WO2015105225A1 - Method for preparing nickel-cobalt-manganese composite precursor - Google Patents

Abstract

The present invention relates to a method for preparing Ni_xCo_yMn_1-x-y(OH)₂, which is a nickel-cobalt-manganese composite precursor used as a positive electrode material by being mixed with lithium in a nickel secondary battery or the like, and more specifically, to a technique capable of preparing a precursor which has a smaller and more uniform particle size and a wider specific surface area compared with a co-precipitation method of the prior art.

Description

Process for preparing nickel-cobalt-manganese composite precursor

The present invention is to prepare a Ni _x Co _y Mn _1-xy (OH) ₂ (hereinafter abbreviated as "NCM-based precursor") which is a nickel-cobalt-manganese composite precursor used as a cathode material by mixing with lithium in a lithium secondary battery, etc. In particular, the present invention relates to a technique capable of producing a precursor having a smaller particle size and uniformity and a higher sphericity than a precursor prepared by a conventional coprecipitation method.

With the spread of portable small electric and electronic devices, new secondary batteries such as nickel-metal hydride batteries and lithium secondary batteries have been actively developed. Among them, a lithium secondary battery is a battery in which carbon such as graphite is used as a negative electrode active material, a metal oxide containing lithium is used as a positive electrode active material, and a nonaqueous solvent is used as an electrolyte. Lithium is a metal that has a high tendency to ionize and is a material that is attracting attention in a battery having high energy density because it can express high voltage.

Lithium transition metal oxides containing lithium are mainly used as positive electrode active materials for lithium secondary batteries, and layered lithium transition metal oxides such as cobalt-based, nickel-based, and ternary divisions in which cobalt, nickel, and manganese coexist. More than% are used.

For example, Li ₂ CO ₃ and an NCM precursor are mixed and plasticized to be used as a cathode material. Particle size and specific surface area of the NCM-based precursor has a great influence on the realization of high power of the medium-large lithium battery for electric vehicles (HEV, PHEV, EV). As the particle size of NCM cathode material increases, the specific surface area increases, and the diffusion distance of lithium ions is shortened to facilitate the diffusion and entry of lithium ions smoothly and quickly. In order to minimize the particle size of the precursor is necessary.

In general, NCM-based precursors are prepared by coprecipitation, and nickel, manganese, and cobalt salts are dissolved in distilled water, and then precipitated in a reactor with aqueous ammonia solution (chelating agent) and aqueous NaOH solution (basic solution). . Conventional coprecipitation has made it difficult to prepare precursor small particles having a uniform particle size, which affects the sphericity and shape of the precursor. It is possible to reduce the size of the precursor to reduce the size of the precursor by reducing the coprecipitation time by the conventional coprecipitation method, but in this case, the output performance is remarkably degraded when used as a secondary battery cathode device due to the low density of the precursor.

On the other hand, when the small particle size of the NCM precursor prepared by the conventional coprecipitation method using a mechanical means such as a ball mill (ball mill) can be reduced, but the sphericity and morphology of the particles is very poor In addition, this also had a problem in that the electrical properties deteriorate when used as an anode device.

It is an object of the present invention to provide a method for small particle formation of an NCM precursor. In particular, it is an object of the present invention to provide a method for producing a precursor having a smaller particle size and uniformity compared to that produced by a conventional coprecipitation method while maintaining a uniform spherical morphology.

The present invention comprises a first coprecipitation step (1) for producing Ni _x Co _y Mn _1-xy (OH) ₂ by the coprecipitation method;

A mechanical grinding step (2) of grinding the Ni _x Co _y Mn _1-xy (OH) ₂ prepared in the step (1) into a small size by a mechanical means; And

Ni _x Co _y Mn _1-xy (OH) ₂ was prepared by coprecipitation with a mixed aqueous solution of nickel, cobalt and manganese together with Ni _x Co _y Mn _1-xy (OH) ₂ pulverized in step (2). A second co-precipitation step (3),

In the step (3) Ni _x Co _y Mn _1- characterized in that the pulverized _{Ni x Co y Mn 1-xy} (OH) of the step ₍₂₎ to act as a seed (seed) in a second stage co-precipitation Provided is a process for preparing _xy (OH) ₂ .

In particular, the mechanical grinding of the step (2) is preferably performed by a ball mill.

In particular, the particle size of Ni _x Co _y Mn _1-xy (OH) ₂ finely granulated by mechanical grinding in step (2) is preferably 0.5 to 2 μm.

