Positive electrode for stacked rechargeable lithium battery and stacked rechargeable lithium battery

Abstract

The present application provides a positive electrode for a stack-type rechargeable lithium battery and a stack-type rechargeable lithium battery including the same. A positive electrode for a stacked rechargeable lithium battery includes a positive electrode current collector, a first positive electrode active material layer on one surface of the positive electrode current collector, and a second positive electrode active material layer on the other surface of the positive electrode current collector, wherein a loading level of the first positive electrode active material layer is about 5% or more higher than a loading level of the second positive electrode active material layer, each of the first positive electrode active material layer and the second positive electrode active material layer includes a first positive electrode active material in the form of a secondary particle and a second positive electrode active material in the form of a single particle, the average particle size of the secondary particles of the first positive electrode active material is larger than the average particle size of the individual particles of the second positive electrode active material.

Description

Technical Field

[0001] One or more embodiments of the present disclosure relate to a positive electrode for a stacked or stacked-type rechargeable lithium battery (eg, a stacked rechargeable lithium battery) and a stacked or stacked-type rechargeable lithium battery including the positive electrode. Background Art

[0002] Portable information devices (such as cellular phones, laptop computers, smart phones, etc.) and / or electric vehicles have used rechargeable lithium batteries with relatively high energy density and easy portability as driving power sources. Recently, research has been actively conducted to use rechargeable lithium batteries with high energy density as driving power sources for hybrid and / or electric vehicles and / or power storage power sources for home power storage units (e.g., power walls).

[0003] In order to increase the energy density of rechargeable lithium batteries, it is important to improve the positive electrode active material and it has been studied. Recently, positive electrode active materials have been developed to increase the nickel content (e.g., amount) and reduce the cobalt content (e.g., amount), thereby increasing the energy density of rechargeable lithium batteries and reducing unit costs. This high nickel-based positive electrode active material or cobalt-free nickel-based positive electrode active material can achieve a relatively high capacity, but has the disadvantage of relatively low charge / discharge efficiency due to cation mixing during its synthesis, etc. For this reason, the positive electrode with relatively low charge / discharge efficiency is greatly affected by the battery cell design, resulting in significant changes in electrochemical properties (such as capacity and cycle life characteristics, etc.). Accordingly, it is necessary to improve or optimize the battery cell design in a rechargeable lithium battery to which a material with relatively low charge / discharge efficiency is applied to improve the cycle life characteristics and maintain high energy density. Summary of the invention

[0004] According to one or more aspects of the present disclosure, by improving or optimizing the battery cell design in a stacked or stacked positive electrode having high capacity but relatively low charge / discharge efficiency, the utilization rate of the same positive electrode active material (e.g., a positive electrode active material having relatively low charge / discharge efficiency) inside the battery cell is increased (increasing the battery cell capacity) and / or improving the cycle life characteristics. Additional aspects will be stated in part in the subsequent description and will be apparent in part from the description or can be understood by practicing the embodiments presented in the present disclosure.

[0005] According to one or more embodiments of the present disclosure, a positive electrode for a stacked or stacked-type rechargeable lithium battery includes a positive electrode current collector, a first positive electrode active material layer on one surface of the positive electrode current collector, and a second positive electrode active material layer on the other surface of the positive electrode current collector (e.g., a surface opposite to the one surface), wherein the loading level of the first positive electrode active material layer is higher than the loading level of the second positive electrode active material layer by about 5% or more, each of the first positive electrode active material layer and the second positive electrode active material layer includes a first positive electrode active material in the form of secondary particles including a plurality of primary particles (e.g., each secondary particle is made by aggregating a plurality of primary particles) and a second positive electrode active material in the form of a single particle (e.g., each is a single integral particle), and an average particle size (D 50 ) is larger than the average particle size (D 50 ), the first positive electrode active material and the second positive electrode active material each independently include a compound represented by Chemical Formula 1 or a compound represented by Chemical Formula 2.

[0006] According to one or more embodiments of the present disclosure, a stacked or stacked type rechargeable lithium battery includes a positive electrode and a negative electrode.

[0007] A stacked or stacked type positive electrode and a rechargeable lithium battery according to one or more embodiments have improved cycle-life characteristics and specific capacity while implementing high energy density. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The above and other aspects, features and advantages of certain embodiments of the present disclosure will become more apparent from the following description taken in conjunction with the accompanying drawings.

[0009] Figure 1 Graphs showing cycle-life characteristics of stacked or stacked-type rechargeable lithium battery cells of Example 1 and Comparative Example 1.

[0010] Figure 2 Graphs showing cycle-life characteristics of stacked or stacked-type rechargeable lithium battery cells of Comparative Examples 2 and 3. DETAILED DESCRIPTION

[0011] Hereinafter, example embodiments will be described in more detail so that those skilled in the art can easily implement them. However, the present disclosure may be embodied in many different forms and is not to be construed as limited to the example embodiments set forth herein.

[0012] The terms used in this article are only used to describe the embodiments and are not intended to limit the present disclosure. As used herein, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. In addition, the use of "may" when describing embodiments of the present disclosure refers to "one or more embodiments of the present disclosure".

[0013] As used herein, "combinations thereof" may refer to mixtures, laminates, composites, copolymers, alloys, blends, reaction products, and the like, of the components.

[0014] In this document, it should be understood that terms such as “includes,” “comprising,” or “having” are intended to indicate the presence of embodied features, quantities, operations, elements, and / or their (e.g., any appropriate) combinations thereof, but do not exclude the possibility of the presence or addition of one or more other features, quantities, operations, elements, and / or their (e.g., any appropriate) combinations thereof.

[0015] In the accompanying drawings, the thickness of layers, films, panels, regions, etc. may be exaggerated for clarity, and throughout the present disclosure, the same reference numerals represent the same elements, and for the sake of brevity, repeated descriptions thereof may not be provided. It will be understood that if (for example, when) an element (such as a layer, film, region, or substrate) is referred to as being "on" another element, it may be directly on the other element, or there may also be intervening elements. In contrast, if (for example, when) an element is referred to as being "directly on" another element, there are no intervening elements.

[0016] In one or more embodiments, the term “layer” as used herein may include not only a shape or layer formed on the entire surface if (eg, when) viewed from a plan view, but also a shape or layer formed on a partial surface.

[0017] In one or more embodiments, the average particle size of the particles can be measured by a method that is well suited to those skilled in the art, for example, by a particle size analyzer (e.g., HORIBA, LA-950 laser particle size analyzer), or by a transmission electron microscope (TEM) or a scanning electron microscope (SEM). In one or more embodiments, the average particle size value can be obtained by measuring using a dynamic light scattering method, performing data analysis, counting the number of particles in each particle size range, and calculating based on the data. Unless otherwise specified, the average particle size (D 50) may refer to the diameter of particles whose cumulative volume is 50% by volume in a particle size distribution. D50 refers to the average diameter (or size) of particles whose cumulative volume corresponds to 50% by volume in a particle size distribution (e.g., cumulative distribution), and refers to a value corresponding to 50% of the particle size from the smallest particle when the total number of particles is 100% in a distribution curve accumulated in the order of the smallest particle size to the largest particle size. In the present disclosure, when the particles are spherical, "diameter" indicates the average particle diameter, and when the particles are non-spherical, "diameter" indicates the major axis length.

