KR101250496B1 - Positive composition for Lithium secondary battery and manufacturing method thereof - Google Patents

Abstract

The present invention relates to a cathode material for a non-aqueous lithium secondary battery and a method for manufacturing the same. A spherical spinel type having high density between primary particles by preparing a high-density spherical precursor through high dispersion of slurry and spray drying thereof. It is to improve the charge and discharge efficiency and output characteristics while producing a lithium manganese oxide while suppressing deterioration. According to the present invention, a slurry is prepared by uniformly wet grinding by mixing lithium raw material, manganese raw material, aluminum raw material and magnesium raw material. A highly dispersed slurry was prepared by rotating the slurry at a constant speed. The highly dispersed slurry is hot-air dried to prepare a spherical precursor. And a cathode precursor is manufactured by heat-treating a spherical precursor. In this case, the lithium raw material, manganese raw material, aluminum raw material and magnesium raw material may be represented by the formula: Li _{1 + x} Mn _2-y Mg _z Al _w O ₄ (0.00 <x≤0.20, 0.00 <y≤0.20, 0.00 <z≤0.10, 0.00 < It mixes so that it may have a composition ratio of w <= 0.10, x + w + z = y), and wet-pulverizes within 20 to 40% of solid content. The prepared anode material has an internal density of 95% or more between spherical primary particles.

Description

Positive material for non-aqueous lithium secondary battery and manufacturing method thereof {Positive composition for Lithium secondary battery and manufacturing method}

The present invention relates to a non-aqueous secondary battery and a method for manufacturing the same, and more particularly, high-density spherical density between primary particles by manufacturing a high-density spherical precursor through high dispersion of the prepared slurry and spray drying thereof. The present invention relates to a cathode material for a non-aqueous lithium secondary battery having a spinel-type lithium manganese oxide having excellent deterioration and suppressing deterioration, and having excellent output and discharge characteristics.

With the spread of portable small electric electronic devices, new secondary batteries such as nickel-metal hydride batteries and lithium secondary batteries have been actively developed. Among them, the lithium secondary battery is a battery using carbon such as graphite as an anode active material, using an oxide containing lithium as a cathode active material, and using a non-aqueous solvent as an electrolyte. Since lithium is a metal having a very high ionization tendency, development of a battery having a high energy density is possible because high voltage can be expressed.

Lithium transition metal oxides containing lithium are mainly used as the positive electrode active material used therein, and more than 90% of layered lithium transition metal oxides such as cobalt, nickel, and ternary systems in which cobalt, nickel, and manganese coexist are used have.

However, the layered lithium transition metal oxide, which is widely used as a positive electrode active material, participates in the reaction by desorption of oxygen in the lattice in a non-ideal state (overcharge and high temperature state), thereby causing abnormal behavior such as battery ignition. In order to overcome the drawbacks of the layered lithium metal oxide, studies on cathode active materials having spinel-based and olivine-based structures have been conducted.

As a means of solving the problem of the lithium secondary battery, which is deteriorated in safety due to the deterioration of the positive electrode, it has been proposed to use spinel-based lithium manganese oxide instead of layered lithium transition metal oxide as the positive electrode material.

Spinel-based lithium manganese oxide has a three-dimensional structure instead of the conventional layered structure, which enables the structure to be more stable than the conventional layered structure.This cathode material has excellent safety when applied to batteries. Can be given. Among them, spinel-based lithium manganese oxide (LiMn ₂ O ₄ ) has a high pyrolysis temperature of 300 ° C. or more even in a charged state, and thus, high power and high safety applications of lithium secondary batteries for HEVs have recently been used.

However, the spinel-based lithium manganese oxide has a defect that the density of the particles or the non-spherical shape is mostly due to the problem of elution of manganese (Mn) at high temperature and high voltage, resulting in poor battery performance and poor life characteristics.

Accordingly, an object of the present invention is to provide a cathode material for a non-aqueous lithium secondary battery and a method of manufacturing the same, which can not only suppress manganese (Mn) elution due to side reaction with the electrolyte, but also improve the output characteristics.

  Another object of the present invention is a positive electrode material for a non-aqueous lithium secondary battery, which is a spherical spinel-type lithium manganese oxide having a high internal density of 95% or more by introducing a high dispersion process in a manufacturing process, thereby allowing a high density of primary particles. To provide.

