KR20160038984A - Heat treatment method for reducing remaining lithium cathode active materials and lithiumsecondary battery using the same, and preparation method thereof - Google Patents

Abstract

The present invention relates to a heat treatment method for removing a remaining lithium ion, a manufacturing method of a positive electrode active material using the heat treatment method, and a positive electrode active material and a lithium secondary battery manufactured by the manufacturing method. More specifically, in a heat treatment method for manufacturing a positive electrode active material, the heat treatment method includes the following steps: manufacturing a precursor; manufacturing a mixed powder by mixing potassium ion salts and lithium hydroxide with the precursor; heating the mixed powder; and cooling the mixed powder.

Description

TECHNICAL FIELD The present invention relates to a heat treatment method for removing residual lithium ions, a method for producing a cathode active material using the heat treatment method, a cathode active material produced by the method, and a lithium secondary battery using the lithium secondary battery , and preparation method thereof}

The present invention relates to a heat treatment method for removing residual lithium ions, a method for producing an anti-cathode active material using the heat treatment method, a cathode active material produced by the method, and a lithium secondary battery.

Recently, miniaturization of electronic devices has been diversified into mobile phones, notebook computers (PCs), and portable personal digital assistants (PDAs), and the interest in energy storage technology has been increasing.

In addition, in the case of batteries used in hybrid vehicles (HEV) and electric vehicles (EV), not only high capacity and high output, but also stability are a big problem. As the application field is expanded, research and development on storage technologies are being actively carried out. In this respect, there is a growing interest in the development of secondary batteries capable of charging and discharging.

The secondary battery is composed of a positive electrode, a negative electrode, and an electrolyte, and the ratio of the positive electrode is the most important. The cathode material is a cathode active material and generally has a high energy density during charging and discharging, and the structure should not be destroyed by intercalation or desorption of reversible lithium ions. In addition, the electrical conductivity should be high, and the chemical stability of the organic solvent used as the electrolyte should be high. It should be a material that has low manufacturing cost and minimizes environmental pollution problems.

Examples of the positive electrode active material of such a lithium ion secondary battery include lithium nickel oxide (LiNiO ₂ ), lithium cobalt oxide (LiCoO ₂ ), lithium manganese oxide (LiMnO ₂ ), and the like, which are layered compounds capable of intercalating and deintercalating lithium ions. Lithium nickel oxide (LiNiO ₂ ) has a high electric capacity, but it has not been put to practical use due to problems such as cycle characteristics and stability during charging and discharging. In addition, lithium cobalt oxide (LiCoO ₂ ) is advantageous in terms of cycle life and rate capability as well as capacity, and is easy to synthesize. However, since cobalt is expensive and harmful to human body, thermal instability And the like.

In addition, the cathode active material is prepared by mixing lithium hydroxide and a precursor with heat treatment. After the heat treatment, residual LiOH and Li ₂ CO ₃ that are not involved in the cathode active material reaction exist.

Such residual LiOH increases the pH of the slurry in the process of producing the slurry, causing the solidification of the slurry to cause problems in the production of the electrode plate. In addition, residual Li ₂ CO ₃ increases cell swelling and not only reduces the cycle, but also causes the battery to swell.

Therefore, there is a demand for a heat treatment method for reducing the concentration of such residual lithium ions.

Korea Patent Publication No. 2014-0001720 Korean Patent Publication No. 2013-0030479

SUMMARY OF THE INVENTION Accordingly, the present invention has been made to solve the above-mentioned problems occurring in the prior art, and it is an object of the present invention to provide a lithium secondary battery which can reduce the concentration of residual lithium ions in a cathode active material, The surface agglomeration phenomenon is controlled and the surface roughness is also decreased to increase the surface area, to develop the layered structure, to decrease the charge transfer resistance and to increase the lithium diffusion, A method of manufacturing a cathode active material to which the heat treatment method is applied, a cathode active material manufactured by the method, and a lithium secondary battery.

It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are not intended to limit the invention to the precise form disclosed. It can be understood.

