Negative electrode and rechargeable lithium battery comprising the same

Abstract

Some example embodiments provide a negative electrode and a rechargeable lithium battery including the same, the negative electrode including: a negative electrode current collector; a negative electrode active material layer on the negative electrode current collector and including a negative electrode active material; and an edge portion on the negative electrode current collector and disposed at an edge of the negative electrode active material layer, wherein the edge portion includes metal particles that alloy with lithium.

Description

Technical Field

[0001] Embodiments of this disclosure relate to a negative electrode and a rechargeable lithium battery including the negative electrode. Background Technology

[0002] Recently, with the rapid proliferation of battery-powered electronic devices such as mobile phones, laptops, and electric vehicles, the demand for rechargeable batteries with high energy density and high capacity is increasing rapidly. Therefore, research and development are actively underway to improve the performance of rechargeable lithium batteries.

[0003] A rechargeable lithium battery includes a positive electrode and a negative electrode as well as an electrolyte. The positive and negative electrodes include active materials capable of inserting and deintercalating lithium ions, and the rechargeable lithium battery generates electrical energy through oxidation and reduction reactions when (for example, when) lithium ions are inserted into and deintercalated from the positive and negative electrodes.

[0004] Because rechargeable lithium batteries, which can be recharged after being discharged and used continuously (e.g., substantially continuously), exhibit performance differences depending on their charge / discharge state, efforts are being made to improve the performance of rechargeable lithium batteries by improving charging methods. Summary of the Invention

[0005] Some exemplary embodiments of this disclosure provide negative electrodes capable of preventing or reducing diaphragm rupture by growing lithium dendrites in a flat and uniform (e.g., substantially uniform) manner.

[0006] Some example embodiments provide rechargeable lithium batteries that have excellent thermal safety by including the aforementioned negative electrode.

[0007] Some example embodiments provide a negative electrode comprising: a negative electrode current collector; a negative electrode active material layer on the negative electrode current collector and including the negative electrode active material; and an edge portion on the negative electrode current collector and disposed at the edge of the negative electrode active material layer, wherein the edge portion includes metal particles alloyed with lithium.

[0008] Some example embodiments provide a negative electrode comprising: a negative electrode current collector; and an uncoated region, a first region, a second region, and a third region sequentially disposed on the negative electrode current collector in a direction parallel (e.g., substantially parallel) to the negative electrode current collector, wherein the first region comprises metal particles alloyed with lithium, the second region comprises a negative electrode active material and metal particles alloyed with lithium, and the third region comprises a negative electrode active material.

[0009] Some example embodiments provide a rechargeable lithium battery including the negative electrode.

[0010] The negative electrode according to some example embodiments has the characteristic that it can prevent or reduce membrane rupture by allowing lithium dendrites to grow flat and uniformly (e.g., substantially uniformly), and the rechargeable lithium battery according to some example embodiments has the characteristic that it has excellent thermal safety because it includes the negative electrode. Attached Figure Description

[0011] The accompanying drawings, together with the specification, illustrate embodiments of the subject matter of this disclosure, and together with the description, serve to explain the principles of the embodiments of the subject matter of this disclosure.

[0012] Figure 1 A cross-sectional view of a negative electrode according to some example embodiments is shown schematically.

[0013] Figure 2 This is a scanning electron microscope (SEM) image showing the shape of lithium dendrites accumulated on the active material layer of the contrasting negative electrode.

[0014] Figures 3 to 6 This is a schematic diagram illustrating a rechargeable lithium battery according to some example embodiments.

[0015] Figure 7 This is a SEM image of a portion of the cross-section of the edge of the negative electrode of a rechargeable lithium-ion battery cell according to Example 1-1. Figure 8 This is a SEM image of a portion of the cross-section of the edge of the negative electrode of a rechargeable lithium battery cell according to Example 1-2.

[0016] Figure 9 This is a SEM image of a portion of the cross-section of the edge of the negative electrode of a rechargeable lithium-ion battery cell according to Example 2-1. Figure 10 This is a SEM image of a portion of the cross-section of the edge of the negative electrode of a rechargeable lithium battery cell according to Example 2-2.

[0017] Figure 11 This is a SEM image of a portion of the cross-section of the edge of the negative electrode of a rechargeable lithium-ion battery cell, based on Example 3-1. Figure 12 This is a SEM image of a portion of the cross-section of the edge of the negative electrode of a rechargeable lithium battery cell according to Example 3-2.

[0018] Figure 13 This is a SEM image of a portion of the cross-section of the edge of the negative electrode of a rechargeable lithium-ion battery cell, based on Example 4-1. Figure 14 This is a SEM image of a portion of the cross-section of the edge of the negative electrode of a rechargeable lithium battery cell according to Example 4-2.

[0019] Figure 15It is a SEM image of a portion of the cross-section of the edge of the negative electrode of the rechargeable lithium battery cell according to Example 5. Detailed Implementation

[0020] The embodiments will be described in more detail below. However, these embodiments are presented by way of example, and the present disclosure is not limited thereto, which is defined by the scope of the claims described below and their equivalents.

