Positive electrode active material, method for preparing same, positive electrode, rechargeable lithium battery, and all-solid-state rechargeable battery

Abstract

The present application provides a method for preparing a positive electrode active material, a positive electrode active material, a positive electrode, a rechargeable lithium battery, and an all-solid-state rechargeable battery. A method of preparing a positive electrode active material includes mixing a nickel manganese-based composite hydroxide and a lithium raw material, and subjecting them to a primary heat treatment at about 200 DEG C to about 350 DEG C and a secondary heat treatment at about 800 DEG C to about 1000 DEG C.

Description

Technical Field

[0001] According to one or more embodiments, the present disclosure relates to a positive electrode active material, a method for preparing the same, a positive electrode including the positive electrode active material, and a rechargeable lithium battery and an all-solid-state rechargeable battery including the positive electrode. Background Art

[0002] Portable information devices (such as, cellular phones, laptop computers, smart phones, etc.) and / or electric vehicles may use a rechargeable lithium battery having a relatively high energy density and relatively high portability (e.g., easy portability) as a driving power source. Recently, research has been actively conducted to use a rechargeable lithium battery having a relatively high energy density as a driving power source for a hybrid vehicle and / or an electric vehicle, or as a power storage source for residential power storage (e.g., a power wall).

[0003] One or more suitable positive electrode active materials have been studied to obtain or implement a rechargeable lithium battery for these uses. That is, various suitable positive electrode active materials have been studied to develop a rechargeable lithium battery for these applications. Among them, lithium nickel-based oxides, lithium nickel manganese cobalt composite oxides, lithium nickel cobalt aluminum composite oxides, and lithium cobalt-based oxides are mainly (primarily) used as positive electrode active materials. However, although the demand for large-sized, high-capacity, or high-energy density rechargeable lithium batteries has recently increased, the supply of positive electrode active materials including cobalt (a rare metal) is expected to be severely short. For example, since cobalt is expensive and the remaining reserves are not much, it is desired (or necessary) to develop a positive electrode active material that does not contain cobalt or reduces its content (e.g., significantly reduces). Summary of the Invention

[0004] One or more aspects relate to a positive electrode active material including a lithium nickel manganese-based composite oxide. In the positive electrode active material, cation mixing is reduced and lithium ion diffusion is promoted to improve capacity, efficiency, and rate capability, and structural stability is enhanced to improve cycle life characteristics.

[0005] One or more aspects relate to a method for preparing a positive electrode active material, which includes: mixing a nickel manganese-based composite hydroxide and a lithium raw material, applying a primary heat treatment at about 200°C to about 350°C, and applying a secondary heat treatment at about 800°C to about 1000°C.

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

[0007] One or more embodiments provide a positive electrode active material including a layered lithium nickel manganese-based composite oxide represented by Chemical Formula 1.

[0008] Chemical Formula 1

[0009] Li a1 Ni x1 Mn y1 M 1 z1 M 2 w1 O 2-b1 X b1

[0010] In Chemical Formula 1, 0.9 ≤ a1 ≤ 1.2, 0.7 ≤ x1 ≤ 0.8, 0.2 ≤ y1 ≤ 0.3, 0 ≤ z1 ≤ 0.05, 0 ≤ w1 ≤ 0.05, 0.9 ≤ x1 + y1 + z1 + w1 ≤ 1.1, 0 ≤ b1 ≤ 0.1, M 1 is Co, M 2 is at least one element selected from Al, B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ti, V, W, and Zr, and X is at least one element selected from F, P, and S.

[0011] One or more embodiments provide a positive electrode for a rechargeable lithium battery, which includes a positive electrode active material.

[0012] One or more embodiments provide a rechargeable lithium battery, which includes a positive electrode, a negative electrode, and an electrolyte. One or more embodiments provide a all-solid-state rechargeable battery, which includes a positive electrode, a negative electrode, and a solid electrolyte layer between the positive electrode and the negative electrode.

[0013] The positive electrode active material according to one or more embodiments increases or maximizes the capacity while minimizing or reducing the production cost, reduces cation mixing, promotes the diffusion of lithium ions, improves the charge and discharge efficiency and high-rate capability, and ensures the structural stability to guarantee the high-temperature cycle life characteristics. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figures 1 to 4 Each is a schematic diagram schematically showing a rechargeable lithium battery according to one or more embodiments.

[0015] Figure 5 is a heat treatment temperature curve of the positive electrode active material according to Comparative Example 1 depending on a one-step (e.g., action or task) synthesis method.

[0016] Figure 6 is a heat treatment temperature curve of the positive electrode active material according to Example 2 depending on a two-step (e.g., action or task) synthesis method.

[0017] Figure 7The scanning electron microscope (SEM) image (lower part) and transmission X-ray microscope (TXM) analysis image (upper part) showing the cross section of the positive electrode active material prepared in Comparative Example 1 cut by a focused ion beam (FIB) are shown.

[0018] Figure 8 The SEM image (lower part) and TXM analysis image (upper part) showing the cross section of the positive electrode active material prepared in Example 2 cut by FIB are shown.

[0019] Figure 9 A graph showing the internal porosity of the positive electrode active materials of Comparative Example 1 and Example 2 is shown.

[0020] Figure 10 A graph for the rate evaluation of the rechargeable lithium battery cells of Comparative Example 1 and Example 2 is shown.

[0021] Figure 11 A differential thermogravimetry-differential scanning calorimetry (DTG-DSC) analysis chart of a transition metal hydroxide sample (upper part) and a DTG-DSC analysis chart of a mixed sample of a transition metal hydroxide and lithium hydroxide (lower part) are shown.

[0022] Figure 12 For Figure 11 An enlarged view of the region of about 200 °C to 350 °C in

[0023] Reference numerals

[0024] 100: Rechargeable lithium battery 10: Positive electrode

[0025] 11: Positive electrode lead tab 12: Positive electrode terminal

[0026] 20: Negative electrode 21: Negative electrode lead tab

[0027] 22: Negative electrode terminal 30: Separator

[0028] 40: Electrode assembly 50: Housing

[0029] 60: Sealing member 70: Electrode tab

[0030] 71: Positive electrode tab 72: Negative electrode tab Detailed description of the embodiments

[0031] Hereinafter, specific embodiments will be described in more detail so that those of ordinary skill in the art can easily implement them. Examples of the embodiments are illustrated in the accompanying drawings and are described by referring to the drawings to explain aspects of the present description. However, the present disclosure may be implemented in many different forms and should not be construed as limited to the example embodiments stated herein, but the present disclosure is defined by the scope of the claims.

[0032] The terms used herein are for the purpose of describing embodiments only and are not intended to limit the disclosure. Singular expressions "a", "an", and "the" include plural expressions, including "at least one", unless the context clearly indicates otherwise.

[0033] As used herein, "a combination thereof" refers to a mixture, laminate, composite, copolymer, alloy, blend, reaction product, etc. of the respective components.

