Negative electrode for rechargeable lithium battery and rechargeable lithium battery including same

Abstract

Provided are a negative electrode for a rechargeable lithium battery and a rechargeable lithium battery including the same, the negative electrode including a current collector, a negative electrode active material layer on the current collector, and an organic-inorganic composite layer on and integrated with the negative electrode active material layer. The negative electrode active material layer includes a negative electrode active material and a first binder, the organic-inorganic composite layer includes a second binder, and the first binder and the second binder include a copolymer including a structural unit derived from a (meth) acrylonitrile monomer.

Description

Technical Field

[0001] Disclosed are a negative electrode for a rechargeable lithium battery and a rechargeable lithium battery including the negative electrode. Background Art

[0002] With the increasing popularity of electronic devices using batteries, such as mobile phones, laptop computers, electric vehicles, etc., the demand for rechargeable lithium batteries with high energy density and high capacity is rapidly increasing. Therefore, research and development to improve the performance of rechargeable lithium batteries is actively underway.

[0003] Rechargeable lithium batteries include positive and negative electrodes having active materials capable of intercalating and deintercalating lithium ions and an electrolyte, and generate electric energy through oxidation and reduction reactions when lithium ions are intercalated and deintercalated with respect to the positive and negative electrodes.

[0004] An example of a method for increasing the capacity of a lithium-ion rechargeable battery is to use an active material containing Si (silicon) for the negative electrode. When an active material including Si (which has a larger lithium insertion / deinsertion amount than a conventional graphite-based active material) is applied, an improvement in battery capacity can be produced. However, because the silicon-containing active material has a large volume change accompanying lithium insertion / deinsertion, the negative electrode active material layer expands and contracts significantly during charging and discharging. As a result, the electronic conductivity between the negative electrode active material will be reduced, the conductive path between the negative electrode active material and the current collector will be hindered or blocked, and the cycle characteristics of the rechargeable battery will deteriorate. Summary of the invention

[0005] Some example embodiments include a negative electrode for a rechargeable lithium battery having improved adhesion and improved thermal shrinkage.

[0006] Some example embodiments include rechargeable lithium batteries that include a negative electrode and that exhibit desirable, improved, or advantageous high-rate capability and cycle-life characteristics.

[0007] In some example embodiments, a negative electrode for a rechargeable lithium battery includes a current collector, a negative electrode active material layer on the current collector, and an organic-inorganic composite layer on and integrated with the negative electrode active material layer, wherein the negative electrode active material layer includes the negative electrode active material layer and a first binder. The organic-inorganic composite layer includes a second binder, and the first binder and the second binder include a copolymer including a structural unit derived from a (meth)acrylonitrile monomer.

[0008] Some example embodiments include a rechargeable lithium battery including the negative electrode, the positive electrode, and an electrolyte A negative electrode for a rechargeable lithium battery according to some example embodiments may have improved adhesion and improved thermal shrinkage.

[0009] Rechargeable lithium batteries according to some example embodiments may exhibit desirable, improved, or advantageous high-rate capability and cycle-life characteristics. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figures 1 to 4 is a cross-sectional view schematically illustrating a rechargeable lithium battery according to some example embodiments. DETAILED DESCRIPTION

[0011] Hereinafter, exemplary embodiments of the present invention will be described in detail. However, these embodiments are examples, the present invention is not limited thereto, and the present invention is defined by the scope of the claims.

[0012] As used herein, when no specific definition is provided otherwise, it will be understood that when 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.

[0013] As used herein, when no specific definition is otherwise provided, the singular may also include the plural. In addition, unless otherwise specified, "A or B" may mean "including A, including B, or including A and B".

[0014] As used herein, "combinations thereof" may refer to mixtures, stacks, composites, copolymers, alloys, blends, and reactants of components.

[0015] As used herein, when no definition is provided otherwise, the particle size may be the average particle size. Particle size means average particle size (D50), which is the diameter of particles with a cumulative volume of 50% by volume in a particle size distribution. The average particle size (D50) can be measured by methods well known to those skilled in the art (e.g., by a particle size analyzer, or by a transmission electron microscope image or a scanning electron microscope image). Alternatively, a dynamic light scattering measurement device is used for data analysis, and the number of particles in each particle size range is counted. Thus, the average particle size (D50) value can be easily obtained by calculation. Laser diffraction can also be used. When measured by laser diffraction, for example, using an ultrasonic wave of about 28kHz, the particles to be measured are dispersed in a dispersion medium, and then introduced into a commercially available laser diffraction particle size measurement device (e.g., MT 3000 available from Microtrac Co., Ltd.), and after irradiation with a power of 60W, the average particle size (D50) based on 50% particle size distribution in the measurement device can be calculated.

[0016] As used herein, when no definition is otherwise provided, "substituted" means that at least one hydrogen of the compound is replaced with a substituent selected from the group consisting of C1 to C30 alkyl, C2 to C30 alkynyl, C6 to C30 aryl, C7 to C30 alkylaryl, C1 to C30 alkoxy, C1 to C30 heteroalkyl, C3 to C30 heteroalkylaryl, C3 to C30 cycloalkyl, C3 to C15 cycloalkenyl, C6 to C30 cycloalkynyl, C2 to C30 heterocycloalkyl, halogen (F, Cl, Br or I), hydroxyl (-OH), nitro (-NO2), cyano (-CN), amino (-NRR', wherein R and R' are each independently hydrogen or C1 to C6 alkyl), thiobetainyl (-RR'N + (CH2) n SO3 - , wherein R and R' are each independently C1 to C20 alkyl), carboxybetaine (-RR'N + (CH2) n COO - , wherein R and R' are each independently C1 to C20 alkyl), azido (-N3), amidino (-C(=NH)NH2), hydrazine (-NHNH2), hydrazo (-N(NH2)-), aldehyde (-C(=O)H), carbamoyl (-C(O)NH2), thiol (-SH), ester (-C(=O)OR, wherein R is C1 to C6 alkyl or C6 to C12 aryl), carboxyl (-COOH) or a salt thereof (-C(=O)OM, wherein M is an organic or inorganic cation), sulfonic acid (-SO3H) or a salt thereof (-SO3M, wherein M is an organic or inorganic cation), phosphate (-PO3H2) or a salt thereof (-PO3MH or -PO3M2, wherein M is an organic or inorganic cation) and combinations thereof.

[0017] Hereinafter, C1 to C3 alkyl refers to methyl, ethyl or propyl. C1 to C10 alkylene may be or include, for example, C1 to C6 alkylene, C1 to C5 alkylene or C1 to C3 alkylene, and may be or include, for example, methylene, ethylidene or propylene. C3 to C20 cycloalkylene may be or include, for example, C3 to C10 cycloalkylene or C5 to C10 cycloalkylene, for example, cyclohexylene. C6 to C20 arylene may be or include, for example, C6 to C10 arylene, for example, benzylidene or phenylene. C3 to C20 heterocyclic radical may be or include, for example, C3 to C10 heterocyclic radical, for example, pyridyl.

[0018] Hereinafter, "hetero" means including at least one or more heteroatoms selected from N, O, S, Si and P.

[0019] In addition, in a chemical formula, the symbol * refers to a portion linked to the same or different atoms, groups or units.

[0020] As used herein, when no definition is otherwise provided, "copolymerization" refers to block copolymerization, random copolymerization, graft copolymerization or alternating copolymerization, and "copolymer" refers to block copolymer, random copolymer, graft copolymer or alternating copolymer.

[0021] When the term "about" or "substantially" is used with a numerical value in this specification, it is meant that the relevant numerical value includes a tolerance of ±10% around the stated numerical value. In addition, when percentages are mentioned in this specification, it is meant that these percentages are based on weight, i.e., weight percentages. The expression "at most" includes an amount from zero to the upper limit expressed and all values ​​therebetween. When a range is specified, the range includes all values ​​therebetween, such as in increments of 0.1%.

