Method for producing positive electrode active material precursor, positive electrode active material precursor, and method for producing positive electrode active material using positive electrode active material precursor

Abstract

This invention relates to a method for preparing a positive electrode active material precursor, the positive electrode active material precursor, and a method for preparing a positive electrode active material using the positive electrode active material precursor. The aforementioned positive electrode active material precursor, by controlling the shape and physical properties of the precursor, achieves specific surface area and internal density that can help improve the capacity characteristics and rate performance of the positive electrode active material.

Description

Technical Field

[0001] This invention relates to a method for preparing a positive electrode active material precursor, the positive electrode active material precursor, and a method for preparing a positive electrode active material using the positive electrode active material precursor. The aforementioned positive electrode active material precursor, by controlling the shape and physical properties of the precursor, achieves specific surface area and internal density that can help improve the capacity characteristics and rate performance of the positive electrode active material. Background Technology

[0002] Batteries use substances capable of electrochemical reactions at the positive and negative electrodes to store electrical energy. As a representative example of such batteries, there are lithium-ion secondary batteries that store electrical energy through the difference in chemical potential during the insertion / extraction of lithium ions at the positive and negative electrodes.

[0003] The aforementioned lithium secondary battery is prepared by using materials capable of reversible lithium-ion insertion / extraction as positive and negative electrode active materials, and filling the space between the positive and negative electrodes with organic or polymer electrolytes.

[0004] Lithium composite oxides are representative materials used as positive electrode active materials in lithium secondary batteries. These lithium composite oxides include oxides composed of LiCoO2, LiMn2O4, LiNiO2, LiMnO2, or Ni, Co, Mn, or Al.

[0005] Among the above-mentioned positive electrode active materials, LiCoO2 is the most widely used due to its excellent lifetime characteristics and charge / discharge efficiency, but it has the following disadvantages: due to the limited resources of cobalt used as a raw material, it is expensive and therefore has limited price competitiveness.

[0006] Lithium manganese oxides such as LiMnO2 and LiMn2O4 have the advantages of excellent thermal stability and low price, but they suffer from small capacity and poor high-temperature performance. In addition, LiNiO2-based cathode active materials show high discharge capacity battery characteristics, but they are difficult to synthesize due to the cation mixing problem between Li and transition metals, thus posing significant challenges in rate performance.

[0007] Furthermore, depending on the degree of this cation mixing, a large amount of Li byproducts will be generated. Most of these Li byproducts contain LiOH and Li₂CO₃, which may cause gelation during the preparation of the cathode slurry or generate gas during repeated charge / discharge cycles after electrode fabrication. In addition, the residual Li₂CO₃ in these Li byproducts will increase the swelling of the battery cells, thus reducing battery life characteristics.

[0008] To overcome the shortcomings of existing positive electrode active materials, various candidate materials have been proposed.

[0009] As an example, research is underway on using lithium-rich manganese oxides, which contain excess Mn in transition metals and have a lithium content greater than the sum of the contents of the transition metals, as positive electrode active materials for lithium secondary batteries. These lithium-rich manganese oxides are sometimes also referred to as overlithiated layered oxides (OLO).

[0010] While the aforementioned OLO (Oxide Lobe) theoretically offers the advantage of high capacity under high-voltage operating conditions, in reality, due to the excessive Mn content in the oxide and its relatively low conductivity, lithium-ion batteries using OLO suffer from lower rate performance. Consequently, lower rate performance may lead to reduced charge / discharge capacity and lifetime efficiency (cycle capacity retention) during lithium-ion battery cycling.

[0011] To address these issues, research has been conducted on changing the composition of OLO, but so far these attempts have not reached a commercial level. Summary of the Invention

[0012] Technical issues In the lithium secondary battery market, as the growth of lithium secondary batteries for electric vehicles plays a market-driving role, the demand for positive electrode active materials used in lithium secondary batteries is also continuously increasing.

[0013] For example, in the prior art, from the point of view of ensuring safety, lithium secondary batteries using lithium iron phosphate (LFP) are mainly used. However, recently, the use of nickel-based lithium composite oxides with a larger energy capacity per unit weight compared to LFP has been expanding.

[0014] Furthermore, nickel-based lithium composite oxides, which have recently become the primary positive electrode active material for high-capacity lithium-ion batteries, must utilize ternary metal elements such as nickel, cobalt, and manganese, or nickel, cobalt, and aluminum. However, cobalt is not only subject to unstable supply and demand but is also too expensive compared to other raw materials. Therefore, there is a need for positive electrode active materials that can reduce the cobalt content or eliminate cobalt from the composition.

[0015] Considering these various factors, while lithium-rich manganese oxides can meet the expectations of the aforementioned markets, to date, these lithium manganese oxides have limitations in terms of insufficient electrochemical properties or stability in replacing high-Ni type cathode active materials such as commercially available ternary lithium composite oxides composed of nickel-cobalt-manganese (NCM) or nickel-cobalt-aluminum (NCA).

[0016] For example, as mentioned earlier, OLO has disadvantages such as lower charge / discharge capacity and rate performance due to the characteristics of its materials (including excess lithium and manganese).

[0017] Therefore, to improve the insufficient electrochemical properties of OLO, increasing the particle size could be considered. However, the particles that typically constitute the precursor of OLO usually grow into thick, plate-like particles. Therefore, as the size of the secondary particles increases, the internal density increases, but due to the low conductivity, this may be accompanied by a decrease in performance.

[0018] However, the inventors have discovered that the shape and physical properties of the precursor can be controlled according to the synthesis (coprecipitation reaction) conditions of the precursor of the lithium manganese oxide. Thus, when a positive electrode active material is prepared using a positive electrode active material precursor that achieves an appropriate specific surface area and internal density, the capacity characteristics and rate performance of the positive electrode active material can be improved.

[0019] Accordingly, the present invention aims to provide a method for preparing a positive electrode active material precursor, which controls the shape and physical properties of the precursor as a reaction product by adjusting the synthesis (coprecipitation reaction) conditions of the precursor of the lithium manganese oxide, thereby achieving an appropriate specific surface area and internal density of the precursor.

[0020] Furthermore, another object of the present invention is to provide a positive electrode active material precursor, which is prepared by the preparation method defined in this application, such that the surface shape of the aforementioned primary particles exposed on the surface has a long axis and a short axis, and achieves an appropriate specific surface area and internal density.

[0021] Furthermore, another object of the present invention is to provide a positive electrode active material precursor, which is prepared by the preparation method defined in this application, thereby inhibiting or mitigating the formation of micropowder and having an appropriate particle size distribution.

[0022] Furthermore, another object of the present invention is to provide a method for preparing a positive electrode active material using the above-mentioned positive electrode active material precursor.

[0023] The objectives of this invention are not limited to those described above. Other objectives and advantages of the invention not mentioned herein will be understood through the following description and will become clearer through embodiments of the invention. Furthermore, it will be readily understood that the objectives and advantages of the invention can be achieved through the means and combinations thereof described in the claims.

[0024] Technical solution To address the aforementioned technical problems, the present invention provides a method for preparing a positive electrode active material precursor that achieves appropriate specific surface area and internal density by controlling the shape and physical properties of the precursor, a positive electrode active material precursor, and a method for preparing a positive electrode active material using the positive electrode active material precursor.

[0025] [1] A method for preparing a positive electrode active material precursor, comprising the steps of adding a transition metal aqueous solution, an ammonium cation complexing agent and an alkaline aqueous solution to a reactor, and performing a co-precipitation reaction under conditions of pH greater than 8.0 and less than 10.0 to form a transition metal hydroxide precursor, wherein the content of manganese (mol%) in the aforementioned transition metal aqueous solution is greater than the content of nickel (mol%).

[0026] [2] According to the preparation method of the positive electrode active material precursor described in [1], the above-mentioned transition metal aqueous solution also contains one or more elements selected from transition metals other than alkali metals, alkaline earth metals, nickel and manganese, post-transition metals and metalloids.

[0027] [3] According to the method for preparing the positive electrode active material precursor according to any one of [1] to [2], the above-mentioned transition metal aqueous solution contains manganese at a rate of 50 mol% or more relative to the total number of moles of the transition metal.

[0028] [4] The coprecipitation reaction described above is carried out at pH 8.5 to 9.5 according to any one of [1] to [3] of the method for preparing the positive electrode active material precursor.

[0029] [5] The coprecipitation reaction is carried out in a non-oxidizing atmosphere or an oxidizing atmosphere according to any one of [1] to [4] of the method for preparing the positive electrode active material precursor.

[0030] [6] In the method for preparing the positive electrode active material precursor according to any one of [1] to [5], the coprecipitation reaction is carried out in an oxidizing atmosphere containing more than or equal to 0.5% by volume and less than 6.0% by volume of oxygen.

[0031] [7] According to any one of [1] to [6], the coprecipitation reaction is carried out at a temperature greater than or equal to 50°C and less than 80°C.

[0032] [8] The present invention provides a positive electrode active material precursor comprising a transition metal hydroxide represented by the following chemical formula 1, wherein the transition metal hydroxide has a secondary particle morphology formed by the aggregation of a plurality of primary particles, and the surface shape of the primary particles exposed on the surface of the transition metal hydroxide, as observed from a surface SEM image of the transition metal hydroxide, has a long axis and a short axis.

[0033] [Chemical Formula 1] [Ni b Co c Mn d M1 e ](OH)2 In the above chemical formula 1, M1 is selected from at least one of Al, P, Nb, B, Si, Ti, Zr, Ba, K, Mo, Fe, Cu, Cr, Zn, Na, Ca, Mg, Pt, Au, Eu, Sm, W, Ce, V, Ta, Sn, Hf, Gd, Y, Ru, Ge, and Nd, where 0 ≤ b < 0.5, 0 ≤ c ≤ 0.2, 0.5 ≤ d < 0.8, and 0 <e≤0.1,b+c+d+e=1。

[0034] [9] According to the positive electrode active material precursor described in [8], the average value of the ratio of the long axis length to the short axis length (long axis length / short axis length) of the surface shape of the primary particles exposed on the surface of the aforementioned transition metal hydroxide is 1.5 or more and 25.0 or less.

[0035]

[10] According to any one of [8] and [9], the average short axis length of the surface shape of the primary particles exposed to the surface of the transition metal hydroxide is 30 nm or more and 270 nm or less.

[0036]

[11] According to any one of [8] to

[10] , the average length of the long axis of the surface shape of the primary particles exposed to the surface of the transition metal hydroxide is 400 nm or more and 2500 nm or less.

[0037]

[12] According to any one of [8] to

[11] , the average particle size (D) of the above transition metal hydroxide is... 50 The value is 5.0. Up to 24.0 The span value of the aforementioned transition metal hydroxide, calculated by Equation 1 below, is 0.90 or less: [Formula 1] Span value = (D) 90 -D 10 ) / D 50

[13] The positive electrode active material precursor according to any one of [8] to

[12] has a BET specific surface area of ​​8.0 m² as determined by nitrogen adsorption method. 2 / g to 28.0m 2 / g.

[0038]

[14] The positive electrode active material precursor according to any one of [8] to

[13] , when X-ray diffraction spectroscopy analysis is performed on the above positive electrode active material precursor, the ratio (a / b) of the diffraction peak intensity (a) appearing in the region of 2θ=11.8±1° to the diffraction peak intensity (b) appearing in the region of 2θ=18.6±1° is 0.25 or less.

