Positive electrode active material for secondary batteries

Abstract

The present invention is directed to a method for producing a crystalline silicon alloy containing a transition metal, having a residual lithium content of 1 wt% or less on the particle surface, and a BET value of 0.4 m 2 / g or more.

Description

[Technical Field]

[0001] The present invention relates to a positive electrode active material for secondary batteries, and provides a positive electrode active material that can exhibit excellent electrochemical properties by having the amount of residual lithium on the particle surface and the BET value within predetermined optimum ranges. [Background technology]

[0002] Lithium secondary batteries have high energy density and voltage, long life, low self-discharge rate, etc., and are used in a variety of fields, from mobile devices to electric vehicles and medium- to large-sized devices such as energy storage devices. In recent years, the demand for electric vehicles has increased significantly, resulting in a demand for positive electrode active materials with high energy density, and high-Ni-based NCM and NCA positive electrode active materials have been mainly developed.

[0003] In the case of high-Ni-based positive electrode active materials, a Ni-O type rock salt structure, which is not electrochemically active, is likely to form during manufacturing, so they are fired at a relatively low temperature and an excess lithium source is added to form a layered structure with high crystallinity.

[0004] However, if an excessive amount of lithium is added, unreacted lithium oxide in the form of Li2O is generated on the surface of the positive electrode active material. This lithium oxide reacts with H2O, CO2, etc. in the atmosphere and converts into LiOH, Li2CO3, etc., known as "residual lithium." The residual lithium generated on the surface makes the NMP solvent alkaline during the production of electrode plate slurry. When the alkaline solvent mixes with the PVdF binder, gelation occurs, making electrode fabrication difficult. Furthermore, it decomposes under high temperatures and voltages, generating gases (H2O, CO2, O2, etc.) inside the battery, which increases internal pressure and reduces battery safety.

[0005] Various methods have been studied to solve this problem, including a method of removing residual lithium through a water washing process, and a method of performing dry or wet coating using a coating agent that is highly reactive with the residual lithium on the surface without performing a water washing process.

[0006] However, when LiOH, Li2CO3, etc. remaining on the surface are removed using the above methods, the amount of residual lithium is reduced and at the same time, lithium ions within the structure are also removed, which can cause changes in the surface structure and degrade the electrochemical properties of the positive electrode active material.

[0007] Therefore, there is a current need in the art for a technology that can effectively remove only the residual lithium present on the surface of a positive electrode active material without removing the internal lithium, while at the same time improving the stability of the particle surface. Summary of the Invention

[0008] An object of the present invention is to solve the above-mentioned problems of the prior art and the technical problems that have been conventionally desired.

[0009] Specifically, as a result of thorough research and repeated various experiments, the present inventors have confirmed that when the residual lithium and BET satisfy specific size ranges as described below, gelation and gas generation can be suppressed and a secondary battery with excellent efficiency and life characteristics can be manufactured, and have completed the present invention based on this. [Means for solving the problem]

[0010] Therefore, the present invention provides a positive electrode active material for a secondary battery, which contains a transition metal, has a residual lithium amount on the particle surface of 1 wt% or less, and has a BET of 0.4m 2 / g or more.

[0011] As mentioned above, it is desirable to minimize the amount of residual lithium that causes gelation and gas generation. However, in the process of removing the residual lithium, some of the lithium ions in the crystal structure, i.e., the internal lithium of the active material, may also be removed, which may result in a deterioration of the electrochemical properties.

[0012] In light of this, the present invention proposes upper and lower limits for the organic correlation between the amount of residual lithium and BET (Brunauer, Emmett, Teller) that allows a secondary battery positive electrode active material to exhibit optimal electrochemical characteristics, and the distinctiveness of these setting conditions can be confirmed from the experiments described below. For example, when the amount of residual lithium on the particle surface is reduced by a water washing process, as the residual lithium is removed, the uneven surface of the particle is exposed, and the BET increases. When this residual lithium amount and BET satisfy the ranges defined above, gelation and gas generation can be suppressed, and efficiency and life characteristics can be improved.

[0013] This residual lithium is typically Li2CO3, LiOH, etc., and the content of Li2CO3 is preferably 0.6 wt% or less, and the content of LiOH is preferably 0.42 wt% or less.

