Non-aqueous electrolyte and lithium secondary battery comprising same

Abstract

The present invention relates to a non-aqueous electrolyte and a lithium secondary battery comprising same. The non-aqueous electrolyte of the present invention comprises a lithium salt, a non-aqueous electrolyte and an additive, wherein the additive can comprise a polymer comprising a repeating unit represented by chemical formula 1.

Description

Non-aqueous electrolyte and lithium secondary battery containing the same

[0001] Cross-citation with related application(s)

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2024-0153868 filed November 1, 2024, and all contents disclosed in the document of said Korean patent application are incorporated herein as part of this specification.

[0003]

[0004] Technology field

[0005] The present invention relates to a non-aqueous electrolyte and a lithium secondary battery containing the same.

[0006] As dependence on electrical energy gradually increases in modern society, the development of large-capacity power storage devices capable of stably supplying power while simultaneously increasing production is emerging. Furthermore, the need for high-capacity portable power is growing due to the performance improvements of electronic products, ranging from small devices such as mobile phones to medium-to-large devices such as electric vehicles. Lithium-ion batteries, which possess the highest potential, satisfy high-capacity power storage performance requirements and are therefore utilized in a wide range of applications, from small electronic devices to electric vehicles (EVs) and energy storage systems (ESS).

[0007] The above lithium secondary battery generally consists of a positive electrode containing a positive active material, a negative electrode containing a negative active material, an electrolyte serving as a medium for transporting lithium ions, and a separator. In this case, carbon-based active materials, silicon-based active materials, lithium transition metal oxides, lithium metal, etc., may be used as the negative electrode active material. Additionally, lithium transition metal oxides such as lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium nickel-cobalt-manganese oxide, and lithium iron phosphate may be used as the positive electrode active material.

[0008] During the charging of a lithium secondary battery, lithium ions are generated from the positive electrode and can be converted into stacked or alloyed forms for storage on the negative electrode, while discharge proceeds in the opposite direction. Theoretically, the movement of lithium ions to the positive and negative electrodes during charging and discharging of such lithium secondary batteries should be reversible; however, in reality, the movement of lithium within the battery may be partially irreversible. Specifically, the medium through which lithium ions can move is the electrolyte. During charging, most lithium ions are stacked or alloyed within the negative electrode active material, but some are reduced together with the organic and inorganic materials constituting the electrolyte to form nano-sized organic-inorganic composites on the surface of the negative electrode material. This formed organic-inorganic film is called a solid electrolyte interface layer (SEI layer). Meanwhile, a solid electrolyte interface layer can also be formed on the surface of the positive electrode active material through the oxidation reaction of the materials constituting the electrolyte.

[0009] While such a solid-electrolyte interface layer causes irreversible permanent loss of lithium ions supplied by the anode during formation, once formed, this irreversible loss is reduced, and a wide driving potential of the electrolyte is secured, enabling smooth reversible movement of lithium ions between the anode and cathode. Depending on its internal composition, this solid-electrolyte interface layer can contribute to lowering the energy barrier required for charge transfer of lithium ions to the cathode or anode, or its stability can determine the lifespan characteristics and durability of the lithium secondary battery.

[0010] Meanwhile, as the charging and discharging of the lithium secondary battery progresses, the deterioration of the initially formed solid-electrolyte interface layer causes the decomposition of the electrolyte, resulting in increased resistance and structural degradation of the cathode material, which leads to the leaching of transition metals from the cathode. The transition metal ions leached out in this way are re-deposited on the cathode, which causes an increase in the resistance of the cathode. Conversely, they move through the electrolyte to the anode and are electrodeposited on the anode, causing self-discharge of the anode. Furthermore, due to the destruction and regeneration of the solid-electrolyte interface layer, additional lithium ions are consumed, causing an increase in resistance and a deterioration of lifespan.

[0011] Therefore, to improve the performance of lithium secondary batteries, strengthening the stability of the solid-electrolyte interface layer formed on the surfaces of the anode and cathode is emerging as an important challenge.

[0012] The present invention aims to solve the above-mentioned problems by providing a non-aqueous electrolyte capable of increasing the stability of the solid-electrolyte interface layer formed between the cathode and the anode, increasing the structural stability of the anode by suppressing lithium loss from the anode, and suppressing the leaching of transition metals from the anode.

[0013] In addition, the present invention provides a lithium secondary battery with improved high-temperature durability by including the above-mentioned non-aqueous electrolyte.

[0014] [1] The present invention provides a non-aqueous electrolyte comprising a lithium salt; a non-aqueous organic solvent and an additive, wherein the additive is a polymer comprising repeating units represented by the following chemical formula 1.

[0015] [Chemical Formula 1]

[0016]

[0017] In the above chemical formula 1,

[0018] R1 is an alkyl group having 1 to 5 carbon atoms that is substituted or unsubstituted with hydrogen or at least one fluorine.

[0019] [2] The present invention provides a non-aqueous electrolyte in which, in [1], R1 in Formula 1 is a carbon-1 to carbon-3 alkyl group substituted or unsubstituted with hydrogen or at least one fluorine.

[0020] [3] The present invention provides a non-aqueous electrolyte in which, in [1] or [2], the compound represented by Formula 1 is selected from at least one of the group consisting of compounds represented by Formulas 1A to 1D.

[0021] [Chemical Formula 1A]

[0022]

[0023] [Chemical Formula 1B]

[0024]

[0025] [Chemical Formula 1C]

[0026]

[0027] [Chemical Formula 1D]

[0028]

[0029] [4] The present invention provides a non-aqueous electrolyte in which, in at least one of [1] to [3], the repeating unit represented by Formula 1 is included in the polymer in an amount of 1 to 99 mol%.

[0030] [5] The present invention provides a non-aqueous electrolyte in which, in at least one of [1] to [4], the polymer further comprises a repeating unit represented by the following chemical formula 2.

[0031] [Chemical Formula 2]

[0032]

[0033] In the above chemical formula 2,

[0034] R2 is *-C(O)-Ra-CN (Ra is an alkylene group having 1 to 10 carbon atoms) or *-C(O)-Rb (Rb is a nitrogen-containing heterocycloalkyl group or a lactam group).

[0035] [6] The present invention provides a non-aqueous electrolyte in which, in [5] the formula 2, R2 is *-C(O)-Ra-CN (Ra is an alkylene group having 1 to 5 carbon atoms) or *-C(O)-Rb (Rb is a nitrogen-containing heterocycloalkyl group or a lactam group).

[0036] [7] The present invention, in [5] or [6], wherein in Formula 2, R2 is *-C(O)-CH2-CN, *-C(O)-CH2CH2-CN, *-C(O)-CH2CH2CH2-CN or Provides phosphorus non-hydrolyzed electrolytes.

[0037] [8] The present invention provides a non-aqueous electrolyte in which, in at least one of [5] to [7], the repeating unit represented by Formula 2 comprises a repeating unit represented by Formula 2A or a repeating unit represented by Formula 2B.

[0038] [Chemical Formula 2A]

[0039]

[0040] [Chemical Formula 2B]

[0041]

[0042] [9] The present invention provides a non-aqueous electrolyte in which, in at least one of [1] to [8], the polymer further comprises a repeating unit represented by the following chemical formula 3.

[0043] [Chemical Formula 3]

[0044]

[0045]

[0010] The present invention provides a non-aqueous electrolyte in which, in at least one of [1] to [9], the polymer is included in an amount of 0.001% to 18% by weight based on the total weight of the non-aqueous electrolyte.

[0046]

[0011] The present invention provides a non-aqueous electrolyte in which, in at least one of [1] to

[0010] , the polymer is included in an amount of 0.01% to 15% by weight based on the total weight of the non-aqueous electrolyte.

[0047]

[0012] The present invention provides a non-aqueous electrolyte, wherein in at least one of [1] to

[0011] the non-aqueous electrolyte further comprises at least one auxiliary additive selected from the group consisting of cyclic carbonate compounds, halogen-substituted carbonate compounds, sulfone compounds, sulfate compounds, phosphate compounds, borate compounds, nitrile compounds, benzene compounds, amine compounds, silane compounds and lithium salt compounds.

[0048]

[0013] The present invention provides a lithium secondary battery comprising: a positive electrode; a negative electrode facing the positive electrode; a separator interposed between the negative electrode and the positive electrode; and a non-aqueous electrolyte according to [1].

[0049] The non-aqueous electrolyte according to the present invention comprises a polymer based on a polyvinyl alcohol structure substituted with a boron-containing aromatic hydrocarbon moiety as an additive, thereby enabling the formation of a highly durable film on the surfaces of the positive and negative electrodes. When this non-aqueous electrolyte of the present invention is applied to a lithium secondary battery, the structural stability of the positive electrode is increased, and the leaching of transition metals from the positive electrode is suppressed, thereby improving high-temperature durability.

