Transition metal precursor having low tap density and lithium transition metal oxide having high particle strength

Abstract

Disclosed are a transition metal precursor for preparation of a lithium transition metal oxide, in which a ratio of tap density of the precursor to average particle diameter D50 of the precursor satisfies the condition represented by Equation 1 below, and a lithium transition metal oxide prepared using the same. $\begin{array}{cc}0<\frac{\mathrm{Tap}\mathrm{density}}{\begin{array}{c}\mathrm{Average}\mathrm{particle}\mathrm{diameter}D50\\ \mathrm{of}\mathrm{transition}\mathrm{of}\mathrm{metal}\mathrm{precursor}\end{array}}<3500\left(g/\mathrm{cc}.Math.\mathrm{cm}\right)& \left(1\right)\end{array}$

Claims

1. A transition metal precursor for preparation of a lithium transition metal oxide, wherein precursor particles constituting the transition metal precursor are transition metal hydroxide particles, wherein the transition metal hydroxide particles are a compound represented by Formula 2 below:
M(OH.sub.1-x).sub.2  (2) wherein M consists of nickel (Ni), cobalt (Co), and manganese (Mn); and 0≤x≤0.5; and wherein a tap density of the transition metal precursor is from 1.3 g/cc to 1.6 g/cc, and a ratio of tap density to average particle diameter D50 of the precursor satisfies a condition represented by Equation 1 below: $\begin{array}{cc}2000<\frac{\mathrm{Tap}\mathrm{density}}{\begin{array}{c}\mathrm{Average}\mathrm{particle}\mathrm{diameter}D50\\ \mathrm{of}\mathrm{transition}\mathrm{of}\mathrm{metal}\mathrm{precursor}\end{array}}<3500\left(g/\mathrm{cc}.Math.\mathrm{cm}\right).& \left(1\right)\end{array}$

2. The transition metal precursor according to claim 1, wherein the transition metal precursor has an average particle diameter D50 of 1 to 30 μm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawing, in which:

(2) FIG. 1 is a graph illustrating a relationship between tap density and average particle diameter D50 of each of transition metal precursors according to examples and comparative examples of the present invention;

(3) FIG. 2 is a graph illustrating a relationship between changes in particle sizes before and after forming into powder of each of lithium transition metal oxides according to examples and comparative examples of the present invention and a degree of particle growth after calcination of the lithium transition metal oxides; and

(4) FIG. 3 is a graph illustrating lifespan characteristics of lithium secondary batteries manufactured using the lithium transition metal oxides of examples and comparative examples of the present invention.

BEST MODE

(5) Now, the present invention will be described in more detail with reference to the following examples. These examples are provided for illustrative purposes only, should not be construed as limiting the scope and spirit of the present invention and are obvious to those of ordinary skill in the art to which the present invention pertains. In addition, those of ordinary skill in the art may carry out a variety of applications and modifications based on the foregoing teachings within the scope of the present invention, and these modified embodiments may also be within the scope of the present invention.

Example 1

(6) Nickel sulfate, cobalt sulfate, and manganese sulfate were mixed in a molar ratio of 0.45:0.15:0.40 to prepare a 1.5 M aqueous transition metal solution, and a 3 M aqueous sodium hydroxide solution was prepared.

(7) The aqueous transition metal solution was added to a wet reactor maintained at 45° C. to 50° C. and containing distilled water, the aqueous sodium hydroxide solution was added thereto so that pH of the distilled water inside the wet reactor was maintained at 10.5 to 11.5, and a 30% ammonia solution as an additive was continuously supplied to the wet reactor at a flow rate of 1/20 to 1/10 that of the aqueous transition metal solution.

(8) The flow rates of the aqueous transition metal solution, the aqueous sodium hydroxide solution, and the ammonia solution were adjusted so that average residence time thereof in the wet reactor was approximately 6 hours.

(9) The number of revolutions per minute of a stirrer during reaction was maintained at 800 to 1000 rpm.

(10) After reaching a normal state, a nickel-cobalt-manganese composite transition metal precursor prepared through continuous reaction for 20 hours was washed several times with distilled water and dried in a constant temperature dryer at 120° C. for 24 hours, resulting in obtainment of a nickel-cobalt-manganese composite transition metal precursor.

Example 2

(11) A transition metal precursor was prepared in the same manner as in Example 1, except that, during reaction, the 30% ammonia solution as an additive was continuously supplied to the wet reactor at a flow rate of 1/10 to ⅕ that of the aqueous transition metal solution.

Example 3

(12) A transition metal precursor was prepared in the same manner as in Example 1, except that the number of revolutions per minute of the stirrer during reaction was maintained at 600 rpm to 800 rpm.

Comparative Example 1

(13) Nickel sulfate, cobalt sulfate, and manganese sulfate were mixed in a molar ratio of 0.45:0.15:0.40 to prepare a 1.5 M aqueous transition metal solution, and a 3 M aqueous sodium hydroxide solution was prepared.

(14) The aqueous transition metal solution was added to a wet reactor maintained at 45° C. to 50° C. and containing distilled water, the aqueous sodium hydroxide solution was added thereto so that pH of the distilled water inside the wet reactor was maintained at 9.5 to 10.5, and a 30% ammonia solution as an additive was continuously supplied to the wet reactor at a flow rate of 1/20 to 1/10 that of the aqueous transition metal solution. The flow rates of the aqueous transition metal solution, the aqueous sodium hydroxide solution, and the ammonia solution were adjusted so that average residence time thereof in the wet reactor was approximately 6 hours.

(15) The number of revolutions per minute of a stirrer during reaction was maintained at 1200 to 1400 rpm.