[0014] The residual lithium, Li2CO3 and LiOH, suppress the gelling phenomenon and gas generation as their content decreases, so it is desirable that the content does not exceed the above range. However, even if these conditions are met, the BET may be different from the above definition and may be 0.4m 2 It goes without saying that if the BET is less than 0.4m / g, the intended effect of the present invention cannot be achieved. 2 / g or more, and the contents of Li2CO3 and LiOH must satisfy the above conditions. In a more desirable example, the content of Li2CO3 is in the range of 0.22 to 0.60 wt%, and the content of LiOH is in the range of 0.37 to 0.40 wt%.

[0015] In the present invention, the amount of residual lithium on the particle surface is A (wt%), and BET is B (m 2 / g) and A / B is defined as C, An organic correlation between the amount of residual lithium and BET can be established to satisfy the condition TIFF2025538792000001.tif7170.

[0016] If C (i.e., A / B), which represents the amount of residual lithium / BET, exceeds 2.4, the residual lithium has not been sufficiently removed, and the amount of residual lithium is large and the BET is small. In this case, problems such as gelation and gas generation occur, which is undesirable.

[0017] As mentioned above, residual lithium can be removed by a water washing process. The longer the washing time, the lower the amount of residual lithium and the higher the BET, thereby satisfying the above-mentioned condition. However, as confirmed by the experiments described below, if the washing time exceeds a certain range, the rate of reduction of the amount of residual lithium decreases and the amount of residual lithium becomes almost constant when C is less than 1.1. In fact, some of the internal lithium of the active material may leak out, causing changes in the surface structure and resulting in degradation of the electrochemical properties. Therefore, in one preferred example, C is in the range of 1.3 to 1.8.

[0018] The amount of residual lithium and the magnitude of BET can be affected by the amount of lithium used in the manufacturing process of the active material. As a specific example, when the Li / Me ratio in the active material is defined as L, they can be set to satisfy the condition (L / C)>0.41.

[0019] If excess lithium is used in the manufacturing process of the active material, the value of L will be large, and therefore it will be necessary to sufficiently remove the residual lithium in order to satisfy the above conditions. The L / C ratio is preferably in the range of 0.41 to 1.1.

[0020] As mentioned above, the main components of residual lithium are Li2CO3 and LiOH, so the range conditions for BET, which has an organic correlation with residual lithium, can be set based on the relationship between the Li2CO3 content and the LiOH content.

[0021] In one specific example, the content of Li2CO3 is defined as Alwt%, and BET is defined as Bm 2 / g, it can be set to satisfy the condition (A1 / B)<1.46, and / or the LiOH content can be defined as A2wt% and BET can be set to Bm 2 / g, it can be set to satisfy the condition (A2 / B)<1.0.

[0022] If (A1 / B) is 1.46 or more, or if (A2 / B) is 1.0 or more, the gelling phenomenon and gas generation problems cannot be suppressed, and the efficiency and life characteristics of the battery may be reduced, so it may be necessary to set the ranges as described above.

[0023] On the other hand, with regard to the lower limit range of the above condition, if (A1 / B) is 0.20 or less, or (A2 / B) is 0.63 or less, some of the internal lithium of the active material will leak out, causing changes in the surface structure and degrading the electrochemical properties. Therefore, the above (A1 / B) is preferably in the range of more than 0.20 and less than 1.46, more preferably in the range of 0.50 to 1.15. The above (A2 / B) is preferably in the range of more than 0.63 and less than 1.00, more preferably in the range of 0.65 to 0.80.

[0024] As described above, the removal of residual lithium tends to remove some of the internal lithium of the active material and cause changes in the crystal structure depending on the degree of the process for removing the residual lithium or the additional post-treatment.

[0025] In one specific example, when the a-axis lattice constant in X-ray diffraction (XRD) analysis is defined as XÅ and the Li / Me ratio of the core is defined as L, the condition (L×0.015+X)>2.8864 can be satisfied. In another specific example, when the cation mixing of the core is defined as C (wt%) and the Li / Me ratio is defined as L, the condition (L×6+C)<7.68 can be satisfied.

[0026] The above conditional expressions are specifically as follows:

[0027] If a change in the crystal structure occurs during the process of removing residual lithium, it can be expressed by the a-axis value and cation mixing value in XRD measurement.

[0028] For example, it can be said that the change in the a-axis value under the same Li / Me conditions relative to the specified residual lithium removal conditions is 0.0003 Å or less. As the Li / Me ratio increases, the optimal a-axis value tends to decrease. However, when calculated as "(Li / Me) × 0.015 + a-axis", this is a condition exceeding 2.8864 as described above, and can be expressed as satisfying the range of preferably 2.8865 to 2.8866.

