KR20230122704A - Method for manufacturing a cathode active material in the form of primary particles from lithium composite metal oxide in the form of secondary particles - Google Patents

Abstract

The present invention relates to a method for producing a positive electrode active material in the form of secondary particles from lithium composite metal oxide in the form of secondary particles, wherein a mixture of lithium composite metal oxide in the form of secondary particles, a lithium precursor, and a nickel precursor is heated to a temperature of 950 ° C. or higher. It includes the step of performing a secondary heat treatment, and the step of performing a secondary heat treatment at 800 ° C to 850 ° C, characterized in that lithium composite metal oxide in the form of primary particles is obtained after the secondary heat treatment.

Description

Method for manufacturing a cathode active material in the form of secondary particles from lithium composite metal oxide in the form of secondary particles

The present invention relates to a method for preparing a positive electrode active material in the form of primary particles from lithium composite metal oxide in the form of secondary particles.

The Ni-based material, which is a positive electrode active material of a lithium secondary battery reported so far, is in the form of secondary particles, and due to the shape of the secondary particles, it is difficult to improve the density of the electrode plate as the secondary particles are broken during the pressing process when forming the electrode.

In addition, during the charging and discharging process of the lithium secondary battery, the inside of the secondary particle reacts with the electrolyte to cause a side reaction, which causes a problem in that a high-resistance layer is generated inside the secondary particle.

One object of the present invention is to provide a method for preparing a positive electrode active material in the form of primary particles from lithium composite metal oxide in the form of secondary particles.

In the method for manufacturing a positive active material material in the form of secondary particles from lithium composite metal oxide in the form of secondary particles according to an embodiment of the present invention, a mixture of lithium composite metal oxide in the form of secondary particles, a lithium precursor, and a nickel precursor is heated to a temperature of 950 ° C. or higher. It may include a first heat treatment step, and a second heat treatment step at 800 ° C to 850 ° C. According to the present invention, lithium composite metal oxide in the form of primary particles can be obtained after the secondary heat treatment.

In one embodiment, the lithium composite metal oxide in the form of secondary particles may be obtained from a cathode active material of a waste lithium battery.

In one embodiment, the lithium composite metal oxide in the form of secondary particles may be represented by Formula 1 below.

[Formula 1]

Li _a Ni _1-xy Co _x Mn _y O ₂

(In Formula 1, 1.0≤a≤1.5, 0.1≤x≤0.5, and 0.1≤y≤0.5.)

Preferably, the lithium composite metal oxide in the form of secondary particles may be represented by Formula 1-1 below.

[Formula 1-1]

Li ₁ Ni _0.6 Co _0.2 Mn _0.2 O ₂

In one embodiment, in the preparation of the mixture containing the lithium composite metal oxide in the form of secondary particles represented by Formula 1 or Formula 1-1, each of the lithium precursor and the nickel precursor contained in the Ni: Li It may be added so that the molar ratio is 0.7 to 0.8: 1.1 to 1.6.

Meanwhile, the lithium composite metal oxide in the form of primary particles obtained according to the present invention may be represented by Formula 2 below.

[Formula 2]

Li _a Ni _1-xy Co _x Mn _y O ₂

(In Formula 2, 1.0≤a≤1.5, 0.05≤x≤0.333, 0.05≤y≤0.333.)

Specifically, the lithium composite metal oxide in the form of primary particles obtained according to the present invention may be represented by Chemical Formula 2-1 below.

[Formula 2-1]

Li ₁ Ni _0.7 Co _0.15 Mn _0.15 O ₂

In one embodiment, the lithium composite metal oxide in the form of primary particles may have a diameter of 5 μm or more. Therefore, the possibility of surface degradation of the lithium composite metal oxide of the present invention may be reduced due to a decrease in the specific surface area due to the shape of the primary particles.

In an embodiment, the lithium precursor may be selected from LiOH, Li ₂ CO ₃ and LiNO ₃ , and the nickel precursor may be selected from NiO, Ni(OH) ₂ and NiSO ₄ .

In one embodiment, the first heat treatment may be performed for 4 to 15 hours, and the second heat treatment may be performed for 5 to 40 hours.

According to the present invention, a mixture in which a nickel precursor and a lithium precursor are added to a lithium composite metal oxide material in the form of secondary particles is changed into a form of primary particles of 5 μm or more through two heat treatments to reduce the specific surface area and reduce the possibility of surface degradation can be reduced, and at the same time, a cathode material having a higher nickel content can be manufactured by changing the composition of the lithium composite metal oxide material in the form of secondary particles, thereby improving the charge/discharge capacity of the cathode material.

