Electrolyte additive, lithium secondary battery electrolyte containing electrolyte additive, and lithium secondary battery

Abstract

An electrolyte additive represented by Chemical Formula 1, an electrolyte for a lithium secondary battery including the electrolyte additive, and a lithium secondary battery are provided. The details of the chemical formula 1 are as described in the specification.

Description

Technical Field

[0001] According to an embodiment, the present disclosure relates to an electrolyte additive and an electrolyte for a lithium secondary battery, and a lithium secondary battery including the electrolyte. Background Art

[0002] Lithium secondary batteries are rechargeable, and have an energy density per unit weight that is three or more times that of comparable lead storage batteries, nickel-cadmium batteries, nickel-metal hydride batteries, nickel-zinc batteries, etc. They can also be charged at a high rate, and are therefore commercially used in the manufacture of laptop computers, cellular phones, power tools, electric bicycles, etc., and research on improving additional energy density has been actively conducted.

[0003] Such a lithium secondary battery is manufactured by injecting an electrolyte into a battery cell including a positive electrode including a positive electrode active material capable of intercalating / deintercalating lithium ions, and a negative electrode including a negative electrode active material capable of intercalating / deintercalating lithium ions.

[0004] The electrolyte serves as a medium for moving lithium ions between the negative electrode and the positive electrode, and generally uses an organic solvent in which a lithium salt is dissolved, and is important for determining the stability and performance of a lithium secondary battery.

[0005] The electrolyte may include, for example, LiPF 6 , LiBF 4 , LiFSI and the like, and a mixed solvent of a high dielectric cyclic carbonate (such as propylene carbonate and ethylene carbonate) and a chain carbonate (such as diethyl carbonate, ethyl methyl carbonate, dimethyl carbonate). As the development of batteries in one or more appropriate fields is activated, the development of batteries with high output and high stability over a wide temperature range becomes more important. As far as the electrolyte is concerned, it is important to develop an optimal or appropriate combination of organic solvents and additives that can improve high output, long cycle life, high temperature storage, and suppress swelling, capacity reduction, and resistance increase. Summary of the invention

[0006]

Technical issues

[0007] According to an embodiment, an electrolyte additive having excellent or appropriate high temperature characteristics is provided.

[0008] According to an embodiment, an electrolyte for a lithium secondary battery includes an additive.

[0009] According to an embodiment, a lithium secondary battery includes an electrolyte.

[0010]

Technical solution

[0011] According to an embodiment, the electrolyte additive is represented by Chemical Formula 1.

[0012] [Chemical formula 1]

[0013]

[0014] In Chemical Formula 1,

[0015] X 1 and X 2 Each independently is N or CR a ,

[0016] X 1 and X 2 At least one of them is N,

[0017] R a and R 1 ~R 3 are each independently hydrogen or substituted or unsubstituted C1-C10 alkyl, and

[0018] n is an integer of 1 to 3.

[0019] n can be an integer of 1 or 2.

[0020] R 1 ~R 3 They may each independently be hydrogen or a substituted or unsubstituted C1-C5 alkyl group.

[0021] R 3 It may be hydrogen.

[0022] The electrolyte additive may be one selected from the compounds listed in Group 1.

[0023] [Group 1]

[0024]

[0025] Another embodiment of the present disclosure provides an electrolyte for a lithium secondary battery, which includes a non-aqueous organic solvent, a lithium salt, and an electrolyte additive.

[0026] The electrolyte additive may be included in an amount of about 0.05 parts by weight to 5.0 parts by weight based on 100 parts by weight of the total weight of the electrolyte for a lithium secondary battery.

[0027] The electrolyte additive may be included in an amount of about 0.05 parts by weight to 3.0 parts by weight based on 100 parts by weight of the total weight of the electrolyte for a lithium secondary battery.

[0028] The electrolyte for the lithium secondary battery may further include vinylene carbonate (VC), fluoroethylene carbonate (FEC), difluoroethylene carbonate, chloroethylene carbonate, dichloroethylene carbonate, bromoethylene carbonate, dibromoethylene carbonate, nitroethylene carbonate, cyanoethylene carbonate, vinylethylene carbonate (VEC), adiponitrile (AN), succinonitrile (SN), 1,3,6-hexanetricyano (HTCN), propene sultone (PST), propane sultone (PS), lithium tetrafluoroborate (LiBF 4 ), lithium difluorophosphate (LiPO 2 F 2 ) and at least one other additive of 2-fluorobiphenyl (2-FBP).

[0029] The non-aqueous organic solvent may consist only of chain carbonate.

[0030] The chain carbonate can be represented by Chemical Formula 2.

[0031] [Chemical formula 2]

[0032]

[0033] In chemical formula 2,

[0034] R 4 and R 5 Each is independently a substituted or unsubstituted C1-C20 alkyl group.

[0035] The non-aqueous organic solvent may be at least two selected from dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), and ethylmethyl carbonate (EMC).

[0036] Another embodiment of the present disclosure provides a lithium secondary battery including: a positive electrode including a positive electrode active material; a negative electrode including a negative electrode active material; and the aforementioned electrolyte for a lithium secondary battery.

[0037] The positive electrode active material may include cobalt-free lithium nickel manganese oxide.

[0038] The cobalt-free lithium nickel manganese oxide may include a lithium composite oxide represented by Chemical Formula 4.

[0039] [Chemical formula 4]

[0040] Li a Ni x Mn y M1 z M2 w O 2±b X c

[0041] In Chemical Formula 4,

[0042] 0.9 ≤ a < 1.2, 0 ≤ b < 0.1, 0 ≤ c < 0.1, 0 ≤ w < 0.1, 0.6 ≤ x < 1.0, 0 < y < 0.4, 0 < z < 0.1, w + x + y + z = 1,

[0043] M1 and M2 are each independently at least one element selected from Al, Mg, Ti, Zr, Cr, Sr, V, B, W, Mo, Nb, Si, Ba, Ca, Ce, Cr, Fe, and Nb, and X is at least one element selected from S, F, P, and Cl.

[0044] Chemical Formula 4 can be represented by Chemical Formula 4-1.

