Electrolyte additive, electrolyte comprising same, and rechargeable lithium battery

Abstract

The invention relates to an electrolyte additive, an electrolyte including the same, and a rechargeable lithium battery. The electrolyte additive is represented by Chemical Formula 1. The description of the chemical formula 1 # imgabs0 # chemical formula 1 follows the specification.

Description

Technical Field

[0001] The present disclosure herein relates to an electrolyte additive, an electrolyte for a rechargeable lithium battery, and a rechargeable lithium battery including the same. Background Art

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

[0003] A rechargeable lithium battery includes a positive electrode and a negative electrode (each including an active material capable of inserting and extracting lithium ions) and an electrolyte. If (eg, when) lithium ions are inserted / extracted at the positive electrode and the negative electrode, electrical energy is generated through oxidation and reduction reactions.

[0004] One of the latest development directions of rechargeable lithium batteries is to improve the high temperature characteristics of the battery. Generally speaking, rechargeable lithium batteries may suffer from problems such as increased resistance, gas generation and / or reduced cycle life at high temperatures. Summary of the invention

[0005] Aspects according to some embodiments relate to an electrolyte additive for a rechargeable lithium battery that improves cycle-life characteristics while suppressing or reducing resistance increase and gas generation of the rechargeable lithium battery at high temperatures.

[0006] Additional aspects will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the presented embodiments of the disclosure.

[0007] According to some embodiments, an electrolyte additive for a rechargeable lithium battery is represented by Chemical Formula 1:

[0008] Chemical formula 1

[0009]

[0010] In chemical formula 1, L 1 may be a substituted or unsubstituted C1-C20 alkylene group; and R 1 ~R 4 Each independently may be a substituted or unsubstituted C6-C20 aryl group.

[0011] According to some embodiments, the electrolyte includes the above-mentioned electrolyte additive.

[0012] According to some embodiments, a rechargeable lithium battery includes the above-mentioned electrolyte.

[0013] The electrolyte additive according to some embodiments may suppress or reduce the dissolution of metal from the positive electrode active material at high temperature, thereby suppressing or reducing resistance increase and gas generation in a rechargeable lithium battery, and improving cycle-life characteristics. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The accompanying drawings are included to provide a further understanding of the present disclosure and are incorporated into and constitute a part of this specification. The drawings illustrate embodiments of the present disclosure and together with the description are used to explain the principles of the present disclosure. In the drawings:

[0015] Figure 1 A schematic diagram illustrating a cylindrical battery according to some embodiments.

[0016] Figure 2 A schematic diagram illustrating a prismatic battery according to some embodiments.

[0017] Figure 3 A schematic diagram illustrating a pouch-type (or type) battery according to some embodiments.

[0018] Figure 4 A schematic diagram illustrating a pouch-type (or type) battery according to some embodiments.

[0019] Description of Reference Numerals

[0020] 100: Rechargeable lithium battery 10: Positive electrode

[0021] 11: Positive electrode lead tab 12: Positive terminal

[0022] 20: Negative electrode 21: Negative electrode lead lug

[0023] 22: Negative terminal 30: Separator

[0024] 40: electrode assembly 50: shell

[0025] 60: Sealing member 70: Electrode terminal piece

[0026] 71: Positive electrode terminal tab 72: Negative electrode terminal tab DETAILED DESCRIPTION

[0027] Hereinafter, embodiments of the present disclosure will be described in more detail. However, these embodiments are examples, the present disclosure is not limited thereto, and the scope of the present disclosure is defined by the claims and their equivalents.

[0028] If (for example, when) specific definitions are provided otherwise, it will be understood that if (for example, when) an element (such as a layer, film, region or substrate) is referred to as being "on" another element (such as a layer, film, region or substrate), it can be directly on the other element (such as a layer, film, region or substrate) or intervening elements may also be present.

[0029] If (for example, when) specific definitions are provided in other ways, singular expressions as used herein may also include plural expressions. In addition, unless otherwise indicated, the term "A or B" may mean "including A, including B, or including A and B".

[0030] The term "combinations thereof" as used herein may refer to mixtures, laminates, composites, copolymers, alloys, blends, and reaction products of the components.

[0031] If (for example, when) a specific definition is provided otherwise, the term "alkyl" as used herein refers to a C1-C20 alkyl group, the term "alkenyl" refers to a C2-C20 alkenyl group, the term "cycloalkenyl" refers to a C3-C20 cycloalkenyl group, the term "heterocycloalkenyl" refers to a C3-C20 heterocycloalkenyl group, the term "aryl" refers to a C6-C20 aryl group, the term "aralkyl" refers to a C6-C20 aralkyl group, the term "alkylene" refers to a C1-C20 alkylene group, the term "arylene" refers to a C6-C20 arylene group, the term "alkylarylene" refers to a C6-C20 alkylarylene group, the term "heteroarylene" refers to a C3-C20 heteroarylene group, and the term "alkyleneoxy" refers to a C1-C20 alkyleneoxy group.