[0021] The terminology used herein is for describing embodiments only and is not intended to limit this disclosure. Unless the context clearly specifies otherwise, singular expressions include plural expressions.

[0022] As used here, “the combination of them” refers to mixtures of components, laminates, complexes, copolymers, alloys, blends, reaction products, etc.

[0023] In the embodiments, it should be understood that terms such as “comprising,” “including,” or “having” are intended to specify the presence of the features, quantities, steps, elements, or combinations thereof embodied, but do not preclude the possibility of the presence or addition of one or more other features, quantities, steps, elements, or combinations thereof.

[0024] In the accompanying drawings, for clarity, the thickness of layers, films, panels, regions, etc., is exaggerated, and the same reference numerals denote the same elements throughout the specification. It will be understood that if (for example, 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 an intermediary element may be present. In embodiments, if (for example, when) an element is referred to as "directly on" another element, then no intermediary element is present.

[0025] In this embodiment, “layer” here includes not only the shape that is on the entire surface when viewed from a plan view, but also the shape that is on a portion of the surface.

[0026] Unless otherwise stated in this specification, things expressed in the singular may also include the plural. In embodiments, unless otherwise stated, "A or B" may mean "including A, including B, or including both A and B".

[0027] As used here, the term "metal" is interpreted as encompassing the concepts of common metals, transition metals, and quasi-metals (semi-metals).

[0028] As used herein, particle size can be the average particle size unless otherwise defined. In embodiments, particle size can refer to the average particle size (Dmin). 50 The average particle size (D) refers to the diameter of particles that constitute 50% of the total volume in the particle size distribution. 50The average particle size (D) can be measured by any suitable method commonly used in the art, such as by a particle size analyzer, by transmission electron microscopy images, and / or scanning electron microscopy images. In this embodiment, data analysis is performed using a dynamic light scattering measurement device, and the number of particles in each particle size range is counted. Thus, the average particle size (D) can be readily obtained by calculation. 50 The average particle size (D) is calculated based on the particle size distribution of 50% of the particle size distribution in the measuring device. In an embodiment, laser diffraction can be used for measurement. If (e.g., when) the measurement is performed by laser diffraction, for example, the particles to be measured are dispersed in a dispersion medium and then introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac MT 3000), and irradiated with approximately 28 kHz ultrasound at an output of 60 W, the average particle size (D) is calculated based on the particle size distribution in the measuring device. 50 ).

[0029] negative electrode Figure 1 This is a schematic cross-sectional view of the negative electrode 20 according to some example embodiments.

[0030] Reference Figure 1 According to some example embodiments, the negative electrode 20 includes: a negative electrode current collector 1; a negative electrode active material layer 2, on the negative electrode current collector 1 and including the negative electrode active material; and an edge portion 3, on the negative electrode current collector 1 and disposed at the edge of the negative electrode active material layer 2. For example, the edge portion 3 may be on the edge of the negative electrode active material layer 2. In embodiments, the edge portion 3 may be superimposed on the negative electrode active material layer 2, for example, including both a portion superimposed on the negative electrode active material layer 2 and another portion not superimposed on the negative electrode active material layer 2.

[0031] For example, the negative electrode 20 may include an uncoated region, a first region, a second region, and a third region on the negative electrode current collector 1 in a direction parallel to (e.g., substantially parallel to) the negative electrode current collector 1.

[0032] The first region can be the region of the edge portion 3 that is not superimposed on the negative electrode active material layer 2, and the second region can be the region of the edge portion 3 that is superimposed on the negative electrode active material layer 2.

[0033] The third region can be a region where the negative electrode active material layer 2 exists but the edge portion 3 does not exist. For example, the third region may include the negative electrode active material layer 2 and contain no or substantially no edge portion 3 (e.g., the third region may not include the edge portion 3). The uncoated region can be a region where neither the negative electrode active material layer 2 nor the edge portion 3 exists. For example, the uncoated region may contain no or substantially no negative electrode active material layer 2 nor the edge portion 3 (e.g., the uncoated region may not include the negative electrode active material layer 2 and the edge portion 3).

[0034] In a comparative battery assembly with a positive electrode / separator / negative electrode structure, the edges of the positive electrode and the edges of the negative electrode face each other.

[0035] Typically, because the composite is less loaded near the edge of the negative electrode active material layer (plate loading-detachment phenomenon), the specific capacity of the negative electrode is lower than that of the positive electrodes facing each other. Therefore, lithium metal, as an irreversible product, may accumulate on the negative electrode active material layer.

[0036] Figure 2 This is a SEM image showing the shape of lithium dendrites accumulated on the active material layer of the contrasting negative electrode. (Refer to...) Figure 2 Irreversible byproducts may include sharp-shaped lithium dendrites, which may grow into sharp and pointed shapes, eventually causing the separator to rupture and short-circuit the battery, leading to a fire problem in the battery.

[0037] According to some example embodiments, the negative electrode (whose edges are coated with metal particles that form an alloy with lithium to control the lithium dendrites to have a flat shape) can prevent short circuits in the battery (or reduce the likelihood, occurrence, or extent of short circuits in the battery) and effectively improve the thermal safety of the battery.

