Electrolyte composition for lithium secondary battery and lithium secondary battery including the same

Abstract

An electrolyte for a lithium secondary battery and a lithium secondary battery are disclosed. The electrolyte for the lithium secondary battery comprises a lithium salt; an organic solvent; and an additive, wherein the additive comprises a compound represented by the following chemical formula 1. In the above chemical formula 1, R1 to R3 are as defined in the detailed description.

Description

Technology Field

[0001] This invention relates to an electrolyte for a lithium secondary battery and a lithium secondary battery containing the same. Background Technology

[0002] Lithium-ion batteries are used as power sources for portable electronic devices such as video cameras, mobile phones, and laptop computers. Compared to conventional lead-acid, nickel-cadmium, nickel-hydrogen, and nickel-zinc batteries, rechargeable lithium-ion batteries have a higher energy density per unit weight and enable fast charging.

[0003] Since lithium-ion batteries operate at high operating voltages, aqueous electrolytes that are highly reactive with lithium cannot be used. Organic electrolytes are generally used for lithium-ion batteries. Organic electrolytes are prepared by dissolving lithium salts in organic solvents. It is desirable for the organic solvent to be stable at high voltages, have high ionic conductivity and dielectric constant, and possess low viscosity.

[0004] However, when an organic electrolyte containing a lithium salt is used as an electrolyte for a lithium secondary battery, side reactions between the negative / positive electrode and the electrolyte can degrade the lifespan characteristics, long-term durability, and high-temperature stability of the lithium secondary battery.

[0005] In particular, when lithium-ion batteries are stored or exposed to high temperatures, there is a risk of the battery exploding due to increased gas emission. To address this, one method involves adding additional substances to the electrolyte to reduce gas generation. However, most materials capable of reducing gas generation at high temperatures exhibit a trade-off characteristic involving high initial resistance. Therefore, there is a need to develop electrolyte additives that maintain the gas generation reduction effect at high temperatures without significantly increasing initial resistance. The problem to be solved

[0006] Lithium-ion batteries are used as power sources for portable electronic devices such as video cameras, mobile phones, and laptop computers. Compared to conventional lead-acid, nickel-cadmium, nickel-hydrogen, and nickel-zinc batteries, rechargeable lithium-ion batteries have a higher energy density per unit weight and enable fast charging.

[0007] Since lithium-ion batteries operate at high operating voltages, aqueous electrolytes that are highly reactive with lithium cannot be used. Organic electrolytes are generally used for lithium-ion batteries. Organic electrolytes are prepared by dissolving lithium salts in organic solvents. It is desirable for the organic solvent to be stable at high voltages, have high ionic conductivity and dielectric constant, and possess low viscosity.

[0008] However, when an organic electrolyte containing a lithium salt is used as an electrolyte for a lithium secondary battery, side reactions between the negative / positive electrode and the electrolyte can degrade the lifespan characteristics, long-term durability, and high-temperature stability of the lithium secondary battery.

[0009] In particular, when lithium-ion batteries are stored or exposed to high temperatures, there is a risk of the battery exploding due to increased gas emission. To address this, one method involves adding additional substances to the electrolyte to reduce gas generation. However, most materials capable of reducing gas generation at high temperatures exhibit a trade-off characteristic involving high initial resistance. Therefore, there is a need to develop electrolyte additives that maintain the gas generation reduction effect at high temperatures without significantly increasing initial resistance. means of solving the problem

[0010] Depending on one aspect,

[0011] It includes a lithium salt; an organic solvent; and an additive,

[0012] The above additive provides an electrolyte for a lithium secondary battery comprising a compound represented by the following chemical formula 1.

[0013] <Chemical Formula 1>

[0014]

[0015] In the above chemical formula 1,

[0016] R 1 is substituted or unsubstituted C1-C 20 It is an alkyl group, and

[0017] R 2 and R 3 Each independently consists of hydrogen, deuterium, -F (fluoro group), -Cl (chloro group), -Br (bromo group), -I (iodo group), hydroxyl group, cyano group, nitro group, amino group, amidino group, hydrazine group, hydrazone group, carboxylic acid or its salt, sulfonic acid or its salt, phosphoric acid or its salt, substituted or unsubstituted C1-C 20 Alkyl groups, substituted or unsubstituted C2-C 20 alkenyl groups, substituted or unsubstituted C2-C 20 alkynyl group, substituted or unsubstituted C1-C 20 Alkoxy groups, substituted or unsubstituted C3-C 20 Cycloalkyl groups, substituted or unsubstituted C2-C 20 Heterocycloalkyl groups, substituted or unsubstituted C3-C 20 Cycloalkenyl group, substituted or unsubstituted C2-C 20 Heterocycloalkenyl groups, substituted or unsubstituted C6-C 20 Aryl group, substituted or unsubstituted C6-C 20 Aryloxy group, substituted or unsubstituted C6-C 20 Arylthio groups, substituted or unsubstituted C2-C 20 Selected from a heteroaryl group, a substituted or unsubstituted monovalent non-aromatic condensed polycyclic group, a substituted or unsubstituted monovalent non-aromatic heterocondensed polycyclic group, -N(Q1)(Q2) and -B(Q6)(Q7), wherein Q1 to Q7 are independently hydrogen, C1-C 20 Alkyl group, C2-C 20 alkenyl group, C2-C 20 alkynyl group, C1-C 20 Alkoxy group, C3-C20 Cycloalkyl group, C2-C 20 Heterocycloalkyl group, C3-C 20 Cycloalkenyl group, C2-C 20 Heterocycloalkenyl group, C6-C 20 Aryl group, C6-C 20 aryloxy group, C6-C 20 Arylthio group, C2-C 20 It is selected from a heteroaryl group, a monovalent non-aromatic condensed polycyclic group and a monovalent non-aromatic heterocondensed polycyclic group.

[0018] Depending on other aspects,

[0019] anode;

[0020] cathode; and

[0021] The above-described electrolyte disposed between the anode and the cathode;

[0022] A lithium secondary battery including is provided. Effects of the invention

[0023] A lithium secondary battery employing an electrolyte for a lithium secondary battery according to one embodiment reduces gas generation even when exposed to high temperatures and can lower the initial capacity. Brief explanation of the drawing

[0024] Figure 1 is a schematic diagram of a lithium secondary battery according to one embodiment. FIG. 2 is a graph evaluating the high-temperature storage characteristics of lithium secondary batteries according to Examples 1 and 2, and Comparative Examples 1 to 8. FIG. 3 is a graph evaluating the high-temperature storage characteristics of lithium secondary batteries according to Examples 3 and 4, and Comparative Examples 9 to 16. Figure 4 is a graph showing a comparison of the amount of gas generated during high-temperature storage of lithium secondary batteries according to Examples 5 and 6 and Comparative Example 17 using Ni-based cathodes, and a comparison of the amount of gas generated during high-temperature storage of lithium secondary batteries according to Examples 7 and 8 and Comparative Example 18 using Co-based cathodes. Specific details for implementing the invention

[0025] In the following, an electrolyte for a lithium secondary battery and a lithium secondary battery including the same will be described in more detail according to exemplary embodiments.

[0026] Conventional materials capable of reducing gas generation at high temperatures mostly exhibit a trade-off characteristic of high initial resistance. The same applies to electrolyte additives of the cyanide group (-CN) ligand type or the cyanide group ligand and double bond hybrid type. The inventors arrived at the present invention by applying a compound represented by the following chemical formula 1 as a novel structure that maintains the gas generation reduction effect exhibited in such structures without additionally increasing the initial resistance significantly.

[0027] An electrolyte for a lithium secondary battery according to one embodiment is,

[0028] It includes a lithium salt; an organic solvent; and an additive,

[0029] The above additive includes a compound represented by the following chemical formula 1.

