Method of manufacturing positive active material for lithium secondary battery and heat treatment device

Abstract

The present invention relates to a method for manufacturing a positive electrode active material for a lithium secondary battery and a heat treatment apparatus for a positive electrode active material. The method for manufacturing a positive electrode active material for a lithium secondary battery comprises a calcination process in which a lithium raw material and a precursor are mixed and calcined. The calcination process comprises a first calcination process and a second calcination process performed at a temperature different from that of the first calcination process, and may include a step of resupplying exhaust gas generated in the second calcination process to the first calcination process.

Description

Technology Field

[0001] The present invention relates to a calcination apparatus, and more specifically, to a method for manufacturing a positive electrode active material for a lithium secondary battery and a heat treatment apparatus. Background Technology

[0002] With the increasing technological development and demand for mobile devices, the demand for secondary batteries as an energy source is rapidly rising. Among secondary batteries, lithium-ion batteries, which exhibit high energy density and operating potential, long cycle life, and low self-discharge rate, have been commercialized and are widely used.

[0003] Furthermore, as interest in environmental issues grows, there is increasing interest in electric vehicles and hybrid electric vehicles that can replace fossil fuel-using vehicles, such as gasoline and diesel vehicles, which are one of the major causes of air pollution; consequently, research is actively underway to use lithium-ion batteries as a power source for the aforementioned electric vehicles and hybrid electric vehicles.

[0004] A lithium secondary battery generally consists of a positive electrode containing a positive active material, a negative electrode containing a negative active material, a separator, and an electrolyte, and charging and discharging are performed through the intercalation and decalation of lithium ions. Since the lithium secondary battery possesses the advantages of high energy density, high electromotive force, and the ability to exhibit high capacity, it is being applied in various fields.

[0005] Regarding the above-mentioned cathode active materials, there is increasing interest in high-nickel (High-Ni) cathode active materials with a high nickel content. To manufacture the above-mentioned cathode active material, a lithium source and a precursor are placed in a calcination vessel, and it is necessary to control a strong oxidation atmosphere with a specific oxygen concentration or higher. To achieve this, it is necessary to continuously supply high-purity oxygen.

[0006] Specifically, as a heat treatment method for manufacturing the above-mentioned positive electrode active material, a powder calcination method is utilized, which is a crystallization process in which the raw material mixture is immediately calcined as a first step; a preliminary calcination method composed of a first step of removing crystal water from the raw material mixture in a low-temperature range within 300 to 500 ℃ and a second step of performing crystallization at the main calcination temperature; and a first and second calcination method is utilized, which is a method in which temporary crystallization is performed on the raw material mixture in a high-temperature range of 700 ℃ or higher, and then additional crystallization is performed at the main calcination temperature.

[0007] The above powder calcination method has problems such as reduced productivity due to the physicochemical characteristics of the raw material mixture and increased oxygen consumption based on production volume. In addition, there is a problem of reduced productivity as the dehydration and crystallization processes are carried out within a single calcination furnace, requiring a long calcination time.

[0008] In addition, the primary and secondary calcination methods are technologies primarily used to increase the productivity of the high-nickel cathode active material, but there is a problem in that oxygen is continuously used in the primary and secondary calcination furnaces, leading to increased oxygen consumption and consequently higher energy costs.

[0009] Therefore, research is actively underway to reduce oxygen consumption in the above-mentioned first and second firing processes and to prevent the problem of increased energy costs through energy recycling. The problem to be solved

[0010] The technical problem that the present invention aims to solve is to provide a method for manufacturing a positive electrode active material for a lithium secondary battery that reduces oxygen consumption and increases energy efficiency during the first and second calcination stages.

[0011] Another technical problem that the present invention aims to solve is to provide a heat treatment apparatus for a positive electrode active material for a lithium secondary battery having the aforementioned advantages. means of solving the problem

[0012] A method for manufacturing a positive electrode active material for a lithium secondary battery according to one embodiment of the present invention comprises a calcination process for mixing a lithium raw material and a precursor and calcining them, wherein the calcination process comprises a first calcination process and a second calcination process performed at a temperature different from that of the first calcination process, and may include a step of resupplying exhaust gas generated in the second calcination process to the first calcination process. In one embodiment, the first calcination process may be performed at a lower temperature than the second calcination process.

