Cathode active material for lithium secondary battery, and lithium secondary battery comprising same

Abstract

The present invention relates to a cathode active material for a lithium secondary battery, the cathode active material comprising a lithium metal oxide having a composition with excess lithium and manganese, wherein the lithium metal oxide has a structure in which lithium layers and transition metal layers are alternately layered, the average interval between the lithium layers is 2.13 angstrom or more, and, in lithium metal oxide, the the molar ratio of cobalt to metals that exclude lithium is 0.05 or less.

Description

Cathode active material for lithium secondary batteries and lithium secondary batteries containing the same

[0001] The present invention relates to a positive electrode active material for a lithium secondary battery and a lithium secondary battery including the same.

[0002]

[0003] As the scope of application of lithium secondary batteries expands from small electronic devices to electric vehicles and power storage devices, the demand for cathode materials with excellent high energy density and high output characteristics is increasing.

[0004] Lithium-rich layered lithium transition metal oxides have a very high capacity of over 240 mAh / g and are attracting attention as candidates for next-generation cathode active materials, and research on them is actively being conducted recently.

[0005] However, lithium-rich layered lithium transition metal oxides utilize oxygen oxidation / reduction reactions in addition to transition metal oxidation / reduction due to the high lithium content and relatively low transition metal ratio in the structure compared to conventional positive electrode materials. Since this oxygen oxidation / reduction reaction is driven at a high voltage during the first charge, it causes electrolyte decomposition due to the high reactivity with the electrolyte on the surface, and since irreversible migration of transition metals occurs, the number of lithium reinsertion sites decreases during discharge, which lowers the initial efficiency. In addition, there is a problem that the cycle characteristics deteriorate due to the acceleration of phase decomposition due to oxygen gas generation and transition metal elution during subsequent cycles.

[0006]

[0007] Accordingly, one object of the present invention is to provide a lithium secondary battery cathode active material having not only excellent capacity as a lithium-excessive layered structure lithium metal oxide but also improved initial efficiency and lifespan characteristics, and a lithium secondary battery including the same.

[0008]

[0009] One embodiment of the present invention provides a cathode active material for a lithium secondary battery, comprising a lithium metal oxide having a lithium and manganese excess composition, wherein the lithium metal oxide has a structure in which lithium layers and transition metal layers are alternately laminated, an average spacing between the lithium layers is 2.13 Å or more, and the lithium metal oxide has a molar ratio of cobalt to a metal other than lithium of 0.05 or less.

[0010] The above lithium metal oxide may have a molar ratio of lithium to lithium metal oxide of 1.1 to 1.3.

[0011] The above lithium metal oxide may have a molar ratio of manganese to metals other than lithium of 0.55 to 0.7.

[0012] The lithium metal oxide may have a transition metal ratio in the lithium layer of 8.0% or less after the first full charge.

[0013] The above lithium metal oxide may be doped with a transition metal element (dopant) that does not have valence electrons in the d orbital.

[0014] The stabilization energy of the dopant in the above lithium layer may be less than 0 eV.

[0015] The transition metal element having no valence electrons in the above d orbital may be Al, Ti, Nb, Ta, W, Mo or a combination thereof.

[0016] A transition metal element that does not have an atomic electron in the above d orbital can be doped more into the lithium layer among the lithium layer and the transition metal layer.

[0017] The content of the transition metal element having no valence electrons in the above d orbital may be 0.2 to 1 mol% based on the total mole number of metals excluding lithium.

[0018] The above lithium metal oxide may have a molar ratio of nickel to metal other than lithium of 0.3 to 0.45.

[0019] The lithium metal oxide includes a first lithium metal oxide and a second lithium metal oxide, and the average particle diameter (D50) of the first lithium metal oxide may be larger than the average particle diameter (D50) of the second lithium metal oxide.

[0020] The above lithium metal oxide can be represented by the following chemical formula 1.

[0021] [Chemical Formula 1]

[0022] Li 1+a (Ni x Co y Mn z M1 w1 M2 w2 ) 1-a O2

[0023] In the above chemical formula 1, 0.1≤a≤0.3, 0.3≤x≤0.45, 0≤y≤0.05, 0.55≤z≤0.7, 0.002≤w1≤0.01, 0≤w2≤0.01, and x+y+z+w1+w2=1, M1 is Al, Ti, Nb, Ta, W, Mo or a combination thereof, and M2 is Zr, B, Y, Mg, Sc, Si, V, Fe, Ce, Hf, La, Sr, Sn, Sb, Zn, Cu, Ge, Ru, Ir or a combination thereof.

[0024]

[0025] Another embodiment of the present invention provides a positive electrode for a lithium secondary battery comprising the positive electrode active material described above.

[0026] Another embodiment of the present invention provides a lithium secondary battery including the positive electrode for the lithium secondary battery.

[0027]

[0028] A cathode active material for a lithium secondary battery according to one embodiment of the present invention is a lithium metal oxide having a lithium-excess composition, which not only has excellent capacity but also has improved structural stability due to a wide interlayer gap between lithium layers, thereby improving initial efficiency and lifespan characteristics.

[0029]

[0030] Figure 1 is a cross-sectional SEM image of a positive electrode active material manufactured according to Example 1 after FIB milling.

[0031] Figure 2 is a cross-sectional SEM image of the positive electrode active material manufactured according to Example 2 after FIB milling.

[0032] Figure 3 is a cross-sectional SEM image of the positive electrode active material manufactured according to Example 3 after FIB milling.

[0033] Figure 4 is a cross-sectional SEM image of the positive electrode active material manufactured according to Example 4 after FIB milling.

[0034] Figure 5 is a cross-sectional SEM image of the positive electrode active material manufactured according to Example 5 after FIB milling.

[0035] Figure 6 is a cross-sectional SEM image of the positive electrode active material manufactured according to Example 6 after FIB milling.

[0036] Figure 7 is a cross-sectional SEM image after FIB milling of a positive electrode active material manufactured according to Comparative Example 1.

[0037] Figure 8 is a graph showing the results of evaluating the initial charge capacity, initial discharge capacity, and initial efficiency of a lithium secondary battery according to Experimental Example 2.

[0038] Figure 9 is a graph showing the results of evaluating the life characteristics of a lithium secondary battery according to Experimental Example 2.

[0039] Figure 10 is a graph showing the results of evaluating the Mn release amount after 50 cycles according to Experimental Example 3.

[0040] Figure 11 is a graph showing the results of evaluating the Ni elution amount after 50 cycles according to Experimental Example 3.

[0041] The terms first, second, and third, etc., are used to describe, but are not limited to, various parts, components, regions, layers, and / or sections. These terms are used only to distinguish one part, component, region, layer, or section from another part, component, region, layer, or section. Accordingly, a first part, component, region, layer, or section described below may be referred to as a second part, component, region, layer, or section without departing from the scope of the present invention.

[0042] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the present invention. As used herein, the singular forms "singular" and "comprising" include plural forms as well, unless the context clearly dictates otherwise. The word "comprising" as used herein specifies a particular feature, region, integer, step, operation, element, and / or component, but does not exclude the presence or addition of other features, regions, integers, steps, operations, elements, and / or components.

[0043] When a part is referred to as being "on" or "over" another part, it can be directly on or over the other part, or there may be other parts intervening. Conversely, when a part is referred to as being "directly on" another part, there are no other parts intervening.

[0044] Although not defined otherwise, all terms, including technical and scientific terms, used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention pertains. Terms defined in commonly used dictionaries are further interpreted to have meanings consistent with the relevant technical literature and the present disclosure, and are not to be construed as ideal or overly formal unless otherwise defined.

[0045] Also, unless otherwise stated, % means weight%, and 1 ppm is 0.0001 weight%.