[0034] In this document, it should be understood that terms such as "comprises", "comprise", "comprising", "includes", "including", "include", "having", "has", and / or "have" are intended to specify the presence of the implemented aspects, quantities, steps (e.g., actions or tasks), elements, and / or their (e.g., any suitable) combinations, but they do not exclude the possibility of the presence or addition of one or more other aspects, quantities, steps (e.g., actions or tasks), elements, and / or their (e.g., any suitable) combinations.

[0035] In the drawings, for clarity, the thickness of layers, films, panels, regions, etc. is exaggerated, and the same reference numerals throughout the drawings denote the same elements, and their repeated description may not be provided in the specification. 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, it may be directly on the other element or an intervening element may also be present. In contrast, if (e.g., when) an element is referred to as "directly on" another element, there is no intervening element.

[0036] The term "layer" as used herein includes not only a shape formed over the entire surface when viewed in plan view (e.g., when), but also a shape formed over a partial surface.

[0037] It will be understood that although the terms "first", "second", "third", etc. may be used herein to describe one or more suitable elements, components, regions, layers, and / or parts, these elements, components, regions, layers, and / or parts should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer, or part from another element, component, region, layer, or part. Thus, without departing from the teachings set forth herein, a first element, component, region, layer, or part described herein may be referred to as a second element, component, region, layer, or part.

[0038] As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items. For example, the phrases "at least one of...", "one of...", and "selected from..." modify the entire list of elements when (e.g., if) they are before or after a list of elements and do not modify individual elements of the list. For example, the phrases "at least one of a to c", "at least one of a, b, and c", and "selected from at least one of a, b, and c" may indicate only a, only b, only c, both a and b (e.g., simultaneously), both a and c (e.g., simultaneously), both b and c (e.g., simultaneously), all of a, b, and c, or variations thereof.

[0039] Spatial relative terms, such as "beneath", "below", "lower", "above", "upper", etc., may be used herein to easily describe one element or feature's relationship to another element or feature. It will be understood that the spatial relative terms are intended to cover different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if (e.g., when) the device in the figures is flipped, an element described as "beneath" or "below" another element or feature will then be oriented "above" the other element or feature. Thus, the example term "beneath" can cover both an orientation of above and below (e.g., simultaneously). The device may be otherwise oriented (rotated 90 degrees or at other orientations), and the spatial relative terms used herein may be interpreted accordingly.

[0040] The terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the disclosure. Unless otherwise defined, all terms used herein (including chemical terms, technical terms, and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and this disclosure and will not be interpreted in an idealized or overly formal sense.

[0041] Example embodiments are described herein with reference to cross-sectional views that are schematic illustrations of idealized embodiments. As such, variations in the shapes of the illustrations due to, for example, manufacturing techniques and / or tolerances are to be expected. Accordingly, the embodiments described herein should not be construed as limited to the particular shapes of regions illustrated herein but should include deviations in shapes that result, for example, from manufacturing. For example, regions that are illustrated or described as flat will typically have rough and / or non-linear features. Also, the sharp corners illustrated may be rounded. Thus, the regions illustrated in the figures are schematic in nature, and their shapes are not intended to illustrate the precise shape of a region and are not intended to limit the scope of the claims.

[0042] The term "may" will be understood to refer to "one or more embodiments of the present disclosure", where some embodiments include the described element, and some embodiments do not include the element and / or include alternative elements. Similarly, alternative language such as "or" refers to "one or more embodiments of the present disclosure" each including the respective listed items.

[0043] In this context, "consisting essentially of" indicates that any additional components do not materially affect the chemical, physical, optical, or electrical properties of the target part.

[0044] Further, in this specification, the phrase "in a plane" or "plan view" indicates observing the target part from the top, and the phrase "in a cross-section" indicates observing a cross-section formed by vertically cutting the target part from the side.

[0045] Definitions

[0046] As used herein, the term "particle size" refers to the average diameter of a particle if (e.g., when) the particle is spherical, and refers to the average major axis length of a particle if (e.g., when) the particle is non-spherical. For example, the average particle size can be measured by methods suitable for those skilled in the art, e.g., by a particle size analyzer or by transmission electron microscopy images or scanning electron microscopy images. In one or more embodiments, by using the dynamic light scattering method for measurement, performing data analysis, counting the number of particles in each particle size range, and thus performing calculations, an average particle size value can be obtained. Unless otherwise defined, the average particle size (D 50 ) may refer to the diameter of the particle with a cumulative volume of 50% by volume in the particle size distribution. If (e.g., when) measured by laser diffraction, more specifically, the particles to be measured are dispersed in a dispersion medium, and then introduced into a laser diffraction particle size measuring device of the related art (e.g., MT 3000 available from Microtrac, Ltd.) using ultrasonic waves of about 28 kHz, and after irradiating with an output power of 60 W, the average particle size (D 50 ) based on 50% of the particle size distribution in the measuring device can be calculated. If (e.g., when) not otherwise provided with a limitation, then as used herein, the average particle size (D 50 ) refers to the diameter of the particle with a cumulative volume of 50% by volume in the particle size distribution obtained by randomly measuring the sizes (diameter or major axis length) of about 20 particles in a scanning electron microscope image.

[0047] As used herein, the term "or" is not interpreted in an exclusive sense, e.g., "A or B" is interpreted to include A, B, A + B, etc.

[0048] In this text, the term "metal" is interpreted to include the concepts of common metals, transition metals, and metalloids (semi-metals).

[0049] Method for preparing a positive electrode active material

[0050] In one or more embodiments, the method for preparing a positive electrode active material includes: mixing a nickel-manganese composite hydroxide and a lithium raw material, applying a primary heat treatment at about 200 °C to about 350 °C (e.g., subjecting them to a primary heat treatment), and applying a secondary heat treatment at about 800 °C to about 1000 °C.

[0051] Due to the recent significant increase in the price of cobalt (a rare metal), there is a demand to develop positive electrode active materials that do not contain cobalt or have reduced content thereof (e.g., amount). Among them, positive electrode active materials having an olivine crystal structure (such as lithium iron phosphate (LFP), lithium manganese phosphate (LMP), lithium manganese iron phosphate (LMFP), etc.) or a spinel crystal structure (such as lithium manganese oxide (LMO), etc.) are each limited in achieving high capacity due to the small amount of available lithium in the structure. Layered lithium nickel manganese-based positive electrode active materials have excellent or appropriate capacity and efficiency characteristics due to the high amount of available lithium in the structure, making them suitable as materials for high-capacity batteries. However, since cobalt, which plays a key role in the layered structure, is removed, the structural stability is reduced, the resistance increases, and it becomes difficult to ensure long cycle life characteristics. Cobalt is suitable for promoting or plays an important role in reducing cationic disorder occurring within the structure. If (e.g., when) cobalt is replaced by Mn, then Ni 3+ Due to Mn 4+ is reduced, resulting in an increase in Ni 2+ ions (e.g., cations), and causing deterioration (e.g., increase) of cationic disorder. If (e.g., when) cationic disorder becomes deteriorated (e.g., increased), then Ni 2+ ions can replace lithium, hindering (e.g., reducing) the diffusion of lithium ions. As a result, the discharge capacity is reduced and the rate capability is deteriorated compared to materials with less deteriorated (e.g., less) cationic disorder.