[0032] If (for example, when) a specific definition is provided otherwise, the term "substituted" as used herein refers to substitution (replacing a hydrogen atom) with a halogen atom (F, Cl, Br, I), a hydroxyl group, a C1-C20 alkoxy group, a nitro group, a cyano group, an amine group, an imino group, an azido group, a carbamimido group, a hydrazine group, a hydrazone group, a carbonyl group, a carbamoyl group, a thiol group, an ester group, an ether 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-C20 alkyl group, a C2-C20 alkenyl group, a C2-C20 alkynyl group, a C6-C20 aryl group, a C3-C20 cycloalkyl group, a C3-C20 cycloalkenyl group, a C3-C20 cycloalkynyl group, a C2-C20 heterocycloalkyl group, a C2-C20 heterocycloalkenyl group, a C2-C20 heterocycloalkynyl group, a C3-C20 heteroaryl group, and / or combinations thereof (for example, any appropriate combination).

[0033] In the chemical formulae in the present specification, unless otherwise defined, if (for example, when) a chemical bond is not drawn at a position where it should be given, it means that hydrogen is bonded at that position.

[0034] Electrolyte Additives

[0035] According to some embodiments, an electrolyte additive for a rechargeable lithium battery is represented by Chemical Formula 1:

[0036] Chemical formula 1

[0037]

[0038] Since the electrolyte additive according to some embodiments symmetrically includes a phosphate group and an aromatic group, it can be oxidized and decomposed on the surface of the positive electrode to form (or provide) a solid electrolyte interface (SEI) film having high stability and heat resistance. The SEI film formed on the surface of the positive electrode can inhibit or reduce the dissolution of metal from the positive electrode active material, thereby improving the cycle life characteristics of the rechargeable lithium battery while inhibiting or reducing resistance increase and gas generation.

[0039] A description of Chemical Formula 1 representing the electrolyte additive is as follows.

[0040] L 1 It may be a substituted or unsubstituted C1-C20 alkylene group.

[0041] For example, L 1 It may be a substituted or unsubstituted C1-C3 alkylene group.

[0042] R 1 ~R 4 Each of them may be independently substituted or unsubstituted C6-C20 aryl. 1 ~R 4 They may all be phenyl.

[0043] Chemical formula 1 can be represented by chemical formula 1-1:

[0044] Chemical formula 1-1

[0045]

[0046] In Chemical Formula 1-1, L 1 The definition of is the same as above.

[0047] Examples of the electrolyte additive represented by Chemical Formula 1 are as follows:

[0048] Chemical formula 1-1-1

[0049]

[0050] Chemical formula 1-1-2

[0051]

[0052] Chemical formula 1-1-3

[0053]

[0054] Electrolyte

[0055] According to some embodiments, an electrolyte for a rechargeable lithium battery includes a non-aqueous organic solvent; a lithium salt; and an electrolyte additive represented by Chemical Formula 1.

[0056] Chemical formula 1

[0057]

[0058] The electrolyte according to some embodiments includes the electrolyte additive described above. The electrolyte additive included in the electrolyte inhibits metal dissolution from the positive electrode active material at high temperature, thereby inhibiting or reducing resistance increase and gas generation of the rechargeable lithium battery and improving cycle life characteristics.

[0059] Based on 100wt% of the electrolyte, the electrolyte additive may be included in an amount of about 0.05wt% to about 3wt%, about 0.05wt% to about 2wt%, or about 0.05wt% to about 1wt%. Within these ranges, the electrolyte additive may be oxidized and decomposed on the surface of the positive electrode to form (or provide) an SEI film having high stability and heat resistance. That is, within these ranges, the SEI film formed on the surface of the positive electrode by oxidation and decomposition of the electrolyte additive may have appropriate (e.g., high) stability and heat resistance.

[0060] Non-aqueous organic solvents

[0061] The nonaqueous organic solvent serves as a medium for transporting (eg, transferring) ions participating in the electrochemical reaction of the battery.

[0062] The non-aqueous organic solvent may include a carbonate-based solvent, an ester-based solvent, an ether-based solvent, a ketone-based solvent, an alcohol-based solvent, an aprotic solvent, and / or combinations thereof (eg, any appropriate combination thereof).

[0063] Carbonate solvents may include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), ethyl methyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), etc. Ester solvents may include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, propyl propionate, decanoic acid lactone, mevalonolactone, valerolactone, caprolactone, etc.

[0064] Ether solvents may include dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, tetrahydrofuran, etc. Ketone solvents may include cyclohexanone, etc. Alcohol solvents may include ethanol, isopropanol, etc. Aprotic solvents may include nitriles (such as R-CN (wherein R is a C2-C20 straight chain, branched chain or cyclic hydrocarbon group, and may include a double bond, an aromatic ring or an ether group)), amides (such as dimethylformamide), dioxolanes (such as 1,3-dioxolane and / or 1,4-dioxolane), sulfolane, etc.

[0065] The nonaqueous organic solvent may be used alone or in combination of two or more.

[0066] In some embodiments, if (eg, when) a carbonate-based solvent is used, a cyclic carbonate and a linear carbonate may be mixed and used, and the cyclic carbonate and the linear carbonate may be mixed in a volume ratio of about 1:1 to about 1:9.

