Positive electrode active material, positive electrode, and lithium secondary battery

Abstract

To provide a bimodal-type positive electrode active material comprising an overlithiated lithium manganese-based oxide which may prevent abrupt degradation in battery performance due to side reactions in an initial battery reaction under a high-voltage condition and can prevent deterioration in the lifetime of a lithium secondary battery.SOLUTION: A bimodal-type positive electrode active material comprises a first lithium manganese-based oxide and a second lithium manganese-based oxide, which have different average particle diameters. The difference in the average particle diameter between the first lithium manganese-based oxide and the second lithium manganese-based oxide is 3 μm or more, and 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 complexed.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a positive electrode active material, a positive electrode, and a lithium secondary battery containing the same. More specifically, the present invention relates to a bimodal type positive electrode active material, a positive electrode, and a lithium secondary battery containing the same, which can improve the low energy density per unit volume of lithium-rich lithium manganese oxide, prevent the deterioration of the electrochemical properties of the lithium secondary battery, including rate characteristics, due to the excess lithium and manganese present in the lithium manganese oxide, and in particular prevent the deterioration of the lifespan of the lithium secondary battery by suppressing or mitigating the elution of transition metals from the lithium manganese oxide. [Background technology]

[0002] Batteries store electricity by using electrochemically reactive materials at the positive and negative electrodes. A typical example of such a battery is the lithium-ion secondary battery, which stores electrical energy through the difference in chemical potential that occurs when lithium ions are intercalated / deintercalated at the positive and negative electrodes.

[0003] The lithium secondary battery is manufactured by using materials capable of reversible intercalation / deintercalation of lithium ions as the positive electrode active material and the negative electrode active material, and by filling the space between the positive electrode and the negative electrode with an organic electrolyte or a polymer electrolyte.

[0004] Typical materials used as positive electrode active materials in lithium secondary batteries include lithium composite oxides. These lithium composite oxides include LiCoO2, LiMn2O4, LiNiO2, LiMnO2, or oxides formed by the combination of Ni, Co, Mn, or Al.

[0005] Among the positive electrode active materials, LiCoO2 is the most widely used due to its excellent lifespan characteristics and charge / discharge efficiency. However, it has the disadvantage of being expensive due to the resource limitations of cobalt used as a raw material, thus limiting its price competitiveness.

[0006] Lithium manganese oxides such as LiMnO2 and LiMn2O4 have advantages such as excellent thermal safety and low cost, but they have the drawbacks of low capacity and poor high-temperature performance. On the other hand, LiNiO2-based cathode active materials exhibit high discharge capacity battery characteristics, but their synthesis is difficult due to cation mixing problems between Li and transition metals, which results in significant problems with their rate characteristics.

[0007] Furthermore, a large amount of Li by-products is generated depending on the degree of deepening of such cation mixing. These Li by-products mostly consist of LiOH and Li2CO3, which may cause gelation during the production of the positive electrode paste or generate gas due to repeated charging and discharging after electrode production. In addition, residual Li2CO3 among the Li by-products increases the swelling phenomenon of the cell, which reduces its lifespan characteristics.

[0008] Various candidate materials have been proposed to compensate for the shortcomings of these conventional cathode active materials.

[0009] As an example, research is being conducted to use lithium-rich lithium-manganese oxides, which contain an excess amount of manganese (Mn) among the transition metals, and whose lithium content exceeds the total content of the transition metals, as positive electrode active materials for lithium secondary batteries. Such lithium-rich lithium-manganese oxides are also called lithium-overlithiated layered oxides (OLOs).

[0010] While the aforementioned OLO has the advantage of theoretically exhibiting high capacity under high-voltage operating conditions, in reality, it has a disadvantage in that its electrical conductivity is relatively low due to the excess amount of Mn contained in the oxide, resulting in poor rate characteristics for lithium secondary batteries using OLO. When rate characteristics are low in this way, problems arise in which the charge / discharge capacity and life efficiency (cycle capacity retention rate) of the lithium secondary battery decrease during charge / discharge cycles.

[0011] Furthermore, due to the material's properties, OLO has a high porosity within its particles, resulting in the disadvantage of a low energy density per unit volume.

[0012] Research has been ongoing to modify the composition of OLO in order to solve the aforementioned problems, but so far, such attempts have not reached a commercial level. [Overview of the project] [Problems that the invention aims to solve]

[0013] In the lithium-ion battery market, the growth of lithium-ion batteries for electric vehicles is driving the market, and this is leading to a sustained increase in the demand for positive electrode active materials used in lithium-ion batteries.

[0014] For example, conventionally, lithium-ion batteries using lithium iron phosphate (LFP) have been primarily used, mainly for safety reasons. However, recently, there has been a growing trend towards the use of nickel-based lithium composite oxides, which have a higher energy capacity per unit weight compared to LFP.

[0015] Furthermore, nickel-based lithium composite oxides, which are now primarily used as positive electrode active materials in high-capacity lithium secondary batteries, require the essential use of ternary metallic elements such as nickel, cobalt, and manganese or nickel, cobalt, and aluminum. However, cobalt is not only subject to unstable supply and demand but is also excessively expensive compared to other raw materials, thus necessitating new compositions of positive electrode active materials that can reduce or eliminate cobalt content.

[0016] Considering these circumstances, lithium-rich lithium manganese oxides can meet the aforementioned market expectations, but they still have limitations in terms of electrochemical properties and stability, making them suitable as a substitute for commercially available ternary lithium composite oxides with nickel-cobalt-manganese (NCM) or nickel-cobalt-aluminum (NCA) compositions.

[0017] For example, as mentioned earlier, OLO has the disadvantage of having a low energy density per unit volume due to its material composition (containing excess lithium) and structural properties (high porosity within the particles).

[0018] However, the inventors have confirmed that by preparing the lithium manganese oxide by separating it into small and large particles, and then providing a bimodal type positive electrode active material as a mixture of the small and large particles, the low energy density per unit volume of lithium-rich lithium manganese oxide can be improved.

[0019] Thus, the present invention aims to provide a bimodal type cathode active material for improving the low energy density per unit volume of lithium-rich lithium manganese oxides.

[0020] Furthermore, the inventors have confirmed that lithium manganese oxides are more likely to leach transition metals from the particle surface due to repeated charging and discharging than ternary lithium composite oxides. In particular, there is a high possibility that excess Mn contained in lithium manganese oxides will leach from the particle surface.

[0021] When a transition metal is leached from the lithium manganese oxide, the leached transition metal can react with the electrolyte on the surface of the lithium manganese oxide to form impurities. These impurities not only increase the surface resistance of the lithium manganese oxide but also act as a cause of reduced intercalation / deintercalation efficiency of lithium ions via the lithium manganese oxide.

[0022] Furthermore, the transition metals dissolved from the lithium manganese oxide, or the impurities formed by the reaction of the dissolved transition metals with the electrolyte, can move to the negative electrode using the electrolyte as a medium and be deposited on the surface of the negative electrode.

[0023] For example, a side reaction may occur with the electrolyte on the surface of the lithium manganese oxide, or an excess amount of Mn may be present in the lithium manganese oxide due to a structural change in the lithium manganese oxide (such as a change in crystal structure). 2+ Mn may dissolve into the electrolyte. 2+ During chemical conversion or charging / discharging, Mn can move to the surface of the negative electrode using the electrolyte as a medium and react with various substances present in the battery (electrons, electrolyte, electrodes, or by-products, etc.), resulting in Mn forming on the surface of the negative electrode. 2+ It will exist as an impurity containing Mn metal or Mn-containing compounds (e.g., MnCO3, MnO, MnF2, etc.).

[0024] The deposition of transition metals or impurities on the surface of the negative electrode can cause a sharp increase in negative electrode resistance, and this abnormal resistance phenomenon is a typical cause of accelerated degradation of the lifespan of lithium secondary batteries.

[0025] In particular, lithium secondary batteries using the aforementioned lithium manganese oxide as the positive electrode active material have a higher operating voltage than lithium secondary batteries using other commercially available ternary lithium composite oxides as the positive electrode active material, and are therefore more susceptible to the aforementioned problems.

[0026] However, currently there is no technology to resolve the issues caused by the leaching of transition metals from lithium-rich lithium-manganese oxides.

[0027] As mentioned above, conventional lithium-rich lithium manganese oxides have disadvantages in terms of electrochemical properties and / or stability when compared with other commercially available types of cathode active materials. However, the inventors have confirmed that lithium-rich lithium manganese oxides can exhibit electrochemical properties and stability at a level suitable for commercialization if the bulk composition of the lithium manganese oxide is controlled and a barrier layer is provided that can suppress or mitigate the elution of transition metals from the surface of the lithium manganese oxide.

[0028] In particular, the inventors have confirmed that the elution of transition metals from the lithium manganese oxide can be suppressed or mitigated by forming the lithium manganese oxide as a core-shell particle exhibiting a concentration gradient of at least one transition metal constituting the lithium manganese oxide from the center to the surface, and by ensuring that the content of a transition metal that is relatively less likely to elute in the region corresponding to the shell is higher than that of other transition metals.

[0029] Furthermore, the inventors have confirmed that when the surface of such core-shell particles, i.e., the surface of the shell, is covered with a barrier layer capable of suppressing the elution of transition metals from the core-shell particles, the elution of transition metals from the lithium manganese-based oxide can be further suppressed or mitigated.

[0030] Accordingly, the present invention aims to provide a bimodal type positive electrode active material comprising small and large particles to improve the low energy density per unit volume of lithium-rich lithium manganese oxide, wherein at least one of the small and large particles is a core-shell particle exhibiting a transition metal concentration gradient, and the content of the transition metal, which is relatively less likely to dissolve in the region corresponding to the shell, is higher than that of the other transition metals, thereby suppressing or mitigating the dissolution of transition metals from the lithium manganese oxide while simultaneously improving the charge-transfer and / or diffusivity (i.e., surface kinetics) of lithium ions on the surface of the lithium manganese oxide.

[0031] Furthermore, the present invention aims to provide a bimodal type positive electrode active material containing small and large particles in order to improve the low energy density per unit volume of lithium-rich lithium manganese oxides, and which can prevent a rapid decrease in battery performance due to side reactions during the initial battery reaction under high voltage conditions.

[0032] Furthermore, the present invention aims to provide a bimodal type positive electrode active material containing small and large particles in order to improve the low energy density per unit volume of lithium-rich lithium manganese oxide, wherein a barrier layer is formed on the surface of at least one of the small and large particles to suppress or mitigate the elution of transition metals from the lithium manganese oxide.

[0033] Furthermore, the present invention aims to provide a lithium secondary battery that, by using a positive electrode containing a bimodal type positive electrode active material as defined in this application, prevents a decrease in the electrochemical properties of the lithium secondary battery, including rate characteristics due to lithium and manganese present in excess in the OLO, and achieves high stability by reducing side reactions between the positive electrode active material and the electrolyte during high-voltage operation. [Means for solving the problem]

[0034] According to one aspect of the present invention for solving the above-mentioned technical problems, a bimodal type cathode active material is provided which includes a first lithium manganese oxide and a second lithium manganese oxide having different average particle sizes.

[0035] In this application, the first lithium manganese oxide may also be called small particles, and the second lithium manganese oxide may also be called large particles. The first lithium manganese oxide and the second lithium manganese oxide constituting the 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.