[0052] Generally, when synthesizing a positive electrode active material, it is suitable that the decomposition reaction of a transition metal hydroxide (which is a precursor of the positive electrode active material) and the insertion (or lithiation) reaction of lithium can each occur at substantially similar temperatures. That is, when synthesizing a positive electrode active material, the decomposition reaction of a transition metal hydroxide (a precursor of the positive electrode active material) and the insertion (or lithiation) reaction of lithium can occur at substantially similar temperatures. Here, when heat-treating a mixture of a transition metal hydroxide and a lithium raw material, one or more embodiments provide a method of performing a primary heat treatment in a temperature range (e.g., preheating) where the insertion reaction of lithium occurs but the decomposition reaction of the transition metal hydroxide does not occur (e.g., not firing them continuously in a substantially same (e.g., preheating) temperature range), and then performing a secondary (e.g., final) heat treatment in a high temperature range. That is, the embodiments provide a method of heat-treating a mixture of a transition metal hydroxide and a lithium raw material. The method includes performing a primary heat treatment in a temperature range where the insertion reaction of lithium occurs but the decomposition reaction of the transition metal hydroxide does not occur. Subsequently, a secondary heat treatment is performed in a higher temperature range. This synthesis method can reduce the cation disorder of the layered lithium nickel manganese composite oxide, thus promoting the diffusion of lithium ions to improve the capacity, efficiency, and high-rate capability and reducing the voids inside the particles, thus improving or ensuring the structural stability to improve the high-temperature cycle life characteristics.

[0053] The primary heat treatment can be referred to as a preheating treatment or an intermediate heat treatment, which can occur in a temperature range where the nickel manganese composite hydroxide does not decompose but the lithium insertion reaction occurs. The primary heat treatment can be performed in a temperature range of about 200 °C to about 350 °C, for example, about 220 °C to about 350 °C, about 220 °C to about 300 °C, or about 250 °C to about 300 °C. After performing the primary heat treatment in the described temperature range, if (e.g., when) a secondary heat treatment is subsequently performed to synthesize the layered lithium nickel manganese positive electrode active material, the cation mixing and the pores inside the particles can be reduced to ensure the structural stability, thus improving the capacity, efficiency, rate capability, and cycle life characteristics of the rechargeable lithium battery.

[0054] The primary heat treatment can be performed in an oxygen atmosphere for about 0.5 hours to about 5 hours, for example, about 1 hour to about 4 hours, or about 1 hour to about 3 hours. If (e.g., when) the primary heat treatment is performed within the described time range, the cation mixing and the voids inside the particles can be reduced to improve or ensure the structural stability. For example, if (e.g., when) the primary heat treatment time is too long (e.g., longer than the above time range), the cation mixing will not be reduced, or the structural stability will not be improved.

[0055] The secondary heat treatment can be expressed as or referred to as the main heat treatment or the final heat treatment, and is carried out at about 800 °C to about 1000 °C, for example, about 800 °C to about 950 °C, about 820 °C to about 900 °C or about 820 °C to about 880 °C. In some embodiments, the secondary heat treatment can be carried out in an oxygen atmosphere for about 4 hours to about 12 hours, about 4 hours to about 8 hours or about 4 hours to about 6 hours. The conditions of the secondary heat treatment (such as temperature, time, etc.) can be adjusted within these ranges respectively to provide a positive electrode active material with improved structural stability by reducing cation mixing and voids in the structure.

[0056] For example, the primary heat treatment time can be less than (e.g., shorter than) the secondary heat treatment time. For example, the ratio of the primary heat treatment time to the secondary heat treatment time can be about 1:2 to about 1:5. The primary heat treatment time and the secondary heat treatment time can be appropriately or suitably adjusted to provide a positive electrode active material with reduced cation disorder and improved structural stability.

[0057] Relative to the total metal of the nickel-manganese composite hydroxide, the nickel-manganese composite hydroxide can have, for example, a nickel content (e.g., amount) of about 70 mol% to about 80 mol%, for example, about 72 mol% to about 78 mol% or about 73 mol% to about 77 mol%. Additionally, in the nickel-manganese composite hydroxide, the manganese content (e.g., amount) relative to the total metal of the nickel-manganese composite hydroxide can be about 20 mol% to about 30 mol%, for example, about 22 mol% to about 28 mol% or about 23 mol% to about 27 mol%.

[0058] For example, the nickel-manganese composite hydroxide can be represented by Chemical Formula 11.

[0059] Chemical Formula 11

[0060] Ni x11 Mn y11 M 1 z11 M 2 w11 (OH)2

[0061] In Chemical Formula 11, 0.7 ≤ x11 ≤ 0.8, 0.2 ≤ y11 ≤ 0.3, 0 ≤ z11 ≤ 0.05, 0 ≤ w11 ≤ 0.05, and 0.9 ≤ x11 + y11 + z11 + w11 ≤ 1.1, and M 1 is Co, and M 2 is at least one (e.g., one or more) element selected from Al, B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ti, V, W, and Zr.

[0062] In Chemical Formula 11, for example, 0.73 ≤ x11 ≤ 0.77 and 0.23 ≤ y11 ≤ 0.27, and 0 ≤ z11 ≤ 0.01, or z11 = 0.

[0063] The nickel-manganese composite hydroxide may be in the form of particles and may have an average particle diameter (D 50 ) of from about 8 micrometers (μm) to about 20 μm, for example, from about 8 μm to about 18 μm, from about 8 μm to about 16 μm, from about 8 μm to about 14 μm, or from about 8 μm to about 12 μm. Additionally, the nickel-manganese composite hydroxide may be in the form of secondary particles formed by aggregating a plurality of primary particles. For example, the secondary particles may (e.g., each) be an aggregate of a plurality of primary particles.

[0064] In the foregoing preparation method, the molar ratio of lithium in the lithium raw material to the total metal of the nickel-manganese composite hydroxide may be, for example, from about 1.0 to about 1.2, from about 1.01 to about 1.15, or from about 1.03 to about 1.1.

[0065] Positive electrode active material

[0066] In one or more embodiments, there is provided a positive electrode active material prepared by the foregoing method.

[0067] In one embodiment, there is provided a positive electrode active material comprising a layered lithium nickel-manganese composite oxide represented by Chemical Formula 1.

[0068] Chemical Formula 1

[0069] Li a1 Ni x1 Mn y1 M 1 z1 M 2 w1 O 2-b1 X b1

[0070] In Chemical Formula 1, 0.9 ≤ a1 ≤ 1.2, 0.7 ≤ x1 ≤ 0.8, 0.2 ≤ y1 ≤ 0.3, 0 ≤ z1 ≤ 0.05, 0 ≤ w1 ≤ 0.05, 0.9 ≤ x1 + y1 + z1 + w1 ≤ 1.1, and 0 ≤ b1 ≤ 0.1, M 1 is Co, M 2 is at least one (e.g., one or more) element selected from Al, B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ti, V, W, and Zr, and X is at least one (e.g., one or more) element selected from F, P, and S.