[0013] In one embodiment, a heat exchange process for controlling the temperature of the exhaust gas may be included. In one embodiment, the step of resupplying the exhaust gas generated in the second calcination process to the first calcination process may include the step of further supplying CFA (CO2-Free Air).

[0014] In one embodiment, the step of resupplying the exhaust gas generated in the second calcination process to the first calcination process may include the step of further supplying fresh supply gas. In one embodiment, the heat exchange process may include the step of controlling the temperature of the fresh supply gas and the CFA (CO2-Free Air).

[0015] In one embodiment, the heat exchange process may lower the temperature of the exhaust gas and raise the temperature of the new supply gas and the CFA. In one embodiment, in the step of further supplying the CFA, the volume ratio of the CFA gas to the exhaust gas may be 50 volume % or less.

[0016] In one embodiment, the oxygen concentration of the first calcination process may be 59 to 97%, and the oxygen concentration of the second calcination process may be 75 to 97%. In one embodiment, the first calcination process may be performed at a temperature of 500 to 900 ℃.

[0017] In one embodiment, the second calcination process may be performed at a temperature of 650 to 900 ℃. In one embodiment, the oxygen concentration of the exhaust gas may be 75 to 97 volume%.

[0018] According to another embodiment of the present invention, a heat treatment apparatus for manufacturing an anode active material relates to a heat treatment apparatus for manufacturing an anode active material that mixes a lithium raw material and an anode active material precursor and calcines them.

[0019] The apparatus includes a primary calcination furnace for primary calcining a mixture of the lithium raw material and the cathode active material precursor, a secondary calcination furnace for secondary calcining a compound discharged from the primary calcination furnace at a temperature different from that of the primary calcination furnace, and an exhaust pipe connecting a discharge pipe for discharging exhaust gas from the secondary calcination furnace to a supply pipe of the primary calcination furnace, wherein exhaust gas provided from the secondary calcination furnace can be supplied to the primary calcination furnace through the exhaust pipe. In one embodiment, the temperature of the primary calcination furnace may be higher than the temperature of the secondary calcination furnace.

[0020] In one embodiment, the heat treatment apparatus for manufacturing the positive electrode active material further includes a heat exchanger for controlling the temperature of the exhaust gas supplied from the secondary kiln, and the exhaust gas may be supplied to the exhaust pipe through the heat exchanger. In one embodiment, the heat exchanger may lower the temperature of the exhaust gas and raise the temperature of the fresh supply gas and the CFA.

[0021] In one embodiment, the exhaust pipe may receive additional external supply gas. In one embodiment, the external supply gas may include at least one of fresh supply gas and CFA (CO2-Free Air). In one embodiment, the heat exchanger may control the temperature of the exhaust gas to 500°C or lower. In one embodiment, the heat exchanger may control the temperature of the CFA (CO2-Free Air) gas and the fresh supply gas to 500°C or lower. Effects of the invention

[0022] A method for manufacturing a positive electrode active material for a lithium secondary battery according to one embodiment of the present invention provides a method for manufacturing a positive electrode active material for a lithium secondary battery that reduces oxygen consumption and increases energy efficiency in the first and second firing stages by reusing the exhaust gas of the second firing furnace in the first firing furnace.

[0023] A method for manufacturing a positive electrode active material for a lithium secondary battery according to another embodiment of the present invention provides, in addition to the aforementioned advantages, a method for manufacturing a positive electrode active material for a lithium secondary battery that reduces oxygen consumption and increases energy efficiency in the first and second firing stages by reusing the exhaust gas generated during the second firing process as the feed gas for another firing furnace.

[0024] A method for manufacturing a positive electrode active material for a lithium secondary battery according to another embodiment of the present invention provides, in addition to the aforementioned advantages, a method for manufacturing a positive electrode active material for a lithium secondary battery that increases energy efficiency by installing a heat exchanger and converting a certain portion of the primary kiln air supply flow rate into CFA, and directly mixing the low-temperature CFA into the secondary kiln exhaust section for cooling.

