KR20150062251A - Anode material for li-ion secondary battery and method for manufacturing the same - Google Patents

Abstract

Disclosed is a manufacturing method of a positive electrode material for a secondary battery. The manufacturing method of a positive electrode material for a secondary battery comprises the steps of: putting distilled water in a reactor, and maintaining the temperature range in 50~60 °C; inputting a metal solution including a complex ion formation agent to the reactor; inputting a deposition agent to the reactor; stirring mixing solution inside the reactor, while maintaining pH 8-10; and washing deposition formed in the reactor, and thermally treating after drying.

Description

TECHNICAL FIELD [0001] The present invention relates to a positive electrode material for a secondary battery, and a method for manufacturing the same. BACKGROUND ART [0002]

The present invention relates to a method for manufacturing a cathode material for a secondary battery, and more particularly, to a method for manufacturing a cathode material for a secondary battery that can prevent environmental pollution and can be manufactured economically.

Lithium secondary batteries have high energy density, excellent output characteristics and light weight, and are widely used as energy storage devices for mobile communication devices, hybrid electric vehicles, and household appliances.

The core materials of lithium secondary batteries are classified into anodes, cathodes, electrolytes, and separators. LiCoO ₂ accounts for more than 70% of the total cathode material market as a cathode material for commercialized lithium secondary batteries.

LiCoO2, a layered rock salt structure, has a relatively high price of cobalt contained therein, which is a burden on the cost of the product. Therefore, alternative materials for replacing cobalt have been actively developed, and lithium nickel cobalt manganese oxide (NCM) Development of the cathode material of the series is one such activity.

For the production of the lithium secondary battery cathode material, precursors include metal hydroxide, metal carbonate, metal oxalate, and metal oxide.

Metal hydroxide is precipitated in the form of metal hydroxide (Me (OH) _x ) by reaction of metal ion with hydroxide ion (OH-). It dissolves metal nitrate, sulfate in water and is used at concentration of 1-2.5M And an aqueous solution of about 2 to 5 M sodium hydroxide (NaOH) is used as a precipitant. At this time, in order to secure the size of the precipitated precursor to about 10 탆, NH ₄ OH is added as an ion complexing agent to control the precipitation reaction rate of the metal ion.

Since NH ₄ OH contains the most widely used complex ionizing agent or nitrogen, costly treatment methods are required to remove nitrogen below a certain concentration in wastewater treatment, which causes cost increase.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a method of manufacturing a cathode material without using NH ₄ OH in the production of a cathode material for a secondary battery.

In addition, the present invention is characterized in that the cathode material has a high capacitance and a low stability with a difference in the composition of the center portion and the surface portion of the cathode material. The surface portion of the cathode material has a relatively low capacity but relatively high stability, And at the same time securing stability.

In order to accomplish the above object, a method for manufacturing a cathode material for a secondary battery according to an embodiment of the present invention includes the steps of maintaining distilled water in a reactor at a temperature ranging from 50 to 60 ° C, Mixing the metal solution for forming the surface portion with the metal solution while gradually changing the mixing ratio of the metal solution for forming the surface portion from 100: 0 vol% to 0: 100 vol%, injecting the mixture into the reactor, injecting the precipitant into the reactor, Maintaining the pH at 8 to 10 with stirring, and washing and drying the precipitate formed in the reactor, followed by heat treatment.

The metal solution may be prepared by dissolving at least one selected from the group consisting of metal sulfate, metal nitrate and metal hydrochloride in distilled water at a concentration of 2 to 3 mol / L of the total solution containing the metal solution and complex ion forming agent.

The complex ion forming agent may be selected from the group consisting of lactic acid, succinic acid, formic acid, acetic acid, dimethyl sulfoxide, methanesulfonic acid, dimethyl sulfone ), Ethylene glycol, propylene glycol, ethylene carbonate, ethyl acetate, glycerin, 1,3-butylene glycol, , Gluconic acid, and the like.

The complex ion forming agent may be 0.03 to 0.3 mol / L of the total solution containing the metal solution and the complex ion forming agent.

The precipitating agent is a mixture of sodium (NaOH) and sodium carbonate (Na ₂ CO ₃₎ hydroxide, sodium carbonate (Na ₂ CO ₃₎ may be 0.03 ~ 0.3mol / L of total solution containing sodium carbonate and sodium hydroxide (NaOH) .

The inside of the reactor can be maintained in a nitrogen atmosphere.

The heat treatment may be performed by calcining the precipitate together with lithium carbonate (Li ₂ CO ₃ ) or lithium hydroxide (LiOH) at a temperature of 800 ° C to 900 ° C.

The composition of the cathode material is represented by the following formula (1) and the surface part of the cathode material by the following formula (2).

