Rechargeable lithium battery

Abstract

Disclosed is a rechargeable lithium battery including: a positive electrode including a positive electrode active material; a negative electrode including a negative electrode active material; and an electrolyte solution including a lithium salt, a non-aqueous organic solvent, and an additive, in which the positive electrode active material includes a cobalt-free lithium nickel manganese-based oxide, the non-aqueous organic solvent includes ethylene carbonate in an amount of less than or equal to about 5 wt% based on a total amount of the electrolyte solution, and the additive includes a phosphorus-based compound including a trialkylsilyl group.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to and the benefit of Korean Patent Application No. 10-2023-0083708 filed in the Korean Intellectual Property Office on June 28, 2023, the entire contents of which are incorporated herein by reference. Technical Field

[0003] A rechargeable lithium battery is disclosed. Background Art

[0004] Recently, with the rapid popularization of electronic devices using batteries (such as, for example, mobile phones, laptop computers and electric vehicles), interest in rechargeable batteries with high energy density and high capacity has increased rapidly. Accordingly, research and development to improve the performance of rechargeable lithium batteries is actively underway.

[0005] Rechargeable lithium batteries include positive and negative electrodes including active materials capable of intercalating and deintercalating lithium ions, and an electrolyte solution, and generate electrical energy through oxidation and reduction reactions if lithium ions are intercalated / deintercalated into / from the positive and negative electrodes.

[0006] As IT devices become more and more high-performance, high-capacity batteries are beneficial, where high capacity can be achieved by expanding the voltage region to increase energy density, but there is a problem that in the high voltage region, the electrolyte solution oxidizes, thereby deteriorating the performance of the positive electrode.

[0007] For example, cobalt-free lithium nickel manganese-based oxide is a positive electrode active material that does not include cobalt but includes nickel, manganese, etc. as main components in its composition, and accordingly, a positive electrode including the positive electrode active material can be economical and achieve high energy density, thus Cobalt-free lithium nickel manganese oxide It has attracted much attention as the next generation positive electrode active material.

[0008] However, if a positive electrode including a cobalt-free lithium nickel manganese-based oxide is used in a high voltage environment, transition metals may be dissolved due to structural collapse of the positive electrode, leading to problems such as gas generation inside the battery cell, reduced capacity, etc. Such transition metal dissolution tends to be aggravated in a high temperature environment, where the dissolved transition metal is precipitated on the surface of the negative electrode and may cause side reactions, thereby increasing battery resistance and deteriorating battery cycle life and output characteristics.

[0009] Accordingly, a technology for suppressing or reducing the structural collapse of a positive electrode including a cobalt-free lithium nickel manganese-based oxide even under high voltage conditions and high temperature conditions would be beneficial. Summary of the invention

[0010] Some embodiments of the present disclosure provide a rechargeable lithium battery that suppresses or reduces structural collapse of a positive electrode including a cobalt-free lithium nickel manganese-based oxide even under high voltage conditions and high temperature conditions.

[0011] Some embodiments provide:

[0012] A rechargeable lithium battery comprising:

[0013] a positive electrode including a positive electrode active material; a negative electrode including a negative electrode active material; and an electrolyte solution including a lithium salt, a nonaqueous organic solvent and an additive,

[0014] The positive electrode active material includes a cobalt-free lithium nickel manganese oxide.

[0015] The nonaqueous organic solvent includes (eg, based on the total amount of the electrolyte solution) less than or equal to about 5 wt % of ethylene carbonate, and

[0016] The additive includes a phosphorus-based compound containing a trialkylsilyl group.

[0017] A rechargeable lithium battery according to some embodiments uses a positive electrode including a cobalt-free lithium nickel manganese-based oxide, suppressing or reducing structural collapse of the positive electrode even under high voltage conditions and high temperature conditions, thereby improving stability and cycle-life characteristics. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings, together with the specification, illustrate embodiments of the presently disclosed subject matter, and, together with the description, serve to explain principles of embodiments of the presently disclosed subject matter.

[0019] Figure 1 is a schematic diagram illustrating a rechargeable lithium battery according to some embodiments.

[0020] Description of Reference Numerals

[0021] 100: Rechargeable lithium battery

[0022] 10: Positive electrode

[0023] 20: Negative electrode

[0024] 30: Diaphragm

[0025] 50: Shell

[0026] 60: Sealing member 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 present disclosure is defined by the scope of the claims and their equivalents.

[0028] As used herein, if no specific definitions are provided otherwise, it will be understood that if an element such as a layer, film, region, or substrate is referred to as being “on” another element, it can be directly on the other element or intervening elements may also be present.

[0029] As used herein, if no specific limitation is provided otherwise, the singular may also include the plural. In some embodiments, "A or B" may mean "including A, including B, or including A and B", unless otherwise specified.

[0030] As used herein, "combination thereof" may mean a mixture, stack, composite, copolymer, alloy, blend, and / or reaction product of the components.

[0031] As used herein, if no specific limitation is otherwise provided, "substituted" means that at least one hydrogen in a substituent or a compound is replaced by deuterium, a halogen atom, a hydroxyl group, an amino group, a substituted or unsubstituted C1-C30 amine group, a nitro group, a substituted or unsubstituted C1-C40 silyl group, a C1-C30 alkyl group, a C1-C10 alkylsilyl group, a C6-C30 arylsilyl group, a C3-C30 cycloalkyl group, a C3-C30 heterocycloalkyl group, a C6-C30 aryl group, a C2-C30 heteroaryl group, a C1-C20 alkoxy group, a C1-C10 fluoroalkyl group, a cyano group or a combination thereof.

