Positive active material and lithium secondary battery comprising the same

Abstract

The present invention relates to a positive electrode active material and a lithium secondary battery containing the same. More specifically, the present invention relates to a bimodal type positive electrode active material for improving the low energy density per unit volume of lithium-excess lithium manganese-based oxides and a lithium secondary battery containing the same.

Description

Technology Field

[0001] The present invention relates to a positive electrode active material and a lithium secondary battery containing the same. More specifically, the present invention relates to a bimodal type positive electrode active material for improving the low energy density per unit volume of lithium-excess lithium manganese-based oxides and a lithium secondary battery containing the same. Background Technology

[0003] Batteries store electricity by using materials capable of electrochemical reactions at the positive and negative electrodes. A representative example of such a battery is the lithium secondary battery, which stores electrical energy based on the difference in chemical potential when lithium ions are intercalated or deintercalated at the positive and negative electrodes.

[0004] The above lithium secondary battery is manufactured by using materials capable of reversible intercalation / deintercalation of lithium ions as positive and negative active materials, and by filling an organic electrolyte or a polymer electrolyte between the positive and negative electrodes.

[0005] Representative materials used as positive electrode active materials for lithium secondary batteries include lithium composite oxides. The lithium composite oxides include LiCoO2, LiMn2O4, LiNiO2, LiMnO2, or oxides composited with Ni, Co, Mn, or Al, as disclosed in Korean Patent Publication No. 10-2015-0069334 (published June 23, 2015).

[0006] Among the aforementioned cathode active materials, LiCoO2 is the most widely used due to its excellent lifespan characteristics and charge / discharge efficiency; however, it has the disadvantage of limited price competitiveness because it is expensive due to the resource limitations of cobalt used as a raw material.

[0007] Lithium manganese oxides such as LiMnO2 and LiMn2O4 have the advantages of excellent thermal stability and low cost, but they have problems such as low capacity and poor high-temperature performance. In addition, LiNiO2-based cathode active materials exhibit high discharge capacity battery characteristics, but synthesis is difficult due to cation mixing between Li and transition metals, and consequently, there are significant problems with rate characteristics.

[0008] In addition, a large amount of Li byproducts is generated depending on the degree of intensification of this cation mixing. Most of the above Li byproducts consist of LiOH and Li2CO3, and can cause gelation during the manufacture of anode paste or generate gas during repeated charging and discharging after electrode manufacturing. Furthermore, residual Li2CO3 among the above Li byproducts acts as a cause of reduced lifespan characteristics by increasing the swelling phenomenon of the cell.

[0009] Various candidate materials are being proposed to compensate for the shortcomings of these existing cathode active materials.

[0010] For example, research is underway to use lithium-excess lithium manganese oxides, which contain an excess of Mn among the transition metals and have a lithium content greater than the sum of the transition metal contents, as cathode active materials for lithium secondary batteries. Such lithium-excess lithium manganese oxides are also referred to as overlithiated layered oxides (OLO).

[0011] Although the above OLO theoretically has the advantage of being able to exhibit high capacity under high-voltage operating environments, in reality, due to the excess Mn contained in the oxide, it has a relatively low electrical conductivity, and consequently, there is a disadvantage that the rate characteristics of lithium secondary batteries using OLO are low. As such, when rate characteristics are low, problems arise in which the charge / discharge capacity and lifespan efficiency (cycle capacity retention rate) of the lithium secondary battery decrease during cycling.

[0012] In addition, OLO has the disadvantage of low energy density per unit volume due to the high porosity within the particles resulting from the material's characteristics.

[0013] Research on modifying the composition of OLO to address the aforementioned problems has been ongoing, but these attempts have not yet reached the level of commercialization. Prior art literature

[0015] Korean Published Patent Application No. 10-2015-0069334 (Published June 23, 2015) The problem to be solved

[0016] In the lithium secondary battery market, the growth of lithium secondary batteries for electric vehicles is acting as a driving force, and accordingly, the demand for cathode active materials used in lithium secondary batteries is also continuously increasing.

[0017] For example, in the past, lithium secondary batteries using lithium iron phosphate (LFP) were mainly used for the sake of ensuring safety, but recently, there has been a growing trend of using nickel-based lithium composite oxides, which have a higher energy capacity per unit weight compared to LFP.

[0018] In addition, nickel-based lithium composite oxides, which are primarily used as cathode active materials for high-capacity lithium secondary batteries, necessarily utilize ternary metal elements such as nickel, cobalt, and manganese or nickel, cobalt, and aluminum. However, since the supply of cobalt is unstable and it is excessively expensive compared to other raw materials, there is a need for cathode active materials with new compositions that can reduce the cobalt content or exclude cobalt.

[0019] Considering all these circumstances, while lithium-excess lithium manganese-based oxides can meet the aforementioned market expectations, there are limitations in that the lithium manganese-based oxides still lack electrochemical properties or stability to replace commercially available cathode active materials such as ternary lithium composite oxides with nickel-cobalt-manganese (NCM) or nickel-cobalt-aluminum (NCA) compositions.

[0020] For example, it has been previously mentioned that OLO has the disadvantage of low energy density per unit volume due to the high porosity within the particles resulting from the material's properties.

[0021] However, the inventors have confirmed that the low energy density per unit volume of lithium-excess lithium-manganese oxide can be improved to some extent by preparing the above-mentioned lithium manganese-based oxide by dividing it into elementary particles and conjugates, respectively, and then providing a bimodal type cathode active material as a mixture of the elementary particles and conjugates.

[0022] Accordingly, the present invention aims to provide a bimodal type cathode active material for improving the low energy density per unit volume of lithium-excess lithium manganese-based oxides.

[0023] In addition, the present invention aims to provide a positive electrode active material capable of further improving the energy density per unit volume of a bimodal type positive electrode active material by including at least one of the subatomic particles and the alleles as a secondary particle in which the growth of the primary particle is induced.

[0024] In particular, secondary particles in which the growth of primary particles included in at least one of the subatomic particles and alleles is induced can contribute to the improvement of energy density per unit volume of a bimodal type cathode active material as the internal porosity of the secondary particles (porosity between primary particles) decreases.

[0025] In addition, as the specific surface area of ​​the secondary particle, in which the growth of the primary particle included in at least one of the elementary particle and the allele is induced, decreases, it is possible to prevent the rapid deterioration of battery performance due to side reactions during the initial battery reaction under high voltage conditions.

[0026] In addition, the present invention aims to provide a lithium secondary battery capable of achieving high stability by using a cathode comprising a bimodal type cathode active material as defined herein, thereby preventing the degradation of electrochemical characteristics of the lithium secondary battery, such as rate characteristics, caused by excess lithium and manganese present in the existing OLO, and by reducing side reactions between the cathode active material and the electrolyte during high-voltage operation. means of solving the problem

[0028] According to one aspect of the present invention for solving the aforementioned technical problem, a bimodal type positive electrode active material comprising a first lithium manganese-based oxide as a subatomic particle and a second lithium manganese-based oxide as an allotrope is provided.

[0029] The first lithium manganese-based oxide and the second lithium manganese-based oxide constituting the above-mentioned bimodal type positive electrode active material are oxides in which a phase belonging to the C2 / m space group and a phase belonging to the R3-m space group are solid solution or composite.

[0030] Generally, commercially available ternary lithium composite oxides of nickel-cobalt-manganese (NCM) or nickel-cobalt-aluminum (NCA) compositions have a phase belonging to the R3-m space group existing as a single phase, whereas the lithium-excess lithium manganese-based oxide defined herein is characterized by a solid solution or composite of a phase belonging to the C2 / m space group and a phase belonging to the R3-m space group.

[0031] In one embodiment, the first lithium manganese-based oxide and the second lithium manganese-based oxide include secondary particles formed by aggregating a plurality of primary particles.

[0032] Specifically, the first lithium manganese-based oxide and the second lithium manganese-based oxide each independently include at least one type of secondary particle selected from a secondary particle in which a plurality of large-sized primary particles are aggregated and a secondary particle in which a plurality of small-sized primary particles are aggregated.

[0033] At this time, the energy density per unit volume of the bimodal type cathode active material can be improved by including at least one selected from the first lithium manganese-based oxide and the second lithium manganese-based oxide in a form in which a plurality of large-diameter primary particles are aggregated.

[0034] In one embodiment, among the first lithium manganese-based oxide, the secondary particles in which a plurality of large-sized primary particles are aggregated and the secondary particles in which a plurality of small-sized primary particles are aggregated may be included in a weight ratio of 10:90 to 100:0.

[0035] Here, the average value of the short axis length of the primary large particle is 100 nm or more and 500 nm or less, and the average value of the short axis length of the primary small particle is 50 nm or more and 300 nm or less, wherein the average value of the short axis length of the primary small particle is smaller than the average value of the short axis length of the primary large particle.

[0036] The average value of the short axis length of the primary particle can be measured for the primary particle exposed on the surface of the secondary particle from the SEM image of the secondary particle (for example, calculated from 20 primary particles selected in order of longest short axis length among the primary particles exposed on the surface of the secondary particle from the SEM image of the secondary particle).

[0037] In one embodiment, among the second lithium manganese-based oxide, the secondary particles in which a plurality of large-sized primary particles are aggregated and the secondary particles in which a plurality of small-sized primary particles are aggregated may be included in a weight ratio of 10:90 to 100:0.

[0038] Here, the average value of the short axis length of the primary large particle is 100 nm or more and 500 nm or less, and the average value of the short axis length of the primary small particle is 50 nm or more and 300 nm or less, wherein the average value of the short axis length of the primary small particle is smaller than the average value of the short axis length of the primary large particle.

[0039] The first lithium manganese-based oxide and the second lithium manganese-based oxide may each independently comprise at least one selected from nickel, cobalt, and manganese.

[0040] More specifically, the first lithium manganese-based oxide and the second lithium manganese-based oxide can each be independently represented by the following chemical formula 1.