[0071] In Chemical Formula 1, 0.72 ≤ x1 ≤ 0.78 and 0.22 ≤ y1 ≤ 0.28, or 0.73 ≤ x1 ≤ 0.77 and 0.23 ≤ y1 ≤ 0.27. Additionally, 0 ≤ z1 ≤ 0.01 or z1 = 0. Additionally, 1 ≤ a1 ≤ 1.15, or 1.03 ≤ a1 ≤ 1.1. For example, x1 + y1 + z1 + w1 = 1. For example, 1.0 ≤ a1 / (x1 + y1 + z1 + w1) ≤ 1.2.

[0072] The positive electrode active material may be in the form of secondary particles formed by aggregating a plurality of primary particles. For example, the secondary particles of the positive electrode active material may (e.g., each) be an aggregate of a plurality of primary particles. In one or more embodiments, the average particle size (D 50 ) of the positive electrode active material may be from about 8 μm to about 20 μm, for example, from about 8 μm to about 18 μm, from about 8 μm to about 16 μm, from about 8 μm to about 14 μm, or from about 8 μm to about 12 μm.

[0073] The cation mixing ratio of the positive electrode active material according to one or more embodiments may be less than or equal to about 3.5%, for example, less than or equal to about 3.2%, less than or equal to about 3%, or less than or equal to about 2.6%, for example, from about 1% to about 3.5%.

[0074] In one or more embodiments, the porosity within the particles of the positive electrode active material may be less than or equal to about 5% by volume, based on 100% by volume of the positive electrode active material, for example, less than or equal to about 4% by volume, or may be from about 1% by volume to about 5% by volume. Herein, the porosity may be measured, for example, by transmission X-ray microscopy (TXM).

[0075] Positive electrode

[0076] In one or more embodiments, there is provided a positive electrode for a rechargeable lithium battery including the aforementioned positive electrode active material. For example, in one or more embodiments, the positive electrode includes a positive electrode current collector and a positive electrode active material layer on the positive electrode current collector, wherein the positive electrode active material layer includes the aforementioned positive electrode active material. In one or more embodiments, in addition to the positive electrode active material described herein, the positive electrode active material layer may further include other types (kinds) of positive electrode active materials. Additionally, the positive electrode active material layer may optionally further include a binder, a conductive material, and / or a combination thereof (e.g., any suitable combination).

[0077] Binder

[0078] The binder can improve the binding characteristics between the positive electrode active material particles and / or the binding characteristics between the positive electrode active material particles and the positive electrode current collector. Examples of the binder 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)acrylate esterified styrene-butadiene rubber, epoxy resin, (meth)acrylic resin, polyester resin, and nylon.

[0079] Conductive material

[0080] A conductive material (e.g., an electrical conductor) is included to provide electrode conductivity, and any conductive material can be used as the conductive material unless it causes a chemical change. Examples of the conductive material may include carbonaceous materials (such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber, carbon nanotube, etc.); metallic materials including metal powders or metal fibers such as copper, nickel, aluminum, silver, etc.; conductive polymers (such as polyphenylene derivatives); and / or mixtures thereof (e.g., any suitable mixture).

[0081] Based on 100 wt% of the positive electrode active material layer, the respective contents (e.g., amounts) of the binder and the conductive material may be about 0.5 wt% to about 5 wt%.

[0082] The positive electrode current collector may include Al (aluminum) foil, SUS (stainless steel) foil, etc., but the present disclosure is not limited thereto.

[0083] Rechargeable lithium battery

[0084] Some embodiments provide a rechargeable lithium battery including the aforementioned positive electrode, negative electrode, and electrolyte. As an example, the rechargeable lithium battery may include a positive electrode, a negative electrode, a separator between the positive electrode and the negative electrode, and an electrolyte. Some embodiments provide a all-solid-state rechargeable battery including a positive electrode, a negative electrode, and a solid electrolyte layer between the positive electrode and the negative electrode. The solid electrolyte layer in the context of the present disclosure is a material that conducts ions between the positive electrode and the negative electrode while remaining in a solid state. Different from the liquid electrolyte, the solid electrolyte provides improved safety, stability, and potentially higher energy density. Hereinafter, for convenience, the configuration of a lithium-ion battery using an electrolyte solution (e.g., a liquid electrolyte) will be described in more detail.

[0085] According to the shape, the rechargeable lithium battery can be classified into a cylindrical battery, a prismatic battery, a pouch battery, a coin-shaped battery, etc. Figures 1 to 4 Each is a schematic diagram showing a rechargeable lithium battery according to one or more embodiments, wherein Figure 1 is a cylindrical battery,Figure 2 is a prismatic battery, and Figure 3 and Figure 4 are each a pouch battery. Referring to Figures 1 to 4 , the rechargeable lithium battery 100 includes: an electrode assembly 40 having a separator 30 interposed between a positive electrode 10 and a negative electrode 20, and a housing 50 that houses the electrode assembly 40 therein. The positive electrode 10, the negative electrode 20, and the separator 30 can be impregnated with an electrolyte solution. As Figure 1 shown in Figure 2 , the rechargeable lithium battery 100 can include a sealing member 60 that seals the housing 50. Additionally, in Figure 3 and Figure 4 , the rechargeable lithium battery 100 includes electrode tabs 70, for example, a positive electrode tab 71 and a negative electrode tab 72, which serve as a circuit path for leading the current formed in the electrode assembly 40 to the outside.

[0086] Negative electrode

[0087] The negative electrode can include a negative electrode current collector and a negative electrode active material layer on the negative electrode current collector, and the negative electrode active material layer can include a negative electrode active material, a binder, a conductive material, and / or a combination thereof (e.g., any suitable combination).

[0088] Negative electrode active material

[0089] The negative electrode active material can include a material that reversibly intercalates / deintercalates lithium ions, lithium metal, a lithium metal alloy, a material capable of doping / dedoping lithium, or a transition metal oxide.

[0090] The material that reversibly intercalates / deintercalates lithium ions can include, for example, crystalline carbon, amorphous carbon, and / or a combination thereof (e.g., any suitable combination) as a carbon-based negative electrode active material. The crystalline carbon can be natural graphite or artificial graphite in an amorphous or flaky, lamellar, spherical, or fibrous form (e.g., in a fibrous form). The amorphous carbon can be soft carbon, hard carbon, mesophase pitch carbonization product, calcined coke, etc.

[0091] 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.

[0092] The material capable of doping / dedoping lithium can be a Si-based negative electrode active material or a Sn-based negative electrode active material. The Si-based negative electrode active material can include silicon, a silicon-carbon composite, SiO x(0 < x ≤ 2), Si-Q alloy (where Q is an element 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 / or their (e.g., any suitable) combinations, such as 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 / or their (e.g., any suitable) combinations) and / or their (e.g., any suitable) combinations. The Sn-based negative electrode active material can be Sn, SnO2, SnO x (0 < x < 2), Sn alloy and / or their (e.g., any suitable) combinations.

