WO2015102202A1 - Non-aqueous electrolyte solution for lithium secondary battery, and lithium secondary battery comprising same - Google Patents

Non-aqueous electrolyte solution for lithium secondary battery, and lithium secondary battery comprising same Download PDF

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Publication number
WO2015102202A1
WO2015102202A1 PCT/KR2014/008084 KR2014008084W WO2015102202A1 WO 2015102202 A1 WO2015102202 A1 WO 2015102202A1 KR 2014008084 W KR2014008084 W KR 2014008084W WO 2015102202 A1 WO2015102202 A1 WO 2015102202A1
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lithium
secondary battery
lithium secondary
electrolyte
libf
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PCT/KR2014/008084
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French (fr)
Korean (ko)
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박민제
정기영
고주환
서진아
조정주
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삼성정밀화학 주식회사
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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
    • 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
    • H01M10/0568—Liquid materials characterised by the solutes
    • 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 a non-aqueous electrolyte for lithium secondary batteries and a lithium secondary battery comprising the same, and more particularly to a non-aqueous electrolyte for lithium secondary batteries and a lithium secondary battery comprising the same can improve the high temperature life characteristics and high temperature storage characteristics. .
  • lithium secondary batteries developed in the early 1990s are charge and discharge cycles as lithium ions are inserted and desorbed from the positive and negative electrodes, and can convert chemical energy into electrical energy through a redox reaction. have.
  • LiPF 6 and LiBF 4 are used as an electrolyte solvent
  • an electrolyte solution is prepared using lithium salts such as LiPF 6 and LiBF 4 as electrolyte salts.
  • LiPF 6 and LiBF 4 have advantages in obtaining high capacity and high voltage, but because they react very sensitively to moisture, they may react with moisture present in the battery manufacturing process or in the battery to form hydrofluoric acid.
  • LiPF 6 lithium salts are unstable at high temperatures, so that anions may be thermally decomposed to produce acidic materials such as hydrofluoric acid (HF). These acidic substances cause the following problems.
  • the SEI membrane in which the carbonate-based organic solvent reacts with lithium ions in the electrolyte and forms on the surface of the negative electrode during initial charging of the secondary battery prevents the electrolyte solvent having a large molecular weight from being co-calated on the negative electrode. It serves as a protective film to prevent destruction of the negative electrode structure, the contact of the electrolyte and the negative electrode is prevented by the SEI film can minimize the decomposition of the electrolyte and the reduction of the amount of reversible lithium.
  • gases such as CO, CO 2 , CH 4 , and C 2 H 6 may be generated, thereby degrading the high temperature life characteristics and the high temperature storage characteristics of the battery.
  • the solvent may be polymerized by the acidic material, thereby increasing the ionic resistance of the electrolyte.
  • the acidic substance may react with the positive electrode active material to elute the metal in the positive electrode active material.
  • Patent Document 1 Republic of Korea Patent Publication 10-2009-0042979
  • the present invention includes lithium difluorophosphate (LiPO 2 F 2 ) and lithium tetrafluoroborate (LiBF 4 ), the content of the lithium difluorophosphate (LiPO 2 F 2 ) is 0.2 to 3.0 compared to the total non-aqueous electrolyte By weight, the content of the lithium tetrafluoroborate (LiBF 4 ) is to provide a non-aqueous electrolyte for lithium secondary battery is 0.1 to 2.0% by weight relative to the total non-aqueous electrolyte. In addition, the present invention is to provide a lithium secondary battery with improved life characteristics and high temperature storage characteristics.
  • an aspect of the present invention may be an electrolyte solution for a lithium secondary battery including lithium difluorophosphate (LiPO 2 F 2 ) and lithium tetrafluoroborate (LiBF 4 ).
  • the electrolyte of this aspect may contain 0.2 to 3.0% by weight of lithium difluorophosphate (LiPO 2 F 2 ) relative to the total nonaqueous electrolyte, and 0.1 to 2.0% by weight of lithium tetrafluoroborate (LiBF 4) relative to the total nonaqueous electrolyte. ) May be contained.
  • LiPO 2 F 2 lithium difluorophosphate
  • LiBF 4 lithium tetrafluoroborate
  • Another aspect of the present invention may be a lithium secondary battery including the electrolyte of the front side.
  • lithium tetrafluoroborate (LiBF 4 ) and lithium tetrafluoroborate (LiBF 4 ) are added to a lithium secondary battery electrolyte to stabilize anion of lithium salt (LiPF 6 ), thereby decomposing LiPF 6 . Due to this, it is possible to suppress adverse reactions of acidic substances (HF, POF 3, etc.) generated, that is, side reactions such as electrolyte decomposition and elution of the positive electrode active material, and to increase resistance to improve high temperature life characteristics and high temperature storage characteristics of lithium secondary batteries. .
  • acidic substances HF, POF 3, etc.
  • One aspect of the present invention may be a non-aqueous solvent, a lithium salt, and an electrolyte for a lithium secondary battery including lithium difluorophosphate (LiPO 2 F 2 ) and lithium tetrafluoroborate (LiBF 4 ) as an additive.
  • LiPO 2 F 2 lithium difluorophosphate
  • LiBF 4 lithium tetrafluoroborate
  • nonaqueous solvent one or more selected from the group consisting of carbonate-based, ester-based, ether-based and ketone-based organic solvents can be used.
  • PC Propylene carbonate
  • EC ethylene carbonate
  • DEC diethyl carbonate
  • DMC dimethyl carbonate
  • DPC dipropyl carbonate
  • MPC methyl propyl carbonate
  • dimethyl sulfoxide aceto Nitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran
  • NMP N-methyl-2-pyrrolidone
  • EMC ethylmethyl carbonate
  • GBL gamma butyrolactone
  • VBL vanethylmethyl carbonate
  • FEC fluoroethylene carbonate
  • FEC fluoroethylene carbonate
  • FEC fluoroethylene carbonate
  • FEC fluoroethylene carbonate
  • FEC fluoroethylene carbonate
  • FEC fluoroethylene carbonate
  • FEC fluoro
  • the said materials can be used individually or in mixture of 2 or more types.
  • it can use combining a nonaqueous solvent as follows. (1) ethylene carbonate (EC), dimethyl carbonate (DMC) and diethyl carbonate (DEC), (2) ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC), (3) ethylene carbonate (EC), ethylmethyl carbonate (EMC) and diethyl carbonate (DEC) can be used in combination.
  • ethylene carbonate (EC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) can also be used in combination.
  • the electrolyte may contain LiPF 6 , which is a kind of lithium salt, and may further contain other lithium salts.
  • the lithium salt a material generally used in the lithium secondary battery field may be used. Specifically, LiSbF 6 , LiAsF 6 , LiClO 4 , LiCF 3 SO 3 , LiN (CF 3 SO 2 ) 2 , LiN (C 2 F 5 SO 2 ) 2 , LiAlO 4 , LiAlCl 4 , LiSO 3 CF 3 , LiN ( At least one selected from the group consisting of CF 3 SO 2 ) (C 4 F 9 SO 2 ) and LiC (CF 3 SO 2 ) 3 may be used.
  • concentration of the lithium salt in electrolyte solution is 0.8-2.0 M. If the concentration is less than 0.8 M, the lithium ion may have a low concentration, thereby degrading the performance of the battery. If the concentration is greater than 2 M, the electrolyte may have a large viscosity, and thus the ion conductivity in the battery may be reduced.
  • Lithium difluorophosphate (LiPO 2 F 2 ) and lithium tetrafluoroborate (LiBF 4 ) may be added to the electrolyte solution.
