Lithium secondary battery and method for manufacturing the lithium secondary battery

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 the contents disclosed in the documents of the Korean patent applications are incorporated herein by reference.

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

Background Art

[0003] In recent years, the application fields of lithium secondary batteries have rapidly expanded not only to power supply for electronic devices such as electric, electronic, communication, and computer devices, but also to power storage and power supply for large-area devices such as automobiles and power storage devices. Along with this, the need for secondary batteries with high capacity, high output, and high stability has been increasing.

[0004] A lithium secondary battery generally includes 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 transmitting lithium ions, and a separator. At this time, as the negative electrode active material, a carbon-based active material, a silicon-based active material, etc. can be used. Also, as the positive electrode active material, lithium transition metal oxides such as lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), and lithium nickel-cobalt-manganese composite oxide can be used.

[0005] On the other hand, in order to configure a high-capacity secondary battery, improvements have been made to the characteristics of each of the positive electrode, negative electrode, electrolyte, and separator.

Summary of the Invention

Problems to be Solved by the Invention

[0006] One object of the present invention is to provide a lithium secondary battery containing a hyperlithiated manganese-rich oxide as a positive electrode active material, which reduces the amount of gas generation such as CO2 at the positive electrode interface during high voltage or high temperature driving, reduces gas generation during initial activation and charge / discharge, and suppresses the elution of transition metals from the positive electrode active material, thereby improving both the high-temperature life, resistance reduction, and gas generation prevention effects.

Means for Solving the Problems

[0007] One embodiment of the present invention includes 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 contains a positive electrode active material, and the positive electrode active material contains at least about 50 mol% of Mn in all metals excluding lithium and includes a hyperlithiated manganese-rich oxide in which the molar ratio of lithium to transition metal exceeds about 1. The non-aqueous electrolyte contains a lithium salt and an organic solvent, the organic solvent contains a first organic solvent and a second organic solvent, the first organic solvent contains ethylene carbonate, and the second organic solvent contains diethyl carbonate and propyl propionate, thereby providing a lithium secondary battery.

Effect of the Invention

[0008] The lithium secondary battery according to one embodiment of the present invention uses a hyperlithiated manganese-rich oxide as a positive electrode active material, and is characterized in that the organic solvent contained in the non-aqueous electrolyte contains ethylene carbonate, diethyl carbonate, and propyl propionate. According to one embodiment of the present invention, the above combination of organic solvents significantly reduces the amount of gas generation at the positive electrode interface containing the hyperlithiated manganese-rich oxide, improves the life performance of the negative electrode, and as a result, a lithium secondary battery having excellent capacity retention and gas generation reduction performance can be realized. The lithium secondary battery according to one embodiment of the present invention can particularly have excellent life performance and gas reduction performance at high temperature and high voltage.

Mode for Carrying Out the Invention

[0009] The terms and words used in this specification and in the claims should not be interpreted in a manner limited to their ordinary or dictionary meanings, but rather in a manner consistent with the technical idea of ​​the present invention, in accordance with the principle that inventors may appropriately define the concepts of terms in order to best describe their invention.

[0010] In this specification, terms such as “includes,” “equip,” or “have” are intended to specify the presence of implemented features, figures, steps, components, or combinations thereof, and should be understood not to preemptively exclude the presence or possibility of adding one or more other features, figures, 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 The particle size can be measured, for example, by laser diffraction. This laser diffraction method can generally measure particle sizes from the submicron region to several millimeters in size, and can yield highly reproducible and high-resolution results.

[0012] As used herein, “approximately,” “abstractly,” and “substantially” are used to mean a range of numerical values ​​or degrees, or close to them, taking into account inherent manufacturing and material tolerances, and are used to prevent infringers from unfairly exploiting disclosures that refer to precise or absolute numerical values ​​provided for the understanding of the invention.