[0067] Lithium salts

[0068] The lithium salt dissolved in the non-aqueous organic solvent supplies lithium ions in the battery, ensures 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 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+1 SO2) (x and y are each independently an integer of 1 to 20), one or more of lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium difluorobis(oxalato)phosphate (LiDFOB) and lithium bis(oxalato)borate (LiBOB).

[0069] Rechargeable lithium battery

[0070] According to some 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 including a non-aqueous organic solvent, a lithium salt, and an electrolyte additive represented by Chemical Formula 1:

[0071] Chemical formula 1

[0072]

[0073] A rechargeable lithium battery according to some embodiments includes an electrolyte, the electrolyte including the electrolyte additive described above. The electrolyte additive included in the electrolyte inhibits the dissolution of metal from the positive electrode active material at high temperatures, thereby inhibiting or reducing resistance increase and gas generation in the rechargeable lithium battery and improving cycle life characteristics.

[0074] Positive electrode active material

[0075] The positive electrode active material may be a compound capable of intercalating and deintercalating lithium (lithiated intercalation compound). For example, a composite oxide of lithium and one or more types (species) of metals selected from cobalt, manganese, nickel, and combinations thereof (eg, any appropriate combination thereof) may be used.

[0076] The composite oxide may be a lithium transition metal composite oxide, and examples thereof may include lithium nickel composite oxides, lithium cobalt composite oxides, lithium manganese composite oxides, lithium iron phosphate compounds, cobalt-free lithium nickel manganese composite oxides and / or combinations thereof (e.g., any appropriate combination thereof).

[0077] As an example, a compound represented by any one of the following chemical formulas can be used. a A 1-b X b O 2-c D c (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05); Li a Mn 2-b X b O 4-c D c (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05); Li a Ni 1-b-c 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 eO2 (0.90≤a≤1.8, 0≤b≤0.9, 0≤c≤0.5, 0≤d≤0.5, 0≤e≤0.1); Li a NeG b O2(0.90≤a≤1.8, 0.001≤b≤0.1); Li a CoG b O2(0.90≤a≤1.8, 0.001≤b≤0.1); Li a Mn 1-b G b O2(0.90≤a≤1.8, 0.001≤b≤0.1); Li a Mn b O4(0.90≤a≤1.8, 0.001≤b≤0.1); Li a Mn 1-g G g PO4(0.90≤a≤1.8, 0≤g≤0.5); Li (3-f) Fe2(PO4)3(0≤f≤2); and / or Li a FePO4(0.90≤a≤1.8).

[0078] In the above chemical formula, A is Ni, Co, Mn and / or a combination thereof (e.g., any suitable combination thereof); X is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element and / or a combination thereof (e.g., any suitable combination thereof); D is O, F, S, P and / or a combination thereof (e.g., any suitable combination thereof); G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V and / or a combination thereof (e.g., any suitable combination thereof); and L 1 is Mn, Al, and / or combinations thereof (eg, any suitable combination thereof).

[0079] As an example, based on 100 mol% of the metal excluding lithium in the lithium transition metal composite oxide, the positive electrode active material may be a high nickel-based positive electrode active material having a nickel content (e.g., amount) greater than or equal to about 80 mol%, greater than or equal to about 85 mol%, greater than or equal to about 90 mol%, greater than or equal to about 91 mol%, or greater than or equal to about 94 mol% and less than or equal to about 99 mol%. The high nickel-based positive electrode active material can achieve high capacity and can be applied to high capacity, high energy density rechargeable lithium batteries.

[0080] The positive electrode active material may include a lithium nickel-based composite oxide represented by Chemical Formula 11:

[0081] Chemical formula 11

[0082] Li a1 Nix1 M 1 y1 M 2 z1 O 2-b1 X b1

[0083] In Chemical Formula 11, 0.9 ≤ a1 ≤ 1.8 (for example, 0.9 ≤ a1 ≤ 1.2), 0.7 ≤ x1 ≤ 1, 0 ≤ y1 ≤ 0.3, 0 ≤ z1 ≤ 0.3, 0.9 ≤ x1 + y1 + z1 ≤ 1.1, and 0 ≤ b1 ≤ 0.1; M 1 and M 2 may each independently be one or more elements selected from Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sr, Ti, V, W, and Zr; and X may be one or more elements selected from F, P, and S.

[0084] In Chemical Formula 11, in an embodiment, 0.75 ≤ x1 ≤ 1, 0 ≤ y1 ≤ 0.28, and 0 ≤ z1 ≤ 0.08; 0.85 ≤ x1 ≤ 1, 0 ≤ y1 ≤ 0.15, and 0 ≤ z1 ≤ 0.15; or 0.9 ≤ x1 ≤ 1, 0 ≤ y1 ≤ 0.1, and 0 ≤ z1 ≤ 0.1.