In order to achieve the above object, the present invention is a wet grinding step of producing a slurry by uniformly wet grinding by mixing a lithium raw material, manganese raw material, aluminum raw material and magnesium raw material, high dispersion slurry obtained by rotating the slurry at a constant speed Of the positive electrode material for a non-aqueous lithium secondary battery comprising a high dispersion step of manufacturing, hot air drying the high dispersion slurry to prepare a spherical precursor, and a heat treatment step of heat-treating the spherical precursor to produce a positive electrode material It provides a manufacturing method.

In the method for producing a cathode material for a non-aqueous lithium secondary battery according to the present invention, in the wet grinding step, the lithium raw material, manganese raw material, aluminum raw material and magnesium raw material of the formula, Li _{1 + x} Mn _2-y Mg _z Al _w O ₄ (0.00 <x≤0.20, 0.00 <y≤0.20, 0.00 <z≤0.10, 0.00 <w≤0.10, x + w + z = y) and mix to have a composition ratio of 20% to 40% Can be crushed.

In the method of manufacturing a cathode material for a non-aqueous lithium secondary battery according to the present invention, in the wet grinding step, the slurry may be wet grinding so that the slurry has an average particle size of 200 ~ 800nm.

In the method of manufacturing a cathode material for a non-aqueous lithium secondary battery according to the present invention, in the high dispersion step, the constant speed may be a linear speed of 20 ~ 80m / s.

In the method for producing a cathode material for a non-aqueous lithium secondary battery according to the present invention, in the spray drying step, the spherical precursor may have an average particle size of 5 ~ 20㎛.

In the method of manufacturing a cathode material for a non-aqueous lithium secondary battery according to the present invention, the heat treatment step may be a cathode material by performing a heat treatment at 700 ~ 900 ℃ in an air atmosphere. At this time, the heat treatment of the positive electrode material has an internal density of 95% or more between spherical primary particles.

The method of manufacturing a cathode material for a non-aqueous lithium secondary battery according to the present invention may further include a pulverizing step of pulverizing and powdering the heat treated cathode material, which is performed after the heat treatment step.

And the present invention also provides a cathode material for a non-aqueous lithium secondary battery produced by the above-described manufacturing method.

According to the present invention, by producing a high-density spherical precursor for the positive electrode material through a high dispersion process and spray drying process of the prepared slurry, the positive electrode material of the spinel-type lithium manganese oxide of high spherical spinel type lithium manganese oxide between primary particles effectively produced In this way, the cathode material prepared in this way is capable of expressing at least 90% of the initial capacity even after 50 times of charge and discharge at an ambient temperature of 5C at a temperature of 85C or more at a temperature of 60C and at a high temperature of 60 ° C.

In addition, since the cathode material according to the present invention is a spherical spinel-type lithium manganese oxide having an internal density of 95% or more between primary particles, it is possible not only to suppress the elution of manganese (Mn) due to side reaction with the electrolyte, but also to improve the output characteristics. Can be improved.

1 is a flow chart according to a method of manufacturing a cathode material for a non-aqueous lithium secondary battery according to the present invention.
FIG. 2 is an internal density image of a cathode material for a non-aqueous lithium secondary battery manufactured by the manufacturing method of Example 1 of the manufacturing method of FIG. 1.
3 is an internal density image of a cathode material for a non-aqueous lithium secondary battery manufactured by the manufacturing method of Comparative Example 5.
Figure 4 is a graph showing the charge and discharge output characteristics at room temperature of the cathode material prepared by the manufacturing method of Example 1.
5 is a graph showing charge and discharge output characteristics at room temperature of the cathode material prepared by the manufacturing method of Comparative Example 5.

In the following description, only parts necessary for understanding the operation according to the embodiment of the present invention will be described, it should be noted that the description of other parts will be omitted so as not to distract from the gist of the present invention.