[0018] In this article, "or" is not interpreted as an exclusive meaning, for example, "A or B" is interpreted as including A, B, A+B, etc. In addition, as used in this article, the term "and / or" includes any and all combinations of one or more related enumerated items. When expressions such as "at least one of", "one of", and "selected from" are before / after the list of elements, the entire list of elements is modified without modifying the individual elements of the list. For example, "at least one of a, b, and c", "selected from at least one of a, b, and c", "selected from at least one of a to c", etc., can indicate only a, only b, only c, both a and b (for example, at the same time), both a and c (for example, at the same time), both b and c (for example, at the same time), all a, b, and c or their variations. The " / " used in this article can be interpreted as "and" or "or" depending on the situation.

[0019] The term "metal" as used herein is interpreted as a concept including ordinary metals, transition metals, and metalloids (semimetals).

[0020] Positive electrode

[0021] In one or more embodiments, a positive electrode for a stacked or stacked type rechargeable lithium battery may include a positive electrode current collector, a first positive electrode active material layer on one surface of the positive electrode current collector, and a second positive electrode active material layer on another surface of the positive electrode current collector (e.g., a surface opposite to the one surface), wherein the loading level of the first positive electrode active material layer is about 5% or more higher than the loading level of the second positive electrode active material layer. In one or more embodiments, each of the first positive electrode active material layer and the second positive electrode active material layer may include a first positive electrode active material in the form of secondary particles including a plurality of primary particles (e.g., each secondary particle is made by aggregating a plurality of primary particles) and a second positive electrode active material in the form of a single particle (e.g., each is a single integral particle), and the average particle size (D) of the secondary particles of the first positive electrode active material is about 1000 Å. 50 ) is larger than the average particle size (D 50), the first positive electrode active material and the second positive electrode active material may each independently include a compound represented by Chemical Formula 1 or a compound represented by Chemical Formula 2.

[0022] Chemical Formula 1

[0023] Li a1 Ni x1 M 1 y1 M 2 z1 O 2-b1 X b1

[0024] In Chemical Formula 1, 0.9 ≤ a1 ≤ 1.2, 0.88 ≤ x1 ≤ 1, 0 ≤ y1 ≤ 0.12, 0 ≤ z1 ≤ 0.12, 0.9 ≤ x1 + y1 + z1 ≤ 1.1, and 0 ≤ b1 ≤ 0.1, M 1 and M 2 may each independently be (for example, selected from) one or more elements of aluminum (Al), boron (B), barium (Ba), calcium (Ca), cerium (Ce), cobalt (Co), chromium (Cr), copper (Cu), iron (Fe), magnesium (Mg), manganese (Mn), molybdenum (Mo), niobium (Nb), silicon (Si), tin (Sn), strontium (Sr), titanium (Ti), vanadium (V), tungsten (W), zinc (Zn), and zirconium (Zr), and X may be (for example, selected from) one or more elements of fluorine (F), phosphorus (P), and sulfur (S).

[0025] Chemical Formula 2

[0026] Li a2 Ni x2 Mn y2 M 3 z2 O 2-b2 X b2

[0027] In Chemical Formula 2, 0.9 ≤ a2 ≤ 1.8, 0.7 ≤ x2 < 1, 0 < y2 ≤ 0.3, 0 ≤ z2 ≤ 0.3, 0.9 ≤ x2 + y2 + z2 ≤ 1.1, and 0 ≤ b2 ≤ 0.1, M 3 may be (for example, selected from) one or more elements of Al, B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ti, V, W, Zn, and Zr, and X may be (for example, selected from) one or more elements of F, P, and S.

[0028] In one or more embodiments, the first positive electrode active material layer may include both the first positive electrode active material and the second positive electrode active material (e.g., the first positive electrode active material and the second positive electrode active material are included at the same time), and the second positive electrode active material layer may include both the first positive electrode active material and the second positive electrode active material (e.g., the first positive electrode active material and the second positive electrode active material are included at the same time), wherein the loading level of the first positive electrode active material layer is about 5% or more higher than the loading level of the second positive electrode active material layer. The first positive electrode active material is in the form of secondary particles and has an average particle size larger than the average particle size of the second positive electrode active material, and thus may be represented herein as a large particle body, a large particle, etc. The second positive electrode active material is in the form of a single particle rather than a secondary particle, and has an average particle size smaller than the average particle size of the secondary particles of the first positive electrode active material, and thus may be represented herein as a small particle body, a small particle, etc.

[0029] The composition of the first positive electrode active material and the composition of the second positive electrode active material may be the same or different. The first positive electrode active material and the second positive electrode active material each independently include a compound represented by Chemical Formula 1 or a compound represented by Chemical Formula 2. Based on the total molar number of metals other than lithium included in the compound, the compound represented by Chemical Formula 1 may be a high nickel lithium composite oxide having a nickel content (e.g., amount) greater than or equal to about 88 mol%. The compound represented by Chemical Formula 2 may be represented as a cobalt-free lithium composite oxide or a cobalt-free lithium nickel manganese oxide. In the present disclosure, "not including one or any 'component'", "excluding one or any 'component'", "no 'component'", etc. refer to "components" that are not added, selected or used as components in the composition / element / structure, but, in some embodiments, due to other impurities and / or external factors, less than an appropriate amount of "components" may still be included.

[0030] The positive electrode active material according to one or more embodiments has a high nickel composition of Chemical Formula 1 or a cobalt-free composition of Chemical Formula 2 and a mixture of secondary particles and single particles, and the positive electrode containing the positive electrode active material can achieve high capacity and high energy density, but has the disadvantage of relatively low charge and discharge efficiency. This type or kind of positive electrode has electrochemical characteristics that vary significantly depending on the battery cell design, and therefore an optimal or appropriate design is desired or required. In some embodiments, the load levels on the two surfaces (e.g., opposite surfaces or opposite sides) of the positive electrode current collector are designed to be different, and the load level of the first positive electrode active material layer on one surface is about 5% or more higher than the load level of the second positive electrode active material layer on the other surface, so that the second positive electrode active material layer with a relatively low load level improves the cycle life characteristics, and the first positive electrode active material layer with a high load level compensates for the capacity, thereby improving the cycle life characteristics and increasing the specific capacity, while maintaining the energy density and charge / discharge efficiency of the positive electrode at substantially the same level. These effects can be maximized or increased in positive electrodes having relatively low charge / discharge efficiency by applying high-nickel positive electrode active materials or cobalt-free high-nickel positive electrode active materials. For example, in a comparative embodiment of a positive electrode using a lithium-cobalt positive electrode active material that generally has a high charge / discharge efficiency, even if the load levels on the two surfaces (e.g., opposite surfaces or opposite sides) of the positive electrode are designed differently as in some embodiments of the present disclosure, no effect of improving the cycle life characteristics is found, and even in a comparative embodiment of a high-nickel high-efficiency positive electrode consisting only of secondary particles, even if the load levels on the two surfaces (e.g., opposite surfaces or opposite sides) of the positive electrode are changed, the cycle life characteristics, etc. are not improved. In addition, the effect of the battery cell design according to one or more embodiments of the present disclosure is maximized or increased in the structure of a stacked or stacked rechargeable lithium battery. For example, it is difficult to apply the same logic or strategy to a winding or winding rechargeable lithium battery.

