KR102282278B1 - Method for preparing positive electrode active material precursor for lithium secondary battery - Google Patents

Abstract

The present invention relates to a method for producing a cathode active material precursor for a lithium secondary battery using a production device in which at least two or more filtration devices are installed outside the batch-type reactor, wherein the transition metal containing a transition metal cation in the batch-type reactor continuously introducing a reaction solution including the solution containing solution, the solution containing ammonium ions, and the basic aqueous solution; When the batch-type reactor is full, adding the slurry in the reactor to a first filtration device installed outside the reactor; The slurry introduced into the first filtration device is separated into a reaction mother liquid that has passed through the filter unit and a concentrated slurry that has not passed through the filter unit, of which the reaction mother liquid is introduced into a back washing tank, and the concentrated slurry is reintroducing the reaction mother liquid stored in a back washing tank into the batch reactor; And, the concentrated slurry reintroduced into the batch-type reactor to form a cathode active material precursor through particle growth; provides a method for producing a cathode active material precursor comprising a.

Description

Manufacturing method of a cathode active material precursor for a lithium secondary battery {METHOD FOR PREPARING POSITIVE ELECTRODE ACTIVE MATERIAL PRECURSOR FOR LITHIUM SECONDARY BATTERY}

The present invention relates to a method for producing a cathode active material precursor for a secondary battery, and a lithium secondary battery including the same.

As technology development and demand for mobile devices increase, the demand for secondary batteries as an energy source is rapidly increasing. Among these secondary batteries, a lithium secondary battery having a high energy density and voltage, a long cycle life, and a low self-discharge rate has been commercialized and widely used.

A lithium transition metal oxide is used as a cathode active material for a lithium secondary battery, and among them, lithium cobalt oxide of _{LiCoO 2 having a high operating voltage and excellent capacity characteristics was mainly used.} However, LiCoO ₂ has very poor thermal properties due to destabilization of the crystal structure due to lithium removal and is expensive, so there is a limit to mass use as a power source in fields such as electric vehicles.

As a material for replacing LiCoO ₂ , lithium manganese oxide (LiMnO ₂ or LiMn ₂ O _4, etc.), lithium iron phosphate compound (LiFePO ₄ etc.), or lithium nickel oxide (LiNiO ₂ etc.), etc. have been developed. Among them, research and development of lithium nickel oxide, which has a high reversible capacity of about 200 mAh/g, and is easy to implement in a large-capacity battery, is being studied more actively. However, LiNiO ₂ has _{poor thermal stability compared to LiCoO 2 ,} and when an internal short circuit occurs in a charged state due to external pressure or the like, the positive active material itself is decomposed to cause rupture and ignition of the battery.

Accordingly, as a method for improving the low thermal stability while maintaining the excellent reversible capacity of _{LiNiO 2 , LiNi 1 - α} Co _α O ₂ (α=0.1~0.3) in which a part of nickel is substituted with cobalt, or a part of nickel A nickel-cobalt-manganese-based lithium composite metal oxide substituted with Mn and Co (hereinafter simply referred to as 'NCM-based lithium oxide') has been developed. In addition, a lithium transition metal oxide having a concentration gradient of a metal composition has also been proposed in order to solve the stability problem due to the elution of metal elements while having excellent output characteristics.

As a method of manufacturing such a cathode active material, a method of preparing a cathode active material precursor using a continuous reactor (CSTR) and a method of preparing a cathode active material precursor using a batch type reactor are typically used. A continuous reactor (CSTR) is a method in which raw materials are input and co-precipitated while simultaneously discharging a precursor formed into particles. .

In general, the continuous reactor (CSTR) method has the advantage of easy control of the metal composition ratio, but since raw material input and product discharge are performed continuously at the same time, the residence time and reaction time of the cathode active material precursors generated in the reactor are reduced. There may be deviations, and accordingly, there is a problem in that the size and composition of the generated particles are also non-uniform.

Therefore, it is easy to control the particle size and tends to adopt a batch method capable of producing a cathode active material precursor having a uniform particle size, but has a uniform particle size distribution even using a batch type reactor. It is difficult to prepare a cathode active material precursor, and there is a problem in that productivity is significantly lowered compared to the continuous reactor (CSTR) method.

Japanese Patent Laid-Open No. 2017-130395

In order to solve the above problems, the first technical problem of the present invention is a method for producing a cathode active material precursor for a lithium secondary battery using a batch reactor, the particle size control is easy, the particle size is uniform, , to provide a method for producing a positive electrode active material precursor that can significantly increase the productivity of the positive electrode active material precursor within a short time.

A second technical object of the present invention is to provide a method of manufacturing a positive active material having a uniform particle size.

In addition, a third technical object of the present invention is to provide a positive electrode and a lithium secondary battery including the positive electrode active material prepared above.

The present invention provides a method for manufacturing a cathode active material precursor for a lithium secondary battery using a manufacturing device in which at least two or more filtration devices, including a first filtration device and a second filtration device, are installed outside a batch-type reactor, continuously introducing a reaction solution including a transition metal-containing solution containing a transition metal cation, an ammonium ion-containing solution, and a basic aqueous solution into a batch reactor; When the batch-type reactor is full, adding the slurry in the reactor to a first filtration device installed outside the reactor; After filtering the slurry fed into the first filtration device, re-introducing the concentrated concentrated slurry into the batch reactor; and, forming a cathode active material precursor through particle growth of the concentrated slurry re-introduced into the batch reactor; and, when clogging of the first filtration device occurs by the concentrated slurry, the Locking the valve connected to the first filtration device, and opening the valve connected to the second filtration device, the slurry in the reactor is introduced into the second filtration device and filtered, to provide a method for producing a cathode active material precursor.

In addition, the present invention provides a method for producing a cathode active material for a lithium secondary battery, comprising the step of mixing the cathode active material precursor prepared by the method for preparing a cathode active material precursor for a lithium secondary battery with a lithium-containing raw material and then calcining.

