Lithium secondary battery and battery system including the same

Abstract

The present invention relates to a lithium secondary battery and a battery system including the same. The battery includes a positive electrode, a negative electrode, a polyolefin multi-layer separator, and a non-aqueous electrolyte, the positive electrode uses a nickel-cobalt-manganese active material, the nickel-cobalt-manganese active material is sequentially coated with i) a lithium-magnesium inner layer and ii) a lithium layer containing titanium, molybdenum, or tin, the negative electrode is formed of lithium metal, a carbonaceous material, a silicon alloy, or a metal oxide, and the polyolefin multi-layer separator has a ceramic coating layer.

Description

[0001] Cross-references to related applications

[0002] This application claims the benefit of Korean Patent Application No. 10-2025-0015033, filed with the Korean Intellectual Property Office on February 6, 2025, the entire disclosure of which is incorporated herein by reference. Technical Field

[0003] This invention relates to a lithium secondary battery and a battery system including the lithium secondary battery. Background Technology

[0004] In recent years, lithium-ion batteries have become a subject of active research due to the increasing demand for applications requiring high energy density, such as electric vehicles and energy storage systems (ESS). In particular, increasing battery energy density is a crucial issue for extending the driving range of electric vehicles. To achieve this, the capacity of the cathode and anode materials used must be increased, or the battery's operating voltage must be raised.

[0005] LiNiCoMnO2 (NCM811) with a nickel (Ni) content of 80% or higher provides a high discharge capacity of 220 mAh / g at high voltages. Energy density can be significantly improved by increasing the nickel content and raising the operating voltage above 4.5V. However, when operating NCM811 at high voltages, oxygen species are released from the surface of the cathode material due to the overlap of transition metal 3d orbital electrons and oxygen 2p orbital electrons during charging. This leads to the disruption of the layered structure starting from the cathode material surface and reduces the reversible lithium insertion and extraction process.

[0006] Furthermore, with repeated charge-discharge processes, volume changes occur in the cathode material, leading to the formation of internal microcracks and increasing side reactions due to the reaction with the electrolyte. These side reactions result in the formation of the CEI layer, which hinders the movement of lithium ions. Additionally, during charging, nickel ions (Ni... 2+ (It has the properties of lithium ions (Li) + Similar ionic radii migrate to lithium ion vacancies, leading to cation mixing, which reduces the structural stability of the cathode material.

[0007] Therefore, there is an urgent need to develop a lithium secondary battery that ensures the stability of the electrolyte and positive electrode interface, thereby suppressing oxygen release and preventing structural degradation of the positive electrode material during high-voltage operation. Summary of the Invention

[0008] The present invention aims to provide a lithium secondary battery with improved electrolyte-cathode interface stability.

[0009] Furthermore, the present invention aims to provide a lithium secondary battery with improved positive electrode structure stability during high-voltage charging.

[0010] Furthermore, the present invention aims to provide a lithium secondary battery suitable for the field of green technology (e.g., a battery for electric vehicles).

[0011] Some embodiments of the present invention provide a lithium secondary battery comprising a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte, wherein the positive electrode comprises a nickel-cobalt-manganese-based positive electrode active material having a first coating formed on at least a portion of its surface and a second coating formed on at least a portion of the surface on which the first coating is formed, the first coating comprising at least one selected from lithium and magnesium, the second coating comprising at least one selected from lithium, titanium, molybdenum, and tin, and the non-aqueous electrolyte comprising an organic solvent, a lithium salt, and functional additives.

[0012] According to one embodiment, the first coating may comprise lithium and magnesium in a molar ratio of 1:0.1 to 1:2.

[0013] According to one embodiment, the second coating may comprise lithium in a molar ratio of 1:0.1 to 1:2 and any one selected from titanium, molybdenum, and tin.

[0014] According to one embodiment, the weight ratio of the nickel-cobalt-manganese-based positive electrode active material to the first coating can be from 1:0.001 to 1:0.1.

[0015] According to one embodiment, the weight ratio of the nickel-cobalt-manganese-based positive electrode active material to the second coating can be from 1:0.001 to 1:0.1.

