KR20230135847A - Method for preparing positive electrode active material precursor for lithium secondary battery - Google Patents

Abstract

The present invention relates to a method for manufacturing a cathode active material precursor using a production device in which a continuous reactor and a batch reactor are connected through a transfer pipe. The purpose of the present invention is to provide the method for manufacturing the cathode active material precursor that significantly has improved productivity while manufacturing a doped or coated positive electrode active material precursor.

Description

Method for manufacturing cathode active material precursor for lithium secondary battery {METHOD FOR PREPARING POSITIVE ELECTRODE ACTIVE MATERIAL PRECURSOR FOR LITHIUM SECONDARY BATTERY}

The present invention relates to a method of producing a positive electrode active material precursor using a production device in which a continuous reactor and a batch reactor are connected through a transfer pipe.

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, lithium secondary batteries, which have high energy density and voltage, long cycle life, and low self-discharge rate, have been commercialized and are widely used.

Lithium transition metal oxide is used as a positive electrode active material for lithium secondary batteries, and among these, lithium cobalt oxide of LiCoO ₂ , which has a high operating voltage and excellent capacity characteristics, is mainly used. However, LiCoO ₂ has very poor thermal properties due to destabilization of the crystal structure due to delithiation, and because it is expensive, there are limits to its mass use as a power source in fields such as electric vehicles.

As materials to replace 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.) have been developed. Among these, research and development on lithium nickel oxide, which has a high reversible capacity of about 200 mAh/g and makes it easy to implement large-capacity batteries, is being studied more actively. However, LiNiO ₂ has poor thermal stability compared to LiCoO ₂ , and if an internal short circuit occurs due to external pressure during charging, the positive electrode active material itself decomposes, resulting in rupture and ignition of the battery.

Accordingly, as a method to improve 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 part of the nickel is replaced with cobalt or part of the nickel is replaced with cobalt. A nickel-cobalt-manganese-based lithium composite metal oxide substituted with Mn and Co (hereinafter simply referred to as 'NCM-based lithium oxide') was developed. In addition, a lithium transition metal oxide with a concentration gradient of metal composition was also proposed to solve stability problems caused by elution of metal elements while providing excellent output characteristics.

Typical methods for producing such a positive electrode active material include a method of producing a positive electrode active material precursor using a continuous reactor (CSTR) and a method of producing the positive electrode active material precursor using a batch reactor. The continuous reactor (CSTR) is a method of injecting raw materials to co-precipitate and simultaneously discharging precursors formed into particles, while the batch type is a method of reacting by inputting raw materials according to the volume of the reactor for a certain period of time and discharging the precursors after the reaction is completed. .

In general, the continuous reactor (CSTR) method has the advantage of easy control of the metal composition ratio, but since the input of raw materials and discharge of the product occur simultaneously and continuously, the residence time and reaction time of the positive electrode active material precursors generated within the reactor are affected. There may be deviations, and as a result, there is a problem of non-uniformity in the size and composition of the generated particles. In addition, even if it was attempted to further perform a post-treatment process of doping or coating the positive electrode active material precursor, it was difficult to introduce the doping or coating process in a continuous reactor because there was no concept of the reaction end point when the production of the positive active material precursor was completed.

Accordingly, there is a tendency to adopt a batch method, which is easy to control the particle size and can produce a positive electrode active material precursor with a uniform particle size. However, even if a batch reactor is used, the positive electrode active material precursor with a uniform particle size distribution can be produced. There was a problem in manufacturing, and productivity was significantly reduced compared to the continuous reactor (CSTR) method.

Japanese Patent Publication No. 2017-130395

The purpose of the present invention is to provide a method for manufacturing a positive electrode active material precursor that significantly improves productivity while manufacturing a doped or coated positive electrode active material precursor.

In order to solve the above problem, the present invention relates to a method for producing a positive electrode active material precursor using a production device in which a continuous reactor and a batch reactor are connected through a transfer pipe, (S1) a transition metal-containing solution and a basic aqueous solution in the continuous reactor. and preparing a reaction slurry containing a positive electrode active material precursor by adding a solution containing ammonium ions and carrying out a coprecipitation reaction. (S2) transferring the reaction slurry to a batch reactor through a transfer pipe; And (S3) At the point when the transferred reaction slurry occupies more than 70% by volume of the batch reactor, the transfer pipe is closed, and the doping raw material or coating raw material is added to the batch reactor to dope or coat the positive electrode active material precursor in the reaction slurry. It provides a method for producing a positive electrode active material precursor, including the step of:

According to the present invention, the problem of not being able to manufacture a doped or coated positive electrode active material precursor when using an existing continuous process can be solved, and at the same time, the productivity of the positive electrode active material precursor manufacturing method can be significantly increased.

Figure 1 is a diagram schematically showing a method of manufacturing a positive electrode active material precursor according to Example 1.
Figure 2 is an SEM image of the positive electrode active material precursor prepared in Example 1.
Figure 3 is an SEM image of the positive electrode active material precursor prepared in Comparative Example 1.
Figure 4 is an SEM image of the positive electrode active material precursor prepared in Comparative Example 2.
Figure 5 is an SEM image of the positive electrode active material precursor prepared in Comparative Example 3.
Figure 6 is a graph showing the particle size distribution of the positive electrode active material precursor prepared in Example 1.

