Precursor-active material intermediate and cathode active material prepared using same

Abstract

The present invention provides a precursor-active material intermediate which comprises a transition metal precursor and can be sintered into a cathode active material, wherein the angle of repose of a granular material satisfies a range of 20 to 39° for better flowability, the angle of repose being the inclination angle at which the granular material can be piled relative to the horizontal plane.

Description

Precursor-active material intermediate and positive electrode active material prepared therefrom

[0001] The present invention relates to a precursor-active material intermediate and an anode active material prepared therefrom, and more specifically, to a precursor-active material intermediate that can be prepared into an anode active material through calcination, comprising a transition metal precursor, and satisfying conditions for an angle of repose within a specific range to improve fluidity, and an anode active material prepared therefrom.

[0002] Generally, a Roller Hearth Kiln (RHK) is used for heat treatment during the manufacturing of cathode active materials. The RHK is installed horizontally in an elongated manner and is divided into multiple zones; since the temperature can be set for each zone, the calcination temperature is configured to gradually rise and fall.

[0003] Conventional methods for manufacturing positive electrode active materials using RHK require a long time and a large site because the material is fired while moving through a long kiln. Additionally, energy costs and gas consumption are high because the entire kiln maintains a high temperature and introduces atmosphere-forming gas. Furthermore, maintenance and management costs are incurred because a firing vessel is required, and there is a problem where the productivity of the positive electrode active material decreases by the weight of the firing vessel due to the maximum load of the rollers.

[0004] To address this, attempts are being made to manufacture cathode active materials using a 'Rotary Kiln (RK)' to improve cost and productivity. A rotary kiln is a device that manufactures active materials by introducing lithium sources, metal sources, etc., into a cylindrical furnace (retort) positioned at a slight incline, and continuously applying heat from the outside while the retort rotates.

[0005] The active material introduced into the cylindrical core tube gradually moves toward the outlet located at the opposite end of the inlet as the core tube rotates in a tilted state. The rotation of the core tube enables continuous mixing during the firing process, allowing for a uniform reaction and reducing production time, thereby increasing production yield.

[0006] Therefore, in a rotary kiln (RK), the reactants must flow continuously. However, if the fluidity of the reactants is low, the raw materials or reactants may stick to the inner surface of the core tube, leading to uneven reactions and a decrease in yield. In addition, if the fluidity of the reactants is excessively high, the raw materials or reactants may scatter and be lost to the outside, which may also result in a decrease in yield.

[0007] Moreover, cathode active materials such as NMC and LCO require firing conditions in an oxygen atmosphere, but when fired at high temperatures, components constituting the inner core (especially Cr) are leached out as impurities, which can have a fatal effect on battery characteristics.

[0008] Therefore, there is a high need in the industry for new technology that can solve these problems all at once.

[0009] The present invention aims to solve the problems of the prior art described above and technical challenges that have been requested over time.

[0010] After conducting in-depth research and various experiments, the inventors of this application confirmed that when an intermediate at the stage immediately preceding calcination satisfies a specific range of angle of repose conditions when manufacturing a positive electrode active material from a precursor, it provides a high yield in the calcination process due to excellent fluidity, and the positive electrode active material produced therefrom also provides excellent battery characteristics, thereby completing the present invention.

[0011] Accordingly, the precursor-active material intermediate according to the present invention is a material that can be manufactured into an anode active material through calcination,

[0012] It includes a transition metal precursor,

[0013] To improve fluidity, the angle of repose, which is the angle of inclination at which granular materials can be stacked relative to a horizontal plane, is characterized by satisfying a range of 20° to 39°.

[0014]

[0015] The term "precursor-active material intermediate" used in the present invention refers to an intermediate product in the stage prior to calcination during the process of converting a precursor into an active material, and means a material obtained when raw materials such as lithium precursors and transition metal precursors are converted into a form or state suitable for the calcination process for manufacturing an active material, and is clearly distinguished from precursors and active materials.

[0016] The inventors of the present application have confirmed that among the material forms or properties of such intermediates, the range condition of the angle of repose is essential for improving fluidity, and that such improvement in fluidity is important in the calcination process in which the intermediate is converted into an anode active material. That is, when the intermediate satisfies the set range of the angle of repose, it exhibits appropriate fluidity, thereby preventing it from adhering to the inner surface of the calcination means (device, etc.) during the calcination process, failing to participate in the reaction, undergoing deterioration, or scattering into the surrounding calcination atmosphere and being lost.