[0039]

[15] The present invention provides a method for preparing a positive electrode active material, comprising: a step of performing a first heat treatment on a positive electrode active material precursor according to any one of [8] to

[14] to form an oxide precursor; and a step of performing a second heat treatment on the oxide precursor and a lithium raw material to form a lithium manganese oxide in solid solution form, wherein the phase belonging to the C2 / m space group and the phase belonging to the R-3m space group exist in solid solution form.

[0040] Beneficial effects According to the present invention, the limitations of existing lithium-rich lithium manganese oxides, which have various disadvantages in terms of electrochemical properties and / or stability compared with commercially available ternary lithium composite oxides composed of nickel-cobalt-manganese or nickel-cobalt-aluminum, can be overcome.

[0041] Specifically, according to the present invention, the shape and physical properties of the precursor can be controlled according to the synthesis (co-precipitation reaction) conditions of the precursor of the lithium manganese oxide. As a result, it is expected that the capacity characteristics and rate performance of the positive electrode active material prepared using the precursor with appropriate specific surface area and internal density can be improved.

[0042] Furthermore, the positive electrode active material precursor prepared by the preparation method defined in this application suppresses or mitigates the formation of micropowder and has an appropriate particle size distribution. By suppressing the formation of impurity phases, it is expected that the capacity characteristics and rate performance of the positive electrode active material prepared using the above-mentioned precursor will be improved.

[0043] In addition to the effects described above, the specific effects of the present invention will be described in conjunction with the specific embodiments of the invention described below. Detailed Implementation

[0044] To facilitate understanding of the invention, specific terms are defined herein for convenience. Unless otherwise defined herein, scientific and technical terms used in this invention should have the meanings commonly understood by those skilled in the art. Furthermore, unless specifically specified in the context, it should be understood that singular terms also include their plural forms, and plural terms also include their singular forms.

[0045] This invention provides a method for preparing a positive electrode active material precursor that achieves appropriate specific surface area and internal density by controlling the shape and physical properties of the precursor, as well as the positive electrode active material precursor and the method for preparing a positive electrode active material using the positive electrode active material precursor. The invention will be described in more detail below.

[0046] Preparation method of positive electrode active material precursor According to one aspect of the present invention, a method for preparing a positive electrode active material precursor is provided, comprising the steps of adding an aqueous solution of a transition metal, an ammonium cation complexing agent and an alkaline aqueous solution to a reactor, and carrying out a co-precipitation reaction under conditions of pH greater than 8.0 and less than 10.0 to form a transition metal hydroxide precursor.

[0047] The reactor described above can be a batch reactor or a continuous reactor. Regardless of the type of reactor, the method for preparing the positive electrode active material precursor as defined in this application can be applied.

[0048] The aforementioned aqueous solution of the transition metal can be prepared by adding a raw material containing the transition metal to deionized water or a mixed solvent containing deionized water, or by mixing an aqueous solution containing the transition metal. The mixed solvent containing deionized water may contain an organic solvent (e.g., an alcohol) that is homogeneous with water.

[0049] The aforementioned raw materials containing transition metals can be sulfates, acetates, nitrates, halides, sulfides, hydroxides, oxides, and / or hydroxyoxides containing at least one transition metal.

[0050] The aforementioned transition metal aqueous solution may contain nickel-containing raw materials and manganese-containing raw materials.

[0051] The aforementioned nickel-containing raw materials can be nickel-containing acetates, nitrates, sulfates, halides, sulfides, hydroxides, oxides, hydroxyoxides, or combinations thereof. For example, the aforementioned nickel-containing raw materials can be Ni(OH)2, NiO, NiOOH, NiCO3·2Ni(OH)2·4H2O, NiC2O4·2H2O, Ni(NO3)2·6H2O, NiSO4·6H2O, nickel salts of fatty acids, nickel halides, or combinations thereof, but are not limited thereto.

[0052] The aforementioned manganese-containing raw materials can be manganese-containing acetates, nitrates, sulfates, halides, sulfides, hydroxides, oxides, hydroxyoxides, or combinations thereof. For example, the aforementioned manganese-containing raw materials can be manganese oxides such as Mn2O3, MnO2, and Mn3O4; manganese salts such as MnCO3, Mn(NO3)2·4H2O, MnSO4·H2O, manganese acetate, manganese dicarboxylate, manganese citrate, and manganese salts of fatty acids; manganese hydroxyoxides, manganese chloride, or combinations thereof, but are not limited thereto.

[0053] The aforementioned aqueous solution of transition metals may also contain one or more elements selected from transition metals other than alkali metals, alkaline earth metals, nickel, and manganese, post-transition metals, and metalloids.

[0054] The aforementioned transition metal aqueous solution may selectively contain cobalt-containing raw materials.

[0055] The aforementioned cobalt-containing raw materials can be cobalt-containing acetates, nitrates, sulfates, halides, sulfides, hydroxides, oxides, hydroxyoxides, or combinations thereof. For example, the aforementioned cobalt-containing raw materials can be Co(OH)2, CoOOH, Co(OCOCH3)2·4H2O, Co(NO3)2·6H2O, CoSO4, CoSO4·7H2O, Co(SO3)2, or combinations thereof, but are not limited thereto.

[0056] The aforementioned transition metal aqueous solution may selectively contain dopant-containing raw materials.

[0057] The dopant can be at least one selected from Al, P, Nb, B, Si, Ti, Zr, Ba, K, Mo, Fe, Cu, Cr, Zn, Na, Ca, Mg, Pt, Au, Eu, Sm, W, Ce, V, Ta, Sn, Hf, Gd, Y, Ru, Ge and Nd; at least one selected from Al, P, Nb, B, Si, Ti, Zr, Ba, K, Mo, Ca, Mg, W, Ce, V, Ta and Y; or at least one selected from Al, P, B, Si, Ti, Zr and W.

[0058] The aforementioned dopant-containing raw materials may be contained in the above-mentioned transition metal aqueous solution in the form of sulfates, acetates, nitrates, halides, sulfides, hydroxides, oxides and / or hydroxyoxides.

[0059] The manganese content (mol%) in the aforementioned transition metal aqueous solution may be greater than the nickel content (mol%). For example, the aforementioned transition metal aqueous solution may contain manganese at a rate of 50 mol% or more relative to the total moles of the transition metal.

[0060] As described below, in order for the positive active material prepared using the positive active material precursor defined in this application to form a solid solution consisting of a phase belonging to the C2 / m space group and a phase belonging to the R-3m space group, preferably, the content (mol%) of manganese in the above-mentioned transition metal aqueous solution is greater than or equal to 50 mol% and less than 80 mol% relative to the total number of moles of the transition metal.

[0061] The aforementioned ammonium cation complexing agent can be, for example, NH4OH, (NH4)2SO4, NH4NO3, NH4Cl, CH3COONH4, NH4CO3, or combinations thereof, but is not limited thereto. The aforementioned ammonium cation complexing agent can be used in the form of an aqueous solution. An aqueous solution containing the aforementioned ammonium cation complexing agent can be prepared by adding the aforementioned ammonium cation complexing agent to deionized water or a mixed solvent containing deionized water.

[0062] The aforementioned alkaline aqueous solution can be an alkali metal or alkaline earth metal hydroxide, oxide, or combination thereof, such as NaOH, KOH, or Ca(OH)₂. The aforementioned alkaline aqueous solution can be used in aqueous solution form. The aforementioned alkaline aqueous solution can be prepared by adding an alkali metal or alkaline earth metal hydroxide, oxide, or combination thereof to deionized water or a mixed solvent containing deionized water.

[0063] The alkaline aqueous solution described above can be used to adjust the pH when a transition metal aqueous solution, an ammonium cation complexing agent, and an alkaline aqueous solution are added to the reactor to carry out a coprecipitation reaction.

[0064] In this application, the coprecipitation reaction can be carried out under conditions of pH greater than 8.0 and less than pH 10.0, pH greater than 8.1 and less than pH 9.9, pH greater than 8.2 and less than pH 9.8, pH greater than 8.3 and less than pH 9.7, pH greater than 8.4 and less than pH 9.6, or pH greater than 8.5 and less than pH 9.5.

[0065] The pH during the coprecipitation reaction can affect the coprecipitation rate of the transition metals. Therefore, it is preferable to keep the pH constant during the coprecipitation reaction.

[0066] When the pH during the coprecipitation reaction is above 10.0, the primary particles constituting the cathode active material precursor become thicker (the short axis length of the primary particles increases), which may lead to an excessive reduction in the specific surface area of ​​the cathode active material precursor. If the specific surface area of ​​the cathode active material precursor is excessively reduced, the surface kinetic properties of the cathode active material prepared using the cathode active material precursor may decrease.

[0067] When the pH during the co-precipitation reaction is below 8.0, the decrease in the co-precipitation rate of nickel leads to a larger deviation between the nickel content in the cathode active material precursor and the designed composition, resulting in a less uniform particle size distribution and potential excessive formation of microparticles. The more uneven the particle size distribution and the higher the microparticle content of the cathode active material precursor, the larger the span value and BET specific surface area calculated based on the particle size distribution. This can reduce the capacity characteristics and rate performance of the cathode active material prepared using the precursor, and may even promote side reactions with the electrolyte.

[0068] In this application, the coprecipitation reaction can be carried out in a non-oxidizing atmosphere or an oxidizing atmosphere. As an example, the coprecipitation reaction can be started after purging the reactor with an inert gas such as nitrogen (N2) or argon (Ar) to form a non-oxidizing atmosphere.

[0069] As another example, after purging the reactor with an inert gas such as nitrogen or argon to create a non-oxidizing atmosphere, a predetermined oxidizing atmosphere can be created by supplying a mixed gas containing oxygen (O2), and then the coprecipitation reaction can begin. The mixed gas can be a mixture of oxygen and an inert gas (e.g., nitrogen).

[0070] If the above coprecipitation reaction is carried out in an oxidizing atmosphere, the shape of the primary particles constituting the positive electrode active material precursor can be controlled, and the BET specific surface area can be increased to an appropriate level. Specifically, if the above coprecipitation reaction is carried out in an oxidizing atmosphere, the long axis length of the primary particles can be reduced, thereby increasing the internal porosity of the positive electrode active material precursor to an appropriate level.

[0071] In this application, the coprecipitation reaction described above can be carried out in an oxidizing atmosphere containing more than or equal to 0.5 vol% and less than 6.0 vol%, more than 0.5 vol% and less than 5.0 vol%, more than 0.5 vol% and less than 4.0 vol%, or more than or equal to 0.5 vol% and less than 3.0 vol%. The oxidizing atmosphere containing more than or equal to 0.5 vol% and less than 6.0 vol% oxygen can be formed by supplying a mixed gas containing more than or equal to 0.5 vol% and less than 6.0 vol% oxygen into the reactor described above. The balance of the mixed gas other than oxygen can be an inert gas (e.g., nitrogen).

[0072] When the oxygen content in the mixed gas supplied to the reactor is 6.0% by volume or more, the primary particles constituting the positive electrode active material precursor become thicker, and the proportion of impurity phase in the positive electrode active material precursor may increase.

[0073] In this application, the coprecipitation reaction can be carried out at a temperature greater than or equal to 50°C and less than 80°C, above 50°C and below 75°C, or above 50°C and below 70°C.

[0074] If the temperature during the coprecipitation reaction is below 50°C, not only will the energy required for the reaction be insufficient, but the content of impurity phases in the positive electrode active material precursor will also increase, resulting in insufficient overall particle growth or potentially excessively high internal porosity. Conversely, if the temperature during the coprecipitation reaction is above 80°C, the primary particles constituting the positive electrode active material precursor may become excessively thick. The thicker the primary particles constituting the positive electrode active material precursor, the lower the internal porosity, and consequently, the specific surface area of ​​the precursor may decrease dramatically.

