Positive electrode material, and positive electrode comprising same and lithium secondary battery

Abstract

The present invention relates to a positive electrode material capable of improving the performance of a lithium secondary battery, and relates to a positive electrode material, a positive electrode comprising same, and a lithium secondary battery, the positive electrode material comprising: a first positive electrode active material having an olivine structure; and a second positive electrode active material having a layered structure, wherein the first positive electrode active material has a voltage drop (x) according to equation 1 described in the present specification, satisfying a specific range.

Description

Cathode material, cathode containing same, and lithium secondary battery

[0001] Cross-citation with related applications

[0002] This application claims the benefit of priority from Korean Patent Application No. 10-2024-0009718, filed January 22, 2024, the entire contents of which are incorporated herein by reference.

[0003] Technology field

[0004] The present invention relates to a cathode material, a cathode including the same, and a lithium secondary battery.

[0005]

[0006] With the recent technological development and increasing demand for mobile devices and electric vehicles, the demand for secondary batteries as an energy source is rapidly increasing. Among these secondary batteries, lithium secondary batteries, which boast high energy density and voltage, long cycle life, and low self-discharge rates, are commercialized and widely used.

[0007] Lithium secondary batteries are composed of four major components: a cathode, an anode, a separator, and an electrolyte. Among these, the cathode active material contained in the cathode plays a significant role in determining the battery's capacity, output, and lifespan. For lithium secondary batteries to achieve high energy density, output, and lifespan, improving the performance of the cathode active material is essential. Consequently, extensive research has been conducted recently to develop high-performance cathode active materials.

[0008] Lithium transition metal oxides such as lithium cobalt oxides such as LiCoO2, lithium nickel oxides such as LiNiO2, lithium manganese oxides such as LiMnO2 or LiMn2O4, and lithium iron phosphate compounds such as LiFePO4 have been developed as positive electrode active materials for lithium secondary batteries, and recently, Li[Ni a Co b Mn c ]O2, Li[Ni a Cob Al c ]O2, Li[Ni a Co b Mn c Al d ] Lithium composite transition metal oxides containing two or more transition metals, such as O2, have been developed and are widely used.

[0009] Meanwhile, lithium iron phosphate compounds with an olivine structure are promising active materials because they have excellent structural stability, excellent life characteristics, and superior safety in all aspects, including overcharge and overdischarge.

[0010] In particular, LiFePO4 has excellent high-temperature stability due to the strong bonding force of PO4, and because it contains iron, which is abundant and inexpensive, it is cheaper than the aforementioned LiCoO2, LiNiO2, or LiMn2O4, and has low toxicity, so it has less impact on the environment. However, since LiFePO4 has low electrical conductivity, there is a problem that the internal resistance of the battery increases when LiFePO4 is used as a positive electrode active material. This causes the polarization potential to increase when the battery circuit is closed, which reduces the battery capacity. In addition, since LiFePO4 has a lower density than typical positive electrode active materials, there is a limitation in that it cannot sufficiently increase the energy density of the battery, and since it usually has the form of secondary particles in which primary particles are assembled, there is a problem that the interfacial resistance between the primary particles is large, resulting in low output characteristics.

[0011] To address this issue, attempts have been made to combine lithium complex transition metal oxides with lithium iron phosphate compounds. However, lithium iron phosphate compounds have a lower operating voltage than lithium complex transition metal oxides, so lithium complex transition metal oxides operate independently at high voltages. This presents a challenge for applications where life and output characteristics are particularly important.

[0012]

[0013] [Prior Art Literature]

[0014] [Patent Document]

[0015] Japanese Patent Publication No. 2002-075368

[0016]

[0017] The present invention is intended to solve the above problems and to provide a cathode material capable of improving the life characteristics of a battery.

[0018] In addition, the present invention seeks to provide a cathode and secondary battery having excellent life characteristics, including the cathode material as described above.

[0019]

[0020] (1) The present invention provides a cathode material comprising a first cathode active material having an olivine structure; and a second cathode active material having a layered structure; wherein the first cathode active material has a voltage drop (χ) of 0.50 V or less according to the following equation 1.

[0021] [Formula 1]

[0022] Voltage drop (χ) [V] = (open circuit voltage (α) measured after a rest period of 4.25 - 20 minutes) [V]

[0023] In the above equation 1, α is the open circuit voltage measured immediately after charging a lithium secondary battery including a positive electrode including a positive electrode active material layer containing a positive electrode active material in a content of 80 wt% or more and 98 wt% or less based on the total weight of the positive electrode active material layer to 4.25 V using the CC (0.1 C)-CV (Cut off current: 0.05 C) method at 25°C and leaving it for 20 minutes.

[0024] (2) The present invention provides a cathode material in which, in the above (1), the first cathode active material includes a lithium iron phosphate compound having a composition represented by the following chemical formula 1.

[0025] [Chemical Formula 1]

[0026] Li 1+x Fe 1-a M1 a PO4

[0027] In the above chemical formula 1, M 1 is at least one selected from Al, Mg, Ni, Co, Mn, Ti, Ga, Cu, V, Nb, Zr, Ce, In, Zn, Na, Si, Ca, B and Y, and -0.1≤x≤0.1, 0.0≤a≤0.8.

[0028] (3) The present invention provides a cathode material in (2) above, wherein the first cathode active material further includes a coating layer including carbon (C) formed on the lithium iron phosphate compound.

[0029] (4) The present invention provides a positive electrode material in which, in the above (3), the content of carbon (C) included in the coating layer is 1.50 wt% or more and 5.00 wt% or less with respect to the total weight of the first positive electrode active material.

[0030] (5) The present invention provides a cathode material in any one of the above (1) to (4), wherein the first cathode active material has an average crystallite size of 80.00 nm or more and 150.00 nm or less.

[0031] (6) In any one of (1) to (5), the first positive electrode active material has an average particle diameter (D 50 ) provides a cathode material having a thickness of 0.30㎛ or more and 8.00㎛ or less.

[0032] (7) The present invention provides a cathode material in which the weight ratio of the first cathode active material and the second cathode active material is 10:90 to 90:10 in any one of the above (1) to (6).

[0033] (8) The present invention provides a cathode material in which the weight ratio of the first cathode active material and the second cathode active material is 10:90 to 80:20 in any one of the above (1) to (7).

[0034] (9) The present invention provides a cathode material in any one of the above (1) to (8), wherein the second cathode active material has a composition represented by the following chemical formula 2.

[0035] [Chemical Formula 2]

[0036] Li 1+y1 Ni p1 Mn q1 Co r1 M 2 s1 O2

[0037] In the above chemical formula 2, M 2 is at least one selected from Zr, Al, Re, V, Cr, Fe, Ga, Si, B, Ru, Ti, Nb, Mo, Mg, W, Na, and Pt, and 0.00≤y1≤0.50, 0.00 <p1<1.00, 0.00<q1<0.50, 0.00<r1<0.50, 0.000≤s1≤0.010이다.

[0038] (10) In any one of (1) to (9), the second positive electrode active material has an average particle diameter (D 50 ) provides a cathode material having a thickness of 4㎛ or more and 13㎛ or less.

[0039] (11) The present invention provides a cathode comprising a cathode material according to any one of (1) to (10).

[0040] (12) The present invention provides a lithium secondary battery including a positive electrode according to (11) above.