[0017] The angle of repose, which is directly related to fluidity in the present invention, refers to the steepest angle of inclination relative to a horizontal plane where granular materials can be stacked without falling over, as defined above, and can be measured, for example, in the manner of Experimental Example 2 described below.

[0018] Although conditions regarding the angle of repose are sometimes considered for the pulverized active material after calcination—that is, the final product—this is intended to optimize the adhesion between the current collector and conductive materials, as well as electrode density, during the process of manufacturing electrodes using the active material. Therefore, it clearly differs from the present invention, which defines the angle of repose for the intermediate in the state prior to calcination for the manufacture of the active material. Furthermore, since the active material undergoes a grinding process to achieve a predetermined particle size when applied to the electrode, the angle of repose of the active material inevitably differs significantly from that of the intermediate.

[0019] The present invention can be preferably applied to a technology in which firing is carried out in a rotary kiln (RK) where the fluidity of the intermediate may be particularly important.

[0020]

[0021] The range of such angles of repose is 20° to 39° as defined above.

[0022] When particles have weak mutual physical and electrostatic attraction and flow easily, the angle of repose becomes small, which means that the fluidity is good. Therefore, when the angle of repose is 39° or less, the particles flow well inside the reactor, resulting in a uniform reaction and a high yield. However, if the fluidity becomes excessively large with an angle of repose of less than 20°, the likelihood of powder scattering and loss increases, which actually lowers the yield, so this is not desirable.

[0023]

[0024] In one preferred example, the transition metal precursor may be a precursor containing Fe.

[0025] Examples of such transition metal precursors include, but are not limited to, FePO4, FeTiPO4, and FeMnPO4, which can be used to manufacture cathode active materials such as lithium iron phosphate (LFP) by calcining them in a rotary kiln (RK) under an inert atmosphere.

[0026] As explained above, in the case of a positive electrode active material that requires firing in an oxygen atmosphere, the components constituting the inner core of the RK are leached out as impurities when fired at high temperatures, which adversely affects the characteristics of the positive electrode active material. In contrast, a positive electrode active material manufactured by firing in an inert atmosphere such as N2 does not have such problems and may be particularly desirable.

[0027]

[0028] In one specific example, the precursor-active material intermediate may be in a form in which one or more selected from the group consisting of alkali metal precursors, alkaline earth metal precursors, dopant precursors, and carbon precursors are mixed with a transition metal precursor.

[0029] That is, the above intermediate essentially includes a transition metal precursor and may exist as particles in which alkali metal / earth metal precursors, dopant precursors, carbon precursors, etc. are optionally mixed. The mixed state described above refers to a state in which the components are physically in contact or attached rather than chemically bonded. Preferably, alkali metal / earth metal precursors and transition metal precursors are included in the intermediate in a mixed form to improve mutual reactivity during calcination. More preferably, dopant precursors, alkali metal / earth metal precursors, and transition metal precursors may be included in the intermediate in a mixed form, and carbon precursors may be further included when manufacturing active materials such as LFP.

[0030]

[0031] The above transition metal precursor may have a composition of, for example, Chemical Formula 1.

[0032] MP x1 O y1 (1)

[0033] In the above formula,

[0034] 0≤x1≤2, 0≤y1≤4;

[0035] M is one or more selected from alkaline earth metals, transition metals, post-transition metals, metalloids, nonmetals, lanthanides, and actinides.

[0036] Preferably, the above chemical formula 1 may be the following chemical formula 1a.

[0037] MP x1' O y1' (1a)

[0038] In the above formula,

[0039] 0 <x1'≤2, 0<y1'≤4;

[0040] M is one or more transition metals.

[0041]

[0042] The above alkaline earth metal precursor may have a composition of, for example, Chemical Formula 2 below.

[0043] (1-a1-b1)A2CO3*a1AOH*b1A2O (2)

[0044] In the above formula,

[0045] 0≤a1≤1, 0≤b1≤1, 0≤1-a1-b2≤1;

[0046] A is one or more selected from alkali metals and alkaline earth metals.

[0047]

[0048] The above dopant precursor may have, for example, the composition of Chemical Formula 3 below.

[0049] (1-a2-b2-c2)D2CO3* a2DOH * b2D2O * c2DSO4(3)

[0050] In the above formula,

[0051] 0≤a2≤1, 0≤b2≤1, 0≤c2≤1, 0≤1-a2-b2-c2≤1;

[0052] D is one or more selected from alkaline earth metals, transition metals, post-transition metals, metalloids, nonmetals, lanthanides, and actinides.

