Nonaqueous electrolyte and lithium secondary battery containing same

Abstract

The present invention provides a non-aqueous electrolyte comprising a lithium salt, an organic solvent, and an additive, the additive comprising a compound represented by a specific chemical formula. The non-aqueous electrolyte of the present invention contains an additive that is excellent in protecting the electrode film and in scavenging oxygen, and can improve both the cycle characteristics and resistance characteristics of a lithium secondary battery containing the non-aqueous electrolyte.

Description

[Technical Field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0125852, filed on September 30, 2022, and all contents disclosed in the documents of this Korean patent application are incorporated herein by reference.

[0002] The present invention relates to a non-aqueous electrolyte and a lithium secondary battery containing the same. [Background technology]

[0003] In recent years, the application areas of lithium secondary batteries have rapidly expanded from power supply for electronic devices such as electrical, electronic, communication, and computer equipment to power storage and supply for large-area devices such as automobiles and power storage devices. Accordingly, there has been an increasing demand for high-capacity, high-power, and highly stable secondary batteries.

[0004] In particular, high capacity, high output, and long life characteristics are important for lithium secondary batteries used in automobiles. To increase the capacity of lithium secondary batteries, it is considered to operate them at high voltage.

[0005] However, when a lithium secondary battery is operated under such high voltages, side reactions caused by electrolyte degradation as charging and discharging progress can cause deterioration of the coatings formed on the surfaces of the positive and negative electrodes or the structure of the electrode surfaces, leading to the elution of transition metal ions from the surface of the positive electrode. The eluted transition metal ions are then electro-deposited on the negative electrode, reducing the passivation ability of the negative electrode's solid electrolyte interface (SEI) coating, leading to the problem of negative electrode degradation. This secondary battery degradation phenomenon tends to accelerate when the positive electrode potential is increased or the battery is exposed to high temperatures.

[0006] Furthermore, when a lithium secondary battery is operated under such high voltages, there is a problem that active oxygen is released from the positive electrode active material contained in the positive electrode, which causes a side reaction with an organic solvent such as a cyclic carbonate in the non-aqueous electrolyte, generating gases such as CO or CO2, and persistently reducing the durability of the battery. Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to provide a non-aqueous electrolyte that can reduce electrolyte side reactions by forming a stable coating on the positive electrode / negative electrode, suppresses the elution of transition metals, has an excellent O scavenging effect, and is effective in reducing the resistance of secondary batteries.

[0008] Another object of the present invention is to provide a lithium secondary battery containing the above-mentioned non-aqueous electrolyte, which has reduced resistance and excellent life performance. [Means for solving the problem]

[0009] The present invention provides a non-aqueous electrolyte comprising a lithium salt, an organic solvent, and an additive, wherein the additive comprises a compound represented by the following Chemical Formula 1:

[0010] [ka]

[0011] In Chemical Formula 1, R1 to R6 each independently comprise hydrogen, a halogen, a nitrile group, a propargyl group, an ester group, an ether group, a ketone group, a carboxy group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted alkynyl group, a substituted or unsubstituted alkoxy group, a boron group, a borate group, an isocyanate group, an isothiocyanate group, a silyl group, a siloxane group, a sulfone group, a sulfonate group, a sulfate group, or a combination of two or more thereof, and at least one of R1 to R6 comprises a nitrile group.

[0012] The present invention also provides a lithium secondary battery including: a positive electrode containing a positive electrode active material; a negative electrode containing a negative electrode active material; a separator interposed between the positive electrode and the negative electrode; and the nonaqueous electrolyte. [Effects of the Invention]

[0013] The nonaqueous electrolyte of the present invention is characterized by including, as an additive, a chromone-based compound substituted with a substituent containing a nitrile group. The additive enables the formation of a coating with excellent durability and reduced resistance on the positive and negative electrodes, thereby suppressing electrolyte side reactions in the electrodes. Furthermore, the nonaqueous electrolyte of the present invention has the effect of suppressing electrolyte decomposition and gas generation (O2 scavenging effect) by bonding with reactive oxygen compounds generated at the positive electrode and the chromone structure contained in the compound represented by Chemical Formula 1. Furthermore, the nitrile group substituted with the chromone structure can prevent performance degradation at high temperatures and suppress the elution of transition metals from the positive electrode active material.

[0014] Therefore, the lithium secondary battery containing the non-aqueous electrolyte can have improved resistance characteristics and life characteristics. DETAILED DESCRIPTION OF THE INVENTION

[0015] The terms and words used in this specification and claims should not be interpreted in a limited way to their ordinary or dictionary meanings, but should be interpreted in a way that is consistent with the technical idea of ​​the present invention, based on the principle that the inventors can appropriately define the concepts of terms in order to best explain their inventions.

[0016] As used herein, the terms "comprises," "comprises," or "having" are intended to specify the presence of embodied features, numbers, steps, components, or combinations thereof, and should be understood as not precluding the presence or possible addition of one or more other features, numbers, steps, components, or combinations thereof.

[0017] On the other hand, before describing the present invention, unless otherwise specified in the present invention, "*" means a linking portion (bonding site) between the ends of the same or different atoms or chemical formulae.

[0018] Furthermore, in the description of "number of carbon atoms a to b" herein, "a" and "b" refer to the number of carbon atoms contained in a specific functional group. That is, the functional group may contain "a" to "b" carbon atoms. For example, "an alkyl group having 1 to 5 carbon atoms" refers to an alkyl group containing 1 to 5 carbon atoms, i.e., CH3-, CH3CH2-, CH3CH2CH2-, (CH3)2CH-, CH3CH2CH2CH2-, (CH3)2CHCH2-, CH3CH2CH2CH2CH2-, (CH3)2CHCH2CH2-, CH3)2CHCH2CH2-, (CH3)2CHCH2CH2-, etc.