[0075] The coprecipitation reaction time can vary depending on the particle size of the positive electrode active material precursor to be prepared. For example, the coprecipitation reaction can be carried out for 5 to 120 hours, but is not limited to this.

[0076] After the coprecipitation reaction is completed, the positive electrode active material precursor can be washed and / or dried. The washing and drying processes can be performed using methods known in the art. For example, the positive electrode active material precursor can be washed with ultrapure water and dried using methods such as vacuum drying, natural drying, or spray drying.

[0077] Positive electrode active material precursor According to another aspect of the present invention, a positive electrode active material precursor comprising a transition metal hydroxide represented by the following chemical formula 1 is provided.

[0078] [Chemical Formula 1] [Ni b Co c Mn d M1 e ](OH)2 In the above chemical formula 1, M1 is selected from at least one of Al, P, Nb, B, Si, Ti, Zr, Ba, K, Mo, Fe, Cu, Cr, Zn, Na, Ca, Mg, Pt, Au, Eu, Sm, W, Ce, V, Ta, Sn, Hf, Gd, Y, Ru, Ge, and Nd, where 0 ≤ b < 0.5, 0 ≤ c ≤ 0.2, 0.5 ≤ d < 0.8, and 0 <e≤0.1,b+c+d+e=1。

[0079] The aforementioned transition metal hydroxide has a secondary particle morphology formed by the aggregation of multiple primary particles. The surface shape of the primary particles exposed on the surface of the transition metal hydroxide, as observed in SEM images of the surface, may have a long axis and a short axis. The surface of the secondary particles corresponds to the set of exposed surfaces of the primary particles located on the outermost side of the secondary particles.

[0080] The shape of the primary particle can be inferred from the surface shape of the primary particle exposed on the surface of the secondary particle as observed in the surface SEM image of the secondary particle, and from the cross-sectional SEM image of the primary particle as observed in the cross-sectional SEM image of the secondary particle.

[0081] The average value of the ratio of the major axis length to the minor axis length (major axis length / minor axis length) of the surface shape of the primary particles exposed to the surface of the aforementioned transition metal hydroxide can be 1.5 or more and 25.0 or less, 2.0 or more and 24.0 or less, 3.0 or more and 23.0 or less, 4.0 or more and 23.0 or less, or 4.7 or more and 22.4 or less.

[0082] As a result of the aforementioned co-precipitation reaction, if the primary particles grow too thick or too small, the average ratio of the major axis length to the minor axis length (major axis length / minor axis length) of the primary particles exposed on the surface of the transition metal hydroxide may be less than 1.5. If the primary particles grow too thick, the surface porosity of the lithium manganese oxide obtained by calcining the transition metal hydroxide decreases, and the surface kinetics decrease, thus posing a risk of reduced electrochemical properties. Furthermore, if the primary particles have too small a size, the specific surface area of ​​the lithium manganese oxide obtained by calcining the transition metal hydroxide increases sharply, thereby potentially increasing side reactions between the lithium manganese oxide and the electrolyte.

[0083] On the other hand, if the average ratio of the long axis length to the short axis length (long axis length / short axis length) of the surface shape of the primary particles exposed to the surface of the aforementioned transition metal hydroxide is greater than 25.0, the number of primary particles with excessively thin shapes increases, leading to an increase in the porosity of the lithium manganese oxide obtained by calcining the aforementioned transition metal hydroxide, thereby reducing the energy density per unit volume or increasing the specific surface area, thus increasing the risk of side reactions between the aforementioned lithium manganese oxide and the aforementioned electrolyte.

[0084] The average value of the minor axis length of the surface shape of the primary particles exposed to the surface of the aforementioned transition metal hydroxide can be 30 nm or more and 270 nm or less, 50 nm or more and 270 nm or less, 70 nm or more and 270 nm or less, 80 nm or more and 270 nm or less, or 84 nm or more and 260 nm or less.

[0085] If the average short axis length of the surface shape of the primary particles exposed on the surface of the aforementioned transition metal hydroxide is less than 30 nm, then the size of the primary particles exposed on the surface of the lithium manganese oxide obtained by calcining the aforementioned transition metal hydroxide is too small or too thin, and therefore it may be difficult to reduce the side reactions between the aforementioned lithium manganese oxide and the aforementioned electrolyte.

[0086] Conversely, if the average short axis length of the surface shape of the primary particles exposed on the surface of the aforementioned transition metal hydroxide is greater than 270 nm, then the size of the primary particles exposed on the surface of the lithium manganese oxide obtained by calcining the aforementioned transition metal hydroxide is too large, and therefore surface dynamic properties such as lithium ion conductivity may be reduced.

[0087] The average length of the major axis of the surface shape of the primary particles exposed on the surface of the aforementioned transition metal hydroxide can be 400 nm or more and 2500 nm or less, 400 nm or more and 2400 nm or less, 400 nm or more and 2300 nm or less, 500 nm or more and 2300 nm or less, 500 nm or more and 2200 nm or less, 500 nm or more and 2100 nm or less, 600 nm or more and 2000 nm or less, or 600 nm or more and 1900 nm or less.

[0088] If the average length of the major axis of the primary particles exposed on the surface of the aforementioned transition metal hydroxide is less than 400 nm, then the size of the primary particles exposed on the surface of the lithium manganese oxide obtained by calcining the aforementioned transition metal hydroxide is too small, and therefore it may be difficult to reduce the side reactions between the aforementioned lithium manganese oxide and the aforementioned electrolyte.

[0089] Conversely, if the average length of the major axis of the primary particles exposed on the surface of the aforementioned transition metal hydroxide is greater than 2500 nm, the size of the primary particles exposed on the surface of the lithium manganese oxide obtained by calcining the aforementioned transition metal hydroxide is too large, and therefore the surface dynamic properties such as lithium ion conductivity may be reduced.

[0090] The average particle size (D) of the above transition metal hydroxides 50 The value is 5.0. Up to 24.0 6.0 Up to 20.0 Or 7.0 Up to 15.0 .

[0091] On the other hand, the transition metal hydroxides defined in this application can be used as precursors for preparing large particles of positive electrode active materials exhibiting a bimodal or trimodal particle size distribution, or as precursors for preparing medium particles of positive electrode active materials exhibiting a trimodal particle size distribution. The aforementioned medium particles refer to particles with an average particle size between small and large particles in positive electrode active materials exhibiting a trimodal particle size distribution.

[0092] The average particle size (D) of the above-mentioned transition metal hydroxides used to prepare large particles of positive electrode active materials exhibiting bimodal or trimodal particle size distributions is... 50 It can be 5.0. Up to 24.0 6.0 Up to 20.0 6.0 Up to 18.0 6.0 Up to 16.0 Or 6.0 Up to 15.0 .

[0093] The average particle size (D) of the above-mentioned transition metal hydroxides used to prepare medium-sized particles of positive electrode active materials exhibiting a trimodal particle size distribution 50 It can be 5.0. Up to 15.0 5.0 Up to 10.0 Or 5.0 Up to 8.0 .

[0094] The span value of the particle size of the above-mentioned transition metal hydroxide calculated by the following formula 1 can be 0.90 or less, or 0.88 or less.

[0095] [Formula 1] Span value = (D) 90 -D 10 ) / D 50 If the particle size span of the aforementioned transition metal hydroxide is greater than 0.90, then the particle size distribution of the aforementioned positive electrode active material precursor is uneven, and the aforementioned positive electrode active material precursor may contain too much micro powder.

[0096] The BET specific surface area of ​​the above-mentioned positive electrode active material precursor, as determined by nitrogen adsorption, is 8.0 m². 2 / g to 28.0m 2 / g, 10.0m 2 / g to 28.0m2 / g, 11.0m 2 / g to 28.0m 2 / g, 12.0m 2 / g to 27.0m 2 / g, or 13.2m 2 / g to 26.2m 2 / g.

[0097] If the BET specific surface area of ​​the above-mentioned positive electrode active material precursor is less than 8.0 m² 2 If the specific surface area of ​​the lithium manganese oxide prepared using the above-mentioned positive electrode active material precursor is less than 28.0 m² / g, the capacity characteristics and rate performance of the positive electrode active material containing the above-mentioned lithium manganese oxide may be difficult to improve. Conversely, if the BET specific surface area of ​​the above-mentioned positive electrode active material precursor is greater than 28.0 m² / g, the specific surface area will be significantly reduced. 2 If the specific surface area of ​​the lithium manganese oxide prepared using the above-mentioned positive electrode active material precursor is excessively increased, the possibility of side reactions between the lithium manganese oxide and the electrolyte increases, which may lead to a decrease in the stability of the positive electrode active material containing the above-mentioned lithium manganese oxide.

[0098] When the above-mentioned positive electrode active material precursor is subjected to X-ray diffraction spectroscopy analysis, the ratio (a / b) of the diffraction peak intensity (a) appearing in the region of 2θ=11.8±1° to the diffraction peak intensity (b) appearing in the region of 2θ=18.6±1° can be less than 0.25, less than 0.20, less than 0.15, less than 0.11, less than 0.105, or less than 0.103.

[0099] When performing X-ray diffraction spectroscopy analysis on the above-mentioned positive electrode active material precursor, the diffraction peak appearing in the region of 2θ = 18.6 ± 1° corresponds to the [Ni] represented by the above chemical formula 1. b Co c Mn d M1 e The peak of ](OH)2, the diffraction peak appearing in the region of 2θ=11.8±1°, corresponds to the peak of the MnO2 phase.

[0100] When X-ray diffraction spectroscopy analysis was performed on the above-mentioned cathode active material precursor, the ratio (a / b) of the diffraction peak intensity (a) appearing in the 2θ=11.8±1° region to the diffraction peak intensity (b) appearing in the 2θ=18.6±1° region was greater than 0.25, indicating that the proportion of MnO2 as an impurity phase in the above-mentioned cathode active material precursor was too high. In this case, the capacity characteristics and rate performance of the cathode active material prepared using the above-mentioned cathode active material precursor may be reduced.

[0101] Preparation method of positive electrode active material According to another aspect of the present invention, a method for preparing a positive electrode active material using a positive electrode active material precursor as defined in this application is provided.

[0102] According to the present invention, the shape and physical properties of the precursor can be controlled according to the synthesis (coprecipitation reaction) conditions of the precursor of the lithium manganese oxide, thereby improving the capacity characteristics and rate performance of the positive electrode active material prepared using the precursor with appropriate specific surface area and internal density.

[0103] The above-mentioned method for preparing the positive electrode active material includes: a first heat treatment of the positive electrode active material precursor (specifically, the transition metal hydroxide represented by the above-mentioned chemical formula 1) to form an oxide precursor; and a second heat treatment of the oxide precursor with lithium raw material to form a lithium manganese oxide in solid solution form, wherein the phase belonging to the C2 / m space group and the phase belonging to the R-3m space group exist in solid solution form.

[0104] The transition metal hydroxide represented by the above chemical formula 1 can be converted into an oxide precursor by undergoing a first heat treatment in an air-atmosphere furnace at 300°C to 700°C, 400°C to 600°C, or 450°C to 550°C for 1 hour to 36 hours.

[0105] Next, after mixing the aforementioned oxide precursor with lithium raw material to prepare a mixture, the mixture is subjected to a second heat treatment in a calcination furnace under an O2 atmosphere at 700°C to 1000°C, 800°C to 950°C, or 850°C to 950°C for 2 to 36 hours, thereby obtaining a positive electrode active material consisting of a phase belonging to the C2 / m space group and a phase belonging to the R-3m space group existing in solid solution form of lithium manganese oxide.

