JP7216059B2 - Positive electrode active material composition for lithium secondary battery and lithium secondary battery including the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to a positive electrode active material composition for a lithium secondary battery and a lithium secondary battery including the same, and more particularly, lithium comprising a mixture of particles manufactured at the same heat treatment temperature but having different Ni compositions and sizes. The present invention relates to a positive electrode active material composition for secondary batteries and a lithium secondary battery including the same.

Secondary batteries, especially lithium secondary batteries, are widely used in the field of small advanced electronic devices such as mobile devices and notebook computers. Medium and large-sized batteries are being developed, and in particular, due to the spread of electric vehicles (EV), the development of high-capacity, electrochemically stable lithium secondary batteries is in progress.

Among the components of a lithium secondary battery, a positive electrode active material plays an important role in determining the capacity and performance of the battery.

Manufacturers of secondary batteries increase the capacity of the secondary battery by improving the density of the mixture of the positive electrode plate based on the optimization of the average particle size and particle size distribution of the positive electrode active material.

Lithium cobalt oxide (LiCoO ₂ ), which has relatively excellent physical properties such as excellent cycle characteristics, is mainly used as a positive electrode active material. Cobalt used in LiCoO ₂ is a so-called rare metal. Since it is a metal, reserves are small and production areas are unevenly distributed, which poses the problem of unstable supply. In addition, due to the unstable supply of cobalt and the increased demand for lithium secondary batteries, LiCoO ₂ is expensive.

Against this background, research into positive electrode active materials that can replace LiCoO ₂ is steadily progressing, and lithium-containing manganese oxides such as LiMnO ₂ and spinel crystal structure LiMn ₂ O ₄ , and lithium-containing nickel oxides ( _{LiNiO 2} ) has also been considered, but due to the characteristics of its manufacturing method, _{LiNiO 2} is difficult to apply to actual mass production processes at reasonable _costs . Lithium manganese oxide has the disadvantage of poor cycle characteristics.

Recently, lithium composite transition metal oxides containing two or more transition metals selected from nickel (Ni), manganese (Mn), and cobalt (Co) or lithium transition metal phosphorus have been proposed as representative substitutes. Methods of using oxides as positive electrode active materials have been studied, and in particular, studies on the use of ternary layered oxides of Ni, Mn, and Co have progressed steadily.

On the other hand, in order to increase the energy density of the positive electrode active material, it is advantageous to appropriately mix large particles and small particles to increase the density. Large particles and small particles have their respective optimum heat treatment temperatures depending on the content of nickel (Ni). (Li) can be absorbed. However, the temperature interval for developing optimum capacity for small particles is lower than for large particles.

In addition, since the temperature range in which the mixed composition exhibits optimum performance depends on the temperature of the large particles with a high mixing ratio, small particles with a relatively low mixing ratio can exhibit optimum performance in the mixed composition. was difficult.

Therefore, it is necessary to develop a cathode active material that can satisfy the optimum temperatures of large particles and small particles at the same time.

As a result of intensive research efforts in order to overcome the above-mentioned problems of the prior art, the inventors of the present invention have found that the Ni composition of large and small particles and the ratio of small particles in the Ni composition mixture are controlled. In the case of the positive electrode active material composition for the next battery, it was confirmed that a mixed composition with improved output and life can be produced by optimizing the heat treatment temperature by adjusting the composition of Ni of large particles and small particles. Now complete inventions.

Korean Patent Publication No. 10-2014-0098433

In order to solve the problems of the prior art as described above, the present invention provides a novel positive electrode active material composition in which particles of different sizes are mixed and the composition is changed according to the particle size. intended to provide

A further object of the present invention is to provide a lithium secondary battery containing the positive electrode active material.

