Electrolyte for rechargeable lithium battery and rechargeable lithium battery

Abstract

The present invention relates to an electrolyte for a rechargeable lithium battery and a rechargeable lithium battery. The electrolyte for a rechargeable lithium battery includes a non-aqueous organic solvent, a lithium salt and an additive, wherein the additive includes a compound represented by Chemical Formula 1 and a compound represented by Chemical Formula 2: Chemical Formula 1#imgabs0# Chemical Formula 2#imgabs1# wherein X is a fluorine group, a chlorine group, a bromine group or an iodine group, and A is a C1 to C10 alkylene group or (C2H4-O-C2H4) m , wherein m is an integer selected from 1 to 10.

Description

Technical Field

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

[0002] The rechargeable lithium battery can be recharged and can have a high energy density per unit weight that is three times or more times that of a lead battery, a nickel-cadmium battery, a nickel-metal hydride battery, and / or a nickel-zinc battery, etc. It can also be charged at a high rate and is therefore commercially suitable for laptop computers, cellular phones, power tools, and / or electric bicycles, etc., and research is being conducted on further increasing the energy density.

[0003] An example rechargeable lithium battery is manufactured by injecting an electrolyte into a battery cell including a positive electrode including a positive active material capable of intercalating / deintercalating lithium ions and a negative electrode including a negative active material capable of intercalating / deintercalating lithium ions.

[0004] The electrolyte includes an organic solvent in which a lithium salt is dissolved, and may decisively determine the stability and performance of a rechargeable lithium battery.

[0005] LiPF6 is the most commonly used lithium salt in electrolytes, but there is a problem that it tends to react with the solvent in the electrolyte, causing solvent consumption and generating a large amount of gas. When LiPF6 decomposes, it generates LiF and PF5, resulting in electrolyte consumption in the battery, causing high temperature performance degradation and / or poor safety.

[0006] There is a need for an electrolyte that inhibits or reduces the side reactions of such lithium salts and improves the performance of the battery. Summary of the invention

[0007] One or more aspects of embodiments of the present disclosure are directed to an electrolyte for a rechargeable lithium battery that suppresses an increase in resistance during high-temperature storage and improves battery performance by reducing gas generation.

[0008] One or more aspects of embodiments of the present disclosure are directed to a rechargeable lithium battery including an electrolyte for a rechargeable lithium battery.

[0009] One or more embodiments of the present disclosure provide an electrolyte for a rechargeable lithium battery, the electrolyte for a rechargeable lithium battery including a non-aqueous organic solvent, a lithium salt, and an additive, wherein the additive includes a compound represented by Chemical Formula 1 and a compound represented by Chemical Formula 2.

[0010] Chemical formula 1

[0011]

[0012] In Chemical Formula 1,

[0013] X may be a fluoro group, a chloro group, a bromo group or an iodo group,

[0014] R 1 To R 6 may each independently be hydrogen, cyano, substituted or unsubstituted C1 to C20 alkyl, substituted or unsubstituted C1 to C20 alkoxy, substituted or unsubstituted C2 to C20 alkenyl, substituted or unsubstituted C2 to C20 alkynyl, substituted or unsubstituted C3 to C20 cycloalkyl, substituted or unsubstituted C6 to C20 aryl, or substituted or unsubstituted C2 to C20 heteroaryl, and

[0015] n can be an integer of 0 or 1,

[0016] Chemical formula 2

[0017]

[0018] Wherein, in Chemical Formula 2,

[0019] A may be C1 to C10 alkylene or (C2H4-O-C2H4) m , wherein m may be an integer selected from 1 to 10. Preferably, A is a C1 to C3 alkylene group.

[0020] The compound represented by Chemical Formula 1 may be represented by Chemical Formula 1-1 or Chemical Formula 1-2:

[0021]

[0022] In Chemical Formula 1-1 and Chemical Formula 1-2,

[0023] R 1 To R 6 and R are each independently hydrogen, substituted or unsubstituted C1 to C10 alkyl, substituted or unsubstituted C1 to C10 alkoxy, substituted or unsubstituted C2 to C10 alkenyl, or substituted or unsubstituted C2 to C10 alkynyl. 1 To R 6 Each of may be hydrogen.

[0024] The compound represented by Chemical Formula 1 may be 2-fluoro-1,3,2-dioxaphospholane.

[0025] The compound represented by Chemical Formula 2 can be represented by Chemical Formula 2-1:

[0026] Chemical formula 2-1

[0027]

[0028] A weight ratio of the compound represented by Chemical Formula 1 to the compound represented by Chemical Formula 2 may be about 1:1 to about 3:1.

[0029] A weight ratio of the compound represented by Chemical Formula 1 to the compound represented by Chemical Formula 2 may be about 1:1 to about 2:1.

[0030] The compound represented by Chemical Formula 1 may be included in an amount of about 0.05 wt % to about 3 wt % based on 100 wt % of the non-aqueous organic solvent.

