Lithium secondary battery and method for manufacturing the same

Abstract

One embodiment of the present invention relates to a lithium secondary battery including a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte, wherein the positive electrode includes a positive electrode active material that includes a perlithiated manganese-rich oxide containing 50 mol % or more of Mn based on all metals excluding lithium and having a molar ratio of lithium to transition metals exceeding 1, and the non-aqueous electrolyte includes a lithium salt and an organic solvent, the organic solvent including a first organic solvent and a second organic solvent, the first organic solvent including ethylene carbonate, and the second organic solvent including diethyl carbonate and propyl propionate.

Description

[Technical Field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2023-0035847 filed on March 20, 2023 and Korean Patent Application No. 10-2023-0183779 filed on December 15, 2023, and all contents disclosed in the documents of said Korean patent applications are incorporated herein by reference.

[0002] The present invention relates to a lithium secondary battery. [Background technology]

[0003] In recent years, the application areas of lithium secondary batteries have rapidly expanded from power supply to electronic devices such as electrical, electronic, communication, and computer devices to power storage and power supply for large-area devices such as automobiles and power storage devices. Accordingly, there is an increasing need for secondary batteries with high capacity, high output, and high stability.

[0004] A lithium secondary battery typically comprises a positive electrode containing a positive electrode active material, a negative electrode containing a negative electrode active material, an electrolyte serving as a medium for transferring lithium ions, and a separator. The negative electrode active material may be a carbon-based active material or a silicon-based active material. The positive electrode active material may be a lithium transition metal oxide such as lithium cobalt oxide (LiCoO), lithium nickel oxide (LiNiO), or lithium nickel-cobalt-manganese composite oxide.

[0005] On the other hand, in order to construct a high-capacity secondary battery, improvements have been made to the properties of each of the positive electrode, negative electrode, electrolyte, and separator. Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a lithium secondary battery that includes a perlithiated manganese-rich oxide as a positive electrode active material, which reduces the amount of gas such as CO2 generated at the positive electrode interface during high-voltage or high-temperature operation, reduces gas generation during initial activation and charge / discharge, and suppresses the elution of transition metals from the positive electrode active material, thereby improving the lifespan at high temperatures, reducing resistance, and preventing gas generation. [Means for solving the problem]

[0007] One embodiment of the present invention provides a lithium secondary battery including a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte, wherein the positive electrode includes a positive electrode active material, the positive electrode active material including a perlithiated manganese-rich oxide containing about 50 mol % or more of Mn based on all metals excluding lithium, and having a molar ratio of lithium to transition metals of more than about 1, and the non-aqueous electrolyte includes a lithium salt and an organic solvent, the organic solvent including a first organic solvent and a second organic solvent, the first organic solvent including ethylene carbonate, and the second organic solvent including diethyl carbonate and propyl propionate. [Effects of the Invention]

[0008] A lithium secondary battery according to one embodiment of the present invention uses a perlithiated manganese-rich oxide as a positive electrode active material, and the organic solvent contained in the non-aqueous electrolyte includes ethylene carbonate, diethyl carbonate, and propyl propionate. According to one embodiment of the present invention, the combination of the above organic solvents significantly reduces the amount of gas generation at the interface of the positive electrode containing the perlithiated manganese-rich oxide, improving the life performance of the negative electrode. As a result, a lithium secondary battery with excellent capacity retention and reduced gas generation performance can be realized. The lithium secondary battery according to one embodiment of the present invention can exhibit excellent life performance and reduced gas generation performance, particularly at high temperatures and high voltages. DETAILED DESCRIPTION OF THE INVENTION

[0009] 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.

[0010] 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.

[0011] In this specification, the average particle size (D 50 The average particle size (D) can be defined as the particle size corresponding to 50% of the cumulative volume in the particle size distribution curve. 50 ) can be measured, for example, by the laser diffraction method. The laser diffraction method is generally capable of measuring particle sizes from the submicron range to several mm, and can provide results with high reproducibility and high resolution.

[0012] As used in this specification, the terms "about," "approximately," and "substantially" are used to mean a numerical value, a range of degree, or a value close to that range, taking into account inherent manufacturing and material tolerances, and are used to prevent infringers from unfairly taking advantage of the disclosure content in which exact or absolute numerical values ​​provided for understanding the present invention are mentioned.

[0013] Perlithiated manganese-rich oxide has attracted attention as a next-generation positive electrode active material for constructing high-capacity batteries. Perlithiated manganese-rich oxide contains a high content of manganese (Mn), which is relatively inexpensive and abundant in reserves. Lithium secondary batteries incorporating this material have the advantage of high capacity. However, when using perlithiated manganese-rich oxide, there is a problem of significant increase in the generation of gases such as CO2 due to electrolyte side reactions at the positive electrode interface during operation at high voltages (e.g., 4.35 V or higher) or high temperatures. Furthermore, the use of perlithiated manganese-rich oxide is limited due to the following issues: reactive oxygen generated by the phase transformation of the positive electrode active material during activation and charge / discharge processes accelerates electrolyte decomposition, resulting in significant increase in the generation of gases such as CO2; and transition metals eluted from the positive electrode active material are electrodeposited on the negative electrode, destroying the negative electrode's solid electrolyte interphase (SEI) coating.

