KR20180027906A - Nanoporous cobalt hydroxide for lithium battery, electrode, lithium battery including the cobalt hydroxide - Google Patents

Abstract

One embodiment of the present invention relates to a manufacturing method of nanoporous cobalt hydroxide which comprises: a first step of drying a cobalt sulfate-colloid silica mixed solution to obtain cobalt sulfate/silica composite particles; and a second step of adding the composite particles to a sodium hydroxide solution. The nanoporous cobalt hydroxide having a large specific surface area and a large pore volume can be provided through the manufacturing method of the present invention.

Description

[0001] The present invention relates to a nanoporous cobalt hydroxide for lithium battery, an electrode material including the nanoporous cobalt hydroxide, and a lithium battery,

The present invention relates to a method for producing cobalt hydroxide including nano-sized pores, an electrode material containing the same, and a lithium battery.

Lithium battery is a chemical battery which can repeatedly charge and discharge by using electrochemical reaction. It is leading the weight saving and high performance of small electronic devices as a main energy source of portable information communication terminals. In order to improve the performance of a lithium battery required for high performance of various electronic devices, it is essential to develop a reliable high-capacity electrode material.

Recently, researches on the anode materials of lithium secondary batteries have been focused on non-carbon anode materials in order to overcome the limit of low theoretical capacity of carbon-based materials with the aim of high capacity, And oxide-based materials that generate lithium oxide.

On the other hand, in the case of an oxide-based cathode material, a transition reaction of an oxide forming a nano-sized metal occurs upon reaction with lithium based on a transition metal oxide, and metal is distributed in lithium oxide. It is known that the reverse reaction of forming a transition metal oxide from lithium oxide acting as a continuous phase can be caused by the high surface energy of a finely dispersed nano-sized metal.

Such an oxide-based anode material has an advantage in that it has a high capacity over three times as high as that of a carbon-based material and has an excellent lifetime characteristic as compared with a metallic material. Therefore, it is necessary to carry out various studies on such an oxide-based anode material.

It is an object of the present invention to provide a method for producing an electrode material for a high capacity lithium battery.

One embodiment of the present invention is a method for preparing a cobalt sulfate / silica composite particle, comprising: a first step of preparing a cobalt sulfate / silica composite particle by drying a cobalt sulfate and a colloidal silica mixed solution; And a second step of adding the composite particles to a sodium hydroxide solution.

In another embodiment, through the second step, the cobalt sulfate of the multiparticulate is formed into cobalt hydroxide and at the same time the silica is removed and becomes porous.

In another embodiment, the second step is carried out two or more times.

In another embodiment, the method further comprises, after the second step, a third step of washing and drying with H ₂ O and acetone.

In another embodiment, the cobalt sulfate / silica composite particle of the first step comprises (1-a) dissolving Co (NO ₃ ) ₂ .6H ₂ O in an H ₂ O solvent; (1-b) mixing the colloidal silica solution with the mixture prepared in the step (1-a); (1-c) mixing an aqueous sulfuric acid solution with the mixture prepared in the step (1-b); And (2-c), a step including a defect at a high temperature. The sintering can be performed in the atmosphere.

In another embodiment, the step (1-a) comprises dissolving Co (NO ₃ ) ₂ .6H ₂ O in an H ₂ O solvent using a magnetic stirrer.

In another embodiment, the step (1-b) comprises mixing the colloidal silica solution with the mixture prepared in step (1-a) by a dropwise method.

In another embodiment, the first step comprises the steps of (1-a ') dissolving CoSO ₄ .7H ₂ O in H ₂ O solvent and adding a colloidal silica solution to the mixture prepared in step (1-a') (1-b ').≪ / RTI >

In another embodiment, the step (1-a ') employs a magnetic stirrer to dissolve CoSO ₄ .7H ₂ O in an H ₂ O solvent.

In another embodiment, the step (1-b ') comprises mixing the colloidal silica solution with the mixture prepared in step (1-a') by a dropwise method.

In another embodiment, the present invention relates to an electrode material for a lithium battery comprising cobalt hydroxide, a conductive material and a binder, which is produced by any one of the above-mentioned production methods.

In another embodiment, the present invention relates to a lithium battery including an electrode made of the electrode material.

The nanoporous cobalt hydroxide having a large specific surface area and a large pore volume can be provided through the process for producing cobalt hydroxide which is one embodiment of the present invention. In addition, through this, a high capacity lithium battery can be provided.