[0029] As another example, a battery can be said to have excellent characteristics when the change in cation mixture under the same Li / Me ratio relative to the specified residual lithium removal conditions is less than 0.1%. The optimal cation mixture tends to decrease as the Li / Me ratio increases. This means that, when calculated as "(Li / Me) × 6 + cation mixture," the cation mixture is less than 7.68, as described above. Preferably, the cation mixture is greater than 7.61 and less than 7.68.

[0030] Residual lithium can also be expressed as total lithium (TTL). In one specific example, the total amount of residual lithium is defined as T (wt%) and the Li / Me ratio is defined as L. It can be set to meet the condition TIFF2025538792000002.tif8170.

[0031] For example, it can be said that excellent battery characteristics are exhibited when a TTL of 0.16 to 0.22% is satisfied under the same Li / Me conditions for predetermined residual lithium removal conditions. As the Li / Me ratio increases, the optimum TTL also tends to increase, and this can be expressed as a condition where, when calculated as "(Li / Me)÷TTL", it is 4.6 or more as described above, and preferably satisfies the range of 4.6 to 7.3.

[0032] The removal of residual lithium can be achieved by various methods, typically by water washing, as shown in the experimental results described below, or by using a coating agent highly reactive with residual lithium without water washing. For example, when water washing is used, the degree of removal of residual lithium can be controlled by various process factors, such as the washing time, the stirring speed during washing, and the amount of washing solution. However, it can be understood from the above that in order to obtain an active material with excellent electrochemical properties, it is desirable to effectively remove residual lithium from the particle surface while minimizing the loss of internal lithium.

[0033] In one specific example, the positive electrode active material according to the present invention may include a composition represented by the following Chemical Formula 1. TIFF2025538792000003.tif7170

[0034] In the above formula, M is one or more transition metal elements that are stable in a tetracoordinated or hexacoordinated state; D is one or more elements selected from alkaline earth metals, transition metals, and nonmetals as a dopant; Q is an anion containing one or more elements selected from F, S, and P; The file is TIFF2025538792000004.tif7170.

[0035] Representative examples of the transition metal (M) include one or more of Ni, Co, Mn, etc., and preferably, Ni is contained in an amount of at least 60 mol % or more, and more preferably 70 mol % or more, based on the total content of the transition metals.

[0036] In relation to the elemental composition, in the examples and comparative examples described below, for example, when preparing a cathode active material, 0.002 mol of Zr and 0.021 mol of Al were used as doping materials capable of stabilizing the structure, and the Li / Me ratio was adjusted and primary firing was performed at 740°C. The fired cathode active material was then washed to remove residual lithium impurities, and secondary firing was performed at 305°C using, for example, H3BO3 as a coating material capable of surface stabilization, to prepare a final cathode active material.

[0037] In the above manufacturing process, ZrO2 and Al(OH)3 are used as doping materials, and H3BO3 is used as coating material, but these materials are not limited to these, and one or more of the following elements can be used: W, Ti, B, Zr, Mo, Cr, Co, Al, Mg, Ta, Nb, F, Na, and S. The firing temperature is also not limited to these temperatures. The range can be TIFF2025538792000005.tif8170.

[0038] The present invention also provides a lithium secondary battery comprising the above-described positive electrode active material. Other configurations and manufacturing methods of lithium secondary batteries are known in the art, and therefore, detailed descriptions thereof will be omitted herein. [Effects of the Invention]

[0039] As described above, the positive electrode active material for a secondary battery according to the present invention provides a technology for improving battery performance by appropriately controlling the BET and the amount of residual lithium, and can provide a secondary battery that is excellent in efficiency and life characteristics by suppressing problems such as gelation and gas generation. DETAILED DESCRIPTION OF THE INVENTION

[0040] The present invention will be described in more detail below with reference to examples of the present invention, but the scope of the present invention is not limited thereto.

[0041] Example 1 (Production of positive electrode active material) Ni0.5% Ni:Co:Mn content ratio is 90:6:4 mol%, and D50 is approximately 15 μm. 90 Co0. 06 Mn0. 04 The (OH)2 precursor particles were dry-mixed with 0.002 mol of ZrO2 (Zr source), 0.021 mol of Al(OH)3 (Al source), and LiOH (Li source) so that the molar ratio of Li / Me was 1.00. The dry mixture was filled into a mullite fireproof container (sagger) and heat-treated for 30 hours at 740°C in an O2 atmosphere. The resulting fired material was crushed and classified to produce a positive electrode active material with a particle size of approximately 14-15 μm.