[0041]

[0042] The cathode material according to the present invention includes a first cathode active material having an olivine structure; and a second cathode active material having a layered structure; and when the first cathode active material satisfies a specific condition (a voltage drop (χ) according to Equation 1 described herein is 0.50 V or less), the life characteristics at high voltage of a battery including the cathode material according to the present invention can be improved.

[0043]

[0044] Figure 1 is XRD data of the first positive electrode active material manufactured in Manufacturing Example 2.

[0045]

[0046] Hereinafter, the present invention will be described in more detail to help understand the present invention.

[0047] Terms or words used in this specification and claims should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted as meanings and concepts that conform to the technical spirit of the present invention, based on the principle that the inventor can appropriately define the concept of the term to explain his or her own invention in the best possible manner.

[0048] In this specification, it should be understood that terms such as “include,” “have,” or “have” are intended to specify the presence of a feature, number, step, component, or combination thereof, but do not preclude the possibility of the presence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0049] In this specification, 'crystallite' means a particle unit having substantially the same crystal orientation.

[0050] In this specification, the 'average crystallite size' can be quantitatively analyzed using X-ray diffraction analysis (XRD) using Cu Kα X-rays. Specifically, XRD data of the synthesized positive electrode active material were obtained using Bruker's D8 XRD equipment (Cu-target, voltage: 45 kV, current: 40 mA, 2θ: 10° to 80°). For the obtained data, structural analysis was performed using the Rietveld refinement method, which is a general structural analysis method, using Malvern panalytical's Highscore software.

[0051] The Rietveld refinement method calculates a diffraction pattern from an initial structural model of the crystal structure of a material, compares it with the measured diffraction pattern of an actual synthetic material, and gradually adjusts it by introducing various structural factors and changing their values ​​until the two patterns match well.

[0052] This method iterates until the difference between the calculated and measured patterns is minimized, judging validity based on the difference between the two patterns. Among the structural factors that can be introduced during this process, crystal size can be determined using the peak full width at half maximum (FWHM) of each crystal plane appearing in the measured diffraction pattern.

[0053] In this specification, the average particle diameter (D 50 ) can be defined as the particle size corresponding to 50% of the volume cumulative distribution in the particle size distribution curve (graph curve of particle size distribution) of each particle. The above average particle size is calculated by dispersing the powder to be measured in a dispersion medium, introducing it into a commercially available laser diffraction particle size measuring device (e.g., Mastersizer3000 of Malvern), and measuring the difference in diffraction pattern according to particle size when the particles pass through the laser beam, and calculating the particle diameter at the point where it becomes 50% of the volume cumulative distribution according to the particle size in the measuring device, thereby obtaining D 50 can be measured.

[0054] In this specification, the content of each element in the lithium iron phosphate compound may be measured through ICP (Inductive Coupled Plasma) analysis using an inductively coupled plasma optical emission spectrometer (ICP-OES; Agilent 5110, Agilent).

[0055]

[0056] cathode material

[0057] Hereinafter, the cathode material according to the present invention will be described.

[0058] The cathode material according to the present invention includes a first cathode active material having an olivine structure; and a second cathode active material having a layered structure; wherein the first cathode active material has a voltage drop (χ) of 0.50 V or less according to the following equation 1.

[0059] [Formula 1]

[0060] Voltage drop (χ) [V] = (open circuit voltage (α) measured after a rest period of 4.25 - 20 minutes) [V]

[0061] In the above equation 1, α is the open circuit voltage measured immediately after charging a lithium secondary battery including a positive electrode including a positive electrode active material layer containing a positive electrode active material in a content of 80 wt% or more and 98 wt% or less based on the total weight of the positive electrode active material layer to 4.25 V using the CC (0.1 C)-CV (Cut off current: 0.05 C) method at 25°C and leaving it for 20 minutes.

[0062]

[0063] The present inventors have found that in the case of a cathode material including a first cathode active material having an olivine structure and a voltage drop (χ) of 0.50 V or less according to Equation 1 described herein; and a second cathode active material having a layered structure, the voltage drop of the first cathode active material is reduced at the operating voltage of the cathode material, so that the first cathode active material and the second cathode active material operate evenly during battery charging and discharging, thereby improving output characteristics, resistance characteristics, and life characteristics, and have completed the present invention.

[0064] The voltage drop according to Equation 1 described in this specification is determined by a complex interaction of various factors, such as the composition of the cathode material, particle size, content of carbon (C) in the cathode active material, and average crystallite size.

[0065] With respect to Equation 1 described herein, the voltage drop (χ) was calculated as the difference between 4.25 V, which is the operating voltage of the positive electrode material, and α. α is the open circuit voltage measured immediately after charging a lithium secondary battery including a positive electrode including a positive electrode active material layer containing a positive electrode active material in a content of 80 wt% or more and 98 wt% or less based on the total weight of the positive electrode active material layer to 4.25 V using the CC (0.1 C)-CV (Cut off current: 0.05 C) method at 25°C and leaving it for 20 minutes. Specifically, a lithium secondary battery including a positive electrode including a positive electrode active material layer containing the first positive electrode active material at a content of 90 wt% based on the total weight of the positive electrode active material layer and a voltage of 4.25 V is manufactured, and the battery is charged to 4.25 V at 25° C. in a CC (0.1 C)-CV (Cut off current: 0.05 C) manner, and then the voltage drop (χ) of the first positive electrode active material can be calculated as the difference of the open circuit voltage α measured immediately after a rest period of 20 minutes. A smaller α means a larger voltage drop at 4.25 V. A voltage drop (χ) of 0 V, i.e., α of 4.25 V, means that a lithium secondary battery including a positive electrode including a positive electrode active material layer containing a positive electrode active material in a content of 80 wt% or more and 98 wt% or less based on the total weight of the positive electrode active material layer is charged to 4.25 V by the CC (0.1 C)-CV (Cut off current: 0.05 C) method at 25°C, and an open circuit voltage measured immediately after a 20-minute rest period, and no voltage drop occurs.

[0066]

[0067] Meanwhile, although the first positive electrode active material has excellent stability, there is a problem that the resistance characteristics and output characteristics are poor in the high voltage range, and although the second positive electrode active material has high output, its use is sometimes limited due to low stability, and there is an economic disadvantage. In addition, when the first positive electrode active material and the second positive electrode active material are included, but the voltage drop (χ) according to Equation 1 described in the present specification of the first positive electrode active material exceeds 0.50 V, the voltage drop of the first positive electrode active material is large at the operating voltage of the positive electrode material, so that it acts as a resistor, and there is a problem that the life characteristics of the secondary battery including the positive electrode material are poor at high voltage.

[0068] Specifically, the voltage drop (χ) according to Equation 1 described herein may be 0.00 V or more, 0.10 V or more, 0.20 V or more, or 0.25 V or more, and may be 0.50 V or less, 0.49 V or less, 0.48 V or less, 0.47 V or less, 0.46 V or less, 0.45 V or less, 0.44 V or less, 0.42 V or less, 0.41 V or less, 0.40 V or less, 0.39 V or less, 0.38 V or less, 0.37 V or less, 0.36 V or less, 0.35 V or less, or 0.34 V or less. When the voltage drop (χ) is within the above range, the voltage drop of the first positive electrode active material is reduced at the operating voltage of the positive electrode material including the first positive electrode active material and the second positive electrode active material, and the first positive electrode active material and the second positive electrode active material operate evenly during charge and discharge, thereby improving the life characteristics.