[0019] In this specification, the alkyl group, alkenyl group, or alkynyl group may be substituted or unsubstituted. Unless otherwise defined, the term "substituted" means that at least one hydrogen atom bonded to a carbon atom is replaced with an element other than hydrogen, such as an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an alkynyl group having 2 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, a cycloalkenyl group having 3 to 12 carbon atoms, a cycloalkynyl group having 3 to 12 carbon atoms, a heterocycloalkyl group having 3 to 12 carbon atoms, a heterocycloalkenyl group having 3 to 12 carbon atoms, a heterocycloalkynyl group having 2 to 12 carbon atoms, an aryloxy group having 6 to 12 carbon atoms, a halogen atom, a fluoroalkyl group having 1 to 20 carbon atoms, a nitro group, an aryl group having 6 to 20 carbon atoms, a heteroaryl group having 2 to 20 carbon atoms, or a haloaryl group having 6 to 20 carbon atoms.

[0020] The present invention will now be described in more detail.

[0021] <Non-aqueous electrolyte> The present invention relates to a non-aqueous electrolyte. More specifically, the non-aqueous electrolyte may be a non-aqueous electrolyte for a lithium secondary battery.

[0022] The non-aqueous electrolyte according to the present invention includes a lithium salt, an organic solvent, and an additive, and the additive includes a compound represented by the following Chemical Formula 1:

[0023] [ka]

[0024] In Chemical Formula 1, R1 to R6 each independently comprise hydrogen, a halogen, a nitrile group, a propargyl group, an ester group, an ether group, a ketone group, a carboxy group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted alkynyl group, a substituted or unsubstituted alkoxy group, a boron group, a borate group, an isocyanate group, an isothiocyanate group, a silyl group, a siloxane group, a sulfone group, a sulfonate group, a sulfate group, or a combination of two or more thereof, and at least one of R1 to R6 comprises a nitrile group.

[0025] The nonaqueous electrolyte of the present invention is characterized by including, as an additive, a chromone-based compound substituted with a substituent containing a nitrile group. The additive enables the formation of a coating with excellent durability and reduced resistance on the positive and negative electrodes, thereby suppressing electrolyte side reactions in the electrodes. Furthermore, the nonaqueous electrolyte of the present invention exhibits an O scavenging effect, as the reactive oxygen compounds generated at the positive electrode bond with the chromone structure contained in the compound represented by Chemical Formula 1. Furthermore, the nitrile group substituted with the chromone structure prevents performance degradation at high temperatures and suppresses the elution of transition metals from the positive electrode active material. Therefore, lithium secondary batteries containing the nonaqueous electrolyte can exhibit improved resistance and life characteristics.

[0026] (1) Lithium salt As the lithium salt used in the present invention, various lithium salts that are commonly used in non-aqueous electrolytes for lithium secondary batteries can be used without any limitation. For example, the lithium salt may contain Li as a cation. + and the anion is F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , AlO4 - , AlCl4 - , PF6 - , SbF6 - , AsF6 - , B 10 Cl 10 - , BF2C2O4 - , BC4O8 - , PF4C2O4 - , PF2C4O8 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , CF3SO3 - , C4F9SO3 - , CF3CF2SO3 - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , CH3SO3 - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - , and (CF3CF2SO2)2N - The composition may include at least one selected from the group consisting of:

[0027] Specifically, the lithium salts include LiCl, LiBr, LiI, LiBF4, LiClO4, LiAlO4, LiAlCl4, LiPF6, LiSbF6, LiAsF6, LiB10 Cl 10 , LiBOB (LiB(C2O4)2), LiCF3SO3, LiFSI (LiN(SO2F)2), LiCH3SO3, LiCF3CO2, LiCH3CO2, and LiBETI (LiN(SO2CF2CF3)2). Specifically, the lithium salt may include at least one selected from the group consisting of LiBF4, LiClO4, LiPF6, LiBOB (LiB(C2O4)2), LiCF3SO3, LiTFSI (LiN(SO2CF3)2), LiFSI (LiN(SO2F)2), and LiBETI (LiN(SO2CF2CF3)2).

[0028] The lithium salt may be contained in the non-aqueous electrolyte at a concentration of 0.5 M to 5 M, specifically, at a concentration of 0.8 M to 4 M, more specifically, at a concentration of 0.8 M to 2.0 M. When the concentration of the lithium salt satisfies the above range, the lithium ion transport number (Li + The transference number and dissociation degree of lithium ions are improved, which can improve the output characteristics of the battery.

[0029] (2) Organic Solvent The organic solvent is not particularly limited as long as it is a non-aqueous solvent commonly used in lithium secondary batteries and minimizes decomposition due to oxidation reactions during charging and discharging of the secondary battery.

[0030] Specifically, the organic solvent may include at least one selected from the group consisting of cyclic carbonate organic solvents, linear carbonate organic solvents, linear ester organic solvents, and cyclic ester organic solvents.

[0031] Specifically, the organic solvent may include a cyclic carbonate organic solvent, a linear carbonate organic solvent, or a mixture thereof.

[0032] The cyclic carbonate organic solvent is a highly viscous organic solvent that has a high dielectric constant and easily dissociates the lithium salt in the electrolyte. Specifically, the cyclic carbonate organic solvent may include at least one organic solvent selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate, and vinylene carbonate, and more specifically, may include ethylene carbonate.

[0033] The linear carbonate organic solvent is an organic solvent having low viscosity and low dielectric constant, and may specifically include at least one selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethyl methyl carbonate (EMC), methyl propyl carbonate, and ethyl propyl carbonate, and more specifically may include ethyl methyl carbonate (EMC).