[0025] According to another embodiment of the present invention, a heat treatment apparatus provides a method for manufacturing a positive electrode active material for a lithium secondary battery that reduces oxygen consumption and increases energy efficiency in the first and second calcination stages by utilizing a method having the aforementioned advantages. Brief explanation of the drawing

[0026] FIG. 1 relates to a method for manufacturing a positive electrode active material for a lithium secondary battery according to one embodiment of the present invention. FIG. 2 relates to a method for manufacturing a positive electrode active material for a lithium secondary battery according to another embodiment of the present invention. FIG. 3 is a schematic illustration of a two-stage kiln according to one embodiment of the present invention. FIG. 4 is a schematic illustration of a two-stage kiln according to another embodiment of the present invention. Specific details for implementing the invention

[0027] Terms such as first, second, and third are used to describe various parts, components, regions, layers, and / or sections, but are not limited thereto. These terms are used solely to distinguish one part, component, region, layer, or section from another part, component, region, layer, or section. Accordingly, the first part, component, region, layer, or section described below may be referred to as the second part, component, region, layer, or section without departing from the scope of the present invention.

[0028] The technical terms used herein are for the reference of specific embodiments only and are not intended to limit the invention. The singular forms used herein include plural forms unless phrases clearly indicate otherwise. As used in the specification, the meaning of "comprising" specifies certain characteristics, areas, integers, steps, actions, elements, and / or components, and does not exclude the presence or addition of other characteristics, areas, integers, steps, actions, elements, and / or components.

[0029] When it is stated that one part is "on" or "on" another part, it may be directly on or on the other part, or another part may be involved in between. In contrast, when it is stated that one part is "directly on" another part, no other part is interposed in between.

[0030] Unless otherwise defined, all terms used herein, including technical and scientific terms, have the same meaning as generally understood by those skilled in the art to which this invention pertains. Terms defined in commonly used dictionaries are further interpreted to have meanings consistent with relevant technical literature and the present disclosure, and are not interpreted in an ideal or highly formal sense unless otherwise defined.

[0031] Hereinafter, embodiments of the present invention will be described in detail. However, these are presented as examples and are not intended to limit the present invention, and the present invention is defined only by the scope of the claims set forth below.

[0032] FIG. 1 relates to a method for manufacturing a positive electrode active material for a lithium secondary battery according to one embodiment of the present invention.

[0033] Referring to FIG. 1, a method for manufacturing a positive electrode active material for a lithium secondary battery comprises a calcination process in which a lithium raw material and a precursor are mixed and calcined.

[0034] The above mixing process (S10) is a step of mixing a lithium source and a precursor. The lithium source may be a lithium-containing source, such as, for example, lithium carbonate, lithium acetate, lithium nitrate, lithium hydroxide, lithium chloride, or lithium sulfate.

[0035] The above precursor may be a nickel-based transition metal hydroxide or oxide containing nickel. Specifically, the nickel-based transition metal hydroxide or oxide may be prepared by co-precipitating a transition metal-containing solution containing a nickel raw material and a doping raw material that optionally includes Co, Mn, Zr, Al, Mg, Ti, Nb, W, Sc, Si, V, Fe, Y, Mo, Ce, Hf, Ta, La, Sr, or a combination thereof, by adding an ammonia solution and an alkaline aqueous solution such as caustic soda.

[0036] In another embodiment, the precursor may be a transition metal hydroxide or oxide comprising a nickel raw material, a cobalt raw material, and a manganese raw material, optionally a doping raw material comprising Co, Mn, Zr, Al, Mg, Ti, Nb, W, Sc, Si, V, Fe, Y, Mo, Ce, Hf, Ta, La, Sr, or a combination thereof.