1 is a graph showing the results of X-ray diffraction experiments for Examples 1 and 2 and Comparative Examples.
2 is a graph showing the results of X-ray diffraction experiments for Example 1 and Comparative Example.
3 (a) is an isothermal sorption desorption curve for Examples 1 and 2 and Comparative Example, and (b) is a pore size distribution diagram.
4 is an SEM image of Examples 1 and 2 and Comparative Example.
FIG. 5 is a graph showing a charge / discharge test result of a lithium battery manufactured using Example 1 and a comparative example, in which (a) is a first cycle charging / discharging curve and (b) is a lifetime characteristic graph.
6 is a graph showing the charge / discharge test results of a lithium battery manufactured by using Example 1 and Comparative Example.

The terminology used in this application is used only to describe a specific embodiment and is not intended to limit the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In the present application, the term "comprises" or "having" is intended to designate the presence of stated features, elements, etc., and not one or more other features, It does not mean that there is none.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the contextual meaning of the related art and are to be interpreted as either ideal or overly formal in the sense of the present application Do not.

One embodiment of the present invention relates to a process for preparing porous cobalt hydroxide, comprising a first step of preparing a cobalt sulfate / silica composite particle and a second step of adding the composite particle to a sodium hydroxide solution.

The above-described first step is not limited to the method described below, but can be explained by dividing it into two kinds of methods. The first method uses Co (NO ₃ ) ₂ .6H ₂ O as the initial initiator, and the second method uses CoSO ₄ .7H ₂ O as the initial initiator.

According to a first method, the first step comprises the steps of (1-a) dissolving Co (NO ₃ ) ₂ .6H ₂ O (cobalt nitrate hexahydrate) in an H ₂ O solvent, (1-b) mixing colloidal silica solution to the mixture prepared in step (1-b), (1-c) mixing the aqueous solution of sulfuric acid in the mixture prepared in step (1-b) And then (1-d) sintering at a high temperature.

Specifically, Co (NO ₃ ) ₂ .6H ₂ O is prepared, and the prepared Co (NO ₃ ) ₂ .6H ₂ O is dissolved in an H ₂ O solvent, and then mixed using a magnetic stirrer. Then, the colloidal silica solution is mixed. At this time, it is preferable to mix by a dropwise method. At this time, it is preferable to stir the mixed solution at 70 캜. Then, heat treatment can be performed at 550 캜 for 3 hours in an air atmosphere. The cobalt sulfate / silica composite particles can be prepared by the above-described method, and the first step can be carried out.

According to the second method, the first step is a step (1-a ') in which CoSO ₄ .7H ₂ O (cobalt sulfate heptahydrate) is dissolved in a H ₂ O solvent, and a step (1-b ') in which the colloidal silica solution is mixed with the resulting mixture.

More specifically, CoSO ₄ · are mixed using a magnetic stirrer after dissolving 7H ₂ O to H ₂ O solvent. Thereafter, the colloidal silica solution is mixed. At this time, it is preferable to mix by a dropwise method. It is preferable to dry at 70 캜. The cobalt sulfate / silica composite particles can be prepared by the above-described method, and the first step can be carried out.

The sintering step is preferably carried out in an atmospheric environment.

Here, through the second step, the silica is removed while sodium hydroxide converts sulfuric acid of cobalt sulfate to hydroxy. The sodium hydroxide solution may be 2M, and the reaction can be conducted for about 1 hour. However, in the case where the silica can not be removed as much as desired by the present invention by one execution, washing twice or more can be repeatedly performed. At this time, it is preferable to discard the once-used sodium hydroxide solution and treat with a fresh sodium hydroxide solution. Even in the case of treating with sodium hydroxide solution three times or more, it is preferable to discard the previously used sodium hydroxide and treat with a fresh sodium hydroxide solution. Through the second step, the cobalt sulfate of the composite particles is formed into cobalt hydroxide and at the same time, the silica is removed to become porous.

In addition, after the second step, the cobalt hydroxide prepared in the second step may be further washed and dried with H ₂ O and acetone.

An electrode material for a lithium battery according to another embodiment of the present invention includes cobalt hydroxide, a conductive material and a binder prepared by any one of the above-described methods. The cobalt hydroxide has nano-sized porosity and can be used as a high-performance electrode active material. The conductive material and the binder are not particularly limited, but are included for manufacturing the electrode material for a lithium battery intended in the present invention, and any material may be used as long as such an object is satisfied.

A lithium battery according to another embodiment of the present invention includes an electrode made of an electrode material including cobalt hydroxide, a conductive material, and a binder manufactured by any one of the above-described methods. Other components other than the above-described electrode are not particularly limited, but are for producing a lithium battery intended in the present invention, and any of them may be used as long as they satisfy this intention.

Hereinafter, the present invention will be described in detail with reference to experimental examples.