[0030] <Chemical Formula 1>

[0031]

[0032] In the above chemical formula 1,

[0033] R 1 is substituted or unsubstituted C1-C 20 It is an alkyl group, and

[0034] R 2 and R 3 Each independently consists of hydrogen, deuterium, -F (fluoro group), -Cl (chloro group), -Br (bromo group), -I (iodo group), hydroxyl group, cyano group, nitro group, amino group, amidino group, hydrazine group, hydrazone group, carboxylic acid or its salt, sulfonic acid or its salt, phosphoric acid or its salt, substituted or unsubstituted C1-C 20 Alkyl groups, substituted or unsubstituted C2-C 20 alkenyl groups, substituted or unsubstituted C2-C 20alkynyl group, substituted or unsubstituted C1-C 20 Alkoxy groups, substituted or unsubstituted C3-C 20 Cycloalkyl groups, substituted or unsubstituted C2-C 20 Heterocycloalkyl groups, substituted or unsubstituted C3-C 20 Cycloalkenyl group, substituted or unsubstituted C2-C 20 Heterocycloalkenyl groups, substituted or unsubstituted C6-C 20 Aryl group, substituted or unsubstituted C6-C 20 Aryloxy group, substituted or unsubstituted C6-C 20 Arylthio groups, substituted or unsubstituted C2-C 20 Selected from a heteroaryl group, a substituted or unsubstituted monovalent non-aromatic condensed polycyclic group, a substituted or unsubstituted monovalent non-aromatic heterocondensed polycyclic group, -N(Q1)(Q2) and -B(Q6)(Q7), wherein Q1 to Q7 are independently hydrogen, C1-C 20 Alkyl group, C2-C 20 alkenyl group, C2-C 20 alkynyl group, C1-C 20 Alkoxy group, C3-C 20 Cycloalkyl group, C2-C 20 Heterocycloalkyl group, C3-C 20 Cycloalkenyl group, C2-C 20 Heterocycloalkenyl group, C6-C 20 Aryl group, C6-C 20 aryloxy group, C6-C 20 Arylthio group, C2-C 20 It is selected from a heteroaryl group, a monovalent non-aromatic condensed polycyclic group and a monovalent non-aromatic heterocondensed polycyclic group.

[0035] The compound represented by Chemical Formula 1 above has a structure that is not hybridized while having a cyanide (-CN) ligand and a double bond together, and furthermore, an alkyl group is introduced at the end of the double bond, so that it can not only reduce gas generation at high temperatures but also exhibit an effect of not significantly increasing initial resistance. The compound represented by Chemical Formula 1 above may show a greater improvement in gas reduction compared to a simple cyanide ligand type additive, a cyanide ligand and double bond hybrid type additive, or a case where an alkyl group is not introduced at the end of the double bond.

[0036] Therefore, when the above compound is used as an electrolyte additive for a lithium secondary battery, lifespan characteristics can be improved by reducing gas generation and improving initial resistance during high-temperature storage in the lithium secondary battery.

[0037] According to one embodiment, in the above formula 1, R 1 is substituted or unsubstituted C1-C 20 It is an alkyl group, and R 2 and R 3 Each is independently hydrogen, or substituted or unsubstituted C1-C 20 It can be an alkyl group.

[0038] According to one embodiment, in the above formula 1, R 1 is an unsubstituted linear or branched C1-C 20 It is an alkyl group, and R 2 and R 3 It can be hydrogen.

[0039] In the above Chemical Formula 1, R1 is, for example, a methyl group, ethyl group, n-propyl group, n-butyl group, n-pentyl group, n-hexyl group, n-heptyl group, n-octyl group, n-nonyl group, n-decyl group, n-undecyl group, n-dodecyl group, n-tridecyl group, n-tetradecyl group, n-pentadecyl group, n-hexadecyl group, n-heptadecyl group, n-octadecyl group, n-nonadecyl group, n-eicosanyl group, iso-propyl group, sec-butyl group, iso-butyl group, tert-butyl group, 1-methylbutyl group, 1-ethylpropyl group, 2-methylbutyl group, iso-pentyl group, neo-pentyl group, 1,2-dimethylpropyl group, 1,1-dimethylpropyl group, tert-pentyl group, 1,3-dimethylbutyl group, It may be a 3,3-dimethylbutyl group, a 2-ethylbutyl group, a 2-ethyl-2-methylpropyl group, a straight-chain or branched heptyl group, a 1-methylheptyl group, a 2-ethylhexyl group, a 1,5-dimethylhexyl group, a tert-octyl group, a branched nonyl group, a branched decyl group, a branched undecyl group, a branched dodecyl group, a branched tridecyl group, a branched tetradecyl group, a branched pentadecyl group, a branched hexadecyl group, a branched heptadecyl group, a branched octadecyl group, a straight-chain or branched nonadecyl group, or a straight-chain or branched eicosanyl group.

[0040] Among the above groups, methyl group, ethyl group, n-propyl group, n-butyl group, n-pentyl group, n-hexyl group, n-heptyl group, n-octyl group, n-nonyl group, n-decyl group, n-undecyl group, n-dodecyl group, n-tridecyl group, n-tetradecyl group, iso-propyl group, sec-butyl group, iso-butyl group, tert-butyl group, 1-methylbutyl group, 1-ethylpropyl group, 2-methylbutyl group, iso-pentyl group, neo-pentyl group, 1,2-dimethylpropyl group, 1,1-dimethylpropyl group, tert-pentyl group, 1,3-dimethylbutyl group, 3,3-dimethylbutyl group, 2-ethylbutyl group, 2-ethyl-2-methylpropyl group, linear or branched heptyl group, 1-methylheptyl group, 2-ethylhexyl group, A 1,5-dimethylhexyl group, a tert-octyl group, a branched nonyl group, or a branched decyl group may be preferred.

[0041] Among the above groups, methyl group, ethyl group, n-propyl group, n-butyl group, n-pentyl group, n-hexyl group, n-heptyl group, n-octyl group, n-nonyl group, n-decyl group, iso-propyl group, sec-butyl group, iso-butyl group, tert-butyl group, 1-methylbutyl group, 1-ethylpropyl group, 2-methylbutyl group, iso-pentyl group, neo-pentyl group, 1,2-dimethylpropyl group, 1,1-dimethylpropyl group, tert-pentyl group, 1,3-dimethylbutyl group, 3,3-dimethylbutyl group, 2-ethylbutyl group, and 2-ethyl-2-methylpropyl group may be more preferred.

[0042] According to one embodiment, the compound can be represented by the following chemical formula 2.

[0043] <Chemical Formula 2>

[0044]

[0045] In the above chemical formula 2,

[0046] R 1 is substituted or unsubstituted C1-C 20 It is an alkyl group.

[0047] In the above chemical formula 2, R1 may be selected from, for example, a methyl group, an ethyl group, a propyl group, an iso-propyl group, a butyl group, an iso-butyl group, a sec-butyl group, a tert-butyl group, a pentyl group, an iso-pentyl group, and a neo-pentyl group.

[0048] For example, the above additive may include at least one of the compounds represented by the following chemical formulas 3 to 6.

[0049] <Chemical Formula 3>

[0050]

[0051] <Chemical Formula 4>

[0052]

[0053] <Chemical Formula 5>

[0054]

[0055] <Chemical Formula 6>

[0056]

[0057] The above-described electrolyte for a lithium secondary battery includes the aforementioned compound as an additive, thereby suppressing gas generation when the lithium secondary battery is exposed to high temperatures, which not only improves high-temperature stability but also has the effect of lowering initial resistance.

[0058] Furthermore, the above-described electrolyte for a lithium secondary battery can provide a lithium secondary battery with improved lifespan and high-temperature stability by having an excellent resistance suppression effect at high temperatures for a lithium secondary battery containing a lithium transition metal oxide with a high nickel content as a positive electrode active material.

[0059] Unless otherwise defined in this specification, the term "substitution" means that a hydrogen atom in a compound is a halogen atom (F, Br, Cl, or I), a hydroxyl group, an alkoxy group, a nitro group, a cyano group, an amino 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, a carboxyl group or its salt, a sulfonic acid group or its salt, a phosphoric acid or its salt, 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 C7 to C30 arylalkyl group, a C1 to C4 alkoxy group, a C1 to C20 heteroalkyl group, a C3 to C20 heteroarylalkyl group, a C3 to C30 cycloalkyl group, a C3 to C15 cycloalkenyl group, a C6 to C15 cycloalkynyl group, or a C2 to It means substituted with a substituent selected from a C20 heterocycloalkyl group and combinations thereof.