[0037] The above nickel salt is not particularly limited as long as it is used in the industry for manufacturing a cathode active material precursor. As a non-limiting example, the above nickel raw material may be a nickel-containing sulfate, acetate, nitrate, halide, sulfide, hydroxide, oxide, or oxyhydroxide, and specifically, may be NiSO4, NiSO4·6H2O, Ni(OH)2, NiO, NiOOH, NiCO3·2Ni(OH)2·4H2O, NiC2O2·2H2O, Ni(NO3)2·6H2O, fatty acid nickel salt, nickel halide, or a combination thereof.

[0038] The above metal salt aqueous solution may further include cobalt salt, manganese salt, aluminum salt, etc., in addition to nickel salt.

[0039] The above cobalt salt may be, as a non-limiting example, a manganese-containing sulfate, acetate, nitrate, halide, sulfide, hydroxide, oxide, oxyhydroxide, or a combination thereof, and specifically, may be a cobalt salt such as CoSO4, CoSO4·7H2O, CoCO3, Co(NO3)2, Co(NO3)2·6H2O, cobalt acetate, cobalt dicarboxylate, cobalt citrate, and fatty acid cobalt salt, cobalt oxide, oxyhydroxide, cobalt chloride, or a combination thereof.

[0040] The above manganese salt may be, as a non-limiting example, a manganese-containing sulfate, acetate, nitrate, halide, sulfide, hydroxide, oxide, oxyhydroxide, or a combination thereof, and specifically, may be a manganese salt such as MnSO4, MnSO4·H2O, MnCO3, Mn(NO3)2, manganese acetate, manganese dicarboxylate, manganese citrate, and manganese fatty acid, manganese oxide such as Mn2O3, MnO2, and Mn3O4, oxyhydroxide, manganese chloride, or a combination thereof.

[0041] The above aluminum salt may be, for example, aluminum sulfate, aluminum nitrate, aluminum chloride, aluminum fluoride, or a combination thereof.

[0042] Nickel-based transition metal hydroxides and oxides can be prepared by mixing the above metal salts. Specifically, nickel-based transition metal hydroxides and oxides can be prepared through the co-precipitation of a combination of metal salts.

[0043] The above pH adjuster may be a caustic soda solution and may include an alkali compound of an alkali metal or alkaline earth metal such as NaOH, KOH, or Ca(OH)2, a hydrate thereof, or a combination thereof. The above caustic soda solution may also be used in the form of an aqueous solution, wherein water or a mixture of water and an organic solvent such as an alcohol that is uniformly miscible with water may be used as the solvent.

[0044] The above ammonia solution may include, as a complex-forming agent, NH3, NH4OH, (NH4)2SO4, NH4NO3, NH4Cl, CH3COONH4, NH4CO3, or combinations thereof, as non-limiting examples. Meanwhile, the above ammonia solution may also be used in the form of an aqueous solution, wherein water or a mixture of water and an organic solvent that is uniformly miscible with water, such as alcohol, may be used as the solvent.

[0045] The mixing process (S10) may obtain a powdered mixture by crushing or breaking down the lithium raw material and the precursor and mixing them. The mixing process (S10) may be a step of breaking up clumps of raw materials such as the lithium raw material and the precursor.

[0046] Precision grinders, such as ball mills, jet mills, or sand mills, may be used as grinders for grinding raw materials. The step of grinding the raw materials may be performed by a dry or wet process. If the step of grinding the raw materials is performed by a wet process, the raw material slurry obtained by the wet process may be aggregated and dried by, for example, a dryer. The dryer may be, for example, a spray dryer, a fluidized bed dryer, or an evaporator.

[0047] Specifically, the nickel-based transition metal hydroxide and oxide may be high-nickel transition metal hydroxide and oxide containing 70% or more nickel as shown in Chemical Formula 1 below. The high-nickel transition metal may refer to a compositional region or higher where the firing atmosphere must be oxygenated during firing.

[0048] The above calcination process includes a first calcination process (S20) and a second calcination process (S30) performed at a temperature different from that of the first calcination process (S20). The calcination process involves a series of low-temperature and high-temperature processes to control the crystallization of the mixture that has undergone the mixing process (S10). Specifically, the first calcination process (S20) may be performed at a temperature different from that of the second calcination process (S30), and the raw material in the mixture state may be controlled into a compound state in the first calcination process (S20), and the semi-finished product in the compound state may be manufactured into a cathode active material in the form of a finished product in the second calcination process (S30).

