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

Abstract

A negative electrode for a rechargeable lithium battery and a rechargeable lithium battery including the negative electrode are provided. The negative electrode includes: a first negative electrode active material layer including a crystalline carbon negative electrode active material; a second negative electrode active material layer including a silicon-carbon composite; and a current collector between the first negative electrode active material layer and the second negative electrode active material layer.

Description

Technical Field

[0001] Embodiments of the present disclosure relate to a negative electrode for a rechargeable lithium battery and a rechargeable lithium battery including the negative electrode. Background Art

[0002] Recently, the rapid increase in electronic devices using batteries, such as mobile phones, laptop computers, and electric vehicles, has led to a surprising increase in desire and / or demand for rechargeable batteries having relatively high capacity and light weight.

[0003] The development of high energy density batteries has been expected and / or required recently, which in turn has led to an increase in the expectation / demand for high capacity negative electrode active materials. Attempts have been made to use Si-based negative electrode active materials as such high capacity negative electrode active materials. Summary of the invention

[0004] An aspect of one or more embodiments of the present disclosure is directed to a negative electrode for a rechargeable lithium battery having suppressed or reduced volume expansion during charge and discharge.

[0005] An aspect of one or more embodiments of the present disclosure is directed to a rechargeable lithium battery including the negative electrode.

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

[0007] One or more embodiments of the present disclosure provide a negative electrode for a rechargeable lithium battery, the negative electrode comprising: a first negative electrode active material layer comprising a crystalline carbon negative electrode active material; a second negative electrode active material layer comprising a silicon-carbon composite; and a current collector between the first negative electrode active material layer and the second negative electrode active material layer.

[0008] According to one or more embodiments of the present disclosure, a rechargeable lithium battery includes: a negative electrode; a positive electrode; and an electrolyte.

[0009] A negative electrode for a rechargeable lithium battery according to one or more embodiments may exhibit improved battery characteristics due to suppression or reduction of volume expansion during charge and discharge. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 is a schematic diagram illustrating a negative electrode for a rechargeable lithium battery according to one or more embodiments of the present disclosure.

[0011] Figures 2 to 5 Each is a schematic diagram showing a rechargeable lithium battery according to one or more embodiments of the present disclosure. DETAILED DESCRIPTION

[0012] The present disclosure can be modified in many alternative forms, and therefore specific embodiments will be shown in the drawings and described in more detail. However, it should be understood that this is not intended to limit the present disclosure to the specific form disclosed, but is intended to cover all modifications, equivalents and substitutes that fall within the spirit and scope of the present disclosure. Embodiments are provided as examples so that the present disclosure will be thorough and complete, and will fully convey the aspects and features of the present disclosure to those skilled in the art. Therefore, processes, elements and techniques that are not necessary for those of ordinary skill in the art to fully understand the aspects and features of the present disclosure may not be described.

[0013] The terms used herein are only used for the purpose of describing specific embodiments and are not intended to limit the present disclosure. As used herein, unless the context clearly indicates otherwise, the singular forms "a", "one (kind / person)" and "the (said)" are also intended to include plural forms.

[0014] As used herein, the term "combination thereof" may include mixtures, laminates, composites, copolymers, alloys, blends, reactants of the components.

[0015] It will also be understood that when the terms "includes," "comprising," "having" and variations thereof are used in this specification, it indicates the presence of the stated features, integers, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof.

[0016] In the accompanying drawings, for the sake of clarity, the relative sizes of elements, layers and regions may be exaggerated. For example, the accompanying drawings may have an enlarged thickness so as to clearly show the various layers and regions. Unless otherwise noted, the same reference numerals represent the same elements throughout the drawings and the specification, and therefore, their repeated descriptions may not be provided. When an element such as a layer, film, region, plate, etc. is referred to as "on" or "above" another element, it may be directly on or above the other element, or one or more intervening elements may be present. On the contrary, when an element is referred to as "directly on" another element, there is no intervening element. In addition, it will also be understood that when an element is referred to as "between" two elements, it may be the only element between the two elements, or one or more intervening elements may also be present.

[0017] Here, when viewed from a plan view (eg, a plan view), a “layer” includes a shape completely formed on an entire surface or a shape formed on a portion of a surface.

[0018] Here, "or" is not interpreted as exclusive, for example, "A or B" is interpreted to include A, B, A+B, etc. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0019] Unless otherwise apparent from the disclosure, expressions such as “at least one of…,” “a plurality of…,” “one of…,” and other prepositional phrases, when preceding or following a list of elements, should be understood to include the disjunct (if written as a conjunction list), and vice versa. For example, the expressions “at least one of a, b, or c,” “at least one of a, b, and / or c,” “one selected from the group consisting of a, b, and c,” “at least one selected from a, b, and c,” “at least one of a, b, and c,” “one of a, b, and c,” “at least one from a to c” mean only a, only b, only c, both a and b, both a and c, both b and c, all of a, b, and c, or variations thereof.

[0020] It will be understood that, although the terms "first", "second", "third", etc. may be used herein to describe various elements, components, regions, layers and / or parts, these elements, components, regions, layers and / or parts should not be limited by these terms. These terms are used to distinguish one element, component, region, layer or part from another element, component, region, layer or part. Therefore, without departing from the spirit and scope of the present disclosure, the first element, component, region, layer or part described below may be referred to as a second element, component, region, layer or part.

[0021] In the present disclosure, when no definition is provided in addition, particle diameter or particle size can be average particle diameter. When the particle is spherical, "diameter" represents particle diameter or average particle diameter, and when the particle is non-spherical, "diameter" represents major axis length or average major axis length. Such particle diameter represents the average particle diameter (D50) or average particle size (D50) of 50% by volume of particles whose cumulative volume corresponds to particle size distribution (e.g., cumulative distribution), and refers to the value of particle size corresponding to 50% from the smallest particle in the distribution curve accumulated in the order of minimum particle size to maximum particle size when the total number of particles is 100%. Particle size can be measured by a method generally available and / or suitable for 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). In one or more embodiments, data analysis is performed using a dynamic light scattering measurement device, and the number of particles in each size range is counted, so that average particle diameter (D50) value can be easily obtained by calculation.