  • LiPO 2 F 2 Lithium difluorophosphate
  • LiBF 4 lithium tetrafluoroborate
  • the content of lithium difluorophosphate (LiPO 2 F 2 ) may be 0.2 to 3.0 wt% based on the total amount of the nonaqueous electrolyte. Preferably it may be 0.5 to 2.0% by weight, more preferably 0.5 to 1.0% by weight. When the content of lithium difluorophosphate (LiPO 2 F 2 ) is 0.2 to 3.0% by weight relative to the total non-aqueous electrolyte, the lithium secondary battery manufactured using the electrolyte may exhibit excellent high temperature life and high temperature storage characteristics.
  • lithium difluorophosphate LiPO 2 F 2
  • the effect of adding lithium difluorophosphate does not appear (improved high temperature life characteristics and high temperature storage characteristics)
  • the resistance may be increased to reduce the life characteristics of the battery.
  • the content of lithium tetrafluoroborate (LiBF 4 ) may be 0.1 to 2.0% by weight, preferably 0.1 to 1.0% by weight, and more preferably 0.1 to 0.5% by weight relative to the total nonaqueous electrolyte.
  • the content of lithium tetrafluoroborate (LiBF 4 ) is 0.1 to 2.0% by weight relative to the total nonaqueous electrolyte, the lithium secondary battery manufactured using the electrolyte may exhibit excellent high temperature life and high temperature storage characteristics.
  • the content of lithium tetrafluoroborate (LiBF 4 ) is less than 0.1 wt%, the above effect of addition of lithium tetrafluoroborate (LiBF 4 ) does not appear. Can be.
  • additives may be added to the electrolyte to improve the performance of the lithium secondary battery.
  • additives include overcharge inhibitors such as cyclohexylbenzene and biphenyl; Cathode film formers such as vinylene carbonate, vinyl ethylene carbonate, fluoroethylene carbonate and succinic anhydride; And ethylene sulfite, propylene sulfite, dimethyl sulfite, propanesultone, butanesultone, methyl methane sulfonate, methyl toluene sulfonate, dimethyl sulfate, ethylene sulfate, sulfolane, dimethyl sulfone, diethyl sulfone, dimethyl sulfoxide, diethyl sulfoxide, tetra
  • positive electrode protective agents such as methylene sulfoxide, diphenyl sulfide, thioanisole, diphenyl sulfide and dipy
  • Another aspect of the present invention may be a lithium secondary battery including the electrolyte of the front side. That is, the lithium secondary battery of the present aspect may include a positive electrode, a negative electrode, a separator, and an electrolyte in front of the lithium secondary battery.
  • the positive electrode and the negative electrode of the lithium secondary battery it can be manufactured using a generally known active material.
  • the active material, the binder, and the conductive agent may be mixed with a solvent to prepare a slurry, and the slurry may be applied to a current collector such as aluminum, followed by drying and pressing to prepare a positive electrode and a negative electrode.
  • a lithium composite oxide such as LiM x O 2 (M represents one or more transition metals by Co, Ni, Mn, Fe, Al, V, Ti, etc., and x is usually 0.05 or more and 1.10 or less) can be used.
  • M transition metal
  • Co, Ni and Mn are preferable.
  • LiCoO 2 , LiNiO 2 , LiNi y Co 1- y O 2 (0 ⁇ y ⁇ 1), LiMn 2 O 4 , or the like can be used.
  • Li x Fe 1-y M y PO 4 (M is at least one of Mn, Cr, V, Cu, Ni, V, Mo, Ti, Zn, Al, Ga, Mg, B and Nb as a cathode active material , x is 0.05 to 1.2, y is 0 to 0.8) may be used, specifically, LiFePO 4 may be used.
  • metal sulfides or metal oxides such as TiS 2 , MoS 2 , NbSe 2 , and V 2 O 5 may also be used as the positive electrode active material.
  • the negative electrode active material natural graphite, artificial graphite, carbon fiber, coke, carbon black, activated carbon, lithium metal or lithium alloy can be used.
  • the negative electrode active material, the binder, and the conductive agent may be mixed with a solvent to form a slurry, and then coated on the negative electrode current collector, followed by drying and pressing to prepare a negative electrode.
  • the binder binds the active material and the conductive agent to fix the current collector, and is a lithium secondary battery such as polyvinylidene fluoride, polypropylene, carboxymethyl cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, and polyvinyl alcohol. Those conventionally used in the battery can be used.
  • Examples of the conductive agent include artificial graphite, natural graphite, acetylene black, ketjen black, channel black, lamp black, thermal black, conductive fibers such as carbon fibers and metal fibers, conductive metal oxides such as titanium oxide, metal powders such as aluminum and nickel, and the like. This can be used.
  • the separator is a porous membrane existing between the anode and the cathode, which prevents electrical short between the two electrodes and functions as a passage for ion transfer.
  • Separators include single olefins or composites such as polyethylene (PE) and polypropylene (PP), polyamide (PA), polyacrylonitrile (PAN), polyethylene oxide (PEO), polypropylene oxide (PPO), polyethylene glycol di Acrylate (PEGA), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), polyvinyl chloride (PVC) and the like can be used.
  • Lithium secondary battery according to this aspect is excellent in high temperature life characteristics and high temperature storage characteristics because it uses an electrolyte containing lithium difluorophosphate (LiPO 2 F 2 ) and lithium tetrafluoroborate (LiBF 4 ) in a certain range. .
  • Ethylene carbonate (Ethylene Carbonate), ethyl methyl carbonate (EthylMethyl Carbonate) and dimethyl carbonate (DiMethyl Carbonate) were mixed in a volume ratio of 20:40:40 to prepare a non-aqueous solvent.
  • LiPF 6 was dissolved in a nonaqueous solvent with a lithium salt to prepare a nonaqueous electrolyte having a lithium salt concentration of 1.15M.
  • lithium difluorophosphate LiPO 2 F 2
  • lithium tetrafluoroborate LiBF 4
  • a pouch cell was prepared using 3O 2 , graphite as the cathode, a porous polyethylene membrane as the separator, and the nonaqueous electrolyte as the electrolyte.
  • An electrolyte solution was prepared according to the same method as Example 1 except that the contents of lithium difluorophosphate (LiPO 2 F 2 ) and lithium tetrafluoroborate (LiBF 4 ) were changed (see Table 1). A secondary battery pouch cell was produced.
  • LiPO 2 F 2 lithium difluorophosphate
  • LiBF 4 lithium tetrafluoroborate
  • the pouch cell was placed in a chamber maintained at 45 ° C., charged to 1C using a charge / discharger (Toyo-System Co., LTD, TOSCAT-3600), and then repeatedly discharged to 1C.
  • the cycle life at which the capacity was reduced to 80% of the initial capacity was measured to evaluate the high temperature life characteristics.
  • the pouch cell was placed in a chamber maintained at 25 ° C, and a charge / discharge test was performed as follows using a charge / discharger. First, the battery was charged to 50% of SOC (state of charge) at 0.5C and then discharged at 1C for 10 seconds. Then, it was charged for 20 seconds at 0.5C and then discharged at 2C for 10 seconds. Then, the battery was charged at 0.5C for 40 seconds and then discharged at 3C for 10 seconds. Finally, it charged to 4.2V at 0.5C. Using the voltage values after 1C, 2C, and 3C discharge, the slope of the trend line of the voltage-to-current graph was calculated to determine the initial impedance (DC-IR).
