KR20190055700A - Cathode Active Material for Lithium Secondary Battery and Lithium Secondary Battery Comprising the Same - Google Patents

Abstract

The present invention relates to a positive electrode active material composition for a lithium secondary battery, and a lithium secondary battery comprising the same. More particularly, the present invention relates to a positive electrode active material composition for a lithium secondary battery which comprises a mixture of particles heat-treated at the same temperature with different Ni compositions and particles sizes, and to a lithium secondary battery comprising the positive electrode active material composition. According to the present invention, the optimum capacity expression temperature of major and minor particles can be regulated similarly by controlling the Ni content of the major and minor particles, and thereby a lithium secondary battery having enhanced output and lifetime can be manufactured.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cathode active material composition for a lithium secondary battery and a lithium secondary battery comprising the cathode active material composition,

The present invention relates to a cathode active material composition for a lithium secondary battery and a lithium secondary battery comprising the same, and more particularly, to a cathode active material composition for a lithium secondary battery comprising a mixture of particles having different Ni composition and size, And more particularly, to a lithium secondary battery including the lithium secondary battery.

Among them, lithium secondary batteries are widely used in small-sized high-end electronic devices such as mobile devices and notebook computers. Development of mid- and large-sized batteries is also being carried out. Especially, development of high capacity electrochemically stable lithium secondary batteries is under development due to the spread of electric vehicles (EV).

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

Secondary battery manufacturers are increasing the capacity of secondary batteries by improving the density of the positive electrode plates, based on optimization of average particle size and particle size distribution of the cathode active material.

Lithium cobalt oxide (LiCoO ₂ ), which has excellent physical properties such as excellent cycle characteristics, is mainly used as a cathode active material. However, since cobalt used in LiCoO ₂ is a metal called a rare metal, There is an unstable problem in. In addition, LiCoO ₂ has a problem of high cost due to unstable supply of cobalt and increased demand of lithium secondary batteries.

In this background, studies on a cathode active material capable of replacing LiCoO ₂ have been progressing steadily, and studies have been made on a lithium-containing manganese oxide such as LiMnO ₂ , LiMn ₂ O _{4 having a} spinel crystal structure, and a lithium-containing nickel oxide (LiNiO ₂ ) It is difficult to apply LiNiO ₂ to actual mass production process at a reasonable cost due to the characteristics of LiNiO _{2 according} to its production method, and lithium manganese oxides such as LiMnO ₂ and LiMn ₂ O ₄ have disadvantages such as poor cycle characteristics Lt; / RTI >

Recently, a method using a lithium-transition metal oxide or a lithium transition metal phosphate containing two or more transition metals among nickel (Ni), manganese (Mn), and cobalt (Co) In particular, studies on the use of three-component layered oxides of Ni, Mn, and Co have been carried out steadily.

On the other hand, in order to increase the energy density of the cathode active material, it is advantageous to increase the density by appropriately mixing the major particles and the minor particles. The major and minor particles have the optimal heat treatment temperature according to the content of nickel. Since the specific surface area is larger than that of the major particles, it can absorb a large amount of lithium Li even at a relatively low heat treatment temperature. However, the temperature range that expresses the optimum capacity of the particles is inevitably lower than that of the opponent.

In addition, since the temperature range for optimum performance of the mixed composition depends on the temperature of the allergic mixture having a high mixing ratio, it is difficult for the fine particles having a relatively low mixing ratio to achieve optimal performance in the mixed composition.

Therefore, it is necessary to develop a cathode active material capable of simultaneously satisfying the optimum temperatures of the large particles and the large particles.

As a result, the present inventors have made intensive studies to overcome the problems of the prior art. As a result, in the case of a cathode active material composition for a lithium secondary battery in which the Ni composition of the major and minor particles and the ratio of the small particles in the mixed composition are controlled, It is possible to prepare a mixed composition having improved output and lifetime by adjusting the composition of Ni to optimize the heat treatment temperature, thereby completing the present invention.

