KR20140015865A - Cathode active materials and manufacturing method thereof, and cathode and lithium battery using the same - Google Patents

Abstract

The present invention relates to a lithium secondary battery, and more particularly, to a cathode active material including 70 to 95 wt% of a nickel-based composite oxide of Formula 1, 5 to 30 wt% of carbonaceous material, and other unavoidable impurities, and a preparation thereof. The present invention relates to a positive electrode and a lithium battery employing the same.
Formula 1
LiNiO ₂

Description

Cathode active materials, a method of manufacturing the same, and a cathode and a lithium battery employing the same {CATHODE ACTIVE MATERIALS AND MANUFACTURING METHOD THEREOF, AND CATHODE AND LITHIUM BATTERY USING THE SAME}

The present invention relates to a lithium secondary battery, and more particularly, to a cathode active material for a lithium battery with improved capacity and stability, a method of manufacturing the same, and a cathode and a lithium battery employing the same.

The use of lithium batteries has been expanded to electronic devices, electric vehicles, and renewable energy storage devices that require high energy density, and for this purpose, high capacity and lifetime characteristics at room temperature and high temperature of lithium batteries have become important.

Currently, lithium cobalt oxide (LiCoO ₂ ) having good lifespan is used as a cathode active material used in commercialized lithium batteries, but lithium cobalt oxide (LiCoO ₂ ) has a high raw material and a driving voltage of about 3.8V. The effective capacity is about 50% of the theoretical capacity. In particular, the dissolution of cobalt generated during overcharging causes a safety problem of the lithium battery, and the capacitance decreases rapidly as the charge / discharge cycle progresses.

To solve this problem, LiNiO ₂ , LiNi _1/3 Co _1/3 Mn _1/3 O ₂ , LiMn ₂ O ₄ , LiFePO ₄ , LiNi _x Co _{1 - x} O ₂ (0≤x≤ 1), LiNi _{1- x- y} Co _x Mn _y O ₂ (0 ≦ _x ≦ 0.5, 0 _{≦ y} ≦ 0.5), Li [Li _x M ′ _{1 -x} ] O ₂ (x> 0, M 'is plural Studies on transition metal compounds such as transition metals) or lithium oxides.

However, although LiNiO ₂ or _{LiNi 1/3 Co 1/3} Mn 1/3 O 2 has the effective capacity is high and the similar, low cost, stability, and lithium cobalt oxide (LiCoO ₂₎ the driving voltage is about 4V, the high temperature operation transition metal Elution reduces the charge and discharge efficiency and lowers the life characteristics. In addition, LiMn ₂ O ₄ has an effective amount similar to that of lithium cobalt oxide (LiCoO ₂ ), low cost, high stability, and a driving voltage of about 4V, but poor cycle characteristics. In addition, LiFePO ₄ has an effective amount similar to that of lithium cobalt oxide (LiCoO ₂ ), low cost, and high stability, but low driving voltage of about 3.5V. Also, LiNi _x Co _{1 -} positive electrode active material, such as _x O ₂ (0≤x≤1) or _{LiNi 1 -x- y Co x Mn y} O 2 (0≤x≤0.5, 0≤y≤0.5) is at a high temperature Swelling suppression characteristics are poor. In addition, lithium metal oxides in the form of Li [Li _x M ' _{1 -x} ] O ₂ (x> 0, M' is a plurality of transition metals) provide an increased capacitance of 250-280 mAh / g. , The lithium metal oxide containing the excess lithium is poor in cycle characteristics and stability at high temperatures.

Therefore, it is required to introduce a positive electrode active material capable of realizing a lithium battery having a high capacity and high stability characteristics to solve this problem.

The present invention provides a positive electrode active material for a lithium battery, a method of manufacturing the same, and a positive electrode and a lithium battery employing the same in a lithium secondary battery, which not only improves conductivity, but also inhibits dissolution of transition metals at high temperatures. will be.

The technical objects to be achieved by the present invention are not limited to the above-mentioned technical problems.

The positive electrode active material for a lithium battery according to an embodiment of the present invention for realizing the above object may include 70 to 95 wt% of a nickel-based composite oxide of Formula 1, 5 to 30 wt% of a carbon material, and other unavoidable impurities. have.

