Electrolyte for lithium secondary battery and lithium secondary battery comprising same

Abstract

Provided is a lithium secondary battery including: positive and negative electrode current collectors; and the above-described electrolyte disposed between the positive and negative electrode current collectors. In chemical formula 1, A represents a chemical bond or is -(CH2)k- (k is an integer from 1 to 3), a and b are each independently 0 or an integer from 1 to 3, except when a and b are both 0, R, R1, R2 , and R3 are each independently hydrogen, a C1-C10 alkyl group, or F.

Description

Electrolyte for lithium secondary batteries and lithium secondary batteries containing the same

[0001] The present invention relates to an electrolyte for a lithium secondary battery and a lithium secondary battery including the same.

[0002] Lithium secondary batteries are rechargeable and can replace conventional lead-acid batteries, nickel-cadmium batteries,

[0003] Compared to nickel-hydrogen batteries and nickel-zinc batteries, it has an energy density per unit weight that is more than three times higher and allows for fast charging, so it is being commercialized for use in laptops, cell phones, power tools, and electric bicycles, and research and development is actively underway to further improve energy density.

[0004] In particular, as IT devices become more high-performance, high-capacity batteries are required.

[0005] In this situation, energy density can be increased by implementing high capacity through expansion of the voltage range, but there is a problem that the electrolyte is oxidized in the high voltage range, which deteriorates the performance of the battery's positive electrode.

[0006] For example, LiPF6, which is most commonly used as a lithium salt in electrolytes, is

[0007] LiPF6 reacts with solvents, accelerating their depletion and generating large amounts of gas. As LiPF6 decomposes, it produces decomposition products such as HF and PF5, which deplete the electrolyte in the battery, resulting in deteriorated high-temperature performance and safety vulnerabilities.

[0008] The decomposition products of the electrolyte are deposited in the form of a film on the electrode surface and are stored inside the battery.

[0009] It increases resistance and ultimately causes problems such as reduced battery performance and shortened lifespan. In particular,

[0010] At high temperatures, where the reaction rate is faster, these side reactions are further accelerated, and as side reactions

[0011] The generated gas components increase the pressure inside the battery, which may lower the stability of the battery.

[0012] Can be.

[0013] One aspect is to provide an electrolyte for lithium secondary batteries that is stable even under high-voltage and high-temperature conditions corresponding to a high-capacity cathode by suppressing decomposition of the electrolyte and reducing side reactions due to electrolyte oxidation occurring on the surface of the cathode.

[0014] Another aspect is to provide a lithium secondary battery using the electrolyte for a lithium secondary battery described above.

[0015] In a lithium secondary battery including a positive electrode, a negative electrode current collector, and an electrolyte disposed between the positive electrode and the negative electrode current collector according to one aspect,

[0016] A lithium secondary battery is provided in which the electrolyte includes an additive represented by the following chemical formula 1.

[0017] <Chemical Formula 1>

[0018]

[0019] In chemical formula 1, A represents a chemical bond or -(CH2) k -(k is an integer from 1 to 3),

[0020] a and b are independently 0 or integers from 1 to 3,

[0021] However, this does not apply to cases where both a and b are 0.

[0022] R, R1, R2 and R3 are each independently hydrogen, a C1 to C10 alkyl group or F.

[0023] According to another aspect, an electrolyte for a lithium secondary battery is provided, which includes an additive represented by the chemical formula 1 described above.

[0024] According to one aspect, an electrolyte for a lithium secondary battery having improved oxidation resistance by having a high oxidation reaction potential is provided, and when this electrolyte is applied to a high-voltage cathode, the life characteristics are improved and HF, which is a cause of deterioration, can be removed, thereby providing a lithium secondary battery having improved performance at high temperatures.

[0025] Figures 1 to 4 are cross-sectional views schematically showing a lithium secondary battery according to one embodiment.

[0026] Figure 5a schematically illustrates a laminated structure of a lithium secondary battery according to an embodiment.

[0027] Figure 5b schematically illustrates a laminated structure of a lithium secondary battery according to another embodiment.

[0028] <Explanation of key symbols in the drawing>

[0029] 100: Lithium secondary battery 10: Cathode

[0030] 11: Positive lead tab 12: Positive terminal

[0031] 20: Negative lead tab 21: Negative lead tab

[0032] 22: Negative terminal 30: Separator

[0033] 40: Electrode assembly 50: Case

[0034] 60: Sealing member 70: Electrode tab

[0035] 71: Positive tab 72: Negative tab

[0036] The present inventive concept described below is capable of various modifications and embodiments. Specific embodiments are illustrated in the drawings and described in detail. However, this is not intended to limit the present inventive concept to specific embodiments, and should be understood to encompass all modifications, equivalents, or alternatives within the technical scope of the present inventive concept.

[0037] The terminology used below is only used to describe specific embodiments and is not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly indicates otherwise. Hereinafter, the terms "comprises" or "has" and the like are intended to indicate the presence of a feature, number, step, operation, component, part, ingredient, material, or combination thereof described in the specification, but should be understood to not preclude the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, ingredients, materials, or combinations thereof. The " / " used below may be interpreted as "and" or "or" depending on the context.

[0038] In order to clearly express various layers and regions in the drawings, the thickness is shown enlarged or reduced. Similar parts are designated by the same drawing reference numerals throughout the specification. When a part such as a layer, film, region, or plate is said to be "on" or "above" another part throughout the specification, this includes not only cases where it is directly above the other part, but also cases where there is another part in between. Terms such as first, second, etc. may be used throughout the specification to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. In this specification and the drawings, components having substantially the same functional configuration are referred to by the same reference numerals, and redundant descriptions are omitted.

[0039] In the present disclosure, the "particle diameter" or "particle size" of a particle refers to the average diameter when the particle is spherical, and the average major axis length when the particle is non-spherical. The particle diameter of a particle can be measured using a particle size analyzer (PSA), for example, a HORIBA, LA-950 laser size analyzer. The "particle diameter" of a particle is, for example, the average particle diameter. The average particle diameter is, for example, the median particle diameter (D50). The median particle diameter (D50) is the size of the particle corresponding to 50% of the cumulative volume, calculated from the side of the particle having a small particle size in the size distribution of the particle measured by, for example, laser diffraction. The average particle diameter and average major axis length of the particle can be measured using a scanning electron microscope. When the particle size is measured using a scanning electron microscope, it is determined as the average value of 30 or more randomly selected particles having a size of 1 μm or more, excluding fine particles.

[0040] In this disclosure, “metal” includes both metals and metalloids such as silicon and germanium, in their elemental or ionic states.

[0041] In this disclosure, “alloy” means a mixture of two or more metals.

[0042] In the present disclosure, “positive electrode active material” means a positive electrode material capable of undergoing lithiation and delithiation, and “negative electrode active material” means a negative electrode material capable of undergoing lithiation and delithiation.

[0043] In the present disclosure, “lithiation” and “lithiating” mean a process of adding lithium to a positive electrode active material or a negative electrode active material, and “delithiation” and “delithiating” mean a process of removing lithium from a positive electrode active material or a negative electrode active material.

[0044] In this disclosure, "charging" and "charging" refer to a process of providing electrochemical energy to a battery. And in this disclosure, "discharging" and "discharging" refer to a process of removing electrochemical energy from a battery.

[0045] In the present disclosure, "positive electrode" and "cathode" mean an electrode where electrochemical reduction and lithiation occur during a discharge process. And in the present disclosure, "negative electrode" and "anode" mean an electrode where electrochemical oxidation and delithiation occur during a discharge process.

[0046] In the present disclosure, thickness means average thickness.

[0047] Hereinafter, a lithium secondary battery electrolyte according to an embodiment and a lithium secondary battery containing the same will be described in more detail.

[0048] Typically, when an electrolyte containing LiPF6 as lithium is exposed to high temperatures, the lithium salt LiPF6 decomposes into LiF and PF5 in the electrolyte containing a small amount of water. HF generated from these decomposition products reacts with organic solvents to generate gas and reacts with the positive electrode to release metal ions. As a result, the high-temperature stability and lifespan characteristics of lithium secondary batteries may deteriorate.

[0049] In addition, electrolyte oxidation is accelerated in the high voltage range, and long-term charge / discharge

[0050] The resistance of the electrode increases significantly in the process. Accordingly, even under high voltage and high temperature conditions,

[0051] A suitable electrolyte is required. That is, the electrolyte must ensure excellent ionic conductivity and stability, and in particular, it must be highly stable so that no side reactions occur even under high voltages of 4.5 V or higher and high temperatures.

[0052] To obtain an electrolyte with excellent high-voltage characteristics, the use of nitrile compounds as electrolyte additives has been proposed. However, the oxidation reaction potential characteristics of currently known nitrile compounds are not satisfactory, and improvements in this area are required.

[0053] Accordingly, the present disclosure provides an electrolyte for a lithium secondary battery containing an additive of chemical formula 1, which is a nitrile compound. This electrolyte has a high oxidation reaction potential and thus has high oxidation resistance, thereby improving life characteristics when applied to a high-voltage cathode and enabling the removal of HF, which is a cause of deterioration at high temperatures. Therefore, by using this electrolyte, a lithium secondary battery with improved high-temperature characteristics can be provided.

[0054] An electrolyte for a lithium secondary battery according to an embodiment of the present invention includes an additive represented by the following chemical formula 1.

[0055] <Chemical Formula 1>

[0056]

[0057] In chemical formula 1, A represents a chemical bond or -(CH2) k -(k is an integer from 1 to 3),

[0058] a and b are independently 0 or integers from 1 to 3,

[0059] However, this does not apply to cases where both a and b are 0.

[0060] R, R1, R2 and R3 are each independently hydrogen, a C1 to C10 alkyl group or F.

[0061] In chemical formula 1, k is an integer of 1, 2, or 3.

[0062] In addition, a lithium secondary battery according to an embodiment includes a positive electrode, a negative electrode current collector, and an electrolyte disposed between the positive electrode and the negative electrode current collector, and the electrolyte includes an additive represented by the above-described chemical formula 1.

[0063] In the present disclosure, the C1 to C10 alkyl group may include, for example, a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, etc.

[0064] In chemical formula 1, at least one of a or b is 0.

[0065] The additive represented by the above chemical formula 1 is an organic material capable of electrical behavior in high temperature, high voltage environments, and such organic material has high oxidation resistance. In addition, as can be seen in chemical formula 1, when the NF functional group and the nitrile (-C≡N) terminal group are applied, the oxidation reaction potential increases, and when LiPF6 is used as the lithium salt, HF, which is a decomposition product of the lithium salt at high temperatures, can be removed. HF is the most important side reaction-inducing substance that induces the dissolution of transition metals from the positive electrode at high temperatures, inducing deterioration of the positive electrode and causing an increase in resistance. As described above, when the electrolyte according to one embodiment is used, since HF is removed, a lithium secondary battery with improved high temperature and high voltage characteristics can be provided.

[0066] The additive represented by the above chemical formula 1 may include, for example, one or more compounds selected from the compounds represented by the following chemical formulas 2 to 8.

[0067] <Chemical Formula 2> <Chemical Formula 3>

[0068]

[0069] <Chemical Formula 4> <Chemical Formula 5>

[0070]

[0071] <Chemical Formula 6> <Chemical Formula 7>

[0072]

[0073] <Chemical Formula 8>

[0074]

[0075] The content of the additive represented by the above chemical formula 1 is 0.1 to 10 wt%, 0.1 to 8 wt%, 0.1 to 6 wt%, 0.1 to 5 wt%, 1 to 5 wt%, 1 to 4 wt%, or 1 to 3 wt% based on the total weight of the electrolyte. When the content of the additive of the chemical formula 1 is within the above range, a lithium secondary battery with improved high-voltage characteristics, high-temperature storage characteristics, and lifespan characteristics can be manufactured.

