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

Abstract

A negative electrode for a rechargeable lithium battery and a rechargeable lithium battery are disclosed. The negative electrode includes a current collector and a negative electrode active material layer, in which the negative electrode active material layer includes: a first active material layer on the current collector and including first crystalline carbon, a Si-C composite, and a first binder; and a second active material layer on the first active material layer and including second crystalline carbon, an Si-C composite, and a second binder, the particle size of the first crystalline carbon being smaller than the particle size of the second crystalline carbon, and the amount of the first binder being greater than the amount of the second binder based on the total anode active material layer, the amount of the Si-C composite being less than the amount of the second binder based on 100 wt% of the anode active material layer, and the amount of the Si-C composite being less than the amount of the second binder based on 100 wt% of the anode active material layer. The amount of Si is about 3 wt% or greater.

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 development of electronic devices such as mobile phones, laptop computers, and electric vehicles using batteries has led to a surprisingly increased interest in rechargeable batteries having a relatively high energy density and high capacity. Research and development for improving the performance of rechargeable lithium batteries are being actively conducted.

[0003] A rechargeable lithium battery may include a positive electrode and a negative electrode including an active material capable of intercalating and deintercalating lithium ions, and an electrolyte, and if lithium ions intercalate / deintercalate at the positive electrode and the negative electrode, the rechargeable lithium battery may generate electric energy through oxidation and reduction reactions. Summary of the Invention

[0004] One or more embodiments of the present disclosure provide a negative electrode for a rechargeable lithium battery, which exhibits excellent adhesion and low ionic resistance.

[0005] Embodiments provide a rechargeable lithium battery including the negative electrode.

[0006] Some embodiments provide a negative electrode for a rechargeable lithium battery, the negative electrode including a current collector and a negative electrode active material layer, wherein the negative electrode active material layer includes: a first active material layer on the current collector and including first crystalline carbon, a Si-C composite, and a first binder; and a second active material layer on the first active material layer and including second crystalline carbon, a Si-C composite, and a second binder, the particle size of the first crystalline carbon being smaller than the particle size of the second crystalline carbon, in the entire negative electrode active material layer, the amount of the first binder being greater than the amount of the second binder, based on 100 wt% of the negative electrode active material layer, the amount of Si being about 3 wt% or more, and the DD (divergence) value defined by Equation 1 being about 30 or more.

[0007] [Equation 1]

[0008] DD (divergence) = (I a / I 总 ) × 100

[0009] Wherein,

[0010] I a is the sum of peak intensities at non-planar angles measured by X-ray powder diffraction (XRD) using CuKα radiation, and I 总 is the sum of peak intensities at all angles measured by XRD using CuKα radiation.

[0011] An embodiment provides a rechargeable lithium battery, which includes: a negative electrode; a positive electrode; and a non-aqueous electrolyte.

[0012] The negative electrode for the rechargeable lithium battery can exhibit improved adhesion and low ionic resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The drawings, together with the specification, illustrate embodiments of the subject matter of the present disclosure and, together with the description, are used to explain the principles of the embodiments of the subject matter of the present disclosure.

[0014] Figure 1 is a schematic diagram showing the orientation of the negative electrode active material according to an embodiment.

[0015] Figure 2 is a cross-sectional view schematically showing the negative electrode for the rechargeable lithium battery according to some embodiments.

[0016] Figure 3 is a graph showing the stress during charging and discharging.

[0017] Figures 4 to 7 is a cross-sectional view of the rechargeable lithium battery according to an embodiment. DETAILED DESCRIPTION

[0018] The subject matter of the present disclosure may be modified in many alternative forms, and thus example embodiments will be shown in the drawings and described in more detail. However, it should be understood that it is not intended to limit the present disclosure to the specific forms disclosed, but is intended to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure.

[0019] Hereinafter, embodiments of the present disclosure will be described in more detail. However, these embodiments are merely examples, and the present disclosure is not limited thereto, and the present disclosure is defined by the scope of the appended claims and their equivalents.

[0020] In the present disclosure, if no other definition is provided, it will be understood that if an element such as a layer, film, region, or substrate is referred to as "on" another element, it may be directly on the other element, or there may also be an intervening element therebetween.

[0021] Unless otherwise specified in the specification, the singular forms "a," "an," "one," and "the" are also intended to include the plural forms. Further, when describing embodiments of the present disclosure, the use of "may" refers to "one or more embodiments of the present disclosure." As used herein, "A and / or B" may indicate "A or B or both of them (e.g., concurrently or simultaneously)." Further, " / " used herein may be interpreted as "and" or interpreted as "or" depending on the circumstances. Expressions such as "at least one (kind / type / person) of...," "one (kind / type / person) of...," and "selected from..." modify the entire list of elements when before or after a list of elements, rather than individual elements of the list. For example, "at least one (kind / type / person) of a, b, or c," "at least one (kind / type / person) of a, b, and / or c," "at least one (kind / type / person) selected from a, b, and c," "at least one (kind / type / person) selected from among a to c," etc. may indicate only a, only b, only c, both a and b (e.g., concurrently or simultaneously), both a and c (e.g., concurrently or simultaneously), both b and c (e.g., concurrently or simultaneously), all of a, b, and c, or variations thereof.

[0022] As used herein, the term "their combination" may include mixtures, laminates, composites, copolymers, alloys, blends, and / or reactants of components (e.g., reaction products of reactants).

[0023] As used herein, if no other definition is provided, the particle size / diameter may be the average particle size. Such particle size / diameter indicates the average particle size / diameter (D50) at which the cumulative volume in the particle size distribution is about 50 vol%. The particle size / diameter (D50) may be measured by any suitable method commonly used in the art (e.g., by a particle size analyzer and / or by transmission electron microscope (TEM) images and / or scanning electron microscope (SEM) images). In some embodiments, a dynamic light scattering measurement device may be used to perform data analysis, count the number of particles for each particle size range, and from this data, the average particle size / diameter (D50) value may be easily obtained by calculation. The particle size may be measured by a laser diffraction method. Laser diffraction may be performed by the following steps: distributing the particles to be measured in a distribution solvent and introducing it into a commercially available laser diffraction particle measurement device (e.g., MT 3000 available from Microtrac), irradiating an ultrasonic wave of about 28 kHz with a power of about 60 W, and calculating the average particle size / diameter (D50) of the 50% standard particle distribution in the measurement device.

[0024] In some embodiments, the average particle size may be measured by various suitable techniques and, for example, may be measured by a particle size analyzer.

[0025] In some embodiments, the thickness can be measured by SEM and / or TEM images of the cross-section, but is not limited thereto, and it can be measured by any suitable technique as long as it can measure the relevant thickness in the relevant field. The thickness can be an average thickness.

[0026] As used herein, soft carbon refers to graphitizable carbon materials and is easily graphitized by heat treatment at a high temperature (e.g., about 2800 °C), and hard carbon refers to non-graphitizable carbon materials and is substantially non- and / or slightly graphitized by heat treatment. The soft carbon and the hard carbon can be any suitable carbon commonly used in the related art.

[0027] One or more embodiments provide a negative electrode for a rechargeable lithium battery, the negative electrode including: a current collector; and a negative electrode active material layer, and the negative electrode active material layer includes a first active material layer on the current collector and a second active material layer on the first active material layer. The first active material layer includes a first crystalline carbon, a Si-C composite, and a first binder, and the second active material layer includes a second crystalline carbon, a Si-C composite, and a second binder. The Si-C composite in the first active material layer can be the same as or different from the Si-C composite in the second active material layer. The particle size of the first crystalline carbon is smaller than the particle size of the second crystalline carbon, and based on the total negative electrode active material layer, the amount of the first binder is greater than the amount of the second binder. Based on 100 wt% of the negative electrode active material layer, the amount of Si in the negative electrode active material layer is about 3 wt% or more. The negative electrode has a DD (divergence) value of about 30 or more defined by Equation 1.

[0028] In some embodiments, the DD can be from about 30 to about 60.

[0029] Equation 1

[0030] DD (divergence) = (I a / I 总 ) × 100

[0031] In Equation 1,

[0032] I a is the sum of the peak intensities at non-planar angles measured by X-ray powder diffraction (XRD) using CuKα radiation, and I 总 is the sum of the peak intensities at all angles measured by XRD using CuKα radiation.

[0033] The non-planar angles are represented by XRD measurements using CuKα radiation at 2θ = 42.4 ± 0.2°, 43.4 ± 0.2°, 44.6 ± 0.2° and 77.5 ± 0.2°, corresponding to the (100) plane, (101)R plane, (101)H plane and (110) plane, respectively. Generally, graphite has structures classified into a rhombohedral structure and a hexagonal structure with an ABAB-type (or similar) stacking order according to the stacking order of graphene layers, where the R plane represents the rhombohedral structure and the H plane represents the hexagonal structure.

[0034] Therefore, I a can be the sum of the peak intensities that appear at 2θ = 42.4 ± 0.2°, 43.4 ± 0.2°, 44.6 ± 0.2° and 77.5 ± 0.2° by XRD measurements using CuKα radiation.