[0053]

[0054] The above carbon precursor may have, for example, the composition of Chemical Formula 4 below.

[0055] C x2 H y2 O z2 (4)

[0056] In the above formula,

[0057] 0 <x2≤20, 0≤y2≤42, 0≤z2≤10.

[0058]

[0059] The improved fluidity of the intermediate intended in the present invention can be set to a specific range for the Hausner ratio, an indicator of powder fluidity, and Carr's index, an indicator of powder compressibility, respectively, through the interrelationship between apparent density and tap density.

[0060] First, the Hausner ratio is defined as follows, and in the present invention, it may be a condition satisfying the range of 1 to 1.5.

[0061]

[0062] The intermediate of the present invention has a relatively large particle size and exhibits excellent fluidity, and accordingly, the density (apparent density) immediately after the powder is accumulated is greater than in the case of small particle sizes, so the lower limit of the Hausner ratio range can approach 1.

[0063] On the other hand, if the value exceeds 1.5, which is the upper limit of the Hausner ratio range, the apparent density is low and the overall particle size is small, resulting in reduced fluidity.

[0064]

[0065] Carr's index is defined as follows, and in the present invention, it may be a condition satisfying the range of 9 to 30.

[0066]

[0067] As the fluidity improves, the apparent density becomes similar to the tap density, and thus, it can be confirmed from the results of Example 1 described later that the intermediate of the present invention has a relatively small Carr's index. However, if the Carr's index is less than 9, the fluidity is excessive and a problem of powder scattering may occur, and conversely, if it exceeds 30, the fluidity decreases, which is undesirable.

[0068]

[0069] The intermediate of the present invention satisfying these conditions has a BET of 15 to 30 m 2 / g and / or the apparent density may be, for example, 0.6 to 0.8 g / cc.

[0070] The above BET is a factor influenced by the overall size of the particles; as the overall particle size increases, BET tends to decrease, and accordingly, it can be interpreted that fluidity improves as BET decreases.

[0071] The aforementioned apparent density is a factor influenced by the overall size of the particles, similar to BET. Since the apparent density tends to increase as the overall particle size increases, it can be interpreted that fluidity improves as the apparent density increases.

[0072] Therefore, BET is 30 m 2 If it exceeds / g or the apparent density is less than 0.6 g / cc, the particles become smaller overall, which may reduce fluidity, and conversely, if the BET is 15 m 2 If the density is less than / g or the apparent density exceeds 0.8 g / cc, the particles become too large overall, which can lead to excessive fluidity and cause powder scattering problems, so this is not desirable.

[0073]

[0074] As explained regarding the angle of repose, the aforementioned BET, apparent density, and tap density inevitably differ between the intermediate and the active material. This is because when the active material is manufactured by calcining the intermediate, the sintered active material particles undergo a grinding process to obtain powders of an appropriate size. Consequently, the Hausner ratio and Carr's index of the intermediate, obtained based on the aforementioned densities, also differ between the intermediate and the active material.

[0075]

[0076] The present invention also provides a positive active material prepared by calcining the precursor-active material intermediate, and a secondary battery comprising such a positive active material.

[0077] As previously explained, the precursor-active material intermediate of the present invention is particularly desirable when performing calcination in a rotary kiln (RK), as the intermediate exhibits appropriate fluidity to prevent it from adhering to the inner surface of the calcination means (device, etc.) during the calcination process, thereby preventing it from being unreacted or altered, or from being scattered and lost into the surrounding calcination atmosphere, which can provide a high yield.

[0078] Furthermore, when the above-mentioned positive active material is lithium iron phosphate (LFP), it is calcined in an inert atmosphere, so unlike positive active materials that require calcination in an oxygen atmosphere, it is desirable that the components constituting the inner core of RK do not leach out as impurities when calcined at high temperatures.

[0079] Since the calcination process for manufacturing the positive electrode active material and the configuration and manufacturing method of the secondary battery are known in the art, a detailed description thereof is omitted in this specification.

[0080] As explained above, the precursor-active material intermediate according to the present invention has excellent fluidity as the angle of repose satisfies the set range condition. This can solve the problem of reduced yield caused by the intermediate adhering to the inside of the calcination apparatus during the calcination process due to low fluidity, thereby preventing it from participating in the reaction or causing deterioration, and the cathode active material obtained through calcination can also exhibit excellent battery characteristics.