1 is a schematic diagram showing a method for manufacturing a positive electrode active material in the form of primary particles from lithium composite metal oxide in the form of secondary particles according to an embodiment of the present invention.
2 shows a state in which lithium composite metal oxide in the form of secondary particles is converted into a cathode active material in the form of primary particles according to an embodiment of the present invention.
3A is a SEM image of a positive electrode active material in the form of primary particles manufactured according to an embodiment of the present invention.
3B is a SEM image of a cathode active material prepared according to Comparative Example 1;
3C is a SEM image of the cathode active material prepared according to Comparative Example 2.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Since the present invention may have various changes and various forms, specific embodiments are illustrated in the drawings and described in detail in the text. However, this is not intended to limit the present invention to a specific form disclosed, and should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention. Like reference numerals have been used for like elements throughout the description of each figure.

Terms used in this application are only used to describe specific embodiments and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise. In this application, terms such as "comprise" or "have" are intended to designate that there is a feature, step, operation, component, part, or combination thereof described in the specification, but one or more other features or steps However, it should be understood that it does not preclude the possibility of existence or addition of operations, components, parts, or combinations thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the related art, and unless explicitly defined in the present application, they should not be interpreted in an ideal or excessively formal meaning. don't

1 is a schematic diagram showing a method for manufacturing a positive active material material in the form of primary particles from a lithium composite metal oxide in the form of secondary particles according to an embodiment of the present invention.

Referring to FIG. 1, a method for manufacturing a positive active material material in the form of primary particles from lithium composite metal oxide in the form of secondary particles according to an embodiment of the present invention is a mixture of lithium composite metal oxide in the form of secondary particles, a lithium precursor, and a nickel precursor. It may include the step of first heat treatment at a temperature of 950 ° C or higher, and the step of second heat treatment at 800 ° C to 850 ° C.

The primary heat treatment step is a step for forming secondary particle type lithium composite metal oxide in primary particle form, and a mixture of secondary particle form lithium composite metal oxide, lithium precursor and nickel precursor is heated to a temperature of 950 ° C. or higher. The shape of the lithium composite metal oxide may be controlled by performing the primary heat treatment for 15 hours. Preferably, the first heat treatment may be performed at 950°C or more and 1000°C or less for 4 to 15 hours, and most preferably at 980°C for 5 hours. When the first heat treatment is performed at a temperature of less than 950 ° C., the shape of the primary particles is not controlled.

In one embodiment, the lithium composite metal oxide in the form of secondary particles used in the present invention may be obtained from a cathode active material of a waste lithium battery. In addition, the lithium precursor may be selected from LiOH, Li ₂ CO ₃ and LiNO ₃ , and the nickel precursor may be selected from NiO, Ni(OH) ₂ and NiSO ₄ .

In one embodiment, the lithium composite metal oxide in the form of secondary particles may be represented by Formula 1 below.

[Formula 1]

Li _a Ni _1-xy Co _x Mn _y O ₂

In Formula 1, 1.0≤a≤1.5, 0.1≤x≤0.5, and 0.1≤y≤0.5.

Preferably, the lithium composite metal oxide in the form of secondary particles may be a compound represented by Formula 1-1 below. (See Fig. 2)

[Formula 1-1]

Li ₁ Ni _0.6 Co _0.2 Mn _0.2 O ₂

In one embodiment, when preparing a mixture containing a lithium composite metal oxide in the form of secondary particles represented by Formula 1 or Formula 1-1, each of the lithium precursor and the nickel precursor contained in the mixture Ni: Li molar ratio It is preferable to add so that it becomes 0.7-0.8: 1.1-1.6. This is because lithium is partially lost through the high-temperature primary heat treatment step, and an excess amount of lithium precursor can be added to the mixture so that the amount of lithium relative to 1 mol of the transition metal is 1 mol or more after the secondary heat treatment step. . In addition, the nickel precursor is added to increase the nickel content of the lithium transition metal oxide obtained after the second heat treatment step, and thereby the charge and discharge capacity of the positive electrode active material material obtained after the second heat treatment step can be improved.

The secondary heat treatment step is a structural stabilization step for stabilizing the structure of the primary particles, and the secondary heat treatment is performed at 800 ° C to 850 ° C for 5 to 40 hours to obtain lithium composite metal oxide in the form of primary particles as shown in FIG. can be obtained. Most preferably, the secondary heat treatment may be performed at a temperature of 800° C. for 15 hours. When the secondary heat treatment is performed at less than 800° C., the structure of the primary particles is not stabilized.

In one embodiment, the lithium composite metal oxide in the form of primary particles may have a diameter of 5 μm or more. Therefore, the lithium composite metal oxide in the form of primary particles prepared according to the present invention has a reduced possibility of surface degradation compared to the secondary particle type cathode material due to the size of 5 μm or more and the decrease in the specific surface area, and due to the form of the primary particles, lithium When used as an electrode cathode active material, it has the effect of suppressing the deterioration phenomenon that occurs on the surface.

