a nonwoven fabric may be used, but is not particularly limited thereto. .
상기 폴리올레핀계 다공성 막의 예로는, 고밀도 폴리에틸렌, 선형 저밀도 폴리에틸렌, 저밀도 폴리에틸렌, 초고분자량 폴리에틸렌과 같은 폴리에틸렌, 폴리프로필렌, 폴리부틸렌, 폴리펜텐 등의 폴리올레핀계 고분자를 각각 단독으로 또는 이들을 혼합한 고분자로 형성한 막(membrane)을 들 수 있다.Examples of the polyolefin-based porous membrane, polyolefin-based polymers, such as polyethylene, polypropylene, polybutylene, polypentene, such as high density polyethylene, linear low density polyethylene, low density polyethylene, ultra high molecular weight polyethylene, respectively, or a mixture thereof One membrane may be mentioned.
상기 부직포로는 폴리올레핀계 부직포 외에 예를 들어, 폴리에틸렌 테레프탈레이트(polyethyleneterephthalate), 폴리부틸렌 테레프탈레이트(polybutyleneterephthalate), 폴리에스테르(polyester), 폴리아세탈(polyacetal), 폴리아미드(polyamide), 폴리카보네이트 (polycarbonate), 폴리이미드(polyimide), 폴리에테르에테르케톤(polyetheretherketone), 폴리에테르설폰(polyethersulfone), 폴리페닐렌 옥사이드(polyphenyleneoxide), 폴리페닐렌 설파이드(polyphenylenesulfide) 및 폴리에틸렌 나프탈레이트(polyethylenenaphthalate) 등을 각각 단독으로 또는 이들을 혼합한 고분자로 형성한 부직포를 들 수 있다. 상기 부직포의 구조는 장섬유로 구성된 스폰본드 부직포 또는 멜트 블로운 부직포일 수 있다.The nonwoven fabric may be, for example, polyethylene terephthalate, polybutylene terephthalate, polyester, polyacetal, polyamide, polycarbonate, or polycarbonate. ), Polyimide, polyetheretherketone, polyethersulfone, polyphenyleneoxide, polyphenylenesulfide and polyethylenenaphthalate alone Or the nonwoven fabric formed from the polymer which mixed these is mentioned. The structure of the nonwoven fabric may be a spunbond nonwoven fabric or a melt blown nonwoven fabric composed of long fibers.
상기 다공성 기재의 두께는 특별히 제한되지 않으나, 1 내지 100 ㎛, 바람직하게는 5 내지 50 ㎛일 수 있다. The thickness of the porous substrate is not particularly limited, but may be 1 to 100 μm, preferably 5 to 50 μm.
상기 다공성 기재에 존재하는 기공의 크기 및 기공도 역시 특별히 제한되지 않으나 각각 0.001 내지 50 ㎛ 및 10 내지 95 %일 수 있다.The pore size and pore present in the porous substrate are also not particularly limited, but may be 0.001 to 50 μm and 10 to 95%, respectively.
본 발명에 따른 리튬 이차전지는 일반적인 공정인 권취(winding) 이외에도 세퍼레이터와 전극의 적층(lamination, stack) 및 접음(folding) 공정이 가능하다.The lithium secondary battery according to the present invention may be a lamination (stacking) and folding (folding) process of the separator and the electrode in addition to the winding (winding) which is a general process.
상기 리튬 이차전지의 형상은 특별히 제한되지 않으며 원통형, 적층형, 코인형 등 다양한 형상으로 할 수 있다.The shape of the lithium secondary battery is not particularly limited and may be in various shapes such as cylindrical, stacked, coin type.
또한, 본 발명은 상기 리튬 이차전지를 단위전지로 포함하는 전지모듈을 제공한다.In addition, the present invention provides a battery module comprising the lithium secondary battery as a unit cell.