[0031] In other words, designing the load levels on the two surfaces (e.g., opposite surfaces or opposite sides) of the positive electrode differently means designing the N / P ratio (the ratio of the negative electrode plate capacity to the positive electrode plate capacity, and the electrode plate capacity is the active material capacity × (i.e., multiplied by) the amount of active material × (multiplied by) the load level) of the two surfaces (e.g., opposite surfaces or opposite sides) of the positive electrode to be different. According to one or more embodiments, the N / P ratio of the first positive electrode active material layer is designed to be lower than the N / P ratio of the second positive electrode active material layer. For example, the first positive electrode active material layer is designed to have a higher load level and a lower N / P ratio than the second positive electrode active material layer. In one or more embodiments, it may mean that in a stacked or stacked type rechargeable lithium battery, the load levels on the two surfaces (e.g., opposite surfaces or opposite sides) of the negative electrode are designed to be substantially the same, and only the load levels on the two surfaces (e.g., opposite surfaces or opposite sides) of the positive electrode are designed to be different, so that the N / P ratios on the two surfaces (e.g., opposite surfaces or opposite sides) of the positive electrode are designed to be different from each other.

[0032] In this context, the term "loading level" refers to the weight per unit area (mg / cm 2 ), and a loading level that is about 5% or more higher means that if (for example, when) the loading level of the first positive electrode active material layer is A and the loading level of the second positive electrode active material layer is B, the value of {(AB) / A×100} is about 5% or more. In one or more embodiments, the loading level of the first positive electrode active material layer may be about 5% or more higher than the loading level of the second positive electrode active material layer, for example, about 6% or more higher, about 7% or more higher, about 8% or more higher, or about 9% or more higher. Compared with the loading level of the second positive electrode active material layer, the loading level of the first positive electrode active material layer may be about 1 mg / cm higher. 2 or higher, about 1.5 mg / cm 2 or higher or about 2.0 mg / cm 2 If designed in this manner, based on the use of the same positive electrode active material, the utilization rate in the battery cell can be increased and the cycle life characteristics can be improved.

[0033] The N / P ratio of the first positive electrode active material layer during discharge may be about 5% or more lower than the N / P ratio of the second positive electrode active material layer during discharge, for example, about 6% or more lower, about 7% or more lower, about 8% or more lower, or about 9% or more lower. This means that if (for example, when) the N / P ratio of the first positive electrode active material layer is C and the N / P ratio of the second positive electrode active material layer is D, the value of {(DC) / C×100} is about 5% or more. If (for example, when) the N / P ratio when the first positive electrode active material layer is discharged is about 0.1 or more lower than the N / P ratio when (for example, when) the second positive electrode active material layer is discharged. If designed in this way, the battery cell capacity can be increased by improving the cycle life characteristics and increasing the utilization rate. The discharge may be performed at 25° C. under a constant current condition in the range of 0.1C to 1.0C or 0.1C to 0.33C (eg, under a constant current condition of 0.2C), from 4.5V to 3.0V or from 4.25V to 3.0V.

[0034] In one or more embodiments, the N / P ratio of the second positive electrode active material layer during charging may be about 1.00 or more, for example, about 1.10 or more. Charging may be, for example, charging from 3.0V to 4.25V at 25°C under a constant current condition of 0.2C or a constant current condition of 0.2C followed by a constant voltage.

[0035] The positive electrode according to one or more embodiments may be a high-density, low-efficiency positive electrode design. For example, the initial charge / discharge efficiency of the positive electrode may be less than about 89%, for example, about 88% or less or about 87% or less. This can be expressed as an initial charge / discharge efficiency of the entire positive electrode active material including the first positive electrode active material and the second positive electrode active material in the positive electrode may be less than about 89%. In other words, it may be a positive electrode using a positive electrode active material with an efficiency of less than about 89%. In addition, the current density of the positive electrode may be about 4 (e.g., 4.0) mA / cm 2 or greater, for example, about 4.1 mA / cm 2 or greater or about 4.2mA / cm 2 or larger.

[0036] The compound represented by Chemical Formula 1 may be a high nickel lithium composite compound. In Chemical Formula 1, the nickel content (e.g., amount) may be about 88 mol% or more, about 90 mol% or more, or about 91 mol% or more based on the total molar number of metals other than lithium included in the compound. In Chemical Formula 1, 0.9≤x1≤1, 0≤y1≤0.1, and 0≤z1≤0.1, or 0.91≤x1≤1, 0≤y1≤0.09, and 0≤z1≤0.09.

[0037] In one or more embodiments, the high-nickel compound represented by Chemical Formula 1 may be, for example, a lithium nickel cobalt composite oxide represented by Chemical Formula 3, or in some embodiments, a compound represented by Chemical Formula 4, i.e., lithium nickel cobalt aluminum oxide or lithium nickel cobalt manganese oxide.

[0038] Chemical Formula 3

[0039] Li a3 Ni x3 Co y3 M 4 z3 O 2-b3 X b3

[0040] In Chemical Formula 3, 0.9 ≤ a3 ≤ 1.2, 0.88 ≤ x3 < 1, 0 < y3 ≤ 0.12, 0 ≤ z3 ≤ 0.12, 0.9 ≤ x3 + y3 + z3 ≤ 1.1, and 0 ≤ b3 ≤ 0.1, M 4 may be one or more elements selected from (for example) Al, B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, and Zr, and X may be one or more elements selected from (for example) F, P, and S.

[0041] In some embodiments, in Chemical Formula 3, 0.88 ≤ x3 ≤ 0.99, 0.01 ≤ y3 ≤ 0.12, and 0 ≤ z3 ≤ 0.12, or 0.9 ≤ x3 ≤ 0.99, 0.01 ≤ y3 ≤ 0.1, and 0.01 ≤ z3 ≤ 0.1.

[0042] Chemical Formula 4

[0043] Li a4 Ni x4 Co y4 M 5 z4 M 6 w4 O 2-b4 X b4

[0044] In Chemical Formula 4, 0.9 ≤ a4 ≤ 1.2, 0.88 ≤ x4 ≤ 0.98, 0.01 ≤ y4 ≤ 0.11, 0.01 ≤ z4 ≤ 0.11, 0 ≤ w4 ≤ 0.10, 0.9 ≤ x4 + y4 + z4 + w4 ≤ 1.1, and 0 ≤ b4 ≤ 0.1, M 5 may be one or more elements selected from (for example) Al and Mn, M 6It may be (for example, selected from) one or more elements of B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ti, V, W and Zr, and X may be (for example, selected from) one or more elements of F, P and S.

[0045] In some embodiments, in Chemical Formula 4, for example, 0.9≤x4≤0.98, 0.01≤y4≤0.09, 0.01≤z4≤0.09, and 0≤w4≤0.08.

[0046] In one or more embodiments, based on all metals except lithium included in the cobalt-free compound, the nickel content (e.g., amount) in the cobalt-free compound represented by Chemical Formula 2 may be about 70 mol% or more, for example, about 75 mol% or more, about 80 mol% or more, or about 90 mol% or more. In this article, cobalt-free means that there is no cobalt, no cobalt is used, or only a very small amount of cobalt is contained. In one or more embodiments, the compound represented by Chemical Formula 2 may also be a layered cobalt-free positive electrode active material. In Chemical Formula 2, based on all metals except lithium included in the compound, the manganese content (e.g., amount) may be about 0 mol% or more, for example, about 1 mol% or more, about 5 mol% or more, or about 10 mol% or more. In Chemical Formula 2, for example, 0.7≤x2≤0.99, 0.01≤y2≤0.3, and 0≤z2≤0.29; 0.75≤x2≤0.99, 0.01≤y2≤0.25, and 0≤z2≤0.24; or 0.75≤x2≤0.95, 0.05≤y2≤0.25, and 0≤z2≤0.24.