[0060] The content of the compound represented by Chemical Formula 1 above may be in the range of 0.001 to 20 parts by weight per 100 parts by weight of an electrolyte composed of a lithium salt and an organic solvent. The upper limit of the content range of the compound may be 20 parts by weight per 100 parts by weight of an electrolyte composed of a lithium salt and an organic solvent, for example, 15 parts by weight, 10 parts by weight, 5 parts by weight, 3 parts by weight, or 1 part by weight. The lower limit of the content range of the compound may be 0.001 parts by weight per 100 parts by weight of an electrolyte composed of a lithium salt and an organic solvent, for example, 0.01 parts by weight, 0.05 parts by weight, 0.07 parts by weight, 0.1 parts by weight, 0.2 parts by weight, 0.3 parts by weight, 0.4 parts by weight, or 0.5 parts by weight. Within the above range, characteristics such as high-temperature storage characteristics and low-temperature discharge capacity of the lithium secondary battery can be effectively improved, but are not limited thereto; they can be adjusted within a normal range by considering combinations with other additives and the use of materials such as positive electrode active materials and negative electrode active materials.

[0061] According to one embodiment, the electrolyte may further include other additives, and the other additives may include at least one of vinylene carbonate (VC), fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), chloroethylene carbonate (CEC), dichloroethylene carbonate (DCEC), bromoethylene carbonate (BEC), dibromoethylene carbonate (DBEC), nitroethylene carbonate, cyanoethylene carbonate, vinylethylene carbonate (VEC), succinonitrile (SN), adiponitrile (AN), 1,3,6-hexane tricyanide (HTCN), propensulfone (PST), propanesulfone (PS), lithium tetrafluoroborate (LiBF4), lithium difluorophosphate (LiPO2F2), and 2-fluorobiphenyl (2-FBP).

[0062] The content of the above other additives may be included in an amount of 0.2 to 20 parts by weight per 100 parts by weight of the electrolyte composed of a lithium salt and an organic solvent, specifically 0.2 to 15 parts by weight, for example 0.2 to 10 parts by weight. Within the above range, the increase in film resistance caused by the other additives can be minimized, thereby contributing to the improvement of battery performance.

[0063] According to one embodiment, the lithium salt is LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiCF3SO3, Li(CF3SO2)2N, LiC4F9SO3, LiAlO2, LiAlCl4, LiN(C x F 2x+1 SO2)(C y F 2y+1 It may include one or more selected from the group consisting of SO2)(2≤x≤20, 2≤y≤20), LiCl, LiI, lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(oxalate)borate (LiBOB), LiPO2F2, and compounds represented by the following chemical formulas 7 to 10, but is not limited thereto, and any that can be used as a lithium salt in the relevant technical field may be used.

[0064] <Chemical Formula 7> <Chemical Formula 8>

[0065]

[0066] <Chemical Formula 9> <Chemical Formula 10>

[0067]

[0068] The concentration of the lithium salt in the above electrolyte is 0.01 to 5.0 M, for example, 0.05 to 5.0 M, for example, 0.1 to 5.0 M, for example, 0.1 to 2.0 M. When the concentration of the lithium salt is within the above range, further improved lithium secondary battery characteristics can be obtained.

[0069] The organic solvent may be one or more selected from carbonate-based solvents, ester-based solvents, ether-based solvents, and ketone-based solvents.

[0070] As carbonate-based solvents, ethyl methyl carbonate (EMC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), propylene carbonate (PC), ethylene carbonate (EC), fluoroethylene carbonate (FEC), vinylene carbonate (VC), vinylethylene carbonate (VEC), butylene carbonate (BC), etc. may be used; as ester-based solvents, methyl propionate, ethyl propionate, propyl propionate, ethyl butyrate, methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, gamma-butyrolactone, decanolide, gamma-valerolactone, mevalonolactone, caprolactone, etc. may be used; and as ether-based solvents, dibutyl ether, Tetraglame, diglame, dimethoxyethane, 2-methyltetrahydrofuran, tetrahydrofuran, etc. may be used; cyclohexanone, etc. may be used as a ketone-based solvent; and acetonitrile (AN), succinonitrile (SN), adiponitrile, etc. may be used as a nitrile-based solvent. Other solvents such as dimethyl sulfoxide, dimethylformamide, dimethylacetamide, and tetrahydrofuran may be used, but are not necessarily limited to these; any solvent that can be used as an organic solvent in the relevant technical field is acceptable. For example, the organic solvent may include a mixed solvent of 50 to 95 vol% of chain-type carbonate and 5 to 50 vol% of cyclic carbonate, for example, a mixed solvent of 70 to 95 vol% of chain-type carbonate and 5 to 30 vol% of cyclic carbonate. For example, the organic solvent may be a mixed solvent of three or more organic solvents.

[0071] According to one embodiment, the organic solvent may include one or more selected from the group consisting of ethylmethyl carbonate (EMC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), propylene carbonate (PC), ethylene carbonate (EC), fluoroethylene carbonate (FEC), vinylene carbonate (VC), vinylethylene carbonate (VEC), butylene carbonate, ethylpropionate, propylpropionate, ethyl butyrate, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, gamma-valerolactone, gamma-butyrolactone, and tetrahydrofuran, but is not limited thereto, and any that can be used as an organic solvent in the art may be used.

[0072] The above electrolyte may be in a liquid or gel state. The above electrolyte may be prepared by adding a lithium salt and the aforementioned additive to an organic solvent.

[0073] A lithium secondary battery according to another embodiment comprises: a positive electrode comprising a positive electrode active material; a negative electrode comprising a negative electrode active material; and the above-described electrolyte disposed between the positive electrode and the negative electrode.

[0074] By including the above compound, the above lithium secondary battery can improve the high-temperature stability and initial resistance characteristics of the lithium secondary battery.

[0075] The cathode active material is a lithium-containing metal oxide, and any that is commonly used in the industry may be used without limitation. For example, one or more composite oxides of lithium and a metal selected from cobalt, manganese, nickel, and combinations thereof may be used, and specific examples include Li a A 1-b B 1 b D 1 2 (wherein, 0.90 ≤ a ≤ 1.8, and 0 ≤ b ≤ 0.5); Li a E1-b B 1 b O 2-c D 1 c (In the above formula, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); LiE 2-b B 1 b O 4-c D 1 c (In the above equation, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); Li a Ni 1-b-c Co b B 1 c D 1 α (In the above equation, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α ≤ 2); Li a Ni 1-b-c Co b B 1 c O 2-α F 1 α (In the above equation, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni 1-b-c Co b B 1 c O 2-α F 1 2(in the above equation, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni 1-b-c Mn b B 1 c D α (In the above equation, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α ≤ 2); Li a Ni 1-b-c Mn b B 1 c O2-α F 1 α (In the above equation, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni 1-b-c Mn b B 1 c O 2-α F 1 2(in the above equation, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni b E c G d O2(wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0.001 ≤ d ≤ 0.1); Li a Ni b Co c Mn d GeO2(wherein the above formula, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤ 0.5, 0.001 ≤ e ≤ 0.1); Li a NiG b O2(in the above equation, 0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); Li a CoG b O2(in the above equation, 0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); Li a MnG b O2(in the above equation, 0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); Li a Mn2G b O4(wherein 0.90 ≤ a ≤ 1.8 and 0.001 ≤ b ≤ 0.1); QO2; QS2; LiQS2; V2O5; LiV2O5; LiIO2; LiNiVO4; Li (3-f) J2(PO4)3(0 ≤ f ≤ 2); Li (3-f)Fe2(PO4)3(0 ≤ f ≤ 2); compounds represented by any one of the chemical formulas of LiFePO4 may be used:

[0076] In the above chemical formula, A is Ni, Co, Mn, or a combination thereof; and B 1 is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements or combinations thereof; D 1 is O, F, S, P, or a combination thereof; E is Co, Mn, or a combination thereof; and F 1 is F, S, P, or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; Q is Ti, Mo, Mn, or a combination thereof; I is Cr, V, Fe, Sc, Y, or a combination thereof; and J may be V, Cr, Mn, Co, Ni, Cu, or a combination thereof.