[0050] The terms and words used in this specification and claims are used merely to describe exemplary embodiments and should not be interpreted as being limited to their ordinary or dictionary meanings, and should be interpreted in a meaning and concept consistent with the technical spirit of the invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention.

[0051] For example, in this specification, terms such as “comprising,” “having,” or “having” are intended to specify the existence of the implemented features, numbers, steps, components, or combinations thereof, and should be understood as not excluding in advance the existence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0052] In addition, in the description of “carbon number a to b” within this specification, “a” and “b” refer to the number of carbon atoms included in a specific functional group. That is, the functional group may include “a” to “b” carbon atoms. For example, “alkylene group having 1 to 5 carbon atoms” refers to an alkylene group containing carbon atoms having 1 to 5 carbon atoms, namely -CH2-, -CH2CH2-, -CH2CH2CH2-, -CH2(CH3)CH-, -CH2CH2CH2CH2CH2-, and -CH(CH3)CH2CH2-, etc.

[0053] Additionally, in this specification, the term “alkylene group” means a branched or unbranched aliphatic hydrocarbon group or a functional group in which one hydrogen atom is removed from each carbon atom located at both ends of the aliphatic hydrocarbon group. In one embodiment, the alkylene group may be substituted or unsubstituted. The alkylene group includes, but is not limited to, methylene groups, ethylene groups, propylene groups, isopropylene groups, butylene groups, isobutylene groups, tert-butylene groups, pentylene groups, 3-pentylene groups, etc., and each of these may be optionally substituted in other embodiments.

[0054] Additionally, in this specification, the “weight-average molecular weight (Mw)” of a polymer is a value measured using gel permeation chromatography (GPC). For example, after preparing a sample of a certain concentration, the Alliance 4 GPC measurement system instrument is stabilized, and then a standard sample and the sample are injected into the instrument to obtain a chromatogram, after which the molecular weight can be calculated according to the analysis method (System: Alliance 4, Column: Ultrahydrogel linear×2, Eluent: 0.1M NaNO3 (pH 7.0 phosphate buffer, flow rate: 0.1 mL / min, temp: 40℃, injection: 100μL)

[0055] Additionally, in this specification, “substitution” means that at least one hydrogen bonded to carbon is substituted with another element, such as fluorine, unless otherwise defined.

[0056] Additionally, in this specification, “*” refers to a connected portion between the terminals of a chemical formula unless otherwise defined.

[0057] Additionally, in this specification, “%” means weight % unless otherwise explicitly indicated.

[0058]

[0059] The present invention will be described in detail below.

[0060] The non-aqueous electrolyte and lithium secondary battery according to the present invention comprise at least one of the configurations disclosed below, and may comprise any combination of technically feasible configurations among the configurations below.

[0061]

[0062] Non-aqueous electrolytes

[0063] The present invention relates to a non-aqueous electrolyte, and more specifically, to a non-aqueous electrolyte for a lithium secondary battery.

[0064] Specifically, the non-aqueous electrolyte of the present invention comprises a lithium salt; a non-aqueous organic solvent and an additive, wherein the additive may comprise a polymer comprising a repeating unit represented by the following chemical formula 1.

[0065] [Chemical Formula 1]

[0066]

[0067] (In the above chemical formula 1,

[0068] R1 is an alkyl group having 1 to 5 carbon atoms that is substituted or unsubstituted with hydrogen or at least one fluorine.

[0069]

[0070] The non-aqueous electrolyte according to the present invention comprises a polymer with a polyvinyl alcohol-based structure substituted with a boron-containing aromatic hydrocarbon moiety as an additive, thereby enabling the formation of a durable film on the surfaces of the anode and cathode. Accordingly, when this non-aqueous electrolyte of the present invention is applied to a lithium secondary battery, high-temperature durability can be improved.

[0071]

[0072] (1) Lithium salt

[0073] As the lithium salt used in the present invention, various lithium salts commonly used in non-aqueous electrolytes for lithium secondary batteries may be used without limitation. For example, Li as a cation + It includes, and as anion, F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , B 10 Cl 10 - , AlCl4 - , AlO4 - , PF6 - , CF3SO3 - , CH3CO2 - , CF3CO2 - , AsF6 - , SbF6 - , CH3SO3 - , (CF3CF2SO2)2N - , (CF3SO2)2N - , (FSO2)2N - , BF2C2O4 - , BC4O8 - , PF4C2O4 - , PF2C4O8 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , C4F9SO3 - , CF3CF2SO3 - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , CF3(CF2)7SO3 - and SCN - At least one selected from the group consisting of can be cited.

[0074] Specifically, the lithium salt is LiCl, LiBr, LiI, LiBF4, LiClO4, LiB 10 Cl 10 It may include a single substance selected from the group consisting of LiAlCl4, LiAlO4, LiPF6, LiCF3SO3, LiCH3CO2, LiCF3CO2, LiAsF6, LiSbF6, LiCH3SO3, LiN(SO2F)2(Lithium bis(fluorosulfonyl)imide, LiFSI), LiN(SO2CF2CF3)2(lithium bis(pentafluoroethanesulfonyl)imide, LiBETI), and LiN(SO2CF3)2(lithium bis(trifluoromethanesulfonyl)imide, LiTFSI), or a mixture of two or more substances. Specifically, the lithium salt may include at least one selected from the group consisting of LiBF4, LiClO4, LiPF6, LiBOB (LiB(C2O4)2), LiCF3SO3, LiTFSI (LiN(SO2CF3)2), LiFSI (LiN(SO2F)2) and LiBETI (LiN(SO2CF2CF3)2).

[0075] The above lithium salt can be appropriately modified within a range that is typically usable, but in order to obtain the effect of forming a corrosion-preventing film on the optimal electrode surface, it may be included in the electrolyte at a concentration of 0.8M to 4.0M, specifically at a concentration of 1.0M to 3.0M.

[0076] When the concentration of the above lithium salt is included within the above range, the viscosity of the non-aqueous electrolyte can be controlled to achieve optimal impregnation, and the mobility of lithium ions can be improved to obtain the effect of improving the capacity characteristics and cycle characteristics of the lithium secondary battery.

[0077]

[0078] (2) Non-aqueous organic solvent

[0079] The above-mentioned non-aqueous organic solvent is a non-aqueous solvent commonly used in lithium secondary batteries, and is not particularly limited as long as it minimizes decomposition due to oxidation reactions, etc., during the charging and discharging process of the secondary battery.

[0080] The above-mentioned non-aqueous organic solvent may be included in the non-aqueous electrolyte in the remainder excluding lithium salts and additives, for example.

[0081] Specifically, the above-mentioned non-aqueous organic solvent may include a carbonate-based organic solvent. Specifically, the carbonate-based organic solvent may include at least one selected from (i) a cyclic carbonate-based organic solvent and (ii) a linear carbonate-based organic solvent, and more specifically, may include (iii) a mixed solvent of a cyclic carbonate-based organic solvent and a linear carbonate-based organic solvent.

[0082] The above (i) cyclic carbonate-based organic solvent is a high-viscosity organic solvent that has a high dielectric constant and effectively dissociates lithium salts in a non-aqueous electrolyte, and as a specific example, it may include at least one organic solvent selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate, and vinylene carbonate, and among these, it may include at least one of ethylene carbonate and propylene carbonate.

[0083] The above (ii) linear carbonate-based organic solvent is an organic solvent having low viscosity and low dielectric constant, and as specific examples thereof, it may include at least one selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethyl methyl carbonate (EMC), methyl propyl carbonate and ethyl propyl carbonate, and specifically, it may include one of dimethyl carbonate and ethyl methyl carbonate.

[0084] In order to secure a higher ionic conductivity, the non-aqueous electrolyte of the present invention may use (iii) the cyclic carbonate-based organic solvent and the linear carbonate-based organic solvent in combination, in which case the cyclic carbonate-based organic solvent and the linear carbonate-based organic solvent may be mixed in a volume ratio of 10:90 to 50:50, specifically 20:80 to 40:60.

[0085] In addition, the non-aqueous electrolyte of the present invention may further include at least one organic solvent among (iv) a linear ester-based organic solvent and (v) a cyclic ester-based organic solvent, which has a lower melting point and higher stability at high temperatures compared to the cyclic carbonate-based organic solvent and / or the linear carbonate-based organic solvent, together with the carbonate-based organic solvent.

[0086] The above (iv) linear ester-based organic solvent may include, as a representative example, at least one organic solvent selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, and butyl propionate, and specifically may include at least one of ethyl propionate and propyl propionate.

[0087] The above (v) cyclic ester-based organic solvent may include at least one selected from the group consisting of γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone, and ε-caprolactone.

[0088] Meanwhile, the above organic solvent may consist solely of the carbonate-based organic solvent. Even if only the carbonate-based organic solvent is used as the organic solvent, it is preferable in that it facilitates the dissolution of non-aqueous electrolyte components, such as the additives described later, and enables the realization of appropriate mobility of the lithium salt and viscosity of the non-aqueous electrolyte.