상기 전지모듈은 고온 안정성, 긴 사이클 특성 및 높은 용량 특성 등이 요구되는 중대형 디바이스의 전원으로 사용될 수 있다.The battery module may be used as a power source for medium and large devices requiring high temperature stability, long cycle characteristics, and high capacity characteristics.
상기 중대형 디바이스의 예로는 전지적 모터에 의해 동력을 받아 움직이는 파워 툴(power tool); 전기자동차(electric vehicle, EV), 하이브리드 전기자동차(hybrid electric vehicle, HEV), 플러그-인 하이브리드 전기자동차(plug-in hybrid electric vehicle, PHEV) 등을 포함하는 전기차; 전기 자전거(E-bike), 전기 스쿠터(E-scooter)를 포함하는 전기 이륜차; 전기 골프 카트(electric golf cart); 전력저장용 시스템 등을 들 수 있으나, 이에 한정되는 것은 아니다.Examples of the medium-to-large device include a power tool that is driven by an electric motor; Electric vehicles including electric vehicles (EVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and the like; Electric motorcycles including electric bicycles (E-bikes) and electric scooters (E-scooters); Electric golf carts; Power storage systems and the like, but is not limited thereto.
이하 본 발명의 이해를 돕기 위하여 바람직한 실시예를 제시하나, 하기 실시예는 본 발명을 예시하는 것일 뿐 본 발명의 범주 및 기술사상 범위 내에서 다양한 변경 및 수정이 가능함은 당업자에게 있어서 명백한 것이며, 이러한 변경 및 수정이 첨부된 특허청구범위에 속하는 것도 당연한 것이다.Hereinafter, preferred examples are provided to help the understanding of the present invention, but the following examples are merely for exemplifying the present invention, and various changes and modifications within the scope and spirit of the present invention are apparent to those skilled in the art. It goes without saying that changes and modifications belong to the appended claims.
실시예 1: 리튬-황 전지 제조Example 1: Lithium-Sulfur Battery Preparation
리튬 금속 음극과 S/C 양극을 대면하도록 위치시키고, 그 사이에 PE(polyethylene) 분리막을 게재한 후, 전해질 70 ㎕를 주입하여 코인셀 형태의 리튬-황 전지를 제조하였다.The lithium metal negative electrode and the S / C positive electrode were positioned to face each other, and a PE (polyethylene) separator was placed therebetween, and 70 μl of the electrolyte was injected to prepare a coin-cell lithium-sulfur battery.
상기 전해질로는 첨가제 0.1 중량%를 포함하는 전해액(E1)을 사용하였으며, 상기 첨가제는 폴리에틸렌 글리콜 메틸 에테르 티올(mPEG-SH, 분자량: 800)이다. 상기 전해액(E1)은 용매로서 DOL/DME(1:1, v/v)을 사용하고, 1M LiTFSI와 3 중량%의 LiNO3를 포함하는 전해액이다 (DOL: 디옥솔란, DME: 디메톡시에탄).As the electrolyte, an electrolyte solution (E1) containing 0.1 wt% of an additive was used, and the additive is polyethylene glycol methyl ether thiol (mPEG-SH, molecular weight: 800). The electrolyte solution (E1) is an electrolyte solution containing 1M LiTFSI and 3% by weight of LiNO 3 using DOL / DME (1: 1, v / v) as a solvent (DOL: Dioxolane, DME: Dimethoxyethane) .
비교예 1: 리튬-황 전지 제조Comparative Example 1: Lithium-Sulfur Battery Preparation
실시예 1과 동일한 방법으로 실시하되, 상기 전해질로서 첨가제를 포함하지 않는 전해액(E1)을 사용하여 코인셀 형태의 리튬-황 전지를 제조하였다.A lithium-sulfur battery in the form of a coin cell was prepared in the same manner as in Example 1, but using an electrolyte solution E1 containing no additive as the electrolyte.