[0038] For example, the edge portion 3 includes metal particles that form an alloy with lithium. In the following text, the metal particles that form an alloy with lithium may be simply referred to as metal particles.

[0039] For example, the first region may include metal particles that form an alloy with lithium, the second region may include a negative electrode active material and metal particles that form an alloy with lithium, and the third region may include a negative electrode active material.

[0040] For example, the metal particles that form an alloy with lithium may include Ag, Sn, Bi, Zn, Mg, In, Al, or combinations thereof.

[0041] For example, metal particles can be used as nuclei for the deposition of lithium metal accumulated at the negative electrode. The metal particles can serve as centers, allowing lithium to be deposited on the surface to form an alloy with the metal particles, wherein the lithium can be deposited in a flat and uniform form (e.g., substantially uniform form).

[0042] For example, if (e.g., when) a rechargeable lithium battery is being charged, lithium dendrites can grow on the edge portion 3 of the negative electrode current collector 1 along the charging direction. In an embodiment, the lithium dendrites can grow in the form of an alloy formed by depositing lithium metal around metal particles.

[0043] For example, in edge portion 3, lithium dendrites can grow flatly from the bottom or top of the metal particles.

[0044] The location of lithium dendrite growth can vary appropriately depending on the type (or variety) of metal particles, the ratio of the metal particles to lithium forming an alloy, whether spherical (e.g., approximately spherical) graphite, which will be further described herein, the battery operating temperature, the size of the pores present in the edge, etc.

[0045] For example, the higher the ratio of metal particles to lithium forming an alloy, the higher the battery operating temperature, and / or the smaller the size of the holes in the edges, the flatter the lithium dendrites grow from the top of the metal particles.

[0046] In both cases, lithium dendrites can grow in a flattened manner, thereby effectively improving the thermal safety of the battery.

[0047] For example, metal particles can have the same or similar lattice parameters as lithium.

[0048] Lattice parameters are physical dimensions and angles that define the shape of a unit lattice (unit cell) in the crystal structure of a particle.

[0049] When metal particles and lithium have the same or similar lattice parameters, they can easily form alloys because unit lattices can have the same or similar size, allowing them to substitute for each other and mix stably.

[0050] The lattice parameters of the metal particles and lithium can be measured by X-ray diffraction (XRD) analysis using Cu K-α rays.

[0051] In the embodiments, measurements can be performed under suitable conditions commonly used in the relevant field. These measurement conditions may be, for example, an output of 35kV to 40kV, 90mA to 100mA, 2θ = 10° to 90°, a step time of 25s to 55s, and a step size (° / step) of 0.01 to 0.02.

[0052] Since metal particles and lithium have the same or similar lattice parameters, metal particles can reduce the nucleation overpotential during lithium (Li) deposition and also lower the diffusion barrier of lithium. Therefore, lithium can be controlled to be deposited uniformly (e.g., substantially uniformly) around the metal particles, as the diffusivity of lithium can be increased and lithium movement can be promoted through lithium (Li) creep.

[0053] Therefore, lithium dendrites generated during battery operation can be controlled to a flat shape to prevent or reduce separator rupture, thereby improving battery thermal safety.

[0054] Previously, insulating materials such as metal oxides, rather than the metal particles of this disclosure, had been coated at the edges of the negative electrode. However, although such insulating materials could form alloys with lithium, they never played a role in controlling the shape of lithium dendrites and did not provide the function of preventing or reducing membrane rupture.

[0055] Based on 100 wt% of the edge portion, metal particles alloyed with lithium may be included in an amount from about 10 wt% to about 99 wt%, for example, from about 10 wt% to about 95 wt%, from about 20 wt% to about 95 wt%, or from about 25 wt% to about 95 wt%. Within the aforementioned numerical range, the edge portion may include an optimal amount of metal particles to control the lithium dendrites to have a flat and uniform shape (e.g., substantially uniform shape).

[0056] For example, the edge portion may also include an alloy of lithium and metal particles. The alloy of lithium and metal particles may be produced by combining the metal particles with lithium that accumulates at the negative electrode as described above during battery operation.

[0057] Based on a total amount of 100 wt% metal particles and alloys, the amount may be from about 10 wt% to about 90 wt%, for example, from about 10 wt% to about 85 wt%, from about 20 wt% to about 90 wt%, or from about 30 wt% to about 90 wt% of an alloy comprising lithium and metal particles.

[0058] If (for example, when) based on a total amount of 100 wt% metal particles and alloy, with the amount of alloy as described above, the shape of lithium dendrites can be controlled to be flat and uniform (e.g., substantially uniform).

[0059] For example, the edge may also include an adhesive. The adhesive may be a non-aqueous adhesive, an aqueous adhesive, a dry adhesive, or a combination thereof.

[0060] 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.

[0061] 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, and combinations thereof.

[0062] The dry binder can be a polymeric material that is capable of being fibrous (e.g., capable of being fibrous), and can be, for example, polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, or a combination thereof.

