Electrolyte for rechargeable lithium battery and rechargeable lithium battery including same

Abstract

The present disclosure relates to an electrolyte for a rechargeable lithium battery and a rechargeable lithium battery including the same. An electrolyte for a rechargeable lithium battery includes a lithium salt; a non-aqueous organic solvent; a first additive represented by Chemical Formula 1; and a second additive represented by Chemical Formula 2: A rechargeable lithium battery of Chemical Formula 1 # imgabs0 # Chemical Formula 2 # imgabs1 # includes a positive electrode including a positive electrode active material; a negative electrode containing a negative electrode active material; and an electrolyte solution.

Description

Technical Field

[0001] One or more embodiments of the present disclosure relate to an electrolyte for a rechargeable lithium battery, and discloses a rechargeable lithium battery including the same. Background Art

[0002] Recently, with the rapid popularization of the use of electronic devices (such as mobile phones, laptop computers and / or electric vehicles) using batteries, the demand for rechargeable batteries with relatively high energy density and relatively high capacity has been rapidly increasing. Accordingly, research and development to improve the performance of rechargeable lithium batteries is being actively carried out.

[0003] A rechargeable lithium battery includes positive and negative electrodes containing active materials capable of inserting and deinserting lithium ions, and an electrolyte, and generates electric energy through oxidation and reduction reactions if (e.g., when) lithium ions are inserted into / deinserted from the positive and negative electrodes.

[0004] One of the latest development directions of rechargeable lithium batteries has been to improve high voltage and / or high temperature characteristics. In the related art, at relatively high voltage and / or relatively high temperature, rechargeable lithium batteries may experience reduced cycle life and / or increased resistance. Summary of the invention

[0005] One or more aspects of embodiments of the present disclosure are directed to an electrolyte that can be used in a rechargeable lithium battery and that improves high voltage and / or high temperature characteristics of the rechargeable lithium battery.

[0006] One or more aspects of embodiments of the present disclosure are directed to a rechargeable lithium battery including an electrolyte.

[0007] Additional aspects will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the presented embodiments of the disclosure.

[0008] According to one or more embodiments of the present disclosure, an electrolyte that can be used for a rechargeable lithium battery includes a lithium salt; a non-aqueous organic solvent; a first additive represented by Chemical Formula 1; and a second additive represented by Chemical Formula 2:

[0009] Chemical formula 1

[0010]

[0011] Chemical formula 2

[0012]

[0013] An electrolyte (eg, for a rechargeable lithium battery) according to one or more embodiments may improve high voltage and / or high temperature characteristics of the rechargeable lithium battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] These and / or other aspects will become apparent and readily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0015] Figure 1 to Figure 4 Each is a schematic diagram showing a rechargeable lithium battery according to one or more embodiments.

[0016] Reference numerals

[0017] 100: Rechargeable lithium battery 10: Positive electrode

[0018] 11: Positive electrode lead tab 12: Positive terminal

[0019] 20: Negative electrode 21: Negative electrode lead lug

[0020] 22: Negative terminal 30: Separator

[0021] 40: electrode assembly 50: shell

[0022] 60: Sealing member 70: Electrode terminal piece

[0023] 71: Positive electrode terminal tab 72: Negative electrode terminal tab DETAILED DESCRIPTION

[0024] Hereinafter, embodiments of the present disclosure will be described in more detail. However, these embodiments are examples, the present disclosure is not limited thereto, and the present disclosure is defined by the scope of the appended claims and their equivalents.

[0025] As used herein, if (for example, when) no specific limitations are otherwise provided, it will be understood that if (for example, when) an element (such as a layer, film, region or substrate) is referred to as being "on" another element (such as a layer, film, region or substrate), it can be directly on the other element (such as a layer, film, region or substrate) (for example, without any intervening elements therebetween), or intervening elements may also be present.

[0026] As used herein, if (for example, when) no specific limitation is provided in other ways, the singular may also include the plural. In one or more embodiments, unless otherwise indicated, "A or B" may mean "including A, including B, or including A and B".

[0027] As used herein, "combinations thereof" may refer to mixtures, stacks, composites, copolymers, alloys, blends, and / or reaction products of the components.

[0028] As used herein, “active mass density of the negative electrode” is a value calculated by dividing the weight of components (active material, conductive material, binder, etc.) in the negative electrode except for the negative electrode current collector by the volume of the components.

[0029] As used herein, if (e.g., when) no definition is otherwise provided, in a chemical formula, if (e.g., when) a chemical bond is not drawn at a position where a chemical bond should be drawn, a hydrogen atom is bonded to that position.

[0030] As used herein, "fluoroalkyl" refers to an alkyl group in which one, some or all of the hydrogen atoms are replaced by fluorine atoms.

[0031] As used herein, "perfluoroalkyl" refers to an alkyl group in which all hydrogen atoms are replaced by fluorine atoms.

[0032] It will be understood that although the terms first, second, etc. may be used to describe various elements in this article, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element. Therefore, without departing from the teachings of the present invention, the first element may be referred to as the second element. Similarly, the second element may be referred to as the first element.

