Crucible and crucible assembly for manufacturing positive electrode active material

Abstract

A crucible assembly for manufacturing a positive electrode active material is provided, which includes a first crucible having an open top and a predetermined internal space, and a second crucible disposed below the first crucible and disposed at the upper end of each side wall, but having a cut groove with a preset open area.

Description

Technical Field

[0001] The present invention relates to a crucible and a crucible assembly for manufacturing a positive electrode active material.

Background Art

[0002] After lithium secondary batteries were commercialized by Sony in 1991, the demand has been increasing rapidly in various fields from small household appliances to medium and large electric vehicles and energy storage systems. In particular, for medium and large electric vehicles and energy storage systems, a low-cost, high-energy positive electrode material is essential. However, cobalt, which is the main raw material of single-crystalline LiCoO2 (LCO), the currently commercialized positive electrode active material, is expensive.

[0003] Therefore, recently, as a positive electrode active material for medium and large secondary batteries, instead of LCO, LiNi in which a part of Co is replaced with another transition metal x Co y Mn z O2 (NCM) (x + y + z = 1) and LiNi x Co y Al zUsing a Ni-based cathode active material represented by O2(NCA)(x + y + z = 1), such NCM-based and NCA-based cathode active materials have the advantages that the raw material nickel is inexpensive and has a high reversible capacity. In particular, in terms of high capacity, NCM and NCA with a Ni molar ratio of 50 mol% or more have attracted attention. Generally, such Ni-based cathode active materials are manufactured by mixing a transition metal compound precursor synthesized by a coprecipitation method with a lithium source and then performing solid-phase synthesis. However, the Ni-based cathode material synthesized in this way exists in the form of secondary particles in which small primary particles are agglomerated, and there is a problem that micro-cracks occur inside the secondary particles during a long-term charge-discharge process. The micro-cracks induce side reactions between a new interface of the cathode active material and the electrolyte, resulting in battery performance degradation such as a decrease in stability due to gas generation and a decrease in battery performance due to electrolyte depletion. In addition, in order to realize a high energy density, an increase in electrode density (>3.3 g / cc) is required, which induces the collapse of secondary particles, induces electrolyte depletion due to side reactions with the electrolyte, and induces a sharp drop in the initial life. Eventually, it means that the Ni-based cathode active material in the form of secondary particles synthesized by the existing coprecipitation method cannot realize a high energy density.

[0004] To solve the problems of the above-mentioned Ni-based cathode active material in the form of secondary particles, recently, research has been conducted on single-particle-type Ni-based cathode active materials. The single-crystalline Ni-based cathode active material can exhibit excellent electrochemical performance without particle collapse when the electrode density increases (>3.3 g / cc) for realizing its energy density. However, such a single-crystalline Ni-based cathode active material has been reported to have a problem that the battery stability is reduced due to structural and / or thermal instability caused by unstable Ni 3+ ions, Ni 4+ ions. Therefore, for the development of high-energy lithium secondary batteries, there is still a demand for a technology to stabilize the unstable Ni ions in the single-crystalline Ni-based cathode active material. Summary of the Invention Problems to be Solved by the Invention

[0005] The present invention aims to provide a crucible and a crucible assembly that can produce a cathode active material having a single-particle form and a high energy density. Further, the present invention aims to provide a crucible and a crucible assembly that can produce a Ni-based cathode active material with an extended service life. However, such problems are exemplary and do not limit the scope of the present invention.

Means for Solving the Problems

[0006] One aspect of the present invention provides a crucible assembly for manufacturing a cathode active material, including a first crucible with an open top and a predetermined internal space, and a second crucible disposed below the first crucible and having a cut groove with a preset opening area disposed at the upper end of each side wall.

[0007] Further, the opening area of the cut groove satisfies the following formula:

Number

[0008] Further, the cut groove is also disposed above at the height center of the second crucible.

[0009] Further, the second crucible is disposed such that the side walls face each other, and although a plurality of the cut grooves are provided, they can be disposed so as to overlap the side walls respectively.

[0010] Further, at least one of the first crucible and the second crucible can be formed of a compound represented by the following chemical formula. xAl2O3·yMgO·zSiO2 (0.9 < x < 1, 0 < y < 0.1, 0 < z < 0.1, x + y + z = 1)

[0011] Further, a plurality of the second crucibles are provided, and can be stacked in the height direction below the first crucible.

[0012] Another aspect of the present invention provides a crucible for manufacturing a positive electrode active material having a predetermined internal space formed by a bottom and a side wall, including a slit groove having a preset opening area disposed at an upper end of the side wall, and the opening area of the slit groove is calculated by the following formula:

Equation

[0013] Further, the crucible can be formed of a compound represented by the following chemical formula: xAl2O3·yMgO·zSiO2(0.9 < x < 1, 0 < y < 0.1, 0 < z < 0.1, x + y + z = 1)

[0014] Other aspects, features, and advantages other than those described above will become apparent from the following specific content for implementing the invention, claims, and drawings.

Advantages of the Invention

[0015] The crucible and crucible assembly for manufacturing a positive electrode active material according to the present invention can synthesize a single-particle positive electrode active material. The slit groove is provided on the side wall of the crucible, and high-temperature hot air can sufficiently flow into the internal space of the crucible, enabling the synthesis of a single-particle positive electrode active material.

[0016] The crucible and crucible assembly for manufacturing a positive electrode active material according to the present invention can mass-produce a single-particle positive electrode active material. The crucibles can be stacked in the height direction to form a crucible assembly, and in the stacked crucibles, a large amount of single-particle positive electrode active material can be mass-produced. In particular, since the opening area of the slit groove can be minimized, the amount of positive electrode active material that can be produced in each crucible can be maximized.

[0017] The crucible and crucible assembly for manufacturing a positive electrode active material according to the present invention can produce a positive electrode active material with reduced fine powder of less than 1 μm. By increasing the composition of Al2O3 in the crucible, the amount of fine powder can be minimized in the synthesized positive electrode active material, thereby improving the life stability of the positive electrode active material. Needless to say, the scope of the present invention is not limited by such effects.

Brief Description of the Drawings

[0018]

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Modes for Carrying Out the Invention

[0019] Hereinafter, various embodiments of the present disclosure will be described in relation to the accompanying drawings. The various embodiments of the present disclosure can be modified in various ways and can have various embodiments. Although specific embodiments are illustrated in the drawings and detailed descriptions related thereto are provided, it should be understood that they do not limit the various embodiments of the present disclosure to specific embodiments, but include all modifications and / or equivalents or alternatives included in the spirit and technical scope of the various embodiments of the present disclosure. Regarding the description of the drawings, similar reference numerals are used for similar components.

[0020] Expressions such as "including" or "being inclusive of" that may be used in various embodiments of the present disclosure indicate the presence of the disclosed functions, operations, or components, etc., and do not limit the presence of one or more additional functions, operations, or components, etc. Also, in various embodiments of the present disclosure, terms such as "including" or "having" specify the presence of the features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, and it should not be understood as precluding the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0021] In various embodiments of the present disclosure, expressions such as "or" include any combination and all combinations of the words listed together. For example, "A or B" may include A, may include B, or may include either A or B.

[0022] Expressions such as "first", "second", "initial", or "second" used in various embodiments of the present disclosure can modify various components of the various embodiments, but do not limit the components. For example, the above expressions do not limit the order and / or importance of the components, etc. The above expressions can be used to distinguish one component from another. For example, the first user device and the second user device are both user devices and represent different user devices from each other. For example, without departing from the scope of the rights of various embodiments of the present disclosure, the first component can be named the second component, and similarly, the second component can also be named the first component.

[0023] When it is mentioned that a certain component is "connected" or "attached" to another component, it should be understood that the aforementioned certain component may be directly connected or directly attached to the aforementioned other component, but there may be additional components between the aforementioned certain component and the aforementioned other component. On the other hand, when it is mentioned that a certain component is "directly connected" or "directly attached" to another component, it should be understood that there are no additional components between the aforementioned certain component and the aforementioned other component.

