WO2014046363A1

WO2014046363A1 - Aparatus and method for preparing electrode active material

Info

Publication number: WO2014046363A1
Application number: PCT/KR2013/003617
Authority: WO
Inventors: Ki Taeg Jung; Kyu Ho Song; Seong Jae Lim; Kee Do Han
Original assignee: Hanwha Chemical Corporation
Priority date: 2012-09-21
Filing date: 2013-04-26
Publication date: 2014-03-27
Also published as: KR20140039420A; TW201412393A

Abstract

This invention relates to an apparatus for preparing an electrode active material, including a plurality of pipes, a mixer connected with the plurality of pipes and configured to mix an electrode active material precursor-containing feed and supercritical water, and a reactor for producing the electrode active material, wherein at least one selected from among the feed and the supercritical water is fed into the mixer via the plurality of pipes. According to this invention, in the continuous synthesis process of the electrode active material using a hydrothermal synthesis process under subcritical or supercritical conditions, synthesis conditions can be maintained stable, and operation stability of the synthesis process can be ensured.

Description

APARATUS AND METHOD FOR PREPARING ELECTRODE ACTIVE MATERIAL

The present invention relates to an apparatus and method for preparing an electrode active material and, more particularly, to an apparatus and method for preparing an electrode active material, which enables stable continuous process operation.

A dry burning method and a wet precipitation method are widely known to be conventional methods of preparing an electrode active material. The dry burning method is used to prepare an electrode active material by mixing an oxide or hydroxide of a transition metal such as cobalt (Co), etc., with a lithium source, that is, lithium carbonate or lithium hydroxide, under dry conditions, and then burning the mixture at a high temperature of 700 ~ 1000℃ for 5 ~ 48 hr.

The dry burning method has typically mainly been utilized to prepare the metal oxide and is advantageous in terms of it being a relatively easy approach, but it is difficult to uniformly mix feed materials, making it difficult to obtain a single-phase product. Furthermore, in the case of a multi-component electrode active material comprising two or more transition metals, it is difficult to uniformly arrange two or more elements at an atom level. Moreover, the case of doping with or substitution with a specific metal component to improve electrochemical performance is problematic because it is difficult to uniformly mix the specific metal component added in a small amount, and also because loss is essentially caused in the course of grinding and sorting to obtain particles having a desired size.

Among typical methods of preparing an electrode active material, the wet precipitation method is exemplified. The wet precipitation method is used to prepare an electrode active material by dissolving a salt containing a transition metal such as cobalt (Co), etc., in water, adding an alkali to the salt solution so that the salt solution is precipitated into a transition metal hydroxide, and filtering and drying the precipitate, which is then mixed with a lithium source, that is, lithium carbonate or lithium hydroxide, under dry conditions, and then burned at a high temperature of 700 ~ 1000℃ for 1 ~ 48 hr.

The wet precipitation method is known to easily obtain a uniform mixture by co-precipitating two or more transition metal elements, but is problematic because a precipitation reaction requires a long period of time, the preparation process is complicated, and waste acids and the like are generated as byproducts. In addition, a variety of methods, including a sol-gel method, a hydrothermal method, a spray pyrolysis method, an ion exchange method, etc., have been proposed as methods of preparing an electrode active material for a lithium secondary battery.

Meanwhile, in addition to the above methods, methods of preparing an inorganic compound for an electrode active material by means of a hydrothermal synthesis process using water under subcritical or supercritical conditions are currently being used.

In the case of an electrode active material for a lithium secondary battery, when using a hydrothermal synthesis process under subcritical or supercritical conditions, particle crystallinity is greatly improved, and a single-phase uniform material having a size corresponding to tens of to hundreds of nanometers of the average size of primary particles may be prepared.

In the hydrothermal synthesis process under subcritical or supercritical conditions, research into establishing the mixing and reaction conditions of reaction feeds and into particle crystallinity is ongoing. However, insufficient research has been carried out into continuous preparation of an electrode active material for a secondary battery using the hydrothermal synthesis process under subcritical or supercritical conditions, and only the mixing and addition of reaction feeds have been partially studied.

Upon continuous preparation of an electrode active material using the hydrothermal synthesis process under subcritical or supercritical conditions, nano-sized primary particles may be formed in the course of mixing water under subcritical or supercritical conditions with electrode active material feeds using a mixer. However, if the feeds and the water under subcritical or supercritical conditions are not uniformly mixed, mixing performance may deteriorate, and thus the size distribution of primary particles may become wide, and the size of the primary particles is also increased, or back-flow may be formed in the mixer or the particles may be partially attached to the wall of the mixer, thus closing the outlets of the mixer and the reactor, undesirably causing plugging, making it impossible to perform a continuous operation.