[0106] As lithium raw materials, lithium-containing carbonates (e.g., Li2CO3, etc.), hydrates (e.g., lithium hydroxide hydrate (LiOH·H2O) etc.), hydroxides (e.g., LiOH, etc.), nitrates (e.g., lithium nitrate (LiNO3) etc.), chlorides (e.g., lithium chloride (LiCl) etc.) and combinations thereof can be used.

[0107] The aforementioned lithium raw materials can be mixed such that the Li / Metal molar ratio of lithium to all metal elements present in the precursor in the aforementioned oxide state is greater than 1, or is 1.1 to 1.6, 1.1 to 1.5, 1.2 to 1.6, or 1.2 to 1.5.

[0108] Optionally, a dopant-containing raw material may be mixed prior to the second heat treatment for doping at least one of the phases belonging to the C2 / m space group and the phases belonging to the R-3m space group.

[0109] The dopant can be at least one selected from Al, P, Nb, B, Si, Ti, Zr, Ba, K, Mo, Fe, Cu, Cr, Zn, Na, Ca, Mg, Pt, Au, Eu, Sm, W, Ce, V, Ta, Sn, Hf, Gd, Y, Ru, Ge and Nd; at least one selected from Al, P, Nb, B, Si, Ti, Zr, Ba, K, Mo, Ca, Mg, W, Ce, V, Ta and Y; or at least one selected from Al, P, B, Si, Ti, Zr and W.

[0110] The aforementioned dopant-containing raw materials can be mixed in the form of sulfates, acetates, nitrates, halides, sulfides, hydroxides, oxides and / or hydroxyoxides.

[0111] Optionally, a halogenated raw material that replaces a portion of the oxygen in the aforementioned lithium manganese oxide may be mixed in before the second heat treatment.

[0112] The halogen mentioned above can be F, Cl, Br and / or I, preferably F. To halogen-dope the above-mentioned lithium manganese oxides, at least one anionic dopant selected from LiF, MgF2, HF, F2, XeF2, TbF4, CeF4, CoF3, AgF2, MoF3, AgF, CuF2, FeF3, CuF, VF3, CrF3, ZrF4, BaF2, CaF2, AlF3, NH4F, CeF3 and CsF can be used.

[0113] Positive electrode active material According to another aspect of the present invention, a positive electrode active material comprising a lithium manganese oxide formed by solid solution of a phase belonging to the C2 / m space group and a phase belonging to the R-3m space group is provided.

[0114] The aforementioned positive electrode active material includes lithium manganese oxides prepared using a positive electrode active material precursor prepared by the method defined in this application.

[0115] The phases belonging to the C2 / m space group and the phases belonging to the R-3m space group can be distinguished not only by their constituent phases but also by the characteristic peaks of each phase during XRD analysis. For example, the characteristic peaks of the phases belonging to the C2 / m space group appear in the region of 2θ = 20.8 ± 1°, while the characteristic peaks of the phases belonging to the R-3m space group appear in the region of 2θ = 18.6 ± 1°.

[0116] The aforementioned lithium manganese oxides are composite oxides formed by the solid solution of a phase belonging to the C2 / m space group and a phase belonging to the R-3m space group. Both the C2 / m and R-3m space group phases coexist within these lithium manganese oxides. Furthermore, these lithium manganese oxides differ from composite oxides with a spinel crystal structure belonging to the Fd-3m space group (e.g., LiMn2O4 or oxides with similar compositions).

[0117] The aforementioned lithium-manganese oxides can be composite oxides of lithium, nickel, and manganese. Furthermore, these lithium-manganese oxides may also contain one or more elements selected from alkali metals, alkaline earth metals, transition metals other than nickel and manganese, post-transition metals, and metalloids.

[0118] Since the number of lithium moles in the aforementioned lithium manganese oxides is greater than the sum of the number of moles of other transition metals (usually when the molar ratio of lithium to all metal elements other than lithium in the lithium manganese oxide is greater than 1), the aforementioned lithium manganese oxides are sometimes also called lithium-rich layered oxides (OLO).

[0119] Furthermore, since the manganese content in the aforementioned lithium-manganese oxides is greater than that of other transition metals, these lithium-manganese oxides are sometimes referred to as layered oxides with excess lithium and manganese.

[0120] Generally, considering that the content of manganese in all metal elements other than lithium in commercially available ternary lithium composite oxides composed of nickel-cobalt-manganese or nickel-cobalt-aluminum is less than 20 mol%, the above-mentioned lithium manganese oxides have a relatively higher proportion of manganese in all metal elements (e.g., more than 50 mol%, more than 52 mol%, more than 53 mol%, or more than 55 mol%) compared with commercially available ternary lithium composite oxides.

[0121] Furthermore, considering that the nickel content in all metal elements other than lithium in commercially available ternary lithium composite oxides composed of nickel-cobalt-manganese or nickel-cobalt-aluminum is 60 mol% or more (80 mol% or more in the case of high-nickel types), the aforementioned lithium manganese oxides have a relatively low proportion of nickel in all metal elements (e.g., less than 50 mol%, less than 48 mol%, less than 46 mol%, less than 45 mol%, less than 44 mol%, less than 42 mol%, or less than 40 mol%) compared to commercially available ternary lithium composite oxides.

[0122] The following differences also exist: the Li / Metal molar ratio measured from lithium manganese oxides as defined in this application is greater than that of ternary lithium composite oxides such as nickel-cobalt-manganese or nickel-cobalt-aluminum. For example, the Li / Metal molar ratio of ternary lithium composite oxides such as nickel-cobalt-manganese or nickel-cobalt-aluminum is almost close to 1. Conversely, the Li / Metal molar ratio of lithium manganese oxides as defined in this application is greater than 1, preferably 1.1 to 1.6, 1.1 to 1.5, 1.2 to 1.6, or 1.2 to 1.5.

[0123] Therefore, in this application, lithium manganese oxides can be defined as composite oxides in which the content of manganese in all metal elements other than lithium is 50 mol% or more, or can be defined as composite oxides in which the content of manganese in all metal elements other than lithium is 50 mol% or more and the content of nickel is less than 50 mol%.

[0124] Furthermore, in this application, lithium manganese oxide can be defined as a composite oxide in which the molar ratio of lithium to all metal elements other than lithium is greater than 1, or is 1.1 to 1.6, 1.1 to 1.5, 1.2 to 1.6, or 1.2 to 1.5, and the content of manganese in all metal elements other than lithium is 50 mol% or more; or it can be defined as a composite oxide in which the molar ratio of lithium to all metal elements other than lithium is greater than 1, or is 1.1 to 1.6, 1.1 to 1.5, 1.2 to 1.6, or 1.2 to 1.5, and the content of manganese in all metal elements other than lithium is 50 mol% or more, and the content of nickel is less than 50 mol%.

[0125] Despite the aforementioned differences in composition, the lithium manganese oxides described above can also function as composite metal oxides capable of lithium ion insertion / extraction.

[0126] The lithium manganese oxides included in the positive electrode active material as defined in this application can exist as aggregates formed by the aggregation of multiple primary particles. When the lithium manganese oxides exist as aggregates formed by the aggregation of multiple primary particles, the lithium manganese oxides can be referred to as secondary particles.

[0127] The aforementioned primary particles refer to particle units that do not exhibit grain boundaries when observed using a scanning electron microscope at magnifications of 5,000 to 20,000.

[0128] The primary particles constituting the lithium manganese oxide as defined in this application may have a particle size of 0.05. Up to 5 0.1 Up to 5.0 0.25 Up to 3.0 Or 0.25 Up to 2.0 The average particle size. Here, the average particle size of the aforementioned primary particles can be calculated as the average of the lengths along the major axis and the minor axis of the primary particles ([major axis length + minor axis length] / 2). The average particle size of the aforementioned primary particles can be calculated as the average of the particle sizes of all primary particles observed from the surface SEM images and / or cross-sectional SEM images of the aforementioned lithium manganese oxide.

[0129] If the average particle size of the aforementioned primary particles is less than 0.05... Therefore, the lithium manganese oxide (secondary particles) composed of the aforementioned primary particles has a relatively large specific surface area. In this case, the possibility of the aforementioned lithium manganese oxide undergoing side reactions with the electrolyte during storage or operation of the lithium secondary battery may increase.

[0130] Conversely, if the average particle size of the aforementioned primary particles is greater than 5... If the growth of the primary particles is excessively induced, the diffusion path of lithium ions within the primary particles becomes longer. If the diffusion path of lithium ions within the primary particles is too long, the mobility of lithium ions within the primary particles and the diffusivity of lithium ions through the primary particles decrease, which increases the resistance of the lithium manganese oxide (secondary particles) composed of the primary particles.

[0131] Therefore, in order to reduce the specific surface area of ​​the aforementioned lithium manganese oxides, and simultaneously prevent a decrease in the migration rate of lithium ions within the primary particles and the diffusivity of lithium ions through the primary particles, the average particle size of the primary particles can be 0.05 mm. Up to 5 0.1 Up to 5.0 0.25 Up to 3.0 Or 0.25 Up to 2.0 .

[0132] The average particle size (D) of the above secondary particles 50 It can be 5.0. Up to 24.0 The average particle size (D) of the aforementioned secondary particles 50The size of the secondary particles can vary depending on the number of primary particles that constitute them. The average particle size of the secondary particles can be determined using a laser diffraction method. For example, it can be determined by dispersing the secondary particles in a dispersion medium, introducing them into a commercially available laser diffraction particle size analyzer (e.g., Microtrac MT3000), irradiating them with ultrasound at a frequency of approximately 28 kHz at an output power of 60 W, obtaining a volumetric particle size distribution map, and determining the particle size corresponding to 50% of the volumetric accumulation.

[0133] For example, lithium manganese oxides as defined in this application can be used as positive electrode active materials exhibiting bimodal or trimodal particle size distributions to improve insufficient energy density per unit volume. Accordingly, lithium manganese oxides as defined in this application can be used as small and / or large particles of positive electrode active materials exhibiting bimodal particle size distributions, or as small, medium (particles with an average particle size between small and large particles), and / or large particles of positive electrode active materials exhibiting trimodal particle size distributions.

[0134] When lithium manganese oxides as defined in this application are used as large particles of positive electrode active materials exhibiting a bimodal particle size distribution or a trimodal particle size distribution, the average particle size (D) of the aforementioned secondary particles is... 50 It can be 5.0. Up to 24.0 6.0 Up to 20.0 6.0 Up to 18.0 6.0 Up to 16.0 Or 6.0 Up to 15.0 .

[0135] When lithium manganese oxides as defined in this application are used as medium particles in positive electrode active materials exhibiting a trimodal particle size distribution, the average particle size (D) of the aforementioned secondary particles is... 50 It can be 5.0. Up to 15.0 5.0 Up to 10.0 Or 5.0 Up to 8.0 .

[0136] In this application, “particle size” is used to mean the same as “particle diameter” or “particle size”, and unless otherwise defined, all “average particle size” refers to the particle size of the median volume reference determined by laser diffraction.

[0137] Unless otherwise defined, the term "surface of the above-mentioned primary particles" used in this application refers to the outer surface of the above-mentioned primary particles exposed to the outside. Similarly, the term "surface of the above-mentioned secondary particles" used in this application refers to the outer surface of the above-mentioned secondary particles exposed to the outside. As described above, the "surface of the above-mentioned secondary particles" formed by the aggregation of multiple primary particles corresponds to the exposed surface of the above-mentioned primary particles present in the surface portion of the above-mentioned secondary particles.