(Experimental Example 1)

Example 1 was prepared by the first method described above. Specifically, Co (NO ₃ ) ₂ .6H ₂ O was dissolved in a H ₂ O solvent and mixed using a magnetic stirrer. Thereafter, a solution of colloidal silica (Ludox HS-40) was dropwise mixed and then diluted sulfuric acid aqueous solution was added. The mixed solution was stirred at 70 캜 and dried, and then heat-treated at 550 캜 for 3 hours in the air atmosphere. Thereafter, repeated four times a process of the reaction for 1 hour, placed in 2M NaOH aqueous solution to remove the SiO ₂ and, to form a Co (OH) _2. The filtered powder was washed several times with H ₂ O and acetone and dried to give nanoporous cobalt hydroxide (Co (OH) ₂ ).

Example 2 was prepared by the second method described above. CoSO ₄ · were mixed using a magnetic stirrer after dissolved 7H ₂ O to H ₂ O solvent. Thereafter, a solution of colloidal silica (Ludox HS-40) was dropwise mixed with a drop, followed by stirring at 70 DEG C and drying. Then, to put it in 2M NaOH aqueous solution, repeating the process of reaction for one hour, and removing the SiO _2, to form a Co (OH) _2. The filtered powder was washed several times with H ₂ O and acetone and dried to give nanoporous cobalt hydroxide (Co (OH) ₂ ).

As a comparative example, conventionally used bulk cobalt hydroxide was used.

X-ray diffraction experiments were carried out using Rigaku D / MAX-2200 Ultima diffractometer using Cu K? (1.54 A) for Examples 1 and 2 and Comparative Example. The results are shown in Fig. 1 (Examples 1 and 2) 2 and comparative example) and 2 (example 1 and comparative example). As shown in FIGS. 1 and 2, Examples 1 and 2 prepared as a result of the X-ray diffraction analysis show that Co (OH) ₂ having a hexagonal crystal structure is contained and the same as the bulk powder Crystal structure. In addition, in order to confirm the size of the crystal grains with respect to the (001) diffractive surface shown in FIG. 2, it was calculated by the Scherrer equation. Example 1 was confirmed to be 19.7 nm, and the comparative example was confirmed to be 27.5 nm. As a result, it was confirmed that the grain size of Example 1 was smaller.

(Experimental Example 2)

Nitrogen adsorption / desorption experiments were conducted to confirm the specific surface area, pore volume, and pore size distribution of Examples 1 and 2 and Comparative Examples. The specific surface area was calculated by the BET (Brunauer-Emmett-Teller) method at 0.05-0.20 relative pressure of the nitrogen adsorption / desorption isotherm. The pore size distribution was derived from the Brett-Joyner-Halenda (BJH) method. Table 1 shows specific surface area and pore volume. FIG. 3 graphically shows the results of adsorption amount and pore size.

S _BET (m < 2 > / g) V _T (cm 3 / g) Example 1 68 0.25 Example 2 52 0.24 Comparative Example 20 0.11

As shown in Table 1 and FIG. 3, Example 1 has a uniform size of 2.2 nm, and has a high surface area of 68 m 2 / g and a large pore volume of 0.25 cm 3 / g. Example 2 also had a surface area and pore volume that were slightly lower than those of Example 1, but had excellent surface area and pore volume as compared with Comparative Example.

(Experimental Example 3)

In order to observe the morphology of the pores and particles of Examples 1 and 2 and Comparative Examples, they were observed with a scanning electron microscope (SEM). Each image is shown in Fig. As shown in Fig. 4, it can be seen that Examples 1 and 2 and Comparative Example are composed of polygonal plate-like particles. It can be seen that Examples 1 and 2 have a particle size of 50 nm to 200 nm and a thickness of about 20 nm, which is smaller and thinner than the comparative example. In addition, the roughness of the particle surfaces of Examples 1 and 2 can be observed. As shown in the results of the X-ray diffraction experiment and the nitrogen adsorption / desorption experiment, Examples 1 and 2 have smaller particle sizes, smaller pores of several nanometers, and larger specific surface area , It is confirmed that the characteristics of the nanoporous material can be secured.

(Experimental Example 4)

Using the example 1 and the comparative example obtained in the above Experimental Example 1, each electrode was manufactured and used in a lithium battery, and each lithium battery was subjected to charge-discharge experiments. (Polyamide / imide, PAI) dissolved in N-pyrrolidone (NMP) in an amount of 10 wt.% Were mixed with 70 parts by weight of a carbon conductive material (Super P, MMM) : 15: 15 to prepare a homogeneous slurry, which was then coated on a copper collector using a doctor blade and dried in a convection oven at 80 ° C. Thereafter, the electrode was thermally treated at 200 ° C for 2 hours in a vacuum condition. The prepared electrode was cut into a diameter of 12 mm and used as a working electrode. (Cellgard 3510) as a separation membrane and 1.3M LiPF ₆ as an electrolytic solution using a solution of ethylene carbonate (EC) / diethyl carbonate (DEC) (v / v = 3/7) 2032 type coin cell was prepared.