KR 10-2014-0098433 A

Disclosure of Invention Technical Problem [8] Accordingly, the present invention has been made to solve the above problems occurring in the prior art, and it is an object of the present invention to provide a novel cathode active material composition having particles of different sizes mixed therein.

Another object of the present invention is to provide a lithium secondary battery including the positive electrode active material.

In order to solve the above problems,

Particles 1 represented by the following formula (1) and

1. A cathode active material composition comprising particles 2 represented by the following formula (2)

Li _a1 Ni _x1 Co _y1 Mn _z1 M _1-x1-y1-z1 O ₂

Li a ₂ Ni _{x 2} Co _{y 2} Mn _{z 2} M _{1-x 2-y 2 -z 2} O ₂

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, 0.5? 0.0? 1? Z? 1? 0.3, 0.0? 1-x2-y2-z2? 0.3,

M is selected from the group consisting of B, Ba, Ce, Cr, F, Mg, Al, Cr, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, One or more elements selected from the group consisting of

X1 and x2 satisfy the following condition: 0.01? X1-x2? 0.4.

It is difficult to exhibit the optimal performance of the particles in the mixed composition because the temperature range in which the major and minor particles exhibit the optimum capacity is different in the conventional large particle and small particle mixture and depends on the temperature interval of the large particle having a high mixing ratio.

Accordingly, the present inventors have found that by controlling the nickel (Ni) composition of the major and minor particles, the optimum capacity of the major and minor particles can be controlled and the heat treatment temperatures of the major and minor particles can be made to be the same, The secondary battery can be manufactured, and the present invention has been completed.

In the cathode 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 cathode 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, and is preferably 5 to 40% lower.

In the cathode active material composition for a lithium secondary battery of the present invention, the ratio of the particles 2 is 1 to 40 wt%, preferably 5 to 40 wt%, based on the total weight of the mixed composition.

According to one experimental example of the present invention, the optimum capacity of the mixed composition was observed according to the ratio of the small particles. As a result, 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 to 40% The optimum dose was not expressed when the Ni content of the fine particles was equal to or lower than 10% by mole of the major particle, even though the proportion of the fine particles was 20 mol%.

Further, it was confirmed that the output characteristics and the life characteristics were improved when the Ni composition of the fine particles was 5% lower than that of the major particles and the proportion of the minor particles was 20%. These results indicate that both the Ni composition of the minor particles and the proportion of the minor particles mixed in the total particles can be exerted in the mixed composition and the output characteristics and the life characteristics can be improved.

In the cathode active material composition for a lithium secondary battery of the present invention, the particle 1 represented by Formula 1 has a size of 6 um to 30 um, and the particle 2 represented by Formula 2 has a size of 1 um to 6 um.

The size of Particle 1 represented by Formula 1 and the size of Particle 2 represented by Formula 2 according to the present invention indicate D50 values analyzed by a particle size analyzer.

In the cathode active material composition for a lithium secondary battery of the present invention, the mole fraction of the total average Ni of the cathode active material composition for a lithium secondary battery is 60 to 99%.

In the cathode active material composition for a lithium secondary battery according to the present invention, the optimum capacity of the major and minor particles of the cathode active material according to the present invention is in the range of 860 to 720 ° C.

According to one experimental example of the present invention, it was confirmed that the temperature at which the optimal performance of the first heat treatment was exhibited varied according to the content of nickel, as a result of checking the optimum capacity expression temperature according to the nickel content of the first heat treatment product. It was also confirmed that when the nickel content of the small particles is 5% lower than the nickel content of the major particles, the optimum capacity expression temperatures of the major and minor particles are similar. These results indicate that by adjusting the nickel content of the fine particles, the optimal capacity expression temperature is made to be similar to the optimum capacity expression temperature of the allergen, thereby making the first heat treatment temperature the same and consequently maximizing the optimum performance of the small particles .