(16) After reaching a normal state, a nickel-cobalt-manganese composite transition metal precursor prepared through continuous reaction for 20 hours was washed several times with distilled water and dried in a constant temperature dryer at 120° C. for 24 hours, resulting in obtainment of a nickel-cobalt-manganese composite transition metal precursor.

Comparative Example 2

(17) A transition metal precursor was prepared in the same manner as in Comparative Example 1, except that, during reaction, the ammonia solution as an additive was not continuously supplied.

Experimental Example 1

(18) 50 g of each of the transition metal precursor prepared according to each of Examples 1 to 3 and Comparative Examples 1 and 2 was added to a 100 cc cylinder for tapping using a KYT-4000 measuring device (available from SEISHIN) and then was tapped 3000 times. In addition, powder distribution based on volume was obtained using S-3500 (available from Microtrac), D50 values were measured, and tap density with respect to D50 was calculated. Results are shown in Table 1 below.

(19) TABLE-US-00001 TABLE 1 Tap density Tap density/D50 (g/cc) D50 (μm) (g/cc .Math. cm) Example 1 1.42 5.62 2527 Example 2 1.52 5.66 2686 Example 3 1.60 5.70 2807 Comparative 1.99 5.48 3631 Example 1 Comparative 1.81 5.13 3528 Example 2

(20) As shown in Table 1 above, it can be confirmed that the transition metal precursors according to the present invention (Examples 1 to 3) have a low ratio of tap density to D50, namely, 3500 or less, while the transition metal precursors of Comparative Examples 1 and 2 have a high ratio of tap density to D50, namely, 3500 or more.

Experimental Example 2

(21) Each of the transition metal precursors of Examples 1 to 3 and Comparative Examples 1 and 2 was mixed with Li.sub.2CO.sub.3 so that a molar ratio of Li to Ni+Co+Mn was 1.10 and the mixture was heated at a heating rate of 5° C./min and calcined at 950° C. for 10 hours, to prepare a lithium transition metal oxide powder as a positive electrode active material.

(22) D50 corresponding to powder distribution based on volume of each of the prepared positive electrode active material powders was measured using S-3500 (available from Microtrac) and each positive electrode active material powder was subjected to ultrasonic dispersion for 60 seconds. Subsequently, D50 corresponding to powder distribution based on volume thereof was measured again. Subsequently, changes in particle sizes before and after pulverization following the two processes were calculated, and results are summarized in Table 2 below.

(23) TABLE-US-00002 TABLE 2 D50 of active material/D50 of precursor D50 (μm) D50 (μm) of (changes in particle sizes of precursor active material before and after calcination Example 1 5.62 5.65 1.005 Example 2 5.66 5.64 0.996 Example 3 5.70 5.68 0.996 Comparative 5.48 6.60 1.204 Example 1 Comparative 5.13 6.31 1.230 Example 2

(24) As shown in Table 2 above, it can be confirmed that, in the same transition metal composition, the lithium transition metal oxides prepared from the transition metal precursors according to the present invention (Examples 1 to 3) have small changes in particle sizes before and after calcination, namely, 1.2 or less, while the lithium transition metal oxides prepared from the transition metal precursors of Comparative Examples 1 and 2 have large changes in particle sizes before and after calcination, namely, 1.2 or more.

Experimental Example 3

(25) 10 g of the positive electrode active material powder using each of the transition metal precursors of Examples 1 to 3 and Comparative Examples 1 and 2 was added to a PDM-300 paste mixer, alumina beads with a diameter of 5 mm were added thereto, and each positive electrode active material powder was pulverized using a ball mill under a condition of 600×600 based on revolutions (rpm) per minute (rpm)×revolutions per minute (rpm). The pulverized active material powder was subjected to ultrasonic dispersion for 60 seconds using S-3500 available from Microtrac and then D50 corresponding to powder distribution based on volume thereof was measured again.

(26) Subsequently, changes in particle sizes before and after pulverization following the two processes were calculated, and results are summarized in Table 3 below.

(27) TABLE-US-00003 TABLE 3 D50 D50 (μm) before D50 (μm) after after pulverization/D50 pulverization pulverization before pulverization Example 1 5.65 5.05 0.894 Example 2 5.64 5.00 0.887 Example 3 5.68 4.98 0.847 Comparative 6.60 4.04 0.612 Example 1 Comparative 6.31 4.20 0.666 Example 2

(28) As shown in Table 3 above, it can be confirmed that, in the same transition metal composition, the lithium transition metal oxides prepared from the transition metal precursors according to the present invention (Examples 1 to 3) exhibit small changes in particle sizes during pulverization and, thus, the positive electrode active materials exhibit high strength. On the contrary, the lithium transition metal oxides prepared from the transition metal precursors of Comparative Examples 1 and 2 exhibit low strength.

(29) Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

INDUSTRIAL APPLICABILITY

(30) A transition metal precursor according to the present invention has a lower tap density than conventional transition metal precursors consisting of conventional transition metal precursor particles, when average particle diameter D50 of the transition metal precursor of the present invention is substantially the same as those of conventional transition metal precursors.

(31) In this regard, the expression “substantially the same as” means average particle diameter D50 within a measurement error range of 0.2 μm or less.

(32) As a result, a lithium transition metal oxide prepared using the transition metal precursor according to the present invention exhibits a smaller change in average particle diameter D50 during sintering, when compared with conventional lithium transition metal oxides, and has a higher strength, when compared with lithium transition metal oxides prepared using conventional transition metal precursors.

(33) Therefore, by using a lithium secondary battery using the lithium transition metal oxide as a positive electrode active material, breaking or crushing of lithium transition metal oxide particles during rolling may be minimized and, as such, the lithium secondary battery exhibits improved high temperature characteristics, lifespan characteristics, and safety.

(34) In addition, reduction in capacity may be minimized and output characteristics may be improved.