Positive electrode active material and all-solid battery comprising the same

Abstract

A positive electrode active material according to one embodiment of the present invention is a positive electrode active material comprising a lithium composite metal oxide, wherein the 'relative pressure with respect to the saturated vapor pressure (P0)' for the positive electrode active material is defined by the adsorption isotherm and desorption isotherm of the 'normalized adsorption / desorption amount' graph represented by the following mathematical formula 1, and the 'maximum adsorption / desorption width (DH)' represented by the following mathematical formula 2 may be 0.6 or less. [Mathematical Formula 1] Normalized adsorption amount = (Adsorption amount (cm³ / g) / Total adsorption amount (cm³ / g)) × 100 Normalized Desorption Amount = (Desorption Amount (cm³ / g) / Total Desorption Amount (cm³ / g)) × 100 [Mathematical Formula 2] In the above mathematical formula 2, QDes is the normalized adsorption amount of the above adsorption isotherm, and QAbs is the normalized adsorption amount of the above desorption isotherm, and max(QDes-QAbs) is the maximum value of the difference between the normalized adsorption amount of the adsorption isotherm and the normalized adsorption amount of the desorption isotherm calculated based on the same relative pressure.

Description

Technology Field

[0001] The present invention relates to a positive electrode active material with controlled pore characteristics and an all-solid-state battery comprising the same. Background Technology

[0002] Rechargeable secondary batteries are used not only in small electronic devices such as mobile phones and laptops but also in large transportation vehicles such as hybrid and electric cars. Accordingly, there is a need to develop secondary batteries with higher stability and energy density.

[0003] Most conventional secondary batteries utilize cells based on organic solvents (organic liquid electrolytes), which limits their potential for improving stability and energy density. On the other hand, all-solid-state batteries, which use inorganic solid electrolytes, are receiving significant attention recently because they are based on technology that eliminates organic solvents, allowing for the fabrication of safer and simpler cells.

[0004] In all-solid-state batteries, a solid electrolyte is added to the electrode to facilitate the movement of lithium ions within the electrode. Solid electrolytes can be classified into sulfide-based solid electrolytes and oxide-based solid electrolytes, and sulfide-based solid electrolytes, which have high lithium ion conductivity, are mainly used. In this case, there was a problem in which side reactions occurred between the sulfide-based solid electrolyte and the positive electrode active material, causing a decrease in the battery's lifespan characteristics. Prior art literature

[0005] Korean Patent Publication No. 10-2020-0047960 The problem to be solved

[0006] The objective of the present invention is to provide a positive electrode active material that improves the lifespan characteristics of a battery by controlling the content distribution of micropores, mesopores, and macropores, as well as the closed pore content. means of solving the problem

[0007] (1) The present invention is a positive electrode active material comprising a lithium composite metal oxide, wherein the 'relative pressure with respect to the saturated vapor pressure (P0)' for the positive electrode active material is defined by the adsorption isotherm and desorption isotherm of the 'normalized adsorption / desorption amount' graph represented by the following mathematical formula 1, and the 'maximum adsorption / desorption width (D)' represented by the following mathematical formula 2. H Provides a positive electrode active material in which )' is 0.6 or less:

[0008] [Mathematical Formula 1]

[0009] Normalized adsorption amount = (Adsorption amount (cm³ / g) / Total adsorption amount (cm³ / g)) × 100

[0010] Normalized Desorption Amount = (Desorption Amount (cm³ / g) / Total Desorption Amount (cm³ / g)) × 100

[0012] [Mathematical Formula 2]

[0013]

[0014] In the above mathematical formula 2,

[0015] Q Des is the normalized adsorption amount of the above adsorption isotherm, and

[0016] Q Abs is the normalized adsorption amount of the above desorption isotherm, and

[0017] max(Q Des -Q Abs ) is the maximum value of the difference between the normalized adsorption amount of the adsorption isotherm and the normalized adsorption amount of the desorption isotherm calculated based on the same relative pressure.

[0018] (2) The present invention provides an anode active material in which hysteresis defined by the adsorption isotherm and the desorption isotherm is not observed in the above (1).

[0019] (3) The present invention provides a positive electrode active material according to (1) or (2), wherein the lithium composite metal oxide particles comprise micropores with a diameter of less than 2 nm; mesopores with a diameter of 2 nm or more and 50 nm or less; and macropores with a diameter exceeding 50 nm.

[0020] (4) The present invention provides an anode active material in any one of (1) to (3), wherein the pore volume distribution value of the pores corresponding to the micropores and the mesopores is smaller than the pore volume distribution value of the pores corresponding to the macropores.

[0021] (5) The present invention, in any one of (1) to (4), wherein the rate of change (ΔQ) of the relative pressure and the desorption isotherm is a factor NA Provides a positive active material in which no peak is observed in the graph.

[0022] (6) The present invention provides a positive electrode comprising a positive electrode active material according to any one of (1) to (5).