실시예 2: 리튬-리튬 대칭전지 제조Example 2: lithium-lithium symmetric battery
리튬 금속 음극과 리튬 금속 양극을 대면하도록 위치시키고, 그 사이에 PE(polyethylene) 분리막을 게재한 후, 전해질 100 ㎕를 주입하여 코인셀 형태의 리튬-리튬 전지를 제조하였다.A lithium metal anode and a lithium metal anode were positioned to face each other, a PE (polyethylene) separator was placed therebetween, and 100 µl of an electrolyte was injected to prepare a coin-cell lithium-lithium battery.
상기 전해질로는 첨가제 0.1 중량%를 포함하는 전해액(E2)을 사용하였으며, 상기 첨가제는 폴리에틸렌 글리콜 메틸 에테르 티올(mPEG-SH, 분자량: 800)이다. 상기 전해액(E2)는 용매로서 DOL/DME(1:1, v/v)을 사용하고, 1M LiTFSI를 포함하는 전해액이다 (DOL: 디옥솔란, DME: 디메톡시에탄).As the electrolyte, an electrolyte solution (E2) containing 0.1 wt% of an additive was used, and the additive is polyethylene glycol methyl ether thiol (mPEG-SH, molecular weight: 800). The electrolyte solution (E2) is an electrolyte solution containing 1 M LiTFSI using DOL / DME (1: 1, v / v) as a solvent (DOL: Dioxolane, DME: Dimethoxyethane).
비교예 2: 리튬-리튬 대칭전지 제조Comparative Example 2: Manufacture of Lithium-Lithium Symmetric Battery
실시예 2와 동일한 방법으로 실시하되, 상기 전해질로서 첨가제를 포함하지 않는 전해액(E2)을 사용하여 코인셀 형태의 리튬-리튬 전지를 제조하였다.A lithium-lithium battery of the coin cell type was prepared in the same manner as in Example 2, but using an electrolyte solution E2 containing no additive as the electrolyte.
실시예 3: 리튬-황 전지 제조Example 3: Lithium-Sulfur Battery Preparation
리튬 금속 음극과 S/C 양극을 대면하도록 위치시키고, 그 사이에 PE(polyethylene) 분리막을 게재한 후, 전해질 70 ㎕를 주입하여 코인셀 형태의 리튬-황 전지를 제조하였다.The lithium metal negative electrode and the S / C positive electrode were positioned to face each other, and a PE (polyethylene) separator was placed therebetween, and 70 μl of the electrolyte was injected to prepare a coin-cell lithium-sulfur battery.
상기 전해질로는 첨가제 0.1 중량%를 포함하는 전해액(E1)을 사용하였으며, 상기 첨가제는 폴리에틸렌 글리콜 메틸 에테르 티올(mPEG-SH, 분자량: 2,000)이다.As the electrolyte, an electrolyte (E1) containing 0.1 wt% of an additive was used, and the additive is polyethylene glycol methyl ether thiol (mPEG-SH, molecular weight: 2,000).
비교예 3: 리튬-황 전지 제조Comparative Example 3: Lithium-Sulfur Battery Preparation
실시예 3과 동일한 방법으로 실시하되, 상기 전해질로서 첨가제를 포함하지 않는 전해액(E1)을 사용하여 코인셀 형태의 리튬-황 전지를 제조하였다.A lithium-sulfur battery in the form of a coin cell was prepared in the same manner as in Example 3, but using an electrolyte solution E1 containing no additive as the electrolyte.
비교예 4: 리튬-황 전지 제조Comparative Example 4: Lithium-Sulfur Battery Preparation
실시예 3과 동일한 방법으로 실시하되, 상기 전해질로서 첨가제 함량이 1.5 중량%인 전해액(E1)을 사용하여 코인셀 형태의 리튬-황 전지를 제조하였다.In the same manner as in Example 3, a lithium-sulfur battery in the form of a coin cell was manufactured using an electrolyte solution (E1) having an additive content of 1.5 wt% as the electrolyte.