[0046] In this specification, the term "combination(s) thereof" described in the expression in the Makushi format means one or more mixtures or combinations selected from the group consisting of the components described in the expression in the Makushi format, and means including any one or more selected from the group consisting of said components.

[0047] Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement them. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0048]

[0049] 1. Positive active material

[0050] According to one embodiment of the present invention, a cathode active material for a lithium secondary battery comprises a lithium metal oxide having a lithium and manganese-rich composition. Although the lithium transition metal oxide having a lithium and manganese-rich composition has a low nickel content, it can involve oxidation / reduction reactions of not only transition metals but also anions (oxygen) during battery operation. In addition, since the excess lithium can exist in the transition metal layer in addition to the lithium layer, the insertion and deintercalation efficiency of lithium ions can be increased. As a result, the initial discharge capacity can be 240 mAh / g or more, which is significantly improved in capacity characteristics compared to a cathode material having a conventional NCM composition. In addition, it is economical because the content of relatively expensive nickel and cobalt can be reduced and the content of inexpensive manganese can be increased.

[0051] More specifically, the lithium metal oxide may have a molar ratio of lithium to lithium metal oxide of 1.1 to 1.3. As the molar ratio of lithium to lithium metal oxide increases, the amount of lithium that can participate in the insertion and deintercalation of lithium ions increases, thereby improving capacity characteristics. However, if the molar ratio of lithium to lithium metal oxide is too large, a problem of phase stability may occur due to excessive occurrence of oxygen oxidation / reduction reactions, which may result in a deterioration of life characteristics.

[0052] In addition, the lithium metal oxide may have a molar ratio of manganese to metals other than lithium of 0.55 to 0.7. If the manganese content is too low, manufacturing costs increase, the safety of the active material decreases, and the capacity improvement effect due to excessive manganese content may be minimal. If the manganese content is too high, the life characteristics may be deteriorated due to excessive use of oxygen oxidation / reduction reactions, and there may be a problem of manganese dissolution.

[0053] In addition, the lithium metal oxide may have a molar ratio of nickel to metals other than lithium of 0.3 to 0.45. When the nickel content satisfies the above range, the capacity, output, and life characteristics of the battery can be more preferably implemented. More specifically, if the nickel content is too low, the amount of oxygen oxidation / reduction reaction increases too much, which may deteriorate the life characteristics. If the nickel content is too high, the amount of oxygen oxidation / reduction reaction decreases, which may deteriorate the capacity and output characteristics.

[0054] Meanwhile, the lithium transition metal oxide according to one embodiment of the present invention is in the form of a secondary particle formed by agglomeration of a plurality of primary particles. As used herein, the term “primary particle” refers to the smallest particle unit that can be distinguished as a single lump when observing the cross-section of the positive electrode active material through a scanning electron microscope (SEM), and may be formed of a single crystal grain or a plurality of crystal grains. As used herein, the term “crystal grain” refers to a distinct region in which atoms in a primary particle form a lattice structure with a certain direction. At this time, the lithium transition metal oxide according to the present invention may include a hollow space in the secondary particle, and the primary particle may have a box-shaped, spherical, or plate-shaped shape.

[0055] However, the lithium metal oxide of the above composition utilizes the oxidation / reduction reaction of oxygen in addition to the oxidation / reduction of the transition metal due to the high lithium content and relatively low transition metal ratio in the structure compared to the conventional positive electrode active material. Since this oxidation / reduction reaction of oxygen is driven at a high voltage during the first charge, it causes electrolyte decomposition due to the high reactivity with the electrolyte on the surface, and since irreversible migration of the transition metal occurs, the number of lithium reinsertion sites decreases during discharge, which lowers the initial efficiency, and there is a problem that the life characteristics deteriorate due to the acceleration of oxygen gas generation during the subsequent cycle.

[0056]

[0057] Accordingly, the lithium metal oxide according to the present invention has a structure in which lithium layers and transition metal layers are alternately laminated, and the average spacing between the lithium layers is controlled to be 2.13 Å or more.

[0058] In conventional lithium metal oxides of standard composition, cation mixing occurs immediately after synthesis, in which some transition metals are substituted within the lithium layer. However, the amount of this cation mixing does not change as charging and discharging proceeds.

[0059] In contrast, in lithium metal oxides with a lithium and manganese excess composition, a large amount of transition metals (nickel, cobalt, manganese, etc.) in the transition metal layer migrate into the lithium layer from the point of utilizing oxygen oxidation / reduction during charging, and then migrate back to the original transition metal layer simultaneously with discharge. That is, as charging and discharging progress, a large amount of transition metals repeatedly migrate between the lithium layer and the transition metal layer. However, since this migration of transition metals due to charge and discharge is difficult to completely reversibly return to the original layer, some of the transition metals irreversibly accumulate in the lithium layer with repeated cycles, and thus the irreversible capacity increases. However, this causes changes in electrochemical characteristics, such as a decrease in initial efficiency due to the increase in irreversible capacity in the battery, and a deterioration in life characteristics due to a decrease in structural stability.

[0060] In contrast, the lithium metal oxide according to the present invention has a sufficiently wide average spacing between lithium layers, thereby suppressing the movement of transition metals between the lithium layers and transition metal layers during charging and discharging. Accordingly, the initial efficiency and life characteristics of the battery can be improved.

[0061] Meanwhile, the “average lithium interlayer spacing” in lithium metal oxide can be measured using XRD and computational chemistry methods.

[0062]

[0063] In addition, the lithium metal oxide may have a transition metal ratio within the lithium layer of 8.0% or less after the first full charge. That is, as mentioned above, the lithium metal oxide according to the present invention has a wide average spacing between lithium layers, so that the migration of transition metals (nickel, cobalt, manganese, etc.) within the transition metal layer into the lithium layer can be suppressed during charging. Accordingly, the ratio of the transition metal within the lithium layer after the first full charge can be sufficiently low as in the above range, and as a result, the initial efficiency and life characteristics of the battery can be improved. Meanwhile, the “transition metal ratio within the lithium layer” can be measured through XRD analysis.

[0064] The lithium metal oxide may be doped with a transition metal element (hereinafter also referred to as a “dopant” in the present specification) that does not have valence electrons in its d orbital. A transition metal element that does not have valence electrons in its d orbital has a larger ionic radius than nickel, cobalt, or manganese. In addition, when doped into the lithium metal oxide, the element located in the lithium layer among the lithium layer and the transition metal layer is energetically stable, so doping into the lithium layer occurs more easily. Therefore, when the transition metal element that does not have valence electrons in the d orbital of the lithium metal oxide is doped, the gap between the lithium layers can be widened, and the movement of nickel, cobalt, or manganese in the transition metal layer into the lithium layer can be suppressed. As a result, the structural stability of the lithium metal oxide can be improved, so that the initial efficiency and life characteristics of the battery can be improved.

[0065] More specifically, the transition metal element having no valence electrons in the d orbital may be, but is not necessarily limited to, Al, Ti, Nb, Ta, W, Mo, or a combination thereof.

[0066] Additionally, transition metal elements that do not have valence electrons in the d orbitals can be more heavily doped into the lithium layer among the lithium layer and the transition metal layer. This doping site preference can be confirmed through computational chemistry methods.

[0067] Accordingly, the stabilization energy of the dopant in the lithium layer may be less than 0 eV. Since the stabilization energy of the dopant in the lithium layer is sufficiently small, the dopant may prefer to be located in the lithium layer, thereby maintaining a wide interplanar distance. As a result, the structural stability of the lithium layer may be improved, so that the migration of the transition metal between the lithium layer and the transition metal layer according to charge and discharge may be suppressed, and as a result, the initial efficiency and life characteristics of the battery may be improved. Meanwhile, the stabilization energy of the dopant in the lithium layer may be measured using a computational chemistry method.

