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 including the same are provided. The negative electrode includes: a negative electrode current collector including a carbon layer and a silicon layer, the carbon layer including a first porous substrate and a carbon-based material present inside the first porous substrate, and the silicon layer including a second porous substrate and a silicon-based negative electrode active material present inside the second porous substrate; and a negative electrode active material layer disposed on a surface of the negative electrode current collector and including a negative electrode active material.

Description

Negative electrode for a rechargeable lithium battery and a rechargeable lithium battery including the negative electrode. Technical Field

[0001] One or more embodiments of this disclosure relate to a negative electrode for a rechargeable lithium battery and a rechargeable lithium battery including the negative electrode. Background Technology

[0002] Rechargeable lithium batteries, known for their portability and high energy density, are widely used as power sources in mobile information devices (terminals) such as smartphones and laptops. Recently, there has been active research into developing rechargeable lithium batteries with enhanced safety and capacity for applications as power sources in hybrid and / or electric vehicles or for power storage devices (e.g., power storage systems).

[0003] To develop electrodes for rechargeable lithium-ion batteries with high capacity and high energy density, the use of high-density electrode plates is desirable. However, as electrode plates are packaged more densely, efforts have been made to reduce their internal resistance.

[0004] Among various methods, carbon foil (CLF) substrates have been considered for use as negative electrode current collectors. CLF substrates are formed by coating a carbon layer onto a metal foil (e.g., copper foil) that is typically used as a negative electrode current collector, and have advantages such as improved adhesion between the electrode plate and the substrate and / or reduced interfacial resistance.

[0005] However, the thickness of the carbon coating can negatively impact the battery's energy density due to the CLF substrate. To mitigate this issue, increasing the electrode plate density has been proposed. However, this can lead to increased resistance, which may negatively affect overall battery performance. Summary of the Invention

[0006] One or more aspects of embodiments of this disclosure relate to a negative electrode for a rechargeable lithium battery that improves adhesion strength and reduces interfacial resistance without affecting the energy density of the rechargeable lithium battery.

[0007] One or more aspects of embodiments of this disclosure relate to rechargeable lithium batteries that have excellent or suitable battery performance by including a negative electrode.

[0008] Additional aspects will be set forth in part in the description which follows, and in part will be apparent from the description, or may be learned by practice of the embodiments presented.

[0009] According to one or more embodiments of the present disclosure, a negative electrode for a rechargeable lithium battery includes: a negative electrode current collector comprising a carbon layer and a silicon layer, the carbon layer comprising a first porous substrate and a carbon-based material within the first porous substrate (e.g., in the first porous substrate), the silicon layer comprising a second porous substrate and a silicon-based negative electrode active material within the second porous substrate (e.g., in the second porous substrate); and a negative electrode active material layer comprising the negative electrode active material and disposed (e.g., on) at least one surface of the negative electrode current collector.

[0010] According to one or more embodiments of this disclosure, a rechargeable lithium battery includes a positive electrode, a negative electrode, and an electrolyte.

[0011] The negative electrode for a rechargeable lithium battery according to one or more embodiments can improve adhesion strength and interface resistance without affecting the energy density of the rechargeable lithium battery.

[0012] By incorporating the aforementioned negative and positive electrodes, rechargeable lithium-ion batteries according to one or more embodiments can exhibit excellent or suitable battery performance. For example, the integration of the negative electrode structure—characterized by carbon-based materials and silicon-based negative electrode active materials within a porous substrate—should significantly enhance the overall electrochemical stability and efficiency of the battery system. This construction not only improves the mechanical integrity and adhesion between electrode layers but also facilitates efficient lithium-ion transport and charge transfer during cycling. Consequently, the battery can achieve higher capacity retention, reduced internal resistance, and improved rate performance, all of which contribute to enhanced performance in both high-power and long-duration applications. Furthermore, the enhanced electrode design supports the development of compact and lightweight battery cells, making them advantageous for use in electric vehicles, portable electronic devices, and / or energy storage systems. Attached Figure Description

[0013] The accompanying drawings are included to provide a further understanding of this disclosure, and are incorporated in and constitute a part of this disclosure. The drawings illustrate embodiments of the present disclosure and, together with the description, serve to explain the principles of the disclosure. The above and other aspects, features, and advantages of certain embodiments of the present disclosure will become more apparent from the following description taken in conjunction with the accompanying drawings.

[0014] Figure 1 is a plan view of a porous substrate according to one or more embodiments of the present disclosure.

[0015] Figure 2 is a schematic cross-sectional view of a negative electrode current collector according to one or more embodiments of the present disclosure.

[0016] Figures 3 through 6 are each schematic diagrams illustrating a rechargeable lithium battery according to one or more embodiments of the present disclosure. Detailed Implementation

[0017] In the following description, one or more embodiments of this disclosure will be described in more detail so that those skilled in the art can readily implement them and understand the disclosure. However, this disclosure may be implemented in many different forms and is not to be construed as limited to the embodiments set forth herein.

[0018] The terminology used herein is for descriptive purposes only and is not intended to limit this disclosure. Unless the context clearly indicates otherwise, singular expressions in this disclosure may include plural expressions. For example, unless the context clearly indicates otherwise, the singular forms “a,” “an,” “an,” and “the (described)” are also intended to include the plural forms. Furthermore, when describing embodiments of this disclosure, the use of “may” means “one or more embodiments of this disclosure.”

[0019] As used herein, “combination of” refers to mixtures, laminates, complexes, copolymers, alloys, blends, reaction products, etc. of the components.

[0020] Here, it should be understood that terms such as “including and variants thereof,” “containing and variants thereof,” and / or “having and variants thereof” are intended to specify the presence of the features, quantities, steps (e.g., actions or tasks), elements (components), or combinations thereof embodied, but do not preclude the possibility of the presence or addition of one or more other features, quantities, steps (e.g., actions or tasks), elements (components), or combinations thereof. Furthermore, the terms “including and variants thereof,” “containing and variants thereof,” “having and variants thereof,” or other similar terms include or support the terms “consisting of…” and “substantially consisting of…”, which indicate the presence of the stated features, quantities, steps, operations, elements (components), and / or components, while other features, quantities, steps, operations, elements (components), components, and / or groups thereof are absent or substantially absent.

[0021] In the accompanying drawings, for clarity, the thickness of layers, films, panels, regions, etc., may be exaggerated, and throughout the disclosure, the same reference numerals denote the same elements, and for brevity, their repeated descriptions may be omitted. It will be understood that if (e.g., when) an element such as a layer, film, region, or substrate is referred to as "on" another element, the element may be directly on said other element, or one or more intervening elements may exist between them. Conversely, if (e.g., when) an element is referred to as "directly on" another element, no intervening elements exist between them.

[0022] Additionally, as used herein, “layer” includes not only shapes that form across the entire surface when viewed from a plan view, but also shapes that form on a portion of the surface (e.g., a part of the entire surface).

[0023] The average particle size / size can be measured by methods well-suited to those skilled in the art, such as by a particle size analyzer or by using transmission electron microscopy images and / or scanning electron microscopy images. In one or more embodiments, it can be obtained using dynamic light scattering by measuring the sample, performing data analysis, counting the number of particles for each particle size range, and calculating from the collected data to obtain the average particle size value. Unless otherwise defined, the average particle size / size can refer to the diameter / size (D) of particles having a cumulative volume of 50% of the particle size distribution. 50 In other words, D 50 This refers to the average diameter (or size) of the particles whose cumulative volume corresponds to 50% of the particles in a particle size distribution (e.g., a cumulative distribution), and specifically, in a distribution curve accumulated from smallest to largest particle size, the value corresponding to 50% of the particle size starting from the smallest particle when the total number of particles is 100%. In this disclosure, when the particles are spherical, "diameter" refers to the particle size or average particle size, and when the particles are non-spherical, "diameter" refers to the major axis length or average major axis length. For example, in one or more embodiments, if (e.g., when) no further definition is provided, the average particle size / size refers to the diameter (Di) of the particles whose cumulative volume is 50% of the particles in the particle size distribution obtained by randomly measuring the size (diameter or major axis length) of approximately 20 particles in a scanning electron microscope image. 50 ).

