Rechargeable lithium battery

Abstract

A lithium secondary battery comprising a positive electrode plate; a negative electrode plate; and an electrolyte including an electrolyte additive, wherein the current density of the positive electrode plate and the electrolyte additive are each controlled. Detailed information regarding the current density of the positive electrode plate and the electrolyte additive is as described in the specification.

Description

Technology Field

[0001] This description relates to a lithium secondary battery. Background Technology

[0002] Lithium secondary batteries are rechargeable and have an energy density more than three times higher per unit weight than conventional lead-acid batteries, nickel-cadmium batteries, nickel-hydrogen batteries, and nickel-zinc batteries, and can be fast-charged. As a result, they are being commercialized for laptops, mobile phones, power tools, and electric bicycles, and research and development to further improve energy density is actively underway.

[0003] These lithium secondary batteries are used by injecting an electrolyte into a battery cell containing a positive electrode plate and a negative electrode plate.

[0004] Recently, the development direction of lithium secondary batteries has focused on increasing capacity, lifespan characteristics, and rapid charging performance. However, when the capacity of a lithium secondary battery is increased by increasing the current density of the positive electrode plate, the wettability to the electrolyte decreases, causing lithium dendrites to precipitate on the surface of the negative electrode plate (specifically, the interface between the negative electrode plate and the electrolyte), and as a result, the battery's lifespan characteristics and rapid charging performance deteriorate.

[0005] Accordingly, there is a demand for electrolytes that can increase the capacity of lithium secondary batteries while improving lifespan characteristics and rapid charging performance. The problem to be solved

[0007] One embodiment increases the capacity of the lithium secondary battery by increasing the current density of the positive electrode plate, while also improving lifespan characteristics and rapid charging performance through the use of the electrolyte additive. means of solving the problem

[0009] One embodiment of the present invention provides a lithium secondary battery comprising a positive electrode plate; a negative electrode plate; and an electrolyte comprising an electrolyte additive, wherein the current density of the positive electrode plate and the additive are each controlled. Effects of the invention

[0011] In a lithium secondary battery of one embodiment, the electrolyte additive acts as a surfactant. Accordingly, in a lithium secondary battery containing the electrolyte additive, the wettability of the positive electrode plate with respect to the electrolyte can be improved even when the current density of the positive electrode plate is increased.

[0012] Furthermore, if the wettability of the positive electrode plate with respect to the electrolyte is improved, a lithium cation flux (Li) at the interface between the positive electrode plate and the electrolyte + ) is uniformly formed, so that the precipitation of lithium dendrites on the surface of the negative electrode plate is suppressed, and ultimately, the life characteristics and rapid charging performance of the lithium secondary battery can be secured. Brief explanation of the drawing

[0014] FIG. 1 is a schematic diagram illustrating a lithium secondary battery according to one embodiment of the present invention. Specific details for implementing the invention

[0015] Unless specifically stated in this specification, "substitution" means that at least one hydrogen atom in a compound is a halogen atom (F, Cl, Br, I), a hydroxyl group, a C1 to C20 alkoxy group, a nitro group, a cyano group, an amine group, an imino group, an azido group, an amidino group, a hydrazino group, a hydrazono group, a carbonyl group, a carbamyl group, a thiol group, an ester group, an ether group, a carboxyl group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid or a salt thereof, a C1 to C20 alkyl group, a C2 to C20 alkenyl group, a C2 to C20 alkynyl group, a C6 to C30 aryl group, a C3 to C20 cycloalkyl group, a C3 to C20 cycloalkenyl group, a C3 to C20 cycloalkynyl group, a C2 to C20 heterocycloalkyl group, a C2 to C20 heterocycloalkenyl group, C2 to It means substituted with a C20 heterocycloalkynyl group or a combination thereof.

[0016] Unless otherwise specifically stated in this specification, "heterocycloalkyl group," "heterocycloalkenyl group," "heterocycloalkynyl group," and "heterocycloalkylene group" each mean that at least one heteroatom of N, O, S, or P is present in a ring compound of cycloalkyl, cycloalkenyl, cycloalkynyl, and cycloalkylene.

[0017] Unless otherwise defined in the chemical formulas within this specification, if a chemical bond is not drawn at a position where a chemical bond should be drawn, it means that a hydrogen atom is bonded at said position.

[0018] In this specification, "current density of the electrode plate" refers to the magnitude (density) of the current flowing per unit area of ​​the positive electrode plate or the negative electrode plate.

[0019] In this specification, "loading amount of electrode plate" is a value calculated by dividing the weight of the components (active material, conductive material, binder, etc.) excluding the current collector in the positive electrode plate or negative electrode plate by the area.

[0020] In this specification, "composite density of the electrode plate" is a value calculated by dividing the weight of the components (active material, conductive material, binder, etc.) excluding the current collector in the positive electrode plate or negative electrode plate by the volume.

[0021] In this specification, "weight-average molecular weight" is a value measured by gel permeation chromatography (GPC: gel permeation chromatography, PL GPC220, Agilent Technologies) and corrected as a cubic function using polystyrene.

[0023] Hereinafter, a lithium secondary battery according to one embodiment of the present invention will be described in detail with reference to the attached drawings. However, this is presented as an example and the present invention is not limited thereby, and the present invention is defined only by the scope of the claims set forth below.

[0025] In one embodiment of the present invention, a lithium secondary battery comprising a positive electrode plate; a negative electrode plate; and an electrolyte including an additive, wherein the current density is 5.4 mA / cm² 2 Up to 6.6 mA / cm 2 And, the above electrolyte additive provides a lithium secondary battery comprising a polyalkylene glycol-based copolymer.

[0027] In a lithium secondary battery of one embodiment, the electrolyte additive acts as a surfactant. Accordingly, in a lithium secondary battery containing the electrolyte additive, (5.4 mA / cm² 2 Above) Even if the current density is increased, the wettability of the electrode with respect to the electrolyte can be improved.

[0028] Furthermore, if the wettability of the positive electrode plate with respect to the electrolyte is improved, lithium cations (Li) at the interface between the positive electrode plate and the electrolyte + ) is uniformly formed, thereby suppressing the precipitation of lithium dendrites on the surface of the negative electrode plate, and ultimately securing the lifespan characteristics and rapid charging performance of the lithium secondary battery.

