Positive active material, method for producing same, and positive active material layer

Abstract

The invention provides a positive active material, a method for preparing the same, and a positive active material layer. By controlling the sintering condition and composition of the positive electrode active material, the positive electrode active material having a controlled specific surface area, the preparation method thereof, and the positive electrode including the same may have an optimized density of the positive electrode active material, thereby maximizing output characteristics of an all-solid-state battery including the same. The positive electrode active material may include a lithium composite oxide capable of intercalating or deintercalating lithium, in which a ratio (Sm / Sc) of a specific surface area (Sm) measured based on a Brunauer-Emmet-Teller (BET) method to a specific surface area (Sc) calculated based on a particle size distribution (PSD) analysis result is within a first range of 2.0 to 3.3.

Description

Technical Field

[0001] The present disclosure relates to a positive electrode active material. Background Art

[0002] A battery is configured to store electric power by using materials capable of undergoing an electrochemical reaction in a positive electrode and a negative electrode. A representative example of such a battery is a lithium secondary battery, which stores electrical energy through a chemical potential difference when lithium ions are intercalated into or deintercalated from the positive electrode and the negative electrode. Lithium secondary batteries are used not only in small electronic devices such as mobile phones and laptop computers, but also in large vehicles for transportation such as hybrid vehicles and electric vehicles. Therefore, there is a need to develop secondary batteries with higher stability and energy density.

[0003] Generally, such a lithium secondary battery operates by using materials capable of reversibly intercalating or deintercalating lithium ions as positive and negative electrode active materials and filling an organic electrolyte or a polymer electrolyte between the positive electrode and the negative electrode. Most existing secondary batteries have batteries based on organic liquid electrolytes, and thus show limitations in improving stability and density.

[0004] An all-solid-state battery, which has drawn attention as a next-generation secondary battery to solve such problems, consists of all solid components and is thus advantageous because it has a lower risk of fire and explosion and higher mechanical strength compared to a lithium secondary battery using a combustible organic solvent as an electrolyte. Such an all-solid-state battery generally includes a positive electrode active material layer joined to a positive electrode current collector, a negative electrode active material layer joined to a negative electrode current collector, and a solid electrolyte layer located between the positive electrode active material layer and the negative electrode active material layer.

[0005] However, in order to widely apply such an all-solid-state battery in technical fields that require high output such as electric vehicles, it is necessary to improve the output characteristics of the positive electrode including the positive electrode active material. Summary of the Invention

[0006] The present disclosure relates to a positive electrode active material having a controlled specific surface area, a method for preparing the same, and a positive electrode including the same. Specifically, the density of the positive electrode active material can be optimized by controlling the sintering conditions and composition of the positive electrode active material, thereby maximizing the output characteristics of an all-solid-state battery including the same.

[0007] Some embodiments of the present disclosure can solve the above problems to obtain the optimal density of the positive electrode active material, thereby maximizing the output characteristics of the positive electrode including the same. Some embodiments of the present disclosure can provide the optimal density of the positive electrode active material by controlling the sintering conditions and composition of the positive electrode active material.

[0008] The advantages of the present disclosure are not limited to those mentioned herein. The above and other advantages of the present disclosure can be understood from the following description and from the appended claims and their combinations.

[0009] One embodiment of the present disclosure may provide a positive electrode active material for an all-solid-state battery, the active material including a lithium composite oxide capable of intercalating or deintercalating lithium, wherein, in the lithium composite oxide, the specific surface area (S m ) measured based on the Brunauer-Emmett-Teller (BET) method and the specific surface area (S c ) calculated based on the particle size distribution (PSD) analysis result, the ratio (S m / S c ) is in the range of 2.0 to 3.3.

[0010] In one embodiment, the calculated specific surface area (S c ) may satisfy the following formula:

[0011]

[0012] (Here, d represents any positive electrode active material, Size d is the particle diameter of the positive electrode active material d, and %Chan d is the ratio, expressed in %, of the positive electrode active material having the particle diameter Size d to the entire positive electrode active material).

[0013] In one embodiment, the lithium composite oxide may be represented by Formula 1.

[0014] [Formula 1]

[0015] LiNi 1-x-y Co x Mn y M 1 z O2

[0016] (Here, x, y, and z may satisfy 0 < x < 0.4, 0 < y < 0.4, 0 ≤ z < 0.4, and 0 < x + y + z ≤ 0.4, and M 1 may include at least one element selected from the group consisting of Ti, Zr, Nb, W, P, Al, Mg, V, Ca, Sr, and Cr.

[0017] In one embodiment, the ratio of the specific surface area (S m ) measured based on the Brunauer-Emmett-Teller (BET) method and the specific surface area (S c ) calculated based on the particle size distribution (PSD) analysis result (Sm / S c ) can be in the range of 2.59 to 3.05.

[0018] In one embodiment, a positive electrode active material layer for an all-solid-state battery is provided, which may include a positive electrode active material and a sulfide-based solid electrolyte.

