KR102182289B1 - Manufacturing method for high density Ni-Co-Mn composite precursor - Google Patents

Abstract

The present invention is a nickel-cobalt-manganese composite precursor [Ni _x Co _y Mn _1-xy (OH) _2, wherein, In order to solve the problem that the density decreases due to the occurrence of voids in 0<x<1, 0<y<1, 0<x+y<1], a solution containing a nanoscale transition metal is used in the initial stage of the coprecipitation reaction. It relates to a technique for doping the complex precursor seed.

Description

Manufacturing method for high density Ni-Co-Mn composite precursor {Manufacturing method for high density Ni-Co-Mn composite precursor}

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

In particular, the present invention does not increase the density by allowing the composite precursor particles to be well-mixed during the manufacture of the composite precursor, but prevents the occurrence of voids in the individual composite precursor itself, thereby increasing the density of the individual composite precursor itself. It is about the technology to do.

With the spread of portable small electric and electronic devices, the development of new secondary batteries such as nickel hydride batteries and lithium secondary batteries is actively progressing. In addition, as secondary batteries are used in hybrid vehicles (HEVs) and electric vehicles (EV), etc., research and development on secondary batteries are being actively conducted as the fields of application are expanded.

Among the secondary batteries, a lithium secondary battery is a battery using carbon such as graphite as a negative electrode active material, a metal oxide containing lithium as a positive electrode active material, and a non-aqueous solvent as an electrolyte. As a positive electrode active material used in a lithium secondary battery, the positive electrode properties such as energy density and electrical conductivity are satisfied by mixing nickel, cobalt, manganese, and the like, instead of lithium alone.

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

Manufacturing 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 has become a research theme. Due to the voids in the composite precursor particles, the density of the precursor decreases, the particle strength in the positive electrode active material stage decreases, and it is also a reason for lowering the power efficiency of the secondary battery.

In Patent Publication No. 10-2015-0059820 as a prior art related to the density control of such a composite precursor, a metal salt aqueous solution, a chelating agent, and a basic aqueous solution are supplied to the reactor to coprecipitate to prepare a coprecipitation compound, the coprecipitation compound In the method of producing a cathode active material precursor for a lithium secondary battery by a coprecipitation method comprising the step of preparing an active material precursor by drying or heat treatment, and preparing a lithium composite metal oxide by mixing and firing the active material precursor and a lithium salt, In the step of preparing a coprecipitation compound by supplying the aqueous metal salt solution, a chelating agent, and a basic aqueous solution to the reactor and coprecipitation to prepare a co-precipitating compound, the rate of supplying the aqueous metal salt solution to the reactor is increased according to an increase in the particle size of the co-precipitating compound. Disclosed is a method of manufacturing a battery positive electrode active material. That is, Patent Laid-Open No. 10-2015-0059820 discloses a technology in which the supply rate of the metal salt is adjusted according to the increase in the particle diameter during the co-precipitation reaction, thereby showing a high tap density across the particles and thus improving battery characteristics.

In addition, Patent Publication No. 10-2014-0098347 is a positive electrode in which a positive electrode mixture including a positive electrode active material, a conductive material, and a binder is coated on a current collector, and the positive electrode active material is composed of small particles and large particles having different average particle diameters. It is revealing a high-density cathode active material in a modal form.

In Patent Publication No. 10-2015-0059820, the tap density was adjusted by controlling the supply rate of the metal salt, but it is not practically easy to control the supply rate of the metal salt itself, and even if the method of the above patent is followed, it has a sufficient high density. There is a problem in that it is difficult to manufacture a composite precursor. In addition, Patent Publication No. 10-2014-0098347 differs from the present invention in that the density is controlled through mixing of small particles and large particles, rather than a method of increasing the 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 of 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 implementing high density of the entire composite precursor through the high density of the composite precursor itself, rather than implementing high density by mixing large particles and small particle composite precursors in the prior art.

In particular, an object of the present invention is 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, In a method for producing 0<x<1, 0<y<1, 0<x+y<1], the method comprising: preparing an aqueous metal 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, wherein in the step of preparing the composite precursor, a solution containing nano-sized particles is added only to some reactions during the co-precipitation reaction, thereby providing a high-density nickel-cobalt having few pores inside. -Provides a method of manufacturing manganese composite precursors.