[0023] (7) The present invention provides an all-solid-state battery comprising a positive electrode according to (8); a solid electrolyte layer; and a negative electrode.

[0024] (8) The present invention is a solid-state battery in which the solid electrolyte layer comprises a sulfide-based solid electrolyte, as described in (7). Effects of the invention

[0025] A positive electrode active material according to one embodiment of the present invention improves the lifespan characteristics of a battery by controlling the content distribution of micropores, mesopores, and macropores, as well as the closed pore content. Brief explanation of the drawing

[0026] Figure 1 is an SEM image of a positive electrode active material according to Example 1 of the present invention. Figure 2 is an SEM image of the positive electrode active material according to Comparative Example 1 of the present invention. Figure 3 is an SEM image of the positive electrode active material according to Comparative Example 4 of the present invention. FIG. 4 is a graph showing the adsorption isotherms and desorption isotherms of the positive active material according to Examples 1 to 3 of the present invention. FIG. 5 is a graph showing the adsorption isotherms and desorption isotherms of the positive active material according to Comparative Examples 1 to 4 of the present invention. FIG. 6 is a graph of the pore volume distribution according to the pore diameter of the positive active material according to Examples 1 to 3 of the present invention. FIG. 7 is a graph of the pore volume distribution according to the pore diameter of the positive electrode active material according to Comparative Examples 1 to 4 of the present invention. FIG. 8 shows the rate of change (ΔQ) of the desorption isotherm according to the relative pressure of the anode active material according to Examples 1 to 3 of the present invention. NA It is a graph. FIG. 9 shows the rate of change (ΔQ) of the desorption isotherm according to the relative pressure of the anode active material according to Comparative Examples 1 to 4 of the present invention. NA It is a graph. FIG. 10 is a graph of the capacity retention rate (%) per cycle of an all-solid-state battery containing a positive electrode active material according to an embodiment and a comparative example of the present invention. Specific details for implementing the invention

[0027] Hereinafter, the present invention will be described in more detail to aid in understanding the invention. In this case, terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted in a meaning and concept consistent with the technical spirit of the invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention.

[0028] In the present invention, the term 'primary particle' refers to a minimum particle unit that is distinguished as a single mass when the cross-section of the positive active material is observed through a scanning electron microscope (SEM), and may consist of multiple crystal grains.

[0029] In the present invention, the term 'secondary particle' refers to a secondary structure formed by the aggregation of a plurality of primary particles. The average particle size of the secondary particles can be measured using a particle size analyzer.

[0030] In the present invention, 'average particle size (D 50 )’ refers to the particle size at the 50% point of the volume cumulative distribution according to particle size. The above average particle size can be measured by dispersing the powder to be measured in a dispersion medium, introducing it into a commercially available laser diffraction particle size measuring device (e.g., Microtrac’s S3500), measuring the difference in diffraction patterns according to particle size as the particles pass through a laser beam to calculate the particle size distribution, and calculating the particle diameter at the point that is 50% of the volume cumulative distribution according to particle size in the measuring device.

[0032] <Cathode Active Material>

[0033] The present invention provides a positive electrode active material.

[0034] A positive electrode active material according to one embodiment of the present invention is at least a positive electrode active material comprising lithium composite metal oxide particles, defined by the 'relative pressure with respect to the saturated vapor pressure (P0)' for the positive electrode active material and the adsorption isotherm and desorption isotherm of the 'normalized adsorption / desorption amount' graph represented by the following Equation 1, and the 'maximum adsorption / desorption width (D)' represented by the following Equation 2. H )' is 0.6 or less.

[0035] [Mathematical Formula 1]

[0036] Normalized adsorption amount = (Adsorption amount (cm³ / g) / Total adsorption amount (cm³ / g)) × 100

[0037] Normalized Desorption Amount = (Desorption Amount (cm³ / g) / Total Desorption Amount (cm³ / g)) × 100

[0039] [Mathematical Formula 2]

[0040]

[0041] In the above mathematical formula 2,

[0042] Q Des is the normalized adsorption amount of the above adsorption isotherm, and

[0043] Q Abs is the normalized adsorption amount of the above desorption isotherm, and

[0044] max(Q Des -Q Abs ) is the maximum value of the difference between the normalized adsorption amount of the adsorption isotherm and the normalized adsorption amount of the desorption isotherm calculated based on the same relative pressure.

[0046] Generally, all-solid-state batteries mainly use sulfide-based solid electrolytes with high lithium-ion conductivity as solid electrolytes. In this case, unlike liquid electrolytes, sulfide-based solid electrolytes form a solid interface through physical contact with the positive electrode active material. Therefore, if there are micropores on the surface of the positive electrode active material, there is a problem in that the lifespan characteristics of the battery are degraded due to losses in the movement path of ions or electrons.

[0047] In one embodiment of the present invention, the positive electrode active material controls the content distribution of micropores, mesopores, and macropores and the closed pore content, thereby preventing the loss of electron and ion pathways within the positive electrode active material even if side reactions with a sulfide-based solid electrolyte occur, which can improve the lifespan characteristics of the battery.