[0019] In one example, the sulfide-based solid electrolyte may be represented by Formula 2.

[0020] [Formula 2]

[0021] Li 3-2X M 2 X In 1-Y M 3 Y L 6-Z L' Z

[0022] (Here, M 2 and M 3 are each independently one selected from the group consisting of S, Sn, Mg, Ba, B, Al, Ga, In, Si, Ge, Pb, N, P, As, Sb, Bi, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Hf, Ta, W, La, and combinations thereof, L and L' are each independently one selected from the group consisting of Cl, Br, I, and combinations thereof, and X, Y, and Z satisfy 0 ≤ X < 1.5, 0 ≤ Y < 1, and 0 ≤ Z ≤ 6, respectively.)

[0023] Embodiments of the present disclosure may provide a method for preparing a positive electrode active material for an all-solid-state battery, the method may include: synthesizing a hydroxide precursor containing a transition metal; and obtaining a lithium composite oxide by mixing a lithium precursor with the hydroxide precursor and then subjecting the resulting mixture to a heat treatment, wherein the heat treatment is performed at a temperature higher than 700 °C and lower than 800 °C.

[0024] In one example, in the lithium composite oxide prepared according to the embodiment of the preparation method, the specific surface area (S m ) measured based on the BET method and the specific surface area (S c ) calculated based on the particle size distribution (PSD) analysis result m / S c ) can be in the range of 1.5 to 2.5.

[0025] In one example, the calculated specific surface area (S c ) may satisfy the following formula:

[0026] (Here, d represents any positive electrode active material, and Size d is the particle diameter of the positive electrode active material d, and %Chan d is the ratio, expressed as %, of the positive electrode active material having a particle diameter Size d to the entire positive electrode active material).

[0027] In one embodiment, the lithium composite oxide prepared according to the preparation method embodiment can be represented by Formula 1.

[0028] [Formula 1]

[0029] LiNi 1-x-y Co x Mn y M 1 z O2

[0030] (Here, x, y, and z can satisfy 0 < x < 0.4, 0 < y < 0.4, 0 ≤ z < 0.4, and 0 < x + y + z ≤ 0.4, and M 1 can include at least one element selected from the group consisting of Ti, Zr, Nb, W, P, Al, Mg, V, Ca, Sr, and Cr.)

[0031] In one embodiment, in the lithium composite oxide prepared according to the preparation method embodiment, the ratio (S m ) of the specific surface area measured based on the BET method to the specific surface area (S c ) calculated based on the PSD analysis result (S m / S c ) can be in the range of 2.59 to 3.05.

[0032] In one embodiment, the heat treatment can be performed for 10 to 12 hours.

[0033] According to an embodiment of the present disclosure, by controlling the sintering conditions and composition of the positive electrode active material, a positive electrode active material in which pores are not formed in the lithium composite oxide can be obtained. Therefore, the output characteristics of the positive electrode including the positive electrode active material can be improved.

[0034] The effects of the present disclosure are not limited to the above effects. It can be understood that the effects of the present disclosure include all effects that can be derived from the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 Schematically shows the structure of a all-solid-state battery including a positive electrode active material according to an embodiment of the present disclosure.

[0036] Figure 2 Shows the evaluation results of charging and discharging a half-cell according to an example and a comparative example and according to some embodiments of the present disclosure. Detailed embodiments

[0037] The above and other features and advantages of the present disclosure can be understood from the following exemplary embodiments associated with the drawings. However, the present disclosure is not limited to the exemplary embodiments described herein and can be embodied in other forms. The exemplary embodiments described herein are provided so that the present disclosure can be thorough and complete, and the spirit of the present disclosure can be fully conveyed to those skilled in the art.

[0038] Throughout the drawings, the same elements may be represented by the same reference numerals. In the drawings, for the clarity of the present disclosure, the size of the structure may be larger than the actual size. The terms "first", "second", etc. used herein may be used to describe various components, but the components do not have to be construed as limited to these terms. These terms may be used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present disclosure, the first component may be referred to as the second component, and the second component may also be referred to as the first component. Unless the context clearly indicates otherwise, singular expressions may include plural expressions.

[0039] It can be further understood that the terms "comprises", "includes", or "has" used herein specify the presence of the described features, regions, wholes, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, regions, wholes, steps, operations, elements, components, and / or combinations thereof. It can also be understood that when an element such as a layer, film, region, or sheet is referred to as being "on" another element, it can be directly on the other element, or there may be an intermediate element therebetween. Similarly, when an element such as a layer, film, region, or sheet is referred to as being "under" another element, it can be directly under the other element, or there may be an intermediate element therebetween.