[0013] Perlithiated manganese-rich oxides are attracting attention as next-generation positive electrode active materials for constructing high-capacity batteries. Perlithiated manganese-rich oxides have a higher content of manganese (Mn), which is relatively inexpensive and abundant in reserves, and lithium secondary batteries using them have the advantage of high capacity. However, when using such perlithiated manganese-rich oxides, there is a problem in that the amount of gases such as CO2 generated due to electrolyte side reactions at the positive electrode interface increases significantly when operated at high voltage (e.g., 4.35V or higher) or high temperature. In addition, the use of perlithiated manganese-rich oxides is limited due to problems such as the decomposition of the electrolyte by reactive oxygen generated by the phase conversion of the positive electrode active material during the activation (formation) and charge / discharge processes, which greatly increases the amount of gases such as CO2, and the electrodeposition of transition metals dissolved from the positive electrode active material onto the negative electrode, which destroys the SEI (Solid Electrolyte Interphase) coating of the negative electrode.

[0014] The present invention provides a lithium secondary battery that overcomes the aforementioned gas generation problem and the problem of SEI film breakdown on the negative electrode, while applying a perlithitated manganese-rich oxide as the positive electrode active material.

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

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

[0017] The present invention provides a lithium secondary battery comprising a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte, wherein the positive electrode comprises a positive electrode active material, the positive electrode active material comprises a perlithitated manganese-rich oxide containing about 50 mol% or more of Mn in the total metals excluding lithium, and having a molar ratio of lithium to transition metals of about 1 or more, the non-aqueous electrolyte comprises 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, and the second organic solvent comprises 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 housing an electrode assembly including the positive electrode, a 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 a non-aqueous electrolyte into the battery case.

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

[0020] In one embodiment, the positive electrode active material includes a perlithitated manganese-rich oxide. The perlithitated manganese-rich oxide contains about 50 mol% or more of Mn in the total metal excluding lithium, and the molar ratio of lithium to the transition metal may exceed about 1.

[0021] The aforementioned perlithitated manganese-rich oxide is attracting attention as a next-generation high-capacity cathode active material, but its use is limited due to the inherent structural degradation of the material. For example, when perlithitated manganese-rich oxide is used as a cathode active material, electrolyte side reactions occur at the cathode interface, leading to a significant increase in the generation of gases such as carbon dioxide (CO2). Furthermore, during the initial activation of lithium secondary batteries containing perlithitated manganese-rich oxide, the reactive oxygen released from the perlithitated manganese-rich oxide decomposes and consumes organic solvents (such as ethylene carbonate) contained in the non-aqueous electrolyte, generating gas byproducts, which leads to problems such as reduced lifespan and performance, increased resistance, and reduced safety. In addition, during the charge-discharge process of lithium secondary batteries containing perlithitated manganese-rich oxide, manganese (Mn) is leached out to achieve charge balance due to the release of reactive oxygen. In this process, the eluted manganese electrodeposits onto the negative electrode, causing damage to the SEI (Solid Electrolyte Interphase) coating. Furthermore, reactive oxygen released during the charge-discharge process continuously decomposes and consumes the organic solvent in the non-aqueous electrolyte, increasing the generation of gas byproducts. This consumption of the non-aqueous electrolyte, structural breakdown of the overlithified manganese-rich oxide, and increased gas byproducts significantly degrade the lifespan, resistance characteristics, and safety of the lithium-ion secondary battery. These problems are exacerbated under high-temperature and high-voltage conditions.

[0022] To solve such problems, a lithium secondary battery according to an embodiment of the present invention is characterized in that, as described below, as an organic solvent of a non-aqueous electrolyte, it contains ethylene carbonate, diethyl carbonate, and propyl propionate. According to an embodiment of the present invention, due to the above combination of organic solvents, the amount of gas generated at the positive electrode interface containing over-lithiated manganese-rich oxide is significantly reduced, the life performance of the negative electrode is improved, and as a result, a lithium secondary battery having excellent capacity retention rate and gas generation reduction performance can be realized compared with a conventional lithium secondary battery. The lithium secondary battery according to an embodiment of the present invention can particularly have excellent life performance and gas reduction performance at high temperature and high voltage.

[0023] The over-lithiated manganese-rich oxide may contain 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 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, 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. For example, in the chemical formula A, 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 may be satisfied. Or, 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, 0 ≦ z ≦ 0.50 may be satisfied.