Hereinafter, the present invention will be described in more detail to facilitate understanding of the present invention.

Terms or words used in the description and claims of the present invention should not be construed as limited to their usual or dictionary meanings, and the inventor appropriately defines the concept of terms in order to explain his or her invention in the best way. Based on the principle that it can be done, it must be interpreted with a meaning and concept consistent with the technical idea of the present invention.

Manufacturing method of positive electrode active material precursor

The method for producing a positive electrode active material precursor of the present invention uses a production device in which a continuous reactor and a batch reactor are connected through a transfer pipe, and (S1) a transition metal-containing solution, a basic aqueous solution, and an ammonium ion-containing solution are added to the continuous reactor. preparing a reaction slurry containing a positive electrode active material precursor by subjecting it to a coprecipitation reaction; (S2) transferring the reaction slurry to a batch reactor through a transfer pipe; And (S3) At the point when the transferred reaction slurry occupies more than 70% by volume of the batch reactor, the transfer pipe is closed, and the doping raw material or coating raw material is added to the batch reactor to dope or coat the positive electrode active material precursor in the reaction slurry. It is characterized in that it includes a step of doing.

Hereinafter, each step will be described in detail.

Step (S1)

The manufacturing method of the present invention uses a manufacturing apparatus in which a continuous reactor and a batch reactor are connected through transfer pipes. The transfer pipe may be equipped with a device, such as a valve, that opens or closes the transfer pipe to control the movement of materials between the continuous reactor and the batch reactor.

1 is a diagram schematically showing a method of manufacturing a positive electrode active material precursor according to an embodiment of the present invention.

Referring to FIG. 1, a transition metal-containing solution, a basic aqueous solution, and an ammonium ion-containing solution are added to a continuous reactor 100 and subjected to coprecipitation reaction to prepare a reaction slurry containing a positive electrode active material precursor. At the start of step (S1), the transfer pipe 10 connecting the continuous reactor 100 and the batch reactor 200 is closed.

In the manufacturing method of the present invention, a coprecipitation reaction for producing a positive electrode active material precursor is performed using the continuous reactor 100, and thus the high productivity and efficiency of the continuous reactor 100 can be realized.

The transition metal-containing solution, basic aqueous solution, and ammonium ion-containing solution may be continuously supplied to the reactor through an inlet provided in the continuous reactor 100. They are mixed inside the continuous reactor 100 to form a reaction solution, and positive electrode active material precursor particles are formed through a coprecipitation reaction of the reaction solution.

The transition metal-containing solution may include cations 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 metal, and is not particularly limited as long as it is soluble in water.

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, fatty acid nickel salt, nickel halide, etc., and any one or a mixture of two or more of these may be used.

The cobalt (Co) may be included as Co(OH) ₂ , CoOOH, Co(OCOCH ₃ ) ₂ ㆍ4H ₂ O, Co(NO ₃ ) ₂ ㆍ6H ₂ O or Co(SO ₄ ) ₂ ㆍ7H ₂ O, etc. Any one or a mixture of two or more of these may be used.

The manganese (Mn) includes manganese oxides 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 salt, manganese citrate and fatty acid manganese salt; It may include oxyhydroxide, manganese chloride, etc., and any one or a mixture of two or more of these may be used.

If the final manufactured positive electrode active material precursor further contains another metal element (M) in addition to nickel (Ni), manganese (Mn), and cobalt (Co) (for example, M is W, Mo, Cr, Al, Zr, One or two or more elements selected from the group consisting of Ti, Mg, Ta, and Nb), and raw materials containing the metal element (M) may be optionally further added when preparing the transition metal-containing solution.

The raw materials containing the metal element (M) include acetate, nitrate, sulfate, halide, sulfide, hydroxide, oxide, or oxyhydroxide containing the metal element (M), one or two of these. Mixtures of the above may be used. For example, when M is W, tungsten oxide, etc. may be used.

For example, when the transition metal-containing solution contains cations of nickel, cobalt, and manganese, the transition metal-containing solution mixes nickel-containing raw materials, cobalt-containing raw materials, and manganese-containing raw materials with a solvent, specifically water, or water. It is manufactured by adding to a mixed solvent of organic solvents (for example, alcohol, etc.) that can be mixed uniformly, or by mixing an aqueous solution of a nickel-containing raw material, an aqueous solution of a cobalt-containing raw material, and a manganese-containing raw material. You can.

The basic aqueous solution may include at least one selected from the group consisting of alkali metal hydrate, alkali metal hydroxide, alkaline earth metal hydrate, and alkaline earth metal hydroxide. For example, it may include at least one selected from the group consisting of NaOH, KOH, and Ca(OH) ₂ , and the solvent may be water, or a mixture of water and an organic solvent (specifically, alcohol, etc.) that is uniformly miscible with water. This can be used. At this time, the concentration of the basic aqueous solution may be 2M to 10M, preferably 2.5M to 3.5M, but is not limited thereto. When the concentration of the basic aqueous solution is 2M to 10M, precursor particles of uniform size can be formed, the formation time of the precursor particles is fast, and the yield can 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. The solvent may be water or a mixture of water and an organic solvent (specifically, alcohol, etc.) that is uniformly miscible with water.