The present invention also provides a lithium secondary battery comprising the cathode active material composition.

The present invention also relates to

Preparing and mixing a first precursor represented by Formula 3 below and a second precursor represented by Formula 4 to prepare a precursor composition;

???????? Ni _x1 Co _y1 Mn _z1 M _1-x1-y1-z1 (OH) ₂ ?????

???????? Ni _x2 Co _y2 Mn _z2 M _1-x2-y2-z2 (OH) ₂ ?????

X1-y1-z1? 0.3, 0.0? Y2? 0.3, 0.0, 0.0? Y1? 0.3, 0.0? Y1? 0.3, 0.0? Lt; z2 < 0.3, 0.0 < = x2-y2-

M is selected from the group consisting of B, Ba, Ce, Cr, F, Mg, Al, Cr, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, One or more elements selected from the group consisting of

Mixing the lithium compound and the precursor composition and conducting a first heat treatment at a first temperature;

The above mixture is mixed with B, Ba, Ce, Cr, F, Mg, Al, Cr, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, And a second heat treatment at a second temperature. The present invention also provides a method for preparing the cathode active material composition according to the present invention.

The method for preparing a cathode active material composition according to the present invention comprises the steps of washing and rinsing a mixture obtained by the second heat treatment with distilled water; As shown in FIG.

The method for preparing a cathode active material composition according to the present invention comprises the steps of preparing a first precursor and a second precursor which are different in particle size and Ni content from each other and mixing the first precursor and the second precursor and then mixing the first precursor and the second precursor Is subjected to a first heat treatment at the same temperature.

In the cathode active material composition for a lithium secondary battery according to the present invention, the optimum capacity of the major and minor particles of the cathode active material according to the present invention is in the range of 860 to 720 ° C.

As a result of examining the optimal capacity expression temperature according to the nickel content of the positive electrode active material in the present invention, the temperature at which the optimum performance of the heat treatment product is exhibited changes depending on the content of nickel, and the nickel content of the small- It was confirmed that the optimum capacity expression temperatures of the large-sized particles and the small-sized particles became similar to each other.

The present invention provides a method of controlling the nickel content of particles having a small size by first heat treating the first precursor and the second precursor at the same temperature by causing the optimal capacity expression temperature to be similar to the optimum capacity expression temperature of particles having a large size, The particles having a small size exhibit an optimum capacity so that the cathode active material composition can maximally exhibit the optimum performance.

In the method for producing a cathode active material composition according to the present invention, x1 and x2 are characterized by satisfying the condition of 0.01? X1-x2? 0.4.

In the method of preparing a cathode active material composition according to the present invention, in the step of mixing the precursor composition, the second precursor is mixed at a ratio of 5 to 40% by weight based on the total weight of the precursor composition.

In the method of preparing a cathode active material composition according to the present invention, the size of the first precursor particles represented by Formula 3 is 6 袖 m to 30 袖 m, and the size of the second precursor particles represented by Formula 4 is 1 袖 m to 6 袖 m .

The cathode active material composition for a lithium secondary battery according to the present invention is composed of a mixture of particles having different sizes. The Ni composition of the particles having a smaller size than the Ni composition of the larger particles and the mixing ratio of the smaller particles The optimum capacity expression temperature can be similarly controlled, thereby making it possible to produce a lithium secondary battery having improved output and lifetime.

1 is a graph showing the results of checking the discharge capacity of the cathode active material according to the heat treatment temperature.
2 is a SEM photograph of the cathode active material of the present invention (Example 1).
3 is a graph showing the results of confirming optimal capacity expression of a lithium secondary battery comprising the mixed composition of the present invention.
4 is a graph showing the output characteristics of a lithium secondary battery including the mixed composition of the present invention.
5 is a graph showing the results of confirming the life characteristics of a lithium secondary battery including the mixed composition of the present invention.