[0022] Negative electrode A negative electrode for a rechargeable lithium battery according to some example embodiments includes a current collector, a negative electrode active material layer on the current collector, and an organic-inorganic composite layer on and integrated with the negative electrode active material layer.

[0023] The negative electrode active material layer includes a negative electrode active material and a first binder, the organic-inorganic composite layer includes inorganic particles and a second binder, and the first binder and the second binder include a copolymer including a structural unit derived from a (meth)acrylonitrile monomer.

[0024] In a negative electrode for a rechargeable lithium battery, by applying a binder including a copolymer containing structural units derived from the same (meth)acrylonitrile monomer to a negative electrode active material layer and an organic-inorganic composite layer, the bonding strength between the negative electrode active material layer and the current collector can be improved, and by adding and arranging the organic-inorganic composite layer, the thermal shrinkage and expansion of the negative electrode active material can be reduced or prevented to increase the safety of the rechargeable battery.

[0025] In the case of a binder including the aforementioned copolymer including a structural unit derived from a (meth)acrylonitrile monomer, the modulus is higher than that of other acrylic compounds, so that expansion of the negative electrode active material can be reduced due to low deformation and adhesive strength can be improved.

[0026] First binder The first binder is included in the negative electrode active material layer, and plays a role in attaching the negative electrode active material particles to each other and also adhering the negative electrode active material to the current collector.

[0027] The first binder includes a copolymer including a structural unit derived from a (meth)acrylonitrile monomer.

[0028] The structural unit derived from the (meth)acrylonitrile monomer may refer to a repeating unit of a polymer formed by a polymerization reaction of the (meth)acrylonitrile monomer, or may refer to a repeating unit including a nitrile group.

[0029] As an example, the first binder may include a copolymer (A) including at least one of a structural unit (a-1) derived from a (meth)acrylonitrile monomer and a structural unit (a-2) derived from a (meth)acrylic monomer.

[0030] The structural unit (a-1) derived from a (meth)acrylonitrile monomer may be included in an amount of about 35 wt % to about 65 wt % based on 100 wt % of the copolymer (A).

[0031] When the content of the structural unit (a-1) derived from the (meth)acrylonitrile monomer is less than about 35 wt % based on 100 wt % of the copolymer (A), the bonding strength between the negative electrode active material layer and the current collector may be reduced, and when the content exceeds 65 wt %, the copolymer (A) has a water-insoluble property, which may reduce the dispersibility of the negative electrode active material and deteriorate the storage stability of the negative electrode slurry.

[0032] The structural unit (a-2) derived from the (meth)acrylic monomer may be included in an amount of about 35 wt % to about 65 wt % based on 100 wt % of the copolymer (A).

[0033] When the content of the structural unit (a-2) derived from the (meth)acrylic monomer is less than about 35 wt % based on 100 wt % of the copolymer (A), the structural unit may not be desirable for the negative electrode due to the water-insoluble property, the dispersibility of the active material may be reduced, and the storage stability of the negative electrode slurry may be deteriorated, and when the content exceeds 65 wt %, cracks may be generated in the electrode (negative electrode) during coating and drying of the negative electrode slurry, making it difficult to manufacture the negative electrode.

[0034] As an example, the structural unit derived from a (meth)acrylonitrile monomer may be represented by Chemical Formula 1.

[0035] [Chemical formula 1]

[0036] In Chemical Formula 1, R 1 is hydrogen or C1 to C3 alkyl, L 1 is -C(=O)-, -C(=O)O-, -OC(=O)-, -O- or -C(=O)NH-, L 2is a substituted or unsubstituted C1 to C10 alkylene group, a substituted or unsubstituted C3 to C20 cycloalkylene group, a substituted or unsubstituted C6 to C20 arylene group, or a substituted or unsubstituted C3 to C20 heterocyclic group, x is an integer from 0 to 2, and y is an integer from 0 to 2.

[0037] As an example, the structural unit derived from a (meth)acrylonitrile monomer may be or include a unit derived from (meth)acrylonitrile, alkene nitrile, cyanoalkyl (meth)acrylate, or 2-(vinyloxy)alkane nitrile.

[0038] Here, the olefin may be or include C1 to C20 olefin, C1 to C10 olefin or C1 to C6 olefin, the alkyl may be or include C1 to C20 alkyl, C1 to C10 alkyl or C1 to C6 alkyl, and the alkane may be or include C1 to C20 alkane, C1 to C10 alkane or C1 to C6 alkane.

[0039] The olefin nitrile may be or include, for example, allyl cyanide, 4-pentenenitrile, 3-pentenenitrile, 2-pentenenitrile or 5-hexenenitrile.

[0040] The cyanoalkyl (meth)acrylate may be or include, for example, cyanomethyl (meth)acrylate, cyanoethyl (meth)acrylate, cyanopropyl (meth)acrylate, or cyanooctyl (meth)acrylate.

[0041] The 2-(vinyloxy)alkanenitrile can be or include, for example, 2-(vinyloxy)acetonitrile or 2-(vinyloxy)propionitrile.

[0042] As an example, the (meth)acrylic monomer may include (meth)acrylic acid, an alkali metal salt of (meth)acrylic acid, an ammonium salt of (meth)acrylic acid, or a combination thereof.

[0043] As an example, the (meth)acrylic acid may include acrylic acid or methacrylic acid.

[0044] As an example, the alkali metal salt of (meth)acrylic acid may include sodium acrylate, lithium acrylate, potassium acrylate, calcium acrylate, magnesium acrylate, sodium methacrylate, lithium methacrylate, potassium methacrylate, calcium methacrylate, or a combination thereof, and another example may be sodium acrylate.

[0045] As an example, the ammonium salt of (meth)acrylic acid may include an ammonia neutralization product of (meth)acrylic acid, a monoethanolamine neutralization product, a diethanolamine neutralization product, a hydroxylamine neutralization product, or a combination thereof, and another example may be or include an ammonia neutralization product of acrylic acid.

[0046] In the negative electrode active material layer prepared using the first binder including the copolymer (A), even when the negative electrode active material layer is repeatedly charged / discharged, since the copolymer (A) can follow the expansion and contraction of the Si (silicon)-based active material and / or the Sn (tin)-based active material, the peeling of the electrode layer can be reduced or suppressed, and as a result, the cycle-life can be improved.

[0047] As an example, the copolymer (A) may further include structural units derived from (meth) acrylonitrile monomers and / or other monomers copolymerizable with (meth) acrylic monomers. Based on 100 wt % of the copolymer (A), the content of the other monomers may be from about 0 wt % to about 10 wt %. When the content of the other monomers is as described above relative to 100 wt % of the copolymer (A), the cycle-life and output characteristics of the rechargeable lithium battery may be further improved.

[0048] Other monomers may include hydroxyl group-containing monomers or amide group-containing monomers.

[0049] For example, the hydroxyl-containing monomer may be 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 2-hydroxyhexyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, (4-hydroxymethylcyclohexyl)methacrylate, N-hydroxymethyl (meth)acrylamide, N-hydroxy (meth)acrylamide, vinyl alcohol, allyl alcohol, 2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether, diethylene glycol monovinyl ether, and the like.

[0050] Examples of amide-containing monomers may include acrylamide, methacrylamide, diethyl(meth)acrylamide, N-vinylpyrrolidone, N-vinyl-2-pyrrolidone, N-(meth)acryloylpyrrolidone, N,N-dimethylacrylamide, N,N-dimethylmethacrylamide, N,N-diethylacrylamide, N,N-diethylmethacrylamide, N,N'-methylenebisacrylamide, N,N-dimethylaminopropylacrylamide, N,N-dimethylaminopropylmethacrylamide, and the like.

[0051] The first binder may also include a binder selected from styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, polyethylene oxide, polyvinyl pyrrolidone, polyepichlorohydrin, polyphosphazene, ethylene propylene diene copolymer, polyvinyl pyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol and combinations thereof.

[0052] Negative electrode active material layer The negative electrode active material layer may include a negative electrode active material and a first binder, and may further include a conductive material.