Formula 1

LiNiO ₂

Specifically, the nickel-based composite oxide, cobalt (Co), aluminum (Al), and at least one of the additional metal (M) may be selectively added to be made of the formula (2).

(2)

LiNi _{1 -x- y} Co _x Al _y M _{y - z} O ₂

Here, 0 ≦ x ≦ 0.95, 0 ≦ y ≦ 0.5, 0 ≦ z ≦ 0.1, and M may be one element selected from Mg, Cu, Zn, Ga, Sb, Sn, Mn, and As.

The carbon material may be graphene.

In addition, the method for manufacturing a cathode active material for a lithium battery according to an embodiment of the present invention for realizing the above object is a step of mixing a nickel-based composite oxide and a carbon material with a solvent, a solvent in which the nickel-based composite oxide and carbon material is mixed Stirring, and drying the solvent mixed with the nickel-based composite oxide and the carbon material.

Specifically, the nickel-based composite oxide, it may be made of the formula (3).

(3)

LiNi _{1 -x- y} Co _x Al _y M _{y - z} O ₂

Here, 0 ≦ x ≦ 0.95, 0 ≦ y ≦ 0.5, 0 ≦ z ≦ 0.1, and M may be one element selected from Mg, Cu, Zn, Ga, Sb, Sn, Mn, and As.

The carbon material may be graphene.

In the mixing step, the carbon material may be mixed in a ratio of 0.05 to 0.5 based on the weight 1 of the nickel-based composite oxide.

Stirring the mixed solvent may be made by a milling method or a mechanical alloying method.

In addition, a positive electrode including the positive electrode active material may be manufactured.

In addition, it is possible to manufacture a lithium battery containing the positive electrode active material.

According to the cathode active material according to the present invention and the manufacturing method according to the configuration as described above, it is possible to easily prepare a composite of the nickel-based composite oxide and carbon material of the type in which the nickel-based composite oxide is surrounded by a carbon material (graphene). have.

In addition, by employing the composite of the nickel-based composite oxide and the carbon material of the present invention as a positive electrode active material, it is possible to manufacture a positive electrode and a lithium battery having improved rate characteristics, stability, and high temperature life characteristics.

1 is a scanning electron microscope (SEM) photograph of the positive electrode active material of the present invention and the positive electrode active material prepared according to the manufacturing method thereof.
2 is a flowchart illustrating a method of manufacturing a cathode active material of the present invention in order.
Figure 3 is a graph showing the results of the high temperature charge and discharge experiments of the embodiments of the present invention and the comparative example.
Figure 4 is a graph showing the results of the room temperature rate characteristics of the Examples and Comparative Examples of the present invention.
Figure 5 is a graph showing the results of the room temperature impedance test of the embodiments of the present invention and the comparative example.

Hereinafter, a cathode active material according to a preferred embodiment of the present invention, a manufacturing method thereof, and a cathode and a lithium battery employing the same will be described in detail with reference to the accompanying drawings and photographs. In the present specification, the same or similar reference numerals are given to different embodiments in the same or similar configurations.

The cathode active material 100 of the present invention employed in the lithium battery may include 70 to 95 wt% of the nickel-based composite oxide 101, 5 to 30 wt% of the carbon material 105, and other unavoidable impurities.

Here, the nickel-based composite oxide 101 may be made of Chemical Formula 1 below.

Formula 1

LiNiO ₂

In addition, the nickel-based composite oxide 101 may be made of Chemical Formula 2 by selectively adding at least one of cobalt (Co), aluminum (Al), and additional metal (M) to the compound of Formula 1.

(2)

LiNi _{1 -x- y} Co _x Al _y M _{y - z} O ₂

Here, 0 ≦ x ≦ 0.95, 0 ≦ y ≦ 0.5, 0 ≦ z ≦ 0.1, and M may be one element selected from Mg, Cu, Zn, Ga, Sb, Sn, Mn, and As.

In addition, the nickel-based composite oxide 101 may be in the form of a layered structure. As described above, when the nickel-based composite oxide 101 has a layered structure, a high effective amount can be obtained. However, a lithium battery employing a positive electrode active material made of only the nickel-based composite oxide 101 may cause deterioration of lifetime characteristics and rate characteristics due to elution of nickel at a high temperature.