In particular, it is preferable to adjust the coprecipitation time so that the particle size of Ni _x Co _y Mn _1-xy (OH) ₂ prepared in step (3) becomes 3 to 5 μm.

In particular, the step (3) is preferably nickel, cobalt and sulfuric acid using nickel sulfate, cobalt sulfate and manganese sulfate, respectively.

In particular, the step (3) is preferably made at a temperature condition of 50 ~ 70 ℃, pH 9.5 ~ 10.5.

Through the method of the present invention, it is possible to produce Ni _x Co _y Mn _1-xy (OH) ₂ particles having a small size, for example, 3 μm or less, which cannot be prepared by conventional coprecipitation, and have a uniform particle size. High sphericity can be produced. Particularly, in the present invention, the Ni _x Co _y Mn _1-xy (OH) ₂ having a size of 9 μm manufactured by the conventional coprecipitation method is made into particles having a small size, for example, 1.4 μm through mechanical grinding, and then again the 1.4 ㎛ size of the _{Ni x Co y Mn 1-xy} (OH) through the co-precipitation and then a mixture of a 1.4 ㎛ size of the _{Ni x Co y Mn 1-xy} (OH) _2, nickel, cobalt and manganese made of an aqueous solution ₂ The seed may be grown as Ni _x Co _y Mn _1-xy (OH) ₂ having a size of 3 μm. In particular, since it was grown with a small size of crushed Ni _x Co _y Mn _1-xy (OH) ₂ as a seed, Ni _x Co _y Mn _1-xy (OH) made into a small size by simple mechanical grinding. Unlike ₂ , the particle size is uniform and the degree of sphericity is very high, so it is used together with lithium in the anode device to show excellent electrical properties.

1A and 1B are SEM photographs measured at different magnifications of a Ni _0.5 Co _0.2 Mn _0.3 (OH) ₂ precursor prepared by a conventional coprecipitation method, and FIG. 1C is a particle size distribution diagram.

FIG. 2 is a particle size distribution diagram of a Ni _0.5 Co _0.2 Mn _0.3 (OH) ₂ precursor prepared by a conventional coprecipitation method after grinding for 10 hours using a ball mill.

3A and 3B are SEM photographs taken at different magnifications of the Ni _0.5 Co _0.2 Mn _0.3 (OH) ₂ precursor prepared by the method of the present invention, and FIG. 3C is a particle size distribution diagram.

Figure 4a is a SEM measurement of the cathode material to which the precursor prepared by the method of the present invention is applied, Figure 4b is a SEM measurement of the cathode material to which the precursor prepared by a conventional coprecipitation method as a comparative example, Figure 4c is the anode of Figure 4a The charge and discharge test results of the ash, Figure 4d is a charge and discharge test results of the positive electrode material of the comparative example of Figure 4b.

Hereinafter, the present invention will be described, in the following description, "precursor" means Ni _x Co _y Mn _1-xy (OH) ₂ precursor, wherein 0 <x <1, 0 <y <1, 0 <x + y <1. In addition, unless otherwise stated, precursor particle size means median value.

Conventional coprecipitation has made it difficult to prepare precursor small particles having a uniform particle size, which affects the sphericity and shape of the precursor. It is possible to reduce the size of the precursor to reduce the size of the precursor by reducing the coprecipitation time by the conventional coprecipitation method, but in this case, the output performance is remarkably degraded when used as a secondary battery cathode device due to the low density of the precursor. Accordingly, an object of the present invention is to provide a precursor manufacturing method that is used as an anode element while making the precursor small particles to have excellent electrical output performance.

The present invention proposes the following method to realize the above object.

The present invention comprises a first coprecipitation step (1) for producing Ni _x Co _y Mn _1-xy (OH) ₂ by the coprecipitation method; A mechanical grinding step (2) of grinding the Ni _x Co _y Mn _1-xy (OH) _{2 prepared} in the step (1) to a size smaller than the step (1) by mechanical means; And producing a pulverized Ni _x Co _y Mn _1-xy (OH) Ni _x Co _y Mn _1-xy (OH) by a mixed aqueous solution of nickel, cobalt and manganese with ₂ Coprecipitation Method ₂ of Step (2) It comprises a second co-precipitation step (3).

Hereinafter, each step will be described.

First copulation step (1)

A Ni _x Co _y Mn _1-xy (OH) ₂ precursor is prepared using a conventional coprecipitation method. Such precursors are typically 8-9 μm in size and have poor sphericity.