[0014] The present invention provides a lithium secondary battery that uses a perlithiated manganese-rich oxide as a positive electrode active material, while overcoming the aforementioned problems of gas generation and destruction of the SEI coating film on the negative electrode.

[0015] The present invention will now be described in more detail.

[0016] Lithium secondary battery An embodiment of the present invention relates to a lithium secondary battery.

[0017] One embodiment of the present invention provides a lithium secondary battery including a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte, wherein the positive electrode includes a positive electrode active material, and the positive electrode active material includes a perlithiated manganese-rich oxide containing about 50 mol % or more of Mn based on all metals excluding lithium, and having a molar ratio of lithium to transition metals of more than about 1, and the non-aqueous electrolyte includes a lithium salt and an organic solvent, the organic solvent including a first organic solvent and a second organic solvent, the first organic solvent including ethylene carbonate, and the second organic solvent including diethyl carbonate and propyl propionate.

[0018] The lithium secondary battery includes a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte. For example, the lithium secondary battery includes a positive electrode, a negative electrode facing the positive electrode, a separator interposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte. The lithium secondary battery can be manufactured by placing an electrode assembly including the positive electrode, the negative electrode facing the positive electrode, and a separator interposed between the positive electrode and the negative electrode in a battery case, and then injecting the non-aqueous electrolyte into the battery case.

[0019] (1) Positive electrode The positive electrode includes a positive electrode active material.

[0020] According to one embodiment, the positive electrode active material includes a perlithiated manganese-rich oxide, which may contain at least about 50 mol% Mn based on all metals excluding lithium, and may have a lithium to transition metal molar ratio greater than about 1.

[0021] While perlithiated manganese-rich oxide has been attracting attention as a next-generation high-capacity positive electrode active material, its application is limited due to its inherent structural degradation. For example, when perlithiated manganese-rich oxide is used as a positive electrode active material, electrolyte side reactions occur at the positive electrode interface, resulting in significant increases in the generation of gases such as carbon dioxide (CO2). Furthermore, during the initial activation of a lithium secondary battery containing perlithiated manganese-rich oxide, reactive oxygen released from the perlithiated manganese-rich oxide decomposes and consumes the organic solvent (e.g., ethylene carbonate) contained in the nonaqueous electrolyte, thereby generating gas byproducts, resulting in reduced lifespan and performance, increased resistance, and reduced safety. Furthermore, during the charge and discharge process of a lithium secondary battery containing perlithiated manganese-rich oxide, manganese (Mn) is leached out due to charge balance achieved by the release of reactive oxygen. In this case, the eluted manganese is electrodeposited on the negative electrode, causing problems such as destruction of the SEI (Solid Electrolyte Interphase) coating. Furthermore, reactive oxygen released during the charge / discharge process continues to decompose and consume the organic solvent in the non-aqueous electrolyte, resulting in increased generation of gas by-products. The consumption of the non-aqueous electrolyte, the structural collapse of the perlithiated manganese-rich oxide, and the increase in gas by-products significantly reduce the lifespan, resistance characteristics, and safety of lithium secondary batteries. Furthermore, these problems become even more severe under high temperature and high voltage conditions.

[0022] To solve these problems, a lithium secondary battery according to one embodiment of the present invention is characterized in that the organic solvent in the non-aqueous electrolyte contains ethylene carbonate, diethyl carbonate, and propyl propionate, as described below. According to one embodiment of the present invention, the combination of the above organic solvents significantly reduces the amount of gas generation at the interface of the positive electrode containing the perlithiated manganese-rich oxide, improving the life performance of the negative electrode. As a result, a lithium secondary battery with superior capacity retention and reduced gas generation performance compared to conventional lithium secondary batteries can be realized. The lithium secondary battery according to one embodiment of the present invention can have excellent life performance and reduced gas generation performance, particularly at high temperatures and high voltages.

[0023] The perlithiated manganese-rich oxide may include a compound represented by the following chemical formula A:

[0024] [Chemical formula A] Li 1+s [Ni t Co u Mn v M 1 w ]O 2+z

[0025] In the above chemical formula A, M 1 is one or more elements 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 satisfies the following conditions: 0.05≦s≦1, 0≦t≦0.5, 0≦u≦0.3, 0.5≦v<1.0, 0≦w≦0.2, 0≦z≦1. For example, in Chemical Formula A, the following conditions may be satisfied: 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. Alternatively, in the chemical formula A, 0.10≦s≦0.50, 0.1≦t≦0.5, 0≦u≦0.1, 0.6≦v<1.0, 0≦w≦0.1, and 0≦z≦0.50 may be satisfied.

[0026] In one embodiment, the perlithiated manganese-rich oxide may include a compound represented by the following formula B:

[0027] [Chemical formula B] XLi2MnO3·(1-X)Li[Ni 1-y-z-w Mn y Co z M 1 w ]O2

[0028] In the above chemical formula B, M 1 is one or more elements 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 the chemical formula B, 0.1≦X≦0.5, 0.5≦y<1, 0≦z≦0.3, 0≦w≦0.2 may be satisfied, for example, 0.2≦X≦0.5, 0.5≦y<1, 0≦z≦0.1, 0≦w≦0.2, or 0.3≦X≦0.5, 0.6≦y<1, 0≦z≦0.1, 0≦w≦0.2.