[0040] Unless otherwise specified, the numerical values, values, and / or representations of the amounts of components, reaction conditions, polymer compositions, and mixtures used herein can be approximate values, including various uncertainties inherent in obtaining these values that affect the measurement, etc., and thus can be understood to be modified by the term "about". In addition, when a numerical range is disclosed in this specification, the range can be continuous and can include all values from the minimum value to the maximum value of the range, unless otherwise indicated. In addition, when such a range relates to integer values, all integers from the minimum value to the maximum value can be included, unless otherwise indicated.

[0041] As used herein, when a range is described for a variable, the variable can be understood to include all values within the range, including the endpoints of the range. For example, the range "5 to 10" includes the values 5, 6, 7, 8, 9, and 10, as well as any sub-ranges, such as 6 to 10, 7 to 10, 6 to 9, and 7 to 9. It should be understood that any value between reasonable integers within the range is included, such as 5.5, 6.5, 7.5, 5.5 to 8.5, and 6.5 to 9. Additionally, for example, the range "10% to 30%" includes values such as 10%, 11%, 12%, and 13%, as well as all integers up to and including 30%, and any sub-ranges such as 10% to 15%, 12% to 18%, and 20% to 30%. It can be understood that any value between reasonable integers within the range is included, such as 10.5%, 15.5%, and 25.5%.

[0042] Figure 1 A solid-state battery including a positive electrode active material according to an embodiment of the present disclosure is shown. The solid-state battery may be a stack including a positive electrode current collector 10, a positive electrode active material layer 20, a solid electrolyte layer 30, a negative electrode active material layer 40, and a negative electrode current collector 50.

[0043] The positive electrode current collector 10 may include a conductive substrate having a plate-like form. The positive electrode current collector 10 may include aluminum foil. In such an embodiment case, the thickness of the positive electrode current collector 10 is not particularly limited, but may be, for example, in the range of 1 to 500 μm.

[0044] The positive electrode active material layer 20 may include a positive electrode active material. According to an embodiment of the present disclosure, the positive electrode active material may include a lithium composite oxide capable of intercalating or deintercalating lithium, wherein, in the lithium composite oxide, the specific surface area (S m ) measured by the BET method and the specific surface area (S c ) calculated based on the particle size distribution (PSD) analysis result have a ratio (S m / S c ) in the range of 2.0 to 3.3.

[0045] In the present disclosure, the ratio (S m ) of the actually measured specific surface area measured by the BET method and the specific surface area (S c ) calculated based on the PSD analysis result (S m / S c ) can be adjusted to fall within a set or predetermined numerical range to optimize the density of the positive electrode active material particles, thereby reducing the resistance in the solid-state battery. Therefore, in one embodiment, a solid-state battery with improved output can be obtained.

[0046] The BET method in this article may refer to a method of calculating the specific surface area, pore size, and distribution of a solid sample by adsorbing and desorbing a specific gas (e.g., nitrogen) onto the surface of the solid sample using the equation developed by Brunauer, Emmett, and Teller. Known methods in the art for measuring the specific surface area of the positive electrode active material using the BET method can be used.

[0047] The particle size distribution (PSD) in this article can be measured using a laser diffraction type particle size distribution analyzer. The particle size refers to the size of the particles, which can mean, for example, the particle diameter.

[0048] In one embodiment, the calculated specific surface area (S c ) of the positive electrode active material calculated using the PSD analysis results can satisfy the following equation:

[0049]

[0050] (Here, d represents any positive electrode active material, Size d is the particle diameter of the positive electrode active material d, and %Chan d is the ratio of the positive electrode active material having the particle diameter Size d to all the positive electrode active material, expressed as a percentage).

[0051] The calculated specific surface area (S c ) of the positive electrode active material can refer to the average surface area per unit mass of the positive electrode active material. The average weight of a single positive electrode active material particle for calculating this value can be expressed as follows:

[0052]

[0053] (Here, is the volume of the positive electrode active material d used for calculating the positive electrode active material having the particle diameter Size d , and “%Chan d ” and “100” are the distribution for calculating the average mass of the positive electrode active material and the coefficients generated by the process of expressing the distribution as a percentage, respectively. In addition, “4.77 g / cm 3 ” can refer to the theoretical density of the positive electrode active material to calculate the mass based on the measured volume of the positive electrode active material).

[0054] “Size d ” can refer to the particle diameter of the positive electrode active material d that can be observed when measuring the positive electrode active material containing two or more types of positive electrode active material particles using a particle size distribution analyzer. For example, the particle diameter “Size d ” of the positive electrode active material can be measured to be greater than 0 μm and less than or equal to 15 μm.

[0055] The average surface area of a single positive electrode active material particle can be expressed as follows:

[0056]

[0057] (Here, and "4π" are used to calculate the surface area of the positive electrode active material d with a particle diameter of "Size d ", and "%Chan d " and "100" are the distribution for calculating the average surface area of the positive electrode active material and the coefficient generated by the process of expressing the distribution in %, respectively).

