WO2012124970A2 - Manufacturing method for anode material for lithium secondary battery and anode material for lithium secondary battery made thereby - Google Patents

Abstract

The present invention relates to a method of manufacturing anode materials for lithium secondary batteries and the anode materials for lithium secondary batteries prepared thereby, and more specifically, relates to a method of manufacturing anode materials for lithium secondary batteries in which an additional salt is added by mixture to adjust the reactivity and the speed of reaction of the reacting solvent, and the anode materials for lithium secondary batteries thus prepared.

Description

Method for manufacturing positive electrode active material for lithium secondary battery and positive electrode active material for lithium secondary battery manufactured thereby

The present invention relates to a method for preparing a cathode active material for a lithium secondary battery and a cathode active material for a lithium secondary battery manufactured by the same, and more specifically, to a lithium secondary battery, further comprising mixing a salt capable of controlling reaction rate and reactivity to a reaction solvent. It relates to a method for producing a battery positive electrode active material and a cathode active material for a lithium secondary battery produced thereby.

In recent years, miniaturization, light weight, and high performance of portable electronic devices such as video cameras, portable CDs, cellular phones, PDAs, and notebook computers are progressing. There is a need for a secondary battery having high capacity and high stability for power of portable electronic devices. Nickel cadmium accumulators have been used as secondary batteries consistent with this purpose, but lithium secondary batteries have been put into practical use as nickel hydrogen accumulator batteries and nonaqueous electrolyte secondary batteries as batteries having higher energy density.

Conventional small lithium secondary batteries generally use LiCoO ₂ for the positive electrode and carbon for the negative electrode. LiCoO ₂ is an excellent material having stable charge and discharge characteristics, excellent electronic conductivity, high stability, and flat discharge voltage characteristics. However, Co has low reserves, is expensive, and toxic to humans. LiNiO ₂ having a layered structure such as LiCoO ₂ exhibits a large discharge capacity but has not been commercialized due to problems in cycle life, thermal instability, and safety at high temperatures. LiNi _x Co _1-x O ₂ (x = 1, 2) or LiNi _1-xy Co _x Mn _y O ₂ (0≤x≤0.5, 0≤y≤0.5) Many improved compositions of positive electrode active materials such as

A method of manufacturing a cathode active material for a secondary battery is largely divided into a solid phase reaction method and a wet method. The solid phase reaction method consists of a process of baking and pulverizing several times by mixing each component raw material powder. This solid phase method has a disadvantage in that the composition is non-uniform, and there is a high possibility of introducing impurities during pulverization, and the energy consumption is high because it needs to be fired several times at high temperature.

In addition, the wet method includes spray pyrolysis and coprecipitation. Spray pyrolysis is a method of dissolving a constituent raw material in a solvent to generate droplets of a certain size and firing them instantaneously to obtain a metal oxide. Thus, since the time for forming a stable crystal structure between metal atoms is not secured, charge / discharge as a cathode active material for secondary batteries is prevented. When repeated, the crystal structure easily collapses, causing a shortening of the battery life. In the coprecipitation method, metal hydroxides are obtained by dissolving a constituent raw material in a solvent and adjusting pH, which usually requires a reaction time of 5 hours or more and vigorous stirring. In this case, when a batch type tank reactor is used, particle size control is easy and mold exchange is free, but there is a disadvantage that there is no reactor stabilization time and mass production of a uniform composition is difficult. Therefore, in general, continuous productivity (CSTR, continuous stirring tank reactor) is mainly used.

However, in continuous reactors, the particle size grows with time, and because of the difference in retention time due to irregular flow in the reactor, a mixture of overgrown particles and ungrown fines relative to the desired size coexists, product To be discharged. That is, in the early stages of synthesis, composites having inhomogeneous size, physical and chemical properties were discharged and the size, physical, and chemical properties tended to be homogeneous as the reaction time elapsed, so that it was difficult to obtain particles of the same quality continuously.