[0032] In the examples of the present disclosure, "substituted" refers to at least one hydrogen in a substituent or compound being replaced by deuterium, a halogen atom, a C1-C30 alkyl group, a C1-C10 alkylsilyl group, a C6-C30 arylsilyl group, a C3-C30 cycloalkyl group, a C3-C30 heterocycloalkyl group, a C6-C30 aryl group, a C2-C30 heteroaryl group, a C1-C10 fluoroalkyl group, or a cyano group. In some embodiments, in the examples of the present disclosure, "substituted" refers to at least one hydrogen in a substituent or compound being replaced by deuterium, a halogen atom, a C1-C20 alkyl group, a C6-C30 aryl group, a C1-C10 fluoroalkyl group, or a cyano group. In some embodiments, in the examples of the present disclosure, "substituted" refers to at least one hydrogen in a substituent or compound being replaced by deuterium, a halogen atom, a C1-C5 alkyl group, a C6-C18 aryl group, a C1-C5 fluoroalkyl group, or a cyano group. In some embodiments, in the examples of the present disclosure, "substituted" refers to that at least one hydrogen in a substituent or compound is replaced by deuterium, cyano, a halogen atom, methyl, ethyl, propyl, butyl, phenyl, biphenyl, terphenyl, trifluoromethyl or naphthyl.

[0033] Rechargeable lithium battery

[0034] Some embodiments provide a rechargeable lithium battery comprising: a positive electrode including a positive electrode active material;

[0035] a negative electrode including a negative electrode active material; and

[0036] An electrolyte solution comprising a lithium salt, a non-aqueous organic solvent and an additive,

[0037] The positive electrode active material includes a cobalt-free lithium nickel manganese oxide.

[0038] The nonaqueous organic solvent includes (eg, based on the total amount of the electrolyte solution) less than or equal to about 5 wt % of ethylene carbonate, and

[0039] The additive includes a phosphorus-based compound containing a trialkylsilyl group.

[0040] In other rechargeable lithium batteries, cobalt-free lithium nickel manganese-based oxides have significant structural instability, resulting in the dissolution of transition metals (especially Ni) under high voltage conditions and a rapid decrease in the stability and cycle life of the rechargeable lithium battery.

[0041] However, in a rechargeable lithium battery according to some embodiments, when a positive electrode including a cobalt-free lithium nickel manganese-based oxide is used, structural collapse of the positive electrode can be suppressed or reduced even under high voltage conditions and high temperature conditions, and stability and cycle life characteristics can be improved.

[0042] The aforementioned effects are due to the combination of the non-aqueous organic solvent including less than or equal to about 5 wt % (based on the total amount of the electrolyte solution) of ethylene carbonate and the phosphorus-based compound additive including a trialkylsilyl group.

[0043] Hereinafter, elements constituting the rechargeable lithium battery will be described in more detail.

[0044] additive

[0045] The additive includes a phosphorus-based compound containing a trialkylsilyl group.

[0046] The phosphorus-based compounds containing trialkylsilyl groups effectively reduce the dissolution of transition metals from cobalt-free lithium nickel manganese-based oxides under high voltage and high temperature conditions, while inhibiting or reducing the collapse of the positive electrode structure, thereby improving the stability and cycle life characteristics of rechargeable lithium batteries.

[0047] The additive may include a phosphate-based compound including a trialkylsilyl group, a phosphite-based compound including a trialkylsilyl group, or a combination thereof.

[0048] For example, the additive may include a compound represented by Chemical Formula 1, a compound represented by Chemical Formula 2, or a combination thereof:

[0049] Chemical formula 1

[0050]

[0051] Chemical formula 2

[0052]

[0053] In Chemical Formula 1 and Chemical Formula 2, R 1 ~R 6 Each is independently the same or different and is a substituted or unsubstituted C1-C20 alkyl group.

[0054] For example, in Formula 1 and Formula 2, R 1 ~R 6 All of them may be methyl groups. For example, the additive may include tris(trimethylsilyl)phosphate (TMSPa), tris(trimethylsilyl)phosphite (TMSPi), or a combination thereof.

[0055] The additive may be included in an amount of about 0.1 wt % to about 10.0 wt %, such as about 0.5 wt % to about 8.0 wt %, or such as about 0.1 wt % to about 5.0 wt %, based on the total amount of the electrolyte solution. Within the aforementioned range, if stored at high temperatures, the cycle life of the rechargeable lithium battery can be further improved, or the gas generated from the positive electrode and the negative electrode can be effectively controlled.

[0056] In some embodiments, the additive may further include at least one of other additives selected from the following: vinylene carbonate (VC), fluoroethylene carbonate (FEC), difluoroethylene carbonate, chloroethylene carbonate, dichloroethylene carbonate, bromoethylene carbonate, dibromoethylene carbonate, nitroethylene carbonate, cyanoethylene carbonate, vinylethylene carbonate (VEC), adiponitrile (AN), succinonitrile (SN), 1,3,6-hexanetrinitrile (HTCN), propene sultone (PST), propane sultone (PS), lithium tetrafluoroborate (LiBF 4 ), lithium difluorophosphate (LiPO 2 F 2 ) and 2-fluorobiphenyl (2-FBP). If combined with a phosphorus compound containing a trialkylsilyl group, the other additive can produce a synergistic effect.

[0057] The other additives may be included in an amount of about 0.1 wt % to about 5.0 wt %, for example about 0.1 wt % to about 3.0 wt % or for example about 0.1 wt % to about 1.0 wt %, based on 100 wt % of the electrolyte solution for a rechargeable lithium battery.