[0045] [Chemical Formula 4-1]

[0046] Li a Ni x1 Mn y1 Al z1 M2 w1 O 2±b X c

[0047] In Chemical Formula 4-1,

[0048] 0.9 ≤ a < 1.2, 0 ≤ b < 0.1, 0 ≤ c < 0.1, 0 ≤ w1 < 0.1, 0.6 ≤ x1 < 1.0, 0 < y1 < 0.4, 0 < z1 < 0.1, w1 + x1 + y1 + z1 = 1, M2 is an element selected from Mg, Ti, Zr, Cr, Sr, V, B, W, Mo, Nb, Si, Ba, Ca, Ce, Cr, Fe, and Nb, and X is at least one element selected from S, F, P, and Cl.

[0049] In Chemical Formula 4-1, x1 can be 0.6 ≤ x1 ≤ 0.79, y1 can be 0.2 ≤ y1 ≤ 0.39, and z1 can be 0.01 ≤ z1 < 0.1.

[0050] The negative electrode active material may include at least one of graphite and a Si composite.

[0051] The Si composite may include a core containing Si-based particles and an amorphous carbon coating.

[0052] The Si-based particles may include at least one of Si particles, Si-C composites, SiO x (0 < x ≤ 2) and Si alloys.

[0053]

Beneficial Effects

[0054] According to the embodiments, the lithium secondary battery can suppress an increase in battery resistance during high-temperature storage and implement excellent or appropriate cycle-life characteristics. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 is a schematic diagram of a lithium secondary battery according to one or more embodiments of the present disclosure.

[0056] Figure 2 Graphs showing the results of negative electrode cyclic voltammetry (CV) at room temperature of electrolytes prepared in Examples and Comparative Examples according to one or more embodiments of the present disclosure.

[0057] <Description of Reference Numerals>

[0058] 100: Lithium secondary battery

[0059] 112: Negative electrode

[0060] 113: Diaphragm

[0061] 114: Positive electrode

[0062] 120: Battery housing

[0063] 140: Sealing member DETAILED DESCRIPTION

[0064] Hereinafter, a lithium secondary battery according to one or more embodiments of the present disclosure will be described in more detail with reference to the accompanying drawings. However, these embodiments are examples, the present disclosure is not limited thereto, and the present disclosure is defined by the scope of the claims.

[0065] As used herein, when no further limitation is provided, "substituted" means that the hydrogen of the compound is replaced by a substituent selected from the following: deuterium, halogen, hydroxyl, amino, substituted or unsubstituted C1-C30 amine, nitro, substituted or unsubstituted C1-C40 silyl, C1-C30 alkyl, C1-C10 alkylsilyl, C6-C30 arylsilyl, C3-C30 cycloalkyl, C3-C30 heterocycloalkyl, C6-C30 aryl, C2 to C30 heteroaryl, C1-C20 alkoxy, C1-C10 fluoroalkyl, cyano and / or combinations thereof.

[0066] As used herein, when no limitation is otherwise provided, "substituted" refers to the substitution of at least one hydrogen of a substituent or compound by deuterium, halogen, C1-C30 alkyl, C1-C10 alkylsilyl, C6-C30 arylsilyl, C3-C30 cycloalkyl, C3-C30 heterocycloalkyl, C6-C30 aryl, C2 to C30 heteroaryl, C1-C10 fluoroalkyl or cyano. In some embodiments, in specific embodiments of the present disclosure, "substituted" refers to the substitution of at least one hydrogen of a substituent or compound by deuterium, halogen, C1-C20 alkyl, C6-C30 aryl, C1-C10 fluoroalkyl or cyano. In some embodiments, in specific embodiments of the present disclosure, "substituted" refers to the substitution of at least one hydrogen of a substituent or compound by deuterium, halogen, C1-C5 alkyl, C6-C18 aryl, C1-C5 fluoroalkyl or cyano. In some embodiments, in specific examples of the present disclosure, "substituted" means that at least one hydrogen of the compound is replaced by a substituent selected from the following: deuterium, cyano, halogen, methyl, ethyl, propyl, butyl, phenyl, biphenyl, terphenyl, trifluoromethyl or naphthyl.

[0067] According to the types of separators and electrolytes, lithium secondary batteries can be divided into lithium ion batteries, lithium ion polymer batteries and lithium polymer batteries. According to the shape, it can also be classified into cylindrical, prismatic, coin-shaped, bag-shaped, etc. In addition, it can be divided into block type and film type. The structure and manufacturing method for lithium ion batteries disclosed in the present invention are very suitable for this field.

[0068] Herein, a cylindrical lithium secondary battery will be exemplarily described as an example of the lithium secondary battery. Figure 1 The structure of a lithium secondary battery according to one or more embodiments is schematically shown. Figure 1 According to one or more embodiments, a lithium secondary battery 100 includes a battery cell, a battery case 120 that accommodates the battery cell, and a sealing member 140 that seals the battery case 120. The battery cell includes a positive electrode 114, a negative electrode 112 facing the positive electrode 114, a separator 113 between the positive electrode 114 and the negative electrode 112, and an electrolyte (not shown) that impregnates the positive electrode 114, the negative electrode 112, and the separator 113.

[0069] Hereinafter, an electrolyte additive according to one or more embodiments will be described.

[0070] The additive according to one or more embodiments of the present disclosure is represented by Chemical Formula 1.

[0071] [Chemical formula 1]

[0072]

[0073] In Chemical Formula 1,

[0074] X 1 and X 2 Each independently is N or CR a ,

[0075] X 1 and X 2 At least one of them is N,

[0076] R a and R 1 ~R 3 are each independently hydrogen or substituted or unsubstituted C1-C10 alkyl, and

[0077] n is an integer of 1 to 3.

[0078] The pyridyl or pyrimidyl and alkynyl groups included in Chemical Formula 1 can capture PF5 - Acts as a lone pair electron donor.