[0049] Specifically, the first calcination process (S20) is a step of performing temporary crystallization of the mixture that has undergone the mixing process (S10). Specifically, the temporary crystallization is a step of converting a mixture of two or more raw materials mixed in the mixing process (S10) into a single-phase compound, and such processes as increasing the density of the material to be calcined and pre-removing by-products originating from the raw materials are carried out, which can significantly increase the yield and productivity of the final product.

[0050] In one embodiment, the first calcination process (S20) may be performed in a temperature range of 900°C or lower. Specifically, the first calcination process (S20) may be performed in a temperature range of 500°C to 900°C, and more specifically, the first calcination process (S20) may be performed in a temperature range of 725°C to 900°C. Specifically, the temperature of the aforementioned first calcination process (S20) may be different from the temperature of the second calcination process (S30). Specifically, the temperature of the first calcination process (S20) may be higher than the temperature of the second calcination process (S30), and the temperature of the first calcination process (S20) may be lower than the temperature of the second calcination process (S30). In one embodiment, by performing the first calcination process (S20) at a temperature lower than the temperature of the second calcination process (S30), crystallization of the mixture can be easily performed. In another embodiment, if the temperature of the first firing process (S20) is higher than the temperature of the second firing process (S30), the mixture can be single-crystallized.

[0051] If the upper limit of the above temperature range is exceeded, the crystallization of the mixture proceeds excessively, leading to a problem of performance degradation in the final product. If the lower limit of the above temperature is exceeded, crystallization cannot be easily performed due to insufficient heat for the mixture, leading to a problem of performance degradation in the final product.

[0052] In one embodiment, in the first calcination process (S20), the oxygen concentration may be 50 to 99 volume%. Specifically, the oxygen concentration may be 59 to 97 volume%, and more specifically 75 volume% or more. Specifically, by satisfying the aforementioned range of oxygen concentration, there is a manufacturing advantage in the synthesis of high-nickel cathode materials. If the oxygen concentration deviates from the lower limit value, there is a problem in that the stable oxidation of nickel during the calcination process cannot be controlled, resulting in a decrease in performance.

[0053] The second calcination process (S30) is a step in which the compound temporarily crystallized through the first calcination process (S20) is calcined at a second calcination temperature to proceed with additional crystallization. Specifically, the material to be calcined in the form of a compound temporarily crystallized in the first calcination process (S20) may have an unstable structural state, and the crystallization structure can be stabilized through the addition of additional energy in the second calcination process (S30).

[0054] In one embodiment, the second firing process (S30) may be performed in a temperature range of 900 ℃ or lower. Specifically, the second firing process (S30) may be performed in a temperature range of 650 to 900 ℃, and more specifically, the second firing process (S30) may be performed in a temperature range of 690 to 900 ℃.

[0055] If the upper limit of the above temperature range is exceeded, the crystallization of the material to be fired proceeds excessively, resulting in a problem of performance degradation in the final product. If the lower limit of the above temperature is exceeded, crystallization does not proceed properly due to insufficient heat for the material to be fired, resulting in a problem of performance degradation in the final product.

[0056] For example, if the temperature of the first firing process (S20) is 500 to 900 ℃, the temperature of the second firing process (S30) may be 650 to 900 ℃, and if the temperature of the first firing process (S20) is 500 ℃ to 900 ℃, the temperature of the second firing process (S30) may be 900 ℃ or lower. If the temperature of the first firing process (S20) is 900 ℃ or lower, the temperature of the second firing process (S30) may be 650 ℃ or higher. In this case, the temperature of the first firing process (S20) may be maintained higher than the temperature of the second firing process (S30). In another embodiment, the temperature of the first firing process (S20) may be maintained lower than the temperature of the second firing process (S30).