[0063] Based on 100wt% of the edge portion, the adhesive may be included in an amount of about 1wt% to about 10wt%, for example, about 1wt% to about 8wt%, about 1wt% to about 5wt%, or about 1wt% to about 2.5wt%.

[0064] For example, the diameter of the metal particles alloyed with lithium can be from about 10 nm to about 500 nm, for example, from about 10 nm to about 400 nm, from about 10 nm to about 250 nm, or from about 10 nm to about 100 nm. For example, the diameter of the metal particles can be smaller than the diameter of the carbon-based negative electrode active material described further herein. The diameter of the metal particles can be measured as the average particle size (D0) using a laser diffraction particle size analyzer. 50 For example, by dispersing particles in a dispersion medium, introducing the dispersion into a commercially available laser diffraction device (e.g., Microtrac MT-3000), applying ultrasonic irradiation at approximately 28 kHz with 60 W, and calculating D based on 50% of the particle size distribution. 50 value.

[0065] For example, the edge portion may also include spherical (e.g., substantially spherical) graphite. The spherical graphite may be crystalline carbon, and may include spherical (e.g., substantially spherical) natural graphite, spherical (e.g., substantially spherical) synthetic graphite, or combinations thereof. For example, the spherical graphite may be Super C65, Super P, Vulcan XC-72, or combinations thereof.

[0066] If, for example, spherical graphite is also included, the pores formed between the spherical graphite particles (e.g., between the spherical graphite grains) can facilitate the passage of lithium, allowing lithium to move at a faster speed. Therefore, depending on the charging direction of the negative electrode, the likelihood of flattened lithium dendrites growing upwards from the spherical graphite increases, which can further enhance the safety of the rechargeable lithium battery.

[0067] For example, based on the total amount of 100 wt% spherical graphite and metal particles alloyed with lithium, the spherical graphite can be included in an amount of about 50 wt% to about 80 wt%, for example, about 55 wt% to about 80 wt%, or about 60 wt% to about 75 wt%. If (for example, when) the above numerical range is met, the lithium dendrites grow flat and uniformly (for example, substantially uniformly), making the thermal safety of the rechargeable lithium battery very excellent.

[0068] For example, the edge portion can be formed on the current collector in the following manner.

[0069] First, prepare the edge slurry. The edge slurry can be prepared by mixing metal particles and binder or optional spherical (e.g., approximately spherical) carbon in NMP (N-methyl-2-pyrrolidone) solvent or IPA (isopropanol) solvent.

[0070] For example, the negative electrode active material slurry can be coated onto the current collector first, and then the edge slurry can be coated onto the edge of the negative electrode active material slurry. The negative electrode active material slurry and the edge slurry can be dried and compressed together to form the edge.

[0071] As another example, the negative electrode active material slurry can be first coated, dried and compressed onto the current collector to form a negative electrode active material layer, and then the edge slurry can be separately coated, dried and compressed onto the edge of the current collector to form an edge.

[0072] The negative electrode active material layer includes a negative electrode active material and may also include a binder and / or a conductive material (e.g., an electrically conductive material).

[0073] The negative electrode active material may include materials capable of reversibly inserting / deintercalating lithium ions, lithium metal, lithium metal alloys, materials capable of doping / dedoping lithium, and / or transition metal oxides.

[0074] For example, negative electrode active materials may include carbon-based negative electrode active materials capable of reversibly inserting / deintercalating lithium ions.

[0075] For example, carbon-based negative electrode active materials may include crystalline carbon, amorphous carbon, or combinations thereof. Crystalline carbon may be graphite, such as amorphous, sheet-like, flake-like, spherical, and / or fibrous natural graphite and / or artificial graphite, while amorphous carbon may be soft carbon, hard carbon, mesophase pitch carbonization products, calcined coke, etc.

[0076] For example, the diameter of the active material in a carbon-based negative electrode can be from about 0.1 μm to about 35 μm, such as from about 0.1 μm to about 20 μm, from about 0.1 μm to about 10 μm, from about 0.1 μm to about 5 μm, or from about 0.1 μm to about 2.5 μm. The diameter of the active material in the carbon-based negative electrode can be measured as the average particle size (D) using a laser diffraction particle size analyzer. 50 For example, by dispersing particles in a dispersion medium, introducing the dispersion into a commercially available laser diffraction device (e.g., Microtrac MT-3000), applying ultrasonic irradiation at approximately 28 kHz with 60 W, and calculating D based on 50% of the particle size distribution. 50 value.

[0077] The lithium metal alloy includes an alloy of lithium and a metal selected from Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn.

[0078] The material capable of doping / dedoping lithium can be a Si-based negative electrode active material and / or a Sn-based negative electrode active material. The Si-based negative electrode active material can be silicon, a silicon-carbon composite, SiO x (0 < x ≤ 2), a Si-Q alloy (where Q is selected from alkali metals, alkaline earth metals, group 13 elements, group 14 elements (excluding Si), group 15 elements, group 16 elements, transition metals, rare earth elements, and combinations thereof), or a combination thereof. The Sn-based negative electrode active material can be Sn, SnO2, a Sn-based alloy, or a combination thereof.