[0016] The organic solvent according to one embodiment may include a first organic solvent and a second organic solvent, the first organic solvent including a fluorinated ether solvent having lithium salt non-dissociation properties, and the second organic solvent including a carbonate solvent having lithium salt dissociation properties.

[0017] The first organic solvent may include at least one fluorinated ether solvent selected from 1,1,2,3,3,3-hexafluoropropyl methyl ether, 2,2,2-trifluoroethyl-difluoromethyl ether, 2,2,3,3,3-pentafluoropropyl difluoromethyl ether, 2,2,3,3,3-pentafluoropropyl-1,1,2,2-tetrafluoroethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether and 2,2,3,4,4,4-hexafluorobutyl-difluoromethyl ether.

[0018] The second organic solvent may include at least one carbonate solvent selected from dimethyl carbonate, ethylene carbonate, ethyl methyl carbonate, propylene carbonate, methyl propyl carbonate, and ethyl methyl carbonate.

[0019] According to one embodiment, the organic solvent may include a first organic solvent and a second organic solvent in a volume ratio of 30:70 to 90:10.

[0020] According to one embodiment, the lithium salt may include those selected from Li(CF3SO2)2N (LiTFSI), Li(SO2F)2N (LiFSI), LiPF6, LiBF4, LiClO4, LiCl, LiBr, LiI, and LiB. 10 Cl 10 At least one of LiCF3SO3, LiCF3CO2, LiAsF6, LiSbF6, LiAlCl4, CH3SO3Li, CF3SO3Li, LiN(SO2C2F5)2, LiC4F9SO3 and LiB(C6H5)4.

[0021] According to one embodiment, the concentration of the lithium salt can be from 0.1 mol to 3.0 mol.

[0022] Functional additives may include at least one selected from fluoroethylene carbonate, vinylene carbonate, tris(pentafluorophenyl)borane, propylene sulfite, and 1,3,2-dioxazothiophene-2,2-dioxide.

[0023] Some embodiments of the present invention provide a battery system including a lithium secondary battery.

[0024] Some embodiments of the present invention provide a lithium secondary battery comprising: a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte, wherein the separator comprises a polyolefin-based polymer selected from polyethylene and polypropylene, and the separator has a multilayer structure and a coating comprising a ceramic component.

[0025] The membrane may include micropores through which ions pass.

[0026] Batteries can have shapes selected from cylindrical cans, squares, pouches, and coins.

[0027] Some embodiments of the present invention provide a lithium secondary battery, the lithium secondary battery comprising: a positive electrode and a negative electrode, the negative electrode comprising at least one negative electrode active material, the negative electrode active material being selected from lithium metal, graphitizable carbon, non-graphitizable carbon, graphite, silicon, silicon alloy, Sn oxide, Si oxide, Ti oxide, I oxide, Fe oxide and lithium-titanium oxide.

[0028] The organic solvent may include a first organic solvent having lithium salt non-dissociation and a second organic solvent having lithium salt dissociation, wherein the first organic solvent and the second organic solvent are present in a volume ratio of about 30:70 to 90:10.

[0029] Non-aqueous electrolytes may contain lithium salts with a total concentration of about 0.1 mol to 3.0 mol.

[0030] The lithium salt may include at least one salt selected from Li(CF3SO3), LiN(SO2)2, LiPF6, LiBF4, LiFSi and LiTFSi.

[0031] The lithium secondary battery of the present invention can ensure improved structural stability even at high voltages of 4.5V or higher.

[0032] The lithium secondary battery of the present invention can form a stable electrolyte-positive electrode interface, thereby exhibiting improved cycle life characteristics.

[0033] As discussed, the methods and systems appropriately include the use of controllers or processors.

[0034] In another embodiment, a vehicle is provided that includes the apparatus disclosed herein. Attached Figure Description

[0035] The following detailed description of the foregoing and other aspects, features, advantages, and embodiments will be better understood when read in conjunction with the accompanying drawings. However, the invention is not intended to be limited to the details shown in the drawings, and various modifications and structural changes can be made therein without departing from the spirit of the invention and within the scope of the claims and their equivalents. The same reference numerals and names in the various drawings denote the same elements.

