Method for manufacturing a cathode active material for a lithium secondary battery, a cathode for a lithium secondary battery including the cathode active material manufactured by the method, and a lithium secondary battery

Abstract

To solve the problem that required is development of a manufacturing method capable of achieving an improvement effect of productivity by improving reactivity with a precursor when synthesizing a positive electrode active material.SOLUTION: There are provided, a manufacturing method of a positive electrode active material for a lithium secondary battery including: a first step of dry-mixing a transition metal hydroxide and an anhydrous lithium raw material; a second step of subjecting the mixture of the transition metal oxide and the anhydrous lithium raw material to primarily firing; and a third step of finely pulverizing and mixing the primarily fired material and performing secondary firing, and thus obtaining a lithium transition metal oxide, wherein in the first step, the anhydrous lithium raw material is mixed at 40 parts by weight or less based on 100 parts by weight of the transition metal hydroxide, a positive electrode for a lithium secondary battery including a positive electrode active material manufactured by the above-described manufacturing method, and a lithium secondary battery.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2020-0003833, filed on January 10, 2020, and all contents disclosed in the documents of that Korean patent application are incorporated herein by reference.

[0002] The present invention relates to a method for producing a positive electrode active material for a lithium secondary battery, a positive electrode for a lithium secondary battery including the positive electrode active material produced by the method, and a lithium secondary battery. [Background technology]

[0003] As technological development and demand for mobile devices increase, the demand for secondary batteries as energy sources is rapidly increasing. Among such 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.

[0004] Lithium-transition metal composite oxides are used as the positive electrode active material for lithium secondary batteries. Among them, lithium-cobalt composite metal oxides such as LiCoO2 are mainly used because of their high operating voltage and excellent capacity characteristics. However, LiCoO2 has very poor thermal properties due to the instability of its crystal structure upon lithium removal. In addition, the high cost of LiCoO2 limits its mass use as a power source in fields such as electric vehicles.

[0005] Lithium manganese composite metal oxides (e.g., LiMnO2 or LiMn2O4), lithium iron phosphate compounds (e.g., LiFePO4), and lithium nickel composite metal oxides (e.g., LiNiO2) have been developed as alternatives to LiCoO2. Among these, research and development into lithium nickel composite metal oxides, which have a high reversible capacity of approximately 200 mAh / g and facilitate the realization of high-capacity batteries, is currently underway. However, LiNiO2 has inferior thermal stability compared to LiCoO2, and if an internal short circuit occurs due to external pressure during charging, the positive electrode active material itself decomposes, resulting in battery explosion and fire.

[0006] Therefore, lithium transition metal oxides in which part of the Ni is replaced with Co, Mn, or Al have been developed as a way to improve the low thermal stability of LiNiO2 while maintaining the excellent reversible capacity. Also, lithium transition metal oxides with a concentration gradient of the metal composition have been proposed to solve the stability problem caused by the elution of metal elements while maintaining excellent output characteristics.

[0007] A typical method for producing such a positive electrode active material is to synthesize it by mixing a positive electrode active material precursor and a lithium source material and calcining the mixture, through an oxidation reaction of lithium and the precursor. Conventionally, the lithium source material has been in the form of a hydrate, LiOH·HO.

[0008] However, when a hydrated form of LiOH·H2O is used as the lithium source material, the reactivity between the lithium source material and the precursor decreases, resulting in a decrease in yield and productivity.

[0009] Therefore, there is a need to develop a production method that can achieve an improved effect on productivity by improving the reactivity with precursors during synthesis of a positive electrode active material. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Patent No. 2673009 Summary of the Invention [Problem to be solved by the invention]

[0011] In order to solve the above problems, a first technical object of the present invention is to provide a method for producing a cathode active material that can improve the reactivity between a precursor and a lithium source material and thereby improve the production yield and productivity of the cathode active material.

[0012] A second technical object of the present invention is to provide a positive electrode containing a positive electrode active material produced by the method for producing a positive electrode active material according to the present invention.

[0013] A third technical object of the present invention is to provide a lithium secondary battery including the positive electrode. [Means for solving the problem]

[0014] The present invention provides a method for producing a positive electrode active material, comprising: a first step of dry-mixing a transition metal hydroxide and a lithium source material in an anhydrous form; a second step of primarily firing the mixture; and a third step of finely pulverizing the primarily fired product, mixing the resulting mixture, and subsequently firing the resulting mixture in a second step to produce a lithium transition metal oxide, wherein in the first step, 40 parts by weight or less of the lithium source material in an anhydrous form is mixed with 100 parts by weight of the transition metal hydroxide.

[0015] The present invention also provides a positive electrode for a lithium secondary battery, which includes the positive electrode active material produced by the method for producing a positive electrode active material.

[0016] The present invention also provides a lithium secondary battery including the positive electrode for the lithium secondary battery. [Effects of the Invention]

[0017] The manufacturing method of the present invention uses an anhydrous lithium source material that has excellent reactivity with a cathode active material precursor during the manufacture of a cathode active material, thereby reducing the amount of lithium source material used and improving production yield, and preventing deterioration of the quality of the cathode active material due to moisture contained in the lithium source material. As a result, the manufacturing method of the present invention increases productivity and enables the manufacture of cathode active materials with uniform and excellent quality.

[0018] Furthermore, due to the improved reactivity between the anhydrous lithium source material and the positive electrode active material precursor, a high-quality positive electrode active material can be easily synthesized using a relatively smaller amount of lithium source material or by shortening the calcination time compared to when a conventional hydrated lithium source material is used.

[0019] Furthermore, according to the manufacturing method of the present invention, the cathode active material is calcined in two stages, and the reaction by-products, moisture and / or carbon dioxide, are removed during the primary calcination, thereby increasing the true density of the primary calcined product. This allows a larger amount of reactants to be placed in a reactor of the same volume during the secondary calcination, thereby significantly increasing production yield. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a graph showing the quality distribution of secondary batteries including the positive electrode active materials of Example 1 and Comparative Example 1 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0021] The present invention will now be described in more detail. The terms and words used in this specification and claims should not be interpreted in a limited way to their ordinary or dictionary meanings, but should be interpreted in a way that is consistent with the technical idea of the present invention, based on the principle that the inventors can appropriately define the concepts of terms in order to best explain their inventions.