[0058] If the content of the additive is as described above, it can contribute to improving battery performance by minimizing or reducing an increase in membrane resistance.

[0059] Non-aqueous organic solvent

[0060] The nonaqueous organic solvent serves as a medium for transmitting ions participating in the electrochemical reaction of the battery.

[0061] The non-aqueous organic solvent may be a carbonate solvent, an ester solvent, an ether solvent, a ketone solvent, an alcohol solvent, an aprotic solvent or a combination thereof.

[0062] Carbonate solvents may include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), ethyl methyl carbonate (EMC), 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, decanoic acid lactone, mevalonate lactone, valerolactone, caprolactone, etc. Ether solvents may include dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran and / or tetrahydrofuran. Ketone solvents may include cyclohexanone. Alcohol solvents may include ethanol, isopropanol, etc., and / or aprotic solvents may include nitriles (such as R-CN (wherein R is a C2-C20 straight chain hydrocarbon group, a branched hydrocarbon group and / or a cyclic hydrocarbon group, and may include a double bond, an aromatic ring and / or an ether group)), amides (such as, for example, dimethylformamide), dioxolanes (such as 1,3-dioxolane and / or 1,4-dioxolane), sulfolane, etc.

[0063] The nonaqueous organic solvents may be used alone or in combination of two or more.

[0064] For example, the nonaqueous organic solvent may include less than or equal to about 5 wt % of ethylene carbonate based on the total amount of the electrolyte solution.

[0065] If the content of ethylene carbonate exceeds the above-mentioned range, the activity of Ni increases during high voltage operation, and the oxidation state of Ni has a strong tendency to be reduced from a tetravalent state to a divalent state, and ethylene carbonate having low oxidation stability undergoes oxidative decomposition, resulting in Ni dissolution and precipitation on the negative electrode.

[0066] In some embodiments, the non-aqueous organic solvent may consist of only chain carbonates. In those embodiments, since the resistance increase rate during high-temperature storage is significantly reduced, excellent high-temperature storage characteristics may be achieved.

[0067] In this specification, the meaning of "consisting only of linear carbonates" means that the non-aqueous organic solvent contains a single or combination of organic solvents that are not mixed with cyclic carbonates and belong to the category of linear carbonates. For example, in some embodiments, the electrolyte solution and / or the non-aqueous organic solvent are substantially free of cyclic carbonates, so that the electrolyte solution and / or the non-aqueous organic solvent include cyclic carbonates (if any) only as incidental impurities. In some embodiments, the electrolyte solution and / or the non-aqueous organic solvent are completely free of cyclic carbonates.

[0068] The chain carbonate can be represented by Chemical Formula 3.

[0069] Chemical formula 3

[0070]

[0071] In chemical formula 3, R 7 and R 8 Each is independently a substituted or unsubstituted C1-C20 alkyl group.

[0072] For example, R in Formula 3 7 and R 8 Each of them can be independently a substituted or unsubstituted C1-C10 alkyl group. 7 and R 8 Each independently may be a substituted or unsubstituted C1-C5 alkyl group.

[0073] For example, R in Formula 3 7 and R 8 Each independently may be substituted or unsubstituted methyl, substituted or unsubstituted ethyl, substituted or unsubstituted n-propyl, substituted or unsubstituted n-butyl, substituted or unsubstituted n-pentyl, substituted or unsubstituted isobutyl or substituted or unsubstituted neopentyl.

[0074] For example, the nonaqueous organic solvent may be at least two types (or species) selected from dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), and ethylmethyl carbonate (EMC).

[0075] For example, the nonaqueous organic solvent may be a mixed solvent of dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC).

[0076] The non-aqueous organic solvent may include ethyl methyl carbonate (EMC) and dimethyl carbonate (DMC) in a volume ratio of about 10:90 to about 50:50.

[0077] In terms of improving battery characteristics, the nonaqueous organic solvent may include more than 50 volume % of dimethyl carbonate (DMC) based on the total volume of the nonaqueous organic solvent.

[0078] The non-aqueous organic solvent may include ethyl methyl carbonate (EMC) and dimethyl carbonate (DMC) in a volume ratio of about 10:90 to about 40:60 or about 10:90 to about 30:70.

[0079] Lithium salts

[0080] 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 the lithium salt may include a lithium ion selected from LiPF 6 , LiBF 4 、LiSbF 6 、LiAsF 6 、LiClO 4 、LiAlO 2 、LiAlCl 4 、LiPO 2 F 2 、LiCl、LiI、LiN(SO 3 C 2 F 5 ) 2 、Li(FSO 2 ) 2 N(lithium bis(fluorosulfonyl)imide, LiFSI), LiC 4 F 9 SO 3 、LiN(C p F 2p+1 SO 2 )(C q F 2q+1 SO 2 )(wherein p and q are integers of 1 to 20), at least one of lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium difluorobis(oxalato)phosphate (LiDFOB) and lithium bis(oxalato)borate (LiBOB).

[0081] Positive electrode active material

[0082] The positive electrode active material may include a cobalt-free lithium nickel manganese-based oxide.

[0083] In the present disclosure, a cobalt-free lithium nickel manganese oxide as a positive electrode active material means a positive electrode active material mainly composed of nickel, manganese, etc., and cobalt is not included in the composition of the positive electrode active material. For example, in some embodiments, the cobalt-free lithium nickel manganese oxide and / or the positive electrode active material is substantially free of cobalt, so that it includes cobalt (if any) only as an incidental impurity. In some embodiments, the cobalt-free lithium nickel manganese oxide and / or the positive electrode active material is completely free of cobalt.