[0036] Figure 1 SEM images of the surface of a positive electrode manufactured according to embodiments and comparative embodiments of the present invention are shown.

[0037] Figure 2 A graph showing the initial capacity of the positive electrode included in the lithium secondary battery according to embodiments and comparative embodiments of the present invention.

[0038] Figure 3 A graph illustrating the cycle life characteristics of the positive electrode included in the lithium secondary battery according to embodiments and comparative embodiments of the present invention.

[0039] Figure 4 The image shows a cross-sectional image of the particles of the positive electrode included in the lithium secondary battery according to embodiments and comparative embodiments of the present invention after 100 cycles. Detailed Implementation

[0040] The invention described above is not limited to the aspects described herein and the accompanying drawings. It will be apparent to those skilled in the art that various substitutions, changes, and modifications can be made that are not illustrated herein but still fall within the spirit and scope of the invention. Therefore, the scope of the invention is not defined by the specific description but by the claims and their equivalents, and all variations within the scope of the claims and their equivalents are to be interpreted as included in the invention.

[0041] The invention will now be described in more detail. However, the following embodiments are provided merely as a reference for describing the invention in detail, and the invention is not limited thereto, but can be implemented in various forms.

[0042] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0043] The terminology used herein is intended only to effectively describe particular embodiments and is not intended to limit the invention.

[0044] Unless the context clearly indicates otherwise, the singular forms “a,” “an,” and “the” used in the specification and appended claims are intended to include plural objects.

[0045] Unless otherwise stated, all units used in this specification are based on weight. For example, units such as “%” or “ratio” represent weight percentage (wt%) or weight ratio, respectively. Unless otherwise defined, weight percentage (wt%) refers to the proportion of a particular component in the total composition, expressed as a percentage by weight.

[0046] When a part is described as "including" or "containing" a component, it means, unless otherwise stated otherwise, that other components are not excluded, and additional components may also be included.

[0047] Furthermore, the numerical ranges used in this specification may include all values ​​between the lower and upper limits, all values ​​obtained by logical increment within the shape and width of the defined range, all double-limited values, and all possible combinations of the upper and lower limits of different defined numerical ranges. Unless otherwise defined in the specification of this invention, values ​​outside the defined numerical range that may occur due to experimental errors or rounding are also included within the defined numerical range.

[0048] It should be understood that the term "vehicle" or "of a vehicle" or other similar terms used herein generally include motor vehicles, such as passenger cars including sport utility vehicles (SUVs), buses, trucks, various commercial vehicles, boats and vessels including various vessels and ships, aircraft, etc., including hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen-powered vehicles, and other alternative fuel vehicles (e.g., vehicles derived from non-petroleum fuels). As mentioned herein, a hybrid vehicle is a vehicle with two or more power sources, such as a vehicle that combines gasoline and electric power.

[0049] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used herein, unless the context clearly indicates otherwise, the singular forms “a,” “an,” and “described” are intended to include the plural forms as well. These terms are intended only to distinguish one component from another, and the terms do not limit the characteristics, order, or sequence of the constituent components. As used herein, the term “and / or” includes any and all combinations of one or more of the associated enumerated items. Furthermore, the terms “unit,” “device,” “component,” and “module” described in the specification mean a unit for performing at least one function and operation, and can be implemented by hardware components or software components and combinations thereof.

[0050] Although the exemplary embodiments are described as using multiple units to perform the exemplary process, it should be understood that the exemplary process can also be performed by one or more modules. Furthermore, it should be understood that the term controller / control unit refers to a hardware device that includes a memory and a processor and is specifically programmed to perform the processes described herein. The memory is configured to store the modules, and the processor is specifically configured to execute the modules, thereby performing one or more processes further described below.

[0051] Furthermore, the control logic of this disclosure can be embodied in a non-transitory computer-readable medium, including executable program instructions that can be executed by a processor, controller, etc. Examples of computer-readable media include, but are not limited to, ROM, RAM, optical disc (CD)-ROM, magnetic tape, floppy disk, flash drive, smart card, and optical data storage device. The computer-readable medium can also be distributed across a network-connected computer system, allowing it to be stored and executed in a distributed manner, for example, via a telematics server or a controller area network (CAN).