[0029] 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 is contained in the positive electrode active material layer.

[0030] 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. For example, 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, or in one embodiment, may include aluminum.

[0031] The positive electrode current collector usually has a thickness of about 3 μm to 500 μm.

[0032] 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.

[0033] The positive electrode active material layer may be disposed on at least one surface of the positive electrode current collector, for example, on one surface or both surfaces of the positive electrode current collector.

[0034] The positive electrode active material may be contained in the positive electrode active material layer in an amount of about 80 wt % to 99 wt %, for example, about 92 wt % to 98.5 wt %, in consideration of sufficient capacity of the positive electrode active material.

[0035] Other details about the positive electrode active material have been described above and will be omitted here.

[0036] The positive electrode active material layer may further include a binder and / or a conductive material in addition to the positive electrode active material.

[0037] The binder is a component that assists in binding the active material and conductive material, etc., and in binding to the current collector, and may include, for example, 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, or in one embodiment, may include polyvinylidene fluoride.

[0038] The binder may be contained in the positive electrode active material layer in an amount of about 1 wt % to 20 wt %, for example, about 1.2 wt % to 10 wt %, in order to ensure sufficient binding strength between components such as the positive electrode active material.

[0039] 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. For example, 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. In one embodiment, the positive electrode conductive material may include carbon nanotubes to improve conductivity.

[0040] In order to ensure sufficient electrical conductivity, the conductive material may be contained in the positive electrode active material layer in an amount of about 1% by weight to 20% by weight, for example, about 1.2% by weight to 10% by weight.

[0041] The thickness of the positive electrode active material layer may be about 30 μm to 400 μm, for example, about 40 μm to 110 μm.

[0042] 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.

[0043] The solvent for forming the positive electrode slurry may include an organic solvent such as N-methyl-2-pyrrolidone (NMP), and the solid content of the positive electrode slurry may be about 40% by weight to 90% by weight, for example, about 50% by weight to 80% by weight.

[0044] (2) Negative electrode The negative electrode faces the positive electrode.

[0045] The negative electrode includes a negative electrode active material.

[0046] 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, for example, at least one selected from a carbon-based active material and a (quasi-)metal-based active material.

[0047] 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 may include, for example, at least one selected from the group consisting of artificial graphite and natural graphite.

[0048] The average particle size (D 50 ) may be about 10 μm to 30 μm, for example, about 15 μm to 25 μm, in order to ensure structural stability during charge and discharge and reduce side reactions with the electrolyte.

[0049] For example, the (quasi)metallic active material may include at least one selected from the group consisting of (quasi)metals, alloys of (quasi)metals and lithium, oxides of (quasi)metals, lithium titanium oxide (LTO), and lithium vanadium oxide.

[0050] The (quasi)metal may include at least one 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.

[0051] The alloy of (quasi)metal and lithium may comprise an alloy of lithium with 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.

[0052] The (quasi)metal oxide may comprise 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.

[0053] In one embodiment, the (quasi)metallic active material may include a silicon-based active material.

[0054] The silicon-based active material is SiO x (0≦x<2). Since SiO2 does not react with lithium ions and therefore cannot store lithium, x is selected within the above range, excluding 2, and in one embodiment, the silicon-based active material may be SiO.

[0055] The average particle size (D 50 ) may be about 1 μm to 30 μm, for example, about 2 μm to 15 μm, in order to ensure structural stability during charge and discharge and reduce side reactions with the electrolyte.

[0056] 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 is contained in the negative electrode active material layer.

[0057] 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. For example, 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.

[0058] The negative electrode current collector usually has a thickness of about 3 μm to 500 μm.

[0059] 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.

[0060] The negative electrode active material layer may be disposed on at least one surface of the negative electrode current collector, for example, on one or both surfaces of the negative electrode current collector.

[0061] The negative electrode active material may be contained in the negative electrode active material layer in an amount of about 60% to 99% by weight, for example, about 75% to 95% by weight.

[0062] Other details about the negative electrode active material have been described above and will be omitted here.

[0063] The negative electrode active material layer may further include a binder and / or a conductive material in addition to the negative electrode active material.

[0064] 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.

[0065] The binder may be included in the negative electrode active material layer in an amount of about 0.5% by weight to 10% by weight, for example, about 1% by weight to 5% by weight.

[0066] 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.

[0067] The conductive material may be contained in the negative electrode active material layer in an amount of about 0.5% by weight to 10% by weight, for example, about 1% by weight to 5% by weight.

[0068] The thickness of the negative electrode active material layer may be about 10 μm to 200 μm, for example, about 20 μm to 150 μm.

[0069] 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.

[0070] 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, in order to facilitate dispersion of the negative electrode active material, binder, and / or conductive material. In one embodiment, the solvent may include distilled water. The solid content of the negative electrode slurry may be about 30% by weight to 80% by weight, for example, about 40% by weight to 70% by weight.

