KR20200075356A - Manufacturing method for high density Ni-Co-Mn composite precursor - Google Patents

Abstract

The present invention relates to a technique for doping a composite precursor seed with a solution containing a nano-sized transition metal in an initial stage of a coprecipitation reaction, in order to address an issue that density decreases due to generation of pores in a nickel-cobalt-manganese composite precursor, [Ni_xCo_yMn_1-x-y(OH)_2, where 0 < x < 1, 0 < y < 1, 0 < x + y < 1].

Description

Manufacturing method for high density nickel-cobalt-manganese composite precursors {Manufacturing method for high density Ni-Co-Mn composite precursor}

The present invention relates to a method for manufacturing a three-component composite precursor (Ni _x Co _y Mn _1-xy (OH) ₂ ) of nickel-cobalt-manganese. More specifically, in a method for producing a three-component composite precursor of nickel-cobalt-manganese used as a cathode active material for a lithium secondary battery, it relates to a technique for increasing the density of the composite precursor.

In particular, the present invention does not increase the density by mixing well between the composite precursor particles when manufacturing the composite precursor, but by preventing the voids in the individual composite precursor itself, the density of the individual composite precursor itself increases It is about technology.

With the proliferation of portable small-sized electric and electronic devices, development of new secondary batteries such as nickel-metal hydride batteries and lithium secondary batteries is actively progressing. In addition, secondary batteries are used in hybrid vehicles (HEVs), electric vehicles (EVs), etc., and research and development of secondary batteries have been actively conducted as the field of application has expanded.

Among the secondary batteries, the lithium secondary battery is a battery that uses carbon such as graphite as a negative electrode active material, uses a metal oxide containing lithium as a positive electrode active material, and uses a non-aqueous solvent as an electrolyte. As a positive electrode active material used in a lithium secondary battery, nickel, cobalt, manganese, etc., not lithium alone, are mixed and manufactured as a positive electrode active material to satisfy positive electrode properties such as energy density and electrical conductivity.

For example, Li ₂ CO ₃ and a nickel-cobalt-manganese precursor (Ni _x Co _y Mn _1-xy ) are mixed and calcined to be used as a positive electrode active material. Usually, the precursor is prepared using a co-precipitation method. After dissolving nickel salts, manganese salts, and cobalt salts in distilled water, the precursors are precipitated by adding them to the reactor together with an aqueous ammonia solution (chelating agent) and an aqueous NaOH solution (basic aqueous solution). This happens.

Producing a nickel-cobalt-manganese composite precursor having a uniform particle distribution is one research theme in the related art, but also solving the problem of voids in the composite precursor particles is becoming a research theme. Due to the voids in the composite precursor particles, the density of the precursor is lowered, the particle strength in the positive electrode active material stage is lowered, and this may be a reason to decrease the power efficiency of the secondary battery.

In the prior art related to density control of such a composite precursor, in Patent Publication No. 10-2015-0059820, a metal salt aqueous solution, a chelating agent, and a basic aqueous solution are supplied to a reactor to coprecipitate to prepare a coprecipitation compound. In the manufacturing method of the positive electrode active material precursor for a lithium secondary battery by a co-precipitation method comprising the step of preparing an active material precursor by drying or heat treatment, and mixing and firing the active material precursor and a lithium salt to produce a lithium composite metal oxide, Lithium secondary characterized in that by increasing the particle size of the coprecipitation compound in the step of preparing the coprecipitation compound by supplying the metal salt aqueous solution, the chelating agent, and the basic aqueous solution to the reactor to coprecipitate A method of manufacturing a positive electrode active material for a battery has been disclosed. That is, Patent Publication No. 10-2015-0059820 discloses a technique that exhibits a high tap density across the particles by controlling the supply speed of the metal salt according to an increase in particle size during the co-precipitation reaction, thereby improving battery characteristics.

In addition, in Patent Publication No. 10-2014-0098347, the positive electrode mixture comprising a positive electrode active material, a conductive material and a binder is a positive electrode coated on a current collector, wherein the positive electrode active material is made of small particles and opposite particles having different average particle diameters. A high-density positive electrode active material in a bimodal form is disclosed.

In the patent publication No. 10-2015-0059820, the tap density was adjusted by adjusting the supply speed of the metal salt, but it is not practically easy to control the supply speed of the metal salt, and it is of sufficient high density even if the method of the above patent is applied. There is a problem that it is difficult to manufacture a composite precursor. In addition, Patent Publication No. 10-2014-0098347 differs from the present invention in that it controls density through mixing of small particles and alleles rather than a method of increasing density by reducing the voids of the composite precursor itself.

Patent Publication No. 10-2015-0059820 Patent Publication No. 10-2014-0098347 Patent registration No. 10-1275845 Patent Publication No. 10-2013-0111413 Patent Publication No. 10-2013-0123910

An object of the present invention is to provide a method for manufacturing a high-density precursor by minimizing voids in a nickel-cobalt-manganese composite precursor.