In order to solve the above problems, the present invention
Particles 1 represented by Chemical Formula 1 below, and
In a positive electrode active material composition composed of particles 2 represented by Chemical Formula 2 below,

(In the above chemical formulas 1 and 2, 0.6 ≤ x1 ≤ 0.99, 0.59 ≤ x2 ≤ 0.98, 0.5 ≤ a1 ≤ 1.5, 0.5 ≤ a2 ≤ 1.5, 0 .0≤y1≤0.3, 0.0≤y2≤0.3, 0.0≤z1≤0.3, 0.0≤z2≤0.3, 0.0≤1-x1-y1-z1 ≤0.3, 0.0≤1-x2-y2-z2≤0.3;
M is B, Ba, Ce, Cr, F, Mg, Al, Cr, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, P, Sr, and these It is one or more elements selected from the group consisting of combinations. )
The x1 and x2 provide a cathode active material satisfying the condition of 0.01≦x1-x2≦0.4.

Conventionally, in a mixed composition of large particles and small particles, the temperature range in which the large particles and small particles express the optimum capacity is different, and it depends on the temperature range of the large particles with a high mixing ratio. It was difficult to demonstrate the performance of

Therefore, the inventors have found that while adjusting the nickel (Ni) composition of the large and small particles to adjust the optimum capacity of the large and small particles, the heat treatment temperature of the large and small particles can be adjusted as well. Thus, it was confirmed that a lithium secondary battery with improved output and life could be manufactured, and the present invention was completed.

In the positive electrode active material composition for a lithium secondary battery of the present invention, x1 and x2 satisfy the condition of 0.01≦x1−x2≦0.4.

That is, in the positive electrode active material composition for a lithium secondary battery of the present invention, the Ni composition of the particles 2 is 1 to 40% lower than the Ni composition of the particles 1, preferably 5 to 40% lower. Characterized by

In the positive electrode active material composition for a lithium secondary battery of the present invention, the ratio of the particles 2 is 1 to 40% by weight, preferably 5 to 40% by weight, based on the total weight of the mixture composition. characterized by being

According to an experimental example of the present invention, as a result of confirming the optimum capacity expression depending on the ratio of small particles in the mixed composition, the Ni composition of small particles is 5% lower than that of large particles, and the ratio of small particles is 20 to 40%. At some point, when the Ni composition of the small particles was the same as that of the large particles, or 10 mol% lower than that of the large particles, even though the proportion of the small particles was 20 mol%, the optimum capacity was obtained. capacity could not be expressed.

Further, it was confirmed that when the Ni composition of the small particles was 5% lower than that of the large particles and the ratio of the small particles was 20%, the output characteristics and life characteristics were improved. These results indicate that the Ni composition of small particles to large particles and the ratio of small particles mixed in the whole particles are all satisfied, and the optimum capacity can be exhibited in the mixed composition, and the output characteristics and life characteristics can be improved.

In the cathode active material composition for a lithium secondary battery of the present invention, the size of particles 1 represented by Chemical Formula 1 is 6 μm to 30 μm, and the size of particles 2 represented by Chemical Formula 2 is 1 μm to 6 μm. It is characterized by

The size of the particles 1 represented by the chemical formula 1 and the size of the particles 2 represented by the chemical formula 2 according to the present invention represent D50 values analyzed by a particle size analyzer.

The positive electrode active material composition for a lithium secondary battery of the present invention is characterized in that the overall average Ni mole fraction of the positive electrode active material composition for a lithium secondary battery is 60 to 99%.

In the positive electrode active material composition for a lithium secondary battery of the present invention, the large particles and small particles of the positive electrode active material according to the present invention have an optimum capacity development temperature of 860 to 720.degree.

According to an experimental example of the present invention, as a result of confirming the optimum capacity development temperature according to the nickel content of the first heat-treated product, it was confirmed that the temperature at which the first heat-treated product exhibits optimum performance varies depending on the nickel content. It was also confirmed that when the nickel content of the small particles was 5% lower than the nickel content of the large particles, the optimum capacity development temperatures of the large and small particles were similar. These results suggest that by adjusting the nickel content of the small particles to make the optimum capacity development temperature similar to that of the large particles, the first heat treatment temperature will be similar, and as a result, the small particles It means that the optimum performance can be exhibited most.

The present invention further provides a lithium secondary battery comprising the positive electrode active material composition.