Accordingly, the present invention has been made keeping in mind the above problems occurring in the related art, and an object of the present invention is to provide a continuous synthesis process of an electrode active material using a hydrothermal synthesis process under subcritical or supercritical conditions, wherein the synthesis conditions are maintained stable and the operation stability of the synthesis process is ensured.

An aspect of the present invention provides an apparatus for preparing an electrode active material, comprising a plurality of pipes, a mixer connected with the plurality of pipes and configured to mix an electrode active material precursor-containing feed and supercritical water, and a reactor for producing the electrode active material, wherein at least one selected from among the feed and the supercritical water is fed into the mixer via the plurality of pipes.

In an embodiment of the apparatus of the present invention, the plurality of pipes may be at least one selected from among a plurality of single pipes, a double pipe, and a multi-pipe system, the feed may be fed into the mixer using at least one selected from among a plurality of single pipes, a double pipe, and a multi-pipe system, and the supercritical water may be fed into the mixer using at least one selected from among a plurality of single pipes, a double pipe, and a multi-pipe system.

In an embodiment of the apparatus of the present invention, the reactor may be operated at a pressure of 150 ~ 700 bar and a temperature of 200 ~ 700℃.

Another aspect of the present invention provides a method of preparing an electrode active material, comprising (a) feeding at least one selected from among an electrode active material precursor-containing feed and supercritical water into a mixer via a plurality of pipes so that the feed and the supercritical water are mixed, thus obtaining a reaction mixture, and (b) feeding the reaction mixture into a reactor, thus producing the electrode active material.

In an embodiment of the method of the present invention, the plurality of pipes may be at least one selected from among a plurality of single pipes, a double pipe, and a multi-pipe system, the feed may be fed into the mixer using at least one selected from among a plurality of single pipes, a double pipe, and a multi-pipe system, and the supercritical water may be fed into the mixer using at least one selected from among a plurality of single pipes, a double pipe, and a multi-pipe system.

In an embodiment of the method of the present invention, (b) may be performed using a reactor at a pressure of 150 ~ 700 bar and a temperature of 200 ~ 700℃.

According to the present invention, in the case where an electrode active material is continuously prepared, changes in conditions (reaction temperature, reaction pressure) for preparing the electrode active material are suppressed, and continuous mixing and reaction equipment operation are possible, thus reducing the process maintenance and repair costs, and decreasing the production cost. Furthermore, equipment stability in the process under subcritical or supercritical conditions can be improved, thus increasing the lifespan of equipment.

Also, the electrode active material prepared according to the present invention is improved in particle crystallinity and uniformity, thus facilitating handling of particles upon drying and burning, and increasing the product performance.

FIG. 1 is a schematic view illustrating a preparation process using an apparatus for preparing an electrode active material according to an embodiment of the present invention;

FIG. 2 is a side cross-sectional view illustrating an apparatus for preparing an electrode active material according to an embodiment of the present invention;

FIG. 3A is a cross-sectional view illustrating an apparatus for preparing an electrode active material according to an embodiment of the present invention, and FIG. 3B is a side cross-sectional view illustrating an inflow pipe comprising a double pipe including an inner pipe and an outer pipe, in the apparatus; and

FIG. 4A is a cross-sectional view illustrating an apparatus for preparing an electrode active material according to the embodiment of the present invention, and FIG. 4B is a side cross-sectional view illustrating an inflow pipe comprising a double pipe including an inner pipe and an outer pipe, in the apparatus.

The present invention may be variously modified, and may have a variety of embodiments, and is intended to illustrate specific embodiments. However, the following description does not limit the present invention to specific embodiments, and should be understood to include all variations, equivalents or substitutions within the spirit and scope of the present invention. Furthermore, in the description of the present invention, when it is determined that the detailed description of the related art would obscure the gist of the present invention, the description thereof will be omitted.

Also, in the following description, the terms “first,” “second” and the like are used to differentiate a certain component from other components, but the configuration of such components should not be construed to be limited by the terms. For example, a first component may be referred to as a second component, and also, a second component may be referred to as a first component, within the scope of the present invention.

Also, when any one component is mentioned to be “formed” on another component, it may be directly attached to the entire surface or one surface of another component, or a further component may be additionally interposed therebetween.

Unless otherwise stated, the singular expression includes a plural expression. In this application, the terms “include” or “have” are used to designate the presence of features, numbers, steps, operations, components, parts or combinations thereof described in the specification, and should be understood so as not to exclude the presence or additional probability of one or more different features, numbers, steps, operations, components, parts or combinations thereof.

As used herein, the term “supercritical water” refers to a liquid stream or slurry stream including water under subcritical or supercritical conditions, regardless of the name thereof.