[0084] The cobalt-free lithium nickel manganese-based oxide may include at least one type (or kind) of lithium composite oxide represented by Chemical Formula 4:

[0085] Chemical formula 4

[0086] Li a Ni x Mn y M 1 z M 2 w O 2±b X c .

[0087] In chemical formula 4,

[0088] 0.5≤a<1.8,0≤b≤0.1,0≤c≤0.1,0≤w<0.1,0.6≤x<1.0,0 <y<0.4,0<z<0.1,w+x+y+z=1,

[0089] M 1 and M 2 Each is independently one or more elements selected from Al, Mg, Ti, Zr, Cr, Sr, V, B, W, Mo, Nb, Si, Ba, Ca, Ce, Cr, Fe and Nb, and X is one or more elements selected from S, F, P and Cl.

[0090] For example, Chemical Formula 4 can be represented by Chemical Formula 4-1:

[0091] Chemical formula 4-1

[0092] Li a Ni x1 Mn y1 Al z1 M 2 w1 O 2±b X c .

[0093] In chemical formula 4-1,

[0094] 0.5≤a<1.8,0≤b≤0.1,0≤c≤0.1,0≤w1<0.1,0.6≤x1<1.0,0 <y1<0.4,0<z1<0.1,w1+x1+y1+z1=1,

[0095] M 2 is one or more elements selected from Mg, Ti, Zr, Cr, Sr, V, B, W, Mo, Nb, Si, Ba, Ca, Ce, Cr, Fe and Nb, and X is one or more elements selected from S, F, P and Cl.

[0096] In Chemical Formula 4-1, x1 may be 0.6≤x1≤0.79, y1 may be 0.2≤y1≤0.39, and z1 may be 0.01≤z1<0.1.

[0097] Positive electrode

[0098] 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 (eg, an electrically conductive material).

[0099] For example, the positive electrode may further include an additive that may function as a sacrificial positive electrode.

[0100] The positive electrode active material may be included in an amount of about 90 wt % to about 99.5 wt % based on 100 wt % of the positive electrode active material layer, and the binder and the conductive material may be included in an amount of about 0.5 wt % to about 5 wt %, respectively.

[0101] The binder is used to bind the positive electrode active material particles well to each other, and also to bind the positive electrode active material well to the positive electrode current collector. Examples of binders may include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth) acrylated styrene-butadiene rubber, epoxy resin, (meth) acrylic resin, polyester resin, nylon, etc., but are not limited thereto.

[0102] The conductive material can be used to impart conductivity (e.g., electrical conductivity) to the electrode, and any suitable material that does not cause chemical changes (e.g., does not cause undesirable chemical changes in the rechargeable lithium battery) and conducts electrons can be used for the rechargeable lithium battery. Examples of the conductive material may include: carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber, and carbon nanotube; metal-based materials including copper, nickel, aluminum, silver, etc. in the form of metal powder and / or metal fiber; conductive polymers (e.g., conductive polymers) such as polyphenylene derivatives; or mixtures thereof.

[0103] The positive electrode current collector may include Al foil, but is not limited thereto.

[0104] Negative electrode active material

[0105] The negative electrode active material may include a material that reversibly intercalates / deintercalates lithium ions, lithium metal, a lithium metal alloy, a material capable of doping / dedoping lithium, and / or a transition metal oxide.

[0106] Materials capable of reversibly embedding / desorbing lithium ions may include carbonaceous negative electrode active materials, such as crystalline carbon, amorphous carbon, or a combination thereof. The crystalline carbon may be graphite, such as amorphous, flaky, scaly, spherical, and / or fibrous natural graphite and / or artificial graphite. The amorphous carbon may be soft carbon, hard carbon, mesophase pitch carbonization products (e.g., coal pitch), calcined coke, etc.

[0107] 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.

[0108] Materials capable of doping / dedoping lithium may be Si-based negative electrode active materials and / or Sn-based negative electrode active materials. The Si-based negative electrode active materials may include silicon, silicon-carbon composites, SiO x (0 < x ≤ 2) and / or Si-Q alloys (where Q is selected from alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements (excluding Si), Group 15 elements, Group 16 elements, transition metals, rare earth elements, and combinations thereof). The Sn-based negative electrode active materials may include Sn, SnO 2 , Sn-based alloys, or combinations thereof.

[0109] 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 (shell) on the surface of the secondary particles. The amorphous carbon may also be between the primary silicon particles, and for example, the primary silicon particles may be coated with amorphous carbon. The secondary particles may be dispersed in the amorphous carbon matrix.

[0110] The silicon-carbon composite may further include crystalline carbon. For example, the silicon-carbon composite may include a core containing crystalline carbon and silicon particles and an amorphous carbon coating on the surface of the core.

[0111] The Si-based negative electrode active materials and / or the Sn-based negative electrode active materials may be used in combination with the carbonaceous negative electrode active materials.

[0112] Negative electrode

[0113] The negative electrode for a rechargeable lithium battery includes a negative electrode current collector and a negative electrode active material layer on the negative electrode current collector. The negative electrode active material layer includes negative electrode active materials and may further include a binder and / or a conductive material (e.g., a conductive material).

[0114] For example, the negative electrode active material layer may include about 90 wt % to about 99 wt % of the negative electrode active material, about 0.5 wt % to about 5 wt % of the binder, and about 0.5 wt % to about 5 wt % of the conductive material based on 100 wt % of the negative electrode active material layer.

[0115] The binder can be used to well bind the negative electrode active material particles to each other and also to well bind 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 or a combination thereof.