[0030] On the other hand, in a lithium secondary battery that does not include the above-mentioned electrolyte additive, the wettability of the positive electrode plate with respect to the electrolyte may be insufficient when increasing the current density of the positive electrode plate.

[0031] As such, if the wettability of the positive electrode plate with respect to the electrolyte is insufficient, lithium cation flux (Li) at the interface between the positive electrode plate and the electrolyte + ) is formed unevenly, and is deposited as sharp lithium dendrites on the surface of the negative electrode plate, which can ultimately impair the lifespan characteristics and rapid charging performance of the lithium secondary battery.

[0033] In summary, one embodiment increases the current density of the positive electrode plate to increase the capacity of the lithium secondary battery, while also improving lifespan characteristics and rapid charging performance through the use of the electrolyte additive.

[0035] The above-mentioned lithium secondary battery is described in more detail below.

[0037] The current density of the above positive electrode plate is 5.4 mA / cm² 2 Up to 6.6 mA / cm 2 , specifically 5.4 mA / cm 2 Up to 6.3 mA / cm 2 , for example 5.4 mA / cm 2 Up to 5.8 mA / cm 2 It could be.

[0038] The current density of the above positive electrode plate is 5.4 mA / cm² 2 If it is less than that, there are limitations in realizing a high-capacity secondary battery. Meanwhile, the current density of the positive electrode plate is 6.6 mA / cm² 2 If it exceeds, the thickness of the positive electrode plate becomes excessively thick, and the wettability of the positive electrode plate may decrease.

[0040] The above electrolyte additive may be a polyalkylene glycol copolymer.

[0041] Specifically, the electrolyte additive may be a copolymer comprising the following repeating unit 1. The following repeating unit 1 corresponds to an alkylene glycol-based repeating unit:

[0042] [Repeat Unit 1]

[0043]

[0044] In the above repeating unit 1, R is a hydrogen atom or an alkyl group having 1 to 20 carbon atoms; and x is an integer from 1 to 20.

[0045] More specifically, the electrolyte additive may be a block copolymer comprising the following repeating units 1-1 and 1-2.

[0046] [Repeat Unit 1-1]

[0047]

[0048] [Repetition Unit 1-2]

[0049]

[0050] In the above repetition units 1-1 and 1-2, R 1 is an alkyl group having 1 to 20 carbon atoms; x1 and x2 are each independently integers from 1 to 20.

[0051] The above repeating unit 1-1 corresponds to an ethylene glycol repeating unit.

[0052] Meanwhile, R 1 It can be an alkyl group having 1 carbon atom (i.e., a methyl group). In this case, the repeating unit 1-2 corresponds to a propylene glycol repeating unit.

[0053] More specifically, the electrolyte additive is a block copolymer represented by the following chemical formula 1, and may also be represented as PEG-b-PPP-b-PEG:

[0054] [Chemical Formula 1]

[0055]

[0056] In the above chemical formula 1, x11, x12, and x21 are each independently integers from 1 to 20.

[0057] When the above electrolyte additive is a block copolymer comprising the three types of repeating units, the weight-average molecular weight of the above electrolyte additive may be 800 g / mol to 1500 g / mol, specifically 900 g / mol to 1300 g / mol, for example 1000 g / mol to 1200 g / mol.

[0058] If the weight-average molecular weight of the above electrolyte additive exceeds 1500 g / mol, it becomes a block copolymer containing four or more repeating units, which excessively increases the viscosity of the electrolyte and may impair the lifespan characteristics and rapid charging performance of the lithium secondary battery. On the other hand, if the weight-average molecular weight of the above electrolyte additive is 800 g / mol, it becomes a block copolymer or homopolymer containing two or fewer repeating units, which has a negligible effect as a surfactant and may impair the lifespan characteristics and rapid charging performance of the lithium secondary battery.

[0060] The content of the electrolyte additive in 100% by weight of the electrolyte may be 0.03% to 0.5% by weight, specifically 0.03% to 0.3% by weight, for example 0.1% to 0.3% by weight.

[0061] If the content of the electrolyte additive in 100% by weight of the electrolyte exceeds 0.5% by weight, the viscosity of the electrolyte is excessively increased, which may impair the lifespan characteristics and rapid charging performance of the lithium secondary battery. On the other hand, if the content of the electrolyte additive in 100% by weight of the electrolyte is less than 0.03%, the effect as a surfactant is negligible, which may impair the lifespan characteristics and rapid charging performance of the lithium secondary battery.

[0063] The above lithium salt is a material that dissolves in a non-aqueous organic solvent and acts as a source of lithium ions within the battery, enabling the basic operation of a lithium secondary battery and facilitating the movement of lithium ions between the positive and negative electrode plates. Representative examples of such lithium salts include LiPF6, LiBF4, LiDFOP, LiDFOB, LiPO2F2, LiSbF6, LiAsF6, LiN(SO2C2F5)2, Li(CF3SO2)2N, LiN(SO3C2F5)2, Li(FSO2)2N (lithium bis(fluorosulfonyl)imide (LiFSI), LiC4F9SO3, LiClO4, LiAlO2, LiAlCl4, LiN(C x F 2x+1 SO2)(C y F 2y+1 SO2)(where x and y are natural numbers, for example, integers from 1 to 20), LiCl, LiI, and LiB(C2O4)2 (one or more selected from the group consisting of lithium bis(oxalato) borate (LiBOB). It is preferable to use a lithium salt concentration within the range of 0.1 M to 2.0 M. When the lithium salt concentration falls within the above range, the electrolyte has appropriate conductivity and viscosity, so it can exhibit excellent electrolyte performance and lithium ions can move effectively.

[0065] The above-mentioned non-aqueous organic solvent serves as a medium through which ions involved in the electrochemical reaction of the battery can move.

[0066] The above-mentioned non-aqueous organic solvent may be a carbonate-based, ester-based, ether-based, ketone-based, alcohol-based, or aprotic solvent.

