Cathode active material for lithium secondary battery, method for manufacturing same, 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 of a lithium-excess composition containing iron (Fe) and manganese (Mn), wherein the lithium metal oxide has a molar ratio (Fe / Me) of iron to all metals excluding lithium of 0.15 to 0.49, the lithium metal oxide has a molar ratio (Mn / Me) of manganese to all metals excluding lithium of 0.51 to 0.85, and the lithium metal oxide has a molar ratio of lithium thereto of 1.05 to 1.4.

Description

A positive electrode active material for a lithium secondary battery, a method for manufacturing the same, and a lithium secondary battery including the same

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

[0002] This application claims priority to Korean Patent Application No. 10-2024-0173639 filed on November 28, 2024, the entire contents of which are incorporated herein by reference.

[0003]

[0004] To facilitate the rapid expansion of the lithium-ion battery market, the cost of cathode materials, which account for the largest proportion of the cell, is being reduced; accordingly, LiFePO4 (hereinafter "LFP"), LiFe a Mn 1-a PO4 (hereinafter "LFMP") cathode materials are gaining attention. This is because Fe is one of the most common elements on Earth and is very inexpensive compared to Ni, Co, and others, while Mn is also relatively inexpensive.

[0005] However, the above-mentioned cathode materials are LiCoO2 (hereinafter "LCO"), represented by LiMO-2 materials, and LiNi x Mn y Co z Compared to O2 (hereinafter "NCM"), etc., the proportion of light elements such as phosphorus and oxygen in the composition is high, so the capacity per unit weight is low (at the level of 150-160 mAh / g), and the true density of the material itself is low (at the level of 3.47 g / cc, whereas LCO and NCM are at the level of 5.0~5.1 g / cc).

[0006] The main reason for having the above characteristics is the PO4 functional group, which also causes additional problems such as significantly degrading capacity if the primary particles are not nanosized, as the space occupied within the crystal structure blocks the lithium diffusion channel and forces only one-dimensional (1D) lithium diffusion channels, and the kinetic properties are poor.

[0007] In other words, the aforementioned cathode material, in addition to its inherently low true density, causes particle packing degradation due to nanosizing, resulting in low tap density, pellet density, and electrode density, which causes a significant deterioration in the battery's energy density (per volume).

[0008]

[0009] Accordingly, one objective of the present invention is to provide a positive electrode active material for a lithium secondary battery capable of improving the energy density (per volume) of the battery while using inexpensive iron (Fe) and manganese (Mn) as main components, a method for manufacturing the same, and a lithium secondary battery including the same.

[0010]

[0011] One embodiment of the present invention provides a positive electrode active material for a lithium secondary battery comprising a lithium metal oxide containing iron (Fe) and manganese (Mn) having a lithium-excess composition, wherein the lithium metal oxide has a molar ratio of iron (Fe / Me) to the total metal excluding lithium of 0.15 to 0.49, the lithium metal oxide has a molar ratio of manganese (Mn / Me) to the total metal excluding lithium of 0.51 to 0.85, and the lithium metal oxide has a molar ratio of lithium to the lithium metal oxide (normalized to a molar ratio of oxygen of 2) of 1.05 to 1.4.

[0012] The above lithium metal oxide may have a structure in which a layered crystal structure in which lithium layers and transition metal layers are alternately stacked, and a disordered rocksalt crystal structure in which lithium and transition metals are arranged in a disordered manner are mixed.

[0013] In the above lithium metal oxide, lithium ions can move through the lithium layer and the transition metal layer during charging and discharging.

[0014] The lithium metal oxide above is in the form of secondary particles formed by the aggregation of a plurality of primary particles, and the average particle size of the primary particles may be 0.3 to 2 μm.

[0015] The above positive active material may have a sphericity of 0.9 or higher.

[0016] The above positive active material may have a tap density of 2.1 g / cc or more.

[0017] The above positive active material may have a pellet density of 2.7 g / cc or higher.

[0018] The above lithium metal oxide may have a disordered cation mixed structure.

[0019] The above lithium metal oxide may have a peak intensity ratio (I(003) / I(104)) of the (003) plane to the (104) plane when analyzed by X-ray diffraction (XRD) pattern analysis, which is 0.8 to 1.3.

[0020] When analyzing the X-ray diffraction (XRD) pattern of the above lithium metal oxide, the superstructure peak that is expressed in the region where 2θ is 20 to 30° (relative to the Cu target source) may appear as a single broad peak.

[0021] The above lithium metal oxide can be represented by the following chemical formula 1.

[0022] [Chemical Formula 1]

[0023] Li 1+x (Fe a Mn b M c ) 1-x O2

[0024] In the above chemical formula 1, 0.05≤x≤0.4, 0.15≤a≤0.49, 0.51≤b≤0.85, 0≤c≤0.1, a+b+c=1, and M is an other doping element such as Cr, Ni, Zr, Al, B, Y, Co, Cu, Zn, Ga, Ge, Ru, Rh, Sn, Sb, Re, Ir, Pt, Pb, Bi, Na, K, Rb, Cs, Ca, Sr, Ba, Mg, Si, Sc, Ti, Nb, W, V, Mo, Ta, or a combination thereof.

[0025]

[0026] Another embodiment of the present invention provides a method for manufacturing a positive electrode active material for a lithium secondary battery, comprising the steps of: preparing an iron (Fe) and manganese (Mn) containing metal hydroxide precursor by a co-precipitation process; and mixing the metal hydroxide precursor and a lithium raw material, and then calcining to form an iron (Fe) and manganese (Mn) containing lithium metal oxide with an excess lithium composition, wherein the lithium metal oxide has a molar ratio of iron (Fe / Me) to the total metal excluding lithium of 0.15 to 0.49, the lithium metal oxide has a molar ratio of manganese (Mn / Me) to the total metal excluding lithium of 0.51 to 0.85, and the lithium metal oxide has a molar ratio of lithium to the lithium metal oxide of 1.05 to 1.4.

[0027]

[0028] Another embodiment of the present invention provides a positive electrode for a lithium secondary battery comprising the aforementioned positive electrode active material.

[0029] Another embodiment of the present invention provides a lithium secondary battery comprising a positive electrode for the lithium secondary battery.

[0030]

[0031] A positive electrode active material for a lithium secondary battery according to one embodiment of the present invention comprises a lithium metal oxide containing iron (Fe) and manganese (Mn) with a lithium-excess composition, wherein the composition is appropriately controlled to improve lithium ion mobility, thereby improving capacity and rate characteristics.

[0032] In addition, a positive electrode active material for a lithium secondary battery according to one embodiment of the present invention comprises a lithium metal oxide containing iron (Fe) and manganese (Mn) with a lithium-excess composition, wherein the composition is appropriately controlled so that the density (tap density, pellet density, electrode density) can be improved.

[0033] Accordingly, the positive active material according to one embodiment of the present invention can ultimately maximize the energy density (per volume) of the battery.

[0034]

[0035] Figure 1 is an XRD analysis graph of the cathode active material prepared according to Example 2, Comparative Example 2, and Comparative Example 3.