[0079] In lithium secondary batteries, nonaqueous electrolytes decompose during initial charge and discharge, and thus form a film with passivation ability on the surface of the positive and negative electrodes. This film improves storage characteristics at high temperatures, but may be blocked by lithium salts (LiPF) widely used in lithium-ion batteries. 6 Acids (such as HF) generated by thermal decomposition of - and PF5 - ) damage. This acid corrosion dissolves transition metal elements from the positive electrode and thus increases the sheet resistance of the electrode due to structural changes on the surface. Due to the loss of metal elements as redox centers, acid corrosion / dissolution reduces the theoretical capacity, thereby deteriorating the expression capacity. For example, the dissolved transition metal ions are electrodeposited on the negative electrode reacting in a strong reduction potential band. The transition metal ions may consume electrons and / or destroy the film during electrodeposition and expose the surface of the negative electrode, thereby additionally causing a decomposition reaction of the electrolyte. As a result, as the resistance of the negative electrode increases, and the irreversible capacity increases, they may lead to continuous degradation of the battery capacity. In the present disclosure, the pyridyl or pyrimidyl and alkynyl groups of the additive represented by Chemical Formula 1 provide non-shared electron pairs to remove the acid caused by the decomposition of the lithium salt, thereby strengthening the solid electrolyte interface (SEI) film on the surface of the negative electrode, and preventing or reducing the degradation of the SEI film during high temperature storage, the dissolution of the transition metal at the positive electrode, and the like.

[0080] In particular, when present in the meta position relative to the acetate group, the N of the pyridyl or pyrimidyl group can act as a more favorable or enhanced donor of an unshared electron pair.

[0081] As described herein, inhibition of electrolyte decomposition and inhibition of side reactions with the electrolyte may be maximized or increased by using additives with a positive electrode including a cobalt-free lithium nickel manganese oxide as described elsewhere herein.

[0082] For example, n may be one of integers of 1 to 3, and for example, n may be an integer of 1 or 2.

[0083] When n is within the above range, since the alkylene chain between the alkyne and the acetate in Chemical Formula 1 maintains a suitable or appropriate length, an increase in resistance due to the thickness of the SEI film may be suppressed or reduced.

[0084] For example, R 1 ~R 3 They may each independently be hydrogen or a substituted or unsubstituted C1-C5 alkyl group.

[0085] For example, R 3 It may be hydrogen.

[0086] In one or more embodiments, the additive represented by Chemical Formula 1 may be selected from the compounds listed in Group 1.

[0087] [Group 1]

[0088]

[0089] An electrolyte for a lithium secondary battery according to another embodiment includes a nonaqueous organic solvent, a lithium salt, and the aforementioned electrolyte additive.

[0090] The additive may be included in an amount of about 0.05 parts by weight to 5.0 parts by weight based on 100 parts by weight of the total weight of the electrolyte for a lithium secondary battery.

[0091] For example, the additive may be included in an amount of about 0.05 parts by weight to 3.0 parts by weight based on 100 parts by weight of the total weight of the electrolyte for a lithium secondary battery.

[0092] When the content of the additive is within the above range, a lithium secondary battery having enhanced or improved cycle-life characteristics and output characteristics may be realized by preventing or reducing an increase in resistance at high temperatures.

[0093] The electrolyte for the lithium secondary battery may further include vinylene carbonate (VC), fluoroethylene carbonate (FEC), difluoroethylene carbonate, chloroethylene carbonate, dichloroethylene carbonate, bromoethylene carbonate, dibromoethylene carbonate, nitroethylene carbonate, cyanoethylene carbonate, vinylethylene carbonate (VEC), adiponitrile (AN), succinonitrile (SN), 1,3,6-hexanetricyano (HTCN), propene sultone (PST), propane sultone (PS), lithium tetrafluoroborate (LiBF 4 ), lithium difluorophosphate (LiPO 2 F 2 ) and at least one other additive of 2-fluorobiphenyl (2-FBP).

[0094] By further including the aforementioned other additives, the cycle life may be further enhanced or improved, or the gases generated from the positive electrode and the negative electrode may be effectively controlled or selected during high-temperature storage.

[0095] The other additives may be included in an amount of about 0.2 to 20 parts by weight, specifically about 0.2 to 15 parts by weight, for example, about 0.2 to 10 parts by weight, based on 100 parts by weight of the total weight of the electrolyte for a lithium secondary battery.

[0096] When the contents of other additives are as described above, the increase in membrane resistance can be minimized or reduced, thereby contributing to the improvement of battery performance.

[0097] The nonaqueous organic solvent serves as a medium for transporting ions participating in the electrochemical reaction of the battery.

[0098] The non-aqueous organic solvent may be a carbonate, ester, ether, ketone, alcohol or an aprotic solvent.

[0099] Carbonate solvents may include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), etc. Ester solvents may include methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, decanoic acid lactone, mevalonate lactone, caprolactone, etc. Ether solvents may include dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, ethylene glycol dimethyl ether, 2-methyltetrahydrofuran, tetrahydrofuran, etc. In addition, ketone solvents may include cyclohexanone, etc. Alcohol solvents may include ethanol, isopropanol, etc., and aprotic solvents may include nitriles (such as R 1 -CN, where R 1is a hydrocarbon group having a C2-C20 straight chain, branched chain or ring structure, and may include a double bond, an aromatic ring or an ether bond), a dioxolane (such as 1,3-dioxolane), sulfolane, and the like.

[0100] The nonaqueous organic solvent may be used alone or in a mixture. When the nonaqueous organic solvent is used in a mixture, the mixture ratio may be controlled or selected according to the desired battery performance.

[0101] For example, the nonaqueous organic solvent may consist of only a chain carbonate. In this case, since the resistance increase rate during high-temperature storage is significantly reduced, excellent or appropriate high-temperature storage characteristics can be achieved.

[0102] As used herein, "consisting only of chain carbonate" means that an organic solvent including a chain carbonate is used alone or in combination without being mixed with a cyclic carbonate or the like.

[0103] As a specific example, the chain carbonate may be represented by Chemical Formula 2.

[0104] [Chemical formula 2]

[0105]

[0106] In chemical formula 2

[0107] R 4 and R 5 Each is independently a substituted or unsubstituted C1-C20 alkyl group.

[0108] For example, R in Formula 2 4 and R 5 may be independently substituted or unsubstituted C1-C10 alkyl, and for example R 4 and R 5 Each independently may be a substituted or unsubstituted C1-C5 alkyl group.