[0031] The compound represented by Chemical Formula 2 may be included in an amount of about 0.05 wt % to about 3 wt % based on 100 wt % of the non-aqueous organic solvent.

[0032] One or more embodiments of the present disclosure provide a rechargeable lithium battery including a positive electrode, a negative electrode, and an electrolyte.

[0033] A rechargeable lithium battery having excellent or appropriate high-temperature storage characteristics can be realized by suppressing an increase in resistance and reducing gas generation during high-temperature storage. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 is an exploded perspective view of a rechargeable lithium battery according to an embodiment.

[0035] Description of some symbols

[0036] 31: Rechargeable lithium battery

[0037] 32: Negative electrode

[0038] 33: Positive electrode

[0039] 34: Partition

[0040] 35: Battery housing

[0041] 36: Capping accessories DETAILED DESCRIPTION

[0042] Hereinafter, the embodiments 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 claims.

[0043] It will be understood that although the terms first, second, etc. may be used herein to describe various elements, 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.

[0044] As used herein, singular forms such as "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "includes", "including", "comprises", and / or "comprising", when used in this specification, specify the presence of the recited features, steps, operations, elements, components, and / or groups thereof, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and / or groups thereof. The terms "use", "using", and "used" may be considered synonymous with the terms "utilize", "utilizing", and "utilized", respectively.

[0045] 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. The term “and / or” includes any and all combinations of one or more of the associated listed items.

[0046] The term "may" will be understood to refer to "one or more embodiments", some of which include the described elements, and some of which do not include the elements and / or include alternative elements. Similarly, optional language such as "or" refers to "one or more embodiments", each of which includes the corresponding listed items.

[0047] As used herein, when a definition is not otherwise provided, "substituted" refers to a compound in which a hydrogen atom is replaced by a substituent selected from the group consisting of a halogen atom (F, Br, Cl or I), a hydroxyl group, an alkoxy group, a nitro group, a cyano group, an amino group, an azido group, an amidino group, a hydrazine group, a hydrazone group, a carbonyl group, a carbamoyl group, a thiol group, an ester group, a carboxyl group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphate group or a salt thereof, a C1 to C20 alkyl group, a C2 to C20 alkenyl group, a C2 to C20 alkynyl group, a C6 to C30 aryl group, a C7 to C30 aralkyl group, a C1 to C4 alkoxy group, a C1 to C20 heteroalkyl group, a C3 to C20 heteroaralkyl group, a C3 to C30 cycloalkyl group, a C3 to C15 cycloalkenyl group, a C6 to C15 cycloalkynyl group, a C2 to C20 heterocycloalkyl group, and combinations thereof.

[0048] As used herein, when no definition is otherwise provided, "hetero" indicates that the group, moiety, etc. includes 1 to 3 heteroatoms selected from nitrogen (N), oxygen (O), sulfur (S) and phosphorus (P).

[0049] Hereinafter, an electrolyte for a rechargeable lithium battery according to an embodiment is described.

[0050] An electrolyte for a rechargeable lithium battery according to an embodiment includes a nonaqueous organic solvent, a lithium salt, and an additive, wherein the additive includes a compound represented by Chemical Formula 1 and a compound represented by Chemical Formula 2.

[0051] Chemical formula 1

[0052]

[0053] In Chemical Formula 1,

[0054] X is a fluoro group, a chloro group, a bromo group or an iodo group,

[0055] R 1 To R 6 may each independently be hydrogen, cyano, substituted or unsubstituted C1 to C20 alkyl, substituted or unsubstituted C1 to C20 alkoxy, substituted or unsubstituted C2 to C20 alkenyl, substituted or unsubstituted C2 to C20 alkynyl, substituted or unsubstituted C3 to C20 cycloalkyl, substituted or unsubstituted C6 to C20 aryl, or substituted or unsubstituted C2 to C20 heteroaryl, and

[0056] n can be an integer of 0 or 1.

[0057] Chemical formula 2

[0058]

[0059] In chemical formula 2,

[0060] A may be C1 to C10 alkylene or (C2H4-O-C2H4) m , wherein m can be an integer selected from 1 to 10.

[0061] The compound represented by Chemical Formula 2 includes a difluorophosphite (—OPF2) group having excellent or appropriate electrical and chemical reactivity at a terminal (eg, two difluorophosphite groups, respectively, at opposite terminals).

[0062] The compound represented by Chemical Formula 1 is used to prevent or reduce hydrolysis by stabilizing the LiPF6 salt in the electrolyte. For example, the compound represented by Chemical Formula 1 can be oxidized on the surface of the positive electrode to form a phosphate functional group (e.g., a compound including one or more phosphate functional groups), and the phosphate functional group can be used as an anion receptor to stably form PF6 - (For example, make PF6 - Stable) and increase Li + and PF6 - The ion pair separation increases the solubility of LiF in the electrolyte and reduces the interfacial resistance.