[0076] The additive of Chemical Formula 1 is a substance with very strong lithium cation and anion interactions. Using an electrolyte containing this additive of Chemical Formula 1 can induce anions to migrate along with lithium ions as they migrate from the positive electrode to the negative electrode during initial charge. This results in more anions present at the negative electrode. Consequently, the abundance of clustered solvation structures allows for the formation of a robust film rich in boron and fluorine anions.

[0077] Lithium secondary batteries include, for example, lithium ion batteries, lithium metal batteries, and solid secondary batteries.

[0078] electrolyte

[0079] An electrolyte for a lithium secondary battery may include a non-aqueous organic solvent and a lithium salt.

[0080] The above non-aqueous organic solvent acts as a medium through which ions involved in the electrochemical reaction of the battery can move.

[0081] Lithium salt is a substance that dissolves in an organic solvent and acts as a source of lithium ions in a lithium secondary battery, enabling the basic operation of the lithium secondary battery and promoting the movement of lithium ions between the positive and negative electrodes.

[0082] Representative examples of lithium salts include LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, LiN(SO2C2F5)2, Li(FSO2)2N (lithium bis(fluorosulfonyl)imide (LiFSI), Li(SO2CF3) (LiTFSI), LiC4F9SO3, LiN(C x F 2x+1 SO2)(C y F 2y+1 SO2) (x and y are integers from 1 to 20), LiSO3CF3 (lithium trifluoromethane sulfonate), LiSO3C2F5 (lithium tetrafluoroethane sulfonate), LiSO3C2F4 (lithium tetrafluoroethanesulfonate), lithium difluorobis(oxalato)phosphate (LiDFOB), lithium bis(oxalato)borate (LiBOB).

[0083] According to one embodiment, the lithium salt includes a first lithium salt and a second lithium salt. By including the first lithium salt and the second lithium salt in the electrolyte, the ionic conductivity of the electrolyte can be improved.

[0084] The first and second lithium salts are borate-based lithium salts. Compared to phosphorus-based lithium salts, borate-based lithium salts exhibit improved high-temperature stability and can suppress the production of hydrofluoric acid (HF). By including borate-based lithium salts in the first and second lithium salts, the high-temperature cycling characteristics of lithium batteries can be improved.

[0085] The first lithium salt and the second lithium salt may be, for example, independently of each other, a fluorine-containing borate-based lithium salt. By including a fluorine-containing borate-based lithium salt in the first lithium salt and the second lithium salt, the composition of the SEI (solid electrolyte interphase) layer formed during charge and discharge of a lithium battery can be more effectively modified. For example, by increasing the fluorine (F) content of the SEI layer, the structural stability of the SEI layer can be increased, and side reactions with a non-aqueous organic solvent can be effectively suppressed. As a result, the reversibility of the electrode reaction of the lithium secondary battery can be improved.

[0086] The first lithium salt and the second lithium salt may be, for example, a non-cyclic borate lithium salt and a cyclic borate lithium salt. Since the first lithium salt is a non-cyclic borate lithium salt, the ionic conductivity of the electrolyte can be more effectively increased. Since the second lithium salt is a cyclic borate lithium salt, the aggregation of anions is increased, so that it can more effectively participate in the composition modification of the SEI layer, and the high-temperature stability of the electrolyte can be improved.

[0087] Fluorine-containing borate lithium salts may include, for example, LiBF4, LiBF3(C2F5), compounds represented by chemical formulae 1-1 to 1-12, or combinations thereof.

[0088] <Chemical Formula 1-1> <Chemical Formula 1-2>

[0089]

[0090] <Chemical Formula 1-3> <Chemical Formula 1-4>

[0091]

[0092] <Chemical Formula 1-5> <Chemical Formula 1-6>

[0093]

[0094] <Chemical Formula 1-7> <Chemical Formula 1-8>

[0095]

[0096] <Chemical Formula 1-9> <Chemical Formula 1-10>

[0097]

[0098] <Chemical Formula 1-11>> <Chemical Formula 1-12>>

[0099]

[0100] The first lithium salt may include, for example, LiBF4, and the second lithium salt may include a compound selected from compounds represented by chemical formulae 1-1 to 1-12.

[0101] The first lithium salt may include LiBF4, and the second lithium salt may include lithium difluoro(oxalato)borate (LiDFOB) of chemical formula 1-1, for example.

[0102] The content ratio of the first lithium salt and the second lithium salt may be, for example, 1:9 to 9:1, 3:7 to 7:3, or 4:6 to 6:4. When the first lithium salt and the second lithium salt have a content ratio within this range, the gel polymer electrolyte can simultaneously provide excellent ionic conductivity and the formation of a structurally stable SEI layer. The content ratio of the first lithium salt and the second lithium salt may be, for example, a molar ratio.

[0103] According to one embodiment, the mixing molar ratio of lithium difluorodioxalatoborate (LiDFOB) and lithium tetrafluoroborate (LiBF4) is 1:2 to 1:0.3 or 1:1.5 to 1:0.5. When the concentration of the lithium salt and the mixing molar ratio of LiDFOB and LiBF4 are within the above ranges, a lithium secondary battery having improved performance can be manufactured. If the content of LiBF4 is greater than the above range, the nitrile-based compound exhibits better interaction with LiDFOB, but the probability of encountering LiDFOB is greatly reduced, which may be disadvantageous for film formation, and if the content of LiDFOB is greater than the above range, the viscosity of the electrolyte increases, which may lower the mobility, thereby reducing the initial capacity of the lithium secondary battery.

[0104] The concentration of the lithium salt in the electrolyte is 0.01 to 5.0 M, for example, 0.05 to 5.0 M, for example, 0.1 to 5.0 M, 0.1 to 3 M, 0.1 to 2.4 M, 0.3 to 1.5 M, 0.5 to 1.2 M, or 0.8 to 1.2 M. Here, the lithium salt may include a first lithium salt and a second lithium salt. When the concentration of the lithium salt is within the above range, further improved lithium secondary battery characteristics can be obtained.

[0105] The non-aqueous organic solvent may be, for example, one or more selected from among carbonate solvents, ester solvents, ether solvents, nitrile solvents, and ketone solvents.

[0106] As carbonate 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), butylene carbonate (BC), etc. can be used.

[0107] As ester solvents, methyl propionate, ethyl propionate, ethyl butyrate, methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, gamma butyrolactone, decanolide, gamma valerolactone, mevalonolactone, caprolactone, etc. can be used; as ether solvents, dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, tetrahydrofuran, etc. can be used; as ketone solvents, cyclohexanone, etc. can be used; and as nitrile solvents, acetonitrile (AN), succinonitrile (SN), adiponitrile, butyronitrile, etc. can be used.

[0108] Examples of ether solvents that can be used include dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, tetrahydrofuran, 1,3-dioxolane, 1,4-dioxolane, and other dioxolanes. In addition, cyclohexanone and the like can be used as ketone solvents. Examples of alcohol solvents that can be used include ethyl alcohol and isopropyl alcohol, and other solvents that can be used include nitriles such as R-CN (where R is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and may include a double bond, an aromatic ring, or an ether group); amides such as dimethylformamide; and phosphates such as ethylmethoxyethyl sulfolane, ethylmethyl sulfolane, sulfolane, and trimethyl phosphate.

[0109] The above non-aqueous organic solvents can be used alone or in combination of two or more.

[0110] In addition, when using a carbonate solvent, a cyclic carbonate and a chain carbonate can be mixed and used, and the cyclic carbonate and the chain carbonate can be mixed in a volume ratio of 1:1 to 1:9.

[0111] Other solvents that can be used in the electrolyte include, but are not limited to, dimethyl sulfoxide, dimethyl formamide, dimethyl acetamide, tetrahydrofuran, etc., and any organic solvent that can be used in the relevant technical field can be used. For example, the organic solvent may include a mixed solvent of 50 to 95 vol% of a chain carbonate and 5 to 50 vol% of a cyclic carbonate, for example, a mixed solvent of 70 to 95 vol% of a chain carbonate and 5 to 30 vol% of a cyclic carbonate. For example, the organic solvent may be a mixed solvent of three or more organic solvents.

[0112] According to one embodiment, the electrolyte includes a nitrile compound, a lithium salt, and a carbonate compound, wherein the lithium salt includes lithium difluorodioxalatoborate (LiDFOB) and lithium tetrafluoroborate (LiBF4).

[0113] The nitrile compound is, for example, butyronitrile, valeronitrile, propionitrile, acetonitrile, or a combination thereof. A lithium secondary battery is provided in which the content of the nitrile compound is 3 wt% to 45 wt% based on 100 wt% of the total weight of the electrolyte.

[0114] A lithium metal layer may be included between the negative electrode current collector and the electrolyte.

[0115] The oxidation reaction potential of the electrolyte for a lithium secondary battery according to one embodiment is 4.50 to 5.40 V, or 4.52 to 5.32 V. In the present disclosure, the term "oxidation reaction potential" means the potential at which the oxidation reaction starts, i.e., the decomposition start voltage. This oxidation reaction potential may change depending on the type of organic solvent of the electrolyte used together with the additive, and in the present disclosure, it means the value that appears when the oxidation reaction potential is measured using a carbonate-based solvent as the organic solvent of the electrolyte. That is, even if a different solvent is used in the actual electrolyte, the above value is satisfied when the oxidation reaction potential is measured using the electrolyte additive and the organic solvent according to one embodiment. In addition, the decomposition start voltage is 0.00001 A / cm in current value. 2 It means the potential at which the change in current value begins to appear, and the measurement conditions at this time are the air atmosphere at room temperature of 20 to 25℃. In addition, the content of the additive of Chemical Formula 1 is a value measured by adding 0.1 to 10 wt% based on the total weight of the electrolyte. When the electrolyte additive is added at 0.1 to 1 wt% based on the total weight of the electrolyte, it is easy to visually confirm the peak size of the current value change.

[0116] The electrolyte according to the present invention includes an additive having the aforementioned oxidation reaction potential, which enables the additive to react quickly during overcharge, thereby ensuring safety. This enables the achievement of both resilience during storage and safety during overcharge, both of which are difficult to achieve with additives alone.

[0117] The HF concentration (ppm) of a lithium secondary battery using an electrolyte according to an embodiment of the present invention after storage at a high temperature (60°C) in a state of being charged (100%) for 7 days is 20 ppm or less, 15 ppm or less, 13 ppm or less, or 12 ppm or less. The HF concentration (ppm) of a lithium secondary battery using an electrolyte after storage at a high temperature (60°C) can be evaluated as described in Evaluation Example 2 described below.

[0118] The electrolyte according to one embodiment may be in a liquid or gel state. The electrolyte may be prepared by adding a lithium salt and the above-described additives to a non-aqueous organic solvent.

[0119] A lithium secondary battery according to an embodiment includes a positive electrode including a positive electrode active material; a negative electrode current collector; and the above-described electrolyte disposed between the positive electrode and the negative electrode current collector.

[0120] [anode]

[0121] A lithium secondary battery according to one embodiment includes a cathode, and the cathode includes a cathode current collector and a cathode active material layer disposed on one surface of the cathode current collector. The lithium secondary battery is, for example, a lithium metal battery.