  • SOC state of charge
  • the battery was placed in a chamber maintained at 60 ° C. and left for 50 days, and then the battery was taken out and maintained at room temperature for 4 hours. Then, the charge and discharge test was performed as above and the impedance (DC-IR) was calculated. The results are shown in Table 1.
  • the content of LiPO 2 F 2 is 0.5 to 2.0% by weight and at the same time the content of LiBF 4 is 0.1 to 1.0% by weight is better, the content of LiPO 2 F 2 is 0.5 to 1.0% by weight and at the same time LiBF When the content of 4 is 0.1 to 0.5% by weight it can be seen that even more excellent.

Abstract

The present invention relates to a non-aqueous electrolyte solution for a lithium secondary battery having improved high-temperature lifespan properties and high-temperature storage properties, and to a lithium secondary battery comprising the electrolyte solution. The present invention is characterized by comprising lithium difluorophosphate (LiPO2F2) and lithium tetrafluoroborate (LiBF4). The present invention provides a lithium secondary battery having improved high-temperature lifespan properties and high-temperature storage properties.

Description

리튬 이차전지용 비수 전해액 및 이를 포함하는 리튬 이차전지Non-aqueous electrolyte solution for lithium secondary batteries and lithium secondary battery comprising same
본 발명은 리튬 이차전지용 비수 전해액 및 이를 포함하는 리튬 이차전지에 관한 것으로, 보다 상세하게는 고온 수명 특성 및 고온 저장 특성이 향상시킬 수 있는 리튬 이차전지용 비수 전해액 및 이를 포함하는 리튬 이차전지에 관한 것이다.The present invention relates to a non-aqueous electrolyte for lithium secondary batteries and a lithium secondary battery comprising the same, and more particularly to a non-aqueous electrolyte for lithium secondary batteries and a lithium secondary battery comprising the same can improve the high temperature life characteristics and high temperature storage characteristics. .
휴대폰, 캠코더 및 노트북 PC, 나아가 전기 자동차까지 적용 분야가 확대되면서 전기화학 소자의 연구와 개발에 대한 노력이 점점 구체화되고 있다. 현재 적용되고 있는 이차전지 중에서 1990년대 초에 개발된 리튬 이차전지는 양극 및 음극에서 리튬 이온이 삽입 및 탈리되면서 충방전이 반복되는 전지로서, 산화 환원 반응을 통해 화학적 에너지를 전기적 에너지로 전환시킬 수 있다.As the field of application extends to mobile phones, camcorders, notebook PCs, and even electric vehicles, efforts for research and development of electrochemical devices are becoming more concrete. Among the secondary batteries currently applied, lithium secondary batteries developed in the early 1990s are charge and discharge cycles as lithium ions are inserted and desorbed from the positive and negative electrodes, and can convert chemical energy into electrical energy through a redox reaction. have.
일반적으로 에틸렌카보네이트(Ethylene Carbonate), 디메틸카보네이트(DiMethylCarbonate) 등의 카보네이트계 유기용매를 전해액 용매로 사용하고, LiPF6, LiBF4등의 리튬염을 전해질염으로 하여 전해액을 제조한다. LiPF6, LiBF4등의 불소계 리튬염은 고용량 및 고전압을 얻는데 유리한 장점이 있으나, 수분에 매우 민감하게 반응하기 때문에 전지의 제조 과정 중 또는 전지 내에 존재하는 수분과 반응하여 불산을 형성할 수 있다. 또한, LiPF6 리튬염은 고온에서 불안정하므로 음이온이 열 분해되어 불산(HF)과 같은 산성 물질이 생성될 수 있다. 이러한 산성 물질로 인하여 다음과 같은 문제가 초래된다. Generally, carbonate-based organic solvents such as ethylene carbonate (Ethylene Carbonate) and dimethyl carbonate (DiMethylCarbonate) are used as an electrolyte solvent, and an electrolyte solution is prepared using lithium salts such as LiPF 6 and LiBF 4 as electrolyte salts. Fluorine-based lithium salts such as LiPF 6 and LiBF 4 have advantages in obtaining high capacity and high voltage, but because they react very sensitively to moisture, they may react with moisture present in the battery manufacturing process or in the battery to form hydrofluoric acid. In addition, LiPF 6 lithium salts are unstable at high temperatures, so that anions may be thermally decomposed to produce acidic materials such as hydrofluoric acid (HF). These acidic substances cause the following problems.
일반적으로 이차전지의 초기 충전시 상기 카보네이트계 유기용매가 전해액 내의 리튬 이온과 반응하여 음극 표면상에 형성하는 SEI막은, 리튬 이온만 통과시키고 분자량이 큰 전해질 용매가 음극에 코인터칼레이션 되는 것을 막아 음극 구조의 파괴를 방지하는 보호막으로서의 역할을 하고, SEI막에 의해 전해액과 음극과의 접촉이 방지되어 전해액의 분해 및 가역성 리튬 양의 감소를 최소화할 수 있다. 그러나, 이러한 SEI막은 전지 내 존재하는 산성 물질, 예를 들면 HX(X=F, Cl, Br, I)와 반응성이 강하여 쉽게 파괴될 수 있으며, 이로 인해 SEI막의 계속적인 재생성이 유도되어 전지의 용량이 저하될 수 있다. 또한, SEI막의 재생성 과정 중 카보네이트 유기용매의 분해로 인해 CO, CO2, CH4, C2H6 등의 기체가 발생함으로써, 전지의 고온 수명 특성 및 고온 저장 특성이 저하될 수 있다. 또한, 산성물질에 의하여 용매가 고분자화되어 전해액의 이온 저항이 증가될 수 있다. 또한, 산성 물질은 양극 활물질과 반응하여 양극 활물질 내 금속을 용출시킬 수도 있다. In general, the SEI membrane in which the carbonate-based organic solvent reacts with lithium ions in the electrolyte and forms on the surface of the negative electrode during initial charging of the secondary battery prevents the electrolyte solvent having a large molecular weight from being co-calated on the negative electrode. It serves as a protective film to prevent destruction of the negative electrode structure, the contact of the electrolyte and the negative electrode is prevented by the SEI film can minimize the decomposition of the electrolyte and the reduction of the amount of reversible lithium. However, this SEI film is highly reactive with acidic substances present in the battery, such as HX (X = F, Cl, Br, I), and can be easily destroyed, thereby inducing continuous regeneration of the SEI film, thereby causing the battery capacity. This can be degraded. In addition, due to decomposition of the carbonate organic solvent during the regeneration of the SEI film, gases such as CO, CO 2 , CH 4 , and C 2 H 6 may be generated, thereby degrading the high temperature life characteristics and the high temperature storage characteristics of the battery. In addition, the solvent may be polymerized by the acidic material, thereby increasing the ionic resistance of the electrolyte. In addition, the acidic substance may react with the positive electrode active material to elute the metal in the positive electrode active material.
리튬염의 음이온을 안정화시킴으로서 이러한 문제점을 해결하고자 하는 노력이 꾸준히 이루어지고 있다. Efforts have been made to solve these problems by stabilizing the anion of lithium salts.