[0063] In particular, the compound represented by Chemical Formula 1 has an oxidation potential lower than that of the solvent, and thus forms a SEI film on the surface of the negative electrode before the electrolyte is decomposed, resulting in preventing or reducing oxidation of the electrolyte on the negative electrode.

[0064] In some embodiments, the product (i.e., phosphite) from the oxidation of the compound represented by Chemical Formula 1 on the positive electrode may move (e.g., diffuse) to the negative electrode, and thus a SEI film may be formed on the negative electrode by reduction of the phosphite, thereby inhibiting or reducing side reactions with the electrolyte.

[0065] In some embodiments, the compound represented by Chemical Formula 2 can form a stable SEI film having high heat resistance through a synergistic effect with the phosphite functional group of the compound represented by Chemical Formula 1, so that the SEI film can remain firm (e.g., stable) even when stored for a long time at high temperature. Since the SEI film is maintained, the SEI film can prevent or reduce the exposure of the surface of the positive electrode, and thus can more effectively inhibit or reduce the reaction with the electrolyte at the interface of the positive electrode, inhibit or reduce the generation of high-temperature gas due to the stable film at high temperature, and also inhibit or reduce the decomposition of the solvent of the electrolyte, thereby improving the high-temperature storage characteristics of the rechargeable lithium battery.

[0066] As a result, the compounds represented by Chemical Formula 1 and Chemical Formula 2 are used together to form an SEI film on the surface of the negative electrode or to form a protective layer on the surface of the positive electrode to improve thermal stability, thereby providing a rechargeable lithium battery with excellent or appropriate temperature stability and cycle life characteristics.

[0067] In some embodiments, the compound represented by Chemical Formula 1 may be represented, for example, by Chemical Formula 1-1 or Chemical Formula 1-2.

[0068]

[0069] In Chemical Formula 1-1 and Chemical Formula 1-2,

[0070] R 1 To R 6 Each may independently be hydrogen, a substituted or unsubstituted C1 to C10 alkyl group, a substituted or unsubstituted C1 to C10 alkoxy group, a substituted or unsubstituted C2 to C10 alkenyl group, or a substituted or unsubstituted C2 to C10 alkynyl group.

[0071] In an embodiment, R 1 To R 6 may be each independently hydrogen or a substituted or unsubstituted C1 to C10 alkyl group, or R 1 To R 6 may each independently be hydrogen.

[0072] The compounds represented by Chemical Formula 1-1 and Chemical Formula 1-2 each have an electron-accepting fluorine substituent directly bonded to the central atom phosphorus (P(III)), so that the stability of the SEI film present on the surface of the negative electrode can be further improved.

[0073] In an embodiment, the compound represented by Chemical Formula 1 may be 2-fluoro-1,3,2-dioxaphospholane.

[0074] The compound represented by Chemical Formula 2 can be represented by Chemical Formula 2-1:

[0075] Chemical formula 2-1

[0076]

[0077] The weight ratio of the compound represented by Chemical Formula 1 to the compound represented by Chemical Formula 2 may be about 1: 1 to about 3: 1. When the compound represented by Chemical Formula 1 and the compound represented by Chemical Formula 2 are used within the above weight ratio range, stability during high temperature storage may be further improved.

[0078] For example, the weight ratio of the compound represented by Chemical Formula 1 to the compound represented by Chemical Formula 2 may be about 1:1 to about 3:1, about 1:1 to about 2.5:1, about 1:1 to about 2:1, about 1:1 to about 1.5:1, or about 1:1. For example, the compound represented by Chemical Formula 1 may be included in an amount greater than that of the compound represented by Chemical Formula 2. For example, the weight ratio of the compound represented by Chemical Formula 1 to the compound represented by Chemical Formula 2 may be about 2:1.

[0079] The compound represented by Chemical Formula 1 may be included in an amount of about 0.05 wt % to about 3 wt %, for example, about 0.3 wt % to about 5 wt %, about 0.5 wt % to about 3 wt %, about 0.5 wt % to about 1.5 wt %, about 0.5 wt % to about 1 wt %, or about 1 wt % to about 1.5 wt %, based on 100 wt % of the non-aqueous organic solvent.

[0080] When the content (eg, amount) of the compound represented by Chemical Formula 1 is within the above range, high temperature storage performance of the battery may be improved.

[0081] The compound represented by Chemical Formula 2 may be included in an amount of about 0.05 wt % to about 3 wt %, for example, about 0.3 wt % to about 5 wt %, about 0.5 wt % to about 3 wt %, about 0.5 wt % to about 1.5 wt %, about 0.5 wt % to about 1 wt %, or about 1 wt % to about 1.5 wt %, based on 100 wt % of the non-aqueous organic solvent.

[0082] When the content (eg, amount) of the compound represented by Chemical Formula 2 is within the above range, heat resistance of a film formed on the surface of the positive electrode may be improved.