[0122] [Anode: Anode active material layer]

[0123] A compound capable of reversible intercalation and deintercalation of lithium (a lithiated intercalation compound) can be used as a cathode active material. Specifically, one or more of a composite oxide of lithium and a metal selected from cobalt, manganese, nickel, and combinations thereof can be used.

[0124] The above composite oxide may be a lithium transition metal composite oxide, and specific examples thereof include lithium nickel-based oxide, lithium cobalt-based oxide, lithium manganese-based oxide, lithium iron phosphate-based compound, cobalt-free nickel-manganese-based oxide, or a combination thereof.

[0125] As an example, a compound represented by any one of the following chemical formulas may be used: Li a A 1-b X b O 2-c D c (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05); Li a Mn 2-b X b O 4-c D c (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05); Li aNi 1-b-c Co b X c O 2-α D α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, 0<α<2); Li a Ni 1-b-c Mn b X c O 2-α D α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, 0<α<2); Li a Ni b Co c L 1 d G e O2(0.90≤a≤1.8, 0≤b≤0.9, 0≤c≤0.5, 0≤d≤0.5, 0≤e≤0.1); Li a NiG b O2(0.90≤a≤1.8, 0.001≤b≤0.1); Li a CoG b O2(0.90≤a≤1.8, 0.001≤b≤0.1); Li a Mn 1-b G b O2(0.90≤a≤1.8, 0.001≤b≤0.1); Li a Mn2G b O4(0.90≤a≤1.8, 0.001≤b≤0.1); Li a Mn 1-g G g PO4(0.90≤a≤1.8, 0≤g≤0.5); Li (3-f) Fe2(PO4)3(0≤f≤2); Li a FePO4(0.90≤a≤1.8).

[0126] In the above chemical formula, A is Ni, Co, Mn, or a combination thereof; X is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, or a combination thereof; D is O, F, S, P, or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; L 1is Mn, Al or a combination thereof.

[0127] The cathode active material may include, for example, a lithium transition metal oxide represented by the following chemical formulas 25 to 32:

[0128] <Chemical Formula 25>

[0129] Li a Ni x Co y M z O 2-b A b

[0130] In the above chemical formula 25, 1.0≤a≤1.2, 0≤b≤0.2, 0.8≤x<1, 0≤y≤0.3, 0 <z≤0.3, 및 x+y+z=1이고,

[0131] M is manganese (Mn), niobium (Nb), vanadium (V), magnesium (Mg), gallium (Ga), silicon (Si), tungsten (W), molybdenum (Mo), iron (Fe), chromium (Cr), copper (Cu), zinc (Zn), titanium (Ti), aluminum (Al), boron (B), or a combination thereof,

[0132] A is F, S, Cl, Br or a combination thereof,

[0133] <Chemical Formula 26>

[0134] LiNi x Co y Mn z O2

[0135] <Chemical Formula 27>

[0136] LiNi x Co y Al z O2

[0137] In the above chemical formulas 26 and 27, 0.8≤x≤0.95, 0≤y≤0.2, 0 <z≤0.2 및 x+y+z=1이며,

[0138] <Chemical Formula 28>

[0139] LiNi x Co y Mn z Al w O2

[0140] In the above chemical formula 28, 0.8≤x≤0.95, 0≤y≤0.2, 0 <z≤0.2, 0<w≤0.2, 및 x+y+z+w=1이며,

[0141] <Chemical Formula 29>

[0142] Li a Co x M y O 2-b A b

[0143] In the above chemical formula 29, 1.0≤a≤1.2, 0≤b≤0.2, 0.9≤x≤1, 0≤y≤0.1, and x+y=1,

[0144] M is manganese (Mn), niobium (Nb), vanadium (V), magnesium (Mg), gallium (Ga), silicon (Si), tungsten (W), molybdenum (Mo), iron (Fe), chromium (Cr), copper (Cu), zinc (Zn), titanium (Ti), aluminum (Al), boron (B) or a combination thereof, and A is F, S, Cl, Br or a combination thereof.

[0145] <Chemical Formula 30>

[0146] Li a Ni x Mn y M' z O 2-b A b

[0147] In chemical formula 30, 1.0≤a≤1.2, 0≤b≤0.2, 0 <x≤0.3, 0.5≤y<1, 0<z≤0.3, 및 x+y+z=1이고, M'는 코발트(Co), 니오븀(Nb), 바나듐(V), 마그네슘(Mg), 갈륨(Ga), 실리콘(Si), 텅스텐(W), 몰리브덴(Mo), 철(Fe), 크롬(Cr), 구리(Cu), 아연(Zn), 티타늄(Ti), 알루미늄(Al), 보론(B) 또는 이들의 조합이고, A는 F, S, Cl, Br 또는 이들의 조합이며,

[0148] <Chemical Formula 31>

[0149] Li a M1x M2 y PO 4-b X b

[0150] In the above chemical formula 31, 0.90≤a≤1.1, 0≤x≤0.9, 0≤y≤0.5, 0.9 <x+y<1.1, 0≤b≤2 이며,

[0151] M1 is chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zirconium (Zr) or a combination thereof,

[0152] M2 is magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), titanium (Ti), zinc (Zn), boron (B), niobium (Nb), gallium (Ga), indium (In), molybdenum (Mo), tungsten (W), aluminum (Al), silicon (Si), chromium (Cr), vanadium (V), scandium (Sc), yttrium (Y) or a combination thereof, and X is O, F, S, P or a combination thereof.

[0153] <Chemical Formula 32>

[0154] Li a M3 z PO4

[0155] In the above chemical formula 32, 0.90≤a≤1.1, 0.9≤z≤1.1, and M3 is chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zirconium (Zr), or a combination thereof.

[0156] The cathode active material layer may further include a conductive material. Examples of conductive materials include, but are not limited to, Denka black, carbon black, graphite particles, natural graphite, artificial graphite, acetylene black, Ketjen black, carbon fibers, carbon nanotubes, metal powders or metal fibers or metal tubes such as copper, nickel, aluminum, and silver, and conductive polymers such as polyphenylene derivatives. Any conductive material used in the art may be used. Alternatively, the cathode may not include a separate conductive material, for example.

[0157] The cathode active material layer may further include, for example, a binder. Examples of binders that may be used include vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polytetrafluoroethylene (PTFE), a mixture of the aforementioned polymers, and a styrene butadiene rubber-based polymer.

[0158] The content of the positive electrode active material included in the positive electrode active material layer may be 80 wt% to 99 wt%, 90 wt% to 99 wt%, or 95 wt% to 99 wt% of the total weight of the positive electrode active material layer (12).

[0159] The conductive material content included in the positive electrode active material layer may be 0.1 wt% to 10 wt% or 0.1 wt% to 5 wt% of the total weight of the positive electrode active material layer (12).

[0160] The binder content included in the positive electrode active material layer may be 0.1 wt% to 10 wt% or 0.1 wt% to 5 wt% of the total weight of the positive electrode active material layer (12).

[0161] The contents of the cathode active material, conductive agent, and binder contained in the cathode are at levels typically used in lithium batteries. Depending on the intended use and configuration of the lithium battery, one or more of the conductive agent and binder may be omitted.

[0162] For example, the cathode active material may be a high-nickel cathode active material in which the nickel content is 80 mol% or more, 85 mol% or more, 90 mol% or more, 91 mol% or more, or 94 mol% or more and 99 mol% or less, based on 100 mol% of metals excluding lithium in the lithium transition metal composite oxide. The high-nickel cathode active material can realize high capacity and thus can be applied to high-capacity, high-density lithium secondary batteries.

[0163] [Anode: Anode current collector]

[0164] The material constituting the positive electrode collector may be any material that does not react with lithium, i.e., does not form an alloy or compound with lithium, and has conductivity. The positive electrode collector is, for example, a metal or an alloy. The positive electrode collector (11) may be made of, for example, aluminum (Al), indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), germanium (Ge), or an alloy thereof. The positive electrode collector may have a form selected from, for example, a sheet, a foil, a film, a plate, a porous body, a mesoporous body, a body containing through-holes, a polygonal ring body, a mesh body, a foam body, and a non-woven body, but is not necessarily limited to these forms, and any form used in the relevant technical field may be used.

[0165] Alternatively, the positive electrode current collector may include, for example, a base film and a metal layer disposed on one or both sides of the base film. The base film may include, for example, a polymer. The polymer may be, for example, a thermoplastic polymer. The polymer may include, for example, polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyimide (PI), or a combination thereof. The polymer may be an insulating polymer. Since the base film includes an insulating thermoplastic polymer, the base film may soften or liquefy when a short circuit occurs, thereby blocking battery operation and suppressing a sudden increase in current. The metal layer may include, for example, aluminum (Al), indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), germanium (Ge), or an alloy thereof. The positive electrode current collector may additionally include a metal piece and / or a lead tab. For more specific details regarding the base film, metal layer, metal chip, and lead tab of the positive electrode current collector (11), refer to the positive electrode current collector (11) described above. By having this structure, the positive electrode current collector (11) can reduce the weight of the positive electrode, and consequently, improve the energy density of the positive electrode and lithium battery.

[0166] A positive electrode for a lithium secondary battery may include a current collector and a positive electrode active material layer formed on the current collector. The positive electrode active material layer includes a positive electrode active material and may further include a binder and / or a conductive material.

[0167] For example, the anode may further include an additive that can act as a sacrificial anode.

[0168] The content of the positive electrode active material may be 90 wt% to 99.5 wt% with respect to 100 wt% of the positive electrode active material layer, and the contents of the binder and conductive material may be 0.5 wt% to 5 wt%, respectively, with respect to 100 wt% of the positive electrode active material layer.

[0169] The above binder serves to adhere the positive electrode active material particles well to each other and also to adhere the positive electrode active material well to the current collector. Representative examples of the binder include, but are not limited to, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, epoxy resin, (meth)acrylic resin, polyester resin, nylon, etc.

[0170] The conductive material is used to provide conductivity to the electrode, and any material that does not cause chemical changes and is electronically conductive can be used in the battery. Examples of the conductive material include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber, and carbon nanotube; metal-based materials containing copper, nickel, aluminum, silver, etc. in the form of metal powder or metal fiber; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0171] Al may be used as the above current collector, but is not limited thereto.

[0172] [cathode]

[0173] A lithium secondary battery according to an embodiment includes a negative electrode, and the negative electrode includes a negative electrode collector.

[0174] [Cathode: Negative current collector]

[0175] The negative current collector includes, for example, a metal substrate. The metal substrate includes a first metal as a main component or is made of the first metal. The metal substrate includes a first metal as a main component or is made of the first metal. The content of the first metal included in the metal substrate is, for example, 90 wt% or more, 95 wt% or more, 99 wt% or more, or 99.9 wt% or more based on the total weight of the metal substrate. The metal substrate may be made of, for example, a material that does not react with lithium, i.e., does not form an alloy and / or compound with lithium. The first metal is, for example, copper (Cu), nickel (Ni), stainless steel (SUS), iron (Fe), and cobalt (Co), but is not necessarily limited thereto, and any metal used as a current collector in the art may be used. The first metal substrate may be made of, for example, one of the above-described metals, or may be made of an alloy of two or more metals. The metal substrate is, for example, in the form of a sheet or foil. The thickness of the negative electrode current collector may be, for example, 5 µm to 50 µm, 10 µm to 50 µm, 10 µm to 40 µm, or 10 µm to 30 µm, but is not necessarily limited to this range and may be selected depending on the characteristics of the required lithium metal battery.