[0069]

[0070] According to one embodiment of the present invention, the first positive electrode active material may include a lithium iron phosphate compound having a composition represented by the following chemical formula 1.

[0071] [Chemical Formula 1]

[0072] Li 1+x Fe 1-a M 1 a PO4

[0073] In the above chemical formula 1,

[0074] M 1 is at least one selected from Al, Mg, Ni, Co, Mn, Ti, Ga, Cu, V, Nb, Zr, Ce, In, Zn, Na, Si, Ca, B and Y,

[0075] -0.1≤x≤0.1, 0.0≤a≤0.8.

[0076] Above M 1 is a doping element, specifically the above M 1 The M may be at least one selected from Al, Mg, Ni, Co, Mn, Ti, Ga, Cu, V, Nb, Zr, Ce, In, Zn, Na, Si, Ca, B and Y. 1 Although it is not essential to include it, if included in an appropriate amount, the particle shape of the positive electrode active material is improved, the stability of the crystal structure is enhanced, and the rate characteristics of the secondary battery to which it is applied can be improved.

[0077] Meanwhile, the above x may be -0.1 or more, or 0.0 or more, and 0.05 or less, or 0.1 or less. When x satisfies the above range, structural stability may be improved.

[0078] The above a may be 0.0 or more, 0.1 or more, or 0.2 or more, and may be 0.3 or less, 0.4 or less, or 0.8 or less. When a satisfies the above range, a high energy density may be exhibited, thereby realizing high-capacity characteristics.

[0079]

[0080] According to one embodiment of the present invention, the first positive electrode active material may further include a coating layer comprising carbon (C) formed on the lithium iron phosphate compound. By further including a coating layer comprising carbon (C), the electronic conductivity of the positive electrode active material can be improved.

[0081] Meanwhile, the content of carbon (C) included in the coating layer may be 1.50 wt% or more and 5.00 wt% or less based on the total weight of the first positive electrode active material. Specifically, the content of carbon (C) included in the coating layer may be 1.50 wt% or more, or 2.00 wt% or more, and 3.00 wt% or less, 3.50 wt% or less, 4.00 wt% or less, or 5.00 wt% or less based on the total weight of the first positive electrode active material. In particular, when the content of carbon (C) included in the coating layer is within the above range, the electronic conductivity of the positive electrode active material may be improved without acting as a resistor.

[0082]

[0083] According to one embodiment of the present invention, the first positive electrode active material may have an average crystallite size of 80.00 nm or more and 150.00 nm or less. Specifically, the first positive electrode active material may have an average crystallite size of 80.00 nm or more, 90.00 nm or more, or 94.00 nm or more, 97.00 nm or less, 100.00 nm or less, 120.00 nm or less, or 150.00 nm or less. When the average crystallite size of the first positive electrode active material is within the above range, the capacity characteristics and rate characteristics of the positive electrode active material may be improved.

[0084]

[0085] According to one embodiment of the present invention, the first positive electrode active material has an average particle diameter (D 50 ) may be 0.30㎛ or more and 8.00㎛ or less. The first positive electrode active material may have an average particle diameter (D 50 ) may be 0.30㎛ or more, or 1.00㎛ or more, and may be 6.50㎛ or less, 7.00㎛ or less, 7.50㎛ or less, or 8.00㎛ or less. The first positive electrode active material may have an average particle diameter (D 50 ) is within the above range, the electrode density can be increased.

[0086]

[0087] According to one embodiment of the present invention, the weight ratio of the first positive electrode active material and the second positive electrode active material may be 10:90 to 90:10. Specifically, the weight ratio may be 10:90 to 90:10, 10:90 to 80:20, 20:80 to 90:10, 20:80 to 80:20, 30:70 to 90:10, 30:70 to 80:20, 40:60 to 90:10, or 40:60 to 80:20. When the weight ratio is within the above range, there is an effect of improving stability while exhibiting excellent resistance and output characteristics at high voltage. The operating voltages of the first positive electrode active material and the second positive electrode active material are different, and in particular, when the weight ratio of the first positive electrode active material and the second positive electrode active material is 10:90 to 80:20, the voltage drop of the first positive electrode active material in the operating voltage of the positive electrode material is reduced, so that the first positive electrode active material and the second positive electrode active material operate evenly during battery charging and discharging, and the life characteristics, etc. can be improved.

[0088]

[0089] According to one embodiment of the present invention, the second positive electrode active material may have a composition represented by the following chemical formula 2.

[0090] [Chemical Formula 2]

[0091] Li 1+y1 Ni p1 Mn q1 Co r1 M 2 s1 O2

[0092] In the above chemical formula 2,

[0093] M 2 is at least one selected from Zr, Al, Re, V, Cr, Fe, Ga, Si, B, Ru, Ti, Nb, Mo, Mg, W, Na and Pt,

[0094] 0.00≤y1≤0.50, 0.00 <p1<1.00, 0.00<q1<0.50, 0.00<r1<0.50, 0.000≤s1≤0.010이다.

[0095] Above M 2 is a doping element, specifically the above M 2 M may be at least one selected from Zr, Al, Re, V, Cr, Fe, Ga, Si, B, Ru, Ti, Nb, Mo, Mg, W, Na and Pt. 2 Although not necessarily included, if included in an appropriate amount, the particle shape of the positive electrode active material can be improved and the stability of the crystal structure can be enhanced.

[0096] Meanwhile, the above y1 may be 0.00 or more, 0.10 or more, or 0.20 or more, and may be 0.30 or less, 0.40 or less, or 0.50 or less. When y1 satisfies the above range, high capacity characteristics and high energy density per unit volume can be realized.

[0097] The above p1 is the molar ratio of nickel (Ni) among all metals excluding lithium in the lithium composite transition metal oxide, and may be greater than 0.00, 0.20 or more, 0.40 or more, 0.50 or more, 0.60 or more, 0.70 or more, or 0.80 or more, and may be 0.90 or less, or less than 1.00. When p1 satisfies the above range, high energy density is exhibited, so that high-capacity characteristics can be realized.

[0098] The above q1 is the molar ratio of manganese (Mn) among all metals excluding lithium in the lithium composite transition metal oxide, and may be greater than 0.00, or 0.20 or less, 0.30 or less, 0.40 or less, or less than 0.50. When q1 satisfies the above range, high-capacity characteristics can be realized. In addition, high-temperature stability can be increased, and the decomposition reaction of the electrolyte can be relatively reduced.

[0099] The above r1 is the molar ratio of cobalt (Co) among all metals excluding lithium in the lithium composite transition metal oxide, and may be greater than 0.00, or less than or equal to 0.10, less than or equal to 0.20, less than or equal to 0.30, less than or equal to 0.40, or less than 0.50. When r1 satisfies the above range, structural stability may be improved.

[0100] The above s1 is M among all metals except lithium in the lithium composite transition metal oxide. 2 The molar ratio may be 0.000 or more, 0.002 or more, or 0.004 or more, and may be 0.006 or less, 0.008 or less, or 0.010 or less. When s1 satisfies the above range, the particle shape of the positive electrode active material may be improved, and the stability of the crystal structure may be enhanced.