[0026] In one embodiment, the over-lithiated manganese-rich oxide may contain a compound represented by the following chemical 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 aforementioned chemical formula B, 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 the chemical formula B, 0.1≦X≦0.5, 0.5≦y<1, 0≦z≦0.3, and 0≦w≦0.2 may be, 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 side of the positive electrode current collector. In this case, the positive electrode active material is included 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 contain at least one selected from the group consisting of copper, stainless steel, aluminum, nickel, titanium, calcined carbon, and aluminum-cadmium alloy, or in one embodiment, it may contain aluminum.

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

[0032] The positive electrode current collector may have fine irregularities formed on its surface to strengthen the bonding force of the positive electrode active material. For example, the positive electrode current collector can be used in various forms such as film, sheet, foil, mesh, porous material, foam, or nonwoven fabric.

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

[0034] The positive electrode active material may be included in the positive electrode active material layer in an amount of approximately 80% to 99% by weight, for example, approximately 92% to 98.5% by weight, taking into consideration the sufficient capacity of the positive electrode active material.

[0035] Furthermore, the explanation of the positive electrode active material has been given above, so it will be omitted here.

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

[0037] The binder is a component that assists in the binding of the active material to the conductive material and to the current collector, and may include, for example, at least one selected from the group consisting of polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, and fluororubber, or in one embodiment, it may include polyvinylidene fluoride.

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

[0039] The conductive material is used to assist and improve the conductivity of a secondary battery and is not particularly limited as long as it does not cause chemical changes and is conductive. For example, the positive electrode conductive material may include at least one selected from the group consisting of graphite such as natural graphite or 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, carbon nanotubes may be included to improve conductivity.

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

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

[0042] The positive electrode can be manufactured by coating a positive electrode slurry containing a positive electrode active material, and selectively a binder, a conductive material, and a solvent for forming the positive electrode slurry onto the positive electrode current collector, followed by drying and rolling.

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

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

[0045] The aforementioned negative electrode contains 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 carbon-based active materials, (quasi)metallic active materials, and lithium metal. For example, it may include at least one selected from carbon-based active materials and (quasi)metallic active materials.

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

[0048] The average particle size (D) of the carbon-based active material 50 The thickness of the ) can be approximately 10 μm to 30 μm, for example, approximately 15 μm to 25 μm, in order to ensure structural stability during charging and discharging and to 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)metallic element 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)metallic metal and lithium may include an alloy of lithium with at least one (quasi)metallic 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)metallic oxide may include at least one (quasi)metallic oxide 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 The compound may be represented by (0≦x<2). Since SiO2 does not react with lithium ions and therefore cannot store lithium, x is selected to be within the above range that does not include 2, and in one embodiment, the silicon-based active material may be SiO.

[0055] The average particle size (D) of the silicon-based active material 50 The thickness of the ) can be approximately 1 μm to 30 μm, for example, approximately 2 μm to 15 μm, in order to ensure structural stability during charging and discharging and to 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 side of the negative electrode current collector. In this case, the negative electrode active material is included 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, calcined carbon, copper or stainless steel with a surface treatment of carbon, nickel, titanium, silver, etc., or an aluminum-cadmium alloy.

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

[0059] The negative electrode current collector may have fine irregularities formed on its surface to strengthen the bonding force of the negative electrode active material. For example, the negative electrode current collector can be used in various forms such as film, sheet, foil, mesh, porous material, foam, or nonwoven fabric.

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

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

[0062] Furthermore, the explanation of the negative electrode active material has been given above, so it will be omitted here.

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

[0064] The binder is used to improve the performance of the battery by improving the adhesion between the negative electrode active material layer and the negative electrode current collector, and may contain, for example, at least one selected from the group consisting of polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethyl methacrylate, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, and substances in which the hydrogen of these substances is substituted with Li, Na, or Ca, or may contain various copolymers thereof.

[0065] The binder may be present in the negative electrode active material layer in an amount of about 0.5% to 10% by weight, for example, about 1% 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. Examples include graphite such as natural graphite or 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.