[선행기술문헌][Preceding technical literature]
[특허문헌][Patent Documents]
(특허문헌 1) 대한민국공개특허공보 10-2009-0042979(Patent Document 1) Republic of Korea Patent Publication 10-2009-0042979
본 발명은 리튬디플루오로포스페이트(LiPO2F2) 및 리튬테트라플루오로보레이트(LiBF4)를 포함하고, 상기 리튬디플루오로포스페이트(LiPO2F2)의 함량은 비수 전해액 전체 대비 0.2 내지 3.0 중량%이고, 상기 리튬테트라플루오로보레이트(LiBF4)의 함량은 비수 전해액 전체 대비 0.1 내지 2.0 중량%인 리튬 이차전지용 비수 전해액을 제공하고자 한다. 또한, 본 발명은 수명 특성 및 고온 저장 특성이 향상된 리튬 이차전지를 제공하고자 한다. The present invention includes lithium difluorophosphate (LiPO 2 F 2 ) and lithium tetrafluoroborate (LiBF 4 ), the content of the lithium difluorophosphate (LiPO 2 F 2 ) is 0.2 to 3.0 compared to the total non-aqueous electrolyte By weight, the content of the lithium tetrafluoroborate (LiBF 4 ) is to provide a non-aqueous electrolyte for lithium secondary battery is 0.1 to 2.0% by weight relative to the total non-aqueous electrolyte. In addition, the present invention is to provide a lithium secondary battery with improved life characteristics and high temperature storage characteristics.
상기 과제를 해결하기 위한, 본 발명의 일 측면은 리튬디플루오로포스페이트(LiPO2F2) 및 리튬테트라플루오로보레이트(LiBF4)를 포함하는 리튬 이차전지용 전해액일 수 있다.In order to solve the above problems, an aspect of the present invention may be an electrolyte solution for a lithium secondary battery including lithium difluorophosphate (LiPO 2 F 2 ) and lithium tetrafluoroborate (LiBF 4 ).
본 측면의 전해액에는 비수 전해액 전체 대비 0.2 내지 3.0 중량%의 리튬디플루오로포스페이트(LiPO2F2) 가 함유될 수 있고, 비수 전해액 전체 대비 0.1 내지 2.0 중량%의 리튬테트라플루오로보레이트(LiBF4)가 함유될 수 있다.The electrolyte of this aspect may contain 0.2 to 3.0% by weight of lithium difluorophosphate (LiPO 2 F 2 ) relative to the total nonaqueous electrolyte, and 0.1 to 2.0% by weight of lithium tetrafluoroborate (LiBF 4) relative to the total nonaqueous electrolyte. ) May be contained.
본 발명의 다른 측면은 앞 측면의 전해액을 포함하는 리튬 이차전지일 수 있다.Another aspect of the present invention may be a lithium secondary battery including the electrolyte of the front side.
본 발명에 의하면,리튬 이차전지용 전해액에 리튬테트라플루오로보레이트(LiBF4) 및 리튬테트라플루오로보레이트(LiBF4)를 일정량 첨가하여 리튬염(LiPF6)의 음이온을 안정화시킴으로써, LiPF6의 분해로 인하여 생성되는 산성 물질(HF, POF3 등)의 폐해, 즉 전해액 분해 및 양극 활물질 금속 용출 등의 부반응을 억제하고, 저항 증가를 막아 리튬 이차전지의 고온 수명 특성 및 고온 저장 특성을 향상시킬 수 있다.According to the present invention, lithium tetrafluoroborate (LiBF 4 ) and lithium tetrafluoroborate (LiBF 4 ) are added to a lithium secondary battery electrolyte to stabilize anion of lithium salt (LiPF 6 ), thereby decomposing LiPF 6 . Due to this, it is possible to suppress adverse reactions of acidic substances (HF, POF 3, etc.) generated, that is, side reactions such as electrolyte decomposition and elution of the positive electrode active material, and to increase resistance to improve high temperature life characteristics and high temperature storage characteristics of lithium secondary batteries. .
이하, 본 발명의 바람직한 실시 형태들을 설명한다. 본 발명의 실시 형태는 여러 가지 다른 형태로 변형될 수 있으며, 본 발명의 범위가 이하 설명하는 실시 형태로 한정되는 것은 아니다.Hereinafter, preferred embodiments of the present invention will be described. Embodiment of the present invention can be modified in various other forms, the scope of the present invention is not limited to the embodiments described below.
본 발명의 일 측면은 비수 용매, 리튬염, 그리고 첨가제로서 리튬디플루오로포스페이트(LiPO2F2) 및 리튬테트라플루오로보레이트(LiBF4)를 포함하는 리튬 이차전지용 전해액일 수 있다. One aspect of the present invention may be a non-aqueous solvent, a lithium salt, and an electrolyte for a lithium secondary battery including lithium difluorophosphate (LiPO 2 F 2 ) and lithium tetrafluoroborate (LiBF 4 ) as an additive.
비수 용매로는 카보네이트계, 에스테르계, 에테르계 및 케톤계 유기 용매로 이루어지는 그룹에서 선택되는 1종 이상을 사용할 수 있다. 이에 제한되는 것은 아니나, 프로필렌카보네이트(PC), 에틸렌카보네이트(EC), 디에틸카보네이트(DEC), 디메틸카보네이트(DMC), 디프로필카보네이트(DPC), 메틸프로필카보네이트(MPC), 디메틸설폭사이드, 아세토니트릴, 디메톡시에탄, 디에톡시에탄, 테트라하이드로퓨란, N-메틸-2-피롤리돈(NMP), 에틸메틸카보네이트(EMC), 부티로락톤, 감마부티로락톤(GBL), 발레로락톤, 카프로락톤, 플루오르에틸렌카보네이트(FEC), 포름산메틸, 포름산에틸, 포름산프로필, 초산메틸, 초산에틸, 초산프로필, 초산펜틸, 프로피온산메틸, 프로피온산에틸, 프로피온산프로필, 프로피온산부틸 또는 이들의 할로겐 유도체 등을 사용할 수 있다.As the nonaqueous solvent, one or more selected from the group consisting of carbonate-based, ester-based, ether-based and ketone-based organic solvents can be used. Propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), dimethyl sulfoxide, aceto Nitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran, N-methyl-2-pyrrolidone (NMP), ethylmethyl carbonate (EMC), butyrolactone, gamma butyrolactone (GBL), valerolactone, Caprolactone, fluoroethylene carbonate (FEC), methyl formate, ethyl formate, propyl formate, methyl acetate, ethyl acetate, propyl acetate, pentyl acetate, methyl propionate, ethyl propionate, propyl propionate, butyl propionate or halogen derivatives thereof Can be.
상기 물질을 단독으로 또는 2종 이상을 혼합하여 사용할 수 있다. 예를 들면, 하기와 같이 비수 용매를 조합하여 사용할 수 있다. 즉, (1) 에틸렌카보네이트(EC), 디메틸카보네이트(DMC) 및디에틸카보네이트(DEC), (2) 에틸렌카보네이트 (EC), 디메틸카보네이트(DMC) 및에틸메틸카보네이트(EMC), (3) 에틸렌카보네이트 (EC), 에틸메틸카보네이트(EMC) 및디에틸카보네이트(DEC)를 조합하여 사용할 수 있다. 또한, (4) 에틸렌카보네이트(EC), 디메틸카보네이트(DMC), 에틸메틸카보네이트(EMC) 및 디에틸카보네이트(DEC)의 4종을 조합하여 사용할 수도 있다.The said materials can be used individually or in mixture of 2 or more types. For example, it can use combining a nonaqueous solvent as follows. (1) ethylene carbonate (EC), dimethyl carbonate (DMC) and diethyl carbonate (DEC), (2) ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC), (3) ethylene carbonate (EC), ethylmethyl carbonate (EMC) and diethyl carbonate (DEC) can be used in combination. Moreover, (4) four types of ethylene carbonate (EC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) can also be used in combination.