[0071] (3) Separator The separator may be interposed between the positive electrode and the negative electrode.

[0072] 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.

[0073] (4) Nonaqueous electrolyte The non-aqueous electrolyte contains a lithium salt and an organic solvent.

[0074] 1) Lithium salt The lithium salt used in the present invention is not limited to any of various lithium salts that are commonly used in non-aqueous electrolytes for lithium secondary batteries. For example, the lithium salt may contain Li as a cation. + and as an anion, 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 present invention may include at least one selected from the group consisting of:

[0075] For example, the lithium salt may be LiCl, LiBr, LiI, LiBF, LiClO, LiAlO, LiAlCl, LiPF, LiSbF, LiAsF, LiB 10 Cl 10 , LiBOB (LiB(C2O4)2), LiCF3SO3, LiFSI (LiN(SO2F)2), LiCH3SO3, LiCF3CO2, LiCH3CO2, and LiBETI (LiN(SO2CF2CF3)2). For example, 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).

[0076] The lithium salt may be contained in the non-aqueous electrolyte at a concentration of about 0.5 M to 5 M, for example, about 0.8 M to 4 M, or about 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.

[0077] 2) Organic solvents The organic solvent includes a first organic solvent and a second organic solvent.

[0078] The first organic solvent includes ethylene carbonate.

[0079] The ethylene carbonate is a highly viscous organic solvent having a high dielectric constant, and can function as an organic solvent that easily dissociates the lithium salt in the electrolyte.

[0080] The first organic solvent may further include, in addition to the ethylene carbonate, at least one selected from the group consisting of fluoroethylene carbonate (FEC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate, vinylene carbonate, γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone, and ε-caprolactone, but is not limited thereto.

[0081] The second organic solvent includes diethyl carbonate and propyl propionate. In the lithium secondary battery according to one embodiment of the present invention, the use of a combination of diethyl carbonate and propyl propionate as the second organic solvent significantly reduces the amount of gas generated when a perlithiated manganese-rich oxide is used as a positive electrode component, thereby significantly improving the life performance of the lithium secondary battery.

[0082] For example, even when propyl propionate is decomposed, it generates less carbon dioxide (CO2) than when other organic solvents such as ethyl methyl carbonate are used. Furthermore, propyl propionate has low reactivity with reactive oxygen that can be released from the perlithiated manganese-rich oxide, which further reduces the amount of gas generated. In other words, the use of propyl propionate provides superior effects compared to the use of other ester-based solvents such as ethyl propionate, which have lower oxidation stability than propyl propionate. While propyl propionate is used as the second organic solvent in this embodiment, this is not limiting. Any solvent can be used as the second organic solvent as long as it can reduce the amount of carbon dioxide (CO2) generated when the perlithiated manganese-rich oxide is used as a positive electrode component and has low reactivity with reactive oxygen that can be released from the perlithiated manganese-rich oxide.

[0083] However, despite the above advantages, propyl propionate has low reduction stability and may be decomposed at the negative electrode, resulting in reduced lifespan. Therefore, rather than using propyl propionate alone as the second organic solvent component, these drawbacks can be overcome by using it in combination with another solvent.

[0084] In one embodiment, the present invention uses diethyl carbonate as a component of the second organic solvent together with propyl propionate. Because diethyl carbonate is a relatively stable solvent in both oxidation and reduction, when diethyl carbonate and propyl propionate are used together, only the advantages of propyl propionate, such as its gas generation reduction effect, can be realized. Therefore, in one embodiment of the present invention, by using the first organic solvent (containing ethylene carbonate) and the second organic solvent (containing diethyl carbonate and propyl propionate), excellent capacity retention and reduced gas generation can be achieved, for example, preventing cell volume expansion. In one embodiment, diethyl carbonate is used as the second organic solvent together with propyl propionate, but this is not limiting. For example, any solvent that can complement the reduction stability of propyl propionate can be selected as the second organic solvent together with propyl propionate.

[0085] On the other hand, cyclic carbonate solvents such as dimethyl carbonate and ethyl methyl carbonate, instead of diethyl carbonate, have low oxidation stability and are highly reactive to reactive oxygen derived from perlithiated manganese-rich oxide, so they are easily decomposed, and there is a risk of gas generation and increased resistance. However, if these problems can be appropriately overcome, they can be used as the second organic solvent together with propyl propionate.

[0086] As described above, the effect of one embodiment of the present invention, such as the feature of reducing the amount of gas generated from a lithium secondary battery, is an effect that is exhibited specifically when a perlithiated manganese-rich oxide is used as the positive electrode active material. However, for limited purposes, the organic solvent of the present invention may also be used in combination with other positive electrode active materials, such as high-nickel lithium-nickel-manganese-cobalt transition metal oxides (e.g., NCM-based active materials containing 80 mol % or more of Ni among the transition metals), in which the generation of reactive oxygen and excessive elution of Mn are not significant problems.

