KR101388919B1 - Lithium manganese oxide for lithium secondary battery and preparation method thereof - Google Patents

Abstract

The present invention relates to a lithium manganese oxide that can be used in a lithium secondary battery, by adding an appropriate amount of binder in preparing a lithium manganese oxide by the spray drying method, it is possible to produce a spherical particle of a large particle size during spray drying and subsequent firing Since the specific surface area is very small as the sphere is maintained in the process, performance decrease due to manganese elution does not occur when used in a lithium secondary battery.

Description

Lithium Manganese Oxide for Lithium Secondary Battery and Manufacturing Method Thereof {LITHIUM MANGANESE OXIDE FOR LITHIUM SECONDARY BATTERY AND PREPARATION METHOD THEREOF}

The present invention relates to a lithium manganese oxide that can be used in a lithium secondary battery and a method for manufacturing the same.

Lithium secondary batteries are currently widely used in small home appliances such as mobile phones and laptops, and these lithium secondary batteries are required to be miniaturized and high in capacity for portability and long-term use.

In recent years, as the use of lithium secondary batteries in electric vehicles and power storage has been expanded, demands for high output performance for large-sized lithium secondary batteries and their application to electric vehicles have arisen. .

In the past, lithium cobalt oxide (LCO) was mainly used as a cathode active material constituting a lithium secondary battery. However, due to cobalt supply and demand instability and high price, development of a substitute material is required.

Lithium manganese oxide (LMO) is currently in the spotlight as an alternative material. Lithium manganese oxide has high safety and high output characteristics due to its large size, and is advantageous for application to electric vehicles. Because. However, it is pointed out that the improvement of the problem that the performance due to the manganese elution at high temperature needs to be improved.

The degradation of performance due to the elution of manganese of the positive electrode active material using lithium manganese oxide has been analyzed due to the elution due to HF attack resulting from decomposition of LiPF ₆ , an electrolyte component.

In order to improve this, the spherical particles are manufactured to reduce the specific surface area and to reduce the contact area with HF, or to make the HF durable by surface coating. In addition, a method of reducing the number of moles of Mn ³⁺ participating in elution by doping has been devised. Lithium manganese oxide of spinel (LiMn ₂ O _4), the Mn ³⁺ and Mn ^4+, and there is present at the same rate, so the manganese dissolution problem occurs due to Mn ^3+, +1, +2 or +3 valence element Mn ³⁺ can be reduced by substituting for the Mn site. However, a decrease in Mn ³⁺ , which determines battery capacity, can lead to a decrease in battery capacity, so that a substitution above a certain concentration is meaningless.

As a conventional method of making such a lithium manganese oxide for a lithium secondary battery, the solid-state method and the spray drying method are mentioned.

First, the solid phase method is to produce a powder by mixing lithium raw materials (lithium carbonate, lithium hydroxide, etc.) and manganese raw materials (MnO ₂ , Mn ₃ O ₄ , MnCO _3, etc.), heat treatment at 700-900 ° C., and then grind them. Is amorphous, and due to its large specific surface area, manganese elution is severe and there is a problem in that the uniformity of mixing of raw materials is limited.

Next, in the spray drying method, the same raw materials as in the solid phase method are wet pulverized and spray-dried to aggregate the pulverized primary particles to form spherical secondary particles, which are prepared by heat treatment at 700 to 900 ° C. This spray drying method has the advantage that uniform mixing is possible because spherical particles are formed to reduce the specific surface area and the raw material compound is pulverized to a size of less than micron. In order to reduce the specific surface area, the particles are spherical in shape and larger in size, but according to the spray drying method, when the cohesive force between the pulverized primary particles is weak, they are not made large. There is a possibility that the spherical shape may collapse.

Accordingly, the present invention provides a lithium manganese oxide in the form of a spherical powder having a small specific surface area and a method of preparing the same.