[0093] The silicon-carbon composite can be a composite of silicon and amorphous carbon. The average particle size (D 50 ) can be, for example, about 0.5 μm to about 20 μm. According to one or more embodiments, the silicon-carbon composite can be in the form of silicon particles (e.g., silicon primary particles) and amorphous carbon coated on the surface of the silicon particles (e.g., silicon primary particles). For example, it can include secondary particles (cores) in which silicon primary particles are aggregated (e.g., agglomerated or coagulated) and an amorphous carbon coating (shell) on the surface of the secondary particles. Amorphous carbon can also be present between the silicon primary particles. For example, the silicon primary particles can be coated with amorphous carbon. The secondary particles can be dispersed in the amorphous carbon matrix.

[0094] The silicon-carbon composite can further include crystalline carbon. For example, the silicon-carbon composite can include: a core including crystalline carbon and silicon particles (e.g., silicon primary particles) and an amorphous carbon coating on the surface of the core. The crystalline carbon can be artificial graphite, natural graphite, and / or their (e.g., any suitable) combinations. The amorphous carbon can include soft carbon, hard carbon, mesophase pitch carbonized products, and calcined coke.

[0095] When the silicon-carbon composite includes silicon and amorphous carbon, based on 100 wt% of the silicon-carbon composite, the content (e.g., amount) of silicon can be about 10 wt% to about 50 wt% and the content (e.g., amount) of amorphous carbon can be about 50 wt% to about 90 wt%. In one or more embodiments, when the silicon-carbon composite includes silicon, amorphous carbon, and crystalline carbon, based on 100 wt% of the silicon-carbon composite, the content (e.g., amount) of silicon can be about 10 wt% to about 50 wt%, the content (e.g., amount) of crystalline carbon can be about 10 wt% to about 70 wt%, and the content (e.g., amount) of amorphous carbon can be about 20 wt% to about 40 wt%.

[0096] In addition, the thickness of the amorphous carbon coating may be from about 5 nanometers (nm) to about 100 nm. The average particle size (D 50 ) of the silicon particles (e.g., silicon primary particles) may be from about 10 nm to about 1 μm or from about 10 nm to about 200 nm. The silicon particles (e.g., silicon primary particles) may exist alone as silicon, in the form of a silicon alloy, or in the oxidized form of silicon. The oxidized form of silicon may be represented by SiO x (0 < x ≤ 2). In one or more embodiments, the atomic content (e.g., amount) ratio of Si:O indicating the degree of oxidation may be from about 99:1 to about 33:67. As used herein, when no other definition is provided, the average particle size (D 50 ) indicates the diameter of the particles in the particle size distribution with a cumulative volume of about 50 vol%.

[0097] The Si-based negative electrode active material or the Sn-based negative electrode active material may be mixed with the carbon-based negative electrode active material. If (e.g., when) the Si-based negative electrode active material or the Sn-based negative electrode active material and the carbon-based negative electrode active material are mixed and used, the mixing ratio may be a weight ratio of from about 1:99 to about 90:10.

[0098] Binder

[0099] The binder is used to bond the negative electrode active material particles to each other well and is also used to bond the negative electrode active material to the negative electrode current collector. The binder may be a non-aqueous binder, an aqueous binder, a dry binder, and / or a combination thereof (e.g., any suitable combination).

[0100] The non-aqueous binder may include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide, and / or a combination thereof (e.g., any suitable combination).

[0101] The aqueous binder may include styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluororubber, polyethylene oxide, polyvinylpyrrolidone, epichlorohydrin rubber, polyphosphazene, poly(meth)acrylonitrile, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, and / or a combination thereof (e.g., any suitable combination).

[0102] If (e.g., when) an aqueous binder is used as the binder in the negative electrode active material layer, a cellulose compound capable of imparting viscosity may be further included. As the cellulose compound, one or more of carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, and their alkali metal salts may be mixed and used. The alkali metal may be Na, K, or Li.

[0103] The dry binder may be a polymer material capable of fibrillation and may be, for example, polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride - hexafluoropropylene copolymer, polyethylene oxide, and / or a combination thereof (e.g., any suitable combination).

[0104] Conductive material

[0105] A conductive material (e.g., an electrical conductor) is included to provide electrode conductivity, and any electrically conductive material may be used as the conductive material unless it causes a chemical change. Examples of the conductive material include carbon - based materials (such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber, carbon nanotube, etc.); metal - based materials including metal powders or metal fibers such as copper, nickel, aluminum, silver, etc.; conductive polymers (such as polyphenylene derivatives); and / or a mixture thereof (e.g., any suitable mixture).

[0106] Based on 100 wt% of the negative electrode active material layer, the content (e.g., amount) of the negative electrode active material may be about 95 wt% to about 99.5 wt%, and based on 100 wt% of the negative electrode active material layer, the content (e.g., amount) of the binder may be about 0.5 wt% to about 5 wt%. For example, the negative electrode active material layer may include about 90 wt% to about 99 wt% of the negative electrode active material, about 0.5 wt% to about 5 wt% of the binder, and about 0 wt% to about 5 wt% of the conductive material.

[0107] Current collector

[0108] The negative electrode current collector may include, for example, indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or an alloy thereof, and may be in the form of a foil, sheet, or foam. The thickness of the negative electrode current collector may be, for example, about 1 μm to about 20 μm, about 5 μm to about 15 μm, or about 7 μm to about 10 μm.

[0109] Electrolyte

[0110] For example, the electrolyte for a rechargeable lithium battery may be an electrolyte solution, which may include a non - aqueous organic solvent and a lithium salt.

[0111] The non-aqueous organic solvent serves as a medium for transporting ions participating in the electrochemical reaction of the battery. The non-aqueous organic solvent can be a carbonate solvent, an ester solvent, an ether solvent, a ketone solvent, an alcohol solvent, an aprotic solvent, and / or a combination thereof (e.g., any suitable combination).

[0112] The carbonate solvents can include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), etc. The ester solvents can include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanolide, mevalonolactone, valerolactone, caprolactone, etc. The ether solvents can include dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, tetrahydrofuran, etc. In one or more embodiments, the ketone solvents can include cyclohexanone, etc. The alcohol solvents can include ethanol, isopropanol, etc., and the aprotic solvents can include nitriles (such as R-CN where R is a C2-C20 straight-chain, branched-chain, or cycloalkyl group and may include double bonds, aromatic rings, or ether bonds, etc.); amides (such as dimethylformamide); dioxolanes (such as 1,3-dioxolane, 1,4-dioxolane, etc.); sulfolane, etc.

[0113] The non-aqueous organic solvent can be used alone or in a mixture of two or more types (or kinds), and if (e.g., when) used in a mixture of two or more types (kinds), the mixing ratio can be appropriately or suitably adjusted according to the desired or appropriate battery performance, which is widely applicable to those skilled in the art.