[0176] The negative electrode current collector may further include a coating layer (not shown) comprising a second metal on a metal substrate. The negative electrode current collector may include, for example, a metal substrate; and a coating layer disposed on the metal substrate and comprising a second metal. The second metal has a higher Mohs hardness than the first metal. That is, since the coating layer comprising the second metal is harder than the metal substrate comprising the first metal, deterioration of the first metal substrate can be prevented. The Mohs hardness of the material constituting the metal substrate is, for example, 5.5 or less. The Mohs hardness of the first metal is, for example, 5.5 or less, 5.0 or less, 4.5 or less, 4.0 or less, 3.5 or less, or 3.0 or less. The Mohs hardness of the first metal may be, for example, 2.0 to 6.0. The Mohs hardness of the material constituting the coating layer is, for example, 6.0 or more. For example, the Mohs hardness of the second metal is 6.0 or more, 6.5 or more, 7.0 or more, 7.5 or more, 8.0 or more, 8.5 or more, or 9.0 or more. The Mohs hardness of the second metal may be, for example, 6.0 to 12. If the Mohs hardness of the second metal is too low, it may be difficult to suppress deterioration of the negative electrode current collector. If the Mohs hardness of the second metal is too high, processing may not be easy. The second metal is, for example, one or more selected from titanium (Ti), manganese (Mn), niobium (Nb), tantalum (Ta), iridium (Ir), vanadium (V), rhenium (Re), osmium (Os), tungsten (W), chromium (Cr), boron (B), ruthenium (Ru), and rhodium (Rh). The thickness of the coating layer can be, for example, 10 nm to 1 μm, 50 nm to 500 nm, 50 nm to 200 nm, or 50 nm to 150 nm.

[0177] Alternatively, the negative electrode current collector may include, for example, a base film and a metal layer disposed on one or both sides of the base film. The base film may include, for example, a polymer. The polymer may be, for example, a thermoplastic polymer. The polymer may include, for example, polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyimide (PI), or a combination thereof. The base film may be, for example, an insulator. Since the base film includes an insulating thermoplastic polymer, the base film may soften or liquefy when a short circuit occurs, thereby blocking battery operation and suppressing a sudden increase in current. The metal layer may include, for example, copper (Cu), nickel (Ni), stainless steel (SUS), iron (Fe), and cobalt (Co), or an alloy thereof. The metal layer may act as an electrochemical fuse, which may be cut off in the event of an overcurrent to prevent a short circuit. The limit current and maximum current can be controlled by adjusting the thickness of the metal layer. The metal layer can be plated or deposited on the base film. When the thickness of the metal layer is reduced, the limit current and / or maximum current of the negative electrode current collector (21) decreases, thereby improving the stability of the lithium battery in the event of a short circuit. A lead tab can be added on the metal layer for connection to the outside. The lead tab can be welded to the metal layer or the metal layer / base film laminate by ultrasonic welding, laser welding, spot welding, etc. During welding, the base film and / or the metal layer melts, so that the metal layer can be electrically connected to the lead tab. In order to strengthen the welding of the metal layer and the lead tab, a metal chip can be added between the metal layer and the lead tab. The metal chip can be a thin piece of the same material as the metal of the metal layer.The metal piece may be, for example, a metal foil, a metal mesh, etc. The metal piece may be, for example, an aluminum foil, a copper foil, a SUS foil, etc. After the metal piece is placed on the metal layer, the lead tab may be welded to the metal piece / metal layer laminate or the metal piece / metal layer / base film laminate by welding the lead tab. During welding, the base film, the metal layer, and / or the metal piece may melt, so that the metal layer or the metal layer / metal piece laminate may be electrically connected to the lead tab. A metal chip and / or a lead tab may be added to a portion of the metal layer. The base film may have a thickness of, for example, 1 to 50 ㎛, 1.5 to 50 ㎛, 1.5 to 40 ㎛, 1 to 30 ㎛, 1 to 20 ㎛, or 1 to 10 ㎛. When the base film has a thickness in this range, the weight of the electrode assembly can be more effectively reduced. The melting point of the base film may be, for example, 100 to 300°C, 100 to 250°C or less, or 100 to 200°C. Since the base film has a melting point within this range, the base film can be melted and easily bonded to the lead tab during the welding process of the lead tab. To improve the adhesion between the base film and the metal layer, a surface treatment such as corona treatment may be performed on the base film. The thickness of the metal layer may be, for example, 0.01 to 3 μm, 0.1 to 3 μm, 0.1 to 2 μm, or 0.1 to μm. Since the metal layer has a thickness within this range, conductivity can be maintained while ensuring the stability of the electrode assembly. The thickness of the metal piece may be, for example, 2 to 10 μm, 2 to 7 μm, or 4 to 6 μm. Since the metal piece has a thickness within this range, the connection between the metal layer and the lead tab can be performed more easily. By having this structure, the negative electrode current collector (21) can reduce the weight of the negative electrode and consequently improve the energy density of the negative electrode and lithium battery.

[0178] [Cathode: Lithium metal layer]

[0179] The lithium secondary battery may further include a lithium metal layer disposed between the negative electrode current collector and the electrolyte layer after being charged. The lithium metal layer corresponds to the first negative electrode active material layer.

[0180] The lithium metal layer is a metal layer containing lithium or a lithium alloy. The lithium metal layer contains lithium or a lithium alloy. The lithium metal layer (22) acts as, for example, a lithium reservoir. The lithium alloy includes, but is not limited to, a Li-Al alloy, a Li-Sn alloy, a Li-In alloy, a Li-Ag alloy, a Li-Au alloy, a Li-Zn alloy, a Li-Ge alloy, a Li-Si alloy, etc., and any lithium alloy used in the art may be used. The lithium metal layer (22) may be made of one of these alloys or lithium, or may be made of several types of alloys. The lithium metal layer is, for example, a plated layer. The lithium metal layer is deposited between the electrolyte layer and the negative electrode current collector, for example, during the charging process of a lithium secondary battery.

[0181] The thickness of the lithium metal layer is not particularly limited, but is, for example, 1 to 200 μm, 1 to 150 μm, 1 to 100 μm, 1 to 50 μm, 1 to 30 μm, 1 to 22 μm, or 1 μm to 10 μm. If the thickness of the lithium metal layer (23) is too thin, it is difficult for the lithium metal layer (22) to perform the role of a lithium reservoir. If the thickness of the lithium metal layer is too thick, the volume of the lithium secondary battery may excessively increase, and the cycle characteristics of the lithium secondary battery may rather deteriorate.

[0182] The thickness of the lithium metal layer may be, for example, smaller than the thickness of the electrolyte layer. The thickness of the lithium metal layer may be, for example, 70% or less, 60% or less, 50% or less, 40% or less, or 30% or less of the thickness of the electrolyte layer. The thickness of the lithium metal layer (22) may be, for example, 1 to 70%, 1 to 60%, 1 to 50%, 1 to 40%, or 1 to 30% of the thickness of the electrolyte layer (30). Since the thickness of the lithium metal layer is smaller than the thickness of the electrolyte layer, volume change during charge and discharge of the lithium secondary battery can be suppressed. As a result, deterioration due to volume change of the lithium secondary battery can be suppressed.

[0183] The thickness of the lithium metal layer may be, for example, smaller than the thickness of the positive electrode active material layer. The thickness of the lithium metal layer (22) may be, for example, 70% or less, 60% or less, 50% or less, 40% or less, or 30% or less of the thickness of the positive electrode active material layer. The thickness of the lithium metal layer may be, for example, 1 to 70%, 1 to 60%, 1 to 50%, 1 to 40%, or 1 to 30% of the thickness of the positive electrode active material layer. Since the thickness of the lithium metal layer is smaller than the thickness of the positive electrode active material layer, volume change during charge and discharge of the lithium secondary battery can be suppressed. As a result, deterioration due to volume change of the lithium secondary battery can be suppressed.

[0184] In the XPS analysis of the surface of the lithium metal layer, for example, the peak intensity derived from the fluorine (F) element may be greater than the peak intensity derived from the oxygen (O) element. In the XPS analysis of the surface of the lithium metal layer, for example, the peak intensity derived from the fluorine (F) element may be more than 100%, 105% or more, 110% or more, or 120% or more of the peak intensity derived from the oxygen (O) element. In the XPS analysis of the surface of the lithium metal layer, for example, the peak intensity derived from the fluorine (F) element may be more than 100% to 200%, 105% to 200%, 110% to 200%, or 120% to 200% of the peak intensity derived from the oxygen (O) element. Since the SEI layer formed on the surface of the lithium metal layer mainly includes an inorganic compound containing fluorine (F), the structural stability of the SEI layer may be improved. As a result, the cycle characteristics of a lithium secondary battery may be improved. In contrast, when the SEI layer formed on the surface of the lithium metal layer mainly includes organic compounds containing oxygen (O), the structural stability of the SEI layer may be reduced. The peak derived from the fluorine (F) element may be, for example, a peak derived from the fluorine (F) 1s orbital. The peak derived from the oxygen (O) element may be, for example, a peak derived from the oxygen (O) 1s orbital.

[0185] After assembling a lithium secondary battery, a lithium metal layer is deposited by charging, and since the lithium metal layer is not included during the assembly of the lithium secondary battery, the energy density of the lithium secondary battery increases. When a lithium metal layer is additionally deposited by charging after assembling a lithium secondary battery, the region between the negative electrode, i.e., the negative electrode current collector, and the electrolyte layer is a Li-free region that does not contain lithium (Li), for example, in the initial state of the lithium secondary battery or in the state after complete discharge.

[0186] A lithium metal layer is further included between the electrolyte layer and the negative electrode current collector of a lithium secondary battery according to an embodiment of the present invention, and in XPS analysis of the surface of the lithium metal layer, the intensity of the fluorine peak is greater than the intensity of the oxygen peak.

[0187] Additionally, a second negative electrode active material layer including a negative electrode active material may be further included between the lithium metal layer and the electrolyte layer, and a protective layer may be further included disposed on the lithium metal layer.

[0188] According to another embodiment, a second negative electrode active material layer including a negative electrode active material may be included between the negative electrode current collector and the electrolyte layer.

[0189] [Cathode: Cathode active material layer]

[0190] A negative electrode active material layer may be placed on top of the negative electrode current collector.

[0191] The above negative electrode active material includes a material capable of reversibly intercalating / deintercalating lithium ions, lithium metal, an alloy of lithium metal, a material capable of doping and dedoping lithium, or a transition metal oxide.

[0192] The material capable of reversibly intercalating / deintercalating the lithium ions may include a carbon-based negative electrode active material, for example, crystalline carbon, amorphous carbon, or a combination thereof. Examples of the crystalline carbon include graphite such as natural graphite or artificial graphite in an amorphous, plate-like, flake-like, spherical, or fibrous form, and examples of the amorphous carbon include soft carbon or hard carbon, mesophase pitch carbide, calcined coke, and the like.

[0193] As the above lithium metal alloy, an alloy of lithium and a metal selected from Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn can be used.

[0194] As the material capable of doping and dedoping the lithium, a Si-based negative electrode active material or a Sn-based negative electrode active material may be used. The Si-based negative electrode active material may be silicon, a silicon-carbon composite, SiOx (0 < x < 2), a Si-Q alloy (wherein Q is selected from alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements (excluding Si), Group 15 elements, Group 16 elements, transition metals, rare earth elements, and combinations thereof), or a combination thereof. The Sn-based negative electrode active material may be Sn, SnO2, a Sn-based alloy, or a combination thereof.