[0024] Here, "and / or" and "or" will not be interpreted as exclusive. For example, "A or B", "A and / or B", "A / B" can be interpreted as including A, B, A+B, etc.

[0025] As used herein, “metal” is interpreted as including one or more of the concepts selected from common metals, transition metals, and metalloids (semi-metals).

[0026] In one or more embodiments of this disclosure, the negative electrode includes: a negative electrode current collector comprising a carbon layer and a silicon layer, the carbon layer comprising a first porous substrate and a carbon-based material within the first porous substrate (e.g., in the first porous substrate), the silicon layer comprising a second porous substrate and a silicon-based negative electrode active material within the second porous substrate (e.g., in the second porous substrate); and a negative electrode active material layer comprising the negative electrode active material and disposed (e.g., on) at least one surface of the negative electrode current collector.

[0027] Unlike a CLF substrate in which a carbon layer comprising carbon-based materials is coated on the surface of a metal foil, the negative electrode according to one or more embodiments uses a porous substrate instead of a metal foil. This allows the carbon-based materials to be incorporated into the pores within the porous substrate, and the metal foil and carbon layer are not separate layers but rather combined into a single layer. This does not affect the energy density of the rechargeable lithium battery while improving adhesion and reducing interfacial resistance. Furthermore, by further including a silicon layer containing silicon-based negative electrode active materials within the porous substrate, the energy density of the rechargeable lithium battery can be improved.

[0028] The negative electrode current collector and the negative electrode active material layer will be described in more detail below.

[0029] According to one or more embodiments of the present disclosure, the negative electrode current collector may include a carbon layer and a silicon layer, the carbon layer comprising a first porous substrate and a carbon-based material inside the first porous substrate (e.g., within the first porous substrate), and the silicon layer comprising a second porous substrate and a silicon-based negative electrode active material inside the second porous substrate (e.g., within the second porous substrate).

[0030] According to one or more embodiments, the negative electrode current collector uses a porous substrate with a large number of pores instead of the non-porous metal foil that is usually used as a negative electrode current collector, and combines the porous substrate with the corresponding material in the internal pores of the porous substrate, such that layers including carbon-based materials or silicon-based negative electrode active materials (referring to carbon layers and silicon layers as described above) are stacked, thereby solving the difficulties and problems of the negative impact on energy density on the metal film in the CLF substrate according to the thickness of the carbon layer, while enhancing energy density and adhesion strength, and reducing interface resistance.

[0031] Both the first porous substrate and the second porous substrate refer to substrates having multiple pores. Here, the terms "first" and "second" are used to identify porous substrates included in carbon layers and porous substrates included in silicon layers, respectively, in a porous substrate region with a carbon layer and a porous substrate region with a silicon layer. Furthermore, the first porous substrate and the second porous substrate can refer to two regions within a substrate that are separated by layers; for example, the first porous substrate and the second porous substrate can be understood as stacked structures, interconnected stacked structures, or contacting stacked structures. The first porous substrate and the second porous substrate can differ in material, shape, porosity, etc., or they can be identical. In one or more embodiments, the first porous substrate and the second porous substrate can be entirely identical in material, shape, porosity, etc.

[0032] Because a porous substrate refers to replacing a non-porous thin film used as an existing negative electrode current collector with a porous substrate having a large number of pores, materials suitable for use as negative electrode current collectors that are conductive without causing chemical changes in rechargeable lithium batteries can be used as constituent materials. The first and second porous substrates can each independently include a metal. The metal can include copper, nickel, stainless steel, titanium, aluminum, or combinations thereof. For example, the porous substrate can be made of a metal.

[0033] The porous substrate can have one or more suitable structures, and its type (variety) is not limited, as long as it includes multiple pores and the aforementioned carbon-based materials and silicon-based negative electrode active materials can be impregnated into the pores. For example, in one or more embodiments, the porous substrate can have a structure such as a metal foam, or it can have a structure such as a mesh. The pores within the porous substrate can be substantially continuous or discontinuous in the thickness direction and / or planar direction. For example, the pores inside the porous substrate can be substantially continuous in the thickness direction but discontinuous in the planar direction, or discontinuous in the thickness direction but substantially continuous in the planar direction, or substantially continuous in both the thickness direction and the planar direction (e.g., simultaneously), or discontinuous in both the thickness direction and the planar direction (e.g., simultaneously).

[0034] Figure 1 is a plan view of a porous substrate according to one or more embodiments of the present disclosure. Referring to Figure 1, in one or more embodiments, the porous substrate 4 has rhomboid-shaped metal (e.g., a metal structure) and internal pores 5 therebetween, and in the porous substrate 4, the rhomboid-shaped metal (e.g., the metal structure) may be continuous in the thickness direction of the porous substrate (e.g., forming a honeycomb structure). The pores inside the porous substrate according to Figure 1 may be discontinuous in the planar direction, but may be continuous in the thickness direction. For example, the porous substrate 4 is characterized by repeating rhomboid-shaped metal structures, with internal pores located between these structures. Although the pores may appear discontinuous across the surface plane, they may be continuous over the entire thickness of the porous substrate, possibly forming a honeycomb structure.

[0035] Figure 1 is an example of a plan view of a porous substrate with diamond-shaped holes as viewed from above. However, the shape of the holes can be fixed when viewed from above (e.g., when the porous substrate is viewed from above), and the shape can include, for example, polygonal shapes, circular shapes, cylindrical shapes, slit shapes, irregular holes, and / or diamond shapes.

[0036] The thickness of the first porous substrate and the thickness of the second porous substrate can each be from about 5 μm to about 500 μm. For example, the thickness of the first porous substrate and the thickness of the second porous substrate can each be from about 10 μm to about 500 μm, from about 50 μm to about 500 μm, from about 100 μm to about 500 μm, from about 150 μm to about 450 μm, or from about 200 μm to about 400 μm.

[0037] The porosity of the first and second porous substrates can each independently be greater than or equal to about 50%. For example, the porosity of the first and second porous substrates can each independently be greater than or equal to about 55%, greater than or equal to about 60%, greater than or equal to about 65%, greater than or equal to about 70%, greater than or equal to about 75%, or greater than or equal to about 80%, and there is no particular upper limit, but it can be, for example, less than or equal to about 99%, less than or equal to about 95%, or less than or equal to about 90%. If (for example, when) the porosity of the porous substrate meets the above range, the carbon-based or silicon-based negative electrode active material described below can be appropriately or suitablely filled into the pores of the porous substrate, thereby improving the adhesion strength and reducing the interfacial resistance. Porosity can be measured according to ASTM D-2873 by liquid or gas adsorption methods.

[0038] The pore size in each of the first and second porous substrates can independently be from about 300 micrometers (μm) to about 1,000 μm. The pore size can be the average pore diameter. For example, in one or more embodiments, the pore size in each of the first and second porous substrates can independently be from about 300 μm to about 900 μm, from about 300 μm to about 800 μm, or from about 300 μm to about 700 μm. If (for example, when) the pore size meets the above ranges, the electron mobility can be improved by increasing the contact area between the negative electrode active material and the negative electrode current collector. The pore size can be measured by the Brunauer-Emmett-Teller (BET) 6-point method, by nitrogen adsorption flow method, or using scanning electron microscopy (SEM) images, a mercury porosimeter, a capillary flow porosimeter, or a porosity analyzer (Bell Japan Inc, Bellsorp-IImini). In cases where the pores within a porous substrate according to one or more embodiments are discontinuous in the planar direction but continuous in the thickness direction, the pore size of the porous substrate can be measured by measuring the pore size when viewed from above. The top of the porous substrate refers to the portion in the direction perpendicular to the thickness direction of the negative electrode current collector (i.e., when viewed in the planar direction). As shown in FIG1, if (for example, when) according to one or more embodiments, the pore is rhomboid, the pore size can be calculated by measuring the minor axis length and major axis length of one rhomboid shaped pore present on the upper surface and calculating their average value.