[0057] In one embodiment, in the second calcination process (S30), the oxygen concentration may be 75 to 99 volume%. Specifically, the oxygen concentration may be 75 to 97 volume%, and more specifically 90 volume% or more. If the oxygen concentration exceeds the lower limit value, there is a problem in that the stable oxidation of nickel during the calcination process is not controlled, resulting in a decrease in performance.

[0058] The step of resupplying the exhaust gas generated in the second firing process (S30) to the first firing process (S20) can be performed by supplying the exhaust gas generated from the second firing process (S30) to the first firing process (S20), thereby enabling the reuse of the exhaust gas.

[0059] The exhaust gas is generated from the material to be fired in the second firing process (S30) and has almost no by-products, so the composition and purity of the exhaust gas may be similar to the state of the supply gas introduced into the first firing process (S20).

[0060] The oxygen concentration of the exhaust gas may be 59 to 99 volume%. Specifically, the oxygen concentration may be 75 to 97 volume%. If the oxygen concentration deviates from the lower limit value, there is a problem of performance degradation due to reduced reactivity between lithium and nickel during the calcination process.

[0061] The exhaust gas, in which the oxygen concentration satisfies the aforementioned range, is supplied back to the first calcination process (S20), thereby recycling the gas having an oxygen purity similar to that of the supply gas and reducing the input of oxygen gas during the heat treatment process for manufacturing the cathode active material, so as to increase energy efficiency.

[0062] FIG. 2 relates to a method for manufacturing a positive electrode active material for a lithium secondary battery according to another embodiment of the present invention.

[0063] In one embodiment, the method for manufacturing a positive electrode active material for a lithium secondary battery may further include a heat exchange process (S31), which is a step of controlling the temperature of the gas. The heat exchange process (S31) may be a process of cooling high-temperature exhaust gas containing high-purity oxygen discharged from the second calcination process (S30) to a temperature below a certain level so that it can be directly used in the first calcination process (S20). Specifically, in addition to the cooling effect of controlling the temperature of the gas for direct use in the first calcination process (S20), the heat exchange process (S31) can reduce the energy cost of the calcination furnace by heating the shortfall in the total amount of new supply gas required for the second calcination process (S30) and the supply gas required for the first calcination process (S20).

[0064] In one embodiment, the temperature of the exhaust gas in the heat exchange process (S31) may be performed in a temperature range of 900 ℃ or lower. Specifically, the temperature of the exhaust gas may be 500 ℃ or lower, more specifically, in a temperature range of 100 to 500 ℃.

[0065] If the upper limit of the above temperature range is exceeded, it causes an overload on the equipment, making it difficult to recirculate exhaust gas, and if the lower limit of the above temperature is exceeded, there may be a problem of reduced heat exchange effect for new supply gas.

[0066] In one embodiment, the step of resupplying the exhaust gas generated in the second calcination process (S30) to the first calcination process (S20) may include the step of further supplying CFA (CO2-Free Air) gas. The CFA (CO2-Free Air) gas refers to gas from which carbon dioxide has been removed. By using the CFA gas mixed with the high-purity exhaust gas, the temperature of the exhaust gas can be lowered, thereby reducing the energy costs required for the heat treatment.

[0067] In one embodiment, the volume ratio of CFA gas to exhaust gas may be 50 volume % or less. Specifically, the ratio may be 30 to 50 volume %. If the ratio exceeds the upper limit, the oxygen concentration required in the first calcination process (S20) is insufficient, resulting in a problem of performance degradation in the final product. If the ratio exceeds the lower limit, there is a problem of reduced energy cost savings.

[0068] In one embodiment, the heat exchange process (S31) can control the temperatures of the exhaust gas, the CFA gas, and the new supply gas. Specifically, the heat exchange process (S31) can lower the temperature of the exhaust gas in the second calcination process (S30) to a controllable level and reintroduce it into the first calcination process (S20). At this time, the temperature of the new supply gas for the second calcination process (S30) can be raised through the heat exchange process (S31) to increase process efficiency.

[0069] More specifically, in the heat exchange process (S31), the temperature of the exhaust gas is controlled to be low, and the temperature of the CFA gas and the new supply gas to the second calcination process is controlled to be high, so that gas with high oxygen purity and high self-temperature is introduced into the first calcination process (S20) and the second calcination process (S30) to increase process efficiency.