[0036]

[0037] Terms such as first, second, and third are used to describe various parts, components, regions, layers, and / or sections, but are not limited thereto. These terms are used solely to distinguish one part, component, region, layer, or section from another part, component, region, layer, or section. Accordingly, the first part, component, region, layer, or section described below may be referred to as the second part, component, region, layer, or section without departing from the scope of the present invention.

[0038] The technical terms used herein are for the reference of specific embodiments only and are not intended to limit the invention. The singular forms used herein include plural forms unless phrases clearly indicate otherwise. As used in the specification, the meaning of "comprising" specifies certain characteristics, areas, integers, steps, actions, elements, and / or components, and does not exclude the presence or addition of other characteristics, areas, integers, steps, actions, elements, and / or components.

[0039] When it is stated that one part is "above" or "on" another part, it may be directly above or on the other part, or other parts may be involved in between. In contrast, when it is stated that one part is "directly above" another part, no other parts are interposed in between.

[0040] Unless otherwise defined, all terms used herein, including technical and scientific terms, have the same meaning as generally understood by those skilled in the art to which this invention pertains. Terms defined in commonly used dictionaries are further interpreted to have meanings consistent with relevant technical literature and the present disclosure, and are not interpreted in an ideal or highly formal sense unless otherwise defined.

[0041] Also, unless otherwise specified, % means weight %, and 1 ppm is 0.0001 weight %.

[0042] In this specification, the term “combination(s) of these” described in the Markush-type expression means one or more mixtures or combinations selected from the group consisting of the components described in the Markush-type expression, and means including any one or more selected from the group consisting of said components.

[0043] Hereinafter, embodiments of the present invention are described in detail so that those skilled in the art can easily implement the invention. However, the present invention may be embodied in various different forms and is not limited to the embodiments described herein.

[0044]

[0045] 1. Cathode active material

[0046] A positive electrode active material for a lithium secondary battery according to one embodiment of the present invention comprises a lithium metal oxide containing iron (Fe) and manganese (Mn) with a lithium-excess composition.

[0047] The lithium metal oxide according to the present invention may have a structure in which a layered crystal structure in which lithium layers and transition metal layers are alternately stacked is mixed with a disordered rocksalt crystal structure in which lithium and transition metals are arranged in a disordered manner.

[0048] In addition, the lithium metal oxide according to the present invention may be in the form of secondary particles formed by the aggregation of a plurality of primary particles. In this specification, "primary particle" refers to a minimum particle unit distinguished as a single mass when observing the cross-section of the positive electrode active material through a scanning electron microscope (SEM), and may consist of a single crystal grain or a plurality of crystal grains. In this specification, "crystal grain" refers to a distinct region in which atoms within the primary particle form a lattice structure in a specific direction.

[0049] The lithium metal oxide according to the present invention has a composition based on inexpensive iron and manganese, thereby enabling the reduction of the cathode material cost.

[0050] Meanwhile, conventional LFP or LMFP cathode materials based on iron composition had a problem in which PO4 functional groups in the structure blocked lithium diffusion channels, forming only one-dimensional (1D) lithium diffusion channels, resulting in significantly reduced capacity and rate characteristics. On the other hand, if the primary particle size is reduced to nano-size to solve this problem, particle packing becomes difficult, resulting in low tap density, pellet density, and electrode density, which, along with low true density, caused a problem of significantly degrading the energy density (per volume) of the battery.

[0051] On the other hand, the lithium metal oxide according to the present invention is an oxide in which the PO4 functional group is replaced with O2 to exhibit very high density characteristics. However, in this case, the lithium diffusion active channel may be blocked because iron (Fe) becomes disordered, but through a superlithic composition, the lithium diffusion channel can be sufficiently secured, and as a result, lithium ion mobility can be improved.

[0052] In addition, the lithium metal oxide according to the present invention has the iron and manganese content based on the total metal excluding lithium precisely controlled. Accordingly, lithium ion mobility can be further maximized.

[0053] That is, the lithium metal oxide according to the present invention has a lithium-excess composition in which the PO4 functional group is replaced with O2 compared to conventional LFP or LMFP cathode materials, and the iron and manganese content is precisely controlled, thereby maximizing lithium ion mobility.

[0054] Accordingly, the lithium metal oxide according to the present invention may have a three-dimensional (3D) lithium ion transport mechanism in which lithium ions move through the lithium layer and the transition metal layer during charging and discharging. As a result, capacity and rate characteristics can be greatly improved.

[0055]

[0056] In addition, the lithium metal oxide according to the present invention can have its true density significantly improved compared to conventional LFP or LMFP cathode materials due to the inherent characteristics of the composition itself.

[0057] In addition, since the lithium metal oxide according to the present invention has fundamentally excellent capacity and rate characteristics, the limitation on the particle size of primary or secondary particles is reduced, so the particle size can be sufficiently increased, and there is no need to additionally perform carbon coating, etc.

[0058] That is, the lithium metal oxide according to the present invention may have an average particle size of primary particles that is sufficiently large, ranging from 0.3 to 2 μm, more specifically from 0.6 to 2 μm. In this specification, the average particle size of primary particles can be obtained by separating all primary particles visible when observing secondary particles with an SEM image using a segmentation method with image software and calculating the average of the longest side lengths.

[0059] In addition, the lithium metal oxide according to the present invention may have an average particle size (D50) of secondary particles sufficiently large, ranging from 3 to 20 μm, more specifically from 6 to 20 μm. In this specification, the average particle size (D50) of secondary particles may be defined as the particle size corresponding to 50% of the volume accumulation in the particle size distribution curve of secondary particles. The average particle size (D50) of secondary particles may be measured, for example, using a laser diffraction method.

[0060] As a result, the lithium metal oxide according to the present invention can have its density (tap density, pellet density, electrode density) greatly improved as the effect of improving particle size and the effect of having high true density itself work complementarily with the effect of improving particle size compared to conventional LFP or LMFP cathode materials.

[0061] In one embodiment, the positive active material according to the present invention may have a tap density of 2.1 g / cc or more, and more specifically, 2.15 g / cc or more.

[0062] In this specification, the tap density of the positive electrode active material can be measured based on ASTM B527 by adding 3g of positive electrode active material powder to a 50mL container and tapping 2000 times at 120 times / min.

[0063] In one embodiment, the positive active material according to the present invention may have a pellet density of 2.7 g / cc or higher, and more specifically, 2.75 g / cc or higher.

[0064] In this specification, the pellet density of the positive active material can be measured by placing 3g of the positive active material into a mold with a diameter of 1cm and applying a pressure of 6 tons.

[0065]

[0066] Ultimately, the lithium metal oxide according to the present invention can maximize the energy (per volume) of the battery by simultaneously improving capacity and density.

[0067]

[0068] Hereinafter, the composition of the lithium metal oxide according to the present invention will be described in more detail.