[0058] When the average surface area of a single positive electrode active material particle is divided by the average mass of a single positive electrode active material particle, and then the coefficients and units are arranged, the calculated specific surface area (S c ) of the positive electrode active material calculated using the particle size distribution analysis results can be derived.

[0059] In the case where there are multiple pores in the lithium composite oxide or the positive electrode active material, the weight decreases and the surface area increases for the same volume, thereby increasing the calculated specific surface area (S c ).

[0060] In the lithium composite oxide, the ratio (S m ) of the specific surface area (S c ) measured by the BET method falling within the range of 2.0 to 3.3 to the calculated specific surface area (S m / S c ) obtained using the PSD analysis results and the above formula can mean that the specific surface area of the positive electrode active material calculated using the particle size and particle size distribution is similar to the specific surface area of the positive electrode active material actually measured by the BET method, which corresponds to preventing the formation of pores in the positive electrode active material, and the true density can be high. Therefore, the output of the positive electrode or the all-solid-state battery containing the positive electrode active material can be increased.

[0061] In the lithium composite oxide, the ratio (S m ) of the specific surface area (S c ) measured by the BET method to the calculated surface area (S m / S c ) obtained using the PSD analysis results and the above formula can be in the range of 2.59 to 3.05.

[0062] In the lithium composite oxide, when the ratio (S m ) of the specific surface area (S c ) measured by the BET method to the calculated specific surface area (S m / S c)When it may exceed 3.3, multiple pores can be formed in the positive electrode active material, resulting in a decrease in the true density and deterioration of the output characteristics.

[0063] In one embodiment, the lithium composite oxide can be represented by Formula 1.

[0064] [Formula 1]

[0065] LiNi 1-x-y Co x Mn y M 1 z O2

[0066] Here, x, y, and z can satisfy 0 < x < 0.4, 0 < y < 0.4, 0 ≤ z < 0.4, and 0 < x + y + z ≤ 0.4. In addition, M 1 can include at least one element selected from the group consisting of Ti, Zr, Nb, W, P, Al, Mg, V, Ca, Sr, and Cr.

[0067] The positive electrode active material can further include a coating layer coating its surface. The coating layer can block the physical contact between the positive electrode active material and the solid electrolyte, thereby preventing side reactions from occurring between the two components. The material of the coating is not particularly limited, but can include LiNbO3, Li2CO3, and Li3BO3. In addition, the thickness of the coating is not particularly limited, but can be in the range of 5 to 500 nm or 10 to 100 nm.

[0068] In one embodiment, the positive electrode active material layer 20 can further include a solid electrolyte, a binder, a conductive additive, etc. The solid electrolyte can include oxide-based solid electrolytes, sulfide-based solid electrolytes, etc. In such an embodiment, a sulfide-based solid electrolyte with high ionic conductivity can be used.

[0069] The sulfide-based solid electrolyte can include Li2S-P2S5, Li2S-P2S5-LiI, Li2S-P2S5-LiCl, Li2S-P2S5-LiBr, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-Z m S n(wherein, m and n are each independently a positive integer, and Z is one of Ge, Zn, and Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li x MO y (wherein, x and y are each independently a positive integer, and M is one of P, Si, Ge, B, Al, Ga, and In), Li 10 GeP2S 12 and so on. The sulfide-based solid electrolyte can be represented by Formula 2.

[0070] [Formula 2]

[0071] Li 3-2X M 2 X In 1-Y M 3 Y L 6-Z L' Z

[0072] Herein, M 2 and M 3 are metal elements and can each independently be, for example, one selected from the group consisting of S, Sn, Mg, Ba, B, Al, Ga, In, Si, Ge, Pb, N, P, As, Sb, Bi, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Hf, Ta, W, La, and combinations thereof. L and L' are halogen elements and can each independently be, for example, one selected from the group consisting of Cl, Br, I, and combinations thereof.

[0073] In addition, X, Y, and Z can respectively satisfy 0 ≤ X < 1.5, 0 ≤ Y < 1, and 0 ≤ Z ≤ 6. At least one of M 2 and M 3 may contain sulfur (S).

[0074] Examples of the oxide-based solid electrolyte can include perovskite-type LLTO (Li 3x La 2 / 3-x TiO3), phosphate-based NASICON-type LATP (Li 1+x Al x Ti 2-x (PO4)3), and so on.

[0075] Examples of the binder may include butadiene rubber (BR), nitrile rubber (NBR), hydrogenated nitrile rubber (HNBR), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), carboxymethyl cellulose (CMC), etc.

[0076] Examples of the conductive additive may include carbon black, conductive graphite, ethylene black, vapor-grown carbon fiber, graphene, etc.

[0077] The positive electrode active material layer 20 may include a positive electrode active material and a solid electrolyte in a mass ratio ranging from 6:4 to 9:1. When the mass ratio of the positive electrode active material is low, the capacity of the all-solid-state battery may decrease. On the contrary, when the mass ratio of the positive electrode active material is high, the amount of the solid electrolyte can be reduced, and thus the lithium ion conductivity in the positive electrode active material layer 20 may decrease.