[0022] Method for producing positive electrode active material The present inventors have discovered that the productivity and quality of positive electrode active materials can be dramatically improved by using an anhydrous lithium raw material and performing calcination in two stages when producing the positive electrode active material, and have completed the present invention.

[0023] Specifically, the method for producing a positive electrode active material of the present invention includes a first step of dry-mixing a transition metal hydroxide and an anhydrous lithium source material; a second step of primarily firing the mixture of the transition metal hydroxide and the anhydrous lithium source material; and a third step of finely pulverizing the primarily fired product, mixing the resulting mixture, and subsequently firing the resulting mixture to produce a lithium transition metal oxide. In the first step, 40 parts by weight or less of the anhydrous lithium source material is mixed with 100 parts by weight of the transition metal hydroxide.

[0024] The method for producing a positive electrode active material according to the present invention will be described in more detail below.

[0025] First, a transition metal hydroxide is prepared. The transition metal hydroxide according to the present invention may contain at least one transition metal selected from nickel, cobalt, and manganese, and may preferably be represented by the following Chemical Formula 1.

[0026] [Chemical formula 1] Ni x Co y M 1 z (OH)2 In the above Chemical Formula 1, the M 1 may be Mn, Al, or a combination thereof, and preferably may be Mn.

[0027] On the other hand, the x indicates the molar ratio of nickel element in the transition metal hydroxide, and is 0 <x<1、0.3≦x<1、0.6≦x<1、0.8≦x<1、または0.85≦x<1であってもよい。

[0028] The y represents the molar ratio of cobalt in the transition metal hydroxide, and is 0 <y<1、0<y≦0.5、0<y≦0.3、0<y≦0.2、または0<y≦0.15であってもよい。

[0029] The z is the metal element M in the transition metal hydroxide. 1 and may be 0≦z<1, 0≦z≦0.5, 0≦z≦0.3, 0≦z≦0.2, or 0≦z≦0.15.

[0030] When the molar ratios x, y, and z of the transition metals in the transition metal hydroxide satisfy the above ranges, a positive electrode active material that is excellent in energy density and exhibits high capacity characteristics can be obtained.

[0031] The transition metal hydroxide represented by Chemical Formula 1 may be a commercially available product, or may be prepared by a method for preparing transition metal hydroxides, such as a coprecipitation method, which is well known in the art.

[0032] The transition metal hydroxide and the anhydrous lithium source material prepared above are dry mixed (first step). The anhydrous lithium source material may be, for example, anhydrous lithium hydroxide (LiOH).

[0033] Previously, the lithium raw material used in the manufacture of cathode active materials was mainly the hydrate LiOH·H2O. Generally, a chemical refining process is used to increase the purity of lithium hydroxide, and water molecules are generated during this process, resulting in the production of hydrated lithium hydroxide.

[0034] To convert hydrated lithium hydroxide into anhydrous lithium hydroxide, water contained in the lithium hydroxide must be removed by a drying process. Drying bulk lithium hydroxide hydrate requires a large amount of energy and is a complex process. Therefore, hydrated lithium hydroxide has traditionally been used as a lithium source material for preparing cathode active materials.

[0035] However, when hydrated lithium hydroxide is used, the reactivity between lithium and the transition metal hydroxide is inhibited by water molecules contained in the lithium hydroxide at the time of lithium transformation to the transition metal hydroxide in the early stage of the reaction, and therefore, a relatively excessive amount of lithium hydroxide must be used to produce a high-quality cathode active material, resulting in a reduced production yield of the cathode active material.Furthermore, when a hydrated lithium source material and a transition metal hydroxide are mixed and fired, the provided heat energy is consumed to vaporize the water, thereby reducing the heat energy participating in the reaction between the lithium source material and the transition metal hydroxide, and therefore a relatively high firing temperature is required to ensure sufficient reaction.

[0036] In addition, as water contained in the lithium raw material evaporates, crater-like holes are generated on the surface of the fired product, which can cause quality deviation and localized performance degradation in the final cathode active material.

[0037] On the other hand, when anhydrous lithium hydroxide is used as the lithium source material as in the present invention, the reactivity between the transition metal hydroxide and the lithium source material is improved because the lithium source material does not contain water molecules. This makes it possible to produce a high-quality cathode active material using a relatively smaller amount of lithium source material than in the past, thereby improving the production yield of the cathode active material.

[0038] In addition, when anhydrous lithium hydroxide is used, no thermal energy is consumed for the vaporization of water molecules, so compared to when a hydrated lithium raw material is used, a positive electrode active material with excellent physical properties can be produced even when fired at a lower temperature. In addition, since there is no generation of surface holes due to the vaporization of water molecules, the quality uniformity of the positive electrode active material is also excellent.

[0039] Meanwhile, the anhydrous lithium hydroxide (LiOH) used in the present invention may be prepared by, for example, primarily pulverizing hydrated lithium hydroxide (LiOH HO), vacuum-drying the primarily pulverized lithium hydroxide, and then secondary pulverizing the vacuum-dried lithium hydroxide.

[0040] More specifically, the anhydrous form of lithium hydroxide (LiOH) of the present invention has an average particle size D 50 The lithium hydroxide in the hydrate form having an average particle size D 50 The lithium hydroxide is then subjected to primary pulverization so that the average particle size D is 50 to 250 μm, preferably 50 to 150 μm, and then the primary pulverized lithium hydroxide is vacuum dried at 100° C. to 150° C. for 1 to 30 hours, preferably 10 to 30 hours, and then the average particle size D 50 Alternatively, the powder may be produced by secondary pulverization until the particle size reaches 5 to 30 μm, preferably 10 to 20 μm.