[0138] In addition, unless otherwise defined, the term "surface portion of the particle" used in this application refers to the region relatively close to the "outermost surface" of the particle, and the term "central portion of the particle" refers to the region relatively close to the "exact center" of the particle with respect to the above-mentioned "surface portion". Accordingly, the "surface portion of the primary particle" refers to the region relatively close to the "outermost surface" of the above-mentioned primary particle, and the "central portion of the primary particle" refers to the region relatively close to the "exact center" of the above-mentioned primary particle with respect to the above-mentioned "surface portion". Similarly, the "surface portion of the secondary particle" refers to the region relatively close to the "outermost surface" of the above-mentioned secondary particle, and the "central portion of the secondary particle" refers to the region relatively close to the "exact center" of the above-mentioned secondary particle with respect to the above-mentioned "surface portion".

[0139] At this time, the region other than the "surface portion of the particle" in any particle can be defined as the "central portion of the particle".

[0140] In this application, when the radius of the above-mentioned lithium manganese-based oxide measured from the cross-sectional SEM image of the above-mentioned lithium manganese-based oxide is set to R, the region where the distance (d) from the center of the above-mentioned lithium manganese-based oxide is (1 / 2)R < d can be defined as the surface portion, and the region where the distance (d) from the center of the above-mentioned lithium manganese-based oxide is 0 ≤ d ≤ (1 / 2)R can be defined as the center portion. Here, it is premised that the above-mentioned lithium manganese-based oxide is a secondary particle.

[0141] Since the above-mentioned secondary particle may not have a perfect spherical shape, the radius (R) of the above-mentioned secondary particle can be calculated from the average value of the long-axis length and the short-axis length of the above-mentioned lithium manganese-based oxide measured from the cross-sectional SEM image of the above-mentioned secondary particle. That is, the radius (R) of the above-mentioned secondary particle can be regarded as half of the average value of the long-axis length and the short-axis length of the above-mentioned lithium manganese-based oxide measured from the cross-sectional SEM image of the above-mentioned secondary particle.

[0142] The above-mentioned lithium manganese-based oxide defined in this application can be represented by the following Chemical Formula 2 or Chemical Formula 3. <​​​​​​​c Mn d M1 e )O 2-f X f In the above chemical formula 2, M1 is selected from at least one of Al, P, Nb, B, Si, Ti, Zr, Ba, K, Mo, Fe, Cu, Cr, Zn, Na, Ca, Mg, Pt, Au, Eu, Sm, W, Ce, V, Ta, Sn, Hf, Gd, Y, Ru, Ge, and Nd. X is a halogen capable of replacing some of the oxygen present in the aforementioned lithium manganese oxides. 0 <a≤0.7,0≤b<0.5,0≤c≤0.2,0.5≤d<0.8,0<e≤0.1,0≤f≤0.1。

[0144] [Chemical Formula 3] rLi2MnO 3-p X p ·(1-r)Li u Ni w Co x Mn y M2 z O 2-p' X' p' In the above chemical formula 3, M2 is selected from at least one of Al, P, Nb, B, Si, Ti, Zr, Ba, K, Mo, Fe, Cu, Cr, Zn, Na, Ca, Mg, Pt, Au, Eu, Sm, W, Ce, V, Ta, Sn, Hf, Gd, Y, Ru, Ge, and Nd. X and X' are halogens capable of replacing some of the oxygen present in the aforementioned lithium manganese oxides. 0.2 <r≤0.7,0<u≤1,0≤w≤1,0≤x≤0.2,0.3<y<1,0<z≤0.1,0≤p≤0.1,0≤p'≤0.1。

[0145] In chemical formulas 2 and 3 above, X and X' are each independently a halogen element capable of replacing a portion of the oxygen present in the aforementioned lithium manganese oxides. Referring to the periodic table, F, Cl, Br, and / or I can be used as halogens for X and X', with F being preferred.

[0146] In the above chemical formulas 2 and 3, M1 and M2 can each independently be at least one selected from Al, P, Nb, B, Si, Ti, Zr, Ba, K, Mo, Fe, Cu, Cr, Zn, Na, Ca, Mg, Pt, Au, Eu, Sm, W, Ce, V, Ta, Sn, Hf, Gd, Y, Ru, Ge and Nd, at least one selected from Al, P, Nb, B, Si, Ti, Zr, Ba, K, Mo, Ca, Mg, W, Ce, V, Ta and Y, and at least one selected from Al, P, B, Si, Ti, Zr and W.

[0147] The Li / Metal molar ratio measured from the lithium manganese oxide represented by the above-described chemical formula 2 or 3 can be greater than 1, or 1.1 to 1.6, 1.1 to 1.5, 1.2 to 1.6, or 1.2 to 1.5. The Li / Metal molar ratio measured from the above-described lithium manganese oxide should be at least greater than 1 to form a lithium-rich lithium manganese oxide. Furthermore, in order to appropriately form a solid solution of the above-described lithium manganese oxide with a phase belonging to the C2 / m space group and a phase belonging to the R-3m space group, and to exhibit high capacity under high-voltage operating conditions, the Li / Metal molar ratio of the above-described lithium manganese oxide is preferably 1.1 to 1.5, 1.2 to 1.6, or 1.2 to 1.5.

[0148] Furthermore, in order to properly form a solid solution formed by the solid solution of a phase belonging to the C2 / m space group and a phase belonging to the R-3m space group, preferably, the content of manganese in all metal elements other than lithium present in the lithium manganese oxide represented by the above chemical formula 2 or the above chemical formula 3 is 50 mol% or more.

[0149] To enable the aforementioned lithium manganese oxides to exhibit high-capacity OLO performance under high-voltage operating conditions, the manganese content in all metal elements other than lithium in the aforementioned lithium manganese oxides can be greater than or equal to 50 mol% and less than 80 mol%, greater than or equal to 51 mol% and less than 80 mol%, greater than or equal to 52 mol% and less than 80 mol%, greater than or equal to 53 mol% and less than 80 mol%, greater than or equal to 54 mol% and less than 80 mol%, greater than or equal to 55 mol% and less than 80 mol%, 50 mol% or more and less than 75 mol%, 51 mol% or more and less than 75 mol%, 52 mol% or more and less than 75 mol%, 53 mol% or more and less than 75 mol%, 54 mol% or more and less than 75 mol%, or 55 mol% to 75 mol%. If the manganese content in the aforementioned lithium manganese oxides is greater than 80 mol%, a phase transition may occur due to the migration of transition metals (especially manganese) within the aforementioned lithium manganese oxides during the formation of the lithium secondary battery and / or operation. This phase transformation forms a spinel phase, which, as an impurity in the aforementioned lithium manganese oxides, may cause a reduction in charge / discharge capacity or voltage decay during lithium secondary battery cycling. Furthermore, if the manganese content in the aforementioned lithium manganese oxides is greater than 80 mol%, it may be difficult to sufficiently generate a phase belonging to the R-3m space group.

[0150] In order to properly form a solid solution consisting of a phase belonging to the C2 / m space group and a phase belonging to the R-3m space group, the content of nickel in all metal elements other than lithium present in the lithium manganese oxide represented by the above chemical formula 2 or the above chemical formula 3 may be greater than or equal to 0 mol% and less than 50 mol%, more than 5 mol% and less than 48 mol%, more than 10 mol% and less than 46 mol%, more than 15 mol% and less than 45 mol%, more than 20 mol% and less than 44 mol%, more than 20 mol% and less than 42 mol%, or more than 20 mol% and less than 40 mol%.

[0151] If the nickel content in the aforementioned lithium manganese oxide is 50 mol% or more, the C2 / m phase may be difficult to form sufficiently, or the phase belonging to the C2 / m space group and the phase belonging to the R-3m space group may not be able to form a sufficient solid solution, which may cause phase separation in the formation and / or operation of lithium secondary batteries.

[0152] The lithium manganese oxide represented by Chemical Formula 2 or Chemical Formula 3 above may selectively contain cobalt. When the lithium manganese oxide contains cobalt, the molar fraction of cobalt relative to the total number of metal elements in the lithium manganese oxide may be 20% or less, 15% or less, or 10% or less. In other cases, the lithium manganese oxide represented by Chemical Formula 2 or Chemical Formula 3 above may have a cobalt-free composition.

[0153] In commercially available ternary lithium composite oxides composed of nickel-cobalt-manganese or nickel-cobalt-aluminum, the phase belonging to the R-3m space group exists as a single phase.

[0154] Conversely, the lithium-rich lithium manganese oxides represented by the above chemical formula 2 or the above chemical formula 3, as oxides of the phase belonging to the C2 / m space group represented by Li2MnO3 (hereinafter referred to as 'C2 / m phase'), and the oxides of Li u Ni w Co x Mn y M2 z O2 represents a composite oxide formed by the solid solution of an oxide belonging to the R-3m space group (hereinafter referred to as the 'R-3m phase'). For example, the above-mentioned lithium manganese oxide can exist as a solid solution of an oxide of the C2 / m phase and an oxide of the R-3m phase.

[0155] At this point, a composite oxide in which the phase belonging to the C2 / m space group and the phase belonging to the R-3m space group are only physically and / or chemically combined or attached is not a solid solution as defined in this application.

[0156] For example, a composite oxide consisting of a metal oxide having a phase belonging to the C2 / m space group and a metal oxide having a phase belonging to the R-3m space group, or having a metal oxide having a phase belonging to the R-3m space group coated on its surface, is not a solid solution as defined in this application.

[0157] If r is greater than 0.7 in the lithium manganese oxide represented by the above chemical formula 3, then the proportion of Li2MnO3, which is an oxide belonging to the C2 / m space group, is excessive. Consequently, as the irreversible capacity and resistance of the positive electrode active material increase, there is a risk of a decrease in discharge capacity. That is, in order to fully activate the oxide belonging to the C2 / m space group with relatively high resistance in the above lithium manganese oxide to improve surface kinetic properties, preferably, the oxide belonging to the R-3m space group is present in a predetermined proportion or higher. The ratio of the C2 / m space group phase to the R-3m space group phase in the above lithium manganese oxide can be calculated by the composition ratio of lithium to transition metal present in the above lithium manganese oxide.

[0158] Lithium secondary batteries According to another aspect of the present invention, a positive electrode can be provided comprising a positive current collector and a positive active material layer formed on the positive current collector. The positive active material layer may comprise lithium manganese oxide as the positive active material according to various embodiments of the present invention described above.

[0159] Therefore, a detailed description of lithium manganese oxides is omitted; the following description will only cover the remaining components not previously mentioned. Furthermore, for convenience, the aforementioned lithium manganese oxides will be referred to as positive electrode active materials.

[0160] There are no particular restrictions on the aforementioned positive electrode current collector, as long as it does not induce chemical changes in the battery and has conductivity. For example, stainless steel, aluminum, nickel, titanium, sintered carbon, or surface-treated aluminum or stainless steel using carbon, nickel, titanium, silver, etc., can be used. Furthermore, the aforementioned positive electrode current collector typically has 3... Up to 500 The thickness can also be increased by forming fine irregularities on the surface of the current collector to improve the adhesion of the positive electrode active material. For example, it can be used in various forms such as thin film, sheet, foil, mesh, porous body, foam, and non-woven body.

[0161] The aforementioned positive electrode active material layer can be prepared by coating the aforementioned positive electrode current collector with a positive electrode slurry composition comprising the aforementioned positive electrode active material, a conductive material, and, if desired, a binder.