[0116] 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, or a combination thereof.

[0117] The aqueous binder can be selected from styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluororubber, polyethylene oxide, polyvinyl pyrrolidone, polyepichlorohydrin, polyphosphazene, poly(meth)acrylonitrile, ethylene propylene diene copolymer, polyvinyl pyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenol resin, epoxy resin, polyvinyl alcohol and combinations thereof.

[0118] If the aqueous binder is used as the negative electrode binder, it may further include a cellulose compound capable of imparting or increasing viscosity. The cellulose compound includes one or more of carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose and alkali metal salts thereof. The alkali metal may be Na, K and / or Li.

[0119] The dry binder may be a polymer material capable of fiberization, and may be, for example, polytetrafluoroethylene, polyvinylidene fluoride, a polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, or a combination thereof.

[0120] The conductive material can be used to impart conductivity (e.g., electrical conductivity) to the electrode, and any suitable material that does not cause chemical changes (e.g., does not cause undesirable chemical changes in the rechargeable lithium battery) and conducts electrons can be used for the rechargeable lithium battery. Examples of the conductive material may be: carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber, carbon nanotube, etc.; metal-based materials such as copper, nickel, aluminum silver, etc. in the form of metal powder and / or metal fiber; conductive polymers (e.g., conductive polymers) such as polyphenylene derivatives; or mixtures thereof.

[0121] 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 (eg, an electrically conductive metal), and combinations thereof, but is not limited thereto.

[0122] Diaphragm

[0123] Depending on the type of the rechargeable lithium battery, the rechargeable lithium battery may further include a separator between the negative electrode and the positive electrode. Examples of suitable separator materials include polyethylene, polypropylene, polyvinylidene fluoride, and multilayers thereof (such as polyethylene / polypropylene double-layer separator, polyethylene / polypropylene / polyethylene three-layer separator, and polypropylene / polyethylene / polypropylene three-layer separator).

[0124] The separator may include a porous substrate and a coating on one or both surfaces (eg, opposite surfaces) of the porous substrate, the coating including an organic material, an inorganic material, or a combination thereof.

[0125] The porous substrate may be a polymer film formed from any one of a polymer selected from polyolefins (such as polyethylene and / or polypropylene), polyesters (such as polyethylene terephthalate or polybutylene terephthalate), polyacetals, polyamides, polyimides, polycarbonates, polyether ketones, polyarylether ketones, polyetherimides, polyamideimides, polybenzimidazoles, polyethersulfones, polyphenylene ethers, cyclic olefin copolymers, polyphenylene sulfide, polyethylene naphthalate, glass fibers, TEFLON (tetrafluoroethylene) and polytetrafluoroethylene, and / or a polymer film formed from a copolymer or mixture of two or more thereof.

[0126] The organic material may include a polyvinylidene fluoride-based polymer and / or a (meth)acrylic-based polymer.

[0127] The inorganic material may include a 2 O 3 、SiO 2 、TiO 2 SnO 2 、CeO 2 , MgO, NiO, CaO, GaO, ZnO, ZrO 2 , Y 2 O 3 、SrTiO 3 、BaTiO 3 Mg(OH) 2 , boehmite and inorganic particles in combinations thereof, but are not limited thereto.

[0128] An organic material and an inorganic material may be mixed together in one coating layer, or a coating layer including an organic material and a coating layer including an inorganic material may be stacked.

[0129] Rechargeable lithium battery

[0130] Figure 1 is a partially exploded perspective view of a rechargeable lithium battery according to some embodiments. Figure 1 , the rechargeable lithium battery 100 may include an electrode assembly and a case 50, the electrode assembly including a separator 30 between a positive electrode 10 and a negative electrode 20, and the electrode assembly is accommodated in the case 50. The positive electrode 10, the negative electrode 20, and the separator 30 may be impregnated with an electrolyte solution. Figure 1 As shown in FIG. 1 , the rechargeable lithium battery 100 may include a sealing member 60 that seals the case 50 .

[0131] A rechargeable lithium battery according to some embodiments may be applied to batteries of various appropriate types (or kinds), such as cylindrical, prismatic, and / or pouch types, but the present disclosure is not limited thereto.

[0132] A rechargeable lithium battery according to some embodiments may be applied to automobiles, mobile phones, and / or various appropriate types (or kinds) of electronic devices, but the present disclosure is not limited thereto.

[0133] Charging upper limit voltage

[0134] The rechargeable lithium battery may have a charge upper limit voltage greater than or equal to about 4.35V, for example, about 4.35V to about 4.55V, for example, about 4.35V to about 4.75V.

[0135] Hereinafter, examples and comparative examples of the present disclosure are described. However, these examples are by no means interpreted as limiting the scope of the present disclosure.

[0136] (Preparation Example / Comparative Preparation Example)

[0137] Preparation Example 1

[0138] LiPF 6 It was dissolved in a nonaqueous organic solvent including ethyl methyl carbonate (EMC) and dimethyl carbonate (DMC) mixed together at a volume ratio of 20:80 at a concentration of 1.5 M, and 0.1 wt % of tris(trimethylsilyl) phosphate (TMSPa) was added to prepare an electrolyte solution.

[0139] However, in the composition of the electrolyte solution, "wt%" refers to the relative weight of the additive based on the total weight of the electrolyte solution including the electrolyte solution components (lithium salt + non-aqueous organic solvent + additives). The same applies to the following.

[0140] Preparation Example 2

[0141] A rechargeable lithium battery cell was prepared in substantially the same manner as in Example 1, except that 1.0 wt % of tris(trimethylsilyl)phosphate was added.