[0195] The silicon-carbon composite may be a composite of silicon and amorphous carbon. According to one embodiment, the silicon-carbon composite may be in the form of silicon particles and amorphous carbon coated on the surface of the silicon particles. For example, the composite may include secondary particles (cores) in which silicon primary particles are assembled and an amorphous carbon coating layer (shell) positioned on the surface of the secondary particles. The amorphous carbon may also be positioned between the silicon primary particles, such that, for example, the silicon primary particles may be coated with amorphous carbon. The secondary particles may be dispersed and present in an amorphous carbon matrix.

[0196] The silicon-carbon composite may further comprise crystalline carbon. For example, the silicon-carbon composite may comprise a core comprising crystalline carbon and silicon particles and an amorphous carbon coating layer positioned on the surface of the core.

[0197] The above Si-based negative electrode active material or Sn-based negative electrode active material can be used in a mixture with a carbon-based negative electrode active material.

[0198] According to another embodiment, a negative electrode for a lithium secondary battery includes a current collector and a negative electrode active material layer positioned on the current collector. The negative electrode active material layer includes a negative electrode active material and may further include a binder and / or a conductive material.

[0199] For example, the negative electrode active material layer may include 90 to 99 wt% of the negative electrode active material, 0.5 to 5 wt% of the binder, and 0 to 5 wt% of the conductive material.

[0200] The above binder serves to adhere the negative electrode active material particles well to each other and also to adhere the negative electrode active material well to the negative electrode current collector. The binder may be a non-aqueous binder, an aqueous binder (e.g., a water-dispersible binder), a dry binder, or a combination thereof.

[0201] Examples of the non-aqueous binder include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide, or combinations thereof.

[0202] The above-mentioned aqueous binder may be selected from styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluoroelastomer, polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, poly(meth)acrylonitrile, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenol resin, epoxy resin, polyvinyl alcohol, and combinations thereof.

[0203] When using an aqueous binder as the above-mentioned negative electrode binder, a cellulose-based compound capable of imparting viscosity may be further included. The cellulose-based compound may be a mixture of one or more of carboxymethyl cellulose, hydroxypropylmethyl cellulose, methyl cellulose, or an alkali metal salt thereof. The alkali metal may be Na, K, or Li.

[0204] The above dry binder is a polymeric material capable of being fiberized, and may be, for example, polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, or a combination thereof.

[0205] The conductive material is used to provide conductivity to the electrode, and any material that does not cause chemical changes and is electronically conductive can be used in the battery. Specific examples include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanofibers, and carbon nanotubes; metal-based materials in the form of metal powder or metal fibers, including copper, nickel, aluminum, and silver; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0206] The negative electrode current collector may be selected from copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, and a combination thereof.

[0207] [Separator]

[0208] Depending on the type of lithium secondary battery, a separator may exist between the positive and negative electrode current collectors.

[0209] The pore diameter of the separator is generally 0.01 to 10 μm, and the thickness can generally be 5 to 20 μm. Examples of such separators include sheets or non-woven fabrics made of olefin-based polymers such as polypropylene, glass fiber, or polyethylene. When a solid polymer electrolyte is used as the electrolyte, the solid polymer electrolyte may also function as the separator.

[0210] The above separator may include a porous substrate and a coating layer including an organic material, an inorganic material, or a combination thereof located on one or both sides of the porous substrate.

[0211] By forming a coating layer (e.g., a ceramic coating layer), the cell performance of a lithium secondary battery can be improved by suppressing lithium dendrite formation through the rigidity of the ceramic coating layer without significantly increasing the resistance of the cell. In addition, by employing a separator having the above-described ceramic coating layer, heat resistance is secured, thereby improving heat shrinkage characteristics, and the material cost of a lithium secondary battery is reduced by reducing the separator margin for ensuring safety during cell design. In addition, the growth of dendrites on the negative electrode is physically suppressed, thereby improving the long-term lifespan at both room temperature and high temperature.

[0212] The porous substrate may be, for example, a porous membrane. The porous membrane may be, for example, a microporous membrane. The porous membrane may be, for example, a woven fabric or a non-woven fabric. The porous membrane may be any material commonly used in lithium batteries. The porous membrane may include, for example, glass fiber, an olefin-based resin, a fluoropolymer, an ester-based resin, an imide-based resin, an acrylic resin, a cellulose-based resin, or a combination thereof. The olefin-based resin may include, for example, polyethylene, polypropylene, or a combination thereof. The fluoropolymer-based resin may include, for example, polyvinylidene fluoride, polytetrafluoroethylene, or a combination thereof. The ester-based resin may include, for example, polyethylene terephthalate, polybutylene terephthalate, or a combination thereof. The imide-based resin may include, for example, polyamideimide, polyetherimide, or a combination thereof. Acrylic resins may include, for example, polyacrylonitrile, polyacrylate, or combinations thereof. Cellulosic resins may include, for example, carboxymethylcellulose, microbial cellulose, plant cellulose, animal cellulose, or combinations thereof.

[0213] The above porous substrate may be a polymer film formed of any one polymer selected from polyolefins such as polyethylene and polypropylene, polyesters such as polyethylene terephthalate and polybutylene terephthalate, polyacetal, polyamide, polyimide, polycarbonate, polyether ketone, polyarylether ketone, polyetherimide, polyamideimide, polybenzimidazole, polyethersulfone, polyphenylene oxide, cyclic olefin copolymer, polyphenylene sulfide, polyethylene naphthalate, glass fiber, Teflon, and polytetrafluoroethylene, or a copolymer or mixture of two or more thereof.

[0214] The organic material may include a polyvinylidene fluoride polymer or a (meth)acrylic polymer.

[0215] The above inorganic materials are Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, Mg(OH)2, boehmite, AIN (Aluminum Nitride), SiC (Silicon Carbide), BoN (Boron Nitride), BaTiO3, Pb(Zr,Ti)O3 (PZT), Pb 1-a La a Zr 1-b Ti b O3 (PLZT, where, 0 <a<1, 0<b<1임), Pb(Mg 1 / 3 Nb 2 / 3 )O3-PbTiO3 (PMN-PT), hafnia (HfO2), SrTiO3, SiC, lithium phosphate (Li3PO4), lithium titanium phosphate (Li c Ti d (PO4)3, 0 <d<2, 0<d<3), 리튬알루미늄티타늄포스페이트 (Li a1 Al b1 Ti c1(PO4)3, 0 <a1<2, 0<b1<1, 0<c1<3), 14Li2O-9Al2O3-38TiO2-39P2O5 등과 같은 (LiAlTiP) a2 O b2 Series Glass (0) <a2<4, 0<b2<13), 리튬란탄티타네이트 (Li a3 La b3 TiO3, 0 <a3<2, 0<b3<3), Li 3.25 Ge 0.25 P 0.75 Lithium germanium thiophosphate (Li) such as S4 a4 Ge b4 P c2 S d , 0 <a4<4, 0<b4<1, 0<c2<1, 0<d<5), Li3N 등과 같은 리튬나이트라이드 (Li a5 N b5 , 0 <a5<4, 0<b5<2), Li3PO4-Li2S-SiS2 등과 같은 SiS2 계열 글래스 (Li a6 Si b6 S c3 , 0 <a6<3, 0<b6<2, 0<c3<4), LiI-Li2S-P2S5 등과 같은 P2S5 계열 글래스 (Li a7 P b7 S c5 , 0 <a7<3, 0<b7<3, 0<c5<7) 또는 이들의 조합에서 선택되는 무기 입자를 포함할 수 있으나, 이에 한정되는 것은 아니다.

[0216] The organic and inorganic substances may be mixed and present in one coating layer, or a coating layer including an organic substance and a coating layer including an inorganic substance may be present in a laminated form.

[0217] [Lithium secondary battery]

[0218] Lithium secondary batteries can be classified into cylindrical, square, pouch, coin, etc. types according to their shapes. FIGS. 1 to 4 are schematic diagrams illustrating lithium secondary batteries according to one embodiment, wherein FIG. 1 can be said to be a cylindrical battery, FIG. 2 a square battery, and FIGS. 3 and 4 a pouch battery. Referring to FIGS. 1 to 4, a lithium secondary battery (100) may include an electrode assembly (40) having a separator (30) interposed between a positive electrode (10) and a negative electrode (20), and a case (50) in which the electrode assembly (40) is built. The positive electrode (10), the negative electrode (20), and the separator (30) may be impregnated with an electrolyte (not shown) according to one embodiment. The lithium secondary battery (100) may include a sealing member (60) that seals the case (50) as shown in FIG. 1. In addition, in FIG. 2, the lithium secondary battery (100) may include a positive lead tab (11), a positive terminal (12), a negative lead tab (21), and a negative terminal (22). As in FIGS. 3 and 4, the lithium secondary battery (100) may include electrode tabs (70), i.e., a positive tab (71) and a negative tab (72), which serve as electrical paths for guiding the current formed in the electrode assembly (40) to the outside.

[0219] The above positive electrode (10) may include a positive electrode current collector and a positive electrode active material layer. The above negative electrode (20) may include a negative electrode current collector and a negative electrode active material layer.

[0220] According to one embodiment, a lithium secondary battery having a negative electrode current collector, a positive electrode, and an electrolyte layer disposed therebetween may further include a lithium metal layer disposed on the negative electrode current collector. The lithium metal layer includes a lithium metal foil, a lithium metal powder, a lithium alloy foil, a lithium alloy powder, or a combination thereof.

[0221] The above lithium alloy foil and lithium alloy powder contain lithium and a first metal, wherein the first metal is indium (In), silicon (Si), gallium (Ga), tin (Sn), aluminum (Al), titanium (Ti), zirconium (Zr), niobium (Nb), germanium (Ge), antimony (Sb), bismuth (Bi), gold (Au), platinum (Pt), palladium (Pd), magnesium (Mg), silver (Ag), zinc (Zn), nickel, iron, cobalt, chromium, cesium, sodium, potassium, calcium, yttrium, bismuth, tantalum, hafnium, barium, vanadium, strontium, lanthanum, or a combination thereof.

[0222] The above negative electrode contains a negative electrode active material layer between a lithium metal layer and an electrolyte layer, and the negative electrode active material layer contains a carbon-based material; a mixture of a carbon-based material and at least one selected from a metal and a metalloid; a composite of a carbon-based material and at least one selected from a metal and a metalloid; or a combination thereof.

[0223] The carbon-based material comprises amorphous carbon (e.g., in particle form), the amorphous carbon having an average particle diameter of 10 nm to 100 nm, and the carbon-based material comprises carbon black, carbon nanotubes, carbon nanofibers, fullerene, activated carbon, carbon fibers, or a combination thereof.

[0224] The above negative electrode further includes a protective layer disposed on the lithium metal layer.

[0225] The electrolyte includes a liquid electrolyte, a gel electrolyte, a solid electrolyte, or a combination thereof, and the solid electrolyte includes an oxide-based solid electrolyte, a sulfide-based solid electrolyte, a polymer solid electrolyte, or a combination thereof.

[0226] Referring to Fig. 5a, a separator (30) is laminated on a negative electrode current collector (21). The negative electrode (20) contains a negative electrode current collector (21), and the negative electrode active material layer is absent.

[0227] The above separator (30) contains an electrolyte containing an additive of chemical formula 1 according to an embodiment.

[0228] Although the lithium secondary battery (e.g., lithium metal battery) of FIG. 5a shows a structure in which a separator (30) is disposed on a negative electrode current collector (21), it may have a structure in which an electrolyte layer containing an electrolyte according to an embodiment is disposed instead of the separator (30). The electrolyte may be a solid electrolyte, a gel electrolyte, a liquid electrolyte, or a combination thereof. Here, the solid electrolyte and the gel electrolyte may contain an electrolyte containing an additive of Chemical Formula 1.