[0068] In addition, the content of the transition metal element having no valence electrons in the d orbital may be 0.2 to 1 mol%, and more specifically, 0.2 to 0.8 mol%, based on the total mole number of metals excluding lithium. If the content of the transition metal element having no valence electrons in the d orbital is too small, the aforementioned doping effect, that is, the effect of improving the initial efficiency and lifespan characteristics of the battery, may be minimal. If the content of the transition metal element having no valence electrons in the d orbital is too large, it is not effectively inserted into the structure but exists in an impurity state, which may rather lower the initial efficiency and lifespan characteristics of the battery.

[0069] In particular, the lithium metal oxide according to the present invention has a molar ratio of cobalt to metals other than lithium of 0.05 or less, and more specifically, 0.03, 0.01 or less, or may not contain cobalt. Cobalt is usually added in a certain amount to improve the structural stability of lithium metal oxide and thereby the lifespan and output characteristics of the battery, but it has the problem of being expensive. The lithium metal oxide according to the present invention can compensate for the effect of cobalt addition by controlling the average spacing between lithium layers by the doping agent as described above, so that even if the cobalt content is reduced to the above range, good electrochemical characteristics can be implemented. In addition, the inventors of the present invention confirmed that when the cobalt content is too high, the average spacing between lithium layers of the lithium metal oxide narrows when the doping agent is applied, and the ratio of transition metals in the lithium layers becomes too high after the first full charge, thereby deteriorating the structural stability of the active material. The inventors believe this is because the presence of cobalt ions inhibits the effective insertion of the dopant into the lithium layer. This result is noteworthy compared to conventional technologies that typically introduce cobalt in excess of a certain amount, even at a higher cost, to improve the lifespan characteristics of active materials.

[0070] Meanwhile, the lithium metal oxide includes a first lithium metal oxide and a second lithium metal oxide, and the average particle diameter (D50) of the first lithium metal oxide may be larger than the average particle diameter (D50) of the second lithium metal oxide. Accordingly, the positive electrode mixture density may be improved, thereby improving the battery energy density. In the present specification, the average particle diameter (D50) may be defined as a particle diameter corresponding to 50% of the volume accumulation amount in a particle diameter distribution curve of particles. The average particle diameter (D50) may be measured, for example, using a laser diffraction method.

[0071]

[0072] The above lithium metal oxide can be represented by the following chemical formula 1.

[0073] [Chemical Formula 1]

[0074] Li 1+a (Ni x Co y Mn z M1 w1 M2 w2 ) 1-a O2

[0075] In the above chemical formula 1, 0.1≤a≤0.3, 0.3≤x≤0.45, 0≤y≤0.05, 0.55≤z≤0.7, 0.002≤w1≤0.01, 0≤w2≤0.01, and x+y+z+w1+w2=1, M1 is Al, Ti, Nb, Ta, W, Mo or a combination thereof, and M2 is Zr, B, Y, Mg, Sc, Si, V, Fe, Ce, Hf, La, Sr, Sn, Sb, Zn, Cu, Ge, Ru, Ir or a combination thereof.

[0076] In the lithium transition metal oxide of the above chemical formula 1, lithium may be included in an amount corresponding to 1+a, where a may be 0.1≤a≤0.3. If a is too small, the effect of improving capacity characteristics due to excessive lithium content may be minimal. However, if a is too large, the life characteristics may deteriorate due to decreased phase stability.

[0077] In the lithium transition metal oxide of the above chemical formula 1, nickel may be included in an amount corresponding to x, i.e., 0.3≤x≤0.45. If the nickel content is too low, the amount of oxygen oxidation / reduction reaction may increase too much, which may deteriorate the life characteristics. If the nickel content is too high, the amount of oxygen oxidation / reduction reaction may decrease, which may deteriorate the capacity and output characteristics.

[0078] In the lithium transition metal oxide of the above chemical formula 1, cobalt may be included in an amount corresponding to y, i.e., 0≤y≤0.05 or 0≤y≤0.02. If the cobalt content is too low, it may be difficult to achieve sufficient rate characteristics. If the cobalt content is too high, the overall cost of the raw material may increase and the reversible capacity may decrease.

[0079] In the lithium transition metal oxide of the above chemical formula 1, manganese may be included in a content corresponding to z, i.e., 0.55≤z≤0.7. If the manganese content is too low, production costs may increase and capacity may deteriorate. If the manganese content is too high, there may be a decrease in life characteristics due to excessive use of oxygen oxidation / reduction reactions and manganese dissolution problems.

[0080] In the lithium transition metal oxide of the above chemical formula 1, the doping element M1 may be included in a content corresponding to w1, i.e., 0.002≤w1≤0.01 or 0.002≤w1≤0.008. In this case, M1 is Al, Ti, Nb, Ta, W, Mo, or a combination thereof.

[0081] In the lithium transition metal oxide of the above chemical formula 1, the other doping element M2 may be included in a content corresponding to w2, that is, 0≤w2≤0.01. In this case, M2 is Zr, B, Y, Mg, Sc, Si, V, Fe, Ce, Hf, La, Sr, Sn, Sb, Zn, Cu, Ge, Ru, Ir, or a combination thereof. The other doping element M2 may be included in an appropriate content to implement other doping effects within a range in which the electrochemical characteristics of the battery are not deteriorated.

[0082]

[0083] 2. Method for manufacturing positive electrode active material

[0084] A method for manufacturing a cathode active material for a lithium secondary battery according to another embodiment of the present invention comprises the steps of preparing a manganese-rich metal precursor having a molar ratio of manganese to the total metal of 0.55 to 0.7; and the steps of mixing the metal precursor, a lithium raw material, and a doping raw material, and then calcining the mixture to form a lithium metal oxide having a lithium and manganese-rich composition.

[0085] Hereinafter, a method for manufacturing a positive electrode active material for a lithium secondary battery according to another embodiment of the present invention will be described step by step.

[0086]

[0087] First, a manganese-excess metal precursor is prepared in which the molar ratio of manganese to the total metal is 0.55 to 0.7.

[0088] The above metal precursor may more specifically be a metal hydroxide.

[0089] The above metal precursor may be prepared by, for example, adding a complexing agent-containing solution and a pH adjusting agent-containing solution to a metal-containing solution including a nickel raw material, a manganese raw material, and optionally a cobalt raw material, and performing a co-precipitation reaction.

[0090] The above nickel raw material is not particularly limited as long as it is used in the art for manufacturing a positive electrode active material precursor. For example, the nickel raw material may be a nickel-containing sulfate, acetate, nitrate, halide, sulfide, hydroxide, oxide, or oxyhydroxide, and specifically, may be NiSO4, NiSO4·6H2O, Ni(OH)2, NiO, NiOOH, NiCO3·2Ni(OH)2·4H2O, NiC2O2·2H2O, Ni(NO3)2·6H2O, fatty acid nickel salt, nickel halide, or a combination thereof, but is not limited thereto.

[0091] The above cobalt raw material is not particularly limited as long as it is used in the art for manufacturing a positive electrode active material precursor. For example, the cobalt raw material may be a cobalt-containing sulfate, acetate, nitrate, halide, sulfide, hydroxide, oxide, or oxyhydroxide, and specifically, CoSO 4, It may be, but is not limited to, CoSO4ㆍ7H2O, Co(OH)2, CoOOH, Co(OCOCH3)2ㆍ4H2O, Co(NO3)2ㆍ6H2O or a combination thereof.