[0069] First, the lithium metal oxide may have a molar ratio of lithium to the lithium metal oxide (normalized to a molar ratio of oxygen of 2) of 1.05 to 1.4, and more specifically, 1.15 to 1.4. If the lithium content is too low, the electrochemical activation effect is reduced, which may lead to a decrease in capacity and rate characteristics. If the lithium content is too high, the utilization rate of the oxygen redox reaction increases, leading to an increase in gas generation, a decrease in lifespan, and problems such as a decrease in cell energy density due to a very high initial charge amount relative to subsequent cycles.

[0070] In addition, the above lithium metal oxide may have a molar ratio of iron (Fe / Me) to the total metal excluding lithium of 0.15 to 0.49, and more specifically, 0.18 to 0.47. If the iron content is too low, structural stability during charging and discharging decreases, and lifespan characteristics may deteriorate. If the iron content is too high, the proportion of LiFeO2 phases having a rock salt structure within the lithium metal oxide increases, which may significantly reduce capacity and rate characteristics.

[0071] In addition, the above lithium metal oxide may have a molar ratio of manganese to the total metal excluding lithium (Mn / Me) of 0.51 to 0.85, and more specifically, 0.53 to 0.83. If the manganese content is too low, the oxygen oxidation-reduction reaction capable of generating capacity may be insufficient, which may result in a decrease in capacity and energy density of the cell. If the manganese content is too high, problems such as transition metal migration and oxygen gas generation during charging and discharging may become severe, leading to a deterioration in lifespan characteristics.

[0072] Meanwhile, the cathode active material according to the present invention can be easily manufactured through a co-precipitation method because the pH range in which the precipitation reaction occurs from the seed formation of manganese and iron is not significantly different. Compared to the solid-state method, the co-precipitation method can increase the particle size of the cathode active material particles, narrow the particle size distribution, and improve the degree of sphericity.

[0073] Accordingly, the positive electrode active material according to the present invention may have a degree of sphericity of 0.9 or higher. As the degree of sphericity of the positive electrode active material is improved, the electrode density can be further enhanced, thereby maximizing the effect of improving battery energy density. In addition, since a high degree of sphericity of the positive electrode active material minimizes the reaction surface area with the electrolyte, there may be advantages such as improved high-temperature durability.

[0074] In this specification, sphericity is a numerical expression of the degree to which a particle is close to being spherical, and refers to the value obtained by dividing the circumference of a circle having the same area as the particle projection shape by the actual circumference of the particle projection shape using a flow-type particle analysis device. This sphericity can be measured using an analyzer for obtaining optical images (Fluid Imaging Technologies, Flowcam 8100) and analysis software (visual spreadsheet).

[0075]

[0076] Meanwhile, the lithium metal oxide according to the present invention may have a disordered cation mixed structure. That is, the lithium metal oxide according to the present invention may have a structure in which a LiFeO2 phase with a disordered rock salt structure and a Li2MnO3 phase with a layered crystal structure are mixed, and the degree of disorder may increase in proportion to the iron content.

[0077] Accordingly, the lithium metal oxide according to the present invention may have a peak intensity ratio (I(003) / I(104)) of the (003) plane to the (104) plane when analyzing the X-ray diffraction (XRD) pattern of 0.8 to 1.3, and more specifically, 0.85 to 1.2. By satisfying the above range, the effect of improving capacity and rate characteristics can be more preferably realized, and life characteristics can also be improved.

[0078] More specifically, in the lithium metal oxide composition according to the present invention, the peak intensity ratio (I(003) / I(104)) can represent a measure of the expression ratio of the LiFeO2 phase with a disordered rock salt structure and the Li2MnO3 phase with a layered crystal structure. As the LiFeO2 phase is expressed more, the peak intensity ratio (I(003) / I(104)) may decrease. At this time, if the LiFeO2 phase is expressed too much, electrochemical activity may decrease, and capacity and rate characteristics may be reduced. On the other hand, if the Li2MnO3 phase is expressed too much, lifespan characteristics may be reduced. Therefore, when the peak intensity ratio (I(003) / I(104)) of the lithium metal oxide satisfies the above range, the LiFeO2 phase and the Li2MnO3 phase are expressed in an appropriate ratio, and excellent capacity, rate characteristics, and lifespan characteristics can be achieved.

[0079] In addition, when analyzing the X-ray diffraction (XRD) pattern of the lithium metal oxide according to the present invention, the superstructure peak that is expressed in the region where 2θ is 20 to 30° (relative to the Cu target source) may appear as a single broad peak. Furthermore, one to four small peaks within the single broad peak may not be expressed. This may be a result of the LiFeO2 phase and Li2MnO3 phase being expressed in appropriate proportions within the lithium metal oxide, and accordingly, excellent capacity, rate characteristics, and lifespan characteristics can be achieved.

[0080]

[0081] Meanwhile, the lithium metal oxide according to the present invention can be represented more specifically by the following chemical formula 1.

[0082] [Chemical Formula 1]

[0083] Li 1+x (Fe a Mn b M c ) 1-x O2

[0084] In the above chemical formula 1, 0.05≤x≤0.4, 0.15≤a≤0.49, 0.51≤b≤0.85, 0≤c≤0.1, a+b+c=1, and M is an other doping element such as Cr, Ni, Zr, Al, B, Y, Co, Cu, Zn, Ga, Ge, Ru, Rh, Sn, Sb, Re, Ir, Pt, Pb, Bi, Na, K, Rb, Cs, Ca, Sr, Ba, Mg, Si, Sc, Ti, Nb, W, V, Mo, Ta, or a combination thereof.

[0085] In the lithium metal oxide of Chemical Formula 1 above, lithium may be included in an amount corresponding to 1+x, where x may be 0.05≤x≤0.4. The technical significance of controlling the lithium content is the same as previously mentioned and is therefore omitted.

[0086] In the lithium metal oxide of Chemical Formula 1 above, iron may be included in an amount corresponding to a, i.e., 0.15≤a≤0.49, and more specifically, 0.18≤a≤0.47. The technical significance of controlling the iron content is the same as previously mentioned and is therefore omitted.

[0087] In the lithium metal oxide of Chemical Formula 1 above, manganese may be included in an amount corresponding to b, i.e., 0.51≤b≤0.85, and more specifically, 0.53≤b≤0.83. The technical significance of controlling the manganese content is the same as previously mentioned and is therefore omitted.

[0088] In the lithium metal oxide of Chemical Formula 1 above, the other doping element M may be included in an amount corresponding to c, i.e., 0≤c≤0.1. The content of the doping element can be appropriately selected and controlled to implement a doping effect within a range that does not degrade the electrochemical properties of the positive electrode active material. In this case, M is Cr, Ni, Zr, Al, B, Y, Co, Cu, Zn, Ga, Ge, Ru, Rh, Sn, Sb, Re, Ir, Pt, Pb, Bi, Na, K, Rb, Cs, Ca, Sr, Ba, Mg, Si, Sc, Ti, Nb, W, V, Mo, Ta, or a combination thereof.