[0101] The above p1, q1, r1, s1 can be p1+q1+r1+s1=1.

[0102]

[0103] According to one embodiment of the present invention, the second positive electrode active material has an average particle diameter (D 50 ) may be 4㎛ or more and 13㎛ or less. Specifically, the second positive electrode active material has an average particle diameter (D 50 ) may be 4 ㎛ or more, 5 ㎛ or more, 6 ㎛ or more, 7 ㎛ or more, 8 ㎛ or more, or 9 ㎛ or more, and may be 10 ㎛ or less, 11 ㎛ or less, 12 ㎛ or less, or 13 ㎛ or less. The second positive electrode active material may have an average particle diameter (D 50 ) is within the above range, the average particle diameter (D) of the first positive electrode active material 50 ) and the average particle diameter (D) of the second positive electrode active material 50 ) can be adjusted to improve the electrode density.

[0104]

[0105] The first cathode active material of the present invention can be manufactured using conventional methods in the art. For example, it can be manufactured by calcining a precursor and a lithium raw material.

[0106] Specifically, the first positive electrode active material of the present invention can be manufactured by a method of manufacturing a first positive electrode active material including a lithium iron phosphate compound by (a) mixing a lithium-containing raw material and iron phosphate (FePO4) to manufacture a mixture; and (b) calcining the mixture.

[0107] The lithium-containing 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-containing raw material may be Li2CO3, LiNO3, LiNO2, LiOH, LiOHㆍH2O, LiH, LiF, LiCl, LiBr, LiI, CH3COOLi, Li2O, Li2SO4, CH3COOLi, or Li3C6H5O7, and any one of these or a mixture of two or more thereof may be used.

[0108] When preparing the mixture in the above step (a), a raw material containing a doping element, for example, a raw material containing manganese, etc., may be further mixed.

[0109] According to the present invention, in the step (a), the lithium-containing raw material and iron phosphate (FePO4) can be mixed in an amount such that they have a composition represented by the chemical formula 1 described herein.

[0110] After the above step (a), it may include a step of additionally mixing a carbon-containing coating raw material.

[0111] The above carbon-containing coating raw material may be at least one selected from sucrose, glucose, polyethylene glycol, polyvinyl alcohol, and polyvinyl acetate.

[0112] The above carbon-containing coating raw material may be mixed in an amount of 1.5 wt% or more and 5 wt% or less based on the total weight of the first positive electrode active material.

[0113] The above step (b) may be to manufacture a lithium iron phosphate compound by calcining the mixture at a temperature of 500°C to 1,000°C.

[0114] The first positive electrode active material manufactured according to the above first positive electrode active material manufacturing method may have a composition represented by the chemical formula 1 described herein.

[0115] The first positive electrode active material manufactured according to the above method for manufacturing the first positive electrode active material may include a coating layer including carbon (C) formed on a lithium iron phosphate compound.

[0116]

[0117] The second cathode active material of the present invention can be manufactured using conventional methods in the art. For example, it can be manufactured by calcining a cathode active material precursor and a lithium-containing raw material.

[0118] Specifically, the second positive electrode active material of the present invention can be manufactured by a method for manufacturing a second positive electrode active material, including (A) a step of mixing a positive electrode active material precursor, which is a composite transition metal hydroxide, a composite transition metal oxyhydroxide, or a combination thereof, and a lithium-containing raw material to manufacture a mixture; and (B) a step of calcining the mixture to manufacture a lithium composite transition metal oxide.

[0119] The lithium-containing 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-containing raw material may be Li2CO3, LiNO3, LiNO2, LiOH, LiOHㆍH2O, LiH, LiF, LiCl, LiBr, LiI, CH3COOLi, Li2O, Li2SO4, CH3COOLi, or Li3C6H5O7, and any one of these or a mixture of two or more thereof may be used.

[0120] The above complex transition metal hydroxide, complex transition metal oxyhydroxide or combination thereof and the lithium-containing raw material may be mixed so that the ratio of the number of moles of lithium (Li) included in the lithium-containing raw material to the total number of moles (M'') of transition metals included in the complex transition metal hydroxide, complex transition metal oxyhydroxide or combination thereof (Li / M'') is 1.00 or more, 1.01 or more, or 1.02 or more, 1.03 or more, 1.04 or more, 1.05 or more, and 1.06 or less, 1.07 or less, 1.08 or less, 1.09 or less, or 1.10 or less.

[0121] When preparing the mixture in step (A) above, a raw material containing a doping element, for example, an aluminum-containing raw material, a zirconium-containing raw material, a yttrium-containing raw material, etc., may be further mixed.

[0122] According to one embodiment of the present invention, in step (A), a composite transition metal hydroxide containing cobalt, nickel, and manganese, a lithium (Li)-containing raw material, and a doping element-containing raw material may be mixed in an amount such that the composition is represented by the chemical formula 2 described herein.

[0123] The above step (B) may be to produce a lithium composite transition metal oxide by calcining the mixture at a temperature of 700°C to 1,000°C.

[0124] The above firing may be performed under an oxygen atmosphere.

[0125] The second positive electrode active material manufactured according to the above method for manufacturing the second positive electrode active material may have a composition represented by the chemical formula 2 described herein.

[0126]

[0127] The cathode material of the present invention can be manufactured using conventional methods in the art. Specifically, it can be manufactured by mixing a first cathode active material and a second cathode active material.

[0128]

[0129] anode

[0130] Next, the anode according to the present invention will be described.

[0131] The positive electrode according to the present invention comprises a positive electrode active material layer comprising a positive electrode material according to the present invention. Specifically, the positive electrode comprises a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector, and comprising the positive electrode material. Since the positive electrode material has been described above, a detailed description thereof will be omitted, and only the remaining components will be described in detail below.

[0132]

[0133] 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 µm to 500 µm, and fine unevenness may be formed on the surface of the positive electrode current collector to increase the adhesive strength 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.

[0134]

[0135] The above-mentioned positive electrode active material layer may include a positive electrode material, a conductive material, and a binder. In this case, the positive electrode material may be included in an amount of 80 wt% to 99 wt%, more specifically 85 wt% to 98.5 wt%, based on the total weight of the positive electrode active material layer, and excellent capacity characteristics may be exhibited within this range.

[0136]

[0137] The conductive material is used to provide conductivity to the electrode, and in the battery to be formed, 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 of these may be used. The conductive material may be included in an amount of 0.1 wt% to 15 wt% based on the total weight of the positive electrode active material layer.

[0138]

[0139] The above binder serves to improve the adhesion between positive electrode active material particles and the adhesion between the positive electrode material and the 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, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluoroelastomer, or various copolymers thereof, and one of these may be used alone or a mixture of two or more thereof. The binder may be included in an amount of 0.1 wt% to 15 wt% based on the total weight of the positive electrode active material layer.

[0140]

[0141] The above-mentioned positive electrode can be manufactured according to a conventional positive electrode manufacturing method, except that the above-mentioned positive electrode material is used. Specifically, the positive electrode can be manufactured by coating a composition for forming a positive electrode active material layer, which is manufactured by dissolving or dispersing the above-mentioned positive electrode material and optionally a binder and a conductive agent in a solvent, on a positive electrode current collector, followed by drying and rolling. At this time, the types and contents of the positive electrode material, binder, and conductive agent are as described above. Alternatively, the positive electrode can be manufactured by casting the composition for forming a positive electrode active material layer on a separate support, and then laminating the film obtained by peeling it from the support on a positive electrode current collector.