[0024] The terms used in the various embodiments of the present disclosure are merely used to describe specific embodiments and are not intended to limit the various embodiments of the present disclosure. Singular expressions include plural expressions unless the context clearly indicates otherwise.

[0025] Unless otherwise defined, all terms, including those of a technical and scientific nature, used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the various embodiments of the present disclosure belong.

[0026] Commonly used and pre-defined terms should be interpreted as having a meaning consistent with their meaning in the context of the related art and should not be interpreted in an ideal or overly formal sense unless clearly defined in the various embodiments of the present disclosure.

[0027] FIG. 1 is a perspective view showing a crucible assembly 100 for manufacturing a positive electrode active material according to an embodiment of the present invention, FIG. 2 is a perspective view showing a crucible according to an embodiment of the present invention, FIG. 3 is a drawing showing one side wall of the crucible of FIG. 2, and FIG. 4 is a drawing showing a positive electrode active material manufacturing apparatus 1 using the crucible for manufacturing a positive electrode active material of FIG. 1.

[0028] Referring to FIGS. 1 to 4, in the crucible assembly 100 for manufacturing a positive electrode active material, a plurality of crucibles can be stacked in the height direction. Each crucible has a predetermined internal space and can pass through the positive electrode active material manufacturing apparatus 1.

[0029] The positive electrode active material manufacturing apparatus 1 can include a chamber 11 provided with a heat source 12. The chamber 11 can extend in the longitudinal direction and can have a rail 13 that circulates in the longitudinal direction. The crucible assembly 100 for manufacturing a positive electrode active material is provided on the rail 13, and when moving along the rail 13, a positive electrode active material is generated in the crucible assembly 100 by the heat supplied from the heat source 12.

[0030] The crucible assembly 100 for manufacturing a positive electrode active material can have various shapes having an internal space. For example, the crucible assembly 100 for manufacturing a positive electrode active material can have a polyhedral shape or a spherical shape. However, in the following, for the sake of convenience of explanation, an embodiment in which each crucible generally has a hexahedral shape will be mainly described.

[0031] The crucible assembly 100 for manufacturing a positive electrode active material can include a first crucible 110 and a second crucible 120.

[0032] The first crucible 110 has an open upper portion and can have a predetermined internal space. The first crucible 110 is disposed at the uppermost part of the crucible assembly 100 for manufacturing a positive electrode active material. Materials for manufacturing a positive electrode active material can be stored in the internal space of the first crucible 110. While the crucible assembly 100 for manufacturing a positive electrode active material passes through the positive electrode active material manufacturing apparatus 1, the materials can be synthesized into a positive electrode active material.

[0033] The bottom and side walls of the first crucible 110 are not open, but the upper portion can be open. Since the upper portion of the first crucible 110 is open, sufficient heat can be transferred from the positive electrode active material manufacturing apparatus 1. Since the first crucible 110 passes through the positive electrode active material manufacturing apparatus 1 with the upper portion open, the heat generated in the positive electrode active material manufacturing apparatus 1 can directly flow into the internal space.

[0034] Since the bottom and the side wall of the first crucible 110 are closed, sufficient heat for manufacturing the positive electrode active material can be maintained. If heat is transferred to the first crucible 110, the compound constituting the bottom and the side wall maintains the heat for a long time. Therefore, in the first crucible 110, a high-quality positive electrode active material can be manufactured.

[0035] The second crucible 120 is disposed below the first crucible 110. The second crucible 120 may include a bottom 121 and a side wall 122. The upper part of the second crucible 120 is opened together with the first crucible 110. The second crucible 120 has a predetermined internal space formed by the bottom 121 and the side wall 122, and the material for manufacturing the positive electrode active material can be stored therein.

[0036] The second crucible 120 may have a cut groove OP. The cut groove OP is disposed at the upper end of each side wall 122 and may have a preset opening area.

[0037] In one embodiment, the cut groove OP may be disposed above at the center in the height direction of the second crucible 120. The cut groove OP may be disposed at the center of the width of the side wall 122 of the second crucible 120. Referring to FIG. 3, the cut groove OP may be disposed above the center line CL. Since the cut groove OP is disposed at the upper end of the side wall 122, the second crucible 120 can secure a space in which the material for manufacturing the positive electrode active material can be stored. Since the material can be stored up to the cut groove OP, a large amount of positive electrode active material can be manufactured in the second crucible 120.

[0038] In one embodiment, the side walls 122 of the second crucible 120 are arranged to face each other, and a plurality of cut grooves OP may be provided and arranged to overlap the side walls 122 respectively. Referring to FIG. 2, the first cut groove OP1 and the second cut groove OP2 are arranged to face each other in the x-axis direction, and the third cut groove OP3 and the fourth cut groove OP4 are also arranged to face each other in the y-axis direction. Since the cut grooves OP are arranged to face each other, the heat generated in the positive electrode active material manufacturing apparatus 1 can easily move in the internal space of the second crucible 120.

[0039] In one embodiment, the opening area of the incision groove OP can be set by the following formula:

Number

[0040] FIG. 5 is a scanning electron microscope (SEM) photograph of the positive electrode active materials of Examples 1 to 5, and FIG. 6 is a scanning electron microscope (SEM) photograph of the positive electrode active materials of Comparative Examples 1 to 5.

[0041] Referring to FIGS. 5, 6 and Table 1, the positive electrode active materials synthesized by the crucible assemblies according to Examples 1 to 5 can be compared.

[0042] A crucible assembly is provided by stacking crucibles in three stages. Each crucible has a width of W1 (horizontal and vertical lengths) and a height of H1 as shown in FIG. 3, and the incision groove has a width of W2 and a height of H2. In each example and comparative example, W2 and H2 are adjusted, and the ratio (A O / A T ) occupied by the opening area of the incision groove in the area of the side wall is set to be different.

[0043]

Table 1

[0044] In Examples 1 to 5 and Comparative Examples 1 to 5, the positive electrode active material is synthesized by the following method. First, 2,000 g of Ni 0.8 Co 0.1 Mn 0.1(OH)2, 836 g of Li2CO3, 6 g of (NH4)2HPO4, 60 g of WO3, 9 g of NaOH, and 15 g of (NH4)2S are mechanically mixed for about 15 minutes. The mixed powder is weighed into the crucibles of each example and comparative example, and a positive electrode active material is obtained through firing at 1,000 °C for 4 hours and 700 °C for 10 hours. Figure 5 shows the scanning electron microscope (SEM) images of Examples 1 to 5. As in Examples 1 to 5, A O / A T In the crucible where is 0.05 or more, it can be confirmed that a single-particle type Ni-based positive electrode active material was synthesized.

[0045] Figure 6 shows the scanning electron microscope (SEM) images of Comparative Examples 1 to 5. As in Comparative Examples 1 to 5, A O / A T In the crucible where is less than 0.05, a multi-particle type Ni-based positive electrode active material in which small particles with a size of several hundred nm are agglomerated was manufactured.

[0046] The positive electrode active material (lithium transition metal oxide) synthesized according to Examples 1 to 5 is also a single particle. A single particle is a concept that is distinguished from a secondary particle formed by aggregating a plurality of particles, or a particle (multi-particle) formed by aggregating a plurality of particles and coating the periphery of the aggregate. Since the lithium transition metal oxide has the form of a single particle, it is possible to prevent the particles from collapsing even at a high electrode density. Therefore, it is possible to realize a high energy density of the positive electrode active material. Also, compared to secondary particles formed by aggregating a plurality of single particles, it is suppressed from collapsing during rolling, and it is possible to realize a high energy density, and it is also possible to prevent deterioration of the life due to the particles collapsing.

[0047] A second crucible 120 according to an embodiment of the present invention sets the opening area (A T ) of the minimum cut groove with respect to one side wall surface (A O ), and a single-particle type positive electrode active material can be manufactured. A O / A TIf the ratio is 0.05 or more, the positive electrode active material synthesized through the crucible assembly 100 has a single particle form. Therefore, even at a high electrode density, the particles can be prevented from collapsing, enabling the realization of a high energy density and also preventing the deterioration of the lifespan due to the collapse of the particles. Further, although the minimum area occupied by the cut groove OP can be set, the internal space of the second crucible 120 can be maximized, and the amount of the single particle positive electrode active material obtained per time can be maximized.