[0039] The carbon layer includes a first porous substrate and a carbonaceous material present within (e.g., present in) the first porous substrate. The carbonaceous material (e.g., carbonaceous material) may include amorphous carbon, and amorphous carbon may include carbon black, carbon nanotubes, soft carbon, hard carbon, mesophase pitch carbonization products, calcined coke, or combinations thereof.

[0040] In one or more embodiments, in addition to the aforementioned carbon-based materials, the carbon layer may also include a binder, and the carbon layer may include an excess of binder.

[0041] The binder is used to enable carbonaceous material particles to adhere well to each other and also to enable carbonaceous materials to adhere well to silicon layers. The binder may include non-aqueous (e.g., water-insoluble) binders, aqueous (water-soluble) binders, dry binders, or combinations thereof.

[0042] Non-aqueous adhesives may include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene-propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamide-imide, polyimide, or combinations thereof.

[0043] Waterborne adhesives may be selected from styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluororubber, polyethylene oxide, polyvinylpyrrolidone, polyepoxychloropropane, polyphosphazene, poly(meth)acrylonitrile, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, poly(meth)acrylic acid, and combinations thereof.

[0044] When using an aqueous adhesive as a binder, the adhesive may also include a cellulose compound capable of imparting viscosity. The cellulose compound may include at least one of carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, and their alkali metal salts. The alkali metal may include Na, K, or Li.

[0045] The dry binder can be a fibrous polymer material, and can be, for example, polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, or a combination thereof.

[0046] For example, in one or more embodiments, based on a 100 wt% carbon layer, the amount of carbonaceous material in the carbon layer can be from about 10 wt% to about 30 wt%, and based on the 100 wt% carbon layer, the amount of binder can be from about 70 wt% to about 90 wt%. When the carbonaceous material and binder meet the above-mentioned amount ranges within the carbon layer, the carbonaceous material can be well dispersed, thereby promoting the formation of the carbon layer. As used herein, 100 wt% carbon layer means 100 wt% of the total weight of the carbon layer excluding the first porous substrate.

[0047] The silicon layer comprises a second porous substrate and a silicon-based negative electrode active material within the second porous substrate (e.g., within the second porous substrate). The silicon-based negative electrode active material may be silicon, a silicon-carbon composite, or SiO₂. x(0 < x ≤ 2), a Si-Q alloy (where Q is an element selected from the group consisting of alkali metals, alkaline earth metals, group 13 elements, group 14 elements, group 15 elements, group 16 elements, transition metals, rare earth elements, and combinations thereof, but not Si), or a combination thereof. The element Q may be selected from magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), radium (Ra), scandium (Sc), yttrium (Y), titanium (Ti), zirconium (Zr), hafnium (Hf), ruthenium (Rf), vanadium (V), niobium (Nb), tantalum (Ta), dubnium (Db), chromium (Cr), molybdenum (Mo), tungsten (W), seaborgium (Sg), technetium (Tc), rhenium (Re), bohrium (Bh), iron (Fe), lead (Pb), ruthenium (Ru), osmium (Os), hassium (Hs), rhodium (Rh), iridium (Ir), palladium (Pd), platinum (Pt), copper (Cu), silver (Ag), gold (Au), zinc (Zn), cadmium (Cd), boron (B), aluminum (Al), gallium (Ga), tin (Sn), indium (In), thallium (Tl), germanium (Ge), phosphorus (P), arsenic (As), antimony (Sb), bismuth (Bi), sulfur (S), selenium (Se), tellurium (Te), polonium (Po), and combinations thereof. In one or more embodiments, the silicon-based negative electrode active material may include a silicon-carbon composite.

[0048] The silicon-carbon composite may be in the form of particles, and the average particle size (D 50 ) may be, for example, from about 0.5 μm to about 20 μm. The average particle size (D 50 ) is measured using a particle size analyzer and refers to the diameter of the particle at which the cumulative volume in the particle size distribution is 50% by volume. Based on the total weight of 100 wt% of the silicon-carbon composite particles, silicon may be included in an amount of about 10 wt% to about 60 wt%, and carbon may be included in an amount of about 40 wt% to about 90 wt%. For example, in one or more embodiments, the silicon-carbon composite particles may each include a core containing silicon particles and a carbon coating on the surface of the core. In the core, the average particle size (D 50 ) of the silicon particles may be from about 10 nanometers (nm) to about 1 μm or from about 10 nm to about 200 nm. The silicon particles may exist alone as silicon, in the form of a silicon alloy, or in an oxidized form. The oxidized form of silicon may be represented by SiO x (0 < x ≤ 2). Additionally, the thickness of the carbon coating may be from about 5 nm to about 100 nm.

[0049] In one or more embodiments, the silicon-carbon composite particles may each comprise: a core comprising silicon particles and crystalline carbon; and a carbon coating disposed on the surface of the core and comprising amorphous carbon. For example, in one or more embodiments, in each of the silicon-carbon composite particles, amorphous carbon may not be present in the core, but only in the carbon coating. The crystalline carbon may be artificial graphite, natural graphite, or a combination thereof, and the amorphous carbon may be formed from coal tar pitch, mesophase pitch, petroleum tar pitch, coal oil, heavy petroleum, or polymer resins (phenolic resins, furan resins, polyimide resins, etc.). Here, based on 100 wt% of the total weight of the silicon-carbon composite particles, the amount of crystalline carbon may be from about 10 wt% to about 70 wt%, and the amount of amorphous carbon may be from about 20 wt% to about 40 wt%.

[0050] In silicon-carbon composite particles, the core may include a pore at its center. The radius of the pore can be approximately 30% to approximately 50% of the length of the silicon-carbon composite particle.

[0051] The aforementioned silicon-carbon composite particles can effectively suppress or reduce problems such as volume expansion, structural collapse or particle breakage caused by charging and discharging, prevent or reduce the disconnection of conductive paths, achieve high capacity and high efficiency, and are beneficial for use under high voltage or high rate charging conditions.

[0052] In addition to silicon-based negative electrode active materials, the silicon layer may optionally include binders, conductive materials, or combinations thereof.

[0053] The binder is used to ensure good adhesion between silicon-based negative electrode active material particles and also to ensure good adhesion between the silicon-based negative electrode active material and the carbon layer. The binder may include non-aqueous (e.g., water-insoluble) binders, aqueous (water-soluble) binders, dry binders, or combinations thereof.

[0054] Non-aqueous adhesives may include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene-propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamide-imide, polyimide, or combinations thereof.

[0055] Waterborne adhesives may be selected from styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluororubber, polyethylene oxide, polyvinylpyrrolidone, polyepoxychloropropane, polyphosphazene, poly(meth)acrylonitrile, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, poly(meth)acrylic acid, and combinations thereof.

[0056] When using an aqueous adhesive as a binder, the adhesive may also include a cellulose compound capable of imparting viscosity. The cellulose compound may include at least one of carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, and their alkali metal salts. The alkali metal may include Na, K, or Li.

[0057] The dry binder can be a fibrous polymer material, and can be, for example, polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, or a combination thereof.

[0058] Conductive materials can be used to provide conductivity to the silicon layer, and any material that does not cause chemical changes and is conductive can be used in the constructed battery. Non-limiting examples of conductive materials may include: carbon-based materials, such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanofibers, carbon nanotubes, etc.; metallic materials such as metal powders or metal fibers, including copper, nickel, aluminum, silver, etc.; conductive polymers, such as polyphenylene derivatives; and / or mixtures thereof.