[0034] The organic solvent may be a mixture of a cyclic carbonate organic solvent and a linear carbonate organic solvent. In this case, the cyclic carbonate organic solvent and the linear carbonate organic solvent may be mixed at a volume ratio of 10:90 to 40:60, specifically a volume ratio of 10:90 to 30:70, more specifically a volume ratio of 15:85 to 30:70. When the mixing ratio of the cyclic carbonate organic solvent and the linear carbonate organic solvent satisfies the above range, both high dielectric constant and low viscosity characteristics are satisfied, and excellent ionic conductivity characteristics can be achieved.

[0035] In order to produce an electrolyte having high ionic conductivity, the organic solvent may further contain at least one ester organic solvent selected from the group consisting of linear ester organic solvents and cyclic ester organic solvents in addition to the at least one carbonate organic solvent selected from the group consisting of cyclic carbonate organic solvents and linear carbonate organic solvents.

[0036] Specifically, the linear ester organic solvent may include at least one selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, and butyl propionate.

[0037] The cyclic ester organic solvent may specifically include at least one selected from the group consisting of γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone, and ε-caprolactone.

[0038] Meanwhile, the organic solvent may further include, as needed, any organic solvent commonly used in non-aqueous electrolytes, for example, at least one of an ether-based organic solvent, a glyme-based organic solvent, and a nitrile-based organic solvent.

[0039] The ether solvent may be any one selected from the group consisting of dimethyl ether, diethyl ether, dipropyl ether, methyl ethyl ether, methyl propyl ether, ethyl propyl ether, 1,3-dioxolane (DOL), and 2,2-bis(trifluoromethyl)-1,3-dioxolane (TFDOL), or a mixture of two or more of these, but is not limited thereto.

[0040] The glyme-based solvent has a higher dielectric constant and lower surface tension than linear carbonate-based organic solvents and is less reactive with metals, and may include at least one selected from the group consisting of dimethoxyethane (glyme, DME), diethoxyethane, diglyme, triglyme, and tetraglyme (TEGDME), but is not limited thereto.

[0041] The nitrile solvent may be one or more selected from the group consisting of acetonitrile, propionitrile, butyronitrile, valeronitrile, caprylonitrile, heptanenitrile, cyclopentanecarbonitrile, cyclohexanecarbonitrile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2-fluorophenylacetonitrile, and 4-fluorophenylacetonitrile, but is not limited thereto.

[0042] (3) Additives The non-aqueous electrolyte according to the present invention contains a compound represented by the following chemical formula 1.

[0043] [ka]

[0044] In Chemical Formula 1, R1 to R6 each independently comprise hydrogen, a halogen, a nitrile group, a propargyl group, an ester group, an ether group, a ketone group, a carboxy group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted alkynyl group, a substituted or unsubstituted alkoxy group, a boron group, a borate group, an isocyanate group, an isothiocyanate group, a silyl group, a siloxane group, a sulfone group, a sulfonate group, a sulfate group, or a combination of two or more thereof, and at least one of R1 to R6 comprises a nitrile group.

[0045] The compound represented by Chemical Formula 1 is a chromone-based compound containing a substituent that contains a nitrile group. The chromone structure contained in Chemical Formula 1 has a higher reaction energy with active oxygen than organic solvents such as ethylene carbonate, so when active oxygen is generated, it binds with the active oxygen before the organic solvent. Therefore, when the compound represented by Chemical Formula 1 is contained in a non-aqueous electrolyte, the reactive oxygen compounds generated at the positive electrode bind with the chromone structure contained in the compound represented by Chemical Formula 1, thereby suppressing electrolyte decomposition and gas generation.

[0046] In addition, the compound represented by Chemical Formula 1 can be rapidly reductively decomposed during initial activation to form a stable SEI (Solid Electrolyte Interphase) coating on the surface of the negative electrode. The chromone structure contained in the compound represented by Chemical Formula 1 has strong reducibility at the negative electrode, and the ring structure is opened during initial activation of the lithium secondary battery, allowing the formation of a polyethylene oxide-based polymer-type SEI layer. Such a polymer-type SEI layer has the advantages of excellent flexibility and recovery.

[0047] In addition, the nitrile group contained in the compound represented by Chemical Formula 1 not only prevents the deterioration of secondary battery performance at high temperatures but also plays a role in suppressing the elution of transition metals from the positive electrode active material.

[0048] Therefore, a non-aqueous electrolyte containing the compound of Chemical Formula 1, which has both a chromone structure and a nitrile group-containing substituent, as an additive can form an SEI coating on the negative electrode that has reduced resistance and excellent durability, thereby significantly improving the life performance and resistance characteristics of a lithium secondary battery containing the same.

[0049] Specifically, the compound represented by Chemical Formula 1 may include a compound represented by Chemical Formula 2A below.

[0050] [ka]

[0051] In Chemical Formula 2A, R2 is as defined in Chemical Formula 1, and R2 contains a nitrile group.

[0052] When R2 is substituted with chromone as in Chemical Formula 2A, this is preferable because it can further improve the durability of the coating.

[0053] More specifically, the compound represented by Chemical Formula 1 may include a compound represented by Chemical Formula 3A below.

[0054] [ka]

[0055] The compound represented by Chemical Formula 1 may be included in the non-aqueous electrolyte in an amount of 0.01 wt % to 5 wt %, specifically 0.05 wt % to 4.5 wt %, more specifically 0.2 wt % to 1.5 wt %, and even more specifically 0.4 wt % to 0.8 wt %. When the content of the compound represented by Chemical Formula 1 satisfies the above range, the above-mentioned electrode interface protection effect, organic solvent decomposition and side reaction prevention effect are fully exhibited, and an increase in the resistance of the lithium secondary battery due to the addition of an excessive amount, and the resulting decrease in life performance, are prevented, which is preferable.

