Electrolyte for rechargeable lithium battery and rechargeable lithium battery including same

Abstract

The invention provides an electrolyte for a rechargeable lithium battery and a rechargeable lithium battery including the electrolyte. The electrolyte solution includes a non-aqueous organic solvent and a lithium salt, and the non-aqueous organic solvent includes about 10 vol% to about 30 vol% of a compound represented by Chemical Formula 1 based on a total amount of the non-aqueous organic solvent. Chemical formula 1 # imgabs0 #

Description

Technical Field

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

[0002] Rechargeable lithium batteries are gaining attention as driving power sources for information technology (IT) devices because they are relatively light in weight and have relatively high energy density.

[0003] In addition, as the performance of information technology (IT) devices becomes higher and higher, the capacity of rechargeable lithium batteries becomes higher and higher. In order to realize a rechargeable lithium battery with high capacity, the charging voltage must be increased, but electrolytes suitable for these applications have not been properly proposed.

[0004] The electrolyte widely and most commonly used in rechargeable lithium batteries to date is an electrolyte using a carbonate-based non-aqueous organic solvent, which has a high tendency to electrochemical oxidation and decomposition under high charging voltage conditions. For example, an electrolyte using a carbonate-based non-aqueous organic solvent may cause side reactions on the surface of the positive electrode, thereby forming an impedance layer. Electrolytes using these solvents may also cause complications (such as gas generation and electrolyte consumption), which continuously impair the cycle life characteristics of rechargeable lithium batteries. Summary of the invention

[0005] Various aspects of example embodiments relate to an electrolyte for a rechargeable lithium battery in which oxidative decomposition of a non-aqueous organic solvent is suppressed or reduced, for example, even if the charging voltage increases (e.g., when the charging voltage increases). Additional aspects will be set forth in part in the description that follows and in part will be obvious from the description, or may be learned by practicing the presented embodiments of the present disclosure.

[0006] Some example embodiments provide an electrolyte for a rechargeable lithium battery, comprising a non-aqueous organic solvent and a lithium salt. In some embodiments, the non-aqueous organic solvent comprises about 10 volume percent (vol%) to about 30 vol% of a compound represented by Chemical Formula 1 based on the total amount of the non-aqueous organic solvent:

[0007] Chemical formula 1

[0008]

[0009] In Chemical Formula 1, each X may be the same or different, and may independently be a hydrogen atom or a fluorine atom.

[0010] The nonaqueous organic solvent may include the compound represented by Chemical Formula 1 in an amount of about 10 vol% to about 20 vol% based on the total amount of the nonaqueous organic solvent.

[0011] In Chemical Formula 1, all Xs may be fluorine atoms (eg, each X is a fluorine atom).

[0012] The non-aqueous organic solvent may further include a carbonate-based non-aqueous organic solvent, an ester-based non-aqueous organic solvent, or a combination thereof.

[0013] The carbonate non-aqueous organic solvent may include at least one selected from the following: a cyclic carbonate non-aqueous organic solvent, including ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC) or a combination thereof; and a linear carbonate non-aqueous organic solvent, including at least one selected from dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), ethyl methyl carbonate (MEC) and a combination thereof.

[0014] The ester non-aqueous organic solvent may include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, propyl propionate (PP), decanoic acid lactone, mevalonolactone, valerolactone, caprolactone, or a combination thereof.

[0015] The non-aqueous organic solvent may include a carbonate-based non-aqueous organic solvent and an ester-based non-aqueous organic solvent in a volume ratio of about 1:1.5 to about 1:3.

[0016] The carbonate-based nonaqueous organic solvent may include ethylene carbonate (EC) and propylene carbonate (PC).

[0017] The ester-based non-aqueous organic solvent may include propyl propionate (PP).

[0018] The lithium salt may include a lithium salt selected from the group consisting of LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, LiN(SO3C2F5)2, Li(FSO2)2N(lithium bis(fluorosulfonyl)imide (LiFSI), LiC4F9SO3, LiN(C x F 2x+1 SO2)(C y F 2y+1 SO2) (x and y are integers of 1 to 20), at least one (e.g., one, two or more) of lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium difluorobis(oxalato)phosphate (LiDFOB) and lithium bis(oxalato)borate (LiBOB).

[0019] The electrolyte may further include a carbonate additive, a sultone additive, a nitrile additive, a lithium salt additive, or a combination thereof.

[0020] In some example embodiments, a rechargeable lithium battery includes: a positive electrode including a positive electrode active material; a negative electrode including a negative electrode active material; and an electrolyte.

[0021] The rechargeable lithium battery may have a charging voltage greater than or equal to about 4.45V.

[0022] The positive electrode active material may include lithium cobalt oxide.

[0023] The negative electrode active material may include graphite.

[0024] The electrolyte for a rechargeable lithium battery according to some example embodiments suppresses oxidative decomposition of a non-aqueous organic solvent even if a charging voltage increases (eg, when the charging voltage increases), thereby realizing a rechargeable lithium battery having a high capacity. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a schematic diagram showing a rechargeable lithium battery according to one or more embodiments of the present disclosure.

[0026] Figure 2 are results of charge and discharge experiments of rechargeable lithium batteries according to one or more embodiments of the present disclosure.