[0087] In one embodiment, the volume ratio of the diethyl carbonate to the propyl propionate may be about 1:99 to 99:1, for example, about 5:95 to 95:5, about 12:88 to 88:12, or about 40:60 to 60:40. When the volume ratio is within the above range, gas generation at high temperatures in the lithium secondary battery can be suppressed as described above, and the capacity retention effect can be achieved by ensuring the stability of the negative electrode.

[0088] The second organic solvent may further contain other additional second organic solvents in addition to the diethyl carbonate and the propyl propionate, as long as the above-mentioned effects are not inhibited.

[0089] For example, the second organic solvent may further contain at least one selected from the group consisting of ethyl methyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, and butyl propionate, in addition to diethyl carbonate and propyl propionate, and in one embodiment, may further contain ethyl methyl carbonate from the viewpoint of improving ionic conductivity.

[0090] The volume ratio of the first organic solvent to the second organic solvent may be about 10:90 to 50:50, for example, about 15:85 to 40:60, or about 15:85 to 35:65. When the volume ratio is within the above range, the nonaqueous electrolyte can achieve high ion transfer properties and an appropriate level of viscosity, while reducing gas generation in the perlithiated manganese-rich oxide and further improving the life performance of the positive and negative electrodes.

[0091] The organic solvent may contain about 10% to 50% by volume of the ethylene carbonate, about 5% to 80% by volume of the diethyl carbonate, and about 5% to 80% by volume of the propyl propionate; for example, about 15% to 40% by volume of the ethylene carbonate, about 8% to 75% by volume of the diethyl carbonate, and about 8% to 75% by volume of the propyl propionate; or about 15% to 35% by volume of the ethylene carbonate, about 30% to 50% by volume of the diethyl carbonate, and about 30% to 50% by volume of the propyl propionate. When the concentrations are within the above ranges, the nonaqueous electrolyte achieves high ion transport properties and an appropriate level of viscosity, while reducing gas generation in the perlithiated manganese-rich oxide and further improving the life performance of the positive and negative electrodes.

[0092] Meanwhile, the organic solvent may be any organic solvent commonly used in non-aqueous electrolytes, without limitation, if necessary, and may include at least one additional organic solvent selected from the group consisting of an ether-based organic solvent, a glyme-based organic solvent, and a nitrile-based organic solvent.

[0093] 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.

[0094] 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.

[0095] 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.

[0096] 3) Additives The non-aqueous electrolyte may further include an additive in addition to the lithium salt and the organic solvent. The additive may be added to the non-aqueous electrolyte to exhibit a scavenging effect for reactive oxygen from the perlithiated manganese-rich oxide, to strengthen the SEI coating of the positive and negative electrodes to prevent gas generation due to electrolyte side reactions, to prevent the non-aqueous electrolyte from decomposing and causing the negative electrode to collapse 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.

[0097] The additive may include at least one selected from the group consisting of coumarine, vinylene carbonate, vinyl ethylene carbonate, fluoroethylene carbonate, propane sultone, propene sultone, succinonitrile, adiponitrile, ethylene sulfate, lithium difluoro phosphate (LiDFP), lithium tetrafluoroborate (LiBF4), lithium difluoro(oxalato)borate (LiODFB), lithium bis-(oxalato)borate (LiBOB), 3-trimethoxysilanyl-propyl-N-aniline (TMSPa), tris(trimethylsilyl)phosphate (TMSPi), and a compound represented by the following chemical formula 1:

[0098] [Chemical formula 1] [ka]

[0099] The additive may include, for example, at least one selected from the group consisting of vinylene carbonate, propane sultone, ethylene sulfate, LiDFP, LiBF4, and the compound represented by Chemical Formula 1.

[0100] The additive may be contained in the non-aqueous electrolyte in an amount of about 0.1% by weight to 15% by weight.

[0101] 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.

[0102] The present invention will be described in more detail below with reference to 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 modifications and variations are possible within the scope and technical concept of the present description, and it goes without saying that such modifications and variations are within the scope of the appended claims.

[0103] Examples and Comparative Examples Example 1 (Production of non-aqueous electrolyte) The organic solvent used was a mixture of ethylene carbonate, diethyl carbonate, and propyl propionate in a volume ratio of 20:40:40.

[0104] A non-aqueous electrolyte was prepared by adding LiPF6 as a lithium salt, vinylene carbonate (VC), propane sultone (PS), ethylene sulfate (ESa), LiDFP, LiBF4 as additives, and the compound represented by Chemical Formula 1 to the organic solvent.

[0105] The LiPF6 was contained in the non-aqueous electrolyte at a molar concentration of 1.2M.

[0106] The non-aqueous electrolyte contained 0.5 wt % vinylene carbonate, 0.8 wt % propane sultone, 1.0 wt % ethylene sulfate, 1.0 wt % LiDFP, 0.5 wt % LiBF, and 0.1 wt % of the compound represented by Chemical Formula 1.