In addition, the present invention provides a positive electrode for a lithium secondary battery and a lithium secondary battery comprising the positive electrode active material manufactured by the method for producing the positive electrode active material.

According to the present invention, it is possible to produce a positive electrode active material precursor for a lithium secondary battery having a uniform particle size and easier particle size control than when manufacturing in a conventional batch method, and the conventional batch method It is possible to significantly increase the productivity of the positive electrode active material by solving the problem of low productivity, which was a disadvantage of the

In addition, by installing at least two or more filtration devices outside the batch-type reactor, even if clogging of the filtration devices occurs in the process of generating, filtering, and concentrating the cathode active material precursor, a flexible response is possible.

1 is a view schematically showing an apparatus for manufacturing a cathode active material precursor according to Example 1. Referring to FIG.
2 is a view schematically showing an apparatus for manufacturing a cathode active material precursor according to Example 2. Referring to FIG.

Hereinafter, the present invention will be described in more detail.

The terms or words used in the present specification and claims should not be construed as being limited to their ordinary or dictionary meanings, and the inventor may properly define the concept of the term in order to best describe his invention. It should be interpreted as meaning and concept consistent with the technical idea of the present invention based on the principle that there is.

Method for producing a cathode active material precursor

In the method of manufacturing a cathode active material precursor for a lithium secondary battery by using a manufacturing device installed outside the batch-type reactor, wherein at least two or more filtration devices, including a first filtration device and a second filtration device, are installed, the batch-type reactor continuously adding a reaction solution including a transition metal-containing solution containing a transition metal cation, an ammonium ion-containing solution, and a basic aqueous solution; When the batch-type reactor is full, adding the slurry in the reactor to a first filtration device installed outside the reactor; After filtering the slurry fed into the first filtration device, re-introducing the concentrated concentrated slurry into the batch reactor; And, the concentrated slurry re-introduced into the batch reactor to form a cathode active material precursor through particle growth; is prepared, including, and the clogging of the first filtration device by the concentrated slurry occurs , by closing the valve connected to the first filtration device and opening the valve connected to the second filtration device, the slurry in the reactor is introduced into the second filtration device and filtered.

Hereinafter, each step will be described in more detail.

First, a reaction comprising a transition metal-containing solution containing a transition metal cation, an ammonium ion-containing solution, and a basic aqueous solution in a batch reactor in which at least two or more filtering devices, including the first and second filtering devices, are installed outside The solution is added continuously.

According to the present invention, as the cathode active material precursor is prepared using a batch reactor, the reaction conditions such as the concentration, temperature, and residence time of the reactants in the reactor are the same as compared to the continuous reactor (CSTR), so a relatively uniform product without deviation is produced can do.

In addition, as the apparatus for preparing the cathode active material precursor according to the present invention includes at least two or more filtration devices outside the batch-type reactor, as shown in FIG. 1 , when the cathode active material precursor is prepared, the When the clogging phenomenon of the first filtration device occurs, the input of the slurry into the first filtration device may be stopped, and the slurry may be introduced into another filtration device (second filtration device) to proceed with filtration, , during filtration using the second filtration device, the clogging of the first filtration device in which the clogging occurred can be resolved through backwashing and acid washing, thereby preventing a decrease in the filtration flow rate and producing more in a short time. It is possible not only to manufacture many positive electrode active material precursor particles, but also to quickly respond to process problems such as filter clogging.

The transition metal-containing solution may contain a cation of at least one transition metal selected from the group consisting of nickel, cobalt and manganese.

The transition metal-containing solution may include acetate, nitrate, sulfate, halide, sulfide, hydroxide, oxide or oxyhydroxide of the transition metals, and is not particularly limited as long as it is soluble in water.

For example, the cobalt (Co) is Co(OH) ₂ , CoOOH, Co(OCOCH ₃ ) ₂ ·4H ₂ O, Co(NO ₃ ) ₂ ·6H ₂ O or Co(SO ₄ ) ₂ ·7H ₂ O and the like, and any one or a mixture of two or more thereof may be used.

In addition, the nickel (Ni) is Ni(OH) ₂ , NiO, NiOOH, NiCO ₃ ·2Ni(OH) ₂ ·4H ₂ O, NiC ₂ O ₂ ·2H ₂ O, Ni(NO ₃ ) ₂ ·6H ₂ O , NiSO ₄ , NiSO ₄ ·6H ₂ O, and may be included as a fatty acid nickel salt or nickel halide, and any one or a mixture of two or more thereof may be used.

In addition, the manganese (Mn) is manganese oxide such as _{Mn 2} O ₃ , MnO ₂ , and Mn ₃ O _{4 ;} manganese salts such as MnCO ₃ , Mn(NO ₃ ) ₂ , MnSO ₄ , manganese acetate, dicarboxylic acid manganese salts, manganese citrate and fatty acid manganese salts; Oxy hydroxide, and manganese chloride may be included, and any one or a mixture of two or more thereof may be used.

In addition, when the finally prepared precursor further includes another metal element (M) in addition to nickel (Ni), manganese (Mn) and cobalt (Co) (for example, M is W, Mo, Cr, Al, Zr, Any one or two or more elements selected from the group consisting of Ti, Mg, Ta and Nb) and the transition metal-containing solution may be optionally further added to the metal element (M)-containing raw material.

Examples of the metal element (M)-containing raw material include acetate, nitrate, sulfate, halide, sulfide, hydroxide, oxide or oxyhydroxide containing the metal element (M). A mixture of the above may be used. For example, when M is W, tungsten oxide or the like may be used.

The basic aqueous solution may include at least one selected from the group consisting of NaOH, KOH, Ca(OH) ₂ , and the solvent is water or an organic solvent that can be uniformly mixed with water (specifically, alcohol, etc.) and Mixtures of water may be used. At this time, the concentration of the basic aqueous solution may be 2M to 10M, preferably 2.5M to 3.5M. When the concentration of the basic aqueous solution is 2M to 10M, precursor particles having a uniform size may be formed, the formation time of the precursor particles may be fast, and the yield may also be excellent.