In particular, it is an object of the present invention to provide a method of realizing high density of the entire composite precursor through high density of the composite precursor itself, rather than realizing high density by mixing the large-particle and small-particle composite precursors in the prior art.

In particular, the present invention aims to provide a method for producing a high-density small particle precursor.

The present invention is a nickel-cobalt-manganese composite precursor [Ni _x Co _y Mn _1-xy (OH) _2, wherein, A method for preparing 0<x<1, 0<y<1, 0<x+y<1], the method comprising: preparing a metal aqueous solution of nickel sulfate, cobalt sulfate, and manganese sulfate in a coprecipitation reactor; Preparing a solution containing nano-sized particles; And preparing a composite precursor through a co-precipitation reaction, in the step of preparing the composite precursor, a solution containing nano-sized particles is added to only some of the reactions during the co-precipitation reaction, thereby providing a high density nickel-cobalt with less voids therein. -Provides a method of manufacturing a manganese composite precursor.

In particular, the nano-sized particles are preferably transition metal particles.

In particular, the transition metal particles may be any one of ZrO ₂ , WO ₂ and TiO ₂ .

In particular, the solution containing the nano-sized particles can be added only during the initial seed formation process of the precursor.

By reducing the voids in the composite precursor particles through the method of the present invention, a high-density composite precursor can be produced. For example, the composite precursor according to the prior art has a tap density of 1.44 g/cm ³ , but the composite precursor produced by the present invention has a tap density of 1.53 g/cm ³ to improve the tap density of 0.9 g/cm ³ . It was confirmed by experiment.

In particular, in the present invention, it is possible to obtain an effect of improving tap density even if the seed particles of the composite precursor are coated with nano-sized transition metal particles only in the initial 10 minutes of the co-precipitation reaction, for example, in the initial 10 minutes of the co-precipitation reaction.

1 and 2 are SEM measurement pictures of different magnifications of the composite precursor according to the comparative example.
Figure 3 is a SEM measurement of the cross section of the composite precursor prepared by the comparative example.
4 and 5 are SEM measurement pictures of different magnifications of the composite precursor prepared by the present invention.
Figure 6 is a SEM measurement of the cross section of the composite precursor prepared by the present invention.

The present invention is a nickel-cobalt-manganese composite precursor [Ni _x Co _y Mn _1-xy (OH) _2, wherein, In manufacturing 0<x<1, 0<y<1, 0<x+y<1], it relates to a method of increasing the density of the entire composite precursor by reducing the occurrence of voids in the composite precursor. In particular, the present invention, unlike the conventional technique of increasing the density through the combination of allelic precursors and small particle precursors, by increasing the density of the composite precursor particles themselves by reducing the voids in the composite precursor particles themselves, it is possible to increase the density of the entire composite precursor. It is about technology.

In order to achieve the above object, the present invention is characterized in that the nanoparticle solution is doped in the coprecipitation reaction of the coprecipitation solution. The doping of the nanoparticle solution can greatly improve the density of the composite precursor that is finally produced even if it is involved only in a very short step of the co-precipitation process, that is, the process of generating the initial composite precursor. For example, when the total co-precipitation process of the composite precursor is 12 hours, even if the nanoparticle solution is doped for only the initial 10 minutes, the density of the composite precursor finally produced is greatly improved.

In addition, in the case of performing a multi-step coprecipitation reaction, even if the transition metal is doped with the seed of the complex precursor with a nanoparticle solution only in the first step, it is possible to obtain a density improvement effect of the finally produced complex precursor. In the prior art, there was doping of a transition metal, but this is different from doping the transition metal separately after completion of the complex precursor, or doping in the entire process of manufacturing the complex precursor, in the present invention, the purpose of reducing voids in the complex precursor is only at the initial stage of coprecipitation. The difference is that it has a short time doping.

The nano-sized particles preferred in the present invention may be nano-particles of a transition metal oxide, for example, ZrO ₂ , WO ₂ and TiO ₂ .

Hereinafter, the present invention will be described through experimental examples.

Comparative example

First, as a comparative example, a nickel-cobalt-manganese composite precursor prepared through a co-precipitation reaction with a co-precipitation solution of nickel sulfate, cobalt sulfate, and manganese sulfate was prepared, and the tap density and SEM of the surface and cross section were measured.

Nickel sulfate, cobalt sulfate, and manganese sulfate were mixed at a ratio of 0.6:0.2:0.2 (molar ratio) to prepare a 2.5 M concentration coprecipitation solution, and an aqueous 50% sodium hydroxide solution was prepared. The coprecipitation solution was supplied at a rate of 6.5 to 7.0 L/hr to a 100 L coprecipitation reactor, which is a double water tank structure containing deionized water maintained at 50 to 60°C, and the pH inside the coprecipitation reactor was maintained at 10.5 to 11.0. Aqueous sodium hydroxide solution was added.