[0053] The negative electrode active material may include a material capable of reversibly inserting / extracting lithium ions, lithium metal, a lithium metal alloy, a material capable of doping / dedoping lithium, or a transition metal oxide.

[0054] The material capable of reversibly inserting / extracting lithium ions may be or include a carbon-based negative electrode active material, and may include, for example, crystalline carbon, amorphous carbon, or a combination thereof. The crystalline carbon may be amorphous, or natural graphite or artificial graphite in the form of plates, flakes, spheres, or fibers. The amorphous carbon may be or include at least one of soft carbon, hard carbon, mesophase pitch carbonization products, calcined coke, etc.

[0055] The lithium metal alloy includes an alloy of lithium and a metal selected from at least one of Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn.

[0056] The material capable of doping / dedoping lithium may be or include a Si-based negative electrode active material or a Sn-based negative electrode active material.

[0057] The Si-based negative electrode active material may be silicon, a silicon-carbon composite, SiO x (0 < x < 2), a Si-Q alloy (where Q is selected from alkali metals, alkaline earth metals, group 13 elements, group 14 elements other than Si, group 15 elements, group 16 elements, transition metals, rare earth elements, and combinations thereof).

[0058] The Sn-based negative electrode active material may be Sn, SnO2, a Sn-based alloy, or a combination thereof.

[0059] The silicon-carbon composite may be or include a composite of silicon and amorphous carbon. According to some exemplary embodiments, the silicon-carbon composite may include silicon particles and an amorphous carbon coating on the surface of the silicon particles. For example, it may include secondary particles (cores) assembled from silicon primary particles and an amorphous carbon coating layer (shells) on the surface of the secondary particles. Amorphous carbon may also be present between the silicon primary particles. For example, the silicon primary particles may be coated with amorphous carbon. The secondary particles may be dispersed in the amorphous carbon matrix.

[0060] 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 layer on the surface of the core.

[0061] The silicon-carbon composite may be in the form of particles, and its average particle size (D50) may be, for example, about 0.5 μm to about 20 μm. Here, the average particle size is measured with a particle size analyzer, and may refer to the diameter of particles having a cumulative volume of 50% by volume in a particle size distribution. Based on 100 wt % of the silicon-carbon composite, silicon may be included in an amount of about 10 wt % to about 60 wt %, and carbon may be included in an amount of about 40 wt % to about 90 wt %.

[0062] The silicon-carbon composite may include a void located in a central portion of the particle. The radius of the void may be about 30% to about 50% of the radius of the silicon-carbon composite particle.

[0063] Silicon-carbon composite particles can effectively reduce or inhibit problems such as volume expansion, structural collapse or particle crushing due to charging and discharging, reduce or prevent disconnection of conductive paths, achieve high capacity and high efficiency, and can be used under high voltage or high rate charging conditions.

[0064] The Si-based negative electrode active material or the Sn-based negative electrode active material may be used by being mixed with the carbon-based negative electrode active material.

[0065] In some example embodiments, the negative electrode active material may include a carbon-based negative electrode active material and a Si-based negative electrode active material. Here, based on 100 wt% of the total negative electrode active material, the Si-based negative electrode active material may be included in an amount of about 0.1 wt% to about 10 wt% (e.g., about 0.5 wt% to about 7 wt% or about 1 wt% to about 4 wt%). When the Si-based negative electrode active material satisfies the above content range, high capacity can be achieved while improving battery cycle-life characteristics without increasing resistance.

[0066] 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 first binder, and about 0 wt % to about 5 wt % of the conductive material.

[0067] Conductive materials can be used to provide conductivity to the electrodes, and in the battery being constructed, any electrically conductive material can be used as long as the electrically conductive material does not cause chemical changes. Examples of conductive materials include at least one of the following: carbon-based materials, such as at least one of natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanotubes, etc.; metal-based materials, in the form of, for example, metal powder or metal fiber and including at least one of copper, nickel, aluminum, silver, etc.; conductive polymers, such as polyphenylene derivatives; or mixtures thereof.

[0068] The negative electrode current collector may include at least one of a copper foil, a nickel foil, a stainless steel foil, a titanium foil, a nickel foam, a copper foam, a polymer substrate coated with a conductive metal, and a combination thereof.

[0069] Second binder The second binder may be included in the organic-inorganic composite layer and in a composition for forming an inorganic layer included in the organic-inorganic composite layer, and may be configured to disperse inorganic particles and ensure good integration of the organic-inorganic composite layer and the negative electrode active material layer.

[0070] The second binder may include a copolymer (B) including a structural unit (b-1) derived from a (meth)acrylonitrile monomer.

[0071] The structural unit (b-1) derived from a (meth)acrylonitrile monomer may be included in an amount of about 35 wt % to about 65 wt % based on 100 wt % of the copolymer (B).

[0072] When the content of the structural unit (b-1) derived from the (meth)acrylonitrile monomer is as described above, a negative electrode having improved adhesion and improved thermal shrinkage can be achieved.

[0073] As an example, the structural unit derived from a (meth)acrylonitrile monomer may be represented by Chemical Formula 1.

[0074] [Chemical formula 1]

[0075] In Chemical Formula 1, R 1 is hydrogen or C1 to C3 alkyl, L 1 is -C(=O)-, -C(=O)O-, -OC(=O)-, -O- or -C(=O)NH-, L 2 is a substituted or unsubstituted C1 to C10 alkylene group, a substituted or unsubstituted C3 to C20 cycloalkylene group, a substituted or unsubstituted C6 to C20 arylene group, or a substituted or unsubstituted C3 to C20 heterocyclic group, x is an integer from 0 to 2, and y is an integer from 0 to 2.

[0076] As an example, the structural unit derived from a (meth)acrylonitrile monomer may be or include a unit derived from (meth)acrylonitrile, alkene nitrile, cyanoalkyl (meth)acrylate, or 2-(vinyloxy)alkane nitrile.

[0077] Here, the olefin may be or include at least one of C1 to C20 olefin, C1 to C10 olefin, and C1 to C6 olefin, the alkyl may be or include at least one of C1 to C20 alkyl, C1 to C10 alkyl, and C1 to C6 alkyl, and the alkane may be or include at least one of C1 to C20 alkane, C1 to C10 alkane, and C1 to C6 alkane.

[0078] The olefin nitrile may be or include, for example, at least one of allyl cyanide, 4-pentenenitrile, 3-pentenenitrile, 2-pentenenitrile, and 5-hexenenitrile.

[0079] The cyanoalkyl (meth)acrylate may be or include, for example, at least one of cyanomethyl (meth)acrylate, cyanoethyl (meth)acrylate, cyanopropyl (meth)acrylate, or cyanooctyl (meth)acrylate.

[0080] The 2-(vinyloxy)alkanenitrile can be or include, for example, 2-(vinyloxy)acetonitrile or 2-(vinyloxy)propionitrile.

[0081] Organic-inorganic composite layer The organic-inorganic composite layer may be or include a layer that is located on the negative electrode active material layer and may be integrated with the negative electrode active material layer.

[0082] The organic-inorganic composite layer may be disposed between the negative electrode and the positive electrode, and may be configured as a separator to reduce or prevent a short circuit. Therefore, the rechargeable lithium battery according to some example embodiments may not include a separate separator. When the rechargeable lithium battery does not include a separate separator, it may no longer be necessary to perform a lamination process for combining the separator with the electrode, so that the battery can be manufactured economically.

[0083] In another example, the actual situation that the organic-inorganic composite layer is integrated with the negative electrode active material layer does not mean that the organic-inorganic composite layer is formed as a layer separate from the negative electrode active material layer, and since the organic-inorganic composite layer is directly formed on the negative electrode active material layer, some of the organic-inorganic composite layer can be applied to the negative electrode active material layer and dried, so that the negative electrode active material layer and the organic-inorganic composite layer can be more firmly bonded. In this way, the actual situation that the organic-inorganic composite layer is integrated with the negative electrode active material layer is that when the negative electrode is measured with, for example, a scanning electron microscope (SEM) or other imaging techniques, the negative electrode active material layer and the organic-inorganic composite layer can be distinguished, but the interface (boundary portion) between the negative electrode active material layer and the organic-inorganic composite layer is presented as an uneven state (such as taking an uneven shape as an example).