In order to solve the above problems, the present invention is a method for producing a positive electrode active material for a lithium secondary battery having a homogeneous, high tap density and excellent capacity characteristics per unit volume, even if a continuous reactor is used, and the lithium produced thereby It aims to provide the positive electrode active material for secondary batteries.

The present invention to solve the above object is

(a) stirring the salt and ammonia represented by the formula (1) with distilled water to prepare a solution;

C ⁺ X ^- --------------------- formula (1)

(In the formula (1), and C ⁺ is _{^{Na +, K +, NH 4}} +, and at least one selected from the group consisting of Li ^+, X ^- is _{^{SO 4 2-, NO 3 -,}} Cl -, CO ₃ ^2- , and COO ⁻ , at least one selected from the group consisting of:

(b) preparing a metal complex hydroxide by coprecipitation by mixing a solution prepared in step (a) with a mixed solution of nickel salt, cobalt salt, and manganese salt, a hydroxide salt solution and a complexing agent as a pH adjusting agent;

(c) preparing a lithium metal composite hydroxide by mixing the metal complex hydroxide and the lithium compound obtained in step (b); And

(d) calcining the lithium metal composite hydroxide obtained in step (c) to produce a lithium metal composite oxide; provides a method of manufacturing a cathode active material for a lithium secondary battery.

In the present invention, the concentration of X ^- ions in the solution prepared in step (a) is characterized in that 10 to 20% by weight.

In the present invention, (b) the nickel salt in the step, a cobalt salt, and manganese are the X ^- is a nickel salt, a cobalt salt, and manganese is characterized in that it comprises a.

In the present invention, in the step (b), the complexing agent is ammonia, and continuously mixed so that the ratio of the concentration of the mixed solution of the nickel salt, cobalt salt, and manganese salt and the ammonia is 1: 0.7 to 1: 0.9. And, the pH is characterized in that to maintain the range of 10.5 to 12.5.

In the present invention, the hydroxide solution is characterized in that the hydroxide solution containing the C ⁺ .

In the present invention, the step (c) is characterized in that the mixing ratio of the concentration of the metal complex hydroxide and the lithium compound obtained in the step (b) is 1: 1.05 to 1: 1.15.

In the present invention, the step (d) is characterized in that the lithium metal composite hydroxide is calcined by heat treatment at 800 to 1100 ℃ for 8 to 12 hours.

The present invention also provides a cathode active material for a lithium secondary battery produced by the production method of the present invention.

According to the method of manufacturing a cathode active material for a lithium secondary battery of the present invention, it is possible to obtain a homogeneous cathode active material particles irrespective of the reaction time, productivity is increased, the tap density is high, the electrochemical properties are excellent and the capacity characteristics per unit volume is excellent An active material can be obtained.

1 is a graph showing a tap density and a compressive density of a cathode active material for a lithium secondary battery according to an embodiment of the present invention.

2 is a SEM image ((a) Example 1, (b) Comparative Example 1) of a cathode active material for a rechargeable lithium battery according to one embodiment of the present invention.

3 to 10 are cross-sectional SEM photographs of the positive electrode active material for a lithium secondary battery according to an embodiment of the present invention.

11 is a cross-sectional SEM photograph of a cathode active material for a lithium secondary battery according to a comparative example of the present invention.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily implement the present invention.

The present invention comprises the steps of (a) preparing a solution by stirring the salt and ammonia represented by the formula (1) with distilled water;

C ⁺ X ^- --------------------- formula (1)

(In the formula (1), and C ⁺ is _{^{Na +, K +, NH 4}} +, and at least one selected from the group consisting of Li ^+, X ^- is _{^{SO 4 2-, NO 3 -,}} Cl -, CO ₃ ^2- , and COO ⁻ , at least one selected from the group consisting of:

(b) preparing a metal complex hydroxide by coprecipitation by mixing a solution prepared in step (a) with a mixed solution of nickel salt, cobalt salt, and manganese salt, a hydroxide salt solution and a complexing agent as a pH adjusting agent;

(c) preparing a lithium metal composite hydroxide by mixing the metal complex hydroxide and the lithium compound obtained in step (b); And

(d) calcining the lithium metal composite hydroxide obtained in step (c) to produce a lithium metal composite oxide; provides a method of manufacturing a cathode active material for a lithium secondary battery.