[0033] It will be further understood that when used in this specification, the terms “includes,” “including,” “comprises,” and / or “comprising” indicate the presence of stated features, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and / or groups thereof.

[0034] As used herein, the terms "use," "using," and "used" may be considered synonymous with the terms "utilize," "utilizing," and "utilized," respectively.

[0035] As used herein, expressions such as "at least one of," "one of," and "selected from," when preceding / following a list of elements, modify the entire list of elements and do not modify the individual elements of the list. For example, "selected from at least one of a, b, and c," "at least one of a, b, and c," and the like may indicate only a, only b, only c, both a and b (e.g., simultaneously), both a and c (e.g., simultaneously), both b and c (e.g., simultaneously), all of a, b, and c, or variations thereof.

[0036] As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0037] Further, when describing embodiments of the present disclosure, the use of “may” refers to “one or more embodiments of the present disclosure.”

[0038] As used herein, the terms "substantially," "about," and similar terms are used as terms of approximation rather than as terms of degree, and are intended to account for the inherent deviations in measured or calculated values ​​that will be recognized by one of ordinary skill in the art. "About" or "approximately" and similar terms as used herein include the stated value and mean within an acceptable range of deviations of the particular value determined by one of ordinary skill in the art taking into account the measurement in question and the errors associated with the measurement of the particular quantity (i.e., the limitations of the measurement system). For example, "about" may mean within one or more standard deviations, or within ±30%, ±20%, ±10%, or ±5% of the stated value.

[0039] Any numerical range set forth in this article is intended to include all sub-ranges of the same numerical precision falling within the set forth range. For example, the range of "1.0-10.0" is intended to be included between the set forth minimum value 1.0 and the set forth maximum value 10.0 (and including the end value), that is, all sub-ranges (such as, for example, 2.4-7.6) having a minimum value equal to or greater than 1.0 and a maximum value equal to or less than 10.0. Any maximum numerical limit set forth in this article is intended to include all lower numerical limits falling therein, and any minimum numerical limit set forth in this specification is intended to include all higher numerical limits falling therein. Accordingly, the applicant reserves the right to modify this specification (including claims) to explicitly set forth any sub-range falling within the range explicitly set forth in this article.

[0040] Electrolyte

[0041] Some embodiments provide an electrolyte for a rechargeable lithium battery, which includes a lithium salt; a non-aqueous organic solvent; a first additive represented by Chemical Formula 1; and a second additive represented by Chemical Formula 2:

[0042] Chemical formula 1

[0043]

[0044] Chemical formula 2

[0045]

[0046] The first additive functions as a surfactant having both a hydrophilic group and a hydrophobic group in one molecule (eg, simultaneously).

[0047] The first additive includes a keto group at the center and fluorine atoms and / or fluoroalkyl groups having 1 to 10 carbon atoms at both sides. Herein, the keto group is a hydrophilic group, and the fluorine atoms and fluoroalkyl groups having 1 to 10 carbon atoms are each a hydrophobic group.

[0048] Accordingly, if (for example, when) the electrolyte including the first additive is used, the wettability of the electrolyte to the positive electrode and the negative electrode can be improved, and the lithium cation (Li + ) can be uniformly (substantially uniformly) formed at the interface between the positive electrode and the electrolyte, and a suitably stable SEI film can be formed at the interface between the negative electrode and the electrolyte, thereby inhibiting or reducing the precipitation of lithium dendrites.

[0049] In one or more embodiments, the second additive is an oxalatoborate compound substituted with a fluorine group, wherein the fluorine group is used to properly stabilize the lithium salt (eg, LiPF6).

[0050] Accordingly, if (for example, when) an electrolyte including the second additive is used, the generation of HF can be suppressed or reduced, and the dissolution of transition metals from the positive electrode active material and / or damage to the SEI film at the interface between the negative electrode and the electrolyte can be prevented or reduced.

[0051] Therefore, if (for example, when) an electrolyte including the first additive and the second additive is used, the dissolution of transition metals from the positive electrode active material can be inhibited or reduced, and a suitably stable SEI film can be formed on the negative electrode surface, thereby improving the relatively high voltage and / or relatively high temperature characteristics of the rechargeable lithium battery.

[0052] Hereinafter, an electrolyte according to one or more embodiments for a rechargeable lithium battery will be described in more detail.

[0053] First Additive

[0054] In Chemical Formula 1, R 1 and R 2 Each independently may be a fluorine atom or a C1-C10 fluoroalkyl group.

[0055] For example, R 1It may be a fluoroalkyl group having 2 carbon atoms, for example, a perfluoroalkyl group having 2 carbon atoms.

[0056] In some embodiments, R 2 It may be a fluoroalkyl group having 3 carbon atoms, a fluoroalkyl group having 3 carbon atoms, or a perfluoroalkyl group.

[0057] The first additive can be represented by Chemical Formula 1-1:

[0058] Chemical formula 1-1

[0059]

[0060] In Chemical Formula 1-1, R 11 ~R 15 are each a hydrogen atom or a fluorine atom, provided that R 11 ~R 15 At least one of is a fluorine atom; and R 21 ~R 27 are each a hydrogen atom or a fluorine atom, provided that R 21 ~R 27 At least one of them is a fluorine atom.