[0047] The first positive electrode active material may be in the form of a secondary particle in which at least two primary particles are aggregated (for example, in a polycrystalline form). The second positive electrode active material is in the form of a single particle, exists independently without a grain boundary within the particle, is composed of one particle, and has a single particle, a monolithic structure, a one-piece structure, or a non-aggregated particle in which the particles are not aggregated with each other but exist as independent phases in terms of morphology, and can be represented as a single particle (one-piece particle, single grain), for example, can be represented as a single crystal.

[0048] The average particle size of the secondary particles of the first positive electrode active material is greater than the average particle size of the single particles of the second positive electrode active material. For example, the average particle size of the secondary particles of the first positive electrode active material may be about 5 micrometers (μm) to about 25 μm, about 7 μm to about 25 μm, about 10 μm to about 20 μm, or about 12 μm to about 18 μm. The average particle size of the single particles of the second positive electrode active material may be about 1 μm to about 10 μm, for example, about 1 μm to about 8 μm, about 1 μm to about 6 μm, or about 2 μm to about 5 μm. When the first positive electrode active material and the second positive electrode active material each meet the above average particle size range, the density of the mixture can be improved, and high capacity and energy density can be achieved. In this article, in one or more embodiments, about 20 secondary particles can be randomly selected from a scanning electron micrograph of the positive electrode active material and the diameter (D 50 ) as the average particle diameter. In one or more embodiments, the average particle diameter of the first positive electrode active material can be measured by randomly selecting about 20 individual particles from a scanning electron micrograph of the positive electrode active material and using the diameter (D 50 ) is measured as the average particle size of the second positive electrode active material.

[0049] In a positive electrode active material layer, that is, in any one selected from the first positive electrode active material layer and the second positive electrode active material, based on the total amount of the first positive electrode active material and the second positive electrode active material, the first positive electrode active material can be included in an amount of about 60wt% to about 95wt%, and the second positive electrode active material can be included in an amount of about 5wt% to about 40wt%. For example, in some embodiments, the first positive electrode active material can be included in an amount of about 60wt% to about 90wt% or about 70wt% to about 90wt%, and the second positive electrode active material can be included in an amount of about 10wt% to about 40wt% or about 10wt% to about 30wt%. When the content (e.g., amount) ratio of the first positive electrode active material and the second positive electrode active material satisfies the above range, the positive electrode active material can achieve high capacity, improve the density of the mixture, and exhibit high energy density.

[0050] In one or more embodiments, the positive electrode active material layer (eg, any one selected from the first positive electrode active material layer and the second positive electrode active material layer) may further include a binder and / or a conductive material in addition to the aforementioned positive electrode active material.

[0051] The binder improves the bonding properties of the positive electrode active material particles to each other and the bonding properties of the positive electrode active material particles to the positive electrode current collector. Examples of binders may include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin and / or nylon, but the embodiments of the present disclosure are not limited thereto. Based on the total weight of the positive electrode active material layer, the content (e.g., amount) of the binder in the positive electrode active material layer may be approximately about 0.1wt% to about 5wt% or about 0.5wt% to about 3wt%.

[0052] A conductive material may be included to provide electrode conductivity, and any conductive material may be used as a conductive material unless it causes a chemical change. Examples of conductive materials may 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 of copper, nickel, aluminum, silver, etc.; conductive polymers (such as polyphenylene derivatives); or (e.g., any suitable) mixtures thereof. The content (e.g., amount) of the conductive material in the positive electrode active material layer may be about 0.1 wt% to about 5 wt% or about 0.5 wt% to about 3 wt%, based on the total weight of the positive electrode active material layer.

[0053] The positive electrode current collector may use aluminum foil, stainless steel (SUS), or the like, but the embodiments of the present disclosure are not limited thereto.

[0054] Stacked or stacked type rechargeable lithium battery

[0055] According to one or more embodiments of the present disclosure, a stacked or stacked type rechargeable lithium battery may include the aforementioned positive electrode and negative electrode. The rechargeable lithium battery may be a lithium ion battery of a type or kind including a separator between the positive electrode and the negative electrode and a liquid electrolyte, but the embodiments of the present disclosure are not limited thereto. A stacked or stacked type rechargeable lithium battery may refer to a battery in which electrode plates are stacked, and is different from a winding or pole core type battery or a winding or pole core type battery, and may also be referred to as a stacked or stacked type battery. The battery cell design according to one or more embodiments may be applicable to a stacked or stacked type battery. A stacked or stacked type battery here refers to a structure in which the pole core of the positive electrode-separator-negative electrode combination is substantially uniformly in contact on all surfaces without any curved surface, and is repeatedly stacked in a positive electrode-separator-negative electrode-separator-positive electrode combination.

[0056] Negative electrode

[0057] The negative electrode for a rechargeable lithium battery may include a negative electrode current collector and a negative electrode active material layer on the negative electrode current collector. The negative electrode active material layer may include a negative electrode active material, and may further include a binder and / or a conductive material.

[0058] The negative electrode active material may include a material that reversibly intercalates / deintercalates lithium ions, lithium metal, a lithium metal alloy, a material capable of doping / dedoping lithium, and / or a transition metal oxide.

[0059] The material that reversibly intercalates / deintercalates lithium ions may 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 may be irregularly shaped or flaky, sheet-like, spherical, or fibrous natural graphite or artificial graphite. The amorphous carbon may be soft carbon, hard carbon, mesophase pitch carbonization product, calcined coke, etc.

[0060] The lithium metal alloy may include an alloy of lithium and a metal (e.g., selected from) sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), francium (Fr), beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), silicon (Si), antimony (Sb), lead (Pb), indium (In), zinc (Zn), barium (Ba), radium (Ra), germanium (Ge), aluminum (Al), and tin (Sn).

[0061] The material capable of doping / dedoping lithium may be an Si-based negative electrode active material or an Sn-based negative electrode active material. The Si-based negative electrode active material may include silicon, silicon-carbon composite particles, SiO x (0 < x ≤ 2), an Si-Q alloy (where Q is an alkali metal, alkaline earth metal, Group 13 element, Group 14 element (excluding Si), Group 15 element, Group 16 element, transition metal, rare earth element, and / or a combination thereof (e.g., any suitable combination)), and the Sn-based negative electrode active material may include Sn, SnO2, an Sn-R alloy (where R is an alkali metal, alkaline earth metal, Group 13 element, Group 14 element (excluding Sn), Group 15 element, Group 16 element, transition metal, rare earth element, and / or a combination thereof (e.g., any suitable combination)). At least one of these materials (e.g., selected from) may be mixed with SiO2. The element Q and the element R may be (e.g., selected from) magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), radium (Ra), scandium (Sc), yttrium (Y), titanium (Ti), zirconium (Zr), hafnium (Hf), rutherfordium (Rf), vanadium (V), niobium (Nb), tantalum (Ta), dubnium (Db), chromium (Cr), molybdenum (Mo), tungsten (W), (Sg), technetium (Tc), rhenium (Re), (Bh), iron (Fe), lead (Pb), ruthenium (Ru), osmium (Os), (Hs), rhodium (Rh), iridium (Ir), palladium (Pd), platinum (Pt), copper (Cu), silver (Ag), gold (Au), zinc (Zn), cadmium (Cd), boron (B), aluminum (Al), gallium (Ga), tin (Sn) (R does not include Sn), indium (In), thallium (Tl), germanium (Ge), phosphorus (P), arsenic (As), antimony (Sb), bismuth (Bi), sulfur (S), selenium (Se), tellurium (Te), polonium (Po), and one or more of its (e.g., any suitable) combinations.