[0022] Negative electrode

[0023] A negative electrode for a rechargeable lithium battery according to one or more embodiments includes: a first negative active material layer including a crystalline carbon negative active material; a second negative active material layer including a silicon-carbon composite; and a current collector.

[0024] In one or more embodiments, the first negative electrode active material layer and the second negative electrode active material layer are respectively positioned on both sides (eg, different sides or opposite sides) of the current collector. To illustrate this more clearly, Figure 1 , a negative electrode 1 according to one or more embodiments of the present disclosure is shown, and the negative electrode 1 includes a current collector 5, a first negative electrode active material layer 3, and a second negative electrode active material layer 7. For the purpose of description, Figure 1 The first negative electrode active material layer 3 at the bottom and the second negative electrode active material layer 7 at the top are shown, but in one or more embodiments, the first negative electrode active material layer 3 may be positioned at the top, and the second negative electrode active material layer 7 may be positioned at the bottom. For example, in the negative electrode according to one or more embodiments, as long as the first negative electrode active material layer and the second negative electrode active material layer are respectively positioned on different sides of the current collector in the negative electrode, the position does not need to be limited to the top or the bottom.

[0025] In the negative electrode according to one or more embodiments, the negative electrode active materials in the first negative electrode active material layer and the second negative electrode active material positioned on respective sides (e.g., opposite sides) of the current collector are different from each other, and the negative electrode active material in the first negative electrode active material layer is a crystalline carbon negative electrode active material, and the negative electrode active material in the second negative electrode active material layer is a silicon-carbon composite negative electrode active material.

[0026] Because the negative electrode active material in the first negative electrode active material layer is different from the negative electrode active material in the second negative electrode active material layer, the volume expansion of silicon caused during charging and discharging can be effectively suppressed or reduced, which allows the use of high-capacity silicon as the negative electrode active material, and thus, a battery exhibiting excellent or suitable capacity can be achieved.

[0027] In one or more embodiments, the crystalline carbon negative electrode active material included in the first negative electrode active material layer can effectively control and / or reduce the volume expansion caused by the silicon-carbon composite in the second negative electrode active material layer during charging and discharging. The crystalline carbon negative electrode active material can be natural graphite, and can also include artificial graphite, and can be, for example, a mixture of natural graphite and artificial graphite. Natural graphite or artificial graphite can have an unspecified shape, a sheet shape, a flake shape, a spherical shape, and / or a fiber shape.

[0028] Natural graphite is softer than artificial graphite, and therefore, it can be more effectively used as a buffer for the volume expansion of silicon. If a mixture of natural graphite and artificial graphite is used as a crystalline carbon negative electrode active material (for example, when a mixture of natural graphite and artificial graphite is used as a crystalline carbon negative electrode active material), the mixing ratio of natural graphite and artificial graphite can be about 50:50 to about 90:10 by weight.

[0029] The silicon-carbon composite included in the second negative electrode active material layer may include silicon particles and amorphous carbon. For example, the silicon-carbon composite may include silicon nanoparticles (e.g., nanometer (nm) silicon particles) and an amorphous carbon coating layer on the surface of the silicon nanoparticles. In one or more embodiments, the silicon-carbon composite may include secondary particles in which silicon primary particles are agglomerated and an amorphous carbon coating layer on the surface of the secondary particles.

[0030] Amorphous carbon can be positioned between silicon primary particles to coat the silicon primary particles, or the silicon primary particles can be coated with amorphous carbon. In one or more embodiments, the Si-C composite can include a core in which silicon particles (e.g., silicon nanoparticles or silicon primary particles) are distributed in an amorphous carbon matrix and an amorphous carbon coating layer on the surface of the core.

[0031] The secondary particles are (eg, all) located at the center of the Si-C composite, and therefore, are referred to as a core or central portion. The amorphous carbon coating layer refers to an outer portion or shell.

[0032] According to one or more embodiments, the silicon nanoparticles (in nanometer scale) may have a particle size of about 10 nm to about 1000 nm, about 10 nm to about 200 nm, or about 20 nm to about 150 nm. If the particle size of the silicon nanoparticles is within the above range (e.g., when the particle size of the silicon nanoparticles is within the above range), the extreme volume expansion caused during charging and discharging can be suppressed or reduced, and the destruction of the conductive path due to particle crushing can be prevented or reduced.

[0033] In the amorphous carbon coating layer, the amorphous carbon may be soft carbon, hard carbon, mesophase pitch carbide, burnt coke, or any suitable combination thereof. The thickness of the amorphous carbon coating layer may be about 1 nm to about 2 μm, about 1 nm to about 500 nm, about 10 nm to about 300 nm, or about 20 nm to about 200 nm. If the thickness of the amorphous carbon coating layer is within the above range (e.g., when the thickness of the amorphous carbon coating layer is within the above range), the volume expansion of silicon may be effectively suppressed or reduced during charge and discharge.

[0034] The silicon-carbon composite may also include crystalline carbon, and for example, the silicon-carbon composite may include silicon particles, crystalline carbon, and amorphous carbon. Such a silicon-carbon composite may include a core comprising silicon nanoparticles and crystalline carbon and an amorphous carbon coating layer on the surface of the core. For example, the silicon-carbon composite may include secondary particles in which (for example, each of which) silicon primary particles (for example, silicon nanoparticles) and crystalline carbon are agglomerated, and an amorphous carbon coating layer on the surface of the secondary particles.