[0114] If (e.g., when) carbonate solvents are used, the cyclic carbonate and the chain carbonate can be used in combination, and the cyclic carbonate and the chain carbonate can be mixed in a volume ratio of about 1:1 to about 1:9.

[0115] The non-aqueous organic solvent can further include aromatic hydrocarbon organic solvents. For example, the carbonate solvent and the aromatic hydrocarbon organic solvent can be used in combination in a volume ratio of about 1:1 to about 30:1.

[0116] The electrolyte solution can further include vinylene ethylene carbonate, vinylene carbonate, or ethylene carbonate compounds to improve the battery cycle life.

[0117] Examples of the ethylene carbonate compounds can include fluoroethylene carbonate, difluoroethylene carbonate, chloroethylene carbonate, dichloroethylene carbonate, bromoethylene carbonate, dibromoethylene carbonate, nitroethylene carbonate, and cyanoethylene carbonate.

[0118] Lithium salts dissolved in organic solvents supply lithium ions in the battery, ensuring the basic operation of rechargeable lithium batteries and improving the transport of lithium ions between the positive and negative electrodes. Examples of lithium salts may include at least one 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+1 SO2)(where x and y are integers from 1 to 20), lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium difluoro bis(oxalato)phosphate (LiDFBOP), and lithium bis(oxalato)borate (LiBOB).

[0119] The concentration of the lithium salt can be in the range of about 0.1 M to about 2.0 M. If (for example, when) the concentration of the lithium salt is within the described range, the electrolyte solution can have suitable or appropriate ionic conductivity and viscosity, so excellent or appropriate performance can be achieved, and lithium ions can move effectively.

[0120] Separator

[0121] Depending on the type (or kind) of rechargeable lithium battery, the separator may be present between the positive and negative electrodes. The separator may include a polyethylene separator, a polypropylene separator, a polyvinylidene fluoride separator, a polytetrafluoroethylene separator, or a multilayer film of two or more layers thereof (such as a polyethylene / polypropylene two-layer separator, a polyethylene / polypropylene / polyethylene three-layer separator, a polypropylene / polyethylene / polypropylene three-layer separator, etc.).

[0122] The separator may include a porous substrate and a coating on the surface (e.g., one or two surfaces (e.g., opposite surfaces or surfaces)) of the porous substrate, and the coating includes an organic material, an inorganic material, and / or a combination thereof (e.g., any suitable combination).

[0123] The porous substrate may be a polymer film formed from any one of the following polymers or a copolymer or mixture of two or more thereof: polyolefins (such as polyethylene and polypropylene), polyesters (such as polyethylene terephthalate and polybutylene terephthalate), polyacetals, polyamides, polyimides, polycarbonates, polyether ketones, polyaryl ether ketones, polyether imides, polyamide imides, polybenzimidazoles, polyether sulfones, polyphenylene ethers, cycloolefin copolymers, polyphenylene sulfides, polyethylene naphthalate, glass fiber, and polytetrafluoroethylene (e.g., Teflon).

[0124] The porous substrate may have a thickness of about 1 μm to about 40 μm, for example, about 1 μm to about 30 μm, about 1 μm to about 20 μm, about 5 μm to about 15 μm, or about 10 μm to about 15 μm.

[0125] The organic material may include a (meth)acrylic copolymer, which includes: a first structural unit derived from (meth)acrylamide, and a second structural unit including at least one of a structural unit derived from (meth)acrylic acid or (meth)acrylate and a structural unit derived from (meth)acrylamidosulfonic acid or a salt thereof.

[0126] The inorganic material 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 (e.g., any suitable combination), but the present disclosure is not limited thereto. The average particle size (D 50 ) may be about 1 nm to about 2000 nm, for example, about 100 nm to about 1000 nm, or about 100 nm to about 700 nm.

[0127] The organic material and the inorganic material may be mixed in one coating, or may exist in a form where a coating including the organic material and a coating including the inorganic material are stackable.

[0128] The thickness of the coating may be about 0.5 μm to about 20 μm, for example, about 1 μm to about 10 μm, or about 1 μm to about 5 μm.

[0129] Terms such as "substantially", "about", and "approximate" are used as relative terms and not as terms of degree, and are intended to account for the inherent deviations of measured or calculated values that would be recognized by a person of ordinary skill in the art. They include the recited value and the acceptable range of deviations determined by a person of ordinary skill in the art taking into account the limitations and errors associated with the measurement of that quantity. For example, "about" may refer to one or more standard deviations, or ±30%, ±20%, ±10%, or ±5% of the recited value.

[0130] The numerical ranges disclosed herein include and are intended to disclose all included sub-ranges of the same numerical precision. For example, the range of "1.0 to 10.0" includes all sub-ranges having a minimum value equal to or greater than 1.0 and a maximum value equal to or less than 10.0 (e.g., taking 2.4 to 7.6 as an example). Therefore, the applicant reserves the right to modify this specification (including the claims) to expressly set forth any sub-ranges included within the ranges expressly set forth herein.

[0131] Embodiments and comparative examples of the present disclosure are described in more detail below. However, the following embodiments are merely examples of the present disclosure, and the present disclosure is not limited to the following embodiments.

[0132] Embodiment

[0133] Comparative Example 1

[0134] 1. Preparation of positive electrode active material

[0135] The average particle size (D 50 ) is about 10 μm in the form of secondary particles and has Li 1.037 (Ni 0.75 Mn 0.25 ) 0.963 O2 composition positive electrode active material is prepared as follows: Ni with an average particle size (D 50 ) of about 10 μm 0.75 Mn 0.25 (OH)2 is mixed with LiOH to have a Li / (Ni + Mn) ratio of 1.077, the temperature is raised for 6 hours, the mixture is heat-treated in an oxygen atmosphere at 850 °C for 8 hours, and then cooled to room temperature. Figure 5 Shows the heat treatment temperature curve of the one-step (e.g., action or task) synthesis method of the positive electrode active material according to Comparative Example 1.

[0136] 2. Manufacture of rechargeable lithium battery cell

[0137] 98.5 wt% of the positive electrode active material, 1.0 wt% of the polyvinylidene fluoride binder, and 0.5 wt% of the carbon nanotube conductive material are mixed to prepare a positive electrode active material layer slurry, and the positive electrode active material layer slurry is coated on an aluminum foil current collector, and then dried and pressed to manufacture a positive electrode.

[0138] 97.5 wt% of the graphite negative electrode active material, 1.5 wt% of carboxymethyl cellulose, and 1 wt% of styrene-butadiene rubber are mixed in an aqueous solvent to prepare a negative electrode active material layer slurry. The negative electrode active material layer slurry is coated on a copper foil current collector, and then dried and pressed to manufacture a negative electrode.

[0139] A polytetrafluoroethylene separator is used, and an electrolytic solution (which is prepared by dissolving 1 M LiPF6 in a mixed solvent of ethylene carbonate and dimethyl carbonate with a volume ratio of 3:7) is used to manufacture a rechargeable lithium battery cell by a conventional method.