[0067] The above carbonate-based solvents may include ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), etc. The above ester-based solvents may include methyl acetate, ethyl acetate, n-propyl acetate, t-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, decanolide, mevalonolactone, caprolactone, etc. The above ether-based solvent may include dibutyl ether, tetraglame, diglame, dimethoxyethane, 2-methyltetrahydrofuran, tetrahydrofuran, etc. Additionally, the above ketone-based solvent may include cyclohexanone, etc. Additionally, the above alcohol-based solvent may include ethyl alcohol, isopropyl alcohol, etc., and the above aprotic solvent may include nitriles such as R-CN (where R is a straight-chain, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and may include a double bond, a directional ring, or an ether bond), amides such as dimethylformamide, dioxolanes such as 1,3-dioxolane, sulfolanes, etc.

[0068] The above-mentioned non-aqueous organic solvents may be used alone or in a mixture of one or more. When used in a mixture of one or more, the mixing ratio can be appropriately adjusted according to the desired battery performance, which is widely understood by those engaged in the relevant field.

[0069] In addition, for the above carbonate-based solvent, it is preferable to use a mixture of cyclic carbonates and chain carbonates. In this case, using a mixture of cyclic carbonates and chain carbonates in a volume ratio of 5:95 to 50:50 can result in excellent performance of the electrolyte.

[0070] Specifically, ethylene carbonate (EC) may be used as the cyclic carbonate, and ethylmethyl carbonate (EMC) and dimethyl carbonate (DMC) may be used as the linear carbonates.

[0071] More specifically, the above-mentioned non-aqueous organic solvent may include a carbonate-based solvent mixed with ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC). For example, the performance of the electrolyte may be excellent when the above-mentioned carbonate-based solvent mixed with ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) is mixed and used in a volume ratio of EC:EMC:DMC = 1:0.5:5 to 5:3:10.

[0072] The above-mentioned non-aqueous organic solvent may further include an aromatic hydrocarbon organic solvent in addition to the carbonate-based solvent. In this case, the carbonate-based solvent and the aromatic hydrocarbon solvent may be mixed in a volume ratio of 1:1 to 30:1.

[0073] As the above aromatic hydrocarbon solvent, an aromatic hydrocarbon compound of the following chemical formula 3 may be used.

[0074] [Chemical Formula 3]

[0075]

[0076] In the above chemical formula 3, R 201 to R 206 The groups are identical or different and are selected from the group consisting of hydrogen, halogen, alkyl groups having 1 to 20 carbon atoms, haloalkyl groups, and combinations thereof.

[0077] Specific examples of the above aromatic hydrocarbon solvents include benzene, fluorobenzene, 1,2-difluorobenzene, 1,3-difluorobenzene, 1,4-difluorobenzene, 1,2,3-trifluorobenzene, 1,2,4-trifluorobenzene, chlorobenzene, 1,2-dichlorobenzene, 1,3-dichlorobenzene, 1,4-dichlorobenzene, 1,2,3-trichlorobenzene, 1,2,4-trichlorobenzene, iodobenzene, 1,2-diiodobenzene, 1,3-diiodobenzene, 1,4-diiodobenzene, 1,2,3-triiodobenzene, 1,2,4-triiodobenzene, toluene, fluorotoluene, 2,3-difluorotoluene, 2,4-difluorotoluene. It is selected from the group consisting of 2,5-difluorotoluene, 2,3,4-trifluorotoluene, 2,3,5-trifluorotoluene, chlorotoluene, 2,3-dichlorotoluene, 2,4-dichlorotoluene, 2,5-dichlorotoluene, 2,3,4-trichlorotoluene, 2,3,5-trichlorotoluene, iodotoluene, 2,3-diiodotoluene, 2,4-diiodotoluene, 2,5-diiodotoluene, 2,3,4-triiodotoluene, 2,3,5-triiodotoluene, xylene, and combinations thereof.

[0078] The above electrolyte may further include vinylene carbonate, vinyl ethylene carbonate, or an ethylene-based carbonate compound of the following chemical formula 4 as a life-enhancing additive to improve battery life.

[0079] [Chemical Formula 4]

[0080]

[0081] In the above chemical formula 4, R 207 and R 208 The groups are identical or different from each other and are selected from the group consisting of hydrogen, halogen groups, cyano groups (CN), nitro groups (NO2), and fluorinated alkyl groups having 1 to 5 carbon atoms, and the R 207 and R 208At least one of the groups is selected from the group consisting of a halogen group, a cyano group (CN), a nitro group (NO2), and a fluorinated alkyl group having 1 to 5 carbon atoms, provided that R 207 and R 208 Not all of it is hydrogen.

[0082] Representative examples of the above-mentioned ethylene-based carbonate compounds include difluoroethylene carbonate, chloroethylene carbonate, dichloroethylene carbonate, bromoethylene carbonate, dibromoethylene carbonate, nitroethylene carbonate, cyanoethylene carbonate, or fluoroethylene carbonate. When using more of these lifespan-enhancing additives, the amount used can be appropriately controlled.

[0084] The loading amount of the above positive electrode plate is 50.1 mg / cm² 2 to 65.0 mg / cm² 2 , specifically 50.1 mg / cm² 2 Up to 59.1 mg / cm² 2 It may be. In addition, the density of the composite of the anode plate may be 2.0 g / cc to 6.0 g / cc, specifically 3.0 g / cc to 5.0 g / cc.

[0085] When each of the above ranges is satisfied, the energy density of the lithium secondary battery can be increased.

[0086] The above positive electrode plate comprises a positive current collector and a positive composite layer located on the positive current collector, and the positive composite layer comprises a positive active material.

[0087] As the above-mentioned positive electrode active material, a compound capable of reversible intercalation and deintercalation of lithium (a lithated intercalation compound) may be used.

[0088] Specifically, at least one type of composite oxide of lithium and a metal selected from cobalt, manganese, nickel, and combinations thereof may be used.

[0089] Of course, a coating layer on the surface of the above-mentioned composite oxide may be used, or a mixture of the above-mentioned composite oxide and the composite oxide having a coating layer may be used. This coating layer may include at least one coating element compound selected from the group consisting of oxides of coating elements, hydroxides of coating elements, oxyhydroxides of coating elements, oxycarbonates of coating elements, and hydroxycarbonates of coating elements. The compounds forming these coating layers may be amorphous or crystalline. As coating elements included in the above-mentioned coating layer, Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or mixtures thereof may be used. For the coating layer formation process, any coating method may be used as long as the compound can be coated using these elements in a way that does not adversely affect the physical properties of the cathode active material (e.g., spray coating, immersion method, etc.). Since this is a matter that is well understood by those engaged in the relevant field, a detailed explanation will be omitted.