[0109] In an exemplary embodiment, R of Chemical Formula 2 4 and R 5 Each independently may be substituted or unsubstituted methyl, substituted or unsubstituted ethyl, substituted or unsubstituted n-propyl, substituted or unsubstituted n-butyl, substituted or unsubstituted n-pentyl, substituted or unsubstituted isobutyl or substituted or unsubstituted neopentyl.

[0110] For example, the nonaqueous organic solvent according to a specific embodiment may be at least two selected from dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), and ethylmethyl carbonate (EMC).

[0111] The non-aqueous organic solvent according to the most specific embodiment may be a mixed solvent of dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC).

[0112] The non-aqueous organic solvent may further include an aromatic hydrocarbon-based organic solvent in addition to the carbonate-based solvent. Herein, the carbonate-based solvent and the aromatic hydrocarbon-based organic solvent may be mixed in a volume ratio of about 1:1 to about 30:1.

[0113] The aromatic hydrocarbon organic solvent may be an aromatic hydrocarbon compound of Chemical Formula 3.

[0114] [Chemical formula 3]

[0115]

[0116] In chemical formula 3, R 7 ~R 12 are the same or different and are selected from hydrogen, halogen, C1-C10 alkyl, C1-C10 haloalkyl and / or combinations thereof.

[0117] Specific examples of aromatic hydrocarbon organic solvents may be selected from 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, 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 / or combinations thereof.

[0118] The lithium salt dissolved in the non-organic solvent supplies lithium ions in the battery, ensures the basic operation of the lithium secondary battery, and improves the transport of lithium ions between the positive electrode and the negative electrode. Examples of the lithium salt include those selected from LiPF 6 , LiBF 4 、LiSbF 6 、LiAsF 6 、LiN(SO 2 C 2 F 5 ) 2 、Li(CF 3 SO 2 ) 2N、LiN(SO 3 C 2 F 5 ) 2 、Li(FSO 2 ) 2 N(Lithium bis(fluorosulfonyl)imide: LiFSI), LiC 4 F 9 SO 3 、LiClO 4 、LiAlO 2 、LiAlCl 4 、LiPO 2 F 2 、LiN(C x F 2x+1 SO 2 )(C y F 2y+1 SO 2 )(wherein x and y are natural numbers, such as integers ranging from 1 to 20), LiCl, LiI, LiB(C 2 O 4 ) 2 (lithium bis(oxalato)borate: LiBOB), LiDFOB (lithium difluoro(oxalato)borate) and Li[PF 2 (C 2 O 4 ) 2 ](lithium difluoro(bisoxalato)phosphate). The lithium salt may be used in a concentration range of about 0.1 M to about 2.0 M. When the lithium salt is included in the above concentration range, the electrolyte may have excellent or appropriate performance and lithium ion mobility due to optimal or appropriate electrolyte conductivity and viscosity.

[0119] Another embodiment provides a lithium secondary battery including: a positive electrode including a positive electrode active material; a negative electrode including a negative electrode active material; and the aforementioned electrolyte.

[0120] The positive electrode includes a positive electrode current collector and a positive electrode active material layer on the positive electrode current collector, and the positive electrode active material layer includes a positive electrode active material.

[0121] The positive electrode active material may include cobalt-free lithium nickel manganese oxide.

[0122] In the present disclosure, the cobalt-free lithium nickel manganese-based oxide as a positive electrode active material refers to a positive electrode active material including nickel, manganese, etc. but not including cobalt in the composition of the positive electrode active material.

[0123] For example, the cobalt-free lithium nickel manganese-based oxide may include at least one type of lithium composite oxide represented by Chemical Formula 4.

[0124] [Chemical formula 4]

[0125] Li a Ni x Mn y M1 z M2 w O 2±b X c

[0126] In chemical formula 4,

[0127] 0.9≤a<1.2,0≤b<0.1,0≤c<0.1,0≤w<0.1,0.6≤x<1.0,0 <y<0.4,0<z<0.1,w+x+y+z=1,

[0128] M1 and M2 are each independently at least one element selected from Al, Mg, Ti, Zr, Cr, Sr, V, B, W, Mo, Nb, Si, Ba, Ca, Ce, Cr, Fe and Nb, and X is at least one element selected from S, F, P and Cl.

[0129] The lithium composite oxide may have a coating on the surface, or may be mixed with another lithium composite oxide having a coating. The coating may include at least one coating element compound selected from an oxide of the coating element, a hydroxide of the coating element, an oxyhydroxide of the coating element, an oxycarbonate of the coating element, and a hydroxycarbonate of the coating element. The compound used for the coating may be amorphous or crystalline. The coating element included in the coating may include Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or a mixture thereof. By utilizing these elements in the compound, a coating may be formed or provided in a method that has no adverse effect on the characteristics of the positive electrode active material. For example, the method may include any coating method (e.g., spraying, dipping, etc.) applicable to the relevant technology or field.

[0130] For example, Chemical Formula 4 can be represented by Chemical Formula 4-1.

[0131] [Chemical formula 4-1]

[0132] Li a Ni x1 Mn y1 Al z1 M2 w1 O 2±b X c

[0133] In chemical formula 4-1,

[0134] 0.9 ≤ a < 1.2, 0 ≤ b < 0.1, 0 ≤ c < 0.1, 0 ≤ w1 < 0.1, 0.6 ≤ x1 < 1.0, 0 < y1 < 0.4, 0 < z1 < 0.1, w1 + x1 + y1 + z1 = 1, M2 is an element selected from Mg, Ti, Zr, Cr, Sr, V, B, W, Mo, Nb, Si, Ba, Ca, Ce, Cr, Fe, and Nb, and X is at least one element selected from S, F, P, and Cl.

[0135] In Chemical Formula 4-1, x1 can be 0.6 ≤ x1 ≤ 0.79, y1 can be 0.2 ≤ y1 ≤ 0.39, and z1 can be 0.01 ≤ z1 < 0.1.

[0136] Based on the total weight of the positive electrode active material layer, the positive electrode active material can be included in an amount of about 90 wt% to about 98 wt%.

[0137] Based on the total weight of the positive electrode active material layer, the content of each of the conductive material and the binder can be about 1 wt% to about 5 wt%.

[0138] The positive electrode active material layer further includes a conductive material and a binder.