Therefore, the cathode active material 100 of the present invention is characterized by forming a composite by mixing the nickel-based composite oxide 101 and the carbon material 105. Specifically, as described above, the cathode active material 100 of the present invention is made of 70-95 wt% of the nickel-based composite oxide 101, 5-30 wt% of the carbon material 105, and other unavoidable impurities. In this case, when the content of the nickel-based composite oxide 101 in the total cathode active material 100 is greater than 95 wt% or the carbon material 105 is less than 5 wt%, nickel is excessively eluted at a high temperature, and the nickel-based composite oxide is present. If the content of (101) is less than 70 wt% or the carbon material 105 is more than 30 wt%, it may be difficult to expect a high effective amount due to the nickel-based composite oxide (101).

In this case, the carbon material 105 may be graphene. Graphene is a basic material for making fullerene (C60), carbon nanotubes (CNT), graphite, and the like having a planar structure composed of only carbon atoms having a thickness of one atom. Here, graphene includes both natural graphene separated from pure graphite by mechanical peeling, and artificial graphene made by synthetic methods such as chemical vapor deposition (CVD), redox, and silicon carbide (SiC) sublimation.

As a raw material for synthesizing the graphene, at least one or more carbon materials such as non-graphitized carbon, reverse graphitized carbon, graphite, and thermally bonded carbons can be selected and used. In addition, the shape of such graphene raw material is not limited to a single thin film, spherical shape, granularity or the like. In addition, the graphene may exist in amorphous single form or in a single sheet form, and it is also possible to exist in crystalline form depending on the manufacturing process.

In addition, other unavoidable impurities may be included. Other unavoidable impurities may be a solvent added to facilitate mixing of the nickel-based composite oxide 101 and the carbon material 105 when the cathode active material 100 is manufactured. Such a solvent may be left in the cathode active material 100 without drying all during the manufacturing process of the cathode active material 100 of the present invention, but the content is considered to be insignificant and does not affect the characteristics of the present invention.

As described above, the cathode active material 100 including the composite of the nickel crab composite oxide and the carbon material 105 of the present invention formed as described above has a carbon material 105 around the crystalline nickel-based composite oxide 101. It is preferred to exist in a distributed and enclosed form.

In other words, when the composite is formed by mixing the nickel-based composite oxide 101 and the carbon material 105, problems of deterioration of life characteristics and rate characteristics at high temperatures may be improved.

In the cathode active material 100 of the present invention, as shown in the flowchart of FIG. 2, mixing the nickel-based composite oxide and a carbon material with a solvent (S10), and after the nickel-based composite oxide and the carbon material are combined In order to form a complex, it may include the step of stirring the solvent (S20), and the step of drying the solvent (S30). At this time, the characteristics of the nickel-based composite oxide and the carbon material mixed to form a composite is the same as described above with respect to the positive electrode active material.

First, in order to manufacture the cathode active material of the present invention, a nickel-based composite oxide and a carbon material are mixed with a solvent. (S10) Here, the carbon material is mixed at a ratio of 0.05 to 0.5 based on the weight 1 of the nickel-based composite oxide. do. In addition, the solvent is a material to be dried and removed in a subsequent process, and the amount of the solvent is not particularly limited, and it is preferable to mix N-methylpyrrolidone, ethanol, acetone, or water, which is generally used for manufacturing a lithium battery. Do. The mixed nickel-based composite oxide and the carbon material and the solvent are 70 to 95 wt% of the nickel-based composite oxide 101, 5 to 30 wt% of the carbon material 105, and the like after the solvent is removed in a subsequent process. It is characterized by being made of a positive electrode active material containing inevitable impurities.

In addition, the nickel-based composite oxide may be stirred in order to uniformly mix the carbon material and the solvent. In this case, the agitation may be performed by using ultrasonic agitation to increase the uniformity of the mixture and to minimize physical and chemical modification of the material.

Subsequently, in order to form a composite of the nickel-based composite oxide and the carbon material, the nickel-based composite oxide and the carbon material composite are nickel-based composite oxide and the carbon material after stirring the solvent (S20). It is prepared by drying a solvent in which the composite oxide and the carbon material are mixed (S30).