[0078] The solid electrolyte layer 30 is located between the positive electrode active material layer 20 and the negative electrode active material layer 40, and may include a solid electrolyte having lithium ion conductivity.

[0079] The solid electrolyte may include oxide-based solid electrolytes, sulfide-based solid electrolytes, etc. In such an example case, a sulfide-based solid electrolyte having high ionic conductivity can be used.

[0080] Examples of the sulfide-based solid electrolyte may include Li2S-P2S 5、 Li2S-P2S5-LiI, Li2S-P2S5-LiCl, Li2S-P2S5-LiBr, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS 2、 Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-Z m S n (wherein, m and n are each independently a positive integer, and Z is one of Ge, Zn, and Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li x MO y (wherein, x and y are each independently a positive integer, and M is one of P, Si, Ge, B, Al, Ga, and In), Li 10 GeP2S 12 etc.

[0081] Examples of the oxide-based solid electrolyte may include perovskite-type LLTO (Li3x La 2 / 3-x (TiO3), phosphate-based NASICON-type LATP (Li 1+x Al x Ti 2-x (PO4)3), etc.

[0082] The negative electrode active material layer 40 may include a negative electrode active material, a binder, etc.

[0083] The negative electrode active material may include a carbon-based negative electrode active material, a non-carbon-based negative electrode active material, etc.

[0084] The carbon-based negative electrode active material may include graphite (such as mesocarbon microbeads (MCMB) and highly oriented pyrolytic graphite (HOPG)) or amorphous carbon (such as hard carbon and soft carbon). The non-carbon-based negative electrode active material may include a metal, a metal oxide, etc. containing at least one selected from the group consisting of In, Al, Si, Sn, and combinations thereof.

[0085] Examples of the binder may include butadiene rubber (BR), nitrile rubber (NBR), hydrogenated nitrile rubber (HNBR), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), carboxymethyl cellulose (CMC), etc.

[0086] The negative electrode current collector 50 may be a conductive substrate having a plate-like form. Specifically, the negative electrode current collector 50 may have the form of a sheet, a film, or a foil. The negative electrode current collector 50 may include a material that does not react with lithium. Specifically, the negative electrode current collector 50 may include at least one selected from the group consisting of Ni, Cu, stainless steel (SUS), and combinations thereof.

[0087] The thickness of the negative electrode current collector 50 is not particularly limited, but may be, for example, in the range of 1 to 500 μm.

[0088] Hereinafter, an exemplary method for preparing a positive electrode active material will be described.

[0089] Embodiment of the preparation method of the positive electrode active material

[0090] Embodiments of the present disclosure may provide a method for preparing a positive electrode active material for an all-solid-state battery, including: synthesizing a hydroxide precursor containing a transition metal; and obtaining a lithium composite oxide by mixing a lithium precursor with the hydroxide precursor and then subjecting the resulting mixture to a heat treatment, wherein the heat treatment is performed at a temperature higher than 700 °C and lower than 800 °C.

[0091] The hydroxide precursor containing transition metals can be synthesized using the co - precipitation method. Specifically, after adding water to the reactor, salts of each transition metal that match the composition of the desired positive electrode active material can be mixed. While maintaining the temperature of the reactor within the range of 50 °C to 80 °C, an inert gas can be introduced into the reactor to prevent the prepared hydroxide precursor from being oxidized. After the synthesis and stirring are completed, the hydroxide precursor can be obtained by washing and dehydration using a filter - press (F / P) device.

[0092] Alternatively, salts of each transition metal that match the composition of the desired positive electrode active material can be dissolved in water to prepare an aqueous solution. Then, the aqueous solution can be introduced into a sodium hydroxide solution while stirring. When stirring the resulting product, a hydroxide - type precursor containing transition metals can be precipitated.

[0093] After synthesizing the hydroxide precursor by this method, a lithium precursor or lithium raw material can be added. The lithium precursor is not particularly limited. For example, lithium hydroxide (LiOH) etc. can be used.

[0094] According to the composition of the desired positive electrode active material, the lithium precursor and the hydroxide precursor can be weighed and mixed, and then heat treatment can be carried out. In one embodiment, the heat treatment can be carried out at a temperature higher than 700 °C and lower than 800 °C for 10 to 12 hours. When the heat treatment is carried out at a temperature below 700 °C, the low sintering temperature of the positive electrode active material may deteriorate its quality. On the contrary, when the heat treatment is carried out at a temperature of 800 °C or higher, many pores may be formed in the positive electrode active material, resulting in a decrease in true density and deterioration of output characteristics.

[0095] In addition, when the heat treatment is carried out for 10 to 12 hours, a sufficient amount of heat supplied during the preparation of the positive electrode active material can prevent the formation of pores in the positive electrode active material, and the true density can increase, thereby improving the output characteristics.