In accordance with the above object, the present invention is a powder containing a compound of formula (1), the average specific surface area of 0.47 m 2 / g or less, the average particle diameter of 6 to 20 ㎛, used as a cathode active material in lithium secondary batteries, lithium manganese Provides oxides:

[Chemical Formula 1]

Li _{1 + x} [Mn _(2-pq) M1 _p M2 _q ] O _4-a A _a

Wherein x is 0 to 0.2; p is 0 to 0.2; q is 0 to 0.02; a is 0 to 0.2; M 1 is a +1, +2 or + trivalent element or a combination thereof; M 2 is an element having a melting point of 800 ° C. or lower in the oxide form or a combination thereof; A is a -1 or -2-valent element or a combination thereof.

In addition, the present invention comprises the steps of (a) mixing a raw material compound containing lithium and manganese in a solvent to obtain a slurry and then grinding; (b) spray drying the pulverized slurry to obtain a powder of secondary particles in which fine particles are aggregated; And (c) calcining the powder of the secondary particles, wherein the binder is 0.1 based on 100 parts by weight of the solids of the slurry in the slurry before grinding in step (a) or the slurry before spray drying in step (b). It provides a method for producing the lithium manganese oxide, comprising the step of adding to less than 1.0 parts by weight.

In the lithium manganese oxide of the present invention, by adding an appropriate amount of binder in the manufacturing process by the spray drying method, it is possible to generate spherical particles having a large particle size during spray drying, and to maintain the spherical shape in the subsequent firing step, Since the surface area is very small, performance degradation due to manganese elution does not occur when it is used in a lithium secondary battery.

1 is an electron microscope image of a secondary particle powder obtained before firing in Comparative Example 1. FIG.
2 is an electron microscope image of secondary particle powders obtained after firing in Comparative Example 1 and Examples 1 to 5 (x is the amount of binder added).
Figure 3 shows the average particle diameter of secondary particle powders obtained before firing in Comparative Example 1 and Examples 1 to 5.
Figure 4 shows the average particle diameter of the secondary particle powders obtained after firing in Comparative Example 1 and Examples 1 to 5.
FIG. 5 shows specific surface area (SSA) of secondary particle powders obtained after firing in Comparative Example 1 and Examples 1 to 5. FIG.

Hereinafter, the present invention will be described more specifically.

Lithium manganese oxide for a lithium secondary battery according to the invention is characterized in that it comprises a compound of formula (1):

[Chemical Formula 1]

Li _{1 + x} [Mn _(2-pq) M1 _p M2 _q ] O _4-a A _a

Where

x is 0 to 0.2, preferably 0.04 to 0.15;

p is 0 to 0.2, preferably 0.001 to 0.08;

q is 0 to 0.02, preferably 0.005 to 0.015;

a is 0-0.2, Preferably it is 0-0.1.

In addition, M1 is a +1, +2 or + trivalent element or a combination thereof, for example Mg, Al, Cr, Co, Ni, Zn, or a combination thereof;

M 2 is an element having a melting point of 800 ° C. or lower in the oxide form or a combination thereof, for example B, P, K, V, Ge, As, Rb, Tl, or a combination thereof;

A is a -1 or -divalent element or a combination thereof, for example F, S, or a combination thereof.

The lithium manganese oxide of the present invention is a spherical powder, characterized by an average specific surface area of 0.47 m 2 / g or less and an average particle diameter of 6 to 20 µm. The average specific surface area is more preferably 0.4 m 2 / g or less, for example, 0.1 to 0.4 m 2 / g, and more preferably 9 to 20 m. The powder of the present invention has the form of spherical secondary particles in which many fine particles (primary particles) are aggregated (see FIG. 2). The size of the primary particles may be 0.5 to 5 μm, more preferably 1 to 3 μm based on the average particle diameter (D50). When the size of the primary particles is smaller than the above range, the high temperature characteristics are deteriorated due to the increase in specific surface area. On the contrary, when larger than the above, output characteristics may decrease due to an increase in the lithium ion path.