[0139] A conductive material is included to provide positive electrode conductivity, and any conductive material can be used as the conductive material unless it causes a chemical change. Examples of the conductive material include carbon-based materials (such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, etc.); metal-based materials including metal powders or metal fibers such as copper, nickel, aluminum silver, etc.; conductive polymers (such as poly(phenylene) derivatives); or mixtures thereof.

[0140] The binder improves the binding characteristics between the positive electrode active material particles and the binding characteristics between the positive electrode active material particles and the current collector. Examples thereof can be polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, a polymer 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.

[0141] Al can be used as the positive electrode current collector, but is not limited thereto.

[0142] The negative electrode includes a negative electrode current collector and a negative electrode active material layer formed on the negative electrode current collector and including a negative electrode active material.

[0143] The negative electrode active material can include a material that reversibly intercalates / deintercalates lithium ions, lithium metal, a lithium metal alloy, a material capable of doping / dedoping lithium, and / or a transition metal oxide.

[0144] Materials that can reversibly embed / desorb lithium ions may include carbon materials. The carbon materials can be any commonly used carbonaceous negative electrode active materials in lithium secondary batteries. Examples thereof can be crystalline carbon, amorphous carbon, or a mixture thereof. The crystalline carbon can be amorphous, or natural graphite and / or artificial graphite in the form of flakes, platelets, spheres, and / or fibers. The amorphous carbon can be soft carbon, hard carbon, mesophase pitch carbonized product, calcined coke, etc.

[0145] The lithium metal alloy includes an alloy of lithium and a metal selected from Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn.

[0146] Materials that can be doped / undoped with lithium can be Si, Si-C composites, SiO x (0 < x < 2), Si-Q alloys (where Q is an element selected from alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements (except Si), Group 15 elements, Group 16 elements, transition metals, rare earth elements, and combinations thereof), Sn, SnO 2 , Sn-R 11 alloy (where R 11 is an element selected from alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements (except Si), Group 15 elements, Group 16 elements, transition metals, rare earth elements, and combinations thereof), etc. At least one of these materials can be mixed with SiO 2 .

[0147] Elements Q and R 11 can be selected from 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.

[0148] The transition metal oxide can be vanadium oxide, lithium vanadium oxide, or lithium titanium oxide.

[0149] In one or more embodiments, the negative electrode active material can include at least one selected from graphite and Si composites.

[0150] The Si composite can include a core containing Si-based particles and an amorphous carbon coating. For example, the Si-based particles can include at least one of Si particles, Si composites, SiO x (0 < x ≤ 2), and Si alloys.

[0151] For example, a void may be included in the central portion of the core including the Si-based particles, and the radius of the central portion corresponds to 30% to 50% of the radius of the Si composite. The average particle size of the Si composite may be about 5 μm to about 20 μm, and the average particle size of the Si-based particles may be about 10 nm to about 200 nm.

[0152] As used herein, the average particle size may be a particle size at 50 volume % (D50) in a cumulative size distribution curve.

[0153] When the Si-based particles have an average particle diameter within this range, volume expansion during charge and discharge may be suppressed or reduced, and interruption of a conductive path due to particle breakage during charge and discharge may be prevented or reduced.

[0154] The core including the Si-based particle may further include amorphous carbon, wherein the central portion may not include the amorphous carbon, and the amorphous carbon may exist only on a surface portion of the Si composite.

[0155] Herein, the surface portion indicates a region from the outermost surface of the central portion to the outermost surface of the Si composite.

[0156] In one or more embodiments, the Si-based particles are substantially uniformly included on the Si composite, that is, exist in a substantially uniform concentration in a central portion and a surface portion thereof.

[0157] The amorphous carbon may be soft carbon, hard carbon, a mesophase pitch carbonization product, calcined coke, or a combination thereof.

[0158] For example, the Si—C composite may include Si particles and crystalline carbon.

[0159] The Si particles may be included in an amount of about 1 wt % to about 60 wt %, for example, about 3 wt % to about 60 wt %, based on the total weight of the Si—C composite.

[0160] The crystalline carbon may be, for example, graphite, and, for example, natural graphite, artificial graphite, or a combination thereof.

[0161] The average particle size of the crystalline carbon may be about 5 μm to about 30 μm.

[0162] When the negative electrode active material includes graphite and the Si composite, the graphite and the Si composite may be included as a mixture, wherein the graphite and the Si composite may be included in a weight ratio of about 99:1 to about 50:50.

[0163] In one or more embodiments, the graphite and the Si composite may be included in a weight ratio of about 97:3 to about 80:20, or about 95:5 to about 80:20.

[0164] The precursor of amorphous carbon may include coal pitch, mesophase pitch, petroleum pitch, coal oil, petroleum heavy oil or a polymer resin (such as phenolic resin, furan resin or polyimide resin).

[0165] In the negative electrode active material layer, the negative electrode active material may be included in an amount of about 95 wt % to about 99 wt % based on the total weight of the negative electrode active material layer.

[0166] The negative electrode active material layer includes a binder and an optional conductive material. In the negative electrode active material layer, the content of the binder may be about 1wt% to about 5wt% based on the total weight of the negative electrode active material layer. When the negative electrode active material layer includes a conductive material, the negative electrode active material layer includes about 90wt% to about 98wt% of the negative electrode active material, about 1wt% to about 5wt% of the binder, and about 1wt% to about 5wt% of the conductive material.

[0167] The binder improves the bonding properties between the negative electrode active material particles and the bonding properties between the negative electrode active material particles and the current collector. The binder includes a non-water-soluble binder, a water-soluble binder or a combination thereof.

[0168] The non-water-soluble binder may be selected from polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamide-imide, polyimide or a combination thereof.

[0169] The water-soluble binder can be a rubber binder or a polymer resin binder. The rubber binder can be selected from styrene-butadiene rubber, acrylated styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber, acrylic rubber, butyl rubber, fluororubber and combinations thereof. The polymer resin binder can be selected from polytetrafluoroethylene, ethylene-propylene copolymer, polyethylene oxide, polyvinyl pyrrolidone, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, polystyrene, ethylene-propylene-diene copolymer, polyvinyl pyridine, chlorosulfonated polyethylene, latex, polyester resin, acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol and combinations thereof.