A first object of the present invention is to provide a method of heat treatment comprising the steps of: preparing a precursor; Mixing lithium hydroxide with the precursor to produce a cathode active material; Mixing the potassium ion salt with the cathode active material; Heating the cathode active material mixed with the potassium ion salt; And a cooling step for removing residual lithium ions.

A second object of the present invention is to provide a heat treatment method for producing a cathode active material, comprising the steps of: preparing a precursor; Mixing the potassium ion salt and lithium hydroxide in the precursor to prepare a mixed powder; Heating the mixed powder; And a cooling step for removing residual lithium ions.

The lithium ion salt may be at least one selected from the group consisting of KCl, KOH, KOH.H ₂ O, KI, KIO ₃ , KF, K ₂ CO ₃ , KNO ₃ , K ₂ S, K ₂ SO ₄ , K ₂ CrO ₇ , KMnO ₄ , KBr, KCN, KH ₂ PO ₄ , K ₂ CrO ₄ , CH ₃ COOK and C ₆ H ₇ KO ₂ .

Further, in the second object, the molar ratio of the precursor to the potassium ion salt and lithium hydroxide may be 1: 0.9 to 1.4.

The potassium ion salt may be 0.1 to 10 wt% of KCl.

A third object of the present invention is to provide a method of heat treatment comprising the steps of: preparing a precursor; Mixing lithium hydroxide with the precursor to produce a cathode active material; Mixing the potassium ion salt with the cathode active material; Heating the cathode active material mixed with the potassium ion salt to 400 to 1000 ° C at a heating rate of 5 ° C / minute to 20 ° C / minute; Maintaining the heating at the elevated temperature; And a cooling step for removing residual lithium ions.

A fourth object of the present invention is to provide a heat treatment method for producing a cathode active material, comprising: preparing a precursor; Mixing the potassium ion salt and lithium hydroxide in the precursor to prepare a mixed powder; Heating the mixed powder to 400 to 1000 ° C at a heating rate of 5 ° C / min to 20 ° C / min; Maintaining the heating at the elevated temperature; And a cooling step for removing residual lithium ions.

The maintaining step may be 9 to 11 hours.

Also, the heat treatment process may be performed for 22 to 26 hours under an atmosphere of air, oxygen, nitrogen, and argon.

Also, the precursor may be prepared by preparing an aqueous metal solution from nickel, cobalt or manganese; Mixing the metal aqueous solution with sodium carbonate as a precipitant and ammonia water as a co-precipitator, adding the mixture to a continuous reactor and stirring to obtain a precipitate; And filtering and washing the precipitate and drying the precipitate to prepare a precursor.

And, the precursor is composed of Ni _x Co _y Mn _z (OH) ₂ , x is 0.5 or more, y is 0.2 to 0.4, and z is 0.05 to 0.15.

In addition, the precursor may be a core-shell structure or a single structure.

A fifth object of the present invention can be attained by a method for producing a cathode active material, wherein the method of heat treatment according to the second or seventh aspect is applied to the method for producing a cathode active material.

A sixth object of the present invention can be achieved as a cathode active material for a lithium secondary battery, which is produced by the production method according to the fifth object in the cathode active material.

A seventh object of the present invention can be attained by a secondary battery comprising the cathode active material for a lithium secondary battery manufactured by the manufacturing method of claim 14, a cathode, and an electrolyte solution.

According to one embodiment of the present invention, KCl added as a dopant material decreases the concentration of residual lithium ions in the cathode active material, and also increases the surface area by controlling the surface agglomeration phenomenon from the addition of KCl and also reducing the surface roughness And the layered structure is developed. The charge transfer resistance is decreased and the lithium diffusion is increased, so that it easily acts on the insertion / removal of lithium, thereby increasing the discharge capacity.