[0096] In one embodiment, in the lithium composite oxide prepared according to one embodiment of the preparation method, the specific surface area (S m ) measured based on the BET method and the specific surface area (S c ) calculated based on the particle size distribution (PSD) analysis results, the ratio (S m / S c ) can be in the range of 2.0 to 3.3.

[0097] In one embodiment, the calculated specific surface area (S c ) can satisfy the following formula:

[0098]

[0099] (Here, d represents any positive electrode active material, Size d is the particle diameter of the positive electrode active material d, and %Chan d is the ratio, expressed in %, of the positive electrode active material having a particle diameter of Size d to all the positive electrode active materials.)

[0100] In one embodiment, the lithium composite oxide prepared according to the preparation method embodiment can be represented by Formula 1.

[0101] [Formula 1]

[0102] LiNi 1-x-y Co x Mn y M 1 z O2

[0103] Here, x, y, and z can satisfy 0 < x < 0.4, 0 < y < 0.4, 0 ≤ z < 0.4, and 0 < x + y + z ≤ 0.4. Further, M 1 can include at least one element selected from the group consisting of Ti, Zr, Nb, W, P, Al, Mg, V, Ca, Sr, and Cr.

[0104] In one embodiment, in the lithium composite oxide prepared according to the preparation method embodiment, the ratio (S m ) of the specific surface area (S c ) measured based on the BET method to the specific surface area (S m / S c ) calculated based on the PSD analysis result can be in the range of 2.59 to 3.05.

[0105] The lithium composite oxide prepared according to the preparation method embodiment and the positive electrode active material containing the same can be substantially the same as those described above, and thus redundant detailed descriptions will be omitted.

[0106] Hereinafter, the present disclosure will be described in detail with reference to the following examples and comparative examples. However, the technical concept of the present disclosure is not necessarily limited thereto or restricted thereby.

[0107] Preparation of the positive electrode active material

[0108] (1) Preparation Example 1

[0109] Spherical Ni 0.80 Co 0.10 Mn 0.10(OH)2 hydroxide precursor. Specifically, in a 90-L reactor, 25 wt% NaOH and 30 wt% NH4OH were introduced into an aqueous solution of 1.5 M sulfuric acid of a transition metal complex, where nickel sulfate, cobalt sulfate, and manganese sulfate were mixed in a molar ratio of 80:1:1. The pH in the reactor was maintained at 11.5 while the temperature of the reactor was maintained at 60 °C. An inert gas N2 was introduced into the reactor to prevent the prepared precursor from being oxidized. After the synthesis and stirring were completed, Ni 0.8 Co 0.1 Mn 0.1 (OH)2 hydroxide precursor.

[0110] Next, LiOH (lithium precursor) was added to the synthesized hydroxide precursor, and then the obtained product was sintered to prepare a lithium composite oxide. Specifically, after mixing LiOH with the hydroxide precursor, the obtained mixture was subjected to a heating temperature of 10 hours while maintaining O2 gas in a sintering furnace by raising the temperature to 780 °C at a rate of 1 °C per minute, and then naturally cooled to obtain the lithium composite oxide.

[0111] (2) Preparation Example 2

[0112] Except that in the process of preparing the lithium composite oxide, after mixing LiOH with the hydroxide precursor, the obtained mixture was subjected to a heating temperature of 11 hours while maintaining O2 gas in a sintering furnace by raising the temperature to 750 °C at a rate of 1 °C per minute, and then naturally cooled, the positive electrode active material was prepared in the same manner as in Preparation Example 1.

[0113] (3) Comparative Preparation Example 1

[0114] Except that in the process of preparing the lithium composite oxide, after mixing LiOH with the hydroxide precursor, the obtained mixture was subjected to a heating temperature of 12 hours while maintaining O2 gas in a sintering furnace by raising the temperature to 700 °C at a rate of 1 °C per minute, and then naturally cooled, the positive electrode active material was prepared in the same manner as in Preparation Example 1.

[0115] (4) Comparative Preparation Example 2

[0116] Except that in the process of preparing the lithium composite oxide, after mixing LiOH with the hydroxide precursor, the obtained mixture was subjected to a heating temperature of 10 hours while maintaining O2 gas in a sintering furnace by raising the temperature to 800 °C at a rate of 1 °C per minute, and then naturally cooled, the positive electrode active material was prepared in the same manner as in Preparation Example 1.

[0117] Manufacture of the half cell

[0118] (1) Example 1

[0119] The solid electrolyte layer 30 is formed by compressing a sulfide-based solid electrolyte doped with indium (In) at a pressure of about 10 MPa for 10 seconds.

[0120] A mixture containing the positive electrode active material, sulfide-based solid electrolyte, and conductive additive according to Preparation Example 1 in a mass ratio of 69:29:2 is prepared. The mixture is applied to the first surface of the solid electrolyte layer 30 at a loading of about 13 mg / cm 2 A lithium-indium thin film is attached to the second surface of the solid electrolyte layer 30 as a negative electrode, which serves as a counter electrode. A half-cell is obtained by compressing the stack thus obtained at a pressure of about 32 MPa for 5 minutes.