[0142]

[0143] The solvent may be a solvent generally used in the relevant technical field, such as dimethyl sulfoxide (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.

[0144]

[0145] lithium secondary battery

[0146] Next, a lithium secondary battery according to the present invention will be described.

[0147]

[0148] The present invention can manufacture an electrochemical device including the above-described positive electrode. The electrochemical device may be, specifically, a battery, a capacitor, or the like, and more specifically, a lithium secondary battery.

[0149]

[0150] The lithium secondary battery specifically includes a positive electrode, a negative electrode positioned opposite the positive electrode, and a separator and electrolyte interposed between the positive electrode and the negative electrode. Since the positive electrode is the same as described above, a detailed description thereof will be omitted, and only the remaining components will be described in detail below.

[0151]

[0152] In addition, the 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.

[0153]

[0154] In the above lithium secondary battery, the negative electrode includes a negative electrode current collector and a negative electrode active material layer positioned on the negative electrode current collector.

[0155] 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.

[0156]

[0157] The above negative electrode active material layer optionally includes a binder and a conductive material together with the negative electrode active material.

[0158]

[0159] As the negative electrode active material, a compound capable of reversible intercalation and deintercalation of lithium may be used. Specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloy, Sn alloy, or Al alloy; SiO β (0<β<2), SnO2, vanadium oxide, lithium vanadium oxide, and other metal oxides capable of doping and dedoping lithium; or composites containing the above 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.

[0160] The above negative electrode active material may be included in an amount of 80% to 99% by weight based on the total weight of the negative electrode active material layer.

[0161]

[0162] The above binder is a component that assists in bonding between the conductive material, the active material, and the current collector, and can typically be added in an amount of 0.1 wt% to 10 wt% based on the total weight of the negative electrode active material layer. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluororubber, and various copolymers thereof.

[0163]

[0164] The conductive agent is a component for further improving the conductivity of the negative electrode active material, and may be added in an amount of 10 wt% or less, specifically, 5 wt% or less, based on the total weight of the negative electrode active material layer. The conductive agent is not particularly limited as long as it has conductivity and does not cause a chemical change in the battery, and examples thereof include graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fiber or metal fiber; metal powders such as fluorocarbon, aluminum, and nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives.

[0165]

[0166] The negative electrode active material layer may be manufactured by applying and drying a composition for forming a negative electrode active material layer prepared by dissolving or dispersing a negative electrode active material, and optionally a binder and a conductive material in a solvent, on a negative electrode current collector, or by casting the composition for forming a negative electrode active material layer on a separate support, and then laminating the film obtained by peeling it off from the support on a negative electrode current collector.

[0167]

[0168] Meanwhile, in the lithium secondary battery, the separator separates the negative electrode and the positive electrode and provides a passage for lithium ions to move. Any separator commonly used in lithium secondary batteries can be used without special restrictions, and in particular, one 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, can 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. can also be used. In addition, a coated separator containing a ceramic component or a polymer material to secure heat resistance or mechanical strength can be used, and can optionally be used in a single-layer or multi-layer structure.

[0169]

[0170] In addition, examples of the electrolyte used in the present invention include, but are not limited to, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in the manufacture of lithium secondary batteries.

[0171] Specifically, the electrolyte may include an organic solvent and a lithium salt.

[0172] As the organic solvent, any solvent that can serve as a medium through which ions involved in the electrochemical reaction of the battery can move may be used without particular limitation. Specifically, the organic solvent includes 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), ethylmethylcarbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); Alcohol solvents such as ethyl alcohol, isopropyl alcohol, etc.; nitriles such as R-CN (R is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and may include a double-bonded aromatic ring or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes, etc. can be used. Among these, carbonate solvents are preferable, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate) having high ionic conductivity and high dielectric constant that can improve the charge / discharge performance of a battery and a low-viscosity linear carbonate compound (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate) 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.

[0173]

[0174] 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. The concentration of the lithium salt is preferably used within the range of 0.1 to 5.0 M, specifically, 0.1 to 3.0 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.

[0175]

[0176] 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, hexaphosphoric 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 additive may be included in an amount of 0.1 to 10 wt%, specifically, 0.1 to 5 wt%, based on the total weight of the electrolyte.

[0177]

[0178] As described above, a lithium secondary battery including a cathode material according to the present invention exhibits excellent resistance characteristics, 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).

[0179] Accordingly, according to another embodiment of the present invention, a battery module including the lithium secondary battery as a unit cell and a battery pack including the same are provided.

[0180] 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.

[0181] There is no particular limitation on the external shape of the lithium secondary battery of the present invention, but it may be a cylindrical shape using a can, a square shape, a pouch shape, or a coin shape.

[0182] The lithium secondary battery according to the present invention can be used not only as a battery cell used as a power source for a small device, but can also be preferably used as a unit battery in a medium- to large-sized battery module including a plurality of battery cells.

[0183]

[0184] 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.

[0185]

[0186] Manufacturing example

[0187] Manufacturing Example 1

[0188] Li2CO3 and FePO4 are mixed so that the molar ratio of Li:Fe is 1.05:1, and mixed with water so that the solid concentration is 20 wt%, and then wet-milled with a bead mill to make a slurry (D 50 :200 nm) was prepared. Thereafter, sucrose was mixed into the slurry to prepare a mixture. At this time, sucrose was mixed in an amount of 12 wt% based on the total weight of Li2CO3 and FePO4.

[0189] After spray drying the above mixture (inlet temperature 230°C, outlet temperature 95°C), the mixture was calcined at a temperature of 700°C for 10 hours under a nitrogen atmosphere to produce a first positive electrode active material in which a coating layer including carbon (C) was formed on a lithium iron phosphate compound having a composition represented by LiFePO4.

[0190]

[0191] Manufacturing Example 2

[0192] A first positive electrode active material was manufactured in which a coating layer including carbon (C) was formed on a lithium iron phosphate compound having a composition represented by LiFePO4 in the same manner as in Manufacturing Example 1, except that the mixture was spray-dried (inlet temperature 230°C, outlet temperature 95°C), calcined at a temperature of 700°C for 10 hours in a nitrogen atmosphere, and then pulverized with a jet mill.

[0193]

[0194] Manufacturing Example 3

[0195] A first positive electrode active material was manufactured in which a coating layer including carbon (C) was formed on a lithium iron phosphate compound having a composition represented by LiFePO4 in the same manner as in Manufacturing Example 1, except that sucrose was mixed in an amount of 10 wt% based on the total weight of Li2CO3 and FePO4, the mixture was spray-dried (inlet temperature 230°C, outlet temperature 95°C), and then calcined at a temperature of 700°C for 10 hours under a nitrogen atmosphere.

[0196]

[0197] Manufacturing Example 4

[0198] A first positive electrode active material was manufactured in which a coating layer including carbon (C) was formed on a lithium iron phosphate compound having a composition represented by LiFePO4 in the same manner as in Manufacturing Example 3, except that the mixture was spray-dried (inlet temperature 230°C, outlet temperature 95°C), calcined at a temperature of 700°C for 10 hours in a nitrogen atmosphere, and then pulverized with a jet mill.