[0035] The crystalline carbon may be natural graphite and / or artificial graphite in an unspecified shape, flake, flaky, spherical or fibrous form.

[0036] If the silicon-carbon composite includes silicon nanoparticles and an amorphous carbon coating layer (for example, when the silicon-carbon composite includes silicon nanoparticles and an amorphous carbon coating layer), the amount of the silicon nanoparticles may be about 30 wt % to about 70 wt % or about 40 wt % to about 65 wt % based on a total of 100 wt % of the silicon-carbon composite. The amount of the amorphous carbon coating layer may be about 30 wt % to about 70 wt % or about 35 wt % to about 60 wt % based on a total of 100 wt % of the silicon-carbon composite.

[0037] If the silicon-carbon composite further includes crystalline carbon (for example, when the silicon-carbon composite further includes crystalline carbon), the amount of the silicon nanoparticles may be about 20 wt % to about 70 wt % or about 25 wt % to about 65 wt % based on a total of 100 wt % of the silicon-carbon composite. The amount of amorphous carbon may be about 25 wt % to about 70 wt % or about 25 wt % to about 60 wt % based on a total of 100 wt % of the silicon-carbon composite, and the amount of crystalline carbon may be about 1 wt % to about 20 wt % or about 5 wt % to about 15 wt %.

[0038] The particle size of the Si—C composite may be appropriately or suitably adjusted according to desire and / or need.

[0039] In one or more embodiments, the thickness of the first negative electrode active material layer and the thickness of the second negative electrode active material layer may be about 120 μm to about 250 μm, respectively. The ratio of the thickness of the first negative electrode active material layer to the thickness of the second negative electrode active material layer may be appropriately adjusted so that the capacities of the first negative electrode active material layer and the second negative electrode active material layer are substantially equal. For example, because the capacity of the silicon-carbon composite is greater than the capacity of the crystalline carbon, the first negative electrode active material layer may be thicker than the second negative electrode active material layer, so that the thickness of the first negative electrode active material layer may be greater than the thickness of the second negative electrode active material layer, but the ratio of the thickness is not necessarily limited thereto, and any suitable modified ratio may be used.

[0040] In one or more embodiments, the first negative electrode active material layer may include a binder and may also include a conductive material (e.g., a conductor). In the first negative electrode active material layer, the amount of the crystalline carbon negative electrode active material may be about 90 wt% to about 98 wt% based on the total weight of the first negative electrode active material layer, and the amount of the binder may be about 1 wt% to about 5 wt% based on the total weight of the first negative electrode active material layer. In one or more embodiments including a conductive material, the crystalline carbon negative electrode active material may be included in an amount of about 90 wt% to about 98 wt%, the binder may be included in an amount of about 1 wt% to about 5 wt%, and the conductive material may be included in an amount of about 1 wt% to about 5 wt% based on the total weight of the first negative electrode active material layer.

[0041] The second negative electrode active material layer may also include a binder and may also include a conductive material. In the second negative electrode active material layer, the amount of the silicon-carbon composite negative electrode active material may be about 90wt% to about 98wt% based on the total weight of the second negative electrode active material layer, and the amount of the binder may be about 1wt% to about 5wt% based on the total weight of the second negative electrode active material layer. In one or more embodiments including a conductive material, the silicon-carbon composite negative electrode active material may be included in an amount of about 90wt% to about 98wt%, the binder may be included in an amount of about 1wt% to about 5wt%, and the conductive material may be included in an amount of about 1wt% to about 5wt% based on the total weight of the second negative electrode active material layer.

[0042] The binder and the conductive material in the first negative electrode active material layer and the second negative electrode active material layer may be the same as or different from each other.

[0043] The binder improves the bonding properties between the negative electrode active material particles and between the negative electrode active material particles and the current collector. The binder may be a non-aqueous binder, an aqueous binder or any suitable combination thereof.

[0044] The non-aqueous binder may be ethylene propylene copolymer, polyacrylonitrile, polystyrene, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide, or any suitable combination thereof.

[0045] The aqueous binder can be styrene-butadiene rubber, acrylated styrene-butadiene rubber (ABR), acrylonitrile-butadiene rubber, acrylic rubber, butyl rubber, fluororubber, polyethylene oxide, polyvinyl pyrrolidone, polypropylene, ethylene propylene copolymer, polyepichlorohydrin, polyphosphazene, ethylene propylene diene copolymer, polyvinyl pyridine, chlorosulfonated polyethylene, latex, polyester resin, acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol or any suitable combination thereof.

[0046] The negative electrode binder may also include a cellulose compound. In one or more embodiments, in addition to the cellulose compound, the negative electrode binder may also include an aqueous binder. The cellulose compound may include one or more of carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose and / or an alkali metal salt thereof. The alkali metal may be Na, K or Li. The cellulose compound may be used to impart viscosity, and therefore may be referred to as a thickener, and it may also be used as a binder, and therefore may be referred to as a binder. The amount of the cellulose compound may be appropriately or suitably adjusted within the amount of the binder, and for example, based on 100 parts by weight of the negative electrode active material, the amount may be from about 0.1 parts by weight to about 3 parts by weight. However, the present disclosure is not limited thereto.

[0047] A conductive material is included to provide electrode conductivity, and any conductive material can be used as the conductive material unless it causes a chemical change. Examples of the conductive material may be: a carbon-based material such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, etc.; a metal-based material including metal powder or metal fiber of copper, nickel, aluminum, silver, etc.; a conductive polymer such as a polyphenylene derivative; or any suitable combination thereof.

[0048] The current collector may include one of copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, and / or any suitable combination thereof (for example, one selected from copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, and / or any suitable combination thereof), but the present disclosure is not limited thereto.

[0049] Method for preparing negative electrode

[0050] Crystalline carbon, a binder, and an optional conductive material are mixed in a solvent to prepare a first negative active material layer slurry.