[0089] Meanwhile, the remainder of the non-aqueous electrolyte of the present invention, excluding the lithium salt, the electrolyte additive, and the auxiliary additive described below, may all be organic solvents unless otherwise noted.

[0090]

[0091] (3) Additives

[0092] The non-aqueous electrolyte of the present invention may include a polymer comprising repeating units represented by the following chemical formula 1 as an additive.

[0093] [Chemical Formula 1]

[0094]

[0095] (In the above chemical formula 1,

[0096] R1 is an alkyl group having 1 to 5 carbon atoms that is substituted or unsubstituted with hydrogen or at least one fluorine.

[0097]

[0098] The polymer containing the repeating unit represented by Chemical Formula 1 above is a poly(vinyl-borate) based compound, and by replacing the existing -OH terminal group with a functional group having a BO bond structure centered on boron, it is possible to maintain the flexibility and volume expansion buffering properties of the polymer on the anode and cathode surfaces, and at the same time form a durable film that can effectively suppress side reactions between the -OH group and moisture and LiPF6 byproducts in the electrolyte.

[0099] Since the polymer containing the repeating unit represented by Chemical Formula 1 above contains boron (B), which has strong interactions with metals within its structure, it can form a uniform and highly durable CEI (cathode electrolyte interphase) by inducing interactions with oxygen species on the anode surface through Lewis acid properties, thereby forming a stable BO-metal bond network on the anode surface. Therefore, by preventing side reactions between the electrolyte and the anode, the leaching of transition metals from the anode can be effectively suppressed, and even if transition metals are leached from the anode, they can be captured to prevent dissolution in the electrolyte.

[0100] In addition, the polymer containing the repeating unit represented by Chemical Formula 1 can increase the mechanical strength of the polymer within the film through π-π interactions and strengthening of inter-chain bonds by the aromatic ring bonded to boron, and contribute to suppressing cracking of the film layer on the anode surface, improving adhesion, and preventing collapse of the anode structure. Therefore, it is possible to manufacture a lithium secondary battery with excellent high-temperature durability and minimized loss of reversible lithium ions.

[0101]

[0102] Meanwhile, in the above chemical formula 1, R1 may be an alkyl group having 1 to 3 carbon atoms that is substituted or unsubstituted with hydrogen or at least one fluorine.

[0103] Specifically, the repeating unit represented by the above chemical formula 1 may be at least one selected from the group consisting of repeating units represented by the following chemical formulas 1A to 1D.

[0104] [Chemical Formula 1A]

[0105]

[0106] [Chemical Formula 1B]

[0107]

[0108] [Chemical Formula 1C]

[0109]

[0110] [Chemical Formula 1D]

[0111]

[0112] Meanwhile, the repeating unit represented by Chemical Formula 1 may be included in the polymer in an amount of 1 mol% or more, 5 mol% or more, 10 mol% or more, 15 mol% or more, 20 mol% or more, 25 mol% or more, 30 mol% or more, 35 mol% or more, 40 mol% or more, 45 mol% or more, or 50 mol% or more. Additionally, the repeating unit represented by Chemical Formula 1 may be included in the polymer in an amount of 99 mol% or less, 97 mol% or less, 95 mol% or less, 93 mol% or less, 90 mol% or less, 85 mol% or less, 83 mol% or less, 80 mol% or less, 75 mol% or less, 70 mol% or less, 65 mol% or less, or 60 mol% or less. The above ranges may be combined with each other without limitation. For example, the repeating unit represented by the above chemical formula 1 may be included in the polymer in an amount of 1 mol% to 99 mol%, 5 mol% to 99 mol%, 10 mol% to 99 mol%, 10 mol% to 90 mol%, 15 mol% to 90 mol%, 20 mol% to 85 mol%, 20 mol% to 80 mol%, or 30 mol% to 80 mol%.

[0113] When the repeating unit represented by Chemical Formula 1 satisfies the above numerical range, the adsorption characteristics on the anode surface are improved, and thereby a stable CEI can be formed on the anode surface. That is, when the content of the repeating unit represented by Chemical Formula 1 is 99 mol% or less, the degree of film hardening caused by an excess amount of repeating unit is suppressed, thereby ensuring the elasticity of the CEI film, and thus preventing cracking of the film during charging and discharging.

[0114]

[0115] Meanwhile, the polymer of the present invention may additionally include a repeating unit represented by the following chemical formula 2.

[0116] [Chemical Formula 2]

[0117]

[0118] (In the above chemical formula 2,

[0119] R2 is *-C(O)-Ra-CN (Ra is an alkylene group having 1 to 10 carbon atoms), or -C(O)-Rb (Rb is a nitrogen-containing heterocycloalkyl group or a lactam group).

[0120]

[0121] The repeating unit represented by the above chemical formula 2 includes a moiety containing a nitrogen atom having a non-covalent electron pair as a terminal group, thereby forming a solid-electrolyte film that is durable and can reduce resistance on the surfaces of the anode and cathode. As a result, it is possible to effectively suppress the leaching of transition metals from the anode by preventing side reactions between the electrolyte and the anode / cathode, and also prevent side reactions by capturing transition metal ions leached from the anode.

[0122] Specifically, in the above chemical formula 2, R2 may be *-C(O)-Ra-CN (Ra is an alkylene group having 1 to 5 carbon atoms), or *-C(O)-Rb (Rb is a nitrogen-containing heterocycloalkyl group or a lactam group).

[0123] In the above chemical formula 2, R2 is *-C(O)-CH2-CN, *-C(O)-CH2CH2-CN, *-C(O)-CH2CH2CH2-CN or It could be.

[0124] More specifically, the repeating unit represented by the above chemical formula 2 may be a repeating unit represented by the following chemical formula 2A or a repeating unit represented by the following chemical formula 2B.

[0125] [Chemical Formula 2A]

[0126]

[0127] [Chemical Formula 2B]

[0128]

[0129] Meanwhile, the repeating unit represented by Chemical Formula 2 above may be included in the polymer in an amount of 0 mol% or more, 1 mol% or more, 5 mol% or more, 10 mol% or more, 15 mol% or more, 20 mol% or more, or 30 mol% or more. Additionally, the repeating unit represented by Chemical Formula 1 above may be included in the polymer in an amount of 99 mol% or less, 95 mol% or less, 93 mol% or less, 90 mol% or less, 85 mol% or less, 83 mol% or less, 80 mol% or less, 75 mol% or less, 70 mol% or less, 65 mol% or less, 60 mol% or less, 55 mol% or less, or 50 mol% or less. The above ranges may be combined with each other without limitation. For example, the repeating unit represented by Chemical Formula 2 may be included in the polymer in an amount of 0 mol% to 99 mol%, 1 mol% to 99 mol%, 1 mol% to 80 mol%, 1 mol% to 70 mol%, 5 mol% to 60 mol%, 5 mol% to 50 mol%, or 10 mol% to 50 mol%. When the repeating unit represented by Chemical Formula 2 satisfies the above numerical range, it can be robust on the anode and cathode surfaces and improve metal leaching removal characteristics. Meanwhile, the repeating unit represented by Chemical Formula 2 has higher cathodic reactivity and lower structural toughness compared to the repeating unit represented by Chemical Formula 1. Therefore, when the repeating unit represented by Chemical Formula 2 is included in a lower amount than the repeating unit represented by Chemical Formula 1, a more robust film can be formed.

[0130]

[0131] In addition, the polymer of the present invention may further include a repeating unit represented by the following chemical formula 3.

[0132] [Chemical Formula 3]

[0133]

[0134] The repeating unit represented by Chemical Formula 3 above may be included in the polymer in an amount of 0 mol% or more, 1 mol% or more, 3 mol% or more, 5 mol% or more, 7 mol% or more, 10 mol% or more, 13 mol% or more, or 15 mol% or more. Additionally, the repeating unit represented by Chemical Formula 3 above may be included in the polymer in an amount of 99 mol% or less, 95 mol% or less, 90 mol% or less, 85 mol% or less, 83 mol% or less, 80 mol% or less, 75 mol% or less, 70 mol% or less, 65 mol% or less, 60 mol% or less, 55 mol% or less, 50 mol% or less, 45 mol% or less, 40 mol% or less, 35 mol% or less, 30 mol% or less, or 20 mol% or less. The above ranges may be combined with each other without limitation. For example, the repeating unit represented by Chemical Formula 3 may be included in the polymer in an amount of 0 mol% to 99 mol%, 0 mol% to 50 mol%, 1 mol% to 50 mol%, 1 mol% to 30 mol%, or 1 mol% to 20 mol%. In this case, if the repeating unit represented by Chemical Formula 3 is included in a smaller amount than the repeating unit represented by Chemical Formula 2, the rigidity of the film may be improved.

