WO2017164625A2 - Non-aqueous electrolyte additive, non-aqueous electrolyte containing same for lithium secondary battery, and lithium secondary battery - Google Patents

Abstract

The present invention relates to a non-aqueous electrolyte additive, a non-aqueous electrolyte containing the same for a lithium secondary battery, and a lithium secondary battery. Specifically, the present invention relates to a non-aqueous electrolyte additive having a nitrile group and a propargyl group, to a non-aqueous electrolyte for a lithium secondary battery, the non-aqueous electrolyte being capable of improving high-temperature capacity characteristics and cycle life characteristics by containing the non-aqueous electrolyte additive, and to a lithium secondary battery.

Description

Non-aqueous electrolyte additive, Non-aqueous electrolyte and lithium secondary battery for lithium secondary battery comprising the same

Cross Citation with Related Application (s)

This application is filed with Korean Patent Application No. 10-2016-0034809 filed March 23, 2016, Korean Patent Application No. 10-2016-0049963 filed April 25, 2016, and Korean Patent Application No. 10-2017 dated March 20, 2017. Claiming the benefit of priority based on -0034826, all contents disclosed in the literature of the relevant Korean patent application are incorporated as part of this specification.

Technical Field

The present invention relates to a non-aqueous electrolyte additive, a non-aqueous electrolyte and a lithium secondary battery for a lithium secondary battery comprising the same, a non-aqueous electrolyte additive that can improve the capacity characteristics and cycle life characteristics at high temperature storage, a non-aqueous electrolyte for lithium secondary batteries comprising the same and It relates to a lithium secondary battery.

As electronic devices become smaller, lighter, thinner, and portable in accordance with the development of the information and communication industry, the demand for high energy density of batteries used as power sources for such electronic devices is increasing.

Lithium batteries, specifically lithium ion batteries (LIBs), are batteries that can best meet these needs, and have been adopted as power sources for many portable devices due to their high energy density and easy design.

Recently, as the range of use of lithium secondary batteries has been expanded from small electronic devices to large electronic devices, automobiles, and smart grids, lithium secondary batteries are required to maintain excellent performance not only at room temperature but also in more severe external environments such as high or low temperature environments. have.

The lithium ion secondary battery is composed of a carbon material negative electrode capable of storing and releasing lithium ions, a positive electrode made of a lithium-containing transition metal oxide and a non-aqueous electrolyte, and lithium ions derived from the positive electrode active material by the first charge are negative electrode active materials, such as Charge and discharge are possible because it plays a role of transferring energy while reciprocating both electrodes such as being inserted into the carbon particles and detached again during discharge.

However, as the charge and discharge proceeds, the cathode active material is structurally collapsed, resulting in a decrease in the performance of the anode. In addition, when the anode structure collapses, metal ions eluted from the surface of the anode deteriorate the cathode while electro-deposition to the cathode. Such deterioration of battery performance tends to be accelerated when the potential of the positive electrode is increased or when the battery is exposed to high temperature.

Therefore, the situation is required to develop a new configuration of the positive electrode, the electrolyte or the like that can solve this problem.

Prior art literature

Korean Patent Registration Publication No. 10-1278692

Korean Patent Publication No. 10-2014-0127741

In order to solve the above problems, a first object of the present invention is to provide a nonaqueous electrolyte additive excellent in the adsorption effect on the metal ions eluted from the anode.

Another object of the present invention is to provide a nonaqueous electrolyte solution for a lithium secondary battery including the nonaqueous electrolyte additive.

Another object of the present invention is to provide a lithium secondary battery having improved overall performance by including the nonaqueous electrolyte for lithium secondary batteries.

In order to achieve the above object, in one embodiment of the present invention

There is provided a non-aqueous electrolyte additive comprising at least one compound selected from the group consisting of compounds represented by formulas (I) and (II):

[Formula 1]

In Chemical Formula I,

R ₁ is a linear or nonlinear alkylene group having 1 to 5 carbon atoms unsubstituted or substituted with at least one nitrile group, or an aromatic group having 6 to 8 carbon atoms unsubstituted or substituted with at least one nitrile group,

R ₂ is a linear or nonlinear alkylene group having 1 to 5 carbon atoms unsubstituted or substituted with at least one nitrile group, an aromatic group having 6 to 8 carbon atoms unsubstituted or substituted with at least one nitrile group, or substituted or unsubstituted with at least one nitrile group A substituted heteroaromatic group having 6 to 8 carbon atoms, a linear or nonlinear alkenyl group having 2 to 5 carbon atoms, or -C (O) -R _9- , wherein R ₉ is substituted or substituted with at least one nitrile group and having 1 to 1 carbon atoms 3 is a linear or nonlinear alkylene group,

R ₃ is when m = 0 it is a linear or nonlinear alkyl group having 1 to 5 carbon atoms unsubstituted or substituted with hydrogen or at least one nitrile group, when m = 1 is a linear or nonlinear alkylene group having 1 to 5 carbon atoms,

R ₄ is an alkylene group having 1 to 3 carbon atoms or -R ₁₀ -C (O)-, R ₁₀ is an alkylene group having 1 to 3 carbon atoms,

n and m are each independently an integer of 0 or 1.

[Formula II]

In Chemical Formula II,

R ₅ is a linear or nonlinear alkyl group having 1 to 5 carbon atoms unsubstituted or substituted with hydrogen or at least one nitrile group,

R ₆ to R ₈ are each independently a linear or nonlinear alkylene group having 1 to 5 carbon atoms.

In addition, in one embodiment of the present invention

Ionizable lithium salts; Organic solvents; And it provides a non-aqueous electrolyte for lithium secondary battery comprising the non-aqueous electrolyte additive of the present invention.

The nonaqueous electrolyte additive may be included in an amount of 0.5 wt% to 5 wt%, specifically 1 wt% to 5 wt%, based on the total amount of the nonaqueous electrolyte.