[0062] In one or more embodiments, the negative electrode active material may include silicon-carbon composite particles. The average particle diameter (D 50 ) may be, for example, about 0.5 μm to about 20 μm. The average particle diameter (D 50 ) is measured by a particle size analyzer and refers to the diameter of the particles with a cumulative volume of 50% by volume in the particle size distribution. Based on 100 wt% of the silicon-carbon composite particles, silicon may be included in an amount of about 10 wt% to about 60 wt%, and carbon may be included in an amount of about 40 wt% to about 90 wt%. In some embodiments, the silicon-carbon composite particles may include a core containing silicon particles and a carbon coating on the surface of the core. The average particle diameter (D 50 ) of the silicon particles in the core may be about 10 nm to about 1 μm or about 10 nm to about 200 nm. The silicon particles may exist alone as silicon, in the form of a silicon alloy, or in an oxidized form. The oxidized form of silicon may be represented by SiO x (0 < x < 2). In one or more embodiments, the thickness of the carbon coating may be about 5 nm to 100 nm.

[0063] In one or more embodiments, the silicon-carbon composite particles may include a core containing silicon particles and crystalline carbon and a carbon coating on the surface of the core and including amorphous carbon. For example, in some embodiments, in the silicon-carbon composite particles, amorphous carbon may not exist in the core but only in the carbon coating. The crystalline carbon may be artificial graphite, natural graphite, and / or one or more of its (e.g., any suitable) combinations, and the amorphous carbon may be formed from coal-based pitch, mesophase pitch, petroleum-based pitch, coal-based oil, heavy petroleum, or polymer resins (phenolic resin, furan resin, polyimide resin, etc.). In one or more embodiments, based on 100 wt% of the silicon-carbon composite particles, the content (e.g., amount) of the crystalline carbon may be about 10 wt% to about 70 wt%, and the content (e.g., amount) of the amorphous carbon may be about 20 wt% to about 40 wt%.

[0064] In the silicon-carbon composite particles, the core may include voids in the center. The radius of the voids may be about 30% to about 50% of the radius of the silicon-carbon composite particles.

[0065] The aforementioned silicon-carbon composite particles can effectively inhibit or reduce problems such as volume expansion, structural collapse or particle breakage caused by charging and discharging, prevent or reduce the disconnection of the conductive path, achieve high capacity and high efficiency, and are conducive to use under high voltage or fast charging conditions.

[0066] 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. When the Si-based negative electrode active material or the Sn-based negative electrode active material is mixed and used with the carbon-based negative electrode active material, the mixing ratio may be about 1:99 to about 90:10 by weight.

[0067] In the negative electrode active material layer, the negative electrode active material may be included in an amount of about 95 wt % to about 99 wt % based on the total weight of the negative electrode active material layer.

[0068] In one or more embodiments, the negative electrode active material layer further includes a binder, and optionally further includes a conductive material. Based on the gross weight of the negative electrode active material layer, the content (e.g., amount) of the binder in the negative electrode active material layer may be about 1wt% to about 5wt%. In one or more embodiments, if (e.g., when) a conductive material is further included, the negative electrode active material layer may include about 90wt% to about 98wt% of the negative electrode active material, about 1wt% to about 5wt% of the binder, and about 1wt% to about 5wt% of the conductive material.

[0069] The binder is used to bind the negative electrode active material particles well to each other and also to bind the negative electrode active material to the negative electrode current collector. The binder may be a water-insoluble binder, a water-soluble binder and / or (eg, any appropriate) combination thereof.

[0070] Non-limiting examples of water-insoluble binders may include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, ethylene propylene copolymers, polystyrene, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide and / or (e.g., any suitable) combinations thereof.

[0071] The water-soluble binder may include a rubber binder and / or a polymer resin binder. The rubber binder may be (e.g., selected from) one or more of styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile-butadiene rubber, acrylic rubber, butyl rubber, fluororubber, and (e.g., any appropriate) combinations thereof. The polymer resin binder may be (e.g., selected from) one or more of polyethylene oxide, polyvinyl pyrrolidone, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, ethylene propylene diene copolymer, polyvinyl pyridine, chlorosulfonated polyethylene, latex, polyester resin, acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, and (e.g., any appropriate) combinations thereof.

[0072] If (for example, when) a water-soluble binder is used as a negative electrode binder, a cellulose compound capable of imparting viscosity (for example, as a thickener) may be further included. As the cellulose compound, one or more of (for example, selected from) carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose and alkali metal salts thereof may be mixed and used. The alkali metal may be Na, K or Li. Based on 100 parts by weight of the negative electrode active material, the amount of the thickener used may be about 0.1 parts by weight to about 3 parts by weight.

[0073] In one or more embodiments, a conductive material may be included to provide electrode conductivity, and any conductive material may be used as the conductive material unless it causes a chemical change. Non-limiting examples of conductive materials may 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 of copper, nickel, aluminum, silver, etc.; conductive polymers (such as polyphenylene derivatives); or (e.g., any suitable) mixtures thereof.

[0074] The negative electrode current collector may include one of (eg, selected from) copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, and (eg, any appropriate) combinations thereof.

[0075] In one or more embodiments, the negative electrode may include a negative electrode current collector, a first negative electrode active material layer on one surface of the negative electrode current collector, and a second negative electrode active material layer on another surface of the negative electrode current collector (e.g., a surface opposite to the one surface). In this regard, the load levels on the two surfaces (e.g., opposite surfaces or opposite sides) of the negative electrode current collector may be substantially the same. For example, in one or more embodiments, the difference between the load level of the first negative electrode active material layer and the load level of the second negative electrode active material layer may be about 0 mg / cm 2 ~about 0.6mg / cm 2 , about 0mg / cm 2~about 0.5mg / cm 2 , about 0mg / cm 2 ~about 0.4mg / cm 2 , about 0mg / cm 2 ~about 0.3mg / cm 2 , about 0mg / cm 2 ~about 0.2mg / cm 2 or about 0mg / cm 2 ~about 0.1mg / cm 2 In a stacked or stacked-type rechargeable lithium battery according to one or more embodiments, the load levels on both surfaces (e.g., opposite surfaces or opposite sides) of the negative electrode are designed to be substantially the same, and only the load levels on both surfaces (e.g., opposite surfaces or opposite sides) of the positive electrode are designed to be different, which may mean that the N / P ratios on both surfaces (e.g., opposite surfaces or opposite sides) of the positive electrode are designed to be different from each other.

[0076] Electrolytes

[0077] The electrolyte (eg, liquid electrolyte) may include a non-aqueous organic solvent and a lithium salt.