Chemical reaction formula of the reaction occurring in the conventional manufacturing process of the positive electrode active material is as follows. For convenience, the coefficients of chemical reactions are omitted.

(Ni, Co, Mn) X + COH (Ni, Co, Mn) OH + C + X - ------- chemical reaction formula 1

As a result of the chemical reaction between the metal salt and the pH regulator, a metal complex hydroxide, a precursor of the positive electrode active material, is formed, and a C ⁺ X ^- salt is formed as an accompaniment.

In the present invention, the reaction rate and reactivity can be controlled by intentionally adding C ⁺ X ^- to the solvent before the start of the reaction.

The chemical reaction formula of the reaction according to the present invention is as follows. For convenience, the coefficients of chemical reactions are omitted.

By adding C ⁺ X ^- to the solvent, the reaction rate and reactivity change as X ^- acts as a common ion in the reactants and products of Scheme 2 below, shifting the chemical equilibrium.

(Ni, Co, Mn) X + COH + C + X - (Ni, Co, Mn) OH + C + X - --- 2 Chemical Equations

Hereinafter, a method of manufacturing the cathode active material for a lithium secondary battery will be described in more detail.

First, (a) a salt and ammonia represented by the formula (1) are stirred with distilled water to prepare a solution.

C ⁺ X ^- ---------------------------- formula (1)

(In the formula (1) C ⁺ is Na ^+, K ^+, and NH ^4+, one or more selected from the group consisting of Li ^+, X ^- is _{^{SO 4 2, NO 3 -,}} Cl -, CO 3 2 ^-, COO ^- at least one selected from the group consisting of a)

The concentration of X ⁻ ions in the solution made in step (a) is preferably 10 to 20%. As can be seen in Experimental Example 2 to be described later, the tap density and the compression density are the highest when the concentration of X ^- ion is in the above range.

As long as the C ⁺ X ^- salts are the same type of X ^- anion, C ⁺ cations may be mixed with various kinds of salts. Even in this case, it is preferable that the sum of the total concentration of X ⁻ ions in the solution is 10 to 20% by weight.

In preparing the solution in this step, it is preferable to raise the temperature to 40 to 60 ° C. and stir for about 1 hour.

Then, (b) a mixed solution of nickel salt, cobalt salt, and manganese salt containing the X ⁻ as an anion as nickel salt, cobalt salt, and manganese salt in the solution prepared in step (a), pH adjusting agent a hydroxide solution (C ⁺ OH ^-) containing the C ⁺ mixing and complexing agent to prepare a composite metal hydroxide as a co-precipitation.

Coprecipitation is a method of simultaneously depositing different ions in an aqueous solution or non-aqueous solution. The nickel, cobalt, and manganese mixed metal salts react with the nickel, cobalt, manganese metal mixture solution, complexing agent, and pH adjusting agent to the reactor. It is to prepare a composite hydroxide.

The concentration of metal ions in the mixed solution of nickel salt, cobalt salt, and manganese salt is preferably 1.5 to 3.5 M. If the concentration of metal ions is 1.5M or less, the productivity is poor due to the small amount of material produced. If the concentration of metal ions is 3.5M or more, metal salts may precipitate in the storage tank or the input pipe. This is because the concentration of the metal solution is difficult to control the particles formed by coprecipitation because the reaction can proceed quickly.

As the complexing agent, ammonia (NH ₃ ), ammonium sulfate ((NH ₄ ) ₂ SO ₄ ), ammonium nitrate (NH ₄ NO ₃ ), and first ammonium phosphate ((NH ₄ ) ₂ HPO ₄ ) may be used. And preferably ammonia. Ammonia used as a complexing agent serves to control the shape of the metal complex hydroxide formed.