[0081] Figure 1 is an SEM image of the precursor-active material intermediate of Comparative Example 3 obtained in Experimental Example 1;

[0082] FIG. 2 is an SEM image of the precursor-active material intermediate of Example 3 obtained in Experimental Example 1;

[0083] Figure 3 is a photograph showing the results of the sedimentation test performed in Experimental Example 1;

[0084] Figure 4 is an image showing the method of measuring the angle of repose performed in Experimental Example 2.

[0085] The present invention will be described further below with reference to embodiments thereof, but the scope of the invention is not limited by them.

[0086]

[0087] Comparative Example 1

[0088] A mixture of Li2CO3 and FePO4 precursors as lithium raw materials (Li / Me (metal) = 1.040 mixing ratio) and sugars (glucose, fructose, sucrose, etc.) as carbon sources were added to distilled water as a solvent at approximately 10 wt% based on the total weight including the lithium raw materials and precursors (solid content = approximately 40%), and then stirred for 1 hour to prepare a composite raw material solution.

[0089] Wet coarse grinding was performed on the composite raw material solution prepared above to produce a wet coarse grinding solution with a particle size D50 of 1.0 to 2.0 μm. For wet coarse grinding, an Attrition mill (Nanointec Co.) with Beads size Φ2.0 mm was used, and the equipment operating conditions were set to a pump pressure of 300 rpm and a grinding speed of 1000 rpm, respectively.

[0090] Wet fine grinding was performed on the wet coarse grinding solution prepared above to produce a wet fine grinding solution with a D50 of 0.3 to 0.5 μm. A fine grinding machine (Daehwa Tech Co.) was used for wet fine grinding, and the operating conditions of the machine were set to a pump pressure of 300 rpm and a grinding pressure of 2200 ppm.

[0091] The wet fine grinding solution prepared above was spray-dried using a nozzle-type spray dry device (RL-5: Okawara Co., Ltd.), which is a spray dry device that sprays directly using pressure or air, to produce a spray-dried product (precursor-active material intermediate) with a thickness of at least 2 μm to a maximum of 10 μm (2 ~ 10 μm). For the equipment operation conditions for spray drying, the spray pressure was set to 3.0 ~ 4.5 bar, the nozzle spray in-let temperature to 220°C, and the out-let temperature to 100°C.

[0092] The spray-dried product prepared above was fed into a batch-type lab-scale rotary kiln (Woongbi Machinery Co., Ltd.) in an amount of approximately 12 kg and calcined at 700 to 760°C for 8 to 10 hours in an inert atmosphere (to maintain the inert atmosphere, liquid nitrogen with a purity of 99.999% was injected at a rate of 5 L / min or more). The rotation conditions of the rotary kiln (RK) were set to a range of 5 to 8 Hz, and after calcination, the calcined product was recovered through the discharge port by tilting the RK equipment more than 60 degrees.

[0093] The recovered calcined product was ground several times using a high-speed centrifugal mill (Ultra-centrifugal Mill FM200: Poutec Korea) at 16,000 to 18,000 rpm to finally produce a LiFePO4 cathode active material.

[0094]

[0095] Comparative Example 2

[0096] A precursor-active material intermediate and a LiFePO4 cathode active material with a thickness of 2 to 15 μm were prepared using the same method as Comparative Example 1, except that the spray pressure for spray drying was changed to 1.6 to 2.9 bar.

[0097]

[0098] Comparative Example 3

[0099] A precursor-active material intermediate and a LiFePO4 cathode active material with a thickness of 2 to 20 μm were prepared using the same method as Comparative Example 1, except that the spray pressure for spray drying was changed to 1.1 to 1.5 bar.

[0100]

[0101] Comparative Example 4

[0102] A precursor-active material intermediate and a LiFeTiPO4 cathode active material with a diameter of 2 to 10 μm were prepared in the same manner as in Comparative Example 1, except that an FeTiPO4 precursor was used instead of an FePO4 precursor.

[0103]

[0104] Comparative Example 5

[0105] A precursor-active material intermediate and a LiFeTiPO4 cathode active material with a diameter of 2 to 15 μm were prepared in the same manner as Comparative Example 2, except that an FeTiPO4 precursor was used instead of an FePO4 precursor.