Meanwhile, the lithium composite metal oxide in the form of primary particles obtained according to the present invention may be represented by Formula 2 below.

[Formula 2]

Li _a Ni _1-xy Co _x Mn _y O ₂

(In Formula 2, 1.0≤a≤1.5, 0.05≤x≤0.333, 0.05≤y≤0.333.)

Specifically, the lithium composite metal oxide in the form of primary particles obtained according to the present invention may be represented by Chemical Formula 2-1 below.

[Formula 2-1]

Li ₁ Ni _0.7 Co _0.15 Mn _0.15 O ₂

As such, since the lithium composite metal oxide in the form of primary particles prepared according to the present invention has a higher nickel content than the lithium composite metal oxide in the form of secondary particles while having the form of primary particles, the charging and discharging capacity is improved.

Hereinafter, various embodiments and experimental examples of the present invention will be described in detail. However, the following examples are merely some examples of the present invention, and the present invention should not be construed as being limited to the following examples.

<Cathode Active Material Manufacturing>

[Example]

A mixture was prepared by mixing LiOH and NiO, a cathode active material for a waste lithium battery in the form of secondary particles having a composition of LiNi _0.6 Co _0.2 Mn _0.2 O ₂ , so that the Li : Ni molar ratio of the total mixture was 1.096 : 0.7 (a). As another example, a mixture was prepared such that the Li:Ni molar ratio of the mixture was 1:0.7 (b).

Next, heat treatment (sintering step) was performed to form primary particles and structures of the mixture.

Specifically, in order to form the mixture in the form of secondary particles into primary particles, a primary heat treatment was performed at 980° C. for 5 hours.

Next, a secondary heat treatment was performed at 800° C. for 15 hours to improve the structural stability of the cathode active material. (See Figures 1 and 2)

[Comparative Example 1]

A cathode active material was prepared in the same manner as in Example, except that the first heat treatment was performed at a temperature of 880 °C.

[Comparative Example 2]

A cathode active material was prepared in the same manner as in Example, except that the first heat treatment was performed at a temperature of 800 °C.

<Cathode active material material characteristics>

SEM images of the cathode active material materials prepared according to Examples and Comparative Examples 1 and 2 are shown in FIGS. 3A to 3C , and the characteristics of the cathode active material materials prepared are summarized in Table 1.

Example
(980 ℃) Comparative Example 1
(880℃) Comparative Example 2
(800℃) mixture
amount of lithium 1.096 mol 1 mol 1.096 mol 1 mol< 1.096 mol 1 mol< Anode material after manufacturing
amount of lithium 1 mol ≒ 1 mol< 1 mol ≒ 1 mol< 1 mol ≒ 1 mol< primary particle
Formed or not
(particle size) O
(10-7
um) O
(10-7um) △
(1-5 μm) △
(2-3 μm) X X

Referring to Table 1 and FIG. 3a , it can be observed that the positive electrode material prepared by including the first heat treatment step at 980° C. according to the embodiment exhibits a primary particle shape of about 5 μm or more. When the specific surface area is reduced by the formation of such primary particles, the possibility of surface deterioration of the cathode material may be reduced.

On the other hand, in the case of Comparative Example 1, which was subjected to the first heat treatment at a temperature of 880 ° C., as shown in Table 1 and FIG. 3B, although the primary particle form was formed as small particles with a size of less than 5 μm, the specific surface area of the example positive electrode material gave greater results than In addition, Comparative Example 2, which was subjected to the first heat treatment at a temperature of 800 ° C., showed the result of maintaining the secondary particle form without producing the cathode material in the form of primary particles, as observed in Table 1 and FIG. 3c.

Meanwhile, ICP analysis of the cathode material prepared according to the embodiment of the present invention was performed to confirm the composition, and the results are shown in Table 2.

As a result of the calculation through the ICP analysis result, the cathode material of the present invention was analyzed to have a composition of LiNi _0.7 Co _0.15 Mn _0.15 O ₂ , and through this, the nickel content increased compared to the cathode active material material of the waste lithium battery. It can be confirmed.

<Evaluation of electrochemical performance of cathode active material>

A cathode material (hereinafter referred to as R711-1, R711-2) prepared by including a first heat treatment step at 980 ° C according to the embodiment through a constant current and constant voltage test method and a lithium composite metal oxide in the form of secondary particles (R622- bare) was evaluated electrochemically. Here, the constant current and constant voltage test methods were tested after a voltage stabilization time of 20 hours. A constant current test method was used to apply a constant current at a rate of 0.1 C-rate in the voltage range of 4.3 - 2.7 V. At the same time, after achieving a voltage of 4.3 V through the constant current test method, a constant voltage of 4.3 V was applied to / 20 C-rate was carried out a constant voltage test method. The specific conditions for progress are shown in Table 3. In addition, the electrochemical evaluation results are shown in Table 4 below.