[0083] The lithium salt is dissolved in the organic solvent, supplies lithium ions to the battery, enables the basic operation of the rechargeable lithium battery, and improves the transport of lithium ions between the positive electrode and the negative electrode. Examples of lithium salts may include at least one supporting salt selected from the following: LiPF6, LiBF4, LiSbF6, LiAsF6, LiN(SO2C2F5)2, Li(CF3SO2)2N, LiN(SO3C2F5)2, Li(FSO2)2N (lithium bis(fluorosulfonyl)imide, LiFSI), LiC4F9SO3, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiN(C x F 2x+1 SO2)(C y F 2y+1 SO2) (wherein x and y are natural numbers, such as integers selected from 1 to 20), lithium difluorobis(oxalato)phosphate, LiCl, LiI, LiB(C2O4)2 (lithium bis(oxalato)borate, LiBOB) and lithium difluoro(oxalato)borate (LiDFOB). The lithium salt can be utilized in a concentration range of about 0.1 M to about 2.0 M. When the lithium salt is included in the above concentration range, the electrolyte can have excellent or appropriate performance and / or lithium ion mobility due to optimal or appropriate electrolyte conductivity and / or viscosity.

[0084] The nonaqueous organic solvent serves as a medium for transporting ions participating in the electrochemical reaction of the battery.

[0085] The non-aqueous organic solvent may include carbonates, esters, ethers, ketones, alcohols and / or aprotic solvents.

[0086] For example, the non-aqueous organic solvent may be a solvent including ethylene carbonate, ethyl methyl carbonate, dimethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, diethyl carbonate (DEC), dipropyl carbonate, propylene carbonate (PC), ethylene carbonate (EC), fluoroethylene carbonate (FEC), butylene carbonate, ethyl propionate, ethyl butyrate, acetonitrile, succinonitrile (SN), dimethyl sulfoxide, dimethylformamide, dimethylacetamide, γ-valerolactone, γ-butyrolactone tetrahydrofuran or any combination thereof.

[0087] When a mixture of organic solvents is utilized, the mixing ratio may be appropriately adjusted according to desired or suitable battery performance, as will be widely understood by those skilled in the art.

[0088] Another embodiment provides a rechargeable lithium battery including a positive electrode, a negative electrode, and the aforementioned electrolyte.

[0089] The positive electrode may include a current collector and a positive active material layer including a positive active material formed on the current collector.

[0090] The positive active material may include a lithiated intercalation compound that reversibly intercalates and deintercalates lithium ions.

[0091] For example, at least one composite oxide of lithium and a metal selected from the group consisting of cobalt, manganese, nickel, aluminum, and combinations thereof may be used.

[0092] Non-limiting examples of the positive active material may include compounds represented by the following chemical formula.

[0093] Li a A 1-b X b D2(0.90≤a≤1.8, 0≤b≤0.5); 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 E 1-b X b O 2-c D c (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05); Li a E 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 D α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, 0<α≤2); Li a Ni 1-b-c Co b X c O 2-α T α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05, 0<α<2); Li a Ni 1-b-c Co b X c O 2-α T2(0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05, 0<α<2); Li a Ni 1-b-c Mnb X c D α (0.90≤a≤1.8,0≤b≤0.5,0≤c≤0.05\0<α≤2);Li a Nor 1-b-c Mn b X c O 2-α T α (0.90≤a≤1.8,0≤b≤0.5,0≤c≤0.05\0<α<2);Li a Nor 1-b-c Mn b X c O 2-α T2(0.90≤a≤1.8,0≤b≤0.5,0≤c≤0.05,0<α<2);Li a Nor b E c G d O2(0.90≤a≤1.8,0≤b≤0.9,0≤c≤0.5,0.001≤d≤0.1);Li a Nor b Co c Mn d G e O2(0.90≤a≤1.8,0≤b≤0.9,0≤c≤0.5,0≤d≤0.5,0.001≤e≤0.1);Li a NiG b O2(0.90≤a≤1.8,0.001≤b≤0.1);Li a CoG b O2(0.90≤a≤1.8,0.001≤b≤0.1);Li a Mn 1-b G b O2(0.90≤a≤1.8,0.001≤b≤0.1);Li a Mn2G b O4(0.90≤a≤1.8,0.001≤b≤0.1);Li a Mn 1-g G g PO4(0.90≤a≤1.8,0≤g≤0.5);QO2;QS2;LiQS2;V2O5;LiV2O5;LiZO2;LiVO4;Li (3-f) J2(PO4)3(0≤f≤2);Li (3-f) Fe2(PO4)3(0≤f≤2);Li a FePO4(0.90≤a≤1.8)。

[0094] In the above chemical formula, A is selected from Ni, Co, Mn and combinations thereof; X is selected from Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements and combinations thereof; D is selected from O, F, S, P and combinations thereof; E is selected from Co, Mn and combinations thereof; T is selected from F, S, P and combinations thereof; G is selected from Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V and combinations thereof; Q is selected from Ti, Mo, Mn and combinations thereof; Z is selected from Cr, V, Fe, Sc, Y and combinations thereof; and J is selected from V, Cr, Mn, Co, Ni, Cu and combinations thereof.