In the present invention, producing a positive electrode active material precursor through a coprecipitation reaction may be performed under pH 11 to 13, specifically pH 12 to 13, and more specifically pH 12.5 to 13.0.

Meanwhile, the coprecipitation reaction may be performed at a temperature of 40°C to 70°C in an inert atmosphere such as nitrogen or argon, but is not limited thereto.

In the present invention, the coprecipitation reaction may be performed for 10 hours or more, specifically 10.5 to 13.5 hours, or 11 to 13 hours. That is, the residence time of the materials in the continuous reactor 100 may be within the above range. When the time required for the coprecipitation reaction is within the above range, there is an advantage in that a positive electrode active material precursor with uniform physical properties can be manufactured by introducing the reaction material into the continuous reactor 100 at an appropriate rate.

Step (S2)

The reaction slurry prepared in step (S1) is transferred to the batch reactor 200 through the transfer pipe 10.

Here, the time at which the reaction slurry containing the positive electrode active material precursor prepared by coprecipitation reaction in the continuous reactor 100 is transferred to the batch reactor 200 through the transfer pipe 10 is when the continuous reactor 100 is full. It may be time. That the continuous reactor 100 is full may mean that the volume of the solutions added in step (S1) is 95 to 100% of the volume of the continuous reactor 100.

When producing the positive electrode active material precursor through the continuous reactor 100 as in step (S1), there is an advantage in maximizing productivity because there is no reaction end point, but particle uniformity is reduced and the positive active material precursor continuously escapes. Therefore, it is difficult to change the composition or perform additional post-treatment processes such as doping and coating as needed.

In the manufacturing method of the present invention, in order to effectively dope or coat the positive electrode active material precursor with high productivity in step (S1), the positive electrode active material precursor prepared in the continuous reactor 100 is transferred to the batch reactor 200. It is transported to perform a doping or coating process.

The positive electrode active material precursor is transferred from the continuous reactor 100 to the batch reactor 200 using a transfer pipe 10 connecting the continuous reactor 100 and the batch reactor 200 and a pump located externally. It can be performed by running, but is not limited to this.

Step (S3)

At the point when the reaction slurry transferred in step (S2) occupies more than 70% by volume of the batch reactor 200, the transfer pipe 10 is closed, and the doping raw material or coating raw material is introduced into the batch reactor 200. Doping or coating the positive electrode active material precursor in the reaction slurry.

Specifically, the transfer pipe 10 may be closed when the reaction slurry transferred in step (S2) occupies more than 70 vol% or more than 80 vol% of the batch reactor 200.

When the transfer piping 10 is closed to stop the transfer from the continuous reactor 100 to the batch reactor 200 within the above range, self-nucleus generation in the batch reactor 200 is prevented to perform the doping or coating process. This is performed smoothly and a positive electrode active material precursor with a uniform particle size distribution can be finally obtained.

In the manufacturing method of the present invention, as the positive electrode active material precursor is doped or coated using the batch reactor 200, reactants and products are continuously discharged when only the continuous reactor is used, so after doping or coating the positive electrode active material precursor The problem that the treatment process could not be performed was solved.

In addition, because the reaction conditions such as concentration, temperature, and residence time of the reactants in the batch reactor 200 are the same, a uniform product can be obtained without any change in the physical properties of the positive electrode active material precursor other than changes due to the intended doping or coating. there is.

The doping raw material is a material that supplies a doping element to be doped inside the positive electrode active material precursor.

The doping raw material may include at least one doping element selected from the group consisting of Al, Mg, Co, V, Ti, Zr, and W, preferably Co, and is obtained by doping the positive electrode active material precursor with the above-mentioned doping element. The structural and thermal stability improvement effects of the final manufactured positive electrode active material are further improved.

The doping raw material may be manufactured by adding a doping element or an alkoxide, salt, or oxide containing a doping element to a volatile organic solvent or water solvent, but is not limited thereto.

Examples of alkoxides containing the doping elements include methoxide, ethoxide, and isopropoxide, and representative examples of salts or oxides containing the doping elements include ammonium vanadate (NH ₄ (VO ₃ )). Examples include, but are not limited to, vanadate, nitrate such as Al(NO ₃ ) ₃ , and vanadium oxide (V ₂ O ₅ ).

The volatile organic solvent can dissolve or uniformly disperse the doping element or the doping element-containing raw material, and any solvent can be used as long as it is easily volatilized, and representative examples include methanol, ethanol, propanol, or isopropyl alcohol. Likewise, straight-chain or branched alcohol, ether, methylene carbonate, or acetate having a carbon number of C ₁ to C ₄ may be mentioned. When using water as a solvent, it is preferable to further perform a drying process for a certain period of time, for example, about 24 hours, to remove the solvent.

The doping raw material may include either a homogeneous suspension or a solution, but is not limited thereto.

The coating raw material is a material that supplies coating elements that form a coating layer on part or all of the surface of the positive electrode active material precursor.

The coating raw material may include at least one coating element selected from the group consisting of Al, Mg, Co, Ti, Zr, and B, and preferably at least one coating element selected from the group consisting of Al, Co, and B. It may contain a coating element, and more preferably, it may contain at least one coating element selected from the group consisting of Al and B.

The coating raw material protects the surface of the positive electrode active material precursor and prevents changes in physical properties such as structural collapse.