실시예 4: 리튬-황 전지 제조Example 4: Lithium-Sulfur Battery Preparation
실시예 1과 동일한 방법으로 실시하되, 상기 전해질의 첨가제로서 4arm-PEG5k-SH (분자량: 5,000)을 사용하였으며, 상기 첨가제에서 티올의 질량 비율은 3 wt% 이다.In the same manner as in Example 1, 4arm-PEG5k-SH (molecular weight: 5,000) was used as an additive of the electrolyte, and the mass ratio of thiol in the additive was 3 wt%.
비교예 5: 리튬-황 전지 제조Comparative Example 5: Lithium-Sulfur Battery Preparation
실시예 4와 동일한 방법으로 실시하되, 상기 전해질로서 첨가제를 포함하지 않는 전해액(E1)을 사용하여 코인셀 형태의 리튬-황 전지를 제조하였다.A lithium-sulfur battery in the form of a coin cell was prepared in the same manner as in Example 4 but using an electrolyte solution E1 containing no additive as the electrolyte.
실험예Experimental Example 1: 첨가제의 함량 및 첨가제 내의  1: content of additives and in additives 티올Thiol 함량에 따른 리튬-황 전지의 성능 실험 Performance Test of Lithium-Sulfur Battery According to Contents
전해질에 포함되는 첨가제 유무에 따른 리튬-황 전지의 성능 평가를 위하여, 실시예 1 및 비교예 1에서 각각 제조된 리튬-황 전지에 대해서 충방전 실험을 실시하였다. 실험 조건은 0.6 mA·cm-2 충전/ 0.6 mA·cm-2 방전 또는 1.2 mA·cm-2 충전/ 1.2 mA·cm-2 방전 조건으로 하였다.In order to evaluate the performance of the lithium-sulfur battery according to the presence or absence of an additive included in the electrolyte, charge and discharge experiments were performed on the lithium-sulfur batteries prepared in Example 1 and Comparative Example 1, respectively. The test conditions were 0.6 mA cm -2 charge / 0.6 mA cm -2 discharge or 1.2 mA cm -2 charge / 1.2 mA cm -2 discharge conditions.
도 1은 실시예 1 및 비교예 1에서 각각 제조된 리튬-황 전지에 대한 충방전 실험 결과를 나타낸 것이다.Figure 1 shows the charge and discharge test results for the lithium-sulfur battery prepared in Example 1 and Comparative Example 1, respectively.
도 1을 참조하면, 전해질 첨가제로서 mPEG-SH를 포함하는 실시예 1은 비교예 1에 비해 충방전시 과전압이 개선되고 발현되는 용량이 증가한 것을 알 수 있다. Referring to FIG. 1, it can be seen that Example 1 including mPEG-SH as an electrolyte additive improves overvoltage and increases expressed capacity when charging and discharging.
또한, 전해질에 포함되는 첨가제 함량에 따른 리튬-황 전지의 성능 평가를 위하여, 실시예 3 및 비교예 3,4에서 각각 제조된 리튬-황 전지에 대해서 충방전 사이클 진행에 따른 방전 용량 및 쿨롱 효율을 측정하여 전지 성능 평가를 실시하였다. 실험 조건은 0.6 mA·cm-2 충전/0.6 mA·cm-2 방전 및 1.2 mA·cm-2 충전/1.2 mA·cm-2 방전 조건으로 하여, 6 사이클 동안 충방전을 실시한 후, 방전 용량을 평가하였다In addition, in order to evaluate the performance of the lithium-sulfur battery according to the additive content included in the electrolyte, the discharge capacity and the coulombic efficiency of the lithium-sulfur battery prepared in Example 3 and Comparative Examples 3 and 4, respectively, according to the charge and discharge cycles Was measured and battery performance evaluation was performed. The test conditions were 0.6 mA cm -2 charge / 0.6 mA cm -2 discharge and 1.2 mA cm -2 charge / 1.2 mA cm -2 discharge conditions. Evaluated
도 2는 실시예 3 및 비교예 3,4에서 각각 제조된 리튬-황 전지에 대한 방전 용량 측정 실험 결과를 나타낸 것이다.Figure 2 shows the discharge capacity measurement test results for the lithium-sulfur battery prepared in Example 3 and Comparative Examples 3,4, respectively.
