Cathode active material for lithium secondary battery, fabrication method therefor, and lithium secondary battery comprising same

Abstract

The positive electrode active material for a lithium secondary battery has a nickel content of 45 mol% (exclusive) to 80 mol% (inclusive) among the remaining components excluding lithium and oxygen, and exhibits a thermogravimetric analysis (TGA) result satisfying Equation 1 below: [Equation 1] 0.3(%) < △W300(%)·300(K) / Tonset(K)< 1.5(%), wherein Tonset(K) is an onset temperature in Kelvin (K) in a first-stage collapse section of the positive electrode active material, △W300(%)=Wonset(%)-Wonset+300K(%), Wonset(%) is a weight (%) at Tonset(K), and Wonset+300K(%) is a weight (%) at Tonset(K)+300(K).

Description

A positive electrode active material for a lithium secondary battery, a method for manufacturing the same, and a lithium secondary battery including the same

[0001] The present invention relates to a positive electrode active material for a lithium secondary battery, a method for manufacturing the same, and a lithium secondary battery including the same. More specifically, the invention relates to a positive electrode active material for a lithium secondary battery with excellent structural stability selected through thermogravimetric analysis (TGA) of the positive electrode active material, a method for manufacturing the same, and a lithium secondary battery including the same.

[0002] Various cathode active materials are used in lithium secondary batteries applied in fields such as electric vehicles (EVs) and energy storage systems (ESS). Among these cathode active materials for lithium secondary batteries, lithium composite metal oxides containing nickel as a main component and one or more components from cobalt, manganese, and aluminum are widely used as cathode active materials.

[0003] When the nickel content is increased to achieve a high capacity of the above-mentioned lithium composite metal oxide, the structural stability of the cathode active material decreases compared to a cathode active material with a relatively low nickel content, resulting in a problem of reduced lifespan and stability of the lithium secondary battery.

[0004] Specifically, as charging and discharging proceed, the expansion and contraction of the cathode active material in lithium-ion batteries induce microcracks within the material. In the case of cathode active materials with a relatively high nickel content, structural stability is reduced, leading to more severe microcracks and consequently causing problems such as reduced battery lifespan and stability.

[0005] Therefore, there is a need to develop cathode active materials that can improve the lifespan and stability of lithium secondary batteries by having excellent structural stability.

[0006] [Prior Art Literature]

[0007] Published Patent Application No. 10-2019-0069073 (February 15, 2021)

[0008] Published Patent Application No. 10-2019-0046425 (May 7, 2019)

[0009] The present invention aims to provide a positive electrode active material for a lithium secondary battery with excellent structural stability selected through thermogravimetric analysis (TGA) of the positive electrode active material.

[0010] In addition, a method for manufacturing a positive electrode active material for a lithium secondary battery with excellent structural stability through stepwise heat treatment can be provided.

[0011] In addition, a cathode for a lithium secondary battery with excellent structural stability can be provided.

[0012] In addition, it is possible to provide a lithium secondary battery with excellent structural stability.

[0013] A first aspect of the present invention for solving the above problem may be a positive electrode active material for a lithium secondary battery, wherein the nickel content among the remaining components excluding lithium and oxygen is greater than 45 mol% and less than or equal to 80 mol%, and the thermogravimetric analysis (TGA) result satisfies the following Equation 1:

[0014] [Equation 1] 0.3(%) < △W 300 (%)·300(K) / T onset (K)< 1.5(%),

[0015] T onset (K) is the onset Kelvin temperature (K) in the first stage decay region of the cathode active material, and △W 300 (%)=W onset (%)-W onset+300K (%) and W onset (%) is T onset Weight (%) at (K), and W onset+300K (%) is T onset It is the weight (%) at (K)+300(K).

[0016] In this aspect, the nickel (Ni) content may be greater than 55 mol% and less than or equal to 80 mol%.

[0017] In this aspect, the nickel (Ni) content may be greater than 65 mol% and less than or equal to 80 mol%.

[0018] In this respect, the lower limit of Equation 1 may be 0.5 (%) and the upper limit may be 1.2 (%).

[0019] In this aspect, the positive electrode active material may include a lithium complex transition metal oxide having nickel as a main component and containing one or more components among cobalt, manganese, and aluminum.

[0020] This aspect may further include a doping material, and the doping element may include one or more selected from the group consisting of Mg, Ca, Sr, Ba, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, B, Al, Si, Sn, P, Sb, Bi, S, F, Zr, Nb, Mo, Hf, Ta, W, Sc, Y, La, and Ce.

[0021] In this aspect, the content of the doping substance may be 5.0 mol% or less among the remaining components excluding lithium and oxygen.

[0022] This aspect may optionally further include a coating material, and the coating material may include one or more selected from the group consisting of Li, Mg, Ca, Sr, Ba, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, B, Al, Si, Sn, P, Sb, Bi, S, F, Zr, Nb, Mo, Hf, Ta, W, Sc, Y, La, and Ce.

[0023] In this aspect, the content of the coating element may be 3.0 mol% or less among the remaining components excluding lithium and oxygen.

[0024] A second aspect of the present invention may be a method for manufacturing a positive electrode active material for a lithium secondary battery, comprising the steps of: a) a precursor manufacturing step for manufacturing a precursor for a positive electrode active material; b) a step of manufacturing a primary positive electrode active material by first heat treating a material containing the manufactured precursor; and c) a step of manufacturing a secondary positive electrode active material by second heat treating a material containing the primary positive electrode active material.

[0025] In this aspect, after step c), d) optionally, a step of preparing a third positive active material by heat-treating a material containing a second positive active material may be further included.

[0026] A third aspect of the present invention may be a positive electrode for a lithium secondary battery comprising the positive electrode active material of the first aspect.

[0027] A fourth aspect of the present invention may be a lithium secondary battery comprising the positive electrode of the third aspect.

[0028] According to the present invention, a positive electrode active material for a lithium secondary battery with excellent structural stability selected through thermogravimetric analysis can be provided.

[0029] In addition, a method for manufacturing a positive electrode active material for a lithium secondary battery with excellent structural stability through stepwise heat treatment can be provided.

[0030] In addition, a cathode for a lithium secondary battery with excellent structural stability can be provided.

[0031] In addition, it is possible to provide a lithium secondary battery with excellent structural stability.

[0032] Figures 1a to 1c are schematic diagrams for explaining the TGA graph step by step.

[0033] Figure 2 shows △W of Equations 1 and 2. 300 (%) and T onset This is a schematic diagram to explain (K).

[0034] Figure 3 is △W 300 (%)·300(K) / Tonset This is a graph showing the correlation between the (K) value and the discharge capacity (mAh / g, @100cycle) value at 100 cycles.

[0035] Figure 4 is △W 300 (%)·300(K) / T onset This is a graph showing the correlation between the (K) value and the discharge capacity (mAh / g, @100 cycle) based on 1.0 mol of nickel.

[0036] Preferred embodiments of the present invention will be described below with reference to the attached drawings. Embodiments of the present invention may be modified in various different forms, and the scope of the present invention is not limited to the embodiments described below. Embodiments of the present invention are provided to more fully explain the present invention to those with average knowledge in the art. Accordingly, the shapes and sizes of elements in the drawings may be exaggerated for clearer explanation, and elements indicated by the same reference numerals in the drawings are the same elements. In the present invention, the expressions "first" or "second" do not imply order or importance, but are merely for distinguishing components.

[0037]

[0038] The first aspect of the present invention may be a positive active material satisfying Formula 1 below. The positive active material of the present aspect has excellent structural stability and can improve the capacity retention rate in a lithium secondary battery.

[0039] [Equation 1]

[0040] 0.3(%) < △W 300 (%)·300(K) / T onset (K) < 1.5(%)

[0041] Here,

[0042] T onset (K) is the onset Kelvin temperature (K) in the first stage decay region of the positive active material, and

[0043] △W 300 (%)=Wonset (%)-W onset+300K (%) and,

[0044] W onset (%) is T onset It is the weight (%) at (K), and

[0045] W onset+300K (%) is T onset It is the weight (%) at (K)+300(K).

[0046]

[0047] The positive electrode active material of this aspect may be a lithium composite metal oxide having nickel as a main component and containing one or more components among cobalt, manganese, and aluminum.

[0048] The positive electrode active material may have a nickel content of more than 45 mol% and less than or equal to 80 mol% among the remaining components excluding lithium and oxygen. In other words, among the remaining components excluding lithium and oxygen, the nickel content may be more than 45 mol% and less than or equal to 80 mol% among the total components including the main component (e.g., one or more components among nickel, cobalt, manganese, and aluminum), the doping material, the coating material, and even impurities.

[0049] Preferably, in order to increase the capacity of the positive electrode active material, the nickel content among the remaining components excluding lithium and oxygen may be greater than 55 mol% and less than or equal to 80 mol%, and more preferably, the nickel content among the remaining components excluding lithium and oxygen may be greater than 65 mol% and less than or equal to 80 mol%.

[0050] Thermogravimetric Analysis (TGA)

[0051] In the present invention, TGA for the positive electrode active material was carried out under conditions of a temperature range of 1,200°C (up to 1,500°C if necessary) at room temperature, a heating rate of 5°C / min, and an oxygen atmosphere (oxygen supplied at a flow rate of 20 mL / min).

[0052] Figure 1a shows a TGA graph for the cathode active material. Referring to Figure 1a, the TGA graph can be divided into sections I to IV. However, depending on the type of cathode active material, up to 1,200°C, there may be cases where no decay stages of the cathode active material appear, as shown in Figure 1b, or cases where more decay stages appear than in Figure 1a, as shown in Figure 1c.

[0053] In section I, the weight may decrease mainly because moisture adsorbed on the positive active material is removed.

[0054] In section II, the weight may decrease mainly due to the decomposition of lithium hydroxide formed on the surface of the positive electrode active material.

[0055] In section III, the weight is reduced mainly due to oxygen release caused by the first-stage structural breakdown of the positive electrode active material, and some of the weight may be reduced due to carbon dioxide emission caused by the decomposition of lithium carbonate present on the surface of the positive electrode active material.

[0056] Lithium carbonate decomposes during battery charging and discharging, generating carbon dioxide which causes swelling of the battery and can ultimately lead to a decrease in battery lifespan and stability. Generally, if the lithium carbonate content is 5,000 ppm or less according to the titration method, it has almost no effect on battery lifespan and stability. The cathode active material of the present invention can also satisfy the requirement that the lithium carbonate content formed on the surface of the cathode active material is 5,000 ppm or less according to the titration method.