[0106]

[0107] Comparative Example 6

[0108] A precursor-active material intermediate and a LiFeTiPO4 cathode active material with a diameter of 2 to 15 μm were prepared in the same manner as in Comparative Example 3, except that an FeTiPO4 precursor was used instead of an FePO4 precursor.

[0109]

[0110] Comparative Example 7

[0111] A precursor-active material intermediate and a LiFeMnPO4 cathode active material with a diameter of 2 to 10 μm were prepared in the same manner as in Comparative Example 1, except that an FeMnPO4 precursor was used instead of an FePO4 precursor.

[0112]

[0113] Comparative Example 8

[0114] A precursor-active material intermediate and a LiFeMnPO4 cathode active material with a diameter of 2 to 15 μm were prepared in the same manner as Comparative Example 2, except that an FeMnPO4 precursor was used instead of an FePO4 precursor.

[0115]

[0116] Comparative Example 9

[0117] A precursor-active material intermediate and a LiFeMnPO4 cathode active material with a diameter of 2 to 20 μm were prepared in the same manner as Comparative Example 3, except that an FeMnPO4 precursor was used instead of an FePO4 precursor.

[0118]

[0119] Comparative Example 10

[0120] A precursor-active material intermediate and a LiFePO4 cathode active material with a thickness of 2 to 25 μm were prepared in the same manner as Comparative Example 1, except that spray drying was performed using an Atomizer-type spray drying device (TS-Minor, M02 / 4: Ein System Co., Ltd.) which is a spray drying device that uses centrifugation of a rotating disk instead of a nozzle-type spray drying device, and the spray pressure was set to 5.5 to 6.5 bar, the spray in-let temperature to 300℃, the cyclone out-let temperature to 100℃, and the spray rotation to a range of 17,000 to 36,000 rpm.

[0121]

[0122] Example 1

[0123] A precursor-active material intermediate and a LiFePO4 cathode active material with a diameter of 10 to 40 μm were prepared using the same method as Comparative Example 10, except that the spray pressure was set to 3.0 to 4.5 bar.

[0124]

[0125] Example 2

[0126] A precursor-active material intermediate and a LiFePO4 cathode active material with a diameter of 10 to 50 μm were prepared using the same method as Comparative Example 10, except that the spray pressure was set to 1.6 to 2.9 bar.

[0127]

[0128] Example 3

[0129] A precursor-active material intermediate and a LiFePO4 cathode active material with a thickness of 10 to 80 μm were prepared using the same method as Comparative Example 10, except that the spray pressure was set to 1.1 to 1.5 bar.

[0130]

[0131] Comparative Example 11

[0132] A precursor-active material intermediate and a LiFePO4 cathode active material with a diameter of 10 to 100 μm were prepared using the same method as Comparative Example 10, except that the spray pressure was set to 0.5 to 0.8 bar.

[0133]

[0134] Example 4

[0135] A precursor-active material intermediate and a LiFeTiPO4 cathode active material with a diameter of 10 to 40 μm were prepared in the same manner as in Example 1, except that an FeTiPO4 precursor was used instead of an FePO4 precursor.

[0136]

[0137] Example 5

[0138] A precursor-active material intermediate and a LiFeTiPO4 cathode active material with a diameter of 10 to 50 μm were prepared in the same manner as in Example 2, except that an FeTiPO4 precursor was used instead of an FePO4 precursor.

[0139]

[0140] Example 6

[0141] A precursor-active material intermediate and a LiFeTiPO4 cathode active material with a diameter of 10 to 80 μm were prepared in the same manner as in Example 3, except that an FeTiPO4 precursor was used instead of an FePO4 precursor.

[0142]

[0143] Example 7

[0144] A precursor-active material intermediate and a LiFeMnPO4 cathode active material with a diameter of 10 to 40 μm were prepared in the same manner as in Example 1, except that an FeMnPO4 precursor was used instead of an FePO4 precursor.

[0145]

[0146] Example 8

[0147] A precursor-active material intermediate and a LiFeMnPO4 cathode active material with a diameter of 10 to 50 μm were prepared in the same manner as in Example 2, except that an FeMnPO4 precursor was used instead of an FePO4 precursor.

[0148]

[0149] Example 9

[0150] A precursor-active material intermediate and a LiFeMnPO4 cathode active material with a diameter of 10 to 80 μm were prepared in the same manner as in Example 3, except that an FeMnPO4 precursor was used instead of an FePO4 precursor.