[0090] Specifically, the positive electrode active material may include a lithium nickel-based composite oxide represented by the following chemical formula A1:

[0091] [Chemical Formula A1]

[0092] Li a1 Ni x1 M 1 y1 M 2 z1 O 2-b1 X b1

[0093] In the above formula A1, 0.9≤a1≤1.2, 0.7≤x1≤1, 0≤y1≤0.2, 0≤z1≤0.2, 0.9≤x1+y1+z1≤1.1, and 0≤b1≤0.1; and M 1 and M 2Each is independently one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sr, Ti, V, W, and Zr; and X is one or more elements selected from the group consisting of F, P, and S.

[0094] In the above formula A1, 0.75≤x1≤1, 0≤y1≤0.18, and 0≤z1≤0.18; or 0.85≤x1≤1, 0≤y1≤0.15, and 0≤z1≤0.15; or 0.9≤x1≤1, 0≤y1≤0.1, and 0≤z1≤0.1.

[0095] For example, the above positive active material may include a lithium nickel-based complex oxide represented by the following chemical formula A2. The compound represented by the following chemical formula A2 may be a lithium nickel cobalt-based complex oxide:

[0096] [Chemical Formula A2]

[0097] Li a2 Ni x2 Co y2 M 3 z2 O 2-b2 X b2

[0098] In the above chemical formula A2, 0.9≤a2≤1.8, 0.7≤x2<1, 0 <y2≤0.2, 0≤z2≤0.2, 0.9≤x2+y2+z2≤1.1, 및 0≤b2≤0.1이고 M 3 is one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Cr, Fe, Mg, Mn, Mo, Nb, Si, Sr, Ti, V, W, and Zr, and X is one or more elements selected from the group consisting of F, P, and S.

[0099] In the above formula A2, 0.75≤x2≤0.99, 0≤y2≤0.15, and 0≤z2≤0.15; or 0.85≤x2≤0.99, 0.01≤y2≤0.15, and 0.01≤z2≤0.15; or 0.9≤x2≤0.99, 0.01≤y2≤0.1, and 0.01≤z2≤0.1.

[0100] For example, the above-mentioned positive electrode active material may include a lithium nickel-based composite oxide represented by the following chemical formula A3. The compound of the following chemical formula A3 may be a lithium nickel-cobalt-aluminum oxide or a lithium nickel-cobalt-manganese oxide.

[0101] [Chemical Formula A3]

[0102] Li a3 Ni x3 Co y3 M 4 z3 M 5 w3 O 2-b3 X b3

[0103] In the above chemical formula A3, 0.9≤a3≤1.8, 0.7≤x3≤0.98, 0.01≤y3≤0.19, 0.01≤z3≤0.19, 0≤w3≤0.19, 0.9≤x3+y3+z3+w3≤1.1, and 0≤b3≤0.1, and M 4 is one or more elements selected from the group consisting of Al, and Mn, and M 5 is one or more elements selected from the group consisting of B, Ba, Ca, Ce, Cr, Fe, Mg, Mo, Nb, Si, Sr, Ti, V, W, and Zr, and X is one or more elements selected from the group consisting of F, P, and S.

[0104] In the above formula A3, 0.75≤x3≤0.98, 0≤y3≤0.16, and 0≤z3≤0.16; or 0.85≤x3≤0.98, 0.01≤y3≤0.14, 0.01≤z3≤0.14, and 0≤w3≤0.14; or 0.9≤x3≤0.98, 0.01≤y3≤0.09, 0.01≤z3≤0.09, and 0≤w3≤0.09.

[0105] For example, the above-mentioned positive electrode active material may include a lithium nickel-based composite oxide represented by the following chemical formula A4. The compound of the following chemical formula A4 may be described as a cobalt-free lithium nickel-manganese-based oxide.

[0106] [Chemical Formula A4]

[0107] Li a4 Ni x4 Mn y4 M 6 z4 O 2-b4 X b4

[0108] In the above chemical formula A4, 0.9≤a2≤1.8, 0.7≤x4<1, 0 <y4≤0.2, 0≤z4≤0.2, 0.9≤x4+y4+z4≤1.1, 및 0≤b4≤0.1이고 M 6 is one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Cr, Fe, Mg, Mo, Nb, Si, Sr, Ti, V, W, and Zr, and X is one or more elements selected from the group consisting of F, P, and S.

[0110] In the positive electrode plate of one embodiment, the content of the positive active material may be 50% to 99% by weight, 60% to 99% by weight, 70% to 99% by weight, 80% to 99% by weight, or 90% to 99% by weight based on the total weight of the positive composite layer.

[0111] In one embodiment of the present invention, the anode composite layer may optionally include a conductive material and a binder. In this case, the content of the conductive material and the binder may each be 1.0 weight% to 5.0 weight% with respect to the total weight of the anode composite layer.

[0112] The above conductive material is used to impart conductivity to the positive electrode plate, and in the battery being constructed, any electronically conductive material that does not cause chemical changes can be used, such as carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber; metal-based materials such as metal powder or metal fiber such as copper, nickel, aluminum, silver; conductive polymers such as polyphenylene derivatives; or conductive materials including mixtures thereof.

[0113] The above binder serves to adhere the positive active material particles well to each other and also to adhere the positive active material well to the current collector. Representative examples include polyvinyl alcohol, carboxymethylcellulose, hydroxypropylcellulose, diacetylcellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, etc., but are not limited thereto.

[0114] Al may be used as the anode current collector, but is not limited thereto.

[0116] The loading amount of the above cathode plate is 28.2 mg / cm² 2 to 39.2 mg / cm² 2 , specifically 28.2 mg / cm² 2 Up to 33.5 g mg / cm² 2 It could be.

[0117] In addition, the density of the composite of the above-mentioned cathode plate may be 2.0 g / cc to 1.0 g / cc, specifically 1.74 g / cc to 1.54 g / cc.

[0118] When each of the above ranges is satisfied, the energy density of the lithium secondary battery can be increased.

[0119] The above-mentioned negative electrode plate includes a negative current collector and a negative active material layer comprising a negative active material formed on the negative current collector.