[0042] The resulting cathode active material was placed in distilled water and washed by stirring at 300 rpm for 30 seconds to remove lithium impurities. The resulting active material was then filtered using a filter press. The washed cathode active material was then dried in a vacuum oven at 150°C. 100 parts by weight of the cathode active material were then dry-mixed with 0.57 parts by weight of boric acid (H3BO3) and heat-treated at 305°C for 12 hours in an O2 atmosphere. Finally, a cathode active material was produced with Zr and Al doped into the core and boron coated on the surface. The resulting lithium metal oxide was a secondary particle formed by the aggregation of primary particles, with a D50 of approximately 15μm.

[0043] (Cathode manufacturing) The cathode active material prepared above, the conductive agent Super-P, and the binder PVdF were mixed in a weight ratio of 96.5:1.5:2.0 in N-methylpyrrolidone (NMP) as a solvent to prepare a cathode active material paste. The cathode active material paste prepared in this manner was applied to an aluminum current collector, dried in an oven at 120°C, and then rolled to produce a cathode.

[0044] (Lithium secondary battery manufacturing) An electrode assembly was fabricated using the positive electrode fabricated above and Li metal as the counter electrode, a negative electrode, with a porous polyethylene film interposed between them as a separator. This electrode assembly was then placed inside a battery case, and an electrolyte solution was then poured into the battery case to fabricate a lithium secondary battery. The electrolyte solution used was 1.0 M lithium hexafluorophosphate (LiPF6) dissolved in an organic solvent consisting of ethylene carbonate / dimethyl carbonate / diethyl carbonate (EC / DMC / DEC = 1 / 2 / 1 volume ratio) with vinylene carbonate (VC, 2 wt%) added.

[0045] Example 2 A positive electrode active material, a positive electrode, and a lithium secondary battery including the same were produced under the same conditions as in Example 1, except that the water washing time was changed to 60 seconds.

[0046] Example 3 A positive electrode active material, a positive electrode, and a lithium secondary battery including the same were produced under the same conditions as in Example 1, except that the Li / Me ratio was set to 1.02 mol.

[0047] Example 4 A positive electrode active material, a positive electrode, and a lithium secondary battery including the same were produced under the same conditions as in Example 3, except that the water washing time was changed to 60 seconds.

[0048] Example 5 A positive electrode active material, a positive electrode, and a lithium secondary battery including the same were produced under the same conditions as in Example 1, except that the Li / Me ratio was 1.04 mol.

[0049] Example 6 A positive electrode active material, a positive electrode, and a lithium secondary battery including the same were produced under the same conditions as in Example 5, except that the water washing time was changed to 60 seconds.

[0050] Example 7 A positive electrode active material, a positive electrode, and a lithium secondary battery including the same were produced under the same conditions as in Example 1, except that the Li / Me ratio was set to 1.06 mol.

[0051] Example 8 A positive electrode active material, a positive electrode, and a lithium secondary battery including the same were produced under the same conditions as in Example 7, except that the water washing time was changed to 60 seconds.

[0052] Example 9 A positive electrode active material, a positive electrode, and a lithium secondary battery including the same were produced under the same conditions as in Example 1, except that the Li / Me ratio was set to 1.08 mol.

[0053] Example 10 A positive electrode active material, a positive electrode, and a lithium secondary battery including the same were produced under the same conditions as in Example 9, except that the water washing time was changed to 60 seconds.

[0054] Comparative Example 1 A positive electrode active material, a positive electrode, and a lithium secondary battery including the same were produced under the same conditions as in Example 1, except that the water washing time was set to 10 seconds.

[0055] Comparative Example 2 A positive electrode active material, a positive electrode, and a lithium secondary battery including the same were produced under the same conditions as in Example 1, except that the water washing time was set to 90 seconds.

[0056] Comparative Example 3 A positive electrode active material, a positive electrode, and a lithium secondary battery including the same were produced under the same conditions as in Example 1, except that the water washing time was 120 seconds.

[0057] Comparative Example 4 A positive electrode active material, a positive electrode, and a lithium secondary battery including the same were produced under the same conditions as in Example 3, except that the water washing time was set to 10 seconds.

[0058] Comparative Example 5 A positive electrode active material, a positive electrode, and a lithium secondary battery including the same were produced under the same conditions as in Example 3, except that the water washing time was set to 90 seconds.

[0059] Comparative Example 6 A positive electrode active material, a positive electrode, and a lithium secondary battery including the same were produced under the same conditions as in Example 3, except that the water washing time was 120 seconds.