Hereinafter, the present invention will be described in more detail with reference to Examples. These embodiments are only for illustrating the present invention, and thus the scope of the present invention is not construed as being limited by these embodiments.

Production Example: Preparation of cathode active material

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

division Precursor The content of nickel (Ni) Production Example 1 Small particle 90% Production Example 2 Small particle 85% Production Example 3 Small particle 80% Production Example 4 Small particle 60% Production Example 5 Small particle 55% Production Example 6 Small particle 50% Production Example 7 Opposition 90% Production Example 8 Opposition 85% Production Example 9 Opposition 80% Production Example 10 Opposition 60% Production Example 11 Opposition 55% Production Example 12 Opposition 50%

The lithium compound of LiOH or Li ₂ CO ₃ is added to the prepared precursor and the mixture is maintained at a 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, 0 to 10 mol% of a compound containing Al was mixed and subjected to a second heat treatment to prepare a cathode active material for a lithium secondary battery.

Then, distilled water was prepared, and the distilled water was kept constant at 5 to 40 캜. The prepared cathode active material for lithium secondary battery was put into distilled water and was rinsed for 0.1 to 10 hours while maintaining the temperature.

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

Experimental Example 1: Determination of Optimum Capacity Expression Temperature and Discharge Capacity

Experiments were conducted to confirm the primary heat treatment temperature expressing the optimum capacity for the particles of Production Examples 1 to 12.

In addition, a battery containing the produced particles was prepared and the capacity was measured. The results are shown in Table 2 and FIG.

division Optimum capacity expression temperature (캜) Capacity (mAh / g) Production Example 1 (Ni 90%, small particles) 680 224.8 Production Example 2 (Ni 85%, small particles) 720 219.6 Production Example 3 (Ni 80%, small particles) 780 211.1 Production Example 4 (Ni 60%, small particles) 820 204.5 Production Example 5 (Ni 55%, small particles) 840 200.1 Production Example 6 (Ni 50%, small particles) 860 195.6 Production Example 7 (Ni 90%, major particle) 720 228.5 Production Example 8 (Ni 85%, major particle) 780 223.1 Production Example 9 (Ni 80%, major particle) 800 212.2 Production Example 10 (Ni 60%, major particle) 840 206.8 Production Example 11 (Ni 55%, major particle) 860 200.3 Production Example 12 (Ni 50%, major particle) 900 197.1

As a result, as shown in Table 2 and FIG. 1, it can be seen that when the Ni content of the small particles is about 5% lower than that of the major particles, the primary heat treatment temperature that expresses the optimum capacity of the small particles becomes similar to the major particles .

Comparative Examples 1 to 4 and Examples 1 to 6: Preparation of mixed cathode active material composition

The precursors were first prepared according to the Ni composition in Table 3 below. Next, a lithium compound of LiOH or Li ₂ CO ₃ is added to the precursor thus prepared, and the mixture is heated at a rate of 1 ° C / min to 20 ° C / min in the presence of N ₂ , O ₂ / (1 to 100 LPM) After the primary heat treatment for 20 hours (based on the maintenance period), the compound containing Al was mixed with 0 to 10 mol% and subjected to a secondary heat treatment to prepare a cathode active material for a lithium secondary battery.

Then, distilled water was prepared, and the distilled water was kept constant at 5 to 40 캜. The prepared cathode active material for lithium secondary battery was put into distilled water and was rinsed for 0.1 to 10 hours while maintaining the temperature.

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

division Active material composition Ni composition Small particle
ratio Ni: Co: Mn Opposition Small particle Comparative Example 1 90: 8: 2 90.0 90.0 20 Comparative Example 2 88: 8: 4 90.0 80.0 20 Comparative Example 3 60:20:20 60.0 60.0 20 Comparative Example 4 58:20:22 60.0 50.0 20 Example 1 88: 8: 4 90.0 85.0 40 Example 2 89: 8: 3 90.0 85.0 20 Example 3 90: 8: 2 90.0 85.0 5 Example 4 58:20:22 60.0 55.0 40 Example 5 59:20:21 60.0 55.0 20 Example 6 60:20:20 60.0 55.0 5

Experimental Example 2: SEM measurement of the cathode active material

Particles were observed with a scanning electron microscope (SEM) to confirm the particle size of all the cathode active materials prepared in the above examples (Example 1), and the results are shown in FIG.