[0051] The silicon-carbon composite, a binder, and an optional conductive material are mixed in a solvent to prepare a second negative active material layer slurry.

[0052] On one side of the current collector, the first negative electrode active material layer slurry is applied and dried to form a first coating layer. Thereafter, on one side of the current collector corresponding to the opposite side of the side on which the first coating layer is formed, the second negative electrode active material layer slurry is applied and dried. Thereafter, pressurization is performed to prepare a negative electrode in which the first negative electrode active material layer and the second negative electrode active material layer are formed on respective sides (e.g., opposite sides) of the current collector.

[0053] In this process, the coating of the second negative active material layer slurry may be performed before the coating of the first negative active material layer slurry. For example, in one or more examples, the order of slurry coating does not significantly affect the negative electrode.

[0054] Rechargeable lithium battery

[0055] One or more embodiments of the present disclosure provide a rechargeable lithium battery including a negative electrode, a positive electrode, and an electrolyte. The rechargeable lithium battery may further include a separator between the positive electrode and the negative electrode.

[0056] In one or more embodiments, the first negative electrode active material layer of the negative electrode may be positioned on the side adjacent to the positive electrode, or the second negative electrode active material layer may be positioned on the side adjacent to the positive electrode. In one or more embodiments, if the rechargeable lithium battery includes at least one negative electrode and a positive electrode (for example, when the rechargeable lithium battery includes at least one negative electrode and a positive electrode), the positions of the first negative electrode active material layer and the second negative electrode active material layer may be appropriately adjusted.

[0057] For example, if (for example, when) the rechargeable lithium battery includes a first negative electrode / first separator / positive electrode / second separator / second negative electrode / third separator / positive electrode, the negative electrode active material layer in contact with the first separator and the third separator may be equally the first negative electrode active material layer or the second negative electrode active material layer. The negative electrode active material layer in contact with the first separator and the third separator may be the first negative electrode active material layer, and the negative electrode active material layer in contact with the second separator may be the second negative electrode active material layer. In one or more embodiments, the negative electrode active material layer in contact with the first separator and the third separator may be the second negative electrode active material layer, and the negative electrode active material layer in contact with the second separator may be the first negative electrode active material layer.

[0058] Here, the negative electrode active material layer adjacent to the positive electrode refers to the negative electrode active material layer in contact with the separator. For example, it means that one side of the separator is in contact with the positive electrode active material layer, and the other side of the separator opposite to the one side is in contact with the first negative electrode active material layer.

[0059] In this way, in one or more embodiments, regardless of the position of the first negative electrode active material layer or the second negative electrode active material layer adjacent to the positive electrode, the effect of forming the first negative electrode active material layer and the second negative electrode active material layer on respective sides (e.g., opposite sides) of the current collector can be fully achieved.

[0060] Positive electrode

[0061] The positive electrode may include a current collector and a positive active material layer on the current collector.

[0062] The positive electrode active material may include a compound capable of inserting and extracting lithium (lithiated insert compound). In one or more embodiments, at least one of a composite oxide of lithium and a metal selected from cobalt, manganese, nickel, or any suitable combination thereof may be used. For example, a compound represented by one or more of the following chemical formulas may be used: Li a A 1-b X b D 1 2(0.90≤a≤1.8, 0≤b≤0.5); Li a A 1-b X b O 2-c1 D 1 c1 (0.90≤a≤1.8, 0≤b≤0.5, 0≤c1≤0.05); Li a E 1-b X b O 2-c1 D 1 c1 (0.90≤a≤1.8, 0≤b≤0.5, 0≤c1≤0.05); Li a E 2-b X b O 4-c1 D 1 c1 (0.90≤a≤1.8, 0≤b≤0.5, 0≤c1≤0.05); Li a Ni 1-b-c Co b X c D 1 α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, 0<α≤2); Li a Ni 1-b-c Co b X c O 2-α T α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5,, 0<α<2); Li a Ni 1-b- c Co b X c O 2-α T2(0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, 0<α<2); Li a Ni 1-b-c Mn b X c D 1 α(0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.5, 0 < α ≤ 2); Li a Ni 1-b-c Mn b X c O 2-α T α (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.5, 0 < α < 2); Li a Ni 1-b-c Mn b X c O 2-α T2(0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.5, 0 < α < 2); Li a Ni b E c G d O2(0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0.001 ≤ d ≤ 0.1; Li a Ni b Co c L 1 d G e O2(0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤ 0.5, 0 ≤ e ≤ 0.1); Li a NiG b O2(0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); Li a CoG b O2(0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); Li a Mn 1-b G b O2(0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); Li a Mn2G b O4(0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); Li a Mn 1-g G g PO4(0.90 ≤ a ≤ 1.8, 0 ≤ g ≤ 0.5); QO2; QS2; LiQS2; V2O5; LiV2O5; LiZO2; LiNiVO4; Li (3-f) J2(PO4)3(0 ≤ f ≤ 2); Li (3-f) Fe2(PO4)3(0 ≤ f ≤ 2); and / or Li a FePO4(0.90 ≤ a ≤ 1.8).

[0063] In the above chemical formula, A can be Ni, Co, Mn or any suitable combination thereof (for example, selected from Ni, Co, Mn or any suitable combination thereof); X can be Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element or any suitable combination thereof (for example, selected from Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element or any suitable combination thereof); D 1 can be O, F, S, P, or any suitable combination thereof (e.g., selected from O, F, S, P, or any suitable combination thereof); E can be Co, Mn, or any suitable combination thereof (e.g., selected from Co, Mn, or any suitable combination thereof); T can be F, S, P, or any suitable combination thereof (e.g., selected from F, S, P, or any suitable combination thereof); G can be Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or any suitable combination thereof (e.g., selected from Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or any suitable combination thereof); Q can be Ti, Mo, Mn, or any suitable combination thereof (e.g., selected from Ti, Mo, Mn, or any suitable combination thereof); Z can be Cr, V, Fe, Sc, Y, or any suitable combination thereof (e.g., selected from Cr, V, Fe, Sc, Y, or any suitable combination thereof); J can be V, Cr, Mn, Co, Ni, Cu, or any suitable combination thereof (e.g., selected from V, Cr, Mn, Co, Ni, Cu, or any suitable combination thereof); L 1 It may be Mn, Al or any suitable combination thereof (eg, selected from Mn, Al or any suitable combination thereof).