In the present invention, in order to sufficiently dope or coat the positive electrode active material precursor, the doping or coating in step (S3) may be performed for 6 to 10 hours, specifically 6.5 to 9.5 hours, or 7 to 9 hours. You can.

When the time required for doping or coating is within the above range, the input of the reaction material and the coprecipitation reaction proceed at an appropriate rate in the continuous reactor 100 to produce a positive electrode active material precursor with uniform physical properties, and at the same time, the batch reactor 100 In (200), new nucleation of the positive electrode active material precursor can be prevented and the positive electrode active material precursor transferred from the continuous reactor (100) can be efficiently doped or coated.

In the present invention, the doping or coating of step (S3) may be performed under pH 11 to 12, specifically may be performed under pH 11.2 to 12.0, or may be performed under pH 11.5 to 12.0.

Within the above range, the doping or coating raw material does not generate nuclei on its own and the coprecipitation reaction on the surface of the positive electrode active material precursor transferred from the continuous reactor 100 is active, so that uniform doping or coating is performed. there is.

Step (S4)

The manufacturing method of the present invention may further include transferring the product of step (S3) to the water collection tank 300, opening the transfer pipe 10, and repeating steps (S2) and (S3).

The manufacturing method of the present invention performs the doping or coating process using the batch reactor 200, but the coprecipitation reaction for producing the positive electrode active material precursor uses the continuous reactor 100, so the reactor is operated after discharging all products. Unlike the batch reaction process, which requires resetting and process replacement, it is possible to obtain continuously doped or coated positive electrode active material precursors.

To this end, the product of step (S3) prepared in the batch reactor 200 is transferred to the sump 300, the transfer pipe 10 is opened, and the positive electrode active material precursor prepared in the continuous reactor 100 is transferred to the transfer pipe ( The step (S2) of transferring to the batch reactor 200 through 10) can be started again.

The sump 300 is for receiving the product of step (S3) discharged from the batch reactor 200. The final product can be obtained by separating the doped or coated positive electrode active material precursor from the product transferred to the water collection tank 300, washing it, and drying it.

The positive electrode active material precursor manufactured according to the present invention may have an average particle diameter (D ₅₀ ) of 0.8 to 1.5 ㎛, specifically 1.0 to 1.4 ㎛.

Additionally, the positive electrode active material precursor may have a span value of 1.5 or less according to Equation 1 below. Specifically, it may be 1.4 or less, and more specifically, it may be 1.3 or less. That is, according to the present invention, a positive electrode active material precursor with a uniform particle size can be manufactured.

[Equation 1]

Span = (D ₉₀ -D ₁₀ )/D ₅₀

Manufacturing method of positive electrode active material

In addition, according to the present invention, a positive electrode active material can be manufactured by mixing the positive electrode active material precursor prepared by the above production method with lithium-containing raw material and calcining.

The lithium-containing raw material is not particularly limited as long as it is a compound containing a lithium source, but is 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 can be used.

The positive electrode active material precursor and lithium-containing raw material may be mixed at a molar ratio of 1:0.8 to 1:1.5. If lithium-containing raw materials are mixed below the above range, the capacity of the manufactured positive electrode active material may decrease, and if lithium-containing raw materials are mixed beyond the above range, the particles may be sintered during the firing process, making the production of positive electrode active materials difficult. It may be difficult, and capacity reduction and separation of positive electrode active material particles may occur after firing.

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

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

anode

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

At this time, since the positive electrode active material is the same as described above, 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 is conductive without causing chemical changes in the battery, for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or carbon, nickel, titanium on the surface of aluminum or stainless steel. , surface treated with silver, etc. may be used. Additionally, the positive electrode current collector may typically have a thickness of 3 to 500㎛, and fine irregularities may be formed on the surface of the current collector to increase the adhesion of the positive electrode active material. For example, it can be used in various forms such as films, sheets, foils, nets, porous materials, foams, and non-woven materials.

The positive electrode active material layer may optionally include a conductive material and a binder as needed, along with the positive electrode active material.

At this time, the positive electrode 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 electrode active material layer. When included in the above content range, excellent capacity characteristics can be exhibited.

The conductive material is used to provide conductivity to the electrode, and can be used without particular limitation as long as it does not cause chemical change and has electronic conductivity in the battery being constructed. 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, etc., of which one type alone or a mixture of two or more types 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 electrode active material layer.

The binder serves to improve adhesion between positive electrode active material particles and 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, and carboxymethyl cellulose. Woods (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, Examples include styrene butadiene rubber (SBR), fluorine rubber, and various copolymers thereof, and one type of these may be used alone or a mixture of two or more types 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 electrode active material layer.

The positive electrode can be manufactured according to a conventional positive electrode manufacturing method except for using the positive electrode active material described above. Specifically, the composition for forming a positive electrode active material layer prepared by dissolving or dispersing the above-mentioned positive electrode active material and, optionally, a binder and a conductive material in a solvent may be applied on a positive electrode current collector, followed by drying and rolling.

The solvent may be a solvent commonly used in the art, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or Water, etc. may be used, and one type of these may be used alone or a mixture of two or more types may be used. The amount of solvent used is sufficient to dissolve or disperse the positive electrode active material, conductive material, and binder in consideration of the application thickness and manufacturing yield of the slurry, and to have a viscosity that can exhibit excellent thickness uniformity when applied for subsequent positive electrode production. do.