[0095] The positive electrode active material may include a positive electrode active material with a coating, or a mixture of a positive electrode active material and a positive electrode active material coated with a coating. The coating may include a coating element compound selected from an oxide or hydroxide of a coating element, an oxyhydroxide of a coating element, an oxycarbonate of a coating element, or a basic carbonate of a coating element. The compound used for the coating may be amorphous or crystalline. The coating element included in the coating may be magnesium (Mg), aluminum (Al), cobalt (Co), potassium (K), sodium (Na), calcium (Ca), silicon (Si), titanium (Ti), vanadium (V), tin (Sn), germanium (Ge), gallium (Ga), boron (B), arsenic (As), zirconium (Zr), or a mixture thereof. The coating process may include any appropriate process (e.g., spraying, dipping, etc.) as long as it does not cause any adverse effects on the characteristics of the positive electrode active material.

[0096] The amount of the positive active material may be about 90 wt % to about 98 wt % based on the total weight of the positive active material layer.

[0097] In an embodiment, the positive active material layer may include a binder and a conductive material. Herein, the amount of the binder and the conductive material may be each independently about 1 wt % to about 5 wt % based on the total weight of the positive active material layer.

[0098] The binder can improve the bonding properties of the positive electrode active material particles to each other and to the current collector. Examples thereof may include (for example,) 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, acrylated styrene-butadiene rubber, epoxy resin and / or nylon, but are not limited thereto.

[0099] It includes a conductive material to improve the conductivity of the electrode. Any conductive material can be used as the conductive material unless it causes unwanted chemical changes. Examples of the conductive material can include carbonaceous materials (such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, and / or carbon fiber, etc.); metallic materials including metal powders or metal fibers such as copper, nickel, aluminum, and / or silver, etc.; conductive polymers (such as polyphenylene derivatives); or mixtures thereof.

[0100] The current collector can be Al foil, but is not limited thereto.

[0101] The negative electrode includes a current collector and a negative electrode active material layer formed on the current collector.

[0102] The negative electrode active material can be a material that can reversibly intercalate / deintercalate lithium ions, lithium metal, a lithium metal alloy, a material capable of doping and dedoping lithium, or a transition metal oxide.

[0103] The material that can reversibly intercalate / deintercalate lithium ions includes carbon materials. The carbon materials can be any common carbonaceous negative electrode active materials in rechargeable lithium-ion batteries. Examples of the carbon materials include crystalline carbon, amorphous carbon, and combinations thereof. The crystalline carbon can be amorphous; or flaky, scaly, spherical, or fibrous natural graphite or artificial graphite. The amorphous carbon can be soft carbon, hard carbon, products of mesophase pitch carbonization, and / or calcined coke, etc.

[0104] The lithium metal alloy can include lithium and a metal selected from sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), francium (Fr), beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), silicon (Si), antimony (Sb), lead (Pb), indium (In), zinc (Zn), barium (Ba), radium (Ra), germanium (Ge), aluminum (Al), and tin (Sn).

[0105] The material capable of doping and dedoping lithium can include Si, 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 metal elements, rare earth elements, and any combination thereof), Sn, SnO2, and / or Sn-R alloys (where R is an alkali metal, alkaline earth metal, Group 13 element, Group 14 element excluding Sn, Group 15 element, Group 16 element, transition metal element, rare earth element, or any combination thereof), etc. At least one of them can be mixed with SiO2. The elements Q and R can be selected from magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), radium (Ra), scandium (Sc), yttrium (Y), titanium (Ti), zirconium (Zr), hafnium (Hf), (Rf), vanadium (V), niobium (Nb), tantalum (Ta), thorium (Db), chromium (Cr), molybdenum (Mo), tungsten (W), (Sg), technetium (Tc), rhenium (Re), (Bh), iron (Fe), lead (Pb), ruthenium (Ru), osmium (Os), (Hs), rhodium (Rh), iridium (Ir), palladium (Pd), platinum (Pt), copper (Cu), silver (Ag), gold (Au), zinc (Zn), cadmium (Cd), boron (B), aluminum (Al), gallium (Ga), tin (Sn), indium (In), thallium (Tl), germanium (Ge), phosphorus (P), arsenic (As), antimony (Sb), bismuth (Bi), sulfur (S), selenium (Se), tellurium (Te), polonium (Po), and combinations thereof.

[0106] The transition metal oxide may be vanadium oxide and / or lithium vanadium oxide, etc.

[0107] In the negative active material layer, the negative active material may be included in an amount of about 95 wt % to about 99 wt % based on the total weight of the negative active material layer.