[0085] For example, the positive electrode active material may include a lithium nickel-based composite oxide represented by Chemical Formula 12. The compound represented by Chemical Formula 12 may be referred to as a lithium nickel cobalt-based composite oxide:

[0086] Chemical Formula 12

[0087] Li a2 Ni x2 Co y2 M 3 z2 O 2-b2 X b2

[0088] In Chemical Formula 12, 0.9 ≤ a2 ≤ 1.8, 0.7 ≤ x2 < 1, 0 < y2 ≤ 0.2, 0 ≤ z2 ≤ 0.2, 0.9 ≤ x2 + y2 + z2 ≤ 1.1, and 0 ≤ b2 ≤ 0.1, M 3 may be one or more elements selected from Al, B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sr, Ti, V, W, and Zr, and X may be one or more elements selected from F, P, and S.

[0089] In Chemical Formula 12, in an embodiment, 0.75≤x2≤0.99, 0≤y2≤0.15, and 0≤z2≤0.15; 0.85≤x2≤0.99, 0.01≤y2≤0.15, and 0.01≤z2≤0.15; or 0.9≤x2≤0.99, 0.01≤y2≤0.1, and 0.01≤z2≤0.1.

[0090] As an example, the positive electrode active material may include a lithium nickel-based composite oxide represented by Chemical Formula 13. The compound of Chemical Formula 13 may be referred to as a lithium nickel cobalt aluminum-based composite oxide or a lithium nickel cobalt manganese-based composite oxide.

[0091] Chemical formula 13

[0092] Li a3 Ni x3 Co y3 M 4 z3 M 5 w3 O 2-b3 X b3

[0093] In Chemical Formula 13, 0.9≤a3≤1.8, 0.7≤x3≤0.98, 0.01≤y3≤0.19, 0.01≤z3≤0.19, 0≤w3≤0.19, 0.9≤x3+y3+z3+w3≤1.1, and 0≤b3≤0.1, M 4 It can be one or more elements selected from Al and Mn, M 5 It may be one or more elements selected from B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mo, Nb, Si, Sr, Ti, V, W and Zr, and X may be one or more elements selected from F, P and S.

[0094] In Chemical Formula 13, in an embodiment, 0.75≤x3≤0.98, 0.01≤y3≤0.16, 0.01≤z3≤0.16 and 0≤w3≤0.16; 0.85≤x3≤0.98, 0.01≤y3≤0.14, 0.01≤z3≤0.14, and 0≤w3≤0.14; or 0.9≤x3≤0.98, 0.01≤y3≤0.09, 0.01≤z3≤0.09, and 0≤w3≤0.09.

[0095] As an example, the positive electrode active material may include a lithium nickel-based composite oxide represented by Chemical Formula 14. The compound of Chemical Formula 14 may be referred to as a cobalt-free lithium nickel manganese-based composite oxide.

[0096] Chemical formula 14

[0097] Li a4Ni x4 Mn y4 M 6 z4 O 2-b4 X b4

[0098] In Chemical Formula 14, 0.9 ≤ a4 ≤ 1.8, 0.7 ≤ x4 < 1, 0 < y4 ≤ 0.3, 0 ≤ z4 ≤ 0.1, 0.9 ≤ x4 + y4 + z4 ≤ 1.1, and 0 ≤ b4 ≤ 0.1, M 6 may be one or more elements selected from Al, B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mo, Nb, Si, Sr, Ti, V, W, and Zr, and X may be one or more elements selected from F, P, and S.

[0099] Cobalt-free lithium nickel manganese composite oxides have strong structural instability (e.g., poor structural stability), and their structures can collapse under high voltage and / or high temperature conditions, causing transition metal (e.g., Ni) dissolution, and the stability and cycle life of rechargeable lithium batteries can deteriorate rapidly.

[0100] However, according to some embodiments of the electrolyte additive, even under high voltage and / or high temperature conditions, even if (e.g., when) used in combination with cobalt-free lithium nickel manganese composite oxides, the structural collapse of cobalt-free lithium nickel manganese composite oxides can be sufficiently suppressed, thereby improving the stability and cycle life characteristics of rechargeable lithium batteries.

[0101] Positive electrode

[0102] The positive electrode for a rechargeable lithium battery may include a positive electrode current collector and a positive electrode active material layer on the positive electrode current collector. The positive electrode active material layer may include a positive electrode active material and may further include a binder and / or a conductive material.

[0103] For example, the positive electrode may further include an additive that can be used as a sacrificial positive electrode.

[0104] Based on 100 wt% of the positive electrode active material layer, the content (e.g., amount) of the positive electrode active material may be about 90 wt% to about 99 wt%, and the content (e.g., amount) of the binder and the conductive material may each be about 0.5 wt% to about 5 wt%.

[0105] The binder is used to properly (e.g., well) attach the positive electrode active material particles to each other, and also properly (e.g., well) attach the positive electrode active material to the positive electrode current collector. Non-limiting examples of binders may include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers including ethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth) acrylated styrene-butadiene rubber, epoxy resin, (meth) acrylic resin, polyester resin, nylon, etc.

[0106] Conductive materials can be used to impart conductivity (e.g., electrical conductivity) to electrodes. Any material that does not cause chemical changes (e.g., does not cause undesirable chemical changes in a rechargeable lithium battery) and conducts electrons can be used as the conductive material in the battery. Examples of conductive materials may include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanofibers, and / or carbon nanotubes; metal-based materials containing copper, nickel, aluminum, silver, etc. in the form of metal powder or metal fiber; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0107] In some embodiments, Al foil may be used as a current collector, but the present disclosure is not limited thereto.