[0142] Preparation Example 3

[0143] A rechargeable lithium battery cell was prepared in substantially the same manner as in Example 1, except that 5.0 wt % of tris(trimethylsilyl)phosphate was added.

[0144] Preparation Example 4

[0145] A rechargeable lithium battery cell was prepared in substantially the same manner as in Example 1, except that 0.1 wt % of tris(trimethylsilyl)phosphite (TMSPi) was added.

[0146] Preparation Example 5

[0147] A rechargeable lithium battery cell was prepared in substantially the same manner as in Example 1, except that 1.0 wt % of tris(trimethylsilyl)phosphite was added.

[0148] Preparation Example 6

[0149] A rechargeable lithium battery cell was prepared in substantially the same manner as in Example 1, except that 5.0 wt % of tris(trimethylsilyl)phosphite was added.

[0150] Comparative Preparation Example 1

[0151] LiPF 6 It was dissolved in a nonaqueous organic solvent containing ethyl methyl carbonate (EMC) and dimethyl carbonate (DMC) mixed together in a volume ratio of 20:80 at a concentration of 1.5 M, and 20 wt % of ethylene carbonate (EC) based on the total amount of the electrolyte solution was added to prepare an electrolyte solution.

[0152] Comparative Preparation Example 2

[0153] By adding LiPF 6 The electrolyte solution was prepared by dissolving in a non-aqueous organic solvent containing ethyl methyl carbonate (EMC) and dimethyl carbonate (DMC) mixed together in a volume ratio of 20:80 at a concentration of 1.5 M.

[0154] Using LiNi 0.75 Mn 0.23 Al 0.02 O 2 Examples of positive electrode active materials

[0155] Example 1-1

[0156] LiNi as the positive electrode active material 0.75 Mn 0.23 Al 0.02 O 2, polyvinylidene fluoride as a binder, and acetylene black as a conductive material were mixed together in a weight ratio of 96:3:1, and then dispersed in N-methylpyrrolidone to prepare a positive electrode active material slurry.

[0157] The positive electrode active material slurry was coated on an Al foil to a thickness of 15 μm, dried at 100° C., and pressed to prepare a positive electrode.

[0158] A negative electrode active material slurry was prepared by using a mixture of artificial graphite and silicon-carbon composite in a weight ratio of 93:7 as a negative electrode active material, mixing the negative electrode active material, a styrene-butadiene rubber binder, and carboxymethyl cellulose together in a weight ratio of 98:1:1, and dispersing the mixture in distilled water.

[0159] Herein, the silicon-carbon composite includes artificial graphite and silicon particles as a core and coal tar pitch coated on the surface of the core.

[0160] The negative electrode active material slurry was coated on a 10 μm thick Cu foil, dried at 100° C., and pressed to prepare a negative electrode.

[0161] The prepared positive electrode and negative electrode were assembled with a 10 μm thick polyethylene separator to prepare an electrode assembly, and the electrolyte solution of Preparation Example 1 was injected therein to prepare a rechargeable lithium battery cell.

[0162] Example 1-2

[0163] A rechargeable lithium battery cell was prepared in substantially the same manner as in Example 1-1, except that the electrolyte solution of Preparation Example 2 was used.

[0164] Examples 1-3

[0165] A rechargeable lithium battery cell was prepared in substantially the same manner as in Example 1-1, except that the electrolyte solution of Preparation Example 3 was used.

[0166] Examples 1-4

[0167] A rechargeable lithium battery cell was prepared in substantially the same manner as in Example 1-1, except that the electrolyte solution of Preparation Example 4 was used.

[0168] Examples 1-5

[0169] A rechargeable lithium battery cell was prepared in substantially the same manner as in Example 1-1, except that the electrolyte solution of Preparation Example 5 was used.

[0170] Examples 1-6

[0171] A rechargeable lithium battery cell was prepared in substantially the same manner as in Example 1-1, except that the electrolyte solution of Preparation Example 6 was used.

[0172] Comparative Example 1-1

[0173] A rechargeable lithium battery cell was prepared in substantially the same manner as Example 1-1, except that the electrolyte solution of Comparative Preparation Example 1 was used.

[0174] Comparative Example 1-2

[0175] A rechargeable lithium battery cell was prepared in substantially the same manner as Example 1-1, except that the electrolyte solution of Comparative Preparation Example 2 was used.

[0176] Using LiCoO 2 As an example of positive electrode active material

[0177] Comparative Example 2-1

[0178] A rechargeable lithium battery cell was prepared in substantially the same manner as in Comparative Example 1-1, except that LiCoO 2 Used as positive electrode active material.

[0179] Comparative Example 2-2

[0180] A rechargeable lithium battery cell was prepared in substantially the same manner as in Comparative Example 1-2, except that LiCoO 2 Used as positive electrode active material.

[0181] Comparative Example 2-3

[0182] A rechargeable lithium battery cell was prepared in substantially the same manner as in Example 1-1, except that LiCoO 2 Used as positive electrode active material.

[0183] Comparative Examples 2-4

[0184] A rechargeable lithium battery cell was prepared in substantially the same manner as in Example 1-2, except that LiCoO 2 Used as positive electrode active material.

[0185] Comparative Examples 2-5

[0186] A rechargeable lithium battery cell was prepared in substantially the same manner as in Example 1-3, except that LiCoO 2 Used as positive electrode active material.

[0187] Comparative Examples 2-6

[0188] A rechargeable lithium battery cell was prepared in substantially the same manner as in Examples 1-4, except that LiCoO 2Used as positive electrode active material.