[0061] The first additive is represented by chemical formula 1-1-1:

[0062] Chemical formula 1-1-1

[0063]

[0064] Second additive

[0065] In chemical formula 2, R 3 and R 4 Each of them may be independently a halogen atom or a C1-C10 fluoroalkyl group. In this context, the halogen atom may be a fluorine atom, a chlorine atom, a bromine atom and / or an iodine atom.

[0066] For example, R 3 and R 4 Both may (eg, simultaneously) be fluorine atoms.

[0067] A representative example of the second additive is represented by Chemical Formula 2-1:

[0068] Chemical formula 2-1

[0069]

[0070] The second additive represented by Chemical Formula 2-1 is lithium difluoro(oxalato)borate (LiDFOB).

[0071] Content (eg, amount) of the first additive and the second additive

[0072] The first additive may be included in an amount of about 0.1 wt % to about 10 wt %, about 0.5 to about 5 wt %, or about 1 wt % to about 3 wt % based on 100 wt % of the total amount of the electrolyte.

[0073] If the first additive is included in excess of the above range, the viscosity of the electrolyte including the first additive may be excessively increased (or undesirably increased), and the wettability of the electrolyte to the positive electrode and the negative electrode may actually be reduced. If the first additive is included in a small amount below the above range, the effect of the first additive as a surfactant may be minimal or inappropriate.

[0074] The second additive may be included in an amount of about 0.1 wt % to about 5 wt %, about 0.3 wt % to about 4 wt %, or about 0.5 wt % to about 2 wt % based on 100 wt % of the total amount of the electrolyte.

[0075] If the second additive is included in excess of the above range, a side reaction may occur. If the second additive is included in a small amount below the above range, the effect of the second additive as a surfactant may be minimal or inappropriate.

[0076] The weight ratio of the first additive to the second additive in the electrolyte may be about 1:5 to about 10:1, about 1:2 to about 5:1, or about 1:1 to about 4:1.

[0077] When the weight ratio of the first additive to the second additive in the electrolyte is within these ranges, the effects of the first additive and the second additive can be coordinated.

[0078] Non-aqueous organic solvent

[0079] The nonaqueous organic solvent serves as a medium for transporting ions participating in the electrochemical reaction of the battery.

[0080] The non-aqueous organic solvent may include a carbonate-based solvent, an ester-based solvent, an ether-based solvent, a ketone-based solvent, an alcohol-based solvent, an aprotic solvent, and / or (eg, any appropriate) combinations thereof.

[0081] Carbonate solvents may include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), ethyl methyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), etc. Ester solvents may include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, propyl propionate, decanoic acid lactone, mevalonolactone, valerolactone, caprolactone, etc.

[0082] Ether solvents may include dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, tetrahydrofuran, etc. Ketone solvents may include cyclohexanone, etc. Alcohol solvents may include ethanol, isopropanol, etc., and aprotic solvents may include nitrile (such as R-CN (wherein R is a C2-C20 straight chain, branched chain or cyclic hydrocarbon group, and includes a double bond, an aromatic ring or an ether group)), amide (such as dimethylformamide), dioxolane (such as 1,3-dioxolane and / or 1,4-dioxolane), sulfolane, etc.

[0083] The nonaqueous organic solvent may be used alone or in combination of two or more thereof.

[0084] In the case of being used in combination of two or more of the nonaqueous organic solvents, the nonaqueous organic solvent may include a carbonate-based solvent and a propionate-based solvent.

[0085] The propionate-based solvent may be included in an amount of greater than or equal to about 70 volume % based on 100 volume % of the total amount of the non-aqueous organic solvent. In this case, high voltage and / or high temperature characteristics of a rechargeable lithium battery may be improved.

[0086] For example, the nonaqueous organic solvent may be a mixed solvent of ethylene carbonate (EC), propylene carbonate (PC), and propyl propionate (PP).

[0087] Lithium salts

[0088] The lithium salt dissolved in the nonaqueous organic solvent supplies lithium ions in the battery, ensures (or facilitates) the basic operation of the rechargeable lithium battery, and improves the transport of lithium ions between the positive electrode and the negative electrode.

[0089] For example, LiPF6 may be used as the lithium salt, and its structure may be stabilized by the second additive.

[0090] The concentration of the lithium salt may be about 0.1M to about 2.0M.

[0091] Rechargeable lithium battery

[0092] Some embodiments of the present disclosure provide a rechargeable lithium battery including a positive electrode including a positive electrode active material; a negative electrode including a negative electrode active material; and an electrolyte.

[0093] Because the rechargeable lithium battery according to one or more embodiments includes the electrolyte of the aforementioned embodiments, high voltage and / or high temperature characteristics may be improved.

[0094] Hereinafter, a description repeated with the above will be omitted (eg, will not be provided), and a rechargeable lithium battery according to one or more embodiments will be described in more detail.