In addition, in one embodiment of the present invention

Provided is a negative electrode, a positive electrode, a separator interposed between the negative electrode and the positive electrode, and a lithium secondary battery having a nonaqueous electrolyte of the present invention.

According to an embodiment of the present invention, the metal ions eluted from the anode during charge and discharge and a non-aqueous electrolyte additive capable of forming a complex with the metal foreign matters mixed in the manufacturing process, thereby preventing the metal ions from being deposited on the surface of the cathode It is possible to produce a nonaqueous electrolytic solution which can suppress and form a more stable ionic conductive film on the cathode and anode surfaces. Furthermore, by including the nonaqueous electrolyte, a lithium secondary battery having improved overall performance such as capacity characteristics and cycle life characteristics at high temperature storage may be manufactured.

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

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 explain their invention in the best way possible. 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.

Among the electrochemical devices, lithium secondary battery forms a passivation film by electrochemical oxidative decomposition reaction of electrolyte at the surface of the battery's positive electrode, especially in the presence of surface bond or activation position. Increase impedance to co-intercalation. In addition, as lithium ions are excessively released from the positive electrode during overcharging or high temperature storage, structural disintegration of the positive electrode active material or a chemical dissolution reaction occurs by the electrolyte solution, and ions such as Co, Mn, and Ni are eluted from the positive electrode active material. These reactions lead to deterioration of the performance of the positive electrode itself, and also cause side reactions of the electrolyte as well as collapse of the negative electrode structure, thereby degrading overall performance of the secondary battery.

In the present invention, by including at least one nitrile group and propargyl group having a metal ion adsorption performance in the structure, to provide a non-aqueous electrolyte additive that can suppress the generation of metal ions in the battery.

In addition, the present invention provides a nonaqueous electrolyte solution for a lithium secondary battery in which side reactions are reduced by including the nonaqueous electrolyte additive.

In addition, the present invention includes a non-aqueous electrolyte solution for a lithium secondary battery, thereby providing a lithium secondary battery having improved overall performance of a battery, such as capacity characteristics and cycle life characteristics at high temperature storage.

Specifically, in one embodiment of the present invention

It provides a non-aqueous electrolyte additive comprising at least one compound selected from the group consisting of compounds represented by the following formula (I) and formula (II).

[Formula 1]

In Chemical Formula I,

R ₁ is a linear or nonlinear alkylene group having 1 to 5 carbon atoms unsubstituted or substituted with at least one nitrile group, or an aromatic group having 6 to 8 carbon atoms unsubstituted or substituted with at least one nitrile group,

R ₂ is a linear or nonlinear alkylene group having 1 to 5 carbon atoms unsubstituted or substituted with at least one nitrile group, an aromatic group having 6 to 8 carbon atoms unsubstituted or substituted with at least one nitrile group, or substituted or unsubstituted with at least one nitrile group A substituted heteroaromatic group having 6 to 8 carbon atoms, a linear or nonlinear alkenyl group having 2 to 5 carbon atoms, or -C (O) -R _9- , wherein R ₉ is substituted or substituted with at least one nitrile group and having 1 to 1 carbon atoms 3 is a linear or nonlinear alkylene group,

R ₃ is when m = 0 it is a linear or nonlinear alkyl group having 1 to 5 carbon atoms unsubstituted or substituted with hydrogen or at least one nitrile group, when m = 1 is a linear or nonlinear alkylene group having 1 to 5 carbon atoms,

R ₄ is an alkylene group having 1 to 3 carbon atoms or -R ₁₀ -C (O)-, R ₁₀ is an alkylene group having 1 to 3 carbon atoms,

n and m are each independently an integer of 0 or 1.

[Formula II]

In Chemical Formula II,

R ₅ is a linear or nonlinear alkyl group having 1 to 5 carbon atoms unsubstituted or substituted with hydrogen or at least one nitrile group,

R ₆ to R ₈ are each independently a linear or nonlinear alkylene group having 1 to 5 carbon atoms.

Specific examples of the compound represented by Formula I include at least one compound selected from the group consisting of compounds represented by Formulas I-1 to I-39.

Formula I-1

Formula I-2

Formula I-3

Formula I-4

Formula I-5

Formula I-6

Formula I-7

Formula I-8

Formula I-9

Formula I-10

Formula I-11

Formula I-12

Formula I-13

Formula I-14

Formula I-15

Formula I-16

Formula I-17

Formula I-18

Formula I-19

Formula I-20

Formula I-21

Formula I-22

Formula I-23

Formula I-24

Formula I-25

Formula I-26

Formula I-27

Formula I-28

Formula I-29

Formula I-30

Formula I-31

Formula I-32

Formula I-33

Formula I-34

Formula I-35

Formula I-36

Formula I-37

Formula I-38

Formula I-39

In addition, the compound represented by Chemical Formula II may include at least one compound selected from the group consisting of compounds represented by the following Chemical Formulas II-1 to II-4.

Formula II-1

Formula II-2

Formula II-3

Formula II-4

The polar nitrile group (ie cyano group) having a high dipole moment contained in the compounds represented by the above formulas I or II is Co, Mn eluted from the positive electrode by the chemical dissolution reaction of the electrolyte in the charge and discharge repeating process of the battery The tendency to adsorb metal ions such as, or Ni, or to adsorb metallic foreign substances mixed in raw materials or manufacturing processes is very high. Furthermore, the nitrile group, in addition to the adsorption of metal ions, the non-covalent electrons of N stabilize the anion of the salt, thereby inhibiting HF generation due to salt decomposition, and form a complex structure or ligand by forming a stronger bond with the surface of the anode, especially at high temperature, A stable ion conductive film can be formed on the surface of the anode. Therefore, not only a part of the transition metal is eluted and deposited on the cathode during high temperature storage, but also a safe film is formed on the surface of the anode to suppress various side reactions and gas generation between the electrolyte and the anode, thereby swelling the battery. The ring can be prevented to further improve high temperature storage characteristics such as remaining capacity and recovery capacity during high temperature storage.