[0089]

[0090] 2. Method for manufacturing positive electrode active material

[0091] Another embodiment of the present invention provides a method for manufacturing a positive electrode active material for a lithium secondary battery, comprising the steps of: preparing an iron (Fe) and manganese (Mn) containing metal hydroxide precursor by a co-precipitation process; and mixing the metal hydroxide precursor and a lithium raw material, and then calcining to form an iron (Fe) and manganese (Mn) containing lithium metal oxide with an excess lithium composition, wherein the lithium metal oxide has a molar ratio of iron (Fe / Me) to the total metal excluding lithium of 0.15 to 0.49, the lithium metal oxide has a molar ratio of manganese (Mn / Me) to the total metal excluding lithium of 0.51 to 0.85, and the lithium metal oxide has a molar ratio of lithium to the lithium metal oxide of 1.05 to 1.4.

[0092] 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 in detail step by step.

[0093]

[0094] First, iron (Fe) and manganese (Mn)-containing metal hydroxide precursors are prepared through a co-precipitation process.

[0095] More specifically, the metal hydroxide precursor can be prepared by the steps of: preparing a metal-containing solution by mixing an iron raw material, a manganese raw material, and a solvent; introducing the metal-containing solution, a complexing agent-containing solution, and a pH adjuster-containing solution into a reactor to form a reaction solution; and forming a metal hydroxide precursor by co-precipitating the reaction solution.

[0096] First, a metal-containing solution is prepared by mixing iron raw material, manganese raw material, and a solvent.

[0097] Of course, other doping element raw materials may also be mixed in as needed.

[0098] The above iron raw material is not particularly limited as long as it is used in the industry for the manufacture of cathode active material precursors. For example, the above iron raw material may be Fe scrab, FeO, Fe2O3, FeCl2, FeCl3, FeBr2, FeOOH, Fe(CO)5, Fe(C5H7O2)3, Fe4(P2O7)3, Fe(CO2CH3)2, FeS2, FeSO4, Fe(NO3)3, or a combination thereof.

[0099] The above manganese raw material is not particularly limited as long as it is used in the industry for the manufacture of cathode active material precursors. For example, the above manganese raw material may be a manganese-containing sulfate, acetate, nitrate, halide, sulfide, hydroxide, oxide, oxyhydroxide, or a combination thereof. Specifically, it may be a manganese salt such as MnSO4, MnCO3, Mn(NO3)2, manganese acetate, manganese dicarboxylate, manganese citrate, and manganese fatty acid, manganese oxide such as Mn2O3, MnO2, and Mn3O4, oxyhydroxide, manganese chloride, or a combination thereof, but is not limited thereto.

[0100] The above solvent is not particularly limited as long as it is capable of dissolving the metal raw materials, but, for example, it may be water.

[0101] Next, the metal-containing solution, the complexing agent-containing solution, and the pH adjuster-containing solution are introduced into a reactor to form a reaction solution.

[0102] The above-mentioned complexing agent-containing solution performs the role of forming a complex, and may include, for example, NH3, NH4OH, (NH4)2SO4, NH4NO3, NH4Cl, CH3COONH4, NH4CO3, or a combination thereof as the complexing agent, but is not limited thereto. Meanwhile, the above-mentioned complexing agent-containing solution may be used in the form of an aqueous solution, and in this case, water or a mixture of water and an organic solvent that is uniformly miscible with water (e.g., alcohol, etc.) may be used as the solvent.

[0103] The above-mentioned solution containing a pH adjuster performs the role of a precipitating agent or a pH adjuster and may include alkali compounds such as hydroxides of alkali metals or alkaline earth metals like NaOH, KOH, or Ca(OH)2, their hydrates, or combinations thereof. Meanwhile, the above-mentioned solution containing a pH adjuster may also be used in the form of an aqueous solution, in which case water or a mixture of water and an organic solvent that is uniformly miscible with water (e.g., alcohol) may be used as the solvent.

[0104] Next, the above reaction solution is subjected to a co-precipitation reaction to form a metal hydroxide precursor.

[0105] The above co-precipitation reaction can be carried out by stirring the reaction solution.

[0106] At this time, the above co-precipitation reaction can be carried out under an inert atmosphere such as nitrogen or argon.

[0107] In addition, the above co-precipitation reaction can be carried out at a temperature of 30 to 70°C, and more specifically, at a temperature of 40 to 60°C.

[0108] In addition, the above co-precipitation reaction can be carried out in a pH range of 8 to 12.

[0109] Through the process described above, particles of iron-manganese (-doping element) hydroxide are generated and precipitated in the reaction solution. The precipitated precursor particles can be separated by conventional methods, washed, and dried to obtain precursor powder. The precursor powder may be secondary particles formed by the aggregation of primary particles.

[0110] At this time, the molar ratio of iron, manganese, and other doping elements in the metal hydroxide precursor can be controlled by adjusting the concentrations of the iron raw material, manganese raw material, and other doping element raw material.

[0111] Accordingly, the molar ratio of iron (Fe) to the total metal (Me) in the metal hydroxide precursor may be 0.15 to 0.49. In addition, the molar ratio of manganese (Mn) to the total metal (Me) in the metal hydroxide precursor may be 0.51 to 0.85. The technical significance of controlling the content of each metal is as described above and is therefore omitted.

[0112] The above metal hydroxide precursor can be represented more specifically by the following chemical formula 2.

[0113] [Chemical Formula 2]

[0114] (Fe a Mn b M c )(OH)2

[0115] In the above chemical formula 2, 0.15≤a≤0.49, 0.51≤b≤0.85, 0≤c≤0.1, a+b+c=1, and M is an other doping element such as Cr, Ni, Zr, Al, B, Y, Co, Cu, Zn, Ga, Ge, Ru, Rh, Sn, Sb, Re, Ir, Pt, Pb, Bi, Na, K, Rb, Cs, Ca, Sr, Ba, Mg, Si, Sc, Ti, Nb, W, V, Mo, Ta, or a combination thereof.

[0116] The technical significance of controlling the content of each metal element in the metal hydroxide precursor is the same as the technical significance of controlling the content of each metal element in the lithium metal oxide, so it is omitted.

[0117]

[0118] Next, the above metal hydroxide precursor and lithium raw material are mixed and then calcined to form a lithium metal oxide containing iron (Fe) and manganese (Mn) with an excess lithium composition.

[0119] At this time, a lithium raw material is introduced such that the molar ratio (Li / M) of lithium to the total metal in the metal hydroxide precursor is 1.22 to 2.33. As the amount of lithium raw material introduced is controlled to the above range, the lithium content in the lithium metal oxide can be appropriately controlled to the range according to the present invention.

[0120] The above lithium raw material may be a lithium-containing sulfate, nitrate, acetate, carbonate, oxalate, citrate, halide, hydroxide, or oxyhydroxide, and is not particularly limited as long as it is soluble in water. Specifically, the above lithium raw material may be Li2CO3, LiNO3, LiNO2, LiOH, LiOH·H2O, LiH, LiF, LiCl, LiBr, LiI, CH3COOLi, Li2O, Li2SO4, CH3COOLi, Li3C6H5O7, or a combination thereof, but is not limited thereto.