[0170] When a water-soluble binder is used as a negative electrode binder, a cellulose compound may be further used as a thickener to provide viscosity. The cellulose compound includes one or more of carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, or an alkali metal salt thereof. The alkali metal may be Na, K, or Li. Such a thickener may be included in an amount of about 0.1 to about 3 parts by weight based on 100 parts by weight of the negative electrode active material.

[0171] A conductive material is included to provide electrode conductivity, and any conductive material can be used as the conductive material unless it causes a chemical change. Examples of the conductive material include carbon-based materials (such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, etc.); metal-based materials including metal powders or metal fibers of copper, nickel, aluminum, silver, etc.; conductive polymers (such as polyphenylene derivatives); or mixtures thereof.

[0172] The negative electrode current collector may include one 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.

[0173] According to the type of lithium secondary battery, the lithium secondary battery may further include a separator between the negative electrode and the positive electrode. Such a separator may be a porous substrate or a composite porous substrate.

[0174] The porous substrate may be a substrate including pores, and lithium ions may move through the pores. Examples of the porous substrate include polyethylene, polypropylene, polyvinylidene fluoride, and multilayers thereof, such as a polyethylene / polypropylene double-layer separator, a polyethylene / polypropylene / polyethylene three-layer separator, and a polypropylene / polyethylene / polypropylene three-layer separator.

[0175] The composite porous substrate may have a form including a porous substrate and a functional layer on the porous substrate. From the perspective of realizing additional functions, the functional layer may be, for example, at least one of a heat-resistant layer and an adhesive layer. For example, the heat-resistant layer may include a heat-resistant resin and an optional filler.

[0176] In some embodiments, the adhesive layer may include an adhesive resin and optionally a filler.

[0177] The filler may be an organic filler or an inorganic filler.

[0178] The lithium secondary battery may have a charge upper limit voltage greater than or equal to about 4.45 V. For example, the charge upper limit voltage may be about 4.45 V to about 4.55 V.

[0179]

Invention Mode

[0180] Hereinafter, examples and comparative examples of the present disclosure are described. However, these examples are not to be construed as limiting the scope of the present disclosure in any sense.

[0181] (Synthesis Example: Synthesis of Additives)

[0182] Synthesis Example 1: Synthesis of Chemical Formula 1a

[0183] [Reaction Scheme 1]

[0184]

[0185] First, nicotinic acid is contacted (e.g., reacted) with DCC (N,N'-dicyclohexylcarbodiimide) and DMAP (4-dimethylaminopyridine) in MC (dichloromethane) for 30 minutes. 2 Under the charging environment, propargyl alcohol was slowly added dropwise thereto.

[0186] After filtering the mixture and removing the solvent from the filtrate, the residue was subjected to silica filtration to obtain the compound represented by Chemical Formula 1a.

[0187] Comparative Synthesis Example 1: Synthesis of Chemical Formula C1

[0188] A compound represented by Chemical Formula C1 was obtained in substantially the same manner as in Synthesis Example 1, except that nicotinic acid was replaced with pyridine-2-carboxylic acid.

[0189] [Chemical formula C1]

[0190]

[0191] Comparative Synthesis Example 2: Synthesis of Chemical Formula C2

[0192] A compound represented by Chemical Formula C2 was obtained in substantially the same manner as in Synthesis Example 1, except that isonicotinic acid was used instead of nicotinic acid.

[0193] [Chemical formula C2]

[0194]

[0195] (Example: Production of lithium secondary battery)

[0196] Example 1

[0197] LiNi as the positive electrode active material 0.75 Mn 0.23 Al 0.02 O 2 , polyvinylidene fluoride as a binder, and acetylene black as a conductive material were mixed in a weight ratio of 96:3:1, and then dispersed in N-methylpyrrolidone to prepare a positive electrode active material slurry.

[0198] The positive electrode active material slurry was coated on a 15 μm thick Al foil, dried at 100° C., and pressed to produce a positive electrode.

[0199] A negative electrode active material slurry was also prepared by using a mixture of artificial graphite and Si-C composite in a weight ratio of 93:7 as a negative electrode active material, then mixing the negative electrode active material, styrene-butadiene rubber binder and carboxymethyl cellulose in a weight ratio of 98:1:1, and dispersing the obtained mixture in distilled water.

[0200] For the Si-C composite, the surface of a core including artificial graphite and silicon particles is coated with coal pitch.

[0201] The negative electrode active material slurry was coated on a 10 μm thick Cu foil, dried at 100° C., and pressed to manufacture a negative electrode.

[0202] The manufactured positive electrode and negative electrode were assembled with a 10 μm thick polyethylene separator to manufacture an electrode assembly, and an electrolyte was injected therein to manufacture a lithium secondary battery.

[0203] The electrolyte has the following composition.

[0204] (Electrolyte composition)

[0205] Salt: 1.5M LiPF 6

[0206] Solvent: ethylene carbonate: ethyl methyl carbonate: dimethyl carbonate (EC:EMC:DMC=20:10:70 volume ratio)

[0207] Additives: 0.25 parts by weight of the compound represented by Chemical Formula 1a, 10 parts by weight of fluoroethylene carbonate (FEC), and 0.5 parts by weight of succinonitrile (SN)

[0208] (However, in the above composition of the electrolyte, "parts by weight" refers to the relative weight of the additive with respect to 100 parts by weight of the total weight of the electrolyte (lithium salt+nonaqueous organic solvent) (excluding the additive)).

[0209] Example 2 and Example 3

[0210] A lithium secondary battery was manufactured in substantially the same manner as Example 1, except that the contents of the compound represented by Chemical Formula 1a were changed to 0.5 parts by weight and 1.0 parts by weight, respectively.

[0211] Embodiment 4 to Embodiment 6

[0212] A lithium secondary battery was manufactured in substantially the same manner as in Examples 1 to 3, except that the electrolyte was prepared with (by using) a solvent including ethyl methyl carbonate (EMC) and dimethyl carbonate (DMC) in a volume ratio of 60:40.

[0213] Comparative Example 1

[0214] A lithium secondary battery was manufactured in substantially the same manner as in Example 1, except that an electrolyte including no additive was used.