In addition, the triple bond propazyl group contained in the compounds represented by the formula (I) or (II) is known to have a metal ion adsorption performance, and further complexes with other metal foreign substances that do not form a complex with the nitrile group. can do. Furthermore, since the propazyl group can be reduced on the surface of the negative electrode to form a stable ion conductive film on the negative electrode surface, smooth storage and release of lithium ions from the negative electrode even during high temperature storage can improve the life characteristics of the secondary battery. have.

On the other hand, one end of the triple bond is represented by the formulas (I-24), (I-37 to I-39) in which long functional groups are symmetrically bonded to both sides of the triple bond as compared to compounds containing hydrogen or short substituents. In the case of the compounds, the resulting polymerized film is relatively thick and the resistance is large, so that the cycle capacity retention ratio is relatively slightly decreased, whereas the adsorption effect with the metal foreign material is better, so that the voltage after high temperature storage may be relatively high. .

As described above, in the present invention, at least one or more of the compounds represented by the formula (I) or (II) having two functional groups such as nitrile group and propazyl group is used as a non-aqueous electrolyte additive, thereby eluting from the positive electrode during charge and discharge. The formation of complexes with metal ions and / or metal foreign matters incorporated in the manufacturing process can suppress the electrodeposition of metal ions on the surface of the cathode, and can form a more stable ion conductive film on the electrode surface, resulting in high temperature storage. It is possible to manufacture a secondary battery having improved performance such as time capacity characteristics and cycle life characteristics.

In addition, in one embodiment of the present invention

Ionizable lithium salts; Organic solvents; And

It provides a nonaqueous electrolyte for a lithium secondary battery comprising the nonaqueous electrolyte additive.

The nonaqueous electrolyte additive may be included in an amount of about 0.5 wt% to 5 wt%, specifically 1 wt% to 5 wt%, based on the total weight of the nonaqueous electrolyte. If the content of the additive is less than 0.5% by weight, the effect of inhibiting dissolution of the metal ions described below and the improvement of capacity characteristics at high temperature storage may be insignificant. If the content of the additive is more than 5% by weight, the side reaction of the surplus nonaqueous electrolyte additive Due to the decrease in the capacity of the battery, the increase in the viscosity of the electrolyte, thereby increasing the resistance and the decrease in the ionic conductivity may cause a decrease in overall performance of the secondary battery.

In one embodiment, the lithium salt contained in the non-aqueous electrolyte of the present invention may be used without limitation those conventionally used in the lithium secondary battery electrolyte, for example, the lithium salt includes Li ⁺ as a cation, anion include ^{F -, Cl -, Br -} , I -, NO 3 -, N (CN) 2 -, BF 4 -, ClO 4 -, AlO 4 -, AlCl 4 -, PF 6 -, SbF 6 -, AsF _{^{6 -, BF 2 C 2 O}} 4 -, BC 4 O 8 -, (CF 3) 2 PF 4 -, (CF 3) 3 PF 3 -, (CF 3) 4 PF 2 -, (CF 3) 5 PF _{^{-, (CF 3) 6 P}} -, CF 3 SO 3 -, C 4 F 9 SO 3 -, CF 3 CF 2 SO 3 -, (CF 3 SO 2) 2 N -, (F 2 SO 2) 2 N _{^{-, CF 3 CF 2 (CF}} 3) 2 CO -, (CF 3 SO 2) 2 CH -, CF 3 (CF 2) 7 SO 3 -, CF 3 CO 2 -, CH 3 CO 2 -, SCN - and (CF ₃ CF ₂ SO ₂ ) ₂ N ⁻ It may include at least one selected from the group consisting of. The said lithium salt can also be used 1 type or in mixture of 2 or more types as needed. The lithium salt may be appropriately changed within a range generally available, but may be included in an electrolyte solution at a concentration of 0.8 M to 1.5 M in order to obtain an effect of forming an anti-corrosion coating on the surface of the electrode.

In addition, the organic solvent included in the nonaqueous electrolyte of the present invention can be used without limitation those conventionally used in the electrolyte for lithium secondary batteries, for example, ether compounds, ester compounds, amide compounds, linear carbonate compounds, or cyclic carbonate compounds Etc. can be used individually or in mixture of 2 or more types, respectively. Representatively, it may include a cyclic carbonate compound, a linear carbonate compound, or a mixture thereof.

Among them, carbonate compounds which are typically cyclic carbonates, linear carbonates, or mixtures thereof may be included. 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 and fluoroethylene carbonate (FEC) are any one selected from the group consisting of or mixtures of two or more thereof. In addition, specific examples of the linear carbonate compound include dimethyl carbonate (dimethyl carbonate, DMC), diethyl carbonate (diethyl carbonate, DEC), dipropyl carbonate, ethyl methyl carbonate (EMC), methylpropyl carbonate and ethylpropyl carbonate Any one selected from, or a mixture of two or more thereof may be representatively used, but is not limited thereto.

In particular, ethylene carbonate and propylene carbonate, which are cyclic carbonates among the carbonate-based organic solvents, are highly viscous organic solvents, and thus may be preferably used because they dissociate lithium salts in the electrolyte well. When the same low viscosity, low dielectric constant linear carbonate is mixed and used in an appropriate ratio, an electrolyte having high electrical conductivity can be made, and thus it can be used more preferably.

In addition, the ether in the organic solvent may be any one selected from the group consisting of dimethyl ether, diethyl ether, dipropyl ether, methyl ethyl ether, methyl propyl ether and ethyl propyl ether, or a mixture of two or more thereof. It is not limited to this.

And esters in the organic solvent include linear esters such as methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, butyl propionate; And cyclic esters such as γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone, or ε-caprolactone, or mixtures of two or more thereof. It may be, but is not limited thereto.

The nonaqueous electrolyte of the present invention may further include an additive for forming an SEI film, if necessary. As the additive for forming SEI film which can be used in the present invention, vinylene carbonate, vinyl ethylene carbonate, fluoroethylene carbonate, vinyl ethylene carbonate, cyclic sulfite, saturated sultone, unsaturated sultone, acyclic sulfone, etc. may be used alone or in combination. It can mix and use the above.