[0108] In an embodiment, the negative electrode active material layer may include a binder and an optional conductive material. In the negative electrode active material layer, the amount of the binder may be about 1wt% to about 5wt% based on the total weight of the negative electrode active material layer. When the negative electrode active material layer further includes a conductive material, it may include about 90wt% to about 98wt% of the negative electrode active material, about 1wt% to about 5wt% of the binder and about 1wt% to about 5wt% of the conductive material.

[0109] The binder can improve the bonding properties between the negative electrode active material particles and between the negative electrode active material particles and the current collector. The binder can be a non-water-soluble binder, a water-soluble binder, or any combination thereof.

[0110] The non-water-soluble binder may be polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide, or any combination thereof.

[0111] The water-soluble binder can be a rubber-based binder or a polymer resin binder. The rubber-based binder can be selected from styrene-butadiene rubber, acrylated styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber, acrylic rubber, butyl rubber, fluororubber and a combination thereof. The polymer resin binder can be selected from polytetrafluoroethylene, polyethylene, polypropylene, ethylene propylene copolymer, polyethylene oxide, polyvinyl pyrrolidone, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, polystyrene, ethylene propylene diene copolymer, polyvinyl pyridine, chlorosulfonated polyethylene, latex, polyester resin, acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol and a combination thereof.

[0112] When a water-soluble binder is used as a negative electrode binder, a cellulose compound may be further utilized, for example, as a thickener to provide viscosity. The cellulose compound may include one or more of carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, and alkali metal salts thereof. The alkali metal may be Na, K, or Li. Based on 100 parts by weight of the negative electrode active material, such a thickener may be included in an amount of about 0.1 parts by weight to about 3 parts by weight.

[0113] A conductive material is included to provide electrode conductivity. Any conductive material can be used as the conductive material unless it causes a chemical change. Examples thereof may include carbon-based materials (such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black and / or carbon fiber, etc.); metal-based materials (such as metal powder or metal fiber of copper, nickel, aluminum and / or silver, etc.); conductive polymers (such as polyphenylene derivatives, etc.), or mixtures thereof.

[0114] The 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.

[0115] The rechargeable lithium battery may further include a separator between the negative electrode and the positive electrode, depending on the type or kind of battery. Such a separator may be a porous substrate or a composite porous substrate.

[0116] The porous substrate may be a substrate including pores, and lithium ions may move through the pores. The porous substrate may, for example, include polyethylene, polypropylene, polyvinylidene fluoride, and multilayers thereof (such as polyethylene / polypropylene double-layer separators, polyethylene / polypropylene / polyethylene three-layer separators, and polypropylene / polyethylene / polypropylene three-layer separators).

[0117] The composite porous substrate may have a form including a porous substrate and a functional layer on the porous substrate. From the perspective of ensuring additional functions, the functional layer may be, for example, at least one of a heat-resistant layer and a binder layer. For example, the heat-resistant layer may include a heat-resistant resin and an optional filler.

[0118] In some embodiments, the binder layer may include a binder resin and optionally a filler.

[0119] The filler may be an organic filler or an inorganic filler.

[0120] Figure 1 is an exploded perspective view of a rechargeable lithium battery according to an embodiment. The rechargeable lithium battery according to the embodiment is illustrated as a cylindrical battery, but is not limited thereto and may have any suitable form or shape such as a prismatic or pouch form.

[0121] refer to Figure 1, the rechargeable lithium battery 31 according to the embodiment includes: a positive electrode 33 including a positive active material, a negative electrode 32, and a separator 34. The positive electrode 33 including the aforementioned positive active material, the negative electrode 32, and the separator 34 are wound or folded and housed in a battery case 35. Then, an organic electrolyte is injected into the battery case 35, and is sealed with a cap fitting 36 to complete the rechargeable lithium battery 31.

[0122] 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.

[0123] Manufacturing of rechargeable lithium battery cells

[0124] Example 1

[0125] LiNi as the positive electrode active material 0.8 Co 0.15 Al 0.05 O2, polyvinylidene fluoride as a binder, and carbon black as a conductive material were mixed at a weight ratio of 92:4:4, respectively, and then, dispersed in N-methylpyrrolidone to prepare a positive electrode active material slurry.

[0126] The positive electrode active material slurry was applied to an Al foil to a thickness of 15 μm, dried at 100° C., and pressed to produce a positive electrode.

[0127] Graphite as a negative electrode active material, polyvinylidene fluoride as a binder, and Ketjen black as a conductive material were mixed at a weight ratio of 98:1:1, and then, dispersed in N-methylpyrrolidone to prepare a negative electrode active material slurry.

[0128] The negative electrode active material slurry was applied to a thickness of 10 μm on a Cu foil, dried at 100° C., and pressed to produce a negative electrode.

[0129] The fabricated positive and negative electrodes, a 25 μm thick polyethylene separator and an electrolyte solution were used to fabricate a rechargeable lithium battery cell. The electrolyte solution of the rechargeable lithium battery cell had the following composition.