[0027] Description of Reference Numerals

[0028] 100: Rechargeable lithium battery

[0029] 10: Positive electrode

[0030] 20: Negative electrode

[0031] 30: Diaphragm

[0032] 40: Electrode assembly

[0033] 50: Shell

[0034] 70: Electrode terminal DETAILED DESCRIPTION

[0035] Hereinafter, the rechargeable lithium battery according to some embodiments will be described in more detail with reference to the attached drawings, wherein the same reference numerals refer to the same elements throughout the text, and their repeated description may not be provided. In this regard, the present embodiment may be modified to have different forms and should not be interpreted as being limited to the description set forth herein. On the contrary, the present disclosure is intended to cover all modifications, equivalents, and alternatives that fall within the spirit and scope of the present disclosure. Accordingly, the embodiments are described only by reference to the accompanying drawings to explain various aspects of the present description. However, these embodiments are only examples, and the present disclosure is not limited thereto, but the present disclosure is limited by the scope of the claims.

[0036] As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items. Expressions such as "at least one of," if following a list of elements (e.g., when following a list of elements), modify the entire list of elements and do not modify the individual elements of the list.

[0037] If an element is described as being “on”, “connected to” or “coupled to” another element (for example, when an element is described as being “on”, “connected to” or “coupled to” another element), it will be understood that the element may be provided directly on the other element, or another element may be interposed between them. On the other hand, if an element is described as being “directly on” another element (for example, when an element is described as being “directly on” another element), another element is interposed between them.

[0038] It will be understood that although the terms "first", "second", and "third" may be used herein to describe one or more appropriate elements, components, regions, layers, and / or portions, these elements, components, regions, layers, and / or portions should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer, and / or portion from another element, component, region, layer, or portion. Therefore, without departing from the teachings of this specification, a first element, component, region, layer, or portion described herein may be referred to as a second element, component, region, layer, or portion.

[0039] As used herein, the singular forms "a", "an", and "the" are not to be construed as limited to the singular, but are intended to include the plural forms, including "at least one", unless the content (e.g., amount) is clearly indicated otherwise. As used herein, expressions such as "at least one", "one of", and "selected from", if preceding / following a list of elements (e.g., when preceding / following a list of elements), may modify the entire list of elements without modifying the individual elements of the list. For example, the expressions "at least one of a to c", "at least one of a, b, and c", and "at least one of a, b, and / or c" 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.

[0040] If used in the detailed description (for example, when used in the detailed description), the terms "include", "includes", "including", "comprise", "comprises", "comprising", "having", "has" and / or "have" indicate the presence of stated features, regions, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components, and / or groups thereof.

[0041] Spatially relative terms such as "below," "below," "below," "above," and "on" may be used herein to easily describe the relationship of one element or feature to another element or feature. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation illustrated in the drawings. For example, if the device in the drawings is flipped (e.g., when the device in the drawings is flipped), the elements described as "below" or "below" other elements or features are oriented "above" or "on" the other elements or features. Therefore, the example term "below" may encompass both (e.g., relative) orientations of above and below. The device may be oriented in other ways (rotated 90 degrees or in other orientations), and the spatially relative terms used herein may be interpreted accordingly.

[0042] As used herein, the terms "use," "using," and "used" may be considered synonymous with the terms "utilized," "utilizing," and "utilized," respectively.

[0043] The term "may" will be understood to refer to "one or more embodiments of the present disclosure," some of which include the described elements, and some of which exclude the elements and / or include alternative elements. Similarly, alternative language such as "or" refers to "one or more embodiments of the present disclosure" that each includes the corresponding listed items.

[0044] The term "combinations thereof" may include mixtures, laminates, composites, copolymers, alloys, blends, reactants, and the like, of the components.

[0045] Unless otherwise defined, all terms used in this article (including chemical terms, technical terms and scientific terms) have the same meaning as those commonly understood by those skilled in the art to which the present disclosure belongs. In some embodiments, it will be further understood that terms (such as those defined in commonly used dictionaries) should be interpreted as having a meaning consistent with their meaning in the context of the relevant field and the present disclosure, and will not be interpreted in an idealized or overly formal sense unless explicitly defined in this article.

[0046] In this context, "consisting essentially of" means that any additional components do not substantially affect the chemical, physical, optical, or electrical properties of the semiconductor film.

[0047] Furthermore, in this specification, the phrase "on a plane" or "plan view" means observing a target portion from the top, and the phrase "in a cross section" means observing a cross section formed by vertically cutting the target portion from the side.

[0048] definition

[0049] As used herein, if the particle is spherical (for example, when the particle is spherical), the term "particle size" of the particle refers to the average diameter, and if the particle is non-spherical (for example, when the particle is non-spherical), the term "particle size" of the particle refers to the average major axis length. The particle size of the particle can be measured using a particle size analyzer (PSA). The "particle size" of the particle is, for example, the "average particle size". The average particle size refers to, for example, the median particle size (D50). The median particle size (D50) is the particle size corresponding to 50% cumulative volume if the particle size distribution measured by the laser diffraction method is calculated by particles with a smaller particle size (for example, when the particle size distribution measured by the laser diffraction method is calculated by particles with a smaller particle size). In some embodiments, "particle size" or "average particle size" can be measured by transmission electron microscopy (TEM) images, scanning electron microscopy (SEM) images, etc.

[0050] If the particle size distribution measured by the laser diffraction method is calculated starting from particles with smaller particle sizes (eg, when the particle size distribution measured by the laser diffraction method is calculated starting from particles with smaller particle sizes), D50 refers to a particle size corresponding to 50% cumulative volume.