[0135]

[0136] Meanwhile, the polymer included as an additive of the present invention is a random polymer that includes the repeating unit represented by Chemical Formula 1 as an essential component and additionally includes at least one repeating unit among the repeating unit represented by Chemical Formula 2 and the repeating unit represented by Chemical Formula 3 below, and is preferably composed of the repeating units described above.

[0137] In addition, the weight-average molecular weight (Mw) of the polymer of the present invention may be 1,000 g / mol or more, 1,500 g / mol or more, 2,000 g / mol or more, 2,500 g / mol or more, 3,000 g / mol or more, 3,500 g / mol or more, 4,000 g / mol or more, 4,500 g / mol or more, 5,000 g / mol or more, 5,500 g / mol or more, 6,000 g / mol or more, 6,500 g / mol or more, 7,000 g / mol or more, 7,500 g / mol or more, 8,000 g / mol or more, 8,500 g / mol or more, 9,000 g / mol or more, or 10,000 g / mol or more. In addition, the weight-average molecular weight (Mw) of the polymer of the present invention may be 1,000,000 g / mol or less, 950,000 g / mol or less, 900,000 g / mol or less, 850,000 g / mol or less, 800,000 g / mol or less, 750,000 g / mol or less, 700,000 g / mol or less, 650,000 g / mol or less, 600,000 g / mol or less, 550,000 g / mol or less, 500,000 g / mol or less, 450,000 g / mol or less, 400,000 g / mol or less, 350,000 g / mol or less, 300,000 g / mol or less, 250,000 g / mol or less, or 200,000 g / mol or less. When the weight-average molecular weight of the above polymer is within the above range, the affinity between the polymer and the ionic solution is improved, thereby improving the solubility of the polymer, improving the ion transfer ability of the polymer electrolyte, and reducing the surface tension between the electrolyte and the membrane using a hydrophobic compound, so that the electrolyte wetting phenomenon can be improved.

[0138]

[0139] Meanwhile, the polymer included as an additive may be 0.001 wt% or more, 0.005 wt% or more, 0.01 wt% or more, 0.02 wt% or more, 0.03 wt% or more, 0.04 wt% or more, 0.05 wt% or more, 0.06 wt% or more, 0.07 wt% or more, 0.08 wt% or more, 0.09 wt% or more, 0.1 wt% or more, 0.1 wt% or more, 0.2 wt% or more, 0.3 wt% or more, 0.4 wt% or more, 0.5 wt% or more, 0.6 wt% or more, 0.7 wt% or more, 0.8 wt% or more, 0.9 wt% or more, or 1 wt% or more, based on the total weight of the non-aqueous electrolyte. In addition, the polymer may be 18 wt% or less, 17 wt% or less, 16 wt% or less, 15 wt% or less, 14 wt% or less, 13 wt% or less, 12 wt% or less, 11 wt% or less, 10 wt% or less, 9 wt% or less, 8 wt% or less, 7 wt% or less, 6 wt% or less, or 5 wt% or less, based on the total weight of the non-aqueous electrolyte.

[0140] The above ranges may be combined without limitation. For example, the polymer may be included in an amount of 0.001 wt% to 18 wt%, 0.001 wt% to 15 wt%, 0.01 wt% to 15 wt%, 0.01 wt% to 10 wt%, or 0.1 wt% to 10 wt%, 0.5 wt% to 10 wt%, or 0.5 wt% to 5 wt% based on the total weight of the non-aqueous electrolyte. When the polymer content satisfies the above numerical range, a stable CEI / SEI can be formed on the anode and cathode surfaces while suppressing disadvantages such as side reactions caused by the additive, capacity reduction, and increased resistance as much as possible, and high-temperature durability can be significantly improved as a result. That is, when the additive content is 18 wt% or less, the increase in viscosity of the electrolyte can be prevented, thereby improving the deterioration of physical / mechanical properties, and a stable film can be formed, thereby effectively improving overall performance such as suppressing the increase in initial resistance and improving output characteristics.

[0141]

[0142] Meanwhile, a polymer comprising a repeating unit represented by Chemical Formula 1 included in the non-aqueous electrolyte of the present invention can be prepared by a method comprising: (a) reacting a polyvinyl alcohol (PVA) represented by Chemical Formula 3 with a compound represented by Chemical Formula 4 in the presence of dimethyl sulfoxide (DMSO); and (b) reacting the product of step (a) with polyvinyl alcohol (PVA) and a compound represented by Chemical Formulas I / II.

[0143] [Chemical Formula 4]

[0144]

[0145] (In the above chemical formula 4, R1 is an alkyl group having 1 to 5 carbon atoms substituted or unsubstituted with hydrogen or at least one fluorine)

[0146] [Chemical Formula I]

[0147]

[0148] In the above chemical formula I, Rb' is a nitrogen-containing heterocycloalkyl group or a lactam group.

[0149] [Chemical Formula II]

[0150]

[0151] In the above chemical formula II, Ra' is an alkylene group having 1 to 10 carbon atoms.

[0152] In the above method, step (a) can be performed at approximately 130 to 160°C while stirring for 5 to 15 hours. Additionally, in the above method, step (b) can be performed at approximately 70 to 100°C while stirring for 5 to 15 hours.

[0153]

[0154] Meanwhile, the non-aqueous electrolyte of the present invention may additionally include auxiliary additives within the electrolyte as needed to prevent the decomposition of the electrolyte in a high-power environment from causing cathode collapse, or to further improve low-temperature high-rate discharge characteristics, high-temperature stability, prevention of overcharging, and suppression of battery expansion at high temperatures. If auxiliary additives are additionally included in the non-aqueous electrolyte, the polymer may be named as the first additive, and the auxiliary additive may be named as the second additive.

[0155] The above auxiliary additive may include at least one selected from the group consisting of cyclic carbonate compounds, halogen-substituted carbonate compounds, sulfone compounds, sulfate compounds, phosphate compounds, borate compounds, nitrile compounds, benzene compounds, amine compounds, silane compounds, and lithium salt compounds.

[0156] Examples of the above-mentioned cyclic carbonate compounds include vinylene carbonate (VC) or vinylethylene carbonate.

[0157] Examples of the above halogen-substituted carbonate compounds include fluoroethylene carbonate (FEC).

[0158] The above sulfone-based compound may include at least one compound selected from the group consisting of 1,3-propane sulfone (PS), 1,4-butane sulfone, ethen sulfone, 1,3-propene sulfone (PRS), 1,4-butene sulfone, and 1-methyl-1,3-propene sulfone.

[0159] Examples of the above sulfate compounds include ethylene sulfate (Esa), trimethylene sulfate (TMS), or methyl trimethylene sulfate (MTMS).

[0160] The above phosphate-based compounds may include one or more compounds selected from the group consisting of lithium difluoro(bisoxalato)phosphate, lithium difluorophosphate, tris(trimethylsilyl)phosphate, tris(2,2,2-trifluoroethyl)phosphate, and tris(trifluoroethyl)phosphate.

[0161] Examples of the above borate compounds include tetraphenylborate and lithium oxalyl difluoroborate.

[0162] The above nitrile-based compound may be at least one compound selected from the group consisting of succinonitrile, adiponitrile, acetonitrile, propionitrile, butyronitrile, valeronitrile, caprylonitrile, heptanitrile, cyclopentane carbonitrile, cyclohexane carbonitrile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2-fluorophenylacetonitrile, and 4-fluorophenylacetonitrile.

[0163] Examples of the above benzene-based compounds include fluorobenzene, and examples of the above amine-based compounds include triethanolamine or ethylenediamine.

[0164] Tetravinylsilane can be cited as the above silane compound.

[0165] The above lithium salt-based compound is a compound different from the lithium salt included in the electrolyte, and may include one or more compounds selected from the group consisting of LiPO2F2, LiODFB, LiBOB (lithium bisoxalate toborate (LiB(C2O4)2)) and LiBF4.

[0166] Among these auxiliary additives, if vinylene carbonate, vinylethylene carbonate, or succinonitrile is included, a more robust SEI film can be formed on the negative electrode surface during the initial activation process of the secondary battery.

[0167] Meanwhile, the above auxiliary additives may be used in a mixture of two or more types and may be included in an amount of 30% by weight or less, specifically 0.01% to 10% by weight, based on the total weight of the electrolyte, and preferably 0.05% to 5% by weight. If the content of the above auxiliary additive is less than 0.01% by weight, the effect of improving low-temperature output, high-temperature storage characteristics, and high-temperature life characteristics of the battery is negligible, and if the content of the above auxiliary additive exceeds 30% by weight, there is a possibility that excessive side reactions may occur within the electrolyte during charging and discharging of the battery. In particular, when the above SEI film-forming additives are added in excess, they may not decompose sufficiently at high temperatures and may remain as unreacted substances or precipitated within the electrolyte at room temperature. Accordingly, side reactions that degrade the lifespan or resistance characteristics of the secondary battery may occur.