[0056] The additive may further include an additional additive in addition to the compound of Formula 1. The additional additive may be included in the non-aqueous electrolyte to prevent the non-aqueous electrolyte from being decomposed and causing the collapse of the negative electrode in a high-power environment, or to improve low-temperature high-rate discharge characteristics, high-temperature stability, prevent overcharge, and suppress battery expansion at high temperatures.

[0057] Specifically, the additional additive may be at least one selected from the group consisting of vinylene carbonate, vinyl ethylene carbonate, fluoroethylene carbonate, 1,3-propane sultone, propene sultone, succinonitrile, adiponitrile, ethylene sulfate, LiPO2F2, lithium difluorooxalatoborate (LiODFB), lithium bis(oxalato)borate (LiBOB), 3-trimethoxysilanyl-propyl-N-aniline (TMSPa), and tris(trimethylsilyl)phosphate (TMSPi), and more specifically, at least one selected from the group consisting of vinylene carbonate and 1,3-propane sultone.

[0058] The additional additive may be included in the non-aqueous electrolyte in an amount of 0.1 wt % to 15 wt %.

[0059] <Lithium secondary battery> The present invention also provides a lithium secondary battery containing the above-mentioned non-aqueous electrolyte.

[0060] Specifically, the lithium secondary battery may include a positive electrode including a positive electrode active material, a negative electrode including a negative electrode active material, a separator interposed between the positive electrode and the negative electrode, and the non-aqueous electrolyte.

[0061] The lithium secondary battery of the present invention can be manufactured by a conventional method known in the art, for example, by forming an electrode assembly in which a positive electrode, a negative electrode, and a separator are sequentially stacked between the positive electrode and the negative electrode, inserting the electrode assembly into a battery case, and injecting the nonaqueous electrolyte according to the present invention into the battery case.

[0062] (1) Positive electrode The positive electrode includes a positive electrode active material.

[0063] The positive electrode may include a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector, wherein the positive electrode active material may be contained in the positive electrode active material layer.

[0064] The positive electrode current collector is not particularly limited as long as it does not cause chemical changes in the battery and has high conductivity. Specifically, the positive electrode current collector may include at least one selected from the group consisting of copper, stainless steel, aluminum, nickel, titanium, sintered carbon, and an aluminum-cadmium alloy, and preferably aluminum.

[0065] The positive electrode current collector usually has a thickness of 3 μm to 500 μm.

[0066] The positive electrode current collector may have a surface with fine irregularities to enhance the bonding strength of the positive electrode active material. For example, the positive electrode current collector may be used in various forms such as a film, sheet, foil, mesh, porous material, foam, or nonwoven fabric.

[0067] The positive electrode active material layer may be disposed on at least one surface of the positive electrode current collector. Specifically, the positive electrode active material layer may be disposed on one or both surfaces of the positive electrode current collector.

[0068] The positive electrode active material layer may include a positive electrode active material.

[0069] The positive electrode active material is a compound capable of reversible intercalation and deintercalation of lithium, and specifically may include a lithium transition metal composite oxide containing lithium and at least one transition metal selected from nickel, cobalt, manganese, and aluminum, preferably a lithium transition metal composite oxide containing lithium and a transition metal including nickel, cobalt, and manganese.

[0070] For example, as the lithium transition metal composite oxide, there are lithium-manganese-based oxides (e.g., LiMnO2, LiMn2O4, etc.), lithium-cobalt-based oxides (e.g., LiCoO2, etc.), lithium-nickel-based oxides (e.g., LiNiO2, etc.), lithium-nickel-manganese-based oxides (e.g., LiNi 1-Y Mn Y O2 (where 0 < Y < 1), LiMn 2-Z Ni Z O4 (where 0 < Z < 2), etc.), lithium-nickel-cobalt-based oxides (e.g., LiNi 1-Y1 Co Y1 O2 (where 0 < Y' < 1), etc.), lithium-manganese-cobalt-based oxides (e.g., LiCo 1-Y2 Mn Y2 O2 (where 0 < Y2 < 1), LiMn 2-Z1 Co Z1 [[ID=XX]]O4 (where 0 < Z1 < 2), etc.), lithium-nickel-manganese-cobalt-based oxides (e.g., Li(Ni p Co q Mn r1 )O2 (where 0 < p < 1, 0 < q < 1, 0 < r1 < 1, p + q + r1 = 1) or Li(Ni p1 Co q1 Mn r2 )O4 (where 0 < p1 < 2, 0 < q1 < 2, 0 < r2 < 2, p1 + q1 + r2 = 2), etc.), or lithium-nickel-cobalt-transition metal (M) oxides (e.g., Li(Ni p2 Co [[ID=3XX]] q2 Mn r3 M S2 )O2 (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 the atomic fractions of the respective independent elements, 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 them, from the viewpoint of enhancing the capacity characteristics and stability of the battery, the lithium transition metal composite oxide is LiCoO2, LiMnO2, LiNiO2, lithium nickel-manganese-cobalt oxide (e.g., Li(Ni It should be noted that there seems to be an error in the original text where "LiMn 2-Z Ni Z O4(ここで、0<Z<2)など)" was likely intended to be something like "LiNiMn Z O4(where 0 < Z < 2), etc.", and I've made a best - effort correction in the translation for better readability. Also, "XX" was added in the translation where the numbering seemed incorrect in the original for better continuity. The tags 1-Y - S2 are preserved as they are.0.6 Mn 0.2 Co 0.2 )O2, Li(Ni 0.5 Mn 0.3 Co 0.2 )O2, Li(Ni 0.7 Mn 0.15 Co 0.15 )O2, or Li(Ni 0.8 Mn 0.1 Co 0.1 )O2), or lithium nickel cobalt aluminum oxide (e.g., Li(Ni 0.8 Co 0.15 Al 0.05 )O2, etc.), and in consideration of the remarkable improvement effect by controlling the types and content ratios of constituent elements forming the lithium transition metal composite oxide, the lithium transition metal composite oxide may be Li(Ni 0.6 Mn 0.2 Co 0.2 )O2, Li(Ni 0.5 Mn 0.3 Co 0.2 )O2, Li(Ni 0.7 Mn 0.15 Co 0.15 )O2, or Li(Ni 0.8 Mn 0.1 Co 0.1 )O2, etc., and any one or a mixture of two or more of these can be used.