전해액에는 리튬염의 일종인 LiPF6가 함유될 수 있으며, 그 외 리튬염이 더 함유될 수 있다. 이러한 리튬염으로는 리튬 이차전지 분야에서 일반적으로 널리 사용되는 물질을 사용할 수 있다. 구체적으로는 LiSbF6, LiAsF6, LiClO4, LiCF3SO3, LiN(CF3SO2)2, LiN(C2F5SO2)2, LiAlO4, LiAlCl4, LiSO3CF3, LiN(CF3SO2)(C4F9SO2) 및LiC(CF3SO2)3 로 이루어진 그룹에서 선택되는 1종 이상을 사용할 수 있다. 무기 리튬염의 2 종을 병용하거나 무기 리튬염과 불소 함유 유기 리튬염을 병용하면, 충전시의 가스 발생을 억제하거나 고온 보존 후의 열화를 억제할 수 있다. 전해액 중 리튬염의 농도는 0.8 내지 2.0 M 인 것이 바람직하다. 0.8 M 미만이면 리튬 이온의 농도가 낮아 전지의 성능이 저하될 수 있고, 2 M 초과시에는 전해액의 점도가 커서 전지 내 이온전도도가 오히려 감소할 수 있다.The electrolyte may contain LiPF 6 , which is a kind of lithium salt, and may further contain other lithium salts. As the lithium salt, a material generally used in the lithium secondary battery field may be used. Specifically, LiSbF 6 , LiAsF 6 , LiClO 4 , LiCF 3 SO 3 , LiN (CF 3 SO 2 ) 2 , LiN (C 2 F 5 SO 2 ) 2 , LiAlO 4 , LiAlCl 4 , LiSO 3 CF 3 , LiN ( At least one selected from the group consisting of CF 3 SO 2 ) (C 4 F 9 SO 2 ) and LiC (CF 3 SO 2 ) 3 may be used. When two kinds of inorganic lithium salts are used in combination, or inorganic lithium salts and fluorine-containing organolithium salts are used together, gas generation during charging can be suppressed or deterioration after high temperature storage can be suppressed. It is preferable that the density | concentration of the lithium salt in electrolyte solution is 0.8-2.0 M. If the concentration is less than 0.8 M, the lithium ion may have a low concentration, thereby degrading the performance of the battery. If the concentration is greater than 2 M, the electrolyte may have a large viscosity, and thus the ion conductivity in the battery may be reduced.
전해액에는 첨가제로서 리튬디플루오로포스페이트(LiPO2F2) 및 리튬테트라플루오로보레이트(LiBF4)를 첨가할 수 있다. 상기 두 물질을 조합하여 첨가함으로써 리튬 염의 음이온을 안정화시킬 수 있고, 그 결과 리튬 이차전지의 고온 수명 특성 및 고온 저장 특성이 향상될 수 있다.Lithium difluorophosphate (LiPO 2 F 2 ) and lithium tetrafluoroborate (LiBF 4 ) may be added to the electrolyte solution. By adding the two materials in combination, the anion of the lithium salt may be stabilized, and as a result, the high temperature life characteristics and the high temperature storage characteristics of the lithium secondary battery may be improved.
리튬디플루오로포스페이트(LiPO2F2)의 함량은 비수 전해액 전체 대비 0.2 내지 3.0 중량%일 수 있다. 바람직하게는 0.5 내지 2.0 중량%일 수 있고, 더욱 바람직하게는 0.5 내지 1.0 중량%일 수 있다. 리튬디플루오로포스페이트(LiPO2F2)의 함량이 비수 전해액 전체 대비 0.2 내지 3.0 중량%인 경우에 상기 전해액을 이용하여 제조된 리튬 이차전지는 우수한 고온 수명 특성 및 고온 저장 특성을 발휘할 수 있다. 리튬디플루오로포스페이트(LiPO2F2)의 함량이 0.2 중량% 보다 적으면 리튬디플루오로포스페이트(LiPO2F2)를 첨가한 효과(고온 수명 특성 및 고온 저장 특성의 향상)가 나타나지 않고, 3.0 중량% 보다 많으면 저항이 상승하여 전지의 수명 특성이 저하될 수 있다.The content of lithium difluorophosphate (LiPO 2 F 2 ) may be 0.2 to 3.0 wt% based on the total amount of the nonaqueous electrolyte. Preferably it may be 0.5 to 2.0% by weight, more preferably 0.5 to 1.0% by weight. When the content of lithium difluorophosphate (LiPO 2 F 2 ) is 0.2 to 3.0% by weight relative to the total non-aqueous electrolyte, the lithium secondary battery manufactured using the electrolyte may exhibit excellent high temperature life and high temperature storage characteristics. When the content of lithium difluorophosphate (LiPO 2 F 2 ) is less than 0.2% by weight, the effect of adding lithium difluorophosphate (LiPO 2 F 2 ) does not appear (improved high temperature life characteristics and high temperature storage characteristics), When more than 3.0% by weight, the resistance may be increased to reduce the life characteristics of the battery.
리튬테트라플루오로보레이트(LiBF4)의 함량은 비수 전해액 전체 대비 0.1 내지 2.0 중량%일 수 있으며, 바람직하게는 0.1 내지 1.0 중량%일 수 있고, 더욱 바람직하게는 0.1 내지 0.5 중량%일 수 있다. 리튬테트라플루오로보레이트(LiBF4)의 함량이 비수 전해액 전체 대비 0.1 내지 2.0 중량%인 경우에 상기 전해액을 이용하여 제조된 리튬 이차전지는 우수한 고온 수명 특성 및 고온 저장 특성을 발휘할 수 있다. 리튬테트라플루오로보레이트(LiBF4)의 함량이 0.1 중량% 보다 적으면 리튬테트라플루오로보레이트(LiBF4)를 첨가한 상기 효과가 나타나지 않고, 2.0 중량% 보다 많으면 저항이 상승하여 전지의 수명이 저하될 수 있다. The content of lithium tetrafluoroborate (LiBF 4 ) may be 0.1 to 2.0% by weight, preferably 0.1 to 1.0% by weight, and more preferably 0.1 to 0.5% by weight relative to the total nonaqueous electrolyte. When the content of lithium tetrafluoroborate (LiBF 4 ) is 0.1 to 2.0% by weight relative to the total nonaqueous electrolyte, the lithium secondary battery manufactured using the electrolyte may exhibit excellent high temperature life and high temperature storage characteristics. When the content of lithium tetrafluoroborate (LiBF 4 ) is less than 0.1 wt%, the above effect of addition of lithium tetrafluoroborate (LiBF 4 ) does not appear. Can be.
전해액에는 기타 다른 첨가제를 더첨가하여 리튬 이차전지의 성능을 향상시킬 수 있다. 이러한 첨가제로는, 시클로헥실벤젠 및 비페닐과 같은 과충전 방지제; 비닐렌카보네이트, 비닐에틸렌카보네이트, 플루오로에틸렌카보네이트 및 숙신산무수물과 같은 음극막 형성제; 및 아황산에틸렌, 아황산프로필렌, 아황산디메틸, 프로판술톤, 부탄술톤, 메탄술폰산메틸, 톨루엔술폰산메틸, 황산디메틸, 황산에틸렌, 술포란, 디메틸술폰, 디에틸술폰, 디메틸술폭시드, 디에틸술폭시드, 테트라메틸렌술폭시드, 디페닐술피드, 티오아니솔, 디페닐술피드 및 디피리디늄디술피드와 같은 양극 보호제를 들 수 있다.Other additives may be added to the electrolyte to improve the performance of the lithium secondary battery. Such additives include overcharge inhibitors such as cyclohexylbenzene and biphenyl; Cathode film formers such as vinylene carbonate, vinyl ethylene carbonate, fluoroethylene carbonate and succinic anhydride; And ethylene sulfite, propylene sulfite, dimethyl sulfite, propanesultone, butanesultone, methyl methane sulfonate, methyl toluene sulfonate, dimethyl sulfate, ethylene sulfate, sulfolane, dimethyl sulfone, diethyl sulfone, dimethyl sulfoxide, diethyl sulfoxide, tetra And positive electrode protective agents such as methylene sulfoxide, diphenyl sulfide, thioanisole, diphenyl sulfide and dipyridinium disulfide.