[0092] The manganese raw material is not particularly limited as long as it is used in the art for manufacturing a precursor of a cathode active material. For example, the manganese raw material may be a manganese-containing sulfate, acetate, nitrate, halide, sulfide, hydroxide, oxide, oxyhydroxide, or a combination thereof, and specifically, may be a manganese salt such as MnSO4, MnCO3, Mn(NO3)2, manganese acetate, manganese dicarboxylic acid salt, manganese citrate, and manganese fatty acid salt, manganese oxide such as Mn2O3, MnO2, and Mn3O4, oxyhydroxide, manganese chloride, or a combination thereof, but is not limited thereto.

[0093] The above metal-containing solution may be prepared by adding nickel raw material, manganese raw material, and optionally cobalt raw material to a solvent, specifically water, or a mixture of water and an organic solvent (e.g., alcohol, etc.) that can be uniformly mixed with water.

[0094] The above complexing agent-containing solution performs the function of forming a complex, and may include, but is not limited to, NH3, NH4OH, (NH4)2SO4, NH4NO3, NH4Cl, CH3COONH4, NH4CO3 or a combination thereof as the complexing agent. Meanwhile, the complexing agent-containing solution may be used in the form of an aqueous solution, and at this time, water or a mixture of water and an organic solvent (e.g., alcohol, etc.) that can be uniformly mixed with water may be used as the solvent.

[0095] The above pH adjusting agent-containing solution acts as a precipitant or pH adjusting agent, and may include an alkaline compound such as a hydroxide of an alkali metal or alkaline earth metal, such as NaOH, KOH, or Ca(OH)2, a hydrate thereof, or a combination thereof. Meanwhile, the pH adjusting agent-containing solution may also be used in the form of an aqueous solution, and at this time, water or a mixture of water and an organic solvent (e.g., alcohol, etc.) that can be uniformly mixed with water may be used as the solvent. At this time, the pH adjusting agent-containing solution may be added in an amount such that the pH of the reaction solution becomes 10 to 13.

[0096] The above coprecipitation reaction can be performed under an inert atmosphere such as nitrogen or argon, can be performed at a temperature of 30 to 70°C, and can be performed at a pH of 10 to 13.

[0097] Nickel-manganese(-cobalt) hydroxide particles are generated through the above process and precipitated within the reaction solution. The precipitated precursor particles can be separated, washed, and dried using conventional methods to obtain the precursor. The precursor may be a secondary particle formed by the agglomeration of primary particles.

[0098] At this time, the molar ratio of nickel, cobalt, and manganese in the precursor can be controlled by controlling the concentration of nickel raw material, cobalt raw material, and manganese raw material.

[0099] Accordingly, the molar ratio of manganese (Mn) to metal (M) in the metal precursor (Mn / M) may be 0.55 to 0.7. In addition, the molar ratio of nickel (Ni) to metal (M) in the metal precursor (Ni / M) may be 0.3 to 0.45. In addition, the molar ratio of cobalt (Co) to metal (M) in the metal precursor (Co / M) may be 0.05 or less, more specifically, 0.02 or less, and the metal precursor may not contain cobalt. The technical significance of controlling the content of each metal is as described above, and thus is omitted.

[0100]

[0101] Next, the metal precursor, lithium raw material, and doping raw material are mixed and then calcined to form a lithium metal oxide with an excess composition of lithium and manganese.

[0102] At this time, it can be performed so that the molar ratio of lithium to the entire metal in the metal precursor (Li / Me) is 1.1 or more. When the molar ratio of lithium to the entire metal in the metal precursor satisfies the above range, a lithium metal oxide having a lithium-excess composition can be formed.

[0103] In addition, the lithium raw material may be lithium-containing sulfate, nitrate, acetate, carbonate, oxalate, citrate, halide, hydroxide, or oxyhydroxide, and is not particularly limited as long as it can be dissolved in water. Specifically, the lithium raw material may be Li2CO3, LiNO3, LiNO2, LiOH, LiOHㆍH2O, LiH, LiF, LiCl, LiBr, LiI, CH3COOLi, Li2O, Li2SO4, CH3COOLi, Li3C6H5O7, or a combination thereof, but is not limited thereto.

[0104] In addition, the doping raw material may be a compound containing a transition metal element that does not have an atomic electron in the d orbital. For example, the doping raw material may be Al(OH)3, Al2O3, TiO2, Nb2O5, Ta2O5, WO3, MoO -3 Or it may be a combination of these, but is not necessarily limited to these.

[0105] Of course, the above doping raw material may further include a compound containing other doping elements in addition to a compound containing a transition metal element that does not have an atomic electron in the d orbital. In this case, the other doping elements may be Zr, B, Y, Mg, Sc, Si, V, Fe, Ce, Hf, La, Sr, Sn, Sb, Zn, Cu, Ge, Ru, Ir, or a combination thereof.

[0106] In particular, the above doping raw material may have an average particle diameter (D50) of 400 nm or less, and more specifically, 300 or 200 nm or less. If the average particle diameter (D50) of the doping raw material is too large, even if the doping element in the doping raw material is appropriate, the reactivity with the transition metal element-containing compound is very low, so that it is not sufficiently inserted into the crystal structure, and the average spacing between lithium layers may be formed narrowly, and after full charge, the ratio of the transition metal in the lithium layer may become too high, reducing the effect of improving the structural stability of the active material.

[0107] Additionally, the atmosphere during the above-mentioned firing is not particularly limited, but may be performed in an air atmosphere, for example. Accordingly, there may be an advantage of low process costs.

[0108] Additionally, the firing may be performed at a temperature of 820 to 900°C. If the firing temperature is too low, grain growth may not occur, which may result in reduced capacity, output, and lifespan characteristics. If the firing temperature is too high, over-firing may occur, resulting in grain enlargement, which may result in reduced output characteristics.

[0109] Additionally, the firing can be performed for 8 to 15 hours. If the firing time is too short, the crystal grains may not grow sufficiently and a layered structure may not be formed, which may lead to problems with reduced capacity, output, and life characteristics. If the firing time is too long, the firing cost may increase significantly.

[0110] Accordingly, a lithium metal oxide having a lithium and manganese excess composition according to the present invention can be formed, and the lithium metal oxide having a lithium and manganese excess composition can be appropriately obtained with properties including an average spacing between lithium layers within the range according to the present invention.

[0111]

[0112] 3. Cathode ray and lithium secondary battery

[0113] Another embodiment of the present invention provides a positive electrode for a lithium secondary battery comprising the positive electrode active material described above.

[0114] More specifically, the positive electrode may include a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector, and including the positive electrode active material described above.

[0115] The positive electrode current collector is not particularly limited as long as it is conductive and does not cause a chemical change in the battery, and for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. may be used. In addition, the positive electrode current collector may typically have a thickness of 3 to 500 μm, and fine unevenness may be formed on the surface of the positive electrode current collector to increase the adhesion of the positive electrode active material. For example, the positive electrode current collector may be used in various forms such as a film, sheet, foil, net, porous body, foam, or non-woven fabric.

[0116] The above-described positive electrode active material layer may include a binder and / or a conductive material together with the above-described positive electrode active material.

[0117] At this time, the binder plays a role of improving the adhesion between the positive electrode active material particles and the adhesive strength between the positive electrode active material and the positive electrode current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer rubber (EPDM rubber), sulfonated-EPDM, styrene butadiene rubber (SBR), fluororubber, or various copolymers thereof, and one kind alone or a mixture of two or more kinds thereof may be used, but is not limited thereto. The binder may be included in an amount of 1 to 30 wt% based on the total weight of the positive electrode active material layer.

[0118] And, the conductive material is used to provide conductivity to the electrode, and in the battery to be constructed, as long as it does not cause a chemical change and has electronic conductivity, it can be used without any special restrictions. 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, summer black, and carbon fiber; metal powder or metal fiber such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and the like. One type alone or a mixture of two or more types among these may be used, but the present invention is not limited thereto. The conductive material may typically be included in an amount of 1 to 30 wt% based on the total weight of the positive electrode active material layer.