[0071] More specifically, the positive electrode active material may be a lithium transition metal composite oxide containing 60 mol% or more of nickel based on the total number of moles of transition metals contained in the lithium transition metal composite oxide. Specifically, the positive electrode active material may be a lithium transition metal composite oxide containing nickel and at least one selected from manganese, cobalt, and aluminum, and containing 60 mol% or more, specifically 60 mol% to 90 mol%, of the transition metals based on the total number of moles of the transition metals. When such a lithium transition metal composite oxide containing a high content of nickel is used together with the nonaqueous electrolyte solution, it is preferable because it can reduce by-products in the gas generated by structural collapse.

[0072] The positive electrode active material may include a lithium composite transition metal oxide represented by the following Chemical Formula 5:

[0073] [Chemical formula 5] Li 1+x (Ni a Co b Mn c M d )O2

[0074] In the above Chemical Formula 5, M is one or more selected from W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo, and 1+x, a, b, c, and d are atomic fractions of each independent element, and 0≦x≦0.2, 0.50≦a<1, 0 <b≦0.25、0<c≦0.25、0≦d≦0.1、a+b+c+d=1である。

[0075] Preferably, a, b, c, and d may be in the ranges 0.70≦a≦0.95, 0.025≦b≦0.20, 0.025≦c≦0.20, and 0≦d≦0.05, respectively.

[0076] Furthermore, the a, b, c, and d may be in the ranges 0.80≦a≦0.95, 0.025≦b≦0.15, 0.025≦c≦0.15, and 0≦d≦0.05, respectively.

[0077] Furthermore, the a, b, c, and d may be 0.85≦a≦0.90, 0.05≦b≦0.10, 0.05≦c≦0.10, and 0≦d≦0.03, respectively.

[0078] On the other hand, the positive electrode active material may include a perlithiated manganese-rich oxide containing 50 mol % or more of Mn among all metals excluding lithium, and having a molar ratio of lithium to transition metals of more than 1.

[0079] When the perlithiated manganese-rich oxide is used as a cathode active material, active oxygen is generated during the decomposition of the rock salt phase of the perlithiated manganese-rich oxide during the initial activation process. Active oxygen attacks and decomposes organic solvents, such as ethylene carbonate, producing gas and antibody by-products, which degrades the physical properties of the battery. However, in the present invention, the non-aqueous electrolyte contains the compound represented by Chemical Formula 1, which is more reactive with active oxygen than the organic solvent. Therefore, the active oxygen generated during the initial activation process binds to the compound represented by Chemical Formula 1 before the organic solvent, minimizing side effects caused by the decomposition of the organic solvent.

[0080] The perlithiated manganese-rich oxide may be a compound represented by the following formula 6:

[0081] [Chemical formula 6] Li 1+s [Ni t Co u Mn v M 1 w ]O 2+z

[0082] In the above chemical formula 6, M 1 is one or more selected from W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo. In addition, in Chemical Formula 6, the following relationships may be satisfied: 0.05≦s≦1, 0≦t≦0.5, 0≦u≦0.3, 0.5≦v<1.0, 0≦w≦0.2, 0≦z≦1, preferably 0.05≦s≦1.0, 0.1≦t≦0.5, 0≦u≦0.1, 0.5≦v<1.0, 0≦w≦0.2, 0≦z≦1, and more preferably 0.10≦s≦0.50, 0.1≦t≦0.5, 0≦u≦0.1, 0.6≦v<1.0, 0≦w≦0.1, 0≦z≦0.50.

[0083] More specifically, the perlithiated manganese-rich oxide may be a compound represented by the following formula 6-1.

[0084] [Chemical formula 6-1] X Li2MnO3·(1-X)Li[Ni 1-y-z-w Mn y Co z M 1 w ]O2

[0085] In the above chemical formula 6-1, M 1 is one or more selected from W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo. In addition, in Chemical Formula 6-1, the following relationships may be satisfied: 0.1≦X≦0.5, 0.5≦y<1, 0≦z≦0.3, 0≦w≦0.2, preferably 0.2≦X≦0.5, 0.5≦y<1, 0≦z≦0.1, 0≦w≦0.2, and more preferably 0.3≦X≦0.5, 0.6≦y<1, 0≦z≦0.1, 0≦w≦0.2.

[0086] The positive electrode active material may be contained in the positive electrode active material layer in an amount of 80% by weight to 99% by weight, preferably 92% by weight to 98.5% by weight, in consideration of sufficient capacity of the positive electrode active material.

[0087] The positive electrode active material layer may further contain a binder and / or a conductive material in addition to the positive electrode active material.

[0088] The binder is a component that assists in binding the active material and conductive material, etc., and in binding them to the current collector, and specifically may contain at least one selected from the group consisting of polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, and fluororubber, and preferably polyvinylidene fluoride.

[0089] The binder may be contained in the positive electrode active material layer in an amount of 1 to 20% by weight, preferably 1.2 to 10% by weight, in order to ensure sufficient binding strength between components such as the positive electrode active material.