[0229] A positive electrode (10) is placed on top of the above separator (30). The positive electrode (10) contains a positive electrode active material layer (12) and a positive electrode current collector (11).

[0230] An electrolyte may be further included between the separator (30) and the anode (10). The electrolyte may be a gel electrolyte, a solid electrolyte, a liquid electrolyte, or a combination thereof.

[0231] A protective layer may be further disposed on the negative electrode collector (21).

[0232] A liquid electrolyte is contained in the pores of a separator (30) containing a porous substrate, or

[0233] A gel-type polymer electrolyte containing a liquid electrolyte and a cross-linked polymer may be contained.

[0234] The above liquid electrolyte contains a lithium salt and an organic solvent (i.e., a non-aqueous organic solvent).

[0235] As shown in Fig. 5b, a lithium metal layer (22) can be placed between the negative electrode collector (21) and the separator (30).

[0236] According to one embodiment, the lithium metal layer (22) can be arranged during the assembly of the lithium metal battery. According to another embodiment, the negative electrode active material layer can include a negative electrode active material layer by plating lithium metal after charging. The negative electrode active material layer can be a lithium plating layer (plated lithium layer).

[0237] The above lithium metal layer (22) includes lithium metal or a lithium alloy.

[0238] The thickness of the lithium metal layer is 1 to 500 um or 10 to 500 um. When the thickness of the lithium metal layer is within the above range, the cycle characteristics of the lithium metal battery are improved without reducing the energy density.

[0239] An anode active material layer may further be included between the anode current collector and the separator. The anode active material layer may be positioned between the lithium metal layer and the separator.

[0240] According to one embodiment, the negative active material layer may contain a carbon-based material; a mixture of a carbon-based material and one or more selected from metals and metalloids; a composite of a carbon-based material and one or more selected from metals and metalloids; or a combination thereof.

[0241] The carbon-based material includes amorphous carbon, and the average particle diameter of the amorphous carbon is 10 nm to 100 nm, and the carbon-based material includes carbon black (CB), acetylene black (AB), furnace black (FB), ketjen black (KB), graphene, or a combination thereof.

[0242] The above negative active material layer includes a lithium metal foil, a lithium metal powder, a lithium alloy foil, a lithium alloy powder, or a combination thereof, wherein the lithium alloy foil and the lithium alloy powder contain lithium and a first metal.

[0243] The first metal is indium (In), silicon (Si), gallium (Ga), tin (Sn), aluminum (Al), titanium (Ti), zirconium (Zr), niobium (Nb), germanium (Ge), antimony (Sb), bismuth (Bi), gold (Au), platinum (Pt), palladium (Pd), magnesium (Mg), silver (Ag), zinc (Zn), nickel, iron, cobalt, chromium, cesium, sodium, potassium, calcium, yttrium, bismuth, tantalum, hafnium, barium, vanadium, strontium, lanthanum, or a combination thereof.

[0244] The lithium metal layer (22) may include, for example, lithium foil, lithium powder, or a combination thereof. The lithium foil may include, for example, lithium metal foil, lithium alloy foil, or a combination thereof. The lithium powder may include lithium metal powder, lithium alloy powder, or a combination thereof. A lithium alloy is an alloy of lithium and another metal that can be alloyed with lithium, such as a lithium-silver alloy, a lithium-zinc alloy, a lithium-magnesium alloy, or a lithium-tin alloy. The negative electrode active material layer including a lithium metal foil may be, for example, a lithium metal layer. The negative electrode active material layer including a lithium alloy foil may be, for example, a lithium alloy layer. The negative electrode active material layer including a lithium metal powder and / or a lithium alloy powder may be introduced by coating a slurry including lithium powder and a binder, etc., on a negative electrode current collector. The binder may be, for example, a fluorine-based binder such as polyvinylidene fluoride (PVDF). The negative electrode active material layer may not include a carbon-based negative electrode active material. Therefore, the negative electrode active material layer can be made of a metal-based negative electrode active material.

[0245] The negative electrode current collector is composed of a material that does not react with lithium, i.e., does not form an alloy or compound. The material constituting the negative electrode current collector includes, but is not limited to, copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), and nickel (Ni), and any material that is used as an electrode current collector in the relevant technical field may be used. The negative electrode current collector may be composed of one of the above-mentioned metals, or may be composed of an alloy or a coating material of two or more metals. The negative electrode current collector is, for example, in the form of a plate or foil.

[0246] In a lithium metal battery according to an embodiment, a protective layer may be further introduced between the negative electrode current collector and the separator. It is also possible to introduce a protective layer further between the negative electrode active material layer and the separator.

[0247] The protective layer contains a polymer such as polyvinyl alcohol, polyimide, vinylidene fluoride-hexafluoropropylene copolymer, polyvinylidene fluoride, carboxymethyl cellulose, styrene butylene rubber, or a polymer and an inorganic filler. Inorganic fillers include, for example, SiO2, Al2O3, Al(OH)3, AlO(OH), TiO2, BaTiO3, ZnO2, Mg(OH)2, Aluminum Nitride (AlN), Silicon Carbide (SiC), Boron Nitride (BoN), or a combination thereof. Introducing an additional protective layer in this way can minimize contact between lithium and the electrolyte, thereby reducing side reactions, and can suppress lithium dendrite growth by creating a uniform flow of lithium ions throughout the electrode.

[0248] The thickness of the protective layer is, for example, 1 to 20 um.

[0249] The negative electrode active material layer may contain a negative electrode active material and a binder.

[0250] The negative active material has, for example, a particle form. The average particle diameter of the negative active material having a particle form is, for example, 10 nm to 4 ㎛, 10 nm to 1 ㎛, 10 nm to 500 nm, 10 nm to 100 nm, or 20 nm to 80 nm. When the negative active material has an average particle diameter in this range, reversible plating and / or dissolution of lithium can be facilitated during charge and discharge. The average particle diameter of the negative active material is, for example, a median diameter (D50) measured using a laser particle size distribution analyzer.

[0251] The negative electrode active material may include, for example, at least one selected from a carbon-based negative electrode active material and a metal or metalloid negative electrode active material. The carbon-based negative electrode active material may be, for example, amorphous carbon. Examples of the carbon-based negative electrode active material include, but are not limited to, carbon black (CB), acetylene black (AB), furnace black (FB), ketjen black (KB), graphene, etc., and any material classified as amorphous carbon in the relevant technical field may be used. Amorphous carbon is carbon that has no crystallinity or very low crystallinity, and is distinguished from crystalline carbon or graphite-based carbon. The metal or metalloid negative electrode active material includes, but is not limited to, one or more selected from the group consisting of gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn), and any metal or metalloid negative electrode active material that forms an alloy or compound with lithium in the relevant technical field may be used. For example, nickel (Ni) does not form an alloy with lithium, and therefore is not a metal negative electrode active material in the present specification. The negative electrode active material layer includes a type of negative electrode active material among these negative electrode active materials, or includes a mixture of a plurality of different negative electrode active materials. For example, the negative electrode active material layer may include a mixture of amorphous carbon and one or more selected from the group consisting of gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn). The mixing ratio of the mixture may be, for example, 10:1 to 1:2, 10:1 to 1:1, 7:1 to 1:1, 5:1 to 1:1, or 4:1 to 2:1 by weight.The negative electrode active material included in the negative electrode active material layer may include a mixture of first particles made of, for example, amorphous carbon and second particles made of a metal or a metalloid. The metal includes, for example, gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn). The content of the second particles is 8 to 60 wt%, 10 to 50 wt%, 15 to 40 wt%, or 20 to 30 wt% based on the total weight of the mixture. When the second particles have a content in this range, the cycle characteristics of, for example, a lithium metal battery are further improved.

[0252] The binder included in the negative electrode active material layer may be, for example, styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, vinylidene fluoride / hexafluoropropylene copolymer, polyacrylonitrile, polymethyl methacrylate, etc., but is not necessarily limited thereto, and any binder used in the relevant technical field may be used. The binder may be composed of a single binder or a plurality of different binders. When the negative electrode active material layer does not include a binder, the negative electrode active material layer can be easily separated from the ceramic coating layer (21) or the negative electrode current collector (21). The content of the binder included in the negative electrode active material layer may be, for example, 1 to 20 wt% based on the total weight of the negative electrode active material layer.

[0253] When the negative electrode active material layer is present, the thickness of the negative electrode active material layer may be, for example, 1% to 50%, 1% to 30%, 1% to 10%, or 1% to 5% of the thickness of the positive electrode active material layer. If the thickness of the negative electrode active material layer is too thin, lithium dendrites formed between the negative electrode active material layer and the negative electrode current collector may collapse the negative electrode active material layer, making it difficult to improve the cycle characteristics of the lithium metal battery. If the thickness of the negative electrode active material layer increases excessively, the energy density of the lithium metal battery employing the negative electrode (20) may decrease, and it may be difficult to improve the cycle characteristics.

[0254] [Method for manufacturing lithium secondary batteries]

[0255] A lithium secondary battery according to an embodiment can be manufactured through the steps of: preparing a negative electrode; preparing a positive electrode; preparing an assembly using the positive electrode and the negative electrode; and providing an electrolyte including an additive represented by the following chemical formula 1 according to an embodiment to the assembly.

[0256] <Chemical Formula 1>

[0257]

[0258] In chemical formula 1, A represents a chemical bond or -(CH2) k -(k is an integer from 1 to 3),

[0259] a and b are independently 0 or integers from 1 to 3,

[0260] However, this does not apply to cases where both a and b are 0.

[0261] R, R1, R2 and R3 are each independently hydrogen, a C1 to C10 alkyl group or F.

[0262] An assembly can be prepared by interposing a separator between the positive and negative electrodes.

[0263] The above electrolyte may further include a solid electrolyte, a liquid electrolyte, a gel electrolyte, or a combination thereof. The solid electrolyte includes an oxide-based solid electrolyte, a sulfide-based solid electrolyte, a polymer solid electrolyte, or a combination thereof.

[0264] The above gel electrolyte can be formed by injecting and crosslinking a gel-type electrolyte composition comprising a polymerizable monomer, a liquid electrolyte, and an initiator into an assembly. The step of injecting the composition for forming a gel-type polymer electrolyte into the assembly can be performed as an impregnation step under vacuum so that the composition can sufficiently penetrate into the pores of the porous substrate.

[0265] Methods for forming a gel-type polymer electrolyte include curing using heat, UV, or high-energy radiation (electron beam, γ-ray). The curing reaction using heat can be carried out at a temperature of 40 to 120°C, for example, 50 to 90°C, for 30 to 120 minutes.

[0266] The above heat treatment varies depending on the type of polymerizable monomer, but is performed at, for example, 40 to 120°C.

[0267] The composition for forming the above gel-type polymer electrolyte may further include a crosslinking agent, a temperature-responsive initiator, etc. to assist in crosslinking of the crosslinkable monomer. The crosslinking agent, initiator, etc. are not particularly limited as long as they are commonly used in the relevant technical field.

[0268] Trimethylolpropane triacrylate, etc. can be used as a crosslinking monomer.

[0269] The initiator can be, for example, benzoin ethyl ether.