At this time, the cyclic sulfites include ethylene sulfite, methyl ethylene sulfite, ethyl ethylene sulfite, 4,5-dimethyl ethylene sulfite, 4,5-diethyl ethylene sulfite, propylene sulfite, 4,5-dimethyl Propylene sulfite, 4,5-diethyl propylene sulfite, 4,6-dimethyl propylene sulfite, 4,6-diethyl propylene sulfite, 1,3-butylene glycol sulfite, and the like. Examples thereof include 1,3-propane sultone and 1,4-butane sultone. Examples of unsaturated sultone include ethene sultone, 1,3-propene sultone, 1,4-butene sultone, 1-methyl-1,3 -Propene sulfone, and the like, and acyclic sulfones include divinyl sulfone, dimethyl sulfone, diethyl sulfone, methylethyl sulfone, and methyl vinyl sulfone.

In addition, in one embodiment of the present invention,

In the secondary battery comprising a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode and a non-aqueous electrolyte, it provides a lithium secondary battery comprising the non-aqueous electrolyte of the present invention as the non-aqueous electrolyte.

Specifically, the lithium secondary battery of the present invention may be prepared by injecting the nonaqueous electrolyte of the present invention into an electrode structure consisting of a cathode, a cathode, and a separator interposed between the cathode and the anode. At this time, the positive electrode, the negative electrode, and the separator constituting the electrode structure may be used all those conventionally used in the manufacture of a lithium secondary battery.

In this case, the positive electrode may be manufactured by forming a positive electrode mixture layer on the positive electrode current collector.

The cathode mixture layer may be formed by coating a cathode slurry including a cathode active material, a binder, a conductive material, a solvent, and the like, followed by drying and rolling.

The positive electrode current collector is not particularly limited as long as it has conductivity without causing chemical changes in the battery. For example, the positive electrode current collector may be formed of stainless steel, aluminum, nickel, titanium, calcined carbon, or carbon on the surface of aluminum or stainless steel. Surface treated with nickel, titanium, silver, or the like may be used.

The positive electrode active material is a compound capable of reversible intercalation and deintercalation of lithium, and may specifically include a lithium composite metal oxide containing lithium and one or more metals such as cobalt, manganese, nickel or aluminum. have. More specifically, the lithium composite metal oxide may be lithium-manganese oxides (eg, LiMnO ₂ , LiMn ₂ O _4, etc.), lithium-cobalt oxides (eg, LiCoO _2, etc.), lithium-nickel oxides, and the like. (for example, LiNiO ₂ and the like), lithium-nickel-manganese-based oxide (for example, LiNi _1-Y Mn _Y O ₂ (where, 0 <Y <1), LiMn _2-z Ni _z O ₄ ( here, 0 <Z <2) and the like), lithium-nickel-cobalt oxide (e.g., LiNi _1-Y1 Co _Y1 O ₂ (here, 0 <Y1 <1) and the like), lithium-manganese-cobalt oxide (e. g., LiCo _1-Y2 Mn _Y2 O ₂ (here, 0 <Y2 <1), LiMn 2 - z1 Co z1 O 4 ( here, 0 <z1 <2) and the like), lithium-nickel Manganese-cobalt-based oxides (e.g., Li (Ni _p Co _q Mn _r1 ) O ₂ , where 0 <p <1, 0 <q <1, 0 <r1 <1, p + q + r1 = 1) or Li (Ni _p1 Co _q1 Mn _r2 ) O ₄ (where 0 <p1 <2, 0 <q1 <2, 0 <r2 <2, p1 + q1 + r21 = 2, etc.), or lithium- nickel-cobalt-transition metal (M) oxide (e.g., Li (Ni Co _{p2 q2} Mn _r3 M _S2) O ₂ (W Where M is selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg and Mo, and p2, q2, r3 and s2 are atomic fractions of the independent elements, respectively, 0 <p2 <1, 0 <Q2 <1, 0 <r3 <1, 0 <s2 <1, p2 + q2 + r3 + s2 = 1), etc.), and any one or two or more of these compounds may be included. Among the lithium composite metal oxides, LiCoO ₂ , LiMnO ₂ , LiNiO ₂ , and lithium nickel manganese cobalt oxides (eg, Li (Ni _0.6 Mn _0.2 Co _0.2 ) O ₂ may be improved in capacity and stability of the battery. , Li (Ni _0.5 Mn _0.3 Co _0.2) O ₂ or _{Li (Ni 0.8 Mn 0.1 Co 0.1} ) O 2 ), or lithium nickel cobalt aluminum oxide (for _{example, LiNi 0. 8 Co 0.} 15 Al 0. 05 O _2, etc.), and the lithium composite metal oxide is Li (Ni _0.6 Mn _0.2 Co _0.2 ) O ₂ in consideration of the remarkable improvement effect according to the type and content ratio control of the element forming the lithium composite metal oxide. , Li (Ni _0.5 Mn _0.3 Co _0.2 ) O ₂ , Li (Ni _0.7 Mn _0.15 Co _0.15 ) O _2, or Li (Ni _0.8 Mn _0.1 Co _0.1 ) O ₂ , and the like, and any one or a mixture of two or more thereof may be used. have.

The cathode active material may be included in an amount of 80 wt% to 99 wt% based on the total weight of the cathode slurry.

The conductive material is typically added at 1 to 30% by weight based on the total weight of the positive electrode slurry.

Such a conductive material is not particularly limited as long as it has conductivity without causing chemical change in the battery, and examples thereof include graphite; Carbon-based materials such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black; Conductive fibers such as carbon fibers and metal fibers; Metal powders such as carbon fluoride powder, aluminum powder and nickel powder; Conductive whiskeys such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives and the like can be used. Specific examples of commercially available conductive materials include Chevron Chemical Company, Denka Singapore Private Limited, Gulf Oil Company, Ketjenblack, and EC, which are acetylene black series. (Armak Company), Vulcan XC-72 (manufactured by Cabot Company), and Super P (manufactured by Timcal).