[0052] Unless otherwise stated or obvious from the context, as used herein, the term “about” is understood to mean within the normal tolerance range in the field, for example, within 2 standard deviations of the mean. “About” can be understood as within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05%, or 0.01% of the specified value. All numerical values ​​provided herein are modified by the term “about” unless obvious from the context.

[0053] A more detailed description of the invention is provided below.

[0054] The present invention provides a lithium secondary battery comprising a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte. The positive electrode comprises a nickel-cobalt-manganese-based positive electrode active material having a first coating formed on at least a portion of its surface and a second coating formed on at least a portion of the surface on which the first coating is formed. The first coating comprises at least one selected from lithium and magnesium, and the second coating comprises at least one selected from lithium, titanium, molybdenum, and tin. The non-aqueous electrolyte comprises an organic solvent, a lithium salt, and functional additives.

[0055] The coating contains metal and can suppress oxygen release, thereby improving the structural stability of the positive electrode during high-voltage charging, improving the stability of the electrolyte-positive electrode interface, and enabling the lithium secondary battery to ensure excellent cycle life characteristics.

[0056] In one embodiment of the invention, the first coating may comprise lithium and magnesium in a molar ratio of 1:0.1 to 1:2, specifically 1:0.2 to 1:1.5, and more specifically 1:0.5 to 1:1. When this range is met, the effect of improving the structural stability of the cathode and the stability of the electrolyte-cathode interface is improved.

[0057] In one embodiment of the invention, the second coating may comprise lithium and any one selected from titanium, molybdenum, and tin in a molar ratio of 1:0.1 to 1:2, specifically 1:0.2 to 1:1.5, more specifically 1:0.5 to 1:1. When this range is met, the effect of improving the structural stability of the cathode and the stability of the electrolyte-cathode interface is improved.

[0058] In one embodiment of the invention, the weight ratio of the nickel-cobalt-manganese-based cathode active material to the first coating can be from 1:0.001 to 1:0.1. When this range is met, side reactions at the electrolyte-cathode interface are significantly reduced, and appropriate lithium-ion conductivity for battery operation can be ensured.

[0059] In one embodiment of the invention, the weight ratio of the nickel-cobalt-manganese-based cathode active material to the second coating, according to one embodiment, can be from 1:0.001 to 1:0.1. When this range is met, side reactions between the electrolyte and cathode interface are significantly reduced, and appropriate lithium-ion conductivity for battery operation can be ensured.

[0060] In one embodiment of the present invention, the lithium salt may include those selected from Li(CF3SO2)2N (LiTFSI), Li(SO2F)2N (LiFSI), LiPF6, LiBF4, LiClO4, LiCl, LiBr, LiI, and LiB. 10 Cl 10 At least one of LiCF3SO3, LiCF3CO2, LiAsF6, LiSbF6, LiAlCl4, CH3SO3Li, CF3SO3Li, LiN(SO2C2F5)2, LiC4F9SO3 and LiB(C6H5)4, and specifically may include Li(CF3SO2)2N(LiTFSI).

[0061] In one embodiment of the invention, the lithium salt may be present in the non-aqueous electrolyte at a total concentration of 0.1 mol to 3.0 mol, specifically 0.5 mol to 2.5 mol, more specifically 1.0 mol to 1.5 mol. When this range is met, appropriate ionic conductivity for battery operation is ensured, and phase separation of the electrolyte does not occur.

[0062] In one embodiment of the invention, the functional additive may include at least one selected from fluoroethylene carbonate, vinylene carbonate, tris(pentafluorophenyl)borane, propylene sulfite, and 1,3,2-dioxazolthiophene-2,2-dioxide, and specifically may include fluoroethylene carbonate. The functional additive can be used to form a protective film on the negative electrode, but is not limited thereto. In some aspects, the functional additive does not contain a polymer component, or is not a polymer. In some aspects, the functional additive has a molecular weight less than 1500, 1400, 1200, 1000, 800, 600, or 500, and the functional additive typically has a molecular weight of at least 30, 40, 50, 60, or 80. In some aspects, the functional additive has a halogen (F, Cl, Br, and / or I, especially F) substituent, or has one or more heteroatoms (e.g., O, N, or S, especially O or S).