[0168]

[0169] lithium secondary battery

[0170] In addition, another embodiment of the present invention provides a lithium secondary battery comprising: a positive electrode; a negative electrode facing the positive electrode; a separator interposed between the negative electrode and the positive electrode; and the aforementioned non-aqueous electrolyte.

[0171] The lithium secondary battery of the present invention can be manufactured by forming an electrode assembly in which a positive electrode, a separator, and a negative electrode are sequentially stacked, housing this in a battery case, and then introducing the electrolyte of the present invention. The method for manufacturing the lithium secondary battery of the present invention can be manufactured and applied according to conventional methods known in the art.

[0172] As the non-aqueous electrolyte has been described above, the anode, cathode, and separator will be described below.

[0173]

[0174] (1) positive electrode

[0175] The above anode may include an anode active material.

[0176] The above-mentioned cathode active material is a compound capable of reversible intercalation and deintercalation, and is not particularly limited as long as it is a cathode active material used in the field; specifically, it may include a lithium metal composite oxide. More specifically, the lithium metal composite oxide is a layered compound such as lithium cobalt oxide (LiCoO2) or lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; lithium iron oxide such as LiFe3O4; lithium iron phosphate such as LiFePO4; and a compound with the chemical formula Li 1+c1 Mn 2-c1 Lithium manganese oxides such as O4 (0≤c1≤0.33), LiMnO3, LiMn2O3, LiMnO2, etc.; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, V2O5, Cu2V2O7, etc.; chemical formula LiNi 1-c2 M c2 Ni-site type lithium nickel oxide represented by O2 (wherein M is at least one selected from the group consisting of Co, Mn, Al, Cu, Fe, Mg, B, and Ga, satisfying 0.01≤c2≤0.3); chemical formula LiMn 2-c3 M c3Lithium manganese composite oxides represented by O2 (wherein M is at least one selected from the group consisting of Co, Ni, Fe, Cr, Zn and Ta, satisfying 0.01≤c3≤0.1) or Li2Mn3MO8 (wherein M is at least one selected from the group consisting of Fe, Co, Ni, Cu and Zn); etc., but are not limited to these. The anode may also be a Li-metal anode.

[0177] More specifically, the lithium metal composite oxide may include at least one selected from the group consisting of lithium cobalt oxide (LiCoO2), lithium nickel-cobalt-manganese oxide, lithium-manganese-rich oxide, and lithium iron phosphate.

[0178] The above lithium nickel-cobalt-manganese oxide can be represented by the following chemical formula P-1.

[0179] [Chemical Formula P-1]

[0180] Li 1+a Ni x Co y M 1 z M 2 w O2

[0181] In the above chemical formula P-1,

[0182] M 1 is Mn, Al, or a combination thereof, and

[0183] M 2 is at least one selected from the group consisting of Al, Zr, W, Ti, Mg, Ca, and Sr, and 0≤a≤0.5, 0.55 <x<1.0, 0<y≤0.4, 0<z≤0.4, 0≤w≤0.1 이다. 이때, x+y+z+w는 1일 수 있다.

[0184] In the above chemical formula P-1, 1+a represents the molar ratio of lithium in the lithium nickel-cobalt-manganese oxide, and may be 0≤a≤0.5, preferably 0≤a≤0.2, more preferably 0≤a≤0.1.

[0185] In the above chemical formula P-1, x represents the molar ratio of nickel among the total transition metals excluding lithium in the lithium nickel-cobalt-manganese oxide, 0.55 <x<1.0, 더욱 구체적으로는 0.6≤x≤0.98, 보다 더 구체적으로는 0.6≤x≤0.95일 수 있다.

[0186] In the above chemical formula P-1, y represents the molar ratio of cobalt among the total transition metals excluding lithium in the lithium nickel-cobalt-manganese oxide, where 0 <y≤0.4, 구체적으로 0<y≤0.3, 더욱 구체적으로는 0.05≤y≤0.3일 수 있다.

[0187] In the above chemical formula P-1, z is M among the total transition metals excluding lithium in the lithium nickel-cobalt-manganese oxide. 1 Representing the molar ratio of elements, 0 <z≤0.4, 바람직하게는 0<z≤0.3, 더 바람직하게는 0.01≤z≤0.3일 수 있다.

[0188] In the above chemical formula P-1, w is M among the total transition metals excluding lithium in the lithium nickel-cobalt-manganese oxide. 2 Representing the molar ratio of elements, 0 <w≤0.1, 바람직하게는 0<w≤0.05, 더 바람직하게는 0<w≤0.02이다.

[0189] The above lithium nickel-cobalt-manganese oxide is Li(Ni with a Ni content of 0.55 atm% or more to realize a high-capacity battery. 0.6 Mn 0.2 Co 0.2 )O2, Li(Ni) 0.7 Mn 0.15 Co 0.15 )O2, Li(Ni 0.7 Mn 0.2 Co 0.1)O2, Li(Ni 0.8 Mn 0.1 Co 0.1 )O2, Li(Ni 0.8 Co 0.15 Al 0.05 )O2, Li(Ni 0.86 Mn 0.07 Co 0.05 Al 0.02 )O2, Li(Ni 0.90 Mn 0.05 Co 0.05 )O2 or Li(Ni 0.9 Mn 0.03 Co 0.06 Al 0.01 It can be )O2).

[0190] Meanwhile, the above-mentioned positive active material may be in the form of particles. Specifically, the average particle size (D) of the above-mentioned positive active material. 50 ) can be 1㎛ to 30㎛.

[0191]

[0192] The above positive electrode may include a positive current collector; and a positive active material layer disposed on at least one surface of the positive current collector. In this case, the positive active material layer may include the aforementioned positive active material.

[0193] The thickness of the above positive current collector can typically be 3 to 500 μm.

[0194] The above positive current collector may form fine irregularities on its surface to strengthen the bonding force of the positive active material. For example, the above positive current collector can be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0195] The positive active material layer is disposed on at least one surface of the positive current collector. Specifically, the positive active material layer may be disposed on one or both surfaces of the positive current collector.

[0196] The above-mentioned positive active material may be included in the positive active material layer in an amount of 70% to 99% by weight, specifically 80% to 98% by weight, taking into consideration the sufficient capacity exertion of the positive active material.

[0197]

[0198] The above positive active material layer may further include a binder and / or a conductive material together with the aforementioned positive active material.

[0199] The above binder serves to improve the adhesion between positive active material particles and the adhesion between the positive active material and the current collector.

[0200] Examples of such binders include fluoropolymer binders comprising polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE); rubber binders comprising styrene butadiene rubber (SBR), acrylonitrile-butadiene rubber, or styrene-isoprene rubber; cellulose binders comprising carboxyl methyl cellulose (CMC), starch, hydroxypropyl cellulose, or regenerated cellulose; polyalcohol binders comprising polyvinyl alcohol; polyolefin binders comprising polyethylene or polypropylene; polyimide binders; polyester binders; and silane binders, either alone or as a mixture of two or more.

[0201] The above binder may be included in an amount of 0.1 to 15 weight%, preferably 0.1 to 10 weight%, based on the total weight of the positive active material layer.

[0202]

[0203] Next, the conductive material is used to impart conductivity to the electrode, and in the battery being constructed, it may be used without special limitations as long as it has electronic conductivity without causing chemical changes. Specific examples include carbon black such as acetylene black (or Denka black), Ketjen black, channel black, furnace black, lamp black, or thermal black; graphite powder such as natural graphite, artificial graphite, or graphite with a highly developed crystal structure; conductive fibers such as carbon fibers or metal fibers; conductive powders such as carbon fluoride powder, aluminum powder, or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; polyphenylene derivatives, etc., and one of these alone or a mixture of two or more may be used.

[0204] The above conductive material may be included in an amount of 0.1 to 10 weight%, preferably 0.1 to 5 weight%, based on the total weight of the positive active material layer.

[0205] The thickness of the above positive active material layer may be 5㎛ to 500㎛, preferably 20㎛ to 200㎛.

[0206]

[0207] The anode may be manufactured by coating an anode slurry comprising an anode active material and optionally a binder, a conductive material, and a solvent for forming an anode slurry onto the anode current collector, and then drying and rolling. Alternatively, the anode may be manufactured by mixing an anode active material and optionally a binder, a conductive material, etc. to produce a film, and then laminating it onto an anode current collector.

[0208] The solvent for forming the anode slurry may include, for example, at least one selected from the group consisting of distilled water, N-methylpyrrolidone, ethanol, methanol, and isopropyl alcohol, preferably N-methylpyrrolidone, in order to facilitate the dispersion of the anode active material, binder, and / or conductive material. The amount of the solvent used is not particularly limited, provided that it is sufficient to allow the anode composite to have an appropriate viscosity, taking into account the coating thickness, manufacturing yield, workability, etc. of the anode composite.