Mechanical grinding stage (2)

The precursor (generally 8-9 μm in size) made by the coprecipitation method is pulverized small by a physical method. This milling is possible via various mechanical milling means, but in the following experiments milling was carried out via a ball mill. For example, if the target mean particle size of the precursor produced via secondary coprecipitation is 3 μm, the precursor must be ground to 3 μm or less in the mechanical grinding step. At this time, the pulverized precursor has a very low sphericity and cannot be used as an anode device because the size of the particles is not uniform.

Considering that the target size of the precursor prepared through the secondary coprecipitation described below is 3 to 5 μm or less, the size of the precursor to be crushed through the mechanical grinding step (2) is 0.5 to 2 μm is suitable, but is not limited thereto. no.

Second Coprecipitation Step (3)

Reprecipitation is performed but co-precipitation is performed by including the pulverized precursor in a co-precipitation solution of nickel, cobalt and manganese to seed the pulverized precursor. The precursor pulverized in the reprecipitation step serves as a seed so that the particles grow from the precursor pulverized in the reprecipitation step. Although the size of the precursor is naturally larger than that of the precursor acting as a seed through the second coprecipitation step (3), in the pulverization step (2), the precursor particles, which are not uniform in size and shape, grow to be uniform in size and spherical in shape. This results in small particles, spheronization and homogenization of the precursors.

Experimental Example

Precursors prepared by the method of the present invention are small particles to have a large specific surface area, as well as a high sphericity, which is used as a positive electrode device to exhibit high output characteristics. In the following description, but to be described with respect to the present invention through the experiment, with the precursor _{Ni x Co y Mn 1-xy} (OH) in ₂ x = 0.5, y = 0.2 of _{Ni 0.5 Co 0.2 Mn 0.3 (OH} ) 2 Examples Let's explain.

Experimental Example 1 Ni before the ball mill _0.5 Co _0.2 Mn _0.3 (OH) ₂  Precursor measurement experiment

1A and 1B are SEM photographs taken at different magnifications of a Ni _0.5 Co _0.2 Mn _0.3 (OH) ₂ precursor prepared by a conventional coprecipitation method, and FIG. 1C is a particle size distribution diagram. The size of the Ni _0.5 Co _0.2 Mn _0.3 (OH) ₂ precursor before the ball mill was about 8.9 μm.

Experimental Example 2: Ni after ball mill _0.5 Co _0.2 Mn _0.3 (OH) ₂  Precursor measurement experiment

The particle size distribution of the Ni _0.5 Co _0.2 Mn _0.3 (OH) ₂ precursor of Experimental Example 1 after grinding for 10 hours using a ball mill was as shown in FIG. 2. As shown in FIG. 2, the Ni _0.5 Co _0.2 Mn _0.3 (OH) ₂ precursor was about 1.4 μm in size by pulverization by a ball mill. As shown in FIG. 2, the particle size distribution was very wide, and thus the size was not constant. That is, the particle size can be reduced by pulverization, but it was found that it is not suitable as a positive electrode device of a lithium secondary battery due to its low sphericality and uniformity.

Experimental Example 3: Ni prepared by the method of the present invention _0.5 Co _0.2 Mn _0.3 (OH) ₂  Precursor measurement experiment

3L of distilled water was charged to a 5L double tank reactor, and the temperature was raised to 50 to 70 ° C. using a temperature maintaining apparatus. Before the reaction, the ball mill of Experiment 2 was pulverized for 10 hours, and 100 g of Ni _0.5 Co _0.2 Mn _0.3 (OH) ₂ having a median size of about 1.4 μm was placed in 500 ml of NH ₄ OH solution, and then, the impeller was used at 900 to 1000 rpm. Stir at speed.

Nickel sulfate, cobalt sulfate, and manganese sulfate were mixed in a molar ratio of 0.5: 0.2: 0.3 to prepare a 2.5M metal solution, and 2L of a 30-40% sodium hydroxide solution was prepared. The aqueous metal solution was pumped continuously to the reactor with a metering pump at 0.48 L / hr, which was mixed with ₂ L / m of N ₂ gas and introduced into the reactor. The aqueous sodium hydroxide solution was used to adjust the pH atmosphere during the reaction, the pH was pumped into the reactor in conjunction with the pump through the control equipment to maintain a pH of 9.5 ~ 10.5. The reaction proceeded for 3 hours.

After completion of the reaction, the three-component transition metal precursor obtained was washed with distilled water several times by a filtering method, and dried in a constant temperature dryer for 20 hours to obtain Ni _0.5 Co _0.2 Mn _0.3 (OH) _2, which is a nickel-cobalt-manganese three-component precursor. .