[0095] Active mass density of negative electrode

[0096] Conventionally known rechargeable lithium batteries may utilize a negative electrode having an active mass density of less than about 1.7 g / cc, but a rechargeable lithium battery according to one or more embodiments of the present disclosure utilizes a negative electrode having an active mass density (e.g., a mixture density) greater than or equal to about 1.7 g / cc.

[0097] The upper limit of the active mass density for the negative electrode is not particularly limited, but may be less than or equal to about 2.0 g / cc, less than or equal to about 1.9 g / cc, or less than or equal to about 1.8 g / cc.

[0098] Charging upper limit voltage

[0099] Since the rechargeable lithium battery according to one or more embodiments includes the electrolyte of the aforementioned embodiments, an increase in battery thickness and a decrease in cycle life may be suppressed or reduced even at a relatively high voltage.

[0100] For example, a rechargeable lithium battery may have a charge upper limit voltage greater than or equal to about 4.5V.

[0101] Positive electrode active material

[0102] The positive electrode active material may be a compound capable of inserting and extracting lithium (lithiated inserting compound). For example, a composite oxide of lithium and one or more types (species) of metals selected from cobalt, manganese, nickel and combinations thereof (eg, any appropriate combination thereof) may be used.

[0103] The composite oxide may be a lithium transition metal composite oxide, and non-limiting examples may include lithium nickel-based oxides, lithium cobalt-based oxides, lithium manganese-based oxides, lithium iron phosphate-based compounds, cobalt-free lithium nickel manganese-based oxides and / or (e.g., any appropriate) combinations thereof.

[0104] As an example, a compound represented by any one of the following chemical formulas (eg, selected from any one of the following chemical formulas) may be used. 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 a Ni 1-b-c Cob 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 NeG 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 Mn 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); and / or Li a FePO4(0.90≤a≤1.8).

[0105] In the above chemical formula, A may be Ni, Co, Mn, and / or (e.g., any suitable) combination thereof; X may be Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, and / or (e.g., any suitable) combination thereof; D may be O, F, S, P, and / or (e.g., any suitable) combination thereof; G may be Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, and / or (e.g., any suitable) combination thereof; and L 1 It may be Mn, Al, and / or (eg, any suitable) combination thereof.

[0106] As an example, based on 100 mol% of metals other than lithium in the lithium transition metal composite oxide, the positive electrode active material may have a nickel content (e.g., amount) of greater than or equal to about 80 mol%, greater than or equal to about 85 mol%, greater than or equal to about 90 mol%, greater than or equal to about 91 mol%, or greater than or equal to about 94 mol%, and may be a high nickel-based positive electrode active material having a nickel content (e.g., amount) of less than or equal to about 99 mol%. The high nickel-based positive electrode active material can achieve a relatively high capacity and can be applied to high-capacity, high-density rechargeable lithium batteries.

[0107] The positive electrode active material may be, for example, a lithium nickel-based oxide represented by Chemical Formula 11, a lithium cobalt-based oxide represented by Chemical Formula 12, a lithium iron phosphate-based compound represented by Chemical Formula 13, a cobalt-free lithium nickel manganese-based oxide represented by Chemical Formula 14, and / or a combination thereof (e.g., any appropriate one).

[0108] Chemical formula 11

[0109] Li a1 Ni x1 M 1 y1 M 2 z1 O 2-b1 X b1 .

[0110] In Chemical Formula 11, 0.9≤a1≤1.8, 0.3≤x1≤1, 0≤y1≤0.7, 0≤z1≤0.7, 0.9≤x1+y1+z1≤1.1, and 0≤b1≤0.1, M 1 and M 2 Each of the above elements may be independently one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W and Zr, and X may be one or more elements selected from the group consisting of F, P and S.

[0111] In Chemical Formula 11, 0.6≤x1≤1, 0≤y1≤0.4, and 0≤z1≤0.4, or 0.8≤x1≤1, 0≤y1≤0.2, and 0≤z1≤0.2.

[0112] Chemical formula 12

[0113] Li a2 Co x2 M 3 y2 O 2-b2 X b2 .

[0114] In Chemical Formula 12, 0.9 ≤ a2 ≤ 1.8, 0.7 ≤ x2 ≤ 1, 0 ≤ y2 ≤ 0.3, 0.9 ≤ x2 + y2 ≤ 1.1, and 0 ≤ b2 ≤ 0.1, M 3 may be one or more elements selected from Al, B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mn, Mo, Ni, Se, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr, and X may be one or more elements selected from F, P, and S.

[0115] Chemical Formula 13

[0116] Li a3 Fe x3 M 4 y3 PO 4-b3 X b3 。

[0117] In Chemical Formula 13, 0.9 ≤ a3 ≤ 1.8, 0.6 ≤ x3 ≤ 1, 0 ≤ y3 ≤ 0.4, 0.9 ≤ x3 + y3 ≤ 1.1, and 0 ≤ b3 ≤ 0.1, M 4 may be one or more elements selected from Al, B, Ba, Ca, Ce, Co, Cr, Cu, Mg, Mn, Mo, Ni, Se, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr, and X may be one or more elements selected from F, P, and S.