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

Lithium secondary battery

Additionally, the present invention can manufacture an electrochemical device including the anode. The electrochemical device may specifically be a battery, a capacitor, etc., and more specifically may be a lithium secondary battery.

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

Additionally, the lithium secondary battery may optionally further include a battery container that accommodates the electrode assembly of the positive electrode, negative electrode, and separator, and a sealing member that seals the battery container.

In the lithium secondary battery, the negative electrode includes a negative electrode current collector and a negative electrode active material layer located 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 changes in the battery. For example, it can be used on the surface of copper, stainless steel, aluminum, nickel, titanium, fired carbon, copper or stainless steel. Surface treatment with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. can be used. In addition, the negative electrode current collector may typically have a thickness of 3㎛ to 500㎛, and like 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 can be used in various forms such as films, sheets, foils, nets, porous materials, foams, and non-woven materials.

The negative electrode active material layer optionally includes a binder and a conductive material along with the negative electrode active material.

A compound capable of reversible intercalation and deintercalation of lithium may be used as the negative electrode active material. Specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; Metallic compounds that can be alloyed with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloy, Sn alloy, or Al alloy; Metal oxides that can dope and undope lithium, such as SiOβ (0 < β < 2), SnO ₂ , vanadium oxide, and lithium vanadium oxide; Alternatively, a composite containing the above-described metallic compound and a carbonaceous material, such as a Si-C composite or Sn-C composite, may be used, and any one or a mixture of two or more of these may be used. Additionally, a metallic lithium thin film may be used as the negative electrode active material. Additionally, as the carbon material, both low-crystalline carbon and high-crystalline carbon can be used. Representative examples of low-crystalline carbon include soft carbon and hard carbon, and high-crystalline carbon includes amorphous, plate-shaped, flaky, spherical, or fibrous natural graphite, artificial graphite, and Kish graphite. graphite, pyrolytic carbon, mesophase pitch based carbon fiber, meso-carbon microbeads, mesophase pitches, and petroleum or coal tar pitch. High-temperature calcined carbon such as derived cokes is a representative example.

The negative electrode active material may be included in an amount of 80% by weight to 99% by weight based on the total weight of the negative electrode 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 usually added in an amount of 0.1% to 10% by weight based on the total weight of the negative electrode active material layer. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, and tetrafluoride. Roethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluorine rubber, and various copolymers thereof.

The conductive material is a component to further improve the conductivity of the negative electrode active material, and may be added in an amount of 10% by weight or less, preferably 5% by weight or less, based on the total weight of the negative electrode active material layer. These conductive materials are not particularly limited as long as they have conductivity without causing chemical changes in the battery, and examples include 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 fiber and metal fiber; 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; Conductive materials such as polyphenylene derivatives may be used.

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

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

Meanwhile, in the lithium secondary battery, the separator separates the negative electrode and the positive electrode and provides a passage for lithium ions to move. It can be used without particular restrictions as long as it is normally used as a separator in a lithium secondary battery, especially for the movement of ions in the electrolyte. It is desirable to have low resistance and excellent electrolyte moisturizing ability. Specifically, porous polymer films, for example, porous polymer films made of polyolefin polymers such as ethylene homopolymer, propylene homopolymer, ethylene/butene copolymer, ethylene/hexene copolymer, and ethylene/methacrylate copolymer, or these. A laminated structure of two or more layers may be used. In addition, conventional porous non-woven fabrics, for example, non-woven fabrics made of high melting point glass fibers, polyethylene terephthalate fibers, etc., may be used. In addition, a coated separator containing ceramic components or polymer materials may be used to ensure heat resistance or mechanical strength, and may optionally be used in a single-layer or multi-layer structure.

In addition, electrolytes used in the present invention include organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in the production of lithium secondary batteries, and are limited to these. It doesn't work.

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, the organic solvent includes ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; Ether-based solvents such as dibutyl ether or tetrahydrofuran; Ketone-based solvents such as cyclohexanone; Aromatic hydrocarbon solvents such as benzene and fluorobenzene; Dimethylcarbonate (DMC), diethylcarbonate (DEC), methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), propylene carbonate (propylene carbonate) Carbonate-based solvents such as PC); Alcohol-based solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (R is a straight-chain, branched or ring-structured hydrocarbon group having 2 to 20 carbon atoms and may include a double bond aromatic ring or ether bond); Amides such as dimethylformamide; Dioxolanes such as 1,3-dioxolane; Alternatively, sulfolane, etc. may be used. Among these, carbonate-based solvents are preferable, and cyclic carbonates (e.g., ethylene carbonate or propylene carbonate, etc.) with high ionic conductivity and high dielectric constant that can improve the charge/discharge performance of the battery, and low-viscosity linear carbonate-based compounds ( For example, ethylmethyl carbonate, dimethyl carbonate, diethyl carbonate, etc.) are more preferable. In this case, excellent electrolyte performance can be obtained by mixing cyclic carbonate and chain carbonate in a volume ratio of about 1:1 to about 1:9.

The lithium salt can be used without particular restrictions as long as it is a compound that can provide lithium ions used in lithium secondary batteries. 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 etc. 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 lithium salt is within the above range, the electrolyte has appropriate conductivity and viscosity, so excellent electrolyte performance can be achieved and lithium ions can move effectively.