[0035] If measured by XRD using CuKα radiation, all angles are represented by 2θ = 26.5 ± 0.2°, 42.4 ± 0.2°, 43.4 ± 0.2°, 44.6 ± 0.2°, 54.7 ± 0.2° and 77.5 ± 0.2°, corresponding to the (002) plane, (100) plane, (101)R plane, (101)H plane, (004) plane and (110) plane, respectively. By overlapping the peak of the (101)R plane of the carbon-based material with another peak of the (111) plane of the current collector (e.g., Cu), a peak at 2θ = 43.4 ± 0.2° can also appear.

[0036] Therefore, if measured by XRD using CuKα radiation, I 总 can be the sum of the peak intensities that appear at 2θ = 26.5 ± 0.2°, 42.4 ± 0.2°, 43.4 ± 0.2°, 44.6 ± 0.2°, 54.7 ± 0.2° and 77.5 ± 0.2°.

[0037] Generally, the peak intensity indicates the height of the peak or the integrated area of the peak, and according to the embodiments, the peak intensity indicates the integrated area of the peak.

[0038] In some embodiments, XRD is measured using CuKα radiation as the target radiation, and is measured under measurement conditions of a scanning speed (° / S) of 2θ = 10° to 80° and a step size (° / step) of 0.044 to 0.089, and by removing the monochromator to improve the peak intensity resolution when using CuKα radiation as the target radiation, but the present disclosure is not limited thereto.

[0039] The DD value indicates that the negative electrode active material included in the negative electrode active material layer is oriented at a set or predetermined angle, and a larger value indicates that the negative electrode active material is well oriented. For example, as Figure 1As schematically shown, if the negative electrode active material A is oriented at an angle a to one side of the substrate S, the angle a increases as the DD value increases. The DD value can be maintained after charging and discharging.

[0040] In some embodiments, if the DD value of the negative electrode is about 30 or greater, the volume expansion of the negative electrode during charging and discharging can be reduced. If the DD value of the negative electrode is less than about 30, the effect of suppressing or reducing the volume expansion of the negative electrode during charging and discharging cannot be achieved. For example, the horizontal volume expansion that occurs when a negative electrode including a Si-C composite is charged and discharged can be effectively suppressed or reduced.

[0041] In some embodiments, the DD value is obtained by the following method: charging and discharging a rechargeable lithium battery including a negative electrode, disassembling the battery to obtain the negative electrode if it is fully discharged, and performing XRD measurement on the negative electrode. Charging and discharging are performed one or two times at about 0.1C to about 0.2C.

[0042] In some embodiments, the DD value of the first active material layer can be the same as the DD value of the second active material layer.

[0043] The negative electrode according to some embodiments includes two layers, a first active material layer and a second active material layer. The first active material layer is on the current collector, for example, positioned in contact with the current collector, and the second active material layer is positioned on the first active material layer and, for example, positioned on the outermost surface of the negative electrode active material layer.

[0044] In some embodiments, the first active material layer includes first crystalline carbon, a Si-C composite, and a first binder, and the second active material layer includes second crystalline carbon, a Si-C composite, and a second binder, and the particle size of the first crystalline carbon is smaller than the particle size of the second crystalline carbon. In some embodiments, the first crystalline carbon, the Si-C composite, and the second crystalline carbon are all negative electrode active materials. For example, the first active material layer includes the first crystalline carbon and the Si-C composite as negative electrode active materials, and the second active material layer includes the second crystalline carbon and the Si-C composite as negative electrode active materials.

[0045] In one or more embodiments, the ratio of the particle size of the first crystalline carbon to the particle size of the second crystalline carbon can be about 1:1.5 to about 1:4, about 1:2 to about 1:4, or about 1:2 to about 1:3. If the ratio of the particle size of the first crystalline carbon to the particle size of the second crystalline carbon satisfies the above range, the adhesion characteristics between the current collector and the active material can be further enhanced and the large distribution on the surface of the active material layer can be suppressed or reduced, thereby reducing the ionic resistance.

[0046] If the particle size of the first crystalline carbon included in the first active material layer in direct contact with the current collector is smaller than the particle size of the second crystalline carbon included in the second active material layer provided as an upper layer, the cohesive force of the binder in the first active material layer can be suppressed or reduced, thereby achieving an anchoring effect, and thus excellent adhesion between the current collector and the active material layer can be achieved.

[0047] The particle size of the first crystalline carbon can be about 4 μm to about 10 μm, about 5 μm to about 10 μm, or about 6 μm to about 10 μm.

[0048] The particle size of the second crystalline carbon can be about 6 μm to about 20 μm, about 10 μm to about 20 μm, or about 12 μm to about 20 μm.

[0049] The particle size can be the average particle size (D50).

[0050] In some embodiments, if the particle size of the first crystalline carbon is smaller than the particle size of the second crystalline carbon, and the particle sizes of the first crystalline carbon and the second crystalline carbon are within the above ranges, the adhesion between the current collector and the active material layer can be further improved.

[0051] The first crystalline carbon and the second crystalline carbon can be the same or different, and can be artificial graphite, natural graphite or a combination thereof with an unspecified shape, flake shape, lamellar shape, spherical shape and / or fibrous shape.

[0052] In some embodiments, the amount of the first binder is greater than the amount of the second binder. The amount of the binder represents the amount based on the total amount of the negative electrode active material layer, and if the amount of each layer is considered to be 100 wt%, the amount of the binder does not represent the amount included in each layer. For example, if the total amount of the first active material layer and the second active material layer is converted to 100 wt%, the amount of the first binder is greater than the amount of the second binder.

[0053] If the amount of the first binder is greater than the amount of the second binder, the adhesion between the current collector and the active material layer can be further improved, and the ionic resistance can be reduced.

[0054] In the entire negative electrode active material layer, the ratio of the amount of the first binder to the amount of the second binder can be about 60:40 to about 90:10, about 65:35 to about 90:10, or about 70:30 to about 90:10 by weight ratio. If the total amount included in the negative electrode active material layer is converted to 100 wt%, the ratio of the amount of the first binder to the amount of the second binder represents the distribution ratio between the binders included in the first active material layer and the second active material layer. For example, a ratio of the amount of the first binder to the amount of the second binder of about 60:40 means that, based on the amount of 100 wt% of the binder included in the total negative electrode active material layer, the amount of the first binder is about 60 wt% and the amount of the second binder is about 40 wt%.

[0055] If the amount of the first binder included in the first active material layer in direct contact with the current collector is about 60 to about 90 by weight ratio, the adhesion force between the current collector and the active material layer can be further enhanced. If the amount of the second binder included in the second active material layer provided in the upper layer is about 40 to about 10 by weight ratio, the low amount of the binder can improve the tortuosity, thereby further reducing the ionic resistance.

[0056] In some embodiments, based on 100 wt% of the negative electrode active material layer, the amount of the first binder can be about 1.5 wt% to about 5 wt%, about 2 wt% to about 5 wt%, about 2 wt% to about 4 wt%, or about 2 wt% to about 3 wt%. Here, 100 wt% of the negative electrode active material layer means the total amount obtained by adding the amounts of the first active material layer and the second active material layer and converting it to 100 wt%. For example, if the amount of the first binder is 4.4 wt% based on 100 wt% of the first active material layer, then this amount is converted (transformed) to 2.2 wt% based on 100 wt% of the negative electrode active material layer. If the amount of the first binder satisfies the above range, the adhesion force between the current collector and the active material layer can be further enhanced, and the separation of the active material during charging and discharging can be more effectively prevented or reduced.

[0057] Based on 100 wt% of the negative electrode active material layer, the amount of the second binder can be about 0.3 wt% to about 1 wt%, about 0.3 wt% to about 0.8 wt%, or about 0.3 wt% to about 0.7 wt%. If the amount of the second binder is within the above range, the ionic resistance can be further reduced and the migration of the binder can be further inhibited or reduced.

[0058] The first binder and the second binder can be the same as or different from each other, and can be a non-aqueous binder, an aqueous binder, or a combination thereof.

[0059] The non-aqueous binder may be polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene-propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide, or a combination thereof.

[0060] The aqueous binder may be selected from styrene-butadiene rubber, (meth)acrylate esterified styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluororubber, polyethylene oxide, polyvinylpyrrolidone, epichlorohydrin, polyphosphazene, poly(meth)acrylonitrile, ethylene-propylene-diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, and combinations thereof.

[0061] The aqueous binder may further include a cellulose compound. The cellulose compound includes one or more selected from carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, and alkali metal salts thereof. The alkali metal may be Na, K, and / or Li.

[0062] Figure 2 The negative electrode 1 including the first active material layer 5 between the current collector 3 and the second active material layer 7 according to some embodiments is schematically shown. The first active material layer 5 includes a first active material 5a and a first binder 5b, and the second active material layer 7 includes a second active material 7a and a second binder 7b. As Figure 2 shown, the first active material 5a has a smaller particle size than the second active material 7a, and the first binder 5b is included in a larger amount than the second binder 7b.