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

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

[0069] The negative electrode can be manufactured 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 contain, for example, at least one selected from the group consisting of distilled water, NMP (N-methyl-2-pyrrolidone), ethanol, methanol, and isopropyl alcohol, or in one embodiment, distilled water, from the viewpoint of facilitating the dispersion of the negative electrode active material, binder, and / or conductive material. The solid content of the negative electrode slurry may be about 30% to 80% by weight, for example, about 40% to 70% by weight.

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

[0072] Furthermore, the separator may be a conventional porous polymer film, such as a porous polymer film made from polyolefin polymers like ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, used alone or in a laminated configuration. Alternatively, a conventional porous nonwoven fabric, such as a nonwoven fabric made from high-melting-point glass fibers or polyethylene terephthalate fibers, may be used, but is not limited to these. In addition, a coated separator containing ceramic components or polymeric substances may be used to ensure heat resistance or mechanical strength, and may be selectively used as a single-layer or multi-layer structure.

[0073] (4) Non-aqueous electrolytes The non-aqueous electrolyte comprises a lithium salt and an organic solvent.

[0074] 1) Lithium salt The lithium salt used in this invention is not limited to any particular type of lithium salt commonly used in non-aqueous electrolytes for lithium secondary batteries. For example, the lithium salt may contain Li as a cation. + It includes, 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 - It may include at least one selected from the group consisting of the following.

[0075] For example, the lithium salts are LiCl, LiBr, LiI, LiBF4, LiClO4, LiAlO4, LiAlCl4, LiPF6, LiSbF6, LiAsF6, LiB 10 Cl 10 The lithium salt may include at least one selected from the group consisting of 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 included 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 the degree of lithium ion dissociation are improved, which can enhance the battery's output characteristics.

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

[0078] The first organic solvent contains ethylene carbonate.

[0079] The ethylene carbonate is a highly viscous organic solvent that has a high dielectric constant and can function as an organic solvent that readily dissociates lithium salts in electrolytes.

[0080] The first organic solvent may, but is not limited to, further include, 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, together with the ethylene carbonate.

[0081] The second organic solvent comprises diethyl carbonate and propyl propionate. In a lithium secondary battery according to one embodiment of the present invention, by using a combination of diethyl carbonate and propyl propionate as the second organic solvent, the amount of gas generated when a perlithiated manganese-rich oxide is used as the positive electrode component can be significantly reduced, and the life performance of the lithium secondary battery can be significantly improved.

[0082] For example, even when propylpropionate decomposes, it generates less carbon dioxide (CO2) compared to when other organic solvents such as ethyl methyl carbonate are used. Furthermore, because propylpropionate has low reactivity with reactive oxygen that can be released from perlithiated manganese-rich oxides, the amount of gas generated can be further reduced. In other words, using propylpropionate yields even better results compared to using other ester-based solvents such as ethylpropionate, which have lower oxidation stability than propylpropionate. On the other hand, although propylpropionate is used as the second organic solvent in this embodiment, it is not limited to this, and any solvent that can reduce the amount of carbon dioxide (CO2) generated when a perlithiated manganese-rich oxide is used as the positive electrode component and has low reactivity with reactive oxygen that can be released from the perlithiated manganese-rich oxide can be used as the second organic solvent.

[0083] However, despite the advantages mentioned above, propylpropionate has low reduction stability and may lead to reduced lifespan due to decomposition at the negative electrode. Therefore, rather than using propylpropionate alone as the second organic solvent component, these drawbacks can be overcome by using it in combination with other solvents, for example.

[0084] In one embodiment, the present invention uses diethyl carbonate as a component of the second organic solvent together with propyl propionate. Since 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 exhibited. Thus, in one embodiment, by using the first organic solvent (containing ethylene carbonate) and the second organic solvent (containing diethyl carbonate and propyl propionate), it is possible to have an excellent volume retention rate, reduce the amount of gas generated, and prevent, for example, cell volume expansion. In one embodiment, diethyl carbonate is applied together with propyl propionate as the second organic solvent, but the invention is not limited to this, and 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, rather than diethyl carbonate, have low oxidation stability and are highly reactive to reactive oxygen derived from perlithiated manganese-rich oxides, making them prone to decomposition and potentially leading to gas generation and increased resistance. However, if these problems can be adequately overcome, they can be used as a secondary organic solvent together with propyl propionate.