[0057] The extent to which lithium carbonate affects weight reduction based on Section III can be explained as follows.

[0058] Assuming that the amount of lithium carbonate formed on the surface of the cathode active material is 5,000 ppm or less according to the titration method and that the content of lithium carbonate decomposed in Section III is the same 5,000 ppm, and considering that the weight loss when lithium carbonate decomposes while emitting carbon dioxide is approximately 60% and that the temperature range in which lithium carbonate decomposes is approximately 700 to 1,000°C, the weight loss due to the decomposition of lithium carbonate in Section III will be approximately 0.3 wt% (5,000 ppm x 60%) or less.

[0059] That is, considering that the difference between W11, which is the weight % at T11, the temperature at which structural breakdown of the cathode active material begins, and W31, which is the weight % at T31, the temperature at which section IV ends, is approximately 6 wt.%, it can be estimated that among the 6 wt.% weight loss in sections III and IV, the loss due to structural breakdown of the cathode active material is approximately 5.7 wt% or more (95% of the total 6%), and the loss due to lithium carbonate decomposition is 0.3 wt.% or less (5% of the total 6%).

[0060] In summary, more than 95% of the weight loss in section III where the cathode active material collapses is due to the collapse of the cathode active material, and less than 5% is due to the decomposition of lithium carbonate present on the surface of the cathode active material; thus, the weight loss in the section where the cathode active material collapses in TGA can be attributed to the release of oxygen due to the structural collapse of the cathode active material itself.

[0061] In section IV, weight may decrease due to oxygen release caused by the two-stage structural collapse of the positive active material. In the case of the positive active material, as the temperature rises, the surface portion of the positive active material collapses first, and then the collapse may proceed step by step to the center.

[0062]

[0063] Referring to Fig. 1a, the starting temperature of section III, T11, and the starting temperature of section IV (the end temperature of section III), T21, can be determined using the inflection point of the derivative TG (DTG) curve, which is the first derivative graph of the TGA graph.

[0064] In the TGA graph, the respective weights (%) corresponding to T11 and T21 can be referred to as W11 and W21.

[0065] In the case of a ternary cathode active material with a nickel content of more than 45 mol% and less than or equal to 80 mol%, the temperature at which structural breakdown of the cathode active material begins may be 600 to 1,100°C.

[0066] The temperature at which structural breakdown of the cathode active material begins can be closely related to the structural stability of the cathode active material. In the case of the cathode active material of this aspect, which contains nickel as a main component and includes one or more components among cobalt, manganese, and aluminum, the temperature at which structural breakdown begins decreases as the nickel content increases. A cathode active material with a low temperature at which structural breakdown begins has relatively lower structural stability, which can consequently lead to a deterioration in the capacity retention rate characteristics of the battery. To improve the structural stability of the cathode active material, it is necessary to raise the temperature at which structural breakdown begins. To this end, changing the precursor, changing the heat treatment method, or adding doping materials can be one solution.

[0067] Once the structural breakdown of the cathode active material begins, the rate of weight loss may vary as the temperature increases. If the rate of weight loss is high, structural breakdown may occur more rapidly (or easily) after the onset, potentially resulting in relatively lower structural stability. To improve the structural stability of the cathode active material, it is necessary to reduce the rate of weight loss as the temperature increases after the structural breakdown begins. To achieve this, modifying the precursor, changing the heat treatment method, or adding doping materials can be effective solutions.

[0068] Section III is the first stage structural collapse section of the cathode active material, and when the temperature changes from T11 to T21 (△T1=T21-T11), the weight changes from W11 to W21 (△W1=W11-W21). The greater the slope of the weight change due to temperature change (△W1 / △T1) and the greater the amount of weight change due to temperature change (△W1·△T1), the more the structural stability of the cathode active material may be relatively poor. Accordingly, we intended to investigate the correlation with the capacity retention rate in the battery using the slope of the weight change due to temperature change (△W1 / △T1) and / or the amount of weight change due to temperature change (△W1·△T1) in the first stage structural collapse section of the cathode active material in Section III. However, depending on the type of cathode active material, there are cases where the first stage of structural collapse of the cathode active material continues up to 1,200°C as shown in Fig. 1b, or cases where there are more stages of collapse than in the case of Fig. 1a as shown in Fig. 1c, so it was difficult to determine the correlation with the capacity retention rate in the battery using the characteristics of the first stage of structural collapse of the cathode active material.

[0069] Accordingly, instead of the characteristics of the first-stage structural collapse region of the cathode active material, the correlation with electrochemical properties was evaluated for 1) the temperature at which the first-stage structural collapse of the cathode active material begins (corresponding to T11, T12, and T13) and 2) the characteristics of weight change with increasing temperature (+100℃, +200℃, and +300℃) starting from the temperature at which the first-stage structural collapse begins. Among these, the correlation at an increase in temperature of +300℃ was found to be the best. That is, in the case of a cathode active material satisfying Equation 1 below, the structural stability is excellent, which can improve the capacity retention rate of the lithium secondary battery.

[0070] [Equation 1]

[0071] 0.3(%) < △W 300 (%)·300(K) / T onset (K)< 1.5(%),

[0072] Here,

[0073] T onset (K) is the onset Kelvin temperature (K) in the first stage decay region of the positive active material, and

[0074] △W 300 (%)=W onset (%)-W onset+300K (%) and,

[0075] W onset (%) is T onset It is the weight (%) at (K), and

[0076] W onset+300K (%) is T onset It is the weight (%) at (K)+300(K).

[0077] T onset The temperature of (K) was expressed in Kelvin (K) rather than Celsius (°C). Compared to the application of Celsius, the application of Kelvin temperature showed better results in terms of correlation with the electrochemical characteristics of the positive electrode active material.

[0078] Cases that deviate from the upper limit of Equation 1 may include: ① a positive active material that has no doping material, has a low content of doping material, or has an unsuitable composition of doping material, and / or ② a positive active material that has not been properly sintered due to incorrect heat treatment conditions and / or the number of heat treatments, or has low crystallinity or many crystal defects.

[0079] Cases that deviate from the lower limit of Equation 1 may include ① a positive active material with an excessive amount of doping material and / or, ② a positive active material that has been excessively sintered or whose structure has collapsed due to incorrect heat treatment conditions and / or the number of heat treatments.

[0080] Referring to Fig. 1a, T onset (K) may correspond to T11, the starting temperature of Section III. △W 300 (%) is T onset (K) and T onset It may show a decreasing trend in weight (%) at (K)+300(K). △W300 (%)·300(K) is T onset T in (K) onset It relates to the amount of structural collapse as the temperature increases up to (K)+300(℃), and can mostly represent the amount of oxygen gas released due to the structural collapse of the cathode active material. △W 300 (%)·300(K) / T onset (K) is △W 300 (%)·300(K) to T onset (K) is expressed as a reference, and the T of the positive active material onset The (K) value can reflect the influence of structural stability. 0.3(%) < △W 300 (%)·300(K) / T onset (K) < 1.5(%) is △W 300 (%)·300(K) / T onset If the (K) value is within the range of greater than 0.3 (%) and less than 1.5 (%), it satisfies the requirement of a lithium composite metal oxide cathode active material with excellent structural stability.

[0081] Furthermore, in the case of Formula 2 below, which has a narrower range, the structural stability of the positive active material may be even better.

[0082] [Equation 2]

[0083] 0.5(%) < △W 300 (%)·300(K) / T onset (K) < 1.20(%)

[0084] Generally, there was a difficulty in having to fabricate and evaluate a battery to observe the lifespan characteristics of a positive electrode active material, but using the above Equations 1 and 2, the lifespan characteristics in the battery can be predicted using only the TGA results of the positive electrode active material, which is very useful.

[0085] FIG. 2 shows T of Equations 1 and 2 above. onset (K), △W 300 This is a schematic diagram of the TGA of the cathode active material presented to aid in understanding the definition of (%).

[0086]

[0087] doping substances

[0088] The doping material can improve the structural stability of the cathode active material and may include one or more selected from the group consisting of Mg, Ca, Sr, Ba, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, B, Al, Si, Sn, P, Sb, Bi, S, F, Zr, Nb, Mo, Hf, Ta, W, Sc, Y, La, and Ce, but is not limited thereto.

[0089] The content of the doping material may vary depending on the type of doping material, but it is preferable to have 5.0 mol% or less based on the remaining components excluding lithium and oxygen in the positive electrode active material. If the content of the doping material exceeds 5 mol%, the capacity of the positive electrode active material decreases and the movement of lithium ions is hindered, which may lead to a decrease in capacity retention rate and output characteristics.

[0090] The structural stability of the cathode active material may be affected depending on the type and content of the doping material, heat treatment conditions, and the step and method of introducing the doping material (e.g., wet mixing or dry mixing).

[0091] The steps and methods for introducing one or more doping materials into a positive electrode active material may include: ① a method in which the precursor constituent material and the doping material are co-precipitated together and introduced into the precursor during the preparation of the positive electrode active material precursor, and then introduced into the primary positive electrode active material through a primary heat treatment; ② a method in which the positive electrode active material precursor without the doping material is mixed with the lithium compound and the doping material in a dry or wet manner, and then introduced into the primary positive electrode active material through a primary heat treatment; ③ a method in which the primary positive electrode active material without the doping material introduced is mixed with the doping material in a dry or wet manner, and then introduced into the secondary positive electrode active material through a secondary heat treatment; and ④ a method in which the secondary positive electrode active material without the doping material introduced is mixed with the doping material in a dry or wet manner, and then introduced into the tertiary positive electrode active material through a tertiary heat treatment.

[0092] The positive electrode active material may include one of the methods ① to ④, or two or more of the methods ① to ④ applied in combination or mixed.

[0093] One or more doping materials in the positive electrode active material may exist in a manner such as ① the doping material being present in a uniform amount in the region of the positive electrode active material, ② the doping material being present in a non-uniform amount in the region of the positive electrode active material, or a mixture of ① and ②.

[0094] The region of the positive electrode active material refers to the crystal excluding the coating portion in the case of a single-crystal positive electrode active material, the crystal excluding the boundary portion between the coating portion and the crystal in the case of a single-crystal positive electrode active material in which several crystals are aggregated, and the crystal excluding the boundary portion between the coating portion and the crystal in the case of a polycrystalline positive electrode active material formed by aggregating many crystals (primary particles) (secondary particles).