[0270] The content of the crosslinking agent, initiator, etc. may be within a typical range. For example, the content of the initiator may be used in a range of 0.1 to 5 parts by weight, or 0.2 to 3 parts by weight, based on 100 parts by weight of the total content of the monomer for forming the crosslinking polymer. Using the gel polymer electrolyte formed in this way, the ionic conductivity can be maintained at a value close to that of the liquid electrolyte, and the gel polymer electrolyte inside the positive and negative electrodes can play a role in preventing leakage of the liquid electrolyte. The electrolyte can be trapped in the polymer matrix of the gel polymer electrolyte and maintained within the polymer matrix, thereby helping the smooth movement of lithium ions. In addition, the excellent electrochemical properties of the polymer can suppress the electrolyte decomposition reaction within the range of -1 V to 5 V.

[0271] The ionic conductivity of the gel polymer electrolyte is 0.26 mS / cm or more, for example, 0.26 to 1.0 mS / cm, or 0.3 to 1.0 mS / cm.

[0272] A lithium secondary battery according to one embodiment of the present invention can be applied to automobiles, mobile phones, and / or various types of electrical devices, but the present invention is not limited thereto.

[0273] 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 are not intended to limit the scope of the present invention.

[0274] (Electrolyte production)

[0275] Manufacturing Example 1: Electrolyte (additive of Chemical Formula 2 (5 wt%), 1M LiPF6, EC:EMC:DMC (4:3:3))

[0276] An electrolyte was prepared by adding 1M LiPF6 and an additive of the following chemical formula 2 to a mixed solvent of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a weight ratio of 4:3:3. Here, the content of the additive is 2 wt% based on 100 wt% of the total weight of the liquid electrolyte.

[0277] <Chemical Formula 2>

[0278]

[0279] Manufacturing Example 2: Electrolyte (additive of chemical formula 3 (2 wt%), 1M LiPF6, EC:EMC:DMC (4:3:3))

[0280] An electrolyte was manufactured in the same manner as in Manufacturing Example 1, except that the additive of Chemical Formula 3 was used instead of the additive of Chemical Formula 2.

[0281] <Chemical Formula 3>

[0282]

[0283] Manufacturing Example 3: Electrolyte (additive of Chemical Formula 4 (2 wt%), 1M LiPF6, EC:EMC:DMC (4:3:3))

[0284] An electrolyte was manufactured in the same manner as in Manufacturing Example 1, except that the additive of Chemical Formula 4 was used instead of the additive of Chemical Formula 2.

[0285] <Chemical Formula 4>

[0286]

[0287] Manufacturing Example 4: Electrolyte (additive of Chemical Formula 5 (2 wt%), 1M LiPF6, EC:EMC:DMC (4:3:3))

[0288] An electrolyte was manufactured in the same manner as in Manufacturing Example 1, except that the additive of Chemical Formula 5 was used instead of the additive of Chemical Formula 2.

[0289] <Chemical Formula 5>

[0290]

[0291] Manufacturing Example 5: Electrolyte (additive of chemical formula 6 (2 wt%), 1M LiPF6, EC:EMC:DMC (4:3:3))

[0292] An electrolyte was manufactured in the same manner as in Manufacturing Example 1, except that the additive of Chemical Formula 6 was used instead of the additive of Chemical Formula 2.

[0293] <Chemical Formula 6>

[0294]

[0295] Manufacturing Example 6: Electrolyte (additive of Chemical Formula 2 (10 wt%), 1M LiPF6, EC:EMC:DMC (4:3:3))

[0296] An electrolyte was manufactured in the same manner as in Manufacturing Example 1, except that the content of the additive of Chemical Formula 2 was changed to 10 wt%.

[0297] Manufacturing Example 7: Electrolyte (additive of chemical formula 2 (5 wt%), 1M LiPF6, EC:EMC:DMC (4:3:3))

[0298] An electrolyte was manufactured in the same manner as in Manufacturing Example 1, except that the content of the additive of Chemical Formula 2 was changed to 1 wt%.

[0299] Manufacturing Example 8: Electrolyte (additive of Chemical Formula 2 (2 wt%), FEC and DEC in a weight ratio of 42:48, 0.6 M LiDFOB and 0.6 M LiBF 4)

[0300] An electrolyte was prepared by adding 0.6 M LiDFOB (lithium difluoro(oxalate)borate), 0.6 M LiBF4, and an additive of the following chemical formula 2 to a mixed solvent of fluoroethylene carbonate (FEC) and diethyl carbonate (DEC) in a weight ratio of 45:55. Here, the content of the additive is 2 wt% based on 100 wt% of the total weight of the liquid electrolyte. Based on 100 wt% of the total content of FEC, additive, and DEC, the content of FEC is 46 wt%, the content of the additive is 2 wt%, and the content of DEC is 52 wt%.

[0301] <Chemical Formula 2>

[0302]

[0303] Comparative Manufacturing Example 1-16

[0304] An electrolyte was manufactured in the same manner as in Manufacturing Example 1, except that each of the compounds of the following chemical formulas 9 to 24 was used as an electrolyte additive.

[0305] <Chemical Formula 9> <Chemical Formula 10>

[0306]

[0307] <Chemical Formula 11>

[0308]

[0309] <Chemical Formula 12> <Chemical Formula 13>

[0310]

[0311] <Chemical Formula 14>

[0312]

[0313]

[0314] <Chemical Formula 15> <Chemical Formula 16>

[0315]

[0316] <Chemical Formula 17>

[0317]

[0318] <Chemical Formula 18> <Chemical Formula 19>

[0319]

[0320] <Chemical Formula 20>

[0321]

[0322] <Chemical Formula 21> <Chemical Formula 22>

[0323]

[0324] <Chemical Formula 23> <Chemical Formula 24>

[0325]

[0326] The electrolytes of Comparative Examples 2 to 16 used the same amount of lithium salt and organic solvent as the electrolyte of Comparative Example 1.

[0327] Lithium metal batteries were used as lithium secondary batteries.

[0328] (Manufacturing of lithium metal batteries)

[0329] Example 1: Electrolyte (additive of chemical formula 2 (2 wt%), 1M LiPF6, EC:EMC:DMC (4:3:3))

[0330] A polyethylene single film with a thickness of 20 μm was laminated as a separator on a copper foil with a thickness of 10 μm, which was a negative current collector, and a positive electrode was laminated on the other side of the separator to manufacture a laminate. A lithium metal battery was manufactured by injecting the liquid electrolyte of Manufacturing Example 1 into the prepared laminate.

[0331] Lithium metal batteries have a cathode / separator / negative current collector structure.

[0332] Li 1.04 Ni 0.88 Co 0.1 Al0.02 O2 powder and carbon conductive material (Super-P; Timcal Ltd.) were uniformly mixed at a weight ratio of 90:5, and then a PVDF (polyvinylidene fluoride) binder solution was added to prepare a positive electrode active material slurry so that the weight ratio of active material:carbon conductive material:binder = 95.5:2:2.5.

[0333] The manufactured slurry was coated on a 15 ㎛ thick aluminum substrate using a coater, dried under reduced pressure at 120°C, and rolled using a roll press to form a sheet to manufacture a positive electrode.

[0334] Example 2: Electrolyte (additive of chemical formula 3 (2 wt%), 1M LiPF6, EC:EMC:DMC (4:3:3))

[0335] An electrolyte and a lithium metal battery were manufactured in the same manner as in Example 1, except that the electrolyte of Manufacturing Example 2 was used as the liquid electrolyte.

[0336] Example 3: Electrolyte (additive of chemical formula 4 (2 wt%), 1M LiPF6, EC:EMC:DMC (4:3:3))

[0337] An electrolyte and a lithium metal battery were manufactured in the same manner as Example 1, except that the electrolyte of Manufacturing Example 3 was used as the liquid electrolyte.

[0338] Example 4: Electrolyte (additive of formula 5 (2 wt%), 1M LiPF6, EC:EMC:DMC (4:3:3))

[0339] An electrolyte and a lithium metal battery were manufactured in the same manner as Example 1, except that the electrolyte of Manufacturing Example 4 was used as the liquid electrolyte.

[0340] Example 5: Electrolyte (additive of chemical formula 6 (2 wt%), 1M LiPF6, EC:EMC:DMC (4:3:3))

[0341] An electrolyte and a lithium metal battery were manufactured in the same manner as Example 1, except that the electrolyte of Manufacturing Example 5 was used as the liquid electrolyte.

[0342] Example 6: Electrolyte (additive of formula 2 (10 wt%), 1M LiPF6, EC:EMC:DMC (4:3:3))

[0343] An electrolyte and a lithium metal battery were manufactured in the same manner as in Example 1, except that the electrolyte of Manufacturing Example 6 was used as the liquid electrolyte.

[0344] Example 7: Electrolyte (additive of formula 2 (5 wt%), 1M LiPF6, EC:EMC:DMC (4:3:3))

[0345] An electrolyte and a lithium metal battery were manufactured in the same manner as Example 1, except that the electrolyte of Manufacturing Example 7 was used as the liquid electrolyte.

[0346] Example 8: Electrolyte (additive of formula 2 (2 wt%), FEC and DEC in a weight ratio of 42:48, 0.6 M LiDFOB and 0.6 M LiBF4)

[0347] A polyethylene single film with a thickness of 20 μm was laminated as a separator on a copper foil with a thickness of 10 μm, which was a negative current collector, and a positive electrode was laminated on the other side of the separator to manufacture a laminate. A lithium metal battery was manufactured by injecting the liquid electrolyte of Manufacturing Example 8 into the prepared laminate.

[0348] Lithium metal batteries have a cathode / separator / negative current collector structure.

[0349] Li 1.04 Ni 0.88 Co 0.1 Al 0.02 O2 powder and carbon conductive material (Super-P; Timcal Ltd.) were uniformly mixed at a weight ratio of 90:5, and then a PVDF (polyvinylidene fluoride) binder solution was added to prepare a positive electrode active material slurry so that the weight ratio of active material:carbon conductive material:binder = 95.5:2:2.5.

[0350] The manufactured slurry was coated on a 15 ㎛ thick aluminum substrate using a coater, dried under reduced pressure at 120°C, and rolled using a roll press to form a sheet to manufacture a positive electrode.

[0351] Comparative Example 1-16

[0352] A lithium metal battery was manufactured in the same manner as Example 1, except that the electrolytes of Comparative Manufacturing Examples 1 to 16 were used instead of the electrolyte of Manufacturing Example 1 as the electrolyte.

[0353] Evaluation Example 1: Oxidation Reaction Potential

[0354] The electrolytes of Manufacturing Examples 1 to 5 and the electrolytes of Comparative Manufacturing Examples 1 to 16 were each measured at a potential at which oxidation current was confirmed while increasing the oxidation reaction potential by 5 mV using a Pt electrode. The results of the oxidation reaction potential measurement are shown in Table 1 below.

[0355] Evaluation Example 2: High-temperature storage (HF concentration)

[0356] In order to evaluate the electrolyte stability of the lithium secondary batteries according to Examples 1-5 and Comparative Examples 1 to 16, each lithium secondary battery was left in a state of charge (SOC, state of charge = 100%) at 60°C for 7 days, and the HF concentration during storage (leaving) at high temperature (60°C) was evaluated by the following method.

[0357] 400 ppm of H2O was added to each of the electrolytes of Manufacturing Examples 1 to 5 and the electrolytes of Comparative Manufacturing Examples 1 to 16, and then the peak current at 2.6 V, which is the HF reduction potential, was converted to the ref material after measurement based on the Randles-Sevcik equation. The results of the HF concentration measurement are shown in Table 1 below.