[0086] As described above, the effects of one embodiment of the present invention, such as the reduction in gas generation in lithium secondary batteries, are effects that specifically appear when a perlithitated 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-containing lithium nickel manganese cobalt transition metal oxides (for example, NCM-based active materials containing 80 mol% or more of Ni in the transition metal), where the generation of reactive oxygen and excessive dissolution of Mn are not major problems.

[0087] In one embodiment, the volume ratio of diethyl carbonate to 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 ratio is within the above range, it is possible to suppress gas generation at high temperatures in the lithium secondary battery and achieve capacity maintenance by ensuring the stability of the negative electrode, as described above.

[0088] The second organic solvent may further contain other additional second organic solvents together with the diethyl carbonate and the propyl propionate, as long as they do not inhibit the effects described above.

[0089] For example, the second organic solvent may further include, along with diethyl carbonate and propyl propionate, at least one selected from the group consisting of ethyl methyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, and ethyl propyl carbonate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, and butyl propionate, and in one embodiment, ethyl methyl carbonate may be further included to improve 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. Within this range, high ion transfer characteristics and an appropriate level of viscosity can be achieved for the non-aqueous electrolyte, while reducing gas generation in the aforementioned perlithiated manganese-rich oxide and further improving the life performance of the positive / negative electrodes.

[0091] Furthermore, the organic solvent may contain about 10% to 50% by volume of ethylene carbonate, about 5% to 80% by volume of diethyl carbonate, and about 5% to 80% by volume of propyl propionate; for example, it may contain about 15% to 40% by volume of ethylene carbonate, about 8% to 75% by volume of diethyl carbonate, and about 8% to 75% by volume of propyl propionate; or it may contain about 15% to 35% by volume of ethylene carbonate, about 30% to 50% by volume of diethyl carbonate, and about 30% to 50% by volume of propyl propionate. When the concentrations are within the above ranges, high ion transfer characteristics and appropriate levels of viscosity can be achieved with non-aqueous electrolytes, while reducing gas generation in the aforementioned perlithitated manganese-rich oxide and further improving the lifespan of the positive / negative electrodes.

[0092] On the other hand, the organic solvent may be used in addition to any organic solvent commonly used with non-aqueous electrolytes, if necessary. For example, the organic solvent may include at least one additional organic solvent from among ether-based organic solvents, glyme-based solvents, and nitrile-based organic solvents.

[0093] The ether-based solvent can 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 to these.

[0094] The aforementioned glyme-based solvent is a solvent that has a higher dielectric constant and lower surface tension than linear carbonate-based organic solvents, and has low reactivity with metals, and may include, but is not limited to, at least one selected from the group consisting of dimethoxyethane (glyme, DME), diethoxyethane, diglylme, triglyme, and tetraglyme (TEGDME).

[0095] The nitrile solvent may be one or more selected from the group consisting of acetonitrile, propionitrile, butyronitrile, valeronitrile, caprylonitrile, heptanenitrile, cyclopentanecarbonile, cyclohexanecarbonile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2-fluorophenylacetonitrile, and 4-fluorophenylacetonitrile, but is not limited to these.

[0096] 3) Additives The non-aqueous electrolyte may further contain additives along with the lithium salt and the organic solvent. These additives may be included in the non-aqueous electrolyte to provide a scavenging effect for reactive oxygen of the perlithitated manganese-rich oxide, to strengthen the SEI coating on the positive / negative electrodes to prevent gas generation due to electrolyte side reactions, to prevent the non-aqueous electrolyte from decomposing and causing negative electrode collapse in high-power environments, or to provide low-temperature high-rate discharge characteristics, high-temperature stability, overcharge prevention, and suppression of battery swelling at high temperatures.