[0048] FIG. 7 is a scanning electron microscope (SEM) photograph of the positive electrode active materials of Example 6, Comparative Example 6-1, and Comparative Example 6-2.

[0049] Referring to FIG. 7 and Table 2, the positive electrode active materials synthesized in the crucible assemblies according to Example 6, Comparative Example 6-1, and Comparative Example 6-2 can be compared.

[0050] A crucible assembly is provided by stacking crucibles in three stages. Each crucible has a width of W1 (horizontal length and vertical length) and a height of H1, and the cut groove has a width of W2 and a height of H2. In each of the examples and comparative examples, W2 and H2 are adjusted, and in terms of the area of the side wall, the ratio (A O / A T ) occupied by the opening area of the cut groove is set to be different.

[0051]

Table 2

[0052] In Example 6, Comparative Example 6-1, and Comparative Example 6-2, the positive electrode active material is synthesized by the following method. First, 2,000 g of Ni 0.9 Co 0.1(OH)2, 836 g of Li2CO3, 6 g of (NH4)2HPO4, 60 g of WO3, 9 g of NaOH, and 15 g of (NH4)2S are mechanically mixed for about 15 minutes. The mixed powder is weighed into each crucible, and the positive electrode active material is obtained through firing at 940 °C for 4 hours and 700 °C for 10 hours. Figure 7 shows the scanning electron microscope (SEM) images of Example 6, Comparative Example 6-1, and Comparative Example 6-2. As in Example 6, A O / A T In the crucible where is 0.05, it can be confirmed that a single-particle type Ni-based positive electrode active material was synthesized. In contrast, as in Comparative Example 6-1 and Comparative Example 6-2, A O / A T In the crucible where is less than 0.05, a multi-particle type Ni-based positive electrode active material in which small particles with a size of several hundred nm are agglomerated was produced. A O / A T Even when is 0.0417, it can be confirmed that a multi-particle type Ni-based positive electrode active material was produced.

[0053] Figure 8 is a scanning electron microscope (SEM) photograph of the positive electrode active materials of Example 7, Comparative Example 7-1, and Comparative Example 7-2.

[0054] Referring to Figure 8 and Table 3, the positive electrode active materials synthesized in the crucible assemblies according to Example 7, Comparative Example 7-1, and Comparative Example 7-2 can be compared.

[0055] Three crucibles are stacked to provide a crucible assembly, and each crucible has a width (horizontal and vertical) of W1 and a height of H1. The cut groove has a width of W2 and a height of H2. In each example and comparative example, W2 and H2 are adjusted, and in terms of the area of the side wall, the ratio (A O / A T ) occupied by the opening area of the cut groove is set to be different.

[0056]

Table 3

[0057] In Example 7, Comparative Example 7-1, and Comparative Example 7-2, the positive electrode active material was synthesized by the following method. First, 2,000 g of Ni 0.88 Co 0.09 Al 0.03 (OH)2, 836 g of Li2CO3, 6 g of (NH4)2HPO4, 60 g of WO3, 9 g of NaOH, and 15 g of (NH4)2S were mechanically mixed for about 15 minutes. The mixed powder was weighed into a crucible, and a positive electrode active material was obtained through firing at 1,000 °C for 4 hours and 700 °C for 10 hours. Figure 8 shows the scanning electron microscope (SEM) images of Example 7, Comparative Example 7-1, and Comparative Example 7-2. As in Example 7, in the crucible where A O / A T is 0.05, it can be confirmed that a single-particle type Ni-based positive electrode active material was synthesized. In contrast, as in Comparative Example 7-1 and Comparative Example 7-2, in the crucible where A O / A T is less than 0.05, a multi-particle type Ni-based positive electrode active material in which particles with a size of several hundred nm are agglomerated was produced. Even when A O / A T is 0.0417, it can be confirmed that a multi-particle type Ni-based positive electrode active material was produced.

[0058] Figure 9 is a scanning electron microscope (SEM) photograph of the positive electrode active materials of Example 8, Comparative Example 8-1, and Comparative Example 8-2.

[0059] Referring to Figure 9 and Table 4, the positive electrode active materials synthesized in the crucible assemblies according to Example 8, Comparative Example 8-1, and Comparative Example 8-2 can be compared.

[0060] The crucibles are stacked in three layers to provide a crucible assembly, each crucible having a width (horizontal and vertical) of W1 and a height of H1, and the cut groove having a width of W2 and a height of H2. In each example and comparative example, W2 and H2 are adjusted, and in terms of the area of the side wall, the ratio (A O / A T ) occupied by the opening area of the cut groove is set to be different.

[0061]

Table 4

[0062] In Example 8, Comparative Example 8-1, and Comparative Example 8-2, the positive electrode active material is synthesized by the following method. First, 2,000 g of Ni 0.8 Mn 0.2 (OH)2, 836 g of Li2CO3, 6 g of (NH4)2HPO4, 60 g of WO3, 9 g of NaOH, and 15 g of (NH4)2S are mechanically mixed for about 15 minutes. The mixed powder is weighed into a crucible, and a positive electrode active material is obtained through firing at 950 °C for 4 hours and 700 °C for 10 hours. FIG. 9 shows the scanning electron microscope (SEM) images of Example 8, Comparative Example 8-1, and Comparative Example 8-2. As in Example 8, in the crucible where A O / A T is 0.05, it can be confirmed that a single-particle type Ni-based positive electrode active material was synthesized. In contrast, as in Comparative Example 8-1 and Comparative Example 8-2, in the crucible where A O / A T is less than 0.05, a multi-particle type Ni-based positive electrode active material in which small particles with a size of several hundred nm are agglomerated is produced. Even when A O / A T is 0.0417, it can be confirmed that a multi-particle type Ni-based positive electrode active material was produced.

[0063] In one embodiment, at least one of the first crucible 110 and the second crucible 120 is formed of a compound represented by the following chemical formula. Desirably, the first crucible 110 and the second crucible 120 are formed of a compound represented by the following chemical formula: xAl2O3·yMgO·zSiO2 (0.9 < x < 1, 0 < y < 0.1, 0 < z < 0.1, x + y + z = 1)

[0064] The crucible components for synthesizing the powders of the comparative examples and examples are shown in Table 5 below. The crucibles specified in Table 5 are composed of a three-component system of Al2O3, MgO, and SiO2, and crucible A is a commercially available mullite crucible.

[0065] Crucibles B and C have compositions that satisfy the chemical formula, while crucible A has a composition that deviates from the chemical formula. Crucible A was used for the synthesis of the comparative example, and crucibles B and C were used for the synthesis of the examples.

[0066]

Table 5

[0067] Figure 10 is a graph showing the particle size distributions of the cathode active materials of Example 9-1, Example 9-2, and Comparative Example 9. Example 9-1, Example 9-2, and Comparative Example 9 each contain 100 g of Ni 0.8 Co 0.1 Mn 0.1 (OH)2, 41.8 g of Li2CO3, 0.30 g of (NH4)2HPO4, 3.0 g of WO3, 0.45 g of NaOH, and 0.75 g of (NH4)2S are mechanically mixed for about 15 minutes. The mixed powder is weighed into crucible A (Comparative Example 9), crucible B (Example 9-1), and crucible C (Example 9-2), and a cathode active material is obtained through firing at 1,000 °C for 4 hours and 700 °C for 1 hour.

[0068] Figure 10 shows the particle size distribution results of the cathode active materials produced by Example 9-1, Example 9-2, and Comparative Example 9. Example 9-1, Example 9-2, and Comparative Example 9 are LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811). It can be known that as the Al2O3 composition in the crucible increases, the content of fine powder less than 1 μm is reduced. Furthermore, the average particle size (D 50) It can also be known that the crucible will become larger as the Al2O3 composition in the crucible increases. This is because among the three components constituting the crucible, Al2O3 has the highest thermal conductivity. As the Al2O3 content in the crucible increases, even when fired at the same temperature, the average temperature of the crucible is higher, and the particles can further grow.