[0119] The above positive electrode can be manufactured according to a conventional positive electrode manufacturing method, except that the above positive electrode active material is used.

[0120] Specifically, the positive electrode can be manufactured by applying a composition for forming a positive electrode active material layer, including the positive electrode active material described above and optionally a binder, a conductive agent, or a solvent, on a positive electrode current collector, followed by drying and rolling. At this time, the types and contents of the positive electrode active material, binder, and conductive agent are as described above.

[0121] The solvent may be a solvent generally used in the relevant technical field, such as dimethylsulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water. One of these may be used alone or a mixture of two or more thereof may be used. The amount of the solvent used is sufficient to dissolve or disperse the positive electrode active material, conductive material, and binder, taking into account the coating thickness and manufacturing yield of the slurry, and to have a viscosity that can exhibit excellent thickness uniformity when applied thereafter for manufacturing the positive electrode.

[0122] Alternatively, the positive electrode may be manufactured by casting the composition for forming the positive electrode active material layer on a separate support, and then laminating the resulting film on a positive electrode current collector by peeling it off from the support.

[0123]

[0124] Another embodiment of the present invention provides a lithium secondary battery including the positive electrode for a lithium secondary battery as described above.

[0125] The above lithium secondary battery may more specifically include a positive electrode; a negative electrode; a separator; and an electrolyte.

[0126] The above lithium secondary battery may optionally further include a battery container that houses the electrode assembly of the positive electrode, the negative electrode, and the separator, and a sealing member that seals the battery container.

[0127] The above negative electrode may include a negative electrode current collector and a negative electrode active material layer positioned on the negative electrode current collector.

[0128] The negative electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. can be used. In addition, the negative electrode current collector can typically have a thickness of 3 to 500 ㎛, and like the positive electrode current collector, fine unevenness can be formed on the surface of the current collector to strengthen the bonding strength of the negative electrode active material. For example, it can be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, a non-woven fabric, etc.

[0129] The negative electrode active material layer may optionally include a binder and a conductive material together with the negative electrode active material. As an example, the negative electrode active material layer may be manufactured by applying a composition for forming a negative electrode active material layer comprising the negative electrode active material and optionally a binder and a conductive material onto a negative electrode current collector and drying the composition, or by casting the negative electrode forming composition onto a separate support and then laminating the resulting film onto a negative electrode current collector by peeling the film off from the support.

[0130] As the negative electrode active material, a compound capable of reversible intercalation and deintercalation of lithium may be used. Specific examples thereof 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 alloy, Sn alloy, and Al alloy; metallic oxides capable of doping and dedoping lithium, such as SiOβ (0 < β < 2), SnO2, vanadium oxide, and lithium vanadium oxide; or composites comprising the metallic compounds and carbonaceous materials, such as Si-C composites or Sn-C composites, and any one or a mixture of two or more of these may be used. In addition, a metallic lithium thin film may be used as the negative electrode active material. In addition, both low-crystalline carbon and high-crystalline carbon may be used as the carbonaceous material. Representative examples of low-crystalline carbon include soft carbon and hard carbon, and representative examples of high-crystalline carbon include natural graphite or artificial graphite in the form of amorphous, plate-like, flaky, spherical, or fiber-like forms, 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.

[0131] The above binder and conductive material may be the same as those described above for the positive electrode.

[0132]

[0133] The above separator separates the negative electrode and the positive electrode and provides a passage for lithium ions to move. Any separator commonly used as a separator in lithium secondary batteries can be used without any particular restrictions. In particular, a separator having low resistance to ion movement of the electrolyte and excellent electrolyte moisture absorption capacity is preferable. Specifically, a porous polymer film, for example, a porous polymer film made of a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof, may be used. In addition, a conventional porous nonwoven fabric, for example, a nonwoven fabric made of high-melting-point glass fiber, polyethylene terephthalate fiber, etc. may be used. In addition, a coated separator containing a ceramic component or a polymer material to secure heat resistance or mechanical strength may be used, and may optionally be used in a single-layer or multi-layer structure.

[0134]

[0135] The above electrolyte may include, but is 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.

[0136] Specifically, the organic liquid electrolyte may include an organic solvent and a lithium salt.

[0137] The organic solvent may be used without any particular limitation as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the organic solvent may include ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; Carbonate solvents such as dimethylcarbonate (DMC), diethylcarbonate (DEC), methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); alcohol solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (wherein R is a C2 to C20 linear, branched, or cyclic hydrocarbon group, and may include a double-bonded aromatic ring or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes can be used. Among these, a carbonate solvent is preferable, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate, etc.) having high ionic conductivity and high dielectric constant that can improve the charge / discharge performance of the battery and a linear carbonate compound having low viscosity (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate, etc.) is more preferable.In this case, the performance of the electrolyte may be improved when the cyclic carbonate and the chain carbonate are mixed and used in a volume ratio of about 1:1 to about 1:9.

[0138] The lithium salt may be used without any particular limitation as long as it is a compound capable of providing lithium ions used in a lithium secondary battery. Specifically, the lithium salt may be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAl04, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2. LiCl, LiI, or LiB(C2O4)2. It is preferable that the concentration of the lithium salt be used within the range of 0.1 to 2.0 M. When the concentration of the lithium salt is within the above range, the electrolyte can exhibit excellent electrolyte performance because it has appropriate conductivity and viscosity, and lithium ions can move effectively.

[0139] In addition to the electrolyte components, the electrolyte may further include one or more additives, such as haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethylphosphite, triethanolamine, cyclic ethers, ethylene diamine, n-glyme, hexamethylphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride, for the purpose of improving the life characteristics of the battery, suppressing battery capacity decrease, and improving the discharge capacity of the battery. At this time, the additives may be included in an amount of 0.1 to 5 wt% based on the total weight of the electrolyte.

[0140] As described above, a lithium secondary battery including a cathode active material according to the present invention stably exhibits excellent discharge capacity, output characteristics, and capacity retention, and is therefore useful in portable devices such as mobile phones, laptop computers, and digital cameras, and electric vehicles such as hybrid electric vehicles (HEVs).

[0141] Accordingly, another embodiment of the present invention provides a battery module including the lithium secondary battery as a unit cell and a battery pack including the same.

[0142] The above battery module or battery pack can be used as a power source for one or more medium- to large-sized devices, such as a power tool; an electric vehicle (EV), a hybrid electric vehicle, and a plug-in hybrid electric vehicle (PHEV); or a power storage system.

[0143]

[0144] Hereinafter, embodiments of the present invention will be described in more detail through examples. However, the following examples are merely preferred embodiments of the present invention, and the present invention is not limited to the following examples.

[0145]

[0146] Example 1

[0147] (1) Manufacturing of positive electrode active material

[0148] 1) Manufacturing of first lithium metal oxide (large particle size)

[0149] (Metal precursor preparation) Nickel cobalt manganese hydroxide was prepared using a 20L co-precipitation reactor.

[0150] First, a 3M metal salt aqueous solution was prepared by dissolving NiSO4·6H2O and MnSO4·H2O in DI water at a molar ratio of 35:65.

[0151] Afterwards, the metal salt aqueous solution, NH4(OH) as a complexing agent, and NaOH as a pH regulator were added to the co-precipitation reactor to cause a co-precipitation reaction, thereby producing a metal hydroxide. At this time, N2 was purged to prevent oxidation of the metal ions during the co-precipitation reaction, the temperature inside the co-precipitation reactor was maintained at 30°C, and the co-precipitation reaction time was controlled to prepare a metal hydroxide with an average particle size (D50) of 10 μm.