[0036] Generally, commercially available ternary lithium composite oxides with nickel-cobalt-manganese (NCM) or nickel-cobalt-aluminum (NCA) compositions have a single phase belonging to the R3-m space group, whereas the lithium-rich lithium manganese oxides defined in this application are characterized by solid solution or composite formation of a phase belonging to the C2 / m space group and a phase belonging to the R3-m space group.

[0037] In one embodiment, the first lithium manganese oxide and the second lithium manganese oxide may each independently contain at least one selected from nickel, cobalt, and manganese.

[0038] The first lithium manganese oxide and the second lithium manganese oxide can each be independently represented by the following chemical formula 1.

[0039] [Chemical formula 1] Li(Li a M1 x M2 y )O 2-b X b (Here, 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, and M2 does not overlap with M1. X is a halogen capable of substituting at least a part of the oxygen present in the lithium manganese oxide. 0 < a ≤ 0.7, 0 ≤ b ≤ 0., 0 < x ≤ 1, 0 ≤ y < 1, 0 < x + y ≤ 1.

[0040] In another embodiment, the first lithium manganese oxide and the second lithium manganese oxide may each independently be represented by the following Chemical Formula 1-1.

[0041] [Chemical Formula 1-1] rLi2MnO 3-b″ X′ b″ ·(1 - r)Li a′ M1 x′ M2 y′ O 2-b′ X b′ (Here, 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, and M2 does not overlap with M1. X and X′ are halogens capable of substituting at least a part of the oxygen present in the lithium manganese oxide. 0 < r ≤ 0.7, 0 < a′ ≤ 1, 0 ≤ b′ ≤ 0.1, 0 ≤ b″ ≤ 0.1, 0 < x′ ≤ 1, 0 ≤ y′ < 1, 0 < x′ + y′ ≤ 1.

[0042] Furthermore, at least one of the first lithium manganese-based oxide and the second lithium manganese-based oxide can be provided in the form of core-shell particles exhibiting at least one concentration gradient selected from nickel and manganese from the center to the surface.

[0043] In this case, by ensuring that the content of transition metals that are relatively less likely to dissolve in the region corresponding to the shell is higher than that of other transition metals, the possibility of transition metals dissolving from the core-shell particles can be reduced.

[0044] Furthermore, by providing at least one of the first lithium manganese-based oxide and the second lithium manganese-based oxide in the form of core-shell particles, the charge-transfer and / or diffusivity (i.e., surface kinetics) of lithium ions on the surface of the core-shell particles can be improved.

[0045] In one embodiment, a barrier layer may be present on at least a portion of the surface of at least one of the first lithium manganese oxide and the second lithium manganese oxide. The barrier layer covering at least a portion of the surface of the first lithium manganese oxide and / or the second lithium manganese oxide can suppress or mitigate the elution of transition metals from the first lithium manganese oxide and / or the second lithium manganese oxide.

[0046] The barrier layer may contain an oxide comprising at least one selected from metallic elements, metalloid elements, and phosphorus (P).

[0047] Specifically, the barrier layer may include at least one selected from the first oxide represented by the following chemical formula 2, the second oxide represented by the following chemical formula 3, and the third oxide represented by the following chemical formula 4.

[0048] [Chemical formula 2] Li cB d M3 e O f (Here, M3 is at least one selected from Ni, Mn, Co, Al, Nb, 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, 0 ≦ c ≦ 8, 0 < d ≦ 8, 0 ≦ e ≦ 8, 2 ≦ f ≦ 13.)

[0049] [Chemical Formula 3] Li g M4 h O i (Here, M4 is at least one selected from Ni, Mn, Co, Al, Nb, 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, 0 ≦ g ≦ 8, 0 ≦ h ≦ 8, 2 ≦ i ≦ 13, and the case where g and h are both 0 is excluded.)

[0050] [Chemical Formula 4]<{ Li j M5 k (P l O m ) n (Here, M5 is at least one selected from Ni, Mn, Co, Al, 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, 0 ≦ j ≦ 10, 0 ≦ k ≦ 8, 0 < l ≦ 4, 0 < m ≦ 10, 0 < n ≦ 13, and the case where j and k are both 0 is excluded.)

[0051] Also, according to another aspect of the present invention, a positive electrode containing the above-described positive electrode active material is provided.

[0052] Furthermore, according to yet another aspect of the present invention, a lithium secondary battery is provided in which the above-described positive electrode is used. [Effects of the Invention]

[0053] According to the present invention, it is possible to improve upon the limitations of conventional lithium-rich lithium manganese oxides, which have various disadvantages in terms of electrochemical properties and / or stability when compared with commercially available ternary lithium composite oxides of nickel-cobalt-manganese (NCM) or nickel-cobalt-aluminum (NCA) composition.

[0054] Specifically, according to the present invention, by separating the lithium manganese oxide into small particles and large particles and then providing a bimodal type positive electrode active material as a mixture of the small and large particles, the low energy density per unit volume of lithium-rich lithium manganese oxide can be improved.

[0055] Furthermore, according to the present invention, by forming small particles and / or large particles as core-shell particles exhibiting a concentration gradient of transition metals, and by ensuring that the content of transition metals that are relatively less likely to dissolve in the region corresponding to the shell is higher than that of other transition metals, the dissolution of transition metals from the lithium manganese oxide can be suppressed or mitigated.

[0056] By forming small and / or large particles as core-shell particles exhibiting a concentration gradient of transition metals, the charge-transfer and / or diffusivity (i.e., surface kinetics) of lithium ions on the surface of the lithium manganese oxide can be improved.

[0057] Furthermore, if the surface of such core-shell particles, i.e., the surface of the shell, is covered with a barrier layer capable of suppressing or mitigating the elution of transition metals from the core-shell particles, the elution of transition metals from small particles and / or large particles can be further suppressed or mitigated.

[0058] By suppressing or mitigating the leaching of transition metals from small and / or large particles, it is possible to prevent the formation of impurities by the reaction of the leached transition metals with the electrolyte on the surface of the lithium manganese oxide.

[0059] Transition metals leached from the lithium manganese oxide and / or impurities formed by the reaction of the leached transition metals with the electrolyte can move to the negative electrode using the electrolyte as a medium, and these impurities can deposit on the surface of the negative electrode, causing a rapid increase in the negative electrode resistance. As a result, it is necessary to restrict the unintended movement of transition metals within the lithium secondary battery, as described in the present invention.

[0060] In other words, according to the present invention, by forming a barrier layer on at least a portion of the surface of small particles and / or large particles, it is possible to prevent the accelerated deterioration of the lifespan of the lithium secondary battery as impurities are deposited on the positive and / or negative electrodes by transition metals leached from the lithium manganese oxide.

[0061] Furthermore, the barrier layer can act as a physical barrier between small and / or large particles and the electrolyte. In particular, while OLOs such as lithium manganese oxides have the advantage of exhibiting high capacity under high-voltage operating conditions, the possibility of side reactions between the lithium manganese oxide and the electrolyte can be promoted as the operating voltage increases. Therefore, it is important to reduce side reactions between the lithium manganese oxide and the electrolyte.

[0062] Therefore, by forming a barrier layer on at least a portion of the surface of the small and / or large particles, the side reactions between the lithium manganese oxide and the electrolyte are reduced, thereby improving the stability and lifespan of the lithium secondary battery used as a bimodal type positive electrode active material as defined in this application. In particular, a positive electrode active material in which side reactions with the electrolyte are suppressed can drive the lithium secondary battery at a higher voltage.

[0063] Along with the effects described above, the specific effects of the present invention will be described below while explaining the specific matters for carrying out the invention. [Modes for carrying out the invention]

[0064] For the convenience of making the present invention easier to understand, certain terms are defined in this application. Unless otherwise specifically defined in this application, the scientific and technical terms used in this invention have meanings that are generally understood by those of ordinary skill in the art. Furthermore, unless otherwise specified in the context, singular terms should be understood to include their plural forms, and plural terms should be understood to include their singular forms.

[0065] The following describes in more detail some embodiments of the present invention, specifically positive electrode active materials containing lithium-rich lithium manganese oxides and lithium secondary batteries containing such positive electrode active materials.

[0066] positive electrode active material According to one aspect of the present invention, a positive electrode active material is provided which contains a lithium manganese oxide 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.

[0067] Here, the lithium manganese oxide can be classified into a first lithium manganese oxide as small particles and a second lithium manganese oxide as large particles based on the average particle size, and the positive electrode active material defined in this application is a bimodal type positive electrode active material containing a first lithium manganese oxide as small particles and a second lithium manganese oxide as large particles.

[0068] In the following, unless otherwise defined, the lithium manganese oxide shall be understood to refer to the first lithium manganese oxide and the second lithium manganese oxide.

[0069] The aforementioned lithium manganese oxide is also called an overlithiated layered oxide (OLO) if the lithium content in the lithium manganese oxide is greater than the total content of other transition metals (generally, if the molar ratio of lithium to all other metal elements in the lithium manganese oxide (Li / Metal molar ratio) is greater than 1).

[0070] Furthermore, the lithium manganese oxide comprises at least one selected from nickel, cobalt, and manganese. That is, the first lithium manganese oxide and the second lithium manganese oxide each independently comprise at least one selected from nickel, cobalt, and manganese.

[0071] Generally, considering that commercially available ternary lithium composite oxides with nickel-cobalt-manganese (NCM) or nickel-cobalt-aluminum (NCA) compositions have a manganese content of 20 mol% or less in the total metal elements excluding lithium, the lithium manganese-based oxides have a relatively higher proportion of manganese (e.g., 50 mol% or more, preferably 55 mol% to 75 mol%) in the total metal elements compared to commercially available ternary lithium composite oxides.

[0072] Furthermore, considering that commercially available ternary lithium composite oxides with nickel-cobalt-manganese (NCM) or nickel-cobalt-aluminum (NCA) compositions have a nickel content of 60 mol% or more (80 mol% or more in the case of high-Ni types) among all metal elements excluding lithium, the lithium manganese-based oxide has a relatively lower proportion of nickel among all metal elements (for example, less than 50 mol%, preferably 25 mol% to 45 mol%) compared to commercially available ternary lithium composite oxides.

[0073] Another difference is that the Li / Metal molar ratio measured from lithium manganese oxides as defined in this application 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) is close to 1. On the other hand, the Li / Metal molar ratio of lithium manganese oxides as defined in this application is greater than 1, preferably between 1.1 and 1.7.

[0074] Despite the aforementioned compositional differences, the lithium manganese-based oxide can also function as a composite metal oxide capable of lithium ion intercalation / deintercalation.

[0075] In one embodiment, the first lithium manganese oxide and the second lithium manganese oxide include secondary particles formed by the aggregation of a plurality of primary particles.

[0076] The primary particles may have a rod shape, an elliptical shape, and / or an amorphous shape. Furthermore, unless specifically intended in the manufacturing process, primary particles of various shapes may exist within the same positive electrode active material.

[0077] The primary particles may have an average particle size of 0.05 μm to 5 μm, preferably 0.1 μm to 1.0 μm, and more preferably 0.25 μm to 0.75 μm. In this case, the average particle size of the primary particles can be calculated using the average value of the length in the long axis direction and the length in the short axis direction of the primary particles ([long axis length + short axis length] / 2).

[0078] When the average particle size of the primary particles is smaller than 0.05 μm, the specific surface area of ​​the lithium manganese oxide (secondary particles) composed of the primary particles is relatively large. In this case, there is a higher possibility that the lithium manganese oxide and the electrolyte will undergo a side reaction during storage or operation of the lithium secondary battery.