More specifically, the agitation of the solvent in which the nickel-based composite oxide and the carbon material are mixed is performed by mechanical agitation. (S20) Such mechanical agitation is easy to control the conditions such as agitation time, inclination of the agitation device, agitation speed, and the like. The composite oxide and the carbon material are mixed homogeneously, thereby physically combining the nickel-based composite oxide and the carbon material. Preferably, the solvent in which the nickel-based composite oxide and the carbon material are mixed may be stirred by a milling method or a mechanical alloying method.

Subsequently, the homogeneously mixed nickel-based composite oxide and the carbon-mixed solvent are subjected to a drying process. (S30) The solvent may be dried at room temperature, medium temperature, and high temperature, and may be dried in an air or vacuum state. It is also possible. Preferably drying in a vacuum at medium temperature (about 50 ~ 150 ℃) is good to minimize the physical and chemical deformation of the positive electrode active material prepared by the above-described method.

On the other hand, it is possible to manufacture a positive electrode comprising a positive electrode active material prepared by the above-described method. Specifically, the cathode active material is mixed with a conductive material, a binder solvent, and the like to prepare a cathode active material slurry, and then a cathode active material layer is formed on the surface of the current collector using the cathode active material, followed by drying the current collector on which the cathode active material layer is formed. Can be prepared. At this time, it is preferable to use an aluminum current collector as the current collector constituting the positive electrode.

More specifically, the positive electrode active material slurry is prepared by mixing a positive electrode active material, a conductive material, a binder, and a solvent. Here, the positive electrode active material is a positive electrode active material produced through the present invention, the conductive material may be used without limitation, materials used in the art, including carbon black, graphite fine particles and the like. In addition, the binder may also be used in the art without limitation, vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethyl methacrylate, Preference is given to using polytetrafluoroethylene (PTFE) and mixtures thereof, or styrene butadiene rubber-based polymers (SBR). In addition to the solvent, materials used in the art may be used without limitation, but N-methylpyrrolidone, ethanol, acetone, or water may be used. However, depending on the use and configuration of the positive electrode or lithium battery to be manufactured, it may be possible to omit one or more of the above-described materials and to be mixed.

Using the cathode active material slurry prepared in this way to form a cathode active material layer on the surface of the current collector. In this case, the positive electrode active material layer may be directly coated on the surface of the current collector and coated, or may be formed in advance in the form of a positive electrode active material film to be laminated on the current collector surface. Here, the positive electrode active material film can be formed by casting the positive electrode active material of the present invention on a separate support and peeling from the support.

On the other hand, it is possible to manufacture a lithium battery employing a positive electrode including a positive electrode active material prepared by the above-described method.

Specifically, first, a positive electrode prepared by the above-described method is prepared.

Thereafter, a negative electrode active material slurry is prepared by mixing a negative electrode active material, a conductive material, a binder, and a solvent. The preparation of the negative electrode active material and the negative electrode may be made through the same method as the preparation of the positive electrode active material and the positive electrode described above. That is, the negative electrode active material slurry is directly coated on the surface of the current collector and coated, or prepared in the form of a negative electrode active material film and laminated on the surface of the current collector to prepare a negative electrode.

Here, the current collector for manufacturing the negative electrode may be made of one material selected from copper, nickel, or SUS material.

In addition, the negative electrode active material may be used without limitation in the materials used in the art, specifically, lithium metal, a metal alloyable with lithium, a transition metal oxide, a material capable of topping and undoping lithium, and reversible lithium ions. As long as insertion and detachment are possible, all can be utilized. In this case, examples of the transition metal oxide may include lithium titanium oxide, titanium oxide, molybdenum oxide, tungsten oxide, and vanadium oxide. In addition, examples of the material capable of doping and undoping lithium include silicon, silicon oxide, silicon alloy, tin, and tin oxide. As the carbon-based material reversibly inserting and detaching lithium ions, any carbon-based negative electrode active material generally used in a lithium battery may be used. For example, crystalline carbon, amorphous carbon, or a mixture thereof may be used.

On the other hand, during the formation of the positive electrode or negative electrode prepared in this way, by further adding a plasticizer to the positive electrode active material slurry or the negative electrode active material slurry, it is also possible to form pores in the positive electrode or the negative electrode.