[0048] Hereinafter, a positive electrode active material according to one embodiment of the present invention will be described in detail.

[0050] According to one embodiment of the present invention, the positive active material is an active material that is a lithium ion (Li +A material capable of reversibly absorbing and releasing ) may include a complex oxide of lithium and metal, namely a lithium complex metal oxide.

[0051] According to one embodiment of the present invention, the lithium composite metal oxide is, as a specific example, a lithium-manganese-based oxide (e.g., LiMnO2, LiMn2O2). 4　 etc.), lithium-cobalt oxides (e.g., LiCoO2, etc.), lithium-nickel oxides (e.g., LiNiO2, etc.), lithium-nickel-manganese oxides (e.g., LiNi 1-Y Mn Y O2(here, 0 <Y<1), LiMn 2-z Ni z O4 (where 0 < Z < 2), etc.), lithium-nickel-cobalt oxides (e.g., LiNi 1-Y1 Co Y1 O2(here, 0 <Y1<1) 등), 리튬-망간-코발트계 산화물(예를 들면, LiCo 1-Y2 Mn Y2 O2(here, 0 <Y2<1), LiMn 2-z1 Co z1 O4 (where 0 < Z1 < 2), etc.), lithium-nickel-manganese-cobalt oxides (e.g., Li(Ni p Co q Mn r1 )O2(where, 0<p<1, 0<q<1, 0<r1<1, p+q+r1=1) or Li(Ni p1 Co q1 Mn r2 )O4 (where 0<p1<2, 0<q1<2, 0<r2<2, p1+q1+r2=2), etc.), or lithium-nickel-cobalt-transition metal (M) oxide (e.g., Li(Ni p2 Co q2 Mn r3 M S2)O2(wherein M is selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg and Mo, and p2, q2, r3 and s2 are each atomic fractions of independent elements, such that 0<p2<1, 0<q2<1, 0<r3<1, 0<s2<1, p2+q2+r3+s2=1) etc.) etc., and any one or more of these may be.

[0052] Among these, the lithium composite metal oxides mentioned above include LiCoO2, LiMnO2, LiNiO2, and lithium nickel manganese cobalt oxide (e.g., Li(Ni)) in that they can improve the capacity characteristics and stability of the battery. 1 / 3 Mn 1 / 3 Co 1 / 3 )O2, Li(Ni 0.6 Mn 0.2 Co 0.2 )O2, 　 Li(Ni) 0.5 Mn 0.3 Co 0.2 )O2, Li(Ni 0.7 Mn 0.15 Co 0.15 )O2 and Li(Ni 0.8 Mn 0.1 Co 0.1 )O2, etc.), or lithium nickel-cobalt-aluminum oxide (e.g., Li(Ni 0.8 Co 0.15 Al 0.05 It may be )O2, etc., and considering the significant improvement effect resulting from controlling the type and content ratio of constituent elements forming the lithium composite metal oxide, the lithium composite metal oxide is Li(Ni 0.6 Mn 0.2 Co 0.2 )O2, 　 Li(Ni) 0.5 Mn 0.3 Co 0.2 )O2, Li(Ni 0.7 Mn 0.15 Co 0.15 )O2 and Li(Ni 0.8 Mn 0.1 Co 0.1It may be O2, etc., and any one of these or a mixture of two or more may be used.

[0053] According to one embodiment of the present invention, the positive electrode active material may further include a coating layer surrounding the lithium composite metal oxide, and the coating layer may include boron (B) or LiNbO. By further including the coating layer, the structural stability of the positive electrode active material may be further improved.

[0055] According to one embodiment of the present invention, pores may be formed in the lithium composite metal oxide, and the pores may be classified according to their diameter size. Specifically, the pores may be classified into micropores with a pore diameter of less than 2 nm, mesopores with a pore diameter of 2 nm or more and 50 nm or less, and macropores with a pore diameter exceeding 50 nm.

[0056] According to one embodiment of the present invention, the lithium composite metal oxide may include micropores, mesopores, and macropores, and the content distribution of each of these may be appropriately controlled, and accordingly, the loss of electron and ion pathways within the positive electrode active material is prevented, thereby improving the lifespan characteristics of the battery.

[0057] A positive electrode active material according to one embodiment of the present invention is defined by the 'relative pressure with respect to the saturated vapor pressure (P0)' for the positive electrode active material and the adsorption isotherm and desorption isotherm of the 'normalized adsorption / desorption amount' graph represented by Equation 1, by controlling the content distribution of mesopores of the lithium composite metal oxide, and the 'maximum adsorption / desorption width (D)' represented by Equation 2 below. H )' can be 0.6 or less.