[0097] The aforementioned additive may include at least one selected from the group consisting of coumarin, vinylene carbonate, vinyl ethylene carbonate, fluoroethylene carbonate, propane sultone, propene sultone, succinonitrile, adiponitrile, ethylene sulfate, LiDFP (Lithium difluoro phosphate), LiBF4 (Lithium tetrafluoroborate), LiODFB (Lithium difluoro(oxalato)borate), LiBOB (Lithium bis-(oxalato)borate), TMSPa (3-trimethoxysilanyl-propyl-N-aniline), TMSPi (Tris(trimethylsilyl)Phosphite), 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 the chemical formula 1.

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

[0101] The external shape of the lithium secondary battery of the present invention is not particularly limited, but may be cylindrical, rectangular, pouch-shaped, or coin-shaped, using a can.

[0102] The present invention will be described more specifically below with reference to examples. However, the following examples are merely illustrative for understanding the present invention and do not limit its scope. It will be obvious to those skilled in the art that various modifications and alterations are possible within the scope and technical concept described herein, and it goes without saying that such modifications and alterations fall within the scope of the appended claims.

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

[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, and the compound represented by chemical formula 1 to the aforementioned organic solvent.

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

[0106] Furthermore, the non-aqueous electrolyte was configured to contain 0.5% by weight of vinylene carbonate, 0.8% by weight of propane sultone, 1.0% by weight of ethylene sulfate, 1.0% by weight of LiDFP, 0.5% by weight of LiBF, and 0.1% by weight of the compound represented by chemical formula 1.

[0107] (Manufacturing of lithium-ion batteries) Cathode active material (Li 1.3 [Ni 0.35 Mn 0.65 ]O 2.33A cathode mixture slurry (48% solids by weight) was prepared by adding perlithiated manganese-rich oxide, a conductive material (carbon nanotubes), and a binder (PVdF) in a weight ratio of 97.4:0.6:2.0 to the solvent N-methyl-2-pyrrolidone (NMP). The cathode mixture slurry was applied to one surface of a 12 μm thick cathode current collector (a thin Al film), and the cathode was manufactured by drying and roll pressing.

[0108] A negative electrode slurry (70% solids by weight) was prepared by adding a negative electrode active material (a mixture of artificial graphite, natural graphite, and SiO), a conductive material (carbon black), and a binder (PVdF) in a weight ratio of 95.7:1.0:3.3 to distilled water, which was used as a solvent. The negative electrode slurry was applied to one surface of a negative electrode current collector (a thin film of Cu) with a thickness of 8 μm, and the negative electrode was manufactured by drying and roll pressing.

[0109] In a dry room, a polyethylene porous film separator was interposed between the positive electrode and negative electrode manufactured as described above, and then the non-aqueous electrolyte manufactured as described above was injected to produce a secondary battery.

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

[0111] Example 3 A lithium secondary battery was manufactured in the same manner as in Example 1, except that a mixture of ethylene carbonate, diethyl carbonate, and propyl propionate was used as the organic solvent for the non-aqueous electrolyte in a different proportion than that described in Examples 1 and 2, namely, a volume ratio of 20:70:10.

[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, in Comparative Example 1, ethylene carbonate, diethyl carbonate, and propyl propionate were used as organic solvents, while in Comparative Example 1, propyl propionate was not used as an organic solvent, and only ethylene carbonate and diethyl carbonate were used to manufacture the lithium secondary battery.

[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, in Comparative Example 2, instead of using ethylene carbonate, diethyl carbonate, and propyl propionate as organic solvents in Example 1, diethyl carbonate was not used as an organic solvent, and only ethylene carbonate and propyl propionate were used to manufacture the lithium secondary battery.

[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, in Comparative Example 3, ethylene carbonate and ethyl propionate were used instead of ethylene carbonate, diethyl carbonate, and propyl propionate as organic solvents in Example 1 to manufacture the lithium secondary battery.

[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, in Comparative Example 4, ethylene carbonate and ethyl methyl carbonate were used instead of ethylene carbonate, diethyl carbonate, and propyl propionate as organic solvents in Example 1 to manufacture the lithium secondary battery.

[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. In other words, in Comparative Example 5, a lithium secondary battery was manufactured using dimethyl carbonate as the organic solvent instead of diethyl carbonate as 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. In other words, in Comparative Example 6, a lithium secondary battery was manufactured using ethyl methyl carbonate as the organic solvent instead of diethyl carbonate as in Example 1.