[0063] In some embodiments, based on the total 100 wt% of the negative electrode active material layer, the amount of Si may be about 3 wt% or more, about 3 wt% to about 10 wt%, or 5 wt% to 10 wt%. In some embodiments, the amount of Si represents the amount of Si included in the Si-C composite and represents the total amount of Si included in the first active material layer and the second active material layer. If the amount of Si is about 3 wt% or more based on the total 100 wt% of the negative electrode active material layer, a high capacity can be obtained and an excellent energy density can be obtained. Considering the energy density, the amount of Si may be at most about 10 wt% based on the total 100 wt% of the negative electrode active material layer.

[0064] According to some embodiments, the negative electrode includes an Si-C composite as one of the negative electrode active materials. In the negative electrode, a Si amount of about 3 wt% or more based on the total 100 wt% of the negative electrode active material layer can achieve a high capacity, and the volume expansion caused by the high Si amount during charging and discharging can be suppressed or reduced by the negative electrode active material serving as an alignment layer having a DD value of about 30 or more. For example, as Figure 3 shown in, the volume expansion of the negative electrode including Si occurs in the horizontal direction. However, if the alignment layer has a DD value of about 30 or more, the negative electrode active material is included in the negative electrode active material layer at a set or predetermined angle with respect to the current collector (e.g., standing upright in the vertical direction), and thus, the expansion of the negative electrode active material layer can occur in the vertical direction. This enables the horizontal expansion and the vertical expansion of the negative electrode active material layer to absorb each other, thereby effectively suppressing or reducing the volume expansion.

[0065] The amount of the binder in the first active material layer being greater than the amount of the binder in the second active material layer can improve the adhesion between the current collector and the active material layer and reduce the ionic resistance.

[0066] In one or more embodiments, the Si-C composite in the first active material layer or the Si-C composite in the second active material layer may include Si and amorphous carbon. For example, the Si-C composite may include silicon particles and amorphous carbon coated on the surface of the silicon particles. For example, the silicon-carbon composite may include silicon particles and an amorphous carbon coating layer on the surface of the silicon particles. In some embodiments, the silicon-carbon composite may include secondary particles (e.g., nuclei) in which silicon primary particles are aggregated and an amorphous carbon coating layer (e.g., a shell) on the surface of the secondary particles. The amorphous carbon may be between the silicon primary particles, e.g., coated on the silicon primary particles. For example, the secondary particles may be provided by being distributed in an amorphous carbon matrix. The silicon primary particles may be nano-silicon particles. The nano-silicon particles may have a particle size of about 10 nm to about 900 nm, about 10 nm to about 800 nm, about 10 nm to about 500 nm, about 10 nm to about 300 nm, or about 10 nm to about 200 nm. If the average particle size of the nano-silicon particles is within the above range, the extreme volume expansion caused during charging and discharging can be suppressed or reduced, and the breakage of the conduction path due to particle fragmentation can be prevented or reduced. In some embodiments, the particle size of the silicon secondary particles is not necessarily limited.

[0067] The amorphous carbon may include soft carbon, hard carbon, mesophase pitch carbonization products, calcined coke, etc. The thickness of the amorphous carbon coating layer can be adjusted appropriately or suitably, and for example, it can be about 2 nm to about 800 nm, about 5 nm to about 600 nm, about 10 nm to about 400 nm, or about 20 nm to about 200 nm. In one or more embodiments, the thickness of the amorphous carbon coating layer can be measured by SEM images and / or TEM images of the cross-section of the Si-C composite, but is not limited thereto. Thus, it can be measured by any suitable technique as long as the thickness of the amorphous carbon coating layer is measured appropriately.

[0068] Based on 100 wt% of the Si-C composite, the amount of silicon particles can be about 30 wt% to about 70 wt%, or about 40 wt% to about 65 wt%. Based on the total 100 wt% of the Si-C composite, the amount of amorphous carbon can be about 30 wt% to about 70 wt%, or about 35 wt% to about 60 wt%. If the amounts of silicon particles and amorphous carbon are within the above ranges, higher capacities can be achieved.

[0069] In an embodiment, the Si-C composite may include Si, amorphous carbon, and crystalline carbon. In some embodiments, the Si-C composite may include a core containing silicon particles and crystalline carbon and an amorphous carbon coating layer on the surface of the core. For example, the Si-C composite may include a core and an amorphous carbon coating layer on the core, and the core includes secondary particles in which silicon primary particles and crystalline carbon are aggregated. The amorphous carbon may be between the silicon primary particles and / or between the crystalline carbons such that the amorphous carbon fills between the silicon primary particles and / or between the crystalline carbons.

[0070] The crystalline carbon may include natural graphite and / or artificial graphite having unspecified shapes, flakes, lamellae, spheres, and / or fibers.

[0071] Based on the total 100 wt% of the silicon particles, amorphous carbon, and crystalline carbon, the amount of crystalline carbon can be about 1 wt% to about 20 wt%, for example, about 3 wt% to about 17 wt%, or about 5 wt% to about 15 wt%. If the crystalline carbon is included in the above range, the conductivity (e.g., electrical conductivity) can be further enhanced.

[0072] The particle size of the Si-C composite can be adjusted appropriately or suitably, and for example, it can be about 30 μm or less, for example, about 1 μm to about 30 μm, about 2 μm to about 25 μm, about 3 μm to about 20 μm, or about 5 μm to about 15 μm.

[0073] The first active material layer and the second active material layer may further include a conductive material (e.g., an electrically conductive material).

[0074] It may include a conductive material to provide electrode conductivity (e.g., electrical conductivity). Any suitable conductive material can be used as the conductive material (e.g., electrical conductive material), unless it causes a chemical change (e.g., an undesirable chemical change in a rechargeable lithium battery). Non-limiting examples of the conductive material can be: carbonaceous materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, etc.; metallic materials including metal powders and / or metal fibers such as copper, nickel, aluminum, silver, etc.; conductive polymers (e.g., electrical conductive polymers) such as polyphenylene derivatives; or a mixture (and / or combination) of one or more of them.

[0075] Hereinafter, the compositions for each layer will be further described.

[0076] In the first active material layer, based on the total 100 wt% of the first active material layer, the amount of the first crystalline carbon can be about 78 wt% to about 95 wt%, or about 80 wt% to about 95 wt%. Based on the total 100 wt% of the first active material layer, the amount of the Si-C composite can be about 3 wt% to about 20 wt%, or about 3 wt% to about 18 wt%.

[0077] Based on the total 100 wt% of the first active material layer, the amount of the first binder can be about 2 wt% to about 10 wt%.

[0078] If the first active material layer further includes a conductive material, based on the total 100 wt% of the first active material layer, the amount of the conductive material can be about 0.02 wt% to about 0.1 wt%.

[0079] In the second active material layer, based on the total 100 wt% of the second active material layer, the amount of the second crystalline carbon can be about 78 wt% to about 95 wt%, or about 80 wt% to about 95 wt%. Based on the total 100 wt% of the second active material layer, the amount of the Si-C composite can be about 3 wt% to about 20 wt%, or about 3 wt% to about 18 wt%.

[0080] Based on the total 100 wt% of the second active material layer, the amount of the second binder can be about 0.3 wt% to about 2 wt%.

[0081] If the second active material layer further includes a conductive material, based on the total 100 wt% of the second active material layer, the amount of the conductive material can be about 0.02 wt% to about 0.1 wt%.

[0082] The first active material layer can have a thickness of about 20 μm to about 150 μm, about 30 μm to about 150 μm, or about 50 μm to about 150 μm. If the thickness of the first active material layer falls within the above range, the binder can be more appropriately or suitably distributed.

[0083] The second active material layer may have a thickness of about 100 μm to about 300 μm, about 130 μm to about 250 μm, or about 150 μm to about 250 μm. If the thickness of the second active material layer is within the above range, the pores can be more appropriately or suitably distributed.

[0084] The current collector may include one selected from copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal (e.g., an electrically conductive metal), and combinations of one or more thereof, but the embodiments of the present disclosure are not limited thereto.

[0085] The active body density of the negative electrode may be about 1.0 g / cc to about 2.0 g / cc, about 1.2 g / cc to about 1.8 g / cc, or about 1.3 g / cc to about 1.7 g / cc. In some embodiments, the active body represents a solid mixture of an active material, a binder, and an optional conductive material. For example, the active body represents the active material layer. In some embodiments, the active body density may be the density of the active material layer. If the active body density of the negative electrode is within the above range, a battery with a higher capacity can be provided.

[0086] Method for preparing a negative electrode for a rechargeable lithium battery

[0087] According to one or more embodiments, the negative electrode can be formed by coating a negative electrode active material composition on a current collector while applying a magnetic field. Each step will be described in more detail below.

[0088] Place a magnet below the current collector, and coat and dry a first active material layer composition on the current collector to prepare a first active material layer. Thereafter, a second active material layer composition can be coated on the first active material layer, dried, and pressed (e.g., compacted) to prepare a second active material layer.