[0199]

[0200] Manufacturing Example 5

[0201] A first positive electrode active material was manufactured in which a coating layer including carbon (C) was formed on a lithium iron phosphate compound having a composition represented by LiFePO4 in the same manner as in Manufacturing Example 1, except that sucrose was mixed in an amount of 6 wt% based on the total weight of Li2CO3 and FePO4, the mixture was spray-dried (inlet temperature 230°C, outlet temperature 95°C), and then calcined at a temperature of 750°C for 10 hours under a nitrogen atmosphere.

[0202]

[0203] Manufacturing Example 6

[0204] A first positive electrode active material was manufactured in which a coating layer including carbon (C) was formed on a lithium iron phosphate compound having a composition represented by LiFePO4 in the same manner as in Manufacturing Example 5, except that the mixture was spray-dried (inlet temperature 230°C, outlet temperature 95°C), calcined at a temperature of 750°C for 10 hours under a nitrogen atmosphere, and then pulverized with a jet mill.

[0205]

[0206] Examples and Comparative Examples

[0207] Example 1

[0208] Li 1.03 Ni 0.86 Mn 0.07 Co 0.05 Al 0.02 O2 (Manufacturer: LG Chemical, D 50 : A second positive electrode active material having a composition represented by (10㎛, secondary particle form) was prepared.

[0209] A cathode material was manufactured by mixing the first cathode active material manufactured in Manufacturing Example 1 and the second cathode active material in a weight ratio of 40:60.

[0210]

[0211] Example 2

[0212] A cathode material was manufactured in the same manner as in Example 1, except that the weight ratio of the first cathode active material and the second cathode active material was mixed to be 80:20.

[0213]

[0214] Example 3

[0215] Li 1.03 Ni 0.86 Mn 0.07 Co 0.05 Al 0.02 O2 (Manufacturer: LG Chemical, D 50 : A second positive electrode active material having a composition represented by (10㎛, secondary particle form) was prepared.

[0216] A cathode material was manufactured by mixing the first cathode active material manufactured in Manufacturing Example 2 and the second cathode active material in a weight ratio of 40:60.

[0217]

[0218] Example 4

[0219] A cathode material was manufactured in the same manner as in Example 3, except that the weight ratio of the first cathode active material and the second cathode active material was mixed to be 80:20.

[0220]

[0221] Example 5

[0222] Li 1.03 Ni 0.81 Mn 0.12 Co 0.05 Al 0.02 O2 (Manufacturer: LG Chemical, D 50 : A second positive electrode active material having a composition represented by (4㎛, secondary particle form) was prepared.

[0223] A cathode material was manufactured by mixing the first cathode active material manufactured in Manufacturing Example 2 and the second cathode active material in a weight ratio of 40:60.

[0224]

[0225] Example 6

[0226] A cathode material was manufactured in the same manner as in Example 5, except that the weight ratio of the first cathode active material and the second cathode active material was mixed to be 80:20.

[0227]

[0228] Example 7

[0229] Li 1.03 Ni 0.86 Mn 0.07 Co 0.05 Al 0.02 O2 (Manufacturer: LG Chemical, D 50 : A second positive electrode active material having a composition represented by (10㎛, secondary particle form) was prepared.

[0230] A cathode material was manufactured by mixing the first cathode active material manufactured in Manufacturing Example 3 and the second cathode active material in a weight ratio of 40:60.

[0231]

[0232] Example 8

[0233] Li 1.03 Ni 0.86 Mn 0.07 Co 0.05 Al 0.02 O2 (Manufacturer: LG Chemical, D 50 : A second positive electrode active material having a composition represented by (10㎛, secondary particle form) was prepared.

[0234] A cathode material was manufactured by mixing the first cathode active material manufactured in Manufacturing Example 4 and the second cathode active material in a weight ratio of 40:60.

[0235]

[0236] Example 9

[0237] A cathode material was manufactured in the same manner as in Example 3, except that the weight ratio of the first cathode active material and the second cathode active material was mixed to be 90:10.

[0238]

[0239] Comparative Example 1

[0240] Li 1.03 Ni 0.86 Mn 0.07 Co 0.05 Al 0.02 O2 (Manufacturer: LG Chemical, D 50 : A second positive electrode active material having a composition represented by (10㎛, secondary particle form) was prepared.

[0241] A cathode material was manufactured by mixing the first cathode active material manufactured in Manufacturing Example 5 and the second cathode active material in a weight ratio of 40:60.

[0242]

[0243] Comparative Example 2

[0244] A cathode material was manufactured in the same manner as in Comparative Example 1, except that the weight ratio of the first cathode active material and the second cathode active material was mixed to be 80:20.

[0245]

[0246] Comparative Example 3

[0247] Li 1.03 Ni 0.86 Mn 0.07 Co 0.05 Al 0.02 O2 (Manufacturer: LG Chemical, D 50 : A second positive electrode active material having a composition represented by (10㎛, secondary particle form) was prepared.

[0248] A cathode material was manufactured by mixing the first cathode active material manufactured in Manufacturing Example 6 and the second cathode active material in a weight ratio of 40:60.

[0249]

[0250] Comparative Example 4

[0251] A cathode material was manufactured in the same manner as in Comparative Example 3, except that the weight ratio of the first cathode active material and the second cathode active material was mixed to be 80:20.

[0252]

[0253] Comparative Example 5

[0254] The first positive electrode active material of Manufacturing Example 2 was used as the positive electrode material of Comparative Example 6.

[0255]

[0256] Experimental example

[0257] Experimental Example 1: XRD Analysis

[0258] XRD analysis was performed on each of the first positive electrode active materials used in all examples, and the XRD data of the first positive electrode active material manufactured in Manufacturing Example 2 is shown in Fig. 1, and the average crystallite size (nm) of the first positive electrode active material used in all examples is shown in Table 3 below.

[0259] At this time, the XRD measurement was performed using Bruker's D8 XRD equipment, and 2 to 3 g of positive electrode active material particles were collected from the positive electrode active material powder, and measured under the conditions of Cu-Kα line (wavelength 1.54 Å), acceleration voltage 45 kV, and current 40 mA, at a scan speed of 0.2 ° / sec from 2θ: 10° to 80°.

[0260] Figure 1 is XRD data of the first positive electrode active material manufactured in Manufacturing Example 2.

[0261] Through Fig. 1, it was confirmed that the first positive electrode active material manufactured in Manufacturing Example 2 included an olivine structure.

[0262]

[0263] Experimental Example 2: Battery Characteristics Evaluation 1

[0264] Coin-type half-cell manufacturing

[0265] A positive electrode slurry was prepared by mixing 90 wt% of the first positive electrode active material used in all examples, 5.0 wt% of carbon black as a conductive agent, and 5.0 wt% of polyvinylidene fluoride (PVDF) as a binder in an N-methylpyrrolidone (NMP) solvent. The prepared positive electrode slurry was applied to one surface of an aluminum current collector, dried at 130°C, and then rolled to prepare a positive electrode.