[0063] Organic solvents can be used by mixing a first organic solvent with low reactivity to impart oxidative stability to the electrolyte with a second organic solvent with lithium salt dissociation properties.

[0064] In one embodiment of the present invention, the first organic solvent may include at least one fluorinated ether solvent selected from 1,1,2,3,3,3-hexafluoropropyl methyl ether, 2,2,2-trifluoroethyl-difluoromethyl ether, 2,2,3,3,3-pentafluoropropyl difluoromethyl ether, 2,2,3,3,3-pentafluoropropyl-1,1,2,2-tetrafluoroethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, and 2,2,3,4,4,4-hexafluorobutyl-difluoromethyl ether. The fluorinated ether solvent may have lithium salt non-dissociation properties. Specifically, the first organic solvent may include 1,1,2,3,3,3-hexafluoropropyl methyl ether (hereinafter referred to as "HFPME") represented by Formula 1.

[0065] [Chemical Formula 1]

[0066]

[0067] 1,1,2,3,3,3-Hexafluoropropylmethyl ether (HFPME) exhibits excellent oxidative stability and can improve cycle life and output characteristics when used as a solvent in high-concentration salt electrolytes.

[0068] However, since the first organic solvent is non-dissociable with lithium salts, an organic solvent can be prepared by mixing the first organic solvent with a second organic solvent that is dissociable with lithium salts, so that the lithium salt constituting the electrolyte will dissociate.

[0069] In one embodiment of the invention, the second organic solvent may include at least one carbonate solvent selected from dimethyl carbonate, ethylene carbonate, ethyl methyl carbonate, propylene carbonate, methyl propyl carbonate, and ethyl methyl carbonate. The carbonate solvent may have lithium salt dissociation properties. Specifically, the second organic solvent may be dimethyl carbonate.

[0070] Here, dimethyl carbonate (DMC), used as the second organic solvent, can compensate for the non-dissociation of the lithium salt in 1,1,2,3,3,3-hexafluoropropylmethyl ether (HFPME), used as the first organic solvent, and enable the lithium salt to dissociate.

[0071] However, when dimethyl carbonate (DMC) is used as the second organic solvent, dissociated lithium ions may be electrodeposited on the negative electrode surface. In this case, 1,1,2,3,3,3-hexafluoropropyl methyl ether (HFPME), used as the first organic solvent, can suppress this reaction.

[0072] Therefore, it is desirable to limit the mixing ratio of the first organic solvent and the second organic solvent so that they compensate for each other's disadvantages while maintaining their respective advantages of oxidative stability and lithium salt dissociation.

[0073] In one embodiment of the invention, the organic solvent may include a first organic solvent and a second organic solvent with a volume ratio of 30:70 to 90:10, specifically 50:50 to 90:10, and more specifically 70:30 to 90:10. When this range is met, the high-voltage stability and cycle life characteristics of the battery can be improved, while exhibiting improved output characteristics.

[0074] The negative electrode and separator materials used in this invention are not particularly limited and can be selected from materials known in the art. Some detailed embodiments are as follows.

[0075] In one embodiment of the present invention, the positive electrode and the negative electrode can be prepared by mixing and stirring the positive electrode active material and the negative electrode active material with a solvent, and, if necessary, a binder, a conductive material and a dispersant to prepare a mixture, then coating the mixture onto a metal current collector, drying the mixture and pressing it.

[0076] The negative electrode active material can be any active material commonly used in the negative electrode of a lithium secondary battery. Preferably, the negative electrode active material of a lithium secondary battery is a material capable of lithium intercalation. In one embodiment of the invention, the negative electrode active material may comprise one or more materials selected from lithium (metallic lithium), graphitizable carbon, non-graphitizable carbon, graphite, silicon, Sn alloys, Si alloys, Sn oxides, Si oxides, Ti oxides, Ni oxides, Fe oxides (FeO), and lithium-titanium oxides (LiTiO2, Li4Ti5O). 12 (materials).