[0051] If the particle size distribution measured by the laser diffraction method is calculated starting from particles with smaller particle sizes (eg, when the particle size distribution measured by the laser diffraction method is calculated starting from particles with smaller particle sizes), D90 refers to the particle size corresponding to 90% cumulative volume.

[0052] If the particle size distribution measured by the laser diffraction method is calculated starting from particles with smaller particle sizes (eg, when the particle size distribution measured by the laser diffraction method is calculated starting from particles with smaller particle sizes), D10 refers to a particle size corresponding to 10% cumulative volume.

[0053] In some embodiments, the term "group" may refer to a group (i.e., column) of elements in the periodic table according to the International Union of Pure and Applied Chemistry ("IUPAC") group classification system of Groups 1 to 18. In some embodiments, the term "group" may refer to a chemical functional group, for example, an "alkyl group."

[0054] As used herein, the term "electrode active material" refers to an electrode material that can undergo lithiation and delithiation.

[0055] The term "negative electrode active material" as used herein refers to a negative electrode material that can undergo lithiation and delithiation.

[0056] As used herein, the terms "lithiate" and "lithiating" refer to the process of adding lithium to an electrode active material.

[0057] As used herein, the terms "delithiate" and "delithiating" refer to the process of removing lithium from an electrode active material.

[0058] As used herein, the terms "charge" and "charging" refer to the process of providing electrochemical energy to a battery.

[0059] As used herein, the terms "discharge" and "discharging" refer to the process of removing electrochemical energy from a battery.

[0060] The term "positive electrode" as used herein refers to the electrode that undergoes electrochemical reduction and lithiation during the discharge process.

[0061] The term "negative electrode" as used herein refers to the electrode that undergoes electrochemical oxidation and delithiation during the discharge process.

[0062] Electrolyte

[0063] As mentioned above, the most widely used electrolyte to date is an electrolyte using a carbonate-based non-aqueous organic solvent. However, carbonate-based non-aqueous organic solvents have a high tendency to electrochemically oxidize and decompose under high charging voltage conditions, resulting in one or more undesirable side reactions.

[0064] Some example embodiments provide an electrolyte for a rechargeable lithium battery, including a non-aqueous organic solvent and a lithium salt, wherein the non-aqueous organic solvent includes a compound represented by Chemical Formula 1 based on the total amount of the non-aqueous organic solvent:

[0065] Chemical formula 1

[0066]

[0067] In Chemical Formula 1, each X may be the same or different, and may independently be a hydrogen atom or a fluorine atom.

[0068] The nonaqueous organic solvent functions (eg, serves as) a medium for transporting ions participating in an electrochemical reaction of a battery.

[0069] Auxiliary solvent

[0070] Compared to carbonate-based non-aqueous organic solvents, the compound represented by Chemical Formula 1 avoids oxidative decomposition (e.g., suppresses oxidative decomposition of the non-aqueous organic solvent) under high voltage charging conditions (e.g., even if the charging voltage increases (e.g., when the charging voltage increases)). Therefore, a rechargeable lithium battery with high capacity can be achieved by using the compound represented by Chemical Formula 1.

[0071] In addition, the compound represented by Chemical Formula 1 has higher electrochemical stability than the non-aqueous organic solvent (e.g., N,N-diethyltrifluoromethanesulfonamide, DETMSA) represented by Chemical Formula 2, thereby reducing side reactions even if the charge and discharge cycle of the rechargeable lithium battery is repeated (e.g., when the charge and discharge cycle of the rechargeable lithium battery is repeated). This can be confirmed from the analysis of the battery capacity retention rate after a long-term charge and discharge cycle of the rechargeable lithium battery or the amount of decomposition products of the lithium salt, etc.

[0072] Chemical formula 2

[0073]

[0074] The non-aqueous organic solvent may include the compound represented by Chemical Formula 1 as an "auxiliary solvent" relative to the total amount of the non-aqueous organic solvent. Herein, the "auxiliary solvent" refers to a solvent including less than about 50 vol% relative to the total amount of the non-aqueous organic solvent, which functions to assist (e.g., remainder of) the "main solvent".

[0075] If an excess amount of the compound represented by Chemical Formula 1 is used as the "main solvent" (for example, when an excess amount of the compound represented by Chemical Formula 1 is used as the "main solvent"), it may undergo reduction-decomposition with the negative electrode and thus reduce the capacity, but if a small amount of the compound represented by Chemical Formula 1 is used as the "auxiliary solvent" (for example, when a small amount of the compound represented by Chemical Formula 1 is used as the "auxiliary solvent"), it may improve the solvent oxidation resistance and improve the high voltage performance.

[0076] For example, the nonaqueous organic solvent may include about 10 vol% to about 30 vol%, or about 10 vol% to about 20 vol% of the compound represented by Chemical Formula 1, based on the total amount of the nonaqueous organic solvent.

[0077] In Chemical Formula 1, all Xs may be fluorine atoms. In this case, the compound represented by Chemical Formula 1 may be N,N-dimethyltrifluoromethanesulfonamide (DMTMSA).

[0078] Main solvent

[0079] The non-aqueous organic solvent may further include a “main solvent.” In some embodiments, the main solvent may be or may include a carbonate-based non-aqueous organic solvent, an ester-based non-aqueous organic solvent, or a combination thereof.