[0041] [Chemical Formula 1]

[0042] rLi2MnO3 - b' X b ' ·(1-r)Li a M1 x M2 y M3 z O2 - b X b

[0043] (Here,

[0044] M1 is at least one selected from Ni and Mn, and

[0045] M2 is at least one selected from Ni, Mn, Co, Al, P, Nb, B, Si, Ti, Zr, Ba, K, Mo, Fe, Cu, Cr, Zn, Na, Ca, Mg, Pt, Au, Eu, Sm, W, Ce, V, Ta, Sn, Hf, Gd and Nd, and

[0046] M3 is at least one selected from W, Mo and Nb, and

[0047] M1 to M3 do not overlap with each other, and

[0048] X and X' are halogens capable of substituting at least some of the oxygen present in the lithium manganese-based oxide, and

[0049] 0 <r≤0.7, 0<a≤1, 0≤b≤0.1, 0≤b'≤0.1, 0<x≤1, 0≤y<1, 0≤z≤0.1 and 0 <x+y+z≤1이다)

[0050] At least one selected from the first lithium manganese-based oxide and the second lithium manganese-based oxide may include a secondary particle doped with at least one dopant selected from a metal cation dopant and a halogen anion dopant, and preferably, the secondary particle in the form of an aggregate of the plurality of large-diameter primary particles may be doped with at least one dopant selected from a metal cation dopant and a halogen anion dopant.

[0051] At this time, the metal cation dopant is at least one selected from W, Mo, and Nb, and the halogen anion dopant may be fluorine.

[0052] In addition, according to another aspect of the present invention, a positive electrode comprising the positive electrode active material described above is provided.

[0053] In addition, according to another aspect of the present invention, a lithium secondary battery using the anode described above is provided. Effects of the invention

[0055] According to the present invention, it is possible to improve the limitations of existing lithium-excess lithium manganese-based oxides, which have several disadvantages in terms of electrochemical properties and / or stability compared to commercially available ternary lithium composite oxides of nickel-cobalt-manganese (NCM) or nickel-cobalt-aluminum (NCA) compositions.

[0056] Specifically, according to the present invention, the low energy density per unit volume of lithium-excess lithium-manganese oxide can be improved to a certain extent by preparing the lithium manganese-based oxide by dividing it into elementary particles and constituents, respectively, and then providing a bimodal type positive electrode active material as a mixture of elementary particles and constituents.

[0057] In addition, according to the present invention, it is possible to further improve the energy density per unit volume of a bimodal type cathode active material by including at least one of the elementary particles and the alleles as a secondary particle in which the growth of the primary particle is induced (a secondary particle in which the primary particle of a large diameter is aggregated).

[0058] In particular, secondary particles in the form of aggregated large-diameter primary particles included in at least one of the elementary particles and alleles can contribute to further improvement of the energy density per unit volume of the bimodal type cathode active material as the internal porosity (porosity between primary particles) decreases.

[0059] In addition, secondary particles in the form of aggregated large-diameter primary particles included in at least one of the elementary particles and alleles can prevent the rapid deterioration of battery performance due to side reactions during the initial battery reaction under high voltage conditions as the specific surface area decreases.

[0060] For example, if the specific surface area of ​​the subparticles and / or allotropes is reduced, it is possible to reduce side reactions between the subparticles and / or allotropes and the electrolyte. In particular, OLOs such as the lithium manganese-based oxide have the advantage of exhibiting high capacity under high-voltage operating environments; however, since the likelihood of side reactions occurring between the lithium manganese-based oxide and the electrolyte can be accelerated as the operating voltage increases, it is important to reduce side reactions between the lithium manganese-based oxide and the electrolyte.

[0061] Accordingly, as side reactions between the subatomic particles and / or alleles and the electrolyte are reduced, the stability and lifespan of a lithium secondary battery used as a bimodal type positive electrode active material as defined herein can be improved. In particular, a positive electrode active material with suppressed side reactions with the electrolyte makes it possible to operate the lithium secondary battery at a higher voltage.

[0062] In addition to the effects described above, the specific effects of the present invention are described together with the specific details for implementing the invention below. Specific details for implementing the invention

[0064] For convenience, specific terms are defined herein to facilitate a better understanding of the present invention. Unless otherwise defined herein, scientific and technical terms used in this invention shall have the meanings generally understood by those skilled in the art. Furthermore, unless specifically indicated in the context, terms in their singular form shall be understood to include their plural form, and terms in their plural form shall be understood to include their singular form.

[0066] Hereinafter, a positive electrode active material comprising a lithium manganese-based oxide with excess lithium according to some embodiments of the present invention and a lithium secondary battery comprising said positive electrode active material will be described in more detail.

[0068] positive electrode active material

[0069] According to one aspect of the present invention, a positive electrode active material is provided comprising a lithium manganese-based oxide in which a phase belonging to the C2 / m space group and a phase belonging to the R3-m space group are dissolved or combined.

[0070] Here, the lithium manganese-based oxide can be classified into a first lithium manganese-based oxide which is a fine particle and a second lithium manganese-based oxide which is an opposite particle based on the average particle size, and the positive electrode active material defined herein is a bimodal type positive electrode active material comprising a first lithium manganese-based oxide which is a fine particle and a second lithium manganese-based oxide which is an opposite particle.

[0071] The above lithium manganese oxide is also referred to as an overlithiated layered oxide (OLO) because the lithium content present in the lithium manganese oxide is greater than the sum of the contents of other transition metals (generally, when the molar ratio of lithium to all metal elements other than lithium in the lithium manganese oxide (Li / Metal molar ratio) is greater than 1).

[0072] Additionally, the lithium manganese-based oxide comprises at least one selected from nickel, cobalt, and manganese. That is, the first lithium manganese-based oxide and the second lithium manganese-based oxide each independently comprise at least one selected from nickel, cobalt, and manganese.

[0073] Generally, considering that commercially available ternary lithium composite oxides of nickel-cobalt-manganese (NCM) or nickel-cobalt-aluminum (NCA) compositions contain 20 mol% or less of manganese among all metal elements excluding lithium, the lithium manganese-based oxide has a relatively high proportion of manganese (e.g., 50 mol% or more, preferably 55 mol% to 75 mol%) among all metal elements compared to commercially available ternary lithium composite oxides.

[0074] In addition, considering that commercially available ternary lithium composite oxides of nickel-cobalt-manganese (NCM) or nickel-cobalt-aluminum (NCA) compositions contain 60 mol% or more of nickel among all metal elements excluding lithium (80 mol% or more in the case of high-Ni type), the lithium manganese-based oxide has a relatively lower proportion of nickel among all metal elements (e.g., less than 50 mol%, preferably 25 mol% to 45 mol%) compared to commercially available ternary lithium composite oxides.

[0075] There is also a difference in that the Li / Metal molar ratio measured from the lithium manganese-based oxides defined herein is greater than that of ternary lithium composite oxides such as nickel-cobalt-manganese (NCM) or nickel-cobalt-aluminum (NCA). For example, the Li / Metal molar ratio of ternary lithium composite oxides such as nickel-cobalt-manganese (NCM) or nickel-cobalt-aluminum (NCA) has a value close to 1. On the other hand, the Li / Metal molar ratio of the lithium manganese-based oxides defined herein is greater than 1, and preferably has a value of 1.1 to 1.7.

[0076] Despite the aforementioned differences in composition, the lithium manganese-based oxide can also function as a complex metal oxide capable of lithium ion intercalation / deintercalation.

[0077] In one embodiment, the first lithium manganese-based oxide and the second lithium manganese-based oxide include secondary particles formed by aggregating a plurality of primary particles.

[0078] Specifically, the first lithium manganese-based oxide and the second lithium manganese-based oxide each independently include at least one type of secondary particle selected from a secondary particle in which a plurality of large-sized primary particles are aggregated and a secondary particle in which a plurality of small-sized primary particles are aggregated.

[0079] In the present invention, the above-mentioned small-sized primary particles and the above-mentioned large-sized primary particles may be classified based on the average value of the short axis length of the primary particles.

[0080] The terms "small diameter" and "large diameter" used herein are relative concepts used to describe the size of primary particles constituting secondary particles. Accordingly, the terms "small diameter" and "large diameter" should be understood as having a meaning distinct from "small particle" and "large particle," which are terms used to describe the size of secondary particles.

[0081] If the first lithium manganese-based oxide or the second lithium manganese-based oxide each includes secondary particles with different sizes of primary particles, the primary particles constituting the secondary particles in an aggregated form of primary particles having a relatively small average particle size among the secondary particles may be referred to as "small-sized primary particles." Conversely, the primary particles constituting the secondary particles in an aggregated form of primary particles having a relatively large average particle size among the secondary particles may be referred to as "large-sized primary particles."

[0082] The above-mentioned small-sized primary particles and large-sized primary particles may have various shapes within the range defined herein.

[0083] Conventional lithium-excess lithium manganese-based oxides have a form in which multiple primary particles are aggregated into secondary particles, generally having an average particle size of several to tens of nm.

[0084] On the other hand, the primary particles constituting the lithium manganese-based oxide defined herein may have an average particle size of 0.05 μm to 5 μm, preferably 0.05 μm to 1.0 μm. More specifically, the small particle size primary particles may have an average particle size of 0.05 μm to 5 μm, preferably 0.05 μm to 1.0 μm, more preferably 0.10 μm to 0.50 μm, and the large particle size primary particles may have an average particle size of 0.05 μm to 5 μm, preferably 0.05 μm to 1.0 μm, more preferably 0.15 μm to 0.75 μm.

[0085] For example, if the first lithium manganese-based oxide contains both secondary particles in the form of aggregated primary particles of a plurality of large particle sizes and secondary particles in the form of aggregated primary particles of a plurality of small particle sizes, the average particle size of the primary particles of a plurality of aggregated primary particles constituting the secondary particles of a plurality of aggregated primary particles will be larger than the average particle size of the primary particles of a plurality of aggregated primary particles constituting the secondary particles of a plurality of aggregated primary particles.

[0086] The major axis length of the primary particle, the minor axis length of the primary particle, the ratio of the major axis length to the minor axis length of the primary particle (major axis length / minor axis length), and the average particle size of the primary particle ([major axis length + minor axis length] / 2) can be calculated as the average value of the major axis length and minor axis length of the primary particle exposed to the surface of the secondary particle, respectively, after measuring them.