[0064] The compound may have a coating layer on the surface, or may be mixed with another compound having a coating layer. The coating layer may include at least one coating element compound of the following substances (e.g., selected from the group consisting of the following substances): an oxide of a coating element; a hydroxide of a coating element; an oxyhydroxide of a coating element; an oxycarbonate of a coating element; and / or a hydroxycarbonate of a coating element. The compound used for the coating layer may be amorphous or crystalline. The coating elements included in the coating layer may include Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or any suitable combination thereof. The coating layer may be provided by using these elements in the compound in a method that has no adverse effect on the properties of the positive active material, and for example, the method may include any coating method such as spraying, dipping, etc., but these methods will not be described in more detail because they are generally available or used in the relevant field.

[0065] In the positive electrode, the amount of the positive active material may be about 90 wt % to about 98 wt % based on the total weight of the positive active material layer.

[0066] In one or more embodiments, the positive electrode active material layer may further include a binder and a conductive material, and may include the binder and the conductive material in an amount of about 1 wt % to about 5 wt % based on the total amount of the positive electrode active material layer.

[0067] The binder improves the bonding properties between the positive electrode active material particles and between the positive electrode active material particles and the current collector. Examples of the binder may be polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, etc., but the present disclosure is not limited thereto.

[0068] A conductive material is included to provide electrode conductivity, and any conductive material can be used as the conductive material unless it causes a chemical change. Examples of the conductive material may be: a carbon-based material such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, etc.; a metal-based material including metal powder or metal fiber of copper, nickel, aluminum, silver, etc.; a conductive polymer such as a polyphenylene derivative; or any suitable combination thereof.

[0069] The current collector may include Al, but the present disclosure is not limited thereto.

[0070] Electrolyte

[0071] The electrolyte includes a non-aqueous organic solvent and a lithium salt.

[0072] The non-aqueous organic solvent serves as a medium for transporting ions participating in the electrochemical reaction of the battery.

[0073] The non-aqueous organic solvent may include a carbonate solvent, an ester solvent, an ether solvent, a ketone solvent, an alcohol solvent, or an aprotic solvent.

[0074] Carbonate solvents may include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), ethyl methyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), etc., ester solvents may include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, decalactone, valerolactone, mevalonolactone, caprolactone, etc. Ether solvents may include dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, tetrahydrofuran, etc., and ketone solvents may include cyclohexanone, etc. Alcohol solvents may include ethanol, isopropanol, etc., and aprotic solvents may include: nitriles, 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.); amides, such as dimethylformamide; dioxolanes, such as 1,3-dioxolane, 1,4-dioxolane, etc.; cyclopentane sulfone, etc.

[0075] The organic solvent may be used alone or in a mixture. If the organic solvent is used in a mixture (eg, when the organic solvent is used in a mixture), the mixing ratio may be controlled or selected according to the desired battery performance and may be conventionally available to those skilled in the art.

[0076] If a non-aqueous organic solvent is mixed and used (for example, when a non-aqueous organic solvent is mixed and used), a mixed solvent of a cyclic carbonate and a linear carbonate, a mixed solvent of a cyclic carbonate and a propionate solvent, or a mixed solvent of a cyclic carbonate, a linear carbonate and a propionate solvent can be used. The propionate solvent can be methyl propionate, ethyl propionate, propyl propionate or any suitable combination thereof.

[0077] If cyclic carbonate is mixed with linear carbonate or cyclic carbonate is mixed with propionate solvent (for example, when cyclic carbonate is mixed with linear carbonate or cyclic carbonate is mixed with propionate solvent), they can be mixed with a volume ratio of about 1:1 to about 1:9, so the performance of the electrolyte can be improved. If cyclic carbonate, linear carbonate and propionate solvent are mixed (for example, when cyclic carbonate, linear carbonate and propionate solvent are mixed), they can be mixed with a volume ratio of about 1:1:1 to about 3:3:4. The mixing ratio of the solvent can be appropriately adjusted according to the desired property.

[0078] In addition to the carbonate-based solvent, the non-aqueous organic solvent may further include an aromatic hydrocarbon-based solvent. The carbonate-based solvent and the aromatic hydrocarbon-based solvent may be mixed together in a volume ratio of about 1:1 to about 30:1.

[0079] The aromatic hydrocarbon organic solvent may be an aromatic hydrocarbon compound represented by Chemical Formula 1.

[0080] Chemical formula 1

[0081]

[0082] In Chemical Formula 1, R1 to R6 may be independently the same or different, and may be hydrogen, halogen, C1 to C10 alkyl, halogenated alkyl and / or any suitable combination thereof (e.g., selected from hydrogen, halogen, C1 to C10 alkyl, halogenated alkyl and / or any suitable combination thereof).