[0095]

[0096] coating material

[0097] The coating material can suppress side reactions with the electrolyte on the surface of the positive electrode active material and suppress side reactions in the battery caused by lithium components through chemical and physical bonding with lithium compounds present on the surface of the positive electrode active material. Additionally, depending on the type of coating material and heat treatment conditions, the coating material can penetrate into the interior of the surface of the positive electrode active material, thereby improving structural stability.

[0098] The coating material may include at least one selected from the group consisting of Li, Mg, Ca, Sr, Ba, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, B, Al, Si, Sn, P, Sb, Bi, S, F, Zr, Nb, Mo, Hf, Ta, W, Sc, Y, La, and Ce. However, it is not limited thereto.

[0099] The content of the coating material is preferably 3.0 mol% or less based on the total positive electrode active material. If the content of the coating material exceeds 3 mol%, the capacity of the positive electrode active material decreases and the movement of lithium ions is hindered, which may lead to a decrease in lifespan retention rate and output characteristics.

[0100] Although the coating material has a smaller effect on the structural stability of the cathode active material compared to the doping material, it can affect the structural stability of the cathode active material depending on the type, content, heat treatment conditions of the coating material, and the step and method of introducing the coating material (e.g., wet mixing or dry mixing).

[0101] The steps and methods for introducing one or more coating materials into the positive electrode active material may include: ① a method of mixing the primary positive electrode active material, which has undergone primary heat treatment, and the coating material in a dry or wet manner, and then introducing them into the secondary positive electrode active material through secondary heat treatment; and ② a method of mixing the secondary positive electrode active material, which has undergone secondary heat treatment without the coating material introduced, and the coating material in a dry or wet manner, and then introducing them into the tertiary positive electrode active material through tertiary heat treatment.

[0102] The positive active material may include one without a coating material, one to which any one of methods ① to ② is applied, or two or more of methods ① to ② are applied in combination or mixed.

[0103] One or more coating materials may exist in the form of coatings and / or individual and / or colonies on the surface of crystals in single-crystal positive active materials, and in the form of coatings and / or individual and / or colonies on the surface of crystals (primary particles) in polycrystalline positive active materials, and these crystals may aggregate to form polycrystalline (secondary particles).

[0104]

[0105] Methods ③ and ④ for introducing doping materials are identical to methods ① and ② for introducing coating materials, but depending on the mixing process and heat treatment conditions, doping and / or coating may occur. If a material exists inside (inside the crystal) starting from the crystal surface of a single-crystal or polycrystalline positive electrode active material, it can act as a doping material, and if it exists outside the crystal surface of a single-crystal or polycrystalline positive electrode active material, it can act as a coating material. In the process of coating a specific material in the form of a covering and / or individual and / or colony on the outer part of the surface starting from the crystal surface of a single-crystal or polycrystalline positive electrode active material, if a portion of the specific material penetrates into the inside of the surface starting from the crystal surface, this specific material can serve as both a coating and a doping material.

[0106]

[0107] The crystallinity of the positive electrode active material is not particularly limited and may include single crystalline, polycrystalline, and intermediate states between single and polycrystalline, that is, having both single and polycrystalline crystallinity. In addition, a mixture of a single-crystalline positive electrode active material and a polycrystalline positive electrode active material in a predetermined ratio may be included.

[0108] The particle size of the positive active material is the particle size of the anode (average particle size (D 50 It may include )< 7μm), medium particles (7μm ≤ average particle size ≤ 13μm), large particles > 13μm), and mixtures thereof. However, it is not limited thereto.

[0109] The particle size distribution of the cathode active material may include narrow (Span value < 0.8), normal (0.8 ≤ Span value ≤ 1.5), wide (Span value > 1.5), and a mixture of these in a predetermined ratio (Span value is [(D 90 -D 10 ) / D 50 ] value). However, it is not limited to this.

[0110] When the positive electrode active material is a single crystal, the shape of the positive electrode active material may include spherical, elliptical, rhomboidal, rectangular, cuboidal, random, and mixtures thereof. However, it is not limited thereto.

[0111] In the case where the positive active material is a polycrystalline material having a secondary particle shape formed by aggregating multiple primary particles, the shapes of the primary particles and secondary particles may include spherical, elliptical, rhombus-shaped, rectangular, cubic, random shapes, and mixtures thereof. However, it is not limited thereto.

[0112]

[0113] A second aspect of the present invention may be a method for manufacturing a positive electrode active material comprising: 1) a precursor manufacturing step for manufacturing a precursor for a positive electrode active material; 2) a step of manufacturing a primary positive electrode active material by first heat treating a material containing the manufactured precursor; 3) a step of manufacturing a secondary positive electrode active material by second heat treating a material containing the primary positive electrode active material; and 4) optionally, a step of manufacturing a tertiary positive electrode active material by third heat treating a material containing the secondary positive electrode active material.

[0114] 1) Preparation of precursors for positive electrode active materials

[0115] The precursor for the positive electrode active material may be a precursor prepared by the co-precipitation method.

[0116] Depending on the method of preparation, a precursor prepared by the co-precipitation method may include: 1) a precursor prepared by a continuous (CSTR) method; 2) a precursor prepared by a batch type method; 3) a precursor in which the content ratio of the components constituting the precursor is uniform within the precursor particles; 4) a precursor in which the content ratio of the components constituting the precursor is non-uniform within the precursor particles (e.g., a precursor having a concentration gradient or a precursor having a core-shell structure); 5) a precursor containing a doping substance among the components constituting the precursor; and 6) a precursor not containing a doping substance among the components constituting the precursor.

[0117] Differences in the method of manufacturing these precursors can affect the structural stability of the cathode active material.

[0118] Specifically, when a cathode active material is manufactured under identical conditions using precursors having identical physical properties except for particle size distribution, the structural stability of the cathode active material manufactured using a batch-type precursor may be superior to that of the cathode active material manufactured using a continuous-type precursor. This is because batch-type precursors contain relatively less fine powder, which is detrimental to structural stability, compared to continuous-type precursors.

[0119] Furthermore, when a cathode active material is manufactured under identical conditions using precursors having identical physical properties, except for differences in the content ratio of the constituent components within the precursor particles, the structural stability of a cathode active material manufactured using a precursor with a lower nickel content relative to the center compared to a cathode active material manufactured using a precursor with a uniform content ratio of constituent components within the precursor particles or a precursor with a higher nickel content relative to the center compared to a cathode active material manufactured using a precursor may be superior. This is attributed to the fact that structural collapse caused by structural instability of the cathode active material intensifies as the nickel content increases.

[0120] Furthermore, when a positive electrode active material is manufactured under identical conditions using precursors with identical physical properties, except for the difference in whether or not a doping substance is present among the constituent components, the structural stability of the positive electrode active material manufactured using a precursor containing a doping substance may be superior. This is attributed to the contribution of the doping substance to the structural stability of the positive electrode active material.

[0121] The precursor for the positive electrode active material of the present invention can be manufactured by a method other than the co-precipitation method.

[0122] Methods other than the co-precipitation method may include wet mixing, dry mixing, spray drying, and spray thermal decomposition methods. The wet mixing method may be characterized by dissolving part or all of the cathode active material components in a solvent and then drying them while stirring. The dry mixing method may be characterized by mixing part or all of the cathode active material components in a solid state and then uniformly grinding the solid-state mixed components through a milling process. The spray drying method may be characterized by dissolving part or all of the cathode active material components in a solvent and then spray drying them. The spray thermal decomposition method may be characterized by dissolving part or all of the cathode active material components in a solvent and then spray thermal decomposing them at a high temperature.

[0123] Precursors prepared by manufacturing methods other than the co-precipitation method may have different physical properties, and these differences in properties may affect the structural stability of the cathode active material.

[0124] Precursors prepared by methods other than the co-precipitation method may require different processes for manufacturing the cathode active material, and these differences in manufacturing processes may affect the structural stability of the cathode active material.

[0125]

[0126] 2) Preparation of positive electrode active material

[0127] The following describes a process for manufacturing an anode active material using a precursor prepared by a co-precipitation method.

[0128] 2.1) Preparation of primary cathode active material by primary heat treatment of the precursor (primary heat treatment)

[0129] A material obtained by first heat-treating a precursor can be called a primary positive active material.

[0130] The materials subject to the first heat treatment can be classified into ① a mixture of a precursor and a lithium compound containing a doping material prepared by a co-precipitation method, and ② a mixture of a precursor, a lithium compound, and a doping material that does not contain a doping material prepared by a co-precipitation method, depending on whether the precursor contains a doping material.

[0131] In the primary heat treatment process, 1) the heating rate, 2) the presence of pre-thermal treatment at a temperature lower than the maximum temperature, 3) the maximum temperature, 4) the holding time at the maximum temperature, 5) the cooling rate, and 6) the atmosphere gas conditions may affect the structural stability of the primary cathode active material.

[0132] 1) The heating rate is preferably 0.5 to 5°C / min based on a box furnace. If the heating rate is lower than 0.5°C / min, it helps improve the structural stability of the cathode active material, but it may result in a decrease in productivity efficiency.

[0133] 2) It is desirable to perform a preliminary heat treatment at 400 to 500°C, which is approximately ±50°C around the melting point of lithium hydroxide (462°C), for 5 to 20 hours. If the time is less than 5 hours, it does not help improve the structural stability of the cathode active material, and if the time exceeds 20 hours, although it helps improve structural stability, a problem may arise where productivity efficiency decreases.

[0134] 3) The maximum heat treatment temperature is preferably 600 to 1,100°C. Below 600°C, sintering is not performed properly, which may result in a lower capacity of the cathode active material and reduced structural stability. Above 1,100°C, sintering is excessive, which may lead to a lower capacity of the cathode active material and structural collapse.

[0135] 4) The holding time at the maximum temperature is preferably 10 to 40 hours. If it is less than 10 hours, sintering is not done properly, which may result in a lower capacity of the cathode active material and reduced structural stability; if it exceeds 40 hours, while it helps improve structural stability, it may lead to a problem of reduced productivity efficiency.

[0136] 5) Lowering the cooling rate more slowly than the natural cooling rate helps improve the structural stability of the cathode active material, but it may result in additional costs and reduced productivity efficiency.

[0137] 6) While a higher amount of oxygen per unit time that the atmosphere gas contacts the positive active material helps improve the structural stability of the positive active material, it may lead to increased costs.

[0138] 2.2) Preparation of secondary cathode active material by heat-treating the primary cathode active material (secondary heat treatment)

[0139] A material obtained by secondarily heat-treating a primary positive active material can be called a secondary positive active material.