[0059] In one or more embodiments, the silicon layer may include a silicon-based negative electrode active material, a binder, and a conductive material. In these embodiments, based on 100 wt% of the silicon layer, the amount of the silicon-based negative electrode active material in the silicon layer may be from 89 wt% to about 99.9 wt%, the amount of the binder may be from about 1 wt% to about 10 wt%, and the amount of the conductive material may be from about 0.1 wt% to about 1 wt%. By including a silicon layer containing a silicon-based negative electrode active material, the energy density can be improved without increasing the electrode plate thickness. As used herein, 100 wt% of the silicon layer means 100 wt% of the total weight of the silicon layer excluding the second porous substrate.

[0060] The negative electrode current collector may include a carbon layer and a silicon layer, and may have a two-layer structure in which the carbon layer and silicon layer are stacked in a carbon-silicon layer sequence, or the negative electrode current collector may have a multi-layer structure, such as a three-layer structure in which the carbon layer, silicon layer, and carbon layer are stacked in a carbon-silicon-carbon layer sequence. In one or more suitable structures, the porous substrate portion in which the carbon layer is disposed may be referred to as the first porous substrate, and the porous substrate portion in which the silicon layer is disposed may be referred to as the second porous substrate.

[0061] For example, in one or more embodiments, the negative electrode current collector may include a first carbon layer (1A), a silicon layer on the first carbon layer (1A), and a first carbon layer (1B) on the silicon layer. The first carbon layer (1A) may include a first porous substrate (1A) and a first carbon-based material (1A) present inside the first porous substrate (1A) (e.g., present in the first porous substrate (1A)), and the first carbon layer (1B) may include a first porous substrate (1B) and a first carbon-based material (1B) present inside the first porous substrate (1B) (e.g., present in the first porous substrate (1B)). Here, the first carbon layer (1A) and the first carbon layer (1B) are used only to distinguish between the carbon layer existing below the silicon layer and the carbon layer existing above the silicon layer, and the specific details of the first carbon layer (1A) and the first carbon layer (1B) can be independently the same as the specific details described for the carbon layer, and the descriptions of the first porous substrate (1A), the first porous substrate (1B), the first carbon-based material (1A) and the first carbon-based material (1B) are also the same as the descriptions of the first porous substrate and the carbon-based material provided above.

[0062] A negative electrode current collector according to one or more embodiments of the present disclosure is shown in FIG2. FIG2 is a schematic diagram of a negative electrode current collector 1. Here, the negative electrode current collector 1 has a structure in which a first carbon layer (1A) 2a, a silicon layer 3 and a first carbon layer (1B) 2b are sequentially stacked. The first carbon layer (1A) 2a includes a first porous substrate (1A) and a first carbon-based material (1A) present inside the first porous substrate (1A) (e.g., present in the first porous substrate (1A)). The silicon layer 3 includes a second porous substrate and a silicon-based negative electrode active material present inside the second porous substrate (e.g., present in the second porous substrate). The first carbon layer (1B) 2b includes a first porous substrate (1B) and a first carbon-based material (1B) present inside the first porous substrate (1B) (e.g., present in the first porous substrate (1B)). According to one or more embodiments, the negative electrode current collector 1 has a structure in which carbon layers 2a, 2b are arranged on two surfaces (e.g., two opposing surfaces) of the silicon layer 3 (e.g., simultaneously), such that the carbon layers 2a, 2b on the two surfaces (e.g., opposing surfaces) can function in controlling the contraction and expansion of the silicon-based negative electrode active material included in the silicon layer 3 according to charging and discharging.

[0063] In Figure 2, the first porous substrate (1A) refers to the region where the first carbon layer (1A) 2a is disposed, the second porous substrate refers to the region where the silicon layer 3 is disposed, and the first porous substrate (1B) refers to the region where the first carbon layer (1B) 2b is disposed. The first porous substrate (1A) and the first porous substrate (1B) correspond to the aforementioned example of the first porous substrate. The first porous substrate (1A), the second porous substrate, and the first porous substrate (1B) can refer to three regions within a substrate that are distinguished in the form of layers. For example, the first porous substrate (1A), the second porous substrate, and the first porous substrate (1B) can be understood as a stacked structure, a structure that is stacked and connected to each other, or a structure that is stacked in a contact state, etc.

[0064] The thickness of the silicon layer 3 can be about 50% to about 99% based on 100% of the thickness of the negative electrode current collector 1, for example, about 60% to about 95% or about 70% to about 90%. In other words, the thickness of the silicon layer 3 can be about 50% to about 99% based on 100% of the total thickness of the negative electrode current collector 1, for example, about 60% to about 95% or about 70% to about 90%.

[0065] In addition, based on the 100% thickness of the negative electrode current collector 1, the sum of the thickness of the first carbon layer (1A) 2a and the thickness of the first carbon layer (1B) 2b can be about 1% to about 50%, for example, about 5% to about 40% or about 10% to about 30%.

[0066] According to one or more embodiments, the thickness ratio of the first carbon layer (1A) 2a to the first carbon layer (1B) 2b can be from about 1:9 to about 9:1, for example, from about 2:8 to about 8:2, from about 3:7 to about 7:3, or from about 4:6 to about 6:4. In one or more embodiments, the thicknesses of the first carbon layer (1A) and the first carbon layer (1B) can be substantially the same, that is, the thickness ratio of the first carbon layer (1A) to the first carbon layer (1B) can be about 1:1.

[0067] According to one or more embodiments, the negative electrode current collector can have reduced interfacial resistance and improved adhesion strength to the external electrode plate through the first carbon layer (1A) and the first carbon layer (1B), and the volume expansion of the silicon-based negative electrode active material can be effectively suppressed or reduced by positioning the silicon layer between the first carbon layer (1A) and the first carbon layer (1B). Compared with a structure having a carbon layer on one surface of the silicon layer, a negative electrode current collector having carbon layers on both surfaces (e.g., opposite surfaces) of the silicon layer (e.g., simultaneously) can exhibit improved processability while exhibiting the aforementioned effects.

[0068] If (for example, when) the negative electrode current collector has the aforementioned structure, the negative electrode current collector can be manufactured according to a suitable method.

[0069] For example, the negative electrode current collector according to one or more embodiments can be manufactured by: preparing a porous substrate; preparing a composition for forming a carbon layer and a composition for forming a silicon layer, respectively; impregnating a portion of the porous substrate with the composition for forming the carbon layer; drying and heat-treating to form a carbon layer; and coating and impregnating the portion of the porous substrate on which the carbon layer is not formed (e.g., the portion on the formed carbon layer) with the composition for forming the silicon layer, and drying and heat-treating to form a silicon layer. In the above method, after forming the silicon layer, the composition for forming the carbon layer is coated and impregnated on another portion of the porous substrate on which the carbon layer is not formed and the silicon layer is not formed (e.g., the other portion on the formed silicon layer), and dried and heat-treated to further form a carbon layer, thereby having the structure shown in FIG2.

[0070] The composition for forming a carbon layer can be prepared, for example, by mixing a carbon-based material and a binder in a certain weight ratio and then dispersing the mixture in an aqueous solvent, and the composition for forming a silicon layer can be prepared by mixing a silicon-based negative electrode active material, a binder, and a conductive material in a certain weight ratio and then dispersing the mixture in an aqueous solvent.

[0071] In one or more embodiments, the negative electrode active material layer is disposed on (e.g., at least one) surface of the aforementioned negative electrode current collector and includes negative electrode active material.

[0072] Negative electrode active materials include materials capable of reversibly inserting / deintercalating lithium ions, lithium metal, lithium metal alloys, materials capable of doping and dedoping lithium, and / or transition metal oxides.

[0073] Materials capable of reversibly inserting / deintercalating lithium ions can be carbon-based negative electrode active materials.