[0041] When hydrated lithium hydroxide is subjected to primary grinding and then vacuum drying as in the present invention, anhydrous lithium hydroxide can be obtained using far less energy than when bulk lithium hydroxide hydrate is dried.

[0042] However, if the particle size of lithium hydroxide after primary pulverization is too small, the amount of fine powder generated increases, and side effects such as the fine powder scattering during the vacuum drying process and clogging the filter may occur, resulting in a decrease in drying yield. On the other hand, if the particle size of lithium hydroxide is too large, the vacuum drying time increases, increasing energy consumption and decreasing the efficiency of secondary pulverization. Therefore, primary pulverization is performed using an average particle size D of lithium hydroxide. 50 It is preferable that the thickness is set to about 50 to 250 μm, and more preferably about 50 to 150 μm.

[0043] On the other hand, if the vacuum drying temperature is too low or the vacuum drying time is too short, the water molecules in the lithium source material may not be completely removed, and if the vacuum drying temperature is too high or the vacuum drying time is too long, the lithium hydroxide may be transformed into lithium carbonate during the drying process. Therefore, the vacuum drying is preferably carried out at 100°C to 150°C for 1 hour to 30 hours, preferably 10 hours to 30 hours.

[0044] On the other hand, if the average particle size of the lithium hydroxide after secondary pulverization is too large, the reactivity between the transition metal hydroxide and the lithium hydroxide will decrease, which may adversely affect the performance of the final positive electrode active material. On the other hand, if the average particle size is too small, the flowability will decrease, the lithium hydroxide will be vulnerable to moisture, and problems such as clogging of piping may occur. Therefore, the average particle size D of the lithium hydroxide after secondary pulverization is set to 1 / 2. 50 It is preferable that the thickness is set to about 5 to 30 μm, and more preferably about 10 to 20 μm.

[0045] At this time, the average particle size D 50 means the particle size at the 50% point of the cumulative distribution of the volume according to the particle size. 50 can be measured using the laser diffraction method. Specifically, the powder to be measured is dispersed in a dispersion medium (distilled water) and then introduced into a commercially available laser diffraction particle size analyzer (e.g., Microtrac S3500). When the particles pass through a laser beam, the difference in diffraction pattern according to particle size is measured, and the particle size distribution can be calculated.

[0046] When anhydrous lithium hydroxide is used as the lithium source material as in the present invention, the oxidation reaction between lithium and the transition metal hydroxide occurs easily due to the improved reactivity with the transition metal hydroxide, even when a relatively small amount of the lithium source material is added, and a lithium transition metal oxide can be easily synthesized. Furthermore, by reducing the amount of the lithium source material added, a lithium transition metal oxide can be easily synthesized even if the subsequent calcination time, etc., is shorter than when lithium hydroxide hydrate is used.

[0047] Preferably, in the present invention, 40 parts by weight or less, preferably 0.2 to 40 parts by weight, 10 to 40 parts by weight, 20 to 40 parts by weight, or 25 to 35 parts by weight of an anhydrous lithium source material may be dry-mixed with 100 parts by weight of a transition metal hydroxide.

[0048] When an anhydrous lithium source material is added in an amount exceeding 40 parts by weight, excessive lithium enters the structure of the final cathode active material, resulting in excessive substitution of lithium at nickel sites (Ni sites) in the cathode active material, reducing the amount of nickel that contributes to capacity and degrading capacity characteristics. Furthermore, the amount of unreacted residual lithium increases in response to the addition of excessive lithium, which may increase gas generation during battery operation.

[0049] Meanwhile, the dry mixing of the anhydrate form lithium source material and the transition metal hydroxide may be performed using a commonly used dry mixing method, such as a grinder mixing method, a mechanofusion method, or a general dry mixer (e.g., a Henschel mixer, an intensive mixer, or a Loedige mixer), but is not limited thereto.

[0050] When a lithium source material and a transition metal hydroxide are mixed by a wet method, even if an anhydrous lithium source material is used, the anhydrous lithium source material is dissolved in a solvent, and therefore, the effects of improving reactivity and increasing productivity that would be achieved by using an anhydrous lithium source material cannot be achieved.

[0051] Meanwhile, when mixing the lithium source material and the transition metal hydroxide, an additional metal element-containing material may be further mixed, if necessary. In this case, the additional metal element may be M 1 Metal or M 2 may be a metal, 1 The metal may be Mn, Al, or a combination thereof, and M 2The metal may be one or more selected from the group consisting of W, Cu, Fe, V, Cr, Ti, Zr, Zn, Ta, Y, In, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo.

[0052] The additional metal element-containing substance is 1 element or M 2 The additional metal element-containing substance may be an element-containing acetate, nitrate, sulfate, halide, sulfide, hydroxide, oxide, or oxyhydroxide, etc. Preferably, the additional metal element-containing substance may be an Al-containing substance, such as Al(OH)3, Al2O3, Al2(SO4)3, AlCl3, Al(NO3)3, or a combination thereof.

[0053] Next, the mixture obtained in the first step is subjected to primary baking (second step). The primary firing may be performed in an oxygen atmosphere, preferably an oxygen atmosphere with an oxygen concentration of 80 vol% or more. When the primary firing is performed in an oxygen atmosphere, lithium can easily enter the precursor, preventing the formation of residual lithium on the surface of the final cathode active material. Furthermore, surface defects can be reduced, thereby improving the electrochemical properties and cycle characteristics.

[0054] Meanwhile, the primary calcination may be carried out in an oxygen atmosphere at 400°C to 700°C, preferably 550°C to 700°C. When the primary calcination temperature is within this range, lithium ions can diffuse smoothly into the transition metal hydroxide, and as moisture and / or gas, which are reaction by-products, are removed during the primary calcination process, the volume of the primary calcined product decreases compared to the reactants, resulting in an increase in true density. Therefore, during the secondary calcination described below, a larger amount of reactants (primary calcined product) can be introduced into a reactor of the same volume compared to when primary calcination is not performed, resulting in a significant increase in production volume.