[0083] Examples of aromatic hydrocarbon organic solvents include benzene, fluorobenzene, 1,2-difluorobenzene, 1,3-difluorobenzene, 1,4-difluorobenzene, 1,2,3-trifluorobenzene, 1,2,4-trifluorobenzene, chlorobenzene, 1,2-dichlorobenzene, 1,3-dichlorobenzene, 1,4-dichlorobenzene, 1,2,3-trichlorobenzene, 1,2,4-trichlorobenzene, iodobenzene, 1,2-diiodobenzene, 1,3-diiodobenzene, 1,4-diiodobenzene, 1,2,3-triiodobenzene, 1,2,4-triiodobenzene, toluene, fluorotoluene, 2,3-difluorotoluene, and 1,2-dichlorobenzene. , 2,4-difluorotoluene, 2,5-difluorotoluene, 2,3,4-trifluorotoluene, 2,3,5-trifluorotoluene, chlorotoluene, 2,3-dichlorotoluene, 2,4-dichlorotoluene, 2,5-dichlorotoluene, 2,3,4-trichlorotoluene, 2,3,5-trichlorotoluene, iodotoluene, 2,3-diiodotoluene, 2,4-diiodotoluene, 2,5-diiodotoluene, 2,3,4-triiodotoluene, 2,3,5-triiodotoluene, xylene or any suitable combination thereof (for example, can be selected from them).

[0084] The electrolyte may further include ethyl vinyl carbonate, vinylene carbonate, or an ethylene carbonate-based compound represented by Chemical Formula 2 as an additive for improving cycle life.

[0085] Chemical formula 2

[0086]

[0087] In Chemical Formula 2, R7 and R8 may be independently the same or different, and may be independently hydrogen, halogen, cyano (CN), nitro (NO2) or C1 to C5 fluoroalkyl, provided that at least one of R7 and / or R8 is halogen, cyano (CN), nitro (NO2) or C1 to C5 fluoroalkyl, and R7 and R8 are not hydrogen at the same time (e.g., concurrently).

[0088] Examples of ethylene carbonate compounds may include difluoroethylene carbonate, chloroethylene carbonate, dichloroethylene carbonate, bromoethylene carbonate, dibromoethylene carbonate, nitroethylene carbonate, cyanoethylene carbonate, fluoroethylene carbonate, etc. In the case of further using an additive for improving cycle life, the amount of the additive may be appropriately controlled or selected within an appropriate or suitable range.

[0089] The lithium salt dissolved in the organic solvent supplies lithium ions to the battery, enables the basic operation of the rechargeable lithium battery, and improves the transport of lithium ions between the positive electrode and the negative electrode. Examples of lithium salts include at least one of the following (e.g., at least one selected from the following): LiPF6, LiBF4, LiSbF6, LiAsF6, LiN(SO2C2F5)2, Li(CF3SO2)2N, LiN(SO3C2F5)2, Li(FSO2)2N (lithium bis(fluorosulfonyl)imide: LiFSI), LiC4F9SO3, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiN(C x F 2x+1 SO2)(C y F 2y+1 SO2) (wherein, x and y are natural numbers, x and y are integers from 1 to 20), lithium difluoro(bis(oxalato)phosphate, LiCl, LiI, LiB(C2O4)2 (lithium bis(oxalato)borate: LiBOB) and / or lithium difluoro(oxalato)borate (LiDFOB). The concentration of the lithium salt may be in the range of about 0.1 M to about 2.0 M. If the lithium salt is included in the above concentration range (for example, when the lithium salt is included in the above concentration range), the electrolyte may have excellent or suitable performance and lithium ion mobility due to optimal or suitable electrolyte conductivity and viscosity.

[0090] Diaphragm

[0091] The separator may be made of polyethylene, polypropylene, polyvinylidene fluoride or a multilayer having two or more layers thereof, and may be a mixed multilayer such as a polyethylene / polypropylene double-layer separator, a polyethylene / polypropylene / polyethylene three-layer separator, a polypropylene / polyethylene / polypropylene three-layer separator, etc.

[0092] The separator may include a porous substrate and a ceramic coating layer on at least one side of the porous substrate. The ceramic may include SiO2, Al2O3, Al(OH)3, AlO(OH), TiO2, BaTiO2, ZnO2, Mg(OH)2, MgO, Ti(OH)4, ZrO2, aluminum nitride, silicon carbide, boron nitride, or any suitable combination thereof.

[0093] According to one or more embodiments, the diaphragm may include a composite porous diaphragm including a porous substrate and a functional layer on the porous substrate. The functional layer may have additional functions, for example, may be at least one of a heat-resistant layer and / or an adhesive layer. The heat-resistant layer may include a heat-resistant resin and an optional filler. The adhesive layer may include an adhesive resin and an optional filler. The filler may be an organic filler, an inorganic filler, or any suitable combination thereof. The heat-resistant resin, the adhesive resin, and the filler may be any material that can be used in the diaphragm in the related art.

[0094] Rechargeable lithium batteries may be classified into cylindrical, prismatic, pouch-type (or-like) or coin-type (or-like) batteries, etc., according to their shapes. Figures 2 to 5 Each is a schematic diagram showing a rechargeable lithium battery according to one or more embodiments of the present disclosure. Figure 2 A cylindrical battery is shown, Figure 3 A prismatic cell is shown, and Figure 4 and Figure 5 Pouch type (or similar) battery is shown. Figures 2 to 5 , the rechargeable lithium battery 100 may include an electrode assembly 40 and a case 50 in which the electrode assembly 40 is included, and the electrode assembly 40 includes a separator 30 between the positive electrode 10 and the negative electrode 20. The positive electrode 10, the negative electrode 20, and the separator 30 may be impregnated with an electrolyte. The rechargeable lithium battery 100 may include a sealing member 60 that seals the case 50, such as Figure 2 As shown in Figure 3 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 4 and Figure 5 As shown in , the rechargeable lithium battery 100 may include electrode tabs 70 serving as electrical paths for guiding current formed in the electrode assembly 40 to the outside, and the electrode tabs 70 may be, for example, a positive electrode tab 71 and a negative electrode tab 72 .

[0095] As a non-limiting example, a rechargeable lithium battery according to one or more embodiments may be applied to automobiles, mobile phones, and / or one or more suitable types (kinds) of electrical devices.