[0089] Coating can be performed by moving the current collector in the coating direction while the magnet is located below the current collector. For example, the magnetic field (magnetic flux) formed by the magnet is formed vertically with respect to the current collector, but the magnetic field is formed at a set or predetermined angle as a vector function according to the coating speed (the speed of moving the current collector). For example, crystalline carbon, which is one of the negative electrode active materials, can be oriented at a set or predetermined angle with respect to the current collector.

[0090] If the first negative electrode active material layer (i.e., the first active material layer) and the second negative electrode active material layer (i.e., the second active material layer) are on opposite sides of the current collector, the first negative electrode active material layer is on one side of the current collector; the other first negative electrode active material layer is on the corresponding side where the first negative electrode active material layer is not formed relative to the side on which the first negative electrode active material layer is formed; and the second negative electrode active material layer is on the two first negative electrode active material layers. In some embodiments, the first negative electrode active material layer and the second negative electrode active material layer may be sequentially on one side of the current collector, and the first negative electrode active material layer and the second negative electrode active material layer may be sequentially on the other side corresponding to the side of the current collector.

[0091] The magnet may have a magnetic field strength of about 2500 Gauss to about 10000 Gauss. The negative electrode active material composition may be coated on the current collector and held for about 3 seconds to about 15 seconds. For example, it may be exposed to the magnetic field for about 3 seconds to about 15 seconds. In one embodiment, the exposure time to the magnetic field may be about 3 seconds to about 12 seconds. Depending on the exposure time to the magnetic field, the obtained DD value may vary.

[0092] The DD value can also be obtained by adjusting the viscosity of the negative electrode active material layer composition.

[0093] The viscosity of the active material layer composition may be about 2000 cps to about 4000 cps, about 2000 cps to about 3500 cps, or about 2500 cps to about 3500 cps at room temperature (about 20 °C to about 25 °C). In some embodiments, the viscosity may be measured at room temperature (e.g., about 20 °C to about 25 °C) using a Brookfield viscometer. In some embodiments, the viscosities of the first active material layer composition and the second active material layer composition can be adjusted identically.

[0094] If the viscosities of the first negative electrode active material layer composition and the second negative electrode active material layer composition satisfy the above ranges, a first negative electrode active material layer and a second negative electrode active material layer with a desired DD value can be obtained.

[0095] If the viscosities of the first negative electrode active material layer composition and the second negative electrode active material layer composition are each lower than the above ranges, it may cause an extreme increase in the verticality of the crystalline carbon-based negative electrode active material, which results in insufficient contact or inappropriate contact of the negative electrode active material particles. Therefore, the electron migration resistance will increase, while a higher viscosity above the above ranges will reduce the orientation effect, thereby reducing the impregnability of the electrolyte.

[0096] The first active material layer composition and the second active material layer composition can be prepared by mixing crystalline carbon, Si-C composite, binder, and an optional conductive material (e.g., an electrically conductive material) in a solvent.

[0097] The solvent may be an organic solvent such as N-methylpyrrolidone or water, and if an aqueous binder is used as the binder, the solvent may be water.

[0098] Rechargeable lithium battery

[0099] Another embodiment provides a rechargeable lithium battery including a negative electrode, a positive electrode, and an electrolyte.

[0100] Positive electrode

[0101] The positive electrode may include a current collector and a positive electrode active material layer on the 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 (e.g., an electrically conductive material).

[0102] For example, the positive electrode may further include an additive that can serve as a sacrificial positive electrode.

[0103] Based on 100 wt% of the positive electrode active material layer, the amount of the positive electrode active material may be about 90 wt% to about 99.5 wt%, and based on 100 wt% of the positive electrode active material layer, the amounts of the binder and the conductive material may be 0.5 wt% to 5 wt% respectively.

[0104] The positive electrode active material may include a compound capable of intercalating and deintercalating lithium (e.g., a lithiated intercalation compound). In some embodiments, at least one of a composite oxide of lithium and a metal selected from cobalt, manganese, nickel, and combinations thereof may be used.

[0105] The composite oxide may be a lithium transition metal composite oxide, and examples thereof may include lithium nickel-based oxides, lithium cobalt-based oxides, lithium manganese-based oxides, lithium iron phosphate-based compounds, cobalt-free nickel manganese-based oxides, or combinations thereof.

[0106] For example, a compound represented by any of the following chemical formulas may be used: Li a A 1-b X b O 2-c D c (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); Li a Mn 2-b X b O 4-c D c (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); Li a Ni 1-b-c Co b X c O 2-α D α(0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.5, 0 < α < 2); Li a Ni 1-b-c Mn b X c O 2-α D α (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.5, 0 < α < 2); Li a Ni b Co c L 1 d G 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); Li (3-f) Fe2(PO4)3(0 ≤ f ≤ 2); Li a FePO4(0.90 ≤ a ≤ 1.8).

[0107] In the above chemical formulas, A is Ni, Co, Mn, or a combination thereof; X is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, or a combination thereof; D is O, F, S, P, or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; and L 1 is Mn, Al, or a combination thereof.

[0108] For example, the positive electrode active material may be a high-nickel type positive electrode active material. Based on 100 mol% of the metals other than lithium in the lithium transition metal composite oxide, the nickel content of the high-nickel type 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%. The high-nickel type positive electrode active material can achieve high capacity and can be applied to high-capacity and high-density rechargeable lithium batteries.

[0109] The binder improves the binding 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, a polymer containing ethylene oxide, polyvinylpyrrolidone, 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.

[0110] A conductive material is included to provide electrode conductivity (e.g., electrical conductivity), and any suitable conductive material can be used as the conductive material (e.g., electrical conductive material) unless it causes a chemical change (e.g., an undesired chemical change in a rechargeable lithium battery). Examples of the conductive material may include: carbonaceous materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber, carbon nanotube, etc.; metallic materials including metal powders and / or metal fibers such as copper, nickel, aluminum, silver, etc.; conductive polymers (e.g., electrical conductive polymers) such as polyphenylene derivatives; or mixtures thereof.

[0111] The current collector may include Al, but is not limited thereto.

[0112] Electrolyte

[0113] The electrolyte includes a non-aqueous organic solvent and a lithium salt.

[0114] The non-aqueous organic solvent serves as a medium for transporting ions participating in the electrochemical reaction of the battery.

[0115] The non-aqueous organic solvent may include carbonate solvents, ester solvents, ether solvents, ketone solvents, alcohol solvents, and / or aprotic solvents.

[0116] Carbonate solvents may include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), etc.

[0117] Ester solvents may include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanolide, mevalonolactone, valerolactone, caprolactone, etc.

[0118] Ether solvents may include dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, tetrahydrofuran, etc. Ketone solvents may include cyclohexanone, etc. Alcohol solvents may include ethanol, isopropanol, etc., and aprotic solvents may include: nitriles, such as R-CN (wherein, R is a C2 to C20 straight-chain, branched-chain or cyclic hydrocarbon group, and may include double bonds, aromatic rings and / or ether bonds, etc.); amides, such as dimethylformamide; dioxolanes, such as 1,3-dioxolane, 1,4-dioxolane, etc.; sulfolane, etc.

[0119] The organic solvent can be used alone or in a mixture of two or more thereof.

[0120] If a carbonate solvent is used, the cyclic carbonate and the chain carbonate can be used together, and the cyclic carbonate and the chain carbonate can be mixed together at a volume ratio of about 1:1 to about 1:9.

[0121] The lithium salt dissolved in the organic solvent supplies lithium ions to the battery, basically operates a rechargeable lithium battery, and improves the transport of lithium ions between the positive electrode and the negative electrode. Examples of the lithium salt include one or at least two supporting electrolyte salts selected from LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, LiN(SO3C2F5)2, Li(FSO2)2N (lithium bis(fluorosulfonyl)imide, LiFSI), LiC4F9SO3, LiN(C x F2 x+1 SO2)(C y F 2y+1 SO2) (wherein, x and y are integers from 1 to 20), lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium difluoro bis(oxalate) phosphate (LiDFOP), and lithium bis(oxalate) borate (LiBOB).

[0122] Separator

[0123] Depending on the type (or kind) of the rechargeable lithium battery, the separator can be between the positive electrode and the negative electrode. The separator can be made of polyethylene, polypropylene, polyvinylidene fluoride, or a multilayer thereof with two or more layers, and can be a mixed multilayer, such as a polyethylene / polypropylene bilayer separator, a polyethylene / polypropylene / polyethylene trilayer separator, a polypropylene / polyethylene / polypropylene trilayer separator, etc.

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

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

[0126] The organic material can include polyvinylidene fluoride-based polymers and / or (meth)acryloyl-based polymers.

[0127] The inorganic material can be inorganic particles selected from Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, Mg(OH)2, boehmite, or a combination thereof, but not limited thereto.

[0128] The organic material and the inorganic material can be mixed together in one coating layer, or the coating layer including the organic material and the coating layer including the inorganic material can be stacked.