[0077] For example, LiCoO2, LiMn x O 2x (x=1, 2), LiNi 1-x Mn x O 2x (0 <x<1), LiNi 1-x-y Co x Mn y O2 (0≤x≤0.5, 0≤y≤0.5), LiFePO4, etc.

[0078] Of course, a coating layer having a surface on the above-mentioned compound may be used, or a mixture of the above-mentioned compound and a compound having a coating layer may be used. This coating layer may include a coating element compound of an oxide, hydroxide, oxyhydroxide, oxycarbonate, or hydroxycarbonate of a coating element. 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 a mixture thereof may be used. For the coating layer formation process, any coating method may be used as long as the above-mentioned 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.

[0079] According to one embodiment, the cathode active material may include a lithium transition metal oxide comprising nickel and other transition metals. In the lithium transition metal oxide comprising nickel and other transition metals, the nickel content may be 60 mol% or more, for example 75 mol% or more, for example 80 mol% or more, for example 85 mol% or more, for example 90 mol% or more, with respect to the total molar amount of transition metals, and less than 100 mol%.

[0080] For example, the lithium transition metal oxide may be a compound represented by the following chemical formula 11:

[0081] <Chemical Formula 11>

[0082] Li a Ni x Co y M z O 2-b A b

[0083] In the above chemical formula 11, 1.0≤a≤1.2, 0≤b≤0.2, 0.6≤x<1, 0 <y≤0.3, 0<z≤0.3, x+y+z=1, M은 망간(Mn), 바나듐(V), 마그네슘(Mg), 갈륨(Ga), 실리콘(Si), 텅스텐(W), 몰리브덴(Mo), 철(Fe), 크롬(Cr), 구리(Cu), 아연(Zn), 티타늄(Ti), 알루미늄(Al) 및 보론(B)으로 이루어진 군으로부터 선택된 하나 이상이고, A는 F, S, Cl, Br 또는 이들의 조합이다. 예를 들어, 0.7≤x<1, 0<y≤0.3, 0<z≤0.3; 0.8≤x<1, 0<y≤0.3, 0<z≤0.3; 0.8≤x<1, 0<y≤0.2, 0<z≤0.2; 0.83≤x<0.97, 0<y≤0.15, 0<z≤0.15; 또는 0.85≤x<0.95, 0<y≤0.1, 0<z≤0.1;일 수 있다.

[0084] For example, the lithium transition metal oxide may be at least one of the compounds represented by the following chemical formulas 12 and 13:

[0085] <Chemical Formula 12>

[0086] LiNi x Co y Mn z O2

[0087] In the above chemical formula 12, 0.6≤x≤0.95, 0 <y≤0.2, 0<z≤0.1이다. 예를 들어, 0.7≤x≤0.95, 0<y≤0.3, 0<z≤0.3이다.

[0088] <Chemical Formula 13>

[0089] LiNi x Co y Al z O2

[0090] In the above chemical formula 13, 0.6≤x≤0.95, 0 <y≤0.2, 0<z≤0.1이다. 예를 들어, 0.7≤x≤0.95, 0<y≤0.3, 0<z≤0.3이다. 예를 들어, 0.8≤x≤0.95, 0<y≤0.3, 0<z≤0.3이다. 예를 들어, 0.82≤x≤0.95, 0<y≤0.15, 0<z≤0.15이다. 예를 들어, 0.85≤x≤0.95, 0<y≤0.1, 0<z≤0.1이다.

[0091] For example, lithium transition metal oxides are LiNi 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.88 Co 0.08 Mn 0.04 O2, LiNi 0.8 Co 0.15 Mn 0.05 O2, LiNi 0.8 Co 0.1 Mn 0.1 O2, LiNi 0.88 Co 0.1 Mn 0.02 O2, LiNi 0.8 Co 0.15 Al 0.05 O2, LiNi 0.8 Co 0.1 Mn 0.2 O2, LiNi 0.88 Co 0.1 Al 0.02 O2 or LiNi 0.915 Co 0.07 Al 0.015 It could be O2.

[0092] According to another embodiment, the positive electrode active material comprises at least one active material selected from the group consisting of Li-Ni-Co-Al (NCA), Li-Ni-Co-Mn (NCM), lithium cobalt oxide (LiCoO2), lithium manganese oxide (LiMnO2), lithium nickel oxide (LiNiO2), and lithium iron phosphate (LiFePO4).

[0093] The negative electrode active material is a silicon-based compound, a carbon-based material, a composite of a silicon-based compound and a carbon-based compound, and silicon oxide (SiO₂). x , 0 <x<2) 중에서 선택된 하나 이상을 포함할 수 있다. 실리콘계 화합물은 실리콘 입자, 실리콘 합금 입자 등일 수 있다.

[0094] The size of the silicon-based compound is less than 200 nm, for example, 10 to 150 nm. The term “size” may indicate the average particle size when the silicon-based compound is spherical, and the average major axis length when the silicon particles are non-spherical.

[0095] When the size of the silicon-based compound is within the above range, the lifespan characteristics are excellent, so when the electrolyte according to one embodiment is used, the lifespan of the lithium secondary battery is further improved.

[0096] The carbon-based material may be crystalline carbon, amorphous carbon, or a mixture thereof. The crystalline carbon may be graphite such as natural graphite or artificial graphite in amorphous, plate-like, flake-like, spherical, or fibrous forms, and the amorphous carbon may be soft carbon (low-temperature calcined carbon), hard carbon, mesophase pitch carbide, calcined coke, etc.

[0097] A composite of a silicon-based compound and a carbon-based compound may be a composite having a structure in which silicon nanoparticles are disposed on top of a carbon-based compound, a composite in which silicon particles are contained on the surface and inside of a carbon-based compound, or a composite in which silicon particles are coated with a carbon-based compound and contained inside a carbon-based compound. In a composite of a silicon-based compound and a carbon-based compound, the carbon-based compound may be graphite, graphene, graphene oxide, or a combination thereof.

[0098] The composite of silicon-based compounds and carbon-based compounds may be an active material obtained by dispersing silicon nanoparticles with an average particle size of about 200 nm or less on carbon-based compound particles and then carbon coating, an active material in which silicon (Si) particles exist on top of and inside graphite, etc. The average particle size of the secondary particles of the composite of silicon-based compounds and carbon-based compounds may be 5 μm to 20 μm. The average particle size of the silicon nanoparticles may be 5 nm or more, for example, 10 nm or more, for example, 20 nm or more, for example, 50 nm or more, for example, 70 nm or more. The average particle size of the silicon nanoparticles may be 200 nm or less, 150 nm or less, 100 nm or less, 50 nm or less, 20 nm or less, or 10 nm or less. For example, the average particle size of the silicon nanoparticles may be 100 nm to 150 nm.

[0099] The average particle size of the secondary particles of the composite of silicon-based compounds and carbon-based compounds may be 5 µm to 18 µm, for example 7 µm to 15 µm, for example 10 µm to 13 µm.

[0100] As other examples of the composite of the above silicon-based compound and carbon-based compound, the porous silicon composite cluster of Korean Patent Publication No. 10-2018-0031585 and the porous silicon composite cluster structure disclosed in Korean Patent Publication No. 10-2018-0056395 may be used. Korean Patent Publication No. 10-2018-0031586 and Korean Patent Publication No. 10-2018-0056395 are incorporated herein by reference.

[0101] A silicon-carbon-based compound composite according to one embodiment is a porous silicon composite cluster comprising a porous core containing porous silicon composite secondary particles and a shell containing second graphene disposed on top of the core, wherein the porous silicon composite secondary particles comprise aggregates of two or more silicon composite primary particles, and the silicon composite primary particles comprise silicon; and silicon oxide (SiOx) (O) disposed on the silicon <x<2) 및 상기 실리콘 산화물 상에 배치된 제1그래핀을 포함하는 다공성 실리콘 복합체 클러스터일 수 있다.