[0151]

[0152] Experimental Example 1

[0153] SEM images were obtained for the precursor-active material intermediates prepared in Comparative Example 3 and Example 3, respectively, and are shown in Figures 1 and 2.

[0154] In addition, the precursor-active material intermediates of Comparative Example 3 and Example 3 were placed in a vial containing distilled water and shaken, and a sedimentation test was performed to evaluate the settling of the powder immediately after and after 120 minutes, and the results are shown in Fig. 3.

[0155] First, referring to FIGS. 1 and FIGS. 2, the intermediate of Comparative Example 3 (Fig. 1) has generally small particle sizes and a high distribution of particles smaller than 20 μm, whereas the intermediate of Example 3 (Fig. 2) has generally large particle sizes and a high distribution of particles larger than 20 μm.

[0156] In addition, the fact that such differences in particle size have a significant effect on fluidity (flowability) can be indirectly confirmed through sedimentation tests. Referring to Figure 3, it can be seen that while the intermediate of Comparative Example 3 has a large amount floating in distilled water even at the 120-minute mark, most of the intermediate of Example 3 has settled at the 120-minute mark.

[0157]

[0158] Experimental Example 2

[0159] The angle of repose was measured for the precursor-active material intermediates prepared in Comparative Examples 1 to 11 and Examples 1 to 9, respectively, using a power tester (Hosokawa Micron Korea: model PT-S), and the results are shown in Table 1 below.

[0160] Specifically, a sample of 50 g or less was sampled onto a specimen with a diameter of 5 cm for 3 minutes, and after impacting the specimen three times with a hammer, a photograph was taken at a distance of about 10 cm from the center of the specimen, and as shown in Fig. 4, the angle of repose of the powder was measured by applying a protractor to the photograph.

[0161]

[0162] In addition, BET, apparent density, and tap density were measured for the precursor-active material intermediate using the following method, and the results are shown together in Table 1 below.

[0163]

[0164] <BET 측정 방법>

[0165] (BET Sample Preprocessing)

[0166] The preprocessing equipment used was 'VacPrep 061', and the preprocessing method is as follows.

[0167] (1) Measure the weight of the empty sample tube (fourth decimal place)

[0168] (2) After adding the sample weight (1g) to the sample tube, record the weight.

[0169] (3) Set temperature after mounting sample tube in port

[0170] (4) Precursor: Preheat at 100°C for 1 hour, then apply vacuum and pretreat at the set temperature for 2 hours.

[0171] (5) Cool for 1 hour after pretreatment

[0172] (6) After removing the vacuum atmosphere, introduce N2 gas

[0173] (7) Weight measurement after preprocessing is complete.

[0174]

[0175] (BET sample measurement)

[0176] The analysis instrument used was the 'Micromeritics TriStar 3020', and the measurement method is as follows.

[0177] (1) Liquid nitrogen is injected into the dewar bottle

[0178] (Fill until it reaches between the hole and the bottom of the fluid dipstick)

[0179] (2) Enter sample information after running Win3000 SW

[0180] (3) Insert range when measuring specific surface area

[0181] When measuring specific surface area and pore volume, insert predefine tjsxor

[0182] (4) Pressure range setting

[0183] (5) Enter Report Options (typically Isothem, BET Surface Area, BJH Adsoption, BJH Desortion Option, Summary, Sample Log)

[0184] (6) Sample analysis

[0185]

[0186] Bulk Density Measurement Method

[0187] The 'BT-101 (K-One Nano)' was used to measure the volume density, which is the apparent density, and the measurement method is as follows.

[0188] (1) Weigh the sample receiving cup on the scale to zero it out.

[0189] (2) Use a spoon to place a certain amount of the sample onto the mesh.

[0190] (3) Stir evenly with a brush so that the sample comes out well.

[0191] (4) Repeat the above process 3 to 4 times until the receiving cup is filled with the sample and overflows.

[0192] (5) Using a spatula for bulk density, scoop out the mixture along the top edge of the cup until it is flat.

[0193] (6) Gently tap the cup to settle the sample.

[0194] (7) Remove the sample stuck around the cup with a brush and weigh it with a scale.

[0195] (8) Calculate the apparent density by substituting the measured weight into the following formula.

[0196] - Apparent density (g / cm³) 3 ) = Mass of sample in cup (g) / Volume of cup (cm²) 3 )

[0197] (Cup volume = 25 cm 3 )

[0198]

[0199] <Method for Measuring Tap Density>

[0200] 'Micromeritics GeoPyc' was used for tap density measurement, and the measurement method is as follows.