[0084] In various examples, since the organic-inorganic composite layer is integrated with the negative electrode active material layer, the organic-inorganic composite layer can be in a state of being more firmly bonded to the negative electrode active material layer. In addition, when repeatedly charged and discharged, the polypropylene film commonly used as a separator will change the value due to thermal shrinkage, and will deteriorate the separation function of the positive electrode and the negative electrode, resulting in problems such as short circuits. However, in the negative electrode according to some example embodiments, the organic-inorganic composite layer that can be used as a separator can be integrated with the negative electrode active material layer, so that problems such as thermal shrinkage are not generated or are less generated.

[0085] In addition, by integrating the organic-inorganic composite layer with the negative electrode active material layer, the resistance can be reduced while improving heat resistance and insulation. When the organic-inorganic composite layer is not integrated with the negative electrode active material layer, but the organic-inorganic composite layer and the negative electrode active material layer are combined after forming a separate layer, because the organic-inorganic composite layer and the negative electrode active material layer are not integrated, the lithium transfer resistance increases, and there is a disadvantage that an additional process for integration is required.

[0086] As an example, the organic-inorganic composite layer may include an organic layer and an inorganic layer.

[0087] The organic layer and the inorganic layer may be disposed such that the organic layer is in contact with the negative electrode active material layer, or the inorganic layer may be disposed in contact with the negative electrode active material layer. As another example, the inorganic layer may be in contact with the negative electrode active material layer.

[0088] In the negative electrode according to some example embodiments, the negative electrode active material layer and the organic-inorganic composite layer are integrated, and thus sizes of the negative electrode active material layer and the organic-inorganic composite layer in a width direction may be substantially the same.

[0089] The organic layer may include a heat-resistant polymer, and the heat-resistant polymer may be a highly heat-resistant engineering resin.

[0090] As an example, the heat-resistant polymer may include a polymer such as polyethylene (PE), polypropylene (PP), polyester, polyamide, polyimide (PI), polyamideimide (PAI), polyetherimide, polyacrylonitrile (PAN), polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), polycarbonate (PC), polyvinyl chloride (PVC), polyvinylidene chloride, polyethylene glycol derivatives, polyoxides, polyvinyl acetate, polystyrene (PS), polyvinyl pyrrolidone (PVP), their copolymers and their combinations.

[0091] Heat-resistant polymers are non-aqueous polymers, and when aqueous polymers are used, it may be difficult to form fibers by electrospinning.

[0092] The inorganic layer may include inorganic particles and a second binder, and the inorganic particles may include, for example, at least one of alumina (Al2O3), boehmite (aluminum hydroxide oxide), zirconia, titanium dioxide (TiO2), silicon dioxide (SiO2), and combinations thereof.

[0093] Because the organic-inorganic composite layer includes an organic layer and an inorganic layer, the organic-inorganic composite layer can provide a heat-resistant effect and flexibility to the negative electrode by including a polymer (particularly, a heat-resistant polymer), thereby reducing or suppressing the possibility that the negative electrode may be damaged during the battery manufacturing process. In addition, the organic-inorganic composite layer is effective in reducing or suppressing the generation of lithium dendrites during charging and discharging, and can obtain the effect of increasing heat resistance and mechanical strength by including an inorganic substance. This effect is generally difficult to obtain when a polymer and an inorganic material are mixed to form a single layer.

[0094] In the example, when the organic layer is used alone (e.g., without the organic-inorganic composite layer), specifically, when the organic layer having a textile structure (e.g., a mesh structure) is included alone, during charging, the positive electrode and the negative electrode may directly contact each other, or Li dendrites may be generated, which may cause a short circuit, thereby making the battery inoperable. In the case where the organic layer is included alone, a similar problem may occur even if the organic layer is formed to have a two-layer structure.

[0095] In another example, when only an inorganic layer is included without an organic layer, the negative electrode may lack flexibility, which may cause particles of the inorganic material layer to separate during battery assembly, resulting in the generation of Li dendrites. In addition, the generation of Li dendrites may cause a short circuit, which is disadvantageous.

[0096] In various examples, the organic layer may have a textile structure (eg, a mesh structure), and the organic layer having the mesh structure may be formed by electrospinning. However, the method of forming the organic layer is not limited to the electrospinning method, but may include any method capable of forming an organic layer having a mesh structure.

[0097] According to the example, when the organic layer has a textile structure (e.g., a mesh structure), there may be an advantage of reducing or minimizing the resistance to Li ion migration. Because the organic layer having a textile structure exists as a porous layer having pores, when the organic layer is formed into a dense layer, the distance of Li ion migration increases, which results in a relatively increased resistance to Li ion migration. In addition, the organic layer is not integrated with the active material layer, but is separated from the active material layer.

[0098] In the example, because the inorganic layer exists as a dense layer, the inorganic layer can be formed, for example, by an electrostatic spraying method. The method of forming the inorganic layer is not limited to the electrostatic spraying method, but may include any method capable of forming the inorganic layer into a dense layer, for example, a conventional coating method such as a scraper, etc. When the inorganic layer exists as a dense layer, the formation of Li dendrites can be more effectively reduced or suppressed. When the inorganic layer exists as a porous layer, a short circuit may be generated during its charging and discharging.

[0099] When the organic layer is formed first, since the organic layer is formed into a textile shape due to electrospinning, when the inorganic layer is formed on the organic layer by electrostatic spraying, the composition for forming the inorganic layer can be inserted into the organic layer, resulting in the integration of the organic-inorganic layer and the negative electrode active material layer.

[0100] In addition, when the inorganic layer is formed first, the composition for forming the organic layer may be at least partially applied to the inorganic layer to form an organic-inorganic layer, which may be integrated with the negative electrode active material layer.

[0101] The method for manufacturing the negative electrode may be as follows.

[0102] A negative electrode active material layer is formed on the current collector by mixing a negative electrode active material, the aforementioned first binder, and an optional conductive material in a solvent to prepare a slurry-type negative electrode active material composition, applying the negative electrode active material composition to the current collector, and drying it.

[0103] Next, an organic-inorganic composite layer including an organic layer and an inorganic layer is formed on the negative electrode active material layer to manufacture a negative electrode in which the negative electrode active material layer and the organic-inorganic composite layer are integrated.

[0104] Regardless of the formation order of the organic layer or the inorganic layer, the organic layer may be formed by electrospinning the composition for forming the organic layer onto the target substrate. The composition for forming the organic layer may include a polymer and a solvent.

[0105] The electrospinning process can be performed, for example, by positioning a nozzle group consisting of tips having a hole size of 23G (gauge) to 30G and a collecting roller at predetermined intervals, adding a composition for forming an organic layer to the tips, placing a target substrate on the collecting roller, and applying a voltage of about 35 kV to about 50 kV to the tips. The number of tips can be appropriately adjusted according to the type of polymer included in the composition for forming an organic layer, for example, in the range of about 20 to about 60.

[0106] The desired or predetermined distance between the nozzle bank and the target object may be about 10 cm to about 20 cm.

[0107] When the hole size of the tip is 25G to 30G, it is appropriate because an organic layer in a desired shape can be formed.

[0108] According to the electrospinning process, a polymer solution is sprayed and stretched into the form of a fiber, and then spun into a cone shape on a target substrate to form an organic layer. Here, the composition for forming the organic layer is suspended at the end of the tip in the form of a droplet due to surface tension, and when a voltage is applied thereto, it begins to deform in the direction opposite to the surface tension of the solution because of the charge repulsion force generated, and then the polymer solution is ejected from the tip of the droplet, so that the jet flow of the composition (also referred to herein as a Taylor cone) can be collected in a collection roller to form an organic layer.