[0055] Next, the primary fired product is finely pulverized, mixed and secondary fired to produce a lithium transition metal oxide (third step). The primary fired product may be pulverized by a common pulverization method known in the art, such as, but not limited to, a ball mill, a jet mill, ACM (air classify milling) using an internal hammer, or sieving.

[0056] The primary-sintered product obtained after the primary firing may partially undergo particle agglomeration. Therefore, by pulverizing and homogenizing the agglomerated particles, the quality uniformity of the final cathode active material can be improved.

[0057] Next, the secondary firing may be carried out in an oxygen atmosphere, preferably in an oxygen atmosphere with an oxygen concentration of 80 vol % or more. The secondary firing may be performed at a higher temperature than the primary firing, for example, at 700° C. to 900° C., preferably 750° C. to 850° C. When the secondary firing is performed within this temperature range, the crystalline structure of the positive electrode active material is well developed, and a positive electrode active material having excellent capacity characteristics, life characteristics, and high-temperature characteristics can be produced.

[0058] The positive electrode active material of the present invention produced by the above-described method may be a lithium transition metal oxide represented by the following chemical formula 2.

[0059] [Chemical formula 2] Li 1+a [Ni x Co y M 1 Z M 2 w ]O2 In the above chemical formula 2, M 1 may be Mn, Al, or a combination thereof, and preferably may be Mn or a combination of Mn and Al.

[0060] Said M2 may be one or more selected from the group consisting of W, Cu, Fe, V, Cr, Ti, Zr, Zn, Ta, Y, In, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo.

[0061] The 1+a indicates the molar ratio of lithium in the lithium transition metal oxide, and may be −0.2≦a≦0.2 or −0.1≦a≦0.1.

[0062] The x represents the molar ratio of nickel in the metal components excluding lithium in the lithium transition metal oxide, and is 0 <x<1、0.3≦x<1、0.6≦x<1、0.8≦x<1、または0.85≦x<1であってもよい。

[0063] The y represents the molar ratio of cobalt in the metal components excluding lithium in the lithium transition metal oxide, and is 0 <y<1、0<y≦0.5、0<y≦0.3、0<y≦0.2、または0<y≦0.15であってもよい。

[0064] The z is M in the metal component other than lithium in the lithium transition metal oxide. 1 and may be 0≦z<1, 0≦z≦0.5, 0≦z≦0.3, 0≦z≦0.2, or 0≦z≦0.15.

[0065] The w is the M in the metal components other than lithium in the lithium transition metal oxide. 2 and may be 0≦w≦0.2, 0≦w≦0.1, or 0≦w≦0.05.

[0066] More preferably, the positive electrode active material may be a lithium transition metal oxide represented by the following chemical formula 2-1.

[0067] [Chemical formula 2-1] Li 1+a [Ni x Co y Mn z1 Al z2 M2 w ]O2 In the above chemical formula 2-1, the M 2 may be one or more selected from the group consisting of W, Cu, Fe, V, Cr, Ti, Zr, Zn, Ta, Y, In, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo.

[0068] The 1+a indicates the molar ratio of lithium in the lithium transition metal oxide, and may be −0.2≦a≦0.2 or −0.1≦a≦0.1.

[0069] The x indicates the molar ratio of nickel in the metal components excluding lithium in the lithium transition metal oxide, and may be 0.8≦x<1 or 0.85≦x<1.

[0070] The y represents the molar ratio of cobalt in the metal components excluding lithium in the lithium transition metal oxide, and is 0 <y<0.2、または0<y<0.15であってもよい。

[0071] The z1 represents the molar ratio of manganese in the metal components excluding lithium in the lithium transition metal oxide, and is 0 <z1<0.2、または0<z1<0.15であってもよい。

[0072] The z2 represents the molar ratio of aluminum in the metal components excluding lithium in the lithium transition metal oxide, and is 0 <z2<0.2、または0<z2<0.15であってもよい。

[0073] The w is the M in the metal components other than lithium in the lithium transition metal oxide. 2 and may be 0≦w<0.2, 0≦w≦0.1, or 0≦w≦0.05.

[0074] Meanwhile, the method for preparing a positive electrode active material according to the present invention may optionally further include, after the third step, a step of mixing the lithium transition metal oxide with a washing solution to remove lithium by-products present on the surface of the lithium transition metal oxide (a fourth step).

[0075] For example, the water washing step may be performed by mixing the prepared cathode active material with a washing solution (preferably distilled water) at 5°C to 80°C, preferably 10°C to 60°C, followed by stirring and filtering. The washing solution may be added in an amount of 30% to 80%, preferably 40% to 70%, based on the weight of the cathode active material to wash the cathode active material. However, in terms of removing lithium by-products, the amount of the washing solution added may not be particularly limited.

[0076] The water washing step allows lithium by-products on the surface of the positive electrode active material to dissociate in the water washing solution and be easily removed from the surface of the positive electrode active material. After water washing, a drying step of drying the washed product may be further included.

[0077] Furthermore, optionally, after the fourth step, a coating layer containing at least one selected from the group consisting of B, Al, Nb, W, Mo, Zr, Ti, Y, Ce, yttria stabilized zirconia (YSZ), calcia stabilized zirconia (CSZ), indium tin oxide (ITO), and Sr can be formed on the surface of the lithium transition metal oxide (fifth step).

[0078] For example, a coating element-containing raw material containing at least one selected from the group consisting of B, Al, Nb, W, Mo, Zr, Ti, Y, Ce, YSZ, CSZ, ITO, and Sr can be mixed with the dried lithium transition metal oxide and heat-treated at 150° C. to 500° C. Preferably, the coating element-containing raw material contains at least one coating element selected from the group consisting of B, Al, and W.

[0079] For example, the coating element-containing raw material may include an oxide, a hydrate, a hydroxide, a chloride, or an oxalate of the above-mentioned coating element. Preferably, the coating element-containing raw material is LiB a1 O b1 (1≦a1≦10, 1≦b1≦10), LiW a2 O b2 (1≦a2≦10, 1≦b2≦10), H3BO3, Al2O3, WO3, and B2O3.