The binder is a component that assists in bonding the active material and the conductive material and bonding to the current collector, and is generally added in an amount of 1 to 30 wt% based on the total weight of the positive electrode slurry. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoro Low ethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, fluorine rubber, various copolymers, and the like.

The solvent may include an organic solvent such as N-methyl-2-pyrrolidone (NMP), and may be used in an amount that becomes a desirable viscosity when including the positive electrode active material and optionally a binder and a conductive material. For example, the concentration of the solids in the positive electrode active material and, optionally, the slurry including the binder and the conductive material may be 50 wt% to 95 wt%, preferably 70 wt% to 90 wt%.

In addition, the negative electrode may be prepared by forming a negative electrode mixture layer on the negative electrode current collector.

The negative electrode mixture layer may be formed by coating a slurry including a negative electrode active material, a binder, a conductive material, a solvent, and the like, followed by drying and rolling.

The negative electrode current collector generally has a thickness of 3 to 500 μm. Such a negative electrode current collector 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, calcined carbon, copper or stainless steel Surface-treated with carbon, nickel, titanium, silver, and the like on the surface, aluminum-cadmium alloy and the like can be used. In addition, like the positive electrode current collector, fine concavities and convexities may be formed on the surface to enhance the bonding strength of the negative electrode active material, and may be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric.

As the negative electrode active material, natural graphite, artificial graphite, carbonaceous material; Metals (Me) that are lithium-containing titanium composite oxide (LTO), Si, Sn, Li, Zn, Mg, Cd, Ce, Ni, or Fe; Alloys composed of the metals (Me); Oxides of the above metals; And one or two or more negative electrode active materials selected from the group consisting of the above metals and a composite of carbon.

The negative active material may be included in an amount of 80 wt% to 99 wt% based on the total weight of the negative electrode slurry.

The binder is a component that assists the bonding between the conductive material, the active material and the current collector, and is typically added in an amount of 1 to 30 wt% based on the total weight of the negative electrode slurry. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluor Low ethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, fluorine rubber, various copolymers thereof, and the like.

The conductive material is a component for further improving the conductivity of the negative electrode active material, and may be added in an amount of 1 to 20 wt% based on the total weight of the negative electrode slurry. Such a conductive material is not particularly limited as long as it has conductivity without causing chemical change in the battery, and examples thereof include graphite such as natural graphite and artificial graphite; Carbon blacks such as acetylene black, Ketjen black, channel black, furnace black, lamp black and thermal black; Conductive fibers such as carbon fibers and metal fibers; Metal powders such as carbon fluoride powder, aluminum powder and nickel powder; Conductive whiskeys such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives and the like can be used.

The solvent may include an organic solvent such as water or NMP, alcohol, etc., and may be used in an amount that becomes a desirable viscosity when including the negative electrode active material and optionally a binder and a conductive material. For example, the concentration of the solids in the slurry including the negative electrode active material, and optionally the binder and the conductive material may be 50% to 95% by weight, preferably 70% to 90% by weight.

In addition, as the separator, conventional porous polymer films conventionally used as separators, for example, polyolefins such as ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer and ethylene / methacrylate copolymer, etc. The porous polymer film made of the polymer may be used alone or by laminating them, or a conventional porous nonwoven fabric, for example, a non-woven fabric made of high melting point glass fiber, polyethylene terephthalate fiber, or the like may be used. It is not.

The external shape of the lithium secondary battery of the present invention is not particularly limited, but may be cylindrical, square, pouch type, or coin type using a can.

Hereinafter, the present invention will be described in detail with reference to Examples. However, embodiments according to the present invention can be modified in many different forms, the scope of the present invention should not be construed as limited to the embodiments described below. The embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art.

Example

Example 1

(Non-aqueous electrolyte preparation)

After dissolving 1M LiPF ₆ in a mixed organic solvent of ethylene carbonate (EC), propylene carbonate (PC) and ethylene carbonate (EMC) (20:10:70 vol%), the following formula (I-1) Was added to prepare a non-aqueous electrolyte.

(Anode manufacturing)

Lithium cobalt composite oxide (LiCO ₂ ) as a positive electrode active material particle, carbon black as a conductive material, and polyvinylidene fluoride (PVDF) as a binder in a ratio of 90: 5: 5 (wt%) as a solvent N-methyl-2- A positive active material slurry was prepared by adding pyrrolidone (NMP) in a ratio of 100: 40 parts by weight. The positive electrode active material slurry was applied to a positive electrode current collector (Al thin film) having a thickness of 100 μm, dried, and roll pressed to prepare a positive electrode.

 (Cathode production)

Natural graphite as a negative electrode active material, PVDF as a binder and carbon black as a conductive material were added to NMP as a solvent at a ratio of 100: 100 parts by weight to prepare a negative electrode active material slurry. The negative electrode active material slurry was applied to a negative electrode current collector (Cu thin film) having a thickness of 90 μm, dried, and roll pressed to prepare a negative electrode.

(Secondary Battery Manufacturing)

The positive electrode and the negative electrode prepared by the above-described method were laminated together with a polyethylene porous film to prepare an electrode assembly. Then, the prepared nonaqueous electrolyte was poured into the battery case, and the lithium secondary battery was prepared by sealing.

Examples 2 to 28

In the preparation of the non-aqueous electrolyte of Example 1, except that each of the additives in the amount shown in Table 1, the same method as in Example 1 to the non-aqueous electrolyte of Examples 2 to 28 and a secondary battery comprising the same Were prepared respectively.

Example 29

(Non-aqueous electrolyte preparation)

After dissolving 1M LiPF ₆ in a mixed organic solvent of ethylene carbonate (EC), propylene carbonate (PC) and ethylene carbonate (EMC) (20:10:70 vol%), the following formula (I-1) was used. Was added to prepare a non-aqueous electrolyte.