[0130] Electrolyte solution composition

[0131] Salt: 1.15M LiPF6

[0132] Solvent: ethylene carbonate: ethyl methyl carbonate: dimethyl carbonate = 2:1:7 (EC:EMC:DMC = 2:1:7 volume ratio)

[0133] Additives: 0.5 wt% of 2-fluoro-1,3,2-dioxaphospholane as the compound represented by Chemical Formula 1, and 0.5 wt% of the compound represented by Chemical Formula 2-1 as the compound represented by Chemical Formula 2

[0134] Chemical formula 2-1

[0135]

[0136] Herein, in the electrolytic composition, "wt%" is based on 100wt% of the solvent.

[0137] Example 2

[0138] A rechargeable lithium battery cell was manufactured according to substantially the same method as Example 1, except that the content (eg, amount) of the compound represented by Chemical Formula 1 was changed to 0.75 wt %.

[0139] Example 3

[0140] A rechargeable lithium battery cell was manufactured according to substantially the same method as Example 1, except that the content (eg, amount) of the compound represented by Chemical Formula 1 was changed to 1 wt %.

[0141] Example 4

[0142] A rechargeable lithium battery cell was manufactured according to substantially the same method as Example 1, except that the content (eg, amount) of the compound represented by Chemical Formula 1 was changed to 1.25 wt %.

[0143] Comparative Example 1

[0144] A rechargeable lithium battery cell was manufactured according to substantially the same method as Example 1, except that the contents of the compound represented by Chemical Formula 1 and the compound represented by Chemical Formula 2 were changed to 0 wt % and 0.5 wt %, respectively.

[0145] Comparative Example 2

[0146] A rechargeable lithium battery cell was manufactured according to substantially the same method as Example 1, except that the contents of the compound represented by Chemical Formula 1 and the compound represented by Chemical Formula 2 were changed to 0.5 wt % and 0 wt %, respectively.

[0147] Comparative Example 3

[0148] A rechargeable lithium battery cell was manufactured according to substantially the same method as Example 1, except that the compound represented by Chemical Formula 3 was used instead of the compound represented by Chemical Formula 1, and the contents of the compound represented by Chemical Formula 3 and the compound represented by Chemical Formula 2 were changed to 0.5 wt % and 0.5 wt %, respectively:

[0149] Chemical formula 3

[0150]

[0151] Comparative Example 4

[0152] A rechargeable lithium battery cell was manufactured according to substantially the same method as Example 1, except that both the compound represented by Chemical Formula 1 and the compound represented by Chemical Formula 2 were not used (eg, simultaneously).

[0153] Evaluation of battery characteristics 1: Measurement of resistance increase rate during high temperature storage

[0154] The rechargeable lithium battery cells according to Examples 1 to 4 and Comparative Examples 1 to 4 were placed in a charged state (SOC (state of charge) = 100%) at 60°C for 30 days, and then, the direct current internal resistance (DC-IR) resistance increase rate after storage at a high temperature of 60°C was evaluated, and the results are shown in Table 1.

[0155] The DC-IR resistance increase rate (%) after high-temperature storage is the percentage of DC-IR after standing at a high temperature of 60° C. for 30 days relative to the initial DC-IR.

[0156] Table 1

[0157]

[0158] As shown in Table 1, rechargeable lithium battery cells using an electrolyte including compounds represented by Chemical Formula 1 and Chemical Formula 2 in a weight ratio of 1:1 to 3:1 (according to Examples 1 to 4) each exhibited a low DC-IR resistance increase rate during high temperature storage and thus exhibited excellent or suitable storage characteristics at high temperatures, compared to rechargeable lithium battery cells using the following: (a) an electrolyte including only one of the compounds represented by Chemical Formula 1 and Chemical Formula 2 (according to Comparative Examples 1 and 2), (b) an electrolyte including neither the compound represented by Chemical Formula 1 nor the compound represented by Chemical Formula 2 (according to Comparative Example 4), or (c) an electrolyte including a compound represented by Chemical Formula 3 instead of the compound represented by Chemical Formula 1 (according to Comparative Example 3).

[0159] Evaluation of battery characteristics 2: Gas generation

[0160] The battery cells according to Example 2 and Comparative Examples 1 to 3 were left at 60° C. for 30 days, and then the gas generation amount (mL) was measured by refinery gas analysis (RGA).

[0161] Table 2

[0162]

[0163] Referring to Table 2, the rechargeable lithium battery cell according to Example 2 using an electrolyte including compounds represented by Chemical Formula 1 and Chemical Formula 2 at a weight ratio of 1:1 to 3:1 exhibits a smaller amount of gas generation after storage at high temperature, compared to a rechargeable lithium battery cell using (a) an electrolyte including only one of the compounds represented by Chemical Formula 1 and Chemical Formula 2 (according to Comparative Examples 1 and 2), (b) an electrolyte including neither the compound represented by Chemical Formula 1 nor the compound represented by Chemical Formula 2 (according to Comparative Example 4), or (c) an electrolyte including a compound represented by Chemical Formula 3 instead of the compound represented by Chemical Formula 1 according to Comparative Example 3. Accordingly, when the electrolyte according to the embodiment of the present invention is included, the storage characteristics of the rechargeable lithium battery cell at high temperature are improved.