[0090] The conductive material is used to assist and improve the conductivity of the secondary battery, and is not particularly limited as long as it does not cause chemical changes and has conductivity. Specifically, the positive electrode conductive material may include at least one selected from the group consisting of graphite such as natural graphite and artificial graphite; carbon black 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; conductive tubes such as carbon nanotubes; fluorocarbons; metal powders such as aluminum and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and polyphenylene derivatives. Preferably, the positive electrode conductive material may include carbon black in order to improve conductivity.

[0091] In order to ensure sufficient electrical conductivity, the conductive material may be contained in the positive electrode active material layer in an amount of 1 to 20% by weight, preferably 1.2 to 10% by weight.

[0092] The thickness of the positive electrode active material layer may be 30 μm to 400 μm, and preferably 40 μm to 110 μm.

[0093] The positive electrode may be fabricated by coating a positive electrode slurry containing a positive electrode active material, and optionally a binder, a conductive material, and a solvent for forming the positive electrode slurry, on the positive electrode current collector, followed by drying and rolling.

[0094] The solvent for forming the positive electrode slurry may include an organic solvent such as NMP (N-methyl-2-pyrrolidone), etc. The solid content of the positive electrode slurry may be 40% by weight to 90% by weight, specifically 50% by weight to 80% by weight.

[0095] (2) Negative electrode The negative electrode faces the positive electrode.

[0096] The negative electrode includes a negative electrode active material.

[0097] The negative electrode may include a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode active material may be included in the negative electrode active material layer.

[0098] The negative electrode current collector is not particularly limited as long as it does not cause chemical changes in the battery and has high conductivity. Specifically, the negative electrode current collector may be made of copper, stainless steel, aluminum, nickel, titanium, baked carbon, copper or stainless steel whose surface is treated with carbon, nickel, titanium, silver, or the like, or an aluminum-cadmium alloy.

[0099] The negative electrode current collector usually has a thickness of 3 μm to 500 μm.

[0100] The negative electrode current collector may have a surface with fine irregularities to enhance the bonding strength of the negative electrode active material. For example, the negative electrode current collector may be used in various forms such as a film, sheet, foil, mesh, porous material, foam, or nonwoven fabric.

[0101] The negative electrode active material layer may be disposed on at least one surface of the negative electrode current collector. Specifically, the negative electrode active material layer may be disposed on one or both surfaces of the negative electrode current collector.

[0102] The negative electrode active material layer may include a negative electrode active material.

[0103] The negative electrode active material is a material capable of reversibly intercalating / deintercalating lithium ions, and may include at least one selected from the group consisting of a carbon-based active material, a (quasi)metal-based active material, and lithium metal, and specifically may include at least one selected from a carbon-based active material and a (quasi)metal-based active material.

[0104] The carbon-based active material may include at least one selected from the group consisting of artificial graphite, natural graphite, hard carbon, soft carbon, carbon black, graphene, and fibrous carbon, and preferably includes at least one selected from the group consisting of artificial graphite and natural graphite.

[0105] The average particle size (D 50 ) may be 10 μm to 30 μm, preferably 15 μm to 25 μm, in order to ensure structural stability during charge and discharge and reduce side reactions with the electrolyte.

[0106] Specifically, the (quasi-)metallic active material may include at least one (quasi-)metal selected from the group consisting of Cu, Ni, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, V, Ti, and Sn; an alloy of at least one (quasi-)metal selected from the group consisting of Cu, Ni, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, V, Ti, and Sn; an oxide of at least one (quasi-)metal selected from the group consisting of Cu, Ni, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, V, Ti, and Sn; lithium titanium oxide (LTO); lithium vanadium oxide; and the like.

[0107] More specifically, the (quasi)metallic active material may include a silicon-based active material.

[0108] The silicon-based active material is SiO x (0≦x<2). SiO2 does not react with lithium ions and therefore cannot store lithium. Therefore, x is preferably within the above range, and more preferably, the silicon-based active material may be SiO.

[0109] The average particle size (D 50) may be 1 μm to 30 μm, preferably 2 μm to 15 μm, from the viewpoint of improving structural stability during charge and discharge and reducing side reactions with the electrolyte.

[0110] The negative electrode active material may be contained in the negative electrode active material layer in an amount of 60% by weight to 99% by weight, preferably 75% by weight to 95% by weight.

[0111] The negative electrode active material layer may further include a binder and / or a conductive material in addition to the negative electrode active material.

[0112] The binder is used to improve the adhesive strength between the negative electrode active material layer and the negative electrode current collector, thereby improving battery performance. For example, the binder may include at least one selected from the group consisting of polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethylmethacrylate, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, and substances in which hydrogen is substituted with Li, Na, Ca, or the like, or may include various copolymers thereof.

[0113] The binder may be contained in the negative electrode active material layer in an amount of 0.5% by weight to 10% by weight, preferably 1% by weight to 5% by weight.

[0114] The conductive material is not particularly limited as long as it does not cause a chemical change in the battery and is conductive. For example, graphite such as natural graphite and artificial graphite; carbon black 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; conductive tubes such as carbon nanotubes; fluorocarbons; metal powders such as aluminum and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives may be used.

[0115] The conductive material may be contained in the negative electrode active material layer in an amount of 0.5% by weight to 10% by weight, preferably 1% by weight to 5% by weight.

[0116] The thickness of the negative electrode active material layer may be 10 μm to 100 μm, and preferably 50 μm to 80 μm.

[0117] The negative electrode may be prepared by coating at least one surface of a negative electrode current collector with a negative electrode slurry containing a negative electrode active material, a binder, a conductive material, and / or a solvent for forming the negative electrode slurry, followed by drying and rolling.