[0140] Example 1

[0141] The positive electrode active material and the rechargeable lithium battery cell are manufactured in substantially the same manner as in Comparative Example 1, except that the positive electrode active material is prepared as follows: Ni0.75 Mn 0.25 (OH)2 and LiOH are mixed, and then the mixture is subjected to a primary heat treatment (e.g., the first heat treatment) at 200 °C for about 2 hours by raising the temperature, and a secondary heat treatment (e.g., heat treating it again) at 850 °C for 6 hours by raising the temperature for 4 hours, and then it is cooled to room temperature.

[0142] Example 2

[0143] The positive electrode active material and the rechargeable lithium battery cell are manufactured in substantially the same manner as in Example 1, except that the primary heat treatment temperature is changed to 250 °C. Figure 6 Shows the heat treatment temperature curve of the two-step (e.g., action or task) synthesis method of the positive electrode active material according to Example 2.

[0144] Example 3

[0145] The positive electrode active material and the rechargeable lithium battery cell are manufactured in substantially the same manner as in Example 1, except that the primary heat treatment temperature is changed to 300 °C.

[0146] Example 4

[0147] The positive electrode active material and the rechargeable lithium battery cell are manufactured in substantially the same manner as in Example 1, except that the primary heat treatment temperature is changed to 350 °C.

[0148] Comparative Example 2

[0149] The positive electrode active material and the rechargeable lithium battery cell are manufactured in substantially the same manner as in Example 1, except that the primary heat treatment temperature is changed to 400 °C.

[0150] Evaluation Example 1: Cation mixing

[0151] By X-ray diffraction analysis (XRD) and Rietveld analysis, the cation mixing ratio of each of the positive electrode active materials of Examples 1 to 4 and Comparative Examples 1 and 2 is measured, which is the percentage (%) of nickel ions (Ni 2+ ) entering the lithium (Li) site, and the results are shown in Table 1. For example, the cation mixing ratio can be calculated as the ratio of the peak intensity of the (003) plane to the peak intensity of the (104) plane, as shown in the following formula.

[0152] Cation mixing ratio (%) = I (003) / I (104) x100

[0153] In XRD, the peak of the (003) plane can appear at 2θ of about 18° to about 19°, and the peak of the (104) plane can appear at 2θ of about 44.5°. The peak of the (003) plane can provide information about the layered phase of the positive electrode active material, and the peak of the (104) plane can provide information about the layered structure and the cubic rock salt structure. The (003) plane refers to the lattice plane corresponding to the Miller index (003).

[0154] Table 1

[0155] Primary heat treatment (°C) Secondary heat treatment (°C) Cation mixing ratio (%) Comparative Example 1 - 850 4.38 Example 1 200 850 3.27 Example 2 250 850 2.42 Example 3 300 850 2.59 Example 4 350 850 2.87 Comparative Example 2 400 850 4.71

[0156] Referring to Table 1, in Examples 1 to 4 in which a two-step (e.g., action or task) synthesis method according to one or more embodiments is applied, the cation mixing in the positive electrode active material is reduced, which is beneficial to the diffusion of lithium ions and improves the charge and discharge efficiency, rate capability, etc. That is, in Examples 1 to 4 in which the two-step synthesis method is applied, the cation mixing in the positive electrode active material is reduced. This reduction is beneficial to the diffusion of lithium ions and improves the charge and discharge efficiency, rate capability, and other related performance indicators.

[0157] Evaluation Example 2: Internal pore analysis

[0158] The positive electrode active materials of Comparative Example 1 and Example 2 were cut with FIB, and scanning electron microscope (SEM) images of their cross-sections were obtained. The SEM images and the images of analyzing the pores and voids inside the particles with a transmission X-ray microscope (TXM) are shown respectively in the lower part and the upper part of each of Figure 7 and Figure 8 . Comparing Figure 7 with Figure 8 , compared with Comparative Example 1, Example 2 shows a significant reduction in the voids (internal voids) inside the secondary particles and the pores (internal pores) inside the primary particles, and achieves increased structural stability.

[0159] In one or more embodiments, the porosity of the positive electrode active materials of Comparative Example 1 and Example 2 was analyzed by TXM analysis, which is shown in Figure 9 . Figure 9 The porosity shown in refers to the volume percentage of pores based on the total pores of the positive electrode active material particles of 100 volume%. Refer to Figure 9, compared with 6.62% by volume in Comparative Example 1, the porosity of Example 2 was reduced to 3.51% by volume. Accordingly, a two-step (e.g., action or task) synthesis method according to one or more embodiments is applied to reduce pores in the positive electrode active material and improve structural stability, thereby improving cycle life characteristics. That is, the two-step synthesis method is applied to reduce pores in the positive electrode active material, enhance structural stability, and thus improve cycle life characteristics. TXM specifically refers to full-field TXM using equipment developed by Pohang Accelerator Laboratory. TXM can be described as an analytical method for identifying the entire pore structure within individual secondary particles.

[0160] Evaluation Example 3: Initial charge / discharge capacity and efficiency, cycle life characteristics, and rate capability

[0161] The rechargeable lithium battery cells according to Comparative Example 1 and Examples 2 and 3 were charged at a constant current of 0.2C to 4.5V and then charged at a constant voltage to 0.05C, and then discharged at 0.2C to 3.0V at 25°C to perform initial charge and discharge. In Table 2, the initial charge capacity, the initial discharge capacity, and the ratio of the latter to the former are provided as the initial charge and discharge efficiency.

[0162] Subsequently, the rechargeable lithium battery cells were repeatedly charged and discharged at 0.5C in the voltage range of 2.8V to 4.7V at 45°C for 100 times to calculate the ratio of the 100th discharge capacity to the initial discharge capacity, which is provided in Table 2 as the cycle life.

[0163] Independently, the rechargeable lithium battery cells of Comparative Example 1 and Example 2 were charged to 4.5V at 0.2C and then discharged at 0.1C, 0.5C, 1C, 2C, 5C, and 0.5C at 25°C for rate evaluation, and the results are shown in Figure 10 as follows.

[0164] Table 2

[0165]

[0166] Referring to Table 2, in each of Example 2 and Example 3, compared with Comparative Example 1, the initial discharge capacity increased, and the initial charge and discharge efficiency and cycle life characteristics were improved. In the positive electrode active materials of Example 2 and Example 3, cracks and voids within the secondary particles were reduced, improving the high-temperature cycle life performance.

[0167] Referring to Figure 10, Example 2 demonstrated excellent or appropriate discharge capacity characteristics compared to Comparative Example 1 at high rates of 2C and 5C. In Example 2, due to the reduction of cationic disorder in the positive electrode active material, the diffusion of lithium ions was promoted, and accordingly, the rate characteristics were improved.