Hereinafter, a description is given of an apparatus and method for preparing an electrode active material according to the present invention with reference to the schematic view, and a detailed description thereof using a mixer is also given.

With reference to FIG. 1, electrode active material feeds are fed into a mixer 1a via a path 10a, and the mixer 1a functions to mix the electrode active material feeds to produce an electrode active material or an electrode active material precursor, which is then discharged via a path 20a. Present in the mixer 1a may be a zone where a fluid is transferred to a subcritical or supercritical phase from a liquid phase and a zone in a subcritical or supercritical phase.

A reactor 2a is used to synthesize the electrode active material or to crystallize primary particles of the electrode active material, so that the resulting product is discharged via a path 30a, and the fluid in the reactor 2a is maintained in a subcritical or supercritical phase.

Heat exchangers

3a, 4a, 6a are disposed downstream of the reactor 2a, and are used to cool an electrode active material-containing fluid to a liquid phase from the subcritical or supercritical phase. Cooling may be performed over multiple stages using a plurality of heat exchangers. Among the heat exchangers, the heat exchanger 3a positioned to be the closest to the reactor 2a functions to cool the fluid in a subcritical or supercritical phase so as to obtain a fluid in a subcritical phase or a liquid phase. The cooler 3a is preferably a double pipe type heat exchanger.

A furnace 5a may be provided, which preheats deionized water discharged via a path 80a from the cooler 3a so that the preheated water is fed into the mixer 1a. Also, a pressure reducer 7a and a concentrator 8a may be provided downstream of the cooler.

The pressure reducer 7a is used to reduce the pressure of a reaction mixture at high pressure fed via a path 100a to a low pressure (1 ~ 50 bar).

The concentrator 8a functions to concentrate the electrode active material-containing fluid fed via a path 110a. The concentrator 8a may adopt a type wherein a liquid phase is passed through a filter.

In the mixer, in the case where electrode active material precursor-containing feeds and supercritical water are fed and mixed via respective pipes and mixed, it is difficult to efficiently mix the feeds and the supercritical water and layer separation may occur, thus causing plugging, increasing the size of synthesized primary particles, and decreasing crystallinity, undesirably deteriorating cell performance.

Below, the apparatus for preparing an electrode active material according to the present invention is described based on the mixer and the pipes which are connected to the mixer and into which the feeds or the supercritical water are fed.

With reference to FIGS. 2 to 4, an aspect of the invention may provide an electrode active material preparation apparatus 1, 1’, comprising a plurality of pipes 20; a mixer 10 connected with the plurality of pipes 20 and configured to mix electrode active material precursor-containing feeds and supercritical water; and a reactor 30 for producing an electrode active material, wherein the feeds are fed into the mixer 10 via the plurality of pipes 20 (211, 213, 215), or the supercritical water is fed into the mixer via the plurality of pipes, or the feeds and the supercritical water are fed into the mixer via the plurality of pipes.

In the present invention, the plurality of pipes 20 may be at least one selected from among a plurality of single pipes 20 (211, 213, 215), a double pipe 20 (221, 223), and a multi-pipe system, and the feeds (S11, S12, S13; S21, S22, S23) may be fed into the mixer via at least one selected from among a plurality of single pipes 20 (211, 213, 215), a double pipe 20 (221, 223), and a multi-pipe system.

Also in the present invention, the plurality of pipes 20 may be at least one selected from among a plurality of single pipes 20 (211, 213, 215), a double pipe 20 (221, 223), and a multi-pipe system, and the supercritical water (S11, S12, S13; S21, S22, S23) may be fed into the mixer via at least one selected from among a plurality of single pipes 20 (211, 213, 215), a double pipe 20 (221, 223), and a multi-pipe system.

Below is a description of the case where the plurality of pipes is a plurality of single pipes.

An embodiment of the present invention provides an electrode active material preparation apparatus 1, comprising a plurality of inflow pipes 20 (211, 213, 215), a mixer 10 connected with the plurality of inflow pipes, and a reactor 30, wherein any one selected from among electrode active material precursor-containing feeds and supercritical water (S11, S12, S13) is fed into the mixer 10 via two or more of the plurality of inflow pipes, and the feeds and the supercritical water are mixed using the mixer 10 to produce an electrode active material precursor-containing mixture (S14), which is fed into the reactor 30, so that the electrode active material precursor-containing mixture (S14) is reacted using a hydrothermal synthesis process in the reactor 30, thereby producing an electrode active material.