도 2를 참조하면, 전해질 첨가제로서 mPEG-SH를 포함하는 실시예 3은 비교예 3,4에 비해 높은 방전 용량을 나타내는 확인하였으며, 이로부터 상기 전해질 첨가제를 적정 함량으로 첨가할 경우 전지의 성능 향상에 유리한 것을 알 수 있었다.2, Example 3 including mPEG-SH as an electrolyte additive was confirmed to exhibit a high discharge capacity compared to Comparative Examples 3 and 4, from which the performance of the battery is improved when the electrolyte additive is added in an appropriate amount It was found to be advantageous.
또한, 전해질의 첨가제에 포함된 티올(-SH)의 함량에 따른 리튬-황 전지의 성능 평가를 위하여, 실시예 4 및 비교예 5에서 각각 제조된 리튬-황 전지에 대해서 충방전 실험을 실시하였다. 실험 조건은 0.6 mA·cm-2 충전/ 0.6 mA·cm-2 방전 3 사이클 후 1.2 mA·cm-2 충전/ 1.2 mA·cm-2 방전 3 사이클 후 1.8 mA·cm-2 충전/ 3 mA·cm-2 방전 조건으로 하였다.In addition, in order to evaluate the performance of the lithium-sulfur battery according to the content of thiol (-SH) contained in the additive of the electrolyte, charge and discharge experiments were performed on the lithium-sulfur batteries prepared in Examples 4 and 5, respectively. . The experimental conditions were 0.6 mAcm -2 charge / 0.6 mAcm -2 discharge / 3 mA discharge 1.2 mA cm -2 charge / 1.2 mA cm -2 discharge after 3 cycles 1.8 mA cm -2 charge / 3 mA cm- 2 discharge conditions.
도 3은 실시예 4 및 비교예 5에서 각각 제조된 리튬-황 전지에 대한 방전 용량 측정 실험 결과를 나타낸 것이다.Figure 3 shows the discharge capacity measurement test results for the lithium-sulfur battery prepared in Example 4 and Comparative Example 5, respectively.
도 3을 참조하면, 전해질의 첨가제로서 4arm-PEG5k-SH (분자량: 5,000)을 사용하며, 상기 첨가제에서 티올의 질량 비율이 3 wt%인 실시예 4는 첨가제를 포함하지 않아 티올의 함량이 0 중량%인 비교예 5에 비해 높은 방전 용량을 나타내는 것을 알 수 있다.Referring to FIG. 3, 4arm-PEG5k-SH (molecular weight: 5,000) is used as an additive of an electrolyte, and Example 4, in which the mass ratio of thiol is 3 wt% in the additive, does not include an additive and thus the content of thiol is 0. It can be seen that the discharge capacity is higher than that in Comparative Example 5, which is% by weight.
또한, 실시예 2에서 제조된 리튬 금속전지에 대해서 충방전 사이클 진행 후 리튬 금속 음극 표면을 관찰하여 비교하였다. 실험 조건은 1.3 mA·cm-2 충전/ 1.3 mA·cm-2 방전 조건, DOD는 83%으로 하여, 10 사이클 동안 충방전을 실시한 후, 코인셀을 분해하여 리튬 금속 음극의 표면을 관찰하였다.In addition, the lithium metal battery prepared in Example 2 was observed by comparing the surface of the lithium metal negative electrode after the charge and discharge cycle progress. The experimental conditions were 1.3 mA · cm −2 charge / 1.3 mA · cm −2 discharge conditions, and the DOD was 83%. After charging and discharging for 10 cycles, the coin cell was decomposed to observe the surface of the lithium metal negative electrode.