[0107] (Lithium secondary battery manufacturing) Cathode active material (Li 1.3 [Ni 0.35 Mn 0.65 ]O 2.33A cathode mixture slurry (solid content 48 wt%) was prepared by adding a conductive material (carbon nanotubes) and a binder (PVdF) in a weight ratio of 97.4:0.6:2.0 to a solvent, N-methyl-2-pyrrolidone (NMP). The cathode mixture slurry was applied to one side of a 12 μm-thick cathode current collector (Al thin film), dried, and roll-pressed to prepare a cathode.

[0108] Anode active material (a mixture of artificial graphite, natural graphite, and SiO), conductive material (carbon black), and binder (PVdF) were mixed in a weight ratio of 95.7:1.0:3.3 with distilled water as a solvent to prepare anode mixture slurry (solid content 70 wt%). The anode mixture slurry was applied to one side of an 8 μm-thick anode current collector (Cu thin film), dried, and roll-pressed to prepare anode.

[0109] 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.

[0110] Example 2 A lithium secondary battery was produced in the same manner as in Example 1, except that a mixture of ethylene carbonate, diethyl carbonate, and propyl propionate in a volume ratio different from that in Example 1, i.e., 20:10:70, was used as the organic solvent for the non-aqueous electrolyte.

[0111] Example 3 A lithium secondary battery was produced in the same manner as in Example 1, except that a mixture of ethylene carbonate, diethyl carbonate, and propyl propionate in a volume ratio different from that in Examples 1 and 2, i.e., 20:70:10, was used as the organic solvent for the nonaqueous electrolyte.

[0112] Comparative Example 1 A lithium secondary battery was manufactured in the same manner as in Example 1, except that a mixture of ethylene carbonate and diethyl carbonate in a volume ratio of 20:80 was used as the organic solvent for the non-aqueous electrolyte. That is, while ethylene carbonate, diethyl carbonate, and propyl propionate were used as organic solvents in Example 1, in Comparative Example 1, a lithium secondary battery was manufactured using only ethylene carbonate and diethyl carbonate without using propyl propionate as the organic solvent.

[0113] Comparative Example 2 A lithium secondary battery was manufactured in the same manner as in Example 1, except that a mixture of ethylene carbonate and propyl propionate in a volume ratio of 20:80 was used as the organic solvent for the non-aqueous electrolyte. That is, instead of using ethylene carbonate, diethyl carbonate, and propyl propionate as organic solvents in Example 1, in Comparative Example 2, a lithium secondary battery was manufactured using only ethylene carbonate and propyl propionate without using diethyl carbonate as the organic solvent.

[0114] Comparative Example 3 A lithium secondary battery was manufactured in the same manner as in Example 1, except that a mixture of ethylene carbonate and ethyl propionate in a volume ratio of 20:80 was used as the organic solvent for the non-aqueous electrolyte. That is, instead of using ethylene carbonate, diethyl carbonate, and propyl propionate as the organic solvent in Example 1, a lithium secondary battery was manufactured in Comparative Example 3 using ethylene carbonate and ethyl propionate.

[0115] Comparative Example 4 A lithium secondary battery was manufactured in the same manner as in Example 1, except that a mixture of ethylene carbonate and ethyl methyl carbonate in a volume ratio of 20:80 was used as the organic solvent for the non-aqueous electrolyte. That is, instead of using ethylene carbonate, diethyl carbonate, and propyl propionate as the organic solvent in Example 1, a lithium secondary battery was manufactured in Comparative Example 4 using ethylene carbonate and ethyl methyl carbonate.

[0116] Comparative Example 5 A lithium secondary battery was manufactured in the same manner as in Example 1, except that a mixture of ethylene carbonate, dimethyl carbonate, and propyl propionate in a volume ratio of 20:40:40 was used as the organic solvent. That is, in Comparative Example 5, a lithium secondary battery was manufactured using dimethyl carbonate as the organic solvent instead of diethyl carbonate in Example 1.

[0117] Comparative Example 6 A lithium secondary battery was manufactured in the same manner as in Example 1, except that a mixture of ethylene carbonate, ethyl methyl carbonate, and propyl propionate in a volume ratio of 20:40:40 was used as the organic solvent. That is, in Comparative Example 6, a lithium secondary battery was manufactured using ethyl methyl carbonate as the organic solvent instead of diethyl carbonate in Example 1.

[0118] Experimental example Experimental Example 1: Evaluation of high-temperature cycle capacity retention The lithium secondary batteries of Examples 1 to 3 and Comparative Examples 1 to 6 manufactured as described above were charged to 4.35 V, 1 / 40 C under CC / CV, 0.33 C conditions at 45°C using an electrochemical charger / discharger, and then discharged to 2.0 V under CC, 0.33 C conditions, with 200 charge / discharge cycles being considered as one cycle.

[0119] The capacity retention rate was calculated using the following formula, and the results are shown in Table 1 below.

[0120] Capacity retention rate (%) = {(discharge capacity after 200 cycles) / (discharge capacity after 1 cycle)} × 100

[0121] Experimental example 2: Evaluation of volume increase rate after high-temperature cycle charge / discharge The lithium secondary batteries of Examples 1 to 3 and Comparative Examples 1 to 6 manufactured above were subjected to 200 cycles of charge and discharge using an electrochemical charger / discharger in the same manner as in Experimental Example 1. At this time, the volume of the lithium secondary battery before charge and discharge (initial volume) and the volume of the lithium secondary battery after 200 cycles were measured, and the volume increase rate was calculated using the following formula, and the results are shown in Table 1 below.