According to an embodiment of the present invention, in the electrode active material preparation apparatus 1, the plurality of inflow pipes 20 may include a first inflow pipe 211, a second inflow pipe 213 and a third inflow pipe 215, and the feeds (S11, S12) may include a first feed (S11) and a second feed (S12), and the first feed (S11) may be fed via the first inflow pipe 211, the second feed (S12) may be fed via the second inflow pipe 213, and the supercritical water (S13) may be fed via the third inflow pipe 215.

According to another embodiment of the invention, the plurality of inflow pipes 20 may include a first inflow pipe 211, a second inflow pipe 213 and a third inflow pipe 215, and the supercritical water (S11, S12) may include first supercritical water (S11) and second supercritical water (S12). The feed (S13) may be fed via the third inflow pipe 215, the first supercritical water (S11) may be fed via the first inflow pipe 211, and the second supercritical water (S12) may be fed via the second inflow pipe 213.

Below is a description of the case where the plurality of pipes is a double pipe.

With reference to FIG. 3, another aspect of the present invention provides an electrode active material preparation apparatus 1’ comprising a plurality of inflow pipes 20 (221, 223), a mixer 10 connected with the plurality of inflow pipes, and a reactor 30, wherein at least one of the plurality of inflow pipes is a double pipe including an inner pipe 2233 and an outer pipe 2231, and the double pipe includes an inside 2235 of the inner pipe and a space portion 2237 defined between the inner and outer pipes, and any one (S21, S22, S23) selected from among electrode active material precursor-containing feeds and supercritical water may be fed into the mixer 20 via the inside 2235 of the inner pipe and the space portion 2237.

The feeds and the supercritical water are mixed using the mixer, thus producing an electrode active material precursor-containing mixture (S24), which is then fed into the reactor 30, so that the electrode active material precursor-containing mixture (S24) is reacted using a hydrothermal synthesis process in the reactor 30, thereby obtaining an electrode active material. FIG. 3B is a side cross-sectional view taken along the line A-A’ of FIG. 3A.

In the present invention, the cross-sectional shape of the inner and outer pipes may be a circular shape or a polygonal shape including a triangular shape, a rectangular shape, a pentagonal shape, etc., and is preferably a circular shape, but the present invention is not limited thereto.

Also according to an embodiment of the invention, the feeds (S21, S22) may include a first feed (S21) and a second feed (S22), the plurality of inflow pipes may include a first inflow pipe 223 and a second inflow pipe 221, and the first inflow pipe 223 may be a double pipe including an inner pipe 2233 and an outer pipe 2231. The second feed (S22) may be fed via the inside 2235 of the inner pipe, the first feed (S21) may be fed via the space portion 2237 formed between the inner and outer pipes, and the supercritical water (S23) may be fed via the second inflow pipe 221.

Also according to another embodiment of the invention, the feeds (S22, S23) may include a first feed (S22) and a second feed (S23), the plurality of inflow pipes may include a first inflow pipe 223 and a second inflow pipe 221, and the first inflow pipe 223 may be a double pipe including an inner pipe 2233 and an outer pipe 2231. The first feed (S22) may be fed via the inside 2235 of the inner pipe 2233, the supercritical water (S21) may be fed via the space portion 2237 formed between the inner and outer pipes, and the second feed (S23) may be fed via the second inflow pipe 221.

Also according to still another embodiment of the invention, the feeds (S21, S23) may include a first feed (S21) and a second feed (S23), the plurality of inflow pipes may include a first inflow pipe 223 and a second inflow pipe 221, and the first inflow pipe 223 may be a double pipe including an inner pipe and an outer pipe. The supercritical water (S22) may be fed via the inside 2235 of the inner pipe 2233, the first feed (S21) may be fed via the space portion 2237 formed between the inner and outer pipes, and the second feed (S23) may be fed via the second inflow pipe 221.

With reference to FIGS. 3 and 4, the mixer is configured such that the longitudinal direction of the double pipe at a connection portion between the mixer and the double pipe is parallel (FIG. 3) or perpendicular (FIG. 4) to the longitudinal direction of the discharge pipe at a connection portion between the mixer and the discharge pipe.

Below is a description of the case where the plurality of pipes is a multi-pipe system.

Another aspect of the present invention may provide an electrode active material preparation apparatus, comprising a plurality of inflow pipes, a mixer connected with the plurality of inflow pipes, and a reactor, wherein at least one of the plurality of inflow pipes includes a multi-pipe system, any one selected from among electrode active material precursor-containing feeds and supercritical water is fed into the mixer via the multi-pipe system, and the feeds and the supercritical water are mixed using the mixer thus producing an electrode active material precursor-containing mixture which is then fed into the reactor, so that the electrode active material precursor-containing mixture is reacted using a hydrothermal synthesis process in the reactor, thereby obtaining an electrode active material.