Electrode ratio Mass loading Electrode density Electrolyte Formation AM:BM:CM=90:5:5 ~ 2.0 mg/cm ² ~ 5.5 g/cm ³ 1.3M LiPF ₆ in EC/EMC/DEC (=3/5/2,v/v/v)
+ 10% FEC + 0.5% VC + 1% PS + 0.2% LiBF ₄ CC_0.1C @ 2.7-4.3V
CV_0.05C @ 4.3V

Sample Charge capacity
(mAh g ^-One ) Discharge capacity
(mAh g ^-One ) R711-1 204.58 180.36 R711-2 207.28 182.35 R622-bare 181.19 171.89

Referring to Table 4, it was confirmed that the capacity of the cathode materials (R711-1 and R711-2) prepared according to the present invention was improved compared to the lithium composite metal oxide (R622-bare) in the form of secondary particles.

Although the above has been described with reference to preferred embodiments of the present invention, those skilled in the art can variously modify and change the present invention without departing from the spirit and scope of the present invention described in the claims below. You will understand that you can.

Claims (10)

Primary heat treatment of a mixture of the lithium composite metal oxide in the form of secondary particles, a lithium precursor, and a nickel precursor at a temperature of 950° C. or higher; and
Including; secondary heat treatment at 800 ° C to 850 ° C;
After the secondary heat treatment, lithium composite metal oxide in the form of primary particles is obtained,
Method for producing a positive electrode active material in the form of primary particles from lithium composite metal oxide in the form of secondary particles. According to claim 1,
Characterized in that the lithium composite metal oxide in the form of secondary particles is obtained from a cathode active material of a waste lithium battery,
Method for producing a positive electrode active material in the form of primary particles from lithium composite metal oxide in the form of secondary particles. According to claim 1,
The lithium composite metal oxide in the form of secondary particles is represented by Formula 1 below, a method for producing a positive electrode active material material in the form of primary particles from lithium composite metal oxide in the form of secondary particles.
[Formula 1]
Li _a Ni _1-xy Co _x Mn _y O ₂
(In Formula 1, 1.0≤a≤1.5, 0.1≤x≤0.5, and 0.1≤y≤0.5.) According to claim 1,
The lithium composite metal oxide in the form of secondary particles is represented by Formula 1-1 below, a method for producing a positive electrode active material material in the form of primary particles from lithium composite metal oxide in the form of secondary particles.
[Formula 1-1]
Li ₁ Ni _0.6 Co _0.2 Mn _0.2 O ₂ According to claim 3 or 4,
In the preparation of the mixture, each of the lithium precursor and the nickel precursor is added so that the molar ratio of Ni: Li contained in the mixture is 0.7 to 0.8: 1.1 to 1.6,
Method for producing a positive electrode active material in the form of primary particles from lithium composite metal oxide in the form of secondary particles. According to claim 5,
The lithium composite metal oxide in the form of primary particles is represented by Formula 2 below, a method for producing a positive electrode active material material in the form of primary particles from lithium composite metal oxide in the form of secondary particles.
[Formula 2]
Li _a Ni _1-xy Co _x Mn _y O ₂
(In Formula 2, 1.0≤a≤1.5, 0.05≤x≤0.333, 0.05≤y≤0.333.) According to claim 5,
The lithium composite metal oxide in the form of primary particles is represented by Formula 2-1 below, a method for producing a positive electrode active material material in the form of primary particles from lithium composite metal oxide in the form of secondary particles.
[Formula 2-1]
Li ₁ Ni _0.7 Co _0.15 Mn _0.15 O ₂ According to claim 1,
The lithium composite metal oxide in the form of primary particles has a diameter of 5 μm or more,
Method for producing a positive electrode active material in the form of primary particles from lithium composite metal oxide in the form of secondary particles. According to claim 1,
The lithium precursor is selected from LiOH, Li ₂ CO ₃ and LiNO ₃ ,
The nickel precursor is selected from NiO, Ni(OH) ₂ and NiSO ₄ ,
Method for producing a positive electrode active material in the form of primary particles from lithium composite metal oxide in the form of secondary particles. According to claim 1,
The first heat treatment step is performed for 4 to 15 hours,
The secondary heat treatment is performed for 5 to 40 hours,
Method for producing a positive electrode active material in the form of primary particles from lithium composite metal oxide in the form of secondary particles.