[0087] For example, the average value of the result measured from all primary particles exposed to the surface of the secondary particles, or the average value of the result measured from a plurality of primary particles selected among the primary particles exposed to the surface of the secondary particles (e.g., calculated from a plurality of primary particles selected in order of longest short axis length among the primary particles exposed to the surface of the secondary particles from an SEM image of the secondary particles (e.g., 10 primary particles, 20 primary particles, etc.)) may be used.

[0088] When the average particle size of the primary particles is smaller than 0.1 μm, the specific surface area of ​​the lithium manganese-based oxide (secondary particles) composed of the primary particles is relatively large. In this case, the likelihood of side reactions between the lithium manganese-based oxide and the electrolyte occurring during storage or operation of the lithium secondary battery may increase.

[0089] On the other hand, if the average particle size of the primary particle is greater than 5 μm, the growth of the primary particle is excessively induced, and consequently, the diffusion path of lithium ions within the primary particle also becomes longer. If the diffusion path of lithium ions within the primary particle is excessively long, the mobility of lithium ions within the primary particle and the diffusivity of lithium ions mediated by the primary particle are reduced, which causes an increase in the resistance of the lithium manganese-based oxide (secondary particle) composed of the primary particle.

[0090] The first lithium manganese-based oxide may comprise only at least one type of secondary particle selected from a secondary particle in which a plurality of small-sized primary particles are aggregated, or only a secondary particle in which a plurality of large-sized primary particles are aggregated, or may comprise a secondary particle in which a plurality of large-sized primary particles are aggregated and a secondary particle in which a plurality of small-sized primary particles are aggregated.

[0091] The second lithium manganese-based oxide may comprise only at least one type of secondary particle selected from a secondary particle in which a plurality of small-sized primary particles are aggregated, or only a secondary particle in which a plurality of large-sized primary particles are aggregated, or may comprise a secondary particle in which a plurality of large-sized primary particles are aggregated and a secondary particle in which a plurality of small-sized primary particles are aggregated.

[0092] At this time, at least one selected from the first lithium manganese-based oxide and the second lithium manganese-based oxide may include secondary particles in the form of aggregated primary particles of a plurality of large particle sizes, thereby improving the energy density per unit volume of the bimodal type positive electrode active material defined herein.

[0093] In one embodiment, among the first lithium manganese-based oxide, the secondary particles formed by the aggregation of a plurality of large-sized primary particles and the secondary particles formed by the aggregation of a plurality of small-sized primary particles may be included in a weight ratio of 10:90 to 100:0. At this time, the average value of the short axis length of the small-sized primary particles is smaller than the average value of the short axis length of the large-sized primary particles.

[0094] The average value of the short length of the above-mentioned primary particles of large particle size may be 100 nm or more and 500 nm or less, preferably 150 nm or more and 400 nm or less. As described above, the average value of the short length of the above-mentioned primary particles of large particle size may be the average value of the short length measured from a plurality of primary particles (e.g., 10 primary particles, 20 primary particles, etc.) selected in order of longest short length among the primary particles exposed on the surface of secondary particles in the form of aggregated secondary particles of multiple primary particles of large particle size, or primary particles exposed on the surface of secondary particles in the form of aggregated secondary particles of multiple primary particles of large particle size.

[0095] When the average value of the short axis length of the above-mentioned large-sized primary particles is smaller than 100 nm, the size of the particles is substantially similar to that of the above-mentioned small-sized primary particles, so even if a secondary particle in the form of aggregated multiple large-sized primary particles and a secondary particle in the form of aggregated multiple small-sized primary particles are used, the degree of improvement in energy density per unit volume may be negligible.

[0096] On the other hand, the fact that the average value of the short length of the primary large-diameter particles is greater than 500 nm means that the growth of the primary large-diameter particles has been excessively induced overall. As the growth of the primary particles is unnecessarily promoted, there is a concern that the mobility of lithium ions within the primary particles and the diffusion of lithium ions mediated by the primary particles may be reduced.

[0097] In addition, with respect to reducing the deviation in the short-axis length of the large-diameter primary particle exposed on the surface of the secondary particle, the minimum value of the short-axis length measured for the large-diameter primary particle exposed on the surface of the secondary particle is 50 nm or more, preferably 80 nm or more, and the maximum value of the short-axis length measured for the large-diameter primary particle exposed on the surface of the secondary particle may be 1 μm or less, preferably 750 nm or less, more preferably 500 nm or less. The smaller the deviation in the short-axis length of the large-diameter primary particle exposed on the surface of the secondary particle, the more uniformly the surface kinetic of the secondary particle can be maintained.

[0098] The average value of the short axis length of the above-mentioned small-sized primary particles may be 50 nm or more and 300 nm or less, preferably 60 nm or more and 200 nm or less. As described above, the average value of the short axis length of the above-mentioned small-sized primary particles may be the average value of the short axis length measured from a plurality of primary particles (e.g., 10 primary particles, 20 primary particles, etc.) selected in order of longest short axis length among the primary particles exposed on the surface of the secondary particles in which a plurality of small-sized primary particles are aggregated, or among the primary particles exposed on the surface of the secondary particles in which a plurality of small-sized primary particles are aggregated.

[0099] If the average value of the short axis length of the primary particles of the small particle size is smaller than 50 nm, the specific surface area of ​​the secondary particles composed of the primary particles of the small particle size becomes relatively larger, and thus the likelihood of side reactions between the lithium manganese-based oxide and the electrolyte during storage or operation of the lithium secondary battery may increase.

[0100] On the other hand, if the average value of the short axis length of the primary particles of the small particle size is greater than 300 nm, the size of the particles is substantially similar to that of the primary particles of the large particle size, so even if secondary particles in the form of aggregated primary particles of the large particle size and secondary particles in the form of aggregated primary particles of the small particle size are used, the degree of improvement in energy density per unit volume may be negligible.

[0101] In addition, with respect to reducing the deviation in the short-axis length of the small-diameter primary particles exposed on the surface of the secondary particles, the minimum value of the short-axis length measured for the small-diameter primary particles exposed on the surface of the secondary particles may be 20 nm or more, preferably 40 nm or more, and the maximum value of the short-axis length measured for the small-diameter primary particles exposed on the surface of the secondary particles may be 500 nm or less, preferably 300 nm or less. The smaller the deviation in the short-axis length of the small-diameter primary particles exposed on the surface of the secondary particles, the more uniformly the surface kinetic of the secondary particles can be maintained.

[0102] Despite the difference in the size of the primary particles mentioned above, the difference in average particle size between the secondary particles formed by the aggregation of multiple large-sized primary particles and the secondary particles formed by the aggregation of multiple small-sized primary particles may not be significant. For example, if the number of primary particles constituting the secondary particles formed by the aggregation of multiple large-sized primary particles is less than the number of primary particles constituting the secondary particles formed by the aggregation of multiple small-sized primary particles, the average particle size of the secondary particles formed by the aggregation of multiple large-sized primary particles and the secondary particles formed by the aggregation of multiple small-sized primary particles may be similar.

[0103] That is, the secondary particles formed by the aggregation of a plurality of large-sized primary particles constituting the first lithium manganese-based oxide and the secondary particles formed by the aggregation of a plurality of small-sized primary particles have an average particle size of 2 μm to 5 μm.

[0104] In addition, it is preferable that the interparticle porosity measured from a cross-sectional SEM image of a secondary particle in which the large-sized primary particle is aggregated is smaller than the interparticle porosity measured from a cross-sectional SEM image of a secondary particle in which the small-sized primary particle is aggregated.

[0105] Specifically, the interparticle porosity measured from a cross-sectional SEM image of a secondary particle in which the primary particle of the large diameter is aggregated may be 10% or less, preferably 5% or less.

[0106] In addition, when the distance from the center of the secondary particle to the surface of the secondary particle set from the cross-sectional SEM image of the secondary particle is denoted as r, and the region with a distance of 0.5r to 1.0r from the center of the secondary particle is defined as the outer bulk region, the porosity within the outer bulk region measured from the cross-sectional SEM image of the secondary particle in which the large-sized primary particle is aggregated may be smaller than the porosity within the outer bulk region measured from the cross-sectional SEM image of the secondary particle in which the small-sized primary particle is aggregated.

[0107] Specifically, the porosity within the outer bulk region measured from a cross-sectional SEM image of a secondary particle in which the primary particle of the large diameter is aggregated may be 1% or less, or 0.5% or less.

[0108] As the voids between the primary large-diameter particles within the secondary particles in which the primary large-diameter particles are aggregated are reduced, the energy density per unit volume of the first lithium manganese-based oxide, and furthermore, the bimodal type positive electrode active material including the first lithium manganese-based oxide, can be improved.

[0109] That is, by replacing some of the secondary particles in which a plurality of small-sized primary particles constituting the first lithium manganese-based oxide in the bimodal type positive electrode active material are aggregated with secondary particles in which a plurality of large-sized primary particles are aggregated, or by making the first lithium manganese-based oxide contain only secondary particles in which a plurality of large-sized primary particles are aggregated, the energy density per unit volume can be improved more than that of a bimodal type positive electrode active material in which small particles and opposites simply coexist.

[0110] In one embodiment, among the second lithium manganese-based oxide, the secondary particles formed by the aggregation of a plurality of large-sized primary particles and the secondary particles formed by the aggregation of a plurality of small-sized primary particles may be included in a weight ratio of 10:90 to 100:0. At this time, the average value of the short axis length of the small-sized primary particles is smaller than the average value of the short axis length of the large-sized primary particles.

[0111] The average value of the short length of the above-mentioned primary particles of large particle size may be 100 nm or more and 500 nm or less, preferably 130 nm or more and 400 nm or less. As described above, the average value of the short length of the above-mentioned primary particles of large particle size may be the average value of the short length measured from a plurality of primary particles (e.g., 10 primary particles, 20 primary particles, etc.) selected in order of longest short length among the primary particles exposed on the surface of secondary particles in the form of aggregated secondary particles of multiple primary particles of large particle size, or primary particles exposed on the surface of secondary particles in the form of aggregated secondary particles of multiple primary particles of large particle size.