[0079] The silicon-carbon composite can be a composite of silicon and amorphous carbon. According to some exemplary embodiments, the silicon-carbon composite can be in the form of silicon particles and an amorphous carbon coating on the surface of the silicon particles. For example, the silicon-carbon composite can include secondary particles (cores) assembled from silicon primary particles and an amorphous carbon coating layer (shells) on the surface of the secondary particles. Amorphous carbon can also be between the silicon primary particles, and for example, the silicon primary particles can be coated with amorphous carbon. The secondary particles can be dispersed in an amorphous carbon matrix.

[0080] The silicon-carbon composite can also include crystalline carbon. For example, the silicon-carbon composite can include a core containing crystalline carbon and silicon particles and an amorphous carbon coating layer on the surface of the core.

[0081] The Si-based negative electrode active material and / or the Sn-based negative electrode active material can be used in combination with a carbon-based negative electrode active material.

[0082] For example, the negative electrode active material layer can include about 90 wt% to about 99 wt% of the negative electrode active material, about 0.5 wt% to about 5 wt% of the binder, and about 0 wt% to about 5 wt% of the conductive material.

[0083] The binder is used to make the negative electrode active material particles adhere well to each other and also to make the negative electrode active material adhere well to the current collector. The binder can include a non-aqueous binder, an aqueous binder, a dry binder, or a combination thereof.

[0084] The non-aqueous binder can include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene-propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide, or a combination thereof.

[0085] 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, and combinations thereof.

[0086] If, for example, an aqueous binder is used as the negative electrode binder, it may also include a cellulose compound capable of imparting or increasing 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, and / or Li.

[0087] The dry binder can be a polymeric material that is capable of being fibrous (e.g., capable of being fibrous), and can be, for example, polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, or a combination thereof.

[0088] Conductive materials are included to provide electrode conductivity (e.g., electrical conductivity), and any suitable electrically conductive material can be used as a conductive material unless it causes a chemical change (e.g., an undesirable chemical change in a rechargeable lithium battery). Examples of conductive materials include: carbon-based materials such as natural graphite, synthetic graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanofibers, carbon nanotubes, etc.; metallic materials such as metal powders and / or metal fibers, including copper, nickel, aluminum, silver, etc.; conductive polymers (e.g., electrically conductive polymers), such as polyphenylene derivatives; or mixtures thereof.

[0089] The negative electrode current collector can be selected from copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, polymer substrate coated with a conductive metal (e.g., electrically conductive metal), and combinations thereof.

[0090] Rechargeable lithium batteries In some example embodiments, the rechargeable lithium battery includes: the aforementioned negative electrode; a positive electrode; and a separator between the positive and negative electrodes. Because lithium dendrites grow uniformly in a flat shape when the battery is in operation (e.g., when), a rechargeable lithium battery including a negative electrode can have excellent battery thermal safety.

[0091] Rechargeable lithium batteries can be classified according to their shape, such as cylindrical, prismatic, pouch-shaped, and coin-shaped. Figures 3 to 6 This is a schematic diagram illustrating a rechargeable lithium battery according to some example embodiments. Figure 3 A cylindrical battery is shown. Figure 4A prismatic battery is shown. Figure 5 and Figure 6 A pouch-type battery is shown.

[0092] Reference Figures 3 to 6 The rechargeable lithium battery 100 includes an electrode assembly 40 and a housing therein containing the electrode assembly 40. The electrode assembly 40 includes a separator 30 between a positive electrode 10 and a negative electrode 20. The positive electrode 10, the negative electrode 20, and the separator 30 may be impregnated with an electrolyte.

[0093] like Figure 3 As shown, the rechargeable lithium battery 100 may include a sealing member 60 of the sealed housing 50. Figure 4 In this context, 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. For example... Figure 5 and Figure 6 As shown, the rechargeable lithium battery 100 includes electrode terminals 70 that serve as electrical paths to guide current formed in the electrode assembly 40 to the outside. Figure 6 For example, positive electrode terminal 71 and negative electrode terminal 72 ( Figure 5 ).

[0094] Rechargeable lithium batteries according to some example embodiments can be used in automobiles, mobile phones and / or various types (or kinds) of electrical devices, but this disclosure is not limited thereto.

[0095] The components constituting a rechargeable lithium battery, other than the aforementioned negative electrode, are described in more detail below.

[0096] positive electrode The positive electrode for a rechargeable lithium battery may include a current collector and a layer of positive electrode active material on the current collector. The positive electrode active material layer includes positive electrode active material and may also include a binder and / or a conductive material (e.g., an electrically conductive material).

[0097] For example, the positive electrode may also include additives that can act as a sacrificial positive electrode.

[0098] As the positive electrode active material, compounds capable of intercalating and deintercalating lithium (lithium-intercalating compounds) can be used. For example, a composite oxide of lithium and at least one metal selected from cobalt, manganese, nickel and combinations thereof can be used.

[0099] The composite oxide can be a lithium transition metal composite oxide, and examples of it can include lithium nickel oxides, lithium cobalt oxides, lithium manganese oxides, lithium iron phosphate compounds, cobalt-free lithium nickel manganese oxides, or combinations thereof.