[0080] A coating layer of lithium transition metal oxide can be formed by mixing 0.01 to 1 part by weight, preferably 0.05 to 0.5 parts by weight, of a coating element-containing raw material with 100 parts by weight of the lithium transition metal oxide, and then heat treating the mixture at 150°C to 500°C, more preferably 200°C to 400°C.

[0081] The formation of the coating layer can prevent contact between the positive electrode active material and the electrolyte solution contained in the lithium secondary battery, thereby suppressing side reactions and improving the surface safety of the positive electrode active material. For example, if the coating element-containing raw material is contained in an amount less than the above range, the effect of suppressing side reactions due to the formation of the coating layer is negligible. If the coating element-containing raw material is contained in an amount exceeding the above range, the content of the coating layer increases excessively, and the coating layer may act as a resistance layer, thereby reducing capacity and resistance characteristics and deteriorating battery life characteristics.

[0082] positive electrode The present invention also provides a positive electrode for a lithium secondary battery, which includes a positive electrode active material produced by the above-described method for producing a positive electrode active material and has improved productivity.

[0083] Specifically, the positive electrode includes a positive electrode current collector and a positive electrode active material layer located on at least one surface of the positive electrode current collector and including the above-described positive electrode active material.

[0084] The positive electrode current collector is not particularly limited as long as it does not induce chemical changes in the battery and is conductive. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. may be used. The positive electrode current collector may typically have a thickness of 3 to 500 μm, and the surface of the current collector may be formed with fine irregularities to enhance adhesion of the positive electrode active material. The positive electrode current collector may be used in various forms, such as a film, sheet, foil, mesh, porous material, foam, or nonwoven fabric.

[0085] The positive electrode active material layer may contain a conductive material and a binder in addition to the positive electrode active material.

[0086] In this case, the positive electrode active material may be contained in an amount of 80 to 99 wt %, more specifically 85 to 98 wt %, based on the total weight of the positive electrode active material layer. When contained in the above range, excellent capacity characteristics can be exhibited.

[0087] The conductive material is used to impart conductivity to the electrode and can be any material that does not cause chemical changes in the resulting battery and has electronic conductivity. Specific examples include graphite, such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fiber; metal powder or metal fiber, such as copper, nickel, aluminum, or silver; conductive whiskers, such as zinc oxide or potassium titanate; conductive metal oxides, such as titanium oxide; and conductive polymers, such as polyphenylene derivatives. One or more of these materials may be used alone or in combination. The conductive material may be present in an amount of 1 to 30 wt % based on the total weight of the positive electrode active material layer.

[0088] The binder improves adhesion between positive electrode active material particles and between the positive electrode active material and the current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, and various copolymers thereof. One or more of these may be used alone or in combination. The binder may be included in an amount of 1 to 30 wt % based on the total weight of the positive electrode active material layer.

[0089] The positive electrode may be manufactured by a conventional positive electrode manufacturing method, except for using the positive electrode active material described above. Specifically, the positive electrode may be manufactured by dissolving or dispersing the positive electrode active material described above, and optionally a binder and a conductive material, in a solvent to prepare a positive electrode composite, which is then coated on a positive electrode current collector, followed by drying and rolling. In this case, the types and contents of the positive electrode active material, binder, and conductive material are as described above.

[0090] The solvent may be a solvent commonly used in the art, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water, and may be used alone or in combination. The amount of solvent used is sufficient to dissolve or disperse the cathode active material, conductive material, and binder, and to provide a viscosity that allows excellent thickness uniformity during subsequent application to produce a cathode, taking into consideration the coating thickness of the slurry and the production yield.

[0091] Alternatively, the positive electrode may be produced by casting the positive electrode mixture on a separate support, peeling it off from the support, and laminating the resulting film on a positive electrode current collector.

[0092] Lithium secondary battery The present invention also provides an electrochemical device including the positive electrode. The electrochemical device may be, for example, a battery or a capacitor, and more specifically, a lithium secondary battery.

[0093] Specifically, the lithium secondary battery includes a positive electrode, a negative electrode facing the positive electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte. Since the positive electrode is the same as that described above, a detailed description thereof will be omitted, and only the remaining components will be described in detail below.

[0094] The lithium secondary battery may further include a battery container that houses the electrode assembly of the positive electrode, the negative electrode, and the separator, and a sealing member that seals the battery container.

[0095] 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.

[0096] The negative electrode current collector is not particularly limited as long as it does not induce chemical changes in the battery and has high conductivity, and examples thereof include copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surfaces treated with carbon, nickel, titanium, silver, or the like, and aluminum-cadmium alloys. The negative electrode current collector may typically have a thickness of 3 μm to 500 μm, and, like the positive electrode current collector, the surface of the current collector may be formed with fine irregularities to strengthen the binding force of the negative electrode active material. The negative electrode current collector may be used in various forms, such as a film, sheet, foil, mesh, porous material, foam, or nonwoven fabric.

[0097] The negative electrode active material layer includes a negative electrode active material, and optionally a binder and a conductive material.

[0098] The negative electrode active material may be a compound capable of reversible intercalation and deintercalation of lithium. Specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys, and Al alloys; and SiO. βExamples of the negative electrode active material include metal oxides capable of doping and dedoping lithium, such as SnO2, vanadium oxide, and lithium vanadium oxide (0<β<2); or composites containing the metallic compounds and carbonaceous materials, such as Si-C composites and Sn-C composites. A mixture of two or more of these may be used. A thin film of metallic lithium may also be used as the negative electrode active material. The carbon material may be either low-crystalline carbon or high-crystalline carbon. Typical low-crystalline carbons are soft carbon and hard carbon, while typical high-crystalline carbons are amorphous, plate-like, flake-like, spherical, or fibrous natural or artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, mesocarbon microbeads, mesophase pitches, and high-temperature-calcined carbons such as petroleum or coal tar pitch-derived cokes.

[0099] The negative electrode active material may be contained in an amount of 80 wt % to 99 wt % based on the total weight of the negative electrode active material layer.