[0121] (2) Example 2

[0122] A half-cell is prepared in the same manner as in Example 1, except that the positive electrode active material according to Preparation Example 2 is used.

[0123] (3) Comparative Example 1

[0124] A half-cell is prepared in the same manner as in Example 1, except that the positive electrode active material according to Comparative Preparation Example 1 is used.

[0125] (4) Comparative Example 2

[0126] A half-cell is prepared in the same manner as in Example 1, except that the positive electrode active material according to Comparative Preparation Example 2 is used.

[0127] Experimental Example 1 - Particle Size Distribution (PSD) Analysis and Specific Surface Area (S c ) Calculation

[0128] The particle size distributions of the positive electrode active materials according to Preparation Examples 1 and 2 and Comparative Preparation Examples 1 and 2 are measured using a particle size analyzer. The results are shown in Table 1 below. In Table 1 below, only the start of the part where the particle diameter ratio of the positive electrode active material is 0% is shown.

[0129] [Table 1]

[0130]

[0131]

[0132] The calculated specific surface area is obtained by substituting the values listed in Table 1 above into the following formula, and the results are shown in Table 2:[[]]

[0133]

[0134] (Here, d represents any positive electrode active material, Size dis the particle diameter of the positive electrode active material d, %Chan d is the ratio of the positive electrode active material having a particle diameter of Size d to all the positive electrode active materials (expressed in %).

[0135] [Table 2]

[0136] Preparation Example 1 Preparation Example 2 Comparative Preparation Example 1 Comparative Preparation Example 2 <![CDATA[S c (m 2 / g)]]> 0.2164 0.1681 0.1191 0.0827

[0137] Experimental Example 2 - Ratio of BET specific surface area to specific surface area (S m / S c )

[0138] The BET specific surface area (S m ) of the positive electrode active materials according to Preparation Examples 1 and 2 and Comparative Preparation Examples 1 and 2 was measured using a BET specific surface area analyzer. Subsequently, the measured specific surface area (S m ) was divided by the calculated specific surface area (S c ) obtained by calculation in Experimental Example 1. The results are shown in Table 3 below.

[0139] [Table 3]

[0140] Classification Sintering conditions <![CDATA[S C > <![CDATA[S m > <![CDATA[S m / S c > Preparation Example 1 780 °C / 10 hours 0.2164 0.5622 2.59 Preparation Example 2 750 °C / 11 hours 0.1681 0.5122 3.05 Comparative Preparation Example 1 700 °C / 12 hours 0.1191 0.4775 4.01 Comparative Preparation Example 2 800 °C / 10 hours 0.0827 0.4726 5.71

[0141] It can be confirmed from Table 3 that, according to Preparation Examples 1 and 2, the S m / S c value in the positive electrode active material shows a range of 2.0 to 3.3.

[0142] Experimental Example 3 - Charge and discharge evaluation

[0143] The half-cells according to Examples 1 and 2 and Comparative Examples 1 and 2 were charged at a constant current (CC) of 0.188C to a voltage level of -3.68V at a temperature of 30°C, and then discharged at a constant current of 0.1C to a voltage level of 1.88V. Subsequently, while maintaining the same voltage level, the half-cells were charged and discharged at 0.05C, 0.1C, 0.33C, 0.5C, 1C, and 2C. The results are shown in Figure 2 .

[0144] From Figure 2 it can be confirmed that Examples 1 and 2, in which the parameter value (S m / S c ) is small, exhibit better output characteristics than Comparative Examples 1 and 2. Specifically, it can be confirmed that the output characteristics deteriorate in the range where the parameter value (S m / S c ) exceeds 3.3. Specifically, it was confirmed that by Figure 2The 0.5-C retention (%) (0.5-C capacity / 0.1-C capacity) of each determined positive electrode active material is as follows: 90% in Example 1, 82.6% in Example 2, 76.4% in Comparative Example 1, and 74.3% in Comparative Example 2. This is because, according to Comparative Examples 1 and 2, multiple pores can be formed in the positive electrode active material, resulting in a decrease in the particle density compared to the particle densities of Examples 1 and 2, and the pores thus formed can increase the internal resistance, resulting in a decrease in output.

[0145] Although the exemplary embodiments of the present disclosure have been disclosed for illustrative purposes, those skilled in the art can understand that various changes and modifications can be made by adding, changing, deleting, etc. elements without departing from the spirit and scope of the present disclosure.

Claims

1. A positive electrode active material for an all-solid-state battery, the positive electrode active material comprising a lithium composite oxide capable of intercalating or deintercalating lithium, wherein, In the lithium composite oxide, the ratio (S m / S c ) of the specific surface area (S m ) measured based on the Brunauer-Emmett-Teller method to the specific surface area (S c ) calculated based on the particle size distribution analysis results is within a first range of 2.0 to 3.