[0069] In the following, the fine powder of the positive electrode active material is defined as those with a size less than 1 μm generated in the synthesized positive electrode active material. Through firing at a high temperature, if an excessive amount of fine powder (1 < μm) is formed during the synthesis process of the single-particle type Ni-based positive electrode active material, the specific surface area of the positive electrode active material powder will increase, resulting in a decrease in electrochemical performance.

[0070] In particular, the unstable Ni ions on the surface of the positive electrode particles promote side reactions of the electrolyte during continuous charge and discharge, and form electrochemically inactive phases, deteriorating the lifespan. If electrochemically inactive phases are generated, oxygen is released inside the structure of the positive electrode active material, reducing the stability of the positive electrode active material. Such structural instability is also related to the specific surface area of the powder, which means that in order to ensure long-life stability, it is essential to reduce the specific surface area of the powder by removing fine powder (1 < μm).

[0071] The crucible assembly according to one embodiment contains 90% or more of Al2O3, and the positive electrode active material synthesized with the crucible assembly can reduce the content of fine powder less than 1 μm and reduce the specific surface area of the powder.

[0072] Referring to FIG. 10 and Table 6, it can be seen that as the content of Al2O3 in the crucible increases, the excessive fine powder present on the particle surface is reduced, and it can be known that the average size of the powder has further grown. If the average size of the powder increases, as shown in Table 7, the specific surface area of the powder can be reduced. Comparing each specific surface area, Comparative Example 9 is 0.67 m2 / g, Example 9-1 is 0.58 m2 / g, and Example 9-2 is 0.35 m2 / g. This means that the electrochemical lifespan is improved through reducing the specific surface area of the positive electrode active material.

[0073]

Table 6

[0074]

Table 7

[0075] Figure 11 is a graph of the life maintenance rate related to the half cells of Example 9-1, Example 9-2, and Comparative Example 9. For the electrochemical evaluation of the examples, a 2032 R coin type half cell (Welcos) was used. The composition of the positive electrode active material plate for the lithium secondary battery is composed of a positive electrode active material, a conductive material (Super-P), and a binder (PVdF) (KF9300) at a weight ratio of 94:3:3. The loading level of the plate is 11 mg / cm 2 , and the electrode density is 3.6 g / cc. As the electrolyte, 1.3 M LiPF6 in EC (ethylene carbonate) / EMC (ethly methyl carbonate) / DMC (dimethyl carbonate) = 3 / 4 / 3 (v / v / v) was used.

[0076] The electrochemical evaluation of the comparative example is the same as the evaluation method of the example. For the initial formation evaluation, after a 10-hour rest process of the assembled cell, it was charged in the CC (constant current) mode to 4.3 V at 0.1 C, and then charged in the CV (constant voltage) mode to a current corresponding to 0.05 C. Next, it was discharged in the CC mode to 3.0 V at 0.1 C. For the normal temperature life evaluation, after charging in the CC mode to 4.3 V at 0.5 C, charging was advanced in the CV mode to a current corresponding to 0.05 C. Next, discharging was advanced in the CC mode to 3.0 V at 1 C, and this process was repeated 50 times in total.

[0077] The capacity retention rate after 50 charge and discharge cycles with respect to the initial capacity was calculated, and the results are shown in Table 8 below. Also, a graph showing the capacity retention rate by cycle is shown in Figure 11.

[0078]

Table 8

[0079] Referring to Table 8 and Figure 11, according to the room temperature life results of Example 9-1, Example 9-2 and Comparative Example 9, Example 9-1 shows a life retention rate about 6% higher after 50 cycles compared to Comparative Example 9, and Example 9-2 shows a life retention rate about 12% higher compared to Comparative Example 9. This indicates that the life retention rate is improved by reducing the specific surface area of the powder through fine powder control. Figure 12 is a graph of the life retention rate related to the half cells of Example 10-1, Example 10-2 and Comparative Example 10.

[0080] Example 10-1, Example 10-2 and Comparative Example 10 each contain 100 g of Ni 0.80 Co 0.15 Al 0.05 (OH)2, 42.0 g of Li2CO3, and 0.30 g of (NH4)2HPO4, 3.0 g of WO3, 0.45 g of NaOH, and 0.75 g of (NH4)2 S are mechanically mixed for about 15 minutes. The mixed powder is weighed into crucible A (Comparative Example 10), crucible B (Example 10-1), and crucible C (Example 10-2), and a positive electrode active material is obtained through firing at 1,000 °C for 4 hours and 700 °C for 10 hours.

[0081] For Example 10-1, Example 10-2 and Comparative Example 10, the capacity retention rate after 50 charge and discharge cycles with respect to the initial capacity was calculated respectively, and the results are shown in Table 9 below. Also, a graph showing the capacity retention rate by cycle is shown in Figure 12.

[0082]

Table 9

[0083] Referring to Table 9 and FIG. 12, according to the normal temperature life results of Example 10-1, Example 10-2 and Comparative Example 10, Example 10-1 shows a life maintenance rate about 6% higher compared with Comparative Example 10, and Example 10-2 shows a life maintenance rate about 12% higher compared with Comparative Example 10. This indicates that the life maintenance rate is improved by reducing the specific surface area of the powder through fine powder control. FIG. 13 is a graph of the life maintenance rate related to the half cells of Example 11-1, Example 11-2 and Comparative Example 11.

[0084] Example 11-1, Example 11-2 and Comparative Example 11 each contain 100 g of Ni 0.9 0Co 0.1 0(OH)2, 41.5 g of Li2CO3, 0.30 g of (NH4)2HPO4, 3.0 g of WO3, 0.45 g of NaOH, and 0.75 g of (NH4)2S are mechanically mixed for about 15 minutes. The mixed powder is weighed into crucible A (Comparative Example 11), crucible B (Example 11-1), and crucible C (Example 11-2), and cathode active materials are obtained through firing at 940 °C for 4 hours and 700 °C for 10 hours.

[0085] For Example 11-1, Example 11-2 and Comparative Example 11, the capacity retention rates after 50 charge and discharge cycles are calculated for their initial capacities respectively, and the results are shown in Table 10 below. Also, the graph showing the capacity retention rate by cycle is shown in FIG. 13.

[0086]

Table 10

[0087] Referring to Table 10 and FIG. 13, according to the room temperature life results of Example 11-1, Example 11-2 and Comparative Example 11, Example 11-1 shows a life maintenance rate approximately 3% higher compared to Comparative Example 11, and Example 11-2 shows a life maintenance rate approximately 7% higher compared to Comparative Example 11. This indicates that the life maintenance rate is improved by reducing the specific surface area of the powder through fine powder control. FIG. 14 is a graph of the life maintenance rate related to the half cells of Example 12-1, Example 12-2 and Comparative Example 12.

[0088] Example 12-1, Example 12-2 and Comparative Example 12 each contain 100 g of Ni 0.80 Mn0.10(OH)2, 41.3 g of Li2CO3, 0.30 g of (NH4)2HPO4, 3.0 g of WO3, 0.45 g of NaOH, and 0.75 g of (NH4)2S are mechanically mixed for about 15 minutes. The mixed powder is weighed into crucible A (Comparative Example 12), crucible B (Example 12-1), and crucible C (Example 12-2), and the positive electrode active material is obtained through firing at 950 °C for 4 hours and 700 °C for 10 hours.

[0089] For Example 12-1, Example 12-2 and Comparative Example 12, the capacity retention rate after 50 charge and discharge cycles is calculated based on the initial capacity, and the results are shown in Table 11 below. Also, the graph showing the capacity retention rate by cycle is shown in FIG. 14.