[0120] The above-mentioned negative electrode active material includes a material capable of reversibly intercalating / deintercalating lithium ions, lithium metal, an alloy of lithium metal, a material capable of doping and dedoping lithium, or a transition metal oxide.

[0121] As a material capable of reversibly intercalating / deintercalating the above lithium ions, any carbon-based negative electrode active material commonly used in lithium secondary batteries can be used, and representative examples include crystalline carbon, amorphous carbon, or a combination thereof. Examples of the above crystalline carbon include graphite such as amorphous, plate-like, flake-like, spherical, or fibrous natural graphite or artificial graphite, and examples of the above amorphous carbon include soft carbon or hard carbon, mesophase pitch carbide, calcined coke, etc.

[0122] As the above lithium metal alloy, an alloy of a metal selected from the group consisting of lithium, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn may be used.

[0123] Materials capable of doping and undoping the above lithium include Si, Si-C composites, SiOx (0 < x < 2), Si-Q alloys (wherein Q is an element selected from the group consisting of alkali metals, alkaline earth metals, group 13 elements, group 14 elements, group 15 elements, group 16 elements, transition metals, rare earth elements, and combinations thereof, and is not Si), Sn, SnO2, Sn-R (wherein R is an element selected from the group consisting of alkali metals, alkaline earth metals, group 13 elements, group 14 elements, group 15 elements, group 16 elements, transition metals, rare earth elements, and combinations thereof, and is not Sn), and at least one of these may also be mixed with SiO2.

[0124] The above elements Q and R may be selected from the group consisting of Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Tl, Ge, P, As, Sb, Bi, S, Se, Te, Po, and combinations thereof.

[0125] Examples of the above transition metal oxides include vanadium oxide, lithium vanadium oxide, or lithium titanium oxide.

[0126] In one embodiment, the negative electrode active material may include at least one of graphite and Si composites.

[0127] The above Si composite comprises a core containing Si particles and amorphous carbon, for example, the Si particles are a Si-C composite, SiO x It may include one or more of (0 < x ≤ 2) and Si alloys.

[0128] For example, the above Si-C composite may include a core containing Si particles and amorphous carbon.

[0129] The core may include a void in the center, and the radius of the center may correspond to 30% to 50% of the radius of the Si-C composite.

[0130] The average particle size of the above Si particles may be 10 nm to 200 nm.

[0131] In this specification, the average particle size may be the particle size (D50) at 50% by volume ratio in the cumulative size-distribution curve.

[0132] If the average particle size of the above Si particles falls within the above range, volume expansion occurring during charging and discharging can be suppressed, and the disruption of the conductive path due to particle fragmentation during charging and discharging can be prevented.

[0133] The above Si particles may be included in an amount of 1 to 60 weight% with respect to the total weight of the Si-C composite, for example, 3 It may be included in an amount of up to 60 weight%.

[0134] The above central part does not contain amorphous carbon, and amorphous carbon may exist only on the surface of the negative electrode active material.

[0135] In this case, the surface region refers to the area from the center to the outermost surface of the cathode active material.

[0136] In addition, Si particles are substantially uniformly incorporated throughout the cathode active material, that is, they can exist at a substantially uniform concentration in the center and on the surface.

[0137] The above amorphous carbon may be soft carbon, hard carbon, mesophase pitch carbide, calcined coke, or a combination thereof.

[0138] The above-mentioned cathode active material may further include crystalline carbon.

[0139] When the above-mentioned cathode active material includes a Si-C composite and crystalline carbon together, the Si-C composite and crystalline carbon may be included in the form of a mixture, in which case the Si-C composite and crystalline carbon may be included in a weight ratio of 1:99 to 50:50. More specifically, the Si-C composite and crystalline carbon may be included in a weight ratio of 3:97 to 20:80 or a weight ratio of 5:95 to 20:80.

[0140] The above crystalline carbon may be, for example, graphite, and more specifically may include natural graphite, artificial graphite, or a mixture thereof.

[0141] The average particle size of the crystalline carbon above may be 5 μm to 30 μm.

[0142] As the above amorphous carbon precursor, coal-based pitch, mesophase pitch, petroleum-based pitch, coal-based oil, petroleum-based heavy oil, or polymer resins such as phenolic resin, furan resin, and polyimide resin may be used.

[0143] The content of the negative electrode active material in the above negative electrode active material layer may be 95% to 99% by weight with respect to the total weight of the negative electrode active material layer.

[0144] In one embodiment of the present invention, the negative electrode active material layer comprises a binder and may optionally further comprise a conductive material. The content of the binder in the negative electrode active material layer may be 1% to 5% by weight with respect to the total weight of the negative electrode active material layer. Additionally, when further comprising a conductive material, the negative electrode active material may be used in an amount of 90% to 98% by weight, the binder in an amount of 1% to 5% by weight, and the conductive material in an amount of 1% to 5% by weight.

[0145] The above binder serves to effectively bond the negative electrode active material particles to each other and also to effectively bond the negative electrode active material to the current collector. As the binder, a water-insoluble binder, a water-soluble binder, or a combination thereof may be used.

[0146] Examples of the above-mentioned water-insoluble binders include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide, or combinations thereof.

[0147] Examples of the above water-soluble binders include rubber-based binders or polymer resin binders. The above rubber-based binder may be selected from styrene-butadiene rubber, acrylated styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber, acrylic rubber, butyl rubber, fluororubber, and combinations thereof. The above polymer resin binder may be selected from polytetrafluoroethylene, ethylene-propylene copolymer, polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, polystyrene, ethylene-propylene-diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, and combinations thereof.

[0148] When a water-soluble binder is used as the above-mentioned cathode binder, a cellulose-based compound capable of imparting viscosity may be further included as a thickener. As this cellulose-based compound, one or more types such as carboxymethyl cellulose, hydroxypropylmethyl cellulose, methyl cellulose, or alkali metal salts thereof may be mixed and used. Na, K, or Li may be used as the alkali metal. The content of such a thickener may be 0.1 to 3 parts by weight per 100 parts by weight of the cathode active material.

[0149] The above conductive material is used to impart conductivity to the electrode, and any electronically conductive material that does not cause chemical changes can be used in the battery being constructed. Examples include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, and carbon fibers; metal-based materials such as metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive polymers such as polyphenylene derivatives; or conductive materials comprising a mixture thereof.