Production Example: Preparation of Cell

A battery comprising the following mixed cathode active material composition was prepared.

1) Preparation of positive electrode slurry [based on 5g] and electrode plate production

Mix 19 wt% of the active material, 3 wt% of the conductive agent (super-P) and 3 wt% of the binder (PVDF) at a ratio of 4.7 g: 0.15 g: 0.15 g at 1900 rpm / 10 min using an Auto Mixer. Then, it is applied to Al-foil [15 μm] and then pressed with a Micro film-applicator. And then dried in a 135 ° C dry-oven for 4 hours.

2) Coin-cell fabrication

Lithium metal foil was used as a cathode, W-Scope-20um polypropylene was used as a separator, and 1.15M LiPF _{6 having an} EC / EMC = 7/3 composition as an electrolyte was prepared by punching a coating electrode plate as a positive electrode with a unit area of 2 cm ² . Lt; / RTI > Coin-cell size is assembled in an argon-filled glove box using the CR2016 and CR2032 types.

EXPERIMENTAL EXAMPLE 3: Determination of Optimal Capacity Expression According to Particle Size in Mixture Composition

The optimum capacity expressions of the coin cells of Examples 1 to 6 and Comparative Examples 1 and 4 were confirmed, and the results are shown in Table 4 and FIG.

division Charge Capacity (mAh / g) Discharge Capacity (mAh / g) One ^st  Efficiency (%) Example 1 241.9 223.7 92.5 Example 2 241.6 226.3 93.7 Example 3 241.6 224.2 92.8 Example 4 224.3 205.6 91.7 Example 5 225.3 206.5 91.7 Example 6 225.5 204.9 90.9 Comparative Example 1 241.7 222.8 92.2 Comparative Example 2 236.6 219.1 92.6 Comparative Example 3 222.6 203.5 91.4 Comparative Example 4 223.5 204.1 91.3

As can be seen from Table 4 and FIG. 3, it was confirmed that the optimal dose was expressed when the Ni composition of the granules was 5% lower than that of the major particles and the ratio of the minor particles was 20% in the mixed composition.

EXPERIMENTAL EXAMPLE 4: Confirmation of Output Characteristics of Large Mixture Composition

The 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.

division unit 0.2C 0.5 C 1.0 C 1.5 C 2.0C 5.0 C Example 1 mAh / g 215.9 205.8 198.6 195.5 193 183.8 % 96.5 92 88.8 87.4 86.3 82.2 Example 2 mAh / g 219.2 208.7 201.3 197.8 195.2 186.4 % 96.9 92.2 89 87.4 86.3 82.4 Example 3 mAh / g 216.9 206.5 199.5 196 193.9 184.8 % 96.7 92.1 89 87.4 86.5 82.4 Example 4 mAh / g 200.0 192.4 185.0 181.3 178.5 167.0 % 97.2 93.5 89.9 88.2 86.8 81.2 Example 5 mAh / g 200.9 193.1 186.0 182.3 179.8 169.2 % 97.3 93.5 90.1 88.3 87.1 81.9 Example 6 mAh / g 198.8 190.8 183.6 179.7 176.2 164.7 % 97.0 93.1 89.6 87.7 86.0 80.4 Comparative Example 1 mAh / g 214.7 204.3 196.6 193.1 191.1 181.7 % 96.3 91.7 88.2 86.6 85.8 81.5 Comparative Example 2 mAh / g 211.7 201.9 195.1 192 189.5 180.5 % 96.6 92.2 89 87.6 86.5 82.4 Comparative Example 3 mAh / g 198.7 189.9 182.9 179.3 176.1 164.2 % 97.6 93.3 89.8 88.1 86.5 80.7 Comparative Example 4 mAh / g 198.3 190.6 182.9 179.0 176.0 164.0 % 97.1 93.4 89.6 87.7 86.2 80.3