[0118] The solvent for forming the negative electrode slurry may include, for example, at least one selected from the group consisting of distilled water, N-methyl-2-pyrrolidone (NMP), ethanol, methanol, and isopropyl alcohol, preferably distilled water, in order to facilitate dispersion of the negative electrode active material, binder, and / or conductive material. The solid content of the negative electrode slurry may be 30% by weight to 80% by weight, specifically 40% by weight to 70% by weight.

[0119] (3) Separator The separator may be a conventional porous polymer film, such as a porous polymer film made of a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, or an ethylene / methacrylate copolymer, either alone or in a laminate, or a conventional porous nonwoven fabric, such as a nonwoven fabric made of a high-melting point glass fiber or polyethylene terephthalate fiber, but is not limited to these. Furthermore, to ensure heat resistance or mechanical strength, a coated separator containing a ceramic component or a polymer material may be used, and may be selectively used as a single-layer or multi-layer structure.

[0120] The external shape of the lithium secondary battery of the present invention is not particularly limited, and may be a cylindrical shape using a can, a square shape, a pouch shape, a coin shape, or the like.

[0121] The present invention will be described in more detail below with reference to specific examples. However, the following examples are merely illustrative for understanding the present invention and are not intended to limit the scope of the present invention. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the present description and technical concept, and it goes without saying that such changes and modifications fall within the scope of the appended claims.

[0122] <Examples and Comparative Examples> Example 1 (Production of non-aqueous electrolyte) The organic solvent used was a mixture of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 30:70.

[0123] A non-aqueous electrolyte was prepared by adding LiPF6 as a lithium salt, a compound represented by the following Chemical Formula 3A, and vinylene carbonate and 1,3-propane sultone as additional additives to the organic solvent.

[0124] The LiPF6 was contained in the non-aqueous electrolyte at a concentration of 1.0 M.

[0125] The compound represented by the following Chemical Formula 3A was contained in the non-aqueous electrolyte at 0.5 wt %.

[0126] The non-aqueous electrolyte contained vinylene carbonate and 1,3-propane sultone in an amount of 0.5 wt % each.

[0127] [ka]

[0128] (Lithium secondary battery manufacturing) Cathode active material (Li 1.35 [Ni 0.35 Mn 0.65 ]O2, perlithiated manganese-rich oxide), conductive material (carbon black), and binder (polyvinylidene fluoride) were added to N-methyl-2-pyrrolidone (NMP) as a solvent in a weight ratio of 96.0:1.5:2.5 to prepare a positive electrode slurry (solid content 60 wt%). The positive electrode slurry was applied to one side of a 13.5 μm-thick positive electrode current collector (Al thin film), dried, and roll-pressed to prepare a positive electrode.

[0129] Anode active material (graphite), conductive material (carbon black), and binder (styrene-butadiene rubber) were mixed in a weight ratio of 97:1:2 with distilled water as a solvent to prepare anode slurry (solid content 60 wt%). The anode slurry was applied to one side of anode current collector (Cu thin film) with a thickness of 6 μm, dried, and roll-pressed to prepare anode.

[0130] A polyethylene porous film separator was interposed between the positive electrode and negative electrode prepared above in a dry room, and the non-aqueous electrolyte prepared above was then injected to prepare a secondary battery.

[0131] Example 2 A non-aqueous electrolyte and a secondary battery were produced in the same manner as in Example 1, except that the compound represented by Chemical Formula 3A was added to the non-aqueous electrolyte in an amount of 0.3 wt %.

[0132] Example 3 A non-aqueous electrolyte and a secondary battery were produced in the same manner as in Example 1, except that the compound represented by Chemical Formula 3A was added to the non-aqueous electrolyte in an amount of 1.0 wt %.

[0133] Comparative Example 1 A non-aqueous electrolyte and a lithium secondary battery were prepared in the same manner as in Example 1, except that the compound represented by Chemical Formula 3A was not added.

[0134] Comparative Example 2 A non-aqueous electrolyte and a lithium secondary battery were prepared in the same manner as in Example 1, except that a compound represented by the following chemical formula X was added to the non-aqueous electrolyte in an amount of 0.5 wt % instead of the compound represented by chemical formula 3A.

[0135] [ka]

[0136] Comparative Example 3 A non-aqueous electrolyte and a lithium secondary battery were prepared in the same manner as in Example 1, except that a compound represented by the following chemical formula Y was added to the non-aqueous electrolyte in an amount of 0.5 wt % instead of the compound represented by chemical formula 3A.

[0137] [ka]

[0138] <Experimental Example> Experimental Example 1: Evaluation of cycle capacity retention rate The lithium secondary batteries of Examples 1 to 3 and Comparative Examples 1 to 3 manufactured as described above were charged to 4.35 V, 1 / 40 C under conditions of CC / CV, 0.33 C at 45° C. using an electrochemical charger / discharger, and then discharged to 2.0 V under conditions of CC, 0.33 C, with one cycle being defined as 150 charge / discharge cycles, and the capacity retention rate was measured.

[0139] The capacity retention rate was calculated using the following formula, and the results are shown in Table 1 below.

[0140] Capacity retention rate (%) = {(discharge capacity after 150 cycles / discharge capacity after 1 cycle)} × 100

[0141] Experimental Example 2: Resistance Evaluation The lithium secondary batteries of Examples 1 to 3 and Comparative Examples 1 to 3 manufactured as described above were charged at 45°C under CC / CV and 0.33C conditions up to 4.35V and 1 / 40C, and then discharged under CC and 0.33C conditions down to 2.0V, and the batteries were subjected to 150 charge-discharge cycles.

[0142] After one charge / discharge cycle, the discharge capacity after one cycle was measured using an electrochemical charge / discharge device, and after adjusting the SOC to 50%, a 2.5C pulse was applied for 10 seconds, and the initial resistance was calculated from the difference in voltage before and after the pulse application.