[0079] On the other hand, if the average particle size of the primary particles is greater than 5 μm, the growth of the primary particles is excessively induced, which lengthens the diffusion pathway of lithium ions within the primary particles. When the diffusion pathway of lithium ions within the primary particles is excessively long, the mobility of lithium ions within the primary particles and the diffusivity of lithium ions mediated by the primary particles decrease, which increases the resistance of the lithium manganese oxide (secondary particles) composed of the primary particles.

[0080] 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, the energy density per unit volume of the bimodal cathode active material can be increased.

[0081] The main peak of the volume-based particle size distribution graph (x-axis: particle size (μm), Y-axis: volume %) for the first lithium manganese oxide may preferably be located between 1 μm and 8 μm, more preferably between 2 μm and 7 μm. Furthermore, 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 oxide ([long axis length + short axis length] / 2) may be between 2 μm and 6 μm.

[0082] The main peak of the volume-based particle size distribution graph (x-axis: particle size (μm), Y-axis: volume %) for the second lithium manganese oxide may preferably be located between 6 μm and 24 μm, more preferably between 8 μm and 22 μm. Furthermore, the average particle size calculated as the average of the length in the long axis direction and the length in the short axis direction ([long axis length + short axis length] / 2) of the second lithium manganese oxide may be between 7 μm and 14 μm.

[0083] Furthermore, in order 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 in the cathode active material are present in a weight ratio of 10:90 to 80:20.

[0084] The first lithium manganese oxide may exist in a form that fills the gaps between the second lithium manganese oxides, or it may exist in a form in which the first lithium manganese oxides aggregate together.

[0085] If the proportion of the first lithium manganese oxide in the positive electrode active material is excessively low compared to the second lithium manganese oxide, the first lithium manganese oxide may not adequately fill the voids formed by the second lithium manganese oxide.

[0086] On the other hand, if the proportion of the first lithium manganese oxide in the positive electrode active material is excessively high compared to the second lithium manganese oxide, the energy density per unit volume of the positive electrode active material may decrease.

[0087] Unless otherwise defined, the term "surface of the primary particle" as used in this application means the outer surface of the primary particle that is exposed to the outside. Similarly, the term "surface of the secondary particle" as used in this application means the outer surface of the secondary particle that is exposed to the outside. In this case, the "surface of the secondary particle" formed by the aggregation of multiple primary particles corresponds to the exposed surface of the primary particle present on the surface portion of the secondary particle.

[0088] Furthermore, unless otherwise defined, the terms "particle surface" as used in this application mean the region relatively close to the "surface" of the particle, and "particle center" means the region relatively closer to the "center" of the particle than the "surface." Thus, "primary particle surface" means the region relatively close to the "surface" of the primary particle, and "primary particle center" means the region relatively closer to the "center" of the primary particle than the "surface." Similarly, "secondary particle surface" means the region relatively close to the "surface" of the secondary particle, and "secondary particle center" means the region relatively closer to the "center" of the secondary particle than the "surface."

[0089] In this case, the region within any particle excluding the "particle surface" can be defined as the "particle's central region."

[0090] For example, if the radius of the primary particle is r, the region at a distance of 0 to 0.5r from the surface of the primary particle can be defined as the surface portion of the primary particle, and the region at a distance of 0 to 0.5r from the center of the primary particle can be defined as the center portion of the primary particle. If the radius of the primary particle is 0.5 μm, the surface portion of the primary particle can be defined as the region at a distance of 0 to 0.25 μm from the surface of the primary particle, and the center portion of the primary particle can be defined as the region at a distance of 0 to 0.25 μm from the center of the primary particle.

[0091] Furthermore, if necessary, when the radius of the primary particle is denoted as r, the region at which the distance from the surface of the primary particle is 0 to 0.1r or 0 to 0.2r can be defined as the surface portion of the primary particle, and the region at which the distance from the center of the primary particle is 0 to 0.2r or 0 to 0.5r can be defined as the center portion of the primary particle.

[0092] Similarly, when the radius of the secondary particle is denoted as r, the region at a distance of 0 to 0.5r from the surface of the secondary particle can be defined as the surface portion of the secondary particle, and the region at a distance of 0 to 0.5r from the center of the secondary particle can be defined as the center portion of the secondary particle. If the radius of the secondary particle is 2.0 μm, the surface portion of the secondary particle can be defined as the region at a distance of 0 to 1.0 μm from the surface of the secondary particle, and the center portion of the secondary particle can be defined as the region at a distance of 0 to 1.0 μm from the center of the secondary particle.

[0093] Furthermore, if necessary, when the radius of the secondary particle is denoted as r, the region at which the distance from the surface of the secondary particle is 0 to 0.1r or 0 to 0.2r can be defined as the surface portion of the secondary particle, and the region at which the distance from the center of the secondary particle is 0 to 0.2r or 0 to 0.5r can be defined as the center portion of the secondary particle.

[0094] In one embodiment, the first lithium manganese oxide and the second lithium manganese oxide as defined in this application may each be independently lithium-rich lithium manganese oxides represented by the following chemical formula 1. The composition represented by the following chemical formula 1 can represent an average composition that reflects the composition of a barrier layer present on at least a portion of the surface of the lithium manganese oxide.

[0095] [Chemical formula 1] Li(Li a M1 x M2 y )O 2-b X b Here, 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, and M2 does not overlap with M1. X is a halogen capable of substituting at least a portion of the oxygen present in the lithium manganese oxide, and 0 <a≦0.7、0≦b≦0.1、0<x≦1、0≦y<1、0<x+y≦1である。

[0096] The types of halogens that can be used as X are determined by referring to the periodic table, and can be F, Cl, Br and / or I, and preferably F.

[0097] A gradient may be formed in which the ratio of at least one selected from x and y in the chemical formula 1 changes from the surface of the primary particle toward the center of the primary particle.

[0098] Furthermore, a gradient may be formed in which the ratio of at least one selected from x and y in the chemical formula 1 changes from the surface of the secondary particle toward the center of the secondary particle.

[0099] Furthermore, the lithium-rich lithium manganese oxide represented by chemical formula 1 may further contain a spinel phase in addition to the phases belonging to the C2 / m space group and the phases belonging to the R3-m space group.

[0100] In other embodiments, the first lithium manganese oxide and the second lithium manganese oxide as defined in this application may each be independently lithium-rich lithium manganese oxides represented by the following chemical formula 1-1. The composition represented by the following chemical formula 1-1 can represent an average composition that reflects the composition of a barrier layer present on at least a portion of the surface of the lithium manganese oxide.

[0101] [Chemical formula 1-1] rLi2MnO 3-b″ X' b″ (1-r)Li a′ M1 x′ M2 y′ O 2-b′ X b′ Here, 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. M2 does not overlap with M1. X and X' are halogens capable of substituting at least a part of the oxygen present in the lithium manganese-based oxide, where 0 < r ≤ 0.7, 0 < a' ≤ 1, 0 ≤ b' ≤ 0.1, 0 ≤ b'' ≤ 0.1, 0 < x' ≤ 1, 0 ≤ y' < 1, and 0 < x' + y' ≤ 1. The types of halogens that can be used as X and X' can be referred to the periodic table, and F, Cl, Br, and / or I, etc. can be used. Preferably, F can be used.

[0102] In the chemical formula 1 and the chemical formula 1-1, when M1 is Ni, M2 may contain Mn; when M1 is Mn, M2 may contain Ni. Also, when M1 is Ni and Mn, M2 may not exist, or if it exists, it may be other elements excluding Ni and Mn.

[0103] That is, when M1 is Ni, M2 may contain at least one (preferably at least one selected from Co, Al, P, Nb, B, Ti, Zr, Ba, K, Mo, Si, Fe, Cu, Cr, Zn, Na, Ca, Mg, Pt, Au, Eu, Sm, W, Ce, V, Ta, Sn, Hf, Gd and Nd; more preferably at least one selected from Co, P, B, Si, Ti, Zr and W; even more preferably at least one selected from P, B and Si) selected from Co, Al, P, Nb, B, Ti, Zr, Ba, K, Mo, Si, Fe, Cu, Cr, Zn, Na, Ca, Mg, Pt, Au, Eu, Sm, W, Ce, V, Ta, Sn, Hf, Gd and Nd and Mn.

[0104] If M1 is Mn, then M2 may include at least one selected from Co, Al, P, Nb, B, Ti, Zr, Ba, K, Mo, Si, Fe, Cu, Cr, Zn, Na, Ca, Mg, Pt, Au, Eu, Sm, W, Ce, V, Ta, Sn, Hf, Gd, and Nd (preferably at least one selected from Co, Al, P, Nb, B, Si, Ti, Zr, Ba, K, Mo, and W; more preferably at least one selected from Co, P, B, Ti, Zr, Si, and W; even more preferably at least one selected from P, B, and Si) and Ni.

[0105] If M1 is Ni and Mn, then M2 may include at least one selected from Co, Al, P, Nb, B, Ti, Zr, Ba, K, Mo, Si, Fe, Cu, Cr, Zn, Na, Ca, Mg, Pt, Au, Eu, Sm, W, Ce, V, Ta, Sn, Hf, Gd, and Nd, preferably at least one selected from Co, Al, P, Nb, B, Ti, Zr, Ba, K, Mo, Si, and W, more preferably at least one selected from Co, P, B, Ti, Zr, Si, and W, and even more preferably at least one selected from P, B, and Si.

[0106] The lithium manganese oxide represented by chemical formula 1 or chemical formula 1-1 may selectively 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.

[0107] The Li / Metal molar ratio measured from the lithium manganese oxide represented by chemical formula 1 or chemical formula 1-1 is greater than 1, preferably between 1.1 and 1.7. When the Li / Metal molar ratio measured from the lithium manganese oxide is greater than 1, it is possible to form a lithium-rich lithium manganese oxide.

[0108] Furthermore, in order to appropriately form a solid solution in which the lithium manganese oxide contains a phase belonging to the C2 / m space group and a phase belonging to the R3-m space group in solid solution or composite form, and at the same time to exhibit high capacity under high voltage operating conditions, the Li / Metal molar ratio of the lithium manganese oxide is preferably 1.1 to 1.6.

[0109] Furthermore, in order to properly form a solid solution in which the phase belonging to the C2 / m space group and the phase belonging to the R3-m space group are in solid solution or composite, it is preferable that the manganese content in the total metal elements excluding lithium present in the lithium manganese oxide represented by chemical formula 1 or chemical formula 1-1 is 50 mol% or more.

[0110] To enable the lithium manganese oxide to exhibit OLO characteristics that allow it to exert high capacity under high-voltage operating conditions, the manganese content in the total metal elements excluding lithium present in the lithium manganese oxide is more preferably 50 mol% or more and less than 80 mol%, and even more preferably 55 mol% to 75 mol%.

[0111] When the manganese content in the lithium manganese oxide exceeds 80 mol%, a phase transition may occur in the lithium secondary battery due to the migration of transition metals (especially manganese) within the lithium manganese oxide during conversion and / or operation. Such a phase transition forms a spinel phase, and this spinel phase, acting as an impurity in the lithium manganese oxide, can induce a decrease in charge / discharge capacity or voltage decay during the charge / discharge cycle of the lithium secondary battery.