[0058] As a specific example, the above maximum adsorption / desorption width (D H) may be 0.55 or less, 0.5 or less, 0.45 or less, 0.4 or less, 0.35 or less, or 0.3 or less, and may also be 0.005 or more, 0.01 or more, 0.015 or more, 0.02 or more, or 0.03 or more. If the above-described range is satisfied, the content distribution of mesopores in the lithium composite metal oxide is appropriately controlled, thereby preventing electron and ion path loss within the cathode active material and improving the lifespan characteristics of the battery. If, the maximum adsorption / desorption width (D H If the above-described range is exceeded, the content distribution of mesopores in the lithium composite metal oxide becomes excessively high, leading to an increase in the formation of a deterioration layer due to side reactions with the solid electrolyte, and consequently, the lifespan characteristics of the battery may be degraded.

[0060] In a positive electrode active material according to one embodiment of the present invention, the ratio of micropores and mesopores and the ratio of macropores of the lithium composite metal oxide are appropriately controlled, so that in a pore volume distribution graph according to pore diameter for the positive electrode active material, the pore volume distribution values ​​of the pores corresponding to the micropores and mesopores may be smaller than the pore volume distribution values ​​of the pores corresponding to the macropores. Here, the pore volume distribution may be defined by the following Equation 3.

[0061] [Mathematical Formula 3]

[0062]

[0063] In the above mathematical formula 3,

[0064] dlog(D) is a small change in the log value of the pore diameter (D), and

[0065] dV is the amount of minute volume change of the pore corresponding to the pore diameter (D) above.

[0067] Specifically, according to one embodiment of the present invention, in a graph of pore volume distribution according to pore diameter for the positive electrode active material, all pore volume distribution values ​​in the region with a pore diameter of 50 nm or less may be smaller than all pore volume distribution values ​​in the region with a pore diameter exceeding 50 nm. In addition, the positive electrode active material according to one embodiment of the present invention may have a tendency for the pore volume distribution values ​​in the region with a pore diameter exceeding 50 nm to generally trend upward in a graph of pore volume distribution according to pore diameter. By having a graph shape as described above, the ratio of micropores and mesopores and the ratio of macropores of the lithium composite metal oxide are appropriately controlled, thereby preventing electron and ion path loss within the positive electrode active material and improving the lifespan characteristics of the battery. If there is a pore volume distribution value in the region with a pore diameter of 50 nm or less that is larger than the pore volume distribution value in the region with a pore diameter exceeding 50 nm, it means that the ratio of micropores and mesopores and the ratio of macropores are appropriately controlled compared to the lithium composite metal oxide, and accordingly, the formation of a degradation layer due to side reactions with the solid electrolyte increases, which may degrade the lifespan characteristics of the battery.

[0069] According to one embodiment of the present invention, the content distribution of micropores, mesopores, and macropores of the lithium composite metal oxide can be controlled by adjusting the calcination temperature, calcination time, precursor form, dopant (Ti, W, Mo, Zr, Ta, Nb, etc.), surface coating, etc., when manufacturing the cathode active material.

[0071] According to one embodiment of the present invention, the pores may be classified according to their shape. Specifically, the pores may be classified as closed pores or open pores depending on their shape. In the present invention, the closed pore is understood to include not only an independent pore formed with a structure in which all pore walls are closed and not connected to other pores or the outside, but also a pore in which some of the pore walls are not closed, thereby forming an opening through which substances can enter and exit from the outside, wherein the width of the opening is smaller than the width inside the pore. Furthermore, the open pore refers to a pore that is not a closed pore, and may mean a pore in which some of the pore walls are not closed, thereby forming an opening through which substances can enter and exit from the outside.

[0072] According to one embodiment of the present invention, the lithium composite metal oxide may have a closed pore content that is appropriately controlled, and accordingly, the loss of electron and ion pathways within the positive electrode active material is prevented, thereby improving the lifespan characteristics of the battery.

[0073] According to one embodiment of the present invention, by appropriately controlling the closed pore content of the lithium composite metal oxide, the positive electrode active material has a rate of change (ΔQ) of the desorption isotherm according to relative pressure. NA Peaks may not appear in the , %) graph.

[0075] According to one embodiment of the present invention, the peak is the rate of change of the desorption isotherm according to relative pressure (ΔQ NA It refers to a peak with an intensity of 0.2% or greater in the , %) graph, and specifically, it may refer to a peak with an intensity of 0.22% or greater, 0.24% or greater, 0.26% or greater, 0.28% or greater, 0.3% or greater, 0.32% or greater, 0.34% or greater, 0.36% or greater, 0.38% or greater, or 0.4% or greater. If the rate of change of the desorption isotherm with respect to relative pressure (ΔQ NAIf a peak with an intensity within the range described above is observed in the , %) graph, it indicates that the closed pore content has exceeded an appropriate range, and the formation of a deterioration layer due to side reactions with the solid electrolyte may increase, thereby degrading the lifespan characteristics of the battery.

[0077] According to one embodiment of the present invention, the closed pore content of the lithium composite metal oxide can be controlled by adjusting the calcination temperature, calcination time, precursor form, dopant (Ti, W, Mo, Zr, Ta, Nb, etc.), surface coating, etc., when manufacturing the cathode active material.