[0078] The non-aqueous organic solvent is used as a medium for transmitting ions involved in the electrochemical reaction of the battery. The non-aqueous organic solvent may be a carbonate solvent, an ester solvent, an ether solvent, a ketone solvent, an alcohol solvent or an aprotic solvent. Non-limiting examples of carbonate solvents may include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), ethyl methyl carbonate (MEC), ethylene carbonate (EC) propylene carbonate (PC), butylene carbonate (BC), etc. Non-limiting examples of ester solvents may include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, γ-butyrolactone, decalactone, valerolactone, mevalonolactone, caprolactone, etc. The ether solvent may be dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, dimethoxyethane, 2-methyltetrahydrofuran, tetrahydrofuran, etc., and the ketone solvent may be cyclohexanone, etc. In one or more embodiments, the alcohol solvent may be ethanol, isopropanol, etc., and the aprotic solvent may be nitriles (such as R-CN, wherein R is a C2-C20 straight chain, branched chain or cyclic hydrocarbon group, and may include a double bond, an aromatic ring or an ether bond), an amide (such as dimethylformamide), a dioxolane (such as 1,3-dioxolane), sulfolane, etc.

[0079] The nonaqueous organic solvent may be used alone or in a mixture. If (eg, when) the nonaqueous organic solvent is used in a mixture, the mixing ratio may be controlled or selected according to desired battery performance.

[0080] In one or more embodiments, for carbonate solvents, a mixture of cyclic carbonate and linear carbonate can be used. In these embodiments, if (for example, when) cyclic carbonate and linear carbonate are mixed in a volume ratio of about 1:1 to about 1:9, the electrolyte solution (i.e., liquid electrolyte) can show excellent or appropriate performance.

[0081] In one or more embodiments, the non-aqueous organic solvent may further include an aromatic hydrocarbon organic solvent in addition to the linear carbonate solvent. In these embodiments, the linear carbonate solvent and the aromatic hydrocarbon organic solvent may be mixed in a volume ratio of about 1:1 to about 30:1.

[0082] The aromatic hydrocarbon organic solvent may be an aromatic hydrocarbon compound represented by Chemical Formula I.

[0083] Chemical formula I

[0084]

[0085] In Formula I, R 4 To R 9 may be the same or different, and may each independently be one of (eg, selected from) hydrogen, halogen, C1-C10 alkyl, C1-C10 haloalkyl, and (eg, any appropriate) combinations thereof.

[0086] Non-limiting examples of the aromatic hydrocarbon organic solvent may be benzene, fluorobenzene, 1,2-difluorobenzene, 1,3-difluorobenzene, 1,4-difluorobenzene, 1,2,3-trifluorobenzene, 1,2,4-trifluorobenzene, chlorobenzene, 1,2-dichlorobenzene, 1,3-dichlorobenzene, 1,4-dichlorobenzene, 1,2,3-trichlorobenzene, 1,2,4-trichlorobenzene, iodobenzene, 1,2-diiodobenzene, 1,3-diiodobenzene, 1,4-diiodobenzene, 1,2,3-triiodobenzene, 1,2,4-triiodobenzene, toluene, 2,3-fluorotoluene, and the like. Difluorotoluene, 2,4-difluorotoluene, 2,5-difluorotoluene, 2,3,4-trifluorotoluene, 2,3,5-trifluorotoluene, chlorotoluene, 2,3-dichlorotoluene, 2,4-dichlorotoluene, 2,5-dichlorotoluene, 2,3,4-trichlorotoluene, 2,3,5-trichlorotoluene, iodotoluene, 2,3-diiodotoluene, 2,4-diiodotoluene, 2,5-diiodotoluene, 2,3,4-triiodotoluene, 2,3,5-triiodotoluene, xylene and / or (e.g., any suitable) combination thereof.

[0087] In one or more embodiments, the electrolyte solution may further include vinylene carbonate or an ethylene carbonate-based compound represented by Chemical Formula II as an additive to improve the cycle life of the battery.

[0088] Chemical formula II

[0089]

[0090] In Chemical Formula II, R 10 and R 11 may be the same or different and may each independently be (for example, selected from) one of hydrogen, halogen, cyano, nitro and fluorinated C1-C5 alkyl, provided that R 10 and R 11 At least one of them is halogen, cyano, nitro or fluorinated C1-C5 alkyl, and R 10 and R 11 Not simultaneously (eg, synchronously) hydrogen.

[0091] Non-limiting examples of ethylene carbonate compounds may be difluoroethylene carbonate, chloroethylene carbonate, dichloroethylene carbonate, bromoethylene carbonate, dibromoethylene carbonate, nitroethylene carbonate, cyanoethylene carbonate and / or fluoroethylene carbonate. The amount of the additive for improving the cycle life may be used within an appropriate or suitable range.

[0092] The lithium salt dissolved in the non-organic solvent supplies lithium ions in the battery, ensures the basic operation of the rechargeable lithium battery, and improves the transport of lithium ions between the positive electrode and the negative electrode.

[0093] Non-limiting examples of lithium salts may include (e.g., selected from) LiPF6, LiBF4, LiSbF6, LiAsF6, LiN(SO2C2F5)2, Li(CF3SO2)2N, LiN(SO3C2F5)2, Li(FSO2)2N (lithium bis(fluorosulfonyl)imide; LiFSI), LiC4F9SO3, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiN(C x F 2x+1 SO2)(C y F 2y+1 SO2) (wherein x and y are each a natural number, for example, an integer in the range of 1 to 20), at least one carrier salt selected from lithium difluoro(oxalato)phosphate, LiCl, LiI, LiB(C2O4)2 (lithium bis(oxalato)borate; LiBOB) and lithium difluoro(oxalato)borate (LiDFOB).

[0094] The lithium salt may be used in a concentration range of about 0.1 M to about 2.0 M. When the lithium salt is included in the above concentration range, the electrolyte may have excellent or appropriate performance and lithium ion mobility due to optimal or appropriate electrolyte conductivity and viscosity.

[0095] Diaphragm

[0096] The separator separates the positive electrode from the negative electrode and provides a channel for the movement of lithium ions, and any type or species commonly used in lithium ion batteries can be used. In other words, the separator can have a relatively low ion transport resistance and can have excellent or appropriate impregnation for the electrolyte. For example, the separator can be (for example, selected from) one of glass fiber, polyester, polyethylene, polypropylene, polytetrafluoroethylene and its (for example, any appropriate) combination. The separator can have the form of a non-woven fabric or a textile. For example, in lithium ion batteries, polyolefin polymers (such as polyethylene and polypropylene) separators are mainly used. In order to ensure heat resistance or mechanical strength, in one or more embodiments, a coated separator including a ceramic component and / or a polymer material can be used. In one or more embodiments, the separator can have a single-layer structure or a multilayer structure.

[0097] Rechargeable lithium batteries can be classified as lithium ion batteries, lithium ion polymer batteries, or lithium polymer batteries, depending on the presence of a separator and the type or kind of electrolyte used therein. Rechargeable lithium batteries can have various shapes and sizes, and include cylindrical, prismatic, coin, or pouch-type batteries or cylindrical, prismatic, coin, or pouch-type batteries, and can be thin film batteries or can be quite bulky in size. The structures and manufacturing methods for the rechargeable lithium batteries related to the present disclosure are well known in the art.

[0098] The rechargeable lithium battery according to one or more embodiments has high capacity and has excellent or appropriate storage stability, cycle life characteristics, and high rate characteristics at high temperatures, so that it can be used in electric vehicles (EVs), hybrid vehicles such as plug-in hybrid electric vehicles (PHEVs), and also in portable electronic devices.

[0099] Hereinafter, Examples and Comparative Examples are described. However, it is to be understood that the Examples are for illustrative purposes and are not to be construed as limiting the present disclosure.