[0143] After 150 cycles of charge and discharge, the resistance after 150 cycles was calculated in the same manner as above, and the results are shown in Table 1 below.

[0144] [Table 1]

[0145] Referring to Table 1, it can be seen that the lithium secondary batteries of Examples 1 to 3, which use a non-aqueous electrolyte containing the compound represented by Chemical Formula 1, have improved cycle life performance and resistance characteristics compared to the lithium secondary batteries of Comparative Examples 1 to 3.

[0146] In particular, the nonaqueous electrolyte of Comparative Example 3 uses as an additive a compound in which a benzene group, rather than a nitrile group, is substituted with a chromone structure. Such a compound has very low solubility in organic solvents, and the presence of the benzene group during the formation of the SEI coating reduces the flexibility of the SEI coating, resulting in a significant decrease in the life performance of the secondary battery and an increase in resistance, which are undesirable.

[0147] Experimental Example 3: Evaluation of metal elution amount The secondary batteries of Example 1, Comparative Example 1, and Comparative Example 2 were charged to 4.35 V, 1 / 40 C at 45°C under CC / CV and 0.33 C conditions, and then discharged to 2.0 V under CC and 0.33 C conditions, with one cycle being defined as 150 charge-discharge cycles.

[0148] The total metal concentrations dissolved in the electrolyte were then measured using an inductively coupled plasma optical emission spectrophotometer (ICP-OES). The amounts of metals measured by ICP analysis are shown in Table 2 below.

[0149] [Table 2]

[0150] Referring to Table 2, it can be seen that the secondary battery using the nonaqueous electrolyte of Example 1 has a significantly reduced amount of metal elution during cycle charge / discharge compared to the secondary batteries of Comparative Examples 1 and 2, due to the use of a chromone compound with a nitrile group substituted as an electrolyte additive.

Claims

1. A lithium salt, an organic solvent; an additive, The additive comprises a compound represented by the following chemical formula 1: 【Chemical 1】 (In the above chemical formula 1, R １ ~R ６ each independently comprise a hydrogen atom, a halogen atom, a nitrile group, a propargyl group, an ester group, an ether group, a ketone group, a carboxy group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted alkynyl group, a substituted or unsubstituted alkoxy group, a boron group, a borate group, an isocyanate group, an isothiocyanate group, a silyl group, a siloxane group, a sulfone group, a sulfonate group, a sulfate group, or a combination of two or more thereof; R １ ~R ６ At least one of the groups contains a nitrile group.

2. The non-aqueous electrolyte according to claim 1 , wherein the compound represented by Chemical Formula 1 includes a compound represented by Chemical Formula 2A: 【Chemistry 2】 (In the chemical formula 2A, R ２ is as defined in Chemical Formula 1, R ２ contains a nitrile group.)

3. The non-aqueous electrolyte according to claim 1 , wherein the compound represented by Chemical Formula 1 includes a compound represented by Chemical Formula 3A: 【Chemistry 3】

4. The non-aqueous electrolyte according to claim 1 , wherein the compound represented by Chemical Formula 1 is contained in the non-aqueous electrolyte in an amount of 0.01 wt % to 10 wt %.

5. The lithium salts include LiCl, LiBr, LiI, and LiBF. ４ , LiClO ４ , LiAlO ４ , LiAlCl ４ , LiPF ６ , LiSbF ６ , LiAsF ６ , LiB １０ Cl １０ , LiBOB(LiB(C ２ O ４ ) ２ ), LiCF ３ SO ３ , LiFSI (LiN(SO ２ F) ２ ), LiCH ３ SO ３ , LiCF ３ CO ２ , LiCH ３ CO ２ , and LiBETI(LiN(SO ２ CF ２ CF ３ ) ２ 2. The non-aqueous electrolyte according to claim 1, comprising at least one selected from the group consisting of:

6. 2. The non-aqueous electrolyte according to claim 1, wherein the lithium salt is contained in the non-aqueous electrolyte at a molar concentration of 0.5 M to 5.0 M.

7. 2. The nonaqueous electrolyte according to claim 1, wherein the organic solvent includes at least one selected from the group consisting of a cyclic carbonate organic solvent, a linear carbonate organic solvent, a linear ester organic solvent, and a cyclic ester organic solvent.

8. The additives include vinylene carbonate, vinylethylene carbonate, fluoroethylene carbonate, propane sultone, propene sultone, succinonitrile, adiponitrile, ethylene sulfate, LiPO ２ F ２ 2. The non-aqueous electrolyte according to claim 1, further comprising at least one additional additive selected from the group consisting of LiODFB (Lithium difluorooxalatoborate), LiBOB (Lithium bis-(oxalato)borate), TMSPa (3-trimethoxysilanyl-propyl-N-aniline), and TMSPi (Tris(trimethylsilyl)phosphate).

9. a positive electrode including a positive electrode active material; a negative electrode including a negative electrode active material; a separator interposed between the positive electrode and the negative electrode; A lithium secondary battery comprising the non-aqueous electrolyte according to claim 1.

10. 10. The lithium secondary battery according to claim 9, wherein the positive electrode active material contains 50 mol % or more of Mn among all metals excluding lithium, and includes a perlithiated manganese-rich oxide in which the molar ratio of lithium to transition metals exceeds 1.

11. 11. The lithium secondary battery of claim 10, wherein the perlithiated manganese-rich oxide is a compound represented by the following Chemical Formula 6: [Chemical formula 6] Li １＋ｓ [Ni ｔ Co ｕ Mn ｖ M １ ｗ ]O ２＋ｚ (In the above chemical formula 6, M １ is one or more selected from W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo, and 0.05≦s≦1, 0≦t≦0.5, 0≦u≦0.3, 0.5≦v<1.0, 0≦w≦0.2, 0≦z≦1.

Images