In addition to the electrolyte components, the electrolyte includes, for example, haloalkylene carbonate-based compounds such as difluoroethylene carbonate, pyridine, and trifluoroethylene for the purpose of improving battery life characteristics, suppressing battery capacity reduction, and improving battery discharge capacity. Ethyl phosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, hexanoic acid triamide, nitrobenzene derivative, sulfur, quinone imine dye, N-substituted oxazolidinone, N,N-substituted imida. One or more additives such as zolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxy ethanol, or aluminum trichloride may be further included. At this time, 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, the lithium secondary battery containing the positive electrode active material according to the present invention stably exhibits excellent discharge capacity, output characteristics, and lifespan characteristics, and is therefore widely used in portable devices such as mobile phones, laptop computers, digital cameras, and hybrid electric vehicles ( It is useful in electric vehicle fields 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; Electric vehicles, including electric vehicles (EV), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEV); Alternatively, it can be used as a power source for any one or more mid- to large-sized devices among power storage systems.

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 square shape, a pouch shape, or a coin shape.

The lithium secondary battery according to the present invention can not only be used in battery cells used as a power source for small devices, but can also be preferably used as a unit cell in medium to large-sized battery modules containing a plurality of battery cells.

Hereinafter, the present invention will be described in detail with reference to examples. However, the embodiments according to the present invention may be modified into various other forms, and the scope of the present invention should not be construed as being limited to the embodiments described in detail below. Examples of the present invention are provided to more completely explain the present invention to those with average knowledge in the art.

Example

Hereinafter, the present invention will be described in more detail through examples. However, the following examples are for illustrative purposes only and do not limit the scope of the present invention.

Example 1

A transition metal aqueous solution was prepared by mixing NiSO ₄ , CoSO ₄ , and MnSO ₄ in water in an amount such that the molar ratio of nickel:cobalt:manganese was 95.5:3.5:1. In addition, a doping raw material containing CoSO ₄ at a concentration of 2.4M was prepared.

As shown in Figure 1, the transition metal aqueous solution, NaOH aqueous solution, and NH ₄ OH aqueous solution were prepared and connected to a continuous reactor corresponding to a total reactor volume of 10 L through a reaction solution input line.

After adding 2.6 L of deionized water to the continuous reactor, nitrogen gas was purged into the reactor at a rate of 1 L/min to remove dissolved oxygen in the water, and a non-oxidizing atmosphere was created in the reactor. Afterwards, 13.8 mL of a 25% by weight NaOH aqueous solution and 134.3mL of a 9% by weight aqueous NH ₄ OH solution were added, and then stirred at 50°C at a stirring speed of 150 rpm to maintain the pH in the reactor at pH 12.5-13.0. .

Thereafter, the transition metal-containing solution was added to the continuous reactor at a rate of 490 mL/hour, the NaOH aqueous solution at 290 mL/hour, and the NH ₄ OH aqueous solution at a rate of 46 mL/hour, and reacted for more than 10 hours to grow particles of nickel cobalt manganese hydroxide. and continued until the continuous reactor was full.

When the continuous reactor was full, the transfer pipe connected to the batch reactor was opened to transfer nickel cobalt manganese hydroxide to the batch reactor. Afterwards, when the transferred nickel cobalt manganese hydroxide accounted for 83% of the volume of the batch reactor, the transfer pipe was closed. In the batch reactor, use an aqueous NaOH solution and an aqueous NH ₄ OH solution to maintain the pH inside the batch reactor at 11.6 to 12.0, then add the doping raw material prepared above, and dope while staying in the batch reactor for 6 to 10 hours. The reaction proceeded. In the batch reactor, the Co-doped positive electrode active material precursor was transferred to a sump, and the transfer pipe was reopened to repeat the previous process to obtain a Co-doped positive active material precursor.

Comparative Example 1

A transition metal aqueous solution was prepared by mixing NiSO ₄ , CoSO ₄ , and MnSO ₄ in water in an amount such that the molar ratio of nickel:cobalt:manganese was 95.5:3.5:1. In addition, a doping raw material containing CoSO ₄ at a concentration of 2.4M was prepared.

The transition metal aqueous solution, NaOH aqueous solution, and NH ₄ OH aqueous solution were prepared and connected through a reaction solution input line to a continuous reactor corresponding to a total reactor volume of 10 L, respectively.

After adding 2.6 L of deionized water to the continuous reactor, nitrogen gas was purged into the reactor at a rate of 1 L/min to remove dissolved oxygen in the water, and a non-oxidizing atmosphere was created in the reactor. Afterwards, 13.8 mL of a 25 wt% NaOH aqueous solution and 134.3 mL of a 9 wt% aqueous NH ₄ OH solution were added, and then stirred at 50°C at a stirring speed of 150 rpm to maintain the pH in the reactor at pH 12.5-13.0. .

Thereafter, the transition metal-containing solution was added to the continuous reactor at a rate of 490 mL/hour, the NaOH aqueous solution at 290 mL/hour, and the NH ₄ OH aqueous solution at a rate of 46 mL/hour, and reacted for more than 10 hours to grow particles of nickel cobalt manganese hydroxide. and continued until the continuous reactor was full.