The present invention further provides
preparing a first precursor represented by Chemical Formula 3 and a second precursor represented by Chemical Formula 4 below and mixing them to prepare a precursor composition;

(In the above chemical formulas 3 and 4, 0.6 ≤ x1 ≤ 0.99, 0.59 ≤ x2 ≤ 0.98, 0.0 ≤ y1 ≤ 0.3, 0.0 ≤ z1 ≤ 0.3, 0.0 ≤1-x1-y1-z1≤0.3, 0.0≤y2≤0.3, 0.0≤z2≤0.3, 0.0≤1-x2-y2-z2≤0.3 ,
M is B, Ba, Ce, Cr, F, Mg, Al, Cr, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, P, Sr, and these It is one or more elements selected from the group consisting of combinations. )
mixing a lithium compound and the precursor composition and subjecting the precursor composition to a first heat treatment at a first temperature;
B, Ba, Ce, Cr, F, Mg, Al, Cr, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, P, Sr, and these and mixing one or more elements selected from the group consisting of combinations and subjecting the mixture to a second heat treatment at a second temperature.

The method of manufacturing a cathode active material composition according to the present invention may further include washing and drying the second heat-treated mixture with distilled water.

A method for producing a cathode active material composition according to the present invention comprises producing a first precursor and a second precursor having different particle sizes and Ni contents, and mixing the first precursor and the second precursor. After that, the first precursor and the second precursor are subjected to a first heat treatment at the same temperature.

In the positive electrode active material composition for a lithium secondary battery of the present invention, the large particles and small particles of the positive electrode active material according to the present invention have an optimum capacity development temperature of 860 to 720.degree.

As a result of confirming the optimum capacity expression temperature depending on the nickel content of the positive electrode active material in the present invention, the temperature at which the optimum performance of the heat-treated product is expressed varies depending on the nickel content, and the nickel content of the small-sized particles is the nickel content of the large-sized particles. It was determined that the optimum capacity onset temperatures for large and small sized particles were similar when 5% lower.

Thus, the present invention provides the first and second precursors by adjusting the nickel content of the smaller sized particles so that the optimum capacity onset temperature is similar to the optimum capacity onset temperature of the larger sized particles. The body is subjected to the first heat treatment at the same temperature so that even small-sized particles can exhibit optimum capacity, so that the cathode active material composition can best exhibit optimum performance.

In the method for producing a positive electrode active material composition according to the present invention, x1 and x2 satisfy the condition of 0.01≦x1−x2≦0.4.

In the method for producing a positive electrode active material composition according to the present invention, in the step of mixing the precursor composition, the second precursor is added in an amount of 5 to 40% by weight with respect to the total weight of the precursor composition. It is characterized by being mixed.

In the method for producing a cathode active material composition according to the present invention, the size of the first precursor particles represented by Chemical Formula 3 is 6 μm to 30 μm, and the size of the second precursor particles represented by Chemical Formula 4 is 6 μm to 30 μm. The size is characterized by being between 1 μm and 6 μm.

The positive electrode active material composition for a lithium secondary battery according to the present invention is composed of a mixture of particles with different sizes, and the Ni composition of small-sized particles with respect to the Ni composition of large-sized particles and the size of the Ni composition of small-sized particles and the composition of the entire mixture. By controlling the mixing ratio of the small particles, the optimum capacity development temperature can be similarly controlled, thereby manufacturing a lithium secondary battery with improved output and life.

FIG. 4 is a graph showing the results of confirming the discharge capacity of the positive electrode active material of the present invention depending on the heat treatment temperature; 1 is a SEM photograph of the positive electrode active material of the present invention (Example 1). FIG. 4 is a diagram showing the results of confirming the optimum capacity development of a lithium secondary battery containing the mixed composition of the present invention; FIG. 3 is a diagram showing the results of confirming the output characteristics of a lithium secondary battery containing the mixed composition of the present invention; FIG. 4 is a diagram showing the results of confirming the life characteristics of a lithium secondary battery containing the mixed composition of the present invention;

The present invention will be described in more detail below by way of examples. These examples are merely illustrative of the invention and are not to be construed as limiting the scope of the invention.