[0189] Comparative Examples 2-7

[0190] A rechargeable lithium battery cell was prepared in substantially the same manner as in Example 1-5, except that LiCoO 2 Used as positive electrode active material.

[0191] Comparative Examples 2-8

[0192] A rechargeable lithium battery cell was prepared in substantially the same manner as in Example 1-6, except that LiCoO 2 Used as positive electrode active material.

[0193] Using LiNi 0.94 Co 0.03 Al 0.03 O 2 As an example of positive electrode active material

[0194] Comparative Example 3-1

[0195] A rechargeable lithium battery cell was prepared in substantially the same manner as in Comparative Example 1-1, except that LiNi 0.94 Co 0.03 Al 0.03 O 2 Used as positive electrode active material.

[0196] Comparative Example 3-2

[0197] A rechargeable lithium battery cell was prepared in substantially the same manner as in Comparative Example 1-2, except that LiNi 0.94 Co 0.03 Al 0.03 O 2 Used as positive electrode active material.

[0198] Comparative Example 3-3

[0199] A rechargeable lithium battery cell was prepared in substantially the same manner as in Example 1-1, except that LiNi 0.94 Co 0.03 Al 0.03 O 2 Used as positive electrode active material.

[0200] Comparative Examples 3-4

[0201] A rechargeable lithium battery cell was prepared in substantially the same manner as in Example 1-2, except that LiNi 0.94 Co 0.03 Al 0.03 O 2 Used as positive electrode active material.

[0202] Comparative Examples 3-5

[0203] A rechargeable lithium battery cell was prepared in substantially the same manner as in Example 1-3, except that LiNi 0.94 Co 0.03 Al 0.03 O 2 Used as positive electrode active material.

[0204] Comparative Examples 3-6

[0205] A rechargeable lithium battery cell was prepared in substantially the same manner as in Examples 1-4, except that LiNi 0.94 Co 0.03 Al 0.03 O 2 Used as positive electrode active material.

[0206] Comparative Examples 3-7

[0207] A rechargeable lithium battery cell was prepared in substantially the same manner as in Example 1-5, except that LiNi 0.94 Co 0.03 Al 0.03 O 2 Used as positive electrode active material.

[0208] Comparative Examples 3-8

[0209] A rechargeable lithium battery cell was prepared in substantially the same manner as in Example 1-6, except that LiNi 0.94 Co 0.03 Al 0.03 O 2 Used as positive electrode active material.

[0210] Evaluate

[0211] Assessment 1: Assessment of high temperature storage characteristics

[0212] The rechargeable lithium battery cells of the embodiments and comparative examples were measured for ΔV / ΔI (voltage change / current change) to obtain the initial DC internal resistance (DCIR), and after the internal maximum energy state inside the battery cell was set to a fully charged state (SOC 100%) and the battery cell was stored in this state at a high temperature of 60°C for 30 days, the DC internal resistance was measured again, which was used to calculate the DCIR increase rate (%) according to Equation 1, and the results are shown in Table 1.

[0213] Equation 1

[0214] DCIR increase rate = {(DCIR after 30 days - initial DCIR) / initial DCIR}×100%

[0215] Table 1

[0216]

[0217]

[0218] Assessment 2: Measurement of the amount of gas generated after high temperature storage

[0219] Each of the rechargeable lithium battery cells of the embodiments and comparative examples was left at 60°C for 10 days or 30 days, and the amount of gas generated (ml) was measured on the 10th day or the 30th day by using a refinery gas analyzer (RGA), which was used to calculate the reduction rate (%) according to Equation 2, and the results are shown in Table 2.

[0220] Equation 2

[0221] Amount reduction rate = {(amount of gas generated by the rechargeable lithium battery cell for 30 days - a reference amount of gas generated for 30 days) / a reference amount of gas generated for 30 days} × 100%

[0222] Table 2

[0223]

[0224] Evaluation 3: Evaluation of high temperature cycle life characteristics

[0225] The rechargeable lithium battery cells of the examples and comparative examples were charged and discharged once at 0.2 C to measure the charge and discharge capacities.

[0226] In addition, the rechargeable lithium battery cells of the embodiment and the comparative example were charged to the upper limit voltage of the charge (4.35 V or 4.45 V), and discharged to 2.5 V at a constant current of 0.2 C to measure the initial discharge capacity at each charge voltage.

[0227] Subsequently, the battery cell was charged at 0.33C (CC / CV, 4.35V or 4.45V, 0.025C cutoff) / discharged at 1.0C (CC, 2.5V cutoff) for 200 cycles at 45°C to measure the discharge capacity. The ratio of the discharge capacity to the initial discharge capacity was calculated, and the results are shown in Table 3 as the capacity retention rate. These results were used to calculate the increase rate according to Equation 3, and further results are also shown in Table 3.

[0228] Equation 3

[0229] Increase rate = {(capacity retention rate of the rechargeable lithium battery cell after 200 cycles - reference capacity retention rate after 200 cycles) / reference capacity retention rate after 200 cycles} × 100%

[0230] Table 3

[0231]

[0232] Referring to Table 1, if a cobalt-free lithium nickel manganese-based oxide positive electrode active material is used, the DCIR increase rate exhibited by the rechargeable lithium battery cells is generally reduced compared to the cobalt-containing positive electrode active material.

[0233] In addition, referring to Tables 2 and 3, when a cobalt-free lithium nickel manganese oxide positive electrode active material is used, if an electrolyte solution including a lithium salt, a non-aqueous organic solvent and an additive (including a phosphorus compound containing a trialkylsilyl group) is used at the same time, the stability and cycle life characteristics of the rechargeable lithium battery cell are improved.