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, it is possible to manufacture a high-density composite precursor. 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 , which has an effect of improving the tap density of 0.9 g/cm ³ . It could be confirmed by experiment.

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

1 and 2 are SEM photographs of different magnifications of a composite precursor according to a comparative example.
3 is a SEM measurement photograph of a cross section of a composite precursor prepared according to a comparative example.
4 and 5 are SEM photographs of different magnifications of the composite precursor prepared according to the present invention.
6 is an SEM measurement photograph of a cross section of a composite precursor prepared according to 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 increases the density of the entire composite precursor by increasing the density of the composite precursor particle itself by reducing the voids in the composite precursor particle itself, unlike the conventional technique of increasing the density through a combination of a large particle precursor and a small particle precursor. It's about the technology that exists.

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. Doping of the nanoparticle solution can greatly improve the density of the finally produced composite precursor even if it is only involved in a very short step in the co-precipitation process, that is, the process of generating the initial composite precursor. For example, if the total coprecipitation 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 multi-stage coprecipitation, even if the transition metal is doped to the composite precursor seed with a nanoparticle solution only in the first step, the density improvement effect of the finally produced composite precursor can be obtained. In the prior art, there was also doping of a transition metal, but this is different from the doping of the transition metal separately after completion of the composite precursor or doping throughout the entire manufacturing process of the composite precursor, in the present invention, only at the beginning of co-precipitation for the purpose of reducing the voids of the composite precursor. The difference is that it is doped for a short time.

Preferred nano-sized particles in the present invention may be nanoparticles of transition metal oxides, 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 coprecipitation reaction with a nickel sulfate, cobalt sulfate, and manganese sulfate coprecipitation solution as in the prior art was prepared, and the tap density and SEM measurements of the surface and cross section were performed.

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

As an additive, 3 L of a 28% aqueous ammonia solution was supplied before the transition metal aqueous solution was added. The co-precipitation reaction was carried out for 12 hours by setting the nickel-cobalt-manganese composite hydroxide and removing the supernatant.

As a result, SEM photographs of the prepared composite precursor are 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, FIG. 3 is an SEM measurement photograph of a cross section of the composite precursor prepared in Comparative Example, and it was confirmed that many voids were formed therein.

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

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

As an additive, 3 L of a 28% aqueous ammonia solution was supplied before the transition metal aqueous solution was added. The co-precipitation reaction was carried out for 12 hours by setting the nickel-cobalt-manganese composite hydroxide and removing the supernatant.

As a result, SEM photographs of the prepared composite precursor 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 that of 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. Comparing the tap density, it was confirmed that the tap density was greatly improved in the case of the composite precursor of the example by 1.44 g/cm ³ -> 1.53 g/cm ³ . In particular, in the case of tap density, unlike other indicators, the above degree of improvement can be interpreted as a very significant increase.

6 is a SEM measurement photograph of the cross section of the composite precursor prepared in the Example, and it can be seen that the internal voids were significantly reduced compared to the Comparative Example of FIG. 3. In particular, through doping of a transition metal for a short time of 10 minutes in the initial co-precipitation process, the voids inside the composite precursor are rapidly reduced, thereby improving physical properties and increasing power density.

In addition, although the experimental results were not described in the present specification, when doping WO ₂ and TiO _{2 at the} initial stage of the composite precursor, the effect of increasing the tap density was confirmed as in the case of ZrO ₂ .

Claims (4)

Nickel-cobalt-manganese composite precursor [Ni _x Co _y Mn _1-xy (OH) _2, where, In the method of producing 0<x<1, 0<y<1, 0<x+y<1],
Preparing an aqueous metal solution of nickel sulfate, cobalt sulfate, and manganese sulfate in a coprecipitation reactor;
Preparing a solution containing nano-sized transition metal particles; And
Including the step of preparing a composite precursor through a co-precipitation reaction,
In the step of preparing the composite precursor, a method of producing a high-density nickel-cobalt-manganese composite precursor having a small void inside by adding a solution containing the nano-sized transition metal particles only within 10 minutes of the initial co-precipitation reaction.
The method of claim 1, wherein the nano-sized transition metal particle is any one of ZrO ₂ , WO ₂ and TiO ₂ , and has a high density nickel-cobalt-manganese composite precursor.
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