[0121] The above calcination can be performed at a temperature of 800 to 900°C. If the calcination temperature is too low, there may be problems such as the electrochemical performance deteriorating due to unreacted phases remaining, or residual lithium remaining making slurry formation difficult or reducing capacity. If the calcination temperature is too high, there may be problems such as increased side reactions at high temperatures and a significant decrease in rate characteristics due to the destruction of secondary particles caused by excessive growth of the primary particle size.

[0122] The above firing atmosphere is not particularly limited and can be performed, for example, in an oxygen (O2) or air atmosphere.

[0123]

[0124] Thus, the lithium metal oxide according to the present invention can be finally manufactured. The lithium metal oxide has improved capacity and density, which can ultimately maximize the energy density (per volume) of the battery.

[0125]

[0126] 3. Anodes and Lithium Secondary Batteries

[0127] Another embodiment of the present invention provides a positive electrode for a lithium secondary battery comprising the aforementioned positive electrode active material.

[0128] More specifically, the anode may include an anode current collector and an anode active material layer disposed on the anode current collector and comprising the aforementioned anode active material.

[0129] The above positive current collector is not particularly limited as long as it is conductive without causing chemical changes in the battery, and for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface treated with carbon, nickel, titanium, silver, etc. may be used. In addition, the above positive current collector may typically have a thickness of 3 to 500 μm, and fine irregularities may be formed on the surface of the positive current collector to increase the adhesion of the positive active material. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0130] The above positive active material layer may include a binder and / or a conductive material together with the aforementioned positive active material.

[0131] At this time, the binder serves to improve adhesion between positive active material particles and adhesion between the positive active material and the positive 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, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer rubber (EPDM rubber), sulfonated-EPDM, styrene butadiene rubber (SBR), fluororubber, or various copolymers thereof. One of these alone or a mixture of two or more may be used, but is not limited thereto. The binder may be included in an amount of 1 to 30 weight% based on the total weight of the positive active material layer.

[0132] In addition, the conductive material is used to impart conductivity to the electrode, and in the battery being constructed, any material that possesses electronic conductivity without causing chemical changes may be used without any particular limitations. 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 fibers; 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 alone or a mixture of two or more may be used, but is not limited thereto. The conductive material may typically be included in an amount of 1 to 30 weight percent relative to the total weight of the positive electrode active material layer.

[0133] The above-mentioned anode can be manufactured according to a conventional anode manufacturing method, except for using the above-mentioned anode active material.

[0134] Specifically, the anode can be manufactured by applying a composition for forming an anode active material layer, comprising the aforementioned anode active material and optionally a binder, conductive material, or solvent as needed, onto an anode current collector, followed by drying and rolling. At this time, the types and contents of the anode active material, binder, and conductive material are as described above.

[0135] The above solvent may be a solvent commonly used in the relevant technical field, such as dimethylsulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water, and one of these alone or a mixture of two or more may be used. The amount of the above solvent used is sufficient if it has a viscosity that allows for the dissolution or dispersion of the anode active material, conductive material, and binder, taking into account the coating thickness of the slurry and the manufacturing yield, and subsequently provides excellent thickness uniformity when coated for anode manufacturing.

[0136] Alternatively, the anode may be manufactured by casting the composition for forming the anode active material layer onto a separate support, and then laminating the film obtained by peeling off from the support onto an anode current collector.

[0137]

[0138] Another embodiment of the present invention provides a lithium secondary battery comprising a positive electrode for a lithium secondary battery as described above.

[0139] More specifically, the above lithium secondary battery may include a positive electrode; a negative electrode; a separator; and an electrolyte.

[0140] The above lithium secondary battery may optionally further include a battery container that accommodates the electrode assembly of the positive electrode, negative electrode, and separator, and a sealing member that seals the battery container.

[0141] The above cathode may include a cathode current collector and a cathode active material layer located on the cathode current collector.

[0142] The above-mentioned negative current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloy may be used. In addition, the above-mentioned negative current collector may typically have a thickness of 3 to 500 μm, and, similar to the positive current collector, fine irregularities may be formed on the surface of the current collector to strengthen the bonding strength of the negative active material. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0143] The above-mentioned cathode active material layer may optionally include a binder and a conductive material together with the cathode active material. The above-mentioned cathode active material layer may be manufactured, as an example, by applying a composition for forming a cathode active material layer, comprising a cathode active material and optionally a binder and a conductive material, onto a cathode current collector and drying it, or by casting the composition for forming a cathode onto a separate support and then laminating the film obtained by peeling it off from the support onto a cathode current collector.

[0144] As the above-mentioned 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; metal oxides capable of doping and dedoping lithium, such as SiOβ (0 < β < 2), SnO2, vanadium oxide, and lithium vanadium oxide; or composites comprising the above-mentioned metallic compounds and carbonaceous materials, such as Si-C composites or Sn-C composites, and any one or more of these may be used. Additionally, a metallic lithium thin film may be used as the above-mentioned negative electrode active material. Furthermore, the carbon material may include both low-crystallinity carbon and high-crystallinity carbon. Representative examples of low-crystallinity carbon include soft carbon and hard carbon, while representative examples of high-crystallinity carbon include amorphous, plate-like, flake-like, spherical, or fibrous natural or artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, meso-carbon microbeads, mesophase pitches, and high-temperature calcined carbon such as petroleum or coal tar pitch-derived cokes.

[0145] The binder and conductive material mentioned above may be the same as those previously described in the anode.

[0146]

[0147] The above separator separates the negative electrode and the positive electrode and provides a pathway for the movement of lithium ions. It can be used without special restrictions as long as it is typically used as a separator in a lithium secondary battery, and it is particularly desirable that it has low resistance to the movement of electrolyte ions and excellent electrolyte wettability. Specifically, a porous polymer film, such as a porous polymer film made of a polyolefin-based polymer like ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof may be used. In addition, a conventional porous nonwoven fabric, such as a nonwoven fabric made of high-melting-point glass fiber or polyethylene terephthalate fiber, may be used. Furthermore, a coated separator containing ceramic components or polymer materials may be used to ensure heat resistance or mechanical strength, and it may optionally be used in a single-layer or multi-layer structure.

[0148]

[0149] The above electrolytes include organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, molten inorganic electrolytes, etc., which can be used in the manufacture of lithium secondary batteries, but are not limited to these.

[0150] Specifically, the organic liquid electrolyte may include an organic solvent and a lithium salt.

[0151] The above organic solvent may be used without special restrictions as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the above organic solvent may include ester-based solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether-based solvents such as dibutyl ether or tetrahydrofuran; ketone-based solvents such as cyclohexanone; and aromatic hydrocarbon-based solvents such as benzene and fluorobenzene. Carbonate-based solvents such as dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); alcohol-based solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (where R is a straight-chain, branched, or cyclic hydrocarbon group having C2 to C20 structures and may include a double bond, a directional ring, or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes may be used. Among these, a carbonate-based solvent is preferred, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate, etc.) having high ionic conductivity and high dielectric constant that can improve the charge / discharge performance of the battery, and a low-viscosity linear carbonate-based compound (e.g., ethylmethyl carbonate, dimethyl carbonate or diethyl carbonate, etc.) is more preferred.In this case, using a mixture of cyclic carbonate and chain carbonate in a volume ratio of about 1:1 to about 1:9 can result in excellent performance of the electrolyte.