[0168] Evaluation Example 4: DTG-DSC

[0169] For Ni 0.75 Mn 0.25 (OH)2 samples and Ni 0.75 Mn 0.25 (OH)2 and LiOH mixed samples (with a Li / (Ni + Mn) ratio of 1.077) were subjected to differential thermogravimetry - differential scanning calorimetry (DTG-DSC) analysis, and the results are shown in Figure 11 as follows. Figure 11 The upper figure (upper part) of Figure 11 shows the results of a single transition metal hydroxide sample, confirming that its decomposition occurs at a temperature of 300 °C. Figure 12 The lower figure (lower part) of Figure 11 shows the results of a mixed sample of a transition metal hydroxide and a lithium raw material, confirming that its decomposition occurs at a temperature below 300 °C. Figure 12 is an enlarged view in the region of approximately 200 °C to 350 °C, including curves corresponding to the insertion of lithium and the decomposition of the transition metal hydroxide precursor, labeled "Li insertion" and "NM(OH)2 decomposition" respectively. See Figure 12 that lithium insertion occurred at approximately 250 °C without decomposition of the transition metal precursor, where after primary heat treatment in this temperature range, secondary heat treatment was carried out at a higher temperature to reduce cationic disorder and pores within the particles, thus improving the structure and chemical stability. That is, as

[0170] The battery (e.g., positive electrode active material) manufacturing apparatus, battery management system (BMS) apparatus, and / or any other relevant apparatus or components described herein according to embodiments of the present disclosure can be implemented using any suitable hardware, firmware (e.g., application specific integrated circuit), software, or a combination of software, firmware, and hardware. For example, the various components of the apparatus can be formed on one integrated circuit (IC) chip or on separate IC chips. Additionally, the components of the apparatus can be implemented on a flexible printed circuit film, tape carrier package (TCP), or printed circuit board (PCB), or formed on a substrate. Further, the components of the apparatus can be processes or threads running on one or more processors in one or more computing devices, executing computer program instructions and interacting with other system components to perform the functions described herein. The computer program instructions are stored in a memory, which can be implemented using standard memory devices (e.g., taking random access memory (RAM) as an example) in the computing device. The computer program instructions can also be stored in other non-transitory computer-readable media (e.g., taking CD-ROM, flash drive, etc. as an example). Moreover, those skilled in the art should recognize that, without departing from the scope of the present disclosure, the functions of various computing devices can be combined or integrated into a single computing device, or the functions of a particular computing device can be distributed over one or more other computing devices.

[0171] In the context of the present application and unless otherwise defined, the terms "use", "using", and "used" can be considered to be synonymous with the terms "utilize", "utilizing", and "utilized", respectively.

[0172] In view of the overall content of the present disclosure, those of ordinary skill in the art will recognize that each appropriate feature of the various embodiments of the present disclosure can be partially or fully combined or combined with each other, and can be technically connected and operated in various appropriate ways, and each embodiment can be implemented independently of each other or in combination with each other in any appropriate way, unless otherwise stated or implied.

[0173] Although the present disclosure has been described in connection with what are presently considered to be practical example embodiments, it is to be understood that the present disclosure is not limited to the disclosed embodiments. In contrast, the present disclosure is intended to cover one or more appropriate modifications and equivalent arrangements included within the spirit and scope of the claims and their equivalents.

Claims

1. A method comprising: mixing a nickel-manganese composite hydroxide and a lithium raw material to form a mixture; applying a primary heat treatment to the mixture at 200°C to 350°C; as well as applying a secondary heat treatment to the mixture at 800°C to 1000°C, The method described therein is a method for preparing a positive electrode active material.

2. The method of claim 1, wherein The temperature of the initial heat treatment is 220°C to 300°C.

3. The method of claim 1, wherein The primary heat treatment is applied in an oxygen atmosphere for 0.5 hour to 5 hours.

4. The method of claim 1, wherein The secondary heat treatment is applied in an oxygen atmosphere for 4 to 12 hours.

5. The method of claim 1, wherein The time of the primary heat treatment is shorter than the time of the secondary heat treatment.

6. The method of claim 1, wherein The nickel content of the nickel-manganese-based composite hydroxide is 70 mol% to 80 mol% relative to the total metal content of the nickel-manganese-based composite hydroxide.

7. The method of claim 1, wherein The nickel-manganese composite hydroxide is represented by Chemical Formula 11: Chemical formula 11 Ni x11 Mn y11 M 1 z11 M 2 w11 (OH)2, in, In Chemical Formula 11, 0.7≤x11≤0.8， 0.2≤y11≤0.3， 0≤z11≤0.05， 0≤w11≤0.05， 0.9≤x11+y11+z11+w11≤1.1, M 1 is Co, and M 2 It is at least one element selected from Al, B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ti, V, W and Zr.

8. The method of claim 1, wherein The nickel-manganese composite hydroxide includes an average particle size D 50 The particles are 8μm to 20μm.

9. The method of claim 1, wherein The molar ratio of lithium in the lithium raw material to the total metal of the nickel-manganese composite hydroxide is 1.0 to 1.

2.

10. A positive electrode active material, comprising a layered lithium nickel manganese composite oxide represented by Chemical Formula 1: Chemical formula 1 Li a1 Ni x1 Mr y1 M 1 z1 M 2 w1 O 2-b1 X b1 in, In Chemical Formula 1, 0.9≤a1≤1.2， 0.7≤x1≤0.8， 0.2≤y1≤0.3， 0≤z1≤0.05， 0≤w1≤0.05， 0.9≤x1+y1+z1+w1≤1.1, 0≤b1≤0.1， M 1 For Co, M 2 is at least one element selected from the group consisting of Al, B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ti, V, W and Zr, and X is at least one element selected from F, P and S.

11. The positive electrode active material according to claim 10, wherein In Chemical Formula 1, 0.73≤x1≤0.77 and 0.23≤y1≤0.

27.

12. The positive electrode active material according to claim 10, wherein In Chemical Formula 1, 0≤z1≤0.

01.

13. The positive electrode active material according to claim 10, wherein In Chemical Formula 1, 1.03≤a1≤1.

1.

14. The positive electrode active material according to claim 10, wherein The positive electrode active material includes secondary particles, each of which is an aggregate of a plurality of primary particles.

15. The positive electrode active material according to claim 14, wherein The secondary particles of the positive electrode active material have an average particle size D of 8 μm to 20 μm. 50 .

16. The positive electrode active material according to claim 10, wherein The cation mixing ratio of the positive electrode active material is less than or equal to 3.5%.

17. The positive electrode active material according to claim 10, wherein The porosity within particles of the positive electrode active material measured by transmission X-ray microscopy analysis is less than or equal to 5 volume % based on 100 volume % of the positive electrode active material.

18. A positive electrode comprising the positive electrode active material prepared as claimed in any one of claims 1 to 9 or the positive electrode active material as claimed in any one of claims 10 to 17, The positive electrode is used in a rechargeable lithium battery.

19. A rechargeable lithium battery comprising The positive electrode according to claim 18, negative electrode, and Electrolytes.

20. An all-solid-state rechargeable battery comprising The positive electrode according to claim 18, negative electrode, and A solid electrolyte layer is between the positive electrode and the negative electrode.

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