[0090]

Table 11

[0091] Referring to Table 11 and FIG. 14, according to the room temperature life results of Example 12-1, Example 12-2 and Comparative Example 12, Example 12-1 shows a life maintenance rate approximately 13% higher compared to Comparative Example 12, and Example 12-2 shows a life maintenance rate approximately 19% higher compared to Comparative Example 12. This indicates that the life maintenance rate is improved by reducing the specific surface area of the powder through fine powder control. The positive electrode active material produced by the crucible and crucible assembly of the examples of the present invention is as follows.

[0092] The positive electrode active material according to one aspect also includes a core containing a lithium transition metal oxide containing W and B, and a phosphorus-containing coating layer containing a phosphorus-containing compound disposed on the surface of the core.

[0093] In the positive electrode active material, when B element and W element are introduced into the lithium transition metal oxide, the ordering of Ni ions contained in the transition metal oxide is increased, so that the structural stability is improved, the binding force between the transition metal and oxygen is increased, oxygen release is suppressed during charging and discharging of the lithium battery, and through this, side reactions with the electrolyte are suppressed, and electrolyte depletion can be prevented.

[0094] In addition, by including a phosphorus-containing coating layer containing a phosphorus-containing compound on the surface of the core containing the lithium transition metal oxide, the phosphorus-containing compound preferentially reacts with HF derived from the binder and the electrolyte, not only suppressing side reactions with the lithium transition metal oxide, but also the phosphorus-containing compound preferentially reacts with moisture present in the electrolyte, suppressing side reactions with the lithium transition metal oxide. As a result, by suppressing deterioration due to side reactions of the lithium transition metal oxide, the life characteristics are improved.

[0095] According to one embodiment, in the positive electrode active material, the lithium transition metal oxide may be represented by the following Chemical Formula 1: (Chemical Formula 1) Li 1-x A x W α B β M 1-α-β O 2-y T y In Chemical Formula 1, A is one or more elements selected from the group consisting of Na, K, Rb, and Cs, T is one or more elements selected from the group consisting of S, F, and P, M includes one or more elements selected from the group consisting of Ni, Co, Mn, Al, Mg, V, Ti, and Ca, 0 < x ≤ 0.01, 0 < y ≤ 0.01, 0 < α ≤ 0.01, 0 < β ≤ 0.01.

[0096] In addition to containing W and B, when a part of Li in the lithium transition metal oxide is substituted with a small amount of an alkali metal as represented by the chemical formula 1, during charging of the lithium battery, the structural deformation due to the desorption of Li ions is suppressed, and the structural stability of the lithium transition metal oxide is improved.

[0097] Also, as represented by the chemical formula 1, when a part of oxygen in the lithium transition metal oxide is substituted with any one of S, F, and P having a higher electronegativity than oxygen, compared with the case of binding with oxygen, the transition metal can be retained in the structure by a stronger binding force, the binding force between elements located at the peroxide lattice sites is increased, the electron mobility is improved, and the conductivity is improved. Therefore, the high-rate cycle characteristics can also be improved.

[0098] In addition to containing W and B, when a part of Li in the lithium transition metal oxide is substituted with a small amount of an alkali metal as represented by the chemical formula 1, during charging of the lithium battery, the structural deformation due to the desorption of Li ions is suppressed, and the structural stability of the lithium transition metal oxide is improved.

[0099] Also, as represented by the chemical formula 1, when a part of oxygen in the lithium transition metal oxide is substituted with any one of S, F, and P having a higher electronegativity than oxygen, compared with the case of binding with oxygen, the transition metal can be retained in the structure by a stronger binding force, the binding force between elements located at the peroxide lattice sites is increased, the electron mobility is improved, and the conductivity is improved. Therefore, the high-rate cycle characteristics can also be improved.

[0100] According to an embodiment, in the chemical formula 1, A is also Na, and T is also S.

[0101] According to one embodiment, in Chemical Formula 1, M includes M1, M2, and M3, M1 is Ni, M2 and M3 are, independently of each other, elements selected from Co, Mn, Al, Mg, V, Ti, and Ca, and in M, the molar ratio of Ni is 75 mol% or more.

[0102] According to another embodiment, in Chemical Formula 1, M includes M1, M2, and M3, M1 is Ni, M2 is Co, M3 is an element selected from Mn, Al, Mg, V, Ti, and Ca, and in M, the molar ratio of Ni is 75 mol% or more.

[0103] According to still another embodiment, in Chemical Formula 1, M includes M1 and M2, M1 is Ni, M2 is Co, and in M, the molar ratio of Ni is 75 mol% or more.

[0104] According to one embodiment, the lithium transition metal oxide may be represented by any one of the following Chemical Formulas 2 to 4:

Chemical Formula

[0105] According to one embodiment, the lithium transition metal oxide is also a single particle. The single particle is a concept distinguishable from secondary particles formed by aggregation of a plurality of particles or particles formed by aggregation of a plurality of particles and coating around the aggregate. By having the lithium transition metal oxide in the form of a single particle, it is possible to prevent the particles from collapsing even at a high electrode density. Therefore, it is possible to realize a high energy density of the positive electrode active material. In addition, compared with secondary particles formed by aggregation of a plurality of single particles, it is suppressed from collapsing during rolling, it is possible to realize a high energy density, and it is also possible to prevent deterioration of the lifespan due to collapse of the particles.

[0106] According to an embodiment, the lithium transition metal oxide may have a single crystal. The single crystal has a concept distinct from that of a single particle. The single particle refers to a particle formed by one particle regardless of the type and number of internal crystals, and the single crystal means having only one crystal in the particle. By having a single crystal in the core, not only is the structural stability very high, but also lithium ion conduction is easier compared to polycrystals, and the high-rate charging characteristics are excellent compared to the active materials of polycrystals.

[0107] According to an embodiment, the positive electrode active material is a single crystal and a single particle. By being formed of the single crystal and the single particle, it is structurally stable and it is possible to realize a high-density electrode, and a lithium secondary battery including the same can simultaneously have improved life characteristics and high energy density.

[0108] The positive electrode active material represented by Chemical Formulas 2 to 4 has a single crystal and a single particle, and by substituting a part of Li in the lithium transition metal oxide with Na, a part of the transition metal with W and B, and a part of O with S, the structural stability is significantly improved and long-life characteristics can be exhibited.

[0109] In the case of a cathode active material containing a general high-nickel lithium nickel cobalt manganese oxide, stabilization of unstable Ni ions is essential. However, by introducing W and B into some of the transition metal sites within the crystal, the cathode active material can achieve overall charge balance, suppress the oxidation of unstable Ni(III) or Ni(IV) ions from Ni(II) ions, and the unstable Ni(III) or Ni(IV) can be reduced to Ni(II). Note that the loss of conductivity due to substituting some of the transition metals with the heterogeneous elements B and W is compensated by substituting some of the O with S, and by substituting some of the Li with Na, and suppressing the decrease in Li conductivity due to structural deformation during charge and discharge, a single-crystalline, structurally stable, high-capacity, and long-life cathode active material can be obtained. Furthermore, in order to suppress the side reaction between the lithium transition metal oxide and the electrolyte or moisture, a phosphorus-containing coating layer containing a phosphorus-containing compound, for example, Li3PO4, is introduced on the surface of the lithium transition metal oxide. Such a phosphorus-containing compound prevents side reactions with HF derived from the electrolyte or moisture present in the electrolyte, thereby guaranteeing high stability and long-life characteristics.

[0110] According to one embodiment, the core containing the lithium transition metal compound may have a uniform composition throughout. Thereby, a structurally stable structure can be maintained even during charging and discharging, and it does not interfere with the movement of lithium, so it has high-rate characteristics.

[0111] According to one embodiment, the phosphorus-containing compound is also crystalline, amorphous, or a combination thereof.

[0112] For example, the phosphorus-containing compound contains crystalline Li3PO4 or an amorphous phosphorus-containing compound containing lithium atoms, phosphorus atoms, and oxygen atoms.

[0113] According to one embodiment, the molar ratio of the phosphorus (P) element in the cathode active material is also 0.2 mol% or less in the total elements contained in the cathode active material.

[0114] According to one embodiment, the phosphorus-containing compound may also include a compound represented by the following chemical formula 5: (Chemical formula 5)Li a PbO c 0 < a ≤ 3, 0 < b ≤ 1, and 0 < c ≤ 4.