[0215] Comparative Example 2 and Comparative Example 3

[0216] A lithium secondary battery was manufactured in substantially the same manner as in Example 1, except that the compound represented by Chemical Formula C1 and the compound represented by Chemical Formula C2 were used as additives instead of the compound represented by Chemical Formula 1a, respectively.

[0217] Each component of the electrolyte additive according to Examples 1 to 6 and Comparative Examples 1 to 3 is shown in Table 1.

[0218] (Table 1)

[0219]

[0220]

[0221] Evaluation 1: Evaluation of CV characteristics

[0222] In order to evaluate the electrochemical stability of the electrolytes according to Comparative Example 1 and Example 1, cyclic voltammetry (CV) measurements were performed, and the results are shown in Figure 2 Shown in.

[0223] Negative electrode cyclic voltammetry (CV) measurements were performed using a three-electrode electrochemical cell using a graphite negative electrode as the working electrode and Li metal as the reference electrode and counter electrode. In this paper, three cycles were scanned from 3V to 0V and from 0V to 3V at a scan rate of 0.1mV / sec.

[0224] Figure 2 Graph showing the results of negative electrode cyclic voltammetry (CV) of the electrolytes according to Example 1 and Comparative Example 1 at room temperature.

[0225] As in Figure 2 As shown in , the electrolyte of Example 1 including the additive according to the present disclosure exhibits a reduction decomposition peak at about 1.0 V or higher.

[0226] In contrast, the electrolyte of Comparative Example 1 including no additive exhibited a reductive decomposition peak at a lower potential.

[0227] This should show or prove that the electrolyte containing the additive according to the exemplary embodiment of the present disclosure interacts with the solvent at a relatively high reduction potential, and accordingly, the electrolyte according to Example 1 is configured to form an initial SEI film on the negative electrode in a wide voltage range before the solvent decomposes during charging when lithium ions are inserted into the negative electrode. Therefore, compared with the lithium secondary battery using the electrolyte of Comparative Example 1 that does not form an initial SEI film, the lithium secondary battery using the electrolyte of Example 1 is configured or designed to exhibit excellent or appropriate battery performance.

[0228] Evaluation 2: Evaluation of room temperature charge / discharge cycle characteristics

[0229] The lithium secondary battery cells according to Examples 1 to 6 and Comparative Examples 1 to 3 were charged and discharged, and then the cycle characteristics were measured, and the results are shown in Table 2.

[0230] The battery cells were charged and discharged for 200 cycles at 25°C under the conditions of 0.33C charge (CC / CV, 4.45V, 0.025C cutoff) / 1.0C discharge (CC, 2.5V cutoff), and then the capacity retention and direct current internal resistance (DC-IR) changes were measured.

[0231] According to Equations 1 and 2, DC-IR was calculated based on the voltage changed by applying a current of SOC 50C (a state of charging to 50% of the charge capacity when the total charge capacity is 100%) to the battery cell for 30 seconds, and the results are shown in Table 2.

[0232] [Equation 1]

[0233] Capacity retention rate = (capacity after 200th cycle / capacity after 1st cycle)*100

[0234] [Equation 2]

[0235] DC internal resistance change = {(DC-IR after 200th cycle – DC-IR after 1st cycle) / (DC-IR after 1st cycle)}*100

[0236] (Table 2)

[0237]

[0238] Referring to Table 2, when the additive according to the present disclosure is used, the room temperature cycle life characteristics are improved.

[0239] Evaluation 3: Evaluation of high temperature (45°C) cycle life characteristics

[0240] The lithium secondary battery cells according to Examples 1 to 6 and Comparative Examples 1 to 3 were charged and discharged for 200 cycles at 45° C. under the conditions of 0.33C charge (CC / CV, 4.45 V, 0.025C cutoff) / 1.0C discharge (CC, 2.5 V cutoff), and then the changes in capacity retention and direct current internal resistance (DC-IR) were measured.

[0241] According to Equations 1 and 2, DC-IR was calculated based on a voltage changed when the battery cell was discharged by applying a current of SOC 50C for 30 seconds, and the results are shown in Table 3.

[0242] (Table 3)

[0243]

[0244]

[0245] Referring to Table 3, when the additive according to the present disclosure is used, the high temperature cycle life characteristics are improved.

[0246] Evaluation 4: Evaluation of high temperature storage characteristics (capacity retention rate / capacity recovery rate / DC-IR)

[0247] The lithium secondary battery cells according to Examples 1 to 6 and Comparative Examples 1 to 3 were charged and discharged once at 0.33 C, and then the charge and discharge capacities (before storage at high temperature) were measured.

[0248] In addition, the lithium secondary battery cells according to Examples 1 to 6 and Comparative Examples 1 to 3 were charged to SOC 100% (a state of charging to 100% of the charge capacity based on 100% of the total charge capacity), stored at 60° C. for 30 days, and discharged to 3.0 V at 0.33 C under constant current conditions, and then the initial discharge capacity was measured.

[0249] The battery cell was recharged to 4.3V at 0.33C under constant current conditions, and cut off at 0.02C under constant voltage conditions, and discharged to 3.0V at 0.33C under constant current conditions, and then the discharge capacity was measured twice. The ratio of the first discharge capacity to the initial discharge capacity is shown as the capacity retention rate (retention capacity), and the second discharge capacity is shown as the capacity recovery rate (recovery capacity).

[0250] For the lithium secondary battery cells according to Examples 1 to 6 and Comparative Examples 1 to 3, ΔV / ΔI (voltage change / current change) was measured as the initial DC resistance (DCIR), and the DC resistance was measured after the maximum energy state inside the battery cell was changed to a fully charged state (SOC 100%) and the battery cell was stored at a high temperature (60°C) for 30 days in this state to calculate the DCIR increase rate (%) according to Equation 3, and the results are shown in Table 4.

[0251] [Equation 3]

[0252] DCIR increase rate = (DCIR after the 30th day / initial DCIR)*100

[0253] (Table 4)

[0254]

[0255]

[0256] Referring to Table 4, the lithium secondary battery cells according to Examples 1 to 6 each exhibited improved capacity retention and capacity recovery rates, while suppressing or reducing resistance change rates during high temperature storage, compared to Comparative Examples 1 to 3.