It should be understood, however, that the effects obtained by the present invention are not limited to the above-mentioned effects, and other effects not mentioned may be clearly understood by those skilled in the art to which the present invention belongs It will be possible.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate preferred embodiments of the invention and, together with the description, serve to further the understanding of the technical idea of the invention, It should not be construed as limited.
1 is a flow chart of a method of manufacturing a cathode active material to which a heat treatment method for removing residual lithium ions according to an embodiment of the present invention is applied,
FIG. 2 is a graph showing the relationship between residual cathode active material prepared according to the first embodiment of the present invention and residual LiOH, Li ₂ CO ₃ Contrast table,
FIG. 3 is a graph showing a temperature-rising temperature velocity graph according to a second embodiment of the present invention,
4 is a graph showing the relationship between the temperature rise rate according to the second embodiment of the present invention at 5 ° C or higher per minute and the residual LiOH, Li ₂ CO ₃ data,
FIG. 5 is a graph showing the results of the heat treatment of KCI mixed with the cathode active material according to the third embodiment of the present invention and the residual LiOH, Li ₂ CO ₃ data,
6 is a SEM surface analysis image of Examples and Comparative Examples of the present invention,
FIG. 7 shows AFM surface analysis images of Examples and Comparative Examples of the present invention,
8 is a graph showing an XRD pattern of an embodiment of the present invention and a comparative example,
Fig. 9 is a graph showing the lattice constant data of the embodiment and the comparative example calculated from the XRD data of Fig. 8,
FIG. 10 is a graph showing the relationship between the initial charge and discharge graphs of the present invention and the comparative example when the current density is 17 mA / g (0.1 C) at a voltage range of 3.0 to 4.3 V,
FIG. 11 is a graph showing discharge capacity data of the embodiment and the comparative example according to the result of FIG. 10,
FIG. 12 is a graph showing an impedance analysis result for observing electrode resistance characteristics according to an embodiment of the present invention and a comparative example,
13 is a graph showing the lithium ion diffusion coefficient measured according to Examples and Comparative Examples of the present invention,
FIG. 14 shows data of impedance and lithium diffusion coefficient analysis results of the examples and comparative examples according to the results of FIGS. 12 and 13.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the detailed description of known functions and configurations incorporated herein will be omitted when it may unnecessarily obscure the subject matter of the present invention.

The same reference numerals are used for portions having similar functions and functions throughout the drawings. Throughout the specification, when a part is connected to another part, it includes not only a case where it is directly connected but also a case where the other part is indirectly connected with another part in between. In addition, the inclusion of an element does not exclude other elements, but may include other elements, unless specifically stated otherwise.

≪ Process for producing a cathode active material to which a heat treatment method for removing residual lithium ions is applied &

Hereinafter, a heat treatment method for removing residual lithium ions according to an embodiment of the present invention and a method for manufacturing a cathode active material applying the heat treatment method will be described. FIG. 1 is a flowchart illustrating a method of manufacturing a cathode active material to which a heat treatment method for removing residual lithium ions according to an embodiment of the present invention is applied.

First, a precursor for the production of a cathode active material by heat treatment is prepared (S1). The precursors according to one embodiment of the present invention are not limited to specific compositions, compositions, and production methods, but are preferably made of nickel-rich materials.

Also, the structure of such a precursor may have a core shell structure or a single structure. The preparation of the precursor is generally such that a metal aqueous solution is prepared from nickel, cobalt and manganese, and sodium carbonate as a precipitating agent and ammonia water as a co-precipitating agent are mixed in a metal aqueous solution and the mixture is stirred in a continuous reactor to obtain a precipitate. And washing and drying to produce a precursor.

The precursor produced by this method has a composition formula of Ni _x Co _y Mn _z (OH) ₂ . These precursors correspond to precursors of the high nickel type with x> 0.5, and y ranges from about 0.2 to 0.4. z corresponds to about 0.05 to 0.15.