Preparation Example: Preparation of Cathode Active Material To prepare a cathode active material, first, a precursor represented by NiCoMn(OH) ₂ was prepared by a coprecipitation reaction. The Ni composition of the precursor was prepared as shown in Table 1 below.

A lithium compound such as LiOH or Li ₂ CO ₃ is added to the prepared precursor, and heated at a heating rate of 1° C./min to 20° C./min in the presence of N ₂ , O ₂ /(1 to 100 LPM). After the first heat treatment for ~20 hours (based on the maintenance interval), 0-10 mol% of a compound containing Al was mixed and the second heat treatment was performed to prepare a cathode active material for a lithium secondary battery.

Next, distilled water was prepared, and the distilled water was maintained at a constant temperature of 5 to 40°C. Washed with water for 1 to 10 hours.

The washed cathode active material was filtered and dried at 50 to 300° C. for 3 to 24 hours.

Experimental Example 1 Confirmation of Optimal Capacity Expression Temperature and Discharge Capacity An experiment was conducted to confirm the primary heat treatment temperature at which the particles of Production Examples 1 to 12 exhibit the optimum capacity.

Also, a battery containing the prepared particles was manufactured and the capacity was measured, and the results are shown in Table 2 and FIG. 1 below.

As a result, as can be seen from Table 2 and FIG. 1, when the Ni content of the small particles is about 5% lower than that of the large particles, the primary heat treatment temperature for developing the optimum capacity of the small particles is similar to that of the large particles. I understand.

Comparative Examples 1 to 4 and Examples 1 to 6: Preparation of Mixed Positive Electrode Active Material Compositions Precursors were first prepared according to the Ni compositions shown in Table 3 below. Next, LiOH or Li ₂ CO ₃ lithium compound is added to the precursor prepared above and heated at 1° C./min to 20° C./min in the presence of N ₂ , O ₂ /(1 to 100 LPM). After the first heat treatment at a temperature rising rate of 4 to 20 hours (based on the maintenance interval), 0 to 10 mol% of a compound containing Al was mixed and the second heat treatment was performed to prepare a cathode active material for a lithium secondary battery.

Next, distilled water was prepared, and the distilled water was maintained at a constant temperature of 5 to 40°C. Washed with water for 1 to 10 hours.

The washed cathode active material was filtered and dried at 50 to 300° C. for 3 to 24 hours.

Experimental Example 2: SEM measurement of positive electrode active material In order to confirm the particle size of all the positive electrode active materials (Example 1) produced in the above examples, the particles were observed with a scanning electron microscope (SEM). is shown in FIG.

Production Example: Production of Battery A battery containing the following mixed cathode active material composition was produced.
1) Production of positive electrode slurry [5 g standard] and production of electrode plate Active material 94 wt. %, conductive agent (super-P) 3 wt. %, Binder (PVDF) 3 wt. % of 4.7 g:0.15 g:0.15 g using an Auto Mixer at 1900 rpm/10 min. Next, it is manufactured by applying to Al-foil [15 μm] and pressing with a Micro film-applicator. After fabrication, it is dried in a dry-oven at 135° C. for 4 hours.
2) Manufacture of coin-cell A coated electrode plate was prepared by punching with a unit area of 2 cm ² as a positive electrode, lithium metal foil as a negative electrode, W-Scope-20 μm polypropylene as a separation membrane, and electrolysis. 1.15M LiPF ₆ having a composition of in EC/EMC=7/3 is used as the liquid. In addition, the coin-cell size uses CR2016 and CR2032 types and is assembled and manufactured in an argon-filled glove box in the usual manner.

Experimental Example 3: Confirmation of Optimal Capacity Expression by Ratio of Small Particles in Mixed Composition Optimal capacity expression of the coin cells of Examples 1 to 6 and Comparative Examples 1 and 4 was confirmed, and the results are shown in Table 4 and FIG. It was shown to.