[Chemical Formula 1]

_A1 M1 _x M2 M3 _{y1 z1} Li M4 _w O _{2 + δ}

(2)

Li a ₂ M 1 _x M 2 _{y 2} M 3 _{z 2} M 4 _w O _{2 + δ}

(M1, M2, M3 are selected from the group consisting of Ni, Co, Mn and combinations thereof, M4 is Fe, Na, Mg, Ca, Ti, V, Cr, Cu, Zn, Ge, La, Ce, Ta, Sr, Al, Ag, Ba, Zr, Nb, Mo, Ga, B , and is selected from the group consisting _{of, 0 <a 1 ≤1.1, 0} <a 2 ≤ _{1.1, 0≤x≤1, 0≤y 1 ≤1,} 0≤y 2 ≤1, 0≤z 1 ≤1, 0≤z 2 ≤1, 0≤w≤0.1, 0.0≤δ≤0.02, 0 < and _{x + y 1 + z 1 ≤1} , 0 <x + y 2 + z 2 ≤1, y 1 is _{≤y 2, z 2 ≤z 1.} )

Secondary battery positive electrode material production method according to the invention is due to not using a complex of ammonium hydroxide (NH ₄ OH) ion forming agent, ammonium hydroxide (NH ₄ OH) supply taenggeu (feed tank) production cost, ammonium hydroxide (NH ₄ OH The operation cost of the chiller for suppressing volatilization of the wastewater, and the processing cost for reducing the total nitrogen amount of the wastewater to a certain level or less.

In the conventional co-precipitation method using ammonium hydroxide (NH ₄ OH), precipitation occurs when the NH ₄ OH and the metal solution meet. Therefore, NH ₄ OH, a metal solution, and an aqueous NaOH solution are introduced into the reactor There is a problem in that they should not be mixed with each other before. However, in the present invention, materials used as complex ion-forming agents do not react with metal solutions and do not cause precipitation. Therefore, a complex ion-forming agent can be added directly to the metal solution so that the manufacturing process is simplified.

In addition, the center portion of the cathode material has a high capacity but a low stability due to a difference in the composition of the center portion and the surface portion of the cathode material. The surface portion of the cathode material has a relatively low capacity but relatively high stability. can do.

1 is a graph showing the results of evaluating characteristics of a coin cell using a cathode material according to the present invention.

Advantages and features of the present invention and methods of achieving them will become apparent with reference to the embodiments described in detail below. However, it is to be understood that the present invention is not limited to the disclosed embodiments, but may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. It is intended that the disclosure of the present invention be limited only by the terms of the appended claims. Like reference numerals refer to like elements throughout the specification.

A method for manufacturing a cathode material for a secondary battery according to an embodiment of the present invention includes: maintaining distilled water in a reactor at a temperature ranging from 50 to 60 ° C; Mixing the metal solution for forming a center part and the metal part for forming a surface part, which contains a complex ion forming agent, at a mixing ratio of 100: 0 vol% to 0: 100 vol%, and injecting the mixture into the reactor; Injecting a precipitant into the reactor; Maintaining the pH of the mixed solution in the reactor at 8 to 10 and stirring; And washing and drying the precipitate formed in the reactor, followed by heat treatment.

When the temperature in the reactor is lower than 50 캜 in the step of adding distilled water to the reactor and maintaining the temperature range at 50 to 60 캜, the precursor particles grow slowly. Therefore, even if the reaction is performed for 20 hours or more, This is difficult. If the temperature in the reactor exceeds 60 ° C, the particle size increases but the particle growth rate becomes faster and dense particles are not obtained.

In the step of mixing the metal solution for forming the center part and the metal part for forming the surface part containing the complex ion forming agent while gradually changing the mixing ratio from 100: 0 vol% to 0: 100 vol% and injecting the mixture into the reactor, The metal solution for the surface portion and the metal solution for forming the surface portion may be at least one selected from metal sulfate, metal nitrate and metal hydrochloride in the distilled water.

The metal solution for forming the center portion and the metal solution for forming the surface portion include Ni, Co, and Mn,

At least one selected from Fe, Na, Mg, Ca, Ti, V, Cr, Cu, Zn, Ge, La, Ce, Ta, Sr, Al, Ag, Ba, Zr, Nb, .

Also, the concentration (atom%) of Ni in the metal solution for forming the central portion should be higher than the concentration (atom%) of Ni in the metal solution for forming the surface portion.

In order to increase the stability of the cathode material, the metal solution for forming the surface portion has lower Ni concentration than the metal solution for forming the center portion and the metal solution for forming the center portion has higher Ni concentration than the metal solution for forming the surface portion to increase the capacity of the cathode material.