[0140] Depending on the type of primary cathode active material, the target material for the secondary heat treatment can be classified into ① the primary cathode active material alone, and ② a mixture of the primary cathode active material and doping and / or coating materials.

[0141] In the secondary heat treatment process, 1) the heating rate, 2) the maximum temperature, 3) the holding time at the maximum temperature, and 4) the cooling rate can affect the structural stability of the secondary cathode active material.

[0142] 1) A heating rate of 0.5 to 5℃ / min may be preferable. If the heating rate is lower than 0.5℃ / min, it helps improve the structural stability of the cathode active material, but it may result in a decrease in productivity efficiency.

[0143] 2) The maximum temperature may be 0 to 500°C lower than the maximum temperature of the first heat treatment. If the maximum temperature is higher than the maximum temperature of the first heat treatment, excessive sintering may occur, resulting in a decrease in the capacity of the cathode active material and structural collapse. If the maximum temperature is more than 500°C lower than the temperature of the first heat treatment, the structural stability of the cathode active material may not be improved.

[0144] 3) A holding time of 5 to 20 hours at the maximum temperature may be desirable. If it is less than 5 hours, it does not help improve the structural stability of the cathode active material, and if it exceeds 20 hours, it helps improve structural stability but may result in a problem of reduced productivity efficiency.

[0145] 4) If the cooling rate is lower than the natural cooling rate, it helps improve the structural stability of the cathode active material, but it may result in additional costs and reduced productivity efficiency.

[0146] The secondary positive active material can satisfy the following Equation 1.

[0147] [Equation 1]

[0148] 0.3(%) < △W 300 (%)·300(K) / T onset (K)< 1.5(%),

[0149] Here,

[0150] T onset (K) is the onset Kelvin temperature (K) in the first stage decay region of the positive active material, and

[0151] △W 300 (%)=W onset (%)-W onset+300K (%) and,

[0152] W onset (%) is T onset It is the weight (%) at (K), and

[0153] W onset+300K (%) is T onsetIt is the weight (%) at (K)+300(K).

[0154] 2.3) Prepare a tertiary cathode active material by heat-treating the secondary cathode active material (tertiary heat treatment)

[0155] A material obtained by performing a third heat treatment on a second positive active material can be called a third positive active material. The third heat treatment can be performed selectively if necessary. That is, the second positive active material may not satisfy Equation 1, in which case a positive active material satisfying Equation 1 can be manufactured through the third heat treatment.

[0156] The material subject to the third heat treatment can be classified, depending on the type of secondary cathode active material, into ① the secondary cathode active material alone or ② a mixture of the secondary cathode active material and doping and / or coating materials.

[0157] In the third heat treatment process, 1) the heating rate, 2) the maximum temperature, 3) the holding time at the maximum temperature, and 4) the cooling rate can affect the structural stability of the third cathode active material.

[0158] 1) A heating rate of 0.5 to 5℃ / min may be preferable. If the heating rate is lower than 0.5℃ / min, it helps improve the structural stability of the cathode active material, but it may result in a decrease in productivity efficiency.

[0159] 2) The maximum temperature may be 0 to 500°C lower than the maximum temperature of the first heat treatment. If the maximum temperature is higher than the maximum temperature of the first heat treatment, excessive sintering may occur, resulting in a decrease in the capacity of the positive active material and structural collapse; if the maximum temperature is more than 500°C lower than the temperature of the first heat treatment, the structural stability of the positive active material may not be improved.

[0160] 3) A holding time of 5 to 20 hours at the maximum temperature may be desirable. If it is less than 5 hours, it does not help improve the structural stability of the cathode active material, and if it exceeds 20 hours, it helps improve structural stability but may result in a problem of reduced productivity efficiency.

[0161] 4) If the cooling rate is lower than the natural cooling rate, it helps improve the structural stability of the cathode active material, but it may result in additional costs and reduced productivity efficiency.

[0162] The tertiary cathode active material can satisfy Formula 1 below.

[0163] [Equation 1]

[0164] 0.3(%) < △W 300 (%)·300(K) / T onset (K)< 1.5(%),

[0165] Here,

[0166] T onset (K) is the onset Kelvin temperature (K) in the first stage decay region of the positive active material, and

[0167] △W 300 (%)=W onset (%)-W onset+300K (%) and,

[0168] W onset (%) is T onset It is the weight (%) at (K), and

[0169] W onset+300K (%) is T onset It is the weight (%) at (K)+300(K).

[0170] Details regarding doping and coating materials are the same as those explained in the previous section, so they will be omitted below.

[0171]

[0172] A third aspect of the present invention may be a positive electrode for a lithium secondary battery comprising a positive electrode active material of the front side. The positive electrode of this aspect may include a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector. The positive electrode active material layer may include a positive electrode active material on the front side of the positive electrode.

[0173] Aluminum thin films may be used as the positive current collector, but are not limited thereto. The positive active material layer may include a positive active material, a binder, and a conductive material. The positive active material layer may include a positive active material according to the present invention. The binder may include a polymer having a fluorine (F) component, for example, polyvinyl fluoride (PVF), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), and modified versions thereof. The conductive material is used to impart conductivity to the electrode, and any electronically conductive material that does not cause chemical changes in the battery may be used. For example, natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, etc. may be used.

[0174]

[0175] A fourth aspect of the present invention may be a lithium secondary battery comprising a positive electrode on the front side.

[0176] The lithium secondary battery of this aspect may include a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte on the front side.

[0177] The cathode may include a cathode current collector and a cathode active material layer formed on the current collector. A copper thin film may be used as the cathode current collector, but is not limited thereto. The cathode active material layer may include a cathode active material, a binder composition, and / or a conductive material.

[0178] The separator is inserted between the anode and the cathode to separate them, and may be one that has low resistance to the movement of electrolyte ions and excellent electrolyte wettability. For example, it may be selected from glass fiber, polyester, Teflon, polyethylene, polypropylene, polytetrafluoroethylene, or combinations thereof, and may be in the form of a nonwoven or woven fabric.

[0179] The electrolyte can be prepared by dissolving a lithium salt in an organic solvent. Any organic solvent and lithium salt that can be generally used as an organic solvent in the relevant technical field may be used. In addition, solid electrolytes such as organic solid electrolytes and inorganic solid electrolytes may be used as the electrolyte. When a solid electrolyte is used, the solid electrolyte may also serve as a separator.

[0180]

[0181] Hereinafter, the present invention will be described in detail with reference to examples to specifically explain the invention. However, the embodiments according to the present invention may be modified in various different forms, and the scope of the present invention should not be interpreted as being limited to the embodiments described below. The embodiments of the present invention are provided to more completely explain the invention to those with average knowledge in the art.

[0182]

[0183] 1. Preparation of precursors for cathode active materials

[0184] 1) Preparation Example 1: Preparation of Precursor 1

[0185] As shown below, the chemical formula is Ni in a continuous method 0.5 Co 0.2 Mn 0.3 A precursor 1 was prepared in which (OH)2, the concentrations of each component within the precursor were constant, and no doping material was added.

[0186] ① Nickel sulfate, cobalt sulfate, and manganese sulfate were dissolved in deionized water to prepare a solution with a mole ratio of Ni:Co:Mn = 0.5:0.2:0.3.

[0187] ② Deionized water was filled into a continuous reactor, the water temperature of the reactor was set to 60℃, stirring was started, ammonia water was added to adjust the ammonia concentration to 2.2-2.5 g / L, sodium hydroxide solution was added to adjust the pH to 11.0-11.2, and nitrogen was injected (injected until the end of the co-precipitation reaction) to remove dissolved oxygen.

[0188] ③ The solution of ①, ammonia water, and sodium hydroxide solution were introduced into a reactor to start a co-precipitation reaction, at which time the ammonia concentration in the reactor was maintained at 2.2-2.5 g / L and the pH at 11.0-11.2.

[0189] ④ While continuously maintaining the state of ③ above, when the average particle size (D50) of the particles in the solution overflowing from the reactor becomes 10~11μm, the co-precipitation reaction is stopped, and then spherical precursor 1 is prepared through filtration, washing, drying, sieving, and iron removal processes.

[0190]

[0191] 2) Preparation Example 2: Preparation of Precursor 2

[0192] As shown below, the chemical formula is Ni in a continuous method 0.6 Co 0.2 Mn 0.2 A precursor 2 was prepared in which (OH)2, the concentrations of each component within the precursor are constant, and no doping material is added.

[0193] ① Nickel sulfate, cobalt sulfate, and manganese sulfate were dissolved in deionized water to prepare a solution with a molar ratio of Ni:Co:Mn = 0.6:0.2:0.2.

[0194] ② Deionized water was filled into a continuous reactor, the water temperature of the reactor was set to 60℃, stirring was started, ammonia water was added to adjust the ammonia concentration to 2.4-2.7 g / L, sodium hydroxide solution was added to adjust the pH to 11.1-11.3, and nitrogen was injected (injected until the end of the co-precipitation reaction) to remove dissolved oxygen.

[0195] ③ The solution of ①, ammonia water, and sodium hydroxide solution were introduced into a reactor to start a co-precipitation reaction, at which time the ammonia concentration in the reactor was maintained at 2.4-2.7 g / L and the pH at 11.1-11.3.

[0196] ④ While continuously maintaining the state of ③ above, when the average particle size (D50) of the particles in the solution overflowing from the reactor becomes 10~11μm, the co-precipitation reaction is stopped, and then spherical precursor 2 is produced through filtration, washing, drying, sieving, and iron removal processes.

[0197]

[0198] 3) Preparation Example 3: Preparation of Precursor 3

[0199] As shown below, the chemical formula is Ni in a continuous method 0.8 Co 0.1 Mn 0.1 A precursor 3 was prepared in which (OH)2, the concentrations of each component within the precursor were constant, and no doping material was added.

[0200] ① Nickel sulfate, cobalt sulfate, and manganese sulfate were dissolved in deionized water to prepare a solution with a molar ratio of Ni:Co:Mn = 0.8:0.1:0.1.

[0201] ② Deionized water was filled into a continuous reactor, the water temperature of the reactor was set to 60℃, stirring was started, ammonia water was added to adjust the ammonia concentration to 3.0-3.3 g / L, sodium hydroxide solution was added to adjust the pH to 11.3-11.5, and nitrogen was injected (injected until the end of the co-precipitation reaction) to remove dissolved oxygen.