[0112] When the average value of the short axis length of the above-mentioned large-sized primary particles is smaller than 100 nm, the size of the particles is substantially similar to that of the above-mentioned small-sized primary particles, so even if a secondary particle in the form of aggregated multiple large-sized primary particles and a secondary particle in the form of aggregated multiple small-sized primary particles are used, the degree of improvement in energy density per unit volume may be negligible.

[0113] On the other hand, the fact that the average value of the short length of the primary large-diameter particles is greater than 500 nm means that the growth of the primary large-diameter particles has been excessively induced overall. As the growth of the primary particles is unnecessarily promoted, there is a concern that the mobility of lithium ions within the primary particles and the diffusion of lithium ions mediated by the primary particles may be reduced.

[0114] In addition, with respect to reducing the deviation in the short-axis length of the large-diameter primary particle exposed on the surface of the secondary particle, the minimum value of the short-axis length measured for the large-diameter primary particle exposed on the surface of the secondary particle is 50 nm or more, preferably 75 nm or more, and the maximum value of the short-axis length measured for the large-diameter primary particle exposed on the surface of the secondary particle may be 1 μm or less, preferably 750 nm or less, more preferably 500 nm or less. The smaller the deviation in the short-axis length of the large-diameter primary particle exposed on the surface of the secondary particle, the more uniformly the surface kinetic of the secondary particle can be maintained.

[0115] The average value of the short axis length of the above-mentioned small-sized primary particles may be 50 nm or more and 300 nm or less, preferably 60 nm or more and 200 nm or less. As described above, the average value of the short axis length of the above-mentioned small-sized primary particles may be the average value of the short axis length measured from a plurality of primary particles (e.g., 10 primary particles, 20 primary particles, etc.) selected in order of longest short axis length among the primary particles exposed on the surface of the secondary particles in which a plurality of small-sized primary particles are aggregated, or among the primary particles exposed on the surface of the secondary particles in which a plurality of small-sized primary particles are aggregated.

[0116] If the average value of the short axis length of the primary particles of the small particle size is smaller than 50 nm, the specific surface area of ​​the secondary particles composed of the primary particles of the small particle size becomes relatively larger, and thus the likelihood of side reactions between the lithium manganese-based oxide and the electrolyte during storage or operation of the lithium secondary battery may increase.

[0117] On the other hand, if the average value of the short axis length of the primary particles of the small particle size is greater than 300 nm, the size of the particles is substantially similar to that of the primary particles of the large particle size, so even if secondary particles in the form of aggregated primary particles of the large particle size and secondary particles in the form of aggregated primary particles of the small particle size are used, the degree of improvement in energy density per unit volume may be negligible.

[0118] In addition, with respect to reducing the deviation in the short-axis length of the small-diameter primary particles exposed on the surface of the secondary particles, the minimum value of the short-axis length measured for the small-diameter primary particles exposed on the surface of the secondary particles may be 20 nm or more, preferably 40 nm or more, and the maximum value of the short-axis length measured for the small-diameter primary particles exposed on the surface of the secondary particles may be 500 nm or less, preferably 300 nm or less. The smaller the deviation in the short-axis length of the small-diameter primary particles exposed on the surface of the secondary particles, the more uniformly the surface kinetic of the secondary particles can be maintained.

[0119] Despite the difference in the size of the primary particles mentioned above, the difference in average particle size between the secondary particles formed by the aggregation of multiple large-sized primary particles and the secondary particles formed by the aggregation of multiple small-sized primary particles may not be significant. For example, if the number of primary particles constituting the secondary particles formed by the aggregation of multiple large-sized primary particles is less than the number of primary particles constituting the secondary particles formed by the aggregation of multiple small-sized primary particles, the average particle size of the secondary particles formed by the aggregation of multiple large-sized primary particles and the secondary particles formed by the aggregation of multiple small-sized primary particles may be similar.

[0120] In addition, it is preferable that the interparticle porosity measured from a cross-sectional SEM image of a secondary particle in which the large-sized primary particle is aggregated is smaller than the interparticle porosity measured from a cross-sectional SEM image of a secondary particle in which the small-sized primary particle is aggregated.

[0121] Specifically, the interparticle porosity measured from a cross-sectional SEM image of a secondary particle in which the primary particle of the large particle size is aggregated may be 15% or less, preferably 10% or less, and more preferably 5% or less.

[0122] In addition, when the distance from the center of the secondary particle to the surface of the secondary particle set from the cross-sectional SEM image of the secondary particle is denoted as r, and the region with a distance of 0.5r to 1.0r from the center of the secondary particle is defined as the outer bulk region, the porosity within the outer bulk region measured from the cross-sectional SEM image of the secondary particle in which the large-sized primary particle is aggregated may be smaller than the porosity within the outer bulk region measured from the cross-sectional SEM image of the secondary particle in which the small-sized primary particle is aggregated.

[0123] Specifically, the porosity within the outer bulk region measured from a cross-sectional SEM image of a secondary particle in which the primary particle of the large diameter is aggregated may be 1% or less, or 0.5% or less.

[0124] As the voids between the primary large-diameter particles within the secondary particles in which the primary large-diameter particles are aggregated are reduced, the energy density per unit volume of the second lithium manganese-based oxide, and furthermore, the bimodal type positive electrode active material including the second lithium manganese-based oxide, can be improved.

[0125] That is, by replacing some of the secondary particles in which a plurality of small-sized primary particles are aggregated and constituting the second lithium manganese-based oxide in the bimodal type positive electrode active material with secondary particles in which a plurality of large-sized primary particles are aggregated, or by making the second lithium manganese-based oxide contain only secondary particles in which a plurality of large-sized primary particles are aggregated, the energy density per unit volume can be improved more than that of a bimodal type positive electrode active material in which small particles and opposites simply coexist.

[0126] The energy density per unit volume of the bimodal cathode active material can be increased by making the difference between the average particle size of the second lithium manganese-based oxide and the average particle size of the first lithium manganese-based oxide 3 μm or more, preferably 4 μm or more.

[0127] At this time, the average particle size calculated as the average value of the length in the long axis direction and the length in the short axis direction of the first lithium manganese-based oxide ([long axis length + short axis length] / 2) may be 2 μm to 5 μm, and the average particle size calculated as the average value of the length in the long axis direction and the length in the short axis direction of the second lithium manganese-based oxide ([long axis length + short axis length] / 2) may be 6 μm to 14 μm.

[0128] As previously mentioned, the terms “small particle” and “large particle” used herein are relative terms used to describe the size of secondary particles, and it should be understood that in this document, the small particle refers to the first lithium manganese-based oxide and the large particle refers to the second lithium manganese-based oxide.

[0129] In addition, to optimize the energy density per unit volume of the bimodal cathode active material, it is preferable that the first lithium manganese-based oxide and the second lithium manganese-based oxide among the cathode active materials be included in a weight ratio of 10:90 to 80:20.

[0130] The first lithium manganese-based oxide may exist in a form filled within the voids between the second lithium manganese-based oxides, attached to the surface of the second lithium manganese-based oxides, or aggregated with each other.

[0131] If the ratio of the first lithium manganese oxide to the second lithium manganese oxide among the above positive active materials is excessively low, it may be difficult for the first lithium manganese oxide to be sufficiently filled within the voids formed by the second lithium manganese oxide.

[0132] On the other hand, if the ratio of the first lithium composite oxide to the second lithium manganese-based oxide among the positive electrode active materials is excessively high, the energy density per unit volume of the positive electrode active material may decrease.

[0133] The first lithium manganese-based oxide and the second lithium manganese-based oxide defined herein can each be independently represented by the following chemical formula 1.

[0134] [Chemical Formula 1]

[0135] rLi2MnO3 - b' X b ' ·(1-r)Li a M1 x M2 y M3 z O2 - b X b

[0136] Here,

[0137] M1 is at least one selected from Ni and Mn, and

[0138] M2 is at least one selected from Ni, Mn, Co, Al, P, Nb, B, Si, Ti, Zr, Ba, K, Mo, Fe, Cu, Cr, Zn, Na, Ca, Mg, Pt, Au, Eu, Sm, W, Ce, V, Ta, Sn, Hf, Gd and Nd, and

[0139] M3 is at least one selected from W, Mo and Nb, and

[0140] M1 to M3 do not overlap with each other, and

[0141] X and X' are halogens capable of substituting at least some of the oxygen present in the lithium manganese-based oxide, and

[0142] 0 <r≤0.7, 0<a≤1, 0≤b≤0.1, 0≤b'≤0.1, 0<x≤1, 0≤y<1, 0≤z≤0.1 및 0<x+y+z≤1이다.

[0143] In the above chemical formula 1, if M1 is Ni, M2 may include Mn, and if M1 is Mn, M2 may include Ni. Additionally, if M1 is Ni and Mn, M2 may not exist, or if it exists, it may be an element other than Ni and Mn.

[0144] Refer to the periodic table for the types of halogens that can be used as X and X', such as F, Cl, Br and / or I, and preferably F.

[0145] In one embodiment, to synthesize secondary particles in which the large-diameter primary particles are aggregated, a method may be used in which the oxide precursor of the lithium manganese-based oxide is doped with a metal cation dopant and / or a halogen anion dopant while inducing the growth of the primary particles during calcination.

[0146] At this time, the metal cation dopant may include at least one selected from W, Mo, and Nb, and the halogen anion dopant may include fluorine.

[0147] In the above chemical formula 1, the metal cation dopant is represented as M3, and the halogen anion dopant is represented as X.

[0148] As described above, when doping with a halogen to induce the growth of the primary particles constituting the lithium manganese-based oxide, preferably, at least some of the oxygen present in the lithium manganese-based oxide can be replaced with a halogen.