[0266] An electrode assembly was manufactured using a lithium metal electrode as the negative electrode and a porous polyethylene separator interposed between the positive and negative electrodes. This was placed inside a battery case, and a coin-type half-cell was manufactured by injecting an electrolyte solution containing 1.0 M LiPF6 dissolved in an organic solvent containing ethylene carbonate (EC): ethyl methyl carbonate (EMC): diethyl carbonate (DEC) in a volume ratio of 3:4:3.

[0267]

[0268] Battery Characteristics Evaluation 1

[0269] The initial charge-discharge process was performed by charging to 3.65 V using the CC (0.1 C)-CV (Cut off current: 0.05 C) method at 25°C, discharging to 2.5 V using the CC (0.1 C) method immediately after a 20-minute rest period, and measuring the open circuit voltage (OCV) at this time. The measured open circuit voltage (V) at 3.65 V is shown in Table 1 below.

[0270] After performing the initial charge-discharge process as described above, the battery was charged to 4.25 V using the CC (0.1 C)-CV (Cut off current: 0.05 C) method at 25°C, and immediately after a 20-minute rest period, it was discharged to 2.5 V using the CC (0.1 C) method, and the open circuit voltage (OCV) at this time was measured. The measured open circuit voltage (V) at 4.25 V is shown in Table 2 below.

[0271] Open circuit voltage [V] @ 3.65 V @ 3.65 V Drop [V] Manufacturing example 13.540 0.11 Manufacturing example 23.534 0.116 Manufacturing example 33.551 0.099 Manufacturing example 43.545 0.105 Manufacturing example 53.447 0.203 Manufacturing example 63.435 0.215

[0272] Open circuit voltage [V] @ 4.25 V Voltage drop 0.5 V or less @ 4.25 V @ 4.25 V Drop (χ) [V] Manufacturing example 13.963 0.287 ○ Manufacturing example 23.960 0.290 ○ Manufacturing example 33.917 0.333 ○ Manufacturing example 43.915 0.335 ○ Manufacturing example 53.735 0.515 X Manufacturing example 63.721 0.529 X

[0273] Through Tables 1 and 2, it was confirmed that the open circuit voltage drop at 3.65 V measured by the method described in this specification for the first positive electrode active material manufactured in Manufacturing Example was about 0.099 V to 0.215 V, and the open circuit voltage drop at 4.25 V measured by the method described in this specification was about 0.28 V to 0.53 V, confirming that the open circuit voltage drop at 4.25 V was greater than the open circuit voltage drop at 3.65 V. Meanwhile, when the open circuit voltage drop at 4.25 V measured by the method described in this specification for the first positive electrode active material manufactured in Manufacturing Example was 0.5 V or less, the voltage drop of the first positive electrode active material at the operating voltage (4.25 V) of the positive electrode material is small, so that the first positive electrode active material and the second positive electrode active material operate evenly during battery charging and discharging, thereby improving the life characteristics.

[0274] Referring to Table 2 above, it was confirmed that the open circuit voltage drop at 4.25 V measured by the method described in this specification was the largest for the first positive electrode active materials manufactured in Preparation Examples 5 and 6, followed by the first positive electrode active materials manufactured in Preparation Examples 3 and 4, and the smallest for the first positive electrode active materials manufactured in Preparation Examples 1 and 2. Referring to Table 1 above, with respect to the open circuit voltage drop at 3.65 V measured by the method described in this specification, the first positive electrode active materials manufactured in Preparation Examples 5 and 6 were the largest, followed by the first positive electrode active materials manufactured in Preparation Examples 1 and 2, and the smallest for the first positive electrode active materials manufactured in Preparation Examples 3 and 4, and thus it can be seen that the open circuit voltage drop at 4.25 V measured by the method described in this specification has a different tendency from the open circuit voltage drop at 3.65 V measured by the method described in this specification.

[0275] In conclusion, it was confirmed that the cathode material according to the present invention has a technical characteristic in that the open circuit voltage drop according to Equation 1 described in the present specification is a result of a complex interaction of the composition, particle size, content of carbon (C) in the cathode active material, average crystallite size, etc.

[0276]

[0277] Experimental Example 3: Measurement of Carbon (C) Content

[0278] The carbon (C) content in each of the first positive electrode active materials used in all examples was measured, and the carbon (C) content (carbon (C) content (weight %) of the first positive electrode active material) relative to the total weight of the first positive electrode active material is shown in Table 3 below.

[0279] The above carbon content is measured using a carbon-sulfur analyzer (CS844, LECO). Specifically, 1 g of a positive electrode active material powder sample is collected, placed in a crucible, and installed in a high-frequency induction furnace, and analysis is performed automatically. The C gas of the sample generated in the high-frequency induction furnace combines with the combustion gas O2 to produce CO and CO2. Since C is measured by a CO2 infrared detector, all CO-type gas is converted to CO2 through CuO, and then the carbon content in the CO2-type gas is measured using a CO2 infrared absorption detector.

[0280]

[0281] Experimental Example 4: Measurement of average particle size

[0282] In order to measure the average particle size of each of the first positive electrode active material particles used in all examples and the second positive electrode active material particles used in the examples and comparative examples, the particle size was measured using PSA (Malvern, Mastersizer3000), and the results are shown in Table 3 below.

[0283] Classification 1 Positive electrode active material Carbon (C) content (weight%) of the positive electrode active material Average crystallite size (nm) of the positive electrode active material Average particle diameter (D) 50)(㎛) First positive electrode active material Second positive electrode active material Example 1 Manufacturing example 12.6094.026.2510 Example 2 Manufacturing example 12.6094.026.2510 Example 3 Manufacturing example 22.6094.021.1210 Example 4 Manufacturing example 22.6094.021.1210 Example 5 Manufacturing example 22.6094.021.124 Example 6 Manufacturing example 22.6094.021.124 Example 7 Manufacturing example 32.2396.355.7210 Example 8 Manufacturing example 32.2396.350.8910 Example 9 Manufacturing example 22.6094.021.1210 Comparative example Manufacturing Example 1 51.38174.056.4210 Comparative Example 2 Manufacturing Example 51.38174.056.4210 Comparative Example 3 Manufacturing Example 61.38174.051.1010 Comparative Example 4 Manufacturing Example 61.38174.051.1010 Comparative Example 5 Manufacturing Example 22.6094.021.1210

[0284] Through Table 3, it was confirmed that the content of carbon (C) in the first positive electrode active material used in the example was 1.50 wt% or more and 5.00 wt% or less based on the total weight of the first positive electrode active material, and the first positive electrode active material used in the example had an average crystallite size of 80 nm or more and 150 nm or less. In addition, the first positive electrode active material had an average particle diameter (D 50 ) was confirmed to be 0.3㎛ or more and 8.0㎛ or less, and the second positive electrode active material had an average particle diameter (D 50 ) was confirmed to be 4㎛ or more and 13㎛ or less.

[0285]

[0286] Experimental Example 5: Battery Characteristics Evaluation 2

[0287] Coin-type half-cell manufacturing

[0288] A positive electrode slurry was prepared by mixing 90 wt% of the positive electrode materials manufactured in the above examples and comparative examples, 5.0 wt% of carbon black as a conductive material, and 5.0 wt% of polyvinylidene fluoride (PVDF) as a binder in an N-methylpyrrolidone (NMP) solvent. The prepared positive electrode slurry was applied to one surface of an aluminum current collector, dried at 130°C, and then rolled to prepare a positive electrode.