[0358] Dispersion reaction potential (V) HF concentration after high temperature storage (ppm) Dispersion reaction potential (V) HF concentration after high temperature storage (ppm) Example 14.52212 Comparative example 74.28712 Example 24.6748 Comparative example 84.75252 Example 34.8929 Comparative example 95.07764 Example 45.314 Comparative example 104.92304 Example 55.323 Comparative example 114.75392 Comparative example 15.28448 Comparative example 124.89396 Comparative example 25.16360 Comparative example 134.9998 Comparative example 34.52336 Comparative example 144.91684 Comparative example 45.00128Comparative Example 154.92824Comparative Example 54.09568Comparative Example 165.04384Comparative Example 63.70772

[0359] Based on Table 1, the electrolytes of Examples 4 and 5 had higher oxidation reaction potentials than the electrolytes of Comparative Examples 1 to 16, thereby exhibiting improved oxidation resistance and being useful as high-voltage solvents. In addition, the electrolytes of Examples 1 to 3 had higher oxidation reaction potentials than the electrolytes of Comparative Examples 3 and 5-7, thereby exhibiting improved oxidation resistance.

[0360] In comparison, it was found that the electrolytes of comparative manufacturing examples 1-2, 4, 8, and 9-16 had high oxidation reaction potentials, but the HF concentration after high-temperature storage was very high, making application difficult.

[0361] In addition, it was found that the electrolyte additives used in the manufacture of lithium metal batteries of Examples 1 to 5 had a significantly reduced HF concentration after high-temperature storage compared to the electrolyte additives of Comparative Examples 1 to 16. From this, it was found that the electrolyte additives of Examples 1 to 5 had an excellent effect of suppressing side reactions with the electrolyte when stored at high temperatures.

[0362] Evaluation Example 3: High Temperature (45℃) Lifespan

[0363] The charge / discharge characteristics of the lithium metal batteries of Examples 1 to 5 and Comparative Examples 1 and 7 were evaluated under the following conditions.

[0364] The battery was charged at a constant current of 0.1 C rate at 45°C until the voltage reached 4.3 V (vs. Li), and then cut-off at a current of 0.05 C rate while maintaining 4.3 V in constant voltage mode. Subsequently, the battery was discharged at a constant current of 0.1 C rate until the voltage reached 3.0 V (vs. Li) during discharge (formation cycle).

[0365] The lithium metal battery that had undergone the Mars cycle was charged at a constant current of 0.2 C rate at 45°C until the voltage reached 4.3 V (vs. Li), and then cut-off at a current of 0.05 C rate while maintaining 4.3 V in constant voltage mode. Subsequently, the battery was discharged at a constant current of 0.5 C rate until the voltage reached 3.0 V (vs. Li) (1 st cycle). These cycles are 200 th The cycle was repeated under the same conditions.

[0366] In all charge / discharge cycles, a 10-minute pause was observed after each charge / discharge cycle. The number of cycles was evaluated, and the results are shown in Table 3 below.

[0367] The cycle count is the number of cycles required for the discharge capacity to decrease to 90% of the standard capacity after the second cycle. A higher cycle count is considered to indicate better life characteristics.

[0368] Lifespan (SOH90@) Example 180 Example 272 Example 379 Example 4 > 150 Example 5 > 150 Comparative Example 160 Comparative Example 745

[0369] As shown in Table 2, the lithium metal batteries of Comparative Examples 1 and 7 had a reduced lifespan due to lithium and electrolyte side reactions resulting from dendrite growth.

[0370] In comparison, the lithium metal batteries of Examples 1 to 5 had improved lifespans, unlike the lithium metal batteries of Comparative Examples 1 and 7.

[0371] While exemplary embodiments have been described in detail with reference to the attached drawings, the present invention is not limited to these examples. It is self-evident that those skilled in the art to which the present invention pertains can devise various modifications or variations within the scope of the technical concepts described in the patent claims, and these also naturally fall within the technical scope of the present invention.

Claims

1. In a lithium secondary battery including a positive electrode, a negative electrode current collector, and an electrolyte disposed between the positive electrode and the negative electrode current collector, A lithium secondary battery, wherein the electrolyte comprises an additive represented by the following chemical formula 1: <Chemical formula 1> In chemical formula 1, A represents a chemical bond or -(CH 2 ) k -(k is an integer from 1 to 3), a and b are independently 0 or integers from 1 to 3, However, this excludes the case where a and b are both 0. R, R 1 , R 2 and R 3 are independently hydrogen, a C1 to C10 alkyl group, or F.

2. A lithium secondary battery in claim 1, wherein the additive represented by the chemical formula 1 is at least one compound selected from compounds represented by the following chemical formulas 2 to 8. <Chemical Formula 2> <Chemical Formula 3> <Chemical Formula 4> <Chemical Formula 5> <Chemical Formula 6> <Chemical Formula 7> <Chemical Formula 8> 3. A lithium secondary battery in paragraph 1, wherein the content of the additive represented by the chemical formula 1 is 0.1 to 10 wt% based on the total weight of the electrolyte.

4. A lithium secondary battery according to claim 1, wherein the oxidation reaction potential of the electrolyte is 4.5 to 5.4 V.

5. In the first paragraph, the electrolyte contains a lithium salt, The concentration of the lithium salt is 0.01 to 5.0 M, The above lithium salt is LiPF 6 , LiBF 4 , LiSbF 6 , LiAsF 6 , LiClO 4 , LiAlO 2 , LiAlCl 4 , LiPO 2 F 2 , LiCl, LiI, LiN(SO 3 C 2 F 5 ) 2 , Li(FSO 2 ) 2 N, LiC 4 F 9 SO 3 , LiN(C x F 2x+1 SO 2 )(C y F 2y+1 SO 2 ) (x and y are independently integers from 1 to 20), a lithium secondary battery comprising one or more selected from lithium trifluoromethane sulfonate, lithium tetrafluoroethane sulfonate, lithium difluorobis(oxalato)phosphate (LiDFOB), and lithium bis(oxalato)borate (LiBOB).

6. In paragraph 1, the electrolyte contains a lithium salt, The above lithium salt comprises a first lithium salt and a second lithium salt, wherein the first lithium salt and the second lithium salt independently comprise a fluorine-containing borate lithium salt, The above fluorine-containing borate lithium salt is LiBF 4 , LiBF 3 (C 2 F 5 ), a lithium battery comprising a compound represented by the following chemical formulas 1-1 to 12-1 or a combination thereof. <Chemical Formula 1-1> <Chemical Formula 1-2> <Chemical Formula 1-3> <Chemical Formula 1-4> <Chemical Formula 1-5> <Chemical Formula 1-6> <Chemical Formula 1-7> <Chemical Formula 1-8> <Chemical Formula 1-9> <Chemical Formula 1-10> <Chemical Formula 1-11>> <Chemical Formula 1-12>> .

7. In the 6th paragraph, the first lithium salt is LiBF 4 and wherein the second lithium salt comprises a compound selected from compounds represented by the chemical formulas 1-1 to 12, The contents of the first lithium salt and the second lithium salt are each greater than 0 and less than or equal to 1.2 M, A lithium secondary battery, wherein the weight ratio of the first lithium salt and the second lithium salt is 1:9 to 9:

1.

8. In paragraph 1, the electrolyte contains a lithium salt, The above lithium salts are lithium difluoro(oxalato)borate (LiDFOB) and lithium tetrafluoroborate (LiBF). 4 ) and The above lithium difluorodioxalatoborate (LiDFOB) and lithium tetrafluoroborate (LiBF) 4 ) A lithium secondary battery having a mixing weight ratio of 1:2 to 1:0.

3.

9. In paragraph 1, the electrolyte contains an organic solvent, A lithium secondary battery, wherein the organic solvent comprises at least one selected from the group consisting of fluoroethylene carbonate, dimethyl carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl isopropyl carbonate, dipropyl carbonate, dibutyl carbonate, propylene carbonate (PC), ethylene carbonate (EC), fluoroethylene carbonate (FEC), vinylene carbonate (VC), vinylethylene carbonate (VEC), butylene carbonate, ethyl propionate, ethyl butyrate, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, gamma-valerolactone, gamma-butyrolactone, and tetrahydrofuran.

10. In the first paragraph, the electrolyte further includes a nitrile compound, A lithium secondary battery, wherein the nitrile compound is butyronitrile, valeronitrile, propionitrile, acetonitrile, or a combination thereof.

11. A lithium secondary battery in the first paragraph, wherein the negative electrode collector comprises copper (Cu), nickel (Ni), nickel-coated copper, stainless steel (SUS), iron (Fe), cobalt (Co), or an alloy thereof.

12. A lithium secondary battery, wherein the HF concentration (ppm) of the lithium secondary battery including the electrolyte in the first paragraph is 20 ppm or less after storage at a high temperature (60°C).

13. A lithium secondary battery further comprising a lithium metal layer between the negative electrode current collector and the electrolyte in the first paragraph.

14. A lithium secondary battery in accordance with claim 13, wherein the lithium metal layer comprises a lithium metal foil, a lithium metal powder, a lithium alloy foil, a lithium alloy powder, or a combination thereof.

15. In the 14th paragraph, the lithium alloy foil and lithium alloy powder contain lithium and a first metal, A lithium secondary battery, wherein the first metal is indium (In), silicon (Si), gallium (Ga), tin (Sn), aluminum (Al), titanium (Ti), zirconium (Zr), niobium (Nb), germanium (Ge), antimony (Sb), bismuth (Bi), gold (Au), platinum (Pt), palladium (Pd), magnesium (Mg), silver (Ag), zinc (Zn), nickel, iron, cobalt, chromium, cesium, sodium, potassium, calcium, yttrium, bismuth, tantalum, hafnium, barium, vanadium, strontium, lanthanum or a combination thereof.

16. A lithium secondary battery according to claim 1, wherein the lithium secondary battery further includes a separator.

17. In the 16th paragraph, the separator comprises a porous substrate, The above porous substrate is a woven fabric or non-woven fabric, The above porous substrate includes an olefin resin, a fluorine resin, an ester resin, an imide resin, an acrylic resin, a cellulose resin or a combination thereof. The above olefin resin includes polyethylene, polypropylene or a combination thereof, The above fluorine resin includes polyvinylidene fluoride, polytetrafluoroethylene or a combination thereof, The above ester resin includes polyethylene terephthalate, polybutylene terephthalate or a combination thereof, The above imide resin includes polyamideimide, polyetherimide or a combination thereof, The above acrylic resin comprises polyacrylonitrile, polyacrylate or a combination thereof, A lithium secondary battery, wherein the cellulose-based resin comprises carboxymethyl cellulose, microbial cellulose, plant cellulose, animal cellulose, or a combination thereof.

18. In the first paragraph, a negative electrode active material layer is included between the negative electrode collector and the electrolyte, A lithium secondary battery, wherein the negative active material layer contains a carbon-based material; a mixture of a carbon-based material and at least one selected from a metal and a metalloid; a composite of a carbon-based material and at least one selected from a metal and a metalloid; or a combination thereof.

19. In the first paragraph, the positive electrode includes a positive electrode current collector and a positive electrode active material layer, At least one of the positive electrode current collector and the negative electrode current collector includes a base film and a metal layer disposed on one or both sides of the base film, The above base film contains a polymer, The above polymer comprises polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyimide (PI) or a combination thereof, A lithium secondary battery, wherein the metal layer comprises indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or an alloy thereof.

20. An electrolyte for a lithium secondary battery comprising an additive represented by the following chemical formula 1: <Chemical formula 1> In chemical formula 1, A represents a chemical bond or -(CH2) k -(k is an integer from 1 to 3), a and b are independently 0 or integers from 1 to 3, However, this excludes the case where a and b are both 0. R, R 1 , R 2 and R 3 are independently hydrogen, a C1 to C10 alkyl group, or F.

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