[0077] In one embodiment of the present invention, conventional conductive carbon materials can be used as conductive materials without any particular limitations.

[0078] In one embodiment of the invention, the metal current collector can be any metal with high conductivity, which allows for easy adhesion of the positive or negative electrode active material mixture and is non-reactive within the voltage range of the battery. Non-limiting examples of the positive electrode current collector include foils made of aluminum, nickel, or combinations thereof, and non-limiting examples of the negative electrode current collector include foils made of copper, gold, nickel, copper alloys, or combinations thereof.

[0079] In one embodiment of the invention, the separator can be a separator having micropores through which ions can pass, and by way of non-limiting example, it can be one or more combinations selected from glass fiber, polyester, polyethylene, polypropylene, and polytetrafluoroethylene, and can be in the form of non-woven or woven fabric. Specifically, lithium secondary batteries can primarily use separators made of polyolefin-based polymers (e.g., polyethylene and polypropylene), but the invention is not limited thereto. Furthermore, to improve heat resistance or mechanical strength, separators coated with compositions comprising ceramic components or polymeric materials can also be used. The separator can optionally have a single-layer or multi-layer structure, and separators known in the art can be used, but the invention is not limited thereto.

[0080] There are no particular restrictions on the shape of lithium secondary batteries, but they can be selected from, for example, cylindrical cans, squares, pouches, or coin shapes.

[0081] Various embodiments and comparative embodiments of the present invention will be described below. However, the following embodiments are merely examples of the present invention, and the present invention is not intended to be limited thereto.

[0082] Example 1

[0083] The non-aqueous electrolyte is prepared by adding 1.5 M of lithium LiTFSI and 5 wt% of fluoroethylene carbonate (FEC) to an organic solvent containing dimethyl carbonate (DMC) and 1,1,2,3,3,3-hexafluoropropylmethyl ether (HFPME) mixed in a volume ratio of 1:9.

[0084] Artificial graphite was prepared as the negative electrode.

[0085] NCM83 was treated with a metal precursor mixture of CH3COOLi·4H2O and Mg(OC2H5)2 in a molar ratio of 2:1, at 5 wt% relative to the weight of NCM83. Then, the coated NCM83 was further treated with a metal precursor mixture of CH3COOLi·4H2O and TiCl4 in a molar ratio of 2:1, at 5 wt% relative to the weight of NCM83, to achieve a double-layer coating of NCM83 using Li2MgO2-Li2TiO3. Then, the double-coated NCM83, polyvinylidene fluoride (PVdF) as a positive electrode binder, and super-P carbon as a conductive agent were mixed at a weight ratio of 93:3:4. This mixture was then dispersed in N-methyl-2-pyrrolidone (NMP) to prepare a positive electrode slurry. The slurry was then coated onto an aluminum foil with a thickness of 30 μm, dried once at 100 °C, and then dried again at 120 °C to prepare the positive electrode.

[0086] Porous polypropylene material is used as the separator, and the lithium secondary battery is manufactured using conventional methods.

[0087] Example 2

[0088] The lithium secondary battery was manufactured in the same manner as in Example 1, except that MoCl3 was used instead of TiCl4 to perform a double coating of NCM83 with Li2MgO2-Li2MoO4.

[0089] Example 3

[0090] The lithium secondary battery was manufactured in the same manner as in Example 1, except that Sn(OCH3)4 was used instead of TiCl4 to perform a double coating of NCM83 with Li2MgO2-Li2SnO3.

[0091] Comparative Example 1

[0092] The lithium secondary battery was manufactured in the same manner as in Example 1, except that the non-aqueous electrolyte was prepared by adding 1.0 M of LiPF6 lithium salt to an organic solvent consisting of a mixture of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 1:1, and NCM83 was not coated.

[0093] Comparative Example 2

[0094] The lithium secondary battery was manufactured in the same manner as in Example 1, except that NCM83 was not coated.