도 4는 실시예 2에서 제조된 리튬 금속전지를 충방전시킨 후 리튬 금속 음극 표면의 사진이다 (동일한 충방전 실험을 2회 실시 후 찍은 사진이다).Figure 4 is a photograph of the surface of the lithium metal negative electrode after charging and discharging the lithium metal battery prepared in Example 2 (photograph taken after performing the same charge and discharge experiment twice).
도 4를 참조하면, 리튬 금속전지를 10회 충방전 하고 난 후에도, 실시예 2의 리튬 금속 음극은 균일한 표면 형상을 나타내는 것을 확인할 수 있다. Referring to FIG. 4, even after charging and discharging the lithium metal battery 10 times, it can be confirmed that the lithium metal negative electrode of Example 2 exhibits a uniform surface shape.
실험예Experimental Example 2: 화학식 1에서 n의 수치를 달리하여 첨가제를 적용할 경우의 전지 성능실험 2: Battery performance test when the additive is applied by changing the value of n in Chemical Formula 1
전해질에 포함되는 첨가제인, 화학식 1에서 n의 수치에 따른 리튬-황 전지의 성능 평가를 위하여, 실시예 3 및 비교예 3에서 각각 제조된 리튬-황 전지에 대해서 충방전 실험을 실시하였다. 실험 조건은 0.6 mA·cm-2 충전/ 0.6 mA·cm-2 방전 2.5 사이클 후, 1.2 mA·cm-2 충전/ 1.2 mA·cm-2 방전 3 사이클 후, 1.8 mA·cm-2 충전/ 3.0 mA·cm-2 방전 조건으로 하였다.In order to evaluate the performance of the lithium-sulfur battery according to the value of n in Formula 1, which is an additive included in the electrolyte, charge and discharge experiments were performed on the lithium-sulfur batteries prepared in Example 3 and Comparative Example 3, respectively. Experimental conditions: 0.6 mAcm -2 charge / 0.6 mAcm -2 discharge 2.5 cycles, 1.2 mAcm -2 charge / 1.2 mAcm -2 discharge 3 cycles, 1.8 mAcm -2 charge / 3.0 cycles It was set as mA cm- 2 discharge conditions.
도 5는 실시예 3 및 비교예 3에서 각각 제조된 리튬-황 전지에 대한 충방전 사이클 진행에 따른 방전 용량 및 쿨롱 효율 측정 결과를 나타낸 것이다.FIG. 5 shows discharge capacity and coulombic efficiency measurement results of charging and discharging cycles of lithium-sulfur batteries prepared in Example 3 and Comparative Example 3, respectively.
도 5를 참조하면, 전해질 첨가제로서 mPEG-SH를 포함하는 실시예 3은 비교예 3에 비해 증가한 사이클 수명을 나타내는 것을 알 수 있다.Referring to FIG. 5, it can be seen that Example 3 including mPEG-SH as an electrolyte additive exhibits increased cycle life compared to Comparative Example 3.
이상에서 본 발명은 비록 한정된 실시예와 도면에 의해 설명되었으나, 본 발명은 이것에 의해 한정되지 않으며, 본 발명이 속하는 기술분야에서 통상의 지식을 가진 자에 의해 본 발명의 기술사상과 아래에 기재될 특허청구범위의 균등범위 내에서 다양한 수정 및 변형이 가능함은 물론이다.Although the present invention has been described above by means of limited embodiments and drawings, the present invention is not limited thereto. Various modifications and variations are possible without departing from the scope of the appended claims.

Claims (9)

  1. 리튬 이차전지용 전해질에 있어서,In the electrolyte for lithium secondary batteries,
    상기 전해질은 하기 화학식 1로 표시되는 첨가제를 포함하는, 리튬 이차전지용 전해질: The electrolyte includes a lithium secondary battery electrolyte, comprising an additive represented by the following formula (1):
    [화학식 1][Formula 1]
    X-(CH2-CH2-O)n-SHX- (CH 2 -CH 2 -O) n -SH
    상기 식에서, X는 메틸(methyl, CH3) 또는 티올(thiol, SH)이고, n은 5 내지 45 인 정수이다.Wherein X is methyl (methyl, CH 3 ) or thiol (SH) and n is an integer from 5 to 45.