[0080] The carbonate non-aqueous organic solvent may include at least one selected from cyclic carbonate non-aqueous organic solvents and chain carbonate non-aqueous organic solvents. For example, the carbonate non-aqueous organic solvent may be: a cyclic carbonate non-aqueous organic solvent, including ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC) or a combination thereof; and a chain carbonate non-aqueous organic solvent, including at least one selected from dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC) and a combination thereof. In addition, if a carbonate non-aqueous organic solvent is used (for example, when a carbonate non-aqueous organic solvent is used), cyclic carbonates and chain carbonates may be mixed and used. For example, cyclic carbonates and chain carbonates may be mixed in a volume ratio of about 1:1 to about 1:9.

[0081] The ester non-aqueous organic solvent may include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, propyl propionate (PP), decanoic acid lactone, mevalonolactone, valerolactone, caprolactone, or a combination thereof.

[0082] The non-aqueous organic solvent as the "main solvent" may include a carbonate non-aqueous organic solvent and an ester non-aqueous organic solvent in a volume ratio of about 1:1.5 to about 1:3. Herein, the carbonate non-aqueous organic solvent may include ethylene carbonate (EC) and propylene carbonate (PC); and the ester non-aqueous organic solvent may include propyl propionate (PP).

[0083] Lithium salts

[0084] The lithium salt dissolved in the organic solvent supplies lithium ions in the battery, ensures the general (i.e., basic or proper) operation of the rechargeable lithium battery, and improves the transport of lithium ions between the positive electrode and the negative electrode. Representative examples of the lithium salt may include those selected from LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, LiN(SO3C2F5)2, Li(FSO2)2N(Lithium bis(fluorosulfonyl)imide (LiFSI), LiC4F9SO3, LiN(C x F 2x+1 SO2)(C y F 2y+ 1SO2) (wherein x and y are integers of 1 to 20), at least one (e.g., or more) of lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium difluorobis(oxalato)phosphate (LiDFOB) and lithium bis(oxalato)borate (LiBOB).

[0085] The lithium salt may be used at a concentration in the range of about 0.1 M to about 2.0 M. If the concentration of the lithium salt is within the disclosed range (e.g., when the concentration of the lithium salt is within the disclosed range), the electrolyte has suitable or appropriate ion conductivity and viscosity, and thus excellent or appropriate performance may be achieved, and lithium ions may be efficiently moved.

[0086] additive

[0087] The electrolyte may further include carbonate additives, sultone additives, nitrile additives, lithium salt additives or a combination thereof to improve the battery cycle life.

[0088] The carbonate-based additive may include vinyl ethyl carbonate, vinylene carbonate, or ethylene carbonate-based compounds.

[0089] Representative examples of the ethylene carbonate-based compounds may include fluoroethylene carbonate (FEC), vinylethylene carbonate (VEC), difluoroethylene carbonate, chloroethylene carbonate, dichloroethylene carbonate, bromoethylene carbonate, dibromoethylene carbonate, nitroethylene carbonate, and / or cyanoethylene carbonate.

[0090] The nitrile additive may include a dinitrile compound, a polynitrile compound, or a combination thereof.

[0091] Representative examples of the dinitrile compound may include succinonitrile (SN), glutaronitrile, adiponitrile (AN), pimelonitrile, suberonitrile, azelaic acid dinitrile, octanonitrile, ethylene glycol (bispropionitrile) ether (nitrile ether), fumaronitrile, and the like.

[0092] Representative examples of the polynitrile compounds may include 1,3,6-hexanetricarbonitrile (HTCN), 1,2,6-hexanetricarbonitrile, 1,3,5-pentanetricarbonitrile, nonanetricarbonitrile, 1,3,5-benzenetricarbonitrile, 2,4,6-trifluorobenzene-1,3,5-tricarbonitrile, 1,3,5-cyclohexanetricarbonitrile, 1,2,3-propionitrile, 1,2,3-tris(2-cyano)propane, and the like.

[0093] Sultone additives may include propylene sultone (PST), propane sultone (PS), etc.; and lithium salt additives may include lithium tetrafluoroborate (LiBF4), lithium difluorophosphate (LiPO2F2), lithium difluoro(fluoromalonate)borate (LFMB), etc.

[0094] Rechargeable lithium battery

[0095] Some example embodiments 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 the aforementioned electrolyte.

[0096] In a rechargeable lithium battery including the disclosed electrolyte, even if the charging voltage increases (eg, when the charging voltage increases), oxidative decomposition of the nonaqueous organic solvent may be suppressed or reduced, and the capacity may be increased.

[0097] For example, the rechargeable lithium battery may have a charging voltage greater than or equal to about 4.45V, or greater than or equal to about 4.5V.

[0098] Positive electrode active material

[0099] The positive electrode active material may be a compound capable of reversibly intercalating and deintercalating lithium (lithiated intercalation compound). For example, one or more types (species) of composite oxides of lithium and a metal selected from cobalt, manganese, nickel, and combinations thereof may be used.

[0100] The composite oxide may be a lithium transition metal composite oxide, and specific examples may include lithium nickel-based oxides, lithium cobalt-based oxides, lithium manganese-based oxides, lithium iron phosphate-based compounds, cobalt-free nickel manganese-based oxides, or combinations thereof.

[0101] As an example, the positive electrode active material may be a high nickel positive electrode active material, and its nickel content (e.g., amount) is about 80 mol% or more of the metal other than lithium in the high nickel positive electrode active material based on 100 mol%. Based on 100 mol% of the metal other than lithium in the high nickel positive electrode active material, the nickel content (e.g., amount) in the high nickel positive electrode active material may be about 85 mol% or more, about 90 mol% or more, about 91 mol% or more, or about 94 mol% or more, and about 99 mol% or less. High nickel positive electrode active materials can achieve high capacity and can be applied to high capacity, high density rechargeable lithium batteries.