[0152] The above lithium salt can be used without special restrictions as long as it is a compound capable of providing lithium ions used in lithium secondary batteries. Specifically, the lithium salt may be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2. The concentration of the lithium salt is preferably used within the range of 0.1 to 2.0 M. When the concentration of the lithium salt falls within the above range, the electrolyte has appropriate conductivity and viscosity, so it can exhibit excellent electrolyte performance and allow lithium ions to move effectively.

[0153] In addition to the above electrolyte components, the above electrolyte may further include one or more additives for the purpose of improving the lifespan characteristics of the battery, suppressing the decrease in battery capacity, and improving the discharge capacity of the battery, such as, for example, haloalkylene carbonate-based compounds like difluoroethylene carbonate, pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, hexamethylphosphate triamide, nitrobenzene derivative, sulfur, quinone imine dye, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, or aluminum trichloride. In this case, the additive may be included in an amount of 0.1 to 5 weight% based on the total weight of the electrolyte.

[0154] As described above, since the lithium secondary battery containing the positive electrode active material according to the present invention stably exhibits excellent discharge capacity, output characteristics, and capacity retention rate, it is useful in portable devices such as mobile phones, laptop computers, and digital cameras, as well as in the field of electric vehicles such as hybrid electric vehicles (HEVs).

[0155] Accordingly, another embodiment of the present invention provides a battery module comprising the lithium secondary battery as a unit cell and a battery pack comprising the same.

[0156] The above battery module or battery pack can be used as a power source for one or more medium-to-large devices, including a power tool; an electric vehicle (EV), a hybrid electric vehicle, and a plug-in hybrid electric vehicle (PHEV); or a power storage system.

[0157]

[0158] The embodiments of the present invention will be described in more detail below through examples. However, the following examples are merely preferred embodiments of the present invention, and the present invention is not limited by the following examples.

[0159]

[0160] Example 1

[0161] (1) Manufacturing of positive electrode active material

[0162] Fe through the coprecipitation process 0.45 Mn 0.55 (OH) 2 - A hydroxide precursor was prepared. Subsequently, LiOH·H2O was mixed so that the molar ratio of lithium to the total metal in the hydroxide precursor, i.e., the Li / Me (Fe and Mn) ratio, was 1.55, and then calcined at 800°C under an air atmosphere to produce a lithium-excess composition of Li. 1.22 Fe 0.35Mn 0.43 O 2 - Lithium metal oxide was manufactured.

[0163] (2) Lithium secondary battery manufacturing

[0164] The slurry for electrode manufacturing was prepared by mixing the above-prepared cathode active material, conductive material (carbon black, Denka black), and binder (PVDF, KF1100) in a ratio of 92.5 : 3.5 : 4 wt%, and adding NMP (N-Methyl-2-pyrrolidone) to adjust the viscosity so that the solid content was approximately 30%. The prepared slurry was coated onto a 15 µm thick Al foil using a doctor blade and then dry-rolled. The electrode loading amount was 14.6 mg / cm². 2 It was, and the rolled density (25℃, 20kN) was 3.1 g / cm³ 3 It was.

[0165] A coin cell was manufactured using an electrolyte of 1M LiPF6 in EC:EMC=3:7 (vol%) with 1.0 vol% VC and 0.5 wt% LiBF4 added relative to the total amount of the electrolyte, a PP separator, and a lithium anode (200 μm, Honzo metal).

[0166]

[0167] Example 2

[0168] Fe through the coprecipitation process 0.4 Mn 0.6 (OH) 2 - A positive electrode active material and a lithium secondary battery were prepared by carrying out the same procedure as in Example 1, except that a hydroxide precursor was prepared and LiOH·H2O was mixed so that the Li / Me ratio was 1.60. Thus, Li of a lithium-excess composition 1.23 Fe 0.31 Mn 0.46 O 2 - Lithium metal oxide was manufactured.

[0169]

[0170] Example 3

[0171] Fe through the coprecipitation process 0.3 Mn 0.7 (OH) 2 - A positive electrode active material and a lithium secondary battery were prepared by carrying out the same procedure as in Example 1, except that a hydroxide precursor was prepared and LiOH·H2O was mixed so that the Li / Me ratio was 1.70. Thus, Li of a lithium-excess composition 1.26 Fe 0.22 Mn 0.52 O 2 - Lithium metal oxide was manufactured.

[0172]

[0173] Example 4

[0174] Fe through the coprecipitation process 0.2 Mn 0.8 (OH) 2 - A positive electrode active material and a lithium secondary battery were prepared by carrying out the same procedure as in Example 1, except that a hydroxide precursor was prepared and LiOH·H2O was mixed so that the Li / Me ratio was 1.80. Thus, Li of a lithium-excess composition 1.29 Fe 0.14 Mn 0.57 O 2 - Lithium metal oxide was manufactured.

[0175]

[0176] Comparative Example 1

[0177] Final composition Li 1.20 Fe 0.4 Mn 0.4 After solid-state mixing of raw materials Fe2O3, MnO2, and LiOH·H2O according to the stoichiometric ratio of O2, Li is calcined at a temperature of 800℃ 1.20 Fe 0.4 Mn 0.4 O2 lithium metal oxide was prepared. Subsequently, a lithium secondary battery was prepared in the same manner as in Example 1.

[0178]

[0179] Comparative Example 2

[0180] Fe through the coprecipitation process 0.5 Mn0.5 (OH) 2 - A positive electrode active material and a lithium secondary battery were prepared by carrying out the same procedure as in Example 1, except that a hydroxide precursor was prepared and LiOH·H2O was mixed so that the Li / Me ratio was 1.50. Thus, Li of a lithium-excess composition 1.20 Fe 0.4 Mn 0.4 O 2 - Lithium metal oxide was manufactured.

[0181]

[0182] Comparative Example 3

[0183] Fe through the coprecipitation process 0.1 Mn 0.9 (OH) 2 - A positive electrode active material and a lithium secondary battery were prepared by carrying out the same procedure as in Example 1, except that a hydroxide precursor was prepared and LiOH·H2O was mixed so that the Li / Me ratio was 1.9. Thus, Li of a lithium-excess composition 1.31 Fe 0.07 Mn 0.62 O2 - Lithium metal oxide was manufactured.

[0184]

[0185] Comparative Example 4

[0186] LiFe as a conventional general solid-state method for manufacturing LFP cathode active materials 0.4 Mn 0.6 After preparing lithium iron phosphate with a PO4 olivine structure, a positive electrode active material was prepared by performing a carbon (C) coating using a conventional method. Subsequently, a lithium secondary battery was prepared in the same manner as in Example 1.