When the continuous reactor was full, the overflow tube was opened to obtain nickel cobalt manganese hydroxide. In addition, from that point on, the inside of the continuous reactor was maintained at pH 11.6 to 12.0 using an aqueous NaOH solution and an aqueous NH ₄ OH solution, then the doping raw material prepared above was added, and the doping material was kept in the continuous reactor for 6 to 10 hours. A doping reaction was performed.

Comparative Example 2

A transition metal aqueous solution was prepared by mixing NiSO ₄ , CoSO ₄ , and MnSO ₄ in water in an amount such that the molar ratio of nickel:cobalt:manganese was 95.5:3.5:1. In addition, a doping raw material containing CoSO ₄ at a concentration of 2.4M was prepared.

The transition metal aqueous solution, NaOH aqueous solution, and NH ₄ OH aqueous solution were prepared and connected to a batch reactor corresponding to a total reactor volume of 10 L through a reaction solution input line.

After adding 2.6 L of deionized water to the batch reactor, nitrogen gas was purged into the reactor at a rate of 1 L/min to remove dissolved oxygen in the water and create a non-oxidizing atmosphere in the reactor. Afterwards, 13.8 mL of a 25 wt% NaOH aqueous solution and 134.3 mL of a 9 wt% aqueous NH ₄ OH solution were added, and then stirred at 50°C at a stirring speed of 150 rpm to maintain the pH in the reactor at pH 12.5-13.0. .

Afterwards, the transition metal-containing solution was added to the batch reactor at a rate of 490 mL/hour, the NaOH aqueous solution at 290 mL/hour, and the NH ₄ OH aqueous solution at a rate of 46 mL/hour, and reacted for 8 hours to grow particles of nickel cobalt manganese hydroxide. After 8 hours, the inside of the batch reactor was maintained at pH 11.6 to 12.0 using an aqueous NaOH solution and an aqueous NH ₄ OH solution, and then the doping raw material prepared above was added and kept in the batch reactor for 6 to 10 hours. A doping reaction was performed. Finally, a Co-doped precursor was obtained on the surface of nickel cobalt manganese hydroxide.

Comparative Example 3

A transition metal aqueous solution was prepared by mixing NiSO ₄ , CoSO ₄ , and MnSO ₄ in water in an amount such that the molar ratio of nickel:cobalt:manganese was 95.5:3.5:1. In addition, a doping raw material containing CoSO ₄ at a concentration of 2.4M was prepared.

As a reactor, the device shown in FIG. 1 was used in the same manner as in Example 1. The transition metal aqueous solution, NaOH aqueous solution, and NH ₄ OH aqueous solution were prepared and connected through a reaction solution input line to a continuous reactor corresponding to a total reactor volume of 10 L, respectively.

After adding 2.6 L of deionized water to the continuous reactor, nitrogen gas was purged into the reactor at a rate of 1 L/min to remove dissolved oxygen in the water, and a non-oxidizing atmosphere was created in the reactor. Afterwards, 13.8 mL of a 25 wt% NaOH aqueous solution and 134.3 mL of a 9 wt% aqueous NH ₄ OH solution were added, and then stirred at 50°C at a stirring speed of 150 rpm to maintain the pH in the reactor at pH 12.5-13.0. .

Thereafter, the transition metal-containing solution was added to the continuous reactor at a rate of 490 mL/hour, the NaOH aqueous solution at 290 mL/hour, and the NH ₄ OH aqueous solution at a rate of 46 mL/hour, and reacted for more than 10 hours to grow particles of nickel cobalt manganese hydroxide. and continued until the continuous reactor was full.

When the continuous reactor was full, the transfer pipe connected to the batch reactor was opened to transfer nickel cobalt manganese hydroxide to the batch reactor. Afterwards, when the transferred nickel cobalt manganese hydroxide took up 60% of the volume of the batch reactor, the transfer pipe was closed. The doping raw materials prepared above were added to the batch reactor, and the inside of the batch reactor was maintained at pH 11.6~12.0 using NaOH aqueous solution and NH ₄ OH aqueous solution, and the doping reaction was carried out while staying in the batch reactor for 6~10 hours. proceeded. In the batch reactor, the Co-doped positive electrode active material precursor was transferred to a sump, and the transfer pipe was reopened to repeat the previous process to obtain a Co-doped positive active material precursor.

Experimental Example 1

For Example 1, the positive electrode active material precursor of the nickel cobalt manganese hydroxide prepared in a continuous reactor and the Co-doped nickel cobalt manganese hydroxide finally obtained in a batch reactor were compared, and were placed without changing the physical properties of the positive electrode active material precursor itself. In the formula reactor, it was confirmed that only the intended doping reaction proceeded effectively.

(1) SEM image

The surface properties of the positive electrode active material precursor prepared in Example 1 were confirmed using a scanning electron microscope.

Figure 2 is an SEM image showing the surface characteristics of the positive electrode active material precursor discharged from the continuous reactor and the Co-doped positive electrode active material precursor discharged from the batch reactor, respectively.

(2) Particle size distribution

The particle size of the positive electrode active material precursor was measured using a Microtrac S3500 particle size analyzer.