[0074] Carbon-based negative electrode active materials can include crystalline carbon, amorphous carbon, or combinations thereof. Crystalline carbon can be irregularly shaped, sheet-like, flake-like, spherical, or fibrous natural or artificial graphite. Amorphous carbon can be soft carbon, hard carbon, mesophase pitch carbonization products, calcined coke, etc. Soft carbon refers to carbon materials that can be graphitized, and is easily graphitized by heat treatment at high temperatures (e.g., about 2800°C). Hard carbon is carbon materials that cannot be graphitized or can be finely graphitized by heat treatment.

[0075] In one or more embodiments, in addition to carbon-based negative electrode active materials, the negative electrode active material layer may also include other types (categories) of negative electrode active materials, and may also include, for example, lithium metal, lithium metal alloys, materials capable of doping and dedoping lithium, etc.

[0076] As an alloy of lithium metal, an alloy of lithium and a metal selected from sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), francium (Fr), beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), silicon (Si), antimony (Sb), lead (Pb), indium (In), zinc (Zn), barium (Ba), radium (Ra), germanium (Ge), aluminum (Al), and tin (Sn) can be used.

[0077] As a material capable of doping and de-doping lithium, a silicon-based negative electrode active material or a tin-based negative electrode active material can be used. The silicon-based negative electrode active material is the same as described above. The tin-based negative electrode active material can include Sn, SnO x (0 < x ≤ 2) (for example, SnO2), Sn-R alloy (where R is an element selected from alkali metals, alkaline earth metals, group 13 elements, group 14 elements, group 15 elements, group 16 elements, transition metals, rare earth elements, and combinations thereof, but not Sn), etc. In one or more embodiments, at least one selected therefrom can be mixed and used with SiO2. Here, the element R can be selected from Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Tl, Ge, P, As, Sb, Bi, S, Se, Te, Po, and combinations thereof.

[0078] The specific details of the silicon-based negative electrode active material are the same as the specific details in the silicon layer described above.

[0079] In one or more embodiments, the silicon-based negative electrode active material and / or the tin-based negative electrode active material can be mixed and used with a carbon-based negative electrode active material. In one or more embodiments, the negative electrode active material layer can include a carbon-based negative electrode active material, a silicon-based negative electrode active material, or a combination thereof. If (for example, when) the carbon-based negative electrode active material and the silicon-based negative electrode active material are mixed and used, the mixing ratio can be from about 10:90 to about 99:1.

[0080] In the negative electrode active material layer, based on 100 wt% of the total weight of the negative electrode active material layer, the content of the negative electrode active material can be from about 95 wt% to about 99 wt%.

[0081] In addition to the negative electrode active material, the negative electrode active material layer can optionally further include a binder, a conductive material, or a combination thereof. Regarding the binder and the conductive material, the types of binders and conductive materials that can be included in the carbon layer and the silicon layer can be used. Therefore, the description of the binder and the conductive material will not be repeated here.

[0082] In one or more embodiments, the negative electrode active material may be included in an amount of about 90 wt% to about 99.8 wt% or about 94 wt% to about 99 wt% based on 100 wt% of the total weight of the negative electrode active material layer; the binder may be included in an amount of about 0.1 wt% to about 5 wt% or about 0.5 wt% to about 3 wt% based on 100 wt% of the total weight of the negative electrode active material layer; and the conductive material may be included in an amount of about 0.1 wt% to about 5 wt% or about 0.5 wt% to about 3 wt% based on 100 wt% of the total weight of the negative electrode active material layer.

[0083] The negative electrode active material layer on at least one surface of the negative electrode current collector can have a multilayer structure with one layer or two or more layers. If (for example, when) the negative electrode active material layer has a single-layer structure, it can be as described above, and if (for example, when) the negative electrode active material layer has a multilayer structure, the type (variety) and amount of each of the negative electrode active material, binder, and conductive material included in each layer of the negative electrode active material layer can be the same or different. If (for example, when) the negative electrode active material layer has a multilayer structure, it can have a structure of 2 to 5 layers, or 2 to 4 layers, or 2 to 3 layers.

[0084] The negative electrode active material layer can be arranged in a specific direction to simplify the movement path of lithium ions. For example, it can be manufactured by coating a composition (typically the same as a "negative electrode slurry") for forming the negative electrode active material layer onto the aforementioned negative electrode current collector, and then applying a magnetic field to align the negative electrode active materials in substantially the same direction within the magnetic field. The negative electrode active materials can be arranged in a direction parallel to the negative electrode current collector or in a direction perpendicular to the negative electrode current collector. The specific details are explained in more detail below.

[0085] In one or more embodiments, the negative electrode active material layer may have a divergence (DD) value greater than or equal to about 19 (e.g., about 19 to about 60 or about 30 to about 60) as defined by Equation 1.

[0086]

Equation 1

[0087] If (for example, when) XRD measurements are performed using CuKα rays, the non-planar angles are represented as 2θ = 42.4 ± 0.2°, 2θ = 43.4 ± 0.2°, 2θ = 44.6 ± 0.2°, and 2θ = 77.5 ± 0.2°, i.e., the (100) plane, (101)R plane, (101)H plane, and (110) plane. Typically, graphite has structures classified as rhombic and hexagonal structures with an ABAB type (class) stacking order based on the stacking sequence of the graphene layers, with the R plane representing the rhombic structure and the H plane representing the hexagonal structure.

[0088] Therefore, I a It can be the sum of the peak intensities at 2θ=42.4±0.2°, 2θ=43.4±0.2°, 2θ=44.6±0.2° and 2θ=77.5±0.2° as measured by XRD using CuKα rays.

[0089] If, for example, when measured using CuKα rays by XRD, all angles represent 2θ = 26.5 ± 0.2°, 2θ = 42.4 ± 0.2°, 2θ = 43.4 ± 0.2°, 2θ = 44.6 ± 0.2°, 2θ = 54.7 ± 0.2°, and 2θ = 77.5 ± 0.2°, i.e., the (002) plane, (100) plane, (101)R plane, (101)H plane, (004) plane, and (110) plane. In one or more embodiments, the peak at 2θ = 43.4 ± 0.2° can also be considered to occur by the overlap of a peak on the (101)R plane of the carbonaceous material with another peak on the (111) plane of the negative electrode current collector (e.g., Cu).

[0090] Therefore, I 总 It can be the sum of the peak intensities at 2θ=26.5±0.2°, 2θ=42.4±0.2°, 2θ=43.4±0.2°, 2θ=44.6±0.2°, 2θ=54.7±0.2° and 2θ=77.5±0.2° as measured by XRD using CuKα rays.

[0091] Typically, peak intensity represents the height of a peak or the integral area of ​​a peak, and according to one or more embodiments, peak intensity represents the integral area of ​​a peak.

[0092] In one or more embodiments, XRD is measured using CuKα rays as the target ray but removing the monochromator to improve peak intensity resolution under measurement conditions of 2θ = 10° to 80°, a scan rate (° / s) (i.e., degrees / second) of 0.044 to 0.089, and a step size (° / step) of 0.013 to 0.039.

[0093] 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, the larger the DD value, the larger the angle of orientation of the negative electrode active material relative to a surface of the porous substrate. Furthermore, the DD value is maintained after charge and discharge.

[0094] In one or more embodiments, the DD value of the negative electrode can be greater than or equal to about 19, for example, about 20 to about 60, about 25 to about 60, about 30 to about 60, about 30 to about 55, about 35 to about 55, or about 40 to about 55. A DD value of about 19 or greater for the negative electrode means that the negative electrode active material is substantially perpendicular to the negative electrode current collector at a specific angle; this means that the negative electrode active material layer of the negative electrode is an orientation layer. For example, a substantially perpendicular standing position does not necessarily mean standing at an angle of about 90° relative to the negative electrode current collector (e.g., relative to the surface of the negative electrode current collector on which the negative electrode active material layer is disposed), but rather at an angle close to 90° (e.g., about 90°).