[0187]

[0188] Table 1 below summarizes the synthesis methods and compositions of the positive electrode active materials of the examples and comparative examples.

[0189] Synthetic method composition specific composition formula xabC Example 1 Co-precipitate Li 1.22 Fe 0.35 Mn 0.43O20.220.450.550 Example 2 Co-precipitation Li 1.23 Fe 0.31 Mn 0.46 O20.230.40.60 Example 3 Co-precipitation Li 1.26 Fe 0.22 Mn 0.52 O20.260.30.70 Example 4 Co-precipitation Li 1.29 Fe 0.14 Mn 0.57 O20.290.20.80 Comparative Example 1 Solid Li 1.20 Fe 0.4 Mn 0.4 O20.20.50.50 Comparative Example 2 Co-precipitation Li 1.20 Fe 0.4 Mn 0.4 O20.20.50.50 Comparative Example 3 Co-precipitation Li 1.31 Fe 0.07 Mn 0.62 O20.310.10.90 Comparative Example 4 Solid LiFe 0.4 Mn 0.6 PO4----

[0190] (In Table 1, x, a, and b represent the compositions of the lithium metal oxides of Examples 1 to 4 and Comparative Examples 1 to 3, Li 1+x (Fe a Mn b M c ) 1-x (Represents the coefficients of x, a, b, and c assuming O2)

[0191] Tables 2 to 4 below summarize the results of the evaluation of the physical properties of the cathode active material and the electrochemical characteristics of the lithium secondary battery according to Experimental Example 1 and Experimental Example 2 described below.

[0192] Cathode Active Material Properties Primary particle average diameter (μm) Secondary particle average diameter (D50, μm) Presence or absence of carbon coating Degree of sphericity I (003) / I (104) Superstructure Peak shape Example 10.88 None 0.9 10.94 One broad peak Example 20.88 None 0.9 30.97 One broad peak Example 30.88 None 0.9 11.03 One broad peak Example 40.88 None 0.9 01.07 One broad peak Comparative Example 10.8- (Single particle shape) None 0.6 0.78 None Comparative Example 20.88 None 0.8 80.79 None Comparative Example 30.88 None 0.8 21.41 Four small peaks within one broad peak Comparative Example 40.2- (Single particle Type) U0.57-None

[0193] Cathode Active Material Physical Properties Tap Density (g / cc) Pellet Density (g / cc) Electrode Limit Rolled Density (g / cc) Example 1 2.23 2.813 Example 2 2.21 2.833 Example 3 2.2 2.773 Example 4 2.18 2.783 Comparative Example 11.32 2.18 2.1 Comparative Example 22.18 2.693 Comparative Example 32.15 2.63 2.95 Comparative Example 41.4 2.3 2.5

[0194] Battery Performance Initial Discharge Capacity (mAh / g) Capacity Retention Rate (25℃, 50 cycles, %) Rate Characteristic (1C / 0.1C, %) Battery Energy Density (Pouch Cell) (Wh / L) Example 1 16296.489563 Example 2 17495.991.2558 Example 3 17595.592.1546 Example 4 17894.689.8540 Comparative Example 1 15193.288.5414 Comparative Example 2 14896.486.3521 Comparative Example 3 14293.274.3487 Comparative Example 4 15497.485.8432

[0195] Experimental Example 1: Evaluation of Physical Properties of Anode Active Material

[0196] (1) Average particle size of primary particles

[0197] The average particle size of the primary particles was determined by separating all primary particles visible when observing the secondary particles with SEM images using a segmentation method with image software and calculating the average of the longest side lengths.

[0198] (2) Average particle size of secondary particles (D50)

[0199] For the active material powder, the particle size corresponding to 50% of the volume accumulation was measured using the laser diffraction method.

[0200] (3) Sphericity

[0201] The degree of sphericity was evaluated by dividing the circumference of a circle with the same area as the particle projection shape by the actual circumference of the particle projection shape using a flow-type particle analysis device. At this time, measurements were taken using an analyzer for obtaining optical images (Fluid Imaging Technologies, Flowcam 8100) and analysis software (visual spreadsheet).

[0202] (4) XRD analysis

[0203] For the manufactured cathode active material, the diffraction pattern analyzed using X-ray diffraction analysis equipment was quantitatively calculated by applying Rietveld refinement and the Scherrer equation to evaluate the peak intensity ratio of the (003) plane to the (104) plane (I(003) / I(104)) and the superstructure peak shape. In this regard, Figure 1 is an XRD analysis graph of the cathode active material manufactured according to Example 2, Comparative Example 2, and Comparative Example 3.

[0204] (5) Tap density

[0205] Based on ASTM B527, 3g of positive electrode active material powder is placed in a 50mL container and then tapped 2000 times at 120 times / min to measure.

[0206] (6) Pellet density

[0207] After loading 3g of powder into a mold with a diameter of 1cm, a pressure of 6 tons was applied to evaluate the pellet density.

[0208] (7) Electrode limit rolling density

[0209] The rolling-capable electrode density was evaluated while checking for damage to the electrode-free portion by adjusting the gap of the rolling mill.

[0210]

[0211] Experimental Example 2: Evaluation of Electrochemical Characteristics of Lithium Secondary Battery

[0212] (1) Initial discharge capacity

[0213] After fabricating a lithium secondary battery half cell, it was aged at 25°C for 12 hours, and then a charge-discharge test was conducted at 25°C. To evaluate the initial capacity, the reference capacity was set to 200 mAh / g, and the battery was charged to 4.4V with a constant current of 0.1C. Then, the voltage was switched to a constant voltage, and charging continued until the terminal current reached 0.05C. After a 10-minute rest time following charging, the battery was discharged until it reached 2.0V with a constant current of 0.1C and a reference capacity of 200 mAh / g.

[0214] (2) Capacity retention rate

[0215] After fabricating a lithium secondary battery half cell, it was charged to 4.65V at 45°C with a constant current of 0.1C, then switched to a constant voltage and charged until the termination current reached 0.05C. After a 10-minute rest time following charging, it was discharged at a constant current of 0.1C until it reached 2.0V. Subsequently, it was transferred to a room temperature chamber at 25°C and 50 charge-discharge cycles were performed under these conditions, and the capacity retention rate of the 50th cycle was calculated relative to the first cycle.

[0216] (3) Rate characteristic (1C / 0.1C)

[0217] After the formation at 45°C was completed, it was moved to a room temperature chamber at 25°C and 0.1C charge / discharge was performed twice in the same manner as the formation. Then, additional cycles were performed with a charge of 0.1C and a discharge of 1.0C, and the rate characteristics were evaluated by comparing the discharge capacity of 1.0C with the previous capacity of 0.1C.

[0218] (4) Energy density (per volume) of a battery

[0219] A secondary battery was designed using a pouch-type battery design, and the energy density was evaluated by calculating the average voltage, capacity, and battery volume, reflecting the density of the electrodes using each material. Here, the electrode density was calculated using the weight of the electrode per unit area and the thickness obtained at maximum rolling.