[0162] At this point, the content of the positive electrode active material relative to the total weight of the positive electrode active material layer can be from 80% to 99% by weight, more specifically from 85% to 98.5% by weight. When the positive electrode active material is included in the above content range, excellent capacity characteristics can be exhibited, but it is not limited thereto.

[0163] The aforementioned conductive materials are used to impart conductivity to the electrodes. In the constructed battery, they can be used without restriction as long as they do not cause chemical changes and possess electronic conductivity. Specific examples include graphite such as natural 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 powders or fibers such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives. One or more mixtures of these materials may be used. The total weight of the positive electrode active material layer may range from 0.1% to 15% by weight of the aforementioned conductive materials.

[0164] The aforementioned binder enhances the adhesion between multiple positive electrode active material particles and the bonding force between the positive electrode active material and the current collector. Specific examples include polyvinylidene fluoride (PVDF), ethylene-vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene propylene diene monomer (EPDM), sulfonated ethylene propylene diene monomer (EPDM), styrene-butadiene rubber (SBR), fluororubber, or various copolymers thereof; one or more mixtures thereof may be used. The binder may comprise 0.1% to 15% by weight of the aforementioned binder relative to the total weight of the positive electrode active material layer.

[0165] In addition to utilizing the aforementioned positive electrode active material, the positive electrode can be prepared according to conventional positive electrode preparation methods. Specifically, it can be prepared by coating a positive electrode slurry composition onto a positive electrode current collector and then drying and calendering it. The positive electrode slurry composition is prepared by dissolving or dispersing the aforementioned positive electrode active material in a solvent and selectively dissolving or dispersing the binder and conductive material in the solvent.

[0166] The solvents mentioned above can be solvents commonly used in this technical field, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methyl-2-pyrrolidone (NMP), acetone, or water, and one or more mixtures thereof can be used. Considering the coating thickness and preparation yield of the slurry, the amount of the solvent used should be sufficient to dissolve or disperse the positive electrode active material, conductive material, and binder, and to have a viscosity that exhibits excellent thickness uniformity when coated for the preparation of the positive electrode.

[0167] Furthermore, in another embodiment, the positive electrode can also be prepared by casting the positive electrode slurry composition onto a separate support, and then laminating the thin film obtained by peeling off the support onto the positive electrode current collector.

[0168] Furthermore, according to another aspect of the present invention, an electrochemical device including the aforementioned positive electrode can be provided. Specifically, the aforementioned electrochemical device can be a battery, a capacitor, etc., and more specifically, it can be a lithium secondary battery.

[0169] Specifically, the aforementioned lithium secondary battery may include a positive electrode, a negative electrode disposed opposite to the positive electrode, and a separator and electrolyte disposed between the positive electrode and the negative electrode. The positive electrode is the same as described above; therefore, for convenience, a detailed description is omitted. The remaining components not previously described will be specifically described below.

[0170] The aforementioned lithium secondary battery may optionally include: a battery container for housing the electrode assembly containing the positive electrode, the negative electrode, and the separator; and a sealing component for sealing the battery container.

[0171] The aforementioned negative electrode may include a negative electrode current collector and a layer of negative electrode active material located on the aforementioned negative electrode current collector.

[0172] There are no particular restrictions on the aforementioned negative electrode current collector, as long as it does not induce chemical changes in the battery and has high conductivity. For example, copper, stainless steel, aluminum, nickel, titanium, sintered carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloys can be used. Furthermore, the aforementioned negative electrode current collector typically has 3... Up to 500 Similar to the thickness of the positive electrode current collector, the bonding force of the negative electrode active material can be enhanced by forming fine irregularities on the surface of the current collector. For example, it can be used in various forms such as thin films, sheets, foils, meshes, porous bodies, foams, and nonwovens.

[0173] The aforementioned negative electrode active material layer can be prepared by coating the aforementioned negative electrode current collector with a negative electrode slurry composition comprising the aforementioned negative electrode active material and conductive material, and selectively including a binder as needed.

[0174] As the aforementioned negative electrode active material, compounds capable of reversible lithium insertion and extraction can be used. Specific examples include carbon materials such as artificial graphite, natural graphite, graphitized carbon fibers, and amorphous carbon; metal compounds capable of alloying with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys, or Al alloys; metal oxides capable of doping and dedoping lithium, such as SiOβ (0 < β < 2), SnO2, vanadium oxide, and lithium vanadium oxide; or composites containing the aforementioned metal compounds and carbon materials, such as Si-C composites or Sn-C composites. One or more mixtures of these can be used. Furthermore, lithium metal thin films can also be used as the aforementioned negative electrode active material. Both low-crystalline and high-crystalline carbon can be used as carbon materials. Representative low-crystalline carbons are soft carbon and hard carbon, while representative high-crystalline carbons are amorphous, plate-like, flake-like, spherical or fibrous natural or artificial graphite, condensed graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, meso-carbon microbeads, mesophase pitch, and high-temperature calcined carbons such as petroleum or coal tar pitch-derived cokes.

[0175] Based on the total weight of the negative electrode active material layer, it may contain 80% to 99% of the aforementioned negative electrode active material.

[0176] The aforementioned binder is a component that facilitates the bonding between the conductive material, the active material, and the current collector. Typically, 0.1% to 10% by weight of the binder can be added based on the total weight of the negative electrode active material layer. Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose, starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene propylene diene monomer (EPDM), sulfonated EPDM, styrene-butadiene rubber, nitrile rubber, fluororubber, and various copolymers thereof.

[0177] The aforementioned conductive material is a component used to further improve the conductivity of the negative electrode active material. Based on the total weight of the negative electrode active material layer, up to 10% by weight of the aforementioned conductive material can be added, preferably up to 5% by weight. There are no particular limitations on this conductive material as long as it does not induce chemical changes in the corresponding battery and possesses conductivity. For example, graphite such as natural graphite or artificial graphite can be used; carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fiber or metal fiber; metal powders such as fluorinated carbon, 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.

[0178] In one embodiment, the aforementioned negative electrode active material layer can be prepared by coating a negative electrode slurry composition onto a negative electrode current collector and drying it. The negative electrode slurry composition is prepared by dissolving or dispersing the negative electrode active material in a solvent and selectively dissolving or dispersing the binder and conductive material in the solvent. Alternatively, the negative electrode slurry composition can be cast onto a separate support, and then a thin film layer obtained by peeling off the support can be pressed onto the negative electrode current collector.

[0179] In another embodiment, the aforementioned negative electrode active material layer can be prepared by coating a negative electrode slurry composition onto a negative electrode current collector and drying it. The negative electrode slurry composition is prepared by dissolving or dispersing the negative electrode active material in a solvent and selectively dissolving or dispersing the binder and conductive material in the solvent. Alternatively, the negative electrode slurry composition can be cast onto a separate support, and then a thin film layer obtained by peeling off the support can be pressed onto the negative electrode current collector.

[0180] On the other hand, in the aforementioned lithium secondary battery, the separator is used to separate the negative electrode and the positive electrode and provide a channel for the movement of lithium ions. Any separator commonly used in lithium secondary batteries can be used without limitation. In particular, it is preferable to have low impedance and excellent electrolyte moisture-holding capacity for ion movement of the electrolyte. Specifically, porous polymer films can be used, for example, porous polymer films prepared using polyolefin polymers such as ethylene homopolymers, propylene homopolymers, ethylene / butene copolymers, ethylene / hexene copolymers, and ethylene / methacrylate copolymers, or laminated structures of two or more layers thereof. Furthermore, conventional porous nonwoven fabrics can also be used, for example, nonwoven fabrics made of high-melting-point glass fibers, polyethylene terephthalate fibers, etc. Moreover, to ensure heat resistance or mechanical strength, separators coated with ceramic components or polymeric substances can also be used, selectively in single-layer or multi-layer structures.

[0181] Furthermore, examples of electrolytes used in this invention include organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in the preparation of lithium secondary batteries, but are not limited to them.

[0182] Specifically, the electrolyte may contain organic solvents and lithium salts.

[0183] As the aforementioned organic solvents, any organic solvent capable of acting as a medium for the movement of ions participating in the electrochemical reaction of the battery can be used without limitation. Specifically, as the aforementioned organic solvents, ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone can be used; ether solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; dimethyl carbonate (DMC), diethyl carbonate (DEC), methylethyl carbonate (MEC), ethylmethyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate can be used. Carbonate solvents such as carbonate (PC); alcohol solvents such as ethanol and isopropanol; nitriles such as R-CN (where R is a straight-chain, branched, or cyclic hydrocarbon group with 2 to 20 carbon atoms, which may contain double bonds, aromatic rings, or ether bonds); amides such as dimethylformamide; dioxanes such as 1,3-dioxane; or sulfolane, etc. Among these, carbonate solvents are preferred, and mixtures of cyclic carbonates (e.g., ethylene carbonate or propylene carbonate, etc.) with high ionic conductivity and high dielectric constant, and low-viscosity linear carbonate compounds (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate, etc.) that can improve the charge-discharge performance of the battery are more preferred. In this case, when the cyclic carbonate and the linear carbonate are mixed in a volume ratio of about 1:1 to about 1:9, excellent electrolyte performance can be observed.

[0184] The lithium salts described above can be any compound capable of providing lithium ions for use in lithium secondary batteries, without limitation. Specifically, the lithium salts can be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2, etc. Preferably, the concentration of the lithium salts is used in the range of 0.1M to 2.0M. When the concentration of the lithium salt is within the above range, the electrolyte has appropriate conductivity and viscosity, thus exhibiting excellent electrolyte performance and enabling efficient movement of lithium ions.

[0185] When the electrolyte used in this application is a solid electrolyte, such as sulfide solid electrolytes, oxide solid electrolytes, nitride solid electrolytes, halide solid electrolytes, etc., solid inorganic electrolytes can be used. Preferably, sulfide solid electrolytes can be used.

[0186] As materials for sulfide-based solid electrolytes, solid electrolytes containing Li, X (where X is at least one selected from P, As, Sb, Si, Ge, Sn, B, Al, Ga, and In) and S can be used. Examples of the aforementioned sulfide-based solid electrolyte materials include Li₂S-P₂S₅, Li₂S-P₂S₅-LiX (where X is a halogen element such as I or Cl), Li₂S-P₂S₅-Li₂O, Li₂S-P₂S₅-Li₂O-LiI, Li₂S-SiS₂, Li₂S-SiS₂-LiI, Li₂S-SiS₂-LiBr, Li₂S-SiS₂-LiCl, Li₂S-SiS₂-B₂S₃-LiI, Li₂S-SiS₂-P₂S₅-LiI, Li₂S-B₂S₃, and Li₂S-P₂S₅-Z. m S n (Where m and n are integers, and Z is Ge, Zn, or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q (Where p and q are integers, and M is P, Si, Ge, B, Al, Ga, or In, etc.)

[0187] The solid electrolyte, preferably, is a sulfide-based solid electrolyte, which can be amorphous, crystalline, or a mixture of amorphous and crystalline states.

[0188] Examples of oxide-based solid electrolytes include Li7La3Zr2O. 12 Li 7-x La3Zr1-x Nb x O 12 Li 7- 3x La3Zr2Al x O 12 Li 3x La 2 / 3-x TiO3, Li 1+x Al x Ti 2-x (PO4)3, Li 1+x Al x Ge 2-x (PO4)3, Li3PO4, Li 3+x PO 4-x N x (LiPON), Li 2+2x Zn 1-x GeO4 (LISICON), etc.