[0202] ③ The solution of ①, ammonia water, and sodium hydroxide solution were introduced into a reactor to start a co-precipitation reaction, at which time the ammonia concentration in the reactor was maintained at 3.0-3.3 g / L and the pH at 11.3-11.5.

[0203] ④ While continuously maintaining the state of ③ above, when the average particle size (D50) of the particles in the solution overflowing from the reactor becomes 10~11μm, the co-precipitation reaction is stopped, and then spherical precursor 3 is produced through filtration, washing, drying, sieving, and iron removal processes.

[0204]

[0205] 4) Preparation Example 4: Preparation of Precursor 4

[0206] As shown below, the chemical formula is Ni in a continuous method 0.8 Co 0.1 Mn 0.1 Zr 0.01 (OH)( >2 ) and the concentrations of each component within the precursor were constant, and a precursor 4 was prepared in which Zr was added as a doping material.

[0207] ① Nickel sulfate, cobalt sulfate, and manganese sulfate were dissolved in deionized water to prepare a solution with a molar ratio of Ni:Co:Mn = 0.8:0.1:0.1.

[0208] ② A solution was prepared by dissolving zirconium acetate in deionized water and adding a small amount of dispersant.

[0209] ③ Deionized water was filled into a continuous reactor, the water temperature of the reactor was set to 60℃, stirring was started, ammonia water was added to adjust the ammonia concentration to 3.0-3.3 g / L, sodium hydroxide solution was added to adjust the pH to 11.3-11.5, and nitrogen was injected (injected until the co-precipitation reaction was finished) to remove dissolved oxygen.

[0210] ④ The solution of ① above, the solution of ② above, ammonia water, and sodium hydroxide solution were introduced into a reactor to start a co-precipitation reaction, at which time the ammonia concentration in the reactor was maintained at 3.0-3.3 g / L and the pH at 11.3-11.5.

[0211] ⑤ While continuously maintaining the state of ④ above, when the average particle size (D50) of the particles in the solution overflowing from the reactor becomes 10~11μm, the co-precipitation reaction is stopped, and then spherical precursor 4 is prepared through filtration, washing, drying, sieving, and iron removal processes.

[0212]

[0213] 5) Preparation Example 5: Preparation of Precursor 5

[0214] The chemical formula is Ni as follows, using the batch method. 0.8 Co 0.1 Mn 0.1 It is (OH)2, has a core-shell structure, and the core composition is Ni 0.9 Co 0.1 (OH)2, and the shell has a concentration gradient, with the outermost composition being Ni 0.4 Co 0.1 Mn 0.5 A precursor 5 was prepared that is (OH)2 and has no doping material added.

[0215] ① Nickel sulfate and cobalt sulfate were dissolved in deionized water to prepare a solution with a molar ratio of Ni:Co = 0.9:0.1.

[0216] ② Nickel sulfate, cobalt sulfate, and manganese sulfate were dissolved in deionized water to prepare a solution with a molar ratio of Ni:Co:Mn = 0.4:0.1:0.5.

[0217] ③ Deionized water was filled into a batch reactor, the water temperature of the reactor was set to 65℃, stirring was started, ammonia water was added to adjust the ammonia concentration to 3.2-3.5 g / L, sodium hydroxide solution was added to adjust the pH to 11.7-11.9, and nitrogen was injected (injected until the co-precipitation reaction was finished) to remove dissolved oxygen.

[0218] ④ The solution of ① above, ammonia water, and sodium hydroxide solution were introduced into a reactor to start a co-precipitation reaction, at which time the ammonia concentration in the reactor was maintained at 3.2-3.5 g / L and the pH at 11.7-11.9.

[0219] ⑤ When the size of the particles formed in the reactor reached 2~3μm, the amount of sodium hydroxide solution added was gradually reduced to lower the pH to 10.6-10.8 to grow the particles.

[0220] ⑥ When the average particle size (D50) of the particles formed in the reactor becomes 8~9 μm, the reaction is stopped and the precursor of the core part is prepared through filtration, washing, drying, sieving, and iron removal processes.

[0221] ⑦ Deionized water was filled into a batch reactor, the precursor of the core part obtained in ⑤ was introduced, the water temperature of the reactor was set to 65℃, stirring was started, ammonia water was added to adjust the ammonia concentration to 4.0-4.3 g / L, sodium hydroxide solution was added to adjust the pH to 10.4-10.6, and nitrogen was injected (injected until the co-precipitation reaction was finished) to remove dissolved oxygen.

[0222] ⑧ A mixed solution of ① and ② (the solution of ① was reduced by a constant ratio and the solution of ② was increased by a constant ratio over time, while the total amount of the mixture was kept constant), ammonia water, and sodium hydroxide solution were introduced into a reactor to start a co-precipitation reaction to form a shell portion, at which time the ammonia concentration in the reactor was maintained at 4.0-4.3 g / L and the pH at 10.4-10.6.

[0223] ⑨ While continuously maintaining the state of ⑦ above, when the average particle size (D50) of the particles in the reactor becomes 10~11μm, the co-precipitation reaction is stopped, and then a precursor 5 having a spherical core-shell structure is prepared through filtration, washing, drying, sieving, and iron removal processes.

[0224]

[0225] 6) Preparation Example 6: Preparation of Precursor 6

[0226] As shown below, by the spray drying method, the chemical formula Li 1.03 (Ni 0.8 Co 0.1 Mn 0.1 )(O n ·OH m )2,(n+m=1), and a precursor 6 was prepared in which the concentrations of each component within the precursor were constant and no doping material was added.

[0227] ① Lithium nitrate, nickel nitrate, cobalt nitrate, and manganese nitrate were dissolved in deionized water to make a molar ratio of Li:Ni:Co:Mn = 1.03:0.8:0.1:0.1, and then a small amount of complexing agent was added to prepare a solution.

[0228] ② The solution of ① above was spray-dried instantaneously using hot air while spraying it into small droplet shapes using a spray drying device to pulverize it, and then a primary powder was produced using a centrifugal device.

[0229] ③ The primary powder obtained in ② above was heat-treated in a kiln at 450°C for 3 hours in an oxygen atmosphere to remove residual moisture and complexing agent.

[0230] ④ The heat-treated primary powder of ③ and deionized water were placed in a ball mill device and milled to produce a slurry.

[0231] ⑤ The slurry prepared in ④ is secondarily spray-dried using a spray drying device to obtain an average particle size (D 50 A spherical precursor 6 with a diameter of 3.3 μm was prepared.

[0232]

[0233] 2. Preparation of positive electrode active material

[0234] The mixing molar ratios for the materials in the following cathode active material preparation are based on the metal (or main component), and the results of the mixing molar ratios are shown in the experimental formulas in "Table 1" of "3. Evaluation" below.

[0235] 1) Example 1: Preparation of Cathode Active Material 1

[0236] A positive electrode active material 1 was prepared as follows using precursor 1 prepared in Preparation Example 1.

[0237] ① The above precursor 1, lithium carbonate, and zirconium oxide (ZrO2) were added to a mixing container in a molar ratio of 1.00 to 1.01 to 0.01 and mixed uniformly.

[0238] ② The mixed powder of ① was subjected to primary heat treatment in a box kiln under the following conditions.

[0239] - Atmosphere gas: Air

[0240] - Heating rate: Heating from room temperature to 920℃ at a rate of 2℃ / min

[0241] - Holding time: Maintain at 920℃ for 20 hours

[0242] - Cooling method: Natural cooling

[0243] ③ The primary heat-treated material of ② was crushed and classified, then subjected to washing, filtration, drying, classification, and iron removal processes.

[0244] ④ The material obtained in ③ and boric acid (H3BO3) were added to a mixing container in a molar ratio of 1.00 to 0.01 and mixed uniformly.

[0245] ⑤ The mixed powder of ④ was subjected to secondary heat treatment in a box kiln under the following conditions.

[0246] - Atmosphere gas: air

[0247] - Heating rate: Heating from room temperature to 450℃ at a rate of 2℃ / min

[0248] - Holding time: Hold at 450℃ for 10 hours

[0249] - Cooling method: Natural cooling

[0250] ⑥ The secondary heat-treated material of ⑤ was crushed and classified, and then subjected to a deironing process to produce a positive electrode active material 1.

[0251]

[0252] 2) Comparative Example 1: Preparation of Comparative Anode Active Material 1

[0253] A comparative cathode active material 1, having the same chemical formula as cathode active material 1, was prepared by keeping the rest the same except that the primary heat treatment conditions of ② in Example 1 were changed as follows.

[0254] - Atmosphere gas: Air

[0255] - Heating rate: Heating from room temperature to 1,350℃ at a rate of 2℃ / min

[0256] - Holding time: Maintain at 1,350℃ for 20 hours

[0257] - Cooling method: Natural cooling

[0258]

[0259] 3) Example 2: Preparation of Cathode Active Material 2

[0260] Anode active material 2 was prepared as follows using precursor 2 prepared in Preparation Example 2.

[0261] ① Precursor 2, lithium carbonate, and zirconium oxide were added to a mixing container in a molar ratio of 1.00 to 1.01 to 0.01 and mixed uniformly.

[0262] ② The mixed powder of ① was subjected to primary heat treatment in a box kiln under the following conditions.

[0263] - Atmosphere gas: Air

[0264] - Heating rate: Heating from room temperature to 870℃ at a rate of 2℃ / min

[0265] - Holding time: Maintain at 870℃ for 20 hours

[0266] - Cooling method: Natural cooling

[0267] ③ The primary heat-treated material of ② was crushed and classified, then subjected to washing, filtration, drying, classification, and iron removal processes.

[0268] ④ The substance obtained in ③ and boric acid were added to a mixing container in a molar ratio of 1.00 to 0.01 and mixed uniformly.

[0269] ⑤ The mixed powder of ④ was subjected to secondary heat treatment in a box kiln under the following conditions.

[0270] - Atmosphere gas: Air

[0271] - Heating rate: Heating from room temperature to 450℃ at a rate of 2℃ / min

[0272] - Holding time: Hold at 450℃ for 10 hours

[0273] - Cooling method: Natural cooling

[0274] ⑥ The secondary heat-treated material of ⑤ was crushed and classified, and then subjected to a deironing process to produce the cathode active material 2.

[0275]

[0276] 4) Comparative Example 2: Preparation of Comparative Anode Active Material 2

[0277] A comparative positive active material 2, having the same chemical formula as positive active material 2, was prepared by carrying out the rest in the same manner as in Example 2 above, except that the first heat treatment conditions of ② were changed as follows.