[0095] Comparative Example 3

[0096] The lithium secondary battery was manufactured in the same manner as in Example 1, except that the non-aqueous electrolyte was prepared by adding 1.0 M of LiPF6 lithium salt and an organic solvent in which ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed in a 1:1 volume ratio.

[0097] Comparative Example 4

[0098] The lithium secondary battery was manufactured in the same manner as in Example 2, except that the non-aqueous electrolyte was prepared by adding 1.0 M of LiPF6 lithium salt and an organic solvent in which ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed in a 1:1 volume ratio.

[0099] Comparative Example 5

[0100] The lithium secondary battery was manufactured in the same manner as in Example 3, except that the non-aqueous electrolyte was prepared by adding 1.0 M of LiPF6 lithium salt and an organic solvent in which ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed in a 1:1 volume ratio.

[0101] Experimental Example 1: Observation of the Positive Electrode Surface

[0102] To compare the surfaces of the double-coated positive electrodes of Examples 1 to 3 with the uncoated (bare) positive electrode of Comparative Example 1, SEM images of the positive electrode surfaces were taken, and the results show... Figure 1 middle.

[0103] from Figure 1 It can be seen that the positive electrode of Comparative Example 1 has a smooth surface, while the positive electrodes of Examples 1 to 3 can be confirmed to have a surface coated with metal.

[0104] Experimental Example 2: Initial Capacity Performance Evaluation Test

[0105] To determine the initial capacity performance of the positive electrode portion based on the presence or absence of a coating and the type of electrolyte, the initial capacity performance of lithium secondary batteries according to the examples and comparative examples was evaluated, and the results show... Figure 2 And in Table 1.

[0106] [Table 1]

[0107]

[0108] As can be seen from Table 1, for Examples 1 to 3 (which are combinations of bimetallic coated positive electrodes and specific non-aqueous electrolytes), it was confirmed that the constant voltage charge was less and the initial discharge capacity was similar compared to the comparative examples that did not have this feature.

[0109] Experimental Example 3: Cyclic Performance Evaluation Test

[0110] To determine the cycle life characteristics of the positive electrode portion based on the presence or absence of a coating and the type of electrolyte, the cycle performance of lithium secondary batteries according to the examples and comparative examples was evaluated, and the results are shown in Table 2.

[0111] [Table 2]

[0112]

[0113] As can be seen from Table 2, Examples 1 to 3 (which are combinations of bimetallic coated cathodes and specific non-aqueous electrolytes) exhibit significantly superior cycle life characteristics compared to the comparative examples without these features. This indicates that the bimetallic coated cathode portion reduces side reactions between the cathode and the non-aqueous electrolyte, and improves interfacial stability.

[0114] In addition, from Figure 4 (It shows the cross-section of the particle after 100 cycles.) It can be seen that in the cases of Examples 1 to 3, the structural stability is excellent and no cracks appear even after 100 cycles.

[0115] The features, structures, effects, etc., described in the above exemplary embodiments are included in at least one embodiment of the present invention, and are not necessarily limited to a single embodiment. Furthermore, the features, structures, effects, etc., exemplified in each exemplary embodiment can be combined or modified by those skilled in the art in other embodiments. Therefore, such combinations and modifications should be interpreted as being within the scope of the present invention.

Claims

1. A lithium secondary battery, the lithium secondary battery comprising: Positive electrode, wherein the positive electrode comprises a nickel-cobalt-manganese-based positive electrode active material; A first coating is formed on at least a portion of the surface of the positive electrode active material, the first coating comprising lithium and / or magnesium; A second coating is formed on at least a portion of the surface of the positive electrode active material on which the first coating is formed, the second coating comprising lithium, titanium, molybdenum and / or tin; negative electrode; Diaphragm; and A non-aqueous electrolyte comprising an organic solvent, a lithium salt, and functional additives.

2. The lithium secondary battery according to claim 1, wherein, The first coating comprises lithium and magnesium in a molar ratio of 1:0.1 to 1:

2.

3. The lithium secondary battery according to claim 1, wherein, The second coating comprises lithium in a molar ratio of 1:0.1 to 1:2 and any one selected from titanium, molybdenum and tin.