[0122] Volume increase rate (%) = {(volume of lithium secondary battery after 200 cycles - initial volume) / (initial volume)} × 100

[0123] [Table 1]

[0124] Referring to Table 1, it can be seen that the lithium secondary batteries of Examples 1 to 3, which are lithium secondary batteries combining a positive electrode containing a perlithiated manganese-rich oxide with a non-aqueous electrolyte containing ethylene carbonate, diethyl carbonate, and propyl propionate as organic solvents, have significantly improved capacity retention rates and volume increase rates during high-temperature cycle charge / discharge, compared to Comparative Examples 1 to 6, which were produced without using propyl propionate as the organic solvent or with a combination different from that of Examples 1 to 3.

[0125] Reference example Reference example 1 (1) Production of non-aqueous electrolyte A non-aqueous electrolyte was produced in the same manner as in Example 1.

[0126] (2) Manufacture of lithium secondary batteries Cathode active material (LiNi 0.85 Co 0.05 Mn 0.07 Al 0.03A cathode mixture slurry (solid content 76.5 wt %) was prepared by adding a conductive material (carbon nanotubes) and a binder (polyvinylidene fluoride) in a weight ratio of 98.0:0.7:1.3 to a solvent, N-methyl-2-pyrrolidone (NMP). The cathode mixture slurry was applied to one side of a 12 μm-thick cathode current collector (Al thin film), followed by drying and roll pressing to prepare a cathode. That is, in Reference Example 1, a cathode was prepared using a different type of cathode active material from that used in Example 1, for example, a high-nickel lithium-nickel-cobalt-manganese oxide.

[0127] Anode active material (artificial graphite), conductive material (carbon black), and binder (styrene-butadiene rubber) were mixed in a weight ratio of 96.5:1.5:2.0 with distilled water as a solvent to prepare anode mixture slurry (solid content 50 wt%). The anode mixture slurry was applied to one side of an 8 μm-thick anode current collector (Cu thin film), dried, and roll-pressed to prepare anode.

[0128] 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.

[0129] Reference example 2 A lithium secondary battery was produced in the same manner as in Reference Example 1, except that the nonaqueous electrolyte produced in Comparative Example 1 was used instead of the nonaqueous electrolyte produced in Example 1.

[0130] Reference example 3 A lithium secondary battery was produced in the same manner as in Reference Example 1, except that the nonaqueous electrolyte produced in Comparative Example 2 was used instead of the nonaqueous electrolyte produced in Example 1.

[0131] Reference Experiment Example 1: Evaluation of High-Temperature Cycle Capacity Retention Rate The lithium secondary batteries of Reference Examples 1 to 3 manufactured above were charged to 4.2 V, 1 / 40 C under CC / CV, 0.33 C conditions at 45°C, and then discharged to 2.5 V at 0.33 C using an electrochemical charger / discharger, and 200 charge / discharge cycles were carried out.

[0132] The capacity retention rate was calculated using the following formula, and the results are shown in Table 2 below.

[0133] Capacity retention rate (%) = {(discharge capacity after 200 cycles) / (discharge capacity after 1 cycle)} × 100

[0134] Reference Experiment Example 2: Evaluation of volume increase rate after high-temperature cycle charge / discharge The lithium secondary batteries of Reference Examples 1 to 3 manufactured above were subjected to 200 cycles of charge and discharge using an electrochemical charger / discharger in the same manner as in Reference Experimental Example 1. At this time, the volume of the lithium secondary battery before charge and discharge (initial volume) and the volume of the lithium secondary battery after 200 cycles were measured, and the volume increase rate was calculated using the following formula. The results are shown in Table 2 below.

[0135] Volume increase rate (%) = {(volume of lithium secondary battery after 200 cycles - initial volume) / (initial volume)} × 100

[0136] [Table 2]

[0137] Referring to Table 2, the secondary battery of Reference Example 1, which used a high-nickel lithium nickel-cobalt manganese oxide as the positive electrode active material, showed poor effects in not only the capacity retention rate but also the volume increase rate, despite containing an organic solvent containing all of ethylene carbonate, diethyl carbonate, and propyl propionate in the non-aqueous electrolyte, compared to the secondary battery of Reference Example 2, which used only ethylene carbonate and diethyl carbonate as the organic solvent. This shows that when perlithiated manganese-rich oxide is not used as the positive electrode active material, the effect of using a combination of ethylene carbonate, diethyl carbonate, and propyl propionate as the organic solvent is limited compared to when perlithiated manganese-rich oxide is used as the positive electrode active material.

[0138] Furthermore, when comparing Reference Examples 2 and 3, it can be seen that when a high-nickel-content lithium nickel cobalt manganese oxide is used as the positive electrode active material instead of a perlithiated manganese-rich oxide, the use of propyl propionate as an organic solvent contributes only to limited effects such as improving the cycle life of the manufactured lithium secondary battery and preventing cell volume expansion.