[0152] Afterwards, the manufactured metal hydroxide was filtered, washed with DI water, and vacuum dried in an oven at 110°C for 48 h. As a result, Ni 0.35 Mn 0.65 A metal precursor with the composition (OH)2 was prepared.

[0153] (Manufacturing of lithium metal oxide) Afterwards, LiOH·H2O is added so that the molar ratio of lithium to the entire metal in the metal precursor is 1.31, and Al(OH) is added so that the molar ratio of Al to the entire metal in the lithium metal oxide is 0.005. 3- And, after mixing the above metal precursors, calcining at 900℃ for 10 hours in an air atmosphere to obtain Li having an average particle size (D50) of 10μm. 1.13 Ni 0.303 Mn 0.562 Al 0.004 A first lithium metal oxide having an O2 composition was prepared. At this time, the average particle diameter (D50) of the Al(OH)3 powder, which was the doping raw material, was 200 nm.

[0154] 2) Manufacturing of secondary lithium metal oxide (small particle size)

[0155] (Metal precursor preparation) Nickel cobalt manganese hydroxide was prepared using a 20L co-precipitation reactor.

[0156] First, a 3M metal salt aqueous solution was prepared by dissolving NiSO4·6H2O, CoSO4·6H2O, and MnSO4·H2O in DI water at a molar ratio of 35:65.

[0157] Afterwards, the metal salt aqueous solution, NH4(OH) as a complexing agent, and NaOH as a pH regulator were added to the co-precipitation reactor to cause a co-precipitation reaction, thereby producing a metal hydroxide. At this time, N2 was purged to prevent oxidation of the metal ions during the co-precipitation reaction, the temperature inside the co-precipitation reactor was maintained at 30°C, and the co-precipitation reaction time was controlled to prepare a metal hydroxide with an average particle diameter (D50) of 3 μm.

[0158] Afterwards, the manufactured metal hydroxide was filtered, washed with DI water, and vacuum dried in an oven at 110°C for 48 h. As a result, Ni 0.35 Mn 0.65 A metal precursor with the composition (OH)2 was prepared.

[0159] (Manufacturing of lithium metal oxide) Afterwards, LiOH·H2O is added so that the molar ratio of lithium to the entire metal in the metal precursor is 1.31, and Al(OH) is added so that the molar ratio of Al to the entire metal excluding lithium in the lithium metal oxide is 0.005. 3- And, after mixing the above metal precursors, calcining at 850℃ for 10 hours in an air atmosphere to obtain Li having an average particle size (D50) of 3μm. 1.13 Ni 0.303 Mn 0.562 Al 0.004 A second lithium metal oxide having an O2 composition was prepared. At this time, the average particle diameter (D50) of the Al(OH)3 powder, which was the doping raw material, was 200 nm.

[0160] 3) Manufacturing of positive electrode active materials

[0161] Thereafter, the first lithium metal oxide and the second lithium metal oxide were mixed in a weight ratio of 70:30 to manufacture a positive electrode active material.

[0162] (2) Lithium secondary battery manufacturing

[0163] The slurry for manufacturing the electrode plate was mixed with the above-mentioned positive electrode active material: conductive material (carbon black, Denka black): binder (PVDF, KF1100) = 92.5:3.5:4 wt%, and the viscosity was adjusted so that the solid content was approximately 30% by adding NMP (N-Methyl-2-pyrrolidone). The manufactured slurry was coated on a 15 μm thick Al foil using a doctor blade, and then dried and rolled. The electrode loading was 14.6 mg / cm 2 and the rolling density (25℃, 20kN) was 3.1 g / cm 3 It was.

[0164] The electrolyte was 1M LiPF6in EC:DMC:EMC=3:4:3 (vol%), and 1.0 wt% VC, 1 wt% FEC, and 0.5 wt% LiBF4 were added to the total amount of the electrolyte. A coin cell was manufactured using a PP separator and a lithium negative electrode (200 μm, Honzo metal).

[0165]

[0166] Example 2

[0167] When manufacturing the first lithium metal oxide and the second lithium metal oxide, instead of Al(OH)3, TiO is used so that the molar ratio of Ti to the entire metal except lithium in the lithium metal oxide is 0.005. 2- A cathode active material and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the doping raw material, TiO2 powder, was mixed. At this time, the average particle diameter (D50) of the doping raw material, TiO2 powder, was 200 nm.

[0168]

[0169] Example 3

[0170] When manufacturing the first lithium metal oxide and the second lithium metal oxide, instead of Al(OH)3, Nb2O is used so that the molar ratio of Nb to the entire metal except lithium in the lithium metal oxide is 0.005. 5-Except for mixing, the cathode active material and lithium secondary battery were manufactured in the same manner as in Example 1. At this time, the doping raw material Nb2O 5- The average particle diameter (D50) of the powder was 200 nm.

[0171]

[0172] Example 4

[0173] When manufacturing the first lithium metal oxide and the second lithium metal oxide, Ta2O is used so that the molar ratio of Ta to the entire metal except lithium in the lithium metal oxide is 0.005 instead of Al(OH)3. 5- Except for mixing, the cathode active material and lithium secondary battery were manufactured in the same manner as in Example 1. At this time, the doping raw material Nb2O 5- The average particle diameter (D50) of the powder was 200 nm.

[0174]

[0175]

[0176] Example 5

[0177] When manufacturing the first lithium metal oxide and the second lithium metal oxide, WO is used instead of Al(OH)3 so that the molar ratio of W to the entire metal except lithium in the lithium metal oxide is 0.005. 3- Except for mixing, the positive electrode active material and lithium secondary battery were manufactured in the same manner as in Example 1. At this time, WO as a doping raw material 3- The average particle diameter (D50) of the powder was 200 nm.

[0178]

[0179] Example 6

[0180] When manufacturing the first lithium metal oxide and the second lithium metal oxide, instead of Al(OH)3, MoO is used so that the molar ratio of Mo to the entire metal except lithium in the lithium metal oxide is 0.005. 3-A cathode active material and a lithium secondary battery were manufactured in the same manner as in Example 1, except that MoO was mixed. At this time, the doping raw material was MoO 3- The average particle diameter (D50) of the powder was 200 nm.

[0181]

[0182] Example 7

[0183] The composition of the precursor in the production of the first lithium metal oxide and the second lithium metal oxide is Ni 0.35 Co 0.05 Mn 0.6 (OH)2, and instead of Al(OH)3, TiO is used so that the molar ratio of Ti to the entire metal except lithium in the lithium metal oxide is 0.005. 2- Except for mixing, the cathode active material and lithium secondary battery were manufactured in the same manner as in Example 1. At this time, the doping raw material TiO 2- The average particle diameter (D50) of the powder was 200 nm.

[0184]

[0185] Comparative Example 1

[0186] A positive electrode active material and a lithium secondary battery were manufactured in the same manner as in Example 1, except that Al(OH)3 was not mixed when manufacturing the first lithium metal oxide and the second lithium metal oxide.

[0187]

[0188] Comparative Example 2

[0189] When manufacturing the first lithium metal oxide and the second lithium metal oxide, instead of Al(OH)3, Ni(OH) is used so that the molar ratio of doping Ni to the entire metal except lithium in the lithium metal oxide is 0.005. 2- A positive electrode active material and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the mixture was mixed.

[0190]

[0191] Comparative Example 3

[0192] When manufacturing the first lithium metal oxide and the second lithium metal oxide, instead of Al(OH)3, Co(OH) is used so that the molar ratio of doping Co to the entire metal except lithium in the lithium metal oxide is 0.005. 2- A positive electrode active material and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the mixture was mixed.