Next, in the first embodiment of the present invention, a potassium ion salt is added to the prepared precursor to reduce lithium hydroxide (LiOH.H ₂ O) and residual lithium ion (S2). The potassium ion salt according to the first embodiment of the present invention may be any salt including potassium ion (K ⁺ ), and specifically, KCl, KOH, KOH.H ₂ O, KI, KIO ₃ , KF, K ₂ CO ₃ , KNO ₃ , K ₂ S, K ₂ SO ₄ , K ₂ CrO ₇ , KMnO ₄ , KBr, KCN, KH ₂ PO ₄ , K ₂ CrO ₄ , CH ₃ COOK and C ₆ H ₇ KO ₂ Do.

The lithium hydroxide (LiOH.H ₂ O) and the potassium ion salt according to the first embodiment of the present invention are added in an amount of about 0.9 to 1.4 mol per 1 mol of the precursor.

Lithium hydroxide (LiOH.H ₂ O) and potassium ion salt are mixed in the precursor and mixed by a dry method (S3), and the mixture is heated and cooled.

In the second embodiment of the present invention, a precursor is prepared in the same manner as in the first embodiment, and lithium hydroxide (LiOH.H ₂ O) and potassium ion salt are added to the prepared precursor in order to reduce residual lithium ion (S2). The potassium ion salt according to the second embodiment of the present invention is capable of all salts including potassium ion (K ⁺ ) as in the first embodiment, specifically, KCl, KOH, KOH.H ₂ O, KI _{, KIO 3, KF, K 2} CO 3, KNO 3, K 2 S, K 2 SO 4, K 2 CrO 7, KMnO 4, KBr, KCN, KH 2 PO 4, K 2 CrO 4, CH 3 COOK, C ₆ H ₇ KO ₂ is possible.

Lithium hydroxide (LiOH.H ₂ O) and potassium ion salt are mixed in the precursor and mixed by a dry method (S3), and the mixed powder is heated at an elevated temperature (S4). The step of heating by heating is heated to 400 to 1000 ° C at a rate of about 5 ° C to 20 ° C per minute, and after the heating of the temperature, the heating is maintained at 400 to 1000 ° C for about 9 to 11 hours (S 5) . Finally, the cathode active material is naturally cooled to produce a cathode active material (S6). The heat treatment process is carried out under an oxygen atmosphere for a total of 24 hours.

In addition, according to the third embodiment of the present invention, it is also possible to mix lithium hydroxide with the precursor to produce a cathode active material, followed by mixing the potassium ion salt and heat treatment.

That is, in the third embodiment of the present invention, the cathode precursor is mixed with lithium hydroxide (LiOH.H ₂ O) and heat-treated to produce a cathode active material. Then, potassium ion salt is added to the completed cathode active material.

The potassium ionic salt added to the completed cathode active material according to the third embodiment of the present invention can be any salt including potassium ion (K ⁺ ), specifically, KCl, KOH, KOH.H ₂ O, KI, _{KIO 3, KF, K 2 CO} 3, KNO 3, K 2 S, K 2 SO 4, K 2 CrO 7, KMnO 4, KBr, KCN, KH 2 PO 4, K 2 CrO 4, CH 3 COOK, C 6 H ₇ KO ₂ and so on.

Then, the potassium ion salt is mixed with the completed cathode active material, and the lithium ion is removed by heat treatment. The potassium ion salt is mixed with the thus-prepared cathode active material and then heat-treated. The heating method, which is the same method as the above-described second embodiment, can be applied.

<Experimental Example>

The preparation of the cathode active material according to the first embodiment of the present invention applied to the experimental example of the present invention uses Ni _{0 .631} Co _{0 .258} Mn _{0 .111} (OH) ₂ as a precursor, 1 wt% of potassium chloride (KCl) and lithium hydroxide (LiOH.H ₂ O) were mixed. 1.0 mol of KCl and lithium hydroxide were added to 1 mol of the precursor and mixed by a dry method. Heated and cooled.