It is preferable to manufacture the lithium manganese oxide for lithium secondary batteries which concerns on this invention after adding a binder component to a raw material in a manufacturing process, and baking.

The binder component is not particularly limited as long as it can be dissolved in a solvent. For example, when the solvent is water, water-soluble polymers such as polyvinyl alcohol (PVA), polyvinyl butyral (PVB), and polyacrylic acid (PAA) may be used. have.

In addition, the amount of the binder compound added is 0.1 parts by weight or more and less than 1.0 parts by weight based on 100 parts by weight of the total raw material solids, more preferably 0.3 to 0.8 parts by weight.

Lithium manganese oxide of the present invention, (a) mixing a raw material compound containing lithium and manganese in a solvent to obtain a slurry and then pulverizing; (b) spray drying the pulverized slurry to obtain a powder of secondary particles in which fine particles are aggregated; And (c) calcining the powder of the secondary particles, the method comprising adding a binder to the slurry before grinding in step (a) or the slurry before spray drying in step (b). Can be.

Step (a) is a step of preparing a slurry by mixing the raw material with a solvent, and then grinding using a ball mill or a bead mill.

As a raw material, lithium (Li); Manganese (Mn); +1, +2 or + trivalent element (M1); Element M2 having a melting point of 800 ° C. or lower in oxide form; And compounds containing -1 or -divalent element (A). The mixing ratio of each of these raw materials is the molar ratio of Li: Mn: M1: M2: A is 1 + x: 2-pq: p: q: a (x is 0 to 0.2, p is 0 to 0.2, q is 0 to 0.02 It is preferable to mix so that a may become 0-0.2).

At this time, lithium carbonate, lithium hydroxide, a mixture thereof, or the like can be used as a raw material of Li; Manganese oxide (manganese dioxide, dimanganese trioxide, trimanganese tetraoxide), manganese carbonate, manganese sulfate, manganese nitrate, a mixture thereof, etc. can be used as a raw material of Mn; As the raw material of M1, oxides, hydroxides, carbonates, sulfates, nitrates, or mixtures thereof of +1, +2 or + trivalent element (M1) can be used; As the raw material of M2, an oxide of an element (M2) having a melting point of 800 ° C. or less, an oxide, a mixture thereof, or the like may be used as the raw material of M2; As the raw material of A, organic / inorganic fluorides, sulfides, oxides, oxyanions, halides, halogen oxides, metal sulfides, organic sulfides and mixtures thereof of the -1 or -divalent element (A) may be used. It is not limited to this. The solvent is not particularly limited, but water is advantageous in terms of the manufacturing process.

In addition, when the raw material is mixed with the solvent, it is preferable to mix the solid to have a solid content concentration of 20 to 50% by weight, more preferably 25 to 40% by weight, and the higher the content, the higher the productivity may be. It is preferable to grind | pulverize so that the size of particle | grains (primary particle) may be 0.05-1 micrometer, More preferably, 0.1-0.5 micrometer on the basis of D50.

The step (b) is a step of obtaining a spherical secondary particles in which fine particles are agglomerated by spray drying the solvent using a wet dryer or a spray dryer.

As process conditions for spray drying, the inlet temperature is preferably 180 to 300 ° C, more preferably 200 to 250 ° C, and the outlet temperature is 80 to 150 ° C, more preferably 90 to 120 ° C.

The binder may be added before the wet grinding in step (a) or before the spray drying in step (b), but if the binder is added before the wet grinding in advance, the processability of the wet grinding may be deteriorated. It is desirable to add before drying.