[0189] The aforementioned solid electrolyte can be arranged as a separate layer (solid electrolyte layer) between the positive and negative electrodes. Furthermore, the aforementioned solid electrolyte can be partially contained independently of the aforementioned solid electrolyte layer within the positive electrode active material layer of the positive electrode, or the aforementioned solid electrolyte can be partially contained independently of the aforementioned solid electrolyte layer within the negative electrode active material layer of the negative electrode.

[0190] In addition to the electrolyte components described above, for the purpose of improving battery life characteristics, suppressing battery capacity reduction, and increasing battery discharge capacity, the electrolyte may also contain one or more additives such as halogenated alkylene carbonate compounds like difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glycol dimethyl ether, triammonium hexaphosphate, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N,N-substituted imidazolides, ethylene glycol dialkyl ethers, ammonium salts, pyrroles, 2-methoxyethanol, or aluminum trichloride. In this case, the electrolyte may contain 0.1% to 5% by weight of the aforementioned additives relative to its total weight.

[0191] As described above, lithium secondary batteries containing the positive electrode active material of the present invention stably exhibit excellent discharge capacity, output characteristics and lifespan characteristics, and therefore can be used in portable devices such as mobile phones, laptops, and digital cameras, as well as electric vehicles such as hybrid electric vehicles (HEVs).

[0192] The lithium secondary battery according to the present invention has no particular limitation on its shape and can be cylindrical, prismatic, pouch-shaped, or coin-shaped, etc. Furthermore, the lithium secondary battery can be used not only as a battery cell for powering small devices, but also preferably as a unit battery in medium or large battery modules comprising multiple battery cells.

[0193] According to another aspect of the invention, a battery module comprising the aforementioned lithium secondary battery as a single unit and / or a battery pack comprising the same can be provided.

[0194] The aforementioned battery module or battery pack can be used as a power tool; an electric vehicle, including electric vehicles (EVs), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEVs); or as a power source for any one or more medium or large-sized equipment in an energy storage system.

[0195] The invention will be described in more detail below by way of examples. However, these examples are merely illustrative and the scope of the invention should not be construed as being limited by these examples.

[0196] Preparation Example 1. Preparation of positive electrode active material precursor Comparative Example 1 A 2.5M aqueous solution of transition metals (NiSO4·6H2O and MnSO4·H2O in a 40:60 molar ratio), a 6.3M solution of NaOH (aq), and a 7.2M solution of NH4OH (aq) were introduced into a 90L reactor, which was purged with nitrogen to create a non-oxidizing atmosphere. The reactor was stirred at 400 rpm. The aqueous solution of transition metals was then added to the reactor at a rate of 1.1 L / hr, the NaOH (aq) at a rate of 0.61 L / hr, and the NH4OH (aq) at a rate of 0.18 L / hr.

[0197] The temperature inside the reactor was maintained at 50°C and the pH at 10.0. Nitrogen gas was supplied to the reactor at a rate of 1 L / min, and a co-precipitation reaction was carried out for 24 hours.

[0198] After the coprecipitation reaction was completed, the precursor was separated and washed with deionized water, and dried at 120°C for 10 hours to obtain the positive electrode active material precursor.

[0199] Example 1 Except for maintaining the pH in the reactor at 9.5, a co-precipitation reaction was carried out in the same manner as in Comparative Example 1 to prepare the positive electrode active material precursor. The above-mentioned transition metal aqueous solution was added to the above-mentioned reactor at 1.1 L / hr, the above-mentioned NaOH (aq) was added at 0.57 L / hr, and the above-mentioned NH4OH (aq) was added at 0.18 L / hr.

[0200] Example 2 Except for maintaining the pH in the reactor at 9.3, a co-precipitation reaction was carried out in the same manner as in Comparative Example 1 to prepare the positive electrode active material precursor. The above-mentioned transition metal aqueous solution was added to the above-mentioned reactor at 1.1 L / hr, the above-mentioned NaOH (aq) was added at 0.55 L / hr, and the above-mentioned NH4OH (aq) was added at 0.18 L / hr.

[0201] Example 3 Except for maintaining the pH in the reactor at 9.0, a co-precipitation reaction was carried out in the same manner as in Comparative Example 1 to prepare the positive electrode active material precursor. The above-mentioned transition metal aqueous solution was added to the above-mentioned reactor at 1.1 L / hr, the above-mentioned NaOH (aq) was added at 0.52 L / hr, and the above-mentioned NH4OH (aq) was added at 0.18 L / hr.

[0202] Example 4 Except for maintaining the pH in the reactor at 8.5, a co-precipitation reaction was carried out in the same manner as in Comparative Example 1 to prepare the positive electrode active material precursor. The above-mentioned transition metal aqueous solution was added to the above-mentioned reactor at 1.1 L / hr, the above-mentioned NaOH (aq) was added at 0.48 L / hr, and the above-mentioned NH4OH (aq) was added at 0.18 L / hr.

[0203] Comparative Example 2 Except for maintaining the pH in the reactor at 8.0, a co-precipitation reaction was carried out in the same manner as in Comparative Example 1 to prepare the positive electrode active material precursor. The above-mentioned transition metal aqueous solution was added to the above-mentioned reactor at 1.1 L / hr, the above-mentioned NaOH (aq) was added at 0.42 L / hr, and the above-mentioned NH4OH (aq) was added at 0.18 L / hr.

[0204] Example 5 A 2.5M aqueous solution of transition metals (NiSO4·6H2O and MnSO4·H2O in a 40:60 molar ratio), a 6.3M solution of NaOH (aq), and a 7.2M solution of NH4OH (aq) were introduced into a 90L reactor, which was purged with nitrogen to create a non-oxidizing atmosphere. The reactor was stirred at 400 rpm. The aqueous solution of transition metals was then added to the reactor at a rate of 1.1 L / hr, the NaOH (aq) at a rate of 0.52 L / hr, and the NH4OH (aq) at a rate of 0.18 L / hr.

[0205] The temperature inside the reactor was maintained at 50°C and the pH was maintained at 9.0. A mixed gas containing nitrogen and oxygen (containing 0.5% by volume of O2) was supplied to the reactor at a rate of 0.5 L / min, and a co-precipitation reaction was carried out for 24 hours.

[0206] After the coprecipitation reaction was completed, the precursor was separated and washed with deionized water, and dried at 120°C for 10 hours to obtain the positive electrode active material precursor.

[0207] Example 6 In addition to supplying a mixed gas containing nitrogen and oxygen (containing 1.0 vol% O2) to the reactor at a rate of 0.5 L / min, a co-precipitation reaction was carried out in the same manner as in Example 5 to prepare the positive electrode active material precursor.

[0208] Example 7 In addition to supplying a mixed gas containing nitrogen and oxygen (containing 2.0 vol% O2) to the reactor at a rate of 0.5 L / min, a co-precipitation reaction was carried out in the same manner as in Example 5 to prepare the positive electrode active material precursor.

[0209] Example 8 In addition to supplying a mixed gas containing nitrogen and oxygen (containing 3.0 vol% O2) to the reactor at a rate of 0.5 L / min, a co-precipitation reaction was carried out in the same manner as in Example 5 to prepare the positive electrode active material precursor.

[0210] Comparative Example 3 In addition to supplying a mixed gas containing nitrogen and oxygen (containing 6.0% by volume O2) to the reactor at a rate of 0.5 L / min, a co-precipitation reaction was carried out in the same manner as in Example 5 to prepare the positive electrode active material precursor.

[0211] Example 9 A 2.5M aqueous solution of transition metals (NiSO4·6H2O and MnSO4·H2O in a 40:60 molar ratio), a 6.3M solution of NaOH (aq), and a 7.2M solution of NH4OH (aq) were introduced into a 90L reactor, which was purged with nitrogen to create a non-oxidizing atmosphere. The reactor was stirred at 400 rpm. The aqueous solution of transition metals was then added to the reactor at a rate of 1.1 L / hr, the NaOH (aq) at a rate of 0.52 L / hr, and the NH4OH (aq) at a rate of 0.18 L / hr.

[0212] The temperature inside the reactor was maintained at 60°C and the pH was maintained at 9.0. A mixed gas containing nitrogen and oxygen (containing 1.0% by volume of O2) was supplied to the reactor at a rate of 0.5 L / min, and a co-precipitation reaction was carried out for 24 hours.

[0213] After the coprecipitation reaction was completed, the precursor was separated and washed with deionized water, and dried at 120°C for 10 hours to obtain the positive electrode active material precursor.

[0214] Example 10 Except for maintaining the temperature of the reactor at 70°C, a co-precipitation reaction was carried out in the same manner as in Example 9 to prepare the positive electrode active material precursor.

[0215] Comparative Example 4 Except for maintaining the temperature of the reactor at 80°C, a co-precipitation reaction was carried out in the same manner as in Example 9 to prepare the positive electrode active material precursor.

[0216] Comparative Example 5 Except for maintaining the temperature of the reactor at 45°C, a co-precipitation reaction was carried out in the same manner as in Example 9 to prepare the positive electrode active material precursor.

[0217] Example 11 Except for maintaining the temperature of the reactor at 70°C and supplying a mixed gas containing nitrogen and oxygen (containing 2.0% by volume O2) into the reactor at a rate of 0.5 L / min, a co-precipitation reaction was carried out in the same manner as in Example 9 to prepare the positive electrode active material precursor.

[0218] Preparation Example 2. Preparation of Positive Electrode Active Material Positive electrode active materials were prepared using the various positive electrode active material precursors prepared according to Preparation Example 1.

[0219] Specifically, the hydroxide precursors obtained in Preparation Example 1 were heat-treated at 550°C for 5 hours in an air-atmosphere calcination furnace and then furnace-cooled to convert them into precursors in the oxide state.

[0220] Next, a mixture was prepared by mixing the above-mentioned oxide precursor with LiOH (molar ratio of Li / (metal other than Li) = 1.22) as a lithium raw material.

[0221] Next, the mixture was heat-treated at 900°C for 8 hours in a sintering furnace under an O2 atmosphere and then furnace cooled to obtain a positive electrode active material consisting of a phase belonging to the C2 / m space group and a phase belonging to the R-3m space group existing in solid solution form of lithium manganese oxide.

[0222] Preparation Example 3. Preparation of Lithium Secondary Battery (Half-Cell) A positive electrode slurry was prepared by dispersing 90 wt% of each positive electrode active material, 4.5 wt% of carbon black, and 5.5 wt% of PVDF binder prepared according to Preparation Example 2 in N-methyl-2-pyrrolidone (NMP). The above positive electrode slurry was then uniformly coated onto a substrate with a thickness of 15 mm. A positive electrode for lithium secondary batteries was prepared by vacuum drying on an aluminum thin film at 135°C. For this positive electrode, lithium foil was used as the counter electrode, and a porous polyethylene film (Celgard 2300, thickness: 25) was used. A half-cell was prepared using LiPF6 as the separator and an electrolyte in which ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate were mixed in a solvent at a volume ratio of 2:4:4. The electrolyte was 1.15 M.

[0223] Experimental Example 1. Physical Properties and Shape Analysis of Positive Electrode Active Material Precursor The physical properties and shapes of the various positive electrode active material precursors prepared according to Preparation Example 1 were analyzed, and the results are shown in Table 1 below.

[0224] (1) Particle size analysis of positive electrode active material precursor The particle size distribution of each positive electrode active material precursor prepared according to Preparation Example 1 was analyzed using a known laser diffraction method. Specifically, after dispersing each positive electrode active material precursor in a dispersion medium, a cumulative particle size distribution map was obtained by irradiating the precursor with ultrasound at a frequency of approximately 28 kHz using a laser diffraction particle size analyzer (Microtrac MT 3000) at an output power of 60 W.