[0060] Comparative Example 7 A positive electrode active material, a positive electrode, and a lithium secondary battery including the same were produced under the same conditions as in Example 5, except that the water washing time was set to 10 seconds.

[0061] Comparative Example 8 A positive electrode active material, a positive electrode, and a lithium secondary battery including the same were produced under the same conditions as in Example 5, except that the water washing time was set to 90 seconds.

[0062] Comparative Example 9 A positive electrode active material, a positive electrode, and a lithium secondary battery including the same were produced under the same conditions as in Example 5, except that the water washing time was 120 seconds.

[0063] Comparative Example 10 A positive electrode active material, a positive electrode, and a lithium secondary battery including the same were produced under the same conditions as in Example 7, except that the water washing time was set to 10 seconds.

[0064] Comparative Example 11 A positive electrode active material, a positive electrode, and a lithium secondary battery including the same were produced under the same conditions as in Example 7, except that the water washing time was set to 90 seconds.

[0065] Comparative Example 12 A positive electrode active material, a positive electrode, and a lithium secondary battery including the same were produced under the same conditions as in Example 7, except that the water washing time was 120 seconds.

[0066] Comparative Example 13 A positive electrode active material, a positive electrode, and a lithium secondary battery including the same were produced under the same conditions as in Example 9, except that the water washing time was set to 10 seconds.

[0067] Comparative Example 14 A positive electrode active material, a positive electrode, and a lithium secondary battery including the same were produced under the same conditions as in Example 9, except that the water washing time was set to 90 seconds.

[0068] Comparative Example 15 A positive electrode active material, a positive electrode, and a lithium secondary battery including the same were produced under the same conditions as in Example 9, except that the water washing time was 120 seconds.

[0069] [Experimental Example 1] The positive electrode active materials prepared in Examples 1 to 10 and Comparative Examples 1 to 15 were measured for residual lithium (Li2CO3, LiOH), BET, a-axis length in the crystal structure, cation mixing, etc., and the results are shown in Tables 1 and 2 below.

[0070] The amount of residual lithium was measured under the following conditions: 5 g of sample (error range ±0.02 g) and 100 g of distilled water were placed in a beaker with a magnetic stirrer and stirred for 10 minutes. The stirred sample was then naturally filtered through filter paper, and the filtrate was placed in the beaker and titrated. 0.1 N HCl was used as the titrant, and after removing air bubbles from the burette (cylinder), the DET (Dynamic Equivalence Point Titration) method was used as the titration dispensing method. The automatic titration termination conditions were set to pH 2.5, the calculation method was FP(1) = 4.5, EP(1), and the titration speed was set to maximum, and the measurement of residual lithium was completed.

[0071] BET was measured under the following conditions. A Micromeritics TriStar II 3020 device was used, and samples were pretreated using a VacPrep061 device. The pretreatment was performed at 100°C for 80 minutes and then at 300°C for 150 minutes. The amount of adsorption was then measured using a BET measurement device at a temperature of -77 K and a relative pressure (P / P) range of 0.05 to 0.3, and the BET was calculated.

[0072] The a-axis length and the amount of mixed cations were confirmed from the results obtained by XRD analysis.

[0073] Furthermore, the initial capacity and life characteristics of the lithium secondary batteries produced in Examples 1 to 10 and Comparative Examples 1 to 15 were measured, and the results are shown in Table 3 below.

[0074] TIFF2025538792000006.tif163170

[0075] TIFF2025538792000007.tif210170

[0076] TIFF2025538792000008.tif162170

[0077] First, referring to the results in Table 1, it can be seen that for cathode active materials obtained under various Li / Me conditions (1.00, 1.02, 1.04, 1.06, 1.08), varying the rinsing time resulted in a decrease in residual lithium and an increase in BET. This is because the longer the rinsing time, the easier it becomes to remove residual lithium from the surface, and as more of the residual lithium is removed, the surface becomes more exposed.

[0078] On the other hand, at 90 seconds and above, the increase in rinsing time did not significantly affect the residual lithium, but only increased BET. Therefore, it can be predicted that rinsing times exceeding 60 seconds would wash away the lithium ions within the structure along with the residual lithium already present on the surface of the positive electrode active material, potentially resulting in a deterioration in electrochemical performance. This can be confirmed by changes in the a-axis length of the crystalline structure and the amount of mixed cations. In relation to this, referring to Table 2, when comparing the initial capacity and capacity retention of the positive electrode active material, it can be seen that as the rinsing time increases beyond 60 seconds, the capacity remains at a similar or lower level, but the capacity retention performance deteriorates.