[0079] A positive electrode active material according to one embodiment of the present invention has an average particle size (D 50 The depth may be 1㎛ or more and 7㎛ or less, and as a specific example, it may be 1.2㎛ or more, 1.4㎛ or more, 1.6㎛ or more, 1.8㎛ or more, or 2㎛ or more, and may also be 6.8㎛ or less, 6.6㎛ or less, 6.4㎛ or less, 6.2㎛ or less, or 6㎛ or less. If the above-described range is satisfied, it may be easier to prevent electron and ion path loss inside the cathode active material.

[0080] A positive electrode active material according to one embodiment of the present invention has a BET specific surface area of ​​0.6 m² 2 It may be less than / g, and as a specific example, 0.58 m 2 / g or less, 0.56 m 2 / g or less, 0.54 m 2 / g or less, 0.52 m 2 / g or less or 0.5 m 2 It may be less than / g, and also, 0.2 m 2 / g or more, 0.22 m 2 / g or more, 0.24 m 2 / g or more, 0.26 m 2 / g or more, 0.28 m 2 / g or more or 0.3 m 2It may be greater than / g. If the above-mentioned range is satisfied, it may be easier to prevent electron and ion path loss within the positive electrode active material.

[0082] All-solid-state battery

[0083] The present invention provides an all-solid-state battery comprising the above positive active material.

[0084] According to one embodiment of the present invention, the all-solid-state battery may be a stack of a negative electrode current collector, a negative electrode active material layer, a solid electrolyte layer, a positive electrode active material layer, and a positive electrode current collector.

[0086] According to one embodiment of the present invention, the negative current collector may be a plate-shaped substrate having electrical conductivity. Specifically, the negative current collector may have the form of a sheet, a thin film, or a foil.

[0087] According to one embodiment of the present invention, the negative electrode current collector may include a material that does not react with lithium. Specifically, the negative electrode current collector may include at least one selected from the group consisting of Ni, Cu, SUS (Stainless Steel), and combinations thereof.

[0088] According to one embodiment of the present invention, the negative electrode active material layer may include a negative electrode active material, a solid electrolyte, a binder, etc.

[0089] According to one embodiment of the present invention, the negative electrode active material is not particularly limited but may be, for example, a carbon active material or a metal active material.

[0090] According to one embodiment of the present invention, the carbon active material may be amorphous carbon such as mesocarbon microbeads (MCMB), graphite such as highly oriented graphite (HOPG), hard carbon, and soft carbon.

[0091] According to one embodiment of the present invention, the metal active material may be an alloy containing at least one of In, Al, Si, Sn, and elements thereof.

[0092] According to one embodiment of the present invention, the solid electrolyte may be an oxide-based solid electrolyte or a sulfide-based solid electrolyte. It may be preferable to use a sulfide-based solid electrolyte with high lithium ion conductivity. Since the description of the sulfide-based solid electrolyte has been described above, a detailed description thereof will be omitted below.

[0093] According to one embodiment of the present invention, the conductive material is configured to form an electron conduction path within the electrode. The conductive material may be an sp2 carbon material such as carbon black, conducting graphite, ethylene black, carbon nanotube, etc., or graphene.

[0094] According to one embodiment of the present invention, the binder may be BR (butadiene rubber), NBR (nitrile butadiene rubber), HNBR (hydrogenated nitrile butadiene rubber), PVDF (polyvinylidene difluoride), PTFE (polytetrafluoroethylene), CMC (carboxymethylcellulose), etc.

[0095] According to one embodiment of the present invention, the solid electrolyte layer is configured to transfer lithium ions between the anode and the cathode and may include a solid electrolyte having lithium ion conductivity. The solid electrolyte may include at least one selected from the group consisting of oxide-based solid electrolytes, sulfide-based solid electrolytes, polymer electrolytes, and combinations thereof, and preferably may include a sulfide-based solid electrolyte.

[0096] According to one embodiment of the present invention, the sulfide-based solid electrolyte is Li6PS5X (X = one or more selected from the group consisting of Cl, Br, and I), Li 10 GeP2S 12 , Li3PS4, Li7P3S 11 , Li2S-P2S5, Li2S-P2S5-LiI, Li2S-P2S5-LiCl, Li2S-P2S5-LiBr, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2SSiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-Z m S n (where m and n are positive numbers, and Z is one of Ge, Zn, or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li x MO y (where x and y are positive numbers, and M is one of P, Si, Ge, B, Al, Ga, In) and may include one or more selected from the group consisting of combinations thereof.

[0097] According to one embodiment of the present invention, the positive active material layer may include a positive active material, a solid electrolyte, a conductive material, a binder, etc. Since the detailed description of the positive active material is as described above, a detailed description thereof will be omitted below.

[0098] According to one embodiment of the present invention, the solid electrolyte may be an oxide-based solid electrolyte or a sulfide-based solid electrolyte. It may be preferable to use a sulfide-based solid electrolyte with high lithium ion conductivity.