[0095] If (for example, when) the DD value of the negative electrode is less than about 19, the included negative electrode active material layer corresponds to a non-oriented layer, or even if the negative electrode active material layer is an oriented layer, the expansion effect is low, and therefore it is not suitable.

[0096] In this way, because the negative electrode active material is arranged perpendicularly to the negative electrode current collector, volume expansion may occur in the horizontal direction (e.g., in the planar direction) during the charging and discharging of the battery including the negative electrode. Therefore, it can effectively suppress or reduce excessive vertical volume expansion that may occur if (e.g., when) a silicon-based negative electrode active material is used, thereby significantly reducing the rate of increase in battery thickness and preventing or mitigating the phenomenon of the active material layer detaching from the negative electrode current collector. Therefore, silicon-based negative electrode active materials that can improve energy density can be readily applied to rechargeable lithium batteries.

[0097] In one or more embodiments, a rechargeable lithium battery is provided, comprising a positive electrode, the aforementioned negative electrode, and an electrolyte.

[0098] The positive electrode may include a positive electrode current collector and a layer of positive electrode active material on the positive electrode current collector. The positive electrode active material layer includes (e.g., in particulate form) positive electrode active material, and may optionally include a binder, a conductive material, or a combination thereof.

[0099] There are no particular limitations on the positive electrode current collector, as long as it is conductive (e.g., a conductor) and does not cause chemical changes in the rechargeable lithium battery. In one or more embodiments, the positive electrode current collector may be aluminum foil.

[0100] As the positive electrode active material, compounds capable of intercalating and deintercalating lithium (lithium-intercalating compounds) can be used. For example, in one or more embodiments, a composite oxide of lithium with at least one metal selected from cobalt, manganese, nickel, and combinations thereof can be used.

[0101] The composite oxide can be a lithium transition metal composite oxide, and non-limiting examples may include lithium nickel oxides, lithium cobalt oxides, lithium manganese oxides, lithium iron phosphate compounds, cobalt-free lithium nickel manganese oxides, lithium manganese-rich composite oxides, or combinations thereof.

[0102] In one or more embodiments, 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 Gb 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); and Li a FePO4 (0.90≤a≤1.8).

[0103] In the aforementioned chemical formula, A can be nickel (Ni), cobalt (Co), manganese (Mn), or a combination thereof; X can be aluminum (Al), Ni, Co, Mn, chromium (Cr), iron (Fe), magnesium (Mg), strontium (Sr), vanadium (V), rare earth elements, or a combination thereof; D can be oxygen (O), fluorine (F), sulfur (S), phosphorus (P), or a combination thereof; G can be Al, Cr, Mn, Fe, Mg, lanthanum (La), cerium (Ce), Sr, V, or a combination thereof; and L 1 It is Mn, Al, or a combination thereof.

[0104] In one or more embodiments, the positive electrode active material may include lithium nickel composite oxides represented by Formula 6, lithium cobalt composite oxides represented by Formula 7, or combinations thereof.

[0105] [Chemical Formula 6] Li a6 Ni x6 M 6 y6 M 7 z6 O 2-b6 X b6 In chemical formula 6, 0.9 ≤ a6 ≤ 1.8, 0.3 ≤ x6 ≤ 1, 0 ≤ y6 ≤ 0.7, 0 ≤ z6 ≤ 0.7, 0.9 ≤ x6 + y6 + z6 ≤ 1.1 and 0 ≤ b6 ≤ 0.1, M 6 and M 7 Each element can be independently selected from one or more elements chosen from Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr, and X can be selected from one or more elements chosen from F, P, and S.

[0106] In one or more embodiments, in chemical formula 6, 0.6 ≤ x6 ≤ 1, 0 ≤ y6 ≤ 0.4 and 0 ≤ z6 ≤ 0.4; or 0.8 ≤ x6 ≤ 1, 0 ≤ y6 ≤ 0.2 and 0 ≤ z6 ≤ 0.2.

[0107] [Chemical Formula 7] Li a7 Co x7 M 8 y7 O 2-b7 X b7 In chemical formula 7, 0.9 ≤ a7 ≤ 1.8, 0.7 ≤ x7 ≤ 1, 0 ≤ y7 ≤ 0.3, 0.9 ≤ x7 + y7 ≤ 1.1 and 0 ≤ b7 ≤ 0.1, M 8 It can be one or more elements selected from Al, B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mn, Mo, Ni, Se, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr, and X can be one or more elements selected from F, P, and S.

[0108] In one or more embodiments, in chemical formula 7, 0.8 ≤ x7 ≤ 1 and 0 ≤ y7 ≤ 0.2; or 0.7 ≤ x7 ≤ 0.9 and 0 ≤ y7 ≤ 0.2.

[0109] In one or more embodiments, the positive electrode active material can be a high-nickel positive electrode active material. Based on 100 mol% of the total metals other than lithium in the lithium transition metal composite oxide, the nickel content (e.g., amount) in the high-nickel positive electrode active material is greater than or equal to about 80 mol%, greater than or equal to about 85 mol%, greater than or equal to about 90 mol%, greater than or equal to about 91 mol%, or greater than or equal to about 94 mol% and less than or equal to about 99 mol%. High-nickel positive electrode active materials can achieve high capacity and can be applied to high-capacity, high-density rechargeable lithium batteries.

[0110] Based on 100 wt% of the total weight of the positive electrode active material layer, the amount of positive electrode active material may be about 60 wt% to about 99.9 wt%, about 70 wt% to about 99.8 wt%, about 80 wt% to about 99 wt%, or about 90 wt% to about 99.8 wt%, or about 94 wt% to about 99 wt%.

[0111] The binder improves the adhesion properties between the positive electrode active materials and between the positive electrode active materials and the positive electrode current collector. Examples of binders may include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers including ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, epoxy resin, (meth)acrylate resin, polyester resin, nylon, etc., but the embodiments of this disclosure are not limited thereto.

[0112] Conductive materials are used to impart electrical conductivity (e.g., electrical conductivity) to electrodes, and any material that does not cause chemical changes and conducts electrons can be used in rechargeable lithium batteries. Non-limiting examples of conductive materials may include: carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanofibers and / or carbon nanotubes; metallic materials in the form of metal powders or metal fibers, including copper, nickel, aluminum, silver, etc.; conductive polymers, such as polyphenylene derivatives; or mixtures thereof.

[0113] In the positive electrode active material layer, the amount of binder may be about 0.1 wt% to about 5 wt% or about 0.5 wt% to about 3 wt% based on 100 wt% of the total weight of the positive electrode active material layer, and the content of conductive material may be about 0.1 wt% to about 5 wt% or about 0.5 wt% to about 3 wt% based on 100 wt% of the total weight of the positive electrode active material layer.

[0114] Since the specific details regarding the negative electrode are the same as those described above, they will not be repeated here.

[0115] Electrolytes, for example, can be electrolyte solutions that may include non-aqueous organic solvents and lithium salts for rechargeable lithium batteries.

[0116] Non-aqueous organic solvents are used as media for transporting ions that participate in the electrochemical reactions of rechargeable lithium batteries.

[0117] Non-aqueous organic solvents can be carbonate solvents, ester solvents, ether solvents, ketone solvents, alcohol solvents, aprotic solvents, or combinations thereof.

[0118] Carbonate solvents can include ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), ethylene carbonate (EC), propylene carbonate (PC), and butyl carbonate (BC), etc. Ester solvents can include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanolactone, mevalonolactone, valproic acid lactone, caprolactone, etc. Ether solvents can include dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, tetrahydrofuran, etc. Additionally, ketone solvents can include cyclohexanone, etc. Alcohol solvents may include ethanol, isopropanol, etc., while aprotic solvents may include: nitriles, such as R-CN (where R is a C2 to C20 straight-chain, branched, or cyclic hydrocarbon group, and may include double bonds, aromatic rings, or ether bonds, etc.); amides, such as dimethylformamide; dioxolane, such as 1,3-dioxolane, 1,4-dioxolane, etc.; sulfolane; etc.