[0109] Here, the electrospinning process may be performed at about 20° C. to about 30° C. at a relative humidity of about 40% to about 60%. When the electrospinning process is performed under desired temperature and relative humidity conditions, it may be advantageous to maintain a predetermined fiber thickness while spinning the composition.

[0110] In addition, the rolling speed of the collecting roller can be adjusted to be in the range of about 1m / min to about 3m / min, so that the organic layer can be formed to have an appropriate thickness (e.g., a certain thickness). In addition, the composition for forming the organic layer discharged from the tip can be adjusted to be discharged at a solid content of about 20μl / min to about 200μl / min. In addition, the interference between the tips can be reduced or minimized by appropriately controlling the tip air to ensure uniform electrospinning. The tip air can be controlled by flowing compressed air at a pressure of about 0.1MPa to about 0.2MPa.

[0111] After performing the electrospinning process, a drying process may be performed by using hot air at about 70° C. to about 110° C.

[0112] In the composition for forming the organic layer, the polymer may be used by mixing at least one of the aforementioned polymers, and the solvent may be or include dimethyl acetate, dimethylformamide, acetone, or a combination thereof.

[0113] In the example, the polymer may be the aforementioned heat-resistant polymer, and because the heat-resistant polymer is non-aqueous, the solvent may be an organic solvent. Therefore, when an aqueous polymer is used, an aqueous solvent should be used, but because an aqueous solvent is difficult to electrospin, there is a problem that may damage the electrode, i.e., a spring back problem, but some example embodiments use an organic solvent without this problem.

[0114] In the composition for forming the organic layer, based on the composition of 100wt% total amount, the content of the polymer can be about 5wt% to about 20wt%. When the content of the polymer is included in the described range, the organic layer can be formed to have a suitable thickness. When the content of the polymer is less than about 5wt%, it will be difficult to form fibers during electrostatic spinning, but when the content of the polymer is greater than about 20wt%, the tip is hindered or blocked during electrostatic spinning, making it difficult to carry out electrostatic spinning itself or making the fiber uneven or too thick.

[0115] When the organic layer is formed by electrospinning, the organic layer may have a textile structure (e.g., a mesh structure). When the organic layer is formed by directly coating the composition or immersing the target object in the composition rather than by electrospinning, the organic layer may be dense, and the electrode plate may become too thick due to the solvent remaining on the electrode plate, which may result in the energy density per battery volume not being improved. In addition, the densely formed organic layer itself may act as a resistive layer, and thus increase the resistance to Li ion migration, which may lead to degradation of battery performance. However, as in some example embodiments, when the organic layer is formed by an electrospinning process, the solvent can be well volatilized and thus well reduce or inhibit the rebound phenomenon of the solvent causing damage to the negative electrode.

[0116] The inorganic layer may be formed by electrostatically spraying the composition for the inorganic layer. The composition for the inorganic layer may include inorganic particles, a second binder, and a solvent.

[0117] The electrostatic spraying process can be performed, for example, by positioning a nozzle group consisting of a tip having a hole size of 23G to 30G and a collecting roller at predetermined intervals, adding a composition for an inorganic layer to the tip, placing a target object on the collecting roller, and applying a voltage in a range of about 35 kV to about 50 kV to the tip.

[0118] The number of the tips may be appropriately adjusted, for example, within a range of about 20 to about 60, according to the type and content of the inorganic material included in the composition for the inorganic layer, and the like.

[0119] The predetermined interval between the nozzle group and the target object may be about 10 cm to about 20 cm.

[0120] When the tip has a hole size of 25G to 30G, an inorganic layer having a desired shape can be formed.

[0121] In the electrostatic spraying process, the inorganic layer forming layer composition is sprayed in the form of dots and sprayed onto the target substrate to form an inorganic layer. When the inorganic layer is formed by directly coating the composition or immersing the target object in the composition instead of by electrostatic spraying, the thickness of the electrode plate will be excessively increased due to the residual solvent in the electrode plate, and the energy density per battery volume cannot be properly improved. In addition, since the inorganic layer is formed by the electrostatic spraying process, the solvent can be fully volatilized, thereby fully reducing or inhibiting the rebound phenomenon of the solvent causing damage to the negative electrode.

[0122] In addition, the rolling speed of the collecting roller can be controlled, for example, in the range of about 0.5 m / min to about 3.0 m / min to ensure the appropriate thickness of the inorganic layer. In addition, the composition for the inorganic layer discharged from the tip can be adjusted to be discharged at a solid content of about 20 μl / min to about 100 μl / min.

[0123] In addition, interference between tips can be reduced or minimized by appropriately controlling the tip air to ensure uniform electrostatic spraying. The tip air is controlled by flowing compressed air at a pressure of about 0.1 MPa to about 0.2 MPa.

[0124] After the electrostatic spraying process, a drying process may be performed using hot air at about 90° C. to about 110° C.

[0125] In the composition for the inorganic layer, the inorganic particles and the second binder are the same as described above, and the solvent can be or include at least one of dimethyl acetate, N-methylpyrrolidone, dimethylformamide, acetone and a combination thereof. In the composition for the inorganic layer, the content of the inorganic particles can be about 85wt% to about 96wt% based on 100wt% of the total content of the composition.

[0126] After the organic-inorganic composite layer is formed, rolling may be further performed. The rolling process may be performed at about 25° C. to about 110° C. When the rolling process is further performed, the organic-inorganic composite layer may be compacted to shorten the path of Li ion migration, which may facilitate Li ion migration during charge / discharge.

[0127] In the example, as the composition for the organic layer is electrospun, the composition for forming the organic layer is inserted into the pores naturally formed in the negative electrode active material layer and integrated therewith, and further, because the organic layer can have a textile structure (e.g., a mesh structure including pores), the composition for the inorganic layer can also be inserted into the pores to form an organic-inorganic layer, which can be integrated with the negative electrode active material layer.

[0128] In addition, when the inorganic layer is formed first, the composition for the inorganic layer can be inserted into the naturally formed pores in the negative electrode active material layer and thus integrated therewith. In addition, when the composition for the organic material is electrospun thereon, the composition can be partially applied to the inorganic layer to form an organic-inorganic layer, and the organic-inorganic layer can be integrated with the negative electrode active material layer.

[0129] Additionally, by performing a roll-pressing process, this integration can be produced more efficiently.

[0130] Rechargeable lithium battery Some example embodiments include a rechargeable lithium battery including the aforementioned negative electrode, a positive electrode, and an electrolyte.

[0131] Rechargeable lithium batteries may be classified into cylindrical, prismatic, pouch-shaped, coin-shaped, etc. according to their shapes.

[0132] Figures 1 to 4 is a schematic diagram illustrating a rechargeable lithium battery according to some example embodiments. Figure 1 A cylindrical battery is shown, Figure 2 A prismatic cell is shown, and Figure 3 and Figure 4 A pouch-type battery is shown.

[0133] Reference Figures 1 to 4 , the rechargeable lithium battery 100 includes an electrode assembly 40 including a separator 30 between a positive electrode 10 and a negative electrode 20, and a case 50 contained in the case 50. The positive electrode 10, the negative electrode 20, and the separator 30 may be impregnated with an electrolyte (not shown).

[0134] like Figure 1 As shown in FIG. 1 , in addition to the separator 30 between the positive electrode 10 and the negative electrode 20 and the case 50, the rechargeable lithium battery 100 may further include a sealing member 60 that seals the case 50. 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 As shown in FIG. 1 , the rechargeable lithium battery 100 includes a positive electrode tab 71 and a negative electrode tab 72 serving as an electrical path for extracting current formed in the electrode assembly 40 to the outside. Figure 4 As shown in FIG. 1 , the rechargeable lithium battery 100 includes an electrode terminal tab 70. The electrode terminal tab 70 includes Figure 3 4. Referring to the positive electrode tab 71 and the negative electrode tab 72 shown in FIG. 4, the electrode tab 70 is configured to provide an electrical path for extracting current formed in the electrode assembly 40 to the outside.