[0150] The above-mentioned cathode current collector may be selected from the group consisting of copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, and combinations thereof.

[0152] Depending on the type of lithium secondary battery, a separator may be present between the positive electrode plate and the negative electrode plate. This separator may be a porous substrate; or a composite porous substrate.

[0153] The porous substrate is a substrate containing pores through which lithium ions can move. The porous substrate may be, for example, polyethylene, polypropylene, polyvinylidene fluoride, or a multilayer film of two or more layers thereof, and of course, a mixed multilayer film such as a polyethylene / polypropylene two-layer separator, a polyethylene / polypropylene / polyethylene three-layer separator, or a polypropylene / polyethylene / polypropylene three-layer separator may be used.

[0154] The above composite porous substrate may be in the form of a porous substrate and a functional layer located on the porous substrate. From the perspective of enabling the addition of additional functions, the functional layer may be, for example, at least one of a heat-resistant layer and an adhesive layer, and for example, the heat-resistant layer may include a heat-resistant resin and optionally a filler.

[0155] In addition, the adhesive layer may include an adhesive resin and optionally a filler.

[0156] The above filler may be an organic filler or an inorganic filler.

[0158] Referring to FIG. 1, a lithium secondary battery (100) according to one embodiment comprises a battery cell including a negative electrode plate (112), a positive electrode plate (114) positioned opposite to the negative electrode plate (112), a separator (113) disposed between the negative electrode plate (112) and the positive electrode plate (114), and an electrolyte (not shown) impregnating the negative electrode plate (112), the positive electrode plate (114), and the separator (113); a battery container (120) containing the battery cell; and a sealing member (140) sealing the battery container (120).

[0160] Examples and comparative examples of the present invention are described below. The following examples are merely embodiments of the present invention, and the present invention is not limited to the following examples.

[0162] Preparation of electrolyte for lithium secondary batteries

[0163] Preparation Example 1

[0164] As a non-aqueous organic solvent, a carbonate-based solvent mixed in a volume ratio of ethylene carbonate (EC): ethylmethyl carbonate (EMC): dimethyl carbonate (DMC) = 20:10:70 was used.

[0165] A 1.5 M lithium salt (LiPF6) was mixed with the above-mentioned non-aqueous organic solvent, and 0.03 wt% of a block copolymer represented by the following chemical formula 1 was added as an electrolyte additive to finally obtain an electrolyte for a lithium secondary battery:

[0166] [Chemical Formula 1]

[0167]

[0168] In the above chemical formula 1, x11, x12, and x21 are each independently integers from 1 to 20.

[0169] The block copolymer represented by the above chemical formula 1 has a weight-average molecular weight of about 1,100 g / mol, measured by GPC (gel permeation chromatography, PL GPC220, Agilent Technologies) and corrected as a cubic function using polystyrene.

[0170] In addition, the content (weight%) of the electrolyte additive above refers to the content (weight%) in 100 weight% of the electrolyte for the lithium secondary battery (non-aqueous organic solvent + lithium salt + additive). The same applies below.

[0171] Preparation Example 2

[0172] An electrolyte for a lithium secondary battery was prepared in the same manner as in Preparation Example 1, except that 0.1 wt% of a block copolymer represented by the following chemical formula 1 was added as an electrolyte additive.

[0173] Preparation Example 3

[0174] An electrolyte for a lithium secondary battery was prepared in the same manner as in Preparation Example 1, except that 0.3 weight% of a block copolymer represented by the following chemical formula 1 was added as an electrolyte additive.

[0175] Preparation Example 4

[0176] An electrolyte for a lithium secondary battery was prepared in the same manner as in Preparation Example 1, except that 0.5 weight% of a block copolymer represented by the following chemical formula 1 was added as an electrolyte additive.

[0177] Manufacturing Comparative Example 1

[0178] An electrolyte for a lithium secondary battery was prepared in the same manner as in Preparation Example 1, except that no electrolyte additives were added.

[0179] Comparative Manufacturing Example 2

[0180] 0.1 weight% of a homopolymer containing only the following repeating unit 1-1 is added as an electrolyte additive.

[0181] [Repeat Unit 1-1]

[0182]

[0183] In the above repetition unit 1-1, x is an integer from 1 to 20.

[0184] The homopolymer containing only repeating unit 1-1 has a weight-average molecular weight of about 1,000 g / mol, measured by GPC (gel permeation chromatography, PL GPC220, Agilent Technologies) and corrected as a cubic function using polystyrene.

[0186] Production of lithium secondary batteries

[0187] Example 1-1

[0188] (1) Manufacturing of positive electrode plates

[0189] LiNi as a positive electrode active material 0.88 Co 0.07 Al 0.05 O2, polyvinylidene fluoride as a binder, and Ketjen black as a conductive material are mixed in a weight ratio of 97:2:1, respectively. N - An anode slurry was prepared by dispersing in methylpyrrolidone.

[0190] The above anode slurry was coated onto an Al foil with a thickness of 14 μm, dried at 110°C, and then pressed to manufacture an anode plate.

[0191] The above positive electrode plate has a loading amount of 50.1 mg / cm² 2 and, the density of the mixture is 4.0 g / cc, and the current density is 5.4 mA / cm² 2 am.

[0192] Each of the above measurement methods is the same in the following examples and comparative examples.

[0193] (2) Manufacturing of the negative electrode plate

[0194] A mixture of artificial graphite and a Si-C composite mixed in a weight ratio of 93:7 was used as the cathode active material, and a cathode slurry was prepared by mixing the cathode active material, a styrene-butadiene rubber binder, and carboxymethylcellulose in a weight ratio of 97:1:2, respectively, and dispersing them in distilled water.

[0195] The above Si-C composite comprises a core containing artificial graphite and silicon particles, and a coal-based pitch coated on the surface of the core.

[0196] The above cathode slurry was coated onto a 10㎛ thick Cu foil, dried at 100℃, and then pressed to manufacture a cathode plate.

[0197] The above cathode plate has a loading amount of 50.1 mg / cm² 2 And, the density of the mixture is 1.64 g / cc.

[0198] Each of the above measurement methods is the same in the following examples and comparative examples.

[0199] (3) Production of lithium secondary batteries

[0200] An electrode assembly was manufactured by assembling the above positive electrode plate and the above negative electrode plate with a separator made of polyethylene material with a thickness of 25 μm, and a lithium secondary battery was manufactured by injecting the electrolyte for a lithium secondary battery of Manufacturing Example 1.