As can be seen in Table 4 and FIG. 3, it was confirmed that the optimum capacity was achieved when the Ni composition of the small particles was 5% lower than that of the large particles, and the proportion of the small particles in the mixed composition was 20%. bottom.

Experimental Example 4 Confirmation of Output Characteristics of Large and Small Particle Mixed Composition Output characteristics of the coin cells of Examples 1 to 6 and Comparative Examples 1 and 4 were confirmed, and the results are shown in Table 5 and FIG. 4 below.

Experimental Example 5 Life Characteristics of Mixed Large and Small Particle Compositions Life characteristics of the coin cells of Examples 1 to 6 and Comparative Examples 1 and 4 were confirmed, and the results are shown in Table 6 and FIG. 5 below.

As a result, as can be seen from Table 6 and FIG. 5, it can be seen that Example 2 has the longest life.

Claims (6)

Particles 1 represented by Chemical Formula 1 below, and
In a positive electrode active material composition composed of particles 2 represented by Chemical Formula 2 below,

(In the above chemical formulas 1 and 2, 0.8 ≤ x1 ≤ 0.99, 0.8 ≤ x2 ≤ 0.98, 0.5 ≤ a1 ≤ 1.5, 0.5 ≤ a2 ≤ 1.5, 0 .0≤y1≤0.3, 0.0≤y2≤0.3, 0.0≤z1≤0.3, 0.0≤z2≤0.3, 0.0≤1-x1-y1-z1 ≤0.3, 0.0≤1-x2-y2-z2≤0.3;
M is B, Ba, Ce, Cr, F, Mg, Al, Cr, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, P, Sr, and these It is one or more elements selected from the group consisting of combinations. )
The particles 1 represented by the chemical formula 1 are larger in size than the particles 2 represented by the chemical formula 2,
The x1 and x2 satisfy the condition of 0.01≤x1 -x2≤0.1 ,
The positive electrode active material composition, wherein the particles 2 are mixed at a ratio of 5 to 40% by weight with respect to the total weight of the positive electrode active material composition. The lithium secondary battery according to claim 1, wherein the size of the particles 1 represented by the chemical formula 1 is greater than 6 µm and 30 µm or less , and the size of the particles 2 represented by the chemical formula 2 is 1 µm to 6 µm. A positive electrode active material composition. A lithium secondary battery comprising the positive electrode active material composition according to any one of claims 1 and 2 . (a) preparing and mixing a first precursor represented by Formula 3 and a second precursor represented by Formula 4 below to manufacture a precursor composition;

( 0.8 ≤ x1 ≤ 0.99, 0.8 ≤ x2 ≤ 0.98, 0.0 ≤ y1 ≤ 0.3, 0.0 ≤ y2 ≤ 0.3, 0.0 in the above chemical formulas 3 and 4 ≤ z1 ≤ 0.3 , 0.0 ≤ z2 ≤ 0.3, 0.0 ≤ 1-x1-y1-z1 ≤ 0.3, 0.0 ≤ 1-x2-y2-z2 ≤ 0.3 ,
M is B, Ba, Ce, Cr, F, Mg, Al, Cr, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, P, Sr, and these One or more elements selected from the group consisting of combinations ,
The x1 and the x2 satisfy the condition of 0.01≦x1−x2≦0.1. )
(b) mixing the lithium compound and the precursor composition and subjecting the precursor composition to a first heat treatment at a first temperature;
(c) washing and drying the first heat-treated mixture with distilled water;
A method for producing a positive electrode active material composition according to any one of claims 1 to 2, comprising Between step (b) and step (c), B, Ba, Ce, Cr, F, Mg, Al, Cr, V, Ti, Fe are added to the lithium compound and the precursor composition mixture. , Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, P, Sr, and one or more elements selected from the group consisting of combinations thereof, and a second heat treatment at a second temperature 5. The method for producing a cathode active material composition according to claim 4 , comprising the step of : 4. The size of the first precursor particles represented by the chemical formula 3 is greater than 6 μm and 30 μm or less , and the size of the second precursor particles represented by the chemical formula 4 is 1 μm to 6 μm. A method for producing the positive electrode active material composition according to 1.

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