[0225] Next, the particle size (D) corresponding to 10% of the total volumetric size was determined from the aforementioned volumetric particle size distribution map. 10), corresponding to 50% of the volumetric cumulative particle size (D 50 ) and the particle size corresponding to 90% of the volumetric accumulation (D 90 The span value is calculated using Equation 1 below.

[0226] [Formula 1] Span value = (D) 90 -D 10 ) / D 50 (2) Particle shape analysis of positive electrode active material precursor Scanning electron microscopy (SEM) was used to capture surface SEM images of the secondary particle morphology precursors prepared in Preparation Example 1. Using Image-Pro image analysis software for SEM, 30% (20 particles) of all primary particles exposed on the surface of the secondary particles were randomly selected from the surface SEM images. The major axis length and minor axis length of the surface shape of the selected primary particles were measured, and their average values ​​were calculated. Furthermore, the major axis / minor axis ratio, which is the ratio of the average major axis length to the average minor axis length of the primary particles, was calculated.

[0227] (3) BET specific surface area analysis of positive electrode active material precursor The BET specific surface area of ​​each positive electrode active material precursor prepared in Preparation Example 1 was calculated using the nitrogen adsorption amount at liquid nitrogen temperature (77 K) using the BELSORP-mini II from Bel Japan, Inc.

[0228] (4) Composition analysis of positive electrode active material precursor The composition (Ni and Mn content) of each positive electrode active material precursor prepared in Preparation Example 1 was analyzed using the known inductively coupled plasma optical emission spectrometry (ICP-OES).

[0229] (5) XRD analysis of positive electrode active material precursor X-ray diffraction (XRD) analysis was performed on each of the positive electrode active material precursors prepared in Preparation Example 1, and the ratio (a / b) of the diffraction peak intensity (a) appearing in the region of 2θ = 11.8 ± 1° to the diffraction peak intensity (b) appearing in the region of 2θ = 18.6 ± 1° was calculated. The above XRD analysis was performed using a Bruker D8 Advance diffractometer with Cu-Kα radiation (1.540598 Å).

[0230] [Table 1]

[0231] Referring to the results of Examples 1 to 4, Comparative Examples 1 and 2, it can be confirmed that when the pH during the co-precipitation reaction is too high (Comparative Example 1), the primary particles are formed to be thicker (the short axis length of the primary particles increases), thus excessively reducing the specific surface area of ​​the positive electrode active material precursor. Conversely, when the pH is too low (Comparative Example 2), the nickel content in the precursor deviates significantly from the designed composition, and the particle size distribution is uneven. The higher span value of Comparative Example 2 suggests that excessive micronization occurred due to the excessively low pH. Furthermore, it can be confirmed that the specific surface area of ​​Comparative Example 2 is excessively increased.

[0232] Referring to the results of Examples 5 to 8 and Comparative Example 3, it can be confirmed that the long axis length of the primary particles decreases due to the supply of a gas mixed with O2 during the coprecipitation reaction. The shorter the long axis length of the primary particles, the greater the internal porosity of the precursor, thereby increasing the specific surface area to an appropriate level. However, when the O2 content in the gas supplied during the coprecipitation reaction is excessive (Comparative Example 3), it can be confirmed that the primary particles thicken again, and the intensity of the diffraction peak appearing in the 2θ = 11.8 ± 1° region increases. The diffraction peak appearing in the 2θ = 11.8 ± 1° region corresponds to the MnO2 phase, and the greater the intensity of the diffraction peak appearing in the 2θ = 11.8 ± 1° region, the higher the proportion of impurity phase in the precursor.

[0233] Comparing the results of Examples 6 with those of Examples 9 to 11, it is evident that the higher the reaction temperature during the coprecipitation reaction, the lower the span value. This confirms that at relatively high reaction temperatures, the formation of micropowder is suppressed, resulting in a precursor with a uniform particle size distribution. Furthermore, it is confirmed that higher reaction temperatures during the coprecipitation reaction further suppress the formation of impurity phases. Conversely, comparing the results of Examples 9 to 11 with those of Comparative Example 4, it is evident that when the reaction temperature during the coprecipitation reaction is too high (e.g., above 80°C), the primary particles become excessively thick. The thicker the primary particles, the lower the internal porosity, which may drastically reduce the specific surface area of ​​the precursor. On the other hand, referring to the results of Comparative Example 5, it is confirmed that due to the low reaction temperature during the coprecipitation reaction, overall particle growth is insufficient.

[0234] Experimental Example 2. Evaluation of the electrochemical characteristics of lithium secondary batteries (half-cells) For the lithium secondary battery (half-cell) prepared in Preparation Example 3, the initial charge capacity, initial discharge capacity, initial efficiency, and 2.0C / 0.1C discharge capacity ratio (rate capability, C-rate) were determined by charge / discharge experiments using an electrochemical analysis apparatus (TOYO SYSTEM Co., Ltd., Toscat-3100) at 25°C, a voltage range of 2.0V to 4.6V, and a discharge rate of 0.1C to 5.0C.

[0235] The results of the above measurements are shown in Table 2 below.

[0236] [Table 2]

[0237] Comparing the results of Examples 1 to 4 with those of Comparative Examples 1 and 2 confirms that the charge / discharge capacity and the 2.0C / 0.1C discharge capacity are relatively low when the pH during the coprecipitation reaction is too high (Comparative Example 1) or too low (Comparative Example 2). That is, it can be confirmed that using a precursor obtained through a coprecipitation reaction at a pH greater than 8.0 and less than 10.0, preferably at pH 8.5 to 9.5, helps to improve charge / discharge capacity and rate performance.

[0238] Comparing the results of Examples 1 to 4 with those of Examples 5 to 8, it is evident that supplying a gas mixture containing O2 during the co-precipitation reaction further improves the charge / discharge capacity and rate performance of the positive electrode active material. Conversely, comparing the results of Examples 5 to 8 with those of Comparative Example 3, it is evident that an excessive proportion of O2 in the supplied mixed gas during the co-precipitation reaction induces excessive changes in the physical properties and shape of the precursor, potentially reducing the charge / discharge capacity and rate performance of the positive electrode active material.

[0239] Comparing the results of Examples 6 with Examples 9 to 11, it is evident that even with increased reaction temperature during the co-precipitation reaction, the reduction in charge / discharge capacity and rate performance of the positive electrode active material is minimal. Conversely, comparing the results of Examples 9 to 11 with Comparative Examples 4 and 5, it is evident that when the reaction temperature during the co-precipitation reaction is higher or lower than an appropriate level, excessive changes in the physical properties and shape of the precursor are induced, potentially reducing the charge / discharge capacity and rate performance of the positive electrode active material.

[0240] The embodiments of the present invention have been described above. However, those skilled in the art can make various modifications and alterations to the present invention by adding, changing, deleting, or adding constituent elements without departing from the spirit of the present invention as described in the claims. These modifications and alterations should also be included within the scope of the claims of the present invention.

Claims

1. A method for preparing a positive electrode active material precursor, characterized in that, The process includes the steps of introducing an aqueous solution of a transition metal, an ammonium cation complexing agent, and an alkaline aqueous solution into a reactor, and carrying out a co-precipitation reaction under conditions of pH greater than 8.0 and less than 10.0 to form a transition metal hydroxide precursor. In the aforementioned aqueous solution of transition metals, the content of manganese is greater than that of nickel, measured in molar percentage.

2. The method for preparing the positive electrode active material precursor according to claim 1, characterized in that, The aforementioned aqueous solution of transition metals also contains one or more elements selected from transition metals, post-transition metals, and metalloids other than alkali metals, alkaline earth metals, nickel, and manganese.

3. The method for preparing the positive electrode active material precursor according to claim 1, characterized in that, The aforementioned aqueous solution of transition metals contains manganese at a rate of 50 mol% or more relative to the total molar percentage of the transition metals.

4. The method for preparing the positive electrode active material precursor according to claim 1, characterized in that, The above coprecipitation reaction was carried out at pH 8.5 to 9.

5.

5. The method for preparing the positive electrode active material precursor according to claim 1, characterized in that, The above coprecipitation reaction was carried out in a non-oxidizing atmosphere or an oxidizing atmosphere.

6. The method for preparing the positive electrode active material precursor according to claim 1, characterized in that, The above coprecipitation reaction was carried out in an oxidizing atmosphere containing more than or equal to 0.5% by volume and less than 6.0% by volume of oxygen.

7. The method for preparing the positive electrode active material precursor according to claim 1, characterized in that, The above coprecipitation reaction was carried out at a temperature greater than or equal to 50°C and less than 80°C.

8. A precursor for a positive electrode active material, characterized in that, Including transition metal hydroxides represented by the following chemical formula 1, The aforementioned transition metal hydroxides exhibit a secondary particle morphology formed by the aggregation of multiple primary particles. The surface shape of the primary particles exposed on the surface of the aforementioned transition metal hydroxide, as observed from the surface SEM images, has a long axis and a short axis: [Chemical Formula 1] [Ni b Co c Mr d M1 e ](OH)2 In the above chemical formula 1, M1 is selected from at least one of Al, P, Nb, B, Si, Ti, Zr, Ba, K, Mo, Fe, Cu, Cr, Zn, Na, Ca, Mg, Pt, Au, Eu, Sm, W, Ce, V, Ta, Sn, Hf, Gd, Y, Ru, Ge, and Nd. 0≤b<0.5, 0≤c≤0.2, 0.5≤d<0.8, 0 <e≤0.1,b+c+d+e=1。 9. The positive electrode active material precursor according to claim 8, characterized in that, The average ratio of the major axis length to the minor axis length of the surface shape of the primary particles exposed to the surface of the aforementioned transition metal hydroxide is 1.5 or more and 25.0 or less.

10. The positive electrode active material precursor according to claim 8, characterized in that, The average length of the minor axis of the surface shape of the primary particles exposed to the surface of the aforementioned transition metal hydroxide is 30 nm or more and 270 nm or less.

11. The positive electrode active material precursor according to claim 8, characterized in that, The average length of the major axis of the surface shape of the primary particles exposed to the surface of the aforementioned transition metal hydroxide is 400 nm or more and 2500 nm or less.

12. The positive electrode active material precursor according to claim 8, characterized in that, The average particle size (D) of the above transition metal hydroxides 50 The value is 5.

0. Up to 24.0 , The particle size span of the above-mentioned transition metal hydroxide, calculated by Equation 1 below, is 0.90 or less: [Formula 1] Span value = (D) 90 -D 10 ) / D 50 .

13. The positive electrode active material precursor according to claim 8, characterized in that, The BET specific surface area, as determined by nitrogen adsorption, is 8.0 m². 2 / g to 28.0m 2 / g.

14. The positive electrode active material precursor according to claim 8, characterized in that, When performing X-ray diffraction spectroscopy analysis on the above-mentioned positive electrode active material precursor, the ratio (a / b) of the diffraction peak intensity (a) appearing in the 2θ=11.8±1° region to the diffraction peak intensity (b) appearing in the 2θ=18.6±1° region is less than 0.

25.

15. A method for preparing a positive electrode active material, characterized in that, include: The step of subjecting the positive electrode active material precursor according to any one of claims 8 to 14 to a first heat treatment to form an oxide precursor; as well as The step involves mixing the aforementioned oxide precursor with lithium raw materials and then subjecting it to a second heat treatment to form a lithium manganese oxide in solid solution form, consisting of a phase belonging to the C2 / m space group and a phase belonging to the R-3m space group.

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