[0108] Negative electrode active material

[0109] 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, and / or a transition metal oxide.

[0110] The material that reversibly intercalates / deintercalates lithium ions may include a carbon-based negative electrode active material, for example, crystalline carbon, amorphous carbon, and / or a combination thereof (e.g., any suitable combination thereof). The crystalline carbon may be graphite, such as amorphous (e.g., irregularly shaped), flaky, thin, spherical or fibrous natural graphite or artificial graphite. The amorphous carbon may be soft carbon, hard carbon, a mesophase pitch carbonization product (e.g., coal pitch), calcined coke, etc.

[0111] The lithium metal alloy may include lithium and a metal selected from Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn.

[0112] The material capable of being doped / undoped with lithium may be a Si-based negative electrode active material or a Sn-based negative electrode active material. The Si-based negative electrode active material may include silicon, a silicon-carbon composite (Si-C composite), SiO x(0 < x ≤ 2), Si-Q alloy (where Q is selected from alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements (excluding Si), Group 15 elements, Group 16 elements, transition metals, rare earth elements, and / or combinations thereof (e.g., any suitable combination thereof)). The Sn-based negative electrode active material may include Sn, SnO x (0 < x ≤ 2) (e.g., SnO2), Sn-based alloys, and / or combinations thereof (e.g., any suitable combination thereof).

[0113] The silicon-carbon composite may be a composite of silicon and amorphous carbon. According to some 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 primary silicon particles are aggregated and an amorphous carbon coating (shells) located on the surface of the secondary particles. Amorphous carbon may also be located between the primary silicon particles, and, for example, the primary silicon particles may be coated with amorphous carbon. The secondary particles may be dispersed in an amorphous carbon matrix.

[0114] 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 located on the surface of the core.

[0115] The Si-based negative electrode active material or the Sn-based negative electrode active material may be used in combination with a carbon-based negative electrode active material.

[0116] Negative electrode

[0117] 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.

[0118] For example, based on 100 wt% of the negative electrode active material layer, the negative electrode active material layer may include about 90 wt% to about 99 wt% of the negative electrode active material, about 0.5 wt% to about 5 wt% of the binder, and about 0 wt% to about 5 wt% of the conductive material.

[0119] The binder may be used to appropriately (e.g., well) attach the negative electrode active material particles to each other and also to appropriately (e.g., well) attach the negative electrode active material to the negative electrode current collector. The binder may include a non-aqueous binder, an aqueous binder, a dry binder, and / or combinations thereof (e.g., any suitable combination thereof).

[0120] The non-aqueous binder may include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide, and / or combinations thereof (e.g., any suitable combination thereof).

[0121] 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 / or combinations thereof (e.g., any suitable combination thereof).

[0122] When the aqueous binder is used as a binder in the negative electrode active material layer, it may further include a cellulose compound capable of imparting viscosity. The cellulose compound 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.

[0123] The dry binder may be a polymer material capable of fiberization, and may be, for example, polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, and / or combinations thereof (eg, any appropriate combination thereof).

[0124] A conductive material is included to provide electrode conductivity, and any conductive material can be used as the conductive material unless it causes chemical changes (e.g., it should not cause undesirable chemical changes in a rechargeable lithium battery). Examples of the conductive material may include (e.g., may be) a carbon-based material such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber, carbon nanotube, etc.; a metal-based material containing copper, nickel, aluminum, silver, etc. in the form of (or provided as) a metal powder or metal fiber; a conductive polymer such as a polyphenylene derivative; or a mixture thereof (e.g., any suitable one).

[0125] The negative electrode current collector may include one selected from copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, and / or combinations thereof (eg, any appropriate combination thereof), but the present disclosure is not limited thereto.

[0126] Diaphragm

[0127] Depending on the type or kind of the rechargeable lithium battery, the separator may be present between the positive electrode and the negative electrode. The separator may include a polyethylene separator, a polypropylene separator, a polyvinylidene fluoride separator, or a multilayer film of two or more layers thereof (such as a polyethylene / polypropylene two-layer separator, a polyethylene / polypropylene / polyethylene three-layer separator, a polypropylene / polyethylene / polypropylene three-layer separator, etc.).

[0128] The membrane may include a porous substrate and a coating located on a surface of the porous substrate (e.g., on one surface or both surfaces or on one side or both sides (e.g., on opposite surfaces)), the coating including an organic material, an inorganic material and / or a combination thereof (e.g., any suitable combination thereof).

[0129] The porous substrate may be a polymer film formed of any one selected from polyolefins (such as polyethylene and / or polypropylene), polyesters (such as polyethylene terephthalate and / or polybutylene terephthalate), polyacetals, polyamides, polyimides, polycarbonates, polyether ketones, polyarylether ketones, polyetherimides, polyamideimides, polybenzimidazoles, polyethersulfones, polyphenylene oxides, cyclic olefin copolymers, polyphenylene sulfide, polyethylene naphthalate, glass fibers, and polytetrafluoroethylene (e.g., Teflon), or may be a polymer film formed of a copolymer or a mixture of two or more thereof.