[0289] An electrode assembly was manufactured using a lithium metal electrode as the negative electrode and a porous polyethylene separator interposed between the positive and negative electrodes. This was placed inside a battery case, and a coin-type half-cell was manufactured by injecting an electrolyte solution containing 1.0 M LiPF6 dissolved in an organic solvent containing ethylene carbonate (EC): ethyl methyl carbonate (EMC): diethyl carbonate (DEC) in a volume ratio of 3:4:3.

[0290]

[0291] Battery Characteristics Evaluation 2

[0292] Using the above coin-type half-cell, it was charged to 4.25 V using the CC (0.1 C)-CV (Cut off current: 0.05 C) method at 25 ℃, and discharged to 2.5 V using the CC (0.1 C) method. Then, it was charged to 4.25 V using the CC (0.33 C)-CV (Cut off current: 0.05 C) method at 45 ℃, and discharged to 2.5 V using the CC (0.33 C) method. One cycle was considered as 1 cycle, and a total of 30 cycles of charging and discharging were repeated, and the resistance was measured through the voltage change for 60 seconds in the first and 30th cycles. The percentage (resistance increase rate (%)) of the resistance (Ω) of the 30th cycle to the resistance (Ω) of the measured first cycle is shown in Table 4 below.

[0293] Increase rate of resistance (%) @ 4.25 V Example 15.7 Example 215.7 Example 37.2 Example 416.9 Example 56.9 Example 616.4 Example 76.0 Example 87.8 Example 920.5 Comparative Example 121.1 Comparative Example 230.2 Comparative Example 326.8 Comparative Example 432.5 Comparative Example 521.1

[0294] Through Table 4, it was confirmed that in the case of a secondary battery including a positive electrode material including a positive electrode layer including a positive electrode active material layer containing the first positive electrode active material in an amount of 80 wt% or more and 98 wt% or less based on the total weight of the positive electrode active material layer, a positive electrode material manufactured in Examples 1 to 9, that is, a positive electrode having a voltage drop (χ) of 0.5 V or less according to Equation 1) that satisfies the specific conditions described herein; and a second positive electrode active material, the resistance increase rate (%) is lower compared to a secondary battery including a positive electrode material manufactured in Comparative Examples 1 to 4, that is, a positive electrode material including a first positive electrode active material that does not satisfy the specific conditions described herein; and a second positive electrode active material. Specifically, in the case of a first positive electrode active material that does not satisfy the specific conditions described herein; And in the case of including a second positive electrode active material, the voltage drop of the first positive electrode active material is large at the operating voltage (4.25 V) of the positive electrode material, so that the first positive electrode active material and the second positive electrode active material do not operate evenly during battery charging and discharging, and the positive electrode material deteriorates during charging and discharging, thereby increasing the resistance increase rate. Meanwhile, in the case of a battery including a positive electrode material manufactured in Example 9 (the weight ratio of the first positive electrode active material and the second positive electrode active material is 90:10), it was confirmed that the resistance increase rate was higher than that of a battery including a positive electrode material manufactured in Examples 1 to 8 (the weight ratio of the first positive electrode active material and the second positive electrode active material is 10:90 to 80:20).

[0295] In addition, in the case of secondary batteries including the positive electrode materials manufactured in Examples 1 to 9, i.e., the first positive electrode active material having an olivine structure; and the second positive electrode active material having a layered structure, it was confirmed that the resistance increase rate (%) was lower compared to the secondary battery including the positive electrode material manufactured in Comparative Example 5, i.e., the positive electrode material not including the second positive electrode active material having a layered structure. Specifically, in the case of the positive electrode material manufactured in Comparative Example 5, i.e., not including the second positive electrode active material having a layered structure, and only including the first positive electrode active material having an olivine structure, it was confirmed that the deterioration of the positive electrode material occurred rapidly in a voltage range exceeding the operating voltage of the first positive electrode active material (4.25 V), so that the resistance increase rate of the secondary battery including the positive electrode material tended to be high.

[0296] In conclusion, in the case of a cathode material comprising a first cathode active material having an olivine structure and satisfying the specific conditions described herein; and a second cathode active material having a layered structure, it can be seen that a secondary battery comprising the cathode material is relatively stable even when charge and discharge cycles are performed at the operating voltage of the cathode material.

Claims

1. A first positive electrode active material having an olivine structure; and a second positive electrode active material having a layered structure; The above first positive electrode active material is a positive electrode material having a voltage drop (χ) of 0.50 V or less according to the following equation 1: [Formula 1] Voltage drop (χ) [V] = (open circuit voltage (α) measured after a rest period of 4.25 - 20 minutes) [V] In the above equation 1, α is the open circuit voltage measured immediately after charging a lithium secondary battery including a positive electrode including a positive electrode active material layer containing a positive electrode active material in a content of 80 wt% or more and 98 wt% or less based on the total weight of the positive electrode active material layer to 4.25 V using the CC (0.1 C)-CV (Cut off current: 0.05 C) method at 25°C and leaving it for 20 minutes.

2. In claim 1, The first positive electrode active material is a positive electrode material including a lithium iron phosphate compound having a composition represented by the following chemical formula 1: [Chemical Formula 1] Li 1+x Fe 1-a M 1 a PO4 In the above chemical formula 1, M 1 is at least one selected from Al, Mg, Ni, Co, Mn, Ti, Ga, Cu, V, Nb, Zr, Ce, In, Zn, Na, Si, Ca, B and Y, -0.1≤x≤0.1, 0.0≤a≤0.

8.

3. In claim 2, A cathode material wherein the first cathode active material further includes a coating layer including carbon (C) formed on the lithium iron phosphate compound.

4. In claim 3, A cathode material having a carbon (C) content included in the coating layer of 1.50 wt% or more and 5.00 wt% or less based on the total weight of the first cathode active material.

5. In claim 1, The above first positive electrode active material is a positive electrode material having an average crystallite size of 80.00 nm or more and 150.00 nm or less.

6. In claim 1, The above first positive electrode active material has an average particle diameter (D 50 ) is a cathode material having a thickness of 0.30㎛ or more and 8.00㎛ or less.

7. In claim 1, A cathode material wherein the weight ratio of the first cathode active material and the second cathode active material is 10:90 to 90:

10.

8. In claim 1, A cathode material wherein the weight ratio of the first cathode active material and the second cathode active material is 10:90 to 80:

20.

9. In claim 1, The above second positive electrode active material is a positive electrode material having a composition represented by the following chemical formula 2: [Chemical Formula 2] Li 1+y1 Ni p1 Mr q1 Co r1 M 2 s1 O2 In the above chemical formula 2, M 2 is at least one selected from Zr, Al, Re, V, Cr, Fe, Ga, Si, B, Ru, Ti, Nb, Mo, Mg, W, Na and Pt, 0.00≤y1≤0.50, 0.00 <p1<1.00, 0.00<q1<0.50, 0.00<r1<0.50, 0.000≤s1≤0.010이다.

10. In claim 1, The above second positive electrode active material has an average particle diameter (D 50 ) A cathode material having a thickness of 4㎛ or more and 13㎛ or less.

11. A cathode comprising a cathode material according to any one of claims 1 to 10.

12. A lithium secondary battery comprising a positive electrode according to claim 11.

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