[0118] Chemical Formula 14

[0119] Li a4 Ni x4 Mn y4 M 5 z4 O 2-b4 X b4 。

[0120] In Chemical Formula 14, 0.9 ≤ a4 ≤ 1.8, 0.8 ≤ x4 < 1, 0 < y4 ≤ 0.2, 0 ≤ z4 ≤ 0.2, 0.9 ≤ x4 + y4 + z4 ≤ 1.1, and 0 ≤ b4 ≤ 0.1. M 5 may be one or more elements selected from Al, B, Ba, Ca, Ce, Cr, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ti, V, W, and Zr, and X may be one or more elements selected from F, P, and S.

[0121] For example, the electrolyte of the foregoing embodiment can significantly improve the high-voltage and / or high-temperature characteristics of the battery by using the lithium cobalt-based oxide represented by Chemical Formula 12.

[0122] Positive electrode

[0123] The positive electrode for a rechargeable lithium battery may include a positive electrode current collector and a positive electrode active material layer on the positive electrode current collector. The positive electrode active material layer may include a positive electrode active material, and may further include a binder and / or a conductive material.

[0124] For example, the positive electrode may further include an additive that may function as a sacrificial positive electrode.

[0125] The content (eg, amount) of the positive electrode active material may be about 90 wt % to about 99 wt % based on 100 wt % of the positive electrode active material layer, and the content (eg, amount) of the binder and the conductive material may be about 0.5 wt % to about 5 wt %, respectively.

[0126] The binder is used to attach the positive electrode active material particles to each other well or properly, and also to attach the positive electrode active material to the positive electrode current collector well or properly. Examples of binders may include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, 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. as non-limiting examples.

[0127] Conductive materials can be used to impart electrical conductivity (e.g., electrical conductivity) to the electrodes. Any suitable material that does not cause chemical changes (e.g., does not cause undesirable chemical changes in a rechargeable lithium battery) and that appropriately conducts electrons can be used in the battery. Examples of conductive materials may include carbon-based materials (such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanofibers, and / or carbon nanotubes); metal-based materials in the form of metal powders or metal fibers including copper, nickel, aluminum, silver, etc.; conductive polymers (such as polyphenylene derivatives); and / or (e.g., any suitable) mixtures thereof.

[0128] Al foil may be used as a positive electrode current collector, but the present disclosure is not limited thereto.

[0129] Negative electrode active material

[0130] The negative electrode active material may be a material capable of reversibly intercalating / deintercalating lithium ions, lithium metal, a lithium metal alloy, a material capable of doping / dedoping lithium, and / or a transition metal oxide.

[0131] Materials capable of reversibly embedding / desorbing lithium ions may include carbonaceous negative electrode active materials, such as crystalline carbon, amorphous carbon, and / or combinations thereof (e.g., any suitable combination). The crystalline carbon may be graphite, such as amorphous, flaky, lamellar, spherical, and / or fibrous natural graphite and / or artificial graphite. The amorphous carbon may be soft carbon, hard carbon, mesophase pitch carbonized product, calcined coke, etc.

[0132] The lithium metal alloy may include lithium and at least one metal selected from Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn.

[0133] Materials capable of doping / dedoping lithium may be Si-based negative electrode active materials and / or Sn-based negative electrode active materials. The Si-based negative electrode active materials may include silicon, silicon-carbon composites, SiO x (0 < x ≤ 2), Si-Q alloys (where 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 / or combinations thereof (e.g., any suitable combination)). The Sn-based negative electrode active materials may include Sn, SnO x (0 < x ≤ 2) (e.g., SnO2), Sn-based alloys, and / or combinations thereof (e.g., any suitable combination).

[0134] The silicon-carbon composite may be a composite of silicon and amorphous carbon. According to one or more embodiments, the silicon-carbon composite may be or include silicon particles and amorphous carbon coated on the surface of the silicon particles. For example, the silicon-carbon composite may include secondary particles (cores) in which primary silicon particles are aggregated and an amorphous carbon coating (shell) on the surface of the secondary particles. The amorphous carbon may also be between the primary silicon particles, and, for example, the primary silicon particles may be coated with amorphous carbon. The secondary particles may be dispersed in an amorphous carbon matrix.

[0135] The silicon-carbon composite may further include crystalline carbon. For example, the silicon-carbon composite may include a core containing crystalline carbon and silicon particles and an amorphous carbon coating on the surface of the core.

[0136] The Si-based negative electrode active materials or the Sn-based negative electrode active materials may be used in combination with the carbonaceous negative electrode active materials.

[0137] Negative electrode

[0138] The negative electrode for a rechargeable lithium battery includes a negative electrode current collector and a negative electrode active material layer on the negative electrode current collector. The negative electrode active material layer includes negative electrode active materials and may further include a binder and / or a conductive material.

[0139] For example, the negative electrode active material layer may include about 90 wt % to about 99 wt % of the negative electrode active material, about 0.5 wt % to about 5 wt % of the binder, and about 0 wt % to about 5 wt % of the conductive material based on the total amount of the negative electrode active material layer.