[0201] (1) After dry filtration is completed, 10±0.01 g is taken from the sampled sample before packaging.

[0202] (2) Insert a TAP density measuring cylinder with a standard size of 19.1 mm and mount it on the main body.

[0203] (3) Press 2nd → Analyze on the measuring device to start the measurement.

[0204] (4) Enter the sample weight to 4 decimal places in sample weight and press Enter.

[0205] (5) After entering the chamber diameter of 19.1 mm, load the stored blank data.

[0206] (6) The number of measurements per session is set to an average of 3 times.

[0207] (7) Set the consolidation force to 108 N and the conversion factor to 0.2907 cm³ / mm.

[0208] (8) "Press [Enter] to start sample analysis, or press [Enc] to cancel." When this window appears, press Enter to start the measurement.

[0209]

[0210] In Table 1 above, "Hausner ratio" is obtained by calculating with the formula "tap density / apparent density", and "Carr's index" is obtained by calculating with the formula "(tap density - apparent density) / tap density × 100".

[0211]

[0212] The following facts can be confirmed through the results of Table 1 above.

[0213]

[0214] First, in Comparative Examples 1 to 9, which use a spray drying device that sprays directly using pressure or air, the diameter of the particles is generally small and thus has a high angle of repose, resulting in reduced fluidity. On the other hand, in the Examples, which use a spray drying device that sprays using the centrifugation of a rotating disk, the particle diameter is generally large and has excellent fluidity due to a small angle of repose.

[0215] For reference, a preferred example of a spray dry device that sprays directly using pressure or air as described above is a nozzle-type spray dry device, and a preferred example of a spray dry device that sprays using the centrifugation of a rotating disk is an atomizer-type spray dry device.

[0216] However, although Comparative Examples 10 and 11 used an Atomizer type-Spray Dry device, as in Comparative Example 10, if the spray intensity is too strong (5.5 to 6.5 bar), the droplets are formed small, resulting in a small intermediate size and consequently reduced fluidity; and as in Comparative Example 11, if the spray intensity is too weak (0.5 to 0.8 bar), the intermediate size becomes too large and clogged, so the spraying itself does not work well, and even if a small amount is sprayed, the fluidity is excessively secured, and the problem of scattering occurs within the RK.

[0217]

[0218] Second, the intermediates of the examples have generally large particle sizes, satisfying the Hausner ratio range of 1 to 1.5 and the Carr's index range of 9 to 30, whereas the intermediates of Comparative Examples 1 to 10 fall outside all of these ranges. Since particle size is directly related to fluidity, it can be seen that the Hausner ratio and Carr's index, which define the relationship between density and particle size, also have different values ​​in the examples and comparative examples. In the case of Comparative Example 11, the intermediate has a large particle size, so the Hausner ratio satisfies the range defined in the present invention, but the Carr's index is 2.88, which is less than 9, the lower limit of the set range defined in the present invention. This indicates that the fluidity is excessive, which leads to a low yield in the calcination process, as can be confirmed in Table 2 of Experimental Example 3, which will be explained later.

[0219]

[0220] Third, regarding BET and apparent density, which are highly correlated with particle size and directly affect particle fluidity, the intermediates of the examples have a BET of 15 to 30 m 2 While satisfying the condition of having a density of 0.6 to 0.8 g / cc and an apparent density of 0.6 to 0.8 g / cc, the precursors of the comparative examples do not satisfy these conditions. Comparative Example 11 has an apparent density of 0.81 g / cc, which is close to the upper limit of the above range, but its BET is 10 m 2 It can be seen that as / g, it falls far short of the above range.

[0221]

[0222] Experimental Example 3

[0223] A positive electrode active material slurry was prepared by adding the positive electrode active materials prepared in Comparative Examples 1 to 11 and Examples 1 to 9, respectively, along with a PVdF binder (KF1100) and a conductive material (Super-P), to an N-methyl-2-pyrrolidone (NMP) solvent in a weight ratio of 95:2.5:2.5. The slurry was coated onto an aluminum foil (Al foil, thickness 20 μm) serving as a positive electrode current collector, dried at 120°C, and rolled to produce a positive electrode plate. The loading level of the rolled positive electrode was 12 mg / cm². 2 The rolled density is 2.40 g / cm³ 3 The above positive electrode plate was stamped to 13.8Φ, and a 2032 coin-type half cell was manufactured using lithium metal as the negative electrode and an electrolyte (EC / DMC 1:1 + LiPF61mol).