(Anode manufacturing)

Lithium cobalt composite oxide (LiCO ₂ ) as a positive electrode active material particle, carbon black as a conductive material, and polyvinylidene fluoride (PVDF) as a binder in a ratio of 90: 5: 5 (wt%) as a solvent N-methyl-2- A positive active material slurry was prepared by adding pyrrolidone (NMP) in a ratio of 100: 40 parts by weight. The positive electrode active material slurry was applied to a positive electrode current collector (Al thin film) having a thickness of 100 μm, dried, and roll pressed to prepare a positive electrode.

(Secondary Battery Manufacturing)

The prepared positive electrode was punched out for a coin-type battery, and then fixed with three Fe powders having an average particle diameter (D50) of about 200 μm on the surface of the positive electrode, and then the non-aqueous electrolyte was injected to prepare a coin-type half battery.

Examples 30-56

In the preparation of the non-aqueous electrolyte of Example 29, except that each of the additives in the amounts shown in Table 2, the same method as in Example 29, the non-aqueous electrolyte of Examples 30 to 56 and a secondary battery comprising the same Were prepared respectively.

Comparative Example 1

A nonaqueous electrolyte and a secondary battery including the same were prepared in the same manner as in Example 1, except that no additive was included in the preparation of the nonaqueous electrolyte of Example 1.

Comparative Example 2

As shown in Table 1, the non-aqueous electrolyte was prepared in the same manner as in Example 1, except that 0.3 g of the compound of Formula a was included instead of the compound of Formula I-1 when preparing the non-aqueous electrolyte of Example 1. And a secondary battery comprising the same was prepared.

[Formula a]

Comparative Example 3

As shown in Table 1 below, except for containing 0.5 g of the compound of Formula a when preparing the non-aqueous electrolyte of Comparative Example 2, the non-aqueous electrolyte and a secondary battery comprising the same in the same manner as in Comparative Example 2 Prepared.

Comparative Example 4

As shown in Table 1, except for including the compound of Formula a 7g when preparing the non-aqueous electrolyte of Comparative Example 2, a non-aqueous electrolyte and a secondary battery comprising the same in the same manner as in Comparative Example 2 It was.

Comparative Example 5

As shown in Table 1 below, except that 0.5g of the compound of Formula b was included in the preparation of the nonaqueous electrolyte of Comparative Example 2, a nonaqueous electrolyte and a secondary battery including the same were prepared in the same manner as in Comparative Example 2. It was.

 [Formula b]

Comparative Example 6

As shown in Table 1 below, except that 0.3g of the compound of Chemical Formula c is included in the preparation of the nonaqueous electrolyte solution of Comparative Example 2, the nonaqueous electrolyte solution and the secondary battery including the same in the same manner as in Comparative Example 2 Prepared.

[Formula c]

Comparative Example 7

As shown in Table 1 below, except that 0.5 g of the compound of Formula c was included in the preparation of the non-aqueous electrolyte of Comparative Example 2, the non-aqueous electrolyte and the secondary battery comprising the same in the same manner as in Comparative Example 2 Prepared.

Comparative Example 8

As shown in Table 1 below, except for including the compound of Formula c 7g when preparing the non-aqueous electrolyte of Comparative Example 2, a non-aqueous electrolyte and a secondary battery comprising the same by the same method as in Comparative Example 2 It was.

Comparative Example 9

As shown in Table 1 below, except that 0.5g of the compound of the formula d is included in the preparation of the non-aqueous electrolyte of Comparative Example 2, the non-aqueous electrolyte and the secondary battery including the same in the same manner as in Comparative Example 2 Prepared.

[Formula d]

Comparative Example 10

A nonaqueous electrolyte and a coin-type half-cell including the same were prepared in the same manner as in Example 29, except that no additive was included in the preparation of the nonaqueous electrolyte of Example 29.

Comparative Example 11

As shown in Table 1, the non-aqueous electrolyte and coin-type halves containing the same in the same manner as in Comparative Example 10, except that 0.3g of the compound of Formula a was included in the preparation of the non-aqueous electrolyte of Comparative Example 10 A secondary battery was prepared.

Comparative Example 12

As shown in Table 1 below, except that 0.5g of the compound of Formula a was included in the preparation of the nonaqueous electrolyte of Comparative Example 10, the non-aqueous electrolyte and the coin-type half containing the same in the same manner as in Comparative Example 10 A secondary battery was prepared.

Comparative Example 13

As shown in Table 1 below, except that the compound 7g of Formula a was included in the preparation of the non-aqueous electrolyte of Comparative Example 10, the non-aqueous electrolyte and the coin-type half-cell including the same in the same manner as in Comparative Example 10 Was prepared.

Comparative Example 14

As shown in Table 1 below, except that 0.5g of the compound of Formula b was included in the preparation of the nonaqueous electrolyte of Comparative Example 10, the nonaqueous electrolyte and the coin-type halves including the same in the same manner as in Comparative Example 10 A secondary battery was prepared.

Comparative Example 15

As shown in Table 1 below, except that 0.3g of the compound of Chemical Formula c was included in the preparation of the nonaqueous electrolyte of Comparative Example 10, the nonaqueous electrolyte and the coin-type halves including the same in the same manner as in Comparative Example 10 A secondary battery was prepared.

Comparative Example 16

As shown in Table 1 below, except that 0.5g of the compound of Formula c was included in the preparation of the non-aqueous electrolyte of Comparative Example 10, the non-aqueous electrolyte and the secondary battery including the same in the same manner as in Comparative Example 10 Prepared.

Comparative Example 17

As shown in Table 1, except for including the compound 7g of Formula c, a non-aqueous electrolyte and a secondary battery comprising the same was prepared in the same manner as in Comparative Example 10.

Comparative Example 18

As shown in Table 1, except for containing 0.5 g of the compound of Formula d, a non-aqueous electrolyte and a secondary battery comprising the same was prepared in the same manner as in Comparative Example 10.