The binder is added in an amount of 0.1 parts by weight or more and less than 1.0 parts by weight based on 100 parts by weight of the solid content of the slurry, and more preferably 0.3 to 0.8 parts by weight. When the amount of the binder added is greater than 1.0 part by weight, the nozzle of the spray dryer may be clogged due to an increase in the viscosity of the slurry and an increase in the cohesive force between the primary particles, and may remain after firing, which may adversely affect the performance of the product. When the amount of binder added is less than 0.1 part by weight, it is difficult to make the product more than a certain size, and even if it is made, it is difficult to maintain the spherical shape due to thermal shock during firing due to weak bonding force between primary particles. Or an increase in manganese elution.

The binder component is not particularly limited as long as it can be dissolved in a solvent. For example, when the solvent is water, water-soluble polymers such as polyvinyl alcohol (PVA), polyvinyl butyral (PVB), and polyacrylic acid (PAA) may be used. have.

Step (c) is a step of firing the powder spray drying is completed. Firing may be carried out by heat treatment at 700 to 900 ° C. for 5 to 20 hours.

The lithium manganese oxide of the present invention may have a difference in particle size before and after firing, because crystal grains grow, densification and crystallization occur during firing. The change in particle size according to the firing is slightly different depending on the firing temperature, firing time, heating rate, lowering speed, etc., but the primary particles become larger and the secondary particles become slightly smaller by firing. For example, in the case of primary particles, the size of the primary particles obtained after spray drying in step (b) is 0.05 to 1 μm, more preferably 0.1 to 0.5 μm based on D50, but is calcined in step (c). The size of the primary particles thus obtained may be 0.5 to 5 μm, more preferably 1 to 3 μm, based on D50.

In addition, in the case of secondary particles, the size of the secondary particles obtained after spray drying in step (b) may be 8 to 25 ㎛ on the basis of D50, the size of the secondary particles obtained after firing in step (c) is D50 It may be 6 to 20 ㎛, more preferably 9 to 20 ㎛ on the basis.

As described above, the lithium manganese oxide of the present invention is capable of producing spherical particles having a large particle size during spray drying by adding an appropriate amount of binder in the manufacturing process by the spray drying method, and then maintaining the spherical shape in the firing process. The specific surface area is very small, and when used in a lithium secondary battery, there is no performance degradation due to manganese elution.

Hereinafter, the present invention will be described in more detail with reference to the following examples, which are intended to illustrate the present invention and the present invention is not limited thereto.

Comparative Example 1

Lithium carbonate, manganese dioxide, aluminum hydroxide, magnesium carbonate and boric acid were blended so that the molar ratio of Li: Mn: Al: Mg: B was 1.040: 1.885: 0.050: 0.060: 0.005, and the mixture was mixed with water to give a solid having a solid content of 30% by weight. Was prepared.

The slurry was wet milled using a bead mill (trade name: MiniCer, manufactured by Netzsch).

The wet pulverized slurry is spray-dried using a spray dryer (product name: Mobile MINOR, manufacturer: GEA-NIRO) under conditions of a hot air inlet temperature of 240 ° C. and an outlet temperature of 100 ° C. to form a secondary particle powder in which fine particles are aggregated. Obtained.

The powder of the obtained secondary particles was calcined in air at 850 ° C. for 8 hours.

Examples 1-5 and Comparative Examples 2 and 3

Powder was obtained in the same manner as in Comparative Example 1 except that polyacrylic acid (PAA) was added to the wet pulverized slurry in the amount shown in Table 1 below.

Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 2 Comparative Example 3 PAA addition amount 0.05 0.1 0.3 0.5 0.8 1.0 1.5 * The said PAA addition amount (weight part) is a value based on 100 weight part of solid content of a slurry.

Test Example 1: Morphology of Powder

Figure 2 is an electron microscope image of the final powder obtained after firing in Comparative Example 1 and Examples 1 to 5 (x is the amount of binder added). As shown in Figure 2, it can be seen that the larger the amount of the binder is better maintained the sphere, in particular, when the binder addition amount is 0.3 to 0.8 parts by weight it can be seen that the sphere is best maintained after firing.