[0224] The coin-type half cells prepared above were aged at room temperature for 10 hours, after which charge-discharge tests were conducted, and the results are shown in Table 2 below. Capacity evaluation was based on 150 mAh / g at a 0.1C rate, and charge-discharge conditions were performed using constant current (CC) and constant voltage (CV) within a voltage range of 3.7 to 2.5.

[0225]

[0226] In addition, the yield was measured based on the calculation of {(amount discharged after firing / amount of spray drying input) × firing loss (0.75)} × 100, and the results are shown together in Table 2 below.

[0227]

[0228] As shown in Table 2 above, the yield of the examples is very high, at least 60% or more, whereas the yield of the comparative examples does not exceed 40% at its highest value. This difference in yield is because the intermediate of the comparative examples sticks to the inside of the kiln due to low fluidity during the firing process, preventing the proper firing process from proceeding.

[0229] In addition, it can be seen that the secondary batteries of the examples are significantly superior in terms of battery characteristics, particularly charge-discharge efficiency, of the secondary batteries manufactured therefrom.

[0230]

[0231] The present invention is not limited to the above embodiments and can be manufactured in various different forms, and those skilled in the art will understand that the invention can be implemented in other specific forms without changing the technical concept or essential features of the invention. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive.

Claims

1. A material that can be manufactured into a positive electrode active material through calcination, It includes a transition metal precursor, A precursor-active material intermediate characterized by satisfying an angle of repose, which is an angle of inclination at which granular materials can be stacked with respect to a horizontal plane, in the range of 20° to 39° to improve fluidity.

2. A precursor-active material intermediate according to claim 1, characterized in that the transition metal precursor comprises Fe.

3. In claim 1, the precursor-active material intermediate is, A precursor-active material intermediate characterized by being in a mixed form of one or more selected from the group consisting of alkali metal precursors, alkaline earth metal precursors, dopant precursors, and carbon precursors, and a transition metal precursor.

4. In Paragraph 3, A precursor-active material intermediate characterized in that the transition metal precursor has the composition of Formula 1, the alkali metal precursor and alkaline earth metal precursor have the composition of Formula 2, the dopant precursor has the composition of Formula 3, and the carbon precursor has the composition of Formula 4. MP x1 THE y1 (1) In the above formula, 0≤x1≤2, 0≤y1≤4; M is one or more selected from alkaline earth metals, transition metals, post-transition metals, metalloids, nonmetals, lanthanides, and actinides, and (1-a1-b1)A2CO3*a1AOH*b1A2O (2) In the above formula, 0≤a1≤1, 0≤b1≤1, 0≤1-a1-b2≤1; A is one or more selected from alkali metals and alkaline earth metals, and (1-a2-b2-c2)D2CO3* a2DOH * b2D2O * c2DSO4(3) In the above formula, 0≤a2≤1, 0≤b2≤1, 0≤c2≤1, 0≤1-a2-b2-c2≤1; D is one or more selected from alkaline earth metals, transition metals, post-transition metals, metalloids, nonmetals, lanthanides, and actinides, and C x2 H y2 O z2 (4) In the above formula, 0 <x2≤20, 0≤y2≤42, 0≤z2≤10.

5. A precursor-active material intermediate according to claim 4, characterized in that the above chemical formula 1 is the following chemical formula 1a: MP x1' THE y1' (1a) In the above formula, 0 <x1'≤2, 0<y1'≤4; M is one or more transition metals.

6. A precursor-active material intermediate characterized in that, in claim 1, the Hausner ratio satisfies the range of 1 to 1.

5.

7. A precursor-active material intermediate according to claim 1, characterized by having a Carr's index of 9 to 30.

8. In claim 1, BET is 15 to 30 m 2 A precursor-active substance intermediate characterized by being / g.

9. A precursor-active material intermediate according to claim 1, characterized by having an apparent density of 0.6 to 0.8 g / cc.

10. A positive electrode active material characterized by being manufactured by calcining a precursor-active material intermediate according to claim 1.

11. An anode active material according to claim 10, characterized in that the calcination of the precursor-active material intermediate is performed in a rotary kiln (RK).

12. A positive active material according to claim 10, characterized in that the positive active material is lithium iron phosphate (LFP).

13. A secondary battery characterized by including a positive electrode active material according to claim 10.

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