EXPERIMENTAL EXAMPLE 5: Life characteristics of large premixed composition

The 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.

division Capacity Retention
(50 cycles,%) Comparative Example 1 91.7 Comparative Example 2 89.9 Comparative Example 3 88.2 Comparative Example 4 89.8 Example 1 93.7 Example 2 95.0 Example 3 93.1 Example 4 94.4 Example 5 94.9 Example 6 94.3

As a result, as shown in Table 6 and FIG. 5, it can be seen that the lifetime of Embodiment 2 is the highest.

Claims (8)

Particles 1 represented by the following formula (1) and
1. A cathode active material composition comprising particles 2 represented by the following formula (2)
Li _a1 Ni _x1 Co _y1 Mn _z1 M _1-x1-y1-z1 O ₂
Li a ₂ Ni _{x 2} Co _{y 2} Mn _{z 2} M _{1-x 2-y 2 -z 2} O ₂
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, 0.5? 0.0? 1? Z? 1? 0.3, 0.0? 1-x2-y2-z2? 0.3,
M is selected from the group consisting of B, Ba, Ce, Cr, F, Mg, Al, Cr, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, One or more elements selected from the group consisting of
X1 and x2 satisfy the condition of 0.01? X1-x2? 0.4,
Cathode active material composition.
The method according to claim 1,
And the particles 2 are mixed in a proportion of 5 to 40% by weight based on the total weight of the cathode active material composition
Cathode active material composition for lithium secondary battery.
The method according to claim 1,
The size of the particle 1 represented by the formula 1 is 6 탆 to 30 탆, and the size of the particle 2 represented by the formula 2 is 1 탆 to 6 탆.
Cathode active material composition for lithium secondary battery.
A lithium secondary battery comprising the cathode active material composition according to any one of claims 1 to 3.
Preparing a first precursor represented by Formula 3 below and a second precursor represented by Formula 4;
???????? Ni _x1 Co _y1 Mn _z1 M _1-x1-y1-z1 (OH) ₂ ?????
???????? Ni _x2 Co _y2 Mn _z2 M _1-x2-y2-z2 (OH) ₂ ?????
(In the above formulas 3 and 4, 0.6? X1? 0.99, 0.59? X2? 0.98, 0.0? Y1? 0.3, 0.0? Y2? 0.3, 0.0? Z1? 0.3, -z1? 0.3, 0.0? 1-x2-y2-z2? 0.3,
M is selected from the group consisting of B, Ba, Ce, Cr, F, Mg, Al, Cr, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, One or more elements selected from the group consisting of
Mixing the lithium compound and the precursor composition and conducting a first heat treatment at a first temperature;
Wherein the lithium compound and the precursor composition mixture contain at least one element selected from the group consisting of B, Ba, Ce, Cr, F, Mg, Al, Cr, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, , Sr, and a combination thereof, and performing a second heat treatment at a second temperature; And
Washing the second heat-treated mixture with distilled water and drying; Containing
A method for producing a cathode active material composition according to claim 1.
6. The method of claim 5,
X1 and x2 satisfy the condition of 0.01? X1-x2? 0.4,
A method for producing a cathode active material composition.
6. The method of claim 5,
And the second precursor is mixed in a proportion of 5 to 40% by weight based on the total weight of the precursor composition in the step of mixing the precursor composition
A method for producing a cathode active material composition.
6. The method of claim 5,
The size of the first precursor particle represented by Formula 3 is 6 um to 30 um, and the size of the second precursor particle represented by Formula 4 is 1 um to 6 um.
A method for producing a cathode active material composition.

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