3.

2. The positive electrode active material according to claim 1, wherein, The calculated specific surface area (S c ) satisfies wherein, d represents the positive electrode active material, wherein, Size d is the particle diameter of the positive electrode active material, and wherein, %Chan d is the ratio, expressed as a percentage, of the positive electrode active material having the particle diameter of Size d to the entire positive electrode active material.

3. The positive electrode active material according to claim 1, wherein, The lithium composite oxide is represented by LiNi 1-x-y Co x Mn y M 1 z O2, where x, y, and z satisfy 0 < x < 0.4, 0 < y < 0.4, 0 ≤ z < 0.4, and 0 < x + y + z ≤ 0.4, and where M 1 comprises at least one element selected from the group consisting of Ti, Zr, Nb, W, P, Al, Mg, V, Ca, Sr, and Cr.

4. The positive electrode active material according to claim 1, wherein, The ratio (S m / S c ) is within a second range of 2.59 to 3.

05.

5. A positive electrode active material layer, comprising: A positive electrode active material, the positive electrode active material including a lithium composite oxide capable of allowing lithium to be intercalated or deintercalated, wherein, In the lithium composite oxide, the specific surface area (S m ) and the specific surface area (S c ) ratio (S m / S c ) is in a first range of 2.0 to 3.3; and A sulfide-based solid electrolyte.

6. The positive electrode active material layer according to claim 5, wherein, The calculated specific surface area (S c ) satisfies Wherein, d represents the positive electrode active material, wherein, Size d is the particle diameter of the positive electrode active material, and wherein, %Chan d is the ratio, expressed as a percentage, of the positive electrode active material having the particle diameter of Size d to the entire positive electrode active material.

7. The positive electrode active material layer according to claim 5, wherein, The lithium composite oxide is represented by the following: LiNi 1-x-y Co x Mn y M 1 z O2, Wherein, x, y, and z satisfy 0 < x < 0.4, 0 < y < 0.4, 0 ≤ z < 0.4, and 0 < x + y + z ≤ 0.4, and Among them, M 1 contains at least one element selected from the group consisting of Ti, Zr, Nb, W, P, Al, Mg, V, Ca, Sr, and Cr.

8. The positive electrode active material layer according to claim 5, wherein The ratio (S m / S c ) is within a second range of 2.59 to 3.

05.

9. The positive electrode active material layer according to claim 5, wherein The sulfide-based solid electrolyte is represented by the following: Li 3-2X M 2 X In 1-Y M 3 Y L 6-Z L' Z , Wherein, M 2 and M 3 are each independently one selected from the group consisting of: S, Sn, Mg, Ba, B, Al, Ga, In, Si, Ge, Pb, N, P, As, Sb, Bi, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Hf, Ta, W, La, and any combination thereof. Wherein, L and L' are each independently one selected from the group consisting of Cl, Br, I, and any combination thereof, and Wherein, X, Y, and Z respectively satisfy 0 ≤ X < 1.5, 0 ≤ Y < 1, and 0 ≤ Z ≤ 6.

10. A method for preparing a positive electrode active material for a all-solid-state battery, the method comprising: Synthesizing a hydroxide precursor containing a transition metal; Obtaining a lithium composite oxide by mixing a lithium precursor with the hydroxide precursor; And After obtaining the lithium composite oxide, subjecting the resulting mixture to a heat treatment, wherein the heat treatment is carried out in a temperature range higher than 700 °C and lower than 800 °C.

11. The method according to claim 10, wherein, In the lithium composite oxide, the ratio (S m / S c ) of the specific surface area (S m ) measured based on the Brunauer-Emmett-Teller method to the specific surface area (S c ) calculated based on the particle size distribution analysis results is in a first range of 2.0 to 3.

3.

12. The method according to claim 11, wherein The calculated specific surface area (S c ) satisfies where d represents the positive electrode active material, where Size d is the particle diameter of the positive electrode active material, and where %Chan d is the ratio, expressed as a percentage, of the positive electrode active material having the particle diameter of Size d to the entire positive electrode active material.

13. The method according to claim 10, wherein The lithium composite oxide is represented by the following: LiNi 1-x-y Co x Mn y M 1 z O, Wherein, x, y, and z satisfy 0 < x < 0.4, 0 < y < 0.4, 0 ≤ z < 0.4, and 0 < x + y + z ≤ 0.4, and Among them, M 1 contains at least one element selected from the group consisting of Ti, Zr, Nb, W, P, Al, Mg, V, Ca, Sr, and Cr.

14. The method according to claim 11, wherein, The ratio (S m / S c ) is within a second range from 2.59 to 3.

05.

15. The method according to claim 10, wherein, The heat treatment is carried out for 10 to 12 hours.

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