[0102] As an example, at least one compound represented by any one of the following chemical formulas may be used as the positive electrode active material: 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 a Ni 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 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 aMn 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 Li a FePO4(0.90≤a≤1.8).

[0103] In the above chemical formula, A may be Ni, Co, Mn or a combination thereof; X may be Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element or a combination thereof; D may be O, F, S, P or a combination thereof; G may be Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V or a combination thereof; Q may be Ti, Mo, Mn or a combination thereof; Z may be Cr, V, Fe, Sc, Y or a combination thereof; and L 1 It can be Mn, Al or a combination thereof.

[0104] Positive electrode

[0105] A positive electrode for a rechargeable lithium battery may include a positive electrode current collector and a positive electrode active material layer formed on the positive electrode 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.

[0106] The content (eg, amount) of the positive electrode active material may be about 90 wt % to about 99.5 wt % based on 100 wt % of the positive electrode active material layer.

[0107] In some example embodiments, the positive electrode active material layer may further include a binder and a conductive material. At this time, the content (eg, amount) of each of the binder and the conductive material may be about 0.5 wt % to about 5 wt % based on 100 wt % of the positive electrode active material layer.

[0108] The binder is used to ensure that the positive electrode active material particles are bonded to each other and also to the positive electrode active material to the positive electrode current collector. Representative examples of the binder 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 and / or nylon, but are not limited thereto.

[0109] A conductive material is used to impart conductivity to the electrode, and in the configured battery, any conductive material may be used as long as it does not cause chemical changes. Examples of the conductive material may include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber, and / or carbon nanotube; metal-based materials including copper, nickel, aluminum, silver, etc. in the form of metal powder or metal fiber; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0110] Al foil may be used as a positive electrode current collector, but is not limited thereto.

[0111] Negative electrode active material

[0112] The negative electrode active material may be a material that reversibly intercalates / deintercalates lithium ions, lithium metal, a lithium metal alloy, a material capable of doping and dedoping lithium, or a transition metal oxide.

[0113] The material that reversibly intercalates / deintercalates lithium ions may be a carbon-based negative electrode active material, such as crystalline carbon, amorphous carbon, or a combination thereof. Examples of crystalline carbon may include graphite, such as irregular, plate-like, flaky, spherical, or fibrous natural graphite or artificial graphite, and examples of amorphous carbon may include soft carbon or hard carbon, mesophase pitch carbonization products, calcined coke, and the like.

[0114] The lithium metal alloy may include an alloy comprising lithium and a metal selected from the group consisting of Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn.

[0115] Si-based negative electrode active materials or Sn-based negative electrode active materials can be used as materials capable of doping and dedoping lithium. Si-based negative electrode active materials may include silicon, silicon-carbon composites, SiOx (0<x≤2), Si-Q alloys (wherein Q is an element 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, such as Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Tl, Ge, P, As, Sb, Bi, S, Se, Te, Po, and combinations thereof) or combinations thereof. The Sn-based negative electrode active material may be Sn, SnO2, Sn alloy or a combination thereof.

[0116] The silicon-carbon composite may be a composite of silicon and amorphous carbon. The average particle size (D 50 ) may be, for example, about 0.5 micrometers (μm) to about 20 μm. According to some example embodiments, 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 silicon-carbon composite may include secondary particles (cores) in which silicon primary particles are aggregated and an amorphous carbon coating (shell) on the surface of the secondary particles. Amorphous carbon may also be provided between silicon primary particles, and, for example, silicon primary particles may be coated with amorphous carbon. Secondary particles may be dispersed in an amorphous carbon matrix.

[0117] The silicon-carbon composite may further include crystalline carbon. For example, the silicon-carbon composite may include: a core including crystalline carbon and silicon particles and an amorphous carbon coating on the surface of the core. The crystalline carbon may be artificial graphite, natural graphite, or a combination thereof. The amorphous carbon may include soft carbon or hard carbon, a mesophase pitch carbonization product (e.g., coal pitch), and calcined coke.

[0118] If the silicon-carbon composite includes silicon and amorphous carbon (e.g., when the silicon-carbon composite includes silicon and amorphous carbon), the content (e.g., amount) of silicon may be about 10 wt% to about 50 wt% based on 100 wt% of the silicon-carbon composite, and the content (e.g., amount) of amorphous carbon may be about 50 wt% to about 90 wt%. In some embodiments, if the silicon-carbon composite includes silicon, amorphous carbon, and crystalline carbon (e.g., when the silicon-carbon composite includes silicon, amorphous carbon, and crystalline carbon), the content (e.g., amount) of silicon may be about 10 wt% to about 50 wt%, the content (e.g., amount) of crystalline carbon may be about 10 wt% to about 70 wt%, and the content (e.g., amount) of amorphous carbon may be about 20 wt% to about 40 wt% based on 100 wt% of the silicon-carbon composite.

[0119] In addition, the thickness of the amorphous carbon coating layer may be about 5 nanometers (nm) to about 100 nm. The average particle size (D 50 ) may be about 10 nm to about 1 μm, or about 10 nm to about 200 nm. The silicon particles (i.e., silicon primary particles) may exist in the form of a single silicon, a silicon alloy, or an oxidized form. In some embodiments, the oxidized form of silicon may be composed of SiO x (0<x<2) indicates. In some embodiments, the atomic content (e.g., amount) ratio of Si:O indicating the degree of oxidation of the oxidized form of silicon may be about 99:1 to about 33:67. In this specification, as used herein, if a definition is not provided otherwise (e.g., when a definition is not provided otherwise), the average particle size (D 50 ) indicates the particle size where the cumulative volume in the particle size distribution is about 50 vol%.