(3) Tap density

After filling 50 g of the obtained positive electrode active material precursor in a 100 mL container, the apparent density of the obtained particles was measured by vibrating under certain conditions. Specifically, the tab density of the positive electrode active material precursor was measured using a tab density tester (KYT-4000, Seishin). The measurement results are shown in Table 1 below.

NCM composition D ₅₀ (㎛) (D ₉₀ -D ₁₀ )/D ₅₀ Tap Density (g/mL) Obtained in a continuous reactor
(Anode active material precursor) 95.7 / 3.3 / 1.0 1.19 1.01 1.43 Obtained from batch reactor
(Co doped anode active material precursor) 94.7 / 4.3 / 1.0 1.34 1.21 1.39

As shown in Table 1 above, when the manufacturing method of the present invention is followed, nucleation of a new positive electrode active material precursor does not proceed in a batch reactor, but the existing physical properties of the positive electrode active material precursor prepared by coprecipitation reaction in a continuous reactor remain the same. It was confirmed that the Co doping process of the positive electrode active material precursor proceeded efficiently.

Experimental Example 2

The physical properties of the positive electrode active material precursors prepared in Example 1 and Comparative Examples 1 to 3 were confirmed using the same method as Experiment 1.

Nickel-cobalt-manganese composition D ₅₀ (㎛) (D ₉₀ -D ₁₀ )/D ₅₀ Tap Density (g/mL) Example 1 94.7 / 4.3 / 1.0 1.34 1.21 1.39 Comparative Example 1 93.6 / 4.9 / 1.5 1.09 3.10 1.42 Comparative Example 2 94.7 / 4.3 / 1.0 2.01 1.59 1.57 Comparative Example 3 93.5 / 5.5 / 1.0 1.26 1.47 1.22

As shown in the results above, in Example 1, a Co-doped positive electrode active material precursor was obtained, and it was confirmed that the particle size distribution was also uniform (FIG. 2).

On the other hand, in the case of Comparative Example 1, only a continuous reactor was used, but since the composition of the transition metal aqueous solution and the nickel-cobalt-manganese composition of the obtained positive electrode active material precursor were different, Co doping could not proceed in some nickel cobalt manganese hydroxides. In order to perform the doping process in the same continuous reactor where the coprecipitation reaction was performed without transferring nickel cobalt manganese hydroxide, particle agglomeration occurred in the process of changing the pH, resulting in a high value of (D ₉₀ -D ₁₀ )/D ₅₀ . It can be seen that (Figure 3).

In the case of Comparative Example 2, because only a batch reactor was used, not only did productivity decrease, but particle growth inevitably occurred as the positive electrode active material precursor produced in the reactor was concentrated over time (Figure 4). The particle size increased unexpectedly, making it impossible to maintain a particle size of about 1㎛.

In addition, in the case of Comparative Example 3, the transfer pipe was closed and the doping process was started earlier than in Example 1, and the composition of the transition metal aqueous solution and the nickel-cobalt-manganese composition of the obtained positive electrode active material precursor were different, indicating that the doping raw material It can be seen that the material was added in an excessive amount compared to the transferred nickel cobalt manganese hydroxide, so that self-generating nuclei began in addition to the doping process. In addition, as shown in FIG. 5, surface co-precipitation of nickel cobalt manganese hydroxide did not proceed properly due to self-nucleation, resulting in a decrease in sphericity.

100: Continuous reactor
200: batch reactor
300: Sump tank
10: Transfer piping

Claims (9)

In the method of producing a positive electrode active material precursor using a production device in which a continuous reactor and a batch reactor are connected through a transfer pipe,
(S1) preparing a reaction slurry containing a positive electrode active material precursor by adding a transition metal-containing solution, a basic aqueous solution, and an ammonium ion-containing solution to a continuous reactor and performing a coprecipitation reaction;
(S2) transferring the reaction slurry to a batch reactor through a transfer pipe; and
(S3) At the point when the transferred reaction slurry occupies more than 70% by volume of the batch reactor, the transfer pipe is closed, and the doping raw material or coating raw material is added to the batch reactor to dope or coat the positive electrode active material precursor in the reaction slurry. step;
Method for producing a positive electrode active material precursor, including.
In claim 1,
(S4) transferring the product of step (S3) to a sump, opening the transfer pipe, and repeating steps (S2) and (S3);
A method for producing a positive electrode active material precursor, further comprising:
In claim 1,
A method for producing a positive electrode active material precursor, wherein the coprecipitation reaction in step (S1) is performed for more than 10 hours.
In claim 1,
A method for producing a positive electrode active material precursor, wherein the doping or coating in step (S3) is performed for 6 to 10 hours.
In claim 1,
A method for producing a positive electrode active material precursor, wherein the coprecipitation reaction in step (S1) is performed under pH 11 to 13.
In claim 1,
A method for producing a positive electrode active material precursor, wherein the doping or coating in step (S3) is performed under pH 11 to 12.
In claim 1,
The transition metal-containing solution includes cations of at least one transition metal selected from the group consisting of nickel, cobalt, and manganese.
In claim 1,
The basic aqueous solution includes at least one selected from the group consisting of alkali metal hydrate, alkali metal hydroxide, alkaline earth metal hydrate, and alkaline earth metal hydroxide.
A method of producing a positive electrode active material comprising: mixing the positive electrode active material precursor prepared according to claim 1 with a lithium-containing raw material and then calcining it.

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