The hydroxide solution as the pH adjusting agent is a hydroxide solution containing the C ⁺ , specifically, alkali, such as lithium hydroxide (LiOH), sodium hydroxide (NaOH), potassium hydroxide (KOH) and ammonia water (NH ₄ OH) An aqueous solution can be used. The pH adjusting agent serves as a precipitating agent, and serves to maintain a pH suitable for coprecipitation in the mixed aqueous solution. In this case, the reactor may use a volume of 1 to 10,00 L, and preferably 50 to 500 L of reactor.

In the step (b), the complexing agent is ammonia, and the ratio of the concentration of the mixed solution of nickel salt, cobalt salt, and manganese salt containing X ⁻ and the manganese salt as the anion and the ammonia is continuously 1: 0.7 to 1: 0.9. It is preferable to mix with and to keep the pH in the range of 10.5 to 12.5. Coprecipitation can occur most effectively at concentrations and pH conditions within this range.

In addition, the feed rate into the reactor is 0.7 to 0.9 L / h, it is preferable to maintain the temperature of the reactor at 45 to 55 ℃. Maintaining the temperature in the above range is less influenced by the external temperature to prevent the precipitation of metal in the cold winter, as well as to make the viscosity of the metal mixed solution constant, so that the amount of the metal mixed solution to be added is kept more constant. To stabilize the reactor.

Then, (c) a lithium metal composite hydroxide is prepared by mixing the metal complex hydroxide and the lithium compound obtained in step (b).

The metal complex hydroxide obtained in the step (b) is filtered and washed, and then heat-treated at 80 to 140 ° C. for 8 to 16 hours. Then for mixing with the lithium compound to the lithium source role, the lithium compound, lithium hydroxide (LiOH), lithium nitrate (LiNO ₃₎ and to use the compounds used to prepare the general cathode active material such as lithium carbonate (LiCO ₃₎ However, it is not necessarily limited thereto.

The ratio of the concentration of the metal complex hydroxide and the lithium compound obtained in step (b) is preferably mixed so as to be 1: 1.05 to 1: 1.15. If it is less than 1.05, the capacity of the final cathode active material is lowered, which is not preferable. If it exceeds 1.15, an unreacted lithium compound is formed and the capacity is reduced, and there is a risk of gas generation at a high temperature.

Finally, (d) calcining the lithium metal composite hydroxide to produce a lithium metal composite oxide. At this time, the lithium metal composite hydroxide is preferably baked by heat treatment for 8 to 12 hours at 800 to 1100 ℃.

The method of the present invention described above is capable of producing a cathode active material having superior density characteristics by adding a salt capable of controlling a reaction rate to an existing solvent and having excellent capacity characteristics per unit volume.

The present invention is described in more detail through the following implementation. However, the examples are provided to illustrate the present invention, and the scope of the present invention is not limited only to these examples.

<Example 1>

30% distilled water relative to the total reaction capacity was added to the reaction tank to start stirring, and the temperature was raised to 50 ° C, and Na ₂ SO ₄ was added at a ratio of 5% by weight relative to distilled water and stirred for 1 hour. And ammonia was added at a rate of 0.8 mol and stirred until it was sufficiently mixed.

Then, a 2.5 mol metal mixed solution and an ammonia solution in which the molar ratio of nickel sulfate, cobalt sulfate and manganese sulfate were mixed in a ratio of 0.5: 0.2: 0.3 were added to the reactor at a ratio of 0.8 to 0.8 L /. It was dosed continuously in h. In addition, a 25% sodium hydroxide solution was supplied to maintain the pH at 11.5, the average residence time of the solution was 13 hours, the average temperature of the reactor was maintained at 45 to 55 ℃.