The ammonium ion-containing solution may include at least one selected from the group consisting _{of NH 4} OH, (NH ₄ ) ₂ SO ₄ , NH ₄ NO ₃ , NH ₄ Cl, CH ₃ COONH ₄ , and NH ₄ CO _{3 .} there is. As the solvent, water or a mixture of water and an organic solvent uniformly miscible with water (specifically, alcohol, etc.) and water may be used.

Forming the positive electrode active material precursor particles, by adjusting the amount of the basic aqueous solution and the ammonium ion-containing solution to co-precipitate at pH 9 to pH 13 to form particle nuclei, after generating the nuclei, the basic aqueous solution and ammonium ion It may be carried out including the step of growing the particles by adjusting the amount of the solution containing the co-precipitation reaction at pH 7 to pH 12.

That is, at the beginning of the reaction, a basic aqueous solution and an ammonium ion-containing solution are first added to have a pH in the range of 9 to pH 13, and thereafter, particle nuclei can be generated while introducing a transition metal-containing solution into the reactor. At this time, since the pH value changes as the particle nuclei are generated by the input of the transition metal-containing solution, the basic aqueous solution and the ammonium ion-containing solution are continuously added together with the introduction of the transition metal-containing solution to maintain pH 9 to pH 13 can do. When the above pH value range is satisfied, the generation of particle nuclei occurs preferentially, and the growth of the particle may hardly occur.

After completing the particle nucleation, the amount of the basic aqueous solution and the ammonium ion-containing solution may be adjusted to be in the range of pH 7 to pH 12, and the generated particle nuclei may be grown while the transition metal-containing solution is added. At this time, similarly, since the pH value changes as the particles grow by the addition of the transition metal-containing solution, the aqueous alkali solution and the ammonium ion-containing solution are continuously added together with the transition metal-containing solution to maintain pH 7 to pH 12. can do. When the range of the pH value is satisfied, new particle nuclei are hardly generated, and particle growth may occur preferentially.

Meanwhile, as the transition metal-containing solution, a first transition metal-containing solution containing at least one transition metal cation selected from the group consisting of nickel, cobalt and manganese and at least one or more selected from the group consisting of nickel, cobalt and manganese A precursor having a concentration gradient in the transition metal composition in the particles may be prepared by using a solution containing a cation of a transition metal but having a concentration different from that of the solution containing the first transition metal.

While gradually changing the mixing ratio of the first transition metal-containing solution and the second transition metal-containing solution, the first transition metal-containing solution and the second transition metal-containing solution are mixed to gradually remove the transition metal from the center of the particle to the surface. It may be to form positive electrode active material precursor particles having a concentration gradient.

Specifically, the preparation of the precursor having a concentration gradient in the transition metal composition in the particles may be prepared using the cathode active material precursor preparation apparatus shown in FIG. 2 , for example, the first transition metal-containing solution , the second transition metal-containing solution, the ammonium ion-containing solution, and the basic aqueous solution may be individually introduced into the reactor, or some or all solutions may be pre-mixed before the reactor input and then introduced into the reactor. For example, the first transition metal-containing solution and the second transition metal-containing solution are mixed using a static mixer, etc. and then introduced into the reactor, and the ammonium ion-containing solution and the basic aqueous solution are directly introduced into the reactor. The reaction solution can be added to

The introduction rate of the reaction solution including the transition metal-containing solution, the ammonium ion-containing solution and the basic aqueous solution into the batch reactor may satisfy Equation 1 below.

[Equation 1]

1.5 x V/t ≤ υ ₁ +υ ₂ +υ ₃ ≤ 10 x V/t

In Equation 1, V is the volume of the batch reactor, t is the total reaction time (min), υ ₁ is the input flow rate of the transition metal-containing solution (mL/min), υ ₂ is the input flow rate of the ammonium ion-containing solution (mL) /min), and v ₃ is the input flow rate (mL/min) of the basic aqueous solution.

Specifically, when the reaction solution including the transition metal-containing solution, the ammonium ion-containing solution and the basic aqueous solution is introduced into the batch reactor at an input rate satisfying Equation 1, it is about 1.5 times the time it takes to fill the reactor in the past. The reactor can be full within 10 times faster, and more cathode active material precursor particle nuclei can be generated in a short time in a reactor of the same size.

If the input rate of the reaction solution is slower than the range of Equation 1, productivity may be reduced, and if it is faster than the range of Equation 1, stable particle nucleation may not occur and particle size distribution control may be difficult.

Then, when the batch reactor is full, the slurry in the reactor is introduced into a first filtration device installed outside the reactor.

When the reactor is full, it means that the volume of the inputted reaction solutions occupies 90% to 100% of the total volume of the reactor.

The rate at which the slurry in the reactor is fed into the first filtration device installed outside the reactor may be the same as or slower than the rate at which the reaction solution is fed. For example, when the rate at which the reaction solution is fed into the reactor is the same as the rate at which the slurry is fed into the first filtration device, the reactor water level is maintained to increase the productivity of the cathode active material precursor. For example, when the input rate of the reaction solution is slower than the rate at which the slurry is introduced into the first filtration device, the reactor water level may be reduced, and when the reactor water level is reduced, a lower limit is set up to a specific water level, When the lower limit is reached, the filtration device does not filter the reactants, and only circulation to the reactor can occur. On the other hand, when the rate at which the reaction solution is fed into the reactor is faster than the rate at which the slurry is fed into the first filtration device, the continuous reaction may not be possible due to an increase in the water level of the reactor.

The slurry introduced into the first filtration device is separated into a reaction mother liquid that has passed through the filter unit and a concentrated slurry that has not passed through the filter unit, of which the reaction mother liquid is introduced into a back washing tank, and the concentrated slurry is Using the reaction mother liquid stored in the back washing tank, it is reintroduced into the batch reactor.

More specifically, the concentrated slurry that has not passed through the filter unit remains in the first filtering device. By driving a back washing pump connected to the back washing tank to backwash the reaction mother liquid stored in the back washing tank to the filtering device, the concentrated slurry may be re-injected into the reactor. As the precursor particles stuck in the filter unit are also re-injected into the reactor by the back washing, the clogging phenomenon of the filter unit is also eliminated.