[0118] Experimental example Experimental Example 1: Evaluation of High-Temperature Cycle Capacity Maintenance Rate The lithium secondary batteries of Examples 1-3 and Comparative Examples 1-6, manufactured as described above, were charged to 4.35V and 1 / 40C at 45°C under CC / CV and 0.33C conditions using an electrochemical charge / discharger, and then discharged to 2.0V under CC and 0.33C conditions. One cycle was defined as this charge / discharge cycle, and 200 cycles were performed.

[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 1-3 and Comparative Examples 1-6, manufactured as described above, were charged and discharged 200 times using an electrochemical charger in the same manner as in Experimental Example 1. During this process, the volume of the lithium secondary battery before charging and discharging (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 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 above, it can be seen that the lithium secondary batteries of Examples 1 to 3, which are lithium secondary batteries in which a positive electrode containing a perlithitated manganese-rich oxide is combined with a non-aqueous electrolyte containing ethylene carbonate, diethyl carbonate, and propyl propionate as organic solvents, show a significant improvement in both capacity retention rate and volume increase rate during high-temperature cycle charge-discharge compared to Comparative Examples 1 to 6, which were manufactured either without using propyl propionate as an organic solvent or with a different combination than that of Examples 1 to 3.

[0125] Reference example Reference example 1 (1) Production of non-aqueous electrolytes A non-aqueous electrolyte was prepared using the same method as in Example 1.

[0126] (2) Manufacturing 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% by weight) was prepared by adding O2, a conductive material (carbon nanotube), and a binder (polyvinylidene fluoride) in a weight ratio of 98.0:0.7:1.3 to the solvent N-methyl-2-pyrrolidone (NMP). The cathode mixture slurry was applied to one surface of a 12 μm thick cathode current collector (Al thin film), and the cathode was manufactured by drying and roll pressing. In other words, in Reference Example 1, a cathode was manufactured using a different type of cathode active material than that used in Example 1, for example, high nickel-containing lithium nickel cobalt manganese oxide as the cathode active material.

[0127] A negative electrode slurry (50% solids by weight) was prepared by adding a negative electrode active material (artificial graphite), a conductive material (carbon black), and a binder (styrene-butadiene rubber) in a weight ratio of 96.5:1.5:2.0 to distilled water, which was used as a solvent. The negative electrode slurry was applied to one surface of a negative electrode current collector (Cu thin film) with a thickness of 8 μm, and the negative electrode was manufactured by drying and roll pressing.

[0128] In a dry room, a polyethylene porous film separator was interposed between the positive electrode and negative electrode manufactured as described above, and then the non-aqueous electrolyte manufactured as described above was injected to produce a secondary battery.

[0129] Reference example 2 A lithium secondary battery was manufactured in the same manner as in Reference Example 1, except that a non-aqueous electrolyte manufactured in Comparative Example 1 was used instead of the non-aqueous electrolyte manufactured in Example 1.

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

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

[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 1-3, manufactured as described above, were charged and discharged 200 times using an electrochemical charger in the same manner as in Reference Experiment Example 1. During this process, the volume of the lithium secondary battery before charging and discharging (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 above, the secondary battery of Reference Example 1, which used high-nickel lithium nickel-cobalt manganese oxide as the positive electrode active material, showed poor performance in both capacity retention and volume increase compared to the secondary battery of Reference Example 2, which used only ethylene carbonate and diethyl carbonate as the organic solvent, despite containing organic solvents containing ethylene carbonate, diethyl carbonate, and propyl propionate as the non-aqueous electrolyte. From this, it can be seen 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, comparing Reference Examples 2 and 3, it can be confirmed that when using high-nickel-containing lithium nickel cobalt manganese oxide as the positive electrode active material instead of perlithitated manganese-rich oxide, using propyl propionate as the organic solvent contributes only to limited effects such as preventing the cycle life and cell volume expansion of the manufactured lithium secondary battery.