[0193]

[0194] Comparative Example 4

[0195] When manufacturing the first lithium metal oxide and the second lithium metal oxide, instead of Al(OH)3, Mn(OH) is used so that the molar ratio of doping Mn to the entire metal except lithium in the lithium metal oxide is 0.005. 2- A positive electrode active material and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the mixture was mixed.

[0196]

[0197] Comparative Example 5

[0198] When manufacturing the first lithium metal oxide and the second lithium metal oxide, instead of Al(OH)3, Fe2O is used so that the molar ratio of Fe to the entire metal except lithium in the lithium metal oxide is 0.005. 3- A positive electrode active material and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the mixture was mixed.

[0199]

[0200] Comparative Example 6

[0201] When manufacturing the first lithium metal oxide and the second lithium metal oxide, instead of Al(OH)3, V2O is used so that the molar ratio of V to the entire metal except lithium in the lithium metal oxide is 0.005. 5- A positive electrode active material and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the mixture was mixed.

[0202]

[0203] Comparative Example 7

[0204] When manufacturing the first lithium metal oxide and the second lithium metal oxide, a positive electrode active material and a lithium secondary battery were manufactured in the same manner as in Example 1, except that Cr2O3 was mixed instead of Al(OH)3 so that the molar ratio of Cr to the entire metal excluding lithium in the lithium metal oxide was 0.005.

[0205]

[0206] Comparative Example 8

[0207] A cathode active material and a lithium secondary battery were manufactured in the same manner as in Example 2, except that when manufacturing the first lithium metal oxide and the second lithium metal oxide, the molar ratio of Ti to the total metal excluding lithium in the lithium metal oxide was set to 0.001.

[0208]

[0209] Comparative Example 9

[0210] When producing the first lithium metal oxide and the second lithium metal oxide, the composition of the metal precursor is Ni 0.37 Co 0.13 Mn 0.50 A positive electrode active material and a lithium secondary battery were manufactured in the same manner as in Example 2, except that the cobalt content was increased by changing to (OH)2.

[0211]

[0212] Comparative Example 10

[0213] When manufacturing the first lithium metal oxide and the second lithium metal oxide, TiO is used as a doping raw material. 2- A positive electrode active material and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the average particle diameter (D50) of the powder was changed to 800 nm.

[0214]

[0215] Table 1 below summarizes the process conditions for examples and comparative examples.

[0216] Lithium metal oxide composition Doping element type Doping element content (mol%) based on total moles of metals excluding lithium Co content (mol%) based on total moles of metals excluding lithium Doping raw material Average particle size (D50) (nm) Example 1 Li 1.13 Ni 0.303 Mn 0.562 Al 0.004 O2Al0.50200Example 2Li 1.13 Ni 0.303 Mn 0.562 Ti 0.004 O2Ti0.50200Example 3Li 1.13 Ni 0.303 Mn 0.562 Nb 0.004 O2Nb0.50200Example 4Li 1.13 Ni 0.303 Mn 0.562 Ta 0.004 O2Ta0.50200Example 5Li 1.13 Ni 0.303 Mn 0.562 W 0.004 O2W0.50200 Example 6Li 1.13 Ni 0.303 Mn 0.562 Mo 0.004 O2Mo0.50200Example 7Li 1.13 Ni 0.260 Co 0.042 Mn 0.562 Ti 0.004 O2Ti0.55200Comparative Example 1Li 1.13 Ni 0.304 Mn 0.565 O2--0-Comparative Example 2Li 1.13 Ni 0.307 Mn 0.562 O2Ni0.50200Comparative Example 3Li 1.13 Ni 0.303 Mn 0.562 Co 0.004 O2Co0.50200Comparative Example 4Li 1.13 Ni 0.303 Mn 0.566 O2Mn0.50200Comparative Example 5Li 1.13 Ni 0.303 Mn 0.562 Fe 0.004 O2Fe0.50200Comparative Example 6Li 1.13 Ni 0.303Mn 0.562 V 0.004 O2V0.50200 Comparison Example 7Li 1.13 Ni 0.303 Mn 0.562 Cr 0.004 O2Cr0.50200 Comparative Example 8Li 1.13 Ni 0.304 Mn 0.565 Ti 0.001 O2Ti0.10200Comparative Example 9Li 1.13 Ni 0.224 Co 0.079 Mn 0.562 Ti 0.004 O2Ti0.59200Comparative Example 10Li 1.13 Ni 0.303 Mn 0.562 Ti 0.004 O2Ti0.50800

[0217]

[0218] Experimental Example 1: Cross-sectional SEM image of the positive electrode active material after FIB milling.

[0219] Cross-sectional SEM images of the positive electrode active materials of Examples 1 to 5 and Comparative Example 1 were observed after FIB (Focused Ion Beam) milling, and these are shown in FIGS. 1 to 6, respectively.

[0220] Referring to FIGS. 1 to 6, it was confirmed that the positive electrode active materials of the examples and comparative examples were secondary particles formed by agglomeration of plate-shaped primary particles, and had a structure in which a hollow space was formed among the secondary particles.

[0221]

[0222] Experimental Example 2: Evaluation of the properties of positive electrode active materials

[0223] (1) Evaluation of the stabilization energy of the dopant in the lithium layer and its preference for the lithium layer or transition metal layer.

[0224] Using the VASP program, unit cells with a total number of 150 atoms were constructed, and dopants were placed in the lithium layer and transition metal layer, respectively, and their respective energies were calculated. The stabilization energy of the dopant in the lithium layer was evaluated based on the energy difference between the two structures.

[0225] (2) Evaluation of average gap between lithium layers (before charging)

[0226] The average interlayer spacing of each synthesized sample was evaluated using XRD.

[0227] (3) Evaluation of the transition metal ratio in the lithium layer after full charge (charge termination voltage 4.65 V)

[0228] The transition metal ratio within the lithium layer was evaluated using XRD after full charge with a charge termination voltage of 4.65 V.

[0229] Stabilization energy of dopant in lithium layer (eV) Doping element Doping site preference Average spacing between lithium layers (Å) Transition metal ratio in lithium layer after full charge (%) Example 1 - 0.1 Lithium layer, transition metal layer 2.13827.3 Example 2 - 0.48 Lithium layer 2.14747.5 Example 3 - 0.81 Lithium layer 2.15197.5 Example 4 - 0.73 Lithium layer 2.15317.2 Example 5 - 1.29 Lithium layer 2.15827.1 Example 6 - 0.74 Lithium layer 2.15117.7 Example 7 - 0.54 Lithium layer 2.14747.5 Comparative Example 1 - 2.117510.4 Comparative Example 20.93Transition metal layer 2.11689.8Comparative example 31.21Transition metal layer 2.12179.5Comparative example 41.13Transition metal layer 2.11839.7Comparative example 51.58Transition metal layer 2.11999.9Comparative example 60.85Transition metal layer 2.117410.3Comparative example 71.32Transition metal layer 2.11649.9Comparative example 8-0.48Lithium layer 2.12119.2Comparative example 9-0.13Lithium layer, transition metal layer 2.12429.1Comparative example 10-0.48Lithium layer 2.12848.9

[0230]

[0231] Referring to Table 2, in the case of Examples 1 to 7 in which the process conditions, including the type and content of the doping element, were appropriately controlled, it was confirmed that all physical properties, such as the average spacing between lithium layers, were appropriately obtained within the range according to the present invention. On the other hand, in the case of Comparative Examples 1 to 7 in which there was no doping element or the type of the doping element was outside the range according to the present invention, it was confirmed that all physical properties, such as the average spacing between lithium layers, were outside the range according to the present invention.

[0232] In addition, in the case of Comparative Example 8, the type of doping element was appropriate, but the doping amount was too small, so the average spacing between lithium layers was too narrow, and the ratio of transition metals in the lithium layers after full charge was too high.