[0112] 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 in solid solution or composite, it is preferable that the nickel content in the total metal elements excluding lithium present in the lithium manganese oxide represented by chemical formula 1 or chemical formula 1-1 is less than 50 mol%.

[0113] When the nickel content in the lithium manganese oxide is 50 mol% or more, the C2 / m phase may not form sufficiently, 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 can cause phase separation during conversion and / or operation of the lithium secondary battery.

[0114] If the first lithium manganese oxide or the second lithium manganese oxide is a core-shell particle exhibiting a concentration gradient of at least one selected from nickel and manganese from the core to the shell, the nickel content in the core-shell particle is preferably 25 mol% to 45 mol% in order to ensure that sufficient nickel is present on the surface of the core-shell particle.

[0115] Generally, commercially available ternary lithium composite oxides with nickel-cobalt-manganese (NCM) or nickel-cobalt-aluminum (NCA) compositions have a single-phase phase belonging to the R3-m space group.

[0116] On the other hand, lithium-rich lithium manganese oxides represented by chemical formula 1 or chemical formula 1-1 are rLi2MnO 3-b″ X' b″ Oxides of phases belonging to the C2 / m space group represented by (hereinafter also referred to as "C2 / m phase") and (1-r)Li a′ M1 x′ M2 y′ O 2-b′ X b′ The oxides of the phases belonging to the R3-m space group (hereinafter also referred to as the "R3-m phase") are present as solid solutions or composite oxides. For example, the lithium manganese-based oxide may exist in a state in which the oxide of the C2 / m phase and the oxide of the R3-m phase form a solid solution.

[0117] In this case, composite oxides 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 do not fall under the definition of a solid solution as defined in this application.

[0118] For example, a composite oxide having a phase belonging to the C2 / m space group, obtained by mixing a metal oxide having a phase belonging to the C2 / m space group with a metal oxide having a phase belonging to the R3-m space group, and having the surface coated with a metal oxide having a phase belonging to the R3-m space group, does not fall under the definition of a solid solution as defined in this application.

[0119] In the lithium manganese oxide represented by the chemical formula 1-1, if r exceeds 0.7, then the C2 / m phase oxide Li2MnO is present in the lithium manganese oxide. 3-b″ X' b″ If the proportion of R3-m becomes excessively high, this may ultimately lead to a decrease in discharge capacity as the irreversible capacity and resistance of the positive electrode active material increase. In other words, in order to sufficiently activate the C2 / m phase oxide, which has relatively high resistance, in the lithium manganese-based oxide and improve the surface kinetics, it is preferable that the R3-m phase oxide be present in a predetermined proportion or higher.

[0120] As described above, at least one of the first lithium manganese oxide and the second lithium manganese oxide may be a core-shell particle exhibiting a concentration gradient of at least one selected from nickel and manganese from the core to the shell. In this case, the elution of transition metals from the core-shell particle can be suppressed or mitigated by ensuring that the content of transition metals that are relatively less likely to elute in the shell region is higher than that of other transition metals.

[0121] Furthermore, by providing at least one of the first lithium manganese-based oxide and the second lithium manganese-based oxide in the form of core-shell particles, the charge-transfer and / or diffusivity (i.e., surface kinetics) of lithium ions on the surface of the core-shell particles can be improved.

[0122] If the concentrations of transition metals present in the shell (or surface) and core (or center) of any given particle are different, the particle may be referred to as a core-shell particle. That is, the lithium manganese oxide is a core-shell particle, and the average composition of all metal elements constituting the lithium manganese oxide in the core and the shell may be different from each other. As a result, the ratio of the phases belonging to the C2 / m space group and the phases belonging to the R3-m space group in the core may be different from the ratio of the phases belonging to the C2 / m space group and the phases belonging to the R3-m space group in the shell.

[0123] The shell can occupy at least a portion of the surface of the core. That is, the shell can be partially present on the surface of the core or it can occupy the entire surface of the core.

[0124] In this application, the number of moles of all metal elements in the lithium manganese oxide is M. 1 He said, the number of moles of nickel is M 2 When defined as such, M is calculated from the average composition of all metal elements in the core of the lithium manganese oxide. 2 / M1 And M calculated from the average composition of all metal elements within the shell of the lithium manganese oxide 2 / M 1 They may be different from one another.

[0125] It is well known that lithium-rich lithium-manganese oxides containing an excess amount of Mn have lower electrical conductivity than lithium-cobalt oxides or ternary lithium composite oxides with a nickel-cobalt-manganese (NCM) or nickel-cobalt-aluminum (NCA) composition containing a relatively excess amount of Ni. Furthermore, ternary lithium composite oxides also have the problem that their electrical conductivity decreases as the Mn content increases.

[0126] While various reactions occur on the surface of the diverse types of positive electrode active materials mentioned above, the higher the Mn content in the positive electrode active material, the more the charge-transfer and / or diffusion of lithium ions on the surface is hindered. This phenomenon can be referred to as a decrease in surface kinetic or intra-surface reaction kinetic.

[0127] As described above, the bimodal type cathode active material as defined in this application can improve surface kinetics by providing at least one of the first lithium manganese-based oxide and the second lithium manganese-based oxide in the form of core-shell particles in which a transition metal concentration gradient exists between the core and the shell.

[0128] In one embodiment, the first lithium manganese-based oxide may be a core-shell particle exhibiting a concentration gradient of at least one selected from nickel and manganese from the central part (also called the core) toward the surface (also called the shell).

[0129] In this case, the second lithium manganese oxide may be a particle (also called bulk or bulk particle) in which the concentrations of nickel and manganese within the particle are constant (i.e., the concentrations of nickel and manganese are constant from the center to the surface), or a particle exhibiting a concentration gradient having a smaller slope than the concentration gradient that appears in the first lithium manganese oxide. Here, the constant concentrations of nickel and manganese within the particle means that the concentration of nickel or manganese can partially increase or decrease in any region within the particle, but there is no tendency for the concentration of nickel or manganese to increase or decrease from the center (core) of the particle towards the surface (shell).

[0130] In the bimodal type cathode active material, the first lithium manganese oxide exists in a relatively uniformly dispersed state, and the specific surface area of ​​the first lithium manganese oxide is larger than that of the second lithium manganese oxide. As a result, even by selectively providing the first lithium manganese oxide as core-shell particles, it is possible to improve the overall surface kinetics of the bimodal type cathode active material.

[0131] Furthermore, since the second lithium manganese oxide is larger than the first lithium manganese oxide, it is difficult to achieve an overall concentration gradient within the particles. Therefore, the kinetic improvement effect that can be obtained by applying a concentration gradient to the first lithium manganese oxide is unlikely to be expected from the second lithium manganese oxide.

[0132] Therefore, by selectively providing the first lithium manganese-based oxide from among the bimodal type positive electrode active materials as core-shell particles exhibiting a concentration gradient, the manganese content (mol%) relative to the total transition metal in the first lithium manganese-based oxide becomes smaller than the manganese content (mol%) relative to the total transition metal in the second lithium manganese-based oxide.

[0133] Furthermore, the manganese content (mol%) relative to the total transition metal in the first lithium manganese oxide can be adjusted such that the manganese content (mol%) relative to the total transition metal present on the surface of the first lithium manganese oxide is smaller than the manganese content (mol%) relative to the total transition metal present on the surface of the second lithium manganese oxide.

[0134] Furthermore, the core-shell particles can be provided as primary particles and / or secondary particles.

[0135] In one embodiment, the primary particles may be core-shell particles exhibiting a concentration gradient of at least one transition metal from the center of the primary particle toward the surface of the primary particle. Thus, the first lithium manganese oxide and / or the second lithium manganese oxide existing as secondary particles may be aggregates of primary particles existing as core-shell particles as defined above.

[0136] When the primary particles exist as core-shell particles exhibiting a concentration gradient of at least one transition metal from the core to the shell, the surface kinetics of the primary particles and the surface kinetics of the secondary particles formed by the aggregation of the primary particles can be improved.

[0137] For example, the primary particle may exhibit a concentration gradient from the core to the shell in which at least one concentration selected from nickel and manganese is increased. More specifically, the primary particle may exhibit a concentration gradient from the core to the shell in which the concentration of nickel increases while the concentration of manganese decreases.

[0138] Furthermore, if the primary particles are provided as core-shell particles as defined above, abrupt changes in the concentration of the metal element between the core and shell of the primary particles can be reduced. By preventing abrupt changes in the concentration of the metal element within the primary particles, instability in the crystal structure of the primary particles can be prevented.

[0139] When the region in which a transition metal concentration gradient exists among the primary particles that exist as core-shell particles as described above is called the shell of the primary particles, the average thickness of the shell may be 0.1 nm to 2 μm, preferably 50 nm to 1 μm. If the thickness of the shell of the primary particles is less than 0.1 nm, it is difficult to sufficiently improve the surface kinetics of the primary particles. On the other hand, if the thickness of the shell of the primary particles is greater than 2 μm, it is disadvantageous to exhibit high capacity under high voltage operating conditions, which is one of the advantages of the lithium manganese oxide. The thickness of the shell of the primary particles can be varied depending on the average particle size of the primary particles.

[0140] In other embodiments, the secondary particles may be core-shell particles exhibiting a concentration gradient of at least one transition metal from the center of the secondary particle toward the surface of the secondary particle.

[0141] For example, the secondary particles may exhibit a concentration gradient from the core to the shell in which at least one concentration selected from nickel and manganese is present. More specifically, the secondary particles may exhibit a concentration gradient from the core to the shell in which the concentration of nickel increases while the concentration of manganese decreases.

[0142] When the region in which a transition metal concentration gradient exists among the secondary particles that exist as core-shell particles as described above is called the shell of the secondary particles, the average thickness of the shell may be 0.1 nm to 5 μm, preferably 100 nm to 2 μm. If the thickness of the shell of the secondary particles is less than 0.1 nm, it is difficult to sufficiently improve the surface kinetics of the secondary particles. On the other hand, if the thickness of the shell of the secondary particles is greater than 5 μm, it is disadvantageous to exhibit high capacity under high voltage operating conditions, which is one of the advantages of the lithium manganese oxide. The thickness of the shell of the secondary particles can be varied depending on whether the secondary particles are small or large particles.

[0143] The aforementioned concentration gradients within primary and / or secondary particles can suppress and / or mitigate phase transitions caused by unintended movement of transition metals within the particles.

[0144] Furthermore, if the content of transition metals that are relatively less likely to dissolve in the region corresponding to the shell is higher than that of other transition metals, the dissolution of transition metals from the lithium manganese oxide can be suppressed or mitigated. By suppressing or mitigating the dissolution of transition metals from the lithium manganese oxide, it is possible to prevent the formation of impurities by the reaction of the dissolved transition metals with the electrolyte on the surface.

[0145] When the surface of the core-shell particles as defined in this application, i.e., the surface of the shell, is covered with a barrier layer capable of suppressing or mitigating the elution of transition metals from the core-shell particles, the elution of transition metals from the lithium manganese oxide can be further suppressed or mitigated.

[0146] When the secondary particles exist as core-shell particles, the barrier layer can suppress or mitigate the elution of transition metals from the secondary particles by covering at least a portion of the surface of the secondary particles. Furthermore, by covering the surface of the secondary particles, the barrier layer can prevent side reactions between the surface of the secondary particles and the electrolyte.