Next, a separator to be inserted between the positive electrode and the negative electrode is prepared. The separator may be used without limitation in the materials used in the art, and more specifically, it is more preferable that the separator has a low resistance to ion movement of the electrolyte and an excellent electrolyte-moisture capability. In one example, it is selected from glass fiber, polyester, Teflon, polyethylene, polypropylene, polytetrafluoroethylene (PTFE), or a combination thereof, and may be in the form of nonwoven or woven fabric.

Then, an electrolyte solution filled between the positive electrode, the negative electrode, and the separator to move ions is prepared. The electrolyte may be in a solid, liquid, or gel state. For example, an organic electrolyte, boron oxide, lithium oxynitride, or the like may be used.

In particular, when the electrolyte solution is a solid electrolyte, it can be deposited on the prepared cathode top by a method such as sputtering or vapor deposition.

In addition, when the electrolyte is an organic electrolyte, such an organic electrolyte is prepared by dissolving a lithium salt in an organic solvent. The organic solvent for this may be all solvents commonly used in the art, for example propylene carbonate, ethylene carbonate, fluoroethylene carbonate, diethyl carbonate, methylethyl carbonate, methylpropyl carbonate, butylene carbonate, benzo Nitrile, acetonitrile, tetrahydrofuran, 2-methyltetrahydrofuran, γ-butyrolactone, dioxolane, 4-methyldioxolane, N, N-dimethylformamide, dimethylacetamide, dimethylsulfoxide, di Oxane, 1,2-dimethoxyethane, sulfolane, dichloroethane, chlorobenzene, nitrobenzene, dimethyl carbonate, methyl isopropyl carbonate, ethyl propyl carbonate, dipropyl carbonate, dibutyl carbonate, diethylene glycol, dimethyl ether or these And mixtures thereof. In addition, lithium salts for this may be all solvents commonly used in the art, for example, LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , Li (CF ₃ SO ₂ ) ₂ N, LiC ₄ F ₉ SO ₃ , LiAlO ₂ , LiAlCl ₄ , LiN (C _x F _{2x + 1} SO ₂ ) (CyF _{2y + 1} SO ₂ ) (where x and y are natural numbers), LiCl, LiI or mixtures thereof Etc.

Thereafter, the positive electrode, the negative electrode, and the separator thus prepared are accommodated in the battery case, and an electrolyte solution is filled therebetween to manufacture a lithium battery. Specifically, the positive electrode, the negative electrode, and the separator accommodated inside the battery case are accommodated inside the battery case in a wound or folded state. Then, the organic electrolyte is injected into the battery case and sealed with a cap assembly to manufacture a lithium battery.

In this case, the battery case may be cylindrical, rectangular, thin film, or the like. Characteristically, the thin film lithium battery can be manufactured by the method of the present invention. Alternatively, the lithium ion battery may be manufactured through the present invention. Alternatively, the lithium ion polymer battery may be manufactured through the present invention. In the lithium ion polymer battery, a positive electrode, a negative electrode, and a separator are formed in one set, and a battery structure in which the positive electrode, the separator, and the negative electrode are formed is formed, stacked in a bi-cell structure, and then impregnated with an organic electrolyte solution. It can be prepared by receiving it in a pouch and sealing it. Alternatively, a plurality of the above-described battery structures may be stacked to form a battery pack, and the battery pack itself may be used in a device requiring high capacity and high output.

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

Example 1 Anode Active Material

Graphene present in the nickel composite oxide _{LiNi 0 .8 Co 0 .15 Al 0} .05 O 2 and group synthesized by co-precipitation 90: After mixing for 1 hour in isopropyl alcohol in a weight ratio of 10, 2 Ultrasonic time was used to obtain a uniformly dispersed powder.

Wherein the uniformly dispersed graphene and nickel composite oxide LiNi prepared in _0.8 Co _0.15 Al _0.05 O ₂ to 80 ^o C 24 hours of drying, the graphene and nickel composite oxide LiNi _{0 .8 0} during the condition _{Co. 15,} the Al _{0 .05} O ₂ in a weight ratio of zirconium to see and 1:10, Ar atmosphere, to thereby prepare a composite positive electrode active material is mechanically milled using the Fritsch's Planetary ball mill device for 30 minutes at 200 rpm condition.