In addition, only the potassium chloride (KCl) was not added to the cathode active material according to the comparative example applied to the experimental example under the same conditions as those of the example. That is, in the same manner as in Example, was used as the _{Ni 0 .631 Co 0 .258 Mn 0} .111 (OH) 2 as a precursor, and mixed with lithium hydroxide (LiOH · H ₂ O) in such precursors. To 1 mol of the precursor, 1.05 mol of lithium hydroxide was added and mixed by a dry method. Then, the mixed powder was heated at a rate of 5 ° C / min to raise the temperature to 800 ° C, maintained at 800 ° C for 10 hours, and then cooled naturally to prepare a cathode active material according to a comparative example.

FIG. 2 is a graph showing the relationship between residual cathode active material prepared according to the first embodiment of the present invention and residual LiOH, Li ₂ CO ₃ FIG. The data shown in Figure 3 confirmed the concentration of residual lithium using an automatic regulator. As shown in FIG. 3, residual Li ₂ CO ₃ of the cathode active material according to Experimental Example is slightly increased. However, by confirming that the concentration of residual LiOH is decreased by 1,890 ppm from the addition of KCl, I can confirm that it is effective.

In the second embodiment of the present invention, Ni _{0 .631} Co _{0 .258} Mn _{0 .111} (OH) ₂ was used as a precursor. To this precursor, 1 wt% potassium chloride (KCl) and lithium hydroxide LiOH.H ₂ O) were mixed. 1.0 mol of KCl and 1.05 mol of lithium hydroxide were added to 1 mol of the precursor and mixed by a dry method. The mixed powder was heated at a rate of 5 ° C to 20 ° C per minute to 800 ° C to 1000 ° C, 10 hours, and then cooled naturally to prepare a cathode active material according to the examples.

FIG. 3 is a time-temperature graph illustrating a temperature raising process according to a second embodiment of the present invention. FIG. 4 is a graph showing the relationship between the residual LiOH and Li ₂ CO ₃ of the cathode active material prepared according to the second embodiment of the present invention and the cathode active material prepared according to the comparative example FIG.

The data shown in Figure 4 confirmed the concentration of residual lithium using an automatic regulator. As shown in Figure 4, the concentration of residual Li ₂ CO ₃ and LiOH residue of the positive electrode active material according to the experimental example confirmed that the effective residual Li ₂ CO ₃ and LiOH residual concentration reduced by ensuring that all decreased.

As described above, Ni _{0 .631} Co _{0 .258} Mn _{0 .111} (OH) ₂ was used as a precursor in the production of the cathode active material according to the third embodiment of the present invention. Lithium hydroxide (LiOH.H ₂ O) was mixed with these precursors and heat treated to prepare cathode active material. Then, the completed cathode active material was mixed with potassium chloride (KCl) as a potassium ion salt, followed by heating and cooling.

FIG. 5 is a graph showing the relationship between the material prepared according to the third embodiment of the present invention and the residual LiOH, Li ₂ CO ₃ FIG. The data shown in Figure 5 confirmed the concentration of residual lithium using an automatic regulator. As shown in Figure 5, that the residual Li ₂ CO3 in the positive electrode active material according to the experimental example reduced by 1801ppm, effective on the residual Li ₂ CO ₃ and the residual LiOH concentration is reduced by the concentration of the residual LiOH is confirmed that the degree of reduction 77ppm Can be confirmed.

Fig. 6 shows SEM surface analysis images of Examples and Comparative Examples of the present invention. As shown in Fig. 6, in the case of the comparative example, it is understood that the surfaces are cohered and the degree of roughness of the prismatic primary particles becomes high.

On the other hand, in the case of the embodiment of the present invention, it is confirmed that the surface agglomeration phenomenon is reduced from the addition of KCl, and the shape of the prismatic primary particles becomes clear. In this case, it can be seen that the surface area of the cathode active material according to the embodiment is increased.

From the increase of the surface area, as described later, better electrical characteristics can be expected because lithium insertion / removal is useful in charge and discharge processes. In summary, the addition of KCl can control surface agglomeration and cause surface area increase.

7 shows an AFM surface analysis image of an embodiment of the present invention and a comparative example. When the surface roughness of the comparative example and the comparative example are compared and analyzed, it can be seen that the surface roughness decreases from 82.06 to 73.92 as shown in Fig. These results support the SEM analysis and show that the addition of KCl is effective in controlling the surface agglomeration phenomenon.