On the other hand, in addition to the first filtration device and the second filtration device, a plurality of filtration devices may be additionally provided depending on the usage or the size of the cathode active material precursor preparation device.

Specifically, when a clogging phenomenon occurs in the filter part of the first filtration device by the concentrated slurry, the batch reactor and the valve connected to the first filtration device are closed, and the batch reactor and the second filtration device are closed. By opening a valve connected to the device, the slurry in the reactor may be introduced into the second filtering device and filtered. At the same time, the clogging phenomenon of the first filtration device can be eliminated by backwashing the reaction mother liquid stored in the back washing tank with the clogging filtration device, thereby eliminating the clogging of the filter unit of the first filtration device.

In addition, after the back washing, it may further include performing acid washing of the first filtration device. For example, the acid washing is performed using an aqueous solution containing nitric acid, so that the precursor particles that are not removed by the back washing can be completely removed from the filtration device.

In addition, even if the clogging phenomenon of the second filtration device connected to the batch reactor occurs, by the reverse operation to the above, the valve connected to the second filtration device is closed, and the clogging phenomenon is eliminated in the first filtration device or the additional filtration device. After opening the connected valve and introducing the slurry in the reactor into an additional filtration device in which the clogging phenomenon is resolved or the clogging phenomenon does not occur, the clogging phenomenon of the second filtration device in which the clogging phenomenon occurs simultaneously with filtration may be resolved.

Therefore, even if the filter part of the filtration device is clogged, the rate at which the slurry in the reactor is fed into the filtration device installed outside the reactor can be maintained without dropping, and thus more positive electrode active material precursor particles can be produced within a short time. Flexible responses to process problems such as filter clogging are possible.

The first filtering device and/or the second filtering device may include any one of a metal filter and a ceramic filter. As described above, when a filter made of a metal material or a ceramic material is used, the flow rate passing through the filter medium relative to the same surface area is greater than that of the filter cloth, and thus the filtration efficiency may be excellent. In addition, the filter made of a metal material or a filter made of a ceramic material has acid resistance, which is advantageous in cleaning and regenerating the filter through acid treatment.

Finally, the concentrated slurry reintroduced into the batch reactor undergoes particle growth to form a cathode active material precursor.

As described above, by re-injecting the concentrated slurry into the reactor, the cathode active material precursor particles can be further grown, the productivity can be improved by increasing the solid content per the same reactor, and the particle size can be controlled and the precursor particles with a uniform particle size are produced. can do.

Meanwhile, the filtration device may use at least one of a filtration unit and a cross-flow filter unit including a filter unit therein.

For example, when a cross flow filtration unit is used as the filtration device, the slurry continuously flows through the filtration device and the reaction mother liquid is continuously extracted, so that the clogging of the filter part of the filtration device is reduced and concentration is continuously and stably can be done

Method for manufacturing a cathode active material

In addition, according to the present invention, the positive electrode active material precursor prepared by the above method may be mixed with a lithium-containing raw material and fired to prepare a positive electrode active material.

The lithium-containing raw material is not particularly limited as long as it is a compound containing a lithium source, but preferably lithium carbonate (Li ₂ CO ₃ ), lithium hydroxide (LiOH), LiNO ₃ , CH ₃ COOLi and Li ₂ (COO) At least one selected from the group consisting of _{2 may be used.}

The cathode active material precursor and the lithium-containing raw material may be mixed in a molar ratio of 1:0.8 to 1:1.5. When the lithium-containing raw material is mixed below the above range, there is a risk that the capacity of the produced cathode active material is reduced, and when the lithium-containing raw material is mixed in excess of the above range, the particles are sintered during the firing process, making it difficult to manufacture the cathode active material It may be difficult, and separation of the positive active material particles may occur after capacity reduction and firing.

The firing may be performed at a temperature of 600°C to 1,000°C. When the calcination temperature is less than 600° C., the raw material remains in the particles due to insufficient reaction, which may reduce the high-temperature stability of the battery, and the bulk density and crystallinity may decrease, resulting in poor structural stability. On the other hand, when the sintering temperature exceeds 1,000° C., non-uniform growth of particles may occur, and since the particle size becomes too large, the amount of particles that can be included per unit area is reduced, and thus the volumetric capacity of the battery may be reduced. Meanwhile, in consideration of particle size control, capacity, stability, and reduction of lithium-containing by-products of the prepared positive active material, the sintering temperature may be more preferably 700°C to 900°C.

The calcination may be performed for 5 to 50 hours. If the calcination time is less than 5 hours, the reaction time may be too short to obtain a highly crystalline positive active material, and if it exceeds 50 hours, the particle size may become excessively large, and production efficiency may be reduced.

anode

In addition, there is provided a positive electrode for a lithium secondary battery comprising the positive electrode active material according to the present invention. Specifically, the positive electrode for a secondary battery includes a positive electrode current collector, a positive electrode active material layer formed on the positive electrode current collector, and the positive electrode active material layer includes the positive electrode active material according to the present invention. It provides a positive electrode for a lithium secondary battery.

At this time, since the positive active material is the same as described above, a detailed description will be omitted, and only the remaining components will be described in detail below.

The positive electrode current collector is not particularly limited as long as it has conductivity without causing chemical change in the battery, and for example, stainless steel, aluminum, nickel, titanium, fired carbon, or carbon, nickel, titanium on the surface of aluminum or stainless steel. , silver or the like surface-treated may be used. In addition, the positive electrode current collector may typically have a thickness of 3 to 500 μm, and may increase the adhesion of the positive electrode active material by forming fine irregularities on the surface of the current collector. For example, it may be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, a non-woven body, and the like.

The positive active material layer may optionally include a binder along with the positive active material, a conductive material, and if necessary.

In this case, the positive active material may be included in an amount of 80 to 99% by weight, more specifically, 85 to 98.5% by weight based on the total weight of the positive active material layer. When included in the above content range, it can exhibit excellent capacity characteristics.