[0096] The following examples and comparative examples are provided to highlight the features of one or more embodiments, but it will be understood that the examples and comparative examples are not to be construed as limiting the scope of the present disclosure, and the comparative examples are not to be construed as being outside the scope of the embodiments. In addition, it will be understood that the present disclosure is not limited to the specific details described in the examples and comparative examples.

[0097] Example 1

[0098] 97.5 wt % of a natural graphite first negative active material, 1.5 wt % of carboxymethyl cellulose, and 1 wt % of styrene butadiene rubber were mixed in a water solvent to prepare a first negative active material layer slurry.

[0099] 97.5 wt % of a silicon-carbon composite second negative active material, 1.5 wt % of carboxymethyl cellulose, and 1 wt % of styrene butadiene rubber were mixed in a water solvent to prepare a second negative active material layer slurry.

[0100] The silicon-carbon composite includes secondary particles in which (e.g., each of them) silicon nanoparticles (e.g., silicon primary particles) having an average particle size of 100 nm are agglomerated and a soft carbon coating layer (thickness of the soft carbon coating layer: 2 nm) on the surface of the secondary particles (e.g., each of the secondary particles), and based on a total of 100 wt % of the silicon-carbon composite, the amount of silicon nanoparticles is 30 wt % and the amount of soft carbon amorphous carbon is 70 wt %.

[0101] On one side of the Cu foil current collector, a first negative electrode active material layer slurry is applied and dried to form a first coating layer. Thereafter, on the other side of the current collector corresponding to the opposite side of the side where the first coating layer is formed, a second negative electrode active material layer slurry is applied and dried. Thereafter, pressurization is performed to prepare a negative electrode in which the first negative electrode active material layer and the second negative electrode active material layer are formed on each side (e.g., opposite sides) of the current collector. The thickness of the first negative electrode active material layer is 150 μm, and the thickness of the second negative electrode active material layer is 140 μm.

[0102] A half-cell was fabricated by conventional procedures using a negative electrode, a lithium metal counter electrode and an electrolyte. The electrolyte was prepared by dissolving 1M LiPF6 in a mixed solvent of ethylene carbonate and dimethyl carbonate (3:7 volume ratio).

[0103] Example 2

[0104] 97.5 wt % of artificial graphite first negative active material, 1.5 wt % of carboxymethyl cellulose, and 1 wt % of styrene butadiene rubber were mixed in a water solvent to prepare a first negative active material layer slurry.

[0105] A negative electrode in which the first negative electrode active material layer and the second negative electrode active material layer were formed on respective sides (e.g., opposite sides) of a current collector was prepared by substantially the same procedure as in Example 1, except that the first negative electrode active material layer slurry was used. The thickness of the first negative electrode active material layer was 150 μm, and the thickness of the second negative electrode active material layer was 140 μm.

[0106] A half-cell was fabricated using the negative electrode and the lithium metal counter electrode of Example 1 and the electrolyte.

[0107] Comparative Example 1

[0108] 97.5 wt % of Si—M alloy (wherein M is Fe) negative electrode active material, 1.5 wt % of carboxymethyl cellulose, and 1 wt % of styrene butadiene rubber were mixed in a water solvent to prepare a first negative electrode active material layer slurry.

[0109] 97.5 wt % of Si—M alloy (wherein M is Fe) negative electrode active material, 1.5 wt % of carboxymethyl cellulose, and 1 wt % of styrene butadiene rubber were mixed in a water solvent to prepare a second negative electrode active material layer slurry.

[0110] On one side of the Cu foil current collector, a first negative electrode active material layer slurry is applied and dried to prepare a first coating layer. Thereafter, on the other side of the current collector corresponding to the opposite side of the side on which the first coating layer is formed, a second negative electrode active material layer slurry is applied and dried. Thereafter, pressurization is performed to prepare a negative electrode in which the first negative electrode active material layer and the second negative electrode active material layer are formed on respective sides (e.g., opposite sides) of the current collector.

[0111] The thickness of the first negative electrode active material layer was 150 μm, and the thickness of the second negative electrode active material layer was 140 μm.

[0112] A half-cell was fabricated using the negative electrode and the lithium metal counter electrode of Example 1 and the electrolyte.

[0113] Comparative Example 2

[0114] 97.5wt% SiO x (wherein x is 4) The negative electrode active material, 1.5 wt % of carboxymethyl cellulose and 1 wt % of styrene butadiene rubber were mixed in an aqueous solvent to prepare a first negative electrode active material layer slurry.

[0115] 97.5wt% SiO x (wherein x is 4) The negative electrode active material, 1.5 wt % of carboxymethyl cellulose and 1 wt % of styrene butadiene rubber were mixed in an aqueous solvent to prepare a second negative electrode active material layer slurry.

[0116] A negative electrode was prepared by substantially the same procedure as that in Example 1, except that the first negative electrode active material layer slurry and the second negative electrode active material layer slurry were used.

[0117] A half-cell was fabricated using the negative electrode and the lithium metal counter electrode of Example 1 and the electrolyte.

[0118] Comparison Example 3

[0119] 97.5 wt % of a silicon-carbon composite first negative active material, 1.5 wt % of carboxymethyl cellulose, and 1 wt % of styrene butadiene rubber were mixed in a water solvent to prepare a first negative active material layer slurry.

[0120] 97.5 wt % of a silicon-carbon composite second negative active material, 1.5 wt % of carboxymethyl cellulose, and 1 wt % of styrene butadiene rubber were mixed in a water solvent to prepare a second negative active material layer slurry.

[0121] A negative electrode was prepared by substantially the same procedure as that in Example 1, except that the first negative electrode active material layer slurry and the second negative electrode active material layer slurry were used.

[0122] A half-cell was fabricated using the negative electrode and the lithium metal counter electrode of Example 1 and the electrolyte.