[0149] If a supercalcination method is used to heat treat at a relatively high temperature without halogen doping to induce crystal growth or particle growth of the primary particles constituting the lithium manganese-based oxide, growth of the primary particles is possible, but damage to the crystal structure of the primary particles may occur, potentially leading to premature degradation of the cathode active material.

[0150] When fluorine is used as an anion dopant during the growth of the primary particles, the growth of the primary particles can be induced within a range that mitigates the decrease in the diffusivity of lithium ions mediated by the primary particles.

[0151] For fluorine doping of the above primary particles, at least one anionic dopant selected from LiF, MgF2, HF, F2, XeF2, TbF4, CeF4, CoF3, AgF2, MoF3, AgF, CuF2, FeF3, CuF, VF3, CrF3, ZrF4, BaF2, CaF2, AlF3, NH4F, CeF3, and CsF, preferably at least one anionic dopant selected from LiF and MgF2, may be used.

[0152] When simultaneous doping is induced by additionally using an M3-containing dopant in addition to the aforementioned anion dopant during the calcination of the oxide precursor, the primary particles may grow into a shape close to spherical instead of growing in a plate-like shape.

[0153] As the above M3-containing dopant, at least one selected from hydroxides, oxides, carbonates, nitrides, sulfides, and phosphates containing at least one element selected from tungsten, molybdenum, and niobium may be used.

[0154] As described above, when the aforementioned anion dopant and M3-containing dopant are used in combination during the calcination of the oxide precursor to induce simultaneous doping of the primary particles and growth of the primary particles, it is possible to reduce the porosity of the secondary particles formed by the aggregation of the primary particles while simultaneously making the shape of the primary particles closer to a spherical shape.

[0155] If the porosity in the above lithium manganese-based oxide is reduced, the capacity per unit volume can be increased, thereby compensating for the insufficient electrochemical characteristics of the cathode active material containing the above lithium manganese-based oxide.

[0156] In addition, when the aforementioned anion dopant and M3-containing dopant are used in combination during the calcination of the oxide precursor to induce simultaneous doping of the primary particles and growth of the primary particles, it may be effective to reduce the porosity, particularly at the surface of the secondary particles.

[0157] The lithium manganese oxide represented by Chemical Formula 1 above may optionally contain cobalt. When the lithium manganese oxide contains cobalt, the mole fraction of cobalt relative to the total number of moles of metal elements in the lithium manganese oxide may be 20% or less, preferably 15% or less, and more preferably 10% or less. In other cases, the lithium manganese oxide represented by Chemical Formula 1 may have a cobalt-free composition that does not contain cobalt.

[0158] The Li / Metal molar ratio measured from the lithium manganese-based oxide represented by Chemical Formula 1 above may be greater than 1, preferably 1.1 to 1.7. It is possible to form a lithium manganese-based oxide with an excess of lithium only if the Li / Metal molar ratio measured from the lithium manganese-based oxide has a value greater than at least 1. In addition, it is preferable that the Li / Metal molar ratio of the lithium manganese-based oxide be 1.1 to 1.7 in order to appropriately form a solid solution in which a phase belonging to the C2 / m space group and a phase belonging to the R3-m space group are dissolved or combined, and at the same time exhibit high capacity under a high-voltage operating environment.

[0159] In addition, in order to appropriately form a solid solution in which a phase belonging to the C2 / m space group and a phase belonging to the R3-m space group are in solid solution or composite, it is preferable that the content of manganese among the total metal elements excluding lithium present in the lithium manganese-based oxide represented by Chemical Formula 1 is 50 mol% or more. In order for the lithium manganese-based oxide to have the characteristics of an OLO that exhibits high capacity under a high voltage operating environment, it is more preferable that the content of manganese among the total metal elements excluding lithium present in the lithium manganese-based oxide is 50 mol% or more and less than 80 mol%, and even more preferable that it is 55 mol% to 75 mol%.

[0160] If the manganese content in the above lithium manganese-based oxide exceeds 80 mol%, a phase transition may occur due to the movement of transition metals (especially manganese) within the lithium manganese-based oxide during formation and / or operation of the lithium secondary battery. This phase transition forms a spinel phase, and the spinel phase, which acts as an impurity in the lithium manganese-based oxide, may cause a decrease in charge / discharge capacity or voltage decay during the cycling of the lithium secondary battery.

[0161] In order to properly form a solid solution in which a phase belonging to the C2 / m space group and a phase belonging to the R3-m space group are combined, it is preferable that the content of nickel among the total metal elements, excluding lithium present in the lithium manganese-based oxide represented by Chemical Formula 1, be less than 50 mol%.

[0162] If the nickel content in the above lithium manganese-based oxide is 50 mol% or more, it may be difficult to sufficiently form the C2 / m phase, or the phase belonging to the C2 / m space group and the phase belonging to the R3-m space group may not form a sufficient solid solution, which may cause phase separation during formation and / or operation of the lithium secondary battery.

[0163] In general, commercially available ternary lithium composite oxides of nickel-cobalt-manganese (NCM) or nickel-cobalt-aluminum (NCA) compositions have a single phase in which a phase belonging to the R3-m space group exists.

[0164] On the other hand, the lithium-excess lithium manganese-based oxide represented by the above chemical formula 1 is rLi2MnO 3-b' X b' Oxides of a phase belonging to the C2 / m space group represented by (hereinafter referred to as the 'C2 / m phase') and (1-r)Li a M1 x M2 y M3 z O2 - b X b An oxide of a phase belonging to the R3-m space group represented by (hereinafter referred to as the 'R3-m phase') exists as a solid solution or as a composite oxide. For example, the lithium manganese-based oxide may exist in a state where the oxide of the C2 / m phase and the oxide of the R3-m phase form a solid solution.

[0165] In this case, a complex oxide in which a phase belonging to the C2 / m space group and a phase belonging to the R3-m space group are simply physically and / or chemically bonded or attached does not correspond to a solid solution as defined herein.

[0166] For example, a composite oxide having a phase in the C2 / m space group, formed by mixing a metal oxide having a phase in the C2 / m space group and a metal oxide having a phase in the R3-m space group and coating the surface with a metal oxide having a phase in the R3-m space group, does not correspond to a solid solution as defined herein.

[0167] In the lithium manganese-based oxide represented by the above chemical formula 1, when r exceeds 0.7, Li2MnO3, which is the oxide of the C2 / m phase among the lithium manganese-based oxides. - b' X b ' There is a concern that the discharge capacity may decrease as the proportion becomes excessively high, and consequently, the manganese content in the cathode active material becomes excessively high. That is, in order to improve surface kinetics by sufficiently activating the oxide on the C2 / m phase, which has relatively high resistance among the lithium manganese-based oxides, it is desirable for the oxide on the R3-m phase to exist in a predetermined proportion or higher.

[0169] lithium secondary battery

[0170] According to another aspect of the present invention, an anode may be provided comprising an anode current collector and an anode active material layer formed on the anode current collector. Herein, the anode active material layer may comprise a lithium manganese-based oxide according to various embodiments of the present invention described above as an anode active material.

[0171] Therefore, a detailed description of the lithium manganese-based oxide is omitted, and only the remaining unmentioned components will be described below. Additionally, for convenience, the aforementioned lithium manganese-based oxide will be referred to as the positive electrode active material below.

[0172] The above positive current collector is not particularly limited as long as it is conductive without causing chemical changes in the battery, and for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface treated with carbon, nickel, titanium, silver, etc. may be used. In addition, the above positive current collector may typically have a thickness of 3 μm to 500 μm, and fine irregularities may be formed on the surface of the current collector to increase the adhesion of the positive active material. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0173] The above positive active material layer can be manufactured by applying a positive slurry composition, which includes a conductive material and optionally a binder together with the positive active material, to the positive current collector.

[0174] At this time, the positive active material may be included in an amount of 80 wt% to 99 wt%, more specifically 85 wt% to 98.5 wt%, based on the total weight of the positive active material layer. Excellent capacity characteristics may be exhibited when included within the above-mentioned content range, but it is not necessarily limited thereto.

[0175] The above conductive material is used to impart conductivity to the electrode, and in the battery being constructed, it may be used without special limitations as long as it possesses electronic conductivity without causing chemical changes. Specific examples include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fiber; metal powder or metal fiber such as copper, nickel, aluminum, or silver; conductive whiskey such as zinc oxide or potassium titanate; conductive metal oxide such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and one of these alone or a mixture of two or more may be used. The above conductive material may be included in an amount of 0.1 wt% to 15 wt% based on the total weight of the positive electrode active material layer.

[0176] The above binder serves to improve adhesion between positive active material particles and adhesion between the positive active material and the current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluororubber, or various copolymers thereof, and one of these alone or a mixture of two or more may be used. The above binder may be included in an amount of 0.1 wt% to 15 wt% based on the total weight of the positive active material layer.

[0177] The above-described anode can be manufactured according to a conventional anode manufacturing method, except for using the above-described anode active material. Specifically, it can be manufactured by applying an anode slurry composition, prepared by dissolving or dispersing the above-described anode active material and optionally a binder and a conductive material in a solvent, onto an anode current collector, and then drying and rolling.

[0178] The above solvent may be a solvent commonly used in the relevant technical field, and may include dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water, and one of these alone or a mixture of two or more may be used. The amount of the above solvent used is sufficient if it has a viscosity that dissolves or disperses the anode active material, conductive material, and binder, taking into account the coating thickness of the slurry and the manufacturing yield, and subsequently provides excellent thickness uniformity when coated for anode manufacturing.

[0179] In addition, in another embodiment, the anode may be manufactured by casting the anode slurry composition onto a separate support and then laminating the film obtained by peeling off from the support onto an anode current collector.

[0180] In addition, according to another aspect of the present invention, an electrochemical device comprising the anode described above may be provided. Specifically, the electrochemical device may be a battery, a capacitor, etc., and more specifically, a lithium secondary battery.

[0181] Specifically, the above lithium secondary battery may include a positive electrode, a negative electrode positioned opposite to the positive electrode, and a separator and an electrolyte interposed between the positive electrode and the negative electrode. Here, since the positive electrode is the same as previously described, a detailed description is omitted for convenience, and only the remaining components not previously mentioned are described in detail below.