[0115] According to one embodiment, the coating layer may have a continuous coating layer on the core surface or an island-shaped coating layer partially present on the core surface. For example, the coating layer may have an island-shaped coating layer on the core surface.

[0116] According to one embodiment, the coating layer may have a thickness of several nm. For example, the coating layer may also be 1 nm to 10 nm.

[0117] According to one embodiment, the positive electrode active material may have peaks at 2θ = 20° to 25° in the X-ray diffraction spectrum obtained by XRD (X-ray diffraction) analysis using CuKα rays.

[0118] For example, the positive electrode active material may have peaks at at least 2θ = 22.3° ± 0.5, 23.0° ± 0.5, and 24.8° ± 0.5 in the X-ray diffraction spectrum obtained by XRD analysis using CuKα rays.

[0119] In the X-ray diffraction spectrum, the peaks at 2θ = 20° to 25° indicate the presence of Li3PO4. Also, as will be described later, since such peaks are observed in the coating layer of the positive electrode active material, it can be known that the positive electrode active material does not contain P element inside the core.

[0120] The coating layer containing the phosphorus-containing compound, for example, Li3PO4, is a reaction product of a residual lithium compound generated during the synthesis process of the Ni-based cathode active material, such as Li2CO3 and LiOH, and the phosphorus-containing compound. Thereby, gas generation due to the side reaction between the residual lithium compound and the electrolyte is suppressed, and the stability of the battery is improved. Not only that, the coating layer containing Li3PO4 has high ionic conductivity and can promote the diffusion of lithium ions.

[0121] According to one embodiment, the average particle size (D 50 ) of the cathode active material is also 0.1 μm to 20 μm. For example, the average particle size (D 50 ) is 0.1 μm to 15 μm, 0.1 μm to 10 μm, 1 μm to 20 μm, 5 μm to 20 μm, 1 μm to 15 μm, 1 μm to 10 μm, 5 μm to 15 μm, or 5 μm to 10 μm. When the average particle size of the cathode active material belongs to the above range, the desired energy density per volume can be realized. When the average particle size of the cathode active material exceeds 20 μm, it will cause a sharp decrease in the charge-discharge capacity. When it is 0.1 μm or less, it is difficult to obtain the desired energy density per volume.

[0122] Hereinafter, the manufacturing method of the cathode active material according to one aspect will be described in detail.

[0123] The manufacturing method of the cathode active material according to one embodiment includes mixing a Li element-containing compound, a W element-containing compound, a B element-containing compound, an A element-containing compound, an M element-containing compound, a T element-containing compound, and a P element-containing compound to obtain a lithium transition metal oxide precursor, and heat-treating the precursor to obtain a cathode active material containing a lithium transition metal oxide represented by the following Chemical Formula 1. The lithium transition metal oxide includes a phosphorus-containing coating layer on its surface: (Chemical Formula 1) Li 1-x A x W α B β M 1-α-β O 2-y T y

[0124] In the formula (1), A is one or more elements selected from the group consisting of Na, K, Rb, and Cs; T is one or more elements selected from the group consisting of S, F, and P; M contains one or more elements selected from the group consisting of Ni, Co, Mn, Al, Mg, V, Ti, and Ca; 0 < x ≤ 0.01, 0 < y ≤ 0.01, 0 < α ≤ 0.01, and 0 < β ≤ 0.01.

[0125] For specific descriptions related to the formula (1), refer to the above.

[0126] The mixing step includes mechanically mixing the specific element-containing compound. The mechanical mixing is performed dry. The mechanical mixing is to apply mechanical force, crush and mix the substances to be mixed to form a uniform mixture. The mechanical mixing can be carried out using a mixing device such as a ball mill, a planetary mill, a stirred ball mill, or a vibrating mill that utilizes beads that are chemically inert, for example. At this time, in order to maximize the mixing effect, a small amount of an alcohol such as ethanol or a higher fatty acid such as stearic acid can be selectively added.

[0127] The mechanical mixing is carried out in an oxidizing atmosphere to prevent the reduction of transition metals in the transition metal source (e.g., Ni compound) and to realize the structural stability of the active material.

[0128] The lithium element-containing compound may include, but is not limited to, lithium hydroxide, lithium oxide, lithium nitride, lithium carbonate, or a combination thereof. For example, the lithium precursor may also be LiOH or Li2CO3.

[0129] The A element-containing compound may include, but is not limited to, hydroxides, oxides, nitrides, carbonates, or combinations thereof of one or more elements selected from the group consisting of Na, K, Rb, and Cs. For example, it may also be NaOH, Na2CO3, KOH, K2CO3, RbOH, Rb2CO3, CsOH, or Cs2CO3.

[0130] The W precursor may include, but is not limited to, hydroxides, oxides, nitrides, carbonates, or combinations thereof of W. For example, it may also be W(OH)6, WO3, or combinations thereof.

[0131] The B element-containing compound may include, but is not limited to, hydroxides, oxides, nitrides, carbonates, or combinations thereof of B. For example, it may also be B(OH)3, B2O3, or combinations thereof.

[0132] The M element-containing compound may include, but is not limited to, hydroxides, oxides, nitrides, carbonates, or combinations thereof of one or more elements among Ni, Co, Mn, Al, Mg, V, Ti, and Ca.

[0133] The T element-containing compound may include, but is not limited to, hydroxides, oxides, nitrides, carbonates, ammonium compounds, or combinations thereof of one or more elements among S, F, and P. For example, it may also be (NH4)2S.

[0134] The P element-containing compound includes any compound that can provide the P element. For example, it may also be (NH4)2HPO4.

[0135] After the mixing step, it also includes a heat treatment step. The heat treatment step also includes a first heat treatment step and a second heat treatment step. The first heat treatment step and the second heat treatment step may be carried out continuously or may have a rest period after the first heat treatment step. Also, the first heat treatment step and the second heat treatment step may be carried out in the same chamber or in different chambers from each other.

[0136] The heat treatment temperature in the first heat treatment step is higher than the heat treatment temperature in the second heat treatment step.

[0137] The first heat treatment step can be carried out at a heat treatment temperature of 800°C to 1,200°C. The heat treatment temperature can be, for example, 850°C to 1,200°C, 860°C to 1,200°C, 870°C to 1,200°C, 880°C to 1,200°C, 890°C to 1,200°C, or 900°C to 1,200°C, but is not limited thereto, and any range formed by selecting any two points within the above range is included.

[0138] The second heat treatment step can be carried out at a heat treatment temperature of 700°C to 800°C. The heat treatment temperature can be 710°C to 800°C, 720°C to 800°C, 730°C to 800°C, 740°C to 800°C, 750°C to 800°C, 700°C to 780°C, 700°C to 760°C, 700°C to 750°C, or 700°C to 730°C, but is not limited thereto, and any range formed by selecting any two points within the above range is included.

[0139] According to one embodiment, the heat treatment time in the first heat treatment step is shorter than the heat treatment time in the second heat treatment step.

[0140] For example, in the first heat treatment stage, the heat treatment time is 3 to 5 hours, 4 to 5 hours, or 3 to 4 hours, but is not limited thereto, and any range formed by selecting any two points within the above range is included.

[0141] For example, in the second heat treatment stage, the heat treatment time is 10 to 20 hours, 10 to 15 hours, but is not limited thereto, and any range formed by selecting any two points within the above range is included.

[0142] The first heat treatment stage also includes a stage of heat treatment at a heat treatment temperature of 800°C to 1,200°C for 3 to 5 hours.

[0143] The second heat treatment stage also includes a stage of heat treatment at a heat treatment temperature of 700°C to 800°C for 10 to 20 hours.