[0119] Non-aqueous organic solvents can be used alone or in mixtures of two or more types (classes).

[0120] Additionally, if (for example, when) carbonate solvents are used, cyclic carbonates and chain carbonates can be mixed and used, and cyclic carbonates and chain carbonates can be mixed in a volume ratio of about 1:1 to about 1:9.

[0121] Lithium salts dissolved in non-aqueous organic solvents supply lithium ions in rechargeable lithium batteries, enabling basic operation and improving lithium ion transport between the positive and negative electrodes. For example, lithium salts may include those selected from LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, LiN(SO3C2F5)2, Li(FSO2)2N (lithium bis(fluorosulfonyl)imide; LiFSI), LiC4F9SO3, LiN(C x F 2x+1 SO2)(C y F 2y+ At least one of 1SO2 (where x and y are integers from 1 to 20), lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium difluorobis(oxalate)phosphate (LiDFBOP), and lithium bis(oxalate)borate (LiBOB).

[0122] Depending on the type of rechargeable lithium battery, the separator can be located between the positive and negative electrodes. The separator can include polyethylene, polypropylene, polyvinylidene fluoride, or two or more layers of other multilayer membranes. For example, it can include hybrid multilayer membranes, such as a polyethylene / polypropylene two-layer separator, a polyethylene / polypropylene / polypropylene three-layer separator, or a polypropylene / polypropylene / polypropylene three-layer separator.

[0123] The membrane may include a porous substrate and a coating on one or both surfaces (e.g., two opposing surfaces) of the porous substrate, comprising an organic material, an inorganic material, or a combination thereof.

[0124] The porous substrate can be a polymer membrane, which is formed from any of the following: polyolefins (such as polyethylene and / or polypropylene), polyesters (such as polyethylene terephthalate and / or polybutylene terephthalate), polyacetal, polyamide, polyimide, polycarbonate, polyetherketone, polyaryletherketone, polyetherimide, polyamideimide, polybenzimidazole, polyethersulfone, polyphenylene ether, cyclic olefin copolymers, polyphenylene sulfide, polyethylene naphthalate, glass fiber, and polytetrafluoroethylene (e.g., TEFLON). ®Alternatively, polymer films may include copolymers or mixtures of two or more of them.

[0125] Organic materials may include polyvinylidene fluoride polymers and / or (meth)acrylic acid polymers.

[0126] Inorganic materials may include inorganic particles selected from Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, Mg(OH)2, boehmite and combinations thereof, but the embodiments disclosed herein are not limited thereto.

[0127] In one or more embodiments, organic and inorganic materials may be mixed in a coating, or coatings comprising organic materials and coatings comprising inorganic materials may be stacked.

[0128] Rechargeable lithium batteries can be classified according to their shape into cylindrical, prismatic, pouch, coin-shaped, etc. Figures 3 to 6 are schematic diagrams illustrating one or more embodiments of a rechargeable lithium battery according to this disclosure. Figure 3 shows a cylindrical battery, Figure 4 shows a prismatic battery, and Figures 5 and 6 each show a pouch-type battery. Referring to Figures 3 to 6, the rechargeable lithium battery 100 may include an electrode assembly 40 and a housing. The electrode assembly 40 includes a separator 30 between a positive electrode 10 and a negative electrode 20, and the electrode assembly 40 is housed within the housing. The positive electrode 10, the negative electrode 20, and the separator 30 may be impregnated with an electrolyte. In one or more embodiments, as shown in Figure 3, the rechargeable lithium battery 100 may include a sealing member 60 for sealing the housing 50. In one or more embodiments, as shown in Figure 4, the rechargeable lithium battery 100 may include a positive electrode lead connector 11, a positive electrode terminal 12, a negative electrode lead connector 21, and a negative electrode terminal 22. In one or more embodiments, as shown in Figures 5 and 6, the rechargeable lithium battery 100 may include electrode terminals 70, namely, positive electrode terminal 71 and negative electrode terminal 72, serving as electrical paths to guide current formed in the electrode assembly 40 to the outside.

[0129] Examples and comparative examples of this disclosure will be described in more detail below. However, the following examples are merely examples of this disclosure, and this disclosure is not limited to these examples.

[0130] Example 1 (1) Fabrication of the negative electrode current collector: The fabrication comprises copper, a porous substrate with a porosity of approximately 80%, a pore size of approximately 480 μm, and a thickness of approximately 300 μm. When viewed from above, the porous substrate has rhomboid pores, and the pore size is obtained by measuring the major axis length and minor axis length of each pore when viewed from above, and then calculating their average value. Here, the major axis length is approximately 640 μm, and the minor axis length is approximately 320 μm.

[0131] A composition for forming a carbon layer was prepared by mixing carbon black as a carbon material and styrene-butadiene rubber (SBR) as a binder in a weight ratio of 30:70 (carbon material: binder) and dispersing the mixture in an aqueous solvent.

[0132] By using SiO2 as the active material for silicon-based negative electrodes x A composition for forming a silicon layer was prepared by mixing silicon-carbon composites of SCN, polyacrylic acid as a binder, and carbon nanotubes as a conductive material in a weight ratio of 94:5:1 (silicon-based negative electrode active material: binder: conductive material) and dispersing the mixture in an aqueous solvent.

[0133] A portion of a porous substrate is immersed in a composition for forming a carbon layer, then dried and heat-treated to form a carbon layer. On the formed carbon layer (i.e., the first carbon layer (1A)), a composition for forming a silicon layer is coated and impregnated, then dried and heat-treated to form a silicon layer. On the formed silicon layer, a composition for forming a carbon layer is coated and impregnated, then dried and heat-treated to form another carbon layer (i.e., the first carbon layer (1B)). The final negative electrode current collector has a stacked structure in which the first carbon layer (1A), the silicon layer, and the first carbon layer (1B) are sequentially stacked, and the material in each layer is completely impregnated into the pores inside the porous substrate.

[0134] Here, based on the 100% thickness of the negative electrode current collector, the first carbon layer (1A), the silicon layer and the first carbon layer (1B) have thicknesses of 10%, 80% and 10%, respectively.

[0135] (2) Fabrication of the negative electrode: A composition for forming the negative electrode active material layer is prepared by mixing graphite as the negative electrode active material, a mixture of carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR) in a weight ratio of 1:1 as a binder, and carbon nanotubes (CNTs) as a conductive material in a weight ratio of 97.5:2:0.5 (negative electrode active material: binder: conductive material), and then dispersing the resulting mixture in an aqueous solvent. The composition for forming the negative electrode active material layer is coated onto the fabricated negative electrode current collector, and then dried and compressed to fabricate the negative electrode.

[0136] (3) The manufacturing of rechargeable lithium battery cells involves using LiNi as the positive electrode active material. 0.94 Co 0.04 Al 0.01 Mn 0.01 A positive electrode active material composition was prepared by mixing O2, polyvinylidene fluoride as a binder, and carbon nanotubes as a conductive material in a weight ratio of 96:2:2 (positive electrode active material: binder: conductive material). This positive electrode active material composition was dispersed in N-methylpyrrolidone solvent to prepare a positive electrode active material slurry, which was then coated onto a 15 μm thick aluminum foil, dried, and compressed to fabricate the positive electrode.

[0137] An electrode assembly is fabricated by placing a 10 μm thick polyethylene separator between the positive and negative electrodes. The electrode assembly is then inserted into a housing, and an electrolyte is injected into it, thereby fabricating a rechargeable lithium-ion battery cell (100mAh-class pouch cell). The electrolyte is prepared by mixing EC (ethylene carbonate):EMC (ethyl methyl carbonate):DMC (dimethyl carbonate) in a volume ratio of 2:4:4 and dissolving 1.15M LiPF6 in the mixed solvent.