[0139] Although the present invention has been described above with reference to preferred embodiments, it will be understood that those skilled in the art or those having ordinary knowledge in the art can make various modifications and changes to the present invention without departing from the spirit and technical scope of the present invention as defined in the appended claims. Therefore, the technical scope of the present invention is not limited to the contents described in the detailed description of the specification, but is determined solely by the claims.

Claims

1. a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte; the positive electrode includes a positive electrode active material, the positive electrode active material contains 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 greater than 1; the non-aqueous electrolyte contains a lithium salt and an organic solvent; the organic solvent comprises a first organic solvent and a second organic solvent; the first organic solvent comprises ethylene carbonate; The second organic solvent includes diethyl carbonate and propyl propionate.

2. 2. The lithium secondary battery according to claim 1, wherein the perlithiated manganese-rich oxide is a compound represented by the following chemical formula A: [Chemical formula A] Li １＋ｓ [Ni ｔ Co ｕ Mn ｖ M １ ｗ ]O ２＋ｚ (In the above chemical formula A, 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; 0.05≦s≦1, 0≦t≦0.5, 0≦u≦0.3, 0.5≦v<1.0, 0≦w≦0.2, 0≦z≦1.)

3. 2. The lithium secondary battery according to claim 1, wherein a volume ratio of the first organic solvent to the second organic solvent is 10:90 to 50:

50.

4. 2. The lithium secondary battery according to claim 1, wherein the volume ratio of the diethyl carbonate and the propyl propionate is 1:99 to 99:

1.

5. 2. The lithium secondary battery according to claim 1, wherein a volume ratio of said diethyl carbonate and said propyl propionate is 12:88 to 88:

12.

6. 2. The lithium secondary battery according to claim 1, wherein the organic solvent comprises 10% by volume to 50% by volume of the ethylene carbonate, 5% by volume to 80% by volume of the diethyl carbonate, and 5% by volume to 80% by volume of the propyl propionate.

7. 2. The lithium secondary battery according to claim 1, wherein the second organic solvent further comprises at least one selected from the group consisting of ethyl methyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, and butyl propionate.

8. The lithium secondary battery according to claim 1 , wherein the second organic solvent further comprises ethyl methyl carbonate.

9. The non-aqueous electrolyte further contains an additive, The additives include coumarin, vinylene carbonate, vinyl ethylene carbonate, fluoroethylene carbonate, propane sultone, propene sultone, succinonitrile, adiponitrile, ethylene sulfate, LiDFP (lithium difluorophosphate), and LiBF. ４ 2. The lithium secondary battery of claim 1, comprising at least one selected from the group consisting of Lithium tetrafluoroborate (LiODFB), Lithium difluoro(oxalato)borate (LiBOB), Lithium bis-(oxalato)borate (LiBOB), 3-trimethoxysilanyl-N-aniline (TMSPa), Tris(trimethylsilyl)phosphate (TMSPi), and a compound represented by the following Chemical Formula 1: [Chemical formula 1] 【Chemistry 1】

10. 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 lithium secondary battery according to claim 1, comprising at least one selected from the group consisting of:

11. 2. The lithium secondary battery 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.

12. the negative electrode includes a negative electrode active material, 2. The lithium secondary battery according to claim 1, wherein the negative electrode active material comprises at least one selected from a carbon-based active material and a (quasi-)metal-based active material.

13. placing an electrode assembly including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode in a battery case; and injecting a non-aqueous electrolyte into the battery case containing the electrode assembly. the positive electrode includes a positive electrode active material, the positive electrode active material contains 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 greater than 1; the non-aqueous electrolyte contains a lithium salt and an organic solvent; the organic solvent comprises a first organic solvent and a second organic solvent; the first organic solvent comprises ethylene carbonate; The method for manufacturing a lithium secondary battery, wherein the second organic solvent contains diethyl carbonate and propyl propionate.

14. The method for producing a lithium secondary battery according to claim 13, wherein the perlithiated manganese-rich oxide is a compound represented by the following chemical formula A: [Chemical formula A] Li １＋ｓ [Ni ｔ Co ｕ Mn ｖ M １ ｗ ]O ２＋ｚ (In the above chemical formula A, 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; 0.05≦s≦1, 0≦t≦0.5, 0≦u≦0.3, 0.5≦v<1.0, 0≦w≦0.2, 0≦z≦1.)

15. The method for producing a lithium secondary battery according to claim 13, wherein a volume ratio of the first organic solvent to the second organic solvent is 10:90 to 50:

50.

16. The method for producing a lithium secondary battery according to claim 13, wherein the volume ratio of the diethyl carbonate to the propyl propionate is 1:99 to 99:

1.

17. The method for producing a lithium secondary battery according to claim 13, wherein a volume ratio of the diethyl carbonate to the propyl propionate is 12:88 to 88:

12.

18. 14. The method for producing a lithium secondary battery according to claim 13, wherein the organic solvent contains 10% by volume to 50% by volume of the ethylene carbonate, 5% by volume to 80% by volume of the diethyl carbonate, and 5% by volume to 80% by volume of the propyl propionate.

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