Also in the present invention, the conditions of the reactor are set to a pressure of 150 ~ 700 bar and a temperature of 200 ~ 700℃ to produce the electrode active material.

Below is a description of a method of preparing the electrode active material according to the present invention.

The method of preparing the electrode active material according to the present invention comprises (a) feeding electrode active material precursor-containing feeds into a mixer via a plurality of pipes, feeding supercritical water into a mixer via a plurality of pipes, or feeding electrode active material precursor-containing feeds and supercritical water into a mixer via a plurality of pipes, thus mixing the feeds and the supercritical water; and (b) feeding the reaction mixture obtained in (a) into a reactor thus producing an electrode active material.

The mixer may be configured such that the longitudinal direction of a double pipe at a connection portion between the mixer and the double pipe is parallel or perpendicular to the longitudinal direction of a discharge pipe at a connection portion between the mixer and the discharge pipe.

In the case where the electrode active material precursor-containing feeds and the supercritical water are fed into the mixer via respective pipes, mixing of the feeds and the supercritical water is not efficiently performed, and layer separation may occur, thus causing plugging, an increase in the size of synthesized primary particles and low crystallinity, undesirably deteriorating cell performance. Thus, in the present invention, the feeds are fed into the mixer using the plurality of pipes, or the supercritical water is fed into the mixer using the plurality of pipes. The inflow part of the pipe into which the feed or the supercritical water is fed may be the inside of a single pipe when using the single pipe, or may be the inside of an inner pipe or the space portion formed between inner and outer pipes when using a multiple pipe, for example, a double pipe. Also, the inflow part thereof may be any one internal pipe when using a multi-pipe system.

(a): Feeding the electrode active material precursor-containing feeds into a mixer via a plurality of pipes, or feeding the supercritical water into a mixer via a plurality of pipes, thus mixing the feeds and the supercritical water

Useful in the present invention, a mixer may be configured such that at least one flow of the electrode active material precursor-containing feeds and the supercritical water may be fed into the mixer using two or more pipes, and the pipe used in the mixer may be a single pipe, a double pipe, or a multi-pipe system having holes, and a pipe system having branched single pipes.

In the case where such pipes are used, layer separation does not occur when the supercritical water and the feeds are mixed in the mixer, and the speed of mixing is increased, thus avoiding plugging, and the reaction of the feeds takes place under supercritical conditions. Furthermore, particles may be rapidly synthesized, thus suppressing particle growth, thereby synthesizing primary particles having a desired size.

The inflow part is connected to the mixer, and may be an inflow pipe into which the feed or the supercritical water is fed, wherein the inflow pipe may be a single pipe, a double pipe, a multiple pipe, or a multi-pipe system.

When using a plurality of single pipes

This case is described with reference to FIG. 2. According to the present invention, the electrode active material preparation apparatus 1 includes a plurality of inflow pipes 20, and the electrode active material precursor-containing feeds or the supercritical water may be fed via the plurality of inflow pipes, in which the plurality of inflow pipes may be a plurality of single pipes.

Also in an embodiment of the invention, the plurality of inflow pipes may include a first inflow pipe 211, a second inflow pipe 213 and a third inflow pipe 215. As such, each of the inflow pipes is a single pipe. The feeds (S11, S12) may include a first feed (S11) and a second feed (S12). In this case, the first feed (S11) may be fed via the first inflow pipe 211, the second feed (S12) may be fed via the second inflow pipe 213, and the supercritical water (S13) may be fed via the third inflow pipe 215.

Also in another embodiment of the invention, the plurality of inflow pipes 20 may include a first inflow pipe 211, a second inflow pipe 213 and a third inflow pipe 215. The supercritical water (S11, S12) may include first supercritical water (S11) and second supercritical water (S12). The feed (S13) may be fed via the third inflow pipe 215, the first supercritical water (S11) may be fed via the first inflow pipe 211, and the second supercritical water (S12) may be fed via the second inflow pipe 213.

When using a double pipe

This case is described with reference to FIGS. 3 and 4. According to the present invention, the electrode active material preparation apparatus 1’ includes a plurality of inflow pipes 20 (221, 223), wherein the plurality of inflow pipes may be a double pipe. The electrode active material precursor-containing feeds or the supercritical water may be fed via the plurality of inflow pipes. Either of the feeds and the supercritical water may be supplied into the mixer 10 via an inside 2235 of an inner pipe of a double pipe including an inner pipe 2233 and an outer pipe 2231; and a space portion 2237 formed between the inner and outer pipes of the double pipe. The foregoing is described using the double pipe, but a multiple pipe, including a triple pipe, a quadruple pipe, etc., may be used in the present invention.