[0182] The above lithium secondary battery may optionally further include a battery container that accommodates the electrode assembly of the positive electrode, the negative electrode, and the separator, and a sealing member that seals the battery container.

[0183] The above cathode may include a cathode current collector and a cathode active material layer located on the cathode current collector.

[0184] The above-mentioned negative current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloy may be used. In addition, the above-mentioned negative current collector may typically have a thickness of 3 μm to 500 μm, and, similar to the positive current collector, fine irregularities may be formed on the surface of the current collector to strengthen the bonding strength of the negative active material. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0185] The above-mentioned cathode active material layer can be manufactured by applying a cathode slurry composition, which includes a conductive material and, if necessary, a binder, together with the above-mentioned cathode active material, to the above-mentioned cathode current collector.

[0186] As the above-mentioned negative electrode active material, a compound capable of reversible intercalation / deintercalation of lithium may be used. Specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys, or Al alloys; and SiO₂ βExamples include metal oxides capable of doping and dedoping lithium, such as (0 < β < 2), SnO2, vanadium oxide, and lithium vanadium oxide; or composites comprising the metal compound and carbonaceous material, such as Si-C composites or Sn-C composites, and any one or more of these may be used. Additionally, a metallic lithium thin film may be used as the negative electrode active material. Furthermore, the carbon material may include low-crystallinity carbon and high-crystallinity carbon. Representative examples of low-crystallinity carbon include soft carbon and hard carbon, while representative examples of high-crystallinity carbon include amorphous, plate-like, flake-like, spherical, or fibrous natural or artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, meso-carbon microbeads, mesophase pitches, and high-temperature calcined carbon such as petroleum or coal tar pitch-derived cokes.

[0187] The above negative electrode active material may be included in an amount of 80 wt% to 99 wt% based on the total weight of the negative electrode active material layer.

[0188] The above binder is a component that assists in the bonding between the conductive material, the active material, and the current collector, and can typically be added in an amount of 0.1 wt% to 10 wt% based on the total weight of the negative active material layer. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluororubber, and various copolymers thereof.

[0189] The above conductive material is a component for further improving the conductivity of the negative electrode active material, and may be added in an amount of 10 wt% or less, preferably 5 wt% or less, based on the total weight of the negative electrode active material layer. Such conductive material is not particularly limited as long as it is conductive without causing chemical changes in the battery, and for example, graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black; conductive fibers such as carbon fiber or metal fiber; metal powder such as carbon fluoride, aluminum, or nickel powder; conductive whiskey such as zinc oxide or potassium titanate; conductive metal oxide such as titanium oxide; conductive materials such as polyphenylene derivatives may be used.

[0190] In one embodiment, the negative active material layer may be manufactured by applying a negative slurry composition, prepared by dissolving or dispersing a negative active material and optionally a binder and a conductive material in a solvent, onto a negative current collector and drying it, or by casting the negative slurry composition onto a separate support and then laminating the film obtained by peeling it off from the support onto a negative current collector.

[0191] In addition, in another embodiment, the negative active material layer may be manufactured by applying a negative slurry composition prepared by dissolving or dispersing a negative active material and optionally a binder and a conductive material in a solvent onto a negative current collector and drying it, or by casting the negative slurry composition onto a separate support and then laminating the film obtained by peeling it off from the support onto a negative current collector.

[0192] Meanwhile, in the above-mentioned lithium secondary battery, the separator separates the negative electrode and the positive electrode and provides a pathway for the movement of lithium ions. Any separator typically used in lithium secondary batteries can be used without special limitations, and it is particularly desirable that it has low resistance to the movement of electrolyte ions and excellent electrolyte moisture retention capacity. Specifically, a porous polymer film, such as a porous polymer film made of a polyolefin-based polymer like ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof may be used. In addition, a conventional porous nonwoven fabric, such as a nonwoven fabric made of high-melting-point glass fiber or polyethylene terephthalate fiber, may be used. Furthermore, a coated separator containing ceramic components or polymer materials may be used to ensure heat resistance or mechanical strength, and may optionally be used in a single-layer or multi-layer structure.

[0193] In addition, the electrolytes used in the present invention may include organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, molten inorganic electrolytes, etc., which are usable when manufacturing lithium secondary batteries, but are not limited to these.

[0194] Specifically, the electrolyte may include an organic solvent and a lithium salt.

[0195] The above organic solvent may be used without special restrictions as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the above organic solvent may include ester-based solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether-based solvents such as dibutyl ether or tetrahydrofuran; ketone-based solvents such as cyclohexanone; and aromatic hydrocarbon-based solvents such as benzene and fluorobenzene. Carbonate-based solvents such as dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); alcohol-based solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (where R is a straight-chain, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and may include a double bond, a directional ring, or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes may be used. Among these, a carbonate-based solvent is preferred, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate, etc.) having high ionic conductivity and high dielectric constant that can improve the charge / discharge performance of the battery, and a low-viscosity linear carbonate-based compound (e.g., ethylmethyl carbonate, dimethyl carbonate or diethyl carbonate, etc.) is more preferred.In this case, using a mixture of cyclic carbonate and chain carbonate in a volume ratio of about 1:1 to about 1:9 can result in excellent performance of the electrolyte.

[0196] The above lithium salt may be used without special restrictions as long as it is a compound capable of providing lithium ions used in lithium secondary batteries. Specifically, the above lithium salt is LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2 . LiCl, LiI, or LiB(C2O4)2, etc., may be used. It is preferable to use the lithium salt within a concentration range of 0.1M to 2.0M. When the concentration of the lithium salt falls within the above range, the electrolyte has appropriate conductivity and viscosity, so it can exhibit excellent electrolyte performance and lithium ions can move effectively.

[0197] When the electrolyte used in the present invention is a solid electrolyte, for example, solid inorganic electrolytes such as sulfide-based solid electrolytes, oxide-based solid electrolytes, nitride-based solid electrolytes, halide-based solid electrolytes, etc. may be used, and preferably, sulfide-based solid electrolytes may be used.

[0198] As a material for a sulfide-based solid electrolyte, a solid electrolyte containing Li, an element X (wherein X is at least one selected from P, As, Sb, Si, Ge, Sn, B, Al, Ga, and In) and S may be used. Examples of the above-mentioned sulfide-based solid electrolyte materials include Li2S-P2S5, Li2S-P2S-LiX (wherein X is a halogen element such as I or Cl), 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, and Li2S-P2S5-Z m S n (Here, m and n are integers, and Z is Ge, Zn, or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q (Here, p and q are integers, and M is P, Si, Ge, B, Al, Ga, or In) etc.

[0199] The solid electrolyte, preferably a sulfide-based solid electrolyte, may be amorphous or crystalline, or may be in a mixed state of amorphous and crystalline.

[0200] Li7La3Zr2O is a material for oxide-based solid electrolytes. 12 , Li7 - x La3Zr1 - x Nb x O 12 , Li7 -3x La3Zr2Al x O 12 , Li 3x La2 / 3- x TiO3, Li1 + x Al x Ti2 -x(PO4)3, Li1 + x Al x Ge2 -x (PO4)3, Li3PO4, Li3 + x PO4 -x N x (LiPON), Li2 + 2x Zn1 - x There are GeO4 (LISICON), etc.

[0201] The aforementioned solid electrolyte may be disposed as a separate layer (solid electrolyte layer) between the anode and the cathode. Additionally, the solid electrolyte may be partially included within the anode active material layer of the anode independently of the solid electrolyte layer, or the solid electrolyte may be partially included within the cathode active material layer of the cathode independently of the solid electrolyte layer.

[0202] In addition to the above electrolyte components, the above electrolyte may further include one or more additives for the purpose of improving the lifespan characteristics of the battery, suppressing the decrease in battery capacity, and improving the discharge capacity of the battery, such as, for example, haloalkylene carbonate-based compounds like difluoroethylene carbonate, pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, triamide hexaphosphate, nitrobenzene derivative, sulfur, quinone imine dye, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, or aluminum trichloride. In this case, the additive may be included in an amount of 0.1 wt% to 5 wt% based on the total weight of the electrolyte.

[0203] As described above, since the lithium secondary battery containing the positive electrode active material according to the present invention stably exhibits excellent discharge capacity, output characteristics, and lifespan characteristics, it is useful in portable devices such as mobile phones, laptop computers, and digital cameras, as well as in the field of electric vehicles such as hybrid electric vehicles (HEVs).

[0204] The external shape of the lithium secondary battery according to the present invention is not subject to any particular limitations, but may be cylindrical, prismatic, pouch, or coin-shaped using a can. In addition, the lithium secondary battery can be used not only as a battery cell used as a power source for small devices, but can also preferably be used as a unit cell in a medium-to-large battery module containing a plurality of battery cells.

[0205] According to another aspect of the present invention, a battery module comprising the lithium secondary battery as a unit cell and / or a battery pack comprising the same may be provided.

[0206] The battery module or the battery pack may be used as a power source for one or more medium-to-large devices, including a power tool; an electric vehicle (EV), a hybrid electric vehicle, and a plug-in hybrid electric vehicle (PHEV); or a power storage system.

[0208] The present invention will be described in more detail below through examples. However, these examples are intended solely to illustrate the present invention and should not be interpreted as limiting the scope of the present invention.

[0210] Preparation Example 1. Preparation of positive electrode active material

[0211] Preparation Example 1-1. Preparation of the first lithium manganese-based oxide (A-1)

[0212] (a) Preparation of precursors

[0213] An aqueous solution of NiSO4·6H2O and MnSO4·H2O mixed in a molar ratio of 40:60, along with NaOH and NH4OH, was introduced into the reactor while stirring. The reactor temperature was maintained at 45°C, and the precursor synthesis reaction was carried out while introducing N2 gas. After the reaction was completed, the material was washed and dehydrated to obtain NiO . 4Mn0 .6 A hydroxide precursor of (OH)2 composition (average particle size 3.0 μm) was obtained.