[0257] While the present disclosure has been described in conjunction with what are presently considered to be practical example embodiments, it should be understood that the present disclosure is not limited to the disclosed embodiments, but on the contrary is intended to cover one or more suitable modifications and equivalent arrangements included within the spirit and scope of the appended claims and their equivalents.

Claims

1. An electrolyte additive represented by chemical formula 1: [Chemical formula 1] in, In Chemical Formula 1, X 1 and X 2 Each independently is N or CR a , X 1 and X 2 At least one of them is N, R a and R 1 ~R 3 are each independently hydrogen or substituted or unsubstituted C1-C10 alkyl, and n is an integer of 1 to 3.

2. The electrolyte additive according to claim 1, wherein The n is an integer of 1 or 2.

3. The electrolyte additive according to claim 1, wherein R 1 ~R 3 Each is independently hydrogen or substituted or unsubstituted C1-C5 alkyl.

4. The electrolyte additive according to claim 1, wherein R 3 For hydrogen.

5. The electrolyte additive according to claim 1, wherein The additive is selected from the compounds of Group 1: [Group 1] 6. An electrolyte for a lithium secondary battery, comprising A non-aqueous organic solvent, a lithium salt and the electrolyte additive according to claim 1.

7. The electrolyte for a lithium secondary battery according to claim 6, wherein The amount of the additive is about 0.05 parts by weight to 5.0 parts by weight based on 100 parts by weight of the total weight of the electrolyte for a lithium secondary battery.

8. The electrolyte for a lithium secondary battery according to claim 6, wherein The amount of the additive is about 0.05 parts by weight to 3.0 parts by weight based on 100 parts by weight of the total weight of the electrolyte for a lithium secondary battery.

9. The electrolyte for a lithium secondary battery according to claim 6, wherein The electrolyte for lithium secondary battery further includes vinylene carbonate (VC), fluoroethylene carbonate (FEC), difluoroethylene carbonate, chloroethylene carbonate, dichloroethylene carbonate, bromoethylene carbonate, dibromoethylene carbonate, nitroethylene carbonate, cyanoethylene carbonate, vinylethylene carbonate (VEC), adiponitrile (AN), succinonitrile (SN), 1,3,6-hexanetricyano (HTCN), propene sultone (PST), propane sultone (PS), lithium tetrafluoroborate (LiBF 4 ), lithium difluorophosphate (LiPO 2 F 2 ) and at least one other additive of 2-fluorobiphenyl (2-FBP).

10. The electrolyte for a lithium secondary battery according to claim 6, wherein The non-aqueous organic solvent consists only of chain carbonate.

11. The electrolyte for a lithium secondary battery according to claim 10, wherein The chain carbonate is represented by Chemical Formula 2: [Chemical formula 2] in, In chemical formula 2 R 4 and R 5 Each is independently a substituted or unsubstituted C1-C20 alkyl group.

12. The electrolyte for a lithium secondary battery according to claim 6, wherein The non-aqueous organic solvent is at least two selected from dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC) and ethyl methyl carbonate (EMC).

13. A lithium secondary battery comprising a positive electrode, including a positive electrode active material; a negative electrode including a negative electrode active material; and The electrolyte for a lithium secondary battery according to claim 6.

14. The lithium secondary battery according to claim 13, wherein The positive electrode active material includes cobalt-free lithium nickel manganese oxide.

15. The lithium secondary battery according to claim 14, wherein The cobalt-free lithium nickel manganese oxide includes a lithium composite oxide represented by Chemical Formula 4: [Chemical formula 4] The a Nor x Mn y M1 z M2 w O 2±b X c in, In chemical formula 4, 0.9≤a<1.2,0≤b<0.1,0≤c<0.1,0≤w<0.1,0.6≤x<1.0,0 <y<0.4,0<z<0.1,w+x+y+z=1, M1 and M2 are each independently at least one element selected from Al, Mg, Ti, Zr, Cr, Sr, V, B, W, Mo, Nb, Si, Ba, Ca, Ce, Cr, Fe and Nb, and X is at least one element selected from S, F, P and Cl.

16. The lithium secondary battery according to claim 15, wherein Chemical formula 4 is represented by Chemical formula 4-1: [Chemical formula 4-1] <h2 style=";text-align:left;direction:ltr">Li<h2 style=";text-align:left;direction:ltr"> a <h2 style=";text-align:left;direction:ltr"> Ni<h2 style=";text-align:left;direction:ltr"> x1 <h2 style=";text-align:left;direction:ltr"> Mn<h2 style=";text-align:left;direction:ltr"> y1 <h2 style=";text-align:left;direction:ltr"> Al<h2 style=";text-align:left;direction:ltr"> z1 <h2 style=";text-align:left;direction:ltr"> M2<h2 style=";text-align:left;direction:ltr"> w1 <h2 style=";text-align:left;direction:ltr"> O<h2 style=";text-align:left;direction:ltr"> 2±b <h2 style=";text-align:left;direction:ltr"> X<h2 style=";text-align:left;direction:ltr"> c in, In chemical formula 4-1, 0.9≤a<1.2,0≤b<0.1,0≤c<0.1,0≤w1<0.1,0.6≤x1<1.0,0 <y1<0.4,0<z1<0.1,w1+x1+y1+z1=1, M2 is an element selected from the group consisting of Mg, Ti, Zr, Cr, Sr, V, B, W, Mo, Nb, Si, Ba, Ca, Ce, Cr, Fe and Nb, and X is at least one element selected from S, F, P and Cl.

17. The lithium secondary battery according to claim 16, wherein In Chemical Formula 4-1, x1 is 0.6≤x1≤0.79, y1 is 0.2≤y1≤0.39, and z1 is 0.01≤z1<0.

1.

18. The lithium secondary battery according to claim 13, wherein The negative electrode active material includes at least one selected from graphite and Si composite.

19. The lithium secondary battery according to claim 18, wherein The Si composite includes a core including Si-based particles and an amorphous carbon coating.

20. The lithium secondary battery according to claim 19, wherein The Si-based particles include at least one selected from Si particles, Si-C composites, SiO x (0 < x ≤ 2) and Si alloys.

21. The lithium secondary battery according to claim 13, wherein The lithium secondary battery has a charge upper limit voltage greater than or equal to about 4.45V.

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