As such, the cross-sectional shape of the inner and outer pipes may be a circular shape or a polygonal shape including a triangular shape, a rectangular shape, a pentagonal shape, etc., and is preferably a circular shape, but the present invention is not limited thereto.

In an embodiment of the invention, the feeds (S21, S22) may include a first feed (S21) and a second feed (S22). The plurality of inflow pipes may include a first inflow pipe 223 and a second inflow pipe 221. As such, the first inflow pipe 223 is a double pipe including an inner pipe 2233 and an outer pipe 2231. The second feed (S22) may be fed via the inside 2235 of the inner pipe, the first feed (S21) may be fed via the space portion 2237 formed between the inner and outer pipes, and the supercritical water (S23) may be fed via the second inflow pipe 221.

Also in another embodiment of the invention, the feeds (S22, S23) may include a first feed (S22) and a second feed (S23). The plurality of inflow pipes may include a first inflow pipe 223 and a second inflow pipe 221, and the first inflow pipe 223 is a double pipe including an inner pipe 2233 and an outer pipe 2231. The first feed (S22) may be fed via the inside 2235 of the inner pipe 2233, the supercritical water (S21) may be fed via the space portion 2237 formed between the inner and outer pipes, and the second feed (S23) may be fed via the second inflow pipe 221.

Also in still another embodiment of the invention, the feeds (S21, S23) may include a first feed (S21) and a second feed (S23). The plurality of inflow pipes may include a first inflow pipe 223 and a second inflow pipe 221, and the first inflow pipe 223 is a double pipe including an inner pipe and an outer pipe. The supercritical water (S22) may be fed via the inside 2235 of the inner pipe 2233, the first feed (S21) may be fed via the space portion 2237 formed between the inner and outer pipes, and the second feed (S23) may be fed via the second inflow pipe 221.

With reference to FIGS. 3 and 4, according to the embodiment of the present invention, the mixer may be configured such that the longitudinal direction of the double pipe at a connection portion between the mixer and the double pipe is parallel (FIG. 3) or perpendicular (FIG. 4) to the longitudinal direction of the discharge pipe at a connection portion between the mixer and the discharge pipe. Thus, the direction of stream of the introduced feed or supercritical water may be parallel or perpendicular to the direction of stream of the discharged feed or supercritical water.

When using a multi-pipe system

According to the present invention, either of the electrode active material precursor-containing feeds and the supercritical water may be fed into the mixer via two or more of a plurality of pipes in a multi-pipe system.

The shape of any one of the plurality of pipes in the multi-pipe system may be a circular shape or a polygonal shape including a triangular shape, a rectangular shape, a pentagonal shape, etc., but the present invention is not limited thereto and a variety of shapes may be exemplified. The number of pipes in the multi-pipe system may be 2, 3, 4, or 5 or more.

According to the embodiment of the present invention, the feeds may include a first feed and a second feed. The plurality of inflow pipes may include a first inflow pipe and a second inflow pipe. The first inflow pipe may be a multi-pipe system including a plurality of pipes therein. The first feed may be fed via the first pipe among the plurality of pipes, the second feed may be fed via the second pipe, and the supercritical water may be fed via the second inflow pipe.

(b): Feeding the reaction mixture obtained in (a) into a reactor to produce an electrode active material

Water and the feeds for the electrode active material are mixed in the mixer, thus forming a slurry mixture where the fluid contains the electrode active material or the electrode active material precursor. As such, present in the mixer may be a zone where the fluid is transferred to a subcritical or supercritical phase from a liquid phase, and a zone in a subcritical or supercritical phase.

The slurry mixture where the fluid contains the electrode active material or the electrode active material precursor is fed into the reactor.

The slurry mixture where the fluid contains the electrode active material or the electrode active material precursor is reacted at a pressure of 150 ~ 700 bar and at a temperature of 200 ~ 700℃, thus preparing the electrode active material.

In the reactor, the electrode active material is synthesized, or primary particles of the electrode active material are crystallized, and the fluid in the reactor is maintained in a subcritical or supercritical phase.

Examples of the electrode active material prepared according to the present invention may include an anode active material and a cathode active material for a secondary battery. Examples of the anode active material for a secondary battery may include oxides and non-oxides, and the oxides may include an olivine structure (LiMXO₄), a lamellar structure (LiMO₂), a spinel structure (LiM₂O₄), a nasicon structure (Li₃M₂(XO₄)₃) (wherein M is any one or a combination of two or more selected from among transition metals and alkali metals). The average particle size of the electrode active material may fall in the range from 50 nm to 5 ㎛.

A better understanding of the present invention may be obtained through the following examples which are set forth to illustrate, but are not to be construed as limiting the present invention.