The conductive material is used to impart conductivity to the electrode, and in the configured battery, it can be used without any particular limitation as long as it has electronic conductivity without causing chemical change. Specific examples include graphite such as natural graphite and artificial graphite; carbon-based materials such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, summer black, and carbon fiber; metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive whiskeys such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and the like, and one type alone or a mixture of two or more types thereof may be used. The conductive material may be included in an amount of 0.1 to 15% by weight based on the total weight of the positive active material layer.

The binder serves to improve adhesion between the positive active material particles and the adhesion between the positive active material and the current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylalcohol, polyacrylonitrile, carboxymethylcellulose Woods (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluororubber, or various copolymers thereof, and any one of them or a mixture of two or more thereof may be used. The binder may be included in an amount of 0.1 to 15% by weight based on the total weight of the positive active material layer.

The positive electrode may be manufactured according to a conventional positive electrode manufacturing method except for using the above positive electrode active material. Specifically, the cathode active material and, optionally, a composition for forming a cathode active material layer prepared by dissolving or dispersing a binder and a conductive material in a solvent may be coated on a cathode current collector, and then dried and rolled.

The solvent may be a solvent commonly used in the art, dimethyl sulfoxide (DMSO), isopropyl alcohol (isopropyl alcohol), N-methylpyrrolidone (NMP), acetone (acetone) or water and the like, and any one of them or a mixture of two or more thereof may be used. The amount of the solvent used is enough to dissolve or disperse the positive electrode active material, the conductive material and the binder in consideration of the application thickness of the slurry and the production yield, and to have a viscosity capable of exhibiting excellent thickness uniformity during application for the production of the positive electrode thereafter. do.

Also, as another method, the positive electrode may be prepared by casting the composition for forming the positive electrode active material layer on a separate support, and then laminating a film obtained by peeling from the support on the positive electrode current collector.

lithium secondary battery

In addition, the present invention can manufacture an electrochemical device including the positive electrode. The electrochemical device may specifically be a battery, a capacitor, or the like, and more specifically, a lithium secondary battery.

The lithium secondary battery specifically includes a positive electrode, a negative electrode positioned to face the positive electrode, and a separator and an electrolyte interposed between the positive electrode and the negative electrode, and the positive electrode is the same as described above, so detailed description is omitted, Hereinafter, only the remaining components will be described in detail.

In addition, the lithium secondary battery may optionally further include a battery container for accommodating the electrode assembly of the positive electrode, the negative electrode, and the separator, and a sealing member for sealing the battery container.

In the lithium secondary battery, the negative electrode includes a negative electrode current collector and a negative electrode active material layer positioned on the negative electrode current collector.

The negative electrode current collector is not particularly limited as long as it has high conductivity without causing chemical change in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, sintered carbon, copper or stainless steel surface. Carbon, nickel, titanium, one surface-treated with silver, an aluminum-cadmium alloy, etc. may be used. In addition, the negative electrode current collector may have a thickness of typically 3 μm to 500 μm, and similarly to the positive electrode current collector, fine irregularities may be formed on the surface of the current collector to strengthen the bonding force of the negative electrode active material. For example, it may be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam body, a nonwoven body, and the like.

The anode active material layer optionally includes a binder and a conductive material together with the anode active material.

As the anode active material, a compound capable of reversible intercalation and deintercalation of lithium may be used. Specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metal compounds capable of alloying with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloy, Sn alloy, or Al alloy; metal oxides capable of doping and dedoping lithium, such as SiOβ (0 < β < 2), SnO _{2 , vanadium oxide, and lithium vanadium oxide;} Alternatively, a composite including the above-mentioned metallic compound and a carbonaceous material such as a Si-C composite or a Sn-C composite may be used, and any one or a mixture of two or more thereof may be used. In addition, a metal lithium thin film may be used as the negative electrode active material. In addition, as the carbon material, both low crystalline carbon and high crystalline carbon may be used. As low crystalline carbon, soft carbon and hard carbon are representative, and as high crystalline carbon, natural or artificial graphite of amorphous, plate-like, flaky, spherical or fibrous shape, and Kish graphite (Kish) graphite), pyrolytic carbon, mesophase pitch based carbon fiber, meso-carbon microbeads, liquid crystal pitches (Mesophase pitches), and petroleum and coal tar pitch (petroleum or coal tar pitch) High-temperature calcined carbon such as derived cokes) is a representative example.

The anode active material may be included in an amount of 80 wt% to 99 wt% based on the total weight of the anode active material layer.

The binder is a component that assists in bonding between the conductive material, the active material, and the current collector, and is typically added in an amount of 0.1 wt% to 10 wt% based on the total weight of the anode active material layer. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoro roethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluororubber, and various copolymers thereof.

The conductive material is a component for further improving the conductivity of the anode active material, and may be added in an amount of 10 wt% or less, preferably 5 wt% or less, based on the total weight of the anode active material layer. Such a conductive material is not particularly limited as long as it has conductivity without causing a chemical change in the battery. For example, graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fibers and metal fibers; metal powders such as carbon fluoride, aluminum, and nickel powder; conductive whiskeys such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; A conductive material such as a polyphenylene derivative may be used.

For example, the anode active material layer is prepared by applying and drying a composition for forming an anode active material layer prepared by dissolving or dispersing a cathode active material, and optionally a binder and a conductive material in a solvent, on the anode current collector and drying, or the anode active material layer It can be prepared by casting the composition for forming an active material layer on a separate support, and then laminating a film obtained by peeling it off from the support on a negative electrode current collector.

The anode active material layer is, as an example, a composition for forming an anode active material layer prepared by dissolving or dispersing an anode active material, and optionally a binder and a conductive material in a solvent on an anode current collector and drying, or for forming the anode active material layer It can also be prepared by casting the composition onto a separate support and then laminating a film obtained by peeling it from the support onto a negative electrode current collector.