Experimental Example

Experimental Example 1.

Each of the secondary batteries prepared in Examples 1 to 28 and Comparative Examples 1 to 9 was subjected to constant current / constant voltage condition charging and 0.05C cut off charging to 4.35V at 0.8C rate, and discharged to 0.5C 3.0V (initial) Discharge capacity). Then, constant current / constant voltage condition charging and 0.05C cut off charging were performed up to 4.35V at 0.8C rate and stored at 60 ° C. for 2 weeks. Thereafter, the battery was discharged at 0.5C 3.0V at room temperature, and the discharge amount thereof was measured (remaining discharge amount). The discharge amount was measured again by charging the constant current / constant voltage condition up to 0.8C rate, 4.35V, 0.05C cut off charging, and 0.5C 3.0V (recovery discharge amount).

The remaining discharge amount and the recovery discharge amount are expressed in% relative to the initial discharge amount, and are shown in Table 1 below.

Experimental Example 2.

Each of the secondary batteries prepared in Examples 1 to 28 and Comparative Examples 1 to 9 was subjected to constant current / constant voltage condition charging and 0.05C cut off charging to 0.85C at 4.35V, and discharged at 0.5C to 3.0V. Then, the cycle capacity retention after 200 cycles was performed by performing constant current / constant voltage condition charging and 0.05C cut-off charging up to 4.35V at 0.8C rate, and discharging at 0.5C 3.0V at room temperature as one cycle. It is shown in Table 1, expressed as a percentage of one cycle capacity.

As shown in Table 1, in the case of the secondary batteries of Examples 1 to 28 having a non-aqueous electrolyte solution containing a compound containing a nitrile group and a propazyl group of the present invention as an additive, the amount of residual discharge at high temperature storage was about It can be seen that the recovery discharge amount is 80% or more, about 92% or more, and the cycle capacity retention rate is about 87% or more.

On the other hand, the secondary battery of Comparative Example 1, which does not use an additive, has a residual discharge amount of about 64%, a recovery discharge amount of about 80%, and a cycle capacity retention rate of about 60% at high temperature storage. It can be seen that the degradation compared to the secondary battery of 28 to.

In addition, the residual discharge amount at the high temperature storage of the secondary batteries of Comparative Examples 2 to 9 including the compound of Formulas a to d as an additive as a non-aqueous electrolyte additive is 80% or less, recovery discharge amount is 87% or less, and the capacity retention ratio is 70 It can be confirmed that all of the secondary batteries of Examples 1 to 28 are lowered to less than or equal to%.

Experimental Example 3.

Each coin-type secondary battery manufactured in Examples 29 to 56 and Comparative Examples 10 to 18 was subjected to constant current / constant voltage condition charging and 0.05C cut off charging to 4.35V at 0.8C rate, and discharged to 0.5C 3.0V. It was. Each battery is made of five batteries, and the number of batteries capable of charging and discharging is shown in Table 2 below.

In addition, the battery capable of charging and discharging was charged under constant current / constant voltage conditions up to 4.35 V at 0.8 C rate and stored at 45 ° C. for 6 days. The voltage at 45 ° C. after storage was measured and the results are shown in Table 2 below.

As shown in Table 2, the secondary batteries of Examples 29 to 56, since the compounds containing the nitrile group and the propazyl group included as additives form a complex with Fe foreign material to suppress metal elution, most of the batteries It can be seen that charging and discharging are possible and the voltage is maintained at about 4.01V or higher even after high temperature storage.

On the other hand, the secondary battery of Comparative Example 10 that does not use an additive is mostly not charged and discharged, it can be seen that the voltage is reduced to 2.65V after high temperature storage.

In addition, the secondary batteries of Comparative Examples 11, 12, 14, 15, 16, and 18 including the compounds of Formulas (a) to (d) as non-aqueous electrolyte additives were able to be charged and discharged in some cells, but the voltage was weak after high temperature storage. It can be seen that the drop below 3.7V.

On the other hand, in the secondary batteries of Comparative Examples 13 and 17, the number of chargeable and dischargeable batteries and the high temperature compared to the secondary batteries of Comparative Examples 11, 12, 14, 15, 16, and 18 while containing an excessive amount of additives that can suppress metal elution After storage the voltage increased. However, it can be seen that the voltage decreases after high temperature storage rather than the secondary batteries of Examples 29 to 56 due to the increased resistance in the secondary batteries.

Claims (9)

1. A non-aqueous electrolyte additive comprising at least one compound selected from the group consisting of compounds represented by formula (I) and formula (II):

   [Formula 1]

   

   In Chemical Formula I,

   R ₁ is a linear or nonlinear alkylene group having 1 to 5 carbon atoms unsubstituted or substituted with at least one nitrile group, or an aromatic group having 6 to 8 carbon atoms unsubstituted or substituted with at least one nitrile group,

   R ₂ is a linear or nonlinear alkylene group having 1 to 5 carbon atoms unsubstituted or substituted with at least one nitrile group, an aromatic group having 6 to 8 carbon atoms unsubstituted or substituted with at least one nitrile group, or substituted or unsubstituted with at least one nitrile group A substituted heteroaromatic group having 6 to 8 carbon atoms, a linear or nonlinear alkenyl group having 2 to 5 carbon atoms, or -C (O) -R _9- , wherein R ₉ is substituted or substituted with at least one nitrile group and having 1 to 1 carbon atoms 3 is a linear or nonlinear alkylene group,

   R ₃ is when m = 0 it is a linear or nonlinear alkyl group having 1 to 5 carbon atoms unsubstituted or substituted with hydrogen or at least one nitrile group, when m = 1 is a linear or nonlinear alkylene group having 1 to 5 carbon atoms,

   R ₄ is an alkylene group having 1 to 3 carbon atoms or -R ₁₀ -C (O)-, R ₁₀ is an alkylene group having 1 to 3 carbon atoms,

   n and m are each independently an integer of 0 or 1.