8 is a graph showing an XRD pattern of an embodiment of the present invention and a comparative example. 9 shows lattice constant value data of the embodiment and the comparative example calculated from the XRD data of FIG.

As shown in FIGS. 8 and 9, all the samples had a general layered R-3m space group, and no other impurity peak was found from the addition of KCl. (006) / (012) peak and (018) / (110) peaks contributed to the development of the stratified structure. In FIG. 8, the difference in the peak cracks is apparent. That is, when KCl was added, it was confirmed that the peaks were clearly separated when compared with the comparative examples. Thus, it can be said that the characteristic of the layered structure developed through the addition of KCl is shown.

As can be seen from the lattice constant values calculated through the XRD structure analysis result shown in FIG. 9, the ((006) + (012)) / (101) ratio (R-factor) indicates hexagonal crystal structure formation, The lower the value, the more hexagonal crystal structure formation in the structure increases and the crystallinity increases. Thus, the results of the example decreased from 0.4188 to 0.3865, indicating an increase in crystallinity in the structure. From these results, it can be seen that the addition of KCl has a positive effect on the crystallinity increase in the structure.

FIG. 10 is a graph showing an initial charge / discharge graph when an experiment was conducted at a constant current density of 17 mA / g (0.1 C) at a voltage range of 3.0 to 4.3 V according to an embodiment of the present invention and a comparative example. 11 shows the discharge capacity data of the example according to the result of FIG. 10 and the comparative example.

The voltage range was 3.0 to 4.3 V and the current density was measured at 17 mA / g (0.1 C). As shown in Figs. 8 and 9, the comparative example shows an initial discharge capacity of 176.39 mAh / g, On the other hand, in the case of the embodiment, an improved discharge capacity of 182.73 mAh / g appears. The improved discharge capacity can be interpreted as a result of the increase in the crystallinity in the structure from the structural analysis results of the examples, and it can be confirmed that the addition of KCl is also effective in improving the initial discharge capacity.

FIG. 12 is a graph showing impedance analysis results for observing electrode resistance characteristics according to Examples and Comparative Examples of the present invention. FIG. 13 is a graph showing a measured lithium ion diffusion coefficient according to an embodiment of the present invention and a comparative example. 14 shows data of impedance and lithium diffusion coefficient analysis results of the examples and comparative examples according to the results shown in Figs. 12 and 13. Fig.

In the impedance graph shown in Fig. 12, the interface resistance associated with the charge transfer in the first semicircular region and the straight line extending at 45 [deg.] Indicate diffusion of lithium ions. Example The electrode shows an interface resistance associated with a charge transfer of 99 Ω which is 40 Ω lower than the comparative example, which is a result that can support the results of the initial discharge capacity.

Also, the lithium diffusion rate of the measured impedance value is calculated by the following Equations (1) and (2).

As shown in FIG. 14, the electrode of Example shows a high diffusion coefficient of lithium ions, and thus a lithium ion diffusion coefficient of 6.08 X 10 ^-16 cm ² / s. From the results, it can be seen that the electrode of the embodiment is easy to insert and desorb lithium ions.

As a whole, KCl added as a dopant decreases the concentration of residual lithium to be solved first, and also increases the surface area by controlling surface cohesion and decreasing surface roughness from the addition of KCl, , It can be expected that the crystallinity and the development of the layered structure will increase. As a result of the resistance analysis and the analysis of the lithium diffusion coefficient, the charge transfer resistance decreases and the lithium diffusion increases. As a result of the discharge analysis, it was found that the increase of the discharge capacity was obtained, and therefore, it is effective to add KCl to the cathode active material synthesis.