[0070] In one embodiment, the heat exchange process (S31) can control the temperature of the CFA gas to 500°C or lower. Specifically, the temperature can be controlled to 100°C to 500°C.

[0071] In one embodiment, the step of resupplying the exhaust gas generated in the second calcination process (S30) to the first calcination process (S20) may include the step of further supplying a new supply gas. The new supply gas may be a gas containing high-purity oxygen and may be resupplyed to the first calcination process (S20) together with the exhaust gas.

[0072] The above new supply gas can be supplied to the first calcination process (S20) together with the exhaust gas by lowering the temperature, similar to the above CFA gas. Specifically, by introducing the temperature-controlled exhaust gas, the above CFA gas, and the above new supply gas into the first calcination process (S20), the oxygen consumption throughout the process can be reduced, and the energy cost for high-temperature heating in the first calcination process (S20) can be reduced.

[0073] FIG. 3 is a schematic illustration of a two-stage kiln according to one embodiment of the present invention.

[0074] Referring to FIG. 3, the heat treatment apparatus for manufacturing a positive electrode active material relates to a heat treatment apparatus for manufacturing a positive electrode active material that mixes and calcines a lithium raw material and a positive electrode active material precursor, comprising a primary calcination furnace (10) that calcines the mixture of the lithium raw material and the positive electrode active material precursor first, a secondary calcination furnace (20) that calcines the compound discharged from the primary calcination furnace (10) at a different temperature secondarily, and an exhaust pipe (not shown) that connects the exhaust pipe for discharging exhaust gas from the secondary calcination furnace (20) and the supply pipe of the primary calcination furnace, wherein the exhaust gas provided from the secondary calcination furnace (20) can be supplied to the primary calcination furnace (10) through the exhaust pipe.

[0075] The first calcination furnace (10) and the second calcination furnace (20) may refer to the first calcination process (S20) and the second calcination process (S30) of the aforementioned method for manufacturing a positive electrode active material to a non-contradictory extent. The temperature and oxygen concentration of the first calcination furnace (10) and the second calcination furnace (20) may be controlled as described above in the first calcination process (S20) and the second calcination process (S30).

[0076] In one embodiment, the secondary kiln (20) may be configured as a closed structure. The secondary kiln (20) may be formed as a closed structure that facilitates the formation of internal positive pressure, and exhaust gas generated inside the secondary kiln (20) may be discharged through a discharge pipe disposed in the secondary kiln (20).

[0077] In one embodiment, the discharge pipe of the secondary kiln (20) can be directly connected to the supply pipe of the primary kiln (10). The discharge pipe and the supply pipe are connected to the exhaust pipe so that exhaust gas discharged from the secondary kiln can be easily introduced into the primary kiln (10).

[0078] In one embodiment, the heat treatment device for manufacturing an anode active material may further include a heat exchanger for controlling the temperature of exhaust gas supplied from a secondary kiln (20). Specifically, the heat exchanger is positioned at the beginning of the exhaust gas outlet of the secondary kiln (20) and can control the temperature of the new supply gas introduced into the secondary kiln (20) and the exhaust gas discharged to the temperature for supplying air to the primary kiln (10) and the secondary kiln (20).

[0079] FIG. 4 is a schematic illustration of a two-stage kiln according to another embodiment of the present invention.

[0080] In one embodiment, the exhaust pipe may receive additional external supply gas. The external supply gas may be at least one of fresh air supply gas and CFA gas. By additionally supplying the external supply gas to the exhaust pipe, the amount of oxygen used in the heat treatment device can be reduced, and the energy cost for heat treatment in the heat treatment device can be reduced.

[0081] In one embodiment, the external supply gas may be directly injected into the exhaust pipe. In another embodiment, the temperature of the external supply gas may be controlled in a heat exchanger. Specifically, the new supply gas or the CFA gas may be heated in the heat exchanger to allow it to be injected into the primary kiln (10). Specifically, the new supply gas or the CFA gas may be able to raise the temperature of the primary kiln (10) while lowering the temperature of the secondary kiln exhaust gas. This allows for a reduction in energy costs for raising the temperature of the kiln.