[0100] As an example, a compound represented by any of the following chemical formulas can 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); and Li aFePO4 (0.90≤a≤1.8).

[0101] 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, rare earth elements, 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 It is Mn, Al, or a combination thereof.

[0102] For example, the positive electrode active material can be a high-nickel positive electrode active material. In a high-nickel positive electrode active material, based on 100 mol% of metals other than lithium in the lithium transition metal composite oxide, the nickel content 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.

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

[0104] The binder is used to ensure good adhesion between the positive electrode active material particles and also to ensure good adhesion of the positive electrode active material to the current collector. Examples of binders may include, but are not limited to, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing 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.

[0105] Conductive materials are used to impart electrical conductivity (e.g., conductivity) to electrodes and can be any suitable material that does not cause chemical changes in the battery (e.g., does not cause undesirable chemical changes in a rechargeable lithium battery) and conducts electrons. Examples of conductive materials can include: carbon-based materials such as natural graphite, synthetic graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanofibers, and carbon nanotubes; metallic materials in the form of metal powders and / or metal fibers, including copper, nickel, aluminum, silver, etc.; conductive polymers (e.g., electrically conductive polymers), such as polyphenylene derivatives; or mixtures thereof.

[0106] The current collector may include, but is not limited to, Al.

[0107] electrolyte Electrolytes used in rechargeable lithium batteries include non-aqueous organic solvents and lithium salts.

[0108] Non-aqueous organic solvents are used as media for transporting ions that participate in the electrochemical reactions of the battery.

[0109] Non-aqueous organic solvents can be carbonate solvents, ester solvents, ether solvents, ketone solvents, alcohol solvents, aprotic solvents, or combinations thereof.

[0110] 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), butyl carbonate (BC), etc. Ester solvents may include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanolactone, mevalonolactone, valproic acid lactone, caprolactone, etc. Ether solvents may include dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, tetrahydrofuran, etc. In the examples, ketone solvents may include cyclohexanone, etc. Alcohol solvents may include ethanol, isopropanol, etc., and 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 and / or ether bonds, etc.); amides, such as dimethylformamide; dioxolane, such as 1,3-dioxolane, 1,4-dioxolane, etc.; sulfolane, etc.

[0111] Non-aqueous organic solvents can be used alone or in mixtures of two or more types (or kinds).

[0112] In the embodiments, if (for example, when) a carbonate solvent is used, cyclic carbonates and chain carbonates can be mixed and used, and the cyclic carbonates and chain carbonates can be mixed in a volume ratio of about 1:1 to about 1:9.

[0113] Lithium salts dissolved in organic solvents supply lithium ions in batteries, enabling basic operation of rechargeable lithium batteries 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, and LiN(C x F 2x+1 SO2)(C y F 2y+1 At least one of the following: (SO2) (x and y are integers from 1 to 20), lithium trifluoromethane sulfonate, lithium tetrafluoroethane sulfonate, lithium difluorobis(oxalate)phosphate (LiDFBOP), lithium difluoro(oxalate)borate (LiDFOB), and lithium bis(oxalate)borate (LiBOB).

[0114] diaphragm Depending on the type (or category) of the rechargeable lithium battery, a separator may be present between the positive and negative electrodes. The separator may include polyethylene, polypropylene, polyvinylidene fluoride, or a multilayer membrane of two or more layers thereof (e.g., mixed multilayer membranes, such as polyethylene / polypropylene two-layer separators, polyethylene / polypropylene / polyethylene three-layer separators, polypropylene / polypropylene / polypropylene three-layer separators, etc.).

[0115] The membrane may include a porous substrate and a coating layer on one or two surfaces (e.g., two opposing surfaces) of the porous substrate, comprising organic materials, inorganic materials, or combinations thereof.

[0116] The porous substrate can be a polymer membrane formed from any polymer selected from the following polymers: polyolefins (such as polyethylene and polypropylene), polyesters (such as polyethylene terephthalate and polybutylene terephthalate), polyacetals, polyamides, polyimides, polycarbonates, polyetherketones, polyaryletherketones, polyetherimides, polyamideimides, polybenzimidazoles, polyethersulfones, polyphenylene ethers, cyclic olefin copolymers, polyphenylene sulfide, polyethylene naphthalate, glass fibers, and polytetrafluoroethylene (e.g., TEFLON). ® ( ) or copolymers or mixtures of two or more of them.

[0117] Organic materials may include polyvinylidene fluoride polymers and / or (meth)acrylic acid polymers.

[0118] Inorganic materials may include, but are not limited to, 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.

[0119] Organic and inorganic materials can be mixed in a single coating layer, or coating layers comprising organic materials and coating layers comprising inorganic materials can be stacked.

[0120] Examples and comparative examples of this disclosure are described below. However, the following examples are merely examples of this disclosure, and this disclosure is not limited to these examples.