Example 2 Anode Active Material

In the same manner as in Example 1, uniformly dispersed graphene and a nickel-based composite oxide LiNi _0.8 Co _0.15 Al _0.05 O ₂ were obtained.

Wherein the uniformly dispersed graphene and nickel composite oxide LiNi prepared in _0.8 Co _0.15 Al _0.05 O ₂ to 80 ^o C 24 hours of drying, the graphene and nickel composite oxide LiNi _{0 .8 0} during the condition _{Co. 15,} the Al _{0 .05} O ₂ in a weight ratio of zirconium to see and 1: 10, to prepare an Ar atmosphere, 300 rpm conditions 30 minutes composite positive electrode active material is mechanically milled using the Fritsch Planetary ball mill's equipment during the.

Example 3 Anode Active Material

Nickel-based composite oxide LiNi _0.8 Co _0.15 Al _0.05 O ₂ synthesized by the solid phase method and graphene present in a single thin plate were mixed in isopropyl alcohol at a weight ratio of 90:10 for 1 hour, and then ultrasonic waves were used for 1 hour. To obtain a uniformly dispersed powder.

A composite cathode active material was prepared in the same manner as in Example 1.

Example 4 Anode Active Material

In the same manner as in Example 1, uniformly dispersed graphene and a nickel-based composite oxide LiNi _0.8 Co _0.15 Al _0.05 O ₂ were obtained.

Wherein the uniformly dispersed graphene and nickel composite oxide LiNi prepared in _0.8 Co _0.15 Al _0.05 O ₂ to 80 ^o C 24 hours of drying, the graphene and nickel composite oxide LiNi _{0 .8 0} during the condition _{Co. 15,} the Al _{0 .05} O ₂ in a weight ratio of zirconium to see and 1: 10, to prepare an Ar atmosphere, 300 rpm conditions 30 minutes composite positive electrode active material is mechanically milled using the Fritsch Planetary ball mill's equipment during the.

Example 5 Anode and Lithium Battery (Coin Cell)

A slurry was prepared by mixing 94 wt% of the composite cathode active material powder prepared in Example 1, 3 wt% of carbon powder (Super C65, Timcal), and 3 wt% of polyvinylidene fluoride (PVDF) in agate mortar. The slurry was applied to an aluminum foil using a doctor blade to a thickness of about 80 μm, dried at room temperature for 2 hours, and then dried again under vacuum at 120 ^° C. for 2 hours to prepare a positive electrode.

Using this anode, a lithium metal was used as a counter electrode, and a polypropylene separator (Celgard 2400) was used as the separator, and 1M LiPF ₆ was added to EC (ethylene carbonate) + DEC (diethylene carbonate) (1: 1 weight ratio). The dissolved solution was used as an electrolyte to prepare a coin cell of CR-2032 standard.

Example 6 Anode and Lithium Battery

A positive electrode and a lithium battery (coin cell) were manufactured by the method of Example 5 using the positive electrode active material of Example 2.

Example 7 Anode and Lithium Battery

A positive electrode and a lithium battery (coin cell) were manufactured by the method of Example 5 using the positive electrode active material of Example 3.

Example 8 Anode and Lithium Battery

A positive electrode and a lithium battery (coin cell) were manufactured by the method of Example 5 using the positive electrode active material of Example 4.

≪ Comparative Example 1 &

A positive electrode and a lithium battery (coin cell), a nickel composite oxide _{LiNi 0 .8 Co 0 .15 Al 0} .05 O 2 synthesized by co-precipitation by way of Example 5, using as a cathode active material with no other additives were prepared.