On the other hand, Figure 1 is an electron microscope image of the powder before firing in Comparative Example 1, it can be seen that spherical particles are well formed after spray drying even when the binder is not added as in Comparative Example 1, but after firing Figure As you can see from 2, we can't keep the (x = 0.00) sphere.

Test Example  2: measurement of average particle diameter of powder

The average particle diameter (D50) of the secondary particles obtained in Comparative Example 1 and Examples 1 to 5 was analyzed using a laser diffraction scattering method (product name: S3500, manufacturer: Microtrac).

Figure 3 shows the average particle diameter of the secondary particle powders obtained before firing after spray drying, Figure 4 is a result of analyzing the average particle diameter of the secondary particle powders completed after firing.

As shown in Figures 3 and 4, the average particle diameter of the addition was better than the case without addition of the binder, and maintained a good average particle size after the firing. In addition, the average particle diameter showed a tendency to increase according to the amount of the binder added, and especially when the amount of the binder added was 0.3 to 0.8 parts by weight, the average particle diameter characteristics were the best.

When the amount of the binder added was 1.0 parts by weight or more, as in Comparative Examples 2 and 3, the nozzle could not proceed further due to nozzle clogging during spray drying, because the viscosity of the slurry increased and the cohesion between primary particles increased due to the binder. to be.

Test Example 3 Measurement of Specific Surface Area

Figure 5 shows the specific surface area (SSA) for the powders after firing of Comparative Example 1 and Examples 1 to 5 according to the present invention. Specific surface area measurement was performed using the BET method (trade name: QUANRASORB SI, manufacturer: Quantachrome).

In view of this, it can be seen that the specific surface area is lower than when the binder is not added, especially when the binder addition amount is 0.3 to 0.8 parts by weight, the specific surface area is the lowest. This can be interpreted as not only the particle size of the secondary particles is increased by adding the binder but also the degree of sphericity is maintained well.

Claims (9)

delete delete delete (a) mixing raw materials containing lithium and manganese in a solvent to obtain a slurry and then grinding; (b) spray drying the pulverized slurry to obtain a powder of secondary particles in which fine particles are aggregated; And (c) calcining the powder of the secondary particles, wherein the binder is 0.1 based on 100 parts by weight of the solids of the slurry in the slurry before grinding in step (a) or the slurry before spray drying in step (b). Method for producing a lithium manganese oxide comprising the step of adding to less than 1.0 parts by weight or more,
The lithium manganese oxide is a powder containing a compound of formula (1a), the average specific surface area of 0.35 m 2 / g or less, the average particle diameter of 9 to 14 ㎛, used as a cathode active material in a lithium secondary battery, the production of lithium manganese oxide Way:
[Formula 1a]
Li _{1 + x} Mn ₂ O ₄
Wherein x is 0 to 0.2.
5. The method of claim 4,
The amount of the binder added is 0.3 to 0.8 parts by weight based on 100 parts by weight of the solid content of the slurry, the manufacturing method of lithium manganese oxide.
5. The method of claim 4,
The binder is selected from the group consisting of polyvinyl alcohol (PVA), polyvinyl butyral (PVB) and polyacrylic acid (PAA), a method for producing lithium manganese oxide.
5. The method of claim 4,
Step (a) is lithium (Li); Manganese (Mn); +1, +2 or + trivalent element (M1); Element M2 having a melting point of 800 ° C. or lower in oxide form; And -compounding a compound containing -1 or -divalent element (A) to obtain a slurry, and then pulverizing.
5. The method of claim 4,
The size of the secondary particles obtained after spray drying in step (b) is 8 to 25 ㎛, the size of the secondary particles obtained after firing in step (c) is characterized in that 6 to 20 ㎛, lithium manganese oxide Method of preparation.
5. The method of claim 4,
The binder is characterized in that the addition to the slurry before spray drying in step (b), a method for producing lithium manganese oxide.

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