[0120] The Si-based negative electrode active material or the Sn-based negative electrode active material can be used by mixing with the carbon-based negative electrode active material. If a mixture of the Si-based negative electrode active material or the Sn-based negative electrode active material and the carbon-based negative electrode active material is used (for example, when a mixture of the Si-based negative electrode active material or the Sn-based negative electrode active material and the carbon-based negative electrode active material is used), the mixing ratio can be about 1:99 to about 90:10 by weight.

[0121] Negative electrode

[0122] 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 a negative electrode active material and may further include a binder and / or a conductive material.

[0123] Based on 100wt% of the negative electrode active material layer, the content (e.g., amount) of the negative electrode active material may be about 95wt% to about 99.5wt%. Based on 100wt% of the negative electrode active material layer, the content (e.g., amount) of the binder may be about 0.5wt% to about 5wt%. Based on 100wt% of the negative electrode active material layer, the content (e.g., amount) of the conductive material may be about 0.5wt% to about 5wt%. For example, the negative electrode active material layer may include about 90wt% to about 99wt% of the negative electrode active material, about 0.5wt% to about 5wt% of the binder, and about 0.5wt% to about 5wt% of the conductive material.

[0124] The binder is used to bind the negative electrode active material particles to each other and also helps the negative electrode active material to bind to the negative electrode current collector. The binder may be a non-aqueous binder, an aqueous binder, a dry binder or a combination thereof.

[0125] The non-aqueous binder may include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamide-imide, polyimide, or a combination thereof.

[0126] 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, phenol resin, epoxy resin, polyvinyl alcohol and combinations thereof.

[0127] If the aqueous binder is used as a negative electrode binder (for example, when the aqueous binder is used as a negative electrode binder), it may further include a cellulose compound capable of imparting viscosity. As the cellulose compound, one or more types (species) of carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose and alkali metal salts thereof may be used. The alkali metal may be Na, K and / or Li.

[0128] The dry binder may be a polymer material capable of fiberization, and may be, for example, polytetrafluoroethylene, polyvinylidene fluoride, a polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, or a combination thereof.

[0129] The conductive material is used to impart conductivity to the electrode, and in the configured battery, any electronically conductive material may be used as long as it does not cause chemical changes. Specific examples may include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber and / or carbon nanotube; metal-based materials including copper, nickel, aluminum, silver, etc. in the form of metal powder or metal fiber; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0130] 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 combinations thereof.

[0131] Diaphragm

[0132] According to the type or kind of the rechargeable lithium battery, the rechargeable lithium battery may further include a separator between the negative electrode and the positive electrode. Examples of the separator may be or may include a polyethylene separator, a polypropylene separator, a polyvinylidene fluoride separator, and multilayers thereof (such as a polyethylene / polypropylene double-layer separator, a polyethylene / polypropylene / polyethylene three-layer separator, and / or a polypropylene / polyethylene / polypropylene three-layer separator).

[0133] The separator may include a porous substrate and a coating comprising an organic material, an inorganic material, or a combination thereof on one or both (eg, simultaneously) surfaces of the porous substrate.

[0134] The porous substrate may be a polymer film formed of any one selected from polyolefins (such as polyethylene and polypropylene), polyesters (such as polyethylene terephthalate and polybutylene terephthalate), polyacetals, polyamides, polyimides, polycarbonates, polyether ketones, polyaryletherketones, polyetherimides, polyamideimides, polybenzimidazoles, polyethersulfones, polyphenylene oxides, cyclic olefin copolymers, polyphenylene sulfide, polyethylene naphthalate, glass fibers, Teflon and polytetrafluoroethylene, or a polymer film formed of a copolymer or a mixture of two or more thereof.

[0135] The porous substrate may have a thickness of about 1 μm to about 40 μm, for example, about 1 μm to about 30 μm, about 1 μm to about 20 μm, about 5 μm to about 15 μm, or about 10 μm to about 15 μm.

[0136] The organic material may include a (meth)acryl-based copolymer including a first structural unit derived from (meth)acrylamide, and a second structural unit including at least one of a structural unit derived from (meth)acrylic acid or (meth)acrylate and a structural unit derived from (meth)acrylamide sulfonic acid or a salt thereof.

[0137] The inorganic material may include inorganic particles selected from the group consisting of Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, Mg(OH)2, boehmite, and combinations thereof, but is not limited thereto. The average particle size (D 50 ) may be from about 1 nm to about 2000 nm, for example, from about 100 nm to about 1000 nm, or from about 100 nm to about 700 nm.

[0138] The organic material and the inorganic material may be mixed in one coating layer, or may exist in the form of a stack of a coating layer including an organic material and a coating layer including an inorganic material.

[0139] The thickness of the coating layers may each be about 0.5 μm to about 20 μm, for example, about 1 μm to about 10 μm, or about 1 μm to about 5 μm.