[0130] The organic material may include a polyvinylidene fluoride-based polymer or a (meth)acryl-based polymer.

[0131] The inorganic material may include inorganic particles selected from Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, Mg(OH)2, boehmite and / or combinations thereof (e.g., any suitable combination thereof), but the present disclosure is not limited thereto.

[0132] An organic material and an inorganic material may be mixed in one coating layer, or a coating layer including an organic material and a coating layer including an inorganic material may be laminated.

[0133] Rechargeable lithium battery

[0134] Rechargeable lithium batteries may be classified into cylindrical batteries, prismatic batteries, pouch-type (or kind) batteries, coin-type (or kind) batteries, etc. according to their shapes. Figure 1 to Figure 4 A schematic diagram illustrating a rechargeable lithium battery according to one or more embodiments. Figure 1 A cylindrical battery is shown, Figure 2 A prismatic cell is shown, and Figure 3 and Figure 4 Shows a pouch type (or kind) battery. Figure 1 to Figure 4 , the rechargeable lithium battery 100 may include: an electrode assembly 40 including a positive electrode 10, a negative electrode 20, and a separator 30 between the positive electrode 10 and the negative electrode 20; and a case 50 in which the electrode assembly 40 is accommodated. The positive electrode 10, the negative electrode 20, and the separator 30 may be impregnated with an electrolyte (not shown). The rechargeable lithium battery 100 may include a sealing member 60 that seals the case 50, such as Figure 1 As shown in Figure 2 In the embodiment, the rechargeable lithium battery 100 may include a positive electrode lead tab 11, a positive electrode terminal 12, a negative electrode lead tab 21, and a negative electrode terminal 22. Figure 3 and Figure 4 As shown in FIG. 1 , the rechargeable lithium battery 100 may include electrode tabs 70 , which may be, for example, a positive electrode tab 71 and a negative electrode tab 72 serving as electrical paths for guiding (eg, conducting) current formed in the electrode assembly 40 to the outside.

[0135] A rechargeable lithium battery according to some embodiments may be applied to automobiles, mobile phones, and / or one or more appropriate types (kinds) of electronic devices, but the present disclosure is not limited thereto.

[0136] Hereinafter, embodiments 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.

[0137] Synthesis Example 1: Compound represented by Chemical Formula 1-1-1

[0138] 1,2-bis(diphenylphosphino)ethane (0.5mmol, 2.5mg) and hydrogen peroxide (3.0mmol) were added dropwise to a Schlenk flask containing 100mL of dichloromethane, and then stirred at 50°C for 24 hours. Subsequently, the compound obtained by filtering the precipitate therefrom was dissolved in a small amount of acetone. The corresponding solution was slowly added dropwise to 500mL of dichloromethane using a dropping funnel, and then the reactant was filtered, purified and vacuum dried to obtain a compound represented by chemical formula 1-1-1.

[0139] ( 1 H NMR (300MHz): δ = 2.49, 2.50 (4H, CH2P); 7.42 (t, 3JHH = 7.5Hz, 8H); 7.47 (t, 3JHH = 7.4Hz, 4H); 7.68 (dd, 3JHH = 7.5Hz, 3JHP = 12.0Hz, 8H))

[0140] Chemical formula 1-1-1

[0141]

[0142] Example 1

[0143] (1) Preparation of electrolyte

[0144] The electrolyte was prepared by mixing ethylene carbonate (EC), ethyl methyl carbonate (EMC) and dimethyl carbonate (DMC) in a volume ratio of 2:1:7 to obtain a non-aqueous organic solvent, dissolving 1.15M of LiPF6, and adding 0.5wt% of an electrolyte additive represented by Chemical Formula 1-1-1 thereto.

[0145] In the composition of the electrolyte, the content (eg, amount) "wt %" of the electrolyte additive is based on 100 wt % of the total weight of the electrolyte (lithium salt+nonaqueous organic solvent+electrolyte additive).

[0146] (2) Manufacturing of rechargeable lithium battery cells

[0147] LiNi as the positive electrode active material 0.75 Mn 0.23 Al 0.02 O2, polyvinylidene fluoride as a binder, and acetylene black as a conductive material were mixed at a weight ratio of 96:3:1, respectively, and then dispersed in N-methylpyrrolidone to prepare a positive electrode active material slurry.

[0148] The positive electrode active material slurry was coated on a 15 μm thick Al foil, dried at 100° C., and pressed to produce a positive electrode.

[0149] As a negative electrode active material, a mixture of artificial graphite and Si—C composite in a weight ratio of 93:7 was used, and the negative electrode active material, styrene-butadiene rubber binder and carboxymethyl cellulose were mixed and dispersed in distilled water in a weight ratio of 98:1:1 to prepare a negative electrode active material slurry.

[0150] The Si-C composite includes: a core including artificial graphite and silicon particles; and coal tar pitch coated on a surface of the core.

[0151] The negative electrode active material slurry was coated on a 10 μm-thick Cu foil, dried at 100° C., and pressed to manufacture a negative electrode.