본 발명의 다른 측면은, 앞 측면의 전해액을 포함하는 리튬 이차전지일 수 있다. 즉 본 측면의 리튬 이차전지는 양극, 음극, 분리막 및 앞의 전해질을 포함할 수 있다. Another aspect of the present invention may be a lithium secondary battery including the electrolyte of the front side. That is, the lithium secondary battery of the present aspect may include a positive electrode, a negative electrode, a separator, and an electrolyte in front of the lithium secondary battery.
리튬 이차전지의 양극 및 음극으로는 일반적으로 알려진 활물질을 사용하여 제조할 수 있다. 활물질과, 바인더, 및 도전제를 용매와 혼합하여 슬러리를 제조하고, 슬러리를 알루미늄 등의 집전체에 도포한 후 건조 및 압착하여 양극 및 음극을 제조할 수 있다.As the positive electrode and the negative electrode of the lithium secondary battery, it can be manufactured using a generally known active material. The active material, the binder, and the conductive agent may be mixed with a solvent to prepare a slurry, and the slurry may be applied to a current collector such as aluminum, followed by drying and pressing to prepare a positive electrode and a negative electrode.
양극활물질로는 LiMxO2(M은 Co, Ni, Mn, Fe, Al, V, Ti등에 의해 일종 이상의 전이금속을 나타내고, x는 통상 0.05이상 1.10이하)인 리튬 복합산화물 등을 사용할 수 있다. 전이금속(M)으로는 Co, Ni, Mn 이 바람직하다. 구체적으로는 LiCoO2, LiNiO2, LiNiyCo1 -yO2(0〈y〈1), LiMn2O4 등을 사용할 수 있다. 또한, 양극활물질로 LixFe1-yMyPO4(M은 Mn, Cr, V, Cu, Ni, V, Mo, Ti, Zn, Al, Ga, Mg, B 및 Nb중 1종 이상이고, x 는 0.05 내지 1.2,y는 0내지 0.8)를 사용할 수 있으며, 구체적 예로 LiFePO4 를 사용할 수 있다. 그 외에도 TiS2, MoS2, NbSe2, V2O5등의 금속유화물 혹은 금속 산화물도 양극활물질로 사용할 수도 있다.As the positive electrode active material, a lithium composite oxide such as LiM x O 2 (M represents one or more transition metals by Co, Ni, Mn, Fe, Al, V, Ti, etc., and x is usually 0.05 or more and 1.10 or less) can be used. . As the transition metal (M), Co, Ni and Mn are preferable. Specifically, LiCoO 2 , LiNiO 2 , LiNi y Co 1- y O 2 (0 <y <1), LiMn 2 O 4 , or the like can be used. In addition, Li x Fe 1-y M y PO 4 (M is at least one of Mn, Cr, V, Cu, Ni, V, Mo, Ti, Zn, Al, Ga, Mg, B and Nb as a cathode active material , x is 0.05 to 1.2, y is 0 to 0.8) may be used, specifically, LiFePO 4 may be used. In addition, metal sulfides or metal oxides such as TiS 2 , MoS 2 , NbSe 2 , and V 2 O 5 may also be used as the positive electrode active material.
음극활물질로는 천연 흑연, 인조 흑연, 탄소섬유, 코크스, 카본블랙, 활성탄, 리튬 금속이나 리튬 합금 등을 사용할 수 있다. 음극활물질, 바인더 및 도전제를 용매와 혼합하여 슬러리를 형성하고 이를 음극집전체에 도포한 후 건조 및 압착하여 음극을 제조할 수 있다.As the negative electrode active material, natural graphite, artificial graphite, carbon fiber, coke, carbon black, activated carbon, lithium metal or lithium alloy can be used. The negative electrode active material, the binder, and the conductive agent may be mixed with a solvent to form a slurry, and then coated on the negative electrode current collector, followed by drying and pressing to prepare a negative electrode.
바인더는 활물질과 도전제를 결착시켜서 집전체에 고정시키는 역할을 하며, 폴리비닐리덴플로라이드, 폴리프로필렌, 카르복시메틸셀룰로오스, 폴리비닐피롤리돈, 테트라플루오로에틸렌, 폴리에틸렌, 폴리비닐알코올 등 리튬 이차전지에서 통상적으로 사용되는 것들을 사용할 수 있다.The binder binds the active material and the conductive agent to fix the current collector, and is a lithium secondary battery such as polyvinylidene fluoride, polypropylene, carboxymethyl cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, and polyvinyl alcohol. Those conventionally used in the battery can be used.
도전제로는 인조 흑연, 천연 흑연, 아세틸렌 블랙, 케첸 블랙, 채널 블랙, 램프 블랙, 써멀 블랙, 탄소 섬유나 금속 섬유 등의 도전성 섬유, 산화 티탄 등의 도전성 금속산화물, 알루미늄, 니켈 등의 금속 분말 등이 사용될 수 있다.Examples of the conductive agent include artificial graphite, natural graphite, acetylene black, ketjen black, channel black, lamp black, thermal black, conductive fibers such as carbon fibers and metal fibers, conductive metal oxides such as titanium oxide, metal powders such as aluminum and nickel, and the like. This can be used.
분리막은 양극과 음극 사이에 존재하는 다공성 막으로 두 전극간 전기적 단락을 방지하고 이온 전달의 통로로서 기능한다. 분리막으로는 폴리에틸렌(PE)과 폴리프로필렌(PP)과 같은 단일 올레핀 또는 복합체, 폴리아미드(PA), 폴리아크릴로니트릴(PAN), 폴리에틸렌옥사이드(PEO), 폴리프로필렌옥사이드(PPO), 폴리에틸렌글리콜디아크릴레이트(PEGA), 폴리테트라플루오로에틸렌(PTFE), 폴리비닐리덴플루오라이드(PVdF), 폴리비닐클로라이드(PVC) 등을 사용할 수 있다.The separator is a porous membrane existing between the anode and the cathode, which prevents electrical short between the two electrodes and functions as a passage for ion transfer. Separators include single olefins or composites such as polyethylene (PE) and polypropylene (PP), polyamide (PA), polyacrylonitrile (PAN), polyethylene oxide (PEO), polypropylene oxide (PPO), polyethylene glycol di Acrylate (PEGA), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), polyvinyl chloride (PVC) and the like can be used.
본 측면에 따른 리튬 이차전지에는 리튬디플루오로포스페이트(LiPO2F2) 및 리튬테트라플루오로보레이트(LiBF4)를 일정 범위로 함유한 전해액을 사용하기 때문에 고온 수명 특성 및 고온 저장 특성이 우수하다.Lithium secondary battery according to this aspect is excellent in high temperature life characteristics and high temperature storage characteristics because it uses an electrolyte containing lithium difluorophosphate (LiPO 2 F 2 ) and lithium tetrafluoroborate (LiBF 4 ) in a certain range. .
이하 실시예 및 비교예를 통하여 본 발명에 대하여 상세하게 설명한다. 하지만 본 발명이 이에 한정되는 것은 아니다.Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples. However, the present invention is not limited thereto.