   [Formula II]

   

   In Chemical Formula II,

   R ₅ is a linear or nonlinear alkyl group having 1 to 5 carbon atoms unsubstituted or substituted with hydrogen or at least one nitrile group,

   R ₆ to R ₈ are each independently a linear or nonlinear alkylene group having 1 to 5 carbon atoms.
2. The method according to claim 1,

   The non-aqueous electrolyte additive comprises a non-aqueous electrolyte additive comprising at least one compound selected from the group consisting of compounds represented by the following formulas (I-1) to (I-39):

   Formula I-1

   

   Formula I-2

   

   Formula I-3

   

   Formula I-4

   

   Formula I-5

   

   Formula I-6

   

   Formula I-7

   

   Formula I-8

   

   Formula I-9

   

   Formula I-10

   

   Formula I-11

   

   Formula I-12

   

   Formula I-13

   

   Formula I-14

   

   Formula I-15

   

   Formula I-16

   

   Formula I-17

   

   Formula I-18

   

   Formula I-19

   

   Formula I-20

   

   Formula I-21

   

   Formula I-22

   

   Formula I-23

   

   Formula I-24

   

   Formula I-25

   

   Formula I-26

   

   Formula I-27

   

   Formula I-28

   

   Formula I-29

   

   Formula I-30

   

   Formula I-31

   

   Formula I-32

   

   Formula I-33

   

   Formula I-34

   

   Formula I-35

   

   Formula I-36

   

   Formula I-37

   

   Formula I-38

   

   Formula I-39

   
3. The method according to claim 1,

   The non-aqueous electrolyte additive is a non-aqueous electrolyte additive comprising at least one compound selected from the group consisting of compounds represented by the following formulas II-1 to II-4:

   Formula II-1

   

   Formula II-2

   

   Formula II-3

   

   Formula II-4

   
4. Ionizable lithium salts; Organic solvents; And a non-aqueous electrolyte for lithium secondary battery comprising a non-aqueous electrolyte additive,

   The non-aqueous electrolyte additive is a non-aqueous electrolyte lithium secondary battery comprising at least one compound selected from the group consisting of compounds represented by the formula (I) and formula (II):

   [Formula I]

   

   In Chemical Formula I,

   R ₁ is a linear or nonlinear alkylene group having 1 to 5 carbon atoms unsubstituted or substituted with at least one nitrile group, or an aromatic group having 6 to 8 carbon atoms unsubstituted or substituted with at least one nitrile group,

   R ₂ is a linear or nonlinear alkylene group having 1 to 5 carbon atoms unsubstituted or substituted with at least one nitrile group, an aromatic group having 6 to 8 carbon atoms unsubstituted or substituted with at least one nitrile group, or substituted or unsubstituted with at least one nitrile group A substituted heteroaromatic group having 6 to 8 carbon atoms, a linear or nonlinear alkenyl group having 2 to 5 carbon atoms, or -C (O) -R _9- , wherein R ₉ is substituted or substituted with at least one nitrile group and having 1 to 1 carbon atoms 3 is a linear or nonlinear alkylene group,

   R ₃ is when m = 0 it is a linear or nonlinear alkyl group having 1 to 5 carbon atoms unsubstituted or substituted with hydrogen or at least one nitrile group, when m = 1 is a linear or nonlinear alkylene group having 1 to 5 carbon atoms,

   R ₄ is an alkylene group having 1 to 3 carbon atoms or -R ₁₀ -C (O)-, R ₁₀ is an alkylene group having 1 to 3 carbon atoms,

   n and m are each independently an integer of 0 or 1.

   [Formula II]

   

   In Chemical Formula II,

   R ₅ is a linear or nonlinear alkyl group having 1 to 5 carbon atoms unsubstituted or substituted with hydrogen or at least one nitrile group,

   R ₆ to R ₈ are each independently a linear or nonlinear alkylene group having 1 to 5 carbon atoms.
5. The method according to claim 4,

   The non-aqueous electrolyte additive is a non-aqueous electrolyte lithium secondary battery that will be contained in 0.5% by weight to 5% by weight based on the total amount of the non-aqueous electrolyte.
6. The method according to claim 5,

   The non-aqueous electrolyte additive is a non-aqueous electrolyte lithium secondary battery that will be included in 1 to 5% by weight based on the total content of the non-aqueous electrolyte.
7. The method according to claim 4,

   The lithium salt includes Li ⁺ as a cation,

   Anion ^{F -, Cl -, Br -} , I -, NO 3 -, N (CN) 2 -, BF 4 -, ClO 4 -, AlO 4 -, AlCl 4 -, PF 6 -, SbF 6 -, AsF _{^{6 -, BF 2 C 2 O}} 4 -, BC 4 O 8 -, (CF 3) 2 PF 4 -, (CF 3) 3 PF 3 -, (CF 3) 4 PF 2 -, (CF 3) 5 PF _{^{-, (CF 3) 6 P}} -, CF 3 SO 3 -, C 4 F 9 SO 3 -, CF 3 CF 2 SO 3 -, (CF 3 SO 2) 2 N -, (F 2 SO 2) 2 N _{^{-, CF 3 CF 2 (CF}} 3) 2 CO -, (CF 3 SO 2) 2 CH -, CF 3 (CF 2) 7 SO 3 -, CF 3 CO 2 -, CH 3 CO 2 -, SCN - and _{(CF 3 CF 2 SO 2)} 2 N - is the non-aqueous electrolyte lithium secondary battery comprises any one selected from the group consisting of.
8. The method according to claim 4,

   The organic solvent comprises at least one mixture selected from the group consisting of ethers, esters, amides, linear carbonates and cyclic carbonates.
9. In a lithium secondary battery having a negative electrode, a positive electrode, a separator interposed between the negative electrode and the positive electrode, and a nonaqueous electrolyte,

   The nonaqueous electrolyte is a lithium secondary battery comprising a nonaqueous electrolyte for lithium secondary battery of any one of claims 4 to 8.