Table 1 summarizes the preferred embodiments of the present invention prepared as described above.

division material Stirring dry Milling speed Example 1 Cathode active material _{LiNi 0 .8 Co 0 .15 Al 0} .05 O 2 + group graphene ultrasonic wave 80 ℃, 24 hours 200 rpm Example 2 Cathode active material LiNi _0.8 Co _0.15 Al _0.05 O ₂ + Single Graphene ultrasonic wave 80 ℃, 24 hours 300 rpm Example 3 Cathode active material LiNi _0.8 Co _0.15 Al _0.05 O ₂ + single sheet graphene ultrasonic wave 80 ℃, 24 hours 200 rpm Example 4 Cathode active material LiNi _0.8 Co _0.15 Al _0.05 O ₂ + single sheet graphene ultrasonic wave 80 ℃, 24 hours 300 rpm Example 5 Positive and Lithium Batteries A positive electrode manufactured using Example 1, and a lithium battery employing the same Example 6 Positive and Lithium Batteries A cathode fabricated using Example 2, and a lithium battery employing the same Example 7 Positive and Lithium Batteries A cathode fabricated using Example 3, and a lithium battery employing the same Example 8 Positive and Lithium Batteries A cathode fabricated using Example 4, and a lithium battery employing the same Comparative Example 1 Positive and Lithium Batteries LiNi _{0 .8} Co _{0 .15} The positive electrode fabricated using the Al _{0 .05} O ₂ as the positive electrode active material, and a lithium battery employing the same

Referring to Table 1, the positive electrode active material of Examples 1 to 4 is characterized in that it is prepared homogeneously mixed as in the photograph of FIG.

On the other hand, room temperature charge and discharge experiments were performed for the lithium batteries of Examples 5 to 8 and the lithium battery of Comparative Example 1. Specifically, the voltage is 4.3 at a current of 27.8 mA per 1 g of the positive electrode active material of Examples 1 to 4 and Comparative Example 1 included in each of the lithium battery of Examples 5 to 8, and the lithium battery of Comparative Example 1 Charged until V (vs. Li) and discharged again with the same current until voltage reached 3.0V (vs. Li). Subsequently, charging and discharging were repeated 50 times in the same current and voltage section. The results of room temperature charge and discharge experiments are shown in Table 2 below.

Initial Capacity
(mAh / g) Capacity after 50 charge / discharge cycles
(mAh / g) Reduction amount
(mAh / g) Example 5 212 185 27 Example 6 214 185 29 Example 7 211 182 29 Example 8 212 182 30 Comparative Example 1 211 181 30

Referring to Table 2, in the lithium battery of Examples 5 to 8, the decrease in the lithium battery capacity after the room temperature charge / discharge experiment was less than the decrease in the lithium battery capacity after the room temperature charge / discharge experiment of the lithium battery of Comparative Example 1 Or no difference.

In addition, high-temperature charge and discharge experiments were carried out for the lithium batteries of Examples 5 to 6 and the lithium batteries of Comparative Example 1. Specifically, in an oven maintaining a temperature of 55 ^° C, Examples 1 to 2 included in each of the lithium battery of Examples 5 to 6, and Comparative Example 1 and 27.8 per g of the positive electrode active material of Comparative Example 1 Charged at a current of mA until the voltage reached 4.3 V (vs. Li), and again discharged at the same current until the voltage reached 3.0 V (vs. Li). Subsequently, charging and discharging were repeated 80 times in the same current and voltage section. The high temperature charge and discharge test results are shown in FIG. 3.

Referring to the graph of FIG. 3, the lithium battery capacity after the high temperature charge / discharge experiment of the lithium batteries of Examples 5 to 6 was confirmed to be less decreased than the lithium battery capacity after the high temperature charge / discharge experiment of the lithium battery of Comparative Example 1 Can be.

That is, it can be seen from Table 1 and FIG. 3 that the lithium batteries of Examples 5 to 6 exhibited somewhat higher initial capacities than the lithium batteries of Comparative Example 1, as well as markedly improved capacity retention.

And the room temperature rate characteristic experiment was performed about the lithium battery of Example 5 thru | or Example 6, and the lithium battery of the comparative example 1. Specifically, while keeping the voltages of the lithium batteries of Examples 5 to 6 and Comparative Example 1 the same, the current value during charging is the same, and the current value during discharge is different so that the charge / discharge step is performed 10 times in each step. Repeatedly performed. At this time, the current value during charging is 27.8mA per 1g of positive electrode active material, and charges until the voltage reaches 4.3V (vs. Li), and the current value during discharge is 139mA, 278mA, and 834mA for each charge / discharge repeating step. , 1390 mA, 2780 mA, and 5560 mA were discharged until the voltage reached 3.0 V (vs. Li). 4 shows the results of the rate step experiments.