[0147] When the barrier layer covers a portion of the surface of the secondary particles, the barrier layer may exist in an island form. That is, even if the barrier layer covers at least a portion of the surface of the secondary particles in an island form, the elution of transition metals through the region covered by the barrier layer can be suppressed or mitigated. Therefore, the presence of the barrier layer on the surface of the secondary particles must be distinguished from the mere presence of the lithium manganese-based oxide and other oxides dispersed on the surface of the secondary particles.

[0148] Furthermore, grain boundaries may be defined between adjacent primary particles within the secondary particles, and the barrier layer may exist diffused along the grain boundaries from the surface of the secondary particles toward the center of the secondary particles. As the barrier layer diffuses toward the center of the secondary particles, the elements mainly contained in the barrier layer may exhibit a concentration gradient that decreases from the surface of the secondary particles toward the center of the secondary particles.

[0149] The barrier layer forms a gradient from the surface of the secondary particles toward the center of the secondary particles, thereby effectively suppressing or mitigating the elution of transition metals, mainly on the surface of the secondary particles.

[0150] Some of the elements mainly contained in the barrier layer may be doped into the primary particles and / or the secondary particles.

[0151] The average thickness of the barrier layer covering the surface of the secondary particles is preferably 0.1 nm to 1 μm. Furthermore, the average thickness of the barrier layer can vary depending on whether the secondary particles are small or large.

[0152] If the average thickness of the barrier layer covering the secondary particles is less than 0.1 nm, it is difficult to sufficiently suppress the elution of transition metals from the secondary particles. On the other hand, if the average thickness of the barrier layer covering the secondary particles is greater than 1 μm, there is a risk that the surface kinetics of the secondary particles will decrease or the electrical conductivity of the secondary particles will decrease.

[0153] When the primary particles exist as core-shell particles, the barrier layer can suppress or mitigate the elution of transition metals from the primary particles by covering at least a portion of the surface of the primary particles. Furthermore, the barrier layer can prevent side reactions between the primary particle surface and the electrolyte by covering the surface of the primary particles. In this case, the barrier layer can cover at least a portion of the surface of the secondary particles by covering the surface of the primary particles present on the surface of the secondary particles. When the barrier layer covers a portion of the surface of the primary particles and / or the secondary particles, the barrier layer may exist in an island form.

[0154] The average thickness of the barrier layer covering the surface of the primary particles is preferably 0.1 nm to 1 μm.

[0155] If the average thickness of the barrier layer covering the primary particles is less than 0.1 nm, it is difficult to sufficiently suppress the elution of transition metals from the primary particles. On the other hand, if the average thickness of the barrier layer covering the primary particles is greater than 1 μm, there is a risk that the surface kinetics of the primary particles will decrease or the electrical conductivity of the secondary particles will decrease.

[0156] In one embodiment, a barrier layer may be present on at least a portion of the surface of at least one of the first lithium manganese oxide and the second lithium manganese oxide. This barrier layer can suppress or mitigate the elution of transition metals from the first lithium manganese oxide and / or the second lithium manganese oxide. In order to suppress or mitigate the elution of transition metals from the first lithium manganese oxide and the second lithium manganese oxide, the barrier layer may be present on the entire surface of the first lithium manganese oxide and the second lithium manganese oxide.

[0157] The barrier layer may contain an oxide comprising at least one selected from metallic elements, metalloid elements, and phosphorus (P).

[0158] In one embodiment, the barrier layer may contain a first oxide represented by the following chemical formula 2.

[0159] [Chemical formula 2] Li c B d M3 e O f Here, M3 is at least one selected from Ni, Mn, Co, Al, Nb, 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, where 0 ≤ c ≤ 8, 0 <d≦8、0≦e≦8、2≦f≦13である。

[0160] When the first oxide represented by chemical formula 2 is a borate-based compound or an LBO (lithium borate)-based compound, non-restrictive examples of the first oxide include B2O3, Li2O-B2O3, Li3BO3, Li2B4O7, Li2B2O7, and Li2B8O 13 These are some examples. Furthermore, the first oxide may have a composition in which the borate-based compound or lithium borate-based compound described above is selectively doped with a different element, M3.

[0161] In this case, a gradient may be formed in which the concentration of at least one selected from B and M3 decreases from the barrier layer toward the lithium manganese-based oxide core by diffusion and / or doping of the first oxide contained in the barrier layer.

[0162] Such a concentration gradient acts as a pathway for lithium ions to move within and between primary particles, thereby improving the transport / diffusion efficiency of lithium ions mediated by the primary particles.

[0163] In other embodiments, the barrier layer may further include a second oxide represented by Chemical Formula 3 below.

[0164] [Chemical Formula 3] Li g M4 h O i Here, M4 is at least one selected from Ni, Mn, Co, Al, Nb, 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, 0 ≦ g ≦ 8, 0 ≦ h ≦ 8, 2 ≦ i ≦ 13, and the case where g and h are both 0 is excluded.

[0165] Non-limiting examples of the second oxide represented by Chemical Formula 3 include Li g Zr h O i 、Li g Ti h O i 、Li g Ni h O i 、Li g Nb h O i 、Li g Co h O i 、Li g Si h O i 、Li g Al h O i 、Co h O i 、Mn h O i 、Al h O i 、Si h O i 、Zr h O i 、Ti h O i and so on.

[0166] At this time, a gradient in which the concentration of M4 decreases from the barrier layer toward the core of the lithium manganese oxide may be formed due to diffusion and / or doping of the second oxide contained in the barrier layer.

[0167] In still another embodiment, the barrier layer may include a third oxide represented by the following Chemical Formula 4.

[0168] [Chemical Formula 4] Li j M5 k (P l O m ) n Here, M5 is at least one selected from Ni, Mn, Co, Al, 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, 0 ≦ j ≦ 10, 0 ≦ k ≦ 8, 0 < l ≦ 4, 0 < m ≦ 10, 0 < n ≦ 13, and the case where j and k are both 0 is excluded.

[0169] Non-limiting examples of the third oxide represented by Chemical Formula 4 include Li j (P l O m ) n 、Li j Al k (P l O m ) n 、Al k (P l O m ) n 、(P l O m ) n Li j Mn k (P l O m ) n 、Mn k (P l O m ) n 、Li j Ni k (P l O m )n Ni k (P l O m ) n These are some examples.

[0170] In this case, a gradient may be formed in which the concentration of at least one selected from M5 and P decreases from the barrier layer toward the lithium manganese-based oxide core due to the diffusion and / or doping of the third oxide contained in the barrier layer.

[0171] It is known that a decrease in charge / discharge capacity or voltage decay during charge / discharge cycles of lithium secondary batteries using OLO is induced by a phase transition due to the migration of transition metals in lithium manganese oxides. For example, in layered crystalline lithium manganese oxides, if a phase transition is induced by the unintended migration of transition metals, a spinel or similar crystalline structure may be generated entirely and / or partially within the lithium manganese oxide.

[0172] However, unlike the spinel phase formed by a phase transition due to the migration of transition metals in the lithium manganese oxide, when a barrier layer is formed on the surface of the lithium manganese oxide and at the same time a spinel phase is formed on the surface of the primary and / or secondary particles, such a spinel phase not only contributes to the surface stabilization of the lithium manganese oxide but can also act as a two-dimensional and / or three-dimensional pathway for the diffusion of lithium ions within the lithium manganese oxide.

[0173] This allows the lithium manganese oxide to exhibit an appropriate level of electrical conductivity even when the surfaces of the primary and / or secondary particles are covered with the barrier layer, by forming the barrier layer which exists to suppress the elution of transition metals from the primary and / or secondary particles, thereby ensuring that a spinel phase compound is present on the surface of the lithium manganese oxide.

[0174] Furthermore, if necessary, the barrier layer may contain at least two oxides selected from the first to third oxides in order to effectively suppress or mitigate the elution of transition metals from the lithium manganese oxide while simultaneously improving the surface kinetics of the lithium manganese oxide.

[0175] The content of the main constituent elements of the barrier layer, calculated based on all metal elements excluding lithium present in the lithium manganese oxide, is preferably greater than 0.1 mol% and less than 5 mol%. Here, if the first oxide is present in the barrier layer, the main constituent elements of the barrier layer are boron (B) and M3; if the second oxide is present in the barrier layer, the main constituent element of the barrier layer is M4; and if the third oxide is present in the barrier layer, the main constituent element of the barrier layer is M5. Furthermore, if any combination of the first to third oxides is present in the barrier layer, the main constituent elements of the barrier layer are selected from boron (B), M3, M4, and M5.

[0176] The fact that the content of the main constituent elements of the barrier layer is less than 0.1 mol% means that a barrier layer is not adequately formed on the surface of the lithium manganese oxide to suppress or mitigate the elution of transition metals. As a result, it is difficult to effectively prevent the acceleration of the life degradation of the lithium secondary battery due to the deposition of impurities on the positive and / or negative electrodes by transition metals eluted from the lithium manganese oxide.

[0177] On the other hand, if the content of the main constituent elements of the barrier layer is 5 mol% or more, it can actually lower the surface kinetics of the lithium manganese-based oxide, which may result in a decrease in electrochemical properties compared to when the main constituent elements of the barrier layer are present in appropriate amounts.

[0178] Furthermore, in order to effectively suppress or mitigate the elution of transition metals from the surface of the lithium manganese oxide without reducing its surface kinetics, it is more preferable that the content of the main constituent elements of the barrier layer, calculated based on all metal elements excluding lithium present in the lithium manganese oxide, be 1 ± 0.1 mol% or more and 3 ± 0.1 mol% or less.

[0179] Lithium-ion rechargeable battery According to another aspect of the present invention, a positive electrode can be provided comprising a positive electrode current collector and a layer of the positive electrode active material described above formed on the positive electrode current collector. Here, the positive electrode active material layer may contain a lithium manganese-based oxide according to the various embodiments of the present invention described above as the positive electrode active material.

[0180] Therefore, a detailed explanation of lithium manganese oxides will be omitted, and only the remaining components not mentioned above will be described below. Also, for convenience, the lithium manganese oxides mentioned above will be referred to as the positive electrode active material below.

[0181] The positive electrode current collector is not particularly limited as long as it does not induce chemical changes in the battery and is conductive. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel with a surface treatment of carbon, nickel, titanium, silver, etc. may be used. The positive electrode current collector may also have a thickness of 3 to 500 μm, and fine irregularities can be formed on the surface of the current collector to increase the adhesion strength of the positive electrode active material. For example, it may be used in various forms such as film, sheet, foil, net, porous material, foam, or nonwoven fabric.

[0182] The positive electrode active material layer may be manufactured by applying a positive electrode slurry composition, which includes a conductive material and, if necessary, a binder, together with the positive electrode active material, to the positive electrode current collector.

[0183] In this case, the positive electrode active material may be present in an amount of 80 wt% to 99 wt%, more specifically, 85 wt% to 98.5 wt%, relative to the total weight of the positive electrode active material layer. When present within this content range, excellent capacity characteristics can be observed, but the material is not necessarily limited to this range.

[0184] The conductive material is used to impart conductivity to the electrodes and can be used without particular limitations as long as it has electronic conductivity without causing chemical changes in the battery it is configured in. 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 powders or metal fibers such as copper, nickel, aluminum, and silver, conductive whiskers such as zinc oxide and potassium titanate, conductive metal oxides such as titanium oxide, or conductive polymers such as polyphenylene derivatives. One of these may be used alone or a mixture of two or more. The conductive material may be included in an amount of 0.1 wt% to 15 wt% relative to the total weight of the positive electrode active material layer.