Also, at least one of the metal sulfate, metal nitrate, and metal hydrochloride may be 2 to 3 mol / L, preferably 2 to 2.5 mol / L of the total solution containing the metal solution and the complex ion forming agent.

If at least one of the metal sulfate and metal nitrate salts and the metal hydrochloride salt exceeds 3 mol / L of the total solution containing the metal solution and the complex ion forming agent, there arises a problem that the metal sulfate is precipitated. The yield of precursor per unit time in the coprecipitation reaction is small and the productivity is low.

In the step of injecting a metal ion solution containing a complex ion-forming agent into the reactor, the complex ion-forming agent is selected from the group consisting of lactic acid, succinic acid, formic acid, acetic acid, dimethyl sulfoxide, methanesulfonic acid, dimethyl sulfone, ethylene glycol, propylene glycol, ethylene carbonate, ethyl acetate, glycerin, 1,3-butylene glycol, gluconic acid, and the like.

The complex ion forming agent may be added in an amount of 0.03 to 0.3 mol / L of the entire solution containing the metal solution and the complex ion forming agent.

If the complex ion forming agent is less than 0.03 mol / L of the total solution containing the metal solution and the complex ion forming agent, particles of 10 μm can be obtained even if the particle growth rate is slow due to the reaction time and the reaction is continued for 30 hours And when it exceeds 0.3 mol / L, the precursor particles are not densified and the tap density of the cathode material decreases.

In the step of injecting the precipitant into the reactor, the precipitant may be a precursor prepared by adding sodium carbonate (Na ₂ CO ₃ ) to an aqueous solution of sodium hydroxide (NaOH).

The sodium hydroxide (NaOH) may be 4-5 mol / L of the total solution containing sodium carbonate and sodium hydroxide (NaOH).

The sodium carbonate (Na ₂ CO ₃ ) may be 0.03-0.3 mol / L of the total solution containing sodium carbonate and sodium hydroxide (NaOH).

If the concentration of sodium carbonate (Na ₂ CO ₃ ) added to the aqueous sodium hydroxide solution is less than 0.03 mol / L, dense particles can not be obtained. If the concentration is more than 0.3 mol / L, a carbonate carbonate phase is formed, ), There is a problem that pores are formed inside the particles.

When the pH of the mixed solution in the reactor is less than 8, the precipitation of Mn does not occur, and when the pH is more than 12 There is a problem that a dense precursor can not be obtained.

Hereinafter, a method of manufacturing a cathode material for a secondary battery according to the present invention will be described in detail with reference to examples. The following examples are illustrative of the present invention only and are not intended to limit the scope of the present invention.

 [Example]

Distilled water was added to the reactor, and the temperature was set at 50 to 60 ° C. When the set temperature was reached, the internal pH of the reactor was set to 9.

Lactic acid was added as a complex ion forming agent to a metal solution having a ratio of nickel sulfate, cobalt sulfate and manganese sulfate of 8: 1: 1 as a metal solution for forming the center portion.

The metal sulfate was 2 mol / L of the total solution containing the metal solution and the complex ion-forming agent

The complex ion forming agent was added so as to be 0.05 mol / L of the total solution containing the metal solution and the complex ion forming agent.

Also, lactic acid was added as a complex ion forming agent to a metal solution having a ratio of nickel sulfate, cobalt sulfate and manganese sulfate of 5: 3: 2 as a metal solution for surface part formation.

The metal sulfate was 2 mol / L of the total solution containing the metal solution and the complex ion-forming agent

The complex ion forming agent was added so as to be 0.05 mol / L of the total solution containing the metal solution and the complex ion forming agent.

Also, an aqueous solution was prepared by adding sodium carbonate (Na ₂ CO ₃ ) to an aqueous solution of sodium hydroxide (NaOH).

The sodium hydroxide (NaOH) was adjusted to 4 mol / L of the total solution containing sodium carbonate and sodium hydroxide (NaOH).

The sodium carbonate (Na ₂ CO ₃ ) was adjusted to 0.05 mol / L of the total solution containing sodium carbonate and sodium hydroxide (NaOH).

The metal solution for forming the center portion containing the complex ion-forming agent thus prepared is injected into the mixing vessel. The metal solution is injected into the reactor from the mixing vessel at a constant rate. In addition, a metal solution for forming the surface portion is injected into the mixing vessel. By doing so, the proportion of Ni in the metal solution in the mixing vessel gradually changes.

A metal solution of the mixing vessel and an aqueous solution of sodium hydroxide to which sodium carbonate is added are injected into the reactor at a constant rate to obtain a precipitate. Thereafter, the amount of the metal solution for forming the surface portion is gradually increased by gradually reducing the metal solution for forming the center portion. Thus, a precipitate having a concentration gradient of the composition of the central portion and the surface portion can be obtained.