3A and 3B are SEM photographs taken at different magnifications of the precursors prepared by the coprecipitation-> milling-> coprecipitation prepared by the method of the present invention, and the result of measuring the particle size distribution is FIG. 3C.

3A to 3C, the precursor prepared by the method of the present invention has a particle size of about 3 μm, unlike the precursor prepared by the conventional method, the particle size is uniform, and the specific surface area is large due to the small particle size. It can be seen that the increase.

Experimental Example 4 Physical Properties of the Cathode Material

Cathode material Li (Ni _0.5 Co _0.2 Mn _0.3 ) of Comparative Example prepared by mixing a precursor having an average particle size of about 9 μm manufactured by conventional coprecipitation with Li ₂ Co ₃ and then firing at 900 ° C. for 20 hours using a firing furnace. O ₂ and the precursor of Experimental Example 3, prepared by the coprecipitation method of the present invention, were mixed with Li ₂ Co _3, and then calcined at 900 ° C. for 20 hours using a firing furnace, thereby obtaining the cathode material Li (Ni _0.5 Co _0.2). Mn _0.3 ) O ₂ was prepared.

4A is a SEM measured picture of the cathode material of the present invention, and FIG. 4B is a SEM measured picture of the cathode material of the comparative example.

In addition, in order to test the electrical properties of the cathode material prepared above, a coin cell was made for the charge and discharge tests of the cathode material of the comparative example and the present invention. As a result, Figure 4c is a charge and discharge test results of the positive electrode material of the present invention, Figure 4d is a charge and discharge test results of the positive electrode material of the comparative example. In the case of the cathode material to which the precursor prepared by the method of the present invention was applied, the initial capacity (mAh / g) was 162.1, but in the cathode material to which the precursor prepared by the conventional coprecipitation method was applied, the initial capacity was 153.5, indicating that the cathode material of the present invention was excellent. Could know. In addition, when comparing the output efficiency (2C / 0.1C), it was found that the positive electrode material of the present invention is 83.74 and 64.51 for the positive electrode material of the comparative example is excellent in the positive electrode material of the present invention.

This invention relates to the precursor which can be used as a positive electrode material of a secondary battery. In particular, the present invention relates to a method for producing a nickel-cobalt-manganese composite precursor which is mixed with nickel and used as a cathode material.

Claims (6)

1. Ni _x Co _y Mn _1-xy (OH) ₂ (wherein, A first coprecipitation step (1) for producing 0 <x <1, 0 <y <1, 0 <x + y <1);

   A mechanical grinding step (2) of grinding the Ni _x Co _y Mn _1-xy (OH) ₂ prepared in the step (1) into a small size by a mechanical means; And

   By the mixed aqueous solution of nickel, cobalt and manganese with a Ni _x Co _y Mn _1-xy (OH) ₂ pulverized in the above step (2) to the coprecipitation method for preparing a Ni _x Co _y Mn _1-xy (OH) ₂ A second co-precipitation step (3),

   In the step (3) Ni _x Co _y Mn _1- characterized in that the pulverized _{Ni x Co y Mn 1-xy} (OH) of the step ₍₂₎ to act as a seed (seed) in a second stage co-precipitation Process for the preparation of _xy (OH) ₂ .
2. In claim 1, wherein the mechanical pulverization of the step (2) is a ball mill process for producing a (ball mill) Ni _x Co _y Mn _1-xy (OH), characterized in that formed by the _second.
3. In claim 1, wherein the fine-particle formation of Ni _x Co _y Mn _1-xy (OH) ₂ of a particle size of 0.5 ~ 2 ㎛ of Ni _x Co _y Mn _1-xy (OH, characterized in that in said step (2) ₂ ) a method of preparation.
4. According to claim _1, Ni _x Co _y Mn ₁ characterized in that the coprecipitation time is adjusted to have a particle size of 3 ~ 5 ㎛ of Ni _x Co _y Mn _1-xy (OH) ₂ prepared in step (3) Process for the preparation of _-xy (OH) ₂ .
5. The method for preparing Ni _x Co _y Mn _1-xy (OH) _{2 according} to claim 1, wherein the step (3) uses nickel sulfate, cobalt sulfate and manganese sulfate as nickel, cobalt and sulfuric acid, respectively.
6. The method of claim 1, wherein the step (3) is Ni _x Co _y Mn _1-xy (OH) ₂ , characterized in that the temperature is made at 50 ~ 70 ℃, pH 9.5 ~ 10.5.

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