[0185] The binder plays a role in improving the adhesion between positive electrode active material particles and the adhesion between the positive electrode 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, of which one or more may be used. The binder may be included in an amount of 0.1 to 15 wt% relative to the total weight of the positive electrode active material layer.

[0186] The positive electrode may be manufactured by a conventional positive electrode manufacturing method, except that the positive electrode active material is used. Specifically, the positive electrode may be manufactured by applying a positive electrode slurry composition, prepared by dissolving or dispersing the positive electrode active material and selectively a binder and conductive material in a solvent, onto a positive electrode current collector, followed by drying and rolling.

[0187] The solvent may be any solvent commonly used in the art, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water, and one or more of these may be used individually or in mixtures of two or more. The amount of solvent used should be such that it dissolves or disperses the cathode active material, conductive material, and binder, and then provides a viscosity that allows for excellent thickness uniformity during coating for cathode manufacturing, taking into consideration the coating thickness and production yield of the slurry.

[0188] In other embodiments, the positive electrode may be manufactured by casting the positive electrode slurry composition onto a separate support, peeling it off the support, and then laminating the resulting film onto the positive electrode current collector.

[0189] Furthermore, according to yet another aspect of the present invention, an electrochemical element including the aforementioned positive electrode may be provided. Specifically, the electrochemical element may be a battery, a capacitor, or the like, and more specifically, a lithium secondary battery.

[0190] The lithium secondary battery may specifically include a positive electrode, a negative electrode positioned opposite the positive electrode, and a separator and electrolyte interposed between the positive and negative electrodes. Here, since the positive electrode is as described above, for convenience, a detailed explanation will be omitted, and only the remaining components not mentioned above will be described in detail below.

[0191] The lithium secondary battery may further selectively include a battery container for housing the electrode assembly comprising the positive electrode, the negative electrode, and the separator, and a sealing member for sealing the battery container.

[0192] The negative electrode may include a negative electrode current collector and a negative electrode active material layer located on the negative electrode current collector.

[0193] The negative electrode current collector is not particularly limited as long as it has high conductivity without inducing chemical changes in the battery. 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. The negative electrode current collector may also typically have a thickness of 3 μm to 500 μm, and, similar to the positive electrode current collector, fine irregularities can be formed on the surface of the current collector to strengthen the bonding force of the negative electrode active material. For example, it may be used in various forms such as film, sheet, foil, net, porous material, foam, and nonwoven fabric.

[0194] The negative electrode active material layer may be manufactured by applying a negative electrode slurry composition, which includes the negative electrode active material together with a conductive material and, if necessary, a selective binder, to the negative electrode current collector.

[0195] As the negative electrode active material, a compound capable of reversible intercalation and 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 lithium-doped and dedoped metal oxides such as (0<β<2), SnO2, vanadium oxide, and lithium vanadium oxide, or composites containing the metallic compound and carbonaceous material, such as Si-C composites or Sn-C composites. One or more of these mixtures may be used. A metallic lithium thin film may also be used as the negative electrode active material. Furthermore, low-crystalline carbon and high-crystalline carbon may all be used as the carbon material. Typical examples of low-crystalline carbon include soft carbon and hard carbon, while typical examples of high-crystalline carbon include amorphous, plate-like, flaky, 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.

[0196] The aforementioned negative electrode active material may be present in an amount of 80 wt% to 99 wt% based on the total weight of the negative electrode active material layer.

[0197] The binder may be added in an amount of 0.1 wt% to 10 wt% based on the total weight of the negative electrode active material layer, as a component that assists in bonding between the conductive material, active material, and current collector. 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.

[0198] The conductive material may be added as a component to further improve the conductivity of the negative electrode active material, 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 a conductive material is not particularly limited as long as it has conductivity without inducing a chemical change 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, and thermal black, conductive fibers such as carbon fibers and metal fibers, metal powders such as carbon fluoride, aluminum, and nickel powder, conductive whiskers such as zinc oxide and potassium titanate, conductive metal oxides such as titanium oxide, and conductive materials such as polyphenylene derivatives may be used.

[0199] In one embodiment, the negative electrode active material layer may be manufactured by coating a negative electrode slurry composition, which is prepared by dissolving or dispersing a negative electrode active material and a binder and conductive material selectively in a solvent, onto a negative electrode current collector and then drying it, or by casting the negative electrode slurry composition onto a separate support, peeling it off the support, and then laminating the resulting film onto the negative electrode current collector.

[0200] In other embodiments, the negative electrode active material layer may be manufactured by coating a negative electrode slurry composition, prepared by dissolving or dispersing a negative electrode active material and a binder and conductive material selectively in a solvent, onto a negative electrode current collector and drying it, or by casting the negative electrode slurry composition onto a separate support, peeling it off the support, and laminating the resulting film onto the negative electrode current collector.

[0201] On the other hand, in the lithium secondary battery, the separator separates the negative electrode and the positive electrode and provides a passage for lithium ions to move. Generally, any separator commonly used in lithium secondary batteries can be used without particular limitations, and it is especially preferable that the separator has low resistance to ion movement of the electrolyte and excellent electrolyte moisture absorption capacity. Specifically, porous polymer films, such as ethylene homopolymers, propylene homopolymers, ethylene / butene copolymers, ethylene / hexene copolymers, and ethylene / methacrylate copolymers, or laminated structures of two or more layers thereof may be used. Alternatively, ordinary porous nonwoven fabrics, such as nonwoven fabrics made of high-melting-point glass fibers or polyethylene terephthalate fibers, may be used. Furthermore, to ensure heat resistance or mechanical strength, coated separators containing ceramic components or polymeric substances may be used, and may be selectively used as single-layer or multi-layer structures.

[0202] Furthermore, the electrolytes used in the present invention include, but are not limited to, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in the manufacture of lithium secondary batteries.

[0203] Specifically, the electrolyte may include an organic solvent and a lithium salt.

[0204] The organic solvent can be any solvent that serves as a medium through which ions involved in the electrochemical reaction of the battery can move, without any particular limitations. Specifically, the organic solvent may be an ester solvent such as methyl acetate, ethyl acetate, γ-butyrolactone, or ε-caprolactone; an ether solvent such as dibutyl ether or tetrahydrofuran; a ketone solvent such as cyclohexanone; an aromatic hydrocarbon solvent such as benzene or fluorobenzene; dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), or propylene carbonate (propylene Carbonate solvents such as carbonate (PC), alcohol solvents such as ethyl alcohol and isopropyl alcohol, nitriles such as R-CN (where R is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms, and may include a double-bonded aromatic ring or ether bond), amides such as dimethylformamide, dioxolanes such as 1,3-dioxolane, or sulfolanes may be used. Among these, carbonate solvents are preferred, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate) having high ionic conductivity and high dielectric constant that can improve the charge and discharge performance of the battery, and a low-viscosity linear carbonate compound (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate) is more preferred. In this case, the electrolyte performance can be improved by mixing the cyclic carbonate and the linear carbonate in a volume ratio of about 1:1 to about 1:9.

[0205] The lithium salt may be any compound capable of providing lithium ions for use in a lithium secondary battery, without any particular limitations. Specifically, the lithium salt may be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3), LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2, etc. The concentration of the lithium salt is preferably within the range of 0.1 to 2.0 M. When the concentration of the lithium salt falls within this range, the electrolyte has appropriate conductivity and viscosity, so it can exhibit excellent electrolyte performance and lithium ions can move effectively.

[0206] In the present invention, when the electrolyte used is a solid electrolyte, a solid inorganic electrolyte such as a sulfide-based solid electrolyte, oxide-based solid electrolyte, nitride-based solid electrolyte, or halogen-based solid electrolyte may be used, and preferably a sulfide-based solid electrolyte may be used.

[0207] As the material for the sulfide-based solid electrolyte, a solid electrolyte containing Li, element X (where 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 sulfide-based solid electrolyte materials include Li2S-P2S5, Li2S-P2S-LiX (where 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, Li2S-P2S5-ZmSn (where m and n are integers and Z is Ge, Zn, or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, and Li2S-SiS2-Li p MO q(Here, p and q are integers, and M is P, Si, Ge, B, Al, Ga, or In.)

[0208] The solid electrolyte, preferably a sulfide-based solid electrolyte, may be amorphous or crystalline, or a mixture of amorphous and crystalline materials.

[0209] As a material for oxide-based solid electrolytes, Li7La3Zr2O 12 Li 7-x La3Zr 1-x Nb x O 12 Li 7-3x La3Zr2Al x O 12 Li 3x La 2 / 3-x TiO3, Li 1+x Al x Ti 2-x (PO4)3, Li 1+x Al x Ge 2-x (PO4)3, Li3PO4, Li 3+x PO 4-x N x (LiPON), Li 2+2x Zn 1-x Examples include GeO4 (LISICON).

[0210] The aforementioned solid electrolyte may be arranged as a separate layer (solid electrolyte layer) between the positive electrode and the negative electrode. Furthermore, the solid electrolyte may be partially included in the positive electrode active material layer of the positive electrode independently of the solid electrolyte layer, or partially included in the negative electrode active material layer of the negative electrode independently of the solid electrolyte layer.

[0211] In addition to the electrolyte components, the electrolyte may further contain one or more additives for the purpose of improving battery life characteristics, suppressing the decrease in battery capacity, and improving battery discharge capacity, such as haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glyme, hexaphosphate triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride. In this case, the additive may be present in an amount of 0.1 to 5 wt% relative to the total weight of the electrolyte.

[0212] As described above, the lithium secondary battery containing the positive electrode active material according to the present invention exhibits excellent discharge capacity, output characteristics, and life characteristics in a stable manner, making it useful in portable devices such as mobile phones, laptop computers, and digital cameras, as well as in the electric vehicle field, such as hybrid electric vehicles (HEVs).

[0213] The external shape of the lithium secondary battery according to the present invention is not particularly limited, but it may be cylindrical, rectangular, pouch-shaped, or coin-shaped using a can. Furthermore, the lithium secondary battery can be used not only as a battery cell used as a power source for small devices, but may also be preferably used as a unit battery in medium-to-large battery modules containing multiple battery cells.

[0214] According to yet another aspect of the present invention, a battery module and / or a battery pack including the lithium secondary battery as a unit cell can be provided.

[0215] The battery module or battery pack can be used as a power source for one or more medium-to-large devices, including power tools, electric vehicles (EVs), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEVs), or power storage systems.

[0216] The present invention will be described in more detail below with reference to examples. However, these examples are for illustrative purposes only and should not be construed as limiting the scope of the present invention.

[0217] Manufacturing Example 1. Manufacturing of positive electrode active material Manufacturing Example 1-1. Production of Lithium Manganese Oxide No. 1 (A-1) (a) Production of precursors An aqueous solution of NiSO4·6H2O and MnSO4·H2O mixed in a molar ratio of 40:60, along with NaOH and NH4OH, was added to the reactor while stirring. The reactor temperature was maintained at 45°C, and the precursor synthesis reaction was carried out while N2 gas was introduced into the reactor. After the reaction was complete, the product was washed and dehydrated, and Ni 0.4 Mn 0.6 A hydroxide precursor with an (OH)2 composition (average particle size 3.0 μm; known methods can be used to adjust the particle size) was obtained.