[0139] Although preferred embodiments of the present invention have been described above with reference to the present invention, those skilled in the art, or those with ordinary skill in the art, will understand that they can modify and change the present invention in various ways without departing from the spirit and technical scope of the invention as set forth in the appended claims. Therefore, the technical scope of the present invention is not limited to what is described in the detailed description of the specification, but is determined solely by the claims.

Claims

1. It comprises 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 50 mol% or more of Mn in the total metal excluding lithium, and includes a perlithitated manganese-rich oxide in which the molar ratio of lithium to the transition metal is greater than 1. The non-aqueous electrolyte comprises a lithium salt and an organic solvent. The aforementioned organic solvent includes a first organic solvent and a second organic solvent. The first organic solvent comprises ethylene carbonate, The second organic solvent is a lithium secondary battery comprising diethyl carbonate and propylpropionate.

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

50.

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

1.

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

12.

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

7. The lithium secondary battery according to claim 1 or 2, 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, and 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 or 2, wherein the second organic solvent further comprises ethyl methyl carbonate.

9. The nonaqueous electrolyte further contains additives, The additives include at least one selected from the group consisting of coumarin, vinylene carbonate, vinyl ethylene carbonate, fluoroethylene carbonate, propane sultone, propene sultone, succinonitrile, adiponitrile, ethylene sulfate, LiDFP (lithium difluoro phosphate), LiBF ４ (lithium tetrafluoroborate), LiODFB (lithium difluoro(oxalato)borate), LiBOB (lithium bis-(oxalato)borate), TMSPA (3-trimethoxysilyl-propyl-N-aniline), TMSPi (Tris(trimethylsilyl)Phosphite), and the compound represented by the following Chemical Formula 1, the lithium secondary battery according to Claim 1 or 2. [Chemical formula 1] 【Chemistry 1】

10. The lithium secondary battery according to claim 9, wherein the additive comprises a compound represented by the chemical formula 1.

11. The lithium salts mentioned above are 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 A lithium secondary battery according to claim 1 or 2, comprising at least one selected from the group consisting of ).

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

13. A lithium secondary battery according to claim 1 or 2, wherein one cycle is defined as charging to 4.35V and 1 / 40C at 45°C under CC / CV and 0.33C conditions, and then discharging to 2.0V under CC and 0.33C conditions, and after 200 charge-discharge cycles, the volume increase rate (%) = {(Volume of lithium secondary battery after 200 cycles - initial volume) / (initial volume)} × 100 is 26.3% or less.

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

15. The steps include: housing an electrode assembly, which includes a positive electrode, a negative electrode, and a separator interposed between the positive and negative electrodes, in a battery case; The step includes injecting a non-aqueous electrolyte into a battery case in which the electrode assembly is housed, The positive electrode includes a positive electrode active material. The positive electrode active material contains 50 mol% or more of Mn in the total metal excluding lithium, and includes a perlithitated manganese-rich oxide in which the molar ratio of lithium to the transition metal is greater than 1. The non-aqueous electrolyte comprises a lithium salt and an organic solvent. The aforementioned organic solvent includes a first organic solvent and a second organic solvent. The first organic solvent comprises ethylene carbonate, A method for producing a lithium secondary battery, wherein the second organic solvent comprises diethyl carbonate and propyl propionate.

16. The method for producing a lithium secondary battery according to claim 15, wherein the perlithitated 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.)

17. A method for manufacturing a lithium secondary battery according to claim 15 or 16, wherein the volume ratio of the first organic solvent and the second organic solvent is 10:90 to 50:

50.

18. A method for producing a lithium secondary battery according to claim 15 or 16, wherein the volume ratio of the diethyl carbonate and the propyl propionate is 1:99 to 99:

1.

19. A method for manufacturing a lithium secondary battery according to claim 15 or 16, wherein the volume ratio of the diethyl carbonate and the propyl propionate is 12:88 to 88:

12.

20. A method for producing a lithium secondary battery according to claim 15 or 16, wherein the organic solvent comprises 10% to 50% by volume of ethylene carbonate, 5% to 80% by volume of diethyl carbonate, and 5% to 80% by volume of propyl propionate.

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