[0278] - Atmosphere gas: Air

[0279] - Heating rate: Heating from room temperature to 550℃ at a rate of 2℃ / min

[0280] - Holding time: Hold at 550℃ for 20 hours

[0281] - Cooling method: Natural cooling

[0282]

[0283] 5) Example 3: Preparation of Cathode Active Material 3

[0284] A positive electrode active material 3 was prepared as follows using precursor 3 prepared in Preparation Example 3.

[0285] ① A material was prepared in which magnesium oxide (MgO) and zirconium oxide were mixed in a molar ratio of 1.0 to 2.0.

[0286] ② A substance was prepared in which aluminum oxide and boric acid were mixed in a molar ratio of 1.0 to 4.0.

[0287] ③ Precursor 3, lithium hydroxide, and the mixture of ① above were added to a mixing container in a molar ratio of 1.00 to 1.03 to 0.03 and mixed uniformly.

[0288] ④ The mixed powder of ③ was subjected to primary heat treatment in a box kiln under the following conditions.

[0289] - Atmosphere gas: Oxygen

[0290] - Pre-heat treatment: Increase temperature from room temperature to 450℃ at a rate of 2℃ / min, and maintain at 450℃ for 10 hours.

[0291] - Heating rate: Heating from 450℃ to 770℃ at a rate of 2℃ / min

[0292] - Holding time: Maintain at 770℃ for 30 hours

[0293] - Cooling method: Natural cooling

[0294] ⑤ The primary heat-treated material of ④ was crushed and classified, then subjected to washing, filtration, drying, classification, and iron removal processes.

[0295] ⑥ The substance obtained in ⑤ and the mixture of ② were added to a mixing container in a molar ratio of 1.00 to 0.02 and mixed uniformly.

[0296] ⑦ The mixed powder of ⑥ was subjected to secondary heat treatment in a box kiln under the following conditions.

[0297] - Atmosphere gas: Oxygen

[0298] - Heating rate: Heating from room temperature to 450℃ at a rate of 2℃ / min

[0299] - Holding time: Hold at 450℃ for 10 hours

[0300] - Cooling method: Natural cooling

[0301] The secondary heat-treated material of ⑧ and ⑦ was crushed and classified, and then subjected to a deironing process to produce the cathode active material 3.

[0302]

[0303] 6) Comparative Example 3: Preparation of Comparative Anode Active Material 3

[0304] A comparative cathode active material 3, which has the same chemical formula as cathode active material 3, was prepared by carrying out the rest in the same manner as in Example 3, except that the first heat treatment conditions of ④ were changed as follows.

[0305] - Atmosphere gas: Air

[0306] - Heating rate: Heating from room temperature to 770℃ at a rate of 2℃ / min

[0307] - Holding time: Maintain at 770℃ for 7 hours

[0308] - Cooling method: Natural cooling

[0309]

[0310] 7) Example 4: Preparation of Cathode Active Material 4

[0311] A positive electrode active material 4 was prepared as follows using precursor 4 prepared in Preparation Example 4.

[0312] ① A material was prepared in which aluminum oxide and magnesium oxide were mixed in a molar ratio of 1.0 to 4.0.

[0313] ② The above precursor 4, lithium hydroxide, and the mixture of ① were added to a mixing container in a molar ratio of 1.00 to 1.03 to 0.02 and mixed uniformly.

[0314] ③ The mixed powder of ① was subjected to primary heat treatment in a box kiln under the following conditions.

[0315] - Atmosphere gas: Oxygen

[0316] - Heating rate: Heating from room temperature to 770℃ at a rate of 2℃ / min

[0317] - Holding time: Maintain at 720℃ for 20 hours

[0318] - Cooling method: Natural cooling

[0319] ④ The primary heat-treated material of ③ was crushed and classified, then subjected to washing, filtration, drying, classification, and iron removal processes.

[0320] ⑤ The material obtained in ③ above and aluminum oxide were added to a mixing container in a molar ratio of 1.00 to 0.01 and mixed uniformly.

[0321] ⑥ The mixed powder of ⑤ was subjected to secondary heat treatment in a box kiln under the following conditions.

[0322] - Atmosphere gas: Oxygen

[0323] - Heating rate: Heating from room temperature to 450℃ at a rate of 2℃ / min

[0324] - Holding time: Hold at 450℃ for 10 hours

[0325] - Cooling method: Natural cooling

[0326] ⑦ The secondary heat-treated material of ⑥ was crushed and classified, and then subjected to a deironing process.

[0327] ⑧ The material obtained in ⑦ and boron oxide were added to a mixing container in a molar ratio of 1.00 to 0.01 and mixed uniformly.

[0328] The mixed powder of ⑨ and ⑧ was subjected to a third heat treatment in a box kiln under the following conditions.

[0329] - Atmosphere gas: Oxygen

[0330] - Heating rate: Heating from room temperature to 450℃ at a rate of 2℃ / min

[0331] - Holding time: Hold at 450℃ for 10 hours

[0332] - Cooling method: Natural cooling

[0333] The cathode active material 4 was prepared by crushing and classifying the 3rd heat-treated material of ⑨ and then undergoing a deironing process.

[0334]

[0335] 8) Comparative Example 4: Preparation of Comparative Anode Active Material 4

[0336] A comparative positive active material 4, having the same chemical formula as positive active material 4, was prepared by carrying out the rest in the same manner as in ③ of Example 4, except that the first heat treatment conditions were changed as follows.

[0337] - Atmosphere gas: Oxygen

[0338] - Heating rate: Heating from room temperature to 550℃ at a rate of 2℃ / min

[0339] - Holding time: Hold at 550℃ for 20 hours

[0340] - Cooling method: Natural cooling

[0341]

[0342] 9) Example 5: Preparation of Cathode Active Material 5

[0343] A positive electrode active material 5 was prepared as follows using precursor 5 prepared in Preparation Example 5.

[0344] ① A material was prepared in which magnesium oxide and zirconium oxide were mixed in a molar ratio of 1.0 to 2.0.

[0345] ② The above precursor 5, lithium hydroxide, and the mixture of ① were added to a mixing container in a molar ratio of 1.00 to 1.03 to 0.01 and mixed uniformly.

[0346] ③ The mixed powder of ② was subjected to primary heat treatment in a box kiln under the following conditions.

[0347] - Atmosphere gas: Oxygen

[0348] - Pre-heat treatment: Increase temperature from room temperature to 450℃ at a rate of 2℃ / min, and maintain at 450℃ for 10 hours.

[0349] - Heating rate: Heating from 450℃ to 770℃ at a rate of 2℃ / min

[0350] - Holding time: Maintain at 770℃ for 20 hours

[0351] - Cooling method: Natural cooling

[0352] ④ The primary heat-treated material of ③ was crushed and classified, then subjected to washing, filtration, drying, classification, and iron removal processes.

[0353] ⑤ The material from the first heat treatment of ④ was subjected to a second heat treatment in a box kiln under the following conditions.

[0354] - Atmosphere gas: Oxygen

[0355] - Heating rate: Heating from room temperature to 450℃ at a rate of 2℃ / min

[0356] - Holding time: Hold at 450℃ for 10 hours

[0357] - Cooling method: Natural cooling

[0358] ⑥ The secondary heat-treated material of ⑤ was crushed and classified, and then subjected to a deironing process to produce the positive electrode active material 5.

[0359]

[0360] 10) Comparative Example 5: Preparation of Comparative Anode Active Material 5

[0361] A comparative cathode active material 5, having the same chemical formula as cathode active material 5, was prepared by carrying out the rest in the same manner as in ③ of Example 5, except that the first heat treatment conditions were changed as follows.

[0362] - Atmosphere gas: Oxygen

[0363] - Pre-heat treatment: Increase temperature from room temperature to 450℃ at a rate of 2℃ / min, and maintain at 450℃ for 10 hours.

[0364] - Heating rate: Heating from 450℃ to 1,350℃ at a rate of 2℃ / min

[0365] - Holding time: Maintain at 1,350℃ for 20 hours

[0366] - Cooling method: Natural cooling

[0367]

[0368] 11) Example 6: Preparation of Cathode Active Material 6

[0369] A positive electrode active material 6 was prepared as follows using precursor 6 prepared in Preparation Example 6.

[0370] ① A material was prepared in a mixing container in which titanium oxide (TiO2), aluminum oxide, and monoammonium phosphate ((NH4)H2PO4) were mixed in a molar ratio of 2.0 to 1.0 to 1.0.

[0371] ② The above precursor 6 and the above mixture of ① were added to a mixing container in a molar ratio of 1.00 to 0.01 and mixed uniformly.

[0372] ③ The mixed powder of ② was subjected to primary heat treatment in a box kiln under the following conditions.

[0373] - Atmosphere gas: Oxygen

[0374] - Maintain at intermediate temperature: Increase temperature from room temperature to 550℃ at a rate of 2℃ / min, and maintain at 550℃ for 10 hours.

[0375] - Heating rate: Heating from 550℃ to 950℃ at a rate of 2℃ / min

[0376] - Holding time: Maintain at 950℃ for 20 hours

[0377] - Cooling method: Natural cooling

[0378] ④ The primary heat-treated material of ③ was crushed and classified, then subjected to washing, filtration, drying, classification, and iron removal processes.

[0379] ⑤ The material obtained in ④ and the cobalt nitrate solution were added to a mixing container in a molar ratio of 1.00 to 0.01 (based on Co metal) and uniformly mixed to form a slurry, and then subjected to stirring, drying, classification, and iron removal processes.

[0380] ⑥ The material obtained in ⑤ was subjected to secondary heat treatment in a box kiln under the following conditions.

[0381] - Atmosphere gas: Oxygen

[0382] - Heating rate: Heating from room temperature to 450℃ at a rate of 2℃ / min

[0383] - Holding time: Hold at 450℃ for 10 hours

[0384] - Cooling method: Natural cooling

[0385] ⑦ The secondary heat-treated material of ⑥ was crushed and classified, and then subjected to a deironing process to produce a single-crystal cathode active material 6.

[0386]

[0387] 12) Comparative Example 6: Preparation of Comparative Anode Active Material 6

[0388] A comparative cathode active material 6, having the same chemical formula as cathode active material 6, was prepared by carrying out the rest in the same manner as in ⑥ of Example 6, except that the secondary heat treatment conditions were changed as follows.

[0389] ⑥ The material obtained in ⑤ was subjected to secondary heat treatment in a box kiln under the following conditions.