[0152] An electrode assembly was manufactured by assembling a positive electrode, a negative electrode, and a separator made of polyethylene having a thickness of 10 μm, and an electrolyte was injected, thereby manufacturing a rechargeable lithium battery cell.

[0153] Example 2

[0154] An electrolyte and a rechargeable lithium battery cell were manufactured in substantially the same manner as in Example 1, except that the content (eg, amount) of the electrolyte additive was changed to 1 wt %.

[0155] Example 3

[0156] An electrolyte and a rechargeable lithium battery cell were manufactured in substantially the same manner as in Example 1, except that the content (eg, amount) of the electrolyte additive was changed to 2 wt %.

[0157] Example 4

[0158] The electrolyte and the rechargeable lithium battery cell were manufactured in substantially the same manner as in Example 1, except that the positive electrode active material was changed to LiNi 0.9 Co 0.05 Al 0.05 O2.

[0159] Example 5

[0160] An electrolyte and a rechargeable lithium battery cell were manufactured in substantially the same manner as in Example 4, except that the content (eg, amount) of the electrolyte additive was changed to 1 wt %.

[0161] Example 6

[0162] An electrolyte and a rechargeable lithium battery cell were manufactured in substantially the same manner as in Example 4, except that the content (eg, amount) of the electrolyte additive was changed to 2 wt %.

[0163] Comparative Example 1

[0164] An electrolyte and a rechargeable lithium battery cell were manufactured in substantially the same manner as in Example 1, except that no electrolyte additives were included (ie, not added).

[0165] Comparative Example 2

[0166] An electrolyte and a rechargeable lithium battery cell were manufactured in substantially the same manner as in Example 1, except that a compound represented by Chemical Formula A (CAS No. 1663-45-2, Aldrich Corporation) was used instead of the electrolyte additive represented by Chemical Formula 1-1-1.

[0167] Chemical formula A

[0168]

[0169] Comparative Example 3

[0170] An electrolyte and a rechargeable lithium battery cell were manufactured in substantially the same manner as in Example 1, except that the compound represented by Chemical Formula B was used instead of the electrolyte additive represented by Chemical Formula 1-1-1.

[0171] Chemical formula B

[0172]

[0173] Comparative Example 4

[0174] The electrolyte and the rechargeable lithium battery cell were manufactured in substantially the same manner as in Comparative Example 1, except that the positive electrode active material was changed to LiNi 0.9 Co 0.05 Al 0.05 O2.

[0175] Comparative Example 5

[0176] The electrolyte and the rechargeable lithium battery cell were manufactured in substantially the same manner as in Comparative Example 2, except that the positive electrode active material was changed to LiNi 0.9 Co 0.05 Al 0.05 O2.

[0177] Comparative Example 6

[0178] The electrolyte and the rechargeable lithium battery cell were manufactured in substantially the same manner as in Comparative Example 3, except that the positive electrode active material was changed to LiNi 0.9 Co 0.05 Al 0.05 O2.

[0179] Evaluation Example 1: Evaluation of high temperature storage characteristics

[0180] (1) DCIR increase rate

[0181] The ΔV / ΔI (voltage change / current change) of the rechargeable lithium battery cells according to Examples 1 to 6 and Comparative Examples 1 to 6 was measured to obtain the initial DC resistance (DCIR), and then the DC resistance was remeasured after each battery cell was in a fully charged state (SOC 100%) as the internal maximum energy state and stored at a high temperature of 60° C. for 30 days to calculate the DCIR increase rate (%) according to Equation 1, and the results are shown in Table 1.

[0182] Equation 1

[0183] DCIR increase rate (%) = (DCIR after 30 days / initial DCIR) × 100

[0184] Table 1

[0185]

[0186]

[0187] (2) Gas generation

[0188] The rechargeable lithium battery cells according to Examples 1 to 3 and Comparative Examples 1 to 3 were placed in a fully charged state (SOC 100%) as the internal maximum energy state and then stored at a high temperature of 60° C. for 1 day or 7 days to evaluate the amount of gas generated thereby, and the results are shown in Table 2.

[0189] The amount of gas thus generated after storage at a high temperature is obtained by measuring the volume change before and after storage and converting it into a mass change by using the Archimedean method.

[0190] Table 2

[0191]

[0192] Evaluation Example 2: Evaluation of high temperature charge and discharge characteristics

[0193] The rechargeable lithium battery cells according to Examples 1 to 3 and Comparative Examples 1 to 3 were charged at 0.33C (CC / CV, 4.45V, 0.025C cutoff) / discharged at 1.0C (CC, 2.5V cutoff) at 45°C for 200 cycles to calculate the capacity retention rate according to Equation 2.

[0194] Equation 2

[0195] Capacity retention rate (%) = (discharge capacity after 200 cycles / discharge capacity after 1 cycle) × 100

[0196] Table 3

[0197]

[0198]

[0199] Summarize

[0200] According to Table 1, the rechargeable lithium battery cells of Examples 1 to 6 each show suppressed or reduced resistance increase at high temperatures compared to the rechargeable lithium battery cells of Comparative Examples 1 to 6 (e.g., the rechargeable lithium battery cells of Examples 1 to 6 each show suppressed or reduced resistance increase at high temperatures).