실시예Example 1 One
에틸렌카보네이트(Ethylene Carbonate), 에틸메틸카보네이트(EthylMethyl Carbonate) 및 디메틸카보네이트 (DiMethyl Carbonate)를 부피비로 20:40:40 으로혼합하여 비수 용매를 마련하였다. 다음으로, 비수 용매에 리튬염으로 LiPF6 을 용해하여 리튬염 농도가 1.15M 인 비수 전해액을 마련하였다. 다음으로, 비수 전해액에 리튬디플루오로포스페이트(LiPO2F2) 및 리튬테트라플루오로보레이트(LiBF4)를 첨가하였다. 리튬디플루오로포스페이트(LiPO2F2) 및 리튬테트라플루오로보레이트(LiBF4)의 함량은 각각 전체 전해액 대비 0.2중량% 및 0.1중량%로 하였다.Ethylene carbonate (Ethylene Carbonate), ethyl methyl carbonate (EthylMethyl Carbonate) and dimethyl carbonate (DiMethyl Carbonate) were mixed in a volume ratio of 20:40:40 to prepare a non-aqueous solvent. Next, LiPF 6 was dissolved in a nonaqueous solvent with a lithium salt to prepare a nonaqueous electrolyte having a lithium salt concentration of 1.15M. Next, lithium difluorophosphate (LiPO 2 F 2 ) and lithium tetrafluoroborate (LiBF 4 ) were added to the nonaqueous electrolyte. The contents of lithium difluorophosphate (LiPO 2 F 2 ) and lithium tetrafluoroborate (LiBF 4 ) were 0.2 wt% and 0.1 wt%, respectively, based on the total electrolyte.
양극으로는 LiNi0.5Co0.2Mn0.3O2을, 음극으로는 그래파이트를, 분리막으로는 다공성 폴리에틸렌막을, 전해액으로는 상기 비수 전해액을 사용하여 파우치 셀을 제작하였다.LiNi 0 as the anode. 5 Co 0 . 2 Mn 0 . A pouch cell was prepared using 3O 2 , graphite as the cathode, a porous polyethylene membrane as the separator, and the nonaqueous electrolyte as the electrolyte.
실시예Example 2 ~20 및  2 to 20 and 비교예Comparative example 1~23 1-23
리튬디플루오로포스페이트(LiPO2F2) 및 리튬테트라플루오로보레이트(LiBF4)의 함량을 다르게 한 점(표 1 참조)을 제외하고는, 실시예 1과 동일한 방법에 따라 전해액을 마련하고 리튬 이차전지파우치셀을 제작하였다.An electrolyte solution was prepared according to the same method as Example 1 except that the contents of lithium difluorophosphate (LiPO 2 F 2 ) and lithium tetrafluoroborate (LiBF 4 ) were changed (see Table 1). A secondary battery pouch cell was produced.
평가evaluation
고온 수명 특성High temperature life characteristics
45℃로 유지되는 챔버 내에 파우치셀을 배치하고, 충방전기(Toyo-System Co., LTD, TOSCAT-3600)를 이용하여 1C로 충전한 후, 1C로 방전시키는 과정을 반복 실시하였다. 용량이 초기 용량의 80%로 감소되는 싸이클 회수를 측정하여 고온 수명 특성을 평가하였다.The pouch cell was placed in a chamber maintained at 45 ° C., charged to 1C using a charge / discharger (Toyo-System Co., LTD, TOSCAT-3600), and then repeatedly discharged to 1C. The cycle life at which the capacity was reduced to 80% of the initial capacity was measured to evaluate the high temperature life characteristics.
고온 저장 특성High temperature storage characteristics
25℃로 유지되는 챔버 내에 파우치 셀을 배치하고, 충방전기를 이용하여 다음과 같이 충방전시험을 하였다. 먼저, 0.5C로 SOC(state of charge)의 50%까지 충전한 후 1C로 10초 동안 방전시켰다. 그 다음, 0.5C로 20초 동안 충전한 후 2C로 10초간 방전시켰다. 그 다음, 0.5C로 40초간 충전한 후 3C로 10초간 방전시켰다. 마지막으로, 0.5C로 4.2V까지 충전하였다. 1C, 2C, 3C 방전 후의 전압값을 이용하여 전압 대 전류 그래프의 추세선의 기울기를 계산하여 초기 임피던스(DC-IR)를 구했다.The pouch cell was placed in a chamber maintained at 25 ° C, and a charge / discharge test was performed as follows using a charge / discharger. First, the battery was charged to 50% of SOC (state of charge) at 0.5C and then discharged at 1C for 10 seconds. Then, it was charged for 20 seconds at 0.5C and then discharged at 2C for 10 seconds. Then, the battery was charged at 0.5C for 40 seconds and then discharged at 3C for 10 seconds. Finally, it charged to 4.2V at 0.5C. Using the voltage values after 1C, 2C, and 3C discharge, the slope of the trend line of the voltage-to-current graph was calculated to determine the initial impedance (DC-IR).
초기 임피던스를 측정한 상기 전지를, 60℃로 유지되는 챔버 내에 넣고 50일 동안 방치한 후에 전지를 꺼내어 4시간 동안 상온에서 유지하였다. 그 다음, 위와 마찬가지로 충방전 시험을 실시하고 임피던스(DC-IR)를 계산하였다. 그 결과를 표 1에 나타내었다.After the initial impedance was measured, the battery was placed in a chamber maintained at 60 ° C. and left for 50 days, and then the battery was taken out and maintained at room temperature for 4 hours. Then, the charge and discharge test was performed as above and the impedance (DC-IR) was calculated. The results are shown in Table 1.