The precipitate had an Ni concentration at the central portion of 80 atom% and a Ni concentration at the surface portion of 50 atom%.

At this time, the pH of the solution in the reactor was maintained at 9, and the rotation speed of the stirrer was maintained at about 700 to 1000 rpm. In the reactor, a nitrogen atmosphere was maintained to prevent the metal ions from being oxidized.

Metal hydroxide (hydroxide) particles are formed when the added metal solution and the precipitant react with each other. As the reaction time increases, the particle size becomes larger. After about 20 to 30 hours, metal hydroxide particles having a size of 10 μm were obtained, washed and dried, and then heat-treated with Li ₂ CO ₃ or LiOH at a temperature of about 800 ° C. to 900 ° C. to obtain a cathode material powder .

FIG. 1 is a graph showing the results of evaluating characteristics of a coin cell using a cathode material according to the present invention. The upward curve is the result of charging, and the downward curve is the result of discharging.

As a result of the test, the capacity of 0.1C up to 195mHA / g was obtained.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, You will understand.

It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. The scope of the present invention is defined by the appended claims rather than the detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be interpreted as being included in the scope of the present invention .

Claims (9)

Adding distilled water to the reactor and maintaining the temperature range at 50 to 60 ° C;
Mixing the metal solution for forming a center part and the metal part for forming a surface part, which contains a complex ion forming agent, at a mixing ratio of 100: 0 vol% to 0: 100 vol%, and injecting the mixture into the reactor;
Injecting a precipitant into the reactor;
Maintaining the pH of the mixed solution in the reactor at 8 to 10 and stirring; And
Washing and drying the precipitate formed in the reactor, followed by heat treatment,
The metal of the center portion forming metal solution and the metal portion of the surface portion forming metal solution include Ni, Co, and Mn, and the concentration (atom%) of Ni in the metal solution for forming the center portion is the Ni concentration %). &Lt; / RTI &gt; The method according to claim 1,
The metal solution for forming the center portion and the metal solution for forming the surface portion may be prepared by adding at least one selected from metal sulfate, metal nitrate and metal hydrochloride to distilled water at a concentration of 2 to 3 mol / L of the total solution containing the metal solution and complex ion forming agent Wherein the positive electrode material is melted. 3. The method of claim 2,
The complex ion forming agent may be selected from the group consisting of lactic acid, succinic acid, formic acid, acetic acid, dimethyl sulfoxide, methanesulfonic acid, dimethyl sulfone ), Ethylene glycol, propylene glycol, ethylene carbonate, ethyl acetate, glycerin, 1,3-tylene glycol, , And gluconic acid. The method for manufacturing a cathode material for a secondary battery according to claim 1, The method of claim 3,
Wherein the complex ion forming agent is 0.03 to 0.3 mol / L of the total solution including the metal solution and the complex ion forming agent. The method of claim 3,
The precipitant is a mixture of sodium hydroxide (NaOH) and sodium carbonate (Na ₂ CO ₃ ), and sodium carbonate (Na ₂ CO ₃ ) is 0.03-0.3 mol / L of the total solution containing sodium carbonate and sodium hydroxide (NaOH) Wherein the positive electrode material is a positive electrode material. 5. The method of claim 4,
Wherein the inside of the reactor is maintained in a nitrogen atmosphere. 6. The method of claim 5,
Wherein the heat treatment is performed by calcining the precipitate together with lithium carbonate (Li ₂ CO ₃ ) or lithium hydroxide (LiOH) at a temperature of 800 ° C to 1000 ° C. 8. The method according to any one of claims 1 to 7,
Wherein the composition of the cathode material is expressed by the following formula (1), and the surface area of the cathode material is represented by the following formula (2).
[Chemical Formula 1]
_A1 M1 _x M2 M3 _{y1 z1} Li M4 _w O _{2 + δ}
(2)
Li a ₂ M 1 _x M 2 _{y 2} M 3 _{z 2} M 4 _w O _{2 + δ}
(M1, M2, M3 are selected from the group consisting of Ni, Co, Mn and combinations thereof, M4 is Fe, Na, Mg, Ca, Ti, V, Cr, Cu, Ba, Zr, Nb, Mo, Ga, B, and combinations thereof, and 0 <a1? 1.1, 0 <a2? 1.1, 0? Y? 1, 0? Y? 1, 0? Y? 1, 0? Z? 1, 0? Z? 2? 1, 0? W? 0.1, 1, 0 < x + y2 + z2? 1, y1? Y2, z2? 9. The method of claim 8, wherein the concentration of Ni in the center portion decreases with a continuous concentration gradient from the center portion to the surface portion.

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