[0102] A silicon-carbon compound composite according to another embodiment comprises: a porous silicon composite cluster comprising a porous silicon composite secondary particle and a second carbon flake on at least one surface of the porous silicon composite secondary particle; and a carbon-based coating film comprising amorphous carbon disposed on the porous silicon composite cluster, wherein the porous silicon composite secondary particle comprises an aggregate of two or more silicon composite primary particles, and the silicon composite primary particle comprises silicon; and silicon oxide (SiOx) (O) on at least one surface of the silicon. <x<2) 및 상기 실리콘 산화물의 적어도 일 면상의 제1탄소 플레이크를 포함하며, 상기 실리콘 산화물은 막(film), 매트릭스(matrix) 또는 그 조합물의 상태로 존재하는 다공성 실리콘 복합체 클러스터 구조체일 수 있다.

[0103] The first carbon flake and the second carbon flake may each exist in the state of a film, particle, matrix, or a combination thereof. In addition, the first carbon flake and the second carbon flake may each be graphene, graphite, carbon fiber, graphene oxide, etc.

[0104] The aforementioned composite of silicon-based and carbon-based compounds may be a composite having a structure in which silicon nanoparticles are disposed on top of a carbon-based compound, a composite in which silicon particles are contained on the surface and inside of a carbon-based compound, or a composite in which silicon particles are coated with a carbon-based compound and contained inside a carbon-based compound. In the composite of silicon-based and carbon-based compounds, the carbon-based compound may be graphite, graphene, graphene oxide, or a combination thereof.

[0105] The above-mentioned lithium secondary battery is not particularly limited in its form and includes lithium-ion batteries, lithium-ion polymer batteries, lithium-sulfur batteries, etc.

[0106] The above lithium secondary battery can be manufactured by the following method.

[0107] First, the positive electrode is prepared.

[0108] For example, a positive active material composition is prepared by mixing a positive active material, a conductive material, a binder, and a solvent. The positive active material composition is directly coated onto a metal current collector to manufacture a positive plate. Alternatively, the positive active material composition may be cast onto a separate support, and then a film peeled from the support is laminated onto a metal current collector to manufacture a positive plate. The positive electrode is not limited to the forms listed above and may be in a form other than those listed above.

[0109] The cathode active material is a lithium-containing metal oxide, and any that is commonly used in the industry may be used without limitation. For example, one or more composite oxides of lithium and a metal selected from cobalt, manganese, nickel, and combinations thereof may be used, and specific examples include Li a A 1-b B 1 b D 1 2 (wherein, 0.90 ≤ a ≤ 1.8, and 0 ≤ b ≤ 0.5); Li a E 1-b B 1b O 2-c D 1 c (In the above formula, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); LiE 2-b B 1 b O 4-c D 1 c (In the above equation, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); Li a Ni 1-b-c Co b B 1 c D 1 α (In the above equation, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α ≤ 2); Li a Ni 1-b-c Co b B 1 c O 2-α F 1 α (In the above equation, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni 1-b-c Co b B 1 c O 2-α F 1 2(in the above equation, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni 1-b-c Mn b B 1 c D α (In the above equation, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α ≤ 2); Li a Ni 1-b-c Mn b B 1 c O 2-α F 1α (In the above equation, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni 1-b-c Mn b B 1 c O 2-α F 1 2(in the above equation, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni b E c G d O2(wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0.001 ≤ d ≤ 0.1); Li a Ni b Co c Mn d GeO2(wherein the above formula, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤ 0.5, 0.001 ≤ e ≤ 0.1); Li a NiG b O2(in the above equation, 0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); Li a CoG b O2(in the above equation, 0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); Li a MnG b O2(in the above equation, 0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); Li a Mn2G b O4(wherein 0.90 ≤ a ≤ 1.8 and 0.001 ≤ b ≤ 0.1); QO2; QS2; LiQS2; V2O5; LiV2O5; LiIO2; LiNiVO4; Li (3-f) J2(PO4)3(0 ≤ f ≤ 2); Li (3-f)Fe2(PO4)3(0 ≤ f ≤ 2); compounds represented by any one of the chemical formulas of LiFePO4 may be used:

[0110] In the above chemical formula, A is Ni, Co, Mn, or a combination thereof; and B 1 is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements or combinations thereof; D 1 is O, F, S, P, or a combination thereof; E is Co, Mn, or a combination thereof; and F 1 is F, S, P, or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; Q is Ti, Mo, Mn, or a combination thereof; I is Cr, V, Fe, Sc, Y, or a combination thereof; and J may be V, Cr, Mn, Co, Ni, Cu, or a combination thereof.

[0111] For example, LiCoO2, LiMn x O 2x (x=1, 2), LiNi 1-x Mn x O 2x (0 <x<1), LiNi 1-x-y Co x Mn y O2 (0≤x≤0.5, 0≤y≤0.5), LiFePO4, etc.

[0112] Of course, a coating layer having a surface on the above-mentioned compound may be used, or a mixture of the above-mentioned compound and a compound having a coating layer may be used. This coating layer may include a coating element compound of an oxide, hydroxide, oxyhydroxide, oxycarbonate, or hydroxycarbonate of a coating element. 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 a mixture thereof may be used. For the coating layer formation process, any coating method may be used as long as the above-mentioned 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.

[0113] The above conductive material may include carbon black, graphite fine particles, etc., but is not limited to these, and any material that can be used as a conductive material in the relevant technical field may be used.

[0114] The above binder may include vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethyl methacrylate, polytetrafluoroethylene and mixtures thereof, or styrene butadiene rubber-based polymer, but is not limited to these, and any that can be used as a binder in the relevant technical field may be used.

[0115] The above solvent may be N-methylpyrrolidone, acetone, or water, but is not limited to these; any solvent that can be used in the relevant technical field may be used.

[0116] The content of the positive electrode active material, conductive material, binder, and solvent mentioned above is at a level typically used in lithium batteries. Depending on the application and composition of the lithium battery, one or more of the conductive material, binder, and solvent may be omitted.

[0117] Next, the cathode is prepared.

[0118] For example, a negative electrode active material composition is prepared by mixing a negative electrode active material, a conductive material, a binder, and a solvent. The negative electrode active material composition is directly coated and dried onto a metal current collector to manufacture a negative electrode plate. Alternatively, the negative electrode active material composition may be cast onto a separate support, and then a film peeled from the support is laminated onto a metal current collector to manufacture a negative electrode plate.

[0119] The above-mentioned negative electrode active material may be any material that can be used as a negative electrode active material for a lithium battery in the relevant technical field. For example, it may include one or more selected from the group consisting of lithium metal, metals alloyable with lithium, transition metal oxides, non-transition metal oxides, and carbon-based materials.

[0120] For example, the metals that can be alloyed with the lithium may be Si, Sn, Al, Ge, Pb, Bi, Sb Si-Y alloys (wherein Y is an alkali metal, alkaline earth metal, group 13 element, group 14 element, transition metal, rare earth element, or a combination thereof, and is not Si), Sn-Y alloys (wherein Y is an alkali metal, alkaline earth metal, group 13 element, group 14 element, transition metal, rare earth element, or a combination thereof, and is not Sn), etc. The above element Y may be 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, Ti, Ge, P, As, Sb, Bi, S, Se, Te, Po, or a combination thereof.

[0121] For example, the transition metal oxide may be lithium titanium oxide, vanadium oxide, lithium vanadium oxide, etc.

[0122] For example, the above non-transfer metal oxides are SnO2, SiO2 x (0 <x<2) 등일 수 있다.

[0123] The carbon-based material may be crystalline carbon, amorphous carbon, or a mixture thereof. The crystalline carbon may be graphite such as natural graphite or artificial graphite in amorphous, plate-like, flake-like, spherical, or fibrous form, and the amorphous carbon may be soft carbon (low-temperature calcined carbon) or hard carbon, mesophase pitch carbide, calcined coke, etc.

[0124] In the cathode active material composition, the conductive material and binder may be the same as those used in the anode active material composition.

[0125] The content of the above-mentioned negative electrode active material, conductive material, binder, and solvent is at a level typically used in lithium batteries. Depending on the application and composition of the lithium battery, one or more of the above-mentioned conductive material, binder, and solvent may be omitted.

[0126] Next, a separator to be inserted between the anode and cathode is prepared.