The compound thus obtained was filtered and washed with water and then dried in a 110 ° C. hot air dryer for 12 hours to obtain a precursor of a metal complex hydroxide form.

Thereafter, lithium carbonate was mixed so as to be 1.10 times the concentration standard of the metal complex hydroxide, and heated at a temperature of 1 ° C./min, and then calcined to heat treatment at 950 ° C. for 10 hours to obtain a cathode active material powder.

<Example 2>

Instead of adding Na ₂ SO ₄ of Example 1 in a 5% by weight ratio of distilled water, 10% by weight was carried out in the same manner as in Example 1 to obtain a positive electrode active material powder.

<Example 3>

The positive electrode active material powder was obtained in the same manner as in Example 1 except that 15 wt% of Na ₂ SO ₄ of Example 1 was added at a ratio of 5 wt% based on the distilled water.

<Example 4>

The positive electrode active material powder was obtained in the same manner as in Example 1 except that 20 wt% of Na ₂ SO ₄ of Example 1 was added at a ratio of 5 wt% based on distilled water.

Example 5

In the same manner as in Example 1 except that Na ₂ SO ₄ of Example 1 was added in an amount of 5% by weight relative to distilled water, and 10% by weight was added and 5% by weight of (NH ₄ ) ₂ SO ₄ was added. It carried out and obtained the positive electrode active material powder.

<Example 6>

In the same manner as in Example 1 except that Na ₂ SO ₄ of Example 1 was added in an amount of 5% by weight relative to distilled water, and 10% by weight of (NH ₄ ) ₂ SO ₄ was added. It carried out and obtained the positive electrode active material powder.

<Example 7>

Instead of adding Na ₂ SO ₄ of Example 1 at a ratio of 5% by weight relative to distilled water, 15% by weight was added, and 5% by weight of (NH ₄ ) ₂ SO ₄ was added in the same manner as in Example 1. It carried out and obtained the positive electrode active material powder.

<Example 8>

Instead of adding Na ₂ SO ₄ of Example 1 at a ratio of 5% by weight relative to distilled water, 15% by weight was added, and 10% by weight of (NH ₄ ) ₂ SO ₄ was added in the same manner as in Example 1. It carried out and obtained the positive electrode active material powder.

Example 9

Instead of adding Na ₂ SO ₄ of Example 1 at a ratio of 5% by weight relative to distilled water, 20% by weight was added, and 5% by weight of (NH ₄ ) ₂ SO ₄ was added in the same manner as in Example 1 above. It carried out and obtained the positive electrode active material powder.

Comparative Example 1

When mixing a 2.5 mole concentration metal mixture solution and an ammonia solution mixed with 0.5: 0.2: 0.3 and a molar ratio of nickel sulfate, cobalt sulfate and manganese sulfate in distilled water as a solvent, the ratio of the concentration of the metal mixture solution and the ammonia solution was 1 The reactor was continuously charged at 0.8 L / h to maintain 0.8. In addition, the pH was maintained at 11.5 by supplying an aqueous 25% sodium hydroxide solution, the average residence time of the solution was 13 hours, the average temperature of the reactor was maintained at 45 to 55 ℃.

The compound thus obtained was filtered and washed with water and then dried in a 110 ° C. hot air dryer for 12 hours to obtain a precursor of a metal complex hydroxide form.

Thereafter, the lithium carbonate was mixed so as to be 1.10 times the concentration standard of the metal complex hydroxide, heated at a temperature of 1 / min, and then calcined to heat treatment at 950 ° C. for 10 hours to obtain a cathode active material powder.

Experimental Example 1 SEM Photograph

SEM pictures of the cathode active material according to Examples 1 to 8 and Comparative Example 1 were taken. The results are shown in FIGS. 2 to 11.

2 is a surface analysis SEM photograph, it can be confirmed that the surface of Example 1 ((a)) is smoother than the surface of Comparative Example 1 ((b)) and the shape is spherical.