표 1
첨가제 함량 고온 수명 특성 고온 저장 특성
LiPO2F2(중량%) LiBF4 (중량%) 초기용량(mAh) 45 싸이클 시험에서 초기용량의 80%가 되는 싸이클(회) 초기임피던스(mΩ) 60에서 50일 저장한 후 측정한 임피던스(mΩ)
비교예 1 0.0 0.0 347 125 155 438
비교예 2 0.1 0.0 351 138 151 420
비교예 3 0.1 0.1 352 126 155 405
비교예 4 0.1 0.5 347 133 149 380
비교예 5 0.1 1.0 347 135 148 386
비교예 6 0.1 2.0 352 137 153 393
비교예 7 0.1 2.5 346 131 147 405
비교예 8 0.2 0.0 349 128 153 403
실시예 1 0.2 0.1 349 206 147 321
실시예 2 0.2 0.5 351 228 151 310
실시예 3 0.2 1.0 350 201 151 337
실시예 4 0.2 2.0 346 198 151 348
비교예 9 0.2 2.5 351 138 149 387
비교예 10 0.5 0.0 347 134 154 392
실시예 5 0.5 0.1 350 377 148 210
실시예 6 0.5 0.5 346 350 147 199
실시예 7 0.5 1.0 347 312 152 272
실시예 8 0.5 2.0 351 217 151 351
비교예 11 0.5 2.5 350 131 150 392
비교예 12 1.0 0.0 352 134 153 411
실시예 9 1.0 0.1 351 359 148 219
실시예 10 1.0 0.5 348 365 152 204
실시예 11 1.0 1.0 347 290 154 259
실시예 12 1.0 2.0 349 170 149 339
비교예 13 1.0 2.5 349 98 147 407
비교예 14 2.0 0.0 352 125 154 439
실시예 13 2.0 0.1 348 300 153 249
실시예 14 2.0 0.5 349 317 153 252
실시예 15 2.0 1.0 349 292 151 268
실시예 16 2.0 2.0 352 170 147 329
비교예 15 2.0 2.5 347 80 148 428
비교예 16 3.0 0.0 346 139 150 405
실시예 17 3.0 0.1 346 163 155 322
실시예 18 3.0 0.5 352 183 151 331
실시예 19 3.0 1.0 349 160 147 319
실시예 20 3.0 2.0 351 174 154 324
비교예 17 3.0 2.5 347 108 151 431
비교예 18 3.5 0.0 347 92 147 395
비교예 19 3.5 0.1 352 81 147 421
비교예 20 3.5 0.5 349 93 149 415
비교예 21 3.5 1.0 349 83 155 400
비교예 22 3.5 2.0 347 88 151 412
비교예 23 3.5 2.5 350 107 148 401
Table 1
Additive content High temperature life characteristics High temperature storage characteristics
LiPO 2 F 2 (% by weight) LiBF 4 (% by weight) Initial capacity (mAh) 45 cycles equivalent to 80% of initial capacity Initial Impedance (mΩ) Impedance measured after 60 to 50 days (mΩ)
Comparative Example 1 0.0 0.0 347 125 155 438
Comparative Example 2 0.1 0.0 351 138 151 420
Comparative Example 3 0.1 0.1 352 126 155 405
Comparative Example 4 0.1 0.5 347 133 149 380
Comparative Example 5 0.1 1.0 347 135 148 386
Comparative Example 6 0.1 2.0 352 137 153 393
Comparative Example 7 0.1 2.5 346 131 147 405
Comparative Example 8 0.2 0.0 349 128 153 403
Example 1 0.2 0.1 349 206 147 321
Example 2 0.2 0.5 351 228 151 310
Example 3 0.2 1.0 350 201 151 337
Example 4 0.2 2.0 346 198 151 348
Comparative Example 9 0.2 2.5 351 138 149 387
Comparative Example 10 0.5 0.0 347 134 154 392
Example 5 0.5 0.1 350 377 148 210
Example 6 0.5 0.5 346 350 147 199
Example 7 0.5 1.0 347 312 152 272
Example 8 0.5 2.0 351 217 151 351
Comparative Example 11 0.5 2.5 350 131 150 392
Comparative Example 12 1.0 0.0 352 134 153 411
Example 9 1.0 0.1 351 359 148 219
Example 10 1.0 0.5 348 365 152 204
Example 11 1.0 1.0 347 290 154 259
Example 12 1.0 2.0 349 170 149 339
Comparative Example 13 1.0 2.5 349 98 147 407
Comparative Example 14 2.0 0.0 352 125 154 439
Example 13 2.0 0.1 348 300 153 249
Example 14 2.0 0.5 349 317 153 252
Example 15 2.0 1.0 349 292 151 268
Example 16 2.0 2.0 352 170 147 329
Comparative Example 15 2.0 2.5 347 80 148 428
Comparative Example 16 3.0 0.0 346 139 150 405
Example 17 3.0 0.1 346 163 155 322
Example 18 3.0 0.5 352 183 151 331
Example 19 3.0 1.0 349 160 147 319
Example 20 3.0 2.0 351 174 154 324
Comparative Example 17 3.0 2.5 347 108 151 431
Comparative Example 18 3.5 0.0 347 92 147 395
Comparative Example 19 3.5 0.1 352 81 147 421
Comparative Example 20 3.5 0.5 349 93 149 415
Comparative Example 21 3.5 1.0 349 83 155 400
Comparative Example 22 3.5 2.0 347 88 151 412
Comparative Example 23 3.5 2.5 350 107 148 401
표 1을 참조하여 고온 수명 특성 및 고온 저장 특성을 살펴보면, LiPO2F2의 함량이 0.2~3.0 중량% 이고, 동시에 LiBF4의 함량이 0.1~2.0 중량%인 경우 고온 수명 특성 및 고온 저장 특성이 우수함을 확인할 수 있다.Looking at the high temperature life characteristics and high temperature storage characteristics with reference to Table 1, when the content of LiPO 2 F 2 is 0.2 to 3.0% by weight, and the content of LiBF 4 is 0.1 to 2.0% by weight, the high temperature life characteristics and high temperature storage characteristics are It can be confirmed that excellent.
또한, LiPO2F2의 함량이 0.5~2.0 중량% 이고, 동시에 LiBF4의 함량이 0.1~1.0 중량% 인 경우에는 더 우수하고, LiPO2F2의 함량이 0.5~1.0 중량% 이고, 동시에 LiBF4의 함량이 0.1~0.5 중량% 인 경우에는 더욱 더 우수함을 확인할 수 있다. In addition, the content of LiPO 2 F 2 is 0.5 to 2.0% by weight and at the same time the content of LiBF 4 is 0.1 to 1.0% by weight is better, the content of LiPO 2 F 2 is 0.5 to 1.0% by weight and at the same time LiBF When the content of 4 is 0.1 to 0.5% by weight it can be seen that even more excellent.
본 발명에서 사용한 용어는 특정한 실시예를 설명하기 위한 것으로, 본 발명을 한정하고자 하는 것이 아니다. 단수의 표현은 문맥상 명백하지 않는 한, 복수의 의미를 포함한다고 보아야 할 것이다. "포함하다" 또는 "가지다" 등의 용어는 명세서 상에 기재된 특징, 숫자, 단계, 동작, 구성 요소 또는 이들을 조합한 것이 존재한다는 것을 의미하는 것이지, 이를 배제하기 위한 것이 아니다. 본 발명은 상술한 실시 형태에 의해 한정되는 것이 아니며, 첨부된 청구범위에 의해 한정하고자 한다. 따라서, 청구범위에 기재된 본 발명의 기술적 사상을 벗어나지 않는 범위 내에서 당 기술 분야의 통상의 지식을 가진 자에 의해 다양한 형태의 치환, 변형 및 변경이 가능할 것이며, 이 또한 본 발명의 범위에 속한다고 할 것이다.The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. Singular expressions should be considered to include plural meanings unless the context clearly dictates them. Terms such as "include" or "have" mean that there is a feature, number, step, operation, component, or combination thereof described on the specification, but not intended to exclude it. The present invention is not limited by the above-described embodiment, but is intended to be limited by the appended claims. Accordingly, various forms of substitution, modification, and alteration may be made by those skilled in the art without departing from the technical spirit of the present invention described in the claims, which are also within the scope of the present invention. something to do.

Claims (2)

  1. 리튬디플루오로포스페이트(LiPO2F2) 및 리튬테트라플루오로보레이트(LiBF4)를 포함하고, 상기 리튬디플루오로포스페이트(LiPO2F2)의 함량은 비수 전해액 전체 대비 0.2 내지 3.0 중량%이고, 상기 리튬테트라플루오로보레이트(LiBF4)의 함량은 비수 전해액 전체 대비 0.1 내지 2.0 중량%인 리튬 이차전지용 비수 전해액.Lithium difluoro phosphate (LiPO 2 F 2 ) and lithium tetrafluoroborate (LiBF 4 ), and the content of the lithium difluoro phosphate (LiPO 2 F 2 ) is 0.2 to 3.0% by weight relative to the total non-aqueous electrolyte , The content of the lithium tetrafluoroborate (LiBF 4 ) is 0.1 to 2.0% by weight compared to the total non-aqueous electrolyte non-aqueous electrolyte for lithium secondary battery.
  2. 제1항에 따른 비수 전해액을 포함하는 리튬 이차전지.Lithium secondary battery comprising a nonaqueous electrolyte according to claim 1.
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