Repeated charging and discharging experiments were carried out using a WBCS3000S charge / discharge device of WANATEC Co., Ltd., in a voltage range of 0.001 to 3.0 V (vs. Li) at a current density of 57.7 mA per 1 g. The experimental results are shown in Fig. 5 and Table 2.

first
Charging capacity
(mAh / g) first
Discharge capacity
(mAh / g) Initial efficiency
(Discharge capacity /
Charging capacity * 100) 30 cycles
Discharge capacity
(mAh / g) Example 1 1700 1112 65.4 1019 Comparative Example 1602 472 29.4 1047

As shown in Fig. 5 and Table 2, Example 1 shows superior initial capacity and initial efficiency as compared with Comparative Example. In addition, it was confirmed that Example 1 exhibits a high initial capacity, and even after 30 cycles, it exhibits a stable cycle retention characteristic that exhibits a capacity of 92% of the initial capacity.

(Experimental Example 5)

The lithium battery including the example 1 and the comparative example used in Experimental Example 4 was again used and the current density (0.1 C rate = 57.7 mA / g, 0.5 C rate = 288.5 mA / g, 1.0 C rate = 577 mA / g), an experiment was conducted to compare the capacity characteristics of a lithium battery. The results of the experiment are shown in Fig. As shown in FIG. 6, in both Example 1 and Comparative Example, the capacity of the battery tended to decrease as the charge-discharge rate increased. However, unlike the comparative example, in Example 1, the capacity expressed at a high rate of charge / discharge (1.0 C-rate) was about 43% at 30 cycles of a low rate charge / discharge cycle (0.1 C-rate). In the case of the comparative example, only a capacity of 4% compared with the low rate charge / discharge was exhibited. As a result, it was confirmed that Embodiment 1 can reduce the decrease in the capacity of the battery in comparison with that in the low rate charging / discharging.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the present invention as defined by the following claims. It can be understood that it is possible.

Claims (13)

Cobalt sulfate and colloidal silica mixed solution to prepare a cobalt sulfate / silica composite particle; And
And a second step of adding the composite particles to a sodium hydroxide solution. The method of claim 1, wherein through the second step, the cobalt sulfate of the composite particles is produced as cobalt hydroxide and at the same time the silica is removed to make the porous cobalt hydroxide porous. 2. The method of claim 1, wherein the second step is carried out two or more times. The method of claim 1, wherein the method further comprises a third step after the second step, wherein the third step is washed with H ₂ O and acetone and dried. The cobalt sulfate / silica composite particle of claim 1, wherein the cobalt sulfate /
(1-a) in which Co (NO ₃ ) ₂ .6H ₂ O is dissolved in an H ₂ O solvent;
(1-b) mixing the colloidal silica solution with the mixture prepared in the step (1-a);
(1-c) mixing an aqueous sulfuric acid solution with the mixture prepared in the step (1-b); And
Wherein the porous cobalt hydroxide is prepared by a process comprising the step (1-d) of sintering at a high temperature after the step (1-c). 6. The method of claim 5, wherein the sintering is conducted in an atmospheric environment. 7. The method for producing porous cobalt hydroxide according to claim 6, wherein the step (1-a) comprises dissolving Co (NO ₃ ) ₂ .6H ₂ O in a H ₂ O solvent using a magnetic stirrer. The method according to claim 6, wherein the step (1-b) is a step of mixing the colloidal silica solution with the mixture prepared in the step (1-a) by dropwise method to prepare porous cobalt hydroxide Way. 2. The method according to claim 1,
_{CoSO 4 · (1-a '} ) to dissolve 7H ₂ O to H ₂ O solvent phase; And
And (1-b ') mixing the colloidal silica solution with the mixture prepared in the step (1-a'). The method according to claim 9, wherein the step (1-a ') comprises dissolving CoSO ₄ · 7H ₂ O in an H ₂ O solvent using a magnetic stirrer. The method according to claim 9, wherein the step (1-b ') comprises the step of mixing the colloidal silica solution with the mixture prepared in step (1-a') by dropwise method, ≪ / RTI > 11. An electrode material for a lithium battery comprising cobalt hydroxide, a conductive material and a binder prepared by any one of claims 1 to 11. A lithium battery comprising an electrode made of the electrode material manufactured according to claim 12.

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