[0121] (Example) Example 1-1 A negative electrode active material slurry was prepared by mixing 97.5 wt% artificial graphite (diameter: 1 μm), 1.0 wt% carboxymethyl cellulose, and 1.5 wt% styrene-butadiene rubber (SBR) in an aqueous solvent. The negative electrode active material slurry was coated onto a copper current collector, then dried and compressed to form a negative electrode active material layer.

[0122] Subsequently, 90 wt% Ag particles (50 nm in diameter) and 10 wt% polyvinylidene fluoride binder were mixed in NMP (N-methyl-2-pyrrolidone) solvent to prepare a slurry for the edge portion. The edge portion slurry was applied to the edge of the negative electrode active material layer formed on the copper current collector, and then dried and compressed to form the edge portion.

[0123] Subsequently, 96 wt% LiCoO2, 2 wt% Ketjen black, and 2 wt% polyvinylidene fluoride were mixed in N-methyl-2-pyrrolidone solvent to prepare a positive electrode active material slurry. The positive electrode active material slurry was coated onto an Al current collector, then dried and compressed to fabricate the positive electrode.

[0124] The positive and negative electrodes are used together with a polyethylene separator and an electrolyte prepared by dissolving 1.15 M LiPF6 in a mixed solvent of EC (ethylene carbonate): EMC (ethyl methyl carbonate): DMC (dimethyl carbonate) (volume ratio = 3:3:4) to manufacture a rechargeable lithium battery cell according to Example 1.

[0125] Example 1-2 The rechargeable lithium-ion battery cell is manufactured in essentially the same manner as in Example 1-1, except that a slurry for the edge portion is prepared by mixing 25 wt% Ag particles (50 nm in diameter), 10 wt% polyvinylidene fluoride binder, and 65 wt% spherical graphite (super C65) in NMP solvent.

[0126] Example 2-1 The rechargeable lithium battery cell of Example 2-1 is manufactured in essentially the same manner as in Example 1-1, except that Sn particles (diameter: 100nm) are used instead of Ag particles in the edge portion.

[0127] Example 2-2 The rechargeable lithium battery cell of Example 2-2 is manufactured in essentially the same manner as in Examples 1-2, except that Sn particles (diameter: 100nm) are used instead of Ag particles in the edge portion.

[0128] Example 3-1 The rechargeable lithium battery cell of Example 3-1 is manufactured in essentially the same manner as in Example 1-1, except that Bi particles (diameter: 100nm) are used instead of Ag particles in the edge portion.

[0129] Example 3-2 The rechargeable lithium battery cell of Example 3-2 is manufactured in essentially the same manner as in Examples 1-2, except that Bi particles (diameter: 100nm) are used instead of Ag particles in the edge portion.

[0130] Example 4-1 The rechargeable lithium battery cell of Example 4-1 is manufactured in essentially the same manner as in Example 1-1, except that Zn particles (diameter: 100nm) are used instead of Ag particles in the edge portion.

[0131] Example 4-2 The rechargeable lithium battery cell of Example 4-2 is manufactured in essentially the same manner as in Examples 1-2, except that Zn particles (diameter: 100nm) are used instead of Ag particles in the edge portion.

[0132] Example 5 The rechargeable lithium battery cell of Example 5 is manufactured in essentially the same manner as in Example 1-1, except that Mg particles (diameter: 100nm) are used instead of Ag particles in the edge portion.

[0133] Evaluation Example Evaluation Example 1: Evaluation of Lithium Dendrite Shape Figure 7 This is a SEM image of a portion of the cross-section of the edge of the negative electrode of a rechargeable lithium-ion battery cell according to Example 1-1. Figure 8 This is a SEM image of a portion of the cross-section of the edge of the negative electrode of a rechargeable lithium battery cell according to Example 1-2.

[0134] Reference Figure 7 It can be seen that the flattened lithium dendrites grow downwards from the Ag particles along the charging direction, and referencing... Figure 8 As can be seen, the flat lithium dendrites grow upwards from the Ag particles and spherical graphite along the charging direction.

[0135] Figure 9 This is a SEM image of a portion of the cross-section of the edge of the negative electrode of a rechargeable lithium-ion battery cell according to Example 2-1. Figure 10 This is a SEM image of a portion of the cross-section of the edge of the negative electrode of a rechargeable lithium battery cell according to Example 2-2.

[0136] Reference Figure 9 It can be seen that the flat lithium dendrites grow downwards from the Sn particles along the charging direction, and referencing... Figure 10 As can be seen, flat lithium dendrites grow upwards from the Sn particles and spherical graphite along the charging direction.

[0137] Figure 11 This is a SEM image of a portion of the cross-section of the edge of the negative electrode of a rechargeable lithium-ion battery cell, based on Example 3-1. Figure 12 This is a SEM image of a portion of the cross-section of the edge of the negative electrode of a rechargeable lithium battery cell according to Example 3-2.

[0138] Reference Figure 11 It can be seen that flat lithium dendrites grow upwards from the Bi particles along the charging direction, and referencing... Figure 12 As can be seen, flat lithium dendrites grow upwards from Bi particles and spherical graphite along the charging direction.