Also, the terms and words used in the present specification and claims should not be construed to be limited to ordinary or dictionary meanings, and the inventor is not limited to the concept of terms in order to describe his invention in the best way. It should be construed in accordance with the meaning and concept consistent with the technical idea of the present invention based on the principle that it can be properly defined. Therefore, the embodiments described in the present specification and the configurations shown in the drawings are merely one preferred embodiment of the present invention, and not all of the technical ideas of the present invention are described. Therefore, It is to be understood that equivalents and modifications are possible.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

A method of manufacturing the cathode material for a non-aqueous lithium secondary battery according to the present invention will be described with reference to FIG. 1. 1 is a flowchart according to a method of manufacturing a cathode material for a non-aqueous lithium secondary battery according to the present invention.

The method for producing a cathode material for a non-aqueous lithium secondary battery according to the present invention is a spinel-type lithium manganese oxide through a wet grinding step (S10), a high dispersion step (S20), a spray drying step (S30) and a heat treatment step (S40). Material can be prepared. That is, in step S10, a lithium raw material, a manganese raw material, an aluminum raw material and a magnesium raw material are mixed and wet pulverized to prepare a slurry. In step S20 to prepare a highly dispersed slurry obtained by rotating the slurry at a constant speed. In step S30 to prepare a spherical precursor by hot air drying the highly dispersed slurry. In operation S40, a spherical precursor is heat-treated to prepare a cathode material. On the other hand, the method for manufacturing a cathode material for a non-aqueous lithium secondary battery according to the present invention may further include a grinding step (S50) for grinding the cathode material prepared in step S40.

Hereinafter, a method of manufacturing the cathode material for a non-aqueous lithium secondary battery according to the present invention will be described in detail.

First, in step S10, a lithium raw material, a manganese raw material, an aluminum raw material and a magnesium raw material are mixed and wet pulverized to prepare a slurry. That is, the lithium, manganese, aluminum and magnesium raw materials are weighed according to the compositional ratio of Formula 1 below, for example, equivalent ratio, and pulverized so that the average particle size is 200 to 800 nm using a wet grinder in the range of 20 to 40% solids. To prepare a slurry.

Here, when the solid content is 20% or less, the amount of the raw material mixture contained in the slurry is relatively insufficient, thereby lowering the internal density of the cathode material to be manufactured. On the other hand, if the solid content is more than 40%, since the amount of the raw material mixture contained in the slurry is relatively high to increase the viscosity, there will be a problem in the high dispersion process according to the step S20 and the spray drying step according to the step S30 to be performed later Can be.

And when the average particle size of the raw material mixture is 300nm or less, the particle size is too fine may reduce the internal density of the cathode material to be produced. On the other hand, if the average particle size of the raw material mixture is 800nm or more, a problem may occur that the particle size is not uniformly mixed.

(0.00 <x≤0.20, 0.00 <y≤0.20, 0.00 <z≤0.10, 0.00 <w≤0.10, x + w + z = y)

Here, lithium manganese oxide according to Formula 1 is a cathode material according to the present invention finally prepared. At this time, the raw material of the positive electrode material is an oxide of each metal (Li, Mn, Mg, Al) included in the positive electrode material or a precursor thereof (a compound of each metal or an individual metal that becomes an oxide when heated). Examples of such metal raw materials are listed below, but the present invention is not limited thereto.

The lithium raw material includes at least one of lithium carbonate, lithium hydroxide, lithium acetate, lithium sulfate, lithium sulfite, lithium acetate, lithium fluoride, lithium chloride, lithium bromide, and lithium oxide.

Manganese raw materials include, but are not limited to, manganese metal, manganese oxide (MnO, Mn ₂ O ₃ , Mn ₃ O ₄ , MnO _2, etc.), manganese oxalate, manganese acetate, and manganese nitrate.

The aluminum raw material includes at least one of aluminum hydroxide, aluminum oxide and aluminum chloride, but is not limited thereto.

The magnesium raw material includes at least one of magnesium hydroxide, magnesium oxide, magnesium carbonate, and magnesium chloride, but is not limited thereto.