[0129] Rechargeable lithium batteries can be classified into cylindrical, prismatic, pouch-shaped, coin-type batteries, etc. according to their shapes. Figures 4 to 7 is a schematic diagram showing a rechargeable lithium battery according to an embodiment, and Figure 4 shows a cylindrical battery, Figure 5 shows a prismatic battery, and Figure 6 and Figure 7 shows a pouch-type battery. Referring to Figures 4 to 7 , the rechargeable lithium battery 100 can include an electrode assembly 40 and a housing 50. The electrode assembly 40 includes a separator 30 between a positive electrode 10 and a negative electrode 20, and the electrode assembly 40 is included in the housing 50. The positive electrode 10, the negative electrode 20, and the separator 30 can be impregnated with an electrolyte. As Figure 5As shown in [reference], the rechargeable lithium battery 100 may include a sealing member 60 that seals the housing 50. In Figure 5 the rechargeable lithium battery 100 may include a positive electrode lead tab 11 and a positive electrode terminal 12, a negative electrode lead tab 21 and a negative electrode terminal 22. As shown in Figure 6 and Figure 7 the rechargeable lithium battery 100 may include electrode tabs 70 ( Figure 7 ) that serve as a circuit path for guiding the current formed in the electrode assembly 40 to the outside, for example, a positive electrode tab 71 and a negative electrode tab 72 ( Figure 6 ).

[0130] As a non-limiting example, the rechargeable lithium battery according to an embodiment may be applied to an automobile, a mobile phone, and / or various suitable types (or kinds) of electrical devices.

[0131] 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 will not be construed as limiting the scope of the embodiments, nor will the comparative examples be construed as being outside the scope of the embodiments. In addition, it will be understood that the embodiments are not limited to the specific details described in the examples and comparative examples.

[0132] Example 1

[0133] 91.2 wt% of artificial graphite (average particle size (D50): 6 μm), 4.4 wt% of Si-C composite, 3.6 wt% of styrene-butadiene rubber, and 0.8 wt% of carboxymethyl cellulose were mixed in an aqueous solvent to prepare a first negative electrode active material layer slurry having a viscosity of 2500 cps (at 25 °C).

[0134] As the Si-C composite, a composite including a core and a soft carbon coating layer on the core was used. The core included secondary particles in which nano-silicon primary particles (average particle size: 100 nm) were aggregated. In the Si-C composite, the amount of nano-silicon primary particles was 70 wt%, the amount of soft carbon was 30 wt%, and the thickness of the soft carbon coating layer was 100 nm.

[0135] 94.4 wt% of artificial graphite (average particle size (D50): 15 μm), 4.4 wt% of Si-C composite, 0.4 wt% of styrene-butadiene rubber, and 0.8 wt% of carboxymethyl cellulose were mixed in an aqueous solvent to prepare a second active material layer slurry having a viscosity of 2650 cps (at 25 °C).

[0136] As the Si-C composite, a composite including a core and a soft carbon coating layer on the core is used. The core includes secondary particles in which nano-silicon primary particles (average particle size: 100 nm) are aggregated. In the Si-C composite, the amount of nano-silicon primary particles is 70 wt%, the amount of soft carbon is 30 wt%, and the thickness of the soft carbon coating layer is 100 nm.

[0137] Place the Cu foil current collector on a magnet with a magnetic field strength of 6000 gauss, and while moving the Cu foil current collector, coat the first active material layer slurry on the Cu foil current collector and expose it to the magnetic field for 10 seconds and dry it to prepare a first active material layer with a thickness of 103 μm.

[0138] Thereafter, coat the second active material layer slurry on the first active material layer and expose it to the magnetic field for 10 seconds and dry it to prepare a second active material layer with a thickness of 206 μm.

[0139] Thereafter, apply pressure to prepare a negative electrode with a bulk density of 1.6 g / cc.

[0140] In the prepared negative electrode, based on the sum of the first active material layer and the second active material layer (i.e., 100 wt% of the total negative electrode active material layer), the amount of Si is 3 wt%.

[0141] Mix 96 wt% of LiCoO2 positive electrode active material, 2 wt% of carbon black conductive agent, and 2 wt% of polyvinylidene fluoride binder in an N-methylpyrrolidone solvent to prepare a positive electrode active material slurry. Coat the prepared slurry on an Al current collector, dry it, and apply pressure to prepare a positive electrode.

[0142] Use the negative electrode, positive electrode, and electrolyte to manufacture a rechargeable lithium full cell. The electrolyte is used by dissolving 1.5 M LiPF6 in a mixed solvent of ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate (volume ratio of 20:10:70).

[0143] Example 2

[0144] Mix 88.6 wt% of artificial graphite (average particle size (D50): 6 μm), 7 wt% of the Si-C composite of Example 1, 3.6 wt% of styrene-butadiene rubber, and 0.8 wt% of carboxymethyl cellulose in an aqueous solvent to prepare a first negative electrode active material layer slurry with a viscosity of 2500 cps (at 25 °C).

[0145] 91.8 wt% artificial graphite (average particle size (D50): 15 μm), 7 wt% of the Si-C composite of Example 1, 0.4 wt% styrene-butadiene rubber, and 0.8 wt% carboxymethyl cellulose were mixed together in an aqueous solvent to prepare a second active material layer slurry having a viscosity of 2650 cps (at 25 °C).

[0146] Except for using this first active material layer slurry and this second active material layer slurry, a negative electrode having a bulk density of 1.6 g / cc was prepared by the same steps as in Example 1.

[0147] In the prepared negative electrode, based on the sum of the first active material layer and the second active material layer (i.e., 100 wt% of the total negative electrode active material layer), the amount of Si was 5 wt%.

[0148] Except for using the above negative electrode, a rechargeable lithium battery was manufactured by the same steps as in Example 1.

[0149] Comparative Example 1

[0150] Except for positioning the Cu foil current collector on a magnet having a magnetic field strength of 2000 gauss while moving the Cu foil current collector, a negative electrode having a bulk density of 1.6 g / cc was prepared by the same steps as in Example 1. The first active material layer slurry of Example 1 was coated on the Cu foil current collector and dried to prepare a first active material layer having a thickness of 103 μm, and the second active material layer slurry of Example 1 was coated on the first active material layer and dried to prepare a second active material layer having a thickness of 206 μm.

[0151] Except for using the above negative electrode, a rechargeable lithium battery was manufactured by the same steps as in Example 1.

[0152] Comparative Example 2

[0153] Except for positioning the Cu foil current collector on a magnet having a magnetic field strength of 2000 gauss while moving the Cu foil current collector, a negative electrode having a bulk density of 1.6 g / cc was prepared by the same steps as in Example 2. The first active material layer slurry of Example 2 was coated on the Cu foil current collector and dried to prepare a first active material layer having a thickness of 103 μm, and the second active material layer slurry of Example 2 was coated on the first active material layer and dried to prepare a second active material layer having a thickness of 206 μm.

[0154] Except for using the above negative electrode, a rechargeable lithium battery was manufactured by the same steps as in Example 1.

[0155] Comparative Example 3

[0156] Mix 96.8 wt% artificial graphite (average particle size (D50): 15 μm), 2 wt% Si-C composite, 0.4 wt% styrene-butadiene rubber, and 0.8 wt% carboxymethyl cellulose in an aqueous solvent to prepare a first negative electrode active material layer slurry with a viscosity of 2530 cps (at 25 °C).

[0157] As the Si-C composite, use a composite including a core and a soft carbon coating layer on the core. The core includes secondary particles in which nano-silicon primary particles (average particle size: 100 nm) are aggregated. In the Si-C composite, the amount of nano-silicon primary particles is 70 wt%, the amount of soft carbon is 30 wt%, and the thickness of the soft carbon coating layer is 100 nm.

[0158] Mix 93.6 wt% artificial graphite (average particle size (D50): 15 μm), 2 wt% Si-C composite, 3.6 wt% styrene-butadiene rubber, and 0.8 wt% carboxymethyl cellulose in an aqueous solvent to prepare a second active material layer slurry with a viscosity of 2560 cps (at 25 °C).

[0159] As the Si-C composite, use a composite including a core and a soft carbon coating layer on the core. The core includes secondary particles in which nano-silicon primary particles (average particle size: 100 nm) are aggregated. In the Si-C composite, the amount of nano-silicon primary particles is 70 wt%, the amount of soft carbon is 30 wt%, and the thickness of the soft carbon coating layer is 100 nm.

[0160] Position a Cu foil current collector on a magnet with a magnetic field strength of 2000 gauss, while moving the Cu foil current collector, coat the first active material layer slurry on the Cu foil current collector to expose it to the magnetic field for 10 seconds and dry it to prepare a first active material layer with a thickness of 102 μm.

[0161] Thereafter, coat the second active material layer slurry on the first active material layer to expose it to the magnetic field for 10 seconds and dry it to prepare a second active material layer with a thickness of 205 μm.

[0162] Thereafter, apply pressure to prepare a negative electrode with a bulk density of 1.6 g / cc.