[0099] According to one embodiment of the present invention, the conductive material and binder are as described above, so a detailed description thereof is omitted.

[0100] According to one embodiment of the present invention, the positive current collector may be a plate-shaped substrate having electrical conductivity. Specifically, the positive current collector may have the form of a sheet or a thin film.

[0101] According to one embodiment of the present invention, the positive current collector may include at least one selected from the group consisting of indium, copper, magnesium, aluminum, stainless steel, iron, and combinations thereof.

[0102] According to one embodiment of the present invention, the solid electrolyte self-supporting film is located between the negative electrode active material layer and the positive electrode active material layer and is configured to facilitate the movement of lithium ions.

[0104] Hereinafter, embodiments of the present invention are described in detail so that those skilled in the art can easily implement the invention. However, the present invention may be embodied in various different forms and is not limited to the embodiments described herein.

[0106] Example 1

[0107] Ni 0.8 Co 0.1 Mn 0.1 A precursor having the composition of O2 is prepared, then lithium hydroxide and a doping element (Ti) are added so that the Li / Me ratio becomes 1.05, and the mixture is calcined at 700°C for 20 hours to obtain an average particle size (D 50 ) is 3.34㎛, and the BET specific surface area is 0.496m 2 A positive electrode active material with a g content was prepared.

[0108] SEM images of lithium composite metal oxide particles included in the manufactured cathode active material are shown in Fig. 1. The average particle size was measured using a Malvern Panalytical mastersizer 3000 laser diffraction particle size analyzer, the BET specific surface area was calculated from the amount of nitrogen gas adsorbed at liquid nitrogen temperature (77K) using a Micromeritics TriStar II, and the SEM images were taken using a scanning electron microscope (FEI Helios 460F1).

[0110] Example 2

[0111] The positive electrode active material was prepared using the same method as in Example 1, except that the calcination temperature was set to 750℃. The average particle size (D) of the prepared positive electrode active material 50 ) is 4.01 µm, and the BET specific surface area is 0.562 m 2 / g. The above average particle size was measured using a Malvern Panalytical mastersizer 3000 laser diffraction particle size measuring device, and the above BET specific surface area was calculated from the amount of nitrogen gas adsorbed at liquid nitrogen temperature (77K) using a Micromeritics TriStar II.

[0113] Example 3

[0114] The cathode active material was prepared using the same method as in Example 1, except that the calcination time was set to 30 hours. The average particle size (D) of the prepared cathode active material. 50 ) is 4.15㎛, and the BET specific surface area is 0.459m 2 / g was. The above average particle size was measured using a Malvern Panalytical mastersizer 3000 laser diffraction particle size measuring device, and the above BET specific surface area was calculated from the amount of nitrogen gas adsorbed at liquid nitrogen temperature (77K) using a Micromeritics TriStar II.

[0116] Comparative Example 1

[0117] A positive electrode active material was prepared using the same method as in Example 1, except that no doping element (Ti) was added, the calcination temperature was set to 750°C, and the calcination time was set to 40 hours. The average particle size (D) of the prepared positive electrode active material 50 ) is 4.23㎛, and the BET specific surface area is 0.753m 2 / g. SEM images of lithium composite metal oxide particles included in the manufactured cathode active material are shown in Fig. 2. The average particle size was measured using a Malvern Panalytical mastersizer 3000 laser diffraction particle size analyzer, the BET specific surface area was calculated from the amount of nitrogen gas adsorbed at liquid nitrogen temperature (77K) using a Micromeritics TriStar II, and the SEM images were taken using a scanning electron microscope (FEI quanta 250 FEF).

[0119] Comparative Example 2

[0120] A positive electrode active material was prepared using the same method as in Example 1, except that no doping element (Ti) was added. The average particle size (D) of the prepared positive electrode active material 50 ) is 3.12 µm, and the BET specific surface area is 0.864 m² 2 / g. The above average particle size was measured using a Malvern Panalytical mastersizer 3000 laser diffraction particle size measuring device, and the above BET specific surface area was calculated from the amount of nitrogen gas adsorbed at liquid nitrogen temperature (77K) using a Micromeritics TriStar II.

[0122] Comparative Example 3

[0123] A positive electrode active material was prepared using the same method as in Example 1, except that the calcination temperature was set to 750°C and the calcination time to 40 hours. The average particle size (D) of the prepared positive electrode active material 50 ) is 4.32 µm, and the BET specific surface area is 0.537 m² 2 / g. The above average particle size was measured using a Malvern Panalytical mastersizer 3000 laser diffraction particle size measuring device, and the above BET specific surface area was calculated from the amount of nitrogen gas adsorbed at liquid nitrogen temperature (77K) using a Micromeritics TriStar II.