Here, the reason for manufacturing the cathode material to have a composition ratio according to Formula 1 is as follows. The molar ratio of Li to manganese (Mn + Li + Mg + Al) in the cathode material of the present invention, that is, the value of x in the formula (1) is more than 0.00 and not more than 0.20. If the molar ratio of x is greater than 0.2, the content of manganese, an electrochemically active species, is reduced, resulting in lower initial discharge capacity. In addition, the molar ratio of Mg and Al with respect to manganese site (Mn + Li + Mg + Al), ie, the z and w values in General formula (1), is more than 0.00 and 0.10 or less. If the molar ratio of Mg and Al is larger than 0.10, the structure will be seriously deformed and the initial discharge capacity will be lowered. This is because the positive electrode material in this range has a discharge capacity of 100 to 105 mAh / g or more and an output characteristic of 85% or more due to an improvement in output characteristics due to substitution, and thus can be sufficiently used in current lithium secondary batteries.

Next, in step S20 to prepare a highly dispersed slurry obtained by rotating the slurry at a constant speed. That is, in order to lower the viscosity and increase the uniformity of the prepared slurry, a highly dispersed slurry is manufactured by rotating at a high speed of 20 to 80 m / s at a high speed using a high dispersion equipment.

Next, hot air-dry the highly dispersed slurry in step S30 to produce a spherical precursor. In other words, the high-dispersion slurry is hot-air dried through a spray dryer to prepare a spherical high density precursor having an average particle of 5 ~ 20㎛. At this time, the average particle size of the spherical high-density precursor can be controlled by controlling the wind speed of the hot air provided during hot air drying.

In operation S40, a spherical precursor may be heat-treated to prepare a cathode material according to Chemical Formula 1. At this time, the heat treatment is carried out in the air atmosphere at 700 ~ 900 ℃ in the air atmosphere to produce the final cathode material. In this case, when the heat treatment is performed at 700 ° C. or less, sufficient heat treatment may not be performed on the spherical precursor, and thus the internal density may be reduced. When the heat treatment is performed at 900 ° C. or higher, the oxidation of the spherical precursor may occur more than necessary, and thus may not be suitable for use as a cathode material. As will be described later, the produced cathode material has an internal density of 95% or more between spherical primary particles.

Meanwhile, in order to manufacture a cathode plate after step S40, the cathode material heat-treated in step S50 may be pulverized and powdered. At this time, the grinding is carried out in a conventional manner. Examples of grinding means include mortars, ball mills, vibratory mills, satellite ball mills, tube mills, rod mills, jet mills, hammer mills, and the like, and if desired, a desired particle size distribution is obtained. The average particle size of the powder of the cathode material of the present invention is preferably within the range of 0.1 to 100 µm.

The lithium secondary battery to which the cathode material of the present invention is applied is not different from the existing lithium secondary battery manufacturing method in terms of other than the cathode material. Although manufacturing of a positive electrode plate and a structure of a lithium secondary battery is demonstrated easily, it is not limited to these.

Production of the positive electrode plate is carried out by adding one or two or more kinds of additives which are commonly used to the powder of the positive electrode material of the present invention, if necessary, as a conductive agent, a binder, a filler, a dispersant, an ion conductive agent, a pressure enhancer, and the like. And slurry to paste with a suitable solvent (organic solvent). The slurry or paste thus obtained is applied to an electrode support substrate by a doctor plate method or the like, dried, and pressed using a rolled roll or the like as the positive electrode plate.

Examples of the conductive agent include graphite, carbon black, acetylene black, Ketjen Black, carbon fiber, metal powder and the like. PVdF, polyethylene, etc. can be used as a binder. The electrode supporting substrate (also referred to as current collector) may be formed of a foil, a sheet, or a carbon fiber, such as copper, nickel, stainless steel, or aluminum.

The lithium secondary battery is manufactured using the positive electrode thus prepared. The shape of the lithium secondary battery may be a coin, a button, a sheet, a cylindrical shape, or a square shape. Cathode materials, electrolytes, separators, etc. of lithium secondary batteries will be used in existing lithium secondary batteries.

Here, as the anode material, one or two or more kinds of carbon materials such as graphite or composite oxides of transition metals can be used. In addition, silicon, tin, and the like can also be used as a negative electrode material.

As the electrolytic solution, either a non-aqueous liquid electrolyte in which a lithium salt is dissolved in an organic solvent, an inorganic solid electrolyte, or a composite material of an inorganic solid electrolyte can be used.

Examples of the solvent for the non-aqueous electrolyte solution include esters such as ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate and methyl ethyl carbonate, lactones such as butyl lactone, 1,2-dimethoxy ethane and ethoxy methoxy ethane. One kind or two or more kinds of nitriles such as ethers, ethers and acetonitrile can be used.