[0163] In the prepared negative electrode, based on the sum of the first active material layer and the second active material layer (i.e., 100 wt% of the total negative electrode active material layer), the amount of Si is 1.5 wt%.

[0164] Except for using the above negative electrode, manufacture a rechargeable lithium battery by the same steps as in Example 1.

[0165] Comparative Example 4

[0166] A negative electrode with an active material density of 1.6 g / cc was prepared by the same steps as in Comparative Example 3, except that the magnetic field strength was changed to 4000 Gauss.

[0167] A rechargeable lithium battery was manufactured by the same steps as in Example 1, except that the above negative electrode was used.

[0168] Comparative Example 5

[0169] 91.2 wt% of artificial graphite (average particle size (D50): 15 μm), 4.4 wt% of the Si-C composite of Example 1, 3.6 wt% of styrene-butadiene rubber, and 0.8 wt% of carboxymethyl cellulose were mixed in an aqueous solvent to prepare a first negative electrode active material layer slurry with a viscosity of 2530 cps (at 25 °C).

[0170] 94.4 wt% of artificial graphite (average particle size (D50): 15 μm), 4.4 wt% of the Si-C composite of Example 1, 0.4 wt% of styrene-butadiene rubber, and 0.8 wt% of carboxymethyl cellulose were mixed in an aqueous solvent to prepare a second active material layer slurry with a viscosity of 2560 cps (at 25 °C).

[0171] A negative electrode with an active material density of 1.6 g / cc was prepared by the same steps as in Comparative Example 3, except that the first active material layer slurry and the second active material layer slurry were coated.

[0172] In the prepared negative electrode, based on the sum of the first active material layer and the second active material layer (i.e., 100 wt% of the total negative electrode active material layer), the amount of Si was 3 wt%.

[0173] A rechargeable lithium battery was manufactured by the same steps as in Example 1, except that the above negative electrode was used.

[0174] Comparative Example 6

[0175] A negative electrode with an active material density of 1.6 g / cc was prepared by the same steps as in Comparative Example 5, except that the magnetic field strength was changed to 6000 Gauss.

[0176] A rechargeable lithium battery was manufactured by the same steps as in Example 1, except that the above negative electrode was used.

[0177] Comparative Example 7

[0178] 88.6 wt% of artificial graphite (average particle size (D50): 15 μm), 7 wt% of the Si-C composite of Example 1, 3.6 wt% of styrene-butadiene rubber, and 0.8 wt% of carboxymethyl cellulose were mixed together in an aqueous solvent to prepare a first negative electrode active material layer slurry having a viscosity of 2530 cps (at 25 °C).

[0179] 91.8 wt% of artificial graphite (average particle size (D50): 15 μm), 7 wt% of the Si-C composite of Example 1, 0.4 wt% of styrene-butadiene rubber, and 0.8 wt% of carboxymethyl cellulose were mixed together in an aqueous solvent to prepare a second active material layer slurry having a viscosity of 2560 cps (at 25 °C).

[0180] Except for using the above first active material layer slurry and second active material layer slurry, a negative electrode having a bulk density of 1.6 g / cc was prepared by the same steps as in Comparative Example 3.

[0181] In the prepared negative electrode, based on the sum of the first active material layer and the second active material layer (i.e., 100 wt% of the total negative electrode active material layer), the amount of Si was 5 wt%.

[0182] Except for using the above negative electrode, a rechargeable lithium battery was manufactured by the same steps as in Example 1.

[0183] Comparative Example 8

[0184] Except for changing the magnetic field strength to 6000 gauss, a negative electrode was prepared by the same steps as in Comparative Example 7.

[0185] Except for using the above negative electrode, a rechargeable lithium battery was manufactured by the same steps as in Example 1.

[0186] Comparative Example 9

[0187] 81.6 wt% of artificial graphite (average particle size (D50): 15 μm), 14 wt% of the Si-C composite of Example 1, 3.6 wt% of styrene-butadiene rubber, and 0.8 wt% of carboxymethyl cellulose were mixed together in an aqueous solvent to prepare a first negative electrode active material layer slurry having a viscosity of 2530 cps (at 25 °C).

[0188] 84.8 wt% of artificial graphite (average particle size (D50): 15 μm), 14 wt% of the Si-C composite of Example 1, 0.4 wt% of styrene-butadiene rubber, and 0.8 wt% of carboxymethyl cellulose were mixed together in an aqueous solvent to prepare a second active material layer slurry having a viscosity of 2560 cps (at 25 °C).

[0189] Except for coating the first active material layer slurry and drying it to prepare a first active material layer with a thickness of 103 μm and coating the second active material layer slurry on the first active material layer to prepare a second active material layer with a thickness of 206 μm, a negative electrode with a bulk density of 1.6 g / cc is prepared by the same steps as in Comparative Example 1. That is, the negative electrode is prepared without using a magnet and without applying a magnetic field.

[0190] In the prepared negative electrode, based on the sum of the first active material layer and the second active material layer (i.e., 100 wt% of the sum of the negative electrode active material layers), the amount of Si is 10 wt%.

[0191] Except for using the above negative electrode, a rechargeable lithium battery is manufactured by the same steps as in Example 1.

[0192] Comparative Example 10

[0193] Except for positioning the Cu foil current collector on a magnet with a magnetic field strength of 2000 gauss while moving the Cu foil current collector, a negative electrode with a bulk density of 1.6 g / cc is prepared by the same steps as in Comparative Example 9. The first active material layer slurry of Comparative Example 9 is coated on the Cu foil current collector and dried to prepare a first active material layer with a thickness of 103 μm, and the second active material layer slurry of Comparative Example 9 is coated on the first active material layer and dried to prepare a second active material layer with a thickness of 206 μm.

[0194] Except for using the above negative electrode, a rechargeable lithium battery is manufactured by the same steps as in Example 1.

[0195] Comparative Example 11

[0196] 88.7 wt% of artificial graphite (average particle size (D50): 6 μm), 8.5 wt% of Si-C composite, 2 wt% of styrene-butadiene rubber, and 0.8 wt% of carboxymethyl cellulose are mixed in an aqueous solvent to prepare a first negative electrode active material layer slurry with a viscosity of 2500 cps (at 25 °C).

[0197] As the Si-C composite, a composite including a core and a soft carbon coating layer on the core is used. The core includes secondary particles in which nano-silicon primary particles (average particle size: 100 nm) are aggregated. In the Si-C composite, the amount of nano-silicon primary particles is 70 wt%, the amount of soft carbon is 30 wt%, and the thickness of the soft carbon coating layer is 100 nm.

[0198] 88.7 wt% of artificial graphite (average particle size (D50): 15 μm), 8.5 wt% of Si-C composite, 2 wt% of styrene-butadiene rubber, and 0.8 wt% of carboxymethyl cellulose were mixed in an aqueous solvent to prepare a second active material layer slurry with a viscosity of 2600 cps (at 25 °C).

[0199] As the Si-C composite, a composite including a core and a soft carbon coating layer on the core was used. The core includes secondary particles in which nano-silicon primary particles (average particle size: 100 nm) are aggregated. In the Si-C composite, the amount of nano-silicon primary particles is 70 wt%, the amount of soft carbon is 30 wt%, and the thickness of the soft carbon coating layer is 100 nm.

[0200] A Cu foil current collector was positioned on a magnet with a magnetic field strength of 2000 gauss while moving the Cu foil current collector, and the first active material layer was coated on the Cu foil current collector to be exposed to the magnetic field for 10 seconds and dried to prepare a first active material layer with a thickness of 103 μm.

[0201] Thereafter, the second active material layer slurry was coated on the first active material layer to be exposed to the magnetic field for 10 seconds and dried to prepare a second active material layer with a thickness of 206 μm.

[0202] Thereafter, pressing was performed to prepare a negative electrode with an active body density of 1.6 g / cc.

[0203] In the prepared negative electrode, based on the sum of the first active material layer and the second active material layer (i.e., 100 wt% of the total negative electrode active material layer), the amount of Si is 6 wt%.

[0204] Except for using the above negative electrode, a rechargeable lithium battery was manufactured by the same steps as in Example 1.

[0205] Comparative Example 12

[0206] 95.9 wt% of artificial graphite (average particle size (D50): 6 μm), 2.9 wt% of Si-C composite, 0.4 wt% of styrene-butadiene rubber, and 0.8 wt% of carboxymethyl cellulose were mixed in an aqueous solvent to prepare a first negative electrode active material layer slurry with a viscosity of 2600 cps (at 25 °C).

[0207] As the Si-C composite, a composite including a core and a soft carbon coating layer on the core was used. The core includes secondary particles in which nano-silicon primary particles (average particle size: 100 nm) are aggregated. In the Si-C composite, the amount of nano-silicon primary particles is 70 wt%, the amount of soft carbon is 30 wt%, and the thickness of the soft carbon coating layer is 100 nm.

[0208] 92.7 wt% of artificial graphite (average particle size (D50): 6 μm), 2.9 wt% of Si-C composite, 3.6 wt% of styrene-butadiene rubber, and 0.8 wt% of carboxymethyl cellulose were mixed together in an aqueous solvent to prepare a second active material layer slurry having a viscosity of 2580 cps (at 25 °C).