[0234] On the other hand, the DCIR increase rate, storage characteristics at high temperature, and high temperature charge and discharge characteristics shown in the examples vary according to the content of the additive. In view of this, the content of the additive may be appropriately or suitably controlled.

[0235] While the subject matter of the present disclosure has been described in connection with what are presently considered to be practical example embodiments, it should be understood that the disclosure is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the claims and their equivalents.

Claims

1. 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 An electrolyte solution comprising a lithium salt, a non-aqueous organic solvent and an additive, The positive electrode active material comprises a cobalt-free lithium nickel manganese oxide. The nonaqueous organic solvent includes less than or equal to 5 wt % of ethylene carbonate based on the total amount of the electrolyte solution, and The additive includes a phosphorus-based compound including a trialkylsilyl group.

2. The rechargeable lithium battery according to claim 1, wherein: The additive includes a phosphate compound containing a trialkylsilyl group, a phosphite compound containing a trialkylsilyl group, or a combination thereof.

3. The rechargeable lithium battery according to claim 1, wherein: The additive includes a compound represented by Chemical Formula 1, a compound represented by Chemical Formula 2, or a combination thereof: Chemical formula 1 Chemical formula 2 Wherein, in Chemical Formula 1 and Chemical Formula 2, R 1 ~R 6 Each is independently the same or different and is a substituted or unsubstituted C1-C20 alkyl group.

4. The rechargeable lithium battery according to claim 1, wherein: The additive includes tris(trimethylsilyl)phosphate, tris(trimethylsilyl)phosphite or a combination thereof.

5. The rechargeable lithium battery according to claim 1, wherein: The additive may be included in an amount of 0.1 wt % to 10.0 wt % based on the total amount of the electrolyte solution.

6. The rechargeable lithium battery according to claim 1, wherein: The additive further includes at least one of other additives selected from the group consisting of vinylene carbonate, fluoroethylene carbonate, difluoroethylene carbonate, chloroethylene carbonate, dichloroethylene carbonate, bromoethylene carbonate, dibromoethylene carbonate, nitroethylene carbonate, cyanoethylene carbonate, vinylethylene carbonate, adiponitrile, succinonitrile, 1,3,6-hexanetrinitrile, propene sultone, propane sultone, lithium tetrafluoroborate, lithium difluorophosphate and 2-fluorobiphenyl.

7. The rechargeable lithium battery according to claim 1, wherein: The non-aqueous organic solvent consists only of chain carbonate.

8. The rechargeable lithium battery according to claim 7, wherein: The chain carbonate is represented by Chemical Formula 3: Chemical formula 3 Wherein, in Chemical Formula 3, R 7 and R 8 Each is independently a substituted or unsubstituted C1-C20 alkyl group.

9. The rechargeable lithium battery according to claim 8, wherein: The non-aqueous organic solvent includes at least two selected from the group consisting of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate and ethylmethyl carbonate.

10. The rechargeable lithium battery according to claim 9, wherein: The non-aqueous organic solvent includes ethyl methyl carbonate and dimethyl carbonate in a volume ratio of 10:90 to 50:

50.

11. The rechargeable lithium battery according to claim 1, wherein: The lithium salt includes a salt selected from LiPF6, LiBF4, lithium difluoro(oxalate)borate, LiPO2F2, LiSbF6, LiAsF6, Li(FSO2)2N, LiC4F9SO3, LiClO4, LiAlO2, LiAlCl4, LiN(C p F 2p+1 SO2)(C q F 2q+1 SO2), LiCl, LiI and LiB(C2O4)2, wherein p and q are integers of 1 to 20.

12. The rechargeable lithium battery according to claim 1, wherein: The cobalt-free lithium nickel manganese-based oxide includes a lithium composite oxide represented by Chemical Formula 4: Chemical formula 4 Li a Ni x Mr y M 1 z M 2 w O 2±b X c Among them, in chemical formula 4, 0.5≤a<1.8,0≤b≤0.1,0≤c≤0.1,0≤w<0.1,0.6≤x<1.0,0 <y<0.4,0<z<0.1,w+x+y+z=1, M 1 and M 2 Each is independently one or more elements selected from Al, Mg, Ti, Zr, Cr, Sr, V, B, W, Mo, Nb, Si, Ba, Ca, Ce, Cr, Fe and Nb, and X is one or more elements selected from S, F, P and Cl.

13. The rechargeable lithium battery according to claim 12, wherein: Chemical formula 4 is represented by Chemical formula 4-1: Chemical formula 4-1 Li a Ni x1 Mr y1 Al z1 M 2 w1 O 2±b X c Among them, in chemical formula 4-1, 0.5≤a<1.8,0≤b≤0.1,0≤c≤0.1,0≤w1<0.1,0.6≤x1<1.0,0 <y1<0.4,0<z1<0.1,w1+x1+y1+z1=1, M 2 Each is independently one or more elements selected from Mg, Ti, Zr, Cr, Sr, V, B, W, Mo, Nb, Si, Ba, Ca, Ce, Cr, Fe and Nb, and X is one or more elements selected from S, F, P and Cl.

14. The rechargeable lithium battery according to claim 13, wherein: In Chemical Formula 4-1, x1 is 0.6≤x1≤0.79, y1 is 0.2≤y1≤0.39, and z1 is 0.01≤z1<0.

1.

15. The rechargeable lithium battery of claim 1, wherein: The charging upper limit voltage of the rechargeable lithium battery is greater than or equal to 4.35V.

Images