[0100] Example 1

[0101] 1. Manufacturing of positive electrode

[0102] The secondary particles prepared by aggregating a plurality of primary particles and having an average particle size (D) of about 15 μm were mixed in a weight ratio of 7:3. 50 ) by the chemical formula Li 1.05 Ni 0.91 Co 0.05 Al 0.04 The first positive electrode active material represented by O2 and in the form of a single particle having an average particle size (D 50 ) by the chemical formula Li 1.05 Ni 0.91 Co 0.05 Al0.04 A second positive electrode active material represented by O2 is prepared to prepare a positive electrode active material.

[0103] 97.7 wt % of the positive electrode active material is mixed with 1.3 wt % of the polyvinylidene fluoride binder and 1.0 wt % of the carbon nanotube conductive material in an N-methylpyrrolidone solvent to prepare a positive electrode active material slurry. The positive electrode active material slurry is coated on both surfaces (e.g., opposite surfaces or opposite sides) of the aluminum current collector, and then dried at 120° C. for 1 hour and rolled to produce a stacked or stacked positive electrode, wherein the loading level of the first positive electrode active material layer on one surface of the aluminum current collector is 26.4 mg / cm 2 , while the loading level of the second positive electrode active material layer on the other surface of the aluminum current collector was 24.0 mg / cm 2 The loading level of the first positive electrode active material layer is about 9.1% or more higher than the loading level of the second positive electrode active material layer. In this article, the positive electrode is designed to have a current of about 4.2 mA / cm 2 of current density.

[0104] 2. Manufacturing of stacked or stacked rechargeable lithium battery cells

[0105] 97 wt % of a graphite negative electrode active material, 1.5 wt % of a styrene butadiene rubber binder, 1.5 wt % of a carboxymethyl cellulose, and a distilled water solvent are mixed to prepare a negative electrode active material slurry, and the negative electrode active material slurry is coated on both surfaces (e.g., opposite surfaces or opposite sides) of a copper current collector, and then dried and roll-pressed to manufacture a negative electrode, and the negative electrode has a carbon fiber content of 33.34 mg / cm on both surfaces (e.g., opposite surfaces or opposite sides). 2 Loading level (single surface: 16.67 mg / cm 2 ).

[0106] After stacking a separator having a polyethylene polypropylene multilayer structure on the positive electrode, a negative electrode is stacked thereon, and this operation is repeated to manufacture a positive electrode-separator-negative electrode-separator-positive electrode multilayer structure battery cell, and the battery cell is inserted into the housing. After ethylene carbonate, ethyl methyl carbonate and dimethyl carbonate are mixed in a volume ratio of 2:4:4, and 1.15M of LiPF6 lithium salt is added thereto to prepare an alkaline electrolyte solution, then 1.5 parts by weight of vinyl carbonate and 0.5 parts by weight of vinyl ethylene carbonate are added to 100 parts by weight of the alkaline electrolyte solution to prepare a final electrolyte solution, which is injected into the housing to manufacture a stacked or stacked type rechargeable lithium battery cell.

[0107] Comparative Example 1

[0108] In addition to the first positive electrode active material layer and the second positive electrode active material layer being formed to have a 25.5 mg / cm 2 A positive electrode and a rechargeable lithium battery cell were manufactured in substantially the same manner as in Example 1, except for the loading level of .

[0109] Comparative Example 2

[0110] In addition to using a plurality of primary particles that are aggregated and have an average particle size (D 50 A positive electrode and a rechargeable lithium battery cell were manufactured in substantially the same manner as in Example 1, except that the secondary particles of ) were used as the second positive electrode active material.

[0111] Comparative Example 3

[0112] In addition to using a plurality of primary particles that are aggregated and have an average particle size (D 50 A positive electrode and a rechargeable lithium battery cell were manufactured in substantially the same manner as in Comparative Example 1, except that the secondary particles of ) were used as the second positive electrode active material.

[0113] Reference Example 1 to Reference Example 3

[0114] In addition to using a fixed 2 The single surface loading level of the double-surface negative electrode is changed to 24.0 mg / cm 2 , 25.5mg / cm 2 and 26.4 mg / cm 2 Each rechargeable lithium battery cell was manufactured in substantially the same manner as in Example 1, except that a positive electrode-separator-negative electrode-separator-positive electrode multilayer bag cell was manufactured. Table 1 shows the N / P ratio during charging and the N / P ratio during discharging according to the load level of each positive electrode. At 25°C, charging and discharging were performed under constant current (0.2C) and then constant voltage (4.25V, 0.05C cut-off), paused for 10 minutes, and discharged to 3.0V under constant current (0.2C).

[0115] Table 1

[0116]

[0117]

[0118] Referring to Table 1, the first positive electrode active material layer of Example 1 exhibited an N / P ratio of 1.04 if (for example, when) discharged according to Reference Example 3, and the second positive electrode active material layer of Example 1 exhibited an N / P ratio of 1.14 if (for example, when) discharged according to Reference Example 1. The N / P ratio of 1.04 of the first positive electrode active material layer during discharge was 9.6% lower than the N / P ratio of 1.14 of the second positive electrode active material ({1.14-1.04} / 1.04×100), wherein each positive electrode active material was used in an amount similar to that of the double surface active material layer under the conditions of Reference Example 2.

[0119] Evaluation Example 1

[0120] The rechargeable lithium battery cells of Example 1 and Comparative Example 1 were each initially charged and discharged under the same conditions as the reference example, and then the initial charge capacity and the initial discharge capacity were measured, which were used to calculate the ratio of the latter (initial discharge capacity) to the former (initial charge capacity), and the results are shown in Table 2 as efficiency. After the initial charge and discharge, the rechargeable lithium battery cells were each charged and discharged 100 times at 0.5C / 0.5C. The ratio of the discharge capacity per cycle to the initial discharge capacity (i.e., the cycle life characteristics) was evaluated, and the results are shown in Table 2. Figure 1 The capacity retention ratio is shown in FIG.

[0121] Table 2

[0122]

[0123] Refer to Table 2 and Figure 1 , compared with Comparative Example 1 having the same loading level on both surfaces (eg, opposite surfaces or opposite sides) of the positive electrode, the positive electrode of Example 1 exhibited increased initial discharge capacity and efficiency, and thus greatly improved cycle life characteristics.

[0124] Evaluation Example 2

[0125] For reference, a coin half cell (referred to as Reference Example 4) was manufactured by using a mixed positive electrode active material of large secondary particles and small secondary particles as in Comparative Examples 2 and 3, and another coin half cell was manufactured by using a mixed positive electrode active material of large secondary particles and small single particles as in Reference Example 1, and the rechargeable lithium battery cells were each initially charged and discharged under the same conditions as in Reference Examples 1 to 3. In Table 3, the initial charge and discharge capacities and efficiencies of the rechargeable lithium battery cells of Reference Examples 1 and 4 are shown.

[0126] Table 3

[0127]

[0128] Referring to Table 3, Reference Example 4 corresponding to Comparative Examples 2 and 3 exhibited an initial charge and discharge efficiency of 89.0% or more, but Reference Example 1 corresponding to the embodiment exhibited an initial charge and discharge efficiency of about 87.2%. Herein, under the same conditions as in Evaluation Example 1, the cycle life characteristics of the rechargeable lithium battery cells of Comparative Examples 2 and 3 were each evaluated, and the results were Figure 2 , there is not much difference between the results of Comparative Example 2 and Comparative Example 3, which are shown as capacity retention rates. In other words, Comparative Examples 2 and 3, which use a type or kind of positive electrode active material with an initial charge and discharge efficiency of 89% or more, have no difference in effect even if they are designed to have different load levels (or different N / P ratios) on the two surfaces (e.g., opposite surfaces or opposite sides) of each positive electrode. In contrast, Example 1, which uses a type or kind of positive electrode active material with an initial charge and discharge efficiency of less than 89% (wherein the load level of each positive electrode is designed to be different at a specific level on two surfaces (e.g., opposite surfaces or opposite sides)), exhibits increased specific capacity and improved cycle life characteristics.