3 to 10 are Examples 1 to 8 and 11 are cross-sectional SEM images of Comparative Example 1, in which the cathode active material according to the embodiment of the present invention had a shape more close to a spherical shape. It can be confirmed that the pores have a small shape.

Experimental Example 2 Measurement of Tap Density and Compression Density

The tap density and the compression density of the cathode active materials according to Examples 1 to 9 and Comparative Example 1 were measured. The results are shown in Table 1 and FIG. 1.

Table 1

	Example 1	Example 2	Example 3	Example 4	Example 5	Example 6	Example 7	Example 8	Example 9	Comparative Example 1
Na 2 SO 4	5%	10%	15%	20%	10%	10%	15%	15%	20%	0%
(NH 4 ) 2 SO 4	0%	0%	0%	0%	5%	10%	5%	10%	5%	0%
Tap density (g / cm 3)	2.19	2.21	2.28	2.25	2.23	2.20	2.17	2.05	2.00	1.95
Compression Density (g / cm 3)	2.98	3.08	3.11	3.05	3.07	3.06	3.30	2.99	2.94	2.79

As can be seen in Table 1 and FIG. 1, the tap density and the compression density have a positive correlation, which is higher than that of the comparative example in all examples, and in particular, in Example 3, both values are the highest. have. It can be seen that the cathode active material prepared according to the present invention has excellent capacity characteristics per unit volume.

Claims (8)

1. (a) stirring the salt and ammonia represented by the formula (1) with distilled water to prepare a solution;

   C ⁺ X ^- --------------------- formula (1)

   (In the formula (1), and C ⁺ is _{^{Na +, K +, NH 4}} +, and at least one selected from the group consisting of Li ^+, X ^- is _{^{SO 4 2-, NO 3 -,}} Cl -, CO ₃ ^2- , and COO ⁻ , at least one selected from the group consisting of:

   (b) preparing a metal complex hydroxide by coprecipitation by mixing a solution prepared in step (a) with a mixed solution of nickel salt, cobalt salt, and manganese salt, a hydroxide salt solution and a complexing agent as a pH adjusting agent;

   (c) preparing a lithium metal composite hydroxide by mixing the metal complex hydroxide and the lithium compound obtained in step (b); And

   (d) calcining the lithium metal composite hydroxide obtained in the step (c) to produce a lithium metal composite oxide; a method of manufacturing a positive electrode active material for a lithium secondary battery, characterized in that consisting of.
2. The method of claim 1,

   The concentration of X ^- ions in the solution prepared in step (a) is 10 to 20% by weight manufacturing method of a positive electrode active material for a lithium secondary battery.
3. The method of claim 1,

   The nickel salt, cobalt salt, and manganese salt in the step (b) is a nickel salt, cobalt salt, and manganese salt containing the X ^- manufacturing method of a positive electrode active material for a lithium secondary battery.
4. The method of claim 1,

   In the step (b), the complexing agent is ammonia, and the mixed solution of the nickel salt, cobalt salt, and manganese salt is continuously mixed so that the ratio of the concentration of the ammonia is 1: 0.7 to 1: 0.9, and the pH is 10.5. Method of manufacturing a cathode active material for a lithium secondary battery, characterized in that to maintain the range of 1 to 12.5.
5. The method of claim 1,

   Hydroxide solution as the pH adjuster is a method for producing a cathode active material for a lithium secondary battery, characterized in that the hydroxide solution containing the C ⁺ .
6. The method of claim 1,

   In the step (c), the method for producing a cathode active material for a lithium secondary battery, characterized in that the mixing ratio of the concentration of the metal complex hydroxide and the lithium compound obtained in the step (b) is 1: 1.05 to 1: 1.15.
7. The method of claim 1,

   In the step (d), the lithium metal composite hydroxide is heat-treated at 800 to 1100 ° C. for 8 to 12 hours to manufacture the positive electrode active material for a lithium secondary battery.
8. The cathode active material for a lithium secondary battery manufactured according to any one of claims 1 to 7.

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