[0233] In addition, in the case of Comparative Example 9, although the type and content of the doping element were appropriate, the cobalt content of the parent material was too high, resulting in the average spacing between lithium layers being too narrow and the ratio of transition metals in the lithium layers being too high after full charging.

[0234] In addition, in the case of Comparative Example 10, although the type and content of the doping element were appropriate, the average particle diameter (D50) of the doping raw material was too large, so the average spacing between lithium layers was too narrow, and the ratio of transition metals in the lithium layers after full charging was too high.

[0235]

[0236] Experimental Example 3: Evaluation of Electrochemical Characteristics of Lithium Secondary Battery

[0237] Electrochemical characteristics of lithium secondary batteries manufactured according to the examples and comparative examples were evaluated, and the results are shown in Table 3 below and Figures 8 to 11.

[0238] (1) Initial capacity and initial efficiency evaluation

[0239] After fabricating a lithium secondary battery half-cell, it was aged at 25°C for 24 hours and then subjected to a charge-discharge test at 45°C. To evaluate the initial capacity, 200 mAh / g was used as the reference capacity, and the battery was charged to 4.65 V at a constant current of 0.1 C. Then, the battery was switched to a constant voltage and charged until the end current reached 0.05 C. After a rest time of 10 minutes after charging, the battery was discharged at a constant current of 0.1 C, using 200 mAh / g as the reference capacity, until the battery reached 2.0 V. The charge-discharge graph at this time is shown in Fig. 8.

[0240] (2) Evaluation of high temperature life characteristics (45℃, 50 cycles)

[0241] After fabricating a full cell of a lithium secondary battery, it was charged to 4.6 V at a constant current of 0.5 C at 45°C, then switched to a constant voltage and charged until the end current reached 0.05 C. After a rest time of 10 minutes after charging, it was discharged at a constant current of 0.5 C until it reached 2.5 V. Under these charge / discharge cycle conditions, 100 charge / discharge cycles were performed, and the capacity retention rate of the 100th cycle compared to the first cycle was calculated. The life retention rate graph is shown in Fig. 9.

[0242] (3) Evaluation of transition metal release after high-temperature cycle (45℃, 50 cycles)

[0243] After high-temperature cycling in full cells, the cells were disassembled after 100 cycles for each set, and the cathodes were collected and the amounts of Mn and Ni each were evaluated using ICP. This is shown in Fig. 10 (Mn dissolution amount) and Fig. 11 (Ni dissolution amount).

[0244] Initial charge capacity (mAh / g) Initial discharge capacity (mAh / g) Initial efficiency (%) High temperature life characteristics (%) Mn release (μg / g) Ni release (μg / g) Example 1 298.2 276.4 92.7 85.3 99.0 14 2.1 Example 2 298.1 277.5 93.1 84.7 91.1 120.3 Example 3 297.2 276.1 92.9 84.8 8.0 13 9.7 Example 4 299.2 275.9 92.2 84.9 74.1 121.4 Example 5 300.9 276.8 92.0 85.0 6 0.6 10 9.4 Example 6298.9277.792.984.883.4110.3 Example 7304.1277.391.284.674.6129.6 Comparative Example 1306.4278.290.883.7170.6195.2 Comparative Example 2306.2277.890.783.8170.0188.2 Comparative Example 3305.3275.790.383.1169.2202.2 Comparative Example 4308.8274.488.982.5175.7190.1 Comparative Example 5305.5271.788.9drop174.7217.2 Comparative Example 6303.8272.089.572.6168.4206.4Comparative example 7308.5270.787.768.2187.3198.8Comparative example 8299.8276.292.183.2125.3156.3Comparative example 9286.2258.890.484.4135.6173.7Comparative example 10307.2276.289.982.5174.4203.1

[0245]

[0246] Referring to Table 3, in the case of an example in which the average spacing between lithium layers and other properties are satisfied according to the present invention, it was confirmed that the initial efficiency and high-temperature life characteristics are very excellent, and the Mn and Ni elution amounts are very small, thereby improving the structural stability of the positive electrode active material. On the other hand, in the case of a comparative example in which the average spacing between lithium layers and other properties of the positive electrode active material are outside the range according to the present invention, the initial efficiency or high-temperature life characteristics are lower than in the example, and the Mn and Ni elution amounts are significantly larger than in the example, thereby deteriorating the structural stability of the positive electrode active material.

[0247] Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications can be made within the scope of the patent claims, the detailed description of the invention, and the attached drawings, and it is obvious that this also falls within the scope of the present invention.

[0248] Accordingly, the actual scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. Containing lithium metal oxide with an excess composition of lithium and manganese, The above lithium metal oxide has a structure in which lithium layers and transition metal layers are alternately laminated, and the average spacing between the lithium layers is 2.13 Å or more. The above lithium metal oxide is a cathode active material for a lithium secondary battery having a molar ratio of cobalt to metals other than lithium of 0.05 or less.

2. In paragraph 1, The above lithium metal oxide is a cathode active material for a lithium secondary battery, wherein the molar ratio of lithium to the lithium metal oxide is 1.1 to 1.3, and the molar ratio of manganese to a metal other than lithium is 0.55 to 0.

7.

3. In paragraph 1, The above lithium metal oxide is a cathode active material for a lithium secondary battery, wherein the transition metal ratio in the lithium layer is 8.0% or less after the first full charge.

4. In paragraph 1, The above lithium metal oxide is a cathode active material for a lithium secondary battery, wherein the cathode active material is doped with a transition metal element (dopant) that does not have an atomic electron in the d orbital.

5. In paragraph 4, A cathode active material for a lithium secondary battery, wherein the stabilization energy of the dopant in the lithium layer is less than 0 eV.

6. In paragraph 4, A transition metal element having no valence electrons in the above d orbital is a cathode active material for a lithium secondary battery, which is Al, Ti, Nb, Ta, W, Mo or a combination thereof.

7. In paragraph 4, A cathode active material for a lithium secondary battery, wherein a transition metal element having no valence electrons in the above d orbital is more doped into the lithium layer among the lithium layer and the transition metal layer.

8. In paragraph 4, A cathode active material for a lithium secondary battery, wherein the content of a transition metal element having no valence electrons in the above d orbital is 0.2 to 1 mol% based on the total mole number of metals excluding lithium.

9. In paragraph 1, The above lithium metal oxide is a cathode active material for a lithium secondary battery having a molar ratio of nickel to metals other than lithium of 0.3 to 0.

45.

10. In paragraph 1, A cathode active material for a lithium secondary battery, wherein the lithium metal oxide includes a first lithium metal oxide and a second lithium metal oxide, and the average particle diameter (D50) of the first lithium metal oxide is larger than the average particle diameter (D50) of the second lithium metal oxide.

11. In paragraph 1, The above lithium metal oxide is a cathode active material for a lithium secondary battery represented by the following chemical formula 1: [Chemical Formula 1] Li 1+a (Ni x Co y Mr z M1 w1 M2 w2 ) 1-a O2 In the chemical formula 1, 0.1≤a≤0.3, 0.3≤x≤0.45, 0≤y≤0.05, 0.55≤z≤0.7, 0.002≤w1≤0.01, 0≤w2≤0.01, and x+y+z+w1+w2=1, M1 is Al, Ti, Nb, Ta, W, Mo or a combination thereof, and M2 is Zr, B, Y, Mg, Sc, Si, V, Fe, Ce, Hf, La, Sr, Sn, Sb, Zn, Cu, Ge, Ru, Ir or a combination thereof.

12. A positive electrode for a lithium secondary battery comprising the positive electrode active material of any one of claims 1 to 11.

13. A lithium secondary battery comprising the positive electrode for a lithium secondary battery of clause 12.

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