  2. 제1항에 있어서,The method of claim 1,
    상기 화학식 1로 표시되는 첨가제의 함량은 상기 전해질의 전체 중량을 기준으로, 0 중량% 초과, 1.0 중량% 이하인 리튬 이차전지용 전해질.The content of the additive represented by Chemical Formula 1 is greater than 0 wt% and 1.0 wt% or less based on the total weight of the electrolyte.
  3. 제1항에 있어서,The method of claim 1,
    상기 화학식 1로 표시되는 첨가제에서 티올(-SH)의 함량은 1 내지 30 중량%인, 리튬 이차전지용 전해질.Thiol (-SH) content in the additive represented by the formula (1) is 1 to 30% by weight, the electrolyte for a lithium secondary battery.
  4. 제1항에 있어서,The method of claim 1,
    상기 화학식 1에서 -(CH2-CH2-O)n- 은 선형 또는 분지형인 리튬 이차전지용 전해질.In the general formula 1 - (CH 2 -CH 2 -O ) n - it is a linear or branched, a lithium secondary battery electrolyte.
  5. 제1항에 있어서,The method of claim 1,
    상기 전해질은 유기용매 및 리튬염을 더 포함하는 리튬 이차전지용 전해질.The electrolyte is a lithium secondary battery electrolyte further comprises an organic solvent and a lithium salt.
  6. 제5항에 있어서,The method of claim 5,
    상기 유기용매는 에테르계 용매, 에스테르계 용매, 아미드계 용매, 선형 카보네이트계 용매 및 환형 카보네이트계 용매로 이루어진 군에서 선택되는 1종 이상인 리튬 이차전지용 전해질. The organic solvent is at least one electrolyte selected from the group consisting of an ether solvent, an ester solvent, an amide solvent, a linear carbonate solvent and a cyclic carbonate solvent.
  7. 제5항에 있어서,The method of claim 5,
    상기 리튬염은 LiFSI, LiPF6, LiCl, LiBr, LiI, LiClO4, LiBF4, LiB10Cl10, LiPF6, LiCF3SO3, LiCF3CO2, LiAsF6, LiSbF6, LiPF6, LiAlCl4, CH3SO3Li, CF3SO3Li, (CF3SO2)2NLi, 클로로 보란 리튬 및 4-페닐 붕산 리튬으로 이루어진 군에서 선택되는 1종 이상인 리튬 이차전지용 전해질.The lithium salt is LiFSI, LiPF 6 , LiCl, LiBr, LiI, LiClO 4 , LiBF 4 , LiB 10 Cl 10 , LiPF 6 , LiCF 3 SO 3 , LiCF 3 CO 2 , LiAsF 6 , LiSbF 6 , LiPF 6 , LiAlCl 4 And at least one electrolyte selected from the group consisting of CH 3 SO 3 Li, CF 3 SO 3 Li, (CF 3 SO 2 ) 2 NLi, chloroborane lithium, and lithium 4-phenyl borate.
  8. 제1항 내지 제7항 중 어느 한 항의 전해질을 포함하는 리튬 이차전지.A lithium secondary battery comprising the electrolyte of any one of claims 1 to 7.
  9. 제8항에 있어서,The method of claim 8,
    상기 리튬 이차전지는 리튬 금속 음극을 포함하는 것인, 리튬 이차전지.The lithium secondary battery is a lithium secondary battery comprising a lithium metal negative electrode.
PCT/KR2019/005637 2018-05-14 2019-05-10 Electrolyte and lithium secondary battery comprising same WO2019221456A1 (en)

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