[0125] Comparative Example 4

[0126] A positive electrode active material was prepared using the same method as in Example 1, except that no doping element (Ti) was added and the calcination time was set to 30 hours. The average particle size (D) of the prepared positive electrode active material 50 ) is 3.68 µm, and the BET specific surface area is 0.590 m² 2 / g. SEM images of lithium composite metal oxide particles included in the manufactured cathode active material are shown in Fig. 3. The average particle size was measured using a Malvern Panalytical mastersizer 3000 laser diffraction particle size analyzer, the BET specific surface area was calculated from the amount of nitrogen gas adsorbed at liquid nitrogen temperature (77K) using a Micromeritics TriStar II, and the SEM images were taken using a scanning electron microscope (FEI quanta 250 FEF).

[0128] Experimental Example 1

[0129] For each of the cathode active materials according to the above examples and comparative examples, the amount of nitrogen gas adsorbed and desorbed at a liquid nitrogen temperature (77K) was measured using Micromeritics’ TriStar II, and the adsorption isotherms and desorption isotherms for the graph of the 'normalized adsorption amount' according to the 'relative pressure' for each of the cathode active materials according to the above examples and comparative examples are shown in FIGS. 4 and 5. In addition, based on the adsorption isotherms and desorption isotherms for each of the cathode active materials according to the examples and comparative examples shown in FIGS. 4 and 5, the 'maximum adsorption / desorption width (D') represented by the following Equation 2 H )' was calculated and recorded in Table 1 below.

[0130] Meanwhile, the above 'normalized adsorption amount' is defined by the following mathematical formula 1, and the above maximum adsorption / desorption width (D H )' is defined by the following mathematical formula 2.

[0131] [Mathematical Formula 1]

[0132] Normalized adsorption amount = (Adsorption amount (cm³ / g) / Total adsorption amount (cm³ / g)) × 100

[0133] Normalized Desorption Amount = (Desorption Amount (cm³ / g) / Total Desorption Amount (cm³ / g)) × 100

[0135] [Mathematical Formula 2]

[0136]

[0137] In the above mathematical formula 2,

[0138] Q Des is the normalized adsorption amount of the above adsorption isotherm, and

[0139] Q Abs is the normalized adsorption amount of the above desorption isotherm, and

[0140] max(Q Des -Q Abs ) is the maximum value of the difference between the normalized adsorption amount of the adsorption isotherm and the normalized adsorption amount of the desorption isotherm calculated based on the same relative pressure.

[0142] Referring to FIGS. 4 and 5, it was confirmed that the adsorption and desorption isotherms of the positive electrode active materials of Examples 1 to 3 had nearly identical profiles, so no hysteresis was observed, whereas the adsorption and desorption isotherms of the positive electrode active materials of Comparative Examples 1 to 4 had different profiles, so hysteresis was observed. This is expected to be due to the formation of relatively more mesopores in the positive electrode active materials of Comparative Examples 1 to 4 compared to the positive electrode active materials of Examples 1 to 3.

[0144] Experimental Example 2

[0145] Micromeritics MicroActive 4.00, Harkins and Jura: Pore diameter (D, nm) and pore volume (V, cm³ / g) were calculated using the Faas Correction model, and graphs of the pore volume distribution according to pore diameter were shown in Figures 6 and 7. The above pore volume distribution is defined by the following Equation 3.

[0146] [Mathematical Formula 3]

[0147]

[0148] In the above mathematical formula 3,

[0149] dlog(D) is a small change in the log value of the pore diameter (D), and

[0150] dV is the amount of minute volume change of the pore corresponding to the pore diameter (D) above.

[0152] Referring to FIGS. 6 and 7, it can be seen that the pore volume distribution graph according to the pore diameter of the cathode active material according to Examples 1 and 2 generally slopes upward to the right. On the other hand, referring to the pore volume distribution graph according to the pore diameter of the cathode active material according to Example 3 and Comparative Examples 1 to 4, it can be seen that the pore volume distribution graph generally slopes upward to the right in the region where the pore diameter is less than 50 nm, and generally slopes downward to the right in the region where the pore diameter exceeds 50 nm, based on the area around the pore diameter of 50 nm.

[0153] This is interpreted as the anode active material according to Examples 1 and 2 having a relatively small proportion of micropores with a diameter of less than 2 nm and a relatively high proportion of macropores with a diameter exceeding 50 nm compared to the anode active material according to Example 3 and Comparative Examples 1 to 4.

[0155] Experimental Example 3

[0156] Rate of change of normalized desorption isotherm (ΔQ) according to each example / comparative example according to relative pressure NA The graphs are shown in FIGS. 8 and 9. In addition, the main peak intensities of each graph shown in FIGS. 8 and 9 are listed in Table 1 below.

[0158] Referring to FIGS. 8 and 9, the rate of change (ΔQ) of the desorption isotherm according to relative pressure of Examples 1 and 2 NA Although no peak is observed in the graph, the rate of change (ΔQ) of the desorption isotherm according to relative pressure of Example 3 and Comparative Examples 1 to 4 NAIt was confirmed that a peak was observed in the graph. This is expected to be due to the formation of relatively many closed pores in the cathode active materials of Example 3 and Comparative Examples 1 to 4 compared to the cathode active materials of Examples 1 and 2.