[0144] In the first heat treatment stage, the lithium transition metal oxide forms a layered cathode active material, induces the growth of particles, and makes the shape of single crystals. In the first heat treatment stage, each primary particle in the secondary particle-shaped lithium transition metal oxide grows rapidly and can no longer withstand the interparticle stress, so that the inside of the primary particles appears and they are fused with each other, and it is considered that a single-crystal cathode active material for a secondary battery is formed. The second heat treatment stage increases the crystallinity of the layered structure generated in the first heat treatment stage by performing heat treatment at a lower temperature for a longer time in the first heat treatment stage. Through the first heat treatment stage and the second heat treatment stage, a nickel-based cathode active material of a single layer, single crystal, and single particle can be obtained.

[0145] According to an embodiment, the lithium transition metal oxide manufactured by the manufacturing method is a single crystal and a single particle, and the single crystal may have a layered structure. Further, the average particle size of the lithium transition metal oxide is also 0.1 μm to 20 μm.

[0146] In addition, in the positive electrode active material manufactured by the method for manufacturing the positive electrode active material, the W element and the B element are substituted at the Ni sites in the structure, and the T element, for example, the S element is substituted at the O site. Further, when the A element is substituted at the Li site, not only the oxidation of the existing Ni is suppressed, but also the reduction of the existing unstable Ni ions to Ni ions is induced. The reduced Ni ions and Li ions have similar ionic radii, which promotes Li / Ni disordering and partially changes the oxygen lattice structure in the core. When the oxygen lattice structure is partially changed, the P element cannot form a PO4 structure by occupying the regular tetrahedral sites in the structure, and the P element cannot penetrate into the regular tetrahedral positions in the core, and thus exists in the form of a phosphorus-containing compound, for example, Li3PO4, on the surface of the positive electrode active material. 2+ not only suppresses the oxidation of the existing Ni, but also the existing unstable Ni 3+ ions of Ni 2+ ions to Ni 2+ ions is induced. The reduced Ni + ions and Li ions have similar ionic radii, which promotes Li / Ni disordering and partially changes the oxygen lattice structure in the core. When the oxygen lattice structure is partially changed, the P element cannot form a PO4 structure by occupying the regular tetrahedral sites in the structure, and the P element cannot penetrate into the regular tetrahedral positions in the core, and thus exists in the form of a phosphorus-containing compound, for example, Li3PO4, on the surface of the positive electrode active material.

[0147] In addition, the positive electrode active material manufactured by the method includes a coating layer containing a phosphorus-containing compound on the surface, so that a positive electrode active material with reduced amounts of residual lithium and unstable Ni ions at the same time is obtained. A lithium secondary battery employing such a positive electrode active material has a high energy density and a long service life.

[0148] According to another aspect, a positive electrode including the aforementioned positive electrode active material is provided.

[0149] According to still another aspect, a lithium secondary battery including the positive electrode, the negative electrode, and an electrolyte is provided.

[0150] The positive electrode and the lithium secondary battery including the same can be manufactured by the following method.

[0151] First, a positive electrode is prepared.

[0152] For example, a positive electrode active material composition in which the aforementioned positive electrode active material, conductive material, binder, and solvent are mixed is prepared. The positive electrode active material composition is directly coated on a metal current collector to manufacture a positive electrode plate. As an alternative, after the positive electrode active material composition is cast on a separate support, a film peeled off from the support can be laminated on the metal current collector to manufacture a positive electrode plate. The positive electrode is not limited to the forms listed above, and may also be in other forms.

[0153] Examples of the conductive material include graphite such as natural graphite and artificial graphite; carbon black; conductive tubes such as carbon nanotubes; conductive whiskers such as fluorocarbon, zinc oxide, and potassium titanate; conductive metal oxides such as titanium oxide; etc. However, they are not limited thereto, and any material that can be used as a conductive material in the technical field can be used.

[0154] Examples of the binder include vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethyl methacrylate, polytetrafluoroethylene, mixtures thereof, metal salts thereof, or styrene-butadiene rubber-based polymers, etc. However, they are not limited thereto, and any material that can be used as a binder in the technical field can be used. Other examples of binders include lithium salts, sodium salts, calcium salts, or Na salts of the aforementioned polymers, etc.

[0155] Examples of the solvent include N-methylpyrrolidone, acetone, or water, etc. However, they are not limited thereto, and any material that can be used in the technical field can be used.

[0156] The contents of the aforementioned positive electrode active material, conductive material, binder, and solvent are at levels generally used in lithium batteries. Depending on the use and configuration of the lithium battery, one or more of the aforementioned conductive material, binder, and solvent can be omitted.

[0157] Next, a negative electrode is prepared.

[0158] For example, a negative electrode active material, a conductive material, a binder, and a solvent are mixed to prepare a negative electrode active material composition. The negative electrode active material composition is directly coated on a metal current collector having a thickness of 3 μm to 500 μm and dried to manufacture a negative electrode plate. As an alternative, after the negative electrode active material composition is cast on a separate support, a film peeled off from the support is laminated on a metal current collector, and a negative electrode plate can be manufactured.

[0159] The negative electrode current collector is not particularly limited as long as it has conductivity without inducing a chemical change in the battery. For example, copper, nickel, or a material obtained by surface-treating the surface of copper with carbon can be used.

[0160] Any negative electrode active material can be used as long as it can be used as a negative electrode active material for a lithium battery in the technical field. For example, it may contain one or more selected from the group consisting of lithium metal, a metal alloyable with lithium, a transition metal oxide, a non-transition metal oxide, and a carbon-based material.

[0161] For example, the metal alloyable with lithium includes Si, Sn, Al, Ge, Pb, Bi, Sb, a Si-Y alloy (where Y is an alkali metal, an alkaline earth metal, a Group 13 element, a Group 14 element, a transition metal, a rare earth element, or a combination thereof, and is not Si), a Sn-Y alloy (where Y is an alkali metal, an alkaline earth metal, a Group 13 element, a Group 14 element, a transition metal, a rare earth element, or a combination thereof, and is not Sn), etc. Examples of the element Y also include 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, Ti, Ge, P, As, Sb, Bi, S, Se, or Te.

[0162] For example, the transition metal oxide may also be lithium titanate, vanadium oxide, lithium vanadate, etc.

[0163] For example, the non-transition metal oxide is SnO2, SiO x (0 < x < 2), etc.

[0164] The carbon-based material may also be crystalline carbon, amorphous carbon, or a mixture thereof. The crystalline carbon may also be graphite such as amorphous, plate-like, flaky, spherical or fibrous natural graphite or artificial graphite, and the amorphous carbon may also be soft carbon (low-temperature calcined carbon) or hard carbon, mesophase pitch carbide, calcined coke, etc.

[0165] In the negative electrode active material composition, the conductive material, binder and solvent can be the same as those in the case of the positive electrode active material composition.

[0166] The contents of the aforementioned negative electrode active material, conductive material, binder and solvent are at levels generally used in lithium batteries. Depending on the use and configuration of the lithium battery, one or more of the aforementioned conductive material, binder and solvent may be omitted.

[0167] Next, a separator inserted between the positive electrode and the negative electrode is prepared.

[0168] Any of the separators can be used as long as they are commonly used in lithium batteries. A separator with low resistance to ion movement of the electrolyte and excellent electrolyte moisture retention ability can be used. The separator can be a single membrane or a multi-layer membrane, and is, for example, selected from among glass fiber, polyester, Teflon (registered trademark), polyethylene, polypropylene, polyvinylidene fluoride, polytetrafluoroethylene (PTFE), or combinations thereof, and can be in the form of a non-woven fabric or a woven fabric. Also, a mixed multi-layer membrane such as a polyethylene / polypropylene two-layer separator, a polyethylene / polypropylene / polyethylene three-layer separator, or a polypropylene / polyethylene / polypropylene three-layer separator can be used. For example, a wound separator such as polyethylene or polypropylene is used for a lithium-ion battery, and a separator with excellent impregnation ability for an organic electrolyte can be used for a lithium-ion polymer battery. For example, the separator can be manufactured by the following method.

[0169] A polymer resin, a filler, and a solvent are mixed to prepare a separator composition. The separator composition can be directly coated on the upper part of the electrode and dried to form a separator. Alternatively, after the separator composition is cast on a support and dried, a separator film peeled from the support can be laminated on the upper part of the electrode to form a separator.