[0127] Any separator commonly used in lithium batteries may be used. One that exhibits low resistance to ion movement of the electrolyte and excellent electrolyte wetting ability may be used. For example, it may be selected from glass fiber, polyester, Teflon, polyethylene, polypropylene, polytetrafluoroethylene (PTFE), or combinations thereof, and may be in the form of a nonwoven or woven fabric. For example, a windable separator such as polyethylene or polypropylene is used in lithium-ion batteries, and a separator with excellent organic electrolyte impregnation ability may be used in lithium-ion polymer batteries. For example, the separator may be manufactured according to the following method.

[0128] A separator composition is prepared by mixing a polymer resin, a filler, and a solvent. The separator composition may be directly coated and dried on the electrode to form a separator. Alternatively, the separator composition may be cast and dried on a support, and then a separator film peeled from the support may be laminated onto the electrode to form a separator.

[0129] The polymer resin used in the manufacture of the above separator is not particularly limited, and any material used as a binder for the electrode plate may be used. For example, vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethyl methacrylate, or mixtures thereof may be used.

[0130] In addition, separators are not limited to but may include, for example, PES (Polyethylene Separator), PPS (Polypropylene Separator), CCS (Ceramic Coated Separator), PCS (Polymer Coated Separator), MCS (Multi-layer Coated Separator), MFS (Multi-Functional Separator), and combinations thereof.

[0131] Next, the aforementioned electrolyte is prepared.

[0132] As shown in FIG. 1, the lithium battery (1) comprises a positive electrode (3), a negative electrode (2), and a separator (4). The aforementioned positive electrode (3), negative electrode (2), and separator (4) are wound or folded and accommodated in a battery case (5). Subsequently, an organic electrolyte is injected into the battery case (5) and sealed with a cap assembly (6) to complete the lithium battery (1). The battery case may be pouch-type, cylindrical-type, prismatic-type, thin-film-type, etc. For example, the lithium battery may be a large-film-type battery. The lithium battery may be a lithium-ion battery.

[0133] A cylindrical battery forms a cylindrical electrode assembly with a separator wound between the positive and negative electrodes, and after being inserted into a cylindrical can, an electrolyte can be injected into the cylindrical can. The cylindrical can may be formed of steel, steel alloy, nickel-plated steel, nickel-plated steel alloy, aluminum, aluminum alloy, or an equivalent thereof, but the material is not limited thereto. In addition, to prevent the cap assembly from detaching outward, a beading part recessed inwardly at the bottom of the cylindrical can and a crimping part bent inwardly at the top may be formed so as to prevent the cap assembly from detaching outward.

[0134] Meanwhile, a plurality of battery structures having a separator disposed between the anode and cathode are stacked to form a battery pack, and such a battery pack can be used in any device requiring high capacity and high output. For example, it can be used in laptops, smartphones, electric vehicles, etc.

[0135] Compared to a lithium secondary battery that employs a general nickel-rich lithium nickel composite oxide as a positive electrode active material, the lithium secondary battery according to the first embodiment can exhibit excellent battery characteristics by significantly reducing the DCIR increase rate.

[0136] The operating voltage of the lithium secondary battery using the above positive electrode, negative electrode, and electrolyte is, for example, a lower limit of 2.5-2.8V and an upper limit of 4.1V or higher, for example, 4.1-4.45V.

[0137] In addition, the above lithium secondary battery may be, for example, a power tool that moves by receiving power from an electric motor; an electric vehicle including an electric vehicle (EV), a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), etc.; an electric two-wheeled vehicle including an electric bicycle (E-bike) and an electric scooter; an electric golf cart; a power storage system, etc., but is not limited thereto.

[0138] In this specification, the term "alkyl group" means a branched or unbranched aliphatic hydrocarbon group. In one embodiment, the alkyl group may be substituted or unsubstituted. The alkyl group includes, but is not limited to, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, hexyl, cyclopropyl, cyclopentyl, cyclohexyl, cycloheptyl, etc., and each of these may be optionally substituted in other embodiments. In other embodiments, the alkyl group may include 1 to 6 carbon atoms. For example, alkyl groups having 1 to 6 carbon atoms include, but are not limited to, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, pentyl, 3-pentyl, hexyl, etc.

[0139] One or more hydrogen atoms of the above alkyls are a halogen atom, a C1-C20 alkyl group substituted with a halogen atom (e.g., CF3, CHF2, CH2F, CCl3, etc.), a C1-C20 alkoxy, a C2-C20 alkoxyalkyl, a hydroxyl group, a nitro group, a cyano group, an amino group, an amidino group, a hydrazine, a hydrazone, a carboxyl group or its salt, a sulfonyl group, a sulfamoyl group, a sulfonic acid group or its salt, a phosphoric acid or its salt, or a C1-C20 alkyl group, a C2-C20 alkenyl group, a C2-C20 alkynyl group, a C1-C20 heteroalkyl group, a C6-C20 aryl group, a C7-C20 arylalkyl group, a C6-C20 heteroaryl group, a C7-C20 heteroarylalkyl group, It can be substituted with a C6-C20 heteroaryloxy group or a C6-C20 heteroaryloxyalkyl group.

[0140] In this specification, "alkenyl group" is a hydrocarbon group having 2 to 20 carbon atoms and comprising one or more carbon-carbon double bonds, including but not limited to ethenyl group, 1-propenyl group, 2-propenyl group, 2-methyl-1-propenyl group, 1-butenyl group, 2-butenyl group, cyclopropenyl group, cyclopentenyl, cyclohexenyl, cyclopentenyl, etc. In other embodiments, the alkenyl group may or may not be substituted. In other embodiments, the number of carbon atoms of the alkenyl group may be 2 to 40.

[0141] In this specification, the term “alkynyl group” refers to a hydrocarbon group having 2 to 20 carbon atoms comprising one or more carbon-carbon triple bonds, including but not limited to ethinyl groups, 1-propynyl groups, 1-butynyl groups, 2-butynyl groups, etc. In other embodiments, the alkynyl group may or may not be substituted. In other embodiments, the number of carbon atoms of the alkynyl group may be 2 to 40.

[0142] In this specification, a substituent is derived from an unsubstituted parent group, wherein one or more hydrogen atoms are substituted for other atoms or functional groups. Unless otherwise indicated, if a functional group is considered "substituted," this is because said functional group is C 1- C 20 Alkyl, C 2- C 20 Alkenyl, C 2- C 20 Alkinyl, C 1- C 20 It means being substituted with one or more substituents independently selected from the group consisting of alkoxy, halogen, cyano, hydroxyl, and nitro groups. If one functional group is described as "optionally substituted," the functional group may be substituted with the substituents described above.

[0143] The term "halogen" includes fluorine, bromine, chlorine, iodine, etc.

[0144] "Alkoxy" represents "alkyl-O-", and alkyl is as described above. Examples of alkoxy groups include methoxy groups, ethoxy groups, 2-propoxy groups, butoxy groups, t-butoxy groups, pentyloxy groups, hexyloxy groups, etc. One or more hydrogen atoms of the above alkoxy groups may be substituted with the same substituents as in the case of the alkyl groups described above.

[0145] "Heteroaryl" refers to a monocyclic or bicyclic organic group comprising one or more heteroatoms selected from N, O, P, or S, and having a carbon ring atom. The heteroaryl group may, for example, comprise 1 to 5 heteroatoms and 5 to 10 ring members. The S or N may be oxidized to have various oxidation states.

[0146] Examples of heteroaryls include thienyl, furyl, pyrrolyl, imidazolyl, pyrazolyl, thiazolyl, isothiazolyl, 1,2,3-oxadiazolyl, 1,2,4-oxadiazolyl, 1,2,5-oxadiazolyl, 1,3,4-oxadiazolyl group, 1,2,3-thiadiazolyl, 1,2,4-thiadiazolyl, 1,2,5-thiadiazolyl, 1,3,4-thiadiazolyl, isothiazol-3-yl, isothiazol-4-yl, isothiazol-5-yl, oxazol-2-yl, oxazol-4-yl, oxazol-5-yl, isooxazol-3-yl, isooxazol-4-yl, isooxazol-5-yl, 1,2,4-triazole-3-yl, Examples include 1,2,4-triazole-5-yl, 1,2,3-triazole-4-yl, 1,2,3-triazole-5-yl, tetrazolyl, pyrid-2-yl, pyrid-3-yl, 2-pyrazine-2-yl, pyrazine-4-yl, pyrazine-5-yl, 2-pyrimidine-2-yl, 4-pyrimidine-2-yl, or 5-pyrimidine-2-yl.