[0160] Experimental Example 4 - Dose Retention Rate

[0161] An all-solid-state battery having a stacked positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer was prepared using each of the positive electrode active materials according to Examples 1 to 3 and Comparative Examples 1 to 4. The composition, content, and manufacturing method of each layer constituting each of the all-solid-state batteries prepared using each of the positive electrode active materials according to Examples 1 to 3 and Comparative Examples 1 to 4 were all kept the same.

[0163] Figure 10 shows the capacity retention rate (%) per cycle, measured for all-solid-state batteries containing the positive active materials of each of the above examples and comparative examples, by defining one cycle as charging to 4.25 V at a current density of 0.5 C in CC-CV mode at 25°C and discharging to 2.5 V at a current density of 0.5 C. In addition, 50 th The dosage retention rate corresponding to the cycle is listed in Table 1 below.

[0165] D 50 (㎛) BET(m 2 / g) Peak intensity (ΔQ NA , %) D H Capacity retention rate (@50th cycle) Example 1 3.34 0.496 - 0.3 92.5 Example 2 4.01 0.562 - 0.2 91.7 Example 3 4.15 0.459 1.18 0.5 91.0 Comparative Example 1 4.23 0.753 7.57 1.4 89.8 Comparative Example 2 3.12 0.864 2.37 0.8 87.5 Comparative Example 3 4.32 0.537 0.47 0.7 88.4 Comparative Example 4 3.68 0.590 3.05 1.6 85.0

[0166] Referring to Table 1 above, the desirable 'maximum adsorption / desorption width (D H It was confirmed that the all-solid-state battery containing the positive active material of Examples 1 to 3 satisfying the range had a superior capacity retention rate compared to the all-solid-state battery containing the positive active material of Comparative Examples 1 to 4 that did not satisfy the desirable closed pore characteristics.

[0167] In addition, a desirable 'maximum adsorption / desorption width (D H Satisfying the range of )', and the rate of change of the normalized desorption isotherm with respect to relative pressure (ΔQ NAFor all-solid-state batteries containing the positive active materials of Examples 1 and 2, where no peak is observed on the graph, the rate of change of the normalized desorption isotherm (ΔQ) according to relative pressure NA It was confirmed that the capacity retention rate was superior compared to the all-solid-state battery containing the positive active material of Example 3, in which a peak was observed on the graph.

[0169] Meanwhile, referring to FIGS. 1 to 3, it was confirmed that the positive active materials of Comparative Examples 1 and 4 had a relatively large number of closed pores compared to the positive active material of Example 1, in which almost no closed pores were observed.

Claims

Claim 1 A positive electrode active material comprising a lithium composite metal oxide, defined by the adsorption isotherm and desorption isotherm of the graph of the 'normalized adsorption / desorption amount' represented by the following Equation 1 and the 'maximum adsorption / desorption width (D)' represented by the following Equation 2, wherein the 'relative pressure with respect to the saturated vapor pressure (P0)' for the positive electrode active material is defined by the adsorption isotherm and the desorption isotherm. H Cathode active material with )' 0.6 or less: [Equation 1] Normalized adsorption amount = (Adsorption amount (cm³ / g) / Total adsorption amount (cm³ / g)) × 100 Normalized desorption amount = (Desorption amount (cm³ / g) / Total desorption amount (cm³ / g)) × 100 [Equation 2] In the above mathematical formula 2, Q Des is the normalized adsorption amount of the above adsorption isotherm, and Q Abs is the normalized adsorption amount of the above desorption isotherm, and max(Q Des -Q Abs ) is the maximum value of the difference between the normalized adsorption amount of the adsorption isotherm and the normalized adsorption amount of the desorption isotherm calculated based on the same relative pressure. Claim 2 A positive active material according to claim 1, wherein hysteresis defined by the adsorption isotherm and the desorption isotherm is not observed. Claim 3 The positive active material according to claim 1, wherein the lithium composite metal oxide particles comprise micropores with a diameter of less than 2 nm; mesopores with a diameter of 2 nm or more and 50 nm or less; and macropores with a diameter exceeding 50 nm. Claim 4 A positive active material according to paragraph 3, wherein the pore volume distribution value of the pores corresponding to the micropores and mesopores is smaller than the pore volume distribution value of the pores corresponding to the macropores. Claim 5 In claim 1, the rate of change (ΔQ) of the relative pressure and the desorption isotherm NA A positive active material in which no peak is observed in the graph. Claim 6 A positive electrode comprising a positive electrode active material according to paragraph 1. Claim 7 An all-solid-state battery comprising a positive electrode according to claim 8; a solid electrolyte layer; and a negative electrode. Claim 8 In claim 7, the all-solid-state battery wherein the solid electrolyte layer comprises a sulfide-based solid electrolyte.

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