On the other hand, in the lithium secondary battery, the separator separates the negative electrode and the positive electrode and provides a passage for lithium ions to move, and as long as it is used as a separator in a lithium secondary battery, it can be used without any particular limitation, especially for the movement of ions in the electrolyte It is preferable to have a low resistance to and excellent electrolyte moisture content. Specifically, a porous polymer film, for example, a porous polymer film made of a polyolefin-based polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene/butene copolymer, an ethylene/hexene copolymer, and an ethylene/methacrylate copolymer, or these A laminate structure of two or more layers of may be used. In addition, a conventional porous nonwoven fabric, for example, a nonwoven fabric made of high melting point glass fiber, polyethylene terephthalate fiber, etc. may be used. In addition, in order to secure heat resistance or mechanical strength, a coated separator containing a ceramic component or a polymer material may be used, and may optionally be used in a single-layer or multi-layer structure.

In addition, examples of the electrolyte used in the present invention include organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in the manufacture of lithium secondary batteries, and are limited to these. it's not going to be

Specifically, the electrolyte may include an organic solvent and a lithium salt.

The organic solvent may be used without particular limitation as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, as the organic solvent, ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, ε-caprolactone; ether-based solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon-based solvents such as benzene and fluorobenzene; dimethylcarbonate (DMC), diethylcarbonate (DEC), methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), propylene carbonate, carbonate-based solvents such as PC); alcohol solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (R is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and may contain a double bond aromatic ring or ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; Or sulfolanes and the like may be used. Among them, a carbonate-based solvent is preferable, and a cyclic carbonate (eg, ethylene carbonate or propylene carbonate, etc.) having high ionic conductivity and high dielectric constant capable of increasing the charge/discharge performance of the battery, and a low-viscosity linear carbonate-based compound ( For example, a mixture of ethyl methyl carbonate, dimethyl carbonate or diethyl carbonate) is more preferable. In this case, when the cyclic carbonate and the chain carbonate are mixed in a volume ratio of about 1:1 to about 1:9, the electrolyte may exhibit excellent performance.

The lithium salt may be used without particular limitation as long as it is a compound capable of providing lithium ions used in a lithium secondary battery. Specifically, the lithium salt is LiPF ₆ , LiClO ₄ , LiAsF ₆ , LiBF ₄ , LiSbF ₆ , LiAl0 ₄ , LiAlCl ₄ , LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , LiN(C ₂ F ₅ SO ₃ ) ₂ , LiN(C ₂ F ₅ SO ₂ ) ₂ , LiN(CF ₃ SO ₂ ) _{2 .} LiCl, LiI, or LiB(C ₂ O ₄ ) ₂ and the like may be used. The concentration of the lithium salt is preferably used within the range of 0.1 to 2.0M. When the concentration of the lithium salt is included in the above range, the electrolyte may exhibit excellent electrolyte performance because it has appropriate conductivity and viscosity, and lithium ions may move effectively.

In addition to the electrolyte components, the electrolyte includes, for example, haloalkylene carbonate-based compounds such as difluoroethylene carbonate, pyridine, tri Ethyl phosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivative, sulfur, quinone imine dye, N-substituted oxazolidinone, N,N-substituted imida One or more additives such as jolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxy ethanol or aluminum trichloride may be further included. In this case, the additive may be included in an amount of 0.1 to 5% by weight based on the total weight of the electrolyte.

As described above, since the lithium secondary battery including the positive active material according to the present invention stably exhibits excellent discharge capacity, output characteristics and lifespan characteristics, portable devices such as mobile phones, notebook computers, digital cameras, and hybrid electric vehicles ( It is useful in the field of electric vehicles such as hybrid electric vehicle, HEV).

Accordingly, according to another embodiment of the present invention, a battery module including the lithium secondary battery as a unit cell and a battery pack including the same are provided.

The battery module or battery pack is a power tool (Power Tool); electric vehicles, including electric vehicles (EVs), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEVs); Alternatively, it may be used as a power source for any one or more medium and large-sized devices in a system for power storage.

The external shape of the lithium secondary battery of the present invention is not particularly limited, but may be a cylindrical shape using a can, a prismatic shape, a pouch type, or a coin type.

The lithium secondary battery according to the present invention may not only be used in a battery cell used as a power source for a small device, but may also be preferably used as a unit cell in a medium or large-sized battery module including a plurality of battery cells.

Hereinafter, examples are given in order to describe the present invention in detail. However, the embodiments according to the present invention may be modified in various other forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. The embodiments of the present invention are provided to more completely explain the present invention to those of ordinary skill in the art.

Example

Example One

NiSO ₄ , CoSO ₄ , MnSO ₄ Nickel: cobalt: manganese in an amount such that the molar ratio of 8:1:1 was mixed in water to prepare a solution containing a transition metal of 2.3M concentration.

As shown in FIG. 1, a vessel containing the transition metal-containing solution, an aqueous NaOH solution having a concentration of 25% by weight and an aqueous solution of NH ₄ OH having a concentration of 15% by weight were prepared and connected to a reactor 250L, respectively.

After putting 57L of deionized water into the reactor, nitrogen gas was purged into the reactor at a rate of 45L/min to remove dissolved oxygen in the water, and a non-oxidizing atmosphere was created in the reactor. Thereafter, 150 mL of a 50% by weight aqueous solution of NaOH and _{4,000 mL of a 15% by weight aqueous solution of NH 4} OH were added, followed by stirring at 50° C. at a stirring speed of 350 rpm, so that the pH in the reactor was maintained at pH 11.9.

Thereafter, the transition metal-containing solution was added at a rate of 240 mL/min, an aqueous NaOH solution of 140 mL/min, and an _{aqueous NH 4} OH solution of 20 mL/min at a rate of 20 mL/min, and reacted for 30 minutes. Particles of nickel cobalt-manganese composite metal hydroxide at pH 11.9 nucleus was formed. Then, the transition metal-containing solution was added at a rate of 240 mL/min, an aqueous NaOH solution of 140 _{mL/min, and an aqueous NH 4} OH solution of 35 mL/min at a rate of 35 mL/min, respectively, to induce the growth of nickel cobalt-manganese composite metal hydroxide particles at pH 11.4. Then, the reaction was maintained for 7 hours to grow the particles, and the reactor (250L) was full.