[0135] A rechargeable lithium battery according to some example embodiments may be used or applied to, for example, automobiles, mobile phones, and / or various types of electrical devices, but the present disclosure is not limited thereto.

[0136] Positive electrode A positive electrode for a rechargeable lithium battery may include a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector. The positive electrode active material layer includes a positive electrode active material and may further include a binder and / or a conductive material.

[0137] For example, the positive electrode may further include an additive that may be configured as a sacrificial positive electrode.

[0138] The positive electrode active material may include a compound capable of intercalating and deintercalating lithium (lithiated intercalation compound). For example, at least one of a composite oxide of lithium and a metal including at least one of cobalt, manganese, nickel, and a combination thereof may be used.

[0139] The composite oxide may be or include a lithium transition metal composite oxide, and other examples of the composite oxide may include at least one of lithium nickel oxides, lithium cobalt oxides, lithium manganese oxides, lithium iron phosphate compounds, cobalt-free lithium nickel manganese oxides, and combinations thereof.

[0140] As an example, a compound represented by any one or more of the following chemical formulae may be used. a A 1- b X b O 2-c D c (0.90≤a≤1.8, 0≤b≤0.5, and 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, and 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, and 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, and 0<α<2); Li aNi b Co c L 1 d G e O2 (0.90≤a≤1.8, 0≤b≤0.9, 0≤c≤0.5, 0≤d≤0.5, and 0≤e≤0.1); Li a NeG b O2 (0.90≤a≤1.8 and 0.001≤b≤0.1); Li a CoG b O2 (0.90≤a≤1.8 and 0.001≤b≤0.1); Li a Mn 1-b G b O2 (0.90≤a≤1.8 and 0.001≤b≤0.1); Li a Mn b O4 (0.90≤a≤1.8 and 0.001≤b≤0.1); Li a Mn 1-g G g PO4 (0.90≤a≤1.8 and 0≤g≤0.5); Li (3-f) Fe2(PO4)3 (0≤f≤2); or Li a FePO4 (0.90≤a≤1.8).

[0141] In the above chemical formula, A is or includes at least one of Ni, Co, Mn and combinations thereof; X is or includes at least one of Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements and combinations thereof; D is or includes at least one of O, F, S, P and combinations thereof; G is or includes at least one of Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V and combinations thereof; and L 1 It is or includes at least one of Mn, Al and a combination thereof.

[0142] For example, the positive electrode active material may be or include a high nickel positive electrode active material, and the nickel content of the high nickel positive electrode active material is 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%, based on 100 mol% of metals other than lithium in the lithium transition metal composite oxide. The high nickel positive electrode active material can achieve high capacity and can be applied to high capacity, high density rechargeable lithium batteries.

[0143] The amount of the positive electrode active material may be about 90 wt % to about 99.5 wt % based on 100 wt % of the positive electrode active material layer, and the amount of the binder and the conductive material may be about 0.5 wt % to about 5 wt % based on 100 wt % of the positive electrode active material layer, respectively.

[0144] The binder may be configured to sufficiently attach the positive electrode active material particles to each other and also to sufficiently attach the positive electrode active material to the current collector. Examples of the binder may include at least one of 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., but are not limited thereto.

[0145] Conductive materials can be used to impart conductivity to electrodes, and any material that does not cause chemical changes and conducts electrons can be used in the battery. Examples of conductive materials may include: carbon-based materials, such as at least one of natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber, and carbon nanotube; metal-based materials, including at least one of copper, nickel, aluminum, silver, etc., in the form of metal powder or metal fiber; conductive polymers, such as polyphenylene derivatives; or mixtures thereof.

[0146] Al may be used as a positive electrode current collector, but the present disclosure is not limited thereto.

[0147] Electrolyte The electrolyte for a rechargeable lithium battery includes a non-aqueous organic solvent and a lithium salt.

[0148] The non-aqueous organic solvent may be configured as a medium for transporting ions participating in an electrochemical reaction of a battery.

[0149] The non-aqueous organic solvent may be or include a carbonate solvent, an ester solvent, an ether solvent, a ketone solvent or an alcohol solvent, an aprotic solvent or a combination thereof.

[0150] The carbonate solvent may include at least one of 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. The ester solvent may include at least one of methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanoic acid lactone, mevalonate lactone, valerolactone, caprolactone, etc. The ether solvent may include at least one of dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, tetrahydrofuran, etc. In addition, the ketone solvent may include cyclohexanone, etc. The alcohol solvent may include at least one of ethanol, isopropanol, etc., and the aprotic solvent may include: nitrile, such as R-CN (wherein R is a C2 to C20 straight chain, branched or cyclic hydrocarbon group, and may include a double bond, an aromatic ring or an ether bond, etc.); amide, such as dimethylformamide; dioxolane, such as 1,3-dioxolane, 1,4-dioxolane, etc.; cyclopentane; etc.

[0151] The nonaqueous organic solvents may be used alone or in combination of two or more.

[0152] In addition, when a carbonate-based solvent is used, a cyclic carbonate and a chain carbonate may be mixed and used, and the cyclic carbonate and the chain carbonate may be mixed in a volume ratio of about 1:1 to about 1:9.

[0153] Lithium salts dissolved in organic solvents supply lithium ions in the battery, enable basic operation of rechargeable lithium batteries, and improve the transport of lithium ions between the positive electrode and the negative electrode. Examples of lithium salts include 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) (wherein x and y are integers of 1 to 20), at least one of lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium difluorobis(oxalato)phosphate (LiDFBOP), lithium difluoro(oxalato)borate (LiDFOB) and lithium bis(oxalato)borate (LiBOB).

[0154] Diaphragm Depending on the type of rechargeable lithium battery, the separator may be present between the positive electrode and the negative electrode. The separator may include polyethylene, polypropylene, polyvinylidene fluoride, or a multilayer film of two or more layers thereof, and a mixed multilayer film of at least one of polyethylene / polypropylene two-layer separator, polyethylene / polypropylene / polyethylene three-layer separator, polypropylene / polyethylene / polypropylene three-layer separator, etc.

[0155] The separator may include a porous substrate and a coating layer including an organic material, an inorganic material, or a combination thereof on one or both surfaces of the porous substrate.

[0156] The porous substrate may be or include a polymer film formed from any one of polyolefins (such as at least one of polyethylene and polypropylene, for example), polyesters (such as polyethylene terephthalate and polybutylene terephthalate), polyacetals, polyamides, polyimides, polycarbonates, polyaryletherketones, polyetherketones, polyetherimides, polyamideimides, polybenzimidazoles, polyethersulfones, polyphenylene oxides, cyclic olefin copolymers, polyphenylene sulfide, polyethylene naphthalate, glass fibers, Teflon (TEFLON) and polytetrafluoroethylene, and copolymers or mixtures of two or more thereof.

[0157] The organic material may include a polyvinylidene fluoride-based polymer or a (meth)acrylic polymer.

[0158] The inorganic material may include inorganic particles, and the inorganic particles include at least one of Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, Mg(OH)2, boehmite and combinations thereof, but are not limited thereto.

[0159] An organic material and an inorganic material may be mixed in one coating layer, or a coating layer including an organic material and a coating layer including an inorganic material may be stacked.

[0160] Examples and comparative examples of the present disclosure are described below. However, the following examples are merely examples of the present disclosure, and the present disclosure is not limited to the following examples.

[0161] Example: Fabrication of negative electrodes for rechargeable batteries Example 1 95 wt % of graphite and 5 wt % of silicon-carbon composite particles were mixed to prepare a negative electrode active material, and 97.5 wt % of the negative electrode active material was mixed with 1.0 wt % of a first binder and 1.5 wt % of styrene butadiene rubber (SBR) in a water solvent to prepare a negative electrode active material slurry.