[0201] Examples 1-2

[0202] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the electrolyte for a lithium secondary battery of Manufacturing Example 2 was injected as the electrolyte.

[0203] Examples 1-3

[0204] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the electrolyte for a lithium secondary battery of Manufacturing Example 3 was injected as the electrolyte.

[0205] Examples 1-4

[0206] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the electrolyte for a lithium secondary battery of Manufacturing Example 4 was injected as the electrolyte.

[0207] Comparative Example 1-1

[0208] A lithium secondary battery was manufactured in the same manner as Example 1, except that the electrolyte for a lithium secondary battery of Comparative Example 1 was used as the electrolyte.

[0209] Comparative Example 1-2

[0210] A lithium secondary battery was manufactured in the same manner as Example 1, except that the electrolyte for a lithium secondary battery of Comparative Example 2 was used as the electrolyte.

[0211] Examples 2 to 4 and Comparative Examples 2 to 6

[0212] A lithium secondary battery was manufactured in the same manner as Example 2 above, except that the loading amount and composite density of the positive electrode plate; and the current density were changed according to Table 1 below.

[0214] Electrolyte Additive Content (Weight%) positive electrode plate cathode plate Current density (mA / cm²) 2 ) Loading amount (mg / cm²) 2 ) Composition density (g / cc) Loading amount (mg / cm²) 2 ) Composition density (g / cc) Comparative Example 1-1 - 5.4 50.1 4.0 28.2 1.64 Comparative Example 1-2 0.1 (repeat unit 1) 5.4 50.1 4.0 28.2 1.64 Example 1-1 0.03 (Chemical Formula 1) 5.4 50.1 4.0 28.2 1.64 Examples 1-2 0.1 (Chemical Formula 1) 5.4 50.1 4.0 28.2 1.64 Examples 1-3 0.3 (Chemical Formula 1) 5.4 50.1 4.0 28.2 1.64 Examples 1-4 0.5 (Chemical Formula 1) 5.4 50.1 4.0 28.2 1.64 Comparative Example 2 - 5.8 55.0 4.0 31.5 1.64 Example 2 0.1 (Chemical Formula 1) 5.8 55.0 4.0 31.5 1.64 Comparative Example 3 - 6.3 59.1 4.0 33.5 1.64 Example 3 0.1 (Chemical Formula 1) 6.3 59.1 4.0 33.5 1.64 Comparative Example 4 - 6.6 65.0 4.0 39.2 1.64 Example 4 0.1 (Chemical Formula 1) 6.6 65.0 4.0 39.2 1.64 Comparative Example 5 - 4.0 44.7 4.0 24.6 1.64 Comparative Example 6 0.1 (Chemical Formula 1) 4.0 44.7 4.0 24.6 1.64 Comparative Example 7 - 3.3 37.7 4.0 20.6 1.64 Comparative Example 8 0.1 (Chemical Formula 1) 3.3 37.7 4.0 20.6 1.64

[0215] Evaluation 1: Evaluation of Electrolyte Impregnation Characteristics

[0216] For each positive electrode plate of the examples and comparative examples, the electrolyte impregnation characteristics were evaluated and listed in Table 2 below.

[0217] Specifically, as the electrolyte, 1.0 M LiPF6 was prepared by dissolving it in a carbonate-based solvent mixed in a volume ratio of ethylene carbonate (EC): ethylmethyl carbonate (EMC): dimethyl carbonate (DMC) = 2:2:4.

[0218] The above electrolyte was dropped onto a positive electrode plate sample with dimensions of 3cm x 3cm, and the area impregnated with the electrolyte was measured.

[0220] Evaluation 2: Life Characteristics Evaluation

[0221] For each lithium secondary battery of the examples and comparative examples, life characteristics were evaluated and listed in Table 2 below.

[0222] After performing 287 charge-discharge cycles under conditions of 25℃, 0.33C charging (CC / CV, 4.45V, 0.025C Cut-off) / 1.0C discharging (CC, 2.5V Cut-off), the capacity retention rate was evaluated according to Equation 1 below.

[0223] [Equation 1]

[0224] Capacity retention rate = (Discharge capacity after 287 cycles / Discharge capacity after 1 cycle) * 100

[0226] Evaluation 3: Evaluation of Li Precipitation Amount

[0227] For each lithium secondary battery of the examples and comparative examples, the amount of Li precipitation was evaluated and listed in Table 2 below.

[0228] The charging capacity was determined by charging to 25℃ and SOC 80%, and the lithium deposition capacity on the surface of the negative electrode plate at the discharge plateau during 1.0C discharge (CC, 2.5V Cut-off) was determined, and the amount of Li deposition was evaluated according to Equation 2 below.

[0229] [Equation 2]

[0230] Li Precipitation Amount: Lithium Precipitation Capacity (Discharge Plateau Period) / Charge Capacity (SOC80 Charge Amount) x 100

[0232] Impregnation characteristics life Li precipitation amount Impregnation area after 10s [cm² 2 ] Capa.[%]@287cy. [%] Comparative Example 1-1 2.913 90.8 1.01 Comparative Example 1-2 2.897 90.5 1.60 Example 1-1 3.801 91.5 1.30 Examples 1-2 3.908 92.2 0.92 Examples 1-3 4.062 92.5 0.90 Examples 1-4 3.950 92.1 0.95 Comparative Example 2 1.799 89.6 1.10 Example 2 3.611 91.9 0.97 Comparative Example 3 0.785 88.0 1.21 Example 3 2.543 91.5 1.03 Comparative Example 4 0.574 85.0 1.70 Example 4 1.713 87.9 1.57 Comparative Example 5 4.203 92.7 0.65 Comparative Example 6 4.213 92.7 0.66 Comparative Example 7 4.525 93.1 0.61 Comparative Example 8 4.520 93.0 0.63

[0233] Referring to Table 2, when the current density of the positive electrode is the same, a lithium secondary battery containing a polyalkylene glycol copolymer as an electrolyte additive exhibits increased lifespan and reduced Li deposition compared to the case where no electrolyte additive is used. However, when the current density of the positive electrode is 5.4 mA / cm² 2 If it is less than that, there are limitations in implementing high-capacity secondary batteries.