[0209]

[0210] (2) Negative electrode

[0211] Next, the cathode is explained.

[0212] The cathode according to the present invention may include a cathode active material.

[0213] The above negative electrode active material is a material capable of reversibly inserting / extracting lithium ions, and may include at least one selected from the group consisting of carbon-based active materials, (quasi)metal-based active materials, and lithium metal, and specifically may include at least one selected from carbon-based active materials and (quasi)metal-based active materials.

[0214] The carbon-based active material may include at least one selected from the group consisting of graphite, hard carbon, soft carbon, carbon black, graphene, and fibrous carbon, and preferably may include graphite. The graphite may be, for example, at least one of artificial graphite and natural graphite.

[0215] Average particle size (D) of the above carbon-based active material 50 ) can be 10㎛ to 30㎛, preferably 15㎛ to 25㎛, in terms of ensuring structural stability during charging and discharging and reducing adverse reactions with the electrolyte.

[0216] Specifically, the (quasi)metallic active material comprises: at least one (quasi)metal selected from the group consisting of Cu, Ni, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Fe, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, V, Ti, and Sn; an alloy of lithium and at least one (quasi)metal selected from the group consisting of Cu, Ni, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Fe, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, V, Ti, and Sn; an oxide of at least one (quasi)metal selected from the group consisting of Cu, Ni, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Fe, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, V, Ti, and Sn; lithium titanium oxide (LTO); and lithium vanadium oxide. It may include the back.

[0217] More specifically, the above (quasi)metallic active material may include a silicon-based active material.

[0218] The above silicon-based active material is SiO x It may include at least one selected from the group consisting of compounds represented by (0≤x<2) and silicon-carbon composites. Since SiO2 does not react with lithium ions and therefore cannot store lithium, it is preferable that x be within the above range, and more preferably, the silicon-based active material may be SiO.

[0219] Average particle size (D) of the above silicon-based active material 50 ) can be 1㎛ to 30㎛, preferably 2㎛ to 15㎛, in terms of reducing adverse reactions with the electrolyte while ensuring structural stability during charging and discharging.

[0220] In addition, the negative electrode active material of the present invention may include a carbon-based negative electrode active material together with a silicon-based negative electrode active material.

[0221] At this time, the weight ratio of the silicon-based active material and the carbon-based active material may be 1:99 to 30:70, specifically 3:97 to 15:85. When the mixing ratio of the silicon-based active material and the carbon-based active material satisfies the above range, excellent cycle performance can be secured by suppressing the volume expansion of the silicon-based active material while improving capacity characteristics.

[0222]

[0223] Meanwhile, the above-mentioned cathode may include a cathode current collector; and a cathode active material layer disposed on at least one surface of the cathode current collector. In this case, the cathode active material may be included in the cathode active material layer.

[0224] The above-mentioned negative current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery. Specifically, the above-mentioned negative current collector may be copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface treated with carbon, nickel, titanium, silver, etc., or aluminum-cadmium alloy.

[0225] The above-mentioned cathode current collector can typically have a thickness of 3 to 500 μm.

[0226] The above-mentioned negative current collector may form fine irregularities on its surface to strengthen the bonding force of the negative active material. For example, the above-mentioned negative current collector can be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0227] The above-mentioned negative electrode active material layer is disposed on at least one surface of the negative electrode current collector. Specifically, the negative electrode active material layer may be disposed on one or both surfaces of the negative electrode current collector.

[0228] The above negative electrode active material may be included in the negative electrode active material layer in an amount of 60% to 99% by weight to minimize the effect of volume expansion / contraction on the battery while sufficiently expressing capacity in the secondary battery.

[0229] The above cathode active material layer may further include a conductive material and / or a binder together with the cathode active material.

[0230] The above conductive material is a component for further improving the conductivity of the negative electrode active material, and may be added in an amount of 10% by weight or less, preferably 5% by weight or less, specifically 0.1% to 5% by weight, based on the total weight of the negative electrode active material layer. Such conductive material is not particularly limited as long as it is conductive without causing chemical changes in the battery, and for example, carbon black such as acetylene black (or Denka black), Ketjen black, channel black, furnace black, lamp black, or thermal black; graphite powder such as natural graphite, artificial graphite, or graphite with a highly developed crystal structure; conductive fibers such as carbon fibers or metal fibers; conductive powders such as carbon fluoride powder, aluminum powder, nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; polyphenylene derivatives, etc. may be used.

[0231] The above binder is a component that assists in the bonding between a conductive material, an active material, and a current collector, and specific examples include a fluoropolymer-based binder comprising polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE); a rubber-based binder comprising styrene butadiene rubber (SBR), acrylonitrile-butadiene rubber, or styrene-isoprene rubber; a cellulose-based binder comprising carboxyl methyl cellulose (CMC), starch, hydroxypropyl cellulose, or regenerated cellulose; a polyalcohol-based binder comprising polyvinyl alcohol; a polyolefin-based binder comprising polyethylene or polypropylene; a polyimide-based binder; a polyester-based binder; and a silane-based binder.

[0232] The above binder may be included in an amount of 0.1 to 15 weight%, preferably 0.1 to 10 weight%, based on the total weight of the negative electrode active material layer.

[0233]

[0234] The thickness of the above negative electrode active material layer may be 5㎛ to 500㎛, preferably 5㎛ to 100㎛.

[0235] The above cathode may be manufactured by coating a cathode slurry comprising a cathode active material and optionally a binder, a conductive material, and a solvent for forming a cathode slurry onto the cathode current collector, and then drying and rolling. Alternatively, the cathode may be manufactured by mixing a cathode active material and optionally a binder, a conductive material, etc. to produce a film, and then laminating it onto a cathode current collector.

[0236] The solvent for forming the above cathode slurry may include, for example, at least one selected from the group consisting of distilled water, N-methylpyrrolidone, ethanol, methanol, and isopropyl alcohol, preferably distilled water, in order to facilitate the dispersion of the cathode active material, binder, and / or conductive material.

[0237]

[0238] (3) Separator

[0239] The above separator separates the negative and positive electrodes and provides a pathway for the movement of lithium ions. It can be used without any specific restrictions as long as it is a separator typically used in lithium secondary batteries, and it is particularly desirable that it has low resistance to the movement of lithium salt ions while having excellent electrolyte moisture retention capacity.

[0240] Specifically, as a separator, a porous polymer film made of a polyolefin-based polymer such as ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof may be used. In addition, a conventional porous nonwoven fabric, such as a nonwoven fabric made of high-melting-point glass fiber or polyethylene terephthalate fiber, may be used. Furthermore, a coated separator containing a ceramic component or a polymer material may be used to ensure heat resistance or mechanical strength, and may optionally be used in a single-layer or multi-layer structure.

[0241]

[0242] The lithium secondary battery according to the present invention as described above can be usefully applied in portable devices such as mobile phones, laptop computers, and digital cameras, as well as in the field of electric vehicles such as hybrid electric vehicles (HEVs).

[0243] The external shape of the lithium secondary battery of the present invention is not particularly limited, but can be a cylindrical shape using a can, a prismatic shape, a pouch shape, or a coin shape.

[0244] The lithium secondary battery according to the present invention can be used not only as a battery cell used as a power source for a small device, but can also preferably be used as a unit cell in a medium-to-large battery module comprising a plurality of battery cells.

[0245]

[0246] Hereinafter, the present invention will be described in detail with reference to examples in order to specifically explain the invention. However, the embodiments according to the present invention may be modified in various different forms, and the scope of the present invention should not be interpreted as being limited to the embodiments described below. The embodiments of the present invention are provided to more completely explain the invention to those with average knowledge in the art.

[0247]

[0248] Examples

[0249] Example 1.

[0250] (Preparation of non-aqueous electrolytes)

[0251] A non-aqueous electrolyte for a lithium secondary battery was prepared by dissolving LiPF6 in a non-aqueous organic solvent mixed with ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a volume ratio of 20:70:10 to a concentration of 1.2 M, and then adding 0.5 wt% of polymer and 0.5 wt% of vinylene carbonate (VC) as electrolyte additives. At this time, the polymer used was a random polymer composed of 70 mol% of repeating units represented by Chemical Formula 1A, 25 mol% of repeating units represented by Chemical Formula 2A, and 5 mol% of repeating units represented by Chemical Formula 3.

[0252]

[0253] (Secondary battery manufacturing)

[0254] Anode active material (Li(Ni) in solvent N-methyl-2-pyrrolidone (NMP) 0.6 Mn 0.3 Co 0.1 An anode slurry (solid content 75.5 wt%) was prepared by adding O2), a conductive material (carbon nanotubes), and a binder (polyvinylidene fluoride) in a weight ratio of 97.74:0.7:1.56. The anode slurry was applied to an anode current collector (Al thin film) with a thickness of 15 μm and dried, then a roll press was performed to produce an anode (thickness: 136.6 μm).