[0162] The first binder includes 45 wt % of a PAN (poly(acrylonitrile)) binder, 45 wt % of a PAA (poly(acrylic acid)) binder, and 10 wt % of a PEGMA (poly(ethylene glycol) methyl ether methacrylate) binder.

[0163] The negative electrode active material slurry is coated on a copper current collector, followed by drying and compression to form a negative electrode active material layer.

[0164] On the negative electrode active material layer, a composition for an inorganic layer is electrostatically sprayed to form an inorganic layer, the composition for an inorganic layer including aluminum oxide, a PAN (polyacrylonitrile) binder as a second binder, and a mixed solvent of dimethyl acetate and acetone (volume ratio of 1:1).

[0165] In the composition for forming the inorganic layer, the content of aluminum oxide was 90 wt % based on 100 wt % of the total amount of the inorganic layer composition.

[0166] The electrostatic spraying process is carried out in the following manner.

[0167] After placing a nozzle group consisting of 52 tips with a hole size of 25G and a collecting roller at intervals of 15 cm, the composition for forming the inorganic layer was added to the tip, and then electrostatic spraying was performed by applying a voltage of 40kV to 50kV to the tip at 26°C and a relative humidity of 50%. Here, the collecting roller was set to a rolling speed of 1m / min to 3m / min, and the composition for the inorganic layer was set to be discharged from the tip at a solid content of 100μl / min. In addition, electrostatic spraying was performed by blowing compressed air at a pressure of 0.1MPa.

[0168] After the electrostatic spraying was completed, drying was performed with hot air at 90° C. Subsequently, a composition for forming an organic layer including a highly heat-resistant engineering resin of polyamideimide and a solvent of dimethyl acetate was electrospun to form an organic layer.

[0169] The electrospinning process was performed in the following manner.

[0170] After placing a nozzle group consisting of 52 tips with a hole size of 25G and a collecting roller at intervals of 15 cm, the composition for forming an organic layer was added to the tip, and then electrospinning was performed by applying a voltage of 40 kV to 50 kV to the tip at 26° C. under a relative humidity of 50%.

[0171] Here, the collecting roller was set to a rolling speed of 1 m / min to 3 m / min, and the composition for the organic layer was set to be discharged from the tip at a solid content of 150 μl / min. In addition, electrospinning was performed by blowing compressed air at a pressure of 0.1 MPa.

[0172] After the electrospinning was completed, it was dried with hot air at 90°C.

[0173] According to the electrospinning, an organic layer with a thickness of 8 μm was formed.

[0174] The process provides a negative electrode in which an organic-inorganic composite layer including an organic layer and an inorganic layer is integrated with a negative electrode active material layer.

[0175] Comparative Example 1 95 wt% of graphite and 5 wt% of silicon-carbon composite particles were mixed to prepare a negative electrode active material, and 97.5 wt% of the negative electrode active material, 1.0 wt% of the first binder same as the first binder used in Example 1, and 1.5 wt% of styrene butadiene rubber (SBR) were mixed in an aqueous solvent to prepare a negative electrode active material slurry. The negative electrode active material slurry was coated on a copper current collector, and then dried and compressed to manufacture a negative electrode. On the negative electrode active material layer, a polyethylene separator was provided without forming an organic-inorganic composite layer.

[0176] Comparative Example 2 A negative electrode was manufactured in the same manner as in Example 1, except that carboxymethyl cellulose (CMC) was used as the first binder.

[0177] Comparison Example 3 A negative electrode was manufactured in the same manner as in Example 1, except that a polyvinylidene fluoride binder was used as the second binder.

[0178] Comparison Example 4 A negative electrode was manufactured in the same manner as in Example 1, except that a polyamideimide binder was used as the second binder.

[0179] Evaluation Example 1: Electrode Adhesion Analysis Adhesion between the negative electrode active material layer and the organic-inorganic composite layer (or between the negative electrode active material layer and the separator) of the negative electrodes according to Example 1 and Comparative Examples 1 to 4 was measured in the following method.

[0180] The adhesion force was measured by peeling each electrode plate sample having a size of 25 mm×100 mm to a peeling length of 20 mm using a universal testing machine (UTM) tensile strength meter (INSTRON) at a measuring speed of 100 mm / min.

[0181] The adhesion measurement results are shown in Table 1.

[0182] Evaluation Example 2: Analysis of electrode thermal shrinkage The thermal shrinkage of the organic-inorganic composite layer or the separator of the negative electrode of Example 1 and Comparative Examples 1 to 4 was measured in the following method. The negative electrodes of Example 1 and Comparative Examples 1 to 4 were cut into a size of 10 cm×10 cm in width (MD)×length (TD) from the center to prepare a sample.

[0183] The obtained sample was dotted at intervals of 50 mm in the MD direction and also at intervals of 50 mm in the TD direction. The median value is the point where two points in the MD direction and two points in the TD direction intersect perpendicularly.

[0184] After each sample was left standing in an oven at 150° C. for 60 minutes, the intervals between the marking points were measured to calculate the thermal shrinkage rate according to Equation 1, and the results are shown in Table 1.

[0185] [Equation 1] Thermal shrinkage (%) = [(L0-L1) / L0] × 100 (L0 = initial median interval, L1 = median interval after 1 hour of standing) (Table 1)

[0186] Referring to Table 1, compared with the negative electrode of Example 1, the negative electrode of Comparative Example 1 including a copolymer including a structural unit derived from a (meth)acrylonitrile monomer as a first binder but not including an organic-inorganic composite layer exhibited almost no adhesion between the negative electrode active material layer and the polyethylene separator, and exhibited a high thermal shrinkage rate of the separator, thereby exhibiting deteriorated heat resistance.

[0187] In addition, compared with the negative electrode of Example 1, the negative electrode of Comparative Example 2 including the organic-inorganic composite layer but not including the copolymer including the structural unit derived from the (meth)acrylonitrile monomer as the first binder exhibited low adhesion and high thermal shrinkage.

[0188] Furthermore, compared with Example 1, Comparative Examples 3 and 4 using an adhesive not including a copolymer including a structural unit derived from a (meth)acrylonitrile monomer as the second adhesive exhibited low adhesion and high heat shrinkage.

[0189] Preparation Example 1 and Comparative Preparation Examples 1 to Comparative Preparation Examples 4: Manufacture of Rechargeable Lithium Battery Cells Preparation Example 1 96 wt% of LiCoO2, 2 wt% of Ketjen black and 2 wt% of polyvinylidene fluoride were mixed in N-methylpyrrolidone solvent to prepare a positive electrode active material slurry. The positive electrode active material slurry was coated on an Al current collector, then dried and compressed to manufacture a positive electrode.

[0190] The positive electrode was contacted with the negative electrode of Example 1 and stacked to manufacture an electrode assembly. Here, the organic-inorganic composite layer of the negative electrode was arranged to contact the positive electrode. The electrode assembly was used together with an electrolyte to manufacture a rechargeable lithium battery cell. The electrolyte was prepared by dissolving LiPF6 in a mixed solvent of ethylene carbonate and ethyl methyl carbonate (volume ratio of 50:50).

[0191] Comparative Preparation Example 1 96 wt% of LiCoO2, 2 wt% of Ketjen black and 2 wt% of polyvinylidene fluoride were mixed in N-methylpyrrolidone solvent to prepare a positive electrode active material slurry. The positive electrode active material slurry was coated on an Al current collector, then dried and compressed to manufacture a positive electrode.

[0192] The negative electrode of Comparative Example 1, the polyethylene separator, and the positive electrode were stacked and then compressed at 90°C for 10 seconds under a load of 270 kg to manufacture an electrode assembly. The electrode assembly was used together with an electrolyte to manufacture a rechargeable lithium battery cell. The electrolyte was prepared by dissolving LiPF6 in a mixed solvent of ethylene carbonate and ethyl methyl carbonate (volume ratio of 50:50).