[0100] The binder is a component that helps bond the conductive material, active material, and current collector together, and may typically be 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, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluororubber, and various copolymers thereof.

[0101] The conductive material is a component for further improving the conductivity of the negative electrode active material and may be added in an amount of 10 wt % or less, preferably 5 wt % or less, based on the total weight of the negative electrode active material layer. The conductive material is not particularly limited as long as it does not induce chemical changes in the battery and is conductive. Examples of the conductive material include graphite such as natural graphite and 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 whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives.

[0102] The negative electrode active material layer may be produced by applying a negative electrode composite, which is prepared by dissolving or dispersing a negative electrode active material, and optionally a binder and a conductive material, in a solvent, onto a negative electrode current collector and drying the applied material. Alternatively, the negative electrode composite may be cast onto a separate support, and then peeled off from the support to obtain a film, which may be laminated onto the negative electrode current collector.

[0103] Meanwhile, in the lithium secondary battery, the separator separates the negative electrode and the positive electrode and provides a path for lithium ions to move. Any separator typically used in secondary batteries can be used without particular limitations. It is particularly preferred that the separator exhibits low resistance to electrolyte ion migration and excellent electrolyte humidification. Specifically, a porous polymer film, such as a porous polymer film made from a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, or an ethylene / methacrylate copolymer, or a laminate structure of two or more layers thereof, may be used. Conventional porous nonwoven fabrics, such as nonwoven fabrics made from high-melting-point glass fibers or polyethylene terephthalate fibers, may also be used. To ensure heat resistance or mechanical strength, a separator coated with a ceramic component or a polymer material may be used, and may be selectively used as a single-layer or multi-layer structure.

[0104] Furthermore, examples of the electrolyte 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, but are not limited to these.

[0105] Specifically, the electrolyte may include an organic solvent and a lithium salt.

[0106] The organic solvent may be any solvent capable of acting as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, examples of the organic solvent include ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents such as dibutyl ether and tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; dimethylcarbonate (DMC), diethylcarbonate (DEC), methylethylcarbonate (MEC), ethylene carbonate (EC), and propylene carbonate. Examples of solvents that can be used include carbonate-based solvents such as ethylene carbonate (PC), alcohol-based solvents such as ethyl alcohol and isopropyl alcohol, nitriles such as R-CN (R is a hydrocarbon group having 2 to 20 carbon atoms and having a linear, branched, or cyclic structure, which may contain a double-bonded aromatic ring or an ether bond), amides such as dimethylformamide, dioxolanes such as 1,3-dioxolane, and sulfolanes. Among these, carbonate-based solvents are preferred, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate) with high ionic conductivity and a high dielectric constant, which can improve the charge / discharge performance of the battery, and a low-viscosity linear carbonate compound (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate) is more preferred.

[0107] The lithium salt may be any compound capable of providing lithium ions used in lithium secondary batteries, without particular limitation. Specifically, examples of the lithium salt include LiPF, LiClO, LiAsF, LiBF, LiSbF, LiAlO, LiAlCl, LiCF, SO, LiCF, SO, LiN(C, F, SO), LiN(C, F, SO), LiN(CF, SO), LiCl, LiI, and LiB(C, O) . The lithium salt is used at a concentration of 0.1 to 4.0 M, preferably 0.1 to 2.0 M. When the lithium salt concentration is within this range, the electrolyte has appropriate conductivity and viscosity, resulting in excellent electrolyte performance and efficient lithium ion migration.

[0108] In addition to the constituent components of the electrolyte, the electrolyte may further contain one or more additives, such as haloalkylene carbonate compounds (e.g., difluoroethylene carbonate), pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinoneimine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride, for the purpose of improving battery life characteristics, suppressing battery capacity reduction, improving battery discharge capacity, etc. In this case, the additives may be contained in an amount of 0.1 to 5 parts by weight per 100 parts by weight of the total weight of the electrolyte.

[0109] As described above, the lithium secondary battery including the positive electrode active material according to the present invention stably exhibits excellent discharge capacity, output characteristics, and life characteristics, and is therefore useful in the fields of portable devices such as mobile phones, notebook computers, and digital cameras, and electric vehicles such as hybrid electric vehicles (HEVs).

[0110] Therefore, according to another embodiment of the present invention, there is provided a battery module including the lithium secondary battery as a unit cell, and a battery pack including the same.

[0111] The battery module or battery pack may be used as a power source for one or more medium- to large-sized devices, including power tools; electric vehicles (EVs), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEVs); or power storage systems.

[0112] The external shape of the lithium secondary battery of the present invention is not particularly limited, and may be a cylindrical shape using a can, a square shape, a pouch shape, a coin shape, or the like.

[0113] The lithium secondary battery according to the present invention may be used not only as a battery cell used as a power source for a small device, but also as a unit battery in a medium- to large-sized battery module including a plurality of battery cells. [Example]

[0114] The present invention will be described in detail below with reference to examples. However, the examples of the present invention can be modified into various other forms, and the scope of the present invention should not be construed as being limited to the examples detailed below. The examples of the present invention are provided to more completely explain the present invention to those skilled in the art.

[0115] Example 1 Hydrated form of lithium hydroxide LiOH·H2O with an average particle size of D 50 After primary grinding to 100 μm, the powder was vacuum dried at 130 °C for 24 hours, and then the average particle size D 50 Secondary pulverization was carried out until the particle size reached 15 μm, producing anhydrous lithium hydroxide LiOH.

[0116] As a precursor of the positive electrode active material, Ni 0.88 Co 0.05 Mn 0.07 24,750 g of (OH), 382 g of Al(OH), and 1,343 g of the anhydrous lithium hydroxide (LiOH) prepared above were mixed together. 5 kg of the mixed powder was placed in each of the upper and lower ends of a 330 mm x 330 mm container, and primary firing was carried out at 630°C for 8 hours in an oxygen atmosphere with an oxygen partial pressure of 80 vol% or more.