Examples of the lithium salt of the non-aqueous liquid electrolyte include LiAsF ₆ , LiBF ₄ , LiPF ₆ , and the like.

As the separation membrane, a porous film made of polyolefin such as PP and / or PE or a porous material such as nonwoven fabric can be used.

Example  And Comparative example

A cathode material according to Example 1 was prepared as follows.

Lithium carbonate, manganese dioxide, aluminum hydroxide, magnesium carbonate was measured to be 1.12: 1.87: 0.02: 0.02, and the slurry was pulverized using a wet mill to obtain an average particle size of 500 nm with a solid content of 30%. In order to reduce the viscosity and increase the uniformity of the prepared slurry, a high-density slurry obtained by high-speed rotation at a linear speed of 40 m / s using a high-dispersion equipment was hot-air-dried through a spray dryer to spherical high density having an average particle of 9 μm. Prepare the precursor. The spherical precursor thus prepared was heat-treated at 850 ° C. in an air atmosphere to prepare a cathode material according to the final example 1.

The powder of the positive electrode material according to Example 1 was classified so as to have an average particle diameter of 10 μm. Slurry was prepared by using 80 wt% of the cathode material, 10 wt% of acetylene black as the conductive agent, and 10 wt% of PVdF of the binder, using NMP as a solvent. The slurry was applied to an Al foil having a thickness of 20 μm, dried, compacted by a press, and dried for 16 hours at 120 ° C. in a vacuum to prepare an electrode with a disc of 16 mm in diameter.

A lithium metal foil punched to a diameter of 16 mm was used as the counter electrode, and a PP film was used as the separator. A mixed solution of EC / DME 1: 1 v / v of 1 M LiPF 6 was used as the electrolyte. After the electrolyte solution was impregnated with the separator, the separator was sandwiched between the working electrode and the counter electrode, and the case of the SUS product was evaluated as a test cell for electrode evaluation.

Cathode materials according to Comparative Examples 1 to 6 and Example 2 were prepared under the conditions as described in Table 1.

sample
ID x
(Li) Substituent High dispersion
fair
Introduction inside
Density
[%] Room temperature
Output characteristics
[%] 60 ^o C
Life characteristic
[%] Remarks z
(Mg) w
(Al) One 0.05 0.00 0.15 N 85 58.5 74.0 Comparative Example 3 2 0.05 0.00 0.15 Y 90 75.3 82.3 Comparative Example 4 3 0.10 0.06 0.00 N 88 77.6 81.2 Comparative Example 5 4 0.10 0.06 0.00 Y 92 82.9 85.8 Comparative Example 6 5 0.10 0.04 0.04 N 89 78.3 83.9 Comparative Example 2 6 0.10 0.04 0.04 Y 95 85.7 91.2 Example 2 7 0.12 0.02 0.02 N 92 87.6 92.1 Comparative Example 1 8 0.12 0.02 0.02 Y 98 91.2 95.6 Example 1

Looking at the image of the internal density of the cathode material prepared according to Example 1 and Comparative Example 5, as shown in Figs. FIG. 2 is an internal density image of a cathode material for a non-aqueous lithium secondary battery manufactured by the manufacturing method of Example 1 of the manufacturing method of FIG. 1. 3 is an internal density image of a cathode material for a non-aqueous lithium secondary battery manufactured by the manufacturing method of Comparative Example 5. Here, the anode material contains spherical spinel type lithium manganese oxide, and the spinel type lithium manganese oxide collects primary particles 61 and 71 to form spherical secondary particles 62 and 72. As the internal density between the primary particles 61 and 71 is higher, fewer empty spaces 63 and 73 are displayed in the images of the secondary particles 62 and 72.

Referring to FIGS. 2 and 3 from this perspective, since the internal density between the primary particles 61 of the cathode material according to Example 1 is high, the void space 63 is the void space 73 of the anode material according to Comparative Example 5. You can easily see something relatively smaller. That is, it can be easily confirmed that the internal density of the positive electrode material according to Example 1 is higher than that of the positive electrode material according to Comparative Example 5. In particular, the internal value density of the positive electrode material according to Example 1 was measured at 98%, as shown in Table 1. In addition, the internal density of the positive electrode material according to Example 2 was also measured at 95%, as shown in Table 1.