[0140] The binder can be used to attach the negative electrode active material particles to each other well or appropriately, and also to attach the negative electrode active material to the negative electrode current collector well or appropriately. The binder may include a non-aqueous binder, an aqueous binder, a dry binder, and / or a combination thereof (e.g., any appropriate one).

[0141] The non-aqueous binder may include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide, and / or (eg, any suitable) combinations thereof.

[0142] The aqueous binder can be selected from styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluororubber, polyethylene oxide, polyvinyl pyrrolidone, polyepichlorohydrin, polyphosphazene, poly(meth)acrylonitrile, ethylene propylene diene copolymer, polyvinyl pyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol and / or (e.g., any suitable) combination thereof.

[0143] When the aqueous binder is used as a binder in the negative electrode active material layer, it may further include a cellulose compound capable of imparting viscosity. The cellulose compound includes one or more of carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose and alkali metal salts thereof. The alkali metal may be Na, K and / or Li.

[0144] The dry binder may be a polymer material capable of fiberization, and may be, for example, polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, and / or (eg, any appropriate) combinations thereof.

[0145] A conductive material is included to provide appropriate electrode conductivity, and any suitable conductive material may be used as the conductive material unless it causes undesirable chemical changes in the battery. Examples of the conductive material may be carbon-based materials (such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber, carbon nanotube, etc.); metal-based materials in the form of metal powder or metal fiber such as copper, nickel, aluminum silver, etc.; conductive polymers (such as polyphenylene derivatives); and / or (e.g., any suitable) mixtures thereof.

[0146] The negative electrode current collector may include one (e.g., any one) selected from copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, and / or (e.g., any appropriate) combination thereof, but the present disclosure is not limited thereto.

[0147] Diaphragm

[0148] Depending on the type or kind of rechargeable lithium battery, the separator may be present between the positive electrode and the negative electrode. The separator may include a polyethylene separator, a polypropylene separator, a polyvinylidene fluoride separator, or a multilayer film of two or more layers thereof, such as a mixed multilayer film (such as a polyethylene / polypropylene two-layer separator, a polyethylene / polypropylene / polyethylene three-layer separator, a polypropylene / polyethylene / polypropylene three-layer separator, etc.).

[0149] The separator may include a porous substrate and a coating on one or both (eg, opposite surfaces or opposite sides) of the porous substrate, the coating including an organic material, an inorganic material, and / or (eg, any suitable) combination thereof.

[0150] The porous substrate may be a polymer film formed from a member selected from the group consisting of polyolefins (such as polyethylene and / or polypropylene), polyesters (such as polyethylene terephthalate and / or polybutylene terephthalate), polyacetals, polyamides, polyimides, polycarbonates, polyetherketones, polyaryletherketones, polyetherimides, polyamideimides, polybenzimidazoles, polyethersulfones, polyphenylene oxides, cyclic olefin copolymers, polyphenylene sulfide, polyethylene naphthalate, glass fibers, and polytetrafluoroethylene (e.g., ) of any one or more polymers, copolymers of two or more thereof and mixtures of two or more thereof.

[0151] The organic material may include a polyvinylidene fluoride-based polymer and / or a (meth)acrylic-based polymer.

[0152] The inorganic material may include inorganic particles selected from Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, Mg(OH)2, boehmite and / or inorganic particles (e.g., any suitable) combinations thereof, but the present disclosure is not limited thereto.

[0153] An organic material and an inorganic material may be mixed in one coating layer, or a coating layer including an organic material and a coating layer including an inorganic material may be stacked.

[0154] Rechargeable lithium battery

[0155] The rechargeable lithium battery may be classified into a cylindrical battery, a prismatic battery, a pouch type or-like battery, a coin type or-like battery, etc., depending on the shape of the rechargeable lithium battery. Figure 1 to Figure 4A schematic diagram illustrating a rechargeable lithium battery according to one or more embodiments. Figure 1 A cylindrical battery is shown, Figure 2 A prismatic cell is shown, and Figure 3 and Figure 4 Pouch type or similar battery is shown. Figure 1 to Figure 4 , the rechargeable lithium battery 100 may include an electrode assembly 40 including a separator 30 between a positive electrode 10 and a negative electrode 20, and a case 50 in which the electrode assembly 40 is accommodated. The positive electrode 10, the negative electrode 20, and the separator 30 may be impregnated with an electrolyte. The rechargeable lithium battery 100 may include a sealing member 60 (such as a sealing member 60) that seals the case 50. Figure 1 ). Figure 2 In the embodiment, the rechargeable lithium battery 100 may include a positive electrode lead tab 11, a positive terminal 12, a negative electrode lead tab 21, and a negative terminal 22. Figure 3 and Figure 4 As shown, the rechargeable lithium battery 100 may include electrode tabs 70 , which may be, for example, a positive electrode tab 71 and a negative electrode tab 72 serving as an electrical path for guiding current formed in the electrode assembly 40 to the outside.

[0156] The rechargeable lithium battery according to one or more embodiments may be used in automobiles, mobile phones, and / or one or more appropriate types (kinds) of electronic devices, but the present disclosure is not limited thereto.