[0215] (b) First heat treatment

[0216] The hydroxide precursor obtained in step (a) was heated in a kiln in an O2 atmosphere at a rate of 2℃ / min and maintained at 550℃ for 5 hours, and then furnace-cooled to obtain a precursor in an oxide state.

[0218] (c) Second heat treatment

[0219] A mixture was prepared by mixing the oxide precursor obtained in step (b) above and LiOH (Li / Metal molar ratio = 1.25), which is a lithium raw material.

[0220] Next, the calcination furnace in an O2 atmosphere was heated at a rate of 2°C / min and then maintained at 900°C, and the mixture was heat-treated for 8 hours and then furnace-cooled to obtain the first lithium manganese-based oxide (A-1).

[0222] Preparation Example 1-2. Preparation of the first lithium manganese-based oxide (A-2)

[0223] (a) Preparation of precursors

[0224] An aqueous solution of NiSO4·6H2O and MnSO4·H2O mixed in a molar ratio of 40:60, along with NaOH and NH4OH, was introduced into the reactor while stirring. The reactor temperature was maintained at 45°C, and the precursor synthesis reaction was carried out while introducing N2 gas. After the reaction was completed, the material was washed and dehydrated to obtain NiO . 4Mn0 .6 A hydroxide precursor of (OH)2 composition (average particle size 3.0 μm) was obtained.

[0226] (b) First heat treatment

[0227] The hydroxide precursor obtained in step (a) was heated in a kiln in an O2 atmosphere at a rate of 2℃ / min and maintained at 550℃ for 5 hours, and then furnace-cooled to obtain a precursor in an oxide state.

[0229] (c) Second heat treatment

[0230] A mixture was prepared by mixing the oxide precursor obtained in step (b) above, LiOH (Li / Metal molar ratio = 1.25) which is a lithium raw material, LiF which has a fluorine (F) content of 1.0 mol% based on the metal element excluding lithium among the precursors, and WO3 which has a tungsten (W) content of 0.75 mol% based on the metal element excluding lithium among the precursors.

[0231] Next, the calcination furnace in an O2 atmosphere was heated at a rate of 2°C / min and then maintained at 900°C, and the mixture was heat-treated for 8 hours and then furnace-cooled to obtain the first lithium manganese-based oxide (A-2).

[0233] Preparation Example 1-3. Preparation of second lithium manganese-based oxide (B-1)

[0234] (a) Preparation of precursors

[0235] An aqueous solution of NiSO4·6H2O and MnSO4·H2O mixed in a molar ratio of 40:60, along with NaOH and NH4OH, was introduced into the reactor while stirring. The reactor temperature was maintained at 45°C, and the precursor synthesis reaction was carried out while introducing N2 gas. After the reaction was completed, the material was washed and dehydrated to obtain NiO . 4Mn0 .6 A hydroxide precursor of (OH)2 composition (average particle size 12.0 μm) was obtained.

[0237] (b) First heat treatment

[0238] The hydroxide precursor obtained in step (a) was heated in a kiln in an O2 atmosphere at a rate of 2℃ / min and maintained at 550℃ for 5 hours, and then furnace-cooled to obtain a precursor in an oxide state.

[0240] (c) Second heat treatment

[0241] A mixture was prepared by mixing the oxide precursor obtained in step (b) above and LiOH (Li / Metal molar ratio = 1.25), which is a lithium raw material.

[0242] Next, the calcination furnace in an O2 atmosphere was heated at a rate of 2°C / min and then maintained at 900°C, and the mixture was heat-treated for 8 hours and then furnace-cooled to obtain a second lithium manganese-based oxide (B-1).

[0244] Preparation Example 1-4. Preparation of second lithium manganese-based oxide (B-2)

[0245] (a) Preparation of precursors

[0246] An aqueous solution of NiSO4·6H2O and MnSO4·H2O mixed in a molar ratio of 40:60, along with NaOH and NH4OH, was introduced into the reactor while stirring. The reactor temperature was maintained at 45°C, and the precursor synthesis reaction was carried out while introducing N2 gas. After the reaction was completed, the material was washed and dehydrated to obtain NiO .4Mn0 .6 A hydroxide precursor of (OH)2 composition (average particle size 12.0 μm) was obtained.

[0248] (b) First heat treatment

[0249] The hydroxide precursor obtained in step (a) was heated in a kiln in an O2 atmosphere at a rate of 2℃ / min and maintained at 550℃ for 5 hours, and then furnace-cooled to obtain a precursor in an oxide state.

[0251] (c) Second heat treatment

[0252] A mixture was prepared by mixing the oxide precursor obtained in step (b) above, LiOH (Li / Metal molar ratio = 1.25) which is a lithium raw material, LiF which has a fluorine (F) content of 1.0 mol% based on the metal element excluding lithium among the precursors, and WO3 which has a tungsten (W) content of 0.75 mol% based on the metal element excluding lithium among the precursors.

[0253] Next, the calcination furnace in an O2 atmosphere was heated at a rate of 2°C / min and then maintained at 900°C, and the mixture was heat-treated for 8 hours and then furnace-cooled to obtain the second lithium manganese-based oxide (B-2).

[0255] Preparation Example 2. Preparation of positive electrode active material

[0256] A positive electrode active material was prepared by mixing the first lithium manganese-based oxide and the second lithium manganese-based oxide prepared according to Preparation Example 1 in the weight ratio listed in Table 1 below.

[0257] division First lithium manganese oxide Secondary lithium manganese oxide A-1 (wt%) A-2 (wt%) B-1 (wt%) B-2 (wt%) Comparative Example 1 - 100 - - Comparative Example 2 - - - 100 Comparative Example 3 60 - 40 - Example 1 54 6 40 - Example 2 30 30 40 - Example 3 - 60 40 - Example 4 60 - 36 4 Example 5 60 - 20 20 Example 6 60 - - 40

[0259] Preparation Example 3. Manufacturing of lithium secondary batteries

[0260] A positive electrode slurry was prepared by dispersing 90 wt% of the positive electrode active material prepared according to Preparation Example 2, 4.5 wt% of carbon black, and 5.5 wt% of PVDF binder in N-methyl-2-pyrrolidone (NMP). The positive electrode slurry was uniformly coated onto an aluminum thin film with a thickness of 15 μm and vacuum dried at 135°C to produce a positive electrode for a lithium secondary battery.

[0261] A half-cell was prepared using a lithium foil as the counter electrode for the above anode, a porous polyethylene membrane (Celgard 2300, thickness: 25 μm) as the separator, and an electrolyte in which LiPF6 is present at a concentration of 1.15 M in a solvent mixed with ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate in a volume ratio of 2:4:4.

[0263] Experimental Example 1. Image analysis of lithium manganese-based oxides

[0264] (1) Secondary particles were selected from each lithium manganese-based oxide prepared according to Preparation Examples 1-1 to 1-4, and then scanned with a scanning electron microscope to obtain SEM images.

[0265] Next, using an image analyzer program, 20 primary particles were selected from the SEM images in order of longest minor axis length among the primary particles exposed on the surface of the secondary particles, and the major axis length and minor axis length were measured for each. From the measurement results, the average value of the minor axis length of the primary particles (A), the maximum value of the minor axis length of the primary particles (B), the minimum value of the minor axis length of the primary particles (C), the average value of the particle diameter of the primary particles (D), the maximum value of the particle diameter of the primary particles (E), and the minimum value of the particle diameter of the primary particles (F) were calculated, respectively. The particle diameter of the primary particles was calculated as the average of the major axis length and the minor axis length of the primary particles ([major axis length + minor axis length] / 2).

[0266] (2) In addition, each of the selected secondary particles was cross-sectioned using a Cross-section Polisher (acceleration voltage 5.0 kV, milling for 4 hours) and then scanned with a scanning electron microscope to obtain cross-sectional SEM images.

[0267] Next, using an image analyzer program, the number of pores (G) was counted from the cross-section of the secondary particle from the cross-sectional SEM image, and the cross-sectional porosity (H) was calculated.

[0268] The cross-sectional porosity (H) was calculated by binarizing the cross-sectional SEM image and then calculating the ratio of the sum of the areas of all pores existing within the secondary particle to the total area of ​​the cross-section of the secondary particle ([sum of the areas of all pores existing within the secondary particle / total area of ​​the cross-section of the secondary particle] / 100).

[0269] In addition, the center of the secondary particle was set from the binarized cross-sectional SEM image, and when the distance from the center of the secondary particle to the surface of the secondary particle is denoted as r, the region with a distance of 0.5r to 1.0r from the center of the secondary particle was defined as the outer bulk region.

[0270] The external bulk porosity (I) was calculated by dividing the sum of the total void areas existing within the external bulk region by the total cross-sectional area of ​​the external bulk region ([sum of the total void areas existing within the external bulk region / total area of ​​the external bulk region] / 100).

[0271] The above measurement results are shown in Table 2 below.

[0272] division unit First lithium manganese oxide Secondary lithium manganese oxide A-1 A-2 B-1 B-2 A nm 95 175 73 155 B nm 162 308 97 247 C nm 48 93 51 86 D nm 135 267 134 198 E nm 195 377 166 282 F nm 82 186 97 127 G ea 107 60 222 52 H % 10.4 2.6 15.4 1.5 I % 1.2 0.09 6.2 0.1

[0274] Experimental Example 2. Measurement of the compressive density of the cathode active material

[0275] 3g of each cathode active material prepared according to Preparation Example 2 was pressed for 5 seconds using a pelletizer under the pressure conditions listed in Table 3 below, and then the compression density was measured.

[0276] The above measurement results are shown in Table 3 below.

[0277] Pressure conditions 2.5 tons 4.5 tons unit g / cc g / cc Comparative Example 1 2.49 2.72 Comparative Example 2 2.52 2.82 Comparative Example 3 2.57 2.84 Example 1 2.62 2.88 Example 2 2.71 2.91 Example 3 2.75 2.95 Example 4 2.64 2.90 Example 5 2.7 2.92 Example 6 2.72 2.93

[0279] Referring to the results of Comparative Examples 1 to 3, it can be seen that the 2.5-ton compression density of Comparative Example 3 (bimodal type cathode active material including A-1 and B-1) is slightly higher than that of Comparative Example 1 (unimodal type cathode active material including A-2) and Comparative Example 2 (unimodal type cathode active material including B-2), but there is no significant difference in the 4.5-ton compression density between Comparative Example 2 and Comparative Example 3.