[0140] Rechargeable lithium battery

[0141] Rechargeable lithium batteries may be classified into cylindrical, prismatic, pouch-type, coin-type, etc. according to their shapes. Figure 1 Schematic diagram showing a rechargeable lithium battery according to some example embodiments. Figure 1The rechargeable lithium battery 100 includes an electrode assembly 40 and a case 50, the electrode assembly 40 includes a separator 30 interposed between a positive electrode 10 and a negative electrode 20, and the electrode assembly 40 is accommodated in the case 50. The positive electrode 10, the negative electrode 20, and the separator 30 may be impregnated with an electrolyte. The rechargeable lithium battery 100 may further include an electrode tab 70, which serves as an electrical path for guiding current generated in the electrode assembly 40 to the outside, such as Figure 1 as shown in .

[0142] Terms such as "substantially," "about," and "approximately" are used as relative terms, not as terms of degree, and are intended to account for the inherent deviations in measured or calculated values ​​that one of ordinary skill in the art would recognize. They may include the stated value as well as an acceptable range of deviation determined by one of ordinary skill in the art taking into account the limitations and errors associated with measuring that amount. For example, "about" may mean within one or more standard deviations of the stated value, or within ±30%, ±20%, ±10%, or ±5% of the stated value.

[0143] The numerical ranges disclosed herein include and are intended to disclose all subranges of the same numerical precision. For example, a range of "1.0 to 10.0" includes all subranges having a minimum value equal to or greater than 1.0 and a maximum value equal to or less than 10.0, such as, for example, 2.4 to 7.6. Therefore, the applicant reserves the right to amend this specification (including the claims) to expressly set forth any subranges contained within the ranges expressly set forth herein.

[0144] Hereinafter, embodiments of the present disclosure and comparative examples will be described.The following embodiments are merely examples of the present disclosure, and the present disclosure is not limited to the following embodiments.

[0145] Example

[0146] Example 1

[0147] (1) Preparation of electrolyte

[0148] As shown in Table 1, a mixed electrolyte was prepared.

[0149] Table 1

[0150]

[0151] In Table 1, in the composition of the electrolyte, the content (e.g., amount) "M" of the lithium salt represents the amount (mol) of the lithium salt in the volume (L) of the entire electrolyte (lithium salt + non-aqueous organic solvent + additive). The content (e.g., amount) "vol%" of the non-aqueous organic solvent is based on 100% by volume of the total non-aqueous organic solvent. The content (e.g., amount) "wt%" of the above-mentioned additives is based on 100% by weight of the total electrolyte (lithium salt + non-aqueous organic solvent + additive).

[0152] (2) Manufacturing of rechargeable lithium battery cells

[0153] LiCoO2 as a positive electrode active material, polyvinylidene fluoride as a binder, and Ketjen black as a conductive material were mixed at a weight ratio of 98.5:0.75:0.75, respectively, and then dispersed in N-methylpyrrolidone to prepare a positive electrode active material slurry.

[0154] The positive electrode active material slurry was coated on a 14 μm thick Al foil, dried at 110° C., and pressed to produce a positive electrode.

[0155] A mixture of artificial graphite and silicon-carbon composite in a weight ratio of 93:7 was prepared as a negative electrode active material. The negative electrode active material, styrene-butadiene rubber binder and carboxymethyl cellulose in a weight ratio of 97:1:2 were dispersed in distilled water to prepare a negative electrode active material slurry.

[0156] The negative electrode active material slurry was coated on a 10 μm thick Cu foil, dried at 100° C., and pressed to produce a negative electrode.

[0157] An electrode assembly is manufactured by assembling the manufactured positive electrode and negative electrode and a 25 μm thick polyethylene separator, the electrode assembly is placed (e.g., contained) in a bag, and a 2032 coin-type or coin-like rechargeable lithium battery cell is manufactured by injecting the electrolyte of Example 1 (e.g., injecting into the rechargeable lithium battery cell).

[0158] Evaluation Example 1: Capacity retention rate of rechargeable lithium battery cells

[0159] After the formation steps of the rechargeable lithium battery cells of Examples 1 to 5 and Comparative Examples 1 to 4 were performed, constant current charging was performed at a current rate of 5C at 45°C until the voltage reached 4.53V (relative to Li), and then the current was cut off at a current rate of 0.075C in a constant voltage mode while maintaining 4.53V. Subsequently, the rechargeable lithium battery cells were discharged at a constant current rate of 0.75C to a voltage of 3.0V (relative to Li). This charge / discharge cycle was repeated 200 times.

[0160] In all charge and discharge cycles, a 10-minute pause was set between each charge / discharge cycle.

[0161] The results of the charge and discharge experiments are shown in Table 2 and Figure 2 The capacity retention rate at the nth cycle is defined by Eq.

[0162] Equation 1

[0163] Capacity retention rate = [discharge capacity at the nth cycle / discharge capacity at the first cycle] × 100

[0164] Table 2

[0165]

[0166]

[0167] According to Table 2, as the charge and discharge cycles of the rechargeable lithium battery cells continued, the cycle lives of Comparative Examples 1 to 4 decreased (eg, decreased rapidly) compared to Examples 1 to 5.

[0168] The results shown in Table 2 show that the compound represented by Chemical Formula 1 has greater (e.g., higher) electrochemical stability than not only carbonate-based non-aqueous organic solvents but also N,N-diethyltrifluoromethanesulfonamide (DETMSA). For example, even if the charge and discharge cycle of the rechargeable lithium battery cell is repeated (e.g., 200 times or more) (e.g., when the charge and discharge cycle of the rechargeable lithium battery cell is repeated (e.g., 200 times or more)), the compound represented by Chemical Formula 1 can also reduce side reactions.