As an additive, an aqueous ammonia solution at a concentration of 28% was supplied with 3 L before the transition metal solution was added. The co-precipitation reaction was performed for 12 hours by sinking the nickel-cobalt-manganese composite hydroxide on a 3 hour basis and removing the supernatant.

As a result, SEM photographs of the prepared composite precursors are shown in FIGS. 1 and 2. The particle size was 4.41 μm, the surface area was 18.82 m ² /g, and the tap density was 1.44 g/cm ³ .

In addition, Figure 3 is a SEM measurement of the cross section of the composite precursor prepared in the comparison, it was confirmed that a lot of voids were formed inside.

Hereinafter, it was confirmed that the composite precursor of the example prepared by the method of the present invention has an increased density compared to the composite precursor of the comparative example.

Example

Unlike the comparative example, in the present invention, nano-sized transition metal particles were added at the initial stage of the co-precipitation reaction of the complex precursor, so that the seed of the complex precursor was doped with the transition metal. In the present invention, unlike the conventional transition metal doping, rather than doping the transition metal after completion of the composite precursor, doping a small amount of nano-sized transition metal at the initial stage of co-precipitation of the composite precursor increases the final density of the composite precursor and the voids. The difference is that it reduces.

Nickel sulfate, cobalt sulfate, and manganese sulfate were mixed at a ratio of 0.6:0.2:0.2 (molar ratio) to prepare a 2.5 M concentration coprecipitation solution, and an aqueous 50% sodium hydroxide solution was prepared. The transition metal aqueous solution was supplied at a rate of 6.5 to 7.0 L/hr to a 100 L coprecipitation reactor, which is a double water tank structure containing deionized water maintained at 50 to 60°C, so that the pH inside the coprecipitation reactor is maintained at 10.5 to 11.0 The aqueous sodium hydroxide solution was added. Meanwhile, a ZrO ₂ solution as a nano-sized particle solution in the co-precipitation solution was simultaneously supplied to the co-precipitation reactor at a concentration of 1.0M at a rate of 1.0 to 1.5 L.hr for only 10 minutes.

As an additive, an aqueous ammonia solution at a concentration of 28% was supplied with 3 L before the transition metal solution was added. The co-precipitation reaction was performed for 12 hours by sinking the nickel-cobalt-manganese composite hydroxide on a 3 hour basis and removing the supernatant.

As a result, SEM photographs of the prepared composite precursors are shown in FIGS. 4 and 5. The particle size was 4.45 μm, the surface area was 17.94 m ² /g, and the tap density was 1.53 g/cm ³ .

The particle size was not significantly different from the comparative example, and the surface area was slightly reduced, but this is also a difference that occurs in the manufacturing process and is not a significant result. When the tap density was compared, it was confirmed that the tap density was greatly improved in the case of the composite precursor of the example, since 1.44 g/cm ³ ->1.53 g/cm ³ . In particular, in the case of tap density, unlike other indicators, it can be interpreted that the improvement of the above degree is a very significant increase.

Figure 6 is a SEM measurement of the cross section of the composite precursor prepared in Example, it can be seen that the pores are much reduced inside compared to the comparative example of FIG. In particular, through the doping of the transition metal for a short time of 10 minutes in the initial coprecipitation process, the pores inside the composite precursor are rapidly reduced, thereby improving physical properties and increasing power density.

In addition, although the experimental results are not described in this specification, the effect of increasing the tap density in the same manner as in the case of ZrO ₂ can be confirmed when WO ₂ and TiO ₂ are doped at the beginning of the composite precursor.

Claims (4)

Nickel-cobalt-manganese composite precursor [Ni _x Co _y Mn _1-xy (OH) _2, where In the method for producing 0 <x <1, 0 <y <1, 0 <x + y <1],
Preparing a metal aqueous solution of nickel sulfate, cobalt sulfate, and manganese sulfate in a co-precipitation reactor;
Preparing a solution containing nano-sized particles; And
Comprising the step of preparing a complex precursor through a co-precipitation reaction,
In the step of preparing the composite precursor, a method of manufacturing a high density nickel-cobalt-manganese composite precursor with a small void therein by adding a solution containing nano-sized particles to only some of the reactions during the coprecipitation reaction.
The method of claim 1, wherein the nano-sized particles are transition metal particles, and a high-density nickel-cobalt-manganese composite precursor is produced.
The method of claim ₂ , wherein the transition metal particles are any one of ZrO ₂ , WO ₂ and TiO ₂ , and a high density nickel-cobalt-manganese composite precursor is produced.
The method of claim 1, wherein the solution containing the nano-sized particles is added only during the initial seed formation process of the nickel-cobalt-manganese composite precursor, a method for preparing a high density nickel-cobalt-manganese composite precursor.

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