Therefore, it can be seen that the cathode material manufactured by the manufacturing method according to the present embodiment has an internal density of 95% or more. That is, the internal density of the cathode material is improved because a high-density spherical precursor can be produced through a high dispersion process and spray drying of the ground slurry.

And the charge and discharge output characteristics at room temperature of the test cell for electrode evaluation made of the positive electrode material according to Example 1 and Comparative Example 5 were measured as shown in Figs. 4 is a graph showing charge and discharge output characteristics at room temperature of the cathode material manufactured by the manufacturing method of Example 1. FIG. 5 is a graph showing charge and discharge output characteristics at room temperature of the cathode material prepared by the manufacturing method of Comparative Example 5. Here, the 60 ° C lifespan characteristics were calculated as% of the initial capacity after 50 charge / discharge cycles at the 60 ° C design.

4 and 5, it can be seen that the cathode material according to Example 1 is 95.6% of the initial capacity after 50 charge and discharge at room temperature output characteristics and 60 ℃ high temperature compared to the cathode material according to Comparative Example 2 have. In addition, in the case of Example 2 it can be confirmed that after the charge and discharge 50 times at 60 ℃ high 91.2% of the initial capacity. That is, the positive electrode material according to Examples 1 and 2 improves the internal density between primary particles, so that the 5C capacity at room temperature is more than 85% of the 0.2C capacity and 90% of the initial capacity after 50 charge / discharge at 60 ° C. It can be confirmed that the above dosage expression is possible.

It should be noted that the embodiments of the present invention disclosed in the present specification and drawings are only illustrative of specific examples for the purpose of understanding and are not intended to limit the scope of the present invention. In addition to the embodiments disclosed herein, it is apparent to those skilled in the art that other modifications based on the technical idea of the present invention may be implemented.

61,71: primary particle
62,72: secondary particles
63,73: free space

Claims (8)

A wet grinding step of preparing a slurry by uniformly wet grinding by mixing lithium raw material, manganese raw material, aluminum raw material and magnesium raw material;
A highly dispersed step of preparing a highly dispersed slurry obtained by rotating the slurry at a constant speed;
Spray drying to hot-dry the highly dispersed slurry to produce a spherical precursor;
A heat treatment step of manufacturing a cathode material by heat-treating the spherical precursor;
In the wet grinding step,
A method for producing a cathode material for a non-aqueous lithium secondary battery, comprising mixing a lithium raw material, a manganese raw material, an aluminum raw material, and a magnesium raw material to have a composition ratio of the following chemical formula, and wet grinding within a solid content of 20 to 40%.
Li _{1 + x} Mn _2-y Mg _z Al _w O ₄ (0.00 <x≤0.20, 0.00 <y≤0.20, 0.00 <z≤0.10, 0.00 <w≤0.10, x + w + z = y) delete The method of claim 1, wherein in the wet grinding step,
Method for producing a cathode material for a non-aqueous lithium secondary battery, characterized in that the slurry is wet pulverized to have an average particle size of 200 ~ 800nm. According to claim 3, In the high dispersion step,
The constant speed is a method for producing a cathode material for a non-aqueous lithium secondary battery, characterized in that the linear speed of 20 ~ 80m / s. The method of claim 4, wherein in the spray drying step,
The spherical precursor is a method for producing a cathode material for a non-aqueous lithium secondary battery, characterized in that it has an average particle size of 5 ~ 20㎛. The method of claim 5, wherein the heat treatment step,
Anode material is prepared by heat treatment at 700 ~ 900 ℃ in an air atmosphere.
The heat treatment of the cathode material is a method for producing a cathode material for a non-aqueous lithium secondary battery, characterized in that the internal density of the spherical primary particles is 95% or more. The method according to any one of claims 1 and 3 to 6, which is carried out after the heat treatment step,
A pulverizing step of pulverizing and powdering the heat-treated positive electrode material;
Method for producing a cathode material for a non-aqueous lithium secondary battery further comprises a A cathode material prepared by the method for producing a cathode material for a non-aqueous lithium secondary battery according to claim 7.

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