[0280] On the other hand, referring to the results of Examples 1 to 6, in which at least one selected from the first lithium manganese-based oxide and the second lithium manganese-based oxide comprises secondary particles in the form of aggregated primary particles of a plurality of large particle sizes, it can be confirmed that there is a significant improvement effect in both 2.5 ton compression density and 4.5 ton compression density compared to Comparative Examples 1 to 3.

[0282] Experimental Example 3. Evaluation of Electrochemical Characteristics of Lithium Secondary Batteries

[0283] For the lithium secondary battery (half-cell) prepared in Preparation Example 3, the initial charge capacity, initial discharge capacity, capacity per volume, initial reversibility efficiency, and rate capability (discharge capacity ratio; rate capability (C-rate)) were measured through charge / discharge experiments using an electrochemical analyzer (Toyo, Toscat-3100) at 25°C, with a voltage range of 2.0V to 4.6V and a discharge rate of 0.1C to 5.0C. The capacity per volume was calculated by multiplying the initial discharge capacity by the compression density (4.5 ton compression density in Table 3).

[0284] In addition, for the same lithium secondary battery, 50 charge / discharge cycles were performed under 1C / 1C conditions within a driving voltage range of 2.0V to 4.6V at 25℃, and the ratio of the discharge capacity at the 50th cycle to the initial discharge capacity (cycle capacity retention rate) was measured.

[0285] The above measurement results are shown in Table 4 below.

[0286] division Initial charging capacity (0.1C-rate) Initial discharge capacity (0.1C-rate) Capacity per unit volume Initial reversible efficiency Discharge capacity ratio (2C / 0.1C) Discharge capacity ratio (5C / 0.1C) Cycle capacity retention rate (1C-rate, 50 cycles) unit mAh / g mAh / g mAh / cc % % % % Comparative Example 1 266 229 626 86.1 74.3 61.7 90.1 Comparative Example 2 260 226 630 86.9 74.4 60.2 91.9 Comparative Example 3 262 228 642 86.7 75.0 62.9 93.2 Example 1 263 228 656 86.7 74.9 62.8 93.1 Example 2 263 228 663 86.7 74.9 62.4 92.6 Example 3 264 229 675 86.8 74.8 61.9 92.0 Example 4 263 228 660 86.5 75.0 62.9 93.1 Example 5 262 227 664 86.6 74.8 62.6 92.6 Example 6 262 227 666 86.6 74.6 62.2 92.0

[0288] Referring to the results of Table 4 above, and referring to the results of Examples 1 to 6 in which at least one selected from the first lithium manganese-based oxide and the second lithium manganese-based oxide comprises secondary particles in the form of aggregated primary particles of a plurality of large particle sizes, it can be confirmed that the capacity per unit volume is improved compared to Comparative Examples 1 to 3.

[0290] Although embodiments of the present invention have been described above, those skilled in the art may modify and change the present invention in various ways by adding, changing, deleting, or adding components, etc., without departing from the spirit of the present invention as described in the claims, and such modifications and changes are also to be included within the scope of the rights of the present invention.

Claims

Claim 1 A bimodal type cathode active material comprising a first lithium manganese-based oxide as a subatomic particle and a second lithium manganese-based oxide as an antagonistic particle, wherein the first lithium manganese-based oxide and the second lithium manganese-based oxide are oxides in which a phase belonging to the C2 / m space group and a phase belonging to the R3-m space group are dissolved or composited, wherein the first lithium manganese-based oxide and the second lithium manganese-based oxide each independently comprise at least one form of secondary particle selected from a secondary particle in which a plurality of large-sized primary particles are aggregated and a secondary particle in which a plurality of small-sized primary particles are aggregated, wherein the average value of the short axis length of the large-sized primary particles is 100 nm or more and 500 nm or less, and the average value of the short axis length of the small-sized primary particles is 50 nm or more and 300 nm or less, wherein the average value of the short axis length of the small-sized primary particles is smaller than the average value of the short axis length of the large-sized primary particles, and wherein the first lithium manganese-based oxide and the At least one selected from a second lithium manganese-based oxide comprises a secondary particle in the form of aggregated primary particles of a plurality of large particle sizes and a secondary particle in the form of aggregated primary particles of a plurality of small particle sizes, and is a positive electrode active material. Claim 2 A positive electrode active material according to claim 1, wherein the secondary particles formed by aggregating a plurality of large-sized primary particles and the secondary particles formed by aggregating a plurality of small-sized primary particles among the first lithium manganese-based oxide are included in a weight ratio of 10:90 to 100:

0. Claim 3 A positive electrode active material, wherein, in paragraph 2, the interparticle porosity measured from a cross-sectional SEM image of a secondary particle in which the large-diameter primary particle is aggregated is smaller than the interparticle porosity measured from a cross-sectional SEM image of a secondary particle in which the small-diameter primary particle is aggregated. Claim 4 A positive electrode active material according to claim 3, wherein the interparticle porosity measured from a cross-sectional SEM image of a secondary particle in which the primary particle of the large diameter is aggregated is 10% or less. Claim 5 In paragraph 2, the distance from the center of the secondary particle to the surface of the secondary particle set from the cross-sectional SEM image of the secondary particle is denoted as r, and the region with a distance from the center of the secondary particle of 0.5r to 1.0r is defined as the outer bulk region, wherein the porosity within the outer bulk region measured from the cross-sectional SEM image of the secondary particle in which the large-sized primary particle is aggregated is smaller than the porosity within the outer bulk region measured from the cross-sectional SEM image of the secondary particle in which the small-sized primary particle is aggregated. Claim 6 A positive active material according to claim 5, wherein the porosity within the outer bulk region, measured from a cross-sectional SEM image of a secondary particle in which the primary particle of the large diameter is aggregated, is 1% or less. Claim 7 A positive active material according to claim 1, wherein the average particle size of the first lithium manganese-based oxide is 2 μm to 5 μm. Claim 8 A positive electrode active material according to claim 1, wherein among the second lithium manganese-based oxide, a plurality of primary particles of large particle size aggregated into secondary particles and a plurality of primary particles of small particle size aggregated into secondary particles are included in a weight ratio of 10:90 to 100:

0. Claim 9 A positive electrode active material, wherein, in claim 8, the interparticle porosity measured from a cross-sectional SEM image of a secondary particle in which the large-diameter primary particle is aggregated is smaller than the interparticle porosity measured from a cross-sectional SEM image of a secondary particle in which the small-diameter primary particle is aggregated. Claim 10 A positive electrode active material according to claim 9, wherein the interparticle porosity measured from a cross-sectional SEM image of a secondary particle in which the primary particle of the large diameter is aggregated is 15% or less. Claim 11 In claim 8, the distance from the center of the secondary particle to the surface of the secondary particle set from the cross-sectional SEM image of the secondary particle is denoted as r, and the region with a distance from the center of the secondary particle of 0.5r to 1.0r is defined as the outer bulk region, wherein the porosity within the outer bulk region measured from the cross-sectional SEM image of the secondary particle in which the large-sized primary particle is aggregated is smaller than the porosity within the outer bulk region measured from the cross-sectional SEM image of the secondary particle in which the small-sized primary particle is aggregated. Claim 12 A positive active material according to claim 11, wherein the porosity within the outer bulk region, measured from a cross-sectional SEM image of a secondary particle in which the primary particle of the large diameter is aggregated, is 6% or less. Claim 13 A positive active material according to claim 1, wherein the average particle size of the second lithium manganese-based oxide is 6 μm to 14 μm. Claim 14 A positive electrode active material according to claim 1, wherein the first lithium manganese-based oxide and the second lithium manganese-based oxide among the positive electrode active materials are included in a weight ratio of 10:90 to 80:

20. Claim 15 A positive electrode active material according to claim 1, wherein the first lithium manganese-based oxide and the second lithium manganese-based oxide each independently comprise at least one selected from nickel, cobalt, and manganese. Claim 16 A positive electrode active material according to claim 1, wherein at least one selected from the first lithium manganese-based oxide and the second lithium manganese-based oxide comprises a secondary particle doped with at least one dopant selected from a metal cation dopant and a halogen anion dopant. Claim 17 In claim 16, the positive active material, wherein the metal cation dopant is at least one selected from W, Mo, and Nb. Claim 18 In Clause 16, the above-mentioned halogen anion dopant is fluorine, a positive active material. Claim 19 In claim 16, the anode active material, wherein the secondary particles in the form of aggregated plurality of large-diameter primary particles are doped with at least one dopant selected from metal cation dopants and halogen anion dopants. Claim 20 In claim 1, the first lithium manganese-based oxide and the second lithium manganese-based oxide are each independently represented by the following chemical formula 1, [Chemical Formula 1]rLi2MnO 3-b' X b' ·(1-r)Li a M1 x M2 y M3 z O 2-b X b (wherein, M1 is at least one selected from Ni and Mn, M2 is at least one selected from Ni, Mn, Co, Al, P, Nb, B, Si, Ti, Zr, Ba, K, Mo, Fe, Cu, Cr, Zn, Na, Ca, Mg, Pt, Au, Eu, Sm, W, Ce, V, Ta, Sn, Hf, Gd and Nd, M3 is at least one selected from W, Mo and Nb, M1 to M3 do not overlap with each other, X and X' are halogens capable of substituting at least some of the oxygen present in the lithium manganese-based oxide, and 0 <r≤0.7, 0<a≤1, 0≤b≤0.1, 0≤b'≤0.1, 0<x≤1, 0≤y<1, 0≤z≤0.1 및 0<x+y+z≤1이다)양극 활물질. Claim 21 A positive electrode comprising a positive electrode active material according to any one of claims 1 to 20. Claim 22 A lithium secondary battery using a positive electrode according to Article 21. Claim 23 delete Claim 24 delete

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