The present invention can also be embodied as computer-readable codes on a computer-readable recording medium. A computer-readable recording medium includes all kinds of recording apparatuses in which data that can be read by a computer system is stored. Examples of the computer-readable recording medium include a ROM, a RAM, a CD-ROM, a magnetic tape, a floppy disk, an optical data storage device, and the like, and may be implemented in the form of a carrier wave (for example, transmission over the Internet) . In addition, the computer-readable recording medium may be distributed over network-connected computer systems so that computer readable codes can be stored and executed in a distributed manner. In addition, functional programs, codes, and code segments for implementing the present invention can be easily inferred by programmers of the technical field to which the present invention belongs.

It should be noted that the above-described apparatus and method are not limited to the configurations and methods of the embodiments described above, but the embodiments may be modified so that all or some of the embodiments are selectively combined .

Claims (14)

In the heat treatment method,
Preparing a precursor;
Mixing lithium hydroxide with the precursor to produce a cathode active material;
Mixing the potassium ion salt with the completed cathode active material;
Heating the cathode active material mixed with the potassium ion salt; And
And a cooling step for removing residual lithium ions.
A heat treatment method for producing a cathode active material,
Preparing a precursor;
Mixing the potassium ion salt and lithium hydroxide in the precursor to prepare a mixed powder;
Heating the mixed powder; And
And a cooling step for removing residual lithium ions.
3. The method according to claim 1 or 2,
The lithium ion salt may be,
KCl, KOH, KOH.H ₂ O, KI, KIO ₃ , KF, K ₂ CO ₃ , KNO ₃ , K ₂ S, K ₂ SO ₄ , K ₂ CrO ₇ , KMnO ₄ , KBr, KCN, KH ₂ PO ₄ , K ₂ CrO ₄ , CH ₃ COOK, and C ₆ H ₇ KO _2, in order to remove residual lithium ions.
3. The method of claim 2,
Wherein the molar ratio of the precursor to the potassium ion salt and lithium hydroxide is 1: 0.9 to 1.4.
3. The method according to claim 1 or 2,
Wherein the potassium ion salt is 0.1-10 wt% KCl.
In the heat treatment method,
Preparing a precursor;
Mixing lithium hydroxide with the precursor to produce a cathode active material;
Mixing the potassium ion salt with the completed cathode active material;
Heating the cathode active material mixed with the potassium ion salt to 400 to 1000 ° C at a heating rate of 5 ° C / minute to 20 ° C / minute; And
Maintaining the heating at the elevated temperature;
And a cooling step for removing residual lithium ions.
A heat treatment method for producing a cathode active material,
Preparing a precursor;
Mixing the potassium ion salt and lithium hydroxide in the precursor to prepare a mixed powder;
Heating the mixed powder to 400 to 1000 ° C at a heating rate of 5 ° C / min to 20 ° C / min; And
Maintaining the heating at the elevated temperature;
And a cooling step for removing residual lithium ions.
3. The method according to claim 1 or 2,
Wherein the heat treatment process is performed for at least one of air, oxygen, nitrogen, and argon for 22 to 26 hours.
3. The method according to claim 1 or 2,
The precursor
Nickel, cobalt or manganese to prepare an aqueous metal solution;
Mixing the metal aqueous solution with sodium carbonate as a precipitant and ammonia water as a co-precipitator, adding the mixture to a continuous reactor and stirring to obtain a precipitate; And
And drying the precipitate by filtration, washing, and drying to produce a precursor.
10. The method of claim 9,
The precursor
Wherein _x is at least 0.5, y is from 0.2 to 0.4, and z is from 0.05 to 0.15. 5. The method of claim 1, wherein the residual lithium ions are selected from the group consisting of Ni _x Co _y Mn _z (OH) ₂ .
11. The method of claim 10,
Wherein the precursor is a core-shell structure or a single structure.
In the method for producing a positive electrode active material,
A method for manufacturing a cathode active material, wherein the heat treatment method according to claim 2 or 7 is applied.
In the cathode active material,
A cathode active material for a lithium secondary battery, which is produced by the manufacturing method of claim 12.
In the secondary battery,
A lithium secondary battery comprising a cathode active material for a lithium secondary battery produced by the method of claim 13, a cathode, and an electrolyte.

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