[0209] As the Si-C composite, a composite including a core and a soft carbon coating layer on the core was used. The core included secondary particles in which nano-silicon primary particles (average particle size: 100 nm) were aggregated. In the Si-C composite, the amount of nano-silicon primary particles was 70 wt%, the amount of soft carbon was 30 wt%, and the thickness of the soft carbon coating layer was 100 nm.

[0210] A Cu foil current collector was positioned on a magnet having a magnetic field strength of 2000 gauss while moving the Cu foil current collector, and the first active material layer was coated on the Cu foil current collector to be exposed to the magnetic field for 10 seconds and dried to prepare a first active material layer having a thickness of 102 μm.

[0211] Thereafter, the second active material layer slurry was coated on the first active material layer to be exposed to the magnetic field for 10 seconds and dried to prepare a second active material layer having a thickness of 204 μm.

[0212] Thereafter, pressing was performed to prepare a negative electrode having a bulk density of 1.6 g / cc.

[0213] In the prepared negative electrode, based on the sum of the first active material layer and the second active material layer (i.e., 100 wt% of the total negative electrode active material layer), the amount of Si was 2.9 wt%.

[0214] Except for using the above negative electrode, a rechargeable lithium battery was manufactured by the same steps as in Example 1.

[0215] Comparative Example 13

[0216] 91.8 wt% of artificial graphite (average particle size (D50): 6 μm), 7 wt% of the Si-C composite of Comparative Example 12, 0.4 wt% of styrene-butadiene rubber, and 0.8 wt% of carboxymethyl cellulose were mixed together in an aqueous solvent to prepare a first negative electrode active material layer slurry having a viscosity of 2600 cps (at 25 °C).

[0217] 88.6 wt% of artificial graphite (average particle size (D50): 6 μm), 7 wt% of the Si-C composite of Comparative Example 12, 3.6 wt% of styrene-butadiene rubber, and 0.8 wt% of carboxymethyl cellulose were mixed together in an aqueous solvent to prepare a second active material layer slurry having a viscosity of 2580 cps (at 25 °C).

[0218] Position the Cu foil current collector on a magnet with a magnetic field strength of 2000 gauss. At the same time, move the Cu foil current collector and coat the first active material layer on the Cu foil current collector, expose it to the magnetic field for 10 seconds, and dry it to prepare the first active material layer with a thickness of 102 μm.

[0219] Thereafter, coat the second active material layer slurry on the first active material layer, expose it to the magnetic field for 10 seconds, and dry it to prepare the second active material layer with a thickness of 204 μm.

[0220] Thereafter, apply pressure to prepare a negative electrode with an active body density of 1.6 g / cc.

[0221] In the prepared negative electrode, based on the sum of the first active material layer and the second active material layer (i.e., 100 wt% of the total negative electrode active material layer), the amount of Si is 5 wt%.

[0222] Except for using the above negative electrode, a rechargeable lithium battery is manufactured by the same steps as in Example 1.

[0223] Comparative Example 14

[0224] Mix 87.1 wt% of artificial graphite (average particle size (D50): 6 μm), 8.5 wt% of Si-C composite, 3.6 wt% of styrene-butadiene rubber, and 0.8 wt% of carboxymethyl cellulose in an aqueous solvent to prepare a first negative electrode active material layer slurry with a viscosity of 2540 cps (at 25 °C).

[0225] As the Si-C composite, use a composite including a core and a soft carbon coating layer on the core. The core includes secondary particles in which nano-silicon primary particles (average particle size: 100 nm) are aggregated. In the Si-C composite, the amount of nano-silicon primary particles is 70 wt%, the amount of soft carbon is 30 wt%, and the thickness of the soft carbon coating layer is 100 nm.

[0226] Mix 90.3 wt% of artificial graphite (average particle size (D50): 15 μm), 8.5 wt% of Si-C composite, 0.4 wt% of styrene-butadiene rubber, and 0.8 wt% of carboxymethyl cellulose in an aqueous solvent to prepare a second active material layer slurry with a viscosity of 2610 cps (at 25 °C).

[0227] As the Si-C composite, use a composite including a core and a soft carbon coating layer on the core. The core includes secondary particles in which nano-silicon primary particles (average particle size: 100 nm) are aggregated. In the Si-C composite, the amount of nano-silicon primary particles is 70 wt%, the amount of soft carbon is 30 wt%, and the thickness of the soft carbon coating layer is 100 nm.

[0228] Position the Cu foil current collector on a magnet with a magnetic field strength of 2000 Gauss. At the same time, move the Cu foil current collector and coat the first active material layer on the Cu foil current collector, expose it to the magnetic field for 10 seconds and dry it to prepare the first active material layer with a thickness of 102 μm.

[0229] Thereafter, coat the second active material layer slurry on the first active material layer, expose it to the magnetic field for 10 seconds and dry it to prepare the second active material layer with a thickness of 204 μm.

[0230] Thereafter, apply pressure to prepare a negative electrode with an active body density of 1.6 g / cc.

[0231] In the prepared negative electrode, based on the sum of the first active material layer and the second active material layer (i.e., 100 wt% of the total negative electrode active material layer), the amount of Si is 6 wt%.

[0232] Except for using the above negative electrode, a rechargeable lithium battery is manufactured by the same steps as in Example 1.

[0233] Experimental Example 1) Measurement of X-ray diffraction characteristics

[0234] Charge and discharge the rechargeable lithium batteries according to Example 1, Example 2 and Comparative Examples 1 to 14 twice at 0.1C and fully discharge them to 2.75V at 0.1C. Disassemble the fully discharged battery cells to obtain the negative electrodes. For these negative electrodes, use an X'Pert (PANalytical B.V.) XRD device with CuKα rays as the target rays, but remove the monochromator device in order to improve the peak intensity resolution, and then measure the XRD. The measurement is carried out under the conditions of 2θ = 10° to 80°, scanning speed (° / S) = 0.06436, and step size of 0.026° / step.

[0235] Based on the measured XRD results, calculate the DD values of each layer, and the results are shown in Table 2.

[0236] Among the XRD results, measure the integral areas of the peaks shown at 2θ = 26.5 ± 0.2° ((002) plane), 42.4 ± 0.2° ((100) plane), 43.4 ± 0.2° ((101)R plane), 44.6 ± 0.2° ((101)H plane), 54.7 ± 0.2° ((004) plane), 77.5 ± 0.2° ((110) plane). Take the sum of the areas of the peaks shown at 2θ = 42.4 ± 0.2° ((100) plane), 43.4 ± 0.2° ((101)R plane), 44.6 ± 0.2° ((101)H plane) and 77.5 ± 0.2° ((110) plane) as I aand the total area of the peaks shown at 2θ = 26.5 ± 0.2° ((002) plane), 42.4 ± 0.2° ((100) plane), 43.4 ± 0.2° ((101)R plane), 44.6 ± 0.2° ((101)H plane), 54.7 ± 0.2° ((004) plane), 77.5 ± 0.2° ((110) plane) is taken as I 总 , and obtaining DD (I a / I 总 ) by calculating from these values.

[0237] The Si content based on 100 wt% of the total negative electrode active material layer is shown in Table 2.

[0238] Experimental Example 2) Evaluation of swelling ratio

[0239] The rechargeable lithium batteries according to Example 1 and Example 2 and Comparative Examples 1 to 14 are charged and discharged at SOC 100 (fully charged, charged to a 100% charge capacity based on the entire battery charge capacity of 100%). The thickness of the battery after charging and discharging is measured.

[0240] For comparison, except that the first active material layer slurry of Example 1 is coated on a Cu foil current collector and dried to prepare a first active material layer with a thickness of 103 μm, and the second active material layer slurry of Example 1 is coated on the first active material layer and dried to prepare a second active material layer with a thickness of 206 μm, a negative electrode with a bulk density of 1.6 g / cc and a rechargeable lithium battery are manufactured by the same steps as in Example 1. That is, the negative electrode is prepared without using a magnet and without applying a magnetic field.

[0241] The manufactured rechargeable lithium battery is charged and discharged at SOC 100, and then the battery thickness is measured. The measured battery thickness is used as a reference value.

[0242] The difference between the battery thickness after charging and discharging of the batteries according to Example 1 and Example 2 and Comparative Examples 1 to 14 and the reference value is calculated. The results are shown in Table 2 as the effect of reducing swelling.

[0243] Experimental Example 3) Evaluation of separation

[0244] The negative electrodes according to Example 1 and Example 2 and Comparative Examples 1 to 14 are fully immersed in 10 ml of electrolyte, and then allowed to stand for 24 hours. The electrolyte is used by dissolving 1.5 M LiPF6 in a mixed solvent of ethylene carbonate, ethyl methyl carbonate and dimethyl carbonate (volume ratio of 20:10:70).

[0245] Through the negative electrode, visually identify the degree of separation of the negative electrode active material layer (the first active material layer and the second active material layer). The results are shown as ○ (separation occurred) and × (no separation occurred) in Table 2.