[0169] Evaluation Example 2: Confirmation of lithium salt decomposition products after evaluating the high temperature cycle life of rechargeable lithium battery cells

[0170] After evaluating the high temperature cycle life of the rechargeable lithium battery cell, the positive electrode was disassembled and analyzed by X-ray photoelectron spectroscopy (XPS), and it was confirmed whether the decomposition product of the lithium salt in the electrolyte adhered to the surface of the negative electrode.

[0171] Representatively, Comparative Examples 1 to 3 and Examples 1 and 3 were examined, and the results are shown in Table 3.

[0172] Table 3 (Unit: wt%)

[0173]

[0174] According to Table 3, in Examples 1 and 3, the detected amounts of F and P, which are decomposition products of the lithium salt (LiPF6), are reduced (eg, the detected amounts are small) as compared to Comparative Examples 1 to 3.

[0175] From these results, it can be confirmed that the compound represented by Chemical Formula 1 reduces the side reaction on the positive electrode surface better than not only the carbonate-based nonaqueous organic solvent but also N,N-diethyltrifluoromethanesulfonamide (DETMSA).

[0176] Any suitable hardware, firmware (e.g., an application specific integrated circuit), software, or a combination of software, firmware, and hardware may be used to implement the battery management system (BMS) device and / or any other related device or component according to an embodiment of the present disclosure described herein. For example, the various components of the device may be formed on an integrated circuit (IC) chip or on separate IC chips. In addition, the various components of the device may be implemented on a flexible printed circuit film, a tape carrier package (TCP), or a printed circuit board (PCB), or formed on a substrate. In addition, the various components of the device may be processes or threads running on one or more processors in one or more computing devices, executing computer program instructions and interacting with other system components for performing the various functions described herein. The computer program instructions are stored in a memory, which may be implemented in a computing device using a standard storage device, such as, for example, a random access memory (RAM). The computer program instructions may also be stored in other non-temporary computer-readable media (such as, for example, a CD-ROM or a flash drive, etc.). Moreover, those skilled in the art should recognize that, without departing from the scope of the present disclosure, the functions of various computing devices may be combined or integrated into a single computing device, or the functions of a particular computing device may be distributed on one or more other computing devices.

[0177] While the subject matter of the present disclosure has been described in connection with what are presently considered to be practical example embodiments, it should be understood that the disclosure is not limited to the disclosed embodiments, but on the contrary is intended to cover one or more suitable modifications and equivalent arrangements included within the spirit and scope of the claims and their equivalents.

Claims

1. An electrolyte for a rechargeable lithium battery, the electrolyte comprising Non-aqueous organic solvent and lithium salt, Wherein, based on the total amount of the non-aqueous organic solvent, the non-aqueous organic solvent includes 10 vol% to 30 vol% of the compound represented by Chemical Formula 1: Chemical formula 1 and in, In Chemical Formula 1, Each X is the same or different and is independently a hydrogen atom or a fluorine atom.

2. The electrolyte according to claim 1, wherein The nonaqueous organic solvent includes 10 vol% to 20 vol% of the compound represented by Chemical Formula 1 based on the total amount of the nonaqueous organic solvent.

3. The electrolyte according to claim 1, wherein In Chemical Formula 1, all Xs are fluorine atoms.

4. The electrolyte according to claim 1, wherein The non-aqueous organic solvent further includes a carbonate non-aqueous organic solvent, an ester non-aqueous organic solvent or a combination thereof.

5. The electrolyte according to claim 4, wherein The carbonate non-aqueous organic solvent comprises at least one selected from the following: Cyclic carbonate non-aqueous organic solvents, including ethylene carbonate, propylene carbonate, butylene carbonate or a combination thereof; and The chain carbonate non-aqueous organic solvent includes at least one selected from dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl ethyl carbonate and a combination thereof.

6. The electrolyte according to claim 5, wherein The carbonate-based non-aqueous organic solvent includes ethylene carbonate and propylene carbonate.

7. The electrolyte according to claim 4, wherein The ester non-aqueous organic solvent includes methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, propyl propionate, decanoic acid lactone, mevalonolactone, valerolactone, caprolactone or a combination thereof.

8. The electrolyte according to claim 7, wherein The ester non-aqueous organic solvent includes propyl propionate.

9. The electrolyte according to claim 4, wherein The non-aqueous organic solvent includes the carbonate non-aqueous organic solvent and the ester non-aqueous organic solvent in a volume ratio of 1:1.5 to 1:

3.

10. The electrolyte according to claim 1, wherein The lithium salt includes at least one selected from the following: LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, LiN(SO3C2F5)2, Li(FSO2)2N, LiC4F9SO3, lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium difluorobis(oxalate)phosphate, lithium bis(oxalate)borate and LiN(C x F 2x+1 SO2)(C y F 2y+1 SO2), wherein x and y are integers from 1 to 20.

11. The electrolyte according to claim 1, wherein The electrolyte further includes carbonate additives, sultone additives, nitrile additives, lithium salt additives or a combination thereof.

12. A rechargeable lithium battery comprising a positive electrode, including a positive electrode active material; a negative electrode including 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 rechargeable lithium battery has a charging voltage greater than or equal to 4.45V.

14. The rechargeable lithium battery of claim 12, wherein The positive electrode active material includes lithium cobalt oxide.

15. The rechargeable lithium battery of claim 12, wherein The negative electrode active material includes graphite.

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