[0157] Hereinafter, examples and comparative examples of the present disclosure are described. However, these examples are not to be construed as limiting the scope of the present disclosure in any sense.

[0158] Examples and Comparative Examples

[0159] The electrolyte and rechargeable lithium battery cells were prepared as follows.

[0160] Example 1

[0161] (1) Preparation of electrolyte

[0162] 1.3 M LiPF6 was dissolved in a non-aqueous organic solvent in which ethylene carbonate (EC), propylene carbonate (PC) and propyl propionate (PP) were mixed in a volume ratio of 10:15:75, and 1 wt% of the first additive and 1 wt% of the second additive were added thereto based on the total amount of the electrolyte to prepare an electrolyte.

[0163] A first additive represented by Chemical Formula 1-1-1 (perfluoro(2-methyl-3-pentanone) (CAS No.: 756-13-8)) was used, and a second additive represented by Chemical Formula 2-1 (lithium difluoro(oxalato)borate (LiDFOB, CAS No.: 409071-16-5)) was used:

[0164] Chemical formula 1-1-1

[0165]

[0166] Chemical formula 2-1

[0167]

[0168] (2) Preparation of rechargeable lithium battery cells

[0169] LiCoO 2 as a positive electrode active material, polyvinylidene fluoride as a binder, and acetylene black as a conductive material were mixed at a weight ratio of 96:3:1, respectively, and then dispersed in N-methylpyrrolidone to prepare a positive electrode active material slurry.

[0170] The positive electrode active material slurry was coated on a 15 μm thick Al foil, dried at 100° C., and pressed to prepare a positive electrode.

[0171] Artificial graphite as a negative electrode active material, a styrene-butadiene rubber binder, and carboxymethyl cellulose were dispersed in distilled water at a weight ratio of about 98:1:1 to prepare a negative electrode active material slurry.

[0172] The negative electrode active material slurry was coated on a 10 μm thick Cu foil, dried at 100° C., and pressed to prepare a negative electrode. At this time, the active mass density of the negative electrode was set to 1.7 g / cc.

[0173] An electrode assembly was prepared by assembling a positive electrode, a negative electrode, and a separator made of polyethylene having a thickness of 10 μm, and an electrolyte was injected to prepare a rechargeable lithium battery cell.

[0174] Example 2

[0175] An electrolyte and a rechargeable lithium battery cell were prepared in substantially the same manner as in Example 1, except that 3 wt % of the first additive and 1 wt % of the second additive were used to prepare the electrolyte.

[0176] Example 3

[0177] An electrolyte and a rechargeable lithium battery cell were prepared in substantially the same manner as in Example 1, except that 2 wt % of the first additive and 0.5 wt % of the second additive were used to prepare the electrolyte.

[0178] Example 4

[0179] An electrolyte and a rechargeable lithium battery cell were prepared in substantially the same manner as in Example 1, except that 2 wt % of the first additive and 2 wt % of the second additive were used to prepare the electrolyte.

[0180] Example 5

[0181] An electrolyte and a rechargeable lithium battery cell were prepared in substantially the same manner as in Example 1, except that 2 wt % of the first additive and 1 wt % of the second additive were used to prepare the electrolyte.

[0182] Comparative Example 1

[0183] An electrolyte and a rechargeable lithium battery cell were prepared in substantially the same manner as in Example 1, except that no additives were added to prepare the electrolyte.

[0184] Comparative Example 2

[0185] An electrolyte and a rechargeable lithium battery cell were prepared in substantially the same manner as in Example 1, except that only 1 wt % of the second additive was used without adding the first additive to prepare the electrolyte.

[0186] Comparative Example 3

[0187] An electrolyte and a rechargeable lithium battery cell were prepared in substantially the same manner as in Example 1, except that the electrolyte was prepared using only 2 wt % of the first additive without adding the second additive.

[0188] Evaluation Example

[0189] The rechargeable lithium battery cells were evaluated in the following manner.

[0190] Evaluation 1: Evaluation of room temperature charge and discharge cycle characteristics

[0191] The rechargeable lithium battery cell was charged and discharged about 400 times under the conditions of 25° C., 2.0 C charge (CC / CV, 4.53 V, 0.025 C cutoff) / 1.0 C discharge (CC, 3 V cutoff).

[0192] The thickness increase rate was calculated according to Equation 1, the capacity retention rate (cycle life) was calculated according to Equation 2, and the results are shown in Table 1.

[0193] Equation 1

[0194] Thickness increase rate = {(fully charged thickness after 400th cycle) - fully charged thickness after 1st cycle)} / (fully charged thickness after 1st cycle) × 100

[0195] In the above Equation 1, "fully charged thickness" refers to the thickness of a rechargeable lithium battery cell measured after charging at SOC 100% (charge 100% state) after each cycle (if (for example, when) the total charge capacity of the battery is set to 100%, then charging to 100% charge capacity).

[0196] Equation 2

[0197] Capacity retention rate = (discharge capacity after 400th cycle / discharge capacity after 1st cycle) × 100

[0198] Table 1

[0199]

[0200] Evaluation 2: Evaluation of storage characteristics at high temperature

[0201] The initial DC internal resistance (initial DC-IR) of the rechargeable lithium battery cell before storage at a relatively high temperature was measured by ΔV / ΔI (voltage change / current change).