[0234] In a lithium secondary battery of one embodiment, the electrolyte additive acts as a surfactant. Accordingly, in a lithium secondary battery containing the electrolyte additive, the wettability of the positive electrode plate with respect to the electrolyte can be improved even when the current density of the positive electrode plate is increased.

[0235] Furthermore, if the wettability of the positive electrode plate with respect to the electrolyte is improved, a lithium cation flux (Li) at the interface between the positive electrode plate and the electrolyte + ) is uniformly formed, so that the precipitation of lithium dendrites on the surface of the negative electrode plate is suppressed, and ultimately, the life characteristics and rapid charging performance of the lithium secondary battery can be secured.

[0237] Although preferred embodiments of the present invention have been described above, the present invention is not limited thereto and can be implemented with various modifications within the scope of the claims, the detailed description of the invention, and the attached drawings, and it is obvious that such modifications also fall within the scope of the present invention. Explanation of the symbols

[0238] 100: Lithium secondary battery 112: Cathode plate 113: Separator 114: Positive electrode plate 120: Battery container 140: Encapsulated member

Claims

Claim 1 A lithium secondary battery comprising a positive electrode plate, a negative electrode plate, and an electrolyte including an electrolyte additive, wherein the current density of the positive electrode plate is 5.4 mA / cm² 2 Up to 6.6 mA / cm 2 And; the above electrolyte additive is a lithium secondary battery comprising a polyalkylene glycol-based copolymer. Claim 2 In claim 1, the above electrolyte additive is a lithium secondary battery comprising a copolymer including the following repeating unit 1: [Repeating unit 1] In the above repeating unit 1, R is a hydrogen atom or an alkyl group having 1 to 20 carbon atoms; and x is an integer from 1 to 20. Claim 3 In paragraph 2, the above electrolyte additive is a lithium secondary battery that is a block copolymer comprising the following repeating units 1-1 and 1-2: [Repeating unit 1-1] [Repetition Unit 1-2] In the above repetition units 1-1 and 1-2, R 1 is an alkyl group having 1 to 20 carbon atoms; x1 and x2 are each independently integers from 1 to 20. Claim 4 In paragraph 3, the above electrolyte additive is a lithium secondary battery that is a block copolymer represented by the following chemical formula 1: [Chemical Formula 1] In the above chemical formula 1, x11, x12, and x21 are each independently integers from 1 to 20. Claim 5 A lithium secondary battery according to claim 1, wherein the content of the electrolyte additive in 100 weight% of the electrolyte is 0.03 weight% to 0.5 weight%. Claim 6 A lithium secondary battery according to claim 1, wherein the electrolyte further comprises a lithium salt and a non-aqueous organic solvent. Claim 7 In claim 6, the lithium salt is LiPF6, LiBF4, LiDFOP, LiDFOB, LiPO2F2, LiSbF6, LiAsF6, LiN(SO2C2F5)2, Li(CF3SO2)2N, LiN(SO3C2F5)2, Li(FSO2)2N (lithium bis(fluorosulfonyl)imide (LiFSI), LiC4F9SO3, LiClO4, LiAlO2, LiAlCl4, LiN(C m F 2m+1 SO2)(C n F 2n+1 A lithium secondary battery comprising one or more selected from the group consisting of SO2)(wherein m and n are each independently integers from 1 to 20), LiCl, LiI, and LiB(C2O4)2 (lithium bis(oxalato) borate (LiBOB). Claim 8 A lithium secondary battery according to claim 6, wherein the concentration of the lithium salt in the electrolyte for the lithium secondary battery is 1.0 M to 2.0 M. Claim 9 In claim 6, the above-mentioned non-aqueous organic solvent comprises a carbonate-based, ester-based, ether-based, ketone-based, alcohol-based, or aprotic solvent for a lithium secondary battery. Claim 10 In claim 9, the above-mentioned non-aqueous organic solvent comprises a carbonate-based solvent in which a cyclic carbonate and a linear carbonate are mixed in a volume ratio of 5:95 to 50:50, for a lithium secondary battery. Claim 11 A lithium secondary battery according to claim 10, comprising ethylene carbonate (EC) as the cyclic carbonate and ethylmethyl carbonate (EMC) and dimethyl carbonate (DMC) as the linear carbonates. Claim 12 In claim 1, the positive electrode plate comprises a positive composite layer, and the loading amount of the positive electrode plate is 50.1 mg / cm² 2 to 65.0 mg / cm² 2 lithium secondary battery. Claim 13 A lithium secondary battery according to claim 12, wherein the composite density of the positive electrode plate is 2.0 g / cc to 6.0 g / cc. Claim 14 In claim 12, the above-mentioned positive composite layer comprises a positive active material, and the above-mentioned positive active material comprises a lithium nickel-based composite oxide represented by the following chemical formula A1, in a lithium secondary battery: [Chemical Formula A1]Li a1 Ni x1 M 1 y1 M 2 z1 O 2-b1 X b1 In the above chemical formula A1, 0.9≤a1≤1.2, 0.7≤x1≤1, 0≤y1≤0.2, 0≤z1≤0.2, 0.9≤x1+y1+z1≤1.1, and 0≤b1≤0.1, and M 1 and M 2 Each is independently one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sr, Ti, V, W, and Zr; and X is one or more elements selected from the group consisting of F, P, and S. Claim 15 In claim 1, the cathode plate comprises a cathode composite layer, and the loading amount of the cathode plate is 28.2 mg / cm² 2 to 39.2 mg / cm² 2 lithium secondary battery. Claim 16 A lithium secondary battery according to claim 15, wherein the composite density of the negative electrode plate is 1.40 g / cc to 1.80 g / cc. Claim 17 A lithium secondary battery according to claim 15, wherein the cathode composite layer comprises a cathode active material, and the cathode active material comprises at least one of graphite and Si composite. Claim 18 In claim 17, the above Si composite is a lithium secondary battery comprising a core containing Si particles and amorphous carbon. Claim 19 In paragraph 18, the core containing the above Si particles is a Si-C complex, SiO k A lithium secondary battery comprising one or more of (0 < k ≤ 2) and Si alloys. Claim 20 In claim 19, the above Si-C composite is a lithium secondary battery comprising a core containing Si particles and amorphous carbon.

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