[0147] The term "heteroaryl" includes cases where a heteroaromatic ring is selectively fused to one or more aryl, cycloaliphatic, or heterocycles.

[0148] The term “carbon ring” refers to a saturated or partially unsaturated non-aromatic monocyclic, bicyclic, or tricyclic hydrocarbon group.

[0149] Examples of the above monocyclic hydrocarbons include cyclopentyl, cyclopentenyl, cyclohexyl, and cyclohexenyl.

[0150] Examples of the above-mentioned bicyclic hydrocarbons include bornyl, decahydronaphthyl, bicyclo[2.1.1]hexyl, bicyclo[2.1.1]heptyl, bicyclo[2.2.1]heptenyl, or bicyclo[2.2.2]octyl.

[0151] Examples of the above tricyclic hydrocarbons include adamantly.

[0152] One or more hydrogen atoms of the above carbon ring can be replaced with a substituent similar to that of the alkyl group described above.

[0153] The present invention is explained in more detail through the following examples and comparative examples. However, the examples are intended to illustrate the present invention and do not limit the scope of the present invention.

[0154] (Manufacturing of lithium-ion batteries)

[0155] Example 1

[0156] An electrolyte for a lithium secondary battery was prepared by adding 1.5 M LiPF6 to a mixed solvent having a volume ratio of 20:10:70 of ethylene carbonate (EC), ethylmethyl carbonate (EMC), and dimethyl carbonate (DMC), and then adding 5.0 parts by weight of FEC and 1.0 parts by weight of a compound represented by the following chemical formula 3 (3-Penetenenitrile, Sigma Aldrich) to 100 parts by weight of an electrolyte composed of a lithium salt and an organic solvent.

[0157] <Chemical Formula 3>

[0158]

[0159] LiNi as a positive electrode active material 0.88 Co 0.105 Al 0.015 A cathode active material slurry was prepared by mixing 297 wt% O, 0.5 wt% artificial graphite powder as a conductive material, 0.8 wt% carbon black, and 1.7 wt% polyvinylidene fluoride (PVdF), adding the mixture to N-methyl-2-pyrrolidone, and stirring for 4 hours using a mechanical stirrer. The slurry was uniformly coated onto a 12 μm thick aluminum current collector using a coater and dried with hot air at 100°C. After drying, the cathode was manufactured by rolling (roll press).

[0160] As a negative electrode active material, 87 wt% of artificial graphite, 10.5 wt% of a silicon composite, 1.5 wt% of SBR, and 1 wt% of CMC were mixed and dispersed in water to prepare a negative electrode active material slurry. The slurry was uniformly coated onto a copper current collector with a thickness of 10 μm in a continuous manner using a coater and dried with hot air at 100°C. Subsequently, a negative electrode was manufactured by rolling (roll press).

[0161] A cylindrical lithium secondary battery with a voltage of 4.2V was manufactured using the above-manufactured positive and negative electrodes, a 14㎛ thick polyethylene separator, and the above-manufactured electrolyte.

[0162] Example 2

[0163] Compound represented by the following chemical formula 6 ( (E) A lithium secondary battery was manufactured by carrying out the same process as in Example 1, except that 1.0 part by weight of -5,5-dimethylhex-3-enenitrile, Aurora Building Blocks1) was added.

[0164] <Chemical Formula 6>

[0165]

[0166] Comparative Example 1

[0167] A lithium secondary battery was manufactured by carrying out the same process as in Example 1, except that an electrolyte without the compound synthesized in Manufacturing Example 1 was used.

[0168] Comparative Example 2

[0169] A lithium secondary battery was manufactured by carrying out the same process as in Example 1, except that succinonitrile represented by the following chemical formula 11 was added instead of the compound synthesized in Preparation Example 1.

[0170] <Chemical Formula 11>

[0171]

[0172] Comparative Example 3

[0173] A lithium secondary battery was manufactured by carrying out the same process as in Example 1, except that fumaronitrile represented by the following chemical formula 12 was added instead of the compound synthesized in Preparation Example 1.

[0174] <Chemical Formula 12>

[0175]

[0176] Comparative Example 4

[0177] A lithium secondary battery was manufactured by carrying out the same process as in Example 1, except that an allyl cyanide represented by the following chemical formula 13 was added instead of the compound synthesized in Manufacturing Example 1 above.

[0178] <Chemical Formula 13>

[0179]

[0180] Comparative Example 5

[0181] A lithium secondary battery was manufactured by carrying out the same process as in Example 1, except that 2,3-dimethylfumaronitrile represented by the following chemical formula 14 was added instead of the compound synthesized in Preparation Example 1.

[0182] <Chemical Formula 14>

[0183]

[0184] Comparative Example 6

[0185] A lithium secondary battery was manufactured by carrying out the same process as in Example 1, except that 3-hexenedinitrile represented by the following chemical formula 15 was added instead of the compound synthesized in Preparation Example 1.

[0186] <Chemical Formula 15>

[0187]

[0188] Comparative Example 7

[0189] A lithium secondary battery was manufactured by carrying out the same process as in Example 1, except that crotononitrile represented by the following chemical formula 16 was added instead of the compound synthesized in Preparation Example 1.

[0190] <Chemical Formula 16>

[0191]

[0192] Comparative Example 8

[0193] A lithium secondary battery was manufactured by carrying out the same process as in Example 1, except that 2-pentenenitrile represented by the following chemical formula 17 was added instead of the compound synthesized in Preparation Example 1.

[0194] <Chemical Formula 13>

[0195]

[0196] Evaluation Example 1: Evaluation of High Temperature (90℃) Storage Characteristics

[0197] To evaluate the high-temperature stability of the lithium secondary batteries prepared in Examples 1 and 2 and Comparative Examples 1 to 8, the CID operation time was measured as follows, and the results are shown in FIG. 2 and Table 1 below.

[0198] First, the charging and discharging of the phosphating system was performed twice at 0.2C / 0.5C, and then a charging and discharging experiment was conducted once each with a standard charging and discharging current density of 0.5C / 0.2C, a charging cutoff voltage of 4.2V (Li / graphite), and a discharging cutoff voltage of 2.6V (Li / graphite). Afterward, the system was left in a 90℃ chamber for 140 hours to measure the activation time of the CID (Current Interrupt Device).

[0199] CID OPEN TIME (hr)(@90℃) Comparative Example 1 98 Comparative Example 2 109 Comparative Example 3 116 Comparative Example 4 126 Comparative Example 5 99 Comparative Example 6 119 Comparative Example 7 121 Comparative Example 8 115 Example 1 135 Example 2 133

[0200] As shown in Table 1 and Figure 2 above, it can be confirmed that Examples 1 and 2, each containing compounds of Formula 3 and 6, respectively, have a delayed CID OPEN time compared to Comparative Examples 1 to 8. That is, it can be seen that the lithium secondary battery according to the present embodiment has a superior effect of suppressing gas generation when left at high temperatures.

[0201] Examples 3 and 4

[0202] LiNi as a positive electrode active material 0.88 Co 0.105 Al 0.015 LiNi instead of O2 0.915 Co 0.07 Al0.015 A lithium secondary battery was manufactured by carrying out the same process as in Examples 1 and 2 above, respectively, except that O2 was used.

[0203] Comparative Examples 9 to 16

[0204] LiNi as a positive electrode active material 0.88 Co 0.105 Al 0.015 LiNi instead of O2 0.915 Co 0.07 Al 0.015 A lithium secondary battery was manufactured by carrying out the same process as Comparative Examples 1 to 8 above, except that O2 was used.

[0205] Evaluation Example 2: Evaluation of CID gas generation during high-temperature (90℃) storage

[0206] To evaluate the high-temperature stability of the lithium secondary batteries prepared in Examples 3 and 4 and Comparative Examples 9 to 16, the CID operation time was measured as in Evaluation Example 1, and the results are shown in FIG. 3 and Table 2 below.