[0129] As used herein, the terms "substantially," "about," and similar terms are used as terms of approximation and not as terms of degree, and are intended to account for the inherent deviations in measured or calculated values ​​that one of ordinary skill in the art would recognize. "About" or "approximately" as used herein also include the stated value and mean within an acceptable range of deviation for the particular value as determined by one of ordinary skill in the art taking into account the measurement in question and the errors associated with the measurement of the particular quantity (i.e., the limitations of the measurement system). For example, "about" may mean within one or more standard deviations of the stated value, or within ±30%, ±20%, ±10%, or ±5% of the stated value.

[0130] Any numerical range set forth in this article is intended to include all subranges of the same numerical precision contained in the range set forth. For example, the range of "1.0-10.0" is intended to include all subranges between the minimum value 1.0 set forth and the maximum value 10.0 set forth (and including 1.0 and 10.0), i.e., all subranges with a minimum value equal to or greater than 1.0 and a maximum value equal to or less than 10.0, such as, for example, 2.4-7.6. Any maximum numerical limit set forth in this article is intended to include all lower numerical limits incorporated therein, and any minimum numerical limit set forth in this specification is intended to include all higher numerical limits incorporated therein. Accordingly, the applicant reserves the right to modify this specification (including claims) to explicitly set forth any subranges incorporated within the range explicitly set forth herein.

[0131] The battery management system (BMS) device and / or any other related device or component according to the embodiment of the present invention described herein may be implemented using any appropriate hardware, firmware (e.g., a dedicated integrated circuit), software, or a combination of software, firmware, and hardware. For example, the various components of the device may be formed on an integrated circuit (IC) chip or may be formed on a separate IC chip. In addition, the various components of the device may be implemented on a flexible printed circuit film, a tape carrier package (TCP), or a printed circuit board (PCB), or may be formed on a substrate. In addition, the various components of the device may 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 various functions described herein. The computer program instructions are stored in a memory, which may be implemented in a computing device using a standard memory device (such as, for example, a random access memory (RAM)). The computer program instructions may also be stored in other non-temporary computer-readable media (such as, for example, a CD-ROM, a flash drive, etc.). Furthermore, those skilled in the art will recognize that the functionality of various computing devices may be combined or integrated into a single computing device, or the functionality of a dedicated computing device may be distributed across one or more other computing devices without departing from the scope of the embodiments of the present disclosure.

[0132] Although the present disclosure has been described in conjunction 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. Instead, it is intended to cover one or more suitable modifications and equivalent arrangements included within the spirit and scope of the claims and their equivalents.

Claims

1. A positive electrode comprising: positive electrode current collector; a first positive electrode active material layer on one surface of the positive electrode current collector; as well as a second positive electrode active material layer on the other surface of the positive electrode current collector, in, the loading level of the first positive electrode active material layer is 5% or more higher than the loading level of the second positive electrode active material layer, Each of the first positive electrode active material layer and the second positive electrode active material layer includes a first positive electrode active material in the form of secondary particles including a plurality of primary particles and a second positive electrode active material in the form of a single particle, The average particle size of the secondary particles of the first positive electrode active material is larger than the average particle size of the individual particles of the second positive electrode active material, and The first positive electrode active material and the second positive electrode active material each independently include a compound represented by Chemical Formula 1 or a compound represented by Chemical Formula 2: Chemical formula 1 Li a1 Ni x1 M 1 y1 M 2 z1 O 2-b1 X b1 In Chemical Formula 1, 0.9≤a1≤1.2, 0.88≤x1≤1, 0≤y1≤0.12, 0≤z1≤0.12, 0.9≤x1+y1+z1≤1.1, and 0≤b1≤0.1, M 1 and M 2 are each independently one or more elements selected from Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, Zn and Zr, and X is one or more elements selected from F, P and S, Chemical formula 2 Li a2 Ni x2 Mr y2 M 3 z2 O 2-b2 X b2 In Chemical Formula 2, 0.9 ≤ a2 ≤ 1.8, 0.7 ≤ x2 < 1, 0 < y2 ≤ 0.3, 0 ≤ z2 ≤ 0.3, 0.9 ≤ x2 + y2 + z2 ≤ 1.1, and 0 ≤ b2 ≤ 0.1, M 3 is one or more elements selected from Al, B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ti, V, W, Zn, and Zr, and X is one or more elements selected from F, P, and S, and The positive electrode is used in a stacked rechargeable lithium battery.

2. The positive electrode according to claim 1, wherein The ratio of the negative electrode plate capacity to the positive electrode plate capacity of the first positive electrode active material layer during discharge is smaller than the ratio of the negative electrode plate capacity to the positive electrode plate capacity of the second positive electrode active material layer during discharge.

3. The positive electrode according to claim 1, wherein The ratio of the negative electrode plate capacity to the positive electrode plate capacity of the first positive electrode active material layer during discharge is 5% or more lower than the ratio of the negative electrode plate capacity to the positive electrode plate capacity of the second positive electrode active material layer during discharge.

4. The positive electrode according to claim 1, wherein The ratio of the negative electrode plate capacity to the positive electrode plate capacity of the second positive electrode active material layer during charging is greater than or equal to 1.

5. The positive electrode according to claim 1, wherein The current density of the positive electrode is greater than or equal to 4 mA / cm 2 .

6. The positive electrode according to claim 1, wherein The initial charge / discharge efficiency of the positive electrode is less than 89%.

7. The positive electrode according to claim 1, wherein The average particle size of the secondary particles of the first positive electrode active material is 5 μm to 25 μm, and The average particle size of the single particles of the second positive electrode active material is 1 μm to 10 μm.

8. The positive electrode according to claim 1, wherein In the positive electrode active material layer selected from the first positive electrode active material layer and the second positive electrode active material layer, based on the total amount of the first positive electrode active material and the second positive electrode active material, the amount of the first positive electrode active material is 60wt% to 95wt% and the amount of the second positive electrode active material is 5wt% to 40wt%.

9. A stacked rechargeable lithium battery comprising the positive electrode and the negative electrode as claimed in any one of claims 1 to 8.

10. The stacked rechargeable lithium battery according to claim 9, wherein: The negative electrode includes a material that reversibly intercalates / deintercalates lithium ions, a material capable of doping / dedoping lithium, lithium metal, a lithium metal alloy, a transition metal oxide, or a combination thereof.

11. The stacked rechargeable lithium battery according to claim 10, wherein: The material that can reversibly embed / de-embed lithium ions is a carbon-based negative electrode active material, The material capable of being doped / dedoped with lithium is a silicon-based negative electrode active material or a tin-based negative electrode active material.

12. The stacked rechargeable lithium battery according to claim 9, wherein: The negative electrode includes a negative electrode current collector, a first negative electrode active material layer on one surface of the negative electrode current collector, and a second negative electrode active material layer on the other surface of the negative electrode current collector, and The difference between the loading level of the first negative electrode active material layer and the loading level of the second negative electrode active material layer is 0 mg / cm 2 ~0.6mg / cm 2 .

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