[0218] (b) First heat treatment After heating an O2 atmosphere furnace at a rate of 2°C / min, the temperature was maintained at 550°C, and the hydroxide precursor obtained in step (a) was heat-treated for 5 hours, followed by furnace cooling to obtain the oxide precursor.

[0219] (c) Second heat treatment The oxide precursor obtained in step (b) above and the lithium raw material LiOH (Li / Metal molar ratio = 1.25) were mixed to prepare a mixture. Next, the firing furnace in an O2 atmosphere was heated at a rate of 2 °C / min, then maintained at 900 °C, and the mixture was heat-treated for 8 hours, followed by furnace cooling to obtain the first lithium manganese-based oxide (A-1).

[0220] Manufacturing Example 1-2. Manufacturing of Lithium Manganese Oxide No. 1 (A-2) (a) Production of the precursor An aqueous solution in which NiSO4·6H2O and MnSO4·H2O were mixed at a molar ratio of 40:60, NaOH and NH4OH were introduced into the reactor while stirring. The temperature in the reactor was maintained at 45 °C, and the precursor synthesis reaction was carried out while introducing N2 gas into the reactor. After completion of the reaction, washing and dehydration were performed to obtain a hydroxide precursor with a Ni 0.4 Mn 0.6 (OH)2 composition (average particle size 3.0 μm, and known methods can be used for adjusting the particle size).

[0221] (b) Precursor coating An NiSO4·6H2O aqueous solution, NaOH and NH4OH were introduced into the reactor in which the precursor obtained in step (a) was being stirred. At this time, NiSO4·6H2O was weighed to be 5 mol% and then introduced. After completion of the reaction, washing and dehydration were performed, and then drying was carried out at 150 °C for 14 hours to obtain a coated precursor.

[0222] ​​​​​​​​​​​Next, the mixture was heat-treated in an O2 atmosphere furnace at a rate of 2°C / min, maintained at 900°C for 8 hours, and then furnace-cooled to obtain the first lithium manganese oxide (A-2). TEM / EDS analysis of the first lithium manganese oxide (A-2) confirmed that, as the precursor coating using Ni was added in step (b), a gradient was formed in which the concentration of Ni increased from the center to the surface and the concentration of Mn decreased.

[0224] Manufacturing Example 1-3. Production of Lithium Manganese Oxide (A-3) (a) Production of precursors An aqueous solution of NiSO4·6H2O and MnSO4·H2O mixed in a molar ratio of 40:60, along with NaOH and NH4OH, was added to the reactor while stirring. The reactor temperature was maintained at 45°C, and the precursor synthesis reaction was carried out while N2 gas was introduced into the reactor. After the reaction was complete, the product was washed and dehydrated, and Ni 0.4 Mn 0.6 A hydroxide precursor with an (OH)2 composition (average particle size 3.0 μm; known methods can be used to adjust the particle size) was obtained.

[0225] (b) Precursor coating In the reactor where the precursor obtained in step (a) was being stirred, an aqueous solution of NiSO4·6H2O, NaOH, and NH4OH were added. At this time, the NiSO4·6H2O was weighed to a concentration of 5 mol% before being added. After the reaction was complete, the mixture was washed and dehydrated, and then dried at 150°C for 14 hours to obtain the coated precursor.

[0226] (c) First heat treatment After heating an O2 atmosphere furnace at a rate of 2°C / min, the temperature was maintained at 550°C, and the hydroxide precursor obtained in step (b) was heat-treated for 5 hours, followed by furnace cooling to obtain the oxide precursor.

[0227] (d) Second heat treatment The oxide precursor obtained in step (c) above and the lithium raw material LiOH (Li / Metal molar ratio = 1.25) were mixed to prepare a mixture. Next, the mixture was heat-treated in an O2 atmosphere furnace at a rate of 2°C / min, maintained at 900°C for 8 hours, and then furnace-cooled to obtain a lithium-rich lithium manganese oxide. TEM / EDS analysis of the lithium manganese oxide confirmed that, as the precursor coating using Ni was added in step (b), a gradient was formed in which the concentration of Ni increased from the center to the surface and the concentration of Mn decreased.

[0228] (e) Third heat treatment (barrier layer formation) The lithium manganese oxide obtained in step (d) and H3BO3 weighed so that the boron content based on the metallic element, excluding lithium from the lithium manganese oxide, is 2.0 mol%, were mixed. Then, the mixture was heat-treated in a calcination furnace under an O2 atmosphere for 8 hours, increasing the temperature to 400°C at a rate of 4.4°C per minute, followed by classification and crushing to obtain a first lithium manganese oxide (A-3) having a barrier layer containing a B-containing compound formed on its surface.

[0229] Manufacturing Example 1-4. Production of Lithium Manganese-based Oxide (B-1) (a) Production of precursors An aqueous solution of NiSO4·6H2O and MnSO4·H2O mixed in a molar ratio of 40:60, along with NaOH and NH4OH, was added to the reactor while stirring. The reactor temperature was maintained at 45°C, and the precursor synthesis reaction was carried out while N2 gas was introduced into the reactor. After the reaction was complete, the product was washed and dehydrated, and Ni 0.4 Mn 0.6 A hydroxide precursor with an (OH)2 composition (average particle size 12.0 μm; known methods can be used to adjust the particle size) was obtained.

[0230] (b) First heat treatment After heating an O2 atmosphere furnace at a rate of 2°C / min, the temperature was maintained at 550°C, and the hydroxide precursor obtained in step (a) was heat-treated for 5 hours, followed by furnace cooling to obtain the oxide precursor.

[0231] (c) Second heat treatment The oxide precursor obtained in step (b) above and the lithium raw material LiOH (Li / Metal molar ratio = 1.25) were mixed to prepare a mixture. Next, the mixture was heat-treated in an O2 atmosphere furnace at a rate of 2°C / min, maintained at 900°C for 8 hours, and then furnace-cooled to obtain a second lithium manganese oxide (B-1).

[0232] Manufacturing Example 1-5. Production of Lithium Manganese Oxide II (B-2) (a) Production of precursors An aqueous solution of NiSO4·6H2O and MnSO4·H2O mixed in a molar ratio of 40:60, along with NaOH and NH4OH, was added to the reactor while stirring. The reactor temperature was maintained at 45°C, and the precursor synthesis reaction was carried out while N2 gas was introduced into the reactor. After the reaction was complete, the product was washed and dehydrated, and Ni 0.4 Mn 0.6 A hydroxide precursor with an (OH)2 composition (average particle size 12.0 μm; known methods can be used to adjust the particle size) was obtained.

[0233] (b) First heat treatment After heating an O2 atmosphere furnace at a rate of 2°C / min, the temperature was maintained at 550°C, and the hydroxide precursor obtained in step (a) was heat-treated for 5 hours, followed by furnace cooling to obtain the oxide precursor.

[0234] (c) Second heat treatment The oxide precursor obtained in step (b) above and the lithium raw material LiOH (Li / Metal molar ratio = 1.25) were mixed to prepare a mixture. Next, the firing furnace in an O2 atmosphere was heated at a rate of 2 °C / min, and then maintained at 900 °C. After subjecting the mixture to heat treatment for 8 hours, it was furnace cooled to obtain a lithium manganese oxide.

[0235] (d) Third heat treatment (barrier layer formation) The lithium manganese oxide obtained in step (c) was mixed with H3BO3 weighed so that the content of boron based on the metal element excluding lithium in the lithium manganese oxide was 2.0 mol%. Then, in a firing furnace, under an O2 atmosphere, it was heated to 400 °C at a rate of 4.4 °C per minute and subjected to heat treatment for 8 hours. After classification and crushing, a second lithium manganese oxide (B-2) with a barrier layer containing a B-containing compound formed on the surface was obtained.

[0236] Manufacturing Example 2. Manufacturing of Cathode Active Material The first lithium manganese oxide and the second lithium manganese oxide produced according to Production Example 1 were mixed at the weight ratios described in Table 1 below to produce a positive electrode active material.

[0237]

Table 1

[0238] Manufacturing Example 3: Manufacturing of Lithium-ion Secondary Batteries (Half-Cells) 90 wt% of each positive electrode active material produced according to Production Example 2, 4.5 wt% of carbon black, and 5.5 wt% of a PVDF binder were dispersed in N-methyl-2-pyrrolidone (NMP) to produce a positive electrode slurry. The positive electrode slurry was uniformly coated on 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.

[0239] A half-cell was manufactured using a lithium foil as the counter electrode for the positive electrode, a porous polyethylene membrane (Celgard 2300, thickness: 25 μm) as the separator, and an electrolyte containing ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate mixed in a volume ratio of 2:4:4, with LiPF6 present at a concentration of 1.15 M.

[0240] Manufacturing Example 4. Manufacturing of Lithium-ion secondary batteries (full cells) A cathode slurry was prepared by dispersing 90 wt% of the cathode active material, 4.5 wt% of carbon black, and 5.5 wt% of the PVDF binder produced by manufacturing example 2 in N-methyl-2-pyrrolidone (NMP). The cathode slurry was uniformly coated onto a 15 μm thick aluminum thin film and vacuum-dried at 135°C to produce a cathode for a lithium secondary battery.

[0241] A graphite electrode was used as the counter electrode to the positive electrode, a porous polyethylene membrane (Celgard 2300, thickness: 25 μm) as the separator, and a full cell was manufactured using an electrolyte solution containing ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate mixed in a volume ratio of 2:4:4, with LiPF6 present at a concentration of 1.15 M.

[0242] Experimental Example 1. XPS Analysis of Lithium Manganese Oxides XPS analysis was performed on each of the lithium manganese oxides produced according to Production Examples 1-1 to 1-5 to measure the content of the target element contained in the lithium manganese oxide.

[0243] Specifically, the change in the content of the target element was measured from the surface of the lithium manganese oxide (secondary particles) toward the lithium manganese oxide (secondary particles) while increasing the etching time on the surface of the lithium manganese oxide (secondary particles) using the XPS depth profile analysis method (Ion energy 2000 eV, spot size 200 μm).

[0244] The results of the XPS analysis are shown in Tables 2 and 3 below.

[0245] [Table 2] *The target element content (at%) is calculated based on all elements excluding lithium in the lithium manganese oxide.

[0246] Referring to the results in Table 2 above, in the cases of A-2 and A-3, it can be confirmed that during the production of lithium manganese oxides, a gradient is formed in which the concentration of Ni increases from the center to the surface and the concentration of Mn decreases as a precursor coating using Ni is added.

[0247] Furthermore, it can be confirmed that the nickel content relative to the total transition metals present on the surface of A-2 and A-3 is greater than the nickel content relative to the total transition metals present on the surface of B-1 and B-2.

[0248] [Table 3] *The target element content (at%) is calculated based on all elements excluding lithium in the lithium manganese oxide.

[0249] Referring to the results in Table 3, it can be confirmed that in cases A-3 and B-2, the content of the target element present on the surface is 20 at% or more when the third heat treatment (barrier layer formation) is performed during the production of lithium manganese oxide. The fact that the content of the target element derived from the raw material used during the third heat treatment is 20 at% or more on the surface of the lithium manganese oxide (secondary particles) is presumed to be due to the formation of a barrier layer on the surface of the lithium manganese oxide (secondary particles).