[0207] CID OPEN TIME (hr)(@90℃) Comparative Example 9 59 Comparative Example 10 87 Comparative Example 11 93 Comparative Example 12 100 Comparative Example 13 79 Comparative Example 14 94 Comparative Example 15 96 Comparative Example 16 92 Example 3 128 Example 4 127

[0208] As shown in Table 2 and Figure 3 above, it can be seen that Examples 3 and 4, each containing compounds of Formula 3 and 6, respectively, have a delayed CID OPEN time compared to Comparative Examples 9 to 16. Furthermore, it can be seen that the gas reduction improvement effect of the compounds of Formula 3 and 6 becomes more pronounced when the Ni content increases.

[0209] Evaluation Example 3: Initial Resistance Evaluation

[0210] To evaluate the initial resistance of the lithium secondary batteries prepared in Examples 1 and 2 and Comparative Examples 1 to 8, DC-IR was measured in the following manner.

[0211] The lithium secondary batteries prepared according to Examples 1 and 2 and Comparative Examples 1 to 8 were charged at room temperature (25°C) at 4A (1.6C) and 4.2V, and then cut off at a current of 100mA when a constant voltage of 4.2V was applied and rested for 30 minutes. Afterward, after discharging at 10A and 10 seconds, 1A and 10 seconds, and 10A and 4 seconds, respectively, the current and voltage at the 18-second and 23-second points were measured, and the initial resistance (the difference between the resistance at the 18-second point and the resistance at the 23-second point) was calculated by the equation ΔR=ΔV / ΔI.

[0212] The measured initial resistance values ​​are shown in Table 3 below.

[0213] Initial DC-IR (mΩ) Comparative Example 1 34.5 Comparative Example 2 35.8 Comparative Example 3 36.6 Comparative Example 4 38.0 Comparative Example 5 36.9 Comparative Example 6 36.8 Comparative Example 7 37.0 Comparative Example 8 36.8 Example 1 35.0 Example 2 35.1

[0214] As shown in Table 3 above, it can be seen that the initial resistance of Examples 1 and 2, each containing compounds of Formula 3 and 6, is improved compared to Comparative Examples 1 to 8.

[0215] Examples 5 and 6

[0216] A lithium secondary battery was manufactured by carrying out the same process as in Examples 1 and 2 above, respectively, except that a pouch-type lithium secondary battery using 4.5V was manufactured instead of a cylindrical lithium secondary battery.

[0217] Comparative Example 17

[0218] A lithium secondary battery was manufactured by carrying out the same process as Comparative Example 1 above, except that a pouch-type lithium secondary battery using 4.5V was manufactured instead of a cylindrical lithium secondary battery.

[0219] Examples 7 and 8

[0220] LiNi as a positive electrode active material 0.88 Co 0.105 Al 0.015A lithium secondary battery was manufactured by carrying out the same process as in Examples 1 and 2 above, respectively, except that LiCoO2 was used instead of O2 and only artificial graphite was used as the negative electrode active material to manufacture a pouch-type lithium secondary battery with a voltage of 4.5V.

[0221] Comparative Example 18

[0222] LiNi as a positive electrode active material 0.88 Co 0.105 Al 0.015 A lithium secondary battery was manufactured by carrying out the same process as Comparative Example 1, except that LiCoO2 was used instead of O2, and only artificial graphite was used as the negative electrode active material instead of an artificial graphite and silicon composite, thereby manufacturing a pouch-type lithium secondary battery with a voltage of 4.5V.

[0223] Evaluation Example 4: Evaluation of gas generation amount during high-temperature (90℃) storage

[0224] To compare the amount of gas generated during high-temperature storage of lithium secondary batteries according to Examples 5 and 6 and Comparative Example 17 using Ni-based cathodes, and the amount of gas generated during high-temperature storage of lithium secondary batteries according to Examples 7 and 8 and Comparative Example 18 using Co-based cathodes, the following evaluations were performed, and the results are shown in FIG. 4.

[0225] First, the charging and discharging of the phosphating system was performed twice at 0.2C / 0.5C, and then a charging and discharging experiment was conducted once each with a standard charging and discharging current density of 0.5C / 0.2C, a charging cutoff voltage of 4.5V (Li / graphite), and a discharging cutoff voltage of 2.6V (Li / graphite). Afterward, the amount of gas generated was measured while leaving the system in a 90℃ chamber for 120 hours.

[0226] As shown in FIG. 4, in the case of the examples and comparative examples using Ni-based cathodes, it can be seen that the amount of gas generated during high-temperature storage of the lithium secondary batteries of Examples 5 and 6 is significantly reduced compared to Comparative Example 17. In addition, in the case of the examples and comparative examples using Co-based cathodes, it can be seen that the amount of gas generated during high-temperature storage of the lithium secondary batteries of Examples 7 and 8 is reduced compared to Comparative Example 18.

[0227] Here, it was confirmed that during high-temperature storage, the gas generation reduction effect was more pronounced in Ni-based anodes than in Co-based anodes.

[0228] Although one embodiment has been described above with reference to the drawings and examples, this is merely illustrative, and those skilled in the art will understand that various modifications and equivalent alternative embodiments are possible therefrom. Accordingly, the scope of protection of the present invention should be determined by the appended claims. Explanation of the symbols

[0229] 1: Lithium secondary battery 2: Negative electrode 3: Anode 4: Separator 5: Battery case 6: Cap assembly

Claims

Claim 1 An electrolyte for a lithium secondary battery comprising a lithium salt; an organic solvent; and an additive, wherein the additive comprises at least one of compounds represented by the following chemical formulas 3 to 6: <Chemical Formula 3> <Chemical Formula 4> <Chemical Formula 5> <Chemical Formula 6> . Claim 2 delete Claim 3 delete Claim 4 delete Claim 5 delete Claim 6 An electrolyte for a lithium secondary battery according to claim 1, wherein the content of the compound represented by the chemical formulas 3 to 6 is in the range of 0.001 to 20 parts by weight per 100 parts by weight of an electrolyte composed of a lithium salt and an organic solvent. Claim 7 An electrolyte for a lithium secondary battery according to claim 1, wherein the electrolyte further comprises other additives, and the other additives comprise at least one of vinylene carbonate (VC), fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), chloroethylene carbonate (CEC), dichloroethylene carbonate (DCEC), bromoethylene carbonate (BEC), dibromoethylene carbonate (DBEC), nitroethylene carbonate, cyanoethylene carbonate, vinylethylene carbonate (VEC), succinonitrile (SN), adiponitrile (AN), 1,3,6-hexane tricyanide (HTCN), propenesulfone (PST), propanesulfone (PS), lithium tetrafluoroborate (LiBF4), lithium difluorophosphate (LiPO2F2), and 2-fluorobiphenyl (2-FBP). Claim 8 An electrolyte for a lithium secondary battery according to claim 7, wherein the content of the above-mentioned other additive is 0.2 to 20 parts by weight per 100 parts by weight of an electrolyte composed of a lithium salt and an organic solvent. Claim 9 A lithium secondary battery comprising: a positive electrode comprising a positive electrode active material; a negative electrode comprising a negative electrode active material; and an electrolyte according to any one of claims 1 and 6 to 8 disposed between the positive electrode and the negative electrode. Claim 10 A lithium secondary battery according to claim 9, wherein the positive electrode active material comprises a lithium transition metal oxide comprising nickel and other transition metals, and the nickel content in the lithium transition metal oxide is 60 mol% or more and less than 100 mol% with respect to the total number of moles of transition metals. Claim 11 In claim 9, a lithium secondary battery comprising a positive electrode active material that is a compound represented by the following chemical formula 11: <Chemical Formula 11>Li a Ni x Co y M z O 2-b A b In the above chemical formula 11, 1.0≤a≤1.2, 0≤b≤0.2, 0.6≤x<1, 0 <y≤0.4, 0<z≤0.4, x+y+z=1, M은 망간(Mn), 바나듐(V), 마그네슘(Mg), 갈륨(Ga), 실리콘(Si), 텅스텐(W), 몰리브덴(Mo), 철(Fe), 크롬(Cr), 구리(Cu), 아연(Zn), 티타늄(Ti), 알루미늄(Al) 및 보론(B)으로 이루어진 군으로부터 선택된 하나 이상이고, A는 F, S, Cl, Br 또는 이들의 조합이다.

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