When the reactor (250L) is full, the input amount of the reaction raw materials is maintained, but the slurry in which the reaction is completed in the reactor is discharged to the first filtration device installed outside the reactor. At this time, the discharge rate of the slurry was the same as the input rate of the reaction raw materials. The slurry introduced into the first filtration device is separated into a reaction mother liquid that has passed through the filter unit and a concentrated slurry that has not passed through the filter unit, of which the reaction mother liquid is transferred to a back washing tank connected to the filter unit, and the concentrated slurry is It was reintroduced into the reactor. At this time, by driving a back washing pump connected to the back washing tank, and feeding the reaction mother liquid stored in the back washing tank to the filtering device at 400 mL/min, the concentrated slurry remaining in the filtering device is backwashed to the reactor was reintroduced at a rate of 400 mL/min, and the reaction was maintained for a total of 60 hours to form a cathode active material precursor. When a clogging phenomenon of the first filtration device occurs during the reaction, the valve connecting the reactor and the first filtration device is closed, and the valve connecting the reactor and the second filtration device is opened, so that the slurry in the reactor is installed outside the reactor. It was put into the second filtration device, and the first filtration device was back washed to eliminate clogging of the filter unit. When the clogging of the second filtration device occurs during the reaction, the valve of the second filtration device is closed in the same manner as above, the valve of the first filtration device is opened, and the slurry in the reactor is introduced into the first filtration device. The operation was performed in the same manner whenever clogging occurred during the reaction.

comparative example One

NiSO ₄ , CoSO ₄ , MnSO _{4 In} an amount such that the molar ratio of nickel:cobalt:manganese is 8:1:1, a 2.3M-concentrated transition metal-containing solution mixed in water is 240mL/min, and an aqueous NaOH solution is 140mL/min. , NH ₄ OH aqueous solution was added to each reactor at a rate of 20 mL/min and reacted for 30 minutes to form particle nuclei of nickel cobalt-manganese composite metal hydroxide at pH 11.9. Thereafter, the transition metal-containing solution was added at a rate of 240 mL/min, an aqueous NaOH solution of 140 mL/min, and an aqueous NH ₄ OH solution at a rate of 35 mL/min, respectively, to induce the growth of nickel cobalt-manganese composite metal hydroxide particles at pH 11.4. Then, the reaction was maintained for 7 hours to grow the particles, and the reactor (250L) was full.

A cathode active material precursor was prepared in the same manner as in Example 1, except that the reaction was terminated by stopping the input of the solutions when the reactor became full.

comparative example 2

NiSO ₄ , CoSO ₄ , MnSO _{4 In} an amount such that the molar ratio of nickel:cobalt:manganese is 8:1:1, 240 mL/min of a 2.3M transition metal-containing solution mixed in water, and 140mL/min of an aqueous NaOH solution Min, NH ₄ OH aqueous solution was added to the reactor at a rate of 20 mL/min, respectively, and reacted for 30 minutes to form particle nuclei of nickel-cobalt-manganese composite metal hydroxide at pH 11.9.

Then, at pH 11.4, the transition metal-containing solution was _{introduced at a rate of 240 mL/min, an aqueous NaOH solution of 140 mL/min, and an aqueous NH 4} OH solution of 35 mL/min at a rate of 35 mL/min to induce the growth of nickel cobalt-manganese composite metal hydroxide particles. Then, the reaction was maintained for 7 hours to grow the particles, and the reactor (250L) was full.

When the reactor is full, the introduction of the transition metal-containing solution, the NaOH aqueous solution and the NH ₄ OH aqueous solution is stopped, the stirring is stopped and the product is precipitated by standing still, and the supernatant is discharged to the outside.

_{After discharging the supernatant, 1,000 mL of an aqueous solution of NH 4} OH having a concentration of 15% by weight was added to have a pH of 11.45. Afterwards, the transition metal-containing solution was added at a rate of 240 mL/min, an aqueous NaOH solution of 140 _{mL/min, and an aqueous NH 4} OH solution at a rate of 35 mL/min, respectively, while maintaining the pH of 11.4, inducing the growth of nickel-cobalt-manganese-based composite metal hydroxide particles did. After removing the supernatant, the particle growth process was repeated three times in total, and the particles of the nickel-manganese-cobalt-based composite metal-containing hydroxide formed as a result were separated, washed with water, and dried in an oven at 130° C. for Ni _0.8 Co _0.1 Mn _0.1 (OH) ₂ precursors were prepared.

comparative example 3

The cathode active material precursor was manufactured using a manufacturing device in which only one filtration device was installed outside the batch reactor. When the batch reactor was full, the reaction slurry was discharged to the filtration device, concentrated and reintroduced into the filtration device. did. A cathode active material precursor was prepared in the same manner as in Example 1, except that the discharge rate of the slurry and the rate of input of the reaction raw material into the reactor decreased as time passed.

Experimental example 1: Confirmation of yield of positive electrode active material precursor

In order to compare the productivity of the positive electrode active material precursors prepared in Example 1 and Comparative Examples 1 and 2, the content of the precursors prepared in Examples 1 and 1 and 2 was measured, and the results are shown in Table 1 below. It was.

Produced precursor content (kg) Conventional (Comparative Example 1) standard yield improvement ratio (%) Example 1 165 825 Comparative Example 1 20 Ref. Comparative Example 2 80 400

As shown in Table 1, compared to the case where the reaction is terminated when the reactor is full as in Comparative Example 1, even when the reactor is full, the reaction raw material is discharged while discharging the reaction solution to the outside using a filtration device. In the case of Example 1, which was continuously added, it was confirmed that the yield of the cathode active material precursor was significantly improved even though a batch reactor of the same size was used for the same time.