[0164] Battery Characteristics Evaluation 3: Room Temperature Cycle Life

[0165] The batteries of Example 2 and Comparative Examples 1 to 4 were charged to 4.45 V with a constant current-constant voltage (CC-CV) of 1 C at room temperature of 25° C., and were cut off at 0.05 C, and discharged to 3.0 V with a constant current of 1.0 C, and then the discharge capacity of 200 cycles was evaluated. The capacity retention rate of each cycle relative to the discharge capacity of the first cycle was calculated, and the results of the batteries after 200 cycles are shown in Table 3.

[0166] Table 3

[0167]

[0168]

[0169] Referring to Table 3, the rechargeable lithium battery cell according to Example 2 utilizing an electrolyte including compounds represented by Chemical Formula 1 and Chemical Formula 2 in a weight ratio of 1:1 to 3:1 exhibits excellent or appropriate cycle life characteristics compared to rechargeable lithium battery cells utilizing the following: (a) an electrolyte solution including only one of the compounds represented by Chemical Formula 1 and Chemical Formula 2 (according to Comparative Examples 1 and 2), (b) an electrolyte including neither the compound represented by Chemical Formula 1 nor the compound represented by Chemical Formula 2 (according to Comparative Example 4), or (c) an electrolyte including a compound represented by Chemical Formula 3 instead of the compound represented by Chemical Formula 1 (according to Comparative Example 3).

[0170] Terms such as "substantially," "about," and "~" are used as terms of approximation, and not as terms of degree, and are intended to take into account the inherent deviations in measurements or calculations that one of ordinary skill in the art will recognize. They may include both the stated value and an acceptable range of deviation determined by one of ordinary skill in the art, taking into account the limitations and errors associated with the measurement of that amount. For example, "about" may refer to one or more standard deviations of the stated value, or ±30%, ±20%, ±10%, or ±5% of the stated value.

[0171] 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 with 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 explicitly set forth any subranges contained within the ranges explicitly set forth herein.

[0172] While the 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 appended claims and their equivalents.

Claims

1. An electrolyte for a rechargeable lithium battery, the electrolyte comprising: Non-aqueous organic solvents, lithium salts and additives, The additive comprises a compound represented by Chemical Formula 1 and a compound represented by Chemical Formula 2: Chemical formula 1 Wherein, in Chemical Formula 1, X is a fluoro group, a chloro group, a bromo group or an iodo group, R 1 To R 6 are each independently hydrogen, cyano, substituted or unsubstituted C1 to C20 alkyl, substituted or unsubstituted C1 to C20 alkoxy, substituted or unsubstituted C2 to C20 alkenyl, substituted or unsubstituted C2 to C20 alkynyl, substituted or unsubstituted C3 to C20 cycloalkyl, substituted or unsubstituted C6 to C20 aryl, or substituted or unsubstituted C2 to C20 heteroaryl, and n is an integer of 0 or 1, Chemical formula 2 and Wherein, in Chemical Formula 2, A is C1 to C10 alkylene or (C2H4-O-C2H4) m , wherein m is an integer selected from 1 to 10, wherein the compound represented by Chemical Formula 1 is included in an amount of 0.05 wt % to 3 wt % based on 100 wt % of the non-aqueous organic solvent, and The compound represented by Chemical Formula 2 is included in an amount of 0.05 wt % to 3 wt % based on 100 wt % of the non-aqueous organic solvent.

2. The electrolyte according to claim 1, wherein the compound represented by Chemical Formula 1 is represented by Chemical Formula 1-1 or Chemical Formula 1-2: and in, In Chemical Formula 1-1 and Chemical Formula 1-2, R 1 To R 6 Each is independently hydrogen, substituted or unsubstituted C1 to C10 alkyl, substituted or unsubstituted C1 to C10 alkoxy, substituted or unsubstituted C2 to C10 alkenyl, or substituted or unsubstituted C2 to C10 alkynyl. 3 . The electrolyte according to claim 1 , wherein the compound represented by Chemical Formula 1 is 2-fluoro-1,3,2-dioxaphospholane.

4. The electrolyte according to claim 1, wherein the compound represented by Chemical Formula 2 is represented by Chemical Formula 2-1: Chemical formula 2-1 5 . The electrolyte according to claim 1 , wherein a weight ratio of the compound represented by Chemical Formula 1 to the compound represented by Chemical Formula 2 is 1:1 to 3:

1. 6 . The electrolyte according to claim 1 , wherein a weight ratio of the compound represented by Chemical Formula 1 to the compound represented by Chemical Formula 2 is 1:1 to 2:

1.

7. A rechargeable lithium battery comprising: Positive electrode; Negative electrode; and The electrolyte according to any one of claims 1 to 6.

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