[0123] Experimental Example 1: Measurement of Thickness Increase Ratio

[0124] The half cells of Examples 1 and 2 and Comparative Examples 1 to 3 were subjected to formation charge and discharge by charging at 0.1C for 500 minutes and discharging for 1000 minutes, charging and discharging at 0.2C for 1500 minutes, and charging and discharging at 0.33C for 2000 minutes.

[0125] The ratio of the battery thickness after the formation charge and discharge to the battery thickness before the formation charge and discharge was calculated. The results are shown in Table 1 as the formation thickness increase ratio (%).

[0126] Table 1

[0127] Thickness increase ratio after chemical formation (%) Example 1 116％ Example 2 120％ Comparative Example 1 133％ Comparative Example 2 142％ Comparison Example 3 800％

[0128] As shown in Table 1, the formation thickness increase ratios of the half cells of Examples 1 and 2 were very small or substantially small compared to Comparative Examples 1 to 3.

[0129] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as those commonly understood by those skilled in the art to which the present disclosure belongs. It will also be understood that terms (such as those defined in commonly used dictionaries) should be interpreted as having a meaning consistent with their meaning in the context of the relevant art and / or this specification, and should not be interpreted in an idealized or overly formal sense, unless explicitly defined as such herein.

[0130] As used herein, the terms "substantially", "about" and similar terms are used as approximate terms rather than as terms of degree, and are intended to account for the inherent deviations of measured or calculated values ​​that will be recognized by those of ordinary skill in the art. As used herein, "substantially" includes the stated value and refers to the acceptable deviation range of the specific value as determined by those of ordinary skill in the art taking into account the measurement in question and the errors associated with the measurement of the specific quantity (i.e., the limitations of the measurement system). For example, "substantially" can mean within one or more standard deviations, or within ±30%, ±20%, ±10%, ±5% of the stated value.

[0131] In addition, any numerical range described herein is intended to include all sub-ranges of the same numerical precision contained in the described range. For example, the range of "1.0 to 10.0" is intended to include all sub-ranges (that is, having a minimum value equal to or greater than 1.0 and a maximum value equal to or less than 10.0) between the described minimum value 1.0 and the described maximum value 10.0 (and including the described minimum value 1.0 and the described maximum value 10.0), such as 2.4 to 7.6. Any maximum numerical limit described here is intended to include all lower numerical limits contained therein, and any minimum numerical limit described in this specification is intended to include all higher numerical limits contained therein. Therefore, the applicant reserves the right to modify this specification (including claims) to explicitly describe any sub-range contained in the range explicitly described here.

[0132] Furthermore, when describing embodiments of the present disclosure, the use of “may” refers to “one or more embodiments of the present disclosure.”

[0133] Portable devices, vehicles and / or batteries (e.g., battery controllers) and / or any other related devices or components according to the embodiments of the present disclosure described herein may be implemented using any suitable hardware, firmware (e.g., application specific integrated circuits), software, or a combination of software, firmware, and hardware. For example, the various components of the device may be formed on an integrated circuit (IC) chip or on separate IC chips. In addition, the various components of the device may be implemented on a flexible printed circuit film, a tape carrier package (TCP), a printed circuit board (PCB), or formed on a substrate. In addition, the various components of the device may be processes or threads that execute computer program instructions and interact with other system components for performing the various functions described herein, running on one or more processors in one or more computing devices. The computer program instructions are stored in a memory that may be implemented in a computing device using a standard memory device (such as a random access memory (RAM) as an example). The computer program instructions may also be stored in other non-temporary computer-readable media (such as a CD-ROM, a flash drive, etc. as an example). In addition, those skilled in the art will recognize that, without departing from the scope of the embodiments of the present disclosure, the functions of various computing devices may be combined or integrated into a single computing device, or the functions of a particular computing device may be distributed across one or more other computing devices.

[0134] Although the embodiments of the present disclosure have been described, it is understood that the present disclosure should not be limited to these embodiments, but a person skilled in the art may make one or more suitable changes and modifications within the spirit and scope of the present disclosure as defined by the appended claims and their equivalents.

Claims

1. A negative electrode, comprising: A first negative electrode active material layer includes a crystalline carbon negative electrode active material; A second negative electrode active material layer includes a silicon-carbon composite negative electrode active material; as well as The current collector is between the first negative electrode active material layer and the second negative electrode active material layer.

2. The negative electrode according to claim 1, wherein The crystalline carbon includes natural graphite or artificial graphite.

3. The negative electrode according to claim 1, wherein The crystalline carbon includes a mixture of natural graphite and artificial graphite.

4. The negative electrode according to claim 3, wherein The mixing ratio of the natural graphite to the artificial graphite is 50:50 to 90:10 by weight.

5. The negative electrode according to claim 1, wherein The silicon-carbon composite negative electrode active material includes silicon particles and amorphous carbon.

6. The negative electrode according to claim 1, wherein The silicon-carbon composite negative active material includes silicon nanoparticles and an amorphous carbon coating layer on surfaces of the silicon nanoparticles.

7. The negative electrode according to claim 1, wherein The silicon-carbon composite negative electrode active material includes silicon particles, crystalline carbon and amorphous carbon.

8. The negative electrode according to claim 1, wherein The silicon-carbon composite negative active material includes a core including silicon nanoparticles and crystalline carbon, and an amorphous carbon coating layer on a surface of the core.

9. The negative electrode according to claim 1, wherein The first negative electrode active material layer has a thickness of 120 μm to 250 μm.

10. The negative electrode according to claim 1, wherein The second negative electrode active material layer has a thickness of 120 μm to 250 μm.

11. The negative electrode according to claim 1, wherein: The thickness of the first negative electrode active material layer is greater than the thickness of the second negative electrode active material layer.

12. A rechargeable lithium battery, comprising: The negative electrode according to any one of claims 1 to 11; Positive electrode; as well as Electrolyte.

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