On the other hand, in the case of Comparative Example 2, when the reactor is full, the product is precipitated and the supernatant is discharged to the outside, and then the reaction raw material is added to the reactor to grow the cathode active material precursor particles, and compared to Comparative Example 1, the cathode active material The yield of the precursor was improved. However, since the input of the reaction raw material is stopped during precipitation and discharging of the supernatant, as in the present invention, when the positive electrode active material slurry in which the reaction has been continuously completed is discharged to the filtration device installed outside the reactor as in the present invention, and the reaction raw material is introduced into the reactor at the same time In comparison, the yield of the cathode active material precursor was low.

Experimental example 2: Check particle size distribution

In order to confirm the particle size distribution of the positive electrode active material precursor prepared in Example 1 and Comparative Examples 1 and 2, the positive electrode active material precursor produced in Example 1 and Comparative Examples 1 and 2 using a Horiba LA 950V2 particle size analyzer. The particle size was measured, and the results are shown in Table 2 below.

D ₁₀ (μm) D ₅₀ (μm) D ₉₀ (μm) (D ₉₀ -D ₁₀ )/D ₅₀ Example 1 12.10 14.40 16.79 0.3256 Comparative Example 1 6.11 9.24 13.51 0.8009 Comparative Example 2 12.56 14.43 16.71 0.2876

Referring to Table 2, according to an embodiment of the present invention, the input rate of the reaction raw material is increased, and when the reactor is full, the positive electrode active material slurry in which the reaction is completed is discharged to a filtration device installed outside and concentrated, and then the concentrated slurry is transferred to the reactor In the case of Example 1, in which particle growth was performed by re-injection, it was confirmed that a more uniform precursor was produced by showing a narrower particle size distribution compared to Comparative Example 1.

10: first filtration device
20: second filtration device
30: back washing tank
100: reactor
110: static mixer

Claims (14)

In the method of manufacturing a cathode active material precursor for a lithium secondary battery using a manufacturing device in which at least two or more filtration devices, including a first filtration device and a second filtration device, are installed outside a batch-type reactor,
continuously introducing a reaction solution including a transition metal-containing solution containing a transition metal cation, an ammonium ion-containing solution, and a basic aqueous solution into the batch reactor;
When the batch-type reactor is full, adding the slurry in the reactor to a first filtration device installed outside the reactor;
After filtering the slurry fed into the first filtration device, re-introducing the concentrated concentrated slurry into the batch reactor; and,
The concentrated slurry reintroduced into the batch reactor is subjected to particle growth to form a cathode active material precursor;
When a clogging phenomenon of the first filtration device occurs by the concentrated slurry, the valve connected to the first filtration device is closed, and the valve connected to the second filtration device is opened, so that the slurry in the reactor is filtered through the second filtration A method of producing a positive electrode active material precursor, which is put into an apparatus and filtered.
According to claim 1,
The input rate of the transition metal-containing solution, the ammonium ion-containing solution, and the basic aqueous solution satisfies the following Equation 1, a method for producing a cathode active material precursor:
[Equation 1]
1.5 x V/t ≤ υ ₁ +υ ₂ +υ ₃ ≤ 10 x V/t
In Equation 1 above,
V is the volume of the batch reactor, t is the total reaction time (min), υ ₁ is the input flow rate of the transition metal-containing solution (mL/min), υ ₂ is the input flow rate of the ammonium ion-containing solution (mL/min), and υ ₃ is the input flow rate (mL/min) of the basic aqueous solution.
According to claim 1,
The transition metal-containing solution includes a cation of at least one transition metal selected from the group consisting of nickel, cobalt, and manganese, a method for producing a positive electrode active material precursor.
According to claim 1,
The transition metal-containing solution includes a first transition metal-containing solution containing a cation of at least one transition metal selected from the group consisting of nickel, cobalt and manganese, and at least one transition selected from the group consisting of nickel, cobalt and manganese A method of manufacturing a positive electrode active material precursor, further comprising a second transition metal-containing solution containing a metal cation but having a different concentration from the first transition metal-containing solution.
5. The method of claim 4,
Positive active material precursor particles having a transition metal concentration gradient by mixing the first transition metal-containing solution and the second transition metal-containing solution while gradually changing the mixing ratio of the first transition metal-containing solution and the second transition metal-containing solution Further comprising forming a, a method for producing a positive electrode active material precursor.
According to claim 1,
The filtration device will include any one of a filter made of a metal material or a filter made of a ceramic material, the method of manufacturing a positive electrode active material precursor.
According to claim 1,
Re-injection of the concentrated slurry into the batch reactor is that the reaction mother liquid that has passed through the filter unit among the slurry introduced into the first filtration device is introduced into a back washing tank, and the slurry introduced into the first filtration device The method for producing a cathode active material precursor, wherein the concentrated slurry that does not pass through the heavy filter unit is re-injected into the batch reactor using the reaction mother liquid stored in a back washing tank.
8. The method of claim 7,
The step of re-injecting the concentrated slurry into the batch-type reactor using the reaction mother liquid stored in the back washing tank may include driving a back washing pump connected to the back washing tank to drive the reaction mother liquid stored in the back washing tank. The method for producing a positive electrode active material precursor, which is carried out by back washing (back washing) to the filtration device.
8. The method of claim 7,
The clogging phenomenon of the filtration device is to be resolved by back washing the reaction mother liquid stored in the back washing tank with the filtration device, the method for producing a cathode active material precursor.
10. The method of claim 9,
After the back washing, the method of manufacturing a cathode active material precursor further comprising performing acid washing.
According to claim 1,
The filtration device further comprises a cross-flow filter unit (cross-flow filter unit), the method for producing a cathode active material precursor.
11. A method of manufacturing a cathode active material for a lithium secondary battery, comprising the step of mixing the cathode active material precursor prepared according to any one of claims 1 to 10 with a lithium-containing raw material and then calcining.
A positive electrode for a lithium secondary battery comprising a positive electrode active material manufactured by the method according to claim 11 .
A lithium secondary battery comprising the positive electrode for a lithium secondary battery according to claim 13 .

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