[0083] Although preferred embodiments have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements by those skilled in the art using the basic concepts defined in the following claims are also included within the scope of the present invention. Explanation of the symbols

[0084] 10: 1st kiln 20: 2nd kiln

Claims

Claim 1 A method for manufacturing a positive electrode active material for a lithium secondary battery, comprising a calcination process for mixing a lithium raw material and a precursor and calcining them, wherein the calcination process comprises a first calcination process and a second calcination process performed at a temperature different from that of the first calcination process, and comprises a step of resupplying exhaust gas generated in the second calcination process to the first calcination process, and comprises a heat exchange process for controlling the temperature of the exhaust gas, wherein the step of resupplying exhaust gas generated in the second calcination process to the first calcination process further comprises a step of supplying a new supply gas and CFA (CO2-Free Air), and wherein the heat exchange process lowers the temperature of the exhaust gas and raises the temperature of the new supply gas and the CFA. Claim 2 A method for manufacturing a positive electrode active material for a lithium secondary battery according to claim 1, wherein the first calcination process is performed at a lower temperature than the second calcination process. Claim 3 delete Claim 4 delete Claim 5 delete Claim 6 delete Claim 7 delete Claim 8 A method for manufacturing a positive electrode active material for a lithium secondary battery according to claim 1, wherein the volume ratio of the CFA gas to the exhaust gas in the step of further supplying the CFA is 50 volume % or less. Claim 9 A method for manufacturing a positive electrode active material for a lithium secondary battery according to claim 1, wherein the oxygen concentration of the first calcination process is 59 to 97% and the oxygen concentration of the second calcination process is 75 to 97%. Claim 10 A method for manufacturing a positive electrode active material for a lithium secondary battery, wherein the first calcination process is performed at a temperature of 500 to 900 ℃. Claim 11 A method for manufacturing a positive electrode active material for a lithium secondary battery according to claim 1, wherein the second calcination process is performed at a temperature of 650 to 900 ℃. Claim 12 A method for manufacturing a positive electrode active material for a lithium secondary battery according to claim 1, wherein the oxygen concentration of the exhaust gas is 75 to 97 volume%. Claim 13 The present invention relates to a heat treatment apparatus for manufacturing a positive electrode active material, comprising mixing and calcining a lithium raw material and a positive electrode active material precursor, the apparatus comprising: a primary calcination furnace for primary calcining the mixture of the lithium raw material and the positive electrode active material precursor; and a secondary calcination furnace for secondary calcining the compound discharged from the primary calcination furnace at a temperature different from that of the primary calcination furnace. The heat treatment device for manufacturing an anode active material includes an exhaust pipe connecting a discharge pipe for discharging exhaust gas from the secondary kiln and a supply pipe of the primary kiln, and supplies exhaust gas provided from the secondary kiln to the primary kiln through the exhaust pipe, and the heat treatment device for manufacturing an anode active material further includes a heat exchanger for controlling the temperature of the exhaust gas supplied from the secondary kiln, the exhaust gas is supplied to the exhaust pipe through the heat exchanger, and the exhaust pipe receives an external supply gas further, the external supply gas includes at least one of a new supply gas and CFA (CO2-Free Air), and the heat exchanger lowers the temperature of the exhaust gas and raises the temperature of the new supply gas and the CFA. Claim 14 In claim 13, a heat treatment apparatus for manufacturing an anode active material in which the temperature of the primary kiln is lower than the temperature of the secondary kiln. Claim 15 delete Claim 16 delete Claim 17 delete Claim 18 delete Claim 19 In claim 13, the heat exchanger is a heat treatment device for manufacturing an anode active material that controls the temperature of the exhaust gas to 500 ℃ or less. Claim 20 In claim 13, the heat exchanger is a heat treatment device for manufacturing anode active material that controls the temperature of the CFA (CO2-Free Air) gas and the fresh supply gas to 500 ℃ or lower.

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