[0201] In addition, referring to Table 2 and Table 3, the rechargeable lithium battery cells of Examples 1 to 3 each have suppressed or reduced gas generation at high temperatures and also exhibited improved cycle-life characteristics compared to the rechargeable lithium battery cells according to Comparative Examples 1 to 3.

[0202] Accordingly, since the electrolyte additive according to some embodiments suppresses or reduces the dissolution of metal from the positive electrode active material at high temperature, the resistance increase and gas generation of the rechargeable lithium battery cell are suppressed or reduced and improved cycle-life characteristics are exhibited.

[0203] Furthermore, even if the electrolyte additive according to some embodiments is mixed with the cobalt-free lithium nickel manganese-based composite oxide, structural collapse of the cobalt-free lithium nickel manganese-based composite oxide under high voltage and / or high temperature conditions is suppressed or reduced.

[0204] When describing embodiments of the present inventive concepts, the use of “may” refers to “one or more embodiments of the present inventive concepts”.

[0205] The term "about" and similar terms as used herein are used as terms of approximation and not as terms of degree, and are intended to account for the inherent deviations in measured or calculated values ​​that will be recognized by those of ordinary skill in the art. The term "about" as used herein includes the stated value and means within the acceptable deviation range of the particular value determined by those of ordinary skill in the art taking into account the measurement in question and the errors associated with the measurement of the particular quantity (i.e., the limitations of the measurement system). For example, "about" may mean within one or more standard deviations, or within ±30%, ±20%, ±10%, or ±5% of the stated value.

[0206] Furthermore, any numerical range set forth herein is intended to include all sub-ranges of the same numerical precision falling within the range set forth. For example, the range of "1.0 to 10.0" is intended to include between the minimum value 1.0 set forth and the maximum value 10.0 set forth (and including 1.0 and 10.0), that is, all sub-ranges 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. Any maximum numerical limit set forth herein is intended to include all lower numerical limits falling therein, and any minimum numerical limit set forth in this specification is intended to include all higher numerical limits falling therein. Accordingly, the applicant reserves the right to modify this specification (including claims) to explicitly set forth any sub-range falling within the range explicitly set forth herein.

[0207] The battery management system (BMS) and / or any other related device or component according to the embodiments of the present invention described herein may be implemented using (e.g., any appropriate) hardware, firmware (e.g., a dedicated integrated circuit), software, or a combination of software, firmware, and hardware. For example, the various components of the device may be formed on an integrated circuit (IC) chip or on a separate IC chip. 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 to perform 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 memory 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, it should be recognized by those skilled in the art that the functions of various computing devices may be combined or integrated into a single computing device, or the functions of a dedicated computing device may be distributed on one or more other computing devices without departing from the scope of the present disclosure.

[0208] 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 should not be limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the claims and their equivalents.

Claims

1. An electrolyte additive represented by chemical formula 1: Chemical formula 1 in, In Chemical Formula 1, L 1 is a substituted or unsubstituted C1-C20 alkylene group; and R 1 ~R 4 are each independently a substituted or unsubstituted C6-C20 aryl group, and The electrolyte additive is used in a rechargeable lithium battery.

2. The electrolyte additive according to claim 1, wherein L 1 It is a substituted or unsubstituted C1~C3 alkylene group.

3. The electrolyte additive according to claim 1, wherein R 1 ~R 4 All are phenyl.

4. The electrolyte additive according to claim 1, wherein The electrolyte additive represented by the chemical formula 1 is represented by the chemical formula 1-1: Chemical formula 1-1 In Chemical Formula 1-1, L 1 Definition of L in claim 1 1 The definition is the same.

5. The electrolyte additive according to claim 1, wherein The electrolyte additive represented by the chemical formula 1 is represented by any one of the chemical formulas 1-1-1 to 1-1-3: Chemical formula 1-1-1 Chemical formula 1-1-2 Chemical formula 1-1-3 6. An electrolyte comprising: Non-aqueous organic solvents; Lithium salts; and The electrolyte additive according to any one of claims 1 to 5, wherein the electrolyte is for use in a rechargeable lithium battery. 7 . The electrolyte according to claim 6 , wherein the amount of the electrolyte additive is 0.05 wt % to 3 wt % based on 100 wt % of the electrolyte.

8. A rechargeable lithium battery comprising: a positive electrode, including a positive electrode active material; a negative electrode, including a negative electrode active material; as well as The electrolyte according to claim 6 or 7.

9. The rechargeable lithium battery of claim 8, wherein The positive electrode active material includes a lithium nickel composite oxide.

10. The rechargeable lithium battery of claim 9, wherein The lithium nickel composite oxide is represented by Chemical Formula 11: Chemical formula 11 Li a1 Ni x1 M 1 y1 M 2 z1 O 2-b1 X b1 in, In Chemical Formula 11, 0.9≤a1≤1.8, 0.7≤x1≤1, 0≤y1≤0.3, 0≤z1≤0.3, 0.9≤x1+y1+z1≤1.1, and 0≤b1≤0.1; M 1 and M 2 Each is independently one or more elements selected from Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sr, Ti, V, W and Zr; and X is one or more elements selected from F, P and S.

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