[0390] - Atmosphere gas: Oxygen

[0391] - Heating rate: Heating from room temperature to 1,350℃ at a rate of 2℃ / min

[0392] - Holding time: Hold at 1,350℃ for 10 hours

[0393] - Cooling method: Natural cooling

[0394]

[0395] 3. Evaluation

[0396] 1) Composition of the positive electrode active material

[0397] Elemental analysis of the cathode active materials of the examples and comparative examples was performed using an ICP-OES analyzer. In the ICP-OES analysis, the analysis of major components was performed using an Agilent 5800 (RF power 1200W) analyzer, and trace elements such as doping and coating materials were analyzed using a Perkin Elmer Avio550 (RF power 1300W).

[0398] Table 1 shows the theoretical chemical formulas for the positive electrode active materials of the above examples and comparative examples, and the analytical chemical formulas obtained using ICP-OES.

[0399] Theoretical Chemical Formula Analysis Chemical Formula Example 1Li 1.01 [(Ni 0.5 Co 0.2 Mn 0.3 )-(Zr 0.01 )-(B 0.01 )]O( >2 )Li 1.003 [(Ni 0.49 Co 0.20 Mn 0.29 )-(Zr 0.010 )-(B 0.010 )]O( >2 )Comparative Example 1Li 1.01 [(Ni 0.5 Co 0.2 Mn 0.3 )-(Zr 0.01 )-(B 0.01 )]O( >2 )Li 0.92 [(Ni 0.49 Co 0.20 Mn 0.29 )-(Zr 0.009 )-(B 0.010 )]O( >2 Example 2Li 1.01 [(Ni 0.6 Co 0.2 Mn 0.2 )-(Zr 0.01 )-(B 0.01 )]O( >2 )Li 1.003 [(Ni 0.59 Co 0.20 Mn 0.19 )-(Zr 0.009 )-(B 0.010 )]O( >2 )Comparative Example 2Li 1.01 [(Ni 0.6 Co 0.2 Mn 0.2 )-(Zr 0.01 )-(B 0.01 )]O( >2 )Li 0.87 [(Ni 0.59 Co 0.20Mn 0.19 )-(Zr 0.010 )-(B 0.010 )]O( >2 )실시예 3Li 1.03 [(Nor 0.8 Co 0.1 Mn 0.1 )-(Mg 1 / 3 Zr 2 / 3 ) 0.03 -(Al 1 / 5 B 4 / 5 ) 0.02 ]O( >2 )The 1.004 [(Nor 0.75 Co 0.10 Mn 0.09 )-(Mg 0.009 Zr 0.019 )-(Al 0.010 B 0.018 )]O( >2 )비교예 3Li 1.03 [(Nor 0.8 Co 0.1 Mn 0.1 )-(Mg 1 / 3 Zr 2 / 3 ) 0.03 -(Al 1 / 5 B 4 / 5 ) 0.02 ]O( >2 )The 0.94 [(Nor 0.75 Co 0.10 Mn 0.09 )-(Mg 0.010 Zr 0.020 )-(Al 0.009 B 0.018 )]O( >2 )실시예 4Li 1.03 [(Nor 0.8 Co 0.1 Mn 0.1 Zr 0.01 )-(Al 1 / 5 Mg 4 / 5 ) 0.02 -(Al 0.01 )-(B 0.01 )]O( >2 )The 1.005 [(Nor 0.76 Co 0.10 Mn 0.09 )-(Zr 0.009 Al 0.014 Mg 0.017)-(B 0.009 )]O( >2 )Comparative Example 4Li 1.03 [(Ni 0.8 Co 0.1 Mn 0.1 Zr 0.01 )-(Al 1 / 5 Mg 4 / 5 ) 0.02 -(Al 0.01 )-(B 0.01 )]O( >2 )Li 0.84 [(Ni 0.75 Co 0.10 Mn 0.10 )-(Zr 0.010 Al 0.013 Mg 0.018 )-(B 0.009 )]O( >2 Example 5Li 1.03 [(Ni 0.8 Co 0.1 Mn 0.1 )-(Mg 1 / 3 Zr 2 / 3 ) 0.01 ]O( >2 )Li 1.004 [(Ni 0.79 Co 0.10 Mn 0.10 )-(Mg 0.004 Zr 0.006 )]O( >2 )Comparative Example 5Li 1.03 [(Ni 0.8 Co 0.1 Mn 0.1 )-(Mg 1 / 3 Zr 2 / 3 ) 0.01 ]O( >2 )Li 0.91 [(Ni 0.79 Co 0.10 Mn 0.10 )-(Mg 0.004 Zr 0.006 )]O( >2 Example 6Li 1.03 [(Ni 0.8 Co 0.1 Mn 0.1 )-(Ti 2 / 4 Al 1 / 4 P 1 / 4 ) 0.01 -(Co) 0.01 ]O(>2 )Li 1.005 [(Ni 0.78 Co 0.10 Mn 0.10 )-(Ti 0.005 Al 0.002 P 0.002 )-(Co) 0.009 ]O( >2 )Comparative Example 6Li 1.03 [(Ni 0.8 Co 0.1 Mn 0.1 )-(Ti 2 / 4 Al 1 / 4 P 1 / 4 ) 0.01 -(Co) 0.01 ]O( >2 )Li 1.003 [(Ni 0.78 Co 0.10 Mn 0.10 )-(Ti 0.005 Al 0.002 P 0.002 )-(Co) 0.009 ]O( >2 )

[0400]

[0401] In Table 1, the “Theoretical” chemical formula is based on the molar ratio values ​​used in the manufacturing method, and the “Analytical” chemical formula is based on 1.0 molar for the remaining components (components shown in the chemical formula) excluding lithium, oxygen, and trace impurities.

[0402] Referring to Table 1, it can be seen that the analytical values ​​for the components other than lithium match well with the theoretical values. In the case of lithium, the analytical value is lower than the theoretical value because lithium compounds present on the surface of the cathode active material are removed during the cleaning process following the first heat treatment in the cathode active material manufacturing process.

[0403] Referring to Table 1, it can be confirmed that in Comparative Examples 1 to 5, the molar concentration of lithium is less than 1.0, indicating a relatively low lithium content compared to other cathode active materials. It can be presumed that in Comparative Examples 1 and 5, the primary heat treatment temperature was too high, causing the structure of the cathode active material to partially collapse. As the structure collapsed, the internal lithium migrated to the surface and was subsequently removed during the cleaning process, resulting in a relatively low lithium concentration. On the other hand, it can be presumed that in Comparative Examples 2 and 4, the primary heat treatment temperature was too low, and in Comparative Example 3, the primary heat treatment time was too short, so sintering did not occur properly. In other words, lithium was not properly inserted into the cathode active material and remained relatively abundant on the surface, after which it was removed during the subsequent cleaning process, resulting in a relatively low lithium concentration.

[0404] A notable point in Table 1 is that in the case of Comparative Example 6, which has a high second heat treatment temperature, the molar concentration of lithium was found to be 1.0 or higher, unlike Comparative Examples 1 and 5, which have high first heat treatment temperatures. This can be presumed to be because the lithium compound was not removed from the surface of the cathode active material due to the absence of a cleaning process after the second heat treatment.

[0405]

[0406] 2) Particle size analysis of cathode active material

[0407] Particle size analysis of the cathode active materials prepared in the examples and comparative examples was performed using a particle size analyzer (Master Sizer 3000), and the results are shown in Table 2.

[0408] D50(μm)Span Example 1 11.2 1.23 Comparative Example 1 10.9 1.22 Example 2 10.5 1.25 Comparative Example 2 10.8 1.23 Example 3 10.7 1.26 Comparative Example 3 10.9 1.24 Example 4 10.8 1.23 Comparative Example 4 11.11.23 Example 5 11.00.77 Comparative Example 5 11.20.82 Example 63.7 2 1.44 Comparative Example 63.8 4 1.47

[0409]

[0410] Referring to Table 2, there is no difference in the average particle size and particle size distribution according to the examples and comparative examples. From this, it can be confirmed that the sintering state according to the heat treatment temperature during the manufacture of the cathode active material has almost no effect on the average particle size and particle size distribution.

[0411]

[0412] 3) Amount of residual lithium on the surface of the positive electrode active material

[0413] The content of residual lithium (lithium hydroxide and lithium carbonate) present on the surface of the cathode active material prepared in the examples and comparative examples was evaluated as follows by titration using a 905 Titrado instrument. Specifically, 10 g of the cathode active material was dispersed in 100 mL of water and then titrated with 0.1 M HCl to obtain a pH titration result, and the content of lithium hydroxide and lithium carbonate present on the surface of the cathode active material was measured using the result, and the results are shown in Table 3.

[0414] LiOH(ppm)Li2CO3(ppm)Example 1 22452463Comparative Example 1 23552552Example 2 23482562Comparative Example 2 36773872Example 3 33393304Comparative Example 3 35623674Example 4 34883692Comparative Example 4 36623812Example 5 32353431Comparative Example 5 32213386Example 6 34553651Comparative Example 6 33483557

[0415]

[0416] Referring to Table 3, it can be confirmed that the residual lithium components, lithium hydroxide and lithium carbonate, are each 5,000 ppm or less. This indicates that the weight loss due to the decomposition of lithium carbonate in the decay region of the cathode active material is very minimal.

[0417]

[0418] 4. Thermogravimetric analysis of the cathode active material

[0419] TGA analysis of the cathode active materials of the examples and comparative examples was performed in the following manner. A NETZSCH STA 2500 TGA analyzer was used, the evaluation temperature range was from room temperature to 1,200°C, the heating rate was 5°C / min, and the atmosphere was oxygen gas flowed at a flow rate of 20 mL / min. The TGA results were summarized and are shown in Table 4.

[0420] T onset (K)△W 300 (%)·300(K)△W 300 (%)·300(K) / T onset (K) Example 1 113 5.456 600.58 Comparative Example 1 116 0.652 100.18 Example 2 111 0.958 400.76 Comparative Example 2 109 6.652 0101.83 Example 3 107 5.751 2301.14 Comparative Example 3 107 1.951 6801.57 Example 4 108 0.451 1401.06 Comparative Example 4 107 4.251 8001.68 Example 5 105 8.551 1101.05 Comparative Example 5 106 7.252 700.25 Example 6 108 6.851 0200.94 Comparative Example 6 109 1.952 400.22

[0421]

[0422] Referring to Table 4, △W between each example and comparative example 300 (%)·300(K) The range of variation of the value is T onset It appears to be relatively larger than the range of variation of (K). This is because T varies depending on changes in precursor type, heat treatment conditions, doping material, coating material, etc. onset △W compared to (K) value 300 It can be confirmed that the (%)·300(K) value can be relatively significantly affected.