[0255] A cathode slurry (solid content: 26 wt%) was prepared by adding a cathode active material (natural graphite), a conductive material (carbon black), and a binder (SBR-CMC) to water in a weight ratio of 96.15:1.55:2.3. The cathode slurry was applied to a copper (Cu) thin film serving as a cathode current collector with a thickness of 15 μm, dried, and then subjected to a roll press to produce a cathode (thickness: 179.8 μm).

[0256] An electrode assembly was manufactured by interposing a porous polypropylene separator between the anode and cathode manufactured above, then housing it in a battery case, and a lithium secondary battery was manufactured by injecting the non-aqueous electrolyte manufactured above.

[0257]

[0258] Example 2.

[0259] (Preparation of non-aqueous electrolytes)

[0260] A non-aqueous electrolyte was prepared in the same manner as in Example 1, except that 1 wt% of polymer and 0.5 wt% of vinylene carbonate (VC) were added as electrolyte additives. At this time, a random polymer consisting of 70 mol% of repeating units represented by Chemical Formula 1A, 25 mol% of repeating units represented by Chemical Formula 2A, and 5 mol% of repeating units represented by Chemical Formula 3 was used as the polymer.

[0261]

[0262] (Secondary battery manufacturing)

[0263] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the above-manufactured non-aqueous electrolyte was injected.

[0264]

[0265] Example 3.

[0266] (Preparation of non-aqueous electrolytes)

[0267] A non-aqueous electrolyte was prepared in the same manner as in Example 1, except that 5 wt% of polymer and 0.5 wt% of vinylene carbonate (VC) were added as electrolyte additives. At this time, a random polymer consisting of 70 mol% of repeating units represented by Chemical Formula 1A, 25 mol% of repeating units represented by Chemical Formula 2A, and 5 mol% of repeating units represented by Chemical Formula 3 was used as the polymer.

[0268]

[0269] (Secondary battery manufacturing)

[0270] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the above-manufactured non-aqueous electrolyte was injected.

[0271]

[0272] Example 4.

[0273] (Preparation of non-aqueous electrolytes)

[0274] A non-aqueous electrolyte was prepared in the same manner as in Example 1, except that 8 wt% of polymer and 0.5 wt% of vinylene carbonate (VC) were added as electrolyte additives. At this time, a random polymer consisting of 70 mol% of repeating units represented by Chemical Formula 1A, 25 mol% of repeating units represented by Chemical Formula 2A, and 5 mol% of repeating units represented by Chemical Formula 3 was used as the polymer.

[0275]

[0276] (Secondary battery manufacturing)

[0277] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the above-manufactured non-aqueous electrolyte was injected.

[0278]

[0279] Example 5.

[0280] (Preparation of non-aqueous electrolytes)

[0281] A non-aqueous electrolyte was prepared in the same manner as in Example 1, except that 10 wt% of polymer and 0.5 wt% of vinylene carbonate (VC) were added as electrolyte additives. At this time, a random polymer consisting of 70 mol% of repeating units represented by Chemical Formula 1A, 25 mol% of repeating units represented by Chemical Formula 2A, and 5 mol% of repeating units represented by Chemical Formula 3 was used as the polymer.

[0282]

[0283] (Secondary battery manufacturing)

[0284] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the above-manufactured non-aqueous electrolyte was injected.

[0285]

[0286] Example 6.

[0287] (Preparation of non-aqueous electrolytes)

[0288] A non-aqueous electrolyte was prepared in the same manner as in Example 1, except that 5 wt% of polymer and 0.5 wt% of vinylene carbonate (VC) were added as electrolyte additives. At this time, a random polymer consisting of 70 mol% of repeating units represented by Chemical Formula 1B, 25 mol% of repeating units represented by Chemical Formula 2A, and 5 mol% of repeating units represented by Chemical Formula 3 was used as the polymer.

[0289]

[0290] (Secondary battery manufacturing)

[0291] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the above-manufactured non-aqueous electrolyte was injected.

[0292]

[0293] Example 7.

[0294] (Preparation of non-aqueous electrolytes)

[0295] A non-aqueous electrolyte was prepared in the same manner as in Example 1, except that 5 wt% of polymer and 0.5 wt% of vinylene carbonate (VC) were added as electrolyte additives. At this time, a random polymer consisting of 70 mol% of repeating units represented by Chemical Formula 1C, 25 mol% of repeating units represented by Chemical Formula 2A, and 5 mol% of repeating units represented by Chemical Formula 3 was used as the polymer.

[0296]

[0297] (Secondary battery manufacturing)

[0298] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the above-manufactured non-aqueous electrolyte was injected.

[0299]

[0300] Example 8.

[0301] (Preparation of non-aqueous electrolytes)

[0302] A non-aqueous electrolyte was prepared in the same manner as in Example 1, except that 5 wt% of polymer and 0.5 wt% of vinylene carbonate (VC) were added as electrolyte additives. At this time, a random polymer consisting of 70 mol% of repeating units represented by Chemical Formula 1D, 25 mol% of repeating units represented by Chemical Formula 2A, and 5 mol% of repeating units represented by Chemical Formula 3 was used as the polymer.

[0303]

[0304] (Secondary battery manufacturing)

[0305] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the above-manufactured non-aqueous electrolyte was injected.

[0306]

[0307] Example 9.

[0308] (Preparation of non-aqueous electrolytes)

[0309] A non-aqueous electrolyte was prepared in the same manner as in Example 1, except that 5 wt% of polymer and 0.5 wt% of vinylene carbonate (VC) were added as electrolyte additives. At this time, a random polymer consisting of 70 mol% of repeating units represented by Chemical Formula 1A, 25 mol% of repeating units represented by Chemical Formula 2B, and 5 mol% of repeating units represented by Chemical Formula 3 was used as the polymer.

[0310]

[0311] (Secondary battery manufacturing)

[0312] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the above-manufactured non-aqueous electrolyte was injected.

[0313]

[0314] Example 10.

[0315] (Preparation of non-aqueous electrolytes)

[0316] A non-aqueous electrolyte was prepared in the same manner as in Example 1, except that 5 wt% of polymer and 0.5 wt% of vinylene carbonate (VC) were added as electrolyte additives. At this time, a random polymer consisting of 70 mol% of repeating units represented by Chemical Formula 1B, 25 mol% of repeating units represented by Chemical Formula 2B, and 5 mol% of repeating units represented by Chemical Formula 3 was used as the polymer.

[0317]

[0318] (Secondary battery manufacturing)

[0319] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the above-manufactured non-aqueous electrolyte was injected.

[0320]

[0321] Example 11.

[0322] (Preparation of non-aqueous electrolytes)

[0323] A non-aqueous electrolyte was prepared in the same manner as in Example 1, except that 15 wt% of polymer and 0.5 wt% of vinylene carbonate (VC) were added as electrolyte additives. At this time, a random polymer consisting of 70 mol% of repeating units represented by Chemical Formula 1A, 25 mol% of repeating units represented by Chemical Formula 2A, and 5 mol% of repeating units represented by Chemical Formula 3 was used as the polymer.

[0324]

[0325] (Secondary battery manufacturing)

[0326] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the above-manufactured non-aqueous electrolyte was injected.

[0327]

[0328] Example 12.

[0329] (Preparation of non-aqueous electrolytes)

[0330] A non-aqueous electrolyte was prepared in the same manner as in Example 1, except that 20 wt% of polymer and 0.5 wt% of vinylene carbonate (VC) were added as electrolyte additives. At this time, a random polymer consisting of 70 mol% of repeating units represented by Chemical Formula 1A, 25 mol% of repeating units represented by Chemical Formula 2A, and 5 mol% of repeating units represented by Chemical Formula 3 was used as the polymer.

[0331]

[0332] (Secondary battery manufacturing)

[0333] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the above-manufactured non-aqueous electrolyte was injected.

[0334]

[0335] Comparative Example 1.

[0336] (Preparation of non-aqueous electrolytes)

[0337] A non-aqueous electrolyte for a lithium secondary battery was prepared by dissolving LiPF6 in a non-aqueous organic solvent to a concentration of 1.0 M, and then adding vinylene carbonate (VC) as an additive to a concentration of 0.5 wt%.

[0338]

[0339] (Secondary battery manufacturing)

[0340] Anode active material (Li(Ni) in solvent N-methyl-2-pyrrolidone (NMP) 0.6 Mn 0.3 Co 0.1 An anode slurry (solid content 75.5 wt%) was prepared by adding O2), a conductive material (carbon nanotubes), and a binder (polyvinylidene fluoride) in a weight ratio of 97.74:0.7:1.56. The anode slurry was applied to an anode current collector (Al thin film) with a thickness of 15 μm and dried, then a roll press was performed to produce an anode (thickness: 136.6 μm).