[0138] In Comparative Example 1, the negative electrode current collector, negative electrode, and rechargeable lithium battery cell are all manufactured in substantially the same manner as in Example 1, except that, in manufacturing the negative electrode current collector, the porous substrate is completely filled with a composition for forming a carbon layer. The negative electrode current collector is formed solely of a carbon layer, and the carbon layer comprises a porous substrate and carbonaceous material present in pores within the porous substrate.

[0139] In Comparative Example 2, the negative electrode current collector, negative electrode, and rechargeable lithium battery cell are all manufactured in substantially the same manner as in Example 1, except that in the manufacture of the negative electrode current collector, the porous substrate is completely filled with the composition used to form the silicon layer. The negative electrode current collector is formed solely of the silicon layer, and the silicon layer comprises the porous substrate and silicon-based negative electrode active material present in pores within the porous substrate.

[0140] The negative electrode of Example 1 comprises a negative electrode current collector having a structure in which a first carbon layer (1A), a silicon layer, and a first carbon layer (1B) are sequentially stacked. The first carbon layers (1A) and (1B) are arranged on two surfaces (e.g., opposite surfaces) of the silicon layer (e.g., simultaneously). When the silicon-based negative electrode active material contracts or expands during charging / discharging, the negative electrode of Example 1 suppresses or reduces the expansion of the silicon-based negative electrode active material. Furthermore, due to the silicon layer containing the silicon-based negative electrode active material in the negative electrode current collector, the negative electrode of Example 1 improves energy density. For example, the carbon layers (1A, 1B) located on opposite sides of the silicon layer mechanically stabilize the electrode by suppressing the volume expansion and contraction of the silicon-based negative electrode active material during repeated charge and discharge cycles. This structural buffering effect helps maintain the integrity of the electrode, thereby enhancing its cycle life and reliability. Moreover, due to the high theoretical capacity of silicon compared to conventional graphite materials, incorporating a silicon layer into a porous substrate contributes to a significant increase in energy density. The porous structure allows for uniform impregnation of the active material and promotes efficient ion transport, which further improves electrochemical performance. In contrast to the comparative example (where the current collector consists of only carbon or silicon), the hybrid layered structure in Example 1 achieves a balanced combination of mechanical durability, conductivity, and high capacity, making it suitable for next-generation high-performance lithium-ion batteries.

[0141] For example, in Comparative Example 1, which uses a negative electrode current collector consisting only of a carbon layer, a negative electrode active material layer including the negative electrode active material needs to be formed separately on the negative electrode current collector. Compared with Example 1, this increases the thickness of the electrode plate and results in a decrease in energy density.

[0142] In addition, in Comparative Example 2, which uses a negative electrode current collector consisting only of a silicon layer, compared to Example 1, the silicon-based negative electrode active material repeatedly contracts and expands due to repeated charging and discharging, resulting in damage to the electrode structure and thus deterioration of battery performance and cycle performance.

[0143] While this disclosure has been described in conjunction with what is now considered an exemplary embodiment, it will be understood that the disclosure is not limited to the disclosed embodiments. Rather, it 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.

[0144] Reference numerals in the figure: 1: Negative electrode current collector; 2a: First carbon layer (1A); 3: Silicon layer; 2b: First carbon layer (1B); 4: Porous substrate; 5: Hole; 100: Rechargeable lithium battery; 10: Positive electrode; 11: Positive electrode lead connector; 12: Positive electrode terminal; 20: Negative electrode; 21: Negative electrode lead connector; 22: Negative electrode terminal; 30: Separator; 40: Electrode assembly; 50: Housing; 60: Sealing member; 70: Electrode connector; 71: Positive electrode connector; 72: Negative electrode connector.

Claims

1. A negative electrode, the negative electrode comprising: A negative electrode current collector includes: a carbon layer comprising a first porous substrate and a carbon-based material within the first porous substrate; a silicon layer comprising a second porous substrate and a silicon-based negative electrode active material within the second porous substrate; and a negative electrode active material layer comprising a negative electrode active material and disposed on the surface of the negative electrode current collector, wherein the negative electrode is a negative electrode for a rechargeable lithium battery.

2. The negative electrode as described in claim 1, wherein, The first porous substrate and the second porous substrate each independently comprise a metal, and the metal comprises copper, nickel, stainless steel, titanium, aluminum, or a combination thereof.

3. The negative electrode as described in claim 1, wherein, The thickness of the first porous substrate is 5 μm to 500 μm, and the thickness of the second porous substrate is 5 μm to 500 μm.

4. The negative electrode as described in claim 1, wherein, The porosity of the first porous substrate is greater than or equal to 50%, and the porosity of the second porous substrate is greater than or equal to 50%.

5. The negative electrode as described in claim 1, wherein, The pores inside the first porous substrate each have a size of 300 μm to 1,000 μm, and the pores inside the second porous substrate each have a size of 300 μm to 1,000 μm.

6. The negative electrode as claimed in claim 1, wherein, The carbon-based materials include amorphous carbon.

7. The negative electrode as claimed in claim 1, wherein, The carbon layer further includes a binder, and the amount of the carbon material in the carbon layer is 10 wt% to 30 wt% based on 100 wt% of the total weight of the carbon layer excluding the first porous substrate, and the amount of the binder is 70 wt% to 90 wt% based on 100 wt% of the total weight of the carbon layer excluding the first porous substrate.

8. The negative electrode as claimed in claim 1, wherein, The silicon-based negative electrode active material includes a silicon-carbon composite.

9. The negative electrode as claimed in claim 1, wherein, The silicon layer further includes an adhesive and a conductive material. Based on 100 wt% of the total weight of the silicon layer excluding the second porous substrate in the silicon layer, the amount of the silicon-based negative electrode active material is 89 wt% to 99.9 wt%. Based on 100 wt% of the total weight of the silicon layer excluding the second porous substrate in the silicon layer, the amount of the adhesive is 1 wt% to 10 wt%. Based on 100 wt% of the total weight of the silicon layer excluding the second porous substrate in the silicon layer, the amount of the conductive material is 0.1 wt% to 1 wt%.

10. The negative electrode as claimed in claim 1, wherein: The carbon layer includes a first carbon layer 1A and a first carbon layer 1B; the first porous substrate includes a first porous substrate 1A and a first porous substrate 1B; and the carbon-based material includes a first carbon-based material 1A and a first carbon-based material 1B, wherein the silicon layer is on the first carbon layer 1A, and the first carbon layer 1B is on the silicon layer, and wherein the first carbon layer 1A includes the first porous substrate 1A and the first carbon-based material 1A inside the first porous substrate 1A, and the first carbon layer 1B includes the first porous substrate 1B and the first carbon-based material 1B inside the first porous substrate 1B.

11. The negative electrode as claimed in claim 10, wherein, Based on 100% thickness of the negative electrode current collector, the thickness of the silicon layer is 50% to 99% thickness, and based on 100% thickness of the negative electrode current collector, the sum of the thicknesses of the first carbon layer 1A and the first carbon layer 1B is 1% to 50% thickness.

12. The negative electrode as claimed in claim 10, wherein, The first carbon layer 1A and the first carbon layer 1B have a thickness ratio of 1:9 to 9:

1.

13. The negative electrode as claimed in claim 1, wherein, The negative electrode active material includes carbon-based negative electrode active materials, silicon-based negative electrode active materials, or combinations thereof.

14. The negative electrode as claimed in claim 1, wherein, The negative electrode active material layer has a structure with one, two, or more layers.

15. A rechargeable lithium battery, the rechargeable lithium battery comprising a positive electrode, a negative electrode according to any one of claims 1 to 14, and an electrolyte.

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