[0423]

[0424] 5. Evaluation of Life Characteristics

[0425] To evaluate the battery performance of the cathode active materials of the examples and comparative examples, a cathode and a lithium battery (coin half-cell) were manufactured using the following method.

[0426] A positive electrode was prepared in which a positive electrode active material layer composed of the respective positive electrode active material of the example and comparative example, carbon conductive material (Super P), and PVDF binder in a weight ratio of 97:1.5:1.5 was formed on an aluminum thin film current collector.

[0427] A coin half-cell was manufactured using the above anode, a lithium metal cathode, a polyethylene separator, and an electrolyte (composed of a mixed solution of ethylene carbonate (EC), dimethyl carbonate (DMC), ethylmethyl carbonate (EMC), and lithium hexafluorophosphate (LiPF6)).

[0428] Lifetime characteristics were evaluated as follows using each of the above-manufactured coin half-cells.

[0429] The coin half-cell was initially charged to 4.3V with a 0.01C cut-off at 25°C using a constant current of 0.2C, and initially discharged to 3.0V using a constant current of 0.2C. Subsequently, the coin half-cell was charged to 4.3V with a 0.05C cut-off using a constant current of 0.5C at 25°C, and discharged to 3.0V using a constant current of 1.0C. This was repeated 100 times, with this as one cycle. The results are shown in Table 5.

[0430] Charging Capacity (mAh / g) Discharging Capacity (mAh / g) Efficiency (%) Discharging Capacity (mAh / g, @100cycle) Capacity Retention Rate (%, @100cycle) Discharging Capacity (mAh / g, @100cycle) Based on 1.0 molar nickel Example 1 184.8 171.3 92.7 169.8 99.1 346.5 Comparative Example 1 137.4 126.2 91.8 107.6 85.3 219.6 Example 2 196.4 180.6 92.0 178.2 98.7 302.0 Comparative Example 2 183.3 169.8 92.6 122.2 72.0 207.1 Example 3 212.7 196.3 92.3 193.1 98.4 257.5 Comparative Example 3189.3167.588.5142.284.9189.6 Example 4213.5196.692.1193.598.4254.6 Comparative Example 4192.7179.293.0121.167.6161.5 Example 5218.3202.192.6197.797.8250.3 Comparative Example 5187.1172.392.1154.689.7195.7 Example 6220.4202.691.9196.997.2252.4 Comparative Example 6190.8175.592.0152.987.1196.0

[0431]

[0432] Referring to Table 5, it can be seen that Comparative Examples 1, 5, and 6 each show a much lower initial charge capacity compared to their respective examples due to the fact that the first and second heat treatment temperatures were too high, causing the structure of the positive active material to partially collapse.

[0433] Referring to Table 5, it can be seen that Comparative Examples 2 and 4 have a much lower initial charge capacity compared to each example due to the insufficient sintering of the cathode active material caused by the first heat treatment temperature being too low and Comparative Example 3 having a sintering time at the highest temperature of the first heat treatment being too short.

[0434] △W of Table 4 in Fig. 3 300 (%)·300(K) / T onset The correlation between the (K) value (horizontal axis) and the discharge capacity (mAh / g, @100cycle) value at 100 cycles in Table 5 (vertical axis) was plotted.

[0435] Referring to Fig. 3, △W 300 (%)·300(K) / T onset It can be confirmed that the discharge capacity (mAh / g, @100cycle) at 100 cycles is clearly distinguishable based on (K) values ​​of 0.3 and 1.5. That is, △W 300 (%)·300(K) / T onset When the (K) value is within the range of 0.3 and 1.5, it can be confirmed that the discharge capacity value at 100 cycles is relatively excellent.

[0436] △W 300 (%)·300(K) / T onset When the (K) value is less than 0.3, the discharge capacity value at 100 cycles is relatively low. This corresponds to a case where the heat treatment temperature is too high and part of the cathode active material structure collapses.

[0437] △W 300 (%)·300(K) / T onset Even when the (K) value is greater than 1.5, the discharge capacity value at 100 cycles is relatively low. This corresponds to a case where the heat treatment is too insufficient.

[0438] In Table 5, the “discharge capacity based on 1.0 mol nickel” value is a value that takes into account the difference in capacity according to the nickel content of the cathode active material, and can be defined as the discharge capacity value at 100 cycles converted to 1.0 mol nickel based on the nickel molar value of the analytical chemical formula in Table 1. This can serve as a more suitable standard for the evaluation criteria of the cathode active material of the present invention, which has high capacity and excellent structural stability, thereby improving the lifespan and stability of the lithium secondary battery, by eliminating deviations according to nickel content.

[0439] △W of Table 4 in Fig. 4 300 (%)·300(K) / T onset The correlation between the (K) value and the discharge capacity (mAh / g, @100 cycle) value based on 1.0 mol nickel in Table 5 was plotted.

[0440] Referring to Fig. 4, as in the case of Fig. 3, △W 300 (%)·300(K) / T onset It can be clearly seen that the discharge capacity (mAh / g, @100cycle) based on 1.0 mole of nickel at 100 cycles is distinctly different based on (K) values ​​of 0.3 and 1.5. The reason for this is the same as the explanation for Figure 3.

[0441] Referring to FIGS. 3 and 4, the discharge capacity value at 100 cycles and the discharge capacity based on 1.0 mol of nickel (mAh / g, @100 cycles) are △W 300 (%)·300(K) / T onset It can be confirmed that the (K) value is relatively superior between 0.3 and 1.5. In particular, △W 300 (%)·300(K) / T onset It can be confirmed that when the (K) value is between 0.5 and 1.2, it exhibits superior characteristics.

[0442] The present invention relates to the correlation between the TGA results of a positive electrode active material, which indicates relative thermal structural stability, and the results of the lifespan characteristics in a battery. Generally, there is a difficulty in having to fabricate and evaluate a battery to observe the lifespan characteristics of a positive electrode active material. However, by using Equations 1 and 2 of the present invention, it is very useful to be able to predict the lifespan characteristics in a battery based solely on the TGA results of the positive electrode active material.

[0443] In conclusion, through the precursor for a positive electrode active material and the method for manufacturing a positive electrode active material presented in the present invention, a positive electrode active material having high capacity and improved structural stability can be manufactured. Furthermore, the lifespan characteristics of such a positive electrode active material can be easily predicted through TGA analysis, and a lithium secondary battery with improved capacity and battery stability can be manufactured using a positive electrode active material having these characteristics.

[0444] The terms used in this invention are intended to describe specific embodiments and are not intended to limit the invention. Unless otherwise evident from the context, singular expressions should be understood to include a plural meaning. Terms such as “comprising” or “having” mean that the features, numbers, steps, actions, components, or combinations thereof described in the specification exist, not that they are excluded.

[0445] The present invention is not limited by the embodiments described above and the attached drawings, but is intended to be limited by the attached claims. Accordingly, various substitutions, modifications, and changes may be made by those skilled in the art within the scope of the technical concept of the present invention as described in the claims, and such should also be considered to fall within the scope of the present invention.

[0446]

Claims

1. Among the remaining components excluding lithium and oxygen, the nickel content is greater than 45 mol% and less than or equal to 80 mol%, and A cathode active material for a lithium secondary battery whose thermogravimetric analysis (TGA) results satisfy the following Equation 1: [Equation 1] 0.3(%) < △W 300 (%)·300(K) / T onset (K)< 1.5(%), T onset (K) is the onset Kelvin temperature (K) in the first stage decay region of the positive active material, and △W 300 (%)=W onset (%)-W onset+300K (%) and, W onset (%) is T onset It is the weight (%) at (K), and W onset+300K (%) is T onset It is the weight (%) at (K)+300(K).

2. In Paragraph 1, A positive electrode active material for a lithium secondary battery having a nickel (Ni) content of more than 55 mol% and less than or equal to 80 mol%.

3. In Paragraph 1, A positive electrode active material for a lithium secondary battery having a nickel (Ni) content of more than 65 mol% and less than or equal to 80 mol%.

4. In Paragraph 1, A positive electrode active material for a lithium secondary battery, wherein the lower limit of Formula 1 is 0.50 (%) and the upper limit is 1.2 (%).

5. In Paragraph 1, The above positive active material is a positive active material for a lithium secondary battery comprising nickel and one or more selected from the group consisting of cobalt, manganese, and aluminum.

6. In any one of paragraphs 1 through 5, A positive electrode active material for a lithium secondary battery, comprising a doping element, wherein the doping element comprises one or more selected from the group consisting of Mg, Ca, Sr, Ba, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, B, Al, Si, Sn, P, Sb, Bi, S, F, Zr, Nb, Mo, Hf, Ta, W, Sc, Y, La, and Ce.

7. In Paragraph 6, A positive electrode active material for a lithium secondary battery, wherein the content of the above-mentioned doping material is 5.0 mol% or less among the remaining components excluding lithium and oxygen.

8. In any one of paragraphs 1 through 5, A positive electrode active material for a lithium secondary battery, comprising a coating element, wherein the coating element comprises one or more selected from the group consisting of Li, Mg, Ca, Sr, Ba, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, B, Al, Si, Sn, P, Sb, Bi, S, F, Zr, Nb, Mo, Hf, Ta, W, Sc, Y, La, and Ce.

9. In Paragraph 8, A positive electrode active material for a lithium secondary battery, wherein the content of the above-mentioned coating element is 3.0 mol% or less among the remaining components excluding lithium and oxygen.

10. A step of manufacturing a positive electrode active material for a lithium secondary battery, a) a precursor manufacturing step for manufacturing a precursor for a positive electrode active material; b) a step of producing a primary positive active material by performing a primary heat treatment on a material containing the manufactured precursor; and c) A step of manufacturing a secondary positive active material by performing a secondary heat treatment on a material containing a primary positive active material; A method for manufacturing a positive electrode active material for a lithium secondary battery, comprising 11. In Paragraph 10, c) After step, d) Optionally, a step of manufacturing a tertiary cathode active material by tertiarily heat-treating a material containing a secondary cathode active material; A method for manufacturing a positive electrode active material for a lithium secondary battery, further comprising 12. A positive electrode for a lithium secondary battery comprising the positive electrode active material of claim 1.

13. A lithium secondary battery comprising the positive electrode of paragraph 12.

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