[0202] After the maximum energy state inside the rechargeable lithium battery cell reached a fully charged state (SOC 100%), the battery cell was then stored at a relatively high temperature (60° C.) for 30 days in this state, and the DC resistance of the battery cell was measured (DC-IR after 30 days).

[0203] The DC-IR increase rate was calculated according to Equation 3, and the results are shown in Table 2.

[0204] Equation 3

[0205] DC-IR increase rate = (DC-IR after 30 days - initial DC-IR) / (initial DC-IR) × 100

[0206] Table 2

[0207]

[0208] summary

[0209] Referring to Tables 1 and 2, compared to an electrolyte that does not include any additives at all (Comparative Example 1) and an electrolyte that includes one type or type of additives from two types (kinds) of additives (Comparative Examples 2 and Comparative Examples 3), the electrolyte that simultaneously (e.g., synchronously) includes the first additive and the second additive (Examples 1 to 5) enables the rechargeable lithium battery cells to exhibit improved high voltage and high temperature characteristics.

[0210] Even if the rechargeable lithium battery cell is charged and discharged under relatively high voltage conditions, the electrolyte (Examples 1 to 5) including the first additive and the second additive simultaneously (eg, synchronously) suppresses or reduces an increase in thickness and improves the cycle life of the battery cell.

[0211] In addition, even if the rechargeable lithium battery cells are stored at a relatively high temperature, the electrolytes (Examples 1 to 5) including the first additive and the second additive simultaneously (eg, simultaneously) suppress or reduce an increase in resistance.

[0212] According to the aforementioned embodiments, in an electrolyte (Examples 1 to 5) that simultaneously (eg, synchronously) includes a first additive and a second additive, the content (eg, amount) of each additive and its mixing ratio may be controlled or selected according to desired or appropriate characteristics.

[0213] While the invention has been described in conjunction with what are presently considered to be exemplary embodiments, it should be understood that the disclosure should not be limited to the disclosed embodiments, but, on the contrary, is intended to cover one or more suitable modifications and equivalent arrangements included within the spirit and scope of the appended claims and their equivalents.

Claims

1. An electrolyte comprising: Lithium salts; Non-aqueous organic solvents; A first additive represented by Chemical Formula 1; as well as The second additive represented by Chemical Formula 2: Chemical formula 1 In Chemical Formula 1, R 1 and R 2 Each is independently a fluorine atom or a C1-C10 fluoroalkyl group; Chemical formula 2 In chemical formula 2, R 3 and R 4 are each independently a halogen atom or a C1-C10 fluoroalkyl group, The electrolyte is used in a rechargeable lithium battery.

2. The electrolyte according to claim 1, wherein The first additive is represented by chemical formula 1-1: Chemical formula 1-1 In Chemical Formula 1-1, R 11 ~R 15 are each a hydrogen atom or a fluorine atom, provided that R 11 ~R 15 At least one of is a fluorine atom; and R 21 ~R 27 are each a hydrogen atom or a fluorine atom, provided that R 21 ~R 27 At least one of them is a fluorine atom.

3. The electrolyte according to claim 1, wherein The first additive is represented by chemical formula 1-1-1: Chemical formula 1-1-1 4. The electrolyte according to claim 1, wherein R 3 and R 4 Both are fluorine atoms.

5. The electrolyte according to claim 1, wherein Based on 100 wt % of the total amount of the electrolyte, the amount of the first additive is 0.1 wt % to 10 wt %.

6. The electrolyte according to claim 1, wherein The amount of the second additive is 0.1 wt % to 5 wt % based on 100 wt % of the total amount of the electrolyte.

7. The electrolyte according to claim 1, wherein The weight ratio of the first additive to the second additive in the electrolyte is 1:5 to 10:

1.

8. The electrolyte according to claim 1, wherein The non-aqueous organic solvent includes carbonate solvents and propionate solvents.

9. The electrolyte according to claim 8, wherein Based on 100 volume % of the total amount of the non-aqueous organic solvent, the amount of the propionate solvent is greater than or equal to 70 volume %.

10. The electrolyte according to claim 1, wherein The lithium salt is LiPF6.

11. The electrolyte according to claim 1, wherein The concentration of the lithium salt is 0.1M to 2.0M.

12. A rechargeable lithium battery comprising a positive electrode comprising a positive electrode active material; a negative electrode comprising a negative electrode active material; and The electrolyte according to any one of claims 1 to 11.

13. The rechargeable lithium battery of claim 12, wherein The positive electrode active material includes lithium nickel oxide, lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate compound, cobalt-free lithium nickel manganese oxide or a combination thereof.

14. The rechargeable lithium battery of claim 12, wherein The negative electrode active material includes a carbon-based negative electrode active material, a Si-based negative electrode active material or a combination thereof.

15. The rechargeable lithium battery of claim 12, wherein The rechargeable lithium battery has a charge upper limit voltage greater than or equal to 4.5V.

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