[0170] The polymer resin used in the manufacture of the separator is not particularly limited, and any substance used as a binder for the electrode plate can be used. For example, a vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethyl methacrylate, or a mixture thereof can be used.

[0171] Next, an electrolyte is prepared.

[0172] For example, the electrolyte may also be an organic electrolyte solution. Further, the electrolyte may also be a solid. For example, it may be a boron oxide, a lithium oxynitride, etc., but is not limited thereto, and any of those that can be used as a solid electrolyte in the relevant technical field can be used. The solid electrolyte can be formed on the negative electrode by a method such as sputtering.

[0173] For example, the organic electrolyte solution can be produced by dissolving a lithium salt in an organic solvent.

[0174] Any of those organic solvents that can be used as an organic solvent in the relevant technical field can be used. For example, cyclic carbonates such as propylene carbonate, ethylene carbonate, fluoroethylene carbonate, butylene carbonate, vinylene carbonate; chain carbonates such as dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl isopropyl carbonate, dipropyl carbonate, dibutyl carbonate; esters such as methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, γ-butyrolactone; ethers such as 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran, 1,2-dioxane, 2-methyltetrahydrofuran; nitriles such as acetonitrile; amides such as dimethylformamide, etc. are available. They can be used alone or in combination of a plurality. For example, a solvent obtained by mixing a cyclic carbonate and a chain carbonate can be used.

[0175] In addition, a gelled polymer electrolyte impregnated with an electrolyte solution in a polymer electrolyte such as polyethylene oxide or polyacrylonitrile, LiI, Li3N, Li x Ge y P z S α 、Li x Ge y P z S α X δInorganic solid electrolytes such as (where X is F, Cl, Br) can be used.

[0176] All of the above lithium salts can be used as long as they can be used as lithium salts in the art. For example, LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiCF3SO3, Li(CF3SO2)2N, LiC4F9SO3, LiAlO2, LiAlCl4, LiN(C x F 2x+1 SO2)(C y F 2y+1 SO2) (where x and y are natural numbers), LiCl, LiI, or a mixture thereof, etc.

[0177] According to an embodiment of the present invention, the positive electrode active material can have excellent stability even when a fluorine-containing electrolyte is used due to the presence of a coating layer containing a phosphorus-containing compound.

[0178] FIG. 15 is a schematic diagram of a lithium battery according to an exemplary embodiment.

[0179] As shown in FIG. 15, the lithium battery 1 includes a positive electrode 3, a negative electrode 2, and a separator 4. The aforementioned positive electrode 3, negative electrode 2, and separator 4 are wound or folded and housed in a battery case 5. Next, an organic electrolyte is injected into the battery case 5, sealed with a cap assembly 6, and the lithium battery 1 is completed. The battery case 5 can also be cylindrical, rectangular, pouch-type, coin-type, or thin-film type, etc. For example, the lithium battery 1 is also a thin-film battery. The lithium battery 1 is also a lithium-ion battery.

[0180] A separator can be disposed between the positive electrode and the electrode to form a battery structure. After the battery structure is laminated in a bicell structure, impregnated with an organic electrolyte, and the resulting product is housed and sealed in a pouch, a lithium-ion polymer battery is completed.

[0181] In addition, a plurality of the battery structures are stacked to form a battery pack, and such a battery pack can be used in all devices that require high capacity and high output. For example, it can be used in a notebook computer, a smartphone, an electric vehicle (EV), and the like.

[0182] In addition, since the lithium battery is excellent in life characteristics and high-rate characteristics, it can be used in an electric vehicle (EV). For example, it can be used in a hybrid vehicle such as a plug-in hybrid electric vehicle (PHEV). Also, it can be used in fields that require a large amount of power storage. For example, it can be used in an electric bicycle, an electric tool, a power storage system, and the like.

[0183] FIG. 16 is a graph showing the amount of residual lithium compound in the positive electrode active material of Examples 1 to 5 and Comparative Examples 1 to 5.

[0184] In Examples 1 to 5 and Comparative Examples 1 to 5, the positive electrode active material is synthesized by the following method. First, 2,000 g of Ni 0.8 Co 0.1 Mn 0.1 (OH)2, 836 g of Li2CO3, 6 g of (NH4)2HPO4, 60 g of WO3, 9 g of NaOH, and 15 g of (NH4)2S are mechanically mixed for about 15 minutes. The mixed powder is weighed into crucibles of the respective examples and comparative examples, and a positive electrode active material is obtained through firing at 1,000 °C for 4 hours and 700 °C for 10 hours.

[0185]

Table 12

[0186] Referring to Table 12 and FIG. 16, the positive electrode active materials produced by the manufacturing methods of Comparative Examples 1 to 5 show high values of the amount of residual lithium, ranging from 56,400 ppm to 33,570 ppm. On the other hand, it can be confirmed that the total amount of residual lithium compounds (Li2CO3, LiOH) in the positive electrode active materials produced by the manufacturing methods of Examples 1 to 5 rapidly decreases to 20,000 ppm or less. A O / A T In the case of Comparative Example 3 where the value is 0.042, the total amount of residual lithium compounds is 31,850 ppm, and in the case of Comparative Example 5 where the value is 0.04, the total amount of residual lithium compounds also reaches 33,570 ppm. A O / A T In Example 1 where the value is 0.05, it can be confirmed that the amount of residual lithium compounds is 19,630 ppm or less, which is reduced by 10,000 ppm or more compared to the comparative examples.

[0187] The amount of residual lithium rapidly decreases until the ratio of the opening area of the slit groove to the side wall area of one crucible becomes 0.05, and thereafter, even when the ratio of the opening area to the side wall area increases, the amount of residual lithium compounds decreases very slowly.

[0188] Since the residual lithium compounds cause side reactions with the electrolytic solution and generate gas, they are an important factor in reducing the stability of the battery. Therefore, when the ratio of the opening area of the slit groove to the side wall area of one crucible is 0.05 or more, the produced positive electrode active material has residual lithium compounds of 20,000 ppm or less, and the stability of the battery can be greatly improved.

[0189] As described above, the present invention has been described with reference to the embodiments illustrated in the drawings, but they are merely exemplary, and those having ordinary knowledge in the relevant technical field will understand that various modifications and equivalent other embodiments are possible. Therefore, the true technical protection scope of the present invention is defined by the technical idea of the claims.

Claims

1. a first crucible having an upper part open and having a predetermined internal space, a second crucible disposed below the first crucible and having a slit groove disposed at an upper end of each side wall and having a preset opening area, the opening area of the slit groove is determined by the following formula, 【Number 1】 AO: opening area of the slit groove AT: side wall area of one second crucible, at least one of the first crucible and the second crucible is, a crucible assembly for manufacturing a positive electrode active material formed of a compound represented by the following chemical formula. (Chemical formula) xAl2O3·yMgO·zSiO2 (0.9 < x < 1, 0 < y < 0.1, 0 < z < 0.1, x + y + z = 1)

2. the slit groove is, disposed above at the height center of the second crucible, the crucible assembly for manufacturing a positive electrode active material according to claim 1.

3. the second crucible is disposed such that the side walls face each other, the slit groove is provided in a plurality, and is disposed so as to overlap the side walls respectively, the crucible assembly for manufacturing a positive electrode active material according to claim 1.

4. the second crucible is provided in a plurality, and is stacked in the height direction below the first crucible, the crucible assembly for manufacturing a positive electrode active material according to claim 1.

5. in a crucible for manufacturing a positive electrode active material having a predetermined internal space by a bottom and side walls, including a slit groove disposed at an upper end of the side wall and having a preset opening area, the opening area of the slit groove is determined by the following formula, 【Number 2】 AO: opening area of the slit groove AT: area of one side wall, the crucible is formed of a compound represented by the following chemical formula, a crucible for manufacturing a positive electrode active material. (Chemical formula) xAl2O3·yMgO·zSiO2 (0.9 < x < 1, 0 < y < 0.1, 0 < z < 0.1, x + y + z = 1)

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