Example 1

With reference to FIG. 2, as feeds for an anode active material LiFePO₄, aqueous ammonia and lithium hydroxide (LiOH·H₂O) were fed into a mixer via a first inflow pipe 211 which is a single pipe, iron sulfate (FeSO₄·7(H₂O)) and phosphoric acid (H₃PO₄) were fed into the mixer via a second inflow pipe 213 which is a single pipe, and supercritical water at 395℃ and 250 bar was fed into the mixer via a third inflow pipe 215, so that they were mixed, thus preparing a LiFePO₄ precursor-containing slurry. The mixer was operated at 386℃ and 250 bar for 100 hr.

With reference to FIG. 1, the LiFePO₄ precursor-containing slurry was fed into a reactor 2a under subcritical or supercritical conditions of 386℃ and 250 bar, thus synthesizing LiFePO₄, which was then fed into a heat exchanger 3a via a path 30a and then into

heat exchangers

4a, 6a, and thus cooled.

The pressure of the cooled product was decreased to 1 ~ 50 bar using a pressure reducer 7a, and the product was concentrated using a concentrator 8a so that LiFePO₄ particles were at a high concentration of 20 wt%, thus obtaining LiFePO₄ particles.

After the process operation was initiated, continuous operation was efficiently performed without plugging in the mixer and subsequent equipment units.

Example 2

With reference to FIG. 2, LiFePO₄ particles were obtained in the same manner as in Example 1, with the exception that 50 wt% of supercritical water based on the total amount of supercritical water added into a mixer was fed into a mixer 10 via a first inflow pipe 211 which is a single pipe, the remaining 50 wt% of supercritical water was fed into the mixer via a second inflow pipe 213 which is a single pipe, and a feed was fed into the mixer via a third inflow pipe 215 which is a single pipe.

Example 3

With reference to FIG. 3, a first inflow pipe 223 is a double pipe including an inner pipe 2233 and an outer pipe 2231. As feeds for an anode active material LiFePO₄, aqueous ammonia and lithium hydroxide (LiOH·H₂O) were fed into a mixer via an inside 2235 of the inner pipe, iron sulfate (FeSO₄·7(H₂O)) and phosphoric acid (H₃PO₄) were fed into the mixer via a space portion 2237 formed between inner and outer pipes, and supercritical water at 395℃ and 250 bar was fed into the mixer via a second inflow pipe 221 which is a single pipe, so that they were mixed, thus preparing a LiFePO₄ precursor-containing slurry. The mixer was operated at 386℃ and 250 bar for 100 hr.

heat exchangers

4a, 6a, and thus cooled.

The pressure of the cooled product was decreased to 5 ~ 30 bar using a pressure reducer 7a, and the product was concentrated using a concentrator 8a so that LiFePO₄ particles were at a high concentration of 20 wt%, thus obtaining LiFePO₄ particles.

Example 4

With reference to FIG. 3, LiFePO₄ particles were obtained in the same manner as in Example 3, with the exception that aqueous ammonia and lithium hydroxide (LiOH·H₂O) were fed into a mixer via an inside 2235 of an inner pipe, a total of supercritical water was fed into the mixer via a space portion 2237 formed between inner and outer pipes, and iron sulfate (FeSO₄·7(H₂O)) and phosphoric acid (H₃PO₄) were fed into the mixer via a second inflow pipe 221 which is a single pipe.

Example 5

With reference to FIG. 3, LiFePO₄ particles were obtained in the same manner as in Example 3, with the exception that a total of supercritical water was fed into a mixer via an inside 2235 of an inner pipe, aqueous ammonia and lithium hydroxide (LiOH·H₂O) were fed into the mixer via a space portion 2237 formed between inner and outer pipes, and iron sulfate (FeSO₄·7(H₂O)) and phosphoric acid (H₃PO₄) were fed into the mixer via a second inflow pipe 221 which is a single pipe. The first inflow pipe comprising the inner pipe and the outer pipe was disposed parallel to the discharge pipe for discharging the product produced in the mixer.

Example 6

With reference to FIG. 4, LiFePO₄ particles were obtained in the same manner as in Example 3, with the exception that a total of supercritical water was fed into a mixer via an inside 2235 of an inner pipe, aqueous ammonia and lithium hydroxide (LiOH·H₂O) were fed into the mixer via a space portion 2237 formed between inner and outer pipes, and iron sulfate (FeSO₄·7(H₂O)) and phosphoric acid (H₃PO₄) were fed into the mixer via a second inflow pipe 221 which is a single pipe. The first inflow pipe comprising the inner pipe and the outer pipe was disposed perpendicular to the discharge pipe for discharging the product produced in the mixer.