[0139] Figure 13 This is a SEM image of a portion of the cross-section of the edge of the negative electrode of a rechargeable lithium-ion battery cell, based on Example 4-1. Figure 14 This is a SEM image of a portion of the cross-section of the edge of the negative electrode of a rechargeable lithium battery cell according to Example 4-2.

[0140] Reference Figure 13 It can be seen that the flat lithium dendrites grow downwards from the Zn particles along the charging direction, and referencing... Figure 14 As can be seen, the flat lithium dendrites grow downwards from the Zn particles and spherical graphite along the charging direction.

[0141] Figure 15 This is a SEM image of a portion of the cross-section of the edge of the negative electrode of the rechargeable lithium-ion battery cell according to Example 5. (Refer to...) Figure 15 As can be seen, the flat lithium dendrites grow upward from the Mg particles along the charging direction.

[0142] In summary, Examples 1-1, 1-2, 2-1, 2-2, 3-1, 3-2, 4-1, 4-2, and 5 demonstrate that as lithium metal and metal particles form an alloy, flat-shaped lithium dendrites grow uniformly, effectively preventing membrane rupture.

[0143] While the subject matter of this disclosure has been described in conjunction with what are now considered practical exemplary embodiments, it will be understood that this disclosure is not limited to the disclosed embodiments. Rather, it is intended to cover various suitable modifications and equivalent arrangements included within the spirit and scope of the appended claims.

[0144] Description of reference numerals in the attached figures 20: Negative electrode 1: Negative electrode current collector 2: Negative electrode active material layer 3: Edges 100: Rechargeable lithium battery 10: Positive electrode 11: Positive electrode lead connector 12: Positive electrode terminal 21: Negative electrode lead connector 22: Negative electrode terminal 30: Diaphragm 40: Electrode assembly 50: Casing 60: Sealing component 70: Electrode connector 71: Positive electrode connector 72: Negative electrode connector.

Claims

1. A negative electrode, the negative electrode comprising: Negative electrode current collector; A negative electrode active material layer is present on the negative electrode current collector and includes negative electrode active material. as well as The edge portion is located on the negative electrode current collector and at the edge of the negative electrode active material layer. The edge portion includes metal particles that form an alloy with lithium.

2. The negative electrode according to claim 1, wherein: The metal particles that form an alloy with lithium include Ag, Sn, Bi, Zn, Mg, In, Al, or combinations thereof.

3. The negative electrode according to claim 1, wherein: The metal particles have the same or similar lattice parameters as lithium.

4. The negative electrode according to claim 1, wherein: Based on 100 wt% of the edge portion, the metal particles are included in an amount ranging from 10 wt% to 99 wt% in an alloy with lithium.

5. The negative electrode according to claim 1, wherein: The edge portion also includes an alloy of lithium and the metal particles.

6. The negative electrode according to claim 5, wherein: The alloy is included in an amount of 10 wt% to 90 wt% based on the total amount of the metal particles and the alloy.

7. The negative electrode according to claim 1, wherein: The diameter of the metal particles that form an alloy with lithium is from 10 nm to 500 nm.

8. The negative electrode according to claim 1, wherein: The edge portion also includes spherical graphite.

9. The negative electrode according to claim 8, wherein: Based on the total amount of the metal particles and the spherical graphite (100 wt%), the spherical graphite is included in an amount of 50 wt% to 80 wt%.

10. The negative electrode according to claim 1, wherein: The negative electrode active material includes carbon-based negative electrode active materials.

11. The negative electrode according to claim 10, wherein: The diameter of the carbon-based negative electrode active material is from 0.1 μm to 35 μm.

12. The negative electrode according to claim 1, wherein: The edge portion also includes an adhesive, and The adhesive includes non-aqueous adhesives, aqueous adhesives, dry adhesives, or combinations thereof.

13. A negative electrode, the negative electrode comprising: Negative electrode current collector; as well as An uncoated area, a first area, a second area, and a third area are sequentially arranged on the negative electrode current collector in a direction parallel to the negative electrode current collector. The first region includes metal particles that form an alloy with lithium. The second region includes the metal particles alloyed with lithium and the negative electrode active material, and The third region includes the negative electrode active material.

14. The negative electrode according to claim 13, wherein: The metal particles that form an alloy with lithium include Ag, Sn, Bi, Zn, Mg, In, Al, or combinations thereof.

15. The negative electrode according to claim 13, wherein: The metal particles have the same or similar lattice parameters as lithium.

16. The negative electrode according to claim 13, wherein: The diameter of the metal particles that form an alloy with lithium is from 10 nm to 500 nm.

17. The negative electrode according to claim 13, wherein: The negative electrode active material includes carbon-based negative electrode active materials.

18. The negative electrode according to claim 17, wherein: The diameter of the carbon-based negative electrode active material is from 0.1 μm to 35 μm.

19. The negative electrode according to claim 13, wherein, The uncoated area does not include the negative electrode active material.

20. A rechargeable lithium battery, said rechargeable lithium battery comprising: The negative electrode according to any one of claims 1 to 19; Positive electrode, including positive electrode active material; as well as A diaphragm is located between the positive electrode and the negative electrode.

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