[0341] A cathode slurry (solid content: 26 wt%) was prepared by adding a cathode active material (natural graphite), a conductive material (carbon black), and a binder (SBR-CMC) to water in a weight ratio of 96.15:1.55:2.3. The cathode slurry was applied to a copper (Cu) thin film serving as a cathode current collector with a thickness of 15 μm, dried, and then subjected to a roll press to produce a cathode (thickness: 179.8 μm).

[0342] An electrode assembly was manufactured by interposing a porous polypropylene separator between the anode and cathode manufactured above, then housing it in a battery case, and a lithium secondary battery was manufactured by injecting the non-aqueous electrolyte manufactured above.

[0343]

[0344] Comparative Example 2.

[0345] (Preparation of non-aqueous electrolytes)

[0346] A non-aqueous electrolyte was prepared in the same manner as in Example 1, except that 5 wt% of polymer and 0.5 wt% of vinylene carbonate (VC) were added as electrolyte additives. At this time, a random polymer consisting of 70 mol% of repeating units represented by Chemical Formula 6, 25 mol% of repeating units represented by Chemical Formula 2A, and 5 mol% of repeating units represented by Chemical Formula 3 was used as the polymer.

[0347] [Chemical Formula 6]

[0348]

[0349]

[0350] (Secondary battery manufacturing)

[0351] A lithium secondary battery was manufactured in the same manner as Comparative Example 1, except that the above-manufactured non-aqueous electrolyte was injected.

[0352]

[0353] Comparative Example 3.

[0354] (Preparation of non-aqueous electrolytes)

[0355] A non-aqueous electrolyte was prepared in the same manner as in Example 1, except that 5 wt% of polymer and 0.5 wt% of vinylene carbonate (VC) were added as electrolyte additives. At this time, a random polymer consisting of 70 mol% of repeating units represented by Chemical Formula 7, 25 mol% of repeating units represented by Chemical Formula 2A, and 5 mol% of repeating units represented by Chemical Formula 3 was used as the polymer.

[0356] [Chemical Formula 7]

[0357]

[0358]

[0359] (Secondary battery manufacturing)

[0360] A lithium secondary battery was manufactured in the same manner as Comparative Example 2, except that the above-mentioned non-aqueous electrolyte was injected.

[0361]

[0362] Experimental Example

[0363] Experimental Example 1. Evaluation of High-Temperature Cycle Characteristics

[0364] For the lithium secondary batteries prepared in the examples and comparative examples, respectively, a formation process was performed by charging at a rate of 0.1C for 3 hours, and then the batteries were fully charged to 100% SOC by charging under constant current / constant voltage conditions (0.05C cut-off) at a rate of 0.33C at 25℃ to 4.2V. The fully charged batteries were charged under constant current / constant voltage conditions at a rate of 0.33C at 45℃ to 4.2V, and discharged under constant current conditions at a rate of 0.33C to 2.8V, with this being defined as one cycle. After performing 300 cycles, the capacity retention rate after 300 cycles was calculated using Equation 1 below, and the results are shown in Table 1 below.

[0365] [Equation 1]

[0366] Capacity Retention Rate (%) = (Capacity after 300 cycles / Capacity after 1 cycle) × 100

[0367]

[0368] Capacitance Retention Rate (%) Resistance Increase Rate (%) Example 18526 Example 28725 Example 38723 Example 48625 Example 58627 Example 68625 Example 78724 Example 88526 Example 98824 Example 108725 Example 118526 Example 127238 Comparative Example 15759 Comparative Example 26052 Comparative Example 36555

[0369]

[0370] Looking at Table 1 above, it can be seen that in the case of the secondary batteries of Examples 1 to 12 of the present invention, the capacity retention rate (%) and resistance increase rate (%) after high-temperature cycling are both improved compared to the lithium secondary batteries of Comparative Examples 1 to 3.

[0371]

[0372] Experimental Example 2. Evaluation of High-Temperature Storage Characteristics

[0373] For the lithium secondary batteries prepared in the examples and comparative examples, respectively, a formation process was performed by charging at a rate of 0.1C for 3 hours, and then the batteries were fully charged to 100% SOC by charging under constant current / constant voltage conditions (0.05C cut-off) at a rate of 0.33C at 25℃ up to 4.2V, and stored at a high temperature (60℃) for 16 weeks. Afterward, the batteries were transferred to a charge / discharger at room temperature (25℃) to measure the resistance, and the resistance increase rate was calculated using Equation 2 below, and the results are shown in Table 2 below.

[0374] [Equation 2]

[0375] Resistance increase rate (%) = {(Resistance after high-temperature storage - Initial resistance) / Initial resistance} × 100

[0376]

[0377] Capacitance Retention Rate (%) Resistance Increase Rate (%) Example 180 22 Example 28 121 Example 38 320 Example 48 322 Example 58 225 Example 68 023 Example 78 224 Example 88 121 Example 98 323 Example 108 123 Example 118 026 Comparative Example 148 49 Comparative Example 25 248 Comparative Example 35 147

[0378]

[0379] Looking at Table 2 above, it can be seen that in the case of the secondary batteries of Examples 1 to 11 of the present invention, the capacity retention rate (%) and resistance increase rate (%) after high-temperature storage are both improved compared to the lithium secondary batteries of Comparative Examples 1 to 3.

[0380]

[0381] Although the present invention has been described above with reference to preferred embodiments, those skilled in the art or those with ordinary knowledge in the relevant technical field will understand that various modifications and changes can be made to the invention without departing from the spirit and technical scope of the invention as set forth in the claims below. Accordingly, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification, but should be determined by the claims.

Claims

1. Lithium salt; comprising a non-aqueous organic solvent and additives, The above additive is a non-aqueous electrolyte that is a polymer comprising repeating units represented by the following chemical formula 1: [Chemical Formula 1] In the above chemical formula 1, R1 is an alkyl group having 1 to 5 carbon atoms that is substituted or unsubstituted with hydrogen or at least one fluorine.

2. In Paragraph 1, In the above chemical formula 1, R1 is a non-aqueous electrolyte having 1 to 3 carbon atoms that is substituted or unsubstituted with hydrogen or at least one fluorine.

3. In Paragraph 1, A non-aqueous electrolyte in which the compound represented by Chemical Formula 1 above is at least one selected from the group consisting of compounds represented by Chemical Formulas 1A to 1D below: [Chemical Formula 1A] [Chemical Formula 1B] [Chemical Formula 1C] [Chemical Formula 1D] .

4. In Paragraph 1, The repeating unit represented by the above chemical formula 1 is a non-aqueous electrolyte included in the polymer in an amount of 1 mol% to 99 mol%.

5. In Paragraph 1, The above polymer is a non-aqueous electrolyte further comprising a repeating unit represented by the following chemical formula 2: [Chemical Formula 2] In the above chemical formula 2, R2 is *-C(O)-Ra-CN (Ra is an alkylene group having 1 to 10 carbon atoms) or *-C(O)-Rb (Rb is a nitrogen-containing heterocycloalkyl group or a lactam group).

6. In Paragraph 5, In the above chemical formula 2, R2 is a non-aqueous electrolyte in which *-C(O)-Ra-CN (Ra is an alkylene group having 1 to 5 carbon atoms) or *-C(O)-Rb (Rb is a nitrogen-containing heterocycloalkyl group or a lactam group).

7. In Paragraph 5, In the above chemical formula 2, R2 is *-C(O)-CH2-CN, *-C(O)-CH2CH2-CN, *-C(O)-CH2CH2CH2-CN or Phosphorus non-aqueous electrolyte.

8. In Paragraph 5, A non-aqueous electrolyte comprising a repeating unit represented by the above chemical formula 2 or a repeating unit represented by the following chemical formula 2A or the following chemical formula 2B: [Chemical Formula 2A] [Chemical Formula 2B] .

9. In Paragraph 1, The above polymer is a non-aqueous electrolyte further comprising a repeating unit represented by the following chemical formula 3: [Chemical Formula 3] .

10. In Paragraph 1, The above polymer is a non-aqueous electrolyte included in an amount of 0.001% to 18% by weight based on the total weight of the non-aqueous electrolyte.

11. In Paragraph 1, The above polymer is a non-aqueous electrolyte included in an amount of 0.01% to 15% by weight based on the total weight of the non-aqueous electrolyte.

12. In Paragraph 1, The above-mentioned non-aqueous electrolyte further comprises at least one auxiliary additive selected from the group consisting of cyclic carbonate compounds, halogen-substituted carbonate compounds, sulfone compounds, sulfate compounds, phosphate compounds, borate compounds, nitrile compounds, benzene compounds, amine compounds, silane compounds, and lithium salt compounds.

13. Anode; A cathode opposite to the anode above; A separator interposed between the above cathode and the above anode; and A lithium secondary battery comprising a non-aqueous electrolyte according to claim 1.

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