[0117] The primary fired product (solid cake) formed by the primary firing was finely pulverized using an ACM device (Hosokawa, model name: 15BC), and then 9 kg of the pulverized product was divided into small portions and placed in a container measuring 330 mm x 330 mm, where it was subjected to secondary firing at 780°C for 10 hours.

[0118] Next, the second-baked product was mixed with deionized water in a weight ratio of 1:1 and washed with water at 25° C. for 5 minutes.

[0119] The washed material was mixed with H3BO3 in a weight ratio of 1:0.006 and heat-treated at 300°C for 10 hours to prepare a cathode active material coated with LiB2O4 on the surface.

[0120] Example 2 A positive electrode active material was prepared in the same manner as in Example 1, except that the amount of lithium anhydrate added was adjusted to 1,318 g.

[0121] Comparative Example 1 4,000 g of the positive electrode active material precursor and 1,982 g of lithium hydrate (LiOH·H2O) were mixed, and 4 kg was divided into portions at the bottom of a 330 mm x 330 mm container and fired at 780°C for 30 hours.

[0122] The fired product was pulverized using an ACM device and then sieved.

[0123] Thereafter, the obtained powder was washed with water and coated with H3BO3 in the same manner as in Example 1 to produce a positive electrode active material.

[0124] Comparative Example 2 A cathode active material was prepared in the same manner as in Comparative Example 1, except that the cathode active material precursor and lithium hydrate were mixed and subjected to primary firing at 630°C for 8 hours, and the primary fired product (cake) was pulverized and then subjected to secondary firing at 780°C for 10 hours.

[0125] Comparative Example 3 A positive electrode active material was prepared in the same manner as in Example 1, except that 1,343 g of lithium hydrate (LiOH·H 2 O) was mixed instead of anhydrous lithium hydrate.

[0126] Comparative Example 4 A positive electrode active material was prepared in the same manner as in Example 1, except that 2,138 g of anhydrous lithium hydrate (LiOH) was mixed.

[0127] Comparative Example 5 A positive electrode active material was produced in the same manner as in Example 1, except that the secondary firing was not performed and the primary firing was performed at 780° C. for 10 hours.

[0128] Experimental Example 1 In order to compare the productivity of the positive electrode active materials produced in Examples 1 and 2 and Comparative Examples 1 to 5, the amounts of the positive electrode active materials produced in the same volume mass-production firing furnaces for one month by the methods of Examples 1 and 2 and Comparative Examples 1 to 5 were measured, and the results are shown in Table 1 below.

[0129] [Table 1]

[0130] As shown in Table 1, the cathode active materials prepared in Examples 1 and 2 were found to have significantly improved productivity compared to the cathode active materials prepared in Comparative Examples 1 to 3, which used lithium hydrate as the lithium source material, and Comparative Example 5, which was calcined in one step. On the other hand, Comparative Example 4, which used lithium anhydrate as the lithium source material and was calcined in two steps, showed productivity at a level equivalent to that of Examples 1 and 2.

[0131] Experimental example 2: Quality spraying To measure the quality distribution of the positive electrode active materials prepared in Example 1 and Comparative Example 1, the amount of excess lithium present on the surface of the positive electrode active materials was measured.

[0132] Specifically, in Example 1 and Comparative Example 1, the lithium transition metal oxides prepared by mixing and calcining the cathode active material precursor and anhydrous lithium hydrate were subjected to pH titration to measure the amount of excess lithium present on the surface before washing with water. A Metrohm pH meter was used, and the pH was recorded by titrating in 1 mL increments. Specifically, 5 g of the lithium transition metal oxide powders of Example 1 and Comparative Example 1 were stirred with 100 mL of distilled water. The pH was measured by adding a 1 M HCl solution to the solution, and the pH was measured. The amount and distribution of excess lithium present on the surface of the cathode active material were measured and shown in Figure 1.

[0133] 1, it was confirmed that the distribution of residual lithium on the surface of the lithium transition metal oxide of Comparative Example 1 before washing with water was significantly wider than the distribution of residual lithium on the surface of the lithium transition metal oxide prepared in Example 1. This means that the content of lithium inserted into the lithium transition metal oxide prepared in Comparative Example 1 was not uniform, and it was therefore predicted that the lithium transition metal oxide of Comparative Example 1 was formed structurally more unstable than the lithium transition metal oxide of Example 1.

[0134] Experimental example 3: High temperature life characteristics Secondary batteries were manufactured using the positive electrode active materials manufactured in Examples 1 and 2 and Comparative Examples 1 to 5, and the high-temperature characteristics of each of the secondary batteries including the positive electrode active materials of Examples 1 and 2 and Comparative Examples 1 to 5 were evaluated.

[0135] First, the positive electrode active materials prepared in Examples 1 and 2 and Comparative Examples 1 to 5, acetylene black conductive material (FX35), and polyvinylidene fluoride binder (KF9700) were mixed in a weight ratio of 97.5:1:1.5 in N-methylpyrrolidone (NMP) solvent to prepare a positive electrode slurry. The positive electrode slurry was applied to an 80 μm-thick aluminum foil, dried at 130°C, and rolled to prepare a positive electrode.

[0136] Meanwhile, graphite (AGP8) was used as the negative active material, carbon black (super C65) as the conductive material, and a mixture of styrene-butadiene rubber binder (BM-L302) and carboxymethyl cellulose (CMC) as the binder. The negative active material:conductive material:binder ratio was 96:2:2, and the mixture was added to water to prepare a negative active material slurry. This slurry was then coated on a 300 μm thick copper foil, dried, and roll-pressed to prepare a negative electrode.

[0137] An electrode assembly was fabricated by interposing a safety reinforced separator (SRS) between the cathode and anode prepared above, and then the assembly was placed inside a battery case. An electrolyte solution was then injected into the case to fabricate a lithium secondary battery. The electrolyte solution was a 30:70 volume ratio mixed organic solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC), in which 0.7M LiPF6 and 0.3M LiFSI were dissolved. Lithium secondary batteries according to Examples 1 and 2 and Comparative Examples 1 to 5 were fabricated.