[0246] Experimental Example 4) Evaluation of ionic resistance

[0247] Measure the ionic resistance of the negative electrodes according to Example 1 and Example 2 and Comparative Examples 1 to 14. The results are shown as Rion in Table 2.

[0248] Measure the ionic resistance by fabricating a symmetric cell including two negative electrodes, setting the amplitude Va value to 5 mV, measuring the SC-EIS (square current electrochemical impedance spectroscopy), and using the transmission line model theory to separate only the ionic transfer resistance (Rion) of the internal resistance of the negative electrode from the measurement results.

[0249] Experimental Example 5) Evaluation of adhesion

[0250] Measure the adhesion of the negative electrodes according to Example 1 and Example 2 and Comparative Examples 1 to 14 through the following steps.

[0251] Attach the tape adhered to the glass slide to the prepared second active material layer, and peel the tape and the second active material layer to measure the adhesion strength using a 180° UTM tensile strength tester. The peeling speed is set to 10 mm / minute, and three measurements are performed to obtain the average value of the force required to peel 40 mm after the start of peeling. The results are shown in Table 2.

[0252] The structures and magnetic field intensities used in the preparations according to Example 1 and Example 2 and Comparative Examples 1 to 14 are summarized and shown in Table 1.

[0253] Table 1

[0254]

[0255] Table 2

[0256]

[0257] As shown in Table 2, the batteries according to Example 1 and Example 2 exhibit a reduced swelling ratio, excellent adhesion, and low ionic resistance.

[0258] Among them, Comparative Examples 1 and 2, where the structures of the first active material layer and the second active material layer and the amount of Si are appropriate, but the DD value is less than 30, exhibit excellent adhesion and low ionic resistance, but the effect of reducing swelling is not significant.

[0259] Among them, artificial graphite with an average particle size of 15 μm was used identically in the first active material layer and the second active material layer. Comparative Example 3 with a low Si content and a DD value of less than 30 showed no separation, but exhibited a poor expansion reduction effect, high ionic resistance, and low adhesion.

[0260] Comparative Example 4, where the DD value is 30 or greater, but artificial graphite with an average particle size of 15 μm was used identically in the first active material layer and the second active material layer and the Si content is low, showed no separation and an excellent expansion reduction effect, but exhibited high ionic resistance and low adhesion.

[0261] Comparative Example 5, where the Si content is 3 wt%, but artificial graphite with an average particle size of 15 μm was used identically in the first active material layer and the second active material layer and the DD value is less than 30, showed no separation, but exhibited a poor expansion reduction effect, high ionic resistance, and low adhesion.

[0262] Comparative Example 6, where the Si content is 3 wt% and the DD value is 30 or greater, but artificial graphite with an average particle size of 15 μm was used identically in the first active material layer and the second active material layer, showed an excellent expansion reduction effect, but exhibited separation, high ionic resistance, and low adhesion.

[0263] Comparative Example 7 and Comparative Example 8, where the Si content is 5 wt%, but artificial graphite with an average particle size of 15 μm was used identically in the first active material layer and the second active material layer, showed an improved expansion reduction effect due to controlling the DD value, but separation, high ionic resistance, and low adhesion were observed similarly to other comparative examples.

[0264] As used herein, the terms "substantially", "about", or similar terms are used as approximate terms and not as terms of degree, and are intended to account for the inherent deviations of measured or calculated values that would be recognized by a person of ordinary skill in the art. Taking into account the measurements discussed and the errors associated with the measurement of a particular quantity (i.e., the limitations of the measurement system), "about" as used herein includes the stated value and refers to within an acceptable deviation of the particular value as determined by a person of ordinary skill in the art. For example, "about" can refer to within one or more standard deviations, or within ±30%, ±20%, ±10%, ±5% of the stated value.

[0265] Any numerical range recited herein is intended to include all sub-ranges having the same numerical precision that are contained within the recited range. For example, a range of "1.0 to 10.0" is intended to include all sub-ranges between the recited minimum value of 1.0 and the recited maximum value of 10.0 (and including the recited minimum and maximum values), that is, having a minimum value equal to or greater than 1.0 and a maximum value equal to or less than 10.0, such as, by way of example, 2.4 to 7.6. Any maximum numerical limit recited herein is intended to include all lower numerical limits contained therein, and any minimum numerical limit recited in this specification is intended to include all higher numerical limits contained therein. Accordingly, the applicant reserves the right to amend this specification and the claims to expressly recite any sub-ranges that are included within the ranges expressly recited herein.

[0266] Although the subject matter of the present disclosure has been described in connection with what are presently considered to be practical example embodiments, it will be understood that the present disclosure is not limited to the disclosed embodiments, but on the contrary, is intended to cover one or more suitable modifications and equivalent arrangements included within the spirit and scope of the appended claims and their equivalents. Accordingly, the foregoing embodiments should be understood as being merely illustrative and in no way limiting of the present disclosure.

Claims

1. A negative electrode for a rechargeable lithium battery, the negative electrode for the rechargeable lithium battery comprising: A current collector; And A negative electrode active material layer, Wherein, the negative electrode active material layer includes: a first active material layer, on the current collector and including first crystalline carbon, a Si-C composite, and a first binder; and a second active material layer, on the first active material layer and including second crystalline carbon, a Si-C composite, and a second binder, The particle size of the first crystalline carbon is smaller than that of the second crystalline carbon, and based on the total negative electrode active material layer, the amount of the first binder is greater than that of the second binder, Based on 100 wt% of the negative electrode active material layer, the amount of Si is 3 wt% or more, and The divergence value defined by Equation 1 is 30 or more, [Equation 1] Divergence = (I a / I 总 ) × 100 Wherein, I a is the sum of the peak intensities at non-planar angles measured by X-ray powder diffraction using CuKα radiation, I 总 is the sum of the peak intensities at all angles measured by X-ray powder diffraction using CuKα radiation.

2. The negative electrode for a rechargeable lithium battery according to claim 1, wherein, The divergence is 30 to 60.

3. The negative electrode for a rechargeable lithium battery according to claim 1, wherein, The first crystalline carbon has a particle size of 6 μm to 10 μm.

4. The negative electrode for a rechargeable lithium battery according to claim 1, wherein, The second crystalline carbon has a particle size of 10 μm to 20 μm.

5. The negative electrode for a rechargeable lithium battery according to claim 1, wherein, The ratio of the particle size of the first crystalline carbon to that of the second crystalline carbon is 1:2 to 1:

3.

6. The negative electrode for a rechargeable lithium battery according to claim 1, wherein, The ratio of the amount of the first binder to that of the second binder is a weight ratio of 60:40 to 90:

10.

7. The negative electrode for a rechargeable lithium battery according to claim 1, wherein, Based on 100 wt% of the negative electrode active material layer, the amount of the first binder is 1.5 wt% to 5 wt%.

8. The negative electrode for a rechargeable lithium battery according to claim 1, wherein, Based on 100 wt% of the negative electrode active material layer, the amount of the second binder is 0.3 wt% to 1 wt%.

9. The negative electrode for a rechargeable lithium battery according to claim 1, wherein, The amount of Si is 3 wt% or more.

10. The negative electrode for a rechargeable lithium battery according to claim 1, wherein, Based on 100 wt% of the negative electrode active material layer, the amount of Si is 3 wt% to 10 wt%.

11. The negative electrode for a rechargeable lithium battery according to claim 1, wherein, The Si-C composite in the first active material layer or the Si-C composite in the second active material layer includes Si and amorphous carbon.

12. The negative electrode for a rechargeable lithium battery according to claim 1, wherein, The Si-C composite includes Si, amorphous carbon, and crystalline carbon.

13. The negative electrode for a rechargeable lithium battery according to claim 1, wherein, The first active material layer has a thickness of 20 μm to 150 μm.

14. The negative electrode for a rechargeable lithium battery according to claim 1, wherein, The second active material layer has a thickness of 130 μm to 250 μm.

15. The negative electrode for a rechargeable lithium battery according to claim 1, wherein, I a is the sum of the peak intensities at 2θ = 42.4 ± 0.2°, 43.4 ± 0.2°, 44.6 ± 0.2° and 77.5 ± 0.2° measured by X-ray powder diffraction using CuKα radiation. I 总 is the sum of peak intensities at 2θ = 26.5 ± 0.2°, 42.4 ± 0.2°, 43.4 ± 0.2°, 44.6 ± 0.2°, 54.7 ± 0.2° and 77.5 ± 0.2° measured by X-ray powder diffraction using CuKα radiation.

16. The negative electrode for a rechargeable lithium battery according to claim 1, wherein, The peak intensity is the peak integral area value.

17. The negative electrode for a rechargeable lithium battery according to claim 1, wherein, The negative electrode has an active body density of 1.0 g / cc to 2.0 g / cc.

18. A rechargeable lithium battery, the rechargeable lithium battery comprising: The negative electrode according to any one of claims 1 to 17; A positive electrode; and A non-aqueous electrolyte.

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