4. The lithium secondary battery according to claim 1, wherein, The weight ratio of the nickel-cobalt-manganese-based positive electrode active material to the first coating is from 1:0.001 to 1:0.

1.

5. The lithium secondary battery according to claim 1, wherein, The weight ratio of the nickel-cobalt-manganese-based positive electrode active material to the second coating is from 1:0.001 to 1:0.

1.

6. The lithium secondary battery according to claim 1, wherein, The organic solvent includes a first organic solvent and a second organic solvent. The first organic solvent includes a fluorinated ether solvent with lithium salt non-dissociation properties, and the second organic solvent includes a carbonate solvent with lithium salt dissociation properties.

7. The lithium secondary battery according to claim 6, wherein, The first organic solvent includes one or more fluorinated ether solvents selected from 1,1,2,3,3,3-hexafluoropropyl methyl ether, 2,2,2-trifluoroethyl-difluoromethyl ether, 2,2,3,3,3-pentafluoropropyl difluoromethyl ether, 2,2,3,3,3-pentafluoropropyl-1,1,2,2-tetrafluoroethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether and / or 2,2,3,4,4,4-hexafluorobutyl-difluoromethyl ether.

8. The lithium secondary battery according to claim 6, wherein, The second organic solvent includes one or more carbonate solvents selected from dimethyl carbonate, ethylene carbonate, ethyl methyl carbonate, propylene carbonate, methyl propyl carbonate and / or methyl ethyl carbonate.

9. The lithium secondary battery according to claim 6, wherein, The organic solvent includes a first organic solvent and a second organic solvent in a volume ratio of 30:70 to 90:

10.

10. The lithium secondary battery according to claim 1, wherein, The lithium salts include Li(CF3SO2)2N, Li(SO2F)2N, LiPF6, LiBF4, LiClO4, LiCl, LiBr, LiI, and LiB. 10 Cl 10 One or more of the following: LiCF3SO3, LiCF3CO2, LiAsF6, LiSbF6, LiAlCl4, CH3SO3Li, CF3SO3Li, LiN(SO2C2F5)2, LiC4F9SO3, and LiB(C6H5)4, and any combination thereof.

11. The lithium secondary battery according to claim 1, wherein, The concentration of the lithium salt is from 0.1 mol to 3.0 mol.

12. The lithium secondary battery according to claim 1, wherein, The functional additives include one or more of the following: fluoroethylene carbonate, vinylene carbonate, tris(pentafluorophenyl)borane, propylene sulfite, 1,3,2-dioxazothiophene-2,2-dioxide, and any combination thereof.

13. A battery system comprising a lithium secondary battery according to any one of claims 1 to 12.

14. A lithium secondary battery, the lithium secondary battery comprising: positive electrode; negative electrode; A separator comprising a polyolefin-based polymer selected from polyethylene and polypropylene, the separator having a multilayer structure and a coating comprising a ceramic component; and Non-aqueous electrolyte.

15. The lithium secondary battery according to claim 14, wherein, The membrane includes micropores through which ions can pass.

16. The lithium secondary battery according to claim 14, wherein, Batteries come in shapes selected from cylindrical cans, squares, pouches, and coins.

17. A lithium secondary battery, the lithium secondary battery comprising: positive electrode; The negative electrode comprises one or more negative electrode active materials selected from lithium metal, graphitizable carbon, non-graphitizable carbon, graphite, silicon, silicon alloy, Sn oxide, Si oxide, Ti oxide, I oxide, Fe oxide and / or lithium-titanium oxide.

18. The lithium secondary battery according to claim 17, wherein, The organic solvent includes a first organic solvent having lithium salt non-dissociation properties and a second organic solvent having lithium salt dissociation properties, wherein the first organic solvent and the second organic solvent are present in a volume ratio of 30:70 to 90:

10.

19. The lithium secondary battery according to claim 17, wherein, The non-aqueous electrolyte contains lithium salts with a total concentration of 0.1 mol to 3.0 mol.

20. The lithium secondary battery according to claim 19, wherein, Lithium salts include one or more salts selected from Li(CF3SO3), LiN(SO2)2, LiPF6, LiBF4, LiFSi and / or LiTFSi.

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