Comparative Example 1

With reference to FIG. 2, LiFePO₄ particles were obtained in the same manner as in Example 1, with the exception that total feeds for an anode active material LiFePO₄ were fed into a mixer via a first inflow pipe 211 which is a single pipe, and a total of supercritical water was fed into the mixer via a second inflow pipe 213 which is a single pipe, without the use of a third inflow pipe 215. The first inflow pipe was disposed parallel to the second inflow pipe, and the movement direction of feed stream in the first inflow pipe was opposite to the movement direction of supercritical water stream in the second inflow pipe.

4 ~ 8 hr after the process operation was initiated, the entire process was stopped due to plugging in the synthesis process, and separation of equipment units and maintenance/repair were performed, and then the experiment was conducted again. Thereafter, the above problem was repeatedly caused, thus requiring the process operation to be stopped and initiated repeatedly.

Comparative Example 2

With reference to FIG. 2, LiFePO₄ particles were obtained in the same manner as in Example 1, with the exception that total feeds for an anode active material LiFePO₄ were fed into a mixer via a first inflow pipe 211 which is a single pipe, and a total of supercritical water was fed into the mixer via a third inflow pipe 215 which is a single pipe, without the use of a second inflow pipe 213. The first inflow pipe was disposed perpendicular to the third inflow pipe, and the movement direction of feed stream in the first inflow pipe was perpendicular to the movement direction of supercritical water stream in the third inflow pipe.

The results of Examples 1 to 6 and Comparative Examples 1 and 2 are summarized in Table 1 below.

Table 1

	Inflow part			Inflow part			Generation of plugging
	Single pipe 1	Single pipe 2	Single pipe 3	Double pipe		Single pipe
	Single pipe 1	Single pipe 2	Single pipe 3	Inside of inner pipe	Space portion between inner and outer pipes	Single pipe
Ex.1	Feed	Feed	Supercrit. Water	-	-	-	X
Ex.2	Supercrit. Water	Supercrit. Water	Feed	-	-	-	X
Ex.3	-	-	-	Feed	Feed	Supercrit. Water	X
Ex.4	-	-	-	Feed	Supercrit. Water	Supercrit. Water	X
Ex.5	-	-	-	Supercrit. Water	Feed	Feed	X
Ex.6	-	-	-	Supercrit. Water	Feed	Feed	X
Comp.Ex.1	Feed	Supercrit. Water	-	-	-	-	Ｏ
Comp.Ex.2	Feed	-	Supercrit. Water	-	-	-	Ｏ

In Table 1, X designates the case where plugging did not occur, and Ｏ designates the case where plugging occurred.

According to the present invention, in the case where an electrode active material is continuously prepared, stable continuous process operation is possible, thus reducing the process maintenance and repair costs, and increasing the lifespan of process equipment. Furthermore, the electrode active material prepared by the method of the invention can be obtained in the form of nano-sized particles and can be increased in crystallinity, thus increasing the lifespan of cells.

Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Claims

An apparatus for preparing an electrode active material, comprising:

a plurality of pipes;

a mixer connected with the plurality of pipes and configured to mix an electrode active material precursor-containing feed and supercritical water; and

a reactor for producing the electrode active material,

wherein at least one selected from among the feed and the supercritical water is fed into the mixer via the plurality of pipes.
The apparatus of claim 1, wherein the plurality of pipes is at least one selected from among a plurality of single pipes, a double pipe, and a multi-pipe system,

the feed is fed into the mixer using at least one selected from among a plurality of single pipes, a double pipe, and a multi-pipe system, and

the supercritical water is fed into the mixer using at least one selected from among a plurality of single pipes, a double pipe, and a multi-pipe system.
The apparatus of claim 1, wherein the reactor is operated at a pressure of 150 ~ 700 bar and a temperature of 200 ~ 700℃.
A method of preparing an electrode active material, comprising:

(a) feeding at least one selected from among an electrode active material precursor-containing feed and supercritical water into a mixer via a plurality of pipes so that the feed and the supercritical water are mixed, thus obtaining a reaction mixture; and

(b) feeding the reaction mixture into a reactor, thus producing the electrode active material.
The method of claim 4, wherein the plurality of pipes is at least one selected from among a plurality of single pipes, a double pipe, and a multi-pipe system,

the feed is fed into the mixer using at least one selected from among a plurality of single pipes, a double pipe, and a multi-pipe system, and

the supercritical water is fed into the mixer using at least one selected from among a plurality of single pipes, a double pipe, and a multi-pipe system.
The method of claim 4, wherein (b) is performed using a reactor at a pressure of 150 ~ 700 bar and a temperature of 200 ~ 700℃.