Referring to the graph of Figure 4, it can be seen that the rate characteristic of the lithium battery of Examples 5 to 6 is superior to the rate characteristic of the lithium battery of Comparative Example 1.

In addition, a room temperature impedance test was conducted on the lithium battery of Example 5 and the lithium battery of Comparative Example 1. Specifically, the battery is charged until the voltage reaches 4.3 V (vs. Li) at a current of 27.8 mA per 1 g of the positive electrode active material of Example 1 and Comparative Example 1 included in each of the lithium batteries of Example 5 and Comparative Example 1. And again, the same current was discharged until the voltage reached 3.0V (vs. Li). Subsequently, after charging and discharging was repeated 30 times in the same current and voltage section, impedance analysis was performed at 50% of the DOD. The mutual impedance results are shown in FIG. 5.

Referring to the graph of Figure 5, it can be seen that the lithium battery of Example 5 is more stable than the lithium battery of Comparative Example 1.

As a result, as shown in Table 1 and Table 2, and the description of Figures 3 to 5, the lithium batteries of the present invention is superior to the lithium battery of Comparative Example 1 in the electrode capacity, room temperature and high temperature cycle life, rate characteristics. It can be seen that. This is the result of the positive electrode of the present invention because the graphene surrounding the nickel-based composite oxide structurally stabilizes the electrode (anode) active material to suppress elution of nickel and also improve electrical properties.

According to the cathode active material according to the present invention and the manufacturing method according to the configuration as described above, it is possible to easily prepare a composite of the nickel-based composite oxide and carbon material of the type in which the nickel-based composite oxide is surrounded by a carbon material (graphene). have.

In addition, by employing the composite of the nickel-based composite oxide and the carbon material of the present invention as a positive electrode active material, it is possible to manufacture a positive electrode and a lithium battery having improved rate characteristics, stability, and high temperature life characteristics.

Such a cathode active material, a method of manufacturing the same, and a cathode and a lithium battery employing the same are not limited to the configuration and operation of the embodiments described above. The embodiments may be configured so that all or some of the embodiments may be selectively combined so that various modifications may be made.

100: cathode active material 101: nickel-based composite oxide
105: carbon material

Claims (10)

A cathode active material comprising 70 to 95 wt% of a nickel-based composite oxide of 5 to 30 wt%, a carbon material, and other unavoidable impurities.
Formula 1
LiNiO ₂
The method according to claim 1,
The nickel-based composite oxide,
At least one of cobalt (Co), aluminum (Al), and additional metal (M) is optionally further added to the positive electrode active material consisting of the formula (2).
Formula 2
LiNi _{1 -x- y} Co _x Al _y M _{y - z} O ₂
Where 0 ≦ x ≦ 0.95, 0 ≦ y ≦ 0.5, 0 ≦ z ≦ 0.1,
M is an element selected from Mg, Cu, Zn, Ga, Sb, Sn, Mn, and As.
The method according to claim 1,
The carbon material is a cathode active material of graphene (Graphene).
Mixing a nickel-based composite oxide and a carbon material with a solvent;
Stirring the solvent in which the nickel-based composite oxide and the carbon material are mixed; And
And drying the solvent in which the nickel-based composite oxide and the carbon material are mixed.
The method of claim 4,
The nickel-based composite oxide is a cathode active material manufacturing method consisting of the formula (3).
Formula 3
LiNi _{1 -x- y} Co _x Al _y M _{y - z} O ₂
Where 0 ≦ x ≦ 0.95, 0 ≦ y ≦ 0.5, 0 ≦ z ≦ 0.1,
M is an element selected from Mg, Cu, Zn, Ga, Sb, Sn, Mn, and As.
The method of claim 4,
The carbon material is graphene (Graphene) positive electrode active material manufacturing method. The method of claim 4,
In the mixing step,
A method of producing a cathode active material in which the carbon material is mixed at a ratio of 0.05 to 0.5 based on the weight 1 of the nickel-based composite oxide.
The method of claim 4,
Stirring the mixed solvent,
A method for producing a positive electrode active material comprising a milling method or a mechanical alloy method.
A positive electrode comprising the positive electrode active material of any one of claims 1 to 3.
Lithium battery comprising the positive electrode active material of any one of claims 1 to 3.

Images