[0079] Referring to Table 2, the positive electrode active materials of the examples according to the present invention are roughly It can be seen that the condition TIFF2025538792000009.tif23170 is met.

[0080] A detailed examination of Tables 1 to 3 shows that, as the rinsing time increased, the amount of LiOH in the residual lithium did not change significantly, the amount of Li2CO3 decreased, and the BET increased in Example 2 and Comparative Examples 2 and 3. It was found that when the residual lithium (Li2CO3 + LiOH) / BET value was in the range of 1.3 to 1.8, the capacity and cycle characteristics were excellent.

[0081] In Comparative Example 1, the water washing time was insufficient, and residual lithium, which is a resistance component on the surface of the positive electrode active material, could not be sufficiently removed, resulting in lower BET, capacity, and cycle characteristics than in the Examples. Comparative Examples 4, 7, 10, and 13 also had reduced battery characteristics for the same reason. In Comparative Examples 2 and 3, the water washing time was too long, and even lithium ions within the structure of the positive electrode active material were washed away, resulting in reduced battery characteristics. In Comparative Examples 5 to 6, 8 to 9, 11 to 12, and 14 to 15, battery characteristics also deteriorated for the same reason.

[0082] The present invention is not limited to the above-described embodiments, and can be embodied in various different forms, and those skilled in the art will understand that the present invention can be embodied in other specific forms without changing the technical idea or essential characteristics of the present invention. Therefore, the above-described embodiments are illustrative in all respects and should not be interpreted as limiting.

Claims

1. It contains a transition metal, the amount of residual lithium on the particle surface is 1 wt% or less, and the BET is 0.4 m ２ / g or more.

2. 2. The positive electrode active material for a secondary battery according to claim 1, wherein Li in the residual lithium ２ CO ３ % or less of the above.

3. 2. The positive electrode active material for a secondary battery according to claim 1, wherein the content of LiOH in the residual lithium is 0.42 wt % or less.

4. 4. The positive electrode active material for a secondary battery according to claim 1, wherein the amount of residual lithium on the particle surface is A (wt%), BET is B (m ２ / g) and A / B is defined as C, The positive electrode active material for a secondary battery is characterized by satisfying the following conditions.

5. 5. The positive electrode active material for a secondary battery according to claim 4, wherein, when the Li / Me ratio is defined as L, the positive electrode active material for a secondary battery satisfies the condition (L / C)>0.

41.

6. 3. The positive electrode active material for a secondary battery according to claim 1, wherein Li in the residual lithium ２ CO ３ The content of A １ (wt%), and BET is defined as B(m ２ / g), (A １ / B)<1.

46.

7. 4. The positive electrode active material for a secondary battery according to claim 1, wherein the content of LiOH in the residual lithium is A ２ (wt%), and BET is defined as B(m ２ / g), (A ２ / B)<1.

0.

8. 2. The positive electrode active material for a secondary battery according to claim 1, wherein, when an a-axis lattice constant is defined as XÅ and a Li / Me ratio of the core is defined as L in an X-ray diffraction (XRD) analysis, the positive electrode active material for a secondary battery satisfies the condition (L × 0.015 + X) > 2.8864.

9. 2. The positive electrode active material for a secondary battery according to claim 1, wherein the positive electrode active material for a secondary battery satisfies the condition (L×6+C)<7.68, where C (wt%) is the amount of cation mixing in the core and L is the Li / Me ratio.

10. 2. The positive electrode active material for a secondary battery according to claim 1, wherein when the total amount of residual lithium (TTL) on the particle surface is defined as T (wt%) and the Li / Me ratio is defined as L, The positive electrode active material for a secondary battery is characterized by satisfying the following conditions.

11. 2. The positive electrode active material for a secondary battery according to claim 1, comprising a composition represented by the following chemical formula 1: In the above formula, M is one or more transition metal elements that are stable in a tetracoordinate or hexacoordinate arrangement; D is one or more elements selected from alkaline earth metals, transition metals, and nonmetals as a dopant; Q is an anion containing one or more elements selected from F, S, and P; A positive electrode active material for a secondary battery, characterized in that:

12. 12. The positive electrode active material for a secondary battery according to claim 11, wherein M contains 60 mol % or more of Ni based on the total content of the transition metals.

13. A secondary battery comprising the positive electrode active material for secondary batteries according to claim 1.

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