[0220]

[0221] Referring to Tables 1 to 4, in the case of Examples 1 to 4, which are manufactured by the co-precipitation method and in which the lithium, iron, and manganese content in the lithium metal oxide is controlled within the range according to the present invention, it was confirmed that the degree of sphericity is good, the I(003) / I(104) peak intensity ratio is appropriately controlled within the range according to the present invention, and the superlattice peak is expressed as a single broad peak. In addition, it was confirmed that the tap density, pellet density, and electrode limit rolling density are all excellent. Accordingly, it was confirmed that the battery capacity, rate characteristics, lifespan (capacity retention rate), and battery energy density are all realized very excellently.

[0222] On the other hand, in the case of Comparative Examples 1 and 2, as a result of the iron content in the lithium metal oxide being too high and the manganese content being too low, the I(003) / I(104) peak intensity ratio fell outside the range according to the present invention, and it was confirmed that the superlattice peak itself was not expressed. In addition, in the case of Comparative Example 1, as a result of being manufactured by the solid-state method, it was confirmed that the degree of sphericity was significantly reduced. This affected the density of the cathode active material, resulting in a significant deterioration of tap density, pellet density, and electrode limit rolling density. Accordingly, it was confirmed that the capacity and rate characteristics of the battery in Comparative Examples 1 and 2 deteriorated compared to the Examples, and consequently, the energy density of the battery deteriorated. In this case, in Comparative Example 1, the degree of deterioration in battery energy density was significant due to the interplay of factors causing the deterioration of the cathode active material density.

[0223] In the case of Comparative Example 3, as a result of the iron content in the lithium metal oxide being too low and the manganese content being too high, the I(003) / I(104) peak intensity ratio was outside the range according to the present invention, and it was confirmed that four small peaks within one broad peak were additionally expressed as superlattice peaks. Accordingly, it was confirmed that the capacity, rate characteristics, lifespan, and energy density of the battery deteriorated compared to the example.

[0224] In the case of Comparative Example 4, when the LMFP composition of the conventional olivine structure was prepared by the solid-state method, it was confirmed that the true density was lowered, and the tap density, pellet density, and electrode limit rolling density of the cathode active material were significantly degraded compared to the example, and the sphericity was also significantly degraded. In addition, it was confirmed that no superlattice peaks were exhibited. In particular, even though the particle size of the primary particles was made much smaller than that of the example to properly express the capacity and rate characteristics of the battery, it was confirmed that they were inferior to the example. Furthermore, it was confirmed that the battery energy density was significantly degraded due to the interplay of factors causing the deterioration of the density of the cathode active material itself and factors causing the deterioration of capacity.

[0225]

[0226] Although preferred embodiments of the present invention have been described above, the present invention is not limited thereto and can be implemented with various modifications within the scope of the claims, the detailed description of the invention, and the attached drawings, and it is obvious that such modifications also fall within the scope of the present invention.

[0227] Therefore, the substantive scope of the present invention shall be defined by the appended claims and their equivalents.

Claims

1. A lithium metal oxide containing iron (Fe) and manganese (Mn) with an excess lithium composition, and The above lithium metal oxide has a molar ratio of iron to the total metal excluding lithium (Fe / Me) of 0.15 to 0.49, and The above lithium metal oxide has a molar ratio of manganese to the total metal excluding lithium (Mn / Me) of 0.51 to 0.85, and The above lithium metal oxide is a positive electrode active material for a lithium secondary battery having a molar ratio of lithium to lithium metal oxide of 1.05 to 1.

4.

2. In Paragraph 1, The above lithium metal oxide is a positive electrode active material for a lithium secondary battery having a structure in which a layered crystal structure in which lithium layers and transition metal layers are alternately stacked is mixed with a disordered rocksalt crystal structure in which lithium and transition metals are arranged in a disordered manner.

3. In Paragraph 2, The above lithium metal oxide is a positive electrode active material for a lithium secondary battery in which lithium ions move through a lithium layer and a transition metal layer during charging and discharging.

4. In Paragraph 1, The above lithium metal oxide is in the form of secondary particles formed by the aggregation of a plurality of primary particles, and the average particle size of the primary particles is 0.3 to 2 μm, and is a positive electrode active material for a lithium secondary battery.

5. In Paragraph 1, A positive electrode active material for a lithium secondary battery having a sphericity of 0.9 or higher.

6. In Paragraph 1, A positive electrode active material for a lithium secondary battery having a tap density of 2.1 g / cc or higher.

7. In Paragraph 1, A positive electrode active material for a lithium secondary battery having a pellet density of 2.7 g / cc or higher.

8. In Paragraph 1, The above lithium metal oxide is a positive electrode active material for a lithium secondary battery having a cation disorder mixed structure.

9. In Paragraph 1, The above lithium metal oxide is a positive electrode active material for a lithium secondary battery having a peak intensity ratio (I(003) / I(104)) of the (003) plane to the (104) plane when analyzed by X-ray diffraction (XRD) pattern analysis of 0.8 to 1.

3.

10. In Paragraph 1, The above lithium metal oxide is a positive electrode active material for a lithium secondary battery in which, when analyzing the X-ray diffraction (XRD) pattern, the superstructure peak that appears in the region where 2θ is 20 to 30° appears as a single broad peak.

11. In Paragraph 1, The above lithium metal oxide is a positive electrode active material for a lithium secondary battery represented by the following chemical formula 1: [Chemical Formula 1] Li 1+x (Fe a Mn b M c ) 1-x O2 In the above chemical formula 1, 0.05≤x≤0.4, 0.15≤a≤0.49, 0.51≤b≤0.85, 0≤c≤0.1, a+b+c=1, and M is an other doping element such as Cr, Ni, Zr, Al, B, Y, Co, Cu, Zn, Ga, Ge, Ru, Rh, Sn, Sb, Re, Ir, Pt, Pb, Bi, Na, K, Rb, Cs, Ca, Sr, Ba, Mg, Si, Sc, Ti, Nb, W, V, Mo, Ta, or a combination thereof.

12. A step of preparing iron (Fe) and manganese (Mn) containing metal hydroxide precursors by a coprecipitation process; and The method includes the step of mixing the metal hydroxide precursor and the lithium raw material, and then calcining to form a lithium metal oxide containing iron (Fe) and manganese (Mn) with an excess lithium composition. A method for manufacturing a positive electrode active material for a lithium secondary battery, wherein the lithium metal oxide has a molar ratio of iron to the total metal excluding lithium (Fe / Me) of 0.15 to 0.49, the lithium metal oxide has a molar ratio of manganese to the total metal excluding lithium (Mn / Me) of 0.51 to 0.85, and the lithium metal oxide has a molar ratio of lithium to the lithium metal oxide of 1.05 to 1.

4.

13. A positive electrode for a lithium secondary battery comprising the positive electrode active material of claim 1.

14. A lithium secondary battery comprising the positive electrode for a lithium secondary battery according to claim 13.

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