[0193] Comparative Preparation Example 2 A rechargeable lithium battery cell was manufactured in the same manner as in Preparation Example 1, except that the negative electrode of Comparative Example 2 was used.

[0194] Comparative Preparation Example 3 A rechargeable lithium battery cell was manufactured in the same manner as in Preparation Example 1, except that the negative electrode of Comparative Example 3 was used.

[0195] Comparative Preparation Example 4 A rechargeable lithium battery cell was manufactured in the same manner as in Preparation Example 1, except that the negative electrode of Comparative Example 4 was used.

[0196] Evaluation Example 3: Evaluation of high rate capability The rechargeable lithium battery cells according to Preparation Example 1 and Comparative Preparation Examples 1 to Comparative Preparation Examples 4 were constant-current charged to 4.4 V at a current of 0.2 C, and constant-voltage charged to a current of 0.025 C while maintaining 4.4 V. The constant-voltage charged cells were constant-current discharged to 2.75 V at 0.2 C, 0.5 C, 1.0 C, and 2.0 C, and then the ratio of the discharge capacity at a C rate of 2.0 C to the discharge capacity at 0.2 C was calculated according to the following Equation 2 and is shown as the discharge rate capability in Table 2.

[0197] [Equation 2] Discharge rate capability (%) = (discharge capacity at 2.0C / discharge capacity at 0.2C) Evaluation Example 4: Evaluation of cycle-life characteristics The rechargeable lithium battery cells of Preparation Example 1 and Comparative Preparation Examples 1 to Comparative Preparation Examples 4 were charged at 25°C with a current constant current of 1C to a voltage of 4.4V, and charged at a current constant voltage of 0.025C while maintaining 4.4V. Subsequently, the cells were discharged at a constant current of 1C to a voltage of 2.75V, and the charge and discharge were repeated 300 times. The ratio of the 300th discharge capacity to the 1st discharge capacity was calculated according to Equation 3, and the results are shown in Table 2 as a capacity retention rate (%).

[0198] [Equation 3] Capacity retention rate (%) = (discharge capacity at the 300th cycle / discharge capacity at the 1st cycle) × 100 (Table 2)

[0199] Referring to Table 2, compared with the rechargeable lithium battery cells of Comparative Preparation Examples 1 to Comparative Preparation Examples 4, the rechargeable lithium battery cell of Preparation Example 1 exhibits desired, improved or favorable high-rate capability and cycle-life characteristics, and thus exhibits desired, improved or favorable cell characteristics.

[0200] While the disclosure has been described in conjunction with what are presently considered to be practical example embodiments, it is to be understood that the invention is not limited to the disclosed example embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

[0201] <Description of the symbol> 100: Rechargeable lithium battery 10: Positive electrode 11: Positive lead lug 12: Positive terminal 20: Negative electrode 21: Negative lead lug 22: Negative terminal 30: Diaphragm 40: Electrode assembly 50: Shell 60: Sealing component 70: Electrode terminal 71: Positive electrode terminal 72: Negative electrode terminal.

Claims

1. A negative electrode for a rechargeable lithium battery, the negative electrode comprising: current collector; a negative electrode active material layer on the current collector; as well as an organic-inorganic composite layer on the negative electrode active material layer and integrated with the negative electrode active material layer, The negative electrode active material layer includes a negative electrode active material and a first binder. The organic-inorganic composite layer includes a second binder, and At least one of the first binder and the second binder includes a copolymer including a structural unit derived from a (meth)acrylonitrile monomer.

2. The negative electrode according to claim 1, wherein The structural unit derived from a (meth)acrylonitrile monomer is represented by Chemical Formula 1: [Chemical formula 1] Wherein, in Chemical Formula 1, R 1 is hydrogen or C1 to C3 alkyl, L 1 For -C(=O)-, -C(=O)O-, -OC(=O)-, -O- or -C(=O)NH-, L 2 is a substituted or unsubstituted C1 to C10 alkylene group, a substituted or unsubstituted C3 to C20 cycloalkylene group, a substituted or unsubstituted C6 to C20 arylene group, or a substituted or unsubstituted C3 to C20 heterocyclic group, x is an integer in the range of 0 to 2, and y is an integer in the range of 0 to 2.

3. The negative electrode according to claim 1, wherein The structural unit derived from a (meth)acrylonitrile monomer includes a unit derived from at least one of (meth)acrylonitrile, alkene nitrile, cyanoalkyl (meth)acrylate, and 2-(vinyloxy)alkanenitrile.

4. The negative electrode according to claim 3, wherein The olefin nitrile includes at least one of allyl cyanide, 4-pentenenitrile, 3-pentenenitrile, 2-pentenenitrile, 5-hexenenitrile and combinations thereof.

5. The negative electrode according to claim 3, wherein The cyanoalkyl (meth)acrylate includes at least one of cyanomethyl (meth)acrylate, cyanoethyl (meth)acrylate, cyanopropyl (meth)acrylate, cyanooctyl (meth)acrylate, and combinations thereof.

6. The negative electrode according to claim 3, wherein The 2-(vinyloxy)alkanenitrile includes at least one of 2-(vinyloxy)acetonitrile and 2-(vinyloxy)propionitrile.

7. The negative electrode according to claim 1, wherein The first binder includes a copolymer including the structural unit derived from a (meth)acrylonitrile monomer and a structural unit derived from a (meth)acrylic monomer.

8. The negative electrode according to claim 7, wherein The structural unit derived from a (meth)acrylonitrile monomer is included in an amount of 35 wt % to 65 wt % based on 100 wt % of the copolymer.

9. The negative electrode according to claim 7, wherein The structural unit derived from a (meth)acrylic monomer is included in an amount of about 35 wt % to about 65 wt % based on 100 wt % of the copolymer.

10. The negative electrode according to claim 7, wherein The copolymer further includes a structural unit derived from a hydroxyl group-containing monomer or an amide group-containing monomer.

11. The negative electrode according to claim 1, wherein The first binder also includes a binder comprising at least one of styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, polyethylene oxide, polyvinyl pyrrolidone, polyepichlorohydrin, polyphosphazene, ethylene propylene diene copolymer, polyvinyl pyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol and combinations thereof.

12. The negative electrode according to claim 1, wherein The structural unit derived from a (meth)acrylonitrile monomer is included in an amount of 35 wt % to 65 wt % based on 100 wt % of the copolymer included in the second binder.

13. The negative electrode according to claim 1, wherein The negative electrode active material includes at least one of a carbon-based negative electrode active material and a Si-based negative electrode active material.

14. The negative electrode according to claim 13, wherein The Si-based negative electrode active material is included in an amount of about 0.1 wt % to about 10 wt % based on 100 wt % of the total weight of the negative electrode active material.

15. The negative electrode according to claim 13, wherein The Si-based negative electrode active material includes a silicon-carbon composite.

16. The negative electrode according to claim 15, wherein The silicon-carbon composite includes a core including silicon particles and a carbon coating layer on a surface of the core.

17. The negative electrode according to claim 1, wherein The organic-inorganic composite layer includes an organic layer and an inorganic layer.

18. The negative electrode according to claim 17, wherein The organic layer includes a polymer, and the polymer includes at least one of polyethylene, polypropylene, polyester, polyamide, polyimide, polyamideimide, polyetherimide, polyacrylonitrile, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polycarbonate, polyvinyl chloride, polyvinylidene chloride, polyethylene glycol derivatives, polyoxides, polyvinyl acetate, polystyrene, polyvinyl pyrrolidone, copolymers thereof, and combinations thereof.

19. The negative electrode according to claim 17, wherein: The inorganic layer includes inorganic particles and the second binder, The inorganic particles include at least one of alumina, boehmite, zirconia, titania, silica, and combinations thereof.

20. The negative electrode according to claim 17, wherein: The organic layer is in the form of a textile, and The inorganic layer is a dense layer.

21. A rechargeable lithium battery, comprising: The negative electrode according to claim 1; Positive electrode; as well as Electrolyte.

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