[0138] The lithium secondary batteries containing the positive electrode active materials of Examples 1 and 2 and Comparative Examples 1 to 5 were charged at 45°C at 1C CC / CV up to 4.25V with a 0.05C cutoff, and then discharged at a constant current of 1C down to 3.0V.

[0139] The above charge and discharge behavior was counted as one cycle, and after repeating this cycle 150 times, the capacity retention rates at 45°C of the lithium secondary batteries of Examples 1 and 2 and Comparative Examples 1 to 5 were calculated, and the results are shown in Table 2 below.

[0140] [Table 2]

[0141] As shown in Table 2, the initial capacity and cycle characteristics of the positive electrode active materials prepared in Examples 1 and 2 were superior to those of the positive electrode active materials prepared in Comparative Examples 1 to 3 and 5.

[0142] On the other hand, in the case of Comparative Example 4, in which an excess amount of anhydrous lithium hydrate was used, it was confirmed that the initial capacity was reduced by 3 to 4% compared to Examples 1 and 2. Considering that in the field of battery technology, it is very difficult to increase the initial capacity by more than 2% for a battery with the same specifications, it can be said that increasing the initial capacity by more than 3 to 4% is a very significant effect.

[0143] Furthermore, Comparative Example 4 showed a high capacity retention rate. However, since the capacity retention rate was measured as a ratio of the capacity after 150 cycles based on the initial capacity, in the case of Comparative Example 4, which has a low initial capacity, the absolute amount of discharge capacity after 150 cycles was smaller than that of Example 1.

[0144] On the other hand, in the case of Comparative Example 5, in which the firing was performed in one step, the initial capacity characteristics were superior to those of Comparative Examples 1 to 4, but it was confirmed that the cycle characteristics were significantly reduced. This is presumably because the crystalline structure of the positive electrode active material was not sufficiently developed with only one firing step.

[0145] Experimental Example 4: High-temperature storage characteristics The storage characteristics at high temperatures of the secondary batteries of Examples 1 and 2 and Comparative Examples 1 to 5 manufactured according to Experimental Example 3 were measured.

[0146] Specifically, the secondary batteries of Examples 1 and 2 and Comparative Examples 1 to 5 were each fully charged to 4.25 V and then stored at 60° C. for 3 weeks.

[0147] Before storage, the discharge capacity and resistance of the fully charged secondary battery were measured.

[0148] The fully charged secondary batteries were moved from the high-temperature chamber to a room-temperature chamber (25°C) every week and subjected to high-speed discharge at a 3C rate at SOC 50. The discharge capacity and resistance were measured and compared with the discharge capacity and resistance values of the secondary batteries measured before storage to calculate the capacity retention rate and resistance increase rate. The results are shown in Table 3 below.

[0149] [Table 3]

[0150] As shown in Table 3, it was confirmed that the capacity retention rate and resistance increase rate after high-temperature storage of the secondary batteries manufactured in Examples 1 and 2 were superior to those of Comparative Examples 1 to 3 and 5.

Claims

1. A first step of dry mixing a transition metal hydroxide and LiOH in anhydrous form; a second step of primary calcining the mixture of the transition metal hydroxide and LiOH in anhydrous form; and a third step of finely pulverizing the primary fired product, mixing the resulting mixture, and secondary firing the mixture to produce a lithium transition metal oxide. In the first step, the anhydrous lithium source material is mixed in an amount of 40 parts by weight or less with respect to 100 parts by weight of the transition metal hydroxide.

2. The LiOH is lithium hydroxide in the hydrate form (LiOH.H ２ 10. The method for producing a positive electrode active material for a lithium secondary battery according to claim 1, wherein the positive electrode active material is produced by primarily pulverizing lithium hydroxide (LiOH) obtained by the method.

11. The method for producing a positive electrode active material for a lithium secondary battery according to claim 1, wherein the positive electrode active material is obtained by vacuum-driing the primary-pulverized lithium hydroxide.

3. The LiOH has an average particle size D ５０ The lithium hydroxide in the hydrate form having an average particle size D ５０ The lithium hydroxide is then subjected to primary pulverization so that the average particle size D is 50 to 250 μm, and the primary pulverized lithium hydroxide is then vacuum dried at 100° C. to 150° C. for 1 to 30 hours. ５０ 3. The method for producing a positive electrode active material for a lithium secondary battery according to claim 2, wherein the positive electrode active material is produced by secondary pulverizing the powder until the powder has a size of 5 to 30 μm.

4. 4. The method for producing a positive electrode active material for a lithium secondary battery according to claim 1, wherein in the first step, 10 parts by weight to 40 parts by weight of an anhydrous lithium source material is mixed with 100 parts by weight of the transition metal hydroxide.

5. The method for producing a positive electrode active material for a lithium secondary battery according to claim 1 , wherein the primary firing and the secondary firing are each carried out in an oxygen atmosphere.

6. The method for producing a positive electrode active material for a lithium secondary battery according to claim 1 , wherein the primary firing and the secondary firing are each performed in an oxygen atmosphere having an oxygen concentration of 80 vol % or more.

7. The method for producing a positive electrode active material for a lithium secondary battery according to any one of claims 1 to 6, wherein the primary baking is carried out at 400°C to 700°C.

8. The method for producing a positive electrode active material for a lithium secondary battery according to any one of claims 1 to 7, wherein the secondary baking is carried out at 700°C to 900°C.

9. 9. The method for producing a positive electrode active material for a lithium secondary battery according to claim 1, further comprising a fourth step of mixing the lithium transition metal oxide with a water washing solution to remove lithium by-products present on the surface of the lithium transition metal oxide after the third step.

10. 10. The method of claim 9, further comprising a fifth step of forming a coating layer on the surface of the lithium transition metal oxide, the coating layer including at least one selected from the group consisting of B, Al, Nb, W, Mo, Zr, Ti, Y, Ce, yttria stabilized zirconia (YSZ), calcia stabilized zirconia (CSZ), indium tin oxide (ITO), and Sr, after the fourth step.

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