[0250] Experimental Example 2. Measurement of Compression Density of Cathode Active Material Three g of each cathode active material produced according to Production Example 2 was pressurized at 4.5 tons for 5 seconds using a pelletizer, and then its compressed density was measured.

[0251] The measurement results are shown in Table 4 below.

[0252] [Table 4]

[0253] Referring to the results in Table 4, it can be confirmed that the 4.5-ton compressed density of Examples 1 to 6, which are bimodal positive electrode active materials in which the first lithium manganese oxide and the second lithium manganese oxide are mixed, is greater than that of Comparative Examples 1 and 2, which are unimodal positive electrode active materials.

[0254] Experimental Example 3. Evaluation of the electrochemical properties of lithium secondary batteries (half-cells). For the lithium secondary batteries (half-cells) manufactured in Manufacturing Example 3, the initial discharge capacity, capacity per unit volume, and rate characteristics (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.

[0255] The capacity per unit volume was calculated by multiplying the initial discharge capacity by the compressive density (4.5-ton compressive density in Table 4).

[0256] The measurement results are shown in Table 5 below.

[0257] [Table 5]

[0258] Referring to the half-cell evaluation results in Table 5, it can be confirmed that the initial discharge capacity and rate characteristics of Examples 1 to 6, which are bimodal positive electrode active materials in which the first lithium manganese oxide and the second lithium manganese oxide are mixed, are improved compared to Comparative Examples 1 and 2, which are unimodal positive electrode active materials.

[0259] In particular, it can be confirmed that the capacity per unit volume of Examples 1 to 6, which are bimodal positive electrode active materials in which the first lithium manganese oxide and the second lithium manganese oxide are mixed, is significantly improved compared to Comparative Examples 1 and 2, which are unimodal positive electrode active materials. Furthermore, comparing the results of Examples 1 to 6, it can be confirmed that despite the similar compressive densities of the positive electrode active materials, the capacity per unit volume of Examples 2 to 6, and especially Examples 3 to 6, is even greater than that of Example 1.

[0260] Experimental Example 4. Evaluation of the electrochemical properties of a lithium secondary battery (full cell). Lithium secondary batteries (full cells) manufactured in Manufacturing Example 4 using the positive electrode active materials from Examples 1 and 6 were subjected to a 6-cycle conversion process at 25°C, a voltage range of 2.0V to 4.6V, and 0.2C / 0.2C using an electrochemical analyzer (Toyo, Toscat-3100). Following this, 500 charge-discharge cycles were performed at 25°C, a voltage range of 2.0V to 4.6V, and 1C / 1C. The initial (first cycle) discharge capacity and the ratio of the discharge capacity at the 100th, 300th, and 500th cycles to the initial discharge capacity (cycle capacity retention) were measured.

[0261] The measurement results are shown in Table 6 below.

[0262] [Table 6]

[0263] Referring to the full-cell evaluation results in Table 6, it can be confirmed that the cycle capacity retention rate in Example 1 is lower than in Example 6. This result is presumed to be due to the leaching of transition metals from the lithium manganese oxide, which caused an abnormal resistance phenomenon in the negative electrode, thereby accelerating the degradation of the lithium secondary battery's lifespan.

[0264] This confirms that the positive electrode active material according to Example 6 is suitable for lithium secondary batteries that require a longer lifespan.

[0265] Experimental Example 5. Experiment on transition metal elution Using the positive electrode active materials from Examples 1 and 6, the lithium secondary battery (full cell) manufactured in Manufacturing Example 4 was subjected to a 6-cycle conversion process at 25°C, a voltage range of 2.0V to 4.6V, and 0.2C / 0.2C using an electrochemical analyzer (Toyo, Toscat-3100). After that, the full cell was stabilized by 2 cycles of charge and discharge at 25°C, a voltage range of 2.0V to 4.6V, and 0.05C / 0.05C. Next, the full cell was disassembled, the negative electrode was washed with diethyl carbonate solvent, vacuum-dried at 60°C, and then recovered.

[0266] The negative electrode active material was separated from the recovered negative electrode Cu foil (current collector), and the separated negative electrode active material was subjected to ICP analysis to measure the Ni and Mn content contained in the negative electrode active material.

[0267] Furthermore, the lithium secondary batteries (full cells) manufactured in Manufacturing Example 4 using the positive electrode active materials from Examples 1 and 6 were subjected to a 6-cycle conversion process using an electrochemical analyzer (Toyo, Toscat-3100) at 25°C, a voltage range of 2.0V to 4.6V, and 0.2C / 0.2C. Following this, 500 charge-discharge cycles were performed at 25°C, a voltage range of 2.0V to 4.6V, and 1C / 1C. Next, each full cell was stabilized by 2-cycle charge-discharge at 25°C, a voltage range of 2.0V to 4.6V, and 0.05C / 0.05C. After disassembling the full cells, the negative electrodes were washed with diethyl carbonate solvent, vacuum-dried at 60°C, and then recovered.

[0268] The negative electrode active material was separated from the recovered negative electrode Cu foil (current collector), and the separated negative electrode active material was subjected to ICP analysis to measure the Ni and Mn content contained in the negative electrode active material.

[0269] The measurement results are shown in Table 7 below.

[0270] [Table 7]

[0271] Referring to the results in Table 7 above, it can be confirmed that the lower cycle capacity retention rate of Example 1 compared to Example 6, as predicted from Experimental Example 4, is due to the increased content of transition metals deposited in the negative electrode active material after chemical conversion and / or after 500 charge-discharge cycles.

[0272] Although embodiments of the present invention have been described above, a person with ordinary skill in the art can modify and change the present invention in various ways, such as by adding, changing, deleting, or adding components, without departing from the spirit of the invention as described in the claims, and this can also be said to be within the scope of the rights of the present invention.

Claims

1. A bimodal type positive electrode active material comprising a first lithium manganese oxide and a second lithium manganese oxide having different average particle sizes, The difference in average particle size between the first lithium manganese oxide and the second lithium manganese oxide is 3 μm or more. The first lithium manganese oxide and the second lithium manganese oxide are lithium-rich lithium manganese oxides 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. The manganese content in the total metal elements excluding lithium present in the first lithium manganese oxide and the second lithium manganese oxide is 50 mol% or more and less than 80 mol%. The average particle size of the first lithium manganese oxide is 2 μm to 6 μm. The average particle size of the second lithium manganese oxide is 7 μm to 14 μm. The first lithium manganese oxide and the second lithium manganese oxide are each independently represented by the following chemical formula 1-1, A positive electrode active material wherein the manganese content (mol%) relative to the total transition metal in the first lithium manganese-based oxide is smaller than the manganese content (mol%) relative to the total transition metal in the second lithium manganese-based oxide. [Chemical formula 1-1] rLi ２ MnO ３－ｂ″ X′ ｂ″ ・(1-r)Li ａ′ M1 ｘ′ M2 ｙ′ O ２－ｂ′ X ｂ′ (Here, M1 is Ni, M2 is at least one selected from 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. X and X' are halogens capable of substituting at least a portion of the oxygen present in the lithium manganese oxide, (0 < r ≤ 0.7, 0 < a' ≤ 1, 0 ≤ b' ≤ 0.1, 0 ≤ b'' ≤ 0.1, 0 < x' ≤ 1, 0 ≤ y' < 1, 0 < x' + y' ≤ 1)

2. The main peak in the volume-based particle size distribution graph for the first lithium manganese oxide (x-axis: particle size (μm), Y-axis: volume %) is located between 1 μm and 8 μm. The positive electrode active material according to claim 1, wherein the main peak of the volume-based particle size distribution graph (x axis: particle size (μm), Y axis: volume %) for the second lithium manganese-based oxide is located between 6 μm and 24 μm.

3. The positive electrode active material according to claim 1, wherein the first lithium manganese-based oxide and the second lithium manganese-based oxide in the positive electrode active material are contained in a weight ratio of 10:90 to 80:

20.

4. The positive electrode active material according to claim 1, wherein the first lithium manganese oxide and the second lithium manganese oxide each independently comprise at least one selected from nickel, cobalt, and manganese.

5. The first lithium manganese oxide and the second lithium manganese oxide are each independently lithium manganese oxides containing nickel and manganese. The positive electrode active material according to claim 1, wherein the manganese content (mol%) relative to the total transition metals present on the surface of the first lithium manganese-based oxide is smaller than the manganese content (mol%) relative to the total transition metals present on the surface of the second lithium manganese-based oxide.

6. The positive electrode active material according to claim 1, wherein at least one of the first lithium manganese-based oxide and the second lithium manganese-based oxide is a core-shell particle exhibiting at least one concentration gradient selected from nickel and manganese from the center toward the surface.

7. The positive electrode active material according to claim 6, wherein the core-shell particles exhibit a gradient in which the nickel concentration increases and the manganese concentration decreases from the center to the surface.

8. The first lithium manganese-based oxide is a core-shell particle exhibiting a concentration gradient of at least one selected from nickel and manganese from the center toward the surface. The positive electrode active material according to claim 1, wherein the second lithium manganese oxide is a particle in which the concentrations of nickel and manganese are constant from the center to the surface, or which exhibits a concentration gradient having a smaller slope than the concentration gradient that appears in the first lithium manganese oxide.

9. The positive electrode active material according to claim 1, wherein a barrier layer is present on at least a portion of the surface of at least one of the first lithium manganese-based oxide and the second lithium manganese-based oxide.

10. The first lithium manganese-based oxide is a core-shell particle exhibiting a concentration gradient from the core to the shell of at least one selected from nickel and manganese. The positive electrode active material according to claim 9, wherein a barrier layer is present on at least a portion of the surface of the shell.

11. The second lithium manganese oxide is a particle in which the concentrations of nickel and manganese are constant from the center to the surface, or which exhibits a concentration gradient having a smaller slope than the concentration gradient that appears in the first lithium manganese oxide. The positive electrode active material according to claim 9, wherein a barrier layer is present on at least a portion of the surface of the second lithium manganese-based oxide.

12. The positive electrode active material according to claim 9, wherein the barrier layer comprises an oxide containing at least one selected from a metallic element, a metalloid element, and phosphorus (P).

13. The positive electrode active material according to claim 9, wherein the barrier layer comprises at least one selected from a first oxide represented by the following chemical formula 2, a second oxide represented by the following chemical formula 3, and a third oxide represented by the following chemical formula 4. [Chemical formula 2] Li ｃ B ｄ M3 ｅ O ｆ (Here, M3 is at least one selected from Ni, Mn, Co, Al, Nb, 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. (0 ≤ c ≤ 8, 0 < d ≤ 8, 0 ≤ e ≤ 8, 2 ≤ f ≤ 13) [Chemical formula 3] Li ｇ M4 ｈ O ｉ (Here, M4 is at least one selected from Ni, Mn, Co, Al, Nb, 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. (Except when g and h are both 0, where 0 ≤ g ≤ 8, 0 ≤ h ≤ 8, and 2 ≤ i ≤ 13.) [Chemical formula 4] Li ｊ M5 ｋ (P ｌ O ｍ ) ｎ (Here, M5 is at least one selected from Ni, Mn, Co, Al, 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. (Except when j and k are both 0, where 0 ≤ j ≤ 10, 0 ≤ k ≤ 8, 0 < l ≤ 4, 0 < m ≤ 10, and 0 < n ≤ 13)

14. A positive electrode comprising the positive electrode active material according to any one of claims 1 to 13.

15. A lithium secondary battery using the positive electrode described in claim 14.

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